Processes for producing polyolefins and impact copolymers with broad molecular weight distribution and high stiffness

Patent metadata

Field	Value
Publication number	US-12435167-B2
Application number	US-202017640172-A
Country	US
Kind code	B2
Filing date	Aug 14, 2020
Priority date	Sep 5, 2019
Publication date	Oct 7, 2025
Grant date	Oct 7, 2025

Abstract

Provided herein are methods of polymerizing α-olefin monomer with a catalyst and hydrogen in a slurry to produce low molecular weight polyolefins. Hydrogen is vented from the low molecular weight polyolefins and then the low molecular weight polyolefins are further polymerized in a gas phase to produce a polyolefin having a molecular weight distribution of between 4.0 and 30 and a flexural modulus between 1500 mPa and 2500 mPa.

First claim

The invention claimed is:

1. A method for producing polyolefin comprising the steps of:
polymerizing α-olefin monomers with a catalyst and hydrogen in a slurry to produce a low molecular weight polyolefin having a weight average molecular weight between 20 kDa to 200 kDa;
venting hydrogen from the low molecular weight polyolefin; and
polymerizing the low molecular weight polyolefin and α-olefin monomers in the presence of catalyst having a mole ratio of hydrogen to α-olefin monomers of between 0 to 0.01 to produce polyolefin having a molecular weight distribution of between 4.0 and 20.0 and a flexural modulus between 1500 mPa and 2500 mPa.

2. The method of claim 1 , wherein the α-olefin monomers are propylene and the polyolefin is polypropylene.

3. The method of claim 2 , further comprising the steps of venting the propylene monomers from the polypropylene and polymerizing the polypropylene with ethylene and propylene in a second gas phase to produce a polypropylene impact copolymer having a weight average molecular weight between 120 kDa and 280 kDa.

4. The method of claim 1 , wherein propylene monomer is recycled to the slurry phase polymerization reactor.

5. The method of claim 1 , wherein the polyolefin has a molecular weight distribution (Mw/Mn) between 5 to 10.

6. The method of claim 1 , wherein pressure of the slurry and/or the slurry polymerization reactor is between 480 psig to 650 psig.

7. The method of claim 1 , wherein temperature of the slurry and/or the slurry polymerization reactor is between 65° C. and 75° C.

8. The method of claim 1 , wherein pressure of the gas phase and/or the gas phase polymerization reactor is between 180 psig to 250 psig.

9. The method of claim 1 , wherein temperature of the gas phase and/or the gas phase polymerization reactor is between 65° C. and 85° C.

10. The method of claim 1 , wherein reaction residence time in the slurry and/or the slurry polymerization reactor is between 40 minutes to 70 minutes.

11. The method of claim 1 , wherein a residence time in the gas phase and/or the gas phase polymerization reactor is between 80 minutes to 150 minutes.

12. The method of claim 1 , wherein hydrogen is fed to the slurry and/or the slurry polymerization reactor at a flow rate between 2500 sccm to 3500 sccm.

13. The method of claim 2 , wherein the polypropylene has a melt flow rate (230° C./2.16 kg) within a range of from 0.1 g/10 min to 500 g/10 min.

14. The method of claim 3 , wherein the impact copolymer has a melt flow rate (230° C./2.16 kg) within a range of from 0.1 g/10 min to 200 g/10 min.

15. The method of claim 1 , wherein the α-olefin monomers, the catalyst and hydrogen are prepolymerized.

16. A method for producing polypropylene comprising the steps of:
reacting propylene monomer with a catalyst and hydrogen in a slurry to produce a low molecular weight polypropylene having a weight average molecular weight (Mw) of between 20 kDa and 150 kDa wherein a mole ratio of hydrogen in the slurry to propylene monomer is between 0.006 to 0.03;
venting hydrogen from the low molecular weight polypropylene; and
polymerizing the low molecular weight polypropylene in a gas phase to produce polypropylene having a weight average molecular weight of between 500 kDa to 800 kDa, a molecular weight distribution of between 6.5 and 30 and a flexural modulus of at least 1500 mPa.

17. A method for producing polypropylene comprising the steps of:
contacting a propylene monomer with a catalyst in hydrogen in a slurry polymerization reactor to produce an effluent comprising a low molecular weight polypropylene having a weight average molecular weight between 20 kDa to 200 kDa, hydrogen, and propylene monomer;
venting hydrogen from the effluent; and
feeding the effluent into a gas phase polymerization reactor to produce polypropylene having a molecular weight distribution of between 4.0 and 30 and a flexural modulus between 1500 mPa and 2500 mPa, wherein a mole ratio of hydrogen to propylene monomer in the gas phase is between 0 to 0.01.

18. The method of claim 17 , wherein the effluent is continuously or intermittently withdrawn from the slurry polymerization reactors.

19. The method of claim 17 , further comprising the step of polymerizing the polypropylene with ethylene and propylene in a second gas phase polymerization reactor and without hydrogen to produce an impact copolymer.

20. The method of claim 19 , wherein a second effluent is drawn from the second gas phase polymerization reactor and the second effluent comprises the impact copolymer.

Assignees

• Exxonmobil Chemical Patents Inc

Inventors

• Zhang Xiaodan
• Bauch Christopher G
• Luo Lubin
• Brinen Jeffrey L
• Pehlert George J
• Edwards Todd S
• Kim Sung A

Classifications

• C08L23/12

  Polypropene · CPC title

• C08L2314/02

  Ziegler natta catalyst · CPC title

• C08L2308/00

  Chemical blending or stepwise polymerisation process with the same catalyst · CPC title

• C08L2205/025

  containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure · CPC title

• C08L23/14

  Copolymers of propene (C08L23/16 takes precedence) · CPC title