Process for polymerization in a fluidized bed reactor

• US 9,708,427 B2
• Filed: 05/24/2016
• Issued: 07/18/2017
• Est. Priority Date: 05/26/2015
• Status: Active Grant

• Current Assignee: Nova Chemicals
• Original Assignee: Nova Chemicals
• Inventors: Guillen-Castellanos, Sergio Alejandro, Ker, Victoria, Jiang, Yan
• Primary Examiner(s): LU, C CAIXIA
• Application Number:
  US15/163,187
• Publication Number:
  US 20160347878A1
• Time in Patent Office: 420 Days
• 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 2/005 by addition of a scale inhibitor to the polymerisation medium
• CPC Class Codes: C08F 2/34 Polymerisation in gaseous state
• 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 2410/02 Anti-static agent incorporated into the catalyst
• CPC Class Codes: C08F 2420/04 Cp or analog not bridged to a non-Cp X ancillary anionic donor
• CPC Class Codes: C08F 2500/04 Broad molecular weight distribution, i.e. Mw/Mn > 6
• CPC Class Codes: C08F 2500/12 Melt flow index or melt flow ratio
• 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 4/6592 containing at least one cyclopentadienyl ring, condensed or not, e.g. an indenyl or a fluorenyl ring
• CPC Class Codes: C08L 23/08 Copolymers of ethene C08L23/16 takes precedence

Abstract

A polymerization process for stable gas phase reactor start-up when making ethylene copolymers having relatively high molecular weight distribution and melt flow ratio.

Claims

1. A process for polymerization in a gas phase reactor, the process comprising:

a) fluidizing a bed of polymer particles in a reactor with a gas mixture comprising ethylene and one or more alpha olefin at a first hydrogen concentration [H₂]^A;

b) introducing a single site catalyst system to the reactor to initiate a polymerization reaction;

c) polymerizing the ethylene and the one or more alpha olefin at a first reactor temperature, T^A to give a first ethylene copolymer with a first melt index, I₂^A, a first melt flow ratio, (I₂₁/I₂)^A, and a first density, d^A, until at least one reactor bed volume has turned over, where a reactor bed volume is defined as the volume of the reactor from a reactor distributor bed plate to the top of the fluidized bed; and

d) subsequently reducing the hydrogen concentration and the reaction temperature to a second hydrogen concentration [H₂]^B and a second reactor temperature T^B, respectively, to give a second ethylene copolymer with a second melt index, I₂^B, a second melt flow ratio, (I₂₁/I₂)^B, and a second density, d^B;

wherein the first melt index, I₂^A is greater than the second melt index, I₂^B.

2. The process of claim 1 wherein the second melt flow ratio, (I₂₁/I₂)^B is greater than the first melt flow ratio, (I₂₁/I₂)^A.

3. The process of claim 1 wherein the first and second ethylene copolymers each have a melt flow ratio, (I₂₁/I₂) of from 20 to 50.

4. The process of claim 2 wherein the first and second ethylene copolymers each have a melt flow ratio, (I₂₁/I₂) of from 20 to 50.

5. The process of claim 1 wherein the first melt flow ratio, (I₂₁/I₂)^A is at least 25.

6. The process of claim 1 wherein the second melt flow ratio, (I₂₁/I₂)^B is at least 30.

7. The process of claim 5 wherein the second melt flow ratio, (I₂₁/I₂)^B is at least 30.

8. The process of claim 1 wherein the first melt flow ratio, (I₂₁/I₂)^A is less than 33.0.

9. The process of claim 1 wherein the second ethylene copolymer has a second melt flow ratio, (I₂₁/I₂)^B of at least 33.0.

10. The process of claim 8 wherein the second ethylene copolymer has a second melt flow ratio, (I₂₁/I₂)^B of at least 33.0.

11. The process of claim 1 wherein the first melt index, I₂^A is greater than 1 g/10 min.

12. The process of claim 1 wherein the second melt index, I₂^B is less than 1 g/10 min.

13. The process of claim 11 wherein the second melt index, I₂^B is less than 1 g/10 min.

14. The process of claim 1 wherein the first density, d^A is greater than the second density, d^B.

15. The process of claim 1 wherein the first and second ethylene copolymers each have a density of from 0.912 to 0.937 g/cm³.

16. The process of claim 14 wherein the first and second ethylene copolymers each have a density of from 0.912 to 0.937 g/cm³.

17. The process of claim 1 wherein the second ethylene copolymer has a molecular weight distribution (M_w/M_n) which is greater than the molecular weight distribution (M_w/M_n) of first ethylene copolymer.

18. The process of claim 1 wherein the first and second ethylene copolymers each have a molecular weight distribution (M_w/M_n) of from 3.5 to 6.0.

19. The process of claim 17 wherein the first and second ethylene copolymers each have a molecular weight distribution (M_w/M_n) of from 3.5 to 6.0.

20. The process of claim 1 wherein the first reactor temperature, T^A and the second reactor temperature, T^B differ by at least 2°

C.

21. The process of claim 1 wherein the first hydrogen concentration [H₂]^A and the second hydrogen concentration [H₂]^B differ by at least 15 ppm.

22. The process of claim 20 wherein the first hydrogen concentration [H₂]^A and the second hydrogen concentration [H₂]^B differ by at least 15 ppm.

23. The process of claim 1 wherein the single site catalyst system comprises a phosphinimine catalyst.

24. The process of claim 1 wherein single site catalyst system comprises a phosphinimine catalyst having the formula:

(L)(PI)MX₂, where M is Ti, Zr or Hf;

PI is a phosphinimine ligand having the formula R₃P═

N—

, where R is independently selected from hydrogen, halogen, and C₁-C₂₀ hydrocarbyl;

L is a ligand selected from indenyl, or substituted indenyl; and

X is an activatable ligand.

25. The process of claim 1 wherein the single site catalyst system comprises a phosphinimine catalyst having the formula:

(1-R²-Indenyl)Ti(N═

P(t-Bu)₃)X₂;

wherein R² is a substituted or unsubstituted alkyl group, a substituted or an unsubstituted aryl group, or a substituted or unsubstituted benzyl group, wherein substituents for the alkyl, aryl or benzyl group are selected from alkyl, aryl, alkoxy, aryloxy, alkylaryl, arylalkyl and halide substituents; and

wherein X is an activatable ligand.