Process for the production of expanded polyester foam beads

Patent metadata

Field	Value
Publication number	US-10138345-B2
Application number	US-201415027803-A
Country	US
Kind code	B2
Filing date	Sep 29, 2014
Priority date	Oct 9, 2013
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

A process for the production of expanded foam beads that are prepared from pellets comprising polyester mixture comprising
a) from 50 to 99% by weight, based on components a and b, of a biodegradable polyester based on aliphatic, or a mixture of aliphatic and aromatic, dicarboxylic acids and an aliphatic diol, and b) from 1 to 50% by weight, based on components a and b, of polylactic acid,

the process comprising the following steps:
(i) providing an aqueous suspension of the polyester pellets, (ii) impregnating the pellets in the suspension of step (i) with at least one physical or chemical blowing agent to provide blowing-agent-loaded pellets in suspension, wherein the impregnation of the at least one blowing agent includes heating the mixture to a depressurization temperature IMT with stirring, and (iii) depressurizing the suspension obtained in step (ii) to provide the expanded foam beads.

The at least one blowing agent is added to the suspension in step (i), or in step (ii) during the heating phase, or immediately after the heating phase, and following the heating of step (ii), the suspension is maintained at a temperature in the range from IMT minus 5° C. to IMT plus 2° C. for a period of 3 to 100 minutes. The invention further relates to expanded foam beads obtained by the process, and to the production of moldings from the expanded foam beads.

First claim

The invention claimed is:

1. A process for the production of expanded foam beads, the foam beads prepared from pellets comprising a polyester mixture comprising
a) from 60 to 95% by weight, based on components a and b, of a biodegradable polyester based on aliphatic, or a mixture of aliphatic and aromatic, dicarboxylic acids and on aliphatic diols, and
b) from 5 to 40% by weight, based on components a and b, of polylactic acid,
the process comprising the following steps:
(i) providing a suspension of the polyester pellets in a suspension medium,
(ii) impregnating the pellets in the suspension of step (i) with at least one physical blowing agent to provide a suspension of blowing-agent-loaded pellets, wherein the impregnating includes heating the suspension of pellets to an impregnation temperature in a range from 100 to 140° C., with stirring, and
(iii) depressurizing and cooling the suspension obtained in step (ii)-to provide the expanded foam beads, wherein the depressurization and cooling is carried out with a liquid coolant in a ratio of coolant to suspension medium of 0.3 to 20,
wherein the at least one blowing agent is added in step (i), or in step (ii) during the heating, or after the heating, and
wherein, following the heating of step (ii) and the addition of the at least one blowing agent, the heated suspension is maintained at a temperature in a range from the impregnation temperature minus 5° C. to the impregnation temperature plus 2° C. for a period of 15 to 40 minutes; wherein the biodegradable polyester comprises:
A1) from 30 to 100 mol %, based on components A1) and A2), of one or more of an aliphatic dicarboxylic acid selected from the group consisting of succinic acid, adipic acid, sebacic acid and mixtures thereof,
A2) from 0 to 70 mol %, based on components A1) and A2), of terephthalic acid,
B) from 98.5 to 100 mol %, based on components A1) and A2), of 1,4-butanediol or 1,3-propanediol; and
C) from 0.05 to 1.5% by weight, based on components A1), A2) and B), of one or more compounds selected from the group consisting of:
C1) glycerol,
C2) hexamethylene diisocyanate, and
C3) a di- or polyfunctional epoxide.

2. The process according to claim 1 , wherein the suspension medium is water.

3. The process according to claim 1 , wherein the biodegradable polyester is polybutylene adipate-co-terephthalate, polybutylene sebacate-co-terephthalate, or a mixture thereof.

4. The process according to claim 1 , wherein the polyester pellets have an arithmetically averaged pellet weight of at least 5 mg and at most 60 mg.

5. The process according to claim 1 , wherein the physical blowing agent n-butane, isobutane, or CO 2 .

6. The process according to claim 1 , wherein the polyester pellet includes from 0.02% to 0.2% by weight, based on the polyester components a) and b), of talc powder as a nucleating agent.

7. The process according to claim 1 , wherein step (ii) further comprises, at a temperature below the first melting point of the polyester mixture, as determined with DSC, increasing the pressure above the suspension to 2 to 15 bar.

8. The process according to claim 1 , wherein the biodegradable polyester comprises from 40 to 60 mol %, based on components A1 and A2, of component A1, and 40 to 60 mol %, based on components A1 and A2, of component A2.

Assignees

• Basf Se

Inventors

• Keppeler Uwe

Classifications

• C08J2367/02

  Polyesters derived from dicarboxylic acids and dihydroxy compounds; (C08J2367/06 takes precedence) · CPC title

• B29C44/3461

  Making or treating expandable particles · CPC title

• C08J9/0061

  characterized by the use of several polymeric components · CPC title

• C08J2205/052

  Closed cells, i.e. more than 50% of the pores are closed · CPC title

• B29C44/3453

  Feeding the blowing agent to solid plastic material · CPC title