Purification, impregnation and foaming of polymer particles.

摘要

Foamed polymer moldings which have reduced levels of low molecular weight materials and which may also be substantially free of residual blowing agent or halogenated hydrocarbons are obtained by continuously extracting polymer particles in a pressure vessel with a fluid at liquid or supercritical conditions to remove low molecular weight compounds while impregnating said particles with the extracting fluid; pre-expanding the purified, impregnated polymer particles recovered from the pressure vessel and molding the pre-expanded particles. In a preferred embodiment, the pre-expanded particles are reimpregnated with a pneumatogen such as solid CO2, air or nitrogen, prior to molding.