Method of forming blown polyethylene terephthalate containers

Claim 2

In a method of forming a blown hollow shape of poly(ethylene terephthalate) having an exterior opaque embossed surface design, the steps of: forming a blowable preform of poly(ethylene terephthalate) having an exterior embossed surface design defined by adjacent thick and thin wall portions destined to form the embossed design in the blown container; thermally conditioning the preform to a temperature in a range where the material is susceptible to strain hardening, and at the same time heating only the raised design portions to a higher temperature at which said raised portions of the preform crystallize and thus becomes opaque; enclosing the blowable preform within a blow mold cavity having a smooth wall portion; introducing blow fluid under pressure into the interior of the preform and thereby (1) expanding the preform outwardly to conform to said cavity, including contacting both the thick and thin wall portions with said blow mold cavity smooth wall portion, (2) strain hardening the preform, and (3), proportionately expanding said thick and thin wall portions; and thereafter venting fluid under pressure from the interior of said blown shape to allow removal from the mold of a transparent, hollow blown shape having said exterior opaque embossed surface design.

Claim 3

The method as defined in claim 1, wherein (a) the preform is formed of poly(ethylene terephthalate) having an inherent viscosity within the range from 0.5 to 1.1 (b) the blow fluid is injected into the preform at a pressure of between about 100 and about 600 psi, and (c) the preform is at a temperature during the expansion step of between about 75 degrees C. and about 110 degrees C.

Claim 6

The method as defined in claim 3, wherein the expanding step includes mechanically stretching the parison along its longitudinal axis and radially expanding the preform by introducing fluid under pressure into its interior.

Claim 7

In a method of forming a plastic container having an embossed exterior surface design on a blown body portion surmounted by a neck, the steps of: providing a blowable poly(ethylene terephthalate) preform having a profiled exterior embossed surface design defined by exterior surface embossments forming preform wall sections which are thicker than the remaining preform wall sections, closing the sections of a blow mold around the preform at a temperature within the range from about 75 degrees C. to about 110 degrees C. where the material is susceptible to strain hardening, the mold section including respective neck defining portions which are closed into engagement with a portion of the preform to form the container neck; in an essentially single operation, injecting blow fluid at a pressure of between about 100 psi and about 600 psi into the interior of the preform, expanding the preform outwardly to conform to said cavity, thus strain hardening the poly(ethylene terephthalate) material and stretching the thicker wall sections of the preform essentially proportionately to the remaining wall sections of the preform, the profiled preform embossed surface region being expanded against an essentially smooth mold wall surface on the mold sections, venting the fluid under pressure from the interior of the blown container to provide the blown container with said embossed surface decoration on the exterior of the blown container, and thereafter opening the mold sections to expose the blown container.

Claim 8

In a method of forming a plastic container having an embossed exterior surface design on a blown body portion surmounted by a neck, the steps of: providing a blowable poly(ethylene terephthalate) preform having a profiled exterior embossed surface design defined by exterior surface embossments forming preform wall sections which are thicker than the remaining preform wall sections, closing the sections of a blow mold around the preform at a temperature within the range from about 75 degrees C. to about 110 degrees C. where the material is susceptible to strain hardening, the mold section including respective neck defining portions which are closed into engagement with a portion of the preform to form the container neck; in an essentially single operation, injecting blow fluid at a pressure of between about 100 psi and about 600 psi into the interior of the preform, expanding the preform outwardly to conform to said cavity, thus strain hardening the poly(ethylene terephthalate) material and stretching the thicker wall sections of the preform essentially proportionately to the remaining wall sections of the preform, the profiled preform embossed surface region being expanded against an essentially smooth mold wall surface on the mold sections, venting the fluid under pressure from the interior of the blown container to provide the blown container with said embossed surface decoration on the exterior of the blown container, and thereafter opening the mold sections to expose the blown container.