Process for producing polydienes
A method for producing a polydiene, the method comprising the steps of (i) forming an active catalyst by combining a lanthanide-containing compound, an alkylating agent, and a halogen source in the substantial absence of an organosulfide; and (ii) polymerizing conjugated diene monomer in the presence of the active catalyst and an organosulfide.
1. A method for producing a polydiene, the method comprising the steps of:
(i) forming an active catalyst by combining a lanthanide-containing compound, an alkylating agent, and a halogen source in the substantial absence of an organosulfide; and
(ii) polymerizing conjugated diene monomer in the presence of the active catalyst and an organosulfide defined by the formula:
R—S—R
where each R is independently a monovalent organic group, or where two R groups combine to form a divalent group.
2. The method of claim 1 , where the active catalyst is preformed.
3. The method of claim 2 , where the active catalyst is preformed in the presence of conjugated diene monomer, and where the amount of the lanthanide-containing compound employed in said step of forming an active catalyst is greater than 2 mmol of lanthanide-containing compound per 100 g of monomer.
4. The method of claim 1 , where the active catalyst employed in said step of polymerizing includes less than 2 mmol of lanthanide-containing compound per 100 g of conjugated diene monomer.
5. The method of claim 1 , where said step of forming takes place in the presence of less than 10 mole of the organosulfide per mole of lanthanide metal in said lanthanide-containing compound.
6. The method of claim 1 , where said step of forming takes place in the complete absence of an organosulfide.
7. The method of claim 1 , where the active catalyst is formed in situ in the presence of the conjugated diene monomer by introducing less than 2 mmol of lanthanide-containing compound per 100 g of the conjugated diene monomer.
8. The method of claim 1 , where the alkylating agent includes methylaluminoxane.
9. The method of claim 8 , where the halogen source includes a bromine-containing compound.
10. The method of claim 1 , where said step of polymerizing takes place within a polymerization mixture including less than 20% by weight of organic solvent based upon the total weight of the polymerization mixture.
11. The method of claim 1 , where the molar ratio of the organosulfide to the lanthanide-containing compound is from about 1 to about 120.
12. The method of claim 1 , where said step of polymerizing produces a polydiene having a reactive chain end, and further comprising the step of reacting a functionalizing agent with the reactive chain end.
13. The method of claim 1 , further comprising the step of introducing the organosulfide to the active catalyst prior to said step of polymerizing.
14. The method of claim 1 , further comprising the step of directly and individually introducing the organosulfide to the conjugated diene monomer.
15. A method for producing a polydiene, the method comprising the steps of:
(i) preparing a preformed catalyst by introducing a lanthanide-containing compound, an alkylating agent, a halogen source, and optionally monomer;
(ii) independent of step (i), introducing a organosulfide; and
(iii) polymerizing conjugated diene monomer with the preformed catalyst in the presence of the organosulfide defined by the formula:
R—S—R
where each R is independently a monovalent organic group, or where two R groups combine to form a divalent group.
16. The method of claim 15 , where said step of introducing an organosulfide to conjugated diene monomer forms an organosulfide/monomer blend, and where said step of polymerizing the conjugated diene monomer takes place within the organosulfide/monomer blend.
17. The method of claim 15 , where the organosulfide and the preformed catalyst are introduced to the conjugated diene monomer simultaneously.
18. The method of claim 17 , where the organosulfide and the preformed catalyst are introduced to the conjugated diene monomer within a single stream.
19. The method of claim 17 , where the organosulfide and the preformed catalyst are introduced separately to the conjugated diene monomer.
20. The method of claim 15 , where the preformed catalyst is introduced to the conjugated diene monomer after said step of introducing an organosulfide to the conjugated diene monomer.
21. The method of claim 15 , where the preformed catalyst is introduced to the conjugated diene monomer prior to said step of introducing a organosulfide to the conjugated diene monomer.