Method of forming container with high-crystallinity sidewall and low-crystallinity base
AssigneeContinental PET Technologies, Inc.
InventorsWayne N. Collette, Suppayan M. Krishnakumar, Chi Ching Lin
Life of this patent
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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.
Claims45
A method of making a container having a sidewall and base comprising the steps of:
- providing a substantially amorphous polyester preform having a sidewall-forming section and a base-forming section, wherein the sidewall-forming section is within the orientation temperature range of the polyester;
- expanding the sidewall-forming section to form an intermediate article having an expanded intermediate sidewall with dimensions substantially equal to or greater than the dimensions of the final container sidewall, while the base-forming section remains substantially unchanged in dimensions;
- heating the expanded intermediate sidewall to crystallize and contract the same below the dimensions of the final container sidewall, while the base-forming section remains substantially amorphous and substantially unchanged in dimensions;
- and
- expanding the contracted intermediate sidewall and base-forming section while in the orientation temperature range to the final dimensions of the container sidewall and base.
A method of making a container having a sidewall and base comprising the steps of:
- providing a substantially amorphous polyester preform body having a sidewall-forming section and a base-forming section, wherein the sidewall- and base-forming sections are within the orientation temperature range of the polyester;
- expanding the sidewall-forming section to form an intermediate article having an intermediate expanded sidewall with dimensions substantially equal to or greater than the dimensions of the final container sidewall, and expanding the base-forming section up to substantially the same dimensions as the final container base;
- heating the expanded intermediate sidewall to crystallize and contract the same below the dimensions of the final container sidewall, while the base substantially maintains its dimensions and percent crystallinity;
- and
- expanding the contracted intermediate sidewall while in the orientation temperature range to the final dimensions of the container sidewall, while the base substantially maintains its dimensions and percent crystallinity.
A container comprising a substantially transparent, biaxially-oriented, free-standing, blow-molded polyester body, the body having a sidewall with an upper tapered shoulder and a substantially cylindrical panel, and a base having a thickened base portion with a wall thickness at least about 3× greater than the thickness of the panel, the panel having an average crystallinity of at least about 25% and the thickened base portion having an average crystallinity of no greater than about 10%.
Dependencies are inferred from the claim text.