Rubber composition

Claim 1

A rubber composition which comprises: (A) 100 parts by weight of a combination composed of (A-1) from 50 to 97% by weight of a rubbery copolymer of ethylene and propylene, and (A-2) from 50 to 3% by weight of an organopolysiloxane represented by the average unit formula R.sup.1.sub.n SiO.sub.(4-n)/2, in which R 1 is a substituted or unsubstituted monovalent hydrocarbon group, the groups denoted by R 1 in a molecule having at least two aliphatically unsaturated linkages, and the subscript n is a positive number in the range from 1.90 to 2.05, and having an average degree of polymerization of at least 500; (B) from 5 to 200 parts by weight of a reinforcing silica filler having a specific surface area of at least 50 m 2 /g; (C) from 1 to 20 parts by weight of a first organosilane compound represented by the general formula R.sup.2.sub.m Si(OX).sub.4-m, in which R 2 is a substituted or unsubstituted monovalent hydrocarbon group selected from the class consisting of alkyl groups having 1 to 6 carbon atoms, cycloalkyl groups having 5 to 8 carbon atoms, phenyl group, vinyl group and 3,3,3-trifluoropropyl group, X is an atom or group selected from the class consisting of hydrogen atom, alkyl groups having 1 to 4 carbon atoms and alkoxy-substituted alkyl groups having 2 to 6 carbon atoms and the subscript m is zero, 1 or 2, or a partial hydrolysis-condensation product thereof having an average degree of polymerization not exceeding 100; and (D) from 0.1 to 10 parts by weight of a second organosilane compound having a thiocarbamyl group in a molecule represented by the general formula (R.sup.3 O).sub.a (R.sup.4).sub.3 --a Si--R.sup.5 --S.sub.b --CS--NR.sup.6.sub.2, in which R 3 is a monovalent group selected from the class consisting of alkyl groups having 1 to 4 carbon atoms, alkoxy-substituted alkyl groups having 2 to 6 carbon atoms, cycloalkyl groups having 5 to 8 carbon atoms and phenyl group, R 4 is a monovalent hydrocarbon group selected from the class consisting of alkyl groups having 1 to 4 carbon atoms, cycloalkyl groups having 5 to 8 carbon atoms and phenyl group, R 5 is a divalent hydrocarbon group of a straightly linear or cyclic structure having 1 to 8 carbon atoms, R 6 is a hydrogen atom or a monovalent hydrocarbon group selected from the class consisting of alkyl groups having 1 to 4 carbon atoms and phenyl group, the subscript a is 1, 2 or 3 and the subscript b is a positive integer of from 2 to 6.