Prodn. of filler-contg. biaxially oriented polymer film

摘要

The invention concerns a process for producing a single or multilayer biaxially oriented foil of a crystallizable thermoplastic polymer which comprises at least one filler-containing layer. According to the invention, at least one melt comprising a homogeneous mixture of the thermoplastic polymer and one or a plurality of fillers is prepared and the melt is extruded to form a preliminary foil which is then stretched biaxially. The at least one melt of thermoplastic polymer and the filler(s) is prepared directly from the filler-free polymer and the powdery filler(s), preferably using a two-worm extruder. The powdery filler can be mixed with filler-free polymer granulates in the extruder inlet region or added to the molten polymer flow in the extruder.