Methods for controlling polymer properties

Patent metadata

Field	Value
Publication number	US-2016297907-A1
Application number	US-201415037548-A
Country	US
Kind code	A1
Filing date	Sep 25, 2014
Priority date	Nov 21, 2013
Publication date	Oct 13, 2016
Grant date	—

Abstract

Disclosed herein are methods of controlling polymer properties in polymerization processes that use a chromium-based catalyst. An embodiment discloses a method of producing a polyolefin comprising: contacting a reaction mixture and a reduced chromium oxide catalyst in a gas-phase reactor to produce the polyolefin, wherein the reaction mixture comprises a monomer and a co-monomer; and changing a reaction temperature in the gas-phase reactor by about 1° C. or more whereby a gas molar ratio of the co-monomer to the monomer is changed by about 2% or more and a co-monomer content of the polyolefin at substantially constant density is changed by about 2% or more. Additional methods and compositions are also provided.

First claim

1 . A method of producing a polyolefin comprising:
contacting a reaction mixture and a reduced chromium oxide catalyst in a gas-phase reactor to produce the polyolefin, wherein the reaction mixture comprises a monomer and a co-monomer; and changing a reaction temperature in the gas-phase reactor by about 1° C. or more whereby a gas molar ratio of the co-monomer to the monomer is changed by about 2% or more and a co-monomer content of the polyolefin at substantially constant density is changed by about 2% or more.

2 . The method of claim 1 wherein the reduced chromium oxide catalyst has been reduced with an alkyl aluminum alkoxide.

3 . The method of claim 2 wherein the alkyl aluminum alkoxide comprises diethyl aluminum ethoxide.

4 . The method of claim 1 wherein the monomer comprises ethylene.

5 . The method of claim 1 wherein the co-monomer comprises an alpha olefin comprising from 3 carbons to 20 carbons.

6 . The method of claim 1 wherein the reaction temperature in the gas-phase reactor is changed by about 2° C. or more.

7 . The method of claim 1 wherein the reaction temperature in the gas-phase reactor is changed by about 5° C. or more.

8 . The method of claim 1 wherein the comonomer content of the polyolefin at substantially constant density is changed by about 5% or more.

9 . The method of claim 1 wherein the comonomer content of the polyolefin at substantially constant density is changed by about 25% or more.

10 . The method of claim 1 wherein the changing the reaction temperature comprises increasing the reaction temperature to lower the comonomer content of the polyolefin.

11 . The method of claim 1 wherein the changing the reaction temperature comprises decreasing the reaction temperature to increase the comonomer content of the polyolefin.

12 . The method according to claim 1 wherein the polyolefin is characterized by (i) a modified-Charpy impact strength of about 20 kJ/m 2 or more and (ii) an equivalent stress cracking resistance of about 50 hours or more determined by notched constant ligament stress.

13 . The method according to claim 1 wherein the polyolefin is characterized by (i) a modified-Charpy impact strength of about 22 kJ/m 2 or more and (ii) an equivalent stress cracking resistance of about 30 hours or more determined by notched constant ligament stress.

14 . The method of claim 1 wherein the polyolefin is characterized by a melt flow index ranging from about 0.1 g/10 min to about 1000 g/10 min.

15 . The method of claim 1 wherein the notched constant ligament stress at 900 psi of the polyolefin is represented by the following formula:
nCLS @900 psi actual,hr=24503.5−21.05×(flow index of the polyolefin)−25415×(density of the polyolefin)−6.539×(modified-Charpy impact strength of the polyolefin@−20° C.,kJ/m 2 ).

16 .- 26 . (canceled)

27 . A composition comprising:
a reduced chromium oxide-catalyzed polyolefin, wherein the reduced chromium oxide-catalyzed polyolefin is characterized by (i) a modified-Charpy impact strength of about 22 kJ/m 2 or more and (ii) an equivalent stress cracking resistance of about 30 hours or more determined by notched constant ligament stress.

28 . The composition of claim 27 wherein the modified-Charpy impact strength of the chromium-catalyzed polyolefin is about 22 kJ/m 2 to 24 about kJ/m 2 .

29 . The composition of claim 27 wherein the equivalent stress cracking resistance of the chromium-catalyzed polyolefin is about 60 hours or more.

30 .- 32 . (canceled)

Assignees

• Univation Tech Llc

Inventors

• Goode Mark G
• Alexandre Francois
• Cann Kevin J
• Kopp Barbara J
• Matthews William A
• Moorehouse John H
• Mure Cliff R

Classifications

• C08L23/08 Primary

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

• C08F2/34 Primary

  Polymerisation in gaseous state · CPC title

• C08F210/16 Primary

  Copolymers of ethene with alpha-alkenes, e.g. EP rubbers · CPC title

• C08F210/14

  Monomers containing five or more carbon atoms · CPC title

• C08L23/0815

  with aliphatic 1-olefins containing one carbon-to-carbon double bond · CPC title