Process for the manufacture of pet containers designed to be filled with a hot liquid

Claim 1

A process for the manufacture of a substantially non-biaxially oriented polyethylene terephthalate (PET) container from a hollow amorphous PET preform comprising an open end and a closed end, the open end forming a neck section having dimensions already conformed to its final size and shape, said container having a volume shrinkage of not more than 1% when filled with a hot liquid which reaches or exceeds a temperature of 85° C., comprising: (a) rapidly heating in an infrared radiating oven only the body of said PET preform for less than one minute, exclusive of the neck section, to a temperature of from 120° C. to 140° C. at which subsequent longitudinal and transverse stretching cause substantially no stresses in the PET; (b) transferring said hot preform from step (a) which is at a temperature of 120° C. to 140° C. to a mold whose walls are at a temperature of from 70° C. to 120° C.; (c) longitudinally stretching the preform body while simultaneously transversely expanding it by blow-molding using a pressurized fluid so as to mold the preform body to the shape of the mold cavity, wherein the longitudinal stretching rate is less than 500 mm/sec so as to induce minimal stresses in the body during molding and, during said blow-molding, the body is prevented from cooling below its glass transition temperature Tg; (d) rapidly evacuating the pressurized fluid from the molded container of step (c) by arresting circulation of the pressurized fluid and by drawing off the pressurized fluid within the container until pressure reaches atmospheric pressure; and (e) removing said container from the mold.