发明授权
US5716570A Process for the production of polypropylene films 失效
生产聚丙烯薄膜的方法

Process for the production of polypropylene films
摘要:
A process for the production of biaxially oriented polypropylene films which include at least one layer is described, in which a propylene polymer B is heated in an extruder and the melt of the propylene polymer B is extruded through a flat sheet die and the melt emerging from the flat sheet die is taken off on one or more rolls and is solidified to give a prefilm and this prefilm is stretched in the longitudinal and transverse direction. A propylene polymer or a propylene polymer mixture A is heated and melted in a second extruder and the melt of the propylene polymer or of the propylene polymer mixture A is fed to the two sides of the propylene polymer melt B so that both melts are extruded together and simultaneously through the flat sheet die. The propylene polymer or the propylene polymer mixture A forms the edge region of the film during the production process, and the edge regions including the propylene polymer or the propylene polymer mixture A are cut off after the longitudinal and transverse stretching of the film.
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