GB672992A - Improvements in or relating to synthetic rubber - Google Patents

Abstract

A synthetic rubber composition is prepared by blending 95-35 parts of a rubbery copolymer of a diolefine and an acrylic nitrile, prepared by copolymerizing mixtures containing from 85-40 parts, preferably 80-60 parts, of a conjugated diolefine containing from 4-6 carbon atoms in the molecule, and from 15-60 parts, preferably 20-40 parts, of an acrylic nitrile, with from 5-65 parts of a solid rubbery polymer of a diolefin having from 4-6 carbon atoms in the molecule, or a copolymer of a mixture of such a diolefine and less than 10 per cent by weight of a copolymerizable ethylenically unsaturated compound, the resultant blend being such that the constituents thereof are immiscible with one another, i.e. the two rubbers exist as two distinct phases, no matter how well homogenized. In the diolefin-nitrile copolymer the conjugated diolefine may be butadiene, isoprene, piperylene, dimethyl butadiene, chloroprene or mixtures thereof, and the acrylic nitrile may be acrylonitrile, methacrylonitrile, ethacrylonitrile, chloracrylonitrile or mixtures thereof. The rubbery diolefine polymer may be homopolymerized butadiene, isoprene, piperylene, dimethyl-butadiene, or mixtures of such homopolymerized diolefines, or a copolymer of such a diolefine with less than 10 per cent of styrene, an acrylic nitrile, methyl acrylate, methyl methacrylate or unsaturated ketone. The blend is preferably prepared by mixing latices of the blend constituents and coagulating together. The composition may be mixed with carbon black, dibutyl phthalate, zinc oxide, stearic acid, sulphur and organic vulcanizing agents, and then vulcanized.