| 摘要 |
Films with excellent machine direction (MD) tear properties comprise at least one layer made from a polymer comprising: (A) at least 50 weight percent (wt %) propylene; and (B) at least 5 wt % ethylene and/or one or more unsaturated comonomers. Representative of component (B) unsaturated comonomers are the C<subscript>4-20 </highlight>alpha-olefins, C<subscript>4-20 </highlight>dienes, styrenic compounds, and the like. Preferably, the film has at least one of a (i) haze value of less than about 10, (ii) 45 degree gloss of greater than about 65, and (iii) dart value of greater than about 100 g/mil. In one preferred embodiment, the layer comprises a compolymer characterized as having at least one of the following properties: (i) <superscript>13>C NMR peaks corresponding to a regio-error at about 14.6 and about 15.7 ppm, the peaks of about equal intensity, (ii) a B-value greater than about 1.4 when the comonomer content, i.e., the units derived from ethylene and/or the unsaturated comonomer(s), of the copolymer is at least about 3 wt %, (iii) a skewness index, S<subscript>ix</highlight>, greater than about -1.20, (iv) a DSC curve with a T<subscript>me </highlight>that remains essentially the same and a T<subscript>max </highlight>that decreases as the amount of comonomer, i.e., the units derived from ethylene and/or the unsaturated comonomer(s), in the copolymer is increased, and (v) an X-ray diffraction pattern that reports more gamma-form crystals than a comparable copolymer prepared with a Ziegler-Natta (Z-N) catalyst.
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