CONDENSATION INJECTION MOLDING METHOD FOR PRODUCING BOTTLE PREFORM OF POLYETHYLENE TEREPHTHALATE AND/OR COPOLYESTER THEREOF AND PREFORM THAT CAN BE PRODUCED BY THE METHOD

摘要

PROBLEM TO BE SOLVED: To produce a bottle preform exceptionally low in acetaldehyde content from a melt of polyethylene terephthalate and/or its copolyester while avoiding a time-consuming process stage in conventional technique. SOLUTION: In a condensation injection molding method for producing a bottle preform from a melt of polyethylene terephthalate and/or its copolyester, inert gas is arbitrarily injected in a continuous or partial stream of a polyester melt with intrinsic viscosity resulting from polycondensation of 0.5-0.75 dl/g. Thereafter, a process for reducing the content of acetaldehyde of the melt after melting to below 10 ppm at 285-260 deg.C under reduced pressure in a condensation reactor is performed for a stagnation time of 60 min and, immediately thereafter, the melt is guided to an injection molding apparatus to be processed into a preform.