Process for production of a plastic bottle

Claim 1

A process for producing a plastic bottle wherein all portions except for the neck have substantially uniform thickness, a density of at least 1.379, and the internal volume increase rate is less than 3.4% when the bottle filled with a liquid at 20° C. containing a two gas volume of CO 2 is immersed in 75° C. water for 30 minutes, which comprises blow stretching a parison of polyethylene terephthalate in a first mold to form an intermediate product, transferring the intermediate product to a second mold while the intermediate product which has undergone shrinkage is still soft, and restretching the intermediate product in the second mold and which process is characterized by the following steps: (A) heating the parison to a temperature 20°-30° C. higher than the glass transition temperature; (B) simultaneously or subsequently to step (A) adjusting the portions of the parison corresponding to the shoulder and bottom portions of the bottle to a stretching temperature higher by from 2° to 5° C. than the temperature of the portion corresponding to the body portion of the bottle at the time of heating the parison in step (A); (C) forming the intermediate product by blow stretching the temperature adjusted parison from 10 to 14 times as a product of the stretching rates in axial and radial directions in the first mold heated to a temperature of at least 150° C. and at least 20° C. below the melting point of the parison and subjecting the intermediate product to heat treatment by maintaining it in intimate contact with the inner wall of the first mold for a predetermined period of time; (D) transferring the intermediate product to a second mold having an internal volume of from 75 to 95% relative to the internal volume of the first mold, and (E) restretching it in the second mold to obtain the bottle.