초록 ▼

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 exhib

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.

대표청구항 ▼

1. 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 fi

1. 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. 2. The method of claim 1, wherein the preform includes a sidewall-forming section which is at least partially expanded in the first expansion step, and wherein the base-forming section has a wall-thickness substantially greater than that of the sidewall-forming section.3. The method of claim 1, wherein the base-forming section is substantially thicker than other sections of the preform so as to resist heating and crystallization during the heating step.4. The method of claim 1, wherein the base-forming section is shielded during the heating step.5. The method of claim 1, wherein the base-forming section is cooled during the heating step.6. The method of claim 1, wherein a contracting centering rod is positioned within the contracting intermediate article to control contraction of the article.7. The method of claim 1, wherein an internal pressure within the intermediate article is provided to control contraction of the article.8. The method of claim 1, wherein the resulting container has a relatively thin sidewall panel portion of high orientation and high crystallinity, and a thickened base portion of low orientation and low crystallinity.9. The method of claim 1, wherein the resulting container has a sidewall panel portion with an average crystallinity of at least 25%, and a base portion with an average crystallinity of no greater than 10%.10. The method of claim 1, wherein the resulting container is a freestanding pressurizable container.11. The method of claim 1, wherein the resulting container is a multilayer carbonated beverage container including one or more layers of biaxially-oriented polyester polymer.12. The method of claim 1, wherein the resulting container is a refillable freestanding pressurizable container including a polyalkylene homopolymer or copolymer.