PROCESS FOR THE PRODUCTION OF EXPANDED PARTICLES OF A POLYPROPYLENE RESIN

摘要

A process for the production of expanded particles, which comprises providing an aqueous dispersion containing expandable particles which are formed of a polypropylene resin and which contain a blowing agent and an expansion aid and maintained at a temperature higher than the softening point of the resin and under a pressurized condition, and subjecting the dispersion to a lower pressure so that the expandable particles are expanded. The expansion aid is organic or inorganic solids having a particle size of 0.1 to 150 .mu.m and a melting point higher than the temperature at which the expansion of the expandable particles is performed and serves to improve the expansion ratio.