Method of Making a Molded Plastic Container

• Main Author: RUPPMAN, KURT H., SR
• Format: Patent
• Language: English
• Published: 03.10.1996
• Edition: 6
• Subjects: AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING; PERFORMING OPERATIONS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDEDFOR; SHAPING OR JOINING OF PLASTICS; TRANSPORTING; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL

A polyethylene terephthalate (PET) preform (11) having a capped cylindrical body (13), a threaded top and collared neck (19) is preheated to soften the PET. The preform (11) is placed in a split mold (26) whose walls are heated to a temperature between 150 DEG C and 177 DEG C. A stretch rod (35), inserted through the top of the preform (11), stretches the preform (11) axially until the preform is the length of the final product (49). The preform (11) is expanded using compressed ambient air, and is molded against the walls (27, 29) of the mold (26). The air is vented, and dry nitrogen at a temperature below -50 DEG C is injected into the molded preform (47) to purge and cool the molded preform (47) while maintaining pressure of at least 520 kPag. The molded preform (47) is held against the mold (36) to anneal the inner and outer surfaces of the molded preform (47). The nitrogen supply is shut off and the final product (49) is released from the mold (26).