Patent ID: 8518313

Claim:
A process for enhancing the compression set resistance of a foamed copolyester thermoplastic elastomer sheet structure comprising: A) providing a foamed copolyester thermoplastic sheet structure comprising gas-encapsulating thermoplastic microspheres; B) annealing said foamed copolyester thermoplastic sheet structure at a temperature of at least 70° C. for a period of 10 to 60 minutes to form an annealed foamed copolyester thermoplastic sheet structure having an uncompressed thickness; C) compressing, at a temperature of at least 70° C., said annealed foamed copolyester thermoplastic sheet structure to a thickness of 20 to 50% of the uncompressed thickness of said sheet structure; D) releasing said compression; E) repeating steps C) and D) at least once; and F) cooling said sheet structure to less than 30° C. to form a foamed copolyester sheet structure having a compression set resistance, as determined according to ISO 1856, 22 hours, 70° C., 30% compression of less than 11%.