JP7262164B2 - 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, there is a strong demand for low fuel consumption in automobiles, and rubber compositions used for automobile tires are also required to be excellent in low fuel consumption. .

As a method of improving fuel efficiency, for example, a method of reducing the amount of reinforcing filler is known, but in this method, wet grip performance and wear resistance are deteriorated due to a decrease in the calorific value and reinforcing properties of the rubber composition. , steering stability, etc. tend to deteriorate. Thus, these performances generally have a conflicting relationship with low fuel consumption, and it is difficult to obtain each performance in a well-balanced manner.

The present invention solves the above-mentioned problems and provides a rubber composition for tires that improves fuel efficiency, wet grip performance, wear resistance and steering stability in a well-balanced manner, and a pneumatic tire produced using the rubber composition. intended to provide

The present invention includes an isoprene rubber, a styrene-butadiene rubber and a styrene resin, and the content of the isoprene-based rubber in 100% by mass of the rubber component is 30% by mass or more, and the content of the styrene-butadiene rubber is 30% by mass or more. The styrene-butadiene rubber has an average molecular weight of 300,000 or less, an average vinyl content of 40% by mass or more, and a tire in which the content of the styrene-butadiene rubber/the content of the styrene-based resin is 15.0 or less. It relates to a rubber composition for

The silica content is preferably 70 parts by mass or more per 100 parts by mass of the rubber component.
The content of carbon black having a CTAB specific surface area of 150 m ² /g or more is preferably 5 to 30 parts by mass with respect to 100 parts by mass of the rubber component.

The oil content is preferably 10 to 30 parts by mass with respect to 100 parts by mass of the rubber component.
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 contains an isoprene rubber, a styrene-butadiene rubber having a predetermined average molecular weight and an average vinyl content, and a styrene resin in predetermined proportions. Performance, wear resistance and handling stability are improved in a well-balanced manner.

The rubber composition for a tire of the present invention contains an isoprene rubber, a styrene-butadiene rubber (SBR) having a predetermined average molecular weight and an average vinyl content, and a styrene resin in a predetermined ratio.

The rubber composition has the above effects, which are presumed to be due to the following effects.
In a compounding system containing a large amount of SBR with a low molecular weight and a large vinyl content, performance other than wet grip performance tends to deteriorate. It is considered that the performance balance among fuel efficiency, wet grip performance, wear resistance and steering stability is remarkably (synergistically) improved by adding a certain amount of styrene resin.

Furthermore, (1) 70 parts by mass or more of silica is blended as a filler, (2) 5 to 30 parts by mass of carbon black having a CTAB specific surface area of 150 m ² /g or more is blended, and (3) the amount of oil is 10 to 30 parts by mass. It is considered that the performance balance is improved more significantly (synergistically) by applying at least one of the techniques.

The isoprene rubber includes natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR, and the like. As NR, for example, those commonly used in the tire industry, such as SIR20, RSS#3, and TSR20, can be used. The IR is not particularly limited, and for example IR2200 or the like commonly used in the tire industry can be used. Modified NR includes deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc. Modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, and the like. These may be used alone or in combination of two or more.

The content of isoprene-based rubber in 100% by mass of the rubber component is 30% by mass or more, preferably 35% by mass or more. By setting it to the lower limit or more, there is a tendency that good fuel economy can be obtained. The content is preferably 60% by mass or less, more preferably 50% by mass or less. By making it below the upper limit, there is a tendency that the amount of SBR is ensured and the performance balance is remarkably improved.

The SBR contained in the rubber composition has an average molecular weight of 300,000 or less. From the viewpoint of the performance balance, the average molecular weight is preferably 280,000 or less, more preferably 260,000 or less. Although the lower limit is not particularly limited, it is preferably 100,000 or more, more preferably 120,000 or more, and still more preferably 140,000 or more from the viewpoint of the performance balance.

Here, the average molecular weight of SBR (average molecular weight of all SBR) is Σ (content ratio of each SBR in all SBR × weight average molecular weight of each SBR), and the content ratio of each SBR is each is the content ratio (mass ratio) of SBR (in the case of a rubber component consisting of 35% by mass of SBR (A), 5% by mass of SBR (B), 35% by mass of NR, and 25% by mass of BR, SBR (A), (B) are 0.875 (=35/(35+5)) and 0.125 (=5/(35+5)), respectively.Therefore, for example, the rubber component is SBR (A) (25% by mass of styrene, vinyl 60% by mass, Mw 150,000) 35% by mass, SBR (B) (styrene content 35% by mass, vinyl content 35% by mass, Mw 1,050,000) 5% by mass, NR 35% by mass, BR 25% by mass, average SBR The molecular weight is 262,500 (262,500 = 0.875 x 150,000 + 0.125 x 1,050,000).

The SBR contained in the rubber composition has an average vinyl content of 40% by mass or more. The lower limit of the average vinyl content is preferably 43% by mass or more, more preferably 45% by mass or more, from the viewpoint of the aforementioned performance balance. The upper limit is preferably 70% by mass or less, more preferably 65% by mass or less, and even more preferably 62% by mass or less, from the viewpoint of the aforementioned performance balance.

Here, the average vinyl content of SBR is {Σ(content ratio of each SBR in all SBR×vinyl content of each SBR×weight average molecular weight of each SBR)}/average molecular weight of all SBR. For example, the rubber component is SBR (A) (styrene content 25 mass%, vinyl content 60 mass%, Mw 150,000) 35 mass%, SBR (B) (styrene content 35 mass%, vinyl content 35 mass%, Mw 1,050,000). 5% by mass, 35% by mass of NR, and 25% by mass of BR, the average vinyl content is 47.5% by mass (= {35/(35+5)×60×150,000+5/(35+5)×35×1,050,000}/ 262,500).

As for the content ratio of the SBR and the styrene-based resin contained in the rubber composition, the content of the styrene-butadiene rubber/the content of the styrene-based resin (mass ratio) is 15.0 or less. From the viewpoint of the aforementioned performance balance, the ratio of "content of styrene-butadiene rubber/content of styrene-based resin" is preferably 12.0 or less, more preferably 10.0 or less. Although the lower limit is not particularly limited, it is preferably 1.0 or more, more preferably 2.0 or more, and still more preferably 2.5 or more from the viewpoint of the performance balance.

Here, the content of SBR/the content of styrene resin is the mass ratio of the total amount of SBR and the total amount of styrene resin contained in the rubber composition. , SBR (B) 5 parts by mass, NR 35 parts by mass, BR 25 parts by mass), styrene resin (A) 5 parts by mass, and styrene resin (B) 5 parts by mass. The content/the content of styrene resin" is 4.0 (=(35+5)/(5+5)).

The styrene content of each SBR is preferably 15% by mass or more, more preferably 20% by mass or more. By making it more than the lower limit, there is a tendency that good wet grip performance and steering stability can be obtained. The styrene content is preferably 50% by mass or less, more preferably 45% by mass or less. By keeping the content below the upper limit, there is a tendency that heat generation is reduced and good fuel efficiency can be obtained.
The styrene content can be measured by the method described in Examples below.

The vinyl content of each SBR is preferably 20% by mass or more, more preferably 30% by mass or more. By making it more than the lower limit, there is a tendency that good wet grip performance and steering stability can be obtained. The vinyl content is preferably 65% by mass or less, more preferably 60% by mass or less. By making it below the upper limit, there is a tendency that good wear resistance can be obtained.
The vinyl content (1,2-bonded butadiene unit content) can be measured by the method described in Examples below.

The weight average molecular weight Mw of each SBR is preferably 100,000 or more, more preferably 120,000 or more. When the content is at least the lower limit, there is a tendency that good fuel efficiency and wear resistance can be obtained. The Mw is preferably 1,100,000 or less, more preferably 1,050,000 or less. By making it below the upper limit, there is a tendency that good workability can be obtained.
From the viewpoint of the aforementioned performance balance, the SBR preferably contains at least one type of SBR having an Mw of 400,000 or less (preferably 300,000 or less, more preferably 200,000 or less).
The Mw can be measured by the method described in Examples below.

The content of SBR in 100% by mass of the rubber component is 30% by mass or more, preferably 35% by mass or more, more preferably 32% by mass or more, from the viewpoint of wet grip performance, steering stability, and wear resistance. From the viewpoint of fuel efficiency, the content is preferably 85% by mass or less, more preferably 75% by mass or less, and even more preferably 65% by mass or less.

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. The SBR may be either unmodified SBR or modified SBR, but from the viewpoint of the performance balance, it is preferable to use at least one type of 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; alkoxysilanes such as methyltriethoxysilane; 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' -(thio)benzophenone compounds having amino groups and/or substituted amino groups such as bis-(tetraethylamino)benzophenone; 4-N,N-dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde, 4-N, Benzaldehyde compounds having amino groups and/or substituted amino groups such as N-divinylaminobenzaldehyde; N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, Nt-butyl- 2-pyrrolidone, N-substituted pyrrolidones such as N-methyl-5-methyl-2-pyrrolidone, N-substituted piperidones such as N-methyl-2-piperidone, N-vinyl-2-piperidone, N-phenyl-2-piperidone ; N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-lauryrolactam, N-vinyl-ω-lauryrolactam, N-methyl-β-propiolactam, N-phenyl - N-substituted lactams such as 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.

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.

Rubber components that can be used in addition to isoprene rubber and SBR include butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). and other diene rubbers. These diene rubbers may be used alone or in combination of two or more. Among these, BR is preferable because it can further improve wear resistance and fuel efficiency.

The BR is not particularly limited, and BR having a high 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. Among them, the cis content of BR is preferably 90% by mass or more (preferably 95% by mass or more) for the reason that wear resistance is improved. 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 is preferably 30% by mass or less, more preferably 25% by mass or less. By keeping the amount below the upper limit, there is a tendency that the amount of isoprene rubber and the amount of SBR are ensured, and the performance balance is remarkably improved. Although the lower limit is not particularly limited, it is preferably 5% by mass or more, more preferably 10% by mass or more when blended.

The styrene-based resin is a polymer using a styrene-based monomer as a constituent monomer, and examples thereof include polymers polymerized using a styrene-based monomer as a main component (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 of other monomers copolymerizable therewith.

Examples of the other monomers include acrylonitrile and methacrylonitrile, acrylics, unsaturated carboxylic acids such as methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, chloroprene, and butadiene. dienes such as isoprene; olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride and acid anhydrides thereof;

Of these, α-methylstyrene resins (α-methylstyrene homopolymers, copolymers of α-methylstyrene and styrene, etc.) are preferred from the viewpoint of the aforementioned performance balance.

The softening point of the styrene-based resin is preferably 30°C or higher, more preferably 60°C or higher, and even more preferably 80°C or higher. When the temperature is 30°C or higher, the desired wet grip performance tends to be obtained. Also, the softening point is preferably 160° C. or lower, more preferably 130° C. or lower, and even more preferably 100° C. or lower. When the temperature is 160°C or lower, the dispersibility of the resin tends to be good, and the wet grip performance and fuel economy tend to improve.
In the present invention, the softening point of the resin is the temperature at which the sphere descends when the softening point specified in JIS K 6220-1:2001 is measured with a ring and ball type softening point measuring device.

The content of the styrene-based resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. Also, the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less. Within the above range, the performance balance is remarkably improved.

In addition to the styrenic resin, the rubber composition may contain other resins that are solid at room temperature (25° C.). Other resins are not particularly limited as long as they are commonly used in the tire industry, and include coumarone-indene resins, terpene resins, pt-butylphenolacetylene resins, acrylic resins, and the like.

A coumarone-indene resin is a resin containing coumarone and indene as monomer components constituting the skeleton (main chain) of the resin. Examples of monomer components contained in the skeleton other than coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

Examples of terpene-based resins include polyterpene, terpenephenol, and aromatic modified terpene resins.
Polyterpenes are resins obtained by polymerizing terpene compounds and hydrogenated products thereof. Terpene compounds are hydrocarbons represented by the composition (C ₅ H ₈ ) _n and their oxygen-containing derivatives, such as monoterpene (C ₁₀ H ₁₆ ), sesquiterpene (C ₁₅ H ₂₄ ), diterpene (C ₂₀ H ₃₂ ) and the like, 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-cineole, α-terpineol, β-terpineol, γ-terpineol and the like.

Examples of polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, β-pinene/limonene resin made from the above-described terpene compounds, and hydrogen obtained by hydrogenating the terpene resin. Additive terpene resins are also included.
Examples of the terpene phenol include a resin obtained by copolymerizing the terpene compound and a phenolic compound, and a resin obtained by hydrogenating the resin. Specifically, the terpene compound, the phenolic compound and formalin are condensed. resin. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol.
Examples of aromatic modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating the resins. The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring. Examples include phenol compounds such as phenol, alkylphenol, alkoxyphenol, unsaturated hydrocarbon group-containing phenol; naphthol compounds such as unsaturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, unsaturated hydrocarbon group-containing styrene; coumarone, indene, and the like.

Examples of pt-butylphenol acetylene resins include resins obtained by condensation reaction of pt-butylphenol and acetylene.

Although the acrylic resin is not particularly limited, solvent-free acrylic resins can be preferably used because they contain few impurities and give a resin with a sharp molecular weight distribution.

Solvent-free acrylic resin can be produced by a high-temperature continuous polymerization method (high-temperature continuous bulk polymerization method) (U.S. Pat. No. 4,414,370) without using auxiliary materials such as polymerization initiators, chain transfer agents, organic solvents, etc. as much as possible. Specification, JP-A-59-6207, JP-B-5-58005, JP-A-1-313522, US Pat. (meth)acrylic resins (polymers) synthesized by the method described in (1)-45, etc.). In the present invention, (meth)acryl means methacryl and acryl.

It is preferable that the acrylic resin substantially does not contain a polymerization initiator, a chain transfer agent, an organic solvent, etc., which are auxiliary materials. Further, the acrylic resin preferably has a relatively narrow composition distribution and molecular weight distribution obtained by continuous polymerization.

As described above, the acrylic resin is preferably one that does not substantially contain auxiliary materials such as a polymerization initiator, a chain transfer agent, an organic solvent, etc., that is, one that has high purity. The purity of the acrylic resin (ratio of resin contained in the resin) is preferably 95% by mass or more, more preferably 97% by mass or more.

Examples of monomer components constituting the acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamides, and (meth)acrylamide derivatives. (Meth)acrylic acid derivatives such as

In addition to (meth)acrylic acid and (meth)acrylic acid derivatives, styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, divinylnaphthalene, etc., may be used as monomer components constituting the acrylic resin. of aromatic vinyls may be used.

The acrylic resin may be a resin composed only of a (meth)acrylic component, or a resin containing components other than the (meth)acrylic component as constituent elements.
Moreover, the acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

Examples of resins such as styrene resins and coumarone-indene resins include Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemicals, Products such as Nichinuri Chemical Co., Ltd., Nippon Shokubai Co., Ltd., JX Energy Co., Ltd., Arakawa Chemical Co., Ltd., Taoka Chemical Co., Ltd. can be used.

In the rubber composition, the total content of the resins (the styrene resin and other resins in a solid state at room temperature (25°C)) is preferably 1 to 50 parts by mass, more preferably 3 to 30 parts by mass, still more preferably 5 to 25 parts by mass.

The rubber composition preferably contains oil as a softening agent.
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, etc. 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, naphthenic process oil is preferable because the effect of the present invention can be obtained more favorably.

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

The content of the oil is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 15 parts by mass or more with respect to 100 parts by mass of the rubber component. Also, the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less. Within the above numerical range, the performance balance tends to be remarkably improved.
The content of oil also includes the amount of oil contained in the rubber (oil-extended rubber).

The rubber composition may contain a liquid diene polymer as a softening agent.
The liquid diene-based polymer is a diene-based polymer that is liquid at normal temperature (25° C.). The liquid diene-based polymer preferably has a polystyrene equivalent weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) of 1.0×10 ³ to 2.0×10 ⁵ , preferably 3.0. More preferably, it is from ×10 ³ to 1.5×10 ⁴ . Liquid diene-based polymers include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), and the like. be done.

In the rubber composition, the total content of the softening agent (the oil, the liquid diene-based polymerization, etc., which is liquid at room temperature (25° C.), resin, etc.) is 100 mass of the rubber component from the viewpoint of the performance balance. parts, preferably 5 to 50 parts by mass, more preferably 10 to 30 parts by mass, still more preferably 15 to 30 parts by mass.

The rubber composition preferably contains silica as a filler. As a result, a reinforcing effect is obtained, wet grip performance and the like are improved, and the effects of the present invention can be favorably obtained. Examples of silica include dry silica (anhydrous silica) and wet silica (hydrous silica). Among them, wet-process silica is preferable because it has many silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 40 m ² /g or more, more preferably 70 m ² /g or more, still more preferably 110 m ² /g or more. By making it more than the lower limit, there is a tendency that sufficient wet grip performance can be obtained. Also, N ₂ SA of silica is preferably 220 m ² /g or less, more preferably 200 m ² /g or less. By making it below the upper limit, there is a tendency that good dispersibility can be obtained.
The N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-93.

The content of silica is preferably 60 parts by mass or more, more preferably 70 parts by mass or more, relative to 100 parts by mass of the rubber component. By making it more than the lower limit, there is a tendency that sufficient wet grip performance can be obtained. The content is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and even more preferably 100 parts by mass or less. By making it below the upper limit, there is a tendency that good dispersibility can be obtained.

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

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; 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; vinyl-based such as methoxysilane; amino-based such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These may be used alone or in combination of two or more. Among them, sulfide-based and mercapto-based are preferable because the effect of the present invention can be obtained more favorably.

Examples of silane coupling agents that can be used include products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azmax Co., Ltd., Dow Corning Toray Co., Ltd., and the like.

The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, relative to 100 parts by mass of silica. When the amount is 3 parts by mass or more, there is a tendency that the effect of addition can be obtained. Moreover, 20 mass parts or less are preferable, and, as for the said content, 15 mass parts or less are more preferable. When it is 20 parts by mass or less, an effect commensurate with the blending amount is obtained, and there is a tendency to obtain good workability during kneading.

From the viewpoint of the performance balance, the rubber composition preferably contains carbon black as a filler. 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 CTAB specific surface area (cetyltrimethylammonium bromide adsorption specific surface area) of carbon black is preferably 150 m ² /g or more, preferably 155 m ² /g or more, from the viewpoint of wet grip performance, abrasion resistance, and steering stability. Although the upper limit is not particularly limited, it is preferably 250 m ² /g or less, more preferably 200 m ² /g or less, from the viewpoint of dispersibility of carbon black.
The CTAB specific surface area is a value measured according to JIS K6217-3:2001.

The iodine adsorption amount (IA) (mg/g) of carbon black is preferably 100-300 mg/g, more preferably 120-230 mg/g, still more preferably 140-190 mg/g. When the iodine adsorption amount (IA) is within the above range, an improvement effect such as wear resistance is suitably obtained, and the performance balance is remarkably improved.
Note that IA is a value measured according to JIS K6217-1:2008.

The ratio of CTAB specific surface area to IA (mg/g) of carbon black (CTAB specific surface area/IA) is preferably 0.8 to 1.2 m ² /mg, more preferably 0.85, from the viewpoint of the performance balance. ~1.15 m ² /mg, more preferably 0.9 to 1.1 m ² /mg.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 165 m ² /g or more, more preferably 170 m 2 /g or more, still more preferably 170 m ² /g or more, from the viewpoint of wet grip performance, wear resistance, and steering stability. 175 m ² /g or more. Although the upper limit is not particularly limited, it is preferably 250 m ² /g or less, more preferably 200 m ² /g or less, from the viewpoint of dispersibility of carbon black.
The N ₂ SA of carbon black can be measured according to JIS K 6217-2:2001.

The content of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. When the content is 1 part by mass or more, there is a tendency that sufficient reinforcement can be obtained and good wear resistance can be obtained. Moreover, the content is preferably 40 parts by mass or less, more preferably 30 parts by mass or less. When it is 40 parts by mass or less, there is a tendency that good rolling resistance can be obtained. The content of carbon black having the CTAB specific surface area, IA, and N ₂ SA is also preferably within the same range.

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.

The rubber composition may contain an inorganic filler or an organic filler other than silica and carbon black.

Examples of the inorganic filler include talc, aluminum hydroxide, aluminum oxide, magnesium hydroxide, magnesium oxide, magnesium sulfate, titanium white, titanium black, calcium oxide, calcium hydroxide, magnesium aluminum oxide, clay, pyrophyllite, bentonite. , aluminum silicate, magnesium silicate, calcium silicate, aluminum calcium silicate, magnesium silicate, silicon carbide, zirconium, zirconium oxide, and the like. Examples of the organic filler include cellulose nanofibers. These may be used alone or in combination of two or more.

The total content of fillers (silica, carbon black, inorganic fillers other than these, organic fillers, etc.) is preferably 50 to 200 parts per 100 parts by mass of the rubber component from the viewpoint of the performance balance. Parts by mass, more preferably 60 to 150 parts by mass, still more preferably 70 to 120 parts by mass.

The rubber composition preferably contains 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.

The content of the wax is preferably 1 to 20 parts by mass, more preferably 1.5 to 10 parts by mass with respect to 100 parts by mass of the rubber component, from the viewpoint of the performance balance.

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.

The rubber composition preferably contains 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-based antioxidants and quinoline-based antioxidants are preferable, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 2,2,4-trimethyl-1 , 2-dihydroquinoline polymers are more preferred.

The content of the anti-aging agent is preferably 1 to 10 parts by mass or more, more preferably 2 to 7 parts by mass or more with respect to 100 parts by mass of the rubber component, from the viewpoint of the performance balance.

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

The rubber composition preferably contains stearic acid. The stearic acid content is preferably 0.5 to 10 parts by mass or more, more preferably 1 to 5 parts by mass or more, based on 100 parts by mass of the rubber component, from the viewpoint of the performance balance.

As the stearic acid, conventionally known ones can be used, for example, NOF Corporation, NOF, Kao Corporation, Wako Pure Chemical Industries, Ltd., Chiba Fatty Acids Co., Ltd. products can be used. .

The rubber composition preferably contains zinc oxide. The content of zinc oxide is preferably 0.5 to 10 parts by mass or more, more preferably 1 to 5 parts by mass or more with respect to 100 parts by mass of the rubber component, from the viewpoint of the above-mentioned performance balance.

As the zinc oxide, conventionally known ones can be used. products can be used.

The rubber composition preferably contains sulfur.
The content of sulfur is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, and even more preferably 1 to 3 parts by mass with respect to 100 parts by mass of the rubber component, from the viewpoint of the performance balance. .

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., Nihon Kantan Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. .

The rubber composition preferably contains a vulcanization accelerator.
The content of the vulcanization accelerator is preferably 1 to 10 parts by mass, more preferably 3 to 7 parts by mass with respect to 100 parts by mass of the rubber component, from the viewpoint of the aforementioned performance balance.

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 preferable from the viewpoint of the aforementioned performance balance.

The rubber composition may contain an organic cross-linking agent.
Examples of the organic cross-linking agent include, but are not limited to, maleimide compounds, alkylphenol/sulfur chloride condensates, organic peroxides, and amine organic sulfides. These may be used alone or in combination of two or more, and may be used in combination with sulfur. The organic cross-linking agent is blended, for example, in an amount of 10 parts by mass or less with respect to 100 parts by mass of the rubber component.

The rubber composition of the present invention is manufactured by a general method. That is, it can be produced by kneading each of the above components with a Banbury mixer, a kneader, an open roll, or the like, and then vulcanizing.

As kneading conditions, in the base kneading step in which additives other than the vulcanizing agent and the vulcanization accelerator are kneaded, the kneading temperature is usually 50 to 200°C, preferably 80 to 190°C, and the kneading time is usually 30°C. seconds to 30 minutes, preferably 1 minute to 30 minutes. In the finishing kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 100°C or lower, preferably room temperature to 80°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 120-200°C, preferably 140-180°C.

The rubber composition of the present invention is suitably used for treads (cap treads), but it is also used for members other than treads, such as sidewalls, base treads, undertreads, clinch apex, bead apex, breaker cushion rubber, and carcass cords. It may be used for coating 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 blended with the above components is extruded in an unvulcanized stage according to the shape of each tire member such as the tread, and molded together with other tire members on a tire molding machine by an ordinary method. to form an unvulcanized tire. A tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

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.
NR: TSR20
SBR1 (modified): modified SBR synthesized in Production Example 1
SBR2 (unmodified): styrene content 35 mass%, vinyl content 35 mass%, weight average molecular weight Mw 1,050,000 BR: unmodified BR (cis content 97 mass%)
Carbon black 1: CTAB 160 m ² /g, N ₂ SA 179 m ² /g, IA 166 mg/g
Carbon black 2: CTAB111m ² /g, N ₂ SA111m ² /g
Silica: N ₂ SA 175 m ² /g
Silane coupling agent: bis(3-triethoxysilylpropyl) disulfide oil: naphthenic process oil styrene resin: copolymer of α-methylstyrene and styrene (softening point 85°C, Tg 43°C)
Wax: Paraffin wax Antioxidant 1: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine Antioxidant 2: Poly(2,2,4-trimethyl-1,2-dihydroquinoline )
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: N-cyclohexyl-2-benzothiazolylsulfenamide vulcanization accelerator 2: Diphenylguanidine

(Production example 1)
In a nitrogen atmosphere, 3-dimethylaminopropyltrimethoxysilane was placed in a 100 ml volumetric flask, and anhydrous hexane was further added to prepare a terminal modifier.
n-Hexane, styrene, butadiene and tetramethylethylenediamine were added to a sufficiently nitrogen-purged pressure vessel, and the temperature was raised to 40°C. Next, after adding butyllithium, the temperature was raised to 50° C. and the mixture was stirred. Next, a silicon tetrachloride/hexane solution was added and stirred. Next, the terminal modifier was added and stirred. After methanol in which 2,6-tert-butyl-p-cresol was dissolved was added to the reaction solution, the reaction solution was placed in a stainless container containing methanol to collect aggregates. The resulting aggregate was dried under reduced pressure for 24 hours to obtain modified SBR1. The resulting modified SBR1 had a styrene content of 25% by mass, a vinyl content of 60% by mass, and a weight average molecular weight Mw of 150,000.

<Analysis of SBR>
The analysis of SBR1 and 2 was performed by the following method.
(Measurement of weight average molecular weight Mw)
The weight average molecular weight Mw of the polymer is measured by a gel permeation chromatograph (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M manufactured by Tosoh Corporation). Based on the value, it was determined as a standard polystyrene conversion value.

(Structure identification)
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 170 ° C. for 10 minutes, and a test tire ( Size: 195/65R15) was manufactured. Evaluation was performed using the obtained test tires, and the results are shown in Table 1.

(Low fuel consumption)
Using a rolling resistance tester, the test tire is run at a rim (15 x 6 JJ), internal pressure (230 kPa), load (3.43 kN), speed (80 km / h), and the rolling resistance is measured and compared. It is indicated as an index when Example 1 is set to 100 (fuel efficiency index). A larger index indicates better fuel efficiency.

(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.

(steering stability)
Each test tire was mounted on all wheels of a vehicle (3000 cc), and the actual vehicle was run on a test course under general running conditions. The stability of control during steering (driving stability) was sensory-evaluated by a test driver, and indexed with Comparative Example 1 being 100. A larger steering stability index indicates better steering stability.

(wear resistance)
Each test tire was mounted on a domestic FF car, the groove depth of the tire tread portion was measured after a running distance of 8000 km, and the running distance when the tire groove depth was reduced by 1 mm was calculated. It is indicated by the index of hours (wear resistance index). The larger the index, the longer the running distance when the tire groove depth is reduced by 1 mm, and the better the wear resistance.

From Table 1, it can be seen that the examples containing isoprene rubber, SBR having a predetermined average molecular weight and average vinyl content, and styrenic resin in a predetermined ratio have the following characteristics: A good balance of fuel efficiency, wet grip performance, wear resistance and steering stability was obtained compared to the comparative examples that did not satisfy the average molecular weight and vinyl content.

Claims (9)

including isoprene-based rubber, styrene-butadiene rubber and styrene-based resin,
The content of the isoprene-based rubber in 100% by mass of the rubber component is 30% by mass or more, and the content of the styrene-butadiene rubber is 30% by mass or more,
The styrene-butadiene rubber has an average molecular weight of 300,000 or less and an average vinyl content of 40% by mass or more,
A rubber composition for tires in which the content of the styrene-butadiene rubber/the content of the styrene-based resin is 1.0 to 7.0 (provided that the rubber component and the silicon content in terms of oxide are 1.0% by mass excluding rubber compositions for tires containing the above zirconium compounds) . 2. The rubber composition for tires according to claim 1, wherein the content of silica is 70 parts by mass or more per 100 parts by mass of the rubber component. 3. The rubber composition for tires according to claim 1, wherein the content of carbon black having a CTAB specific surface area of 150 m ² /g or more is 5 to 30 parts by mass with respect to 100 parts by mass of the rubber component. The rubber composition for tires according to any one of claims 1 to 3, wherein the oil content is 10 to 30 parts by mass with respect to 100 parts by mass of the rubber component. The rubber composition for tires according to any one of claims 1 to 4, wherein the content of butadiene rubber in 100% by mass of the rubber component is 5 to 30% by mass. The iodine adsorption amount (IA) of the carbon black is 100 to 300 mg / g, the ratio of the CTAB specific surface area to the IA (mg / g) (CTAB specific surface area / IA) is 0.8 to 1.2 m ² /mg, nitrogen adsorption specific surface area is 165m ² /g or more, the rubber composition for tires according to any one of claims 3 to 5. The rubber composition for tires according to any one of claims 1 to 6, wherein the styrene-butadiene rubber contains at least one styrene-butadiene rubber having a weight average molecular weight of 200,000 or less. The rubber composition for tires according to any one of claims 1 to 7, wherein the oil content is 5 to 50 parts by mass with respect to 100 parts by mass of the rubber component. A pneumatic tire produced using the rubber composition according to any one of claims 1 to 8 .