Polyethylene naphthalate-polyethylene terephthalate-polyethylene naphthalate polymer film

摘要

A polymeric film comprising a first layer which comprises (a) a mixture comprising 50-99.9 % by weight polyethylene terephthalate (PET) and 0.1-50 % by weight polyethylene naphthalate (PEN) or (b) a copolymer comprising 50 - 99.9 % by weight ethylene terephthalate units and 0.1 - 50 % by weight ethylene naphthalate units, based on the total weight of the first layer, and on a first surface of the first layer a second layer comprising PEN and on a second surface of the first layer a third layer comprising PEN, and optionally further comprising a first intermediate layer interposed between said first and second layers and a second intermediate layer interposed between said first and third layers, wherein each of said intermediate layers comprises (a) a mixture comprising 50-99.9 % by weight polyethylene terephthalate (PET) and 01-50 % by weight polyethylene naphthalate (PEN) or (b) a copolymer comprsing 50 - 99.9 % by weight ethylene terephthalate units and 0.1 - 50 % by weight ethylene naphthalate units, based on the total weight of the layer. The invention further relates to a method of producing such a polymeric film. The polymeric film can be used as insulation in an electric motor or generator and in a magnetic medium or in packaging material.