Production of blow molding polyethylene resin
AssigneeChevron Chemical Company
InventorsRobert L. Batchelor, Gene E. Kellum
Life of this patent
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Abstract
Disclosed is a process for making polyethylene resin by reacting ethylene or ethylene and a C.sub.3 -C.sub.8 alpha-olefin in the presence of a CrO.sub.3 /TiO.sub.2 catalyst on a silica support in a gas-phase polymerization reactor and in the presence of a catalyst productivity reduction agent such as oxygen. The resin in one embodiment has a melt flow ratio between 65 and 140 and a melt index between 0.1 and 0.6 g/10 min. The resin is particularly suitable for use in blow-molding applications.
Claims12
A process for making a polymer which comprises feeding ethylene, or ethylene and a C.sub.3 -C.sub.8 alpha olefin, to a polymerization reaction zone;
- contacting this feed under gas phase polymerization conditions with a catalyst comprising 0.7 to 2 weight percent chromium oxide, calculated as chromium, and 1 to 6 weight percent titanium oxide, calculated as titanium, on a silica support;
- and injecting oxygen as a catalyst productivity reduction agent into the reaction zone, wherein the catalyst productivity reduction agent is injected in an amount that is effective to increase the MFR of the polymer at least 8 units over a polymer obtained off the reactor for the same process conditions but without using oxygen in combination with the above-specified process conditions.
A process comprising:
- A) polymerizing monomer, which consists essentially of ethylene or ethylene and a C.sub.3 -C.sub.8 alpha-olefin comonomer,
- B) in a gas-phase polymerization reactor
- C) and in the presence of
- (1) a polymerization catalyst which comprises
- (a) a silica support,
- (b) about 0.8-1.2 wt. % Cr, and
- (c) about 3-5 wt. % Ti
- 10 wherein the polymerization catalyst is prepared by impregnating a chromium compound and a titanium compound onto the silica support and the catalyst is subsequently activated in an oxygen-containing gas at a temperature of 800.degree.-1600.degree. F. prior to introducing the catalyst into the polymerization reactor;
- and
- (2) oxygen in a ratio of between about 0.05 and about 0.6 moles of oxygen per million moles of fresh ethylene fed to the polymerization reactor
- wherein the process produces resin off the reactor having a melt-flow ratio of at least about 8 units greater than a process at the same processing conditions but without using oxygen in combination with the above-specified process conditions.
Dependencies are inferred from the claim text.