Methods for making polyethylene polymers
AssigneeExxonMobil Chemical Patent Inc.
InventorsBrandon C. Locklear, Haiqing Peng, Bruce J. Savatsky, James M. Farley, Daniel P. Zilker, Robert O. Hagerty, Michael E. Muhle, Fathi D. Hussein
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Abstract
Methods for reducing gels and/or dome sheeting in gas phase polymerization processes and their resulting products are provided. The polymerization processes include polymerizing ethylene and one or more optional comonomers in a fluidized bed reactor in the presence of a metallocene catalyst, hydrogen, and at least one condensing agent.
Claims14
A method for reducing gels in a polyethylene polymer, the method comprising:
- polymerizing ethylene and one or more optional comonomers in a reactor in the presence of a metallocene catalyst, hydrogen, and at least one condensing agent to produce polyethylene polymer granules;
- removing polyethylene polymer granules that are 400 microns or less;
- melting the remaining polyethylene polymer granules after having removed the polyethylene polymer granules that are 400 microns or less;
- and then
- producing a film having an OCS gel count of 175 ppm or less.
A method for reducing dome sheeting in a gas phase, fluidized bed reactor, the method comprising:
- polymerizing ethylene and one or more optional comonomers, at least one condensing agent, and hydrogen, in a fluidized bed reactor in the presence of a supported metallocene catalyst;
- and
- controlling the content of the hydrogen and the at least one condensing agent in the fluidized bed reactor at conditions sufficient to form polyethylene polymer granules having a melt index (I2) of from 0.1 g/10 min to 3.0 g/10 min and a density of from 0.890 g/cm3 to 0.950 g/cm3,
- wherein the conditions sufficient to form the polyethylene polymer granules comprise a reaction temperature of from 60° C. to 120° C., a residence time of from 0.5 hr to 5 hours, and wherein the supported metallocene catalyst has a measured charge of from 0.19 to 0.31 micro-coulombs/gram (negative).
Dependencies are inferred from the claim text.