Biodegradable film and process for producing the same

• US 6,326,440 B1
• Filed: 05/11/2000
• Issued: 12/04/2001
• Est. Priority Date: 11/14/1997
• Status: Expired due to Term

• Current Assignee: Mitsubishi Chemical Corporation (Mitsubishi Chemical Group Corp.)
• Original Assignee: Mitsubishi Plastics Incorporated (Mitsubishi Chemical Group Corp.)
• Inventors: Takagi, Jun, Terada, Shigenori
• Primary Examiner(s): Short, Patricia A.
• Application Number:
  US09/554,236
• Time in Patent Office: 572 Days
• Field of Search: 525/411, 525/437, 525/439, 525/440, 525/450, 525/938
• US Class Current: 525/411
• 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
• CPC Class Codes: Y10S 525/938 Polymer degradation

Abstract

A plastic film is provided in which brittleness has been improved, and which is not too soft, and which has practically satisfactory physical properties, heat-sealability stable with time, and biodegradability in natural environment. The film comprises a polylactic acid-family polymer and other aliphatic polyester at the ratio of 80:20 to 20:80, and the heat of fusion ΔHm1 converted to the polylactic acid-family polymer when the temperature of the film is raised is 35 J/g or under.

Claims

1. A biodegradable film comprising a polylactic acid-family polymer whose fusion heat of crystal Δ

Hm₂ when secondary temperature raising is carried out is 3 J/g or under and other aliphatic polyester than the polylactic acid-family polymer at the weight ratio of 80;

20 to 20;

80, characterized in that the heat for fusion Δ

Hm1 converted to the polylactic acid-family polymer when the temperature of the film is raised is 35 J/g or under.

2. The biodegradable film as claimed in claim 1 characterized in that the aliphatic polyester has a weight-average molecular weight of 20 to 300 thousand and has the structure expressed by the following formula (1)

(wherein R1 and R2 are alkylene or cycloalkylene groups having 2 to 10 carbon atoms, n is the degree of polymerization required for the weight-average molecular weight to be 20-300 thousand, R1 or R2 may be identical to or different from each other, and in the formula, instead of ester-bound residue, urethane-bound residue and/or carbonate-bound residue may be contained up to 5%).

3. The biodegradable film as claimed in claim 2 wherein the glass transition point of said aliphatic polyester is 0°

C. or lower.

4. The biodegradable film as claimed in claim 2 wherein the weight-average molecular weight of said aliphatic polyester is 150 to 250 thousand.

5. The biodegradable film as claimed in claim 2 wherein the weight-average molecular weight of said polylactic acid-family polymer is 100 to 300 thousand.

6. The biodegradable film as claimed in claim 1 wherein the glass transition point of said aliphatic polyester is 0°

C. or lower.

7. The biodegradable film as claimed in claim 1 wherein the weight-average molecular weight of said aliphatic polyester is 150 to 250 thousand.

8. The biodegradable film as claimed in claim 1 wherein the weight-average molecular weight of said polylactic acid-family polymer is 100 to 300 thousand.