INJECTION MOLDING AND STRETCH BLOW MOLDING METHOD FOR PREFORM OF POLYESTER RESIN

摘要

PROBLEM TO BE SOLVED: To prevent the milk-whitening of a molded product generated when a polyester resin composed of a blend of PET(polyethylene terephthalate) and PEN(polyethylene naphthalate) is used as a molding material and the generation of unmelted granules. SOLUTION: A polyester resin composed of a blend of PET and PEN is used as a molding material and this molding material is compressed by the rotation of the screw in a heating cylinder to be melted and the molten material is injected and filled into a mold to mold a desired preform. In this case, a molding material plasticizing zone 13 is set between the compression zone 12 of an injection screw and the metering zone 14 provided to the leading end of the screw. The molding material is melted, relaxed, kneaded and relaxed in the plasticizing zone 13 and the unmelted material is melted and removed until the molten material reaches the metering zone 14.