GB1290005A - - Google Patents

Abstract

1290005 Cellular vinylaromatic polymers MONSANTO CHEMICALS Ltd 16 Nov 1970 [4 Dec 1969] 59291/69 Heading C3C A cellular vinylaromatic polymer, preferably in the form of a board, is made by extruding into air at normal atmospheric pressure and temperature, the polymer in a heated flowable condition in admixture with a blowing agent consisting of a mixture of x molar proportions of methyl chloride, vinyl chloride or mixture thereof, y molar proportions of methylene chloride, vinylidene chloride or mixture thereof, and z molar proportions of dichlorodifluoromethane, wherein x=from 30 to 55, y=from 10 to 25, z=from 30 to 50, and x+y+z=100. The polymer may be a homopolymer of styrene, chlorostyrene, vinyl toluene or alphamethylstyrene or a copolymeric mix of these monomers, or a copolymer of a vinylaromatic compound with acrylonitrile, vinyl chloride, vinyl acetate, methyl acrylate, methylmethacrylate, or ethyl acrylate. Toughened polystyrenes, e.g. modified before or after polymerization with natural or synthetic rubbers may also be used. The preferred blowing agent is a mixture of methyl chloride, methylene dichloride and dichlorodifluoromethane. The foamable resin may also contain a flame retardant agent, e.g. tribromophenyl allyl ether, an anti-oxidant and a nucleating agent such as talc, alumina, zinc stearate, and sodium bicarbonate in conjunction with, if desired, tartaric or citric acid. The extruder employed is preferably of the type described in Specification 1,195,279.