Method of forming container with high-crystallinity sidewall and low-crystallinity base
AssigneeContinental PET Technologies, Inc.
InventorsWayne N. Collette, Suppayan M. Krishnakumar, Chi C. 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 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 at least radially 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 at least radially 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 method of making a container having a sidewall and base comprising the steps of:
- providing a substantially amorphous polyethylene terephthalate preform having a sidewall-forming section and a base-forming section, wherein the sidewall-forming section is within the orientation temperature range of polyethylene terephthalate;
- expanding the sidewall-forming section axially and radially at a planar stretch ratio of about 10-16:1 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, expanding the base-forming section at least radially 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, the contracted intermediate sidewall being stretched at a planar stretch ratio of about 7-15:1 (sidewall:sidewall-forming section) to form the sidewall having a wall thickness of about 0.5 to about 0.7 mm and a percent crystallinity of at least about 20%, and the base having a percent crystallinity of no greater than about 10%.
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, an outer base-forming section, and a central base-forming section, and wherein the sidewall- and outer base-forming sections are within the orientation temperature range of the polyester;
- expanding the sidewall- and outer base-forming sections at least radially to form an intermediate article having an expanded intermediate sidewall and outer base with dimensions substantially equal to or greater than the dimensions of the final container sidewall and outer base, while the central base-forming section remains substantially unchanged in dimensions;
- heating the expanded intermediate sidewall and outer base to crystalize and contract the same below the dimensions of the final container sidewall and outer base, while the central base-forming section remains substantially amorphous and substantially unchanged in dimensions;
- and
- expanding the contracted intermediate sidewall and outer base while in the orientation temperature range to the final dimensions of the container sidewall and outer base, and expanding the central base-forming portion to the final dimensions of the central base.
Dependencies are inferred from the claim text.