Thermoplastic elastomer composition, blends of the composition with olefin plastic, and foamed products of the composition and the blends

A method of producing a thermoplastic composition, which comprises dynamically heat-treating, in the presence of an organic peroxide, a mixture of 100 to 40 parts by weight of (a) a peroxide-curable olefin copolymer rubber selected from the group consisting of ethylene-propylene copolymer rubber and ethylene-propylene-non conjugated diene terpolymer rubber,

• 0 to 60 parts by weight of (b) a peroxide-decomposing olefin plastic selected from the group consisting of isotactic polypropylene and propylene-alpha olefin copolymer,
• wherein the sum of component (a) and component (b) is 100 parts by weight,
• 5 to 100 parts by weight of at least one member of (c) peroxide-non-curable hydrocarbon rubbery material selected from polyisobutylene and butyl rubber, and (d) mineral oil softeners;
• to obtain a thermoplastic elastomer composition (A);
• and then, homogeneously blending 100 to 5 parts by weight of said composition (A) and 0 to 95 parts by weight of (B) an olefin plastic selected from the group consisting of homopolymers of an alpha olefin selected from the group consisting of ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene and 1-octene;
• copolymers therebetween;
• and copolymers thereof with 15 mole % or less of another copolymerizable monomer;
• wherein the sum of said component (b) and said component (B) account for not less than 5 parts by weight among 100 parts of the final product.