Japan Synthetic Rubber Co., Ltd.

Hidekatsu Gotoh

Fumio Tsutsumi

Akihiko Morikawa

Shoei Tsuji

Yoji Mori

An ethylene-.alpha.-olefin-non-conjugated diene copolymer rubber composition comprising a low molecular weight component copolymer composed of an ethylene-.alpha.-olefin-non-conjugated diene copolymer having a Mooney viscosity (ML.sub.1+4, 100.degree. C.) of 10 to 150, an .alpha.-olefin content of 30 to 60% by weight and an iodine value of 37 to 65, and a high molecular weight component copolymer composed of an ethylene-.alpha.-olefin-non-conjugated diene copolymer having a Mooney viscosity (ML.sub.1+4, 100.degree. C.) of 100 to 500, an .alpha.-olefin content of 15 to 50% by weight and an iodine value of 3 to 15, the ratio of the iodine value of the low molecular weight component copolymer to the iodine value of the high molecular weight component copolymer being at least 4/1. The above composition can inhibit a gel from being produced during processing and achieve a high degree of cross-linking and is excellent in compression set, shape-retention and sponge surface skin.

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Suzuka, Japan

Hidekatsu Gotoh