Process for the preparation of multimodal polyethylene resins

• US 20100016526A1
• Filed: 07/16/2008
• Published: 01/21/2010
• Est. Priority Date: 07/16/2008
• Status: Active Grant

• Current Assignee: Equistar Chemicals LP (Lyondellbasell Industries NV)
• Original Assignee: Equistar Chemicals LP (Lyondellbasell Industries NV)
• Inventors: Imfeld, Stephen M., Garrison, Philip J., Etherton, Bradley P.
• Granted Patent: US 7,829,641 B2
• Time in Patent Office: Days
• US Class Current: 526/96
• CPC Class Codes: C08F 2/001 Multistage polymerisation processes characterised by a change in reactor conditions without deactivating the intermediate polymer C08F295/00, C08F297/00 take precedence
• CPC Class Codes: C08F 210/08 Butenes
• CPC Class Codes: C08F 210/14 Monomers containing five or more carbon atoms
• CPC Class Codes: C08F 210/16 Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
• CPC Class Codes: C08F 2500/05 Bimodal or multimodal molecular weight distribution
• CPC Class Codes: C08F 2500/07 High density, i.e. > 0.95 g/cm3
• CPC Class Codes: C08F 2500/12 Melt flow index or melt flow ratio
• CPC Class Codes: C08F 4/65904 in combination with another component of C08F4/64
• CPC Class Codes: C08F 4/65912 in combination with an organoaluminium compound
• CPC Class Codes: C08F 4/65916 supported on a carrier, e.g. silica, MgCl2, polymer
• CPC Class Codes: C08F 4/65925 two cyclopentadienyl rings being mutually non-bridged
• CPC Class Codes: C08F 4/65927 two cyclopentadienyl rings being mutually bridged
• CPC Class Codes: Y02P 20/52 using catalysts, e.g. selective catalysts

Abstract

A two-stage cascade polymerization process for the production of multimodal polyethylene film resins with improved bubble stability is provided. The process comprises polymerizing ethylene or a mixture of ethylene and a C_4-8 α-olefin in two reactors arranged in series using a mixed single-site catalyst comprised of a bridged and a non-bridged indenoindolyl transition metal complex to form a multimodal polyethylene resin comprised of a lower molecular weight, higher density component and a higher molecular weight, lower density component.

Claims

1. A process for making multimodal polyethylene resin comprising:

(a) polymerizing ethylene or mixture of ethylene and C_3-8 α

-olefin in a first reactor in the presence of hydrogen and a catalyst system comprised of a mixed indenoindolyl single site catalyst and an activator, said mixed single site catalyst comprised of a non-bridged indenoindolyl transition metal complex of the formula

2. The process of claim 1 wherein the mixed indenoindolyl single site catalyst is immobilized in an inorganic support selected from the group consisting of silica, alumina, silica-alumina, magnesia, titania, zirconia and magnesium chloride and the mole ratio of non-bridged to bridged indenoindolyl catalyst components is from 1.75:

1 to 1;

2.

3. The process of claim 2 wherein the non-bridged indenoindolyl transition metal complex corresponds to the formula wherein M is zirconium, L₂ is cyclopentadienyl and X is chlorine.

4. The process of claim 2 wherein the bridged indenoindolyl transition metal complex corresponds to the formula wherein M is zirconium, X is chlorine and G is selected from the group consisting of methylene, ethylene, ethylidene, isopropylidene and dimethylsilylene.

5. The process of claim 2 wherein the multimodal resin product has a density from 0.942 to 0.958 g/cm³, HLMI from 7 to 30 g/10 min and is comprised of 35 to 48 weight percent first polyethylene resin and 52 to 65 weight percent second polyethylene resin.

6. The process of claim 1 wherein the polymerizations are carried out in an inert hydrocarbon.

7. The process of claim 1 wherein ethylene is polymerized in the first reactor and a mixture of ethylene and C_3-8 α

-olefin are polymerized in the second reactor.

8. The process of claim 1 wherein the α

-olefin is butene-1.

9. The process of claim 1 wherein the catalyst system includes an organoaluminum cocatalyst of the formula

AlR^l_nY_3-n

wherein R¹ is a C_1-8 hydrocarbon group, Y is a halogen or alkoxy group and n is 1, 2 or 3.

10. The process of claim 9 wherein the organoaluminum cocatalyst is triethylaluminum or triisobutylaluminum.

11. The process of claim 1 comprising polymerizing ethylene and a C_3-8 α

-olefin comonomer in an inert hydrocarbon in the presence of a supported mixed indenoindolyl single site catalyst, an activator, an organoaluminum cocatalyst and hydrogen while maintaining conditions to target the formation of a first polyethylene resin having a density from 0.950 to 0.965 g/cm³ and MI₂ from 0.3 to 4 g/10 min, said mixed catalyst comprised of (5,10-dihydro-5,8-dimethylindeno[1,2-b]indole-10-yl)(cyclopentadienyl)zirconium dichloride and rac-ansa (methylene)bis(2,5-dimethyl-indeno[2,1-b]indolyl)zirconium dichloride present at a mole ratio from 1.75;

1 to 1;

2, and adding ethylene, a C_3-8 α

-olefin comonomer and hydrogen to the second reactor and continuing the polymerization while maintaining conditions to produce a multimodal polyethylene resin having a density from 0.942 to 0.958 g/cm³ and HLMI from 7 to 30 g/10 min comprised of 35 to 48 weight percent first polyethylene resin and 52 to 65 weight percent second polyethylene resin.

12. The process of claim 11 where α

-olefin comonomer is butene-1.

13. The process of claim 12 wherein the multimodal polyethylene resin has a density from 0.945 to 0.956 g/cm³ and HLMI from 7 to 20 g/cm³.

14. A multimodal polyethylene resin comprised of a first lower molecular weight higher density polyethylene component and a second higher molecular weight lower density polyethylene component produced by the process of claim 1.

15. The multimodal polyethylene resin of claim 14 having a density from 0.942 to 0.958 g/cm³, HLMI from 7 to 30 g/10 min and comprised of 35 to 48 weight percent first polyethylene component and 52 to 65 weight percent second polyethylene component.