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

1. A method for producing a conjugated diene polymer, comprising steps A and B:

step A: copolymerizing monomers comprising 1,3-butadiene, styrene and a vinyl compound of formula (IV) below in a hydrocarbon solvent in the presence of an alkali metal catalyst to produce a polymer having an alkali metal originating from the catalyst at at least one terminus of the polymer chain comprising a monomer unit based on 1,3-butadiene, a monomer unit based on styrene and a monomer unit based on the vinyl compound of formula (IV):

wherein X 4 , X 5 , and X 6 independently denote a group of formula (IVa) below, a hydrocarbyl group, or a substituted hydrocarbyl group, and at least one of X 4 , X 5 , and X 6 is a group of formula (IVa):

wherein R 8 and R 9 independently denote a hydrocarbyl group having 1 to 6 carbon atoms, a substituted hydrocarbyl group having 1 to 6 carbon atoms, a silyl group, or a substituted silyl group, and R 8 and R 9 may be bonded so as to form, together with the nitrogen atom, a ring structure; and

wherein the amount of vinyl compound of formula (IV) added, relative to the total amount of 1,3-butadiene and styrene, is at least 0.001 mmol/g but no greater than 0.1 mmol/g, and

step B: reacting the resulting polymer in step A with a compound of formula (II):

wherein n denotes an integer of 1 to 10, R 3 denotes a hydrogen atom, a hydrocarbyl group having 1 to 6 carbon atoms, or a substituted hydrocarbyl group having 1 to 6 carbon atoms, A 1 denotes an oxygen atom or an —NR 4 — group, wherein R 4 denotes a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms, and A 2 denotes a nitrogen atom- and/or oxygen atom-containing functional group.

2. The method for producing a conjugated diene polymer according to claim 1 , wherein R 8 and R 9 in formula (IVa) are hydrocarbyl groups having 1 to 6 carbon atoms.

3. The method for producing a conjugated diene polymer according to claim 1 , wherein two of X 4 , X 5 , and X 6 of formula (IV) are groups of formula (IVa).

4. The method for producing a conjugated diene polymer according to claim 1 , wherein A 2 in formula (II) is a hydroxy group or a group of formula (III):

wherein R 5 and R 6 independently denote a group having 1 to 6 carbon atoms, which may have at least one type of atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom, R 5 and R 6 may be bonded so as to form, together with the nitrogen atom, a ring structure, and R 5 and R 6 may be a single group bonded to the nitrogen via a double bond.

5. The method for producing a conjugated diene polymer according to claim 1 , wherein a vinyl bond content of the conjugated diene polymer is not less than 40 mole % per 100 mole % of the conjugated diene unit.

6. The method for producing a conjugated diene polymer according to claim 1 , wherein the vinyl compound of formula (IV) is bis(diethylamino)methylvinylsilane.