Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives 9780841203884, 9780841204454, 0-8412-0388-1

Table of contents :
Title Page ......Page 1
Half Title Page......Page 3
Copyright......Page 4
ACS Symposium Series......Page 5
FOREWORD......Page 6
PdftkEmptyString......Page 0
PREFACE......Page 7
1 Rayon—A Fiber with a Future......Page 8
Rayon - Its Problems......Page 12
Rayon - Its Opportunities......Page 13
Literature Cited......Page 16
2 A Critical Review of Cellulose Solvent Systems......Page 17
A. Cellulose As A Base......Page 19
B. Cellulose As An Acid......Page 20
C. Cellulose Complexes......Page 22
D. Cellulose Derivatives......Page 23
Literature Cited......Page 27
3 The Spinning of Unconventional Cellulose Solutions......Page 30
Spinning Experiments Using Cellulose Dispersed in Calcium Thiocyanate......Page 31
Spinning Experiments Utilizing Cellulose Dissolved in NO2-DMF......Page 34
Spinning of Cellulose in DMSO - Paraformaldehyde Solutions......Page 40
CONCLUSIONS......Page 43
LITERATURE CITED......Page 44
Introduction......Page 45
Experimental......Page 46
Results and Discussion......Page 47
Acknowledgements......Page 55
Literature Cited......Page 56
Introduction......Page 57
Results and Discussion......Page 59
Introduction......Page 63
Results and Discussion......Page 65
Conclusions......Page 74
Literature Cited......Page 75
Introduction......Page 76
Experimental......Page 77
Results and Discussion......Page 78
Conclusions......Page 84
Literature Cited......Page 85
7 Cytrel® Tobacco Supplement—A New Dimension in Cigarette Design......Page 86
Abstract......Page 97
Literature Cited......Page 98
8 Characterization of Insoluble Cellulose Acetate Residues......Page 99
Fractionation Sequence......Page 100
Analytical Procedures......Page 102
Results and Discussion......Page 108
Conclusions......Page 115
Literature Cited......Page 117
Results and Discussion......Page 118
Literature Cited......Page 127
Experimental......Page 128
Results......Page 132
Discussion......Page 149
Hydroxyethylation......Page 152
Conclusions......Page 154
Part VI: Reaction Stoichiometry......Page 155
II . Discussion of the Probable Mechanisms of the Reaction Between Cellulose and α , β-Amie Acids......Page 158
Experimental......Page 162
Results of the Experiments......Page 166
Volatile Products......Page 188
Pad Bath Stability......Page 190
Conclusions......Page 191
List of References......Page 196
Courtaulds Involvement in Viscose......Page 198
Viloft Development Background......Page 200
What is an Inflated Viscose Fibre?......Page 202
Viloft Manufacture......Page 204
Fibre Properties......Page 206
Processing of Viloft......Page 208
Viloft in Fabrics......Page 209
Materials and Methods......Page 213
Results and Discussion......Page 214
Literature Cited......Page 217
14 A Process for Drying a Superabsorbent Pulp......Page 218
II. First Attempts......Page 219
IV. The drying process......Page 220
A. Flow-sheet......Page 226
B. Mass Balance......Page 228
VII. Other Products......Page 230
Literature Cited......Page 233
Woven Fabrics......Page 234
Non-Woven Fabrics......Page 239
16 Comparison of the Properties of Ultrasonically and Mechanically Beaten Fibers......Page 246
Literature Cited......Page 249
Comparison of Processes......Page 250
Prepolymer Preparation......Page 252
Fabric Treatment......Page 255
Literature Cited......Page 260
C......Page 262
D......Page 263
F......Page 264
Ν......Page 265
P......Page 266
S......Page 267
Ζ......Page 268

Citation preview

Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives Albin F. Turbak,

EDITOR

ITT Rayonier, Inc.

A symposium sponsored by the Cellulose, Paper, and Textile Division at the 173rd Meeting of the American Chemical Society, New Orleans, La., March 21-23,

1977

58

ACS SYMPOSIUM SERIES

AMERICAN

CHEMICAL

SOCIETY

WASHINGTON, D. C. 1977

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Library of CongressCIPData Solvent spun rayon, modified cellulose fibers and derivatives (ACS symposium series; 58) Includes bibliographical references and index. 1. Rayon—Congresses. I. Turbak, Albin F., 1929. II. American Chemical Society. Cellulose, Paper, and Textile Division. III. Series: American Chemical Society. ACS symposium series; 58. TS1688.A1S64 ISBN 0-8412-0388-1

677'.46 ACSMC8

77-12220 58 1-269 (1977)

Copyright © 1977 American Chemical Society All Rights Reserved. No part of this book may be reproduced or transmitted in any form or by any means—graphic, electronic, including photocopying, recording, taping, or information storage and retrieval systems—without written permission from the American Chemical Society. PRINTED IN THE UNITED STATES OF AMERICA

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

ACS Symposium Series Robert F. Gould, Editor

Advisory Board Donald G. Crosby Jeremiah P. Freeman E. Desmond Goddard Robert A. Hofstader John L. Margrave Nina I. McClelland John B. Pfeiffer Joseph V. Rodricks Alan C. Sartorelli Raymond B. Seymour Roy L. Whistler Aaron Wold

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

FOREWORD The ACS S Y M P O S I U M SERIES was founded in 1974

to provide

a medium for publishing symposia quickly in book form. The format of the SERIES parallels that of the continuing A D V A N C E S I N C H E M I S T R Y SERIES except that in order to save time the papers are not typeset but are reproduced as they are submitted by the authors in camera-ready form. As a further means of saving time, the papers are not edited or reviewed except by the symposium chairman, who becomes editor of the book. Papers published in the ACS S Y M P O S I U M SERIES are original contributions not published elsewhere in whole or major part and include reports of research as well as reviews since symposia may embrace both types of presentation.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

PREFACE "Research and development on new products or improved processes for converting natural based materials such as cellulose are now more important than ever, and shrewd managers are scheduling increasing efforts in the cellulose area. It is indeed ironic that the "miracle" synthetic fibers are operating at record losses while rayon and cotton are enjoying rising sales and improved market status. While this may be upsetting to those 'prophets of doom" who have repeatedly forecast the demise of rayon and cellulosic textiles, it comes as no surprise to wiser, more experienced textile people who cellulosic-based materials have to offer. This symposium, held at the New Orleans American Chemical Society Meeting by the Cellulose, Paper and Textile Division, attempts to highlight some of the current research underway in the following areas: • Solvent Spun Rayon. This is thefirsttime a symposium session was ever devoted solely to this topic, and it deals with diverse efforts to develop a totally recoverable and recyclable solvent spinning system to overcome viscose process deficiencies. • Cellulose Ethers and Esters. This section coversfirst-releaseinformation on Cytrel synthetic tobacco as well as added technology on cellulose acetate and amic acid esters. • Modified Cellulosics. This section includes details on the new Viloft hollow rayonfibers,lignin-modified rayon, microscopic techniques for nonwovens, drying of superabsorbent fibers, ultrasonic fiber treatment, and improved celluloseflameretardants. Undoubtedly, a great deal of additional effort is underway in these areas which will be reported at future meetings. It is hoped that this volume will complement and enhance such research. I would like to thank the various authors for their kind cooperation throughout this effort and also to thank their respective companies for encouraging and supporting participation by their personnel in this undertaking. ITT Rayonier, Inc. Whippany,N.J.07981 July 1977

ALBIN F. TURBAK

ix

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

1 Rayon—A Fiber with a Future H. L. HERGERT and G. C. DAUL ITT Rayonier, Inc., Eastern Research Div., Whippany, N.J. 07981

The title of this paper could perhaps more a p p r o p r i a t e l y be called "Rayons - the F i b e r S t r i k e s Back! The ter fibers w i t h a wide range o f p r o p e r t i e s . Depending on the manufacturing process used, rayon can be similar to silk, wool, c o t t o n o r even paper. I t can be weak and extremely water-absorbent or as strong as some of the strongest f i b e r s made, including s t e e l . I t can be produced as continuous f i l a m e n t o r as s t a p l e , cut in lengths o f a few m i l l i m e t e r s t o s e v e r a l centimeters, s t r a i g h t o r crimped, lustrous or dull, p r e c o l o r e d , resistant to-water, -flame, o r c a u s t i c soda, c r o s s l i n k e d o r chemically modified. Of most importance, rayon, like c o t t o n , is h y d r o p h i l i c , bio-degradable and d e r i v e d from the most abundant n a t u r a l polymer in the world cellulose. P e r u s a l o f the pages o f the major commercial chemical j o u r n a l s , such as the Chemical and Engineering News, Chemical Week and o t h e r s , during the past s e v e r a l years might lead t o the c o n c l u s i o n that the p u r e l y s y n t h e t i c man-made fibers are the only textile f i b e r s w i t h a significant f u t u r e . Several l a r g e oil companies w i t h a major stake in supplying petro-chemical intermediates, have tried t o f o s t e r that image by suggesting that s u p p l i e r s of wood p u l p , the b a s i c raw m a t e r i a l f o r v i s c o s e rayon, have insurmountable environmental problems and textile producers in the western world should focus t h e i r f u t u r e on p o l y e s t e r . This h a r d l y represents the f a c t s . Rayon is c u r r e n t l y a viable product and has an attractive f u t u r e , especially if sufficient research and development is committed t o r e d u c t i o n o f chemical and energy usage in the v i s c o s e process o r a new r e g e n e r a t i o n process can be p e r f e c t e d along the l i n e s t o be discussed in the subsequent papers. The production o f man-made fibers from c e l l u l o s e can be traced back to Audemar's d i s c o v e r y of nitrocellulose i n 1855, commercialized as f i l a m e n t s by deChardonnet(1) in 1 8 8 9 · Ralph Nader would have had a ball with this product! Because o f its f l a m m a b i l i t y , it had a p r e d i c t a b l e and unpleasant ending i n 1 9 4 0 , 3

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

4

SOLVENT SPUN RAYON, MODIFIED CELLULOSE FIBERS

w i t h the d e s t r u c t i o n by f i r e of the l a s t producing f a c t o r y i n Brazil. The development of cuprammonium rayon by D e s p a i s s i s ( 2 ) occurred i n time to step i n t o the gap and f l o u r i s h e d as a r t i f i ­ c i a l s i l k . I t s importance as a t e x t i l e f i b e r has g r a d u a l l y diminished u n t i l today i t represents a v e r y s m a l l amount of the t e x t i l e f i b e r s produced. The v i s c o s e p r o c e s s , d i s c o v e r e d by Cross, Bevan, and Beadle i n 1892,(2) was commercialized i n the e a r l y 1900's - f i r s t as continuous f i l a m e n t f o r t e x t i l e s , f o r t i r e yarn and i n d u s t r i a l uses and then i n the 1930 s f o r s t a p l e f i b e r . Rayon p r o d u c t i o n i n the United States peaked i n the 1950's and again i n the 196o's, but i n many cases, p r o f i t s from rayon were used to d i v e r s i f y i n t o s y n t h e t i c f i b e r s . As a r e s u l t , equipment was r e p a i r e d but seldom upgraded and R and D o growth markets have opene nonwovens. Older p l a n t s have been shut down and the s u r v i v i n g North American rayon i n d u s t r y has geared up to meet the t e x t i l e needs of tomorrow. In other p a r t s of the w o r l d , rayon p r o d u c t i o n has had almost steady growth. In R u s s i a f o r example, p r o d u c t i o n of c e l l u l o s i c f i b e r s increased 30$ d u r i n g I 9 7 I - I 9 7 5 , w i t h 6θ# of t h i s growth a t t r i b u t e d to new p l a n t s . Even l a r g e r i n c r e a s e s are p r o j e c t e d f o r the next f i v e - y e a r p l a n . New, more e f f i c i e n t rayon p l a n t s have been b u i l t i n Yugoslavia and Taiwan and other developing countries are s e r i o u s l y c o n s i d e r i n g the p r o d u c t i o n of rayon. Since the I93O's, many v e r s i o n s of rayon have been developed through changes i n the b a s i c v i s c o s e process u s i n g chemical m o d i f i e r s , such as the p o l y - g l y c o l s , amines, and formaldehyde. Other v e r s i o n s , which may or may not r e q u i r e m o d i f i e r s are the p o l y n o s i c s , which because of h i g h D.P. and unique s t r u c t u r e , most c l o s e l y resemble c o t t o n i n end-use p r o p e r t i e s . Some of the p r o p e r t i e s of the v a r i o u s rayons and other major t e x t i l e f i b e r s are shown i n Table I . I t i s seen t h a t many of the p r o p e r t i e s of the rayons o v e r l a p those of the other major t e x t i l e f i b e r s . In F i g u r e 1 t h i s i s f u r t h e r i l l u s t r a t e d by the s t r e s s s t r a i n p r o p e r t i e s of these f i b e r s . At t h i s p o i n t i n our p r e s e n t a t i o n , we had planned a t a b l e showing what might be considered the p r o p e r t i e s of an " i d e a l " rayon f i b e r . A f t e r t h i n k i n g t h i s over, the question kept popping up - i d e a l f o r what? A l i s t of d e s i r a b l e p r o p e r t i e s f o r a t e x ­ t i l e f i b e r might i n c l u d e : 1. Adequate t e n a c i t y (both c o n d i t i o n e d and wet). 2. S u f f i c i e n t l y h i g h wet modulus and r e s i l i e n c e to a f f o r d dimensional s t a b i l i t y i n f a b r i c s . 3. Toughness f o r r e s i s t a n c e to a b r a s i o n . k. Adequate crimp l e v e l to permit ease of p r o c e s s i n g and cover and l o f t i n f a b r i c s . 5 . H y d r o p h i l i c i t y f o r comfort. 6. Resistance to s u n l i g h t , common chemicals, and laundering. f

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

0.1-0.5 0.9-t.5 3-5 t-10

0.3-0.5 2.7-t.5 o.t

-

0.5-0.7 t.5-6.3 10-it 60-80

0.5-1.0 t.5-9.0 7-9 t5-55

10-it

60-70

Moisture Regain, $

Water R e t e n t i o n , $

30-90 t2-100

3.5-7.2 32-65 2.5-6.1 23-55

0.5-2.0 U.5-18

12-55 12-55

2.t-7-0 22-63 2.t-7-0 22-63

Nylon-6

10-12 12-15

3-0-t.5 27-tl 2.0-3.5 18-32

Polyester

7-9 8-10

1.8-3.2 16-29 1.6-3.2 it-29

HWM Rayon

8-10 10-it

3-5-5.0 32-t5 2.5-t.O 23-36

Cotton

Elongation, # Cond. Wet Wet T e n a c i t y a t 5$ E x t e n s i o n , g/d km

Tenacity Cond. g/d km Wet, g/d km

Polynosic Rayon

PHYSICAL PROPERTIES OF MAJOR TEXTILE FIBERS

TABLE I

90-110

10-it

0.1-0.3 0.9-2.7

15-30 20-ho

0.7-3.2 6-29 0.7-1.8 6-16

Regular Rayon

S

S

ρ

SOLVENT SPUN RAYON, MODIFIED CELLULOSE FIBERS

6 8 HT R A Y O N /

6 POLYNOSIC

'NYLON β "POLYESTER

/ HWM RAYON

R

/// f/ /

2

\\v

REGULAR RAYON

wr 2 0

3 0

4

0

Figure 1.

ELONGATION (%)

Fiber stress-strain curves (conditioned)

TABLE I I WORLD FIBER CONSUMPTION* 1972-U

Population ( m i l l

38I7

1985

Change U)

VT59

2k.6

Per C a p i t a l F i b e r Consumption (Kg) F i b e r Consumption (000 t o n s )

6.9 26,978

8Λ 1+0,230

21.7 U9.1

Man-made Rayon and a c e t a t e

3>56^

Non-cellulosic

7,676

k,l90

17.6

18,015

3^.7

15,695

21.0

1,632

5.1

698

-1.8

Natural Cotton

12,970

Wool

1,985

Other

711

* American Dyestuff R e p o r t e r , June, 1976

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

1.

HERGERT AND DAUL

7. 8. 9· 10.

7

RatfOU

Dyeability. Flame retardancy. U n i f o r m i t y and c l e a n l i n e s s of product, Price s t a b i l i t y .

Obviously, there can be no one f i b e r w i t h a l l these prope r t i e s and f o r the m a j o r i t y of end-uses, not a l l are needed. Therein l i e s the s t r e n g t h of the l a r g e f a m i l y of rayon f i b e r s which can be p r a c t i c a l l y tailor-made or engineered to s u i t spec i f i c end-uses. The t e x t i l e i n d u s t r y of today i s , of n e c e s s i t y a c c e p t i n g t h i s f a c t and i s u s i n g combinations of f i b e r s i n blends chosen to produce the f a b r i c s which are most a e s t h e t i c a l l y a p p e a l i n g , u s e f u l , s e r v i c e a b l e and p r o f i t a b l e . For a p p a r e l , blends of c e l l u l o s i c s and s y n t h e t i c s to provide both comfort and u t i l i t y ar of 50$ or more c e l l u l o s i n e c e s s i t y to prevent d i s c o m f o r t , s o i l e d c l o t h e s , and the embarrassment of wet spots on p l a s t i c seat covers. B u i l d i n g water absorbency i n t o p o l y e s t e r has been a longtime goal of t h i s f i b e r i n d u s t r y but has u s u a l l y been at the s a c r i f i c e of some of the important, d e s i r a b l e a t t r i b u t e s of t h i s f i b e r , and r e s u l t s i n i n c r e a s e d c o s t of p r o d u c t i o n . We b e l i e v e that the most i n t e l l i g e n t and economic approach to the t e x t i l e s of the f u t u r e i s to blend the s y n t h e t i c s w i t h c e l l u l o s e , to get the a p p r o p r i a t e balance of s t r e n g t h , easy c a r e , and moisture absorption. In the June, 1976, American Dyestuff Reporter, p r e d i c t i o n s of world f i b e r consumption r e l a t i v e to world p o p u l a t i o n growth through I985 were g i v e n . (Table I I ) . These f i g u r e s show an i n crease of 17· 6$ i n the p r o d u c t i o n of rayon and a c e t a t e . Rayon, of course, w i l l represent the l a r g e r p r o p o r t i o n of t h i s growth. We b e l i e v e these f i g u r e s are c o n s e r v a t i v e f o r man-made c e l l u l o s i c s r e l a t i v e to s y n t h e t i c s and t h a t the d i v i s i o n s could be more f a v o r a b l e to rayon and acetate provided c o s t - e f f e c t i v e improvements are made to the v i s c o s e process or an a l t e r n a t e lowc a p i t a l approach to forming regenerated c e l l u l o s i c f i b e r s i s found. The growth i n world p o p u l a t i o n w i l l o b v i o u s l y r e s u l t i n a demand f o r food production at the expense of c o t t o n , e s p e c i a l l y i n c o u n t r i e s such as I n d i a and P a k i s t a n , where there i s a burgeoning p o p u l a t i o n w i t h increased t e x t i l e and food needs. Rayon - I t s Problems Considering rayon as a f i b e r w i t h a f u t u r e , i t i s necessary to look at the current problems a s s o c i a t e d w i t h i t s manufacture. Simply put, i n t o d a y s economy and w i t h emphasis on energy cons e r v a t i o n and environmental p r o t e c t i o n , the main problems r e l a t e d to the production of f i b e r s by the v i s c o s e process a r e : 1. Undesirable a i r and water emissions, BOD, H S, z i n c . 1

2

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

SOLVENT SPUN RAYON, MODIFIED CELLULOSE FIBERS

8 2. 3. k. 5.

I n t e n s i v e c a p i t a l requirement. Large energy requirements. R e l a t i v e l y l a r g e l a b o r requirements i n most e x i s t i n g plants. Increasing cost of raw m a t e r i a l s .

Other problems r e l a t e d to the e f f e c t s of meeting environmental p r o t e c t i o n r e g u l a t i o n s can have adverse e f f e c t s on q u a l i t y and a v a i l a b i l i t y of raw m a t e r i a l s . Rayon - I t s

Opportunities

The above problems seem insurmountable, but problems are u s u a l l y followed by o p p o r t u n i t i e s , and such i s the case here. Major advances are bein cose rayon p l a n t s to reduc of z i n c by ion-exchange, c r y s t a l l i z a t i o n , or other techniques; use of more p u r i f i e d c e l l u l o s e s ; r e d u c t i o n of gaseous emissions by a b s o r p t i o n or scrubbing; more e f f i c i e n t f i b e r washing and d r y i n g techniques, and the l i k e . Large s c a l e p l a n t s can be designed t o produce f i b e r s f o r more s p e c i f i c , major end-uses and w i t h fewer product l i n e s which w i l l be more e f f i c i e n t i n use of l a b o r and capital. The major advantages possessed by regenerated c e l l u l o s e f i b e r production of today are: 1. A v a i l a b i l i t y of major raw m a t e r i a l s . a) C e l l u l o s e - n a t u r e s renewable polymer. b) CS - recoverable to the extent of 50$· c) S u l f u r i c a c i d and c a u s t i c soda normally i n l a r g e supply. 2. Non-dependence on o i l . 3. P r i c e s t a b i l i t y r e l a t i v e to c o t t o n . 1

2

These advantages have been recognized i n other c o u n t r i e s w i t h the USSR as a prime example. In the May i s s u e of Khimischeskie Volokna, Shimko(t) describes the t e c h n i c a l progress i n the c e l l u l o s i c f i b e r i n d u s t r y and p r o j e c t i o n s f o r the USSR's 10th f i v e year p l a n . He s t a t e s : "The production of c e l l u l o s i c f i b e r s i s planned to increase f u r t h e r i n the 1 0 t h f i v e - y e a r p l a n , the main reason being: the u s e f u l p r o p e r t i e s , e s p e c i a l l y the p h y s i o l o g i c a l ones, of those f i b e r s and the mass-market a r t i c l e s produced from them. An increase i n the output of c e l l u l o s i c f i b e r s w i l l not o n l y help to overcome the shortage of hygroscopic f i b e r s but w i l l a l s o r e s u l t i n a s u b s t a n t i a l savings of m a t e r i a l and labor r e sources. The f a c t that the USSR possesses a huge self-renewing source of the s t a r t i n g m a t e r i a l ( i . e . , wood) i s a f u r t h e r f a c t o r f a v o r i n g an increase i n the production of c e l l u l o s i c f i b e r s . " He f u r t h e r s t a t e s , "the p r i n c i p a l d i r e c t i o n s of t e c h n i c a l progress i n the production of v i s c o s e rayon s t a p l e f i b e r s are: the production of high-modulus and p o l y n o s i c f i b e r s and higher output

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

1.

HERGERT AND DAUL

RdtJOn

9

of b e t t e r q u a l i t y v i s c o s e rayon s t a p l e - high-modulus and polyn o s i c f i b e r s - l i k e c o t t o n , possess good s t r e n g t h and a h i g h modulus when wet. Their wet s t r e n g t h i s b e t t e r than t h a t of ( r e g u l a r ) rayon s t a p l e . Although the c o s t - e f f e c t i v e n e s s of the production of high-modulus f i b e r s i s not very f a v o r a b l e , t h e i r use i n the n a t i o n a l economy, i n place of c o t t o n , i s advantageous." In R u s s i a , as i n other c o u n t r i e s , aside from economics and raw m a t e r i a l a v a i l a b i l i t y , there i s a growing awareness that the comfort ( p h y s i o l o g i c a l ) f a c t o r s inherent i n c e l l u l o s i c f i b e r s are e s s e n t i a l i n blends w i t h the s y n t h e t i c s t o overcome t h i s major d e f i c i e n c y i n these f i b e r s . Even assuming o p p o r t u n i t i e s f o r f u r t h e r expansion of v i s c o s e rayon production i n the USSR and elsewhere, and f o r improving the economics of the v i s c o s e process, we, however, b e l i e v e that s i g n i f i c a n t f u t u r e expansio f i b e r s , w i l l result wit designed to overcome the d e f i c i e n c i e s mentioned b e f o r e . One approach to a new process i n v o l v e s the use of a recoverable and r e c y c l a b l e s o l v e n t (or combination of s o l v e n t s ) which w i l l d i s s o l v e c e l l u l o s e by a simple mixing step followed by ext r u s i o n of the s o l u t i o n to form a f i b e r . A closed-loop system, which would emit p r a c t i c a l l y nothing t o the atmosphere or water, would e l i m i n a t e p o l l u t i o n problems. Several leads i n t h i s d i r e c t i o n have been developed at our l a b o r a t o r i e s i n Whippany, New J e r s e y , and w i l l be described i n d e t a i l i n subsequent papers on t h i s program. However, much more needs to be done to reach the ultimate goals. I d e a l l y , such a process should i n v o l v e use of simple c e l l u l o s e s o l u t i o n s of higher concentrations than those p r e s e n t l y used ( 6 - 9 $ ) , use of low b o i l i n g s o l v e n t s to minimize energy r e q u i r e d for recovery, spinning at h i g h speeds s i m i l a r t o those used i n the acetate and s y n t h e t i c f i b e r i n d u s t r i e s , and p u r i f i c a t i o n without the use of excessive amounts of water f o r washing or l a r g e amounts of heat f o r d r y i n g . Such a p l a n t would, t h e r e f o r e , have most of those a t t r i b u t e s r e q u i r e d to overcome the present-day problems a s s o c i a t e d w i t h the rayon i n d u s t r y . This concept should present a r e a l challenge to c e l l u l o s e research f o r the coming years and the rewards would be enormous. Some of the r e q u i r e ments f o r an i d e a l c e l l u l o s e (rayon) f i b e r p r o d u c t i o n process are shown i n Table I I I . Other approaches a r e , of course, p o s s i b l e . One such i s that e n v i s i o n e d by the eminent polymer s c i e n t i s t , Dr. Herman F. Mark, who r e c e n t l y s a i d ( j j ) , "For the f u t u r e , continued research e f f o r t s w i l l be g r e a t l y i n f l u e n c e d by the f a c t that c e l l u l o s e i s the organic substance produced i n g r e a t e s t q u a n t i t y by nature - a r e newable resource that c o n t r a s t s sharply w i t h c o a l , o i l and gas, the reserves of which are being s e r i o u s l y diminished year-by-year. I t would indeed be a wonderful success s t o r y f o r human endeavor, i f , i n the f u t u r e , we can combine our present knowledge of the s t r u c t u r e and r e a c t i v i t y of c e l l u l o s e w i t h a b e t t e r understanding

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

SOLVENT SPUN RAYON, MODIFIED CELLULOSE FIBERS

TABLE I I I REQUIREMENTS FOR IDEAL RAYON FIBER PRODUCTION PROCESS

A.

Renewable/recoverable raw m a t e r i a l s .

B.

Low C a p i t a l and l a b o r c o s t s , low energy r e q u i r e ment.

C.

Minimal e f f e c t on environment.

D.

Simple solution-makin

E.

Dry and/or s o l v e n t s p i n n i n g .

F.

High c o n v e r s i o n r a t e o f spin-dope t o f i b e r high cellulose/solvent r a t i o ) .

G.

A b i l i t y t o produce a uniform product that w i l l r e q u i r e minimal h a n d l i n g from f i b e r t o end product.

(includes

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

1. HERGERT AND DAUL Rayon

11

of its biosynthesis, in order to produce the cellulose molecule directly from water and CO , with the aid of sunlight, at a rate 5 to 10 times greater than that which occurs in nature." Controlled growth of cellulose in hydroponic factories to produce fibers directly, could be the fulfillment of such a wish or alternately, a means to further extend the capabilities of the world's forest resources to furnish cellulose to produce rayon for the multitude of end-uses required by mankind. Whether it will be made by the viscose process, or spun from solvents, or by some yet to-be-discovered process, or by all three, remains to be seen. To paraphrase a popular automobile commercial — 2

"There Will Be A Rayon In Your Future" Abstract Modern textile blends continue to require the aesthetics and moisture-absorbing properties provided by cellulose in the native state (cotton) or in regenerated form (rayon). Escalating prices and problematical availability of some intermediates for purely synthetic textiles, coupled with gradual conversion of cotton­ -growing land to food production, suggest a careful re-examination of the future of rayon. Wood cellulose, caustic soda and carbon disulfide, the major raw materials for rayon production by the existing viscose process, are not dependent upon o i l and will continue to be available in ample supply. On the other hand, the viscose process is energy intensive and has emission problems. Significant expansion of the rayon industry w i l l , therefore, require development of a totally new process. The needs of such a process in terms of raw materials, type of spinning, investment costs and fiber properties will be detailed in this paper. Literature Cited 1. Chardonnet, H., French Pat. 165,349 (May 12, 1884). 2. Despaissis, L. H., French Pat. (1890). 3. Cross, et al, British Pat. 8700 (April 8, 1893). 4. I. G. Shimko Khimicheski Volokna, No. 3, pp 8-12, May-June 1976. 5. Mark, H. F., Celluloses - Past Present and Future, 50th Anniversary Lecture, Nov. 26, 1975, Dorval, Que. Can.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2 A Critical Review of Cellulose Solvent Systems A.F.TURBAK, R. B. HAMMER, R. E. DAVIES, andN.A.PORTNOY ITT Rayonier, Inc., Eastern Research Div., Whippany,N.J.07981

C e l l u l o s e is the most abundant renewable, organic raw material a v a i l a b l e in th ability, i t has still no areas of application. One o f the major reasons f o r t h i s is t h a t many end-use a p p l i c a t i o n s r e q u i r e t h a t c e l l u l o s e be in a different form from that found in nature. I n most of these applications, it is necessary first to dissolve cellulose in some manner and then t o re-form it from such s o l u t i o n s i n t o the d e s i r e d products. It is this very important d i s s o l v i n g step which has proved to be either cumbersome o r expensive compared t o alternate m a t e r i a l s which compete for market p o s i t i o n s . In many cases only c e l l u l o s e has the d e s i r a b l e p r o p e r t i e s r e q u i r e d f o r end product use and, in these i n s t a n c e s , the methods r e q u i r e d t o achieve cellulose s o l u t i o n present p o t e n t i a l hazards and pollution control problems. Thus, improved techniques f o r d i s s o l v i n g cellul o s e are u r g e n t l y needed if cellulose is to continue t o occupy a c o m p e t i t i v e market position. This is particularly t r u e o f the v i s c o s e i n d u s t r y where pollution control continues to p l a c e ever i n c r e a s i n g restraints on the process. Scientists have long recognized the need f o r more efficient cellulose s o l v e n t systems and hundreds of p u b l i c a t i o n s have been i s s u e d covering a wide range of approaches. S e v e r a l e x c e l l e n t review articles on s w e l l i n g and dissolving cellulose by Warwicker (1,2) Jayme ( 3 ) , Phillip ( 4 , 5 ) , P o l y o l a (6) and Brandrup (7) have been p u b l i s h e d and we shall not attempt simply t o resubmit t h e i r data. Rather, t h i s paper shall attempt t o consider the v a r i o u s processes from the commercial as well as the scientific viewpoint t o emphasize potential areas f o r c o n t r i b u t i o n which still e x i s t , particularly f o r systems capable of producing cellulosic fibers through the use of organic s o l v e n t s . Fundamentally, a l l o f the known methods f o r d i s s o l v i n g c e l l u l o s e can be summarized under f o u r main c a t e g o r i e s : A. C e l l u l o s e As A Base B. C e l l u l o s e As An A c i d C. C e l l u l o s e Complexes D. C e l l u l o s e D e r i v a t i v e s 12

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

TURBAK E T A L .

Cellulose Solvent Systems

13

While each of the above areas has r e c e i v e d e x t e n s i v e study and some have been commercialized, s e v e r a l of the approaches are r e a l l y not completely understood. S t i l l others i n v o l v e mixtures of many i n g r e d i e n t s and could never be v a l u a b l e i n d u s t r i a l l y . In t r y i n g to e x p l a i n why c e r t a i n m a t e r i a l s do i n f a c t d i s s o l v e c e l l u l o s e , s e v e r a l authors have s i m p l i s t i c a l l y i n d i c a t e d that what i s r e q u i r e d i s that the s o l u b i l i t y parameter of the s o l v e n t must be the same as t h a t of c e l l u l o s e . While such s t a t e ments are d i r e c t i o n a l l y c o r r e c t , they are incomplete and, perhaps, even a l i t t l e m i s l e a d i n g , s i n c e many s o l v e n t s having the proper s o l u b i l i t y parameter values w i l l not d i s s o l v e c e l l u l o s e . For example, DMF and DMSO both have s o l u b i l i t y parameters i n the range c a l c u l a t e d f o r c e l l u l o s e but n e i t h e r o f these d i s s o l v e c e l l u l o s e under any known c o n d i t i o n s The s o l u b i l i t y paramete (CED) values r e l a t e d i r e c t l which i s e a s i l y o b t a i n a b l e f o r many l i q u i d s , and w i l l apply d i r e c t l y t o the m i s c i b i H t y of l i q u i d s o r amorphous polymers where (&) values w i l l r e l a t e to simple heats of m i x i n g . When d e a l i n g w i t h polymers i n g e n e r a l , other f a c t o r s may be e q u a l l y as important, o r even more important than s i n g l e s o l u b i l i t y parameter v a l u e s . For example, w i t h c r y s t a l l i n e polymers, the heat o f f u s i o n or m e l t i n g energy, must a l s o be considered as an e n t i r e l y separate f a c t o r . Furthermore, superimposed on these f a c t o r s i s the hydrogen bonding c a p a b i l i t y of the polymer i n q u e s t i o n which may not be c o n s e q u e n t i a l f o r polymers such as c r y s t a l l i n e polypropylene, but which i s extremely important w i t h n a t u r a l polymers such as p r o t e i n s and c e l l u l o s e i n p a r t i c u l a r . These f a c t o r s , as w e l l as second order e f f e c t s were recognized many years ago by Spur l i n , B u r r e l l , and Barton and s e v e r a l exc e l l e n t reviews are a v a i l a b l e f o r f u r t h e r reference (8,9,10)· A combination of such f a c t o r s must be considered i n t r y i n g t o f i n d a s o l v e n t f o r c e l l u l o s e and help to g i v e guidance as t o c o n d i t i o n s as w e l l as compounds which must be employed i f usable c e l l u l o s e s o l u t i o n s are to be o b t a i n e d . Even i f a m a t e r i a l i s a s a t i s f a c t o r y s o l v e n t f o r c e l l u l o s e , i t i s necessary to emphasize two other important f a c t o r s which must be s e r i o u s l y evaluated f o r any p o t e n t i a l l y commercial c e l l u l o s e s o l v e n t system, these are "recovery" and " r e c y c l e " . The recovery and r e c y c l e f a c t o r s , perhaps more than any o t h e r s , are the most important ones which, i n the f i n a l a n a l y s i s , decide whether or not any p a r t i c u l a r approach w i l l be economically feasible. One f i n a l f a c t o r must a l s o be kept i n mind r e l a t i v e t o e v a l u a t i n g a l l o f the d a t a t h a t appear i n the l i t e r a t u r e r e garding c e l l u l o s e s o l v e n t s . S p e c i f i c a l l y i t must be emphasized t h a t v a s t d i f f e r e n c e s e x i s t between being able to coagulate o r

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

SOLVENT SPUN RAYON, MODIFIED CELLULOSE FIBERS

14

p r e c i p i t a t e a s o l i d mass, as compared to t r u l y spinning f i b e r s w i t h reasonable p h y s i c a l p r o p e r t i e s . Keeping these f a c t o r s i n mind, l e t us examine the f o u r c a t e g o r i e s l i s t e d above which encompass e s s e n t i a l l y a l l of the c e l l u l o s e s o l v e n t systems reported i n the l i t e r a t u r e . A.

C e l l u l o s e As A Base

A l l a l c o h o l s , whether polymeric or not, can be f o r c e d t o act as acids or bases r e l a t i v e to other reagents, depending upon the s t r e n g t h of the reagent employed. Thus, c e l l u l o s e w i l l act as a base and become protonated by p r o t o n i c a c i d s or w i l l act as a "Lewis" base and supply e l e c t r o n s from i t s oxygens t o e l e c t r o n r e c e p t i v e centers on "Lewis" a c i d s 1. P r o t o n i c Acid a b i l i t y of 78% phosphoric a c i d , 68% n i t r i c a c i d , 42% h y d r o c h l o r i c a c i d or 70% s u l f u r i c a c i d to d i s s o l v e c e l l u l o s e r a p i d l y at room temperature i s w e l l known. While the l i t e r a t u r e i s f u l l of r e p o r t s i n which the r e s u l t i n g s o l u t i o n s are r e f e r r e d to as hyd r a t e s " , they can a l s o be regarded as protonated hydroxyIs where the s p e c i f i c reagent concentrations employed were the ones needed to provide s u f f i c i e n t a c i d s t r e n g t h to protonate the c e l l u l o s e so that the r e s u l t i n g p o s i t i v e l y changed ROHj c e l l u l o s e moiety i s able to d i s s o l v e i n the excess reagent. I n these cases, recovery and r e c y c l e of the concentrated a c i d s i s the l i m i t i n g f a c t o r , economically. For example, e x c e l l e n t c e l l u l o s e s o l u t i o n s can be r a p i d l y prepared a t room temperature using phosphoric a c i d . However, no one has yet suggested a f e a s i b l e approach to c a s t i n g the c e l l u l o s e and recovering the phosphoric a c i d without n e u t r a l i z a t i o n . In our l a b o r a t o r y , we have t r i e d to p r e c i p i t a t e such phosphoric a c i d s o l u t i o n s i n t o g l a c i a l a c e t i c a c i d i n the a n t i c i p a t i o n that the a c e t i c a c i d could be v o l a t i l i z e d , recovered and r e c y c l e d , along w i t h the r e l e a s e d pure phosphoric a c i d . The i n i t i a l r e s u l t s were not too s u c c e s s f u l s i n c e the p r e c i p i t a t i o n was too slow to be u s e f u l under the p a r t i c u l a r c o n d i t i o n s emp l o y e d . However, the concept of using a weaker, v o l a t i l e a c i d i c m a t e r i a l to coagulate strong a c i d c e l l u l o s e s o l u t i o n s does r e present a n o v e l approach to developing a t o t a l r e c y c l a b l e c e l l u l o s e s o l v e n t system. lf

2. Lewis Acids ( z i n c c h l o r i d e , thiocyanates. iodides» b r o ~ mides). The a b i l i t y of c e r t a i n s a l t s o l u t i o n s to s w e l l and d i s s o l v e c e l l u l o s e i s a l s o reported (11). At the high concentrat i o n s normally necessary to achieve s o l u t i o n , these s a l t s not only provide necessary a c i d f u n c t i o n a l i t y but a l s o s i g n i f i c a n t l y a l t e r the i o n i c nature of the aqueous mediums so as to f u r t h e r a s s i s t d i s s o l u t i o n . The need f o r having a c i d s a l t s i s demonstrated i n the case of thiocyanates where the sodium, potassium and ammonium thiocyanates do not d i s s o l v e c e l l u l o s e w h i l e the calcium and

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

TURBAK E T A L .

Cellulose Solvent Systems

15

s t r o n t i u m s a l t s do g i v e c e l l u l o s e s o l u t i o n s up to about the 400 D.P. l e v e l i n d i c a t i n g t h a t i t i s the t h i o c y a n i c a c i d formed i n s o l u t i o n which i s a c t u a l l y i n v o l v e d i n the d i s s o l v i n g a c t i o n . B.

C e l l u l o s e As An A c i d

Perhaps more work has been undertaken on s w e l l i n g c e l l u l o s e w i t h bases than w i t h any other c l a s s of chemical compounds. The hydrogen atoms on the hydroxyIs of c e l l u l o s e , l i k e most a l c o h o l s , have a degree o f a c i d c h a r a c t e r and t h e r e f o r e r e a d i l y i n t e r a c t w i t h reasonably strong i n o r g a n i c and organic bases. 1. Inorganic Bases (sodium z i n c a t e , hydrazine, i n o r g a n i c hydroxides). I t shoul c e n t r a t i o n of base neede ulose by osmotic a c t i o n i s not the same c o n c e n t r a t i o n that i s r e q u i r e d to e f f e c t a c t u a l compound formation. Thus w h i l e 8-10% NaOH e x h i b i t s the maximum s w e l l i n g o f c e l l u l o s e f i b e r s , concent r a t i o n s of about 18% NaOH are a c t u a l l y r e q u i r e d t o form sodium c e l l u l o s a t e s t r u c t u r e s . Other i n o r g a n i c bases l i k e potassium and l i t h i u m hydroxide have a l s o been used s i m i l a r l y f o r t h e i r s w e l l i n g a c t i o n . Various a d d i t i v e s t o the c a u s t i c soda, such as z i n c oxide, have been used to make sodium z i n c a t e s o l u t i o n s which enhance the a c t i o n of c a u s t i c so higher D.P. m a t e r i a l s can be d i s s o l v e d . The temperatures o f these aqueous bases p l a y a f u r t h e r dominant r o l e i n the s w e l l i n g and d i s s o l v i n g phenomenon; w i t h the c o l d e r c o n d i t i o n s g i v i n g more s w e l l i n g and d i s s o l u t i o n . While a c o n s i d e r a b l e amount o f e f f o r t has been devoted t o aqueous a l k a l i systems, they normally do not d i s p l a y s u f f i c i e n t d i s s o l v ing power to completely overcome the c r y s t a l and hydrogen bonding energies of c e l l u l o s e t o g i v e acceptable s o l u t i o n s of h i g h e r D.P. m a t e r i a l s of i n t e r e s t f o r d i r e c t commercial conversion. I n a d d i t i o n , these aqueous a l k a l i n e systems present s e v e r a l r e covery and r e c y c l e problems. The use of the i n o r g a n i c base, h y d r a z i n e , f o r s w e l l i n g c e l l ulose was considered by Hess and Trogus many years ago.(12) However, they were never able to o b t a i n c e l l u l o s e s o l u t i o n s under the c o n d i t i o n s they employed. More r e c e n t l y , L i t t (13) has r e ported c o n d i t i o n s under which he has been able t o o b t a i n comp l e t e s o l u t i o n s of high D.P. c e l l u l o s e i n hot (150°-200°C) hydrazine and 207-345 kPa (30-50 p s i ) p r e s s u r e . These r e s u l t s serve to demonstrate t h a t s e v e r a l f a c t o r s are important f o r a s w e l l i n g reagent t o become a s o l v e n t . The o r i g i n a l i n v e s t i g a t i o n s i n 1931 by Hess employed hydrazine hydrate but d i d not employ the more extreme c o n d i t i o n s of heat and temperature r e c e n t l y employed by L i t t i n 1976 t o o b t a i n s o l u t i o n s . L i t t was able to get s o l u t i o n s of c e l l u l o s e u s i n g e i t h e r pure hydrazine or hydrazine hydrate p r o v i d i n g he employed elevated temperatures and p r e s s u r e s . I t was noted p r e v i o u s l y that c r y s t a l l i n e f o r c e s

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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SOLVENT SPUN RAYON, MODIFIED CELLULOSE FD3ERS

and hydrogen bonding could be important f a c t o r s and t h i s case c l e a r l y demonstrates t h a t even a m a t e r i a l having the proper s o l u b i l i t y parameter had t o be employed under f o r c i n g c o n d i t i o n s t o overcome these f a c t o r s t o achieve s o l u t i o n . I t has y e t t o be demonstrated, however, i f t e x t i l e q u a l i t y yarns o r packaging q u a l i t y f i l m s can be prepared from such hydrazine s o l u t i o n s . C e r t a i n l y , t o our knowledge no data along these l i n e s have y e t been p u b l i s h e d . 2. Organic Bases ( T r i t o n - q u a t e r n a r y h y d r o x i d e s , amines, DMSO/CH^NH?, amine o x i d e s ) . The a b i l i t y of c e l l u l o s e t o a c t as an a c i d towards v a r i o u s o r g a n i c bases has a l s o been e v a l u a t e d . Perhaps the b e s t known organic bases a r e the v a r i o u s " T r i t o n " bases which are quaternar vent of t h i s s e r i e s i d r o x i d e . I t i s i n t e r e s t i n g again t o note here t h a t the b e n z y l grouping i s f a r more e f f e c t i v e than other groups such as m e t h y l , e t h y l o r p r o p y l and t h i s Improvement has been a t t r i b u t e d t o the f a c t t h a t the b u l k i e r b e n z y l group behaves l i k e a "wedge" t o e f f e c t i v e l y separate the c e l l u l o s e chains once i t has entered the c r y s t a l l i n e region. A c o n s i d e r a b l e amount of work has a l s o been r e p o r t e d by S e g a l and others (14) r e l a t i v e t o the use of v a r i o u s amines and diamines f o r s w e l l i n g c e l l u l o s e . None o f these systems were claimed t o cause s u f f i c i e n t s w e l l i n g t o g i v e c e l l u l o s e s o l u t i o n s . More r e c e n t l y , P h i l l i p and h i s co-workers (15,16) have r e p o r t e d t h a t 16.5% methylamine i n DMSO gave b e t t e r c e l l u l o s e s o l u t i o n s than any other amine o r any other c o n c e n t r a t i o n o f methylamine used. The c e l l u l o s e i s claimed t o d i s s o l v e by r e a c t i o n w i t h an equimolar complex of CH3NH2/DMSO and 80% of the i n t r o d u c e d c e l l u l o s e d i s s o l v e d under c o l d anhydrous c o n d i t i o n s . As exc i t i n g as t h i s seems a t f i r s t g l a n c e , d i s s o l u t i o n of only 80% of the c e l l u l o s e may not be o f v a l u e f o r commercial c o n s i d e r a t i o n . Unless the d i s s o l u t i o n of c e l l u l o s e i s a c t u a l l y b e t t e r than 99%, the system would c e r t a i n l y be too expensive t o use r e l a t i v e t o y i e l d and f i l t r a t i o n c o s t s . The s p e c i f i c i t y of CH3NH2 and i n p a r t i c u l a r the 16.5% c o n c e n t r a t i o n i s i n t r i g u i n g and deserves more study. Perhaps, t h i s system might more p r o p e r l y belong under c o n s i d e r a t i o n as an organic complex r a t h e r than as a pure base system, but more data are needed t o f i r m l y decide the exa^t nature of t h e r e a c t i o n . One other organic base system which d i s s o l v e s c e l l u l o s e as an a c i d i n v o l v e s compounds not normally considered as bases, b u t which i n f a c t , are v e r y good "Lewis" bases. I n 1939, Graenacher and Sallman (17) reported t h a t a l i p h a t i c and c y c l o a l i p h a t i c amine oxides such as t r i e t h y l a m i n e oxide o r c y c l o h e x y l d i m e t h y l amine o x i d e gave 7-10% s o l u t i o n s of c e l l u l o s e a t 50-90°C. More r e c e n t l y , Johnson (18) has r e p o r t e d t h a t a l i c y c l i c amine oxides such as N-methylmorpholine oxide g i v e up t o 6% s o l u t i o n s o f c e l l u l o s e a t 110°C. These m a t e r i a l s are most i n t e r e s t i n g and could

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o f f e r commercial p o s s i b i l i t i e s i f adequate recovery and r e c y c l e procedures c o u l d be e s t a b l i s h e d . To our knowledge, no one has yet p u b l i s h e d any a c t u a l f i b e r o r f i l m d a t a on products d e r i v e d from such systems. Thus, a wide range of i n o r g a n i c and organic bases have been examined f o r d i s s o l v i n g and s w e l l i n g c e l l u l o s e . S e v e r a l systems have achieved a s u f f i c i e n t l y good balance of p r o p e r t i e s t o pro­ v i d e good c e l l u l o s e s o l u t i o n s and i t i s expected t h a t f u r t h e r e f f o r t s w i l l be forthcoming t o achieve a c c e p t a b l e r e c o v e r y / r e c y c l e and p h y s i c a l p r o p e r t i e s which could l e a d t o i n d u s t r i a l acceptance. C.

C e l l u l o s e Complexes

1. I n o r g a n i c Complexe ium). The use of v a r i o u coppe complexe l o s e i s w e l l known. More r e c e n t l y , complexes of cadmium and i r o n have been added t o the l i s t t o reduce the s e n s i t i v i t y of such c e l l u l o s e s o l u t i o n s t o degradation by exposure t o a i r . T h i s work i s reviewed r a t h e r completely by Jayme (3) who, w i t h h i s c o ­ workers, has c o n t r i b u t e d e x t e n s i v e l y t o t h i s a r e a . I n o r g a n i c m e t a l l i c complexes such as cuprammonium have met w i t h o n l y minimal commercial success f o r p r o d u c t i o n f i b e r s and f i l m s f o r two reasons. F i r s t , complete recovery of m e t a l l i c e f f ­ l u e n t contaminants i s d i f f i c u l t a t the extremely low ppm l e v e l s needed t o meet p o l l u t i o n requirements and secondly the o v e r a l l economics and f i b e r p r o p e r t i e s (of the cuprammonium p r o c e s s , a t l e a s t ) were not as good as those of the v i s c o s e p r o c e s s . The second f a c t o r would today be l e s s important than the recovery and p o l l u t i o n aspect and, u n t i l t h i s aspect i s s o l v e d , metal i n o r ­ ganic complexes w i l l continue t o have l i m i t e d u t i l i t y f o r f i l m and f i b e r p r o d u c t i o n . 2 . Organic Complexes (DMSO/CH3NH2, (KOCH2CHOHCH9S) 2. The p o s s i b l e use o f organic complexes t o d i s s o l v e c e l l u l o s e appears to be extremely l i m i t e d . Of a l l the systems r e p o r t e d , o n l y two seem to q u a l i f y as organic complexes. The f i r s t of these uses DMSO/16.5% CH3NH2 and was p r e v i o u s l y d i s c u s s e d under category Β (above) s i n c e i t s a c t i o n may be r e l a t e d more t o i t s b a s i c nature than t o a t r u e complex f o r m a t i o n . The second system was r e p o r t e d by P e t r o v i n 1965 (19) who c l a i m s t h a t c e l l u l o s e d i s s o l v e s d i r e c t l y a t 110°C i n a n e u t r a l s o l v e n t - b i s (φ-Y dihydroxypropyl) d i s u l f i d e - prepared by o x i d a t i o n of t h i o g l y c e r o l . T h i s s o l v e n t works w e l l f o r d i s ­ s o l v i n g cellophane f i l m s a t 300-600 D.P., but i s not good f o r d i r e c t l y d i s s o l v i n g h i g h e r D.P. c o t t o n l i n t e r s o r r e g u l a r p u r i ­ f i e d wood p u l p s . I n any case, i t i s i n t r i g u i n g t o f i n d a n e u t r a l s o l v e n t t h a t appears to be capable o f d i r e c t l y d i s s o l v i n g reason­ ably h i g h D.P. c e l l u l o s e and f u r t h e r work should be undertaken t o a s c e r t a i n why t h i s p a r t i c u l a r s t r u c t u r e seems t o be e f f e c t i v e .

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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D.

Cellulose Derivatives

1. S t a b l e D e r i v a t i v e s ( e s t e r s , e t h e r s ) , A wide v a r i e t y of s t a b l e c e l l u l o s e d e r i v a t i v e s are known and used commercially. The e s t e r s and e t h e r s have found scores of commercial uses but only the acetate and n i t r a t e have ever been u t i l i z e d f o r producing regenerated c e l l u l o s e products; the acetate t o g i v e F o r t i s a n and the n i t r a t e t o make regenerated t u b u l a r c e l l u l o s e f i l m s . 2,

Unstable D e r i v a t i v e s , a.

Sulfur

(xanthates, SC^/amines - s u l f i t e s )

b.

Nitrogen

(DMF/N2O4 DMSO/N

c.

Carbon

(carbonates, formates, DMSO/(CH 0)x me thy l o i ) 2

Unstable c e l l u l o s e d e r i v a t i v e s have been and are being a c t i v e l y i n v e s t i g a t e d i n depth f o r use i n p r e p a r i n g regenerated f i b e r s and f i l m s . This paper w i l l c o n s i d e r such " t r a n s i e n t " d e r i v a t i v e s under three main headings: a) s u l f u r - b) n i t r o g e n and c) carbon-containing i n t e r m e d i a t e s . a) S u l f u r Intermediates: The use of CS to form xanthates some 90 years ago s t i l l forms the backbone of the present day rayon i n d u s t r y . Improved processes are u r g e n t l y needed which can not only overcome the v a r i o u s p o l l u t i o n problems a s s o c i a t e d w i t h the v i s c o s e process, but which might a l s o h o p e f u l l y lower both the i n i t i a l c a p i t a l investment and subsequent o p e r a t i n g c o s t s a s s o c i a t e d w i t h present day rayon p l a n t s . One attempt along these l i n e s i s reported by Kimura et a l (20) who used a m o d i f i e d organic type system f o r x a n t h a t i o n . They used DMSO/CS2/amine to d i s s o l v e c e l l u l o s e and reported f i b e r s having c o n d i t i o n e d and wet t e n a c i t y / e l o n g a t i o n of 3.0 g/d/14% and 1.8 g/d/25% r e s p e c t i v e l y . T h e i r c o a g u l a t i o n and r e g e n e r a t i o n steps d i d not i n v o l v e the use of a c i d s and thus would s i g n i f i c a n t l y reduce part of the p o l l u t i o n l o a d normally a s s o c i ated w i t h rayon p r o d u c t i o n . However, i n i t i a l l a b o r a t o r y attempts to reproduce the r e p o r t e d process gave r i s e to an extremely noxious odor and t h i s could represent s u f f i c i e n t detriment t o o f f s e t other p o s s i b l e advantages. As another p o s s i b l e approach to d i s s o l v i n g c e l l u l o s e , seve r a l i n v e s t i g a t o r s have s t u d i e d the use of S02/amine s o l v e n t s y s tems. E x t e n s i v e work i n t h i s area i s reported by P h i l l i p and h i s coworkers (21) by Yanazaki and Nakao (22) and by Hata and Yokota (23-29). T h e i r e f f o r t s covered a wide range of amines and organic s o l v e n t d i l u e n t s which were both p o l a r and non-polar. 2

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While i n i t i a l l y i t was thought t h a t some type of complex was being formed w i t h the c e l l u l o s e , i t i s now reasonably establ i s h e d that t h i s treatment r e s u l t s i n the formation of amine s a l t s of the r a t h e r unstable c e l l u l o s e s u l f i t e e s t e r . Again f i l a m e n t s r e p o r t e d l y were spun, but no f i b e r p h y s i c a l p r o p e r t i e s were r e p o r t e d . The use of s u l f i t e e s t e r s f o r p r e p a r i n g rayon i n preference t o the v i s c o s e system would c r i t i c a l l y depend on good recovery of a l l s t a r t i n g m a t e r i a l s , and t h i s may be an area worthy of both chemical and engineering e f f o r t . b) Nitrogenous Intermediates: The use o f u n s t a b l e n i t r o genous i n t e r m e d i a t e s f o r a c h i e v i n g c e l l u l o s e s o l u t i o n i n organic s o l v e n t s i s concentrated mainly i n the area of systems i n v o l v i n g n i t r o g e n oxides. I n i t i a l l c e l l u l o s e t o the 6-carbox Kenyon, Y a c k e l , Unruh, Fowler, and McGee i n the 40 s stands as a milestone i n t h i s a r e a . (30-34) More r e c e n t l y , Pavlyuchenko and Ermolenko and coworkers have presented f u r t h e r d e t a i l e d s t u d i e s on the use of N2O4 f o r c e l l u l o s e o x i d a t i o n . (35-39) I n 1947, Fowler e t a l (34) reported t h a t v a r i o u s s o l v e n t s , when used i n c o n j u n c t i o n w i t h N2O4, gave d i f f e r e n t responses t o the a c t i o n of t h i s reagent on c e l l u l o s e and found t h a t many s o l v e n t s a c t u a l l y gave r i s e to s o l u t i o n s o f c e l l u l o s e without h i g h degrees o f o x i d a t i o n o c c u r r i n g . They used over 40 d i f f e r e n t s o l v e n t s where the N2O4 t o s o l v e n t r a t i o s were a t l e a s t 1/1 or h i g h e r and f i n a l l y concluded that the amount of o x i d a t i o n v s . c e l l u l o s e s o l u t i o n was r e l a t e d t o the p o l a r i t y of the s o l v e n t employed. With non-polar s o l v e n t s such as CCI4 e t c . the N2O4 produced mostly o x i d a t i o n w h i l e the more p o l a r s o l v e n t s gave r i s e t o c e l l ulose s o l u t i o n s w i t h g r e a t l y diminished o x i d a t i o n . I f no s o l vents were employed and l a r g e excesses of c o l d l i q u i d N2O4/N2O3 mixtures were used, then c e l l u l o s e d i s s o l v e d w i t h v e r y l i t t l e o x i d a t i o n and could be recovered from such s o l u t i o n s e s s e n t i a l l y c h e m i c a l l y unchanged except f o r a D.P. l o s s . T h i s was f i r s t r e ported by H i a t t and Crane i n 1949 (40) and subsequently s t u d i e d i n great d e t a i l by Chu i n 1970.(41) F o l l o w i n g these c l a s s i c d i s c l o s u r e s by Fowler, other r e searchers began t o examine even more p o l a r s o l v e n t s f o r use w i t h N2O4. Thus, W i l l i a m s (42) s t u d i e d the use o f DMSO/N2O4 as a s o l v e n t system f o r c e l l u l o s e . I t was l a t e r demonstrated r a t h e r c l e a r l y by Hergert and Z o p o l i s (43) t h a t the DMSO/N2O4 system would d i s s o l v e c e l l u l o s e more e f f e c t i v e l y i f t h e r e was a s m a l l amount of water present t o keep the c e l l u l o s e s t r u c t u r e open f o r r e a c t i o n . S u r p r i s i n g l y very l i t t l e more work has been done w i t h the DMSO/N2O4 system up t o the present time. Subsequently, Nakao obtained patent coverage on the use of DMF/N2O4 mixtures t o d i s s o l v e c e l l u l o s e (44,45) and on the a d d i t i o n s o f a wide range o f other polymers i n DMF t o such c e l l u l o s e s o l u t i o n s to produce s p e c i a l types of products. Mahomed (46)

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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S O L V E N T S P U N R A Y O N , MODIFIED C E L L U L O S E FIBERS

d e s c r i b e s the use of cellulose/DMF/N2O4 s o l u t i o n s as c o a t i n g m a t e r i a l s f o r g l a s s f i b e r s t o improve product performance. During t h i s p e r i o d s e v e r a l other workers began to appreciate that very p o l a r s o l v e n t s gave c e l l u l o s e s o l u t i o n s from which c e l l u l o s e could be recovered i n an e s s e n t i a l l y unchanged s t a t e r a t h e r than i n the h i g h l y o x i d i z e d s t a t e p r e v i o u s l y a s s o c i a t e d w i t h N2O4 treatments. A c o n s i d e r a b l e amount of research was p u b l i s h e d t r y i n g to d e f i n e what was o c c u r r i n g when the N2O4 was used w i t h the p o l a r s o l v e n t s . Clermont and Bender and t h e i r a s s o c i a t e s r e p o r t e d s t u d i e s where c e l l u l o s e was d i s s o l v e d i n both c o l d and hot s o l u t i o n s w i t h N2O4/DMF mixtures. (47-49) They found t h a t e s s e n t i a l l y unchanged c e l l u l o s e w i t h no added n i t r o g e n or c a r b o x y l l e v e l s was obtained from c o l d d i s s o l u t i o n , w h i l e waters o l u b l e c e l l u l o s e r e s u l t e d from i n c r e a s e d d i s s o l v i n g temperatures apparently due to the formatio t r a t e s . They subsequentl s o l v e l i g n o c e l l u l o s e removed from wood chips.(50) In a s e r i e s of a r t i c l e s d a t i n g from 1969-1976, Schweiger ha§ been r e p o r t i n g s t u d i e s aimed at t r y i n g to e l u c i d a t e what was happening i n the DMF/N2O4 treatment of c e l l u l o s e and t r i e d to use such s o l u t i o n s f o r forming other d e r i v a t i v e s . (51-56) He was a b l e to i s o l a t e a product from a p y r i d i n e - m o d i f i e d dope which appeared to be an u n s t a b l e c e l l u l o s e n i t r i t e i n t e r m e d i a t e s i n c e i t could produce a l k y l n i t r i t e s when decomposed by lower m o l e c u l a r weight a l c o h o l s . While t h i s i s not a d i r e c t s t r u c t u r a l proof i t c e r t a i n l y i s s u f f i c i e n t t o s u b s t a n t i a t e h i s proposal t h a t c e l l u l o s e r e a c t s w i t h N2O4 to g i v e c e l l u l o s e n i t r i t e and HNO3 r a t h e r than forming some type of N 2 O 4 / c e l l u l o s e a s s o c i a t i o n complex. The c e l l u l o s e n i t r i t e i s subsequently r a p i d l y decom­ posed by p r o t o n i c s o l v e n t s to regenerate the c e l l u l o s e and g i v e HNO2 along w i t h HNO3 f o r recovery and r e c y c l e . The s t r u c t u r e and r e a c t i o n s of N2O4 i n general have been reviewed by Gray (52) w h i l e the r e a c t i o n s of N 0^ to n i t r a t e and n i t r o s a t e a l c o h o l s and amines are reported by White and Feldman. (58) Pasteka and M i s l o v i c o v a s t u d i e d the e f f e c t s of v a r i o u s d i s ­ s o l v i n g c o n d i t i o n s on the D.P. l o s s of c e l l u l o s e i n the DMF/N2O4 system. (59-61) They noted that the moisture content of the system and even the r a t e of s t i r r i n g caused a drop i n D.P. and t h a t the presence of p y r i d i n e or (ΰ2Η5)βΝ d i d not i n h i b i t such l o s s . W h i l e moisture may w e l l r e l a t e to D.P. l o s s , i t i s d i f ­ f i c u l t to understand how s t i r r i n g r a t e could have such an e f f e c t unless i t was r e f l e c t i n g l o c a l temperature r i s e s t h a t occurred under the c o n d i t i o n s employed f o r s t i r r i n g . I n any case, these i n v e s t i g a t o r s again confirmed no i n c r e a s e i n e i t h e r n i t r o g e n or c a r b o x y l content f o r the regenerated c e l l u l o s e . The N2O4 system has a l s o been i n v e s t i g a t e d by s e v e r a l Russians (62-64) who a c t u a l l y r e p o r t p h y s i c a l p r o p e r t i e s f o r f i b e r s spun from DMF/N2O4 and EtOAc/^O^ systems. These f i b e r s are about 120 d e n i e r and have t e n a c i t i e s of 1.6 g/d w i t h 5-6% 2

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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21

e l o n g a t i o n s . Obviously more d e f i n i t i o n of the ^ O ^ o r g a n i c s o l vent system i s needed t o determine i t s p o t e n t i a l as a s o l v e n t based rayon process to s u b s t i t u t e f o r v i s c o s e and t h i s work w i l l be r e p o r t e d l a t e r i n t h i s symposium. f

c. Carbon Intermediates: The use of non-hetero atom-cont a i n i n g m o i e t i e s to make c e l l u l o s e i n t e r m e d i a t e s o f t r a n s i e n t s t a b i l i t y has r e c e i v e d r e l a t i v e l y l i t t l e a t t e n t i o n i n s p i t e of the f a c t that such d e r i v a t i v e s might u l t i m a t e l y o f f e r the b e s t prospects f o r n o n - p o l l u t i n g systems. C e l l u l o s e carbonate has been prepared and r e p o r t e d . However, i t e v i d e n t l y i s so uns t a b l e as to have e s s e n t i a l l y no u t i l i t y as an i n t e r m e d i a t e . A l s o , as prepared from phosgene, i t would f a c e other i n d u s t r i a l problems. C e l l u l o s e formate being r a p i d l y prepared y l o s e . The cleavage of c e l l u l o s e formate by hot steam a l s o r e presents an i n t e r e s t i n g approach f o r "dry s p i n n i n g " t h i s d e r i v a t i v e . While f o r m i c a c i d would not be considered a " m a t e r i a l o f c h o i c e " under most circumstances f o r i n d u s t r i a l use, i t i s c e r t a i n l y no worse than "hydrazine" i n most s a f e t y and h e a l t h cons i d e r a t i o n s and t h i s approach, o r one s i m i l a r t o i t , w i l l undoubtedly see f u r t h e r e f f o r t i n the f u t u r e . R e c e n t l y , N i c h o l s o n and D.C. Johnson reported on t h e i r work on d i s s o l v i n g c e l l u l o s e i n mixtures o f DMSO w i t h paraformaldehyde. (65) I n i t i a l i n d i c a t i o n s are that a c e l l u l o s e m e t h y l o l compound i s formed which i s s t a b l e under the e l e v a t e d temperatures of s o l u t i o n p r e p a r a t i o n and i s subsequently s t a b l e f o r days under storage i n open a i r at room temperature. The extreme s p e c i f i c i t y of t h i s combination of reagents i s p a r t i c u l a r l y n o t a b l e . For example, Seymour and E.L. Johnson (66,67) noted t h a t n e i t h e r DMF, DMAc, acetone, HMPA, nitromethane, a c r y l o n i t r i l e , a c e t o n i t r i l e , nor s u l f o l a n e can be s u b s t i t u t e d f o r the DMSO. Thus DMSO and o n l y DMSO has been found to be e f f e c t i v e t o date f o r a c h i e v i n g c e l l u l o s e s o l u t i o n s w i t h formaldehyde. This extreme s p e c i f i c i t y may w e l l r e l a t e i n some way t o the f a c t t h a t DMSO i t s e l f breaks down i n t o DMS and paraformaldehyde on h e a t i n g (68) or may poss i b l y be i n t e r a c t i n g t o s t a b i l i z e the proposed c e l l u l o s e m e t h y l o l i n t e r m e d i a t e whereas no other reagent i s e v i d e n t l y a b l e t o do so. I t should be f u r t h e r noted that w h i l e o n l y one mole of paraformaldehyde i s r e q u i r e d to h o l d one mole of the c e l l u l o s e i n s o l u t i o n , l a r g e molar excesses of 5/1 (CH20)x/cellulose must be employed i n i t i a l l y f o r d i s s o l u t i o n to occur. Thus t h i s system which appears t o i n i t i a l l y o f f e r an easy route t o c e l l u l o s e s o l u t i o n s , may o f f e r c o n s i d e r a b l e d i f f i c u l t y commercially from the aspects o f s p i n n i n g , recovery and r e c y c l e . F u r t h e r data from t h i s work are to be presented l a t e r i n t h i s symposium.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

22

S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E

FIBERS

Throughout t h i s review, an attempt has been made t o h i g h ­ l i g h t the need f o r a low investment c o s t , n o n - p o l l u t i n g s o l v e n t system f o r c e l l u l o s e t o s u b s t i t u t e f o r the v i s c o s e process. None o f the systems known t o date meet the necessary requirements f o r commercial e x p l o i t a t i o n . However, as has always been the case, whenever a need l i k e t h i s e x i s t s some outstanding s c i ­ e n t i s t s w i l l develop methods t o produce the d e s i r e d r e s u l t s - and t h i s case w i l l be no e x c e p t i o n . The c e l l u l o s e chemists are equal to the c h a l l e n g e and the rewards f o r success w i l l be l a r g e .

Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23.

Warwicker, J.O., J e f f r i e s , R . , Colbran, R.L., and Robinson, R . N . , Shirley Inst. Pamphle No 93 (1966) Manchester England. Warwicker, J.O., High Polymers, V o l . V , Part IV, Wiley -Interscience, N . Y . , 1971. Jayme, G . , High Polymers, V o l . V, Part IV, Wiley-Interscience, N . Y . , 1971. Phillip, B . , Schleicher, H., and Wagenknecht, W., Cellulose Chem. Tech., 9, 265-82 (1975). Phillip, B. Schleicher, H., and Wagenknecht, W., C.A. 83 165567s; Chem. Vlakno 25 (10-22) 1975. Polyola, L., and Aarnikowa, P.L., Kem.-Kemi 2, (1) 27-9 (1975). Brandrup, J. and Immergut, E . H . , Polymer Handbook, 2nd ed. V-101, John Wiley & Sons, N . Y . 1975. Spurlin, H.M., High Polymers Vol. V, Part III, Wiley-Inter­ science, N . Y . (1955). B u r r e l l , H., O f f i c i a l Digest (726-758) 1 9 5 5 . Barton, A.F., Chem. Reviews, 75, No. 6, (731-753) 1975. Williams, H . E . , J. Soc. Chem. Ind., 40, 221T, 1921. Hess, K. and Trogus, C., Z. Phys. Chem., B14, 387 (1931). L i t t , M . , Cell. D i v . Preprints, ACS Mtg., N.Y. 1976. Segal, L., High Polymers, V o l . V, Part IV, Wiley-Intersci­ ence, N.Y. 1971. P h i l l i p , B . , and Schleicher, H., C . A . , 74, 127361b (1971). Koura, Α., Schleicher, H., and Phillip, B . , Faserforsch. T e x t i l t e c h . 23, (3) 128-33 1972; C . A . , 77, 50396u 1972. Graenacher, C., and Sallmann, U.S. 2,179,181 (1939). Johnson, D . L . , U.S. 3,508,941 (1970); B . P . 1,144,048 (1969). Petrov, V . G . , C.A. 63, 10161g, 1965. Kimura, T . , Yamamura, T . , Kawai, Α., and Nagai, S., Japan Patent 69 02,592. P h i l l i p , B., Schleicher, H., and Laskowski, I., Faserforsch Textiltech., 23, 60-65, (1972). Yamazaki, S., and Nakao, O., C . A . , 81, 154860q (1974). Kata, Κ., and Yokota, K . , C.A. 66, 47464g (1967).

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

TURBAK

24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59.

ET

AL.

Cellulose Solvent Systems

23

Hata, K. and Yokota, K., C.A. 70, 69191a, (1969). Hata, K. and Yokota, K., C.A. 70, 69192b, (1969). Hata, K. and Yokota, K., U.S. 3,424,702 (1969). Hata, K. and Yokota, K., C.A., 72, 33464u (1970). Hata, K. and Yokota, K., C.A., 74, 14323x (1971). Hata, K. and Yokota, K., C.A., 75, 153094g (1971). Kenyon, W. and Y a c k e l , E., U.S. 2,448,892. Y a c k e l , E.C. and Kenyon, W., J.A.C.S. 64, 121 (1942). Unruh, C.C. and Kenyon, W., J.A.C.S. 64, 127 (1942). McGee, P., Fowler, W.F., et al, J.A.C.S. 69, 355 (1947). Fowler, W., Unruh, C., McGee, P. and Kenyon, W., J.A.C.S. 69, 1636 (1947). Pavlyuchenko, M. and Ermolenko, I., C.A. 1739d (1956) I z v e s t . Akad. Nauk Ermolenko, I. and Zhur. Obshchei Khim., 28, 722-8 (1958). Pavlyuchenko, M. et al C.A. 20187g (1960) Zhur. Priklad. Khim. 33, 1385-91 (1960). Kuznetsova, Z.I. et al, I z v e s t . Akad. Nauk., SSSR, No. 3, 557-59 (1965). Pavlyuchenko, M. et al, C.A. 83, 166024z (1975), Zhur., Priklad. Khim. 48, 1822-5 (1975). H i a t t , G.D. and Crane, C.L. U.S. 2,473,473 (1949). Chü, N.J., Pulp and Paper I n s t . of Canada. Report #42, 1970. W i l l i a m s , H.D., U.S. 3,236,669 (1966). H e r g e r t , H.L. and Z o p o l i s , P., Fr. P a t . 1,469,890, C.A. 68 41234b (1968). Nakao, O., et al, Canadian P a t e n t 876,148 (1971). Nakao, O., et al, U.S. 3,669,916. Mahomed, R.S., B.P. 1,309,234 (1973). Clermont, L.P., Canadian P a t e n t 899,559 (1969). Clermont, L.P. and Bender, F., J. P o l y . Sci., 10 (6), 1665-77 A-1 (1972). Venkateswaran, A. and Clermont, P., J. A p p l . P o l y .Sci.,18, 133-42 (1974). Bender, F., et al, U.S. 3,715,268 (1973). Schweiger, R.G., Chem. & I n d . 296, (1969). Schweiger, R.G., German Patent 2,120,964 (1971). Schweiger, R.G., U.S. 3,702,843 (1972). Schweiger, R.G., TAPPI. 7th D i s s o l v i n g Pulp Conf., A t l a n t a (1973). Schweiger, R.G., TAPPI. 57 #1, 86-90, 1974. Schweiger, R.G., J. Org. Chem., 41, (1) 90-93 (1976). Gray, P., Chemical Reviews, 1069, (1955). White, E.H. and Feldman, W.R., J.A.C.S. 79, 5832-33 (1957). P a s t e k a , M. and M i s l o v i c o v a , D., C e l l u l o s e Chem. & Tech., 8, 107-114 (1974).

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

24 60. 61. 62. 63. 64. 65. 66. 67. 68.

S O L V E N T SPUN

R A Y O N , MODIFIED C E L L U L O S E

FIBERS

I b i d , 481-486 (1974). ibid, 9, 325-330 (1975). Grinshpan., O., et al, Daklod, Akad. Nauk, B e l l o r o s s , SSSR, 18, (9) 828-31 (1974). Grinshpan, D., K a p u t s k i i , F.N., et al, B e l l o r o s s , Gos. Univ., Minsk., SSSR.; C.A. 194931 (1975). Bashmakov, I.A. et al, Vestsi Akad Nauk, Gos U n i v . B e l l o r o s s SSSR, (4) 29-32 (1973) C.A. 28636u (1973). N i c h o l s o n , M. and Johnson, D.C., TAPPI, 8th D i s s o l v i n g Pulp Conf., Syracuse, N.Y. 1975. Seymour, R.B. and Johnson, E.L., Organic Coatings and Plastics P r e p r i n t s , ACS Mtg. San F r a n c i s c o 665-73 (1976). Seymour, R.B. and Johnson, E.L., Polymer P r e p r i n t s , 17, #2, 382-383 (1976) (ACS Lowe, O.G., J. Org

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

3 The

Spinning of Unconventional Cellulose Solutions

D. M. MacDONALD International Paper Co., Tuxedo Park,N.Y.10987

About ten years ago it became apparent that the v i s c o s e process was encounterin environmental e f f e c t s . erated c e l l u l o s e was i n d i c a t e d and a p r o j e c t t o screen the v a r i o u s c e l l u l o s e s o l v e n t s was s t a r t e d . In this paper, some o f the r e s u l t s will be d e s c r i b e d . In the first experiments, Table I , the s o l u t i o n s were prepared u s i n g k r a f t hardwood d i s s o l v i n g pulps. C e l l u l o s e , dissolved i n 72% sulfuric a c i d , hydrolyzed t o a DP below 30 in less than 15 minutes a t 0°C. Phosphoric a c i d (85%) gave a very v i s c o u s 2% cellulose s o l u t i o n of practical DP, but the presence of g e l s and fibers made filtration very difficult and H PO could not be washed from f i l m s c a s t on g l a s s p l a t e s . N e u t r a l i z a t i o n w i t h 14% ammonium hydroxide, f o l l o w e d by washing, gave complete removal o f phosphate, but higher concentrations o f ammonium hydroxide gave crystalline ammonium phosphate in the film. 3

4

Table I C r i t i q u e o f C e l l u l o s e Solvents F i r s t Examined Solvent 72%

H

Result Excessive DP l o s s

S 0

2 4 85% H P 0

High g e l and f i b e r , H^PO^ hard t o remove

so

2

-NH

Good s o l u t i o n , i m p r a c t i c a l to

regenerate

so

2

- ( C H ) NH

Good s o l u t i o n , i m p r a c t i c a l to

regenerate

3

4

3

3

2

Good s o l u t i o n , very slow c o a g u l a t i o n

64% ZnCl

The extreme difficulty of filtration along with the poor economics a n t i c i p a t e d in u s i n g a 2% solution prompted an exami n a t i o n o f the newer SO -amine s o l v e n t s reported by Hata and Yokota in Japan (1-3). These s o l v e n t s gave good s o l u t i o n s but, 2

25

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

26

S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FIBERS

when regenerated i n water a t 0°C or h i g h e r , S 0 e v o l u t i o n produced a foam. As reported by these Japanese workers Ç3), r e generation at -10 C i n methanol gave a c l e a r f i l m , but the economics of working under pressure at such low temperature seemed d o u b t f u l . The f i n a l s o l v e n t i n Table I , aqueous z i n c c h l o r i d e , gave an e x c e l l e n t s o l u t i o n which, u n f o r t u n a t e l y , could not be coagulated i n a form w i t h s t r e n g t h would permit s p i n n i n g . This was deduced from experiments u t i l i z i n g hand-cast f i l m s which showed l i t t l e or no cohesion. 2

Spinning Experiments Using C e l l u l o s e Dispersed i n Calcium Thiocyanate While examining th i n aqueous c a l c i u m thiocyanat and a c l e a r f i l m was produced. Since f i b e r extruders are used i n p r e p a r i n g s y n t h e t i c f i b e r s , i t seemed p o s s i b l e that t h i s process, i l l u s t r a t e d i n F i g u r e 1, could g i v e a p r a c t i c a l route to regenerated c e l l u l o s e ; t h e r e f o r e , a c l o s e r i n v e s t i g a t i o n of t h i s unusual s o l v e n t system, f i r s t described by Bechtold and Weratz of DuPont (4-6), was commenced. In the a n t i c i p a t e d i n d u s t r i a l process, pulp would be f l o c k e d , mixed w i t h calcium thiocyanate s o l u t i o n , d r a i n e d , and then pressed. These steps are v e r y s i m i l a r to the c a u s t i c s t e e p i n g , p r e s s i n g , and shredding stages of the v i s c o s e process, so v i s c o s e p i l o t p l a n t equipment was used i n our work. The shredded c e l l u l o s e c a l c i u m thiocyanate f i b e r s would be fed i n t o an extruder and extruded through a f i l a m e n t d i e i n t o an aqueous bath c o n t a i n i n g c a l c i u m thiocyanate. A Brabender Model 252 Extruder w i t h four h e a t i n g zones, a H a s t a l l o y b a r r e l , and a chrome-plated, uniform taper screw of 25 f l i t e s w i t h a 3:1 compression r a t i o was used i n the l a b s t u d i e s . Two e i g h t - h o l e c i r c u l a r d i e s (3/4 χ 1/8 i n . ) were used; hole diameters were .013 i n . and .006 i n . ; c a p i l l a r y l e n g t h was .010 i n . ; a 200 χ 1400 Dutch Weave s t a i n l e s s s t e e l f i l t e r was p o s i ­ t i o n e d behind the d i e . The micron r a t i n g of the f i l t e r was 12. The i n i t i a l experiments showed that f i b e r s could be ex­ truded, but that these f i b e r s could not be s t r e t c h e d i n a i r even when the a i r temperature was r a i s e d as h i g h as 180 C, at which p o i n t decomposition of thiocyanate was o c c u r r i n g . Hole blockage was a r e c u r r i n g problem even though the f i l t e r - h o l e s i z e was f a r s m a l l e r than the d i e - h o l e diameter. D i f f i c u l t y was a l s o experienced w i t h feeding the f l o c k e d d i s p e r s i o n to the extruder screw because of blockage at the hopper neck. T h i s problem was solved by c u t t i n g the pulp i n t o 1/4-inch squares a f t e r sheet s t e e p i n g . A problem w i t h v a r i a b l e e x t r u s i o n behavior was f i n a l l y t r a c e d to v a r i a t i o n s i n c a l c i u m thiocyanate composition. C o n s u l t a t i o n s w i t h the manufacturer, Halby Chemical Co., revealed that ammonium thiocyanate was the

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

3.

MACDONALD

Unconventional Cellulose Solutions

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

27

S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FD3ERS

28

most l i k e l y i m p u r i t y , the a d d i t i o n of ammonium thiocyanate to the c a l c i u m thiocyanate s o l u t i o n was examined. About 1% ammonium t h i o c y a n a t e w i t h 52.5% c a l c i u m thiocyanate i s optimum; l e s s than 0.2% ammonium thiocyanate g i v e s an unextrudable d i s p e r s i o n . Table I I i l l u s t r a t e s what seems to be the optimized process. Calcium thiocyanate c o n c e n t r a t i o n s below 45 or 50% do not g i v e a product which can be extruded, and c o n c e n t r a t i o n s of ammonium thiocyanate above 1% cause f i l a m e n t s to s t i c k to godets and guides. An a l k y l a r y l , n o n - i o n i c s u r f a c t a n t was used to a i d p e n e t r a t i o n d u r i n g steeping.. The long steeping time seems unnecessary i f f l o c k i s used r a t h e r than sheets; however, the f l o c k d i d not feed p r o p e r l y as was mentioned p r e v i o u s l y . Our impression i s that f l o c k would very probably feed i n t o a l a r g e e x t r u d e r . Normally, the sheets press e a s i l y , but e x t r u s i o n temperatures above abou ments, apparently due t Table I I Optimum Conditions f o r E x t r u s i o n of the C e l l u l o s e Ca(SCN) D i s p e r s i o n s 2

Pulp:

low v i s c o s i t y , low r e s i n , d i s s o l v i n g grade

Steeping s o l u t i o n : 52.5% Ca(SCN> , 0.3-1.0% NH SCN, 0.1% n o n - i o n i c s u r f a c t a n t , room temperature, 2 days 2

Pulp:

4

S o l u t i o n ( a f t e r p r e s s i n g ) - 1: 2.2-2.8

D i s p e r s i o n form:

1/4-inch

E x t r u s i o n temperature:

squares

110°C

Bath: Water, 25% Ca(SCN)

2>

( a l l 4 zones).

25% NaCl.

Using m a t e r i a l prepared under these optimum s p e c i f i c a t i o n s w i t h the .013-in. hole diameter d i e , f i l a m e n t s could be necked down to .002 i n . dry diameter by speeding up the f i r s t godet. S t r e t c h between the f i r s t and second godets was poor (normally o n l y about 10%) even w i t h 100 C aqueous calcium thiocyanate i n the s t r e t c h bath. With the .006-in. h o l e diameter d i e , f i l a m e n t diameter d i d not decrease p r o p o r t i o n a l l y as s w e l l i n g at the d i e face became much more pronounced. T h i s was i n t e r p r e t e d as showing the need f o r lower v i s c o s i t y and, consequently, a higher pulp: thiocyanate r a t i o . D i l u t i o n of the d i s p e r s i o n w i t h a d d i t i o n a l thiocyanate gave a homogeneous mixture i f done i n a Banbury-type mixer. However, the extruded f i b e r s refused to coagulate p r o p e r l g unless the extruder temperature was reduced to as low as 60 C. F i b e r s t r e n g t h was extremely poor.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

3.

MACDONALD

Unconventional Cellulose Solutions

29

F i n a l l y , a d d i t i o n o f DMSO, methanol, ethylene g l y c o l , b o r i c a c i d , EDTA, hydrazine, and hydroxylamine t o the calcium t h i o cyanate s o l u t i o n was evaluated, but s t r e t c h a b i l i t y was not improved. S y n t h e t i c polymers were a l s o were added without benefit. D i s c u s s i o n t h i s f a r has concerned e x t r u d a b i l i t y o f the v a r i o u s d i s p e r s i o n s . D e l i v e r i e s were low (only 30 g/min a t top extruder speed), and s p i n n i n g speeds above 30 m/min were reached o n l y r a r e l y . Most n o t i c e a b l e was an extreme tendency t o s h r i n k upon d r y i n g . S l a c k - d r i e d yarn s h r i n k s 30% o r more; r e s t r a i n e d d r y i n g on cones gave very f u z z y yarns, due t o f i l a m e n t breakage. T y p i c a l yarn p r o p e r t i e s i l l u s t r a t e d i n Table I I I were v e r y poor, w i t h most runs g i v i n g about 0.3 g/den c o n d i t i o n e d t e n a c i t y (although some yarns have given 0.8 g/den) Elongations were l e s s than 10%, w i t n o t i c e a b l e was the tendenc same s t r e s s , t h e r e f o r e the lowest d e n i e r s always gave the s t r o n g est yarn. Yarn o f s t i l l lower d e n i e r , however, could not be spun w i t h a v a i l a b l e e x t r u s i o n d i e s . Because of s w e l l i n g a t the d i e f a c e , i t i s u n l i k e l y that smaller diameter h o l e s , which a r e very d i f f i c u l t t o d r i l l , would help. **ie a l s o be q u i t e t h i c k as pressures o f 500-4000 l b / i n . have been observed. T h e

m u s t

2

Table I I I T y p i c a l Rayon P r o p e r t i e s from the Thiocyanate C e l l u l o s e D i s p e r s i o n s Cond. Ten., g/den

-

Cond. Elong., %

-

Wet Ten.,

-

0.1-0.3

-

10-20%

g/den

Wet Elong, %

0.1-0.8 4-10%

Spinning Experiments U t i l i z i n g C e l l u l o s e D i s s o l v e d i n NO^-DMF Turning now t o the n i t r o g e n dioxide-DMF s o l v e n t , r e s u l t s i n d i c a t e t h a t i n so f a r as s o l u t i o n p r o p e r t i e s and ease o f s o l u t i o n p r e p a r a t i o n a r e concerned, t h i s i s an e x c e l l e n t comb i n a t i o n that produces yarn p r o p e r t i e s b e t t e r than those o f the thiocyanate c e l l u l o s e - s p u n yarn. Our research was prompted by a paper presented by Schweiger (5) a t the TAPPI D i s s o l v i n g Pulp Conference i n A t l a n t a . I n t h i s paper, Schweiger described both the f a c i l e r e a c t i o n o f c e l l u l o s e w i t h n i t r o g e n d i o x i d e i n dimethylformamide s o l u t i o n (NC^-DMF) t o form a c e l l u l o s e t r i n i t r i t e s o l u t i o n , and the almost i n s t a n t a n eous regeneration o f c e l l u l o s e when t h i s s o l u t i o n i s added t o water.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

SOLVENT SPUN RAYON, MODIFIED CELLULOSE FIBERS

30

CellOH + NO.

^

m

> CellONO

+

HN0

CellOH + HN0

Q

2

Work was i n i t i a t e d to i n v e s t i g a t e the b e l i e f that p r o d u c t i o n of rayon from c e l l u l o s e spun i n NO^-DMF might be f e a s i b l e i f the p l a n t was adjacent t o an ammonium n i t r a t e p l a n t s u p p l y i n g NO^ and ammonia, and which could process the ammonium n i t r a t e by-product. The tonnage of ammonium n i t r a t e would be h i g h - about 3 times more ammonium n i t r a t e would be produced than c e l l u l o s e , A f l o w diagram f o r a h y p o t h e t i c a With t h i s process t r e a t e d w i t h about 2/3 of the r e q u i r e d q u a n t i t y of DMF and, a f t e r about two hours, t h i s would be t r a n s f e r r e d t o a r e a c t o r t o be combined w i t h s i x moles of N0« ( c o r r e c t e d f o r pulp moisture) and the remaining DMF. The s o l u t i o n forms a t room temperature a f t e r 10-30 minutes and would then be f i l t e r e d , w i t h simultaneous d e a e r a t i o n i f a vacuum f i l t e r i s used. Spinning i s i n t o a bath c o n t a i n i n g water, DMF, and ammonium n i t r a t e a t pH 7 to minimize DMF h y d r o l y s i s . DMF i s recovered from excess s p i n bath, e i t h e r by f r a c t i o n a l d i s t i l l a t i o n o r methylene d i c h l o r i d e e x t r a c t i o n , and i s returned t o the DMF r e s e r v o i r . The r e s i d u a l ammonium n i t r a t e s o l u t i o n would be sent f o r recovery of s o l i d ammonium nitrate. Conventional v i s c o s e p r o c e s s i n g equipment was used i n the experiments. The p u l p , u s u a l l y a low v i s c o s i t y , hardwood k r a f t of d i s s o l v i n g grade, was f i r s t f l o c k e d and placed i n a v i s c o s e mixing can w i t h 2/3 of the d e s i r e d DMF. A f t e r two hours, the r e q u i r e d amount o f N0 was added i n the remaining DMF (2.5 p a r t s N0 per p a r t o f c e l l u l o s e was u s u a l l y used) and mixing, w i t h the can p a r t i a l l y submerged i n a 2 C bath, was s t a r t e d . A f t e r 30 minutes (10 minutes seemed s u f f i c i e n t ) , the can was removed from the bath, a standpipe was i n s e r t e d , and the s o l u t i o n was f o r c e d by a p p l i c a t i o n of 50 p s i a i r pressure t o pass through a 6-micron polypropylene f i l t e r i n t o an adjacent, evacuated can. U s u a l l y the vacuum was a p p l i e d f o r about 2 hours a f t e r the end of f i l t r a t i o n t o complete d e a e r a t i o n ; whether t h i s i s necessary i s doubtful. Every time a can was opened and exposed t o the a i r , a few drops o f l i q u i d N 0 were added. T h i s prevents the s k i n formation which occurs r a p i d l y i n a i r , n i t r o g e n , o r even vacuum. Apparentl y , N0« gas e f f e c t i v e l y suppresses r e v e r s a l o f the n i t r i t e formation r e a c t i o n . C e l l u l o s e DP s l o w l y d r i f t s downward on storage of the s o l u t i o n , the best data on t h i s e f f e c t a r e i n c l u d e d i n a paper by Pasteka ( 8 ) . However, many times we have been a b l e t o s p i n s u c c e s s f u l l y a f t e r s t o r i n g the s o l u t i o n o v e r n i g h t . I t i s im2

2

2

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

3.

Unconventional Cellulose Solutions

MACDONALD

31

ι

2

Mixer

Activation

Flock

NQ

Pulp

DMF

DMF

DMF

Reservoir

Ammonium

DMF

Nitrate

Recovery

Solution

Regenerated Cellulose Fiber

^

Spinning

Filter,

Machine

ueaer a i e

NH

3

Ammonium Nitrate Plant

N0

2

Figure 2: Flow diagram for NO -DMF spinning t

300

I-

250

200 VISCOSITY, b a l l f a l l sec

159

100

50

% CELLULOSE

Figure 3: Viscosity-% cel­ lulose relationship for highviscosity Kraft pulp in NOtDMF

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

32

SOLVENT SPUN RAYON, MODIFIED CELLULOSE FIBERS

portant t h a t the s o l u t i o n s be stored a t room temperature, o r lower, and that temperatures above 30 C be avoided d u r i n g d i s ­ s o l u t i o n . F r i c t i o n a l heat o c c u r s , and e f f i c i e n t c o o l i n g d u r i n g s t i r r i n g i s necessary. As Schweiger f i r s t demonstrated, n i t r a ­ t i o n occurs due t o the t r a n s e s t e r i f i c a t i o n w i t h by-product n i t r i c a c i d a t temperatures above room temperature. The data i n Table IV show that l e s s n i t r a t i o n occurs when a pulp o f normal moisture i s used i n p l a c e o f a bone dry pulp. Table IV Cellulose-Bound N i t r o g e n a f t e r Regeneration Compared to S o l u t i o n Age and Pulp M o i s t u r e Pulp M o i s t u r e %

% 1

0 7

0.09 0.03

0.50 0.18

S o l u t i o n v i s c o s i t y was r a t h e r h i g h , as i s i l l u s t r a t e d i n F i g u r e 3, where a h i g h v i s c o s i t y pulp was used. Low v i s c o s i t y pulp w i l l cause the curve to s h i f t about 0.5% t o the l e f t . Spinning was through a 720-hole, .0025-in. hole diameter p l a t i n i u m s p i n n e r e t . Hole blockage was never observed. In the next t a b l e s , some s t r e n g t h r e s u l t s are compared w i t h s p i n bath composition. I n Table V, a few baths which d i d not g i v e s u c c e s s f u l s p i n n i n g are d e s c r i b e d . Included here i s methy­ l e n e d i c h l o r i d e , which i s a low b o i l i n g solvent capable o f e x t r a c t i n g DMF from water. Methylene d i c h l o r i d e b o i l e d a t the spinneret face thereby i n d i c a t i n g a h i g h heat e v o l u t i o n . A l s o weak o r s t r o n g a c i d s , and s t r o n g bases seem harmful, w h i l e DMFNH^NO^ mixtures do not g i v e s u f f i c i e n t l y f a s t c o a g u l a t i o n . Table V Spinbaths found not S u i t a b l e f o r Spinning the C e l l u l o s e - N 0 - DMF S o l u t i o n s 2

1.

Methylene d i c h l o r i d e

2.

Methylene d i c h l o r i d e - DMF - water

3.

A c e t i c a c i d - DMF - water

4.

50 and 75% methanol i n DMF

5.

Rayon-type s p i n baths

6.

Systems cont. NaOH i n s p i n , o r s t r e t c h , baths

7.

DMF - NH,N0

o

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

3.

33

Unconventional Cellulose Solutions

MACDONALD

The a d d i t i o n o f water i n t o DMF/ammonium n i t r a t e mixtures a l l o w s s p i n n i n g t o proceed normally and yarn p r o p e r t i e s were unchanged f o r R.0, NH,N0 -H 0 and DMF-NH N0 -H 0 spinbaths. The r e s u l t s i n Table V I a r e t y p i c a l : s t r e n g t h values were a b i t below o r d i n a r y rayon and e l o n g a t i o n was low when 3% s o l u t i o n s were spun a t 10 m/min. Low e l o n g a t i o n i n d i c a t e s a yarn which i s too b r i t t l e f o r easy t e x t i l e p r o c e s s i n g . 3

2

4

3

2

Table V I E f f e c t of DMF and Ammonium N i t r a t e i n Aqueous Spin Baths a t 24°C (3% c e l l u l o s e , 10m/min) Cond. Ten. (g/den.

Bath Comp.

w*

Wet

Cond.

Wet

12

H0

2.0

4.9

0.8

33N

2.1

3.4

0.8

6.3

44D,37N

1.8

2.1

0.6

3.8

2

*D = DMF, Ν = ΝΗ^Ν0

3

Table V I I shows a few experiments where 5% s o l u t i o n s were spun a t 30 m/min i n t o s p i n baths c o n t a i n i n g v a r y i n g q u a n t i t i e s of DMF-NH^NO^ and water. Again, the t e n s i l e p r o p e r t i e s were not good. Table V I I E f f e c t o f DMF and Ammonium N i t r a t e i n Aqueous Spin Baths a t 24°C (5% c e l l u l o s e , 30 m/min) Bath Comp. (%)*

Cond. Ten. (g/den.)

Cond. Elong.

Wet Ten. (g/den.)

Wet Elong. (%)

41D, 29N

1.7

2.9

0.7

7.5

30D, 26N

1.7

2.9

0.6

9.2

28D, 19N

1.7

2.7

0.7

7.8

16D,

1.7

3.0

0.7

9.5

UN

*D = DMF, Ν =» NH,N0 4 3 o

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

SOLVENT SPUN RAYON, MODIFIED CELLULOSE FIBERS

34

Use o f d i v a l e n t c a l c i u m and t r i v a l e n t aluminum was evaluated as an a i d to c o a g u l a t i o n ; yarn p r o p e r t i e s were unchanged. Table V I I I g i v e s r e s u l t s f o r 24° and 50°C s p i n bath temperature. The 50°C yarn s t r e n g t h r e s u l t s were very s l i g h t l y b e t t e r than the 24°C r e s u l t s . Table V I I I E f f e c t of Aluminum and 'Calcium N i t r a t e s on Spinning 6% S o l u t i o n s a t 40 m/min Bath Comp.

w*

Wet. Elong· (%)

0.6

8.6

4.9

0.5

11.0

5.0

0.7

9.8 9.8

1.6

4.0

14A, 17N (24°C)

1.7

4.

14C, 17N (24°C)

1.6

7A, 23N (50°C)

2.0

7A, 23N (24°C)

Wet. Ten. (g/den.)

Cond. Elong. (%)

Cond. Ten. (g/den.)

7C, 23N (24°C)

7C, 23N (50°C)

1.8

4.2

0.6

14A, 17N (50°C)

1.7

4.0

0.6

8.9

14C, 17N (50°C)

2.1

5.3

0.8

10.3

C « Ca ( N 0 ) . 4 H 0 ; Ν = ΝΗ,ΝΟ 4 3 Spinning speed, % c e l l u l o s e i n the N0 /DMF s o l u t i o n , and the presence of g l y c e r o l i n the s t r e t c h bath gave the yarn p r o p e r t i e s i l l u s t r a t e d i n Table IX. Water a t 95°C seemed best f o r the s t r e t c h bath i n previous experiments. Spinning speeds were 10-60 meters/ min and the range of 3% t o 7% c e l l u l o s e was examined. *A = A 1 ( N 0 ) . 9 H 0 ; 3

3

3

2

2

2

2

Table IX E f f e c t o f Spinning Speed, G l y c e r o l i n S t r e t c h Bath and % C e l l u l o s e on Spinning i n t o water a t 25 C Stretch Bath Comp.

Cell

Spinning Speed m/min

Yarn P r o p e r t i e s Wet Wet Cond. Cond. Elong. Elong. Ten. Ten. (g/den) (%) g/den (%)

3

H 0, 95°C

10

1.8

3.1

0.78

7.1

3

50% g l y c e r o l 92°C

10

1.8

2.3

0.81

6.3

5

H 0, 95°C

30

1.8

3.7

0.76

7.1

5

H 0, 95°C

40

1.7

4.5

0.72

8.0

0.60

9.5

0.78

6.0

2

2

2

5

H 0, 95°C

60

1.6

6.0

7

H 0, 95°C

30

1.8

3.3

2

2

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

3.

MACDONALD

35

Unconventional Cellulose Solutions

A sodium a l k y l s u l f o n a t e w e t t i n g agent i n the s p i n bath d i d not improve the r e s u l t s , shown i n Table X; however, higher s p i n bath temperatures (to 50°C) again gave a very s l i g h t s t r e n g t h improvement without improved e l o n g a t i o n . Table X E f f e c t o f Spin Bath Wetting Agent and Aqueous Spin Bath Temperature on A c e t a k r a f t Spinning a t 30 m/min

Cell.

Spin Bath Comp. and Temp.

Cond. Ten. g/den

Yarn P r o p e r t i e s Cond. Wet Elong. Ten. (%) g/den

Wet Elong.

7

H 0,

7

H O + 1% wett i n g agent, 23 C

2.1

4.2

0.80

6.3

7

H 0 + 1% wett i n g agent, 30 C

2.2

4.0

0.88

7.9

7

H 0 + 1% wett i n g agent, 45 C

2.2

4.1

0.94

15.4

3

H 0,

2.2

4.5

0.73

7.0

2

23°C

2

2

2

50°C

Perhaps the most s t r i k i n g t h i n g about these r e s u l t s i s the l a c k o f response to w i d e l y v a r y i n g s p i n b a t h compositions; i n f a c t , the same yarn p r o p e r t i e s were found f o r s p i n n i n g i n t o methanol. T h i s prompted a b r i e f look at f i b e r e l e c t r o n m i c r o graphs. Gas bubbles, probably from decomposition o f n i t r o u s a c i d to n i t r i c o x i d e , NO, have caused f i b e r damage as shown by the presence o f a h o l l o w core i n F i g u r e 4. A l s o , the f i b e r s have stuck together i n d i c a t i n g that the c o a g u l a t i o n r a t e i s too slow. F i g u r e 5 g i v e s a s i d e view i l l u s t r a t i n g a bundle o f f i b e r s where one f i b e r w a l l has been ruptured by a bubble. As nonaqueous s p i n baths were u n s u c c e s s f u l and c o a g u l a t i o n i n presence of water was i n s u f f i c i e n t l y f a s t t o prevent f i b e r s t i c k i n g and n i t r i c oxide damage, i t was concluded that the N0 -DMF s o l v e n t had l i t t l e chance of i n d u s t r i a l success i n the F i g u r e 2 process. 2

Spinning o f C e l l u l o s e i n DMSO - Paraformaldehyde S o l u t i o n s F i b e r s have a l s o been s u c c e s s f u l l y spun from s o l u t i o n s o f c e l l u l o s e i n DMSO-PF. T h i s i n t e r e s t i n g s o l v e n t system was f i r s t described by D.C. Johnson and coworkers (9, 10). C e l l u l o s e i s suspended i n DMSO and the mixture heated t o about 120°C; s o l i d paraformaldehyde (PF) i s then added. Monomeric formaldehyde smoothly forms and r e a c t s w i t h c e l l u l o s e t o form a m e t h y l o l d e r i v a t i v e . T h i s d e r i v a t i v e i s s t a b l e and s o l u b l e i n DMSO.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

36

S O L V E N T SPUN R A Y O N , MODIFIED

CELLULOSE

Figure 4: Electron micrograph of NO -DMFfibersshowing hollow cores and adhering fibers t

Figure 5: Electron micrograph of NO -DMFfibersshowing wall rupture by a gas bubble t

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

FD3ERS

3.

MACDONALD

Unconventional Cellulose Solutions

>

CH 0 + CellOH 2

37

CellOCH OH 2

DMSO Η or ψθΗ~" CellOH I f the s o l u t i o n i s poured i n t o water, c o a g u l a t i o n occurs. Speed o f c o a g u l a t i o n i s too slow f o r s u c c e s s f u l s p i n n i n g i n t o water. The same i s t r u e f o r acetone, benzene, a c e t i c a c i d , acetone-water and a c e t i c acid-water. As m e t h y l o l decomposition i s c a t a l y s e d by e i t h e r strong a c i d o r strong base, a c i d s and bases were evaluated next f i b e r hav bee s u c c e s s f u l l from both a c i d i c and b a s i MC&B paraformaldehyde and reagent grade DMSO were used. The 6% s o l u t i o n s were prepared i n a 4-1 beaker u s i n g the c o n d i t i o n s d e s c r i b e d by Johnson, and were f i l t e r e d i n the equipment p r e ­ v i o u s l y described f o r N0 -DMF s o l u t i o n s . While f i l t r a t i o n and d e a e r a t i o n d i d not cause problems, the PF must be added v e r y s l o w l y d u r i n g s o l u t i o n p r e p a r a t i o n o r the mixture w i l l c o o l due to the endothermic nature o f the process and the s o l u t i o n w i l l not form. F i b e r s p i n n i n g d i d not take p l a c e i n water, i n 0.5% and 1% H S 0 , o r i n 8% and 20% N a S 0 , as shown i n Table X I . 2

9

A

9

A

Table X I Unsuccessful Spin Baths f o r C e l l u l o s e Regeneration from DMSO - PF S o l u t i o n s

0.5% H S0 2 ' o

1% H S 0 2

A

2

A

20% Na S0 8% H S 0 , F i b e r s were spun w i t h d i f f i c u l t y i n 1% NaOH (Table X I I ) . The yarn was v e r y weak between the spinneret and the f i r s t godet, and frequent breaks o c c u r r e d . Yarn t e s t p r o p e r t i e s were v e r y s i m i l a r t o NO^-DMF yarns and b r i t t l e n e s s i s i l l u s t r a t e d by the low percent e l o n g a t i o n s . Spinning was g r e a t l y improved by use of h i g h NaCl i n presence o f NaOH. The yarn was s t i l l b r i t t l e . 2

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

38

S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FIBERS

Table X I I S u c c e s s f u l Spin baths and Yarn P r o p e r t i e s f o r C e l l u l o s e Regenerated f o r DMSO-PF S o l u t i o n s

and temperature

Cond. Ten,g/den 2.2

1%, NaOH, 55°

1.9

1%, NaOH, 24% NaCl, 55° 10% H, 4.2%

Z, 15.2% N, 25°C 2.6

10% H, 4.2%

Z, 15.2% N

10% H, 4.2%

Z, 15.2% N

Yarn P r o p e r t i e s Wet Wet Cond. Ten,g/den Elong,% Elong, % 0.8

7.5

5.4

1.0

8.1

4.4

1.2

5.1

4.8

H = H S 0 , Ζ = ZnS0 , Ν = Na S0, 2 4 2

4

4

o

A h i g h a c i d , rayon-type s p i n bath c o n t a i n i n g z i n c s u l f a t e gave good s p i n n i n g w i t h 30-40% s t r e t c h i n a 95 C aqueous s t r e t c h bath. Spinning speed was only 6 meters/min; t h i s was d i c t a t e d by the volume o f s o l u t i o n a v a i l a b l e and there does not seem t o be any reason why s p i n n i n g would not succeed a t higher speeds. Yarn p r o p e r t i e s were s t i l l below commercial a c c e p t a b i l i t y ; however, yarn p r o p e r t i e s d i d vary w i t h s p i n bath temperature and t h i s was g r a t i f y i n g i n view o f the independence of NO^-DMF yarn p r o p e r t i e s w i t h regard t o s p i n n i n g c o n d i t i o n s . Yarn t e n a c i t y f a l l s as temperature i s i n c r e a s e d , w h i l e e l o n g a t i o n i n c r e a s e s w i t h temperature. At 50 C, r e s u l t s were q u i t e c l o s e t o com­ mercial acceptability. M i c r o s c o p i c examination o f the yarns showed clumps o f mutually adherent f i b e r s i n a l l yarns, except f o r the sample spun i n 70 C a c i d . Thus, stronger c o a g u l a t i o n c o n d i t i o n s are s t r o n g l y i n d i c a t e d . Higher a c i d and z i n c s u l f a t e , o r replacement of z i n c s u l f a t e w i t h the environmentally more d e s i r a b l e aluminum s u l f a t e , should be t r i e d a t 40 o r 50 C. U n f o r t u n a t e l y , t h i s experiment has not yet been c a r r i e d out. CONCLUSIONS (a)

(b)

(c)

I n d u s t r i a l u t i l i z a t i o n f o r rayon production i s d o u b t f u l f o r c e l l u l o s e d i s p e r s e d i n strong aqueous calcium thiocyanate. Cellulose-N0«-DMF s o l u t i o n s are more promising although use i s d o u b t f u l i n a combined ammonium n i t r a t e - r a y o n process. Cellulose-DMSO-PF s o l u t i o n s are a l s o promising; r e a l d i f f i c u l t y can be foreseen i n d e v i s i n g an e f f i c i e n t recovery system f o r DMSO, formaldehyde, and the s p i n bath components.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

3.

MACDONALD

Unconventional Cellulose Solutions

LITERATURE CITED 1. 2. 3. 4. 5. 6. 7. 8. 9.

10.

Hata, K. and Yokota, Κ., Sen-i G a k k a i s k i , (1966) 22 ( 2 ) , 96-102. Hata, K. and Yokota, Κ., Sen-i G a k k a i s k i , (1968) 24 ( 9 ) , 415-419. Hata, K. and Yokota, Κ., Sen-i G a k k a i s k i , (1968) 24 ( 9 ) , 420-424. Bechtold, M.F. and Werntz, J.H., U.S. 2,737,437 dated March 6, 1956. Bechtold, M.F. and Werntz, J.H., U.S. 2,737,459 dated March 6, 1956. Bechtold, M.F. and Werntz, J.H., U.S. 2,810,162 dated October 22, 1957. Schweiger, R.G., TAPPI Pasteka, M. and M i s l o v i c o v , , (1974) 8, 107-114. Johnson, D.C., N i c h o l s o n , M.D. and Haigh, F.C., J . A p p l . Polymer Sci., A p p l . Polymer Symposia, (1976) 28, 931-943. Swenson, H.A., J . A p p l . Polymer Sci., A p p l . Polymer Symposia, (1976) 28, 945-952.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

4 Production of Rayon from Solutions of Cellulose in N O -DMF 2

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R.B.HAMMER andA.F.TURBAK ITT Rayonier Inc., Eastern Research Div., Whippany,N.J.07981

A wide range o f wood pulps in v a r i o u s p h y s i c a l forms were found t o d i s s o l v e readily centration of pulp d i s s o l v e of p o l y m e r i z a t i o n . Dimethylformamide was compared t o dimethyl s u l f o x i d e and acetonitrile and was found t o be p r e f e r a b l e o v e r a l l w i t h respect t o s o l v e n t power, viscosity of solutions, stability and recovery. The temperature o f N O a d d i t i o n and the r e s u l t a n t time f o r dissolution were found to be critically r e l a t e d t o ultimate fiber p h y s i c a l and analytical p r o p e r t i e s . F i b e r s w i t h a h i g h wet modulus and intermediate t e n a c i t y were readily produced from proton donor systems i n v o l v i n g h y d r o x y l i c c o a g u l a t i o n baths such as water, a l c o h o l s and glycols. A wide variety of fiber cross s e c t i o n s could be produced and proved t o be r e l a t e d t o the nature o f the regenerant employed during s p i n n i n g . 2

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Introduction The most w i d e l y used method f o r c o n v e r t i n g wood pulp i n t o regenerated c e l l u l o s e for films and fiber production is the viscose process. However, there a r e s e v e r a l problems a s s o c i a t e d w i t h the v i s c o s e process which do not appear t o be d i m i n i s h i n g even in view o f c u r r e n t developments. There a r e other processes f o r producing regenerated cellulosic products i n c l u d i n g regeneration from cellulose nitrate which is v e r y hazardous, and cuprammonium hydroxide which forms a s o l u b l e c e l l u l o s e complex. However, the p r o d u c t i o n o f cellulosic articles from these processes is minuscule compared t o the v i s c o s e method. There are entirely different c l a s s e s of chemical systems which are non-aqueous which d i s s o l v e cellulose. D i n i t r o g e n tetr o x i d e , N O , has been used as an agent t o make 6-carboxy cellulose in non-polar s o l v e n t s such as chloroform or carbon t e t r a c h l o r i d e . I n 1947-48 W.F. Fowler e t al(1)evaluated the relative s o l v e n t power o f forty-five organic s o l v e n t s w i t h N O , for 2

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In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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Production of Rayon

d i s s o l v i n g c e l l u l o s e . In separate p a t e n t s , H.D. W i l l i a m s (2) and H.L. Hergert Q ) et a l r e p o r t e d dimethyl s u l f o x i d e as a s p e c i f i c p o l a r s o l v e n t f o r use w i t h N 0 to d i s s o l v e c e l l u l o s e . In l a t e r work, the s o l u t i o n p r o p e r t i e s of c e l l u l o s e / N 0 / D M F s o l u t i o n s or c e l l u l o s e p l u s other polymer/N 0 /DMF s o l u t i o n s were examined. For example, 0. Nakao r e p o r t e d g r a f t copolymers prepared from c e l l u l o s e / N 0 s o l u t i o n s . ^ ) L.P. Clermont(5) and R.G. Schweiger(6) r e p o r t e d t h a t c e r t a i n c e l l u l o s e d e r i v a t i v e s could be prepared through the use of c e l l u l o s e / N 0 / D M F s o l u t i o n s . B a s i c chemical and p h y s i c a l s t u d i e s on t h i s system have been r e ­ ported by N.J. Chu(j) and M. Pasteka and D. M i s l o v i c o v a . ( 8 ) The experiments to be d e s c r i b e d were intended to e x p l o r e the use of c e l l u l o s e s o l u t i o n s i n N 0 /DMF or DMSO f o r the p r o d u c t i o n of regenerated f i b e r s as a p o t e n t i a l replacement f o r the v i s c o s e process. 2

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Experimental Experiments were designed to determine the i n f l u e n c e of the form of the pulp and the degree of p o l y m e r i z a t i o n p r i o r t o d i s ­ s o l u t i o n . Although the m a j o r i t y of the s o l u t i o n s were prepared u s i n g Abbe'cut m a t e r i a l , i . e . a h i g h l y powdered, d e f i b e r e d p u l p , the d i s s o l u t i o n process i s not l i m i t e d w i t h r e s p e c t to the degree of p o l y m e r i z a t i o n or the pulp form. A l l s o l u t i o n compositions are g i v e n as weight percents i n the order p u l p / N 0 / s o l v e n t , eg. 8/15/77 r e p r e s e n t s 8$ c e l l u l o s e , 15$ N 0 and 77$ s o l v e n t . A wide v a r i e t y of c e l l u l o s i c pulps were found to d i s s o l v e i n the Ν 0 s o l v e n t system. Both s u l f a t e and s u l f i t e pulps can r e a d i l y be employed and pulps c u r r e n t l y a v a i l a b l e f o r the v i s c o s e process are among those t h a t may be used. In a d d i t i o n , bleached or non-bleached, barked and non-debarked pulp samples a l s o r e a d i l y d i s s o l v e i n t h i s system. These pulps may c o n s i s t of hardwoods, softwoods or mixtures of the two s p e c i e s . A t y p i c a l example of the s o l u t i o n p r e p a r a t i o n procedure i s d e s c r i b e d below. S i l v a n i e r - J , a prehydrolyzed k r a f t pulp of 1050 D.P., a f t e r c o n v e r t i n g t o a l k a l i c e l l u l o s e by methods w e l l known i n the rayon i n d u s t r y , was a l k a l i n e aged t o a D.P. l e v e l of U 5 0 , n e u t r a l i z e d , washed, d r i e d , then e i t h e r f l u f f e d , d i c e d or d e f i b e r e d . An 8/I5/77 c e l l u l o s e / N 0 / D M F s o l u t i o n was prepared by charging I60 p a r t s of t h i s a l k a l i aged p r e h y d r o l y z e d , k r a f t pulp (D.P. U50) and I5U0 p a r t s of dimethylformamide ( DMF) i n t o a twol i t e r f o u r neck r e s i n r e a c t i o n f l a s k equipped w i t h a s t a i n l e s s s t e e l mechanical s t i r r e r , thermometer, and a 250 ml. e q u a l i z i n g pressure a d d i t i o n f u n n e l . The r e s u l t i n g s l u r r y was s t i r r e d and cooled to below +20°C, p r e f e r a b l y between -5°C and +10°C, w h i l e 300 p a r t s of l i q u i d n i t r o g e n t e t r o x i d e ( N 0 ) was added dropwise over ça. 60 minute time p e r i o d . The temperature of the r e s u l t i n g exothermic r e a c t i o n was maintained below 20°C, p r e f e r a b l y i n the range p r e v i o u s l y s p e c i f i e d d u r i n g N 0 a d d i t i o n and f o r the 2

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In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

S O L V E N T S P U N R A Y O N , MODIFIED C E L L U L O S E FIBERS

42

d u r a t i o n o f the remaining d i s s o l u t i o n process. C e l l u l o s e / N 0 / C H C N s o l u t i o n s o f 8 / 2 0 / 7 2 composition were prepared i n a s i m i l a r manner. C e l l u l o s e / N 0 / D M S 0 s o l u t i o n s o f 8 / I 5 / 7 7 composition were prepared under s i m i l a r c o n d i t i o n s except that the l i q u i d N 0 was f i r s t added t o the DMSO c o n t a i n i n g 1 . 5 p a r t s o f water. The c e l l u l o s e was then added t o the cooled (20°C) N 0 / D M S 0 mixture. A l l s o l u t i o n s were observed m i c r o s c o p i c a l l y t o be f r e e o f g e l s and unreacted f i b e r s . The s o l u t i o n s were f i l t e r e d through a 9 0 mm. diameter n y l o n , i n - l i n e f i l t e r d u r i n g s p i n n i n g . The s o l u t i o n s were deaerated p r i o r t o s p i n n i n g and v i s c o s i t i e s measured by a B r o o k f i e l d Viscometer and found t o be i n the range 2

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of 8 , 0 0 0 - 1 6 , 0 0 0 cps.

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at 2 2 ° C

The m a j o r i t y o f the s p i n n i n g t r i a l s were performed on a bench-scale v e r t i c a l s p i n n i n the a p p r o p r i a t e primar f i b e r s passed v e r t i c a l l y t o a primary godet, then through a sec ondary bath t o a secondary godet, whose speed could be a l t e r e d t o produce d e s i r e d s t r e t c h c o n d i t i o n s . S e v e r a l types o f s p i n n e r e t t e s have been used s u c c e s s f u l l y t o s p i n f i b e r s from these s o l v e n t systems. For example, g o l d - p l a t i num, t y p i c a l f o r the v i s c o s e p r o c e s s , s t a i n l e s s - s t e e l , t y p i c a l f o r c e l l u l o s e acetate s p i n n i n g , and g l a s s . The g l a s s spinner e t t e s have a f f o r d e d the best r e s u l t s and are thus p r e f e r r e d s i n c e they are both inexpensive and o f f e r the advantage o f l a r g e r h o l e length/diameter r a t i o s . R e s u l t s and D i s c u s s i o n The d i s s o l u t i o n o f c e l l u l o s e i n N 0 / s o l v e n t systems i s b e l i e v e d t o r e s u l t from the formation o f a c e l l u l o s e n i t r i t e e s t e r and n i t r i c a c i d . (2) Consequently, the r e g e n e r a t i o n o f c e l l u l o s e d u r i n g s p i n n i n g from a true c e l l u l o s e n i t r i t e e s t e r would r e q u i r e a t r a n s n i t r o s a t i o n r e a c t i o n by some agent t o remove the n i t r i t e and provide a hydrogen i o n t o c e l l u l o s e . These r e quirements are met by p r o t o n i c n u c l e o p h i l i c species such as water, a l c o h o l , and o t h e r s . I f the régénérant-coagulant were water o r a l c o h o l then the spent r e g e n e r a t i o n bath would c o n t a i n n i t r o u s a c i d , H N 0 , and/or the a l k y l n i t r i t e , R0N0, i n a d d i t i o n t o the DMF and HNO3 introduced by the c e l l u l o s e s o l u t i o n . Any unreacted N 0 i n the c e l l u l o s e s o l u t i o n would r e s u l t i n the formation o f a d d i t i o n a l H N 0 (or RONO) and H N 0 . Because o f the r a p i d i t y of c o a g u l a t i o n and r e g e n e r a t i o n o f the c e l l u l o s e from the N 0 s o l u t i o n s , b a s i c f i b e r p r o p e r t i e s a r e determined t o a l a r g e extent by the composition o f the regenerat i o n bath and the s p i n n i n g c o n d i t i o n s employed immediately d u r i n g and a f t e r e x t r u s i o n . Therefore, i n i t i a l j e t s t r e t c h i s important i n determining the o v e r a l l f i b e r p h y s i c a l p r o p e r t i e s . As regene r a t i o n i s r e t a r d e d , godet t o godet s t r e t c h becomes more import a n t and more e f f e c t i v e but i s s t i l l l i m i t e d by the i n i t i a l j e t s t r e t c h . For example, r e g e n e r a t i o n can be r e t a r d e d by the 2

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In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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H A M M E R AND

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TURBAK

a d d i t i o n of bases such as p y r i d i n e to the c e l l u l o s e s o l u t i o n to n e u t r a l i z e the n i t r i c a c i d present. I n t h i s manner, a c e l l u l o s e n i t r i t e f i b e r can be obtained which i n i t i a l l y was observed to r e d i s s o l v e i n dimethylformamide. A wide range of s o l v e n t s may be used to regenerate the s o l u t i o n emerging from the s p i n n e r e t t e . V i r t u a l l y any l i q u i d which i s compatible w i t h and causes e x t r a c t i o n of the organic s o l v e n t and f u r t h e r d e - e s t e r i f i e s the c e l l u l o s e may be employed. A few of the s o l v e n t s which are a p p l i c a b l e to c o a g u l a t i o n i n c l u d e water, a wide range of a l c o h o l s , ethylene g l y c o l and mixtures of these or other p r o t i c s o l v e n t s w i t h dimethylformamide. In some cases, s p i n n i n g and the r e s u l t i n g f i b e r p h y s i c a l p r o p e r t i e s may be aided or improved by the presence of s o l u b l e s a l t s or bases i n the c o a g u l a t i o n bath. However, f o r such a process t o be commercially f e a s i b l e , such composition f i b e r p r o p e r t i e s and th cess f o r the chemicals i n v o l v e d . By v a r y i n g the composition of the r e g e n e r a t i o n or s p i n b a t h , i t i s p o s s i b l e to o b t a i n a wide v a r i e t y of f i b e r p r o p e r t i e s , from those of r e g u l a r rayon s t a p l e to medium-high performance rayon. For example, use of lower molecular weight a l c o h o l s such as methanol or ethanol a f f o r d s f i b e r s w i t h good t e n s i l e p r o p e r t i e s i n c l u d i n g wet modulus. The a d d i t i o n of s o l u b l e bases to such régénérants appears to improve wet s t r e n g t h w h i l e lowering Sg.^ and water r e t e n t i o n v a l u e s . The S g ^ values are an i n d i c a t i o n of a regenerated c e l l u l o s i c f i b e r ' s s o l u b i l i t y i n 6 . 5 $ sodium hydroxide at 20°C. This i s a u s e f u l t e s t f o r determining the p o t e n t i a l r e s i s t a n c e of such f i b e r s or r e s u l t a n t f a b r i c s to a l k a l i n e t r e a t ment such as a l k a l i n e l a u n d e r i n g or m e r c e r i z a t i o n . A c c o r d i n g l y , r e g u l a r v i s c o s e rayon which cannot be mercerized and i s not r e s i s t a n t to a l k a l i n e washing, unless c r o s s l i n k e d , has a r e l a t i v e l y high of from 2 5 - 3 5 $ . On the other hand, the h i g h p e r f o r mance and p o l y n o s i c rayons have s u p e r i o r r e s i s t a n c e to c a u s t i c soda as evidenced by S g ^ values of from 5 - 1 5 $ . We have r e c e n t l y found that i n a d d i t i o n to u s i n g s o l u b l e bases i n the primary r e g e n e r a t i o n b a t h , that t h i s important f i b e r p r o p e r t y can be obtained by c a r e f u l c o n t r o l of the c o n d i t i o n s employed d u r i n g s o l u t i o n p r e p a r a t i o n j l e , the temperature during N 0 a d d i t i o n and the r e s u l t a n t time and temperature f o r t o t a l d i s s o l u t i o n . Our s t u d i e s have d e f i n i t e l y e s t a b l i s h e d t h a t N0 o x i d a t i o n should be minimized so t h a t low temperatures of N 0 a d d i t i o n (below 10°C f o r example w i t h DMF) and short d i s s o l u t i o n times (k hours at l e s s than 20°C) are mandatory i f S g ^ l e v e l s are to be maintained i n a reasonable range ( 1 0 - 3 0 $ ) f o r commerc i a l u s e f u l n e s s of the r e s u l t i n g rayon f i b e r s . I t should be noted f u r t h e r t h a t i n t h i s s p i n n i n g system i t i s r e a d i l y p o s s i b l e to o b t a i n f i b e r s w i t h h i g h wet modulus w i t h out the use of z i n c or other a d d i t i v e s which are r e q u i r e d i n a v i s c o s e s p i n n i n g o p e r a t i o n . In a d d i t i o n , f i b e r s w i t h v e r y f i n e deniers can be r e a d i l y produced, eg. 0 . 5 d e n i e r , w h i l e m a i n t a i n #

e

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In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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Figure 1.

Fiber cross sections resulting from various coaguhnts (430X)

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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i n g reasonable t e n s i l e s t r e n g t h . Although optimum c o n d i t i o n s were not e s t a b l i s h e d , s u c c e s s f u l s p i n n i n g t r i a l s were e a s i l y performed at 115 meters/minute; f a s t e r speeds apparently being l i m i t e d o n l y by equipment and p o s s i b l y by l i q u i d f l o w c h a r a c t e r i s t i c s , but not by k i n e t i c s of r e g e n e r a t i o n . V a r i a t i o n s i n the type of régénérants r e s u l t s i n f i b e r s w i t h d i f f e r e n t c r o s s - s e c t i o n s . Water f o r example gives a s e r r a t e d , gear-shaped c r o s s - s e c t i o n ; methanol y i e l d s a c i r c u l a r c r o s s s e c t i o n ; isopropanol a f f o r d s i r r e g u l a r shapes; isoamyl a l c o h o l g i v e s a t r i l o b a l c r o s s - s e c t i o n ; b e n z y l a l c o h o l gives x-shaped s t r u c t u r e s and o c t a n o l a f f o r d s h o l l o w f i b e r s . S e v e r a l examples of these t y p i c a l c r o s s - s e c t i o n s obtained from c e l l u l o s e / N 0 / D M F s o l u t i o n s are i l l u s t r a t e d i n F i g u r e s 1 and 2 along w i t h those of F i b e r kO and r e g u l a r rayon. S i m i l a r f i b e r c r o s s - s e c t i o n s r e s u l t from c e l l u l o s e / ( N 0 ) / D M S Even the type of h o l l o r e g e n e r a t i o n bath appears to be c o n t r o l l a b l e . Filaments w i t h segments resembling bamboo are o b t a i n a b l e as w e l l as those w i t h v a r i o u s lengths of h o l l o w lumens i n the center of the f i b e r . The frequency of the segmentation appears c o n t r o l l a b l e , w i t h segments occurring 5 P i n c h or 25 per i n c h depending upon the combinat i o n of c o n d i t i o n s employed. In Figure h s t r e s s - s t r a i n curves [^conditioned ( c ) and wet f o r an a l k a l i n e methanol-spun f i b e r are shown f o r comparison w i t h r e g u l a r and high-wet modulus rayon. The shape of the wet curve i s of p a r t i c u l a r importance s i n c e the y i e l d i n g p o r t i o n s i s d i f f e r e n t from that of other rayons. Low e l o n g a t i o n i n the f i b e r r e s u l t s i n the steep slope of the c o n d i t i o n e d s t r e s s - s t r a i n curve f o r these f i b e r s and i s an i n d i c a t i o n of s t i f f n e s s . I f the cond i t i o n e d e l o n g a t i o n could be increased to 1 0 - 1 2 $ or the slope manipulated to f a l l between t h a t of high-wet modulus rayon and c o t t o n f o r example, a s u p e r i o r c e l l u l o s e f i b e r may be o b t a i n a b l e . In f a c t , e l o n g a t i o n s approaching 10$ were observed f o r f i b e r s spun from p y r i d i n e - s t a b i l i z e d c e l l u l o s e / N 0 / D M F s o l u t i o n and from runs employing low j e t s t r e t c h . Some t y p i c a l p h y s i c a l p r o p e r t y data are shown i n Table I emp l o y i n g a v a r i e t y of primary bath coagulants f o r the p r o d u c t i o n of rayon f i b e r s from s p i n n i n g s o l u t i o n s of 8/I5/77 c e l l u l o s e / N 0 / D M F composition. The wide range of p r o p e r t i e s obtained by v a r y i n g the chemical composition of the r e g e n e r a t i o n bath a f f o r d s an a p p r e c i a t i o n of the v e r s a t i l i t y of the system. Some p h y s i c a l property data are shown i n Table I I comparing some commercial rayons w i t h those produced from s p i n n i n g 8/15/77 c e l l u l o s e / N 0 / D M F s o l u t i o n s i n t o an isopropanol primary regenera t i o n bath. 2

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In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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Figure 2. Fiber cross sections resulting from various coagulants compared to viscose rayon (430X)

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Production of RdiJOn

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Figure S. Segmented hollow fiber IC

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STRESS-STRAIN CURVES

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2

4

R E G . RAYON

r

COM.HWM

t

\\ A If• / «

w 1

Ο

/

/

/

' W

•

f

10

20 30 E L O N G A T I O N (%)

Figure 4. Stress-strain curves of regular rayon, commercial high wet modulus rayon and rayon produced by régénérâting cellulose-N 0 -DMF solutions from alkaline methanol t

4

American Chemical Society Library 1155 16th St. N. W. In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; Washington, D. C. Society: 20036Washington, DC, 1977. ACS Symposium Series; American Chemical

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

13.2

9Λ

I.30 I.23 I.51

2.hk 2.29 2Λ8

3.^7 3.29

3.5

1.6

1.25

0.87

1.8

Water

Octanol

Methanol/1.5$ A l k o x i d e

Isopropanol/l.5$ Alkoxide

Methanol/10$ A l k o x i d e

1.90

2.13

11.7

1.U6

3.55

0.81

Methanol

8Λ

6-3

6.7

13.0

11.9

18.9

19.9

15.5

13.5

12.9

6.7

O.80

Isopropanol

2.26

3.58

Denier

Coagulant

Elongation, $ Cond. Wet

4

T e n a c i t y , g/d Cond. Wet

2

PROPERTIES OF FIBERS PREPARED FROM AN 8/I5/77 CELLULOSE/N 0 /DMF SOLUTION

TABLE I

1.19

0.98

0Λ9

0.37

0.51

0.73

0.8U

Wet Modulus,

I

i

Ο

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

3.5-8.Ο

2.0-3.6

High Wet Modulus Rayon

8/15/77 C e l l u l o s e / N 0 /DMF F i b e r

4

3.5-5.0

Intermediate Wet Modulus Rayon

2

1.5-2.8

1.5-2Λ

2.5-6.0

2.5-3.5

1.0-1.8

T e n a c i t y , g/d Cond. Wet

Regular Rayon

Staple Type

6-19

6-ik

12-19

lU-25

10-15

9-18

18-2U

18-35

Elongation, $ Cond. Wet

FIBER PHYSICAL PROPERTIES

TABLE I I

0.7-1.7

0.7-3.0

ΟΛ5-Ο.60

0.18-0.28

&M

Wet Modulus

20-80

5-10

15-20

20-35

50

S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FIBERS

Conclusions A wide range of pulps have been found t o r e a d i l y d i s s o l v e i n the N 0 /DMF system i n c l u d i n g non-debarked experimental samples. However, groundwood f u r n i s h , such as i s employed f o r news p r i n t w i l l not d i s s o l v e i n t h i s system. The pulps may be used i n e i t h e r a f l u f f e d , Abbe^cut, shredded or d i c e d sheet form without encountering d i s s o l u t i o n problems. The c o n c e n t r a t i o n of pulp which can be used depends upon the degree of p o l y m e r i z a t i o n . At 1000 D.P., c o n c e n t r a t i o n s up to 3$ can be spun w h i l e a t U00~500 D.P. up t o 8$ s o l u t i o n s were f e a s i b l e , w h i l e a t 300 D.P. up t o 10$ c e l l u l o s e s o l u t i o n s could be r e a d i l y processed. Dimethyl formamide was found t o be p r e f e r a b l e to d i m e t h y l s u l f o x i d e or a c e t o n i t r i l a l l solution properties e s s e n t i a l l y f r e e from g e l s or f i b e r s t h e r e f o r e r e q u i r i n g o n l y a s i n g l e stage p o l i s h i n g f i l t r a t i o n p r i o r t o s p i n n i n g . The temperature of the N 0 a d d i t i o n and the time of d i s s o l u t i o n were found t o be c r i t i c a l l y r e l a t e d t o the f i n a l Sg c f i b e r l e v e l s . For example, by m a i n t a i n i n g the temperature below 20°C, the S6.5 l e v e l can be h e l d i n the 2 7 - 3 0 $ range which i s s i m i l a r t o t h a t of r e g u l a r rayon. C o a g u l a t i o n and r e g e n e r a t i o n of the c e l l u l o s e / N 0 / D M F s o l u t i o n s i s extremely r a p i d i n the presence of proton donor systems. F i b e r s of e x c e l l e n t h i g h wet modulus eg. up to 1 . 7 g/d can be spun w i t h o u t the need f o r s p i n - b a t h a d d i t i v e s . Spinning speeds of 115 meters per minute were achieved employing o n l y a 3 i n c h primary bath c o a g u l a t i o n t r a v e l l e n g t h . No attempts were made t o o p t i m i z e f i b e r p h y s i c a l p r o p e r t i e s a t t h i s h i g h e r s p i n n i n g speed, which was the maximum speed o b t a i n a b l e and was l i m i t e d by the godet s i z e and motor d r i v e u n i t s . Conditioned f i b e r s t r e t c h g e n e r a l l y was between 7 $ and 10$ which i s n o r m a l l y too low f o r p r o c e s s i n g . However, t h i s l e v e l c o u l d be improved by proper c o n t r o l of j e t s t r e t c h t o godet s t r e t c h r a t i o s . F i b e r cross s e c t i o n a l shapes can be c o n t r o l l e d by the use of v a r i o u s molecular weight a l c o h o l s t o g i v e e i t h e r round, s e r r a t e d , "X" or "Y" shapes or even segmented h o l l o w f i b e r s . These f i b e r s d i s p l a y e x c e l l e n t cover power as compared to r e g u l a r HWM rayon i n k n i t s . 2

4

2

4

2

4

Acknowledgements We are g r a t e f u l t o Dr. A r t h u r C. West* who performed much of the i n i t i a l b a s i c r e s e a r c h and e x p e r i m e n t a t i o n i n v o l v e d i n this investigation. * Present Address - 3-M Company, S t . P a u l , Minnesota

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

4.

H A M M E R AND TURBAK

Literature

51

Production of Rayon

Cited

1.

Fowler, W. F. and Kenyon, W. O., J. Amer. Chem. Soc., 69

2. 3.

W i l l i a m s , H. D., U.S. Patent No. 3 , 2 3 6 , 6 6 9 ( 1 9 6 6 ) . H e r g e r t , H. L. and Z o p o l i s , P. N., French Patent No.

4.

a)

5.

6.

1636

(1947).

1,469,890

(1967).

Nakao, O. et. al Canadian Patent No. 8 7 6 , 1 4 8

b ) U.S. Patent No. 3 , 6 6 9 , 9 1 6

(1971),

(1972).

Clermont, L. P., (a) Canadian Patent No. 8 9 9 , 5 5 9 ( 1 9 7 2 ) ; (b) Monthly Research Notes, Dept. o f F i s h e r y and F o r e s t r y , Canada 2 6 , No. 6, 58 (1970); ( c )J.P o l y . Sci., 1 0 , 1669 ( 1 9 7 2 ) ; (d) J. Appl. Poly. Sci., 1 8 , 133 (1974). Schweiger, R. G. (a) Chemistry and Industry 296 ( 1 9 6 9 ) ; (b) U.S. Patent No.

2,120,964 (1971).

7. 8. 9·

Chu, Ν. J., Pulp and Paper Research I n s t i t u t e o f Canada, Report No. 42 ( 1 9 7 0 ) . Pasteka, M. and M i s l o v i c o v a , D., C e l l u l o s e Chemistry and Technology 8 , 107 (1974). Portnoy, Ν. Α., Unpublished R e s u l t s .

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

5 Chemistry of the

Cellulose-N2O4-DMF

Solution:

Recovery and Recycle of Raw Materials NORMAN A. PORTNOY and DAVID P. ANDERSON ITT Rayonier, Inc., Eastern Research Div., Whippany,N.J.07981

The purpose of th tablish a foundation f o r a technically viable recovery and recycle system based on spinning rayon fibers from the cellulose/ N O /DMF s o l u t i o n . Other papers in this symposium d i s c u s s e d solution makeup, s p i n n i n g , and fiber p r o p e r t i e s . The paper presented h e r e , which is d i v i d e d into two parts, attempts t o e x p l a i n some o f the chemistry of dissolution and r e g e n e r a t i o n as well as our efforts in developing a technically f e a s i b l e recovery and recycle system. 2

A.

4

The Chemistry o f The

Cellulose/N O /DMF 2

4

Solution

Introduction When t h e i n v e s t i g a t i o n of this system was initiated, t h e importance of d e l i n e a t i n g t h e exact mode of dissolution o f t h e cellulose in DMF/N O was r e c o g n i z e d . To understand t h e dissolution step and t o p r o p e r l y formulate a recovery and r e c y c l e system, a thorough study o f the chemistry of cellulose in DMF/N O had t o be undertaken. From a theoretical viewpoint, s e v e r a l possibilities as t o the mechanism of cellulose d i s s o l u t i o n in DMF/N O a r e e v i d e n t . The s i m p l e s t would be a r e a c t i o n between the h y d r o x y l groups of cellulose and N O t o form a cellulose nitrite e s t e r and HNO as shown in equation 1 (mechanism 1). This c e l l u l o s e nitrite e s t e r may then be s o l u b l e in DMF. DMF DMF 1 . ) CellOH + N 0 OCellONO + HNO3 >solution. The components o f such a s o l u t i o n would be c e l l u l o s e n i t r i t e , n i t r i c a c i d (HNO3), unreacted N2O4, and DMF. T h i s k i n d of r e a c t i o n between a l c o h o l s and N2O4 i s w e l l known and has been ext e n s i v e l y documented i n the l i t e r a t u r e f o r a wide range of 2

4

2

2

2

4

4

3

2

4

52

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

4

5.

PORTNOY AND ANDERSON

Cellulose-N0 -DMF Solution t

4

53

a l c o h o l s . Since c e l l u l o s e i s an a l c o h o l i t should r e a c t i n t h e same manner, A second p o s s i b i l i t y i s t h a t a complex, probably of the donor-acceptor type, between c e l l u l o s e and N2O4 forms and t h a t DMF acts as a s o l v e n t f o r t h i s complex as i n equation 2 (mechanism 2) · DMF 2 · ) CellOH + N 0 > CellOH : N 0 > solution 2

4

2

4

In t h i s case the s p i n n i n g s o l u t i o n would c o n t a i n t h e c e l l u l o s e : N2O4 complex, uncomplexed N2O4 and DMF. A t h i r d p o s s i b i l i t y i s t h a t DMF and N2O4 form a donor-acceptor complex i n which c e l l u l o s e i s s o l u b l e as i n equations 3 a and 3b (mechanism 3 ) · eq. 3 a . )

DMF + N2O

eq. 3 b . )

DMF : N C>4 2

+

C e l l O H — > solution

This s o l u t i o n would c o n t a i n unchanged c e l l u l o s e , DMF 1 ^ 0 4 complex and uncomplexed DMF as t h e s o l v e n t . An a d d i t i o n a l p o s s i b i l i t y would be t h a t d i s s o l u t i o n may occur v i a some combination of the above mechanisms. I t f o l l o w s t h a t the mechanism of d i s s o l u t i o n and thus the chemistry of the c e l l u l o s e 1^04:DMF i n t e r a c t i o n s i s v e r y important s i n c e t h i s w i l l determine not only the composition of the s p i n n i n g s o l u t i o n , s p i n n i n g procedures, and f i b e r p r o p e r t i e s , but a l s o the recovery and r e c y c l e process. Since some o f the above mechanisms r e q u i r e complexation between the c e l l u l o s e and N2O4 or between the DMF and N2O4, i t appeared t h a t during s p i n n i n g the c e l l u l o s i c f i b e r s (rayon) might not r e q u i r e a chemical regenerat i n g r e a c t i o n but might be p r e c i p i t a t e d o r coagulated by a nons o l v e n t system. T h i s could be e s p e c i a l l y t r u e f o r mechanism 3 s i n c e i t r e q u i r e s t h a t c e l l u l o s e remain unchanged and be simply s o l v a t e d by a DMF 1 ^ 0 4 complex. However, i f mechanism 1 were o p e r a t i v e , then a t r a n s n i t r o s a t i o n r e a c t i o n such as h y d r o l y s i s or a l c o h o l y s i s would be necessary t o o b t a i n regenerated c e l l u l o s e . One c o n c e i v a b l e advantage of such a system i s the poss i b i l i t y o f c o n t r o l of molecular o r i e n t a t i o n d u r i n g r e g e n e r a t i o n and s p i n n i n g by c o n t r o l of t h e removal of the n i t r i t e groups. Such i n c r e a s e d c o n t r o l would r e s u l t from the p l a s t i c i t y of t h e c e l l u l o s e n i t r i t e d e r i v a t i v e p e r m i t t i n g o r i e n t a t i o n and i s r e s p o n s i b l e f o r t h e l a r g e v a r i e t y of s t r o n g rayon f i b e r s a v a i l a b l e from the v i s c o s e process, i n which case the i n t e r m e d i a t e i s c e l l u l o s e xanthate. By c o n t r a s t , i f c e l l u l o s e i s merely p r e c i p i t a ted or coagulated from a s o l v e n t the p o s s i b i l i t y of t h i s c o n t r o l i s severely l i m i t e d . As a f u r t h e r consequence, the nature of the u l t i m a t e s p i n ning system i s r e l a t e d t o t h e d i s s o l u t i o n mechanism by the a c t u a l composition of t h e cellulose/N204/DMF s o l u t i o n . I f t h e s p i n n i n g s o l u t i o n contained unreacted c e l l u l o s e as i n mechanism 3 ,

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

54

S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FIBERS

then a dry s p i n n i n g system might be developed i n which the c e l l u lose/N204/DMF s o l u t i o n i s spun i n t o an evacuated chamber t o r e move the s o l v e n t s and p r e c i p i t a t e the f i l a m e n t s . This would be s i m i l a r t o the process f o r s p i n n i n g c e l l u l o s e d i a c e t a t e from acetone s o l u t i o n . Advantages t o t h i s are the h i g h speeds o f s p i n ning which are p o s s i b l e and the r e l a t i v e s i m p l i c i t y of the r e covery system which would have only t o r e c y c l e the DMF : N 2 O 4 complex. However, i f c e l l u l o s e had t o be regenerated from a c e l l u l o s e d e r i v a t i v e , i n t h i s case a n i t r i t e e s t e r , more complexity would be i n v o l v e d i n recovery and r e c y c l e . As p r e v i o u s l y e x p l a i n e d , r e g e n e r a t i n g c e l l u l o s e during s p i n n i n g from a t r u e c e l l u l o s e n i t r i t e e s t e r would r e q u i r e a t r a n s n i t r o s a t i o n r e a c t i o n by some agent t o remove the n i t r i t l o s e . These requirement such as water, a l c o h o l , o r o t h e r s . I f the regenerant-coagulant were water o r a l c o h o l , then the spent s p i n bath would c o n t a i n n i t r o u s a c i d , H N O 2 , o r the a l k y l n i t r i t e , RONO, i n a d d i t i o n t o the DMF and H N O 3 from the s p i n n i n g s o l u t i o n , eq, 4 . Any unreacted N 2 O 4 i n the s p i n n i n g s o l u t i o n would make a d d i t i o n a l H N O 2 (or RONO) and H N O 3 i n the s p i n bath, eq. 5 . 4. )

5.

CellONO + H 0 (or ROH) regeneration

C e l l OH + HONO (or RONO)

2

) HOH (or ROH)

+ excess N 04-*HONO (or RONO) + 2

HNO3

T o t a l recovery and r e c y c l e , i n t h i s case, would i n v o l v e s p l i t t i n g the s p i n bath i n t o a t l e a s t 4 components and r e c y c l i n g DMF and H 0 ( o r ROH) w h i l e changing RONO (or HONO) and H N O 3 i n t o a form from which N 2 O 4 could be r e a d i l y obtained. Thus, one of the f i r s t questions t o be answered was whether the s p i n n i n g s o l u t i o n contained c e l l u l o s e n i t r i t e . 2

R e s u l t s and D i s c u s s i o n T h i s q u e s t i o n was answered by chemical and s p e c t r a l s t u d i e s . Because o f the h i g h l y complex nature of the s o l u t i o n , simple s t u d i e s using reagents to measure n i t r i t e composition were not p o s s i b l e . The accuracy o f any method using d i a z o t i z i n g reagents or o x i d a t i o n - r e d u c t i o n r e a c t i o n s to measure the c o n c e n t r a t i o n o f H N O 3 o r CellONO would be hampered by the strong o x i d i z i n g a b i l i t y of the excess N 2 O 4 . Studies i n which the s p i n n i n g s o l u t i o n was p r e c i p i t a t e d w i t h water i n a Waring Blender and the r e s u l t a n t c e l l u l o s i c m a t e r i a l then analyzed f o r n i t r o g e n and c a r b o x y l r e s i dues showed t h a t there was no i n c r e a s e i n these over s t a r t i n g p u l p , but there was a s l i g h t l o s s i n D.P. Thus any n i t r i t e d e r i v a t i v e which was being formed d u r i n g d i s s o l u t i o n was not s t a b l e t o c o a g u l a t i o n w i t h water. T h i s s u b s t a n t i a t e d the claims

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

5.

Cellulose-N O -DM F Solution

PORTNOY A N D ANDERSON

55

4

t

of e a r l i e r workers. I n f r a r e d s t u d i e s were not p e r t i n e n t s i n c e the n i t r i t e (N«0) a b s o r p t i o n occurs a t r*u 6 . Ou which i s i n d i r e c t c o n f l i c t w i t h the amide c a r b o n y l a b s o r p t i o n of DMF so any spect r a l i d e n t i f i c a t i o n on an i n f r a r e d b a s i s would be considered tenuous · Schweiger (1) had reported that a t r u e c e l l u l o s e n i t r i t e e s t e r could be i s o l a t e d from the c e l l u l o s e / N 0 / D M F s o l u t i o n by f i r s t s t a b i l i z i n g the s o l u t i o n w i t h an a c i d scavenger such as p y r i d i n e and then p r e c i p i t a t i n g the n i t r i t e e s t e r by water coagu l a t i o n . These experiments were repeated. P y r i d i n e was added t o the 8/15/77 c e l l u l o s e / N 0 / D M F s o l u t i o n a t a l e v e l of 20% by weight o f the s o l u t i o n and t h i s was spread on a g l a s s p l a t e . The p l a t e was then immersed i n 20% p y r i d i n e / 8 0 % water a t 5°C and an opaque f i l m ( c e l l u l o s e always formed a c l e a r f i l m ) was c o a g u l a t e d This f i l m was s o l u b l e i vents so i t was o b v i o u s l The UV-VIS. spectrum i n the 300 - 450 my r e g i o n of a DMF s o l u t i o n of the r e - d i s s o l v e d f i l m was n e a r l y i d e n t i c a l t o t h a t of i s o p r o p y l - , 1-pentyl- o r c y c l o h e x y l - n i t r i t e which were prepared as model compounds by adding N 0 t o a DMF s o l u t i o n of t h e corresponding a l c o h o l . When s e v e r a l drops o f aqueous H S 0 were added t o the UV c e l l and the s p e c t r a were rescanned, a l l of t h e above, the model a l k y l n i t r i t e s and the r e d i s s o l v e d f i l m , gave e x a c t l y the same spectrum. This new spectrum was i d e n t i c a l t o that o f an a c i d i f i e d DMF s o l u t i o n o f sodium n i t r i t e i n d i c a t i n g t h a t a l l of these compounds, the a l k y l n i t r i t e s and " c e l l u l o s e n i t r i t e " , were r e l e a s i n g n i t r o u s a c i d thus confirming t h a t the new m a t e r i a l d i d c o n t a i n the n i t r i t e moiety. Table I shows the UV-VIS. p o s i t i o n s and i n t e n s i t i e s o f v a r i o u s n i t r i t e m o i e t i e s used f o r comparison purposes i n t h i s s t r u c t u r e p r o o f . Figures 1 and 2 show the UV-VIS. s p e c t r a of DMF s o l u t i o n s of amyl n i t r i t e , " c e l l u l o s e n i t r i t e " , sodium n i t r i t e and sodium n i t r a t e b e f o r e and a f t e r a c i d i f i c a t i o n . When the " c e l l u l o s e n i t r i t e " f i l m was d r i e d , brown gas evolved from the f i l m and i t then became i n s o l u b l e i n those s o l v e n t s i n which i t had p r e v i o u s l y d i s s o l v e d . The i n f r a r e d spectrum of t h i s i n s o l u b l e d r i e d f i l m was i d e n t i c a l t o t h a t of c e l l u l o s e . This s p e c t r a l study r e p r e sents the f i r s t d e f i n i t i v e p r o o f t h a t the m a t e r i a l i s o l a t e d by c o a g u l a t i o n of t h e p y r i d i n e - s t a b i l i z e d c e l l u l o s e / N 2 0 / D M F s o l u t i o n was indeed c e l l u l o s e n i t r i t e . I t was d e s i r a b l e t o have chemical as w e l l as s p e c t r a l i d e n t i f i c a t i o n of the s t r u c t u r e of t h i s new m a t e r i a l . I n t h i s r e gard, a method was developed f o r i s o l a t i n g a s o l i d from the p y r i d i n e - s t a b i l i z e d s o l u t i o n s under anhydrous c o n d i t i o n s . This was accomplished by t h e a d d i t i o n of d i e t h y l ether t o the p y r i dine s t a b i l i z e d c e l l u l o s e / N 0 / D M F s o l u t i o n s causing p r e c i p i t a t i o n of a s o l i d . A d d i t i o n of 1-pentyl a l c o h o l t o the DMF s o l u t i o n of t h i s s o l i d caused p r e c i p i t a t i o n of a w h i t e f i b r o u s m a t e r i a l which was l a t e r i d e n t i f i e d as c e l l u l o s e . D i s t i l l a t i o n 2

2

4

4

2

4

2

4

2

4

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

4

S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FIBERS

56

TABLE I Positions and Intensities of N i t r i t e Ultraviolet Absorption Peaks Sample No.

Compound

Major Peaks max (my) 370 67.2 357 78.9 345 67.2 333 46.8 a

Minor Peaks or Shoulders max (my) a 385 32.2 323 30.2

1.

Amyl N i t r i t e

2.

Isopropyl N i t r i t e

373

55.4

385

31.2

3.

Cyclohexyl N i t r i t e

372 360

58.4 57.8

390 348 338

32.4 44.5 29.7

4.

"Cellulose N i t r i t e "

366 353 341

380 331 320

5.

Sodium N i t r i t e

359

25.5

6.

Sodium Nitrate

310

44

7.

Sodium Nitrate with acid added

270

69

389 375 361 349 338

49.0 80.8 72.0 47.6 37.5

8.

1, 3, 4 or 5 with acid added b

a.) b.)

€

β

molar extinction coefficient.

The values for € are from the experiment i n which H2SO4 was added to the sodium n i t r i t e solution.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

5.

PORTNOY AND ANDERSON

57

Cellulose-N O DMF Solution t

r

a. NaN02, DMF

Figure 2. Uv-vis spectra of aqueous acidified DMF solu­ tions of cellONO or AmylONO as well as NaNO and NaNO before and after aque' ous acidification t

400

Λου WAVELENGTH

(mp)

450

s

, Ί . Γ

. !

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FD3ERS

58

of the supernatant gave a 60% y i e l d of 1-pentyl n i t r i t e which was i d e n t i c a l to commercial m a t e r i a l i n p h y s i c a l and s p e c t r a l properties. Therefore i t was a c e r t a i n t y t h a t the p y r i d i n e - m o d i f i e d cellulose/N^O^/DMF s o l u t i o n contained c e l l u l o s e n i t r i t e . I t could be argued however, t h a t the p y r i d i n e not only s t a b i l i z e d the c e l l u l o s e n i t r i t e but a l s o c a t a l y z e d the f o r m a t i o n of t h i s s p e c i e s as p y r i d i n e i s w i d e l y used i n s y n t h e t i c chemistry f o r c a t a l y s i s i n d e r i v a t i z i n g a l c o h o l s ( c e l l u l o s e i s an a l c o h o l ) w i t h anhydrides (N2O4 i s an a n h y d r i d e ) . S p e c t r o s c o p i c s t u d i e s on the cellulose/N204/DMF s o l u t i o n d i d not show t h a t the n i t r i t e was p r e s e n t , i n f a c t UV-VIS. s p e c t r a of the s o l u t i o n are almost the same as those of n i t r o u s a c i d . T h i s i s the r e s u l t of the excess N2O4 which has b a s i c a l l the same UV-VIS spectrum as n i t r o u s a c i d probably because group. However, s y n t h e t i c o h o l s , such as c y c l o h e x a n o l or i s o p r o p a n o l r e a c t immediately w i t h DMF s o l u t i o n s of N2O4 a t 5°C i n the absence of p y r i d i n e and s i n c e c e l l u l o s e i s an a l c o h o l , i t i s expected t o r e a c t s i m i l a r l y .

B.

Recovery and Recycle of Raw M a t e r i a l s

Introduction The e n t i r e area of research and development a s s o c i a t e d w i t h the recovery and r e c y c l i n g of process chemicals i s c e n t r a l t o the t e c h n i c a l and commercial success of s p i n n i n g f i b e r s from o r ganic s o l v e n t s . With the chemistry background presented e a r l i e r i t appeared necessary to develop the recovery system based on p r o c e s s i n g the f o l l o w i n g : a. ) Dimethylformamide (DMF) b. ) Coagulant ( e i t h e r an a l c o h o l o r water) c. ) N i t r o g e n T e t r o x i d e (N2O4) 1.

When the coagulant i s water, then n i t r o u s a c i d (HNO2) and n i t r i c a c i d (HNO3) are the p r e c u r s o r s to N2O4 recovery.

2.

When the coagulant i s an a l c o h o l , then the a l c o h o l n i t r i t e (RONO) and HNO3 a r e the p r e c u r s o r s to N2O4 recovery.

An i n i t i a l c o n c e p t u a l i z a t i o n of the recovery and r e c y c l e system i s shown i n F i g u r e 3 which served as a p r e l i m i n a r y s k e t c h of the requirements of recovery and r e c y c l e f o r s p i n n i n g rayon f i b e r s from the cellulose/N2O4/DMF system. T h i s f i g u r e shows that the crude spent s p i n bath, c o n t a i n i n g DMF, HNO3, the coagu-

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

SPIN B A T H DMF i-PrOH HNO3 i-PrONO

i-PrOH

4

2

HN0 ,HN03

HNO3

HN02

HNO2

HYDROLYSIS

μρΓΟΝΟ

HNO3

S Ε Ρ A R A Τ I Ο Ν

2

N 0

RAYON FIBER

NOf NO? SALTS

Η

NEUTRALIZATION H ^ J P Y R O L Y S I S

t

k

Figure 3. Initial conceptualization of the total recycle and recovery system for spinning rayonfibersfrom CeUOH-N O -DMF solutions

N2O4 HNO3

Solu. M A K E U P l CallONO DMF

DMF

60

S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FIBERS

l e n t ( e i t h e r HOH o r ROH) and the n l t r o s a t e d coagulant ( e i t h e r HONO o r R0N0) must be separated i n t o f r a c t i o n s o f pure DMF, pure coagulant and the HN0 -HN0 (R0N0) f r a c t i o n s . The DMF must be returned t o the s o l u t i o n makeup, the coagulant t o the s p i n b a t h and the H N O 3 - H N O 2 (R0N0) p o r t i o n of the spent bath must be comb i n e d i n some way f o r c o n v e r s i o n t o N 2 O 4 . I f t h i s i s the o v e r a l l p l a n , then two major areas of r e s e a r c h would be necessary t o answer the f o l l o w i n g two q u e s t i o n s : a.) which methods o f separat i o n would be most e f f e c t i v e f o r the i n i t i a l s e p a r a t i o n o f t h e crude s p i n bath and b.) how can the n i t r i c and n i t r o u s a c i d f r a c t i o n s r e s u l t i n g from c e l l u l o s e d i s s o l u t i o n and r e g e n e r a t i o n be recombined t o form N 2 O 4 . I n a d d i t i o n , i f the n i t r o u s p o r t i o n of the o r i g i n a l N 0 ^ i s i n the a l k y l n i t r i t e form, i . e . because o f an a l c o h o l coagulant-régénérant the method f o c o n v e r t i n HNO3 and R0N0 to N 2 O 4 woul 3

2

2

R e s u l t s and D i s c u s s i o n The recovery and r e c y c l e of N2O4 was s t u d i e d f i r s t . An ext e n s i v e l i t e r a t u r e survey on N 2 O 4 - H N O 3 chemistry uncovered seve r a l commercial processes which i n c l u d e d a step f o r p y r o l y z i n g a metal n i t r a t e s a l t to produce N 2 O 4 i n h i g h y i e l d s . Most of these processes i n v o l v e d decomposing c a l c i u m n i t r a t e i n a CO2 atmosphere (2) o r sodium n i t r a t e i n a CO atmosphere.(3) None of these r e p o r t s mentioned the recovery of N2O4 by p y r o l y z i n g a n i t r i t e s a l t o r a potassium s a l t as an i n d u s t r i a l p r o c e s s . S e v e r a l methods were considered r e l a t i v e t o the conversion of the HNO3 and HNO2 p o r t i o n o f the spent s p i n bath t o a s a l t and r e c o v e r y of t h i s s a l t f o r p y r o l y t i c p r o c e s s i n g . These methods i n c l u d e d : a.) P r e c i p i t a t i o n o f the s a l t - i f the coagulant were aqueous, then the spent s p i n bath c o n t a i n i n g HNO2 and HNO3 c o u l d be n e u t r a l i z e d t o form s a l t s . F o l l o w i n g t h i s , a d d i t i o n of a s u i t a b l e non-solvent such as a l c o h o l c o u l d p r e c i p i t a t e the s a l t s . T h i s presented unique problems s i n c e the s o l u b i l i t y of K N O 3 i s r e l a t i v e l y s m a l l (1.5%) i n M F , but t h a t o f Ca(N0 )2 or NaN03 i s /•^15-20%. I f the s p i n bath contained a l c o h o l as the coagulant then a h y d r o l y s i s s t e p , t o convert R0N0 to HONO, would precede the a c i d n e u t r a l i z a t i o n . However, i n such a non-aqueous b a t h , the p o s s i b i l i t i e s o f u s i n g other water i m m i s c i b l e précipitants such as methylene c h l o r i d e o r ether were r e c o g n i z e d . When s t u d i e s were done, e f f e c t i v e methods o f p r e c i p i t a t i n g K N O 3 and NaNOo but not C a ( N 0 o ) were found as can be seen i n Table I I . 3

2

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

5.

PORTNOY A N D ANDERSON

61

Cellulose-NODMF Solution t r

TABLE I I S o l u b i l i t i e s of N i t r a t e S a l t s i n D M F ^ P r e c i p i t a t i n g Solvent Mixtures ' Salt Left Precipitating % P r e c i p i t a t i n g Solvent* / D i s s o l v e d i n M i x t u r e Pb(N0 ) NaN0 KN0 Solvent Ca(N03) 0

1

e

3

3

3

2

0/1.1

0/14.2

0/18.0

0/130

None ( L i t . ) ( 4 ) 0/1.5

0/15.4

N. A.

N. A.

50/18.0

49/3.3

59.7/4.3

N. D.

N. D.

None (Exp·)

N

15.7/

2°4

0.5

47.5/

1

MeOH

63.4/1.

EtOH

N. D.

i-PrOH

61.5/

0.5

60.3/

1

56.5/18.0

64/

Ether

59.4/

0.5

39.7/

1

61.3/18.0

N. D.

N. D.

N. D.

CH2C1 a) b) c)

2

73/

67/1.2

1

N. A. - not a v a i l a b l e N.D. •» no data obtained N 0 ^ « d i n i t r o g e n t e t r o x i d e , MeOH = methyl a l c o h o l , EtOH = e t h y l a l c o h o l , i-PrOH = i s o p r o p y l a l c o h o l , CH C1 » methylene c h l o r i d e , ether = d i e t h y l e t h e r % P r e c i p i t a t i n g s o l v e n t based on t o t a l mixture g. s a l t / 1 0 0 g DMF 2

2

d) e)

0.5

2

2

b.) D i s t i l l a t i o n of a l l l i q u i d t o leave a s a l t r e s i d u e - i f the coagulant were aqueous, then n e u t r a l i z a t i o n of the a c i d s f o l lowed by d i s t i l l a t i o n t o a s o l i d s a l t r e s i d u e (the p o t e n t i a l f o r d e t o n a t i o n a t t h i s p o i n t due t o the nitrate-DMF mixture was recogn i z e d e a r l y i n our work) would appear t o be v i a b l e . I f the coagul a n t were a l c o h o l , then as s t a t e d above, the h y d r o l y s i s step would precede the n e u t r a l i z a t i o n s t e p . A l t e r n a t e l y , the HNO3 port i o n o f the s p i n bath could be n e u t r a l i z e d p r i o r t o d i s t i l l a t i o n , the s p i n bath d i s t i l l e d t o a s a l t r e s i d u e and the a l c o h o l n i t r i t e p o r t i o n recovered from the d i s t i l l a t i o n , h y d r o l y z e d , n e u t r a l i z e d and then the n i t r i t e s a l t recovered a f t e r l i q u i d s t r i p p i n g . L i t e r a t u r e a v a i l a b l e on the recovery of DMF from aqueous systems i n d i c a t e d that acceptable y i e l d s could be obtained by d i s t i l l a t i o n . (5) The d i s t i n c t d i f f e r e n c e between schemes (a) and (b) was t h a t i n scheme (a) , the DMF would n o t r e q u i r e d i s t i l l a t i o n . H o p e f u l l y t h i s would have l e d t o lower economics f o r scheme (a) than scheme (b).

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

62

S O L V E N T S P U N R A Y O N , MODIFIED C E L L U L O S E FD3ERS

c.) Countercurrent e x t r a c t i o n of the aqueous-DMF spent s p i n bath - t h i s would o n l y a p p l y f o r aqueous s p i n baths. Commercial methods f o r c o u n t e r c u r r e n t e x t r a c t i o n of DMF from aqueous-DMF s o l u t i o n s were d e s c r i b e d i n d e t a i l i n the l i t e r a t u r e . ( 6 ) A v a r i e t y of e x t r a c t a n t s i n c l u d i n g chlorocarbons and hydrocarbons were e v a l u a t e d . The c o n c l u s i o n of t h i s l i t e r a t u r e study was that methylene c h l o r i d e was the most e f f i c i e n t e x t r a c t a n t and t h a t the process was economically f e a s i b l e when the aqueous-DMF contained l e s s than 10% DMF. R e s u l t s i n t h i s l a b o r a t o r y d i d not show p r o mise p r o b a b l y because the aqueous DMF spent s p i n baths contained a c i d or s a l t components which complicated e x t r a c t i o n . Recovery of the coagulant p o r t i o n of the s p i n b a t h , i . e . water or an a l c o h o l would be, i n a s i n s e , a l i m i t i n g f a c t o r s i n c e , depending on the composition of the s p i n b a t h v e r y l a r g e volumes would be i n v o l v e p l a i n e d . Although som 8/25/67 cellulose/NoO^/DMF s o l u t i o n s , a d e c i s i o n was made, based on comparative s t u d i e s between 8/25/67 and 8/15/77 s p i n n i n g s o l u t i o n s , t o make the d e t a i l e d process e v a l u a t i o n on an 8/15/77 c e l l ulose/N204/DMF s o l u t i o n . T h i s r e q u i r e s t h a t 1.88 l b s . of N 04 and 9.63 l b s . of DMF be r e c y c l e d per 1.00 l b . of processed f i b e r i n a d d i t i o n t o the coagulant p o r t i o n of the s p i n b a t h . For example, i f the s p i n bath were at e q u i l i b r i u m and were 58/31/5/6, i s o p r o p y l a l c o h o l (i-PrONO/DMF/HN0 /isopropyl n i t r i t e (i-0r0N0) then a t o t a l of/-' 28.3 l b s . (9.63 l b s . DMF and 18.64 l b s . of i-PrONO) of l i q u i d would have t o be r e c y c l e d per 1.00 l b . of f i b e r processed. I f the s p i n bath were aqueous-DMF at a l e v e l of 20% H2O then a minimum of 12.0 l b s . of l i q u i d would be r e c y c l e d per 1.00 l b . of processed f i b e r . These represent examples of how the s p i n b a t h composition s e t s a lower l i m i t on the amount of chemic a l s which must be processed. Therefore the economics of a comm e r c i a l process depend g r e a t l y on the s p i n b a t h composition. I n i t i a l s p i n n i n g experiments i n d i c a t e d t h a t alcohol-DMF s p i n baths produced b e t t e r f i b e r s than aqueous-DMF s p i n b a t h s . Pure methyl-, e t h y l - or i s o p r o p y l - a l c o h o l as coagulant-regenerants produced f i b e r s w i t h approximately e q u i v a l e n t p h y s i c a l p r o p e r t i e s . Since methyl n i t r i t e i s a t o x i c gas and e t h y l n i t r i t e has a v e r y low b o i l i n g p o i n t , they are d i f f i c u l t t o handle at an e x p e r i mental l e v e l . However, i s o p r o p y l n i t r i t e (i-PrONO) i s reasona b l y easy t o handle and t h e r e f o r e i-PrOH was chosen as the coa g u l a n t - régénérant f o r d e t a i l e d recovery s t u d i e s . The p h y s i c a l p r o p e r t i e s of f i b e r s coagulated i n alcohol-DMF systems decreased as the l e v e l of DMF i n c r e a s e d , the b e s t f i b e r s having been spun from pure a l c o h o l primary s p i n b a t h s . However, i t was apparent t h a t , f o r economic reasons, some l e v e l of a l c o h o l i n DMF would have to be chosen and the f i b e r p r o p e r t i e s maximized f o r t h i s chosen system. An i-PrOH/DMF r a t i o of 2/1 was chosen and thus when r e c o v e r y s t u d i e s were begun, s y n t h e t i c spent s p i n baths of 2

3

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

b. )

80.5 95.5

165.2 99.5

78.0 96.7

76.9

164.3

75.4

96.8

41.1

79.1

23.4

18.5

39.8

5.1 11.0

0.0

0.0

2.4

2

H0

39.8

0.0

0.0

0.0

0.0

HNO3 g.

76.9

i-PrONO g.

T h i s 67.Ig. of DMF i s composed of DMF which i s a v a i l a b l e f o r r e c y c l e by simply d i s t i l l i n g the l i q u i d (28.6g.) and DMF which i s bound to the HNO3 and can be recovered i f the complex i s broken by n e u t r a l i z a t i o n .

a. ) T h i s 76.9g. represents 52.7g. i-PrOH

93.4

408.7

s t a r t i n g s p i n bath

% accounted f o r

381.6

totals

0.0

67.1

120.6

bottoms

4

62.5

4.9

32-46/1

3

18.9

i-PrOH

76.4

88.7

25-32/1

2

-

g.

82.9

95.9

r.t./10

1

DMF

3.4

T o t a l Wt. g.

Conditions bp. °C/mm. Hg

F r a c t i o n No.

Recovery of Process Chemicals by Vacuum D i s t i l l a t i o n of the Crude S p i n Bath

TABLE I I I

g.

S O L V E N T SPUN R A Y O N , MODIFIED

64

CELLULOSE

FD3ERS

2/1 i-PrOH/DMF i n which Ν 0 was added t o b r i n g the HN0 l e v e l near 3, 5 and 10% were e v a l u a t e d . These s o l u t i o n s were vacuum d i s t i l l e d without n e u t r a l i z a t i o n to e s t a b l i s h e x a c t l y how such an a c i d i c s o l u t i o n would behave i n a recovery process. Table I I I shows a synopsis of the d i s t i l l a t i o n of a s p i n bath a t the 10% a c i d l e v e l . The i-PrONO and i-PrOH d i s t i l l e d together as the p r e s s u r e was reduced. The next f r a c t i o n contained i-PrOH/DMF and q u i t e unexpectedly, no HNO3 was found i n t h i s f r a c t i o n . I n f a c t , pure DMF was obtained as d i s t i l l a t e i n the next f r a c t i o n u n t i l the bottom r e s i d u e contained n e a r l y 1.0 mole HNO3/I.O mole DMF. This r e s i d u e was f r a c t i o n a l l y d i s t i l l e d t o g i v e a c l e a r , c o l o r ­ l e s s , o i l y l i q u i d , bp. 94-95°C/8 mm Hg. The l i q u i d had a d e n s i t y of 1.21 g/ml and contained 47.07% HNO3 ( t i t r a t i o n w i t h standard c a u s t i c ) and 48.98% DM t h e o r e t i c a l values ar 53.68% DMF. Thus, t h i s new m a t e r i a l represents a 1:1 molar mix­ t u r e o f HNO3 and DMF i n which there i s o b v i o u s l y some i n t e r a c t i o n between the two molecular s p e c i e s , i . e . complexation t o some ex­ t e n t . T h i s i n t e r a c t i o n i s a l s o suggested by n u c l e a r magnetic resonance (NMR) s t u d i e s which showed a d o w n f i e l d s h i f t o f t h e DMF-aldehyde and N-methyl protons i n the mixture as compared t o these protons i n pure DMF. As these s p e c t r a were taken i n the neat l i q u i d s , no s o l v e n t e f f e c t s could i n t e r f e r e w i t h the r e ­ s u l t s . This d o w n f i e l d s h i f t was a l s o present when the s p e c t r a were taken i n CDCI3/TMS. A t a b u l a t i o n of these s h i f t s a r e shown i n Table I V . 2

4

3

TABLE IV NMR S h i f t s i n DMF and DMF/HNO3 Complex a

Sample

/(ppm)( ->

DMF-HNO3

3.09

3.24

8.28

DMF

2.80

2.98

8.03

0.29

0.26

0.25

a.) Chemical s h i f t s i n ^(ppm) d o w n f i e l d from the i n t e r n a l s t a n ­ dard TMS. The DMF-HNO3 b i n a r y mixture i s i n t r i g u i n g s i n c e i t provides a method of s e p a r a t i n g most of the DMF from the HNO3 even though the b o i l i n g p o i n t of DMF (154°C) i s much g r e a t e r than t h a t of HNO3 (83°C). The d o w n f i e l d chemical s h i f t of the aldehyde and N-methyl resonances i n d i c a t e a decrease i n e l e c t r o n d e n s i t y at

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

PORTNOY AND ANDERSON

5.

Cellulose-N O DMF t

65

Solution

r

the amide carbon atom which i s c o n s i s t e n t w i t h a weak complexing of the amide and HNO3. Attempts t o d i s s o l v e c e l l u l o s e i n t h i s b i n a r y mixture were u n s u c c e s s f u l . Thus vacuum d i s t i l l a t i o n o f a s y n t h e t i c s p i n bath a t concent r a t i o n s expected i n a commercial process gave s e p a r a t i o n of a l l components except that p o r t i o n of the DMF which was i n v o l v e d i n a DMF/HNO3 b i n a r y mixture. This DMF c o u l d be r e l e a s e d by a d d i t i o n of a base and v a r i o u s bases were s t u d i e d f o r t h i s purpose but those d e r i v e d from c a l c i u m were chosen f o r s e v e r a l reasons as e x p l a i n e d below. Calcium carbonate (CaC03>, c a l c i u m hydroxide (Ca(CH)«) or c a l c i u m oxide (CaO) were used t o r e l e a s e the DMF from t h i s DMF/HNO3 mixture. The r e s u l t a n t c l e a r t h i c k s o l u t i o n was vacuum d i s t i l l e d t o recover the DMF l e a v i n g a c a l c i u m n i t r a t e (Ca(N03) ) r e s i d u e . This s o l i d r e s i d u e gave when p y r o l y z e d Thus, t h i s sequence e s t a b l i s h e t o f r a c t i o n a t e the s p i , , from HN0 and o b t a i n N 0 from the HNO3 p o r t i o n of the bath. The choice of c a l c i u m bases f o r n e u t r a l i z a t i o n r e s u l t s from a study which was done on the s t a b i l i t y of DMF under a c i d i c and b a s i c c o n d i t i o n s . The data c l e a r l y showed that DMF i s reasonably s t a b l e i n the presence of a c i d as long as water i s excluded b u t t h a t dimethylamine (DMA) i s formed by h y d r o l y s i s when water i s present. By c o n t r a s t , DMF decomposed r a p i d l y when NaOH o r KOH was added w i t h no a d d i t i o n a l H 0. When C a ( 0 H ) , CaO or CaC03 was added t o DMF, even w i t h a d d i t i o n a l H 0 , no measurable amount of DMA was formed even on prolonged standing a t room temperature. I n a d d i t i o n , the recovery o f N 0 from C a ( N 0 o ) by p y r o l y s i s i s a commercial process r e l a t e d t o the phosphoric a c i d i n d u s t r y and l i t e r a t u r e references were found t o i n d i c a t e t h a t good y i e l d s of N 0 from p y r o l y s i s of C a ( N 0 3 ) were customary.(2) F o l l o w i n g an extensive l i t e r a t u r e search, a p r o j e c t was e s t a b l i s h e d to study the p r o d u c t i o n of N 0 v i a p y r o l y s i s o f v a r i o u s metal n i t r a t e s and n i t r i t e s . A m u f f l e furnace was modif i e d t o h o l d a p y r o l y s i s tube c o n t a i n i n g the s a l t under study. A s t a i n l e s s s t e e l p y r o l y s i s chamber was b u i l t so t h a t d i f f e r e n t sweep gases could be used t o create the d e s i r e d atmosphere i n the p y r o l y s i s tube and t o sweep the product N2O4 gases i n t o a capt u r i n g s o l u t i o n of 1-pentyl a l c o h o l i n IMF. The amount of N 0 c o u l d then be determined by UV-VIS. a n a l y s i s of the amount of 1 - p e n t y l n i t r i t e formed i n the c a p t u r i n g s o l u t i o n . References i n the l i t e r a t u r e i n d i c a t e d good N 0 y i e l d s could be obtained from C a ( N 0 ) a t 600°C i n a C 0 atmosphere (2) or NaN0 i n a CO atmosphere (5) b u t no data were a v a i l a b l e on the p y r o l y s i s o f KNO3 or n i t r i t e s a l t s . I n a d d i t i o n t o o b t a i n i n g the N 0 y i e l d , i t was necessary t o measure the content of unpyrolyzed n i t r a t e and n i t r i t e i n the p y r o l y s i s s a l t r e s i d u e t o determine the s e l e c t i v i t y of the process. Methods f o r these determinations were developed· 2

3

2

4

2

2

2

2

2

2

4

2

4

2

4

2

2

3

2

2

4

3

2

4

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

4

66

S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FIBERS

The expected s a l t m i x t u r e which would be obtained from the recovery process would be an equimolar m i x t u r e o f c a l c i u m n i ­ t r a t e / c a l c i u m n i t r i t e . N i t r i t e s a l t s decompose t o produce one mole of NO and one mole of NO2 per mole of n i t r i t e s a l t thus a d d i t i o n a l o x i d a t i o n i s r e q u i r e d t o o b t a i n N2O4 from t h i s system. Equations 6 and 7 are examples of the c h e m i c a l changes accompanying the r e l e a s e of N2O4 d u r i n g the decomposition of Ca(N0 ) . Although the byproducts v a r y w i t h the d i f f e r e n t sweep gases and s a l t s , the decomposition of c a l c i u m n i t r a t e , Ca(NO^) and c a l c i u m n i t r i t e , Ca(N02>2 i n the presence of CO2 should serve as adequate examples. 3

2

2

6.

Ca(N0 )

2

+ C0 —>CaC0

7.

Ca(N0 )

2

+ C0

3

2

2

3

+ 2N0

2

+ 1/2

0

2

When a m i x t u r e o f n i t r a t e and n i t r i t e i s p y r o l y z e d , 1/2 mole of oxygen i s produced, which i s the r e q u i r e d amount t o convert the NO from n i t r i t e decomposition t o N 2 O / . However, i n the l a b o r a ­ t o r y experiments, oxygen was mixed w i t h the e f f l u e n t gases i n o x i d a t i o n chambers which were p l a c e d b e f o r e the c a p t u r i n g cham­ bers f o r a l l p y r o l y s i s runs which i n c l u d e d n i t r i t e . This assured the b e s t p o s s i b l e y i e l d s . Y i e l d s of N2O4 r e s u l t i n g from p y r o l y s i s experiments are shown i n Table V. The r e s u l t s i n t h i s t a b l e show t h a t 93% N2O4 y i e l d s can be obtained from the p y r o l y ­ s i s of a 1:1 ( C a ( N 0 ) / C a ( N O o ) m i x t u r e a t 800°C i n a C 0 a t ­ mosphere. I f the HONO o r C a ( N 0 ) 2 could be o x i d i z e d t o H N 0 or C a ( N 0 > 2 , then the ^ 0 , recovery would i n v o l v e the p y r o l y s i s of C a ( N 0 o ) which r o u t i n e l y gave 98% y i e l d s of N 0, i n C 0 or N at 800°C. T h i s p a r t of the i n v e s t i g a t i o n e s t a b l i s h e d a route to N 0^ r e c o v e r y , i . e . by p y r o l y s i s of a C a ( N 0 ) / C a ( N 0 2 ) 2 mixture. S i n c e the Ν2Ο4 which i s produced by t h i s p y r o l y s i s i s a c o r r o s i v e , o x i d i z i n g gas, a s p e c i f i c study was made to determine the requirements f o r c o n s t r u c t i o n m a t e r i a l s f o r the p y r o l y s i s furnace. Conferences w i t h f a c u l t y members a t the Engineering School, Rutgers U n i v e r s i t y , New Brunswick, N.J. r e s u l t e d i n the s u g g e s t i o n t h a t a ceramic m a t e r i a l would be r e q u i r e d f o r the i n s i d e of the f u r n a c e . The m a t e r i a l of p r e f e r e n c e was A l 2 0 which i s f r e q u e n t l y used f o r furnace l i n i n g s . P r o t o t y p e l a b ­ o r a t o r y p y r o l y s i s tubes of A 1 0 were designed and obtained from Duramic P r o d u c t s , Inc. P r e l i m i n a r y p y r o l y s i s data from a l i m i t e d number of experiments u s i n g pure c a l c i u m n i t r a t e i n d i c a t e t h a t the y i e l d s of N2O4 are s i m i l a r t o those obtained when s t a i n l e s s s t e e l tubes were used. One of the important remaining steps was c o n v e r s i o n of i s o p r o p y l n i t r i t e i n t o the c a l c i u m n i t r i t e s a l t f o r p y r o l y s i s . Hy­ d r o l y s i s of i-Pr0N0 to HN0 ( n i t r o u s a c i d ) and n e u t r a l i z a t i o n of 3

2

2

2

2

3

3

2

2

2

2

s

2

3

2

3

2

3

2

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

a

l

t

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

g)

f)

c) d) e)

b)

a)

2

2

3

2

2

3

2

3

2

d

e

2

2

e

e

e

2

2

2

75.3/86.5 67.7/84.8 93.3/100.1 97.8/97.8 76.8/84.6 61.9/68.8 57.8/92.8/-

Carbon Dioxide

2

11

-/-/-

53.1/54.1 28.8/33.9

-/-/-

35.0/58.0 11.9/36.6

Carbôn Monoxide

2

2

2

2

-/-

9.6/63.9 6.0/69.2 38.2/95.2 98.1/98.1 20.1/31.7 28.8/38.5 34.0/78.8/-

2

2

13.9/41.0 26.0/84.4/-

-/-

-/-

-/-

-/-

Air

Nitrogen

b

These results are averages of 2-4 pyrolysis experiments. If the salts were not thoroughly dried, lower N 0^ yields resulted. The sweep gas flow rates were 100 ml./min. Stainless steel (310) pyrolysis chambers were used. Results are expressed as % y i e l d of N 04/total % of the starting salt which i s accounted for by the sum of the N 04 yield plus analysis of the pyrolysis residue. Pyrolysis at 600°C resulted i n very low N2O4 yields. Pyrolysis at 800°C resulted i n very low N 04 yields. The pyrolysis of a n i t r i t e salt produces a mole of NO per mole of N0 . Therefore 0 was mixed at 50 ml./min. with the pyrolysis effluent to oxidize any NO to N 04 for capture. Carbon monoxide can reduce N0 to NO by the equation CO + N0 -•NO + C0 therefore 0 was mixed at 50 ml ./min. with these pyrolysis effluent streams. When these measurements were made, no method of residue analysis was available.

3

2

3

C

NaN0 /800/90 KNOJ800/90 Ca(N0 ) /600/120 Ca(N0 ) /800/90 NaN0 :NaN0 /1000/90 KNO3:KNO /1000/90 » Ca(N0 )2 :Ca(N0 ) /600/120 > 8 Ca(N0 )2 :Ca(N0 ) /800/90 » 8

c

Salt/Temp. °C/Time (min.)

3

a

The Effect of Temperature and Sweep Gas on N2O4 Yields from the Pyrolysis of Nitrate Salts or 1:1 Nitrate/Nitrite Salt Mixtures >

TABLE V

3

3

S*

Ο ?

ΐ s:

ο

I

r

Ο

ο

01

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Spin Bath

3

I ο η

t i I I a t

8

D i

£ 2

Kiln

—a—

2

C0

2

2

2

H 0

3

CaC0 |

Ca(N03>2 ]Ca(N0 ^ Neutraliz­ ation DMF ΗΝΟ^,ΗΝΟο,1 i-PrOH, DMF, i - P r O H

H2O

DMF

DMF

CaO

Cellulose Fiber

i-PrOH

->>

H 0 Cycle (alternate) Η NO 3, H N 0 , DMF

{Hydrolysis

i-PrONO

DMF/HNO3

L

i-PrOH

4

trace DMF

2

Ca2

ι

Pyrolysis

t

k

Figure 4. Final technically proven total recycle and recovery system for spinning rayon fibers from CellOH-N O -DMF solutions

i-PrOH,HN0

i-PrONO,DMF

Solu.

DMF

Ν2θ

5.

PORTNOY A N D ANDERSON

Cellulose-N0 -DMF Solution t

4

69

t h i s HONO appeared reasonable. Although t h i s approach was f o l lowed, the problem of e f f i c i e n t c o n v e r s i o n of i-PrONO t o HONO remained one of the weak p o i n t s i n the recovery scheme. A f t e r d e t a i l e d study, i t appeared t h a t the c h o i c e medium f o r the hyd r o l y s i s was the HNO3/DMF obtained as the bottoms f r a c t i o n from d i s t i l l a t i o n o f the crude s p i n b a t h . T h i s was expected s i n c e h y d r o l y s i s i s a c i d c a t a l y z e d . I n a d d i t i o n , the DMF caused the i-PrONO t o be m i s c i b l e w i t h the H2O added f o r h y d r o l y s i s whereas normally i-PrONO and H2O are not m i s c i b l e . The progress i n development of t h i s aspect o f the recovery c y c l e was impeded by one p a r t i c u l a r f a c t o r . A method f o r monit o r i n g e i t h e r the c o n c e n t r a t i o n of i-PrONO o r HNO2 i n the DMF/HNO3/H2O h y d r o l y s i s s o l u t i o n s was not known. The UV-VIS. s p e c t r a of i-PrONO and HNO2 are o v e r l a p p i n g so t h a t t h i s was not a u s e f u l method. A metho n i t r i t e s , ( i s o p r o p y l , amyl s i n c e the n i t r i t e apparently decomposes during chromatography. In fact,_under a l l o f the c o n d i t i o n s attempted, a peak f o r the parent a l c o h o l was observed when the n i t r i t e was i n j e c t e d . I n a d d i t i o n , s e v e r a l peaks, a t t r i b u t a b l e t o n i t r o g e n oxide gases were present i n these chromatograms. The temperature o f the i n j e c t i o n p o r t and the column as w e l l as the gas f l o w r a t e were changed as was the column composition but no s u i t a b l e c o n d i t i o n s were found under which pure n i t r i t e d i d not f u l l y decompose t o i t s parent a l c o h o l . One method f o r a n a l y s i s may be NMR s p e c t r o scopybut t h i s was not r e a d i l y a v a i l a b l e . Thus, the amount of hyd r o l y s i s was c r u d e l y measured by aqueous t i t r a t i o n w i t h standard caustic. M i x t u r e s o f n i t r i t e s , i s o p r o p y l as w e l l as model a l k y l n i t r i t e s , were s t u d i e d i n DMF and H2O w i t h or without a c i d . A m i x t u r e of i-Pr0N0/H20/DMF was s l u r r i e d f o r 15 minutes a t room temperature and then n e u t r a l i z e d w i t h Ca(0H)2 o r CaO. I t was not e f f i c i e n t t o use CaC03. T h i s new mixture was vacuum d i s t i l l e d t o g i v e a powdery r e s i d u e which gave N2O4 on p y r o l y s i s . A d d i t i o n a l experimentation i n d i c a t e d t h a t i t was p o s s i b l e t o r e cover unhydrolyzed n i t r i t e by c a r e f u l f r a c t i o n a l d i s t i l l a t i o n of the n e u t r a l i z e d i s o p r o p y l n i t r i t e h y d r o l y s i s m i x t u r e . A t o t a l recovery of HNO2 (by t i t r a t i o n ) p l u s the recovered unchanged i-PrONO (by d i s t i l l a t i o n ) was 94%, suggesting the p o s s i b l e use of m u l t i p l e h y d r o l y s i s u n i t s . The e n t i r e recovery and r e c y c l e scheme based on t h i s work i s shown i n F i g u r e 4. This i s e s s e n t i a l l y s i m i l a r t o t h a t proposed i n F i g u r e 3 except t h a t a l l o f the loops have been c l o s e d . A r e covery and r e c y c l e scheme such as t h i s should not r e l e a s e any e f f l u e n t t o the environment because i t i s t o t a l l y c y c l i c a l w i t h a l l steps i n c l u d e d i n c l o s e d loops. Conclusions I t has been d e f i n i t i v e l y proven t h a t the m a t e r i a l which i s r e c o v e r a b l e by c o a g u l a t i o n o f a p y r i d i n e s t a b i l i z e d c e l l u l o s e /

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

70

S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FIBERS

N2O4/DMF s o l u t i o n i s c e l l u l o s e n i t r i t e . However, although i t seems reasonable t h a t c e l l u l o s e n i t r i t e i s formed i n the absence of p y r i d i n e t h i s f a c t o r does not l i m i t the u t i l i t y o f the p r o ­ posed r e c y c l e and recovery scheme because t h a t scheme i s d i c t a t e d by the s p i n n i n g system which i s r e q u i r e d t o make the most com­ m e r c i a l l y acceptable rayon f i b e r s . In t h i s case, the s p i n n i n g system of c h o i c e was based on i s o p r o p y l a l c o h o l and t h i s a l c o h o l immediately forms i s o p r o p y l n i t r i t e when i t c o n t a c t s the c e l l u lose/N204/DMF s o l u t i o n i r r e g a r d l e s s of whether the c e l l u l o s e i s complexed or d e r i v a t i z e d . A l l chemical steps r e q u i r e d t o recover and r e c y c l e the DMF, coagulant and N2O4 from the spent s p i n bath have been d e l i n e a t e d and proven to be f e a s i b l e from a t e c h n i c a l s t a n d p o i n t . Abstract The d i s s o l u t i o n of cellulose i n DMF/N O is d i s c u s s e d in terms of t h r e e p o s s i b l e mechanisms, one i n v o l v i n g derivatization of the cellulose and two d e s c r i b i n g dissolution in terms of com­ f o r m a t i o n . Chemical and s p e c t r a l s t u d i e s on the p y r i d i n e stabilized cellulose/N O /DMF s o l u t i o n s t r o n g l y support the mechanism of derivatization of the cellulose by NO. A total recovery and r e c y c l e scheme has been proposed and proven to be t e c h n i c a l l y f e a s i b l e . This scheme i n v o l v e s separa­ tion of the crude spent s p i n b a t h , which c o n t a i n s DMF, NO, i-PrOH and i-PrONO, into four major fractions. These are a.) pure i-PrONO, b.) pure i-PrOH, c.) pure DMF and d.) a 1:1 molar DMF/HNO complex. The DMF/HNO complex is used to c a t a l y z e hy­ drolysis of the i-PrONO to i-PrOH and HNO . T h i s HNO /HNO combination is n e u t r a l i z e d w i t h CaO and the r e s u l t a n t Ca(NO ) / Ca(NO ) is p y r o l y z e d in a CO atmosphere t o recover N O f o r r e c y c l e . Calcium carbonate r e s u l t i n g from the p y r o l y s i s of Ca(NO ) /Ca(NO ) i n CO is converted t o CaO and CO t o continue the cyclical p r o c e s s . 2

2

4

4

2

4

2

3

4

3

2

3

2

3

2

2

3

3

2

2

Literature 1. 2.

3. 4. 5. 6.

2

2

2

2

4

2

Cited

Schweiger, R.G., U.S. P a t e n t No. 3,702,843 (1972). D e l a s s u s , M a r c e l ; Copin, Robert; Hofman, Theophile; S i n n , Robert, S. A f r i c a n Patent No. 68 0155809 (Aug. 1968). CA 70 Ρ 89317z. Industrie-Werke K a r l s r u h e A k t . Ges. German Patent No. 1,014,086 August 22, 1957 CA 53P11412C. Monograph-DMF: A Review of Catalytic Effects and S y n t h e t i c A p p l i c a t i o n s , E . I . duPont de Nemours and Co., Inc., page 3. Monograph-DMF: Recovery and Purification, E . I . duPont de Nemours and Co., I n c . , page 10. Monograph-DMF: Recovery and Purification, E . I . duPont de Nemours and Co., I n c . , page 12.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

6 Production of Rayon Fibers from Solutions of Cellulose in

(CH2O)x-DMSO

R. B. HAMMER, A. F. TURBAK, R. E. DAVIES, N. A. PORTNOY ITT Rayonier, Inc., Eastern Research Div., Whippany,N.J.07981

A wide range o f cellulosic t o d i s s o l v e readily a t e l e v a t e d temperatures in a combination o f (CH O)x/DMSO. The c o n c e n t r a t i o n o f pulp d i s s o l v e d was a direct f u n c t i o n o f the degree o f p o l y m e r i z a t i o n . In g e n e r a l , 6/6/88 cellulose/(CH O)x/DMSO s o l u t i o n s were prepared u s i n g pulps o f 400 t o 600 D.P. The s o l u t i o n s were m i c r o s c o p i c a l l y f r e e o f g e l s and undissolved cellulosic fibers. This d i s s o l u t i o n process was found to be very specific t o the combination o f (CH O)x/DMSO. Other analogous aldehydes and p o l a r organic s o l v e n t s failed to afford cellulose s o l u t i o n s . Cellulosic articles such as fibers and films are easily regenerated from the cellulosic s o l u t i o n in the presence o f aqueous s o l u t i o n s having a pH g r e a t e r than seven, of water s o l u b l e nucleophilic compounds such as ammonia, ammonium salts, and s a t u r a t e d amines. S a l t s o f sulfur compounds in which the s u l f u r has a valence of l e s s than six may a l s o be used. F i b e r s o f h i g h wet modulus, intermediate t e n a c i t y and low e l o n g a t i o n were readily produced from r e g e n e r a t i n g systems such as aqueous ammonia, ammonium carbonate, t e t r a m e t h y l ammonium hydroxide, methyl amine, diethyl amine, t r i m e t h y l amine, sodium sulfide, sodium sulfite and sodium thiosulfate. F i b e r s have been spun w i t h c o n d i t i o n e d and wet t e n a c i t i e s as h i g h as 2 . 7 and 1 . 5 g/d r e s p e c t i v e l y w i t h wet modulus o f as h i g h as 1 g/d and s o l u b i l i t y i n 6.5% NaOH as low as 3-15%. 2

2

2

Introduction Today, rayon i s almost u n i v e r s a l l y produced by the v i s c o s e process. However, the h i g h investment costs and p o t e n t i a l m i l l e f f l u e n t p o l l u t i o n problems a s s o c i a t e d w i t h v i s c o s e rayon p l a n t s makes t h i s process i n c r e a s i n g l y l e s s competitive from both an economic and environmental s t a n d p o i n t . There are other processes f o r producing regenerated c e l l u l o s i c products i n c l u d i n g regenera71

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

72

S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FIBERS

t i o n from c e l l u l o s e n i t r a t e which i s v e r y hazardous o r from cuprammonium hydroxide. However, the p r o d u c t i o n o f c e l l u l o s i c a r t i c l e s from these processes i s minuscule compared t o that from the v i s c o s e process. A number o f h i g h l y p o l a r , a p r o t i c o r g a n i c s o l v e n t s f o r c e l l u l o s e have been d i s c l o s e d i n the l i t e r a t u r e . Two s o l v e n t s which have r e c e i v e d frequent mention are dimethylformamide (DMF)(^), (it)" ( 8 ) and dimethyl s u l f o x i d e , ( l ) , (2), each i n combination w i t h one or more a d d i t i o n a l compounds such as N 0 ( l ) - ( l ) , S 0 ( 8 ) (2) o r an amine.(10) More r e c e n t l y , DMS0-paraformaldehyde has been reported as a solvent f o r c e l l u l o s e . ( 1 1 ) While there has been much d i s c u s s i o n o f these and other s o l vent systems f o r c e l l u l o s e , the l i t e r a t u r e contains l i t t l e i n formation concerning the r e g e n e r a t i o n o f f i b e r s , f i l m s or other regenerated c e l l u l o s i are almost no data i n t i e s o f f i b e r s spun from an o r g a n i c solvent system. I n so f a r as i s known, no economically a c c e p t a b l e commercial solvent-based processes have as yet been d i s c l o s e d f o r producing f i b e r s or f i l m s w i t h acceptable p r o p e r t i e s . 2

4

2

Experimental Experiments were designed t o determine the i n f l u e n c e of the form of the pulp and the degree of p o l y m e r i z a t i o n p r i o r t o d i s s o l u t i o n . Although the m a j o r i t y of the s o l u t i o n s were prepared u s i n g Abbe'cut m a t e r i a l , i . e . a h i g h l y comminuted, d e f i b e r e d p u l p , the d i s s o l u t i o n process i s not l i m i t e d w i t h r e s p e c t t o the degree of p o l y m e r i z a t i o n or the pulp form. A l l s o l u t i o n compositions are g i v e n as weight percents i n the o r d e r , pulp/(CHgOjx/DMSO e£. 6/6/88 represents 6 $ c e l l u l o s e , 6 $ paraformaldehyde and 88$ s o l v e n t . A t y p i c a l example of the s o l u t i o n p r e p a r a t i o n procedure i s d e s c r i b e d below. S i l v a n i e r - J , a prehydrolyzed k r a f t pulp o f 1050 D.P., a f t e r c o n v e r t i n g t o a l k a l i c e l l u l o s e by methods w e l l known i n the rayon i n d u s t r y , was a l k a l i n e aged t o a D.P. l e v e l o f ^ 5 0 , n e u t r a l i z e d , washed, d r i e d , then e i t h e r f l u f f e d , d i c e d o r d e f i b e r e d . A 6/6/88 cellulose/(CH20)x/DMS0 s o l u t i o n was prepared by charging 120 p a r t s o f a l k a l i aged prehydrolyzed k r a f t pulp (D.P. k^o), 120 p a r t s of powdered paraformaldehyde and I760 p a r t s o f DMS0 i n t o a t w o - l i t e r four neck r e s i n r e a c t i o n f l a s k equipped w i t h a s t a i n l e s s - s t e e l mechanical s t i r r e r and thermometer. The r e s u l t i n g s l u r r y was s t i r r e d and heated t o 120°C over a p e r i o d o f one hour. Although d i s s o l u t i o n i s almost complete a t 120°C a f t e r about one hour, the h e a t i n g and s t i r r i n g were continued f o r l ) an a d d i t i o n a l hour a t 120°C o r 2) the l e n g t h o f time r e q u i r e d t o r e move excess formaldehyde. The cellulose/(CHgOjx/DMSO s o l u t i o n s described h e r e i n were o f 6/6/88 composition. By employing low D.P. pulps ie i n the range of 200-UOO D.P. i t i s p o s s i b l e t o prepare DMSO/ÎCHgOjx s o l u t i o n s

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

6.

H A M M E R ET A L .

Rayon Fibers from Cellulose Solutions

73

c o n t a i n i n g 1 0 - 1 2 $ c e l l u l o s e . S o l u t i o n s c o n t a i n i n g 8-10$ cellu­ l o s e can be prepared by u s i n g pulps with.D.P. l e v e l s between UOO and 6θΟ but the r e s u l t i n g v i s c o s i t i e s exceed 3 0 , 0 0 0 cps at ambient temperature. A l l the cellulose/(CI^oJx/DMSO s o l u t i o n s were observed to be m i c r o s c o p i c a l l y f r e e of g e l s and unreacted f i b e r s . The s o l u t i o n s were deaerated p r i o r to s p i n n i n g and v i s c o s i t i e s measured by a B r o o k f i e l d Viscometer. They were i n the range of from 8 , 0 0 0 2 0 , 0 0 0 cps. at ambient temperatures f o r pulps w i t h 1+00-600 D.P. l e v e l s . The s o l u t i o n s were f i l t e r e d through a 90 mm diameter nylon, i n - l i n e f i l t e r during spinning. Several types of s p i n n e r e t t e s have been used s u c c e s s f u l l y to s p i n f i b e r s from t h i s s o l v e n t system. For example, gold-platinum t y p i c a l f o r the v i s c o s e process, s t a i n l e s s s t e e l t y p i c a l f o r c e l l u l o s e acetate s p i n n i n g p r e f e r r e d s i n c e they ar The m a j o r i t y of the s p i n n i n g t r i a l s were performed u s i n g a bench-scale v e r t i c a l s p i n n i n g u n i t . The s o l u t i o n s were spun i n t o the a p p r o p r i a t e primary r e g e n e r a t i o n bath and the r e s u l t i n g f i b e r tow passed v e r t i c a l l y to a primary g l a s s godet then through a secondary bath to a secondary g l a s s godet whose speed could be a l t e r e d to produce the d e s i r e d s t r e t c h c o n d i t i o n s . Spinning speeds g e n e r a l l y ranged between 10 and 70 meters/ minute but no attempt was made to optimize t h i s c o n d i t i o n or the resulting fiber physical properties. The cellulose/(CH 0)x/DMS0 s o l u t i o n s regenerate r a p i d l y i n aqueous s o l u t i o n s of n u c l e o p h i l i c species which a c t as formalde­ hyde scavengers. This c l a s s of compounds i n c l u d e s ammonia, ammonium s a l t s , s a t u r a t e d amines and s a l t s of s u l f u r compounds. A l l f i b e r s were processed as s t a p l e by treatment w i t h 6o-70°C water, a 0 . 3 $ aqueous s o l u t i o n of a f i n i s h i n g agent at 50°C, then c e n t r i f u g e d and oven d r i e d at 100-110°C. The f i b e r s were t e s t e d f o r p h y s i c a l p r o p e r t i e s according to the American S o c i e t y of T e s t i n g and M a t e r i a l s standards D-1577-73 and D - 2 1 0 1 2

72.

R e s u l t s and

Discussion

The s o l v e n t combination of (CHgOjx/DMSO w i l l d i s s o l v e a wide range of c e l l u l o s i c pulps i n e i t h e r f l u f f e d , d i c e d or Abbe' cut form. The percent c e l l u l o s e i n the r e s u l t i n g s o l u t i o n s i s de­ pendent upon the pulp D.P. In g e n e r a l , 6/6/88 c e l l u l o s e / ( C I U 0 ) x / DMS0 spinnable s o l u t i o n s can be prepared from pulps w i t h i n the *Κ)0-6θΟ D.P. range. The pulps may be e i t h e r s u l f a t e or s u l f i t e grades and i n c l u d e many of the pulps t h a t are t y p i c a l l y employed i n the v i s c o s e process. Ground wood i n the form of newsprint d i d not d i s s o l v e i n the paraformaldehyde/DMS0 combination under the c o n d i t i o n s employed. The d i s s o l u t i o n of c e l l u l o s e i n the (CHgOjx/DMSO s o l v e n t system i s b e l i e v e d to r e s u l t from the formation of a hemiacetal

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

74

S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FD3ERS

of c e l l u l o s e i e m e t h y l o l c e l l u l o s e . ( 1 1 ) The d i s s o l u t i o n o f c e l l u l o s e was found t o be v e r y s p e c i f i c to the combination o f DMSO and paraformaldehyde. Organic solvents analogous t o DMSO such as s u l f o l a n e , s u l f o l e n e o r DMF d i d not cause d i s s o l u t i o n i n the presence o f paraformaldehyde. L i k e w i s e , aldehydes s i m i l a r t o formaldehyde o r paraformaldehyde, f o r example c h l o r a l , acetaldehyde, benzaldehyde, and compounds such as t r i o x a n e , methyl formcel and b u t y l formcel i n the presence o f a c i d c a t a l y s t s d i d not y i e l d c e l l u l o s e s o l u t i o n s i n combination w i t h DMSO. Cellulose/(CHgO)x/DMSO s o l u t i o n s can be r a p i d l y coagulated by employing n u c l e o p h i l i c s p e c i e s which a c t as formaldehydescavenging agents. I n g e n e r a l , these régénérants are aqueous s o l u t i o n s o f water s o l u b l e n u c l e o p h i l i c compounds which have a pH g r e a t e r than seven ammonia, ammonium s a l t s pounds i n which the s u l f u r has a valence o f l e s s than s i x . In the case o f the nitrogenous compounds, the coagulant i s a c t u a l l y ammonia o r an amine, the source o f which may be, i n a d d i t i o n t o ammonia o r the amine i t s e l f , an ammonium s a l t , o r , i n some i n s t a n c e s , a b a s i c amine s a l t . Under the a l k a l i n e c o n d i t i o n s of the r e g e n e r a t i o n s o l u t i o n , ammonium o r amine s a l t s w i l l hydrol y z e t o l i b e r a t e the f r e e base i e ammonia o r the amine, respectively. A p a r t i c u l a r l y u s e f u l nitrogenous compound i s ammonium hydroxide. I f the r e g e n e r a t i o n bath i s aqueous ammonium hydroxi d e , then a f t e r r e g e n e r a t i o n o f a f i b r o u s tow, the spent bath would c o n t a i n water, DMSO, ammonia and hexamethylenetetramine. The l a t t e r compound would r e s u l t from the r e a c t i o n o f ammonia and formaldehyde. Other nitrogenous compounds which possess the r e q u i s i t e n u c l e o p h i l i c , s o l u b i l i t y and pH p r o p e r t i e s are s a l t s o f ammonia and a weak a c i d such as ammonium a c e t a t e , ammonium s u l f i d e , ammonium carbonate and ammonium b i s u l f i t e . Amines which are u s e f u l a r e , i n g e n e r a l , s a t u r a t e d a l i p h a t i c , c y c l o a l i p h a t i c and a l i c y c l i c amines. Aromatic amines and amines o f more than s i x carbon atoms are normally i n s o l u b l e o r o f b o r d e r l i n e s o l u b i l i t y i n water. P a r t i c u l a r l y e f f e c t i v e s u l f u r compounds are sodium s u l f i d e , sodium s u l f i t e and sodium t h i o s u l f a t e . The s u l f a t e s , i n which s u l f u r has a valence o f s i x are not u s e f u l . An amount o f the n u c l e o p h i l i c compound as l i t t l e as 0 . 2 5 $ by weight o f the regenera t i o n s o l u t i o n has been found e f f e c t i v e f o r r e g e n e r a t i o n o f the c e l l u l o s e . The maximum c o n c e n t r a t i o n i s l i m i t e d o n l y by the s o l u b i l i t y o f the compounds i n water. Normally the c o n c e n t r a t i o n w i l l range from 3 - 1 5 $ . V a r i a t i o n s i n the composition o f the r e g e n e r a t i o n or s p i n bath d i d not a l t e r the f i b e r c r o s s - s e c t i o n s . Both the n i t r o genous and s u l f u r c o n t a i n i n g régénérants a f f o r d rayon f i b e r s w i t h c i r c u l a r shapes. R e p r e s e n t a t i v e S h i r l e y c r o s s - s e c t i o n s o f f i b e r s spun from cellulose/(CHg0)xAJMS0 s o l u t i o n s are i l l u s t r a t e d i n

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

6.

HAMMER ET AL.

75

Rayon Fibers from Cellulose Solutions

Figure 1. Cross sections of cellulose-(CH O)xDMSO fibers spun from nitrogenous containing régénérants t

Figure 2. Cross sections of cellulose-( CH O)xDMSO fibers spun from nitrogenous and sulfurcontaining régénérants t

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FIBERS

76

F i g u r e s 1 and 2 . The regenerated c e l l u l o s i c f i b e r s produced from some of these nitrogenous o r s u l f u r c o n t a i n i n g compounds a r e f u l l y com­ parable i n p r o p e r t i e s t o c e l l u l o s i c f i b e r s produced by the v i s ­ cose p r o c e s s . They are p a r t i c u l a r l y o u t s t a n d i n g i n having a v e r y low " S g ^ " . The S g 5 v a l u e s are measurements of regenerated c e l l u l o s i c f i b e r s o l u b i l i t y i n 6 . 5 $ sodium hydroxide a t 20°C. This i s a u s e f u l t e s t f o r determining the p o t e n t i a l r e s i s t a n c e of such f i b e r s or r e s u l t a n t f a b r i c s t o a l k a l i n e treatment such as a l k a l i n e l a u n d e r i n g o r mercer.ization. A c c o r d i n g l y , r e g u l a r v i s ­ cose rayon which cannot be mercerized and i s not r e s i s t a n t t o a l k a l i n e washing (unless c r o s s - l i n k e d ) , has a r e l a t i v e l y h i g h S g ^ of from 2 5 - 3 5 $ . On the other hand, the h i g h performance and p o l y n o s i c rayons have s u p e r i o r r e s i s t a n c e t o c a u s t i c soda as evidenced by Sg c v a l u e 5-15$. from cellulose/(cBLo)x/DMS range o f from 3 - 1 5 $ . I t should be noted here t h a t i n t h i s s p i n n i n g system i t i s r e a d i l y p o s s i b l e t o o b t a i n f i b e r s w i t h h i g h wet modulus w i t h o u t the use of z i n c or other a d d i t i v e s which are r e q u i r e d i n a v i s ­ cose s p i n n i n g o p e r a t i o n . In F i g u r e 3 s t r e s s - s t r a i n curves [[conditioned ( c ) and wet (w)] f o r a sodium s u l f i d e spun f i b e r a r e shown f o r comparison w i t h r e g u l a r rayon and h i g h wet modulus rayon. Some t y p i c a l f i b e r p h y s i c a l p r o p e r t y data are shown i n Table I employing a v a r i e t y of primary r e g e n e r a t i o n baths f o r the p r o #

STRESS-STRAIN CURVES

/' /

i i

(CH 0),/DMSO

ι

2

REG. RAYON COM.HWM

ί Γ/·' 1h 1

/—

Ac

5

//

'

f

*· W

f/

Figure 3. Stress-strain curves of regularI rayon, commercial high wet modulus rayon and rayon produced by regenerating cettu-ψ/ lose-(CH O) x-DMSO solutions from aque­ ous sodium sulfide t

r\WC

/

/

/

I/.

ELONGATION

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

(%)

6.

H A M M E R ET

77

Rayon Fibers from Cellulose Solutions

AL.

VO i - i

I f-*

CO

O

ι-·

ON

-=t vo

60

(Τ Lu Û.

50

Σ 40 h- / Lu

30 20

V

/

10

-L 20 30 TIME - MINUTES

40

-L

50

Figure S. Temperature variations during prepolymer preparation

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

17.

ELGAL ET AL.

Flame Retardant Chemicals in Cotton

253

Numerous variations have been tried for the prepolymer preparation, and each has been successful. Three representative preparations are shown i n Table 1. The basic ingredients are THPS solution, phosphoric acid (H^PO^), and ammonia (NH^). TABLE I PREPOLYMER PREPARATION Materials

PP(1)

PP(2)

THPS(75%)

100g

100g

H P0 (85%) 3

4

(NH ) HP0 4

2

(NH ) S0 4

2

Method

24.4g

100g

24.4g

4

14.8g

4

Bubble NH^ gas to saturation while s t i r r i n g and cooling

Heat at 70°C for 2 min.

Ammonia gas can be used alone or i n combination with an ammonium salt such as dibasic ammonium phosphate; alternatively, ammonium sulfate and dibasic ammonium phosphate can be used and the phosphoric acid omitted. When the ammonium salts are used, the mixture must be heated and kept near the boiling point for 2 minutes. In contrast, when ammonia gas i s used, the overall reaction i s exothermic, and the solution must be cooled when i t reaches the boiling point. Formation of byproducts may be the primary cause of the temperature increase. Overheating during prepolymer preparation can reduce the reactivity of the prepolymer [6]. A typical preparation, using the ammonia gas technique, i s as follows: 1. Add about 25 g of H«P0, to 100 g THPS solution (about 75% solids) * 2. heat the acidified THPS solution to about 60°C, 3. bubble NH~ gas into the solution u n t i l boiling (approximately 85*C), 4. quickly cool i n ice bath to 75 C, 5. return to bubbling NH~ gas again, etc., as shown i n figure 3. Three cycles are normally sufficient to produce the desired prepolymer solution. Finally, the prepolymer should be cooled to ambient as quickly as possible to minimize deterioration. A quick test has been used to determine completeness of prepolymer formation. Five m i l l i l i t e r s of prepolymer i s placed in a test tube; 3 to 5 ml of caustic soda (25%) i s added, and the mixture i s stirred with a spatula. A good prepolymer w i l l 0

e

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

SOLVENT SPUN RAYON, MODIFIED CELLULOSE FIBERS

254

flocculate and form a solid mass of white polymer, which can be rinsed with water without dissolution. I f , however, the solution turns milky and foams upon addition of base, the prepolymer pre­ paration i s incomplete. One explanation i s that some molecules remain containing (C^OH^-P- groups, which react with excess base to form hydrogen gas. This same test can be used to determine the reactivity of a prepolymer after ageing, or after preparation wi,th ammonium salts i f overheating i s suspected. Although test tube experiments indicated immediate reaction of the prepolymer upon addition of base, some further insight into the reaction mechanisms was sought. A 5 ml beaker was half f i l l e d with 50% NaOH (Figure 4a) and prepolymer solution was carefully poured on top of the caustic producing a distinct liquid interface. A thin layer of material (about 0.5 mm thick) formed immediately; within 1 minute there wa of "stalagmites" and "stalactites (Figure 4b). Within two minutes the prepolymer had diffused throughout the caustic and had polymerized (or precipitated) (Figure 4c); within 5 minutes the reaction appeared complete and uniformly distributed (Figure 4d). This experiment was repeated at 30°C and 50°C and no significant difference was observed i n rate of reaction. From this experiment, i t was concluded that a diffusion mechanism, rather than a rate of reaction, would be the controlling factor for reaction when the l i q u i d process prepolymer system i s used. A comparison was made between the liquid process prepolymer aystern and the conventional ammonia gaseous system. A test tube was p a r t i a l l y f i l l e d with THPOH prepared by the neutralization of THPS to pH 7 and ammonia gas was injected into the test tube just above the liquid layer. Polymer formation at four progressive time intervals i s shown i n Figure 5. A thin skin of white polymer formed instantaneously at the interface (Figure 5b). In 1 minute the polymer was 1 mm thick (Figure 5C), and i n 2 minutes about 2 mm thick (Figure 5d). Thereafter the polymer layer became impervious and there was no increase i n polymer thickness, even when a j e t of NH^ gas was directed onto the polymer layer. From this experiment we concluded that a diffusion mechanism was again the controlling factor for the polymerization reaction. Fabric Treatment The next series of experiments were designed to determine whether or not the l i q u i d process prepolymer system could be adapted to treat cotton fabric for flame retardancy. Preliminary experiments were conducted on small samples of 100% cotton flannel­ ette. The fabric was saturated with the prepolymer, excess solution squeezed out, the impregnated fabric dried, and caustic applied to the fabric to react i t . In some samples, the drying step was eliminated. Samples dried after impregnation and before application of caustic, did not have as high add-ons as undried βample8.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

17.

ELGAL ET AL.

Flame Retardant Chemicals in Cotton

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

255

SOLVENT SPUN RAYON, MODIFIED CELLULOSE FIBERS

Figure 5. Ammonia gas polymerization of THPOH: a) initial, b) after gas addition, c) after 1 min, d) after 2min

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

17.

ELGAL

ET

AL.

Flame Retardant Chemicals in Cotton

257

Effect of Heat on Prepolymer. An experiment was conducted to determine the sensitivity of the prepolymer to heat* A pltot tube was f i l l e d with prepolymer and placed i n an ovem at 60°C for 3 minutes. Evidence of the decomposition of the prepolymer and vapor formation, which tends to expel the liquid out of the tube i s seen i n Figure 6. Thus, because of the sensitivity of the prepolymer to heat, the elimination of the drying step would be desirable. Because the treatment with caustic i s an exothermic reaction and tends to heat the fabric during reaction, and also because the experiment with the pitot tube verified that heating tends to be detrimental, treatment of fabric was repeated with caustic at 0°C. In addition, the fabric was held for 1 minute i n a chilled environment before i t was passed through pressure r o l l e r s . With this c h i l l i n g variatio caustic bath and the fabri Effect of Caustic Concentration. F i f t y percent caustic was used i n the preliminary experiments. The problems of handling this high concentration and i t s cost made i t desirable to determine the minimum concentration that could be used i n fabric treatment. Data are presented i n Figure 7 to show the effect of caustic concentration on add-on, as measured by phosphorus content i n the treated fabric. The optimum appears at about 25% caustic. In these experiments, samples were padded with prepolymer and then with caustic, or they were f i r s t padded with caustic, dried, and then padded with prepolymer. I t was theorized that the application of the caustic f i r s t would swell the cotton fiber and result i n a higher add-on of polymer. However, i t appeared that the order of application of the prepolymer and caustic had no significant effect on the amount of add-on. There was a greater amount of f i n i s h wash-off into the caustic bath when concentrations lower than 25% were used. Effect of Prepolymer Preparation. As was mentioned earlier, prepolymer was prepared i n a variety of ways. Results are shown in Table 2 of fabric treatments with the prepolymer prepared by 3 typical methods: ammonia gas, ammonia gas plus s a l t , or salt only. The treated fabrics passed a v e r t i c a l flame test (7), had add-ons between 18.2% and 20.8%, phosphorus contents between 4.2% and 4.6%, and nitrogen contents between 1.8 and 2.7%, after one laundry cycle. (These samples had not been given an oxidation step.) The N/P mole ratio was 1.0 to 1.3, about the same as that in samples treated by the conventional THPOH-NH^ method (8). Effect of Prepolymer Age. The durability of the prepolymer i n storage was investigated. Cotton flannelette was treated with freshly prepared prepolymer and with prepolymer that had been stored for 2 weeks and for 4 weeks. After one laundry cycle, the percent add-on, as seen i n Table 3, varied from 13.2% to 18.2%,

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

258

SOLVENT SPUN RAYON, MODIFIED CELLULOSE

TABLE

FD3ERS

2

INFLUENCE OF METHOD OF PREPOLYMER PREPARATION ON FABRIC PROPERTIES

NH

3

NH

3

Ρ %

Ν %

Ν/Ρ Mole Ratio

VFT Inches

20.1

4.6

2.7

1.3

1.8

18.2

4.2

1.8

1.0

2.4

20.8

4.2

2.2

1.2

2.4

Add-on %

Method of Preparation

+ Salt

Salt

Flannelette treate Analysis made on non-oxidized samples after one laundering.

TABLE

3

INFLUENCE OF AGE OF PREPOLYMER ON FABRIC PROPERTIES

Add-on %

Ρ %

Ν %

N/P Mole Ratio

Fresh

18.2

4.2

1.8

1.0

2.4

2 weeks

17.2

3.3

1.6

1.1

BL

4 weeks

13.2

3.0

1.7

1.2

2.5

Age of Prepolymer

VFT Inches

Flannelette treated with prepolymer (2) then with caustic. Analyses made on non-oxidized samples after one laundering. phosphorus contents were from 3.0% to 4.2%, and nitrogen contents were from 1.6% to 1.8%. The N/P mole ratio remained constant at 1.0 to 1.2. Screening v e r t i c a l flame test results indicate some loss i n the effectiveness of the prepolymer at 2 weeks; however, samples treated with the same prepolymer after 4 weeks storage had no failures. These variations may have been due to non­ uniform treatment of fabric; because similar data were accumulated for t w i l l samplee and a l l of them passed the v e r t i c a l flame test. These results are also for non-oxidized samples. When excess caustic was added to a 4 g sample of freshly prepared prepolymer, about 4-6 l/2g of white polymer Cor precipitate) was formed. This quantity was gradually reduced as the prepolymer aged and lost i t s reactivity and appeared dependent

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

17.

ELGAL

ET

AL.

Flame Retardant Chemicals in Cotton

259

upon method of preparation. For better s t a b i l i t y , the prepolymer should be stored i n opaque containers, away from l i g h t , at 10°C, and be free of contamination. These studies are continuing. Summary Preliminary studies were undertaken to minimize problems encountered with the conventional THPOH-NH- process when formulations were altered and processing was modified. A prepolymer was prepared by acidifying the THP salt (THPS) with phosphoric acid to pH 1, then adding ammonia to form a soluble phosphorus-nitrogen prepolymer. After the prepolymer was applied to cotton fabric, i t was made insoluble by the addition of a strong base (25% NaOH)· There was no drying step between application of prepolymer and caustic. The P-N prepolymer wa cotton fabric, and polymerized (or precipitated) by the addition of caustic. The N/P mole ratio was approximately 1 i n the treated fabric. Parameters examined were effect of heat on prepolymer, and effect of caustic concentration, prepolymer preparation, and prepolymer age on polymerization (or precipitation). Abstract The commercially available flame retardant chemical THPS (tetrakis(hydroxymethyl)phosphonium sulfate) was processed into a prepolymer by f i r s t acidifying with an acid or acid salt and then ammoniating under controlled conditions. After the phosphorus-nitrogen prepolymer was applied to the cotton fabric, polymerization (or precipitation) occurred with the addition of base such as sodium hydroxide. The process described is intended as a substitute for the currently used process, i n which the THPS i s alkalized prior to application to cotton cloth and polymerized by exposing the impregnated fabric to gaseous ammonia. The new technique eliminates the need for gaseous ammoniation, which requires specially designed ammonia reactor equipment and involves associated problems of monitoring, control, and hazardous release of ammonia into the environment. With certain alterations i n the processing steps, energy could be conserved through elimination of at least one drying operation. Literature Cited

1. 2.

LeBlanc, R. Bruce, Text. Ind. (1977), 141 (2), 29. Odian, G. "Principles of Polymerization," p. 1-19, 110-124, McGraw-Hill Book Co., New York, 1970. 3. Quinn, F. J. Am. Dyest. Rep. (1974) 63 (5), 24. 4· Donaldson, D. J., Private communication. 5. Daigle, D. J., Pepperman, A. B. and Vail, S. L., U. S. Pat. No. 4,017,462, Apr. 12, 1977.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

260

SOLVENT SPUN RAYON, MODIFIED CELLULOSE FIBERS

6. Daigle, D. J., Pepperman, Α. Β., and Vail, S. L., U. S. Pat. No. 3,961,110. June 1, 1976. 7. U. S. Fed. Supply Service, "Textile Test Methods," Fed. Spec. CCC-T191b, Method 5902, U. S. Gov. Printing Office (1951). 8. Reeves, W. Α., Perkins, R. Μ., Piccolo, B., and Drake, G. L., Jr. Text. Res. J. (1970), 40 (3), 223.

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDEX A Absorbance, relation of turbidity to .. Absorbency Absorption peaks, nitrite ultraviolet .. Acetic acid monohydrate pretreatment Aetone Acetonitrile Acetone soluble secondary cellulose acetate Acetyl value Acetylation behavior of hydroxyethylated wood pulp of D M F - N 2 O 4 , attempted

135 209 56 149 97 40 124 9

Aluminum and calcium nitrates 34 Ammonia 74,152 cure process 249 reactions of cellulose with amic acids and anhydride/ 152 volatile 185 Ammonium hydroxide 74 Ammonium salts 74 Analysis, sugar 100,112 Anhydride/ammonia, reactions of

125 116

Β

of dissolved cellulose, direct 115 Bake reaction, grade and "low purity" wood pulps, pad152-153,158,168,175,180 purity of 97 Base, cellulose as a 14 of homogeneously sulfated cellulose 115 Bases for neutralization, calcium 65 performance, predicting 121 Bases, organic 16 of regenerated cellulose 116 Bases in regeneration bath 43 with homogeneous sulfation 116 Bath, spin 62 Acid(s) Bath, vacuum distillation of synthetic amic 159,190 spin 65 and anhydride/ammonia, reac­ Beaten fibers, comparison of the tions of cellulose with 152 properties of ultrasonically and solutions, stability of 163 mechanically 245 cellulose as an 15 Biological effects of Cytrel 92 esters, cellulose half152 Binder 240 half-amides of dicarboxylic 152 morphology, fiber/ 242 Lewis 14 Bis (β-γ dihydroxypropyl) disulfide .. 17 maleamic 190 Bulky viscose fiber 211 nitric 14 phosphoric 14,25 phthalamic 158,159,175,187 reaction between cellulose and Cadmium and iron complexes 17 α,/î-amic 155 Carbon disulfide 18 succinamic 159,159,170,187 Carbon intermediates 21 sulfuric 14,25 Carboxyl content, determination of ... 100 Acidification 225,226 Calcium bases for neutralization 65 Amic acid(s) 159,190 Calcium nitrates, aluminum and 34 and anhydride/ammonia, reactions Calcium thiocyanate, cellulose of cellulose with 152 dispersed in 26 reaction between cellulose and «,/?- 155 Cellulose 3,96,240 solutions, stability of 163 acetate Amide ammonia 166,185 acetone-soluble secondary 124 Amides of dicarboxylic acids, half- .... 152 chromatograms of 103 Amines, saturated 74 commercial preparation of 96 Aminolysis 158 flake properties 122,123 Alcoholysis 53,156 flakes, intrinsic viscosity of 99 Alkaline methanol-spun fiber 45 moisture content of 99

263

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

264

SOLVENT SPUN RAYON, MODIFIED CELLULOSE

Cellulose acetate (Continued) prepared from a hardwood kraft wood pulp 110 prepared from a softwood kraft wood pulp 106 prepared from a softwood sulfite wood pulp 108 preparation 105 residues, characterization of insoluble 96 secondary 115 as an acid 15 acetylation of homogeneously sulfated 115 acetylation of regenerated 116 with amic acids and anhydride/ ammonia, reactions of 152 and α,/3-amic acids, reaction between 15 as a base 14 carbonate 21 in ( C H 0 ) / D M S O 71 properties offibersprepared from 77 complexes 17 derivatives 18 direct acetylation of dissolved 115 dispersed in calcium thiocyanate .... 26 dissolved in N C V D M F 29 in DMSO-paraformaldehyde solutions 35 fibers, cross-linked 231 formate 21 half-acid esters 152 with homogeneous sulfation, acetylation of regenerated 116 in N 2 O 4 / D M F , production of rayon from 40 N 2 O 4 / D M F solution, recovery and recycle of raw materials 52 nitrite 58,70 solutions, spinning of uncoventional 25 solvent systems 12 during spinning, regenerating 54 xanthate 53 Cellulosic fabrics 152 ( C H 0 ) ,/DMSO, cellulose in 71 properties offibersprepared from 77 Chemical microscopy in applied woven and non-woven technology, use offiberand 233 Chemical structure, THPS 251 Chemicals in cotton, prepolymer preparation and polymerization of flame retardant 249 Chemistry of the cellulose/N 0 / D M F solution, recovery and recycle of raw materials 52 2

x

2

2

4

FD3ERS

AND DERIVATIVES

Chloroform 166,185 Chromatograms of cellulose acetate .. 103 Chemistry of dissolution and regeneration 52 Chromatography, gas 101 Chromatography, gel permeation 101 Cigarette design 83 Cigarettes, techniques to decrease the smoke delivery of 83 Closed-loop process 9, 69 Commercial preparation of cellulose acetate 96 Complex, donor-acceptor 53 Complexes caamium and iron 17 copper 17 cellulose 17 Composition of Cytrel 85 Composition, effect of the pad bath concentration on the residue 173 Composition of the regeneration bath 43 Compositions of Cytrel and tobacco .. 87 Coagulation and regeneration, rapid 42 Coagulants 74 Copper complexes 17 Cotton 152 flannelette 249,257 prepolymer preparation and polymerization of flame retardant chemicals in 249 Viloftvs 209 Countercurrent extraction 62 Cross-linked cellulose fibers 231 Cross-linked lignins, rayon fibers containing 215 Cross-linked sodium lignate, rayon fibers containing formaldehyde . 214 Cross-linked sodium lignosulfonate, rayonfiberscontaining formalde­ hyde 215 Cross-linking 214 Cross-sectioning of fabrics 236 Cuprammonium rayon 4 Cyclohexyl dimethyl amine oxide 16 Cytrel 83 biological effects of 92 composition of 85 and tobacco, compositions of 87 and tobacco, deliveries of various components from 85 tumorigenic activity of 93 D Degree of polymerization Dehydrocyclization to yield imide

40, 71 166,175,191 192

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

265

INDEX

Derivatives, cellulose 18 Fabric(s) (Continued) cross-sectioning of 236 Dicarboxylic acids, half-amides of .... 152 for flame retardancy, treating Diffusion 254 cotton 254 Dimethylformamide (see also D M F ) 72 /dinitrogen tetroxide solvent planar sectioning of 238 rayon non-woven 240 (see also D M F / N 0 ) 115 structure of non-woven 238 Dimethylnitrosamine 92 woven 233 Dimethyl sulfoxide 71 [see also DMSO) 40,41,72 Fiber(s) Dinitrogen tetroxide/dimethyl alkaline methanol-spun 45 /binder morphology 242 formamide 115 Dissolution 53 bulky viscose 211 and regeneration, chemistry of 52 from cellulose/N 0 /DMF solution 48 time for 40 and chemical microscopy in applied Distillation, vacuum 61 woven and non-woven techof the crude spin bath, recovery of nology, use of 233 process chemicals by 63 comparison of the properties of D M F ( see also dimethyl formamide) 121,17 /ammonium nitrate 33 consumption, world 6 - H N O 3 binary mixture 64 containing cross-linked lignins, /N 0 40, 52,116 rayon 215 attempted acetylation 116 containing formaldehyde crossfibers from 48 linked sodium lignate, rayon 214, 215 treatment 20 containing lignin derivatives, precipitating solvent mixtures 61 viscose rayon 212 DMSO (see also dimethyl sulfoxide) cross-linked cellulose 231 /CS /amine 18 cross-sections 74 cellulose in ( C H 0 ) / 71 flexibility 247 methylamine in 16 with high wet modulus 43 -paraformaldehyde (PF) solutions, hollow viscose 199 cellulose in 35,38 kraft pulp 245 paraformaldehyde system 21 physical properties 5,49, 76,78,205 solution, properties offiberspreproduction process, rayon 10 ared from cellulose/ saturation point 247 structure 235 CH 0),/ 77 sulfite 247 Donor-acceptor complex 53 sugar distribution Ill Drying 219,221,225,229 swelling 247 solvent-exchange 218 Viloft vs. other viscose 208 a superabsorbent pulp, process for 217 visible, technique for making £ surface 236 96 Electron micrographs 147 Film castings, solvent 71 scanning 247 Films 131 Elongation 45 Filtration characteristics Esters 18 Flame retardancy, treating cotton fabric for 254 cellulose half-acid 152 Ethers 18 Flame retardant chemicals in cotton, Ethylene oxide, hydroxyethylation prepolymer preparation and with 125 polymerization of 249 Ethylene oxide treatment of a Flexibility, fiber 247 nitration grade pulp 151 Flocculation 221 EtAc/N 0 20 Fractionation 97 Extrudability 29 Freeness 247 Formaldehyde cross-linked sodium F lignate, rayon fibers containing 214,215 Fabric(s) 183 cellulosic 152 Fusion reaction 2

4

2

2

4

4

2

2

x

f

2

2

4

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

SOLVENT SPUN RAYON, MODIFIED CELLULOSE FIBERS AND DERIVATIVES

266

Κ Gas chromatography Gel permeation chromatography Glucose Glycerol Godet stretch Grafting of polyacrylonitrile

101 101 101 91 42,79 227 225

H Half-amides of dicarboxylic acids 152 Hammered bone-dry pulps 129 Hammering 139 Hardwood kraft pulp 109,119 cellulose actate prepared from a .... 110 Hardwood sulfite pulp Ill Heat on prepolymer, effect of 25 Hemicellulose content 149 Hemicelluloses 96 Hollow viscose fiber 199 Homogeneous sulfation 119,121 Hydrazine 15 Hydrolysis 53,168,187,191,225-227 under non-swelling conditions 218 at high pulp concentrations 218 Hydroxides, inorganic 15 Hydroxyethylated pulp 149 acetylation behavior of 125 Hydroxyethylation 139,149 with ethylene oxide 125

I Imide, dehydrocyclization to yield .... 192 Improved saline retention value 229 Inflated viscose fiber 201 Infrared spectroscopy 159 Inorganic bases 15 Inorganic complexes 17 Inorganic hydroxides 15 Insoluble cellulose acetate residues, characterization of 96 Intermediates, carbon 21 Intermediates, nitrogenous 19 Intermediates, sulfur 18 Internal transacylation 191 Intrinsic viscosity 129,143 of cellulose acetate flakes 99 Isoimides 191 Isolation of a cellulose nitrite ester .... 55 Isopropyl alcohol 62 spinning system based on 70 Isopropyl nitrite 62

J Jet stretch

Kraft pulp

245

L Launderability performance 79 Lewis acids 14 Lignate and lignosulfonate, unmodified 213 Lignin 103, 111 derivatives, viscose rayon fibers containing 212 rayon fibers containing cross-linked 215 Lignisulfonate, unmodified lignate and 213

Mannose 101 Manufacture, Viloft 203 Mechanism of dissolution 53 Methanol, methylene chloride/ 102 Methanol wash 223 Methylamine in DMSO 16 Methylene chloride/methanol 102 Methylolcellulose 74 Micrographs, electron 146 scanning 247 Microscopy in applied woven and non-woven technology, use of fiber and chemical 233 Moisture conditioning 131,139,149 Moisture content of cellulose acetate . 99 Molecular weight distribution 101 Monoammonium succinate 187

Ν N 0

(see also dinitrogen tetroxide) 40,72 /DMF 116 attempted acetylation of 116 production of rayon from solutions of cellulose in 40, 48 via pyrolysis of metal nitrates and nitrites, production of 65 recovery and recycle of 60 yields, effect of temperature and sweep gas on 67 Neutralization, calcium bases for 65 Nicotine 85,94 Nitrate salts in DMF/precipitating solvent mixtures, solubilities of .. 61 Nitrates, aluminum and calcium 34 Nitrates and nitrites, production of N 0 via pyrolysis of metal 65 Nitric acid 14 2

4

2

42,79

fibers

4

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

267

INDEX Nitrite ester, isolation of a cellulose ... 55 Nitrite groups, control of the removal of the 53 Nitrite ultraviolet absorption peaks ... 56 Nitrites, production of N 0 via pyrolysis of metal nitrates and ... 65 Nitrocellulose 3 Nitrogen oxides 19 Nitrogenous intermediates > 19 Nitrogen prepolymer, phosphorus 253,259 N 0 - D M F , cellulose dissolved in 29 Non-hydrolyzed PAN absorbent pulp 229 Non-woven fabrics, structure of 238,240 Non-woven technology, use of fiber and chemical microscopy in applied woven and 233 2

4

2

Process (Continued) drying 219,221 for drying a superabsorbent pulp .. 217 rayon fiber production 4,10 viscose 4,40,71,197 Processing of Viloft 207 Production of N 0 via pyrolysis of metal nitrates and nitrites 65 Production, rayon 4,40,197 problems with 7 from solutions of cellulose in N 0 /DMF 40 viscose 197 Properties cellulose acetate flake 122,123 fiber 5,78,205 offibersprepared from cellulose/ 2

2

4

4

Ο

of regenerated cellulosic fibers 76 of ultrasonically and mechanically beaten fibers, comparison of the 245 Viloft tensile 205 yarn 29 Protonic acids 14 Protonic nucleophilic species 42 41 Pad-bake reaction 152,153,168,175,180 Pulp cellulose acetate prepared from a Pad-bath reaction 158 hardwood kraft wood 110 Pad bath stability 187 cellulose acetate prepared from a PAN absorbent pulp, non-hydrolyzed 229 softwood kraft wood 106 Paraformaldehyde 72 cellulose acetate prepared from a Phosphoric acid 14, 25,251,259 softwood sulfite wood 108 Phosphorus-nitrogen prepolymer .253, 259 concentration, hydrolysis at high 218 Phthalamic acid 158,159,175,187 ethylene oxide treatment of a Phthalic anhydride 191 nitration grade 151 Phthalimide 170 to fiber, sugar distribution Ill Physical properties, fiber 5,49,78 fibers, kraft 245 Planar sectioning of fabrics 238 form, influence of 72 Polar aprotic organic solvents 72 hammered bone-dry 129 Polar solvents 20 hardwood kraft 109,119 Polyacrylonitrile, grafting of 225 hardwood sulfite Ill Polyester 199 hydroxyethylated 149 Polymerization, degree of 40, 71 non-hydrolyzed PAN absorbent 229 chemicals in cotton, prepolymer pretreatment of 149 preparation and 249 process for drying a superabsorbent 217 Polyvinyl acetate 240 purity of acetylation grade and Prepolymer, phosphorus*Îow purity" wood 97 nitrogen 253,257,259 in sheet form, superabsorbent 231 Prepolymer preparation 251 softwood kraft 105,119 and polymerization of flame softwood sulfite 107,119 retardant chemicals in cotton 249 structure 146 Pretreatment, acetic acid acetylation behavior of hydroxymonohydrate 149 ethylated wood 125 Pretreatment of pulp 149 Purity of acetylation grade and "low Process purity" wood pulps 97 ammonia cure 249 closed-loop 9 Pyridine 20 Organic bases Organic complexes Organic solvents, polar aprotic

16 17 72

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

268

SOLVENT SPUN RAYON, MODIFIED CELLULOSE

R Rayon 3 fiber production process 10 fibers containing cross-linked lignins 214,215 fibers containing lignin derivatives, viscose 212 cuprammonium 4 non-woven 240 plants, new 4 problems with production of 7 production 4 from solutions of cellulose in N 0 /DMF 40 viscose 197 viscose 152,180 Reaction between cellulose and «,β-amic acids 152,15 Reaction, fusion 18 Reaction, pad-bake .152,153,168,175,180 Reaction, pad-bath 158 Regenerated cellulose with homo­ geneous sulfation acetylation of .. 116 Regenerated cellulosic fibers, properties of 76 Regenerating cellulose during spinning 54 Regeneration 74 bath, composition of 43 chemistry of dissolution and 52 rapid coagulation and 42 Relation of turbidity to absorbance .... 135 Removal of nitrite groups, control of the 53 Recovery of process chemicals by vacuum distillation of the crude spin bath 63 Recovery and recycle 13,52, 53,60 Recycle, recovery and 13,52,58,60 2

4

S S6.5 values 43, 79 Saline retention value, improved 229 Salts of sulfur compounds 74 Saturation point, fiber 247 Scanning electron micrographs 247 Secondary cellulose acetate 115 Sectioning of fabrics, planar 238 S0 72 /amine solvents 18,25 Sodium hydroxide 251 lignate 212,213,214 lignosulfonate 212,213,215 sulfide 74 sulfite 74 thiosulfate 74 zincate 15 2

FD3ERS

AND DERIVATIVES

Softwood kraft pulp 105,119 cellulose acetate prepared from a .. 106 Softwood sulfite pulp 107,119 cellulose acetate prepared from a .. 108 Solubilities of nitrate salts in DMF/precipitating solvent mixtures 61 Solutions of cellulose in N 0 / D M F , production of rayon from 40 Solutions, spinning of unconventional cellulose 25 Solvent-exchange drying 218 Solvent film castings 96 Solvent mixtures, solubilities of nitrate salts in DMF/precipitating 61 Solvents, polar 20 aprotic organic 72 2

4

Spectral studies Spectroscopy, infrared 159 Spin bath 32,38,62 compositions 35 recovery of process chemicals by vacuum distillation of the crude 63 vacuum distillation of a synthetic .. 65 Spinnerettes, types of 42,73 Spinning 42,212 experiments 26,62 regenerating cellulose during 54 speeds 34,50,54,73 system based on isopropyl alcohol.. 70 of unconventional cellulose solutions 25 Stability of the amic acid solutions ... 163 Stability, pad bath 187 Stability of the small particle population 135 Stress-strain curves 45 Stretch, godet 42 Stretch, jet 42 Structure fiber 235 of non-woven fabrics 238 pulp 146 THPS 251 Succinamic acid 158,159,170,187 Succinimide 170 Sugar analysis 100,112 Sulfated cellulose, acetylation of homogeneously 115 Sulfation, homogeneous 116,119,121 Sulfur compounds, salts of 74 Sulfur intermediates 18 Sulfur trioxide 116,124 Sulfuric acid 14,25 Sulfite fibers 247 Superabsorbent pulp in sheet form ... 231

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

269

INDEX Sweep gas on N 0 yields, effect of temperature and Swelling fiber 2

4

67 221 247

Τ

Tar 85,94 Technique for making surface fibers visible 236 Techniques to decrease the smoke delivery of cigarettes 83 Temperature 40 and sweep gas on N 0 yields, effect of 67 Tensile properties, Viloft 205 Tetrahydrofuran 101 Tetrakis ( hy droxymethyl ) phos phonium sulfate (THPS) Textile fibers, physical properties 5 THPOH 254 THPS structure 249,251 Time for dissolution 40 Tobacco compositions of Cytrel 87 deliveries of various components from Cytrel and 85 smoke, relative deliveries of vapor phase components 89 smoke, semivolatile fraction of 90 supplement, Cytrel 83, 84 Transacylation, internal 191 Transnitrosation reaction 53 Triethylamine oxide 16 Triton Β (benzyltrimethylammonium hydroxide) 16 Tumorigenic activity of Cytrel 93 Turbidity 127,131 relation to absorbance 135 2

4

Vacuum distillation of synthetic spin bath 65 Vapor phase components of tobacco smoke, relative deliveries of 89 Viloft 199 manufacture 203 processing of 207 special characteristics 207 tensile properties 205 vs. cotton 209 vs. other viscose fibers 208 Viscose 240 fiber, bulky 211 fiber, hollow 199 fiber, inflated 201 fibers, Viloft vs. other 208 process 4,40, 53,71 rayon production of Viscosity, intrinsic of cellulose acetate VIS spectra, U V Volatile ammonia Volatilization

152,180 197 129,143 flakes 99 55 185 191

W Wet modulus,fiberswith high World fiber consumption Woven fabrics Woven and non-woven technology, use of fiber and chemical microscopy in applied

43 6 233 233

X Xanthates Xylans Xylose

18 121 101

U UV-VIS spectra

Y

55

Yarn properties Yellowness coefficient Vacuum distillation of the crude spin bath, recovery of process chemicals by

29,38 129,146

Ζ 63

Zinc chloride

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

26