Patent GB-781279-A (GB)
Title: Improvements in or relating to vulcanisable compositions and elastomers produced therefrom
IPC: C08L83/04
Filed: 1955-07-29
Abstract: A vulcanizable composition consists essentially of (1) an organic rubber polymer in which at least 0.5 mol. per cent of the polymer units have residual C=C unsaturation; (2) an organo-polysiloxane in which at least 0.01 mol. per cent of the polymer units have at least one silicon-bonded alkenyl radical and in which the ratio of organic groups to Si atoms is less than 3:1, and (3) as a vulcanizing agent, sulphur, a thiuram mono-, di- or tetra-sulphide, a salt of a dithiocarbamate, a xanthate, a xanthogen disulphide, a benzothiazyl derivative of the formula <FORM:0781279/IV (a)/1> where X is a hydrogen atom, a metal atom or the radical <FORM:0781279/IV (a)/2> or any mixture thereof.  The compositions may contain from 0.1 to 99.9 per cent by weight of the natural or synthetic rubber and from 99.9 to 0.1 per cent of the siloxane.  Synthetic rubbers specified are those obtained by polymerizing butadiene, dimethylbutadiene, isoprene and chloroprene or by co-polymerizing two or more thereof or by copolymerizing a diene in amount, for example, as little as 0.5 mol per cent with 99.5 mol. per cent of a vinylic compound such as isobutylene, styrene, acrylonitrile, methyl acrylate, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl carbazole, coumarone, indene and vinyl toluene. The siloxanes used may also contain saturated and halogenated hydrocarbon radicals.  Many examples of siloxanes and vulcanizing agents are given.  The compositions may also contain fillers, e.g. zinc, magnesium, ferric and chromic oxides, titania, glass fibres, clays, diatomaceous earth, crushed quartz, silica aerogels, fume silicas, silica xerogels, carbon black, wood flour, cotton linters and cork, either per se or treated with organosilicon compounds such as organochlorosilanes, compression set additives, oxidation inhibitors, pigments, activators, e.g. zinc oxide, fatty acids, litharge, magnesium oxide and selenium, and vulcanization accelerators, e.g. condensation products of aldehydes with ammonia or amines and substituted guanidines, examples of which are given. The compositions are vulcanized by heating to temperatures, e.g. of from 50 DEG  to 300 DEG  C.  Examples of the compositions are given. Specification 781,278 is referred to.ALSO:A vulcanisable composition consists essentially of (1) an organic rubber polymer in which at least 0,5 mol. per cent of the polymer units have residual c = c unsaturation, (2) an organopolysiloxane in which at least 0,01 mol. per cent of the polymer units have at least one silicon-bonded alkenyl radical and in which the ratio of organic groups to Si atoms is less than 3 : 1, and (3) as a vulcanising agent, sulphur, a thiuram mono-, di- or tetra-sulphide, a salt of a dithiocarbamate, a xanthate, a xanthogen disulphide, a benzothiazyl derivative of the formula: <FORM:0781279/V/1> where X is a hydrogen atom, a metal atom, or the radical <FORM:0781279/V/2> or any mixture thereof.  The compositions may contain from 0,1 to 99,9 per cent by weight of the rubber and from 99,9 to 0,1 per cent of the siloxane, and may also contain fillers, e.g., zinc, magnesium, ferric and chromic oxides, titania, glass fibres, clays, diatomaceous earth, crushed quartz, silica aerogels, fume silicas, silica xerogels, carbon black, wood flour, cotton linters and cork, either per se or treated with organosilicon compounds such as organochlorosilanes, compression set additives, oxidation inhibitors, pigments, activators, e.g. zinc oxide, fatty acids, litharge, magnesia and selenium, and p  vulcanization accelerators, e.g. condensation products of aldehydes with ammonia or amines and substituted guanidines, examples of which are given.  In examples 4, 8, 10, elastomers were made by vulcanizing compositions of natural rubber smoked sheet, certain alkenyl siloxane copolymers and various vulcanizing agents.  Specification 781,278 [Group IV(a)], is referred to.