Method for injection molding of hollow shaped bodies from thermoplastic resins

A method for making a hollow shaped body from a thermoplastic resin by injection molding, which method comprises injecting an amount of molten resin sufficient for the preparation of the hollow shaped body from an injection nozzle into a mold through an injection aperture in said mold, injecting gas under pressure through said injection nozzle and aperture to expand and distribute the molten resin over the interior surfaces of the mold, whereby said hollow shaped body is formed within said mold with a gas entry opening in said hollow shaped body, cooling the hollow shaped resin body so formed to a temperature beneath the softening point of the resin, separating said mold and said injection nozzle after said resin has cooled beneath its softening point, whereby the interior of said hollow shaped body is opened to the atmosphere through said injection aperture and gas-entry opening to equalize the pressure within said body with ambient pressure, and then opening said mold to remove said hollow shaped body.