JP6467820B2 - Rubber composition for tire tread and pneumatic tire - Google Patents

Description

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

In recent years, it has been required to reduce rolling resistance of tires from the viewpoint of low fuel consumption during vehicle travel. In addition, from the viewpoint of safety, improvement in wet performance (braking performance on a wet road surface) is required. On the other hand, a method is known in which silica is blended with the rubber component constituting the tread portion of the tire to achieve both low rolling resistance and wet performance.
However, since silica has low affinity with rubber components and high cohesiveness between silicas, silica is not dispersed even if silica is simply added to the rubber component, reducing rolling resistance and wet performance. There is a problem that the effect of improving cannot be obtained sufficiently.

  On the other hand, Patent Document 1 discloses a conjugated diene rubber obtained by reacting a specific modifier with a specific conjugated diene polymer chain having an active end. According to Patent Document 1, by using the conjugated diene rubber, the affinity between silica and rubber is improved, and the low heat build-up (low rolling resistance) and wet grip properties of the tire can be improved. Have been described.

International Publication No. 2014/050341

  On the other hand, due to environmental problems and resource problems, further low fuel consumption of vehicles is required, and accordingly, further improvement in tire rolling resistance is required. Further, with the improvement of the required safety level, further improvement in wet performance is also required. Furthermore, from the viewpoint of the manufacturing process, reduction in viscosity and improvement in scorch resistance are also demanded.

  Under these circumstances, the present inventors examined the conjugated diene rubber described in Patent Document 1. As a result, the resulting rubber composition has a viscosity, scorch resistance, wet performance and low rolling resistance when used as a tire. It became clear that sex does not necessarily meet the level required recently.

  Therefore, in view of the above circumstances, the present invention provides a tire tread rubber composition having a low viscosity, excellent scorch resistance, excellent wet performance and low rolling resistance when made into a tire, and the tire tread. An object of the present invention is to provide a pneumatic tire using the rubber composition.

As a result of earnestly examining the above problems, the present inventors have used a specific conjugated diene rubber and a specific silane coupling agent (specific polysiloxane) in combination, and blended each component at a predetermined ratio. The present inventors have found that the problem can be solved and have reached the present invention.
That is, the present inventor has found that the above problem can be solved by the following configuration.

(1) Contains a diene rubber, silica, and a silane coupling agent,
The silane coupling agent is a polysiloxane represented by an average composition formula of the following formula (S1),
The diene rubber contains a specific conjugated diene rubber, and the content of the specific conjugated diene rubber in the diene rubber is 30% by mass or more,
The specific conjugated diene rubber is a conjugated diene rubber produced by a method for producing a conjugated diene rubber comprising the following steps A, B and C in this order,
The content of the silica is 30 to 150 parts by mass with respect to 100 parts by mass of the diene rubber.
A rubber composition for a tire tread, wherein a content of the silane coupling agent is 2.0 to 20% by mass with respect to a content of the silica.
(A) _a (B) _b (C) _c (D) _d (E) _e SiO _{(4-2a-b-c-d-e) / 2} (S1)
(In formula (S1), A represents a divalent organic group containing a sulfide group, B represents a monovalent hydrocarbon group having 5 to 20 carbon atoms, C represents a hydrolyzable group, and D represents Represents an organic group containing a mercapto group, E represents a monovalent hydrocarbon group having 1 to 4 carbon atoms, a to e are 0 ≦ a <1, 0 <b <1, 0 <c <3, 0 ≦ d <1, 0 ≦ e <2, 0 <2a + b + c + d + e <4, where at least one of a and d is not 0.)
Step A: by polymerizing a monomer mixture containing isoprene and aromatic vinyl, the isoprene unit content is 80 to 95% by mass, the aromatic vinyl unit content is 5 to 20% by mass, and the weight Step of forming polymer block A having an active terminal having an average molecular weight of 500 to 15,000 and step B: the polymer block A and a monomer mixture containing 1,3-butadiene and aromatic vinyl And the polymerization reaction is continued, and the polymer block B having the active terminal is formed continuously with the polymer block A, thereby having the polymer block A and the polymer block B. Step / Step C for obtaining a conjugated diene polymer chain having a terminal: The polyorganosiloxane represented by the formula (1) described below is attached to the active terminal of the conjugated diene polymer chain. During the step of reacting the down (2) the formula (S1), a is greater than 0, the tire tread rubber composition according to (1).
(3) The rubber composition for a tire tread according to (1) or (2), wherein d is greater than 0 in the formula (S1).
(4) Further contains an alkyltrialkoxysilane represented by the formula (I) described later,
The rubber composition for a tire tread according to any one of (1) to (3), wherein the content of the alkyltrialkoxysilane is 0.2 to 20% by mass with respect to the content of the silica.
(5) Furthermore, an aromatic modified terpene resin having a softening point of 60 to 150 ° C. is contained,
The rubber composition for a tire tread according to any one of (1) to (4), wherein the content of the aromatic modified terpene resin is 3 to 30 parts by mass with respect to 100 parts by mass of the diene rubber. .
(6) A pneumatic tire using the tire tread rubber composition according to any one of (1) to (5) as a tread.

As described below, according to the present invention, a rubber composition for a tire tread having low viscosity, excellent scorch resistance, excellent wet performance and low rolling resistance when formed into a tire, and the tire tread described above. A pneumatic tire using the rubber composition for a vehicle can be provided.
In the following, the fact that the tire is excellent in wet performance is also simply referred to as “excellent in wet performance”. Moreover, when it is made into a tire, it is also simply called "it is excellent in low rolling resistance" that it is excellent in low rolling resistance.

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

Below, the rubber composition for tire treads of this invention and the pneumatic tire using the rubber composition for tire treads of this invention 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.

[Rubber composition for tire tread]
The tire tread rubber composition of the present invention (hereinafter also referred to as the composition of the present invention) contains a diene rubber, silica, and a silane coupling agent.
Here, the silane coupling agent is a polysiloxane represented by an average composition formula of formula (S1) described later.
The diene rubber includes a specific conjugated diene rubber, and the content of the specific conjugated diene rubber in the diene rubber is 30% by mass or more.
The specific conjugated diene rubber is a conjugated diene rubber produced by a method for producing a conjugated diene rubber comprising steps A, B and C described later in this order.
Moreover, content of the said silica is 30-150 mass parts with respect to 100 mass parts of said diene rubbers.
Moreover, content of the said silane coupling agent is 2.0-20 mass% with respect to content of the said silica.
Since the composition of the present invention has such a configuration, it is considered that the composition has low viscosity, excellent scorch resistance, and excellent wet performance and low rolling resistance when formed into a tire. The reason is not clear, but it is presumed that it is as follows.

The composition of the present invention contains a diene rubber including a specific conjugated diene rubber, silica, and a silane coupling agent. Here, as will be described later, the specific conjugated diene rubber forms a rubber-based polymer block B on a polymer block A formed by polymerizing isoprene and further reacts with a specific polyorganosiloxane. Can be obtained. Moreover, the said silane coupling agent is polysiloxane (henceforth specific polysiloxane) represented by the average compositional formula of Formula (S1) mentioned later.
The specific polysiloxane interacts with the diene rubber and silica in the composition to improve the dispersibility of the silica in the diene rubber. As a result, the composition of the present invention has excellent wet performance and low rolling resistance. It is considered to show sex. Here, since the interaction between the polysiloxane structure of the specific polysiloxane and the polymer block A of the specific conjugated diene rubber is extremely strong, it is considered that the above effects are exhibited.
As shown in the comparative examples to be described later, this indicates that the specific polysiloxane is contained but the content of the specific conjugated diene rubber in the diene rubber is less than a predetermined value (Comparative Examples 2 to 3), or the specific conjugate. In the case of containing a diene rubber but not containing a specific polysiloxane (containing a silane coupling agent other than a specific polysiloxane) (Comparative Example 1), wet performance and low rolling resistance are insufficient. Also guessed.

  Hereinafter, each component contained in the composition of this invention is explained in full detail.

[Diene rubber]
The diene rubber contained in the composition of the present invention includes a specific conjugated diene rubber.

<Specific conjugated diene rubber>
As described above, the specific conjugated diene rubber is a conjugated diene rubber manufactured by a method for manufacturing a conjugated diene rubber including the following steps A, B, and C in this order.
Step A: by polymerizing a monomer mixture containing isoprene and aromatic vinyl, the isoprene unit content is 80 to 95% by mass, the aromatic vinyl unit content is 5 to 20% by mass, and the weight Step of forming polymer block A having an active terminal having an average molecular weight of 500 to 15,000 and step B: the polymer block A and a monomer mixture containing 1,3-butadiene and aromatic vinyl And the polymerization reaction is continued, and the polymer block B having the active terminal is formed continuously with the polymer block A, thereby having the polymer block A and the polymer block B. Step / Step C for obtaining a conjugated diene polymer chain having a terminal: The polyorganosiloxane represented by the formula (1) described below is attached to the active terminal of the conjugated diene polymer chain. Step reacting the down will be described in detail for each step.

(Process A)
In Step A, by polymerizing a monomer mixture containing isoprene and aromatic vinyl, the isoprene unit content is 80 to 95% by mass, the aromatic vinyl unit content is 5 to 20% by mass, and the weight A polymer block A having an active terminal having an average molecular weight of 500 to 15,000 is formed.

The monomer mixture may contain only isoprene and aromatic vinyl, or may contain monomers other than isoprene and aromatic vinyl.
The aromatic vinyl is not particularly limited, and examples thereof include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, Examples include 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, vinylnaphthalene, dimethylaminomethylstyrene, and dimethylaminoethylstyrene. Among these, styrene is preferable. These aromatic vinyls can be used alone or in combination of two or more.

  Examples of monomers other than isoprene and aromatic vinyl include 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, and Conjugated dienes other than isoprene such as 1,3-hexadiene; α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids or acid anhydrides such as acrylic acid, methacrylic acid, and maleic anhydride; Unsaturated carboxylic esters such as methyl methacrylate, ethyl acrylate, and butyl acrylate; 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene Non-conjugated dienes such as; Among these, 1,3-butadiene is preferable. These may be used alone or in combination of two or more.

The monomer mixture is preferably polymerized in an inert solvent.
The inert solvent is not particularly limited as long as it is one usually used in solution polymerization and does not inhibit the polymerization reaction. Specific examples thereof include, for example, chain aliphatic hydrocarbons such as butane, pentane, hexane, heptane, and 2-butene; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and cyclohexene; benzene, toluene, and xylene Aromatic hydrocarbons such as; and the like. As for the usage-amount of an inert solvent, a monomer mixture density | concentration is 1-80 mass%, for example, Preferably it is 10-50 mass%.

The monomer mixture is preferably polymerized with a polymerization initiator.
The polymerization initiator is not particularly limited as long as it can polymerize a monomer mixture containing isoprene and aromatic vinyl to give a polymer chain having an active end. As specific examples thereof, for example, a polymerization initiator mainly containing an organic alkali metal compound, an organic alkaline earth metal compound, a lanthanum series metal compound, or the like is preferably used. Examples of the organic alkali metal compound include organic monolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbenelithium; dilithiomethane, 1,4-dilithiobutane, 1, Organic polyvalent lithium compounds such as 4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, and 1,3,5-tris (lithiomethyl) benzene; organic sodium compounds such as sodium naphthalene; potassium naphthalene and the like Organic 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 diisopropoxybarium. , Diethyl mercaptobarium, di-t-butoxybarium, diphenoxybarium, diethylaminobarium, barium distearate, and diketylbarium. Examples of the polymerization initiator having a lanthanum series metal compound as a main catalyst include, for example, a lanthanum series metal comprising a lanthanum series metal such as lanthanum, cerium, praseodymium, neodymium, samarium and 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, it is preferable to use an organic monolithium compound, and it is more preferable to use n-butyllithium. The organic alkali metal compound is used as an organic alkali metal amide compound by previously reacting with a secondary amine such as dibutylamine, dihexylamine, dibenzylamine, pyrrolidine, hexamethyleneimine, and heptamethyleneimine. Also good. These polymerization initiators can be used alone or in combination of two or more.
The amount of the polymerization initiator used may be determined according to the target molecular weight, but is preferably 4 to 250 mmol, more preferably 6 to 200 mmol, and particularly preferably 10 to 70 mmol per 100 g of the monomer mixture. is there.

The polymerization temperature for polymerizing the monomer mixture is, for example, in the range of −80 to + 150 ° C., preferably 0 to 100 ° C., more preferably 20 to 90 ° C.
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 a block shape, a taper shape, and a random shape, for example.
Examples of the method for adjusting the 1,4-bond content in the isoprene unit in the polymer block A include a method in which a polar compound is added to an inert solvent and the amount added is adjusted during the polymerization. Examples of polar compounds include ether compounds such as dibutyl ether, tetrahydrofuran, and 2,2-di (tetrahydrofuryl) propane; tertiary amines such as tetramethylethylenediamine; alkali metal alkoxides; phosphine compounds; Among these, ether compounds and tertiary amines are preferable, and among them, those capable of forming a chelate structure with the metal of the polymerization initiator are more preferable, 2,2-di (tetrahydrofuryl) propane, and tetramethylethylenediamine Is particularly preferred.
What is necessary is just to determine the usage-amount of a polar compound according to the target 1, 4- bond content, and 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 1,4-bond content in the isoprene unit can be easily adjusted, and problems due to the deactivation of the polymerization initiator hardly occur.

The 1,4-bond content in the isoprene unit in the polymer block A is preferably 10 to 95% by mass, and more preferably 20 to 95% by mass.
In addition, in this specification, 1,4-bond content in an isoprene unit refers to the ratio (mass%) of the 1,4-bond isoprene unit with respect to all the isoprene units which the polymer block A has.

The weight average molecular weight (Mw) of the polymer block A is 500-15,000 as a polystyrene conversion value measured by gel permeation chromatography (GPC). Especially, it is more preferable that it is 1,000-12,000, and it is further more preferable that it is 1,500-10,000.
If the weight average molecular weight of the polymer block A is less than 500, the desired low heat build-up and wet performance are hardly exhibited.
If the weight average molecular weight of the polymer block A exceeds 15,000, there is a possibility that the balance between the desired low rolling and viscoelastic properties that serve as an indicator of wet performance may be lost.
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 preferably 1.0 to 1.5, and preferably 1.0 to 1.5. More preferably, it is 1.3. When the molecular weight distribution value (Mw / Mn) of the polymer block A is within the above range, the production of the specific conjugated diene rubber becomes easier. Mw and Mn are both polystyrene-equivalent values measured by GPC.

The isoprene unit content of the polymer block A is not particularly limited, but is preferably 80 to 95% by mass, and more preferably 85 to 95% by mass.
The aromatic vinyl content of the polymer block A is preferably 5 to 20% by mass, more preferably 5 to 15% by mass, and further preferably 5 to 13% by mass.
The content of monomer units other than isoprene and aromatic vinyl in the polymer block A is preferably 15% by mass or less, more preferably 10% by mass or less, and 6% by mass or less. Is more preferable.

(Process B)
In step B, the polymer block A formed in step A described above and a monomer mixture containing 1,3-butadiene and aromatic vinyl are mixed to continue the polymerization reaction, and a polymer having an active end By forming the block B together with the polymer block A, a conjugated diene polymer chain having an active terminal and having the polymer block A and the polymer block B is obtained.

  Specific examples and preferred embodiments of the aromatic vinyl are as described above.

The monomer mixture is preferably polymerized in an inert solvent.
The definition, specific examples and preferred embodiments of the inert solvent are as described above.
The amount of the polymer block A having an active terminal at the time of forming the polymer block B may be determined according to the target molecular weight, but a monomer mixture containing 1,3-butadiene and aromatic vinyl For example, in the range of 0.1 to 5 mmol, preferably 0.15 to 2 mmol, more preferably 0.2 to 1.5 mmol per 100 g.
The mixing method of the polymer block A and the monomer mixture containing 1,3-butadiene and aromatic vinyl is not particularly limited, and the polymer block A is mixed in the monomer mixture containing 1,3-butadiene and aromatic vinyl. Polymer block A having an active end may be added, or a monomer mixture containing 1,3-butadiene and aromatic vinyl may be added to a solution of polymer block A having an active end. From the viewpoint of controlling the polymerization, it is preferable to add the polymer block A having an active end to a solution of a monomer mixture containing 1,3-butadiene and aromatic vinyl.
When polymerizing a monomer mixture containing 1,3-butadiene and aromatic vinyl, the polymerization temperature is, for example, in the range of −80 to + 150 ° C., preferably 0 to 100 ° C., more preferably 20 to 90 ° C. . As the polymerization mode, any mode such as batch mode or continuous mode can be adopted. Of these, the batch type is preferable.
The bonding mode of each monomer of the polymer block B can be various bonding modes such as a block shape, a taper shape, and a random shape. Among these, a random shape is preferable. When the bonding mode of 1,3-butadiene and aromatic vinyl is made random, the ratio of aromatic vinyl to the total amount of 1,3-butadiene and aromatic vinyl in the polymerization system should not be too high. 1,3-butadiene and aromatic vinyl are preferably fed continuously or intermittently into the polymerization system for polymerization.

The 1,3-butadiene unit content of the polymer block B is not particularly limited, but is preferably 55 to 95% by mass, and more preferably 55 to 90% by mass.
The aromatic vinyl unit content of the polymer block B is not particularly limited, but is preferably 5 to 45% by mass, and more preferably 10 to 45% by mass.

The polymer block B may further contain other monomer units in addition to the 1,3-butadiene unit and the aromatic vinyl unit. As other monomers used to constitute other monomer units, those obtained by removing 1,3-butadiene from the above-mentioned “examples other than isoprene among monomers other than isoprene” And isoprene.
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.

In order to adjust the vinyl bond content in the 1,3-butadiene unit in the polymer block B, it is preferable to add a polar compound to the inert solvent during the polymerization. However, when the polymer block A is prepared, a sufficient amount of a polar compound to adjust the vinyl bond content in the 1,3-butadiene unit in the polymer block B is added to the inert solvent. It is not necessary to add a new polar compound. Specific examples of the polar compound used for adjusting the vinyl bond content are the same as the polar compound used for the formation of the polymer block A described above. The amount of the polar compound used may be determined according to the target vinyl bond content, and is preferably adjusted in the range of 0.01 to 100 mol, more preferably 0.1 to 30 mol with respect to 1 mol of the polymerization initiator. do it. When the amount of the polar compound used is in this range, it is easy to adjust the vinyl bond content in the 1,3-butadiene unit, and problems due to the deactivation of the polymerization initiator hardly occur.
The vinyl bond content in the 1,3-butadiene unit in the polymer block B is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, and particularly preferably 25 to 70% by mass.

By steps A and B, a conjugated diene polymer chain having an active terminal and having polymer block A and polymer block B can be obtained.
From the viewpoint of productivity, the conjugated diene polymer chain having an active end is composed of a polymer block A-polymer block B, and the end of the polymer block B is preferably an active end. A plurality of blocks A may be included, or other polymer blocks may be included. For example, polymer block A-polymer block B-polymer block A and polymer block A-polymer block B-blocks consisting only of isoprene and the like conjugated diene polymer chains having an active end can be mentioned. When forming a block consisting only of isoprene on the active terminal side of the conjugated diene polymer chain, the amount of isoprene used is preferably 10 to 100 mol with respect to 1 mol of the polymerization initiator used in the initial polymerization reaction. It is more preferably 15 to 70 mol, and particularly preferably 20 to 35 mol.
The mass ratio between the polymer block A and the polymer block B in the conjugated diene polymer chain having the active terminal (when there are a plurality of polymer blocks A and B, the total mass is based on each) is: As mass of polymer block A) / (mass of polymer block B), it is preferably 0.001 to 0.1, more preferably 0.003 to 0.07, and 0.005 to 0. .05 is particularly preferred.
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 is 1.0 to 3.0. Is more preferable, 1.0 to 2.5 is more preferable, and 1.0 to 2.2 is particularly preferable. When the molecular weight distribution value (Mw / Mn) of the conjugated diene polymer chain having an active end is within the above range, the production of the specific conjugated diene rubber is facilitated. Mw and Mn are both polystyrene-equivalent values measured by GPC.
In the conjugated diene polymer chain having an active terminal, the total content of isoprene units and 1,3-butadiene units is 50 to 99.995% by mass, and the content of aromatic vinyl units is 0.005 to 50% by mass. %, More preferably the total content of isoprene units and 1,3-butadiene units is 55 to 95% by mass, and the content of aromatic vinyl units is 5 to 45% by mass, and isoprene units It is particularly preferable that the total content of 1,3-butadiene units is 55 to 90% by mass, and the content of aromatic vinyl units is 10 to 45% by mass. The vinyl bond content in the isoprene unit and the 1,3-butadiene unit in the conjugated diene polymer chain having an active terminal is the vinyl bond content in the 1,3-butadiene unit in the polymer block B described above. It is the same.

(Process C)
Step C is a step in which the polyorganosiloxane represented by the following formula (1) is reacted with the active terminal of the conjugated diene polymer chain obtained in Step B.

In the above formula _(1), R 1 ~R ₈ is an alkyl group or an aryl group having 6 to 12 carbon atoms, 1 to 6 carbon atoms, which may be different from be the same as each other. X ₁ and X ₄ are composed of a group having 4 to 12 carbon atoms 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. 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 O to 200, and k is an integer of O to 200.

In the polyorganosiloxane represented by the above formula (1), examples of the alkyl group having 1 to 6 carbon atoms represented by R _{1 to} R ₈ , X ₁ and X ₄ include a methyl group, an ethyl group, and n- Examples include 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 production of the polyorganosiloxane itself.

In the polyorganosiloxane represented by the above formula (1), examples of the alkoxy group having 1 to 5 carbon atoms represented by X ₁ , X ₂ and X ₄ include a methoxy group, an ethoxy group, a propoxy group, A propoxy group, a butoxy group, etc. are mentioned. Of these, a methoxy group and an ethoxy group are preferred from the viewpoint of reactivity with the active terminal of the conjugated diene polymer chain.

In the polyorganosiloxane represented by the above formula (1), the group having 4 to 12 carbon atoms containing an epoxy group represented by X ₁ , X ₂ , and X ₄ is represented by the following formula (2). Group.

The formula (2) in, Z ₁ is an alkylene group or an alkyl arylene group having 1 to 10 carbon atoms, Z ₂ is methylene group, a sulfur atom or an oxygen atom, 2 carbon atoms E is an epoxy group To 10 hydrocarbon groups. In the above formula (2), * represents a bonding position.

In the group represented by the formula (2) is preferably a Z ₂ is an oxygen atom, Z ₂ is an oxygen atom, and is more preferable E is a glycidyl group, Z ₁ is C 1 -C Particularly preferred is an alkylene group of ˜3, Z ₂ is an oxygen atom, and E is a glycidyl group.

In the polyorganosiloxane represented by the above formula (1), X ₁ and X ₄ are preferably a group having 4 to 12 carbon atoms or an alkyl group having 1 to 6 carbon atoms containing an epoxy group. X ₂ is preferably an epoxy group-containing group having 4 to 12 carbon atoms, X ₁ and X ₄ are alkyl groups having 1 to 6 carbon atoms, and X ₂ is an epoxy group. It is more preferable that it is a C4-C12 group containing group.

In the polyorganosiloxane represented by the above formula (1), X ₃ , that is, a group containing 2 to 20 alkylene glycol repeating units is preferably a group represented by the following formula (3).

  In said formula (3), t is an integer of 2-20, P is a C2-C10 alkylene group or an alkylarylene group, R is a hydrogen atom or a methyl group, Q is C1-C1. 10 alkoxy groups or aryloxy groups. In the above formula (3), * represents a bonding position. Among these, it is preferable that t is an integer of 2 to 8, P is an alkylene group having 3 carbon atoms, R is a hydrogen atom, and Q is a methoxy group.

  In the polyorganosiloxane represented by the above formula (1), m is an integer of 3 to 200, preferably an integer of 20 to 150, more preferably an integer of 30 to 120. Since m is an integer of 3 or more, the specific conjugated diene rubber has high affinity with silica, and as a result, the tire obtained from the composition of the present invention exhibits excellent low heat build-up. Moreover, since m is an integer of 200 or less, the production of the polyorganosiloxane itself is facilitated, and the viscosity of the composition of the present invention is lowered.

  In the polyorganosiloxane represented by the above formula (1), n is an integer of 0 to 200, preferably an integer of 0 to 150, more preferably an integer of 0 to 120. Moreover, in the polyorganosiloxane represented by the said Formula (1), k is an integer of 0-200, Preferably it is an integer of 0-150, More preferably, it is an integer of 0-130.

  In the polyorganosiloxane represented by the above formula (1), the total number of m, n, and k is preferably 3 to 400, more preferably 20 to 300, and 30 to 250. Is particularly preferred.

  In the polyorganosiloxane represented by the above formula (1), when the epoxy group in the polyorganosiloxane reacts with the active end of the conjugated diene polymer chain, at least a part of the epoxy group in the polyorganosiloxane is opened. By ringing, it is considered that a bond between the carbon atom of the portion where the epoxy group is opened and the active end of the conjugated diene polymer chain is formed. In addition, when the alkoxy group in the polyorganosiloxane reacts with the active end of the conjugated diene polymer chain, at least a part of the alkoxy group in the polyorganosiloxane is eliminated, so that the released alkoxy group is bonded. It is considered that a bond is formed between the silicon atom in the polyorganosiloxane and the active end of the conjugated diene polymer chain.

  The amount of the polyorganosiloxane (hereinafter also referred to as a modifier) is such that the ratio of the total number of moles of epoxy groups and alkoxy groups in the modifier relative to 1 mol of the polymerization initiator used in the polymerization is 0.1 to 1. The amount is preferably in the range of 0.2 to 0.9, more preferably in the range of 0.3 to 0.8.

In the method for producing a conjugated diene rubber, in addition to modifying the conjugated diene polymer chain having an active end with the above-described modifier, a polymerization terminator, a polymerization terminal modifier other than the above-described modifier, and a cup By adding a ring agent or the like into the polymerization system, the active ends of some of the conjugated diene polymer chains may be inactivated so long as the effects of the present invention are not impaired. That is, the specific conjugated diene rubber has a polymerization terminator, a polymerization terminal modifier other than the above-described modifier, and a cup as long as the active ends of some conjugated diene polymer chains do not hinder the effects of the present invention. It may be inactivated by a ring agent or the like.
Examples of the polymerization terminal modifier and coupling agent used at this time include N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, and N-methyl-ε-caprolactam. N-substituted cyclic amides such as; N-substituted cyclic ureas such as 1,3-dimethylethyleneurea and 1,3-diethyl-2-imidazolidinone; 4,4′-bis (dimethylamino) benzophenone, And N-substituted aminoketones such as 4,4′-bis (diethylamino) benzophenone; aromatic isocyanates such as diphenylmethane diisocyanate and 2,4-tolylene diisocyanate; N, such as N, N-dimethylaminopropylmethacrylamide N-disubstituted aminoalkylmethacrylamides; 4-N, N-dimethyl N-substituted aminoaldehydes such as tilaminobenzaldehyde 1 N-substituted carbodiimides such as dicyclohexylcarbodiimide; Schiff bases such as N-ethylethylideneimine and N-methylbenzylideneimine; pyridyl group-containing vinyl compounds such as 4-vinylpyridine Tin tetrachloride; silicon tetrachloride, hexachlorodisilane, bis (trichlorosilyl) methane, 1,2-bis (trichlorosilyl) ethane, 1,3-bis (trichlorosilyl) propane, 1,4-bis (trichlorosilyl) And halogenated silicon compounds such as butane, 1,5-bis (trichlorosilyl) pentane, and 1,6-bis (trichlorosilyl) hexane. A tire obtained using a hyperbranched conjugated diene rubber obtained by using a halogenated silicon compound having 5 or more silicon-halogen atom bonds in one molecule as a coupling agent has excellent steering stability. These polymerization terminal modifiers and coupling agents may be used alone or in combination of two or more.

When the above-mentioned modifier is reacted with the active end of the conjugated diene polymer chain, it is preferable to add the modifier to the solution containing the conjugated diene polymer chain having the active end, and the reaction is good. From the viewpoint of controlling the concentration, it is more preferable to dissolve the modifier in an inert solvent and add it to the polymerization system. The solution concentration is preferably in the range of 1 to 50% by mass.
The timing for adding the modifier is not particularly limited, but the polymerization reaction in the conjugated diene polymer chain having an active end is not completed, and a solution containing a conjugated diene polymer chain having an active end is simple. In a state of containing a monomer, more specifically, a solution containing a conjugated diene polymer chain having an active end is preferably 100 ppm or more, more preferably 300 to 50,000 ppm of monomer. It is desirable to add a denaturing agent or the like to this solution in the contained state. By adding a modifier or the like in this way, it is possible to suppress the side reaction between the conjugated diene polymer chain having an active terminal and impurities contained in the polymerization system, and to control the reaction well. Become.
As conditions for reacting the above-mentioned modifier and the like with the active terminal of the conjugated diene polymer chain, the temperature is, for example, in the range of 0 to 100 ° C., preferably 30 to 90 ° C., and the respective reaction times. Is, for example, in the range of 1 minute to 120 minutes, preferably 2 minutes to 60 minutes.
After reacting a modifier or the like with the active end of the conjugated diene polymer chain, an unreacted active end can be deactivated by adding a polymerization terminator such as alcohol or water such as methanol and isopropanol. preferable.

After deactivating the active end of the conjugated diene polymer chain, polymerize anti-aging agents such as phenol stabilizers, phosphorus stabilizers, sulfur stabilizers, crumbs, and scale inhibitors as desired. After adding to the solution, the polymerization solvent is separated from the polymerization solution by direct drying or steam stripping and the resulting specific conjugated diene rubber is recovered. Before separating the polymerization solvent from the polymerization solution, an extension oil may be mixed into the polymerization solution and the specific conjugated diene rubber may be recovered as an oil extension rubber.
Examples of the extending oil used when the specific conjugated diene rubber is recovered as an oil-extended rubber include paraffinic, aromatic and naphthenic petroleum softeners, plant softeners, and fatty acids. When a petroleum softener is used, it is preferable that the content of polycyclic aromatics extracted by the IP346 method (the testing method of THEINSTITUTEPETROLEUM in the UK) is less than 3%. When using extension oil, the usage-amount is 5-100 mass parts with respect to 100 mass parts of conjugated diene rubbers, Preferably it is 10-60 mass parts, More preferably, it is 20-50 mass parts.

  The specific conjugated diene rubber is a structure in which three or more conjugated diene polymer chains are formed by reacting a conjugated diene polymer chain having an active terminal with the polyorganosiloxane described above (hereinafter referred to as a structure). , “A structure in which three or more conjugated diene polymer chains formed by reacting a conjugated diene polymer chain having an active end with the polyorganosiloxane described above” is simply “three or more It is preferable to contain 5 to 40% by mass, more preferably 5 to 30% by mass, and more preferably 10 to 20% by mass ”of a structure in which a conjugated diene polymer chain is bonded”. % Content is particularly preferable. When the ratio of the structure to which 3 or more conjugated diene polymer chains are bonded is in the above range, the solidification property and the drying property at the time of production are improved, and moreover, when silica is blended, A rubber composition for a tire tread excellent in processability and a tire excellent in lower heat generation can be provided. The ratio (mass fraction) of the structure in which three or more conjugated diene polymer chains are bonded to the total amount of the specific conjugated diene rubber finally obtained is 3 of the conjugated diene polymer chains. Expressed as a coupling ratio above branching. This can be measured by gel permeation chromatography (polystyrene conversion). From the chart obtained by gel permeation chromatography measurement, the area ratio of the peak portion having a peak top molecular weight of 2.8 times or more of the peak top molecular weight indicated by the peak with the smallest molecular weight relative to the total elution area is calculated as the conjugated diene weight. The coupling rate is 3 or more branches of the combined chain.

The aromatic vinyl unit content of the specific conjugated diene rubber 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. preferable.
Although the vinyl bond content of the specific conjugated diene rubber is not particularly limited, it 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 specific conjugated diene type rubber.
The weight average molecular weight (Mw) of the specific conjugated diene rubber is not particularly limited, but for the reason that the effect of the present invention is more excellent, as a value in terms of polystyrene measured by gel permeation chromatography (GPC), 500,000 to It is preferably 800,000, more preferably 600,000 to 700,000.
The molecular weight distribution represented by the ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the specific conjugated diene rubber is preferably 1.1 to 3.0. It is more preferably 2 to 2.5, and particularly preferably 1.2 to 2.2. Mw and Mn are both polystyrene-equivalent values measured by GPC.
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. When the specific conjugated diene rubber is an oil-extended rubber, the Mooney viscosity of the oil-extended rubber is preferably in the above range.

The content of the specific conjugated diene rubber in the diene rubber is 30% by mass or more. Especially, it is preferable that it is 50-90 mass%. The upper limit is not particularly limited and is 100% by mass.
When the content of the specific conjugated diene rubber is less than 30% by mass, the wet performance and the low rolling resistance are insufficient.
The “content of the specific conjugated diene rubber in the diene rubber” refers to the content (% by mass) of the specific conjugated diene rubber with respect to the entire diene rubber.

<Other rubber components>
The diene rubber may contain a rubber component (other rubber components) other than the specific conjugated diene rubber. The rubber component is not particularly limited, but aromatic vinyl-conjugated diene copolymer rubber other than specific conjugated diene rubber, natural rubber, isoprene rubber (IR), butadiene rubber (BR), acrylonitrile-butadiene copolymer. Examples thereof include rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR) and the like. Of these, BR is preferable. Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene butadiene rubber (SBR) other than the specific conjugated diene rubber, styrene isoprene copolymer rubber, and the like.
The content of other rubber components in the diene rubber is not particularly limited, but is preferably 1 to 30% by mass. The “content of other rubber components in the diene rubber” refers to the content (% by mass) of other rubber components with respect to the entire diene rubber.

〔silica〕
The silica contained in the composition of the present invention is not particularly limited, and any conventionally known silica compounded in a rubber composition for uses such as tires can be used.
Examples of the silica include wet silica, dry silica, fumed silica, diatomaceous earth, and the like. As the silica, one type of silica may be used alone, or two or more types of silica may be used in combination.

The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of silica is not particularly limited, is preferably from 100 to 300 m ² / g, more preferably 150 to 200 m ² / g.
In the present specification, the CTAB adsorption specific surface area is a value obtained by measuring the CTAB adsorption amount on the silica surface in accordance with JIS K6217-3: 2001 “Part 3: Determination of specific surface area—CTAB adsorption method”.

In the composition of the present invention, the content of silica is 30 to 150 parts by mass with respect to 100 parts by mass of the diene rubber. Especially, it is preferable that it is 50-100 mass parts.
When the content of the silica is less than 30 parts by mass with respect to 100 parts by mass of the diene rubber, the viscosity is high, and the wet performance and the low rolling resistance are insufficient. Moreover, when the content of the silica exceeds 150 parts by mass with respect to 100 parts by mass of the diene rubber, the viscosity is high, and the scorch resistance and the low rolling resistance become insufficient.

〔Silane coupling agent〕
The silane coupling agent contained in the composition of the present invention is a polysiloxane (specific polysiloxane) represented by an average composition formula of the following formula (S1).
(A) _a (B) _b (C) _c (D) _d (E) _e SiO _{(4-2a-b-c-d-e) / 2} (S1)

In the above formula (S1), A represents a divalent organic group containing a sulfide group (hereinafter also referred to as a sulfide group-containing organic group). Especially, it is preferable that it is group represented by a following formula (S2).
^{_{* - (CH 2) n -S}} x - (CH 2) n - * (S2)
In said formula (S2), n represents the integer of 1-10, and it is preferable that it is an integer of 2-4 especially.
In said formula (S2), x represents the integer of 1-6, and it is preferable that it is an integer of 2-4 especially.
In the above formula (S2), * indicates a bonding position.
Specific examples of the group represented by the above formula (S2), for ^{_{example, * -CH 2 -S 2 -CH 2}} - *, * -C 2 H 4 -S 2 -C 2 H 4 - *, * - _{C 3 H 6 -S 2 -C 3} H 6 - *, * -C 4 H 8 -S 2 -C 4 H 8 - *, * -CH 2 -S 4 -CH 2 - *, * -C 2 H _{4 -S 4 -C 2 H 4 -} *, * -C 3 H 6 -S 4 -C 3 H 6 - *, * -C 4 H 8 -S 4 -C 4 H 8 - * , and the like.

  In the above formula (S1), B represents a monovalent hydrocarbon group having 5 to 20 carbon atoms, and specific examples thereof include a hexyl group, an octyl group, and a decyl group.

In the formula (S1), C represents a hydrolyzable group, and specific examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, and an alkenyloxy group. Especially, it is preferable that it is group represented by a following formula (S3).
^* -OR ² (S3)
In the formula (S3), ^{R 2} is an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group (aryl alkyl group) or an alkenyl group having 2 to 10 carbon atoms having from 6 to 10 carbon atoms In particular, an alkyl group having 1 to 5 carbon atoms is preferable. Specific examples of the alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group, and an octadecyl group. Specific examples of the aryl group having 6 to 10 carbon atoms include a phenyl group and a tolyl group. Specific examples of the aralkyl group having 6 to 10 carbon atoms include a benzyl group and a phenylethyl group. Specific examples of the alkenyl group having 2 to 10 carbon atoms include a vinyl group, a propenyl group, and a pentenyl group.
In the above formula (S3), * indicates a bonding position.

In the above formula (S1), D represents an organic group containing a mercapto group (hereinafter also referred to as a mercapto group-containing organic group). Especially, it is preferable that it is group represented by a following formula (S4).
^{_{* - (CH 2) m -SH}} (S4)
In said formula (S4), m represents the integer of 1-10, and it is preferable that it is an integer of 1-5 especially.
In the above formula (S4), * indicates a bonding position.
Specific examples of the group represented by the formula ^{_{(S4), * -CH 2 SH}} , * -C 2 H 4 SH, * -C 3 H 6 SH, * -C 4 H 8 SH, * -C 5 ^{_{H 10 SH, * -C 6 H}} 12 SH, * -C 7 H 14 SH, * -C 8 H 16 SH, * -C 9 H 18 SH, include _* -C _{10 H} 20 SH.

  In the above formula (S1), E represents a monovalent hydrocarbon group having 1 to 4 carbon atoms.

In the above formula (S1), a to e are relational expressions of 0 ≦ a <1, 0 <b <1, 0 <c <3, 0 ≦ d <1, 0 ≦ e <2, 0 <2a + b + c + d + e <4. Meet.
However, at least one of a and d is not 0. That is, the specific polysiloxane has at least one of a sulfide group-containing organic group and a mercapto group-containing organic group.

In the above formula (S1), a is preferably larger than 0 (0 <a). That is, the specific polysiloxane preferably has a sulfide group-containing organic group. Of these, 0 <a ≦ 0.50 is preferable.
In the above formula (S1), b is preferably 0.10 ≦ b ≦ 0.89.
In the above formula (S1), c is preferably 1.2 ≦ c ≦ 2.0.
In the above formula (S1), d is preferably larger than 0 (0 <d). That is, the specific polysiloxane preferably has a mercapto group-containing organic group. Among these, it is preferable that 0.1 ≦ d ≦ 0.8.
In the formula (S1), d is preferably larger than 0 (0 <d), and both d and a are more preferably larger than 0 (0 <d and 0 <a). That is, the specific polysiloxane preferably has a mercapto group-containing organic group, and more preferably has a sulfide group-containing organic group in addition to the mercapto group-containing organic group.

  The specific polysiloxane is a group represented by the formula (S2) in the formula (S1), and a group represented by the formula (S3) in the formula (S1). It is preferable that D in the formula (S1) is a polysiloxane which is a group represented by the formula (S4).

The weight average molecular weight of the specific polysiloxane is preferably 500 to 2300, and more preferably 600 to 1500. The molecular weight of the specific polysiloxane in the present application is determined in terms of polystyrene by gel permeation chromatography (GPC) using toluene as a solvent.
The mercapto equivalent by the titration method of acetic acid / potassium iodide / potassium iodide / sodium thiosulfate solution of the above specific polysiloxane is preferably 550 to 700 g / mol from the viewpoint of excellent vulcanization reactivity, 600 to More preferably, it is 650 g / mol.

  The specific polysiloxane preferably has 2 to 50 siloxane units (—Si—O—).

  Note that no metal other than a silicon atom (for example, Sn, Ti, Al) exists in the skeleton of the specific polysiloxane.

The method for producing the specific polysiloxane is not particularly limited. As a first preferred embodiment, an organosilicon compound represented by the following formula (S6), an organosilicon compound represented by the following formula (S7), and The method of hydrolyzing and condensing can be mentioned. As a second preferred embodiment, an organosilicon compound represented by the following formula (S5), an organosilicon compound represented by the following formula (S6), and an organosilicon represented by the following formula (S7) The method of hydrolyzing and condensing a compound is mentioned. As a third preferred embodiment, an organosilicon compound represented by the following formula (S5), an organosilicon compound represented by the following formula (S6), and an organosilicon represented by the following formula (S7) The method of hydrolyzing and condensing a compound and the organosilicon compound represented by the following formula (S8) can be given.
Especially, it is preferable that it is the said 2nd suitable aspect.

In the formula ^{(S5), R 51} represents an alkyl group, an aryl group or an alkenyl group having 2 to 10 carbon atoms having 6 to 10 carbon atoms having 1 to 20 carbon atoms, among them, alkyl groups of 1 to 5 carbon atoms It is preferable that Specific examples of the alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group, and an octadecyl group. Specific examples of the aryl group having 6 to 10 carbon atoms include a phenyl group, a tolyl group, and a naphthyl group. Specific examples of the alkenyl group having 2 to 10 carbon atoms include a vinyl group, a propenyl group, and a pentenyl group.
In the formula ^{(S5), R 52} represents an alkyl group or an aryl group having 6 to 10 carbon atoms having 1 to 10 carbon atoms. Specific examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, and a decyl group. Specific examples of the aryl group having 6 to 10 carbon atoms are the same as those for R ⁵¹ described above.
In the above formula (S5), the definition and preferred embodiment of n are the same as n.
In the above formula (S5), the definition and preferred embodiment of x are the same as the above x.
In said formula (S5), y represents the integer of 1-3.

  Specific examples of the organosilicon compound represented by the above formula (S5) include, for example, bis (trimethoxysilylpropyl) tetrasulfide, bis (triethoxysilylpropyl) tetrasulfide, bis (trimethoxysilylpropyl) disulfide, bis (Triethoxysilylpropyl) disulfide and the like.

In the above formula (S6), the definition, specific examples and preferred embodiments of R ⁶¹ are the same as those of R ⁵¹ described above.
In the above formula (S6), the definition, specific examples and preferred embodiments of R ⁶² are the same as those of R ⁵² described above.
In the above formula (S6), the definition of z is the same as y.
In said formula (S6), p represents the integer of 5-10.

  Specific examples of the organosilicon compound represented by the above formula (S6) include, for example, pentyltrimethoxysilane, pentylmethyldimethoxysilane, pentyltriethoxysilane, pentylmethyldiethoxysilane, hexyltrimethoxysilane, and hexylmethyldimethoxysilane. , Hexyltriethoxysilane, hexylmethyldiethoxysilane, octyltrimethoxysilane, octylmethyldimethoxysilane, octyltriethoxysilane, octylmethyldiethoxysilane, decyltrimethoxysilane, decylmethyldimethoxysilane, decyltriethoxysilane, decylmethyl Examples include diethoxysilane.

In the above formula (S7), the definition, specific examples and preferred embodiments of R ⁷¹ are the same as those of R ⁵¹ described above.
In the above formula (S7), the definition, specific examples and preferred embodiments of R ⁷² are the same as those of R ⁵² described above.
In the above formula (S7), the definition and preferred embodiment of m are the same as m.
In the above formula (S7), the definition of w is the same as y.

  Specific examples of the organosilicon compound represented by the above formula (S7) include, for example, α-mercaptomethyltrimethoxysilane, α-mercaptomethylmethyldimethoxysilane, α-mercaptomethyltriethoxysilane, α-mercaptomethylmethyldi Examples include ethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltriethoxysilane, and γ-mercaptopropylmethyldiethoxysilane.

In the above formula (S8), the definition, specific examples and preferred aspects of R ⁸¹ are the same as those of R ⁵¹ described above.
In the above formula (S8), the definition, specific examples and preferred embodiments of R ⁸² are the same as those of R ⁵² described above.
In the formula (S8), the definition of v is the same as y.
In said formula (S8), q represents the integer of 1-4.

  Specific examples of the organosilicon compound represented by the above formula (S8) include, for example, methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, methylethyldiethoxysilane, propyltrimethoxysilane, propylmethyldimethoxysilane, Examples thereof include propylmethyldiethoxysilane.

  When manufacturing the said specific polysiloxane, you may use a solvent as needed. The solvent is not particularly limited, but specifically, aliphatic hydrocarbon solvents such as pentane, hexane, heptane, decane, ether solvents such as diethyl ether, tetrahydrofuran, 1,4-dioxane, formamide, dimethylformamide, N -Amide type solvents such as methylpyrrolidone, aromatic hydrocarbon type solvents such as benzene, toluene and xylene, and alcohol type solvents such as methanol, ethanol and propanol.

When manufacturing the said specific polysiloxane, you may use a catalyst as needed. Examples of the catalyst include acidic catalysts such as hydrochloric acid and acetic acid, Lewis acid catalysts such as ammonium fluoride, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium acetate, potassium acetate, sodium bicarbonate, potassium carbonate, potassium bicarbonate And alkali metal salts such as calcium carbonate, sodium methoxide and sodium ethoxide, and amine compounds such as triethylamine, tributylamine, pyridine and 4-dimethylaminopyridine.
The catalyst is preferably not an organometallic compound containing Sn, Ti or Al as a metal. When such an organometallic compound is used, a metal is introduced into the polysiloxane skeleton, and the specific polysiloxane (metal other than silicon atoms (for example, Sn, Ti, Al) is not present in the skeleton) is obtained. It may not be possible.

  As the organosilicon compound used in producing the specific polysiloxane, a silane coupling agent having a mercapto group [for example, an organosilicon compound represented by the formula (S7)] and a silane cup having a sulfide group or a mercapto group When a silane coupling agent other than a ring agent [for example, an organosilicon compound represented by formula (S6) or formula (S8)] is used in combination, a silane coupling agent having a mercapto group and a silane having a sulfide group or a mercapto group A mixing ratio (molar ratio) with a silane coupling agent other than the coupling agent (a silane coupling agent having a mercapto group / a silane coupling agent other than a silane coupling agent having a sulfide group or a mercapto group) is 1.1. /8.9 to 6.7 / 3.3 is preferable, and 1.4 / 8.6 to 5.0 And more preferably in the range of 5.0.

  As an organosilicon compound used in producing the specific polysiloxane, a silane coupling agent having a mercapto group [for example, an organosilicon compound represented by the formula (S7)] and a silane coupling agent having a sulfide group [ For example, when the organosilicon compound represented by the formula (S5)] is used in combination, the mixing ratio (molar ratio) of the silane coupling agent having a mercapto group and the silane coupling agent having a sulfide group (a silane having a mercapto group) The coupling agent / silane coupling agent having a sulfide group) is preferably 2.0 / 8.0 to 8.9 / 1.1, and 2.5 / 7.5 to 8.0 / 2. More preferably 0.

  As an organosilicon compound used for producing the specific polysiloxane, a silane coupling agent having a mercapto group [for example, an organosilicon compound represented by the formula (S7)], a silane coupling agent having a sulfide group [ For example, an organosilicon compound represented by formula (S5) and / or a silane coupling agent other than a silane coupling agent having a sulfide group or a mercapto group [for example, represented by formula (S6) or formula (S8) When the organosilicon compound] is used in combination, the amount of the silane coupling agent having a mercapto group is preferably 10.0 to 73.0% in the total amount (mol) of the former three. The amount of the silane coupling agent having a sulfide group is preferably 5.0 to 67.0% of the total amount of the former three. The amount of the silane coupling agent other than the silane coupling agent having a sulfide group or mercapto group is preferably 16.0 to 85.0% in the total amount of the former three.

In the composition of the present invention, the content of the silane coupling agent (specific polysiloxane) is 2.0 to 20% by mass with respect to the content of silica described above. Especially, it is preferable that it is 5-15 mass%.
When the content of the silane coupling agent is less than 2.0% by mass with respect to the content of silica, the viscosity is high, and scorch resistance, wet performance, and low rolling resistance are insufficient. Moreover, when content of the said silane coupling agent exceeds 20 mass% with respect to content of silica, scorch resistance will become inadequate.

[Optional ingredients]
The composition of this invention can contain another component (arbitrary component) in the range which does not impair the effect and the objective as needed.
Examples of the optional component include carbon black, filler, silane coupling agent other than the specific polysiloxane, aromatic modified terpene resin, zinc oxide (zinc white), stearic acid, anti-aging agent, wax, and processing aid. And various additives generally used in rubber compositions such as oil, liquid polymer, thermosetting resin, vulcanizing agent (for example, sulfur), and vulcanization accelerator.

<Aromatic modified terpene resin>
The composition of the present invention preferably further contains an aromatic-modified terpene resin for the reason that the scorch resistance and wet performance are more excellent.
The softening point of the aromatic modified terpene resin is not particularly limited, but is preferably 60 to 150 ° C, and more preferably 100 to 130 ° C.
Here, the softening point is a Vicat softening point measured according to JIS K7206: 1999.
In the composition of the present invention, the content of the aromatic modified terpene resin is not particularly limited, but is preferably 3 to 30 parts by mass with respect to 100 parts by mass of the diene rubber, and 5 to 10 parts by mass. More preferably.

<Alkyltrialkoxysilane>
In addition, the composition of the present invention has a lower viscosity, and more excellent low rolling resistance and scorch resistance, so that an alkyltrialkoxysilane represented by the following formula (I) (hereinafter simply referred to as alkyltrialkoxysilane). (Also referred to as alkoxysilane).

In the above formula ^{(I), R 11} represents an alkyl group having 1 to 20 carbon atoms. Among these, an alkyl group having 7 to 10 carbon atoms is preferable. Specific examples of the alkyl group having 1 to 20 carbon atoms of R ¹¹ include, for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group. , Undecyl group, dodecyl group and the like. Of these, an octyl group and a nonyl group are preferable.
In the above formula (I), R ¹² represents a methyl group or an ethyl group. A plurality of R ¹² may be the same or different.

  In the composition of the present invention, the content of the alkyltrialkoxysilane is not particularly limited, but is preferably 0.2 to 20% by mass with respect to the silica content described above, and is 1 to 10% by mass. More preferably.

[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 155 ° 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.

[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 the composition of this invention for the tread.
FIG. 1 shows a schematic partial sectional view of a 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, reference numeral 1 represents a bead portion, reference numeral 2 represents a sidewall portion, and reference numeral 3 represents a tire tread portion.
Further, a carcass layer 4 in which fiber cords are embedded is mounted between the pair of left and right bead portions 1, and the end 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 tire is filled, inert gas, such as nitrogen, argon, helium other than the air which adjusted normal or oxygen partial pressure, can be used.

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

<Production of specific conjugated diene rubber>
Cyclohexane (35 g) and tetramethylethylenediamine (1.4 mmol) were added to a 100 mL ampoule bottle purged with nitrogen, and n-butyllithium (4.3 mmol) was further added. Then, isoprene (21.6 g) and styrene (3.1 g) were slowly added and reacted in an ampoule bottle at 50 ° C. for 120 minutes to obtain a polymer block A having an active end. About this polymer block A, the weight average molecular weight, molecular weight distribution, aromatic vinyl unit content, isoprene unit content, and 1, 4- bond content were measured. The measurement results are shown in Table 1.
Next, cyclohexane (4000 g), 1,3-butadiene (474.0 g), and styrene (126.0 g) were charged in an autoclave equipped with a stirrer under a nitrogen atmosphere, and then the active terminal obtained above was added. The entire amount of the polymer block A was added, and polymerization was started at 50 ° C. After confirming that the polymerization conversion ratio was in the range of 95% to 100%, polyorganosiloxane A represented by the following formula (4) was used with an epoxy group content of 1.42 mmol (used). It was added in the form of a 20% by mass xylene solution so as to be equivalent to 0.33 mol of n-butyllithium, 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 specific conjugated diene rubber. A small amount of an anti-aging agent (Irganox 1520, manufactured by BASF) was added to this solution, and 25 parts of Fukkoreramic 30 (manufactured by Nippon Oil Co., Ltd.) as an extending oil was added to 100 parts by mass of the specific conjugated diene rubber. After addition of parts by mass, solid rubber was recovered by a steam stripping method. The obtained solid rubber was dehydrated with a roll and dried in a drier to obtain a solid specific conjugated diene rubber.

In the formula _{(4), X 1, X} 4, R 1 ~R 3 and R ₅ to R ₈ is a methyl group. In the above formula (4), m is 80 and k is 120. In the above formula (4), X ₂ is a group represented by the following formula (5) (here, * represents a bonding position).

  In addition, about the obtained specific conjugated diene type rubber, the weight average molecular weight, molecular weight distribution, the coupling rate of 3 or more branches, aromatic vinyl unit content, vinyl bond content, and Mooney viscosity were measured. The measurement results are shown in Table 2. The measurement method is as follows.

(Weight average molecular weight, molecular weight distribution, and coupling ratio of 3 or more branches)
Weight average molecular weight, molecular weight distribution, and coupling ratio of 3 or more branches (ratio of “structure in which 3 or more conjugated diene polymer chains are bonded to specific conjugated diene rubber or comparative conjugated diene rubber 2” (mass %)), A chart based on the molecular weight in terms of polystyrene was obtained by gel permeation chromatography and obtained based on the chart. The specific measurement conditions for gel permeation chromatography are as follows.

-Measuring instrument: HLC-8020 (manufactured by Tosoh Corporation)
Column: GMH-HR-H (manufactured by Tosoh Corporation) was connected in series. Detector: differential refractometer RI-8020 (manufactured by Tosoh Corporation)
-Elution night: Tetrahydrofuran-Column temperature: 40 ° C

  Here, the coupling ratio of three or more branches is the peak portion area (s2) having a peak top molecular weight of 2.8 times or more of the peak top molecular weight indicated by the smallest peak of molecular weight with respect to the total elution area (s1). The ratio (s2 / s1).

(Aromatic vinyl unit content and vinyl bond content)
About aromatic vinyl unit content and vinyl bond content, it measured by < ¹ > H-NMR.

(Mooney viscosity)
The Mooney viscosity (ML _{1 + 4} , 100 ° C.) was measured according to JIS K6300-1: 2013.

<Production of Comparative Conjugated Diene Rubber 1>
Into an autoclave reactor with a nitrogen content of 10 L, cyclohexane 4533 g, styrene 338.9 g (3.254 mol), butadiene 468.0 g (8.652 mol), isoprene 20.0 g (0.294 mol) and N, N, N ', N'-tetramethylethylenediamine 0.189 mL (1.271 mmol) was charged and stirring was started. After the temperature of the contents in the reaction vessel was adjusted to 50 ° C., 5.061 mL (7.945 mmol) of n-butyllithium was added. After the polymerization conversion rate reached almost 100%, 12.0 g of isoprene was further added and reacted for 5 minutes, and then 0.281 g (0.318 mmol) of a 40 wt% toluene solution of 1,6-bis (trichlorosilyl) hexane. ) Was added and allowed to react for 30 minutes. Furthermore, the polyorganosiloxane A represented by the above formula (4) is 20% by mass so that the epoxy group content is 1.00 mmol (corresponding to 0.13 mol of n-butyllithium used). It added in the state of the density | concentration xylene solution, and was made to react for 30 minutes. 0.5 mL of methanol was added and stirred for 30 minutes to obtain a solution containing a conjugated diene rubber. A small amount of an anti-aging agent (Irganox 1520, manufactured by BASF) was added to the resulting solution, and 25 parts of Fukkor Elastic 30 (manufactured by Shin Nippon Oil Co., Ltd.) as an extender oil was added to 100 parts by mass of the conjugated diene rubber. After addition of parts by mass, solid rubber was recovered by a steam stripping method. The obtained solid rubber was dehydrated with a roll and dried in a drier to obtain a solid conjugated diene rubber. The obtained conjugated diene rubber is referred to as comparative conjugated diene rubber 1.

<Production of specific polysiloxane 1>
A 2 L separable flask equipped with a stirrer, a reflux condenser, a dropping funnel and a thermometer was charged with 107.8 g (0.2 mol) of bis (triethoxysilylpropyl) tetrasulfide (KBE-846 manufactured by Shin-Etsu Chemical Co., Ltd.), γ-mercapto. Contains 190.8 g (0.8 mol) of propyltriethoxysilane (KBE-803, Shin-Etsu Chemical Co., Ltd.), 442.4 g (1.6 mol) of octyltriethoxysilane (KBE-3083, Shin-Etsu Chemical Co., Ltd.) and 190.0 g of ethanol. Thereafter, a mixed solution of 37.8 g (2.1 mol) of 0.5N hydrochloric acid and 75.6 g of ethanol was added dropwise at room temperature. Then, it stirred at 80 degreeC for 2 hours. Thereafter, filtration, 17.0 g of a 5% KOH / EtOH solution was dropped, and the mixture was stirred at 80 ° C. for 2 hours. Then, 480.1 g of polysiloxane of brown transparent liquid was obtained by concentration under reduced pressure and filtration. As a result of measurement by GPC, the average molecular weight was 840, and the average polymerization degree was 4.0 (set polymerization degree 4.0). Moreover, as a result of measuring mercapto equivalent by acetic acid / potassium iodide / potassium iodate addition-sodium thiosulfate solution titration method, it was 730 g / mol, and it was confirmed that it was the mercapto group content as set. From the above, it is shown by the following average composition formula.
_{(-C 3 H 6 -S 4 -C} 3 H 6 -) 0.071 (-C 8 H 17) 0.571 (-OC 2 H 5) 1.50 (-C 3 H 6 SH) 0.286 SiO _0.75
The obtained polysiloxane is designated as specific polysiloxane 1.

<Production of specific polysiloxane 2>
In a 2 L separable flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermometer, γ-mercaptopropyltriethoxysilane (KBE-803, Shin-Etsu Chemical Co., Ltd.) 190.8 g (0.8 mol), octyltriethoxysilane ( After putting 442.4 g (1.6 mol) and ethanol 162.0 g of Shin-Etsu Chemical KBE-3083), a mixed solution of 0.5N hydrochloric acid 32.4 g (1.8 mol) and ethanol 75.6 g at room temperature. It was dripped. Then, it stirred at 80 degreeC for 2 hours. Thereafter, filtration, 14.6 g of a 5% KOH / EtOH solution was added dropwise, and the mixture was stirred at 80 ° C. for 2 hours. Then, the polysiloxane 412.3 of colorless and transparent liquid was obtained by concentrate | evaporating under reduced pressure and filtering. As a result of measurement by GPC, the average molecular weight was 850, and the average polymerization degree was 4.0 (set polymerization degree 4.0). Moreover, as a result of measuring a mercapto equivalent by the acetic acid / potassium iodide / potassium iodate addition-sodium thiosulfate solution titration method, it was 650 g / mol and it was confirmed that it is a mercapto group content as set. From the above, it is shown by the following average composition formula.
(—C ₈ H ₁₇ ) _0.667 (—OC ₂ H ₅ ) _1.50 (—C ₃ H ₆ SH) _0.333 SiO _0.75
The obtained polysiloxane is designated as specific polysiloxane 2.

<Preparation of rubber composition for tire tread>
The components shown in Table 3 below were blended in the proportions (parts by mass) shown in Table 3 below.
Specifically, first, the components excluding sulfur and the vulcanization accelerator among the components shown in Table 3 below were raised to around 150 ° C. using a 1.7 liter closed Banbury mixer, and then 5 After mixing for a minute, it was discharged and cooled to room temperature to obtain a masterbatch. 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.
In Table 3, for the comparative conjugated diene rubber 1 and the specific conjugated diene rubber, the upper value is the amount of rubber (oil-extended product) (unit: parts by mass), and the lower value is the net value of the rubber. It is an amount (unit: parts by mass).
In Table 3, for the comparative silane coupling agent and silane coupling agent 1-2, the upper value is the amount (part by mass) of the comparative silane coupling agent and silane coupling agent 1-2, A value is content (mass%) of the comparison silane coupling agent with respect to content of a silica, and the silane coupling agents 1-2.

<Evaluation>
The following evaluation was performed about the obtained rubber composition for tire treads.

(Wet performance)
The obtained rubber composition for tire tread (unvulcanized) was press-vulcanized at 160 ° C. for 20 minutes in a mold (15 cm × 15 cm × 0.2 cm) to prepare a vulcanized rubber sheet.
About the produced vulcanized rubber sheet, in accordance with JIS K6394: 2007, using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.), conditions of stretch deformation strain rate 10% ± 2%, frequency 20 Hz, temperature 0 ° C. Then, tan δ (0 ° C.) was measured.
The results are shown in Table 3 ("Wet performance" column in Table 3). The results were expressed as an index with tan δ (0 ° C.) of the standard example as 100. The larger the index, the larger the tan δ (0 ° C.), and the better the wet performance when made into a tire.

(Rolling resistance)
Instead of measuring at a temperature of 0 ° C., tan δ (60 ° C.) was measured according to the same procedure as the wet performance described above except that the measurement was performed at a temperature of 60 ° C.
The results are shown in Table 3 ("Rolling resistance" column in Table 3). The results were expressed as an index with tan δ (60 ° C.) of the standard example as 100. The smaller the index, the smaller the tan δ (60 ° C.), and the lower the rolling resistance when the tire is made (excellent in low rolling resistance).

(viscosity)
With respect to the obtained rubber composition for tire tread (unvulcanized), Mooney viscosity (ML _{1 + 4} ) at 100 ° C. was measured according to the method of JIS K6300-1: 2013. The results are shown in Table 3 ("Viscosity" column in Table 3). The result was expressed as an index with the Mooney viscosity of the standard example as 100. The smaller the index, the lower the viscosity.

(Scorch time)
About the obtained rubber composition for tire treads (unvulcanized | cured), based on JISK6300-1: 2013, the scorch time was measured on the conditions of test temperature 125 degreeC using the L-shaped rotor.
The results are shown in Table 3. The result was expressed as an index with the scorch time of the standard example as 100. The larger the index, the longer the scorch time and the better the scorch resistance.

The details of each component in Table 3 are as follows.
Comparative conjugated diene rubber 1: Comparative conjugated diene rubber 1 produced as described above (containing 25 mass of oil-extended oil with respect to 100 mass parts of rubber) (aromatic vinyl unit content: 42 mass%, vinyl bond Content: 32% by mass, Tg: −25 ° C., Mw: 750,000)
Specific conjugated diene rubber: Specific conjugated diene rubber produced as described above (including 25 parts of oil-extended oil with respect to 100 parts by weight of rubber)
BR: Nipol 1220 (butadiene rubber, manufactured by Nippon Zeon)
Silica: ZEOSIL 1165MP (CTAB adsorption specific surface area: 159 m ² / g, manufactured by Rhodia)
・ Carbon black: Show black N339 (manufactured by Cabot Japan)
Comparative silane coupling agent: KBE-803 (3-mercaptopropyltriethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.)
Silane coupling agent 1: Specific polysiloxane 1 synthesized as described above
Silane coupling agent 2: Specific polysiloxane 2 synthesized as described above
-Alkyltrialkoxysilane: Octyltriethoxysilane (KBE-3083, manufactured by Shin-Etsu Chemical Co., Ltd.)
Aromatic modified terpene resin: YS resin TO-125 (softening point: 125 ± 5 ° C., manufactured by Yasuhara Chemical Co., Ltd.)
・ Oil: Extract No. 4 S (made by Showa Shell Sekiyu KK)
・ Processing aid: Stractol EF44 (manufactured by S & S)
・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
・ Stearic acid: Beads stearic acid (manufactured by NOF Corporation)
・ Sulfur: Fine powder sulfur with Jinhua seal oil (sulfur content 95.24 mass%, manufactured by Tsurumi Chemical Co., Ltd.)
・ Vulcanization accelerator: SANTOCURE CBS (manufactured by FLEXSYS)

As can be seen from Table 3, the rubber composition for tire treads of Examples of the present application containing the specific conjugated diene rubber and the specific polysiloxane has a low viscosity, and excellent scorch resistance, wet performance and low rolling resistance. Showed sex. Among them, Examples 2 to 6 in which the content of the specific conjugated diene rubber in the diene rubber is 50% by mass or more showed lower viscosity, and more excellent wet characteristics and low rolling resistance. .
From the comparison between Examples 2 and 3, Example 2 in which the silica content is 50 parts by mass or more with respect to 100 parts by mass of the diene rubber has a lower viscosity, and more excellent scorch resistance and wetness. Shows performance and low rolling resistance.
Further, from the comparison between Examples 2 and 4, Example 2 in which a in the formula (S1) is larger than 0 (the specific polysiloxane has a sulfide group-containing organic group) has a lower viscosity, and more Excellent scorch resistance.
Further, in comparison with Examples 2 and 5, Example 5 containing an alkyltrialkoxysilane had a lower viscosity, and also exhibited superior scorch resistance, wet characteristics, and low rolling resistance.
From a comparison between Examples 2 and 6, Example 6 containing an aromatic-modified terpene resin had a lower viscosity, and showed better scorch resistance and wet performance.

On the other hand, Comparative Example 1 containing a specific conjugated diene rubber but no specific polysiloxane (containing a silane coupling agent other than the specific polysiloxane) had insufficient wet performance and low rolling resistance.
Further, Comparative Examples 2 and 3, which contain the specific conjugated diene rubber and the specific polysiloxane, but the content of the specific conjugated diene rubber in the diene rubber is less than 30% by mass, are also wet performance and low rolling resistance. Was insufficient.
Further, Comparative Example 4 containing a specific conjugated diene rubber and a specific polysiloxane but having a specific polysiloxane content of less than 2.0% by mass with respect to the silica content has a high viscosity, and has a scorch resistance. , Wet performance and low rolling resistance were insufficient.
Further, Comparative Example 5, which contains the specific conjugated diene rubber and the specific polysiloxane, but the content of the specific polysiloxane exceeds 20% by mass with respect to the content of silica, has insufficient scorch resistance.
Further, Comparative Example 6 in which the silica content was less than 30 parts by mass with respect to 100 parts by mass of the diene rubber had high viscosity, and wet performance and low rolling resistance were insufficient.
Further, Comparative Example 7 in which the silica content exceeds 150 parts by mass with respect to 100 parts by mass of the diene rubber had high viscosity, and the scorch resistance and low rolling resistance were 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 (6)

Containing a diene rubber, silica, and a silane coupling agent,
The silane coupling agent is a polysiloxane represented by an average composition formula of the following formula (S1):
The diene rubber contains a specific conjugated diene rubber, and the content of the specific conjugated diene rubber in the diene rubber is 30% by mass or more,
The specific conjugated diene rubber, I conjugated diene rubber der produced by the production method of the conjugated diene rubber and a and C following steps A and B in this order, the aromatic vinyl unit content 38 to 48 % by mass, Ri conjugated diene rubber der,
The silica content is 30 to 150 parts by mass with respect to 100 parts by mass of the diene rubber.
A rubber composition for a tire tread, wherein a content of the silane coupling agent is 2.0 to 20% by mass with respect to a content of the silica.
(A) _a (B) _b (C) _c (D) _d (E) _e SiO _{(4-2a-b-c-d-e) / 2} (S1)
(In formula (S1), A represents a divalent organic group containing a sulfide group, B represents a monovalent hydrocarbon group having 5 to 20 carbon atoms, C represents a hydrolyzable group, and D represents Represents an organic group containing a mercapto group, E represents a monovalent hydrocarbon group having 1 to 4 carbon atoms, a to e are 0 ≦ a <1, 0 <b <1, 0 <c <3, 0 ≦ d <1, 0 ≦ e <2, 0 <2a + b + c + d + e <4, where at least one of a and d is not 0.)
Step A: by polymerizing a monomer mixture containing isoprene and aromatic vinyl, the isoprene unit content is 80 to 95% by mass, the aromatic vinyl unit content is 5 to 20% by mass, and the weight Step of forming polymer block A having an active terminal having an average molecular weight of 500 to 15,000 and step B: The polymer block A and a monomer mixture containing 1,3-butadiene and aromatic vinyl And the polymerization reaction is continued, and the polymer block B having an active terminal is formed continuously with the polymer block A, thereby having the polymer block A and the polymer block B. Step of obtaining a conjugated diene polymer chain having a terminal and step C: Polyorganosiloxane represented by the following formula (1) at the active terminal of the conjugated diene polymer chain Reacting
(In the formula _(1), R 1 ~R ₈ is an alkyl group or an aryl group having 6 to 12 carbon atoms, 1 to 6 carbon atoms, which may be different from be the same as each other. X ₁ and X ₄ are composed of a group having 4 to 12 carbon atoms 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. Any one of groups selected from the group, which may be the same or different from each other, and X ₂ is an alkoxy group having 1 to 5 carbon atoms, or 4 to 12 carbon atoms containing an epoxy group. of a group, a plurality of X ₂ good .X ₃ be different even identical to one another is a group containing repeating units of alkylene glycol having 2 to 20, when X ₃ have multiple , They may be the same or different from each other. Is an integer of 3 to 200, n is from 0 to 200 integer, k is an integer of 0 to 200.)   The rubber composition for a tire tread according to claim 1, wherein a is greater than 0 in the formula (S1).   The rubber composition for a tire tread according to claim 1, wherein d is greater than 0 in the formula (S1). Furthermore, an alkyltrialkoxysilane represented by the following formula (I) is contained,
The rubber composition for a tire tread according to any one of claims 1 to 3, wherein a content of the alkyltrialkoxysilane is 0.2 to 20 mass% with respect to a content of the silica.

(In formula (I), R ¹¹ represents an alkyl group having 1 to 20 carbon atoms, R ¹² represents a methyl group or an ethyl group. Plural R ¹² may be the same or different.) Furthermore, it contains an aromatic modified terpene resin having a softening point of 60 to 150 ° C.,
The rubber composition for a tire tread according to any one of claims 1 to 4, wherein a content of the aromatic modified terpene resin is 3 to 30 parts by mass with respect to 100 parts by mass of the diene rubber.   The pneumatic tire which used the rubber composition for tire treads of any one of Claims 1-5 for tread.