JP7597484B2 - Method for producing modified conjugated diene polymer, modified conjugated diene polymer, rubber composition, method for producing rubber composition, and method for producing tire - Google Patents

Description

The present invention relates to a method for producing a modified conjugated diene polymer, a modified conjugated diene polymer, a rubber composition, a method for producing a rubber composition, and a method for producing a tire.

From the viewpoint of environmental load, there has been an increasing demand for automobiles to have lower fuel consumption. In particular, there is a demand for improved fuel consumption in the materials used for the tread portion of automobile tires, which is in direct contact with the ground.
In recent years, there has been a demand for the development of materials having low rolling resistance, i.e., low hysteresis loss.
There is also a demand for lighter tires, which requires a reduction in the thickness of the tire tread portion and the use of a material with high abrasion resistance for the tire tread portion.
On the other hand, from the viewpoint of safety, materials used in the tire tread portion are required to have excellent wet skid resistance and sufficient fracture properties for practical use.

Materials that meet the various requirements as described above include rubber materials that contain a rubber-like polymer and a reinforcing filler such as carbon black or silica.
The use of a rubber material containing silica can improve the balance between low hysteresis loss (an index of fuel economy) and wet skid resistance. In addition, by introducing a functional group having affinity or reactivity with silica to the molecular end of a rubber-like polymer with high mobility, the dispersibility of silica in the rubber material can be improved, and further, the mobility of the molecular end of the rubber-like polymer can be reduced by bonding with silica particles, thereby reducing the hysteresis loss.
On the other hand, one method for improving the abrasion resistance is to increase the molecular weight of the rubber-like polymer, but increasing the molecular weight tends to deteriorate the processability when the rubber-like polymer is kneaded with a reinforcing filler.
In view of these circumstances, attempts have been made to introduce a branched structure into rubber-like polymers in order to increase the molecular weight without impairing processability.

For example, a resin composition has been proposed in the past that contains silica and a modified conjugated diene polymer obtained by reacting an alkoxysilane containing an amino group with an active terminal of a conjugated diene polymer.
In addition, modified conjugated diene polymers have been proposed that have a branched structure obtained by subjecting an active terminal of a polymer to a coupling reaction with a polyfunctional silane compound (see, for example, Patent Documents 1 and 2).

International Publication No. 2007/114203 International Publication No. 2016/133154

However, in the method of introducing a branched structure into a conjugated diene polymer by subjecting an active end of the polymer to a coupling reaction with a polyfunctional silane compound, the degree of branching of the modified conjugated diene polymer obtained thereby depends greatly on the number of groups that the polyfunctional silane compound has that can react with the active end of the polymer, and does not exceed the number of reactive groups. From the viewpoint of synthetic feasibility, there is a limit to the number of reactive groups that can be imparted to one polyfunctional silane, and therefore there is a problem in that there is also a limit to the degree of branching of the modified conjugated diene polymer obtained.

The present invention aims to provide a method for producing a modified conjugated diene polymer that can produce a modified conjugated diene polymer with a higher degree of branching than when a branched structure is introduced into the conjugated diene polymer using only a modifier, and that allows the lengths of the main chain and side chains to be adjusted, providing a high degree of freedom in polymer design, thereby providing a modified conjugated diene polymer with excellent processability and abrasion resistance.

Means for Solving the Problems of the Prior Art As a result of intensive research and investigation, the present inventors have found that the above-mentioned problems of the prior art can be solved by reacting a conjugated diene-based polymer having an active terminal with a styrene derivative as a branching agent and then reacting the polymer with a specific modifying agent, thereby completing the present invention.
That is, the present invention is as follows.

[1]
a polymerization step of polymerizing or copolymerizing a conjugated diene compound, or a conjugated diene compound and an aromatic vinyl compound, using an alkali metal compound or an alkaline earth metal compound as a polymerization initiator to obtain a conjugated diene polymer having an active terminal;
a branching step of reacting an active terminal of the conjugated diene polymer with a styrene derivative to introduce a branched structure;
a modification step of reacting an active terminal of the conjugated diene polymer formed after the branching step with a compound [M] having a total of two or more groups "-C(R ¹ )=N-A ¹ " and/or "-N=C(R ¹ )-A ¹ " (wherein R ¹ is a hydrogen atom or a hydrocarbyl group, and A ¹ is a monovalent group having an alkoxysilyl group);
The present invention relates to a method for producing a modified conjugated diene polymer comprising the steps of:
[2]
The method for producing a modified conjugated diene polymer according to the above item [1], wherein the compound [M] is a compound represented by the following formula (A):

(In formula (A), ^R2 and ^R3 are each independently a hydrocarbyl group having 1 to 20 carbon atoms, ^R4 is an alkanediyl group having 1 to 20 carbon atoms, and ^A2 is a group "*-C( ^R1 )=N-" or a group "*-N=C( ^R1 )-" (wherein ^R1 is a hydrogen atom or a hydrocarbyl group, and "*" represents a bond bonded to ^R5 ).
^R5 is an m-valent hydrocarbyl group having 1 to 20 carbon atoms, or an m-valent group having 1 to 20 carbon atoms which has at least one atom selected from the group consisting of nitrogen atoms, oxygen atoms, and sulfur atoms and has no active hydrogen.
n is an integer from 1 to 3, and m is an integer from 2 to 10.
In formula (A), multiple R ² , R ³ , R ⁴ , A ² , and n may be the same or different.

[3]
The styrene derivative is a compound represented by the following formula (1) and/or the following formula (2):
A method for producing the modified conjugated diene polymer according to the above [1] or [2].

In formulas (1) and (2), Q ¹ represents any one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms, and may have a branched structure in part.
X ¹ , X ² and X ³ each represent a single bond or an organic group containing any one selected from the group consisting of carbon, hydrogen, nitrogen, sulfur and oxygen.
^Y1 , ^Y2 , and ^Y3 each represent any one selected from the group consisting of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and a halogen atom. They may be independent and the same or different.

[4]
In the formula (1), Q ¹ is a hydrogen atom, and Y ¹ is any one selected from the group consisting of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and a halogen atom.
[5]
The method for producing a modified conjugated diene polymer according to the above item [3], wherein in the formula (1), Q ¹ is a hydrogen atom, and Y ¹ is an alkoxy group having 1 to 20 carbon atoms or a halogen atom.
[6]
In the formula (2), Y ² is an alkoxy group having 1 to 20 carbon atoms or a halogen atom, and Y ³ is an alkoxy group having 1 to 20 carbon atoms or a halogen atom. The method for producing a modified conjugated diene polymer according to the above [3].
[7]
The method for producing a modified conjugated diene polymer according to the above item [3], wherein in the formula (1), Q ¹ is a hydrogen atom and Y ¹ is an alkoxy group having 1 to 20 carbon atoms.
[8]
In the formula (1), Q ¹ is a hydrogen atom, X ¹ is a single bond, and Y ¹ is an alkoxy group having 1 to 20 carbon atoms.
[9]
In the formula (2), ^X2 is a single bond, ^Y2 is an alkoxy group having 1 to 20 carbon atoms or a halogen atom, ^X3 is a single bond, and ^Y3 is an alkoxy group having 1 to 20 carbon atoms or a halogen atom. The method for producing a modified conjugated diene polymer according to the above item [3].
[10]
a conjugated diene-based polymer having an active end with a branched structure;
a compound [M] having a total of two or more groups "--CR ¹ ═N-A ¹ " and/or "--N═CR ¹ -A ¹ " (wherein R ¹ is a hydrogen atom or a hydrocarbyl group, and A ¹ is a monovalent group having an alkoxysilyl group);
is the reaction product of
Modified conjugated diene polymer.
[11]
The modified conjugated diene polymer according to the above [10], which is represented by the following formula (B):

In formula (B), ^R2 is a hydrocarbyl group having 1 to 20 carbon atoms, ^R6 is a hydrocarbyloxy group having 1 to 20 carbon atoms, or a modified or unmodified branched conjugated diene polymer, ^R4 is an alkanediyl group having 1 to 20 carbon atoms, and Z is a group represented by the following formula (C) or formula (D).
^R5 is an m-valent hydrocarbyl group having 1 to 20 carbon atoms, or an m-valent group having 1 to 20 carbon atoms which has at least one atom selected from the group consisting of nitrogen atoms, oxygen atoms, and sulfur atoms and has no active hydrogen.
n is an integer from 1 to 3, and m is an integer from 2 to 10.
In the formula, multiple R ² , R ⁴ , R ⁶ , Z, and n may be the same or different.

(In formula (C) and formula (D), ^R1 is a hydrogen atom or a hydrocarbyl group, and Poly is a modified or unmodified branched conjugated diene polymer. "*" indicates a bond bonded to ^R5 .)

[12]
A rubber component containing 10% by mass or more of the modified conjugated diene polymer according to [10] or [11] above;
The rubber composition comprises 5.0 parts by mass or more and 150 parts by mass or less of a filler per 100 parts by mass of the rubber component.
[13]
A step of obtaining a modified conjugated diene polymer by the production method according to any one of [1] to [9] above;
obtaining a rubber component containing 10% by mass or more of the modified conjugated diene polymer;
A filler is contained in an amount of 5.0 parts by mass or more and 150 parts by mass or less based on 100 parts by mass of the rubber component.
to obtain a rubber composition;
The method for producing a rubber composition comprising the steps of:
[14]
Obtaining a rubber composition by the method for producing a rubber composition according to [13] above;
molding the rubber composition to obtain a tire;
A tire manufacturing method comprising the steps of:

According to the present invention, it is possible to produce a modified conjugated diene polymer having a higher degree of branching than when only a modifier is used, and it is also possible to provide a production method that allows high freedom in polymer design by adjusting the length of the main chain and side chain, thereby providing a modified conjugated diene polymer that exhibits excellent processability and abrasion resistance.

Hereinafter, an embodiment of the present invention (hereinafter, referred to as "the present embodiment") will be described in detail.
It should be noted that the following embodiment is merely an example for explaining the present invention, and the present invention is not limited to the following embodiment. The present invention can be practiced with appropriate modifications within the scope of the gist thereof.

[Method for producing modified conjugated diene polymer]
The method for producing a modified conjugated diene polymer of the present embodiment includes the steps of:
a polymerization step of polymerizing or copolymerizing a conjugated diene compound, or a conjugated diene compound and an aromatic vinyl compound, using an alkali metal compound or an alkaline earth metal compound as a polymerization initiator to obtain a conjugated diene polymer having an active terminal;
a branching step of reacting an active terminal of the conjugated diene polymer with a styrene derivative as a branching agent to introduce a branched structure;
a modifying step of reacting an active terminal of the conjugated diene polymer formed after the branching step with a compound [M] having a total of two or more modifying groups, the group "-C(R ¹ )=N-A ¹ " and/or the group "-N=C(R ¹ )-A ¹ " (wherein R ¹ is a hydrogen atom or a hydrocarbyl group, and A ¹ is a monovalent group having an alkoxysilyl group);
has.
The conjugated diene polymer constituting the modified conjugated diene polymer may be any of a homopolymer of a single conjugated diene compound, a polymer or copolymer of different types of conjugated diene compounds, and a copolymer of a conjugated diene compound and an aromatic vinyl compound.
According to the present embodiment, by introducing a branch point into the main chain, a modified conjugated diene-based polymer having a higher degree of branching can be produced as compared with a case in which a branched structure is introduced into a conjugated diene-based polymer using only a modifying agent, and a production method can be provided which allows a high degree of freedom in polymer design by adjusting the lengths of the main chain and side chains, thereby providing a modified conjugated diene-based polymer that exhibits excellent processability and abrasion resistance.

(Polymerization process)
In the polymerization step in the method for producing a modified conjugated diene polymer of the present embodiment, an alkali metal compound or an alkaline earth metal compound is used as a polymerization initiator to polymerize or copolymerize a conjugated diene compound, or a conjugated diene compound and an aromatic vinyl compound, to obtain a conjugated diene polymer having an active end.
In the polymerization step, it is preferable to carry out polymerization by a propagation reaction through a living anionic polymerization reaction, whereby a conjugated diene polymer having an active terminal can be obtained.

<Polymerization initiator>
As the polymerization initiator, an alkali metal compound or an alkaline earth metal compound is used.
As the polymerization initiator, an organolithium compound is preferably used, and an organomonolithium compound is more preferably used.
The organomonolithium compound is not limited to the following, but examples thereof include organomonolithium compounds of low molecular weight compounds and solubilized oligomeric organomonolithium compounds.
In addition, the organic monolithium compound can be any of compounds having a carbon-lithium bond, a nitrogen-lithium bond, and a tin-lithium bond in terms of the bonding mode between the organic group and the lithium.

The amount of the polymerization initiator used is preferably determined depending on the targeted molecular weight of the conjugated diene polymer.
The amount of a monomer such as a conjugated diene compound used relative to the amount of a polymerization initiator used relates to the degree of polymerization of a target conjugated diene polymer, i.e., tends to relate to the number average molecular weight and/or weight average molecular weight.
Therefore, in order to increase the molecular weight of the conjugated diene polymer, the amount of the polymerization initiator should be adjusted to decrease, and in order to decrease the molecular weight, the amount of the polymerization initiator should be adjusted to increase.

From the viewpoint that the organomonolithium compound is used as one method for introducing nitrogen atoms into the conjugated diene polymer, it is preferably an alkyllithium compound having a substituted amino group or a dialkylaminolithium.
When these are used as a polymerization initiator, a conjugated diene polymer having a nitrogen atom consisting of an amino group at the polymerization initiation terminal can be obtained.

The substituted amino group is an amino group that does not have an active hydrogen or has a structure in which the active hydrogen is protected.
Examples of alkyllithium compounds having an amino group that does not have an active hydrogen include, but are not limited to, 3-dimethylaminopropyllithium, 3-diethylaminopropyllithium, 4-(methylpropylamino)butyllithium, and 4-hexamethyleneiminobutyllithium.
Examples of alkyllithium compounds having an amino group with an active hydrogen protected structure include, but are not limited to, 3-bistrimethylsilylaminopropyllithium and 4-trimethylsilylmethylaminobutyllithium.

Examples of dialkylaminolithium include, but are not limited to, lithium dimethylamide, lithium diethylamide, lithium dipropylamide, lithium dibutylamide, lithium di-n-hexylamide, lithium diheptylamide, lithium diisopropylamide, lithium dioctylamide, lithium di-2-ethylhexylamide, lithium didecylamide, lithium ethylpropylamide, lithium ethylbutylamide, lithium ethylbenzylamide, lithium methylphenethylamide, lithium hexamethyleneimide, lithium pyrrolidide, lithium piperidide, lithium heptamethyleneimide, lithium morpholide, 1-lithioazacyclooctane, 6-lithio-1,3,3-trimethyl-6-azabicyclo[3.2.1]octane, and 1-lithio-1,2,3,6-tetrahydropyridine.

These organomonolithium compounds having substituted amino groups can also be used as oligomeric organomonolithium compounds solubilized in normal hexane or cyclohexane by reacting them with small amounts of polymerizable monomers such as 1,3-butadiene, isoprene, and styrene.

The organomonolithium compound is preferably an alkyllithium compound from the viewpoints of industrial availability and ease of control of the polymerization reaction, in which case a conjugated diene-based polymer having an alkyl group at the polymerization initiation terminal can be obtained.
Examples of the alkyl lithium compound include, but are not limited to, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, n-hexyl lithium, benzyl lithium, phenyl lithium, and stilbene lithium.
As the alkyllithium compound, n-butyllithium and sec-butyllithium are preferred from the viewpoints of industrial availability and ease of control of the polymerization reaction.

These organomonolithium compounds may be used alone or in combination of two or more kinds, and may also be used in combination with other organometallic compounds.
Examples of the other organometallic compounds include alkaline earth metal compounds, other alkali metal compounds, and other organometallic compounds.
Alkaline earth metal compounds include, but are not limited to, organomagnesium compounds, organocalcium compounds, and organostrontium compounds, as well as alkaline earth metal alkoxides, sulfonates, carbonates, and amides.
Organomagnesium compounds include, for example, dibutylmagnesium and ethylbutylmagnesium.
Other examples of organometallic compounds include organoaluminum compounds.

In the polymerization step, the polymerization reaction mode is not limited to the following modes, but examples thereof include a batchwise polymerization mode (also called a "batch type") and a continuous polymerization mode.
In the continuous system, one or more connected reactors can be used. The continuous reactor may be, for example, a tank type or a tube type equipped with an agitator. In the continuous system, preferably, the monomer, the inert solvent, and the polymerization initiator are continuously fed into the reactor, a polymer solution containing a polymer is obtained in the reactor, and the polymer solution is continuously discharged.
The batch reactor may be, for example, a tank-type reactor equipped with a stirrer. In the batch reactor, preferably, a monomer, an inert solvent, and a polymerization initiator are fed, and if necessary, a monomer is added continuously or intermittently during polymerization to obtain a polymer solution in the reactor, and the polymer solution is discharged after the polymerization is completed.
In the method for producing a modified conjugated diene polymer of this embodiment, in order to obtain a conjugated diene polymer having a high proportion of active ends in the polymerization step, a continuous system is preferred, which allows the polymer to be continuously discharged and subjected to the next reaction in a short time. In the continuous system, the number of reactors is not particularly limited, and one or two or more connected reactors can be used. The reactor is preferably one that can sufficiently contact the monomer and the polymerization initiator in a solution, and a tank type or a tube type with a stirrer is used. The number of reactors can be appropriately selected, but one reactor is preferred from the viewpoint of space saving of the production equipment, and two or more reactors are preferred from the viewpoint of improving productivity. When two or more reactors are used, it is more preferable to add the branching agent to the second or subsequent reactors.

The polymerization step for the conjugated diene polymer is preferably carried out in an inert solvent.
Examples of the inert solvent include hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. Specific examples of the hydrocarbon solvent include, but are not limited to, aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene, and hydrocarbons consisting of mixtures thereof.
By treating the impurities, that is, allenes and acetylenes, with an organometallic compound before subjecting the polymer to the polymerization reaction, a conjugated diene-based polymer having a high concentration of active ends tends to be obtained, which is preferable since a modified conjugated diene-based polymer having a high modification rate tends to be obtained.

In the polymerization step, a polar compound may be added. This allows the aromatic vinyl compound to be randomly copolymerized with the conjugated diene compound. Polar compounds also tend to function as vinylating agents for controlling the microstructure of the conjugated diene portion. Furthermore, they tend to be effective in promoting the polymerization reaction.

Examples of polar compounds include, but are not limited to, ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium tert-amylate, potassium tert-butylate, sodium tert-butylate, and sodium amylate; and phosphine compounds such as triphenylphosphine.
These polar compounds may be used alone or in combination of two or more.

The amount of the polar compound used is not particularly limited and can be selected depending on the purpose, but is preferably 0.01 moles or more and 100 moles or less per mole of the polymerization initiator.
Such a polar compound (vinylating agent) can be used as an adjuster for the microstructure of the conjugated diene portion of the conjugated diene polymer in an appropriate amount according to the desired vinyl bond amount.
Many polar compounds also have an effective randomizing effect in the copolymerization of a conjugated diene compound and an aromatic vinyl compound, and tend to be usable as agents for adjusting the distribution of the aromatic vinyl compound or the amount of styrene blocks.
An example of a method for randomizing a conjugated diene compound and an aromatic vinyl compound is a method described in JP-A-59-140211, in which a copolymerization reaction is initiated with the entire amount of styrene and a portion of 1,3-butadiene, and the remaining 1,3-butadiene is intermittently added during the copolymerization reaction.

The polymerization temperature in the polymerization step is preferably a temperature at which living anionic polymerization proceeds, and from the viewpoint of productivity, is more preferably 0° C. or higher and 120° C. or lower.
By setting the temperature within this range, it is possible to ensure a sufficient amount of the modifying agent reacting with the active terminals after the polymerization is completed.

(Branching process)
In the method for producing a modified conjugated diene polymer of the present embodiment, a styrene derivative is reacted as a branching agent with the active terminal of the conjugated diene polymer obtained in the polymerization step.
While the branching agent maintains its polymerization activity and polymerizes with the monomer, the functional group of the branching agent reacts with the active end of another polymer chain, thereby forming a branched structure in the polymer.
It is also possible to form a further branched structure by polymerizing and reacting the conjugated diene polymer into which a branched structure has been introduced with a monomer and a branching agent, or, as described below, to react the conjugated diene polymer with a modifying agent having a functional group to form a modified conjugated diene polymer, or to carry out a coupling reaction to further extend the polymer chain.
In this way, a branched conjugated diene polymer can be obtained by continuing the polymerization reaction of the aromatic vinyl compound while using, as a branching agent, a styrene derivative whose functional group reacts with the active terminal of the polymer.

<Branching Agent>
From the viewpoints of polymerization continuity and gelation prevention, the styrene derivative used as a branching agent in the branching step is preferably one in which a skeleton having only one active end remaining at a branch site after the branching step becomes the main skeleton, and further, it is preferable that the functional group constituting the styrene derivative has sufficient reactivity to react with the polymerization active end during the branching step.
More specifically, the styrene derivative, which is the branching agent, is preferably a compound having a vinyl group on the benzene ring and a functional group that quantitatively reacts with the polymerization active terminal of living anionic polymerization. The functional group of the styrene derivative reacts with the polymerization active terminal in a one-to-one ratio, and the functional group is eliminated to form a single bond, while the vinyl group is polymerized with other monomers in the reactor, thereby forming a branched structure in the polymer. The functional group other than the vinyl group of the styrene derivative is a group that is eliminated by nucleophilic substitution reaction with the polymerization active terminal of living anionic polymerization, and examples of such groups include alkoxy groups, halogens, ester groups, formyl groups, ketone groups, amide groups, acid chloride groups, acid anhydride groups, and epoxy groups.
By having the above-mentioned structure of the styrene derivative, which is a branching agent, the styrene derivative maintains its polymerization activity as styrene, and the styrene derivative is incorporated into the main chain, and another monomer is polymerized to the terminal where activity is maintained, and the polymer chain is further extended. In addition, the active terminal of another polymer chain reacts with the functional group of the incorporated styrene derivative to form a bond, resulting in a branched structure. By repeating this reaction, the number of branches in the polymer chain increases, the polymer structure becomes more complex, and the molecular weight becomes larger.
From the viewpoint of polymerization continuity and controllability of polymer structure, it is also necessary that the functional group that is eliminated after reacting with the active end of another polymer chain has little inhibitory effect on polymerization. Here, "little inhibitory effect on polymerization" means little side reaction of anionic polymerization, such as chain transfer reaction, deactivation during polymerization, and decrease in activity due to an increase in the degree of association of the polymer.
The functional group of the styrene derivative must not excessively improve the polymerization activity, and must not deactivate the polymerization activity. When polymerizing a polymer by living anionic polymerization, it is important that the functional group does not have a hydrogen atom as a functional group that does not deactivate the active terminal, and is a hard base as defined based on Pearson's HASB rule, and more specifically, an alkoxy group or a halogen group can be mentioned. Among these, the structure of the styrene derivative as the branching agent used in the production method of this embodiment can be selected from the viewpoints of reactivity with the active terminal and that the eliminated functional group does not inhibit polymerization.
More specifically, it is preferable to use a branching agent represented by the following formula (1) having a styrene skeleton as the main skeleton, or a branching agent represented by the following formula (2) having a diphenylethylene skeleton as the main skeleton, from the viewpoints of suppressing chain transfer reactions, suppressing deactivation of active terminals, and preventing gelation.

In formulas (1) and (2), Q ¹ represents any one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms, and may have a branched structure in part.
X ¹ , X ² and X ³ each represent a single bond or an organic group containing any one selected from the group consisting of carbon, hydrogen, nitrogen, sulfur and oxygen.
^Y1 , ^Y2 , and ^Y3 each represent any one selected from the group consisting of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and a halogen atom. They may be independent and the same or different.

From the viewpoint of improving the degree of branching in polymerization, the styrene derivative used as a branching agent in the branching step is preferably such that, in the formula (1), Q ¹ is a hydrogen atom and Y ¹ is any one selected from the group consisting of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and a halogen atom.

In the present embodiment, from the viewpoint of improving the degree of branching, the styrene derivative used as the branching agent in the branching step is preferably such that ^Y2 in the formula (2) is any one selected from the group consisting of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and a halogen atom.

In the present embodiment, from the viewpoint of continuity of polymerization and improvement of the degree of branching, it is more preferable that Q ¹ in the styrene derivative used as a branching agent in the branching step is a hydrogen atom and Y ¹ in the formula (1) is an alkoxy group having 1 to 20 carbon atoms or a halogen atom.

In the present embodiment, from the viewpoint of continuity of polymerization and improvement of the degree of branching, it is more preferable that, in the styrene derivative used as a branching agent in the branching step, ^Y2 in the formula (2) is an alkoxy group having 1 to 20 carbon atoms or a halogen atom, and ^Y3 is an alkoxy group having 1 to 20 carbon atoms or a halogen atom.

In the present embodiment, from the viewpoints of improving the continuity of polymerization, the degree of branching, and the modification rate, it is more preferable that Q ¹ in the styrene derivative used as a branching agent in the branching step is a hydrogen atom and Y ¹ in the formula (1) is an alkoxy group having 1 to 20 carbon atoms.

In the present embodiment, from the viewpoints of continuity of polymerization, improvement of the branching degree, and further improvement of the modification rate, it is even more preferable that Q ¹ is a hydrogen atom, X ¹ is a single bond, and Y ¹ is an alkoxy group having 1 to 20 carbon atoms in the styrene derivative used as a branching agent in the branching step in the above formula (1).

In the present embodiment, from the viewpoints of continuity of polymerization, improvement of the branching degree, and further improvement of the modification rate, it is even more preferable that, in the formula (2), ^X2 is a single bond, ^Y2 is an alkoxy group having 1 to 20 carbon atoms or a halogen atom, and ^X3 is a single bond, and ^Y3 is an alkoxy group having 1 to 20 carbon atoms or a halogen atom, in the styrene derivative used as a branching agent in the branching step.

Examples of the branching agent represented by the formula (1) include, but are not limited to, trimethoxy(4-vinylphenyl)silane, triethoxy(4-vinylphenyl)silane, tripropoxy(4-vinylphenyl)silane, tributoxy(4-vinylphenyl)silane, triisopropoxy(4-vinylphenyl)silane, trimethoxy(3-vinylphenyl)silane, triethoxy(3-vinylphenyl)silane, tripropoxy(3-vinylphenyl)silane, tributoxy(3-vinylphenyl)silane, triisopropoxy(3-vinylphenyl)silane, trimethoxy(2-vinylphenyl)silane, triethoxy(2-vinylphenyl)silane, tripropoxy(2-vinylphenyl)silane, tributoxy(2-vinylphenyl)silane, triisopropoxy(3-vinylphenyl)silane, trimethoxy(2-vinylphenyl)silane, triethoxy(2-vinylphenyl)silane, tripropoxy(2-vinylphenyl)silane, tributoxy(2-vinylphenyl)silane, triisopropoxy(2-vinylphenyl)silane, trimethoxy(2-vinylphenyl)silane, triethoxy(2-vinylphenyl)silane, tripropoxy(2-vinylphenyl)silane, triisoprop ... isopropoxy(2-vinylphenyl)silane, dimethoxymethyl(4-vinylphenyl)silane, diethoxymethyl(4-vinylphenyl)silane, dipropoxymethyl(4-vinylphenyl)silane, dibutoxymethyl(4-vinylphenyl)silane, diisopropoxymethyl(4-vinylphenyl)silane, dimethoxymethyl(3-vinylphenyl)silane, diethoxymethyl(3-vinylphenyl)silane, dipropoxymethyl(3-vinylphenyl)silane, dibutoxymethyl(3-vinylphenyl)silane, diisopropoxymethyl(3-vinylphenyl)silane, dimethoxymethyl(2-vinylphenyl)silane, diethoxymethyl(2-vinylphenyl)silane, dipropoxymethyl(2-vinylphenyl)silane, dibutoxymethyl(2-vinylphenyl)silane dimethylphenyl)silane, diisopropoxymethyl(2-vinylphenyl)silane, dimethylmethoxy(4-vinylphenyl)silane, dimethylethoxy(4-vinylphenyl)silane, dimethylpropoxy(4-vinylphenyl)silane, dimethylbutoxy(4-vinylphenyl)silane, dimethylisopropoxy(4-vinylphenyl)silane, dimethylmethoxy(3-vinylphenyl)silane, dimethylethoxy(3-vinylphenyl)silane, dimethylpropoxy(3-vinylphenyl)silane, dimethylbutoxy(3-vinylphenyl)silane, dimethylisopropoxy(3-vinylphenyl)silane, dimethylmethoxy(2-vinylphenyl)silane, dimethylethoxy(2-vinylphenyl)silane, dimethylpropoxy(2-vinylphenyl)silane, dimethyl Tributoxy(2-vinylphenyl)silane, dimethylisopropoxy(2-vinylphenyl)silane, trimethoxy(4-isopropenylphenyl)silane, triethoxy(4-isopropenylphenyl)silane, tripropoxy(4-isopropenylphenyl)silane, tributoxy(4-isopropenylphenyl)silane, triisopropoxy(4-isopropenylphenyl)silane, trimethoxy(3-isopropenylphenyl)silane, triethoxy(3-isopropenylphenyl)silane, tripropoxy(3-isopropenylphenyl)silane, tributoxy(3-isopropenylphenyl)silane, triisopropoxy(3-isopropenylphenyl)silane, trimethoxy(2-isopropenylphenyl)silane, triethoxy(2-isopropenylphenyl)silane (phenyl)silane, tripropoxy (2-isopropenylphenyl)silane, tributoxy (2-isopropenylphenyl)silane, triisopropoxy (2-isopropenylphenyl)silane, dimethoxymethyl (4-isopropenylphenyl)silane, diethoxymethyl (4-isopropenylphenyl)silane, dipropoxymethyl (4-isopropenylphenyl)silane, dibutoxymethyl (4-isopropenylphenyl)silane, diisopropoxymethyl (4-isopropenylphenyl)silane, dimethoxymethyl (3-isopropenylphenyl)silane, diethoxymethyl (3-isopropenylphenyl)silane, dipropoxymethyl (3-isopropenylphenyl)silane, dibutoxymethyl (3-isopropenylphenyl)silane, diisopropoxy Dimethyl(3-isopropenylphenyl)silane, dimethoxymethyl(2-isopropenylphenyl)silane, diethoxymethyl(2-isopropenylphenyl)silane, dipropoxymethyl(2-isopropenylphenyl)silane, dibutoxymethyl(2-isopropenylphenyl)silane, diisopropoxymethyl(2-isopropenylphenyl)silane, dimethylmethoxy(4-isopropenylphenyl)silane, dimethylethoxy(4-isopropenylphenyl)silane, dimethylpropoxy(4-isopropenylphenyl)silane, dimethylbutoxy(4-isopropenylphenyl)silane, dimethylisopropoxy(4-isopropenylphenyl)silane, dimethylmethoxy(3-isopropenylphenyl)silane, dimethylethoxy(3-isopropenylphenyl)silane (vinylphenyl)silane, dimethylpropoxy(3-isopropenylphenyl)silane, dimethylbutoxy(3-isopropenylphenyl)silane, dimethylisopropoxy(3-isopropenylphenyl)silane, dimethylmethoxy(2-isopropenylphenyl)silane, dimethylethoxy(2-isopropenylphenyl)silane, dimethylpropoxy(2-isopropenylphenyl)silane, dimethylbutoxy(2-isopropenylphenyl)silane, dimethylisopropoxy(2-isopropenylphenyl)silane, trichloro(4-vinylphenyl)silane, trichloro(3-vinylphenyl)silane, trichloro(2-vinylphenyl)silane, tribromo(4-vinylphenyl)silane, tribromo(3-vinylphenyl)silane, tribromo(2-vinylphenyl)silane, methylphenyl)silane, dichloromethyl(4-vinylphenyl)silane, dichloromethyl(3-vinylphenyl)silane, dichloromethyl(2-vinylphenyl)silane, dibromomethyl(4-vinylphenyl)silane, dibromomethyl(3-vinylphenyl)silane, dibromomethyl(2-vinylphenyl)silane, dimethylchloro(4-vinylphenyl)silane, dimethylchloro(3-vinylphenyl)silane, dimethylchloro(2-vinylphenyl)silane, dimethylbromo(4-vinylphenyl)silane, dimethylbromo(3-vinylphenyl)silane, dimethylbromo(2-vinylphenyl)silane, trimethoxy(4-vinylbenzyl)silane, triethoxy(4-vinylbenzyl)silane, tripropoxy(4-vinylbenzyl)silane.
Among these, trimethoxy(4-vinylphenyl)silane, triethoxy(4-vinylphenyl)silane, tripropoxy(4-vinylphenyl)silane, tributoxy(4-vinylphenyl)silane, triisopropoxy(4-vinylphenyl)silane, trimethoxy(3-vinylphenyl)silane, triethoxy(3-vinylphenyl)silane, tripropoxy(3-vinylphenyl)silane, tributoxy(3-vinylphenyl)silane, triisopropoxy(3 ... tripropoxy(3-vinylphenyl)silane, tripropoxy(3-vinylphenyl)silane, tripropoxy(3-vinylphenyl)silane, tripropoxy(3-vinylphenyl)sil Preferred is trimethoxy(4-vinylphenyl)silane, triethoxy(4-vinylphenyl)silane, tripropoxy(4-vinylphenyl)silane, tributoxy(4-vinylphenyl)silane, triisopropoxy(4-vinylphenyl)silane, trimethoxy(4-vinylbenzyl)silane, and triethoxy(4-vinylbenzyl)silane, and further preferred are trimethoxy(4-vinylphenyl)silane and triethoxy(4-vinylphenyl)silane.

Examples of the branching agent represented by the formula (2) include, but are not limited to, 1-bis(4-trimethoxysilylphenyl)ethylene, 1,1-bis(4-triethoxysilylphenyl)ethylene, 1,1-bis(4-tripropoxysilylphenyl)ethylene, 1,1-bis(4-tripentoxysilylphenyl)ethylene, 1,1-bis(4-triisopropoxysilylphenyl)ethylene, 1,1-bis(3-trimethoxysilylphenyl)ethylene, 1,1-bis(3-triethoxysilylphenyl)ethylene, 1,1-bis(3-trippropoxysilylphenyl)ethylene, 1,1-bis(3-tripentoxysilylphenyl)ethylene, 1,1-bis(3-triisopropoxysilylphenyl)ethylene, 1,1-bis(2-trimethoxysilylphenyl)ethylene, 1,1-bis(2-triethoxysilylphenyl)ethylene, 1,1-bis(3-triisopropoxysilylphenyl)ethylene, Examples of such ethylene include 1,1-bis(2-triisopropoxysilylphenyl)ethylene, 1,1-bis(4-(dimethylmethoxysilyl)phenyl)ethylene, 1,1-bis(4-(diethylmethoxysilyl)phenyl)ethylene, 1,1-bis(4-(dipropylmethoxysilyl)phenyl)ethylene, 1,1-bis(4-(dimethylethoxysilyl)phenyl)ethylene, 1,1-bis(4-(diethylethoxysilyl)phenyl)ethylene, 1,1-bis(4-(dipropylethoxysilyl)phenyl)ethylene, 1,1-bis(4-trimethoxysilylbenzyl)ethylene, 1,1-bis(4-triethoxysilylbenzyl)ethylene, 1,1-bis(4-trippropoxysilylbenzyl)ethylene, and 1,1-bis(4-tripentoxysilylbenzyl)ethylene.
Among these, 1,1-bis(4-trimethoxysilylphenyl)ethylene, 1,1-bis(4-triethoxysilylphenyl)ethylene, 1,1-bis(4-tripropoxysilylphenyl)ethylene, 1,1-bis(4-tripentoxysilylphenyl)ethylene and 1,1-bis(4-triisopropoxysilylphenyl)ethylene are preferred, and 1,1-bis(4-trimethoxysilylphenyl)ethylene is more preferred.
By using the branching agents represented by the formulas (1) and (2), the number of branches is increased, and the effects of improving the wear resistance and processability can be obtained.

In the method for producing a modified conjugated diene polymer of the present embodiment, the timing of adding the branching agent is not particularly limited as long as it is during the polymerization step in which a conjugated diene polymer having an active end is present in the reaction system, and can be selected depending on the purpose, etc. From the viewpoint of improving the absolute molecular weight of the conjugated diene polymer and improving the coupling rate, the timing is preferably when the raw material conversion rate after addition of the polymerization initiator is 20% or more, more preferably 40% or more, even more preferably 50% or more, even more preferably 65% or more, and even more preferably 75% or more.
Furthermore, during or after the branching step, a monomer as a desired raw material may be further added, and the polymerization step may be continued after branching, or the above-described contents may be repeated.
The monomer to be added is not particularly limited, but is preferably a conjugated diene compound and/or an aromatic vinyl compound, and in particular, when a monomer is added during the branching step, from the viewpoint of improving the modification rate by alleviating steric hindrance at the branching points of the conjugated diene polymer, the monomer is preferably 5% or more of the total amount of conjugated diene monomers used in the polymerization step, for example, the total amount of butadiene, more preferably 10% or more, even more preferably 15% or more, even more preferably 20% or more, and even more preferably 25% or more. In such a case, it is particularly preferable to add a monomer in an amount of 5% or more of the total amount of conjugated diene monomers used in the polymerization step, for example, the total amount of butadiene, during the branching step, using a continuous polymerization process, from the viewpoint of improving the modification rate.
The length of the main chain and side chains can be adjusted by changing the timing of adding the branching agent and the amount of monomer added, allowing for a high degree of freedom in polymer design.

The branched structure of the conjugated diene polymer having a branched structure introduced therein, which is obtained in the branching step in the method for producing a modified conjugated diene polymer of the present embodiment, preferably has 3 to 24 branches, more preferably 4 to 20 branches, and even more preferably 5 to 18 branches.
By restricting the number of branches to 24 or less, it tends to be easy to react with a functional group-containing modifier in the modification step described below to produce a modified conjugated diene polymer, or to further extend the polymer chain by a coupling reaction. In addition, by restricting the number of branches to 3 or more, the resulting polymer tends to be excellent in processability and abrasion resistance.

The amount of branching agent added is not particularly limited, and can be selected depending on the purpose, etc., but from the viewpoints of improving the terminal termination reaction rate of the conjugated diene polymer, improving the coupling rate, and continuity of polymerization after branching, the amount of branching agent relative to the amount of active polymerization initiator is preferably 1/2 or less and 1/100 or more in molar ratio, more preferably 1/3 or less and 1/50 or more, even more preferably 1/4 or less and 1/30 or more, even more preferably 1/6 or less and 1/25 or more, and even more preferably 1/8 or less and 1/12 or more.

Further, during and/or after the branching step, further monomers may be added and the polymerization step may be continued after branching, or further branching agent may be added after the addition of monomers, and the addition of monomers may be repeated.
By adding monomers, the steric hindrance around the branch points is alleviated, which improves the continuity of the polymerization and the coupling and modification rates, thereby forming branches at desired positions while increasing the molecular weight of the polymer.
The monomer to be added may be an aromatic vinyl compound such as styrene or a conjugated diene compound such as butadiene, or a mixture of these, and may be the same as or different from the type and ratio of the monomer to be polymerized initially, but from the viewpoint of continuity of polymerization, a conjugated diene compound is preferred. From the viewpoint of improving the heat resistance of the polymer, it is preferable to add an aromatic vinyl compound.

The conjugated diene polymer having a branched structure introduced therein, which is obtained in the branching step in the production method of the present embodiment, preferably has a Mooney viscosity measured at 110° C. of 10 or more and 150 or less, more preferably 15 or more and 140 or less, even more preferably 20 or more and 130 or less, and still more preferably 30 or more and 100 or less.
When the Mooney viscosity is within the above range, the modified conjugated diene polymer finally obtained by the production method of the present embodiment tends to have excellent processability and abrasion resistance.

The weight average molecular weight of the conjugated diene polymer having a branched structure introduced therein, which is obtained in the branching step in the production method of the present embodiment, is preferably 10,000 or more and 1,500,000 or less, more preferably 100,000 or more and 1,000,000 or less, and even more preferably 200,000 or more and 900,000 or less.
When the weight average molecular weight is within the above range, the modified conjugated diene polymer finally obtained by the production method of the present embodiment tends to be excellent in processability, abrasion resistance, and a balance of these properties.
When producing a modified conjugated diene polymer in the modification step described below, in order to reach a weight-average molecular weight in the range of 100,000 or more and 1,000,000 or less, it is necessary to control the amount of branching agent added within a range of 1/3 or less and 1/50 or more in molar ratio to the amount of polymerization initiator, thereby preventing the polymerization initiator from being completely consumed before the modification step while forming branches, and to make the number of functional groups of the modifier to be 2 or more. In order to reach a weight-average molecular weight in the range of 200,000 or more and 900,000 or less, it is necessary to control the amount of branching agent added within a range of 1/3 or less and 1/50 or more in molar ratio to the amount of polymerization initiator, and to make the number of functional groups of the modifier to be 3 or more.

The modified conjugated diene polymer obtained by the production method of the present embodiment may be a polymer of a conjugated diene monomer and a branching agent, or a copolymer of a conjugated diene monomer, a branching agent, and a monomer other than these.
For example, when the conjugated diene monomer is butadiene or isoprene and is polymerized with a branching agent containing an aromatic vinyl moiety, the polymer chain is a so-called polybutadiene or polyisoprene, and the branching portion is a polymer containing a structure derived from aromatic vinyl. By having such a structure, it is possible to improve the linearity per polymer chain and improve the crosslinking density after vulcanization, and the effect of improving the abrasion resistance of the polymer is achieved. Therefore, it is suitable for applications such as tires, resin modification, automobile interior and exterior parts, vibration-proof rubber, and footwear.
When the conjugated diene polymer is used for tire tread applications, a copolymer of a conjugated diene monomer, an aromatic vinyl monomer, and a branching agent is suitable, and in the copolymer for this application, the amount of bound conjugated diene is preferably 40% by mass or more and 100% by mass or less, and more preferably 55% by mass or more and 80% by mass or less.
Furthermore, the amount of bound aromatic vinyl in the modified conjugated diene polymer obtained by the production method of this embodiment is not particularly limited, but is preferably 0% by mass or more and 60% by mass or less, and more preferably 20% by mass or more and 45% by mass or less.
When the bound conjugated diene amount and bound aromatic vinyl amount are within the above ranges, the balance between low hysteresis loss and wet skid resistance, abrasion resistance, and fracture properties tend to be excellent when made into a vulcanizate.
Here, the amount of bound aromatic vinyl can be measured by ultraviolet absorption of the phenyl group, and the amount of bound conjugated diene can also be calculated from the amount. Specifically, it can be measured according to the method described in the examples below.

In the modified conjugated diene polymer obtained by the production method of the present embodiment, the amount of vinyl bonds in the conjugated diene bond units is not particularly limited, but is preferably 10 mol % or more and 75 mol % or less, and more preferably 20 mol % or more and 65 mol % or less.
When the vinyl bond amount is within the above range, the balance between low hysteresis loss and wet skid resistance, abrasion resistance, and breaking strength tend to be excellent when made into a vulcanizate.
Here, when the modified conjugated diene polymer is a copolymer of butadiene and styrene, the vinyl bond amount (1,2-bond amount) in the butadiene bond unit can be determined by the Hampton method (R.R. Hampton, Analytical Chemistry, 21, 923 (1949)). Specifically, it can be measured by the method described in the examples below.

Regarding the microstructure of the modified conjugated diene polymer, when the bond amounts in the modified conjugated diene polymer obtained by the production method of the present embodiment are within the above-mentioned numerical ranges, and further, when the glass transition temperature of the modified conjugated diene polymer is within the range of −80° C. or higher and −15° C. or lower, a vulcanizate having an even better balance between low hysteresis loss and wet skid resistance tends to be obtained.
The glass transition temperature is measured in accordance with ISO 22768:2006 by recording a DSC curve while increasing the temperature within a predetermined temperature range, and the peak top (inflection point) of the DSC differential curve is determined as the glass transition temperature.

When the modified conjugated diene polymer obtained by the manufacturing method of this embodiment is a conjugated diene-aromatic vinyl copolymer, it is preferable that the number of blocks having 30 or more aromatic vinyl units chained is small or that there is no block. More specifically, when the modified conjugated diene polymer obtained by the manufacturing method of this embodiment is a butadiene-styrene copolymer, the polymer is decomposed by the Kolthoff method (the method described in I.M. KOLTHOFF, et al., J. Polym. Sci. 1, 429 (1946)) and the amount of polystyrene insoluble in methanol is analyzed. In this method, the amount of blocks having 30 or more aromatic vinyl units chained is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, based on the total amount of the modified conjugated diene polymer.

When the modified conjugated diene polymer obtained by the production method of the present embodiment is a conjugated diene-aromatic vinyl copolymer, it is preferable that the proportion of aromatic vinyl units present alone is high from the viewpoint of improving fuel saving performance.
Specifically, when the modified conjugated diene polymer obtained by the production method of the present embodiment is a butadiene-styrene copolymer, when the modified conjugated diene polymer is decomposed by an ozonolysis method known as the Tanaka et al. method (Polymer, 22, 1721 (1981)) and the styrene chain distribution is analyzed by GPC, it is preferable that the amount of isolated styrene is 40% by mass or more relative to the total bound styrene amount, and the amount of chain styrene structures having 8 or more styrene chains is 5.0% by mass or less.
In this case, the resulting vulcanized rubber tends to have excellent performance, particularly low hysteresis loss.

(Modification step)
In the method for producing a modified conjugated diene polymer of the present embodiment, a modification step is carried out in which a predetermined compound [M] is reacted with an active terminal of the conjugated diene polymer into which a branched structure has been introduced, the active terminal being obtained through the above-mentioned polymerization step and branching step.
The compound [M] is a compound having a total of two or more groups "-CR ¹ ═N-A ¹ " and/or groups "-N═C(R ¹ )-A ¹ ". Hereinafter, these groups are also referred to as "specific imino groups".
Here, R ¹ is a hydrogen atom or a hydrocarbyl group, and A ¹ is a monovalent group having an alkoxysilyl group.
By this modification step, a modified conjugated diene polymer having a large number of branches in the polymer chain and modified with a group that interacts with silica can be obtained.

In the specific imino group, examples of the hydrocarbyl group for R ¹ include an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms.
As long as ^A1 has an alkoxysilyl group, the remaining structure thereof is not particularly limited. However, it is preferable that A1 is a group further having a methylene group or a polymethylene group, and it is more preferable that A1 has a methylene group or a polymethylene group and an alkoxysilyl group, and that the methylene group or the polymethylene group is bonded to a nitrogen atom or a carbon atom constituting a carbon-nitrogen double bond.
The number of specific imino groups contained in the compound [M] may be at least 2, and is preferably from 2 to 6. In addition, a plurality of R ^{1 s} and A ^{1 s} contained in the compound [M] may be the same or different.

As the compound [M], a compound represented by the following formula (A) is particularly preferred.

(In formula (A), R ² and R ³ are each independently a hydrocarbyl group having 1 to 20 carbon atoms, R ⁴ is an alkanediyl group having 1 to 20 carbon atoms, and A ² is a group "*-C(R ¹ )=N-" or a group "*-N=C(R ¹ )-" (wherein R ¹ is a hydrogen atom or a hydrocarbyl group, and "*" represents a bond bonded to R ⁵ ).
^R5 is an m-valent hydrocarbyl group having 1 to 20 carbon atoms, or an m-valent group having 1 to 20 carbon atoms which has at least one atom selected from the group consisting of nitrogen atoms, oxygen atoms, and sulfur atoms and has no active hydrogen.
n is an integer from 1 to 3, and m is an integer from 2 to 10.
In formula (A), multiple R ² , R ³ , R ⁴ , A ² , and n may be the same or different.

In the above formula (A), examples of the hydrocarbyl group having 1 to 20 carbon atoms for R ² and R ³ include an alkyl group having 1 to 20 carbon atoms, an allyl group, a cycloalkyl group having 3 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms.
R ⁴ is an alkanediyl group having 1 to 20 carbon atoms, such as a cycloalkylene group having 3 to 20 carbon atoms, or an arylene group having 6 to 20 carbon atoms. R ⁴ is preferably linear.

The above description of the "specific imino group" applies to ^R1 in ^A2 . n is preferably 2 or 3, and more preferably 3, from the viewpoint of a high effect of improving silica dispersibility.
Examples of the m-valent hydrocarbyl group of ^R5 include groups in which m hydrogen atoms have been removed from a chain hydrocarbon having 1 to 20 carbon atoms, an alicyclic hydrocarbon having 3 to 20 carbon atoms, or an aromatic hydrocarbon having 6 to 20 carbon atoms. From the viewpoint of a high effect of improving the abrasion resistance of the resulting vulcanized rubber, a group in which m hydrogen atoms have been removed from the ring portion of an aromatic hydrocarbon (aromatic ring group) is preferred. Examples of the aromatic hydrocarbon include a ring structure represented by the following formula (A-2) and a polycyclic structure in which two or more of the ring structures are linked together (e.g., a biphenyl group, etc.).

(In formula (A-2), r is an integer from 0 to 5.)

In the formula (A), when R ⁵ is an m-valent group having 1 to 20 carbon atoms which has at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom and has no active hydrogen, preferred specific examples include an m-valent heterocyclic group and an m-valent group having a tertiary amine structure.
The heterocyclic group is preferably a conjugated system, and examples thereof include a monocyclic or fused ring such as pyridine, pyrimidine, pyrazine, quinoline, naphthalidine, furan, or thiophene, or a group in which m hydrogen atoms have been removed from a ring portion of a structure in which a plurality of such monocyclic or fused rings are linked together.
m is an integer from 2 to 10.
m is preferably an integer of 2 to 6 from the viewpoint of processability of the rubber composition.
In this specification, the term "active hydrogen" refers to a hydrogen atom bonded to an atom other than a carbon atom, and preferably refers to one having a bond energy lower than that of the carbon-hydrogen bond of polymethylene.

The compound [M] used in the modification step is not limited to the following, but examples thereof include compounds represented by each of the following formulas (M-1) to (M-23).
The compound [M] may be used alone or in combination of two or more kinds.
In addition, R ⁷ in formula (M-11) represents a hydrogen atom or an alkyl group.
The compounds [M] of the formulae (M-1) to (M-23) shown below are also used in the examples and comparative examples described later.

<Compounds [M] used in the modification process: Formula (M-1) to Formula (M-23)>

In the formulas (M-1) to (M-23), Et is an ethyl group, and Me is a methyl group.

Compound [M] can be synthesized by appropriately combining standard methods in organic chemistry. For example, one example of a method for obtaining the compound represented by the above formula (A) is (i) a method of dehydrating and condensing a monofunctional amine compound having an alkoxysilyl group and R ⁴ (e.g., 3-aminopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, etc.) with a polyfunctional aldehyde compound having R ⁵ (e.g., terephthalaldehyde, isophthalaldehyde, phthaldialdehyde, 2,4-pyridinedicarboxaldehyde, etc.), (ii) a method of dehydrating and condensing a polyfunctional amine compound having R ⁵ (e.g., tris(2-aminoethyl)amine, N,N'-bis(2-aminoethyl)methylamine, etc.) with a monofunctional hydroxyl group-containing compound having an alkoxysilyl group and R ⁴ (e.g., 4-(triethoxysilyl)butanal, etc.), and the like. These synthesis reactions are preferably carried out in a suitable organic solvent, and if necessary, in the presence of a suitable catalyst.
However, the method for synthesizing the compound [M] is not limited to the above method.

The reaction between the conjugated diene polymer having an active terminal obtained in the branching step and the compound [M] can be carried out, for example, as a solution reaction.
The proportion of the compound [M] used (the total amount when two or more kinds are used) is preferably 0.01 mol or more, more preferably 0.05 mol or more, per mol of the metal atom involved in the polymerization of the polymerization initiator, from the viewpoint of sufficiently proceeding with the modification reaction. The upper limit is preferably less than 2.0 mol, more preferably less than 1.5 mol, per mol of the metal atom involved in the polymerization of the polymerization initiator, in order to avoid excessive addition.

The temperature of the modification reaction is usually the same as that of the polymerization reaction, and is preferably -20°C to 150°C, and more preferably 0°C to 120°C. If the reaction temperature is low, the viscosity of the polymer after modification tends to increase, and if the reaction temperature is high, the polymerization active terminals are easily deactivated. The reaction time is preferably 1 minute to 5 hours, and more preferably 2 minutes to 1 hour.

When reacting the conjugated diene polymer having an active end obtained in the branching step with the compound [M], other modifiers or coupling agents may be used together with the compound [M].
The other modifier or coupling agent is not particularly limited as long as it is a compound capable of reacting with the active terminal of the conjugated diene polymer obtained by the above-mentioned polymerization step and branching step, and a compound known as a modifier or coupling agent for a conjugated diene polymer can be used.
When other modifiers or coupling agents are used, the proportion of them used is preferably 10 mol % or less, and more preferably 5 mol % or less.

The branched structure of the modified conjugated diene polymer obtained through the above-mentioned polymerization step, branching step, and modification step by the production method of this embodiment preferably has 8 to 36 branches, more preferably has 10 to 24 branches, and further preferably has 12 to 22 branches.
The total number of branching points in the modified conjugated diene polymer obtained by the production method of this embodiment is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, and even more preferably 5 or more.
When the branched structure and the total number of branching points are within the above ranges, the processability, fuel economy, and abrasion resistance tend to be excellent.
When the branched structure of the modified conjugated diene polymer has 8 or more and 36 or less branches, in order to construct one having a total of 2 or more and 15 or less branching points, it is necessary that the molar ratio of the branching agent is ½ or less and 1/100 or more of the polymerization initiator, and that the number of functional groups of the modifier used is 3 or more.
In order to construct a branched structure having 8 to 36 branches and a total number of branching points of 3 to 12, it is preferable to use a branching agent having a molar ratio of 1/3 or less and 1/50 or more of that of the polymerization initiator and a modifying agent having 4 or more functional groups.
In order to construct a branched structure having 10 to 24 branches and a total number of branching points of 4 to 10, it is preferable to use a branching agent having a molar ratio of 1/6 or less and 1/25 or more of the polymerization initiator and a modifying agent having 5 or more functional groups.
In order to construct a branched structure having 12 to 20 branches and a total number of branching points of 5 to 9, it is preferable to use a branching agent having a molar ratio of 1/8 or less and 1/12 or more of that of the polymerization initiator and a modifying agent having 6 or more functional groups.

(Modified conjugated diene polymer)
The modified conjugated diene polymer of this embodiment is a reaction product of a conjugated diene polymer having an active end with a branched structure, and a compound [M] having a total of two or more groups "-CR ¹ ═N-A ¹ " and/or "-N═CR ¹ -A ¹ " (wherein R ¹ is a hydrogen atom or a hydrocarbyl group, and A ¹ is a monovalent group having an alkoxysilyl group).

The modified conjugated diene polymer of this embodiment is preferably represented by the following formula (B):

In formula (B), ^R2 is a hydrocarbyl group having 1 to 20 carbon atoms, ^R6 is a hydrocarbyloxy group having 1 to 20 carbon atoms, or a modified or unmodified branched conjugated diene polymer, ^R4 is an alkanediyl group having 1 to 20 carbon atoms, and Z is a group represented by the following formula (C) or formula (D).
^R5 is an m-valent hydrocarbyl group having 1 to 20 carbon atoms, or an m-valent group having 1 to 20 carbon atoms which has at least one atom selected from the group consisting of nitrogen atoms, oxygen atoms, and sulfur atoms and has no active hydrogen.
n is an integer from 1 to 3, and m is an integer from 2 to 10.
In the formula, multiple R ² , R ⁴ , R ⁶ , Z, and n may be the same or different.

(In formula (C) and formula (D), ^R1 is a hydrogen atom or a hydrocarbyl group, and Poly is a modified or unmodified branched conjugated diene polymer. "*" indicates a bond bonded to ^R5 .)

In the above formulae (B), (C) and (D), the explanation for formula (A) above applies to R ¹ , R ² , R ⁴ and R ⁵ .
The hydrocarbyloxy group of ^R6 is preferably an ethoxy group or a methoxy group.
The conjugated diene polymer chain of ^R6 and the conjugated diene polymer chain Poly in formula (C) and formula (D) have a structure corresponding to the conjugated diene polymer having an active end obtained in the above polymerization step. These conjugated diene polymer chains may have a functional group at the end that interacts with silica.

(Condensation modification process)
In the method for producing a modified conjugated diene polymer of the present embodiment, a condensation modification step of carrying out a condensation reaction in the presence of a condensation promoter may be carried out after or before the above-mentioned modification step.

(Hydrogenation step)
In the method for producing a modified conjugated diene polymer of the present embodiment, a hydrogenation step of hydrogenating the conjugated diene portion may be carried out.
The method for hydrogenating the conjugated diene portion of the conjugated diene polymer is not particularly limited, and any known method can be used.
A suitable hydrogenation method is to blow gaseous hydrogen into a polymer solution in the presence of a catalyst.
The catalyst is not particularly limited, but examples thereof include heterogeneous catalysts such as catalysts in which a precious metal is supported on a porous inorganic material; catalysts in which a salt of nickel, cobalt, or the like is solubilized and reacted with an organoaluminum, or homogeneous catalysts such as catalysts using metallocenes such as titanocene. Among these, titanocene catalysts are preferred from the viewpoint of being able to select mild hydrogenation conditions. Hydrogenation of aromatic groups can also be carried out by using a supported catalyst of a precious metal.

Examples of hydrogenation catalysts include, but are not limited to, (1) supported heterogeneous hydrogenation catalysts in which metals such as Ni, Pt, Pd, and Ru are supported on carbon, silica, alumina, diatomaceous earth, and the like; (2) so-called Ziegler-type hydrogenation catalysts that use transition metal salts such as organic acid salts or acetylacetone salts of Ni, Co, Fe, Cr, and the like and reducing agents such as organoaluminum; and (3) so-called organometallic complexes such as organometallic compounds of Ti, Ru, Rh, Zr, and the like. Furthermore, examples of hydrogenation catalysts include, but are not limited to, known hydrogenation catalysts described in JP-B-42-8704, JP-B-43-6636, JP-B-63-4841, JP-B-1-37970, JP-B-1-53851, JP-B-2-9041, and JP-A-8-109219. A preferred hydrogenation catalyst is a reaction mixture of a titanocene compound and a reducing organometallic compound.

(Step of adding deactivator and neutralizer)
In the method for producing a modified conjugated diene polymer of the present embodiment, after the above-mentioned modification step, a deactivator, a neutralizer, and the like may be added to the polymer solution, if necessary.
The quenching agent is not limited to the following, but examples thereof include water; and alcohols such as methanol, ethanol, and isopropanol.
Examples of the neutralizing agent include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and versatic acid (a highly branched carboxylic acid mixture having 9 to 11 carbon atoms, with the majority having 10 carbon atoms); aqueous solutions of inorganic acids; and carbon dioxide gas.

(Rubber stabilizer addition process)
In the method for producing the modified conjugated diene polymer of the present embodiment, it is preferable to add a rubber stabilizer from the viewpoint of preventing gel formation after polymerization and improving stability during processing.
The rubber stabilizer is not limited to the following ones, and known ones can be used. For example, antioxidants such as 2,6-di-tert-butyl-4-hydroxytoluene (hereinafter also referred to as "BHT"), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol)propionate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol are preferred.

(Rubber softener addition process)
In the method for producing the modified conjugated diene polymer of the present embodiment, from the viewpoint of further improving the productivity of the modified conjugated diene polymer and the processability when a filler or the like is blended to form a resin composition, a rubber softener can be added as necessary.
The rubber softener is not particularly limited, but examples thereof include extender oil, liquid rubber, and resin.
The method of adding a rubber softener to a modified conjugated diene polymer is not limited to the following, but a preferred method is to add a rubber softener to a modified conjugated diene polymer solution, mix, and remove the solvent from the resulting polymer solution containing the rubber softener.

Examples of preferred extender oils include aromatic oils, naphthenic oils, and paraffin oils. Among these, aromatic substitute oils having a polycyclic aromatic (PCA) content of 3% by mass or less according to the IP346 method are preferred from the viewpoint of environmental safety, oil bleeding prevention, and wet grip properties. Examples of aromatic substitute oils include TDAE (Treated Distillate Aromatic Extracts), MES (Mild Extraction Solvate), and RAE (Residual Aromatic Extracts) shown in Kautschuk Gummi Kunststoffe 52(12)799(1999).
Preferred liquid rubbers include, but are not limited to, liquid polybutadiene, liquid styrene-butadiene rubber, and the like.
The effects of adding liquid rubber include the ability to improve the processability of a resin composition containing the modified conjugated diene polymer and a filler, etc., and the ability to shift the glass transition temperature of the resin composition to a lower temperature, which tends to improve the abrasion resistance, low hysteresis loss, and low-temperature properties of the vulcanized product.
Resins as rubber softeners include, but are not limited to, aromatic petroleum resins, coumarone-indene resins, terpene resins, rosin derivatives (including paulownia oil resins), tall oil, tall oil derivatives, rosin ester resins, natural and synthetic terpene resins, aliphatic hydrocarbon resins, aromatic hydrocarbon resins, mixed aliphatic-aromatic hydrocarbon resins, coumarin-indene resins, phenolic resins, p-tert-butylphenol-acetylene resins, phenol-formaldehyde resins, xylene-formaldehyde resins, monoolefin oligomers, diolefin oligomers, aromatic hydrocarbon resins, aromatic petroleum resins, hydrogenated aromatic hydrocarbon resins, cyclic aliphatic hydrocarbon resins, hydrogenated hydrocarbon resins, hydrocarbon resins, hydrogenated paulownia oil resins, hydrogenated oil resins, esters of hydrogenated oil resins and monofunctional or polyfunctional alcohols, etc. These resins may be used alone or in combination of two or more. When hydrogenating, all of the unsaturated groups may be hydrogenated, or some may be left.
The effects of adding a resin as a rubber softener include the following: when a resin composition is prepared by blending the modified conjugated diene polymer with a filler or the like, the processability can be improved; when a vulcanizate is prepared, the breaking strength tends to be improved; and, by shifting the glass transition temperature of the resin composition to the higher temperature side, the wet skid resistance tends to be improved.

The amount of the rubber softener, such as an extender oil, liquid rubber, or resin, added is not particularly limited, but is preferably 1 part by mass or more and 60 parts by mass or less, more preferably 5 parts by mass or more and 50 parts by mass or less, and even more preferably 10 parts by mass or more and 37.5 parts by mass or less, relative to 100 parts by mass of the modified conjugated diene-based polymer obtained by the production method of the present embodiment.
When the rubber softener is added within the above range, the processability of a resin composition containing the modified conjugated diene polymer obtained by the production method of the present embodiment and a filler or the like is improved, and the breaking strength and abrasion resistance of a vulcanizate tend to be improved.

(Solvent removal process)
In the method for producing the modified conjugated diene polymer of the present embodiment, a known method can be used as a method for obtaining the obtained modified conjugated diene polymer from the polymer solution. The method is not particularly limited, but examples thereof include a method of separating the solvent by steam stripping or the like, filtering the polymer, and further dehydrating and drying it to obtain the polymer, a method of concentrating in a flashing tank and further devolatilizing with a vent extruder or the like, and a method of directly devolatilizing with a drum dryer or the like.

[Rubber composition and method for producing rubber composition]
The rubber composition of the present embodiment contains a rubber component containing 10% by mass or more of the modified conjugated diene-based polymer produced by the production method of the present embodiment described above, and 5.0 parts by mass or more and 150 parts by mass or less of a filler per 100 parts by mass of the rubber component.
The method for producing the rubber composition of the present embodiment includes the steps of obtaining a modified conjugated diene polymer by the above-described production method, obtaining a rubber component containing 10% by mass or more of the modified conjugated diene polymer, and incorporating 5.0 parts by mass or more and 150 parts by mass or less of a filler per 100 parts by mass of the rubber component.
Furthermore, it is preferable for the rubber component to contain 10% by mass of the modified conjugated diene polymer obtained by the production method of the present embodiment from the viewpoints of improving fuel economy performance, processability, and abrasion resistance.

The filler preferably includes a silica-based inorganic filler.
By dispersing a silica-based inorganic filler as a filler, the rubber composition tends to have excellent processability when vulcanized, and the vulcanized product tends to have an excellent balance between abrasion resistance, breaking strength, and low hysteresis loss and wet skid resistance.
The rubber composition preferably contains a silica-based inorganic filler even when it is used for vulcanized rubber applications such as automobile parts such as tires and anti-vibration rubbers, and shoes.

The rubber composition of the present embodiment is obtained by mixing a rubber component containing 10% by mass or more of the modified conjugated diene-based polymer obtained by the above-mentioned production method with the filler.
The rubber component may contain a rubber-like polymer (hereinafter simply referred to as "rubber-like polymer") other than the above-mentioned modified conjugated diene polymer.
Examples of such rubber-like polymers include, but are not limited to, conjugated diene polymers or hydrogenated products thereof, random copolymers of conjugated diene compounds and vinyl aromatic compounds or hydrogenated products thereof, block copolymers of conjugated diene compounds and vinyl aromatic compounds or hydrogenated products thereof, and others include non-diene polymers and natural rubber.

Examples of rubber-like polymers include, but are not limited to, styrene-based elastomers such as butadiene rubber or its hydrogenated product, isoprene rubber or its hydrogenated product, styrene-butadiene rubber or its hydrogenated product, styrene-butadiene block copolymer or its hydrogenated product, and styrene-isoprene block copolymer or its hydrogenated product, and acrylonitrile-butadiene rubber or its hydrogenated product.

Non-diene polymers include, but are not limited to, olefin elastomers such as ethylene-propylene rubber, ethylene-propylene-diene rubber, ethylene-butene-diene rubber, ethylene-butene rubber, ethylene-hexene rubber, and ethylene-octene rubber, butyl rubber, brominated butyl rubber, acrylic rubber, fluororubber, silicone rubber, chlorinated polyethylene rubber, epichlorohydrin rubber, α,β-unsaturated nitrile-acrylate-conjugated diene copolymer rubber, urethane rubber, and polysulfide rubber.

Natural rubber is not limited to the following, but examples include smoked sheets RSS3-5, SMR, and epoxidized natural rubber.

The various rubber-like polymers described above may be modified rubbers to which polar functional groups such as hydroxyl groups and amino groups have been added. When the rubber composition of this embodiment is used as a tire material, the rubber-like polymers preferably used are butadiene rubber, isoprene rubber, styrene-butadiene rubber, natural rubber, and butyl rubber.

From the viewpoint of the balance between various performances and processing characteristics of the resin composition, the weight average molecular weight of the rubber-like polymer is preferably from 2000 to 2,000,000, and more preferably from 5000 to 1,500,000. Also, a low molecular weight rubber-like polymer, so-called liquid rubber, can be used.
These rubber-like polymers may be used alone or in combination of two or more.

In the case where a rubber composition using the modified conjugated diene polymer obtained by the production method of this embodiment is used as a rubber composition containing the above-mentioned rubbery polymer, the content ratio (mass ratio) of the above-mentioned modified conjugated diene polymer to the rubbery polymer (the above-mentioned modified conjugated diene polymer/rubbery polymer) is preferably 10/90 or more and 100/0 or less, more preferably 20/80 or more and 90/10 or less, and even more preferably 50/50 or more and 80/20 or less.
Therefore, the rubber component contains the above-mentioned modified conjugated diene-based polymer in an amount of preferably 10% by mass or more and 100% by mass or less, more preferably 20% by mass or more and 90% by mass or less, and even more preferably 50% by mass or more and 80% by mass or less, based on the total amount (100% by mass) of the rubber component.

When the content ratio of (modified conjugated diene polymer/rubber-like polymer) is within the above range, the vulcanizate tends to have excellent abrasion resistance and fracture strength, and also tends to have a good balance between low hysteresis loss and wet skid resistance.

The filler contained in the rubber composition of the present embodiment is not limited to the following, but examples thereof include, in addition to the silica-based inorganic filler, carbon black, metal oxides, and metal hydroxides. Among these, silica-based inorganic fillers are preferred.
The fillers may be used alone or in combination of two or more.
The content of the filler in the rubber composition is 5.0 parts by mass or more and 150 parts by mass or less, preferably 20 parts by mass or more and 100 parts by mass or less, and more preferably 30 parts by mass or more and 90 parts by mass or less, based on 100 parts by mass of the rubber component containing the modified conjugated diene-based polymer.
In the rubber composition, the content of the filler is 5.0 parts by mass or more per 100 parts by mass of the rubber component from the viewpoint of expressing the effect of adding the filler, and is 150 parts by mass or less per 100 parts by mass of the rubber component from the viewpoint of sufficiently dispersing the filler and making the processability and mechanical strength of the rubber composition practically sufficient.

The silica-based inorganic filler is not particularly limited and any known filler can be used, but solid particles containing _SiO2 or _Si3Al as a constituent unit are preferred, and solid particles containing _SiO2 or _Si3Al as a main component of the constituent unit are more preferred. Here, the main component refers to a component contained in the silica-based inorganic filler in an amount of 50 mass% or more, preferably 70 mass% or more, and more preferably 80 mass% or more.

Examples of silica-based inorganic fillers include, but are not limited to, inorganic fibrous substances such as silica, clay, talc, mica, diatomaceous earth, wollastonite, montmorillonite, zeolite, glass fiber, etc. Other examples include silica-based inorganic fillers whose surfaces have been hydrophobized, and mixtures of silica-based inorganic fillers and inorganic fillers other than silica-based fillers.
Among these, silica and glass fiber are preferred from the viewpoints of strength, abrasion resistance, and the like, and silica is more preferred.
Examples of silica include dry silica, wet silica, and synthetic silicate silica. Among these silicas, wet silica is preferred from the viewpoint of excellent balance between the effect of improving fracture strength and wet skid resistance.

From the viewpoint of obtaining practically good abrasion resistance and breaking strength in the rubber composition, the nitrogen adsorption specific surface area of the silica-based inorganic filler determined by the BET adsorption method is preferably 100 ^m2 /g or more and 300 ^m2 /g or less, and more preferably 170 ^m2 /g or more and 250 ^m2 /g or less.
If necessary, a silica-based inorganic filler having a relatively small specific surface area (e.g., a specific surface area of less than 200 ^m2 /g) can be used in combination with a silica-based inorganic filler having a relatively large specific surface area (e.g., 200 ^m2 /g or more).
In particular, when using a silica-based inorganic filler with a relatively large specific surface area (e.g., 200 ^m2 /g or more), a rubber composition containing the above-mentioned modified conjugated diene polymer improves the dispersibility of silica, is particularly effective in improving abrasion resistance, and tends to achieve a high level of balance between good fracture strength and low hysteresis loss.

The content of the silica-based inorganic filler in the rubber composition is preferably 5.0 parts by mass or more and 150 parts by mass or less, and more preferably 20 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of the rubber component containing the modified conjugated diene polymer obtained by the manufacturing method of this embodiment. In the rubber composition, the content of the silica-based inorganic filler is preferably 5.0 parts by mass or more per 100 parts by mass of the rubber component from the viewpoint of expressing the effect of adding the silica-based inorganic filler, and is preferably 150 parts by mass or less per 100 parts by mass of the rubber component from the viewpoint of sufficiently dispersing the silica-based inorganic filler and making the processability and mechanical strength of the rubber composition practically sufficient.

The carbon black is not limited to the following, but examples thereof include carbon black of various classes such as SRF, FEF, HAF, ISAF, SAF, etc. Among these, carbon black having a nitrogen adsorption specific surface area of 50 ^m2 /g or more and a dibutyl phthalate (DBP) oil absorption of 80 mL/100 g or less is preferred.

In the rubber composition, the content of carbon black is preferably 0.5 parts by mass or more and 100 parts by mass or less, more preferably 3.0 parts by mass or more and 100 parts by mass or less, and even more preferably 5.0 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of the rubber component containing the modified conjugated diene polymer obtained by the manufacturing method of this embodiment. In the rubber composition, the content of carbon black is preferably 0.5 parts by mass or more per 100 parts by mass of the rubber component from the viewpoint of expressing the performance required for applications such as tires, such as dry grip performance and electrical conductivity, and is preferably 100 parts by mass or less per 100 parts by mass of the rubber component from the viewpoint of dispersibility.

Metal oxide refers to solid particles whose main component is a structural unit of the chemical formula MxOy (M represents a metal atom, and x and y each independently represent an integer from 1 to 6).

Metal oxides include, but are not limited to, alumina, titanium oxide, magnesium oxide, and zinc oxide.

Metal hydroxides include, but are not limited to, aluminum hydroxide, magnesium hydroxide, and zirconium hydroxide.

In the method for producing the rubber composition of the present embodiment, a silane modifier may be added.
The silane modifier has a function of strengthening the interaction between the rubber component and the inorganic filler, and has groups that have affinity or binding properties for both the rubber component and the silica-based inorganic filler, and is preferably a compound that has a sulfur bond portion and an alkoxysilyl group or a silanol group portion in one molecule. Examples of such compounds include, but are not limited to, bis-[3-(triethoxysilyl)-propyl]-tetrasulfide, bis-[3-(triethoxysilyl)-propyl]-disulfide, and bis-[2-(triethoxysilyl)-ethyl]-tetrasulfide.

In the rubber composition, the content of the silane modifier is preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 0.5 parts by mass or more and 20 parts by mass or less, and even more preferably 1.0 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the inorganic filler described above. When the content of the silane modifier is within the above range, the above-mentioned effect of adding the silane modifier tends to be more pronounced.

The rubber composition of the present embodiment may contain a rubber softener from the viewpoint of improving its processability.
The amount of rubber softener added is expressed as the total amount including the amount of rubber softener previously contained in the modified conjugated diene polymer or other rubber-like polymers, and the amount of rubber softener added when preparing a rubber composition, per 100 parts by mass of the rubber component containing the modified conjugated diene polymer obtained by the production method of the present embodiment described above.
As the rubber softener, mineral oil or a liquid or low molecular weight synthetic softener is preferable.
Mineral oil-based rubber softeners known as process oils or extender oils, which are used to soften rubber, increase its volume, and improve its processability, are mixtures of aromatic rings, naphthenic rings, and paraffin chains; those in which the carbon number of paraffin chains accounts for 50% or more of the total carbon are called paraffinic; those in which the carbon number of naphthenic rings accounts for 30% to 45% of the total carbon are called naphthenic; and those in which the aromatic carbon number accounts for more than 30% of the total carbon are called aromatic.
When the modified conjugated diene polymer of the present embodiment is a copolymer of a conjugated diene compound and a vinyl aromatic compound, it is preferable to use a rubber softener having an appropriate aromatic content, since it tends to have good compatibility with the copolymer.
In the rubber composition, the content of the rubber softener is preferably 0 parts by mass or more and 100 parts by mass or less, more preferably 10 parts by mass or more and 90 parts by mass or less, and even more preferably 30 parts by mass or more and 90 parts by mass or less, per 100 parts by mass of the rubber component. By making the content of the rubber softener 100 parts by mass or less per 100 parts by mass of the rubber component, bleeding out is suppressed and stickiness of the surface of the rubber composition tends to be suppressed.

The method for mixing the modified conjugated diene polymer obtained by the production method of the present embodiment with various additives such as other rubber-like polymers, silica-based inorganic fillers, carbon black and other fillers, silane modifiers, and rubber softeners is not limited to the following, but examples thereof include a melt-kneading method using a general mixer such as an open roll, a Banbury mixer, a kneader, a single-screw extruder, a twin-screw extruder, or a multi-screw extruder, and a method in which the components are dissolved and mixed and then the solvent is removed by heating.
Among these, the melt kneading method using a roll, a Banbury mixer, a kneader, or an extruder is preferred from the viewpoints of productivity and good kneading properties. In addition, either a method of kneading the rubber component, other fillers, silane modifier, and additives at once or a method of mixing them in several batches can be applied.

The rubber composition of the present embodiment may be a vulcanized composition that has been subjected to a vulcanization treatment with a vulcanizing agent. Examples of the vulcanizing agent include, but are not limited to, radical generators such as organic peroxides and azo compounds, oxime compounds, nitroso compounds, polyamine compounds, sulfur, and sulfur compounds. Examples of the sulfur compounds include sulfur monochloride, sulfur dichloride, disulfide compounds, and polymeric polysulfur compounds.
In the rubber composition of the present embodiment, the content of the vulcanizing agent is preferably 0.01 parts by mass or more and 20 parts by mass or less, and more preferably 0.1 parts by mass or more and 15 parts by mass or less, based on 100 parts by mass of the rubber component. As the vulcanization method, a conventionally known method can be applied, and the vulcanization temperature is preferably 120° C. or more and 200° C. or less, and more preferably 140° C. or more and 180° C. or less.

When vulcanizing, a vulcanization accelerator may be used as necessary. As the vulcanization accelerator, a conventionally known material may be used, and examples thereof include, but are not limited to, sulfenamide-based, guanidine-based, thiuram-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, thiourea-based, and dithiocarbamate-based vulcanization accelerators. In addition, examples of the vulcanization aid include, but are not limited to, zinc oxide and stearic acid. The content of the vulcanization accelerator is preferably 0.01 parts by mass or more and 20 parts by mass or less, and more preferably 0.1 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the rubber component.

In the rubber composition of the present embodiment, various additives such as softeners and fillers other than those described above, heat stabilizers, antistatic agents, weather stabilizers, antioxidants, colorants, and lubricants may be used within the scope that does not impair the object of the present embodiment.
As the other softening agents, known softening agents can be used.
The other fillers are not particularly limited, but include, for example, calcium carbonate, magnesium carbonate, aluminum sulfate, and barium sulfate. As the heat resistance stabilizer, antistatic agent, weather resistance stabilizer, antiaging agent, colorant, and lubricant, known materials can be used.

[Tire and tire manufacturing method]
The tire of the present embodiment contains the rubber composition of the present embodiment described above.
The method for producing a tire of the present embodiment includes a step of obtaining a modified conjugated diene polymer by the production method of the present embodiment, a step of obtaining a rubber composition containing the modified conjugated diene polymer, and a step of molding the rubber composition.
The rubber composition containing the modified conjugated diene polymer obtained by the production method of the present embodiment described above is suitably used as a rubber composition for tires.

The rubber composition for tires is not limited to the following, but can be used in various parts of tires such as fuel-efficient tires, all-season tires, high-performance tires, and studless tires, including the tread, carcass, sidewalls, and bead portions. In particular, the rubber composition for tires has an excellent balance of abrasion resistance, breaking strength, low hysteresis loss, and wet skid resistance when vulcanized, and is therefore suitable for use in the treads of fuel-efficient tires and high-performance tires.

Hereinafter, the present embodiment will be described in more detail with reference to specific examples and comparative examples, but the present embodiment is not limited in any way to the following examples and comparative examples.
Various physical properties in the examples and comparative examples were measured by the methods shown below.
Hereinafter, a conjugated diene polymer that is coupled with a nitrogen atom-containing modifier made of a specific compound will be referred to as a "modified conjugated diene polymer" or a "coupled conjugated diene polymer".
Moreover, an unmodified conjugated diene polymer will be referred to as an "unmodified conjugated diene polymer" or a "conjugated diene polymer".

(Physical Property 1) Polymer Mooney Viscosity An unmodified conjugated diene polymer or a conjugated diene polymer coupled with a nitrogen atom-containing modifier (hereinafter also referred to as a "modified conjugated diene polymer") was used as a sample, and the Mooney viscosity was measured using a Mooney viscometer (manufactured by Ueshima Seisakusho Co., Ltd., product name "VR1132") in accordance with ISO 289 using an L-type rotor.
The measurement temperature was 110° C. when an unmodified conjugated diene polymer was used as the sample, and 100° C. when a modified conjugated diene polymer was used as the sample.
First, the sample was preheated at the test temperature for 1 minute, and then the rotor was rotated at 2 rpm. The torque after 4 minutes was measured and taken as the Mooney viscosity (ML ₍₁₊₄₎ ).

(Physical Property 2) Mooney Relaxation Rate The modified conjugated diene polymer was used as a sample, and the Mooney viscosity was measured using a Mooney viscometer (manufactured by Ueshima Seisakusho Co., Ltd. under the trade name "VR1132") with an L-shaped rotor in accordance with ISO 289. Then, the rotation of the rotor was immediately stopped, and the torque was recorded in Mooney units every 0.1 seconds from 1.6 seconds to 5 seconds after the rotation was stopped. The slope of the straight line obtained by plotting the torque versus time (seconds) on a double logarithmic scale was determined, and the absolute value of the slope was taken as the Mooney relaxation rate (MSR).

(Physical Property 3) Branching Degree (Bn)
The branching degree (Bn) of the modified conjugated diene polymer was measured by a GPC-light scattering method equipped with a viscosity detector as follows.
The modified conjugated diene polymer was used as a sample and was measured using a gel permeation chromatography (GPC) measuring device (manufactured by Malvern under the trade name "GPCmax VE-2001") having three columns packed with polystyrene gel connected together, and three detectors connected in this order: a light scattering detector, an RI detector, and a viscosity detector (manufactured by Malvern under the trade name "TDA305"). Based on standard polystyrene, the absolute molecular weight was determined from the results of the light scattering detector and the RI detector, and the intrinsic viscosity was determined from the results of the RI detector and the viscosity detector.
The linear polymer was used as having an intrinsic viscosity [η] = -3.883 M ^0.771 , and the shrinkage factor (g') was calculated as the ratio of the intrinsic viscosity corresponding to each molecular weight, where M represents the absolute molecular weight.
The obtained shrinkage factor (g') was then used to calculate the branching degree (Bn), defined as g'=6Bn/[(Bn+1)(Bn+2)].
The eluent used was tetrahydrofuran (hereinafter also referred to as "THF") containing 5 mmol/L triethylamine.
The columns used were "TSKgel G4000HXL", "TSKgel G5000HXL", and "TSKgel G6000HXL" manufactured by Tosoh Corporation.
20 mg of a measurement sample was dissolved in 10 mL of THF to prepare a measurement solution, and 100 μL of the measurement solution was injected into a GPC measurement device and measured under conditions of an oven temperature of 40° C. and a THF flow rate of 1 mL/min.

(Physical property 4) Molecular weight <Measurement conditions 1>:
Using unmodified conjugated diene polymers or modified conjugated diene polymers as samples, a GPC measuring device (manufactured by Tosoh Corporation under the trade name "HLC-8320GPC") was used, which had three columns packed with polystyrene gel. The chromatogram was measured using an RI detector (trade name "HLC8020" manufactured by Tosoh Corporation) and the weight average molecular weight (Mw) and number average molecular weight (Mw) were calculated based on a calibration curve obtained using standard polystyrene. The molecular weight (Mn) and molecular weight distribution (Mw/Mn) were determined.
The eluent used was 5 mmol/L triethylamine-containing THF (tetrahydrofuran). Three columns, both of which were manufactured by Tosoh Corporation under the trade name "TSKgel SuperMultiporeHZ-H", were connected, and a guard column, both of which were manufactured by Tosoh Corporation under the trade name "TSKgel SuperMultiporeHZ-H", was connected in front of the columns. "TSKguardcolumn SuperMP(HZ)-H" was connected and used.
10 mg of a measurement sample was dissolved in 10 mL of THF to prepare a measurement solution, and 10 μL of the measurement solution was injected into a GPC measurement device and measured under conditions of an oven temperature of 40° C. and a THF flow rate of 0.35 mL/min.
Among the various samples measured under the above measurement condition 1, samples whose molecular weight distribution (Mw/Mn) was less than 1.6 were measured again under the following measurement condition 2. For samples whose molecular weight distribution was 1.6 or more, measurement was performed under measurement condition 1.
<Measurement condition 2>:
Using an unmodified conjugated diene polymer or a modified conjugated diene polymer as a sample, a chromatogram was measured using a GPC measuring device in which three columns packed with polystyrene gel were connected, and standard polystyrene was used. The weight average molecular weight (Mw) and number average molecular weight (Mn) were determined based on the calibration curve used.
The eluent used was THF containing 5 mmol/L triethylamine. The columns were: guard column: Tosoh Corporation's product name "TSKguardcolumn SuperH-H"; column: Tosoh Corporation's product names "TSKgel SuperH5000" and "TSKgel SuperH6000". "TSKgel Super H7000" was used.
An RI detector (HLC8020, product name, manufactured by Tosoh Corporation) was used under the conditions of an oven temperature of 40° C. and a THF flow rate of 0.6 mL/min. 10 mg of a sample to be measured was dissolved in 20 mL of THF to prepare a measurement solution. Then, 20 μL of the measurement solution was injected into a GPC measurement device and measurement was performed.
For samples that were measured under measurement condition 1 and had a molecular weight distribution value of less than 1.6, measurement was performed under measurement condition 2.

(Physical Property 5) Modification Ratio The modification ratio of the modified conjugated diene polymer was measured by a column adsorption GPC method as follows.
The modified conjugated diene polymer was used as a sample, and the measurement was carried out by utilizing the characteristic of the modified basic polymer component being adsorbed in a GPC column filled with silica gel.
The amount of a sample solution containing a sample and low molecular weight internal standard polystyrene was adsorbed onto the silica-based column by measuring the difference between the chromatogram measured using a polystyrene-based column and the chromatogram measured using a silica-based column, and the modification rate was calculated.
Specifically, it is as follows:
Furthermore, samples that were measured under the above-mentioned (Physical Property 4) Measurement Condition 1 and had a molecular weight distribution value of 1.6 or more were measured under the following Measurement Condition 3. Samples that were measured under the above-mentioned (Physical Property 4) Measurement Condition 1 and had a molecular weight distribution value of less than 1.6 were measured under the following Measurement Condition 4.

<Preparation of sample solution>:
10 mg of a sample and 5 mg of standard polystyrene were dissolved in 20 mL of THF to prepare a sample solution.
<Measurement condition 3>:
GPC measurement conditions using a polystyrene column:
A Tosoh Corporation product name "HLC-8320GPC" was used, and 10 μL of the sample solution was injected into the device using THF containing 5 mmol/L triethylamine as an eluent. A chromatogram was obtained using an RI detector under the conditions of a column oven temperature of 40° C. and a THF flow rate of 0.35 mL/min.
The columns used were three Tosoh Corporation products under the trade name "TSKgel SuperMultiporeHZ-H" connected together, and a Tosoh Corporation product under the trade name "TSKguardcolumn SuperMP(HZ)-H" was connected in front of them as a guard column.
<Measurement condition 4>:
GPC measurement conditions using a polystyrene column:
THF containing 5 mmol/L triethylamine was used as the eluent, and 20 μL of the sample solution was injected into the device for measurement.
The columns used were a guard column manufactured by Tosoh Corporation under the trade name "TSKguardcolumn SuperH-H" and columns manufactured by Tosoh Corporation under the trade names "TSKgel SuperH5000", "TSKgel SuperH6000", and "TSKgel SuperH7000". Measurement was performed using an RI detector (manufactured by Tosoh Corporation, HLC8020) under conditions of a column oven temperature of 40°C and a THF flow rate of 0.6 mL/min to obtain a chromatogram.

GPC measurement conditions using a silica column:
Using a Tosoh Corporation product name "HLC-8320GPC", THF was used as the eluent, 50 μL of the sample solution was injected into the device, and a chromatogram was obtained using an RI detector under the conditions of a column oven temperature of 40° C. and a THF flow rate of 0.5 ml/min. The columns used were Zorbax PSM-1000S, PSM-300S, and PSM-60S, and a guard column "DIOL 4.6×12.5 mm 5 micron" was connected to the front of the columns.

How to calculate the denaturation rate:
The total peak area of the chromatogram using the polystyrene-based column was set to 100, the peak area of the sample was set to P1, the peak area of the standard polystyrene was set to P2, the total peak area of the chromatogram using the silica-based column was set to 100, the peak area of the sample was set to P3, and the peak area of the standard polystyrene was set to P4, and the modification rate (%) was calculated according to the following formula.
Denaturation rate (%) = [1 - (P2 x P3) / (P1 x P4)] x 100
(where P1 + P2 = P3 + P4 = 100)

(Physical Property 6) Bound Styrene Amount A modified conjugated diene polymer not containing a rubber softener was used as a sample, and 100 mg of the sample was dissolved in chloroform up to 100 mL to prepare a measurement sample.
The amount of bound styrene (mass %) relative to 100 mass % of the sample modified conjugated diene polymer was measured based on the amount of absorption of ultraviolet light at wavelengths (around 254 nm) by the phenyl group of styrene (measuring device: Shimadzu Corporation spectrophotometer "UV-2450").

(Physical Property 7) Microstructure of Butadiene Moiety (1,2-Vinyl Bond Amount)
A modified conjugated diene polymer not containing a rubber softener was used as a sample, and 50 mg of the sample was dissolved in 10 mL of carbon disulfide to prepare a measurement sample.
Using a solution cell, an infrared spectrum was measured in the range of 600 to 1000 cm ^-1 , and the microstructure of the butadiene portion, i.e., the amount of 1,2-vinyl bonds (mol%) was determined from the absorbance at a predetermined wave number according to the calculation formula of the Hampton method (the method described in R. R. Hampton, Analytical Chemistry 21, 923 (1949)) (measuring device: Fourier transform infrared spectrophotometer "FT-IR230" manufactured by JASCO Corporation).

(Physical Property 8) Molecular weight measured by GPC-light scattering method (absolute molecular weight Mw-i)
The modified conjugated diene polymer was used as a sample, and a chromatogram was measured using a GPC-light scattering measurement device in which three columns packed with polystyrene gel were connected, and the weight average molecular weight (Mw-i) was determined based on the solution viscosity and the light scattering method (also referred to as the "absolute molecular weight").
The eluent used was a mixed solution of tetrahydrofuran and triethylamine (THF in TEA: prepared by mixing 5 mL of triethylamine in 1 L of tetrahydrofuran).
The columns used were a guard column (manufactured by Tosoh Corporation under the trade name "TSKguardcolumn HHR-H") and columns (manufactured by Tosoh Corporation under the trade names "TSKgel G6000HHR", "TSKgel G5000HHR", and "TSKgel G4000HHR").
A GPC-light scattering measuring device (trade name "Viscotek TDAmax" manufactured by Malvern Instruments) was used under conditions of an oven temperature of 40° C. and a THF flow rate of 1.0 mL/min.
10 mg of a sample to be measured was dissolved in 20 mL of THF to prepare a measurement solution, and 200 μL of the measurement solution was injected into a GPC measurement device and measured.

(Evaluation 9) Change over time (Mooney viscosity increase after one month)
The modified conjugated diene polymer was stored at room temperature and pressure for one month, and the Mooney viscosity after storage was measured, and the difference from the Mooney viscosity measured immediately after polymerization was calculated.
In the table, this is indicated as "δML Mooney viscosity."
The smaller the value, the less change there is over time and the better the quality stability.

[Modified conjugated diene polymer]
(Example 1) Modified conjugated diene polymer (sample 1)
Two tank-type pressure vessels each having an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L/D) of 4.0, an inlet at the bottom and an outlet at the top, and equipped with an agitator as a tank-type reactor and a jacket for temperature control were connected together as polymerization reactors.
1,3-butadiene, which had been previously dehydrated, was mixed under the conditions of 18.6 g/min, styrene at 10.0 g/min, and n-hexane at 175.2 g/min. In a static mixer provided in the middle of the pipe supplying this mixed solution to the inlet of the reactor, n-butyllithium for inactivating remaining impurities was added at 0.103 mmol/min, mixed, and then continuously supplied to the bottom of the reactor. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance was supplied at a rate of 0.081 mmol/min, and n-butyllithium as a polymerization initiator was supplied at a rate of 0.143 mmol/min to the bottom of the first reactor, which was vigorously mixed with a stirrer, and the temperature inside the reactor was maintained at 67°C.
The polymer solution was continuously withdrawn from the top of the first reactor and continuously supplied to the bottom of the second reactor to continue the reaction at 70° C., and further supplied to a static mixer from the top of the second reactor. When the polymerization was sufficiently stabilized, trimethoxy(4-vinylphenyl)silane (abbreviated as "BS-1" in the table) was added as a branching agent from the bottom of the second reactor at a rate of 0.0190 mmol/min while copolymerizing 1,3-butadiene and styrene, and a polymerization reaction and a branching reaction were carried out to obtain a conjugated diene-based polymer having a main chain branched structure.
When the polymerization reaction and the branching reaction became stable, a small amount of the conjugated diene polymer solution before the addition of the modifier was withdrawn, and an antioxidant (BHT) was added in an amount of 0.2 g per 100 g of the polymer, after which the solvent was removed and the Mooney viscosity at 110° C. and various molecular weights were measured. The physical properties are shown in Table 1.
Next, compound M-1 (the compound shown as (M-1) in the above <Compound [M] used in the modification step>. In the table, it is abbreviated as "M-1") was continuously added as a modifying agent to the polymer solution flowing out from the outlet of the reactor at a rate of 0.0360 mmol/min, and mixed using a static mixer to carry out a coupling reaction. At this time, the time until the modifying agent was added to the polymer solution flowing out from the outlet of the reactor was 4.8 minutes, the temperature was 68°C, and the difference between the temperature in the polymerization step and the temperature before the modifying agent was added was 2°C.
A small amount of the conjugated diene polymer solution after the coupling reaction was withdrawn, and an antioxidant (BHT) was added in an amount of 0.2 g per 100 g of the polymer, and the solvent was then removed. The amount of bound styrene (physical property 6) and the microstructure of the butadiene portion (amount of 1,2-vinyl bonds: physical property 7) were measured. The measurement results are shown in Table 1.
Next, an antioxidant (BHT) was continuously added to the polymer solution after the coupling reaction at 0.055 g/min (n-hexane solution) so that the amount was 0.2 g per 100 g of polymer, and the coupling reaction was terminated. Simultaneously with the antioxidant, SRAE oil (JOMO Process NC140, manufactured by JX Nippon Oil & Energy Corporation) was continuously added as a rubber softener so that the amount was 25.0 g per 100 g of polymer, and mixed with a static mixer. The solvent was removed by steam stripping to obtain a modified conjugated diene polymer (sample 1).
The physical properties of Sample 1 are shown in Table 1.
The structure of the modified conjugated diene polymer was identified by comparing the molecular weight measured by GPC and the branching degree measured by GPC with a viscometer for the polymer before the addition of the branching agent, the polymer after the addition of the branching agent, and the polymer in each step after the addition of the modifier. The structure of each sample was similarly identified.

(Example 2) Modified conjugated diene polymer (sample 2)
A modified conjugated diene polymer (sample 2) was obtained in the same manner as in Example 1, except that the modifying agent was changed from compound M-1 to compound M-2 (a compound shown as (M-2) in the above <Compounds [M] used in the modification step>. In the table, it is abbreviated as "M-2") and the amount of the modifying agent was changed to 0.0720 mmol/min. The physical properties of sample 2 are shown in Table 1.

(Example 3) Modified conjugated diene polymer (sample 3)
A modified conjugated diene polymer (sample 3) was obtained in the same manner as in Example 1, except that the modifying agent was changed from compound M-1 to compound M-3 (a compound shown as (M-3) in the above <Compounds [M] used in the modification step>. In the table, it is abbreviated as "M-3") and the amount of the modifying agent was changed to 0.0360 mmol/min. The physical properties of sample 3 are shown in Table 1.

(Example 4) Modified conjugated diene polymer (sample 4)
A modified conjugated diene polymer (sample 4) was obtained in the same manner as in Example 1, except that the modifying agent was changed from compound M-1 to compound M-4 (a compound shown as (M-4) in the above <Compounds [M] used in the modification step>. In the table, it is abbreviated as "M-4") and the amount of the modifying agent was changed to 0.0720 mmol/min. The physical properties of sample 4 are shown in Table 1.

(Example 5) Modified conjugated diene polymer (sample 5)
A modified conjugated diene polymer (sample 5) was obtained in the same manner as in Example 1, except that the modifying agent was changed from compound M-1 to compound M-5 (a compound shown as (M-5) in the above <Compounds [M] used in the modification step>. In the table, it is abbreviated as "M-5") and the amount of the modifying agent was changed to 0.0360 mmol/min. The physical properties of sample 5 are shown in Table 1.

(Example 6) Modified conjugated diene polymer (sample 6)
A modified conjugated diene polymer (sample 6) was obtained in the same manner as in Example 1, except that the modifying agent was changed from compound M-1 to compound M-13 (a compound shown as (M-13) in the above <Compounds [M] used in the modification step>. In the table, it is abbreviated as "M-13") and the amount of the modifying agent was changed to 0.0250 mmol/min. The physical properties of sample 6 are shown in Table 1.

(Example 7) Modified conjugated diene polymer (sample 7)
A modified conjugated diene polymer (sample 7) was obtained in the same manner as in Example 1, except that the amount of compound M-1 (abbreviated as "M-1" in the table) added as the modifying agent was changed to 0.0420 mmol/min. The physical properties of sample 7 are shown in Table 1.

(Example 8) Modified conjugated diene polymer (sample 8)
A modified conjugated diene-based polymer (sample 8) was obtained in the same manner as in Example 1, except that the addition rate of 1,3-butadiene was changed from 18.6 g/min to 24.3 g/min, the addition rate of styrene was changed from 10.0 g/min to 4.3 g/min, and the addition rate of 2,2-bis(2-oxolanyl)propane as a polar substance was changed from 0.081 mmol/min to 0.044 mmol/min. The physical properties of sample 8 are shown in Table 1.

(Example 9) Modified conjugated diene polymer (sample 9)
A modified conjugated diene-based polymer (sample 9) was obtained in the same manner as in Example 1, except that the addition rate of 1,3-butadiene was changed from 18.6 g/min to 17.1 g/min, the addition rate of styrene was changed from 10.0 g/min to 11.5 g/min, and the addition rate of 2,2-bis(2-oxolanyl)propane as a polar substance was changed from 0.081 mmol/min to 0.089 mmol/min. The physical properties of sample 9 are shown in Table 2.

(Example 10) Modified conjugated diene polymer (sample 10)
A modified conjugated diene polymer (sample 10) was obtained in the same manner as in Example 1, except that the addition rate of the polar substance 2,2-bis(2-oxolanyl)propane was changed from 0.081 mmol/min to 0.200 mmol/min. The physical properties of sample 10 are shown in Table 2.

(Example 11) Modified conjugated diene polymer (sample 11)
A modified conjugated diene polymer (sample 11) was obtained in the same manner as in Example 1, except that the branching agent was changed from trimethoxy(4-vinylphenyl)silane to dimethylmethoxy(4-vinylphenyl)silane (abbreviated as "BS-2" in the table) and the amount of the branching agent added was changed to 0.0350 mmol/min. The physical properties of sample 11 are shown in Table 2.

(Example 12) Modified conjugated diene polymer (sample 12)
A modified conjugated diene polymer (sample 12) was obtained in the same manner as in Example 1, except that the branching agent was changed from trimethoxy(4-vinylphenyl)silane to dimethylmethoxy(4-vinylphenyl)silane (abbreviated as "BS-2" in the table), the amount of the branching agent was changed to 0.0350 mmol/min, and the modifying agent was changed from compound M-1 to compound M-3 (the compound shown as (M-3) in the above <Compounds [M] used in the modification step>. Abbreviated as "M-3" in the table). The physical properties of sample 12 are shown in Table 2.

(Example 13) Modified conjugated diene polymer (sample 13)
A modified conjugated diene polymer (sample 13) was obtained in the same manner as in Example 1, except that the branching agent was changed from trimethoxy(4-vinylphenyl)silane to dimethylmethoxy(4-vinylphenyl)silane (abbreviated as "BS-2" in the table), the amount of addition was changed to 0.0350 mmol/min, and the modifying agent was changed from compound M-1 to compound M-13 (the compound shown as (M-13) in the above <Compounds [M] used in the modification step>. Abbreviated as "M-13" in the table), the amount of addition was changed to 0.0160 mmol/min. The physical properties of sample 13 are shown in Table 2.

(Example 14) Modified conjugated diene polymer (sample 14)
A modified conjugated diene polymer (sample 14) was obtained in the same manner as in Example 1, except that the branching agent was changed from trimethoxy(4-vinylphenyl)silane to 1,1-bis(4-(dimethylmethoxysilyl)phenyl)ethylene (abbreviated as "BS-3" in the table) and the amount added was changed to 0.0120 mmol/min. The physical properties of sample 14 are shown in Table 2.

(Example 15) Modified conjugated diene polymer (sample 15)
A modified conjugated diene polymer (sample 15) was obtained in the same manner as in Example 1, except that the branching agent was changed from trimethoxy(4-vinylphenyl)silane to 1,1-bis(4-(dimethylmethoxysilyl)phenyl)ethylene (abbreviated as "BS-3" in the table) and the amount added was changed to 0.0120 mmol/min, and the modifying agent was changed from compound M-1 (abbreviated as "M-1" in the table) to compound M-3 (the compound shown as (M-3) in the above <Compound [M] used in the modification step>. Abbreviated as "M-3" in the table), and the amount added was changed to 0.0360 mmol/min. The physical properties of sample 15 are shown in Table 2.

(Example 16) Modified conjugated diene polymer (sample 16)
A modified conjugated diene polymer (sample 16) was obtained in the same manner as in Example 1, except that the branching agent was changed from trimethoxy(4-vinylphenyl)silane to 1,1-bis(4-(dimethylmethoxysilyl)phenyl)ethylene (abbreviated as "BS-3" in the table) and the amount added was changed to 0.0120 mmol/min, and the modifying agent was changed from compound M-1 (abbreviated as "M-1" in the table) to compound M-13 (the compound shown as (M-13) in the above <Compound [M] used in the modification step>. Abbreviated as "M-13" in the table), and the amount added was changed to 0.0160 mmol/min. The physical properties of sample 16 are shown in Table 2.

(Example 17) Modified conjugated diene polymer (sample 17)
A modified conjugated diene polymer (sample 17) was obtained in the same manner as in Example 1, except that the branching agent was changed from trimethoxy(4-vinylphenyl)silane to 1,1-bis(4-trimethoxysilylphenyl)ethylene (abbreviated as "BS-4" in the table) and the amount of the branching agent added was changed to 0.0210 mmol/min. The physical properties of sample 17 are shown in Table 3.

(Example 18) Modified conjugated diene polymer (sample 18)
A modified conjugated diene polymer (Sample 18) was obtained, except that the branching agent was changed from trimethoxy(4-vinylphenyl)silane to 1,1-bis(4-trimethoxysilylphenyl)ethylene (abbreviated as "BS-4" in the table) and the amount added was changed to 0.0210 mmol/min, and the modifying agent was changed from compound M-1 (abbreviated as "M-1" in the table) to compound M-3 (the compound shown as (M-3) in the above <Compounds [M] used in the modification step>. Abbreviated as "M-3" in the table), and the amount added was changed to 0.0360 mmol/min. The physical properties of Sample 18 are shown in Table 3.

(Example 19) Modified conjugated diene polymer (sample 19)
A modified conjugated diene polymer (sample 19) was obtained in the same manner as in Example 1, except that the branching agent was changed from trimethoxy(4-vinylphenyl)silane to 1,1-bis(4-trimethoxysilylphenyl)ethylene (abbreviated as "BS-4" in the table), the modifying agent was changed from compound M-1 (abbreviated as "M-1" in the table) to compound M-13 (the compound shown as (M-13) in the above <Compounds [M] used in the modification step>. Abbreviated as "M-13" in the table), and the amount of addition was changed to 0.0160 mmol/min. The physical properties of sample 19 are shown in Table 3.

(Example 20) Modified conjugated diene polymer (sample 20)
A modified conjugated diene polymer (sample 20) was obtained in the same manner as in Example 1, except that the branching agent was changed from trimethoxy(4-vinylphenyl)silane to trichloro(4-vinylphenyl)silane (abbreviated as "BS-5" in the table) and the amount of the branching agent added was changed to 0.0190 mmol/min. The physical properties of sample 20 are shown in Table 3.

(Example 21) Modified conjugated diene polymer (sample 21)
A modified conjugated diene polymer (sample 21) was obtained in the same manner as in Example 1, except that the branching agent was changed from trimethoxy(4-vinylphenyl)silane to trichloro(4-vinylphenyl)silane (abbreviated as "BS-5" in the table) and the amount added was changed to 0.0190 mmol/min, and the modifying agent was changed from compound M-1 (abbreviated as "M-1" in the table) to compound M-3 (the compound shown as (M-3) in the above <Compounds [M] used in the modification step>. Abbreviated as "M-3" in the table), and the amount added was changed to 0.0360 mmol/min. The physical properties of sample 21 are shown in Table 3.

(Example 22) Modified conjugated diene polymer (sample 22)
A modified conjugated diene polymer (sample 22) was obtained in the same manner as in Example 1, except that the branching agent was changed from trimethoxy(4-vinylphenyl)silane to trichloro(4-vinylphenyl)silane (abbreviated as "BS-5" in the table) and the amount added was changed to 0.0190 mmol/min, and the modifying agent was changed from compound M-1 (abbreviated as "M-1" in the table) to compound M-13 (the compound shown as (M-13) in the above <Compounds [M] used in the modification step>. Abbreviated as "M-13" in the table), and the amount added was changed to 0.0160 mmol/min. The physical properties of sample 22 are shown in Table 3.

(Example A-1) Coupling conjugated diene polymer (sample A-1)
Two tank-type pressure vessels each having an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L/D) of 4.0, an inlet at the bottom and an outlet at the top, and equipped with an agitator as a tank-type reactor and a jacket for temperature control were connected together as polymerization reactors.
1,3-butadiene, from which moisture had been removed in advance, was mixed at 14.0 g/min, styrene at 10.0 g/min, and n-hexane at 175.2 g/min. In a static mixer provided in the middle of the piping supplying this mixed solution to the inlet of the reactor, n-butyllithium for inactivating remaining impurities was added at 0.103 mmol/min, mixed, and then continuously supplied to the bottom of the reactor. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance was supplied at a rate of 0.081 mmol/min, and n-butyllithium as a polymerization initiator was supplied at a rate of 0.143 mmol/min to the bottom of the first reactor, which was vigorously mixed with a stirrer, and the temperature inside the reactor was maintained at 67°C.
The polymer solution was continuously withdrawn from the top of the first reactor and continuously supplied to the bottom of the second reactor to continue the reaction at 70° C., and further supplied to a static mixer from the top of the second reactor. When the polymerization was sufficiently stabilized, a branching agent, trimethoxy(4-vinylphenyl)silane (abbreviated as "BS-1" in the table) was added from the bottom of the second reactor at a rate of 0.0190 mmol/min, and in parallel, 1,3-butadiene was added at 4.6 g/min, while copolymerizing 1,3-butadiene and styrene, to carry out a polymerization reaction and a branching reaction to obtain a conjugated diene-based polymer having a main chain branched structure.
When the polymerization reaction and the branching reaction became stable, a small amount of the conjugated diene polymer solution before the addition of the coupling agent was withdrawn, and an antioxidant (BHT) was added in an amount of 0.2 g per 100 g of the polymer, after which the solvent was removed and the Mooney viscosity at 110° C. and various molecular weights were measured. The physical properties are shown in Table 4.
Next, compound M-1 (a compound shown as (M-1) in the above <Compound [M] used in the modification step>. In the table, it is abbreviated as "M-1") was used as a coupling agent to the polymer solution flowing out from the outlet of the reactor, and the compound M-1 was continuously added at an addition amount of 0.0360 mmol/min, and mixed using a static mixer to carry out a coupling reaction.
At this time, the time until the coupling agent was added to the polymer solution flowing out from the outlet of the reactor was 4.8 minutes, the temperature was 68°C, and the difference between the temperature in the polymerization process and the temperature until the coupling agent was added was 2°C.
A small amount of the conjugated diene polymer solution after the coupling reaction was withdrawn, and an antioxidant (BHT) was added in an amount of 0.2 g per 100 g of the polymer, and the solvent was then removed. The amount of bound styrene (physical property 6) and the microstructure of the butadiene portion (amount of 1,2-vinyl bonds: physical property 7) were measured. The measurement results are shown in Table 4.
Next, an antioxidant (BHT) was continuously added to the polymer solution after the coupling reaction at a rate of 0.055 g/min (n-hexane solution) so that the amount was 0.2 g per 100 g of polymer, and the coupling reaction was terminated.
Simultaneously with the antioxidant, SRAE oil (JOMO Process NC140, manufactured by JX Nippon Oil & Energy Corporation) was continuously added as a rubber softener in an amount of 25.0 g per 100 g of polymer, and mixed with a static mixer.
The solvent was removed by steam stripping to obtain a coupled conjugated diene polymer (modified conjugated diene polymer) (sample A-1) having, in a part of its main chain, a four-branched structure derived from the branching agent (hereinafter also referred to as "branching agent structure (1)"), which is a compound represented by the above formula (1), and having a four-branched star polymer structure derived from the coupling agent.
The physical properties of sample A-1 are shown in Table 4.
The structure of the coupling conjugated diene polymer was identified by comparing the molecular weight measured by GPC with the branching degree measured by GPC equipped with a viscometer for the polymer before the addition of the branching agent, the polymer after the addition of the branching agent, and the polymer in each step after the addition of the coupling agent. The structure of each sample was similarly identified.

(Example A-2) Coupling conjugated diene polymer (sample A-2)
Two tank-type pressure vessels each having an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L/D) of 4.0, an inlet at the bottom and an outlet at the top, and equipped with an agitator as a tank-type reactor and a jacket for temperature control were connected together as polymerization reactors.
1,3-butadiene, from which moisture had been removed in advance, was mixed under the conditions of 14.0 g/min, styrene at 8.0 g/min, and n-hexane at 175.2 g/min. In a static mixer provided in the middle of the piping supplying this mixed solution to the inlet of the reaction unit, n-butyllithium for inactivating remaining impurities was added at 0.103 mmol/min, mixed, and then continuously supplied to the bottom of the reaction unit. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance was supplied at a rate of 0.081 mmol/min, and n-butyllithium as a polymerization initiator was supplied at a rate of 0.143 mmol/min to the bottom of the first reactor, which was vigorously mixed with a stirrer, and the temperature inside the reactor was maintained at 67°C.
The polymer solution was continuously withdrawn from the top of the first reactor and continuously supplied to the bottom of the second reactor to continue the reaction at 70° C., and further supplied to a static mixer from the top of the second reactor. When the polymerization was sufficiently stabilized, 1,3-butadiene and styrene were copolymerized while a branching agent, trimethoxy(4-vinylphenyl)silane (abbreviated as "BS-1" in the table), was added from the bottom of the second reactor at a rate of 0.0190 mmol/min, and in parallel, 1,3-butadiene was added at 4.6 g/min and styrene was added at 2.0 g/min, to carry out a polymerization reaction and a branching reaction to obtain a conjugated diene-based polymer having a main chain branched structure.
When the polymerization reaction and the branching reaction became stable, a small amount of the conjugated diene polymer solution before the addition of the coupling agent was withdrawn, and an antioxidant (BHT) was added in an amount of 0.2 g per 100 g of the polymer, after which the solvent was removed and the Mooney viscosity at 110° C. and various molecular weights were measured. The physical properties are shown in Table 4.
Next, compound M-1 (a compound shown as (M-1) in the above <Compound [M] used in the modification step>. In the table, it is abbreviated as "M-1") was used as a coupling agent to the polymer solution flowing out from the outlet of the reactor, and the compound M-1 was continuously added at an addition amount of 0.0360 mmol/min, and mixed using a static mixer to carry out a coupling reaction.
At this time, the time until the coupling agent was added to the polymer solution flowing out from the outlet of the reactor was 4.8 minutes, the temperature was 68°C, and the difference between the temperature in the polymerization step and the temperature before the coupling agent was added was 2°C. A small amount of the conjugated diene polymer solution after the coupling reaction was withdrawn, and an antioxidant (BHT) was added so that the amount was 0.2 g per 100 g of polymer, and then the solvent was removed, and the bound styrene amount (physical property 6) and the microstructure of the butadiene portion (1,2-vinyl bond amount: physical property 7) were measured. The measurement results are shown in Table 4.
Next, an antioxidant (BHT) was continuously added to the polymer solution after the coupling reaction at a rate of 0.055 g/min (n-hexane solution) so that the amount was 0.2 g per 100 g of polymer, and the coupling reaction was terminated.
Simultaneously with the antioxidant, SRAE oil (JOMO Process NC140, manufactured by JX Nippon Oil & Energy Corporation) was continuously added as a rubber softener in an amount of 25.0 g per 100 g of polymer, and mixed with a static mixer.
The solvent was removed by steam stripping to obtain a coupled conjugated diene polymer (modified conjugated diene polymer) (sample A-2) having a four-branched structure derived from the branching agent (hereinafter also referred to as "branching agent structure (1)"), which is a compound represented by the above formula (1), in a part of the main chain and a four-branched star polymer structure derived from the coupling agent.
The physical properties of sample A-2 are shown in Table 4.
The structure of the coupling conjugated diene polymer was identified by comparing the molecular weight measured by GPC with the branching degree measured by GPC equipped with a viscometer for the polymer before the addition of the branching agent, the polymer after the addition of the branching agent, and the polymer in each step after the addition of the coupling agent. The structure of each sample was similarly identified.

(Comparative Example 1) Modified conjugated diene polymer (sample 23)
Two tank-type pressure vessels each having an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L/D) of 4.0, an inlet at the bottom and an outlet at the top, and equipped with an agitator as a tank-type reactor and a jacket for temperature control were connected together as polymerization reactors.
1,3-butadiene, which had been previously dehydrated, was mixed under the conditions of 18.6 g/min, styrene at 10.0 g/min, and n-hexane at 175.2 g/min. In a static mixer provided in the middle of the pipe supplying this mixed solution to the inlet of the reactor, n-butyllithium for inactivating remaining impurities was added at 0.103 mmol/min, mixed, and then continuously supplied to the bottom of the reactor. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance was supplied at a rate of 0.081 mmol/min, and n-butyllithium as a polymerization initiator was supplied at a rate of 0.143 mmol/min to the bottom of the first reactor, which was vigorously mixed with a stirrer, and the temperature inside the reactor was maintained at 67°C.
The polymer solution was continuously withdrawn from the top of the first reactor and continuously fed to the bottom of the second reactor to continue the reaction at 70° C., and further fed to a static mixer from the top of the second reactor. When the polymerization was sufficiently stabilized, a small amount of the polymer solution before the addition of the modifier was withdrawn, and an antioxidant (BHT) was added in an amount of 0.2 g per 100 g of polymer, after which the solvent was removed, and the Mooney viscosity at 110° C. and various molecular weights were measured. The physical properties are shown in Table 5.
Next, compound M-1 (a compound shown as (M-1) in the above <Compound [M] used in the modification step>. In the table, it is abbreviated as "M-1") was continuously added as a modifier to the polymer solution flowing out from the outlet of the reactor at a rate of 0.0360 mmol/min, and mixed using a static mixer to carry out a coupling reaction. At this time, the time until the modifier was added to the polymer solution flowing out from the outlet of the reactor was 4.8 minutes, the temperature was 68°C, and the difference between the temperature in the polymerization step and the temperature before the modifier was added was 2°C. A small amount of the conjugated diene polymer solution after the coupling reaction was withdrawn, and an antioxidant (BHT) was added so that the amount was 0.2 g per 100 g of polymer, and then the solvent was removed, and the bound styrene amount (physical property 6) and the microstructure of the butadiene portion (1,2-vinyl bond amount: physical property 7) were measured. The measurement results are shown in Table 5.
Next, an antioxidant (BHT) was continuously added to the polymer solution after the coupling reaction at 0.055 g/min (n-hexane solution) so that the amount was 0.2 g per 100 g of polymer, and the coupling reaction was terminated. Simultaneously with the antioxidant, SRAE oil (JOMO Process NC140 manufactured by JX Nippon Oil & Energy Corporation) was continuously added as a rubber softener so that the amount was 25.0 g per 100 g of polymer, and mixed with a static mixer. The solvent was removed by steam stripping to obtain a modified conjugated diene polymer (sample 23). The physical properties of sample 23 are shown in Table 5.

(Comparative Example 2) Modified conjugated diene polymer (sample 24)
A modified conjugated diene polymer (sample 24) was obtained in the same manner as in Comparative Example 1, except that the modifying agent was changed from compound M-1 (abbreviated as "M-1" in the table) to compound M-2 (a compound shown as (M-2) in the above <Compounds [M] used in the modification step>; abbreviated as "M-2" in the table) and the amount of the modifying agent was changed to 0.0720 mmol/min. The physical properties of sample 24 are shown in Table 5.

(Comparative Example 3) Modified conjugated diene polymer (sample 25)
A modified conjugated diene polymer (sample 25) was obtained in the same manner as in Comparative Example 1, except that the modifying agent was changed from compound M-1 (abbreviated as "M-1" in the table) to compound M-3 (a compound shown as (M-3) in the above <Compounds [M] used in the modification step>; abbreviated as "M-3" in the table) and the amount of the modifying agent was changed to 0.0360 mmol/min. The physical properties of sample 25 are shown in Table 5.

(Comparative Example 4) Modified conjugated diene polymer (sample 26)
A modified conjugated diene polymer (sample 26) was obtained in the same manner as in Comparative Example 1, except that the modifying agent was changed from compound M-1 (abbreviated as "M-1" in the table) to compound M-4 (a compound shown as (M-4) in the above <Compounds [M] used in the modification step>; abbreviated as "M-4" in the table), and the amount of the modifying agent was changed to 0.0720 mmol/min. The physical properties of sample 26 are shown in Table 5.

(Comparative Example 5) Modified conjugated diene polymer (sample 27)
A modified conjugated diene polymer (sample 27) was obtained in the same manner as in Comparative Example 1, except that the modifying agent was changed from compound M-1 (abbreviated as "M-1" in the table) to compound M-5 (a compound shown as (M-5) in the above <Compounds [M] used in the modification step>; abbreviated as "M-5" in the table), and the amount of the modifying agent was changed to 0.0360 mmol/min. The physical properties of sample 27 are shown in Table 5.

(Comparative Example 6) Modified conjugated diene polymer (sample 28)
A modified conjugated diene polymer (sample 28) was obtained in the same manner as in Comparative Example 1, except that the modifying agent was changed from compound M-1 (abbreviated as "M-1" in the table) to compound M-13 (a compound shown as (M-13) in the above <Compounds [M] used in the modification step>; abbreviated as "M-13" in the table) and the amount of the modifying agent was changed to 0.0250 mmol/min. The physical properties of sample 28 are shown in Table 5.

(Example 23) Modified conjugated diene polymer (sample 29)
A temperature-controllable autoclave having an inner volume of 5 L (L/D: 3.4), equipped with a stirrer and a jacket, was used as a reactor. 1995 g of normal hexane and n-butyllithium for neutralizing impurities present in the reactor that may hinder the polymerization reaction were placed in the reactor, and the mixture was stirred at 70° C. for 5 minutes. The mixture was then cooled to room temperature, the solution was removed, and the reactor was emptied.
Next, 1,670 g of normal hexane from which impurities had been removed in advance, 83 g of styrene, 236 g of 1,3-butadiene, and 2.73 mmol of 2,2-bis(2-oxolanyl)propane as a polar substance were placed in a reactor, and when the temperature inside the reactor was 56° C., 2.92 mmol of n-butyllithium (referred to as "NBL" in the table) was added as a polymerization initiator to initiate polymerization.
Immediately after the polymerization started, the temperature in the reactor rose and reached a peak temperature of 79°C. When a drop in temperature was confirmed, 1.50 mmol of trimethoxy(4-vinylphenyl)silane (abbreviated as "BS-1" in the table) was added as a branching agent, and the mixture was stirred for 5 minutes. 0.73 mmol of tetraethoxysilane compound M-1 (the compound shown as (M-1) in the above <Compound [M] used in the modification step>. Abbreviated as "M-1" in the table) was added as a coupling agent, and the mixture was stirred for another 5 minutes. The stirring speed at this time was 200 rpm. The coupling agent was added 7 minutes after the peak temperature was reached.
The reaction was terminated by adding 2.92 mmol of ethanol as a polymerization terminator, to obtain a polymer solution containing a modified conjugated diene polymer.
To the resulting polymerization solution, 0.64 g of 2,6-di-tert-butyl-4-hydroxytoluene was added as an antioxidant, and the solvent was then removed by steam stripping. After vacuum drying, modified conjugated diene polymer 29 was obtained.
The physical properties are shown in Table 6 below.

(Comparative Example 7) Modified conjugated diene polymer (sample 30)
A 5 L internal volume autoclave equipped with a stirrer and a jacket and capable of controlling temperature was used as a reactor. 1,670 g of normal hexane, 83 g of styrene, 236 g of 1,3-butadiene, and 1.91 mmol of 2,2-bis(2-oxolanyl)propane as a polar substance, from which impurities had been removed in advance, were placed in the reactor, and when the temperature inside the reactor was 58° C., 2.55 mmol of a polymerization initiator, n-butyllithium, was added to initiate polymerization.
Immediately after the start of polymerization, the temperature in the reactor rose, and when the temperature reached a peak and a drop in temperature was confirmed, tetraethoxysilane compound M-1 (a compound shown as (M-1) in the above <Compound [M] used in the modification step>. In the table, it is abbreviated as "M-1") was added as a coupling agent, and the mixture was stirred for another 10 minutes. 2.55 mmol of ethanol was added as a polymerization terminator to terminate the reaction, and a polymer solution containing a modified conjugated diene polymer was obtained. 0.64 g of 2,6-di-tert-butyl-4-hydroxytoluene was added as a stabilizer to the obtained polymerization solution, and the solvent was removed by steam stripping, and the mixture was dried in vacuum to obtain a modified conjugated diene polymer 30.
The physical properties are shown in Table 6 below.

(Comparative Example B-1) Coupling Conjugated Diene Polymer (Sample B-1)
Two tank-type pressure vessels each having an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L/D) of 4.0, an inlet at the bottom and an outlet at the top, and equipped with an agitator as a tank-type reactor and a jacket for temperature control were connected together as polymerization reactors.
1,3-butadiene, which had been previously dehydrated, was mixed under the conditions of 18.6 g/min, styrene at 10.0 g/min, and n-hexane at 175.2 g/min. In a static mixer provided in the middle of the pipe supplying this mixed solution to the inlet of the reactor, n-butyllithium for inactivating remaining impurities was added at 0.103 mmol/min, mixed, and then continuously supplied to the bottom of the reactor. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance was supplied at a rate of 0.081 mmol/min, and n-butyllithium as a polymerization initiator was supplied at a rate of 0.143 mmol/min to the bottom of the first reactor, which was vigorously mixed with a stirrer, and the temperature inside the reactor was maintained at 67°C.
The polymer solution was continuously withdrawn from the top of the first reactor and continuously fed to the bottom of the second reactor where the reaction was continued at 70° C., and further fed to a static mixer from the top of the second reactor.
When the polymerization reaction became stable, a small amount of the conjugated diene polymer solution before the addition of the coupling agent was withdrawn, and an antioxidant (BHT) was added in an amount of 0.2 g per 100 g of the polymer, after which the solvent was removed and the Mooney viscosity at 110° C. and various molecular weights were measured. The physical properties are shown in Table 4.
Next, trimethoxy(4-vinylphenyl)silane (abbreviated as "BS-1" in the table) was added to the polymer solution flowing out from the outlet of the reactor at a rate of 0.0190 mmol/min, and simultaneously tetraethoxysilane (abbreviated as "A" in the table) was continuously added at a rate of 0.0480 mmol/min, and mixed using a static mixer to carry out a coupling reaction.
At this time, the time until the coupling agent was added to the polymer solution flowing out from the outlet of the reactor was 4.8 minutes, the temperature was 68° C., and the difference between the temperature in the polymerization step and the temperature before the coupling agent was added was 2° C. A small amount of the conjugated diene polymer solution after the coupling reaction was withdrawn, and an antioxidant (BHT) was added so that the amount was 0.2 g per 100 g of the polymer, and then the solvent was removed, and the bound styrene amount (physical property 6) and the microstructure of the butadiene portion (1,2-vinyl bond amount: physical property 7) were measured.
The measurement results are shown in Table 4.
Next, an antioxidant (BHT) was continuously added to the polymer solution after the coupling reaction at a rate of 0.055 g/min (n-hexane solution) so that the amount was 0.2 g per 100 g of polymer, and the coupling reaction was terminated.
Simultaneously with the antioxidant, SRAE oil (JOMO Process NC140 manufactured by JX Nippon Oil & Energy Corporation) was continuously added as a rubber softener in an amount of 25.0 g per 100 g of the polymer, and mixed with a static mixer. The solvent was removed by steam stripping to obtain a coupling conjugated diene polymer (modified conjugated diene polymer) (sample B-1).
The physical properties of sample B-1 are shown in Table 4.
In Table 4 (Comparative Example B-1) below, "BS-1" is listed in the branching agent column, but in the addition method of this example, it did not act as a branching agent. In (Comparative Example B-1), since "BS-1" was added after the monomer was consumed, it is assumed that after the active end was bonded to the methoxy group of "BS-1", there was almost no monomer to polymerize with the vinyl group of "BS-1". In other words, even when "BS-1" was added, the "branching process" did not occur because there was no monomer.
From the shrinkage factor of (Sample B-1), it can be confirmed that branches are formed only within the range of the number of functional groups of the coupling agent, and it is considered that an increase in the number of branches due to the combination of the main chain branched structure due to "BS-1" and the coupling structure in one polymer does not occur.
The structure of the coupled conjugated diene polymer was identified by comparing the molecular weight measured by GPC and the branching degree measured by viscometer-equipped GPC for the polymer before the addition of "BS-1", the polymer after the addition of "BS-1", and the polymer in each step after the addition of the coupling agent.

(Comparative Example B-2) Coupling conjugated diene polymer (sample B-2)
The coupling agent used was the coupling agent shown in (Z-1) below (abbreviated as "Z-1" in the table), and the amount added was 0.0360 mmol/min. Other conditions were the same as in Comparative Example 1, and a coupled conjugated diene polymer (modified conjugated diene polymer) (sample B-2) having no main chain branching derived from the branching agent and a 10-branched star polymer structure derived from the coupling agent was obtained.
The physical properties of sample B-2 are shown in Table 4.

(Examples 24 to 46, Examples a-1 and a-2, and Comparative Examples 8 to 14, and Comparative Examples b-1 and b-2)
Rubber Compositions Using Samples 1 to 30, A-1 and A-2, and B-1 and B-2 shown in Tables 1 to 6 as raw rubbers, rubber compositions containing each raw rubber were obtained according to the formulation shown below.

(Rubber component)
Modified conjugated diene polymers (samples 1 to 30, samples A-1 and A-2, samples B-1 and B-2)
: 80 parts by mass (parts by mass excluding rubber softener)
- High cis polybutadiene (product name "UBEPOL BR150" manufactured by Ube Industries, Ltd.)
: 20 parts by mass

(Mixing conditions)
The amount of each compounding ingredient added is shown in parts by mass per 100 parts by mass of the rubber component not including the rubber softener.
Silica 1 (product name "Ultrasil 7000GR" manufactured by Evonik Degussa)
Nitrogen adsorption specific surface area 170 m2/g): 50.0 parts by mass Silica 2 (manufactured by Rhodia under the trade name "Zeosil Premium 200MP"
Nitrogen adsorption specific surface area 220 m2/g): 25.0 parts by mass Carbon black (product name "Seat KH (N339)" manufactured by Tokai Carbon Co., Ltd.)
Silane modifier (product name "Si75" manufactured by Evonik Degussa, bis(triethoxysilylpropyl) disulfide): 6.0 parts by mass SRAE oil (product name "Process NC140" manufactured by JX Nippon Oil & Energy Corporation)
42.0 parts by mass (including the amount previously added as a rubber softener contained in Samples 1 to 30, Samples A-1 to 2, and Samples B-1 to 2)
Zinc oxide: 2.5 parts by mass Stearic acid: 1.0 part by mass Antioxidant (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine): 2.0 parts by mass Sulfur: 2.2 parts by mass Vulcanization accelerator 1 (N-cyclohexyl-2-benzothiazylsulfinamide)
: 1.7 parts by mass Vulcanization accelerator 2 (diphenyl guanidine): 2.0 parts by mass Total: 239.4 parts by mass

(Kneading method)
The above materials were kneaded by the following method to obtain rubber compositions. Using an internal mixer (capacity 0.3 L) equipped with a temperature control device, the raw rubber (samples 1 to 30, samples A-1 to 2, samples B-1 to 2), fillers (silica 1, silica 2, carbon black), silane modifier, SRAE oil, zinc oxide, and stearic acid were kneaded in the first stage of kneading under conditions of a filling rate of 65% and a rotor rotation speed of 30 to 50 rpm. At this time, the temperature of the internal mixer was controlled, and each rubber composition (compound) was obtained at a discharge temperature of 155 to 160°C.
Next, in the second mixing step, the mixture obtained above was cooled to room temperature, and then the antioxidant was added and mixed again to improve the dispersion of the silica. In this case, the discharge temperature of the mixture was adjusted to 155 to 160°C by controlling the temperature of the mixer.
After cooling, in the third stage of kneading, sulfur and vulcanization accelerators 1 and 2 were added and kneaded using an open roll set at 70°C.
Thereafter, the product was molded and vulcanized in a vulcanization press at 160° C. for 20 minutes.
The rubber compositions before and after vulcanization were evaluated. Specifically, the evaluation was performed by the following methods.
The evaluation results are shown in Tables 7 to 12.

[Evaluation of characteristics]
(Evaluation 1) Blend Mooney Viscosity The blend obtained above after the second stage kneading and before the third stage kneading was used as a sample, and the viscosity was measured using a Mooney viscometer after preheating at 130°C for 1 minute and rotating the rotor at 2 revolutions per minute for 4 minutes in accordance with ISO 289. The result of Comparative Example 8 was set to 100 and indexed. The smaller the index, the better the processability.

(Evaluation 2) Tensile strength and tensile elongation Tensile strength and tensile elongation were measured according to the tensile test method of JIS K6251, and indexed with the result of Comparative Example 8 set at 100. A larger index indicates better tensile strength and tensile elongation (breaking strength).

(Evaluation 3) Abrasion resistance Using an Acron abrasion tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd.), the amount of abrasion was measured at a load of 44.4 N and 1000 revolutions in accordance with JIS K6264-2, and indexed with the result of Comparative Example 8 being set at 100. A higher index indicates better abrasion resistance.

(Evaluation 4) Viscoelasticity parameters Viscoelasticity parameters were measured in a torsion mode using a viscoelasticity tester "ARES" manufactured by Rheometrics Scientific Co., Ltd. Each measured value was indexed, with the result for the rubber composition of Comparative Example 8 being set at 100.
Tan δ measured at 0° C., a frequency of 10 Hz, and a strain of 1% was used as an index of wet skid resistance. A larger index indicates better wet skid resistance.
In addition, tan δ measured at 50° C., a frequency of 10 Hz, and a strain of 3% was used as an index of fuel economy. A smaller index value indicates better fuel economy.
Furthermore, the elastic modulus (G') measured at 50° C., a frequency of 10 Hz and a strain of 3% was used as an index of steering stability. A larger index indicates better steering stability.

As shown in Tables 7 to 12, in comparison with Comparative Examples 8 to 14 and Comparative Examples b-1 to 2, Examples 24 to 46 and Examples a-1 to 2 showed low compound Mooney viscosity when vulcanized and good processability, and when vulcanized, showed excellent abrasion resistance, handling stability, and breaking strength, and also showed an excellent balance between low hysteresis loss and wet skid resistance.

The modified conjugated diene polymer obtained by the production method of the present invention has industrial applicability in the fields of tire treads, interior and exterior parts of automobiles, anti-vibration rubber, belts, footwear, foams, various industrial products, and the like.

Claims (11)

A conjugated diene compound, or a conjugated diene compound and an aromatic vinyl compound, are polymerized or copolymerized using an alkali metal compound or an alkaline earth metal compound as a polymerization initiator,
a polymerization step for obtaining a conjugated diene-based polymer having an active terminal;
a branching step of reacting an active terminal of the conjugated diene polymer with a styrene derivative to introduce a branched structure;
The active terminal of the conjugated diene polymer formed after the branching step and the group "-C(R ¹ )=
a modification step of reacting a compound [M] having a total of two or more groups "-N-A ¹ " and/or "-N=C(R ¹ )-A ¹ " (wherein R ¹ is a hydrogen atom or a hydrocarbyl group, and A ¹ is a monovalent group having an alkoxysilyl group);
The present invention relates to a method for producing a modified conjugated diene polymer comprising the steps of: The compound [M] is a compound represented by the following formula (A):
A method for producing the modified conjugated diene polymer according to claim 1.
(In formula (A), R ² and R ³ are each independently a hydrocarbyl group having 1 to 20 carbon atoms, R ⁴ is an alkanediyl group having 1 to 20 carbon atoms, and A ² is a group “*-C(R ¹ )═N
-" or a group "*-N=C(R ¹ )-" (wherein R ¹ is a hydrogen atom or a hydrocarbyl group, and "*" indicates a bond bonded to R ⁵ ).
^R5 is an m-valent hydrocarbyl group having 1 to 20 carbon atoms, or an m-valent group having 1 to 20 carbon atoms which has at least one atom selected from the group consisting of nitrogen atoms, oxygen atoms, and sulfur atoms and has no active hydrogen.
n is an integer from 1 to 3, and m is an integer from 2 to 10.
In formula (A), multiple R ² , R ³ , R ⁴ , A ² , and n may be the same or different. The styrene derivative is a compound represented by the following formula (1) and/or the following formula (2):
A method for producing the modified conjugated diene polymer according to claim 1 or 2.
In the formulas (1) and (2), Q ¹ is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or a cyclic alkyl group having 6 carbon atoms.
The aryl group may have a branched structure in part.
X ¹ , X ² and X ³ each represent a single bond or an organic group containing any one selected from the group consisting of carbon, hydrogen, nitrogen, sulfur and oxygen.
^Y1 , ^Y2 , and ^Y3 each represent any one selected from the group consisting of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and a halogen atom. They may be independent and the same or different. The method for producing a modified conjugated diene-based polymer according to claim 3, wherein in the formula (1), Q ¹ is a hydrogen atom, and Y ¹ is any one selected from the group consisting of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and a halogen atom. 4. The method for producing a modified conjugated diene polymer according to claim 3, wherein in the formula (1), Q ¹ is a hydrogen atom, and Y ¹ is an alkoxy group having 1 to 20 carbon atoms or a halogen atom. In the formula (2), Y ² is an alkoxy group having 1 to 20 carbon atoms or a halogen atom, and Y ³
The method for producing a modified conjugated diene polymer according to claim 3, wherein is an alkoxy group having 1 to 20 carbon atoms or a halogen atom. In the formula (1), Q ¹ is a hydrogen atom, and Y ¹ is an alkoxy group having 1 to 20 carbon atoms.
A method for producing the modified conjugated diene polymer according to claim 3. 4. The method for producing a modified conjugated diene polymer according to claim 3, wherein in the formula (1), Q ¹ is a hydrogen atom, X ¹ is a single bond, and Y ¹ is an alkoxy group having 1 to 20 carbon atoms. The method for producing a modified conjugated diene-based polymer according to claim 3, wherein in the formula (2), ^X2 is a single bond, ^Y2 is an alkoxy group having 1 to 20 carbon atoms or a halogen atom, ^X3 is a single bond, and ^Y3 is an alkoxy group having 1 to 20 carbon atoms or a halogen atom. A step of obtaining a modified conjugated diene-based polymer by the production method according to any one of claims 1 to 9;
obtaining a rubber component containing 10% by mass or more of the modified conjugated diene polymer;
A filler is contained in an amount of 5.0 parts by mass or more and 150 parts by mass or less based on 100 parts by mass of the rubber component.
to obtain a rubber composition;
The method for producing a rubber composition comprising the steps of: Obtaining a rubber composition by the method for producing a rubber composition according to claim 10 ;
molding the rubber composition to obtain a tire;
A tire manufacturing method comprising the steps of: