Heat resistant rubber composition having improved mechanical properties

摘要

The rubber composition without formulating a carbon black filler has a remarkably low Mooney viscosity and still is capable of giving a rubber vulcanizate having excellent mechanical properties. The rubber composition comprises, in addition to natural rubber or a diene- based synthetic rubber and a non-carbon inorganic filler, a specific poly(dialkoxysiloxane) terminated at each molecular chain end with a polysulfide linkage-containing group of the formula (RO).sub.3 Si--R.sup. 1 --S.sub.x -- R.sup.1 --bonded to the terminal silicon atom, in which R is an alkyl group, e.g. methyl and ethyl, R.sup.1 is a divalent hydrocarbon group, e.g. --CH.sub.2 CH.sub.2 CH.sub.2 13 , and x is a positive integer of 2 to 6 or, typically, 4.