| 摘要 |
The present invention discloses a process for the manufacture of biaxially oriented polypropylene sheets comprising at least a layer, wherein a propylene polymer B is heated in an extruder, and the melted mass of said propylene polymer B is extruded through a flattened crevice nozzle, the melted mass which is released through the flattened crevice nozzle being removed on one or a plurality of rollers, and subsequently solidified to form said sheet, said sheet being longitudinally and transversally stretched, a propylene polymer, or a mixture of propylene polymers, A, being heated and melted in a second extruder, the melted mass of said propylene polymer, or mixture of propylene polymers, A, being subsequently conducted adjacently both sides of the melted mass of the propylene polymer, B, in such a way so as to allow both melted masses to be simultaneously extruded through the flattened crevice nozzle, while the propylene polymer, or mixture of propylene polymers, A, forms the sheet edge zone during said manufacturing process, said propylene polymer-based edge zones, or mixture of propylene polymers, A, being trimmed after the sheet is longitudinally and transversally streched.
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