Method of making partially crystalline biaxially oriented hollow plastic

Abstract

A method for making a partially crystalline, biaxially oriented heat set hollow polyethylene terephthalate free standing container from a hollow parison having an open end and a closed end including engaging the open end of a plastic parison which is at a temperature within its molecular orientation temperature range, positioning a mold base in axial alignment with said engaged hot parison, enclosing a hot mold about the mold base, the mold being at heat setting temperature and the mold base being at a temperature preferably significantly lower than the mold, expanding the plastic parison within the hot mold and mold base by internal pressurization to induce biaxial orientation of the plastic parison and force the plastic parison into intimate contact and conformance with the hot mold and to maintain contact by such internal pressurization between the mold and mold base and the biaxially oriented container for a time sufficient to induce partial crystallization in the side wall and base of the biaxially oriented container, reducing the internal pressure in the blown container, opening the hot mold while maintaining engagement of the open end of the blown hollow container, disengaging the hot mold base from the blown container, maintaining a lower internal pressurization of the container to prevent significant shrinkage, and engaging a cold mold base with the base of the container, and enclosing a cold mold about the container and the mold base to cool the container while maintaining engagement of the open end with the container and maintaining pressure in the container at least sufficient to prevent shrinkage, and opening the cold mold and releasing the container.