Patent ID: 7671128

Claim:
A rubber composition comprising (A) a first copolymer rubber comprised of repeat units derived from (1) 10 to 99 weight percent of a conjugated diene monomer which contains from 4 to 8 carbon atoms; (2) 0 to 70 weight percent of a vinyl substituted aromatic monomer; and (3) 1 to 20 weight percent of at least one co-monomer selected from the group consisting of the following general formulas I: wherein R represents a hydrogen atom or an alkyl group containing from 1 to 8 carbon atoms; wherein R 1 represents a saturated alcohol group containing from 1 to 8 carbon atoms; and (B) a second copolymer rubber comprised of repeat units derived from (1) 10 to 99 weight percent of a conjugated diene monomer which contains from 4 to 8 carbon atoms; (2) 0 to 70 weight percent of a vinyl substituted aromatic monomer; and (3) 1 to 20 weight percent of at least one co-monomer selected from the group consisting of the following general formulas I: wherein R represents a hydrogen atom or an alkyl group containing from 1 to 8 carbon atoms; wherein R 1 represents a saturated alcohol group containing from 1 to 8 carbon atoms; wherein the first and second copolymer rubbers have a difference in glass transition temperatures ranging from 30° C. to 60° C.