Process for preparing suspension chlorinated crosslinked polyethylene foam

Claim 1

A process for preparing a crosslinked, soft, flexible, closed-cell foam from chlorinated high density polyethylene said foam having a cell size of from about 0.05 to about 2 mm, a density of from about 2.5 to about 50 pcf, a tensile strength of from about 30 to about 600 psi, and a tensile elongation of from about 200 to about 500 percent, said process comprising (a) preparing a foamable mixture by mixing a suspension chlorinated high density polyethylene containing from 25 to about 48 percent of chemically combined chlorine and having a flexural modulus at 25° C. of less than about 15,000 psi as determined by ASTM Test No. 790, Method 1, Procedure A, with a thermally decomposable chemical foaming agent, (b) melt molding said foamable mixture at a temperature below that of the decomposition temperature of said chemical foaming agent, into a molded foamable article having a thickness of between about 0.025" to about 0.4", (c) subjecting said molded foamable article while maintained at a temperature below the decomposition temperature of said foaming agent to an ionizing radiation of about 2.5 to about 6 mrad, for a period of time sufficient to impart crosslinking sufficient to enable said molded foamable article to retain its shape, and (d) contacting the crosslinked molded foamable article, in a substantially oxygen-free environment with a heat transfer medium maintained at a temperature between about 150° C. and about 350° C. for a period of time sufficient to form the desired flexible product.