Method for producing modified conjugated diene polymer, modified conjugated diene polymer, polymer composition, crosslinked polymer, and tire

1. A method for producing a modified conjugated diene-based polymer, wherein the modified conjugated diene-based polymer is a modified product of a conjugated diene-based polymer obtained by polymerizing a conjugated diene compound, or by polymerizing a conjugated diene compound and an aromatic vinyl compound, in the presence of an alkali metal compound or an alkaline-earth metal compound,

the method comprising:

performing a terminal modification that reacts an active terminal of the conjugated diene-based polymer with a compound (A1) comprising a functional group that interacts with silica to obtain the terminal-modified polymer,

wherein the compound (A1) is at least one compound selected from the group consisting of (I) a compound (a-1) of formula (1), (II) a compound (a-2) comprising a functional group (x1)and a group (x2) in its molecule, the functional group (x1) being at least one functional group selected from the group consisting of a cyclic ether group and a (thio)carbonyl group, and the group (x2) comprising at least one atom selected from the group consisting of a nitrogen atom, a phosphorus atom, an oxygen atom, and a sulfur atom, and not comprising active hydrogen, the group (x2) differing from the functional group (x1), and (III) a compound (a-3) comprising two or more iso (thio)cyanate groups in its molecule,

wherein A 1 is a monovalent functional group comprising at least one atom selected from the group consisting of a nitrogen atom, a phosphorus atom, and a sulfur atom, and does not comprise active hydrogen, the monovalent functional group being bonded to R 3 through a nitrogen atom, a phosphorus atom, or a sulfur atom,

R 1 and R 2 are each independently a hydrocarbyl group,

R 3 is a hydrocarbylene group, and

n is an integer from 0 to 2,

provided that a lurality of R 1 are either identical or different when a plurality of R 1 are present, and a plurality of R 2 are either identical or different when a plurality of R 2 are present; and

modifying a main chain of the terminal-modified polymer by reacting at least either an unsaturated bond or a functional group that is comprised in the terminal-modified polymer and is not situated at a terminal of the terminal-modified polymer, with a specific compound that comprises a functional group that interacts with silica, wherein the specific compound is a polymer (P) comprising a repeating unit (p), the repeating unit (p) comprising at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, a phosphorus atom, and a sulfur atom.

2. The method according to claim 1 , wherein a degree of polymerization of the repeating unit (p) in the polymer (P) is from 5 to 200.

3. The method according to claim 1 , wherein the polymer (P) comprises at least one structure selected from the group consisting of a polysiloxane structure, a polyether structure, and a polyimine structure.

4. The method according to claim 1 , wherein the repeating unit (p) is of formula (p-1) or a formula (p-2),

wherein R 11 is a hydrogen atom, a hydrocarbyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an amino group, a hydroxyl group, or an ester group, provided that the hydrocarbyl group having 1 to 10 carbon atoms optionally comprises at least one substituent selected from the group consisting of an epoxy group, an amino group, a carboxyl group, a hydroxyl group, and a mercapto group, and optionally comprises “—O—” or “—COO—” between carbon atoms, R 11 comprised in an identical repeating unit are either identical or different, and R 11 comprised in different repeating units are either identical or different,

wherein R 12 is a hydrogen atom, a hydrocarbyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an amino group, a hydroxyl group, or an ester group, provided that the hydrocarbyl group having 1 to 10 carbon atoms optionally comprises at least one substituent selected from the group consisting of an epoxy group, an amino group, a carboxyl group, a hydroxyl group, and a mercapto group, and optionally comprises “—O—” or “—COO—” between carbon atoms, and n1 is an integer from 1 to 10 , provided that R 12 comprised in an identical repeating unit are either identical or different, R 12 comprised in different repeating units are either identical or different, and n1 are either identical or different between different repeating units.

5. The method according to claim 1 ,

wherein the compound (A1) is of formula (1),

wherein A 1 is a monovalent functional group comprising at least one atom selected from the group consisting of a nitrogen atom, a phosphorus atom, and a sulfur atom, and does not comprise active hydrogen, the monovalent functional group being bonded to R 3 through a nitrogen atom, a phosphorus atom, or a sulfur atom,

R 1 and R 2 are each independently a hydrocarbyl group,

R 3 is a hydrocarbylene group, and

n is an integer from 0 to 2,

provided that a plurality of R 1 are either identical or different when a plurality of R 1 are present, and a plurality of R 2 are either identical or different when a plurality of R 2 are present.

6. A polymer composition, comprising a modified conjugated diene-based polymer obtained by the method according to claim 1 , silica, and a crosslinking agent.

7. A crosslinked polymer, obtained by crosslinking the polymer composition according to claim 6 .

8. A tire, obtained by employing the crosslinked polymer according to claim 7 as a tread material, a sidewall material, or both.