Patent ID: 8470939

Claim:
A process of preparing a polyethylene, the process comprising: (a) in a first stage, pre-treating a Ziegler catalyst by contacting the Ziegler catalyst and co-catalyst with a 1-olefin or a 1-olefin/ethylene mixture having a molar ratio of 1-olefin/ethylene within the range of about 0.8 to about 4.0, at a temperature within the range of about 55° C. to about 120° C., and for a time of from about 15 seconds to about 15 minutes; and (b) in a second stage, polymerizing ethylene or an ethylene/1-olefin mixture having a molar ratio of ethylene/1-olefin within the range of about 1/0.001 to about 1/0.2, in the presence of the pre-treated catalyst, wherein the Ziegler catalyst comprises a transition metal and an alkyl magnesium silyl amide complex, wherein the transition metal is selected from the group consisting of Ti, Zr, V, Cr and mixtures thereof, and an alkyl aluminum co-catalyst, and wherein a polymer produced in the first stage has a density within the range of about 0.88 g/cm 3 to about 0.92 g/cm 3 , a molecular weight distribution less than or equal to about 4.0, and an ER within the range of about 1.0 to about 3.0, and wherein the first and second stages are gas-phase or super-critical phase processes.