GB832821A - Improvements in the production of thermoplastic polymeric materials - Google Patents

Abstract

Graft polymers are prepared by polymerizing 1 to 9 parts of methyl methacrylate, or 1-9 parts of a mixture of methyl methacrylate with up to its own weight of a monoethylenically unsaturated compound(s), in the presence of a stable aqueous dispersion containing 1 part of a rubbery copolymer obtained by polymerizing a mixture of butadiene with up to its own weight of methyl methacrylate. The rubbery copolymer may be obtained by polymerizing a mixture of 70-80% butadiene and 20-30% methyl methacrylate to at least 90% conversion, and preferably to completion. A bifunctional monomeric material, e.g. divinyl benzene or glycol dimethacrylate may be present in amount from 0.1 to 5%. The methyl methacrylate comonomers may be acrylonitrile, methacrylonitrile, methyl or ethyl acrylate and ethyl, propyl or butyl methacrylate, and the grafting may take place in the presence of organic peroxide or hydroperoxide catalysts or azo catalysts or modifiers such as aliphatic mercaptans, and organic polysulphides, the usual emulsifying agents, fillers, pigments and stabilizers. It is preferred to feed a previously prepared stable aqueous dispersion of the rubbery polymer and the monomer continuously into a reaction vessel and to remove the polymerized material continuously from the vessel at a point remote from the point of entry, the rate of flow of the dispersion being such as to allow a residence time of from 5-10 times the time for the polymerization to go to completion in the absence of continuously added fresh reactants. This rate of flow may be controlled so that the heat continuously liberated by the polymerizing material is absorbed by the dispersion fed in, thus maintaining the reaction temperature constant. The products may be shaped, or moulded into articles.