RayonA Fiber with a Future

1 Rayon—A Fiber with a Future H. L. HERGERT and G. C. DAUL

Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives Downloaded from pubs.acs.org by 185.2.32.38 on 02/20/17. For personal use only.

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 With a Future" or facetiously, Rayon S t r i k e s Back! The term rayon now represents many d i f f e r e n t 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

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 on rayon s u f f e r e d . Since that time, new growth markets have opened f o r rayon, such as i n d i s p o s a b l e s and 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

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


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

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 are the accepted norm. We b e l i e v e the use of 50$ or more c e l l u l o s i c f i b e r w i t h p o l y e s t e r i s a p r a c t i c a l 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


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 being made i n m o d i f i c a t i o n and r e d e s i g n of v i s cose rayon p l a n t s to reduce p o l l u t a n t s , f o r example, by recovery 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


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 expansion f o r rayon, or man-made c e l l u l o s i c f i b e r s , w i l l r e s u l t w i t h the development of a t o t a l l y new process, 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


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-making process.

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

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 — Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives Downloaded from pubs.acs.org by 185.2.32.38 on 02/20/17. For personal use only.

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.

RayonA Fiber with a Future

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