GB893084A - Improvements in or relating to polymeric compositions - Google Patents

Abstract

Transparent, rubber-containing polymeric compositions are obtained by polymerizing a mixture of ethylenically unsaturated monomers, e.g. styrene or derivatives thereof, methyl, or N-butyl methacrylate, acrylonitrile and vinyl chloride or acetate, in the presence of natural or synthetic rubber, the monomer mixture being chosen so that a copolymer obtained from the monomers independently of the rubber has a refractive index within 0,02, preferably 0,015, of that of the rubber used. The rubbers exemplified are butadiene-styrene (75-25%), polychloroprene, polybutadiene, and natural rubber, a polymer of any of the monomers, and a styrene-isobutylene copolymer being excluded. The rubber in finely divided form may be dissolved in the monomer mixture, or in a mutual solvent, or used in the form of a dispersion, and is preferably present in a proportion of from 5 to 35% by weight of the final product, and in the case of styrene and methyl methacrylate preferably in a proportion of 6:1. Examples describe the polymerization (1) of a 1:1, 2:1 or 3:2 mixture of styrene-methyl methacrylate with 6% of butadiene-styrene rubber copolymer with a prepolymerization heating stage followed by a multi-stage heat polymerization using a t-butyl perbenzoate catalyst. (4) methyl methacrylate and styrene with 6% polychloroprene using a mixed azo-bis-isobutyronitrile, lauroyl peroxide, and t-butyl perbenzoate catalyst with an organo-tin stabilizer. (5) styrene and acrylonitrile with a 6% butadiene-styrene rubber using a lauroyl peroxide and t-butyl perbenzoate catalyst with an organo-tin stabilizer, (6) methyl methacrylate and styrene with natural rubber using a mixed catalyst as in (4), (7) vinyl toluene and N-butyl methacrylate with butadiene-styrene rubber and (8) vinyl chloride and acetate with a polybutadiene latex.