JP7585669B2 - Rubber composition for tires and tires - Google Patents

Description

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

Various methods for improving fuel economy and chipping resistance have been studied (see, for example, Patent Documents 1 and 2). However, in recent years, further improvements in these overall performances are required.

JP 2000-344955 A JP 2014-012768 A

The present invention aims to provide a rubber composition for tires and a tire that can solve the above problems and improve the overall performance of fuel economy and chipping resistance.

The present invention relates to a rubber composition for tires, which contains a rubber component containing styrene-butadiene rubber and carbon black, in which the total styrene content in the rubber component is 15 mass% or less, the average cetyltrimethylammonium bromide specific surface area of the carbon black is 120 ^m2 /g or more, the proportion of carbon black having a cetyltrimethylammonium bromide specific surface area of 115 ^m2 /g or less in 100 mass% of the carbon black is 50 mass% or more, and the content of the carbon black per 100 mass parts of the rubber component is 20 mass parts or more.

It is preferable that the rubber component contains an isoprene-based rubber, and the content of the isoprene-based rubber is greater than the content of the styrene-butadiene rubber.

It is preferable that the total amount of styrene in the rubber component is 10 mass% or less.

It is preferable that the rubber composition contains silica.

The rubber composition preferably contains a styrene-based resin.

The rubber composition preferably contains a dibenzylamine compound.

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

The present invention provides a rubber composition for tires that contains a rubber component containing styrene-butadiene rubber and carbon black, wherein the total styrene content in the rubber component is 15 mass% or less, the average cetyltrimethylammonium bromide specific surface area of the carbon black is 120 ^m2 /g or more, and the proportion of carbon black having a cetyltrimethylammonium bromide specific surface area of 115 ^m2 /g or less in 100 mass% of the carbon black is 50 mass% or more, and the content of the carbon black per 100 mass parts of the rubber component is 20 mass% or more, thereby providing good overall performance in terms of fuel economy and chipping resistance.

The rubber composition for tires of the present invention contains a rubber component containing styrene-butadiene rubber and carbon black, wherein the total styrene content in the rubber component is 15 mass% or less, the average cetyltrimethylammonium bromide specific surface area of the carbon black is 120 ^m2 /g or more, and the proportion of carbon black having a cetyltrimethylammonium bromide specific surface area of 115 ^m2 /g or less in 100 mass% of the carbon black is 50 mass% or more, and the content of the carbon black per 100 mass parts of the rubber component is 20 mass parts or more.

The reason why the above-mentioned effects are obtained with the above-mentioned rubber composition is presumed to be as follows.
In the above rubber composition, styrene-butadiene rubber and carbon black are blended, and the total amount of styrene in the rubber component and the amount of carbon black are adjusted to fall within a predetermined range, so that the carbon black is less susceptible to the steric hindrance caused by the styrene moiety, which facilitates the generation of an interaction between the rubber component and the carbon black, and promotes the dispersion of the carbon black.
Furthermore, by adjusting the average value of the CTAB specific surface area of the carbon black and the proportion of carbon black having a CTAB specific surface area of 115 m ² /g or less within a predetermined range, the dispersion of the carbon black is further promoted.
It is believed that these actions facilitate the provision of reinforcing properties by carbon black, thereby significantly improving the overall performance of fuel economy and chipping resistance.

The rubber composition contains a rubber component.
Here, the rubber component is a component that contributes to crosslinking, and generally has a weight average molecular weight (Mw) of 10,000 or more.

The weight average molecular weight of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more, and is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. Within the above range, the effect tends to be better.

In this specification, the weight average molecular weight (Mw) can be calculated based on the measured value obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation) and converted into standard polystyrene.

The total amount of styrene in the rubber component may be 15% by mass or less, but is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less, and is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more. If it is within the above range, the effect tends to be better.

Here, the total amount of styrene in the rubber component is the total content (unit: mass%) of the styrene moieties contained in the entire rubber component, and can be calculated by Σ (content of each rubber component x amount of styrene in each rubber component/100). For example, if 100% by mass of the rubber component contains 85% by mass of SBR with a styrene content of 40% by mass, 5% by mass of SBR with a styrene content of 25% by mass, and 10% by mass of BR with a styrene content of 0% by mass, the total amount of styrene in the rubber component is 35.25% by mass (=85 x 40/100 + 5 x 25/100 + 10 x 0/100).

The total vinyl content in the rubber component is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, and is preferably 5% by mass or more, more preferably 8% by mass or more, and even more preferably 12% by mass or more. If it is within the above range, the effect tends to be better.

Here, the total vinyl content in the rubber component is the total content (unit: mass%) of vinyl parts contained in the total rubber component, and can be calculated by Σ (content of each rubber component x vinyl content in each rubber component/100). For example, if 100 mass% of the rubber component contains 85 mass% SBR with a vinyl content of 30 mass%, 5 mass% SBR with a vinyl content of 20 mass%, and 10 mass% BR with a vinyl content of 10 mass%, the total vinyl content in the rubber component is 27.5 mass% (=85 x 30/100 + 5 x 20/100 + 10 x 10/100).

The ratio of the total vinyl content in the rubber component to the total styrene content in the rubber component is preferably 0.5 or more, more preferably 2 or more, even more preferably 3 or more, and particularly preferably 4 or more, and is preferably 8 or less, more preferably 6 or less, and even more preferably 5 or less. Within the above range, the effect tends to be better.

The styrene content and vinyl content in each rubber component can be measured by a nuclear magnetic resonance (NMR) method.
In addition, the total styrene amount and the total vinyl amount in the rubber component are calculated according to the above-mentioned formula in the examples of this specification, but they may be analyzed from the tire using, for example, a pyrolysis gas chromatograph mass spectrometer (Py-GC/MS) or the like.

The rubber composition contains styrene-butadiene rubber (SBR) as a rubber component.
The SBR is not particularly limited, and examples of the SBR that can be used include emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. Commercially available products include those from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc.

The styrene content of SBR is preferably 5% by mass or more, more preferably 8% by mass or more, and even more preferably 10% by mass or more, and is preferably 35% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. If it is within the above range, the effect tends to be better.

The vinyl content of the SBR is preferably 15% by mass or more, more preferably 25% by mass or more, and even more preferably 35% by mass or more, and is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. If it is within the above range, the effect tends to be better.

When there is one type of SBR, the styrene amount and vinyl amount of the SBR refer to the styrene amount and vinyl amount of the SBR, and when there are multiple types of SBR, they refer to the average styrene amount and average vinyl amount.
The average styrene amount of SBR can be calculated by {Σ(content of each SBR × styrene amount of each SBR)}/total content of all SBRs. For example, when 100% by mass of the rubber component contains 85% by mass of SBR with a styrene amount of 40% by mass and 5% by mass of SBR with a styrene amount of 25% by mass, the average styrene amount of the SBR is 39.2% by mass (=(85×40+5×25)/(85+5)).
Similarly, the average vinyl content of SBR can be calculated by {Σ(content of each SBR × vinyl content of each SBR)}/total content of all SBRs. For example, when 100% by mass of the rubber component contains 85% by mass of SBR with a vinyl content of 30% by mass and 5% by mass of SBR with a vinyl content of 20% by mass, the average vinyl content of SBR is 29.4% by mass (=(85×30+5×20)/(85+5)).

The amount of SBR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, and is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. Within the above range, the effect tends to be better.

Other usable rubber components besides SBR include diene rubbers such as isoprene rubber, butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These may be used alone or in combination of two or more. Of these, isoprene rubber and BR are preferred.

Isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR, etc. NR can be, for example, SIR20, RSS#3, TSR20, etc., which are common in the tire industry. IR is not particularly limited, and can be, for example, IR2200, etc., which are common in the tire industry. Modified NR can be, for example, deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc. Modified NR can be, for example, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Modified IR can be, for example, epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. These can be used alone or in combination of two or more. Of these, NR is preferred.

The content of isoprene-based rubber in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 45% by mass or more, and is preferably 75% by mass or less, more preferably 65% by mass or less, and even more preferably 55% by mass or less. Within the above range, the effect tends to be better obtained.

From the viewpoint of overall performance such as fuel economy and chipping resistance, it is preferable that the content of isoprene-based rubber in the above rubber composition is greater than the content of SBR.

In the above rubber composition, the ratio of isoprene rubber content to SBR content is preferably 1.2 or more, more preferably 1.5 or more, and even more preferably 1.8 or more, and is preferably 3.5 or less, more preferably 2.5 or less, and even more preferably 2.2 or less. Within the above range, the effect tends to be better.

In these relationships, the isoprene rubber content and SBR content are the contents (unit: mass%) in 100% by mass of the rubber component.

The BR is not particularly limited, and BR with a high cis content, BR with a low cis content, BR containing syndiotactic polybutadiene crystals, etc. can be used. Commercially available products include those from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, etc.

The cis amount (cis content) of BR is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, and is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less. When it is within the above range, the effect tends to be more favorably obtained.
The cis amount of BR can be measured by infrared absorption spectroscopy.

The above-mentioned cis amount of BR means the cis amount of the BR when there is one type of BR, and means the average cis amount when there are multiple types of BR.
The average cis amount of BR can be calculated by {Σ(content of each BR × cis amount of each BR)}/total content of all BRs. For example, in 100% by mass of the rubber component, when 20% by mass of BR with a cis amount of 90% and 10% by mass of BR with a cis amount of 40% are present, the average cis amount of BR is 73.3% by mass (=(20×90+10×40)/(20+10)).

The BR content in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and is preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 20% by mass or less. Within the above range, the effect tends to be better obtained.

The rubber component may be modified to introduce a functional group that interacts with a filler such as silica.
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, a disulfide 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. These functional groups may have a substituent. Among them, an amino group (preferably an amino group in which a hydrogen atom of an amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferred.

Specific examples of compounds (modifiers) having the above functional groups include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, etc.

The rubber composition contains carbon black.
The carbon black has an average cetyltrimethylammonium bromide (CTAB) specific surface area of 120 m ² /g or more, and the proportion of carbon black with a CTAB specific surface area of 115 m ² /g or less in 100% by mass of carbon black is 50% by mass or more, but the method for satisfying this condition is not particularly limited, and for example, the particle size distribution during the production of carbon black may be adjusted, or two or more types of carbon black may be used in combination. Examples of carbon black that can be used in combination of two or more types include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products include products from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shinnikka Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like.
The CTAB specific surface area of carbon black is a value measured in accordance with JIS K6217-3:2001.

The average CTAB specific surface area of the carbon black may be 120 m ² /g or more, but is preferably 160 m ² /g or less, more preferably 140 m ² /g or less, and even more preferably 130 m ² /g or less. Within the above range, the effect tends to be better.
Here, the average value of the CTAB specific surface area of carbon black can be calculated by {Σ(content of each carbon black × CTAB specific surface area of each carbon black)}/total content of all carbon blacks. For example, when 100 parts by mass of the rubber component contains 30 parts by mass of carbon black with CTAB: 110 ^m2 /g and 20 parts by mass of carbon black with CTAB: 140 ^m2 /g, the average value of the CTAB specific surface area is 122 ^m2 /g (=(30×110+20×140)/(30+20)).

One example of a method for satisfying the above-mentioned carbon black conditions is to use in combination a carbon black having a CTAB specific surface area of 115 ^m2 /g or less (hereinafter also referred to as the first carbon black) and a carbon black having a CTAB specific surface area of 125 ^m2 /g or more (hereinafter also referred to as the second carbon black).

The CTAB specific surface area of the first carbon black may be 115 m ² /g or less, but is preferably 50 m ² /g or more, more preferably 70 m ² /g or more, and even more preferably 90 m ² /g or more. When it is within the above range, the effect tends to be more excellent.

The CTAB specific surface area of the second carbon black may be 125 m ² /g or more, preferably 130 m ² /g or more, and preferably 180 m ² /g or less, more preferably 170 m ² /g or less, and even more preferably 160 m ² /g or less. Within the above range, the effect tends to be more favorable.

The content of the first carbon black in 100% by mass of carbon black may be 50% by mass or more, but is preferably 55% by mass or more, and is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. If it is within the above range, the effect tends to be better.

The content of the second carbon black in 100% by mass of carbon black is preferably 20% by mass or more, preferably 30% by mass or more, preferably 40% by mass or more, and preferably 50% by mass or less, more preferably 45% by mass or less. Within the above range, the effect tends to be better.

The carbon black content (total content) may be 20 parts by mass or more per 100 parts by mass of the rubber component, but is preferably 55 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. If it is within the above range, the effect tends to be better.

The rubber composition preferably contains silica.
Examples of silica include dry silica (anhydrous silicic acid) and wet silica (hydrated silicic acid), but wet silica is preferred because it has many silanol groups. Commercially available products include those from Rhodia, EVONIK, Tosoh Silica, Solvay Japan, and Tokuyama. These may be used alone or in combination of two or more.

The content of silica is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less. Within the above range, the effect tends to be better obtained.

Silica is preferably used in combination with a silane coupling agent.
The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. As commercially available products, for example, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used. These may be used alone or in combination of two or more. Among them, mercapto-based ones are preferred.

In addition to compounds having a mercapto group, compounds having a structure in which the mercapto group is protected by a protecting group (for example, a compound represented by the following formula (S1)) can also be used as mercapto-based silane coupling agents.

（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、ｖは０以上の整数、ｗは１以上の整数である。Ｒ^１１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^１２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^１１とＲ^１２とで環構造を形成してもよい。） Particularly suitable mercapto-based silane coupling agents include silane coupling agents represented by the following formula (S1) and silane coupling agents containing a bond unit A represented by the following formula (I) and a bond unit B represented by the following formula (II).

(In the formula, R ¹⁰⁰¹ is a monovalent group selected from -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 ) (R ¹⁰⁰⁶ , R ¹⁰⁰⁷ and R ¹⁰⁰⁸ may be the same or different, each is a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, and 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, 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, R ¹⁰⁰⁵ is a monovalent hydrocarbon group having 1 to 18 carbon atoms, 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, v is an integer of 0 or more, and w is an integer of 1 or more. R ¹¹ represents hydrogen, halogen, a branched or unbranched alkyl group having 1 to 30 carbon atoms, a branched or unbranched alkenyl group having 2 to 30 carbon atoms, a branched or unbranched alkynyl group having 2 to 30 carbon atoms, or an alkyl group in which the terminal hydrogen atom is substituted with a hydroxyl group or a carboxyl group. R ¹² represents a branched or unbranched alkylene group having 1 to 30 carbon atoms, a branched or unbranched alkenylene group having 2 to 30 carbon atoms, or a branched or unbranched alkynylene group having 2 to 30 carbon atoms. R ¹¹ and R ¹² may form a ring structure.)

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

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

Specific examples of silane coupling agents represented by formula (S1) include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, 3-lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthioethyltrimethoxysilane, 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 preferred.

In the silane coupling agent comprising the bond unit A represented by formula (I) and the bond unit B represented by formula (II), the content of the bond unit A is preferably 30 mol% or more, more preferably 50 mol% or more, and preferably 99 mol% or less, more preferably 90 mol% or less.The content of the bond unit B is preferably 1 mol% or more, more preferably 5 mol% or more, even more preferably 10 mol% or more, and preferably 70 mol% or less, more preferably 65 mol% or less, even more preferably 55 mol% or less.The total content of the bond 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 bond units A and B includes the case where the bond units A and B are located at the terminals of the silane coupling agent. When the bond units A and B are located at the terminals of the silane coupling agent, the form of the bond units A and B is not particularly limited, and it is sufficient that the bond units A and B form units corresponding to the formulas (I) and (II) shown in FIG.

With respect to R ¹¹ in formulae (I) and (II), examples of halogen include chlorine, bromine, and fluorine. Examples of branched or unbranched alkyl groups having 1 to 30 carbon atoms include methyl and ethyl groups. Examples of branched or unbranched alkenyl groups having 2 to 30 carbon atoms include vinyl and 1-propenyl groups. Examples of branched or unbranched alkynyl groups having 2 to 30 carbon atoms include ethynyl and propynyl groups.

With respect to R ¹² in formulae (I) and (II), examples of the branched or unbranched alkylene group having 1 to 30 carbon atoms include an ethylene group, a propylene group, etc. Examples of the branched or unbranched alkenylene group having 2 to 30 carbon atoms include a vinylene group, a 1-propenylene group, etc. Examples of the branched or unbranched alkynylene group having 2 to 30 carbon atoms include an ethynylene group, a propynylene group, etc.

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

The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 6 parts by mass or more, and even more preferably 8 parts by mass or more, relative to 100 parts by mass of silica, and is preferably 15 parts by mass or less, and more preferably 12 parts by mass or less. Within the above range, the effect tends to be better.

The rubber composition preferably contains a resin.
The resin is not particularly limited, but a styrene-based resin can be preferably used. The styrene-based resin is a polymer containing a styrene-based monomer as a constituent monomer, and examples thereof include a homopolymer obtained by polymerizing one type of styrene-based monomer alone, a copolymer obtained by copolymerizing two or more types of styrene-based monomers, and a copolymer of a styrene-based monomer and another monomer that can be copolymerized therewith.

Examples of styrene-based monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene. These may be used alone or in combination of two or more. Of these, styrene and α-methylstyrene are preferred.

Other monomers include, for example, terpene compounds (terpene monomers) such as α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol, and non-conjugated olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene. These may be used alone or in combination of two or more.

From the viewpoint of overall performance such as fuel efficiency and chipping resistance, it is preferable to use a copolymer of a terpene compound and styrene, or a copolymer of styrene and ethylene as the styrene-based resin.

Commercially available examples of the above-mentioned resins include products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., JX Nippon Energy Corporation, Arakawa Chemical Industries Co., Ltd., and Taoka Chemical Co., Ltd.

The resin content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above range, the effect tends to be better obtained.

In the rubber composition, the resin content/carbon black content is preferably 0.1 or more, more preferably 0.2 or more, and is preferably 0.8 or less, more preferably 0.6 or less, and even more preferably 0.4 or less. Within the above range, the effect tends to be better obtained.
In this regard, the resin content and the carbon black content are the contents (unit: parts by mass) relative to 100 parts by mass of the rubber component.

In the rubber composition, the resin content/silica content is preferably 0.1 or more, and is preferably 0.6 or less, more preferably 0.4 or less, and further preferably 0.3 or less. Within the above range, the effect tends to be better obtained.
In this relationship, the resin content and the silica content are amounts (unit: parts by mass) based on 100 parts by mass of the rubber component.

The rubber composition preferably contains a dibenzylamine compound.
The dibenzylamine compound is a compound having at least one group (dibenzylamine group) represented by the following formula:

Specific examples of dibenzylamine compounds include dibenzylamine, tetrabenzylthiuram disulfide (TBzTD), zinc dibenzyldithiocarbamate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. Commercially available products include those from Sanshin Chemical Industry Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., LANXESS, etc. These may be used alone or in combination of two or more. Of these, compounds having two dibenzylamine groups are preferred, and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane is more preferred.

The content of the dibenzylamine compound is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and even more preferably 1.2 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 6 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 2 parts by mass or less. Within the above range, the effect tends to be better obtained.

The rubber composition may contain a processing aid.
Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, etc. Commercially available products include those from Rhein Chemie and Struktol. These may be used alone or in combination of two or more. Among these, fatty acid metal salts are preferred.

The fatty acids constituting the fatty acid metal salt include saturated or unsaturated fatty acids (preferably saturated or unsaturated fatty acids having 6 to 28 carbon atoms (more preferably 10 to 25 carbon atoms, and even more preferably 14 to 20 carbon atoms)), such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid, behenic acid, and nervonic acid. These can be used alone or in combination of two or more. Of these, saturated fatty acids are preferred, and saturated fatty acids having 14 to 20 carbon atoms are more preferred.

Examples of metals constituting fatty acid metal salts include alkali metals such as potassium and sodium, alkaline earth metals such as magnesium, calcium and barium, zinc, nickel, molybdenum, etc. These may be used alone or in combination of two or more. Of these, zinc is preferred.

The content of the processing aid is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 4 parts by mass or less. Within the above range, the effect tends to be better.

The rubber composition may contain oil.
Examples of the oil include process oil, vegetable oil, and mixtures thereof. Examples of the process oil include paraffin-based process oil, aromatic process oil, and naphthenic process oil. Examples of the vegetable oil include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. Examples of commercially available products include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., JXTG Energy Corporation, Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Mill Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and the like. These may be used alone or in combination of two or more.

The oil content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 30 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the rubber component. Within the above range, the effect tends to be better.

The rubber composition may contain an antioxidant.
Examples of the antioxidant include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants 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, and N,N'-di-2-naphthyl-p-phenylenediamine. Examples of the antioxidant include p-phenylenediamine antioxidants such as quinolinone, quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline, monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol, and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Commercially available products include those of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis Co., Ltd. These may be used alone or in combination of two or more.

The content of the anti-aging agent is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 4 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less. Within the above range, the effect tends to be better.

The rubber composition may contain a wax.
The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as vegetable wax and animal wax; and synthetic waxes such as polymers of ethylene, propylene, etc. Commercially available products include those from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. These may be used alone or in combination of two or more kinds.

The wax content is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component. Within the above range, the effect tends to be better.

The rubber composition may contain stearic acid.
As the stearic acid, a conventionally known one can be used, and as a commercially available product, a product from NOF Corp., Kao Corp., Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. can be used. These may be used alone or in combination of two or more kinds.

The content of stearic acid is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component. Within the above range, the effect tends to be better obtained.

The rubber composition may contain zinc oxide.
As the zinc oxide, a conventionally known one can be used, and as a commercially available product, there can be used products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. These may be used alone or in combination of two or more kinds.

The content of zinc oxide is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component. If it is within the above range, the effect tends to be better.

The rubber composition may contain sulfur.
Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. Commercially available products include those from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. These may be used alone or in combination of two or more.

The sulfur content is preferably 0.8 parts by mass or more, more preferably 1.2 parts by mass or more, and even more preferably 1.5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 6 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less. Within the above range, the effect tends to be better obtained.

The rubber composition may contain a vulcanization accelerator.
Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD) and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-orthotolylguanidine, and orthotolylbiguanidine. Commercially available products include products from Sumitomo Chemical Co., Ltd. and Ouchi Shinko Chemical Co., Ltd. These may be used alone or in combination of two or more.

The content of the vulcanization accelerator is preferably 0.8 parts by mass or more, more preferably 1.2 parts by mass or more, and even more preferably 1.5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 8 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less. Within the above range, the effect tends to be better.

In addition to the above components, the rubber composition may further contain additives commonly used in the tire industry, such as organic peroxides; fillers such as talc, alumina, clay, aluminum hydroxide, and mica; etc. The content of these additives is preferably 0.1 to 200 parts by mass per 100 parts by mass of the rubber component.

The rubber composition can be produced, for example, by kneading the above-mentioned components using a rubber kneading device such as an open roll or a Banbury mixer, and then vulcanizing the mixture.

As for kneading conditions, in the base kneading process where additives other than the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C. In the finish kneading process where the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 120°C or lower, preferably 85 to 110°C. Furthermore, the composition kneaded with the vulcanizing agent and 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 vulcanization time is usually 5 to 15 minutes.

The rubber composition can be used (as a rubber composition for tires) in tire components such as treads (cap treads), sidewalls, base treads, under treads, shoulders, clinches, bead apexes, breaker cushion rubber, carcass cord covering rubber, insulation, chafers, inner liners, and the like, as well as side reinforcing layers of run-flat tires. In particular, it is suitable for treads.

The tire of the present invention is produced by a conventional method using the above rubber composition.
That is, the rubber composition is extruded in an unvulcanized state to match the shape of the tread, etc., and molded together with other tire components in a tire building machine by a normal method to form an unvulcanized tire. The unvulcanized tire is then heated and pressurized in a vulcanizer to obtain a tire.

The above tires (pneumatic tires, etc.) can be used for passenger car tires; truck and bus tires; motorcycle tires; high-performance tires; winter tires such as studless tires; run-flat tires with side reinforcing layers; tires with sound absorbing materials that have sound absorbing materials such as sponge in the tire cavity; tires with sealing materials that have a sealant inside or in the tire cavity that can seal in the event of a puncture; tires with electronic components that have electronic components such as sensors and wireless tags inside or in the tire cavity, etc., and are suitable for passenger car tires.

The size of the above tires is not particularly limited, and can be appropriately selected, for example, the tire width within the range of 100 to 400 mm, the aspect ratio within the range of 25 to 85%, and the rim diameter within the range of 10 to 25 inches. Specific examples include 105/50R16, 115/50R17, 125/55R20, 135/45R21, 145/45R21, 155/45R18, 165/45R22, 175/45R23, 185/60R20, 195/55R14, 205/40R16, 215/40R16, 225/40R17, 235/40R17, 245/40R16, 255/40R17, 265/40R17, 275/35R18, 285/30R19, and 295/45R20.

なお、タイヤ外径（Ｄｔ）とは、タイヤを適用リムに装着して内圧２５０ｋＰａ・無負荷とした状態のタイヤの外径である。タイヤ断面幅（Ｗｔ）とは、タイヤを適用リムに装着して内圧２５０ｋＰａ・無負荷とした状態のタイヤ側面の模様又は文字など全てを含むサイドウォール間の直線距離、つまり総幅からタイヤの側面の模様、文字などを除いた幅である。 It is preferable that the tire outer diameter Dt and the tire section width Wt of the tire satisfy the following relational expression.

The tire outer diameter (Dt) is the outer diameter of the tire when mounted on an applicable rim and the internal pressure is 250 kPa with no load. The tire cross-sectional width (Wt) is the linear distance between the sidewalls including all patterns and letters on the tire side when mounted on an applicable rim and the internal pressure is 250 kPa with no load, that is, the width excluding the patterns and letters on the tire side from the total width.

Specific examples of tires that can satisfy the above formula include 145/60R18, 145/60R19, 155/55R18, 155/55R19, 155/70R17, 155/70R19, 165/55R20, 165/55R21, 165/60R19, 165/65R19, 165/70R18, 175/55R19, 175/55R20, 175/55R22, 175/60R18, 185/55R19, 185/60R20, 195/50R20, 195/55R20, etc.

Tires that satisfy the above formula are preferably used as pneumatic tires for passenger cars. This is because pneumatic tires for passenger cars that satisfy the above formula tend to be more suitable for solving the problem in question.

The present invention will be specifically explained based on examples, but the present invention is not limited to these.

The various chemicals used in the examples and comparative examples are described below.

(Rubber component)
Natural rubber: TSR20
SBR1: Modified SBR synthesized in Production Example 1 below (styrene content: 10% by mass, vinyl content: 40% by mass, Mw: 300,000)
SBR2: SBR1502 manufactured by JSR Corporation (styrene content: 24% by mass, vinyl content: 16% by mass)
BR: BR710 manufactured by Ube Industries, Ltd. (cis content: 90% by mass or more, vinyl content: 1.2% by mass)

(Chemicals other than rubber components)
Carbon black 1: N134 (CTAB: 135 ^m2 /g)
Carbon black 2: N220 (CTAB: 111 ^m2 /g)
Silica 1: Ultrasil VN3 (CTAB: 165 m ² /g) manufactured by Evonik Degussa
Silica 2: Ultrasil 9100GR (CTAB: 200 m ² /g) manufactured by Evonik Degussa
Silane coupling agent 1: Si266 (bis(3-triethoxysilylpropyl)disulfide) manufactured by Evonik Degussa
Silane coupling agent 2: NXT (3-octanoylthiopropyltriethoxysilane) manufactured by Momentive
Oil: A/O Mix manufactured by Sankyo Yuka Kogyo Co., Ltd. Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd.
Resin 1: YS Resin TO125 (terpene styrene resin (copolymer of terpene compound and styrene)) manufactured by Yasuhara Chemical Co., Ltd.
Resin 2: Struktol 40MS (a copolymer of styrene and ethylene) manufactured by Struktol
Antioxidant 1: Nocrac 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Antioxidant 2: Nocrac RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Processing aid: EF44 (zinc salt of saturated fatty acid) manufactured by Struktol
Stearic acid: NOF Corporation's "Tsubaki" stearic acid
Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Dibenzylamine compound: Vulcuren VP KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane) manufactured by LANXESS

(Production Example 1)
Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were charged into a nitrogen-substituted autoclave reactor. After adjusting the temperature of the reactor contents to 20°C, n-butyllithium was added to initiate polymerization. Polymerization was performed under adiabatic conditions, with the maximum temperature reaching 85°C. When the polymerization conversion reached 99%, butadiene was added and polymerization was continued for another 5 minutes, after which 3-dimethylaminopropyltriethoxysilane was added as a modifier and the reaction was continued for 15 minutes. After completion of the polymerization reaction, 2,6-di-tert-butyl-p-cresol was added. Next, the solvent was removed by steam stripping, and the mixture was dried with a heated roll adjusted to 110°C to obtain SBR1.

Examples and Comparative Examples
According to the formulation shown in Table 1, materials other than the dibenzylamine compound, sulfur, and vulcanization accelerator were kneaded for 5 minutes under the condition of 150 ° C. using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded product. Next, the dibenzylamine compound, sulfur, and 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 was molded into a tread shape, and laminated together with other tire components to form an unvulcanized tire, which was press-vulcanized for 12 minutes under the condition of 150 ° C. to produce a test tire (size: 175 / 60R18). The following evaluations were performed using the obtained test tire, and the results are shown in Table 1.

(Chipping resistance)
After a vehicle equipped with the above test tires on all wheels was driven for 8000 km, the number of chipping occurrences in the tread portion was counted and expressed as an index with Comparative Example 3 being set at 100. A larger index indicates fewer chipping occurrences and better chipping resistance.

(low fuel consumption)
The rolling resistance was measured using a rolling resistance tester when the test tire was run at a speed (80 km/h), and the rolling resistance was expressed as an index with Comparative Example 2 being set at 100. A larger index indicates a smaller rolling resistance and better fuel economy.

As can be seen from Table 1, the examples were superior to the comparative examples in terms of the overall performance of the desired fuel economy and chipping resistance.

Claims (6)

The rubber component contains styrene-butadiene rubber, carbon black, and silica,
The total styrene content in the rubber component is 15% by mass or less,
the carbon black has an average cetyltrimethylammonium bromide specific surface area of 120 m ² /g or more;
the proportion of carbon black having a cetyltrimethylammonium bromide specific surface area of 115 m ² /g or less is 50% by mass or more relative to 100% by mass of the carbon black;
A rubber composition for tires, wherein the amount of the carbon black per 100 parts by mass of the rubber component is 20 parts by mass or more,
A rubber composition for a tire, in which the ratio of resin content/silica content is 0.1 or more and 0.6 or less (excluding the rubber composition for a tire described in (1) below) .
(1) 100 parts by mass of a rubber component containing 40 to 75% by mass of modified natural rubber having a nitrogen content of 0.40% by mass or less and 10 to 35% by mass of styrene-butadiene rubber;
20 to 60 parts by mass of carbon black having a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 120 m ² /g or more;
0.5 to 3.0 parts by mass of a compound represented by the following formula (A):
A rubber composition for tires comprising:
R ¹ -S-S-Y-S-S-R ² (A)
(In the formula, Y is an alkylene group having 2 to 10 carbon atoms, and R ¹ and R ² are the same or different and each represents a monovalent organic group containing a nitrogen atom.) The rubber component contains an isoprene-based rubber,
2. The rubber composition for tires according to claim 1, wherein the content of said isoprene-based rubber is greater than the content of said styrene-butadiene rubber. The rubber composition for tires according to claim 1 or 2, wherein the total amount of styrene in the rubber component is 10% by mass or less. The rubber composition for tires according to any one of claims 1 to 3, which contains a styrene-based resin. The rubber composition for tires according to any one of claims 1 to 4, which contains a dibenzylamine compound. A tire using the rubber composition according to any one of claims 1 to 5.