Rubber composition for tire tread, tire tread and passenger car tire

Abstract

To provide a rubber composition for a tire tread capable of comprehensively improving fuel economy, wet grip performance, fracture characteristics and processability in a well-balanced manner, a tire tread comprising the rubber composition, and a passenger car tire including the tire tread.SOLUTION: The rubber composition for a tire tread contains: a rubber component containing an isoprene rubber and a styrene-butadiene rubber; a filler containing 20 mass% or more of silica and 20 mass% or more of carbon black; a mercapto-based silane coupling agent; a liquid rubber; and a resin.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rubber composition for a tire tread, a tire tread made of the rubber composition, and a passenger car tire provided with the tire tread.

Background Art

[0002] Conventionally, various performances such as low fuel consumption, wet grip performance, and fracture characteristics have been required for tires.

[0003] For example, Patent Document 1 describes a rubber composition for a tire tread in which a filler containing a predetermined amount of silica is blended with a diene rubber component containing three types of rubbers, namely, a predetermined emulsion-polymerized styrene-butadiene rubber, a terminal-modified solution-polymerized styrene-butadiene rubber, and natural rubber, in a predetermined weight ratio, in order to improve low rolling resistance, wet grip performance, and abrasion resistance.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, a rubber composition in which silica is blended with styrene-butadiene rubber has a problem that its processability deteriorates due to fixation by chemical bonding between styrene-butadiene rubber and silica.

[0006] An object of the present invention is to provide a rubber composition for a tire tread, a tire tread made of the rubber composition, and a passenger car tire provided with the tire tread, which can comprehensively improve low fuel consumption, wet grip performance, fracture characteristics, and processability in a well-balanced manner.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by formulating a rubber component containing an isoprene rubber and a styrene-butadiene rubber with a filler containing a predetermined amount of silica and carbon black, a mercapto-based silane coupling agent, a liquid rubber, and a resin, and have further repeated studies to complete the present invention.

[0008] That is, the present invention provides: [1] A rubber composition for a tire tread, comprising a rubber component containing an isoprene rubber and a styrene-butadiene rubber, a filler containing 20% by mass or more, preferably 21% by mass or more, more preferably 23% by mass or more, still more preferably 25% by mass or more, or preferably 20 to 80% by mass, more preferably 21 to 80% by mass, more preferably 21 to 70% by mass, more preferably 23 to 70% by mass, more preferably 23 to 65% by mass, more preferably 25 to 65% by mass of silica and 20% by mass or more, preferably 25% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, or preferably 20 to 80% by mass, more preferably 25 to 80% by mass, more preferably 25 to 77% by mass, more preferably 30 to 77% by mass, more preferably 30 to 75% by mass, more preferably 35 to 75% by mass of carbon black, a mercapto-based silane coupling agent, a liquid rubber, and a resin. [2] The rubber composition for a tire tread according to [1] above, wherein the content (% by mass) of the isoprene rubber in the rubber component and the content (parts by mass) of the silica with respect to 100 parts by mass of the rubber component satisfy the following formula (A). (Content of isoprene rubber) / (Content of silica) ≦ 2.0 (A) (Preferably, (content of isoprene rubber) / (content of silica) ≤ 1.5, more preferably, (content of isoprene rubber) / (content of silica) ≤ 1.0, still more preferably, (content of isoprene rubber) / (content of silica) ≤ 0.8, even more preferably, (content of isoprene rubber) / (content of silica) ≤ 0.6, or, preferably, 0.1 ≤ (content of isoprene rubber) / (content of silica) ≤ 2.0, more preferably, 0.1 ≤ (content of isoprene rubber) / (content of silica) ≤ 1.5, still more preferably, 0.1 ≤ (content of isoprene rubber) / (content of silica) ≤ 1.0, even more preferably, 0.2 ≤ (content of isoprene rubber) / (content of silica) ≤ 0.8, even more preferably, 0.2 ≤ (content of isoprene rubber) / (content of silica) ≤ 0.6) [3] The rubber composition for tire tread according to [1] or [2] above, wherein the liquid rubber is liquid styrene-butadiene rubber, [4] The rubber composition for tire tread according to any one of [1] to [3] above, wherein the resin is an aromatic resin, [5] The rubber composition for tire tread according to any one of [1] to [4] above, wherein the content (parts by mass) of the liquid rubber and the content (parts by mass) of the silica with respect to 100 parts by mass of the rubber component satisfy the following formula (B), (content of liquid rubber) / (content of silica) ≥ 0.1 (B) (Preferably, (content of liquid rubber) / (content of silica) ≥ 0.2, more preferably, (content of liquid rubber) / (content of silica) ≥ 0.3, or, preferably, 1.0 ≥ (content of liquid rubber) / (content of silica) ≥ 0.1, more preferably, 0.7 ≥ (content of liquid rubber) / (content of silica) ≥ 0.1, still more preferably, 0.5 ≥ (content of liquid rubber) / (content of silica) ≥ 0.2, even more preferably, 0.5 ≥ (content of liquid rubber) / (content of silica) ≥ 0.3) [6] The rubber composition for tire tread according to any one of [1] to [5] above, wherein the content (% by mass) of the isoprene rubber in the rubber component and the content (parts by mass) of the resin with respect to 100 parts by mass of the rubber component satisfy the following formula (C), (Content of isoprene rubber) / (Content of resin) ≤ 13.0 (C) (Preferably, (Content of isoprene rubber) / (Content of resin) ≤ 12.0, more preferably, (Content of isoprene rubber) / (Content of resin) ≤ 10.0, still more preferably, (Content of isoprene rubber) / (Content of resin) ≤ 8.0, or preferably, 0.3 ≤ (Content of isoprene rubber) / (Content of resin) ≤ 13.0, more preferably, 0.7 ≤ (Content of isoprene rubber) / (Content of resin) ≤ 12.0, still more preferably, 1.0 ≤ (Content of isoprene rubber) / (Content of resin) ≤ 10.0, still more preferably, 1.3 ≤ (Content of isoprene rubber) / (Content of resin) ≤ 10.0, still more preferably, 1.3 ≤ (Content of isoprene rubber) / (Content of resin) ≤ 8.0) [7] The rubber composition for tire tread according to any one of [1] to [6] above, wherein the content (parts by mass) of the liquid rubber and the content (parts by mass) of the resin with respect to 100 parts by mass of the rubber component satisfy the following formula (D). (Content of liquid rubber) + (Content of resin) ≥ 11 (D) (Preferably, (Content of liquid rubber) + (Content of resin) ≥ 12, more preferably, (Content of liquid rubber) + (Content of resin) ≥ 13, still more preferably, (Content of liquid rubber) + (Content of resin) ≥ 14, or preferably, 35 ≥ (Content of liquid rubber) + (Content of resin) ≥ 11, more preferably, 30 ≥ (Content of liquid rubber) + (Content of resin) ≥ 12, still more preferably, 25 ≥ (Content of liquid rubber) + (Content of resin) ≥ 13, still more preferably, 25 ≥ (Content of liquid rubber) + (Content of resin) ≥ 14, still more preferably, 22 ≥ (Content of liquid rubber) + (Content of resin) ≥ 14) [8] The rubber composition for tire tread according to any one of [1] to [7] above, wherein the content of the isoprene rubber in the rubber component is less than 50% by mass, preferably 46% by mass or less, more preferably 43% by mass or less, still more preferably 40% by mass or less, or more preferably 5% by mass or more and less than 50% by mass, more preferably 5 - 46% by mass, still more preferably 5 - 43% by mass, still more preferably 10 - 43% by mass, still more preferably 10 - 40% by mass, still more preferably 15 - 40% by mass. [9] The rubber composition for a tire tread according to any one of the above [1] to [8], wherein the mercapto-based silane coupling agent is at least one selected from the group consisting of a compound represented by the following formula (S1), a compound represented by the following formula (1), and a compound containing a bonding unit A represented by the following formula (2) and a bonding unit B represented by the following formula (3), preferably a compound represented by the following formula (S1): [ka] (In the formula, R 1001 -Cl, -Br, -OR 1006 , -O(O=)CR 1006 , -ON=CR 1006 R 1007 , -ON=CR 1006 R 1007 , -NR 1006 R 1007 and -(OSiR 1006 R 1007 ) h (OSiR 1006 R 1007 R 1008 a monovalent group (R 1006 , R 1007 and R 1008 may be the same or different, and each represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, and h has an average value of 1 to 4; 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, and j is an integer of 1 to 4. 1004 is a divalent hydrocarbon group having 1 to 18 carbon atoms, R 1005 represents a monovalent hydrocarbon group having 1 to 18 carbon atoms, and x, y, and z are numbers that satisfy the relationship: x+y+2z=3, 0≦x≦3, 0≦y≦2, 0≦z≦1. [ka] (In the formula, R 101 ~R 103is a linear or branched alkyl group having 1 to 12 carbon atoms, a linear or branched alkoxy group having 1 to 12 carbon atoms, or -O-(R 111 -O) z -R 112 (where z R 111 represents a divalent hydrocarbon group having 1 to 30 carbon atoms, which may be linear or branched. z R 111 may be the same or different from each other. R 112 represents a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group having 7 to 30 carbon atoms. z represents an integer from 1 to 30.). R 101 ~R 103 may be the same or different from each other. R 104 represents a linear or branched alkylene group having 1 to 6 carbon atoms.). [Chemical formula] [Chemical formula] (In the formula, x is an integer of 0 or more, and y is an integer of 1 or more. R 201 each represents a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, a linear or branched alkynyl group having 2 to 30 carbon atoms, or a group in which the terminal hydrogen atom of the alkyl group is substituted with a hydroxyl group or a carboxyl group. R 202 each represents a linear or branched alkylene group having 1 to 30 carbon atoms, a linear or branched alkenylene group having 2 to 30 carbon atoms, or a linear or branched alkynylene group having 2 to 30 carbon atoms. R 201 and R 202 may form a ring structure with each other.),

[10] A tire tread composed of the rubber composition for a tire tread according to any one of [1] to [9] above,

[11] A passenger car tire provided with the tire tread according to

[10] above,

[12] The passenger car tire according to

[11] , wherein the relationship between the tire outer diameter Dt (mm) and the tire section width Wt (mm) satisfies the following formula (α): 1963.4 ≦ (Dt^2 × π / 4) / Wt ≦ 2827.4 (α) (Preferably 1970.0 ≦ (Dt^2 × π / 4) / Wt ≦ 2800.0, more preferably 1980.0 ≦ (Dt^2 × π / 4) / Wt ≦ 2700.0, even more preferably 1990.0 ≦ (Dt^2 × π / 4) / Wt ≦ 2600.0) relates to.

Effect of the Invention

[0009] According to the present invention, it is possible to provide a rubber composition for a tire tread, a tire tread made of the rubber composition, and a passenger car tire equipped with the tire tread, which can comprehensively improve fuel efficiency, wet grip performance, fracture characteristics, and processability in a well-balanced manner.

Mode for Carrying Out the Invention

[0010] One aspect of the present disclosure is a rubber composition for a tire tread, which includes a rubber component containing an isoprene-based rubber and a styrene-butadiene rubber, a filler containing 20% by mass or more of silica and 20% by mass or more of carbon black, a mercapto-based silane coupling agent, a liquid rubber, and a resin.

[0011] Although not intended to be restricted by theory, the following mechanisms are considered for the above effects to be exerted. When the rubber component includes isoprene rubber (IR type) and styrene-butadiene rubber (SBR), an IR phase composed of isoprene rubber and an SBR phase composed of styrene-butadiene rubber form a sea-island structure, that is, an island phase composed of the IR phase and a sea phase composed of the SBR phase. Since these rubber components have different polarities from each other, if only one of silica and carbon black is blended as a filler, there will be a bias in the distribution of the filler in each phase. That is, silica tends to be distributed in the SBR phase and carbon black tends to be distributed in the IR phase. Therefore, both silica and carbon black are evenly blended as fillers to homogenize the dispersion of the filler and improve the fracture properties. However, in this case, the energy loss in the high-frequency range that contributes to the wet grip performance in the SBR phase tends to decrease. Therefore, a resin that interacts with silica is blended to increase the energy loss in the SBR phase and improve the wet grip performance. However, if this is done, then silica and the resin act in the direction of deteriorating the fluidity of the SBR phase and reducing the processability. Therefore, to improve the fluidity of the SBR phase, a liquid rubber that directly contributes to the improvement of fluidity is blended to improve the processability. Also, by blending a mercapto-based silane coupling agent with high reactivity with silica to enhance the dispersibility of silica, it also contributes to the improvement of low fuel consumption and further improvement of wet grip performance. From the above, it is considered that low fuel consumption, wet grip performance, fracture properties, and processability are comprehensively improved in a well-balanced manner.

[0012] The content (mass %) of the isoprene rubber in the rubber component and the content (parts by mass) of the silica with respect to 100 parts by mass of the rubber component preferably satisfy the following formula (A). When the mass ratio of the isoprene rubber to the silica is 2.0 or less, the distribution of the filler to the IR phase and the SBR phase is less likely to be biased, and the silica is more easily dispersed. Therefore, there is a tendency that the low fuel consumption property and the fracture property can be improved more balancedly. The value of (content of isoprene rubber) / (content of silica) is preferably 1.5 or less, more preferably 1.0 or less, still more preferably 0.8 or less, and even more preferably 0.6 or less. Further, the value of (content of isoprene rubber) / (content of silica) is preferably 0.1 or more, more preferably 0.2 or more, for the reason that the effects of the present disclosure can be more suitably obtained. (Content of isoprene rubber) / (Content of silica) ≤ 2.0 (A)

[0013] The liquid rubber is preferably liquid styrene-butadiene rubber. This is because when the liquid styrene-butadiene rubber selectively enters the SBR phase, the fluidity of the SBR phase is improved, and there is a tendency that the effect of improving the processability can be exhibited more favorably.

[0014] The resin is preferably an aromatic resin. Since the aromatic resin has excellent compatibility with SBR, it interacts with the silica in the SBR phase and increases the energy loss in the high-frequency range of the SBR phase, so there is a tendency that the effect of improving the wet grip performance can be exhibited more favorably.

[0015] The content (parts by mass) of the liquid rubber and the content (parts by mass) of the silica with respect to 100 parts by mass of the rubber component preferably satisfy the following formula (B). When the mass ratio of the liquid rubber to the silica is 0.1 or more, the fluidity of the SBR phase is improved by the liquid rubber, the processability is enhanced, and the dispersibility of the silica is easily achieved, contributing to the improvement of low fuel consumption. Therefore, there is a tendency to further improve the low fuel consumption and processability in a more balanced manner. The value of (content of liquid rubber) / (content of silica) is preferably 0.2 or more, more preferably 0.3 or more. Further, the value of (content of liquid rubber) / (content of silica) is preferably 1.0 or less, more preferably 0.7 or less, and even more preferably 0.5 or less because the effects of the present disclosure can be more preferably obtained. (Content of liquid rubber) / (Content of silica) ≥ 0.1 (B)

[0016] The content (mass %) of the isoprene-based rubber in the rubber component and the content (parts by mass) of the resin with respect to 100 parts by mass of the rubber component preferably satisfy the following formula (C). When the mass ratio of the isoprene-based rubber to the resin is 13.0 or less, it becomes easier to exhibit the compounding effect of the resin, increase the energy loss in the high-frequency range in the SBR phase, and easily obtain the effect of improving the fracture characteristics of the isoprene-based rubber itself. Therefore, there is a tendency to further improve the wet grip performance and fracture characteristics in a more balanced manner. The value of (content of isoprene-based rubber) / (content of resin) is preferably 12.0 or less, more preferably 10.0 or less, and even more preferably 8.0 or less. Further, the value of (content of isoprene-based rubber) / (content of resin) is preferably 0.3 or more, more preferably 0.7 or more, still more preferably 1.0 or more, and even more preferably 1.3 or more because the effects of the present disclosure can be more preferably obtained. (Content of isoprene-based rubber) / (Content of resin) ≤ 13.0 (C)

[0017] The content (parts by mass) of the liquid rubber and the content (parts by mass) of the resin with respect to 100 parts by mass of the rubber component preferably satisfy the following formula (D). When the total content of the liquid rubber and the resin is 11 or more, it becomes easier to exhibit the compounding effects of both the resin and the liquid rubber, and while increasing the energy loss in the high-frequency range in the SBR phase, the fluidity is improved. Therefore, there is a tendency that the wet grip performance and processability can be further improved in a more balanced manner. The value of (content of liquid rubber) + (content of resin) is preferably 12 or more, more preferably 13 or more, and even more preferably 14 or more. Further, the value of (content of liquid rubber) + (content of resin) is preferably 35 or less, more preferably 30 or less, still more preferably 25 or less, and even more preferably 22 or less because the effects of the present disclosure can be more suitably obtained. (Content of liquid rubber)+(Content of resin)≧11 (D)

[0018] The content of the isoprene rubber in the rubber component is preferably less than 50% by mass. When it is less than 50% by mass, the IR-based phase is likely to be formed as an island phase. Therefore, there is a tendency that the effect of improving the wet grip performance by the SBR phase is easily exhibited. From the viewpoint of improving processability, the content is preferably 46% by mass or less, more preferably 43% by mass or less, and even more preferably 40% by mass or less. Further, from the viewpoint of improving fracture properties, the content is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more.

[0019] The mercapto-based silane coupling agent is preferably at least one selected from the group consisting of a compound represented by the following formula (S1), a compound represented by the following formula (1), and a compound containing a bonding unit A represented by the following formula (2) and a bonding unit B represented by the following formula (3). Since these compounds have high reactivity with silica, the effect of improving silica dispersion is favorably exhibited, and the effects of the present disclosure can be more favorably exhibited.

Chemical formula

Chemical formula

[0020] Another aspect of the present disclosure is a tire tread composed of the above rubber composition for a tire tread.

[0021] Another aspect of the present disclosure is a passenger car tire provided with the above tire tread.

[0022] The above passenger car tire is preferably applied to a passenger car tire in which the relationship between the tire outer diameter Dt (mm) and the tire section width Wt (mm) satisfies the following formula (α). 1963.4 ≦ (Dt^2 × π / 4) / Wt ≦ 2827.4 (α)

[0023] In addition, in this specification, when indicating a numerical range using "~", unless otherwise specified, it shall include the numerical values at both ends thereof.

[0024] <Rubber component> The rubber component of the present disclosure includes an isoprene rubber and a styrene-butadiene rubber.

[0025] (Isoprene rubber) Examples of the isoprene rubber include natural rubber (NR), modified NR, denatured NR, isoprene rubber (IR), modified IR, etc. As NR, for example, those commonly used in the tire industry such as SIR20, RSS#3, TSR20, etc. can be used. Examples of the modified NR include deproteinized natural rubber (DPNR), high-purity natural rubber, etc., and examples of the denatured NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. IR is not particularly limited, and those commonly used in the tire industry can be used. Examples of the modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. Among them, from the viewpoint of improving the fracture characteristics, it is preferable to include at least one selected from NR, modified NR, and denatured NR. Among these, NR has the property of elongation crystallization and is particularly excellent in tensile strength, so it is more preferable to include NR as the isoprene rubber, and it may be only NR. The isoprene rubber can be used alone or in combination of two or more.

[0026] (Styrene-butadiene rubber) The styrene-butadiene rubber (SBR) is not particularly limited. For example, there are unmodified emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), modified emulsion-polymerized styrene-butadiene rubber (modified E-SBR) obtained by modifying these, modified solution-polymerized styrene-butadiene rubber (modified S-SBR), and other modified SBRs. Examples of the modified SBR include modified SBRs with modified terminals and / or main chains, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.). As for SBR, there are an oil-extended type with extender oil added to adjust flexibility and a non-oil-extended type without extender oil added, and either of these can be used. SBR can be, for example, those manufactured and sold by JSR Corporation, Asahi Kasei Chemicals Corporation, Nippon Zeon Co., Ltd., ZS Elastomer Co., Ltd., etc. Among them, it is preferably to contain at least one of E-SBR and S-SBR, more preferably to contain E-SBR, and even more preferably to contain only E-SBR because it can more balancedly improve low fuel consumption, wet grip performance, and processability. SBR can be used alone or in combination of two or more.

[0027] The styrene content of SBR is not particularly limited, but it is preferably 15.0 mass% to 40.0 mass%. From the viewpoints of rubber strength and grip performance, the styrene content is more preferably 20.0 mass% or more. Also, from the viewpoints of low fuel consumption and abrasion resistance, the styrene content is more preferably 30.0 mass% or less. Note that the styrene content in this specification is 1 a value calculated by 1H-NMR measurement.

[0028] The vinyl content (amount of 1,2-bonded butadiene units) of SBR is not particularly limited, but is preferably 10.0 to 80.0%. From the viewpoints of rubber strength and grip performance, the vinyl content is preferably 13.0% or more, more preferably 15.0% or more. Also, from the viewpoint of low fuel consumption, the vinyl content is preferably 60.0% or less, preferably 40.0% or less, and more preferably 20.0% or less. The vinyl content in this specification is a value measured by infrared absorption spectroscopy analysis.

[0029] The content in the rubber component of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, more preferably 20% by mass or more, more preferably 25% by mass or more, more preferably 30% by mass or more, more preferably 40% by mass or more, more preferably more than 50% by mass, more preferably 55% by mass or more, and even more preferably 60% by mass or more. Also, the content is preferably 95% by mass or less, more preferably 80% by mass or less, and even more preferably 65% by mass or less. When the content of SBR is within the above range, there is a tendency to obtain the effect that the low fuel consumption, wet grip performance, fracture characteristics, and processability can be comprehensively improved more balancedly. Here, for the reason that the effects of the present disclosure can be obtained more preferably, it is preferable that SBR is the main component in the rubber component (that is, the component most contained in the rubber component). When oil-extended type SBR is used as SBR, the content of SBR itself as the solid content contained in the oil-extended type SBR is taken as the content of SBR in the rubber component.

[0030] (Other rubber components) The rubber component may contain rubber components other than the above isoprene rubber and styrene-butadiene rubber (other rubber components). Such other rubber components are not particularly limited, and any of those conventionally used in the rubber industry, such as diene rubbers other than the above isoprene rubber and styrene-butadiene rubber, and non-diene rubbers, can be preferably used. Examples of the diene rubber include butadiene rubber (BR), styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), and the like. Examples of the non-diene rubber include butyl rubber (IIR), hydrogenated nitrile rubber (HNBR), ethylene-propylene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, and the like. The other rubber components can be used alone or in combination of two or more. Among them, BR is preferred because the effects of the present disclosure can be more favorably exhibited. That is, as the rubber component, it is more preferable to include an isoprene rubber, SBR, and BR, and it may be only an isoprene rubber, SBR, and BR.

[0031] BR is not particularly limited, and any of those commonly used in this field can be preferably used. For example, various BRs such as low-cis polybutadiene rubber (low-cis BR), high-cis polybutadiene rubber (high-cis BR), rare-earth-based butadiene rubber synthesized using a rare-earth element-based catalyst (rare-earth-based BR), butadiene rubber containing 1,2-syndiotactic polybutadiene crystals (SPB-containing BR), and modified butadiene rubber (modified BR) can be used. Among them, high-cis BR is preferred. BR can be, for example, those manufactured and sold by Ube Industries, Ltd., Nippon Zeon Co., Ltd., JSR Corporation, LANXESS, and the like. BR can be used alone or in combination of two or more.

[0032] High-cis BR is a butadiene rubber with a cis content (cis-1,4 bond content) of 90% or more. Among them, those with a cis-1,4 bond content of 95% or more are preferred, those with 96% or more are more preferred, and those with 97% or more are even more preferred. By containing high-cis BR, low heat build-up, tensile strength, elongation at break, and abrasion resistance can be improved. The cis content in this specification is a value measured by infrared absorption spectrometry.

[0033] As rare-earth-based BR, it is synthesized using a rare-earth element-based catalyst, and the vinyl content (amount of 1,2-bonded butadiene units) is preferably 1.8% or less, more preferably 1.0% or less, and even more preferably 0.8% or less, and the cis content (cis-1,4 bond content) is preferably 90% or more, more preferably 95% or more, more preferably 96% or more, and even more preferably 97% or more. By having the vinyl content and cis content within the above ranges, the effect that the elongation at break and abrasion resistance of the resulting rubber composition are excellent can be obtained.

[0034] As the rare-earth element-based catalyst used for the synthesis of rare-earth-based BR, known ones can be used. For example, there are lanthanum series rare-earth element compounds, organoaluminum compounds, aluminoxanes, halogen-containing compounds, and catalysts containing a Lewis base as required.

[0035] SPB-containing BR includes those in which 1,2-syndiotactic polybutadiene crystals are not simply dispersed in BR but are dispersed after chemically bonding to BR. Due to the crystals being dispersed after chemically bonding to the rubber component, the complex elastic modulus tends to improve.

[0036] Examples of the modified BR include modified BRs with modified terminals and / or main chains, modified BRs coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.), modified BRs with terminals and / or main chains modified by functional groups having an interaction with silica, and particularly modified BRs having at least one selected from the group consisting of silyl groups, amino groups, amide groups, hydroxyl groups, and epoxy groups. By using the modified BR, an effect of making the interaction with the filler stronger and being excellent in low fuel consumption can be obtained.

[0037] When contained in the rubber component, the content of BR is preferably 5% by mass or more, more preferably 15% by mass or more, and still more preferably 25% by mass or more. Also, the content is preferably 60% by mass or less, more preferably 50% by mass or less, and still more preferably 45% by mass or less. When the content of BR is within the above range, there is a tendency to obtain an effect that low fuel consumption, wet grip performance, fracture characteristics, and processability can be comprehensively improved in a more balanced manner.

[0038] <Filler> The filler of the present disclosure contains 20% by mass or more of silica and 20% by mass or more of carbon black. Among them, for the reason that the effects of the present disclosure can be exhibited better, the filler of the present disclosure is preferably composed of silica and carbon black.

[0039] (Silica) The silica is not particularly limited, and examples thereof include silica prepared by a dry method (anhydrous silicic acid), silica prepared by a wet method (hydrous silicic acid), etc. Among them, silica prepared by a wet method is preferred because it has many silanol groups on the surface and many reaction points with a silane coupling agent. As the silica, those manufactured and sold by, for example, Evonik Degussa, Solvay, Tosoh Silica Corporation, Tokuyama Corporation, etc. can be used. The silica can be used alone or in combination of two or more.

[0040] The nitrogen adsorption specific surface area (N2SA) of the silica is not particularly limited, but from the viewpoints of ensuring low fuel consumption and sufficient reinforcing properties, it is preferably 80 m 2 / g or more, more preferably 90 m 2 / g or more, still more preferably 100 m 2 / g or more, and even more preferably 110 m 2 / g or more. Further, from the viewpoints of the dispersibility and processability of the silica, the N2SA is preferably 500 m 2 / g or less, more preferably 300 m 2 / g or less, still more preferably 170 m 2 / g or less, and even more preferably 150 m 2 / g or less. When the N2SA of the silica is within the above range, the effects of the present disclosure tend to be more favorably exhibited. Note that the N2SA of the silica in this specification is a value measured by the BET method in accordance with ASTM D3037-81.

[0041] The CTAB (cetyltrimethylammonium bromide) specific surface area of the silica is preferably 80 m 2 / g or more, more preferably 90 m 2 / g or more, and still more preferably 100 m 2 / g or more. Further, the CTAB specific surface area is more preferably 300 m 2 / g or less, still more preferably 170 m 2 / g or less, and even more preferably 150 m 2 / g or less. When the CTAB specific surface area of the silica is within the above range, the effects of the present disclosure tend to be more favorably exhibited. Note that the CTAB specific surface area of the silica in this specification is a value measured in accordance with ASTM D3765-92.

[0042] The content of the silica relative to 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 20 parts by mass or more from the viewpoints of ensuring low fuel consumption, wet grip performance, and sufficient reinforcing properties. Further, from the viewpoints of the dispersibility, processability, and wet grip performance of the silica, the content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 60 parts by mass or less.

[0043] (Carbon black) The carbon black is not particularly limited, and those commonly used in the rubber industry, such as GPF, FEF, HAF, ISAF, SAF, etc., can be used. The carbon black can be, for example, those manufactured and sold by Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Columbian Carbon Company, etc. The carbon black can be used alone or in combination of two or more kinds.

[0044] The N2SA of the carbon black is not particularly limited, but from the viewpoint of obtaining sufficient reinforcing property and further improving the fracture characteristics, it is preferably 50 m 2 / g or more, more preferably 70 m 2 / g or more, still more preferably 90 m 2 / g or more, and even more preferably 111 m 2 / g or more. Also, from the viewpoint of excellent dispersibility and low heat generation, the N2SA is preferably 500 m 2 / g or less, more preferably 450 m 2 / g or less, still more preferably 300 m 2 / g or less, even more preferably 250 m 2 / g or less, even more preferably 200 m 2 / g or less, even more preferably 180 m 2 / g or less, even more preferably 160 m 2 / g or less. When the N2SA of the carbon black is within the above range, the effects of the present disclosure tend to be more favorably exhibited. The N2SA of the carbon black in this specification is a value measured in accordance with JIS K 6217-2:2001.

[0045] The dibutyl phthalate (DBP) absorption of carbon black is not particularly limited, but from the viewpoints of obtaining sufficient reinforcing properties and good low fuel consumption, wet grip performance, and abrasion resistance, it is preferably 50 ml / 100 g or more, more preferably 70 ml / 100 g or more, still more preferably 90 ml / 100 g or more, and even more preferably 115 ml / 100 g or more. Also, from the viewpoint of low fuel consumption, the DBP absorption is preferably 220 ml / 100 g or less, more preferably 180 ml / 100 g or less, and still more preferably 130 ml / 100 g or less. When the DBP absorption of carbon black is within the above range, the effects of the present disclosure tend to be more favorably exhibited. The DBP absorption of carbon black in this specification is a value measured in accordance with JIS K 6217-4:2008.

[0046] The content of carbon black relative to 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and still more preferably 30 parts by mass or more. Also, the content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 60 parts by mass or less. When the content of carbon black is within the above range, sufficient breaking characteristics, good dispersion in rubber, and good processability tend to be obtained, and the effects of the present disclosure tend to be more favorably exhibited.

[0047] (Other fillers) As the filler, in addition to silica and carbon black, other fillers may or may not be used. Such fillers are not particularly limited, and for example, any of fillers generally used in this field such as aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, talc, and clay can be used. Other fillers can be used alone or in combination of two or more.

[0048] (Contents of silica and carbon black in the filler) The content of silica and carbon black in the filler is 20% by mass or more of silica and 20% by mass or more of carbon black. When the content of silica and carbon black in the filler is outside the above range, there will be a bias in the distribution of the filler to the IR phase and the SBR phase, and it tends to be difficult to comprehensively improve fuel efficiency, wet grip performance, fracture properties, and processability in a well-balanced manner. The content of silica in the filler can be appropriately adjusted within the above range, but 21% by mass or more is preferable, 23% by mass or more is more preferable, and 25% by mass or more is even more preferable. Also, the content of silica in the filler is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 65% by mass or less. The content of carbon black in the filler can be appropriately adjusted within the above range, but 25% by mass or more is preferable, 30% by mass or more is more preferable, and 35% by mass or more is even more preferable. Also, the content of carbon black in the filler is preferably 80% by mass or less, more preferably 77% by mass or less, and even more preferably 75% by mass or less. When the content of silica and carbon black in the filler is within the above range, both the distribution of carbon black to the IR phase and the distribution of silica to the SBR phase are likely to be effectively carried out, and thus there is a tendency to obtain the effect that fuel efficiency, wet grip performance, fracture properties, and processability can be more comprehensively improved in a better balance.

[0049] (Total content of the filler) From the viewpoint of sufficient reinforcing properties, the total content of the filler is preferably 30 parts by mass or more, more preferably 60 parts by mass or more, and even more preferably 80 parts by mass or more with respect to 100 parts by mass of the rubber component. Also, from the viewpoint of wet grip performance, the content is preferably 250 parts by mass or less, more preferably 180 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 120 parts by mass or less.

[0050] <Mercapto-based silane coupling agent> The rubber composition of the present disclosure contains a mercapto-based silane coupling agent.

[0051] (Mercapto-based silane coupling agent) In the present disclosure, the "mercapto-based silane coupling agent" means a silane coupling agent having a mercapto group and a silane coupling agent having a structure in which the mercapto group is protected by a protecting group. The mercapto-based silane coupling agent is not particularly limited, and for example, it is at least one selected from the group consisting of a compound represented by the following formula (S1), a compound represented by the following formula (1), and a compound containing a bonding unit A represented by the following formula (2) and a bonding unit B represented by the following formula (3). Among them, at least one of a compound represented by the following formula (S1) and a compound containing a bonding unit A represented by the following formula (2) and a bonding unit B represented by the following formula (3) is preferable, and a compound represented by the following formula (S1) is more preferable because the effects of the present disclosure can be exhibited more favorably. [Chemical formula] (In the formula, R 1001 is -Cl, -Br, -OR 1006 , -O(O=)CR 1006 , -ON=CR 1006 R 1007 , -ON=CR 1006 R 1007 , -NR 1006 R 1007 and -(OSiR 1006 R 1007 ) h (OSiR 1006 R 1007 R 1008 ) selected from a monovalent group (R 1006 , R 1007 and R 1008 may be the same or different and are each a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, and h has an average value of 1 to 4). And 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, and j is an integer of 1 to 4).), R 1004 is a divalent hydrocarbon group having 1 to 18 carbon atoms, R 1005represents a monovalent hydrocarbon group having 1 to 18 carbon atoms, and x, y, and z are numbers satisfying the relationships of x + y + 2z = 3, 0 ≦ x ≦ 3, 0 ≦ y ≦ 2, and 0 ≦ z ≦ 1.)

Chem.

Chem.

Chem.

[0052] Mercapto-based silane coupling agents can be those manufactured and sold by, for example, Momentive Performance Materials, Evonik Degussa, etc. Mercapto-based silane coupling agents can be used alone or in combination of two or more kinds.)

[0053] Hereinafter, the compound represented by the above formula (S1) will be described.)

[0054] In formula (S1), R 1005 , R 1006 , R 1007 and R 1008 are each independently preferably a group selected from the group consisting of linear, cyclic or branched alkyl groups, alkenyl groups, aryl groups and aralkyl groups having 1 to 18 carbon atoms. Further, 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 linear, cyclic or branched alkyl groups, alkenyl groups, aryl groups and aralkyl groups. R 1009 is preferably a linear, cyclic or branched alkylene group, particularly preferably a linear one. R 1004 can be, 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, an arylene group having 6 to 18 carbon atoms, 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. As this R 1004 , an alkylene group having 1 to 6 carbon atoms is preferable, and particularly preferably a linear alkylene group, such as a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group.)

[0055] R in formula (S1) 1002 R 1005 R 1006 R 1007 and R 1008 Specific examples of R include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, 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, cyclohexenyl group, phenyl group, tolyl group, xylyl group, naphthyl group, benzyl group, phenethyl group, naphthylmethyl group, and the like.

[0056] Examples of R in formula (S1) 1009 include, as linear alkylene groups, methylene group, ethylene group, n-propylene group, n-butylene group, hexylene group, etc., and as branched alkylene groups, isopropylene group, isobutylene group, 2-methylpropylene group, etc.

[0057] Specific examples of the silane coupling agent 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. Among them, 3-octanoylthiopropyltriethoxysilane is preferred.

[0058] The silane coupling agent represented by the formula (S1) has a thioester structure (i.e., a protected mercapto group) in the molecule, has little reactivity with the rubber component up to high temperatures, can suppress the strong bonding of the rubber component, the silane coupling agent, and silica during kneading, and can disperse the silica appropriately. Therefore, there is a tendency to more favorably exhibit the effects of the present disclosure.

[0059] Next, the compound represented by the above formula (1) will be described.

[0060] R 101 ~R 103 represents a linear or branched alkyl group having 1 to 12 carbon atoms, a linear or branched alkoxy group having 1 to 12 carbon atoms, or a group represented by -O-(R 111 -O) z -R 112 . From the viewpoint of obtaining good effects of the present disclosure, at least one of R 101 ~R 103 is preferably a group represented by -O-(R 111 -O) z -R 112 , more preferably two of them are groups represented by -O-(R 111 -O) z -R 112 , and one of them is a linear or branched alkoxy group having 1 to 12 carbon atoms.

[0061] R 101 ~R 103 Examples of the linear or branched alkyl group having 1 to 12 (preferably 1 to 5) carbon atoms of R

[0062] R 101 ~R 103Examples of the linear or branched alkoxy group having 1 to 12 carbon atoms (preferably 1 to 5 carbon atoms) include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an iso-butoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, a 2-ethylhexyloxy group, an octyloxy group, a nonyloxy group, and the like.

[0063] R 101 ~R 103 In -O-(R 111 -O) z -R 112 wherein R 111 represents a divalent hydrocarbon group having 1 to 30 carbon atoms (preferably 1 to 15 carbon atoms, more preferably 1 to 3 carbon atoms), which may be linear or branched. Examples of the hydrocarbon group include a linear or branched alkylene group having 1 to 30 carbon atoms, a linear or branched alkenylene group having 2 to 30 carbon atoms, a linear or branched alkynylene group having 2 to 30 carbon atoms, and an arylene group having 6 to 30 carbon atoms. Among them, a linear or branched alkylene group having 1 to 30 carbon atoms is preferred.

[0064] R 111 Examples of the linear or branched alkylene group having 1 to 30 carbon atoms (preferably 1 to 15 carbon atoms, more preferably 1 to 3 carbon atoms) of R include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, an undecylene group, a dodecylene group, a tridecylene group, a tetradecylene group, a pentadecylene group, a hexadecylene group, a heptadecylene group, an octadecylene group, and the like.

[0065] R 111Examples of the linear or branched alkenylene group having 2 to 30 carbon atoms (preferably 2 to 15 carbon atoms, more preferably 2 or 3 carbon atoms) include vinylene group, 1-propenylene group, 2-propenylene group, 1-butenylene group, 2-butenylene group, 1-pentenylene group, 2-pentenylene group, 1-hexenylene group, 2-hexenylene group, 1-octenylene group and the like.

[0066] R 111 Examples of the linear or branched alkynylene group having 2 to 30 carbon atoms (preferably 2 to 15 carbon atoms, more preferably 2 or 3 carbon atoms) include ethynylene group, propynylene group, butynylene group, pentynylene group, hexynylene group, heptynylene group, octynylene group, nonynylene group, decynylene group, undecynylene group, dodecynylene group and the like.

[0067] R 111 Examples of the arylene group having 6 to 30 carbon atoms (preferably 6 to 15 carbon atoms) include phenylene group, tolylene group, xylylene group, naphthylene group and the like.

[0068] z is an integer of 1 to 30, preferably 2 to 20, more preferably 3 to 7, and even more preferably 5 or 6.

[0069] R 112 R represents a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 30 carbon atoms. Among them, a linear or branched alkyl group having 1 to 30 carbon atoms is preferred.

[0070] R 112Examples of the linear or branched alkyl group having 1 to 30 carbon atoms (preferably 3 to 25 carbon atoms, more preferably 10 to 15 carbon atoms) include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, 2-ethylhexyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, octadecyl group and the like.

[0071] R 112 Examples of the linear or branched alkenyl group having 2 to 30 carbon atoms (preferably 3 to 25 carbon atoms, more preferably 10 to 15 carbon atoms) include vinyl group, 1-propenyl group, 2-propenyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 2-pentenyl group, 1-hexenyl group, 2-hexenyl group, 1-octenyl group, decenyl group, undecenyl group, dodecenyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, octadecenyl group and the like.

[0072] R 112 Examples of the aryl group having 6 to 30 carbon atoms (preferably 10 to 20 carbon atoms) include phenyl group, tolyl group, xylyl group, naphthyl group, biphenyl group and the like.

[0073] R 112 Examples of the aralkyl group having 7 to 30 carbon atoms (preferably 10 to 20 carbon atoms) include benzyl group, phenethyl group and the like.

[0074] -O-(R 111 -O) z -R 112 Specific examples of the group represented by -O-(C2H4-O)5-C 11 H 23 、-O-(C2H4-O)5-C 12 H 25 、-O-(C2H4-O)5-C 13 H 27 、-O-(C2H4-O)5-C 14 H 29, -O-(C2H4-O)5-C 15 H 31 , -O-(C2H4-O)3-C 13 H 27 , -O-(C2H4-O)4-C 13 H 27 , -O-(C2H4-O)6-C 13 H 27 , -O-(C2H4-O)7-C 13 H 27 , etc. Among them, -O-(C2H4-O)5-C 11 H 23 , -O-(C2H4-O)5-C 13 H 27 , -O-(C2H4-O)5-C 15 H 31 , -O-(C2H4-O)6-C 13 H 27 is preferred.

[0075] R 104 As the linear or branched alkylene group having 1 to 6 carbon atoms (preferably 1 to 5 carbon atoms) of R, for example, the same groups as the linear or branched alkylene group having 1 to 30 carbon atoms of R can be mentioned. 111

[0076] Examples of the compound represented by the above formula (1) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and compounds represented by the following formula. Compounds represented by the following formula can be preferably used. [Chemical formula]

[0077] Next, a compound containing the bonding unit A represented by the above formula (2) and the bonding unit B represented by the above formula (3) will be described.

[0078] The compound containing the linking unit A represented by the above formula (2) and the linking unit B represented by the above formula (3) suppresses the increase in viscosity during processing compared to polysulfide silanes such as bis-(3-triethoxysilylpropyl) tetrasulfide. This is presumably because the sulfide moiety of the linking unit A is a C-S-C bond, which is thermally more stable than tetrasulfide or disulfide, resulting in less increase in Mooney viscosity.

[0079] Also, the shortening of the scorch time is suppressed compared to mercapto silanes such as 3-mercaptopropyltrimethoxysilane. This is because although the linking unit B has the structure of mercapto silane, the -C7H 15 portion of the linking unit A covers the -SH group of the linking unit B, making it difficult to react with the polymer and less likely to cause scorch.

[0080] From the viewpoint of enhancing the effect of suppressing the increase in viscosity during processing and the effect of suppressing the shortening of the scorch time described above, in the silane coupling agent having the above structure, the content of the linking unit A is preferably 30 mol% or more, more preferably 50 mol% or more, preferably 99 mol% or less, and more preferably 90 mol% or less. Also, the content of the linking unit B is preferably 1 mol% or more, more preferably 5 mol% or more, further preferably 10 mol% or more, preferably 70 mol% or less, more preferably 65 mol% or less, and further preferably 55 mol% or less. Also, the total content of the linking units A and B is preferably 95 mol% or more, more preferably 98 mol% or more, and particularly preferably 100 mol%. Note that the contents of the linking units A and B are amounts including the case where the linking units A and B are located at the ends of the silane coupling agent. The form when the linking units A and B are located at the ends of the silane coupling agent is not particularly limited as long as it forms a unit corresponding to the formulas (2) and (3) indicating the linking units A and B.

[0081] R 201 Examples of the halogen atom of R include a chlorine atom, a bromine atom, and a fluorine atom.

[0082] R 201Examples of the linear or branched alkyl group having 1 to 30 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, 2-ethylhexyl group, octyl group, nonyl group, decyl group and the like. The number of carbon atoms of the alkyl group is preferably 1 to 12.

[0083] R 201 Examples of the linear or branched alkenyl group having 2 to 30 carbon atoms include vinyl group, 1-propenyl group, 2-propenyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 2-pentenyl group, 1-hexenyl group, 2-hexenyl group, 1-octenyl group and the like. The number of carbon atoms of the alkenyl group is preferably 2 to 12.

[0084] R 201 Examples of the linear or branched alkynyl group having 2 to 30 carbon atoms include ethynyl group, propynyl group, butynyl group, pentynyl group, hexynyl group, heptynyl group, octynyl group, nonynyl group, decynyl group, undecynyl group, dodecynyl group and the like. The number of carbon atoms of the alkynyl group is preferably 2 to 12.

[0085] R 202 Examples of the linear or branched alkylene group having 1 to 30 carbon atoms include ethylene group, propylene group, butylene group, pentylene group, hexylene group, heptylene group, octylene group, nonylene group, decylene group, undecylene group, dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, octadecylene group and the like. The number of carbon atoms of the alkylene group is preferably 1 to 12.

[0086] R 202 Examples of the linear or branched alkenylene group having 2 to 30 carbon atoms include vinylene group, 1-propenylene group, 2-propenylene group, 1-butenylene group, 2-butenylene group, 1-pentenylene group, 2-pentenylene group, 1-hexenylene group, 2-hexenylene group, 1-octenylene group and the like. The number of carbon atoms of the alkenylene group is preferably 2 to 12.

[0087] R 202 Examples of the linear or branched alkynylene group having 2 to 30 carbon atoms represented by 202 include an ethynylene group, a propynylene group, a butynylene group, a pentynylene group, a hexynylene group, a heptynylene group, an octynylene group, a nonynylene group, a decynylene group, an undecynylene group, a dodecynylene group, and the like. The number of carbon atoms of the alkynylene group is preferably 2 to 12.

[0088] In the compound containing the bonding unit A represented by the above formula (2) and the bonding unit B represented by the above formula (3), the total number of repetitions (x + y) of the number of repetitions (x) of the bonding unit A and the number of repetitions (y) of the bonding unit B is preferably in the range of 3 to 300. When within this range, the mercaptosilane of the bonding unit B can cover -C 15 of the bonding unit A, so that it is possible to suppress a shortening of the scorch time and ensure good reactivity with silica and rubber components.

[0089] From the viewpoint of sufficiently ensuring effects such as low fuel consumption, the content of the mercapto-based silane coupling agent is preferably 0.5 part by mass or more, more preferably 1 part by mass or more, more preferably 2 part by mass or more, more preferably 5 part by mass or more, based on 100 parts by mass of silica. Further, from the viewpoints of the compounding effect of the mercapto-based silane coupling agent commensurate with the increase in cost, rubber strength, and abrasion resistance, the content is preferably 20 parts by mass or less, more preferably 18 parts by mass or less, more preferably 17 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 12 parts by mass or less.

[0090] (Other silane coupling agents) In the present disclosure, the rubber composition may or may not further contain other silane coupling agents in addition to the mercapto-based silane coupling agent. Examples of other silane coupling agents include 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazole tetrasulfide, 3-triethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-triethoxysilylpropyl) tetrasulfide, bis(3-triethoxysilylpropyl) trisulfide, bis(3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) tetrasulfide, bis(3-trimethoxysilylpropyl) tetrasulfide, bis(2-trimethoxysilylethyl) tetrasulfide, bis(3-diethoxymethylsilylpropyl) tetrasulfide, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropyl benzothiazole tetrasulfide, and the like. Other silane coupling agents can be used alone or in combination of two or more.

[0091] <Liquid rubber> In the present disclosure, "liquid rubber" means rubber in a liquid state at normal temperature (25 °C). It is also called "liquid polymer", "liquid diene polymer", etc. The liquid rubber may or may not be hydrogenated, and may or may not be modified with functional groups such as carboxy groups. When the liquid rubber is a copolymer, it may be a random copolymer or a block copolymer of each monomer, but a random copolymer is preferred. Note that the liquid rubber of the present disclosure is not included in the rubber component.

[0092] The liquid rubber is not particularly limited. For example, liquid styrene-butadiene rubber (liquid SBR), liquid butadiene rubber (liquid BR), liquid isoprene rubber (liquid IR), liquid styrene-isoprene rubber (liquid SIR), etc. can be mentioned. The liquid rubber can be, for example, those manufactured and sold by Kuraray Co., Ltd., Nippon Soda Co., Ltd., Cray valley, Noveon, etc. Among them, it is preferably to contain at least one of liquid SBR and liquid BR, more preferably to contain liquid SBR, and it is also preferable to be only liquid SBR. The liquid rubber can be used alone or in combination of two or more.

[0093] (Liquid SBR) The styrene content of the liquid SBR is not particularly limited, but is preferably 15% by mass or more, more preferably 20% by mass or more, and still more preferably 25% by mass or more. Also, the styrene content is preferably 40% by mass or less, more preferably 30% by mass or less, and still more preferably 27% by mass or less. When the styrene content of the liquid SBR is within the above range, there is a tendency that the effects of the present disclosure can be exhibited more favorably.

[0094] The vinyl content (amount of 1,2-bonded butadiene units) of the liquid SBR is not particularly limited, but is preferably 10.0 to 80.0%. The vinyl content is preferably 25% or more, more preferably 40% or more. Also, the vinyl content is preferably 75% or less, more preferably 70% or less. When the vinyl content of the liquid SBR is within the above range, there is a tendency that the effects of the present disclosure can be exhibited more favorably.

[0095] (Liquid BR) As the liquid BR, for example, those with a low vinyl content of 5 to 55% and those with a high vinyl content of vinyl content of 70 to 90% can be used.

[0096] (Number average molecular weight (Mn) of liquid rubber) The number average molecular weight (Mn) of the liquid rubber is preferably less than 50,000, more preferably 25,000 or less, still more preferably 10,000 or less, and even more preferably 7,000 or less. The lower limit of the Mn is not particularly limited, but is preferably 1,000 or more, more preferably 2,500 or more, and still more preferably 3,500 or more. When the Mn of the liquid rubber is within the above range, the liquid rubber is likely to enter between the molecules of styrene-butadiene rubber in the SBR phase, and there is a tendency that the effect of improving processability can be obtained more favorably. The Mn of the liquid rubber in this specification is measured using gel permeation chromatography (GPC) and is a value converted from standard polystyrene.

[0097] (Content of liquid rubber) The content of the liquid rubber with respect to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and still more preferably 10 parts by mass or more. The content is more preferably 50 parts by mass or less, more preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less. When the content of the liquid rubber is within the above range, there is a tendency that the effect of comprehensively improving low fuel consumption, wet grip performance, fracture characteristics and processability can be obtained more favorably while more effectively exerting the effect of improving processability.

[0098] <Resin> The resin is not particularly limited, and resins commonly used in conventional rubber compositions for tires can be used. For example, aromatic resins, aliphatic petroleum resins (e.g., C5 petroleum resins), terpene resins, rosin resins, etc. can be mentioned. Among them, aromatic resins are preferred. The resins can be used alone or in combination of two or more.

[0099] (Aromatic resin) In the present disclosure, the "aromatic resin" means a resin containing an aromatic ring in its structure. The aromatic resin is not particularly limited as long as it is a resin used in this field and contains an aromatic ring. Examples of such resins include C9 petroleum resins, C5C9 petroleum resins, phenolic resins, coumarone resins, aromatic-modified terpene resins, and the like. Among them, C9 petroleum resins can be preferably used because of their particularly excellent compatibility with SBR.

[0100] ≪C9 Petroleum Resin≫ Examples of C9 petroleum resins include resins obtained by cationic polymerization of monomers such as vinyltoluene, alkylstyrene, and indene, which are petroleum fractions (C9 fractions) corresponding to 8 to 10 carbon atoms. Specific examples of C9 petroleum resins include styrene resins. The styrene resin is not particularly limited, but α-methylstyrene resins (AMS) are preferably used. Examples of α-methylstyrene resins include homopolymers of α-methylstyrene (poly-α-methylstyrene) and copolymers of α-methylstyrene and other compounds including aromatic compounds and phenolic compounds. Other compounds that can constitute this copolymer include styrene, methylstyrene, methoxystyrene, divinylbenzene, and the like. As α-methylstyrene resins, those manufactured by Arizona Chemical Company, etc. are preferably used.

[0101] ≪C5C9 Petroleum Resin≫ The C5C9 petroleum resin is a resin obtained by copolymerizing a C5 fraction and a C9 fraction, and is also called an aliphatic / aromatic copolymerized petroleum resin. Also, a hydrogenated product of the above petroleum resin may be used. As the C5C9 petroleum resin, for example, those manufactured and sold by LUHUA, Qilong, Tosoh Corporation, etc. can be used.

[0102] ≪Phenolic Resin≫ Phenolic resins are resins containing a phenol skeleton in their structure. Examples include phenolic formaldehyde resins, alkylphenol formaldehyde resins, alkylphenol acetylene resins, oil-modified phenolic formaldehyde resins, and the like.

[0103] ≪Coumarone resins≫ Coumarone resins are resins with coumarone as the main component. Examples include coumarone resins, coumarone-indene resins, copolymer resins with coumarone, indene, and styrene as the main components, and the like. As coumarone resins, those manufactured and sold by, for example, Nichido Chemical Co., Ltd. can be used.

[0104] ≪Aromatic-modified terpene resins≫ Aromatic-modified terpene resins are resins made from terpene compounds and aromatic compounds. Examples of aromatic compounds used as raw materials for aromatic-modified terpene resins include styrene, α-methylstyrene, vinyltoluene, divinyltoluene, and the like. As aromatic-modified terpene resins, those manufactured and sold by, for example, Yasuhara Chemical Co., Ltd. can be used.

[0105] (Mw of the resin) The weight-average molecular weight (Mw) of the resin is preferably 300 or more, more preferably 400 or more, and even more preferably 500 or more from the viewpoints of being difficult to volatilize and having good grip performance. Also, the Mw is preferably 15000 or less, more preferably 10000 or less, and even more preferably 8000 or less. The weight-average molecular weight (Mw) in this specification can be determined by standard polystyrene conversion based on the measured values obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M manufactured by Tosoh Corporation).

[0106] (Softening point of the resin) From the perspective of grip performance, the softening point of the resin is preferably 160°C or lower, more preferably 145°C or lower, and even more preferably 130°C or lower. Also, from the perspective of grip performance, the softening point is preferably 20°C or higher, more preferably 35°C or higher, and even more preferably 50°C or higher. Note that the softening point in this specification is the temperature at which the sphere drops when measured with a ring and ball softening point measuring device according to the softening point defined in JIS K 6220-1:2001.

[0107] (SP value of the resin) The SP value of the resin is preferably 8.0 or higher, more preferably 8.5 or higher, and even more preferably 9.0 or higher. Also, the SP value is preferably 11.0 or lower, more preferably 10.0 or lower, and even more preferably 9.5 or lower. When the SP value of the resin is within the above range, the compatibility with SBR is improved, and there is a tendency to better exhibit the effects of the present disclosure. Note that the SP value of the resin in this specification means the solubility parameter calculated by the Hoy method based on the structure of the compound, and the smaller the difference in the SP values of the two components, the better the compatibility. The Hoy method is, for example, the calculation method described in K.L. Hoy “Table of Solubility Parameters”, Solvent and Coatings Materials Research and Development Department, Union Carbites Corp. (1985).

[0108] (Content of the resin) The content of the resin relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and even more preferably 4 parts by mass or more. Also, the content is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less. When the content of the resin is within the above range, there is a tendency to better obtain the effect of comprehensively improving low fuel consumption, wet grip performance, fracture characteristics, and processability while better exhibiting the effect of improving wet grip performance.

[0109] <Other components> In addition to the above-described components, the rubber composition of the present disclosure may appropriately contain other components generally used in the production of rubber compositions, such as oils, stearic acid, zinc oxide, antioxidants, waxes, processing aids, vulcanizing agents, vulcanization accelerators, and the like.

[0110] (Oil) The oil is not particularly limited, and any oil commonly used in the rubber industry can be preferably used. Examples thereof include process oils such as paraffinic, aromatic, and naphthenic process oils. In addition, process oils with a low content of polycyclic aromatic compounds (PCA) for environmental measures can be mentioned. Examples of low-PCA content process oils include Treated Distillate Aromatic Extract (TDAE) obtained by re-extracting aromatic process oils, aroma alternative oils which are mixed oils of asphalt and naphthenic oil, mild extraction solvates (MES), and heavy naphthenic oils. Among them, aromatic process oils are preferred, and TDAE oils are more preferred. As the oil, for example, those manufactured and sold by H&R Co., Ltd., JXTG Energy Corporation, Idemitsu Kosan Co., Ltd., Sankyo Oil Chemical Co., Ltd., etc. can be used. The oil can be used alone or in combination of two or more.

[0111] When the oil is contained, the content thereof relative to 100 parts by mass of the rubber component is not particularly limited, but is more preferably 0.5 part by mass or more, more preferably 1 part by mass or more, and even more preferably 3 parts by mass or more. Also, the content is preferably 25 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 7 parts by mass or less. When the content of the oil is within the above range, the balance of low fuel consumption, wet grip performance, fracture characteristics, and processability is excellent, and the effects of the present disclosure tend to be obtained more favorably. Note that the content of the oil includes the amount of oil used in oil extension or oil treatment.

[0112] Stearic acid When containing stearic acid, the content with respect to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1 part by mass or more, from the viewpoint of processability. Further, from the viewpoint of vulcanization rate, the content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0113] Zinc oxide When containing zinc oxide, the content with respect to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1 part by mass or more, from the viewpoint of processability. Further, from the viewpoint of abrasion resistance, the content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0114] Antioxidant The anti-aging agent is not particularly limited, and any of those commonly used in the rubber industry can be preferably used. For example, quinoline-based anti-aging agents, quinone-based anti-aging agents, phenol-based anti-aging agents, phenylenediamine-based anti-aging agents, metal carbamate salts, etc. can be mentioned. Among them, it is preferable to use at least one of a quinoline-based anti-aging agent and a phenylenediamine-based anti-aging agent, and it is more preferable to use them in combination. Examples of the quinoline-based anti-aging agent include 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), etc. Examples of the phenylenediamine-based anti-aging agent include N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N,N'-bis(1-methylheptyl)-p-phenylenediamine, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, N-4-methyl-2-pentyl-N'-phenyl-p-phenylenediamine, N,N'-diaryl-p-phenylenediamine, hindered diaryl-p-phenylenediamine, phenylhexyl-p-phenylenediamine, phenyloctyl-p-phenylenediamine, etc. Among them, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) is preferable. As a preferable specific combination when using a quinoline-based anti-aging agent and a phenylenediamine-based anti-aging agent in combination as the anti-aging agent, the combination of TMDQ and 6PPD can be mentioned. As the anti-aging agent, those manufactured and sold by, for example, Ouchi Shinsei Chemical Industry Co., Ltd., Kawaguchi Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., etc. can be used. The anti-aging agent can be used alone or in combination of two or more.

[0115] When contained, the content of the anti-aging agent relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 0.8 part by mass or more, and still more preferably 1.0 part by mass or more. Also, the content is preferably 7.0 parts by mass or less, more preferably 5.0 parts by mass or less, and still more preferably 3.0 parts by mass or less. When the content of the anti-aging agent is within the above range, the anti-aging effect can be sufficiently obtained, and there is a tendency to suppress discoloration due to the precipitation of the anti-aging agent on the tire surface.

[0116] (Wax) The wax is not particularly limited, and any wax commonly used in the rubber industry can be preferably used. Examples include petroleum waxes, mineral waxes, synthetic waxes, etc. Among them, petroleum waxes are preferred. Examples of petroleum waxes include paraffin wax, microcrystalline wax, and their selected special waxes. As the wax, those manufactured and sold by, for example, Ouchi Shinsei Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., etc. can be used. The wax can be used alone or in combination of two or more.

[0117] When contained, the content of the wax relative to 100 parts by mass of the rubber component is preferably 0.3 part by mass or more, more preferably 0.7 part by mass or more, and still more preferably 0.8 part by mass or more from the viewpoint of the weather resistance of the rubber. Also, from the viewpoint of preventing whitening of the tire due to blooming, the content is preferably 3.0 parts by mass or less, more preferably 2.5 parts by mass or less, and still more preferably 2.0 parts by mass or less.

[0118] (Processing aid) Examples of the processing aid 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. Among them, fatty acid metal salts are preferred. As the processing aid, those manufactured by, for example, Struktol Co., etc. can be used. The processing aid can be used alone or in combination of two or more.

[0119] When containing a processing aid, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 0.8 part by mass or more, and still more preferably 1.0 part by mass or more. Also, the content of the processing aid is preferably 10.0 parts by mass or less, more preferably 8.0 parts by mass or less, and still more preferably 6.0 parts by mass or less. When the content of the processing aid is within the above range, there is a tendency that the effects of the present disclosure can be exhibited more favorably.

[0120] (Vulcanizing agent) The vulcanizing agent is not particularly limited, and known vulcanizing agents can be used. For example, organic peroxides such as dicumyl peroxide, sulfur-based vulcanizing agents, resin vulcanizing agents, metal oxides such as magnesium oxide, etc. can be mentioned. Among them, sulfur-based vulcanizing agents are preferred. As the sulfur-based vulcanizing agent, for example, sulfur, sulfur donors such as morpholine disulfide, etc. can be used. Among these, it is preferable to use sulfur. The vulcanizing agent can be used alone or in combination of two or more.

[0121] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur (oil-treated sulfur, special sulfur treated with a dispersant, masterbatch type sulfur, etc.), insoluble sulfur (oil-treated insoluble sulfur, etc.), and any of them can be suitably used. Sulfur can be used, for example, those manufactured and sold by Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexsys, Nippon Kankyu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc.

[0122] When contained, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and still more preferably 1.5 part by mass or more. Also, the content is preferably 6.0 parts by mass or less, more preferably 5.0 parts by mass or less, and still more preferably 4.0 parts by mass or less. When the content of the vulcanizing agent is within the above range, an appropriate reinforcing effect tends to be obtained, and the effects of the present disclosure tend to be exhibited more favorably. Note that when sulfur is used as the vulcanizing agent, the sulfur content means the content of the sulfur component itself contained in sulfur other components such as oil-treated sulfur when using those containing such components.

[0123] (Vulcanization accelerator) The vulcanization accelerator is not particularly limited, and known vulcanization accelerators can be used. For example, sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, or xanthate-based vulcanization accelerators can be mentioned. Among them, sulfenamide-based, guanidine-based, and thiuram-based are preferable, and it is more preferable to use a combination of sulfenamide-based and guanidine-based. As the vulcanization accelerator, for example, those manufactured and sold by Ouchi Shinsei Chemical Industry Co., Ltd., Sanshin Chemical Industry Co., Ltd., etc. can be used. The vulcanization accelerator can be used alone or in combination of two or more.

[0124] Examples of the sulfenamide-based vulcanization accelerator include N-(tert-butyl)-2-benzothiazole sulfenamide (TBBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), N,N'-dicyclohexyl-2-benzothiazolyl sulfenamide (DZ), etc. Among them, N-(tert-butyl)-2-benzothiazole sulfenamide (TBBS) is preferable because the effects of the present disclosure can be exhibited more favorably.

[0125] Examples of thiuram vulcanization accelerators include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetrabenzylthiuram disulfide (TBzTD), and the like.

[0126] Examples of guanidine vulcanization accelerators include 1,3-diphenylguanidine (DPG), diorthotolylguanidine, orthotolylbiguanidine, and the like. Among them, 1,3-diphenylguanidine (DPG) is preferred because the effects of the present disclosure can be more favorably exhibited.

[0127] A preferred specific combination when using a sulfenamide-based and a guanidine-based vulcanization accelerator in combination is the combination of TBBS and DPG.

[0128] The content of the vulcanization accelerator with respect to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and even more preferably 2.0 part by mass or more. Also, the content is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, and even more preferably 6.0 parts by mass or less. When the content of the vulcanization accelerator is within the above range, the breaking strength and elongation tend to be ensured, and the effects of the present disclosure tend to be more favorably exhibited.

[0129] <Rubber composition for tire tread, tire tread, and tire> The rubber composition for tire tread of the present disclosure is excellent in low fuel consumption, wet grip performance, and fracture characteristics, and thus is used for the tread of a tire. The tread is the part that contacts the road surface. When the tread is composed of two or more different rubber compositions, the rubber composition of the present disclosure can be used in at least one of them. Also, when the tread is composed of two or more layers including a base tread and a cap tread, the rubber composition of the present disclosure can be used at least in the cap tread.

[0130] The rubber composition for a tire tread can be manufactured by a general method. For example, in a known kneader used in the general rubber industry such as a Banbury mixer or a kneader, or an open roll, among the above components, the components other than the vulcanizing agent and the vulcanization accelerator are kneaded (base kneading step), and then, the vulcanizing agent and the vulcanization accelerator are added and further kneaded (finishing kneading step), and it can be manufactured by a method such as vulcanization. Note that a remill (re-kneading step) may be performed between each step.

[0131] The tire tread and the tire can be manufactured by a normal method using the above-described rubber composition for a tire tread. That is, the rubber composition containing the above components is extruded in an unvulcanized state according to the shape of the tire tread, bonded together with other tire members on a tire molding machine, and molded by a normal method to form an unvulcanized tire, and this unvulcanized tire is pressure-vulcanized in a vulcanizer to manufacture a tire provided with a tire tread.

[0132] The kneading conditions are not particularly limited. For example, in the base kneading step, it is kneaded at a discharge temperature of 120 to 170°C for 1 to 15 minutes, in the remilling step, it is kneaded at a discharge temperature of 120 to 170°C for 1 to 15 minutes, and in the finishing kneading step, there is a method of kneading at 70 to 110°C for 1 to 10 minutes. The vulcanization conditions are not particularly limited, and for example, there is a method of vulcanizing at 150 to 200°C for 10 to 30 minutes.

[0133] The tire of the present disclosure may be a pneumatic tire or a non-pneumatic tire, but is preferably a pneumatic tire. Further, the tire of the present disclosure can be used for various tires such as passenger car tires, truck / bus tires, motorcycle tires, high-performance tires such as racing tires, winter tires, and run-flat tires, and can be particularly preferably used as a passenger car tire.

[0134] The passenger car tire of the present disclosure is preferably applied to a passenger car tire in which the relationship between the tire outer diameter Dt (mm) and the tire cross-sectional width Wt (mm) satisfies the following formula (α). A passenger car tire that satisfies the following formula (α) tends to have a problem of low fuel efficiency. Therefore, it is considered that by applying the passenger car tire of the present disclosure, the effect of improving low fuel efficiency can be preferably exerted. The value of (Dt^2×π / 4) / Wt is more preferably 1970.0 or more, still more preferably 1980.0 or more, and even more preferably 1990.0 or more. Further, the value of (Dt^2×π / 4) / Wt is more preferably 2800.0 or less, still more preferably 2700.0 or less, and even more preferably 2600.0 or less. Note that the tire outer diameter Dt and the tire cross-sectional width Wt in the following formula (α) are measured in a state where the tire is incorporated into a predetermined rim (regular rim) and the tire is filled with air so as to have a predetermined internal pressure (regular internal pressure, for example, 250 kPa or more). No load is applied to the tire during the measurement. 1963.4 ≦ (Dt^2×π / 4) / Wt ≦ 2827.4 (α)

[0135] In this specification, the regular rim means the rim defined in the standard on which the tire depends. The "Standard Rim" in the JATMA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are regular rims. In this specification, the regular internal pressure means the internal pressure defined in the standard on which the tire depends. The "Maximum Air Pressure" in the JATMA standard, the "Maximum Value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are regular internal pressures.

[0136] Specific examples of the tire size for a passenger car that satisfies the above formula (α) include 135 / 45R21, 145 / 45R21, 155 / 45R21, 165 / 45R22, 175 / 45R23, 185 / 45R22, 115 / 50R17, 185 / 50R20, 215 / 50R21, 125 / 55R20, 135 / 55R20, 145 / 55R20, 155 / 55R19, 155 / 55R21, 175 / 55R19, 165 / 55R19, 165 / 55R20, 165 / 55R21, 175 / 55R22, 195 / 55R20, 205 / 55R20, 135 / 60R17, 165 / 60R12, 175 / 60R18, 185 / 60R20, 195 / 60R19, 205 / 60R18, 125 / 65R19, 135 / 65R19, 145 / 65R19, 155 / 65R18, 165 / 65R19, 155 / 70R17, 165 / 70R18, 175 / 80R16, etc.

Example

[0137] The present disclosure will be specifically described based on the examples. The present disclosure is not limited to these examples.

[0138] <Various chemicals used in the examples and comparative examples> NR: TSR20 (isoprene rubber) SBR: JSR1502 (E-SBR, styrene content: 23.5% by mass, available from JSR Corporation) BR: Ube Pol BR150B (high cis BR, cis content: 97%, trans content: 2%, vinyl content: 1%, available from Ube Industries, Ltd.) Carbon black: N220 (ISAF, N2SA: 111m 2 / g, DBP oil absorption: 115 ml / 100 g, available from Cabot Japan Ltd.) Silica: Zeoseal 1115MP (N2SA: 115m 2 / g, CTAB: 110m 2 / g, available from Solvay) Silane coupling agent 1: Si266 (sulfide type, bis(triethoxysilylpropyl)disulfide, available from Evonik Degussa) Silane coupling agent 2:NXT (mercapto-based, 3-octanoylthiopropyltriethoxysilane, available from Momentive Performance Materials) Silane coupling agent 3:NXT-Z45 (mercapto-based, copolymer of bonding unit A and bonding unit B (bonding unit A: 55 mol%, bonding unit B: 45 mol%), available from Momentive Performance Materials) Resin: SYLVATRAXX 4401 (α-methylstyrene-based resin, softening point: 85 °C, SP value: 9.1, available from Arizona Chemical) Oil: Vivatec 500 (TDAE oil, available from H&R) Liquid rubber 1: RICON 100 (liquid SBR, random copolymer, styrene content: 25% by mass, vinyl content: 70%, Mn: 4500, available from Cray valley) Liquid rubber 2: Kuraprene LBR-302 (liquid BR, Mn: 5500, available from Kuraray Co., Ltd.) Wax: Oz Ace 0355 (paraffin-based, available from Nippon Seiro Co., Ltd.) Antioxidant 1: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), available from Sumitomo Chemical Co., Ltd.) Antioxidant 2: Antage RD (2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), available from Kawaguchi Chemical Industry Co., Ltd.) Stearic acid: Stearic acid "Tsubaki" (available from NOF Corporation) Zinc oxide: Two types of zinc oxide (available from Mitsui Mining & Smelting Co., Ltd.) Sulfur: HK200-5 (5% oil-containing powdered sulfur, available from Hosoi Chemical Industry Co., Ltd.) Vulcanization accelerator 1: Sanseler NS-G (N-(tert-butyl)-2-benzothiazolesulfenamide (TBBS), available from Sanshin Chemical Industry Co., Ltd.) Vulcanization accelerator 2: Nocceler D (1,3-diphenylguanidine (DPG), available from Ouchi Shinsei Chemical Industry Co., Ltd.)

[0139] Examples and Comparative Examples <Rubber Composition, Manufacture of Tire> According to the compounding formulations shown in Tables 1 and 2, using a 1.7 L sealed Banbury mixer, chemicals other than sulfur and vulcanization accelerators were kneaded for 5 minutes until the discharge temperature reached 170 °C to obtain a kneaded product. Further, the obtained kneaded product was kneaded again (remilled) for 4 minutes at a discharge temperature of 150 °C using the Banbury mixer. Next, using a twin-screw open roll, sulfur and vulcanization accelerators were added to the obtained kneaded product and kneaded for 4 minutes until the temperature reached 105 °C to obtain an unvulcanized rubber composition.

[0140] The unvulcanized rubber composition obtained above was press-vulcanized at 170 °C for 12 minutes to produce a vulcanized rubber composition.

[0141] The unvulcanized rubber composition obtained above was extruded into the shape of a tire tread using an extruder equipped with a die of a predetermined shape, and laminated together with other tire members on a tire molding machine to form an unvulcanized tire, and press-vulcanized at 170 °C for 15 minutes to produce a test tire (size: 175 / 60R18).

[0142] <Evaluation> The following evaluations were performed on the obtained unvulcanized rubber composition, vulcanized rubber composition, and test tire. The results are shown in Tables 1 and 2.

[0143] (Processability) Regarding the obtained unvulcanized rubber composition, according to the method for measuring Mooney viscosity in "Unvulcanized Rubber - Physical Properties - Part 1: Method for Determining Viscosity and Scorch Time by Mooney Viscometer" of JIS K 6300-1, at a temperature condition of 130 °C, the Mooney viscosity (ML 1+4 ) was measured. Taking the ML 1+4 of Comparative Example 1 as 100, the ML 1+4 of each formulation was shown as a processability index according to the following calculation formula. The larger the processability index, the lower the Mooney viscosity and the better the processability. (Processability Index) = (ML 1+4 ) of Comparative Example 1) / (ML of each formulation)1+4 )×100

[0144] (Low fuel consumption) For the test tire, with a maximum load capacity of 615 kg, the rolling resistance coefficient was measured in accordance with JIS D 4234:2009 under other conditions. Taking the rolling resistance coefficient of Comparative Example 1 as 100, the rolling resistance coefficient of each formulation was shown as the low fuel consumption index according to the following calculation formula. The larger the low fuel consumption index, the smaller the rolling resistance, indicating excellent low fuel consumption performance. (Low fuel consumption index) = (Rolling resistance coefficient of Comparative Example 1) / (Rolling resistance coefficient of each formulation) × 100

[0145] (Wet grip performance) Based on the braking performance obtained from the anti-lock braking system (ABS) evaluation test, the wet grip performance was evaluated. That is, the test tire was mounted on a passenger car equipped with an 1800 cc class ABS, and the passenger car was driven on an asphalt road surface (wet road surface condition, skid number approximately 50) at a speed of 100 km / h, and the brakes were applied at the moment of 100 km / h, and the deceleration until the passenger car stopped was calculated. Here, the deceleration is the distance until the passenger car stops. Then, taking the deceleration of Comparative Example 1 as 100, the deceleration of each formulation was shown as the wet grip performance index according to the following calculation formula. The larger the wet grip performance index, the better the braking performance, indicating excellent wet grip performance. (Wet grip performance index) = (Deceleration of Comparative Example 1) / (Deceleration of each formulation) × 100

[0146] (Fracture characteristics) Using a No. 6 dumbbell-shaped test piece made of a vulcanized rubber composition, a tensile test was carried out at 25°C in accordance with JIS K 6251:2010 "Vulcanized Rubber and Thermoplastic Rubber - Method for Determining Tensile Properties", and the breaking strength TB (MPa) and elongation at break EB (%) were measured. Then, the value of TB × EB ÷ 2 (MPa%) was calculated. Taking the value of TB × EB ÷ 2 (MPa%) of Comparative Example 1 as 100, the value of TB × EB ÷ 2 (MPa%) of each formulation was shown as the fracture property index according to the following calculation formula. The larger the fracture property index, the better the fracture property. (Fracture property index) = (Value of each formulation) / (Value of Comparative Example 1) × 100

[0147] (Comprehensive performance) The sum of the numerical values of the low fuel consumption index, wet grip performance index, fracture property index, and processability index was shown as the "comprehensive performance". The larger the numerical value of the comprehensive performance, the better the comprehensive performance of low fuel consumption, wet grip performance, fracture property, and processability.

[0148] [Table 1]

[0149] [Table 2]

[0150] From the results of Tables 1 and 2, it can be seen that the rubber compositions and tires of the examples can comprehensively improve the low fuel consumption, wet grip performance, fracture property, and processability in a well-balanced manner compared with those of the comparative examples.

Claims

1. A rubber composition for a tire tread, comprising a rubber component containing an isoprene rubber and a styrene-butadiene rubber, a filler containing 20% by mass or more of silica and 20% by mass or more of carbon black in 100% by mass of the filler, a mercapto-based silane coupling agent, a liquid rubber, a resin, and sulfur, wherein the styrene-butadiene rubber has the largest content in the rubber component, the resin contains an aromatic resin, a passenger car tire comprising a tire tread made of the rubber composition for a tire tread, wherein the content (% by mass) of the isoprene rubber in the rubber component and the content (parts by mass) of the silica with respect to 100 parts by mass of the rubber component satisfy the following formula (A), the relationship between the tire outer diameter Dt (mm) and the tire section width Wt (mm) satisfies the following formula (α). (Content of isoprene rubber) / (Content of silica) ≤ 2.0 (A) 1963.4 ≤ (Dt^2 × π / 4) / Wt ≤ 2827.4 (α)

2. The passenger car tire according to claim 1, wherein the right side of the formula (A) is 1.

5.

3. The passenger car tire according to claim 1 or 2, wherein the liquid rubber is a liquid styrene-butadiene rubber.

4. The passenger car tire according to any one of claims 1 to 3, wherein the aromatic resin is a C9-based petroleum resin.

5. The passenger car tire according to any one of claims 1 to 4, wherein the content (parts by mass) of the liquid rubber and the content (parts by mass) of the silica with respect to 100 parts by mass of the rubber component satisfy the following formula (B). 1.0 ≥ (Content of liquid rubber) / (Content of silica) ≥ 0.1 (B)

6. The passenger car tire according to any one of claims 1 to 5, wherein the content (% by mass) of the isoprene rubber in the rubber component and the content (parts by mass) of the aromatic resin with respect to 100 parts by mass of the rubber component satisfy the following formula (C). (Content of isoprene rubber) / (Content of aromatic resin) ≤ 13.0 (C)

7. The passenger car tire according to any one of claims 1 to 6, wherein the content (parts by mass) of the liquid rubber and the content (parts by mass) of the aromatic resin with respect to 100 parts by mass of the rubber component satisfy the following formula (D). 35 ≥ (Content of liquid rubber) + (Content of aromatic resin) ≥ 11 (D)

8. The passenger car tire according to any one of claims 1 to 7, wherein the content of the isoprene rubber in the rubber component is less than 50% by mass.

9. The passenger car tire according to any one of claims 1 to 8, wherein the mercapto-based silane coupling agent is at least one selected from the group consisting of a compound represented by the following formula (S1), a compound represented by the following formula (1), and a compound containing a bonding unit A represented by the following formula (2) and a bonding unit B represented by the following formula (3). 【Chemical 1】 (wherein, 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 ) and is a monovalent group selected from (R 1006 , R 1007 and R 1008 may be the same or different and 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. ), and 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, and j is an integer of 1 to 4. ), R 1004 is a divalent hydrocarbon group having 1 to 18 carbon atoms, R 1005 represents a monovalent hydrocarbon group having 1 to 18 carbon atoms, and x, y and z are numbers satisfying the relationships of x + y + 2z = 3, 0 ≦ x ≦ 3, 0 ≦ y ≦ 2, 0 ≦ z ≦ 1. ) 【Chemical Formula 2】 (wherein, R 101 ~R 103 represents a linear or branched alkyl group having 1 to 12 carbon atoms, a linear or branched alkoxy group having 1 to 12 carbon atoms, or -O-(R 111 -O) z -R 112 (z R's 111 represent a divalent hydrocarbon group having 1 to 30 carbon atoms which is linear or branched. The z R's 111 may be the same or different from each other. R 112 represents a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group having 7 to 30 carbon atoms. z represents an integer of 1 to 30.).) represents a group represented by the formula. R 101 ~R 103 may be the same or different from each other. R 104 represents a linear or branched alkylene group having 1 to 6 carbon atoms.) 【Chemical Formula 3】 【Chemical 4】 (wherein x is an integer of 0 or more, and y is an integer of 1 or more. R 201 each represents a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, a linear or branched alkynyl group having 2 to 30 carbon atoms, or a group in which a hydrogen atom at the terminal of the alkyl group is substituted with a hydroxyl group or a carboxyl group. R 202 each represents a linear or branched alkylene group having 1 to 30 carbon atoms, a linear or branched alkenylene group having 2 to 30 carbon atoms, or a linear or branched alkynylene group having 2 to 30 carbon atoms. R 201 and R 202 may form a ring structure therewith.)

10. The passenger car tire according to any one of claims 1 to 9, wherein the total content of the filler with respect to 100 parts by mass of the rubber component is 60 parts by mass or more and 250 parts by mass or less.

11. The passenger car tire according to any one of claims 1 to 10, wherein the rubber component contains 5% by mass or more and 45% by mass or less of butadiene rubber.

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