Method for manufacturing a multi-layer plastic product

A method for manufacturing a multi-layer thermoplastic product using a mold comprising a plurality of mold segments, said mold defining a mold cavity having a desired shape when assembled and including a plurality of supply ports in communication with said mold cavity, comprising the steps of:

• (1) assembling said plurality of mold segments to thereby define said mold cavity with a blow-molded hollow plastic core located in position inside said mold cavity, said core being held in position away from a surface of said mold defining said mold cavity excepting at a plurality of core end portions, each of which portions being in engagement with a corresponding, predetermined portion of said mold;
• (2) supplying a molten thermoplastic material under pressure into an open gap between said core and the surface of said mold defining said mold cavity through said plurality of supply ports;
• (3) setting a pressure of said molten thermoplastic material supplied into said gap at a predetermined shaping pressure, which is approximately equal to or less than 200 kg/cm.sup.2, to form an outer layer having a desired shape on said core to thereby form a multi-layer plastic product;
• and during step (2), regulating an amount of said molten thermoplastic material supplied by any one of said plurality of supply ports such that a surface area of a portion of said outer layer formed by said molten thermoplastic material and supplied by a single port does not exceed approximately 400 cm.sup.2.