JP6996094B2 - Rubber composition for tires and pneumatic tires - Google Patents

Description

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

In recent years, due to growing interest in environmental issues, there is a growing demand for fuel efficiency in automobiles, and rubber compositions used in automobile tires are also required to have excellent fuel efficiency. ..

As a method for improving fuel efficiency, for example, a method of reducing the amount of the reinforcing filler is known, but in this method, the wet grip performance and the dry grip performance are reduced due to the decrease in the calorific value and the reinforcing property of the rubber composition. , Abrasion resistance, etc. tend to deteriorate. As described above, these performances generally have a contradictory relationship with fuel efficiency, and it is difficult to obtain each performance in a well-balanced manner.

The present invention solves the above problems and provides a rubber composition for a tire having improved fuel efficiency, dry grip performance, wet grip performance and wear resistance in a well-balanced manner, and a pneumatic tire produced by using the rubber composition. The purpose is to provide.

The present invention contains styrene-butadiene rubber, butadiene rubber and a resin component, and the content of the styrene-butadiene rubber in 100% by mass of the rubber component is 50% by mass or more, and the content of the butadiene rubber is less than 35% by mass. The styrene-butadiene rubber has an average vinyl content of 40% by mass or more, and the resin component relates to a rubber composition for a tire containing two or more kinds of aromatic ring-containing resins having different softening points of 5 ° C. or more.

The content of carbon black having a CTAB specific surface area of 170 m ² / g or more with respect to 100 parts by mass of the rubber component is preferably 15 to 30 parts by mass.
The content of silica with respect to 100 parts by mass of the rubber component is preferably 65 parts by mass or more.

The content of each of the two or more aromatic ring-containing resins with respect to 100 parts by mass of the rubber component is preferably 3 to 30 parts by mass.
It is preferable that the two or more kinds of aromatic ring-containing resins contain a C5C9 resin and a styrene-based resin.

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

According to the present invention, it is a rubber composition for a tire containing styrene-butadiene rubber having a predetermined average vinyl amount, butadiene rubber, and two or more kinds of aromatic ring-containing resins having different softening points of 5 ° C. or more in a predetermined ratio. Therefore, low fuel consumption, dry grip performance, wet grip performance and wear resistance are improved in a well-balanced manner.

The rubber composition for a tire of the present invention comprises styrene-butadiene rubber (SBR) having a predetermined average vinyl amount, butadiene rubber (BR), and two or more kinds of aromatic ring-containing resins having different softening points of 5 ° C. or more. It is included in proportion.

The rubber composition has the above-mentioned effects, and it is presumed that this is achieved by the following effects.
In a compounding system containing a rubber component obtained by adding BR to SBR as the main component, by increasing the vinyl content of SBR, dry grip performance and wet grip performance are improved, and an aromatic ring-containing resin having high compatibility with SBR. It is considered that the performance balance of fuel efficiency, dry grip performance, wet grip performance and wear resistance is remarkably (synergistically) improved by blending a plurality of types of resins having different softening points.

Further, (1) 15 to 30 parts by mass of carbon black having a CTAB specific surface area of 170 m ² / g or more is blended, (2) 65 parts by mass or more of silica is blended, and (3) the content of each aromatic ring-containing resin is 3. By applying at least one method of adjusting to ~ 30 parts by mass, (4) using C5C9 resin and styrene-based resin as the aromatic ring-containing resin, the performance balance is more significantly (synergistically) improved. It is considered to be.

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 amount is preferably 45% by mass or more, more preferably 50% by mass or more, from the viewpoint of the performance balance. Similarly, from the viewpoint of the performance balance, the upper limit is preferably 70% by mass or less, more preferably 65% by mass or less, and further preferably 62% by mass or less.

Here, the average vinyl amount of SBR is {Σ (content ratio of each SBR in all SBR × vinyl amount of each SBR × weight average molecular weight of each SBR)} / average molecular weight of all SBR.

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 in all SBR. In the case of a rubber component composed of 55% by mass of SBR (A), 10% by mass of SBR (B), 10% by mass of NR, and 25% by mass of BR, the SBR content ratio (mass ratio) is SBR (A), (B). The content ratios of are 0.846 (= 55 / (55 + 10)) and 0.154 (= 10 / (55 + 10)), respectively. Therefore, for example, the rubber component is SBR (A) (styrene content 25% by mass, vinyl). When the amount is 60% by mass, Mw 150,000) 55% by mass, SBR (B) (styrene amount 40% by mass, vinyl amount 30% by mass, Mw 950,000) 10% by mass, NR 10% by mass, BR 25% by mass, the average of SBR The molecular weight is 273,070,000 (273,077 = 55 / (55 + 10) × 150,000 + 10 / (55 + 10) × 950,000).

Therefore, the rubber component is SBR (A) (styrene amount 25% by mass, vinyl amount 60% by mass, Mw 150,000) 55% by mass, SBR (B) (styrene amount 40% by mass, vinyl amount 30% by mass, Mw 950,000). When it is composed of 10% by mass, NR10% by mass, and BR25% by mass, the average vinyl amount is 43.9% by mass (= {55 / (55 + 10) × 60 × 150,000 + 10 / (55 + 10) × 30 × 950,000} /. 273.77 million).

The amount of styrene in each SBR is preferably 5% by mass or more, more preferably 10% by mass or more. By setting it above the lower limit, good dry grip performance and wet grip performance tend to be obtained. The amount of styrene is preferably 50% by mass or less, more preferably 45% by mass or less. By setting it below the upper limit, heat generation tends to be small and good fuel efficiency tends to be obtained.
The amount of styrene can be measured by the method described in Examples described later.

The amount of vinyl in each SBR is preferably 25% by mass or more, more preferably 30% by mass or more. By setting it above the lower limit, good dry grip performance and wet grip performance tend to be obtained. The amount of vinyl is preferably 65% by mass or less, more preferably 60% by mass or less. By setting it below the upper limit, good wear resistance tends to be obtained.
The amount of vinyl (1,2-bonded butadiene unit amount) can be measured by the method described in Examples described later.

The weight average molecular weight Mw of each SBR is preferably 100,000 or more, more preferably 150,000 or more. By setting it above the lower limit, good fuel efficiency and wear resistance tend to be obtained. The Mw is preferably 1.1 million or less, more preferably 1.05 million or less, still more preferably 1 million or less. By setting it below the upper limit, good workability tends to be obtained.
From the viewpoint of the performance balance, the SBR preferably contains at least one SBR having a Mw of 500,000 or more (preferably 750,000 or more, more preferably 850,000 or more).
Mw can be measured by the method described in Examples described later.

The content of SBR in 100% by mass of the rubber component is 50% by mass or more, preferably 55% by mass or more, and more preferably 60% by mass or more from the viewpoint of dry grip performance, wet grip performance, and wear resistance. From the viewpoint of fuel efficiency, the content is preferably 90% by mass or less, more preferably 80% by mass or less, and further preferably 75% 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) and the like can be used. The SBR may be either a non-modified SBR or a modified SBR, but from the viewpoint of the performance balance, it is preferable to use at least one modified SBR.

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

Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group and a disulfide. Examples thereof include a group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group and an epoxy group. .. 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 replaced with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxy group having 1 to 6 carbon atoms). An alkoxysilyl group having 1 to 6 carbon atoms) is preferable.

（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.

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

The modified SBR modified by the compound (modifying agent) represented by the above formula includes, among others, the polymerization terminal (active terminal) of the solution-polymerized styrene-butadiene rubber (S-SBR) using the compound represented by the above formula. Modified SBR (modified SBR or the like described in JP-A-2010-111753) is preferably used.

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

Specific examples of the above modifier include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, and 2-diethylaminoethyltri. Examples thereof include methoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane. Of these, 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropyltriethoxysilane, and 3-diethylaminopropyltrimethoxysilane are preferable. These may be used alone or in combination of two or more.

As the modified SBR, a modified SBR modified with the following compound (modifying agent) can also be preferably used. Examples of the modifier include polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethanetriglycidyl ether, and trimethylolpropane triglycidyl ether; and two or more diglycidylated bisphenol A and the like. Polyepoxidic compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, polyepoxidized liquid polybutadiene; 4,4'-diglycidyl-diphenyl Epoxide group-containing tertiary amines such as methylamine, 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N, N'-diglycidyl-4-glycidyloxyaniline, diglycidyl orthotoluidine, tetraglycidylmethoxylenidin. , Tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, tetraglycidyl-1,3-bisaminomethylcyclohexane and other diglycidylamino compounds;

Amino group-containing acid chlorides such as bis- (1-methylpropyl) carbamate chloride, 4-morpholincarbonyl chloride, 1-pyrrolidincarbonyl chloride, N, N-dimethylcarbamide acid chloride, N, N-diethylcarbamide acid chloride; 1 , 3-Bis- (Glysidyloxypropyl) -Tetramethyldisiloxane, (3-Glysidyloxypropyl) -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- (methyldisilyl) 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' -A (thio) benzophenone compound having an amino group such as bis- (tetraethylamino) benzophenone and / or a substituted amino group; 4-N, N-dimethylaminobenzaldehyde, 4-N, N-diphenylaminobenzaldehyde, 4-N, Benzaldehyde compounds having an amino group and / or a substituted amino group such as N-divinylaminobenzaldehyde; N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-t-butyl- N-substituted pyrrolidone such as 2-pyrrolidone and N-methyl-5-methyl-2-pyrrolidone N-substituted piperidone such as N-methyl-2-piperidone, N-vinyl-2-piperidone and N-phenyl-2-piperidone N-Methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurilolactam, N-vinyl-ω-laurilolactam, 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-dimethylaminoacetophen, 4-N, N-diethylaminoacetophenone, 1,3-bis (diphenyl) Amino) -2-propanone, 1,7-bis (methylethylamino) -4-heptanone and the like can be mentioned. Of these, modified SBR modified with alkoxysilane is preferable.
The modification with the above compound (denaturing agent) can be carried out by a known method.

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

The BR is not particularly limited, and BR having a high cis content, BR containing syndiotactic polybutadiene crystals, and the like can be used. The BR may be either a non-modified BR or a modified BR, and examples of the modified BR include a modified BR into which the above-mentioned functional group has been introduced. These may be used alone or in combination of two or more. In particular, the cis content of BR is preferably 90% by mass or more (preferably 95% by mass or more) because the wear resistance is improved. The cis content can be measured by infrared absorption spectrum analysis.

As the BR, for example, products such as Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Corporation can be used.

The content of BR in 100% by mass of the rubber component is less than 35% by mass, preferably 32% by mass or less, and more preferably 30% by mass or less from the viewpoint of the performance balance. The content is preferably 5% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more. By setting it above the lower limit, good wear resistance and low fuel consumption tend to be obtained.

As rubber components that can be used in addition to SBR and BR, diene-based rubbers such as isoprene-based rubber, acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR) are used. Rubber is mentioned. These diene-based rubbers may be used alone or in combination of two or more. Of these, isoprene-based rubber is preferable because it can further improve fuel efficiency and the like.

Examples of the isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR and the like. As the NR, for example, SIR20, RSS # 3, TSR20 and the like, which are common in the tire industry, can be used. The IR is not particularly limited, and for example, an IR 2200 or the like, which is common in the tire industry, can be used. Modified NR includes deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc., and modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Examples of the 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 the isoprene-based rubber in 100% by mass of the rubber component is preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 15% by mass or less. By setting the value to the upper limit or less, the SBR amount and the BR amount are secured, and the performance balance tends to be remarkably improved. The lower limit is not particularly limited, but when blended, 3% by mass or more is preferable, and 5% by mass or more is more preferable from the viewpoint of fuel efficiency.

The rubber composition contains a resin component containing two or more kinds of aromatic ring-containing resins having different softening points of 5 ° C. or more. The aromatic ring means a conjugated unsaturated ring structure in which the number of electrons contained in the π-electron system on the ring is 4n + 2 (n = 0 or a natural number), and includes both monocyclic and polycyclic rings (both monocyclic and polycyclic). Specifically, aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, phenanthrene, inden, and fluorene).

The aromatic ring-containing resin is a polymer using a monomer having an aromatic ring such as a benzene ring as a constituent monomer. Specifically, it has a homopolymer obtained by independently polymerizing a monomer having an aromatic ring such as a styrene-based monomer described later; a C9 distillate such as vinyl toluene or inden; and having two or more kinds of aromatic rings. In addition to a copolymer obtained by copolymerizing a monomer, a monomer having an aromatic ring and a copolymer of another monomer copolymerizable therewith can also be mentioned.

The difference in softening points between the two or more aromatic ring-containing resins is preferably 7 ° C. or higher, more preferably 8 ° C. or higher, from the viewpoint of the performance balance. The upper limit of the difference in softening points is not particularly limited, but is preferably 30 ° C. or lower, more preferably 20 ° C. or lower, and even more preferably 15 ° C. or lower. When three or more kinds of aromatic ring-containing resins are contained, the difference between the softening points of at least two kinds may be 5 ° C. or more.
In the present invention, the softening point is the temperature at which the ball drops when the softening point defined in JIS K 6220-1: 2001 is measured by a ring-shaped softening point measuring device.

The blending ratio of the aromatic ring-containing resin at the high softening point and the aromatic ring-containing resin at the low softening point (the aromatic ring-containing resin at the high softening point / the aromatic ring-containing resin at the low softening point (mass ratio)) has the above-mentioned performance balance. From the viewpoint, it is preferably 10/90 to 80/20, more preferably 20/80 to 70/30, and even more preferably 23/77 to 68/32.

The softening point of each of the two or more kinds of aromatic ring-containing resins 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 dry grip performance and wet grip performance tend to be obtained. The softening point is preferably 160 ° C. or lower, more preferably 130 ° C. or lower, and even more preferably 110 ° C. or lower. When the temperature is 160 ° C. or lower, the dispersibility of the resin becomes good, and the dry grip performance, the wet grip performance, and the fuel efficiency tend to be improved.

The content of each of the two or more kinds of aromatic ring-containing resins is preferably 3 parts by mass or more, and more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 30 parts by mass or less, more preferably 25 parts by mass or less. Within the above range, a good balance of performance tends to be obtained.

In the rubber composition, the total content of the two or more kinds of aromatic ring-containing resins is preferably 6 parts by mass or more, more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and further preferably 25 parts by mass or less. Within the above range, a good balance of performance tends to be obtained.

As the aromatic ring-containing resin, from the viewpoint of the performance balance, at room temperature (25 ° C.) such as C9 resin, C5C9 resin (copolymer resin using C5 fraction and C9 fraction as raw materials), styrene resin and the like. Solid resin is preferable, and C5C9 resin and styrene resin are particularly preferable.

Examples of the C9 resin include a solid polymer obtained by (co) polymerizing a C9 distillate using a Friedelcrafts-type catalyst or the like, and specific examples thereof include a copolymer containing inden as a main component. Examples thereof include a copolymer containing methyl inden as a main component, a copolymer containing α-methylstyrene as a main component, and a copolymer containing vinyl toluene as a main component. The C5C9 resin is a copolymer resin using a C5 fraction and a C9 fraction such as indene as raw materials. The C5 distillate includes olefin hydrocarbons such as 1-pentene, 2-pentene and 2-methyl-1-butene, 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene and the like. Diolefin hydrocarbons and the like are included.

The styrene-based resin is a polymer using a styrene-based monomer as a constituent monomer, and examples thereof include a polymer obtained by polymerizing a styrene-based monomer as a main component (50% by mass or more). Specifically, styrene-based monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-Chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) are individually polymerized, and in addition to copolymers obtained by copolymerizing two or more styrene-based monomers, styrene-based monomers And other monomer copolymers that can be copolymerized with this.

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

Among them, α-methylstyrene resin (α-methylstyrene homopolymer, copolymer of α-methylstyrene and styrene, etc.) is preferable from the viewpoint of the performance balance.

As the aromatic ring-containing resin, a kumaron indene resin can also be used. The kumaron inden resin is a resin containing kumaron and inden as monomer components constituting the skeleton (main chain) of the resin. Examples of the monomer component contained in the skeleton other than kumaron and indene include styrene, α-methylstyrene, methylindene, vinyltoluene and the like.

The rubber composition may contain a resin in a solid state at room temperature (25 ° C.) other than the C9, C5C9 resin, styrene resin, and Kumaron inden resin. The resin is not particularly limited as long as it is widely used in the tire industry, and examples thereof include a terpene resin, a pt-butylphenol acetylene resin, and an acrylic resin.

Examples of the terpene-based resin include polyterpenes, terpene phenols, aromatic-modified terpene resins and the like.
Polyterpene is a resin obtained by polymerizing a terpene compound and a hydrogenated additive thereof. The _terpene compound is a hydrocarbon having a composition of _{( C 5 H 8} ) _n and an oxygen _- containing derivative _thereof . ), Etc., which are compounds having a terpene as a basic skeleton, for example, α-pinene, β-pinene, dipentene, limonene, milsen, aloocimen, ossimen, α-ferandrene, α-terpinene, γ-terpinene, terpinolene. , 1,8-Cineol, 1,4-Cineol, α-terpineol, β-terpineol, γ-terpineol and the like.

Examples of the polyterpene include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene / limonene resin made from the above-mentioned terpene compound, and hydrogen added to the terpene resin. Additive terpene resin can also be mentioned.
Examples of the terpene phenol include a resin obtained by copolymerizing the above-mentioned terpene compound and the phenol-based compound, and a resin obtained by hydrogenating the resin. Specifically, the above-mentioned terpene compound, the phenol-based compound and the formalin are condensed. Resin is mentioned. Examples of the phenolic compound include phenol, bisphenol A, cresol, xylenol and the like.
Examples of the aromatic-modified terpene resin include a resin obtained by modifying a terpene resin with an aromatic compound, and a resin obtained by hydrogenating the resin. The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and for example, a phenol compound such as a phenol, an alkylphenol, an alkoxyphenol, or an unsaturated hydrocarbon group-containing phenol; naphthol, alkylnaphthol, alkoxynaphthol, etc. Naftor compounds such as unsaturated hydrocarbon group-containing naphthols; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, unsaturated hydrocarbon group-containing styrene; kumaron, inden and the like can be mentioned.

Examples of the pt-butylphenol acetylene resin include a resin obtained by subjecting pt-butylphenol and acetylene to a condensation reaction.

The acrylic resin is not particularly limited, but a solvent-free acrylic resin can be preferably used from the viewpoint that a resin having few impurities and a sharp molecular weight distribution can be obtained.

The solvent-free acrylic resin is a high-temperature continuous polymerization method (high-temperature continuous lump polymerization method) (US Pat. No. 4,414,370) without using polymerization initiators, chain transfer agents, organic solvents, etc. as auxiliary raw materials as much as possible. Japanese Patent Application Laid-Open No. 59-6207, Japanese Patent Application Laid-Open No. 5-58805, Japanese Patent Application Laid-Open No. 1-313522, US Pat. No. 5,010,166, Toa Synthetic Research Annual Report TREND2000 No. 3 p42 Examples thereof include a (meth) acrylic resin (polymer) synthesized by the method described in −45 and the like). In the present invention, (meth) acrylic means methacrylic and acrylic.

It is preferable that the acrylic resin does not substantially contain a polymerization initiator, a chain transfer agent, an organic solvent and the like, which are auxiliary raw 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 a polymerization initiator, a chain transfer agent, an organic solvent, etc., which are auxiliary raw materials, that is, one having high purity. The purity of the acrylic resin (ratio of the resin contained in the resin) is preferably 95% by mass or more, more preferably 97% by mass or more.

Examples of the monomer component constituting the acrylic resin include (meth) acrylic acid, (meth) acrylic acid ester (alkyl ester, aryl ester, aralkyl ester, etc.), (meth) acrylamide, and (meth) acrylamide derivative. (Meta) acrylic acid derivatives such as.

In addition, as the monomer component constituting the acrylic resin, styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, divinylnaphthalene, etc., together with (meth) acrylic acid and (meth) acrylic acid derivative, etc. Aromatic vinyl may be used.

The acrylic resin may be a resin composed of only a (meth) acrylic component or a resin having a component other than the (meth) acrylic component as a component.
Further, the acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

Examples of resins such as aromatic ring-containing resins include Exxon Chemical Co., Ltd., Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Toso Co., Ltd., Rutgers Chemicals Co., Ltd., BASF Co., Ltd., and Arizona Chemical Co., Ltd. Uses products from, Stractol, Line Chemie, Flow Polymer, Nikko Chemical Co., Ltd., Nippon Catalyst Co., Ltd., JX Energy Co., Ltd., Arakawa Chemical Industry Co., Ltd., Taoka Chemical Industry Co., Ltd., etc. can.

In the rubber composition, the total content of the resin component (the aromatic ring-containing resin, the resin in a solid state at room temperature (25 ° C.) such as other resins) is preferably 5% by mass with respect to 100 parts by mass of the rubber component. More than parts, more preferably 8 parts by mass or more. The content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and further preferably 35 parts by mass or less. Within the above range, a good balance of performance tends to be obtained.

The rubber composition preferably contains silica as a filler. As a result, a reinforcing effect is obtained, dry grip performance, wet grip performance and the like are improved, and the effect of the present invention is satisfactorily obtained. Examples of silica include dry silica (anhydrous silica) and wet silica (hydrous silica). Of these, wet silica is preferable because it has a large number of silanol groups.

The content of silica is preferably 55 parts by mass or more, more preferably 60 parts by mass or more, and further preferably 65 parts by mass or more with respect to 100 parts by mass of the rubber component. By setting it above the lower limit, sufficient dry grip performance and wet grip performance tend to be obtained. The content is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, still more preferably 100 parts by mass or less. By setting it below the upper limit, good dispersibility tends to be obtained.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 150 m ² / g or more, more preferably 160 m ² / g or more, and further preferably 165 m ² / g or more. By setting it above the lower limit, sufficient dry grip performance and wet grip performance tend to be obtained. The N ₂ SA of silica is preferably 220 m ² / g or less, more preferably 200 m ² / g or less. By setting it below the upper limit, good dispersibility tends to be obtained.
The N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-93.

As the silica, for example, products such as Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation can be used.

The rubber composition preferably contains a silane coupling agent together with silica.
The silane coupling agent is not particularly limited, and for example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, and the like. 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-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3- Sulfide type such as triethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, Mercapto type such as NXT and NXT-Z manufactured by Momentive, vinyl triethoxysilane, vinyl tri Vinyl-based such as methoxysilane, amino-based such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane. Examples thereof include nitro-based systems such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, and chloro-based systems such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These may be used alone or in combination of two or more. Among them, a sulfide type and a mercapto type are preferable, and a mercapto type is preferable, because the effect of the present invention can be obtained more satisfactorily.

（式中、ｐは１～３の整数、ｑは１～５の整数、ｋは５～１２の整数である。） As the silane coupling agent, it is preferable to use a silane coupling agent represented by the following formula. This tends to provide excellent fuel economy, dry grip performance, and wet grip performance.

(In the formula, p is an integer of 1 to 3, q is an integer of 1 to 5, and k is an integer of 5 to 12.)

p is an integer of 1 to 3, but 2 is preferable. When p is 3 or less, the coupling reaction tends to be fast.
q is an integer of 1 to 5, but 2 to 4 is preferable, and 3 is more preferable. When q is 1 to 5, synthesis tends to be easy.
k is an integer of 5 to 12, preferably 5 to 10, more preferably 6 to 8, and even more preferably 7.

Examples of the silane coupling agent represented by the above formula include 3-octanoylthio-1-propyltriethoxysilane.

As the silane coupling agent, for example, products such as Degussa, Momentive, Shinetsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Toray Dow Corning Co., Ltd. can be used.

The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, based on 100 parts by mass of silica. When it is 3 parts by mass or more, the effect of addition tends to be obtained. The content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. When it is 20 parts by mass or less, an effect commensurate with the blending amount can be obtained, and good processability at the time of kneading tends to be obtained.

From the viewpoint of the performance balance, the rubber composition preferably contains carbon black as a filler. The carbon black is not particularly limited, and examples thereof include 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 170 m ² / g or more, more preferably 175 m ² / g or more, from the viewpoint of dry grip performance, wet grip performance, and wear resistance. The upper limit is not particularly limited, but from the viewpoint of dispersibility of carbon black, 250 m ² / g or less is preferable, and 220 m ² / g or less is more preferable.
The CTAB specific surface area is a value measured in accordance with JIS K6217-3: 2001.

The iodine adsorption amount (IA) (mg / g) of carbon black is preferably 100 to 300 mg / g, more preferably 150 to 250 mg / g, and further preferably 170 to 230 mg / g. When the iodine adsorption amount (IA) is within the above range, the effect of improving wear resistance and the like is suitably obtained, and the performance balance is remarkably improved.
IA is a value measured in accordance with JIS K6217-1: 2008.

The ratio of the CTAB specific surface area to the 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. It is ~ 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, from the viewpoints of dry grip performance, wet grip performance, wear resistance, and steering stability. More preferably, it is 175 m ² / g or more. The upper limit is not particularly limited, but from the viewpoint of dispersibility of carbon black, 250 m ² / g or less is preferable, and 200 m ² / g or less is more preferable.
The carbon black N ₂ SA can be measured in accordance with JIS K 6217-2: 2001.

The content of carbon black is preferably 10 parts by mass or more, and more preferably 15 parts by mass or more with respect to 100 parts by mass of the rubber component. When it is 10 parts by mass or more, sufficient reinforcing property can be obtained, and good wear resistance tends to be obtained. 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, good rolling resistance tends to be obtained. The content of carbon black having the CTAB specific surface area and IA and _N2SA is also preferably in the same range.

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

Inorganic fillers and organic fillers other than silica and carbon black may be blended in the rubber composition.

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 oxide, clay, pyrophyllite, and 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 and the like. These may be used alone or in combination of two or more.

The total content of the filler (silica, carbon black, other inorganic fillers, organic fillers, etc.) is preferably 50 to 200 with respect to 100 parts by mass of the rubber component from the viewpoint of the performance balance. It is by mass, more preferably 60 to 150 parts by mass, and even more preferably 70 to 120 parts by mass.

The rubber composition preferably contains oil as a softener.
Examples of the oil include process oils, vegetable oils and fats, or mixtures thereof. As the process oil, for example, a paraffin-based process oil, an aroma-based process oil, a naphthenic process oil, or the like can be used. Vegetable oils and fats include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut oil, rosin, pine oil, pineapple, tall oil, corn oil, rice oil, beni flower oil, sesame oil, Examples thereof include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used alone or in combination of two or more. Of these, naphthenic process oils are preferable because the effects of the present invention can be obtained better.

Examples of oils include Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H & R Co., Ltd., Toyokuni Seiyu Co., Ltd., Showa Shell Sekiyu Co., Ltd., and Fuji Kosan Co., Ltd. And other products can be used.

The oil content is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. 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 significantly improved.
The oil content also includes the amount of oil contained in rubber (oil spread rubber).

A liquid diene polymer may be added to the rubber composition as a softening agent.
The liquid diene polymer is a diene polymer in a liquid state at room temperature (25 ° C.). The polystyrene-equivalent weight average molecular weight (Mw) of the liquid diene polymer measured by gel permeation chromatography (GPC) is preferably 1.0 × 10 ³ to 2.0 × ¹⁰⁵ , preferably 3.0. More preferably, it is × 10 ³ to 1.5 × 10 ⁴ . Examples of the liquid diene polymer include a liquid styrene butadiene polymer, a liquid butadiene polymer, a liquid isoprene polymer, and a liquid styrene isoprene copolymer.

In the rubber composition, the total content of the softening agent (hydrocarbon, resin, etc. in a liquid state at room temperature (25 ° C.) such as the oil, the liquid diene polymer, etc.) is the rubber component 100 from the viewpoint of the performance balance. It is preferably 5 to 50 parts by mass, more preferably 10 to 30 parts by mass with respect to parts by mass.

The rubber composition preferably contains wax.
The wax is not particularly limited, and examples thereof include petroleum wax such as paraffin wax and microcrystalline wax; natural wax such as plant wax and animal wax; and synthetic wax such as a polymer such as ethylene and propylene. These may be used alone or in combination of two or more. Of these, petroleum wax is preferable, and paraffin wax is more preferable.

From the viewpoint of the performance balance, the wax content 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.

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

The rubber composition preferably contains an anti-aging agent.
Examples of the antiaging agent include naphthylamine-based antiaging agents such as phenyl-α-naphthylamine; diphenylamine-based antiaging agents such as octylated diphenylamine and 4,4'-bis (α, α'-dimethylbenzyl) diphenylamine; N. -Isopropyl-N'-phenyl-p-phenylenediamine, N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, N, N'-di-2-naphthyl-p-phenylenediamine, etc. P-Phenylenediamine-based anti-aging agent; quinoline-based anti-aging agent such as a polymer of 2,2,4-trimethyl-1,2-dihydroquinolin; 2,6-di-t-butyl-4-methylphenol, Monophenolic antioxidants such as styrenated phenol; tetrakis- [methylene-3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] bis, tris, polyphenolic aging such as methane Examples include inhibitors. These may be used alone or in combination of two or more. Of these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferable, and N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1 are preferable. , 2-Dihydroquinoline polymers are more preferred.

The content of the anti-aging agent is preferably 1 to 10 parts by mass, more preferably 2 to 7 parts by mass 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 Co., Ltd. and the like can be used.

The rubber composition preferably contains stearic acid. The content of stearic acid is preferably 0.5 to 10 parts by mass, and more preferably 1 to 5 parts by mass with respect to 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, and for example, products such as NOF Corporation, NOF Corporation, Kao Corporation, Wako Pure Chemical Industries, Ltd., and Chiba Fatty Acid Co., Ltd. can be used. ..

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

As the zinc oxide, conventionally known zinc oxide can be used, for example, Mitsui Metal Mining Co., Ltd., Toho Zinc Co., Ltd., HakusuiTech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. Products can be used.

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

Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur commonly used in the rubber industry. These may be used alone or in combination of two or more.

As the sulfur, for example, products such as Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Corporation, Flexis Co., Ltd., Nippon Kanryo Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd. can be used. ..

The rubber composition preferably contains a vulcanization accelerator.
From the viewpoint of the performance balance, 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.

Examples of the sulfide accelerator include thiazole-based sulfide accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiadylsulfenamide; tetramethylthiuram disulfide (TMTD). ), Tetrabenzyl thiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N) and other thiuram-based sulfide accelerators; N-cyclohexyl-2-benzothiazolesulfenamide, N-t-butyl- 2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N, N'-diisopropyl-2-benzothiazolesulfenamide, etc. Sulfenamide-based sulphurization accelerator; guanidine-based sulphurization accelerators such as diphenylguanidine, dioltotrilguanidine, orthotrilbiguanidine can be mentioned. These may be used alone or in combination of two or more. Among them, a sulfenamide-based vulcanization accelerator and a guanidine-based vulcanization accelerator are preferable from the viewpoint of the performance balance.

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

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

As the kneading conditions, in the base kneading step of kneading additives other than the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 50 to 200 ° C., preferably 80 to 190 ° C., and the kneading time is usually 30. Seconds to 30 minutes, preferably 1 minute to 30 minutes. In the finish 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. Further, the composition in which the vulcanizing agent and the vulcanization accelerator are kneaded is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 120 to 200 ° C, preferably 140 to 180 ° C.

The rubber composition of the present invention is suitably used for treads (cap treads), but members other than treads, such as sidewalls, base treads, under treads, clinch apex, bead apex, breaker cushion rubber, and carcass cord. It may be used for covering rubber, insulation, chafer, inner liner, etc., and a side reinforcing layer of a run-flat tire.

The pneumatic tire of the present invention is manufactured by a usual method using the above rubber composition.
That is, the rubber composition containing the above components is extruded according to the shape of each tire member such as a tread at the unvulcanized stage, and is molded together with other tire members by a normal method on a tire molding machine. By doing so, an unvulcanized tire is formed. A tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

The present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.
The various chemicals used in the examples will be described below.
NR: TSR20
Modified SBR 1: Modified SBR synthesized in Production Example 1
Modified SBR2: Modified SBR synthesized in Production Example 2
Modified SBR3: Modified SBR synthesized in Production Example 3
BR: Non-denatured BR (cis content 97% by mass)
Carbon black 1: CTAB 180m ² / g, N ₂ SA177m ² / g, IA 188mg / g
Carbon black 2: CTAB111m ² / g, N ₂ SA111m ² / g
Silica: N ₂ SA175m ² / g
Silane coupling agent: 3-octanoylthio-1-propyltriethoxysilane oil: Naften-based process oil Styrene-based resin: Copolymer of α-methylstyrene and styrene (softening point 85 ° C, Tg43 ° C)
C5C9 resin: softening point 94 ° C.
Wax: Paraffin wax Anti-aging agent 1: N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine Anti-aging agent 2: Poly (2,2,4-trimethyl-1,2-dihydroquinoline) )
Stearic acid: Stearic acid "Camellia" manufactured by NOF CORPORATION
Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Metal Mining Co., Ltd. Sulfur: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. 1: N-tert-butyl-2-benzothiazolyl sulphenamide vulcanization accelerator 2: Diphenylguanidine

(Manufacturing Example 1)
Under 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 pressure-resistant container sufficiently substituted with nitrogen, 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 the mixture was stirred. Next, the above-mentioned terminal denaturing agent was added, and stirring was performed. After adding methanol in which 2,6-tert-butyl-p-cresol was dissolved in the reaction solution, the reaction solution was placed in a stainless steel container containing methanol to recover the aggregate. The obtained aggregate was dried under reduced pressure for 24 hours to obtain a modified SBR1. The obtained modified SBR1 had a styrene content of 25% by mass, a vinyl content of 60% by mass, and a weight average molecular weight of Mw of 150,000.

(Manufacturing Example 2)
Under a nitrogen atmosphere, 3-diethylaminopropyltrimethoxysilane 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 pressure-resistant container sufficiently substituted with nitrogen, 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 the mixture was stirred. Next, the above-mentioned terminal denaturing agent was added, and stirring was performed. After adding methanol in which 2,6-tert-butyl-p-cresol was dissolved in the reaction solution, the reaction solution was placed in a stainless steel container containing methanol to recover the aggregate. The obtained aggregate was dried under reduced pressure for 24 hours to obtain a modified SBR2. The obtained modified SBR2 had a styrene content of 40% by mass, a vinyl content of 30% by mass, and a weight average molecular weight of Mw of 950,000.

(Manufacturing Example 3)
A nitrogen-substituted 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 polymerization. Polymerization was carried out under adiabatic conditions, and the maximum temperature reached 85 ° C. Butadiene was added when the polymerization conversion rate reached 99%, and the mixture was further polymerized for 5 minutes, and then methyltriethoxysilane was added as a denaturant 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 the mixture was dried by a heat roll adjusted to 110 ° C. to obtain modified SBR3. The obtained modified SBR3 had a styrene content of 10% by mass, a vinyl content of 40% by mass, and a weight average molecular weight Mw of 200,000.

<Analysis of SBR>
The analysis of the modified SBR1 to 3 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). It was calculated as a standard polystyrene conversion value based on the value.

(Structural identification)
The structure identification of SBR (measurement of styrene amount and vinyl amount) was performed using a JNM-ECA series device manufactured by JEOL Ltd. The measurement was carried out by dissolving 0.1 g of the polymer in 15 ml of toluene, slowly pouring it into 30 ml of methanol to reprecipitate, and drying under reduced pressure.

<Examples and comparative examples>
According to the formulation shown in Table 1, using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd., knead the materials other than sulfur and the vulcanization accelerator for 5 minutes under the condition of 150 ° C. to knead the kneaded product. Obtained. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and the mixture was kneaded under the condition of 80 ° C. for 5 minutes using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition is formed into a tread shape and bonded together with other tire members to form an unvulcanized tire, which is press-vulcanized for 10 minutes under the condition of 170 ° C. to obtain a test tire (test tire). Size: 195 / 65R15) was manufactured. Evaluation was performed using the obtained test tires, and the results are shown in Table 1.

(Fuel efficiency)
Using a rolling resistance tester, measure and compare the rolling resistance when the test tire is run at rim (15 x 6JJ), internal pressure (230 kPa), load (3.43 kN), and speed (80 km / h). It is displayed as an index when Example 1 is set to 100 (fuel efficiency index). The larger the index, the better the fuel efficiency.

(Dry grip performance)
The above test tires were attached to the vehicle, and 10 laps of the actual vehicle were run on the test course on the dry asphalt road surface. The test site was the Okayama test course of Sumitomo Rubber Industries, Ltd., and the temperature was 20 to 25 ° C.
Then, the test driver evaluated the stability of the control at the time of steering at that time, and the comparative example 1 was set as 100 and displayed as an exponential notation. The larger the value, the better the grip performance on the dry road surface. If the index is 85 or more, it is a practically possible level.

(Wet grip performance)
Each test tire was attached to all wheels of the vehicle (domestic FF2000cc), the braking distance from the initial speed of 100km / h was obtained on a wet asphalt road surface, and it was displayed as an index when Comparative Example 1 was set to 100 (wet). Grip performance index). The larger the index, the shorter the braking distance and the better the wet grip performance.

(Abrasion resistance)
Each test tire was mounted on a domestic FF vehicle, the groove depth of the tire tread portion after a mileage of 8000 km was measured, the mileage when the tire groove depth was reduced by 1 mm was calculated, and Comparative Example 1 was set to 100. Expressed as an index of time (wear resistance index). The larger the index, the longer the mileage when the tire groove depth is reduced by 1 mm, and the better the wear resistance.

From Table 1, in the examples containing SBR having a predetermined average vinyl amount, BR, and two or more kinds of aromatic ring-containing resins having different softening points of 5 ° C. or more in a predetermined ratio, the compounding of SBR not satisfying the vinyl amount. In addition, a good balance of fuel efficiency, dry grip performance, wet grip performance and wear resistance can be obtained as compared with the comparative example in which the difference in the amount of SBR and the softening point of the aromatic ring-containing resin does not satisfy 5 ° C. or more. It became clear.

Claims (11)

Contains styrene-butadiene rubber, butadiene rubber, isoprene-based rubber and resin components,
The content of the styrene-butadiene rubber in 100% by mass of the rubber component is 50% by mass or more, the content of the butadiene rubber is 20% by mass or more and less than 35% by mass, and the content of the isoprene-based rubber is 3 to 15 % by mass. can be,
The styrene-butadiene rubber has an average vinyl content of 40% by mass or more.
The resin component contains two or more kinds of aromatic ring-containing resins having different softening points of 5 ° C. or more.
The two or more aromatic ring-containing resins contain 10 parts by mass or more of each of the two aromatic ring-containing resins having different constituent monomers with respect to 100 parts by mass of the rubber component.
A rubber composition for tread in which the content of silica with respect to 100 parts by mass of the rubber component is 55 parts by mass or more. The rubber composition for tread according to claim 1, wherein the two or more kinds of aromatic ring-containing resins include a styrene resin and a C9 resin and / or a C5C9 resin. The rubber composition for tread according to claim 1 or 2 , wherein the content of carbon black having a CTAB specific surface area of 170 m ² / g or more with respect to 100 parts by mass of the rubber component is 15 to 30 parts by mass. The rubber composition for tread according to any one of claims 1 to 3, wherein the content of silica with respect to 100 parts by mass of the rubber component is 65 parts by mass or more. The rubber composition for tread according to any one of claims 1 to 4 , wherein the content of each of the two or more aromatic ring-containing resins is 10 to 30 parts by mass with respect to 100 parts by mass of the rubber component. The rubber composition for tread according to any one of claims 1 to 5 , wherein the two or more kinds of aromatic ring-containing resins contain a C5C9 resin and a styrene-based resin. The rubber composition for tread according to any one of claims 1 to 6 , wherein the two or more kinds of aromatic ring-containing resins have a softening point of 30 ° C. or higher. The rubber composition for tread according to any one of claims 1 to 7 , wherein the difference in softening points between the two or more aromatic ring-containing resins is 20 ° C. or lower. The rubber composition for tread according to any one of claims 1 , 2, 4 to 8 , wherein the content of carbon black with respect to 100 parts by mass of the rubber component is 10 to 40 parts by mass. The iodine adsorption amount (IA) of 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, and nitrogen. The rubber composition for tread according to any one of claims 3 to 9 , wherein the element adsorption specific surface area is 165 m ² / g or more. A pneumatic tire having a tread produced by using the rubber composition according to any one of claims 1 to 10 .