Polyester film with high oxygen barrier property, its use and process for its production

摘要

Transparent, biaxially oriented polyester film comprising a thermoplastic polyester base layer with a diethylene glycol content of 0.9-3.0 wt% and outer layer(s) of polymer containing ethylene 2,6-naphthalate (EN) and ethylene terephthalate (ET) units, optionally with other diol and/or diacid units. Transparent, biaxially oriented polyester film with (a) a base layer comprising at least 80 wt.% thermoplastic polyester with a diethylene glycol content of 0.9-3.0 (most preferably 1.2-1.8) wt.% and (b) at least one outer layer consisting of a polymer or mixture of polymers containing at least 40 wt.% EN units, up to 40 wt.% ET units and optionally up to 60 wt.% units derived from cycloaliphatic or aromatic diols and/or dicarboxylic acids. Independent claims are also included for (a) similar film with a base layer as above, in which the outer layer polyester contains at least 5 wt.% EN units, up to 40 wt.% ET units and optionally up to 60 wt.% other units as above, and the film itself shows a Tg2 value above that of the base layer and below that of the outer layer; (b) a process for production of the film, comprising (a) coextrusion of the base layer and outer layer(s), (b) biaxial stretching and (c) thermal fixing.