PRE-EXPANDED POLYPROPYLENE RESIN PARTICLE AND IN-MOLD FOAMED MOLDING

摘要

PROBLEM TO BE SOLVED: To provide pre-expanded particles which can be fused together by heating with a conventional die and a molding machine to give an in-mold expanded molding showing high compressive strength as well as lightweight properties. SOLUTION: The pre-expanded polypropylene resin particles are made from a base resin being an ethylene/propylene random copolymer having a melting point of 1490-157 deg.C, an MI of 1-20 g/10 min and a half-crystallization temperature of 45 sec or below, an ethylene/propylene/1-butene random copolymer having a melting point of 149-157 deg.C, an MI of 1-20 g/10 min and a half-crystallization time of 55 sec or below or a propylene/1-butene random copolymer having a melting point of 149-157 deg.C, an MI of 1-20 g/10 min and a half-crystallization time of 60 sec or below and satisfies the formula: 0.25<=β/(α+β)<=0.60 (whereinαis the melting heat of the endothermic peak attributable to the crystalline state inherent in the base resin in a DSC curve as observed when the sample is heated from 40 deg.C to 200 deg.C at a rate of temperature increase of 10 deg.C/min with a differential scanning calorimeter, andβis the melting heat of the endothermic peak appearing at a temperature higher than that of the former peak.