Patent ID: 8202940

Claim:
A method for making a bimodal polyethylene composition, comprising: polymerizing ethylene and a comonomer in the presence of a mixed catalyst comprising at least one Group-15 containing catalyst in a gas phase polymerization reactor to produce a bimodal polyethylene; heating the bimodal polyethylene to produce a substantially melted bimodal polyethylene; contacting the substantially melted bimodal polyethylene with a gas mixture comprising from about 8 vol % to about 20 vol % oxygen to produce an oxygen tailored bimodal polyethylene, wherein during the oxygen tailoring the amount of phosphorous containing compounds present is less than 0.05 wt % based on the combined weight of the polyethylene resin and phosphorous containing compounds; and cooling the oxygen tailored bimodal polyethylene to produce a bimodal polyethylene composition comprising: a high molecular weight component having a weight average molecular weight (Mw) of from about 500,000 to about 950,000; a low molecular weight component having a weight average molecular weight (Mw) of from about 3,000 to about 100,000, wherein the high molecular weight component is present in an amount ranging from about 25 wt % to about 40 wt % of the bimodal polyethylene composition; wherein the ratio of the weight average molecular weight of the high molecular weight component to the weight average molecular weight of the low molecular weight component is from about 15 to about 35; a melt flow ratio (I 21 /I 2 ) of equal to 200; and a percent die swell of less than about 80%.