Hydrolysis resistant polyester films

摘要

A biaxially oriented polyester film comprising polyester and at least one hydrolysis stabilizer selected from a glycidyl ester of a branched monocarboxylic acid, wherein the monocarboxylic acid has from 5 to 50 carbon atoms, wherein said hydrolysis stabilizer is present in the film in the form of its reaction product with at least some of the end-groups of said polyester, and wherein said reaction product is obtained by the reaction of the hydrolysis stabilizer with the end-groups of the polyester in the presence of a metal cation selected from the group consisting of Group I and Group II metal cations.

主权项

1. A biaxially oriented polyester film comprising polyester and at least one hydrolysis stabiliser selected from a glycidyl ester of a branched monocarboxylic acid in the absence of glycidyl ether compound(s), wherein said polyester is polyethylene terephthalate, wherein the monocarboxylic acid has from 5 to 50 carbon atoms, wherein said hydrolysis stabiliser has formula (I): wherein: R1 and R2 are independently selected from alkyl; R3 is selected from hydrogen and alkyl; and wherein the total number of carbon atoms in the alkyl groups R1, R2 and R3 is from 3 to 48; wherein said hydrolysis stabiliser is present in the film in the form of its reaction product with at least some of the end-groups of said polyester, wherein the hydrolysis stabiliser is present in an amount in the range from 0.3% to 1.5%, relative to the total weight of the film and wherein said reaction product is obtained by the reaction of the hydrolysis stabiliser with the end-groups of the polyester in the presence of sodium cations, wherein the amount of the sodium cations present in the film, and/or present in the reaction mixture during the reaction of the hydrolysis stabiliser with the end-groups of the polyester, is at least 45 ppm by weight, relative to the amount of polyester, wherein the film exhibits an elongation to break, measured according to ASTM D882, of at least 10% after at least 76 hours when aged at 121° C. and 1.2 bar pressure.