JP6841090B2 - 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 has been an increasing 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 wear resistance are reduced due to the decrease in the calorific value and the reinforcing property of the rubber composition. Etc. tend to worsen. 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, wet 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 styrene-butadiene rubber, butadiene rubber and silica, and the content of the styrene-butadiene rubber in 100% by mass of the rubber component is 40% by mass or more, the content of the butadiene rubber is 20% by mass or more, and the rubber component 100. The styrene-butadiene rubber relates to a rubber composition for a tire having an average molecular weight of 800,000 or less and an average vinyl content of 40% by mass or more, wherein the content of the silica with respect to parts by mass is 50 parts by mass or more.

The nitrogen adsorption specific surface area of silica ^{is preferably 150 m 2} / g or more.
^{The content of carbon black having a CTAB specific surface area of 160 m 2} / g or more with respect to 100 parts by mass of the rubber component is preferably 10 to 40 parts by mass.

It preferably contains a C5 resin.
The present invention also relates to pneumatic tires made using the rubber composition.

According to the present invention, the rubber composition for a tire contains styrene-butadiene rubber having a predetermined average molecular weight and average vinyl amount, butadiene rubber, and silica in a predetermined ratio, so that fuel efficiency, wet grip performance, and resistance are high. Abrasion is 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 vinyl amount, butadiene rubber (BR), and silica in a predetermined ratio.

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 large amount of SBR having a molecular weight of 800,000 or less and a large amount of vinyl, performance other than wet grip performance tends to deteriorate. It is considered that the performance balance of fuel efficiency, wet grip performance and abrasion resistance is remarkably (synergistically) improved.

Further, (1) silica having a nitrogen adsorption specific surface area of 150 m ² / g or more is used, (2) ^{10 to 40 parts by mass of carbon black having a CTAB specific surface area of 160 m 2} / g or more is blended, and (3) C5 resin. It is considered that the performance balance is improved more remarkably (synergistically) by applying at least one method.

The SBR contained in the rubber composition has an average molecular weight of 800,000 or less. From the viewpoint of the performance balance, the average molecular weight is preferably 600,000 or less, more preferably 500,000 or less, and even more preferably 450,000 or less. The lower limit is not particularly limited, but similarly, from the viewpoint of the performance balance, 310,000 or more is preferable, 330,000 or more is more preferable, and 340,000 or more 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 composed of 50% by mass of SBR (A), 5% by mass of SBR (B), 15% by mass of NR, and 30% by mass of BR, the content ratio (mass ratio) of SBR is SBR (A), (B). The content ratios of are 0.909 (= 50 / (50 + 5)) and 0.091 (= 5 / (50 + 5)), respectively. Therefore, for example, the rubber component is SBR (A) (styrene content 25% by mass, vinyl). When the amount is 60% by mass, Mw350,000) 50% by mass, SBR (B) (styrene amount 40% by mass, vinyl amount 30% by mass, Mw950,000) 5% by mass, NR15% by mass, BR 30% by mass, the average of SBR The molecular weight is 40,454,500 (404,545 = 50 / (50 + 5) x 350,000 + 5 / (50 + 5) x 950,000).

The SBR contained in the rubber composition has an average vinyl content of 40% by mass or more. The lower limit of the average vinyl 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. For example, the rubber component is SBR (A) (styrene amount 25% by mass, vinyl amount 60% by mass, Mw 350,000) 50% by mass, SBR (B) (styrene amount 40% by mass, vinyl amount 30% by mass, Mw 950,000). When it is composed of 5% by mass, NR15% by mass, and BR30% by mass, the average vinyl amount is 53.6% by mass (= {50 / (50 + 5) × 60 × 350,000 + 5 / (50 + 5) × 30 × 950,000} /. 40.45.45 million).

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 wet grip performance tends to be obtained. The amount of styrene is preferably 50% by mass or less, more preferably 45% by mass or less. By setting the temperature below the upper limit, heat generation tends to be reduced 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 30% by mass or more. By setting it above the lower limit, good wet grip performance tends 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 200,000 or more, still more preferably 300,000 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 40% by mass or more, preferably 45% by mass or more, and more preferably 50% by mass or more from the viewpoint of 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 end), 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 (coupling) with a hydroxyl group. And terminally 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 preferable.

(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 represent the same or different hydrogen atoms or alkyl groups. R ⁴ and R ⁵ may combine 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, a compound represented by the above formula for the polymerization end (active end) of solution-polymerized styrene-butadiene rubber (S-SBR). Modified SBR (modified SBR or the like described in JP-A-2010-111753) is preferably used.

Alkoxy groups are preferable as 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). Alkyl groups (preferably alkyl groups having 1 to 3 carbon atoms) are suitable as R ⁴ and R ^5. 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; 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, tetraglycidyl metaxylene diamine , Tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, tetraglycidyl-1,3-bisaminomethylcyclohexane and other diglycidylamino compounds;

Amino group-containing acid chlorides such as bis- (1-methylpropyl) carbamic acid chloride, 4-morpholincarbonyl chloride, 1-pyrrolidincarbonyl chloride, N, N-dimethylcarbamic acid chloride, N, N-diethylcarbamic 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- (methyldimethoxysilyl) propyl] Sulfide group-containing silane compounds such as propoxysilyl) propyl] sulfide and (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., Nippon Zeon Co., Ltd., 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. Among them, 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 Co., Ltd., 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 20% by mass or more. By setting it above the lower limit, good wear resistance and low fuel consumption tend to be obtained. The content is preferably 40% by mass or less, more preferably 35% by mass or less, from the viewpoint of the performance balance.

Rubber components that can be used in addition to SBR and BR include 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). Rubber is mentioned. These diene 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 that 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 30% by mass or less, more preferably 20% 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, it is preferably 3% by mass or more, and more preferably 5% by mass or more from the viewpoint of fuel efficiency.

The rubber composition contains silica as a filler. As a result, a reinforcing effect is obtained, 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 50 parts by mass or more, preferably 55 parts by mass or more, and more preferably 60 parts by mass or more with respect to 100 parts by mass of the rubber component. By setting it above the lower limit, sufficient wet grip performance tends 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 wet grip performance tends 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, 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- Sulfates such as triethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercaptos such as Momentive's NXT and NXT-Z, vinyltriethoxysilane, vinyltri Vinyl type such as methoxysilane, amino type such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane. Examples thereof include nitro systems such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, and chlorosystems 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 more satisfactorily.

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 the 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 160 m 2} / g or more, more preferably 170 m ² / g or more, and 175 m ² / g from the viewpoint of wet grip performance and wear resistance. The above is more preferable. 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 even more preferably 170 to 230 mg / g. When the iodine adsorption amount (IA) is within the above range, an 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, still more preferably 170 m 2 / g or more, from the viewpoint of wet grip performance, wear resistance, and steering stability. 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 K6217-2: 2001.

The content of carbon black is preferably 10 parts by mass or more, and more preferably 13 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 N ₂ SA 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.

From the viewpoint of the performance balance, the rubber composition is preferably blended with C5, C9, C5 / C9 resins (resins in a solid state at room temperature (25 ° C.)), and C5 resin is particularly preferable.

Examples of the C5 resin include aliphatic petroleum resins obtained by (co) copolymerizing a C5 fraction obtained by thermal decomposition of naphtha in the petrochemical industry. 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. Examples of the C9 resin include a solid polymer obtained by (co) polymerizing a C9 distillate using a Friedelcraft type catalyst or the like, and specifically, 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 C5 resin is preferably an aliphatic type, and the C9 resin is preferably an alicyclic type.

The softening point of the C5, C9, and C5 / C9 resins is preferably 30 ° C. or higher, more preferably 60 ° C. or higher, and even more preferably 80 ° C. or higher. At 30 ° C. or higher, the desired wet grip performance tends 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 is good, and the wet grip performance and fuel efficiency tend to be improved.
In the present invention, the softening point is the temperature at which the ball drops when the softening point defined in JIS K6220-1: 2001 is measured by a ring-ball type softening point measuring device.

The total content of the C5, C9 and C5 / C9 resins is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 25 parts by mass or less, more preferably 20 parts by mass or less. Within the above range, a good balance of performance tends to be obtained. The content of the C5 resin, the C9 resin, and the C5 / C9 mixed resin alone is preferably in the same range.

The rubber composition may contain a resin in a solid state at room temperature (25 ° C.) other than the C5, C9 and C5 / C9 resins. The resin is not particularly limited as long as it is widely used in the tire industry, and examples thereof include styrene resin, kumaron inden resin, terpene resin, pt-butylphenol acetylene resin, and acrylic 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, A homopolymer obtained by independently polymerizing o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.), a copolymer obtained by copolymerizing two or more types of styrene-based monomers, and a styrene-based monomer. And other monomer copolymers that can be copolymerized with this.

Examples of the other monomer include acrylonitrile such as acrylonitrile and methacrylonitrile, 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.

The softening point of the styrene resin is preferably 30 ° C. or higher, more preferably 60 ° C. or higher, and even more preferably 80 ° C. or higher. At 30 ° C. or higher, the desired wet grip performance tends to be obtained. The softening point is preferably 160 ° C. or lower, more preferably 130 ° C. or lower, and even more preferably 100 ° C. or lower. When the temperature is 160 ° C. or lower, the dispersibility of the resin is good, and the wet grip performance and fuel efficiency tend to be improved.

The kumaron inden resin is a resin containing kumaron and indene 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.

Examples of the terpene-based resin include polyterpenes, terpene phenols, and aromatic-modified terpene resins.
Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. The terpene compound is _{a hydrocarbon having a composition of (C 5} H ₈ ) _n and an oxygen-containing derivative thereof, and is a mono terpene (C ₁₀ H ₁₆ ), a sesqui terpene (C ₁₅ H ₂₄ ), and a diterpene (C ₂₀ H _32). ) Etc., and 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, 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 a phenol-based compound, and a resin obtained by hydrogenating the resin. Specifically, the above-mentioned terpene compound, the phenolic 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 the 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 has an aromatic ring, but 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 naphthol; 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 Patent 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, etc., 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 and the like.

Examples of resins such as C5, C9, C5 / C9 resin, styrene resin, and Kumaron inden resin include Exxon Chemical Co., Ltd., Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., and Toso. Products of Rutgers Chemicals Co., Ltd., BASF, Arizona Chemical Co., Ltd., Nikko Chemical Co., Ltd., Nippon Catalyst Co., Ltd., JX Energy Co., Ltd., Arakawa Chemical Co., Ltd., Taoka Chemical Co., Ltd., etc. Can be used.

In the rubber composition, the total content of the resin (the resin in a solid state at room temperature (25 ° C.) such as the C5, C9, C5 / C9 resin, and styrene resin) is preferably based on 100 parts by mass of the rubber component. Is 0.5 parts by mass or more, more preferably 1 part by mass or more. The content is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and further preferably 20 parts by mass or less. 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 naphthenic-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 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 remarkably improved.
The oil content also includes the amount of oil contained in rubber (oil-extended 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.). Liquid diene polymer preferably has a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC) (Mw) is a ^{1.0 × 10 3 ~2.0 × 10 5} , 3.0 More preferably, it is × 10 ^{3 to} 1.5 × 10 ^4. Examples of the liquid diene polymer include a liquid styrene-butadiene copolymer (liquid SBR), a liquid butadiene polymer (liquid BR), a liquid isoprene polymer (liquid IR), and a liquid styrene isoprene copolymer (liquid SIR). Be done.

In the rubber composition, the total content of the softener (hydrocarbon, resin, etc. in a liquid state at room temperature (25 ° C.) such as the oil and liquid diene polymerization) is 100 mass of the rubber component 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 the parts.

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-based 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, and 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., Seiko Kagaku Co., Ltd. can be used.

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

The content of the anti-aging agent is preferably 1 to 10 parts by mass, and 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 Kagaku Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo 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 Mining & Smelting 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. is there.

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

As the sulfur, for example, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Corporation, Flexis Co., Ltd., Nippon Inui Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. 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, and 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-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 sulfide accelerator; guanidine-based sulfide accelerators such as diphenylguanidine, dioltotrilguanidine, orthotrilbiguanidine can be mentioned. These may be used alone or in combination of two or more. Of these, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators 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 final 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 obtained by kneading the vulcanizing agent and the vulcanization accelerator 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 preferably used for treads (cap treads), but members other than treads, such as sidewalls, base treads, under treads, clinch apex, bead apex, breaker cushion rubber, carcass cord. It may be used as a covering rubber, an insulation, a chafer, an inner liner, etc., or as a side reinforcing layer of a run-flat tire.

The pneumatic tire of the present invention is produced 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 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 based on examples, but the present invention is not limited thereto.
The various chemicals used in the examples will be described below.
NR: TSR20
Modified SBR1: Modified SBR synthesized in Production Example 1
Modified SBR2: Modified SBR synthesized in Production Example 2
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: Bis (3-triethoxysilylpropyl) disulfide oil: Naphthenic process oil C5 resin: Softening point 97-103 ° 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 denaturant.
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 aggregates. 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 350,000.

(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 denaturant.
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 aggregates. 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.

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

(Structural identification)
The structure identification of SBR (measurement of the amount of styrene and the amount of vinyl) was performed using an apparatus of the JNM-ECA series 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 Bunbury mixer manufactured by Kobe Steel, Ltd., materials other than sulfur and vulcanization accelerator are kneaded under the condition of 150 ° C. for 5 minutes to prepare the kneaded product. Obtained. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and the mixture was kneaded for 5 minutes under the condition of 80 ° C. 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 a 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.

(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 in which styrene-butadiene rubber having a predetermined average molecular weight and average vinyl amount, butadiene rubber, and silica are contained in a predetermined ratio, the formulation using SBR that does not satisfy the average molecular weight and vinyl amount and the amount of silica are used. Compared with the comparative example which does not satisfy the above conditions, a good balance of fuel efficiency, wet grip performance and wear resistance was obtained.

Claims (7)

Contains styrene-butadiene rubber, butadiene rubber, silica and C5 resin
The content of the styrene-butadiene rubber in 100% by mass of the rubber component is 40% by mass or more, and the content of the butadiene rubber is 20% by mass or more.
The content of the silica is 50 parts by mass or more and the content of the C5 resin is 1 to 4 parts by mass with respect to 100 parts by mass of the rubber component.
The styrene-butadiene rubber is a rubber composition for tires having an average molecular weight of 800,000 or less and an average vinyl content of 40% by mass or more. The rubber composition for a tire according to claim 1, wherein the nitrogen adsorption specific surface area of silica is 150 m ^{2 / g or more.} The rubber composition for a tire according to claim 1 or 2, wherein the content of carbon black ^{having a CTAB specific surface area of 160 m 2} / g or more with respect to 100 parts by mass of the rubber component is 10 to 40 parts by mass. The rubber composition for a tire according to any one of claims 1 to 3, wherein the average amount of vinyl is 50% by mass or more. The iodine adsorption amount (IA) of the carbon black is 100 to 300 mg / g, and the ratio of the CTAB specific surface area to the IA (mg / g) (CTAB specific surface area / IA) is 0.8 to 1.2 m. ² / Mg, nitrogen adsorption specific surface area 165 m ² The rubber composition for a tire according to claim 3 or 4, which is / g or more. The rubber composition for a tire according to any one of claims 1 to 5, wherein the softening point of the C5 resin is 30 ° C. or higher. A pneumatic tire produced by using the rubber composition according to any one of claims 1 to 6.