GB778265A - Improved styrene-acrylonitrile copolymers - Google Patents

Abstract

Graft copolymers having improved toughness are prepared by polymerizing a mixture of 50 to 90 parts of styrene of vinyltoluene with 50 to 10 parts of acrylonitrile and optionally up to 15 per cent of an unsaturated comonomer, e.g. a -methylstyrene, vinyltoluene, ethyl acrylate, butyl acrylate, methyl methacrylate or methacrylonitrile, in which is dispersed 1 to 50 per cent or more of a preformed, gel-containing rubbery copolymer. The rubber may comprise butadiene-1,3, 5 to 50 per cent of acrylonitrile and optionally up to 15 per cent of an unsaturated comonomer, e.g. isoprene, styrene, butyl acrylate, methyl methacrylate or methacrylonitrile, and is intimately dispersed, e.g. by tumbling overnight under nitrogen in sealed tubes in the monomers which are polymerized by mass, solvent, suspension, e.g. in the presence of tricalcium phosphate or vinyl acetate-maleic anhydride copolymers, or emulsion, e.g. in the presence of a water-soluble salt of an alkyl substituted aromatic sulphonate, techniques between 25 DEG and 125 DEG C. Catalysts, e.g. benzoyl peroxide, diacetyl peroxide, dimethylphenyl hydroperoxymethane and alpha, alpha1 - azo - bis - isobutyronitrile may be added. The rubber may be prepared by aqueous emulsion polymerization in the presence of an alkyl mercaptan having 8 to 16 carbon atoms and a catalyst, e.g. a persulphate, or a cumene hydroperoxide-pentamethylene hexamine or ferrous phosphate redox system, stripping and coagulating the latex by adding an acid or salt. Plasticizers, stabilizers, fillers and dyes may be incorporated in the rubber or copolymer before, during or after polymerization. The product may be injection or compression moulded, used to form sheets or, in latex form, emulsion paints. U.S.A. Specifications 2,439,202, 2,505,349 2,550,139 and 2,652,384 are referred to.