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Chapter 22

Synthesis and Characterization of Water-Soluble Nonionic and Anionic Lignin Graft Copolymers John J. Meister, Damodar R. Patil, Cesar Augustin, and James Z. Lai

Downloaded by PURDUE UNIV on August 31, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0397.ch022

Department of Chemistry, University of Detroit, Detroit, MI 48221-9987

A general method of grafting lignin has been developed which allows solvent extracted lignin, steam exploded lignin, and kraft lignin to be converted to complex polymers. The lignins grafted have been obtained from aspen, poplar, and pine. The lignins are research samples, pilot plant products and commercial products from paper production. The types of materials made to date will be illustrated with a series of polymers made as industrial process chemicals. Nonionic copolymers of virtually any composition and molecular weight can be made from lignin and 2-propenamide. A graft terpolymer of lignin has been made by free radical reaction of 2-propenamide and 2,2-dimethyl-3-amino4-oxohex-5-ene-1-sulfonic acid in the presence of kraft pine lignin. The water soluble product is a thickening agent and has limiting viscosity number in water at 30°C which increases as the fraction of sulfonated repeat units in the molecule increases. The grafting reaction is rapid and yields of 80 weight % or more can be obtained in as little as 30 minutes from reactions run in 1,4-dioxacyclohexane or dimethylsulfoxide. The reaction is initiated by a hydroperoxide, chloride ion, and lignin. Hydroxide radicals produced with iron (2+) do not appear to produce grafting. Adding 50 mole % sulfonated monomer to the reaction mixture produces graft copolymers with 12 to 24 times larger limiting viscosity numbers when compared to nonionic poly(lignin-g-1amidoethylene). Adding 20 mole % sulfonated monomer to the reaction mixture increases product limiting viscosity number by a factor of 2 to 5. 0097-6156/89A)397-0294$06.00A) © 1989 American Chemical Society

In Lignin; Glasser, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.


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E v e r y year the U . S paper i n d u s t r y produces over 33 m i l l i o n m e t r i c tons of kraft l i g n i n (1). M o s t of t h i s biomass is b u r n e d as fuel b u t s m a l l a m o u n t s are used as binders, asphalt a d d i t i v e s , or cement a d d i t i v e s . L a r g e r fractions of t h i s waste w o u l d be used i n other i n d u s t r i a l or c o m m e r c i a l processes i f an e c o n o m i c a l way existed to convert l i g n i n i n t o a m a r k e t a b l e p r o d u c t w i t h sufficient profit m a r g i n to compensate for the loss o f the f u e l . A way to make such a conversion has n o w been p r o d u c e d ( 2 , 3 ) . M o r e over, we have developed a c h e m i s t r y for l i g n i n t h a t is a p p a r e n t l y general. It is general i n the lignins used i n t h a t a whole series of lignins w i t h d r a w n f r o m w o o d b y different techniques have been grafted b y t h i s m e t h o d , as s h o w n b y the d a t a of T a b l e I. Since we recognize the p o t e n t i a l for l i g n i n u t i l i z a t i o n i l l u s t r a t e d b y the b r e a d t h of the c h e m i s t r y we have developed, we have u n d e r t a k e n a b r o a d a n d detailed s t u d y of t h e r m o p l a s t i c a n d t h e r moset c o p o l y m e r s of l i g n i n . These derivatives of l i g n i n are b e i n g prepared and e x a m i n e d for their p o t e n t i a l as process chemicals or c o m m e r c i a l a n d engineering m a t e r i a l s . A l l of the samples received were used "as i s " a n d were l a b o r a t o r y , p i l o t p l a n t , or c o m m e r c i a l l y - p r o d u c e d l i g n i n s . T h e reaction converts l i g n i n to a water-soluble c o p o l y m e r or p l a s t i c b y graft p o l y m e r i z a t i o n . T h e graft copolymer is formed b y c o n d u c t i n g a free-radical p o l y m e r i z a t i o n of an a p p r o p r i a t e m o n o m e r o n a n y of the lignins described i n T a b l e I. T h i s report w i l l describe p r e p a r a t i o n a n d testing of water-soluble, graft copolymers made w i t h 2-propenamide a n d 2 , 2 dimethyl-3-amino-4-oxohex-5-ene-l-sulfonic acid i n nitrogen-saturated, organic or a q u e o u s / o r g a n i c solvent c o n t a i n i n g l i g n i n , c a l c i u m chloride, a n d a h y d r o p e r o x i d e . W h i l e the c o p o l y m e r i z a t i o n can be r u n b y a n u m b e r of c o m m o n m e t h o d s , we have used s o l u t i o n p o l y m e r i z a t i o n to prepare l a b o r a t o r y or p i l o t p l a n t scale samples of c o p o l y m e r . W e have s h o w n g r a f t i n g can be done u s i n g a n y of the l i q u i d s i n T a b l e II, w h i c h are now k n o w n to be effective i n s o l u t i o n p o l y m e r i z a t i o n of graft copolymers. T h i s p o l y m e r i z a t i o n process gives us easy heat c o n t r o l a n d r a p i d p r o d u c t i o n of p r o d u c t s for t e s t i n g . T h i s reaction produces graft copolymers t h a t possess side chains c o n t a i n i n g repeated p o l a r u n i t s or m u l t i p l e , i o n i c bonds w h i c h dissociate i n p o l a r solvents. T h e p r o d u c t can be an a n i o n i c or nonionic water-soluble c o p o l y m e r w i t h a l i m i t i n g viscosity n u m b e r i n the range of 0.2 to 11 d L / g . T h e p r o d u c t s increase the viscosity of aqueous s o l u t i o n , act as flocculati n g / d e f l o c c u l a t i n g agents, t h i n n i n g agents, dispersing agents, a n d sequester c a l c i u m ions. I n the following sections, the s y n t h e t i c procedure, p u r i f i c a t i o n procedures, c h a r a c t e r i z a t i o n results, p r o o f of g r a f t i n g , tests of the role of i r o n i n the i n i t i a t i o n of g r a f t i n g , a n d d e t e r m i n a t i o n of extent of r e a c t i o n as a f u n c t i o n of t i m e w i l l be described. Experimental Synthesis. T h e p o l y m e r i z a t i o n can be r u n i n any one of several solvents, listed i n T a b l e I I . D i m e t h y l s u l f o x i d e has been used as the solvent for a l l reactions reported here. In other solvents, the p r o d u c t often precipitates as


LIGNIN: PROPERTIES AND MATERIALS

296


Table I.

Lignins Grafted with Hydroperoxy/chloride

Chemistry

Source Pine

a

Aspen

b

Yellow Poplar

0

Extraction Method Kraft

Solvent Extracted

Steam Exploded

a

P i n e l i g n i n s from the Westvaco Corporation of Charleston, SC. ^Aspen l i g n i n from the Solar Energy Research Institute, of Golden, CO. Yellow poplar l i g n i n s from BioRegional Energy Associates, of Floyd, VA.

c

Table I I .

Liquids Useful in Solution Polymerization of Graft Copolymers

3

Dimethyl S u l f o x i d e (DMSO) 1,4-Dioxacyclohexane Water Dimethylformamide a

a

a

1-Methyl-2-pyrrolidinone Dimethylacetamide Pyridine

Most frequently used l i q u i d s .


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297

the reaction proceeds. T h i s reaction can be successfully r u n w i t h c o n c e n t r a tions or mole ratios of the reactants i n the following ranges: (1) 25 weight % or less reactable solids content; (2) h y d r o p e r o x i d e to c a l c i u m chloride: 0.25 to 32; (3) h y d r o p e r o x i d e to l i g n i n ( M ) : 21 to 113; a n d (4) 0.01 to 0.95 weight f r a c t i o n of m o n o m e r i n reactable solids. T o a d r y E r l e n m e y e r flask of a p p r o p r i a t e size, a d d one h a l f of the r e a c t i o n solvent. A l l reactants, i n c l u d i n g the d r y mass of h y d r o p e r o x i d e , s h o u l d not constitute more t h a n 23 weight % of the r e a c t i o n m i x t u r e or an i n s o l u b l e p r o d u c t may be p r o d u c e d . A d d d r y l i g n i n a n d d r y c a l c i u m chloride to the reaction vessel a n d cap w i t h a s e p t u m or r u b b e r s t o p p e r . I n a separate vessel, dissolve 2-propenamide i n about one quarter to one h a l f of the solvent a n d , i f a p p r o p r i a t e , i n a t h i r d vessel dissolve a second m o n o m e r i n the final one quarter of the solvent. S a t u r a t e b o t h m o n o m e r s o l u t i o n s w i t h N b y b u b b l i n g w i t h the gas for 10 m i n u t e s . S a t u r a t e the l i g n i n s o l u t i o n w i t h N2 for 10 m i n u t e s . A d d the h y d r o p e r o x i d e to the m i x t u r e , b u b b l e w i t h N2 for 5 minutes, cap, a n d stir for 10 m i n u t e s . W h i l e s t i r r i n g the l i g n i n reaction s o l u t i o n , further saturate the m o n o m e r s o l u t i o n s w i t h N 2 . A d d the 2-propenamide s o l u t i o n to the l i g n i n s o l u t i o n w i t h s t i r r i n g a n d under a n N2 b l a n k e t . W a i t 1 m i n u t e . A d d the second m o n o m e r s o l u t i o n to the r e a c t i o n vessel i n the same way. S t i r a n d cap the r e a c t i o n under a n N2 b l a n k e t . P l a c e the reaction vessel i n a 3 0 ° C b a t h for 48 hours. T h e reaction is t e r m i n a t e d w i t h a s m a l l v o l u m e of aqueous, 1% h y d r o q u i n o n e s o l u t i o n a n d a v o l u m e of water equal to 1/3 of the r e a c t i o n s o l u t i o n v o l u m e is added to the p r o d u c t . T h i s s o l u t i o n is added to 10 t i m e s its v o l u m e of 2-propanone a n d the p o l y m e r is recovered by filtration. T h e solids are redissolved i n water. T o remove c a l c i u m i o n f r o m the p r o d u c t , an a m o u n t of Na2C2Û4 equal to the moles of C a C l 2 a d d e d to the r e a c t i o n is placed i n the s o l u t i o n . T h e CaC2Û4 p r e c i p i t a t e is removed b y filtration. T h e filtrate is d i a l y z e d against d i s t i l l e d water for 3 to 5 days u s i n g # 6 Spectropore d i a l y s i s t u b i n g . T h e d i l u t e aqueous s o l u t i o n is t h e n freeze d r i e d to recover the p r o d u c t .


n

2

Assays. A n a l y t i c a l procedures for d e t e r m i n i n g o x i d i z i n g equivalents b y i o d i n e / t h i o s u l f a t e t i t r a t i o n , l i g n i n content b y U V assay, 1-amidoethylene content b y K j e l d a h l assay, l i m i t i n g viscosity n u m b e r , a n d e l e m e n t a l c o m p o s i t i o n are given i n ref. 4. T h e elemental assay for sulfur was done b y A S T M m e t h o d D 3177-82 w i t h the correction t h a t i n step 7.3, the s o l u t i o n is brought to p H ~ 3.8 w i t h 6 M H C 1 rather t h a n 2.5 M N a O H as i n c o r r e c t l y specified i n the procedure. Size exclusion c h r o m a t o g r a p h y was done w i t h a m o b i l e phase of p H = 13, 0.1 M N a C l . A l l solutions were filtered t h r o u g h an 8 μτη N u c l e o p o r e filter before use. T h e flow rate was 0.5 m L / m i n . a n d the mobile phase was not degassed. T h e injected s a m p l e size was 10 μL a n d the c o l u m n s were m a i n t a i n e d at 43°C d u r i n g a l l separations. S p e c t r a were taken f r o m 200 to 420 n m a n d absorbance at 220 n m was p l o t t e d ver sus t i m e for e l u t i o n profile. T o t a l p e r m e a t i o n volume of the c o l u m n s was 44 m L a n d t o t a l p e r m e a t i o n t i m e was 88 m i n . E l e m e n t a l analyses were also performed o n most samples a n d these d a t a were used to calculate the repeat u n i t content of the p r o d u c t s u s i n g



298 the f o l l o w i n g r e l a t i o n s h i p s : WP

S

= 5.0745 χ Ν - 2.217 x S

WP

N

R

N

/

= 7.1499 x S

S

= (2.2889 χ Ν -

S)(S~ ) l

where S = weight percent sulfur i n s a m p l e ; Ν = weight percent n i t r o g e n i n s a m p l e ; WP = weight percent o f s a m p l e as s o d i u m l - ( 2 - m e t h y l p r o p - 2 N yl-sulfonate) a m i d o e t h y l e n e repeat u n i t s ; WPs = weight percent o f s a m p l e as 1-amidoethylene u n i t s ; a n d RNJS is the m o l a r r a t i o of a m i d e repeat u n i t s to N - s u b s t i t u t e d , sulfonate c o n t a i n i n g repeat u n i t s . Downloaded by PURDUE UNIV on August 31, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0397.ch022

S

Materials. L i g n i n , w h i c h makes u p the backbone of the graft c o p o l y m e r s , is a crosslinked, o x y p h e n y l p r o p y l p o l y m e r t h a t acts as a n i n t e r c e l l u l a r glue i n w o o d y p l a n t s . M o s t l i g n i n used i n these studies is a c o m m e r c i a l p r o d uct. T h e m a t e r i a l is a k r a f t pine l i g n i n prepared i n "free a c i d " f o r m w i t h a number-average m o l e c u l a r weight of 9600, a weight-average m o l e c u l a r weight o f 22,000, a n d a p o l y d i s p e r s i t y i n d e x o f 2.29. T h e ash content o f the l i g n i n is 1.0 weight percent or less. T h e m a t e r i a l was used as received. E l e m e n t a l analysis is C 61.66, Ν 0.89, Η 5.73, S 1.57, C a 0.08, a n d Fe 0.014 weight percent. O t h e r lignins used are described i n the text w i t h the results of the reaction or test. 2 - P r o p e n a m i d e ( c o m m o n n a m e a c r y l a m i d e ) used i n a l l reactions was reagent grade m o n o m e r t h a t was r e c r y s t a l l i z e d f r o m t r i c h l o r o m e t h a n e after hot filtration a n d d r i e d under v a c u u m ( P < 1.3 P a ) at r o o m t e m p e r a t u r e for 24 h . T h e a n i o n i c m o n o m e r , 2 , 2 - d i m e t h y l - 3 - i m i n o - 4 - o x o h e x - 5 - e n e - l sulfonic a c i d , was purified b y h e a t i n g a 15.2 weight percent s o l u t i o n i n m e t h a n o l to 6 5 ° C , filtering the hot s o l u t i o n , recovering the p r e c i p i t a t e d m o n o m e r f r o m the cool s o l u t i o n , a n d v a c u u m d r y i n g the s o l i d at r o o m t e m perature for 24 h r . D i m e t h y l s u l f o x i d e was s t a b i l i z e d reagent grade m a t e r i a l t h a t was freshly v a c u u m d i s t i l l e d at 5 0 ° C before use. C a l c i u m chloride a n d other salts used were reagent grade m a t e r i a l s a n d were used as s u p p l i e d . Gases used i n the syntheses were s t a n d a r d c o m m e r c i a l grade c y l i n d e r gases. T h e d i a l y s i s m e m b r a n e used was S p e c t r a p o r no.6, a 1000 u p p e r molecular-weight-cutoff cellulose, 45 m m d i a m e t e r , m e m b r a n e t u b i n g m a d e b y S p e c t r u m M e d i c a l Industries, L o s Angeles, C A . Equipment. L i g n i n s p e c t r a were r u n o n a P e r k i n - E l m e r L a m b d a 3, U V v i s i b l e spectrophotometer. Freeze d r y i n g was done o n a F T S S y s t e m s M o d e l F D X - 1 - 8 4 l y o p h i l i z e r . W e i g h i n g s were done o n a M e t t l e r B 6 b a l ance. T h e viscometers used i n f l u i d p r o p e r t y measurements were C a n o n Fenske c a p i l l a r y viscometers or a B r o o k f i e l d L V T cone a n d p l a t e viscometer. Size e x c l u s i o n separations were performed w i t h a V a r i a n m o d e l 5000 h i g h performance l i q u i d c h r o m a t o g r a p h e q u i p p e d w i t h a R h e o d y n e 10/zL fixedloop injector. T h e c o l u m n s used i n this work were T S K - G e l g u a r d c o l u m n ; T S K - 4 0 0 0 - p w c o l u m n ; a n d T S K - 5 0 0 0 - p w c o l u m n , p l u m b e d i n sequence. T h e detector was a H e w l e t t - P a c k a r d H P - 1 0 4 0 A h i g h speed s p e c t r o p h o t o m e t r i c detector w i t h its s u p p o r t i n g c o m p u t e r , the H P - 8 5 , c o n t a i n i n g 16k


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bytes of a d d i t i o n a l memory. T h i s detector can p e r f o r m absorbance m e a surements at wavelengths f r o m 190 to 600 n m a n d can detect a n d store a n entire s p e c t r u m of the contents of the detector cell over the above wave l e n g t h range every second. T h i s c a p a c i t y allows s p e c t r a to be t a k e n at n u merous times d u r i n g the e l u t i o n of a c h r o m a t o g r a p h i c peak a n d is c r i t i c a l to p r o v i n g the existence of graft copolymers b y m u l t i v a r i a t e curve r e s o l u t i o n (4,5).


Results and Discussion Ρ oly (lignin-g-(l-amidoethylene)). These nonionic molecules are s m a l l i n size, r e a d i l y adsorbed o n s i l i c a surfaces, a n d prone to c o m p l e x d i - a n d t r i valent m e t a l ions f r o m aqueous s o l u t i o n ( 2 , 3 ) . S y n t h e t i c results for several samples of p o l y ( l i g n i n - g - ( l - a m i d o e t h y l e n e ) ) are given i n T a b l e I I I . N o t e t h a t these reactions show t h a t c o p o l y m e r c a n be p r o d u c e d w i t h large weight fractions of l i g n i n i n the molecule. T h i s c h e m i s t r y can be used to place short sidechains o n l i g n i n . O t h e r l i g n i n s can be reacted w i t h t h i s chemistry. T a b l e I V shows s y n t h e t i c d a t a for the p r e p a r a t i o n of p o l y ( l i g n i n g - ( l - a m i d o e t h y l e n e ) ) f r o m several different lignins. S a m p l e 1 is a k r a f t pine l i g n i n grafted i n a reaction c o i n i t i a t e d w i t h s o d i u m c h l o r i d e . T h e l i g n i n used i n these studies is the c o m m e r c i a l p r o d u c t described under Materials. S a m p l e 2 was r u n w i t h a s t e a m - e x p l o d e d , solvent-extracted aspen l i g n i n . T h i s backbone, provide b y the S o l a r E n e r g y Research I n s t i t u t e , G o l d e n , C o l o r a d o , as D J L X 1 3 is a n I - O - T E C H process, w o o d e x t r a c t . A f ter s t e a m decompression to d i s r u p t the w o o d fiber, the w o o d was e x t r a c t e d w i t h t e t r a c h l o r o m e t h a n e at a p p r o x i m a t e l y r o o m t e m p e r a t u r e a n d r e d u c e d pressure. T h e w o o d was then e x t r a c t e d w i t h m e t h a n o l at 60°C a n d reduced pressure. T h e l i g n i n sample used was recovered as the m e t h a n o l e x t r a c t . S a m p l e s 3 a n d 4 are results o n a yellow p o p l a r l i g n i n . T h e m a t e r i a l was p r o d u c e d b y B i o R e g i o n a l E n e r g y Associates of F l o y d , V i r g i n i a . It is p r o duced b y s t e a m e x p l o d i n g the w o o d , w a s h i n g w i t h w a t e r , e x t r a c t i n g w i t h a l k a l i , a n d p r e c i p i t a t i n g w i t h m i n e r a l a c i d . T h e l i g n i n has a h i g h c a r b o x y l i c a c i d content a n d a h i g h level of phenolic h y d r o x y l groups. T h e m o l e c u l a r weight of the p r o d u c t was 1,000 to 1,200. S a m p l e s 5 a n d 6 are p o l y ( l i g n i n g - ( l - a m i d o e t h y l e n e ) ) copolymers made w i t h k r a f t pine l i g n i n a n d r u n as controls at the same t i m e as the reactions were r u n o n p o p l a r l i g n i n . Y i e l d a n d p r o d u c t properties are c o m p a r a b l e for samples 4, 5, a n d 6 b u t the y i e l d of s a m p l e 3 is low. T h i s low y i e l d may be due to loss o f p r o d u c t d u r i n g dialysis. D a t a for a series of graft copolymers m a d e u s i n g 2-propenamide are given i n T a b l e V for copolymers synthesized i n d i m e t h y l s u l f o x i d e . These d a t a show t h a t m a x i m u m y i e l d is o b t a i n e d w h e n the chloride i o n to l i g n i n mole r a t i o is 492. T h e reaction o n l i g n i n w i t h 2 - p r o p e n a m i d e is general i n the c o m p o s i t i o n a n d p r o d u c t properties t h a t m a y be acheived. T a b l e V shows the s p e c t r u m of l i g n i n contents, 2-propenamide contents, a n d reagent ratios t h a t can be used to produce a f u n c t i o n a l c o p o l y m e r of differing c o m p o s i t i o n , s t r u c t u r e , a n d p h y s i c a l properties.


300


T a b l e I I I . Y i e l d and L i m i t i n g V i s c o s i t y Number f o r Lignin-(2-propenamide) Reactions


8

sample no. 1 2 3°

b

c

anhyd CaCl2 in reaction m i x t u r e , wt % 4.0 2.0 2.2

1 3

limiting viscosity no., dL/g

yield g/wt$

3.36 / 90.8 3.64 / 98.4 1.5 /100.0

0.59 0.46 0.21

wt % polymerized 2-propenlignin amide 7.5 6.95 12.4

Ca after ashing

67.6 73.4 48.3

4.91 2.25 6.94

A l l r e a c t i o n m i x t u r e s c o n t a i n e d 20.0 mL o f oxygen-bubbled, i r r a d i a t e d dioxane, 0.5 g o f l i g n i n , and 0.15 mL o f e e r i e s u l f a t e solution. R e a c t i o n s r u n i n a Pyrex f l a s k and c o n t a i n e d 1,4d i o x a n e i r r a d i a t e d f o r 3 h and 0.045 mol (3.2 g) o f 2-propenamide. D e t e r m i n e d i n d i s t i l l e d water a t 30 C. R e a c t i o n run w i t h 0.014 mol (1.0 g) o f 2-propenamide.

T a b l e IV.

P o l y ( l i g n i n - g - ( 1 - a m i d o e t h y l e n e ) ) formed from L i g n i n s and C o i n i t i a t o r s

Composition o f R e a c t i o n ( g ) 2-propene C h l o r i d e HydroperSample L i g n i n amide Salt oxide Solvent 0.50 0.482 mL 21.28 0.68 3.21 0.50 3.20 0.62 0.482 mL 21.28 0.51 0.482 mL 21.30 ,62 21 0.50 20 0.482 mL 21.33 ,62 0.50 0.482 mL 21.39 ,64 3.27 0.50 0.482 mL 21.29 3.22 ,63 a

a

Various

Yield Lignin (g/wt.g) Type 3.46/93.3 Kraft 3.48/94.05 I-O-Tech 2.48/66.67 P o p l a r 3.50/86.48 P o p l a r 3.20/84.88 K r a f t 3.26/87.63 K r a f t

T h e same number o f moles o f c h l o r i d e i o n i s used i n sample 1 and samples 2 t o 4. Sample 1 r e c e i v e d sodium c h l o r i d e w h i l e samples 2 to 4 received calcium chloride.



3.20 3.20 3.20 3.20 3.20 3.20 3.20 3.20 3.20 3.20 3.20 3.20 3.20

1

0.137

4.601 7.00

76.045 66.946 65.79

15.047 13.284 13.034 12.37

0.77 0.35 0.44 0.306

70.07 89.36 90.35 88.73

3.16/2.58 4.31/3.306 4.40/3.34 4.73/3.283

0.15 0.15 0.15 0.15

0.40/.3532

0.25/.2208

0.152/.1342

0.80/.7064

0.50

0.50

0.50

0.50

0.50

0.50

g i v e n as

weight

of

crude

to

pure

the

2-hydroperoxy-

d i m e t h y l s u l f o x i d e save

1,4-dioxacyclohexane.

mL o f

ratios

run in

1,4-dioxacyclohexane.

Results

(§)

run i n 20.0

marked

reactions

for

= Some

lost

units recovery.

repeat during

i n

yield

0.2

11.41

to pure polymer.

on

recovered

pure product

0.679

0.325

15.52 5.62

1.65 0.88

5.45 14.95

0.33

6.54 12.24 13.74

1.007 0.558

8.13

based the

is

product

70.98

79.43

57.41

52.95

57.52

crude percent

of

14.062

15.802

11.516

10.63

11.515

39.53

71.43

14.162 7.950

66.43

ratios Weight

are

1-amidoethylene product

=

recovered. 1-amido

listed recovered.

yields

product

The

*

C

0.56

78.26

4.08/2.896

0.15

0.15

0.1

0.523

88.38

0.15

0.50

0.276

61.29

1.25/.919 3.27/

0.15

0.4/.3532

0.5

0.50

0.15/.1325

0.0113

0.50

3.20 3.20

1.00

0.275

57.14

1.49/.857

0.15

0.15/.1325

0.50

1.00

0.288

70.87

1.12/1.063

0.15

0.15/.1325

0.10 0.0512

0.50

0.192

73.64

0.15

1.00

0.565

57.58

1.84/1.44 2.14/1.105

0.15

0.15/.1325

0.50

1.00

0.15/.1325

0.0107 0.50

0.50

2.00

0.478

84.36

2.68/2.109

0.15

0.15/.1325

0.0516

0.50

2.00

samples

All

19 20

17 18

15 16

14

13

13.197

3.54 6.26 58.81 11.67

0.395

83.64

3.04/2.091

0.15

0.15/.1325

0.10

0.50

2.00

12

0.0949 6.88 59.12 11.74

0.372

84.77

3.10/2.119

0.15

0.15/.1325

0.50

0.50

2.00

0.395

13.734

0.801

77.38

3.46/2.863

0.15

0.15/.1325

4.16 69.42

0.010

4.94 68.89

13.641

0.50

0.757

5.48 68.41

13.55

0.15

0.15/.1325

Ο.0515

0.50

0.666

0.15

0.15/.1325

0 . Ι

0.50

0.615

0.15

0.416

0.50

0.50 84.53

0.15

0.416

0.50

0.50

2.48

2.86

2.89

89.37

4.07/3.307 3.90/3.128

0.15

0.416

0.50

0.50

0.50

6.03 7.21

0.415

4.94

67.91

13.45

62.31

0.73

5.38

67.38

13.34

57.83

0.15

0.40/.3532

0.0503 0.0102

0.69

0.56

69.32

3.30V2.565 2.72V2.14

0.10

0.50

0.15

Ca 2.789

0.40/3532

(1)

0.50

Composition Lignin 6.50 76.73

1-amido

Product

0.15

[n]

0.40/.3532

0.50

Ν 15.21

0

(dL/g) 0.322

Yield wt* 75.68

+

Ce( 4)

Data

g 4.71/2.799

b

DMSO

(mL,.05M)

R0_H

(g) 0.50

CaCl.

3

11

9 10

8

§

ë

e

7fi

6

5

4

3

2

amide(g)

Number

Lignin

Reactants

Lignin-co-O-araidoethylene) samples.

2-propen-

V.

Sample

Table



302


T h e above d a t a , w h e n a n a l y z e d for the effects o f i n d i v i d u a l r e a c t a n t s , shows t h a t chloride i o n is a c r i t i c a l reactant i n c o n t r o l l i n g the y i e l d a n d l i m i t i n g v i s c o s i t y n u m b e r o f the p r o d u c t c o p o l y m e r . T o q u a n t i f y t h i s effect as a first step i n o p t i m i z i n g t h i s synthesis, a series o f tests were r u n i n the above solvent s y s t e m w i t h each r e a c t i o n h a v i n g a different level o f choride i o n content. T h e results o f the reactions are given i n T a b l e V I . T h e c o m p o s i t i o n , r e a c t i o n c o n d i t i o n s , a n d y i e l d for these reactions are also l i s t e d i n T a b l e V I . T h e c o n c e n t r a t i o n o f l i g n i n a n d 2 - p r o p e n a m i d e were k e p t at a r o u n d 1.9 a n d 11.8 t o 1 2 . 5 % b y weight, respectively, w h i l e v a r y i n g the c a l c i u m chloride content f r o m 0.97 t o 3.78 weight % , as s h o w n i n T a b l e V I I . T h i s n o n i o n i c graft c o p o l y m e r i z a t i o n produces a m a x i m u m y i e l d w h e n c o n c e n t r a t i o n o f the c a l c i u m c h l o r i d e is at 2 . 4 1 % b y weight o f t o t a l r e a c t i o n mass, as s h o w n i n F i g u r e 1. Poly(lignin-g-((l-amidoethylene)-co-(sodium l'(2-methylprop-2N-yl-l-sulfonate) amidoethylene))). A s t r o n g l y a n i o n i c p o l y e l e c t r o l y t e c a n be m a d e f r o m l i g n i n b y c o n d u c t i n g a graft p o l y m e r i z a t i o n i n the presence o f 2p r o p e n a m i d e a n d 2 , 2 - d i m e t h y l - 3 - i m i n o - 4 - o x o h e x - 5 - e n e - l - s u l f o n i c a c i d or its s a l t s . D a t a f r o m 22 reactions are given i n T a b l e V I I I . T h i s c o m p o u n d w i l l be c a l l e d c o p o l y m e r 2. A l l reactions, w i t h the e x c e p t i o n o f n u m b e r 10, c o n t a i n e d 0.50 g of k r a f t pine l i g n i n . T h i s series o f reactions was r u n t o d e t e r m i n e : (1) the dependence o f y i e l d o n reactant c o n c e n t r a t i o n s ; (2) a n e s t i m a t e o f extent o f r e a c t i o n as a f u n c t i o n o f t i m e ; a n d (3) the effect o f i r o n c o n t a m i n a t i o n o n r e a c t i o n y i e l d . P r o o f o f graft c o p o l y m e r i z a t i o n m u s t be p r o v i d e d for these r e a c t i o n p r o d u c t s . A l l too frequently, m a t e r i a l s s y n thesized i n the presence o f a possible b a c k b o n e are assumed t o be graft c o p o l y m e r i z e d (7). I n place o f assumed s y n t h e t i c success, we have used a p r e v i o u s l y developed size e x c l u s i o n c h r o m a t o g r a p h y m e t h o d to verify t h a t s i d e c h a i n a n d b a c k b o n e are c h e m i c a l l y b o u n d (2-5). I n t h i s t e c h n i q u e , the absorbance s p e c t r a f r o m 200 t o 6 0 0 n m o f the effluent f r o m the c h r o m a t o g r a p h y c o l u m n is t a k e n i n real t i m e t h r o u g h o u t the e l u t i o n o f a p e a k . T h e s e s p e c t r a a l l o w i d e n t i f i c a t i o n o f the m a t e r i a l i n the detector cell a n d s h o w the presence o f b a c k b o n e or s i d e c h a i n at a n y p o i n t i n the e l u t i o n profile. Size e x c l u s i o n c h r o m a t o g r a m s for pure l i g n i n a n d s a m p l e 8, T a b l e V I I I , are s h o w n i n F i g u r e 2. T h e c o p o l y m e r s a m p l e produces a n absorbance peak at 34 m i n f r o m the i n j e c t i o n o f 10 uL of 1.46 g / d L s a m p l e 8 i n m o b i l e phase. T h e l i g n i n c h r o m a t o g r a m shows a n absorbance m a x i m u m at 38.5 m i n after i n j e c t i o n of 10 μΙ> o f 0.45 g / d L o f l i g n i n . E l u t i o n o f c o p o l y m e r 8 s t a r t s at 25 m i n , 7 m i n ahead o f the 32 m i n s t a r t o f e l u t i o n o f l i g n i n f r o m the c o l u m n s under i d e n t i c a l c o n d i t i o n s . Since the earlier e l u t i o n o f c o p o l y m e r 8 shows i t is a larger-molecular-size m a t e r i a l , these c h r o m a t o g r a m s p r o v i d e s t r o n g s u p p o r t for the f o r m a t i o n o f graft c o p o l y m e r . F i n a l p r o o f is p r o v i d e d b y the u l t r a v i o l e t s p e c t r a o f the e l u t i n g p o l y m e r s . T w o s p e c t r a o f s a m p l e 8 effluent t a k e n at 29.29 a n d 31.96 m i n b o t h s h o w the c h a r a c t e r i s t i c a b s o r p t i o n m a x i m a at 220 n m a n d shoulder at 286 n m c h a r a c t e r i s t i c o f l i g n i n . T h e 31.96 m i n s p e c t r a o f s a m p l e 8 effluent is s h o w n i n F i g u r e 3. Since r e a c t i o n p r o d u c t l i g n i n is e l u t i n g f r o m the c o l u m n before any pure l i g n i n is seen i n the detector, the reaction m u s t have enlarged the r e a c t e d


22.

MEISTERETAL.


303

T a b l e V I . S y n t h e t i c Data o f P o l y ( l i g n i n - g - 2 - p r o p e n a m i d e )


Reactant (weight i n grams) Sample Number Lignin 24-124-1 0.50 24-124-2 0.50 0.50 24-124-3 0.50 24-124-4 0.51 24-134-1 0.51 24-134-2 0.50 24-134-3

Ε CaCl 0.250.38 0.50 0.63 0.77 0.92 1.05

_A 3.21 3.20 3.20 3.20 3.20 3.21 3.23

DMSQ 21.29 21.21 21.27 21.28 22.03 21.35 21.53

(mL) 0.50 0.50 0.50 0.50 0.50 0.50 0.50

CI mmole 4.50 6.85 9.01 11.35 13.87 16.58 18.92

R e a c t i o n parameter Ca/g Yield C l / L Cl/H % 0.97 9.00 1.07 92.17 1.47 13.7 1.63 94.59 1.93 18.02 2.15 96.56 2.41 22.70 2.71 99.20 2.85 27.40 3.31 93.00 3.47 32.51 3.96 87.33 3.92 37.84 4.34 84.18

Note : A: 2-propenamide. E: 30 % hydrogen p e r o x i d e ( e q u i v a l e n t weight : 8.383 meq/mL). Ca/g: c a l c i u m c h l o r i d e c o n t e n t (wt $ ) . C l / L : c h l o r i d e c o n t e n t p e r u n i t weight o f l i g n i n . Cl/H : molar r a t i o o f c h l o r i d e t o hydrogen p e r o x i d e .

Table V I I .

The C o m p o s i t i o n o f R e a c t i o n M i x t u r e s Used t o Make L i g n i n G r a f t Copolymers

Sample number

Total mass

Lignin wt>

24-124-1 24-124-2 24-124-3 24-124-4 24-134-1 24-134-2 24-134-3

25.75 25.79 25.97 26.11 27.01 26.49 26.81

1.94 1.94 1.93 1.91 1.89 1.93 1.86

CaCl. wt* 2

0.97 1.47 1.93 2.41 2.85 3.47 3.92

Monomer wt*

Monomer mmole/g

Yield

12.47 12.41 12.32 12.26 11.85 12.12 12.05

1.75 1.75 1.73 1.72 1.67 1.71 1.69

92.17 94.59 96.56 99.20 93.00 87.33 84.18




304

F i g u r e 1. Y i e l d vs. c a l c i u m chloride content per t o t a l mass i n reactions of the n o n i o n i c c o p o l y m e r .



4.66 1.87 1.86 15.99 1.86 1.86 1.87 1.87 1.76 1.86

1.86 1.87 1.86 1.87 1.87 1.86

2.57 2.56 2.56 2.56 2.56 2.57

H766

5.16 5.16

4.66 4.66 4.66

1.60 1.60 1.60 1.60 1.60 1.60 1.60 2.58 2.56 21.98 2.56 2.56 2.57 2.56 2.57 2.57

(g>

2-prop< ηΑ amide

30 20 20 20 20 20

0.14 0.15 0.15 0.15 0.15 0.26

30 30 30 30 30 219

20 20 20 20 15 20

Dimethyl sulfoxide (mL) 20 50 50 40

Ce(4+) solution (mL) 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 1.28 0.15 0.15 0.15 0.15 0.20 0.15

70.28 51.63* 72.72 18.26 68.29 71.27

0.50 0.50 0.50 0.51 0.50 0.50

Reaction #10

0.34 0.335 0.338 0.34 0.34 0.34

Β Yield (fi) (wt %) 0.15 70.12 0.15 86.98 0.25 78.40 0.40 69.82 0.15 78.79 0.15 77.27 0.15 87.28 0.39 67.89 0.39 79.49 3.35 91.02 0.36 80.69 0.34 315.64 0.34 69.89 0.34 66.79 0.34 18.50 0.34 45.06

2

CaCl. (g) 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.53 4.35 0.50 0.50 0.50 0.50 0.50 0.50

= some product l o s t during p u r i f i c a t i o n . ) A l l reactions, save #10, contained 0.50 g of l i g n i n . contained 4.39 g o f l i g n i n .

17 18 19 20 21 22

9 10 11 12 13 11» 15 16

8

4 5 6 7

3

Sample Number 1 2

Table VIII. Synthesis Data and Physical C h a r a c t e r i s t i c s of Graft Terpolymer

42.55 44.36 42.26 41.77 42.84

42.47 42.25 44.38 44.73 43.88 44.90 42.80

43.31

c 35.41 36.77 36.88 37.74 39.85 38.03 36.51

6.79 7.40 6.89 6.50 6.67 6.50

10.60 11.32 9.91 9.25 10.78 10.76

3

mole s-χ g 0 0 .754 1.5x10" 9.41 1.87x10 9.26 .184 0 0 1.55x10- 3 .780

Repeat Units (wt $) 1-amidoAssays (wt. %) ethylene Η Ν S 14.1 5.94 9.78 7.03 9.54 21.51 6.17 8.39 6.20 22.79 9.19 8.49 22.60 8.47 6.39 9.23 8.61 6.79 9.39 28.63 6.40 9.95 22.33 8.73 16.56 7.74 10.29 6.33 10.92 5.65 42.89 6.65 42.1 10.76 5.66 6.29 43.78 6.21 11.34 6.49 10.84 44.39 4.79 6.83 38.40 6.46 4.70 9.62 6.58 10.82 4.32 45.33 6.82 44.05 4.69 10.73 11.41 6.74 4.75 47.37

D 62.6 61.1 58.8 59.1 55.1 63.7 65.9 40.4 36.2 44.4 34.2 33.6 30.9 33.5 34.0

A) = 2,2-dimethyl-3-imino-4-oxohex-5-ene-1-sulfonic a c i d . B) = Hydroperoxide. Samples 1 to 7: Values are weight o f 1,4-dioxa-2hydroperoxycycloexane i n g. Samples 8 to 22: Values are amount of aqueous solution of 1,2-dioxy-3,3-dimethylbutane i n mL. Equivalent/mL = 7.23x10~ . D) = N-substituted 1-amidoethylene.

[η] (dL/g) 10.52 11.40 7.40 9.30 12.59 6.81 10.46 .953 2.46 1.97



306


Figure 2. Size exclusion chromatogram of lignin and the anionic copolymer as monitored by absorbance at 220 nm.

Figure 3. A n ultraviolet absorbance spectrum of the anionic copolymer showing the characteristic absorbance pattern of lignin.


22.

MEISTER ET AL.

307


l i g n i n molecule b y f o r m i n g a graft c o p o l y m e r . A s p e c t r u m of pure l i g n i n effluent at 36.96 m i n is also given i n F i g u r e 3. These d a t a c o n f i r m t h a t graft c o p o l y m e r has been m a d e . Mechanistic Studies. R e a c t i o n s 1 to 7 were r u n w i t h different mole r a t i o s of l i g n i n to h y d r o p e r o x i d e a n d chloride i o n to h y d r o p e r o x i d e . A m a x i m u m y i e l d of 87 w t . % of p o l y m e r i z a b l e mass i n the r e a c t i o n is o b t a i n e d w h e n the l i g n i n to hydroperoxide mole r a t i o is 4.17 x 1 0 ~ a n d the chloride i o n to h y d r o p e r o x i d e mole r a t i o is 7.21. These ratios o c c u r i n s a m p l e 2. P r e v i o u s studies (2) have s h o w n t h a t the mole r a t i o s between l i g n i n , chloride i o n , a n d h y d r o p e r o x i d e c o n t r o l y i e l d i n the graft c o p o l y m e r i z a t i o n of p o l y ( l i g n i n - g - ( l - a m i d o e t h y l e n e ) ) . These same r a t i o s c o n t r o l y i e l d i n the f o r m a t i o n of p o l y ( l i g n i n - g - ( l - ( 2 - m e t h y l p r o p - 2 N - y l ) s u l f o n i c a c i d ) a m i d o e t h y l e n e ) - c o - ( l - a m i d o e t h y l e n e ) ) ) . These results i m p l y t h a t the g r a f t i n g m e c h a n i s m involves l i g n i n , chloride i o n , a n d h y d r o p e r o x i d e . A n i n i t i a t i o n reaction w h i c h is c o m p a t i b l e w i t h a l l findings t o date is the a t tack o n l i g n i n b y a hydroperoxide-(chloride ion) c o m p l e x to create a site for free r a d i c a l p r o p a g a t i o n . S u c h complexes have been seen i n E S R studies of h y d r o p e r o x i d e s (8). Samples 8 a n d 9 of T a b l e V I I I show t h a t t h i s g r a f t i n g r e a c t i o n c a n also be r u n w i t h a n a l t e r n a t i v e h y d r o p e r o x i d e , 1 , 2 - d i o x y - 3 , 3 - d i m e t h y l b u t a n e . T h i s c o m m e r c i a l l y available h y d r o p e r o x i d e can be used i n place of 1,4dioxacyclohexane-2-hydroperoxide. S a m p l e 10 shows t h a t a m o u n t s o f c o p o l y m e r as large as 40g can be made i n single pot reactions. R e a c tions 11 to 16 of T a b l e V I I I were i d e n t i c a l c o m p o s i t i o n tests r u n for different a m o u n t s of t i m e . S a m p l e 11 was t e r m i n a t e d after 31 m i n , s a m p l e 12 after 1 h r , samples 15 a n d 16 after 3 h r , sample 14 after 24 h r , a n d s a m p l e 13 after 48 h r . These d a t a were gathered to d e t e r m i n e the m i n i m u m d u r a t i o n of the r e a c t i o n . T h e results showed t h a t h i g h yields (samples 11 a n d 16) can be o b t a i n e d i n reaction times as short as 30 m i n . S e v e r a l samples (12 a n d 15) show low yields after reaction t i m e s as l o n g as 3 h r b u t these results were o b t a i n e d f r o m a c o n t a m i n a t e d reaction or a r e a c t i o n c o n t a i n i n g less t h a n the a p p r o p r i a t e a m o u n t of solvent, respectively. P r e v i o u s reactions r u n i n 1,4-dioxacyclohexane gave h i g h yields i n short r e a c t i o n t i m e s ( 2 , 9 ) . These d a t a s u p p o r t a free r a d i c a l p o l y m e r i z a t i o n m e c h a n i s m for ethene m o n o m e r s a d d i n g to l i g n i n ( 2 , 9 ) . Free r a d i c a l reactions have rates w h i c h are insensitive t o change of solvent. S a m p l e s 17 to 22 were i d e n t i c a l , 48 h r reactions r u n w i t h different a m o u n t s o f i r o n ( 2 + ) i n the reaction m i x t u r e . S a m p l e s 17 a n d 21 c o n t a i n o n l y the i r o n added as a 104 p p m c o n t a m i n a n t of l i g n i n . T h e r e a c t i o n m i x ture, i n these cases, contains 9.28 x 1 0 ~ moles of F e . T h e m o l e r a t i o between h y d r o p e r o x i d e a n d i r o n is 1,340. Since i r o n i n n e u t r a l or a c i d i c sol u t i o n is not reduced i n the presence of h y d r o p e r o x i d e , i f the h y d r o p e r o x i d e Fe were a c t i n g as a Fen ton's i n i t i a t o r for free r a d i c a l p o l y m e r i z a t i o n , o n l y 2 % of the l i g n i n i n the reaction m i x t u r e c o u l d be grafted a n d the l i g n i n content of the reaction p r o d u c t w o u l d be 0.2 w t . % . R e a c t i o n p r o d u c t s u s u a l l y c o n t a i n e d between 6 a n d 10 w t . % l i g n i n , a l i g n i n c o n c e n t r a t i o n w h i c h c o u l d not occur unless e x t r e m e l y large a m o u n t s of c h a i n transfer


2

7

2 +

2 +



308

took place. Since l i g n i n forms less reactive, q u i n o i d - t y p e structures w h e n p r o t o n a b s t r a c t e d , h i g h p r o p a g a t i o n rates c o u l d not be achieved b y c h a i n transfer mechanisms. T o c o n f i r m t h a t F e was not a reagent active i n the i n i t i a t i o n o f t h i s r e a c t i o n , several more reactions were r u n w i t h larger concentrations o f F e . R e a c t i o n 22 has a n R 0 2 H / F e mole r a t i o o f 160 b u t has about t h e same y i e l d as a n u n c o n t a m i n a t e d r e a c t i o n , # 1 7 a n d 2 1 . R e a c t i o n 19 has a n R 0 2 H / F e mole r a t i o o f 13.3 b u t a g a i n shows n o change i n y i e l d f r o m t h a t of a n u n c o n t a m i n a t e d r e a c t i o n . S a m p l e 20 has a 1.35 mole r a t i o o f RO2H to F e a n d shows a sharp decrease i n reaction y i e l d a n d g r a f t i n g . Here, the a p p r o x i m a t e l y 1:1 mole r a t i o o f peroxide t o i r o n s h o u l d produce a h i g h c o n c e n t r a t i o n o f h y d r o x i d e radicals a n d extensive p o l y m e r i z a t i o n i f these radicals are p a r t of the p o l y m e r i z a t i o n process. Instead o f a h i g h y i e l d , however, the reaction y i e l d was less t h a n one t h i r d o f t h a t o b t a i n e d i n the absence o f i r o n . Therefore, a F e n t o n ' s i n i t i a t i o n m e c h a n i s m for t h i s react i o n is inconsistent w i t h the d a t a a n d p r o b a b l y does not occur. E l e m e n t a l analysis d a t a of T a b l e V I I I showed t h a t p r o d u c t c o m p o s i t i o n is p r o x i m a t e to, b u t n o t equal t o , reaction m i x t u r e c o m p o s i t i o n . 2 +

2 +

2+

2+


2 +

Properties. T h e l i m i t i n g viscosity number values of these graft copolymers show t h a t the molecules are s h a r p l y expanded b y the a d d i t i o n o f a n i o n i c m o n o m e r t o t h e c h a i n . R e a c t i o n s (3) r u n w i t h the same n u m b e r o f moles of nonionic m o n o m e r (0.045) a n d p r o d u c i n g a p p r o x i m a t e l y the same y i e l d of p r o d u c t gave l i m i t i n g viscosity numbers o f 0.50 d L / g . I n reactions 1 to 7 where 50 m o l e % o f the m o n o m e r is now sulfonated, i o n i c m o n o m e r , the l i m i t i n g viscosity n u m b e r is 12 to 24 times higher. F o r p r o d u c t s 8 to 10, the reaction m i x t u r e contained 20 mole % sulfonated m o n o m e r . T h e l i m i t i n g viscosity numbers for samples 8 t o 10 are 2 t o 5 times higher t h a n those of the n o n i o n i c copolymer, p o l y ( l i g n i n - g - ( l - a m i d o e t h y l e n e ) ) (3). T h e a d d i t i o n of sulfonated repeat u n i t s makes the p o l y m e r a better t h i c k e n i n g agent a n d m a y make i t a better c o m p l e x i n g or flocculating/deflocculating agent. Conclusions A general m e t h o d of g r a f t i n g l i g n i n has been developed w h i c h allows solvent e x t r a c t e d l i g n i n , s t e a m e x p l o d e d l i g n i n , a n d kraft l i g n i n t o be converted t o c o m p l e x p o l y m e r s . T h e l i g n i n s grafted have been o b t a i n e d f r o m aspen, p o p l a r , a n d pine. T h e lignins are research samples, p i l o t p l a n t p r o d u c t s , a n d c o m m e r c i a l p r o d u c t s f r o m paper p r o d u c t i o n . T h e types of m a t e r i a l s m a d e t o date are i n d u s t r i a l process chemicals a n d are n o n i o n i c a n d a n i o n i c graft copolymers of l i g n i n . E x t e n s i v e studies o n the nonionic c o p o l y m e r , p o l y ( l i g n i n - g - ( l - a m i d o e t h y l e n e ) ) , show t h a t the m a t e r i a l c a n be m a d e w i t h a b r o a d s p e c t r u m o f l i g n i n s , t h a t p r o d u c t properties c a n be controlled b y c o n t r o l o f reaction chloride i o n content a n d m o n o m e r content, a n d t h a t v i r t u a l l y a n y l i g n i n content, molecular weight, a n d sidechain content c a n be achieved b y c o n t r o l of synthesis variables. A graft t e r p o l y m e r of l i g n i n has been m a d e by free r a d i c a l reaction o f 2-propenamide a n d 2 , 2 - d i m e t h y l - 3 - a m i n o - 4 - o x o h e x - 5 - e n e - l - s u l f o n i c a c i d i n


22.

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the presence o f k r a f t pine l i g n i n . T h e water soluble p r o d u c t is a t h i c k e n i n g agent a n d has a l i m i t i n g viscosity n u m b e r i n water at 30°C w h i c h increases as the f r a c t i o n o f sulfonated repeat u n i t s i n the molecule increases. T h e g r a f t i n g reaction is r a p i d a n d yields o f 80 w t . % or more can be o b t a i n e d i n as l i t t l e as 30 m i n f r o m reactions r u n i n 1,4-dioxacyclohexane or d i m e t h y l sulfoxide. T h e reaction appears t o be i n i t i a t e d b y a h y d r o p e r o x i d e , chloride i o n , a n d l i g n i n t h o u g h the exact steps of the i n i t i a t i o n are not k n o w n . Since the a d d i t i o n o f F e t o the reaction reduces y i e l d at h y d r o p e r o x i d e t o F e mole ratios of about 1, h y d r o x i d e radicals p r o d u c e d w i t h F e do not appear to produce g r a f t i n g . A d d i n g 50 mole % sulfonated monomer to the r e a c t i o n m i x t u r e produces graft copolymers w i t h 12 t o 24 times larger l i m i t i n g v i s cosity numbers w h e n compared t o nonionic p o l y ( l i g n i n - g - l - a m i d o e t h y l e n e ) . A d d i n g 20 mole % sulfonated m o n o m e r t o the reaction m i x t u r e increases p r o d u c t l i m i t i n g viscosity n u m b e r b y a factor o f 2 t o 5. 2 +

2 +


2 +

For 2-propenamide, the reaction p r o d u c e d a m a x i m u m y i e l d w h e n the c a l c i u m chloride content is at 2 . 4 1 % b y weight o f t o t a l r e a c t i o n mass. I n these nonionic copolymers, the l i m i t i n g viscosity n u m b e r is decreased w i t h an increase o f c a l c i u m chloride content. T h e e l u t i o n v o l u m e o f c o p o l y mers d u r i n g size exclusion c h r o m a t o g r a p h y i n basic aqueous mobile phase is s m a l l e r t h a n t h a t o f l i g n i n . U l t r a v i o l e t spectroscopy a n d size e x c l u sion c h r o m a t o g r a p h y verify the f o r m a t i o n o f graft c o p o l y m e r . These graft copolymers are h i g h l y water soluble, w i l l increase the v i s c o s i t y o f aqueous solutions, a n d can be used as t h i c k e n i n g agents a n d d i s p e r s i n g agents. A cknowledgment s T h i s work was p a r t i a l l y s u p p o r t e d b y the N a t i o n a l Science F o u n d a t i o n under a w a r d number C P E - 8 2 6 0 7 6 6 a n d under N a t i o n a l Science F o u n d a t i o n grant C B T - 8 4 1 7 8 7 6 . S u p p o r t of the copolymer testing p r o g r a m b y A a n d R P i p e l i n e C o m p a n y is gratefully acknowledged. K e v e n A n d e r l e , George M e r r i m a n , J a m e s Z . L a i , D a m o d a r R . P a t i l , M u L a n S h a , N a n c y C h e w , C h i n T i a L i , T h o m a s Bûchers, Cesar A u g u s t i n , H a r v e y C h a n n e l l , a n d others completed a sizable p o r t i o n o f t h i s w o r k a n d their a i d a n d effort is greatly appreciated a n d acknowledged. Literature C i t e d 1. Goheen, D. W . ; Hoyt, C . H . In Kirk-Othmer Encycl. Chem. Technol., 3rd Ed., 1981, 295. 2. Meister, J. J.; Patil, D . R.; Field, L . R.; Nicholson, J. C . J. Polym. Sci., Polym. Chem. Ed. 1984, 22, 1963-1980. 3. Meister, J. J.; Patil, D. R.; Channell, H. J. Appl. Polym. Sci. 1984, 29, 3457-3477. 4. Meister, J. J.; Patil, D. R.; Field, L. R. Macromolecules 1986, 19, 803. 5. Nicholson, J. C.; Meister, J. J.; Patil, D. R.; Field, L . R. Anal. Chem. 1984, 56, 2447-2451. 6. Meister, J. J. In Water-Soluble Polymers in Enhanced Oil Recovery; Stahl, G . Α.; Schulz, D. N . , Eds.; Plenum Publ. Co.: New York, 1988; Ch. 2.



310

7. Meister, J . J. In Renewable-Resource Materials: New Polymer Sources; Carraher, C . E., Jr.; Sperling, L . H . , Eds; Plenum Press: New York, 1985; pp. 305-322. 8. Dixon, W . T . ; Norman R. O. C . J. Chem. Soc. 1963, 5, 3119-3124. 9. Meister, J . J.; Patil, D. R. Macromolecules 1985, 18, 1559-1564.


RECEIVED May 29,1989


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