METHOD OF FORMING CONTAINER WITH HIGH-CRYSTALLINITY SIDEWALLAND LOW-CRYSTALLINITY BASE

摘要

A method of making a polyester container having an enhanced level of crystallinity in the sidewall (18) while maintaining a low level of crystalli nity in a thickened base portion (26). The container is particularly useful as a refillable container which can withstand higher caustic wash temperatures and exhibits reduced flavor carryover, or as a hot-fill container. According to the method, a sidewall-forming section of a preform is initially expanded, heated to contract and crystallize the same, and then reexpanded; a baseforming portion of the preform is shielded from the heat treatment and is expanded either before or after the heat treatment step.