JP7306050B2 - 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.

As a technique for improving wet grip performance, for example, Patent Document 1 discloses a method of blending epoxidized natural rubber, silica, plant-derived oil, silane coupling agent, anionic surfactant, and the like. However, in recent years, there has been a demand for further improvement in wet grip performance.

JP 2005-263956 A

An object of the present invention is to solve the above problems and to provide a tire rubber composition capable of improving wet grip performance, and a pneumatic tire produced using the rubber composition.

The present invention contains a rubber component having a total content of styrene-butadiene rubber and butadiene rubber of 90 mass % or more, silica having a content of 50 mass parts or more per 100 mass parts of the rubber component, and a liquid isoprene rubber. and relates to a tire rubber composition that satisfies the following formulas (A) and (B).
(A) α≧30
(B) α/β≧3
α: Total amount of vinyl in styrene-butadiene rubber and butadiene rubber [% by mass]
β: Content of liquid isoprene rubber per 100 parts by mass of rubber component [parts by mass]

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

It is preferable that the total amount of styrene in the styrene-butadiene rubber and the butadiene rubber is 10% by mass or less.

The nitrogen adsorption specific surface area of the silica is preferably 200 m ² /g or more.

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

According to the present invention, the total content of styrene-butadiene rubber and butadiene rubber is within a predetermined range, a predetermined amount of silica and liquid isoprene rubber are contained, and formulas (A) and (B) are further satisfied. Since it is a rubber composition for tires that satisfies the above conditions, wet grip performance can be improved.

The rubber composition for tires of the present invention has a total content of styrene-butadiene rubber (SBR) and butadiene rubber (BR) within a predetermined range, contains a predetermined amount of silica and a liquid isoprene rubber, and , satisfies equations (A) and (B).

The above-described effects of the rubber composition are obtained, and it is presumed that these effects are brought about by the following effects.
In the rubber composition, the total content of SBR and BR and the content of silica are adjusted to a predetermined range, and further, the total amount of vinyl in SBR and BR, the total amount of vinyl and the content of liquid isoprene rubber Silica and liquid isoprene rubber can be well dispersed in the rubber composition by adjusting the ratio of the amounts within a predetermined range. This is believed to significantly improve wet grip performance.

In addition, the rubber composition tends to improve overall wet grip performance, fuel efficiency, steering stability, and wear resistance.

In the rubber composition, the rubber component is a component that contributes to cross-linking, generally has a weight average molecular weight (Mw) of 10,000 or more (preferably 100,000 or more), and is solid at normal temperature and normal pressure.
Mw is a standard value based on measurements by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation). It can be calculated by polystyrene conversion.

The rubber composition contains SBR and/or BR as a rubber component. It is preferable to use SBR and BR together because the overall performance tends to be good.

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 modifying agent), 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 above 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, 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 5% by mass or more, more preferably 10% by mass or more, and is preferably 60% by mass or less, more preferably 40% by mass or less, and still more preferably 35% by mass or less. Within the above range, the overall performance tends to be good.
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 25% by mass or more, still more preferably 35% by mass or more, and is preferably 65% by mass or less, more preferably 55% by mass or less. Within the above range, the overall performance tends to be good.
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.

When SBR is contained, the content of SBR in 100% by mass of the rubber component is preferably 40% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, and preferably 90% by mass. % or less, more preferably 80 mass % or less. Within the above range, the overall performance tends to be good.

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 30% 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 vinyl content of BR is preferably 1% by mass or more, more preferably 2% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less. Within the above range, the overall performance tends to be good.
The vinyl content (1,2-bonded butadiene unit content) can be measured by the method described in Examples below.

When BR is contained, the content of BR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, and preferably 60% by mass or less, more preferably 40% by mass. % or less, more preferably 30 mass % or less. Within the above range, the overall performance tends to be good.

The total content of SBR and BR in 100% by mass of the rubber component may be 90% by mass or more, preferably 95% by mass or more, and may be 100% by mass. Within the above range, the overall performance tends to be good.
When blending rubber components other than SBR and BR, the upper limit of the above total content is preferably 99% by mass or less, more preferably 95% by mass or less.

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. Of these, isoprene-based rubber is preferred because it tends to improve the above-mentioned overall performance.

As the isoprene rubber, isoprene rubber (IR), natural rubber (NR), epoxidized natural rubber (ENR), and the like can be used. Modified NRs such as deproteinized natural rubber (DPNR) and high purity natural rubber (UPNR) can also be used. These may be used individually by 1 type, and may use 2 or more types together.

When isoprene-based rubber is contained, the content of isoprene-based rubber in 100% by mass of the rubber component is preferably 1% by mass or more, more preferably 3% by mass or more, and preferably 10% by mass or less. Preferably, it is 5% by mass or less. Within the above range, the overall performance tends to be good.

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 150 m ² /g or more, more preferably 200 m ² /g or more, still more preferably 220 m ² /g or more, and preferably 300 m ² /g or less. , more preferably 260 m ² /g or less. Within the above range, the overall performance tends to be good.
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 relative to 100 parts by mass of the rubber component may be 50 parts by mass or more, preferably 65 parts by mass or more, more preferably 75 parts by mass or more, and preferably 150 parts by mass or less, more preferably is 130 parts by mass or less. Within the above range, the overall performance tends to be good.

The rubber composition preferably contains a silane coupling agent together with silica.
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, mercapto-based compounds are more preferable because they tend to improve the overall performance described above.

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、－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 , —NR ¹⁰⁰⁶ R ¹⁰⁰⁷ and —(OSiR ¹⁰⁰⁶ R ¹⁰⁰⁷ ) _h (OSiR ¹⁰⁰⁶ R ¹⁰⁰⁷ R ¹⁰⁰⁸ ) (R ¹⁰⁰⁶ , R ¹⁰⁰⁷ and R ¹⁰⁰⁸ may be the same or different, and each is a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms; , h has an average value of 1 to 4.), R ¹⁰⁰² is R ¹⁰⁰¹ , a hydrogen atom or a monovalent hydrocarbon group having 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, j is an integer of 1 to 4.), R ¹⁰⁰⁴ is a divalent hydrocarbon group having 1 to 18 carbon atoms, and R ¹⁰⁰⁵ is 1 carbon atom to 18 monovalent hydrocarbon groups, and x, y and z are numbers satisfying the relationships x+y+2z=3, 0≤x≤3, 0≤y≤2, 0≤z≤1.)

(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 overall performance tends to be good.

The rubber composition contains liquid isoprene rubber (liquid IR).
Liquid IR is a polyisoprene polymer having isoprene as a structural unit, is liquid at normal temperature and normal pressure, and is not included in the rubber component. Mw of liquid IR is usually less than 100,000 (preferably 80,000 or less).

The liquid IR may be either a non-modified liquid IR or a modified liquid IR. Examples of modified liquid IR include modified liquid IR into which the aforementioned functional groups have been introduced. These may be used individually by 1 type, and may use 2 or more types together.

As the liquid IR, for example, products such as Kuraray Co., Ltd. can be used.

The content of the liquid IR is preferably 1 part by mass or more, more preferably 5 parts by mass or more, still more preferably 8 parts by mass or more, and preferably 30 parts by mass or less, based on 100 parts by mass of the rubber component. It is more preferably 20 parts by mass or less, still more preferably 15 parts by mass or less. Within the above range, the overall performance tends to be good.

In the rubber composition, the total vinyl content in SBR and BR and the liquid IR content satisfy the following formulas (A) and (B).
(A) α≧30
(B) α/β≧3
α: Total amount of vinyl in styrene-butadiene rubber and butadiene rubber [% by mass]
β: Content of liquid isoprene rubber per 100 parts by mass of rubber component [parts by mass]

α (total amount of vinyl in SBR and BR) may be adjusted within a range satisfying formulas (A) and (B), but from the viewpoint of wet grip performance, it is preferably 32% by mass or more, more preferably 35% by mass. % or more, preferably 60% by mass or less, more preferably 45% by mass or less.
Here, the total vinyl content in SBR and BR (ratio of vinyl portion to total content of SBR and BR) is ((Σ (content of each SBR × vinyl content of each SBR/100) + Σ (each BR content x vinyl amount of each BR/100))/Σ (content of each SBR + content of each BR)) x 100. For example, the rubber component is SBR (A) (vinyl content 40% by mass) 85% by mass, SBR (B) (vinyl content 25% by mass) 5% by mass, BR (vinyl content 25% by mass) 5% by mass, NR 5% by mass %, the total vinyl content in SBR and BR is 38.4% by weight (=((85*40/100+5*25/100+5*25/100)/(85+5+5))*100) .

In formula (B), α/β is preferably 3.3 or more, more preferably 3.5 or more, and preferably 10 or less, more preferably 8 or less, from the viewpoint of wet grip performance.

The total styrene content in SBR and BR is preferably 1% by mass or more, more preferably 5% by mass or more, and is preferably 25% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass. It is below. Within the above range, the overall performance tends to be good.
Here, the total styrene content in SBR and BR (the ratio of the styrene part to the total content of SBR and BR) is (Σ (content of each SBR × styrene content of each SBR / 100) / Σ (each SBR content + content of each BR)) x 100. For example, when the rubber component is composed of 85% by mass of SBR (A) (40% by mass of styrene), 5% by mass of SBR (B) (25% by mass of styrene), 5% by mass of BR, and 5% by mass of NR, SBR and the total styrene content in BR is 37.1% by weight (=((85×40/100+5×25/100)/(85+5+5))×100).

The rubber composition may contain a resin other than the liquid IR.
Resins other than liquid IR are not particularly limited as long as they are commonly used in the tire industry. -Butylphenol acetylene resin, acrylic resin and the like. These may be used alone or in combination of two or more. Among them, C5-based resins and terpene-based resins are preferable.

The weight average molecular weight (Mw) of the resin is preferably 200 or more, more preferably 400 or more, and preferably 5000 or less, more preferably 3000 or less. Within the above range, the overall performance tends to be good.

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 (1-pentene, 2-pentene, olefinic hydrocarbons such as 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.

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 ( C5/C9 resins) are more preferred.

When a C5 resin is contained, the content of the C5 resin with respect to 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and still more preferably 25 parts by mass or more. is 50 parts by mass or less, more preferably 35 parts by mass or less. Within the above range, the overall performance tends to be good.

As the terpene-based resin, a polyterpene resin obtained by polymerizing a terpene compound, an aromatic modified terpene resin obtained by polymerizing a terpene compound and an aromatic compound, or the like can be used. Hydrogenated products of these can also be used.

A polyterpene resin is a resin obtained by polymerizing a terpene compound. The terpene compounds are hydrocarbons represented by the composition (C ₅ H ₈ ) _n and oxygen-containing derivatives thereof, and include monoterpene (C ₁₀ H ₁₆ ), sesquiterpene (C ₁₅ H ₂₄ ), diterpene (C ₂₀ H ₃₂ ), etc., which are compounds having a terpene as a basic skeleton, such as α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineol, α-terpineol, β-terpineol, γ-terpineol and the like.

Examples of polyterpene resins include pinene resins, limonene resins, dipentene resins, and pinene/limonene resins made from the above-described terpene compounds. Among them, pinene resin is preferable because it is easy to undergo a polymerization reaction and because natural pine resin is used as a raw material, it is inexpensive. Pinene resins usually contain both α-pinene and β-pinene, which are in an isomer relationship. It is classified as α-pinene resin, which is mainly composed of pinene.

Examples of aromatic modified terpene resins include terpene phenol resins using the above terpene compounds and phenolic compounds as raw materials, and terpene styrene resins using the above terpene compounds and styrene compounds as raw materials. Terpene phenol styrene resins made from the above terpene compounds, phenolic compounds and styrene compounds can also be used. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol. Styrene-based compounds include styrene and α-methylstyrene.

The terpene-based resin is preferably an aromatic modified terpene resin because the above-mentioned overall performance tends to be good.

When a terpene-based resin is contained, the content of the terpene-based resin is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, and still more preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component, Also, it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less. Within the above range, the overall performance tends to be good.

Commercially available resins other than liquid IR include, for example, Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, and Nichinuri Chemical. Co., Ltd., Nippon Shokubai Co., Ltd., JXTG Energy Co., Ltd., Arakawa Chemical Industries, Ltd., Taoka Chemical Industries, Ltd., ExxonMobil, CrayValley, etc. can be used.

The total content of liquid IR and other resins is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 25 parts by mass or more, and particularly preferably 35 parts by mass with respect to 100 parts by mass of the rubber component. parts by mass or more, preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and particularly preferably 60 parts by mass or less. Within the above range, the overall performance tends to be good.
In addition, when not containing resin other than liquid IR, the said total content is synonymous with content of liquid IR.

The rubber composition preferably contains carbon black.
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.

Carbon black has a cetyltrimethylammonium bromide (CTAB) specific surface area of preferably 100 m ² /g or more, more preferably 130 m ² /g or more, and preferably 200 m ² /g or less, more preferably 160 m ² /g. It is below. Within the above range, the overall performance tends to be good.
The CTAB specific surface area of carbon black is a value measured according to JIS K6217-3:2001.

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 1 part by mass or more, more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, or more, with respect to 100 parts by mass of the rubber component. It is preferably 15 parts by mass or less. Within the above range, the overall performance tends to be good.

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. Among them, process oil is preferred.

As oil, for example, Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R, Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd. etc. products can be used.

The content of the oil is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 15 parts by mass or less, and particularly preferably 5 parts by mass or less with respect to 100 parts by mass of the rubber component. The lower limit is not particularly limited, and may be 0 parts by mass. Within the above range, the overall performance tends to be good.

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 2 parts by mass or more, and preferably 20 parts by mass or less, more preferably It is 10 parts by mass or less. Within the above range, the overall performance tends to be good.

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, Monophenol 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 overall performance tends to be good.

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

When stearic acid is contained, the content of stearic acid is preferably 0.5 parts by mass or more, more preferably 1 part 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 overall performance tends to be good.

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 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 overall performance tends to be good.

The rubber composition may contain sulfur.
Sulfur includes powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are 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 1 part 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 overall performance tends to be good.

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 them, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred.

As the vulcanization accelerator, for example, products manufactured by Kawaguchi Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., Sanshin Chemical Industry Co., Ltd., etc. can be used.

When a vulcanization accelerator is contained, the content of the vulcanization accelerator is preferably 2 parts by mass or more, more preferably 4 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 overall performance tends to be good.

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.

Tires for trucks and buses; tires for motorcycles; high-performance tires; winter tires such as studless tires; A tire with a sound absorbing member provided for a tire; a tire with a sealing member that has a sealant that can be sealed in the tire or in the tire cavity when punctured; etc., and is suitable for passenger car 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: Buna VSL5025-2 HM manufactured by LANXESS (styrene content: 25% by mass, vinyl content: 50% by mass)
SBR2: Modified SBR synthesized in Production Example 1 below (styrene content: 10% by mass, vinyl content: 40% by mass, Mw: 200,000)
SBR3: Modified SBR synthesized in Production Example 2 below (styrene content: 35% by mass, vinyl content: 50% by mass, Mw: 600,000)
BR1: BR1280 manufactured by LG Chem (vinyl content: 2% by mass, cis content: 96 mol%)
BR2: N103 manufactured by Asahi Kasei Chemicals Corporation (vinyl content: 12% by mass, cis content: 38% by mass)
Isoprene rubber: TSR20 (natural rubber)
Carbon black 1: N134 (CTAB: 135 m ² /g)
Carbon black 2: N220 (CTAB: 111 m ² /g)
Silica 1: Ultrasil 9000GR (N ₂ SA: 240 m ² /g) manufactured by Evonik Degussa
Silica 2: Ultrasil VN3 from Evonik Degussa (N ₂ SA: 167 m ² /g)
Silane coupling agent 1: Momentive NXT-Z45 (copolymer of bonding unit A and bonding unit B (bonding unit A: 55 mol%, bonding unit B: 45 mol%))
Silane coupling agent 2: NXT (3-octanoylthiopropyltriethoxysilane) manufactured by Momentive
Silane coupling agent 3: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Evonik Degussa
Oil: Liquid A/O mix manufactured by Sankyo Yuka Kogyo Co., Ltd. IR: LIR50 manufactured by Kuraray Co., Ltd. (Mw: 54000, liquid at normal temperature and pressure)
Resin 1: YS resin TO125 manufactured by Yasuhara Chemical Co., Ltd. (aromatic modified terpene resin, Mw: 800)
Resin 2: Ricon 340 (C5/C9 resin, Mw: 240) manufactured by CrayValley
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 CZ (N-cyclohexyl-2 manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.) -benzothiazolylsulfenamide)
Vulcanization accelerator 2: Noxceler D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

(Production example 1)
A nitrogen purged autoclave reactor was charged with cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene. After adjusting the temperature of the contents of the reactor to 20° C., n-butyllithium was added to initiate the polymerization. Polymerization was carried out under adiabatic conditions, and the maximum temperature reached 85°C. When the polymerization conversion rate reached 99%, 1,3-butadiene was added and the mixture was further polymerized for 5 minutes, and then 3-diethylaminopropyltrimethoxysilane was added as a modifier to carry out the reaction. After completion of the polymerization reaction, 2,6-di-tert-butyl-p-cresol was added. Then, the solvent was removed by steam stripping and dried with a hot roll adjusted to 110° C. to obtain SBR1.

(Production example 2)
A nitrogen purged autoclave reactor was charged with cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene. After adjusting the temperature of the contents of the reactor to 20° C., n-butyllithium was added to initiate the polymerization. Polymerization was carried out under adiabatic conditions, and the maximum temperature reached 85°C. When the polymerization conversion rate reached 99%, 1,3-butadiene was added and the mixture was further polymerized for 5 minutes, after which N-(3-dimethylaminopropyl)acrylamide was added as a modifier to carry out the reaction. After completion of the polymerization reaction, 2,6-di-tert-butyl-p-cresol was added. Then, the solvent was removed by steam stripping, and dried with a hot roll adjusted to 110° C. to obtain SBR3.

(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 ( Size: 195/65R15) was manufactured. 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 vehicle (made in Japan FF2000cc), and the braking distance from an initial speed of 100 km / h on a wet asphalt road surface was obtained. grip performance index). A larger index indicates a shorter braking distance and better wet grip performance.

(Low fuel consumption)
Using a rolling resistance tester, measure the rolling resistance when running each test tire with a rim (15 × 6 JJ), internal pressure (230 kPa), load (3.43 kN), speed (80 km / h), It is indicated as an index with Comparative Example 1 as 100 (fuel efficiency index). A larger index indicates lower rolling resistance and better fuel efficiency.

(steering stability)
A test piece cut from the tread of each test tire was measured using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.) under conditions of a temperature of 70 ° C., an initial strain of 10%, and a dynamic strain of 2%. It was measured and displayed as an index with Comparative Example 1 set to 100 (steering stability index). A larger index indicates a larger E* and better steering stability.

(wear resistance)
Mount each test tire on all wheels of a vehicle (made in Japan FF2000cc), measure the groove depth of the tire tread after running 8000km, calculate the running distance when the tire groove depth is reduced by 1mm, and compare It is indicated as an index with Example 1 as 100 (abrasion resistance index). The larger the index, the longer the running distance and the better the wear resistance.

As can be seen from Table 1, the intended wet grip performance was improved in the examples compared to the comparative examples. In addition, the wet grip performance, fuel efficiency, steering stability, and wear resistance (total of each index) were also better than those of the comparative example.

Claims (5)

a rubber component in which the total content of styrene-butadiene rubber and butadiene rubber is 90% by mass or more;
silica having a content of 50 parts by mass or more with respect to 100 parts by mass of the rubber component;
liquid isoprene rubber,
The total styrene content in the styrene-butadiene rubber and the butadiene rubber is 15% by mass or less,
A rubber composition for tires that satisfies the following formulas (A) and (B).
(A) α≧30
(B) α/β≧3
α: Total amount of vinyl in styrene-butadiene rubber and butadiene rubber [% by mass]
β: Content of liquid isoprene rubber per 100 parts by mass of rubber component [parts by mass] The rubber composition for tires according to claim 1, which contains a mercapto-based silane coupling agent. 3. The rubber composition for a tire according to claim 1, wherein the styrene-butadiene rubber and the butadiene rubber have a total styrene content of 10% by mass or less. The rubber composition for tires according to any one of claims 1 to 3, wherein the silica has a nitrogen adsorption specific surface area of 200 m ² /g or more. A pneumatic tire produced using the rubber composition according to any one of claims 1 to 4.