GB1180085A - Transparent Thermoplastic Composition of High Impact Resistance and manufacture thereof - Google Patents

Abstract

1,180,085. Graft copolymers. TOYO RAYON K.K. 8 Feb., 1967 [8 Feb., 1966; 23 Feb., 1966; 3 Aug., 1966; 1 Sept., 1966; 28 Oct., 1966; 8 Nov., 1966; 13 Dec., 1966(2)], No. 5985/67. Heading C3G. An impact-resistant transparent thermoplastic composition comprises butadiene rubber particles in an amount of 0À3 to 20% by weight occluding an isolated or substantially isolated copolymer, in an amount of 99À7 to 80% by weight, of at least 70% by weight of a monoalkenyl aromatic compound and an alkyl methacrylate and homogeneously dispersed in a continuous matrix composed of the said copolymer, characterized in that (i) the average size of the rubber particles is 0À15 to 0À7 Á and the butadiene rubber occludes the copolymer as spherical membranes of average thickness 0À0025 to 0À15Á and not in excess of “ of the said particle size and (ii) the difference in refractive index (# D <SP>23</SP>) between the said copolymer and the rubber does not exceed 0À005. The rubber is e.g. polybutadiene or a butadiene-styrene copolymer. Suitable aromatic monomers are styrene, α-methyl styrene and vinyl toluene and the alkyl methacrylate is derived from a C\ to C 4 alkanol. Up to 30% of another monomer, e.g. methyl, ethyl or n-butyl acrylate or acrylonitrile may be incorporated in the copolymer. The composition is produced by a method comprising (a) dissolving the rubber in a mixture of the aromatic monomer and the alkyl methacrylate, (b) subjecting the solution to bulk polymerization in the presence of a polymerization initiator, which is soluble in the monomer and difficultly water soluble, while stirring at such a rate as to cause phase inversion of the solution and form droplets comprising copolymer derived from the monomeric mixture within an occluding membrane of butadiene rubber, the droplets being dispersed within a matrix derived from the monomeric mixture, said polymerization being effected until 5 to 35% by weight of the monomer mixture is copolymerized, (c) when necessary, mixing the resulting prepolymer dispersion with a solution of the butadiene rubber in the monomeric mixture or with a prepolymer derived therefrom, in such proportions as to introduce droplets of greater or smaller average particle size as may be required and (d) subjecting the resulting prepolymer system to an aqueous suspension polymerization, or (d<SP>1</SP>) subjecting the said prepolymer system to bulk polymerization without substantial stirring.