PRODUCTION OF BRIGHTENING MATERIAL-CONTAINING POLYPROPYLENE-BASED RESIN MOLDED PRODUCT

PROBLEM TO BE SOLVED: To produce a brightening polypropylene-based resin molded product having a high-class metallic appearance and utilizable as automotive parts by carrying out the molding of a brightening material-containing polypropylene- based resin composition with a metal mold having a heat insulating layer provided on the inner surface of a cavity in the metal mold for injection molding. SOLUTION: A resin composition prepared by compounding a polypropylene- based resin (e.g. a random or a block copolymer of ethylene and propylene) with a brightening material such as a metal flake or a pearlescent mica is molded by using a metal mold having a heat insulating layer provided on the inner surface thereof to come into contact with the filled resin to produce a molded product improved in brightness without making a weld line, a flow mark, etc., conspicuous. A heat-resistant plastic, a plastic composite material, a ceramic material, a glass, an enamel and the like are cited as a material constituting the heat insulating layer and the heat conductivity is preferably 1×10-4 to 30×10-4 cal/cm.s. deg.C. The resultant molded product can be utilized as parts of exterior or interior automotive trims, parts of automotive lamp housings, automotive parts around engines or the like.