POST BULK POLYMERIZATION PROCESS FOR POLYVINYL HALIDE AND COMPOSITION THEREOF

摘要

An improved polyvinyl halide or a polyvinyl halide copolymer containing up to 50 percent of a comonomer can be obtained by post polymerizing in a single stage or two-stage bulk process in contact with a base polymer, the same or different monomer as the monomer used to form the base polymer. Compositions produced by the process of the invention are useful in making films, coated fabrics and molded objects. The liquid phase post polymerization process of the invention is applicable to base polymers in powder form prepared by emulsion, suspension and bulk polymerization processes. The base polymer can be present in a polymerization mixture in which only a partial amount of monomer has been converted to base polymer such as in a two-stage polymerization process or the base polymer can be used in dry, solid form. Polymers of the invention have improved bulk density and reduced plasticizer uptake and can be used to prepare fabric coatings. Copolymers prepared by the novel post-polymerization process of the invention which show increased impact strength in addition to improved bulk density and reduced plasticizer uptake are useful in the preparation of molding compounds. In the bulk polymerization process of the invention, the addition of the same monomer or monomers or a different monomer or monomers subsequent to the partial conversion by a two-stage bulk process of polymerization of the vinyl halide monomer or monomers or vinyl halide monomer and comonomer, results in higher yield than can be obtained in the same reaction vessel as compred with a usual two-stage bulk polymerization process. In the two-stage bulk polymerization process of the invention, the use of small amounts of a hydrocarbon rubber dissolved or dispersed in the monomer effectively prevents reactor fouling during polymerization.