Patent ID: 8163217
Filing Date: 2012-04-24
Classification: B29C,B29K

Abstract:
1. A method of making a heat-resistant transparent container which comprises the steps of: performing an initial stretching and heat-setting step in which an amorphous polyethylene terephthalate sheet is heated, initially stretched and then initially heat-set and performing a secondary stretching and heat-setting step in which the sheet treated in the initial stretching and heat-setting step is molded by heating in a mold of a thermoforming machine while secondary stretching is performed followed by secondary heat-setting in the same mold, wherein the initial stretching is uniaxial stretching using treating rolls and carried out at a stretching temperature of 90 to 120° C., a draw ratio of 2.6 to 3.7 times, the initial heat-setting is carried out at a temperature higher than the stretching temperature by 5 to 20° C. through heat-setting rolls which have been heated to a heat-setting temperature while the rotational speed of the heat-setting rolls is 0.5 to 10% slower than that of the treating rolls and the initially stretched sheet is in a stretched form, the treated sheet after the initial stretching and heat-setting step has a crystallinity of at least 22% but less than 30%, the heating in the mold is carried out at a temperature of 80 to 130° C., the secondary heat-setting is carried out at a temperature of 160° C. or higher to form a thermoformed article having a crystallinity of 30% or more.