Polymer composition for injection molding
AssigneeWarner-Lambert Company
InventorsFritz Wittwer, Ivan Tomka
Life of this patent
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Abstract
Capsules and other shaped products formed from a moldable starch composition in an injection molding device is disclosed in the present invention. The composition comprising starch having a molecular mass range of 10,000 to 20,000,000 Dalton, and a water content range from 5 to 30% by weight. The starch contains about 0 to 100% of amylose, and about 100 to 0% of amylo-pectin.
Claims24
A process for forming starch into an article using an injection molding technique which process comprises:
- (A) maintaining a starch/water composition at a water content between 5-30% by weight of the composition under controlled conditions of temperature and pressure,
- (b) heating said starch/water composition at elevated pressure above its glass transition temperature and melting point while maintaining said water content, to form a melt,
- (c) further heating and plasticizing said molten starch/water composition to dissolve the starch in the water to form an essentially molecularly dispersed solution of the melt,
- (d) injecting the starch/water melt into a mold cavity while maintaining said predetermined water content,
- (e) cooling the composition in the mold to form a molded product at a temperature below the glass transition temperature of said composition and,
- (f) ejecting the molded product from said mold.
A starch/water composition characterized in that said composition is obtained by
- (a) maintaining a starch/water composition at a water content of 5-30% by weight of the composition under controlled conditions of temperature and pressure,
- (b) heating said starch/water composition under pressure above its glass transition temperature and melting point while maintaining said water content, to form a melt,
- (c) further heating and plasticizing said molten starch/water composition to dissolve the starch in the water to form melt as a molecularly dispersed solution of said melt.
A self-sustaining molded article made from starch having a microstructure formed by heating a starch-water mixture wherein the water content is between 5 and 30% by weight beyond the glass transition and melting temperatures of starch to form a melt as a molecularly dispersed solution and cooling said melt to minimize shrinkage.
Dependencies are inferred from the claim text.