Viscose Rayon Fibers Containing Lignin Derivatives

13 Viscose Rayon Fibers Containing Lignin Derivatives NEAL E. FRANKS

Downloaded by UNIV OF LEEDS on June 19, 2016 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0058.ch013

American Enka Co., Enka, N.C. 28728

The c o m p a t i b i l i t y o f cellulose w i t h lignin is demonstrated throughout the p l a n t world. This c o m p a t i b i l i t y is not necessarily shown as an i n t i m a t e mixture of the two polymers, but r a t h e r as a m a t r i x s t r u c t u r e o f cellulose f i b e r s in lignin. Although chemical p u l p i n g systems have been developed t o p r o v i d e d i s s o l v i n g pulps f r e e o f lignin, it is s u r p r i s i n g that t h e r e appear t o be no r e p o r t e d attempts t o recombine these two polymers in fibrous form. The v i s c o s e system could be the ideal technique by which t o achieve such fibers, since in the alkaline milieu of the c e l l u l o s e xanthate s o l u t i o n both polymers will demonstrate similar charge effects. The experiments d e s c r i b e d here will outline c o n d i t i o n s necessary t o prepare such fibers and t o d e s c r i b e some o f the p r o p e r t i e s o f the resulting f i b e r s . M a t e r i a l s and Methods The sodium l i g n a t e and sodium l i g n o s u l f o n a t e used were commercially a v a i l a b l e m a t e r i a l s o f h i g h e s t purity. This degree of p u r i t y was deemed necessary due t o the p o s s i b l e c o m p l i c a t i o n s which could a r i s e from the i n t r o d u c t i o n o f f o r e i g n i n o r g a n i c m a t e r i a l s i n t o the v i s c o s e process. T y p i c a l analytical v a l u e s f o r the sodium l i g n a t e and sodium l i g n o s u l f o n a t e used a r e provided in Table 1. It was necessary to purge the alkaline s o l u t i o n s o f t h e sodium lignate with nitrogen prior to use to remove amounts o f ammonia added d u r i n g the p r o c e s s i n g of this m a t e r i a l . The cross-linking trials of either sodium lignate or sodium l i g n o s u l f o n a t e were performed u s i n g a 20-25% polymer l o a d i n g in s o l u t i o n . Spinning trials were performed by adding alkaline s o l u t i o n s of the lignin derivatives to a standard textile viscose stream j u s t before the last filtration stage. T h i s mixture was spun through a 750 h o l e s p i n n e r e t i n t o a rayon s p i n b a t h and s t r e t c h was a p p l i e d in a second bath c o n t a i n i n g hot dilute sulfuric

212

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

FRANKS

213

Vicose Rayon Fibers

acid. The wet y a r n was c o l l e c t e d i n a c e n t r i f u g a l p o t , and t h e wet y a r n c a k e was p u r i f i e d and d r i e d i n n o r m a l f a s h i o n . The t a r g e t d e n i e r i n t h e s e t r i a l s was 1 1 0 0 f o r t h e d r i e d y a r n bundle.


Table 1 .

A n a l y t i c a l Data f o r Sodium L i g n a t e Lignosulfonate. Sodium Lignate ( I n d u l i n AT)

Total sulfur, % S u l f a t e s u l f u r as S, S u l f i t e s u l f u r a s S, CaO, % MgO, % Reducing sugars pH i n w a t e r R e s u l t s and

% %

1.6 0 0

(as

and

Sodium

Sodium Lignosulfonate ( M a r a s p e r s e CB) 2.6 0.1 0 0.03

ether)

Nil Nil Nil

Trace 0 8.5-9.

6

Discussion

U n m o d i f i e d L i g n a t e and L i g n o s u l f o n a t e . The f i b e r d e n i e r v a l u e s o b t a i n e d by a d d i n g an amount o f u n m o d i f i e d s o d i u m l i g n a t e o r sodium l i g n o s u l f o n a t e t o t h e v i s c o s e stream i n amounts t o a c h i e v e 2 0 t o k0% l o a d i n g s , b a s e d on t h e amount o f c e l l u l o s e present, are provided i n Table 2. The d e n i e r v a l u e s shown a r e a v e r a g e v a l u e s o b t a i n e d u s i n g t h e i n s i d e and o u t s i d e v a l u e s o f the y a r n package. Table 2.

R e l a t i v e D e n i e r V a l u e s o f Rayon F i b e r s Spun U s i n g U n m o d i f i e d S o d i u m l i g n a t e and L i g n o s u l f o n a t e .

Sample

Corrected

Control 20% S o d i u m l i g n a t e k0% Sodium l i g n a t e Control 20$ Lignosulfonate

denier

1110 1035 965 1105 93*+

I t c a n be s e e n t h a t t h e r e t e n t i o n o f u n m o d i f i e d s o d i u m l i g n a t e was b e t t e r t h a n t h a t o b s e r v e d f o r s o d i u m l i g n o s u l f o n a t e T h i s d i f f e r e n c e i s b e s t e x p l a i n e d by t h e f a c t t h a t t h e s u l f o n i c a c i d r e s i d u e s present i n the sodium l i g n o s u l f o n a t e cause t h i s p o l y m e r t o be more s o l u b l e i n t h e s u b s e q u e n t p u r i f i c a t i o n stages of the v i s c o s e rayon process a l l o w i n g a greater l o s s of lignosulfonate. I t was f e l t t h a t some t e c h n i q u e was n e e d e d t o i m p r o v e t h e r e t e n t i o n o f b o t h s o d i u m l i g n a t e and l i g n o s u l f o n a t e a method o f c r o s s - l i n k i n g was j u d g e d t h e b e s t p o s s i b i l i t y o f a c h i e v i n g t h i s end.


S O L V E N T SPUN R A Y O N , M O D I F I E D C E L L U L O S E

214

FIBERS

C r o s s - l i n k i n g M e t h o d s . The c h o i c e o f t h e p r o p e r c r o s s l i n k i n g m e t h o d was b a s e d on t h e e a s e a n d r e p r o d u c i b i l i t y o f the technique a v a i l a b l e . O x i d a t i v e c r o s s - l i n k i n g , such as t h a t r e p o r t e d b y N i m z , was e l i m i n a t e d on t h e b a s i s t h a t i t could exascerbate the problem o f color i n the r e s u l t i n g f i b e r . A s e c o n d c r o s s - l i n k i n g method c o n s i d e r e d was t h a t o f e t h e r i f y ing the reactive phenolic hydroxyl residues with multifunction a l c r o s s - l i n k i n g agents such as e p i c h l o r o h y d r o n o r c y a n u r i c chloride . Small scale experiments demonstrated that t h i s method was n o t e a s y t o c o n t r o l . Further, a significant reduction of the phenolic hydroxyl population could adversely affect the s o l u b i l i t y of the l i g n i n derivatives, p a r t i c u l a r l y sodium l i g n a t e , i n t h e v i s c o s e system. The m e t h o d f i n a l l y a d o p t e d f o r c r o s s - l i n k i n g b o t h t h e s o d i u m l i g n a t e a n d l i g n o s u l f o n a t e was t h e u s e o f f o r m a l d e h y d e under a l k a l i n e c o n d i t i o n s . P i l o t e x p e r i m e n t s were p e r f o r m e d by c r o s s - l i n k i n g a t pH 1 0 . 5 - 1 1 ; a c r u d e m e a s u r e o f s u c c e s s was o b t a i n e d by p o u r i n g t h e s e c r o s s - l i n k e d m a t e r i a l s i n t o s p i n bath t o observe the y i e l d o f c r o s s - l i n k e d m a t e r i a l . Optimum f o r m a l d e h y d e l e v e l s w e r e f o u n d t o be 5 $ w/w f o r s o d i u m l i g n a t e and 1 0 $ w/w f o r s o d i u m l i g n o s u l f o n a t e . This difference i s a f u r t h e r r e f l e c t i o n o f t h e s o l u b i l i t y d i f f e r e n c e due t o t h e s u l f o n i c a c i d r e s i d u e s p r e s e n t i n sodium l i g n o s u l f o n a t e . S p i n n i n g t r i a l s were a g a i n p e r f o r m e d , b u t u s i n g t h e c r o s s linked derivatives. The r e s u l t s o b t a i n e d w i t h t h e a d d i t i o n o f 20% a n d k0% l e v e l s o f f o r m a l d e h y d e c r o s s - l i n k e d s o d i u m l i g n a t e are provided i n Table 3. I t i s l i k e l y t h a t some e r r o r occurred i n the determination o f the s o l i d s content o f the c r o s s - l i n k e d s o d i u m l i g n a t e , w h i c h was r e f l e c t e d i n t h e l o w e r f i b e r denier determination. As e x p e c t e d , a d d i t i o n o f a d i l u e n t t o t h e c e l l u l o s i c f i b e r r e d u c e d b o t h t h e c o n d i t i o n e d and wet t e n a c i t i e s a s w e l l a s r e d u c i n g t h e e l o n g a t i o n a t b r e a k . A d e n i e r e r r o r i n t h e o p p o s i t e d i r e c t i o n was o b s e r v e d f o r t h e f i b e r c o n t a i n i n g 20% f o r m a l d e h y d e c r o s s - l i n k e d s o d i u m l i g n o s u l f o n a t e (Table k). 1


2

Table 3.

P h y s i c a l P r o p e r t i e s o f Rayon F i b e r s C o n t a i n i n g Formaldehyde C r o s s - L i n k e d Sodium L i g n a t e . ko% 20% Control

Denier Cond. t e n . (gpd) Cond. e l o n g . (%) Wet t e n . ( g p d ) Wet e l o n g . (%)

1110 2.6

2k.k 1.3 37.0

1075 2.16 21.8

1.03 3U.9

1018

1.9^ 19.6 0.82 30 Λ

This difference i s again attributed t o the d i f f i c u l t y of o b t a i n i n g an a c c u r a t e t o t a l s o l i d s c o n t e n t o f t h e c r o s s l i n k e d mixture. The d e c r e a s e i n t h e o t h e r p h y s i c a l properties c l o s e l y matches t h o s e o b s e r v e d f o r t h e c r o s s - l i n k e d sodium l i g n a t e system.


FRANKS

T a b l e k.

P h y s i c a l P r o p e r t i e s o f Rayon F i b e r C o n t a i n i n g Formaldehyde C r o s s - L i n k e d Sodium L i g n o s u l f o n a t e .

Denier Cond. t e n . (gpd) Cond. e l o n g . {%) Wet t e n . (gpd) Wet e l o n g . {%)


215

Vicose Rayon Fibers

Control

20%

1105 2.67 26.2

ll80 2.22 19-9

1.35

37-0

Ο.96

28.5

D e m o n s t r a t i o n o f I n c l u d e d L i g n i n D e r i v a t i v e s . I t was d e s i r a b l e t o have a method d e m o n s t r a t i n g t h e p r e s e n c e o f t h e c r o s s - l i n k e d l i g n i n d e r i v a t i v e s , i n a d d i t i o n to the denier determinations used i n the e a r l y p o r t i o n of t h i s d i s c u s s i o n . A t t e m p t s w e r e made t o d e m o n s t r a t e t h e p r e s e n c e o f t h e s e a d d e d p o l y m e r s c h e m i c a l l y ; i o d i n a t i o n and measurement o f t h e l e v e l o f i o d i n a t i o n o f t h e p h e n o l i c r e s i d u e s was inconclusive. S e l e c t i v e e x t r a c t i o n of the c e l l u l o s e p o r t i o n of the f i b e r w i t h c u p r i e t h y l e n e d i a m i n e d i s s o l v e d b o t h t h e c e l l u l o s i c and l i g n i n portions of the f i b e r . An e x a m i n a t i o n o f some a d d i t i o n a l p h y s i c a l p r o p e r t i e s ( T a b l e 5 ) showed some s l i g h t d i f f e r e n c e s , b u t n o t h i n g o f s u f f i c i e n t magnitude t o c o n v i n c i n g l y demonstrate the presence o f t h e a d d e d p o l y m e r s . The s l i g h t d e c r e a s e i n w a t e r i m b i b i t i o n o f t h e c r o s s - l i n k e d s o d i u m l i g n a t e f i b e r was i n t h e e x p e c t e d d i r e c t i o n s i n c e t h e l i g n a t e w o u l d be e x p e c t e d t o h a v e some hydrophobic character. L i k e w i s e , t h e c r o s s - l i n k e d sodium l i g n o s u l f o n a t e had an i m p r o v e d w a t e r i m b i b i t i o n . N e i t h e r o f t h e s e v a l u e s w e r e f a r enough f r o m c o n t r o l v a l u e s t o be c o n vincing. The same comments c a n be made f o r t h e X - r a y o r d e r and k n o t t e n a c i t y r e t e n t i o n v a l u e s . Table 5.

Sample

W a t e r I m b i b i t i o n , X-Ray O r d e r , and K n o t T e n a c i t y R e t e n t i o n V a l u e s o f Rayon F i b e r s C o n t a i n i n g Cross-Linked Lignins. Knot T e n a c i t y Water X-Ray Retention, % Imbibition,^ Order

Control

80-90

0.87

79

20% C r o s s - l i n k e d lignate 20$ C r o s s - l i n k e d lignosulfonate

72

0.85

77

96

0.85

71

C o n s i d e r a b l y more s u c c e s s was e x p e r i e n c e d u s i n g i n f r a r e d d i f f e r e n c e spectroscopy i n the 5 . 7 5 - 6 . 2 5 micron region. These s p e c t r a l s t u d i e s w e r e p e r f o r m e d u s i n g b o t h c o n t r o l f i b e r s and s a m p l e f i b e r s i n KBr p e l l e t s . C a l i b r a t i o n c u r v e s were o b t a i n e d by m i x i n g known amounts o f t h e c r o s s - l i n k e d l i g n i n d e r i v a t i v e and c o n t r o l r a y o n f i b e r . By t h i s m e a s u r e , t h e r a y o n f i b e r


216

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

FD3ERS


t h o u g h t t o c o n t a i n 20% c r o s s - l i n k e d s o d i u m l i g n a t e was shown t o c o n t a i n b u t 18% o f t h e i n c l u d e d p o l y m e r . T h i s e x p l a i n s t h e l o w e r t h a n e x p e c t e d ( T a b l e 3) d e n i e r v a l u e s f o r t h i s f i b e r . Color. I t w i l l be a p p r e c i a t e d by t h o s e f a m i l a r w i t h t h e pulp and paper i n d u s t r y t h a t a d d i t i o n o f l i g n i n d e r i v a t i e s t o rayon f i b e r s c r e a t e s a f i b e r t h a t has a d i s t i n c t r e d d i s h b r o w n hue. Q u a n t i t a t i o n o f t h i s c o l o r u s i n g t h e Hunter L A B method i s shown i n T a b l e 6 . I n t h i s system, t h e L value i s a measure o f l i g h n e s s , t h e A v a l u e i n d i c a t e s a r e d hue i f p o s i t i v e a n d a g r e e n hue i f n e g a t i v e , a n d t h e Β v a l u e i n d i c a t e s yellowness i f p o s i t i v e and a blue t i n t i f negative. By t h i s measure, t h e f i b e r c o n t a i n i n g t h e formaldehyde c r o s s - l i n k e d sodium l i g n a t e i s darker t h a n t h e c o r r e s p o n d i n g f i b e r c o n t a i n i n g c r o s s - l i n k e d l i g n o s u l f o n a t e , although i t has a y e l l o w n e s s value. The v a l u e s o b s e r v e d , when compared w i t h a n o r m a l c o n t r o l f i b e r , would imply that t h e f i b e r s c o n t a i n i n g the c r o s s - l i n k e d l i g n i n d e r i v a t i v e s a r e unacceptable f o r normal t e x t i l e uses. T a b l e 6.

H u n t e r L A B V a l u e s f o r Rayon F i b e r s Cross-Linked L i g n i n Derivatives.

Sample

L

Control 85.0 20% C r o s s - l i n k e d l i g n a t e 3U.0 20% C r o s s - l i n k e d l i g n o s u l f o n a t e U 7 . 5

A -3 +6.8 +6.U

Containing

Β +5 +15.1 +19.8

Conclusion I t i s possible t o spin regenerated c e l l u l o s i c f i b e r s c o n t a i n i n g up t o k0% f o r m a l d e h y d e c r o s s - l i n k e d s o d i u m l i g n a t e or l i g n o s u l f o n a t e using t h eviscose process. There i s a corresponding decrease i n t e n a c i t i e s and elongation a t break f o r such f i b e r s . The p r e s e n c e o f t h e a d d e d p o l y m e r s was b e s t shown u s i n g i n f r a r e d d i f f e r e n c e s p e c t r o s c o p y . There i s a considerable increase i n the c o l o r o f the rayon f i b e r s c o n t a i n i n g t h e s e d e r i v a t i v e s due t o t h e c h r o m o p o r i c r e s i d u e s present i n t h e included polymers. Literature Cited 1. 2.

N i m z , H., German P a t e n t 2 , 2 2 1 , 3 5 3 . Allan, G. G., U. S. P a t e n t 3 , 6 0 0 , 3 0 8 .


Viscose Rayon Fibers Containing Lignin Derivatives

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