JP7081082B2 - 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, not only are automobiles required to have lower fuel consumption, but also rubber compositions used in automobile tires are required to be provided with good wear resistance and the like. There is.

In order to ensure safety, tires are required to have grip performance such as wet grip performance and dry grip performance, and styrene-butadiene rubber with a large amount of styrene is widely used as a rubber component, but wear resistance is reduced. Tend. As described above, the grip performance and the wear resistance are in conflict with each other, and it is difficult to obtain the respective performances in a well-balanced manner.

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

The present invention contains a styrene-butadiene rubber and an aromatic ring-containing resin, and the styrene-butadiene rubber has an average molecular weight of 700,000 or more and an average styrene content of 35.0% by mass or more, and the content of the styrene-butadiene rubber / the above. The present invention relates to a rubber composition for a tire in which the content of the aromatic ring-containing resin is 15.0 or less.

The content of carbon black having a nitrogen adsorption specific surface area of 170 m ² / g or more with respect to 100 parts by mass of the rubber component is preferably 35 to 80 parts by mass.
The content of silica with respect to 100 parts by mass of the rubber component is preferably 40 parts by mass or more.

The content of the liquid styrene-butadiene copolymer having a weight average molecular weight of 1 × 10 ³ or more with respect to 100 parts by mass of the rubber component is preferably 20 parts by mass or less.
The aromatic ring-containing resin preferably contains two or more kinds of aromatic ring-containing resins having different softening points of 10 ° C. or more.

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

According to the present invention, the styrene-butadiene rubber contains a styrene-butadiene rubber and an aromatic ring-containing resin, and the styrene-butadiene rubber has an average molecular weight of 700,000 or more, an average styrene content of 35.0% by mass or more, and a content of the styrene-butadiene rubber. / Since the rubber composition for tires has a content of the aromatic ring-containing resin of 15.0 or less, wet grip performance, dry grip performance and wear resistance are improved in a well-balanced manner.

The rubber composition for a tire of the present invention contains styrene-butadiene rubber (SBR) having a predetermined average molecular weight and average styrene amount and an aromatic ring-containing resin in a predetermined ratio.

The rubber composition has the above-mentioned effects, and it is presumed that this is achieved by the following effects.
When SBR with a large amount of styrene is used as the main component of the rubber component, the grip performance is easily improved, but there is a problem that the wear resistance is lowered. By blending an aromatic ring-containing resin, which is presumed to be highly compatible with SBR, in a predetermined ratio, the performance balance between wet grip performance, dry grip performance and wear resistance is significantly (synergistically) improved. Conceivable.

Further, as a filler, 35 to 80 parts by mass of carbon black having a nitrogen adsorption specific surface area of 170 m ² / g or more is blended, (2) 40 parts by mass or more of silica is blended, and (3) as an aromatic ring-containing resin. By applying at least one method, a liquid styrene-butadiene copolymer presumed to have high compatibility with SBR is used, and (4) an aromatic ring-containing resin having a softening point difference of 10 ° C. or higher is used. It is considered that the performance balance is improved more remarkably (synergistically).

The SBR contained in the rubber composition has an average molecular weight of 700,000 or more. The average molecular weight is preferably 740,000 or more, more preferably 770,000 or more, from the viewpoint of the performance balance. The upper limit is not particularly limited, but similarly, from the viewpoint of the performance balance, 1.5 million or less is preferable, 1.3 million or less is more preferable, and 1.1 million or less is further preferable.

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 in all SBR. In the case of a rubber component consisting of 90% by mass of SBR (A), 5% by mass of SBR (B), and 5% by mass of BR, the content ratio of SBR (A) and (B) is , 0.947 (= 90 / (90 + 5)), 0.053 (= 5 / (90 + 5)), respectively. Therefore, for example, the rubber component is SBR (A) (styrene amount 40% by mass, vinyl amount 40% by mass). , Mw 1 million) 90% by mass, SBR (B) (styrene amount 25% by mass, vinyl amount 60% by mass, Mw 150,000) 5% by mass, BR 5% by mass, the average molecular weight of SBR is 95,256,300,000 ( 955,263 = 90 / (90 + 5) x 1 million + 5 / (90 + 5) x 150,000).

The SBR contained in the rubber composition has an average styrene content of 35.0% by mass or more. The average amount of styrene is preferably 37.0% by mass or more, more preferably 39.0% by mass or more, from the viewpoint of the performance balance. The upper limit is not particularly limited, but similarly, from the viewpoint of the performance balance, 50.0% by mass or less is preferable, 45.0% by mass or less is more preferable, and 43.0% by mass or less is further preferable.

Here, the average styrene amount of SBR is {Σ (content ratio of each SBR in all SBR × styrene amount 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 amount 40% by mass, vinyl amount 40% by mass, Mw 1 million) 90% by mass, SBR (B) (styrene amount 25% by mass, vinyl amount 60% by mass, Mw 150,000). When it is composed of 5% by mass and 5% by mass of BR, the average amount of styrene is 39.88% by mass (= {90 / (90 + 5) × 40 × 1,000,000 + 5 / (90 + 5) × 25 × 150,000} / 95.2563 million. ).

The content ratio of the SBR and the aromatic ring-containing resin contained in the rubber composition is such that the content of the styrene-butadiene rubber / the content (mass ratio) of the aromatic ring-containing resin is 15.0 or less. The "content of styrene-butadiene rubber / content of aromatic ring-containing resin" is preferably 12.0 or less, more preferably 10.0 or less, from the viewpoint of the performance balance. The lower limit is not particularly limited, but similarly, from the viewpoint of the performance balance, 2.0 or more is preferable, 3.0 or more is more preferable, and 4.0 or more is further preferable.

Here, the content of SBR / the content of the aromatic ring-containing resin is a mass ratio of the total amount of SBR contained in the rubber composition and the total amount of the aromatic ring-containing resin, respectively, and is, for example, the rubber component (SBR (A) 90). In the case of a rubber composition containing 5 parts by mass of SBR (B), 5 parts by mass of BR), 5 parts by mass of the aromatic ring-containing resin (A), and 5 parts by mass of the aromatic ring-containing resin (B), "Styrene butadiene rubber The content / content of the aromatic ring-containing resin ”is 9.5 (= (90 + 5) / (5 + 5)).

The amount of styrene in each SBR is preferably 15% by mass or more, more preferably 20% 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 20% by mass or more, more preferably 25% 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 120,000 or more. By setting it above the lower limit, good wear resistance tends 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 700,000 or more (preferably 800,000 or more, more preferably 900,000 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 preferably 60% by mass or more, more preferably 75% by mass or more, still more preferably 85% by mass or more from the viewpoint of dry grip performance, wet grip performance, and wear resistance. Is. The upper limit of the content is not particularly limited and may be 100% by mass.

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 the modified SBR is preferable from the viewpoint of the performance balance. The SBR does not contain the liquid styrene-butadiene copolymer described later.

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 polyvalent alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylol ethane triglycidyl ether, and trimethylol propanetriglycidyl ether; and two or more diglycidylated bisphenol A and the like. Polyepoxy compounds of aromatic compounds having a phenol group of; 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, polyepoxidized liquid polybutadiene and other polyepoxy compounds; 4,4'-diglycidyl-diphenyl Epoxy 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- (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- (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, A benzaldehyde compound 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 pyroridone 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-laurilolactum, N-vinyl-ω-laurilolactum, 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.

Rubber components that can be used other than SBR include isoprene-based rubber, butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). Diene rubber such as. These diene-based rubbers may be used alone or in combination of two or more. Of these, isoprene-based rubber and BR are preferable, and BR is more preferable, because wear resistance and fuel efficiency can be further improved.

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 Kosan Co., Ltd., JSR Corporation, Asahi Kasei Co., Ltd., and Nippon Zeon Co., Ltd. can be used.

The content of BR in 100% by mass of the rubber component is preferably 20% by mass or less, more preferably 10% by mass or less. By setting the value to the upper limit or less, the amount of SBR is secured and the performance balance tends to be remarkably improved. The lower limit is not particularly limited, but when blended, it is preferably 3% by mass or more.

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 5% by mass or less, more preferably 3% by mass or less. By setting the value to the upper limit or less, the amount of SBR is secured and the performance balance tends to be remarkably improved. The lower limit is not particularly limited, but when blended, 0.5% by mass or more is preferable.

The rubber composition contains an aromatic ring-containing resin. 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 aromatic ring-containing resin is a solid at room temperature (25 ° C.) such as C9 resin, C5C9 resin (copolymer resin using C5 distillate and C9 distillate as raw materials), styrene resin and the like from the viewpoint of the performance balance. The resin in the state 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.

As the aromatic ring-containing resin, an aromatic hydrocarbon-based resin such as a kumaron resin, an indene resin, or an alkylphenol resin; a mixed resin of the aromatic hydrocarbon-based resin and an aliphatic hydrocarbon-based resin such as C5 resin is also suitable. Can be used. Among them, the mixed resin is preferable.

A styrene-based resin can also be used as the aromatic ring-containing resin. 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-butene 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 softening point of the aromatic ring-containing resin is preferably 40 ° C. or higher, more preferably 70 ° C. or higher, and even more preferably 90 ° C. or higher. When the temperature is 40 ° C. or higher, the desired dry grip performance and wet grip performance tend to be obtained. The softening point is preferably 170 ° C. or lower, more preferably 150 ° C. or lower, and even more preferably 130 ° C. or lower. When the temperature is 170 ° C. or lower, the dispersibility of the resin becomes good, and the dry grip performance and the wet grip performance tend to be improved.

In the rubber composition, the content (total content) of the aromatic ring-containing resin 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.

In the present invention, it is preferable to use two or more kinds of aromatic ring-containing resins having different softening points of 10 ° C. or more as the aromatic ring-containing resin. The difference in softening points between the two or more aromatic ring-containing resins is preferably 12 ° C. or higher, more preferably 13 ° 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 45 ° C. or lower, more preferably 35 ° C. or lower, and even more preferably 30 ° 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 10 ° 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 compounding 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) is the viewpoint of the performance balance. Therefore, it is preferably 20/80 to 90/10, more preferably 40/60 to 80/20, and even more preferably 45/55 to 70/30.

The content of each aromatic ring-containing resin such as the aromatic ring-containing resin having a high softening point and the aromatic ring-containing resin having a low softening point is preferable with respect to 100 parts by mass of the rubber component from the viewpoint of the performance balance. Is 3 to 30 parts by mass, more preferably 5 to 25 parts by mass, and even more preferably 5 to 20 parts by mass.

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. , 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, as well as hydrogen obtained by hydrogenating 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, phenol compounds such as phenol, alkylphenol, alkoxyphenol, and unsaturated hydrocarbon group-containing phenol; naphthol, alkylnaphthol, alkoxynaphthol, and the like. Naftor compounds such as unsaturated hydrocarbon group-containing naphthols; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and 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 a polymerization initiator, a chain transfer agent, an organic solvent, 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, Structor, 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 (the aromatic ring-containing resin, the resin in a solid state at room temperature (25 ° C.) such as other resins) is preferably 5 parts by mass with respect to 100 parts by mass of the rubber component. As mentioned above, it is 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.

It is preferable to add a liquid diene polymer as a softening agent to the rubber composition.
The liquid diene polymer is a diene polymer in a liquid state at room temperature (25 ° C.). The liquid diene polymer preferably has a polystyrene-equivalent weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) of 1.0 × 10 ³ or more, and 1.0 × 10 ³ to 2. It is more preferably 0 × 10 ⁵ and even more preferably 3.0 × 10 ³ to 1.5 × 10 ⁴ . Examples of the liquid diene polymer include a liquid styrene butadiene copolymer, a liquid butadiene polymer, a liquid isoprene polymer, and a liquid styrene isoprene copolymer. Of these, a liquid styrene-butadiene copolymer is preferable.

The content of the liquid diene polymer is preferably 30 parts by mass or less, and more preferably 20 parts by mass or less with respect to 100 parts by mass of the rubber component. The lower limit is preferably 5 parts by mass or more, and more preferably 7 parts by mass or more. Within the above range, a good balance of performance tends to be obtained.

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 naphthen-based 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 10 parts by mass or more, more preferably 20 parts by mass or more, and further preferably 25 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 80 parts by mass or less, more preferably 60 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).

In the rubber composition, the total content of the softening agent (the liquid diene polymer, the hydrocarbon in a liquid state at room temperature (25 ° C.) such as oil, the resin, etc.) is the rubber component 100 from the viewpoint of the performance balance. It is preferably 20 to 120 parts by mass, more preferably 30 to 100 parts by mass, and further preferably 40 to 80 parts by mass with respect to parts by mass.

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 30 parts by mass or more, more preferably 35 parts by mass or more, and further preferably 40 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 100 parts by mass or less, more preferably 80 parts by mass or less, still more preferably 70 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 180 m ² / g or more, and further preferably 190 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 300 m ² / g or less, more preferably 250 m ² / g or less, and further preferably 230 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. Of these, sulfide-based and mercapto-based are preferable because the effects of the present invention can be obtained better.

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 25 parts by mass or less, more preferably 20 parts by mass or less. When it is 25 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 nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 170 m ² / g or more, more preferably 1185 m ² / g or more, and further preferably 190 m from the viewpoint of dry grip performance, wet grip performance, and wear resistance. It is ² / g or more. The upper limit is not particularly limited, but from the viewpoint of dispersibility of carbon black, 300 m ² / g or less is preferable, and 250 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 CTAB specific surface area (cetyltrimethylammonium bromide adsorption specific surface area) of carbon black is preferably 120 m ² / g or more, more preferably 135 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, 200 m ² / g or less is preferable, and 175 m ² / g or less is more preferable.
The CTAB specific surface area is a value measured in accordance with JIS K 6217-3: 2001.

The iodine adsorption amount (IA) (mg / g) of carbon black is preferably 100 to 300 mg / g, more preferably 160 to 260 mg / g, and further preferably 180 to 240 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 K 6217-1: 2008.

The ratio of the CTAB specific surface area to the IA (mg / g) of carbon black (CTAB specific surface area / IA) is preferably 0.3 to 1.0 m ² / mg, more preferably 0.4, from the viewpoint of the performance balance. It is ~ 0.9 m ² / mg, more preferably 0.5 ~ 0.8 m ² / mg.

The content of carbon black is preferably 35 parts by mass or more, and more preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber component. When it is 35 parts by mass or more, sufficient reinforcing property can be obtained, and good wear resistance tends to be obtained. The content is preferably 80 parts by mass or less, more preferably 70 parts by mass or less. When it is 80 parts by mass or less, good dispersibility tends to be obtained. The content of carbon black having N ₂ SA, CTAB specific surface area, and IA 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, calcium aluminum 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 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 antioxidants; quinoline-based antioxidants such as polymers 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 preventive agents. 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. ..

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 vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiadylsulfenamide; tetramethylthiuram disulfide (TMTD). ), Tetrabenzyltiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N) and other thiuram-based vulcanization accelerators; N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl- 2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N, N'-diisopropyl-2-benzothiazolesulfenamide, etc. Sulfenamide-based vulcanization accelerator; guanidine-based vulcanization accelerators such as diphenylguanidine, dioltotrilguanidine, orthotrilviguanidine 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.
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: CTAB148m ² / g, N ₂ SA200m ² / g, IA 215mg / g
Silica: N ₂ SA205m ² / g
Silane coupling agent: Bis (3-triethoxysilylpropyl) disulfide oil: Naften-based process oil Kumaron indene resin: Mw500, hydroxyl value 30 mgKOH / g, Tg70 ° C, softening point 120 ° C)
Mixed resin: A mixture of aromatic hydrocarbon resin and aliphatic hydrocarbon resin (softening point 98-106 ° C)
Liquid styrene-butadiene copolymer: styrene content 25% by mass, Mw4500
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 Kinzoku Mining Co., Ltd. Sulfur: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd .1: N-cyclohexyl-2-benzothiazolyl sulphenamide vulcanization accelerator 2: Diphenylguanidine

(Manufacturing Example 1)
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%, the polymerization was further carried out 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 SBR1. The obtained modified SBR1 had a styrene content of 40% by mass, a vinyl content of 40% by mass, and a weight average molecular weight Mw of 1,000,000.

(Manufacturing Example 2)
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 SBR2. The obtained modified SBR2 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 3)
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 SBR3. The obtained modified SBR3 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.

<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 Toso Co., Ltd., detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M manufactured by Toso Co., Ltd.). 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 unrefined rubber composition is formed into a tread shape and bonded together with other tire members to form an unvultured tire, which is press-sulfurized under the condition of 170 ° C. for 10 minutes to obtain a test tire (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.

(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.

(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.

(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, the examples containing the SBR having a predetermined average molecular weight and the average styrene amount and the aromatic ring-containing resin in a predetermined ratio are comparative examples that do not satisfy the molecular weight, the styrene amount, and the blending ratio of the SBR and the aromatic ring-containing resin. It was clarified that a good balance of dry grip performance, wet grip performance and wear resistance can be obtained.

Claims (13)

It contains styrene-butadiene rubber , an aromatic ring-containing resin, and carbon black having a CTAB specific surface area ratio (CTAB specific surface area / IA) of 0.5 to 0.8 m ² / mg to an iodine adsorption amount (IA).
The styrene-butadiene rubber has an average molecular weight of 700,000 or more and an average styrene content of 35.0% by mass or more.
The aromatic ring-containing resin has a softening point of 40 ° C. or higher and has a softening point of 40 ° C. or higher.
The content of the styrene-butadiene rubber / the content of the aromatic ring-containing resin is 3.0 or more and 15.0 or less.
The content of silica with respect to 100 parts by mass of the rubber component is 30 to 100 parts by mass.
The rubber composition for tread, wherein the average molecular weight is a weight average molecular weight. The rubber composition for tread according to claim 1, wherein the content of carbon black having a nitrogen adsorption ratio surface area of 170 m ² / g or more with respect to 100 parts by mass of the rubber component is 35 to 80 parts by mass. The rubber composition for tread according to claim 1 or 2, wherein the content of silica with respect to 100 parts by mass of the rubber component is 40 parts by mass or more. The rubber composition for tread according to any one of claims 1 to 3, wherein the content of the liquid styrene-butadiene copolymer having a weight average molecular weight of 1 × 10 ³ or more with respect to 100 parts by mass of the rubber component is 20 parts by mass or less. The rubber composition for tread according to any one of claims 1 to 4, wherein the aromatic ring-containing resin contains two or more kinds of aromatic ring-containing resins having different softening points of 10 ° C. or more. The rubber composition for tread according to any one of claims 1 to 5, wherein the content of the styrene-butadiene rubber / the content of the aromatic ring-containing resin is 4.0 to 9.5. The rubber composition for tread according to any one of claims 1 to 6, wherein the styrene-butadiene rubber has an average molecular weight of 1.1 million or less. The rubber composition for tread according to any one of claims 2 to 7, wherein the iodine adsorption amount (IA) of carbon black is 100 to 300 mg / g . The rubber composition for tread according to any one of claims 1 to 8, wherein the content of carbon black with respect to 100 parts by mass of the rubber component is 35 to 80 parts by mass. The rubber composition for tread according to any one of claims 1 to 9, wherein the content of isoprene-based rubber in 100% by mass of the rubber component is 0.5 to 5% by mass. The rubber composition for tread according to any one of claims 1 to 10, wherein the content of butadiene rubber in 100% by mass of the rubber component is 3 to 20% by mass. The rubber composition for tread according to any one of claims 1 to 11, wherein the content of the softener with respect to 100 parts by mass of the rubber component is 20 to 120 parts by mass. A pneumatic tire having a tread produced by using the rubber composition according to any one of claims 1 to 12.