Degradable foam and use of same

• US 5,447,962 A
• Filed: 01/27/1994
• Issued: 09/05/1995
• Est. Priority Date: 04/01/1991
• Status: Expired due to Term

• Current Assignee: Mitsui Chemicals Incorporated (Mitsui Chemicals)
• Original Assignee: Mitsui Chemicals Incorporated (Mitsui Chemicals)
• Inventors: Watanabe, Takayuki, Suzuki, Kazuhiko, Yamaguchi, Akihiro, Kitahara, Yasuhiro, Ajioka, Masanobu, Enomoto, Katashi
• Primary Examiner(s): Foelak, Morton
• Application Number:
  US08/186,920
• Time in Patent Office: 586 Days
• Field of Search: 521/182, 521/79, 521/95, 521/97, 521/916
• US Class Current: 521/79
• CPC Class Codes: C08J 2367/04 Polyesters derived from hydroxy carboxylic acids, e.g. lactones C08J2367/06 takes precedence
• CPC Class Codes: C08J 9/06 by a chemical blowing agent
• CPC Class Codes: C08J 9/14 organic
• CPC Class Codes: Y10S 521/916 Cellular product having enhanced degradability

Abstract

Foams comprising innumerable cells dispersed in thermoplastic polymer compositions substantially consisting of polylactic acid or a copolymer of lactic acid and hydroxycarboxylic acid and having degradable characteristics in the natural environment.

The foams can be used for containers such as food trays and throw away cups comprising molded sheet foam of a thermoplastic and degradable polymer or heat insulating materials and cushioning materials comprising bulk foam.

Claims

1. A method for preparing a degradable foam having numerous cells dispersed throughout a polymer comprised of a polylactic acid or a copolymer of lactic acid and hydroxy carboxylic acid, said method comprising forming a mixture of said polymer and a decomposition foaming agent and decomposing said decomposition type foaming agent to form a melt composition having numerous cells and cooling said composition while maintaining said cells to form said degradable foam.

2. The method of claim 1 wherein said decomposing is by heating the mixture.

3. The method of claim 1 wherein said mixture is melt extruded to form said degradable foam.

4. The method of claim 1 wherein said decomposition type foaming agent is selected from the group consisting of sodium hydrogen carbonate, azodicarbonamide, N,N'"'"'-dinitrosopentamethylenetetramine, p,p'"'"'-oxybis(benzenesulfonylcarbazide), azobisisobutyronitrile, and benzenesulfonylhydrazide.