Patent ID: 7691306

Claim:
A manufacturing method of a transparent polypropylene based sheet that uses a resin composition containing: 70 to 99.8 mass % of a polypropylene resin (a) having an isotactic pentad fraction of 0.85 to 0.99 and a melt flow rate (MFR) of 0.1 to 30 g/10 min; and 30 to 0.02 mass % of a metallocene-type ethylene-α-olefin copolymer (b) that is produced using a metallocene catalyst and having a density of 880 to 920 kg/m 3 and a melt flow rate (MFR) of 1 to 30 g/10 min, the method comprising: a melt extrusion step for melt-extruding the resin composition into a sheet-like shape; a cooling step for quenching the melt-extruded sheet-like resin composition to obtain a sheet-like article; and a heat treatment step for heat-treating the quenched sheet-like article at a heat treatment temperature of 100 to 220° C.