BIAXIALLY ORIENTED POLYESTER FILM WITH A HIGH PORTION OF CYCLOHEXANEDIMETHANOL AND A SECONDARY DIOL PORTION, AND A PRIMARY AND SECONDARY DICARBOXYLIC ACID PORTION AND A METHOD FOR ITS PRODUCTION AND ITS USE

摘要

Biaxially stretched film comprises a polyester, whose: diol component is made up of at least 80 mol.% of 1,4-cyclohexanedimethanol; and dicarboxylic acid component is made up of at least 80 mol.% of one or more benzenedicarboxylic acid and/or one or more naphthalene dicarboxylic acid, a main dicarboxylic acid component with at least 55 mol.%, which is 2,6-naphthalenedicarboxylic acid or terephthalic acid, and para-dicarboxylic acid component with at least 18 mol.%, where the para-dicarboxylic acid component is different from the main dicarboxylic acid component. Independent claims are included for: (1) biaxially oriented polyester film having a transparency of greater than 70%, an opacity of less than 90%, the transparency in the UV-A region at 370 nm of less than 30%, an elastic modulus in the direction of each film of greater than 1500 N/mm 2, but in any film direction, the elastic modulus is greater than 5000 N/mm 2, and a F5-value (force at 5% elongation) in each film direction of greater than 40 N/mm 2, but in any film direction a force at 5% elongation is greater than 140 N/mm 2, a tensile strength in each film direction of greater than 65 N/mm 2, but in any film direction of greater than 290 N/mm 2, a shrinkage at 150[deg] C (15 minutes) in both film directions of less than 3%, but in any film direction of less than -1% (equivalent to 1% elongation), and a dielectric strength (BDV) (50 Hz, 21[deg] C, 50 relative humidity, measured in air) of at least 40 V/mu m and a partial discharge resistance (PDV) of the following equation: PDV[V]is equal to x[V/mu m].film thickness [mu m]+y[V] with an x-value of greater than 0.75 [V/mu m]and a y-value of greater than 100 [V] and a SV-value decomposition rate of greater than -3 SV-E/hour (SV-E is equal to SV-unit); and (2) producing the film, comprising extruding one or more polymer melt through a flat nozzle, for solidification on one or more rolls, reducing and detering to largely amorphous precursor film, reheating this precursor film and biaxially stretching (orienting), thermally fixing the biaxially stretched film and then rolling, where the polymer comprises the polyester.