GB616315A - Improvements in or relating to the production of cellular products from plastic materials - Google Patents

Abstract

Cellular products are obtained by heating a composition comprising an intimate mixture of a thermoplastic polymeric material and a blowing agent comprising biuret, at a temperature between the decomposition temperature of the blowing agent and that of the plastic material. Specified polymeric materials are polyvinyl chloride, polyvinyl acetate, polyvinylidene chloride, polychlorbutadiene, polysulphide condensation products and copolymers of vinyl chloride with vinyl acetate, vinylidene chloride with vinyl chloride or acrylonitride, butadiene with styrene or acrylonitrile and of isobutylene with isoprene. The blowing agent may also comprise urea, the amount of which is preferably from 33 1/3 to 100 per cent by weight of the biuret, and the amount used of the biuret or of the mixture of biuret and urea is preferably from 4 to 15 per cent by weight of the plastic material. The mixture of plastic material and blowing agent may be formed into a shaped article which is a miniature of the required final product and expanded in a heated mould. Additional ingredients present in the plastic compositions may include fillers, plasticizers, stabilizers and curing agents, e.g. carbon black, whiting, magnesia, litharge, zinc oxide, dibutyl phthalate, hydrocarbon oils, stearic acid, phenyl b -naphthylamine, sulphur, tetramethyl thiuram monosulphide, benzothiazyl disulphide, zinc diethyl dithiocarbamate and mercapto-benzothiazole.ALSO:Cellular products are obtained by heating a composition comprising an intimate admixture of natural, reclaimed or synthetic rubber or a thermo-plastic polymeric material such as a polymer or co-polymer of a vinyl or vinylidene compound, and a blowing agent comprising biuret, at a temperature between the decomposition temperature of the blowing agent and that of the plastic material. The blowing agent may also comprise urea, the amount of which is preferably from 33 1/3 to 100 per cent by weight of the biuret, and the amount used of the biuret or of the mixture of biuret and urea is preferably from 4 to 15 per cent by weight of the plastic material. The mixture of plastic material and blowing agent may be formed into a shaped article which is a miniature of the required final product and expanded in a heated mould. Cellular rubber products may be prepared by mechanically incorporating the blowing agent into a rubber composition containing vulcanizing ingredients at a temperature between 70 DEG and 250 DEG F. and thereafter heating at between 266 DEG and 350 DEG F.