Micro-porous multi-layer membrane film based on polypropylene for batteries with a cut-off function

摘要

The invention relates to a biaxially orientated microporous film consisting of at least three co-extruded layers, comprising one internal cut-off layer and two external layers. All three layers contain a mixture of propylene homopolymer and propylene block copolymer and a ß-nucleating agent. The propylene block copolymer I of the external layers has a melting point of more than 140 °C and the propylene block copolymer Il of the inner layer has a melting range that starts at a temperature in the region of between 50 - 120 °C and the melting point of the propylene block copolymers I is higher than the melting point of the propylene block copolymers II.