tire

Abstract

To provide a tire which is excellent in crack resistance.SOLUTION: A rubber composition for a tread constituting a tread 4, and a rubber composition for a side wall constituting at least one of a pair of side walls 6 are composed of different rubber compositions. The surfaces of the side walls 6 are coated with an acrylic resin, and a difference (AEt-AEs) between an acetone extraction amount AEt (mass%) of the rubber composition for the tread and an acetone extraction amount AEs (mass%) of the rubber composition for the side wall is 1.0 mass% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tire. [Background technology]

[0002] The tread and sidewall of a tire are subjected to different inputs during use, such as deformation during rolling and standing, and the presence or absence of wear, so different rubber compositions are generally used to meet these requirements. Tire crack resistance is one example of this, and one possible approach is to increase the amount of antioxidant contained in the sidewall. Other methods proposed to improve crack resistance include increasing the decorativeness of the sidewall (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-17557 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the unvulcanized rubber of the tread and sidewall are bonded together and vulcanized, the antioxidant becomes uniform between the adjacent tread and sidewall due to thermal diffusion during vulcanization, making it difficult to achieve sufficient crack resistance. Furthermore, sidewalls and other side components flex significantly during tire operation, which can lead to problems such as cracks. Possible causes include scratches caused by insufficient fracture strength and the speed at which cracks grow, both of which are contrary to the goal of improving fuel economy.

[0005] An object of the present invention is to solve the above problems and to provide a tire with excellent crack resistance. [Means for solving the problem]

[0006] The present invention provides a tire having a tread and a pair of sidewalls, a tread rubber composition constituting the tread and a sidewall rubber composition constituting at least one of a pair of sidewalls are composed of different rubber compositions, The surface of the sidewall is coated with an acrylic resin, The tire has a difference (AEt-AEs) between the acetone extractable amount AEt (mass%) of the rubber composition for the tread and the acetone extractable amount AEs (mass%) of the rubber composition for the sidewall, of 1.0 mass% or more. [Effects of the Invention]

[0007] The present invention provides a tire having a tread and a pair of sidewalls, wherein a tread rubber composition constituting the tread and a sidewall rubber composition constituting at least one of the pair of sidewalls are made of different rubber compositions, the surface of the sidewall is coated with an acrylic resin, and the difference (AEt-AEs) between the acetone extractable amount AEt (mass%) of the tread rubber composition and the acetone extractable amount AEs (mass%) of the sidewall rubber composition is 1.0 mass% or more, thereby improving crack resistance. [Brief explanation of the drawings]

[0008] [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

[0009] The tire is a tire having a tread and a pair of sidewalls, wherein a rubber composition for a tread constituting the tread and a rubber composition for a sidewall constituting at least one of the pair of sidewalls are made of different rubber compositions, the surface of the sidewall is coated with an acrylic resin, and the difference (AEt - AEs) between the acetone extractable amount AEt (mass%) of the rubber composition for the tread and the acetone extractable amount AEs (mass%) of the rubber composition for the sidewall is 1.0 mass% or more.

[0010] The mechanism by which the above-mentioned tire provides the above-mentioned effects is not entirely clear, but is presumed to be as follows. In the case of silicone resin-based tire waxes, the antioxidant is trapped by the surfactants contained in the silicone resin to disperse it. However, this does not occur in the tire described above, because the sidewall is coated with an acrylic resin, and the antioxidant is retained within the system while protecting the surface. This is thought to slow the rate at which the antioxidant is lost in the sidewall. Furthermore, compared to silicone resins, acrylic resins have higher adhesion to tires and are less likely to cause peeling of the coating, which is thought to make it possible to impart ozone resistance to the entire tire surface. Furthermore, by increasing the acetone extractables (AEt) in the tread (AEt) to a value greater than the acetone extractables (AEs) in the sidewall (AEs), a measure of the amount of plasticizer in a rubber composition, a concentration gradient is created in the amount of plasticizer, facilitating its slow migration from the tread to the sidewall over time after vulcanization. This facilitates the migration of antioxidants from the tread to the sidewall along with the migrating acetone extractables. This allows the antioxidant to be gradually supplied from the tread to the sidewall while slowing the rate at which antioxidant is consumed in the sidewall, thereby improving the crack resistance of the sidewall. It is presumed that the crack resistance of the tire can be improved due to the above mechanism.

[0011] Thus, the tire described above solves the problem (objective) of improving crack resistance by providing a tire having a sidewall surface coated with an acrylic resin with a configuration in which "AEt-AEs is 1.0% by mass or more." In other words, the parameter "AEt-AEs is 1.0% by mass or more" does not define the problem (objective); the object of the present application is to improve crack resistance, and a configuration that satisfies this parameter is used as a means to achieve this.

[0012] The tire includes a tread and a pair of sidewalls. The tread is made of a rubber composition for a tread. The pair of sidewalls is made of a rubber composition for sidewalls, and at least one of the pair of sidewalls is coated with an acrylic resin. The rubber composition for the tread and the rubber composition for the sidewall that constitutes the sidewall coated with the acrylic resin are made of different rubber compositions (rubber compositions with different blendings).

[0013] (drugs) First, chemicals that can be used in common for the tread rubber composition that forms the tread and the sidewall rubber composition that forms a pair of sidewalls, at least one of which is coated with an acrylic resin, will be described below.

[0014] The rubber composition for tread and the composition for sidewall contain 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).

[0015] 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.

[0016] 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).

[0017] 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.

[0018] 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.

[0019] Examples of the rubber component include diene rubber. Examples of diene rubber 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 the rubber component also 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. These may be used alone or in combination of two or more.

[0020] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. NRs such as SIR20, RSS#3, and TSR20 are commonly used in the rubber industry. IRs are not particularly limited, and examples of IRs such as IR2200 are commonly used in the rubber industry. Modified NRs include deproteinized natural rubber (DPNR) and high-purity natural rubber. Modified NRs include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Modified IRs include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more.

[0021] The BR 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. In this specification, the cis content is defined as 13 It can be measured by C-NMR.

[0022] 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)).

[0023] 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.

[0024] As the BR, for example, products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used.

[0025] The SBR is not particularly limited, and examples thereof include emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. These may be used alone or in combination of two or more.

[0026] 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, the effect tends to be more favorable. In this specification, the amount of styrene is 1 It can be measured by H-NMR measurement.

[0027] 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)).

[0028] The vinyl 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 content is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and even more preferably 30% by mass or less. When the vinyl content is within the above range, better effects tend to be obtained. In this specification, the vinyl content (1,2-bonded butadiene unit content) is defined as: 1 It can be measured by H-NMR.

[0029] 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])}.

[0030] 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.

[0031] 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.

[0032] The raw materials (monomers) of synthetic rubbers such as SBR and BR may be derived from petroleum 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 thereof include recycled butadiene and recycled aromatic vinyl. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl include, but are not particularly limited to, styrene. Among these, it is preferable to use recycled butadiene (recycled butadiene) and / or recycled styrene (recycled styrene) as raw materials.

[0033] 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.

[0034] Furthermore, the raw materials (monomers) of synthetic rubbers such as SBR and BR may be derived from biomass. Examples of biomass-derived monomers (biomass monomers) include, but are not limited to, biomass-derived butadiene and biomass-derived aromatic vinyl. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl include, but are not limited to, styrene. Furthermore, methods for producing biomass monomers are also not limited, including, for example, biological and / or chemical and / or physical conversion of animals and plants. A typical example of biological conversion is fermentation using microorganisms, while examples of chemical and / or physical conversion include catalytic, high-temperature, high-pressure, electromagnetic, critical fluid, and combinations thereof. Biomass sources for these monomers include sugar, wood, plant residues after useful components have been extracted, plant-derived ethanol, and biomass naphtha.

[0035] 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.

[0036] Whether the raw material for a polymer is biomass-derived can be determined by the pMC (percent modern carbon) measured in accordance with ASTM D6866-10.

[0037] pMC is the modern standard reference 14 of sample against C concentration 14 This is the ratio of the carbon concentration, and this value is used as an index showing the biomass ratio of the compound (rubber). The significance of this value is explained below.

[0038] 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 elements.

[0039] 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, by using the difference between these values, it is possible to calculate the ratio (biomass ratio) of compounds derived from natural resources (compounds derived from biomass resources) in a certain compound (rubber).

[0040] 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.

[0041] Therefore, if rubber is made from 100% biomass (natural) derived materials, it will show a value of approximately 110 pMC, although there may be regional differences (currently, under normal conditions, it is often not 100). On the other hand, for chemical substances derived from petroleum and other fossil fuels, 14 When the carbon concentration is measured, it will be approximately 0 pMC (for example, 0.3 pMC), which corresponds to the biomass ratio of 0% mentioned above.

[0042] 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.

[0043] The rubber composition for the tread and the rubber composition for the sidewall preferably contain a filler.

[0044] The filler is not particularly limited, and materials known in the rubber field can be used, such as 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-derived fillers (carbon-containing fillers) such as carbon black and silica are preferred. The fillers may be used alone or in combination of two or more. Among these, from the viewpoint of obtaining a greater effect, the rubber composition for a tread preferably contains at least one of silica and carbon black, and more preferably contains silica and carbon black. In addition, from the viewpoint of obtaining a greater effect, the rubber composition for a sidewall preferably contains at least one of silica and carbon black, and more preferably contains at least carbon black.

[0045] The silica that can be used in the tread rubber composition and the sidewall composition 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 the 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 biomass materials such as rice husk), or silica recycled from silica-containing products. 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.

[0046] Silica made from biomass materials (biomass material-derived silica) can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then using the silicate to react with sulfuric acid, as in conventional wet-process silica production, to produce a silicon dioxide precipitate, which is then filtered, washed with water, dried, and pulverized.

[0047] 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.

[0048] 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).

[0049] Amorphous silica extracted from rice husks may be commercially available from Wilmar Co., Ltd., etc.

[0050] 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. In this specification, the N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0051] The carbon black that can be used in the tread rubber composition and the sidewall composition 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 pyrolyzing waste tires. Furthermore, carbon black may be produced by combustion, such as in a furnace process, by hydrothermal carbonization (HTC), or by pyrolysis 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. Carbon black may be used alone or in combination.

[0052] In addition to conventional carbon black made from mineral oil or the like, carbon black made from biomass materials such as lignin may also be used.

[0053] The nitrogen adsorption specific surface area (N2SA) of the above carbon black is 20m 2 / g or more is preferable, and 30m 2 / g or more is more preferable, and 40m 2 / g or more is more preferable. 2 / g or less is preferable, and 150m 2 / g or less is more preferable, and 130m 2 / g or less is more preferable, and 120m 2 Within the above range, the effect tends to be better. In this specification, the nitrogen adsorption specific surface area of ​​carbon black is determined in accordance with JIS K6217-2:2001.

[0054] Examples of the hardly dispersible filler include microfibrillated plant fibers, short fiber cellulose, gel compounds, etc. Among these, microfibrillated plant fibers are preferred.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] When the rubber composition for a tread or the rubber composition for a sidewall contains silica, it is preferable that the rubber composition 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.

[0059] The rubber composition for the tread and the rubber composition for the sidewall preferably contain a plasticizer. In this specification, the term "plasticizer" refers to a material that imparts plasticity to rubber components, and includes both plasticizers that are liquid (liquid state) at room temperature (25°C) and plasticizers that are solid at room temperature (25°C). Examples of plasticizers include resin components, oils, liquid polymers, and ester-based plasticizers. These plasticizers may be derived from petroleum, biomass, or naphtha recycled from rubber or 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.

[0060] Specific examples of the plasticizer include oils, liquid polymers, resins, etc. These may be used alone or in combination of two or more.

[0061] Examples of oils include process oil, vegetable oil, and animal oil. Examples of process oils include paraffinic process oil (mineral oil), naphthenic process oil, and aromatic process oil. Specific examples of process oils 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, process oils with a low content of polycyclic aromatic compounds (PCA) can also be used. Examples of low-PCA process oils include MES, TDAE, and heavy naphthenic oil. Furthermore, from the perspective of life cycle assessment, refined waste oil from rubber mixers and engines, or waste cooking oil from restaurants, may also be used.

[0062] 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 room temperature (25°C). These vegetable oils may be used alone or in combination of two or more.

[0063] 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 ester-bonded to 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. Furthermore, the acylglycerol may be liquid or solid at room temperature (25°C).

[0064] 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 room temperature (25°C) for 24 hours, and after removing the rubber composition, the 1When 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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).

[0070] As the liquid diene polymer, for example, products available from Sartomer Co., Ltd., Kuraray Co., Ltd., etc. can be used.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] The coumarone resin is a resin containing coumarone as a main monomer component constituting the skeleton (main chain) of the resin.

[0076] The indene resin is a resin containing indene as a main monomer component constituting the skeleton (main chain) of the resin.

[0077] 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.

[0078] Examples of the rosin resin include rosin-based resins such as natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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]

[0085] 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.

[0086] 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).

[0087] In the farnesene-vinyl monomer copolymer, the copolymerization ratio by mass of farnesene and vinyl monomer (farnesene / vinyl monomer) is preferably 40 / 60 to 90 / 10.

[0088] 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.

[0089] The farnesene polymer may be in a liquid state or a solid state at room temperature (25° C.), with liquid farnesene polymers being preferred.

[0090] The rubber composition for treads and the composition for sidewalls preferably contain an antioxidant from the viewpoints of crack resistance, ozone resistance, and the like.

[0091] 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.

[0092] The rubber composition for treads and the rubber composition for sidewalls preferably contain stearic acid. As the stearic acid, conventionally known ones can be used, for example, products available from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc.

[0093] The rubber composition for treads and the rubber composition for sidewalls preferably contain zinc oxide. 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.

[0094] The rubber composition for tread and the composition for sidewall may contain wax. The wax is not particularly limited, and any wax commonly used in the tire industry can be suitably used. Examples include petroleum-based waxes, mineral-based waxes, synthetic waxes, and plant-derived waxes. Of these, petroleum-based waxes and plant-derived waxes are preferred, and petroleum-based waxes are more preferred. Examples of plant-derived waxes include rice wax, carnauba wax, and candelilla wax. Examples of petroleum-based 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., and Paramelt Co., Ltd. These waxes may be used alone or in combination of two or more.

[0095] The rubber composition for treads and the composition for sidewalls preferably contain sulfur as a cross-linking agent, in order to form appropriate cross-linked chains in polymer chains and impart good performance.

[0096] 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.

[0097] The rubber composition for a tread and the rubber composition for a sidewall preferably contain a vulcanization accelerator. 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.

[0098] In addition to the above components, the rubber composition for treads and the composition for sidewalls may contain compounding agents generally used in the tire industry, such as materials such as mold release agents, as appropriate.

[0099] 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. The compound of the present invention can be obtained from carbon dioxide by directly converting carbon dioxide or by converting methane obtained through a methanation process in which methane is synthesized from carbon dioxide.

[0100] [Tread (rubber composition for tread)] In order to obtain a greater effect, the rubber composition for a tread constituting the above-mentioned tread preferably contains at least one rubber component selected from the group consisting of an isoprene-based rubber, BR, and SBR, and may contain three rubber components selected from the group consisting of an isoprene-based rubber, BR, and SBR.

[0101] The rubber composition for a tread may or may not contain an isoprene-based rubber (the content of the isoprene-based rubber is 0% by mass in 100% by mass of the rubber component). When the rubber composition for a tread contains an isoprene-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, more preferably 20% by mass or more, and 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 content is within the above ranges, better effects tend to be obtained.

[0102] The rubber composition for a tread may or may not contain BR (the BR content is 0% by mass in 100% by mass of the rubber component). When the rubber composition for a tread contains BR, the BR content in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less. When the content is within the above ranges, better effects tend to be obtained.

[0103] The rubber composition for a tread may or may not contain SBR (the content of SBR in 100% by mass of the rubber component is 0% by mass). When the rubber composition for a tread contains SBR, the content of SBR in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 65% ​​by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less. When the content is within the above ranges, better effects tend to be obtained.

[0104] In the rubber composition for treads, the content of the silica is preferably 20 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 70 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit 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 range, the effect tends to be more favorably obtained.

[0105] In the rubber composition for treads, the content of the carbon black is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less. Within the above ranges, the effect tends to be better obtained.

[0106] The nitrogen adsorption specific surface area (N2SA) of the carbon black contained in the rubber composition for the tread is 50 m 2 / g or more is preferable, and 80m 2 / g or more is more preferable, and 110m 2 / g or more is more preferable. 2 / g or less is preferable, and 150m 2 / g or less is more preferable, and 130m 2 Within the above range, the effect tends to be better.

[0107] In the rubber composition for treads, the content of the filler (total amount of fillers such as carbon black and silica) is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, and even more preferably 75 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 120 parts by mass or less. Within the above range, better effects tend to be obtained.

[0108] In the rubber composition for treads, 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.

[0109] In the rubber composition for treads, the content of the plasticizer (total amount of plasticizer) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 70 parts by mass or less, more preferably 40 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.

[0110] In the rubber composition for treads, the content of the solid plasticizer in a solid state at room temperature (25°C) 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 is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above range, better effects tend to be obtained.

[0111] In the rubber composition for treads, the content of the resin in a solid state at room temperature (25°C) 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 is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above range, better effects tend to be obtained.

[0112] In the rubber composition for treads, the content of the liquid plasticizer that is in a liquid state at room temperature (25°C) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 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 40 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.

[0113] In the rubber composition for treads, the content of the oil is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 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 40 parts by mass or less, and even more preferably 25 parts by mass or less. Within the above range, the effect tends to be more favorably obtained. The oil content includes the amount of oil contained in the oil-extended rubber.

[0114] In the rubber composition for treads, the content of the antioxidant is preferably 0.2 parts by mass or more, more preferably 1.5 parts by mass or more, even more preferably 2.0 parts by mass or more, and particularly preferably 2.5 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 10.0 parts by mass or less, more preferably 7.0 parts by mass or less, and even more preferably 5.0 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0115] In the rubber composition for treads, the content of the 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.

[0116] In the rubber composition for treads, the content of the zinc oxide is preferably 0.5 parts by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 3.0 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.

[0117] In the rubber composition for treads, the content of the wax is preferably 0.5 parts by mass or more, more preferably 2.0 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.

[0118] In the rubber composition for treads, the sulfur content is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, per 100 parts by mass of the rubber component. The sulfur content is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less. Within the above ranges, the effects tend to be more favorably obtained.

[0119] In the rubber composition for treads, 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 2.5 parts by mass or more, and even more preferably 4.0 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.

[0120] [Sidewall (rubber composition for sidewall)] The rubber composition for a sidewall, which constitutes the sidewall coated with the acrylic resin, preferably contains at least one of the isoprene-based rubber, BR, and SBR as a rubber component, and more preferably contains at least an isoprene-based rubber and BR.

[0121] In the rubber composition for sidewalls, the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, and is preferably 80% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 55% by mass or less. Within the above ranges, the effects tend to be more favorable.

[0122] In the rubber composition for sidewalls, the content of the BR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 45% by mass or more, and is preferably 90% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 60% by mass or less. Within the above ranges, the effects tend to be more favorably obtained.

[0123] In the rubber composition for sidewalls, the content of the carbon black is preferably 30 parts by mass or more, more preferably 45 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 100 parts by mass or less, and even more preferably 65 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0124] The nitrogen adsorption specific surface area (N2SA) of the carbon black contained in the rubber composition for sidewalls is 10 m 2 / g or more is preferable, and 30m 2 / g or more is more preferable, and 40m 2 / g or more is more preferable. 2 / g or less is preferable, and 80m 2 / g or less is more preferable, and 60m 2Within the above range, the effect tends to be better.

[0125] In the rubber composition for sidewalls, the content of the filler (total amount of fillers such as carbon black and silica) is preferably 30 parts by mass or more, more preferably 45 parts by mass or more, and even more preferably 53 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 100 parts by mass or less, and even more preferably 65 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0126] In the rubber composition for sidewalls, 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 favorable.

[0127] In the rubber composition for sidewalls, the content of the plasticizer (total amount of plasticizer) is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 12 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 20 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.

[0128] In the rubber composition for sidewalls, the content of the solid plasticizer in a solid state at room temperature (25°C) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 7 parts by mass or less. Within the above range, better effects tend to be obtained.

[0129] In the rubber composition for sidewalls, the content of the resin in a solid state at room temperature (25°C) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 7 parts by mass or less. Within the above range, better effects tend to be obtained.

[0130] In the rubber composition for sidewalls, the content of the liquid plasticizer that is in a liquid state at room temperature (25°C) is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 7 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 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.

[0131] In the rubber composition for sidewalls, the content of the oil is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 7 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 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.

[0132] In the rubber composition for sidewalls, the content of the antioxidant is preferably 0.3 parts by mass or more, more preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 7.0 parts by mass or less, more preferably 5.0 parts by mass or less, even more preferably 4.0 parts by mass or less, and particularly preferably 3.0 parts by mass or less. Within the above ranges, the effect tends to be more favorable.

[0133] Although the mechanism by which greater effects are obtained by adjusting the amount of antioxidant in the sidewall, particularly within the range of 0.3 to 7.0 parts by mass, is unclear, it is believed that incorporating a certain amount or more ensures ozone resistance, and the acrylic resin coating prevents cracking and improves crack resistance. It is also believed that migration of the antioxidant due to precipitation of an excess amount of antioxidant on the tire surface is suppressed, preventing discoloration.

[0134] In the rubber composition for sidewalls, the content of the stearic acid is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2.5 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.

[0135] In the rubber composition for sidewalls, the content of the zinc oxide is preferably 0.5 parts by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 3.0 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.

[0136] In the rubber composition for sidewalls, the content of the wax is preferably 0.5 parts by mass or more, more preferably 1.2 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.

[0137] In the rubber composition for sidewalls, the sulfur content is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, per 100 parts by mass of the rubber component. The sulfur content is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 2.0 parts by mass or less. Within the above ranges, the effects tend to be more favorable.

[0138] In the rubber composition for sidewalls, 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 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.7 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less.

[0139] The above rubber composition for tread and rubber composition for sidewall are 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.

[0140] Regarding kneading conditions, in the base kneading step in which additives other than the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is preferably 50°C or higher, more preferably 190°C or higher, and preferably 200°C or lower, more preferably 190°C or lower. The kneading time is preferably 30 seconds or higher, more preferably 1 minute or higher, and preferably 30 minutes or lower. In the finish kneading step in which the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is preferably 100°C or lower, more preferably 80°C or lower, and preferably room temperature or lower. 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 preferably 120°C or higher, more preferably 140°C or higher, and preferably 200°C or lower, more preferably 180°C or lower.

[0141] In the tire, at least one of the pair of sidewalls has a surface coated with an acrylic resin. It is desirable that the acrylic resin-coated sidewall be coated at least on the surface that comes into contact with the tread or the surface that is disposed near the tread (usually the surface of the sidewall facing outward from the tire). In this case, it is believed that the antioxidant is retained within the sidewall system, the surface is protected, and the rate at which the antioxidant in the sidewall is reduced can be slowed.

[0142] The method for coating the surface of the sidewall with the acrylic resin is not particularly limited as long as it is a method that can form a coating film (film) of the acrylic resin on the surface of the sidewall, and examples thereof include a method of coating with an acrylic resin paint. Specifically, the acrylic resin paint can be coated by applying any method that allows contact, such as applying, spraying, or immersing, on the surface of the sidewall.

[0143] Examples of the acrylic resin paint include known acrylic resin paints, acrylic emulsion resin paints, acrylic urethane emulsion paints, acrylic silicone emulsion paints, and acrylic lacquers.

[0144] The coating film formed of an acrylic resin on the sidewall surface (hereinafter also referred to as an acrylic resin coating film) has a thickness (Ta) of preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more, and is preferably 500 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less. Within the above ranges, better effects tend to be obtained. In this specification, the thickness of the coating film means the thickness of the coating film layer as measured by photographing the cross section of the sidewall on which the coating film is formed using a scanning electron microscope (SEM).

[0145] Although the mechanism by which the effect of adjusting the thickness of the acrylic resin coating film to a range of 10 μm to 500 μm is particularly clear, a thickness of at least the specified value sufficiently blocks ozone and provides ozone resistance, while a thickness of less than the specified value reduces the possibility of coating film peeling and provides protective performance, which is thought to improve crack resistance.

[0146] In the tire, the difference (AEt-AEs) between the acetone extractable amount AEt (mass%) of the tread formed from the tread rubber composition and the acetone extractable amount AEs (mass%) of the at least one sidewall formed from the sidewall rubber composition is 1.0 mass% or more. The AEt-AEs is preferably 2.0% by mass or more, more preferably 2.5% by mass or more, and even more preferably 3.0% by mass or more. There is no particular upper limit to the AEt-AEs, but it is preferably 10.0% by mass or less, more preferably 7.0% by mass or less, and even more preferably 5.0% by mass or less. Within the above range, the effect tends to be better obtained.

[0147] In this specification, the acetone extractables (AE) are measured by the following method: The acetone extractables are measured on the rubber composition after vulcanization. The amount of acetone extractables is measured by the method for measuring the amount of acetone extractables in accordance with JIS K 6229:2015 for samples prepared by collecting samples from the tread and sidewall of a tire (unit: mass % of the rubber composition (sample)).

[0148] The acetone extractables (AE) can be adjusted by any method known to those skilled in the art. For example, the acetone extractables tend to increase as the amount of plasticizers such as oil in the rubber composition increases.

[0149] The above tire is manufactured by a conventional method using a rubber composition for the tread and a rubber composition for the sidewall. That is, the rubber composition for the tread and the rubber composition for the sidewall, which contain the above components, are extruded in the unvulcanized state to match the shapes of the tread and the sidewall. The surface of the sidewall is coated with an acrylic resin coating by a method such as painting. An unvulcanized tire is formed by molding together with other tire components in a tire building machine by a conventional method. The unvulcanized tire is then heated and pressurized in the vulcanizer to obtain a tire.

[0150] The tire is not particularly limited, and examples thereof include pneumatic tires, solid tires, airless tires, etc. Among these, pneumatic tires are preferred.

[0151] 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.

[0152] In the tire having the tread and the pair of sidewalls, the thickness (Ts) of the sidewall at the tire's maximum width position is preferably 1.0 mm or more, more preferably 1.5 mm or more, and even more preferably 2.0 mm or more. The upper limit is preferably 15.0 mm or less, more preferably 10.0 mm or less, and even more preferably 5.0 mm or less. Within the above range, the effect tends to be more favorable.

[0153] Although the mechanism by which the effect of adjusting the thickness Ts to 1.5 mm or more is particularly clear, it is believed that the amount of antioxidant contained in the sidewall rubber can be secured, imparting ozone resistance and providing the required durability against distortion, thereby improving crack resistance.

[0154] In this specification, the term "maximum tire width positions" refers to a pair of positions where the tire has the maximum width in the axial direction. "Sidewall thickness (Ts) at the tire's maximum width point" refers to the thickness of the sidewall in the tire's axial direction at the tire's maximum width point in a radial cross section. The sidewall thickness at the tire's maximum width point is measured in the axial direction from the surface of the sidewall at the tire's maximum width point. The Ts mentioned above is the linear distance in the tire's axial direction from the outer surface to the inner surface of the sidewall at the tire's maximum width point in a radial cross section. If the sidewall is made up of two or more rubber layers, the Ts mentioned above refers to the total thickness of each of the two or more rubber layers of the sidewall. When the surface of the sidewall at the maximum tire width position is coated with an acrylic resin coating film, Ts is the thickness including the acrylic resin coating film, and refers to the linear distance in the tire axial direction from the outermost surface of the acrylic resin coating film at the maximum tire width position to the inner surface of the sidewall.

[0155] In this specification, dimensions such as thickness are measured with the bead portion of the tire aligned to the standard rim width. During measurement, the tire is cut out in the tire radial direction, and both bead ends of the sample are fixed in place with the width of the standard rim.

[0156] In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured under normal conditions. In this specification, the term "normal condition" refers to a state in which the tire is mounted on a normal rim (not shown), inflated to a normal internal pressure, and no load is applied.

[0157] If it is not possible to measure with the tire mounted on a regular rim, the dimensions and angles of each part in the meridian cross section of the tire are measured by cutting the tire along a plane including the axis of rotation, and then matching the distance between the left and right beads in the cross section to the distance between the beads of the tire mounted on a regular rim.

[0158] "Genuine rim" means a rim that is specified for each tire by the standard system that includes the standard on which the tire is based. For example, it means a standard rim for JATMA, a "Design Rim" for TRA, or a "Measuring Rim" for ETRTO. "Normal internal pressure" refers to the air pressure specified for each tire by the above standards. For JATMA, this refers to the maximum air pressure, for TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it refers to "INFLATION PRESSURE." "Normal load" refers to the load specified for each tire by the above standards, and means the maximum load capacity for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO.

[0159] In the tire, the product ((AEt-AEs)×Ta) of the difference (AEt-AEs (mass%)) between the acetone extractable amount AEt (mass%) of the tread formed from the tread rubber composition and the acetone extractable amount AEs (mass%) of at least one of the sidewalls formed from the sidewall rubber composition and the thickness Ta (μm) of the coating film formed of an acrylic resin on the sidewall surface is preferably 10 or more, more preferably 15 or more, even more preferably 30 or more, and particularly preferably 60 or more, and is preferably 300 or less, more preferably 200 or less, and even more preferably 100 or less. When it is within the above range, the effect tends to be more favorable. When it is within the above range, the effect tends to be more favorable.

[0160] The mechanism by which greater effectiveness is achieved by adjusting (AEt-AEs) x Ta within a specified range is not clear, but it is thought that the rate at which the antioxidant in the sidewall is reduced can be suppressed, allowing the antioxidant to be gradually supplied to the sidewall from the tread, and ozone can be sufficiently blocked, thereby improving crack resistance.

[0161] In the tire, the product ((AEt-AEs)×Ts) of the difference (AEt-AEs) between the acetone extractable amount AEt (% by mass) of the tread formed from the tread rubber composition and the acetone extractable amount AEs (% by mass) of at least one sidewall formed from the sidewall rubber composition and the thickness Ts (mm) of the sidewall at the tire maximum width position is preferably 2.0 or more, more preferably 3.0 or more, even more preferably 4.0 or more, and particularly preferably 6.0 or more, and is preferably 20.0 or less, more preferably 15.0 or less, and even more preferably 10.0 or less. When it is within the above range, the effect tends to be more favorable. When it is within the above range, the effect tends to be more favorable.

[0162] The mechanism by which greater effectiveness is achieved by adjusting (AEt-AEs) x Ts within a specified range is not clear, but it is thought that the rate at which the antioxidant in the sidewall is reduced can be slowed while the antioxidant can be gradually supplied to the sidewall from the tread, and the amount of antioxidant contained in the sidewall can be secured, thereby improving crack resistance.

[0163] The tire has a predetermined tread 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.

[0164] In the tire, the groove depth D (mm) of the circumferential grooves formed in the tread is preferably 5.0 mm or more, more preferably 6.0 mm or more, and even more preferably 8.0 mm or more, and is preferably 20.0 mm or less, more preferably 15.0 mm or less, and even more preferably 10.0 mm or less. When it is within the above range, the effect tends to be better obtained.

[0165] The mechanism by which a groove depth D within a specified range provides a greater effect is not clear, but it is believed that adjusting the groove depth to within the specified range ensures rubber strength and improves crack resistance by gradually supplying antioxidant from the tread to the sidewall.

[0166] The product ((AEt-AEs)×D) of the difference (AEt-AEs) between the acetone extractable amount AEt (mass%) of the tread formed with the rubber composition for tread and the acetone extractable amount AEs (mass%) of at least one of the sidewalls formed with the rubber composition for sidewalls and the groove depth D (mm) of the circumferential grooves formed in the tread is preferably 15 or more, more preferably 18 or more, and even more preferably 21 or more, and is preferably 45 or less, more preferably 42 or less, and even more preferably 40 or less. When it is within the above range, the effect tends to be better obtained.

[0167] The mechanism by which greater effectiveness is achieved by adjusting (AEt-AEs) x D within a specified range is not clear, but it is thought that the rate at which the antioxidant in the sidewall is reduced can be suppressed while the antioxidant can be gradually supplied to the sidewall from the tread, and that good rubber strength can be obtained by adjusting the groove depth within the specified range, thereby improving crack resistance.

[0168] An example of a tire will be described below with reference to the drawings, but the tire is not limited to this configuration.

[0169] 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.

[0170] 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.

[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.

[0172] The tread 4 is made of the above-mentioned tread rubber composition, and the sidewall 6 is made of a sidewall rubber composition, with the tread rubber composition and the sidewall rubber composition being made of different rubber compositions. The difference (AEt - AEs) between the acetone extractable amount AEt (mass%) of the tread rubber composition and the acetone extractable amount AEs (mass%) of the sidewall rubber composition is 1.0 mass% or more. The outer surface of the sidewall 6 is coated with an acrylic resin coating film 7 formed of an acrylic resin.

[0173] The radially inner portion of the sidewall 6 is joined to the clinch 10. This sidewall 6 can prevent damage to the carcass 14.

[0174] The tire 2 in FIG. 1 has a maximum tire width position M on the surface of the sidewall 6. In the case of Figure 1, the thickness Ts of the sidewall 6 at the tire maximum width position M refers to the linear distance in the tire axial direction from the outermost tire surface of the acrylic resin coating film 7 at the tire maximum width position M to the interface of the carcass 14 on the tire outermost surface side in the radial cross section of the tire.

[0175] 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.

[0176] 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.

[0177] 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.

[0178] 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.

[0179] 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.

[0180] 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.

[0181] 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.

[0182] 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.

[0183] 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.

[0184] 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.

[0185] 1 constitute a reinforcing layer. The reinforcing layer may be constituted by the belt layer 16 alone.

[0186] 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).

[0187] 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] 2D shows the groove depth of the main groove 42 formed in the tread 4 in the circumferential direction.

[0192] In the tire 2, it is desirable that the content of the antioxidant in the rubber composition for sidewall that constitutes the sidewall 6, the thickness Ta, (AEt-AEs)×Ta, (AEt-AEs)×Ts of the acrylic resin coating film 7 that coats the surface of the sidewall 6, and the groove depth D, (AEt-AEs)×D) are within the above-mentioned ranges. [Example]

[0193] 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.

[0194] The various chemicals used in the production of treads and sidewalls are explained below. If necessary, the chemicals are refined according to standard methods. (tread) NR:TSR20 SBR: HPR850 manufactured by JSR Corporation (styrene content: 27.5% by mass, vinyl content: 59% by mass) BR: BR150B (cis content: 97% by mass) manufactured by Ube Industries, Ltd. Carbon black: Show Black N220 (N2SA: 111m) manufactured by Cabot Japan Co., Ltd. 2 / g) Silica: Ultrasil VN3 (N2SA: 175 ml) manufactured by Evonik 2 / g, CTAB: 175m 2 / g) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa Oil: Idemitsu Kosan Co., Ltd. Diana Process NH-70S (aromatic process oil) Stearic acid: Tsubaki (NOF Corporation) Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Antioxidant 1: Nocrac 6C (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Wax: Ozoace 0355 (manufactured by Nippon Seiro Co., Ltd.) Sulfur: HK-200-5 (powdered sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Noccela CZ-G (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccelaer D (N,N'-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0195] (Sidewall) NR:TSR20 BR: BR01 manufactured by JSR Corporation (cis content: 95% by mass) Carbon black: Diablack N550 (N2SA: 40m) manufactured by Mitsubishi Chemical Corporation 2 / g) Resin: Maruzen Petrochemical Co., Ltd.'s Marukaretzu T-100AS (C5 aliphatic hydrocarbon resin, softening point: 97-103°C) Oil: Idemitsu Kosan Co., Ltd. Diana Process NH-70S (aromatic process oil) Wax: Ozoace 0355 (manufactured by Nippon Seiro Co., Ltd.) Antioxidant 1: Nocrac 6C (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 2: Nocrac 224 (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: Tsubaki (NOF Corporation) Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: HK-200-5 (powdered sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Noccela CZ-G (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0196] (Sidewall surface paint) Acrylic resin paint: "Aquaricoat" manufactured by Edogawa Synthetic Co., Ltd. Oil-based silicone: Gracias Gold Tire Coating by Prostaff Co., Ltd. Water-based silicone: Ishihara Chemical Tire & Leather Wax 248SB

[0197] (Preparation of rubber composition for tread) According to the formulation shown in Table 1, 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 unvulcanized rubber composition for tread.

[0198] (Preparation of rubber composition for sidewall) According to the formulation shown in Table 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 unvulcanized rubber composition for sidewalls.

[0199] <Test tire manufacturing method> According to the specifications in Table 3, the unvulcanized rubber composition for tread (Table 1) is molded into the shape of a tread, and the unvulcanized rubber composition for sidewall (Table 2) is molded into the shape of a sidewall. According to the specifications in Table 3, the acrylic resin paint, oil-based silicone or water-based silicone is applied to the surface of the sidewall facing outward from the tire, to form a coating on the outer surface. The tire is laminated together with other tire components in a tire building machine to form an unvulcanized tire, which is then vulcanized at 170°C for 10 minutes to produce a test tire (size 205 / 70R15, passenger car tire, Figures 1 and 2).

[0200] Table 3 shows the results of calculations based on the following evaluation method, assuming test tires obtained from compositions whose formulations and specifications were changed according to Table 3. The reference comparative example is as follows. Table 3: Comparative Example 5

[0201] <Acetone extractables (AE)> For rubber test pieces (tread, sidewall) cut out from the test tire, the amount of substance (mass%) extracted by acetone contained in the test piece is measured using the acetone extractable amount measurement method in accordance with JIS K 6229:2015. Acetone extractable amount (mass%) = (mass of sample before extraction - mass of sample after extraction) / mass of sample before extraction × 100

[0202] <Crack resistance> The test tire was mounted and driven 30,000 km at a speed of 80 km / h and a load of 4.7 kN, and the amount of crack growth in the sidewall was measured to evaluate crack resistance. The result is expressed as an index, with the reference comparative example being set at 100. The higher the value, the better the crack resistance.

[0203] [Table 1]

[0204] [Table 2]

[0205] [Table 3]

[0206] The present invention (1) is a tire having a tread and a pair of sidewalls, a tread rubber composition constituting the tread and a sidewall rubber composition constituting at least one of a pair of sidewalls are composed of different rubber compositions, The surface of the sidewall is coated with an acrylic resin, In the tire, the difference (AEt-AEs) between the acetone extractable amount AEt (mass%) of the rubber composition for the tread and the acetone extractable amount AEs (mass%) of the rubber composition for the sidewall is 1.0 mass% or more.

[0207] The present invention (2) is the tire according to the present invention (1), wherein the rubber composition for sidewalls contains an antioxidant in an amount of 0.3 parts by mass or more and 7.0 parts by mass or less per 100 parts by mass of the rubber component.

[0208] The present invention (3) is the tire according to the present invention (1) or (2), wherein the thickness of the coating film formed from the acrylic resin is 10 μm or more and 500 μm or less.

[0209] The present invention (4) is a tire in any combination with any of the present inventions (1) to (3), in which the thickness of the sidewall at the maximum width position of the tire is 1.5 mm or more.

[0210] The present invention (5) is a tire in any combination with any of the present inventions (1) to (4), in which the product ((AEt-AEs)×Ta) of the difference (AEt-AEs) between the acetone extractable amount AEt (mass%) of the tread and the acetone extractable amount AEs (mass%) of the sidewall and the thickness Ta (μm) of the coating film formed of an acrylic resin on the surface of the sidewall is 30 or more and 200 or less.

[0211] The present invention (6) is a tire in any combination with any of the present inventions (1) to (5), in which the product ((AEt-AEs)×Ts) of the difference (AEt-AEs) between the acetone extractable amount AEt (mass%) of the tread and the acetone extractable amount AEs (mass%) of the sidewall and the thickness Ts (mm) of the sidewall at the maximum width position of the tire is 4.0 or more and 15.0 or less.

[0212] The present invention (7) is a tire in any combination with any of the present inventions (1) to (6), wherein the groove depth D of the circumferential grooves formed in the tread is 5.0 mm or more and 10.0 mm or less.

[0213] The present invention (8) is a tire in any combination with any of the present inventions (1) to (7), wherein the product ((AEt-AEs)×D) of the difference (AEt-AEs) between the acetone extractable amount AEt (mass%) of the tread and the acetone extractable amount AEs (mass%) of the sidewall and the groove depth D (mm) of the circumferential groove formed in the tread is 21 or more and 40 or less. [Explanation of symbols]

[0214] 2 tires 4 Tread 6 Sidewall 7 Acrylic resin coating 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 M Maximum tire width position Ts Sidewall thickness at widest point of tire D: Depth of the circumferential main groove formed on the tread

Claims

1. A tire having a tread and a pair of sidewalls, a tread rubber composition constituting the tread and a sidewall rubber composition constituting at least one of a pair of sidewalls are composed of different rubber compositions, The surface of the sidewall is coated with an acrylic resin, The tire, wherein the difference (AEt-AEs) between the acetone extractable amount AEt (mass%) of the rubber composition for the tread and the acetone extractable amount AEs (mass%) of the rubber composition for the sidewall is 1.0 mass% or more.

2. The tire according to claim 1, wherein the rubber composition for sidewalls has an antioxidant content of 0.3 parts by mass or more and 7.0 parts by mass or less per 100 parts by mass of the rubber component.

3. 3. The tire according to claim 1, wherein the thickness of the coating film formed from the acrylic resin is 10 μm or more and 500 μm or less.

4. 3. The tire according to claim 1, wherein the thickness of the sidewall at the maximum width position of the tire is 1.5 mm or more.

5. 3. The tire according to claim 1, wherein the product ((AEt-AEs) x Ta) of the difference (AEt-AEs) between the acetone extractable amount AEt (mass%) of the tread and the acetone extractable amount AEs (mass%) of the sidewall and the thickness Ta (μm) of the coating film formed of an acrylic resin on the sidewall surface is 30 or greater and 200 or less.

6. 3. The tire according to claim 1, wherein a product ((AEt-AEs)×Ts) of a difference (AEt-AEs) between an acetone extractable amount AEt (mass%) of the tread and an acetone extractable amount AEs (mass%) of the sidewall and a thickness Ts (mm) of the sidewall at a tire maximum width position is 4.0 or greater and 15.0 or less.

7. The tire according to claim 1 or 2, wherein a groove depth D of the circumferential groove formed in the tread is equal to or greater than 5.0 mm and equal to or less than 10.0 mm.

8. 3. The tire according to claim 1, wherein the product ((AEt-AEs) x D) of the difference (AEt-AEs) between the acetone extractable amount AEt (mass%) of the tread and the acetone extractable amount AEs (mass%) of the sidewall and the groove depth D (mm) of a circumferential groove formed in the tread is 21 or greater and 40 or less.

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