Conjugated diene polymer and method for producing conjugated diene polymer

1. A method for producing a conjugated diene-based polymer comprising:

step 1 in which a polymerization initiator is added to a monomer including a conjugated diene compound in a hydrocarbon solvent to obtain a polymerization solution, and

step 2 in which a polymerization initiator and the monomer including a conjugated diene compound are further added to the polymerization solution either once or two or more times and polymerization reaction is further conducted to obtain a polymer with an active end,

wherein in step 1 and/or step 2, a modifying agent is added which has a functional group that is copolymerizable with the conjugated diene compound.

2. The method for producing a conjugated diene-based polymer according to claim 1 , further comprising step 3 in which the polymer with the active end is reacted with a modifying agent having a functional group that is reactive with the active end, to introduce a unit based on the modifying agent at the polymer end.

3. A method for producing a conjugated diene-based polymer comprising:

step 1 in which a polymerization initiator is added to a monomer including a conjugated diene compound in a hydrocarbon solvent to obtain a polymerization solution,

step 2 in which a polymerization initiator and the monomer including a conjugated diene compound are further added to the polymerization solution either once or two or more times and polymerization reaction is further conducted to obtain a polymer with an active end, and

step 3 in which the polymer with the active end is reacted with a modifying agent having a functional group that is reactive with the active end, to introduce the modifying agent-based unit at the end of the polymer.

4. A conjugated diene-based polymer having at least a peak with a peak top molecular weight greater than 800,000, a peak with a peak top molecular weight in the range of 100,000 to 800,000 and a peak with a peak top molecular weight less than 100,000, as measured by gel permeation chromatography, and having a monomer unit derived from at least one type of modifying agent selected from the group consisting of compounds with the structure represented by the following formula (6), compounds with the structure represented by the following formula (7) and compounds with the structure represented by the following formula (8),

[In formula (6), X 1 , X 2 and X 3 each independently represent a hydrocarbyl group, a hydrocarbyloxy group, a halogen atom or a functional group capable of reacting with the active end of the conjugated diene-based polymer, R 61 and R 62 each independently represent a hydrogen atom or a hydrocarbyl group, and when multiple R 61 and R 62 groups are present they may be the same or different, A 1 represents an organic group having at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, phosphorus atoms, sulfur atoms and silicon atoms, optionally having a ring structure, with a portion of the structure of X 1 , X 2 or X 3 optionally bonded to a portion of A 1 , and “a” represents an integer of 0 to 10],

[In formula (7), R 71 represents a hydrogen atom or a hydrocarbyl group, s represents 0 or 1 (an integer of 0 or 1), R 72 represents a hydrocarbylene group, and A 2 represents a substituted amino group, a nitrogen-containing heterocyclic group or a substituted silyl group],

[In formula (8), R 81 and R 82 each independently represent an optionally substituted hydrocarbyl group, or they represent a hydrocarbylene group wherein a portion of R 81 and a portion of R 82 are bonded, optionally having a nitrogen atom and/or an oxygen atom, or R 84 represents an optionally substituted hydrocarbyl group or a hydrogen atom, or a portion of either R 81 or R 82 and a portion of R 84 are bonded together to form a hydrocarbylene group, which optionally has a nitrogen atom and/or an oxygen atom, R 83 represents a divalent group, and n is 0 or 1.

5. The conjugated diene-based polymer according to claim 4 , wherein the area of the peak of maximum height in a peak top molecular weight range of 100,000 to 800,000 is 40 to 95% of the total peak area.

6. The conjugated diene-based polymer according to claim 4 , wherein the area of the peak of maximum height in a peak top molecular weight range of less than 100,000 is no greater than 20% of the total peak area.

7. The conjugated diene-based polymer according to claim 5 , wherein the area of the peak of maximum height in a peak top molecular weight range of less than 100,000 is no greater than 20% of the total peak area.