Foam of thermoplastic urethane elastomer composition and process for producing the foam

A method for producing a urethane-based thermoplastic elastomer foam comprising the steps of:

• (1) admixing 0.1 to 30 parts by weight of carbon dioxide (B) with 100 parts by weight of a urethane-based thermoplastic elastomer composition (A) in a molten state together with a dynamic heat treatment to form a molten urethane-based thermoplastic elastomer composition (C) which comprises a mixture of the urethane-based thermoplastic elastomer composition (A) and the carbon dioxide (B);
• (2) cooling said molten urethane-based thermoplastic elastomer composition (C),
• (3) exposing said cooled composition (C) to reduced pressure sufficient to produce cell nuclei in the molten urethane-based thermoplastic elastomer composition (C), and
• (4) then foaming said composition (C) while controlling an expansion ratio.

A urethane-based thermoplastic elastomer foam, having

• an average cell diameter of 0.1 to 1,000 μm,
• an average cell number of 103 to 1016/cm3,
• an elongation set of 1 to 100%,
• a bulk density of 0.03 to 1.10 g/cm3, and wherein
• the melting point of the urethane-based thermoplastic elastomer foam (Tm1) and non-foamed resin (Tm2) as determined by DSC satisfy the formula (1):
• Tm1−Tm2≧5° C. (1)
• and being obtained through the steps of dissolving 0.1 to 30 parts by weight of carbon dioxide (B) in 100 parts by weight of a urethane-based thermoplastic elastomer composition (A) of a molten state together with a dynamic heat treatment, wherein said urethane-based thermoplastic elastomer composition (A) comprises a urethane-based thermoplastic elastomer (A-1) and another thermoplastic elastomer (A-2) in a weight ratio of (A-1)/(A-2) of from 20/80 to 99/1 by weight to form a molten urethane-based thermoplastic elastomer composition (C) which comprises a mixture of the urethane-based thermoplastic elastomer composition (A) and the carbon dioxide (B);
• and cooling said molten urethane-based thermoplastic elastomer composition (C).

A urethane-based thermoplastic elastomer foam, having

• an average cell diameter of 0.1 to 1,000 μm,
• an average cell number of 103 to 1016/cm3,
• an elongation set of 1 to 100%,
• a bulk density of 0.03 to 1.10 g/cm3, and wherein
• the melting point of the urethane-based thermoplastic elastomer foam (Tm1) and non-foamed resin (Tm2) as determined by DSC satisfy the formula (1):
• Tm1−Tm2≧5° C. (1)
• and being obtained through the steps of dissolving 0.1 to 30 parts by weight of carbon dioxide (B) in 100 parts by weight of a urethane-based thermoplastic elastomer composition (A) in a molten state together with a dynamic heat treatment to form a molten urethane-based thermoplastic elastomer composition (C) which comprises a mixture of urethane-based thermoplastic elastomer composition (A) and the carbon dioxide (B);
• cooling said molten urethane-based thermoplastic elastomer composition (C);
• and
• exposing said molten urethane-based thermoplastic elastomer composition (C) to a lower pressure than that of the cooling step to produce cell nuclei in said molten urethane-based thermoplastic elastomer composition (C), and controlling an expansion ratio while foaming.