Patent ID: 6136260
Filing Date: 2000-10-24
Classification: B29B,B29C,B29K

Abstract:
A process for injection molding a preform of a polyester resin comprising the steps of compressing and melting a molding material which is a polyester resin composed of a blend of polyethylene terephthalate and polyethylene naphthalate by rotation of a screw within a heating cylinder, and injecting the molding material directly from the cylinder into a mold to mold a desired preform, whereina plastication zone is formed between a compression zone of the screw and a metering zone at the end of the screw and is divided into a melting section, a melting relaxation section, a kneading section and a kneading relaxation section; the melting, relaxation, kneading and relaxation of the molding material are performed in said respective sections of the plastication zone to promote the melting of an unmolten material remaining in the molten material and uniformly knead the molten material so that the unmolten material is molten and kneaded before the molten material reaches the metering zone.