Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1996-02-02
1998-02-03
Kight, John
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
514 60, C08B 3102, A61K 31715
Patent
active
057146012
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for producing starch esters by using a vinyl ester as the esterifying agent, such starch esters, and compositions containing the starch esters. In particular, the present invention relates to a method for producing water-proof starch esters having a high degree of substitution, a high molecular weight and a high mechanical strength, such starch esters, and starch ester compositions.
BACKGROUND OF THE INVENTION
As a synthetic reaction favorable for obtaining starch esters having a low degree of substitution (DS is not larger than 1.0), known is a method of using vinyl acetate as the esterifying agent in an aqueous slurry phase. (See "Handbook of Starch Science", 1st Edition, 1st Print, page 505, published by Asakura Shoten Co., July 1977.)
On the other hand, as a synthetic reaction favorable for obtaining starch esters having a high degree of substitution, known is a method of reacting an acid anhydride and a starch in pyridine in the presence of a catalyst of dimethylaminopyridine or an alkali metal salt. (See "Starch Chemistry & Technology", page 332 to 336, written by Whistler and published by Academic Press.)
As another means of producing starch esters with a high degree of substitution, known is a method of reacting a starch in an acid anhydride at a temperature not lower than 100.degree. C. with an aqueous solution of an alkali metal hydroxide as the catalyst, followed by purifying the resulting ester with an alcohol, as well as the starch ester thus produced. (See Japanese Patent Laid-Open No. 5-508185.) In this laid-open application, referred to is a composition comprising the starch ester produced therein and a plasticizer having an effect specific to the starch ester (the effect is for causing the gellation with the starch ester).
As still another means of producing starch esters with a high degree of substitution, known is a method disclosed by A. M. Mark and C. L. Mehltretter in academic journal of "Die Starke" (March number, page 73, 1972), which is extremely similar to the method disclosed in Japanese Patent Laid-Open No. 5-508185.
However, in the above-mentioned methods for producing starch esters with a high degree of substitution, the effective utilization of the esterifying agents is low or about 40%, and the glycoside bonds (essentially, alpha-1-4 bond) in the starch esters produced are hydrolyzed by the organic acid to be produced as side products and a small amount of water existing in the diluting solvent or water to be added to the reaction system along with the catalyst to give low-molecular starch esters. Even if the formation of such low-molecular starch esters could be prevented as much as possible by some means, it is still impossible to realize the intended stoichiometrical increase in the molecular weight of the starch ester to be produced than the molecular weight of the starting starch.
For the purpose of preventing the formation of low-molecular starch esters by hydrolysis, there is known a means of previously adding an alkaline salt such as sodium bicarbonate or the like to the reaction solvent. Even by this means, the molecular weight of the starch esters to be produced is lowered to about 1/3. Therefore, this means is not so effective.
The starch esters produced by the above-mentioned known methods (such as methods for producing starch esters disclosed in Japanese Patent Laid-Open No. 5-508185 or by A. M. Mark and C. L. Mehltretter, etc.) could be shaped into starch derivative moldings which are fairly good in terms of the water-proofness and the mechanical and physical properties. In practice, however, starch derivative moldings which satisfy the following requirements are desired.
(1) Starch derivative moldings having more increased mechanical strength and more improved physical properties.
(2) Starch derivative moldings having more lowered water (or steam) sensitivity. (In other words, starch derivative moldings whose mechanical and physical properties are influenced little by water or moisture in air
REFERENCES:
patent: 3795670 (1974-03-01), Mark et al.
patent: 4891404 (1990-01-01), Narayan et al.
patent: 5367067 (1994-11-01), Frische et al.
patent: 5462983 (1995-10-01), Bloembergen et al.
A. M. Mark and C. L. Mehltretter, Die Starke 22, Jahrg, 1970/Nr. 4 (pp. 108-110). Publication discussing the `acetylation of high-amylose corn starch`.
A. M. Mark and C. L. Mehltretter, Die Starke 24, Jahrg, 1972/Nr. 3 (pp. 73-76). Publication discussing preparation of starch triacetates.
Journal of Applied Polymer Sciences, vol. 22, 1978 (pp. 459-465), "A New Biodegradable Plastic Made From Starch Graft Poly (methyl acrylate) Copolymer". Publication discussing grafted starch-based, biodegradable plastics.
Okumura Yasuhito
Tanaka Hideyuki
Tanaka Hiroshi
Utsue Isamu
Japan Corn Starch Co., Inc.
Kight John
White Everett
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