Propylene olefin copolymers
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. A process comprising:
contacting propylene and at least one C 6 -C 20 α-olefin in the presence of a metallocene polymerization catalyst comprising a hafnium-containing composition under conditions effective to produce a polymer comprising units derived from the at least one C 6 -C 20 α-olefin and from about 65 wt % to about 95 wt % propylene-derived units, the polymer having a heat of fusion less than about 75 J/g, a melting point of from 25° C. to 70° C., and a crystallinity of from about 20% to about 65% of homoisotactic polypropylene.
2. The process of claim 1 , wherein the α-olefin is hexene.
3. The process of claim 1 , wherein the α-olefin is octene.
4. The process of claim 1 , wherein the polymer has a Mooney viscosity (ML 1+4 @ 125° C.) less than 100.
5. The process of claim 4 , wherein the Mooney viscosity is less than about 75.
6. The process of claim 4 , wherein the Mooney viscosity is less than about 60.
7. The process of claim 1 , further comprising contacting the propylene and the at least one C 6 -C 20 α-olefin in the presence of a catalyst activator, wherein the catalyst activator comprises a non-coordinating compatible anion or an alumoxane.
8. A process comprising:
contacting propylene, ethylene, and one or more of hexene and octene in the presence of a metallocene polymerization catalyst comprising a hafnium-containing composition under conditions effective to produce a polymer comprising units derived from the ethylene and the one or more of hexane and octene and from about 65 wt % to about 95 wt % propylene-derived units, wherein the polymer has a heat of fusion less than about 75 J/g, a melting point of from 25° C. to 70° C., and a crystallinity of from about 20% to about 65% of homoisotactic polypropylene.
9. The process of claim 8 comprising hexene.
10. The process of claim 8 further comprising contacting the propylene and the ethylene and the one or more of hexene and octene in the presence of a catalyst activator, wherein the catalyst activator comprises a non-coordinating compatible anion or an alumoxane.