Films comprising isotactic propylene copolymers

Abstract

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) unsatuarated comonomers are the C 4-20 α-olefins, C 4-20 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) 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 ix , greater than about −1.20, (iv) a DSC curve with a T me that remains essentially the same and a T max 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.

1 . A film comprising a first layer, the first layer comprising a first polymer, the first polymer comprising at least about: 
 (a) 50 weight percent propylene, and    (b) 5 weight percent ethylene;    the first layer characterized as having a: 
 (1) Machine direction tear of at least about 100 g/mil,  
 (2) Haze value of less than about 10 percent,  
 (3) 45° Gloss greater than about 65 percent, and  
 (4) Dart value greater than about 200 g.  
   
     
     
         2 . The film of  claim 1  in which the machine direction tear of the first layer is at least about 125 g/mil.  
     
     
         3 . The film of  claim 2  in which the first layer has a haze value of less than about 9 percent.  
     
     
         4 . The film of  claim 3  in which the first layer has a 45° gloss greater than about 70 percent.  
     
     
         5 . The film of  claim 4  in which the first layer has a dart value greater than about 250 g/mil  
     
     
         6 . The film of  claim 1  in which the machine direction tear of the first layer is greater than about 300 g/mil.  
     
     
         7 . The film of  claim 6  in which the haze value of the first layer is less than about 6 percent.  
     
     
         8 . The film of  claim 7  in which the 45° gloss of the first layer is less than about 80 percent.  
     
     
         9 . The film of  claim 8  in which the dart value of the first layer is greater than about 300 g/mil.  
     
     
         10 . The film of  claim 1  prepared by a blow molding process.  
     
     
         11 . The film of  claim 10  in which the blow molding process includes a water-quench of the film.  
     
     
         12 . The film of  claim 1  comprising a second layer.  
     
     
         13 . The film of  claim 12  in which the composition of the second layer is different than the composition of the first layer.  
     
     
         14 . A film of  claim 13  in which the second layer comprises an α-olefin homopolymer or copolymer.