Conjugated diene polymer, method for producing conjugated diene polymer, and conjugated diene polymer composition

1. A conjugated diene polymer comprising a conjugated diene-based monomer unit and a group represented by Formula (I) below, wherein at least peaks H, M, and L below are present in a molecular weight distribution curve obtained by gel permeation chromatography measurement, and when the total area of the molecular weight distribution curve is 100%, the total peak area of peak H is 3% to 30%, the total peak area of peak M is 5% to 45%, and the total peak area of peak L is 40% to 80%

(in Formula (I), R 1 and R 2 independently denote a hydrocarbon group having 1 to 4 carbon atoms, a hydrocarbonoxy group having 1 to 4 carbon atoms, a hydroxy group, or a polymer chain comprising a conjugated diene-based monomer unit, m denotes an integer of 0 to 10, and A 1 denotes a polar functional group that does not have an active hydrogen)

Peak H: a peak for which the molecular weight at the peak top is higher than the molecular weight at the peak top of peak M

Peak M: a peak for which, when the molecular weight at the peak top of peak H is MH, the molecular weight at the peak top is 0.6×MH to 0.8×MH

Peak L: a peak for which, when the molecular weight at the peak top of peak H is MH, the molecular weight at the peak top is 0.2×MH to 0.4×MH.

2. The conjugated diene polymer according to claim 1 , wherein A 1 in Formula (I) is a group represented by Formula (II) or (III) below

(in Formula (II), R 3 and R 4 independently denote a hydrocarbon group having 1 to 8 carbon atoms and optionally having a nitrogen atom, an oxygen atom, or a silicon atom, or R 3 and R 4 are bonded and represent a divalent hydrocarbon group having 2 to 20 carbon atoms and optionally having a nitrogen atom, an oxygen atom, or a silicon atom)

(in Formula (III), X denotes a divalent hydrocarbon group having 1 to 6 carbon atoms and optionally having an oxygen atom, and R 5 denotes hydrogen or a hydrocarbon group having 1 to 6 carbon atoms).

3. The conjugated diene polymer according to claim 1 , wherein it further comprises an aromatic vinyl-based monomer unit.

4. The conjugated diene polymer according to claim 3 , wherein, when the total amount of the conjugated diene-based monomer unit and the aromatic vinyl-based monomer unit is 100 wt %, the aromatic vinyl-based monomer unit is at least 10 wt % but no greater than 50 wt %.

5. The conjugated diene polymer according to claim 1 , wherein, when the total area of the molecular weight distribution curve is 100%, the total peak area of the peak H is at least 5% but no greater than 25%, the total peak area of the peak M is at least 10% but no greater than 40%, and the total peak area of the peak L is at least 50% but no greater than 70%.

6. The conjugated diene polymer according to claim 1 , wherein it has a Mooney viscosity measured at 100° C. in accordance with JIS K6300 of at least 10 but no greater than 200.

7. The conjugated diene polymer according to claim 1 , wherein, when the content of the conjugated diene-based monomer unit is 100 mole %, the amount of vinyl bonds of the conjugated diene polymer is at least 10 mole % but no greater than 70 mole %.

8. The conjugated diene polymer according to claim 1 , wherein the conjugated diene polymer is a modified conjugated diene polymer obtained by reacting, with a silicon compound represented by Formula (IV), a conjugated diene polymer obtained by polymerization in a hydrocarbon solvent using an alkali metal catalyst

(in Formula (IV), R 6 , R 7 , and R 8 independently denote a hydrocarbon group having 1 to 4 carbon atoms or a hydrocarbonoxy group having 1 to 4 carbon atoms, at least one of R 6 , R 7 , and R 8 is a hydrocarbonoxy group having 1 to 4 carbon atoms, n denotes an integer of 0 to 10, and A 2 denotes a polar functional group that does not have an active hydrogen).

9. A method for producing a conjugated diene polymer, comprising steps 1, 2, and 3 below:

(step 1): a step of polymerizing a conjugated diene-containing monomer in a hydrocarbon solvent in the presence of an alkali metal catalyst, thus giving a conjugated diene polymer having a terminal catalyst-derived alkali metal;

(step 2): a step of adding a silicon compound represented by Formula (IV) below in an amount of 0.05 to 0.35 moles per mole of alkali metal of the alkali metal catalyst used in step 1 to the hydrocarbon solution of the conjugated diene polymer of step 1 and mixing; and

(step 3): a step of adding to the hydrocarbon solution of the conjugated diene polymer of step 2 the silicon compound represented by Formula (IV) below in an amount that together with the amount added in step 2 makes the total amount at least 0.5 moles per mole of alkali metal of the alkali metal catalyst used in step 1 and mixing

(in Formula (IV), R 6 , R 7 , and R 8 independently denote a hydrocarbon group having 1 to 4 carbon atoms or a hydrocarbonoxy group having 1 to 4 carbon atoms, at least one of R 6 , R 7 , and R 8 is a hydrocarbonoxy group having 1 to 4 carbon atoms, n denotes an integer of 0 to 10, and A 2 denotes a polar functional group that does not have an active hydrogen).

10. The method for producing a conjugated diene polymer according to claim 9 , wherein A 2 in Formula (IV) is a group represented by Formula (II) or (III) below

(in Formula (II), R 3 and R 4 independently denote a hydrocarbon group having 1 to 8 carbon atoms and optionally having a nitrogen atom, an oxygen atom, or a silicon atom, or R 3 and R 4 are bonded and represent a divalent hydrocarbon group having 2 to 20 carbon atoms and optionally having a nitrogen atom, an oxygen atom, or a silicon atom)

(in Formula (III), X denotes a divalent hydrocarbon group having 1 to 6 carbon atoms and optionally having an oxygen atom, and R 5 denotes hydrogen or a hydrocarbon group having 1 to 6 carbon atoms).

11. The method for producing a conjugated diene polymer according to claim 9 , wherein all of R 6 , R 7 , and R 8 in Formula (IV) are hydrocarbonoxy groups having 1 to 4 carbon atoms.

12. The method for producing a conjugated diene polymer according to claim 9 , wherein the alkali metal catalyst is an organolithium compound or organosodium compound having 2 to 20 carbon atoms.

13. The method for producing a conjugated diene polymer according to claim 9 , wherein the amount of silicon compound represented by Formula (IV) added in step 2 is 0.1 to 0.3 moles per mole of alkali metal of the alkali metal catalyst, and the amount of silicon compound represented by Formula (IV) added in step 3 is, per mole of alkali metal of the alkali metal catalyst used in step 1, at least 1 mole but no greater than 5 moles as a total amount with the amount added in step 2.

14. The method for producing a conjugated diene polymer according to claim 9 , wherein the polymerization temperature in step 1 is 0° to 100° C., and the polymerization time is 10 minutes to 5 hours.

15. A conjugated diene polymer composition comprising the conjugated diene polymer according to claim 1 combined with silica.

16. The polymer composition according to claim 15 , wherein the amount of silica combined is 10 to 150 parts by weight relative to 100 parts by weight of rubber components including the conjugated diene polymer.