GB1073456A - Polymerisation process - Google Patents

Abstract

An ethylenically unsaturated monomer is polymerized in an aqueous medium in the presence of a catalyst by a process in which a dispersion of one or more monomer- and water-insoluble solid additives in a water-immiscible organic liquid selected from chlorinated paraffins, glyceryl monostearate, epoxidized soya bean oil, dioctyl phthalate and dinonyl phthalate is added to the aqueous medium before or during polymerization. A list of monomers is given, those preferred being vinyl chloride or methyl methacrylate, or a mixture of the former with up to 50% of another monomer. The additive is, e.g. TiO2, MgO, carbon black or a stabilizer such as tribasic lead sulphate. The additive particles may be coated, e.g. with calcium stearate or stearic acid. Polymerization is carried out in emulsion or suspension using peroxy or azo catalysts and suitable emulsifying or granulating agents. In the examples a dispersion of tribasic lead sulphate in a mixture of dioctyl and dinonyl phthalates is added to an aqueous medium containing polyvinyl alcohol, azodiisobutyronitrile, cetyl alcohol and stearyl alcohol, prior to addition of vinyl chloride and polymerization thereof. In Example 2 a dispersion of carbon black, TiO2, ultramarine blue and ultramarine violet in chlorinated paraffins is added along with the vinyl chloride. The polymers produced are extruded to form pipes.