GB828895A - Improvements in the production of rubber-polymer mixtures and compounds - Google Patents

Abstract

Rubber/polymer compounds and mixtures are prepared by the mastication at a temperature in the range within which rubber molecules are ruptured by the applied shear, and under substantially oxygen-free conditions, of a mixture of natural or synthetic rubber and a polymerizable olefinic compound of such proportions that the mixture is rubbery at the temperature of mastication. The rubber may be natural rubber, preferably crepe that has been treated with acetone to remove non-rubber constituents, or a synthetic rubber such as polybutadiene-1,3, or a copolymer of butadiene-1,3, with acrylonitrile, styrene, isobutylene, methyl methacrylate, methyl acrylate, polychloroprene, or polyisobutylene, or an isocyanate-modified polyester or polyesteramide. Antioxidants and "chain stoppers" are first removed from the synthetic rubber by fractional precipitation. The polymerizable olefinic compound may be acrylic acid, methyl, ethyl, or n-butyl acrylate, methacrylic acid, methyl, ethyl, n-butyl, isobutyl, 2-ethoxy-ethyl, 2-chloro-ethyl, nonyl, lauryl, b -ethyl ethoxy, or 2-chloroethyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, N-butyl acrylamide, vinylidene chloride, methyl isopropenyl ketone, styrene, methyl vinyl ketone, N-vinyl pyrollidone, 2-vinyl pyridine, or vinyl carbazole, divinyl benzene, chloroprene, allyl acrylate, or methacrylate, 2,5-dichlorostyrene or ethylene dimethacrylate. The mixture to be masticated may contain two or more rubbers and/or two or more polymerizable olefinic compounds. The rubber or rubbers may be masticated with one olefinic compound before another is added. The mastication is effected on milling rolls or in an extruder or a liquid-cooled internal mixer in which an atmosphere of nitrogen or carbon dioxide is maintained. The temperature of the mixture during mastication should not normally exceed 130 DEG C. and is preferably maintained below 70 DEG C. Vulcanization of the rubber component and/or cross-linking of the polymer component may be effected during or after the mastication by the addition of the necessary agents, e.g. methylmethacrylate polymer may be cross-linked by adding di-cumyl peroxide. Several examples are described. Specification 679,562 is referred to.