PET containers with enhanced thermal properties and process for making same

A process for forming a blow molded PET plastic containers on a blow molding machine, wherein the blow molded PET containers have enhanced thermal properties, the process comprising the steps of:

• at an injection mold station, injecting a molten PET resin into an injection mold cavity to form a preform;
• removing the preform while the preform is at a temperature of from about 75° C. to about 130° C.;
• conveying the preform to at least one conditioning station at a rate such that the temperature of the preform does not decrease more than 5° C.;
• conditioning the preform by selectively heating at least one portion of the preform selected from the group consisting of:
• neck forming portion, barrel forming portion, base forming portion, and heel forming portion, to define a conditioned preform;
• conveying the conditioned preform to a first blow mold station at a rate such that the temperature of the surface of the preform does not decrease more than 5° C.;
• inserting the conditioned preform into a first blow mold having walls that define a blow cavity that defines a shape of a finished article and a first volume, wherein the first mold has at least three temperature zones along an axis of the first mold all of which are above the glass transition temperature of PET;
• blowing the preform into a finished PET container by a stretch blow molding process comprising the steps of:
• i. inserting an elongated stretch blow rod into the conditioned preform to contact a bottom portion of the conditioned preform thereby providing a downward pressure to stretch the conditioned preform to a base portion of the first mold;
• ii. simultaneously injecting low pressure air into the conditioned preform at a pressure of from about 100 psi to about 200 psi to form a pre-blown preform;
• and
• iii. immediately after ii, injecting high pressure air at a pressure of from about 400 psi to 600 psi into the pre-blown preform to expand the pre-blown preform against the walls of the first mold to form an intermediate container;
• iv. holding the intermediate container in the mold for a time period of from about 2 seconds to about 20 seconds;
• v. releasing the intermediate container from the mold wherein the temperature of the finished container is from about 80° C. to about 125° C.;
• vi. conveying the intermediate container to a second mold having walls that define a blow cavity that defines a shape of a finished article and a second volume, wherein the second mold has at least three temperature zones along an axis of the second mold all of which are above the glass transition temperature of PET, and wherein the second volume is the same as the first volume;
• vii. inserting an elongated stretch blow rod into the intermediate container to contact a bottom portion of the intermediate container thereby providing a downward pressure to stretch the intermediate container to a base portion of the second mold and injecting high pressure air at a pressure of from about 400 psi to 600 psi into the intermediate container to expand the intermediate container against the walls of the second mold to form the finished container;
• viii. directing a cooling fluid to an inner surface of the finished container;
• ix. releasing the finished container from the second mold, wherein the finished container is at a temperature of from about 80° C. to about 170° C.;
• and
• x. allowing the finished container to cool to ambient temperature, wherein the process is performed on an integrated system wherein the blow molding machine has both the injection mold station and the blow mold station on one platform,
• wherein the preform is designed such that a density ratio of the finished container relative to the preform is in a range of from about 1.025 to about 1.049.