JP2021028400A - Tread rubber composition and pneumatic tire - Google Patents

Abstract

To provide a tread rubber composition having excellent fuel economy, steering stability, and wear resistance and a pneumatic tire.SOLUTION: The present invention provides a tread rubber composition wherein M200 at 25°C, E* at 30°C, and tanδ at 30°C satisfy the following formula: M200×E*/tanδ≥400.SELECTED DRAWING: None

Description

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

Tire treads are required to have performance such as steering stability performance, wear resistance performance, and fuel efficiency performance during running. For example, the performance is improved by devising rubber components, fillers, etc. used for the tread. ing.

For example, Patent Document 1 discloses a technique of blending a specific modified diene rubber and a specific silica to impart good tire physical properties.

International Publication No. 2013/125614

An object of the present invention is to solve the above problems and to provide a rubber composition for tread and a pneumatic tire having excellent fuel efficiency, steering stability and wear resistance.

The present invention relates to a rubber composition for tread in which M200 at 25 ° C., E ^* at 30 ° C., and tan δ at 30 ° C. satisfy the following formulas.
M200 × E ^* / tan δ ≧ 400

It is preferable that M200, E ^* and tan δ satisfy the following formula.
M200 × E ^* / tan δ ≧ 500

It is preferable that silica is contained in an amount of 75 parts by mass or more with respect to 100 parts by mass of the rubber component.
The present invention also relates to a pneumatic tire having a tread made of the rubber composition.

According to the present invention, since the ^{tread rubber composition has M200 at 25 ° C., E *} at 30 ° C., and tanδ at 30 ° C. ^{satisfying M200 × E *} / tanδ ≧ 400, fuel efficiency and steering stability can be achieved. It is possible to provide a rubber composition for tread and a pneumatic tire having excellent wear resistance.

In the rubber composition for tread of the present invention ^{, M200 at 25 ° C., E *} at 30 ° C., and tanδ at 30 ° C. ^{satisfy M200 × E *} / tanδ ≧ 400. As a result, the overall performance of fuel efficiency, steering stability, and wear resistance can be significantly improved.

Physical properties of the rubber composition (vulcanized) include stress during elongation (modulus), complex elastic modulus, loss tangent, etc. In particular, the present invention includes M200 at 25 ° C, E ^* at 30 ° C, and 30. We have found that when tan δ at ° C satisfies the above formula, the rigidity and durability of the rubber can be ensured and the rolling resistance can be reduced, and the product has been completed. Therefore, according to the rubber composition satisfying the above formula, the total performance of fuel efficiency performance, steering stability performance, and wear resistance performance can be remarkably improved.

The rubber composition for tread (vulcanized) has M200 at 25 ° C. (200% modulus (stress at 200% elongation) [MPa] at 25 ° C.) and E ^* at 30 ° C. (complex elastic modulus at 30 ° C. []. MPa]) and tan δ at 30 ° C. (tangent loss at 30 ° C.) satisfy the following equations.
M200 × E ^* / tan δ ≧ 400
From the viewpoint of overall performance of fuel efficiency, steering stability, and wear resistance, M200 × E ^* / tan δ is preferably 450 or more, more preferably 500 or more, and particularly preferably 510 or more. The upper limit is not particularly limited, but is preferably 800 or less, and more preferably 700 or less.

The rubber composition for tread (vulcanized) preferably has an M200 [MPa] of 8.0 MPa or more, more preferably 8.3 MPa or more, and 8.5 MPa or more at 25 ° C. from the viewpoint of wear resistance and steering stability performance. Is more preferable. The upper limit is not particularly limited, but is preferably 15.0 MPa or less, more preferably 12.0 MPa or less, and even more preferably 11.0 MPa or less.

^{The rubber composition for tread (vulcanized) preferably has an E *} [MPa] of 8.0 MPa or more, more preferably 8.3 MPa or more, and even more preferably 8.5 MPa or more at 30 ° C. from the viewpoint of steering stability performance. .. The upper limit is not particularly limited, but is preferably 15.0 MPa or less, more preferably 12.0 MPa or less, and even more preferably 11.0 MPa or less.

From the viewpoint of fuel efficiency, the tread rubber composition (vulcanized) preferably has a tan δ at 30 ° C. of 0.25 or less, more preferably 0.22 or less, and even more preferably 0.19 or less. The lower limit is not particularly limited, but is preferably 0.10 or more, and more preferably 0.12 or more.

M200 is a value measured by the method based on JIS K6251: 2010 described in Examples, and E ^* and tanδ are values measured by the method described in Examples.

Here, M200, E ^* , and tan δ can be adjusted according to the type and amount of chemicals (particularly, rubber component and filler) blended in the rubber composition. For example, M200 uses a high molecular weight rubber component. ^{E *} tends to increase when a high molecular weight rubber component is used or the amount of filler is increased, and tan δ tends to increase when a modified rubber or silica is used as a filler. is there.

As a method for satisfying M200 × E ^* / tan δ ≧ 400, (a) a method using a high-molecular-weight rubber component polymerized by a continuous polymerization method, (b) a method using a modified rubber in which a modifying group is introduced into the rubber component, Examples thereof include a method of adjusting the amount of silica (c), a method of adjusting the plasticizer, and the like alone or in combination as appropriate. As a result, by satisfying the above equation, the overall performance of fuel efficiency, steering stability, and wear resistance is improved.

The reason why such an action effect is obtained is not clear, but it is presumed as follows.
Generally, the method of ensuring fuel efficiency is to reduce the amount of filler, but the rigidity cannot be ensured, and the filler is insufficiently reinforced and the wear resistance is inferior. Therefore, fuel efficiency, steering stability, and wear resistance are poor. The balance gets worse. In addition, a modified styrene-butadiene copolymer having excellent fuel efficiency is usually produced by batch polymerization, but the molecular weight is often low due to problems such as processability, while styrene produced by a continuous polymerization method. Although the butadiene copolymer has a high molecular weight and is excellent in rigidity and wear resistance, it tends to be inferior in fuel efficiency. On the other hand, for example, by using rubber in which a modifying group is introduced into a high molecular weight styrene-butadiene copolymer polymerized by a continuous polymerization method having excellent wear resistance and satisfying the above formula, fuel efficiency and steering stability are achieved. The overall performance of performance and wear resistance can be significantly improved. This is because the balance between these is improved by ensuring the wear resistance performance by the high molecular weight and the low fuel consumption performance by the modifying group, and the rigidity of the rubber (steering stability performance) is also secured by the high molecular weight, so that the fuel consumption is low. The balance between performance and steering stability is also improved. As a result, it is presumed that the overall performance is significantly improved.

A rubber composition for a tread usually contains a rubber component and a filler.
The rubber components include isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-. Examples thereof include diene rubber such as isoprene-butadiene copolymer rubber (SIBR). Examples of the isoprene rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR and the like. Of these, SBR and BR are preferable from the viewpoints of fuel efficiency, steering stability, and wear resistance. The rubber component may be used alone or in combination of two or more.

As the SBR, an oil-extended styrene-butadiene copolymer can be preferably used.
The oil-extended styrene-butadiene copolymer is obtained by oil-expanding the styrene-butadiene copolymer with an extension oil. As described above, by containing the oil-extended styrene-butadiene copolymer previously oil-expanded with the spreading oil, the extending oil and the filler in the rubber component are compared with the compounded rubber in which the oil is kneaded at the time of compounding the rubber composition. Can improve the dispersibility of.

The content of the oil-extended styrene-butadiene copolymer in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, and further preferably 35% by mass or more. By setting it above the lower limit, good fuel efficiency, steering stability, and wear resistance tend to be obtained. The upper limit is not particularly limited, but 90% by mass or less is preferable, 80% by mass or less is more preferable, and 75% by mass or less is further preferable.

The weight average molecular weight (Mw) of the oil-extended styrene-butadiene copolymer is preferably 400,000 or more, more preferably 600,000 or more, still more preferably 800,000 or more. If it is above the lower limit, the rigidity of the rubber is ensured due to the high molecular weight, and the balance between fuel efficiency performance and steering stability performance tends to be improved. The Mw is not particularly limited, but is preferably 1.5 million or less, more preferably 1.3 million or less, and further preferably 1.1 million or less.

The weight average molecular weight (Mw) / number average molecular weight (Mn) (Mw / Mn) of the oil-extended styrene-butadiene copolymer is preferably 1.5 or more, more preferably 1.7 or more, still more preferably 1.8. It is more than that, preferably 3.0 or less, more preferably 2.7 or less, still more preferably 2.5 or less. Within the above range, good fuel efficiency, steering stability, and wear resistance tend to be obtained.

The styrene content of the oil-extended styrene-butadiene copolymer is preferably 5% by mass or more, more preferably 15% by mass or more, still more preferably 25% by mass or more. By setting it above the lower limit, good wear resistance tends to be obtained. The styrene content is preferably 45% by mass or less, more preferably 40% by mass or less, still more preferably 38% by mass or less. By setting it below the upper limit, good fuel efficiency tends to be obtained.

The vinyl bond amount of the oil-extended styrene-butadiene copolymer is preferably 20% by mass or more, more preferably 25% by mass or more, and further preferably 30% by mass or more. By setting it above the lower limit, good steering stability performance tends to be obtained. The vinyl bond amount is preferably 80% by mass or less, more preferably 70% by mass or less, and further preferably 60% by mass or less. By setting it below the upper limit, good wear resistance tends to be obtained.

In the present specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are gel permeation chromatographs (GPC) (GPC-8000 series manufactured by Toso Co., Ltd., detector: differential refractometer, column: It can be obtained by standard polystyrene conversion based on the measured value by TSKGEL SUPERMULTIPORE HZ-M manufactured by Toso Co., Ltd. The vinyl bond amount (1,2-bonded butadiene unit amount) can be measured by infrared absorption spectrum analysis, and the styrene content ^{can be measured by 1} H-NMR measurement.

The oil-extended styrene-butadiene copolymer preferably has a branched structure introduced therein. As the styrene-butadiene copolymer into which the branched structure is introduced, for example, at least one polyfunctional one selected from the group consisting of an epoxy compound, a halogen-containing silicon compound, and a second alkoxysilane compound at the polymer terminal. Examples thereof include those modified with a sex coupling agent and those polymerized in the presence of a small amount of branching agent. Among these, those in which the polymer terminal is modified with a polyfunctional coupling agent are preferable.

The styrene-butadiene copolymer can be prepared by copolymerizing styrene and butadiene using, for example, a polymerization initiator. As the polymerization initiator, a lithium-based initiator is preferable. As the lithium-based initiator, an organic lithium compound is preferable. Examples of the organic lithium compound include alkyllithiums such as n-butyllithium, sec-butyllithium and t-butyllithium; alkylenedithiums such as 1,4-dilithiumbutane; phenyllithium, stillbenlithium and diisopropenylbenzenelithium, Examples thereof include alkyllithium such as butyllithium and aromatic hydrocarbon lithium such as a reactant such as divinylbenzene; lithium multinuclear hydrocarbon such as lithium naphthalene; aminolithium, tributyltin lithium and the like.

At the time of polymerization, if necessary, an ether compound, an amine or the like can be used as a styrene randomizing agent at the time of copolymerization and as an agent for adjusting the amount of vinyl bond. Examples of the ether compound or amine include dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, triethylamine, pyridine, N-methylmorpholine, N, N, N', N'-tetramethylethylenediamine and dipiperidino. Etan and the like can be mentioned. In addition, activators such as potassium dodecylbenzenesulfonate, potassium linoleate, potassium benzoate, potassium futalate, and potassium tetradecylbenzenesulfonate can also be used for the same purpose.

As the polymerization solvent, n-hexane, cyclohexane, heptane, benzene and the like can be used. The polymerization method may be either a batch polymerization method or a continuous polymerization method, but it is preferable to use the continuous polymerization method from the viewpoint that a styrene-butadiene copolymer having the above-mentioned various properties can be preferably obtained. As the polymerization condition, the polymerization temperature is usually 0 to 130 ° C, preferably 10 to 100 ° C. The polymerization time is usually 5 minutes to 24 hours, preferably 10 minutes to 10 hours. The monomer concentration in the polymerization solvent (total monomer / (total monomer + polymerization solvent)) is usually 5 to 50% by mass, preferably 10 to 35% by mass.

Generally, when a lithium-based initiator is used, the polymerization reaction rate of styrene and the polymerization reaction rate of butadiene are different. In addition, each polymerization reaction rate is affected by the polymerization temperature and the monomer concentration. Therefore, when a simple reaction is carried out, in the latter half of the reaction in which the polymerization temperature rises, a large amount of styrene reacts due to the influence of the polymerization temperature and the high concentration of the styrene monomer, a large number of styrene long chains are generated, and the styrene length is increased. The content ratio of the chain may increase. Therefore, as a method for adjusting the content ratios of the styrene single chain and the styrene long chain to appropriate values, a method of controlling the polymerization temperature at a place where the reaction rates of styrene and butadiene are the same, and a method of charging butadiene before the reaction are used. There is a method of increasing the amount of styrene taken up at the initial stage of polymerization by starting the reaction in a reduced state, and then continuously introducing the reduced amount of butadiene.

As a specific method for introducing a branched structure into a styrene-butadiene copolymer, when modified with a polyfunctional coupling agent, an active polymer having a lithium active terminal obtained by a batch polymerization method or a continuous polymerization method is used. From halogen-containing silicon compounds such as silicon chloride, second alkoxysilane compounds, alkoxysilane sulfide compounds, (poly) epoxy compounds, urea compounds, amide compounds, imide compounds, thiocarbonyl compounds, lactam compounds, ester compounds, and ketone compounds A method of reacting with at least one polyfunctional coupling agent selected from the above group can be mentioned. Among these, halogen-containing silicon compounds such as silicon tetrachloride, second alkoxysilane compounds, alkoxysilane sulfide compounds, and (poly) epoxy compounds are preferable, and halogen-containing silicon compounds, second alkoxysilane compounds, and (poly) epoxys are preferable. Compounds are more preferred. When polymerizing in the presence of a small amount of branching agent, specific examples of the branching agent include divinylbenzene. The amount introduced is preferably 10% by mass or less with respect to 100% by mass of the styrene-butadiene copolymer.

Examples of the spreading oil used for oil spreading of the styrene-butadiene copolymer include naphthenic type, paraffin type, aromatic oil spreading type and the like. Among these, an aromatic oil spreading system is preferable. Further, a naphthenic or paraffinic rubber spreading oil may be used in combination. Examples of the oil spreading method include a method in which a spreading oil is added after the polymerization is completed, and the solvent is removed and dried by a conventionally known method.

The amount of the spreading oil used is preferably 5 to 50 parts by mass, more preferably 10 to 40 parts by mass, and even more preferably 12 to 30 parts by mass with respect to 100 parts by mass of the styrene-butadiene copolymer. By setting it above the lower limit, good fuel efficiency tends to be obtained. By setting it below the upper limit, there is a tendency to secure the degree of freedom in compounding.

As the SBR, a non-oil-extended styrene-butadiene copolymer may be used in combination with the oil-extended styrene-butadiene copolymer.

The content of the non-oil-extended styrene-butadiene copolymer in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more. By setting it above the lower limit, good fuel efficiency, steering stability, and wear resistance tend to be obtained. The upper limit is not particularly limited, but is preferably 50% by mass or less, more preferably 45% by mass or less, and further preferably 40% by mass or less.

The weight average molecular weight (Mw) of the non-oil-extended styrene-butadiene copolymer is preferably 50,000 or more, more preferably 100,000 or more, still more preferably 150,000 or more, and preferably less than 400,000, more preferably. Is 350,000 or less, more preferably 300,000 or less. Within the above range, good fuel efficiency, steering stability, and wear resistance tend to be obtained.

The weight average molecular weight (Mw) / number average molecular weight (Mn) (Mw / Mn) of the non-oil-extended styrene-butadiene copolymer is preferably 1.0 or more, more preferably 1.1 or more, and further preferably 1. It is 2 or more, preferably 2.0 or less, more preferably 1.7 or less, still more preferably 1.5 or less. Within the above range, good fuel efficiency, steering stability, and wear resistance tend to be obtained.

The styrene content of the non-oil-extended styrene-butadiene copolymer is preferably 5% by mass or more, more preferably 15% by mass or more, and further preferably 20% by mass or more. By setting it above the lower limit, good wear resistance tends to be obtained. The styrene content is preferably 40% by mass or less, more preferably 35% by mass or less, still more preferably 30% by mass or less. By setting it below the upper limit, good fuel efficiency tends to be obtained.

The vinyl bond amount of the non-oil-extended styrene-butadiene copolymer is preferably 40% by mass or more, more preferably 45% by mass or more, and further preferably 50% by mass or more. By setting it above the lower limit, good steering stability performance tends to be obtained. The vinyl bond amount is preferably 80% by mass or less, more preferably 75% by mass or less, and further preferably 65% by mass or less. By setting it below the upper limit, good wear resistance tends to be obtained.

As the non-oil-extended styrene-butadiene copolymer, both non-modified SBR and modified SBR can be used, but modified SBR is preferable.

The modified non-oil-extended styrene-butadiene copolymer (modified SBR (non-oil-extended)) may have a functional group that interacts with a filler such as silica. For example, a styrene-butadiene copolymer. At least one end may be a terminal-modified styrene-butadiene copolymer (terminal-modified styrene-butadiene copolymer having the above-mentioned functional group) modified with a compound (modifying agent) having the above-mentioned functional group, or a main chain. A main chain-modified styrene-butadiene copolymer having the above functional group, or a main chain terminal modified styrene-butadiene copolymer having the above functional group at the main chain and the terminal (for example, having the above functional group in the main chain and at least One end is modified (coupling) with a main chain end-modified styrene-butadiene copolymer modified with the above modifier or a polyfunctional compound having two or more epoxy groups in the molecule to form a hydroxyl group or an epoxy group. Examples thereof include terminally modified SBR into which is introduced. These may be used alone or in combination of two or more.

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). Alkoxysilyl groups having 1 to 6 carbon atoms) and amide groups are preferable.

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

The BR is not particularly limited, and BR having a high cis content, BR containing syndiotactic polybutadiene crystals, and the like can be used. The BR may be either a non-modified BR or a modified BR, and examples of the modified BR include a modified BR into which the above-mentioned functional group has been introduced. These may be used alone or in combination of two or more. 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 spectroscopy.

The content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, and more preferably 10% by mass or more. By setting it above the lower limit, good wear resistance tends to be obtained. The upper limit is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less.

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

Examples of the filler include those known in the rubber field such as silica, carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica. Of these, silica and carbon black are preferable.

Examples of silica used in the rubber composition for tread 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.

In the rubber composition for tread, the content of silica is preferably 75 parts by mass or more, more preferably 80 parts by mass or more with respect to 100 parts by mass of the rubber component. By setting it above the lower limit, good fuel efficiency and wear resistance tend to be obtained. The upper limit of the content is not particularly limited, but is preferably 150 parts by mass or less, more preferably 130 parts by mass or less, and further preferably 120 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 80 m ² / g or more, more preferably 120 m ² / g or more, and further preferably 150 m ² / g or more. By setting it above the lower limit, good wear resistance tends to be obtained. The N ₂ SA of silica is preferably 250 m ² / g or less, more preferably 220 m ² / g or less, and further 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 for tread 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 triethoxysilylpropylmethacrylate monosulfide, mercaptos such as 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane, vinyls such as vinyltriethoxysilane and vinyltrimethoxysilane, 3-amino Amino series such as propyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy series such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, 3-nitropropyltrimethoxysilane, Examples thereof include nitro type such as 3-nitropropyltriethoxysilane and chloro type such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. As commercially available products, for example, products such as Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Toray Dow Corning Co., Ltd. can be used. These may be used alone or in combination of two or more. Of these, sulfide-based and mercapto-based silane coupling agents are preferable.

（式中、Ｒ^１００１は−Ｃｌ、−Ｂｒ、−ＯＲ^１００６、−Ｏ（Ｏ＝）ＣＲ^１００６、−ＯＮ＝ＣＲ^１００６Ｒ^１００７、−ＮＲ^１００６Ｒ^１００７及び−（ＯＳｉＲ^１００６Ｒ^１００７）_ｈ（ＯＳｉＲ^１００６Ｒ^１００７Ｒ^１００８）から選択される一価の基（Ｒ^１００６、Ｒ^１００７及びＲ^１００８は同一でも異なっていても良く、各々水素原子又は炭素数１〜１８の一価の炭化水素基であり、ｈは平均値が１〜４である。）であり、Ｒ^１００２はＲ^１００１、水素原子又は炭素数１〜１８の一価の炭化水素基、Ｒ^１００３は−［Ｏ（Ｒ^１００９Ｏ）_ｊ］−基（Ｒ^１００９は炭素数１〜１８のアルキレン基、ｊは１〜４の整数である。）、Ｒ^１００４は炭素数１〜１８の二価の炭化水素基、Ｒ^１００５は炭素数１〜１８の一価の炭化水素基を示し、ｘ、ｙ及びｚは、ｘ＋ｙ＋２ｚ＝３、０≦ｘ≦３、０≦ｙ≦２、０≦ｚ≦１の関係を満たす数である。）

（式中、ｘは０以上の整数、ｙは１以上の整数である。Ｒ^１は水素、ハロゲン、分岐若しくは非分岐の炭素数１〜３０のアルキル基、分岐若しくは非分岐の炭素数２〜３０のアルケニル基、分岐若しくは非分岐の炭素数２〜３０のアルキニル基、又は該アルキル基の末端の水素が水酸基若しくはカルボキシル基で置換されたものを示す。Ｒ^２は分岐若しくは非分岐の炭素数１〜３０のアルキレン基、分岐若しくは非分岐の炭素数２〜３０のアルケニレン基、又は分岐若しくは非分岐の炭素数２〜３０のアルキニレン基を示す。Ｒ^１とＲ^２とで環構造を形成してもよい。） As a particularly suitable mercapto-based silane coupling agent, a silane coupling agent represented by the following formula (S1) and a binding unit A represented by the following formula (I) and a binding unit B represented by the following formula (II) are used. Included silane coupling agents include. Among them, a silane coupling agent containing a binding unit A represented by the following formula (I) and a binding unit B represented by the following formula (II) is preferable.

(In the formula, R ¹⁰⁰¹ is -Cl, -Br, -OR ¹⁰⁰⁶ , -O (O =) CR ¹⁰⁰⁶ , -ON = CR ¹⁰⁰⁶ R ¹⁰⁰⁷ , -NR ¹⁰⁰⁶ R ¹⁰⁰⁷ and-(OSiR ¹⁰⁰⁶ R ¹⁰⁰⁷ ) _h (OSiR ¹⁰⁰⁶ R ¹⁰⁰⁷ R ¹⁰⁰⁸⁾ a monovalent group selected from ^{(R 1006, R 1007} and ^{R 1008} may be the same or different, be each a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms , H has an average value of 1 to 4), R ¹⁰⁰² is R ¹⁰⁰¹ , a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, and R ¹⁰⁰³ is − [O (R ¹⁰⁰⁹ O) _j. ^{] -Group} (R 1009 is an alkylene group having 1 to 18 carbon atoms, j is an integer of 1 to 4), R ¹⁰⁰⁴ is a divalent hydrocarbon group having 1 to 18 carbon atoms, and R ¹⁰⁰⁵ is 1 carbon atom. It represents a monovalent hydrocarbon group of ~ 18, and x, y and z are numbers that satisfy the relationship of x + y + 2z = 3, 0 ≦ x ≦ 3, 0 ≦ y ≦ 2, 0 ≦ z ≦ 1).

(In the formula, x is an integer of 0 or more, y is an integer of 1 or more. R ¹ is hydrogen, halogen, an alkyl group having 1 to 30 branched or unbranched carbon atoms, and 2 to 2 branched or unbranched carbon atoms. 30 alkenyl groups, branched or unbranched alkynyl groups having 2 to 30 carbon atoms, or hydrogens at the ends of the alkyl groups substituted with hydroxyl groups or carboxyl groups. R ² has branched or unbranched carbon atoms. It represents an alkylene group of 1 to 30, a branched or non-branched alkenylene group having 2 to 30 carbon atoms, or a branched or non-branched alkynylene group having 2 to 30 carbon atoms. A ring structure is formed by ^{R 1} and R ^2. May be.)

In formula (S1), R ¹⁰⁰⁵ , R ¹⁰⁰⁶ , R ¹⁰⁰⁷ and R ¹⁰⁰⁸ are independently derived from a linear, cyclic or branched alkyl group having 1 to 18 carbon atoms, an alkenyl group, an aryl group and an aralkyl group, respectively. It is preferable that the group is selected from the group. When R ¹⁰⁰² is a monovalent hydrocarbon group having 1 to 18 carbon atoms, it is selected from the group consisting of a linear, cyclic or branched alkyl group, an alkenyl group, an aryl group and an aralkyl group. It is preferably a group. R ¹⁰⁰⁹ is preferably a linear, cyclic or branched alkylene group, and particularly preferably linear. ^R1004 is, for example, an alkylene group having 1 to 18 carbon atoms, an alkenylene group having 2 to 18 carbon atoms, a cycloalkylene group having 5 to 18 carbon atoms, a cycloalkylalkylene group having 6 to 18 carbon atoms, and an arylene having 6 to 18 carbon atoms. Examples thereof include an aralkylene group having 7 to 18 carbon atoms. The alkylene group and the alkenylene group may be linear or branched, and the cycloalkylene group, the cycloalkylalkylene group, the arylene group and the aralkylene group have a functional group such as a lower alkyl group on the ring. You may be doing it. As the R ¹⁰⁰⁴ , an alkylene group having 1 to 6 carbon atoms is preferable, and a linear alkylene group such as a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group and a hexamethylene group are particularly preferable.

^{Specific examples of R 1002} , R ¹⁰⁰⁵ , R ¹⁰⁰⁶ , R ¹⁰⁰⁷ and R ^{1008 in} the formula (S1) include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group and sec-butyl. Group, tert-butyl group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group, cyclopentyl group, cyclohexyl group, vinyl group, propenyl group, allyl group, hexenyl group, octenyl group, cyclopentenyl group, cyclo Examples thereof include a hexenyl group, a phenyl group, a tolyl group, a xsilyl group, a naphthyl group, a benzyl group, a phenethyl group and a naphthylmethyl group.
^{Examples of R 1009} in the formula (S1) include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, a hexylene group and the like as the linear alkylene group, and examples of the branched alkylene group include a branched alkylene group. Examples thereof include an isopropylene group, an isobutylene group and a 2-methylpropylene group.

Specific examples of the silane coupling agent represented by the formula (S1) include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, and 3-. Lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoy Luciopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthio Examples thereof include ethyltrimethoxysilane, 2-decanoylthioethyltrimethoxysilane, 2-lauroylthioethyltrimethoxysilane and the like. These may be used alone or in combination of two or more. Of these, 3-octanoylthiopropyltriethoxysilane is particularly preferable.

In the silane coupling agent containing the binding unit A represented by the formula (I) and the binding unit B represented by the formula (II), the content of the binding unit A is preferably 30 mol% or more, more preferably 50 mol. % Or more, preferably 99 mol% or less, more preferably 90 mol% or less. The content of the binding unit B is preferably 1 mol% or more, more preferably 5 mol% or more, still more preferably 10 mol% or more, preferably 70 mol% or less, more preferably 65 mol% or less. More preferably, it is 55 mol% or less. The total content of the binding units A and B is preferably 95 mol% or more, more preferably 98 mol% or more, and particularly preferably 100 mol%.
The content of the binding units A and B is an amount including the case where the binding units A and B are located at the ends of the silane coupling agent. The form in which the binding units A and B are located at the ends of the silane coupling agent is not particularly limited, and a unit corresponding to the formulas (I) and (II) representing the binding units A and B may be formed. ..

^{Regarding R 1} in the formulas (I) and (II), examples of the halogen include chlorine, bromine and fluorine. Examples of the branched or non-branched alkyl group having 1 to 30 carbon atoms include a methyl group and an ethyl group. Examples of the branched or non-branched alkenyl group having 2 to 30 carbon atoms include a vinyl group and a 1-propenyl group. Examples of the branched or non-branched alkynyl group having 2 to 30 carbon atoms include an ethynyl group and a propynyl group.

Formula (I), the ^{R 2} in (II), Examples of the branched or unbranched alkylene group having 1 to 30 carbon atoms, an ethylene group, and propylene group. Examples of the branched or non-branched alkenylene group having 2 to 30 carbon atoms include a vinylene group and a 1-propenylene group. Examples of the branched or non-branched alkynylene group having 2 to 30 carbon atoms include an ethynylene group and a propynylene group.

In a silane coupling agent containing the binding unit A represented by the formula (I) and the binding unit B represented by the formula (II), the number of repetitions (x) of the binding unit A and the number of repetitions (y) of the binding unit B The total number of repetitions (x + y) is preferably in the range of 3 to 300.

When the silane coupling agent is contained, the content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and preferably 20 parts by mass with respect to 100 parts by mass of silica. Hereinafter, it is more preferably 15 parts by mass or less.

Examples of the carbon black that can be used in the rubber composition for tread include GPF, FEF, HAF, ISAF, SAF, and the like, but are not particularly limited. As commercial products, products such as 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. are used. it can. By blending carbon black, reinforcing properties are obtained and wear resistance and the like are remarkably improved.

In the rubber composition for tread, the content of carbon black is preferably 1 part by mass or more, and more preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. By setting it above the lower limit, the effect of blending carbon black tends to be obtained. The content of the carbon black is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and further preferably 8 parts by mass or less. By setting it below the upper limit, good dispersibility tends to be obtained.

In the rubber composition for tread, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 80 m ² / g or more, more preferably 100 m ² / g or more, and further preferably 105 m ² / g or more. When it is above the lower limit, good reinforcing properties tend to be obtained. The upper limit of N ₂ SA of carbon black is not particularly limited, but is preferably 180 m ² / g or less, more preferably 150 m ² / g or less, and further preferably 130 m ² / g or less.
The nitrogen adsorption specific surface area of carbon black is determined by the method A of JIS K6217.

The rubber composition for tread preferably contains oil.
Examples of the oil include process oils, vegetable oils and fats, or mixtures thereof. As the process oil, for example, paraffin-based process oil, aroma-based process oil, naphthenic process oil, and 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, process oils are preferable, and aroma-based process oils are particularly preferable.

When oil is contained, the content thereof is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, and preferably 50 parts by mass with respect to 100 parts by mass of the rubber component. It is less than or equal to parts by mass, more preferably 40 parts by mass or less, still more preferably 35 parts by mass or less. The oil content also includes the amount of oil (extended oil) contained in the rubber (oil-extended rubber).

The rubber composition for tread may contain a resin.
The resin is not particularly limited as long as it is widely used in the tire industry, and is rosin-based resin, kumaron inden resin, α-methylstyrene-based resin, terpene-based resin, pt-butylphenol acetylene resin, acrylic-based resin. Examples thereof include resin, C5 resin, and C9 resin. Commercially available products include Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Toso Co., Ltd., Rutgers Chemicals Co., Ltd., BASF, Arizona Chemical Co., Ltd., Nikko Chemical Co., Ltd., Japan Co., Ltd. Products such as catalysts, JX Energy Co., Ltd., Arakawa Chemical Industry Co., Ltd., Taoka Chemical Industry Co., Ltd., and Toa Synthetic Co., Ltd. can be used. These may be used alone or in combination of two or more.

When a resin is contained, the content of the resin is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, more preferably more preferably, with respect to 100 parts by mass of the rubber component. It is 20 parts by mass or less.

The rubber composition for the tread may contain 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.

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.

When wax is contained, the content thereof is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 20 parts by mass or less, based on 100 parts by mass of the rubber component. More preferably, it is 10 parts by mass or less.

The rubber composition for tread may contain 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 Examples include inhibitors. 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.

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.

When the antioxidant is contained, the content thereof is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less with respect to 100 parts by mass of the rubber component. More preferably, it is 5 parts by mass or less.

The rubber composition for tread may contain stearic acid.
As the stearic acid, conventionally known ones can be used, and for example, products such as NOF Corporation, NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., and Chiba Fatty Acid Co., Ltd. can be used. ..

When stearic acid is contained, the content thereof is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. It is preferably 5 parts by mass or less.

The rubber composition for tread may contain zinc oxide.
Conventionally known zinc oxide can be used. For example, products of Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., HakusuiTech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. Can be used.

When zinc oxide is contained, the content thereof is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. It is preferably 5 parts by mass or less.

The rubber composition for tread preferably contains sulfur.
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. and the like can be used.

When sulfur is contained, the content thereof is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and preferably 10 parts by mass or less with respect to 100 parts by mass of the rubber component. It is more preferably 5 parts by mass or less, still more preferably 3 parts by mass or less.

The rubber composition for tread preferably contains a vulcanization accelerator.
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.

When the vulcanization accelerator is contained, the content thereof is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. It is preferably 7 parts by mass or less.

In addition to the above components, other compounding agents (organic cross-linking agents, etc.) generally used in the tire industry may be further added to the rubber composition for tread. The content of these compounding agents is preferably 0.1 to 200 parts by mass with respect to 100 parts by mass of the rubber component.

The rubber composition for tread can be produced, for example, by kneading each of the above components using a rubber kneading device such as an open roll or a Banbury mixer, 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 100 to 180 ° C., preferably 120 to 170 ° C. In the final kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 120 ° C. or lower, preferably 85 to 110 ° C. 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 140 to 190 ° C, preferably 150 to 185 ° C.

The rubber composition for tread is used for treading tires. In the case of a tread composed of a cap tread and a base tread, it can be suitably used for a cap tread.

The pneumatic tire of the present invention is produced by a usual method using the above rubber composition.
That is, the rubber composition is extruded according to the shape of each tire member of the tread at the unvulcanized stage, and is molded together with other tire members by a normal method on a tire molding machine. Form a vulcanized tire. A tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

The tread of the pneumatic tire may be composed of at least a part of the rubber composition, and may be entirely composed of the rubber composition.

The above pneumatic tires can be used for passenger car tires, large passenger car tires, large SUV tires, heavy load tires such as trucks and buses, light truck tires, motorcycle tires, race tires (high performance tires), etc. Is. It can also be used for all-season tires, summer tires, studless tires (winter tires), etc.

The present invention will be specifically described based on Examples, but the present invention is not limited thereto.

[Manufacturing Example 1]
A fully nitrogen-substituted autoclave reaction vessel with an internal volume of 20 L, equipped with a stirrer and a jacket, contains 100 ppm of 1,2-butadiene at a rate of 10.5 g / min of styrene while controlling the temperature at 70 ° C. Continuous 1,3-butadiene at a rate of 19.5 g / min, cyclohexane at a rate of 150 g / min, tetrahydrofuran at a rate of 1.5 g / min, and n-butyllithium at a rate of 0.117 mmol / min. Charged to. Silicon tetrachloride was continuously added at a rate of 0.14 mmol / min at the top outlet of the first reaction vessel and introduced into the second reaction vessel connected to the first reaction vessel. The degeneration reaction was carried out. 2,6-Di-tert-butyl-p-cresol was added to the polymer solution after completion of the denaturation reaction. Next, the product name "VIVATEC500" (manufactured by H & R) was added to 37.5 phr (37.5 parts per 100 rubber components) to spread the oil, and the solvent was removed by steam stripping to adjust the temperature to 110 ° C. It was dried by a hot roll to obtain an oil-expanded styrene-butadiene copolymer (SBR1).
The vinyl bond amount of SBR1 was 39% by mass, the styrene content was 34% by mass, Mw was 850,000, and Mw / Mn was 2.2.

[Manufacturing Example 2]
<Preparation of terminal denaturant>
23.6 g of 3- (N, N-dimethylamino) propyltrimethoxysilane was placed in a fully nitrogen-substituted 100 mL volumetric flask, and anhydrous hexane was further added to make the total volume 100 mL.
<Preparation of modified SBR (non-oil exhibition)>
18 L of n-hexane, 540 g of styrene, 1460 g of butadiene, and 17 mmol of tetramethylethylenediamine were added to a sufficiently nitrogen-substituted 30 L pressure-resistant container, and the temperature was raised to 40 ° C. Next, after adding 10.5 mL of butyllithium, the temperature was raised to 50 ° C. and the mixture was stirred for 3 hours. Next, 3.5 mL of a 0.4 mol / L silicon tetrachloride / hexane solution was added, and the mixture was stirred for 30 minutes. Next, 30 mL of the terminal denaturing agent was added, and the mixture was stirred for 30 minutes. After adding 2 mL of methanol in which 0.2 g of 2,6-tert-butyl-p-cresol was dissolved in the reaction solution, the reaction solution was placed in a stainless steel container containing 18 L of methanol to recover the aggregates. The obtained aggregate was dried under reduced pressure for 24 hours to obtain a modified SBR (SBR4).
The vinyl bond amount of SBR4 was 60% by mass, the styrene content was 28% by mass, Mw was 200,000, and Mw / Mn was 1.3.

[Manufacturing Example 3]
N-Butyllithium at a rate of 11.7 g / min for styrene, 18.3 g / min for 1,3-butadiene containing 100 ppm of 1,2-butadiene, and 7.0 g / min for tetrahydrofuran. An oil-extended styrene-butadiene copolymer (SBR5) was obtained in the same manner as in Production Example 1 except that each was charged at a rate of 0.189 mmol / min.
The vinyl bond amount of SBR5 was 40% by mass, the styrene content was 38% by mass, Mw was 870,000, and Mw / Mn was 2.3.

[Manufacturing Example 4]
In an autoclave reaction vessel with an internal volume of 5 L substituted with nitrogen, 175 g of styrene, 260 g of 1,3-butadiene containing 150 ppm of 1,2-butadiene, 2500 g of cyclohexane, 8.75 g of tetrahydrofuran, and potassium dodecylbenzenesulfonate were placed. 0.068 g was charged. After adjusting the temperature of the contents of the reaction vessel to 15 ° C., 2.83 mmol of n-butyllithium was added to initiate polymerization. From 5 minutes after the start of polymerization, 55 g of 1,3-butadiene was continuously introduced at a flow rate of 5 g / min. After the polymerization conversion rate reached 100%, 3.51 mmol of silicon tetrachloride was added, and a modification reaction was carried out for 15 minutes. 2,6-Di-tert-butyl-p-cresol was added to the polymer solution after completion of the denaturation reaction. Next, the product name "VivaTech500" (manufactured by R & H) was oil-expanded by adding 37.5 phr, the solvent was removed by steam stripping, the rubber was dried by a heat roll adjusted to 110 ° C., and oil-expanded styrene. A butadiene copolymer (SBR6) was obtained.
The vinyl bond amount of SBR6 was 42% by mass, the styrene content was 35% by mass, Mw was 770,000, and Mw / Mn was 1.7.

Various chemicals used in Examples and Comparative Examples will be described together.
SBR1: Production Example 1
SBR2: Nippon Zeon Co., Ltd. Nipol NS522 (styrene content 39% by mass, vinyl bond amount 40% by mass, Mw 650,000, oil content 37.5 parts by mass with respect to 100 parts by mass of rubber solid content)
SBR3: Toughden 3830 manufactured by Asahi Kasei Corporation (styrene content 36% by mass, vinyl bond amount 31% by mass, Mw 420,000, oil content 37.5 parts by mass with respect to 100 parts by mass of rubber solid content)
SBR4: Production Example 2
SBR5: Production Example 3
SBR6: Production Example 4
BR: BR150B manufactured by Ube Industries, Ltd. (cis content 98% by mass)
Silica: Ultrasil VN3 (manufactured by Evonik, N ₂ SA175m ² / g)
Carbon Black: Dia Black N220 (manufactured by Mitsubishi Chemical Corporation, N ₂ SA114m ² / g)
Silane coupling agent 1: Si69 (Evonik, bis (3-triethoxysilylpropyl) tetrasulfide)
Silane coupling agent 2: NXT-Z45 manufactured by Momentive (copolymer of binding unit A and binding unit B (binding unit A: 55 mol%, binding unit B: 45 mol%))
Oil: Diana process oil AH-24 (aroma process oil) manufactured by Idemitsu Kosan Co., Ltd.
Wax: Ozo Ace 0355 (manufactured by Nippon Seiro Co., Ltd.)
Anti-aging agent: Nocrack 6C (N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Stearic acid: Made by NOF Corporation Zinc oxide: 3 types of zinc oxide (made by HakusuiTech Co., Ltd.)
Sulfur: Powdered sulfur (manufactured by Tsurumi Chemical Co., Ltd.)
Vulcanization Accelerator 1: Noxeller NS (N-tert-butyl-2-benzothiazil sulfenamide) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator 2: Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

[Examples and Comparative Examples]
According to the formulation shown in each table, chemicals other than sulfur and vulcanization accelerator are kneaded for 5 minutes under the condition of 150 ° C. using a 1.7L Bunbury mixer manufactured by Kobe Steel, Ltd., and the kneaded product is kneaded. Got 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 cap tread shape and bonded together with other tire members to prepare an unvulcanized tire, which is press-vulcanized for 10 minutes at 170 ° C. for a test tire. (Size: 195 / 65R15) was obtained.

The rubber physical characteristics and tire performance of the produced test tire were evaluated by the following methods. The results are shown in Table 1. In Table 1, Comparative Example 1-2 is used, and in Table 2, Comparative Example 2-2 is a reference comparative example.

(Tensile test)
A No. 3 dumbbell type test piece was prepared from a sample (rubber composition for tread) collected from the cap tread of a test tire, and a tensile test was performed at 25 ° C. based on JIS K6251: 2010 to perform a stress at 200% elongation. (M200) was measured.

(Viscoelasticity test)
Samples taken from the cap tread of a test tire using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.) under the conditions of temperature 30 ° C., frequency 10 Hz, initial strain 10%, and dynamic strain 2%. The complex elastic modulus E ^* (MPa) and loss tangent (tan δ) of (rubber composition for tread) were measured.

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

(Stable steering performance)
Each test tire was attached to all wheels of the vehicle (2000 cc), and the actual vehicle was run on a test course under general driving conditions. The test driver sensory-evaluated the control stability (steering stability) during steering, and displayed the index with 100 as a reference comparison example (steering stability index). The larger the index, the better the steering stability performance.

(Abrasion resistance)
When each test tire is mounted on a domestic FF vehicle, the groove depth of the tread after a mileage of 8000 km is measured, the mileage when the tire groove depth is reduced by 1 mm is calculated, and the reference comparison example is set to 100. Expressed as an index of (wear resistance performance 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 performance is.

From Tables 1 and 2, the tires of the examples having a tread in which M200 (25 ° C.), E ^* (30 ° C.) and tanδ (30 ° C.) ^{satisfy M200 × E *} / tanδ ≧ 400 have low fuel consumption performance and steering stability. The overall performance of performance and wear resistance was excellent.

Claims (6)

A rubber composition for tread in which M200 at 25 ° C., E ^* at 30 ° C., and tan δ at 30 ° C. satisfy the following formula.
The rubber composition for tread contains styrene-butadiene rubber and silica.
A rubber composition for tread containing 75 parts by mass or more of silica with respect to 100 parts by mass of the rubber component.
M200 × E ^* / tan δ ≧ 400
(In the formula, the M200 is a 200% tensile stress [MPa] according to a tensile test performed at 25 ° C. based on JIS K6251: 2010. The E ^* is a temperature of 30 ° C., a frequency of 10 Hz, and an initial strain of 10. The complex elastic modulus [MPa] by the viscoelasticity test under the conditions of% and 2% kinematic strain. The tan δ is the viscoelasticity under the conditions of temperature 30 ° C., frequency 10 Hz, initial strain 10% and kinetic strain 2%. Loss tangent by elastic test.) The rubber composition for tread according to claim 1, wherein the M200, E ^{* and tan δ satisfy the following formula.}
M200 × E ^* / tan δ ≧ 500
(In the formula, the M200 is a 200% tensile stress [MPa] according to a tensile test performed at 25 ° C. based on JIS K6251: 2010. The E ^* is a temperature of 30 ° C., a frequency of 10 Hz, and an initial strain of 10. The complex elastic modulus [MPa] by the viscoelasticity test under the conditions of% and 2% kinematic strain. The tan δ is the viscoelasticity under the conditions of temperature 30 ° C., frequency 10 Hz, initial strain 10% and kinetic strain 2%. Loss tangent by elastic test.) The rubber composition for tread according to claim 1 or 2, which contains 75 to 130 parts by mass of silica with respect to 100 parts by mass of the rubber component. The rubber composition for tread according to any one of claims 1 to 3, which contains 1 to 8 parts by mass of carbon black with respect to 100 parts by mass of the rubber component. The rubber composition for tread according to any one of claims 1 to 4, which comprises a mercapto-based silane coupling agent. A pneumatic tire having a tread made of the rubber composition according to any one of claims 1 to 5.