JP2007262206A - Rubber composition for tire tread and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for tire tread excellent in performances on snow and ice and dry gripping performance, having good wet gripping performance, low fuel cost and abrasion resistance and suitable for e.g. snow tires and all season tires and to provide a pneumatic tire using the rubber composition. <P>SOLUTION: The rubber composition for tire tread comprises (A) 100 pts.mass rubber component containing (A-1) 5-70 mass% modified conjugate diene-based polymer A obtained by modifying an active terminal of a conjugated diene-based polymer having ≥75 mol% content of cis-1,4-bond with at least hydrocarbyloxysilane compound and (A-2) a natural rubber and/or a diene-based synthetic rubber and (B) 30-110 pts.mass filler for reinforcement composed of (B-1) 50-90 mass% silica and (B-2) 50-10 mass% carbon black. The pneumatic tire is obtained by applying the composition to tread rubber. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tire tread and a pneumatic tire using the same. More specifically, the present invention is excellent in performance on ice and snow and dry grip performance, and has good wet grip performance, low fuel consumption, and wear resistance, and is suitable for, for example, snow tires and all-season tires. The present invention relates to a tread rubber composition and a pneumatic tire using the same.

In recent years, due to social demands for energy saving, demands for lower fuel consumption of automobiles are becoming more severe. In order to meet such demands, a reduction in rolling resistance has also been demanded for tire performance. As a technique for reducing the rolling resistance of a tire, a technique by optimizing the tire structure has been studied, but the most common technique is to use a material with less heat generation as a rubber composition.
In addition to low fuel consumption performance, the rubber composition is highly compatible with both wet grip performance and low fuel consumption performance in response to increasing demand for braking performance (wet grip performance) on wet roads from the safety aspect. Is attracting attention.
As a method of obtaining a rubber composition that gives tires such good fuel economy and good wet grip performance at the same time, silica is used instead of carbon black which is a reinforcing filler generally used so far. The method of use has already been performed.
However, it has also been clarified that when silica is used as a reinforcing filler, the fracture strength and wear resistance of the rubber composition are inevitably lowered as compared with carbon black. Further, the dispersibility of silica is poor, and the workability at the time of kneading has become a big problem in actually manufacturing tires.
Therefore, in order to obtain a rubber composition with good exothermic properties with high productivity, not only carbon black or silica is used alone as a reinforcing filler, but also silica and carbon black are used in combination. There is a need for an active site modified polymer that has a wide interaction with the filler and can provide good dispersibility of the filler and wear resistance of the rubber composition.
Therefore, a modified polymer in which an alkoxysilane having a dialkylamino group is introduced at the active end of a polymer obtained by anionic polymerization using alkyllithium or lithium amide as a polymerization initiator is disclosed (for example, Patent Document 1). reference). When this modified polymer is used, good workability, reinforcing properties for silica blending, and a certain dispersion effect for both silica and carbon black are obtained, but it cannot always be said that they are sufficiently satisfactory.

By the way, in winter, there is an increasing demand for so-called all-season tires that can be used in the same way as in summer without changing tires. This type of tire has the same dry grip performance, wet grip performance, wear resistance, and low fuel consumption in winter as in summer, and also has sufficient drivability and braking performance on ice and snow. Is required.
A studless tire is known as a tire with improved performance on snow and snow. For the tread of this studless tire, a soft rubber material such as a polymer mainly having a low glass transition temperature, particularly a rubber mainly composed of butadiene rubber, is used in order to increase the frictional force with the snowy and snowy road surface compared to a normal tire. . Further, in a tire having a tread portion having a cap / tread two-layer structure, the cap rubber on the tread surface portion in contact with the ground is a relatively soft rubber even at a low temperature, for example, a large amount of a softening agent or a foam rubber. The technique of using is used. However, in these cases, although the braking performance on ice and snow is improved to some extent, there is a problem that a reduction in braking performance on a wet road on a general road is unavoidable.
Further, as a means for increasing the friction coefficient on the wet road surface, a rubber composition mainly composed of a styrene-butadiene copolymer exhibiting a relatively high glass transition temperature is used. A technique for increasing tan δ at 0 ° C. as a measure of hysteresis showing a good correlation is known (see, for example, Patent Document 2). However, in this case, with regard to braking performance on ice and snow, the rubber elastic modulus in the low temperature region increases and it becomes impossible to follow the unevenness of the road surface, and the surface of the tread is less on the frozen road surface than the normal road. As a result of less deformation, the energy loss (tan δ) between the rubber and the road surface contributes less to braking on ice.
Further, it is known that the amount of the reinforcing filler should be increased in order to improve the dry grip performance. In this case, however, the fuel efficiency and ice / snow performance are lowered.
As described above, it has been difficult to obtain a rubber composition that balances high performance on ice and snow, dry grip performance, wet grip performance, low fuel consumption and wear resistance.

Japanese Examined Patent Publication No. 6-57767 Japanese Patent Laid-Open No. 5-269884

  Under such circumstances, the present invention has excellent performance on ice and snow and dry grip performance, as well as good wet grip performance, low fuel consumption and wear resistance, such as for snow tires and all-season tires. An object of the present invention is to provide a suitable rubber composition for a tire tread and a pneumatic tire using the rubber composition.

As a result of intensive studies to achieve the above object, the present inventor has found that silica and carbon having a high silica content with respect to a rubber component containing a modified conjugated diene polymer obtained by a specific method in a predetermined ratio. It has been found that the object can be achieved by a rubber composition obtained by blending a reinforcing filler made of black at a predetermined ratio, and the present invention has been completed based on this finding.
That is, the present invention
(1) (A) (A-1) Modified conjugated diene obtained by modifying the active terminal of a conjugated diene polymer having a cis-1,4-bond content of 75 mol% or more with at least a hydrocarbyloxysilane compound (B) (B-1) 50-90 masses of (B) (B-1) silica based on 100 mass parts of (A-2) natural rubber and / or diene synthetic rubber, and 100 mass parts of (A-2) based polymer A And (B-2) a rubber composition for a tire tread, comprising 30 to 110 parts by mass of a reinforcing filler consisting of 50 to 10% by mass of carbon black,
(2) For tire tread as described in the above item (1), comprising (B-1) 15 to 100 parts by mass of silica and (B-2) 10 to 50 parts by mass of carbon black with respect to 100 parts by mass of component (A). Rubber composition,
(3) The tire tread rubber according to (1) or (2) above, further comprising (C) a silane coupling agent in a proportion of 5 to 20% by mass with respect to the silica of the component (B-1). Composition,
(4) The tire tread rubber composition according to any one of (1) to (3) above, further comprising (D) 5 to 30 parts by mass of an inorganic filler,
(5) The modified conjugated diene polymer A as the component (A-1) is first modified with a hydrocarbyloxysilane compound at the active end, and then second modified with a hydrocarbyloxysilane compound in the presence of a condensation accelerator. A rubber composition for a tire tread according to any one of the above (1) to (4),

(6) The modified conjugated diene polymer A as the component (A-1) is obtained by first reacting the active terminal with a hydrocarbyloxysilane compound and then reacting with a carboxylic acid partial ester of a polyhydric alcohol. The rubber composition for a tire tread according to any one of the above (1) to (4),
(7) The hydrocarbyloxysilane compound in which the modified conjugated diene polymer A as the component (A-1) is first modified with the hydrocarbyloxysilane compound at the active end and then introduced into the end in the presence of a condensation accelerator. The rubber composition for a tire tread according to any one of the above (1) to (4), which is obtained by subjecting a residue and an unreacted hydrocarbyloxysilane compound to a condensation reaction;
(8) The modified conjugated diene polymer A as the component (A-1) is obtained by further reacting with a carboxylic acid partial ester of a polyhydric alcohol after the secondary modification. Rubber composition for tire tread,

(9) The tire tread according to (7) above, wherein the modified conjugated diene polymer A as the component (A-1) is further reacted with a carboxylic acid partial ester of a polyhydric alcohol after the condensation reaction. Rubber composition for
(10) The hydrocarbyloxysilane compound is at least one compound selected from the following (a) general formula (I), (b) general formula (II), (c) general formula (III) and partial condensates thereof. A rubber composition for a tire tread according to any one of the above (1) to (9),
(A) General formula (I)

[In the formula, A ¹ represents (thio) epoxy, (thio) isocyanate, (thio) ketone,
At least one selected from (thio) aldehyde, imine, amide, isocyanuric acid trihydrocarbyl ester, (thio) carboxylic acid ester, (thio) carboxylic acid metal salt, carboxylic acid anhydride, carboxylic acid halide and carbonic acid dihydrocarbyl ester R ¹ is a single bond or a divalent inert hydrocarbon group, and R ² and R ³ are each independently a monovalent aliphatic hydrocarbon having 1 to 20 carbon atoms. represents a group or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, n is an integer from 0 to 2, when R ² are a plurality, the plurality of R ² may be the same or different, oR ^When there are a plurality of ³ , the plurality of OR ³ may be the same or different, and the molecule does not contain an active proton or onium salt. ]
(B) General formula (II)

[Wherein, A ² is a monovalent group having at least one functional group selected from cyclic tertiary amine, acyclic tertiary amine, pyridine, sulfide, multisulfide and nitrile, and R ⁴ is a single bond or The divalent inert hydrocarbon group, R ⁵ and R ⁶ each independently represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. , m is an integer from 0 to 2, if R ⁵ there are a plurality, the plurality of R ⁵ may be the same or different, if OR ⁶ there are plural, a plurality of OR ⁶ may be the same or different The molecule does not contain active protons and onium salts. ]
(C) General formula (III)

[Wherein, A ³ represents alcohol, thiol, primary amine and onium salt thereof, cyclic secondary amine and onium salt thereof, acyclic secondary amine and onium salt thereof, onium salt of cyclic tertiary amine, acyclic tertiary amine An onium salt of an amine, a group having an aryl or arylalkyl Sn bond, a monovalent group having at least one functional group selected from sulfonyl, sulfinyl and nitrile, R ⁷ is a single bond or a divalent inert hydrocarbon group, R ⁸ and R ⁹ each independently represent a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, q is an integer of 0 to 2 There, if R ⁸ is plural, R ⁸ may be the same or different, if the OR ⁹ there are a plurality, the plurality of OR ⁹ may be the same or different. ]
(11) The rubber composition for a tire tread according to any one of (6), (8) and (9) above, wherein the carboxylic acid partial ester of the polyhydric alcohol is a monoester, diester or triester of sorbitan fatty acid. ,

(12) The condensation accelerator is at least one selected from compounds represented by the following (d) general formula (IV), (e) general formula (V) and (f) general formula (VI), and water. The rubber composition for a tire tread according to the above item (5) or (7), comprising:
(D) general formula carboxylates of tin having 3 to 20 carbon atoms an oxidation number of 2 represented by ^{(IV) Sn (OCOR 10)} 2 ··· (IV)
[Wherein, R ¹⁰ is an organic group having 2 to 19 carbon atoms, and when there are a plurality of them, they may be the same or different. ]
(E) Tin compound of oxidation number 4 represented by general formula (V) R ¹¹ _r SnA ⁴ _t B ¹ _(4-tr) (V)
[Wherein, r is an integer of 1 to 3, t is an integer of 1 or 2, and t + r is an integer of 3 or 4. R ¹¹ is an aliphatic hydrocarbon group having 1 to 30 carbon atoms, and B ¹ is a hydroxyl group or a halogen. A ⁴ is (a) an aliphatic carboxylic acid residue having 2 to 30 carbon atoms, (b) a 1,3-dicarbonyl-containing group having 5 to 30 carbon atoms, and (c) a hydrocarbyloxy group having 3 to 30 carbon atoms. And (d) a group selected from a siloxy group having a total of three substitutions (which may be the same or different) with a hydrocarbyl group having 1 to 20 carbon atoms and / or a hydrocarbyloxy group having 1 to 20 carbon atoms, and R ¹¹ may if there are multiple the same or different, may be the same or different if A ⁴ have multiple. ]
(F) Titanium compound of oxidation number 4 represented by general formula (VI) A ⁵ xTiB ² _(4-x) (VI)
[Wherein x is an integer of 2 or 4. A ⁵ is (i) a hydrocarbyloxy group having 3 to 30 carbon atoms, (b) a siloxy group that is tri-substituted in total with an alkyl group having 1 to 30 carbon atoms and / or a hydrocarbyloxy group having 1 to 20 carbon atoms, When there are a plurality of A ^{5 s,} they may be the same or different. B ² is a 1,3-dicarbonyl-containing group having 5 to 30 carbon atoms, and when there are a plurality of B ² , they may be the same or different. ]
(13) The rubber composition for a tire tread according to any one of (1) to (12) above, wherein the modified conjugated diene polymer A as the component (A-1) is a modified polybutadiene, and (14) the above A pneumatic tire comprising the rubber composition according to any one of (1) to (13) as a tread rubber;
Is to provide.

  According to the present invention, it is excellent in performance on ice and snow and dry grip performance, and has good wet grip performance, low fuel consumption and wear resistance, and is suitable for, for example, snow tires and all-season tires. A rubber composition and a pneumatic tire using the rubber composition can be provided.

The rubber composition for a tire tread of the present invention (hereinafter sometimes simply referred to as a rubber composition) includes (A) (A-1) a modified conjugated diene polymer A and (A-2) as essential components. ) A component containing natural rubber and / or a diene synthetic rubber, and a reinforcing filler comprising (B) (B-1) silica and (B-2) carbon black.
The (A-1) modified conjugated diene polymer A contained in the rubber component (A) is an active terminal of a conjugated diene polymer having a cis-1,4-bond content of 75 mol% or more. Is obtained by modifying at least hydrocarbyloxysilane with a compound.
The conjugated diene polymer having an active terminal with a cis-1,4-bond content of 75 mol% or more used as an intermediate of the modified diene polymer A is, for example, a conjugated diene compound of a raw material monomer, It can manufacture by polymerizing by methods, such as a solution polymerization method, a gas phase polymerization method, a bulk polymerization method, Preferably, the solution polymerization method using the polymerization catalyst of this. The polymerization mode may be either a batch type or a continuous type.
Examples of the raw material monomer conjugated diene compound include 1,3-butadiene; isoprene; 1,3-pentadiene; 2,3-dimethylbutadiene; 2-phenyl-1,3-butadiene; 1,3-hexadiene and the like. . These may be used alone or in combination of two or more, and among these, 1,3-butadiene is particularly preferable.
Further, a small amount of other hydrocarbon monomers may coexist in these conjugated diene compounds, but the conjugated diene compound is preferably 80 mol% or more of the total monomers.

The polymerization catalyst is preferably a combination of at least one compound selected from the following components (x), (y) and (z).
[(X) component]
The rare earth compound selected from the following (x1) to (x4) may be used as it is as an inert organic solvent solution or may be supported on an inert solid.
(X1) a rare earth compound having an oxidation number of 3, a carboxyl group having 2 to 30 carbon atoms, an alkoxy group having 2 to 30 carbon atoms, an aryloxy group having 6 to 30 carbon atoms, and 1,3-di having 5 to 30 carbon atoms One having a total of three ligands freely selected from carbonyl-containing groups, or a Lewis base compound (in particular, free carboxylic acid, free alcohol, 1,3-diketone, cyclic ether, linear ether, Selected from trihydrocarbyl phosphine, trihydrocarbyl phosphite, and the like. Specific examples include neodymium tri-2-ethylhexanoate, a complex compound thereof with acetylacetone, neodymium trineodecanoate, a complex compound thereof with acetylacetone, neodymium tri-n-butoxide, and the like.
(X2) A complex compound of a rare earth trihalide and a Lewis base. For example, there is a THF complex of neodymium trichloride.
(X3) An organic rare earth compound having an oxidation number of 3 in which at least one (substituted) allyl group is directly bonded to a rare earth atom. For example, there is a salt of tetraallyl neodymium and lithium.
(X4) An organic rare earth compound having an oxidation number of 2 or 3 in which at least one (substituted) cyclopentadienyl group is directly bonded to a rare earth atom, or this compound, a trialkylaluminum or a non-coordinating anion and a counter cation It is a reaction product with an ionic compound. An example is dimethylaluminum (μ-dimethyl) bis (pentamethylcyclopentadienyl) samarium.
As the rare earth element of the rare earth compound, lanthanum, neodymium, praseodymium, samarium and gadolinium are preferable, and lanthanum, neodymium and samarium are more preferable.
Among the above components (x), neodymium carboxylates and samarium substituted cyclopentadienyl compounds are preferred.

[(Y) component]
A plurality of organoaluminum compounds selected from the following one can be used at the same time.
(Y1) A trihydrocarbylaluminum compound represented by the formula R ¹² ₃ A1 (wherein R ¹² is a hydrocarbon group having 1 to 30 carbon atoms, which may be the same as or different from each other).
(Y2) Hydrocarbyl aluminum hydride represented by the formula R ¹³ ₂ A1H or R ¹³ A1H ₂ (wherein R ¹³ is a hydrocarbon group having 1 to 30 carbon atoms, which may be the same or different from each other).
(Y3) A hydrocarbylaluminoxane compound having a hydrocarbon group having 1 to 30 carbon atoms.
Examples of the component (y) include trialkylaluminum, dialkylaluminum hydride, alkylaluminum dihydride, and alkylaluminoxane. These compounds may be used as a mixture. Among the components (y), a combination of an aluminoxane and another organoaluminum compound is preferable.
[(Z) component]
Although it is a compound selected from the following ones, it is not always necessary when (x) contains a halogen or a non-coordinating anion and (y) contains an aluminoxane.
(Z1) An inorganic or organic compound of an element belonging to Group II, III, or IV, or a complex compound of these with a Lewis base, having a hydrolyzable halogen. For example, alkyl aluminum dichloride, dialkyl aluminum chloride, silicon tetrachloride, tin tetrachloride, a complex of zinc chloride and a Lewis base such as alcohol, a complex of magnesium chloride and a Lewis base such as alcohol, or the like.
(Z2) An organic halide having a structure selected from at least one tertiary alkyl halide, benzyl halide, and allyl halide. For example, benzyl chloride, t-butyl chloride, benzyl bromide, t-butyl bromide and the like.
(Z3) A zinc halide or a complex compound of this with a Lewis base.
(Z4) An ionic compound comprising a non-coordinating anion and a counter cation. For example, triphenylcarbonium tetrakis (pentafluorophenyl) borate is preferably used.

For the preparation of the catalyst, in addition to the components (x), (y), and (z), the same conjugated diene compound and / or non-conjugated diene monomer as the polymerization monomer is used in combination as necessary. May be.
Further, a part or all of the component (x) or the component (z) may be supported on an inert solid, and in this case, it can be carried out by so-called gas phase polymerization.
Although the usage-amount of the said catalyst can be set suitably, normally (x) component is about 0.001-0.5 millimoles per 100g of monomers. Moreover, (y) component / (x) component is about 5-1000 and (z) component / (x) component is about 0.5-10 by molar ratio.
Examples of the solvent used in the case of solution polymerization include organic solvents inert to the reaction, for example, hydrocarbon solvents such as aliphatic, alicyclic, and aromatic hydrocarbon compounds. Specifically, those having 3 to 8 carbon atoms are preferred, such as propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene, trans-2-butene, Examples thereof include cis-2-butene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, benzene, toluene, xylene, and ethylbenzene. These may be used alone or in combination of two or more.
The temperature in this polymerization reaction is preferably selected in the range of −80 to 150 ° C., more preferably −20 to 120 ° C. The polymerization reaction can be carried out under generated pressure, but it is usually desirable to operate at a pressure sufficient to keep the monomer in a substantially liquid phase. That is, the pressure will depend on the particular material being polymerized, the polymerization medium used and the polymerization temperature, but higher pressures can be used if desired, and such a pressure can be used with a gas inert to the polymerization reaction. It can be obtained by an appropriate method such as pressurization.
In this polymerization, it is desirable that all raw materials involved in the polymerization, such as a catalyst, a solvent, a monomer, and the like, from which reaction inhibitors such as water, oxygen, carbon dioxide, and protic compounds are substantially removed are used.

The modified conjugated diene polymer A is the activity of the conjugated diene polymer (intermediate polymer) having an active terminal having a cis-1,4-bond content of 75 mol% or more thus obtained. The terminal is modified with at least a hydrocarbyloxysilane compound, and there are five modes as shown below.
First, the first embodiment is a modified conjugated diene system in which the active terminal of the intermediate polymer is first modified with a hydrocarbyloxysilane compound and then secondarily modified with a hydrocarbyloxysilane compound in the presence of a condensation accelerator. It is a polymer.
The second aspect is a modified conjugated diene polymer obtained by first reacting the active terminal of the intermediate polymer with a hydrocarbyloxysilane compound and then reacting with a carboxylic acid partial ester of a polyhydric alcohol.
In a third aspect, the hydrocarbyloxysilane compound residue and the unreacted hydrocarbyloxysilane introduced into the terminal after the primary modification of the active end of the intermediate polymer with a hydrocarbyloxysilane compound and further in the presence of a condensation accelerator It is a modified conjugated diene polymer obtained by condensation reaction with a compound.
A fourth aspect is a modified conjugated diene polymer obtained by reacting with a carboxylic acid partial ester of a polyhydric alcohol after the secondary modification in the first aspect of the previous period.
The fifth aspect is a modified conjugated diene polymer obtained by further reacting with a carboxylic acid partial ester of a polyhydric alcohol after the condensation reaction in the third aspect.

In the primary modification reaction in each of the above-described embodiments, the intermediate polymer used preferably has at least 10% of polymer chains having a living property.
The hydrocarbyloxysilane compound used for modification is at least one selected from the following (a) general formula (I), (b) general formula (II), (c) general formula (III) and partial condensates thereof. Mention may be made of certain compounds.
[(A) Hydrocarbyloxysilane compound]
This hydrocarbyloxysilane compound has the general formula (I)

[Wherein A ¹ is (thio) epoxy, (thio) isocyanate, (thio) ketone, (thio) aldehyde, imine, amide, isocyanuric acid trihydrocarbyl ester, (thio) carboxylic acid ester, (thio) carboxylic acid A monovalent group having at least one functional group selected from metal salts, carboxylic acid anhydrides, carboxylic acid halides and carbonic acid dihydrocarbyl esters, R ¹ is a single bond or a divalent inert hydrocarbon group , R ² and R ³ each independently represent a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and n is an integer of 0 to 2 , and the case where R ² is plural, R ² may be the same or different, if the OR ³ there are a plurality, the plurality of OR ³ may be the same or different, and in the molecule active proton And onium salts are not included. ]
And / or a partial condensate thereof.

In the general formula (1), among the functional groups in A ¹ , imine includes ketimine, aldimine, and amidine, and (thio) carboxylic acid ester includes unsaturated carboxylic acid ester such as acrylate and methacrylate. Examples of the metal of the metal salt of (thio) carboxylic acid include alkali metals, alkaline earth metals, Al, Sn, and Zn.
Preferred examples of the divalent inert hydrocarbon group in R ¹ include an alkylene group having 1 to 20 carbon atoms. The alkylene group may be linear, branched or cyclic, but is particularly preferably linear. Examples of the linear alkylene group include a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, an octamethylene group, a decamethylene group, and a dodecamethylene group.
Examples of R ² and R ³ include an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, and an aralkyl group having 7 to 18 carbon atoms. Here, the alkyl group and alkenyl group may be linear, branched, or cyclic, and examples thereof include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl. Group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group, cyclopentyl group, cyclohexyl group, vinyl group, propenyl group, allyl group, hexenyl group, octenyl group, cyclo A pentenyl group, a cyclohexenyl group, etc. are mentioned.
The aryl group may have a substituent such as a lower alkyl group on the aromatic ring, and examples thereof include a phenyl group, a tolyl group, a xylyl group, and a naphthyl group. Further, the aralkyl group may have a substituent such as a lower alkyl group on the aromatic ring, and examples thereof include a benzyl group, a phenethyl group, and a naphthylmethyl group.
n is an integer of 0 to 2, but 0 is preferable, and it is necessary that this molecule has no active proton and onium salt.

Examples of the hydrocarbyloxysilane compound represented by the general formula (I) include (thio) epoxy group-containing hydrocarbyloxysilane compounds such as 2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, (2-glycidoxyethyl) methyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, (3-glycidoxypropyl) methyldimethoxysilane, 2- (3,4) -Epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyl (methyl) dimethoxysilane and the epoxy group in these compounds as a thioepoxy group Put in There may be mentioned preferably those were example, among these, in particular 3-glycidoxypropyltrimethoxysilane and 2- (3,4-epoxycyclohexyl trimethoxysilane is preferred.
Further, as imine group-containing hydrocarbyloxycyan compounds, N- (1,3-dimethylbutylidene) -3- (triethoxysilyl) -1-propanamine, N- (1-methylethylidene) -3- (triethoxy Silyl) -1-propanamine, N-ethylidene-3- (triethoxysilyl) -1-propanamine, N- (1-methylpropylidene) -3- (triethoxysilyl) -1-propanamine, N- (4-N, N-dimethylaminobenzylidene) -3- (triethoxysilyl) -1-propanamine, N- (cyclohexylidene) -3- (triethoxysilyl) -1-propanamine and their triethoxy Trimethoxysilyl compounds corresponding to silyl compounds, methyldiethoxysilyl compounds, ethyldiethoxysilyl compounds, Preferred examples include tildimethoxysilyl compounds and ethyldimethoxysilyl compounds, among which N- (1-methylpropylidene) -3- (triethoxysilyl) -1-propanamine and N- ( 1,3-dimethylbutylidene) -3- (triethoxysilyl) -1-propanamine is preferred.

Furthermore, the following can be mentioned as another hydrocarbyloxy compound. That is, as imine (amidine) group-containing compounds, 1- [3- (triethoxysilyl) propyl] -4,5-dihydroimidazole, 1- [3- (trimethoxysilyl) propyl] -4,5-dihydro Examples thereof include imidazole, 3- [10- (triethoxysilyl) decyl] -4-oxazoline, and among these, 3- (1-hexamethyleneimino) propyl (triethoxy) silane, (1-hexa Methyleneimino) methyl (trimethoxy) silane, 1- [3- (triethoxysilyl) propyl] -4,5-dihydroimidazole and 1- [3- (trimethoxysilyl) propyl] -4,5-dihydroimidazole are preferred Can be mentioned. N- (3-triethoxysilylpropyl) -4,5-dihydroimidazole, N- (3-isopropoxysilylpropyl) -4,5-dihydroimidazole, N- (3-methyldiethoxysilylpropyl)- 4,5-dihydroimidazole and the like can be mentioned, and among them, N- (3-triethoxysilylpropyl) -4,5-dihydroimidazole is preferable.
Examples of the carboxylic acid ester group-containing compound include 3-methacryloyloxypropyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, and 3-methacryloyloxypropyltriisosilane. Examples thereof include propoxysilane, among which 3-methacryloyloxypropyltrimethoxysilane is preferable. Furthermore, examples of the isocyanate group-containing compound include 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-isocyanatopropylmethyldiethoxysilane, and 3-isocyanatopropyltriisopropoxysilane. Of these, 3-isocyanatopropyltriethoxysilane is preferred. Examples of the carboxylic acid anhydride-containing compound include 3-triethoxysilylpropyl succinic anhydride, 3-trimethoxysilylpropyl succinic anhydride, 3-methyldiethoxysilylpropyl succinic anhydride, and the like. Of these, 3-triethoxysilylpropyl succinic anhydride is preferred.

One of these hydrocarbyloxysilane compounds may be used alone, or two or more thereof may be used in combination. Moreover, the partial condensate of the said hydrocarbyl oxysilane compound can also be used.
[(B) Hydrocarbyloxysilane compound]
This hydrocarbyloxysilane compound has the general formula (II)

Wherein, A ² is a cyclic tertiary amine, acyclic tertiary amines, pyridine, sulfides, monovalent group having at least one functional group selected from among the multi-sulfides and nitriles, R ⁴ is a single bond Or a divalent inert hydrocarbon group, R ⁵ and R ⁶ are each independently a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. indicates, m is an integer from 0 to 2, if R ⁵ there are a plurality, the plurality of R ⁵ may be the same or different, if OR ⁶ have multiple, even if a plurality of OR ⁶ may be the same or different Well, the molecule does not contain active protons and onium salts. ]
And / or a partial condensate thereof.
The hydrocarbyloxysilane compound represented by the general formula (II) and / or a partial condensate thereof is not directly reacted with the active end and remains in the reaction system as unreacted, and thus introduced into the active end. Is consumed for condensation with the hydrocarbyloxysilane compound residue.

In the general formula (II), the acyclic tertiary amine in A ² contains an N, N- (disubstituted) aromatic amine such as N, N- (disubstituted) aniline, and is also a cyclic tertiary amine. The amine can contain a (thio) ether as part of the ring. Divalent inactive hydrocarbon group among R ^4, the R ⁵ and R ⁶ are as described for R ^1, R ² and R ³ in each of the general formula (I). It is necessary that this molecule does not have active protons and onium salts.
Examples of the hydrocarbyloxysilane compound represented by the general formula (II) include 3-dimethylaminopropyl (triethoxy) silane and 3-dimethylaminopropyl (trimethoxy) silane as acyclic tertiary amine group-containing hydrocarbyloxysilane compounds. , 3-diethylaminopropyl (triethoxy) silane, 3-diethylaminopropyl (trimethoxy) silane, 2-dimethylaminoethyl (triethoxy) silane, 2-dimethylaminoethyl (trimethoxy) silane, 3-dimethylaminopropyl (diethoxy) methylsilane, 3, -Dibutylaminopropyl (triethoxy) silane etc. can be mentioned, among these, 3-diethylaminopropyl (triethoxy) silane and 3-dimethylaminopropyl (triethoxy) Silanes are preferred.
Further, as the cyclic tertiary amine group-containing hydrocarbyloxysilane compound, 3- (1-hexamethyleneimino) propyl (triethoxy) silane, 3- (1-hexamethyleneimino) propyl (trimethoxy) silane, (1-hexamethyleneimino ) Methyl (trimethoxy) silane, (1-hexamethyleneimino) methyl (triethoxy) silane, 2- (1-hexamethyleneimino) ethyl (triethoxy) silane, 2- (1-hexamethyleneimino) ethyl (trimethoxy) silane, 3- (1-pyrrolidinyl) propyl (triethoxy) silane, 3- (1-pyrrolidinyl) propyl (trimethoxy) silane, 3- (1-heptamethyleneimino) propyl (triethoxy) silane, 3- (1-dodecamethyleneimino) Propyl (triethoxy) Run, 3- (1-hexamethyleneimino) propyl (diethoxy) methylsilane, 3- (1-hexamethyleneimino) can be preferably exemplified propyl (diethoxy) ethylsilane. In particular, 3- (1-hexamethyleneimino) propyl (triethoxy) silane is preferred.
Furthermore, examples of other hydrocarbyloxysilane compounds include 2- (trimethoxysilylethyl) pyridine, 2- (triethoxysilylethyl) pyridine, 4-ethylpyridine and the like.

One of these hydrocarbyloxysilane compounds may be used alone, or two or more thereof may be used in combination. Moreover, the partial condensate of these hydrocarbyl oxysilane compounds can also be used.
[(C) Hydrocarbyloxysilane compound]
This hydrocarbyloxysilane compound has the general formula (III)

[Wherein, A ³ represents alcohol, thiol, primary amine and onium salt thereof, cyclic secondary amine and onium salt thereof, acyclic secondary amine and onium salt thereof, onium salt of cyclic tertiary amine, acyclic tertiary amine An onium salt of an amine, a group having an aryl or arylalkyl Sn bond, a monovalent group having at least one functional group selected from sulfonyl, sulfinyl and nitrile, R ⁷ is a single bond or a divalent inert hydrocarbon group, R ⁸ and R ⁹ each independently represent a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, q is an integer of 0 to 2 There, if R ⁸ is plural, R ⁸ may be the same or different, if the OR ⁹ there are a plurality, the plurality of OR ⁹ may be the same or different. ]
And / or a partial condensate.

In the general formula (III), the primary amine in A ³ includes aromatic amines such as aniline, and the acyclic secondary amine is N- (monosubstituted) aromatic such as N- (monosubstituted) aniline. Includes amines. Further, onium salts of acyclic tertiary amines include onium salts of N, N- (disubstituted) aromatic amines such as N, N- (disubstituted) aniline. Also. In the case of a cyclic secondary amine or a cyclic tertiary amine, (thio) ether can be contained as a part of the ring. Divalent inactive hydrocarbon group out of R ^7, the R ⁸ and R ⁹ are as described for R ^1, R ² and R ³ in each of the general formula (I).
Examples of the hydrocarbyloxysilane compound represented by the general formula (III) include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, hydroxymethyltrimethoxysilane, hydroxymethyltriethoxysilane, mercaptomethyltrimethoxy. Silane, mercaptomethyltriethoxysilane, aminophenyltrimethoxysilane, aminophenyltriethoxysilane, 3- (N-methylamino) propyltrimethoxysilane, 3- (N-methylamino) propyltriethoxysilane, octadecyldimethyl (3 -Trimethylsilylpropyl) ammonium chloride, octadecyldimethyl (3-triethylsilylpropyl) ammonium chloride, cyanomethyltrimethoxysilane, cyanomethyltrieth Shishiran, it can be exemplified sulfonyl methyltrimethoxysilane, sulfonyl methyltriethoxysilane, sulfinyl methyltrimethoxysilane, a sulfinyl methyl triethoxysilane.

One of these hydrocarbyloxysilane compounds may be used alone, or two or more thereof may be used in combination. Moreover, the partial condensate of the said hydrocarbyl oxysilane compound can also be used.
The partial condensate of the hydrocarbyloxysilane compound represented by the general formulas (I), (II), and (III) means that a part (not all) of the SiOR of the hydrocarbyloxysilane compound is condensed. This refers to SiOSi bonded.
In the present invention, in the case of the first aspect, the third aspect, the fourth aspect, and the fifth aspect, the reaction with the remaining or newly added hydrocarbyloxysilane compound in the presence of a condensation accelerator. First, an intermediate polymer having an active terminal is reacted with a substantially stoichiometric amount of a hydrocarbyloxysilane compound added to the reaction system, so that substantially all of the terminals have hydrocarbyloxysilyl groups. By introducing (primary modification) and reacting the hydrocarbyloxysilyl compound with the hydrocarbyloxysilyl group introduced above, more hydrocarbyloxysilane compound residues than the equivalent amount are introduced into the active terminal. For this reason, since a further effect is acquired with respect to low heat generation property and workability, these aspects are preferable to the second aspect.

  In the present invention, when the hydrocarbyloxysilane compound is an alkoxysilyl compound, the condensation reaction between alkoxysilyl groups in the first aspect, the third aspect, the fourth aspect, and the fifth aspect is (residual or It preferably occurs between the newly added free alkoxysilane and the alkoxysilyl group at the end of the polymer, and in some cases, preferably occurs between the alkoxysilyl groups at the end of the polymer. is necessary. Therefore, when an alkoxysilane compound is newly added, it is preferable from the viewpoint of efficiency that the hydrolyzability of the alkoxysilyl group does not exceed the hydrolyzability of the alkoxysilyl group at the end of the polymer. For example, alkoxysilane I uses a highly hydrolyzable trimethoxysilyl group-containing compound, and newly added alkoxysilane II contains an alkoxysilyl group (for example, triethoxysilyl group) that is less hydrolyzable than this. Combinations using compounds are preferred. Conversely, for example, it is within the scope of the present invention that alkoxysilane I contains a triethoxysilyl group and II contains a trimethoxysilyl group, but is not preferable from the viewpoint of reaction efficiency.

For the modification reaction in the present invention, either a solution reaction or a solid phase reaction can be used, but a solution reaction (a solution containing an unreacted monomer used during polymerization may be suitable). Moreover, there is no restriction | limiting in particular about the form of this modification | denaturation reaction, You may carry out using a batch type reactor, You may carry out by a continuous type using apparatuses, such as a multistage continuous type reactor and an in-line mixer. In addition, it is important to carry out the modification reaction after completion of the polymerization reaction and before performing various operations necessary for solvent removal treatment, water treatment, heat treatment, polymer isolation, and the like.
As the temperature of the modification reaction, the polymerization temperature of the conjugated diene polymer can be used as it is. Specifically, a preferable range is 20 to 100 ° C. If the temperature is low, the viscosity of the polymer tends to increase, and if the temperature is high, the polymerization active terminal tends to be deactivated.
Next, in order to accelerate the secondary modification, it is preferably performed in the presence of a condensation accelerator. As this condensation accelerator, a combination of a metal compound generally known as a curing catalyst for alkoxy condensation curable room temperature crosslinking (RTV) silicone and water can be used. For example, a combination of tin carboxylate and / or titanium alkoxide and water can be preferably exemplified. There is no particular limitation on the method of charging the condensation accelerator into the reaction system. A solution of an organic solvent compatible with water such as alcohol may be used, or water may be directly injected, dispersed, or dissolved in the hydrocarbon solution using various chemical engineering techniques.

As such a condensation accelerator, at least one selected from the compounds represented by the following (d) general formula (IV), (e) general formula (V) and (f) general formula (VI): It is preferable that it consists of water.
(D) a carboxylic acid salt of 3 to 20 carbon atoms of tin of oxidation number 2 represented by the general formula (IV):
Sn (OCOR ¹⁰ ) ₂ (IV)
[Wherein, R ¹⁰ is an organic group having 2 to 19 carbon atoms, and when there are a plurality of them, they may be the same or different. ]
(E) Tin compound having oxidation number 4 represented by general formula (V):
R ¹¹ _r SnA ⁴ _t B ¹ _(4-tr) (V)
[Wherein, r is an integer of 1 to 3, t is an integer of 1 or 2, and t + r is an integer of 3 or 4. R ¹¹ is an aliphatic hydrocarbon group having 1 to 30 carbon atoms, and B ¹ is a hydroxyl group or a halogen. A ⁴ is (a) an aliphatic carboxylic acid residue having 2 to 30 carbon atoms, (b) a 1,3-dicarbonyl-containing group having 5 to 30 carbon atoms, and (c) a hydrocarbyloxy group having 3 to 30 carbon atoms. And (d) a group selected from a siloxy group having a total of three substitutions (which may be the same or different) with a hydrocarbyl group having 1 to 20 carbon atoms and / or a hydrocarbyloxy group having 1 to 20 carbon atoms, and R ¹¹ may if there are multiple the same or different, may be the same or different if A ⁴ have multiple. ]
(F) Titanium compound having an oxidation number of 4 represented by the general formula (VI):
A ⁵ _x TiB ² _(4-x) (VI)
[Wherein x is an integer of 2 or 4. A ⁵ is (i) a hydrocarbyloxy group having 3 to 30 carbon atoms, (b) a siloxy group that is tri-substituted in total with an alkyl group having 1 to 30 carbon atoms and / or a hydrocarbyloxy group having 1 to 20 carbon atoms, When there are a plurality of A ^{5 s,} they may be the same or different. B ² is a 1,3-dicarbonyl-containing group having 5 to 30 carbon atoms, and when there are a plurality of B ² , they may be the same or different. ]

Examples of the carboxylic acid salt of tin having an oxidation number of 2 represented by the general formula (IV) in (d) include bis (2-ethylhexanoic acid) tin, tin dioleate, tin dilaurate, and the like (f). Among the tin compounds of oxidation number 4 represented by the general formula (V), tetravalent dihydrocarbyltin dicarboxylate (bis (hydrocarbyldicarboxylic acid) salt) And (b) mono-carboxylate hydroxide having a 1,3-dicarbonyl-containing group having 5 to 30 carbon atoms such as bis (1,3-diketonate), As those having a hydrocarbyloxy group having 3 to 30 carbon atoms, the alkoxy halide is (d) a total of three substitutions (identical) with a hydrocarbyl group having 1 to 20 carbon atoms and / or a hydrocarbyloxy group having 1 to 20 carbon atoms. And those having a siloxy group which may be different from each other include alkoxy (trihydrocarbylsiloxide), alkoxy (dihydrocarbylalkoxysiloxide), bis (trihydrocarbylsiloxide), bis (dihydrocarbylalkoxysiloxide) Etc. are preferable. The hydrocarbon group condensed with tin preferably has 4 or more carbon atoms, and more preferably has 4 to 8 carbon atoms.
Further, as the titanium compound having an oxidation number of 4 represented by the general formula (VI) of the above (f), a tetraalkoxide or tetrakis (trihydrocarbyloxysiloxide) of titanium having an oxidation number of 4 or diisopropoxybis (acetyl) Dialkoxybis (1,3-diketonate) titanium (titanium chelate compound) such as acetonate) titanium.

The water in the condensation accelerator is preferably used in the form of a simple substance, a solution of alcohol or the like, or a dispersed micelle in a hydrocarbon solvent, and if necessary, such as adsorbed water on the solid surface or hydrated water of hydrate. The water potentially contained in the compound capable of releasing water in the reaction system can also be used effectively.
The metal compound and water forming the condensation accelerator may be added separately to the reaction system or mixed immediately before use as a mixture, but long-term storage of the mixture is preferable because it causes decomposition of the metal compound. Absent.
The amount of the condensation accelerator used is preferably such that the molar ratio of the metal of the metal compound and the water effective for the reaction to the total amount of hydrocarbyloxysilyl groups present in the reaction system is 0.1 or more. Although the upper limit varies depending on the purpose and reaction conditions, it is preferable that there is effective water having a molar ratio of about 0.5 to 3 with respect to the total amount of hydrocarbyloxysilyl groups condensed at the polymer terminal before the condensation treatment. The molar ratio of the metal of the metal compound to water effective for the reaction varies depending on the reaction conditions required, but is preferably about 1: 0.5 to 1:20.

In the present invention, in the second, fourth and fifth aspects of the modified conjugated diene polymer A used as the component (A-1), a carboxylic acid partial ester of a polyhydric alcohol is polymerized. An operation of reacting with a group derived from a hydrocarbyloxysilane compound introduced at the terminal and stabilizing the group is performed.
Here, the carboxylic acid partial ester of a polyhydric alcohol is an ester of a polyhydric alcohol and a carboxylic acid and means a partial ester having one or more hydroxyl groups. Specifically, an ester of a saccharide having 4 or more carbon atoms or a modified saccharide and a fatty acid is preferably used. This ester is more preferably (1) a fatty acid partial ester of a polyhydric alcohol, particularly a partial ester of a saturated higher fatty acid or unsaturated higher fatty acid having 10 to 20 carbon atoms and a polyhydric alcohol (monoester, diester, triester). And (2) ester compounds in which 1 to 3 partial esters of a polyvalent carboxylic acid and a higher alcohol are bonded to the polyhydric alcohol.

The polyhydric alcohol used as the raw material for the partial ester is preferably a saccharide having 5 or 6 carbon atoms having at least three hydroxyl groups (which may be hydrogenated or not hydrogenated), glycol, A polyhydroxy compound or the like is used. The raw fatty acid is preferably a saturated or unsaturated fatty acid having 10 to 20 carbon atoms, and for example, stearic acid, lauric acid, and palmitic acid are used.
Among fatty acid partial esters of polyhydric alcohols, sorbitan fatty acid esters are preferred, and specifically, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate and And sorbitan trioleate.
Commercially available products include “SPAN60” (sorbitan stearate), “SPAN80” (sorbitan monooleate), “SPAN85” (sorbitan trioleate) and the like as trademarks of ICI.
The amount of the partial ester added is preferably about 0.2 to 10 mol, particularly 1 to 10 mol, relative to 1 mol of the hydrocarbyloxysilyl group imparted to the intermediate polymer.

As the modified conjugated diene polymer A of the component (A-1) thus produced, a modified polybutadiene having a cis-1,4-bond amount of 75 mol% or more is a performance of the rubber composition for tire treads. From the point of view, it is preferable.
The modified conjugated diene polymer A as the component (A-1) has a large dispersion improving effect on the reinforcing filler, particularly silica, and lowers E ′ (dynamic storage elastic modulus) in the whole temperature range as a whole. However, it is possible to increase the decrease in E ′ particularly on the low temperature side. Therefore, the required performances (snow and snow performance and dry grip performance) of snow tires and all-season tires can be achieved at a higher level.
In addition, tan δ has a large reduction effect, and since it is possible to increase the decrease in high temperature (60 ° C.) while reducing the decrease at 0 ° C. compared to the case of using ordinary polybutadiene rubber, Filled silica formulation also works to improve the balance between wet grip performance and fuel efficiency. Furthermore, the wear resistance can be improved by the effect of improving the dispersion of the reinforcing filler.

In the rubber composition of the present invention, the content of the modified conjugated diene polymer A in the rubber component (A) is 5 to 70% by mass, preferably 10 to 60% by mass. If the content is less than 5% by mass, the above effect is not sufficiently exhibited, and if it exceeds 70% by mass, workability is deteriorated.
On the other hand, as the diene synthetic rubber in (A-2) natural rubber and / or diene synthetic rubber, for example, polyisoprene synthetic rubber (IR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber ( NBR), chloroprene rubber (CR), butyl rubber (IIR) and the like. The natural rubber or diene synthetic rubber as the component (A-2) may be used alone or in combination of two or more.
The rubber component may contain ethylene-propylene copolymer rubber (EPR, EPDM), and other modified conjugated diene polymers other than the modified conjugated diene polymer A according to the present invention. be able to. For example, by using modified SBR as another modified conjugated diene polymer, the effect of dispersing the reinforcing filler and the inorganic filler is further increased.

In the rubber composition of the present invention, in order to provide excellent performance on ice and snow and dry grip performance, as well as good wet grip performance, performance such as low fuel consumption and wear resistance, and reinforcing properties, In addition to the modified conjugated diene polymer, (B-1) silica and (B-2) carbon black are contained as a reinforcing filler for the component (B).
There is no restriction | limiting in particular as said (B-1) component silica, It can select and use arbitrarily from what was conventionally used as a reinforcing filler of rubber conventionally.
Examples of the silica include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. Wet silica that is noticeable is preferred. The wet silica preferably has a nitrogen adsorption specific surface area (N ₂ SA) according to the BET method of 140 to 280 m ² / g from the viewpoints of balance of reinforcement, workability, wet grip properties, and wear resistance, It is more preferable that it is 170-250 m < ² > / g. Suitable wet silica includes, for example, AQ, VN3, LP, NA, etc. manufactured by Tosoh Silica Co., Ltd. and Ultrazil VN3 (N ₂ SA: 210 m ² / g) manufactured by Degussa.
Moreover, there is no restriction | limiting in particular as carbon black of (B-2) component, For example, SRF, GPF, FEF, HAF, ISAF, SAF etc. are used, iodine adsorption amount (IA) is 60 mg / g or more, and dibutyl phthalate Carbon black having an oil absorption (DBP) of 80 ml / 100 g or more is preferred. By using carbon black, the effect of improving grip performance and fracture resistance is increased, but HAF, ISAF, and SAF, which are excellent in wear resistance, are particularly preferable.

In the reinforcing filler of the component (B), the content ratio of the silica and carbon black is 50 to 90% by mass of silica and 50 to 10% of carbon black from the viewpoint of obtaining a rubber composition having desired performance. % By mass, preferably 50 to 85% by mass of silica and 50 to 15% by mass of carbon black.
Moreover, content of the reinforcing filler of the component (B) is selected in a range of 30 to 110 parts by mass with respect to 100 parts by mass of the rubber component as the component (A). If this content is less than 30 parts by mass, the reinforcing effect is not sufficiently exhibited, and if it exceeds 110 parts by mass, the workability deteriorates.
Furthermore, in order to obtain a rubber composition having desired performance and good workability, the content of the silica is usually 15 to 100 parts by mass with respect to 100 parts by mass of the rubber component of the component (A). The content of carbon black is usually about 10 to 50 parts by weight, preferably 15 to 45 parts by weight, based on 100 parts by weight of the rubber component (A). is there.

In the rubber composition of the present invention, (C) a silane coupling agent can be contained for the purpose of further improving the performance of the component (B-1) silica.
Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, and bis (2-triethoxy). Silylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyl Trimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarb Moyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzoyl tetrasulfide, 3-triethoxysilyl Propyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide , Dimethoxymethylsilylpropylbenzothiazolyl tetrasulfide, and the like. Among these, bis (3-trie Silyl propyl) polysulfide and 3-trimethoxysilylpropyl benzothiazyl tetrasulfide are preferable. One of these silane coupling agents may be used alone, or two or more thereof may be used in combination.

In the rubber composition of the present invention, since a modified polymer having a functional group having high affinity for silica introduced at the molecular end is used as the rubber component, the amount of the silane coupling agent used is usually It can be reduced more than the case. The blending amount of the preferable silane coupling agent varies depending on the type of the silane coupling agent and the like, but is usually selected in the range of 5 to 20% by mass with respect to silica. If the amount is small, the effect as a coupling agent is hardly exhibited, and if it is large, the rubber component may be gelled. From the viewpoint of the effect as a coupling agent and the prevention of gelation, the preferable blending amount of this silane coupling agent is in the range of 5 to 18% by mass.
In the rubber composition of the present invention, (D) an inorganic filler can be contained as desired for the purpose of improving physical properties. Examples of the inorganic filler include compounds represented by the following general formula (VII).

mM ¹ · xSiO _y · zH ₂ O (VII)
(In the formula, M ¹ represents a metal selected from the group consisting of aluminum, magnesium, titanium, calcium, and zirconium, an oxide or hydroxide of these metals, and a hydrate thereof, or carbonic acid of these metals. And m, x, y and z are each an integer of 1 to 5, an integer of 0 to 10, an integer of 2 to 5, and an integer of 0 to 10. In the case where x and z are both 0, the inorganic compound is at least one metal, metal oxide or metal hydroxide selected from aluminum, magnesium, titanium, calcium and zirconium.)
Examples of the inorganic filler represented by the above formula include alumina (Al ₂ O ₃ ) such as γ-alumina and α-alumina, alumina monohydrate (Al ₂ O ₃ .H ₂ O) such as boehmite and diaspore, gibbsite, Aluminum hydroxide such as bayerite [Al (OH) ₃ ], aluminum carbonate [Al ₂ (CO ₃ ) ₂ ], magnesium hydroxide [Mg (OH) ₂ ], magnesium oxide (MgO), magnesium carbonate (MgCO ₃ ) Talc (3MgO · 4SiO ₂ · H ₂ O), attapulgite (5MgO · 8SiO ₂ · 9H ₂ O), titanium white (TiO ₂ ), titanium black (TiO _2n-1 ), calcium oxide (CaO), calcium hydroxide [Ca (OH) ₂ ], aluminum magnesium oxide (MgO.Al ₂ O ₃ ), clay (Al ₂ O ₃ .2SiO ₂ ), kaolin (Al ₂ O ₃ · 2SiO ₂ · 2H ₂ O), pyrophyllite (Al ₂ O ₃ · 4SiO ₂ · H ₂ O), bentonite (Al ₂ O ₃ · 4SiO ₂ · 2H ₂ O), aluminum silicate (Al ₂ SiO ₅ Al ₄ · 3SiO ₄ · 5H ₂ O, etc.), magnesium silicate (Mg ₂ SiO ₄ , MgSiO ₃ etc.), calcium silicate (Ca ₂ · SiO ₄ etc.), aluminum calcium silicate (Al ₂ O ₃ · CaO) 2SiO ₂ ), magnesium calcium silicate (CaMgSiO ₄ ), calcium carbonate (CaCO ₃ ), zirconium oxide (ZrO ₂ ), zirconium hydroxide [ZrO (OH) ₂ .nH ₂ O], zirconium carbonate [Zr (CO ₃ ) ₂ ], crystalline aluminosilicates containing hydrogen, alkali metals or alkaline earth metals that correct the charge, such as various zeolites, can be used. Further, it is preferable that M ¹ in the general formula (I) is at least one selected from aluminum metal, aluminum oxide or hydroxide, hydrates thereof, and aluminum carbonate.
These inorganic fillers represented by the above formula may be used alone or in combination of two or more.
(D) It is preferable to mix | blend 5-30 mass parts of inorganic filler with respect to 100 mass parts of rubber components, and it is more preferable to mix | blend 10-20 mass parts.

In the rubber composition of the present invention, various chemicals usually used in the rubber industry, for example, vulcanizing agents, vulcanization accelerators, process oils, anti-aging agents, as long as the object of the present invention is not impaired. A scorch inhibitor, zinc white, stearic acid and the like can be contained.
As said vulcanizing agent, sulfur etc. are mentioned, The usage-amount is 0.1-10.0 mass parts as a sulfur content with respect to 100 mass parts of rubber components, 0.5-5.0 mass parts is preferable. Is more preferable.
The vulcanization accelerator that can be used in the present invention is not particularly limited, and examples thereof include M (2-mercaptobenzothiazole), DM (dibenzothiazyl disulfide), and CZ (N-cyclohexyl-2-benzothiazyl). Sulfenamide) and other guanidine vulcanization accelerators such as DPG (diphenylguanidine) can be used, and the amount used is 0.1-5. 0 mass part is preferable, More preferably, it is 0.2-3.0 mass part.
Examples of the process oil that can be used in the rubber composition of the present invention include paraffinic, naphthenic, and aromatic oils. Aromatics are used for applications that emphasize tensile strength and wear resistance, and naphthenic or paraffinic systems are used for applications that emphasize hysteresis loss and low-temperature characteristics. The amount used is preferably 0 to 100 parts by mass with respect to 100 parts by mass of the rubber component, and if it is 100 parts by mass or less, the tensile strength and low heat build-up of the vulcanized rubber will be good.

The rubber composition of the present invention can be obtained by kneading using a kneading machine such as a Banbury mixer, roll, internal mixer, etc., vulcanized after molding, and used as a tire tread as a tire application. . In addition, it can also be used for under treads, sidewalls, carcass coating rubber, belt coating rubber, bead filler, chafer, bead coating rubber and the like.
The pneumatic tire of the present invention is produced by a usual method using the above-described rubber composition of the present invention. That is, if necessary, the rubber composition of the present invention containing various chemicals as described above is processed into a tire tread at an unvulcanized stage, and pasted and molded by a normal method on a tire molding machine, A green tire is formed. The green tire is heated and pressed in a vulcanizer to obtain a tire.
The pneumatic tire of the present invention thus obtained is excellent in snow and snow performance and dry grip performance, and has good wet grip performance, low fuel consumption and wear resistance. Suitable for season tires and the like.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
In addition, the vulcanized rubber physical property of the rubber composition obtained in each example was measured according to the following method.
(1) Dry handling stability Using a spectrometer (dynamic viscoelasticity measuring tester) manufactured by Ueshima Seisakusho, measured 30 ° C E 'at a frequency of 52 Hz, initial strain of 10%, measurement temperature of 30 ° C, and dynamic strain of 1%. In addition, E ′ of Comparative Example 1 was expressed as an index with 100 as the index. The larger the index value, the better the dry handling stability.
(2) Stability of wet handling Using a spectrometer (see above), 0 ° C. tan δ was measured at a frequency of 52 Hz, an initial strain of 10%, a measurement temperature of 0 ° C., and a dynamic strain of 1%. displayed. The larger the index value, the better the wet handling stability.
(3) Steering stability on ice and snow Using a spectrometer (supra), -20 ° C E 'was measured at a frequency of 52 Hz, an initial strain of 10%, a measurement temperature of -20 ° C, and a dynamic strain of 1%. The reciprocal of 'is taken as 100 and expressed as an index. The larger the index value, the better the handling stability on ice and snow.
(4) Rolling resistance Using a spectrometer (supra), 60 ° C. tan δ was measured at a frequency of 52 Hz, an initial strain of 10%, a measurement temperature of 60 ° C., and a dynamic strain of 1%, and the reciprocal of tan δ of Comparative Example 1 was taken as an index. displayed. The larger the index value, the lower the rolling resistance and the better the fuel efficiency.
(5) Abrasion resistance In accordance with JIS K 6264: 1993 Lambourne abrasion test, I (wear resistance index (%)) was measured, and this numerical value was displayed as an index with the data of Comparative Example 1 being 100. The larger the index value, the better the wear resistance.

Production Example 1 Production of Modified Polybutadiene A A 5-liter autoclave purged with nitrogen was charged with 2.4 kg of cyclohexane and 300 g of 1,3-butadiene under nitrogen. To these, as a catalyst component, a solution of neodymium versatate (0.09 mmol) in cyclohexane, methylaluminoxane (MAO: PMAO manufactured by Tosoh Akzo) (1.8 mmol) in toluene, diisobutylaluminum hydride (DIBAH: manufactured by Kanto Chemical) ) (5.0 mmol) and a solution of diethylaluminum chloride (0.18 mmol) in toluene and 1,3-butadiene (4.5 mmol) were aged at 50 ° C. for 30 minutes and charged with a catalyst at 80 ° C. for 60 minutes. Polymerization was carried out for minutes. The reaction conversion of 1,3-butadiene was almost 100%. 200 g of this polymer solution was taken out, a methanol solution containing 1.5 g of 2,4-tert-butyl-p-cresol was added, the polymerization was stopped, the solvent was removed by steam stripping, and drying was performed with a roll at 110 ° C. Thus, a pre-modified polymer was obtained. The Mooney viscosity ML _{1 + 4} (100 ° C., conforming to JIS K 6300-1: 2001) of this pre-modified polymer is 21, gel permeation chromatography [GPC: Tosoh HLC-8020, column: Tosoh GMH-XL The molecular weight distribution (Mw / Mn) in terms of polystyrene based on monodisperse polystyrene by (differential refractive index (RI)] is 2.2, and 1 by Fourier transform infrared spectroscopy (FT-IR). The 4-cis bond content was 96.8% and the 1,2-vinyl bond content was 1.2%.
Next, the remaining polymer solution was kept at a temperature of 60 ° C., and a toluene solution of 3-glycidoxypropyltrimethoxysilane (GPMOS) (4.5 mmol) was added and reacted for 30 minutes. Subsequently, a toluene solution of tetraisopropyl titanate (IPOTi) (13.5 mmol) was added and mixed for 30 minutes. Thereafter, a methanol solution containing 1.5 g of 2,4-tert-butyl-p-cresol was added to obtain 2.5 kg of a modified polymer solution.
Further, the modified polymer solution was added to 20 liters of an aqueous solution adjusted to pH 10 with sodium hydroxide, subjected to a condensation reaction with solvent removal at 110 ° C. for 2 hours, and dried with a roll at 110 ° C. to obtain a modified polymer. Obtained. The modified polymer had a Mooney viscosity ML _{1 + 4} (125 ° C.) of 48 and a molecular weight distribution (Mw / Mn) of 2.6.

Production Example 2 Production of Modified Styrene-Butadiene Copolymer 300 g cyclohexane, 40 g 1,3-butadiene, 10 g styrene, 0.16 mmol ditetrahydrofurylpropane were placed in a dry, nitrogen-substituted 800 ml pressure-resistant glass container. And 0.55 mmol of n-butyllithium (BuLi) was added thereto, followed by polymerization at 50 ° C. for 2 hours. From the start to the end of the polymerization, the polymerization system was uniformly transparent with no precipitation. The polymerization conversion was almost 100%. A part of the polymerization solution was sampled, isopropyl alcohol was added, the solid was dried, and a rubber-like copolymer before modification was obtained. The pre-modified copolymer has a polystyrene-reduced weight average molecular weight (Mw) of 190,000, a 1,2-vinyl bond content of 54% by mass by Fourier transform infrared spectroscopy (FT-IR), and a styrene unit. The content (according to the integral ratio of the ¹ H-NMR spectrum) was 20.1.
To this polymerization system was further added 0.55 mmol of N- (1,3-dimethylbutylidene) -3- (triethoxysilyl) -1-propanamine as an endless modifier, followed by a modification reaction for another 30 minutes. . Thereafter, the reaction was stopped by adding 0.5 ml of a 5% by mass solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol to the polymerization system, the solid was dried, A polymer was obtained. The weight average molecular weight (Mw) of this modified copolymer was 268,000.

Examples 1-5 and Comparative Examples 1-10
A rubber composition having the composition shown in Table 1 was prepared.
Each rubber composition was vulcanized at 145 ° C. for 33 minutes, and the physical properties of the vulcanized rubber were measured. The results are shown in Table 1.

［注］
１）スチレン−ブタジエン共重合体ゴム：ＪＳＲ（株）製「ＳＢＲ１７１２」、オイル含量２７．３質量％油展ＳＢＲ
２）スチレン−ブタジエン共重合体ゴム：ＪＳＲ（株）製「ＳＢＲ１５００」
３）製造例２の変性スチレン−ブタジエン共重合体
４）ポリブタジエンゴム：ＪＳＲ（株）製「ＢＲ０１」
５）製造例１の変性ポリブタジエンＡ
６）三共油化工業株式会社製「Ａ／ＯＭＩＸ」
７）新日本石油株式会社製「スーパーオイルＹ２２」
８）ＩＳＡＦ（Ｎ２２０）、東海カーボン（株）製「シースト６」
９）東ソー・シリカ（株）製「ＡＱ」
１０）デグサ社製「Ｓｉ６９」
１１）Ｎ−（１，３−ジメチルブチル）−Ｎ’−フェニル−ｐ−フェニレンジアミン：大内新興化学工業社製「ノクラック６Ｃ」
１２）ジフェニルグアニジン：大内新興化学工業社製「ノクセラーＤ」
１３）Ｎ−シクロヘキシル−２−ベンゾチアジルスルフェンアミド：大内新興化学工業社製「ノクセラーＣＺ」
１４）ジベンゾチアジルジスルフィド：大内新興化学工業社製「ノクセラーＤＭ」

[note]
1) Styrene-butadiene copolymer rubber: “SBR1712” manufactured by JSR Corporation, oil content 27.3 mass% oil-extended SBR
2) Styrene-butadiene copolymer rubber: “SBR 1500” manufactured by JSR Corporation
3) Modified styrene-butadiene copolymer of Production Example 2 4) Polybutadiene rubber: “BR01” manufactured by JSR Corporation
5) Modified polybutadiene A of Production Example 1
6) “A / OMIX” manufactured by Sankyo Oil Chemical Co., Ltd.
7) “Super Oil Y22” manufactured by Nippon Oil Corporation
8) "Seast 6" made by ISAF (N220), Tokai Carbon Co., Ltd.
9) “AQ” manufactured by Tosoh Silica Corporation
10) “Si69” manufactured by Degussa
11) N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine: “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.
12) Diphenylguanidine: "Noxeller D" manufactured by Ouchi Shinsei Chemical Co., Ltd.
13) N-cyclohexyl-2-benzothiazylsulfenamide: “Noxeller CZ” manufactured by Ouchi Shinsei Chemical Co., Ltd.
14) Dibenzothiazyl disulfide: “Noxeller DM” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

As can be seen from Table 1, the compositions of Examples 2 and 3 are better than the composition of Comparative Example 1 in all performance. Further, the composition of Example 1 is equivalent to the composition of Comparative Example 1 in terms of handling stability on ice and snow and rolling resistance, but dry handling stability, wet handling stability and wear resistance are the same as those of Comparative Example 1. It is better than the composition.
The composition of Example 4 is equivalent to the composition of Comparative Example 1 in terms of dry handling stability and wet handling stability, but the handling stability on ice and snow, rolling resistance and wear resistance are Comparative Example 1. It is much better than the other composition.
Further, the composition of Example 5 is equivalent to the composition of Comparative Example 1 in terms of handling stability on ice and snow and rolling resistance, but the dry handling stability and the wet handling stability are compared with those of the composition of Comparative Example 1. The abrasion resistance is also better than that of the composition of Comparative Example 1.

Examples 6 and 7 and Comparative Example 11
The rubber compositions of Examples 2 and 3 and Comparative Example 1 were respectively disposed on the treads of radial tires for passenger cars having a tire size of 185 / 60R14, and the tires of Examples 6 and 7 and Comparative Example 11 were prototyped to stabilize dry handling. Performance, wet handling stability, snow and snow handling stability, low fuel consumption and wear resistance were evaluated. In comparison with the tire of Comparative Example 11, the tires of Examples 6 and 7 were all good in dry handling stability, wet handling stability, driving stability on ice and snow, low fuel consumption, and wear resistance.

  The rubber composition for tire tread of the present invention is excellent in performance on ice and snow and dry grip performance, and has good wet grip performance, fuel efficiency and wear resistance, for example, for snow tires and tires for all seasons, etc. Preferably used.

Claims (14)

  (A) (A-1) Modified conjugated diene polymer obtained by modifying the active terminal of a conjugated diene polymer having a cis-1,4-bond content of 75 mol% or more with at least a hydrocarbyloxysilane compound (B) (B-1) 50 to 90% by mass of silica and (B-2) (B-1) silica component with respect to 100 parts by mass of A5 to 70% by mass, (A-2) natural rubber and / or diene synthetic rubber B-2) A rubber composition for a tire tread, comprising 30 to 110 parts by mass of a reinforcing filler composed of 50 to 10% by mass of carbon black.   The rubber composition for a tire tread according to claim 1, comprising (B-1) 15 to 100 parts by mass of silica and (B-2) 10 to 50 parts by mass of carbon black with respect to 100 parts by mass of component (A).   Furthermore, the rubber composition for tire treads of Claim 1 or 2 which contains (C) silane coupling agent in the ratio of 5-20 mass% with respect to the silica of (B-1) component.   Furthermore, the rubber composition for tire treads in any one of Claims 1-3 containing 5-30 mass parts of (D) inorganic fillers.   The modified conjugated diene polymer A as the component (A-1) is obtained by first modifying the active terminal with the hydrocarbyloxysilane compound after the primary modification with the hydrocarbyloxysilane compound and further with the hydrocarbyloxysilane compound in the presence of the condensation accelerator. The rubber composition for tire treads according to any one of claims 1 to 4.   The modified conjugated diene polymer A as the component (A-1) is obtained by first reacting the active terminal with a hydrocarbyloxysilane compound and then further reacting with a carboxylic acid partial ester of a polyhydric alcohol. The rubber composition for tire treads in any one of -4.   The modified conjugated diene polymer A as the component (A-1) has a hydrocarbyloxysilane compound residue introduced at the terminal after the primary modification of the active terminal with the hydrocarbyloxysilane compound and further in the presence of a condensation accelerator. The rubber composition for a tire tread according to any one of claims 1 to 4, wherein the rubber composition is formed by a condensation reaction with an unreacted hydrocarbyloxysilane compound.   The rubber composition for a tire tread according to claim 5, wherein the modified conjugated diene polymer A as the component (A-1) is further reacted with a carboxylic acid partial ester of a polyhydric alcohol after the secondary modification. object.   The rubber composition for a tire tread according to claim 7, wherein the modified conjugated diene polymer A as the component (A-1) is further reacted with a carboxylic acid partial ester of a polyhydric alcohol after the condensation reaction. The hydrocarbyloxysilane compound is at least one compound selected from the following (a) general formula (I), (b) general formula (II), (c) general formula (III) and partial condensates thereof: The rubber composition for tire treads in any one of 1-9.
(A) General formula (I)

[Wherein A ¹ is (thio) epoxy, (thio) isocyanate, (thio) ketone, (thio) aldehyde, imine, amide, isocyanuric acid trihydrocarbyl ester, (thio) carboxylic acid ester, (thio) carboxylic acid A monovalent group having at least one functional group selected from metal salts, carboxylic acid anhydrides, carboxylic acid halides and carbonic acid dihydrocarbyl esters, R ¹ is a single bond or a divalent inert hydrocarbon group , R ² and R ³ each independently represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and n is an integer of 0 to 2 , and the case where R ² is plural, R ² may be the same or different, if the OR ³ there are a plurality, the plurality of OR ³ may be the same or different, and in the molecule active proton And Bionium salts are not included. ]
(B) General formula (II)

[Wherein, A ² is a monovalent group having at least one functional group selected from cyclic tertiary amine, acyclic tertiary amine, pyridine, sulfide, multisulfide and nitrile, and R ⁴ is a single bond or The divalent inert hydrocarbon group, R ⁵ and R ⁶ each independently represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. , m is an integer of 0 to 2, if R ⁵ there are a plurality, the plurality of R ⁵ may be the same or different, if OR ⁶ there are plural, a plurality of OR ⁶ may be the same or different The molecule does not contain active protons and onium salts. ]
(C) General formula (III)

[Wherein A ³ is alcohol, thiol, primary amine and onium salt thereof, cyclic secondary amine and onium salt thereof, acyclic secondary amine and onium salt thereof, onium salt of cyclic tertiary amine, acyclic tertiary amine Onium salt of amine, group having aryl or arylalkyl Sn bond, monovalent group having at least one functional group selected from sulfonyl, sulfinyl and nitrile, R ⁷ is a single bond or a divalent inert hydrocarbon group , R ⁸ and R ⁹ each independently represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, q is an integer of 0 to 2 , and the case where R ⁸ is plural, R ⁸ may be the same or different, if the OR ⁹ there are a plurality, the plurality of OR ⁹ may be the same or different. ]   The rubber composition for a tire tread according to any one of claims 6, 8 and 9, wherein the carboxylic acid partial ester of the polyhydric alcohol is a monoester, diester or triester of sorbitan fatty acid. The condensation accelerator is composed of at least one selected from the compounds represented by the following formula (d), general formula (IV), (e) general formula (V), and (f) general formula (VI), and water. The rubber composition for a tire tread according to claim 5 or 7, wherein the rubber composition is a tire tread.
(D) general formula carboxylates of tin having 3 to 20 carbon atoms an oxidation number of 2 represented by ^{(IV) Sn (OCOR 10)} 2 ··· (IV)
[Wherein, R ¹⁰ is an organic group having 2 to 19 carbon atoms, and when there are a plurality of them, they may be the same or different. ]
(E) Tin compound of oxidation number 4 represented by general formula (V) R ¹¹ _r SnA ⁴ _t B ¹ _(4-tr) (V)
[Wherein, r is an integer of 1 to 3, t is an integer of 1 or 2, and t + r is an integer of 3 or 4. R ¹¹ is an aliphatic hydrocarbon group having 1 to 30 carbon atoms, and B ¹ is a hydroxyl group or a halogen. A ⁴ is (a) an aliphatic carboxylic acid residue having 2 to 30 carbon atoms, (b) a 1,3-dicarbonyl-containing group having 5 to 30 carbon atoms, and (c) a hydrocarbyloxy group having 3 to 30 carbon atoms. And (d) a group selected from a siloxy group having a total of three substitutions (which may be the same or different) with a hydrocarbyl group having 1 to 20 carbon atoms and / or a hydrocarbyloxy group having 1 to 20 carbon atoms, and R ¹¹ may if there are multiple the same or different, may be the same or different if A ⁴ have multiple. ]
(F) Titanium compound of oxidation number 4 represented by general formula (VI) A ⁵ _x TiB ² _(4-x) (VI)
[Wherein x is an integer of 2 or 4. A ⁵ is (i) a hydrocarbyloxy group having 3 to 30 carbon atoms, (b) a siloxy group that is tri-substituted in total with an alkyl group having 1 to 30 carbon atoms and / or a hydrocarbyloxy group having 1 to 20 carbon atoms, When there are a plurality of A ^{5 s,} they may be the same or different. B ² is a 1,3-dicarbonyl-containing group having 5 to 30 carbon atoms, and when there are a plurality of B ² , they may be the same or different. ]   The rubber composition for a tire tread according to any one of claims 1 to 12, wherein the modified conjugated diene polymer A as the component (A-1) is a modified polybutadiene.   A pneumatic tire using the rubber composition according to any one of claims 1 to 13 as a tread rubber.