Starch-containing biodegradable plastic and method of producing same

• US 5,256,711 A
• Filed: 10/01/1992
• Issued: 10/26/1993
• Est. Priority Date: 10/04/1991
• Status: Expired due to Term

• Current Assignee: Director-General of the Agency of Industrial Science and Technology, the Ministry of International Trade and Industry of Japan (Government of Japan), CHUO Kagaku Company Limited (SENKO Group Holdings Co., Ltd.)
• Original Assignee: Director-General of Agency of Industrial Science, CHUO Kagaku Company Limited (SENKO Group Holdings Co., Ltd.), Technology Research Institute of Innovative Technology For The Earth
• Inventors: Takagi, Sigeyuki, Tokiwa, Yutaka, Koyama, Masatoshi
• Primary Examiner(s): Kight, III, John
• Assistant Examiner(s): BOYKIN, TERRESSA M
• Application Number:
  US07/955,025
• Time in Patent Office: 390 Days
• Field of Search: 523/124, 523/125, 524/47, 525/411, 525/415, 525/450
• US Class Current: 524/47
• CPC Class Codes: C08L 2201/06 Biodegradable
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• CPC Class Codes: C08L 2666/26 Natural polymers, natural resins or derivatives thereof according to C08L1/00 - C08L5/00, C08L89/00, C08L93/00, C08L97/00 or C08L99/00
• CPC Class Codes: C08L 3/02 Starch; Degradation products thereof, e.g. dextrin
• CPC Class Codes: C08L 67/02 Polyesters derived from dicarboxylic acids and dihydroxy compounds C08L67/06 takes precedence
• CPC Class Codes: C08L 67/04 Polyesters derived from hydroxycarboxylic acids, e.g. lactones C08L67/06 takes precedence

Abstract

A biodegradable plastic composition, which may be in the form of a molded dy, includes gelatinized starch and a biodegradable, aliphatic polyester resin having a melting point of 45°-130 ° C. The plastic is produced by kneading a blend containing a starchy substance selected from non-gelatinized, granular starch and gelatinized starch and the aliphatic polyester resin at a temperature higher than the melting point of the aliphatic polyester in the presence of water in an amount of 1-45 % based on the weight of the starchy substance.

Claims

1. A biodegradable plastic material comprising a mixture of gelatinized starch with a biodegradable, aliphatic polyester resin having a melting point of 45°

-130°

C.

2. A biodegradable plastic material as claimed in claim 1, wherein the amount of said gelatinized starch is 2-98% based on the total weight of said aliphatic polyester resin and said gelatinized starch.

3. A biodegradable plastic material as claimed in claim 1, wherein said aliphatic polyester resin is a polycaprolactone.

4. A method of producing a biodegradable plastic material comprising the steps of:

providing a blend containing gelatinized starch and a biodegradable, aliphatic polyester resin having a melting point of 45°

-130°

C.; and

kneading said blend at a temperature higher than the melting point of said aliphatic polyester but lower than the decomposition temperature of said gelatinized starch in the presence of water in an amount of 1-45% based on the weight of said starchy substance.

5. A method as claimed in claim 4, further comprising molding said kneaded blend into a desired shape.

6. A biodegradable plastic material comprising a matrix of a biodegradable, aliphatic polyester resin having a melting point of 45°

-130°

C., and gelatinized starch dispersed in said matrix and is present in an amount of 30-90% based on the total weight of said aliphatic polyester resin and said gelatinized starch.

7. A biodegradable plastic material as claimed in claim 6, wherein said aliphatic polyester resin in a polycaprolactone.

8. A process for producing a biodegradable plastic molding, comprising the steps of:

providing a molten mixture containing a biodegradable, aliphatic polyester resin having a melting point of 45°

-130°

C. and gelatinized starch, wherein the weight ratio of said polyester resin to said gelatinized starch is 10;

90 to 70;

30; and

extruding said mixture through a die under the conditions satisfying the following expressions;

space="preserve" listing-type="equation">100>

n.sub.s /n.sub.e≧

0.8

space="preserve" listing-type="equation">n.sub.e≧

600

wherein n_e and n_s stand for the viscosity, in terms of poise, of the aliphatic polyester resin and the gelatinized starch, respectively, at the extrusion temperature.

9. A process as claimed in claim 8, wherein said molten mixture further contains water in an amount of 1-45% based on the weight of of said gelatinized starch.

10. A method of producing a biodegradable plastic material comprising the steps of:

providing a blend containing a non-gelatinized, granular starch and a biodegradable, aliphatic polyester resin having a melting point of 45°

-130°

C.; and

kneading said blend at a temperature higher than the melting point of said aliphatic polyester but lower than the decomposition temperature of said starch in the presence of water in an amount of 1-45% based on the weight of said starch to gelatinize said starch.

11. A method as claimed in claim 10, further comprising molding said kneaded blend into a desired shape.