| 摘要 |
Films useful as tape backings, and more particularly biaxially oriented polypropylene film backings and tapes including such backings. A brittle, biaxially oriented polypropylene film is provided by minimizing the nucleation density in the extruded and quenched polypropylene polymer cast sheet followed by maximizing the spherulitic growth rate of the resultant quenched polymer. The cast sheet so formed is stretched at higher-than-normal temperatures in the subsequent orientation steps for producing the biaxially oriented polypropylene film. This produces a more brittle film. The polypropylene composition, extrusion temperature, cast roll temperature (i.e., quench temperature), and stretch temperature and other parameters are selected in accordance with the teachings herein such that the resulting backing or tape has the following preferred properties, taken individually or in any preferred combination: A) an MD tensile energy at break of up to about 90 N-mm/mm<3>; B) an MD elongation to break of at least 70%; C) a puncture energy of up to about 130 N-mm; D) a dispense energy of up to about 350 N-cm/cm<2>; E) when disposed on commercially available serrated plastic or metal dispenser blades, the serrated edge of the tape or backing closely follows the contour of the dispensing blade; and F) an ability to be torn by hand.
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