Graft Copolymerization of Lignosulfonate with Methacrylic Acid and

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Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on September 29, 2015 | http://pubs.acs.org Publication Date: June 18, 1982 | doi: 10.1021/bk-1982-0187.ch018

Graft Copolymerization of Lignosulfonate with Methacrylic Acid and Acrylate Monomers RUBIE CHEN and BOHUSLAV V. KOKTA Centre de Recherche en Pâtes et Papiers, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada G9A 5H7

Lignosulfonate from s u l f i t e spent liquor was grafted, after purifying through u l t r a f i l t r a t i o n with acrylic monomers: methyl acrylate, methyl methacrylate and methacrylic acid. Copolymeri zation was redox initiated by peroxide-ferrous ions in aqueous and non-aqueous media under ni trogen atmosphere. The effects of reaction me dium, reaction time, lignin/monomer ratio, pH, and peroxide charge, on the copolymerization were studied. Among the media employed, the magnitude of conversion of acrylate monomer was found to be the highest in water, lower in dioxane, and the lowest in methanol; while for acrylic acid the medium preference of obtaining better conversion was in the order of: water, methanol and dioxane. The best reaction con ditions in water were: 3% peroxide, 1:3 lignin/ monomer without any buffering, under which con version would reach 88-96% and the grafting efficiency 35-62%.

Since the p r i c e s o f petroleum products have soared, v a l o r i z a t i o n o f n a t u r a l resources has i n t e n s i v e l y a t t r a c t e d the a t t e n t i o n o f researchers in d i f f e r e n t f i e l d s . To f u l l y u t i l i z e wood, which i s a renewable raw m a t e r i a l , one must make b e t t e r use o f i t s 25-30% l i g n i n content which forms the p r i n c i p a l d i s s o l v e d m a t e r i a l in the spent l i q u o r o f chemical p u l p i n g processes. The annual p r o d u c t i o n of s u l f i t e pulp in Canada i s approximately 2.6 m i l l i o n tons (data based on 1979), t h u s , a t l e a s t one m i l l i o n tons of l i g n o s u l f o n a t e i s produced, r e p r e s e n t i n g a p o t e n t i a l r e source of raw m a t e r i a l f o r other uses. However, among 35 s u l f i t e m i l l s in Canada, only two o r three o f them possess a recovery system f o r spent l i q u o r , that means a very s m a l l p o r t i o n o f l i g nosulfonate has been recovered. The recovered l i g n i n has been

©

0097-6156/82/0187-0285$6.00/0 1982 American Chemical Society

In Graft Copolymerization of Lignocellulosic Fibers; Hon, D.; ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

GRAFT COPOLYMERIZATION OF LIGNOCELLULOSIC FIBERS


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used, t a k i n g advantage of i t s c o l l o i d a l p r o p e r t i e s , as the agents f o r e m u l s i f i c a t i o n , d e f l o c c u l a t i o n , c h e l a t i o n , adhesion, d r i l l i n g mud a d d i t i v e , e t c . Besides, research has been o r i e n t e d to the u t i l i z a t i o n of l i g n i n in polymer domains, e.g., as a moiety of e i t h e r thermosetting or thermal p l a s t i c s . The g r a f t of l i g n i n w i t h v i n y l monomers has been studied in the l a s t two decades, Koshijima and Muraki published a s e r i e s of reports on r a d i c a l g r a f t i n g of v i n y l monomers onto h y d r o c h l o r i c a c i d l i g n i n , induced by r a d i a t i o n (1, 2^, 3) or by chemical i n i t i a t o r s (4), Nam et a l . Ç5, 6) i n v e s t i g a t e d the g r a f t i n g of methacrylate onto l i g n o s u l f o n a t e , using hydrogen peroxide as an i n i t i a t o r . P h i l l i p s and h i s coworkers (7^, 8^, 9) s t u d i e d the r a d i a t i o n - i n d u c e d g r a f t copolymerization of styrene onto hydroc h l o r i c a c i d l i g n i n as w e l l as v a r i o u s k r a f t softwood l i g n i n s . Naveau (10) prepared m e t h a c r y l i c d e r i v a t i v e s of acid-hydrolyzed l i g n i n through e s t e r i f i c a t i o n . Chernyavskaya and B e r l i n (11) worked on the g r a f t i n g of methyl a c r y l a t e onto hydrolyzed wood l i g n i n using peroxide i n i t i a t o r . Simionescu and h i s coworkers (12, 13) s t u d i e d the r a d i a t i o n g r a f t i n g of h y d r o c h l o r i c a c i d popl a r l i g n i n and reed l i g n i n w i t h v i n y l monomers. G r a f t copolymeri z a t i o n of ozone-activated h y d r o c h l o r i c a c i d l i g n i n w i t h styrene was reported by Katuscak et a l . (14, 15). Through the awareness of t h a t , in t h e i r s t u d i e s , most of the above mentioned researchers used l i g n i n s s p e c i f i c a l l y l a b o r a t o r y -prepared, the main o b j e c t i v e of t h i s work was to d e r i v e l i g n i n p l a s t i c copolymers from l i g n i n a v a i l a b l e commercially; the other o b j e c t i v e s i n v o l v e d the k i n e t i c study and the o p t i m i z a t i o n of r e a c t i o n c o n d i t i o n s . Reported in the present paper are the g r a f t copolymerizations of calcium l i g n o s u l f o n a t e w i t h methyl a c r y l a t e , methyl methacrylate, and w i t h m e t h a c r y l i c a c i d ; the e f f e c t s of s e v e r a l r e a c t i o n v a r i a b l e s (medium, r e a c t i o n time, pH, lignin/monomer r a t i o , and i n i t i a t o r charge) on the copolymerization r e s u l t s are discussed. EXPERIMENTAL M a t e r i a l s . The l i g n i n m a t e r i a l used in t h i s study was a commercial calcium s a l t of l i g n o s u l f o n a t e (LS) ( T o r a n i l B, St. Regis Paper Co.), i s o l a t e d from the spent l i q u o r of softwood s u l f i t e pulping. I t was p u r i f i e d , in our l a b o r a t o r y , through u l t r a f i l t e r i n g a 2% water s o l u t i o n (using a M i l l i p o r e immersible molecular separate k i t ) and d r y i n g the f i l t r a t e under vacuum. The m a t e r i a l as received contained 8.8% methoxyl group ( s p e c i f i e d by the s u p p l i e r ) and i t s l i g n o s u l f o n a t e content was 86.8% w i t h reference to the p u r i f i e d m a t e r i a l (determined in our l a b o r atory by u l t r a v i o l e t absorption at 280 nm). V i n y l monomers, namely, methyl a c r y l a t e (MA), methyl methacrylate (MMA) and metha c r y l i c a c i d (MAA) were d i s t i l l e d under vacuum; d i s t i l l a t i o n was performed over c u p r i c s u l f a t e and through a copper-ring packed column to remove s t a b i l i z e r s . The c e n t r a l cut of each d i s t i l l a -


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t i o n was c o l l e c t e d in a dark b o t t l e and stored in a r e f r i g e r a t o r . Methanol was a l s o p u r i f i e d by vacuum d i s t i l l a t i o n . The other chemicals were of reagent grade and used without f u r t h e r p u r i f i cation. Copolymerization. The d e t a i l experimental procedures of co p o l y m e r i z a t i o n have been reported elsewhere (16), however, the procedures w i l l be described b r i e f l y here and are shown schema t i c a l l y in Figure 1. G r a f t copolymerization was redox i n i t i a t e d using hydrogen peroxide and f e r r o u s c h l o r i d e and was conducted under n i t r o g e n atmosphere w i t h gentle a g i t a t i o n . A f t e r r e a c t i o n , e x t r a c t i o n s were made to separate the r e s u l t i n g copolymer from the v i n y l homopolymer and the unreacted l i g n o s u l f o n a t e . In the L S - a c r y l a t e systems, acetone was used to e x t r a c t homopolymers, and water to e x t r a c t the unreacted l i g n o s u l f o n a t e . In the LS(methacrylic a c i d ) system, because water could d i s s o l v e the unreacted l i g n o s u l f o n a t e and the two r e a c t i o n products ( i . e . * homopolymer and g r a f t e d copolymer), ethanol and methanol were used to e x t r a c t the homopoly(methacrylic a c i d ) and the copolymer, r e s p e c t i v e l y . Wherever no s p e c i f i c a t i o n i s given, the r e a c t i o n c o n d i t i o n s used in t h i s work were f i x e d as f o l l o w s : CaLS = 1 g; monomer = 5ml measured at 25°C (MA = 4.79 g, 5.57x10"" mol; MMA = 4.70 g, 4.70X10" mol; MAA = 5.07 g, 5.90xl0"~ mol); f e r rous c h l o r i d e = 15 mg; hydrogen peroxide = 30 mg; r e a c t i o n me dium = 20 ml. When using water as a r e a c t i o n medium in the LS-MA (or MMA) system, a small q u a n t i t y of e m u l s l f i e r (Tween 20, 1 g /100 ml of medium) was employed. The copolymerization r e s u l t s were i n t e r p r e t e d in terms of the parameters defined below: 2

2

2

T o t a l monomer conversion, % = [(TS - WL)/M] x 100 G r a f t i n g e f f i c i e n c y , % = [1 - HP/(TS - WL)] χ 100 Degree of l i g n o s u l f o n a t e r e a c t e d , % = C(WL - LU)/WL] χ

100

where WL stands f o r the l i g n o s u l f o n a t e used in the r e a c t i o n ; M, the monomer; TS, the t o t a l s o l i d obtained a f t e r r e a c t i o n ; HP, homopolymer; and LU, l i g n o s u l f o n a t e unreacted. A l l these symbols are of the same weight u n i t . RESULTS AND

DISCUSSION

Reaction medium. When l i g n o s u l f o n a t e was subjected to g r a f t copolymerization w i t h v i n y l monomers, the extent of copolymeriza t i o n due to the e f f e c t of medium v a r i e d from one monomer to ano t h e r . In a LS-styrene system (16), i t was found that methanol was a b e t t e r medium than water under c e r t a i n given c o n d i t i o n s ; w h i l e in a L S - a c r y l o n i t r i l e system (17),the c o n t r a r y was t r u e , i . e . , water b e t t e r than methanol. This c o n t r a d i c t i o n was thought due to the f a c t that styrene has e l e c t r o p o s i t i v e ( i . e . , e l e c t r o n r e l e a s i n g ) s u b s t i t u e n t w h i l e a c r y l o n i t r i l e has e l e c t r o n e g a t i v e ( i . e . , e l e c t r o n - a t t r a c t i n g ) s u b s t i t u e n t . In the present study,



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Ca-LS I Ultra filtration

f

Acrylic monomer

Polymerization -^-Peroxide T(°C),0(min) (Nitrogen) --Ferrous 1

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Extraction (acetone)

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ι —

ι

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Figure 1. Schematic diagram of experimental procedures.



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copolymerization of l i g n o s u l f o n a t e and a c r y l a t e or a c r y l i c a c i d was examined in s e v e r a l media commonly used in l i g n i n research work. The r e s u l t i n g k i n e t i c curves are given in Figures 2 and 3, r e s p e c t i v e l y , f o r the LS-(methyl methacrylate) and LS-(methacryl i c a c i d ) systems. I t can be seen that a f t e r 2 hours of r e a c t i o n the t o t a l conversion of methyl methacrylate in the former system a t t a i n e d 88% in water and 60% in dioxane; though the initial con v e r s i o n r a t e s were n e a r l y the same in both media. The lowest conversion, 3%, occurred in methanol. In the second system ( F i g ure 3 ) , the t o t a l conversion of m e t h a c r y l i c a c i d reached 96, 61 and 30% in water, methanol, and dioxane, r e s p e c t i v e l y , w i t h i n i t i a l r a t e decreasing in t h a t order. The medium which brought about higher conversion was found to b r i n g about a l s o higher g r a f t i n g e f f i c i e n c y . For example, the g r a f t i n g e f f i c i e n c i e s of methyl methacrylate onto l i g n o s u l f o n a t e were 30, 19 and 8%, r e s p e c t i v e l y , in water, dioxane and methanol. The medium preference of the LS-(methyl a c r y l a t e ) system was s i m i l a r to that of the LS-(methyl methacrylate). Reaction time. As already seen in Figures 2 and 3, most of the r e a c t i o n s were r a p i d at f i r s t then slowed down. F i g u r e 4 shows t y p i c a l l y the e f f e c t of r e a c t i o n time on c o p o l y m e r i z a t i o n , t a k i n g the L S - ( m e t h a c r y l i c a c i d ) system in aqueous medium as an example. About 80% of the m e t h a c r y l i c a c i d monomer polymerized a f t e r 20 min of r e a c t i o n and the f i n a l 96% conversion reached w i t h i n one hour. The g r a f t i n g e f f i c i e n c y appeared to i n c r e a s e along w i t h the conversion; from 35% at 5 min to i t s p l a t e a u (about 60%) at one hour of r e a c t i o n . However, not so much change in the d e g r e e - o f - l i g n o s u l f o n a t e - r e a c t e d was found during the same p e r i o d , i . e . , from 43% at 5 min to 50% at 1 hour, i m p l y i n g t h a t the number of a c t i v e s i t e s on l i g n i n macromolecules probably be came f i x e d as soon as c o p o l y m e r i z a t i o n s t a r t e d and t h i s number was not a l t e r e d as the r e a c t i o n proceeded. F i g u r e 5 gives ano ther example showing the LS-(methyl a c r y l a t e ) system which a t t a i n e d i t s f i n a l s t a t e s at not longer than 2 hours of r e a c t i o n . R a t i o of LS/monomer. In the previous work (16), i t was r e ported that an unavoidable i n h i b i t i n g e f f e c t , owing to the q u i nonoid s t r u c t u r e of l i g n o s u l f o n a t e , on the p o l y m e r i z a t i o n was observed when studying the g r a f t of styrene onto l i g n o s u l f o n a t e by redox i n i t i a t i o n ; the i n d u c t i o n p e r i o d was p r o p o r t i o n a l to the c o n c e n t r a t i o n of l i g n o s u l f o n a t e , in other words, p r o p o r t i o n a l to the LS/monomer r a t i o . However, in t h i s study, no such evidence was observed in the L S - a c r y l i c systems, though in theory t h i s k i n d of i n h i b i t i n g e f f e c t could a l s o be imposed to these systems; Figures 6 and 7 show the i n f l u e n c e of the LS/monomer r a t i o on c o p o l y m e r i z a t i o n . In g e n e r a l , there was no adverse i n f l u e n c e on the monomer conversion when the LS/monomer r a t i o ( i n weight) was augmented from O.1 to 1.O. In the systems i n v o l v i n g methyl a c r y l a t e and m e t h a c r y l i c a c i d , t o t a l conversions were p r a c t i c a l l y s t a -


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100.

0

3

0

TIME

6 O

0

9

FR E A C T I O N ,

01 2 0 min

Figure 2. Variation of the total monomer conversion with reaction time for the LS-(methyl methacrylate) system at 50°Cindifferent media: V , water; X , waterdioxane 1:1; O, dioxane; Δ, water-methanol 1:1; and ., methanol.

0

3 TIME

0

6 O

0

9

FR E A C T I O N ,

0 1 2 0 min

Figure 3. Variation of the total monomer conversion with reaction time for the LS-(methacrylic acid) system at 30° C in different media: ., water; Δ, dimethylformamide; O, methanol; and ., dioxane.



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AND


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0

1 2 TIME

291

3

OF

REACTION,

h

Figure 4. Influence of reaction time on copolymerization of lignosulfonate and methacrylic acidinwater medium at 30°C: . , total monomer conversion; O, grafting efficiency; A, degree of LS reacted. % -

•

100 •

8 0 — Δ

ΖΛ

is 6 0

Q

4 0 -

0

6

—ο '

0

1

ι

2

8

T I M E

4 O F

6 R E A C T I O N

Figure 5. Influence of reaction time on copolymerization of lignosulfonate and methyl acrylateinwater medium at 30°C: . , total monomer conversion; Δ, degree of LS reacted; O, grafting efficiency.



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w/w

0

O.2 RATIO

O.4 OF

O.6 O.8 L S / M O N O M E R

1.0

Figure 6. Effect of the LS/monomer ratio on the total monomer conversion (Ώ V, Ο) and the degree of LS reacted fl, ψ, Φ) for the systems: Π/Μ ~ (methyl acrylate); V/T, LS-(methyl methacrylate); and Ο/Φ, LS-(methacrylic acid). Conditions: water medium; 30°C.; 120 min reaction time; and LS = 1 g. LS

%| 100o

i=

80-

LL

< ο

w/w

0

O.2 O.4 RATIO OF

O.6 O.8 1.0 L S / M O N O M E R

Figure 7. Effect of the LS/monomer ratio on the grafting efficiency for the sys tems: •, LS-(methyl acrylate); V, LS-(methyl methacrylate); and O, LS-(meth acrylic acid). Conditions: water medium; 30°C.; 120 min reaction time; LS — 1 g.



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b i l i z e d at more than 95 percent; w h i l e in the LS-(methyl meth a c r y l a t e ) system, the conversion seemed t o i n c r e a s e s l i g h t l y from 90 to 94% in the same range of LS/monomer r a t i o . I t i s in t e r e s t i n g to note ( i n F i g u r e 7) t h a t the g r a f t i n g e f f i c i e n c y was improved to a c e r t a i n extent by i n c r e a s i n g the LS/monomer r a t i o then i t remained unchanged. Both the LS-(methyl a c r y l a t e ) and L S - ( m e t h a c r y l i c a c i d ) systems reached t h e i r plateaus of around 60% e f f i c i e n c y at LS/monomer = O.5; whereas the LS-(methyl meth a c r y l a t e ) system a t t a i n e d a p l a t e a u of 35% at LS/monomer = O.3. These two l i m i t s , i . e . , O.5 and O.3, suggested t h a t the i n v o l v e ment of l i g n o s u l f o n a t e in the g r a f t c o p o l y m e r i z a t i o n would reach a s a t u r a t i o n p o i n t in each system. As f o r the d e g r e e - o f - l i g n o s u l f o n a t e - r e a c t e d (Figure 6 ) , a negative i n f l u e n c e was found in all the three systems. I t de creased almost p r o p o r t i o n a l l y to the LS/monomer r a t i o . In the range of the r a t i o s t u d i e d the l a r g e s t decrease was from 90% to 26% in the L S - ( m e t h a c r y l i c a c i d ) system and the s m a l l e s t change was from 86% to 42% in the system of LS-(methyl m e t h a c r y l a t e ) . At t h i s moment and without f u r t h e r d e t a i l i n v e s t i g a t i o n , i t i s unable f o r the authors to e x p l a i n the u n d e s i r a b l e decrease in the d e g r e e - o f - l i g n o s u l f o n a t e - r e a c t e d , except t h a t a s p e c u l a t i o n i s made that the r e l a t i v e r e a c t i v i t y of l i g n o s u l f o n a t e might d i m i n i s h w i t h the LS/monomer r a t i o . I n i t i a l pH. The s o l u b i l i t y of l i g n o s u l f o n a t e in water in creases w i t h i n c r e a s i n g pH,and the hydrodynamic volume of l i g n i n molecule expands correspondingly. Furthermore, the degree of d i s s o c i a t i o n of calcium l i g n o s u l f o n a t e i s l a r g e r at higher pH, and l i g n o s u l f o n i c molecule could thus a t t r a c t e l e c t r i c a l l y more water molecules to i t s surrounding. These water molecules would become more or l e s s o b s t a c l e s to the approaching p o l y v i n y l i c r a d i c a l s . As a consequense, an i n c r e a s e in the initial pH produced a negative i n f l u e n c e on c o p o l y m e r i z a t i o n , which i s e v i d e n t l y shown in Figures 8 and 9. For the LS-(methyl a c r y l a t e ) system (Figure 8 ) , the v a r i a t i o n of conversion w i t h pH was q u i t e moderate in the range be tween 2 and 10, producing a drop of not more than 4% (from 98.2 to 94.4%). G r a f t i n g e f f i c i e n c y d i d not change s i g n i f i c a n t l y , and i t s value s c a t t e r e d around 60%; w h i l e the d e g r e e - o f - l i g n o s u l f o nate-reacted decreased from 62% to about 50%. More s i g n i f i c a n t v a r i a t i o n occurred in the L S - ( m e t h a c r y l i c a c i d ) system (Figure 9) where the conversion was lower in the a l k a l i n e than in the a c i d s i d e and a t t a i n e d a minimum of 80.2% at near n e u t r a l pH. This k i n d of v a r i a t i o n was s i m i l a r to what had been reported f o r the homopolymerization of m e t h a c r y l i c a c i d (18). G r a f t i n g e f f i c i e n c y v a r i e d w i t h pH in a s i m i l a r way as conversion d i d ; i t s minimum occurred at pH = 7 but the e f f i c i e n c i e s at both the h i g h and low pH values ( i . e . , 12 and 2) were almost i d e n t i c a l . The degree-of - l i g n o s u l f o n a t e - r e a c t e d decreased from 53% to near 40% as pH in creased from 2 to 8 and d i d not change w i t h f u r t h e r i n c r e a s e s in pH.



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PH Figure 8. Effect of pH on copolymerization of lignosulfonate and methyl acrylate. Conditions: water medium; 30°C.; 120 min reaction time. Key: ., total monomer conversion; O, grafting efficiency; Δ, degree of LS reacted.

Figure 9. Effect of pH on copolymerization of lignosulfonate and methacrylic acid. Conditions: water medium; 30°C.; 120 min reaction time. Key: ., total monomer conversion; O, grafting efficiency; Δ, degree of LS reacted.


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of Lignosulfonate

295


I t i s known that the c o l o u r of l i g n o s u l f o n a t e i s darker at higher pH, thus the copolymer produced at pH 2 was tan and at pH 10 was dark brown. I t should be pointed out t h a t , without any b u f f e r i n g , the pH values of the L S - a c r y l a t e and L S - ( m e t h a c r y l i c a c i d ) systems were 4.4 and 2.4, r e s p e c t i v e l y . Peroxide charge. Though there are s t a b l e f r e e r a d i c a l s in l i g n i n p r e p a r a t i o n s (19^ 2£, 21), the c o n c e n t r a t i o n of these r a d i c a l s i s f a r from s u f f i c i e n t to provoke c o p o l y m e r i z a t i o n w i t h v i n y l monomers; otherwise, these r a d i c a l s may i n h i b i t e copolymer i z a t i o n . By means of redox a c t i v a t i o n , u s i n g the F e - H 2 U 2 p a i r , c o p o l y m e r i z a t i o n was found to occur r e a d i l y under s u i t a b l e c o n d i t i o n s , which was due to the formation of a greater number of ac t i v e p h e n o l i c r a d i c a l s in the l i g n i n molecule. I t i s w e l l known that the f e r r o u s - H 2 0 2 p a i r i n v o l v e s r e a c t i o n s where f e r r o u s ions are o x i d i z e d to produce Η 0 . and Η Ο 2 . (22) in a c y c l i c a l e q u i l i brium: + 2

Fe

+ 2

Fe

+ 2

Fe

+ 3

+ H 0 2

+

2

+ Η0.

+

+ H2O2

Fe +

+ 3

Fe

+ H0~ + Η 0 .

+ 3

Fe

+ + 2

HO" + H

+ Η 0 .

+

2

I t i s the Η 0 . which induces the v i n y l r a d i c a l s a p a r t of which then g r a f t s onto l i g n i n . Homopolymer Copolymer I t was thought (6) that the f r e s h l y o x i d i z e d f e r r i c i o n might c o m p e t i t i v e l y r e a c t w i t h the l i g n o s u l f o n a t e to generate the l i g n i n m a c r o r a d i c a l , thus making l i g n i n i t s e l f act as an i n i t i a t o r : OCH3

Fe

+2

+

II

S0 (Ca/2) 3

where II

I 0CH

S0 (Ca/2) 3

OCH3

3

S0 (Ca/2) 3




296

These r e a c t i o n s could happen in t h i s work only when s u f f i c i e n t amount of peroxide was present. Thus the q u a n t i t y of peroxide used played an important r o l e in the c o n t r o l of c o p o l y m e r i z a t i o n . F i g u r e 10 demonstrates the i n f l u e n c e of peroxide charge on copo l y m e r i z a t i o n f o r the LS-(methyl methacrylate) system. As shown, there was no d i s t i n g u i s h a b l e v a r i a t i o n in the g r a f t i n g e f f i c i e n c y in the range s t u d i e d ; the values obtained were s i t u a t e d between 20 and 30%. Meanwhile, the t o t a l monomer conversion and the deg r e e - o f - l i g n o s u l f o n a t e - r e a c t e d i n i t i a l l y increased w i t h peroxide charge. When the q u a n t i t y of peroxide augmented from 10 t o 30 mg, both the conversion and the d e g r e e - o f - l i g n o s u l f o n a t e - r e a c t e d increased about two times of t h e i r o r i g i n a l value ( i . e . , from 43 to 90% and from 30 to 61%, r e s p e c t i v e l y ) . A f t e r t h a t , f u r t h e r a d d i t i o n of peroxide r e s u l t e d in only a s m a l l g a i n in conversion and no f u r t h e r augmentation in the d e g r e e - o f - l i g n o s u l f o n a t e - r e acted. This implyed that a l i m i l t e d amount of peroxide reacted d i r e c t l y or i n d i r e c t l y (e.g., v i a o x i d i z e d f e r r i c i o n s ) w i t h the l i g n i n macromolecules t o generate a c t i v e s i t e s f o r g r a f t i n g . Be yond t h a t l i m i t , i t was b e l i e v e d that the excess of peroxide r a d i c a l s worked e s s e n t i a l l y w i t h v i n y l monomers to produce only homopolymers, supported by the v a r i a t i o n of the molecular weight of homopolymers (obtained in the same r e a c t i o n ) w i t h peroxide charge — the molecular weight of homopοly(methyl methacrylate) decreased w i t h i n c r e a s i n g peroxide charge. Copolymer. The appearence and p r o p e r t i e s of a p a r t i c u l a r copolymer obtained depended to a l a r g e degree on the type of mo nomer w i t h which the copolymer was prepared. LS-(methyl a c r y l ate) and LS-(methyl methacrylate) copolymers were brownish amor phous s o l i d s . The former was rubbery and moderately hard; and the l a t t e r was p l a s t i c l i k e and harder than the former. At room temperature, both were i n s o l u b l e in o r d i n a r y s o l v e n t s and q u i c k l y swelled in water to about s i x times in volume. At elevated tem p e r a t u r e , the l i g n i n backbone of these two copolymers could be degraded through a c i d or a l k a l i n e h y d r o l y s i s . L S - ( m e t h a c r y l i c a c i d ) copolymer was brownish b r i t t l e s o l i d which was s o l u b l e in water, methanol, dimethyl formamide, and dimethyl s u l f o x i d e at room temperature. F i g u r e 11 shows the r e duced v i s c o s i t y , n /C., of t h i s copolymer and that of a methacry l i c a c i d homopolymer ( f o r comparison purpose) in methanol at 25°C. From t h i s f i g u r e , an abrupt i n c r e a s e in the copolymer v i s c o s i t y can be observed at very low c o n c e n t r a t i o n , suggesting t h a t t h i s copolymer might form m i c r o g e l (probably owing t o the p a r t i c l e s having extremely h i g h molecular weight or c r o s s l i n k s ) in methanol solution. sp

CONCLUSION Commercially a v a i l a b l e calcium l i g n o s u l f o n a t e can be r e a d i l y and e f f e c t i v e l y g r a f t e d w i t h methyl a c r y l a t e , methyl methacry-


18.

C H E N

A N D


κοκτΑ


Mv-IO"

297

5

Figure 10. Effect of peroxide charge on copolymerization of lignosulfonate and methyl methacrylate. Conditions: water medium; 50°C.; 120 min reaction time. Key: ., total monomer conversion; Δ, degree of LS reacted; O, grafting efficiency; %, molecular weight of MM Λ homopolymer.

8h

0

I

0

,

1

,

1

.

L.

.2 . 4 . 6 CONCENTRATION, g/dl

Figure 11. Reduced viscosity versus concentration at 25°C. Key: O, LS-(meth acrylic acid) copolymer; and Φ, homopolyfmethacrylic acid)inmethanol.


298

GRAFT COPOLYMERIZATION OF LIGNOCELLULOSIC FIBERS + 2

l a t e , and w i t h m e t h a c r y l i c a c i d , using F e - H 0 initiation. Increase in peroxide charge increased the monomer conversion and decreased the molecular weights o f the a c r y l i c homopolymers w h i l e the g r a f t i n g e f f i c i e n c y and the d e g r e e - o f - l i g n o s u l f o n a t e - r e a c t e d approached c e r t a i n l i m i t s . The best r e a c t i o n c o n d i t i o n s in water medium were: 3% peroxide, and lignin/monomer 1:3. Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on September 29, 2015 | http://pubs.acs.org Publication Date: June 18, 1982 | doi: 10.1021/bk-1982-0187.ch018

2

2

ACKNOWLEGEMENTS The authors g r a t e f u l l y acknowledge the f i n a n c i a l a s s i s t a n c e r e c e i v e d from the N a t u r a l Sciences and Engineering Research Counc i l o f Canada and from the M i n i s t r y o f Education of the Province of Québec. The work described in t h i s a r t i c l e forms p a r t o f the research program of the Centre de Recherche en Pâtes et P a p i e r s at Université du Québec à Trois-Rivières. LITERATURE CITED 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

Koshijima, T.; Muraki, Ε.; J. Japan Wood Res. Soc., 1964, 10(3), 110. Koshijima, T.; Muraki, E.; Preprints IUPAC Internatl. Symp. Macromol. Chem. (Tokyo), 1966, Session 3, 60. Koshijima, T.; Muraki, E.; J. Polymer Sci. A1, 1968, 6, 1431. Koshijima, T.; Muraki, E., J. Japan Wood Res. Soc., 1967, 13(8), 355. Nam, C.; Koshijima, T.; Muraki, E.; J. Polymer Sci. A1, 1971, 9, 855. Nam, C.; Maku, T.; Saito, M.; Koshijima, T.: C e l l u l . Chem. Technol., 1974,8,263. P h i l l i p s , R.B.; Brown, W.; Stannett, V.T.; J. Appl. Polymer Sci., 1971, 15, 2929. P h i l l i p s , R.B.; Brown, W.; Stannett, V.T.; J. Appl. Polymer Sci., 1972, 16, 1. P h i l l i p s , R.B.; Brown, W.; Stannett, V., J. Appl. Polymer Sci., 1973, 17, 443. Naveau, H.P., C e l l u l . Chem. Technol., 1975, 9, 71. Chernyavskaya, S.B.; Berlin, A.A.; Khim. Drev., 1978, No. 1, 96. Simionescu, C.; Cernatescu-Asandei, Α.; Stoleru, Α.; C e l l u l . Chem. Technol., 1975, 9(4), 363. Simionescu, C.; Anton, I.; C e l l u l . Chem. Technol., 1969, 3(4), 387. Katuscak, S.; Mahdalik, M.; J. Appl. PolymerSci.,1973, 17, 1919. Katuscak, S.; Hrivik, Α.; Mahdalik, M.; Paperi Puu, 1971, 53, 519. Chen, R.; Kokta, B.V.; Valade, J.L.; J. Appl. Polymer Sci., 1979, 24, 1609. Chen, R.; Kokta, B.V.; Valade, J.L.; J. Appl. Polymer Sci., 1980, 25, 2211.


18.

CHEN

AND

KOKTA



18.

299

Ito, H.; Shimizu, S.; Suzuki, S.; Kogyo Kagaku Zashi, 1958, 58, 194; Chem. Abstr., 1955, 49, 14375d. 19. Steelink, C., Adv. Chem. Ser., 1966, 59, 51. 20. Katuscak, S.; Hrivik, Α.; Macak, K.; Paperi Puu, 1972, 54(4a), 201. 21. Hon, D.N.-S.; Glasser, W.G.; Tappi, 1979, 62(10), 107. 22. Haber, F.; Weiss, J., Proc. Roy. Soc. (London), 1934, A147, 332.

RECEIVED

December 17,

1981.


Graft Copolymerization of Lignosulfonate with Methacrylic Acid and

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