Rubber composition for tire and tire

Abstract

To provide a rubber composition for a tire, and a tire which are excellent in total performance of abrasion resistance and crack growth resistance.SOLUTION: A rubber composition for a tire containing a rubber component containing an epoxidation diene rubber, a divalent or more carboxylic acid compound, and sulfur is such that: a content of the sulfur is 1.0 pt.mass or more based on 100 pts.mass of the rubber component; and a ratio K of a content (pt.mass) of the divalent or more carboxylic acid compound to a content (pt.mass) of the sulfur (content of the divalent or more carboxylic acid compound / content of the sulfur) is 0.10 or more and 10.00 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition for a tire and a tire. Regarding. [Background technology]

[0002] BACKGROUND ART Conventionally, various methods for improving various tire performances have been investigated, and improvements in abrasion resistance, crack growth resistance, and the like have been sought (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-151817 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to solve the above problems and to provide a rubber composition for a tire and a tire that are excellent in overall performance such as abrasion resistance and crack growth resistance. [Means for solving the problem]

[0005] The present invention relates to a rubber composition for tires, which comprises a rubber component containing an epoxidized diene rubber, a divalent or higher carboxylic acid compound, and sulfur, wherein the content of the sulfur per 100 parts by mass of the rubber component is 1.0 part by mass or more, and the ratio K of the content (parts by mass) of the divalent or higher carboxylic acid compound to the content (parts by mass) of the sulfur (content of the divalent or higher carboxylic acid compound / content of sulfur) is 0.10 or more and 10.00 or less. [Effects of the Invention]

[0006] The present invention provides a rubber composition for tires that includes a rubber component containing an epoxidized diene-based rubber, a divalent or higher carboxylic acid compound, and sulfur, in which the amount of sulfur per 100 parts by mass of the rubber component is 1.0 part by mass or more, and the ratio K of the amount of divalent or higher carboxylic acid compound (parts by mass) to the amount of sulfur (parts by mass) (divalent or higher carboxylic acid compound content / sulfur content) is 0.10 or more and 10.00 or less, thereby enabling overall performance improvements in abrasion resistance and crack growth resistance. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view showing a portion of a pneumatic tire. [Figure 2] FIG. 2 is an enlarged cross-sectional view showing the vicinity of the tread of the tire of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0008] The rubber composition for tires includes a rubber component containing an epoxidized diene rubber, a divalent or higher carboxylic acid compound, and sulfur, in which the content of the sulfur per 100 parts by mass of the rubber component is 1.0 part by mass or more, and the ratio K of the content (parts by mass) of the divalent or higher carboxylic acid compound to the content (parts by mass) of the sulfur (content of the divalent or higher carboxylic acid compound / content of sulfur) is 0.10 or more and 10.00 or less.

[0009] The mechanism by which the rubber composition for tires provides the above-mentioned effects is not entirely clear, but is presumed to be as follows. By compounding epoxidized diene rubber with a divalent or higher carboxylic acid compound and sulfur so that K (content of divalent or higher carboxylic acid compound / sulfur content) is between 0.10 and 10.00, reversible hydrogen bonds are formed between the carboxylic acids in addition to sulfur crosslinks. When mechanical stress is applied, hydrogen bonds are more easily broken than sulfur crosslinks, allowing energy to be dissipated during this process, which is thought to improve overall abrasion resistance and crack resistance. Furthermore, because hydrogen bonds are reversible, this effect can be expected to last for a long time. Therefore, it is presumed that the rubber composition for tires improves the overall performance of abrasion resistance and crack growth resistance.

[0010] In this way, the problem (objective) of improving the overall performance of abrasion resistance and crack growth resistance is solved by using a configuration that satisfies the relationship "K (content of divalent or higher carboxylic acid compounds / content of sulfur) is 0.10 or more and 10.00 or less." In other words, the parameter "K (content of divalent or higher carboxylic acid compounds / content of sulfur) is 0.10 or more and 10.00 or less" does not define the problem (objective); the problem of the present application is to improve the overall performance of abrasion resistance and crack growth resistance, and a configuration that satisfies this parameter is used as a means to achieve this.

[0011] The rubber composition for a tire includes a rubber component. In this specification, the rubber component is a component that contributes to crosslinking, and generally corresponds to a polymer component that is a polymer with a weight average molecular weight (Mw) of 10,000 or more and is not extracted with acetone. The rubber component is in a solid state at room temperature (25°C).

[0012] The weight average molecular weight of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, and particularly preferably 270,000 or more, and is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. Within the above ranges, the effect tends to be more favorable.

[0013] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) can be determined in terms of standard polystyrene based on measurements obtained using a gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation; detector: differential refractometer; column: TSKGEL SUPERMULTIPORE HZ-M, manufactured by Tosoh Corporation).

[0014] The rubber component may be either an unmodified rubber or a modified rubber. Examples of modified rubbers include rubbers having functional groups that interact with fillers such as silica. Examples include terminal-modified rubbers (terminal-modified rubbers having the functional groups at the terminals) in which at least one terminal of the rubber has been modified with a compound (modifier) having the functional group, main-chain-modified rubbers having the functional groups in the main chain, main-chain-terminal-modified rubbers having the functional groups in the main chain and at the terminals (for example, main-chain-terminal-modified rubbers having the functional groups in the main chain and at least one terminal modified with the modifier), and terminal-modified rubbers modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having hydroxyl groups or epoxy groups introduced therein.

[0015] Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imido group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, and an epoxy group. These functional groups may have a substituent. Among these, an amino group (preferably an amino group in which a hydrogen atom of the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferred.

[0016] The rubber composition for a tire contains an epoxidized diene rubber as a rubber component. In this specification, the term "epoxidized diene rubber" means a diene rubber having an epoxy group.

[0017] The epoxidized diene rubber is not particularly limited, and examples thereof include epoxidized isoprene rubber (epoxidized natural rubber (ENR), epoxidized isoprene rubber (EIR), etc.), epoxidized butadiene rubber (EBR), epoxidized styrene-butadiene rubber (ESBR), epoxidized isoprene butadiene rubber, epoxidized styrene-butadiene-styrene copolymer, epoxidized butadiene acrylonitrile rubber, and partially hydrogenated versions thereof. These may be used alone or in combination of two or more. Among these, from the viewpoint of obtaining a better effect, it is preferable to contain at least one of epoxidized isoprene-based rubber and EBR, it is more preferable to contain at least one of epoxidized isoprene-based rubber, and it is even more preferable to contain ENR.

[0018] The epoxidized diene rubber may be a commercially available epoxidized diene rubber, or an epoxidized diene rubber (e.g., isoprene rubber, butadiene rubber, etc.). The method for epoxidizing the diene rubber is not particularly limited, and examples thereof include the chlorohydrin method, direct oxidation method, hydrogen peroxide method, alkyl hydroperoxide method, and peracid method (see, for example, JP-B-4-26617, JP-A-2-110182, and UK Patent No. 2113692). Examples of the peracid method include reacting a diene rubber with an organic peracid such as peracetic acid or performic acid. By adjusting the amount of organic peracid and the reaction time, epoxidized diene rubbers with various epoxidation rates can be prepared.

[0019] Examples of isoprene-based rubbers to be epoxidized include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. Examples of NR that can be used include those commonly used in the rubber industry, such as SIR20, RSS#3, and TSR20. Examples of IR are not particularly limited, and examples of IR that can be used include those commonly used in the rubber industry, such as IR2200. Examples of modified NR include deproteinized natural rubber (DPNR) and high-purity natural rubber. Examples of modified NR include hydrogenated natural rubber (HNR) and grafted natural rubber. Examples of modified IR include hydrogenated isoprene rubber and grafted isoprene rubber. These may be used alone or in combination of two or more.

[0020] The butadiene rubber (BR) to be epoxidized is not particularly limited, and examples thereof include high-cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, and BR synthesized using a rare earth catalyst (rare earth BR). These may be used alone or in combination of two or more. Of these, the BR preferably contains high-cis BR with a cis content of 90% by mass or more. The cis content is more preferably 95% by mass or more. The cis content can be measured by infrared absorption spectroscopy.

[0021] In this specification, the cis content of BR means the cis content of the BR when there is one type of BR, and means the average cis content when there are multiple types of BR. The average cis content of BR can be calculated by {Σ(content of each BR × cis content of each BR)} / total content of all BRs. For example, when 100% by mass of the rubber component contains 20% by mass of BR with a cis content of 90% by mass and 10% by mass of BR with a cis content of 40% by mass, the average cis content of BR is 73.3% by mass (=(20×90+10×40) / (20+10)).

[0022] Both unmodified and modified BR can be used. Modified BR includes modified BR with the same functional groups as modified rubber. Hydrogenated butadiene polymer (hydrogenated BR) can also be used.

[0023] As the BR, for example, products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used.

[0024] The epoxidation rate of the epoxidized diene rubber is preferably 0.5 mol% or more, more preferably 1.0 mol% or more, and even more preferably 2.0 mol% or more, and is preferably 50 mol% or less, more preferably 35 mol% or less, and even more preferably 25 mol% or less. When it is within the above range, the effect tends to be more favorable.

[0025] The epoxidation rate of the epoxidized natural rubber (ENR) is preferably 0.5 mol% or more, more preferably 1.0 mol% or more, and even more preferably 2.0 mol% or more, and is preferably 50 mol% or less, more preferably 35 mol% or less, and even more preferably 25 mol% or less. When the epoxidation rate is within the above range, better effects tend to be obtained.

[0026] In this specification, the epoxidation ratio is the ratio (mol %) of the number of epoxidized double bonds to the total number of double bonds in the rubber before epoxidation. In this specification, the epoxidation ratio can be measured by nuclear magnetic resonance (NMR) spectroscopy.

[0027] In the rubber composition for tires, the content of the epoxidized diene rubber in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, and may be 100% by mass. When the content is within the above range, better effects tend to be obtained.

[0028] In the rubber composition for tires, the content of ENR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, and may be 100% by mass. When the content is within the above range, better effects tend to be obtained.

[0029] The rubber composition for a tire may contain a rubber component other than the epoxidized diene rubber. Examples of rubber components other than the epoxidized diene rubber include diene rubbers. Examples of diene rubbers include isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR). Examples of rubber components include butyl rubber and fluororubber. These rubber components may be modified or hydrogenated, and extended rubbers extended with oil, resin, liquid rubber components, or the like may also be used. Among these, it is preferable to include at least one of isoprene rubber, BR, and SBR.

[0030] The raw materials (monomers) for synthetic rubbers such as IR, SBR, and BR may be derived from underground resources such as petroleum and natural gas, or may be recycled from rubber products such as tires or non-rubber products such as polystyrene. Monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled polyisoprene, recycled butadiene, and recycled aromatic vinyls. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyls include, but are not limited to, styrene. Among these, recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) are preferably used as raw materials.

[0031] The method for producing the recycled monomer is not particularly limited, and examples thereof include synthesis from recycled naphtha obtained by decomposing rubber products such as tires. The method for producing recycled naphtha is also not particularly limited, and examples thereof include decomposing rubber products such as tires under high temperature and pressure, decomposing with microwaves, or mechanically crushing and then extracting.

[0032] Furthermore, the raw materials (monomers) of synthetic rubbers such as IR, SBR, and BR may be derived from biomass. In this specification, biomass refers to materials derived from natural resources such as plants. Examples of biomass include, but are not limited to, agricultural, forestry, and fishery products, sugar, wood chips, plant residues after useful components have been extracted, plant-derived ethanol, and biomass naphtha.

[0033] Monomers derived from biomass (biomass monomers) are not particularly limited and include biomass-derived butadiene and biomass-derived aromatic vinyl. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyls include, but are not limited to, styrene. The method for producing biomass monomers is not particularly limited and includes, for example, biological and / or chemical and / or physical conversion of animals and plants. A representative example of biological conversion is fermentation by microorganisms, and examples of chemical and / or physical conversion include catalytic conversion, high heat conversion, high pressure conversion, electromagnetic wave conversion, critical fluid conversion, and combinations thereof.

[0034] The polymer synthesized from a biomass monomer component (biomass polymer) is not particularly limited, and examples thereof include polybutadiene rubber synthesized from biomass-derived butadiene, and aromatic vinyl / butadiene copolymer synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0035] Whether the raw material for a polymer is derived from biomass can be determined by the pMC (percent modern carbon) measured in accordance with ASTM D6866-10.

[0036] pMC is the modern standard reference14 of sample against C concentration 14 This is the ratio of C concentrations and is a value used as an index of the biomass ratio of a compound. The significance of this value is explained below.

[0037] 1 mole of carbon atoms (6.02 × 10 23 ) contains approximately 6.02 × 10 atoms, which is about one trillionth of the number of ordinary carbon atoms. 11 pieces 14 C exists. 14 C is called a radioactive isotope, and its half-life is 5,730 years, and it decreases regularly. It takes 226,000 years for all of it to decay. Therefore, in fossil fuels such as coal, oil, and natural gas, which are thought to have been absorbed and fixed by plants and other organisms more than 226,000 years ago, C was also included in these when it was first fixed. 14 All C elements have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas contain 14 Therefore, chemicals produced from these fossil fuels do not contain any C element. 14 It does not contain any C element.

[0038] on the other hand, 14 C is produced continuously by nuclear reactions in the atmosphere caused by cosmic rays, and this balances with the decrease due to radioactive decay. In the Earth's atmospheric environment, 14 Therefore, the amount of carbon derived from biomass resources currently circulating in the environment is constant. 14 As mentioned above, the C concentration is approximately 1 × 10 -12 The value is approximately mol %. Therefore, the biomass ratio of a certain compound can be calculated by using the difference between these values.

[0039] this 14 C is typically measured using accelerator mass spectrometry based on a tandem accelerator. 13 C concentration ( 13 C / 12 C). 14 C concentration ( 14 C / 12 C) is measured. 14 The modern standard reference for the C concentration is the carbon circulating in nature as of 1950. 14 The specific standard substance used is the oxalic acid standard provided by NIST (National Institute of Standards and Technology). The specific activity of carbon in this oxalic acid (per gram of carbon) is 14 The radioactivity of C is separated into carbon isotopes, 13 The standard value is the value corrected for decay from 1950 to the measurement date. 14 This is used as the C concentration value (100%). The ratio of this value to the value of the actually measured sample is the pMC value.

[0040] Therefore, if rubber is made from 100% biomass-derived materials, although there are regional differences, under normal circumstances, it will usually not reach 100, and will show a value of approximately 110 pMC. On the other hand, for chemical substances derived from petroleum and other fossil fuels, 14 When the carbon concentration is measured, it will show a value of about 0 pMC (for example, 0.3 pMC), which corresponds to the biomass ratio of 0% mentioned above.

[0041] From the above, it is preferable in terms of environmental protection to use a material such as rubber having a high pMC value, that is, a material such as rubber having a high biomass ratio, in a rubber composition.

[0042] Among the rubber components other than the epoxidized diene rubber, examples of the isoprene rubber include the isoprene rubbers described above.

[0043] In the rubber component other than the epoxidized diene rubber, examples of the BR include the above-mentioned BR.

[0044] In the rubber component other than the epoxidized diene rubber, the SBR is not particularly limited, and for example, emulsion polymerized styrene butadiene rubber (E-SBR), solution polymerized styrene butadiene rubber (S-SBR), etc. can be used. These may be used alone or in combination of two or more.

[0045] The styrene content of the SBR is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 24% by mass or more. The styrene content is preferably 60% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less. Within the above range, better effects tend to be obtained. In this specification, the styrene content is 1 It can be measured by H-NMR measurement.

[0046] The styrene content of SBR means the styrene content of the SBR when there is one type of SBR, and means the average styrene content when there are multiple types of SBR. The average styrene amount of SBR can be calculated by {Σ(content of each SBR × styrene amount of each SBR)} / total content of all SBRs. For example, when 100% by mass of the rubber component contains 85% by mass of SBR with a styrene amount of 40% by mass and 5% by mass of SBR with a styrene amount of 25% by mass, the average styrene amount of the SBR is 39.2% by mass (=(85×40+5×25) / (85+5)).

[0047] The vinyl bond content of the SBR is preferably 3% by mass or more, more preferably 10% by mass or more, and even more preferably 17% by mass or more. The vinyl bond content is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. When the vinyl bond content is within the above range, better effects tend to be obtained. In this specification, the vinyl bond amount (amount of 1,2-bonded butadiene units) can be measured by infrared absorption spectroscopy.

[0048] The vinyl content of SBR (amount of 1,2-bonded butadiene units) is the proportion of vinyl bonds (unit: mass%) when the total mass of the butadiene parts in the SBR is taken as 100, and is calculated as vinyl content [mass%] + cis content [mass%] + trans content [mass%] = 100 [mass%]. When there is one type of SBR, it means the vinyl content of that SBR, and when there are multiple types, it means the average vinyl content. The average vinyl content of SBR can be calculated by Σ{content of each SBR × (100 [mass%] - styrene content of each SBR [mass%]) × vinyl content of each SBR [mass%]} / Σ{content of each SBR × (100 [mass%] - styrene content of each SBR [mass%])}. For example, in 100 parts by mass of the rubber component, 75 parts by mass of SBR with a styrene content of 40% by mass and a vinyl content of 30% by mass, 25 parts by mass of styrene and 10 parts by mass of vinyl are used. In the case where 15 parts by mass of SBR with a vinyl content of 20% by mass is used and the remaining 10 parts by mass are other than SBR, the average vinyl content of the SBR is 28% by mass (= {75 × (100 [% by mass] - 40 [% by mass]) × 30 [% by mass] + 15 × (100 [% by mass] - 25 [% by mass]) × 20 [% by mass])} / {75 × (100 [% by mass] - 40 [% by mass]) + 15 × (100 [% by mass] - 25 [% by mass])}.

[0049] Both unmodified and modified SBR can be used. Modified SBR includes modified SBR with the same functional groups as modified rubber. Hydrogenated styrene-butadiene copolymer (hydrogenated SBR) can also be used as SBR.

[0050] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used. SBR synthesized by a known method can also be used.

[0051] When the rubber composition for tires contains an isoprene-based rubber as a rubber component other than the epoxidized diene-based rubber, the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less. Within the above ranges, better effects tend to be obtained.

[0052] When the rubber composition for a tire contains BR as a rubber component other than the epoxidized diene rubber, the content of the BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less. Within the above ranges, better effects tend to be obtained.

[0053] When the rubber composition for tires contains SBR as a rubber component other than the epoxidized diene rubber, the content of the SBR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less. When the content is within the above ranges, better effects tend to be obtained.

[0054] The rubber composition for a tire contains a divalent or higher carboxylic acid compound. In this specification, a divalent or higher carboxylic acid compound means a compound having two or more carboxyl groups.

[0055] In the rubber composition for tires, the content of the divalent or higher carboxylic acid compound (total amount of divalent or higher carboxylic acid compounds) is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 3.6 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 15.0 parts by mass or less, more preferably 10.0 parts by mass or less, and even more preferably 6.0 parts by mass or less. Within the above ranges, the effects tend to be more favorably obtained.

[0056] The divalent or higher carboxylic acid compound is not particularly limited, and examples thereof include linear or branched aliphatic dicarboxylic acid compounds, alicyclic dicarboxylic acid compounds, aromatic dicarboxylic acid compounds, trivalent or higher polycarboxylic acid compounds, etc. These may be used alone or in combination of two or more. Among these, linear or branched aliphatic dicarboxylic acid compounds are preferred from the viewpoint of obtaining a greater effect.

[0057] The carbon number of the linear or branched aliphatic dicarboxylic acid compound is preferably 2 or more, more preferably 3 or more, and is preferably 22 or less, more preferably 16 or less, and even more preferably 12 or less. When the carbon number is within the above range, the effect tends to be better.

[0058] Specific examples of the linear or branched aliphatic dicarboxylic acid compound include oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, and succinic acids substituted with an aliphatic hydrocarbon group having from 1 to 20 carbon atoms (dodecylsuccinic acid, dodecenylsuccinic acid, octenylsuccinic acid, etc.). These may be used alone or in combination of two or more. Among these, from the viewpoint of obtaining a greater effect, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, adipic acid, sebacic acid, and dodecanedioic acid are preferred, and malonic acid and dodecanedioic acid are more preferred.

[0059] When the rubber composition for a tire contains the linear or branched aliphatic dicarboxylic acid compound, the content of the linear or branched aliphatic dicarboxylic acid compound (total amount of the linear or branched aliphatic dicarboxylic acid compound) is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 3.6 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 15.0 parts by mass or less, more preferably 10.0 parts by mass or less, and even more preferably 6.0 parts by mass or less. When the content is within the above range, better effects tend to be obtained.

[0060] Examples of the alicyclic dicarboxylic acid compound include adamantanedicarboxylic acid, norbornenedicarboxylic acid, cyclohexanedicarboxylic acid, and decalindicarboxylic acid. These may be used alone or in combination of two or more.

[0061] Examples of the aromatic dicarboxylic acid compound include phthalic acid, isophthalic acid, and terephthalic acid, which may be used alone or in combination of two or more.

[0062] The trivalent or higher polycarboxylic acid compound is preferably a trivalent carboxylic acid, such as trimellitic acid, which may be used alone or in combination of two or more.

[0063] The rubber composition for tires preferably contains a filler. The filler is not particularly limited, and materials known in the rubber field can be used, including inorganic fillers such as carbon black, silica, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica, biochar, and poorly dispersible fillers. Of these, carbon black and silica are preferred from the viewpoint of obtaining better effects.

[0064] In the rubber composition for tires, the content of the filler (total amount of fillers such as carbon black and silica) is preferably 5 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 100 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0065] Usable carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. The raw material for carbon black may be a biomass material such as lignin or vegetable oil, or pyrolysis oil obtained by pyrolysis of waste tires. Carbon black may be produced by combustion, such as in a furnace, by hydrothermal carbonization (HTC), or by thermal decomposition of methane, such as in a thermal black process. Commercially available carbon blacks include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., and Columbia Carbon Co., Ltd. These may be used alone or in combination.

[0066] The nitrogen adsorption specific surface area (N2SA) of carbon black is 5m 2 / g or more is preferable, and 50m 2 / g or more is more preferable, and 90m 2 / g or more is more preferable. 2 / g or less is preferable, and 130m 2 / g or less is more preferable, and 120m 2 Within the above range, the effect tends to be better. The nitrogen adsorption specific surface area of carbon black can be determined according to JIS K6217-2:2001.

[0067] In the rubber composition for tires, the content of carbon black is preferably 5 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and even more preferably 100 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0068] The silica that can be used in the rubber composition for tires is not particularly limited, and can be, for example, silica prepared by a dry process (anhydrous silica) or silica prepared by a wet process (hydrated silica), which are commonly used in the tire industry. The raw material for silica is not particularly limited, and can be, for example, a mineral-derived raw material such as quartz, a biological raw material such as rice husk (for example, silica made from a biomass material such as rice husk), or silica recycled from a silica-containing product. Among these, hydrated silica prepared by a wet process is preferred because it contains a large number of silanol groups. These silicas can be used alone or in combination of two or more types.

[0069] Silica made from biomass materials can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then reacting the silicate with sulfuric acid in the same manner as conventional wet-process silica to produce a silicon dioxide precipitate, which is then filtered, washed with water, dried, and pulverized.

[0070] Silica recycled from silica-containing products can be, for example, silica recovered from products containing silica, such as electronic components such as semiconductors, tires, desiccants, and filtering materials such as diatomaceous earth. The recovery method is not particularly limited, and examples include thermal decomposition and decomposition by electromagnetic waves. Among these, silica recovered from electronic components such as semiconductors or tires is preferred.

[0071] When silica crystallizes, it becomes insoluble in water, and its component, silicic acid, cannot be utilized. By controlling the combustion temperature and duration, it is possible to suppress the crystallization of silica in rice husk ash (see, for example, JP 2009-2594 A and Akita Prefectural University Web Journal B / 2019, vol. 6, pp. 216-222).

[0072] Amorphous silica extracted from rice husks may be commercially available from Wilmar Co., Ltd., etc.

[0073] In the rubber composition for tires, the content of silica is preferably 5 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and even more preferably 100 parts by mass or less. Within the above ranges, the effect tends to be better obtained.

[0074] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 50 m 2 / g or more, more preferably 100m 2 / g or more, more preferably 150m 2 The upper limit of the N2SA of silica is not particularly limited, but is preferably 350 m 2 / g or less, more preferably 300m 2 / g or less, more preferably 250m 2 Within the above range, there is a tendency for the effect to be better obtained. The N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0075] Examples of the hardly dispersible filler include microfibrillated plant fibers, short fiber cellulose, gel compounds, etc. Among these, microfibrillated plant fibers are preferred.

[0076] The microfibrillated plant fiber is preferably cellulose microfibrils, as they provide good reinforcing properties. The cellulose microfibrils are not particularly limited as long as they are derived from natural products, and examples include those derived from resource biomass such as fruits, grains, and root vegetables; wood, bamboo, hemp, jute, and kenaf; pulp, paper, and cloth obtained from these raw materials; waste biomass such as agricultural waste, food waste, and sewage sludge; unused biomass such as rice straw, wheat straw, and thinned wood; and cellulose produced by sea squirts, acetic acid bacteria, and the like. These microfibrillated plant fibers may be used alone or in combination of two or more.

[0077] In this specification, cellulose microfibrils typically refer to cellulose fibers having an average fiber diameter of 10 μm or less, more typically cellulose fibers having a microstructure formed by the aggregation of cellulose molecules and an average fiber diameter of 500 nm or less. Typical cellulose microfibrils are formed, for example, as an aggregate of cellulose fibers having the above-mentioned average fiber diameter.

[0078] When the rubber composition for a tire contains a hardly-dispersible filler, the content of the hardly-dispersible filler is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less. Within the above range, better effects tend to be obtained.

[0079] When the rubber composition for a tire contains silica, it is preferable that it further contains a silane coupling agent. The silane coupling agent is not particularly limited, and those known in the rubber field can be used, for example, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N, Examples include sulfide-based compounds such as N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z manufactured by Momentive; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercially available products include those from Degussa, Momentive, Shin-Etsu Silicones Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Dow Corning Toray Co., Ltd. These may be used alone or in combination of two or more.

[0080] In the rubber composition for tires, the content of the silane coupling agent is preferably 0.1 parts by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more, relative to 100 parts by mass of silica. The upper limit of the content is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0081] The rubber composition for a tire may contain a plasticizer. In this specification, the term "plasticizer" refers to a material that imparts plasticity to a rubber component, and includes both plasticizers that are liquid at 25°C and plasticizers that are solid at 25°C. Examples of plasticizers include resin components, oils, liquid polymers, and ester-based plasticizers. These plasticizers may be derived from mineral resources such as petroleum and natural gas, biomass-derived plasticizers, or naphtha recycled from rubber and non-rubber products. Low-molecular-weight hydrocarbon components obtained by pyrolysis and extraction of used tires or products containing various components may also be used as plasticizers. These plasticizers may be used alone or in combination.

[0082] Specific examples of the plasticizer include oils, other liquid polymers, resins, etc. These may be used alone or in combination of two or more.

[0083] Examples of oils include mineral oil, vegetable oil, animal oil, etc. From the viewpoint of life cycle assessment, waste oils used in rubber mixers or engines, or refined waste cooking oils used in restaurants may also be used.

[0084] As used herein, mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. Examples of mineral oil include paraffinic oil (mineral oil), naphthenic oil, and aromatic oil. Specific examples of mineral oil include mild extract solvated (MES), distillate aromatic extract (DAE), treated distillate aromatic extract (TDAE), treated residual aromatic extract (TRAE), and residual aromatic extract (RAE). Furthermore, as an environmental measure, oils with a low content of polycyclic aromatic compounds (PCA) can also be used. Examples of low PCA oils include MES, TDAE, and heavy naphthenic oil.

[0085] As used herein, examples of vegetable oils include linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grapeseed oil, and Japan wax. Further examples of vegetable oils include refined oils (such as salad oil) obtained by refining the above-mentioned oils, interesterified oils obtained by interesterifying the above-mentioned oils, hardened oils obtained by hydrogenating the above-mentioned oils, thermally polymerized oils obtained by thermally polymerizing the above-mentioned oils, oxidatively polymerized oils obtained by oxidizing the above-mentioned oils, and waste edible oils recovered from edible oils and the like. Vegetable oils may be liquid or solid at 25°C. These vegetable oils may be used alone or in combination of two or more.

[0086] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxyl group of glycerin is esterified with a fatty acid. The acylglycerol is not particularly limited and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Furthermore, the acylglycerol may be a monomer, a dimer, or a polymer (trimer or higher). Dimer or higher acylglycerols can be obtained by thermal polymerization, oxidative polymerization, or the like. The acylglycerol may be liquid or solid at 25°C.

[0087] The method for confirming whether the rubber composition contains the acylglycerol is not particularly limited, but may be any of the following: 1 For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at 25°C for 24 hours, and after removing the rubber composition, the 1 When H-NMR was measured, signals were observed around 5.26 ppm, 4.28 ppm, and 4.15 ppm when the signal of tetramethylsilane (TMS) was set at 0.00 ppm. These signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atoms of the ester group. In this paragraph, "around" refers to a range of ±0.10 ppm.

[0088] The fatty acid is not particularly limited and may be either an unsaturated fatty acid or a saturated fatty acid. Examples of unsaturated fatty acids include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of saturated fatty acids include butyric acid and lauric acid.

[0089] Among these, it is desirable that the fatty acid contains a fatty acid with few double bonds, i.e., a saturated fatty acid or a monounsaturated fatty acid, and oleic acid is preferred. As a vegetable oil containing such a fatty acid, for example, vegetable oil containing a saturated fatty acid or a monounsaturated fatty acid may be used, or vegetable oil modified by ester exchange or the like may be used. Furthermore, in order to produce vegetable oil containing such a fatty acid, plants may be improved by breeding, genetic modification, genome editing, or the like.

[0090] As the oil, for example, commercially available oils from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoi Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., Fuji Kosan Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0091] Examples of the liquid polymer include liquid diene polymers (liquid rubbers) and liquid farnesene polymers at 25°C. Examples of liquid rubber include liquid styrene butadiene copolymers (liquid SBRs), liquid butadiene polymers (liquid BRs), liquid isoprene polymers (liquid IRs), liquid styrene isoprene copolymers (liquid SIRs), liquid styrene butadiene styrene block copolymers (liquid SBS block polymers), and liquid styrene isoprene styrene block copolymers (liquid SIS block polymers). The terminals or main chains of these may be modified with polar groups. Hydrogenated versions of these compounds can also be used.

[0092] The liquid diene polymer has a weight average molecular weight (Mw) of 1.0×10 in terms of polystyrene as measured by gel permeation chromatography (GPC). 3 ~5.0×10 4 Preferably, it is 3.0 × 10 3 ~1.5×10 4 The lower or upper limit of Mw of the liquid diene polymer may be 4,500 or 8,500. In this specification, the Mw of the liquid diene polymer is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0093] As the liquid diene polymer, for example, products available from Sartomer Co., Ltd., Kuraray Co., Ltd., etc. can be used.

[0094] The resin may be a resin commonly used in tire compounds, and may be liquid or solid at room temperature (25°C). Examples include aromatic vinyl polymers, coumarone-indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, and acrylic resins. The resin may also be a hydrogenated resin (hydrogenated resin). These may be used alone or in combination of two or more. The resin itself may also be a copolymer of monomer components derived from multiple sources. Among these, aromatic vinyl polymers, petroleum resins, terpene resins, and hydrogenated resins thereof are preferred.

[0095] When a resin that is solid at room temperature is used, the softening point of the resin is preferably 50° C. or higher, more preferably 55° C. or higher, even more preferably 60° C. or higher, and particularly preferably 85° C. or higher. Also, the softening point is preferably 160° C. or lower, more preferably 150° C. or lower, even more preferably 140° C. or lower, and particularly preferably 100° C. or lower. Within the above range, better effects tend to be obtained. When the resin is liquid at room temperature, the softening point is preferably 20°C or lower, more preferably 10°C or lower, and even more preferably 0°C or lower. In the case of hydrogenated resins, it is desirable that the softening point is the same as above. The softening point of the resin is the temperature at which the ball drops when the softening point specified in JIS K6220-1:2001 is measured using a ring and ball softening point tester.

[0096] The aromatic vinyl polymer is a polymer containing an aromatic vinyl monomer as a constituent unit. For example, it may be a resin obtained by polymerizing α-methylstyrene and / or styrene, and specifically may be a homopolymer of styrene (styrene resin), a homopolymer of α-methylstyrene (α-methylstyrene resin), a copolymer of α-methylstyrene and styrene, or a copolymer of styrene and another monomer.

[0097] The coumarone-indene resin is a resin containing coumarone and indene as the main monomer components constituting the resin skeleton (main chain). Other monomer components contained in the skeleton besides coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0098] The coumarone resin is a resin containing coumarone as a main monomer component constituting the skeleton (main chain) of the resin.

[0099] The indene resin is a resin containing indene as a main monomer component constituting the skeleton (main chain) of the resin.

[0100] The phenolic resin may be a known polymer obtained by reacting phenol with an aldehyde such as formaldehyde, acetaldehyde, or furfural in the presence of an acid or alkali catalyst. Of these, those obtained by reacting with an acid catalyst (such as novolac phenolic resin) are preferred.

[0101] Examples of the rosin resin include rosin-based resins such as natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

[0102] Examples of the petroleum resin include C5 resin, C9 resin, C5 / C9 resin, dicyclopentadiene (DCPD) resin, C9 / DCPD resin, and hydrogenated versions of these. Of these, DCPD resin, hydrogenated DCPD resin, C9 / DCPD resin, and C9 / hydrogenated DCPD resin are preferred.

[0103] The terpene resin is a polymer containing terpene as a structural unit. Examples include polyterpene resins obtained by polymerizing terpene compounds and aromatic-modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds. Examples of aromatic-modified terpene resins include terpene phenol resins made from terpene compounds and phenolic compounds, terpene styrene resins made from terpene compounds and styrene compounds, and terpene phenol styrene resins made from terpene compounds, phenolic compounds, and styrene compounds. Examples of terpene compounds include α-pinene and β-pinene, phenolic compounds include phenol and bisphenol A, and aromatic compounds include styrene compounds (styrene, α-methylstyrene, etc.). Among these, aromatic-modified terpene resins are preferred.

[0104] The acrylic resin is a polymer containing an acrylic monomer as a constituent unit. For example, a styrene-acrylic resin having a carboxyl group and obtained by copolymerizing an aromatic vinyl monomer component with an acrylic monomer component can be used. Among them, a solvent-free carboxyl-containing styrene-acrylic resin can be preferably used.

[0105] Examples of the resins that can be used include products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, ExxonMobil, KRATON, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., and Taoka Chemical Co., Ltd.

[0106] From the viewpoint of sustainability, it is desirable to use the above-mentioned plant-derived plasticizers such as plant-derived oils and farnesene-based polymers as the plasticizer.

[0107] Farnesene polymers are polymers obtained by polymerizing farnesene and contain structural units based on farnesene. Farnesene has isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecatriene), but (E)-β-farnesene, which has the following structure, is preferred. [ka]

[0108] The farnesene polymer may be a homopolymer of farnesene (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer). These may be used alone or in combination of two or more. Among these, a copolymer of farnesene and a vinyl monomer is preferred.

[0109] Examples of vinyl monomers include aromatic vinyl compounds such as styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, 5-tert-butyl-2-methylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-tert-butylstyrene, 3-tert-butylstyrene, 4-tert-butylstyrene, vinylxylene, vinylnaphthalene, vinyltoluene, vinylpyridine, diphenylethylene, and tertiary amino group-containing diphenylethylene, as well as conjugated diene compounds such as butadiene and isoprene. These may be used alone or in combination of two or more. Among these, butadiene is preferred. That is, the farnesene-vinyl monomer copolymer is preferably a copolymer of farnesene and butadiene (farnesene-butadiene copolymer).

[0110] In the farnesene-vinyl monomer copolymer, the copolymerization ratio by mass of farnesene to vinyl monomer (farnesene / vinyl monomer) is preferably 40 / 60 to 90 / 10.

[0111] The farnesene polymer preferably has a weight average molecular weight (Mw) of 3,000 or more and 300,000 or less. The Mw of the farnesene polymer is preferably 8,000 or more, more preferably 10,000 or more, and is preferably 100,000 or less, more preferably 60,000 or less, and even more preferably 50,000 or less. Within the above ranges, the effects tend to be more favorably obtained.

[0112] The farnesene polymer may be either a liquid or solid at room temperature (25° C.), with liquid farnesene polymers being preferred.

[0113] In the rubber composition for tires, the content of the plasticizer (total amount of plasticizer) is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less. Within the above range, better effects tend to be obtained. The plasticizer content includes the amount of oil and resin contained in the oil-extended rubber and resin-extended rubber.

[0114] In the rubber composition for tires, the content of the solid plasticizer in a solid state at room temperature (25°C) is preferably 20 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of the rubber component, and may be 0 part by mass. When the content is within the above range, better effects tend to be obtained.

[0115] In the rubber composition for tires, the content of the resin in a solid state at room temperature (25°C) is preferably 20 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of the rubber component, and may be 0 part by mass. When the content is within the above range, better effects tend to be obtained.

[0116] In the rubber composition for tires, the content of the liquid plasticizer that is in a liquid state at room temperature (25°C) is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less. Within the above range, better effects tend to be obtained. The content of the liquid plasticizer includes the amount of oil contained in the oil-extended rubber and the amount of liquid resin in the resin-extended rubber extended with the liquid resin.

[0117] In the rubber composition for tires, the oil content is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less. Within the above range, better effects tend to be obtained. The oil content includes the amount of oil contained in the oil-extended rubber.

[0118] The rubber composition for a tire may further contain vulcanized rubber particles. The vulcanized rubber particles are particles made of vulcanized rubber, and specifically, rubber powder as specified in JIS K 6316:2017 can be used. From the standpoint of environmental considerations and cost, recycled rubber powder produced from crushed waste tires is preferred. These may be used alone or in combination of two or more types.

[0119] The vulcanized rubber particles are not particularly limited, and may be unmodified vulcanized rubber particles or modified vulcanized rubber particles.

[0120] As commercially available vulcanized rubber particles, for example, products from Lehigh Corporation, Muraoka Rubber Industries Co., Ltd., etc. can be used.

[0121] In the rubber composition for tires, the content of the vulcanized rubber particles is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the rubber component, and is 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. Within the above ranges, better effects tend to be obtained.

[0122] The rubber composition for tires preferably contains an antioxidant from the viewpoints of crack resistance, ozone resistance, and the like.

[0123] The antioxidant is not particularly limited, and examples thereof include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), and N,N'-ditolyl-p-phenylenediamine. p-phenylenediamine antioxidants such as N-isopropyl-N'-phenyl-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferred, and polymers of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. Commercially available products that can be used include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis, etc.

[0124] In the rubber composition for tires, the content of the antioxidant is preferably 0.2 parts by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 3.4 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 10.0 parts by mass or less, more preferably 6.0 parts by mass or less.

[0125] The rubber composition for tires preferably contains stearic acid. In the rubber composition for treads, the content of stearic acid is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0126] As the stearic acid, conventionally known products can be used, for example, products available from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc.

[0127] The rubber composition for tires preferably contains zinc oxide. In the rubber composition for treads, the content of zinc oxide is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 6.0 parts by mass or less, and more preferably 4.0 parts by mass or less.

[0128] As the zinc oxide, conventionally known products can be used, for example, products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0129] The rubber composition for tires may contain wax. In the rubber composition for tires, the wax content is preferably 0.5 parts by mass or more, more preferably 1.6 parts by mass or more, and preferably 8.0 parts by mass or less, more preferably 5.0 parts by mass or less, per 100 parts by mass of the rubber component.

[0130] The wax is not particularly limited, and any wax commonly used in the tire industry can be suitably used. Examples include mineral waxes and plant-derived waxes. Mineral waxes refer to waxes derived from mineral resources such as oil and natural gas. Plant-derived waxes refer to waxes derived from natural resources such as plants. Among these, mineral waxes are preferred. Examples of plant-derived waxes include rice wax, carnauba wax, and candelilla wax. Examples of mineral waxes include paraffin wax, microcrystalline wax, and selected special waxes thereof, with paraffin wax being preferred. The wax according to this embodiment does not contain stearic acid. Waxes that can be used include those commercially available from, for example, Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., Ltd., etc. These waxes may be used alone or in combination of two or more.

[0131] It is preferable to compound sulfur as a crosslinking agent in the rubber composition for tires, in order to form appropriate crosslinked chains in polymer chains and impart good performance.

[0132] The rubber composition for tires contains sulfur. In the rubber composition for tires, the sulfur content is 1.0 part by mass or more, preferably 1.2 parts by mass or more, more preferably 1.3 parts by mass or more, and even more preferably 1.4 parts by mass or more, per 100 parts by mass of the rubber component. The sulfur content is preferably 7.0 parts by mass or less, more preferably 5.0 parts by mass or less, and even more preferably 4.0 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0133] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. Commercially available products include those from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. These may be used alone or in combination of two or more.

[0134] The rubber composition for a tire preferably contains a vulcanization accelerator. In the rubber composition for tires, the content of the vulcanization accelerator is not particularly limited and may be freely determined according to the desired vulcanization rate and crosslink density, but is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.4 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, and even more preferably 5.0 parts by mass or less.

[0135] The type of vulcanization accelerator is not particularly limited, and commonly used ones can be used. Examples of the vulcanization accelerator include benzothiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-orthotolylguanidine, and orthotolylbiguanidine. These may be used alone or in combination of two or more. Among these, sulfenamide-based, guanidine-based and benzothiazole-based vulcanization accelerators are preferred.

[0136] In addition to the above components, the rubber composition for tires may also contain compounding agents generally used in the tire industry, such as materials such as a mold release agent, as appropriate.

[0137] In this specification, various materials containing carbon atoms (e.g., rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from atmospheric carbon dioxide. As a method for obtaining the above-mentioned compound from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process in which methane is synthesized from carbon dioxide may be converted.

[0138] In the rubber composition for tires, the ratio K (content of divalent or higher carboxylic acid compounds / content of sulfur) of the content of the divalent or higher carboxylic acid compounds (content of divalent or higher carboxylic acid compounds per 100 parts by mass of the rubber component) to the content of the sulfur (content of sulfur per 100 parts by mass of the rubber component) is 0.10 or more and 10.00 or less. The lower limit of K is preferably 0.80 or more, more preferably 1.29 or more, even more preferably 2.00 or more, and particularly preferably 2.58 or more, and is preferably 8.00 or less, more preferably 6.00 or less, and even more preferably 4.00 or less. Within the above ranges, the effect tends to be better.

[0139] In the rubber composition for tires, the ratio of the content of the divalent or higher carboxylic acid compounds (total amount of divalent or higher carboxylic acid compounds) to the content of the epoxidized diene rubber (content of divalent or higher carboxylic acid compounds / content of epoxidized diene rubber) is preferably 0.005 or more and 0.100 or less. The lower limit is preferably 0.009 or more, more preferably 0.015 or more, and even more preferably 0.036 or more, and the upper limit is preferably 0.080 or less, more preferably 0.060 or less, and even more preferably 0.040 or less. Within the above ranges, the effect tends to be more favorable.

[0140] Although the mechanism by which a greater effect is obtained by adjusting the content of the divalent or higher carboxylic acid compound / epoxidized diene rubber to a predetermined range is unclear, by setting the ratio within the predetermined range, the hydrogen bonds are well formed, ensuring abrasion resistance and crack growth resistance, which is thought to improve the overall performance of abrasion resistance and crack growth resistance.

[0141] In the rubber composition for tires, the ratio of the content of the divalent or higher carboxylic acid compounds (total amount of divalent or higher carboxylic acid compounds) to the content of the epoxidized natural rubber (ENR) (content of divalent or higher carboxylic acid compounds / content of ENR) is preferably 0.005 or more and 0.100 or less. The lower limit is preferably 0.009 or more, more preferably 0.018 or more, and even more preferably 0.036 or more, and the upper limit is preferably 0.080 or less, more preferably 0.060 or less, and even more preferably 0.040 or less. Within the above ranges, the effect tends to be more favorable.

[0142] The rubber composition for tires is obtained by kneading the above components using a rubber kneading device such as an open roll or a Banbury mixer, and then crosslinking the components to obtain a crosslinked rubber composition.

[0143] As for kneading conditions, in the base kneading step in which additives other than the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 50 to 200°C, preferably 80 to 190°C, and the kneading time is usually 30 seconds to 30 minutes, preferably 1 minute to 30 minutes. In the finish kneading step in which the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 100°C or lower, preferably room temperature to 80°C. Furthermore, the composition kneaded with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 120 to 200°C, preferably 140 to 180°C.

[0144] The tire components to which the rubber composition for tires is applied are not particularly limited, and examples thereof include tread, sidewall, wing, base tread, undertread, bead apex, clinch, inner liner, and the like.

[0145] Among the tire components, from the viewpoint of obtaining greater effects, it is desirable to apply the rubber composition for a tire to tire surface layer components such as a tread, a sidewall, a wing, a clinch, etc. In this case, the rubber composition for a tire is used as a rubber composition for a tire surface layer component such as a rubber composition for a tread, a rubber composition for a sidewall, a rubber composition for a wing, or a rubber composition for a clinch. In this specification, the term "tire surface layer member" refers to a tire member at least part of which is exposed on the tire surface.

[0146] The tire of the present disclosure is manufactured by a conventional method using the rubber composition for a tire. That is, the composition, to which various additives are optionally blended, is extruded in an uncrosslinked or unvulcanized state to match the shapes of various tire components such as tire surface layer components, molded in a tire building machine by a conventional method, and laminated together with other tire components to form an unvulcanized tire, which is then heated and pressurized in a vulcanizer to manufacture the tire.

[0147] The tire is not particularly limited, and examples thereof include pneumatic tires, solid tires, airless tires, etc. Among these, pneumatic tires are preferred.

[0148] The above-mentioned tires are suitable for use as passenger car tires, large passenger car tires, large SUV tires, truck and bus tires, motorcycle tires, racing tires, winter tires (studless tires, snow tires, studded tires), all-season tires, run-flat tires, aircraft tires, mining tires, etc.

[0149] In a tire having a tire component made of the above rubber composition for a tire, the tire component has a predetermined thickness T (mm). In this specification, the thickness T of a tire component is the thickness of each tire component in a cross section cut along a plane including the tire rotation axis, and unless otherwise defined below, refers to the average value of the thickness of the tire component in the normal direction at each point on the surface of each tire component. Furthermore, unless otherwise defined below, when a tire component is composed of two or more rubber layers, the thickness T of the tire component refers to the total thickness of the two or more rubber layers.

[0150] In the tire, the thickness T (mm) of the tire component is preferably 1.0 mm or more, more preferably 3.0 mm or more, even more preferably 5.0 mm or more, and particularly preferably 6.5 mm or more, and is preferably 20.0 mm or less, more preferably 15.0 mm or less, and even more preferably 12.0 mm or less. Within the above ranges, the effects tend to be favorably obtained.

[0151] Although the mechanism by which adjusting the thickness T of the tire components to fall within a predetermined range provides a better effect is unclear, keeping the thickness of the tire components within the predetermined range ensures the rubber strength, wear resistance, and crack growth resistance. Therefore, it is believed that the overall performance of wear resistance and crack growth resistance is improved.

[0152] When the tire component is a tread, the tread has a predetermined thickness Tt (mm). The tread is the part of the finished tire that is considered to come into contact with the road surface. The tread may be a single-layer tread, a two-layer tread, or a three- or more-layer tread. The tread thickness (Tt) refers to the total thickness of the single-layer tread, two-layer tread, or three- or more-layer tread. In this specification, the tread thickness Tt particularly refers to the thickness of the tread on the tire equatorial plane in the tire radial cross section, and is the linear distance from the tread surface to the radially inner surface of the tread in the tire radial cross section. For example, in the case of a single-layer tread, it is the linear distance from the tread surface of the single-layer tread itself (first rubber layer) to the radially inner surface of the tread. In the case of a two-layer tread consisting of a cap tread (first rubber layer) as the outermost layer and a base tread (second rubber layer) adjacent to the cap tread on the radially inner side, it is the linear distance from the cap tread surface to the radially inner surface of the base tread. In the case of a three-layer or more layer tread consisting of a cap tread (first rubber layer) as the outermost layer, a second rubber layer adjacent to the cap tread on the radially inner side, and another rubber layer disposed on the radially inner side of the second rubber layer, it is the linear distance from the cap tread surface to the radially inner surface of the other rubber layer.

[0153] The thickness of the cap tread in the tread refers to the thickness of the cap tread on the tire equatorial plane in the tire radial cross section, and is the straight-line distance from the tread surface (surface of the cap tread) to the radially inner surface of the cap tread in the tire radial cross section. The thickness of the second rubber layer adjacent to the radially inner side of the cap tread refers to the thickness of the second rubber layer on the tire equatorial plane in the tire radial cross section, and is the straight-line distance from the radially outer surface of the second rubber layer to the radially inner surface of the second rubber layer in the tire radial cross section.

[0154] In this specification, dimensions such as thickness are measured under normal conditions. "Normal conditions" refers to a tire mounted on a normal rim, inflated to the normal internal pressure, and unloaded. Here, "normal rim" refers to a rim specified for each tire by the standard system, including the standard on which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Manufacturers Association), this refers to the standard rim for the applicable size listed in the "JATMA Year Book." In the case of ETRTO (The European Tire and Rim Technical Organization), this refers to the "Measuring Rim" listed in the "Standards Manual." In the case of TRA (The Tire and Rim Association, Inc.), this refers to the "Design Rim" listed in the "Year Book." JATMA, ETRTO, and TRA are referenced in this order, and if an applicable size is available at the time of reference, these standards are followed. For tires not specified by a standard, this refers to a rim that can be mounted on a rim and can maintain internal pressure, i.e., the rim with the smallest rim diameter and the next narrowest rim width, among rims that can prevent air leakage between the rim and tire. Additionally, "normal internal pressure" refers to the air pressure specified for each tire by each standard in the standard system, including the standard on which the tire is based. For JATMA, it refers to "maximum air pressure," for ETRTO, it refers to "INFLATION PRESSURE," and for TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." Refer to JATMA, ETRTO, and TRA in that order, and follow the standard if there is an applicable size at the time of reference. In the case of a tire not specified in the standard, it refers to the normal internal pressure (250 KPa or more) of another tire size (specified in the standard) that is specified using the normal rim as the standard rim. Note that if multiple normal internal pressures of 250 KPa or more are listed, it refers to the smallest value among them.

[0155] In the tire, the tread thickness Tt (mm) is preferably 1.0 mm or more, more preferably 3.0 mm or more, even more preferably 5.0 mm or more, particularly preferably 6.5 mm or more, and is preferably 20.0 mm or less, more preferably 15.0 mm or less, even more preferably 12.0 mm or less, particularly preferably 11.0 mm or less. Within the above ranges, the effects tend to be favorably obtained.

[0156] In the tire, the thickness (mm) of the cap tread is preferably 0.5 mm or more, more preferably 1.0 mm or more, even more preferably 3.0 mm or more, particularly preferably 5.0 mm or more, and is preferably 14.0 mm or less, more preferably 10.5 mm or less, even more preferably 7.0 mm or less. Within the above ranges, the effect tends to be preferably obtained.

[0157] In the tire, the second rubber layer (mm) is preferably 2.0 mm or more, more preferably 2.3 mm or more, and even more preferably 2.6 mm or more, and is preferably 6.0 mm or less, more preferably 4.5 mm or less, and even more preferably 3.0 mm or less. Within the above ranges, the effect tends to be preferably obtained.

[0158] In the tire, it is desirable that the ratio K (content of divalent or higher carboxylic acid compounds / content of sulfur) of the content (parts by mass) of the divalent or higher carboxylic acid compounds contained in the rubber composition for tires constituting the tire components and the thickness T (mm) of the tire components satisfy the following formula: K×T≧3.0 The right side of the above formula is preferably 5.0, more preferably 10.0, and even more preferably 15.0. There is no particular upper limit for K×T, but it is preferably 200.0 or less, more preferably 60.0 or less, and even more preferably 40.0 or less. Within the above range, better effects tend to be obtained.

[0159] Although the mechanism by which a greater effect is obtained by adjusting K×T to a predetermined value is unclear, it is believed that by setting the thickness of the tire components within a predetermined range, the wear resistance and crack growth resistance are improved due to the wear resistance effect of the tire component thickness and the effect of favorable formation of the above-mentioned hydrogen bonds. Therefore, it is believed that the overall performance of wear resistance and crack growth resistance is improved.

[0160] In the tire, it is desirable that the ratio K (content of divalent or higher carboxylic acid compounds / content of sulfur) of the content (parts by mass) of the divalent or higher carboxylic acid compounds contained in the rubber composition for tread constituting the tread and the thickness Tt (mm) of the tread satisfy the following formula: K×Tt≧4.5 The right side of the above formula is preferably 7.5, more preferably 8.5, even more preferably 10.0, and particularly preferably 15.0. There is no particular upper limit for K×Tt, but it is preferably 200.0 or less, more preferably 60.0 or less, and even more preferably 40.0 or less. Within the above range, better effects tend to be obtained.

[0161] The tire having the above tread desirably has a predetermined tread groove depth. The tread groove depth is the radial distance of the tire to the deepest point of grooves extending in any direction that define various tread patterns defined on the tread surface of the tire after vulcanization. In this specification, the groove depth D of the tread means the distance from the extended surface of the circumferential groove that forms the contact patch on the outermost surface of the tread to the deepest groove bottom, measured along the normal to the extended surface of the circumferential groove, and refers to the maximum distance among the groove depths of the circumferential grooves provided.

[0162] In the above tire, the groove depth D (mm) of the circumferential groove formed in the tread is preferably 0.8 mm or more, more preferably 2.5 mm or more, still more preferably 4.5 mm or more, particularly preferably 6.0 mm or more, and is preferably 18.0 mm or less, more preferably 13.0 mm or less, still more preferably 8.0 mm or less. When within the above range, the effect tends to be obtained more favorably.

[0163] In the case of the groove depth D within a predetermined range, the mechanism by which a more favorable effect is obtained is not clear, but by adjusting to the groove depth within a predetermined range, rubber strength can be ensured, and abrasion resistance and crack growth resistance can be ensured. Therefore, it is considered that the overall performance of abrasion resistance and crack growth resistance is improved.

[0164] In a tire having a tread, the ratio K (content (parts by mass) of dicarboxylic acid compound / content (parts by mass) of sulfur) of the content (parts by mass) of the dicarboxylic acid compound having a valence of 2 or more and the content (parts by mass) of sulfur contained in the tread rubber composition constituting the tread (using the above rubber composition for tire as the tread rubber composition), and the groove depth D (mm) of the circumferential groove formed in the tread preferably satisfy the following formula. K×D≧3.0 The right side of the above formula is preferably 3.5, more preferably 4.0. The upper limit of K×D is not particularly limited, but is preferably 180.0 or less, more preferably 50.0 or less, still more preferably 30.0 or less. When within the above range, the effect tends to be obtained more favorably.

[0165] The mechanism by which a more favorable effect is obtained by adjusting to a predetermined K×D is not clear, but the effect of rubber strength adjusted to the groove depth within a predetermined range and the effect of favorably forming the above hydrogen bond are exhibited. Therefore, it is considered that the overall performance of abrasion resistance and crack growth resistance is improved.

[0166] In the above tire, the groove depth D (mm) of the circumferential groove formed in the tread and the thickness Tt (mm) of the tread usually satisfy the relationship D<Tt.

[0167] An example of the tire will be described below with reference to the drawings, but the present invention is not limited to this embodiment.

[0168] 1, the up-down direction is the radial direction of the tire 2, the left-right direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. The tire 2 is symmetrical. The tread 4 has a single-layer structure.

[0169] Although FIG. 1 shows an example of a single-layer structure tread 4, a two-layer structure tread consisting of a cap tread and a base tread, or a tread having a structure of three or more layers may also be used.

[0170] 1, the tread 4 is made of the above-mentioned rubber composition for a tire. That is, the tread 4 is made of the rubber composition for a tread, which includes a rubber component containing an epoxidized diene rubber, a divalent or higher carboxylic acid compound, and sulfur, in which the amount of sulfur per 100 parts by mass of the rubber component is 1.0 part by mass or more, and the ratio K of the amount of the divalent or higher carboxylic acid compound to the amount of sulfur is 0.10 or more and 10.00 or less.

[0171] In the tire 2, each sidewall 6 extends substantially radially inward from an end of the tread 4. A radially outer portion of each sidewall 6 is joined to the tread 4. A radially inner portion of each sidewall 6 is joined to a clinch 10. The sidewall 6 can prevent damage to the carcass 14.

[0172] 1 is located between the tread 4 and the sidewall 6. The wing 8 is joined to each of the tread 4 and the sidewall 6.

[0173] Each clinch 10 is located approximately radially inward of the sidewall 6 and has at least one or more portions that come into contact with the rim.

[0174] The carcass 14 includes a carcass ply 36. In the tire 2, the carcass 14 is made up of one carcass ply 36, but may be made up of two or more carcass plies.

[0175] In the tire 2, the carcass ply 36 is laid between the bead cores 32 on both sides and extends along the tread 4 and the sidewall 6. The carcass ply 36 is folded back from the inside to the outside in the axial direction around each bead core 32. This folding back forms a main portion 36a and a pair of folded-back portions 36b in the carcass ply 36. That is, the carcass ply 36 includes the main portion 36a and the pair of folded-back portions 36b.

[0176] Each bead core 32 includes a bead apex 34 extending radially outward from the bead core 32. The bead core 32 is preferably ring-shaped and includes a wound, non-stretchable wire. The bead apex 34 tapers radially outward.

[0177] Although not shown, the carcass ply 36 preferably comprises a large number of parallel cords and a topping rubber. The absolute value of the angle that each cord forms with respect to the equatorial plane CL is preferably 75° to 90°. In other words, the carcass 14 preferably has a radial structure.

[0178] The belt layer 16 in FIG. 1 is located radially inward of the tread 4. The belt layer 16 is laminated with the carcass 14. The belt layer 16 reinforces the carcass 14. In the tire 2 in FIG. 1, the belt layer 16 is made up of an inner layer 38 and an outer layer 40. As is clear from FIG. 1, it is desirable that the width of the inner layer 38 is slightly larger than the width of the outer layer 40 in the axial direction. In this tire 2, the axial width of the belt layer 16 is preferably 0.6 times or more and 0.9 times or less the cross-sectional width of the tire 2.

[0179] Each of the inner layer 38 and the outer layer 40 preferably comprises a number of parallel-arranged single steel cords (steel monofilaments) and a topping rubber (coating rubber). In other words, the belt layer 16 includes a number of parallel-arranged steel monofilaments.

[0180] 1 is located radially outside the belt layer 16. In the axial direction, the band 18 has a width equal to the width of the belt layer 16. The band 18 may also have a width greater than the width of the belt layer 16.

[0181] Although not shown, the band 18 is preferably made of a cord and a topping rubber. The cord is wound spirally. This band 18 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is preferably 5° or less, and more preferably 2° or less. The cord restrains the belt layer 16, thereby suppressing lifting of the belt layer 16.

[0182] 1 constitute a reinforcing layer. The reinforcing layer may be constituted by the belt layer 16 alone.

[0183] FIG. 2 is an enlarged view of the vicinity of the tread 4 in FIG. The tire in FIG. 2 is a tire 2 having a groove 26 on the tire equatorial plane (CL). In this case, the tread thickness (Tt) is the thickness measured at the center in the tire width direction of the land portion closest to the groove 26 on the tire equatorial plane in the radial cross section of the tire, and is the thickness measured in the normal direction to the surface of the tread 4, and specifically refers to the straight-line distance in the normal direction from the outer surface of the tread 4 in the tire radial direction to the interface with the inner surface of the tread 4 in the tire radial direction.

[0184] The inner liner 20 is located inside the carcass 14. The inner liner 20 is bonded to the inner surface of the carcass 14. A typical base rubber of the inner liner 20 is butyl rubber or halogenated butyl rubber. The inner liner 20 maintains the internal pressure of the tire 2.

[0185] Each chafer 22 is located near a bead 12. In this embodiment, the chafer 22 is preferably made of a cloth with rubber impregnated into the cloth. The chafer 22 may be integral with the clinch 10.

[0186] In this tire 2, the tread 4 has main grooves 42 as the grooves 26. As shown in FIG. 1 , a plurality of main grooves 42, specifically three main grooves 42, are formed in the tread 4. These main grooves 42 are spaced apart in the axial direction. The three main grooves 42 formed in the tread 4 form four ribs 44 extending in the circumferential direction. In other words, the spaces between the ribs 44 constitute the main grooves 42.

[0187] Each main groove 42 extends in the circumferential direction. The main grooves 42 are continuous and uninterrupted in the circumferential direction. The main grooves 42 facilitate the drainage of water present between the road surface and the tire 2, for example, in rainy weather. This allows the tire 2 to maintain sufficient contact with the road surface even when the road surface is wet.

[0188] 2D shows the groove depth of the main groove 42 formed in the tread 4 in the circumferential direction.

[0189] In the tire 2, it is desirable that the ratio K of the content of divalent or higher carboxylic acid compounds to the content of sulfur contained in the tread rubber composition constituting the tread 4, the thickness Tt of the tread 4, and the groove depth D of the circumferential grooves formed in the tread 4 are within the above-mentioned ranges, and it is also desirable that K×T and K×D are within the above-mentioned ranges. [Example]

[0190] Below, examples (embodiments) that are considered preferable for implementation will be shown, but the scope of the present invention is not limited to the examples.

[0191] The various chemicals used in tire manufacturing are summarized below. If necessary, the chemicals may be refined according to standard methods. NR:TSR20 ENR25: ENR manufactured by Kempuran Guthrie (epoxidation ratio: 25 mol%) Carbon black: Show Black N330 (N2SA78m) manufactured by Cabot Japan Co., Ltd. 2 / g) Silica: Ultrasil VN3 (Evonik, N2SA175m 2 / g) Malonic acid: Tokyo Chemical Industry Co., Ltd. Dodecanedioic acid: manufactured by Tokyo Chemical Industry Co., Ltd. Silane coupling agent: Si69 (Evonik, bis(3-triethoxysilylpropyl)tetrasulfide) Oil: Idemitsu Kosan Diana Process Oil AH-24 (aromatic process oil) Wax: Ozoace 0355 (manufactured by Nippon Seiro Co., Ltd.) Antioxidant: Nocrac 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: NOF Corporation Zinc oxide: Three types of zinc oxide (manufactured by Hakusui Tech Co., Ltd.) Sulfur: Powdered sulfur (Tsurumi Chemical Industry Co., Ltd.) Vulcanization accelerator: Noccela NS (N-tert-butyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0192] <Preparation of test tires> According to the formulation shown in Tables 1 and 2, materials other than sulfur and vulcanization accelerator are kneaded for 5 minutes at 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded mixture. Sulfur and a vulcanization accelerator are added to the kneaded mixture, and the mixture is kneaded for 5 minutes at 80°C using an open roll to obtain an uncrosslinked rubber composition. The uncrosslinked rubber composition is molded into the shape of a single-layer tread, and is laminated together with other tire components on a tire building machine to form an unvulcanized tire. The unvulcanized tire is then vulcanized at 170°C for 10 minutes to produce a test tire (size 205 / 55R16, passenger car tire).

[0193] Tables 1 and 2 show the results of calculations based on the following evaluation methods, assuming test tires obtained from compositions whose formulations and specifications were changed according to Tables 1 and 2. The reference comparative example is as follows. Table 1: Comparative Examples 1-4 Table 2: Comparative Example 2-1

[0194] <Wear resistance> The test tires are mounted on a domestic 2-D vehicle, and the tire tread depth is measured after driving a specified distance. The distance traveled when the tire tread depth decreases by 1 mm is calculated and expressed as an index, with the reference comparative example being set at 100. The higher the index, the better the wear resistance.

[0195] <Crack growth resistance> The test tire is mounted on a vehicle and driven a specified distance. After the run, the condition of the tread cracks (depth, number, length) is evaluated and expressed as an index, with the reference comparative example being set at 100. The higher the index, the better the crack growth resistance.

[0196] <Overall performance> The overall performance of abrasion resistance and crack growth resistance is evaluated by the sum of the two indices obtained from the above evaluations of abrasion resistance and crack growth resistance. The larger the value, the better the overall performance.

[0197] [Table 1]

[0198] [Table 2]

[0199] The present invention (1) comprises a rubber component containing an epoxidized diene rubber, a divalent or higher carboxylic acid compound, and sulfur, The amount of sulfur per 100 parts by mass of the rubber component is 1.0 part by mass or more, The rubber composition for tires has a ratio K (content of divalent or higher carboxylic acid compound / content of sulfur) of the content (parts by mass) of the divalent or higher carboxylic acid compound to the content (parts by mass) of the sulfur, which is 0.10 or more and 10.00 or less.

[0200] The present invention (2) is the rubber composition for a tire according to the present invention (1), wherein the K is 0.80 or more and 8.00 or less.

[0201] The present invention (3) is the rubber composition for a tire according to the present invention (1), wherein the K is 2.00 or more and 6.00 or less.

[0202] The present invention (4) is a rubber composition for tires, which is any combination with any of the present inventions (1) to (3), in which the ratio of the content of the divalent or higher carboxylic acid compound to the content of the epoxidized diene rubber is 0.015 or more and 0.080 or less.

[0203] The present invention (5) is a tire having a tire component made of a rubber composition for a tire in any combination with any of the present inventions (1) to (4).

[0204] The present invention (6) is the tire according to the present invention (5), in which a ratio K (content of divalent or higher carboxylic acid compounds / content of sulfur) of the content (parts by mass) of the divalent or higher carboxylic acid compounds contained in the rubber composition for tires constituting the tire member to the content (parts by mass) of sulfur, and a thickness T (mm) of the tire member satisfy the following formula: K×T≧3.0

[0205] The present invention (7) is the tire according to the present invention (6), which satisfies K×T≧5.0.

[0206] The present invention (8) is a tire in any combination with any of the present inventions (5) to (7), in which the thickness T (mm) of the tire member is 1.0 mm or more.

[0207] The present invention (9) is a tire in any combination with any of the present inventions (5) to (7), in which the thickness T (mm) of the tire member is 5.0 mm or more.

[0208] The present invention (10) is a tire in any combination with any of the present inventions (5) to (9), in which the tire member is a tire surface layer member.

[0209] The present invention (11) is the tire according to the present invention (10), wherein the tire surface layer member is at least one selected from the group consisting of a tread, a sidewall, a wing, and a clinch.

[0210] The present invention (12) has a tread, The tire is any combination with any of the present inventions (5) to (11), wherein the groove depth D of the circumferential grooves formed in the tread is 4.5 mm or more.

[0211] The present invention (13) has a tread constituted by the above-mentioned tire rubber composition, The tire is any combination with any of the present inventions (5) to (12), in which the ratio K (content of divalent or higher carboxylic acid compounds / content of sulfur) of the content (parts by mass) of the divalent or higher carboxylic acid compounds contained in the rubber composition for tires to the content (parts by mass) of sulfur, and the groove depth D (mm) of the circumferential grooves formed in the tread, satisfy the following formula: K×D≧3.5 [Explanation of symbols]

[0212] 2 tires 4 Tread 6 Sidewall 8 Wing 10 Clinch 12 beads 14 Carcass 16 Belt Layer 18 bands 20 Inner liner 22 Chafer 24 Tread surface 26 Groove 32 bead core 34 Bead Apex 36 Carcass ply 36a Main part 36b Folded part 38 Inner layer 40 outer layer 42 Main groove 44 Ribs CL Tire equatorial plane Tt tread thickness D Circumferential depth of the main groove formed on the tread

Claims

1. The rubber composition contains a rubber component containing an epoxidized diene rubber, a divalent or higher carboxylic acid compound, and sulfur, the amount of sulfur per 100 parts by mass of the rubber component is 1.0 part by mass or more, a ratio K (content of divalent or higher carboxylic acid compound / content of sulfur) of the content (parts by mass) of the divalent or higher carboxylic acid compound to the content (parts by mass) of the sulfur, which is 0.10 or more and 10.00 or less.

2. The rubber composition for a tire according to claim 1, wherein the K is 0.80 or more and 8.00 or less.

3. The rubber composition for a tire according to claim 1, wherein the K is 2.00 or more and 6.00 or less.

4. 2. The rubber composition for tires according to claim 1, wherein a ratio of the content of the divalent or higher carboxylic acid compound to the content of the epoxidized diene rubber is 0.015 or more and 0.080 or less.

5. A tire having tire components formed from the rubber composition for tires according to claim 1.

6. 6. The tire according to claim 5, wherein a ratio K (content of divalent or higher carboxylic acid compounds / content of sulfur) of a content (parts by mass) of divalent or higher carboxylic acid compounds contained in the rubber composition for a tire constituting the tire member to a content (parts by mass) of sulfur, and a thickness T (mm) of the tire member, satisfy the following formula: K×T≧3.0

7. The tire according to claim 6, wherein K x T ≥ 5.0 is satisfied.

8. The tire according to claim 5, wherein the tire member has a thickness T (mm) of 1.0 mm or more.

9. The tire according to claim 5, wherein the tire member has a thickness T (mm) of 5.0 mm or more.

10. The tire according to claim 5, wherein the tire component is a tire surface layer component.

11. The tire according to claim 10, wherein the tire surface layer member is at least one selected from the group consisting of a tread, a sidewall, a wing, and a clinch.

12. having a tread; The tire according to claim 5, wherein a groove depth D of the circumferential groove formed in the tread is 4.5 mm or more.

13. a tread formed of the tire rubber composition, 6. The tire according to claim 5, wherein a ratio K (content of divalent or higher carboxylic acid compounds / content of sulfur) of a content (parts by mass) of divalent or higher carboxylic acid compounds contained in the rubber composition for tires to a content (parts by mass) of sulfur, and a groove depth D (mm) of circumferential grooves formed in the tread, satisfy the following formula: K×D≧3.5

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