JP6476555B2 - 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. Moreover, the improvement of wet performance is calculated | required from the surface of safety. On the other hand, a method is known in which silica is blended with the rubber component constituting the tread portion of the tire so as 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 was a problem that the effect of improving could not be obtained sufficiently.

  Under such circumstances, Patent Document 1 discloses a rubber composition containing a conjugated diene rubber having an isoprene block. According to Patent Document 1, it is described that by using the above composition, 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. ing.

  In addition, the rubber composition for a tire tread is required to have less crosslinking (rubber burn) at the storage stage or the stage before the vulcanization process. That is, excellent scorch resistance (workability) is required.

International Publication No. 2011/105362

  On the other hand, due to environmental problems and resource problems, further fuel efficiency of vehicles is required, and accordingly, further improvement of tire rolling resistance is required. Further, with the improvement of the required safety level, further improvement in wet performance is also required.

Under such circumstances, when the rubber composition described in Patent Document 1 was examined, it was revealed that although the scorch resistance was excellent, the low rolling resistance and the wet performance did not satisfy the levels required recently. .
Therefore, in view of the above circumstances, an object of the present invention is to provide a rubber composition for a tire tread that is excellent in wet performance and low rolling resistance and excellent in scorch resistance when formed into a tire.

  As a result of intensive studies on the above problems, the present inventors have found that a rubber component containing a specific amount of a specific conjugated diene rubber and a specific silane coupling agent (polyester represented by an average composition formula of formula (1) described later) In combination with (siloxane), it was found that a rubber composition for a tire tread having excellent wet performance and low rolling resistance and excellent scorch resistance when made into a tire can be obtained, leading to the present invention. .

(1) containing a rubber component containing 20% by mass or more of conjugated diene rubber (P), silica (Q), and silane coupling agent (R),
Three or more conjugated diene polymer chains (p1) obtained by reacting the conjugated diene rubber (P) with a conjugated diene polymer chain (p1) and a modifier (p2) are the modifier. Containing 5 mass% or more of the structure (p) formed by bonding via (p2),
The conjugated diene polymer chain (p1) is a conjugated diene polymer chain having an isoprene block containing 70% by mass or more of isoprene units at one end and an active terminal at the other end.
The modifier (p2) has an epoxy group and / or a hydrocarbyloxysilyl group, and the total number of the epoxy group and the hydrocarbyloxy group contained in the hydrocarbyloxysilyl group is 3 or more. Yes,
The silane coupling agent (R) is a polysiloxane represented by an average composition formula of the following formula (1),
Content of the said silane coupling agent (R) is 1.0-20 mass% with respect to content of the said silica (Q),
A rubber composition for a tire tread, wherein the content of the silica (Q) is 60 to 200 parts by mass with respect to 100 parts by mass of the rubber component.
(A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-bcde) / 2} (1)
(In formula (1), A represents a divalent organic group containing a sulfide group, B represents a monovalent hydrocarbon group having 5 to 10 carbon atoms, C represents a hydrolyzable group, and D represents R ¹ represents an organic group containing a mercapto group, R ¹ represents a monovalent hydrocarbon group having 1 to 4 carbon atoms, and 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 (provided that either a or b is not 0).
(2) The rubber composition for a tire tread according to (1), wherein a vinyl bond content derived from an isoprene unit in the isoprene block is 5 to 85% by mass.
(3) The portion other than the isoprene block in the conjugated diene polymer chain (p1) is a homopolymer chain of a conjugated diene monomer or a copolymer of a conjugated diene monomer and an aromatic vinyl monomer. The rubber composition for a tire tread according to the above (1) or (2), which is a polymer chain.
(4) The rubber composition for a tire tread according to any one of (1) to (3), wherein a is greater than 0 in the formula (1).
(5) The rubber composition for tires according to any one of (1) to (4), wherein b is greater than 0 in the formula (1).
(6) The rubber component according to any one of (1) to (5), further including 1 to 30 parts by mass of an aromatic-modified terpene resin having a softening point of 60 to 150 ° C. with respect to 100 parts by mass of the rubber component. Rubber composition for tire tread.
(7) A pneumatic tire using the tire tread rubber composition according to any one of (1) to (6) as a tire tread.

  As shown below, according to the present invention, a tire tread rubber composition excellent in wet performance and low rolling resistance and excellent in scorch resistance when made into a tire, and air using the tire tread An inset tire can be provided.

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.

[Rubber composition for tire tread]
The rubber composition for a tire tread of the present invention contains a rubber component containing 20% by mass or more of a conjugated diene rubber (P), silica (Q), and a silane coupling agent (R). The rubber (P) is obtained by reacting the conjugated diene polymer chain (p1) with the modifier (p2), and the three or more conjugated diene polymer chains (p1) are converted from the modifier (p2). 5% by mass or more of the structure (p) formed by bonding via the copper.
Here, the conjugated diene polymer chain (p1) is a conjugated diene polymer chain having an isoprene block containing 70% by mass or more of isoprene units at one end and an active end at the other end. is there.
The modifier (p2) has an epoxy group and / or a hydrocarbyloxysilyl group, and the total number of the epoxy group and the hydrocarbyloxy group contained in the hydrocarbyloxysilyl group is 3 or more. It is an agent.
Moreover, the said silane coupling agent (R) is polysiloxane represented by the average compositional formula of Formula (1) mentioned later.
Moreover, content of the said silane coupling agent (R) is 1.0-20 mass% with respect to content of the said silica (Q).
Moreover, content of the said silica (Q) is 60-200 mass parts with respect to 100 mass parts of said rubber components.

  The rubber composition for a tire tread of the present invention includes a conjugated diene rubber (P) containing a predetermined amount of a structure (p) described later and a silane coupling agent (R) (an average composition formula of the formula (1) described later). It is considered that the rubber composition for tire treads exhibiting excellent properties in all of wet performance, low rolling resistance and scorch resistance.

The reason is not clear, but it is presumed that it is as follows.
As will be described later, the structure (p) has a structure in which a conjugated diene polymer chain (p1) having an isoprene block is bonded via a modifier (p2). Moreover, the polysiloxane (henceforth a specific polysiloxane) represented by the average compositional formula of Formula (1) mentioned later has a hydrolysable group and a mercapto group.
The rubber composition for a tire tread of the present invention uses the conjugated diene rubber (P) containing the predetermined amount of the structure (p) and the specific polysiloxane in combination, so that the mercapto group of the specific polysiloxane and the hydrolyzability The group interacts with both the isoprene block of the structure (p) and the silica (Q) to improve the dispersibility of the silica (Q) in the rubber component, resulting in excellent wet performance and low It is considered to show rolling resistance. In particular, the strong affinity of the mercapto group for the isoprene block is considered to ensure the excellent characteristics as described above. This is because the conjugated diene rubber (P) and the specific polysiloxane are used rather than the case where the specific polysiloxane is used but the conjugated diene rubber not containing the structure (p) is used (Comparative Examples 4 and 5 described later). Is also inferred from the fact that the wet performance and the low rolling resistance are superior in the case of using together (Examples described later).
Furthermore, it is considered that the mercapto group of the specific polysiloxane is stabilized by the polysiloxane structure of the specific polysiloxane, and excellent scorch resistance is ensured. This is because the case where the specific polysiloxane is used (the application example described later) is more resistant than the case where the mercapto-based silane coupling agent other than the specific polysiloxane is used (Comparative Examples 1 and 2 described later). It is also inferred from the fact that it has excellent scorch properties.

  Hereinafter, each component contained in the rubber composition for a tire tread of the present invention will be described in detail.

[Rubber component]
The rubber component contained in the tire tread rubber composition of the present invention contains 20% by mass or more of a conjugated diene rubber (P) described later. The rubber component may contain a diene rubber other than the conjugated diene rubber (P).

  In the conjugated diene rubber (P), three or more conjugated diene polymer chains (p1) obtained by a reaction between a conjugated diene polymer chain (p1) described later and a modifier (p2) described later are modified. It contains 5% by mass or more of a structure (p) described later formed by bonding via an agent (p2).

<Conjugated diene polymer chain (p1)>
The conjugated diene polymer chain (p1) used to form the structure (p) contained in the conjugated diene rubber (P) is a polymer chain comprising a conjugated diene monomer unit. There is no particular limitation as long as it has an isoprene block at one end and an active end (polymerization active end or living growth end) at the other end.

  The conjugated diene polymer chain (p1) is obtained by, for example, subjecting an isoprene or isoprene mixture containing a predetermined amount of isoprene in an inert solvent by living polymerization using a polymerization initiator (active end (polymerization activity)). Isoprene block having a terminal or living growth terminal), and then a monomer mixture comprising a conjugated diene monomer or a conjugated diene monomer is coupled to an isoprene block having an active terminal, followed by living polymerization Can be obtained. The monomer mixture containing the conjugated diene monomer preferably further contains an aromatic vinyl monomer.

(Isoprene block)
The isoprene block is a homopolymer of isoprene or a copolymer of isoprene and another monomer (monomer), and is a polyisoprene having a content of isoprene units of 70% by mass or more. The content of isoprene units in the isoprene block is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass.

  As described above, the conjugated diene polymer chain (p1) has the isoprene block at one end. An isoprene block may be further included in the chain of the conjugated diene polymer chain (p1). It has an isoprene block at both ends, and an isoprene block at one end of them may have an active end, but it is preferable from the viewpoint of productivity to have an isoprene block only at the end that is not the active end. .

  The weight average molecular weight of the isoprene block is not particularly limited, but is preferably 500 to 25,000, more preferably 1,000 to 15,000, and particularly preferably 1,500 to 10,000 from the viewpoint of strength. is there.

  The molecular weight distribution represented by the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the isoprene block is not particularly limited, but from the viewpoint of productivity, preferably 1.0 to 1. 5, More preferably, it is 1.0-1.4, Most preferably, it is 1.0-1.3.

  The other monomer that can be copolymerized with isoprene used for obtaining the isoprene block is not particularly limited as long as it is copolymerizable with isoprene. For example, 1,3-butadiene, styrene, α-methylstyrene Etc. can be used. Among these, styrene is preferable. In the isoprene block, the content of other monomer units is less than 30% by mass, preferably less than 20% by mass, more preferably less than 10% by mass, and monomers other than isoprene units. It is particularly preferred not to contain.

  As the inert solvent used for the polymerization of isoprene (or isoprene mixture), any solvent that is usually used in solution polymerization and does not inhibit the polymerization reaction can be used without particular limitation. 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; aromatics such as benzene, toluene and xylene. Group hydrocarbons; and the like. The amount of the inert solvent used is not particularly limited, but is usually an amount such that the concentration of all monomers (isoprene and other monomers) is 1 to 50% by mass, preferably 10 to 40% by mass. It is the quantity which becomes.

  The polymerization initiator for synthesizing the isoprene block is not particularly limited as long as it is capable of living polymerizing isoprene (or an isoprene mixture) to give a polymer chain having an active end. A polymerization initiator mainly comprising an alkali metal compound, an organic alkaline earth metal compound, a lanthanum series metal compound, or the like is preferably used. Specific examples of the organic alkali metal compound include, for example, organic monolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbenelithium; dilithiomethane, 1,4-dilithiobutane Organic polyvalent lithium compounds such as 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, and 1,3,5-tris (lithiomethyl) benzene; organic sodium compounds such as sodium naphthalene; Organic potassium compounds such as potassium naphthalene; and the like. Examples of organic alkaline earth metal compounds include di-n-butylmagnesium, di-n-hexylmagnesium, diethoxycalcium, calcium distearate, di-t-butoxystrontium, diethoxybarium, diisopropoxybarium, and diethyl. Examples include mercaptobarium, di-t-butoxybarium, diphenoxybarium, diethylaminobarium, barium distearate, and diketylbarium. As a polymerization initiator having a lanthanum series metal compound as a main catalyst, a lanthanum series metal salt comprising a lanthanum series metal such as lanthanum, cerium, praseodymium, neodymium, samarium and gadolinium, a carboxylic acid, and a phosphorus-containing organic acid As a main catalyst, and a polymerization initiator comprising this and a co-catalyst 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 an organic polyvalent lithium compound, more preferably an organic monolithium compound, and particularly preferably n-butyllithium. In addition, the organic alkali metal compound is a secondary compound such as dibutylamine, dihexylamine, dibenzylamine, pyrrolidine, hexamethyleneimine, and heptamethyleneimine (preferably pyrrolidine, hexamethyleneimine, and heptamethyleneimine). You may make it react with an amine and use it as an organic alkali metal amide compound. 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 30 to 200 mmol, and particularly preferably 40 to 100 mmol per 100 g of isoprene (or isoprene mixture). It is a range.

  When polymerizing isoprene (or isoprene mixture), the polymerization temperature is usually in the range of -80 to 150 ° C, preferably 0 to 100 ° C, more preferably 20 to 90 ° C.

  In order to adjust the vinyl bond content derived from the isoprene unit in the isoprene block, it is preferable to add a polar compound to the inert organic solvent during the polymerization. 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, 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, and 2,2-di (tetrahydrofuryl) propane and tetramethylethylenediamine are particularly preferable. preferable. 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 0.1 to 30 mol, more preferably 0.5 to 10 mol, relative to 1 mol of the polymerization initiator. do it. When the amount of the polar compound used is within this range, the vinyl bond content can be easily adjusted, and problems due to the deactivation of the polymerization initiator hardly occur.

  The vinyl bond content derived from the isoprene unit in the isoprene block is preferably from 5 to 85% by mass, more preferably from 21 to 85% by mass, even more preferably from 50 to 80% by mass, particularly preferably from the reason that wet performance is more excellent. It is 70-80 mass%. The vinyl bond content derived from isoprene units is the total ratio (mass of 1,2-vinyl bond units derived from isoprene units and 3,4-vinyl bond units derived from isoprene units in the isoprene block. %).

(Part other than the isoprene block)
The portion other than the isoprene block in the conjugated diene polymer chain (p1) may be a homopolymer chain of a conjugated diene monomer or a copolymer chain of a conjugated diene monomer and an aromatic vinyl monomer. preferable. The mass ratio of the conjugated diene monomer unit to the aromatic vinyl monomer unit in the portion other than the isoprene block (conjugated diene monomer unit: aromatic vinyl monomer unit) is 100: 0 to 50:50. Preferably, 90:10 to 70:30 is more preferable.

  Although it does not specifically limit as a conjugated diene monomer used in order to obtain parts other than an isoprene block in a conjugated diene type polymer chain (p1), For example, 1, 3- butadiene, isoprene (2-methyl-1,3) -Butadiene), 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, and the like. Among these, 1,3-butadiene or isoprene is preferably used, and 1,3-butadiene is more preferably used. These conjugated diene monomers can be used alone or in combination of two or more.

  In addition, the aromatic vinyl monomer used for obtaining a portion other than the isoprene block in the conjugated diene polymer chain (p1) is not particularly limited, and examples thereof include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t- Examples thereof include butyl-2-methylstyrene, vinylnaphthalene, dimethylaminomethylstyrene, and dimethylaminoethylstyrene. Among these, styrene, α-methylstyrene, and 4-methylstyrene are preferable, and styrene is more preferable. These aromatic vinyl monomers can be used alone or in combination of two or more.

  As a monomer used for obtaining a portion other than the isoprene block in the conjugated diene polymer chain (p1), a conjugated diene monomer and an aromatic vinyl are optionally selected as long as the essential characteristics of the present invention are not impaired. Other monomers other than the monomer can be used. Other monomers include, for example, α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids or acid anhydrides such as acrylic acid, methacrylic acid, and maleic anhydride; methyl methacrylate Unsaturated carboxylic acid esters such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene Non-conjugated dienes can be mentioned. The amount of these monomers used is preferably 10% by mass or less, preferably 5% by mass or less, based on the total amount of monomers used to obtain a portion other than the isoprene block in the conjugated diene polymer chain (p1). Is more preferable.

  The inert solvent used for polymerization of a portion other than the isoprene block in the conjugated diene polymer chain (p1) is the same as the inert solvent used for the synthesis of the above-described isoprene block.

  As the polymerization initiator used for the synthesis of the portion other than the isoprene block in the conjugated diene polymer chain (p1), the above-described isoprene block having an active end is used as it is. The amount of the polymerization initiator used may be determined according to the target molecular weight, but is usually 0.1 to 5 mmol, preferably 0.2 to 2 mmol, more preferably 0 per 100 g of the monomer (mixture). The range is from 3 to 1.5 mmol.

  In polymerizing a portion other than the isoprene block in the conjugated diene polymer chain (p1), the polymerization temperature is usually -80 to 150 ° C, preferably 0 to 100 ° C, more preferably 20 to 90 ° C. is there. As the polymerization mode, any mode such as batch mode or continuous mode can be adopted. When the portion other than the isoprene block in the conjugated diene polymer chain (p1) is a copolymer chain of a conjugated diene monomer and an aromatic vinyl monomer, or two or more conjugated diene monomers In the case where the copolymer chain is made of, a batch system is preferable because the randomness of the bond can be easily controlled.

  When the portion other than the isoprene block in the conjugated diene polymer chain (p1) is a copolymer chain of a conjugated diene monomer and an aromatic vinyl monomer, or two or more conjugated diene monomers The coupling mode of each monomer in the case of forming a copolymer chain comprising, for example, various coupling modes such as a block shape, a taper shape, or a random shape. Among these, a random shape is preferable. When the coupling mode of the conjugated diene monomer and the aromatic vinyl monomer is random, in the polymerization system, the aromatic vinyl monomer with respect to the total amount of the conjugated diene monomer and the aromatic pinyl monomer. It is preferable to polymerize by supplying the conjugated diene monomer or the conjugated diene monomer and the aromatic vinyl monomer continuously or intermittently into the polymerization system so that the ratio of the body does not become too high. .

  In order to adjust the vinyl bond content in the portion other than the isoprene block of the conjugated diene polymer chain (p1), in the same manner as the adjustment of the vinyl bond content derived from the isoprene unit in the isoprene block, an inert organic substance is used during the polymerization. It is preferable to add a polar compound to the solvent. However, when synthesizing the isoprene block, when adding a sufficient amount of a polar compound to the inert organic solvent to adjust the vinyl bond content in the portion other than the isoprene block of the conjugated diene polymer chain, It is not necessary to newly add a polar compound. The specific example about the polar compound used in order to adjust vinyl bond content in parts other than an isoprene block is the same as the polar compound used for the synthesis | combination of the above-mentioned isoprene block. 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 within this range, the vinyl bond content in the portion other than the isoprene block can be easily adjusted, and problems due to the deactivation of the polymerization initiator hardly occur.

The vinyl bond content in the portion other than the isoprene block of the conjugated diene polymer chain (p1) is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, from the viewpoint of the balance between viscoelastic properties and strength. It is.
In addition, vinyl bond content in parts other than an isoprene block is a ratio (mass%) of a vinyl bond unit in parts other than the isoprene block of a conjugated diene polymer chain (p1).

(Molecular weight of conjugated diene polymer chain (p1))
The weight average molecular weight of the conjugated diene polymer chain (p1) is not particularly limited, but is preferably 1,000 to 2,000,000, more preferably 10,000 to 1,500,000, and 100,000 to 1 1,000,000 is particularly preferred. When the weight average molecular weight of the conjugated diene polymer chain (p1) is within the above range, the balance between tire strength and low rolling resistance is good.

  The molecular weight distribution represented by the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the conjugated diene polymer chain (p1) is preferably 1.0 to 3.0, more preferably. Is 1.0 to 2.5, particularly preferably 1.0 to 2.2. When the molecular weight distribution value (Mw / Mn) is within the above range, the production of the conjugated diene rubber (P) is facilitated.

(Method for producing conjugated diene polymer chain (p1))
As described above, the conjugated diene polymer chain (p1) is obtained by, for example, subjecting an isoprene block having an active terminal to living polymerization of isoprene (or a mixture of isoprene) using an initiator in an inert solvent. And then living polymerizing monomers such as conjugated diene monomers using this isoprene block as a new polymerization initiator. At this time, an isoprene block may be added to a monomer solution such as a conjugated diene monomer, or a monomer such as a conjugated diene monomer may be added to a solution of an isoprene block. It is preferable to add an isoprene block in a solution of a monomer such as a diene monomer. Further, when the polymerization conversion rate of a monomer such as a conjugated diene monomer is usually 95% or more, a new conjugated diene polymer chain (p1) is obtained by newly adding isoprene (or an isoprene mixture). An isoprene block can also be formed on the active terminal side of. The amount of isoprene (or isoprene mixture) used is preferably 10 to 100 mol, more preferably 15 to 70 mol, and particularly preferably 20 to 35 mol with respect to 1 mol of the polymerization initiator used in the initial polymerization reaction.

(Preferred embodiment of conjugated diene polymer chain (p1))
The conjugated diene polymer chain (p1) may not contain an aromatic vinyl monomer unit, but preferably contains it. The preferred range of the mass ratio of the conjugated diene monomer unit to the aromatic vinyl monomer unit (conjugated diene monomer unit: aromatic vinyl monomer unit) in the conjugated diene polymer chain (p1) is as described above. This is the same as the portion other than the isoprene block. Moreover, the preferable range of the vinyl bond content in the conjugated diene polymer chain (p1) is also the same as the portion other than the above-described isoprene block. The vinyl bond amount in the conjugated diene polymer chain (p1) is the ratio (% by mass) of vinyl bond units in the conjugated diene polymer chain (p1).

<Modifier (p2)>
The conjugated diene rubber (P) used in the present invention has an active terminal of the conjugated diene polymer chain (p1) obtained as described above, an epoxy group and / or a hydrocarbyloxysilyl group, and An epoxy group and a modifier (p2) in which the total number of hydrocarbyloxy groups (-OR: where R is a hydrocarbon group or aryl group) contained in the hydrocarbyloxysilyl group is 3 or more is reacted. Is.

  In the present specification, the “modifier” is a compound having a functional group that reacts with the active end of the conjugated diene polymer chain (p1) in one molecule. However, the functional group to be contained is limited to those having an affinity for silica. In the present invention, the functional group is an epoxy group or a hydrocarbyloxy group contained in a hydrocarbyloxysilyl group.

  The modifier (p2) used to form the structure (p) contained in the conjugated diene rubber of the present invention has an epoxy group and / or a hydrocarbyloxysilyl group, and the epoxy group and the hydrocarbyloxysilyl group If it is a modifier | denaturant whose total number with the hydrocarbyl oxy group contained in group is 3 or more, it will not specifically limit. That is, as the modifier (p2), those having 3 or more epoxy groups in the molecule, or hydrocarbyloxy groups having hydrocarbyloxysilyl groups in the molecules and bonded to silicon atoms in the hydrocarbyloxysilyl groups. Those having 3 or more in the molecule can be used, and in addition, both the epoxy group and the hydrocarbyloxysilyl group are included in the molecule, and in one molecule, in the epoxy group and the hydrocarbyloxysilyl group Those having a total number of 3 or more of hydrocarbyloxy groups bonded to silicon atoms can also be used. In the case where the molecule has a hydrocarbyloxysilyl group and the hydrocarbyloxysilyl group has two or more hydrocarbyloxy groups bonded to a silicon atom, the silicon atom having one hydrocarbyloxy group Includes two or more, those having two or more hydrocarbyloxy groups on the same silicon atom, and combinations thereof. When an organic group other than the hydrocarbyloxy group is bonded to the silicon atom of the hydrocarbyloxysilyl group, the organic group is not particularly limited.

  When the conjugated diene polymer chain (p1) reacts with the modifier (p2) having an epoxy group, at least a part of the epoxy group in the modifier (p2) is ring-opened so that the epoxy group is It is considered that a bond is formed between the carbon atom of the ring-opened portion and the active end of the conjugated diene polymer chain (p1). Further, when the conjugated diene polymer chain (p1) reacts with the modifier (p2) having a hydrocarbyloxysilyl group, at least a part of the hydrocarbyloxysilyl group in the hydrocarbyloxysilyl group of the modifier (p2) is removed. By separating, it is considered that a bond between the silicon atom contained in the modifier (p2) and the active end of the conjugated diene polymer chain (p1) is formed.

  By using the modifier (p2) in which the total number of epoxy groups and hydrocarbyloxy groups contained in the hydrocarbyloxysilyl group is 3 or more, 3 or more of the conjugated diene polymer chain (p1) is the modifier. A conjugated diene rubber (P) having a structure (p) bonded through (p2) can be obtained.

  Examples of the hydrocarbyloxysilyl group contained in the modifier (p2) include alkoxysilyl groups such as methoxysilyl group, ethoxysilyl group, propoxysilyl group, butoxysilyl group, and aryloxysilyl groups such as phenoxysilyl group. Can be mentioned. Among these, an alkoxysilyl group is preferable and an ethoxysilyl group is more preferable.

  Examples of the hydrocarbyloxy group contained in the hydrocarbyloxysilyl group contained in the modifier (p2) include an alkoxy group such as a methoxy group, an ethoxy group, a propoxy group, and a butoxy group, and an aryloxy group such as a phenoxy group. Can be mentioned. Among these, an alkoxy group is preferable and an ethoxy group is more preferable.

  The modifier (p2) is preferably a polyorganosiloxane because it has better wet performance and low rolling resistance.

  As a suitable aspect of modifier | denaturant (p2), the polyorganosiloxane represented by following formula (A1), the polyorganosiloxane represented by following formula (A2), and the polyorganosiloxane represented by following formula (A3) Examples thereof include siloxane and hydrocarbyloxysilane represented by the following formula (A4). Among these, a polyorganosiloxane represented by the following formula (A1), a polyorganosiloxane represented by the following formula (A2), and a polyorganosiloxane represented by the following formula (A3) are preferable. The polyorganosiloxane represented by (A1) is more preferable.

In said formula (A1), R < ₁ > -R < ₈ > is a C1-C6 alkyl group or a C6-C12 aryl group, and these may mutually be same or different. In the above formula (A1), X ₁ and X ₄ are each an alkoxy group having 1 to 5 carbon atoms, an aryloxy group having 6 to 14 carbon atoms, or a group having 4 to 12 carbon atoms containing an epoxy group, or carbon It is a C1-C6 alkyl group or a C6-C12 aryl group, and X < ₁ > and X < ₄ > may be the same or different. In the above formula (A1), X ₂ is a group having 4 to 12 carbon atoms containing an alkoxy group having 1 to 5 carbon atoms, an aryloxy group having 6 to 14 carbon atoms, or an epoxy group. In the above formula (A1), X ₃ is a group containing 2 to 20 alkylene glycol repeating units. In said formula (A1), m is an integer of 3-200, n is an integer of 0-200, k is an integer of 0-200.

In the formula (A2), R ₉ ~R ₁₆ 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. In the formula (A2), X ₅ ~X ₈ is an alkoxy group having 1 to 5 carbon atoms, a group having 4 to 12 carbon atoms containing an aryl group or an epoxy group, having 6 to 14 carbon atoms, these May be the same or different.

In said formula (A3), R < ₁₇ > -R < ₁₉ > is a C1-C6 alkyl group or a C6-C12 aryl group, and these may mutually be same or different. In the above formula (A3), X _{9 to} X ₁₁ are groups having 4 to 12 carbon atoms containing an alkoxy group having 1 to 5 carbon atoms, an aryloxy group having 6 to 14 carbon atoms, or an epoxy group. May be the same or different. In said formula (A3), s is an integer of 1-18.

In the formula (A4), R ₂₀ is an alkylene group having 1 to 12 carbon atoms. In the formula (A4), R ₂₁ ~R ₂₉ 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. In said formula (A4), r is an integer of 1-10.

In the polyorganosiloxane represented by the above formula (A1), 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 (A1), 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, and an iso group. A propoxy group, a butoxy group, etc. are mentioned. Especially, a methoxy group and an ethoxy group are preferable from a reactive viewpoint with the active terminal of a conjugated diene type polymer chain (p1).

In the polyorganosiloxane represented by the above formula (A1), examples of the aryloxy group having 6 to 14 carbon atoms represented by X ₁ , X ₂ and X ₄ include a phenoxy group and a tolyloxy group. It is done.

In the polyorganosiloxane represented by the above formula (A1), the group having 4 to 12 carbon atoms containing the epoxy group represented by X ₁ , X ₂ and X ₄ is represented by the following formula (A5). Group.

In the formula (A5), 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 is a carbon number 2 having an epoxy group. -10 hydrocarbyl groups (hydrocarbon groups). In the above formula (A5), * represents a bonding position.

In the group represented by the formula (A5), it is preferably one Z ₂ is an oxygen atom, Z ₂ is an oxygen atom, and is more preferable E is a glycidyl group, Z ₁ is 3 carbon atoms Are particularly preferred, wherein Z ₂ is an oxygen atom and E is a glycidyl group.

In the polyorganosiloxane represented by the formula (A1), 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, which contains 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 (A1), the group containing a repeating unit of X ₃ , that is, an alkylene glycol of 2 to 20, is preferably a group represented by the following formula (A6).

  In said formula (A6), 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 (A6), * 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 (A1), m is preferably an integer of 20 to 150, more preferably 30 to 120, for the reason that low rolling resistance and mechanical strength are more excellent.

  In the polyorganosiloxane represented by the above formula (A1), n is preferably an integer of 0 to 150, more preferably an integer of 0 to 120. In the polyorganosiloxane represented by the above formula (A1), k is preferably an integer of 0 to 150, more preferably an integer of 0 to 120.

  In the polyorganosiloxane represented by the above formula (A1), the total number of m, n, and k is preferably 400 or less, more preferably 300 or less, and particularly preferably 250 or less. . When the total number of m, n, and k is 400 or less, the production of the polyorganosiloxane itself is facilitated, the viscosity is not excessively increased, and the handling is facilitated.

In the polyorganosiloxane represented by the above formula (A2), specific examples and preferred embodiments of R _{9 to} R ₁₆ are the same as R _{1 to} R ₈ in the above formula (A1). In the polyorganosiloxane represented by the above formula (A2), specific examples and preferred embodiments of X _{5 to} X ₈ are the same as X ₂ in the above formula (A1).

In the polyorganosiloxane represented by the above formula (A3), specific examples and preferred embodiments of R _{17 to} R ₁₉ are the same as R _{1 to} R ₈ in the above formula (A1). In the polyorganosiloxane represented by the above formula (A3), specific examples and preferred embodiments of X _{9 to} X ₁₁ are the same as X ₂ in the above formula (A1).

In the hydrocarbyloxysilane represented by the above formula (A4), examples of the alkylene group having 1 to 12 carbon atoms represented by R ₂₀ include a methylene group, an ethylene group, and a propylene group. Among these, a propylene group is preferable.
In the hydrocarbyloxysilane represented by the above formula (A4), specific examples and preferred embodiments of R _{21 to} R ₂₉ are the same as R _{1 to} R ₈ in the above formula (A1).

  Specific examples of the hydrocarbyloxysilane represented by the above formula (A4) include N, N-bis (trimethylsilyl) -3-aminopropyltrimethoxysilane and N, N-bis (trimethylsilyl) -3-aminopropyltriethoxy. Examples thereof include silane, N, N-bis (trimethylsilyl) aminoethyltrimethoxysilane, and N, N-bis (trimethylsilyl) aminoethyltriethoxysilane. Among these, it is preferable to use N, N-bis (trimethylsilyl) -3-aminopropyltrimethoxysilane and N, N-bis (trimethylsilyl) -3-aminopropyltriethoxysilane.

  Other examples of the modifier (p2) include tetraalkoxysilane compounds such as tetramethoxysilane; hexaalkoxysilane compounds such as bis (trimethoxysilyl) methane; alkylalkoxysilane compounds such as methyltriethoxysilane; vinyltrimethoxy Alkenylalkoxysilane compounds such as Silane; arylalkoxysilane compounds such as phenyltrimethoxysilane; halogenoalkoxysilane compounds such as triethoxychlorosilane; 3-glycidoxyethyltrimethoxysilane, 3-glycidoxybutylpropyltri Epoxy group-containing alkoxysilane compounds such as methoxysilane and bis (3-glycidoxypropyl) dimethoxysilane; sulfur-containing compounds such as bis (3- (triethoxysilyl) propyl) disulfide Coxisilane compounds; amino group-containing alkoxysilane compounds such as bis (3-trimethoxysilylpropyl) methylamine; isocyanate group-containing alkoxysilane compounds such as tris (3-trimethoxysilylpropyl) isocyanurate; tetraglycidyl-1,3- And epoxy group-containing compounds such as bisaminomethylcyclohexane.

  A modifier | denaturant (p2) may be used individually by 1 type, and can also be used in combination of 2 or more type.

  Although the usage-amount of modifier | denaturant (p2) is not specifically limited, The modifier in the modifier | denaturant (p2) which reacts with the active terminal of a conjugated diene type polymer chain (p1) with respect to the number-of-moles of the polymerization initiator used for polymerization reaction. The ratio of the total number of moles of the epoxy group and the hydrocarbyloxy group contained in the hydrocarbyloxysilyl group is usually from 0.1 to 5, and the reason why the low rolling resistance and mechanical strength are more excellent is 0. It is preferable that it is 5-3.

  The conjugated diene polymer chain (p1) is a polymerization terminator other than the polymerization terminator and the modifier (p2), as long as the effect of the present invention is not impaired before the above modifier (p2) is reacted. A coupling agent or the like may be added to the polymerization system to inactivate a part of the active end of the conjugated diene polymer chain (p1).

  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; 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, N-dimethylaminopropyl methacrylamide and the like N, N-disubstituted aminoalkylmethacrylamides; 4-N, N-di N-substituted aminoaldehydes such as tilaminobenzaldehyde; 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 metal halide compounds such as butane, 1,5-bis (trichlorosilyl) pentane, and 1,6-bis (trichlorosilyl) hexane. Among these, it is preferable to use a metal halide compound as a coupling agent because the coupling efficiency is more excellent. A silicon halide compound having 5 or more silicon-halogen atom bonds in one molecule is used as a coupling agent. More preferably, 1,6-bis (trichlorosilyl) hexane is particularly preferably used.

  The amount of the coupling agent used is not particularly limited as long as the effect of the present invention is not impaired. For example, in the case of a halogenated silicon compound having 5 or more silicon-halogen atom bonds in one molecule, the amount used is as follows. The ratio of the number of moles of silicon-halogen atom bonds of the silicon halide compound to the number of moles of the polymerization initiator used in the polymerization reaction is 0.001 to 0.001 because the low rolling resistance and mechanical strength are more excellent. It is preferable that it is 0.25, and it is more preferable that it is 0.01-0.2.

  The said coupling agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  When adding the modifier (a1) and the coupling agent to the solution containing the conjugated diene polymer chain (a2), they are dissolved in an inert solvent from the viewpoint of controlling the reaction well. It is preferable to add to the polymerization system. The solution concentration is preferably in the range of 1 to 50% by mass.

<Conjugated diene rubber (P)>
The conjugated diene rubber (P) contained in the rubber composition for a tire tread of the present invention is a conjugated diene rubber obtained by reacting a conjugated diene polymer chain (p1) with a modifier (p2). Specifically, it contains 5% by mass or more of a structure in which three or more conjugated diene polymer chains (p1) are bonded via a modifier (p2).

  The reaction of the conjugated diene polymer chain (p1) and the modifier (p2) can be performed, for example, by adding the modifier (p2) to a solution containing the conjugated diene polymer chain (p1). it can. The timing of adding the modifying agent (p2) and the coupling agent is not particularly limited, but the polymerization reaction in the conjugated diene polymer chain (p1) is not completed and the conjugated diene polymer chain (p1) is contained. The solution containing the monomer such as isoprene, more specifically, the solution containing the conjugated diene polymer chain (p1) is preferably 100 ppm or more, more preferably 300 to 50,000 ppm. It is desirable to add a modifier (p2), a coupling agent, and the like to this solution in a state where the monomer is contained. By adding a modifier (p2), a coupling agent, etc., the side reaction between the conjugated diene polymer chain (p1) and impurities contained in the polymerization system is suppressed, and the reaction is controlled well. Is possible.

  In obtaining conjugated diene rubber (P), when two or more modifiers (p2) and coupling agents are used in combination, the order of adding them to the polymerization system is not particularly limited. Even when the modifying agent (p2) and a silicon halide compound as a coupling agent having 5 or more silicon-halogen atom bonds in one molecule are used in combination, the order of addition is not particularly limited. It is preferable to add the agent prior to the addition of the modifier (p2). By adding in this order, it becomes easy to obtain a highly branched conjugated diene rubber obtained via a coupling agent, and a tire obtained using the highly branched conjugated diene rubber has a steering stability. Better.

  As conditions for reacting the modifier (p2), the coupling agent and the like, the temperature is usually in the range of 0 to 100 ° C., preferably 30 to 90 ° C., and each reaction time is usually 1 to 100 ° C. The range is 120 minutes, preferably 2 to 60 minutes.

  After reacting the modifier (p2) with the conjugated diene polymer chain (p1), it is preferable to deactivate the active terminal by adding an alcohol such as methanol or water.

  After deactivating the active end of the conjugated diene polymer chain (p1), an anti-aging agent such as a phenol-based stabilizer, a phosphorus-based stabilizer, and a sulfur-based stabilizer, a crumbing agent, and a scale inhibitor, if desired Are added to the polymerization solution, and then the polymerization solvent is separated from the polymerization solution by direct drying and steam stripping to recover the conjugated diene rubber (P). Before separating the polymerization solvent from the polymerization solution, an extending oil may be mixed into the polymerization solution, and the conjugated diene rubber (P) may be recovered as an oil-extended rubber.

  Examples of the extending oil used when recovering the conjugated diene rubber (P) as an oil-extended rubber include paraffinic, aromatic and naphthenic petroleum softeners, plant softeners, and fatty acids. . When using a petroleum softener, the polycyclic aromatic content is preferably less than 3%. This content is measured by the method of IP346 (the testing method of THE INSTITUTE PETROLEUM, UK). When using the extender oil, the amount used is usually 5 to 100 parts by mass, preferably 10 to 60 parts by mass, more preferably 20 to 50 parts by mass with respect to 100 parts by mass of the conjugated diene rubber (P). It is.

The conjugated diene rubber (P) is more preferably 5% by mass or more of a structure (p) in which three or more conjugated diene polymer chains (p1) are bonded via a modifier (p2). Is contained in an amount of 5 to 40% by mass, particularly preferably 10 to 30% by mass.
The ratio of the structure (p) in which three or more conjugated diene polymer chains (p1) are bonded via the modifier (p2) to the total amount of the conjugated diene rubber (P) finally obtained is expressed as “ It is expressed as “coupling ratio of 3 or more branches (mass%)” (hereinafter also simply referred to as coupling ratio). This can be measured by gel permeation chromatography (polystyrene conversion). From the chart obtained by gel permeation chromatography measurement, the area of the peak portion (s2) 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 (s1). The ratio (s2 / s1) is a coupling rate of three or more branches. In the case where a coupling agent other than the modifying agent (p2) is added before the modification, a sample is taken before the modifying agent (p2) is added, and the coupling agent is measured by measuring GPC. The proportion of the conjugated diene polymer chain bonded only to the monomer can be corrected.

  The weight average molecular weight of the conjugated diene rubber (P) is not particularly limited, but is usually 1,000 to 3,000,000, preferably 100,000 to a value measured by gel permeation chromatography in terms of polystyrene. It is in the range of 2,000,000, more preferably 300,000 to 1,500,000. When the weight average molecular weight is 3,000,000 or less, it becomes easy to mix silica (Q) into the conjugated diene rubber (P), and the scorch resistance of the rubber composition for tire tread becomes more excellent. . Further, when the weight average molecular weight is 1,000 or more, the low rolling resistance of the obtained tire becomes more excellent.

  The molecular weight distribution represented by the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the conjugated diene rubber (P) is not particularly limited, but preferably 1.1 to 3.0. More preferably, it is 1.2-2.5, Most preferably, it is 1.3-2.2. When the molecular weight distribution value (Mw / Mn) is 3.0 or less, the resulting tire has more excellent low rolling resistance.

The Mooney viscosity (ML _{1 + 4} (100 ° C.)) of the conjugated diene rubber (P) is not particularly limited, but is usually in the range of 20 to 100, preferably 30 to 90, and more preferably 40 to 85. When the conjugated diene rubber (P) is an oil-extended rubber, the Mooney viscosity of the oil-extended rubber is preferably in the above range.

<Diene rubber>
As described above, the rubber component contained in the tire tread rubber composition of the present invention may contain a diene rubber other than the conjugated diene rubber (P).
The diene rubber is not particularly limited, and specific examples thereof include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber, acrylonitrile-butadiene copolymer. Polymerized rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR) and the like can be mentioned. The diene rubber may be a single diene rubber or a combination of two or more diene rubbers.

[Silica (Q)]
The silica (Q) contained in the tire tread rubber composition of the present invention is not particularly limited, and any conventionally known silica compounded in the rubber composition for use in tires or the like can be used.
Examples of the silica (Q) include wet silica, dry silica, fumed silica, and diatomaceous earth. As the silica (Q), one type of silica may be used alone, or two or more types of silica may be used in combination.

Silica (Q) preferably has a cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of 100 to 300 m ² / g, and 140 to 260 m ² , because of its superior wet performance and wear resistance when used as a tire. / G is more preferable.
Here, the CTAB adsorption specific surface area is a surrogate property of the surface area that silica can be used for adsorption with the silane coupling agent, and the amount of CTAB adsorption on the silica surface is JIS K6217-3: 2001 “Part 3: Specific surface area of It is a value measured according to “How to obtain—CTAB adsorption method”.

  In the rubber composition for a tire tread of the present invention, the content of the silica (Q) is 60 to 200 parts by mass, preferably 60 to 150 parts by mass with respect to 100 parts by mass of the rubber component. For reasons of better wet performance, low rolling resistance and mixed workability, it is more preferably 65 to 145 parts by mass, and even more preferably 70 to 140 parts by mass.

[Silane coupling agent (R)]
The silane coupling agent (R) used in the rubber composition for a tire tread of the present invention is a polysiloxane (specific polysiloxane) represented by an average composition formula of the following formula (1).
(A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-bcde) / 2} (1)

In the above formula (1), 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 following formula (2).
^{_{* - (CH 2) n -S}} x - (CH 2) n - * (2)
In said formula (2), n represents the integer of 1-10, and it is preferable that it is an integer of 2-4 especially.
In said formula (2), x represents the integer of 1-6, and it is preferable that it is an integer of 2-4 especially.
In the above formula (2), * indicates a bonding position.
Specific examples of the group represented by the formula (2) are, 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 said formula (1), B represents a C1-C10 monovalent hydrocarbon group, As a specific example, a hexyl group, an octyl group, a decyl group etc. are mentioned, for example.

In the above formula (1), C represents a hydrolyzable group, and specific examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, an alkenyloxy group, and the like. Especially, it is preferable that it is group represented by following formula (3).
^* -OR ² (3)
In the above formula (3), 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 (3), * indicates a bonding position.

In said formula (1), D represents the organic group containing a mercapto group. Especially, it is preferable that it is group represented by following formula (4).
^{_{* - (CH 2) m -SH}} (4)
In said formula (4), m represents the integer of 1-10, and it is preferable that it is an integer of 1-5 especially.
In the above formula (4), * indicates a bonding position.
Specific examples of the group represented by the formula _{^{(4), * -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 (1), R ¹ represents a monovalent hydrocarbon group having 1 to 4 carbon atoms.

  In the above formula (1), 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. (However, one of a and b is not 0).

  In the specific polysiloxane, a is preferably larger than 0 (0 <a) because the scorch resistance is more excellent. That is, it preferably has a sulfide group-containing organic group. Especially, it is preferable that 0 <a ≦ 0.50 because the scorch resistance is further excellent.

In the above formula (1), b is preferably 0 <b, more preferably 0.10 ≦ b ≦ 0.89, because the wet characteristics, low rolling resistance and scorch resistance are more excellent. .
In the above formula (1), c is preferably 1.2 ≦ c ≦ 2.0 because wet characteristics, low rolling resistance and scorch resistance are more excellent.
In the above formula (1), d is preferably 0.1 ≦ d ≦ 0.8 because wet characteristics, low rolling resistance and scorch resistance are more excellent.

  In the above formula (1), A is a group represented by the above formula (2) because the specific polysiloxane has good dispersibility of silica and more excellent scorch resistance. It is preferable that C in (1) is a group represented by the above formula (3) and D in the above formula (1) is a polysiloxane which is a group represented by the above formula (4).

The molecular weight of the specific polysiloxane is preferably 500 to 2300 and more preferably 600 to 1500 from the viewpoint of excellent silica dispersibility while ensuring scorch resistance. The molecular weight of the specific polysiloxane is a weight average molecular weight 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 iodate-sodium thiosulfate solution of the specific polysiloxane is preferably 550 to 1900 g / mol from the viewpoint of excellent vulcanization reactivity, 600 to More preferably, it is 1500 g / mol.

  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 (6), an organosilicon compound represented by the following formula (7), and The method of hydrolyzing and condensing can be mentioned. As a second preferred embodiment, an organosilicon compound represented by the following formula (5), an organosilicon compound represented by the following formula (6), and an organosilicon represented by the following formula (7) The method of hydrolyzing and condensing a compound is mentioned. Further, as a third preferred embodiment, an organosilicon compound represented by the following formula (5), an organosilicon compound represented by the following formula (6), and an organosilicon represented by the following formula (7) The method of hydrolyzing and condensing a compound and the organosilicon compound represented by following formula (8) is mentioned.
Especially, it is preferable that it is the said 2nd suitable aspect from the reason which scorch-proof property is more excellent.

In the above formula (5), 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 above formula (5), 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 R ⁵¹ described above.
In the above formula (5), the definition and preferred embodiment of n are the same as those of n.
In the above formula (5), the definition and preferred embodiment of x are the same as the above x.
In said formula (5), y represents the integer of 1-3.

  Specific examples of the organosilicon compound represented by the above formula (5) include, for example, bis (trimethoxysilylpropyl) tetrasulfide, bis (triethoxysilylpropyl) tetrasulfide, bis (trimethoxysilylpropyl) disulfide, bis (Triethoxysilylpropyl) disulfide and the like.

In the above formula (6), the definition, specific examples and preferred embodiments of R ⁶¹ are the same as those of R ⁵¹ described above.
In the above formula (6), the definition, specific examples and preferred embodiments of R ⁶² are the same as those of R ⁵² described above.
In the above formula (6), the definition of z is the same as the above y.
In said formula (6), p represents the integer of 5-10.

  Specific examples of the organosilicon compound represented by the above formula (6) 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 (7), the definition, specific examples and preferred embodiments of R ⁷¹ are the same as R ⁵¹ described above.
In the above formula (7), the definition, specific examples and preferred embodiments of R ⁷² are the same as those of R ⁵² described above.
In the above formula (7), the definition and preferred embodiment of m are the same as m.
In the above formula (7), the definition of w is the same as y.

  Specific examples of the organosilicon compound represented by the above formula (7) 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 (8), the definition, specific examples and preferred embodiments of R ⁸¹ are the same as those of R ⁵¹ described above.
In the above formula (8), the definition, specific examples and preferred embodiments of R ⁸² are the same as R ⁵² described above.
In the above formula (8), the definition of v is the same as y above.
In said formula (8), q represents the integer of 1-4.

  Specific examples of the organosilicon compound represented by the above formula (8) 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.

Moreover, when manufacturing the said specific polysiloxane, you may use a catalyst as needed. The catalyst is not particularly limited, but specifically, acidic catalysts such as hydrochloric acid and acetic acid, Lewis acid catalysts such as tetrabutyl orthotitanate and ammonium fluoride, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium acetate, potassium acetate And alkali metal salts such as sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, 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 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 (7)] 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 (6) or formula (8)] is used in combination, a silane coupling agent having a mercapto group and a silane having a sulfide group or a mercapto group Mixing ratio (molar ratio) with a silane coupling agent other than a 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 a wet performance, From the standpoint of superior rolling resistance and workability, 1.1 / 8.9 Is preferably from 6.7 / 3.3, and more preferably 1.4 / 8.6 to 5.0 / 5.0.

  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 (7)] and a silane coupling agent having a sulfide group [ For example, when the organosilicon compound represented by formula (5) 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 2.0 / 8.0 to 8.9 / 1.1 from the viewpoint of superior wet performance, low rolling resistance, and workability. Preferably, it is 2.5 / 7.5 to 8.0 / 2.0.

  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 (7)], a silane coupling agent having a sulfide group [ For example, an organosilicon compound represented by formula (5) and / or] and a silane coupling agent other than a silane coupling agent having a sulfide group or a mercapto group [for example, represented by formula (6) or formula (8) 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 rubber composition for a tire tread of the present invention, the content of the silane coupling agent (R) is 1.0 to 20% by mass with respect to the content of the silica (Q), and wet performance and low rolling. From the reason that the resistance and scorch resistance are more excellent, it is preferably 4 to 18% by mass, more preferably 5 to 14% by mass, and further preferably 6 to 12% by mass.

[Optional ingredients]
The rubber composition for a tire tread of the present invention may further contain an additive as long as the effect and purpose are not impaired.
Examples of the additive include a silane coupling agent other than the silane coupling agent (R) contained in the tire tread rubber composition of the present invention, a filler other than silica (Q) (for example, carbon black), Commonly used in rubber compositions for tire treads such as zinc oxide, stearic acid, anti-aging agents, processing aids, aroma oils, process oils, liquid polymers, terpene resins, thermosetting resins, vulcanizing agents, vulcanization accelerators Various additives that are commonly used are listed.
The rubber composition for a tire tread of the present invention preferably contains a terpene resin for the reason that wet performance, low rolling resistance and scorch resistance are more excellent. The terpene resin is preferably an aromatic-modified terpene resin (particularly having a softening point of 60 to 150 ° C.). The content of the terpene resin is preferably 1 to 30 parts by mass with respect to 100 parts by mass of the rubber component.

[Method for producing rubber composition for tire tread]
The method for producing the rubber composition for a tire tread of the present invention is not particularly limited, and specific examples thereof include, for example, the above-described components using known methods and apparatuses (for example, a Banbury mixer, a kneader, a roll, etc.). And a kneading method.
Moreover, the rubber composition for tire treads 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 using the above-described rubber composition for a tire tread of the present invention as a tire 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.
In the tire tread 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 pneumatic tire of the present invention is not particularly limited except that the rubber composition for a tire tread of the present invention is used for a tread of a pneumatic tire, and can be produced, 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 Conjugated Diene Rubber 1>
To a 100 ml ampule bottle purged with nitrogen, 28 g of cyclohexane and 8.6 mmol of tetramethylethylenediamine were added, and 6.1 mmol of n-butyllithium was further added. Then, 8.0 g of isoprene was slowly added and reacted in an ampoule bottle at 60 ° C. for 120 minutes to obtain an isoprene block (referred to as initiator 1). About this initiator 1, the weight average molecular weight, molecular weight distribution, and vinyl bond content derived from an isoprene unit were measured. The measurement results are shown in Table 1.

  Next, in a nitrogen atmosphere, 4000 g of cyclohexane, 357.7 g of 1,3-butadiene and 132.3 g of styrene were charged in an autoclave equipped with a stirrer, and then the whole amount of initiator 1 was added, and polymerization was started at 40 ° C. Ten minutes after the start of polymerization, 195.3 g of 1,3-butadiene and 14.7 g of styrene were continuously added over 60 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 was in the range of 95% to 100%, 1,6-bis (trichlorosilyl) hexane 0.08 mmol was then obtained. Was added in the form of a 20% strength by weight cyclohexane solution and allowed to react for 10 minutes. Further, 0.027 mmol of polyorganosiloxane A represented by the following formula (9) was added in the form of a 20% by mass xylene solution 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 the conjugated diene rubber 1. To this solution, 0.15 parts by mass of Irganox 1520L (manufactured by Ciba Specialty Chemicals) as an anti-aging agent was added to 100 parts by mass of the conjugated diene rubber 1, and then the solvent was removed by steam stripping. Then, the solid conjugated diene rubber 1 was obtained by vacuum drying at 60 ° C. for 24 hours.

In the above formula _{(9), X 1, X} 4, R 1 ~R 3 and R ₅ to R ₈ is a methyl group. In the above formula (9), m is 80 and k is 120. In the above formula (9), X ₂ is a group represented by the following formula (10) (here, * represents a bonding position).

  For the conjugated diene rubber 1, the weight average molecular weight, molecular weight distribution, coupling rate, styrene unit content other than the isoprene block, vinyl bond content other than the isoprene block, 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 rate)
About the weight average molecular weight, molecular weight distribution, and coupling rate (ratio (mass%) of structure (p) with respect to conjugated diene rubber (P)), a chart based on polystyrene-converted molecular weight was obtained by gel permeation chromatography. And based on the chart. The specific measurement conditions for gel permeation chromatography are as follows.

・ Measurement device: HLC-8020 (manufactured by Tosoh Corporation)
Column: GMH-HR-H (manufactured by Tosoh Corporation) connected in series Detector: Differential refractometer RI-8020 (manufactured by Tosoh Company)
-Elution night: Tetrahydrofuran-Column temperature: 40 ° C

  Here, the coupling rate is the ratio of the area (s2) 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 smallest peak of molecular weight to the total elution area (s1) (s2 / s1).

(Styrene unit content and vinyl bond content)
The styrene unit content and the vinyl bond content were measured by ¹ H-NMR.

(Mooney viscosity)
The Mooney viscosity (ML _{1 + 4} (100 ° C.)) was measured according to JIS K6300-1: 2001.

<Production of Conjugated Diene Rubber 2>
To a 100 ml ampoule bottle purged with nitrogen, 28 g of cyclohexane and 7.5 mmol of tetramethylethylenediamine were added, and 5.4 mmol of n-butyllithium was further added. Next, 7.0 g of isoprene was slowly added and reacted in an ampoule bottle at 70 ° C. for 120 minutes to obtain an isoprene block (referred to as initiator 2). For this initiator 2, the weight average molecular weight, molecular weight distribution, and content of vinyl bonds derived from isoprene units were measured. The measurement results are shown in Table 1.

  Next, in a nitrogen atmosphere, 4000 g of cyclohexane, 357.7 g of 1,3-butadiene and 132.3 g of styrene were charged in an autoclave equipped with a stirrer, and then the whole amount of initiator 2 was added, and polymerization was started at 40 ° C. Ten minutes after the start of polymerization, 195.3 g of 1,3-butadiene and 14.7 g of styrene were continuously added over 60 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. After confirming that the polymerization conversion was in the range of 95% to 100%, the polyorganosiloxane A0 represented by the above formula (9) was then used. 0.023 mmol was added in the form of a 20% strength by weight xylene solution and allowed to react 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 the conjugated diene rubber 2. To this solution, 0.15 parts by mass of Irganox 1520L (manufactured by Ciba Specialty Chemicals) as an antioxidant is added to 100 parts by mass of the conjugated diene rubber 2, and then the solvent is removed by steam stripping. The solid conjugated diene rubber 2 was obtained by vacuum drying at 60 ° C. for 24 hours.

  For the conjugated diene rubber 2, the weight average molecular weight, molecular weight distribution, coupling rate, styrene unit content in a portion other than the isoprene block, vinyl bond content and Mooney viscosity in a portion other than the isoprene block were measured. The measurement results are shown in Table 2. In addition, it is as a measuring method and above-mentioned.

<Production of Conjugated Diene Rubber 3>
To a 100 ml ampoule bottle purged with nitrogen, 50 g of cyclohexane and 0.9 mmol of tetramethylethylenediamine were added, and 5.4 mmol of n-butyllithium was further added. Next, 9.0 g of isoprene was slowly added and reacted in an ampoule bottle at 70 ° C. for 120 minutes to obtain an isoprene block (referred to as initiator 3). For this initiator 3, the weight average molecular weight, molecular weight distribution, and vinyl bond content derived from isoprene units were measured. The measurement results are shown in Table 1.

  Next, in a nitrogen atmosphere, 4000 g of cyclohexane, 357.7 g of 1,3-butadiene and 132.3 g of styrene were charged in an autoclave equipped with a stirrer, and then the whole amount of initiator 3 was added, and polymerization was started at 40 ° C. After 10 minutes from the start of polymerization, 195.3 g of 1,3-butadiene and 14.7 g of styrene were continuously added over 60 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. After confirming that the polymerization conversion was in the range of 95% to 100%, the polyorganosiloxane A0 represented by the above formula (9) was then used. 0.023 mmol was added in the form of a 20% strength by weight xylene solution and allowed to react 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 the conjugated diene rubber 3. Irganox 1520L (manufactured by Ciba Specialty Chemicals) was added to this solution as an anti-aging agent in an amount of 0.15 parts by mass with respect to 100 parts by mass of the conjugated diene rubber 3, and the solvent was removed by steam stripping. Then, it was vacuum dried at 60 ° C. for 24 hours to obtain a solid conjugated diene rubber 3.

  For the conjugated diene rubber 3, the weight average molecular weight, molecular weight distribution, coupling rate, styrene unit content other than the isoprene block, vinyl bond content and Mooney viscosity in the portion other than the isoprene block were measured. The measurement results are shown in Table 2. In addition, it is as a measuring method and the above-mentioned.

<Manufacture of Conjugated Diene Rubber 4>
To a 100 ml ampoule bottle purged with nitrogen, 50 g of cyclohexane and 7.0 mmol of tetramethylethylenediamine were added, and 5.1 mmol of n-butyllithium was further added. Next, 10.2 g of isoprene was slowly added and reacted for 120 minutes in an ampoule bottle at 60 ° C. to obtain an isoprene block (referred to as initiator 4). For this initiator 4, the weight average molecular weight, molecular weight distribution, and content of vinyl bonds derived from isoprene units were measured. The measurement results are shown in Table 1.

  Next, in a nitrogen atmosphere, 4000 g of cyclohexane, 357.7 g of 1,3-butadiene and 132.3 g of styrene were charged in an autoclave equipped with a stirrer, and then the whole amount of initiator 4 was further added, and polymerization was started at 40 ° C. After 10 minutes from the start of polymerization, 195.3 g of 1,3-butadiene and 14.7 g of styrene were continuously added over 60 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 was in the range of 95% to 100%, N, N-bis (trimethylsilyl) -3-aminopropyl was then obtained. 0.55 mmol of triethoxysilane was added in the form of a 20% by mass concentration xylene solution and reacted 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 the conjugated diene rubber 4. Irganox 1520L (manufactured by Ciba Specialty Chemicals) as an anti-aging agent was added to this solution in an amount of 0.15 parts by mass with respect to 100 parts by mass of the conjugated diene rubber 4, and the solvent was removed by steam stripping. Then, it was vacuum dried at 60 ° C. for 24 hours to obtain a solid conjugated diene rubber 4.

  For the conjugated diene rubber 4, the weight average molecular weight, molecular weight distribution, coupling rate, styrene unit content in the portion other than the isoprene block, vinyl bond content and Mooney viscosity in the portion other than the isoprene block were measured. The measurement results are shown in Table 2. In addition, it is as a measuring method and the above-mentioned.

<Method for producing polysiloxane 1>
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. Thereafter, 412.3 g of a colorless transparent liquid polysiloxane was obtained by concentration under reduced pressure and filtration. 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 polysiloxane 1.

<Method for producing polysiloxane 2>
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 polysiloxane 2.

<Method for producing polysiloxane 3>
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 42.0 g (2.33 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, 18.9 g of 5% KOH / EtOH solution was added dropwise and stirred at 80 ° C. for 2 hours. Then, 560.9 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 1220, and the average polymerization degree was 6.0 (set polymerization degree 6.0). Further, the mercapto equivalent was measured by an acetic acid / potassium iodide / potassium iodate added-sodium thiosulfate solution titration method. As a result, it was 710 g / mol, and it was confirmed that the mercapto group content was 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) 1.334 (-C 3 H 6 SH) 0.286 SiO 0.833
The obtained polysiloxane is designated as polysiloxane 3.

(Method for producing comparative polysiloxane 1)
3-mercaptopropyltrimethoxysilane (0.1 mol) was hydrolyzed with water and concentrated aqueous hydrochloric acid, and then ethoxymethyl polysiloxane (100 g) was added and condensed to obtain polysiloxane. The obtained polysiloxane is referred to as comparative polysiloxane 1.
The comparative polysiloxane 1 has a structure in which the methoxy group of 3-mercaptopropyltrimethoxysilane and the ethoxy group of ethoxymethyl polysiloxane are condensed. That is, the monovalent hydrocarbon group of the comparative polysiloxane 1 is only a methyl group. The comparative polysiloxane 1 does not have a divalent organic group containing a sulfide group.

(Method for producing comparative polysiloxane 2)
Bis (3- (triethoxysilyl) propyl) tetrasulfide (0.1 mol) is hydrolyzed with water and concentrated aqueous hydrochloric acid, and then ethoxymethylpolysiloxane (100 g) is added and condensed to obtain polysiloxane. It was. The obtained polysiloxane is referred to as comparative polysiloxane 2.
The comparative polysiloxane 2 has a structure in which the ethoxy group of bis (3- (triethoxysilyl) propyl) tetrasulfide and the ethoxy group of ethoxymethyl polysiloxane are condensed. That is, the monovalent hydrocarbon group of the comparative polysiloxane 2 is only a methyl group. The comparative polysiloxane 2 does not have an organic group containing a mercapto group.

<Examples 1-9, Comparative Examples 1-11>
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.

<Tan δ (0 ° C.)> (Wet performance index)
The prepared 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 produce a vulcanized rubber sheet.
About the produced vulcanized rubber sheet, in accordance with JIS K6394: 2007, using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho Co., Ltd.) under the conditions of 10% ± 2% elongation deformation strain rate, frequency 20 Hz, temperature 0 ° C. , Tan δ (0 ° C.) was measured.
The results are shown in Table 3. The results were expressed as an index with tan δ (0 ° C.) of Comparative Example 1 as 100. The larger the index, the larger the tan δ (0 ° C.), and the better the wet performance when made into a tire.

<Tan δ (60 ° C.)> (Index of low rolling resistance)
The prepared 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 produce a vulcanized rubber sheet.
About the produced vulcanized rubber sheet, in accordance with JIS K6394: 2007, using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho Co., Ltd.) under the conditions of an elongation deformation strain rate of 10% ± 2%, a frequency of 20 Hz, and a temperature of 60 ° C. , Tan δ (60 ° C.) was measured.
The results are shown in Table 3. The results were expressed as an index with tan δ (60 ° C.) of Comparative Example 1 as 100. The smaller the index, the smaller the tan δ (60 ° C.), and the lower the rolling resistance when the tire is made.

<Mooney viscosity>
For the prepared tire tread rubber composition (unvulcanized), an L-shaped rotor was used according to JIS K6300-1: 2001, preheating time was 1 minute, rotor rotation time was 4 minutes, and test temperature was 100 ° C. The Mooney viscosity was measured.
The results are shown in Table 3. The results were expressed as an index with the value of Comparative Example 1 as 100.

<Mooney scorch> (index for scorch resistance)
With respect to the prepared rubber composition for tire tread (unvulcanized), the scorch time was measured under the condition of a test temperature of 125 ° C. using an L-shaped rotor according to JIS K6300-1: 2001.
The results are shown in Table 3. The results were expressed as an index with the scorch time of Comparative Example 1 as 100. The larger the index, the longer the scorch time and the better the scorch resistance (workability).

Details of each component shown in Table 3 are as follows.
Conjugated diene rubber 1: Conjugated diene rubber 1 produced as described above
Conjugated diene rubber 2: Conjugated diene rubber 2 produced as described above
Conjugated diene rubber 3: Conjugated diene rubber 3 produced as described above
Conjugated diene rubber 4: Conjugated diene rubber 4 produced as described above
Comparative conjugated diene rubber 1: NS616 (manufactured by ZEON Corporation) (terminal modified SSBR for silica)
-Butadiene rubber: Nipo 1122 (made by Nippon Zeon)
Silica (other than Example 9): Zeosil 1165MP (CTAB adsorption specific surface area = 160 m ² / g, manufactured by Rhodia)
Silica (Example 9): Zeosil 1115MP (CTAB adsorption specific surface area = 110 m ² / g, manufactured by Solvey)
Carbon black: Show black N339 (CTAB adsorption specific surface area = 90 m ² / g, manufactured by Cabot Japan)
Comparative silane coupling agent 1: VP Si363 (manufactured by Evonik Degussa) (compound represented by the following formula (11). Here, R ¹¹¹ : —OC ₂ H ₅ , R ¹¹² : —O (C ₂ H) ₄ O) ₅ —C ₁₃ H ₂₇ , R ¹¹⁴ : — (CH ₂ ) ₃ —, l = 1, m = 2, n = 0.)

Comparative silane coupling agent 2: Comparative polysiloxane 1 synthesized as described above
Comparative silane coupling agent 3: Comparative polysiloxane 2 synthesized as described above

Silane coupling agent 1: Polysiloxane 1 synthesized as described above
Silane coupling agent 2: Polysiloxane 2 synthesized as described above
・ Stearic acid: Stearic acid YR (manufactured by NOF Corporation)
・ Hot oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
Anti-aging agent: Santoflex 6PPD (manufactured by Solutia Europe)
・ Process oil: Extract No. 4 S (made by Showa Shell Sekiyu KK)
・ Vulcanization accelerator 1: Noxeller CZ-G (Ouchi Shinsei Chemical Co., Ltd.)
・ Vulcanization accelerator 2: Perkacit DPG (manufactured by Flexsys)
・ Sulfur: Oil-treated sulfur (manufactured by Tsurumi Chemical Co., Ltd.)

As can be seen from Table 3, Examples 1 to 9 of this application using both the conjugated diene rubber (P) and the silane coupling agent (R) exhibited excellent wet performance and low rolling resistance.
From a comparison between Examples 1 and 4, Example 4 in which the silane coupling agent (R) is a polysiloxane having a sulfide group-containing organic group showed better scorch resistance.
From the comparison of Examples 1 to 3, Example 1 in which the content of the silane coupling agent (R) is 5 to 14% by mass with respect to the content of silica (Q) is the wet performance, low rolling resistance and It was the most excellent in terms of the balance of scorch resistance.

Compared with Comparative Examples 1 and 2 containing conjugated diene rubber (P) but not containing silane coupling agent (R) (containing mercapto silane coupling agent other than silane coupling agent (R)) In addition, Examples 1 to 9 of the present application in which the conjugated diene rubber (P) and the silane coupling agent (R) were used in combination showed excellent scorch resistance.
Moreover, compared with the comparative examples 4 and 5 which contain a silane coupling agent (R) but do not contain a conjugated diene rubber (P), a conjugated diene rubber (P) and a silane coupling agent (R) are used. The present Examples 1 to 9 used in combination showed excellent characteristics in any of wet performance, low rolling resistance and scorch resistance.

Conjugated diene rubber (P) and silane coupling agent (R) are used in combination, but the content of silane coupling agent (R) is less than 1.0% by mass with respect to the content of silica (Q). Although Comparative Example 6 was excellent in scorch resistance, it was inferior to Examples 1 to 9 in terms of wet performance and low rolling resistance.
Comparative Example 7 in which the conjugated diene rubber (P) and the silane coupling agent (R) are used in combination, but the content of the silane coupling agent (R) exceeds 20% by mass with respect to the content of silica (Q). Although it was excellent in wet performance and low rolling resistance, it was inferior to Examples 1 to 9 in terms of scorch resistance.

Comparative Example 8 in which the content of silica (Q) is less than 60 parts by mass with respect to 100 parts by mass of the rubber component was inferior to Examples 1 to 9 in terms of wet performance and low rolling resistance.
Further, Comparative Examples 10 and 11 containing conjugated diene rubber (P) but not containing silane coupling agent (R) (containing polysiloxane other than silane coupling agent (R)) have the wet performance of the present application. It was inferior to Examples 1-9.

Conjugated diene rubber (P) and silane coupling agent (R) are used in combination, but compared with Comparative Example 9 in which the content of conjugated diene rubber (P) in the rubber component is less than 20% by mass, The present Examples 1 to 9 in which the content of the conjugated diene rubber (P) in the rubber component is 20 mass or more showed excellent low rolling resistance.

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)

A rubber component containing 20% by mass or more of conjugated diene rubber (P), silica (Q), and silane coupling agent (R);
The conjugated diene rubber (P) is a conjugated diene rubber (P) obtained by a reaction between a conjugated diene polymer chain (p1) and a modifier (p2), the conjugated diene rubber (P) The content ratio [coupling ratio of 3 or more branches] of the structure (p) in which 3 or more of the conjugated diene polymer chains (p1) are bonded via the modifier (p2) is 5 It is a conjugated diene rubber (P) of mass% or more,
The conjugated diene polymer chain (p1) is a conjugated diene polymer chain having an isoprene block containing 70% by mass or more of isoprene units at one end and an active end at the other end.
The modifier (p2) has an epoxy group and / or a hydrocarbyloxysilyl group, and the total number of the epoxy group and the hydrocarbyloxy group contained in the hydrocarbyloxysilyl group is 3 or more. Yes,
The silane coupling agent (R) is a polysiloxane represented by the following average composition formula (1):
Content of the said silane coupling agent (R) is 1.0-20 mass% with respect to content of the said silica (Q),
A rubber composition for a tire tread, wherein a content of the silica (Q) is 60 to 200 parts by mass with respect to 100 parts by mass of the rubber component.
(A) _a (B) _b (C) _c (D) _d (R ¹ ) _e SiO _{(4-2a-bcde) / 2} (1)
(In formula (1), A represents a group represented by the following formula (2), B represents a monovalent alkyl group having 5 to 10 carbon atoms, C represents a hydrolyzable group, and D represents the following. Represents a group represented by the formula (4): R ¹ 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 is satisfied)
^{_{* - (CH 2) n -S}} x - (CH 2) n - * (2)
(In formula (2), n represents an integer of 1 to 10. x represents an integer of 2 to 6. * represents a bonding position.)
^{_{* - (CH 2) m -SH}} (4)
(In the formula (4), m represents an integer of 1 to 10. * indicates a bonding position.)   The rubber composition for tire treads according to claim 1, wherein the content of vinyl bonds derived from isoprene units in the isoprene block is 5 to 85 mass%.   The portion other than the isoprene block in the conjugated diene polymer chain (p1) is a homopolymer chain of a conjugated diene monomer or a copolymer chain of a conjugated diene monomer and an aromatic vinyl monomer. The rubber composition for tire treads according to claim 1 or 2.   The rubber composition for tire treads according to any one of claims 1 to 3, wherein a is greater than 0 in the formula (1). The rubber for tire treads according to any one of claims 1 to 4 , further comprising 1 to 30 parts by mass of an aromatic-modified terpene resin having a softening point of 60 to 150 ° C with respect to 100 parts by mass of the rubber component. Composition. A pneumatic tire using the tire tread rubber composition according to any one of claims 1 to 5 for a tire tread.