Injection stretch blow molding method

Abstract

A required preform 2 is molded by rapidly cooling molten resin which has been injected and filled into an injection mold. The preform 2 is held by its neck portion with a neck mold and is mold-released in a high temperature state. A bottle 1 having a thin body portion 1a is molded by stretch blowing laterally and longitudinally within a blow mold. Among the thickness 2a and length 2b of a stretched portion of the preform 2 which are set according to the volume and weight and body portion thickness 1a of the bottle 1, the thickness 2a is set to be thinner than the usually set thickness. The length 2b is set to be long inversely proportional to the thickness setting. The preform 2 is mold-released at a higher temperature than usual and is stretch-blow molded before its outer surface temperature reaches its peak. By reducing the thickness of the stretched portion of the preform and, on the contrary, increasing the length thereof, it is possible to stretch blow mold a hollow molded product with a usual geometry in which the body portion thickness is below 0.2 mm, even in a hot parison method which carries out mold-release at high temperature.

Dependencies are inferred from the claim text.