JP2019199524A - Rubber composition for tire tread, and pneumatic tire - Google Patents

Abstract

To provide a rubber composition for a tire tread which is excellent in wet performance, rolling performance, and dry steering stability when formed into a tire, and to provide a pneumatic tire using the rubber composition for a tire tread.SOLUTION: The rubber composition for a tire tread contains: a conjugated diene rubber containing 30 mass% or more of a specific conjugated diene rubber produced by a method for producing a conjugated diene rubber comprising specific steps and 20 mass% or more of a styrene-butadiene rubber; a predetermined amount of silica; and a predetermined amount of a silane coupling agent. The content of an aromatic vinyl monomer unit in the specific conjugated diene rubber is 20-45 mass%. The content of vinyl bonds in a conjugated diene monomer unit in the specific conjugated diene rubber is 20-70 mass%. The glass transition temperature and the weight average molecular weight of the specific conjugated diene rubber are within predetermined ranges.SELECTED DRAWING: Figure 1

Description

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

In recent years, from the viewpoint of safety during vehicle travel, improvements in tire wet performance (wet grip performance) (braking performance on wet road surfaces) have been demanded. In addition, from the viewpoint of low fuel consumption during vehicle travel, improvement in tire rolling performance (low rolling resistance) is required. On the other hand, a method is known in which silica is added to a rubber component constituting a tread portion of a tire to improve wet performance and rolling performance.
However, since silica has a low affinity with the rubber component and has high cohesiveness between silicas, even if silica is simply blended with the rubber component, the silica does not disperse and has the effect of improving wet performance and rolling performance. There was a problem that it could not be obtained sufficiently.

  Under such circumstances, for example, Claim 1 of Patent Document 1 includes 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. Things are disclosed. Patent Document 1 describes that the tire tread rubber composition exhibits excellent wet performance and rolling performance when formed into a tire.

JP 2016-47887 A

  In recent years, with the improvement of the required safety level, further improvement of the wet performance of the tire is desired. Further, due to environmental problems and resource problems, further improvements in tire rolling performance are also demanded. Further, further improvement in tire dry handling stability (braking performance on a dry road surface) is also desired.

  Under such circumstances, the present inventors prepared a rubber composition for a tire tread with reference to the example of Patent Document 1, and made wet performance when made into a tire, rolling performance when made into a tire, and made into a tire. When evaluating the stability of dry maneuvering at times, it became clear that further improvements would be desirable in view of demands that would increase further in the future.

  Therefore, the present invention provides a tire tread rubber composition excellent in wet performance when made into a tire, rolling performance when made into a tire, and dry maneuvering stability performance when made into a tire, and the tire tread rubber composition It is an object to provide a pneumatic tire using an object.

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

[1]
A conjugated diene rubber containing 30% by mass or more of a specific conjugated diene rubber and 20% by mass or more of a styrene butadiene rubber other than the specific conjugated diene rubber;
Silica,
Containing 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,
The specific conjugated diene rubber polymerizes a monomer containing a conjugated diene compound and an aromatic vinyl compound in an inert solvent using a polymerization initiator to obtain a conjugated diene polymer chain having an active terminal. In the first step and the conjugated diene polymer chain having the active terminal, polyorganosiloxane represented by the following general formula (1) is used with respect to 1 mol of the polymerization initiator used in the first step. The second step of adding and reacting at a ratio of 1 mol or more in terms of the number of repeating units of the siloxane structure (—Si—O—) in the polyorganosiloxane and the polyorganosiloxane obtained in the second step are reacted. A conjugated diene rubber produced by a method for producing a conjugated diene rubber comprising a third step of reacting a compound represented by the following general formula (2) with the conjugated diene polymer chain thus produced.
The content of the aromatic vinyl monomer unit in the specific conjugated diene rubber is 20 to 45% by mass, and the vinyl bond content in the conjugated diene monomer unit in the specific conjugated diene rubber is 20 to 70. Mass%,
The specific conjugated diene rubber is a rubber composition for tire treads having a glass transition temperature of −35 to −15 ° C. and a weight average molecular weight (Mw) of 350,000 to 1,000,000.
[2]
The rubber composition for a tire tread according to [1], wherein the styrene-butadiene rubber has a functional group that interacts with silica.
[3]
The rubber composition for tire treads according to [1] or [2], wherein the total content of rubber components having functional groups that interact with silica in the conjugated diene rubber is 80% by mass or more.
[4]
The styrene butadiene rubber according to any one of [1] to [3], wherein a molecular weight distribution (Mw / Mn) obtained from a weight average molecular weight (Mw) and a number average molecular weight (Mn) is 2.0 or more. Rubber composition for tire tread.
[5]
The rubber composition for a tire tread according to any one of [1] to [4], wherein the conjugated diene rubber contains 10% by mass or more of a rubber component other than the specific conjugated diene rubber and the styrene butadiene rubber.
[6]
The specific conjugated diene rubber is
A polymer block (A) comprising 80 to 100% by mass of isoprene monomer units and 0 to 20% by mass of aromatic vinyl monomer units;
The polymer block (B) containing 50 to 100% by mass of 1,3-butadiene monomer units and 0 to 50% by mass of aromatic vinyl monomer units has a structure formed in a continuous manner [1 ] The rubber composition for tire treads in any one of [5].
[7]
A pneumatic tire provided with the tire tread part manufactured using the rubber composition for tire treads in any one of [1]-[6].

  As shown below, according to the present invention, wet performance when tired (hereinafter also simply referred to as “wet performance”), rolling performance when tired (hereinafter also simply referred to as “rolling performance”), Also provided are a rubber composition for a tire tread which is excellent in dry handling stability performance (hereinafter also simply referred to as “dry handling stability performance”) when used as a tire, and a pneumatic tire using the rubber composition for tire tread. can do.

It is a partial section schematic diagram of an example of an embodiment of a pneumatic tire of the present invention.

Below, the rubber composition for tire treads of this invention and the pneumatic tire using the said rubber composition for tire treads are demonstrated.
In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
Moreover, each component contained in the rubber composition for tire treads of this invention may be used individually by 1 type, or may use 2 or more types together. Here, when using 2 or more types together about each component, unless there is particular notice, content refers to the total content about the component.
In the present specification, “(meth) acryl” is a notation representing “acryl” 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 “the composition of the present invention”) includes 30% by mass or more of the specific conjugated diene rubber, and the specific conjugated diene system. A conjugated diene rubber containing 20% by mass or more of styrene butadiene rubber other than rubber (hereinafter also referred to as “styrene butadiene rubber (A)”), silica, and a silane coupling agent.
Here, 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 masses with respect to the content of the silica. %.
The specific conjugated diene rubber is obtained by polymerizing a monomer containing a conjugated diene compound and an aromatic vinyl compound in an inert solvent using a polymerization initiator, and having a conjugated diene polymer chain having an active terminal. The polyorganosiloxane represented by the following general formula (1) is added to 1 mol of the polymerization initiator used in the first step in the conjugated diene polymer chain having the active terminal. A second step of adding and reacting at a ratio of 1 mol or more in terms of the number of repeating units of the siloxane structure (-Si-O-) in the polyorganosiloxane, and the polyorganosiloxane obtained in the second step. A conjugated diene rubber produced by a method for producing a conjugated diene rubber comprising a third step of reacting a compound represented by the following general formula (2) with a reacted conjugated diene polymer chain: .
Further, the content of the aromatic vinyl monomer unit in the specific conjugated diene rubber is 20 to 45% by mass, and the vinyl bond content in the conjugated diene monomer unit in the specific conjugated diene rubber is 20%. -70 mass%.
The specific conjugated diene rubber has a glass transition temperature of −35 to −15 ° C. and a weight average molecular weight (Mw) of 350,000 to 1,000,000.
Since the composition of this invention takes such a structure, it is thought that the effect mentioned above is acquired. The reason is not clear, but it is presumed that it is as follows.

As described above, since the composition of the present invention contains silica, it is expected that the wet performance and the rolling performance are compatible at a high level. However, silica easily aggregates, and the above effect is actually satisfied. There is a problem that it is not expressed.
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 silica, the polyorganosiloxane structure has an affinity for silica and prevents aggregation of silica. Conceivable. In addition, since the specific conjugated diene rubber also has a structure derived from a nitrogen atom-containing silane such as aminosilane, it is considered that this promotes silanization between the silane coupling agent and silica and further suppresses aggregation of silica. . As a result, it is considered that the effect of silica (coexisting wet performance and rolling performance at a high level) is sufficiently exhibited.
In addition, it is considered that the increase in the rubber component bonded to the silica improves the reinforcement to the rubber and enhances the rigidity of the rubber compound, thereby sufficiently exhibiting the dry steering stability.

  Hereinafter, each component contained in the composition of this invention is explained in full 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 20% by mass or more of the styrene butadiene rubber (A).
First, the specific conjugated diene rubber will be described, and then the styrene butadiene rubber (A) will be described.

[Specific conjugated diene rubber]
The specific conjugated diene rubber contained in the composition of the present invention is a conjugated diene rubber produced by a method for producing a conjugated diene rubber comprising the following first to third steps.
(1) First Step First, a monomer containing a conjugated diene compound and an aromatic vinyl compound is polymerized in an inert solvent using a polymerization initiator to obtain a conjugated diene polymer chain having an active terminal. Step (2) Second Step 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. The second step (3) and the third step of adding and reacting at a ratio of 1 mol or more in terms of the number of repeating units of the siloxane structure (—Si—O—) in the polyorganosiloxane is obtained in the second step. Third step of reacting a compound represented by the general formula (2) described later with a conjugated diene polymer chain reacted with polyorganosiloxane.

First, the reason why the specific conjugated diene rubber is specified by the production method as described above will be described.
As described above, in the third step, the conjugated diene polymer chain obtained by reacting the polyorganosiloxane obtained in the second step is reacted with a compound represented by the following general formula (2). 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, since the reaction residue generated by the reaction of the conjugated diene polymer chain having an active terminal and the polyorganosiloxane can have various structures, the reaction residue is represented by the general formula (2). The structure after the reaction of a compound is extremely complex, and it is technically impossible to analyze the structure, or it is extremely excessive economic expenditure and time to perform the work of identifying the structure. Cost. Therefore, to describe a specific conjugated diene rubber as “a conjugated diene rubber produced by a method of producing a conjugated diene rubber comprising first to third steps”, there is a so-called “impossible / unpractical situation”. Exists.

  Hereinafter, each step will be described.

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

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

<Aromatic vinyl compound>
In the first step, an aromatic vinyl compound is used together with a conjugated diene compound as a monomer used for polymerization. Aromatic vinyl compounds used as monomers include styrene, methylstyrene, ethylstyrene, t-butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, chlorostyrene, bromostyrene, methoxystyrene, dimethylamino Examples thereof include methyl styrene, dimethylaminoethyl styrene, diethylaminomethyl styrene, diethylaminoethyl styrene, cyanoethyl styrene and vinyl naphthalene. 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 55 to 80% by mass of a conjugated diene monomer unit because the effect of the present invention is more excellent. %, More preferably 20 to 45% by mass of aromatic vinyl monomer units, and more preferably 25 to 45% by mass.

<Other copolymerizable compounds>
Furthermore, in the first step, a compound copolymerizable with the conjugated diene compound (other copolymerizable compounds) 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 chain olefin compounds such as ethylene, propylene and 1-butene; cyclic olefin compounds such as cyclopentene and 2-norbornene; 1,5-hexadiene, 1,6- Non-conjugated diene compounds such as heptadiene, 1,7-octadiene, dicyclopentadiene, 5-ethylidene-2-norbornene; (methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate) (Meth) acrylic acid ester; (meth) acrylonitrile, other (meth) acrylic acid derivatives such as (meth) acrylamide; and the like. For the reason that the effect of the present invention is more excellent, the compounds copolymerizable with these conjugated diene compounds are 10 monomer units in the conjugated diene polymer chain having an active end obtained in the first step. It is preferable to set it as mass% or less, and it is more preferable to set it as 5 mass% or less.

<Inert solvent>
The inert solvent used for the polymerization is not particularly limited as long as it is one usually used in solution polymerization and 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; Etc. These inert solvents may be used individually by 1 type, and may be used in combination of 2 or more type. The amount of the inert solvent used is not particularly limited, but the monomer concentration is, for example, 1 to 50% by mass, and the effect of the present invention is more excellent. preferable.

<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 polymer chain having an active end. Specific examples thereof include a polymerization initiator having 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-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbenelithium; 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, di-t-butoxystrontium, diethoxybarium, and diisopropoxy. Examples include barium, diethyl mercaptobarium, di-t-butoxybarium, diphenoxybarium, diethylaminobarium, barium distearate, and diketylbarium. As a polymerization initiator having a lanthanum series metal compound as a main catalyst, for example, a lanthanum series metal comprising a lanthanum series metal such as lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, a carboxylic acid, and a phosphorus-containing organic acid. And a polymerization initiator composed of this salt and a cocatalyst such as an alkylaluminum compound, an organoaluminum hydride compound, and an organoaluminum halide compound. Among these polymerization initiators, an organic monolithium compound and an organic polylithium compound are preferably used, an organic monolithium compound is more preferably used, and n-butyllithium is particularly preferable because the effect of the present invention is more excellent. 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 form an organic alkali metal amide compound. May be used. These polymerization initiators may be used individually by 1 type, and may be used in combination of 2 or more type.

  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 used suitably.

In General Formula (3), M ¹ represents an alkali metal atom, and R ¹¹ and R ¹² are each independently an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an amino group protecting group, or a hydrolysis group. 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 in the case of forming the ring structure, these are bonded to each other. In addition to the nitrogen atom to be formed, a ring structure may be formed together with a hetero atom other than the nitrogen atom to which they are bonded.

  Although it does not specifically limit as an alkyl group, From the reason for which the effect of this invention is more excellent, a C1-C20 alkyl group is preferable and a C1-C10 alkyl group is more preferable. 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-to. A xyl group, n-heptyl group, n-octyl group, n-decyl group, etc. are mentioned.

  Although it does not specifically limit as a cycloalkyl group, From the reason for which the effect of this invention is more excellent, a C3-C20 cycloalkyl group is preferable and a C3-C12 cycloalkyl group is more preferable. Examples of such cycloalkyl groups include a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and a cyclododecyl group.

  Although it does not specifically limit as an aryl group, From the reason for which the effect of this invention is more excellent, a C6-C12 aryl group is preferable and a C6-C10 aryl group is more preferable. Examples of such an aryl group include a phenyl group, a 1-naphthyl group, and a 2-naphthyl group.

  Although it does not specifically limit as an aralkyl group, From the reason for which the effect of this invention is more excellent, a C7-C13 aralkyl group is preferable and a C7-C9 aralkyl group is more preferable. Examples of such aralkyl groups include benzyl group and phenethyl group.

The amino-protecting group is not particularly limited and may be any group that acts as an amino-protecting 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, and a tert-butyldimethylsilyl group.
In the case where R ¹¹ and / or R ¹² is a protecting group for an amino group, the protecting group for the amino group is removed, so that at one end of the polymer chain forming the resulting conjugated diene rubber, 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 form a hydroxyl group is not particularly limited, and may be any group that generates a hydroxyl group by hydrolysis in the presence of an acid, for example, an alkoxyalkyl group, an epoxy group, and the like. And a group 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, and a propoxyethyl group.
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 General Formula (4), Z ¹ is an alkylene group having 1 to 10 carbon atoms or an alkylarylene group, Z ² is a methylene group, a sulfur atom or an oxygen atom, and E ¹ is a glycidyl group.

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 in this case, formed by R ¹¹ and R ¹² and the nitrogen atom that is bonded to this. Specific examples of the structure include azetidine ring (R ¹¹ and R ¹² are propylene groups), pyrrolidine ring (R ¹¹ and R ¹² are butylene groups), piperidine ring (R ¹¹ and R ¹² are pentylene groups) And hexamethyleneimine ring (R ¹¹ and R ¹² are hexylene groups) 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.

In general formula (3), M ¹ is an alkali metal atom, and examples of such an alkali metal atom include a lithium atom, a sodium atom, and a potassium atom. Among these, from the viewpoint of polymerization activity. A lithium atom is preferable.

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

In general formula (5), R ¹³ and R ¹⁴ each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, a protective group for an amino group, or a hydroxyl group upon hydrolysis. R ¹³ and R ¹⁴ may be bonded to each other to form a ring structure together with the nitrogen atom to which they are bonded, and in the case of forming the ring structure, in addition to the nitrogen atom to which they are bonded, A ring structure may be formed 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-protecting group which can be R ¹³ and R ¹⁴ , or a group capable of hydrolyzing to generate a hydroxyl group include R ¹¹ and R ¹² in formula (3). In the case where R ¹³ and R ¹⁴ are bonded to each other to form a ring structure together with the nitrogen atom to which R ¹³ and R ¹⁴ are bonded, R ¹¹ and R ¹² in the general formula (3) Can be the same.
In addition, the hydrogen atom which can become R < ¹³ >, R < ¹⁴ > is introduce | transduced when the protecting group of an amino group remove | deviates.

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

  The method of adding the organic alkali metal amide compound as a polymerization initiator to the polymerization system is not particularly limited, and a secondary amine compound is reacted with the organic alkali metal compound in advance to obtain an organic alkali metal amide compound. A method of mixing this with a monomer containing a conjugated diene compound and allowing the polymerization reaction to proceed can be employed. Alternatively, an organic alkali metal amide compound is generated in the polymerization system by adding the organic alkali metal compound and the secondary amine compound separately to the polymerization system and mixing them with a monomer containing a conjugated diene compound. Thus, a method of advancing the polymerization reaction may be employed. The reaction conditions such as the reaction temperature are not particularly limited, and may be according to the intended polymerization reaction conditions, for example.

  The amount of 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. 0.2 mmol is preferable, and 0.5 to 1.0 mmol is more preferable.

  The amount of the polymerization initiator used may be determined according to the molecular weight of the target conjugated diene polymer chain, but usually 1 to 50 mmol and 1.5 to 20 mmol are preferred per 1000 g of monomer. A range of ˜15 mmol is more preferred.

<Polymerization temperature>
The polymerization temperature is usually from −80 to + 150 ° C., and the effect of the present invention is more excellent. As the polymerization mode, any of batch type and continuous type can be adopted. However, when copolymerizing a conjugated diene compound and an aromatic vinyl compound, a conjugated diene monomer unit and an aromatic vinyl monomer are used. The batch method is preferable because the randomness of the bond with the unit can be easily controlled.

<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 resulting conjugated diene polymer chain. It 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. Among these, an ether compound and a tertiary amine are preferable, a tertiary amine is more preferable, and tetramethylethylenediamine is particularly preferable because the effect of the present invention is more excellent. These polar compounds may be used singly or in combination of two or more. What is necessary is just to determine the usage-amount of a polar compound according to the vinyl bond content made into the objective, 0.001-100 mol is preferable with respect to 1 mol of polymerization initiators, and 0.01-10 mol is more preferable. When the amount of the polar compound used is within this range, it is easy to adjust the vinyl bond content in the conjugated diene monomer unit, and problems due to the deactivation of the polymerization initiator hardly occur.

<Vinyl bond content>
The vinyl bond content in the conjugated diene monomer unit in the conjugated diene polymer chain having an active end obtained in the first step is preferably 20 to 70% by mass because the effect of the present invention is more excellent. 25-65 mass% is more preferable, and 30-63 mass% is especially preferable.

<Molecular weight>
Although the weight average molecular weight (Mw) of the conjugated diene polymer chain having an active terminal obtained in the first step is not particularly limited, it is measured by gel permeation chromatography in terms of polystyrene because the effect of the present invention is more excellent. The value is preferably 350,000 to 1,000,000, more preferably 400,000 to 900,000, and particularly preferably 450,000 to 800,000.

  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 end 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 production of the conjugated diene rubber is facilitated.

<Preferred embodiment>
The first step is preferably the following step because the effect of the present invention is more excellent.
That is, isoprene or a monomer containing isoprene and an aromatic vinyl compound is polymerized with a polymerization initiator in an inert solvent, and isoprene monomer units 80 to 100% by mass and aromatic vinyl monomer units 0 Step A of forming a polymer block (A) having an active end containing ˜20% by mass;
The polymer block (A) having the active terminal and a monomer containing 1,3-butadiene or 1,3-butadiene and an aromatic vinyl compound are mixed to continue the polymerization reaction, and 1,3 -A polymer block (B) having an active 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 continuously with the polymer block (A). It is preferable to provide Step B to obtain a conjugated diene polymer chain having an active end.
However, the content of at least one aromatic vinyl monomer unit in the polymer block (A) and the polymer block (B) is more than 0% by mass.

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

(Process A)
The polymer block (A) formed in the step A is one containing 80 to 100% by mass of isoprene monomer units and 0 to 20% by mass of aromatic vinyl monomer units in the polymer block (A). However, from the reason that the effect of the present invention is more excellent, those containing 85 to 95% by mass of isoprene monomer units and 5 to 15% by mass of aromatic vinyl monomer units are preferable, and isoprene monomer units 89 to 89%. What contains 95 mass% and 5-11 mass% of aromatic vinyl monomer units is more preferable.

  As the aromatic vinyl compound used for constituting the aromatic vinyl monomer unit contained in the polymer block (A), the same aromatic vinyl compound as described above can be used, and the effect of the present invention is achieved. Of these, styrene is preferred for reasons of superiority. 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 an isoprene monomer unit or an isoprene monomer unit and an aromatic vinyl monomer unit because the effects of the present invention are more excellent. In addition to the monomer unit or the isoprene monomer unit and the aromatic vinyl monomer unit, other monomer units may be included. Other compounds used to constitute other monomer units include 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3 Conjugated diene compounds other than isoprene such as pentadiene and 1,3-hexadiene; α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and maleic anhydride Or acid anhydrides; unsaturated carboxylic esters such as methyl methacrylate, ethyl acrylate, and butyl acrylate; 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5 -Non-conjugated dienes such as ethylidene-2-norbornene; Among these, 1,3-butadiene is preferable because the 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 more preferably 6% by mass or less because the effect of the present invention is more excellent. Further preferred.

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

  In order to form the polymer block (A), the same inert solvent as described above may be used as the inert solvent used for the polymerization of the monomer containing isoprene or isoprene and an aromatic vinyl compound. 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, because the effect of the present invention is more excellent.

  As a polymerization initiator used to form the polymer block (A), isoprene or a monomer containing isoprene and an aromatic vinyl compound is polymerized to give a polymer chain having an active end. If it can do, it will not specifically limit. 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 in accordance with the target molecular weight. However, for the reason that the effect of the present invention is more excellent, it is 4 per 100 g of monomer containing isoprene or isoprene and an aromatic vinyl compound. -250 mmol is preferable, 6-200 mmol is more preferable, and the range of 10-70 mmol is particularly preferable.

  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. A range of 20 to 90 ° C. is particularly preferable. As the polymerization mode, any mode such as batch mode or continuous mode can be adopted. Moreover, as a coupling | bonding mode, it can be set as various coupling | bonding modes, such as block shape, a taper shape, and random shape, for example.

  Moreover, in order to adjust the vinyl bond content in the isoprene monomer unit in the polymer block (A) for the reason that the effect of the present invention is more excellent, a polar compound may be added to the inert solvent during the polymerization. preferable. As a polar compound, the same thing as the polar compound mentioned above can be used. What is necessary is just to determine the usage-amount of a polar compound according to the vinyl bond content made into the objective, 0.01-30 mol is preferable with respect to 1 mol of polymerization initiators, and 0.05-10 mol is more preferable. 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 the deactivation of the polymerization initiator hardly occur. Moreover, the vinyl bond content in an isoprene monomer unit can be increased by increasing the usage-amount of a polar compound within the said range.

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

  The weight average molecular weight (Mw) of the polymer block (A) is preferably from 500 to 15,000 as a polystyrene conversion value measured by gel permeation chromatography because the effect of the present invention is more excellent. 1,000 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) and the number average molecular weight (Mn) of the polymer block (A) is 1.0 because the effect of the present invention is more excellent. -1.5 is preferable and 1.0-1.3 is more preferable. When the value (Mw / Mn) of the molecular weight distribution of the polymer block (A) is within the above range, the production of the conjugated diene rubber becomes easier.

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

  As the aromatic vinyl compound used for constituting the aromatic vinyl monomer unit contained in the polymer block (B), the same aromatic vinyl compound as described above can be used. Styrene is preferred for the reason that the effect of the invention is more excellent.

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

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

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

  When the polymer block (B) is formed, the amount of the polymer block having an active terminal (A) may be determined according to the target molecular weight, but because the effect of the present invention is more excellent, 0.1 to 5 mmol is preferable, 0.15 to 2 mmol is preferable, and 0.1 to 2 mmol is preferable per 100 g of monomer containing 1,3-butadiene or 1,3-butadiene and an aromatic vinyl compound. Particularly preferred is mmol.

  The mixing method of the polymer block (A) and 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 -The 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 in the solution of the polymer block (A) having an active end. A monomer containing butadiene or 1,3-butadiene and an aromatic vinyl compound may be added. From the viewpoint of controlling the polymerization, a method of adding a polymer block (A) having an active end 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 1,3-butadiene or a monomer containing 1,3-butadiene and an aromatic vinyl compound is preferably −80 to + 150 ° C. because the effect of the present invention is more excellent. -100 degreeC is more preferable, and 20-90 degreeC is especially preferable. As the polymerization mode, any mode such as batch mode or continuous mode can be adopted. When the polymer block (B) is used as a copolymer chain, a batch system is preferable because the randomness of the bonds can be easily controlled.

  When the polymer block (B) is used as a copolymer chain, the bonding mode of each monomer may be various bonding modes such as a block shape, a taper shape, and a random shape. Among these, random is preferable because the effect of the present invention is more excellent. In the case where the bonding mode of 1,3-butadiene and the aromatic vinyl compound is random, the total 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. It is preferable.

  Moreover, in order to adjust the vinyl bond content in the 1,3-butadiene monomer unit in the polymer block (B) for the reason that the effect of the present invention is more excellent, the amount of isoprene in the polymer block (A) is adjusted. Similarly to the adjustment of the vinyl bond content in the body unit, it is preferable to add a polar compound to the inert solvent during the polymerization. However, at the time of preparing the polymer block (A), the polar compound in an amount sufficient to adjust the vinyl bond content in the 1,3-butadiene monomer unit in the polymer block (B) to the inert solvent Is added, a new polar compound may not be added. 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 start used for the first polymerization reaction (polymerization reaction for forming the first polymer block (A)) It is preferable to adjust in the range of 0.01-100 mol with respect to 1 mol of agent, and it is more preferable to adjust in the range of 0.1-30 mol. 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 the deactivation of the polymerization initiator hardly occur.

  The vinyl bond content in the 1,3-butadiene monomer unit in the polymer block (B) is preferably 1 to 90% by mass and more preferably 3 to 80% by mass because the effect of the present invention is more excellent. 5 to 70% by mass is particularly preferable.

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

  The mass ratio of the polymer block (A) to the polymer block (B) in the conjugated diene polymer chain having an active end (when there are a plurality of polymer blocks (A) and polymer blocks (B), (Mass ratio based on the total mass of) is 0.001-0 in terms of (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.

  A total monomer unit of an isoprene monomer unit and a 1,3-butadiene monomer unit in a conjugated diene polymer chain having an active end and having a polymer block (A) and a polymer block (B); The content ratio with the aromatic vinyl monomer unit is the reason why the effect of the present invention is more excellent, and isoprene monomer unit and 1,3-butadiene monomer in the conjugated diene polymer chain having an active end. The total monomer unit of 55 to 80% by mass and the aromatic vinyl monomer unit of 20 to 45% by mass are preferable. The total monomer unit of isoprene monomer unit and 1,3-butadiene monomer unit 55 -75 mass% and 25-45 mass% of aromatic vinyl monomer units are more preferable. In addition, vinyl bonds in the isoprene monomer unit and in the 1,3-butadiene monomer unit in the conjugated diene polymer chain having an active end having the polymer block (A) and the polymer block (B). The total content of is preferably 20 to 70% by mass, more preferably 25 to 65% by mass, and particularly preferably 30 to 63% by mass because the effects of the present invention are more excellent.

[Second step]
The second step is a polymerization initiator 1 in which a polyorganosiloxane represented by the following general formula (1) is used in the first step for the conjugated diene polymer chain having an active terminal obtained in the first step. It is a step of adding and reacting at a ratio of 1 mole or more in terms of the number of repeating units of the siloxane structure (—Si—O—) in the polyorganosiloxane with respect to the mole.
Here, the siloxane structure interacts with silica. Therefore, the specific conjugated diene rubber has a functional group that interacts with silica.

In the general formula (1), R ^{1 to} R ⁸ are an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and these may be the same as or different from each other. X ¹ and X ⁴ are each composed of a C 1-6 alkyl group, a C 6-12 aryl group, a C 1-5 alkoxy group, and a C 4-12 group containing an epoxy group. Any group selected from the group may be the same or different. 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 alkylene glycol repeating units, and when there are a plurality of X ³ , they may be the same as 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), the alkyl group having 1 to 6 carbon atoms that can constitute R ^{1 to} R ⁸ , X ¹ and X ⁴ in the general formula (1) is, for example, methyl Group, ethyl group, n-propyl group, isopropyl group, butyl group, pentyl group, hexyl group and 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 ease of production of the polyorganosiloxane itself.

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, a propoxy group, An isopropoxy group, a butoxy group, etc. are mentioned. Among these, a methoxy group and an ethoxy group are preferable from the viewpoint of ease of production of the polyorganosiloxane itself.

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

In addition, 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 effects of the present invention are more excellent among the above. Or, an alkyl group having 1 to 6 carbon atoms is preferable. X ² is preferably a group having 4 to 12 carbon atoms containing an epoxy group because the effects of the present invention are more excellent. Furthermore, from the reason that the effect of the present invention is more excellent, X ¹ and X ⁴ are alkyl groups having 1 to 6 carbon atoms, and X ² is more preferably a group having 4 to 12 carbon atoms containing an epoxy group.

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

In general formula (7), t is an integer of 2 to 20, X ⁵ is an alkylene group or alkylarylene group having 2 to 10 carbon atoms, R ¹⁵ is a hydrogen atom or a methyl group, and X ⁶ is carbon. It is an alkoxy group or aryloxy group of formula 1-10. 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 general formula (7), * is a bonding 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 resulting conjugated diene rubber increases, and as a result, the effects of the present invention are more excellent. Moreover, when m is 200 or less, the production of the polyorganosiloxane itself represented by the general formula (1) becomes easier, and the viscosity does not become too high, and handling becomes easier.

  Moreover, in the polyorganosiloxane represented by General formula (1), n is an integer of 0-200, the integer of 0-150 is preferable and the integer of 0-120 is more preferable. 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 end easily proceeds, and m, When the total number of n and k is 400 or less, the production of the polyorganosiloxane itself represented by the general formula (1) is facilitated, the viscosity thereof is not excessively increased, and the handling is facilitated.

  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 in the polymerization in the first step. 1 to 2.5 mol is preferable, and 1.1 to 2 mol is more preferable from the reason that the effect of the present invention is more excellent.

By making the amount of polyorganosiloxane used 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 is determined. Of the active ends of the conjugated diene polymer chain, substantially all active ends can be reacted with polyorganosiloxane, which is preferable. That is, an alkyl metal group as an active end of the conjugated diene polymer chain having an active end obtained by 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.

  Thus, when the compound represented by the general formula (2) is reacted in the third step to be described later, the compound represented by the general formula (2) is obtained from 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 polymer chain having the. As a result, the compound represented by the general formula (2) is reacted with the reaction residue generated by the reaction between the conjugated diene polymer chain and the polyorganosiloxane represented by the general formula (1). Can react appropriately. And thereby, the modified structure by the compound represented by the general formula (2) is appropriately introduced into the conjugated diene polymer chain via the structure derived from the polyorganosiloxane represented by the general formula (1). Thus, the effects of introducing such a modified structure, that is, excellent wet performance, rolling performance and dry steering stability performance can be realized.

  The method of reacting the polyorganosiloxane and the conjugated diene polymer chain having an active end is not particularly limited, and examples thereof include a method of mixing them in a solvent in which each can be dissolved. As the solvent used in this case, those exemplified as the inert solvent used in the first step described above can be used. In this case, a method of adding polyorganosiloxane to the polymerization solution used for polymerization for obtaining a conjugated diene polymer chain having an active end is simple and preferable. In this case, the polyorganosiloxane is preferably dissolved in an inert solvent and added to the polymerization system, and the solution concentration is preferably in the range of 1 to 50% by mass. Although reaction temperature is not specifically limited, Usually, it is 0-120 degreeC, Reaction time is also not specifically limited, Usually, it is 1 minute-1 hour.

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

In the second step, the polyorganosiloxane as a modifier is reacted with the active end of the conjugated diene polymer chain having the active end obtained in the first step. The active end of the combined chain will react with the silicon atom in the siloxane structure. Alternatively, a part of the active end of the conjugated diene polymer chain is partly an alkoxy group or epoxy group of the side chain of the polyorganosiloxane (an alkoxy group or an epoxy that forms X ² included as an essential component in the general formula (1)) Group) and the like. And according to the 2nd process, the modified structure by a siloxane is introduce | transduced into a conjugated diene type polymer chain by such reaction.

Specifically, the active end of the conjugated diene polymer chain reacts with a silicon atom in the siloxane structure, so that the conjugated diene polymer chain has a relationship between the silicon atom in the siloxane structure and the conjugated diene polymer chain. A new bond is formed between the active end and a 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 A group represented by —O ⁻ M ⁺ (where M is an alkali metal atom, an alkaline earth metal atom, or a lanthanum series metal atom) Is thought to be formed.

Alternatively, the active end of the conjugated diene polymer chain reacts with the epoxy group of the side chain of the polyorganosiloxane, so that the epoxy group is ring-opened, and the carbon atom in the portion where the epoxy group is opened and the conjugated diene-based polymer chain A new bond is formed with the active end of the polymer chain, and 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 It is considered that a group represented by -O ^- M ⁺ is formed as a reactive residue 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, whereby the alkoxy group is eliminated, and the conjugated diene polymer chain is conjugated with the silicon atom in the siloxane structure. A new bond is formed with the active end of the diene polymer chain, and a siloxane structure is introduced at the end of the conjugated diene polymer chain.

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

  In the second step, when the polyorganosiloxane represented by the general formula (1) is reacted with the conjugated diene polymer chain having an active terminal, the effect of the present invention is not impaired. In addition, a part of the active end of the conjugated diene polymer chain having an active end may be subjected to coupling or modification by adding a coupling agent or a modifier that has been conventionally used in the polymerization system. Good.

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

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 end 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, an alkyl metal group as an active end of the conjugated diene polymer chain having an active end obtained in the first step, that is, of -R ^- M ⁺ , Assuming that not all remains, instead of having a group represented by -O ^- M ⁺ as a reaction residue by reaction with the polyorganosiloxane represented by the general formula (1) are, according to the third step of the present invention, compounds represented by the general formula (2) is, as such reaction residues -O ^- group represented by M ⁺ (-O ^- in M ⁺ In which the group represented is hydrolyzed and converted to a hydroxyl group).

That is, according to the present invention, the compound represented by the general formula (2) reacts with the group represented by -R ^- M ⁺ , so that the general formula is directly added to the conjugated diene polymer chain. It is possible to appropriately suppress the introduction of the modified structure due to the compound represented by (2), and thereby to the polyorganosiloxane represented by the general formula (1) in the conjugated diene polymer chain. A modified structure of the compound represented by the general formula (2) through the derived structure can be appropriately introduced. As a result, excellent wet performance, rolling performance, and dry steering stability performance can be realized.

However, the conjugated diene polymer chain reacted with polyorganosiloxane used in the third step is not limited as long as it has undergone the second step described above, and is a conjugated diene polymer introduced with a modified structure by siloxane. In addition to the chain, if the amount is very small (for example, 5% by mass or less), a conjugated diene polymer chain having an unmodified active terminal having no siloxane-modified structure introduced may remain ( That is, if the amount is very small, an alkyl metal group as an active end of the conjugated diene polymer chain having an active end obtained in the first step, that is, a residue of -R ^- M ⁺ is included. At best), and further, modified structure by siloxane is formed a result of the introduction, -O as a reaction residue ^- the M ⁺ portion of hydrolyzed, converted into a hydroxyl group It may include from.

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. From the reason that the effect of the present invention is more excellent, an alkyl group having 1 to 6 carbon atoms is preferable. 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, and a hexyl group. Among these, the effects of the present invention are more effective. A methyl group and an ethyl group are more preferable because of superiority.

In the compound represented by the general formula (2), A ¹ in the general formula (2) represents a reaction residue (typically formed by a reaction between a conjugated diene polymer chain having an active end and a polyorganosiloxane. Is a group capable of reacting with a group represented by —O ^— M ⁺ , and a group represented by —OR ¹⁰ (R ¹⁰ is a hydrogen atom or a hydrocarbyl group) is preferable. 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. Six alkyl groups are 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, and a hexyl group. Among these, the effects of the present invention are more effective. A methyl group and an ethyl group are more preferable because of superiority.

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- Such as Minopuropiru group, and the like. Among these, primary amino groups having an active hydrogen atom such as 3-aminopropyl group, 4-aminobutyl group, 3- (2-aminoethylamino) propyl group, and the like because the effects of the present invention are more excellent. A group containing a secondary amino group having an active hydrogen atom is preferred. The “active hydrogen atom” means a hydrogen atom bonded to an atom other than a carbon atom, and preferably has a bond energy lower than that of a polymethylene chain.

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

Specific examples of the compound represented by the general formula (2) are not particularly limited. For example, A ² in the general formula (2) represents 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 having 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-aminobutyldimethylethoxysilane, 4 Aminobutyl methyl diethoxy silane, a compound having a 4-aminobutyl group as A ^2, such as 4-aminobutyl triethoxysilane; 3- (2-aminoethylamino) propyl dimethyl silane, 3- (2-aminoethylamino ) Propylmethyldimethoxysilane, 3- (2-aminoethylamino) propyltrimethoxysilane, 3- (2-aminoethylamino) propyldimethylethoxysilane, 3- (2-aminoethylamino) propylmethyldiethoxysilane, 3 Examples of A ² such as-(2-aminoethylamino) propyltriethoxysilane include compounds having a 3- (2-aminoethylamino) propyl group.

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 as a ² such as 3- compounds having dimethylaminopropyl group; 3-diethylamino-propyl trimethoxysilane, 3-diethylamino-propyl methyl dimethoxy silane, 3-diethylaminopropyl dimethyl silane, 3-diethylamino B pills triethoxysilane, 3-diethylamino-propyl methyl diethoxy silane, 3-diethylaminopropyl dimethylethoxysilane as A ^2, such as a compound having a 3-diethylamino-propyl; 3-dipropyl-aminopropyltrimethoxysilane, 3-di A such as propylaminopropylmethyldimethoxysilane, 3-dipropylaminopropyldimethylmethoxysilane, 3-dipropylaminopropyltriethoxysilane, 3-dipropylaminopropylmethyldiethoxysilane, 3-dipropylaminopropyldimethylethoxysilane as ^2, 3 compounds with dipropylamino-propyl; 3-dibutyl-aminopropyltrimethoxysilane, 3-dibutyl-aminopropyl methyl dimethoxy silane, 3- Jibuchiruami Dimethyl methoxy silane, 3-dibutyl-aminopropyltriethoxysilane, 3-dibutyl-aminopropyl methyl diethoxy silane, 3 as A ^2, such as dibutyl-aminopropyldimethylethoxysilane, compounds having a 3-dibutyl aminopropyl group; 3- Phenylmethylaminopropyltrimethoxysilane, 3-phenylmethylaminopropylmethyldimethoxysilane, 3-phenylmethylaminopropyldimethylmethoxysilane, 3-phenylmethylaminopropyltriethoxysilane, 3-phenylmethylaminopropylmethyldiethoxysilane, 3 - as a ^2, such as phenyl methyl aminopropyldimethylethoxysilane, compounds having a 3-phenylmethyl-aminopropyl group; 3- (4-methylpiperazinyl) flop Lopyltrimethoxysilane, 3- (4-methylpiperazinyl) propylmethyldimethoxysilane, 3- (4-methylpiperazinyl) propyldimethylmethoxysilane, 3- (4-methylpiperazinyl) propyltriethoxysilane 3- (4-methylpiperazinyl) propylmethyldiethoxysilane, 3- (4-methylpiperazinyl) propyldimethylethoxysilane and the like as A ² , a 3- (4-methylpiperazinyl) propyl group Having a compound;

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 (triethyl A compound having a ryl) aminopropyl group; N, N ′, N′-tris (trimethylsilyl) -N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N, N ′, N′-tris (trimethylsilyl) ) -N- (2-aminoethyl) -3-aminopropyltriethoxysilane, N, N ', N'-tris (trimethylsilyl) -N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N , N ', 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-containing compounds; and the like.

  Although the usage-amount of the compound represented by General formula (2) is not specifically limited, From the reason for which the effect of this invention is more excellent, it is 0.1-5 with respect to 1 mol of polymerization initiators used at the 1st process. Mol is preferable, 0.2 to 2 mol is more preferable, and 0.4 to 1.5 mol is more preferable.

The time when the compound represented by the general formula (2) is added to the solution containing the conjugated diene polymer chain is after the polyorganosiloxane represented by the general formula (1) is added in the second step described above. If it is, it will not be specifically limited. 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 a monomer, more specifically, the conjugated diene. Adding a compound represented by the general formula (2) to this solution in a state where the solution containing the polymer chain contains a monomer of 100 ppm or more, more preferably 300 to 50,000 ppm. Can do. 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 controlled well. It becomes possible. Alternatively, before or after adding the compound represented by the general formula (2) to the solution containing the conjugated diene polymer chain, by adding an alcohol such as water or methanol to the solution, A modification reaction is carried out in a state in which a group represented by -O ^- M ⁺ as a reaction residue formed by reaction with the polyorganosiloxane represented by the general formula (1) is hydrolyzed and converted to a hydroxyl group. May be performed. 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 an inert solvent. However, it may be added directly without dissolving in an inert solvent. The reaction temperature and reaction time are the same as in the first step.

  Then, after reacting the compound represented by the general formula (2), if necessary, a known polymerization terminator or the like is added to deactivate the reaction system, and if desired, a phenol-based stabilizer. Add antioxidants such as phosphorus stabilizers, sulfur stabilizers, crumbs, and scale inhibitors to the reaction solution, and then separate the polymerization solvent from the reaction solution by direct drying or steam stripping. The conjugated diene rubber is recovered. Before separating the polymerization solvent from the reaction solution, an extending oil may be mixed into the polymerization solution and the conjugated diene rubber may be recovered as an oil-extended rubber.

  Examples of the extending oil used when recovering the conjugated diene rubber as an oil-extended rubber include paraffinic, aromatic and naphthenic petroleum softeners, plant softeners, and fatty acids. In the case of using a petroleum softener, the content of polycyclic aromatics extracted by the IP346 method (the inspection method of THE INSTITUTE PETROLEUM in the UK) is preferably less than 3%. When using extension oil, 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, the specific conjugated diene rubber is a polyorganosiloxane represented by the general formula (1) as a modifier in the second step described above with respect to 1 mol of the polymerization initiator used in the first step. Then, the reaction is carried out by adding 1 mol or more in terms of the number of repeating units of the siloxane structure (—Si—O—) in the polyorganosiloxane, and then, as a modifier, It is obtained by carrying out the reaction using the compound represented by the formula (2). Therefore, specific conjugated diene rubbers include those 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. In addition, the polymer chain terminal may include one in which only a modified structure by siloxane is introduced. Furthermore, as long as the effect of the present invention is not inhibited, for example, only a modified structure with a compound represented by the general formula (2) is introduced at the polymer chain end, or any modified structure is introduced. What does not contain etc. may be contained. In particular, in the present invention, from the viewpoint of realizing the effects of the present invention more appropriately, 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 rubber contains 20 to 45% by mass of an aromatic vinyl monomer unit, and preferably contains 25 to 45% by mass because the effect of the present invention is more excellent.
Further, the specific conjugated diene rubber preferably contains 55 to 80% by mass of conjugated diene monomer units, and more preferably contains 55 to 75% by mass because the effect of the present invention is more excellent.

[Vinyl bond content]
The vinyl bond content in the conjugated diene monomer unit in the specific conjugated diene rubber is 20 to 70% by mass, and is preferably 25 to 65% by mass, more preferably 30 to 63% by mass because the effect of the present invention is more excellent. % Is more preferable.

[Coupling rate]
Further, the coupling rate of the specific conjugated diene rubber is not particularly limited, but is preferably 10% by mass or more, more preferably 20% by mass or more, and particularly preferably 40% by mass or more because the effect of the present invention is more excellent. Moreover, 80 mass% or less is preferable, 75 mass% or less is more preferable, and 70 mass% or less is especially preferable. In addition, a coupling rate is made to react with the polyorganosiloxane represented by General formula (1), the compound represented by General formula (2), and the coupling agent and other modifier | denaturant used as needed. It is a mass fraction of the polymer molecule having a molecular weight of 1.8 times or more of 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 is determined as a polystyrene-converted 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, 350,000 to 1,000,000, and 350,000 to 800,000. Preferably, 400,000-700,000 is more preferable. By making the weight average molecular weight of the specific conjugated diene rubber within the above range, the silica can be easily blended into the conjugated diene rubber, and the effects of the present invention will be 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 rubber is 1.1-3. 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, the Mooney viscosity of the oil-extended rubber is preferably in the above range.

〔Glass-transition temperature〕
The glass transition temperature (Tg) of the specific conjugated diene rubber is −35 to −15 ° C., preferably −30 to −15 ° C., and more preferably −30 to −10 ° C. If the glass transition temperature is within the above range, the effect of the present invention is more excellent. If the glass transition temperature of the specific conjugated diene rubber is within the above range, the balance between tan δ (0 ° C.) and tan δ (60 ° C.) can be improved.
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 35% by mass or more is preferable and 40% by mass or more is more preferable because the effect of the present invention is more excellent. The upper limit is preferably 80% by mass or less, more preferably 70% by mass or less, and particularly preferably 60% by mass or less, from the viewpoint that the effects of the present invention are more excellent.

[Styrene butadiene rubber (A)]
The styrene butadiene rubber (A) contained in the composition of the present invention is a styrene butadiene rubber (SBR) other than the specific conjugated diene rubber.

The styrene butadiene rubber (A) can be produced using a styrene monomer and a butadiene monomer.
Although it does not restrict | limit especially as a styrene monomer used for manufacture of a styrene butadiene rubber (A), For example, styrene, (alpha) -methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2- Ethyl styrene, 3-ethyl styrene, 4-ethyl styrene, 2,4-diisopropyl styrene, 2,4-dimethyl styrene, 4-t-butyl styrene, 5-t-butyl-2-methyl styrene, dimethylaminomethyl styrene, And dimethylaminoethylstyrene. Among these, styrene, α-methylstyrene, and 4-methylstyrene are preferable, and styrene is more preferable. These styrene monomers can be used alone or in combination of two or more.
Although it does not restrict | limit especially as a butadiene monomer used for manufacture of a styrene butadiene rubber (A), For example, 1, 3- butadiene, isoprene (2-methyl- 1, 3- butadiene), 2, 3-dimethyl -1,3-butadiene, 2-chloro-1,3-butadiene and the like. Among these, 1,3-butadiene or isoprene is preferably used, and 1,3-butadiene is more preferably used. These butadiene monomers can be used alone or in combination of two or more.

  The production method (polymerization method) of the styrene butadiene rubber (A) is not particularly limited, and examples thereof include solution polymerization and emulsion polymerization.

20-50 mass% is preferable and, as for content of the styrene monomer unit of a styrene butadiene rubber (A), 25-45 mass% is more preferable.
50-80 mass% is preferable and, as for content of the butadiene monomer unit of styrene butadiene rubber (A), 55-75 mass% is more preferable.
The vinyl bond content in the butadiene monomer unit in the styrene butadiene rubber (A) is preferably 10 to 80% by mass and more preferably 10 to 70% by mass because the effect of the present invention is more excellent.

The styrene-butadiene rubber (A) may have a functional group that interacts with silica because the effect of the present invention is more excellent. That is, the styrene butadiene rubber (A) may be modified with a functional group that interacts with silica.
The bonding position of the functional group that interacts with silica is not particularly limited, and examples thereof include the main chain and terminal of the styrene butadiene rubber (A).
Examples of functional groups that interact with silica include hydrocarbyloxysilyl groups, silanol groups, hydroxyl groups (excluding silanol groups), aldehyde groups, carboxyl groups, amino groups, imino groups, epoxy groups, amides, and thiol groups. , Siloxane bond, ether bond and the like.

The styrene butadiene rubber (A) having a functional group that interacts with silica is a styrene butadiene rubber (hereinafter referred to as “styrene butadiene rubber (AS)”) formed by bonding an active terminal of a styrene butadiene polymer chain and a polyorganosiloxane. Preferably).
Here, it is preferable that the styrene butadiene polymer chain has a polymer block X and a polymer block Y formed continuously with the polymer block X.
The polymer block X includes an isoprene unit and a styrene unit, has an isoprene unit content of 80 to 95% by mass, has a styrene unit content of 5 to 20% by mass, and has a weight average molecular weight of 500 to 15,000. It is. The polymer block Y includes 1,3-butadiene units and styrene units.
The styrene butadiene rubber (AS) is preferably a styrene butadiene rubber produced by a method for producing a styrene butadiene rubber comprising the following steps X, Y and Z in this order because the effects of the present invention are more excellent.
Step X: By polymerizing a monomer mixture containing isoprene and styrene, the isoprene unit content is 80 to 95% by mass, the styrene unit content is 5 to 20% by mass, and the weight average molecular weight is 500. Step of forming polymer block X having an active terminal that is ˜15,000 / step Y: Polymerization reaction by mixing polymer block X with a monomer mixture containing 1,3-butadiene and styrene To form a polymer block Y having an active end in a continuous manner with the polymer block X, whereby the styrene-butadiene copolymer having an active end having the polymer block X and the polymer block Y is formed. Step / Step Z for obtaining a polymer chain: Step of reacting a polyorganosiloxane with the active terminal of the styrene-butadiene copolymer chain Specific examples of the steps are as described in paragraphs [0017] to [0054] of JP-A-2016-47883, the contents of which are incorporated herein by reference.

The styrene unit content of the styrene butadiene rubber (AS) is not particularly limited, but is preferably 38 to 48% by mass and more preferably 40 to 45% by mass because the effect of the present invention is more excellent.
The vinyl bond content of the styrene butadiene rubber (AS) is not particularly limited, but is preferably 20 to 35% by mass and more preferably 25 to 30% by mass because the effect of the present invention is more excellent. In addition, vinyl bond content refers to the ratio (mass%) which a vinyl bond accounts among the conjugated diene units contained in styrene butadiene rubber (AS).

[Molecular weight]
The weight average molecular weight (Mw) of the styrene butadiene rubber (A) is a value measured by gel permeation chromatography in terms of polystyrene, preferably 100,000 to 1,800,000, and 300,000 to 1,500,000. Is more preferable.

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 styrene butadiene rubber (A) is preferably 1.2 or more, excellent in workability, and suitable for tires. 2.0 or more is preferable and 3.0 or more is more preferable for the reason that the strength at the time of improvement is further improved.
In addition, when the styrene butadiene rubber (A) is produced by a method in which a monomer and a catalyst are continuously supplied to a reactor (a so-called continuous polymerization process), the above ratio tends to be 2.0 or more. .
Moreover, when the styrene butadiene rubber (A) is produced by an emulsion polymerization method, the above ratio tends to be 3.0 or more.

〔Content〕
The content of the styrene butadiene rubber (A) in the conjugated diene rubber is 20% by mass or more, and 25% by mass or more is preferable and 30% 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, from the viewpoint that the effect of the present invention is more excellent.
The content ratio of the specific conjugated diene rubber and styrene butadiene rubber (A) in the conjugated diene rubber (specific conjugated diene rubber / styrene butadiene rubber (A)) is preferably 0.45 to 4.0, 0.7-2.0 is more preferable.

[Other rubber components]
The conjugated diene rubber may contain rubber components (other rubber components) other than the specific conjugated diene rubber and the styrene butadiene rubber (A).
Such other rubber components include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR). , Cl-IIR), chloroprene rubber (CR) and the like. Among these, natural rubber (NR) or butadiene rubber (BR) is preferable because the effects of the present invention are more excellent.
The content of other rubber components in the conjugated diene rubber is not particularly limited, but is preferably 10% by mass or more, more preferably 10 to 50% by mass, and more preferably 10 to 20% by mass because the effect of the present invention is more excellent. Is particularly preferred.

[Content of rubber component having a functional group that interacts with silica]
The total content of the rubber component having a functional group that interacts with silica in the conjugated diene rubber is preferably 80% by mass or more, more preferably 80 to 100% by mass, because the effect of the present invention is more excellent. 85-100 mass% is especially preferable.
Here, as the rubber component having a functional group that interacts with silica, specifically, a functional group that interacts with silica in the above-described specific conjugated diene rubber and the above-described styrene-butadiene rubber (A). The thing which has.

[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, diatomaceous earth, and the like.

In the composition of the present invention, the content of silica is 30 parts by mass or more with respect to 100 parts by mass of the conjugated diene rubber described above. Especially, 40 mass parts or more are preferable and 50 mass parts or more are more preferable from the reason which the effect of this invention is more excellent.
Although the upper limit of the content of silica is not particularly limited, 250 mass parts or less is preferable and 200 mass parts or less is more preferable with respect to 100 mass parts of the conjugated diene rubber described above because the effect of the present invention is more excellent. 150 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. Among 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 because 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, and a propoxy group.

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

  Specific examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, mercaptopropyltrimethoxy. Silane, mercaptopropyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethylsilyl Propyl-N, N-dimethylthiocarbamoyl-tetrasulfide, 3-octanoylthio-1-propyltriethoxysilane, and the like. May be used in Germany, it may be used in combination of two or more thereof.

The silane coupling agent is preferably represented by the following general formula (S) because the effects of the present invention are more excellent.
_{(C n H 2n + 1 O} ) 3 -Si-C m H 2m -S-CO-C k H 2k + 1 formula (S)
In general formula (S), n represents an integer of 1 to 3, m represents an integer of 1 to 5 (preferably an integer of 2 to 4), and k represents an integer of 1 to 15 (preferably 5 to 5). An integer of 10).

  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. Especially, 5-20 mass% is preferable from the reason which the effect of this invention is more excellent.

  In the composition of the present invention, the content of the silane coupling agent is preferably 1 to 50 parts by mass with respect to 100 parts by mass of the conjugated diene rubber described above, because the effect of the present invention is more excellent. -45 mass parts is more preferable, and 4-40 mass parts is further more preferable.

[4] Optional component The composition of the present invention may contain a component (optional component) other than the components described above, if necessary.
Examples of such components include fillers other than silica (for example, carbon black), terpene resins (preferably aromatic-modified terpene resins), thermally expandable microcapsules, zinc oxide (zinc white), stearic acid, Various additives generally 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. Is mentioned.

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

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

[Method for preparing rubber composition for tire tread]
The production method of the composition of the present invention is not particularly limited, and specific examples thereof include, for example, kneading the above-described components using a known method and apparatus (for example, a Banbury mixer, a kneader, a roll, etc.). The method etc. are 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.) and cooled, and then sulfur or It is preferable to mix a vulcanization accelerator.
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 using the composition of the present invention described above. Especially, it is preferable that it is a pneumatic tire which used (arrange | positioned) the composition of this invention for the tire tread (cap tread).
FIG. 1 shows a partial cross-sectional schematic view of a pneumatic tire representing 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, the code | symbol 1 represents a bead part, the code | symbol 2 represents a sidewall part, and the code | symbol 3 represents a tire tread part.
Further, a carcass layer 4 in which fiber cords are embedded is mounted between the pair of left and right bead portions 1, and an end portion of the carcass layer 4 extends from the inside of the tire to the outside around the bead core 5 and the bead filler 6. Wrapped and rolled up.
Further, in the tire tread portion 3, a belt layer 7 is disposed over the circumference of the tire on the outside of the carcass layer 4.
Moreover, in the bead part 1, the rim cushion 8 is arrange | positioned in the part which touches a rim | limb.
The tire tread portion 3 is formed of the above-described composition of the present invention.

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

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.

[Production of specific conjugated diene rubber and comparative conjugated diene rubber]
Specific conjugated diene rubbers 1 to 4 and comparative conjugated diene rubbers 1 to 4 were produced as follows.
Here, the specific conjugated diene rubbers 1 to 4 are conjugated diene rubbers manufactured by the method for manufacturing a conjugated diene rubber including the first to third steps described above, and correspond to the specific conjugated diene rubbers described above. Further, the specific conjugated diene rubbers 2 and 4 include the process A and the process B described above in the first step, and the specific conjugated diene rubber has a PI block.
On the other hand, the comparative conjugated diene rubbers 1 and 2 are conjugated diene rubbers manufactured by a method for manufacturing a conjugated diene rubber that includes the above-described first and second steps (not including the third step described above). Not applicable to specific conjugated diene rubbers. Further, the comparative diene rubbers 3 to 5 do not correspond to the specific conjugated diene rubber described above.

<Specific conjugated diene rubber 1>
An autoclave equipped with a stirrer was charged with 4000 g of cyclohexane, 3.57 mmol of tetramethylethylenediamine, 252 g of 1,3-butadiene, and 348 g of styrene in a nitrogen atmosphere, and then added with n-butyllithium, and polymerization was started at 50 ° C. (use) The amount of tetramethylethylenediamine as a polar compound present in the reaction system relative to 1 mol of n-butyllithium was 0.85 mol). After 15 minutes from the start of polymerization, 338 g of 1,3-butadiene and 62 g of styrene were continuously added over 60 minutes. The maximum temperature during the polymerization reaction was 70 ° C. After completion of the 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%, the polyorganosiloxane represented by the following formula (11) was changed to 40 In the state of a mass% concentration of xylene solution, 1.51 g (converted to the number of repeating units of siloxane structure (—Si—O—) in polyorganosiloxane, 1.1 times mol of n-butyllithium used) And the reaction was allowed to proceed for 30 minutes. Then, 4.76 mmol of 3- (2-aminoethylamino) propyltrimethoxysilane (an amount corresponding to 1.0 mole of n-butyllithium used) was added and allowed to react for 10 minutes. Thereafter, as a polymerization terminator, an amount of methanol corresponding to twice the mole of n-butyllithium used was added to obtain a solution containing a conjugated diene rubber. After adding 0.15 part of Irganox 1520L (manufactured by BASF) to 100 parts of the conjugated diene rubber as an anti-aging agent, the solvent was removed by steam stripping and the solution was removed at 60 ° C. for 24 hours. Vacuum drying was performed to obtain a solid conjugated diene rubber. The obtained conjugated diene rubber is designated as specific conjugated diene rubber 1. The specific conjugated diene rubber 1 has a weight average molecular weight (Mw) of 570,000, a coupling rate of 45.0%, an aromatic vinyl monomer (styrene monomer) unit content of 41.1% by mass, 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 formula ^{(11), X 1, X} 4, R 1 ~R 3 and ^R 5 to R ⁸ is a methyl group. 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) (here, * represents a bonding position).

<Specific conjugated diene rubber 2>
To an 800 ml ampoule bottle purged with nitrogen, 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). In an amount of 0.10 mol). Subsequently, 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 end. The polymer block (A) has a weight average molecular weight (Mw) of 6,500, a molecular weight distribution (Mw / Mn) of 1.12, and an aromatic vinyl monomer (styrene monomer) unit content of 7.0. The isoprene monomer unit content was 93.0% by mass, and the vinyl bond content was 7.5% by mass.

  In an autoclave equipped with a stirrer, 4000 g of cyclohexane, 3.57 mmol of tetramethylethylenediamine, 252 g of 1,3-butadiene, and 348 g of styrene were charged in a nitrogen atmosphere, and then the polymer block (A) having active ends obtained above was obtained. Was added at a temperature of 50 ° C. (the amount of tetramethylethylenediamine as a polar compound present in the reaction system relative to 1 mol of n-butyllithium used was 0.85 mol). After 15 minutes from the start of polymerization, 338 g of 1,3-butadiene and 62 g of styrene were continuously added over 60 minutes. The maximum temperature during the polymerization reaction was 70 ° C. After completion of the 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%, the polyorganosiloxane represented by the above formula (11) was replaced by 40 In the state of a mass% concentration of xylene solution, 1.51 g (converted to the number of repeating units of siloxane structure (—Si—O—) in polyorganosiloxane, 1.1 times mol of n-butyllithium used) And the reaction was allowed to proceed for 30 minutes. Then, 4.76 mmol of 3- (2-aminoethylamino) propyltrimethoxysilane (an amount corresponding to 1.0 mole of n-butyllithium used) was added and allowed to react for 10 minutes. Thereafter, as a polymerization terminator, an amount of methanol corresponding to twice the mole of n-butyllithium used was added to obtain a solution containing a conjugated diene rubber. After adding 0.15 part of Irganox 1520L (manufactured by BASF) as an anti-aging agent to 100 parts of the conjugated diene rubber, the solvent was removed by steam stripping and the solution was removed at 60 ° C. for 24 hours. Vacuum drying was performed to obtain a solid conjugated diene rubber. The obtained conjugated diene rubber is designated as specific conjugated diene rubber 2. The specific conjugated diene rubber 2 has a weight average molecular weight (Mw) of 570,000, a coupling rate of 45.0%, an aromatic vinyl monomer (styrene monomer) unit content of 41.1% by mass, 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.

<Specific conjugated diene rubber 3>
In an autoclave equipped 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 in a nitrogen atmosphere, 0.79 mmol of n-butyllithium was added, and 60 ° C. The polymerization was started. The polymerization reaction was continued for 60 minutes, and after confirming that the polymerization conversion was in the range of 95% to 100%, the polyorganosiloxane represented by the above formula (11) was converted into a 40% by mass concentration of xylene solution. In this state, 0.26 g (an amount corresponding to 1.1 times mole 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. Next, 0.79 mmol of 3- (2-aminoethylamino) propyltrimethoxysilane (amount corresponding to 1.0-fold mol of n-butyllithium used) was added and stirred for 10 minutes. Thereafter, as a polymerization terminator, an amount of methanol corresponding to twice the mole of n-butyllithium used was added to obtain a solution containing a conjugated diene rubber. Irganox 1520L (manufactured by Ciba Specialty Chemicals) as an anti-aging agent was added to this solution in an amount of 0.15 part per 100 parts of conjugated diene rubber, and the solvent was removed by steam stripping. For 24 hours to obtain a solid conjugated diene rubber. The obtained conjugated diene rubber is designated as specific conjugated diene rubber 3. The specific conjugated diene rubber 3 has a weight average molecular weight (Mw) of 467,000, a coupling rate of 54.4%, an aromatic vinyl monomer (styrene monomer) unit content of 26.9% by mass, 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 4>
To a 100 ml ampoule bottle purged with nitrogen, 50.0 g of cyclohexane and 0.66 mmol of tetramethylethylenediamine were added, and 6.6 mmol of n-butyllithium was further added. Next, 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 end. The polymer block (A) has a weight average molecular weight (Mw) of 3,500, a molecular weight distribution (Mw / Mn) of 1.10, and an aromatic vinyl monomer (styrene monomer) unit content of 7.0. The isoprene monomer unit content was 93.0% by mass, and the vinyl bond content was 7.7% by mass.

  Next, in an autoclave equipped with a stirrer, 4000 g of cyclohexane and tetramethylethylenediamine 11. After charging 1 mmol, 393.0 g of 1,3-butadiene, and 207.0 g of styrene, all of the polymer block (A) having an active terminal obtained above was added, and polymerization was started at 40 ° C. After 10 minutes from the start of 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 completion of the 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 replaced by 40 2.13 g (in terms of mass% concentration of xylene solution), converted to the number of repeating units of siloxane structure (—Si—O—) in polyorganosiloxane, 1.1 times mol of n-butyllithium used And the reaction was allowed to proceed for 30 minutes. Next, 6.6 mmol of 3- (2-aminoethylamino) propyltrimethoxysilane (amount corresponding to 1.0-fold mol of n-butyllithium used) was added and allowed to stir for 10 minutes. Thereafter, as a polymerization terminator, an amount of 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 Specialty 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. It was vacuum-dried for 24 hours to obtain a solid conjugated diene rubber. The obtained conjugated diene rubber is designated as specific conjugated diene rubber 4. The specific conjugated diene rubber 4 has a weight average molecular weight (Mw) of 488,000, a coupling rate of 60.2%, an aromatic vinyl monomer (styrene monomer) unit content of 26.6% by mass, 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 in the same manner 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 referred to as comparative conjugated diene rubber 1. The comparative conjugated diene rubber 1 has a weight average molecular weight (Mw) of 552,000, a coupling rate of 43.0%, an aromatic vinyl monomer (styrene monomer) unit content of 41.0% by mass, 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 equipped 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 in a nitrogen atmosphere, 0.79 mmol of n-butyllithium was added, and 60 ° C. The polymerization was started. The polymerization reaction was continued for 60 minutes, and after confirming that the polymerization conversion was in the range of 95% to 100%, the polyorganosiloxane represented by the above formula (11) was converted into a 40% by mass concentration of xylene solution. In this state, 0.26 g (an amount corresponding to 1.1 times mole 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. Thereafter, as a polymerization terminator, an amount of methanol corresponding to twice the mole of n-butyllithium used was added to obtain a solution containing a conjugated diene rubber. Irganox 1520L (manufactured by Ciba Specialty Chemicals) as an anti-aging agent was added to this solution in an amount of 0.15 part per 100 parts of conjugated diene rubber, and the solvent was removed by steam stripping. For 24 hours to obtain a solid conjugated diene rubber. The obtained conjugated diene rubber is referred to as comparative conjugated diene rubber 2. Comparative conjugated diene rubber 2 has a weight average molecular weight (Mw) of 460,000, a coupling rate of 52.5%, an aromatic vinyl monomer (styrene monomer) unit content of 27.6% by mass, vinyl The bond content was 58.8% 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>
Comparative conjugated diene rubber 3 is NS522 (styrene butadiene rubber, weight average molecular weight (Mw): 960,000, aromatic vinyl monomer (styrene monomer) unit content: 38% by mass, manufactured by Nippon Zeon Co., Ltd. Vinyl bond content: 39% by mass, glass transition temperature: −23 ° C., molecular weight distribution: 1.7).

<Comparative Conjugated Diene Rubber 4>
Comparative conjugated diene rubber 4 is F3420 (styrene butadiene rubber, weight average molecular weight (Mw): 900,000, aromatic vinyl monomer (styrene monomer) unit content: 37% by mass, vinyl, manufactured by Asahi Kasei Corporation. Bond content: 41% by mass, glass transition temperature: −27 ° C., molecular weight distribution: 2.3).

<Comparative conjugated diene rubber 5>
Comparative conjugated diene rubber 5 is Nipol 1739 (styrene butadiene rubber, weight average molecular weight (Mw): 760,000, aromatic vinyl monomer (styrene monomer) unit content: 39% by mass, manufactured by Nippon Zeon Co., Ltd. , Vinyl bond content: 14% by mass, glass transition temperature: −28 ° C., molecular weight distribution: 3.8).

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

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

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

<Wet performance>
About the obtained vulcanized rubber sheet, according to JISK6394: 2007, using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) under the conditions of 10% ± 2% elongation deformation strain, frequency 20 Hz, temperature 0 ° C. Tan δ (0 ° C.) was measured.
The results are shown in Table 1. The results were expressed as an index with Comparative Example 1 as 100. The larger the index, the better the wet performance (wet grip performance). Practically 103 or more is preferable.

<Rolling performance>
About the obtained vulcanized rubber sheet, in accordance with JISK6394: 2007, using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) under the conditions of an elongation deformation strain rate of 10% ± 2%, a frequency of 20 Hz, and a temperature of 0 ° C. Tan δ (60 ° C.) was measured.
The results are shown in Table 1. The results were expressed as 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.

<Dry maneuvering stability>
The pneumatic tire shown in FIG. 1 was manufactured using the obtained rubber composition for a tire tread as a tire tread. At that time, the above-mentioned average main groove depth (the maximum value from the tread surface to the groove bottom of the main groove is indicated. The main groove depth is measured by excluding partial uneven portions formed in the groove bottom. The tread pattern was formed so as to be 6.0 mm.
The obtained pneumatic tire was mounted on a test vehicle having a displacement of 2.0 L, and the sensory evaluation by a test driver was performed on the driving stability performance (dry driving stability performance) on a dry road surface.
The results are shown in Table 1. The results were expressed as an index with Comparative Example 1 as 100. The larger the index, the better the dry steering stability performance. Practically 101 or more is preferable.

The details of each component in Table 1 are as follows. In Table 1, “St” and “Vn” respectively represent the content (mass%) of the aromatic vinyl monomer (styrene monomer) unit in the specific conjugated diene rubber or styrene butadiene rubber (A). ) And 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 styrene butadiene rubber (A), respectively.
Specific conjugated diene rubber 1: Specific conjugated diene rubber 1 produced as described above
Specific conjugated diene rubber 2: Specific conjugated diene rubber 2 produced as described above
Specific conjugated diene rubber 3: Specific conjugated diene rubber 3 produced as described above
Specific conjugated diene rubber 4: Specific conjugated diene rubber 4 produced as described above
Comparative conjugated diene rubber 1: Comparative conjugated diene rubber 1 produced as described above
Comparative conjugated diene rubber 2: Comparative conjugated diene rubber 2 produced as described above
Comparative conjugated diene rubber 3: Comparative conjugated diene rubber 3 described above
Comparative conjugated diene rubber 4: Comparative conjugated diene rubber 4 described above
Comparative conjugated diene rubber 5: Comparative conjugated diene rubber 5 described above
・ NR: Natural rubber (TSR20, manufactured by VON BUNDIT)
BR1220: Nipol BR1220 (butadiene rubber, glass transition temperature: -106 ° C, manufactured by Nippon Zeon Co., Ltd.)
9100GR: ULTRASIL 9100GR (silica, manufactured by Evonik)
・ N339: Show black N339 (carbon black, manufactured by Cabot Japan)
NXT: Silane coupling agent represented by the general formula (S) described above (wherein n = 2, m = 3, and k = 7 in the general formula (S) described above).
・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
・ Stearic acid: Beads stearic acid (manufactured by NOF Corporation)
-Anti-aging agent: Ozonon 6C (manufactured by Seiko Chemical Co., Ltd.)
・ Process oil: Extract No. 4 S (made by Showa Shell Sekiyu KK)
・ Sulfur: Fine powder sulfur with Jinhua seal oil (sulfur content 95.24 mass%, manufactured by Tsurumi Chemical Co., Ltd.)
・ Vulcanization accelerator (CZ): NOCELLER CZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Vulcanization accelerator (DPG): 1,3-diphenylguanidine (Soccinol DG, manufactured by Sumitomo Chemical Co., Ltd.)

As can be seen from Table 1, Examples 1 to 8 containing a predetermined amount of a specific conjugated diene rubber, a predetermined amount of styrene butadiene rubber (A), and a predetermined amount of a silane coupling agent are excellent wet performance, It showed rolling performance and dry maneuvering stability performance. Among them, Examples 2 and 4 to 8 in which the specific conjugated diene rubber contains a PI block were shown to be superior in at least one of wet performance, rolling performance, and dry steering stability performance.
From the comparison of Examples 4 and 6, Example 6 in which the styrene-butadiene rubber (A) has a functional group that interacts with silica showed better wet performance, rolling performance, and dry steering stability performance.
From the comparison of Examples 4, 5 and 7, when the molecular weight distribution of the styrene butadiene rubber (A) was 2.0 or more, better wet performance and dry steering stability performance were exhibited.

  Comparative Examples 1 to 3 in which the content of the specific conjugated diene rubber in the conjugated diene rubber is less than 30% by mass, and Comparative Example 4 in which the content of the silane coupling agent with respect to silica is less than 3% by mass are wet performance. At least one of rolling performance and dry handling stability performance was insufficient.

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 (7)

A conjugated diene rubber containing 30% by mass or more of a specific conjugated diene rubber and 20% by mass or more of a styrene butadiene rubber other than the specific conjugated diene rubber;
Silica,
Containing 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,
The specific conjugated diene rubber polymerizes a monomer containing a conjugated diene compound and an aromatic vinyl compound in an inert solvent using a polymerization initiator to obtain a conjugated diene polymer chain having an active end. In the first step, 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 at a ratio of 1 mol or more in terms of the number of repeating units of the siloxane structure (—Si—O—) in the polyorganosiloxane and the polyorganosiloxane obtained in the second step are reacted. A conjugated diene rubber produced by a method for producing a conjugated diene rubber comprising a third step of reacting the conjugated diene polymer chain with a compound represented by the following general formula (2):
The content of the aromatic vinyl monomer unit in the specific conjugated diene rubber is 20 to 45% by mass, and the vinyl bond content in the conjugated diene monomer unit in the specific conjugated diene rubber is 20 to 70. Mass%,
The specific conjugated diene rubber has a glass transition temperature of −35 to −15 ° C. and a weight average molecular weight (Mw) of 350,000 to 1,000,000.
In the general formula (1), R ^{1 to} R ⁸ are an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and these may be the same as or different from each other.
In General Formula (1), X ¹ and X ⁴ are carbon numbers containing 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. It is any group selected from the group consisting of 4 to 12 groups, and these may be the same as or different from each other.
In General Formula (1), X ² is a C 4-12 group containing an alkoxy group having 1 to 5 carbon atoms or an epoxy group, and a plurality of X ² may be the same as each other. It may be different.
In General Formula (1), X ³ is a group containing 2 to 20 alkylene glycol repeating units, and when there are a plurality of X ³ , they may be the same as or different from each other.
In general formula (1), m is an integer of 3 to 200, n is an integer of 0 to 200, k is an integer of 0 to 200, and m + n + k is 3 or more.
In general formula (2), R ⁹ is a hydrocarbyl group.
In the general formula (2), 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.
In General Formula (2), A ² is a group containing a nitrogen atom.
In general formula (2), p is an integer of 0 to 2, q is an integer of 1 to 3, r is an integer of 1 to 3, and p + q + r = 4.   The rubber composition for a tire tread according to claim 1, wherein the styrene-butadiene rubber has a functional group that interacts with silica.   The rubber composition for a tire tread according to claim 1 or 2, wherein the total content of rubber components having a functional group that interacts with silica in the conjugated diene rubber is 80% by mass or more.   The styrene butadiene rubber has a molecular weight distribution (Mw / Mn) determined from a weight average molecular weight (Mw) and a number average molecular weight (Mn) of 2.0 or more, according to any one of claims 1 to 3. Rubber composition for tire tread.   The rubber composition for a tire tread according to any one of claims 1 to 4, wherein the conjugated diene rubber contains 10% by mass or more of a rubber component other than the specific conjugated diene rubber and the styrene butadiene rubber. The specific conjugated diene rubber is
A polymer block (A) comprising 80 to 100% by mass of isoprene monomer units and 0 to 20% by mass of aromatic vinyl monomer units;
The polymer block (B) containing 50 to 100% by mass of 1,3-butadiene monomer units and 0 to 50% by mass of aromatic vinyl monomer units has a structure formed continuously. The rubber composition for a tire tread according to any one of 1 to 5.   A pneumatic tire provided with the tire tread part manufactured using the rubber composition for tire treads of any one of Claims 1-6.