Patent ID: 8084510

Claim:
Expandable polystyrenic resin particles comprising a volatile blowing agent in polystyrenic resin particles obtained by forming a polystyrenic resin in polyolefin resin particles by impregnating and polymerizing a styrenic monomer; wherein, 140 to 600 parts by weight of the styrenic monomer are impregnated and polymerized to 100 parts by weight of the polyolefin resin particles, wherein an average thickness of the surface layer of the particles observed in scanning electron micrographs obtained by immersing sections cut into halves through the center from the surface of the resin particles in tetrahydrofuran followed by extracting the polystyrenic resin component and capturing cross-sections of said sections is 15 to 150 μm, and the volatile blowing agent is contained at 5.5 to 13.0% by weight of the expandable polystyrenic resin particles.