CROSSLINKED POLYOLEFIN RESIN FOAM

PURPOSE:To obtain the title foam having ultrafine closed cells and a definite cell shape at an arbitrary cross-section by impregnating a preformed polyolefin resin with an organic volatile blowing agent at a specified temperature, cooling the resin and expanding the resin by heating. CONSTITUTION:A polyolefin resin is optionally mixed with a crosslinking agent, and the obtained mixture is molded and crosslinked to obtain a molded polyolefin resin. 100 pts.wt. said resin is impregnated with 0.5-50 pts.wt. organic volatile blowing agent (e.g. dichlorodifluoromethane) at a temperature from the softening point of the resin to its melting temperature to obtain a microscopically heterogeneous expandable composition. This composition is expanded by heating to obtain the title foam having a definite cell shape at an arbitrary cross-section and containing 100/cm or above closed cells.