INJECTION MOLDED PREFORM, METHOD OF TREATING SAME AND CONTAINER FORMED THEREFROM

摘要

A polyester preform which is injection molded preferably of PET and wherein the preform is provided with a molded neck finish or neck portion including threads which are molded to a high tolerance and wherein the neck finish may receive a closure cap of the type having a tamper indicating band which engages over a retaining bead also molded to a high tolerance as part of the neck finish. In order to maintain the container which is blow molded from the preform in axial alignment with the neck finish and thus eliminate the perpendicularity problem, a ring of the preform immediately below the flange which functions as the capping ring, is heated to a high temperature and crystallized. In a like manner, the end sealing surface is also heated to a high temperature and crystallized. The remainder of the neck finish remains in its amorphous state without disturbing the configuration of either the threads or the retaining bead. This combination of crystallized portions with the remainder of the neck finish remaining amorphous assures a high quality connection between a closure cap, whether the closure cap is formed of plastic or metal, while providing the end sealing surface with a hard tough finish resisting deformation and at the same time reducing the closure cap removal torque.