Patent ID: 9416225
Filing Date: 2016-08-16
CPC Classification: C08G,C08J

Claim Text:
1. A process for the manufacture of a biaxially oriented polyester film, wherein the process comprises: (i) extruding a layer of molten polymer comprising polyethylene terephthalate and at least one hydrolysis stabiliser that is a glycidyl ester of a branched monocarboxylic acid, wherein said glycidyl ester of a branched monocarboxylic acid is in the absence of other hydrolysis stabilizers, and wherein the monocarboxylic acid has from 5 to 50 carbon atoms, wherein said hydrolysis stabiliser is present in the extrudate in the form of its reaction product with at least some of the end-groups of said polyester; (ii) quenching the extrudate; (iii) stretching the quenched extrudate in two mutually perpendicular directions; and (iv) heat-setting the film at a temperature within the range of from about 200 to about 225° C.; (v) wherein the hydrolysis stabiliser is introduced during the film-making process by injecting the hydrolysis stabiliser into the molten polymer within the extruder.