Metallocene Catalyst Systems With Chemically-Treated Solid Oxides For Producing Ethylene-Based Plastomers And Elastomers

A gas phase polymerization process for producing an ethylene polymer having a density of less than or equal to about 0.91 g/cm3, the process comprising:

• contacting a catalyst composition with ethylene and an α-olefin comonomer in a gas phase reactor containing an inert gas and a C4-C8 alkane at a polymerization temperature in a range from about 48° C. to about 82° C. to produce the ethylene polymer;
• wherein the catalyst composition comprises a metallocene compound, a chemically-treated solid oxide, and optionally, a co-catalyst;
• and
• wherein a ratio of heavy hydrocarbon partial pressure to vapor pressure (ratio of P/P*) in the gas phase reactor is less than or equal to about 0.95.