The use of a transparent polyester film as a gas/flavor-barrier film

摘要

Transparent, biaxially oriented polyester film used as gas barrier film has a thermoplastic polyester base layer (B) and an outer layer of polymer (A) with ethylene 2,6-naphthalate (EN), ethylene terephthalate (ET) and optionally cycloaliphatic or aromatic diol and/or diacid units, and the film shows a Tg2 value above that of (B) but below that of (A). The use of transparent, biaxially oriented polyester film as a barrier film against water vapor, nitrogen, carbon dioxide, helium and flavor substances is claimed. This film has a base layer (B) comprising at least 80 wt.% thermoplastic polyester and at least one outer layer (A) comprising 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. The Tg2 value of the film is above that of the base layer (B) and below that of outer layer (A).