Transparent polyester multilayer film with high oxygen barrier property, process for its manufacture and its application

摘要

A transparent, biaxially oriented polyester film (I) has a base layer consisting of at least 80 wt.% of a thermoplastic polyester and a covering layer. The covering layer consists of a polymer or mixture of polymers comprising at least 40 wt.% ethylene-2,6-naphthalate units and upto 60 wt.% ethylene terephthalate units and optionally up to 60 wt.% of other cycloaliphatic or aromatic diols and/or dicarboxylic acids. The Tg 2 value of the polyester film is greater than that of the base layer but less than that of the covering layer. Also claimed is a process for the production of (I) by co-extruding the base and covering layer(s) to form a film, biaxially stretching the film followed by thermal fixing.