Method of making a molded plastic container

Abstract

A polyethylene terephthalate (PET) preform (11) having a capped cylindrical body (13), a threaded top and a collared neck (19) is preheated to soften the PET. The preform (11) is placed in a split mold (26) whose walls (27,29) are heated to a temperature between 150.degree. C. and 177.degree. C. A stretch rod (35) is inserted through the top of the preform (11), and stretches the preform (11) axially until the preform (11) is the length of the final product (49). The preform (11) is expanded using compressed ambient air, and is molded against the walls (27,29) of the mold (26). The air is vented, and dry nitrogen at a temperature below -50.degree. C. is injected into the molded preform (47) to purge and cool the molded preform (47) while maintaining pressure of at least 520 kPag. The molded preform (47) is held against the mold (26) for a predetermined time, during which the outer and inner surfaces of the molded preform (11) are annealed, and the molded preform (47) transforms into the final product (49). The nitrogen supply is shut off and the final product (49) is released from the mold (26).

Dependencies are inferred from the claim text.