JP7106980B2 - Rubber composition for tire tread and pneumatic tire - Google Patents

Description

The present invention relates to a tire tread rubber composition and a pneumatic tire.

2. Description of the Related Art In recent years, there has been a demand for improved wet performance (wet grip performance) (braking performance on wet road surfaces) of tires from the standpoint of safety during vehicle travel. In addition, from the aspect of low fuel consumption during vehicle running, there is a demand for improved rolling performance (low rolling resistance) of tires. On the other hand, there is known a method for improving wet performance and rolling performance by blending silica into the rubber component that constitutes the tread portion of the tire.
However, silica has a low affinity with rubber components, and because silica particles tend to cohere with each other, simply adding silica to the rubber component does not disperse the silica, which has the effect of improving wet performance and rolling performance. There was a problem of not getting enough.

Under such circumstances, for example, claim 1 of Patent Document 1 discloses a tire tread rubber composition containing a conjugated diene rubber produced by a method for producing a conjugated diene rubber comprising steps A, B and C in this order. things are disclosed. Patent Document 1 describes that the tire tread rubber composition exhibits excellent wet performance and rolling performance when made into a tire.

Further, in Patent Document 2, a rubber composition containing a diene-based rubber, silica, and a heterocyclic compound having a specific structure, wherein the silica and the heterocyclic compound are in specific amounts, is improved in processability. It states that it is excellent.

JP 2016-47887 A Japanese Patent No. 6299904

In recent years, as safety levels have been demanded to improve, there has been a demand for further improvement in wet performance of tires. In addition, further improvement in rolling performance of tires is required due to environmental problems, resource problems, and the like. Further, from the viewpoint of manufacturing efficiency, further improvement in processability (reduction in viscosity) of the tire tread rubber composition used in the tire tread portion is also desired.

Under such circumstances, the present inventors prepared a rubber composition for a tire tread with reference to Examples of Patent Documents 1 and 2, and evaluated wet performance when made into a tire, rolling performance and workability when made into a tire. After evaluation, it became clear that further improvement is desirable in consideration of the demands that are expected to increase further in the future.

Accordingly, the present invention provides a tire tread rubber composition that is excellent in wet performance when made into a tire, rolling performance and workability when made into a tire, and a pneumatic tire using the above rubber composition for a tire tread. The task is to

As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by using a specific conjugated diene rubber, and have completed the present invention.
That is, the inventors have found that the above problems can be solved by the following configuration.

[1] a conjugated diene rubber containing 30% by mass or more of a specific conjugated diene rubber;
silica;
a silane coupling agent;
containing at least one hydrocarbon group serving as a hydrophobic portion and a heterocyclic compound having a heterocyclic ring,
The content of the silica is 30 parts by mass or more with respect to 100 parts by mass of the conjugated diene rubber,
The content of the silane coupling agent is 3 to 30% by mass with respect to the content of the silica,
The content of the heterocyclic compound is 0.5 to 20% by mass with respect to the content of the silica,
a first step in which the specific conjugated diene-based rubber polymerizes a monomer containing a conjugated diene compound in an inert solvent using a polymerization initiator to obtain a conjugated diene-based polymer chain having an active terminal; A polyorganosiloxane represented by the general formula (1) described later is added to the conjugated diene-based polymer chain having the active terminal, with respect to 1 mol of the polymerization initiator used in the first step, in the polyorganosiloxane A second step in which the siloxane structure (—Si—O—) is added at a rate of 1 mol or more in terms of the number of repeating units and reacted, and a conjugated diene system obtained by reacting the polyorganosiloxane obtained in the second step. A rubber composition for a tire tread, which is a conjugated diene rubber produced by a method for producing a conjugated diene rubber, comprising a third step of reacting a polymer chain with a compound represented by the general formula (2) described later. .
[2] The rubber composition for a tire tread according to [1] above, wherein the heterocyclic compound has one heterocycle per molecule.
[3] The rubber composition for a tire tread according to [1] or [2] above, wherein the heterocycle is composed of at least a nitrogen atom and a carbon atom.
[4] The rubber composition for a tire tread according to any one of [1] to [3] above, wherein the heterocycle is a piperazine ring, a morpholine ring or a thiomorpholine ring.
[5] The rubber composition for a tire tread according to any one of [1] to [4], wherein the hydrocarbon group serving as the hydrophobic portion is a monovalent hydrocarbon group.
[6] The rubber composition for a tire tread according to any one of [1] to [5], wherein the hydrocarbon group serving as the hydrophobic portion has 3 to 30 carbon atoms.
[7] The rubber composition for a tire tread according to any one of [1] to [6], wherein the hydrocarbon group serving as the hydrophobic portion has 8 to 30 carbon atoms.
[8] The rubber composition for a tire tread according to any one of [1] to [7] above, wherein the heterocyclic ring is bonded directly or via an organic group to the hydrocarbon group serving as the hydrophobic portion.
[9] The rubber composition for a tire tread according to any one of [1] to [8] above, wherein the hydrocarbon group serving as the hydrophobic portion consists only of carbon atoms and hydrogen atoms.
[10] The rubber composition for a tire tread according to any one of [1] to [9] above, wherein the heterocyclic compound is a compound represented by formula (I) described below.
[11] the heterocyclic compound is a compound represented by the formula (I), X ₇ is a nitrogen atom, n3 is 1,
The tire tread rubber composition according to [10] above, wherein both X ₁ and X ₂ independently represent formula (I-1) described later.
[12] the heterocyclic compound is a compound represented by the formula (I), X ₇ is a nitrogen atom, n3 is 1,
Only one of X ₁ and X ₂ represents formula (I-1) described later,
[10] above, wherein the remaining groups represent at least one selected from the group consisting of a hydrogen atom, a sulfone-based protecting group, a carbamate-based protecting group and formula (I-3): --(R ₂ --O) _n2 --H ] The tire tread rubber composition according to . In formula (I-3), each R ₂ independently represents a divalent hydrocarbon group, and n2 represents 1-10.
[13] the heterocyclic compound is a compound represented by the formula (I), X ₇ is an oxygen atom or a sulfur atom, n3 is 0,
The rubber composition for a tire tread according to [10] above, wherein X ₁ represents formula (I-1) described later.
[14] The specific conjugated diene rubber is
a polymer block (A) containing 80 to 100% by mass of isoprene monomer units and 0 to 20% by mass of aromatic vinyl monomer units;
The above [ 1] The tire tread rubber composition according to any one of [13].
[15] A pneumatic tire comprising a tire tread portion produced using the tire tread rubber composition according to any one of [1] to [14] above.

As shown below, according to the present invention, wet performance when made into a tire (hereinafter also simply referred to as "wet performance"), rolling performance when made into a tire (hereinafter simply referred to as "rolling performance") and It is possible to provide a tire tread rubber composition with excellent processability, and a pneumatic tire using the tire tread rubber composition.

BRIEF DESCRIPTION OF THE DRAWINGS It is a partial cross-sectional schematic diagram of an example of the embodiment of the pneumatic tire of this invention.

The tire tread rubber composition of the present invention and the pneumatic tire using the tire tread rubber composition are described below.
In this specification, the numerical range represented by "-" means a range including the numerical values described before and after "-" as lower and upper limits.
Moreover, each component contained in the rubber composition for a tire tread of the present invention may be used singly or in combination of two or more. Here, when two or more of each component are used in combination, the content of that component refers to the total content unless otherwise specified.
Further, in the present specification, "(meth)acryl" is a notation representing "acrylic" or "methacryl", and "(meth)acrylonitrile" is a notation representing "acrylonitrile" or "methacrylonitrile". .
Moreover, in this specification, the glass transition temperature may be abbreviated as “Tg”.

[I] Rubber composition for tire tread The rubber composition for tire tread of the present invention (hereinafter also referred to as "composition of the present invention") comprises:
Conjugated diene rubber containing 30% by mass or more of a specific conjugated diene rubber, silica, a silane coupling agent, a heterocyclic compound having at least one hydrocarbon group serving as a hydrophobic portion, and a heterocyclic ring do.
The silica content is 30 parts by mass or more with respect to 100 parts by mass of the conjugated diene rubber.
The content of the silane coupling agent is 3 to 30% by mass with respect to the content of silica.
The content of the heterocyclic compound is 0.5 to 20% by mass with respect to the content of silica.
a first step in which the specific conjugated diene-based rubber polymerizes a monomer containing a conjugated diene compound in an inert solvent using a polymerization initiator to obtain a conjugated diene-based polymer chain having an active terminal; The polyorganosiloxane represented by the following general formula (1) is added to the conjugated diene-based polymer chain having the active terminal, with respect to 1 mol of the polymerization initiator used in the first step, A second step of adding and reacting at a ratio of 1 mol or more in terms of the number of repeating units of the siloxane structure (-Si-O-), and a conjugated diene-based polymer obtained by reacting the polyorganosiloxane obtained in the second step. A conjugated diene rubber produced by a method for producing a conjugated diene rubber, comprising a third step of reacting the combined chain with a compound represented by the following general formula (2).

In the present invention, the above-mentioned "hydrocarbon group serving as a hydrophobic portion" has the same meaning as that the above-mentioned hydrocarbon group is a hydrophobic portion.
Moreover, in the present invention, the above-mentioned "hydrocarbon group serving as a hydrophobic portion" does not include the above-mentioned "heterocyclic ring".

Since the composition of the present invention has such a constitution, it is considered that the above effects can be obtained. Although the reason is not clear, it is presumed to be approximately as follows.
As described above, the composition of the present invention is expected to achieve both wet performance and rolling performance at a high level by using silica. is not satisfactorily expressed. Furthermore, there is also a problem that workability deteriorates due to aggregation of silica.

On the other hand, since the specific conjugated diene rubber contained in the composition of the present invention has a polyorganosiloxane structure having a structure similar to that of silica, the polyorganosiloxane structure has an affinity with silica and prevents aggregation of silica. Conceivable. In addition, since the specific conjugated diene rubber also has a structure derived from a nitrogen atom-containing silane such as aminosilane, it is believed that this promotes silanization between the silane coupling agent and silica, further suppressing aggregation of silica. .

Moreover, the heterocyclic compound contained in the composition of the present invention has a hydrocarbon group serving as a hydrophobic portion and a heterocyclic ring.
In the heterocyclic compound, the hydrocarbon group serving as the hydrophobic portion has hydrophobicity, so it easily interacts with the conjugated diene rubber including the specific conjugated diene rubber, while the heterocyclic ring exhibits hydrophilicity. Therefore, it is thought that it is likely to interact with silica.
Thus, the heterocyclic compound having the hydrocarbon group as the hydrophobic portion and the heterocyclic ring as the hydrophilic portion is a rubber composition containing a conjugated diene rubber including the specific conjugated diene rubber and silica. The present inventors presume that it functions like a surfactant in a substance, increases the dispersibility of silica in the conjugated diene rubber, and contributes to the prevention of aggregation of silica.
As described above, the composition of the present invention contains the specific conjugated diene rubber and the heterocyclic compound, and as a result, the effect of these and silica (wet performance and rolling performance are compatible at a high level) is sufficient. It is considered that the workability is also improved.
Each component contained in the composition of the present invention will be described in detail below.

[1] Conjugated diene rubber The conjugated diene rubber contained in the composition of the present invention contains 30% by mass or more of the specific conjugated diene rubber.
First, the specific conjugated diene rubber will be explained.

[Specific conjugated diene rubber]
The specific conjugated diene rubber contained in the composition of the present invention is a conjugated diene rubber produced by a method for producing a conjugated diene rubber comprising the following first to third steps.
(1) Step 1 In an inert solvent, using a polymerization initiator, a monomer containing a conjugated diene compound is polymerized to obtain a conjugated diene-based polymer chain having an active terminal. Step 2: A polyorganosiloxane represented by the general formula (1) described below is added to a conjugated diene polymer chain having an active terminal, with respect to 1 mol of the polymerization initiator used in the first step, the polyorganosiloxane 2nd step (3) 3rd step reacting by adding at a rate of 1 mol or more in terms of the number of repeating units of the siloxane structure (-Si-O-) in the reaction of the polyorganosiloxane obtained in the 2nd step above A third step of reacting a compound represented by the general formula (2) described later with the conjugated diene-based polymer chain obtained by

First, the reason why the specific conjugated diene rubber is specified by the production method as described above will be explained.
As described above, in the third step, the conjugated diene polymer chain reacted with the polyorganosiloxane obtained in the second step is reacted with a compound represented by general formula (2) described later. Here, A ¹ possessed by the compound represented by the general formula (2) reacts and bonds with the reaction residue produced by the reaction of the conjugated diene polymer chain having an active terminal with the polyorganosiloxane. However, as will be described later, the reaction residue generated by the reaction of the conjugated diene polymer chain having an active terminal with the polyorganosiloxane can have various structures, so the reaction residue is represented by the general formula (2). The structure of the compound after the reaction is extremely complicated, and it is technically impossible to analyze the structure, or the work to identify the structure requires significantly excessive economic expenditure and time. requires. Therefore, describing the specific conjugated diene rubber as "a conjugated diene rubber produced by a method for producing a conjugated diene rubber comprising steps 1 to 3" has so-called "impossible and impractical circumstances". exist.

Each step will be described below.

[First step]
The first step is a step of polymerizing a monomer containing a conjugated diene compound in an inert solvent using a polymerization initiator to obtain a conjugated diene polymer chain having an active terminal.
First, each component and the like used in the first step will be described.

<Conjugated diene compound>
In the first step, the conjugated diene compound used as a monomer to obtain a conjugated diene polymer chain having an active terminal is not particularly limited, but 1,3-butadiene, isoprene, 2,3-dimethyl- 1,3-butadiene, 2-phenyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene and the like can be mentioned. Among these, 1,3-butadiene and isoprene are preferred because the effect of the present invention is superior. These conjugated diene compounds may be used singly or in combination of two or more.

<Aromatic vinyl compound>
Moreover, in the first step, an aromatic vinyl compound may be used together with the conjugated diene compound as a monomer used for polymerization. Examples of aromatic vinyl compounds used as monomers include styrene, methylstyrene, ethylstyrene, t-butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, chlorostyrene, bromostyrene, methoxystyrene, dimethylamino Methylstyrene, dimethylaminoethylstyrene, diethylaminomethylstyrene, diethylaminoethylstyrene, cyanoethylstyrene, vinylnaphthalene and the like. Among these, styrene is preferable because the effects of the present invention are more excellent.

The conjugated diene-based polymer chain having an active end obtained in the first step preferably contains 50 to 100% by mass of conjugated diene monomer units, for the reason that the effect of the present invention is more excellent, and 52 to 95 masses. %, more preferably 0 to 50% by mass of aromatic vinyl monomer units, more preferably 5 to 48% by mass.

<Other copolymerizable compounds>
Furthermore, in the first step, a compound other than the aromatic vinyl compound that can be copolymerized with the conjugated diene compound (another copolymerizable compound) may be used together with the conjugated diene compound. Compounds copolymerizable with such conjugated diene compounds include linear olefin compounds such as ethylene, propylene and 1-butene; cyclic olefin compounds such as cyclopentene and 2-norbornene; 1,5-hexadiene, 1,6- Heptadiene, 1,7-octadiene, dicyclopentadiene, non-conjugated diene compounds such as 5-ethylidene-2-norbornene; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate ( meth)acrylic acid esters; other (meth)acrylic acid derivatives such as (meth)acrylonitrile and (meth)acrylamide; and the like. For the reason that the effects of the present invention are more excellent, these conjugated diene compounds and the compounds copolymerizable with the conjugated diene compounds are added as monomer units in the conjugated diene polymer chain having an active terminal obtained in the first step. It is preferably not more than 5% by mass, more preferably not more than 5% by mass.

<Inert solvent>
The inert solvent used in the polymerization is not particularly limited as long as it is commonly used in solution polymerization and does not inhibit the polymerization reaction. Specific examples of inert solvents include linear aliphatic hydrocarbons such as butane, pentane, hexane and heptane; alicyclic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene; etc. These inert solvents may be used singly or in combination of two or more. The amount of the inert solvent to be used is not particularly limited, but the amount is such that the monomer concentration is, for example, 1 to 50% by mass, and the effect of the present invention is more excellent, so it is preferably 10 to 40% by mass. quantity.

<Polymerization initiator>
The polymerization initiator used for polymerization is not particularly limited as long as it can polymerize a monomer containing a conjugated diene compound to give a conjugated diene-based polymer chain having an active terminal. Specific examples thereof include polymerization initiators using organic alkali metal compounds, organic alkaline earth metal compounds, lanthanide series metal compounds, etc. as main catalysts. Examples of organic alkali metal compounds include organic monolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium and stilbenelithium; organic polyvalent lithium compounds such as 4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene and 1,3,5 tris(lithiomethyl)benzene; organic sodium compounds such as sodium naphthalene; organic compounds such as potassium naphthalene; potassium compound; and the like. Examples of organic alkaline earth metal compounds include di-n-butylmagnesium, di-n-hexylmagnesium, diethoxycalcium, calcium distearate, di-t-butoxystrontium, diethoxybarium, and diisopropoxy. barium, diethylmercaptobarium, di-t-butoxybarium, diphenoxybarium, diethylaminobarium, barium distearate, diketylbarium and the like. Examples of polymerization initiators using lanthanum-based metal compounds as main catalysts include lanthanum-based metals such as lanthanum, cerium, praseodymium, neodymium, samarium, and gadolinium, and lanthanum-based metals composed of carboxylic acids, phosphorus-containing organic acids, and the like. and a polymerization initiator comprising a salt of the main catalyst and a co-catalyst such as an alkylaluminum compound, an organoaluminum hydride compound or an organoaluminum halide compound. Among these polymerization initiators, organic monolithium compounds and organic polyvalent lithium compounds are preferably used, organic monolithium compounds are more preferably used, and n-butyllithium is particularly preferred because the effects of the present invention are more excellent. It is preferably used.
The organic alkali metal compound is reacted in advance with a secondary amine compound such as dibutylamine, dihexylamine, dibenzylamine, pyrrolidine, piperidine, hexamethyleneimine, and heptamethyleneimine to form an organic alkali metal amide compound. may be used. One of these polymerization initiators may be used alone, or two or more thereof may be used in combination.

Examples of the organic alkali metal amide compound include those obtained by reacting an organic alkali metal compound with a secondary amine compound. Compounds represented can be suitably used.

In general formula (3), M ¹ represents an alkali metal atom, R ¹¹ and R ¹² each independently represent an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an amino-protecting group, or a hydrolyzed represents a group capable of forming a hydroxyl group, and R ¹¹ and R ¹² may be bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded; In addition to the nitrogen atoms to which these are bonded, a ring structure may be formed together with heteroatoms other than the nitrogen atoms to which they are bonded.

Although the alkyl group is not particularly limited, an alkyl group having 1 to 20 carbon atoms is preferable, and an alkyl group having 1 to 10 carbon atoms is more preferable, because the effects of the present invention are more excellent. Such alkyl groups include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, n- xyl group, n-heptyl group, n-octyl group, n-decyl group and the like.

Although the cycloalkyl group is not particularly limited, a cycloalkyl group having 3 to 20 carbon atoms is preferable, and a cycloalkyl group having 3 to 12 carbon atoms is more preferable because the effects of the present invention are more excellent. Examples of such cycloalkyl groups include cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl and cyclododecyl groups.

Although the aryl group is not particularly limited, an aryl group having 6 to 12 carbon atoms is preferable, and an aryl group having 6 to 10 carbon atoms is more preferable, because the effects of the present invention are more excellent. Such aryl groups include, for example, phenyl, 1-naphthyl and 2-naphthyl groups.

Although the aralkyl group is not particularly limited, an aralkyl group having 7 to 13 carbon atoms is preferable, and an aralkyl group having 7 to 9 carbon atoms is more preferable, because the effects of the present invention are more excellent. Such aralkyl groups include, for example, a benzyl group and a phenethyl group.

The amino-protecting group is not particularly limited as long as it is a group acting as an amino-protecting group, and examples thereof include an alkylsilyl group. Examples of such alkylsilyl groups include trimethylsilyl, triethylsilyl, triphenylsilyl, methyldiphenylsilyl, ethylmethylphenylsilyl, and tert-butyldimethylsilyl groups.
When R ¹¹ and/or R ¹² is an amino-protecting group, at one end of the polymer chain forming the conjugated diene-based rubber obtained by removing the amino-protecting group, A structure in which R ¹³ and/or R ¹⁴ in general formula (5) described later is a hydrogen atom can be introduced.

The group that can be hydrolyzed to generate a hydroxyl group is not particularly limited, and may be, for example, a group that generates a hydroxyl group by hydrolysis in the presence of an acid, such as an alkoxyalkyl group or an epoxy group. and the like.
Alkoxyalkyl groups include methoxymethyl, ethoxymethyl, ethoxyethyl, propoxymethyl, butoxymethyl, butoxyethyl and propoxyethyl groups.
Further, examples of the group containing an epoxy group include groups represented by the following general formula (4).
-Z ¹ -Z ² -E ¹ (4)
In general formula (4), Z ¹ is an alkylene group or alkylarylene group having 1 to 10 carbon atoms, Z ² is a methylene group, a sulfur atom or an oxygen atom, and E ¹ is a glycidyl group.

In addition, R ¹¹ and R ¹² may be bonded together to form a ring structure together with the nitrogen atom to which they are bonded, and in this case, R ¹¹ and R ¹² and the nitrogen atom bonded thereto Specific examples of such structures include an azetidine ring (R ¹¹ and R ¹² are propylene groups), a pyrrolidine ring (R ¹¹ and R ¹² are butylene groups), and a piperidine ring (R ¹¹ and R ¹² are pentylene groups). , a hexamethyleneimine ring (R ¹¹ and R ¹² are hexylene groups), and the like.
When R ¹¹ and R ¹² are bonded together to form a ring structure with the nitrogen atom to which they are bonded, the ring structure is preferably a 4- to 8-membered ring structure.

Further, in general formula (3), M ¹ is an alkali metal atom, and examples of such an alkali metal atom include a lithium atom, a sodium atom, and a potassium atom. , preferably a lithium atom.

In the first step, when the compound represented by the general formula (3) is used as the polymerization initiator, the amine structure forming the organic alkali metal amide compound remains bonded to the polymerization initiation end of the polymer chain. It will be done. Therefore, when the compound represented by the general formula (3) is used as the polymerization initiator, a structure represented by the following general formula (5) is attached to one end of the polymer chain forming the resulting conjugated diene rubber. is introduced.

In general formula (5), R ¹³ and R ¹⁴ are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an amino-protecting group, or can be hydrolyzed to give a hydroxyl group. represents a group, and R ¹³ and R ¹⁴ may be bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, and when forming the ring structure, in addition to the nitrogen atom to which they are bonded, , may form a ring structure together with a heteroatom other than the nitrogen atom to which they are bonded.

Examples of alkyl groups, cycloalkyl groups, aryl groups, aralkyl groups, amino group-protecting groups, or groups capable of hydrolysis to give hydroxyl groups that can be R ¹³ and R ¹⁴ include R ¹¹ and R ¹² in general formula (3). Also, when R ¹³ and R ¹⁴ are bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, R ¹¹ and R ¹² in general formula (3) can be the same.
Hydrogen atoms that can be R ¹³ and R ¹⁴ are introduced by removing the protecting group of the amino group.

When an organic alkali metal amide compound is used as a polymerization initiator, the resulting specific conjugated diene rubber has an amine structure at one end and a specific structure derived from a modifier at the other end. can be As a result, the effect of the present invention becomes more excellent due to the effect of such an amine structure.

The method of adding the organic alkali metal amide compound as a polymerization initiator to the polymerization system is not particularly limited. , which is mixed with a monomer containing a conjugated diene compound to allow the polymerization reaction to proceed. Alternatively, an organic alkali metal compound and a secondary amine compound are separately added to a polymerization system and mixed with a monomer containing a conjugated diene compound to form an organic alkali metal amide compound in the polymerization system. Therefore, a method of allowing the polymerization reaction to proceed may be adopted. Reaction conditions such as reaction temperature are not particularly limited, and may be, for example, in accordance with intended polymerization reaction conditions.

The amount of the secondary amine compound to be used may be determined according to the desired amount of polymerization initiator to be added. ~1.2 millimoles, more preferably between 0.5 and 1.0 millimoles.

The amount of the polymerization initiator to be used may be determined according to the molecular weight of the desired conjugated diene polymer chain. It is preferably in the range of 2 to 15 millimoles.

<Polymerization temperature, etc.>
The polymerization temperature is usually −80 to +150° C., preferably 0 to 100° C., more preferably 30 to 90° C., because the effects of the present invention are more excellent. As the polymerization mode, any mode such as a batch system or a continuous system can be adopted. A batch system is preferred because it is easy to control the randomness of bonding with the unit.

<Polar compound>
In polymerizing a monomer containing a conjugated diene compound, a polar compound is added to an inert organic solvent in order to adjust the vinyl bond content in the conjugated diene monomer unit in the resulting conjugated diene polymer chain. is preferred. Examples of polar compounds include ether compounds such as dibutyl ether, tetrahydrofuran, and 2,2-di(tetrahydrofuryl)propane; tertiary amines such as tetramethylethylenediamine; alkali metal alkoxides; phosphine compounds; Among these, ether compounds and tertiary amines are preferred, tertiary amines are more preferred, and tetramethylethylenediamine is particularly preferred, because the effects of the present invention are more excellent. These polar compounds may be used individually by 1 type, and may be used in combination of 2 or more type. The amount of the polar compound used may be determined according to the desired vinyl bond content, and is preferably 0.001 to 100 mol, more preferably 0.01 to 10 mol, per 1 mol of the polymerization initiator. be. When the amount of the polar compound used is within this range, the vinyl bond content in the conjugated diene monomer unit can be easily adjusted, and problems due to deactivation of the polymerization initiator are less likely to occur.

<Vinyl bond content>
The vinyl bond content in the conjugated diene monomer unit in the conjugated diene polymer chain having an active end obtained in the first step is preferably 1 to 90% by mass, for the reason that the effect of the present invention is more excellent. More preferably 3 to 80% by mass, particularly preferably 5 to 70% by mass.

<Molecular weight>
The weight-average molecular weight (Mw) of the conjugated diene-based polymer chain having an active end obtained in the first step is not particularly limited, but is measured by gel permeation chromatography in terms of polystyrene for the reason that the effect of the present invention is more excellent. The value is preferably 100,000 to 1,000,000, more preferably 150,000 to 700,000, and particularly preferably 150,000 to 500,000.

In addition, the molecular weight distribution represented by the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the conjugated diene polymer chain having an active terminal obtained in the first step is also particularly limited. Although not required, it is preferably 1.0 to 3.0, more preferably 1.0 to 2.5. When the molecular weight distribution (Mw/Mn) of the conjugated diene-based polymer chains having active terminals is within the above range, the production of the conjugated diene-based rubber is facilitated.

<Preferred embodiment>
For the reason that the effect of the present invention is more excellent, the first step is preferably the following steps.
That is, in an inert solvent, isoprene, or a monomer containing isoprene and an aromatic vinyl compound, is polymerized with a polymerization initiator to obtain 80 to 100% by mass of isoprene monomer units and 0 aromatic vinyl monomer units. A step A of forming a polymer block (A) having an active end containing ~20% by mass;
The polymer block (A) having an active terminal and a monomer containing 1,3-butadiene or 1,3-butadiene and an aromatic vinyl compound are mixed to continue the polymerization reaction, and 1,3 - A polymer block (B) having an active end containing 50 to 100% by mass of butadiene monomer units and 0 to 50% by mass of aromatic vinyl monomer units is continuously formed with the polymer block (A). and a step B of obtaining a conjugated diene-based polymer chain having an active terminal by allowing the reaction to proceed.

By adopting such a step, the conjugated diene polymer chain having an active end obtained in the first step is composed of 80 to 100% by mass of isoprene monomer units and 0 to 20% by mass of aromatic vinyl monomer units. % and a polymer block (B) containing 50 to 100% by mass of 1,3-butadiene monomer units and 0 to 50% by mass of aromatic vinyl monomer units. structure (hereinafter also referred to as “PI block”) formed by In this case, the obtained specific conjugated diene rubber also has PI blocks.
Such aspects will be described below.

(Process A)
The polymer block (A) formed in step A contains 80 to 100% by mass of isoprene monomer units and 0 to 20% by mass of aromatic vinyl monomer units in the polymer block (A). However, for the reason that the effect of the present invention is more excellent, it preferably contains 85 to 95% by mass of isoprene monomer units and 5 to 15% by mass of aromatic vinyl monomer units. It is more preferable to contain up to 95% by mass and 5 to 11% by mass of aromatic vinyl monomer units.

As the aromatic vinyl compound used for constituting the aromatic vinyl monomer unit contained in the polymer block (A), the same aromatic vinyl compound as described above can be used, and the effects of the present invention can be obtained. Styrene is preferred among these for superior reasons. In addition, these aromatic vinyl compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

The polymer block (A) preferably consists of only isoprene monomer units or isoprene monomer units and aromatic vinyl monomer units for the reason that the effects of the present invention are more excellent. In addition to isoprene monomer units, or isoprene monomer units and aromatic vinyl monomer units, other monomer units may be included. Other compounds used to form other monomer units include 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3 - conjugated diene compounds other than isoprene such as pentadiene and 1,3-hexadiene; α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids such as acrylic acid, methacrylic acid and maleic anhydride. or acid anhydrides; unsaturated carboxylic acid esters such as methyl methacrylate, ethyl acrylate, and butyl acrylate; 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5 - non-conjugated dienes such as ethylidene-2-norbornene; Among these, 1,3-butadiene is preferable because the effects of the present invention are more excellent. These other monomers may be used alone or in combination of two or more. The content of other monomer units in the polymer block (A) is preferably 20% by mass or less, more preferably 10% by mass or less, for the reason that the effects of the present invention are more excellent. , 6% by mass or less.

In the present invention, the polymer block (A) in the conjugated diene polymer chain is obtained by polymerizing isoprene or a monomer containing isoprene and an aromatic vinyl compound with a polymerization initiator in an inert solvent. It is formed. The formed polymer block (A) has an active end.

As the inert solvent used for the polymerization of isoprene or a monomer containing isoprene and an aromatic vinyl compound to form the polymer block (A), the same inert solvent as described above can be used. can. The amount of the inert solvent used is such that the monomer concentration is preferably 1 to 80% by mass, more preferably 10 to 50% by mass, for the reason that the effect of the present invention is more excellent. .

As the polymerization initiator used to form the polymer block (A), a polymer chain having an active terminal can be obtained by polymerizing isoprene or a monomer containing isoprene and an aromatic vinyl compound. It is not particularly limited as long as it is possible. As a specific example thereof, the same polymerization initiator as described above can be used.

The amount of the polymerization initiator to be used may be determined according to the target molecular weight, but since the effect of the present invention is more excellent, it is preferably per 100 g of the monomer containing isoprene or isoprene and an aromatic vinyl compound. is in the range of 4 to 250 millimoles, more preferably 6 to 200 millimoles, particularly preferably 10 to 70 millimoles.

The polymerization temperature in polymerizing isoprene or a monomer containing isoprene and an aromatic vinyl compound is preferably −80 to +150° C., more preferably 0 to 100° C., since the effects of the present invention are more excellent. More preferably, it is in the range of 20 to 90°C. As a polymerization mode, any mode such as a batch system or a continuous system can be adopted. In addition, the bonding pattern can be, for example, various bonding patterns such as block, tapered, and random.

In order to adjust the vinyl bond content in the isoprene monomer units in the polymer block (A), a polar compound may be added to the inert solvent during the polymerization for the reason that the effects of the present invention are more excellent. preferable. As the polar compound, the same polar compound as described above can be used. The amount of the polar compound used may be determined according to the desired vinyl bond content, and is preferably 0.01 to 30 mol, more preferably 0.05 to 10 mol, per 1 mol of the polymerization initiator. When the amount of the polar compound used is within the above range, the vinyl bond content in the isoprene monomer unit can be easily adjusted, and problems due to deactivation of the polymerization initiator are less likely to occur. Also, by increasing the amount of the polar compound used within the above range, the vinyl bond content in the isoprene monomer unit can be increased.

The vinyl bond content in the isoprene monomer units in the polymer block (A) is preferably 5 to 90% by mass, more preferably 5 to 80% by mass, because the effects of the present invention are more excellent. In this specification, the vinyl bond content in the isoprene monomer unit means the isoprene monomer unit having a 1,2-structure and the isoprene monomer unit having a 3,4-structure in the isoprene monomer unit. It shall refer to the proportion of the total amount of isoprene monomer units.

The weight average molecular weight (Mw) of the polymer block (A) is preferably from 500 to 15,000 as a polystyrene-equivalent value measured by gel permeation chromatography for the reason that the effect of the present invention is more excellent. It is more preferably 1000 to 12,000, and particularly preferably 1,500 to 10,000.

Further, the molecular weight distribution represented by the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polymer block (A) is 1.0 for the reason that the effect of the present invention is more excellent. It is preferably from 1.5 to 1.5, more preferably from 1.0 to 1.3. When the molecular weight distribution value (Mw/Mn) of the polymer block (A) is within the above range, the production of the conjugated diene rubber becomes easier.

(Step B)
The polymer block (B) in the conjugated diene polymer chain formed in step B contains 50 to 100% by mass of 1,3-butadiene monomer units and an aromatic vinyl monomer in the polymer block (B). It is sufficient if it contains 0 to 50% by mass of the body unit, but since the effect of the present invention is more excellent, 52 to 95% by mass of 1,3-butadiene monomer unit and 5 to 95% by mass of aromatic vinyl monomer unit It preferably contains 48% by mass. When the content ratio of the 1,3-butadiene monomer unit and the aromatic vinyl monomer unit is within the above range, the production of the conjugated diene rubber becomes easier.

As the aromatic vinyl compound used to constitute the aromatic vinyl monomer unit contained in the polymer block (B), the same aromatic vinyl compounds as described above can be used. Styrene is preferred because the effects of the invention are better.

The polymer block (B) consists of only 1,3-butadiene monomer units or 1,3-butadiene monomer units and aromatic vinyl monomer units for the reason that the effects of the present invention are more excellent. However, as long as the essential characteristics of the present invention are not impaired, if desired, 1,3-butadiene monomer units, or 1,3-butadiene monomer units and aromatic vinyl monomers In addition to the units, other monomeric units may be included. As other monomers used to constitute the other monomer units, the same compounds as those exemplified in the polymer block (A) described above (excluding 1,3-butadiene) are used. be able to. Isoprene can also be used as another monomer in the polymer block (B). The content of other monomer units in the polymer block (B) is preferably 50% by mass or less, more preferably 40% by mass or less, and further preferably 35% by mass or less. preferable.

The polymer block (B) in the conjugated diene-based polymer chain includes the above-mentioned polymer block (A) having an active terminal and 1,3-butadiene, or a unit containing 1,3-butadiene and an aromatic vinyl compound. The polymer block (A) is continuously formed by mixing the polymer and continuing the polymerization reaction. The formed polymer block (B) has an active end. On the other hand, the active terminal disappears from the polymer block (A).

Inert used for polymerizing the polymer block (A) with a monomer containing 1,3-butadiene or 1,3-butadiene and an aromatic vinyl compound to form the polymer block (B) The solvent is not particularly limited, and the same inert solvent as described above can be used.

The amount of the polymer block (A) having an active terminal to be used in forming the polymer block (B) may be determined according to the target molecular weight. Per 100 g of a monomer containing 1,3-butadiene or 1,3-butadiene and an aromatic vinyl compound, preferably 0.1 to 5 mmol, more preferably 0.15 to 2 mmol, still more preferably 0.2 ~1.5 millimolar range.

The method of mixing the polymer block (A) with 1,3-butadiene or a monomer containing 1,3-butadiene and an aromatic vinyl compound is not particularly limited. -The polymer block (A) having an active terminal may be added to a solution of monomers containing butadiene and an aromatic vinyl compound, or 1,3 -butadiene, or monomers including 1,3-butadiene and aromatic vinyl compounds may be added. From the viewpoint of polymerization control, a method of adding the polymer block (A) having an active terminal to a solution of monomers containing 1,3-butadiene or 1,3-butadiene and an aromatic vinyl compound is preferred.

The polymerization temperature when polymerizing 1,3-butadiene or a monomer containing 1,3-butadiene and an aromatic vinyl compound is preferably −80 to +150° C., more It is preferably in the range of 0 to 100°C, more preferably in the range of 20 to 90°C. As a polymerization mode, any mode such as a batch system or a continuous system can be adopted. When the polymer block (B) is a copolymer chain, a batch system is preferred because the randomness of bonding can be easily controlled.

When the polymer block (B) is a copolymer chain, each monomer may be bonded in various bonding modes such as block, tapered, and random. Among these, a random shape is preferable because the effects of the present invention are more excellent. In addition, when the bonding pattern of 1,3-butadiene and the aromatic vinyl compound is randomized, the total amount of 1,3-butadiene and the aromatic vinyl compound is 1,3-Butadiene or 1,3-butadiene and an aromatic vinyl compound are continuously or intermittently supplied to the polymerization system so that the ratio of the aromatic vinyl compound to the amount does not become too high. is preferred.

In order to adjust the vinyl bond content in the 1,3-butadiene monomer unit in the polymer block (B), the isoprene monomer in the polymer block (A) is used for the reason that the effect of the present invention is more excellent. As in adjusting the vinyl bond content in the body unit, it is preferred to add a polar compound to the inert solvent during the polymerization. However, during the preparation of the polymer block (A), the inert solvent contains a sufficient amount of a polar compound to adjust the vinyl bond content in the 1,3-butadiene monomer units in the polymer block (B). is added, there is no need to add a new polar compound. As the polar compound used for adjusting the vinyl bond content, the same polar compound as described above can be used. The amount of the polar compound to be used may be determined according to the desired vinyl bond content. It may be adjusted in the range of preferably 0.01 to 100 mol, more preferably 0.1 to 30 mol, per 1 mol of the agent. When the amount of the polar compound is within this range, the vinyl bond content in the 1,3-butadiene monomer unit can be easily adjusted, and problems due to deactivation of the polymerization initiator are less likely to occur.

The vinyl bond content in the 1,3-butadiene monomer unit in the polymer block (B) is preferably 1 to 90% by mass, more preferably 3 to 80% by mass, for the reason that the effects of the present invention are more excellent. , particularly preferably 5 to 70% by mass.

In this way, a conjugated diene-based polymer chain having an active end and having polymer block (A) and polymer block (B) can be obtained. From the viewpoint of productivity, the conjugated diene-based polymer chain having an active terminal is composed of the polymer block (A) and the polymer block (B), and the terminal of the polymer block (B) is the active terminal. However, it may have a plurality of polymer blocks (A), or may have other polymer blocks. Examples thereof include conjugated diene-based polymer chains having an active end such as polymer block (A)-polymer block (B)-polymer block (A). In this case, an active terminal is formed at the terminal of the polymer block (A) formed subsequent to the polymer block (B). When the polymer block (A) is formed on the active terminal side of the conjugated diene polymer chain, the amount of isoprene used in the initial polymerization reaction (the first polymer block It is preferably 10 to 100 mol, more preferably 15 to 70 mol, and 20 to 35 mol with respect to 1 mol of the polymerization initiator used in the polymerization reaction for forming (A)). is particularly preferred.

Mass ratio of the polymer block (A) to the polymer block (B) in the conjugated diene polymer chain having an active terminal (when there are a plurality of polymer blocks (A) and polymer blocks (B), each The mass ratio based on the total mass of ) is (mass of polymer block (A)) / (mass of polymer block (B)) for the reason that the effect of the present invention is more excellent, 0.001 to 0 .1 is preferred, 0.003 to 0.07 is more preferred, and 0.005 to 0.05 is particularly preferred.

Total monomer units of isoprene monomer units and 1,3-butadiene monomer units in a conjugated diene polymer chain having an active end and having polymer block (A) and polymer block (B) , isoprene monomer unit and 1,3-butadiene monomer content in the conjugated diene polymer chain having an active terminal, because the effect of the present invention is more excellent. It is preferable that the total monomer unit of the unit is 50 to 100% by mass and the aromatic vinyl monomer unit is 0 to 50% by mass, and the total amount of isoprene monomer unit and 1,3-butadiene monomer unit More preferably, the body unit content is 52 to 95% by mass and the aromatic vinyl monomer unit content is 5 to 48% by mass. Further, a vinyl bond in the isoprene monomer unit and in the 1,3-butadiene monomer unit in the conjugated diene polymer chain having an active end and having the polymer block (A) and the polymer block (B) The content is preferably in the same range as the vinyl bond content in the 1,3-butadiene monomer units in the polymer block (B) described above, because the effects of the present invention are more excellent.

[Second step]
In the second step, a polyorganosiloxane represented by the following general formula (1) is added to the conjugated diene-based polymer chain having an active terminal obtained in the first step, and the polymerization initiator 1 used in the first step It is a step of adding and reacting at a ratio of 1 mol or more in terms of the number of repeating units of the siloxane structure (-Si-O-) in the polyorganosiloxane per mol.

In general formula (1), R ¹ to R ⁸ are alkyl groups having 1 to 6 carbon atoms or aryl groups having 6 to 12 carbon atoms, which may be the same or different. X ¹ and X ⁴ are an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and a group having 4 to 12 carbon atoms containing an epoxy group. It is any group selected from the group, and these may be the same or different from each other. X ² is an alkoxy group having 1 to 5 carbon atoms or a group having 4 to 12 carbon atoms containing an epoxy group, and multiple X ² may be the same or different. X ³ is a group containing 2 to 20 alkylene glycol repeating units, and when there are a plurality of X ³ , they may be the same or different. m is an integer of 3 to 200, n is an integer of 0 to 200, k is an integer of 0 to 200, and m+n+k is 3 or more.

In the polyorganosiloxane represented by general formula (1), examples of alkyl groups having 1 to 6 carbon atoms that can constitute R ¹ to R ⁸ , X ¹ and X ⁴ in general formula (1) include methyl groups, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl and cyclohexyl groups. The aryl group having 6 to 12 carbon atoms includes, for example, a phenyl group and a methylphenyl group. Among these, a methyl group and an ethyl group are preferred from the viewpoint of ease of production of the polyorganosiloxane itself.

In the polyorganosiloxane represented by the general formula (1), examples of alkoxy groups having 1 to 5 carbon atoms that can constitute X ¹ , X ² and X ⁴ include methoxy group, ethoxy group, propoxy group, Examples include isopropoxy and butoxy groups. Among these, a methoxy group and an ethoxy group are preferred from the viewpoint of ease of production of the polyorganosiloxane itself.

Furthermore, in the polyorganosiloxane represented by the general formula (1), examples of the epoxy group-containing group having 4 to 12 carbon atoms that can constitute X ¹ , X ² and X ⁴ include the following general formula (6 ) and groups represented by.
-Z ³ -Z ⁴ -E ² (6)
In general formula (6), Z ³ is an alkylene group having 1 to 10 carbon atoms or an alkylarylene group, Z ⁴ is a methylene group, a sulfur atom, or an oxygen atom, and E ² is a carbon having an epoxy group. It is a hydrocarbon group of number 2-10.

The group represented by the general formula (6) is preferably one in which Z ^{4 is an oxygen atom, Z 4 is} an oxygen atom, and E ² is a glycidyl group, for the reason that the effects of the present invention are more excellent. Some are more preferred, and Z ³ is an alkylene group having 1 to 3 carbon atoms, Z ⁴ is an oxygen atom, and E ² is a glycidyl group is particularly preferred.

In addition, in the polyorganosiloxane represented by the general formula (1), X ¹ and X ⁴ are, among the above, a group having 4 to 12 carbon atoms containing an epoxy group for the reason that the effects of the present invention are more excellent. , or an alkyl group having 1 to 6 carbon atoms is preferred. As X2, among the above, a group having ⁴ to 12 carbon atoms containing an epoxy group is preferable because the effects of the present invention are more excellent. Furthermore, it is more preferable that X ¹ and X ⁴ are alkyl groups having 1 to 6 carbon atoms, and X ² is an epoxy group-containing group having 4 to 12 carbon atoms, for the reason that the effects of the present invention are more excellent. .

In addition, in the polyorganosiloxane represented by the general formula (1), X ³ , that is, the group containing 2 to 20 alkylene glycol repeating units, has the following general formula ( Groups represented by 7) are preferred.

In general formula (7), t is an integer of 2 to 20, X ⁵ is an alkylene group or alkylarylene group having 2 to 10 carbon atoms, R ¹⁵ is a hydrogen atom or a methyl group, and X ⁶ is a carbon It is an alkoxy group or an aryloxy group of numbers 1 to 10. Among these, those in which t is an integer of 2 to 8, X ⁵ is an alkylene group having 3 carbon atoms, R ¹⁵ is a hydrogen atom, and X ⁶ is a methoxy group are preferred. In addition, in general formula (7), * is a bonding position.

In the polyorganosiloxane represented by the general formula (1), m is an integer of 3-200, preferably an integer of 20-150, more preferably an integer of 30-120. When m is 3 or more, the resulting conjugated diene rubber has a high coupling rate, and as a result, the effects of the present invention are more excellent. Further, when m is 200 or less, the polyorganosiloxane itself represented by the general formula (1) can be produced more easily, its viscosity does not become too high, and its handling becomes easier.

In the polyorganosiloxane represented by the general formula (1), n is an integer of 0-200, preferably an integer of 0-150, more preferably an integer of 0-120. k is an integer of 0-200, preferably an integer of 0-150, more preferably an integer of 0-130.
The total number of m, n and k is 3 or more, preferably 3-400, more preferably 20-300, particularly preferably 30-250. When the total number of m, n and k is 3 or more, the reaction between the polyorganosiloxane represented by the general formula (1) and the conjugated diene-based polymer chain having an active end is likely to proceed. When the total number of n and k is 400 or less, the polyorganosiloxane represented by the general formula (1) can be easily produced, and its viscosity does not become too high, making it easy to handle.

The amount of polyorganosiloxane used in the second step is the number of repeating units of the siloxane structure (—Si—O—) in the polyorganosiloxane per 1 mol of the polymerization initiator used for polymerization in the first step. is 1 mol or more in terms of .

The amount of polyorganosiloxane used is 1 mol or more in terms of the number of repeating units of the siloxane structure (-Si-O-) with respect to 1 mol of the polymerization initiator, thereby removing the active terminal obtained in the first step. Of the active terminals of the conjugated diene-based polymer chain possessed, substantially all of the active terminals can be reacted with the polyorganosiloxane, which is preferable. That is, an alkyl metal group as an active end of the conjugated diene polymer chain having an active end obtained in the first step, i.e., -R ^- M ⁺ (R is a hydrocarbon group forming a polymer chain end , M can be such that substantially no group represented by an alkali metal atom, an alkaline earth metal atom, or a lanthanum series metal atom remains.

Then, as a result, in the third step described later, when the compound represented by the general formula (2) is reacted, the compound represented by the general formula (2) is the active terminal obtained in the first step It is possible to substantially suppress direct reaction with the active terminal of the conjugated diene polymer chain having. As a result, the compound represented by the general formula (2) was added to the reaction residue generated by the reaction between the conjugated diene polymer chain and the polyorganosiloxane represented by the general formula (1). can react appropriately. Thereby, the conjugated diene-based polymer chain appropriately introduces a modified structure by the compound represented by the general formula (2) through the structure derived from the polyorganosiloxane represented by the general formula (1). The effect of introducing such a modified structure, that is, excellent wet performance and rolling performance can be realized. In addition, it is considered that workability is also improved.

The method of reacting the polyorganosiloxane with the conjugated diene polymer chain having an active terminal is not particularly limited, but examples include a method of mixing them in a solvent in which they can be dissolved. As the solvent used at this time, those exemplified as the inert solvent used in the first step can be used. In this case, the method of adding polyorganosiloxane to the polymerization solution used for the polymerization for obtaining the conjugated diene polymer chain having active terminals is simple and preferable. In this case, the polyorganosiloxane is preferably dissolved in an inert solvent and added to the polymerization system, and the solution concentration is preferably in the range of 1 to 50 mass %. Although the reaction temperature is not particularly limited, it is usually 0 to 120° C., and the reaction time is also not particularly limited, but is usually 1 minute to 1 hour.

The timing of adding the polyorganosiloxane to the solution containing the conjugated diene polymer chain having an active terminal is not particularly limited, but the polymerization reaction is not completed and the conjugated diene polymer chain having an active terminal is contained. A state in which the solution containing the monomer also contains a monomer, more specifically, a solution containing a conjugated diene polymer chain having an active terminal has a monomer content of 100 ppm or more, more preferably 300 to 50,000 ppm. It is desirable to add the polyorganosiloxane to this solution while containing the body. By adding polyorganosiloxane in this way, side reactions between the conjugated diene polymer chains having active terminals and impurities contained in the polymerization system can be suppressed, and the reaction can be well controlled. becomes.

In the second step, the active ends of the conjugated diene polymer chains having active ends obtained in the first step are reacted with polyorganosiloxane as a modifier. The active end of the coalescing chain will react with the silicon atoms in the siloxane structure. Alternatively, some of the active terminals of the conjugated diene-based polymer chain are the alkoxy groups or epoxy groups of the side chains of the polyorganosiloxane (in the general formula ( ¹ ), the alkoxy groups or epoxy group, etc.). Then, according to the second step, such a reaction introduces a modified structure by siloxane into the conjugated diene polymer chain.

Specifically, the active terminal of the conjugated diene polymer chain reacts with the silicon atom in the siloxane structure, so that the conjugated diene polymer chain reacts with the silicon atom in the siloxane structure and the conjugated diene polymer chain. Forms a new bond with the active terminal, introduces a modified structure with siloxane to the terminal of the conjugated diene polymer chain, and at the same time, the oxygen atom in the siloxane structure and the active terminal of the conjugated diene polymer chain and the metal atoms that formed the group represented by —O ⁻ M ⁺ (M is an alkali metal atom, an alkaline earth metal atom, or a lanthanum series metal atom) as these reaction residues is thought to be formed.

Alternatively, the active terminal of the conjugated diene polymer chain reacts with the epoxy group of the side chain of the polyorganosiloxane to open the epoxy group, and the carbon atom and the conjugated diene polymer of the part where the epoxy group is ring-opened. A new bond is formed between the active terminal of the combined chain, a siloxane structure is introduced to the terminal of the conjugated diene polymer chain, and the oxygen atom in the epoxy group and the activity of the conjugated diene polymer chain It is considered that a group represented by —O ⁻ M ⁺ is formed as a reaction residue between the terminal metal atom and the metal atom. Alternatively, the active terminal of the conjugated diene polymer chain reacts with the alkoxy group of the side chain of the polyorganosiloxane, the alkoxy group is eliminated, and the conjugated diene polymer chain is conjugated with the silicon atom in the siloxane structure. A new bond is formed with the active terminal of the diene-based polymer chain, and a siloxane structure is introduced to the terminal of the conjugated diene-based polymer chain.

In particular, in the second step, the amount of polyorganosiloxane used is 1 mol or more in terms of the number of repeating units of the siloxane structure (-Si-O-) with respect to 1 mol of the polymerization initiator, Of the conjugated diene polymer chains having active terminals obtained in the first step, almost all of the conjugated diene polymer chains can be introduced with a modified structure by siloxane. Therefore, almost all of the alkyl metal groups as active terminals of the conjugated diene-based polymer chain having active terminals obtained in the first step, that is, -R ^- M ⁺ can be brought into a state in which they do not remain. Instead of this, a group represented by —O ⁻ M ⁺ is formed as a reactive residue. However, in the present invention, a very small amount (for example, 5% by mass or less) may contain a conjugated diene-based polymer chain having an unmodified active terminal that has not been modified with siloxane ( That is, if it is very small, it contains the alkyl metal group as the active end of the conjugated diene polymer chain having the active end obtained in the first step, that is, the residue of -R ^- M ⁺ . well) and does not exclude such cases.

In the second step, before the polyorganosiloxane represented by the general formula (1) is reacted with the conjugated diene polymer chain having an active terminal, the effect of the present invention is not impaired. , A part of the active terminal of the conjugated diene polymer chain having an active terminal may be coupled or modified by adding a conventionally used coupling agent or modifier to the polymerization system. good.

[Third step]
The third step is a step of reacting a compound represented by the following general formula (2) with the conjugated diene polymer chain reacted with the polyorganosiloxane obtained in the second step.

In general formula (2), R ⁹ is a hydrocarbyl group, and A ¹ is a group capable of reacting with a reaction residue generated by the reaction of a conjugated diene polymer chain having an active terminal with polyorganosiloxane. , A ² is a group containing a nitrogen atom, p is an integer of 0 to 2, q is an integer of 1 to 3, r is an integer of 1 to 3, and p+q+r=4.

According to the present invention, in the above ^- mentioned second step, almost all of the alkyl metal groups, i.e. ^, -R All of them are in a state that does not remain, and instead of this, a group represented by —O ⁻ M ⁺ as a reaction residue due to the reaction with the polyorganosiloxane represented by the general formula (1). Therefore, according to the third step of the present invention, the compound represented by the general formula (2) has a group represented by —O ⁻ M ⁺ as such a reactive residue (−O ⁻ M ⁺ (including those in which the represented group is hydrolyzed and converted to a hydroxyl group).

That is, according to the present invention, the compound represented by the general formula (2) reacts with the group represented by -R ^- M ⁺ , so that the conjugated diene polymer chain is directly added to the general formula It is possible to appropriately suppress the introduction of a modified structure due to the compound represented by (2), whereby the conjugated diene polymer chain is added to the polyorganosiloxane represented by the general formula (1). It is possible to appropriately introduce a modified structure by the compound represented by the general formula (2) through the derived structure. As a result, excellent wet performance and rolling performance can be achieved. In addition, it is considered that workability is also improved.

However, the conjugated diene-based polymer chain reacted with polyorganosiloxane used in the third step may be one that has undergone the second step described above, and a conjugated diene-based polymer into which a modified structure by siloxane has been introduced. In addition to the chain, in a very small amount (for example, 5% by mass or less), a conjugated diene-based polymer chain having an unmodified active terminal in which no siloxane-modified structure has been introduced may remain ( That is, if it is very small, it contains the alkyl metal group as the active end of the conjugated diene polymer chain having the active end obtained in the first step, that is, the residue of -R ^- M ⁺ . may also be used), and furthermore, part of -O ^- M ⁺ as a reaction residue formed as a result of introducing a modified structure by siloxane is hydrolyzed and converted to a hydroxyl group. good too.

In the compound represented by the general formula (2), R ⁹ in the general formula (2) is a hydrocarbyl group such as an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an aralkyl group, etc. , is preferably an alkyl group having 1 to 6 carbon atoms because the effects of the present invention are more excellent. Examples of the alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, butyl group, pentyl group and hexyl group. A methyl group and an ethyl group are more preferable for superior reasons.

In the compound represented by the general formula (2), A ¹ in the general formula (2) is a reactive residue (typically is a group capable of reacting with —O ⁻ M ⁺ ), and is preferably a group —OR ¹⁰ (R ¹⁰ is a hydrogen atom or a hydrocarbyl group). Examples of hydrocarbyl groups that can constitute R ¹⁰ include alkyl groups, cycloalkyl groups, alkenyl groups, aryl groups, aralkyl groups and the like. 6 alkyl groups are preferred. Examples of the alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, butyl group, pentyl group and hexyl group. A methyl group and an ethyl group are more preferable for superior reasons.

In the compound represented by the general formula (2), A2 in the general formula ( ² ) is a group containing a nitrogen atom, and is not particularly limited as long as it is a group containing a nitrogen atom. It is preferably an organic group, for example, 3-aminopropyl group, 4-aminobutyl group, 3-(2-aminoethylamino)propyl group, 2-dimethylaminoethyl group, 3-dimethylaminopropyl group, 3- diethylaminopropyl group, 3-dipropylaminopropyl group, 3-dibutylaminopropyl group, 3-phenylmethylaminopropyl group, 3-(4-methylpiperazinyl)propyl group, N,N-bis(trimethylsilyl)aminopropyl group, N,N-bis(triethylsilyl)aminopropyl group, N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyl group, and the like. Among these, primary amino groups having active hydrogen atoms, such as 3-aminopropyl group, 4-aminobutyl group, 3-(2-aminoethylamino)propyl group, etc., and / or a group containing a secondary amino group having an active hydrogen atom is preferred. The term "active hydrogen atom" refers to a hydrogen atom bonded to an atom other than a carbon atom, and preferably has a lower bond energy than the carbon-hydrogen bond of a polymethylene chain.

In the compound represented by the general formula (2), p is an integer of 0 to 2, q is an integer of 1 to 3, r is an integer of 1 to 3, and p+q+r=4. From the viewpoint of reactivity with the reaction residue generated by the reaction of the conjugated diene polymer chain having an active terminal with the polyorganosiloxane, p is preferably an integer of 0 to 1, and q is an integer of 2 to 3. and r is an integer of 1 to 2, more preferably p=0, q=3, r=1. In the case where p is 2, the two groups represented by R ⁹ contained in one molecule of the compound represented by the general formula (2) may be the same or different. may be Similarly, when q is 2 or 3, the groups represented by A ¹ contained in one molecule of the compound represented by the general formula (2) may be the same or It may be different, and when r is 2 or 3, the groups represented by A ² contained in one molecule of the compound represented by the general formula (2) are the same may be different from each other.

Specific examples of the compound represented by the general formula (2) are not particularly limited. For example, A ² in the general formula (2) is a primary amino group having an active hydrogen atom and/or an active hydrogen atom. 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyldimethylethoxysilane, 3-aminopropyl Compounds having a 3-aminopropyl group as ^A2 such as methyldiethoxysilane, 3-aminopropyltriethoxysilane; 4-aminobutyldimethylmethoxysilane, 4-aminobutylmethyldimethoxysilane, 4-aminobutyltrimethoxysilane , 4-aminobutyldimethylethoxysilane, 4-aminobutylmethyldiethoxysilane, 4-aminobutyltriethoxysilane, etc., compounds having a 4-aminobutyl group as A2; 3-( ² -aminoethylamino)propyldimethyl Methoxysilane, 3-(2-aminoethylamino)propylmethyldimethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(2-aminoethylamino)propyldimethylethoxysilane, 3-(2- A2 such as aminoethylamino)propylmethyldiethoxysilane, 3-( ² -aminoethylamino)propyltriethoxysilane, and the like include compounds having a 3-(2-aminoethylamino)propyl group;

Further, as a compound in which A ² in general formula (2) is a group other than a group containing a primary amino group having an active hydrogen atom and/or a secondary amino group having an active hydrogen atom, 3-dimethylamino Propyltrimethoxysilane, 3-dimethylaminopropylmethyldimethoxysilane, 3-dimethylaminopropyldimethylmethoxysilane, 3-dimethylaminopropyltriethoxysilane, 3-dimethylaminopropylmethyldiethoxysilane, 3-dimethylaminopropyldimethylethoxysilane A ² such as compounds having a 3-dimethylaminopropyl group; 3-diethylaminopropyltrimethoxysilane, 3-diethylaminopropylmethyldimethoxysilane, 3-diethylaminopropyldimethylmethoxysilane, 3-diethylaminopropyltriethoxysilane, 3- Compounds having a 3-diethylaminopropyl group as ^A2 such as diethylaminopropylmethyldiethoxysilane, 3-diethylaminopropyldimethylethoxysilane, 3-dipropylaminopropyltrimethoxysilane, 3-dipropylaminopropylmethyldimethoxysilane, 3 -dipropylaminopropyldimethylmethoxysilane, 3-dipropylaminopropyltriethoxysilane, 3-dipropylaminopropylmethyldiethoxysilane, 3-dipropylaminopropyldimethylethoxysilane, etc. as ^A2 , 3-dipropylamino Compounds having a propyl group; 3-dibutylaminopropyltrimethoxysilane, 3-dibutylaminopropylmethyldimethoxysilane, 3-dibutylaminopropyldimethylmethoxysilane, 3-dibutylaminopropyltriethoxysilane, 3-dibutylaminopropylmethyldiethoxy Compounds having a 3-dibutylaminopropyl group as ^A2 such as silane, 3-dibutylaminopropyldimethylethoxysilane; 3-phenylmethylaminopropyltrimethoxysilane, 3-phenylmethylaminopropylmethyldimethoxysilane, 3-phenylmethyl 3-phenylmethylaminopropyl group as ^A2 such as aminopropyldimethylmethoxysilane, 3-phenylmethylaminopropyltriethoxysilane, 3-phenylmethylaminopropylmethyldiethoxysilane, 3-phenylmethylaminopropyldimethylethoxysilane, etc. compound having; 3-(4-methylpiperazide Nyl)propyltrimethoxysilane, 3-(4-methylpiperazinyl)propylmethyldimethoxysilane, 3-(4-methylpiperazinyl)propyldimethylmethoxysilane, 3-(4-methylpiperazinyl)propyltriethoxysilane 3-(4-methylpiperazinyl)propyl group as ^A2 such as silane, 3-(4-methylpiperazinyl)propylmethyldiethoxysilane, 3-(4-methylpiperazinyl)propyldimethylethoxysilane, etc. a compound having

N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, N,N-bis(trimethylsilyl) Compounds having an N,N-bis(trimethylsilyl)aminopropyl group as ^A2 such as aminopropylmethyldiethoxysilane; N,N-bis(triethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl) N,N-bis(triethylsilyl) as ^A2 such as aminopropyltriethoxysilane, N,N-bis(triethylsilyl)aminopropylmethyldimethoxysilane, N,N-bis(triethylsilyl)aminopropylmethyldiethoxysilane ) compounds having an aminopropyl group; N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N,N',N'-tris(trimethylsilyl) -N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N,N',N'-tris(trimethylsilyl)-N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N, N,N',N' ^- tris(trimethylsilyl)-N-( 2-aminoethyl)-3-aminopropyl group-containing compounds; and the like.
Among them, the compound represented by the general formula (2) has a group containing a secondary amino group having an active hydrogen atom as ^A2 from the viewpoint of being superior to the effects of the present invention (especially low rolling resistance). A ² is preferably a compound, more preferably a compound having a group containing a primary amino group having an active hydrogen atom and a secondary amino group having an active hydrogen atom as A 2 , 3-(2-aminoethyl Further preferred are compounds with amino)propyl groups.

The amount of the compound represented by the general formula (2) is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably 0.1 per 1 mol of the polymerization initiator used in the first step. to 5 mol, more preferably 0.2 to 2 mol, still more preferably 0.4 to 1.5 mol.

The timing of adding the compound represented by the general formula (2) to the solution containing the conjugated diene polymer chain is after adding the polyorganosiloxane represented by the general formula (1) in the second step described above. If so, it is not particularly limited. For example, as in the second step described above, the state in which the polymerization reaction is not completed and the solution containing the conjugated diene polymer chain also contains the monomer, more specifically, the conjugated diene Adding a compound represented by the general formula (2) to a solution containing a system polymer chain containing 100 ppm or more, more preferably 300 to 50,000 ppm of a monomer. can be done. By adding the compound represented by the general formula (2) in this manner, side reactions between the conjugated diene polymer chain and impurities contained in the polymerization system are suppressed, and the reaction is well controlled. becomes possible. Alternatively, before or after adding the compound represented by the general formula (2) to the solution containing the conjugated diene polymer chain, by adding an alcohol such as water or methanol to the solution, Hydrolyzing the group represented by -O ^- M ⁺ as a reaction residue formed by the reaction with the polyorganosiloxane represented by the general formula (1) and converting it to a hydroxyl group, a modification reaction may be performed. When adding the compound represented by the general formula (2) to the solution containing the conjugated diene polymer chain, the compound represented by the general formula (2) may be added after being dissolved in an inert solvent. and may be added directly without dissolving in an inert solvent. The reaction temperature and reaction time are the same as in the first step.

Then, after reacting the compound represented by the general formula (2), if necessary, a known polymerization terminator or the like is added to deactivate the reaction system, and if desired, a phenolic stabilizer , anti-aging agents such as phosphorus stabilizers, sulfur stabilizers, crumb agents, scale inhibitors, etc. are added to the reaction solution, and then the polymerization solvent is separated from the reaction solution by direct drying or steam stripping. to recover the conjugated diene rubber. Before separating the polymerization solvent from the reaction solution, an extender oil may be mixed with the polymerization solution to recover the conjugated diene rubber as an oil-extended rubber.

Examples of the extender oil used for recovering the conjugated diene rubber as an oil-extended rubber include paraffinic, aromatic and naphthenic petroleum softeners, vegetable softeners, and fatty acids. When petroleum-based softeners are used, it is preferred that the content of polycyclic aromatics extracted by the IP346 method (inspection method of THE INSTITUTE PETROLEUM, UK) is less than 3%. When an extender oil is used, the amount used is preferably 5 to 100 parts by mass, more preferably 10 to 60 parts by mass, and still more preferably 20 to 50 parts by mass with respect to 100 parts by mass of the conjugated diene rubber. .

As described above, in the above-described second step, the specific conjugated diene rubber is obtained by adding the polyorganosiloxane represented by the general formula (1) as a modifier to 1 mol of the polymerization initiator used in the first step. Then, the siloxane structure (-Si-O-) in the polyorganosiloxane is added at a rate of 1 mol or more in terms of the number of repeating units, and then the reaction is performed. It is obtained by performing a reaction using the compound represented by formula (2). Therefore, the specific conjugated diene rubber includes those in which a modified structure by siloxane and a modified structure by the compound represented by the general formula (2) are introduced at the polymer chain terminal. , may include those in which only a modified structure with siloxane is introduced at the polymer chain end. Furthermore, to the extent that the effect of the present invention is not impaired, for example, only the modified structure by the compound represented by the general formula (2) is introduced at the polymer chain terminal, or any modified structure is introduced. It may contain things that do not exist. In particular, in the present invention, from the viewpoint of more appropriately realizing the effects of the present invention, a modified structure by siloxane and a modified structure by a compound represented by general formula (2) are introduced at the polymer chain terminal. The ratio is preferably 10% by mass or more, more preferably 20% by mass or more. In addition, an upper limit is not specifically limited.

<Monomer unit content>
The specific conjugated diene-based rubber preferably contains 50 to 100% by mass of conjugated diene monomer units, more preferably 52 to 95% by mass, for the reason that the effect of the present invention is more excellent. Those containing 0 to 50% by mass of vinyl monomer units are preferred.

<Vinyl bond content>
The vinyl bond content in the conjugated diene monomer unit in the specific conjugated diene rubber is preferably 1 to 90% by mass, more preferably 3 to 80% by mass, and particularly preferably 5 to 70% by mass.

[Coupling rate]
The coupling rate of the specific conjugated diene rubber is not particularly limited, but is preferably 10% by mass or more, more preferably 20% by mass or more, and particularly preferably 40% by mass or more because the effects of the present invention are more excellent. and is preferably 80% by mass or less, more preferably 75% by mass or less, and particularly preferably 70% by mass or less. The coupling rate is determined by reacting the compound represented by the polyorganosiloxane represented by the general formula (1) and the general formula (2), and the coupling agent and other modifiers used as necessary. is the mass fraction of polymer molecules having a molecular weight of 1.8 times or more the peak top molecular weight of the previous conjugated diene polymer chain having an active terminal, relative to the total amount of the finally obtained conjugated diene rubber, The measurement of the molecular weight at this time shall be obtained as a polystyrene equivalent molecular weight by gel permeation chromatography.

[Molecular weight]
Further, the weight average molecular weight (Mw) of the specific conjugated diene rubber is a value measured by gel permeation chromatography in terms of polystyrene, and is preferably 100,000 to 3,000,000, more preferably 150,000 to 2. ,000,000, particularly preferably 200,000 to 1,500,000. By setting the weight-average molecular weight of the conjugated diene-based rubber within the above range, silica can be easily blended into the conjugated diene-based rubber, and the processability of the rubber composition can be further enhanced. will be better.

The molecular weight distribution represented by the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the specific conjugated diene rubber is 1.1-3. It is preferably 0, more preferably 1.2 to 2.5, and particularly preferably 1.2 to 2.2.

〔viscosity〕
Further, the Mooney viscosity (ML ₁₊₄ , 100°C) of the specific conjugated diene rubber is preferably 20 to 100, more preferably 30 to 90, and particularly preferably 35 to 80, because the effects of the present invention are more excellent. . When the conjugated diene rubber is used as the oil-extended rubber, the Mooney viscosity of the oil-extended rubber is preferably set within the above range.

〔Content〕
As described above, the content of the specific conjugated diene rubber in the conjugated diene rubber is 30% by mass or more.
The upper limit of the specific conjugated diene rubber content in the conjugated diene rubber is not particularly limited, and is 100% by mass. The content of the specific conjugated diene rubber in the conjugated diene rubber is preferably 50% by mass or more, more preferably 60 to 100% by mass, for the reason that the effects of the present invention are more excellent.

[Other rubber components]
The diene rubber may contain rubber components (other rubber components) other than the specific conjugated diene rubber.
Such other rubber components include conjugated diene rubbers (y) other than the specific conjugated diene rubbers.
Examples of the conjugated diene rubber (y) include copolymers of aromatic vinyl and conjugated dienes such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), and styrene-butadiene rubber (SBR). coalesced, acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), and the like. Among them, butadiene rubber (BR), which is a copolymer of aromatic vinyl and conjugated diene, is preferable because the effects of the present invention are more excellent.
The content of other rubber components in the conjugated diene rubber is not particularly limited, but is preferably 0 to 50% by mass, more preferably 10 to 40% by mass, for the reason that the effects of the present invention are more excellent. preferable.

[2] Silica The silica contained in the composition of the present invention is not particularly limited, and any conventionally known silica can be used. Specific examples of the silica include wet silica, dry silica, fumed silica, and diatomaceous earth.

The CTAB adsorption specific surface area of silica is preferably 100 to 250 m ² /g, more preferably 120 to 200 m ² /g, for the reason that the effects of the present invention are more excellent.
Here, the CTAB adsorption specific surface area is a value obtained by measuring the amount of CTAB adsorption to the silica surface according to JIS K6217-3:2001 "Part 3: Determination of specific surface area - CTAB adsorption method".

In the composition of the present invention, the content of silica is 30 parts by mass or more with respect to 100 parts by mass of the conjugated diene rubber. Among them, the amount is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, because the effects of the present invention are more excellent.
The upper limit of the content of silica is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably 200 parts by mass or less, and 150 parts by mass or less with respect to 100 parts by mass of the above-described conjugated diene rubber. is more preferable.

[3] Silane Coupling Agent The silane coupling agent contained in the composition of the present invention is not particularly limited as long as it is a silane compound having a hydrolyzable group and an organic functional group.
Although the hydrolyzable group is not particularly limited, examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, an alkenyloxy group and the like. Among them, an alkoxy group is preferable because the effects of the present invention are more excellent. When the hydrolyzable group is an alkoxy group, the number of carbon atoms in the alkoxy group is preferably 1-16, more preferably 1-4, for the reason that the effects of the present invention are more excellent. The alkoxy group having 1 to 4 carbon atoms includes, for example, methoxy group, ethoxy group, propoxy group and the like.

The organic functional group is not particularly limited, but is preferably a group capable of forming a chemical bond with an organic compound. A mercapto group (protected mercapto group) (e.g., octanoylthio group) and the like, among which a sulfide group (particularly a disulfide group and a tetrasulfide group), a mercapto group, and a blocked mercapto group are included because the effects of the present invention are more excellent. is preferred.

Specific examples of the silane coupling agent include bis(3-triethoxysilylpropyl) tetrasulfide, bis(3-trimethoxysilylpropyl) tetrasulfide, bis(3-triethoxysilylpropyl) disulfide, 3-trimethoxy silylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide A silane coupling agent having a sulfide group such as;
mercaptosilanes such as mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane;
Examples thereof include compounds represented by the following general formula (S) such as 3-octanoylthio-1-propyltriethoxysilane.
(C _n H _2n+1 O) ₃ —Si—C _m H _2m —S—CO—C _k H _2k+1 general formula (S)
In the general formula (S), n represents an integer of 1 to 3, m represents an integer of 1 to 5 (preferably an integer of 2 to 4), k represents an integer of 1 to 15 (preferably an integer of 5 to Integer of 10).
Among these silane coupling agents, one may be used alone, or two or more may be used in combination.

The silane coupling agent is preferably a silane coupling agent having a sulfide group or a compound represented by the general formula (S) because the effects of the present invention are more excellent.

In the composition of the present invention, the content of the silane coupling agent is 3 to 30% by mass based on the silica content described above. Among them, 5 to 20% by mass is preferable because the effects of the present invention are more excellent.

Further, in the composition of the present invention, the content of the silane coupling agent is 1 to 30 parts by mass with respect to 100 parts by mass of the above-described conjugated diene rubber for the reason that the effect of the present invention is more excellent. It is preferably from 2 to 20 parts by mass, and even more preferably from 4 to 10 parts by mass.

[4] Heterocyclic compound The heterocyclic compound contained in the composition of the present invention is a compound having at least one hydrocarbon group serving as the hydrophobic portion and a heterocyclic ring.
In the present invention, the content of the heterocyclic compound is 0.5 to 20% by mass relative to the content of silica.

In the heterocyclic compound, the hydrocarbon can function as a hydrophobic portion.
On the other hand, the heterocycle can function as a hydrophilic moiety.
In the present invention, the “hydrocarbon group serving as a hydrophobic portion” means that the above hydrocarbon group is hydrophobic. On the other hand, the heterocycle can be more hydrophilic than the hydrocarbon group serving as the hydrophobic portion.

<Hydrocarbon group serving as hydrophobic portion>
Examples of the hydrocarbon group that becomes the hydrophobic portion of the heterocyclic compound include aliphatic hydrocarbon groups (including linear, branched and cyclic), aromatic hydrocarbon groups, and combinations thereof. is mentioned.
Among them, an aliphatic hydrocarbon group is preferable, and a saturated aliphatic hydrocarbon group is more preferable, from the viewpoint that the effect of the present invention (especially workability) is superior.

The hydrocarbon group that forms the hydrophobic portion is preferably a monovalent hydrocarbon group from the viewpoint that the effects of the present invention (in particular, low rolling resistance) are superior.

The number of carbon atoms in the hydrocarbon group (for example, a monovalent hydrocarbon group) that serves as the hydrophobic portion is preferably 3 to 30, preferably 8 to 30, from the viewpoint that the effects of the present invention (especially workability) are superior. is more preferred, and 10 to 30 is even more preferred.

The hydrocarbon group (e.g., monovalent hydrocarbon group) serving as the hydrophobic portion is preferably composed of only carbon atoms and hydrogen atoms (consisting of only carbon atoms and hydrogen atoms). .

In the present invention, the heterocyclic compound has at least one hydrocarbon group (for example, a monovalent hydrocarbon group) serving as the hydrophobic portion per molecule.
One of preferred embodiments of the heterocyclic compound includes one or two hydrocarbon groups that serve as the hydrophobic portion.

<Hetero ring>
In the present invention, the heterocyclic compound has a heterocyclic ring.
The heterocycle is not particularly limited. Examples thereof include a cyclic structure composed of carbon atoms and at least one heteroatom selected from the group consisting of oxygen atoms, sulfur atoms and nitrogen atoms.

From the viewpoint that the effect of the present invention (in particular, low rolling resistance) is superior, the heterocyclic ring is preferably composed of at least a nitrogen atom and a carbon atom.
A hetero ring composed of at least a nitrogen atom and a carbon atom may have two or more of the above nitrogen atoms per hetero ring.
In addition, the hetero ring composed of at least a nitrogen atom and a carbon atom may further have an oxygen atom or a sulfur atom as atoms constituting the hetero ring.

Examples of the heterocyclic ring include a 5-membered ring, a 6-membered ring and a 7-membered ring.
Specific examples include a 6-membered ring such as a piperazine ring, morpholine ring or thiomorpholine ring.

The heterocycle is preferably a piperazine ring, a morpholine ring or a thiomorpholine ring, more preferably a piperazine ring or a morpholine ring, and still more preferably a piperazine ring, from the viewpoint that the effects of the present invention (especially low rolling resistance) are superior.

One preferred mode is that the heterocyclic compound has one heterocyclic ring per molecule.
From the viewpoint that the above one hetero ring is more excellent in the effects of the present invention (in particular, low rolling resistance), a piperazine ring, a morpholine ring or a thiomorpholine ring is mentioned as one of preferred embodiments.

(piperazine ring)
Piperazine ring means the skeleton of piperazine. A heterocyclic compound having a piperazine ring as a heterocyclic ring may be hereinafter referred to as a "piperazine compound". In the present invention, the piperazine ring does not contain a triethylenediamine skeleton.
(morpholine ring)
Morpholine ring means the backbone of morpholine. A heterocyclic compound having a morpholine ring as a heterocyclic ring may be hereinafter referred to as a "morpholine compound".
(thiomorpholine ring)
Thiomorpholine ring means the skeleton of thiomorpholine. A heterocyclic compound having a thiomorpholine ring as a heterocyclic ring may be hereinafter referred to as a "thiomorpholine compound".

(Binding of Hydrocarbon Group to Become Hydrophobic Portion and Heterocycle)
In the heterocyclic compound, the hydrocarbon group (for example, monovalent hydrocarbon group) serving as the hydrophobic portion can be bonded to the heterocyclic ring directly or via an organic group.

-Organic group The organic group (linking group) capable of intervening the hydrocarbon group serving as the hydrophobic portion and the hetero ring may be divalent or higher, and may be divalent.
One of preferred aspects is that the organic group is hydrophilic.
Examples of the above-mentioned organic group (entire organic group) include hydrocarbon groups which may have heteroatoms such as oxygen, sulfur and nitrogen atoms.
In the present invention, that the organic group is hydrophilic means that the organic group (the organic group as a whole) is a hydrocarbon group having a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom. do.

When the heteroatom is an oxygen atom, the oxygen atom may form, for example, an ether bond, a hydroxy group or a carbonyl group in the organic group (the whole organic group).
When the organic group is a hydrocarbon group having an oxygen atom at its terminal, the oxygen atom may be combined with the hydrocarbon group (e.g., monovalent hydrocarbon group) serving as the hydrophobic portion to form an ether bond. good.

Examples of the multivalent hydrocarbon group that can (partially) constitute the organic group include a divalent or trivalent hydrocarbon group.
Examples of the multivalent hydrocarbon group include aliphatic hydrocarbon groups (including linear, branched and cyclic), aromatic hydrocarbon groups, and combinations thereof.

For example, at least one selected from the group consisting of an ether bond, a hydroxy group and a carbonyl group can bond to the multivalent hydrocarbon group to form the organic group (linking group).

There is no particular limitation on the position at which the hydrocarbon group serving as the hydrophobic portion is bonded to the hetero ring. For example, the hydrocarbon group that forms the hydrophobic portion can be bonded to the atoms that constitute the hetero ring.
When the heterocyclic ring is composed of at least a nitrogen atom and a carbon atom (e.g., piperazine ring, morpholine ring, thiomorpholine ring), the hydrocarbon group (e.g., monovalent hydrocarbon group) serving as the hydrophobic portion is , is preferably bonded to the nitrogen atom or carbon atom of the heterocyclic ring directly or via an organic group, and more preferably bonded to the nitrogen atom of the heterocyclic ring directly or via an organic group.

- Substituent The heterocyclic compound can further have a substituent other than the hydrocarbon group and the heterocyclic ring that serves as the hydrophobic portion. Examples of the substituent include at least one selected from the group consisting of sulfone-based protecting groups, carbamate-based protecting groups and formula (I-3): --(R ₂ --O) _n2 --H.
When the heterocyclic compound further has the substituent, the heterocyclic compound is preferably a piperazine compound,
More preferably, the substituent is bound to the nitrogen atom of the piperazine ring of the piperazine compound,
In the piperazine compound, one of the hydrocarbon groups (e.g., a monovalent hydrocarbon group) serving as the hydrophobic moiety is bound to one of the two nitrogen atoms of the piperazine ring, and the remaining nitrogen atoms of the piperazine ring are , the above substituents are more preferably bonded.

(Sulfone-based protective group)
Sulfone-based protecting groups include, for example, methanesulfonyl, tosyl and nosyl groups.

(Carbamate-based protecting group)
Carbamate-based protecting groups include, for example, tert-butoxycarbonyl, allyloxycarbonyl, benzyloxycarbonyl and 9-fluorenylmethyloxycarbonyl groups.

(Formula (I-3))
In formula (I-3): --(R ₂ --O) _n2 --H, each R ₂ independently represents a divalent hydrocarbon group.
In formula (I-3), the divalent hydrocarbon group preferably has 2 to 3 carbon atoms.
The divalent hydrocarbon group is preferably an aliphatic hydrocarbon group. Aliphatic hydrocarbon groups may be linear, branched, cyclic, or combinations thereof.
n2 represents 1 to 10, preferably 1 to 5.

式（Ｉ）中、Ｘ₇が、窒素原子、酸素原子または硫黄原子を表し、
Ｘ₃、Ｘ₄、Ｘ₅およびＸ₆は、それぞれ独立に、水素原子または炭化水素基を表す。
Ｘ₇が窒素原子である場合、ｎ３は１であり、Ｘ₁およびＸ₂のうちの一方または両方が、それぞれ独立に、式（Ｉ－１）：－（Ａ₁）_n1-1－Ｒ_1-1を表し、
Ｘ₁およびＸ₂のうちの一方のみが式（Ｉ－１）を表す場合、残りの基が、水素原子、スルホン系保護基、カルバメート系保護基および式（Ｉ－３）：－（Ｒ₂－Ｏ）_n2－Ｈからなる群から選ばれる少なくとも１種を表し、
式（Ｉ－３）中、Ｒ₂は、それぞれ独立に、２価の炭化水素基を表し、
ｎ２は、１～１０を表す。
Ｘ₇が酸素原子または硫黄原子である場合、ｎ３は０を表し、Ｘ₁が、式（Ｉ－１）：－（Ａ₁）_n1-1－Ｒ_1-1を表す。
式（Ｉ－１）中、Ａ₁は、カルボニル基および／または式（Ｉ－２）：－Ｒ_1-2（ＯＨ）－Ｏ－を表し、
ｎ１－１は、０または１を表し、
Ｒ_1-1は、上記疎水部となる上記炭化水素基を表し、
式（Ｉ－２）中、Ｒ_1-2は、３価の炭化水素基を表す。 The heterocyclic compound is preferably a compound represented by the following formula (I) from the viewpoint that the effects of the present invention (especially low rolling resistance) are superior.
The ring structure represented by the following formula (I) (heterocyclic ring composed of N (nitrogen atom), four carbon atoms and X ₇ ) is a six-membered ring. The number of the above ring structures is one per molecule of the compound represented by formula (I).
When X ₇ in formula (I) is a nitrogen atom, the heterocycle represented by formula (I) corresponds to a piperazine ring.
When X ₇ in formula (I) is an oxygen atom, the heterocycle represented by formula (I) corresponds to a morpholine ring.
When X ₇ in formula (I) is a sulfur atom, the heterocycle represented by formula (I) corresponds to a thiomorpholine ring.

_In formula (I), X represents a nitrogen atom, an oxygen atom or a sulfur atom,
X3 _{, X4} , _X5 and X6 _each independently represent a hydrogen atom or a hydrocarbon group.
When X ₇ is a nitrogen atom, n3 is 1 and one or both of X ₁ and X ₂ are each independently represented by formula (I-1): -(A ₁ ) _n1-1 -R ₁ represents _-1 ,
When only one of X ₁ and X ₂ represents formula (I-1), the remaining groups are a hydrogen atom, a sulfone-based protecting group, a carbamate-based protecting group and formula (I-3):-(R ₂ -O) represents at least one selected from the group consisting of _n2 -H,
In formula (I-3), each R ₂ independently represents a divalent hydrocarbon group,
n2 represents 1-10.
When X ₇ is an oxygen atom or a sulfur atom, n3 represents 0 and X ₁ represents formula (I-1): -(A ₁ ) _n1-1 -R _1-1 .
In formula (I-1), A ₁ represents a carbonyl group and/or formula (I-2): —R _1-2 (OH)—O—,
n1-1 represents 0 or 1,
R _1-1 represents the above hydrocarbon group that serves as the above hydrophobic portion,
In formula (I-2), R _1-2 represents a trivalent hydrocarbon group.

In formula (I), one or both of X ₁ and X ₂ each independently represent formula (I-1):-(A ₁ ) _n1-1 -R _1-1 .

(Formula (I-1))
In formula (I-1): -(A ₁ ) _n1-1 -R _1-1 , A ₁ represents a carbonyl group and/or formula (I-2): -R _1-2 (OH)-O- show.
n1-1 represents 0 or 1;
R _1-1 represents the above hydrocarbon group that serves as the above hydrophobic portion. The hydrocarbon group serving as the hydrophobic portion as R _1-1 is the same as the hydrocarbon group serving as the hydrophobic portion of the heterocyclic compound.

(Formula (I-2))
In formula (I-2): -R _1-2 (OH)-O-, R _1-2 represents a trivalent hydrocarbon group.
The number of carbon atoms in the trivalent hydrocarbon group is preferably 3-30.
The trivalent hydrocarbon group is preferably an aliphatic hydrocarbon group. Aliphatic hydrocarbon groups may be linear, branched, cyclic, or combinations thereof.

In formula (I-2), the hydroxy group and the oxygen atom (--O--) may be bonded to any carbon atom constituting R _1-2 .
In formula (I-1), when n1-1 is 1 and A ₁ is formula (I-2), R _1-2 in formula (I-2) is bonded to a hetero ring to form One of preferred embodiments is that the oxygen atom (--O--) of (I-2) is bonded to R _1-1 .

(X3 _{, X4} , _X5 and _X6 )
In Formula (I), X ₃ , X ₄ , X ₅ and X ₆ each independently represent a hydrogen atom or a hydrocarbon group.
The hydrocarbon group is not particularly limited. The hydrocarbon group as X ₃ , X ₄ , X ₅ or X ₆ may be the same as the above hydrocarbon group serving as the hydrophobic portion of the above heterocyclic compound, or may be any other hydrocarbon group. good too.
One of preferred embodiments of X ₃ , X ₄ , X ₅ and X ₆ is a hydrogen atom.

In formula (I), when X ₇ is a nitrogen atom, n3 is 1, and only one of X ₁ and X ₂ represents formula (I-1) above, the remaining groups are hydrogen atoms, It can represent at least one selected from the group consisting of a sulfone-based protecting group, a carbamate-based protecting group and formula (I-3): --(R ₂ --O) _n2 --H.
That is, when X ₁ represents the above formula (I-1), X ₂ represents a hydrogen atom, a sulfone-based protecting group, a carbamate-based protecting group and the formula (I-3): —(R ₂ —O) _n2 —H It can represent at least one selected from the group consisting of
Further, when X ₂ represents the above formula (I-1), X ₁ is a hydrogen atom, a sulfone-based protecting group, a carbamate-based protecting group and the formula (I-3): —(R ₂ —O) _n2 —H. It can represent at least one selected from the group consisting of The sulfone-based protecting group, carbamate-based protecting group and formula (I-3) are respectively the same as described above.

(When the heterocyclic compound is a compound represented by formula (I), _X7 is a nitrogen atom, and n3 is 1)
A heterocyclic compound represented by formula (I), wherein X ₇ is a nitrogen atom and n3 is 1, is represented by the following formula (II).

In formula (II), one or both of X ₁ and X ₂ each independently represent formula (I-1):-(A ₁ ) _n1-1 -R _1-1 .

(Formula (I-1))
In formula (I-1): -(A ₁ ) _n1-1 -R _1-1 , A ₁ represents a carbonyl group and/or formula (I-2): -R _1-2 (OH)-O- show.
n1-1 represents 0 or 1;
R _1-1 represents the above hydrocarbon group that serves as the above hydrophobic portion. The hydrocarbon group serving as the hydrophobic portion as R _1-1 is the same as the hydrocarbon group serving as the hydrophobic portion of the heterocyclic compound.

(Formula (I-2))
In formula (I-2): -R _1-2 (OH)-O-, R _1-2 represents a trivalent hydrocarbon group.
The carbon number of the trivalent hydrocarbon group is preferably 3-30.
The trivalent hydrocarbon group is preferably an aliphatic hydrocarbon group. Aliphatic hydrocarbon groups may be linear, branched, cyclic, or combinations thereof.

In formula (I-2), the hydroxy group and the oxygen atom (--O--) may be bonded to any carbon atom constituting R _1-2 .
In formula (I-1), when n1-1 is 1 and A ₁ is formula (I-2), R _1-2 in formula (I-2) is bonded to the piperazine ring to form One preferred mode is that the oxygen atom (--O--) of (I-2) is bonded to R _1-1 .

(X3 _{, X4} , _X5 and _X6 )
_In formula (II), X3 _, X4, _X5 and X6 _each independently represent a hydrogen atom or a hydrocarbon group.
The hydrocarbon group is not particularly limited. The hydrocarbon group as X ₃ , X ₄ , X ₅ or X ₆ may be the same as the above hydrocarbon group serving as the hydrophobic portion of the above heterocyclic compound, or may be any other hydrocarbon group. good too.
One of preferred embodiments of X ₃ , X ₄ , X ₅ and X ₆ is a hydrogen atom.

In formula (II), when only one of X ₁ and X ₂ represents the above formula (I-1), the remaining groups are a hydrogen atom, a sulfone-based protecting group, a carbamate-based protecting group and the formula (I- 3): It can represent at least one member selected from the group consisting of --(R ₂ --O) _n2 --H.
That is, when X ₁ represents the above formula (I-1), X ₂ represents a hydrogen atom, a sulfone-based protecting group, a carbamate-based protecting group and the formula (I-3): —(R ₂ —O) _n2 —H It can represent at least one selected from the group consisting of
Further, when X ₂ represents the above formula (I-1), X ₁ is a hydrogen atom, a sulfone-based protecting group, a carbamate-based protecting group and the formula (I-3): —(R ₂ —O) _n2 —H. It can represent at least one selected from the group consisting of The sulfone-based protecting group, carbamate-based protecting group and formula (I-3) are respectively the same as described above.

Specific embodiments of the piperazine compound include, for example, the following embodiments 1 and 2.
(Aspect 1 of Piperazine Compound)
Embodiment 1 of the piperazine compound is represented by formula (II),
Both X ₁ and X ₂ are each independently a compound represented by formula (I-1) above.
In Embodiment 1 above, X ₃ , X ₄ , X ₅ and X ₆ are preferably hydrogen atoms.

Specific examples of Aspect 1 include piperazine compounds 3, 5 and 8 represented by the following formulas.

piperazine compound 3

piperazine compound 5

piperazine compound 8 (each R independently represents -C ₁₂ H ₂₅ or -C ₁₃ H ₂₇ );

(Aspect 2 of Piperazine Compound)
Embodiment 2 of the Piperazine Compound is represented by Formula (II),
only one of X ₁ and X ₂ represents formula (I-1),
A compound in which the remaining groups are at least one selected from the group consisting of a hydrogen atom, a sulfone-based protecting group, a carbamate-based protecting group, and the above formula (I-3): --(R ₂ --O) _n2 --H. .
In Mode 2 above, X ₃ , X ₄ , X ₅ and X ₆ are preferably hydrogen atoms.

Specific examples of Aspect 2 include piperazine compounds 1, 2, 4, 6 and 7 represented by the following formulas.

piperazine compound 1

piperazine compound 2 (in the following structural formula, n is 1 to 10, preferably 1 to 5);

piperazine compound 4

piperazine compound 6

Piperazine Compound 7 (R represents —C ₁₂ H ₂₅ or —C ₁₃ H ₂₇ . Piperazine Compound 7 includes a piperazine compound in which R is —C ₁₂ H ₂₅ and a piperazine compound in which R is —C ₁₃ H ₂₇ It may be a mixture with

式（ＩＩＩ）において、Ｘ₁は上記式（Ｉ）の式（Ｉ－１）：－（Ａ₁）_n1-1－Ｒ_1-1と同じであり、Ｘ₃、Ｘ₄、Ｘ₅およびＸ₆は上記式（Ｉ）のＸ₃、Ｘ₄、Ｘ₅およびＸ₆とそれぞれ同じであり、Ｘ₈は酸素原子または硫黄原子である。 (When the heterocyclic compound is a compound represented by formula (I), _X7 is an oxygen atom or a sulfur atom, and n3 is 0)
A heterocyclic compound represented by the formula (I), wherein _X7 is an oxygen atom or a sulfur atom, and n3 is 0, is represented by the following formula (III).

In formula (III), X ₁ is the same as formula (I-1): -(A ₁ ) _n1-1 -R _1-1 of formula (I) above, and X ₃ , X ₄ , X ₅ and X ₆ is the same as X ₃ , X ₄ , X ₅ and X ₆ in formula (I) above, and X ₈ is an oxygen atom or a sulfur atom.

Examples of compounds represented by formula (III) include morpholine compounds 1 to 4 represented by the following formulas.

(morpholine compound 1)

(morpholine compound 2)

(morpholine compound 3)

モルホリン化合物４は、Ｒが－Ｃ₁₂Ｈ₂₅であるモルホリン化合物とＲが－Ｃ₁₃Ｈ₂₇であるモルホリン化合物との混合物である。 (morpholine compound 4)

Morpholine Compound 4 is a mixture of morpholine compounds in which R is -C ₁₂ H ₂₅ and morpholine compounds in which R is -C ₁₃ H ₂₇ .

The heterocyclic compound is not particularly limited in its production method. For example, a conventionally well-known thing is mentioned.
Specifically, for example, at least one selected from the group consisting of optionally substituted piperazine, morpholine and thiomorpholine, a halogen atom (chlorine, bromine, iodine, etc.), an acid halogen group (acid chloride group , an acid bromide group, an acid iodide group, etc.) and a glycidyloxy group, and a hydrocarbon group (e.g., monovalent hydrocarbon group) serving as a hydrophobic portion; can be obtained by reaction, optionally in a solvent. Substituents are the same as above. A hydrocarbon group (for example, a monovalent hydrocarbon group) that becomes a hydrophobic portion of the above hydrocarbon compound is the same as described above.
As for the method for producing a piperazine compound having the above formula (I-3): —(R ₂ —O) _n2 —H like the above piperazine compound 2, for example, a hydroxy A method of reacting a piperazine compound having a group with an alkylene oxide in the presence of a metal alkoxide can be mentioned.

In addition, in the present invention, the heterocyclic compound can be one having no silicon atom.
Also, the heterocyclic compound may not have an enamine structure (NC=C).

<Content of heterocyclic compound>
In the present invention, the content of the heterocyclic compound is 0.5 to 20% by mass relative to the content of silica.
The content of the heterocyclic compound is preferably 0.5 to 15% by mass, preferably 1 to 10% by mass, based on the content of the silica, from the viewpoint that the effect of the present invention (especially low rolling resistance) is excellent. is more preferred.

[5] Optional Components The composition of the present invention can contain components (optional components) other than the components described above, if necessary.
Examples of such components include fillers other than silica (e.g., carbon black), terpene resins (preferably aromatic modified terpene resins), thermally expandable microcapsules, zinc oxide (zinc oxide), stearic acid, Various additives commonly used in rubber compositions such as anti-aging agents, waxes, processing aids, process oils, liquid polymers, thermosetting resins, vulcanizing agents (e.g. sulfur), vulcanization accelerators, etc. is mentioned.

[Carbon black]
The composition of the present invention preferably contains carbon black because the effects of the present invention are more excellent.
The carbon black is not particularly limited, for example, various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, and SRF can be used.
The nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is not particularly limited, but is preferably 50 to 200 m ² /g, more preferably 70 to 150 m ² /g, for the reason that the effects of the present invention are more excellent. is more preferred.
Here, the nitrogen adsorption specific surface area (N ₂ SA) is the amount of nitrogen adsorption on the carbon black surface according to JIS K6217-2:2001 "Part 2: Determination of specific surface area - nitrogen adsorption method - single point method". It is a measured value.

In the composition of the present invention, the content of carbon black is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably 1 to 100 parts by mass with respect to 100 parts by mass of the diene rubber described above. , more preferably 2 to 10 parts by mass.

[Specific alkyltriethoxysilane]
The composition of the present invention preferably contains an alkyltriethoxysilane represented by the following general formula (I) (hereinafter also referred to as "specific alkyltriethoxysilane") for the reason that the effects of the present invention are more excellent. .

In general formula (I) above, R ¹ represents an alkyl group having 7 to 20 carbon atoms. Et represents an ethyl group.
Specific examples of the alkyl group having 7 to 20 carbon atoms include heptyl group, octyl group, nonyl group, decyl group, undecyl group and dodecyl group. Among them, an octyl group and a nonyl group are preferable because the effects of the present invention are more excellent.

In the composition of the present invention, the content of the specific alkyltriethoxysilane is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is 2.0 to 10.0% by mass relative to the silica content described above. is preferably

[Method for preparing rubber composition for tire tread]
The method for producing the composition of the present invention is not particularly limited, and specific examples include, for example, kneading the components described above using known methods and devices (e.g., Banbury mixer, kneader, rolls, etc.). methods and the like. When the composition of the present invention contains sulfur or a vulcanization accelerator, the components other than sulfur and the vulcanization accelerator are first mixed at a high temperature (preferably 100 to 160 ° C.), cooled, and then sulfur or It is preferred to mix a vulcanization accelerator.
Also, the composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[II] Pneumatic Tire The pneumatic tire of the present invention is a pneumatic tire manufactured (produced) using the composition of the present invention described above. Among them, a pneumatic tire in which the composition of the present invention is used (arranged) in the tire tread (cap tread) is preferable.
FIG. 1 shows a schematic partial cross-sectional view of a pneumatic tire showing an example of an embodiment of the pneumatic tire of the present invention, but the pneumatic tire of the present invention is not limited to the embodiment shown in FIG.

In FIG. 1, reference numeral 1 denotes a bead portion, reference numeral 2 denotes a sidewall portion, and reference numeral 3 denotes a tire tread portion.
A carcass layer 4 in which fiber cords are embedded is mounted between the pair of left and right bead portions 1, and the end portion of the carcass layer 4 extends from the inside to the outside of the tire around the bead core 5 and the bead filler 6. folded and rolled up.
Further, in the tire tread portion 3 , a belt layer 7 is arranged outside the carcass layer 4 over one circumference of the tire.
A rim cushion 8 is arranged at a portion of the bead portion 1 that contacts the rim.
The tire tread portion 3 is made of the composition of the present invention described above.

The pneumatic tire of the present invention can be manufactured, for example, according to a conventionally known method. In addition to normal air or air with adjusted oxygen partial pressure, inert gas such as nitrogen, argon, and helium can be used as the gas to be filled in the pneumatic tire.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these.

[Production of specific conjugated diene rubber and comparative conjugated diene rubber]
Specific conjugated diene rubbers 1 to 5 and comparative conjugated diene rubber 1 were produced as follows.
Here, the specific conjugated diene rubbers 1 to 5 are conjugated diene rubbers produced by a method for producing a conjugated diene rubber comprising the first to third steps described above, and correspond to the specific conjugated diene rubbers described above. Further, in the specific conjugated diene rubbers 1 and 2, the first step includes the above-described steps A and B, and the specific conjugated diene rubbers have PI blocks.
On the other hand, the comparative conjugated diene rubber 1 is a conjugated diene rubber produced by a method for producing a conjugated diene rubber comprising the above-described first and second steps (not including the above-described third step). Not applicable to diene rubber.

<Specific conjugated diene rubber 1>
74.3 g of cyclohexane and 0.48 mmol of tetramethylethylenediamine were added to a nitrogen-purged 800 ml ampoule bottle, and 4.76 mmol of n-butyllithium (tetramethylethylenediamine as a polar compound per 1 mol of n-butyllithium of 0.10 mol) was added. Then, 17.3 g of isoprene and 1.3 g of styrene were slowly added and reacted in an ampoule bottle at 50° C. for 120 minutes to obtain a polymer block (A) having active terminals. This polymer block (A) has a weight average molecular weight (Mw) of 6,500, a molecular weight distribution (Mw/Mn) of 1.12, a styrene monomer unit content of 7.0% by mass, and an isoprene monomer unit The content was 93.0% by weight and the vinyl bond content was 7.5% by weight.

An autoclave equipped with a stirrer was charged with 4000 g of cyclohexane, 3.57 mmol of tetramethylethylenediamine, 252 g of 1,3-butadiene, and 348 g of styrene under a nitrogen atmosphere, and then the polymer block (A) having an active terminal obtained above was added. was added to initiate polymerization at 50° C. (the amount of tetramethylethylenediamine as a polar compound present in the reaction system was 0.85 mol with respect to 1 mol of n-butyllithium used). After 15 minutes from the initiation of polymerization, 338 g of 1,3-butadiene and 62 g of styrene were continuously added over 60 minutes. The maximum temperature during the polymerization reaction was 70°C. After the completion of the continuous addition, the polymerization reaction was continued for an additional 15 minutes, and after confirming that the polymerization conversion rate was in the range of 95% to 100%, 40% of the polyorganosiloxane represented by the following formula (11) was added. In the state of a xylene solution with a mass% concentration, 1.51 g (converted to the number of repeating units of the siloxane structure (-Si-O-) in the polyorganosiloxane, 1.1 times the moles of n-butyllithium used ) was added and allowed to react for 30 minutes. Then, 4.76 mmol of 3-(2-aminoethylamino)propyltrimethoxysilane (an amount corresponding to 1.0 moles of n-butyllithium used) was added and allowed to react for 10 minutes. Then, as a polymerization terminator, methanol was added in an amount corresponding to twice the moles of the n-butyllithium used to obtain a solution containing a conjugated diene rubber. To this solution, 0.15 part of Irganox 1520L (manufactured by BASF) was added as an antiaging agent to 100 parts of the conjugated diene rubber, and then the solvent was removed by steam stripping, followed by heating at 60° C. for 24 hours. After vacuum drying, a solid conjugated diene rubber was obtained. The obtained conjugated diene-based rubber is referred to as specific conjugated diene-based rubber 1. Specific conjugated diene rubber 1 has a weight average molecular weight (Mw) of 570,000, a coupling ratio of 45.0%, a styrene monomer unit content of 41.1% by mass, and a vinyl bond content of 33.5% by mass. %Met. The specific conjugated diene rubber 1 had a glass transition temperature of −26° C. and a molecular weight distribution (Mw/Mn) of 1.5.

In formula (11) above, X ¹ , X ⁴ , R ¹ to R ³ and R ⁵ to R ⁸ are methyl groups. In the above formula (11), m is 80 and k is 120. In formula (11) above, X2 is a group represented by formula ( ¹² ) below (where * represents a bonding position).

<Specific conjugated diene rubber 2>
70.0 g of cyclohexane and 0.77 mmol of tetramethylethylenediamine and 7.69 mmol of n-butyllithium were added to a nitrogen-purged 800 ml ampoule bottle. Then, 27.9 g of isoprene and 2.1 g of styrene were slowly added and reacted in an ampoule bottle at 50° C. for 120 minutes to obtain a polymer block (A) having active terminals. The polymer block (A) has a weight average molecular weight (Mw) of 6,500, a molecular weight distribution (Mw/Mn) of 1.10, a styrene monomer unit content of 7.0% by mass, and an isoprene monomer unit. The content was 93.0% by mass, and the vinyl bond content was 7.7% by mass.

Next, an autoclave equipped with a stirrer was charged with 4000 g of cyclohexane, 2.69 mmol of tetramethylethylenediamine, 474 g of 1,3-butadiene, and 126 g of styrene under a nitrogen atmosphere, and then the polymer block having an active terminal obtained above was The total amount of (A) was added, and polymerization was initiated at 50°C. Ten minutes after the initiation of polymerization, 376 g of 1,3-butadiene and 24 g of styrene were continuously added over 60 minutes. The maximum temperature during the polymerization reaction was 75°C. After the completion of the continuous addition, the polymerization reaction was continued for an additional 10 minutes, and after confirming that the polymerization conversion rate was in the range of 95% to 100%, 40% of the polyorganosiloxane represented by the above formula (11) was added. In the state of a xylene solution with a mass% concentration, 2.44 g (converted to the number of repeating units of the siloxane structure (-Si-O-) in the polyorganosiloxane, 1.1 times the mole of n-butyllithium used ) was added and allowed to react for 30 minutes. Then, 7.69 mmol of 3-(2-aminoethylamino)propyltrimethoxysilane (an amount corresponding to 1.0 moles of n-butyllithium used) was added and stirred for 10 minutes. Then, as a polymerization terminator, methanol was added in an amount corresponding to twice the moles of the n-butyllithium used to obtain a solution containing a conjugated diene rubber. To this solution, 0.15 part of Irganox 1520L (manufactured by Ciba Specialty Chemicals Co., Ltd.) was added as an antiaging agent to 100 parts of conjugated diene rubber, and then the solvent was removed by steam stripping and heated at 60°C. After vacuum drying for 24 hours, a solid conjugated diene rubber was obtained. The obtained conjugated diene-based rubber is referred to as specific conjugated diene-based rubber 2 . The specific conjugated diene rubber 2 has a weight average molecular weight (Mw) of 460,000, a coupling ratio of 58.0%, a styrene monomer unit content of 15.0% by mass, and a vinyl bond content of 30.5% by mass. %Met. The specific conjugated diene rubber 2 had a glass transition temperature of −63° C. and a molecular weight distribution (Mw/Mn) of 1.6.

<Specific conjugated diene rubber 3>
An autoclave equipped with a stirrer was charged with 800 g of cyclohexane and 120 g of 1,3-butadiene under a nitrogen atmosphere, and then 1.00 mmol of n-butyllithium was added to initiate polymerization at 80°C. After continuing the polymerization reaction for 90 minutes and confirming that the polymerization conversion rate was in the range of 95% to 100%, 0.32 g of the polyorganosiloxane represented by the above formula (11) ( An amount equivalent to 1.1 moles of the n-butyllithium used in terms of the number of repeating units of the siloxane structure (--Si--O--) was added and reacted for 30 minutes. Then, 1.00 mmol of 3-(2-aminoethylamino)propyltrimethoxysilane (an amount corresponding to 1.0 times mole of n-butyl lithium used) was added and reacted for 10 minutes. Then, as a polymerization terminator, methanol was added in an amount corresponding to twice the moles of the n-butyllithium used to obtain a solution containing a conjugated diene rubber. To this solution, 0.15 part of Irganox 1520L (manufactured by BASF) was added as an antiaging agent to 100 parts of the conjugated diene rubber, and then the solvent was removed by steam stripping, followed by heating at 60° C. for 24 hours. After vacuum drying, a solid conjugated diene rubber was obtained. The resulting conjugated diene-based rubber is referred to as specific conjugated diene-based rubber 3 . The specific conjugated diene rubber 3 had a weight average molecular weight (Mw) of 485,000, a coupling rate of 55.5%, and a vinyl bond content of 9.8% by mass. The specific conjugated diene rubber 3 had a glass transition temperature of −93° C. and a molecular weight distribution (Mw/Mn) of 1.6.

<Specific conjugated diene rubber 4>
An autoclave equipped with a stirrer was charged with 4000 g of cyclohexane, 3.57 mmol of tetramethylethylenediamine, 252 g of 1,3-butadiene, and 348 g of styrene under a nitrogen atmosphere, and then n-butyllithium was added to initiate polymerization at 50°C (using The amount of tetramethylethylenediamine as a polar compound present in the reaction system is 0.85 mol, per 1 mol of n-butyllithium. After 15 minutes from the initiation of polymerization, 338 g of 1,3-butadiene and 62 g of styrene were continuously added over 60 minutes. The maximum temperature during the polymerization reaction was 70°C. After the completion of the continuous addition, the polymerization reaction was continued for an additional 15 minutes, and after confirming that the polymerization conversion rate was in the range of 95% to 100%, 40% of the polyorganosiloxane represented by the above formula (11) was added. In the state of a xylene solution with a mass% concentration, 1.51 g (converted to the number of repeating units of the siloxane structure (-Si-O-) in the polyorganosiloxane, 1.1 times the moles of n-butyllithium used ) was added and allowed to react for 30 minutes. Then, 4.76 mmol of 3-(2-aminoethylamino)propyltrimethoxysilane (an amount corresponding to 1.0 moles of n-butyllithium used) was added and allowed to react for 10 minutes. Thereafter, methanol was added as a polymerization terminator in an amount corresponding to twice the moles of the n-butyllithium used to obtain a solution containing a conjugated diene rubber. To this solution, 0.15 part of Irganox 1520L (manufactured by BASF) was added as an antiaging agent to 100 parts of the conjugated diene rubber, and then the solvent was removed by steam stripping, followed by heating at 60°C for 24 hours. After vacuum drying, a solid conjugated diene rubber was obtained. The obtained conjugated diene-based rubber is referred to as specific conjugated diene-based rubber 4 . The specific conjugated diene rubber 4 has a weight average molecular weight (Mw) of 570,000, a coupling ratio of 45.0%, an aromatic vinyl monomer (styrene monomer) unit content of 41.1% by mass, and a vinyl The bond content was 33.5 mass %, the glass transition temperature (Tg) was -26°C, and the molecular weight distribution (Mw/Mn) was 1.5.

<Specific conjugated diene rubber 5>
An autoclave equipped with a stirrer was charged with 4000 g of cyclohexane, 2.69 mmol of tetramethylethylenediamine, 474 g of 1,3-butadiene, and 126 g of styrene under a nitrogen atmosphere, and then n-butyllithium was added to initiate polymerization at 50°C. Ten minutes after the initiation of polymerization, 376 g of 1,3-butadiene and 24 g of styrene were continuously added over 60 minutes. The maximum temperature during the polymerization reaction was 75°C. After the completion of the continuous addition, the polymerization reaction was continued for an additional 10 minutes, and after confirming that the polymerization conversion rate was in the range of 95% to 100%, 40% of the polyorganosiloxane represented by the above formula (11) was added. In the state of a xylene solution with a mass% concentration, 2.44 g (converted to the number of repeating units of the siloxane structure (-Si-O-) in the polyorganosiloxane, 1.1 times the mole of n-butyllithium used ) was added and allowed to react for 30 minutes. Then, 7.69 mmol of 3-(2-aminoethylamino)propyltrimethoxysilane (an amount corresponding to 1.0 moles of n-butyllithium used) was added and stirred for 10 minutes. Then, as a polymerization terminator, methanol was added in an amount corresponding to twice the moles of the n-butyllithium used to obtain a solution containing a conjugated diene rubber. To this solution, 0.15 part of Irganox 1520L (manufactured by Ciba Specialty Chemicals Co., Ltd.) was added as an antiaging agent to 100 parts of conjugated diene rubber, and then the solvent was removed by steam stripping and heated at 60°C. After vacuum drying for 24 hours, a solid conjugated diene rubber was obtained. The obtained conjugated diene-based rubber is referred to as specific conjugated diene-based rubber 5 . The specific conjugated diene rubber 5 has a weight average molecular weight (Mw) of 460,000, a coupling rate of 58.0%, a styrene monomer unit content of 15.0% by mass, and a vinyl bond content of 30.5% by mass. %, the glass transition temperature (Tg) was −63° C., and the molecular weight distribution (Mw/Mn) was 1.6.

<Comparative conjugated diene rubber 1>
Cyclohexane (35 g) and tetramethylethylenediamine (1.4 mmol) were added to a nitrogen-purged 100 mL ampoule bottle, and further n-butyl lithium (4.3 mmol) was added. Then, isoprene (21.6 g) and styrene (3.1 g) were slowly added and reacted in an ampoule bottle at 50° C. for 120 minutes to obtain polymer block A having active terminals. When the weight average molecular weight, molecular weight distribution, aromatic vinyl monomer unit content, isoprene monomer unit content, and 1,4-bond content of this polymer block A were measured, the weight average molecular weight was 8. , 700, the molecular weight distribution was 1.10, the aromatic vinyl unit content was 12.6% by mass, the isoprene unit content was 87.4% by mass, and the 1,4-bond content was 58.0% by mass. .
Next, an autoclave equipped with a stirrer was charged with cyclohexane (4000 g), 1,3-butadiene (474.0 g), and styrene (126.0 g) under a nitrogen atmosphere, and then having the active end obtained above The total amount of polymer block A was added, and polymerization was initiated at 50°C. After confirming that the polymerization conversion rate was in the range of 95% to 100%, the polyorganosiloxane represented by the above formula (11) was added to an epoxy group content of 1.42 mmol (n - equivalent to 0.33 moles of butyllithium) was added in the form of a xylene solution having a concentration of 20% by mass, and reacted for 30 minutes. Then, as a polymerization terminator, methanol was added in an amount corresponding to twice the moles of the n-butyllithium used to obtain a solution containing a conjugated diene rubber. To this solution, a small amount of an anti-aging agent (Irganox 1520, manufactured by BASF) was added, and 25% Fuccol Ceramic 30 (manufactured by Nippon Oil Co., Ltd.) was added as an extender oil to 100 parts by mass of the specific conjugated diene rubber. After adding parts by mass, a solid rubber was recovered by a steam stripping method. The resulting solid rubber was dehydrated with rolls and dried in a dryer to obtain a solid conjugated diene rubber. The resulting conjugated diene rubber is referred to as comparative conjugated diene rubber 1.
The weight average molecular weight, molecular weight distribution, coupling rate of three or more branches, aromatic vinyl unit content, vinyl bond content, and Mooney viscosity of Comparative Conjugated Diene Rubber 1 were measured, and the weight average molecular weight was 640,000. , the molecular weight distribution is 1.65, the coupling rate is 12.5% by mass, the aromatic vinyl monomer unit content is 42.6% by mass, the vinyl bond content is 29.5% by mass, the Mooney viscosity (ML ₁₊₄ , 100° C.) was 58. The comparative conjugated diene rubber 1 had a glass transition temperature of −27° C. and a molecular weight distribution (Mw/Mn) of 1.7.

[Production of heterocyclic compound]
As heterocyclic compounds, piperazine compound 7-1, piperazine compound 1, and morpholine compounds 3 and 1, which will be described later, were prepared as follows.
The above piperazine compounds 7-1 and 1 and the above morpholine compounds 3 and 1 correspond to predetermined heterocyclic compounds contained in the composition of the present invention.

<Synthesis of piperazine compound 7-1>
C12-13 mixed alcohol glycidyl ether (Epogose (registered trademark) EN manufactured by Yokkaichi Gosei Co., Ltd. A mixture of C12 alcohol glycidyl ether and C13 alcohol glycidyl ether.) 28.4 g, 1-(2-hydroxyethyl) piperazine ( 13.0 g of hydroxyethyl piperazine manufactured by Nippon Nyukazai Co., Ltd. was reacted at 60° C. for 4 hours to obtain piperazine compound 7-1 represented by the following formula. In the formula below, R represents -C ₁₂ H ₂₅ or -C ₁₃ H ₂₇ .
Piperazine Compound 7-1, prepared as described above, is a mixture of Piperazine Compounds in which R is —C ₁₂ H ₂₅ and Piperazine Compounds in which R is —C ₁₃ H ₂₇ .
The piperazine compound 7-1 produced as described above has one —C ₁₂ H ₂₅ or —C ₁₃ H ₂₇ per molecule as a hydrocarbon group serving as a hydrophobic portion, and a piperazine ring as a heterocyclic ring.
(Piperazine compound 7-1)

<Synthesis of piperazine compound 1>
33.3 g of 1-bromooctadecane (manufactured by Tokyo Kasei Kogyo Co., Ltd.) and 13.0 g of 1-(2-hydroxyethyl)piperazine (manufactured by Nippon Nyukazai Co., Ltd.) were dissolved in tetrahydrofuran and dichloromethane at room temperature. was reacted for 1 hour under the conditions of The reaction solution was washed with an aqueous potassium carbonate solution, extracted with dichloromethane, and dried over anhydrous magnesium sulfate. By filtering off anhydrous magnesium sulfate and concentrating, a piperazine compound 1 represented by the following formula was obtained.
Piperazine Compound 1 has one —C ₁₈ H ₃₇ per molecule as a hydrocarbon group serving as a hydrophobic portion, and a piperazine ring as a heterocyclic ring.
(Piperazine compound 1)

<Synthesis of morpholine compound 3>
18.5 g of 2-ethylhexyl glycidyl ether (Epogose registered trademark 2EH manufactured by Yokkaichi Gosei Co., Ltd.) and 8.7 g of morpholine (manufactured by Tokyo Chemical Industry Co., Ltd.) are reacted at 60° C. for 4 hours. to obtain morpholine compound 3 (structure below).
(morpholine compound 3)

<Synthesis of Morpholine Compound 1>
33.3 g of 1-bromooctadecane (manufactured by Tokyo Chemical Industry Co., Ltd.) and 8.7 g of morpholine (manufactured by Tokyo Chemical Industry Co., Ltd.) were reacted in tetrahydrofuran and dichloromethane at room temperature for 1 hour.
The reaction solution was washed with an aqueous potassium carbonate solution, extracted with dichloromethane, and dried over anhydrous magnesium sulfate. Anhydrous magnesium sulfate was filtered off and concentrated to obtain morpholine compound 1 (structure below).
(morpholine compound 1)

[Preparation of rubber composition for tire tread]
The components shown in Table 1 below were blended in proportions (parts by mass) shown in the same table.
Specifically, first, among the components shown in Table 1 below, components other than sulfur and a vulcanization accelerator were heated to around 140° C. using a 1.7-liter internal Banbury mixer, and then mixed for 5 minutes. After mixing, it was discharged and cooled to room temperature to obtain a masterbatch. Further, the obtained masterbatch was mixed with sulfur and a vulcanization accelerator using the Banbury mixer to obtain a rubber composition for a tire tread.
When the rubber component is an oil-extended product, parts by mass represent the net amount of rubber (amount excluding oil).

〔evaluation〕
The obtained rubber composition for tire tread was evaluated as follows.

<Production of vulcanized rubber sheet>
The obtained tire tread rubber composition (unvulcanized) was press-vulcanized in a mold (15 cm×15 cm×0.2 cm) at 160° C. for 40 minutes to prepare a vulcanized rubber sheet.

<Wet Performance>
The resulting vulcanized rubber sheet was measured using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) in accordance with JIS K6394: 2007 under the conditions of an extensional deformation strain rate of 10% ± 2%, a frequency of 20 Hz, and a temperature of 0 ° C. Tan δ (0°C) was measured.
Table 1 shows the results. The results were expressed as indices with Comparative Example 1 being 100. The larger the index, the better the wet performance (wet grip performance). Practically, it is preferably 10 3 or more.

<Rolling performance>
The resulting vulcanized rubber sheet was measured using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) in accordance with JIS K6394: 2007 under the conditions of an extensional deformation strain rate of 10% ± 2%, a frequency of 20 Hz, and a temperature of 60 ° C. Tan δ (60°C) was measured.
Table 1 shows the results. The results were expressed as indices with Comparative Example 1 being 100. The smaller the index, the better the rolling performance (low rolling resistance). Practically, it is preferably 97 or less.

<Viscosity>
The obtained tire tread rubber composition was measured according to JIS K6300-1:2013, using an L-shaped rotor, under the conditions of a preheating time of 1 minute, a rotor rotation time of 4 minutes, and a test temperature of 100 ° C. The Mooney viscosity was measured. It was measured.
Table 1 shows the results. The results were expressed as indices with Comparative Example 1 being 100. The smaller the index, the smaller the viscosity and the better the workability. Practically, it is preferably 97 or less.

Details of each component in Table 1 are as follows.
・Specific conjugated diene rubbers 1 to 5: Specific conjugated diene rubbers 1 to 5 produced as described above
- Comparative conjugated diene rubber 1: Comparative conjugated diene rubber 1 produced as described above
・ Comparative conjugated diene rubber 2: Butadiene rubber (unmodified) (Nipol BR1220 manufactured by Nippon Zeon Co., Ltd., glass transition temperature: -106 ° C.)

・Silica: 7000GR: ULTRASIL 7000GR (silica, CTAB adsorption specific surface area: 160 m ² /g, manufactured by Evonik)
・ Carbon black: Show Black N339 (carbon black, manufactured by Cabot Japan)
- Silane coupling agent: Si69 (silane coupling agent, bis (3-triethoxysilylpropyl) tetrasulfide) (manufactured by Evonik Degussa)

・ Zinc oxide: 3 types of zinc oxide (manufactured by Seido Chemical Industry Co., Ltd.)
・Stearic acid: bead stearic acid (manufactured by NOF Corporation)
・ Anti-aging agent: Ozonon 6C (manufactured by Seiko Chemical Co., Ltd.)
・Process oil: Extract No. 4 S (manufactured by Showa Shell Sekiyu K.K.)

Piperazine Compound 7-1: Piperazine Compound 7-1 prepared as described above
Piperazine Compound 1: Piperazine Compound 1 prepared as described above
Morpholine Compound 3: Morpholine Compound 3 prepared as described above
Morpholine Compound 1: Morpholine Compound 1 prepared as described above

Comparative heterocyclic compound: N-(2-hydroxyethyl)piperazine (hydroxyethylpiperazine manufactured by Nihon Nyukazai Co., Ltd.) (structure below). The above comparative heterocyclic compound does not have a hydrocarbon group serving as a hydrophobic portion.

・ Sulfur: Fine sulfur powder containing Kinkain oil (sulfur content 95.24% by mass, manufactured by Tsurumi Chemical Industry Co., Ltd.)
・Vulcanization accelerator (CZ): Noccellar CZ-G manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
- Vulcanization accelerator (DPG): 1,3-diphenylguanidine (Sokucinol DG, manufactured by Sumitomo Chemical Co., Ltd.)

As can be seen from Table 1, Examples 1-10 containing the specific conjugated diene rubber exhibited excellent wet performance, rolling performance and workability.
From the comparison between Example 1 and Example 6, when the specific conjugated diene rubber had PI blocks, it showed better wet performance, rolling performance and workability. Similar results were obtained by comparing Example 5 and Example 7 as well.
From the comparison between Example 1 and Example 2, the higher the content of the heterocyclic compound, the better the wet performance, rolling performance and workability. Results similar to those described above were obtained by comparing Examples 3 and 4 as well.
From the comparison between Examples 1 and 8 and Examples 9 and 10, when the heterocyclic compound was a piperazine compound, better wet performance, rolling performance and workability were exhibited.
From the comparison between Examples 1, 8 and 10 and Example 9, Examples 1, 8 and 10 showed better wet performance, rolling performance and workability.

On the other hand, Comparative Example 1 containing no specific conjugated diene rubber had insufficient wet performance, rolling performance and workability.
Comparative Example 2, which does not contain the specific conjugated diene rubber and has a heterocyclic compound content less than the predetermined range, was further inferior to Comparative Example 1 in wet performance, rolling performance and workability.
Comparative Examples 3 and 4, in which the content of the heterocyclic compound was less than the predetermined range, were insufficient in wet performance, rolling performance and workability.
Comparative Example 5, which does not contain a predetermined heterocyclic compound and instead contains a comparative heterocyclic compound having no hydrocarbon group serving as a hydrophobic portion, had insufficient wet performance, rolling performance and workability. .

REFERENCE SIGNS LIST 1 bead portion 2 sidewall portion 3 tire tread portion 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 rim cushion

Claims (11)

a conjugated diene rubber containing 30% by mass or more of a specific conjugated diene rubber;
silica;
a silane coupling agent;
containing at least one hydrocarbon group serving as a hydrophobic portion and a heterocyclic compound having a heterocyclic ring,
The number of carbon atoms of the hydrocarbon group serving as the hydrophobic portion is 8 to 30,
the heterocycle is a piperazine ring, a morpholine ring or a thiomorpholine ring,
The silica content is 30 parts by mass or more with respect to 100 parts by mass of the conjugated diene rubber,
The content of the silane coupling agent is 3 to 30% by mass with respect to the content of the silica,
The content of the heterocyclic compound is 0.5 to 20% by mass with respect to the content of the silica,
a first step in which the specific conjugated diene-based rubber polymerizes a monomer containing a conjugated diene compound in an inert solvent using a polymerization initiator to obtain a conjugated diene-based polymer chain having an active terminal; To the conjugated diene polymer chain having an active terminal, a polyorganosiloxane represented by the following general formula (1) is added to 1 mol of the polymerization initiator used in the first step. A second step of adding and reacting at a ratio of 1 mol or more in terms of the number of repeating units of the siloxane structure (-Si-O-), and a conjugated diene-based polymer obtained by reacting the polyorganosiloxane obtained in the second step. A rubber composition for a tire tread, which is a conjugated diene rubber produced by a method for producing a conjugated diene rubber, comprising a third step of reacting the combined chain with a compound represented by the following general formula (2).

In general formula (1), R¹～R⁸is an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, which may be the same or different.
In general formula (1), X¹and X⁴is an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and a group having 4 to 12 carbon atoms containing an epoxy group. These groups may be the same or different from each other.
In general formula (1), X²is an alkoxy group having 1 to 5 carbon atoms or a group having 4 to 12 carbon atoms containing an epoxy group, and a plurality of X²may be the same or different from each other.
In general formula (1), X³is a group containing 2 to 20 alkylene glycol repeating units, and X³When there are a plurality of , they may be the same or different.
In general formula (1), m is an integer of 3 to 200, n is an integer of 0 to 200, k is an integer of 0 to 200, and m+n+k is 3 or more.

In general formula (2), R⁹is a hydrocarbyl group.
In general formula (2), A¹is a group capable of reacting with a reactive residue produced by the reaction of a conjugated diene polymer chain having an active terminal with polyorganosiloxane.
In general formula (2), A²is a group containing a nitrogen atom.
In general formula (2), p is an integer of 0 to 2, q is an integer of 1 to 3, r is an integer of 1 to 3, and p+q+r=4. 2. The rubber composition for a tire tread according to claim 1, wherein said heterocyclic compound has one heterocycle per molecule. 3. The rubber composition for a tire tread according to claim 1 , wherein said hydrocarbon group that serves as said hydrophobic portion is a monovalent hydrocarbon group. The rubber composition for a tire tread according to any one of claims 1 to 3 , wherein the heterocyclic ring is bonded directly or via an organic group to the hydrocarbon group serving as the hydrophobic portion. The rubber composition for a tire tread according to any one of claims 1 to 4 , wherein the hydrocarbon group that serves as the hydrophobic portion consists only of carbon atoms and hydrogen atoms. The rubber composition for a tire tread according to any one of claims 1 to 5 , wherein the heterocyclic compound is a compound represented by the following formula (I).

_In formula (I), X represents a nitrogen atom, an oxygen atom or a sulfur atom,
X ₃ , X ₄ , X ₅ and X ₆ each independently represent a hydrogen atom or a hydrocarbon group.
When X ₇ is a nitrogen atom, n3 is 1 and one or both of X ₁ and X ₂ are each independently represented by formula (I-1): -(A ₁ ) _n1-1 -R ₁ represents _-1 ,
When only one of X ₁ and X ₂ represents formula (I-1), the remaining groups are a hydrogen atom, a sulfone-based protecting group, a carbamate-based protecting group and formula (I-3):-(R ₂ -O) represents at least one selected from the group consisting of _n2 -H,
In formula (I-3), each R ₂ independently represents a divalent hydrocarbon group,
n2 represents 1-10.
When X ₇ is an oxygen atom or a sulfur atom, n3 represents 0 and X ₁ represents formula (I-1): -(A ₁ ) _n1-1 -R _1-1 .
In formula (I-1), A ₁ represents either a carbonyl group or formula (I-2): -R _1-2 (OH)-O-,
n1-1 represents 0 or 1,
R _1-1 represents the hydrocarbon group that becomes the hydrophobic portion,
In formula (I-2), R _1-2 represents a trivalent hydrocarbon group. the heterocyclic compound is a compound represented by the formula (I), X ₇ is a nitrogen atom, n3 is 1,
7. The tire tread rubber composition according to claim 6 , wherein both X ₁ and X ₂ independently represent the formula (I-1). the heterocyclic compound is a compound represented by the formula (I), X ₇ is a nitrogen atom, n3 is 1,
only one of X ₁ and X ₂ represents the formula (I-1);
Claim 6 , wherein the remaining groups represent at least one selected from the group consisting of a hydrogen atom, a sulfone-based protecting group, a carbamate-based protecting group and the formula (I-3): --(R ₂ --O) _n2 --H. The rubber composition for a tire tread according to 1. In formula (I-3), each R ₂ independently represents a divalent hydrocarbon group, and n2 represents 1-10. the heterocyclic compound is a compound represented by the formula (I), X ₇ is an oxygen atom or a sulfur atom, n3 is 0,
7. The rubber composition for a tire tread according to claim 6 , wherein X ₁ represents the formula (I-1). The specific conjugated diene rubber is
a polymer block (A) containing 80 to 100% by mass of isoprene monomer units and 0 to 20% by mass of aromatic vinyl monomer units;
1,3-butadiene monomer units of 50 to 100 mass% and a polymer block (B) containing 0 to 50 mass% of aromatic vinyl monomer units having a structure formed continuously 10. The tire tread rubber composition according to any one of 1 to 9 . A pneumatic tire comprising a tire tread portion manufactured using the tire tread rubber composition according to any one of claims 1 to 10 .

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