| 摘要 |
The invention relates to a method for producing oriented slit film tapes, comprising the following steps: > extruding melt polymer through a die; > simultaneous quenching and melt-drawing of the molten polymer in the cooling device to form a film sheet; > slitting the initial film sheet into a plurality of relatively narrow slit film tapes; > stretching at elevated temperature, by passing the sht film tapes through a heating medium at a temperature just below the softening temperature of the slit film tapes; > annealing and cooling the oriented slit film tapes; > winding the slit film tapes; characterized in that before the stretching step, it has a stage of pre-stretching made by passing the sht film tapes through one set of heated holding rollers turning at a given speed and one set of cooled pre-stretch rollers turning faster than the heated holding tollers, wherein at least one of the rollers of the set of holding rollets is heated and at least one of the rollers of the set of pre-stretch rollers is cooled. The invention also relates to an apparatus for performing this method and to the products obtained by said method. |
