Appartus for blow mold annealing and heat treating thermoplastic articles

摘要

An apparatus for annealing and heat treating biaxially oriented articles is disclosed, particularly blow molded articles prepared from preforms which are simultaneously annealed using warm fluid in a first segmented mold. The blown article is transferred to a second, larger mold where the article is pressurized against the mold to form the final container design and to heat treat at least a portion of the bottle wall to improve crystallinity and strength. Portions of the mold, used to form and anneal the articles, are temperature controlled at various temperatures by passing warm water through conduits in the neck-shoulder portion and body portion of the mold and cold water through the bottom and shoulder portion of the mold to bring the temperature of the article wall to about 65° C. to 95° C. for PET bottles. The second mold is up to 10% larger in volume and preferably employs resistance heating to heat treat the side wall to 110° C. to 220° C. and the neck- shoulder wall to less than the side wall but within the 110. degree. C. to 220° C. temperature range for up to 30 seconds. The article is next cooled by injecting an evaporatable fluid like water which evaporates and immediately cools the article which is then removed from the mold. The heat treatment increases the article's structural strength, does not affect biaxial crystallinity reduces gas permeability, retains transparency and allows for multiple reuse of the article including hot washing thereof.