Methods of making polyethylene polymer comprising polar comonomer and polymer compositions

Patent metadata

Field	Value
Publication number	US-9611343-B2
Application number	US-201314380158-A
Country	US
Kind code	B2
Filing date	Mar 1, 2013
Priority date	Apr 13, 2012
Publication date	Apr 4, 2017
Grant date	Apr 4, 2017

Abstract

A continuous process for producing high pressure polyethylene is described. The process includes contacting first amounts of ethylene, an optional polar comonomer, and a first C 2 to C 12 modifier in the presence of a first amount of initiator in a reaction system under polymerization conditions to form a reaction system effluent comprising a first polyethylene resin having a first concentration of unreacted monomer therein; and directing an ethylene stream and the reaction system effluent to a pressure separation unit operated at separation conditions thereby removing at least a portion of the unreacted monomer from the reaction system effluent.

First claim

What is claimed is:

1. A continuous process for producing high pressure polyethylene, comprising:
contacting a first amount of ethylene feed and a first amount of a C 2 to C 12 modifier in the presence of a first amount of initiator in a reaction system under polymerization conditions to form a reaction system effluent comprising a first polyethylene resin having a first concentration of an unreacted monomer therein;
directing a first ethylene stream and the reaction system effluent to one or more high pressure separation vessel(s) operated at separation conditions thereby removing at least a portion of the unreacted monomer from the reaction system effluent to form i) a polymer-rich liquid comprising the first polyethylene resin and at least a portion of unreacted monomer and ii) an ethylene recycle stream comprising unreacted monomer; and
directing a second ethylene stream and the polymer-rich liquid to one or more low pressure separation vessel(s) operated at separation conditions thereby removing at least a portion of the unreacted monomer from the polymer-rich liquid to form a purified polyethylene resin.

2. The process of claim 1 , further including providing a first amount of polar monomer, and contacting the first amount of ethylene feed, the first amount of a C 2 to C 12 modifier and the first amount of polar monomer, wherein the unreacted monomer comprises unreacted polar monomer.

3. The process of claim 2 , further including providing a second amount of ethylene feed, a second amount of polar monomer, and a second amount of a C 2 to C 12 modifier to the reaction system.

4. The process of claim 1 , wherein the first amount of a C 2 to C 12 modifier includes at least one saturated or unsaturated modifier.

5. The process of claim 1 , wherein at least a portion of the second ethylene stream comprises unreacted monomer from the ethylene recycle stream and the second ethylene stream provides an amount of ethylene at a temperature sufficient to cause a temperature drop at an inlet of the low pressure separation vessel(s) of from 10.0° C. to 140.0° C.

6. The process of claim 1 , wherein the separation conditions comprise a low pressure vessel pressure of less than 3.0 bar.

7. The process of claim 1 , wherein the reaction system is selected from the group consisting of single or multiple reaction zone tubular reactors, autoclave reactors, and combinations thereof.

8. The process of claim 2 , wherein the first amount of the first C 2 to C 12 modifier is from 0.4 wt. % to 4.0 wt. %, based on the total of: the first amount of ethylene, the first amount of C 2 to C 12 modifier, the first amount of polar monomer, and initiator in the reaction system.

9. The process of claim 2 , wherein the process provides a purified polyethylene resin comprising 0 wt. % to 95.0 wt. % polymer units derived from the polar monomer and 5.0 wt. % to 100.0 wt. % polymer units derived from ethylene, based on the total weight of the purified polyethylene resin.

10. The process of claim 1 , wherein the purified polyethylene resin has a second unreacted monomer concentration therein, the second unreacted monomer concentration being at least 50.0 wt. % less than the first concentration of the unreacted monomer in the first polyethylene resin.

11. The process of claim 1 , wherein the purified polyethylene resin has a second unreacted monomer concentration ≦2.5×10 3 ppm.

12. The process of claim 1 , wherein the purified polyethylene resin has a second unreacted monomer concentration ≦1.7×10 3 ppm.

13. The process of claim 1 , wherein the purified polyethylene resin has a melt index of 0.40×10 2 g/10 min. to about 35.0×10 2 g/10 min.

14. The process of claim 1 , wherein directing the second ethylene stream to the low pressure separation vessel(s) provides an amount of ethylene at a temperature sufficient to cause a temperature drop at an inlet of the low pressure separation vessel(s) of from 10.0° C. to 140.0° C.

15. The process of claim 1 , further comprising forming a purge gas stream comprising at least a portion of the unreacted monomer removed from the polymer-rich liquid and wherein the second ethylene stream is provided from the ethylene feed, the ethylene recycle stream, and/or the purge gas stream.

16. The process of claim 2 , wherein the purified polyethylene resin comprises 10.0 wt. % to about 50.0 wt. % polymer units derived from the polar monomer.

17. The process of claim 2 , wherein the purified polyethylene resin comprises 30.0 wt. % to about 35.0 wt. % polymer units derived from the polar monomer and has a melt index between about 0.40×10 2 g/10 min. to about 0.45×10 2 g/10 min.

18. A continuous process for producing a high pressure polyethylene, comprising:
contacting a first amount of ethylene, polar comonomer, and a first amount of a C 2 to C 12 modifier in the presence of a first amount of initiator in a reaction system at polymerization conditions, wherein a reaction system effluent comprises a polyethylene resin having a concentration of unreacted ethylene and polar monomer therein;
directing at least a portion of the unreacted ethylene from the reaction system effluent to an ethylene recycle stream;
directing the reaction system effluent and the ethylene recycle stream to a low pressure separation unit operated at separation conditions, the ethylene recycle stream being at a temperature sufficient to cause a temperature drop at the pressure separator inlet of from 10.0° C. to 140.0° C.;
continuing the reaction in the reaction system by contacting a second amount of ethylene, additional polar comonomer, and a second amount of a C 2 to C 12 modifier, wherein the first and second amounts of a C 2 to C 12 modifier may be the same or different; and
directing a purified polyethylene resin exiting the pressure separation unit to a pelletizing unit,

wherein the separation conditions comprise a separator pressure of 0.75 bar to 1.5 bar;
wherein the pressure separation unit provides the purified polyethylene resin having:
(a) an unreacted polar monomer concentration 50.0 wt. % to 60.0 wt. % less than the concentration of the unreacted polar monomer in the polyethylene resin of the reaction system effluent, wherein the polar monomer concentration is 1.0×10 3 ppm to 2.5×10 3 ppm at a pressure of 1.2 to 2.4 bar; and
(b) an unreacted ethylene concentration 1.5×10 3 ppm to 0.8×10 3 ppm at a pressure of 1.2 to 2.4 bar.

19. The method of claim 18 , wherein the purified polyethylene resin has a melt index of about 0.40×10 2 to 35.0×10 2 dg/min.

20. A pelletized polyethylene homopolymer or ethylene/alpha-olefin copolymer produced in a high pressure polymerization process, comprising at least 50.0 wt. % units derived from ethylene; 0.4 wt. % to 4.0 wt. % units derived from a C 2 to C 12 modifier, based on the total weight of the polyethylene homopolymer or ethylene/alpha-olefin copolymer, the polyethylene homopolymer or ethylene/alpha-olefin copolymer having therein an unreacted ethylene concentration of 1.5×10 3 ppm to 0.8×10 3 ppm; wherein the polyethylene homopolymer or ethylene/alpha-olefin copolymer has a melt index as measured according to ASTM D1238 (2.16 kg, 190° C.) from 0.40×10 2 to 35.0×10 2 dg/min.

21. The pelletized polyethylene homopolymer or ethylene/alpha-olefin copolymer of claim 20 having at least 20.0 wt. % units derived from the polar monomer and having therein an unreacted polar monomer concentration of 1.0×10 3 ppm to 2.5×10 3 ppm.

22.

Assignees

• Exxonmobil Chemical Patents Inc

Inventors

• Garland Jr Don A
• Graham Michael L

Classifications

• C08F6/001 Primary

  Removal of residual monomers by physical means · CPC title

• C08F20/10

  Esters · CPC title

• C08F2/01

  characterised by special features of the polymerisation apparatus used · CPC title

• B01J2219/00006

  Large-scale industrial plants · CPC title

• C08J3/124

  Treatment for improving the free-flowing characteristics · CPC title