JP7247474B2 - Tire rubber composition and pneumatic tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber composition for tires and a pneumatic tire.

In recent years, due to the growing interest in environmental issues, not only are automobiles required to have low fuel consumption, but rubber compositions used in automobile tires are required to have good abrasion resistance. there is

Tires are required to have grip performance such as wet grip performance in order to ensure safety and the like. In order to meet this demand, styrene-butadiene rubber is widely used as a rubber component, but use of styrene-butadiene rubber tends to reduce abrasion resistance. As described above, grip performance and wear resistance are in a conflicting relationship, and it is difficult to improve them comprehensively.

An object of the present invention is to solve the above problems and to provide a tire rubber composition that can comprehensively improve wear resistance and wet grip performance, and a pneumatic tire produced using the rubber composition. .

The present invention comprises a rubber component having a styrene-butadiene rubber content of 50 to 80 mass% and a butadiene rubber content of 20 to 50 mass%, and a rubber component having a content of 80 to 120 mass parts per 100 mass parts of the rubber component. The present invention relates to a rubber composition for tires containing silica, a styrene resin and a C5 resin and satisfying the following formula (A).
(A) α1/β1≦α2/β2
α1: Total amount of styrene in the rubber component [% by mass]
α2: total amount of butadiene in the rubber component [% by mass]
β1: Content of styrene resin per 100 parts by mass of rubber component [parts by mass]
β2: Content of C5 resin per 100 parts by mass of rubber component [parts by mass]

In formula (A), α1/β1 is preferably 2 or less.

In the formula (A), α2/β2 is preferably 3 or more.

The rubber composition preferably satisfies the following formula (B).
(B) β1≧β2
β1: Content of styrene resin per 100 parts by mass of rubber component [parts by mass]
β2: Content of C5 resin per 100 parts by mass of rubber component [parts by mass]

The rubber composition preferably contains carbon black having a cetyltrimethylammonium bromide specific surface area of 160 m ² /g or more.

The nitrogen adsorption specific surface area of the silica is preferably 220 m ² /g or more.

The rubber composition preferably contains a mercapto-based silane coupling agent.

The present invention also relates to a pneumatic tire produced using the rubber composition.

According to the present invention, the rubber composition for a tire containing predetermined amounts of styrene-butadiene rubber, butadiene rubber, and silica, as well as a styrene-based resin and a C5-based resin, and satisfying the formula (A) has excellent wear resistance and wet Overall grip performance can be improved.

The rubber composition for tires of the present invention contains predetermined amounts of styrene-butadiene rubber, butadiene rubber and silica, as well as a styrene-based resin and a C5-based resin, and satisfies formula (A).

The above-described effects of the rubber composition are obtained, and it is presumed that these effects are brought about by the following effects.
When SBR is used as the main component of the rubber component, the grip performance tends to be improved, but the abrasion resistance tends to decrease. On the other hand, in the above rubber composition, BR is used as a rubber component other than SBR, the ratio thereof is adjusted, the amount of silica is adjusted to a specific range, and the total amount of styrene and By adjusting the total butadiene amount, the styrene resin amount, and the C5 resin amount in the rubber component to a specific ratio, silica, styrene resin, and C5 resin are well dispersed in the rubber composition. do. It is believed that this results in an overall improvement in wear resistance and wet grip performance.

The rubber composition contains SBR as a rubber component.
The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. can be used. SBR may be either unmodified SBR or modified SBR.

The modified SBR may be an SBR having a functional group that interacts with a filler such as silica. SBR (end-modified SBR having the above functional group at the end), main chain-modified SBR having the above-mentioned functional group in the main chain, main chain end-modified SBR having the above-mentioned functional group in the main chain and end (for example, the main chain Main chain end-modified SBR having the above functional group and at least one end modified with the above modifier), or modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule, hydroxyl group and terminal-modified SBR into which an epoxy group is introduced.

Examples of the functional groups include amino group, amido group, silyl group, alkoxysilyl group, isocyanate group, imino group, imidazole group, urea group, ether group, carbonyl group, oxycarbonyl group, mercapto group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazo group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group, hydroxyl group, oxy group, epoxy group and the like. . In addition, these functional groups may have a substituent. Among them, an amino group (preferably an amino group in which the hydrogen atom of the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), an alkoxysilyl group ( An alkoxysilyl group having 1 to 6 carbon atoms is preferred.

（式中、Ｒ^１、Ｒ^２及びＲ^３は、同一又は異なって、アルキル基、アルコキシ基、シリルオキシ基、アセタール基、カルボキシル基（－ＣＯＯＨ）、メルカプト基（－ＳＨ）又はこれらの誘導体を表す。Ｒ^４及びＲ^５は、同一又は異なって、水素原子又はアルキル基を表す。Ｒ^４及びＲ^５は結合して窒素原子と共に環構造を形成してもよい。ｎは整数を表す。） As the modified SBR, an SBR modified with a compound (modifying agent) represented by the following formula is particularly suitable.

(wherein R ¹ , R ² and R ³ are the same or different and represent an alkyl group, alkoxy group, silyloxy group, acetal group, carboxyl group (--COOH), mercapto group (--SH) or derivatives thereof (R ⁴ and R ⁵ are the same or different and represent a hydrogen atom or an alkyl group. R ⁴ and R ⁵ may combine to form a ring structure together with a nitrogen atom. n represents an integer.)

As the modified SBR modified with the compound (modifier) represented by the above formula, among others, the polymerization terminal (active terminal) of solution-polymerized styrene-butadiene rubber (S-SBR) is modified with the compound represented by the above formula. Modified SBR (such as the modified SBR described in JP-A-2010-111753) is preferably used.

R ¹ , R ² and R ³ are preferably alkoxy groups (preferably C 1-8 alkoxy groups, more preferably C 1-4 alkoxy groups). An alkyl group (preferably an alkyl group having 1 to 3 carbon atoms) is suitable for R ⁴ and R ⁵ . n is preferably 1-5, more preferably 2-4, even more preferably 3. Also, when R ⁴ and R ⁵ combine to form a ring structure with a nitrogen atom, it is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (cyclohexyloxy group, etc.) and an aryloxy group (phenoxy group, benzyloxy group, etc.).

Specific examples of the modifier include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, methoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane and the like. Among them, 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropyltriethoxysilane, and 3-diethylaminopropyltrimethoxysilane are preferred. These may be used alone or in combination of two or more.

As modified SBR, modified SBR modified with the following compounds (modifying agents) can also be suitably used. Modifiers include, for example, polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having a phenol group of; 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, polyepoxy compounds such as polyepoxidized liquid polybutadiene; 4,4'-diglycidyl-diphenyl epoxy group-containing tertiary amines such as methylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline, diglycidylorthotoluidine, tetraglycidylmetaxylenediamine , tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, tetraglycidyl-1,3-bisaminomethylcyclohexane and other diglycidylamino compounds;

amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamic acid chloride and N,N-diethylcarbamic acid chloride;1 , 3-bis-(glycidyloxypropyl)-tetramethyldisiloxane, (3-glycidyloxypropyl)-pentamethyldisiloxane and other epoxy group-containing silane compounds;

(trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tripropoxysilyl)propyl]sulfide, (trimethylsilyl)[3 -(tributoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(methyldimethoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(methyldiethoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(methyldi sulfide group-containing silane compounds such as propoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide;

N-substituted aziridine compounds such as ethyleneimine and propyleneimine; methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxy Alkoxysilanes such as silane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethyltriethoxysilane; 4-N,N-dimethylaminobenzophenone, 4-N,N- Di-t-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino ) benzophenone, N,N,N',N'-bis-(tetraethylamino)benzophenone and other (thio)benzophenone compounds having amino groups and/or substituted amino groups; 4-N,N-dimethylaminobenzaldehyde, 4- N,N-diphenylaminobenzaldehyde, 4-N,N-divinylaminobenzaldehyde and other benzaldehyde compounds having amino groups and/or substituted amino groups; N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N- N-substituted pyrrolidones such as phenyl-2-pyrrolidone, Nt-butyl-2-pyrrolidone, N-methyl-5-methyl-2-pyrrolidone, N-methyl-2-piperidone, N-vinyl-2-piperidone, N - N-substituted piperidones such as phenyl-2-piperidone; - N-substituted lactams such as methyl-β-propiolactam and N-phenyl-β-propiolactam;

N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), tris-(2,3-epoxypropyl)-1,3,5 -triazine-2,4,6-triones, N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3 -diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophenone, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenyl amino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone and the like. Among them, modified SBR modified with alkoxysilane is preferable.
Modification with the above compound (modifying agent) can be carried out by a known method.

The styrene content of SBR is preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, and is preferably 60% by mass or less, more preferably 40% by mass or less. Within the above range, the effects of the present invention tend to be obtained more favorably.
The styrene content can be measured by the method described in Examples below.

The vinyl content of SBR is preferably 10% by mass or more, more preferably 16% by mass or more, and is preferably 40% by mass or less, more preferably 25% by mass or less. Within the above range, the effects of the present invention tend to be obtained more favorably.
The vinyl content (1,2-bonded butadiene unit content) can be measured by the method described in Examples below.

As SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Co., Ltd., Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., etc. can be used.

The content of SBR in 100% by mass of the rubber component may be 50 to 80% by mass, preferably 60% by mass or more, more preferably 65% by mass or more, and preferably 70% by mass or less. be. Within the above range, the effects of the present invention tend to be obtained more favorably.

The rubber composition contains BR as a rubber component.
The BR is not particularly limited, and BR with a high cis content, BR with a low cis content, BR containing syndiotactic polybutadiene crystals, and the like can be used. BR may be either non-modified BR or modified BR, and modified BR includes modified BR into which the aforementioned functional groups have been introduced. These may be used alone or in combination of two or more. The cis content of BR is preferably 90% by mass or more (preferably 95% by mass or more).
The cis content can be measured by infrared absorption spectrometry.

As BR, for example, products of Ube Industries, Ltd., JSR Corporation, Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., etc. can be used.

The content of BR in 100% by mass of the rubber component may be 20 to 50% by mass, preferably 30% by mass or more, more preferably 35% by mass or more, and preferably 40% by mass or less. be. Within the above range, the effects of the present invention tend to be obtained more favorably.

Rubber components that can be used in addition to SBR and BR include diene rubbers such as isoprene rubber, acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). rubber. These diene rubbers may be used alone or in combination of two or more.

The rubber composition contains silica.
Examples of silica include dry silica (anhydrous silicic acid) and wet silica (hydrated silicic acid), but wet silica is preferred because it contains many silanol groups. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 110 m ² /g or more, more preferably 150 m ² /g or more, still more preferably 200 m ² /g or more, particularly preferably 220 m ² /g or more, Also, it is preferably 300 m ² /g or less, more preferably 260 m ² /g or less. Within the above range, the effects of the present invention tend to be obtained more favorably.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

As silica, for example, products of Degussa, Rhodia, Tosoh Silica, Solvay Japan, Tokuyama, etc. can be used.

The content of silica with respect to 100 parts by mass of the rubber component may be 80 to 120 parts by mass, preferably 90 parts by mass or more, and preferably 100 parts by mass or less. Within the above range, the effects of the present invention tend to be obtained more favorably.

The rubber composition preferably contains a silane coupling agent together with silica. As a result, the effects of the present invention tend to be obtained more favorably.
The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, Bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis ( 3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) ) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3- Sulfides such as triethoxysilylpropyl methacrylate monosulfide, mercaptos such as 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane, vinyls such as vinyltriethoxysilane and vinyltrimethoxysilane, and 3-aminopropyl Amino compounds such as triethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, 3-nitropropyltrimethoxysilane, 3- Examples include nitro-based solvents such as nitropropyltriethoxysilane, and chloro-based solvents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These may be used alone or in combination of two or more. Among these, sulfide-based and mercapto-based agents are preferred, and mercapto-based agents are more preferred, because the effects of the present invention can be obtained more favorably.

As the mercapto-based silane coupling agent, in addition to a compound having a mercapto group, a compound having a structure in which the mercapto group is protected by a protecting group (for example, a compound represented by the following formula (S1)) can also be used. .

（式中、Ｒ^１００１は－Ｃｌ、－Ｂｒ、－ＯＲ^１００６、－Ｏ（Ｏ＝）ＣＲ^１００６、－ＯＮ＝ＣＲ^１００６Ｒ^１００７、－ＯＮ＝ＣＲ^１００６Ｒ^１００７、－ＮＲ^１００６Ｒ^１００７及び－（ＯＳｉＲ^１００６Ｒ^１００７）_ｈ（ＯＳｉＲ^１００６Ｒ^１００７Ｒ^１００８）から選択される一価の基（Ｒ^１００６、Ｒ^１００７及びＲ^１００８は同一でも異なっていても良く、各々水素原子又は炭素数１～１８の一価の炭化水素基であり、ｈは平均値が１～４である。）であり、Ｒ^１００２はＲ^１００１、水素原子又は炭素数１～１８の一価の炭化水素基、Ｒ^１００３は－［Ｏ（Ｒ^１００９Ｏ）_ｊ］－基（Ｒ^１００９は炭素数１～１８のアルキレン基、ｊは１～４の整数である。）、Ｒ^１００４は炭素数１～１８の二価の炭化水素基、Ｒ^１００５は炭素数１～１８の一価の炭化水素基を示し、ｘ、ｙ及びｚは、ｘ＋ｙ＋２ｚ＝３、０≦ｘ≦３、０≦ｙ≦２、０≦ｚ≦１の関係を満たす数である。）

（式中、ｖは０以上の整数、ｗは１以上の整数である。Ｒ^１１は水素、ハロゲン、分岐若しくは非分岐の炭素数１～３０のアルキル基、分岐若しくは非分岐の炭素数２～３０のアルケニル基、分岐若しくは非分岐の炭素数２～３０のアルキニル基、又は該アルキル基の末端の水素が水酸基若しくはカルボキシル基で置換されたものを示す。Ｒ^１２は分岐若しくは非分岐の炭素数１～３０のアルキレン基、分岐若しくは非分岐の炭素数２～３０のアルケニレン基、又は分岐若しくは非分岐の炭素数２～３０のアルキニレン基を示す。Ｒ^１１とＲ^１２とで環構造を形成してもよい。） Particularly suitable mercapto-based silane coupling agents include a silane coupling agent represented by the following formula (S1), or a combination of a bonding unit A represented by the following formula (I) and a bonding unit B represented by the following formula (II). silane coupling agents containing.

(wherein R ¹⁰⁰¹ is -Cl, -Br, -OR ¹⁰⁰⁶ , -O(O=)CR ¹⁰⁰⁶ , -ON=CR ¹⁰⁰⁶ R ¹⁰⁰⁷ , -ON=CR ¹⁰⁰⁶ R ¹⁰⁰⁷ , -NR ¹⁰⁰⁶ R ¹⁰⁰⁷ and -( OSiR ¹⁰⁰⁶ R ¹⁰⁰⁷ ) _h Monovalent groups (R ¹⁰⁰⁶ , R ¹⁰⁰⁷ and R ¹⁰⁰⁸ ) selected from h (OSiR ¹⁰⁰⁶ R ¹⁰⁰⁷ R ¹⁰⁰⁸ ) may be the same or different and each represents a hydrogen atom or a is a monovalent hydrocarbon group, h has an average value of 1 to 4), R ¹⁰⁰² is R ¹⁰⁰¹ , a hydrogen atom or a monovalent hydrocarbon group with 1 to 18 carbon atoms, R ¹⁰⁰³ is - [O(R ¹⁰⁰⁹ O) _j ]—group (R ¹⁰⁰⁹ is an alkylene group having 1 to 18 carbon atoms and j is an integer of 1 to 4), R ¹⁰⁰⁴ is a divalent hydrocarbon having 1 to 18 carbon atoms group, R ¹⁰⁰⁵ represents a monovalent hydrocarbon group having 1 to 18 carbon atoms, x, y and z are in the relationship of x + y + 2z = 3, 0 ≤ x ≤ 3, 0 ≤ y ≤ 2, 0 ≤ z ≤ 1 is a number that satisfies

(Wherein, v is an integer of 0 or more, w is an integer of 1 or more, R ¹¹ is hydrogen, halogen, a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched C 2 to A 30 alkenyl group, a branched or unbranched alkynyl group having 2 to 30 carbon atoms, or an alkyl group in which the terminal hydrogen is substituted with a hydroxyl group or a carboxyl group, where R ¹² is a branched or unbranched carbon number represents an alkylene group having 1 to 30 carbon atoms, a branched or unbranched alkenylene group having 2 to 30 carbon atoms, or a branched or unbranched alkynylene group having 2 to 30 carbon atoms, wherein R ¹¹ and R ¹² form a ring structure; may be used.)

In formula (S1), R ¹⁰⁰⁵ , R ¹⁰⁰⁶ , R ¹⁰⁰⁷ and R ¹⁰⁰⁸ are each independently selected from linear, cyclic or branched alkyl, alkenyl, aryl and aralkyl groups having 1 to 18 carbon atoms. It is preferably a group selected from the group consisting of When R ¹⁰⁰² is a monovalent hydrocarbon group having 1 to 18 carbon atoms, it is selected from the group consisting of linear, cyclic or branched alkyl groups, alkenyl groups, aryl groups and aralkyl groups. It is preferably a group. R ¹⁰⁰⁹ is preferably a linear, cyclic or branched alkylene group, particularly preferably a linear one. R ¹⁰⁰⁴ is, for example, an alkylene group having 1 to 18 carbon atoms, an alkenylene group having 2 to 18 carbon atoms, a cycloalkylene group having 5 to 18 carbon atoms, a cycloalkylalkylene group having 6 to 18 carbon atoms, or an arylene group having 6 to 18 carbon atoms. and an aralkylene group having 7 to 18 carbon atoms. Alkylene groups and alkenylene groups may be linear or branched, and cycloalkylene groups, cycloalkylalkylene groups, arylene groups and aralkylene groups have functional groups such as lower alkyl groups on their rings. You may have R ¹⁰⁰⁴ is preferably an alkylene group having 1 to 6 carbon atoms, more preferably a linear alkylene group such as methylene, ethylene, trimethylene, tetramethylene, pentamethylene and hexamethylene.

Specific examples of R ¹⁰⁰² , R ¹⁰⁰⁵ , R ¹⁰⁰⁶ , R ¹⁰⁰⁷ and R ¹⁰⁰⁸ in formula (S1) include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group and 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, cyclopentenyl group, cyclo hexenyl group, phenyl group, tolyl group, xylyl group, naphthyl group, benzyl group, phenethyl group, naphthylmethyl group and the like.
Examples of R ¹⁰⁰⁹ in the formula (S1) include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, a hexylene group and the like as linear alkylene groups, and branched alkylene groups such as isopropylene group, isobutylene group, 2-methylpropylene group and the like.

Specific examples of the silane coupling agent represented by formula (S1) include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, 3- Lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoy Luthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthio Ethyltrimethoxysilane, 2-decanoylthioethyltrimethoxysilane, 2-lauroylthioethyltrimethoxysilane and the like can be mentioned. These may be used alone or in combination of two or more. Among them, 3-octanoylthiopropyltriethoxysilane is particularly preferred.

In the silane coupling agent containing the linking unit A represented by the formula (I) and the linking unit B represented by the formula (II), the content of the linking unit A is preferably 30 mol% or more, more preferably 50 mol. % or more, preferably 99 mol % or less, more preferably 90 mol % or less. The content of the binding unit B is preferably 1 mol% or more, more preferably 5 mol% or more, still more preferably 10 mol% or more, preferably 70 mol% or less, more preferably 65 mol% or less, More preferably, it is 55 mol % or less. Also, the total content of the binding units A and B is preferably 95 mol % or more, more preferably 98 mol % or more, and particularly preferably 100 mol %.
In addition, the content of the bonding units A and B is the amount including the case where the bonding units A and B are positioned at the terminal of the silane coupling agent. When the bonding units A and B are located at the ends of the silane coupling agent, the form is not particularly limited as long as they form units corresponding to the formulas (I) and (II) representing the bonding units A and B. .

Halogen for R ¹¹ in formulas (I) and (II) includes chlorine, bromine, and fluorine. Examples of the branched or unbranched alkyl group having 1 to 30 carbon atoms include a methyl group and an ethyl group. Examples of the branched or unbranched alkenyl group having 2 to 30 carbon atoms include a vinyl group and a 1-propenyl group. Examples of the branched or unbranched alkynyl group having 2 to 30 carbon atoms include ethynyl group and propynyl group.

Examples of the branched or unbranched alkylene group having 1 to 30 carbon atoms for R ¹² in formulas (I) and (II) include ethylene group and propylene group. Examples of the branched or unbranched alkenylene group having 2 to 30 carbon atoms include vinylene group and 1-propenylene group. Examples of the branched or unbranched alkynylene group having 2 to 30 carbon atoms include an ethynylene group and a propynylene group.

In a silane coupling agent containing a bonding unit A represented by formula (I) and a bonding unit B represented by formula (II), the number of repetitions (v) of bonding unit A and the repetition number (w) of bonding unit B The total number of repetitions (v+w) is preferably in the range of 3-300.

When a silane coupling agent is contained, the content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and preferably 20 parts by mass with respect to 100 parts by mass of silica. Below, more preferably 15 mass parts or less. Within the above range, the effects of the present invention tend to be obtained more favorably.

The rubber composition contains a styrene resin.
Styrene-based resins are polymers containing styrene-based monomers as constituent monomers, and include polymers obtained by polymerizing styrene-based monomers as main components (50% by mass or more). Specifically, styrene monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-Chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.), homopolymers obtained by polymerizing each alone, copolymers obtained by copolymerizing two or more styrene monomers, and styrene monomers and copolymers with other monomers copolymerizable therewith.

Other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, acrylics, unsaturated carboxylic acids such as methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, terpenes, chloroprene, Conjugated dienes such as butadiene isoprene; olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride and acid anhydrides thereof; These may be used individually by 1 type, and may use 2 or more types together.

For the reason that the effects of the present invention tend to be obtained more favorably, styrene-based resins are α-methylstyrene-based resins (α-methylstyrene homopolymers, copolymers of α-methylstyrene and styrene, etc.). is preferred, and a copolymer of α-methylstyrene and styrene is more preferred.

The softening point of the styrene-based resin is preferably 30° C. or higher, more preferably 60° C. or higher, and preferably 120° C. or lower, more preferably 85° C. or lower. Within the above range, the effects of the present invention tend to be obtained more favorably.
In the present invention, the softening point of the resin is the temperature at which the softening point specified in JIS K 6220-1:2001 is measured with a ring and ball type softening point measuring device, and the ball descends.

The number average molecular weight (Mn) of the styrene resin is preferably 500 or more, more preferably 700 or more, and preferably 3000 or less, more preferably 2000 or less. Within the above range, the effects of the present invention tend to be obtained more favorably.
Note that Mn and Mw are values measured by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation). can be obtained by standard polystyrene conversion.

The content of the styrene-based resin with respect to 100 parts by mass of the rubber component may be adjusted within a range that satisfies the formula (A). It is not more than 30 parts by mass, more preferably not more than 30 parts by mass. Within the above range, the effects of the present invention tend to be obtained more favorably.

The rubber composition contains a C5 resin.
The C5-based resin is a polymer containing a C5 fraction as a constituent monomer, and examples thereof include polymers obtained by polymerizing a C5 fraction as a main component (50% by mass or more). Specifically, C5 fractions (olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3 - Diolefinic hydrocarbons such as pentadiene, etc.), copolymers obtained by copolymerizing two or more C5 fractions, C5 fractions, and other copolymers that can be copolymerized therewith. Copolymers with monomers are also included.

Examples of other monomers include C9 fractions such as vinyltoluene, indene, and methylindene. These may be used individually by 1 type, and may use 2 or more types together.

Since the effect of the present invention tends to be obtained more favorably, the C5 resin is preferably a copolymer of the C5 fraction and other monomers, and a copolymer of the C5 fraction and the C9 fraction. Coalescence (C5/C9 resin) is more preferred.

The softening point of the C5 resin is preferably 30° C. or higher, more preferably 60° C. or higher, and preferably 120° C. or lower, more preferably 94° C. or lower. Within the above range, the effects of the present invention tend to be obtained more favorably.
In the present invention, the softening point of the resin is the temperature at which the softening point specified in JIS K 6220-1:2001 is measured with a ring and ball type softening point measuring device, and the ball descends.

The weight average molecular weight (Mw) of the C5 resin is preferably 1000 or more, more preferably 2000 or more, and preferably 5000 or less, more preferably 3900 or less. Within the above range, the effects of the present invention tend to be obtained more favorably.

The number average molecular weight (Mn) of the C5 resin is preferably 500 or more, more preferably 1000 or more, and preferably 2000 or less, more preferably 1200 or less. Within the above range, the effects of the present invention tend to be obtained more favorably.

The content of the C5 resin may be adjusted within a range that satisfies the formula (A) with respect to 100 parts by mass of the rubber component, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and It is preferably 30 parts by mass or less, more preferably 20 parts by mass or less. Within the above range, the effects of the present invention tend to be obtained more favorably.

The rubber composition may contain other resins in addition to the styrene-based resin and the C5-based resin. Other resins are not particularly limited as long as they are commonly used in the tire industry, and include rosin-based resins, coumarone-indene resins, terpene-based resins, pt-butylphenolacetylene resins, acrylic resins, and the like. . These may be used alone or in combination of two or more.

Commercial products of styrene resins, C5 resins, and other resins include, for example, Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Products of Chemical Company, Nikko Kagaku Co., Ltd., Nippon Shokubai Co., Ltd., JX Energy Co., Ltd., Arakawa Chemical Co., Ltd., Taoka Chemical Co., Ltd., etc. can be used.

In the rubber composition, the total styrene content in the rubber component, the total butadiene content in the rubber component, the content of the styrene resin, and the content of the C5 resin satisfy the following formula (A).
(A) α1/β1≦α2/β2
α1: Total amount of styrene in the rubber component [% by mass]
α2: total amount of butadiene in the rubber component [% by mass]
β1: Content of styrene resin per 100 parts by mass of rubber component [parts by mass]
β2: Content of C5 resin per 100 parts by mass of rubber component [parts by mass]

In formula (A), α1/β1 is preferably 0.5 or more, more preferably 0.7 or more, and is preferably 2 or less, more preferably 1.2 or less, and still more preferably 1 or less. . Within the above range, the effects of the present invention tend to be obtained more favorably.

In formula (A), α2/β2 is preferably 3 or more, more preferably 3.5 or more, and is preferably 20 or less, more preferably 15 or less, and still more preferably 10 or less. Within the above range, the effects of the present invention tend to be obtained more favorably.

The total amount of styrene in the rubber component (the total content of styrene parts contained in the total amount of the rubber component) may be adjusted within a range that satisfies the formula (A), but is preferably 15% by mass or more, more preferably 25% by mass. % or more, preferably 60% by mass or less, more preferably 40% by mass or less. Within the above range, the effects of the present invention tend to be obtained more favorably.
Here, the total styrene content in the rubber component is Σ(content of each styrene-containing rubber×styrene content of each styrene-containing rubber/100). For example, when the rubber component consists of SBR (A) (40% by mass of styrene) 90% by mass, 5% by mass of SBR (B) (25% by mass of styrene), and 5% by mass of BR, the total amount of styrene in the rubber component is 37.25% by mass (=90×40/100+5×25/100).

The total amount of butadiene in the rubber component (the total content of butadiene parts contained in the total amount of the rubber component) may be adjusted within a range satisfying the formula (A), preferably 40% by mass or more, more preferably 60% by mass. % or more, preferably 85 mass % or less, more preferably 75 mass % or less. Within the above range, the effects of the present invention tend to be obtained more favorably.
Here, the total butadiene content in the rubber component is Σ(content of each butadiene-containing rubber×butadiene content of each butadiene-containing rubber/100). For example, when the rubber component consists of SBR (A) (40% by mass of styrene) 90% by mass, 5% by mass of SBR (B) (25% by mass of styrene), and 5% by mass of BR, the amount of butadiene in SBR (A) is 60% by mass (=100-40), the butadiene content of SBR (B) is 75% by mass (=100-25), and the butadiene content of BR is 100% by mass. Therefore, the total butadiene content in the rubber component is 62.75% by mass (=90×60/100+5×75/100+5×100/100).

In the rubber composition, the content of the styrene resin and the content of the C5 resin preferably satisfy the following formula (B). As a result, the effects of the present invention tend to be obtained more favorably.
(B) β1≧β2
β1: Content of styrene resin per 100 parts by mass of rubber component [parts by mass]
β2: Content of C5 resin per 100 parts by mass of rubber component [parts by mass]

The rubber composition preferably contains carbon black. As a result, the effects of the present invention tend to be obtained more favorably.
Examples of carbon black include, but are not limited to, N134, N110, N220, N234, N219, N339, N330, N326, N351, N550 and N762. These may be used alone or in combination of two or more.

The cetyltrimethylammonium bromide (CTAB) specific surface area of carbon black is preferably 110 m ² /g or more, more preferably 160 m ² /g or more, still more preferably 170 m ² /g or more, and particularly preferably 180 m ² /g or more. Also, it is preferably 250 m ² /g or less, more preferably 200 m ² /g or less. Within the above range, the effects of the present invention tend to be obtained more favorably.
The CTAB specific surface area of carbon black is a value measured according to JIS K6217-3:2001.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 110 m ² /g or more, more preferably 140 m ² /g or more, still more preferably 177 m ² /g or more, and preferably 250 m ² /g. 200 m 2 /g or less, more preferably 200 m ² /g or less. Within the above range, the effects of the present invention tend to be obtained more favorably.
The N ₂ SA of carbon black is a value measured according to JIS K6217-2:2001.

The iodine adsorption amount (IA) of carbon black is preferably 110 mg/g or more, more preferably 170 mg/g or more, still more preferably 188 mg/g or more, and is preferably 250 mg/g or less, more preferably 200 mg/g. g or less. Within the above range, the effects of the present invention tend to be obtained more favorably.
The IA of carbon black is a value measured according to JIS K6217-1:2008.

As carbon black, for example, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Corporation, Shin Nikka Carbon Co., Ltd., Columbia Carbon Co., Ltd. can be used.

When carbon black is contained, the content of carbon black is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and preferably 50 parts by mass or less, with respect to 100 parts by mass of the rubber component. Preferably, it is 35 parts by mass or less. Within the above range, the effects of the present invention can be obtained more favorably.

The rubber composition may contain oil.
Oils include, for example, process oils, vegetable oils, or mixtures thereof. As the process oil, for example, paraffinic process oil, aromatic process oil, naphthenic process oil, or the like can be used. Vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, Olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil and the like. These may be used alone or in combination of two or more. Of these, process oils are preferable, and aromatic process oils are more preferable, because the effects of the present invention can be obtained satisfactorily.

When oil is contained, the content of oil is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and preferably 50 parts by mass or less, more preferably 100 parts by mass of the rubber component. It is 40 parts by mass or less. Within the above range, the effects of the present invention tend to be obtained more favorably.

The rubber composition may contain wax.
The wax is not particularly limited, and includes petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant waxes and animal waxes; synthetic waxes such as polymers of ethylene and propylene. These may be used alone or in combination of two or more. Among them, petroleum waxes are preferred, and paraffin waxes are more preferred.

As the wax, for example, products of Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., Seiko Kagaku Co., Ltd., etc. can be used.

When wax is contained, the wax content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 20 parts by mass or less, more preferably 100 parts by mass of the rubber component. It is 10 parts by mass or less. Within the above range, the effects of the present invention tend to be obtained more favorably.

The rubber composition may contain an antioxidant.
Examples of anti-aging agents include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; -Isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, etc. p-phenylenediamine-based antioxidants; quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; 2,6-di-t-butyl-4-methylphenol, monophenolic anti-aging agents such as styrenated phenol; inhibitors and the like. These may be used alone or in combination of two or more. Among them, p-phenylenediamine antioxidants and quinoline antioxidants are preferred.

As the anti-aging agent, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo Co., Ltd., Flexis, etc. can be used, for example.

When an anti-aging agent is contained, the content of the anti-aging agent is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 10 parts by mass or less with respect to 100 parts by mass of the rubber component. , more preferably 8 parts by mass or less. Within the above range, the effects of the present invention tend to be obtained more favorably.

The rubber composition may contain stearic acid.
Conventional stearic acid can be used, for example, NOF Corporation, NOF Corporation, Kao Corporation, Wako Pure Chemical Industries, Ltd., Chiba Fatty Acids Co., Ltd. products can be used.

When stearic acid is contained, the content of stearic acid is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, or more, relative to 100 parts by mass of the rubber component. It is preferably 5 parts by mass or less. Within the above range, the effects of the present invention tend to be obtained more favorably.

The rubber composition may contain zinc oxide.
As the zinc oxide, conventionally known ones can be used, for example, products of Mitsui Kinzoku Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

When zinc oxide is contained, the content of zinc oxide is preferably 1 part by mass or more, more preferably 2.5 parts by mass or more, and preferably 10 parts by mass or less with respect to 100 parts by mass of the rubber component. , more preferably 5 parts by mass or less. Within the above range, the effects of the present invention tend to be obtained more favorably.

The rubber composition may contain sulfur.
Sulfur includes powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur and the like commonly used in the rubber industry. These may be used alone or in combination of two or more.

As sulfur, for example, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Io Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis Co., Ltd., Nippon Kantan Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

When sulfur is contained, the content of sulfur is preferably 0.5 parts by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, or more, relative to 100 parts by mass of the rubber component. It is preferably 5 parts by mass or less. Within the above range, the effects of the present invention tend to be obtained more favorably.

The rubber composition may contain a vulcanization accelerator.
Vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram disulfide (TMTD ), tetrabenzyl thiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N) and other thiuram vulcanization accelerators; N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl- 2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N,N'-diisopropyl-2-benzothiazolesulfenamide, etc. and guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine and orthotolylbiguanidine. These may be used alone or in combination of two or more. Among these, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred because the effects of the present invention can be obtained more favorably.

When a vulcanization accelerator is contained, the content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass with respect to 100 parts by mass of the rubber component. parts or less, more preferably 8 parts by mass or less. Within the above range, the effects of the present invention tend to be obtained more favorably.

In addition to the above components, the rubber composition contains additives commonly used in the tire industry, such as organic peroxides; fillers such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. ; and the like may be further added. The content of these additives is preferably 0.1 to 200 parts by mass with respect to 100 parts by mass of the rubber component.

The above rubber composition can be produced, for example, by kneading each of the above components using a rubber kneading apparatus such as an open roll mixer or a Banbury mixer, followed by vulcanization.

As for the kneading conditions, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C in the base kneading step in which additives other than the vulcanizing agent and the vulcanization accelerator are kneaded. In the finishing kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 120°C or lower, preferably 85 to 110°C. A composition obtained by kneading a vulcanizing agent and a vulcanization accelerator is usually subjected to vulcanization treatment such as press vulcanization. The vulcanization temperature is generally 140-190°C, preferably 150-185°C. Vulcanization time is usually 5 to 15 minutes.

The above rubber composition is suitably used for treads (cap treads), but is used for members other than treads, such as sidewalls, base treads, undertreads, clinch apex, bead apex, breaker cushion rubber, and carcass cord coating. It may be used for rubber, insulation, chafer, inner liner, etc., and for side reinforcing layers of run-flat tires.

The pneumatic tire of the present invention is manufactured by a normal method using the rubber composition.
That is, the rubber composition is extruded according to the shape of each tire member of the tread in an unvulcanized stage, and molded together with other tire members on a tire molding machine by a normal method to obtain an unvulcanized rubber composition. Form a vulcanized tire. A tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

The pneumatic tire can be used for passenger car tires, truck and bus tires, motorcycle tires, high-performance tires, etc., and is suitable for motorcycle tires (particularly, motocross tires).

EXAMPLES The present invention will be specifically described based on Examples, but the present invention is not limited to these.
Various chemicals used in the examples are described below.
SBR1: SLR6430 manufactured by Dow (styrene content: 40% by mass, vinyl content: 24% by mass, oil content of 37.5 parts by mass per 100 parts by mass of rubber solids)
SBR2: JSR0122 manufactured by JSR Corporation (styrene content: 38% by mass, vinyl content: 16% by mass)
SBR3: JSR1502 manufactured by JSR Corporation (styrene content: 24% by mass, vinyl content: 16% by mass)
BR: BR730 manufactured by JSR Corporation (cis content: 95% by mass)
Carbon black 1: prototype (CTAB: 180 m ² /g, N ₂ SA: 177 m ² /g, IA: 188 mg/g)
Carbon black 2: N134 (CTAB: 135 m ² /g)
Carbon black 3: N220 (CTAB: 111 m ² /g) manufactured by Mitsubishi Chemical Corporation
Silica 1: Ultrasil 9000GR (N ₂ SA: 240 m ² /g) manufactured by Evonik Degussa
Silica 2: ZEOSIL 1115MP from Rhodia (N ₂ SA: 115 m ² /g)
Silane coupling agent 1: NXT (3-octanoylthiopropyltriethoxysilane) manufactured by Momentive
Silane coupling agent 2: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa
Oil: VIVATEC500 (TDAE oil) manufactured by H&R
C5 resin: Petrotac 100V manufactured by Tosoh Corporation (C5/C9 resin, softening point: 94°C, Mw: 3900, Mn: 1200)
Styrene-based resin: Sylvatraxx 4401 manufactured by Arizona Chemical Co. (α-methylstyrene-based resin (α-methylstyrene-styrene copolymer), Mn: 700, softening point: 85°C)
Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd.
Antiaging agent 1: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Antiaging agent 2: Nocrac RD (poly (2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Stearic acid: stearic acid "Tsubaki" manufactured by NOF Corporation
Zinc oxide: Zinc white No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. Vulcanization accelerator 1: Noccellar NS (N-tert-butyl manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) -2-benzothiazolylsulfenamide)
Vulcanization accelerator 2: Noxceler D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

(Analysis of SBR)
Structural identification of SBR (measurement of styrene content and vinyl content) was performed using a JNM-ECA series device manufactured by JEOL Ltd. For the measurement, 0.1 g of polymer was dissolved in 15 ml of toluene, slowly poured into 30 ml of methanol to reprecipitate, and then dried under reduced pressure.

(Examples and Comparative Examples)
According to the formulation shown in Table 1, using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd., materials other than sulfur and vulcanization accelerator were kneaded at 150 ° C. for 5 minutes, and the kneaded product was obtained. Obtained. Next, sulfur and a vulcanization accelerator were added to the resulting kneaded material, and the mixture was kneaded at 80° C. for 5 minutes using an open roll to obtain an unvulcanized rubber composition. The resulting unvulcanized rubber composition was molded into a tread shape, laminated with other tire members to form an unvulcanized tire, press-vulcanized at 150 ° C. for 12 minutes, and a test tire ( Manufactured motocross tires. The obtained test tires were used for the following evaluations, and the results are shown in Table 1.
In Table 1, the rubber content in the oil-extended rubber is listed in the rubber column, and the oil content in the oil-extended rubber is added to the oil column.

(wet grip performance)
Each test tire was mounted on all wheels of a motocross motorcycle (CRF450R manufactured by Honda Motor Co., Ltd.) (rim size: 6.25 x 17, internal pressure: 290 kPa), and the actual vehicle was run on a test course (wet road surface). The grip performance was evaluated by a test driver and expressed as an index with Comparative Example 1 set to 100 (wet grip performance index). A larger index indicates better wet grip performance. In this embodiment, the target is 110 or more.

(wear resistance)
The amount of remaining groove of the tire tread rubber (20 mm when new) was measured when the actual vehicle was driven under the same conditions as for the wet grip performance, and expressed as an index based on Comparative Example 1 being 100 (wear resistance index). The larger the index, the larger the amount of remaining grooves and the better the wear resistance. In this embodiment, the target is 80 or more.

Claims (9)

a rubber component having a styrene-butadiene rubber content of 50 to 80% by mass and a butadiene rubber content of 20 to 50% by mass;
silica having a content of 80 to 120 parts by mass with respect to 100 parts by mass of the rubber component;
a styrene resin having a softening point of 30 to 120° C .;
and a C5 resin having a softening point of 30 to 120 ° C. ,
satisfying the following formula (A),
A rubber composition for a tire, wherein α1/β1 is 2 or less in the following formula (A).
(A) α1/β1≦α2/β2
α1: Total amount of styrene in the rubber component [% by mass]
α2: total amount of butadiene in the rubber component [% by mass]
β1: Content of styrene resin per 100 parts by mass of rubber component [parts by mass]
β2: Content of C5 resin per 100 parts by mass of rubber component [parts by mass] 2. The rubber composition for tires according to claim 1, wherein the C5 resin is a copolymer of a C5 fraction and a C9 fraction. 3. The rubber composition for tires according to claim 1, wherein said styrenic resin is a copolymer of α-methylstyrene and styrene. 4. The rubber composition for a tire according to any one of claims 1 to 3 , wherein α2/β2 in the formula (A) is 3 or more. The rubber composition for tires according to any one of claims 1 to 4, which satisfies the following formula (B).
(B) β1≧β2
β1: Content of styrene resin per 100 parts by mass of rubber component [parts by mass]
β2: Content of C5 resin per 100 parts by mass of rubber component [parts by mass] The rubber composition for tires according to any one of claims 1 to 5, comprising carbon black having a cetyltrimethylammonium bromide specific surface area of 160 m ² /g or more. The rubber composition for tires according to any one of claims 1 to 6, wherein the silica has a nitrogen adsorption specific surface area of 220 m ² /g or more. The rubber composition for tires according to any one of claims 1 to 7 , which contains a mercapto-based silane coupling agent. A pneumatic tire produced using the rubber composition according to any one of claims 1 to 8 .