Controlling long-chain branch content with dual activator-supports
Methods for controlling the long chain branch content of ethylene homopolymers and copolymers produced in a polymerization process include the steps of contacting a metallocene compound, an organoaluminum compound, a high LCB activator-support, and a low LCB activator-support to form a catalyst composition, contacting the catalyst composition with ethylene and an optional olefin comonomer in a polymerization reactor system under polymerization conditions to produce an ethylene polymer having a LCB content, and controlling the relative amount of the high LCB activator-support and the low LCB activator-support in the catalyst composition to adjust the LCB content of the ethylene polymer.
1. A catalyst composition comprising:
(i) a first activator-support comprising a fluorided silica-coated alumina;
(ii) a second activator-support comprising a sulfated bentonite;
(iii) a metallocene compound; and
(iv) an organoaluminum compound.
2. The composition of claim 1 , wherein:
a weight ratio of the metallocene compound to the activator-supports is in a range from 1:1 to 1:100,000; and
a molar ratio of the organoaluminum compound to the metallocene compound is in a range from 1:1 to 1000:1.
3. The composition of claim 1 , wherein a weight ratio of the first activator-support to the second activator-support is in a range from 10:1 to 1:10.
4. The composition of claim 1 , wherein the catalyst composition is substantially free of aluminoxane compounds, organoboron or organoborate compounds, ionizing ionic compounds, or combinations thereof.
5. The composition of claim 1 , wherein the catalyst composition contains two or more metallocene compounds.
6. The composition of claim 1 , wherein the metallocene compound comprises:
(1) rac-ethylene-bis(1-indenyl) zirconium dichloride;
(2) methyl(buten-3-yl)methylidene(η5-cyclopentadien-1-ylidene)(η5-2,7-di-tert-butylfluoren-9-ylidene) zirconium dichloride;
(3) diphenylmethylidene[η5-[3-(pent-4-enyl)cyclopentadien-1-ylidene]][η5-(2,7-di-tert-butylfluoren-9-ylidene)] hafnium dichloride;
(4) (n-butylcyclopentadienyl)(1-allylindenyl)zirconium dichloride;
(5) rac-dimethylsilylbis(1-indenyl)zirconium dichloride;
(6) 1-ethylpropylidene[(η5-cyclopentadien-1-ylidene)(η5-(3-propyl)inden-1-ylidene)] zirconium dichloride; or
any combination thereof.
7. The composition of claim 1 , wherein the metallocene compound comprises:
a bridged zirconium or hafnium based metallocene compound with a cyclopentadienyl group and a fluorenyl group;
a bridged zirconium based metallocene compound containing two cyclopentadienyl groups, two indenyl groups, or a cyclopentadienyl and an indenyl group;
an unbridged zirconium or hafnium based metallocene compound containing two cyclopentadienyl groups, two indenyl groups, or a cyclopentadienyl and an indenyl group; or
any combination thereof.
8. The composition of claim 1 , wherein the organoaluminum compound comprises trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diisobutylaluminum hydride, diethylaluminum ethoxide, diethylaluminum chloride, or any combination thereof.
9. The composition of claim 8 , wherein a molar ratio of the organoaluminum compound to the metallocene compound is in a range from 2:1 to 200:1.
10. The composition of claim 8 , wherein a weight ratio of the activator-supports to the organoaluminum compound is in a range from 100:1 to 1:100.
11. The composition of claim 8 , wherein a weight ratio of the first activator-support to the second activator-support is in a range from 5:1 to 1:5.
12. The composition of claim 8 , wherein the metallocene compound comprises:
(1) rac-ethylene-bis(1-indenyl) zirconium dichloride; and/or
(5) rac-dimethylsilylbis(1-indenyl)zirconium dichloride.
13. The composition of claim 8 , wherein the fluorided silica-coated alumina comprises from 2 to 15 wt. % fluoride.
14. The composition of claim 8 , wherein the fluorided silica-coated alumina comprises from 15 to 60 wt. % silica, based on a weight of silica-coated alumina.
15. A catalyst composition comprising:
(i) a first activator-support comprising a fluorided silica-coated alumina;
(ii) a second activator-support comprising a sulfated bentonite, the sulfated bentonite containing from 28 to 32 wt. % silicon;
(iii) a metallocene compound; and
(iv) an organoaluminum compound.
16. The composition of claim 15 , wherein the sulfated bentonite contains from 0.08 to 0.14 wt. % sodium.
17. The composition of claim 15 , wherein the sulfated bentonite contains from 2.8 to 4.8 wt. % sulfur.
18. The composition of claim 15 , wherein the sulfated bentonite is characterized by a residual acidity value of from 3 to 14 mg KOH/g.
19. The composition of claim 15 , wherein the fluorided silica-coated alumina comprises from 2 to 15 wt. % fluoride.
20. The composition of claim 15 , wherein the fluorided silica-coated alumina comprises from 15 to 60 wt. % silica, based on a weight of silica-coated alumina.
21. The composition of claim 15 , wherein the metallocene compound comprises:
(1) rac-ethylene-bis(1-indenyl) zirconium dichloride;
(2) methyl(buten-3-yl)methylidene(η5-cyclopentadien-1-ylidene)(η5-2,7-di-tert-butylfluoren-9-ylidene) zirconium dichloride;
(3) diphenylmethylidene[η5-[3-(pent-4-enyl)cyclopentadien-1-ylidene]][η5-(2,7-di-tert-butylfluoren-9-ylidene)] hafnium dichloride;
(4) (n-butylcyclopentadienyl)(1-allylindenyl)zirconium dichloride;
(5) rac-dimethylsilylbis(1-indenyl)zirconium dichloride;
(6) 1-ethylpropylidene[(η5-cyclopentadien-1-ylidene)(η5-(3-propyl)inden-1-ylidene)] zirconium dichloride; or
any combination thereof.