CONTINUOUS SYNTHESIS OF AN ETHYLENE AND BUTADIENE COPOLYMER

• US 20200131288A1
• Filed: 04/16/2018
• Published: 04/30/2020
• Est. Priority Date: 04/18/2017
• Status: Active Grant

• Current Assignee: Compagnie générale des établissements Michelin
• Original Assignee: Compagnie générale des établissements Michelin
• Inventors: THUILLIEZ, Julien, PACHECO, Nuno
• Granted Patent: US 11,136,422 B2
• Time in Patent Office: Days
• CPC Class Codes: C08F 210/02 Ethene
• CPC Class Codes: C08F 236/06 Butadiene
• CPC Class Codes: C08F 2500/03 Narrow molecular weight distribution, i.e. Mw/Mn < 3
• CPC Class Codes: C08F 2500/21 Rubbery or elastomeric properties
• CPC Class Codes: C08F 4/52 selected from boron, aluminium, gallium, indium, thallium or rare earths C08F4/14 takes precedence

Abstract

A process for the synthesis of an ethylene/butadiene copolymer is provided. The process is continuous and comprises:

a. feeding at least one stirred polymerization reactor with a mixture of ethylene, butadiene, hydrocarbon-based solvent and catalytic system allowing the formation of cyclic trans-1,2-cyclohexane units in the polymer chain with a mole ratio of ethylene to the sum of the ethylene and butadiene monomers ranging from 0.5 to 0.99; the concentration of ethylene and butadiene monomers in the polymerization reaction medium being at least 10% by weight relative to the total weight; the operating pressure of the reactor is greater than or equal to the saturated vapour pressure of the polymerization reaction medium;

b. recovering the ethylene/butadiene copolymer, this copolymer comprising, statistically distributed, ethylene units, butadiene units and trans-1,2-cyclohexane units, the molar fraction of ethylene units in the copolymer being greater than or equal to 50%.

Claims

1. A process for the synthesis of an ethylene/butadiene copolymer, wherein the process is continuous and comprises the following steps:

a. feeding at least one stirred polymerization reactor with a mixture of ethylene, butadiene, hydrocarbon-based solvent and catalytic system allowing the formation of cyclic trans-1,2-cyclohexane units in the polymer chain with a mole ratio of ethylene to the sum of the ethylene and butadiene monomers, defined by QnE/(QnE+QnB), with QnE the molar flow rate of ethylene and QnB the molar flow rate of butadiene, ranging from 0.5 to 0.99;

the concentration of ethylene and butadiene monomers in the polymerization reaction medium being at least 10% by weight relative to the total weight;

the operating pressure of the reactor is greater than or equal to the saturated vapour pressure of the polymerization reaction medium; and

b. recovering the ethylene/butadiene copolymer, this copolymer comprising, statistically distributed, ethylene units, butadiene units and trans-1,2-cyclohexane units, the molar fraction of ethylene units in said copolymer being greater than or equal to 50%, relative to the total number of moles of ethylene, butadiene and trans-1,2-cyclohexane units.

2. The synthesis process according to claim 1, wherein the mole ratio of ethylene, (QnE/(QnE+QnB)), ranges from 0.70 to 0.99.

3. The synthesis process according to claim 1, wherein the ratio of flow rate by weight of monomers and of the mixture, defined by (QmE+QmB)/(Qm total), with QmE the flow rate by weight of ethylene, QmB the flow rate by weight of butadiene and Qm total the flow rate by weight of the mixture, ranges from 0.15 to 0.95.

4. The synthesis process according to claim 1, wherein the residence time per polymerization reactor is less than 120 min.

5. The synthesis process according to claim 1, wherein N reactors, where N ranges from 2 to less than 10, are mounted in series and

the first reactor (reactor 1) is fed with ethylene, butadiene, solvent and catalytic system, wherein the mole ratio of ethylene, (QnE/(QnE+QnB)), ranges from 0.70 to 0.99, the ratio of the flow rate by weight of monomers and of the mixture, defined by (QmE+QmB)/(Qm total), with QmE the flow rate by weight of ethylene, QmB the flow rate by weight of butadiene, and Qm total the flow rate by weight of the mixture, ranges from 0.15 to 0.95, and the output thereof feeds the next reactor;

the final reactor (reactor N) is fed from the reactor which precedes it (reactor N−

1), and the output thereof feeds the polymer recovery step;

each reactor between the first and the last (when N is greater than

     2) is fed by the output of the reactor which precedes it (reactor N−

1) and the output thereof feeds the reactor which follows it (reactor N+1).

6. The synthesis process according to claim 5, wherein each reactor, after the first, is also fed with a make-up stream of ethylene and butadiene so that the monomer concentration is identical at each reactor inlet.

7. The synthesis process according to claim 1, wherein the concentration of ethylene and butadiene monomers in the polymerization reaction medium is at least 15% by weight relative to the total weight.

8. The synthesis process according to claim 1, wherein the polymerization temperature is between 50°

C. and 90°

C.

9. The synthesis process according to claim 1, wherein the polymerization temperature is greater than or equal to 90°

C. and the concentration of ethylene and butadiene monomers in the polymerization reaction medium is at least 15% by weight relative to the total weight.

10. The synthesis process according to claim 1, wherein the polymerization reactor is a liquid single-phase reactor.

11. The synthesis process according to claim 10, wherein the operating pressure of the reactor is at least 5 bar greater than the saturated vapour pressure of the mixture fed to the polymerization reactor.

12. The synthesis process according to claim 1, wherein the polymerization reactor is a gas/liquid two-phase reactor and the operating pressure of the reactor is equal to the saturated vapour pressure of the mixture.

13. The synthesis process according to claim 1, wherein the hydrocarbon-based solvent is selected from C₂ to C₃₀ alkanes, branched C₄ to C₃₀ alkanes, cyclic C₅-C₆ alkanes, branched cyclic C₆-C₃₀ alkanes, C₆-C₃₀ aromatic solvents and mixtures of these products.

14. The synthesis process according to claim 1, wherein the catalytic system comprises at least two constituents, the constituents including a metallocene corresponding to formula (I):

[P(Cp¹)(Cp²)Met] 

 

(I)

with;

Met being a group comprising;

at least one scandium or yttrium atom or one atom of lanthanide, the atomic number of which ranges from 57 to 71,

at least one monovalent ligand, belonging to the halogen group, or to the amide, alkyl or borohydride group,

optionally other constituents,

P being a group, based on at least one silicon or carbon atom, bridging the two groups Cp¹ and Cp²

Cp¹ and Cp² are identical to or different from one another,

when Cp¹ and Cp² are identical to one another, they are selected from indenyls substituted in the 2 position, or from substituted or unsubstituted fluorenyls,

when Cp¹ and Cp² are different from one another, Cp¹ is selected from substituted or unsubstituted fluorenyls, and Cp² is selected from cyclopentadienyls substituted in the 2 and 5 positions, from indenyls substituted in the 2 position, or from substituted fluorenyls; and

the constituents including a co-catalyst which is an alkyl magnesium, an alkyl lithium, an alkyl aluminium, a Grignard reagent or a mixture of these constituents.

15. The synthesis process according to claim 1, wherein the microstructure of the copolymer obtained is homogeneous and thus the molar concentration of each of the units is constant all along the copolymer chain.

16. The synthesis process according to claim 1, wherein, in the copolymer obtained, the molar fraction of ethylene units ranges from 50 mol % to 95 mol %, relative to the total number of moles of ethylene, butadiene and trans-1,2-cyclohexane units.

17. The synthesis process according to claim 1, wherein, in the copolymer obtained, the molar fraction of trans-1,2-cyclohexane units is less than or equal to 6%, relative to the total number of moles of ethylene, butadiene and trans-1,2-cyclohexane units.

18. The synthesis process according to claim 1, wherein the copolymer obtained has a degree of crystallinity of less than 20%.

19. The synthesis process according to claim 14, wherein Cp¹ and Cp² are identical to one another and are an indenyl substituted in the 2 position selected from 2-methylindene or 2-phenylindene, or a substituted or an unsubstituted fluorenyl selected from fluorenyl, 2,7-di-tert-butylfluorenyl, or 3,6-di-tert-butylfluorenyl.

20. The synthesis process according to claim 14, wherein Cp1 and Cp2 are different from one another and wherein:

Cp¹ is a substituted or unsubstituted fluorenyl selected from fluorenyl, 2,7-di-tert-butylfluorenyl, or 3,6-di-tert-butylfluorenyl,

Cp² is a cyclopentadienyl substituted in the 2 and 5 positions, said cyclopentadienyl being tetramethylcyclopentadiene, an indenyl substituted in the 2 position selected from 2-methylindene or 2-phenylindene, or a substituted fluorenyl selected from 2,7-di-tert-butylfluorenyl or 3,6-di-tert-butylfluorenyl.