tire

Abstract

To provide a tire with improved durability performance.SOLUTION: A tire comprises a cap tread and a base tread. The cap tread contains a polymer with an ethylene unit, an isoprene rubber and a compound represented by the following formula (1): R1R2 N-(C=S)-Sz(C=S)-NR3R4 (herein, z represents an integer of 1 to 8. R1 to R4 represent the same or different hydrocarbon group having hydrogen atom or 1 to 15 carbon atoms. A content of the isoprene rubber in 100% by mass of rubber constituent is 20% by mass or more, and a content of the isoprene rubber in 100% by mass of rubber constituent of the base tread is more than a content of the isoprene rubber in 100% by mass of rubber constituent of the cap tread.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Conventionally, various performances have been required for tires, and from the viewpoint of recent environmental considerations, it has been desired to improve durability performance and the like.

Summary of the Invention

Problems to be Solved by the Invention

[0003] An object of the present invention is to solve the above problems and provide a tire with improved durability performance.

Means for Solving the Problems

[0004] The present invention relates to a tire including a cap tread and a base tread, wherein the cap tread contains a polymer having an ethylene unit, an isoprene rubber, and a compound represented by the following formula (1), and the content of the isoprene rubber in 100% by mass of the rubber component is 20% by mass or more, and the content of the isoprene rubber in 100% by mass of the rubber component of the base tread is more than the content of the isoprene rubber in 100% by mass of the rubber component of the cap tread. (1)R 1 R 2 N-(C=S)-Sz(C=S)-NR 3 R 4 (In the formula, z represents an integer of 1 to 8. R 1 ~R 4 are the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 15 carbon atoms.)

Effects of the Invention

[0005] The present invention relates to a tire comprising a cap tread and a base tread, wherein the cap tread contains a polymer having ethylene units, an isoprene rubber, and a compound represented by the above formula (1), and the content of the isoprene rubber in 100% by mass of the rubber component is 20% by mass or more, and the content of the isoprene rubber in 100% by mass of the rubber component of the base tread is more than the content of the isoprene rubber in 100% by mass of the rubber component of the cap tread. Since it is a tire characterized by this, the durability performance can be improved.

Brief Description of Drawings

[0006]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0007] The above tire comprises a cap tread and a base tread. The cap tread contains a polymer having ethylene units, an isoprene rubber, and a compound represented by the above formula (1), and the content of the isoprene rubber in 100% by mass of the rubber component is 20% by mass or more. Furthermore, the content of the isoprene rubber in the cap tread is more than the content of the isoprene rubber in the base tread.

[0008] The reason why the above tire obtains the aforementioned effects is not necessarily clear, but it is presumed as follows. A formulation containing a polymer having ethylene units generally has problems such as vulcanization delay and a decrease in compatibility with other rubbers, so there is a concern that interfacial peeling may occur between the cap tread and the base tread. In the above tire, by blending a predetermined amount of an isoprene rubber having high compatibility with the base tread in the cap tread and blending the compound represented by (1) to accelerate vulcanization, the co-crosslinkability between the cap tread and the base tread is improved, and it is considered that interfacial peeling is suppressed. Therefore, it is presumed that the durability performance of the tire is improved.

[0009] Thus, by configuring the tire to include a cap tread and a base tread that satisfy "the content of isoprene rubber in 100% by mass of the rubber component is 20% by mass or more" and "the content of isoprene rubber in 100% by mass of the rubber component of the base tread is more than the content of isoprene rubber in 100% by mass of the rubber component of the cap tread", the problem (objective) of improving the durability performance is solved. That is, the parameters of "the content of isoprene rubber in 100% by mass of the rubber component is 20% by mass or more" and "the content of isoprene rubber in 100% by mass of the rubber component of the base tread is more than the content of isoprene rubber in 100% by mass of the rubber component of the cap tread" do not define the problem (objective). The problem of this application is to improve the durability performance, and for this purpose, the configuration is such that the parameters are satisfied.

[0010] The above tire has a cap tread and a base tread. The cap tread is composed of a rubber composition for cap tread, and the base tread is composed of a rubber composition for base tread.

[0011] Hereinafter, chemicals that can be commonly used in the rubber composition for cap tread and the rubber composition for base tread will be described.

[0012] The rubber composition for cap tread and the rubber composition for base tread contain a rubber component. Here, the rubber component is a component that contributes to crosslinking. Generally, a polymer having a weight average molecular weight (Mw) of 10,000 or more, and a polymer component that is not extracted by acetone corresponds to the rubber component. The elastomer component is in a solid state at normal temperature (25°C).

[0013] The weight average molecular weight of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, still more preferably 200,000 or more, and particularly preferably 270,000 or more. Also, it is preferably 2,000,000 or less, more preferably 1,500,000 or less, and still more preferably 1,000,000 or less. When within the above range, the effects tend to be obtained more favorably.

[0014] In addition, in this specification, the weight average molecular weight (Mw) can be determined by standard polystyrene conversion based on the measured value by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0015] The rubber component that can be used in the rubber composition for cap tread and the rubber composition for base tread may be an unmodified rubber or a modified rubber. Examples of the modified rubber include rubbers having a functional group that interacts with a filler such as silica. For example, a terminal-modified rubber (terminal-modified rubber having the above functional group at the terminal) in which at least one end of the rubber is modified with a compound (modifying agent) having the above functional group, a main-chain modified rubber having the above functional group in the main chain, a main-chain terminal-modified rubber having the above functional group in the main chain and at least one end (for example, a main-chain terminal-modified rubber having the above functional group in the main chain and at least one end modified with the above modifying agent), and a terminal-modified rubber modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or an epoxy group introduced therein, etc. can be mentioned.

[0016] Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group, etc. These functional groups may have substituents. Among them, 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.

[0017] Examples of the rubber component include diene rubbers.

[0018] Examples of the 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), acrylonitrile-butadiene rubber (NBR), etc. In addition, examples of the rubber component also include butyl rubber, fluororubber, etc. These may be used alone or in combination of two or more. Further, these rubber components may be subjected to modification treatment or hydrogenation treatment, and extended rubber extended with an oil, a resin, a liquid rubber component, etc. may also be used. Among the diene rubbers, isoprene rubber, BR, and SBR are desirable.

[0019] Examples of isoprene rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, denatured NR, denatured IR, etc. As NR, for example, SIR20, RSS#3, TSR20, etc., which are common in the rubber industry, can be used. IR is not particularly limited, and for example, IR2200, etc., which are common in the rubber industry, can be used. Examples of modified NR include deproteinized natural rubber (DPNR), high-purity natural rubber, etc. Examples of denatured NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Examples of denatured IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. These may be used alone or in combination of two or more.

[0020] BR is not particularly limited, and for example, high-cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, BR synthesized using a rare earth catalyst (rare earth BR), etc. can be used. These may be used alone or in combination of two or more. Among them, BR preferably contains high-cis BR with a cis content of 90% by mass or more. The cis content is more preferably 95% by mass or more. The cis content can be measured by infrared absorption spectroscopy.

[0021] When BR is a single type, the cis amount of BR means the cis amount of that BR. When there are multiple types, it means the average cis amount. The average cis amount of BR can be calculated by {Σ(content of each BR × cis amount of each BR)} / total content of all BR. For example, in 100% by mass of the rubber component, if BR with a cis amount of 90% by mass is 20% by mass and BR with a cis amount of 40% by mass is 10% by mass, the average cis amount of BR is 73.3% by mass (=(20×90 + 10×40) / (20 + 10)).

[0022] Also, either non-modified BR or modified BR can be used for BR. Examples of modified BR include modified BR into which the same functional groups as those of modified rubber are introduced. Also, hydrogenated butadiene polymer (hydrogenated BR) can be used for BR.

[0023] The SBR is not particularly limited, and for example, emulsion polymerization styrene butadiene rubber (E-SBR), solution polymerization styrene butadiene rubber (S-SBR), etc. can be used. These may be used alone or in combination of two or more.

[0024] The styrene content of the SBR is preferably 5% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more. The styrene content is preferably 60% by mass or less, more preferably 40% by mass or less, still more preferably 35% by mass or less. When within the above range, the effect tends to be obtained more favorably. In addition, in this specification, the styrene content 1 can be measured by 1H-NMR measurement.

[0025] The amount of styrene in the SBR means the amount of styrene in the case where the SBR is of one kind, and means the average styrene amount in the case of a plurality of kinds. The average styrene amount of the SBR can be calculated by {Σ(content of each SBR × styrene amount of each SBR)} / total content of all SBRs. For example, when 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 are in 100% by mass of the rubber component, the average styrene amount of the SBR is 39.2% by mass (=(85×40 + 5×25) / (85 + 5)).

[0026] The vinyl bond amount of the SBR is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 7% by mass or more. The vinyl bond amount is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less. When within the above range, the effect tends to be obtained more favorably. In addition, in this specification, the vinyl bond amount (1,2-bond butadiene unit amount) can be measured by infrared absorption spectrum analysis method.

[0027] The vinyl content (1,2-bonded butadiene unit content) of SBR is the ratio of vinyl bonds when the total mass of the butadiene portion in SBR is taken as 100 (unit: mass %), and 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, if there are 75 parts by mass of SBR with a styrene content of 40 mass % and a vinyl content of 30 mass %, 15 parts by mass of SBR with a styrene content of 25 mass % and a vinyl content of 20 mass %, and the remaining 10 parts by mass are other than SBR, the average vinyl content of SBR is 28 mass % (={75×(100 [mass %]-40 [mass %])×30 [mass %]+15×(100 [mass %]-25 [mass %])×20 [mass %])} / {75×(100 [mass %]-40 [mass %])+15×(100 [mass %]-25 [mass %])}).

[0028] For SBR, either non-modified SBR or modified SBR can be used. Examples of modified SBR include those with functional groups similar to modified rubber introduced. Also, as SBR, hydrogenated styrene-butadiene copolymer (hydrogenated SBR) can be used.

[0029] The raw materials (monomers) for synthetic rubbers such as SBR and BR may be derived from petroleum or recycled from rubber products such as tires and non-rubber products such as polystyrene. The monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled butadiene and recycled aromatic vinyl. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl is not particularly limited, and examples include styrene. Among them, it is preferable to use recycled butadiene (recycled butadiene) and / or recycled styrene (recycled styrene) as raw materials.

[0030] The method for producing recycled monomers is not particularly limited, and examples include being synthesized from recycled naphtha obtained by decomposing rubber products such as tires. The method for producing recycled naphtha is not particularly limited, and for example, rubber products such as tires may be decomposed under high temperature and high pressure, decomposed by microwaves, or extracted after mechanical pulverization.

[0031] Furthermore, the raw materials (monomers) for synthetic rubbers such as SBR and BR may be derived from biomass. The monomers derived from biomass (biomass monomers) are not particularly limited, and examples include biomass-derived butadiene and biomass-derived aromatic vinyl. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl is not particularly limited, and examples include styrene. The method for producing biomass monomers is not particularly limited, and examples include those by biological and / or chemical and / or physical conversion of animals and plants. Fermentation by microorganisms is typical of biological conversion, and examples of chemical and / or physical conversion include those by catalysts, high heat, high pressure, electromagnetic waves, supercritical fluids, and combinations thereof. Examples of the biomass sources of these monomers include sugars, wood, plant residues after obtaining useful components, plant-derived ethanol, biomass naphtha, and the like.

[0032] The polymers synthesized from biomass monomer components (biomass polymers) are not particularly limited, and examples thereof include polybutadiene rubber synthesized from biomass-derived butadiene, and aromatic vinyl / butadiene copolymers 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.

[0033] Whether the raw material of the polymer is derived from biomass can be determined by pMC (percent Modern Carbon) measured in accordance with ASTM D6866-10.

[0034] pMC is the ratio of the 14 C concentration of the sample to the 14 C concentration of the modern standard reference, and this value is used as an index indicating the biomass ratio of the compound (rubber). The significance of this value will be described below.

[0035] In one mole (6.02×10 23 pieces) of carbon atoms, there are approximately 6.02×10 11 pieces of 14 C, which is about one trillionth of the normal carbon atoms. 14 14 14 C is called a radioactive isotope, and its half-life is 5730 years and it decreases regularly. It takes 226,000 years for all of these to decay. Therefore, in fossil fuels such as coal, oil, and natural gas, which are considered to have passed more than 226,000 years after carbon dioxide in the atmosphere was taken up and fixed by plants, etc., all of the 14 C elements contained in them at the time of fixation have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas do not contain any 14 C elements. Therefore, chemical substances produced from these fossil fuels also do not contain any

[0036] On the one hand, 14 C undergoes nuclear reactions in the atmosphere by cosmic rays, is continuously generated, and is balanced with the decrease due to radioactive decay. In the atmospheric environment of the earth, 14 the amount of C is a certain amount. Therefore, the 14 C concentration of the substances derived from biomass resources that are circulating in the current environment is about 1×10 -12 mol% with respect to the entire C atoms as described above. Therefore, by utilizing the difference between these values, the ratio (biomass ratio) of the compounds derived from natural resources (compounds derived from biomass resources) in a certain compound (rubber) can be calculated.

[0037] This 14 C is generally measured as follows. Using accelerator mass spectrometry based on a tandem accelerator, 13 the C concentration ( 13 C / 12 C), 14 the C concentration ( 14 C / 12 C) is measured. In the measurement, 14 as the modern standard reference for the concentration of C, the 14 C concentration in the circulating carbon in nature in 1950 is adopted. As a specific standard substance, the oxalic acid standard provided by NIST (National Institute of Standards and Technology) is used. The specific activity of carbon in this oxalic acid (the radioactive intensity of 14 C per 1 g of carbon) is separated for each carbon isotope, 13 and for 14 C, it is corrected to a certain value, and the value after applying the decay correction from 1950 AD to the measurement date is used as the value (100%) of the standard

[0038] Therefore, if the rubber is made of a 100% biomass (natural-based) material, although there are regional differences, it will show a value of approximately 110 pMC (currently, in the normal state, it often does not reach 100). On the other hand, for chemical substances derived from fossil fuels such as petroleum, when measuring the 14 C concentration, it will show almost 0 pMC (for example, 0.3 pMC). This value corresponds to the biomass ratio of 0% mentioned above.

[0039] From the above, using materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio, in the rubber composition is suitable from the perspective of environmental protection.

[0040] Examples of the above rubber component include polymers having ethylene units (structural units formed from ethylene: -CH2-CH2-). In the above tire, the polymer having ethylene units used in the cap tread is a polymer having high-molecular-weight ethylene units, which is a component that cannot be extracted by an organic solvent such as acetone from the rubber composition after vulcanization and is used as a rubber component. It is desirable that the polymer having high-molecular-weight ethylene units has the weight-average molecular weight of the above rubber component.

[0041] The above polymer having ethylene units is not particularly limited as long as it is a polymer having ethylene units, but from the perspective of obtaining good effects, a multi-component copolymer containing ethylene units, conjugated diene units, and aromatic vinyl units is desirable.

[0042] In the above multi-component copolymer, the conjugated diene units are structural units derived from conjugated diene compounds. Examples of the above conjugated diene compounds include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene, etc. These may be used alone or in combination of two or more, but 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred.

[0043] In the above-mentioned multi-component copolymer, the aromatic vinyl unit is a structural unit derived from an aromatic vinyl compound. Examples of the aromatic vinyl compound include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, and the like. These may be used alone or in combination of two or more. Among them, styrene and α-methylstyrene are preferred, and styrene is more preferred.

[0044] The above-mentioned multi-component copolymer can be prepared, for example, by copolymerizing ethylene, a conjugated diene compound and an aromatic vinyl compound, or by copolymerizing a conjugated diene compound and an aromatic vinyl compound, or ethylene, a conjugated diene compound and an aromatic vinyl compound, and then converting a part of the conjugated diene units into non-conjugated olefin units by hydrogenation. That is, the above-mentioned multi-component copolymer may be a copolymer of ethylene, a conjugated diene compound and an aromatic vinyl compound, or a copolymer of a conjugated diene compound and an aromatic vinyl compound, or a hydrogenated product (hydrogenated copolymer) of a copolymer of ethylene, a conjugated diene compound and an aromatic vinyl compound. These may be used alone or in combination of two or more. Among them, from the viewpoint of obtaining better effects, a hydrogenated product of a copolymer of a conjugated diene compound and an aromatic vinyl compound is preferred, and a hydrogenated styrene-butadiene copolymer is more preferred.

[0045] In preparing the above-mentioned multi-component copolymer, the polymerization method is not particularly limited and may be random polymerization or block polymerization, but random polymerization is preferred.

[0046] When the above-mentioned copolymer is a hydrogenated copolymer, there are no particular limitations on the hydrogenation method and reaction conditions, and hydrogenation may be carried out by known methods and under known conditions. Usually, it is carried out at 20 to 150 °C under a hydrogen pressure of 0.1 to 10 MPa in the presence of a hydrogenation catalyst. Other manufacturing methods and conditions are not particularly limited either. For example, the content described in International Publication No. 2016 / 039005 can be applied.

[0047] In the rubber composition for cap tread, the content of the polymer having the above ethylene unit in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 65% by mass or more, and particularly preferably 70% by mass or more. The upper limit is not particularly limited and may be 100% by mass, but is preferably 95% by mass or less, more preferably 85% by mass or less, and still more preferably 80% by mass or less. When within the above range, the effects tend to be preferably obtained.

[0048] In the rubber composition for cap tread, the content of the isoprene rubber in 100% by mass of the rubber component is 20% by mass or more, preferably 25% by mass or more, and more preferably 30% by mass or more. The upper limit is preferably 60% by mass or less, more preferably 50% by mass or less, and still more preferably 40% by mass or less. When within the above range, the effects tend to be preferably obtained.

[0049] In the rubber composition for base tread, the content of the isoprene rubber in 100% by mass of the rubber component is preferably 60% by mass or more, more preferably 65% by mass or more, still more preferably 75% by mass or more, and also preferably 95% by mass or less, more preferably 90% by mass or less, and still more preferably 85% by mass or less. When within the above range, the effects tend to be preferably obtained.

[0050] In the rubber composition for the base tread, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and is preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 25% by mass or less. When it is within the above range, the effect tends to be preferably obtained.

[0051] In the above tire, the content Ib of the isoprene rubber in 100% by mass of the rubber component of the base tread is more than the content Ic of the isoprene rubber in 100% by mass of the rubber component of the cap tread (Ib > Ic). Ib / Ic is preferably 2.0 or more, more preferably 2.3 or more, still more preferably 2.5 or more. The upper limit is preferably 3.8 or less, more preferably 3.3 or less, still more preferably 3.0 or less. When it is within the above range, the effect tends to be preferably obtained.

[0052] When Ib / Ic is adjusted to be a predetermined value or more, particularly 2.3 or more, the mechanism by which more effects are obtained is not clear, but by increasing the amount of the isoprene rubber in the cap tread relative to the amount of the isoprene rubber in the base tread, the compatibility between the cap tread and the base tread is improved, and it is considered that interfacial delamination is suppressed. Therefore, it is presumed that the durability performance of the tire is improved.

[0053] The rubber composition for the cap tread contains a compound represented by the following formula (1). (1)R 1 R 2 N-(C=S)-Sz(C=S)-NR 3 R 4 (In the formula, z represents an integer from 1 to 8. R 1 ~R 4 are the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 15 carbon atoms.)

[0054] z in the above formula (1) is preferably 1 or more, and is preferably 6 or less, more preferably 3 or less.

[0055] R in the above formula (1) 1 ~R 4 The number of carbon atoms of the hydrocarbon group is preferably 2 or more, more preferably 4 or more, and preferably 12 or less, more preferably 10 or less. R 1 ~R 4 Examples of the hydrocarbon group of R~R include monovalent aliphatic hydrocarbon groups such as alkyl groups and monovalent aromatic hydrocarbon groups such as aryl groups. Preferably, it is an alkyl group, more preferably an alkyl group having a branched structure, and still more preferably a 2-ethylhexyl group.

[0056] Examples of the compound represented by the above formula (1) include Noceller TBzTD (tetrabenzylthiuram disulfide) and Noceller TOT-N (tetrakis(2-ethylhexyl)thiuram disulfide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Among them, tetrabenzylthiuram disulfide is preferable from the viewpoint of obtaining better effects.

[0057] The compound represented by the above formula (1) may also be blended in the rubber composition for the base tread.

[0058] Vulcanization accelerators other than the compound represented by the above formula (1) may be blended in the rubber composition for the cap tread and the rubber composition for the base tread.

[0059] The type of the vulcanization accelerator is not particularly limited, and those commonly used can be used. Examples of the vulcanization accelerator include benzothiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyldisulfide, and N-cyclohexyl-2-benzothiazylsulfenamide; sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolesulfenamide, N-t-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine, and orthotolylbiguanidine. These may be used alone or in combination of two or more. Among them, sulfenamide-based, guanidine-based, and benzothiazole-based vulcanization accelerators are preferred.

[0060] In the rubber composition for the cap tread, the content of the compound represented by the above formula (1) is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, and still more preferably 0.5 part by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 2.0 parts by mass or less, more preferably 1.5 parts by mass or less, and still more preferably 1.0 part by mass or less. When within the above range, the effect tends to be preferably obtained.

[0061] When the content of the compound represented by the above formula (1) is adjusted to a predetermined range, particularly 0.1 to 2.0 parts by mass, the mechanism by which more effects are obtained is not clear, but it is considered that the blending of a predetermined amount of the compound represented by the above formula (1) accelerates the vulcanization rate, thereby improving the co-crosslinkability between the cap tread and the base tread and suppressing interfacial peeling. Therefore, it is presumed that the durability performance of the tire is improved.

[0062] In the rubber composition for cap tread, the content of the vulcanization accelerator (total amount of vulcanization accelerators) is preferably 3.0 parts by mass or more, more preferably 5.0 parts by mass or more, still more preferably 5.3 parts by mass or more, and particularly preferably 5.5 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, and still more preferably 6.0 parts by mass or less. When within the above range, the effect tends to be preferably obtained.

[0063] In the rubber composition for base tread, the content of the vulcanization accelerator (total amount of vulcanization accelerators) is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, and still more preferably 2.0 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 5.0 parts by mass or less, more preferably 4.5 parts by mass or less, and still more preferably 4.0 parts by mass or less. When within the above range, the effect tends to be preferably obtained.

[0064] The rubber composition for cap tread and the rubber composition for base tread preferably contain a plasticizer.

[0065] In this specification, the plasticizer is a material that imparts plasticity to the rubber component, and is a concept that includes both plasticizers that are liquid (liquid state) at normal temperature (25 °C) and plasticizers that are solid at normal temperature (25 °C). Examples of plasticizers include resin components, oils, liquid polymers, ester-based plasticizers, etc. These plasticizers may be derived from petroleum, may be derived from biomass, or may be derived from naphtha recycled from rubber products or non-rubber products. Also, low-molecular-weight hydrocarbon components obtained by thermally decomposing and extracting used tires and products containing various components may be used as plasticizers. These plasticizers may be used alone or in combination of two or more.

[0066] Specific examples of the above plasticizers include oils, liquid polymers, resins, etc. These may be used alone or in combination of two or more.

[0067] Examples of the oil include process oil, vegetable oil, animal oil, etc. Examples of the process oil include paraffinic process oil (mineral oil), naphthenic process oil, aromatic process oil, etc. Specific examples of the process oil include, for example, MES (Mild Extract Solvated), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), RAE (Residual Aromatic Extract), etc. Also, a process oil with a low content of polycyclic aromatic (PCA) compounds can be used for environmental measures. Examples of the low-PCA-content process oil include MES, TDAE, heavy naphthenic oil, etc. Further, from the perspective of life cycle assessment, waste oil after being used in a rubber mixer or an engine, or refined waste cooking oil used in a restaurant may be used.

[0068] In this specification, the vegetable oil refers to, for example, 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, grape seed oil, wood rosin, etc. Further, the vegetable oil includes refined oil (such as salad oil) obtained by refining the above oil, transesterified oil obtained by transesterifying the above oil, hydrogenated oil obtained by hydrogenating the above oil, thermally polymerized oil obtained by thermally polymerizing the above oil, oxidatively polymerized oil obtained by oxidizing the above oil, waste cooking oil recovered from those used as edible oil, etc. Note that the vegetable oil may be liquid or solid at normal temperature (25°C). These vegetable oils may be used alone or in combination of two or more.

[0069] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably contains triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxy group of glycerin and a fatty acid are ester-bonded. The acylglycerol is not particularly limited, and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Further, the acylglycerol may be a monomer, a dimer, or a multimer of trimer or higher. Note that acylglycerols of dimer or higher can be obtained by thermal polymerization, oxidative polymerization, or the like. Also, the acylglycerol may be liquid or solid at room temperature (25°C).

[0070] As a method for confirming whether the acylglycerol is contained in the rubber composition, it is not particularly limited, but 1 it can be confirmed by 1H-NMR measurement. For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at room temperature (25°C) for 24 hours. After removing the rubber composition, 1 1H-NMR is measured. When the signal of tetramethylsilane (TMS) is set to 0.00 ppm, signals around 5.26 ppm, around 4.28 ppm, and around 4.15 ppm are observed, and these signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In this paragraph, "around" means a range of ±0.10 ppm.

[0071] The fatty acid is not particularly limited and may be an unsaturated fatty acid or a saturated fatty acid. Examples of the unsaturated fatty acid include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of the saturated fatty acid include butyric acid and lauric acid.

[0072] Among these, as the fatty acid, it is desirable to contain a fatty acid with few double bonds, that is, a saturated fatty acid or a monounsaturated fatty acid, and oleic acid is preferred. As the vegetable oil containing such a fatty acid, for example, a vegetable oil containing a saturated fatty acid or a monounsaturated fatty acid may be used, or a vegetable oil subjected to modification such as transesterification may be used. Further, in order to produce a vegetable oil containing such a fatty acid, plants may be improved by variety improvement, genetic recombination, genome editing, or the like.

[0073] As the oil, for example, those commercially available from Idemitsu Kosan Co., Ltd., Sankyo Oil & Chemical Co., Ltd., ENEOS Co., Ltd., Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kogyo Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0074] Examples of the liquid polymer include a liquid diene polymer (liquid rubber) and a liquid farnesene polymer at 25°C. Examples of the liquid rubber include a liquid styrene-butadiene copolymer (liquid SBR), a liquid butadiene polymer (liquid BR), a liquid isoprene polymer (liquid IR), a liquid styrene-isoprene copolymer (liquid SIR), a liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), a liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer), etc. These may have their terminals or main chains modified with polar groups. Also, hydrogenated products thereof can be used.

[0075] The weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) of the liquid diene polymer is preferably 1.0×10 3 ~5.0×10 4 and more preferably 3.0×10 3 ~1.5×10 4 Also, the lower limit or upper limit of Mw of the liquid diene polymer may be 4500 or 8500. In this specification, the Mw of the liquid diene polymer is a polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0076] As the above liquid diene polymer, for example, products of Sartomer Company, Kuraray Co., Ltd., etc. can be used.

[0077] As the above resin, as a tire compound, resins (resins) usually used can be used, and they may be liquid or solid at normal temperature (25°C). For example, aromatic vinyl polymers, coumarone-indene resins, coumarone resins, indene resins, phenol resins, rosin resins, petroleum resins, terpene resins, acrylic resins, etc. can be mentioned. Further, the resin may be a hydrogenated resin (hydrogenated resin). These may be used alone or in combination of two or more. Also, the resin itself may be a copolymer of monomer components from a plurality of sources. Among them, from the viewpoint of obtaining better effects, hydrogenated resins are desirable. Also, aromatic vinyl polymers, petroleum resins, terpene resins, and hydrogenated resins thereof are also desirable.

[0078] When a hydrogenated resin is used, the mechanism by which more effects are obtained is not clear, but the compatibility with the polymer having the above ethylene unit is increased, bleeding of the oil is suppressed, and the change in hardness Hs after heat aging is suppressed. Therefore, it is presumed that the comprehensive performance of durability performance and the sustainability of wet grip performance over time is improved.

[0079] When using a resin that is solid at normal temperature, the softening point of the above resin is preferably 50°C or higher, more preferably 55°C or higher, still more preferably 60°C or higher, and particularly preferably 85°C or higher. Also, it is preferably 160°C or lower, more preferably 150°C or lower, still more preferably 140°C or lower, and particularly preferably 100°C or lower. When within the above range, there is a tendency to obtain better effects. When the resin is liquid at normal temperature, the softening point is preferably 20°C or lower, preferably 10°C or lower, and preferably 0°C or lower. In the case of the hydrogenated resin, it is desirable that the softening point be the same as described above. The softening point of the above resin is the temperature at which the ball drops, measured with a ring-and-ball softening point measuring device in accordance with the softening point specified in JIS K6220-1:2001.

[0080] The above aromatic vinyl polymer is a polymer containing an aromatic vinyl monomer as a constituent unit. For example, resins obtained by polymerizing α-methylstyrene and / or styrene can be mentioned. Specifically, homopolymers of styrene (styrene resins), homopolymers of α-methylstyrene (α-methylstyrene resins), copolymers of α-methylstyrene and styrene, copolymers of styrene and other monomers, etc. can be mentioned.

[0081] The above coumarone-indene resin is a resin containing coumarone and indene as the main monomer components constituting the resin skeleton (main chain). As monomer components other than coumarone and indene contained in the skeleton, styrene, α-methylstyrene, methyl indene, vinyl toluene, etc. can be mentioned.

[0082] The above coumarone resin is a resin containing coumarone as the main monomer component constituting the resin skeleton (main chain).

[0083] The above indene resin is a resin containing indene as the main monomer component constituting the resin skeleton (main chain).

[0084] As the above phenolic resin, for example, known ones such as polymers obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde, and furfural in the presence of an acid or alkali catalyst can be used. Among them, those obtained by reacting with an acid catalyst (such as novolak-type phenolic resins) are preferred.

[0085] Examples of the above rosin resin include rosin-based resins typified by natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

[0086] Examples of the petroleum resin include C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene (DCPD) resins, C9 / DCPD resins, and hydrogenated products thereof. Among them, DCPD resins, hydrogenated DCPD resins, C9 / DCPD resins, and C9 / hydrogenated DCPD resins are preferred.

[0087] The terpene resin is a polymer containing terpenes as constituent units. Examples thereof include polyt terpene resins obtained by polymerizing terpene compounds, and aromatic-modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds. Examples of the aromatic-modified terpene resin include terpene phenol resins using terpene compounds and phenolic compounds as raw materials, terpene styrene resins using terpene compounds and styrene-based compounds as raw materials, and terpene phenol styrene resins using terpene compounds, phenolic compounds, and styrene-based compounds as raw materials. Examples of the terpene compound include α-pinene and β-pinene, examples of the phenolic compound include phenol and bisphenol A, and examples of the aromatic compound include styrene-based compounds (styrene, α-methylstyrene, etc.). Among them, aromatic-modified terpene resins are preferred.

[0088] The acrylic resin is a polymer containing acrylic monomers as constituent units. Examples thereof include styrene acrylic resins such as styrene acrylic resins obtained by copolymerizing an aromatic vinyl monomer component and an acrylic monomer component and having a carboxyl group. Among them, solventless carboxyl group-containing styrene acrylic resins can be preferably used.

[0089] Examples of the resin include products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, ExxonMobil, KRATON, Nippon Paint Co., Ltd., Nippon Catalyst Co., Ltd., ENEOS Co., Ltd., Arakawa Chemical Industries, Ltd., Tago Chemical Industry Co., Ltd., etc.

[0090] From a sustainable perspective, it is desirable to use plant-derived plasticizers such as the above-mentioned plant-derived oils and farnesene-based polymers as the plasticizer.

[0091] A farnesene-based polymer is a polymer obtained by polymerizing farnesene and has a structural unit 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 having the following structure is preferred.

Chemical formula

[0092] The farnesene-based 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 them, a copolymer of farnesene and a vinyl monomer is preferred.

[0093] 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-t-butyl-2-methylstyrene, vinyl ethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-t-butylstyrene, 3-t-butylstyrene, 4-t-butylstyrene, vinylxylene, vinylnaphthalene, vinyltoluene, vinylpyridine, diphenylethylene, and tertiary amino group-containing diphenylethylene, and conjugated diene compounds such as butadiene and isoprene. These may be used alone or in combination of two or more. Among them, butadiene is preferred. That is, as the farnesene-vinyl monomer copolymer, a copolymer of farnesene and butadiene (farnesene-butadiene copolymer) is preferred.

[0094] In the farnesene-vinyl monomer copolymer, the copolymerization ratio by mass (farnesene / vinyl monomer) of farnesene and the vinyl monomer is preferably 40 / 60 to 90 / 10.

[0095] Farnesene-based polymers with a weight average molecular weight (Mw) of 3000 or more and 300,000 or less can be preferably used. The Mw of the farnesene-based polymer is preferably 8000 or more, more preferably 10,000 or more, and preferably 100,000 or less, more preferably 60,000 or less, and even more preferably 50,000 or less. When within the above range, the effects tend to be more preferably obtained.

[0096] The farnesene-based polymer may be in a liquid state or a solid state at room temperature (25°C). Among them, a liquid farnesene-based polymer in a liquid state at room temperature (25°C) is desirable.

[0097] In the rubber composition for cap tread, the content of the plasticizer (total amount of plasticizer) is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, still more preferably 50 parts by mass or more, and preferably 100 parts by mass or less, more preferably 80 parts by mass or less, still more preferably 75 parts by mass or less, based on 100 parts by mass of the rubber component. Although the lower limit is not particularly limited, when it is within the above range, the effect tends to be obtained more favorably. Note that the content of the plasticizer includes the amount of oil and resin contained in the oil-extended rubber and resin-extended rubber.

[0098] In the rubber composition for cap tread, the content of the solid plasticizer in a solid state at normal temperature (25 °C) is preferably 15 parts by mass or more, more preferably 25 parts by mass or more, still more preferably 30 parts by mass or more, and preferably 80 parts by mass or less, more preferably 60 parts by mass or less, still more preferably 50 parts by mass or less, based on 100 parts by mass of the rubber component. When it is within the above range, the effect tends to be obtained more favorably.

[0099] In the rubber composition for cap tread, the content of the liquid plasticizer in a liquid state at normal temperature (25 °C) is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, and preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 35 parts by mass or less, based on 100 parts by mass of the rubber component. When it is within the above range, the effect tends to be obtained more favorably. Note that the content of the liquid plasticizer includes the amount of oil contained in the oil-extended rubber and the amount of liquid resin of the resin-extended rubber extended with the liquid resin.

[0100] In the rubber composition for cap tread, the content of the above resin (total amount of resin) is preferably 15 parts by mass or more, more preferably 25 parts by mass or more, still more preferably 30 parts by mass or more, and preferably 80 parts by mass or less, more preferably 60 parts by mass or less, still more preferably 50 parts by mass or less, based on 100 parts by mass of the rubber component. When it is within the above range, the effect tends to be obtained more favorably.

[0101] In the rubber composition for cap tread, the oil content (total amount of oil) is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, and preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 35 parts by mass or less, based on 100 parts by mass of the rubber component. When it is within the above range, the effect tends to be obtained more favorably. Note that the oil content includes the amount of oil contained in the oil-extended rubber.

[0102] In the rubber composition for base tread, the plasticizer content (total amount of plasticizer) is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 7 parts by mass or more, and preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less, based on 100 parts by mass of the rubber component. When it is within the above range, the effect tends to be obtained more favorably. Note that the plasticizer content includes the amounts of oil and resin contained in the oil-extended rubber and the resin-extended rubber.

[0103] In the rubber composition for base tread, the content of the solid plasticizer in a solid state at room temperature (25 °C) is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, and may be 0 parts by mass or less, based on 100 parts by mass of the rubber component. When it is within the above range, the effect tends to be obtained more favorably.

[0104] In the rubber composition for base tread, the content of the liquid plasticizer 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, still more preferably 7 parts by mass or more, and preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less, based on 100 parts by mass of the rubber component. When it is within the above range, the effect tends to be obtained more favorably. In addition, the content of the liquid plasticizer includes the amount of oil contained in the oil-extended rubber and the amount of the liquid resin of the resin-extended rubber extended with the liquid resin.

[0105] In the rubber composition for the base tread, the content of oil (total amount of oil) is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 7 parts by mass or more, and preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less with respect to 100 parts by mass of the rubber component. When it is within the above range, the effect tends to be obtained better. In addition, the content of oil includes the amount of oil contained in the oil-extended rubber.

[0106] From the viewpoint of obtaining better effects, in the above tire, it is desirable that the content Rc (parts by mass) of the resin with respect to 100 parts by mass of the rubber component in the rubber composition for the cap tread is more than the content Ob (parts by mass) of the oil with respect to 100 parts by mass of the rubber component in the rubber composition for the base tread.

[0107] The ratio (Rc / Ob) of Rc to Ob is preferably 2.0 or more, more preferably 4.0 or more, still more preferably 4.3 or more, and preferably 10.0 or less, more preferably 6.0 or less, still more preferably 5.5 or less. When it is within the above range, the effect tends to be obtained better.

[0108] When Rc / Ob is adjusted to a predetermined range, the mechanism by which more effects can be obtained is not clear. However, by blending more of the resin content (Rc) of the cap tread than the oil content (Ob) of the base tread, the change over time in the hardness Hs due to the bleed of oil can be more suppressed. Therefore, it is presumed that the durability performance of the tire is improved.

[0109] The rubber composition for the cap tread and the rubber composition for the base tread preferably contain a filler. The filler is not particularly limited, and materials known in the rubber field can be used. For example, inorganic fillers such as carbon black, silica, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, mica, biochar (BIO CHAR); poorly dispersible fillers, etc. can be mentioned. Among them, from the viewpoint of obtaining more effects, carbon-derived fillers (carbon-containing fillers) such as carbon black and silica are preferred.

[0110] In the rubber composition for cap tread and the rubber composition for base tread, the carbon black that can be used is not particularly limited, but examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. As commercial products, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nippon Chemical Carbon Co., Ltd., Columbian Carbon Company, etc. can be used. These may be used alone or in combination of two or more. In addition to carbon black made from conventional mineral oil and the like as raw materials, carbon black made from biomass materials such as lignin as raw materials may also be used. Further, recycled carbon black obtained by decomposing rubber products, plastic products, etc. containing carbon black such as tires can be appropriately used by substituting an equal amount for the above carbon black.

[0111] The nitrogen adsorption specific surface area (N2SA) of carbon black is preferably 5 m 2 / g or more, more preferably 10 m 2 / g or more, and still more preferably 15 m 2 / g or more. Also, the above N2SA is preferably 150 m 2 / g or less, more preferably 130 m 2 / g or less, and still more preferably 120 m 2 / g or less. When within the above range, the effect tends to be obtained better. Note that the nitrogen adsorption specific surface area of carbon black is determined according to JIS K6217-2:2001.

[0112] The dibutyl phthalate absorption (DBP) of carbon black is preferably 40 ml / 100 g or more, more preferably 60 ml / 100 g or more, still more preferably 70 ml / 100 g or more. Also, when the above DBP is within the range of preferably 200 ml / 100 g or less, more preferably 150 ml / 100 g or less, still more preferably 100 ml / 100 g or less, the effect tends to be obtained more favorably. Incidentally, the DBP of carbon black is determined by the measuring method of JIS K6217-4:2001.

[0113] In the rubber composition for cap tread and the rubber composition for base tread, the silica that can be used is not particularly limited. For example, silica prepared by the dry method (anhydrous silica), silica prepared by the wet method (hydrous silica), etc., which are common in the tire industry, can be used. The raw material of silica is not particularly limited. For example, it may be a raw material derived from minerals such as quartz, or a raw material derived from organisms such as rice husks (for example, silica using biomass materials such as rice husks as raw materials), or silica recycled from products containing silica may be used. Among them, hydrous silica prepared by the wet method is preferable because it has many silanol groups. These silicas may be used alone or in combination of two or more.

[0114] Silica using biomass materials as raw materials can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and reacting the silicate with sulfuric acid in the same manner as conventional wet silica to precipitate silicon dioxide, followed by filtration, washing with water, drying, and pulverization.

[0115] Silica recycled from products containing silica can be used, for example, silica recovered from products containing silica such as electronic parts such as semiconductors, tires, desiccants, and filter materials such as diatomaceous earth. Also, the recovery method is not particularly limited, and examples include pyrolysis and decomposition by electromagnetic waves. Among them, silica recovered from electronic parts such as semiconductors or tires is preferable.

[0116] When silica crystallizes, it becomes insoluble in water and the silicic acid that is its component cannot be utilized. By controlling the combustion temperature and combustion time, crystallization of silica in rice husk ash can be suppressed (see, for example, Japanese Patent Application Laid-Open No. 2009-2594, Akita Prefectural University Web Journal B / 2019, vol. 6, p. 216-222, etc.).

[0117] As the amorphous silica extracted from rice husks, those commercially available from Wilmar Co., Ltd. and others can be used.

[0118] The nitrogen adsorption specific surface area (N2SA) of silica is preferably 50 m 2 / g or more, more preferably 100 m 2 / g or more, still more preferably 150 m 2 / g or more. Also, the upper limit of the N2SA of silica is not particularly limited, but is preferably 350 m 2 / g or less, more preferably 300 m 2 / g or less, still more preferably 250 m 2 / g or less. When within the above range, the effect tends to be obtained more favorably. Note that the N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0119] Examples of the poorly dispersible filler include microfibrillated plant fibers, short fibrous cellulose, gel-like compounds, etc. Among them, microfibrillated plant fibers are preferred.

[0120] As the microfibrillated plant fiber, cellulose microfibril is preferable from the viewpoint of obtaining good reinforcing property. The cellulose microfibril is not particularly limited as long as it is derived from natural products. For example, resource biomass such as fruits, grains, and root vegetables, wood, bamboo, hemp, jute, kenaf, pulp, paper, cloth obtained from these as raw materials, waste biomass such as agricultural crop residues, food waste, and sewage sludge, unused biomass such as rice straw, wheat straw, and thinned wood, and those derived from cellulose produced by tunicates, acetic acid bacteria, etc. may be mentioned. These microfibrillated plant fibers may be used alone or in combination of two or more.

[0121] In the present specification, the cellulose microfibril typically means a cellulose fiber having an average fiber diameter within the range of 10 μm or less, and more typically a cellulose fiber having a fine structure with an average fiber diameter of 500 nm or less formed by an aggregation of cellulose molecules. A typical cellulose microfibril is formed as an aggregate of cellulose fibers having the average fiber diameter as described above, for example.

[0122] In the rubber composition for a cap tread, the content of the filler (total amount of fillers such as silica and carbon black) is preferably 50 parts by mass or more, more preferably 80 parts by mass or more, still more preferably 83 parts by mass or more, and preferably 200 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 100 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the comprehensive performance of the durability performance and the sustainability of the wet grip performance after aging tends to be improved.

[0123] When the content of the filler is adjusted to be a predetermined amount or more, particularly 50 parts by mass or more, the mechanism by which more effects are obtained is not clear, but it is considered that by increasing the amount of the filler, the polymer ratio is reduced, and thereby the change in physical properties after heat aging can be suppressed. Therefore, it is presumed that the comprehensive performance of the durability performance and the sustainability of the wet grip performance after aging is improved.

[0124] In the rubber composition for cap tread, the content of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0125] In the rubber composition for cap tread, the content of silica based on 100 parts by mass of the rubber component is preferably 60 parts by mass or more, more preferably 70 parts by mass or more, still more preferably 75 parts by mass or more, and preferably 150 parts by mass or less, more preferably 130 parts by mass or less, still more preferably 120 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0126] When the rubber composition for cap tread 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, still more preferably 5 parts by mass or more, based on 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, still more preferably 20 parts by mass or less, particularly preferably 10 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0127] In the rubber composition for base tread, the content of the filler (total amount of fillers such as silica and carbon black) is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 30 parts by mass or more, and preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0128] In the rubber composition for the base tread, the content of carbon black is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 30 parts by mass or more, and preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0129] In the rubber composition for the base tread, the content of silica based on 100 parts by mass of the rubber component is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 5 parts by mass or less, and may be 0 parts by mass. When within the above range, the effect tends to be obtained more favorably.

[0130] When the rubber composition for the base tread 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, still more preferably 5 parts by mass or more, based on 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, still more preferably 20 parts by mass or less, particularly preferably 10 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0131] The ratio (Fc / Fb) of the content Fc of the filler based on 100 parts by mass of the rubber component in the rubber composition for the cap tread to the content Fb of the filler based on 100 parts by mass of the rubber component in the rubber composition for the base tread is preferably 1.6 or more, more preferably 2.2 or more, still more preferably 2.5 or more, particularly preferably 2.7 or more. The upper limit of Fc / Fb is not particularly limited, but is preferably 5.0 or less, more preferably 4.5 or less, still more preferably 4.0 or less. When within the above range, the effect tends to be obtained more favorably.

[0132] When Fc / Fb is adjusted to be equal to or greater than a predetermined value, particularly 2.2 or greater, the mechanism by which more effects can be obtained is not clear. However, by formulating the filler content (Fc) of the cap tread to be equal to or greater than a predetermined value more than the filler content (Fb) of the base tread, the polymer ratio in the cap tread is reduced, and thereby, it is considered that changes in physical properties after heat aging can be suppressed. Therefore, it is presumed that the durability performance is improved.

[0133] The ratio (Cc / Cb) of the carbon black content Cc per 100 parts by mass of the rubber component in the rubber composition for the cap tread to the carbon black content Cb per 100 parts by mass of the rubber component in the rubber composition for the base tread is preferably 0.10 or more, more preferably 0.15 or more, and still more preferably 0.17 or more. The upper limit of Cc / Cb is not particularly limited, but is preferably 0.30 or less, more preferably 0.23 or less, and still more preferably 0.20 or less. When within the above range, the effects tend to be obtained more favorably.

[0134] When Cc / Cb is adjusted to be equal to or greater than a predetermined value, particularly 0.15 or greater, the mechanism by which more effects can be obtained is not clear. However, by formulating the carbon black content (Cc) of the cap tread to be equal to or greater than a predetermined value more than the carbon black content (Cb) of the base tread, the polymer ratio in the cap tread is reduced, and thereby, it is considered that changes in physical properties after heat aging can be suppressed. Therefore, it is presumed that the comprehensive performance of the durability performance and the sustainability of the wet grip performance over time is improved.

[0135] When the rubber composition for the cap tread and the rubber composition for the base tread contain silica, it is preferable to further contain 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,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, etc. of the sulfide type, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercapto type such as NXT and NXT-Z manufactured by Momentive, vinyl type such as vinyltriethoxysilane and vinyltrimethoxysilane, amino type such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy type such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, nitro type such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, chloro type such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane, etc. can be mentioned. As commercially available products, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azmax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used. These may be used alone or in combination of two or more kinds.

[0136] In the rubber composition for cap tread and the rubber composition for base tread, the content of the silane coupling agent is preferably 0.1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more with respect 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, still more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0137] The rubber composition for cap tread and the rubber composition for base tread preferably contain an antioxidant from the viewpoints of crack resistance, ozone resistance, etc.

[0138] The anti-aging agent is not particularly limited, but examples include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine-based anti-aging agents such as 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), N,N'-ditoly-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; bis, tris, polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, etc. Among them, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferred, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and polymers of 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. As commercial products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., Flexsys Co., etc. can be used.

[0139] In the rubber composition for cap tread and the rubber composition for base tread, the content of the anti-aging agent is preferably 0.2 parts by mass or more, more preferably 2.0 parts by mass or more, and still more preferably 2.5 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 7.0 parts by mass or less, and more preferably 3.5 parts by mass or less.

[0140] The rubber composition for cap tread and the rubber composition for base tread preferably contain stearic acid. In the rubber composition for cap tread and the rubber composition for base tread, the content of stearic acid is preferably 0.5 parts by mass or more, more preferably 2.0 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component.

[0141] As the stearic acid, conventionally known ones can be used. For example, products of NOF Corporation, Kao Corporation, FUJIFILM Wako Pure Chemical Corporation, Chiba Fatty Acids Co., Ltd., etc. can be used.

[0142] The rubber composition for cap tread and the rubber composition for base tread preferably contain zinc oxide. In the rubber composition for cap tread and the rubber composition for base tread, the content of zinc oxide is preferably 0.5 parts by mass or more, more preferably 2.0 parts by mass or more, and preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, based on 100 parts by mass of the rubber component.

[0143] As the zinc oxide, conventionally known ones can be used. For example, products of Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Shoindo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0144] The rubber composition for cap tread and the rubber composition for base tread may be compounded with wax. In the rubber composition for cap tread and the rubber composition for base tread, the content of wax is preferably 1.0 parts by mass or more, more preferably 1.5 parts by mass or more, and preferably 10.0 parts by mass or less, more preferably 2.0 parts by mass or less, based on 100 parts by mass of the rubber component.

[0145] The wax is not particularly limited, and any wax commonly used in the tire industry can be preferably used. For example, petroleum waxes, mineral waxes, synthetic waxes, plant-derived waxes, etc. can be mentioned. Among them, petroleum waxes and plant-derived waxes are preferred, and petroleum waxes are more preferred. Examples of plant-derived waxes include rice wax, carnauba wax, candelilla wax, etc. Examples of petroleum waxes include paraffin wax, microcrystalline wax, and their selected special waxes, etc., and paraffin wax is preferred. Note that the wax according to this embodiment does not contain stearic acid. As the wax, for example, those commercially available from Ouchi Shinsei Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., etc. can be used. These waxes may be used alone or in combination of two or more.

[0146] For the rubber composition for cap tread and the rubber composition for base tread, it is preferable to compound sulfur in terms of forming appropriate cross-linked chains in the polymer chain and imparting good performance.

[0147] In the rubber composition for cap tread, the sulfur content is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, still more preferably 1.5 part by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, still more preferably 2.0 parts by mass or less.

[0148] In the rubber composition for base tread, the sulfur content is preferably 1.0 part by mass or more, more preferably 2.0 part by mass or more, still more preferably 2.5 part by mass or more, based on 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, still more preferably 4.0 parts by mass or less.

[0149] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. As commercial products, products of companies such as Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexsys, Nippon Retort Industry Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

[0150] In addition to the above components, compounding agents commonly used in the tire industry, such as mold release agents and other materials, may be appropriately compounded into the rubber composition for cap tread and the rubber composition for base tread.

[0151] In this specification, various materials containing carbon atoms (such as rubber, oil, resin, vulcanization accelerator, anti-aging agent, surfactant, etc.) may be derived from carbon dioxide in the atmosphere. As a method for obtaining the above-mentioned compound from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through the methanation process of synthesizing methane from carbon dioxide may be converted.

[0152] From the perspective of the comprehensive performance of the durability performance and the sustainability of the wet grip performance after aging, it is desirable that the content of the polymer having ethylene units in 100% by mass of the rubber component is 50% by mass or more, and the content of the resin with respect to 100 parts by mass of the rubber component is 20 parts by mass or more.

[0153] When the content of the polymer having ethylene units and the content of the resin are adjusted to be above a certain level, the mechanism by which more effects can be obtained is not clear. However, by combining the compound represented by formula (1) with a formulation containing a polymer having ethylene units with few double bonds and good physical properties after heat aging, the mono-crosslinking ratio increases, and furthermore, the change in hardness and the change in tensile properties after heat aging are reduced. Also, by adding more resin, the change in hardness over time is reduced. Therefore, it is considered that the comprehensive performance of the durability performance and the sustainability of the wet grip performance after aging is improved.

[0154] The rubber composition for cap tread and the rubber composition for base tread can be produced, for example, by kneading the above components using a rubber kneading apparatus such as an open roll or a Banbury mixer and then vulcanizing them.

[0155] As the kneading conditions, in the base kneading step of kneading additives other than the crosslinking agent (vulcanizing agent) and the vulcanization accelerator, the kneading temperature is preferably 100 °C or higher, more preferably 120 °C or higher, and preferably 180 °C or lower, more preferably 170 °C or lower. In the finishing kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is preferably 80 °C or higher and preferably 120 °C or lower, more preferably 110 °C or lower. Further, the composition kneaded with the vulcanizing agent and the vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. As the vulcanization temperature, it is preferably 140 °C or higher, more preferably 150 °C or higher, and preferably 190 °C or lower, more preferably 185 °C or lower.

[0156] The rubber composition for cap tread and the rubber composition for base tread are respectively used for the cap tread and the base tread of the tire member.

[0157] In this specification, the cap tread is a rubber layer that forms the outermost layer in the tire radial direction among the rubber layers constituting the tread. When the tread is a single-layer structure tread, it is the single-layer structure tread itself. When the tread is a two-layer structure tread of a cap tread and a base tread, it is the rubber layer that forms the surface layer. When the tread has a structure of three or more layers, it is the rubber layer that forms the outermost layer that corresponds to the cap tread, respectively.

[0158] In this specification, the base tread is a rubber layer disposed inside the cap tread in the tire radial direction, which forms the outermost layer in the tire radial direction among the rubber layers constituting the tread of the multi-layer structure. In the case of a tread with a two-layer structure of a cap tread and a base tread, it is the rubber layer forming the inner side in the tire radial direction. In the case of a tread having a structure of three or more layers, one or more rubber layers disposed inside the cap tread in the tire radial direction correspond to the base tread respectively.

[0159] The above tire is manufactured by a normal method using the above rubber composition for cap tread and rubber composition for base tread. That is, a composition blended with various additives as required is extruded according to the shapes of the cap tread and the base tread at the unvulcanized stage, formed by a normal method on a tire molding machine, bonded together with other tire members to form an unvulcanized tire, and then heated and pressurized in a vulcanizer to manufacture the tire.

[0160] The above tire is not particularly limited, and examples include pneumatic tires, solid tires, airless tires, etc. Among them, pneumatic tires are preferred.

[0161] The above tire is preferably used as a passenger car tire, a large passenger car tire, a large SUV tire, a truck / bus tire, a two-wheeler tire, a racing tire, a winter tire (studless tire, snow tire, stud tire), an all-season tire, a run-flat tire, an aircraft tire, a mining tire, etc.

[0162] In the above tire, the thickness Tc (mm) of the cap tread is preferably 12 mm or less, more preferably 10 mm or less, and still more preferably 9 mm or less. The lower limit is preferably 5 mm or more, more preferably 6 mm or more, and still more preferably 7 mm or more. When within the above range, the effect tends to be preferably obtained.

[0163] In the above tire, the thickness Tb (mm) of the base tread is preferably 4 mm or less, more preferably 3 mm or less. The lower limit is preferably 0.5 mm or more, more preferably 1 mm or more. When within the above range, the effect tends to be preferably obtained.

[0164] Tc / Tb is preferably 1.5 or more, more preferably 2.1 or more, still more preferably 3.0 or more, and particularly preferably 3.5 or more. The upper limit is preferably 9.2 or less, more preferably 7.0 or less, still more preferably 5.0 or less. When within the above range, the effect tends to be preferably obtained.

[0165] When Tc / Tb is adjusted to a predetermined range, the mechanism by which a more effective result is obtained is not clear, but it is considered that the change over time in the hardness Hs due to the bleed of the plasticizer can be more suppressed. Therefore, it is presumed that the durability performance of the tire is improved.

[0166] In the above tire, the ratio (Dc / Tc) of the content Dc (parts by mass) of the compound represented by the above formula (1) to 100 parts by mass of the rubber component in the cap tread rubber composition and the thickness Tc (mm) of the cap tread is preferably 0.01 or more, more preferably 0.02 or more, still more preferably 0.04 or more, and particularly preferably 0.06 or more. The upper limit is preferably 0.15 or less, more preferably 0.12 or less, still more preferably 0.10 or less. When within the above range, the effect tends to be preferably obtained.

[0167] When Dc / Tc is adjusted to a predetermined value or more, the mechanism by which a more effective result is obtained is not clear, but it is considered that by blending a larger amount of the compound of formula (1) per unit thickness, the co-crosslinkability between the cap tread and the base tread is improved, and the change over time in the hardness Hs due to the bleed of the oil can be more suppressed. Therefore, it is presumed that the durability performance of the tire is improved.

[0168] In addition, in this specification, the thickness Tc of the cap tread (cap layer) refers to the thickness of the cap tread on the tire equatorial plane in the radial cross-section of the tire, and in the radial cross-section of the tire, it is the straight-line distance from the tread surface (the surface of the cap tread) to the inner surface of the cap tread in the tire radial direction.

[0169] The thickness Tb of the base tread (base layer) refers to the thickness of the base tread on the tire equatorial plane in the radial cross-section of the tire, and in the radial cross-section of the tire, it is the straight-line distance from the outer surface of the base tread in the tire radial direction to the inner surface of the base tread in the tire radial direction.

[0170] The thicknesses of the cap tread and the base tread on the tire equatorial plane are the respective values measured along the tire equatorial plane from the outermost surface of the cap tread and the outermost surface of the base tread on the tire equatorial plane. When there is an energizing member or the like on the tire equatorial plane, it is the value measured along the tire equatorial plane from the straight line connecting the ends of the interface blocked by the energizing member. When there is a groove on the tire equatorial plane, it is the thickness measured at the center in the tire width direction of the land portion closest to the tire equatorial plane, and is the thickness measured in the normal direction of the outer surface of the cap tread in the tire radial direction and the outer surface of the base tread in the tire radial direction.

[0171] In this specification, dimensions such as thickness are values measured in a normal state. The "normal state" refers to a state where the tire is mounted on a standard rim, filled with the standard internal pressure, and is in an unloaded state. Here, the "standard rim" is the rim defined for each tire in the standard system including the standard on which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Association), it is the standard rim in the applicable size described in the "JATMA YEAR BOOK"; in the case of ETRTO (The European Tyre and Rim Technical Organisation), it is the "Measuring Rim" described in the "STANDARDS MANUAL"; in the case of TRA (The Tire and Rim Association, Inc.), it is the "Design Rim" described in the "YEAR BOOK". Refer to JATMA, ETRTO, and TRA in this order, and follow the standard if there is an applicable size when referring. In the case of a tire not defined in the standard, it refers to the rim with the smallest rim diameter and then the narrowest rim width among the rims that can be mounted on the tire and can hold the internal pressure, that is, the rim that does not cause air leakage between the rim / tire. Also, the "standard internal pressure" refers to the air pressure defined for each tire in the standard system including the standard on which the tire is based. In the case of JATMA, it is the "maximum air pressure"; in the case of ETRTO, it is the "INFLATION PRESSURE"; in the case of TRA, it refers to the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". Refer to JATMA, ETRTO, and TRA in this order, and follow the standard if there is an applicable size when referring. In the case of a tire not defined in the standard, it refers to the standard internal pressure (however, 250 KPa or more) of another tire size (defined in the standard) with the standard rim described as the standard rim. In the case where multiple standard internal pressures of 250 KPa or more are described, it refers to the minimum value among them.

[0172] Hereinafter, an example of the above tire will be described with reference to the drawings, but it is not limited to such a form.

[0173] In FIG. 1, the vertical 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 symmetric about the left - right axis. The tread 4 includes a cap layer 30 (cap tread) and a base layer 28 (base tread).

[0174] In addition, in FIG. 1, an example of a two - layer structure tread 4 composed of a cap layer 30 and a base layer 28 is shown, but a single - layer structure tread or a tread having a structure of three or more layers may also be used.

[0175] In the tire 2 of FIG. 1, the cap layer 30 is composed of the above - mentioned rubber composition for cap tread, and the base layer 28 is composed of the rubber composition for base tread. The cap layer 30 contains a polymer having an ethylene unit, an isoprene - based rubber, and the compound represented by the above formula (1), and the content of the isoprene - based rubber in 100% by mass of the rubber component is 20% by mass or more. Also, the content of the isoprene - based rubber in 100% by mass of the rubber component of the base layer 28 is larger than the content of the isoprene - based rubber in 100% by mass of the rubber component of the cap layer 30.

[0176] In the tire 2, each sidewall 6 extends substantially radially inward from the end of the tread 4. The outer radial portion of this sidewall 6 is joined to the tread 4. The inner radial portion of this sidewall 6 is joined to the clinch 10. This sidewall 6 can prevent damage to the carcass 14.

[0177] Each wing 8 in FIG. 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.

[0178] Each clinch 10 is located substantially radially inside the sidewall 6 and has a portion in contact with the rim at at least one place.

[0179] The carcass 14 is provided with a carcass ply 36. In this tire 2, the carcass 14 consists of one carcass ply 36, but it may be composed of two or more plies.

[0180] In this tire 2, the carcass ply 36 is spanned between the bead cores 32 on both sides and runs along the tread 4 and the sidewall 6. The carcass ply 36 is folded back from the axial inner side to the outer side around each bead core 32. Due to this folding, a main part 36a and a pair of folded parts 36b are formed on the carcass ply 36. That is, the carcass ply 36 is provided with a main part 36a and a pair of folded parts 36b.

[0181] Each bead core 32 is provided with a bead apex 34 that extends radially outward from this bead core 32. The bead core 32 is ring-shaped and preferably includes a wound non-stretchable wire. The bead apex 34 tapers radially outward.

[0182] Although not shown, the carcass ply 36 preferably consists of a number of parallel cords and topping rubber. The absolute value of the angle formed by each cord with respect to the equatorial plane CL is preferably from 75° to 90°. In other words, this carcass 14 preferably has a radial structure.

[0183] The belt layer 16 in FIG. 1 is located radially inside 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 of FIG. 1, the belt layer 16 consists of an inner layer 38 and an outer layer 40. As is clear from FIG. 1, in the axial direction, it is desirable that the width of the inner layer 38 is slightly larger than the width of the outer layer 40. In this tire 2, the axial width of the belt layer 16 is preferably not less than 0.6 times and not more than 0.9 times the cross-sectional width of the tire 2.

[0184] Each of the inner layer 38 and the outer layer 40 preferably consists of a number of parallel single-wire steel cords (steel monofilaments) and topping rubber (coating rubber). In other words, the belt layer 16 includes a number of parallel steel monofilaments.

[0185] The band 18 in FIG. 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. This band 18 may have a width larger than the width of this belt layer 16.

[0186] Although not shown, the band 18 preferably consists of a cord and topping rubber. The cord is wound in a spiral. 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, more preferably 2° or less. Since the belt layer 16 is restrained by this cord, the lifting of the belt layer 16 is suppressed.

[0187] The belt layer 16 and the band 18 in FIG. 1 constitute a reinforcing layer. The reinforcing layer may be constituted by only the belt layer 16.

[0188] FIG. 2 is an enlarged view near the tread 4 in FIG. 1. The tire in FIG. 2 is a tire 2 having a groove 26 on the tire equatorial plane (CL). In this case, the cap tread thickness (Tc) is the thickness measured at the center in the tire width direction of the land portion closest to the groove 26 on the tire equatorial plane in the radial cross-section of the tire, and is the thickness measured in the normal direction of the surface of the cap layer 30 (cap tread). Specifically, it refers to the linear distance in the normal direction from the outer surface of the cap layer 30 in the tire radial direction to the interface on the outermost surface side of the tire of the base layer 28. Further, the thickness (Tb) of the base tread is the thickness measured at the center in the tire width direction of the land portion closest to the groove 26 on the tire equatorial plane in the radial cross-section of the tire, and is the thickness measured in the normal direction of the outer surface of the base layer 28 (base tread) in the tire radial direction. Specifically, it refers to the linear distance in the normal direction from the outer surface of the base layer 28 to the interface on the outermost surface side of the tire of the band 18.

[0189] The inner liner 20 is located inside the carcass 14. The inner liner 20 is joined 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 holds the internal pressure of the tire 2.

[0190] Each chafer 22 is located near the bead 12. In this embodiment, it is desirable that the chafer 22 is composed of a cloth and rubber impregnated in this cloth. This chafer 22 may be integrated with the clinch 10.

[0191] In this tire 2, the tread 4 has main grooves 42 as grooves 26. As shown in FIG. 1, a plurality of, specifically, three main grooves 42 are engraved in this tread 4. These main grooves 42 are arranged at intervals in the axial direction. By engraving three main grooves 42 in this tread 4, four ribs 44 extending in the circumferential direction are formed. That is, the main groove 42 is between the ribs 44.

[0192] Each main groove 42 extends in the circumferential direction. The main groove 42 is continuous without interruption in the circumferential direction. The main groove 42 promotes the drainage of water existing between the road surface and the tire 2, for example, in rainy weather. Therefore, even when the road surface is wet, the tire 2 can sufficiently contact the road surface.

[0193] In tire 2, for the content Rc (parts by mass) of the resin, the content Oc (parts by mass) of the oil, the content Ob (parts by mass) of the oil with respect to 100 parts by mass of the rubber component in the base layer, the content Pc (parts by mass) of the plasticizer with respect to 100 parts by mass of the rubber component in the cap layer 30, the content Pb (parts by mass) of the plasticizer with respect to 100 parts by mass of the rubber component in the base layer 28, the content Fc of the filler with respect to 100 parts by mass of the rubber component in the cap layer 30, the content Fb of the filler with respect to 100 parts by mass of the rubber component in the base layer, the content Cc of carbon black with respect to 100 parts by mass of the rubber component in the cap layer 30, the content Cb of carbon black with respect to 100 parts by mass of the rubber component in the base layer 28, the thickness Tc (mm) of the cap layer 30, and the thickness Tb (mm) of the base layer 28, it is desirable that Rc / Oc, Oc / Ob, Rc / Ob, Pc / Pb, Fc / Fb, Cc / Cb, Tc / Tb, and Rc / Tc are within the aforementioned ranges.

Example

[0194] Hereinafter, examples (examples) considered preferable for implementation will be shown, but the scope of the present disclosure is not limited to the examples.

[0195] Hereinafter, various chemicals used in synthesis and polymerization will be collectively described. The chemicals are purified according to established methods as necessary. n-Hexane: manufactured by Kanto Chemical Co., Inc. Styrene: manufactured by Kanto Chemical Co., Inc. Butadiene: 1,3-butadiene manufactured by Tokyo Chemical Industry Co., Ltd. TMEDA: N,N,N’,N’-tetramethylethylenediamine manufactured by Kanto Chemical Co., Inc. n-Butyllithium solution: 1.6M n-butyllithium hexane solution manufactured by Kanto Chemical Co., Inc.

[0196] Also, the evaluation method of the copolymer will be collectively described below.

[0197] (Measurement of the hydrogenation rate of the conjugated diene part of the copolymer) A solution with a concentration of 15% by mass is prepared using carbon tetrachloride as a solvent, and it is calculated from the spectral reduction rate of the unsaturated bond part of the 100 MHz 1 1H-NMR.

[0198] (Measurement of styrene content) At 25 °C, using a JEOL JNM-A 400 NMR apparatus 1 1H-NMR is measured, and the styrene content is determined from the ratio of phenyl protons based on the styrene unit at 6.5 - 7.2 ppm and vinyl protons based on the butadiene unit at 4.9 - 5.4 ppm obtained from the spectrum.

[0199] (Measurement of weight-average molecular weight (Mw)) The weight-average molecular weight (Mw) of the copolymer is determined by standard polystyrene conversion based on the measured values obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0200] (Production Example 1: Synthesis of hydrogenated styrene-butadiene copolymer 1: Hydrogenation rate 95 mol%) 2000 ml of n-hexane, 60 g of styrene, 140 g of butadiene, 0.93 g of TMEDA, and 0.45 mmol of n-butyllithium are added to a heat-resistant reaction vessel sufficiently purged with nitrogen, and the mixture is stirred at 50 °C for 5 hours to carry out a polymerization reaction. Then, while supplying hydrogen gas at a pressure of 0.4 MPa-Gauge, the mixture is stirred for 20 minutes to react with the unreacted polymer terminal lithium to form lithium hydride. The hydrogen gas supply pressure is set to 0.7 MPa-Gauge and the reaction temperature is set to 90 °C, and hydrogenation is carried out using a catalyst mainly composed of titanocene dichloride. When the integrated amount of hydrogen absorption reaches the target hydrogenation rate, the reaction temperature is returned to room temperature, the hydrogen pressure is returned to normal pressure, and the reaction solution is withdrawn from the reaction vessel and stirred into water to remove the solvent by steam stripping, thereby obtaining hydrogenated styrene-butadiene copolymer 1 (hydrogenation rate: 95 mol%, weight-average molecular weight (Mw): 450,000, styrene content: 30% by mass, butadiene content: 70% by mass).

[0201] (Production Example 2: Synthesis of Hydrogenated Styrene-Butadiene Copolymer 2: Hydrogenation Rate 80 mol%) Except for adjusting the integrated amount of hydrogen suction so as to obtain the target hydrogenation rate, hydrogenated styrene-butadiene copolymer 2 (hydrogenation rate: 80 mol%, weight average molecular weight (Mw): 480,000, styrene content: 30 mass%, butadiene content: 70 mass%) is obtained according to the same formulation as hydrogenated styrene-butadiene copolymer 1.

[0202] Hereinafter, various chemicals used in the production of the cap tread and the base tread will be collectively described. The chemicals are purified according to a conventional method as necessary. (Cap Tread) Hydrogenated styrene-butadiene copolymers 1 to 2: The above Production Examples 1 to 2 (polymers having ethylene units) NR: TSR20 Carbon black: Shaw black N220 manufactured by Cabot Japan Co., Ltd. (N2SA: 111 m 2 / g) Silica: Ultrasil VN3 manufactured by Evonik Degussa GmbH (N2SA: 175 m 2 / g) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa GmbH Wax: Oz Ace 0355 manufactured by Nippon Seiro Co., Ltd. Antioxidant: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Oil: Vivatec 500 (TDAE, aromatic process oil) manufactured by H&R Resin 1: Sylvatraxx 4401 (styrene α-methylstyrene resin (copolymer of styrene and α-methylstyrene)) manufactured by Arizona Chemical Resin 2: PR120 (hydrogenated dicyclopentadiene resin, softening point 120°C) manufactured by ExxonMobil Stearic acid: Tsubaki manufactured by NOF Corporation Zinc Oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd. Vulcanization Accelerator CZ: Nocceler CZ-G (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization Accelerator DPG: Nocceler D (N,N'-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization Accelerator TBzTD: Sanseler TBzTD (tetrabenzylthiuram disulfide) manufactured by Sanshin Chemical Industry Co., Ltd.

[0203] (Base tread) NR: SIR20 BR: BR150B manufactured by Ube Industries, Ltd. Carbon Black: Shaw Black N220 (N2SA: 111 m 2 / g) manufactured by Cabot Japan Ltd. Oil: Aroma Oil manufactured by JX Nippon Oil & Energy Corporation Stearic Acid: Tsubaki manufactured by NOF Corporation Zinc Oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Antioxidant: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Wax: Oz Ace 0355 manufactured by Nippon Seiro Co., Ltd. Sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd. Vulcanization Accelerator TBBS: Nocceler NS (N-tert-butyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0204] (Preparation of Rubber Composition for Cap Tread) According to the formulation shown in Table 1, using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd., materials other than sulfur and vulcanization accelerator were kneaded at 150 °C for 5 minutes to obtain a kneaded product. Sulfur and vulcanization accelerator were added to the kneaded product, and it was kneaded using an open roll at 80 °C for 5 minutes to obtain an unvulcanized rubber composition.

[0205] (Preparation of Rubber Composition for Base Tread) According to the compounding ingredients shown in Table 2, using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd., materials other than sulfur and vulcanization accelerators are kneaded at 150 °C for 5 minutes to obtain a kneaded product. Sulfur and vulcanization accelerators are added to the kneaded product, and it is kneaded at 80 °C for 5 minutes using an open roll to obtain an unvulcanized rubber composition.

[0206] <Manufacturing Method of Test Tires>[ According to the specifications in Table 3, the above unvulcanized cap tread rubber composition is formed into the shape of a cap tread, and the above unvulcanized base tread rubber composition is formed into the shape of a base tread. On a tire molding machine, they are bonded together with other tire members to form an unvulcanized tire, which is vulcanized at 170 °C for 10 minutes to manufacture test tires (size 205 / 70R15, passenger car tires).

[0207] Assuming test tires obtained from compositions with formulations and specifications changed according to Table 3, the results calculated based on the following evaluation methods are shown in each table. Note that the reference comparative examples are as follows. Table 3: Comparative Example 1 (endurance performance), Example 1 (persistence of wet grip performance after aging)

[0208] <Endurance Performance>[ The above test tires are mounted on a rim (17×7.00JJ), filled with an internal pressure of 300 kPa, and carried out in a step speed manner in accordance with the load / speed performance test defined by ECE30 using a drum tester. During the test, the running speed is gradually increased, and the speed and time when the tire breaks are measured. The results are shown as an index with Comparative Example 1 set to 100. The larger the index, the better the endurance performance (high-speed endurance performance).

[0209] <Persistence of Wet Grip Performance after Aging>[ (New) Each test tire is mounted on a domestically produced 2000 cc FF vehicle, and the vehicle is driven on a wet road surface at 25 °C. The vehicle travels at a speed of 150 km / h and the brake is applied until the vehicle stops, and the stopping distance (initial) required until it stops is measured. (Wet grip performance after aging) After the above vehicle running of 20,000 km, the stopping distance (after aging) required until it stops is measured by the same method. Based on the stopping distances of each test tire before and after aging, the maintenance rate (%) of the wet grip performance is calculated. The results are shown by an index with the maintenance rate of Example 1 being 100. The larger the index, the better the durability of the wet grip performance.

[0210] [Table 1]

[0211] [Table 2]

[0212] [Table 3]

[0213] The present invention <1> is a tire provided with a cap tread and a base tread, The cap tread contains a polymer having ethylene units, an isoprene rubber, and a compound represented by the following formula (1), and the content of the isoprene rubber in 100% by mass of the rubber component is 20% by mass or more. A tire characterized in that the content of the isoprene rubber in 100% by mass of the rubber component of the base tread is more than the content of the isoprene rubber in 100% by mass of the rubber component of the cap tread. (1) R 1 R 2 N-(C=S)-Sz(C=S)-NR 3 R 4 (In the formula, z represents an integer from 1 to 8. R1 ~R 4 represents, the same or different, a hydrogen atom or a hydrocarbon group having 1 to 15 carbon atoms.)

[0214] The present invention <2> is the tire according to the present invention <1>, wherein the content of the compound represented by the formula (1) is 0.1 part by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0215] The present invention <3> is that the cap tread is the content of the polymer having an ethylene unit in 100% by mass of the rubber component is 50% by mass or more, and the content of the resin with respect to 100 parts by mass of the rubber component is 20 parts by mass or more is the tire according to the present invention <1> or <2>.

[0216] The present invention <4> is the tire according to the present invention <3>, wherein the resin contains a hydrogenated resin.

[0217] The present invention <5> is the tire in any combination with any one of the present inventions <1> to <4>, wherein the content of the filler with respect to 100 parts by mass of the rubber component in the cap tread is 80 parts by mass or more.

[0218] The present invention <6> is the tire in any combination with any one of the present inventions <1> to <5>, wherein the ratio (Ib / Ic) of the content Ib of the isoprene rubber in 100% by mass of the rubber component of the base tread to the content Ic of the isoprene rubber in 100% by mass of the rubber component of the cap tread is 2.3 or more.

[0219] The present invention <7> is the tire in any combination with any one of the present inventions <1> to <6>, wherein the ratio (Rc / Ob) of the content Rc (parts by mass) of the resin with respect to 100 parts by mass of the rubber component in the cap tread to the content Ob (parts by mass) of the oil with respect to 100 parts by mass of the rubber component in the base tread is 2.0 or more and 10.0 or less.

[0220] The tire of the present invention <8> is a tire which is any combination of any one of the present inventions <1> to <7> in which the ratio (Fc / Fb) of the content Fc of the filler to 100 parts by mass of the rubber component in the cap tread and the content Fb of the filler to 100 parts by mass of the rubber component in the base tread is 2.2 or more.

[0221] The tire of the present invention <9> is a tire which is any combination of any one of the present inventions <1> to <8> in which the ratio (Cc / Cb) of the content Cc of carbon black to 100 parts by mass of the rubber component in the cap tread and the content Cb of carbon black to 100 parts by mass of the rubber component in the base tread is 0.15 or more.

[0222] The tire of the present invention <10> is a tire which is any combination of any one of the present inventions <1> to <9> in which the ratio (Tc / Tb) of the thickness Tc (mm) of the cap tread and the thickness Tb (mm) of the base tread is 2.1 or more and 9.2 or less.

[0223] The tire of the present invention <11> is a tire which is any combination of any one of the present inventions <1> to <10> in which the ratio (Dc / Tc) of the content Dc (parts by mass) of the compound represented by the formula (1) to 100 parts by mass of the rubber component in the cap tread and the thickness Tc (mm) of the cap tread is 0.02 or more.

Explanation of symbols

[0224] 2 Tire 4 Tread 6 Sidewall 8 Wing 10 Clincher 12 Bead 14 Carcass 16 Belt layer 18 Band 20 Inner liner 22 Chafer 24 Tread surface 26 Groove 28 Base layer 30 Cap layer 32 Core 34 Apex 36 Carcass Ply 36a Main Part 36b Folded-back Part 38 Inner Layer 40 Outer Layer 42 Main Groove 44 Rib CL Equatorial Plane of Tire Tc Thickness of Cap Tread Tb Thickness of Base Tread

Claims

1. A tire comprising a cap tread and a base tread, The cap tread contains a polymer having ethylene units, an isoprene rubber, and a compound represented by the following formula (1), and the content of the isoprene rubber in 100% by mass of the rubber component is 20% by mass or more, A tire characterized in that the content of the isoprene rubber in 100% by mass of the rubber component of the base tread is more than the content of the isoprene rubber in 100% by mass of the rubber component of the cap tread. (1) R １ R ２ N-(C=S)-Sz(C=S)-NR ３ R ４ (In the formula, z represents an integer from 1 to 8. R １ to R ４ are the same or different and represent a hydrogen atom or a hydrocarbon group having 1 to 15 carbon atoms.)

2. The tire according to claim 1, wherein the content of the compound represented by formula (1) is 0.1 part by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the rubber component.

3. The cap tread is The content of the polymer having ethylene units in 100% by mass of the rubber component is 50% by mass or more, The content of the resin with respect to 100 parts by mass of the rubber component is 20 parts by mass or more The tire according to claim 1.

4. The tire according to claim 3, wherein the resin contains a hydrogenated resin.

5. The tire according to claim 1, wherein the content of the filler with respect to 100 parts by mass of the rubber component of the cap tread is 80 parts by mass or more.

6. The tire according to claim 1, wherein the ratio (Ib / Ic) of the content Ib of the isoprene rubber in 100% by mass of the rubber component of the base tread to the content Ic of the isoprene rubber in 100% by mass of the rubber component of the cap tread is 2.3 or more.

7. The tire according to claim 1, wherein the ratio (Rc / Ob) of the content Rc (parts by mass) of the resin to 100 parts by mass of the rubber component in the cap tread and the content Ob (parts by mass) of the oil to 100 parts by mass of the rubber component in the base tread is 2.0 or more and 10.0 or less.

8. The tire according to claim 1, wherein the ratio (Fc / Fb) of the content Fc of the filler to 100 parts by mass of the rubber component in the cap tread and the content Fb of the filler to 100 parts by mass of the rubber component in the base tread is 2.2 or more.

9. The tire according to claim 1, wherein the ratio (Cc / Cb) of the content Cc of carbon black to 100 parts by mass of the rubber component in the cap tread and the content Cb of carbon black to 100 parts by mass of the rubber component in the base tread is 0.15 or more.

10. The tire according to claim 1, wherein the ratio (Tc / Tb) of the thickness Tc (mm) of the cap tread and the thickness Tb (mm) of the base tread is 2.1 or more and 9.2 or less.

11. The tire according to claim 1, wherein the ratio (Dc / Tc) of the content Dc (parts by mass) of the compound represented by the formula (1) to 100 parts by mass of the rubber component in the cap tread and the thickness Tc (mm) of the cap tread is 0.02 or more.

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