Method for producing modified conjugated diene-based polymer, modified conjugated diene-based polymer, and modified conjugated diene-based polymer composition

1. A method of producing a modified conjugated diene-based polymer, comprising:

a polymerization step of polymerizing a conjugated diene compound, copolymerizing conjugated diene compounds, or copolymerizing a conjugated diene compound with an aromatic vinyl compound using an alkali metal compound or an alkaline earth metal compound as a polymerization initiator to obtain a conjugated diene-based polymer having an active end, and

a modifying step of reacting a compound represented by following formula (1) with the active end of the conjugated diene-based copolymer:

wherein

R 1 to R 4 each independently represent an alkyl group or aryl group having 1 to 20 carbon atoms;

R 5 represents an alkylene group having 1 to 10 carbon atoms;

R 6 represents an alkylene group having 1 to 20 carbon atoms;

m is an integer of 1 or 2; and

n is an integer of 2 or 3.

2. The method according to claim 1 , wherein in formula (1), m is 2, and n is 3.

3. The method according to claim 1 , wherein in the modifying step, the compound represented by formula (1) is added within a range in which a total number of moles of the alkoxy group bonded to the silyl group in the compound represented by formula (1) is from 0.6 to 3 times the number of moles of the polymerization initiator.

4. A modified conjugated diene-based polymer composition comprising:

100 parts by mass of a rubber component containing not less than 20 parts by mass of a modified conjugated diene-based polymer obtained by the method according to any one of claims 1 to 3 and

0.5 to 300 parts by mass of a silica-based inorganic filler,

wherein

when, in the modified conjugated diene-based polymer, a ratio (Mw/Mn) of a polystyrene equivalent weight average molecular weight (Mw) to the polystyrene equivalent number average molecular weight (Mn) by gel permeation chromatography (GPC) measurement is not less than 1.00 and less than 1.80, a Mooney stress-relaxation rate (MSR) measured at 100° C. of the modified conjugated diene-based polymer is not more than 0.7, and

when, in the modified conjugated diene-based polymer, the ratio (Mw/Mn) of the polystyrene equivalent weight average molecular weight (Mw) to the polystyrene equivalent number average molecular weight (Mn) by gel permeation chromatography (GPC) measurement is not less than 1.80 and not more than 3.50, a Mooney stress-relaxation rate (MSR) of the modified conjugated diene-based polymer measured at 110° C. is not more than 0.35.

5. The method according to claim 1 , wherein

when, in the modified conjugated diene-based polymer, a ratio (Mw/Mn) of a polystyrene equivalent weight average molecular weight (Mw) to the polystyrene equivalent number average molecular weight (Mn) by gel permeation chromatography (GPC) measurement is not less than 1.00 and less than 1.80, a Mooney stress-relaxation rate (MSR) measured at 100° C. of the modified conjugated diene-based polymer is not more than 0.7, and

when, in the modified conjugated diene-based polymer, the ratio (Mw/Mn) of the polystyrene equivalent weight average molecular weight (Mw) to the polystyrene equivalent number average molecular weight (Mn) by gel permeation chromatography (GPC) measurement is not less than 1.80 and not more than 3.50, a Mooney stress-relaxation rate (MSR) of the modified conjugated diene-based polymer measured at 110° C. is not more than 0.35.

6. The method according to claim 1 , wherein the compound represented by formula (1) is selected from the group consisting of

2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane,

2,2-diethoxy-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclopentane,

2,2-dimethoxy-1-(4-trimethoxysilylbutyl)-1-aza-2-silacyclohexane,

2,2-dimethoxy-1-(5-trimethoxysilylpentyl)-1-aza-2-silacycloheptane,

2,2-dimethoxy-1-(3-dimethoxymethylsilylpropyl)-1-aza-2-silacyclopentane,

2,2-diethoxy-1-(3-diethoxyethylsilylpropyl)-1-aza-2-silacyclopentane,

2-methoxy-2-methyl-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane,

2-ethoxy-2-ethyl-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclopentane,

2-methoxy-2-methyl-1-(3-dimethoxymethylsilylpropyl)-1-aza-2-silacyclopentane, and 2-ethoxy-2-ethyl-1-(3-diethoxyethylsilylpropyl)-1-aza-2-silacyclopentane.

7. The method according to claim 1 , wherein the compound represented by formula (1) is

2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane, or

2,2-diethoxy-1-(3-triethoxysilylpropyl)-1-aza-2-silacyclopentane.

8. The method according to claim 1 , wherein the conjugated diene compound is selected from the group consisting of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-heptadiene, and 1,3-hexadiene.

9. The method according to claim 1 , wherein the aromatic vinyl compound is selected from the group consisting of styrene, p-methylstyrene, α-methylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, and diphenylethylene.

10. The method according to claim 1 , wherein the alkali metal compound is used as the polymerization initiator.

11. The method according to claim 10 , wherein the alkali metal compound is selected from the group consisting of organolithium compounds, organosodium compounds, organopotassium compounds, organorubidium compounds, and organocesium compounds.

12. The method according to claim 11 , wherein the alkali metal compound is selected from the group consisting of n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenelithium.

13. The method according to claim 1 , wherein the alkaline earth metal compound is used as the polymerization initiator.

14. The method according to claim 13 , wherein the alkaline earth metal compound is selected from the group consisting of organomagnesium compounds, organocalcium compounds, organostrontium compounds, and alkoxides, sulfonates, carbonates, and amides of alkaline earth metals.

15. The method according to claim 1 , wherein the polymerization step is performed in a solvent.

16. The method according to claim 1 , wherein the polymerization step is performed in a solvent comprising a hydrocarbon solvent.

17. The method according to claim 1 , wherein in the polymerization step, a polar compound is added.

18. The method according to claim 17 , wherein the polar compound is selected from the group consisting of ethers, tertiary amine compounds, alkali metal alkoxide compounds, and phosphine compounds.