Composite metal-coated polyester films with barrier properties

摘要

The invention concerns composite metallized polyester films with good barrier properties relative to gases. More precisely, it concerns a biaxially drawn composite metallized film based on polyester and having improved barrier properties to gases, characterized in that the composite comprises a polyester film base of 5 mum to 50 mum, directly coated on one of its two faces with a layer including a mixture of a polyvinyl alcohol which has an average degree of polymerization in number equal to or in excess of 350 and a water-dispersible copolyester with sulphonyloxy residues, the layer including the polyvinyl alcohol and the water-dispersible copolyester being in turn coated with a metal layer, the composite film exhibiting a permeability to oxygen, measured at 23° C. under 50% relative humidity, equal to or lesser than 0.4 cm3/m2/24 h. The composite metallized polyester films have, besides their barrier properties, excellent resistance to mechanical stresses, such as in particular crumpling.