GB722903A - Improved process for making expanded or cellular bodies of the closed cell type - Google Patents

Abstract

Closed-cell gas-expanded thermoplastic synthetic resin articles are made by heating a thermoplastic resin body and a plasticizer to above 120 DEG C., cooling to obtain an intermediate body having increased elastic limit and tensile strength, subjecting this to gas pressure and heating to expand the body. Specified resins are polyvinyl chloride, vinyl chloride and vinylidene chloride copolymer, polyvinyl alcohol, polyvinyl acetate and butyrate, polyvinyl formal and butyral, polyvinylidene chloride, polystyrene, polydichlorostyrene, polyalphamethylstyrene, polymethylacrylate, polyethylacrylate and polymethylmethacrylate and their mixtures. Specified plasticizers are dimethyl, dibutyl and dioctyl phthalates, tricresyl phosphate, dihydropropylene sebacate, sorbitol and dibenzyl esters. A volatile solvent such as acetone, ethyl acetate and methyl ethyl ketone may also be present in amount from 20 to 100 per cent of the resin. The intermediate body may be formed by heating the resin and plasticizer to above 120 DEG C. and rolling out to the desired thickness. The intermediate body in the form of a thin sheet may be subjected to a gas pressure of at least 400 atms., or several sheets of less than 1 mm. thickness are stacked together and submitted to a gas-pressure of 200-400 atmospheres, preferably after powdering, to prevent sticking, the gas pressure then being lowered to one-third of the total pressure originally used, so welding together the thin sheets of gas-included resin bodies.