Method of forming container with high-crystallinity sidewall and low-crystallinity base
AssigneeGraham Packaging PET Technologies Inc.
InventorsWayne N. Collette, Suppayan M. Krishnakumar, Chi Chung Lin
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Abstract
A method of making a polyester container having an enhanced level of crystallinity in the sidewall while maintaining a low level of crystallinity in a thickened base portion. 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 than reexpanded; a base-forming portion of the preform is shielded from the heat treatment and is expanded either before or after the heat treatment step.
Claims12
A method of making a container having a sidewall and base, the method including:
- a first expansion step in which a substantially amorphous polyester preform is at least partially expanded into an intermediate article, the preform including a base-forming section which is not expanded during the first expansion step,
- a heating step in which the intermediate article is at least partially heated to contract and crystallize the intermediate article, the base-forming section remaining substantially unchanged in crystallinity during the heating step, and
- a second expansion step in which the contracted intermediate article is re-expanded to form the container, the base-forming section being expanded without significant crystallinity change during the second expansion step.
Dependencies are inferred from the claim text.