PRE-EXPANDED POLYPROPYLENE RESIN BEADS AND PROCESS FOR PRODUCING MOLDED OBJECT THEREFROM BY IN-MOLD FOAMING

摘要

Pre-expanded polypropylene resin beads which have an expansibility as represented by the following equation of 1.0 to 1.8: Expansibility = Äexpansion ratio of the beads after steam heatingÜ/Äexpansion ratio of the beads before steam heatingÜ (wherein the "expansion ratio of the beads after steam heating" is the value of expansion ratio obtained through heating with steam at the melting peak temperature of the base resin determined by examining the beads with a differential scanning calorimeter). The beads can be molded by various in-mold foaming techniques in a reduced cooling time. Thus, a molded object can be stably obtained from the pre-expanded beads which is satisfactory in fusion bonding between the beads and in surface appearance and has no difference in density between the surface and inner parts thereof.