Process for making a biaxially stretched polyester film

The method comprises placing a raw material made up of discrete elements in a form of pellets containing polyester of average molecular weight of 18000-40000 and an intrinsic viscosity of 0.6-1.2 dL/g, drying the raw material, mixing the raw material, extruding the raw material to form a mono or multi-layer film, cooling the extruded film, coating faces of the extruded film using resin to confer properties specific to film, biaxial stretching of the coated film according to a stretching rate and a selected stretching temperature, and coating on the faces of the film using resin. The method comprises placing a raw material made up of discrete elements in a form of pellets containing polyester of average molecular weight of 18000-40000 and an intrinsic viscosity of 0.6-1.2 dL/g, drying the raw material, mixing the raw material, extruding the raw material to form a mono or multi-layer film, cooling the extruded film, coating faces of the extruded film using resin to confer properties specific to film, biaxial stretching of the coated film according to a stretching rate and a selected stretching temperature so as to direct macromolecular chains according to two axes privileged in a plane of film and to obtain a crystallinity rate of 25-35 wt.% of the film, coating on the faces of the film using resin to confer properties specific to film, thermofixing the film, transverse relieving the film, winding the film, completing the film by spanning, coating, vacuum metallization, reheating, UV processing, plasma or corona, controlling performance of the polyester film by a method A of measurement of shock-traction resistance and/or a method B of sonic measurement of a module, and taking into account the measurements to modify the parameters in the coating stages to control the resistance of the film. The method includes three modes to control the operational parameters. The first mode obtains the shock-traction resistance of the film measured by the method A to be higher than 300 kJ/m 2>, and a hydrolysis resistance measured in a PCT test for 36 hours at 125[deg] C and a retention rate of elongation at fracture higher than 70%, where the biaxial stretching is implemented by: carrying out longitudinal stretching at the stretching rate in an order of 2-6 or 2.5-5 or 2.9-4.5 and at a stretching temperature in an order of 70-150[deg] C or 85-140[deg] C or 90-135[deg] C; carrying out transverse stretching at the stretching rate in an order of 2-6 or 3.5-5 or 3.9-4.5 and at