High activity, low molecular weight olefin polymerization process
Group 4 metal complexes comprising a polyvalent, heteroaryl donor ligand and their use as components of olefin polymerization catalysts, especially suited for preparing propylene/ethylene copolymer products having high isotacticity and low molecular weight, are disclosed.
1. A propylene/ethylene copolymer having a Mw from 50,000 to 150,000, a Mw/Mn from 2.0 to 10, a density from 0.860 to 0.8775 g/cc, an ethylene content from 5 to 15 weight percent, an isotacticity (percent mm) of at least 90, a Tc between 50°C. and 58.7°C. and a B-value from 1.03 to 1.09 wherein the copolymer is made by the process comprising:
copolymerizing propylene and ethylene at a temperature from 100 to 130° C., a pressure from 100 kPa to 10 MPa, and a propylene/hydrogen flow ratio (g propylene/hr:g H 2 /hr) from 5000 to 50,000 in the presence of a
a metal complex corresponding to the formula:
wherein, X is an anionic ligand group; and
covalent bonds are represented by lines and coordination interactions are represented by arrows.
2. The propylene/ethylene copolymer of claim 1 having a ΔH fusion from 25 to 55 J/g.
3. The propylene/ethylene copolymer of claim 1 having a Mw/Mn from 2.0 to 3.0, an ethylene content from 7 to 12 weight percent, an isotacticity (percent mm) of at least 93, and a B-value from 1.04 to 1.09.
4. The propylene/ethylene copolymer of claim 3 having a ΔH fusion from 25 to 55 J/g.
5. The propylene/ethylene copolymer of claim 1 having a an ethylene content from 7 to 12 weight percent; an isotacticity (percent mm) of at least 93; ΔH fusion from 29 to 52 J/g; and a B-value from 1.04 to 1.09.