Process for producing molded article made of synthetic resin

A process for producing a molded article of a synthetic resin including a first construction portion having a sandwich structure comprised of a core and an outer layer covering the core, and a second construction portion integrally formed to the first construction portion and having a single-layer structure, said first construction portion assuming a conspicuous position while said second construction portion assuming a non-conspicuous position when said molded article is in use, said process comprising the steps of:

• a first step of injecting an outer layer forming material made of polypropylene including a weather resistant stabilizer, into a molding cavity through a gate in a metal mold;
• a second step of injecting a core forming material made of polypropylene, to allow said core forming material to flow into said outer layer forming material existing in said gate and said cavity and to allow said outer layer and core forming materials to flow into said cavity, therein advancing the formation of said first construction portion;
• a third step of allowing a front portion of said core forming material in a flowing direction to break through a front portion of said outer layer forming material in the flowing direction and allowing said core forming material to flow into said cavity ahead of the outer layer material, therein advancing the formation of said second construction portion having the single-layer structure formed from said core forming material under advancement of the formation of said first construction portion having the sandwich structure;
• and
• a fourth step of pushing said outer layer and core forming materials of a double structure existing within said gate into said cavity by said outer layer material, therein completing the formation of said first and second construction portions.