Multi-layer expansion-molded article of polypropylene resin, production process thereof, and container, shock-absorbing material for automobile and automotive member formed of the multi-layer expansion-molded article of polypropylene resin

摘要

Disclosed herein is a multi-layer expansion-molded article (1) of a polypropylene resin, which is obtained by molding a multi-layer parison comprising a foamed resin layer (12) and a resin layer (13) provided on the outer side of the foamed resin layer (12) in a mold in such manner that at least part of the opposed inner surfaces of foamed resin layer in the parison are fusion-bonded to each other, and has a polypropylene resin layer (13) on the surface of a foamed polypropylene resin layer (12), wherein a melt tension, MT (gf) and a melt flow rate, MFR (g/10 min) obtained by measurement to a polypropylene resin forming the foamed resin layer (12) in the expansion-molded article satisfy the following relationship (1), and a melt tension, MT (gf) and a melt flow rate, MFR (g/10 min) obtained by measurement to a polypropylene resin forming the resin layer (13) on the surface of the foamed resin layer (12) satisfy the following relationship (2) when the melt flow rate, MFR is at least 0.3 (g/10 min), or the melt tension, MT is at least 10 (gf) when the melt flow rate, MFR is not lower than 0.2 (g/10 min), but lower than 0.3 (g/10 min): DFG DF NUM="(1)"log MT -0.74 log MFR + 0.66 /DF DF NUM="(2)"log MT -1.02 log MFR + 0.47 /DF/DFG