Abstract: Provided is a rubber composition for a tire containing a rubber component including 15 to 55 wt % of an end modified group-containing cycloolefin ring-opening polymer having a glass transition temperature of ?120 to ?90° C. and 45 to 85 wt % of an end modified group-containing solution polymerized conjugated diene polymer having a glass transition temperature of ?60 to ?10° C. and having an aromatic vinyl monomer unit content ratio of more than 30 wt % and 50 wt % or less, a silica, and a silane coupling agent including a monosulfide group and/or a thiol group, wherein the content of the silica with respect to 100 parts by weight of the rubber component is 30 to 200 parts by weight, and the content of the silane coupling agent including a monosulfide group and/or a thiol group with respect to 100 parts by weight of the silica is 0.3 to 20 parts by weight.

Abstract: A cycloolefin rubber having a weight average molecular weight of 100,000 to 800,000, having a silyl group at the polymer chain end, and containing a fatty acid ester of a polyvalent alcohol. A cycloolefin rubber excellent in processability at the time of blending and kneading and excellent in low heat buildup property can be provided.

Abstract: Provided is a cyclopentene ring-opening copolymer comprising a structural unit derived from cyclopentene and a structural unit derived from a norbornene compound with three or more rings, wherein the content of the structural unit derived from a norbornene compound with three or more rings is 40 to 80 wt % in relation to the whole of the repeating structural units in the cyclopentene ring-opening copolymer.

Abstract: A cycloolefin rubber having a weight average molecular weight of 100,000 to 800,000, having a silyl group at the polymer chain end, and containing a fatty acid ester of a polyvalent alcohol. A cycloolefin rubber excellent in processability at the time of blending and kneading and excellent in low heat buildup property can be provided.

Abstract: A rubber composition for a tire containing a cyclopentene ring-opening polymer and a solution polymerized styrene-butadiene rubber. The rubber composition is a cross-linked rubber with excellent wet grip and low heat buildup properties.

Abstract: Provided is a rubber composition for a tire containing a rubber component including 15 to 55 wt % of an end modified group-containing cycloolefin ring-opening polymer having a glass transition temperature of ?120 to ?90° C. and 45 to 85 wt % of an end modified group-containing solution polymerized conjugated diene polymer having a glass transition temperature of ?60 to ?10° C. and having an aromatic vinyl monomer unit content ratio of more than 30 wt % and 50 wt % or less, a silica, and a silane coupling agent including a monosulfide group and/or a thiol group, wherein the content of the silica with respect to 100 parts by weight of the rubber component is 30 to 200 parts by weight, and the content of the silane coupling agent including a monosulfide group and/or a thiol group with respect to 100 parts by weight of the silica is 0.3 to 20 parts by weight.