Process for continuous solution polymerization

Patent metadata

Field	Value
Publication number	US-9815913-B2
Application number	US-201615144493-A
Country	US
Kind code	B2
Filing date	May 2, 2016
Priority date	Jun 15, 2015
Publication date	Nov 14, 2017
Grant date	Nov 14, 2017

Abstract

Described herein are methods for continuous solution polymerization. The method may comprise polymerizing one or more monomers and comonomers in the presence of a solvent in a polymerization reactor to produce a polymer solution; determining the composition of the polymer solution exiting the polymerization reactor in an on-line fashion; determining at least one of the critical pressure or critical temperature; comparing the critical pressure and/or critical temperature to the actual temperature of the polymer solution and the actual pressure of the polymer solution; heating or cooling the polymer solution to a temperature within 50° C. of the critical temperature; and passing the polymer solution through a pressure letdown valve into a liquid-liquid separator, where the pressure of the polymer solution is reduced or raised to a pressure within 50 psig of the critical pressure to induce a separation of the polymer solution into two liquid phases.

First claim

What is claimed is:

1. A method for continuous solution polymerization comprising:
(a) polymerizing one or more monomers and comonomers in the presence of a solvent in a polymerization reactor to produce a polymer solution comprising solvent, polymer, and unreacted monomer and comonomer;
(b) determining the composition of the polymer solution exiting the polymerization reactor in an on-line fashion;
(c) determining the critical pressure and critical temperature of the polymer solution;
(d) comparing the critical temperature to the actual temperature of the polymer solution and heating or cooling the polymer solution to a temperature within 50° C. of the critical temperature;
(e) comparing the critical pressure to the actual pressure of the polymer solution and passing the polymer solution through a pressure letdown valve into a liquid-liquid separator, where the pressure of the polymer solution is reduced or raised to a pressure within 50 psig of the critical pressure to induce a separation of the polymer solution into two liquid phases, a polymer-rich phase and a polymer-lean phase;
(f) recovering the polymer-rich phase from the liquid-liquid separator;
(g) devolatizing the polymer-rich phase to obtain polymer.

2. The method of claim 1 , wherein the polymerization reactor is a solution polymerization reactor.

3. The method of claim 1 , where the monomer is ethylene and the comonomer comprises propylene and, optionally, diene.

4. The method of claim 1 , wherein the polymer that is obtained is an ethylene-propylene-diene rubber or a propylene-based elastomer.

5. The method of claim 1 , wherein the composition of the polymer solution exiting the polymerization reactor is determined at least once every hour.

6. The method of claim 1 , wherein the composition of the polymer solution exiting the polymerization reactor is determined at least once very twenty minutes.

7. The method of claim 1 , where determining the composition of the polymer solution exiting the polymerization reactor comprises utilizing a gas chromatography analyzer or a Raman analyzer to measure the molar fraction of the solvent, unreacted monomer, unreacted comonomer, and polymer in the polymer solution.

8. The method of claim 1 , wherein the critical pressure and critical temperature are determined utilizing the Heidermann-Khalil formulation of solution criticality which utilizes the Peng-Robinson or Soave-Redlich-Kwong equations of state.

9. The method of claim 1 , wherein the polymer solution is heated to a temperature that is less than the critical temperature.

10. The method of claim 1 , comprising heating the polymer solution to a temperature that is within 10° C. of the critical temperature.

11. The method of claim 1 , comprising reducing the polymer solution to a pressure that is within 20 psig of the critical pressure.

12. The method of claim 1 , wherein the polymer solution comprises 5 to 15 wt % of polymer as it exits the polymerization reactor.

13. The method of claim 1 , wherein the polymer-lean phase comprises less than 0.3 wt % of polymer.

14. The method of claim 1 , wherein the polymer rich phase comprises 20 to 40 wt % of polymer.

Assignees

• Exxonmobil Chemical Patents Inc

Inventors

• Costin Quintin P W
• Duvall Philip M
• Reimers Jay L

Classifications

• C08F210/16

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

• C08F6/12

  Separation of polymers from solutions · CPC title

• C08F210/18

  with non-conjugated dienes, e.g. EPT rubbers · CPC title

• C08F6/003

  from polymer solutions, suspensions, dispersions or emulsions without recovery of the polymer therefrom · CPC title

• C08F2/04 Primary

  Polymerisation in solution (C08F2/32 takes precedence) · CPC title