Process for producing expanded polyolefin resin particles and expanded polyolefin resin particles

Abstract

Provided is a process for producing expanded polyolefin resin particles whose cells are not made nonuniform or extremely smaller as seen in conventional expanded particles, whose cell diameter and expansion ratio can be easily controlled independently, and which, when subjected to in-mold expansion molding, give in-mold expanded molded products satisfactory in fusibility and excellent in surface properties. The process is a process for producing expanded polyolefin resin particles by: dispersing polyolefin resin particles together with an aqueous dispersion medium into a closed vessel; heating the polyolefin resin particles up to or above a softening temperature of the polyolefin resin particles; and releasing the polyolefin resin particles into a zone whose pressure is lower than an internal pressure of the closed vessel, with use as a foaming agent of water serving as the dispersion medium, the polyolefin resin particles being composed of a polyolefin resin composition including: polyolefin resin; a substance selected from among polyethylene glycol, polyvalent alcohol having a carbon number of not less than 3 to not more than 6, and a water-absorbing substance having no function of forming foaming nuclei; and a foam nucleating agent.