US 5,183,623 AGranted

Process for producing transparent and heat-resistant polyester containers

AssigneePolyplastics Co., Ltd.

InventorsKuniaki Kawaguichi, Toshio Nakane, Akihide Shimoda, Kenji Hijikata

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Abstract

A process for producing a transparent and heat-resistant container includes forming a sheet from a melt of a polyester resin having at least 80 mole % ester units derived from 1,3-propanediol and terephthalic acid or an ester-forming derivative thereof. The formed sheet is quenched and solidified so as to have relatively low crystallinity (i.e., less than 50%). The solidified low crystallinity film is then aged and shaped by thermoforming to obtain a container having relatively high crystallinity (i.e., greater than 50%, and preferably greater than 80%). The aging step is most preferably conducted at a temperature which satisfies the relationship represented by the following equation (1): Ta.ltoreq.Tcc wherein Ta is the aging temperature (.degree.C.), and Tcc is the cold crystallization temperature (.degree.C.) as determined by differential thermal analysis at a rate of temperature increase of 10.degree. C./min. Moreover, the aging step is practiced such that the aged sheet satisifies the relationship represented by the following equation (2): (.DELTA.Hcc)a.gtoreq.5.0 (J/g) wherein (.DELTA.Hcc)a is the heat of cold crystallization (J/g) of the aged sheet as determined by differential thermal analysis at a rate of temperature increase of 10.degree. C./min.

Claims1

Dependent claims

A process for producing a transparent and heat-resistant container which comprises the steps of:

(a) forming a sheet from a melt of a polyester resin having at least 80 mole % of ester units derived form 1,3-propanediol and terephthalic acid or an ester-forming derivative thereof;
(b) quenching and solidifying the sheet such that the solidified sheet has low crystallinity;
(c) aging said quenched and solidified sheet so as to obtain a low crystallinity sheet;
and then
(d) thermoforming the resulting low crystallinity sheet to obtain a container, and wherein
said aging step (a) is conducted at a temperature which satisfies the relationship represented by the following equations (1) and (2):
Ta.ltoreq.Tcc (1)
(.DELTA.Hcc)a.gtoreq.5.0 (2)
wherein Ta is the aging temperature (.degree. C.), Tcc is the cold crystallization temperature (.degree. C.), and (.alpha.Hcc)a is the heat of cold crystallization (J/g), said cold crystallization temperature and said heat of cold crystallization each being determined by differential thermal analysis at a rate of temperature increase of 10.degree. C./min;
and wherein
said polyester resin satisfies the relationship represented by the following equation (3):
Tg+65.gtoreq.Tcc (3)
wherein Tg is the glass transition temperature (.degree. C.) of the polyester resin as determined by differential thermal analysis at a rate of temperature increase of 10.degree. C./min, and Tcc is as defined previously.

10 more elements

Dependencies are inferred from the claim text.