JP6791204B2 - Rubber composition for tire tread and pneumatic tire - Google Patents

Description

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

In recent years, improvement of tire rolling performance (low rolling resistance) has been required from the viewpoint of low fuel consumption when the vehicle is running. On the other hand, there is known a method of blending silica with a rubber component constituting a tread portion of a tire to improve rolling performance.
However, since silica has a low affinity with the rubber component and has high cohesiveness between the silicas, even if silica is simply mixed with the rubber component, the silica is not dispersed and the effect of improving the rolling performance is sufficiently obtained. There was a problem that it could not be done.

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

JP-A-2016-47887

In recent years, due to environmental problems and resource problems, further improvement of tire rolling performance is required. Further, from the viewpoint of safety and durability, further improvement of tire wear resistance and breaking elongation is also desired.

Under these circumstances, the present inventors prepared a rubber composition for a tire tread with reference to the examples of Patent Document 1, and applied the rolling performance when made into a tire, the wear resistance when made into a tire, and the tire. When the elongation at break was evaluated, it became clear that further improvement was desirable in consideration of the demands that would be further increased in the future.

Therefore, the present invention is a rubber composition for a tire tread, which is excellent in rolling performance when made into a tire and wear resistance when made into a tire, and has a large breaking elongation when made into a tire, and the above-mentioned rubber composition for tire tread. It is an object of the present invention to provide a pneumatic tire using the tire tread.

As a result of diligent 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 reached the present invention.
That is, the present inventors have found that the above problems can be solved by the following configuration.

[1]
Conjugated diene rubber containing 30% by mass or more of specific conjugated diene rubber and 15% by mass or more of natural rubber,
With silica
Contains a silane coupling agent,
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.
In the first step, 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 general formula (1) described later is added to the conjugated diene polymer chain having the active terminal in the polyorganosiloxane with respect to 1 mol of the polymerization initiator used in the first step. The second step of adding and reacting the siloxane structure (-Si-O-) in a ratio of 1 mol or more in terms of the number of repeating units, and the conjugated diene system obtained by reacting the polyorganosiloxane obtained in the second step. A conjugated diene-based rubber produced by a method for producing a conjugated diene-based rubber, which comprises a third step of reacting a polymer chain with a compound represented by the general formula (2) described later, and is a rubber composition for tire tread. ..
[2]
The specific conjugated diene rubber mentioned above
A polymer block (A) containing 80 to 100% by mass of an isoprene monomer unit and 0 to 20% by mass of an aromatic vinyl monomer unit, and
It has a structure in which a polymer block (B) containing 1,3-butadiene monomer unit 50 to 100% by mass and an aromatic vinyl monomer unit 0 to 50% by mass is continuously formed [1]. ] In the rubber composition for tire tread.
[3]
The rubber composition for tire tread according to [1] or [2], wherein the vinyl bond content in the conjugated diene monomer unit in the specific conjugated diene rubber is 30% by mass or more.
[4]
The rubber composition for tire tread according to any one of [1] to [3], wherein the vinyl bond content in the conjugated diene monomer unit in the specific conjugated diene rubber is 50% by mass or more.
[5]
A pneumatic tire including a tire tread portion manufactured by using the rubber composition for tire tread according to any one of [1] to [4].

As shown below, according to the present invention, the rolling performance when made into a tire (hereinafter, also simply referred to as "rolling performance") and the wear resistance when made into a tire (hereinafter, simply "wear resistance"). Provided are a rubber composition for a tire tread having excellent (also referred to as) excellent elongation at break (hereinafter, also simply referred to as “elongation at break”) when made into a tire, and a pneumatic tire using the above rubber composition for tire tread. Can be done.

It is a partial cross-sectional schematic diagram of an example of embodiment of the pneumatic tire of this invention.

Hereinafter, the rubber composition for a tire tread of the present invention and a pneumatic tire using the rubber composition for a tire tread will be described.
The numerical range represented by using "~" in the present specification means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.
In addition, each component contained in the rubber composition for tire tread of the present invention may be used alone or in combination of two or more. Here, when two or more kinds of each component are used in combination, the content of the component means the total content unless otherwise specified.
Further, in the present specification, "(meth) acrylic" is a notation representing "acrylic" or "methacryl", and "(meth) acrylonitrile" is a notation representing "acrylonitrile" or "methacrylonitrile". ..

[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”) contains 30% by mass or more of a specific conjugated diene rubber and 20% by mass of natural rubber. % Or more, a conjugated diene-based rubber containing, silica, and a silane coupling agent.
Further, the content of the silica is 30 parts by mass or more with respect to 100 parts by mass of the conjugated diene rubber, and the content of the silane coupling agent is 3 to 30 with respect to the content of the silica. It is mass%.
The specific conjugated diene-based rubber is the first step of polymerizing 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 polymer chain having the active terminal with respect to 1 mol of the polymerization initiator used in the first step. The second step of adding and reacting the siloxane structure (-Si-O-) in the medium at a ratio of 1 mol or more in terms of the number of repeating units, and the conjugated diene obtained by reacting the polyorganosiloxane obtained in the second step. It is a conjugated diene rubber produced by a method for producing a conjugated diene rubber, which comprises a third step of reacting a polymer chain with a compound represented by the following general formula (2).
Since the composition of the present invention has such a structure, it is considered that the above-mentioned effects can be obtained. The reason is not clear, but it is presumed to be as follows.

As described above, the composition of the present invention is expected to be excellent in rolling performance by containing silica, but there is a problem that silica is easily aggregated and the above effect is not actually exhibited satisfactorily.
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 is compatible with silica and prevents silica from agglomerating. Conceivable. In addition, since the specific conjugated diene rubber also has a structure derived from nitrogen atom-containing silane such as aminosilane, it is considered that this promotes silanization between the silane coupling agent and silica and further suppresses silica aggregation. .. As a result, it is considered that the effect of silica (improvement of rolling performance) is fully exhibited.
Further, it is considered that the function of silica as a reinforcing material for tires is more exhibited by improving the dispersibility of silica. As a result, it is considered that a tire having excellent wear resistance and excellent breaking elongation (that is, having a large breaking elongation) can be obtained.

Hereinafter, each component contained in the composition of the present invention will be described in detail.

[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 and 15% by mass or more of the natural rubber.
First, the specific conjugated diene-based rubber will be described, and then the natural rubber will be described.

[Specific conjugated diene rubber]
The specific conjugated diene-based rubber contained in the composition of the present invention is a conjugated diene-based rubber produced by a method for producing a conjugated diene-based rubber comprising the following steps 1 to 3.
(1) First step (1) First step (2) First step (2) First 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. 2 steps The polyorganosiloxane represented by the general formula (1) described later is added to the conjugated diene polymer chain having an active end with respect to 1 mol of the polymerization initiator used in the first step. 2nd step (3) 3rd step of adding at a ratio of 1 mol or more in terms of the number of repeating units of the siloxane structure (-Si-O-) in the 3rd step 3rd step The polyorganosiloxane obtained in the above 2nd step is reacted. The third step of reacting the conjugated diene polymer chain with the compound represented by the general formula (2) described later.

First, the reason for specifying the specific conjugated diene rubber by the manufacturing method as described above will be described.
As described above, in the third step, the compound represented by the general formula (2) described later is reacted with the conjugated diene-based polymer chain obtained by reacting the polyorganosiloxane obtained in the second step. Here, A ¹ in the compound represented by the general formula (2) has binds to react with the reactive residues formed by the reaction of a conjugated diene polymer chain polyorganosiloxane having active terminal. However, as will be described later, the reaction residue generated by the reaction between the conjugated diene polymer chain having an active terminal and polyorganosiloxane can have various structures, and therefore the reaction residue is represented by the general formula (2). The structure of a compound after it has reacted is extremely complex, and it is technically impossible to analyze the structure, or the cost and time required to identify the structure are significantly excessive. Needs. Therefore, it is a so-called "impossible / impractical situation" to describe a specific conjugated diene rubber as "a conjugated diene rubber produced by a method for producing a conjugated diene rubber comprising the first to third steps". Exists.

Hereinafter, each step will be described.

[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-based polymer chain having an active terminal.
First, each component and the like used in the first step will be described.

<Conjugated diene compound>
The conjugated diene compound used as a monomer in order to obtain a conjugated diene polymer chain having an active terminal in the first step is not particularly limited, but is limited to 1,3-butadiene, isoprene, and 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-octadien, Examples thereof include 3-butyl-1,3-octadien. Among these, 1,3-butadiene and isoprene are preferable because the effect of the present invention is more excellent. These conjugated diene compounds may be used alone or in combination of two or more.

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

The conjugated diene polymer chain having an active terminal obtained in the first step preferably contains 50 to 100% by mass of a conjugated diene monomer unit for the reason that the effect of the present invention is more excellent, and is 52 to 95% by mass. It is more preferable to contain%, and it is preferable to contain 0 to 50% by mass of the aromatic vinyl monomer unit, and more preferably 5 to 48% by mass.

<Other copolymerizable compounds>
Further, in the first step, a compound copolymerizable with the conjugated diene compound (other copolymerizable compound) other than the aromatic vinyl compound may be used together with the conjugated diene compound. Examples of the compound copolymerizable with such a conjugated diene compound include a chain olefin compound such as ethylene, propylene and 1-butene; a cyclic olefin compound such as cyclopentene and 2-norbornene; 1,5-hexadiene and 1,6- Non-conjugated diene compounds such as heptadiene, 1,7-octadien, dicyclopentadiene, 5-ethylidene-2-norbornene; (meth) methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate and the like ( Meta) acrylic acid esters; other (meth) acrylic acid derivatives such as (meth) acrylonitrile, (meth) acrylamide; and the like. For the reason that the effect of the present invention is more excellent, the compound copolymerizable with these conjugated diene compounds has 10 as a monomer unit in the conjugated diene polymer chain having an active terminal obtained in the first step. It is preferably mass% or less, and more preferably 5 mass% or less.

<Inactive solvent>
The inert solvent used for the polymerization is usually used in solution polymerization and is not particularly limited as long as it does not inhibit the polymerization reaction. Specific examples of the inert solvent include chain aliphatic hydrocarbons such as butane, pentane, hexane and heptane; alicyclic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene; And so on. One of these inert solvents may be used alone, or two or more thereof may be used in combination. The amount of the inert solvent used is not particularly limited, but the monomer concentration is, for example, 1 to 50% by mass, and for the reason that the effect of the present invention is more excellent, the amount is 10 to 40% by mass. More preferred.

<Polymerization initiator>
The polymerization initiator used for the 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 a polymerization initiator using an organic alkali metal compound, an organic alkaline earth metal compound, a lanthanum series metal compound, or the like as a main catalyst. Examples of the organic alkali metal compound include organic monolithium compounds such as n-butyl lithium, sec-butyl lithium, t-butyl lithium, hexyl lithium, phenyl lithium and still benzene lithium; dilithiomethane, 1,4-dilithiobtan, 1, Organic polyvalent lithium compounds such as 4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, 1,3,5-tris (lithiomethyl) benzene; organic sodium compounds such as sodium naphthalene; organic such as potassium naphthalene Potassium compounds; and the like. Examples of the organic alkaline earth metal compound include di-n-butylmagnesium, di-n-hexylmagnesium, diethoxycalcium, calcium distearate, dit-butoxystrontium, diethoxybarium, and diisopropoxy. Examples thereof include barium, diethyl mercaptobarium, dit-butoxybarium, diphenoxybarium, diethylaminobarium, barium distearate, and diketyl barium. Examples of the polymerization initiator using a lanthanum-series metal compound as a main catalyst include lanthanum-series metals such as lanthanum, cerium, placeodim, neodym, samarium, and gadrinium, and lanthanum-series metals composed of carboxylic acids and phosphorus-containing organic acids. Examples thereof include a polymerization initiator composed of a salt of the above as a main catalyst and a co-catalyst such as an alkylaluminum compound, an organoaluminum hydride compound, and 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 preferable, because the effect of the present invention is more excellent. It is preferably used.
The organic alkali metal compound is previously reacted with a secondary amine compound such as dibutylamine, dihexylamine, dibenzylamine, pyrrolidine, piperidine, hexamethyleneimine, and heptamethyleneimine to obtain an organic alkali metal amide compound. You may use it. 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. Among them, the following general formula (3) is used because the effect of the present invention is more excellent. The compound represented can be preferably used.

In the general formula (3), M ¹ represents an alkali metal atom, and R ¹¹ and R ¹² are independent alkyl groups, cycloalkyl groups, aryl groups, aralkyl groups, amino group protective groups, or hydrolysis. 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, and when the ring structure is formed, they are bonded to each other. In addition to the nitrogen atoms to be bonded, a ring structure may be formed with heteroatoms other than the nitrogen atoms to which they are bonded.

The alkyl group is not particularly limited, but an alkyl group having 1 to 20 carbon atoms is preferable, and an alkyl group having 1 to 10 carbon atoms is more preferable, for the reason that the effect of the present invention is more excellent. Examples of such alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group and n-. Examples thereof include a xyl group, an n-heptyl group, an n-octyl group and an n-decyl group.

The cycloalkyl group is not particularly limited, but a cycloalkyl group having 3 to 20 carbon atoms is preferable, and a cycloalkyl group having 3 to 12 carbon atoms is more preferable, for the reason that the effect of the present invention is more excellent. Examples of such a cycloalkyl group include a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclododecyl group and the like.

The aryl group is not particularly limited, but an aryl group having 6 to 12 carbon atoms is preferable, and an aryl group having 6 to 10 carbon atoms is more preferable, for the reason that the effect of the present invention is more excellent. Examples of such an aryl group include a phenyl group, a 1-naphthyl group, a 2-naphthyl group and the like.

The aralkyl group is not particularly limited, but an aralkyl group having 7 to 13 carbon atoms is preferable, and an aralkyl group having 7 to 9 carbon atoms is more preferable, for the reason that the effect of the present invention is more excellent. Examples of such an aralkyl group include a benzyl group and a phenethyl group.

The protecting group for the amino group is not particularly limited as long as it is a group that acts as a protecting group for the amino group, and examples thereof include an alkylsilyl group. Examples of such an alkylsilyl group include a trimethylsilyl group, a triethylsilyl group, a triphenylsilyl group, a methyldiphenylsilyl group, an ethylmethylphenylsilyl group, a tert-butyldimethylsilyl group and the like.
When R ¹¹ and / or R ¹² are amino-protecting groups, at one end of the polymer chain forming the obtained conjugated diene-based rubber by removing the protecting group of the amino group, A structure in which R ¹³ and / or R ¹⁴ in the 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 a group that produces a hydroxyl group by hydrolysis in the presence of an acid or the like. For example, an alkoxyalkyl group or an epoxy group. Examples include groups containing.
Examples of the alkoxyalkyl group include a methoxymethyl group, an ethoxymethyl group, an ethoxyethyl group, a propoxymethyl group, a butoxymethyl group, a butoxyethyl group, a propoxyethyl group and the like.
Examples of the group containing an epoxy group include a group represented by the following general formula (4).
−Z ¹ −Z ² −E ¹ (4)
In the general formula (4), Z ¹ is an alkylene group or an 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.

Further, 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 this case, R ¹¹ and R ¹² are formed by the nitrogen atom bonded thereto. Specific examples of the structure to be formed 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). , hexamethyleneimine ring ^{(R 11} and ^{R 12,} hexylene group) and the like.
When R ¹¹ and R ¹² are bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, the ring structure is preferably a 4- to 8-membered ring structure.

Further, in the 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. Among these, from the viewpoint of polymerization activity. , Lithium atom is preferred.

When a compound represented by the general formula (3) is used as the polymerization initiator in the first step, the amine structure forming the organic alkali metal amide compound remains in a state of being bonded to the polymerization initiation terminal of the polymer chain. Will be done. Therefore, when a compound represented by the general formula (3) is used as the polymerization initiator, a structure represented by the following general formula (5) is formed at one end of the polymer chain forming the obtained conjugated diene rubber. Is introduced.

In the general formula (5), R ¹³ and R ¹⁴ can independently generate a hydroxyl group by hydrogen atom, alkyl group, cycloalkyl group, aryl group, aralkyl group, amino group protective group, or hydrolysis. Representing a group, R ¹³ and R ¹⁴ may be bonded to each other to form a ring structure with the nitrogen atom to which they are bonded, and in the case of forming the ring structure, in addition to the nitrogen atom to which they are bonded. , They may form a ring structure together with a hetero atom other than the nitrogen atom to which they are bonded.

Examples of the alkyl group, cycloalkyl group, aryl group, aralkyl group, amino group protective group, or group that can be hydrolyzed to generate a hydroxyl group as R ¹³ and R ¹⁴ are R ¹¹ and R ¹² in the 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 the general formula (3) can be mentioned. Can be the same.
The hydrogen atoms that can become R ¹³ and R ¹⁴ are introduced when the protecting group of the amino group is removed.

When an organic alkali metal amide compound is used as the polymerization initiator, the obtained specific conjugated diene rubber has an amine structure at one end and a specific structure derived from the 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 the polymerization initiator to the polymerization system is not particularly limited, and the organic alkali metal compound is reacted with the secondary amine compound in advance to obtain the organic alkali metal amide compound. , This can be mixed with a monomer containing a conjugated diene compound to allow the polymerization reaction to proceed. Alternatively, the organic alkali metal compound and the secondary amine compound are separately added to the polymerization system and mixed with a monomer containing a conjugated diene compound to generate an organic alkali metal amide compound in the polymerization system. Therefore, a method of advancing the polymerization reaction may be adopted. The reaction conditions such as the reaction temperature are not particularly limited, and may be, for example, according to the target polymerization reaction conditions.

The amount of the secondary amine compound used may be determined according to the amount of the desired polymerization initiator added, but is usually 0.01 to 1.5 mmol, 0.1 to 1 per 1 mmol of the organic alkali metal compound. It is preferably .2 mmol, more preferably 0.5-1.0 mmol.

The amount of the polymerization initiator used may be determined according to the molecular weight of the desired conjugated diene-based polymer chain, but is usually preferably 1 to 50 mmol or 1.5 to 20 mmol per 1000 g of the monomer, and 2 ~ 15 mmol is more preferred.

<Polymerization temperature, etc.>
The polymerization temperature is usually −80 to + 150 ° C., preferably 0 to 100 ° C., more preferably 30 to 90 ° C. for the reason that the effect of the present invention is more excellent. Any mode such as batch type or continuous type can be adopted as the polymerization mode, but when the conjugated diene compound and the aromatic vinyl compound are copolymerized, the conjugated diene monomer unit and the aromatic vinyl monomer can be used. The batch formula is preferable because it is easy to control the randomness of the combination with the unit.

<Polar compound>
When 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 obtained conjugated diene polymer chain. Is preferable. Examples of the polar compound include ether compounds such as dibutyl ether, tetrahydrofuran and 2,2-di (tetrahydrofuryl) propane; tertiary amines such as tetramethylethylenediamine; alkali metal alkoxides; phosphine compounds; and the like. Among these, ether compounds and tertiary amines are preferable, tertiary amines are more preferable, and tetramethylethylenediamine is particularly preferable, because the effect of the present invention is more excellent. One of these polar compounds may be used alone, or two or more thereof may be used in combination. The amount of the polar compound used may be determined according to the target vinyl bond content, and is preferably 0.001 to 100 mol, more preferably 0.01 to 10 mol, with respect to 1 mol of the polymerization initiator. When the amount of the polar compound used is in 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 unlikely to occur.

<Vinyl bond content>
The vinyl bond content in the conjugated diene monomer unit in the conjugated diene polymer chain having an active terminal obtained in the first step is preferably 1% by mass or more, more preferably 10% by mass or more, and 20% by mass. The above is more preferable, and 30% by mass or more is particularly preferable, and 50% by mass or more is most preferable, because the compatibility between the specific conjugated diene rubber and the natural rubber is improved and the effect of the present invention is more excellent. The upper limit value is preferably 90% by mass or less, more preferably 80% by mass or less.

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

Further, the molecular weight distribution represented by the ratio (Mw / Mn) of the weight average molecular weight (Mw) and 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. However, 1.0 to 3.0 is preferable, and 1.0 to 2.5 is more preferable. When the molecular weight distribution (Mw / Mn) of the conjugated diene polymer chain having an active end is within the above range, the conjugated diene rubber can be easily produced.

<Preferable aspect>
The first step is preferably the following step because the effect of the present invention is more excellent.
That is, in an inert solvent, isoprene or a monomer containing isoprene and an aromatic vinyl compound is polymerized with a polymerization initiator, and isoprene monomer unit 80 to 100% by mass and aromatic vinyl monomer unit 0. Step A to form a polymer block (A) having an active end containing ~ 20% by mass, and
The polymer block (A) having the active terminal is mixed with 1,3-butadiene, or a monomer containing 1,3-butadiene and an aromatic vinyl compound to continue the polymerization reaction, and 1,3 A polymer block (B) having an active terminal containing 50 to 100% by mass of a butadiene monomer unit and 0 to 50% by mass of an aromatic vinyl monomer unit is formed in succession with the polymer block (A). It is preferable that the step B of obtaining a conjugated diene-based polymer chain having an active end is provided.

By adopting such a step, the conjugated diene-based polymer chain having an active terminal obtained in the first step can be obtained in an isoprene monomer unit of 80 to 100% by mass and an aromatic vinyl monomer unit of 0 to 20% by mass. The polymer block (A) containing% and the polymer block (B) containing 1,3-butadiene monomer unit 50 to 100% by mass and aromatic vinyl monomer unit 0 to 50% by mass are continuous. It is possible to include a structure (hereinafter, also referred to as “PI block”) formed in the above. In this case, the obtained specific conjugated diene rubber also has a PI block.
Hereinafter, such an embodiment will be described.

(Step A)
The polymer block (A) formed in the step A may contain 80 to 100% by mass of an isoprene monomer unit and 0 to 20% by mass of an aromatic vinyl monomer unit in the polymer block (A). However, for the reason that the effect of the present invention is more excellent, those containing 85 to 95% by mass of the isoprene monomer unit and 5 to 15% by mass of the aromatic vinyl monomer unit are preferable, and the isoprene monomer unit 89 to 89 to 15% by mass is preferable. More preferably, it contains 95% by mass and 5 to 11% by mass of aromatic vinyl monomer units.

As the aromatic vinyl compound used for forming the aromatic vinyl monomer unit contained in the polymer block (A), the same aromatic vinyl compound as described above can be used, and the effect of the present invention can be obtained. Of these, styrene is preferred for better 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) is preferably composed of only the isoprene monomer unit, or the isoprene monomer unit and the aromatic vinyl monomer unit, for the reason that the effect of the present invention is more excellent, but if desired, isoprene. In addition to the monomeric unit, or isoprene monomeric unit and aromatic vinyl monomeric unit, other monomeric units may be contained. Other compounds used to compose other monomeric 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, methacryl test, 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 -Etidene-2-Non-conjugated diene such as norbornen; etc. Among these, 1,3-butadiene is preferable because the effect of the present invention is more excellent. These other monomers can be used alone or in combination of two or more. The content ratio of the other monomer units in the polymer block (A) is preferably 20% by mass or less, more preferably 10% by mass or less, and 6% by mass or less because the effect of the present invention is more excellent. Especially preferable.

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

As the inert solvent used for polymerizing isoprene or a monomer containing isoprene and an aromatic vinyl compound in order to form the polymer block (A), the same inert solvent as described above may be used. it can. The amount of the inert solvent used is preferably such that the monomer concentration is 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 for forming the polymer block (A), isoprene or a monomer containing isoprene and an aromatic vinyl compound may be polymerized to give a polymer chain having an active terminal. If it can be done, it is not particularly limited. As a specific example thereof, the same polymerization initiator as described above can be used.

The amount of the polymerization initiator used may be determined according to the target molecular weight, but for the reason that the effect of the present invention is more excellent, 4 per 100 g of isoprene or a monomer containing isoprene and an aromatic vinyl compound. It is preferably in the range of 10 to 70 mmol, preferably from 6 to 200 mmol, more preferably from 6 to 200 mmol.

The polymerization temperature when polymerizing isoprene or a monomer containing isoprene and an aromatic vinyl compound is preferably −80 to + 150 ° C., more preferably 0 to 100 ° C., because the effect of the present invention is more excellent. The range of 20 to 90 ° C. is particularly preferable. As the polymerization mode, any mode such as batch type and continuous type can be adopted. Further, as the bonding mode, various bonding modes such as a block shape, a tapered shape, and a random shape can be used.

Further, for the reason that the effect of the present invention is more excellent, in order to adjust the vinyl bond content in the isoprene monomer unit in the polymer block (A), a polar compound may be added to the inert solvent during the polymerization. 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 target vinyl bond content, and is preferably 0.01 to 30 mol, more preferably 0.05 to 10 mol, based on 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 unlikely to occur. Further, 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 unit in the polymer block (A) is preferably 5 to 90% by mass, more preferably 5 to 80% by mass, for the reason that the effect of the present invention is more excellent. In the present specification, the vinyl bond content in the isoprene monomer unit has an isoprene monomer unit having a 1,2-structure and a 3,4-structure in the isoprene monomer unit. It shall refer to the ratio of the total amount of isoprene monomer units.

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

Further, the molecular weight distribution represented by the ratio (Mw / Mn) of the weight average molecular weight (Mw) of the polymer block (A) to the number average molecular weight (Mn) is 1.0 because the effect of the present invention is more excellent. ~ 1.5 is preferable, and 1.0 to 1.3 is more preferable. When the value (Mw / Mn) of the molecular weight distribution of the polymer block (A) is within the above range, the conjugated diene rubber can be more easily produced.

(Step B)
The polymer block (B) in the conjugated diene polymer chain formed in step B is 50 to 100% by mass of 1,3-butadiene monomer unit and a single amount of aromatic vinyl in the polymer block (B). It may contain 0 to 50% by mass of body units, but 1,3-butadiene monomer units 52 to 95% by mass and aromatic vinyl monomer units 5 to 5 for the reason that the effect of the present invention is more excellent. Those containing 48% by mass are preferable. 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 for forming the aromatic vinyl monomer unit contained in the polymer block (B), the same aromatic vinyl compounds as those described above can be used, and among these, the present invention Styrene is preferred because of the greater effect of the invention.

The polymer block (B) is composed of only 1,3-butadiene monomer units, or 1,3-butadiene monomer units and aromatic vinyl monomer units for the reason that the effect of the present invention is more excellent. However, if desired, in addition to the 1,3-butadiene monomer unit, or the 1,3-butadiene monomer unit and the aromatic vinyl monomer unit, as long as the essential properties in the present invention are not impaired. It may also contain other monomeric units. As the other monomer used to form the other monomer unit, the same compound as the compound exemplified in the above-mentioned polymer block (A) (excluding 1,3-butadiene) is used. be able to. Further, in the polymer block (B), isoprene can be used as another monomer. The content ratio of the other monomer units in the polymer block (B) is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 35% by mass or less.

The polymer block (B) in the conjugated diene polymer chain contains the above-mentioned polymer block (A) having an active terminal and 1,3-butadiene, or 1,3-butadiene and an aromatic vinyl compound. By mixing the polymer and the polymer and continuing the polymerization reaction, the polymer block (A) is formed in succession. The polymer block (B) formed has an active terminal. On the other hand, the active terminal disappears from the polymer block (A).

The inertness used to polymerize 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 solvent as the above-mentioned inert solvent 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, but for the reason that the effect of the present invention is more excellent, it may be determined. Per 100 g of the monomer containing 1,3-butadiene, or 1,3-butadiene and an aromatic vinyl compound, 0.1 to 5 mmol is preferable, 0.15 to 2 mmol is more preferable, and 0.2 to 1. The range of 5 mmol is particularly preferred.

The method for 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, and 1,3-butadiene, or 1,3 A polymer block (A) having an active end may be added to a solution of a monomer containing −butadiene and an aromatic vinyl compound, or 1,3 may be added to a solution of the polymer block (A) having an active end. -Butadiene, or monomers containing 1,3-butadiene and aromatic vinyl compounds may be added. From the viewpoint of controlling polymerization, a method of adding the polymer block (A) having an active terminal to a solution of 1,3-butadiene or a monomer containing 1,3-butadiene and an aromatic vinyl compound is preferable.

The polymerization temperature when polymerizing a monomer containing 1,3-butadiene or a monomer containing 1,3-butadiene and an aromatic vinyl compound is preferably −80 to + 150 ° C., and is 0, because the effect of the present invention is more excellent. ~ 100 ° C. is more preferable, and the range of 20 to 90 ° C. is particularly preferable. As the polymerization mode, any mode such as batch type and continuous type can be adopted. When the polymer block (B) is a copolymer chain, the batch type is preferable because it is easy to control the randomness of the bond.

When the polymer block (B) is a copolymer chain, the bonding mode of each monomer can be, for example, various bonding modes such as block-shaped, tapered-shaped, and random-shaped. Among these, the random shape is preferable because the effect of the present invention is more excellent. When the bonding mode of 1,3-butadiene and the aromatic vinyl compound is randomized, the total amount of 1,3-butadiene and the aromatic vinyl compound is added in the polymerization system because the effect of the present invention is more excellent. 1,3-butadiene or 1,3-butadiene and the aromatic vinyl compound are continuously or intermittently supplied into the polymerization system for polymerization so that the ratio of the aromatic vinyl compound to the amount does not become too high. Is preferable.

Further, for the reason that the effect of the present invention is more excellent, in order to adjust the vinyl bond content in the 1,3-butadiene monomer unit in the polymer block (B), a single amount of isoprene in the polymer block (A). It is preferable to add a polar compound to the inert solvent during the polymerization, as in the case of adjusting the vinyl bond content in the body unit. However, when preparing the polymer block (A), an amount of polar compound sufficient to adjust the vinyl bond content in the 1,3-butadiene monomer unit in the polymer block (B) was added to the inert solvent. If is added, it is not necessary 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 used may be determined according to the target vinyl bond content, and the polymerization initiation used in the initial polymerization reaction (polymerization reaction for forming the first polymer block (A)) may be started. It is preferably adjusted in the range of 0.01 to 100 mol, more preferably in the range of 0.1 to 30 mol, with respect to 1 mol of the agent. When the amount of the polar compound used 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 unlikely 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 effect of the present invention is more excellent. , 5 to 70% by mass is particularly preferable.

In this way, a conjugated diene-based polymer chain having an active terminal having a polymer block (A) and a polymer block (B) can be obtained. From the viewpoint of productivity, the conjugated diene-based polymer chain having an active end is composed of a polymer block (A) and a polymer block (B), and the end of the polymer block (B) is the active end. It is preferable, but it may have a plurality of polymer blocks (A), or it may have other polymer blocks. For example, a conjugated diene-based polymer chain having an active terminal such as polymer block (A) -polymer block (B) -polymer block (A) can be mentioned. In this case, the active terminal is formed at the end of the polymer block (A) formed following the polymer block (B). When the polymer block (A) is formed on the active terminal side of the conjugated diene-based polymer chain, the amount of isoprene used is determined by the initial polymerization reaction (first polymer block) because the effect of the present invention is more excellent. With respect to 1 mol of the polymerization initiator used in (polymerization reaction for forming (A)), 10 to 100 mol is preferable, 15 to 70 mol is more preferable, and 20 to 35 mol is particularly preferable.

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

With the total monomer unit of the isoprene monomer unit and the 1,3-butadiene monomer unit in the conjugated diene polymer chain having the polymer block (A) and the polymer block (B) and having an active terminal. , The content ratio with the aromatic vinyl monomer unit is the isoprene monomer unit and the 1,3-butadiene monomer in the conjugated diene polymer chain having an active terminal because the effect of the present invention is more excellent. Total monomer unit 50-100% by mass and aromatic vinyl monomer unit 0-50% by mass are preferable, and total monomer unit 52 of isoprene monomer unit and 1,3-butadiene monomer unit ~ 95% by mass, and 5 to 48% by mass of aromatic vinyl monomer units are more preferable.
Further, vinyl bonds in the isoprene monomer unit and the 1,3-butadiene monomer unit in the conjugated diene-based polymer chain having the polymer block (A) and the polymer block (B) and having an active terminal. The total content of the above is preferably 1% by mass or more, more preferably 10% by mass or more, further preferably 20% by mass or more, and particularly preferably 30% by mass or more, and 50% by mass, for the reason that the effect of the present invention is more excellent. The above is the most preferable. The upper limit value is preferably 90% by mass or less, more preferably 80% by mass or less.

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

In the 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, and these may be the same or different from each other. X ¹ and X ⁴ are composed of 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. Any group selected from the group, which 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 a plurality of X ² may be the same as or different from each other. X ³ is a group containing 2 to 20 repeating units of alkylene glycol, and when there are a plurality of X ³ , they may be the same or different from each other. 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 the general formula (1), examples of the alkyl group having 1 to 6 carbon atoms which can constitute R ^{1 to} R ⁸ , X ¹ and X ⁴ in the general formula (1) are methyl. Examples thereof include a group, an ethyl group, an n-propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group and a cyclohexyl group. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group and a methylphenyl group. Among these, a methyl group and an ethyl group are preferable from the viewpoint of easiness of producing the polyorganosiloxane itself.

Further, in the polyorganosiloxane represented by the general formula (1), examples of the alkoxy group having 1 to 5 carbon atoms that can constitute X ¹ , X ² and X ⁴ include a methoxy group, an ethoxy group, and a propoxy group. Examples thereof include an isopropoxy group and a butoxy group. Among these, a methoxy group and an ethoxy group are preferable from the viewpoint of easiness of producing the polyorganosiloxane itself.

Further, in the polyorganosiloxane represented by the general formula (1), examples of the group having 4 to 12 carbon atoms containing an epoxy group capable of forming X ¹ , X ² and X ⁴ include the following general formula (6). ) Can be mentioned.
-Z ^3- Z ^4- E ² (6)
In the general formula (6), Z ³ is an alkylene group or an alkylarylene group having 1 to 10 carbon atoms, 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 several 2 to 10.

The group represented by the general formula (6), because the effects of the present invention is more excellent, it is preferable that Z ⁴ is an oxygen atom, Z ⁴ is an oxygen atom, and, E ² is glycidyl group Some are more preferable, 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.

Further, in the polyorganosiloxane represented by the general formula (1), X ¹ and X ⁴ are groups having 4 to 12 carbon atoms containing an epoxy group because the effect of the present invention is more excellent than the above. , Or an alkyl group having 1 to 6 carbon atoms is preferable. As the X ^2, among the above, because the effect of the present invention is more excellent group having 4 to 12 carbon atoms containing an epoxy group is preferable. Further, it is more preferable that X ¹ and X ⁴ are alkyl groups having 1 to 6 carbon atoms and X ² is a group having 4 to 12 carbon atoms containing an epoxy group for the reason that the effect of the present invention is more excellent. ..

Further, the polyorganosiloxane expressed by the general formula (1), X ^3, that is, as the group containing repeating units of alkylene glycol having 2 to 20, for reasons that the effect of the present invention is more excellent, the following general formula ( The group represented by 7) is preferable.

In the general formula (7), t is an integer of 2 to 20, X ⁵ is an alkylene group or an 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 having a number of 1 to 10. Among these, it is preferable that 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. In the general formula (7), * is a coupling position.

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

Further, in the polyorganosiloxane represented by the general formula (1), n is an integer of 0 to 200, preferably an integer of 0 to 150, and more preferably an integer of 0 to 120. k is an integer of 0 to 200, preferably an integer of 0 to 150, and more preferably an integer of 0 to 130. The total number of m, n and k is 3 or more, preferably 3 to 400, more preferably 20 to 300, and particularly preferably 30 to 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 polymer chain having an active terminal is likely to proceed, and further, m, When the total number of n and k is 400 or less, the polyorganosiloxane itself represented by the general formula (1) can be easily produced, its viscosity does not become too high, and its handling becomes easy.

The amount of polyorganosiloxane used in the second step is the number of repeating units of the siloxane structure (-Si-O-) in the polyorganosiloxane with respect to 1 mol of the polymerization initiator used for polymerization in the first step described above. 1 to 2.5 mol is preferable, and 1.1 to 2 mol is more preferable, for the reason that the effect of the present invention is more excellent.

By setting the amount of polyorganosiloxane used to 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, the active terminal obtained in the first step can be obtained. Of the active ends of the conjugated diene-based polymer chain having, substantially all the active ends can be reacted with polyorganosiloxane, which is preferable. That is, the alkyl metal group as the active end of the conjugated diene-based polymer chain having the active end obtained in the first step, that is, −R ⁻ M ⁺ (R is a hydrocarbon group forming the polymer chain end). , M can be in a state in which a group represented by an alkali metal atom, an alkaline earth metal atom, or a lanthanum series metal atom) does not substantially remain.

As a result, when the compound represented by the general formula (2) is reacted in the third step described later, the compound represented by the general formula (2) is the active terminal obtained by the first step. It is possible to substantially suppress the direct reaction with the active end of the conjugated diene-based polymer chain having. As a result, with respect to the reaction residue generated by the reaction of the compound represented by the general formula (2) with the conjugated diene polymer chain and the polyorganosiloxane represented by the general formula (1). It can be reacted appropriately. As a result, a modified structure of the compound represented by the general formula (2) is appropriately introduced into the conjugated diene-based polymer chain via the structure derived from the polyorganosiloxane represented by the general formula (1). The effect of introducing such a modified structure, that is, excellent rolling performance, wear resistance and elongation at break can be realized.

The method for reacting the polyorganosiloxane with the conjugated diene polymer chain having an active terminal is not particularly limited, and examples thereof include a method of mixing these in a solvent in which each can be dissolved. As the solvent used at this time, those exemplified as the inert solvent used in the first step described above can be used. Further, in this case, a method of adding polyorganosiloxane to the polymerization solution used for the polymerization for obtaining the conjugated diene polymer chain having an active terminal is convenient 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% by mass. The reaction temperature is not particularly limited, but 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 end is not particularly limited, but the polymerization reaction is not completed and the conjugated diene polymer chain having an active end is contained. The state in which the solution to be prepared also contains a monomer, more specifically, the solution containing a conjugated diene-based polymer chain having an active terminal is a single amount of 100 ppm or more, more preferably 300 to 50,000 ppm. It is desirable to add the polyorganosiloxane to this solution with the body contained. By adding the polyorganosiloxane in this way, it is possible to suppress side reactions between the conjugated diene polymer chain having an active terminal and impurities contained in the polymerization system, and to control the reaction well. It becomes.

In the second step, polyorganosiloxane as a modifier is reacted with the active end of the conjugated diene-based polymer chain having the active end obtained in the first step described above, but the conjugated diene-based weight The active end of the coalesced chain will react with the silicon atom in the siloxane structure. Alternatively, a portion of the active end of the conjugated diene polymer chain, in alkoxy group, or epoxy group in the side chain of the polyorganosiloxane (general formula (1), an alkoxy group or an epoxy to form an X ² contained as an essential It will react with the group etc.). Then, according to the second step, a modified structure with siloxane is introduced into the conjugated diene-based polymer chain by such a reaction.

Specifically, the active end of the conjugated diene polymer chain reacts with the silicon atom in the siloxane structure, so that the conjugated diene polymer chain is formed by the silicon atom in the siloxane structure and the conjugated diene polymer chain. A new bond is formed between the active end and the modified structure by siloxane is introduced at the end of the conjugated diene polymer chain, and the oxygen atom in the siloxane structure and the active end of the conjugated diene polymer chain are introduced. A 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 with the metal atom forming the above. Is considered to be formed.

Alternatively, the active end of the conjugated diene polymer chain reacts with the epoxy group in the side chain of the polyorganosiloxane to open the epoxy group, and the carbon atom in the portion where the epoxy group is opened and the conjugated diene weight. A new bond is formed between the active end of the coalesced chain, a siloxane structure is introduced at the end of the conjugated diene polymer chain, and the oxygen atom in the epoxy group and the activity of the conjugated diene polymer chain are active. It is considered that a group represented by −O ⁻ M ⁺ is formed as these reaction residues with the metal atom forming the terminal. Alternatively, the active end of the conjugated diene polymer chain reacts with the alkoxy group of the side chain of the polyorganosiloxane to eliminate the alkoxy group, and the conjugated diene polymer chain is conjugated with the silicon atom in the siloxane structure. A new bond is formed with the active end of the diene-based polymer chain, and a siloxane structure is introduced at the end 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. Among the conjugated diene-based polymer chains having active terminals obtained in the first step, a modified structure with siloxane can be introduced into almost all the conjugated diene-based polymer chains. Therefore, the alkyl metal group as the active terminal of the conjugated diene polymer chain having the active terminal obtained in the first step, that is, -R ^- M ⁺ , can be brought into a state in which almost all of them do not remain. Instead, a group represented by −O ⁻ M ⁺ as a reaction residue will be formed. However, in the present invention, if it is a very small amount (for example, 5% by mass or less), it may contain a conjugated diene polymer chain having an unmodified active terminal that has not been modified with siloxane (for example, 5% by mass or less). That is, if the amount is very small, the alkyl metal group as the active terminal of the conjugated diene polymer chain having the active terminal obtained in the first step, that is, the one in which −R ⁻ M ⁺ remains is contained. Well), it does not rule out such cases.

In the second step, the effect of the present invention is not impaired in the state before the polyorganosiloxane represented by the general formula (1) is reacted with the conjugated diene polymer chain having an active terminal. , Even if a part of the active end of the conjugated diene polymer chain having an active end is added to the polymerization system with a coupling agent or a modifier which is usually used conventionally to perform coupling or modification. Good.

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

In the general formula (2), R ⁹ is a hydrocarbyl group, and A ¹ is a group capable of reacting with a reaction residue generated by a reaction between a conjugated diene polymer chain having an active terminal and a 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, substantially of 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, −R ⁻ M ^+. It is assumed that all of them are in a state where they do not remain, and instead, they have a group represented by −O ⁻ M ⁺ as a reaction residue by 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 (−O ⁻ M ⁺⁾ represented by −O ⁻ M ⁺ as such a reaction residue. It can be appropriately reacted with (including those in which the represented group is hydrolyzed and converted into a hydroxyl group).

That is, according to the present invention, compounds represented by the general formula (2) is, -R ^- by reacts with the group represented by M ^+, the conjugated diene polymer chain, directly, the general formula It is possible to appropriately suppress the introduction of the modified structure by the compound represented by (2), thereby forming the conjugated diene polymer chain into the polyorganosiloxane represented by the general formula (1). The modified structure of the compound represented by the general formula (2) can be appropriately introduced through the derived structure. As a result, excellent rolling performance, wear resistance and elongation at break can be realized.

However, the conjugated diene polymer chain obtained by reacting the polyorganosiloxane used in the third step may be one that has undergone the second step described above, and is a conjugated diene polymer having a modified structure with siloxane introduced therein. In addition to the chains, if the amount is very small (for example, 5% by mass or less), a conjugated diene polymer chain having an unmodified active terminal into which a siloxane-modified structure has not been introduced may remain (for example, 5% by mass or less). That is, if the amount is very small, the alkyl metal group as the active terminal of the conjugated diene-based polymer chain having the active terminal obtained in the first step, that is, the one in which −R ⁻ M ⁺ remains is contained. (Often), and further, a part of −O ⁻ M ⁺ as a reaction residue formed as a result of introducing a modified structure with siloxane is hydrolyzed and converted into a hydroxyl group. May be good.

In the compound represented by the general formula (2), R ⁹ in the general formula (2) is a hydrocarbyl group, and examples thereof include an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group and an aralkyl group. , An alkyl group having 1 to 6 carbon atoms is preferable because the effect of the present invention is more excellent. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group and the like, and among these, the effect of the present invention is more effective. Methyl group and ethyl group are more preferable for excellent reasons.

In the compound represented by the general formula (2), A ¹ in the general formula (2) is a reaction residue (typically) generated by the reaction of a conjugated diene polymer chain having an active terminal with polyorganosiloxane. is, ^-O - a group capable of reacting with group) represented by ^{M +,} the group represented by -OR 10 ^{(R 10} is a hydrogen atom or a hydrocarbyl group). Examples of the hydrocarbyl group that can constitute R ¹⁰ include an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an aralkyl group, and the like. From the viewpoint of reactivity with the reaction residue, the number of carbon atoms is 1 to 1. The alkyl group of 6 is preferred. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group and the like, and among these, the effect of the present invention is more effective. Methyl group and ethyl group are more preferable for excellent reasons.

In the compound represented by the general formula (2), A ² 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, but has a nitrogen atom. Organic groups are preferred, 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, for the reason that the effect of the present invention is more excellent, primary amino groups having an active hydrogen atom such as 3-aminopropyl group, 4-aminobutyl group, 3- (2-aminoethylamino) propyl group and / Or a group containing a secondary amino group having an active hydrogen atom is preferable. The "active hydrogen atom" refers to a hydrogen atom bonded to an atom other than a carbon atom, and preferably has a lower binding 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 between the conjugated diene polymer chain having an active terminal and the reaction residue generated by the reaction with polyorganosiloxane, p is an integer of 0 to 1, q is an integer of 2 to 3, and r. Is preferably an integer of 1 to 2, and more preferably p = 0, q = 3, and r = 1. When p is 2, the groups represented by R ⁹ contained in one molecule of the compound represented by the general formula (2) may be the same or different from each other. It may be. Similarly, when q is 2 or 3, a group represented by the general formula A ¹ which contains multiple compounds per molecule represented by (2) may be the same, together 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. It may be different from each other.

Specific examples of the compound represented by the general formula (2) are not particularly limited, but 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. As a compound which is a group containing a secondary amino group, 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyldimethylethoxysilane, 3-aminopropyl methyl diethoxy silane, as a ^2, such as 3-aminopropyltriethoxysilane, 3-amino compound having a propyl group; 4-aminobutyl dimethylmethoxysilane, 4-aminobutyl methyl dimethoxy silane, 4-aminobutyl trimethoxysilane 4-amino-butyldimethyl silane, 4-aminobutyl methyl diethoxy silane, 4 compounds having a 4-aminobutyl group as a ^2, such as aminobutyl triethoxysilane; 3- (2-aminoethylamino) propyl dimethyl Methoxysilane, 3- (2-aminoethylamino) propylmethyldimethoxysilane, 3- (2-aminoethylamino) propyltrimethoxysilane, 3- (2-aminoethylamino) propyldimethylethoxysilane, 3- (2-) aminoethylamino) propyl methyl diethoxy silane, as a ^2, such as 3- (2-aminoethylamino) propyltriethoxysilane, compounds having a 3- (2-aminoethylamino) propyl group; and the like.

Further, as a compound in which A ² in the general formula (2) is a group other than a primary amino group having an active hydrogen atom and / or a group containing a secondary amino group having an active hydrogen atom, 3-dimethylamino. Propyltrimethoxysilane, 3-dimethylaminopropylmethyldimethoxysilane, 3-dimethylaminopropyldimethylmethoxysilane, 3-dimethylaminopropyltriethoxysilane, 3-dimethylaminopropylmethyldiethoxysilane, 3-dimethylaminopropyldimethylethoxysilane Such as A ² , a compound having a 3-dimethylaminopropyl group; 3-diethylaminopropyltrimethoxysilane, 3-diethylaminopropylmethyldimethoxysilane, 3-diethylaminopropyldimethylmethoxysilane, 3-diethylaminopropyltriethoxysilane, 3- diethylaminopropyl methyl diethoxy silane, 3 as a ^2, such as diethylaminopropyl dimethyl silane, a compound having a 3-diethylamino-propyl; 3-dipropyl-aminopropyltrimethoxysilane, 3-dipropyl-aminopropyl methyl dimethoxy silane, 3 - dipropyl aminopropyldimethylmethoxysilane, 3-dipropyl-aminopropyltriethoxysilane, 3-dipropyl-aminopropyl methyl diethoxy silane, as a ^2, such as 3-dipropylamino-aminopropyldimethylethoxysilane, 3-dipropylamino Compounds with propyl groups; 3-dibutylaminopropyltrimethoxysilane, 3-dibutylaminopropylmethyldimethoxysilane, 3-dibutylaminopropyldimethylmethoxysilane, 3-dibutylaminopropyltriethoxysilane, 3-dibutylaminopropylmethyldiethoxy silane, 3 as a ^2, such as dibutyl-aminopropyldimethylethoxysilane, 3-compound having dibutyl aminopropyl group; 3-phenyl-methyl aminopropyl trimethoxy silane, 3-phenylmethyl-aminopropyl methyl dimethoxysilane, 3-phenylmethyl aminopropyldimethylmethoxysilane, 3-phenylmethyl-aminopropyltriethoxysilane, 3-phenylmethyl-aminopropyl methyl diethoxy silane, as a ^2, such as 3-phenylmethyl-aminopropyldimethylethoxysilane, 3-phenylmethyl-aminopropyl group Compounds; 3- (4-Methylpiperadi) Nyl) propyltrimethoxysilane, 3- (4-methylpiperazinyl) propylmethyldimethoxysilane, 3- (4-methylpiperazinyl) propyldimethylmethoxysilane, 3- (4-methylpiperazinyl) propyltriethoxy silane, 3- (4-methylpiperazinyl) propyl methyl diethoxy silane, 3- (4-methylpiperazinyl) as ^{a 2,} such as dimethyl silane, 3- (4-methylpiperazinyl) propyl Compounds with;

N, N-bis (trimethylsilyl) aminopropyltrimethoxysilane, N, N-bis (trimethylsilyl) aminopropyltriethoxysilane, N, N-bis (trimethylsilyl) aminopropylmethyldimethoxysilane, N, N-bis (trimethylsilyl) as ^{a 2,} such as amino propyl methyl diethoxy silane, N, compounds with N- bis (trimethylsilyl) aminopropyl groups; N, N- bis (triethylsilyl) aminopropyltrimethoxysilane, N, N- bis (trimethylsilyl) aminopropyltriethoxysilane, N, N- bis (triethylsilyl) aminopropylmethyldimethoxysilane, N, as a ^2, such as N- bis (triethylsilyl) aminopropyl methyl diethoxy silane, N, N- bis (triethylsilyl ) Compounds with aminopropyl groups; 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 ', as ^{a 2,} such as N'- tris (trimethylsilyl) -N- (2-aminoethyl) -3-aminopropyl methyl diethoxy silane, N, N', N'- tris (trimethylsilyl) -N- ( 2-Aminoethyl) -3-aminopropyl group-bearing compounds; and the like.

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, 0.1 to 5 is applied to 1 mol of the polymerization initiator used in the first step. The moles are preferable, 0.2 to 2 moles are more preferable, and 0.4 to 1.5 moles are particularly preferable.

The timing for adding the compound represented by the general formula (2) to the solution containing the conjugated diene-based polymer chain is after the addition of the polyorganosiloxane represented by the general formula (1) in the second step described above. If so, there is no particular limitation. For example, as in the second step described above, the polymerization reaction is not completed, and the solution containing the conjugated diene polymer chain also contains the monomer, more specifically, the conjugated diene. The compound represented by the general formula (2) is added to this solution in a state where the solution containing the system polymer chain contains 100 ppm or more, more preferably 300 to 50,000 ppm of monomer. Can be done. By adding the compound represented by the general formula (2) in this way, side reactions between the conjugated diene polymer chain and impurities contained in the polymerization system are suppressed, and the reaction is satisfactorily controlled. It becomes possible. Alternatively, by adding an alcohol such as water or methanol to the solution containing the conjugated diene polymer chain before or after adding the compound represented by the general formula (2), the solution can be used. A modification reaction in a state where the group represented by −O ⁻ M ⁺ as a reaction residue formed by the reaction with the polyorganosiloxane represented by the general formula (1) is hydrolyzed and converted into a hydroxyl group. May be done. When the compound represented by the general formula (2) is added to the solution containing the conjugated diene polymer chain, the compound represented by the general formula (2) may be added after being dissolved in the inert solvent. However, it may be added directly without being dissolved in the 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 inhibitor or the like is added to inactivate the reaction system, and then, if desired, a phenol-based stabilizer. , Phosphorus stabilizers, antiaging agents such as sulfur stabilizers, crumbing 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. Then, the conjugated diene rubber is collected. Before separating the polymerization solvent from the reaction solution, the polymerization solution may be mixed with the spreading oil and the conjugated diene rubber may be recovered as the oil spreading rubber.

Examples of the spreading oil used when recovering the conjugated diene-based rubber as an oil-extended rubber include paraffin-based, aromatic and naphthen-based petroleum-based softeners, plant-based softeners, and fatty acids. When a petroleum-based softener is used, the content of polycyclic aromatics extracted by the method of IP346 (inspection method of THE INSTITUTE PETROLEUM in the United Kingdom) is preferably less than 3%. When the spreading oil is used, the amount used is preferably 5 to 100 parts by mass, more preferably 10 to 60 parts by mass, and particularly preferably 20 to 50 parts by mass with respect to 100 parts by mass of the conjugated diene rubber.

As described above, in the specific conjugated diene-based rubber, the polyorganosiloxane represented by the general formula (1) as a modifier in the above-mentioned second step is applied 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 ratio of 1 mol or more in terms of the number of repeating units to carry out the reaction, and then, in the third step described above, it is generally used as a modifier. It is obtained by carrying out the reaction using the compound represented by the formula (2). Therefore, the specific conjugated diene-based rubber includes one in which a modified structure by siloxane and a modified structure by a compound represented by the general formula (2) are introduced at the end of the polymer chain, but other than such a rubber. , The polymer chain terminal may include one in which only a modified structure with siloxane is introduced. Further, as long as the effect of the present invention is not impaired, for example, only a modified structure by a compound represented by the general formula (2) is introduced at the end of the polymer chain, or any modified structure is introduced. It may contain something that does not exist. In particular, in the present invention, from the viewpoint of more appropriately realizing the effects of the present invention, a modified structure with siloxane and a modified structure with a compound represented by the general formula (2) are introduced at the end of the polymer chain. The ratio is preferably 10% by mass or more, and more preferably 20% by mass or more. The upper limit is not particularly limited.

[Monomer unit content]
The specific conjugated diene-based rubber preferably contains 50 to 100% by mass of the conjugated diene monomer unit, more preferably 52 to 95% by mass, and is aromatic, 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 preferable, and those containing 5 to 48% by mass are more preferable.

[Vinyl bond content]
The vinyl bond content in the conjugated diene monomer unit in the specific conjugated diene rubber is preferably 1% by mass or more, more preferably 10% by mass or more, further preferably 20% by mass or more, and the effect of the present invention is more excellent. For this reason, 30% by mass or more is particularly preferable, and 50% by mass or more is most preferable. The upper limit value is preferably 90% by mass or less, more preferably 80% by mass or less.

[Coupling rate]
The coupling ratio 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, particularly preferably 40% by mass or more, and particularly preferably 40% by mass or more, for the reason that the effect of the present invention is more excellent. , 80% by mass or less is preferable, 75% by mass or less is more preferable, and 70% by mass or less is particularly preferable. The coupling ratio is determined by reacting with a polyorganosiloxane represented by the general formula (1), a compound represented by the general formula (2), and a coupling agent or other modifier used as necessary. It is the mass fraction of the polymer molecule having a molecular weight of 1.8 times or more the peak top molecular weight of the conjugated diene polymer chain having the previous active end with respect to the total amount of the finally obtained conjugated diene rubber. The molecular weight at this time shall be determined as a polystyrene-equivalent molecular weight by gel permeation chromatography.

[Molecular weight]
The weight average molecular weight (Mw) of the specific conjugated diene rubber is a value measured by gel permeation chromatography in terms of polystyrene, preferably 100,000 to 3,000,000, preferably 150,000 to 2,000,000. More preferably, 200,000 to 1,500,000 is particularly preferable. By setting the weight average molecular weight of the specific conjugated diene rubber within the above range, it becomes easy to blend silica into the conjugated diene rubber, and the effect of the present invention becomes more excellent.

The molecular weight distribution represented by the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the specific conjugated diene-based rubber is described in 1.1 to 1 and 3 because the effect of the present invention is more excellent. 0 is preferable, 1.2 to 2.5 is more preferable, and 1.2 to 2.2 is particularly preferable.

〔viscosity〕
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 effect of the present invention is more excellent. When the conjugated diene rubber is an oil-extended rubber, it is preferable that the Mooney viscosity of the oil-extended rubber is in the above range.

〔Glass-transition temperature〕
The glass transition temperature (Tg) of the specific conjugated diene rubber is preferably −100 to −10 ° C., more preferably −80 to −15 ° C., and particularly preferably −50 to −15 ° C. When the glass transition temperature is within the above range, the effect of the present invention becomes more excellent.
Here, the glass transition temperature is a value measured at a heating rate of 10 ° C./min according to ASTM D3418-82 using a differential thermal analyzer (DSC) manufactured by DuPont.

〔Content〕
The content of the specific conjugated diene rubber in the conjugated diene rubber is 30% by mass or more, and for the reason that the effect of the present invention is more excellent, 35% by mass or more is preferable, 40% by mass is more preferable, and 50% by mass is more preferable. The above is particularly preferable. The upper limit value is preferably 85% by mass or less, more preferably 80% by mass or less, from the viewpoint that the effect of the present invention is more excellent.

[Natural rubber]
The conjugated diene rubber in the composition of the present invention contains a natural rubber.
The content of the natural rubber in the conjugated diene rubber is 15% by mass or more, and 20% by mass or more is more preferable because the effect of the present invention is more excellent. The upper limit is preferably 70% by mass or less, more preferably 60% by mass or less, further preferably 50% by mass or less, and particularly preferably 40% by mass or less, from the viewpoint that the effect of the present invention is more excellent.
The ratio of the content of the specific conjugated diene rubber to the natural rubber in the conjugated diene rubber (specific conjugated diene rubber / natural rubber) is 0.4 to 5.7 because the effect of the present invention is more excellent. Preferably, 1 to 5 are more preferable.

[Other rubber components]
The conjugated diene-based rubber may contain a rubber component (other rubber component) other than the specific conjugated diene-based rubber and the natural rubber.
Such other rubber components include isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), and butyl halide rubber (Br-). IIR, Cl-IIR), chloroprene rubber (CR) and the like.
The content of other rubber components in the conjugated diene rubber is not particularly limited, but is preferably 10% by mass or less, more preferably 0 to 10% by mass, and particularly preferably 0 to 5% by mass.

[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.

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 above-mentioned conjugated diene rubber. Among them, 40 parts by mass or more is preferable, and 50 parts by mass or more is more preferable, because the effect of the present invention is more excellent.
The upper limit of the silica content is not particularly limited, but for the reason that the effect of the present invention is more excellent, 200 parts by mass or less is preferable, and 150 parts by mass or less is more preferable with respect to 100 parts by mass of the above-mentioned conjugated diene rubber. , 100 parts by mass or less 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.
The hydrolyzable group is not particularly limited, and examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, and an alkenyloxy group. Of these, an alkoxy group is preferable because the effect of the present invention is more excellent. When the hydrolyzable group is an alkoxy group, the number of carbon atoms of the alkoxy group is preferably 1 to 16 and more preferably 1 to 4 for the reason that the effect of the present invention is more excellent. Examples of the alkoxy group having 1 to 4 carbon atoms include a methoxy group, an ethoxy group, a propoxy group and the like.

The organic functional group is not particularly limited, but a group capable of forming a chemical bond with an organic compound is preferable, and for example, an epoxy group, a vinyl group, an acryloyl group, a methacryloyl group, an amino group, a sulfide group, a mercapto group, and a block mercapto group ( Protected mercapto group) (for example, octanoylthio group) and the like, and among them, a sulfide group (particularly, a disulfide group and a tetrasulfide group), a mercapto group and a block mercapto group are preferable because the effect of the present invention is more excellent.

Specific examples of the above silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, and mercaptopropyltrimethoxy. Silane, mercaptopropyl triethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethylsilyl Examples thereof include propyl-N, N-dimethylthiocarbamoyl-tetrasulfide, 3-octanoylthio-1-propyltriethoxysilane, and one of these may be used alone or in combination of two or more. ..

In the composition of the present invention, the content of the silane coupling agent is 3 to 30% by mass with respect to the content of silica described above. Of these, 5 to 20% by mass is preferable because the effect of the present invention is more excellent.

Further, in the composition of the present invention, the content of the silane coupling agent is preferably 1 to 30 parts by mass with respect to 100 parts by mass of the above-mentioned conjugated diene rubber because the effect of the present invention is more excellent. ~ 20 parts by mass is more preferable, and 4 to 15 parts by mass is further preferable.

[4] Optional components The composition of the present invention may contain components (arbitrary components) other than the above-mentioned components, if necessary.
Such components include, for example, fillers other than silica (eg, carbon black), terpene resins (preferably aromatic-modified terpene resins), thermosetting microcapsules, zinc oxide (zinc oxide), stearic acid, and the like. Various additives commonly used in rubber compositions such as anti-aging agents, waxes, processing aids, process oils, liquid polymers, thermosetting resins, vulcanizing agents (eg sulfur), vulcanization accelerators, etc. Can be mentioned.

[Carbon black]
The composition of the present invention preferably contains carbon black for the reason that the effect of the present invention is more excellent.
The carbon black is not particularly limited, and 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 50 to 200 m ² / g is preferable, and 70 to 150 m ² / g is more preferable, for the reason that the effect of the present invention is more excellent.
Here, the nitrogen adsorption specific surface area (N ₂ SA) is the amount of nitrogen adsorbed on the carbon black surface according to JIS K6217-2: 2001 "Part 2: How to obtain the specific surface area-Nitrogen adsorption method-Single point method". This is the 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, 1 to 100 parts by mass is preferable with respect to 100 parts by mass of the above-mentioned diene rubber. 10 parts by mass is more preferable.

[Preparation method of rubber composition for tire tread]
The method for producing the composition of the present invention is not particularly limited, and as a specific example thereof, each of the above-mentioned components is kneaded using a known method or apparatus (for example, Banbury mixer, kneader, roll, etc.). The method etc. can be mentioned. When the composition of the present invention contains sulfur or a vulcanization accelerator, 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 preferable to mix the vulcanization accelerator.
In addition, 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 by using the composition of the present invention described above. Of these, a pneumatic tire using (arranging) the composition of the present invention for a 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 represents a bead portion, reference numeral 2 represents a sidewall portion, and reference numeral 3 represents a tire tread portion.
Further, a carcass layer 4 in which a fiber cord is embedded is mounted between the pair of left and right bead portions 1, and the end portion of the carcass layer 4 is placed around the bead core 5 and the bead filler 6 from the inside to the outside of the tire. It is folded back and rolled up.
Further, in the tire tread portion 3, a belt layer 7 is arranged on the outside of the carcass layer 4 over one circumference of the tire.
Further, in the bead portion 1, the rim cushion 8 is arranged at a portion in contact with the rim.
The tire tread portion 3 is formed by 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. Further, as the gas to be filled in the pneumatic tire, an inert gas such as nitrogen, argon, or helium can be used in addition to normal or adjusted oxygen partial pressure.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[Manufacturing of specific conjugated diene rubber and comparative conjugated diene rubber]
Specific conjugated diene rubbers 1 to 3 and comparative conjugated diene rubbers 1 to 3 were produced as follows.
Here, the specific conjugated diene rubbers 1 to 3 are conjugated diene rubbers produced by the method for producing a conjugated diene rubber having the above-mentioned steps 1 to 3, and correspond to the above-mentioned specific conjugated diene rubbers. Further, the specific conjugated diene rubbers 1 and 3 include the above-mentioned steps A and B in the first step, and the specific conjugated diene rubber has a PI block.
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 having the above-mentioned first and second steps (not including the above-mentioned third step), and is a specific conjugated rubber described above. Not applicable to diene rubber. Further, the comparative conjugated diene rubber 2 does not correspond to the specific conjugated diene rubber described above because the amount of the polyorganosiloxane added does not satisfy the second step described above. Further, since the comparative conjugated diene rubber 3 is not a conjugated diene rubber produced by the method for producing a conjugated diene rubber comprising the first to third steps described above, it is not the specific conjugated diene rubber described above.

<Specific conjugated diene rubber 1>
To a nitrogen-substituted 800 ml ampol bottle, 74.3 g of cyclohexane and 0.48 mmol of tetramethylethylenediamine were added, and 4.76 mmol of n-butyllithium (tetramethylethylenediamine as a polar compound with respect to 1 mol of n-butyllithium) was added. The amount of the above is 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 an active terminal. The weight average molecular weight (Mw) of this polymer block (A) is 6,500, the molecular weight distribution (Mw / Mn) is 1.12, and the unit content of aromatic vinyl monomer (styrene monomer) is 7.0. The mass%, the isoprene monomer unit content was 93.0% by mass, and the vinyl bond content was 7.5% by mass.

After charging 4000 g of cyclohexane, 3.57 mmol of tetramethylethylenediamine, 252 g of 1,3-butadiene, and 348 g of styrene in an autoclave with a stirrer under a nitrogen atmosphere, the polymer block (A) having the active terminal obtained above was charged. Was added and polymerization was started 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 start of the 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 continuous addition, the polymerization reaction was continued for another 15 minutes, and after confirming that the polymerization conversion rate was in the range of 95% to 100%, 40 polyorganosiloxane represented by the following formula (11) was added. In the state of a xylene solution having a mass% concentration, 1.51 g (1.1 times the molar amount of n-butyllithium used in terms of the number of repeating units of the siloxane structure (-Si-O-) in the polyorganosiloxane) (Amount corresponding to) was added and reacted for 30 minutes. Then, 4.76 mmol of 3- (2-aminoethylamino) propyltrimethoxysilane (equivalent to 1.0 times the molar amount of n-butyllithium used) was added and reacted for 10 minutes. Then, as a polymerization inhibitor, methanol corresponding to twice the mole of n-butyllithium used was added to obtain a solution containing a conjugated diene rubber. To this solution, 0.15 part of Irganox 1520L (manufactured by BASF) as an anti-aging agent was added to 100 parts of conjugated diene rubber, the solvent was removed by steam stripping, and the temperature was 60 ° C. for 24 hours. Vacuum drying was performed to obtain a solid conjugated diene rubber. The obtained conjugated diene rubber is designated as the specific conjugated diene rubber 1. The weight average molecular weight (Mw) of the specific conjugated diene rubber 1 is 570,000, the coupling rate is 45.0%, the unit content of aromatic vinyl monomer (styrene monomer) is 41.1% by mass, and vinyl. The bond content was 33.5% by mass, the glass transition temperature (Tg) was −26 ° C., and the molecular weight distribution (Mw / Mn) was 1.5.

In the above formula (11), 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 the above formula (11), X ² is a group represented by the following formula (12) (where * represents a bonding position).

<Specific conjugated diene rubber 2>
In an autoclave with a stirrer, 800 g of cyclohexane, 1.42 mmol of tetramethylethylenediamine, 87.6 g of 1,3-butadiene, and 32.4 g of styrene were charged under a nitrogen atmosphere, 0.79 mmol of n-butyllithium was added, and the temperature was 60 ° C. Polymerization was started at. After continuing the polymerization reaction for 60 minutes and 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 a xylene solution having a concentration of 40% by mass. 0.26 g (amount corresponding to 1.1 times the molar amount of n-butyllithium used in terms of the number of repeating units of the siloxane structure (-Si-O-) in the polyorganosiloxane) was added in the above state. And reacted for 30 minutes. Then, 0.79 mmol of 3- (2-aminoethylamino) propyltrimethoxysilane (amount corresponding to 1.0 times the molar amount of n-butyllithium used) was added, and the mixture was stirred for 10 minutes. Then, as a polymerization inhibitor, methanol corresponding to twice the molar amount of n-butyllithium used was added to obtain a solution containing a conjugated diene rubber. To this solution, 0.15 part of Irganox 1520L (manufactured by Ciba Speciality Chemicals) as an anti-aging agent was added to 100 parts of conjugated diene rubber, and then the solvent was removed by steam stripping to remove the solvent at 60 ° C. The mixture was vacuum-dried for 24 hours to obtain a solid conjugated diene-based rubber. The obtained conjugated diene rubber is designated as the specific conjugated diene rubber 2. The weight average molecular weight (Mw) of the specific conjugated diene rubber 2 is 467,000, the coupling rate is 54.4%, the unit content of aromatic vinyl monomer (styrene monomer) is 26.9% by mass, and vinyl. The bond content was 58.5% by mass, the glass transition temperature (Tg) was -22 ° C, and the molecular weight distribution (Mw / Mn) was 1.4.

<Specific conjugated diene rubber 3>
To a nitrogen-substituted 100 ml ampoule bottle, 50.0 g of cyclohexane and 0.66 mmol of tetramethylethylenediamine were added, and 6.6 mmol of n-butyllithium was further added. Then, 11.61 g of isoprene and 0.87 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 an active terminal. The weight average molecular weight (Mw) of this polymer block (A) is 3,500, the molecular weight distribution (Mw / Mn) is 1.10, and the unit content of aromatic vinyl monomer (styrene monomer) is 7.0. The mass%, the isoprene monomer unit content was 93.0 mass%, and the vinyl bond content was 7.7 mass%.

Next, in an autoclave with a stirrer, in a nitrogen atmosphere, 4000 g of cyclohexane and tetramethylethylenediamine 11. After charging 393.0 g of l mmol, 1,3-butadiene and 207.0 g of styrene, all of the polymer block (A) having the active terminal obtained above was added, and polymerization was started at 40 ° C. After 10 minutes from the start of the polymerization, 337.0 g of 1,3-butadiene and 63.0 g of styrene were continuously added over 40 minutes. The maximum temperature during the polymerization reaction was 60 ° C. After the completion of continuous addition, the polymerization reaction was continued for another 20 minutes, and 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 40. In the state of a xylene solution having a mass% concentration, 2.13 g (1.1 times the molar amount of n-butyllithium used in terms of the number of repeating units of the siloxane structure (-Si-O-) in the polyorganosiloxane) Add (equivalent to) and siloxane for 30 minutes. Then, 6.6 mmol of 3- (2-aminoethylamino) propyltrimethoxysilane (amount corresponding to 1.0 times the molar amount of n-butyllithium used) was added, and the mixture was stirred for 10 minutes. Then, as a polymerization inhibitor, methanol corresponding to twice the mole of n-butyllithium used was added to obtain a solution containing a conjugated diene rubber. To this solution, 0.15 part of Irganox 1520L (manufactured by Ciba Speciality Chemicals) as an anti-aging agent was added to 100 parts of conjugated diene rubber, and then the solvent was removed by steam stripping at 60 ° C. Vacuum drying for 24 hours gave a solid conjugated diene rubber. The obtained conjugated diene rubber is designated as the specific conjugated diene rubber 4. The weight average molecular weight (Mw) of the specific conjugated diene rubber 4 is 488,000, the coupling rate is 60.2%, the unit content of aromatic vinyl monomer (styrene monomer) is 26.6% by mass, and vinyl. The bond content was 60.4% by mass, the glass transition temperature (Tg) was -22 ° C, and the molecular weight distribution (Mw / Mn) was 1.4.

<Comparative conjugated diene rubber 1>
A solid conjugated diene rubber was obtained by the same procedure as in the specific conjugated diene rubber 2 except that 4.76 mmol of 3- (2-aminoethylamino) propyltrimethoxysilane was not added. The obtained conjugated diene rubber is designated as the comparative conjugated diene rubber 1. The weight average molecular weight (Mw) of the comparative conjugated diene rubber 1 is 552,000, the coupling rate is 43.0%, the unit content of aromatic vinyl monomer (styrene monomer) is 41.0% by mass, and vinyl. The bond content was 33.0% by mass, the glass transition temperature (Tg) was −27 ° C., and the molecular weight distribution (Mw / Mn) was 1.7.

<Comparative conjugated diene rubber 2>
In an autoclave with a stirrer, 800 g of cyclohexane, 1.42 mmol of tetramethylethylenediamine, 87.6 g of 1,3-butadiene, and 32.4 g of styrene were charged under a nitrogen atmosphere, 0.79 mmol of n-butyllithium was added, and the temperature was 60 ° C. Polymerization was started at. After continuing the polymerization reaction for 60 minutes and 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 a xylene solution having a concentration of 40% by mass. In the state of, 0.16 g (amount corresponding to 0.7 times the molar amount of n-butyllithium used in terms of the number of repeating units of the siloxane structure (-Si-O-) in the polyorganosiloxane) was added. And reacted for 30 minutes. Then, 0.79 mmol of 3-aminopropyltrimethoxysilane (amount corresponding to 1.0 times the molar amount of n-butyllithium used) was added, and the mixture was stirred for 10 minutes. Then, as a polymerization inhibitor, methanol corresponding to twice the molar amount of n-butyllithium used was added to obtain a solution containing a conjugated diene rubber. To this solution, 0.15 part of Irganox 1520L (manufactured by Ciba Speciality Chemicals) as an anti-aging agent was added to 100 parts of conjugated diene rubber, and then the solvent was removed by steam stripping to remove the solvent at 60 ° C. The mixture was vacuum-dried for 24 hours to obtain a solid conjugated diene-based rubber. The obtained conjugated diene rubber is designated as the comparative conjugated diene rubber 2. The weight average molecular weight (Mw) of the comparative conjugated diene rubber 2 is 383,000, the coupling rate is 34.4%, the unit content of aromatic vinyl monomer (styrene monomer) is 26.6% by mass, and vinyl. The bond content was 58.5% by mass, the glass transition temperature (Tg) was -22 ° C, and the molecular weight distribution (Mw / Mn) was 1.4.

<Comparative conjugated diene rubber 3>
The comparative conjugated diene rubber 3 is Nipol NS616 (styrene butadiene rubber, weight average molecular weight (Mw): 450,000, styrene monomer unit content: 21% by mass, vinyl bond content: 63% by mass, manufactured by Nippon Zeon Co., Ltd. %, Glass transition temperature (Tg): -22 ° C., Molecular weight distribution (Mw / Mn): 1.4).

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

[Evaluation]
The obtained rubber composition for tire tread was evaluated as follows.

<Making a vulcanized rubber sheet>
The obtained rubber composition for tire tread (unvulcanized) was press-vulcanized in a mold (15 cm × 15 cm × 0.2 cm) at 160 ° C. for 20 minutes to prepare a vulcanized rubber sheet.

<Rolling performance>
The obtained vulcanized rubber sheet was subjected to a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) in accordance with JIS K6394: 2007 under the conditions of a stretch deformation strain rate of 10% ± 2%, a frequency of 20 Hz, and a temperature of 60 ° C. Tan δ (60 ° C.) was measured.
The results are shown in Table 1. The results are represented by an index with Comparative Example 1 as 100. The smaller the index, the better the rolling performance (low rolling resistance). Practically, 97 or less is preferable.

<Abrasion resistance>
The obtained vulcanized rubber sheet was measured for wear loss under the conditions of a temperature of 20 ° C. and a slip ratio of 50% using a Ramborn wear tester (manufactured by Iwamoto Seisakusho) in accordance with JIS K6264-1, 2: 2005. ..
The results are shown in Table 1. The result was expressed as an index by the following equation, with the wear amount of Comparative Example 1 as 100. The larger the index, the smaller the amount of wear, and the better the wear resistance when used as a tire. Practically, 101 or more is preferable.
Abrasion resistance = (Abrasion amount of Comparative Example 1 / Abrasion amount of sample) × 100

<Breaking elongation>
With respect to the obtained vulcanized rubber sheet, a JIS No. 3 dumbbell type test piece (thickness 2 mm) was punched out according to JIS K6251: 2010, and the elongation at break was measured under the conditions of 20 ° C. and a tensile speed of 500 mm / min.
The measurement result was represented by an index with the value of Comparative Example 1 as 100. The larger the index, the larger the elongation at break (hereinafter, also referred to as "excellent elongation at break"). Practically, 101 or more is preferable.

Details of each component in Table 1 above are as follows. Further, in Table 1, "St" and "Vn" are the contents (mass%) of aromatic vinyl monomer (styrene monomer) units in the specific conjugated diene rubber or the comparative conjugated diene rubber, respectively. And the vinyl bond content (% by mass) in the conjugated diene monomer. “Mw”, “Mw / Mn” and “Tg” mean the weight average molecular weight, molecular weight distribution and glass transition temperature (° C.) of the specific conjugated diene rubber or the comparative conjugated diene rubber, respectively.
-NR: Natural rubber (TSR20, manufactured by VON BUNDIT)
-Specific conjugated diene rubber 1: Specific conjugated diene rubber manufactured as described above 1
-Specific conjugated diene rubber 2: Specific conjugated diene rubber 2 manufactured as described above.
-Specific conjugated diene rubber 3: Specific conjugated diene rubber 3 manufactured as described above.
-Comparative conjugated diene rubber 1: Comparative conjugated diene rubber manufactured as described above 1
-Comparative conjugated diene rubber 2: Comparative conjugated diene rubber 2 manufactured as described above.
-Comparative conjugated diene rubber 3: Comparative conjugated diene rubber 3 manufactured as described above.
-7000GR: ULTRASIL 7000GR (silica, manufactured by Evonik Degussa)
・ N339: Show Black N339 (Carbon Black, manufactured by Cabot Japan)
-Si69: Si69 (silane coupling agent, bis (3-triethoxysilylpropyl) tetrasulfide) (manufactured by Evonik Degussa)
・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
・ Stearic acid: Beaded stearic acid (manufactured by NOF CORPORATION)
・ Anti-aging agent: Ozonon 6C (manufactured by Seiko Kagaku Co., Ltd.)
・ Process oil: Extract No. 4 S (manufactured by Showa Shell Sekiyu Co., Ltd.)
-Sulfur: Fine powdered sulfur with Jinhua stamp oil (sulfur content 95.24% by mass, manufactured by Tsurumi Chemical Industry Co., Ltd.)
-Vulcanization accelerator (CZ): Noxeller CZ-G manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
-Vulcanization accelerator (DPG): 1,3-diphenylguanidine (Soxinol DG, manufactured by Sumitomo Chemical Co., Ltd.)

As can be seen from Table 1, Examples 1 to 3 containing a predetermined amount of the specific conjugated diene rubber, a predetermined amount of natural rubber, a predetermined amount of silica, and a predetermined amount of the silane coupling agent have excellent rolling performance. It showed abrasion resistance and elongation at break.
From the comparison of Examples 2 and 3, Example 3 in which the specific conjugated diene rubber contained a PI block showed better rolling performance, wear resistance and elongation at break.
From the comparison between Examples 1 and 3, Example 3 in which the vinyl bond content in the conjugated diene monomer in the specific conjugated diene rubber is 50% by mass or more has better rolling performance, wear resistance and fracture. It showed growth.

Comparative Examples 1, 4 and 5 in which the content of the specific conjugated diene rubber in the conjugated diene rubber is less than 30% by mass, and the comparative example in which the content of silica with respect to 100 parts by mass of the conjugated diene rubber is less than 30 parts by mass. 2. Comparative Example 3 in which the content of the silane coupling agent with respect to silica is less than 3% by mass, and Comparative Example 6 in which the content of natural rubber is less than 15% by mass, have rolling performance, abrasion resistance and elongation at break. At least one of them was inadequate.

1 Bead part 2 Side wall part 3 Tire tread part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Rim cushion

Claims (5)

Conjugated diene rubber containing 30% by mass or more of specific conjugated diene rubber and 15% by mass or more of natural rubber,
With silica
Contains a silane coupling agent,
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.
In the first step, 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 polymer chain having the active terminal with respect to 1 mol of the polymerization initiator used in the first step, in the polyorganosiloxane. The second step of adding and reacting the siloxane structure (-Si-O-) at a ratio of 1 mol or more in terms of the number of repeating units, and the conjugated diene-based weight obtained by reacting the polyorganosiloxane obtained in the second step. A rubber composition for a tire tread, which is a conjugated diene-based rubber produced by a method for producing a conjugated diene-based rubber, which comprises a third step of reacting a coalesced chain with a compound represented by the following general formula (2).

In the 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, and these may be the same or different from each other.
In the general formula (1), X ¹ and X ⁴ have 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 an epoxy group having an epoxy group. Any group selected from the group consisting of 4 to 12 groups, which may be the same or different from each other.
In the general formula (1), X ² is a group having 4 to 12 carbon atoms containing alkoxy group or an epoxy group, of 1 to 5 carbon atoms, a plurality of X ² may be they are identical to each other It may be different.
In the general formula (1), X ³ is a group containing repeating units of 2 to 20 alkylene glycols, and when there are a plurality of X ³ , they may be the same or different from each other.
In the 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 the general formula (2), R ⁹ is a hydrocarbyl group.
In the general formula (2), A ¹ is Ri Oh a group capable of reacting with the reactive residues formed by the reaction of a conjugated diene polymer chain polyorganosiloxane having active end, -OR 10 ^{(R 10} is Ru Oh a group represented by hydrogen or a hydrocarbyl group).
In the general formula (2), A ² is a monovalent group containing a nitrogen atom (excluding a group containing an oxygen atom).
In 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. The specific conjugated diene rubber
A polymer block (A) containing 80 to 100% by mass of an isoprene monomer unit and 0 to 20% by mass of an aromatic vinyl monomer unit, and
The claim has a structure in which a polymer block (B) containing 50 to 100% by mass of a 1,3-butadiene monomer unit and 0 to 50% by mass of an aromatic vinyl monomer unit is continuously formed. 1 is a rubber composition for tire tread. The rubber composition for a tire tread according to claim 1 or 2, wherein the vinyl bond content in the conjugated diene monomer unit in the specific conjugated diene rubber is 30% by mass or more. The rubber composition for a tire tread according to any one of claims 1 to 3, wherein the vinyl bond content in the conjugated diene monomer unit in the specific conjugated diene rubber is 50% by mass or more. A pneumatic tire including a tire tread portion manufactured by using the rubber composition for tire tread according to any one of claims 1 to 4.