Elastic blends comprising crystalline polymer and crystallizabe polymers of propylene

Abstract

Improved thermoplastic polymer blend compositions comprising an isotactic polypropylene component and an alpha-olefin and propylene copolymer component, said copolymer comprising crystallizable alpha-olefin sequences. In a preferred embodiment, improved thermoplastic polymer blends are provided comprising from about 35% to about 85% isotactic polypropylene and from about 30% to about 70% of an ethylene and propylene copolymer, wherein said copolymer comprises isotactically crystallizable propylene sequences and is predominately propylene. The resultant blends manifest unexpected compatibility characteristics, increased tensile strength, and improved process characteristics, e.g., a single melting point.

1 - 31 . (canceled)  
     
     
         32 . A blend comprising at least one polymer (A) and at least one polymer (B), polymer (A) comprising at least about 88.4 weight percent of units derived from propylene and about 5.8 to about 11.6 weight percent of units derived from ethylene, and is characterized as having a DSC curve with a T me  that remains essentially the same and a T max  that shifts to the left as the amount of comonomer in the copolymer is increased; and polymer (B) comprising a thermoplastic polymer other than polymer (A).  
     
     
         33 . The blend of  claim 32  in which polymer (A) is further characterized as having an X-ray diffraction pattern exhibiting more gamma-form crystals than a comparable copolymer prepared with a Ziegler-Natta catalyst.  
     
     
         34 . The blend of  claim 32  in which the polymer (A) is characterized further as having at least one of the following additional properties: (i) a B-value of about 1.4 when the comonomer content of the copolymer is about 5.8 weight percent, and (ii) a skewness index, Six, of about 0.32.  
     
     
         35 . The blend of  claim 33  in which the polymer (A) is characterized further as having at least one of the following additional properties: (i) a B-value of about 1.4 when the comonomer content of the copolymer is about 5.8 weight percent, and (ii) a skewness index, S ix , of about −0.32.  
     
     
         36 . The blend of  claim 34  in which the polymer (A) is characterized further as having both of the properties of (i)-(ii).  
     
     
         37 . The blend of  claim 35  in which the polymer (A) is characterized further as having both of the properties of (i)-(ii).  
     
     
         36 . The blend of  claim 32  in which polymer (B) is a polyolefin.  
     
     
         39 . The blend of  claim 33  in which polymer (B) is a polyolefin.  
     
     
         40 . The blend of  claim 34  in which polymer (B) is a polyolefin.  
     
     
         41 . The blend of  claim 35  in which polymer (B) is a polyolefin.  
     
     
         42 . The blend of  claim 36  in which polymer (B) is a polyolefin.  
     
     
         43 . The blend of  claim 37  in which polymer (B) is a polyolefin.