| 摘要 |
PROBLEM TO BE SOLVED: To obtain a rubber composition for sponge which has well-balanced flexibility and low-compression plastic strain, an excellent processing property, and so on, by using a specific ethylene-based copolymer rubber as a component. SOLUTION: This composition is obtained by using, as main components, (A) an ethylene-based copolymer rubber having a unit from ethylene, a unit, from a 4-12Cα-olefin, and a unit from an unconjugated polyene shown by the formula (X is a 1-20C saturated or unsaturated hydrocarbon; R<1> and R<2> are each H or a 1-8C alkyl; R<3> is a 1-8C alkyl; R<1> and R<2> are not H at the same time), an (ethylene/α-olefin) molar ratio of (40/60)-(80/20), an iodine number of 15-45, a Mooney viscosity (ML1+4 , at 100 deg.C) of 40-150, a (polystyrene- equivalent weight-average molecular weight/polystyrene-equivalent number- average molecular weight) ratio of 2.5-15 as measured by gel permeation chromatography, a glass-transition temperature at -80 to -50 deg.C as measured by differential scanning calorimetry, and a blanching index of 0.6-0.96, (B) a vulcanizing agent and/or a crosslinking agent, and (C) a forming agent.
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