Round-Table Discussion - ACS Symposium Series (ACS Publications)

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Round-Table Discussion Plastics without Petroleum Rudolph D . Deanin, Plastics Department, Lowell Technological Institute, Lowell, Mass. 01854

Plastics have a g r e a t h i s t o r y ; and, w i t h our h e l p , t h e y can have an even g r e a t e r f u t u r e . Table U.S.

1

P l a s t i c s S a l e s , 1973,

1000 M e t r i c Tons

Low-Density P o l y e t h y l e n e P o l y s t y r e n e & Copolymers P o l y v i n y l C h l o r i d e & Copolymers High-Density Polyethylene Polypropylene Phenolics P o l y u r e t h a n e Foam Polyesters Urea & Melamine R e s i n s Miscellaneous Vinyls Alkyds Acrylics Coumarone-Indene & Petroleum R e s i n s Epoxy R e s i n s Nylon P l a s t i c s Cellulosics Others

(1)

2664 2407 2171 1254 97Ô 654 593 496 464 391 342 233 157 99 00 77 122

13,182 In t h e e a r l y days o f the p l a s t i c s i n d u s t r y , i n d u s t r i a l o r g a n i c c h e m i s t s used a v a r i e t y o f raw m a t e r i a l s t o make their polymers and a d d i t i v e s . C o a l was t h e most versatile raw m a t e r i a l . Coal t a r c h e m i s t r y was t o them what p e t r o c h e m i c a l s are t o us t o d a y . Simple distillation produced many o f the i n t e r m e d i a t e s we still use today: benzene, p h e n o l , c r e s o l s , x y l e n o l s , toluene, n a p h t h a l e n e , comarone, i n d e n e , and c a r b a z o l e (2). Coke was a l s o the s t a r t i n g

163

Deanin; New Industrial Polymers ACS Symposium Series; American Chemical Society: Washington, DC, 1974.

164

NEW

INDUSTRIAL

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m a t e r i a l f o r c a l c i u m cyanamide and a c e t y l e n e w h i c h , particularly in Germany, were the i n t e r m e d i a t e s for a g r e a t v a r i e t y o f polymers and p l a s t i c s c h e m i c a l s : melamine, a c r y l o n i t r i l e , m e t h y l m e t h a c r y l a t e , a c e t i c a c i d and a n h y d r i d e , v i n y l a c e t a t e , b u t y r a l d e h y d e and polyvinyl butyral, vinyl chloride, and c h l o r o p r e n e (3.)· Coke a l s o l e d , t h r o u g h water gas and methanol, t o f o r m a l d e h y d e , still a monomer in a number o f i m p o r t a n t

plastics (4.). Plastics have a l s o been manufactured from a number o f raw m a t e r i a l s o t h e r t h a n p e t r o l e u m ( T a b l e 2 ) . Rubber from t r e e s has been used i n b o t h s o l i d and l a t e x form, and a l s o c o n v e r t e d f u r t h e r i n t o i s o m e r i z e d and c h l o r i n a t e d polymers o f v e r y d i f f e r e n t p r o p e r t i e s and u s e s . Wood from t r e e s i s used d i r e c t l y f o r plywood, c o m p o s i t i o n b o a r d , and w o o d - f l o u r r e i n f o r c e m e n t o f phenolic r e s i n s . The c e l l u l o s e from wood i s p u r i f i e d and used f o r l a m i n a t e s and f o r r e g e n e r a t e d c e l l u l o s e p r o d u c t s s u c h as c e l l o p h a n e , v i s c o s e r a y o n , and vulcanized f i b r e . The l i g n i n from wood has been e x p l o r e d f o r use i n p l a s t i c s , b u t n e v e r c a r r i e d t h r o u g h t o complete commercial s u c c e s s . P l a n t s grown as c r o p s have p r o v i d e d a v a r i e t y o f raw m a t e r i a l s f o r p l a s t i c s . The c e l l u l o s e from c o t t o n has always been t h e q u a l i t y raw m a t e r i a l f o r c e l l u l o s i c plastics. The c e l l u l o s e from o t h e r p l a n t s i s used i n a v a r i e t y of building materials. The o i l s from p l a n t s p r o v i d e d g l y c e r o l , and mono- and d i - b a s i c a c i d s , f o r many p l a s t i c s and p l a s t i c i z e r s . F e r m e n t a t i o n was used s u c c e s s f u l l y t o produce acetone and a number o f a l c o h o l s and a c i d s u s e f u l i n polymers and p l a s t i c i z e r s . Even t h e p r o t e i n i n p l a n t s , and i n a n i m a l b y - p r o d u c t s , has been used i n a number o f p l a s t i c s a p p l i c a t i o n s . I n the p a s t 30 y e a r s , the ready a v a i l a b i l i t y and low c o s t o f p e t r o l e u m and n a t u r a l g a s , p l u s t h e i n g e n u i t y o f p e t r o l e u m c h e m i s t s and e n g i n e e r s , have made t h i s the most c o n v e n i e n t and e c o n o m i c a l raw m a t e r i a l f o r s y n t h e s i s o f p l a s t i c s , t o the p o i n t where we have abandoned many o f the o l d e r p r o c e s s e s , o r a t l e a s t a l l o w e d them t o remain r e l a t i v e l y minor i n importance ( £ ) . Now t h a t the s u p p l y o f p e t r o l e u m and n a t u r a l gas i s d e c r e a s i n g , t h e c o s t becoming g r e a t e r , and the p o l i t i c a l u n c e r t a i n t y o f f o r e i g n s u p p l y becoming a s e r i o u s problem, we can b e s t i n s u r e t h e h e a l t h y f u t u r e growth o f t h e polymer i n d u s t r i e s by t u r n i n g our r e s e a r c h and development e f f o r t s t o t h e v a r i e t y o f raw m a t e r i a l s a v a i l a b l e t o u s , p a r t i c u l a r l y t h o s e which can be grown as commercial c r o p s and a r e t h e r e f o r e r e p l e n i s h a b l e , and a l s o more l i k e l y t o produce waste



Plastics

Low-D P o l y e t h y l e n e PS & Copolymers PVC & Copolymers High-D P o l y e t h y l e n e Polypropylene Phenolics Urethane Foam Polyesters Urea & Melamine Miscellaneous V i n y l s Alkyds Acrylics Coumarone-Indene Epoxy R e s i n s Nylon P l a s t i c s Cellulosics Others Plasticizers

Commet

X Χ Χ X

Χ

Χ Χ

X X

X X

X

X

X X

Χ

X Χ

Χ

Χ

X

Coal Coke D i s t l V i X

Χ

Χ Χ

Χ

X

X

Χ

Trees Rubber Wood C e l l u l o s e

Χ

Χ

X

X

X X

X

X

X X X X X

X X X X X

X

X X

X

X X

X

Plants C e l l o s e O i l Fernfcta P r o t e i n

RAW MATERIALS OTHER THAN PETROLEUM FROM WHICH PLASTICS HAVE BEEN MANUFACTURED

Table 2

NEW

166

p r o d u c t s which can be r e t u r n e d i n t o the efficiently. Literature

INDUSTRIAL POLYMERS

ecocycle

Cited

Modern P l a s t i c s , ( 1 9 7 4 ) , 5 1 ( 1 ), 38. Wakeman, R. L., "The C h e m i s t r y o f Commercial Plastics, Pg. 2 5 , R e i n h o l d , New Y o r k , 1947. 3 . I b i d . , Pg. 31. 4 . I b i d . , Pg. 2 9 . 5. P l a s t i c s T e c h n o l o g y , ( 1 9 7 4 ) , 20 ( 1 ) , 7 9 - 8 0 . 1. 2.

Plastics without Petroleum Richard G . Sinclair, Thomas R. Steadman, Melville E . D . Hillman, and E . S. Lipinsky, Polymer Chemistry and Chemical Economics Sections, Battelle-Columbus Laboratories, 505 King Ave., Columbus Ohio 43201

A major o b j e c t i v e o f polymer t e c h n o l o g y f o r many y e a r s has been the development o f a complete l i n e o f p l a s t i c s from p e t r o c h e m i c a l s . P r o f e s s o r Deanin has a l r e a d y p o i n t e d out t h a t t h i s e f f o r t has been q u i t e successful. However, i n l e s s t h a n one y e a r the s i t u a t i o n has changed r e m a r k a b l y as t h e once abundant s u p p l y o f p e t r o c h e m i c a l s has become s c a r c e . How s e r i o u s i s t h i s s h o r t a g e and how p r o l o n g e d w i l l i t be? I t i s e s t i m a t e d t h a t our p e t r o l e u m i m p o r t s were r e d u c e d by about 15 p e r c e n t by t h e Arab o i l embargo. Since approximately 5 percent of the petroleum f i n d s i t s way i n t o t h e p l a s t i c s i n d u s t r y as monomers, s o l v e n t s , e t c . , i t comes as no s u r p r i s e t h a t t h e r e i s a s h o r t a g e o f monomer and polymer s u p p l i e s . I t i s e s t i m a t e d t h a t t h e s e s h o r t a g e s w i l l r e m a i n t o some e x t e n t f o r many y e a r s . One a l t e r n a t i v e f o r s u p p l y o f p l a s t i c s i s the use o f a g r i c u l t u r a l p r o d u c t s as raw m a t e r i a l s . These a r e renewable r e s o u r c e s . Although incapable of supplying a l l the needs o f t h e p l a s t i c s i n d u s t r y , a g r i c u l t u r a l derived products could, i t i s estimated i n p r i n c i p l e f r o m the a v a i l a b l e growing a c r e a g e , s u p p l y approxima t e l y 10 p e r c e n t o f t h e i n d u s t r y s need. T h i s might be j u s t enough t o o f f s e t the p r o j e c t e d s h o r t a g e s . A second a l t e r n a t i v e i s the use o f c o a l as raw m a t e r i a l . . I t i s s u g g e s t e d t h a t some r e a l i g n m e n t be employed o f our b a s i c thumb r u l e s f o r use o f p l a s t i c s . For example, p o l y s t y r e n e has been e x t e n s i v e l y employed i n 1


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ET

AL.

Round Table Discussion

167

many u s e s because i t was cheap and r e a d i l y a v a i l a b l e . As i t becomes more e x p e n s i v e , perhaps p o l y s t y r e n e w i l l be r e p l a c e d i n some u s e s by o t h e r p l a s t i c s , such as a c r y l i c s o r ABS, which p r e v i o u s l y c o u l d not compete p r i c e w i s e b u t which have g e n e r a l l y s u p e r i o r p r o p e r t i e s . A l o n g t h i s l i n e , e l e g a n t m a t e r i a l s such as thermop l a s t i c e l a s t o m e r s may become i n g r e a t demand. T r a d i t i o n a l l y , cheaper m a t e r i a l s have been g r a f t e d , f i l l e d , b l e n d e d , and c o p o l y m e r i z e d w i t h a v a r i e t y o f other m a t e r i a l s to obtain d e s i r a b l e p r o p e r t i e s . Table 1 shows t h a t some p e t r o c h e m i c a l raw m a t e r i a l s have i n c r e a s e d i n p r i c e by as much as 165 p e r c e n t d u r i n g the p a s t y e a r . Table

1

P r i c e I n c r e a s e s o f Some P e t r o c h e m i c a l Raw M a t e r i a l s f o r P l a s t i c s Dollars/Pound y i ? / 7 4 ^ ) k-W73^2)

Increase, Percent

Ethylene (Contract) 0.06-0.07 0.035-0.0375 Propylene/gal 0.20-0.25 0.145 Benzene/gal 0.759 0.2Ô6 Styrene 0.15-0.25 0.0725-0.09

71-87 30-72 165 107-17Ô

The use o f c o a l as an a l t e r n a t i v e raw m a t e r i a l f o r some p l a s t i c s m a t e r i a l s i s e a s i e r t o see t h a n t h a t o f a g r i c u l t u r a l (renewable) r e s o u r c e s . Thus, polymers and copolymers o f formaldehyde a r e w e l l e s t a b l i s h e d commercial p r o d u c t s . The p r i m a r y raw m a t e r i a l f o r t h e s e polymers, methanol, can be made f r o m c o a l j u s t as r e a d i l y as from n a t u r a l gas o r o i l . C e r t a i n l y , i n the case o f a new p l a n t f o r making methanol, the c o s t and a v a i l a b i l i t y o f n a t u r a l gas o r p e t r o l e u m r e l a t i v e t o c o a l must be weighed c a r e f u l l y . Even an o p e r a t i n g p l a n t might be c o n v e r t e d from n a t u r a l gas t o c o a l as raw m a t e r i a l much more e a s i l y t h a n perhaps any o t h e r petrochemical operation. Literature 1. 2.

Cited

Chemical M a r k e t i n g 30 ff. Chemical Marketing 30 ff.

R e p o r t e r , April R e p o r t e r , April

15, 16,

1974, 1973,


pg. pg.

168

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POLYMERS

Coal—"New" Source for Plastics Irving Skeist, Skeist Laboratories, Inc., 112 Naylon Ave., Livingston, N . J. 07039

C o a l c a n l i b e r a t e t h e U. S. from t h e p l a s t i c s s h o r t a g e as w e l l a s t h e energy c r i s i s . I t i s abundant, and we have t h e t e c h n o l o g y t o c o n v e r t i t t o p r e c u r s o r s f o r p l a s t i c s a t c o s t s t h a t a r e suddenly cheap compared t o the p r i c e t a g s on c h e m i c a l s from imported p e t r o l e u m . E t h y l e n e , p r o p y l e n e , benzene, t o l u e n e , x y l e n e , p h e n o l and o t h e r raw m a t e r i a l s f o r polymers and p l a s t i c s can become p l e n t i f u l a g a i n ; b u t we must speed up R&D as w e l l as p l a n t c o n s t r u c t i o n . The U. S. has more t h a n h a l f the w o r l d s known c o a l r e s e r v e s , over 3 t r i l l i o n t o n s . Only 5$ o f t h i s i s f e a s i b l e t o mine w i t h p r e s e n t t e c h n o l o g y , b u t even t h i s i s a 300 y e a r s u p p l y a t o u r p r e s e n t r a t e o f u s e of 500 m i l l i o n t o n s p e r y e a r . E v o l v i n g t e c h n i q u e s w i l l make much l a r g e r q u a n t i t i e s a v a i l a b l e , however. C o a l i s s i g n i f i c a n t l y h i g h e r i n carbon c o n t e n t and lower i n hydrogen t h a n p e t r o l e u m , and i s i n t h i s r e s p e c t a b e t t e r source f o r p r o d u c t i o n o f aromatics. Other p r o d u c t s a v a i l a b l e from c o a l c o n v e r s i o n i n c l u d e p h e n o l and o t h e r t a r a c i d s , ammonia, s u l f u r and hydrogen, a s w e l l a s r i n g n i t r o g e n compounds. Polymers and p l a s t i c s a r e the major o u t l e t s f o r most o f t h e s e c h e m i c a l s , a s shown i n the f o l l o w i n g table· 1

Table 1 P o l y m e r i c End Uses f o r C o a l Chemicals Chemicals

Percent Going t o Polymers/ Plastics

Ethylene

R

(1,2,2)

Some End P r o d u c t s

PE, PS, ABS, SAN, SBR, PVC, Unsat d. & sat'd. polyesters. PP, EPR, A c r y l i c f i b e r s , SAN, Urethane, P o l y e s t e r , P h e n o l i c , PS, SAN, ABS, SBR, P o l y e s t e r , P h e n o l i c , Epoxy, Nylons 6&66. C o a t i n g s , Urethanes, A r o m s . Polyesters, P l a s t i c i z e r s , Styrene d e r i v a t i v e s . P l a s t i c i z e r s , Alkyds. f

Propylene

64

Benzene

90

Toluene Xylenes & E t h y l Benzene Naphthalene

70 05 60


f

13.

DEANiN E T A L .


169

The naphthenes, o b t a i n a b l e i n h i g h c o n c e n t r a t i o n i n s y n c r u d e s from c o a l , a r e c o n v e r t e d p r e d o m i n a n t l y t o a r o m a t i c s by r e f o r m i n g p r o c e s s e s . Table 2 Major A r o m a t i c P r o d u c t s O b t a i n e d by Reforming Of Naphthenes from C o a l (1,2,2) Naphthene

Aromatics

Methyl cyclopentane, Cyclohexane M e t h y l Cyclohexane D i m e t h y l Cyclohexane

Benzene

T r i m e t h y l Cyclohexane C i s - & Trans-Decahydronaphthalene

Toluene ο-, m-, p - x y l e n e , E t h y l benzene Trimethylbenzenes Naphthalene

I n a d d i t i o n t o t h e s e more o b v i o u s d e r i v a t i v e s , many s p e c i a l t y a r o m a t i c s a r e a v a i l a b l e i n such h i g h p r o p o r t i o n as t o change t h e economics o f t h e polymers based on them. A n o t a b l e example i s durene (1,2,4,5t e t r a m e t h y l b e n z e n e ) , a s t a r t i n g m a t e r i a l f o r pyromell i t i c d i a n h y d r i d e , which i s r e a c t e d w i t h d i a m i n e s t o give the high-temperature-resistant polyimides. G a s o l i n e from c o a l c o n t a i n s about 2% o f durene, some 10 t i m e s t h e volume f o u n d i n t y p i c a l p e t r o l e u m gasolines. C o n c e i v a b l y t h e p r i c e c o u l d be c u t t o a f r a c t i o n of i t s present value, with resultant r e d u c t i o n s i n the cost o f polyimides, polyamide-imides and p o l y e s t e r - i m i d e s . A g r e a t i n c r e a s e i n t h e use o f these m a t e r i a l s i s thus a p o s s i b i l i t y . Among t h e e x o t i c condensed r i n g d e r i v a t i v e s a r e c a r b a z o l e , f r o m which can be made N - v i n y l c a r b a z o l e f o r polymers t o be used as d i e l e c t r i c s and i n photo s e n s i t i v e systems; and pyrene, from which BBB p y r r o n e f i b e r s can be d e r i v e d . The most advanced t e c h n i q u e f o r making g a s o l i n e from c o a l i s t h e COED p r o c e s s , d e v e l o p e d by FMC. Crushed and d r i e d c o a l i s h e a t e d s u c c e s s i v e l y i n f o u r f l u i d i z e d bed r e a c t o r s a t s e l e c t e d t e m p e r a t u r e , e.g. 600, Ô 5 0 , 1000 and 1500°F, t h e t e m p e r a t u r e s j u s t below the l e v e l a t which each type o f c o a l would agglomerate. I n each bed, some v o l a t i l e s a r e r e l e a s e d . Later, the 011 o b t a i n e d by p y r o l y s i s i s p a r t i a l l y hydrogenated(i^). Another t e c h n i q u e f o r p r o d u c i n g syncrude i s t h e Η-Coal p r o c e s s d e v e l o p e d by Hydrocarbon R e s e a r c h I n c . , o f T r e n t o n , N. J . Here powdered c o a l i s hydrogenated


170

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POLYMERS

i n an e b u l l a t i n g bed. Pittsburgh and Midway Coal Mining Co., Kansas C i t y , Mo., has a solvent-refined coal process, using l i g n i t e or bituminous feedstocks. The U. S. O f f i c e of Coal Research has sponsored most of the experimental work on making syncrude and syngas from coal; but EXXON and other energy companies are developing proprietary processes. C l e a r l y , coal i s the f o s s i l of the future! L i t e r a t u r e Cited 1. Skeist Laboratories, Inc., R&D Report #43, Chemical By-Products From Coal, O f f i c e of Coal Research (U. S. Department of the I n t e r i o r ) (Nov. 1968). 2. West, Herbert J . , Ind. Eng. Chem., (1970), 62 (11), 28. 3. S k e i s t , I r v i n g , & West, Herbert J . , Gas & Oil From Coal: A V i a b l e A l t e r n a t i v e , P l a s t i c s Engineering, (1974), 39 (2), 18. 4· Jacobs, Harry E., Jones, J . F., & Eddinger, R. T., Ind. Eng. Chem., Process Des. Devel., (1971), 10 (4), 558. 5. Adapted from Clear Energy from Coal - A National P r i o r i t y , O f f i c e of Coal Research, U. S. Department of the I n t e r i o r (1973 Annual Report). 6. M i l l s , G . Axel, Ind. Eng. Chem., (1969), 61 (7), 6. Renewable Resources and Solar Energy Conversion Systems S. Ingemar Falkehag, Westvaco Research Center, North Charleston, S. C . 29406

Renewable resources, such as wood and the byproducts from the pulp and paper and the a g r i c u l t u r a l i n d u s t r i e s , are becoming i n c r e a s i n g l y a t t r a c t i v e as raw m a t e r i a l sources i n l i g h t of the present shortages i n the petrochemical business. The longer term development i s , however, going to be governed by the economic balances involved, p r i m a r i l y r e l a t e d to the cost of energy. This development i s also most l i k e l y going to be i n favor of renewable resources. E c o l o g i c a l and public concern w i l l also a f f e c t the trends. Carbohydrates and l i g n i n can probably be used to a much greater extent with or without extensive m o d i f i c a t i o n , or they can be used as the feed stock f o r chemicals such as alcohols, ethylene, butadiene, phenols, proteins, e t c . Improvement i n the processes


13.

DEANiN E T A L .


171

f o r t h e s e c o n v e r s i o n s can most l i k e l y be made, but i t must be r e a l i z e d t h a t t h e s e developments a r e more o r l e s s t o t a l l y governed by the economic i n c e n t i v e s . P r o j e c t i o n s about the c r o s s - o v e r p o i n t s i n the c o s t time c u r v e s and the f u t u r e s l o p e s f o r p e t r o l e u m v s . renewable r e s o u r c e s cannot be done j u s t based on p a s t e x p e r i e n c e s o r assumptions about s u r p r i s e - f r e e f u t u r e s . I t appears h i g h l y j u s t i f i e d j u s t now t h a t the r e s e a r c h on renewable r e s o u r c e s i s d r a m a t i c a l l y i n c r e a s e d , and t h a t t h i s i s done w i t h i n the scope o f t h e s e raw m a t e r i a l s b e i n g a p a r t o f s o l a r energy c o n v e r s i o n systems. Land use p o l i c i e s and improvements i n the e f f i c i e n c y o f the use o f s o l a r energy and n u t r i e n t s f o r the p r o d u c t i o n o f o r g a n i c m a t e r i a l s a l s o have t o be b r o u g h t i n t o the p i c t u r e . As a wood chemist I f i n d i t t r a g i c t h a t the ACS d i v i s i o n t h a t used t o have "Wood" i n i t s name now has dropped i t i n f a v o r o f the t e x t i l e a p p l i c a t i o n . I would l i k e t o put y o u r a t t e n t i o n t o a c o n f e r e n c e on "Wood C h e m i c a l s - A F u t u r e C h a l l e n g e , " t o be h e l d i n S y r a c u s e , New Y o r k , May 20-24, 1975· The c o n f e r e n c e i s s p o n s o r e d by the T e c h n i c a l A s s o c i a t i o n o f the P u l p and Paper I n d u s t r y and the S t a t e U n i v e r s i t y o f New York. Those o f you who might be i n t e r e s t e d i n p a r t i c i p a t i n g can c o n t a c t Dr. T. E. T i m e l l a t the C e l l u l o s e R e s e a r c h I n s t i t u t e i n S y r a c u s e . As program co-chairman I am a l s o a n x i o u s t o g e t p r o p o s a l s f o r r e l e v a n t p a p e r s d i s c u s s i n g the f u t u r e t r e n d s o r t e c h n o l o g i e s i n the use o f renewable r e s o u r c e s as a raw m a t e r i a l base f o r the c h e m i c a l i n d u s t r y .

Furfural and Furfuryl Alcohol Gordon D . Brindell, The Quaker Oats Co., John Stuart Research Laboratories, 617 West Main St., Barrington, 111. 60010

I would l i k e t o remind the group o f the u t i l i t y o f f u r f u r a l and f u r f u r y l a l c o h o l i n the making o f many plastic materials. The f u r f u r a l i n d u s t r y i s based on c o n v e r t i n g the pentosan f r a c t i o n o f p l a n t m a t e r i a l s t o furfural. The p r o d u c t s a v a i l a b l e are w e l l known because the t e c h n o l o g y f o r d o i n g t h i s c h e m i s t r y was p i o n e e r e d by the Quaker Oats Company over 50 y e a r s ago. F o r a more d e t a i l e d p i c t u r e o f the p r o d u c t s , the i n t e r e s t e d r e a d e r s h o u l d be r e f e r r e d t o Volume 7 o f the E n c y c l o p e d i a o f Polymer S c i e n c e & T e c h n o l o g y .


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Development of Pullulan: Its Characteristics and Applications Shokichi Yuen, Products Development Department, Hayashibara Biochemical Laboratories, Inc., Okayama, Japan

P u l l u l a n was r e p o r t e d by R. Bauer i n 193 Ô as a p r o d u c t o b t a i n e d on c u l t i v a t i o n o f a y e a s t , P u l l u l a r i a pullulans. I t s e l a b o r a t i o n c o n d i t i o n s , s t r u c t u r e and d e r i v a t i v e s were s t u d i e d and g r a d u a l l y r e v e a l e d by many i n v e s t i g a t o r s who were s t i m u l a t e d by the r e p o r t j however, no s u b s t a n t i a l approaches were attempted on i t s characteristics. W i t h a s p e c i f i c o b j e c t i v e , the r e s e a r c h group o f H a y a s h i b a r a B i o c h e m i c a l has commenced and g r a d u a l l y increased t h e i r production of p u l l u l a n . Eventually t h e y drew t h e i r a t t e n t i o n towards i t s c h a r a c t e r i s t i c s and succeeded i n the e c o n o m i c a l commercial p r o d u c t i o n of p u l l u l a n . P a r t i c u l a r l y , improvement o f the y e a s t s p e c i e s and the s e l e c t i o n o f a s u i t a b l e medium l e d t o f a v o r a b l e y i e l d and t o the development o f a commerc i a l l y f e a s i b l e p u r i f i c a t i o n p r o c e d u r e , which made p r o d u c t i o n more advantageous. P u l l u l a n i s a l i n e a r polymer c o n s i s t i n g o f m a l t o t r i o s e u n i t s , n o n - r e d u c i n g and r e d u c i n g t e r m i n a l groups o f w h i c h a r e l i n k e d r e p e a t e d l y i n ao

Round-Table Discussion - ACS Symposium Series (ACS Publications)

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