Patent ID: 7867416

Claim:
A foam injection molding method comprising: injecting a thermoplastic elastomer composition for core-back system foam injection molding into a cavity space in a metal mold, and opening said metal mold at a mold opening rate of 0.05 to 0.4 mm/sec thereby expanding said cavity space to foam said thermoplastic elastomer composition and forming an injection foaming product having a skin layer and a foamed layer; wherein the thermoplastic elastomer composition for core-back system foam injection molding comprises a thermoplastic elastomer which includes an ethylene•α olefin-based copolymer and a crystalline polyethylene-based resin, wherein said crystalline polyethylene-based resin constitutes a three-dimensional network structure in a matrix formed by said ethylene•α-olefin-based copolymer, a blowing agent and a nucleating agent, and wherein said thermoplastic elastomer has a melt flow rate of 5 g/10 min or more at a temperature of 230° C. and a load of 10 kg, and a melt tension of 3.0 gf or more at a temperature of 210° C. and a pulling rate of 2 m/min.