Tire

Abstract

To provide a tire that is excellent in abrasion resistance at the time of running at high speed.SOLUTION: A tire comprises a tread including rubber components and silica. The rubber components include styrene-butadiene rubber and / or butadiene rubber, and modified isoprene rubber. A total content of the styrene-butadiene rubber and the butadiene rubber in 100 mass% of the rubber components is over 50 mass%, and a content of the modified isoprene rubber is less than 40 mass%. A ratio (S / Ic) of a total styrene amount S (mass%) in the rubber components to the content Ic (mass%) of the modified isoprene rubber is less than 1.00. A ratio (Sc / T) of a content Sc (parts by mass) of the silica with respect to 100 parts by mass of the rubber components to a thickness T (mm) of the tread is over 10.0.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Conventionally, various methods for improving various tire performances have been studied, and in recent years, in particular, improvement in wear resistance during high-speed driving has been demanded.

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 having excellent wear resistance during high-speed driving.

Means for Solving the Problems

[0004] The present invention is a tire including a tread containing a rubber component and silica, wherein the rubber component includes styrene-butadiene rubber and / or butadiene rubber and a modified isoprene-based rubber, the total content of the styrene-butadiene rubber and the butadiene rubber in 100% by mass of the rubber component exceeds 50% by mass, and the content of the modified isoprene-based rubber is less than 40% by mass, the ratio (S / Ic) of the total styrene amount S (% by mass) in the rubber component to the content Ic (% by mass) of the modified isoprene-based rubber is less than 1.00, and relates to a tire in which the ratio (Sc / T) of the content Sc (parts by mass) of the silica to the thickness T (mm) of the tread with respect to 100 parts by mass of the rubber component exceeds 10.0.

Effects of the Invention

[0005] The present invention relates to a tire having a tread containing a rubber component and silica, wherein the rubber component includes styrene-butadiene rubber and / or butadiene rubber and a modified isoprene-based rubber, the total content of the styrene-butadiene rubber and the butadiene rubber in 100% by mass of the rubber component exceeds 50% by mass, the content of the modified isoprene-based rubber is less than 40% by mass, and S / Ic is less than 1.00 and Sc / T exceeds 10.0. Therefore, a tire excellent in wear resistance during high-speed driving can be provided.

Brief Description of Drawings

[0006]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0007] The above tire includes a tread containing a rubber component and silica. The rubber component includes styrene-butadiene rubber and / or butadiene rubber and a modified isoprene-based rubber. The total content of the styrene-butadiene rubber and the butadiene rubber in 100% by mass of the rubber component exceeds 50% by mass, and the content of the modified isoprene-based rubber is less than 40% by mass. Further, the ratio (S / Ic) of the total styrene amount S in the rubber component to the content Ic of the modified isoprene-based rubber is less than 1.00, and the ratio (Sc / T) of the content Sc of the silica in 100% by mass of the rubber component to the thickness T of the tread exceeds 10.0.

[0008] The reason why the above-described effects are obtained by the above tire is not necessarily clear, but it is presumed as follows. To meet a wide variety of requirements, the tread formulation mainly contains a large amount of styrene-butadiene rubber / butadiene rubber, but there is room for improvement in wear resistance during high-speed driving. In the above tire, by blending a modified isoprene rubber in an amount less than the total content of styrene butadiene rubber and butadiene rubber, the modified isoprene rubber is likely to disperse in the rubber layer while dragging silica. As a result, it is considered that a network of silica is formed and the reinforcing property is improved. Further, by blending the modified isoprene rubber so that the total styrene amount S and the content Ic of the modified isoprene rubber satisfy S / Ic < 1.00, it is considered that the modified isoprene rubber penetrates around the styrene portion where it is difficult to obtain reinforcing properties, enabling reinforcement. Furthermore, when the above rubber composition is applied to the tread, by satisfying Sc / T > 10.0 where Sc is the silica content and T is the tread thickness and adjusting the silica amount to a sufficient amount with respect to the tread thickness, it is considered that a network of silica is sufficiently formed also in the thickness direction, and synergistically the wear resistance during high-speed driving is improved. Therefore, it is inferred that the wear resistance during high-speed driving is remarkably improved by the above tire.

[0009] In this way, by adopting a configuration that satisfies the relationships of "S / Ic < 1.00" and "Sc / T > 10.0", the problem (objective) of improving the wear resistance during high-speed driving is solved. That is, the parameters of "S / Ic < 1.00" and "Sc / T > 10.0" do not define the problem (objective). The problem of the present application is to improve the wear resistance during high-speed driving, and as a solution means therefor, a configuration that satisfies the said parameters is adopted.

[0010] The above tire has a tread. The above tread (tread portion) is composed of, for example, the tread itself with a single-layer structure (first rubber layer) in the case of a single-layer structure tread, the cap tread on the outermost layer (first rubber layer) and the base tread (second rubber layer) adjacent to the inner side in the tire diameter direction of the cap tread in the case of a two-layer structure tread composed of the cap tread and the base tread, and the cap tread on the outermost layer (first rubber layer), the second rubber layer adjacent to the inner side in the tire diameter direction of the cap tread, and other rubber layers arranged on the inner side in the tire diameter direction of the second rubber layer in the case of a tread with a structure of three or more layers.

[0011] The above tread is composed of a rubber composition for tread. In the above tire, among the treads, at least one of the first rubber layer, the second rubber layer, and other rubber layers may be composed of the following rubber composition for tread. Among them, in the case of the above single-layer structure tread, it is the tread itself (first rubber layer), in the case of the above two-layer structure tread, it is the cap tread (first rubber layer), and in the case of the above tread with a structure of three or more layers, it is desirable that the cap tread (first rubber layer) and the second rubber layer adjacent to the inner side in the tire diameter direction of the cap tread be composed of the following rubber composition for tread.

[0012] Hereinafter, the chemicals that can be used in the above rubber composition for tread will be described.

[0013] Note that the chemicals in the following rubber composition for tread are applicable to any rubber composition constituting the tread. However, as described above, they are particularly preferably applicable as the rubber composition for cap tread and the rubber composition for the second rubber layer adjacent to the inner side in the tire diameter direction of the cap tread.

[0014] The above rubber composition for tread contains a rubber component. Here, the rubber component is a component that contributes to crosslinking. Generally, a polymer with 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 rubber component is in a solid state at normal temperature (25°C).

[0015] The weight average molecular weight of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, 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, still more preferably 1,000,000 or less. When within the above range, the effect tends to be obtained more favorably.

[0016] In the present specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) can be determined by standard polystyrene conversion based on the measured values by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0017] The rubber composition for the tread contains at least one selected from the group consisting of butadiene rubber (BR) and styrene butadiene rubber (SBR) as the rubber component.

[0018] BR is not particularly limited. For example, high cis-content high cis BR, 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 having 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 spectrum analysis method.

[0019] The cis amount of BR means the cis amount of the BR when there is one type of BR, and means the average cis amount when there are multiple types. 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, when in 100% by mass of the rubber component, 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)).

[0020] Either non-modified BR or modified BR can be used. Examples of the modified BR include BR having a functional group that interacts with a filler such as silica. For example, a terminal-modified BR (a terminal-modified BR having the above functional group at the terminal) obtained by modifying at least one terminal of BR with a compound (modifying agent) having the above functional group, a main-chain modified BR having the above functional group in the main chain, a main-chain terminal-modified BR having the above functional group in the main chain and at the terminal (for example, a main-chain terminal-modified BR having the above functional group in the main chain and at least one terminal modified with the above modifying agent), and a terminal-modified BR 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.

[0021] In the above modified BR, 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. Note that these functional groups may have a substituent. 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 preferable.

[0022] Also, hydrogenated butadiene polymer (hydrogenated BR) can be used as BR.

[0023] 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 45% 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 H-NMR measurement.

[0025] The styrene amount of the SBR means the styrene amount of the SBR when there is one type of SBR, and means the average styrene amount when there are multiple types. 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 25% by mass or less, more preferably 15% by mass or less, still more preferably 13% 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-bonded butadiene unit amount) can be measured by infrared absorption spectrum analysis.

[0027] The vinyl bond amount (1,2-bonded butadiene unit amount) of the SBR is the ratio of vinyl bonds when the total mass of the butadiene part in the SBR is 100 (unit: mass%), and vinyl amount [mass%] + cis amount [mass%] + trans amount [mass%] = 100 [mass%]. When there is one type of SBR, it means the vinyl amount of the SBR, and when there are multiple types, it means the average vinyl amount. 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] Either non-modified SBR or modified SBR can be used for SBR. Examples of the modified SBR include SBR having a functional group that interacts with a filler such as silica. For example, a terminal-modified SBR (terminal-modified SBR having the above functional group at the terminal) in which at least one terminal of SBR is modified with a compound (modifying agent) having the above functional group, a main-chain modified SBR having the above functional group in the main chain, a main-chain terminal-modified SBR having the above functional group in the main chain and at the terminal (for example, a main-chain terminal-modified SBR having the above functional group in the main chain and at least one terminal modified with the above modifying agent), and a terminal-modified SBR 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.

[0029] In the above-mentioned modified SBR, 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.

[0030] In addition, as the SBR, a hydrogenated styrene-butadiene copolymer (hydrogenated SBR) can also be used.

[0031] The raw materials (monomers) of synthetic rubbers such as SBR and BR may be derived from petroleum, or may be recycled from rubber products such as tires 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.

[0032] The method for producing the recycled monomer is not particularly limited, and for example, it can be synthesized from recycled naphtha obtained by decomposing rubber products such as tires. Also, the method for producing recycled naphtha is not particularly limited. For example, rubber products such as tires may be decomposed under high temperature and high pressure, decomposed by microwaves, or extracted after mechanical pulverization.

[0033] Furthermore, the raw materials (monomers) of synthetic rubbers such as SBR and BR may be derived from biomass. The monomer derived from biomass (biomass monomer) is 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. Also, the method for producing the biomass monomer 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.

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

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

[0036] pMC is the ratio of the 14 C concentration of the sample to the 14 C concentration of the standard modern reference, and this value is used as an index indicating the biomass ratio of the compound (rubber). The significance of this value is described below.

[0037] In one mole (6.02×10 23 atoms) of carbon atoms, there are approximately 6.02×10 11 atoms of 14 C, which is about one trillionth of the normal carbon atoms. 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 14 any 14 C elements. Therefore, chemical substances produced from these fossil fuels as raw materials also do not contain

[0038] On the other hand, 14 C is constantly generated by cosmic rays undergoing nuclear reactions in the atmosphere, and the balance between the decrease due to radioactive decay results in a certain amount of 14 C in the Earth's atmospheric environment. Therefore, the 14 C concentration of substances derived from biomass resources circulating in the current environment is about 1×10 -12The value will be on the order of mol%. Therefore, by utilizing the difference between these values, the ratio (biomass ratio) of the compound derived from natural resources (compound derived from biomass resources) in a certain compound (rubber) can be calculated.

[0039] This 14 C is generally measured as follows. Using accelerator mass spectrometry based on a tandem accelerator, 13 C concentration ( 13 C / 12 C), 14 C concentration ( 14 C / 12 C) is measured. In the measurement, 14 As the modern standard reference for the concentration of 14 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 radioactivity of carbon in this oxalic acid (radioactivity intensity of 13 C per gram of carbon) is separated for each carbon isotope, 14 C is corrected to a constant value, and the value after applying the decay correction from 1950 AD to the measurement date is used as the value of the standard 14 C concentration (100%). The ratio of this value to the value of the sample actually measured is the pMC value.

[0040] Therefore, if the rubber is made from a substance 100% derived from biomass (natural), 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 the 14 C concentration is measured, it will show approximately 0 pMC (for example, 0.3 pMC). This value corresponds to the biomass ratio of 0% mentioned above.

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

[0042] In the above rubber composition for tread, the total content Mc (total amount of SBR and BR) of SBR and BR in 100% by mass of the rubber component exceeds 50% by mass, preferably 70% by mass or more, more preferably 75% by mass or more, and still more preferably 80% by mass or more. The total content Mc is 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 effect tends to be preferably obtained. In addition, in the case of the above rubber composition for cap tread and the above rubber composition for the second rubber layer, the same range is desirable.

[0043] In the above rubber composition for tread, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 15% by mass or more, and still more preferably 20% by mass or more, and is preferably 40% by mass or less, more preferably 35% by mass or less, and still more preferably 30% by mass or less. When within the above range, the effect tends to be preferably obtained. In addition, in the case of the above rubber composition for cap tread and the above rubber composition for the second rubber layer, the same range is desirable.

[0044] In the rubber composition for tread, the content of SBR in 100% by mass of the rubber component is preferably 40% by mass or more, more preferably 50% by mass or more, and still more preferably 60% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass or less. When within the above range, the effect tends to be preferably obtained. In addition, in the case of the above rubber composition for cap tread and the above rubber composition for the second rubber layer, the same range is desirable.

[0045] The above rubber composition for tread contains a modified isoprene-based rubber as a rubber component. In this specification, the modified isoprene rubber is obtained by introducing a functional group into natural rubber or synthetic polyisoprene rubber.

[0046] In the above-mentioned modified isoprene rubber, examples of the functional group include those containing a nitrogen atom and / or a silicon atom. Specifically, known functional groups such as amino group, amide group, silyl group, alkoxysilyl group, isocyanate group, imino group, imidazole group, urea group, ether group, carbonyl group, oxycarbonyl group, mercapto group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazo group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group, hydroxyl group, oxy group, epoxy group, etc. may be mentioned. These functional groups may have substituents. Among them, an amino group (preferably an amino group in which the 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.

[0047] Examples of the above-mentioned modified isoprene rubber include isoprene rubber having a functional group that interacts with a filler such as silica. For example, a terminal-modified isoprene rubber (a terminal-modified isoprene rubber having the above-mentioned functional group at the terminal) obtained by modifying at least one terminal of the isoprene rubber with a compound (modifying agent) having the above-mentioned functional group, a main-chain modified isoprene rubber having the above-mentioned functional group in the main chain, a main-chain terminal modified isoprene rubber having the above-mentioned functional group in the main chain and at the terminal (for example, a main-chain terminal modified isoprene rubber having the above-mentioned functional group in the main chain and at least one terminal modified with the above-mentioned modifying agent), and a terminal-modified isoprene 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. may be mentioned.

[0048] In the above rubber composition for tread, the content Ic of the modified isoprene rubber in 100% by mass of the rubber component is less than 40% by mass, preferably 30% by mass or less, more preferably 25% by mass or less, and still more preferably 20% by mass or less. Further, the content Ic is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more. When it is within the above range, the effect tends to be preferably obtained. In addition, in the case of the above rubber composition for cap tread and the above rubber composition for the second rubber layer, the same range is desirable.

[0049] Among the above modified isoprene rubbers, from the viewpoint of obtaining more effects, a modified isoprene rubber having a functional group containing a nitrogen atom and a silicon atom (hereinafter, also referred to as a nitrogen- and silicon-modified isoprene rubber) is desirable.

[0050] The above nitrogen- and silicon-modified isoprene rubber is not particularly limited as long as it has a functional group containing a nitrogen atom and a silicon atom. For example, a terminal-modified rubber in which at least one end of the rubber is modified with a compound having the functional group, a main-chain modified rubber having the functional group in the main chain, a main-chain terminal-modified rubber having the functional group in the main chain and at the end, etc. may be mentioned. Among them, the above terminal-modified rubber is desirable.

[0051] The functional group containing the above nitrogen atom and silicon atom is not particularly limited, but it is preferably one containing the nitrogen atom as an amino group (-NR2: R is a hydrogen atom or a hydrocarbon group), and it is also preferably one containing the silicon atom as a hydrocarbyloxysilyl group (≡SiOR: R is a hydrocarbon group).

[0052] Among them, from the viewpoint of obtaining more effects, the functional group containing the above nitrogen atom and silicon atom is preferably a group represented by the following formula (A).

Chemical formula

[0053] The above-mentioned substituent is not particularly limited as long as it is a monovalent substituent. Examples thereof include a halogen atom, a hydroxy group, a nitro group, a carboxy group, an alkoxy group, an amino group, a mercapto group, an acyl group, an imide group, a phosphino group, a phosphinyl group, a silyl group, and a hydrocarbon group which may have a hetero atom. Examples of the above-mentioned halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and the like. Examples of the hetero atom of the hydrocarbon group which may have the above-mentioned hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom, and the like. Examples of the hydrocarbon group which may have the above-mentioned hetero atom include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a group combining these. The above-mentioned aliphatic hydrocarbon group may be linear, branched, or cyclic. Specific examples of the above-mentioned aliphatic hydrocarbon group include a linear or branched alkyl group (preferably having 1 to 30 carbon atoms), a linear or branched alkenyl group (preferably having 2 to 30 carbon atoms), a linear or branched alkynyl group (preferably having 2 to 30 carbon atoms), and the like. Examples of the above-mentioned aromatic hydrocarbon group include aromatic hydrocarbon groups having 6 to 18 carbon atoms such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and the like.

[0054] R 11 、R 12 each preferably represents a hydrogen atom, an alkyl group (preferably having 1 to 10 carbon atoms), an alkylsilyl group (preferably having 1 to 10 carbon atoms), an aromatic hydrocarbon group (preferably having 6 to 18 carbon atoms), and more preferably a hydrogen atom. R 11 、R 12 may be the same or different, and R 11 、R12 When they are different, R 11 , R 12 The combination of is preferably a combination of a hydrogen atom and an alkyl group (preferably having 1 to 10 carbon atoms), an alkylsilyl group (preferably having 1 to 10 carbon atoms), or an aromatic hydrocarbon group (preferably having 6 to 18 carbon atoms), and more preferably a combination of a hydrogen atom and an alkylsilyl group (preferably having 1 to 10 carbon atoms), and still more preferably a combination of a hydrogen atom and a trialkylsilyl group (preferably having 1 to 10 carbon atoms). Also, among the above substituents, R 11 , R 12 When there are a plurality of each, each R 11 , R 12 may be the same or different.

[0055] R 13 is preferably a hydrocarbyloxy group (-OR group: R is a hydrocarbon group), and more preferably an alkoxy group (preferably having 1 to 10 carbon atoms).

[0056] L 11 Examples of the divalent organic group of include aliphatic hydrocarbon groups such as alkylene groups (preferably having 1 to 10 carbon atoms), aromatic hydrocarbon groups such as arylene groups (preferably having 6 to 18 carbon atoms), -O-, -S-, -SO2-, -N(R)- (R is an alkyl group), -CO-, -NH-, -COO-, -CONH-, or a group combining these (for example, alkyleneoxy group (-C m H 2m O-: m is a positive integer), alkyleneoxycarbonyl group, alkylenecarbonyloxy group, etc.). Among them, L 11 is preferably an alkylene group (preferably having 1 to 10 carbon atoms).

[0057] From the viewpoint of obtaining more effects, n is preferably 2, and m is preferably 1.

[0058] The above nitrogen and silicon-modified isoprene rubber preferably has a weight-average molecular weight (Mw) of 100,000 or more, more preferably 200,000 or more, still more preferably 250,000 or more, and preferably 10,000,000 or less, more preferably 1,000,000 or less, still more preferably 800,000 or less. When within the above range, the effect tends to be preferably obtained.

[0059] The above nitrogen and silicon-modified isoprene rubber preferably has a number-average molecular weight (Mn) of 120,000 or more, more preferably 150,000 or more, and preferably 900,000 or less, more preferably 800,000 or less. When within the above range, the effect tends to be preferably obtained.

[0060] The above nitrogen and silicon-modified isoprene rubber preferably has a molecular weight distribution (Mw / Mn) of 2.0 or less, more preferably 1.7 or less, still more preferably 1.5 or less, and particularly preferably 1.3 or less. The lower limit is not particularly limited, but is usually 1.0 or more. When within the above range, the effect tends to be preferably obtained.

[0061] In the above nitrogen and silicon-modified isoprene rubber, the proportions of 1,2-structure and 3,4-structure are not particularly limited, but are preferably 0 to 10 mol%, more preferably 0 to 5 mol%. When within the above range, the effect tends to be preferably obtained. In this specification, the proportion of 1,2-structure refers to the proportion (mol%) of the repeating units having a 1,2-structure among the repeating units derived from isoprene. The proportion of 3,4-structure refers to the proportion (mol%) of the repeating units having a 3,4-structure among the repeating units derived from isoprene.

[0062] In the above nitrogen and silicon-modified isoprene rubber, the proportion of 1,4-trans structure is not particularly limited, but is preferably 2 mol% or more, more preferably 5 mol% or more, and preferably 90 mol% or less, more preferably 70 mol% or less. When within the above range, the effect tends to be preferably obtained. In the present specification, the proportion of the 1,4-trans structure refers to the proportion (mol%) of the repeating units having the 1,4-trans structure among all the repeating units derived from isoprene.

[0063] In the above nitrogen- and silicon-modified isoprene rubber, the proportion of the 1,4-cis structure is not particularly limited, but is preferably 10 mol% or less, more preferably 30 mol% or less, and also preferably 98 mol% or less. When within the above range, the effect tends to be preferably obtained. In the present specification, the proportion of the 1,4-cis structure refers to the proportion (mol%) of the repeating units having the 1,4-cis structure among all the repeating units derived from isoprene.

[0064] The above nitrogen- and silicon-modified isoprene rubber preferably has a glass transition temperature (Tg) of -100°C or higher, more preferably -90°C or higher, still more preferably -85°C or higher, and also preferably -40°C or lower, more preferably -50°C or lower, still more preferably -60°C or lower. When within the above range, the effect tends to be preferably obtained. In the present specification, the glass transition temperature (Tg) is measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min and calculated by the midpoint method.

[0065] The viscosity of the above nitrogen- and silicon-modified isoprene rubber is preferably 2,000 Pa·s or higher, more preferably 3,000 Pa·s or higher, and also preferably 100,000 Pa·s or lower. When within the above range, the effect tends to be preferably obtained. Also, the viscosity of the isoprene polymer before modifying the above nitrogen- and silicon-modified isoprene rubber is not particularly limited, but is preferably 800 Pa·s or higher, more preferably 1,200 Pa·s or higher, and also preferably 8,000 Pa·s. When within the above range, the effect tends to be preferably obtained. The viscosity of the above nitrogen- and silicon-modified isoprene rubber is preferably 150 to 240% with respect to the viscosity of the isoprene polymer before modification. In this specification, the viscosity shall be measured using a cone and plate viscometer in accordance with JIS K5600-2-3. Also, the above viscosity shall be measured under the condition of 40°C.

[0066] The method for producing the above nitrogen and silicon-modified isoprene rubber is not particularly limited, and a conventionally known method can be used. The method for specifying the molecular weight and molecular weight distribution is not particularly limited, and examples include methods for adjusting the amount ratio of the initiator, monomer, and terminator, reaction temperature, and the rate of adding the initiator. For example, a method of polymerizing isoprene using an organolithium compound and then terminating the polymerization using an electrophilic agent containing a nitrogen atom and a silicon atom can be mentioned.

[0067] The above organolithium compound is not particularly limited, and examples include mono-organolithium compounds such as n-butyllithium, sec-butyllithium, tert-butyllithium, n-propyllithium, isopropyllithium, and benzyllithium; polyfunctional organolithium compounds such as 1,4-dilithiobutane, 1,5-dilithiopentane, 1,6-dilithiohexane, 1,10-dilithiodecane, 1,1-dilithiodiphenylene, dilithiopolybutadiene, dilithiopolyisoprene, 1,4-dithiobenzene, 1,2-dithio-1,2-diphenylethane, 1,4-dithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, and 1,3,5-trilithio-2,4,6-triethylbenzene. Among them, mono-organolithium compounds are preferred, and n-butyllithium, sec-butyllithium, and tert-butyllithium are more preferred.

[0068] The amount of the organolithium compound used is not particularly limited, but it is preferably 0.001 to 10 mol% based on isoprene.

[0069] The method of polymerizing isoprene using an organolithium compound is not particularly limited. For example, an organolithium compound as described above is added to an organic solvent solution containing isoprene, and the mixture is stirred in a temperature range of 0 to 120 °C (preferably 30 to 100 °C).

[0070] In the above method, the polymerization of isoprene is terminated using an electrophile containing a nitrogen atom and a silicon atom. By terminating the polymerization using the above electrophile, a modified isoprene polymer having a functional group containing the above nitrogen atom and silicon atom at the terminal can be obtained. As the above electrophile, various compounds containing a nitrogen atom and a silicon atom can be used. Among them, a compound containing a nitrogen atom as an amino group (-NR2: R is a hydrogen atom or a hydrocarbon group) is preferable, and a compound containing a silicon atom as a hydrocarbyloxysilyl group (≡SiOR: R is a hydrocarbon group) is also preferable.

[0071] As the above electrophile, preferably silazane, more preferably cyclic silazane, can be mentioned. Note that silazane is a compound having a structure in which a silicon atom and a nitrogen atom are directly bonded (a compound having a Si-N bond).

[0072] As the above cyclic silazane, a compound represented by the following formula (B) can be preferably used.

Chemical formula

[0073] R 21 , R 22 , R 23 are, for example, the same as those of the above R 11 , R 12 . Among them, R21 is preferably an alkyl group (preferably having 1 to 10 carbon atoms), an alkylsilyl group (preferably having 1 to 10 carbon atoms), or an aromatic hydrocarbon group (preferably having 6 to 18 carbon atoms), and more preferably an alkylsilyl group. R 22 and R 23 are preferably the same or different and are hydrocarbyloxy groups (-OR groups: R is a hydrocarbon group), and more preferably alkoxy groups (preferably having 1 to 10 carbon atoms).

[0074] L 21 Examples of L 11 include the same ones as those of the above L Among them, L 21 is preferably an alkylene group (preferably having 1 to 10 carbon atoms, more preferably 2 to 8 carbon atoms, and even more preferably 3 to 5 carbon atoms).

[0075] Examples of the compound represented by the above formula (B) include N-n-butyl-1,1-dimethoxy-2-azasilacyclopentane, N-phenyl-1,1-dimethoxy-2-azasilacyclopentane, N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane, N-trimethylsilyl-1,1-diethoxy-2-azasilacyclopentane, and the like. It should be noted that the silicon atom of the cyclic silazane is considered to exhibit electrophilicity.

[0076] The amount of the above electrophilic agent relative to the organolithium compound is not particularly limited, but is preferably 0.1 to 10 in molar ratio, and more preferably 1 to 5.

[0077] In the above rubber composition for tread, the content of the above nitrogen and silicon-modified isoprene rubber in 100% by mass of the rubber component is preferably less than 40% by mass, more preferably 30% by mass or less, still more preferably 25% by mass or less, and particularly preferably 20% by mass or less. Further, the above content is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and there is a tendency that the effect can be preferably obtained within the above range. In addition, in the case of the above rubber composition for cap tread and the above rubber composition for the second rubber layer, the same range is desirable.

[0078] The above rubber composition for tread may contain rubber components other than the above BR, SBR, and modified isoprene rubber. Examples of such rubber components include unmodified isoprene rubber, styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), etc. Further, butyl rubber, fluororubber, etc. are also included. 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 stretched by an oil, a resin, a liquid rubber component, etc. may be used.

[0079] In the above rubber composition for tread, the content of diene rubbers such as the above BR, SBR, and modified isoprene rubber is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 98% by mass or more, and particularly preferably 100% by mass or more in 100% by mass of the rubber component. There is a tendency that the effect can be preferably obtained within the above range. In addition, in the case of the above rubber composition for cap tread and the above rubber composition for the second rubber layer, the same range is desirable.

[0080] Examples of the unmodified isoprene rubber include natural rubber (NR). As NR, for example, those generally used in the rubber industry such as SIR20, RSS#3, and TSR20 can be used. These may be used alone or in combination of two or more.

[0081] The rubber composition for tread contains silica. 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 made from biomass materials such as rice husks), or silica recycled from products containing silica may also be used. Among them, hydrous silica prepared by the wet method is preferred because it has many silanol groups. These silicas may be used alone or in combination of two or more.

[0082] Silica made from biomass materials can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and 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.

[0083] Silica recycled from products containing silica can be used, for example, silica recovered from products containing silica such as electronic components 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 components such as semiconductors or tires is preferred.

[0084] When silica crystallizes, it is 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.).

[0085] Amorphous silica extracted from rice husks can be those commercially available from Wilmar Co., Ltd. and the like.

[0086] 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.

[0087] In the above rubber composition for a tread, the content Sc of silica with respect to 100 parts by mass of the rubber component is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, still more preferably 80 parts by mass or more, particularly preferably 85 parts by mass or more, and is also preferably 200 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 100 parts by mass or less. When within the above range, the effect tends to be obtained more favorably. Note that in the case of the above rubber composition for a cap tread and the above rubber composition for a second rubber layer, the same range is desirable.

[0088] When a large amount of silica, particularly 80 parts by mass or more, is contained, the mechanism by which more effects are obtained is not clear, but it is considered that the reinforcing property is improved and a silica network is sufficiently formed also in the thickness direction. Therefore, it is presumed that the wear resistance during high-speed driving is remarkably improved. It is considered that the wear resistance during high-speed driving is improved.

[0089] The above rubber composition for a tread may contain a filler other than silica. Such fillers are not particularly limited, and materials known in the rubber field can be used. For example, inorganic fillers such as carbon black, 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 are preferred.

[0090] In the above rubber composition for 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 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.

[0091] The nitrogen adsorption specific surface area (N2SA) of carbon black is preferably 50 m 2 / g or more, more preferably 80 m 2 / g or more, and still more preferably 100 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 more favorably. Note that the nitrogen adsorption specific surface area of carbon black is determined according to JIS K6217-2:2001.

[0092] The dibutyl phthalate absorption (DBP) of the 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. Note that the DBP of the carbon black is determined by the measurement method of JIS K6217-4:2001.

[0093] In the above tread rubber composition, the content of the 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 with respect to 100 parts by mass of the rubber component, and is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 10 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably. Note that in the case of the above cap tread rubber composition and the above second rubber layer rubber composition, the same range is desirable.

[0094] Examples of the difficult-to-disperse filler include microfibrillated plant fibers, short fiber-like cellulose, gel-like compounds, etc. Among them, microfibrillated plant fibers are preferred.

[0095] As the above microfibrillated plant fiber, cellulose microfibrils are preferred from the viewpoint of obtaining good reinforcing properties. The cellulose microfibrils are not particularly limited as long as they are derived from natural products. For example, resource biomass such as fruits, grains, and root vegetables, wood, bamboo, hemp, jute, kenaf, and pulp, paper, cloth, agricultural crop waste, food waste, and sewage sludge obtained from these as raw materials, waste biomass such as rice straw, wheat straw, and thinned wood, and cellulose produced by sea squirts, acetic acid bacteria, etc. are included. These microfibrillated plant fibers may be used alone or in combination of two or more.

[0096] In addition, in this 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 microstructure with an average fiber diameter of 500 nm or less formed by an aggregate of cellulose molecules. A typical cellulose microfibril is formed, for example, as an aggregate of cellulose fibers having the above-mentioned average fiber diameter.

[0097] When the above rubber composition for 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, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less. When within the above range, the effect tends to be obtained more favorably. In addition, the same range is desirable also in the case of the above rubber composition for cap tread and the above rubber composition for the second rubber layer.

[0098] In the above rubber composition for 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 85 parts by mass or more, and particularly preferably 90 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 100 parts by mass or less. When within the above range, the effect tends to be obtained more favorably. In addition, the same range is desirable also in the case of the above rubber composition for cap tread and the above rubber composition for the second rubber layer.

[0099] The above rubber composition for tread preferably further contains a silane coupling agent. The silane coupling agent is not particularly limited, and those known in the rubber field can be used. For example, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,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, vinyltriethoxysilane, vinyltrimethoxysilane, etc. of the vinyl type, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, etc. of the amino type, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, etc. of the glycidoxy type, 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, etc. of the nitro type, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, etc. of the chloro type, and the like. 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.

[0100] In the above rubber composition for 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. In addition, in the case of the above rubber composition for cap tread and the above rubber composition for the second rubber layer, the same range is desirable.

[0101] The above rubber composition for tread preferably contains a plasticizer. In this specification, a plasticizer is a material that imparts plasticity to a rubber component, and is a concept including both a plasticizer that is liquid (liquid state) at normal temperature (25 °C) and a plasticizer that is 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. Further, 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.

[0102] Specific examples of the above plasticizer include oils, liquid polymers, resins, etc. These may be used alone or in combination of two or more.

[0103] 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 protection. Examples of the low-PCA-content process oil include MES, TDAE, heavy naphthenic oil, etc. Also, 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.

[0104] 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 wax, 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 after being used as edible oil, etc. Note that the vegetable oil may be liquid or solid at room temperature (25°C). These vegetable oils may be used alone or in combination of two or more.

[0105] 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).

[0106] As a method for confirming whether the acylglycerol is contained in the rubber composition, there is no particular limitation, 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 are observed at around 5.26 ppm, around 4.28 ppm, and around 4.15 ppm. 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.

[0107] 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.

[0108] Among them, 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, etc.

[0109] As the oil, for example, those commercially available from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo 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.

[0110] 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.

[0111] The weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) of the liquid diene polymer is 1.0×10 3 ~5.0×10 4 which is preferably, and more preferably 3.0×10 3 ~1.5×10 4 The lower or upper limit of Mw of the liquid diene polymer may also 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).

[0112] As the above liquid diene polymer, for example, products of Sartomer Company, Kuraray Co., Ltd. etc. can be used.

[0113] As the above resin, as a tire compound, a resin (resin) usually used can be used, which may be liquid or solid at normal temperature (25°C). For example, aromatic vinyl polymers, coumarone-indene resins, coumarone resins, indene resins, phenolic 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, aromatic vinyl polymers, petroleum resins, terpene resins, and hydrogenated resins thereof are desirable.

[0114] 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, the effect tends to be obtained more favorably. 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 a hydrogenated resin, it is desirable that the softening point is the same as above. Note that the softening point of the above resin is measured by a ring and ball softening point measuring device for the softening point defined in JIS K6220-1:2001, and is the temperature at which the ball drops.

[0115] 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.

[0116] 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 contained in the skeleton other than coumarone and indene, styrene, α-methylstyrene, methyl indene, vinyl toluene, etc. can be mentioned.

[0117] The above coumarone resin is a resin containing coumarone as the main monomer component constituting the resin skeleton (main chain).

[0118] The above indene resin is a resin containing indene as the main monomer component constituting the resin skeleton (main chain).

[0119] As the above phenolic resin, for example, known ones such as polymers obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde, and furfural with 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.

[0120] As the above rosin resin, rosin-based resins typified by natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof can be mentioned.

[0121] As the above petroleum resin, C5-based resins, C9-based resins, C5 / C9-based resins, dicyclopentadiene (DCPD) resins, C9 / DCPD resins, hydrogenated products thereof, etc. can be mentioned. Among them, DCPD resins, hydrogenated DCPD resins, C9 / DCPD resins, and C9 / hydrogenated DCPD resins are preferred.

[0122] The above terpene resin is a polymer containing terpenes as constituent units. For example, there are polyterpene resins obtained by polymerizing terpene compounds, aromatic modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds, and the like. Examples of aromatic modified terpene resins include terpene phenol resins using terpene compounds and phenolic compounds as raw materials, terpene styrene resins using terpene compounds and styrene compounds as raw materials, and terpene phenol styrene resins using terpene compounds, phenolic compounds and styrene compounds as raw materials. Examples of terpene compounds include α-pinene, β-pinene, etc., examples of phenolic compounds include phenol, bisphenol A, etc., and examples of aromatic compounds include styrene compounds (styrene, α-methylstyrene, etc.). Among them, aromatic modified terpene resins are preferred.

[0123] The above acrylic resin is a polymer containing acrylic monomers as constituent units. For example, there are styrene acrylic resins such as styrene acrylic resins obtained by copolymerizing an aromatic vinyl monomer component and an acrylic monomer component having a carboxyl group. Among them, a solventless carboxyl group-containing styrene acrylic resin can be preferably used.

[0124] Examples of the above resins 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 Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., Tago Chemical Industry Co., Ltd., etc. can be used.

[0125] From the perspective of sustainability, it is desirable to use plant-derived plasticizers such as the above plant-derived oils and farnesene-based polymers as the above plasticizers.

[0126] The 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

[0127] 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.

[0128] 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.

[0129] In the farnesene-vinyl monomer copolymer, the copolymerization ratio (farnesene / vinyl monomer) based on the mass of farnesene and vinyl monomer is preferably 40 / 60 to 90 / 10.

[0130] 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.

[0131] 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.

[0132] In the above rubber composition for tread, the content of the plasticizer (total amount of plasticizer) is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 10 parts by mass or less, relative to 100 parts by mass of the rubber component. The upper limit is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 8 parts by mass or more. 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 the resin-extended rubber. Also, in the case of the above rubber composition for cap tread and the above rubber composition for the second rubber layer, the same range is desirable.

[0133] In the above rubber composition for tread, the content of the solid plasticizer in a solid state at normal temperature (25 °C) is preferably 30 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component. The lower limit is preferably 1 part by mass or more, more preferably 3 parts by mass or more. When it is within the above range, the effect tends to be obtained more favorably. Note that the content of the resin in a solid state at normal temperature (25 °C), the content of the above resin in a solid state at normal temperature (25 °C), and the above aromatic vinyl polymer in a solid state at normal temperature (25 °C) are also desirably in the same range. Also, in the case of the above rubber composition for cap tread and the above rubber composition for the second rubber layer, the same range is desirable.

[0134] In the above rubber composition, the content of the liquid plasticizer in a liquid state at normal temperature (25 °C) is preferably 30 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component. The lower limit is preferably 1 part by mass or more, more preferably 3 parts by mass or more. 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. The content of the oil in a liquid state at normal temperature (25 °C) is also desirably in the same range. Also, in the case of the rubber composition for cap tread and the rubber composition for the second rubber layer, a similar range is desirable.

[0135] The rubber composition for tread preferably contains an anti-aging agent from the viewpoints of crack resistance, ozone resistance, etc.

[0136] The anti-aging agent is not particularly limited, but naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine, 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditoly-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N,N'-di-2-naphthyl-p-phenylenediamine (DNPD) and other p-phenylenediamine-based anti-aging agents; 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, styrenated phenol; bis, tris, polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane and the like. 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 commercially available products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., Flexsys Co., Ltd. and the like can be used.

[0137] In the above rubber composition for 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, still more preferably 3.0 parts 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. In addition, in the case of the above rubber composition for cap tread and the above rubber composition for the second rubber layer, similar ranges are desirable.

[0138] The above rubber composition for tread preferably contains stearic acid. In the above rubber composition for tread, the content of stearic acid is preferably 0.5 parts by mass or more, more preferably 2.0 parts by mass or more, based on 100 parts by mass of the rubber component, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less. In addition, in the case of the above rubber composition for cap tread and the above rubber composition for the second rubber layer, similar ranges are desirable.

[0139] 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.

[0140] The above rubber composition for tread preferably contains zinc oxide. In the above rubber composition for tread, the content of zinc oxide is preferably 0.5 parts by mass or more, more preferably 2.0 parts by mass or more, based on 100 parts by mass of the rubber component, and is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less. In addition, in the case of the above rubber composition for cap tread and the above rubber composition for the second rubber layer, similar ranges are desirable.

[0141] 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., Sho-Doh Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0142] The rubber composition for the tread may contain wax. In the rubber composition for the tread, the content of wax is preferably 1.0 part 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. In the case of the rubber composition for the cap tread and the rubber composition for the second rubber layer, the same range is desirable.

[0143] 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, those commercially available from, for example, Ouchi Shinko 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.

[0144] In the rubber composition for the tread, it is preferable to compound sulfur in terms of forming appropriate cross-linked chains in the polymer chain and imparting good performance.

[0145] In the rubber composition for the tread, the content of sulfur is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, still more preferably 1.5 parts 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. In the case of the rubber composition for the cap tread and the rubber composition for the second rubber layer, the same range is desirable.

[0146] 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 commercially available products, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Corporation, 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.

[0147] The rubber composition for the tread preferably contains a vulcanization accelerator. In the above rubber composition for the tread, the content of the vulcanization accelerator is not particularly limited and may be freely determined according to the desired vulcanization rate and crosslink density. However, based on 100 parts by mass of the rubber component, it 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. The upper limit is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, still more preferably 6.0 parts by mass or less. In addition, in the case of the above rubber composition for the cap tread and the above rubber composition for the second rubber layer, a similar range is desirable.

[0148] In the above rubber composition for the tread, the content of the vulcanization accelerator is not particularly limited and may be freely determined according to the desired vulcanization rate and crosslink density. However, based on 100 parts by mass of the rubber component, it is preferably 2.0 parts by mass or more, more preferably 3.0 parts by mass or more, still more preferably 4.0 parts by mass or more. The upper limit is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, still more preferably 6.0 parts by mass or less. In addition, in the case of the above rubber composition for the cap tread and the above rubber composition for the second rubber layer, a similar range is desirable.

[0149] 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; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-t-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; 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.

[0150] In addition to the above components, the rubber composition for the tread may be appropriately blended with compounding agents generally used in the tire industry, such as materials for mold release agents and the like.

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

[0152] In the rubber composition for the tread, the ratio (S / Ic) of the total styrene amount S (mass%) in the rubber component to the content Ic (mass%) of the modified isoprene-based rubber in 100 mass% of the rubber component is less than 1.00. S / Ic is preferably 0.90 or less, more preferably 0.80 or less, and still more preferably 0.78 or less. The lower limit of S / Ic is preferably 0.30 or more, more preferably 0.50 or more, and still more preferably 0.60 or more. When within the above range, the effect tends to be obtained more favorably. In addition, in the case of the above-described rubber composition for cap tread and the above-described rubber composition for the second rubber layer, the same range is desirable.

[0153] In the above-described rubber composition for tread, the total styrene amount S in the rubber component is preferably 5% by mass or more, more preferably 8% by mass or more, and still more preferably 10% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 16% by mass or less. When within the above range, the effect tends to be obtained more favorably. In addition, in the case of the above-described rubber composition for cap tread and the above-described rubber composition for the second rubber layer, the same range is desirable.

[0154] In this specification, the total styrene amount in the rubber component is the total content of the styrene part contained in the total amount of the rubber component (unit: mass%), and can be calculated by Σ (content of each rubber component × styrene amount in each rubber component / 100). For example, in 100% by mass of the rubber component, when 85% by mass of styrene-butadiene rubber with a styrene amount of 40% by mass, 5% by mass of styrene-butadiene rubber with a styrene amount of 25% by mass, and 10% by mass of butadiene rubber with a styrene amount of 0% by mass, the total styrene amount in the rubber component is 35.25% by mass (= 85 × 40 / 100 + 5 × 25 / 100 + 10 × 0 / 100).

[0155] In addition, the styrene amount in each rubber component can be measured by nuclear magnetic resonance (NMR) method. Also, regarding the total styrene amount in the rubber component, in the examples of this specification, it is calculated according to the above-described calculation formula, but for example, it may be analyzed from the tire by a pyrolysis gas chromatography mass spectrometer (Py-GC / MS) or the like.

[0156] The above rubber composition for 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 by a method or the like.

[0157] 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.

[0158] The above rubber composition for tread is used for the above tread of the tire member, and is particularly preferably used for the above cap tread and the above second rubber layer.

[0159] The above tire is manufactured by a usual method using the above rubber composition for tread. That is, a composition containing various additives as required is extruded into the shape of various tire members such as a tread at the unvulcanized stage, formed by a usual 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 thereof 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 and bus tire, a two-wheeler tire, a racing tire, a winter tire (a studless tire, a snow tire, a studded tire), an all-season tire, a run-flat tire, an aircraft tire, a mining tire, etc.

[0162] The above tire is provided with a tread made from the above rubber composition. In the above tire, the ratio (Sc / T) of the content Sc (parts by mass) of the above silica to 100 parts by mass of the rubber component of the above tread rubber composition and the thickness T (mm) of the above tread exceeds 10.0. Sc / T is preferably 11.0 or more, more preferably 11.5 or more, still more preferably 12.0 or more. Also, the upper limit of Sc / T is preferably 20.0 or less, more preferably 15.0 or less, still more preferably 14.0 or less. When within the above range, the effect tends to be obtained more favorably. Note that the ratio (Sc / T) of the content Sc (parts by mass) of the above silica to 100 parts by mass of the rubber component of the above cap tread rubber composition and the thickness T (mm) of the above cap tread, and the ratio (Sc / T) of the content Sc (parts by mass) of the above silica to 100 parts by mass of the rubber component of the above second rubber layer and the thickness T (mm) of the above second rubber layer are also preferably in the same range.

[0163] In the above tire, the thickness T (mm) of the above tread is preferably 4.5 mm or more, more preferably 5.5 mm or more, still more preferably 6.5 mm or more, and is also preferably 20.0 mm or less, more preferably 15.0 mm or less, still more preferably 10.0 mm or less, particularly preferably 9.0 mm or less, and most preferably 8.0 mm or less. When within the above range, the effect tends to be obtained suitably. Note that the thickness T (mm) of the above cap tread and the thickness T (mm) of the above second rubber layer are also preferably in the same range.

[0164] When T is equal to or greater than a predetermined value, particularly 5.5 mm or more, the mechanism by which more effects can be obtained is not clear. However, it is presumed that a silica network is sufficiently formed in the thickness direction, and as a result, the wear resistance during high-speed driving is remarkably improved. It is considered that the wear resistance during high-speed driving is improved.

[0165] In the above tire, it is desirable that the ratio (Mc / T) of the total content Mc (mass%) of the styrene-butadiene rubber and butadiene rubber in 100 mass% of the rubber component of the tread rubber composition to the thickness T (mm) of the tread exceeds 10.0. Mc / T is preferably 11.0 or more, more preferably 11.5 or more, and still more preferably 12.0 or more. The upper limit of Mc / T is preferably 20.0 or less, more preferably 15.0 or less, and still more preferably 14.0 or less. When within the above range, the effects tend to be obtained more favorably. In addition, the ratio (Mc / T) of the total content Mc (mass%) of the styrene-butadiene rubber and butadiene rubber in 100 mass% of the rubber component of the cap tread rubber composition to the thickness T (mm) of the cap tread, and the ratio (Mc / T) of the total content Mc (mass%) of the styrene-butadiene rubber and butadiene rubber in 100 mass% of the rubber component of the second rubber layer rubber composition to the thickness T (mm) of the second rubber layer are also preferably in the same range.

[0166] When Mc / T is equal to or greater than a predetermined value, particularly 11.5 or more, the mechanism by which more effects can be obtained is not clear. However, it is presumed that a silica network is sufficiently formed in the thickness direction, and as a result, the wear resistance during high-speed driving is remarkably improved. It is considered that the wear resistance during high-speed driving is improved.

[0167] In the above tire, it is desirable that the ratio (Ic / T) of the content Ic (mass%) of the modified isoprene-based rubber to 100 parts by mass of the rubber component of the tread rubber composition to the thickness T (mm) of the tread exceeds 2.0. Ic / T is preferably 2.5 or more, more preferably 2.8 or more, and still more preferably 3.0 or more. Also, the upper limit of Ic / T is preferably 10.0 or less, more preferably 6.0 or less, and still more preferably 5.0 or less. When within the above range, the effect tends to be obtained more favorably. In addition, the ratio (Ic / T) of the content Ic (mass %) of the modified isoprene rubber to 100 parts by mass of the rubber component of the above cap tread rubber composition and the thickness T (mm) of the above cap tread, and the ratio (Ic / T) of the content Ic (mass %) of the modified isoprene rubber to 100 parts by mass of the rubber component of the above second rubber layer composition and the thickness T (mm) of the above second rubber layer are also preferably in the same range.

[0168] When Ic / T is a predetermined value or more, particularly 2.8 or more, the mechanism by which more effects are obtained is not clear, but it is considered that the modified isoprene rubber drags silica and disperses it in the rubber layer, and a network of silica is sufficiently formed also in the thickness direction. Therefore, it is presumed that the abrasion resistance during high-speed driving is remarkably improved.

[0169] In this specification, the thickness T of the above tread refers to the thickness of the tread on the tire equator 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 to the inner surface of the tread in the tire radial direction. For example, in the case of a single-layer structure tread, it is the straight-line distance from the tread surface of the single-layer structure tread itself (the first rubber layer) to the inner surface of the tread in the tire radial direction. In the case of a two-layer structure tread composed of the outermost cap tread (the first rubber layer) and the base tread (the second rubber layer) adjacent to the inner side of the cap tread in the tire diameter direction, it is the straight-line distance from the cap tread surface and to the inner surface of the base tread in the tire radial direction. In the case of a three-layer or more structure tread composed of the outermost cap tread (the first rubber layer), the second rubber layer adjacent to the inner side of the cap tread in the tire diameter direction, and another rubber layer arranged on the inner side of the second rubber layer in the tire diameter direction, it is the straight-line distance from the cap tread surface and to the inner surface of the rubber layer arranged most on the inner side in the tire radial direction of the other rubber layer.

[0170] The thickness T of the tread on the tire equatorial plane is a value measured along the tire equatorial plane from the outermost surface of the tread on the tire equatorial plane. When there is an energizing member or the like on the tire equatorial plane, it is a value measured along the tire equatorial plane from a 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 tread in the tire radial direction.

[0171] In the above tire, the groove depth D (mm) of the circumferential groove formed in the tread is preferably 1.0 mm or more, more preferably 2.0 mm or more, still more preferably 3.0 mm or more, and is preferably 20.0 mm or less, more preferably 15.0 mm or less, still more preferably 10.0 mm or less, particularly preferably 8.0 mm or less, and most preferably 5.0 mm or less. When within the above range, the effect tends to be obtained more favorably.

[0172] When D is within a predetermined range, particularly in the case of 2.0 mm or more and 8.0 mm, the mechanism by which a more effect is obtained is not clear, but it is considered that the rubber strength can be ensured by adjusting an appropriate groove depth. Therefore, it is presumed that the abrasion resistance during high-speed running is remarkably improved.

[0173] In the above tire, it is desirable that the ratio (Sc / D) of the content Sc (parts by mass) of the above silica to 100 parts by mass of the rubber component of the above tread rubber composition and the groove depth D (mm) of the circumferential groove formed in the above tread is 10.0 or more and 80.0 or less. Sc / D is preferably 20.0 or more, more preferably 25.0 or more, still more preferably 30.0 or more. Also, the upper limit of Sc / D is preferably 50.0 or less, more preferably 45.0 or less, still more preferably 40.0 or less. When within the above range, the effect tends to be obtained more favorably. In addition, the ratio (Sc / D) of the content Sc (parts by mass) of the silica to 100 parts by mass of the rubber component of the rubber composition for the cap tread and the groove depth D (mm) of the circumferential groove formed in the tread, and the ratio (Sc / D) of the content Sc (parts by mass) of the silica to 100 parts by mass of the rubber component of the rubber composition for the second rubber layer and the groove depth D (mm) of the circumferential groove formed in the tread are also desirably in the same range.

[0174] Although the mechanism by which more effects can be obtained when Sc / D is in a predetermined range, particularly 10.0 or more and 50.0 or less, is not clear, it is considered that a silica network is formed, the reinforcing property becomes good, and the rubber strength can be ensured by an appropriate groove depth. Therefore, it is presumed that the abrasion resistance during high-speed driving is remarkably improved.

[0175] In addition, in this specification, the groove depth D of the circumferential groove means the distance from the surface formed by extending the surface forming the ground contact surface of the tread outermost surface to the deepest groove bottom along the normal line of the surface formed by extending the surface forming the ground contact surface, and refers to the maximum distance among the groove depths of the provided circumferential grooves.

[0176] 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 and filled with a 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 based on which the tire is designed. 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 relevant standards if there is an applicable size during the reference. For 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, i.e., the rim that does not cause air leakage between the rim and the tire. Also, the "standard internal pressure" refers to the air pressure defined for each tire in the standard system including the standard based on which the tire is designed. 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 is 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 relevant standards if there is an applicable size during the reference. For a tire not defined in the standard, it refers to the standard internal pressure (however, not less than 250 KPa) of another tire size (defined in the standard) with the standard rim described as the standard rim. When there are multiple standard internal pressures not less than 250 KPa, it refers to the minimum value among them.

[0177] Hereinafter, an example of the above tire will be described with reference to the drawings, but it is not limited to such a form.

[0178] 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 plane of the paper is the circumferential direction of the tire 2. The tire 2 is symmetric about the left - right. The tread 4 includes a cap layer 30 (cap tread) and a base layer 28 (base tread).

[0179] Note that 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.

[0180] In the tire 2 of FIG. 1, the cap layer 30 is composed of the above rubber composition. The cap layer 30 contains a rubber component and silica. The rubber component contains styrene - butadiene rubber and / or butadiene rubber and a modified isoprene - based rubber. The total content of the styrene - butadiene rubber and the butadiene rubber in 100% by mass of the rubber component exceeds 50% by mass, the content of the modified isoprene - based rubber is less than 40% by mass, and the ratio (S / Ic) of the total styrene amount S (% by mass) in the rubber component to the content Ic (% by mass) of the modified isoprene - based rubber is less than 1.00.

[0181] In the tire 2, each sidewall 6 extends radially slightly 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.

[0182] 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.

[0183] Each clinch 10 is located slightly radially inward of the sidewall 6 and has a portion that contacts the rim at at least one place.

[0184] The carcass 14 is provided with a carcass ply 36. In this tire 2, the carcass 14 consists of a single carcass ply 36, but it may be composed of two or more plies.

[0185] In this tire 2, the carcass ply 36 is spanned between the bead cores 32 on both sides and extends along the tread 4 and the sidewall 6. The carcass ply 36 is folded back from the axial inner side toward the outer side around each bead core 32. By 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 includes a main part 36a and a pair of folded parts 36b.

[0186] Each bead core 32 is provided with a bead apex 34 extending 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.

[0187] 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.

[0188] 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 apparent 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.

[0189] Each of the inner layer 38 and the outer layer 40 desirably consists of a large number of parallel single-wire steel cords (steel monofilaments) and topping rubber (coating rubber). In other words, the belt layer 16 includes a large number of parallel steel monofilaments.

[0190] 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 the belt layer 16.

[0191] Although not shown, the band 18 desirably consists of a cord and topping rubber. The cord is spirally wound. 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 constrained by this cord, lifting of the belt layer 16 is suppressed.

[0192] The belt layer 16 and the band 18 in FIG. 1 constitute a reinforcing layer. The reinforcing layer may be constituted only by the belt layer 16.

[0193] 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 tread thickness (T) 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 tread in the tire radial direction, and 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 inner surface of the base layer 28 in the tire radial direction.

[0194] 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 retains the internal pressure of the tire 2.

[0195] Each chafer 22 is located near the bead 12. In this embodiment, it is desirable that the chafer 22 consists of cloth and rubber impregnated in the cloth. This chafer 22 may be integrated with the clinch 10.

[0196] 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.

[0197] 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. For this reason, even when the road surface is wet, the tire 2 can come into sufficient contact with the road surface. D in FIG. 2 shows the groove depth of the circumferential main groove 42 formed in the tread 4.

[0198] In the tire 2, regarding the content Sc of silica with respect to 100 parts by mass of the rubber component in the cap layer 30, the total content Mc of styrene-butadiene rubber and butadiene rubber in 100% by mass of the rubber component, the content Ic (mass%) of modified isoprene rubber with respect to 100 parts by mass of the rubber component, the thickness T (mm) of the cap layer 30, and the groove depth D (mm) of the main groove 42, it is desirable that Mc / T, Ic / T, T, D, and Sc / D are within the aforementioned ranges.

Example

[0199] Hereinafter, examples (embodiments) considered preferable in implementation are shown, but the scope of the present disclosure is not limited to the embodiments.

[0200] Hereinafter, various chemicals used in the production of tires will be collectively described. The chemicals are purified according to established methods as necessary. SBR: HPR850 manufactured by JSR Corporation (styrene content: 26.0% by mass, vinyl bond content: 59.0% by mass) BR: Polybutadiene rubber (BR150B manufactured by Ube Industries, Ltd., cis content: 97% by mass) IR: IR2200 manufactured by JSR Corporation Modified IR1: Production Example 1 below Modified IR2: Production Example 2 below Silica: Ultrasil VN3 manufactured by Evonik Degussa (average particle size: 19 nm, N2SA: 175 m 2 / g) Carbon black: Show black N220 manufactured by Cabot Japan (N2SA: 114 m 2 / g) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl)disulfide) manufactured by Evonik Degussa Oil: Diana Process NH-70S (aromatic process oil) manufactured by Idemitsu Kosan Co., Ltd. Resin: Sylvatraxx 4401 manufactured by Arizona Chemical (copolymer of α-methylstyrene and styrene, softening point: 85°C) Wax: Oz Ace Wax manufactured by Nippon Seiro Co., Ltd. Antioxidant 1: Nocrack 6C (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 2: Antage RD (polymer of 2,2,4-trimethyl-1,2-dihydroquinoline) manufactured by Kawaguchi Chemical Industry Co., Ltd. Zinc oxide: Zinc white No. 2 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Tsubaki manufactured by NOF Corporation Sulfur: Powder sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Nocceler CZ (CBS, N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Nocceler D (DPG, 1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0201] (Production Example 1: Synthesis of Modified IR1) n-BuLi (manufactured by Kanto Chemical: 1.60 mol / L (hexane solution), 9.0 mL, 14.4 mmol) is added to a mixed solution of isoprene (816 g, 12.0 mmol) and cyclohexane (4.0 kg), and the mixture is stirred at 50 °C for 6 hours. After the reaction, N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane (14 mL, 57.4 mmol) represented by the following formula is added to stop the polymerization. The resulting solution is taken out and concentrated under reduced pressure. The concentrated solution is poured into methanol (5.0 L) to separate the methanol-insoluble component, and the following modified IR1 is obtained. Functional group: having a functional group represented by the following formula (A1) at the end Mn: 243,000, Mw: 292,000 Ratio of 1,2-structure and 3,4-structure / ratio of 1,4-trans structure / 1,4-cis structure: 8 / 0 / 92 Tg: -61 °C Viscosity: 8,100 Pa·s [Chemical formula] [Chemical formula]

[0202] (Production Example 2: Synthesis of Modified IR2) n-BuLi (manufactured by Kanto Chemical Co., Inc.: 1.60 mol / L (hexane solution), 16.0 mL, 25.6 mmol) was added to a mixed solution of isoprene (805 g, 11.8 mmol) in cyclohexane (4.1 kg), and the mixture was stirred at 50 °C for 6 hours. After the reaction, N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane (7.0 mL, 28.7 mmol) was added to terminate the polymerization. The resulting solution was taken out and concentrated under reduced pressure. The concentrated solution was poured into methanol (10 L) to separate the methanol-insoluble component, and modified IR2 as follows was obtained. Functional group: having the functional group represented by the above formula (A1) at the terminal Mn: 125,000, Mw: 150,000 Ratio of 1,2-structure and 3,4-structure / ratio of 1,4-trans structure / 1,4-cis structure = 7 / 0 / 93 Tg: -62 °C Viscosity: 6,900 Pa·s

[0203] <Preparation of test tire> According to the compounding content shown in Table 1, using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd., materials other than sulfur and vulcanization accelerators were kneaded at 150 °C for 5 minutes to obtain a kneaded product. Sulfur and vulcanization accelerators were added to the kneaded product, and it was kneaded at 80 °C for 5 minutes using an open roll to obtain an unvulcanized rubber composition. The unvulcanized rubber composition for cap tread was molded into the shape of a cap tread (cap layer), and on a tire molding machine, it was bonded together with other tire members such as a base tread (base layer) to form an unvulcanized tire, which was vulcanized at 170 °C for 10 minutes to manufacture a test tire (size 205 / 70R15, passenger car tire) shown in FIGS. 1 and 2. The cap layer is composed of the tread rubber composition of the present embodiment, and the thickness ratio of the cap layer to the base layer is 4:1.

[0204] Assuming test tires obtained from compositions with formulations and specifications changed according to Table 1, the results calculated based on the following evaluation method are shown in Table 1. Note that the reference comparative example is as follows. Table 1: Comparative Example 5

[0205] <Wear resistance during high-speed driving> Each test tire is mounted on a vehicle, and the groove depth of the tread portion is measured after driving 50,000 km at an average speed of 100 km / h. From the measured values, the wear amount of the tread portion is calculated and expressed as an index with an evaluation criterion of 100. The larger the index, the less the wear amount, indicating better wear resistance during high-speed driving.

[0206]

Table 1

[0207] The present invention (1) is a tire provided with a tread containing a rubber component and silica, wherein the rubber component includes styrene-butadiene rubber and / or butadiene rubber and a modified isoprene-based rubber, the total content of the styrene-butadiene rubber and the butadiene rubber in 100% by mass of the rubber component exceeds 50% by mass, and the content of the modified isoprene-based rubber is less than 40% by mass, the ratio (S / Ic) of the total styrene amount S (% by mass) in the rubber component to the content Ic (% by mass) of the modified isoprene-based rubber is less than 1.00, and the ratio (Sc / T) of the content Sc (parts by mass) of the silica to the thickness T (mm) of the tread is more than 10.0 with respect to 100 parts by mass of the rubber component.

[0208] The present invention (2) is the tire according to the present invention (1), wherein S / Ic is 0.80 or less.

[0209] The present invention (3) is the tire according to the present invention (1) or (2), wherein Sc / T is 11.5 or more.

[0210] The present invention (4) is a tire in any combination with any one of the present inventions (1) to (3), wherein the content Sc of silica with respect to 100 parts by mass of the rubber component is 80 parts by mass or more.

[0211] The tire of the present invention (5) is a tire in any combination of any one of the present inventions (1) to (4) in which the ratio (Mc / T) of the total content Mc (mass%) of styrene-butadiene rubber and butadiene rubber in 100 mass% of the rubber component to the thickness T (mm) of the tread is 11.5 or more.

[0212] The tire of the present invention (6) is a tire in any combination of any one of the present inventions (1) to (5) in which the ratio (Ic / T) of the content Ic (mass%) of the modified isoprene-based rubber to 100 parts by mass of the rubber component to the thickness T (mm) of the tread is 2.8 or more.

[0213] The tire of the present invention (7) is a tire in any combination of any one of the present inventions (1) to (6) in which the thickness T (mm) of the tread is 5.5 mm or more.

[0214] The tire of the present invention (8) is a tire in any combination of any one of the present inventions (1) to (7) in which the groove depth D of the circumferential groove formed in the tread is 2.0 mm or more and 8.0 mm or less.

[0215] The tire of the present invention (9) is a tire in any combination of any one of the present inventions (1) to (8) in which the ratio (Sc / D) of the content Sc (parts by mass) of silica to 100 parts by mass of the rubber component to the groove depth D (mm) of the circumferential groove formed in the tread is 10.0 or more and 50.0 or less.

Explanation of Reference Numerals

[0216] 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 the tire T Thickness of the tread D Depth of the main groove of the circumferential main groove formed in the tread

Claims

1. A tire having a tread containing a rubber component and silica, wherein the rubber component includes styrene-butadiene rubber and / or butadiene rubber and a modified isoprene-based rubber, the total content of the styrene-butadiene rubber and the butadiene rubber in 100% by mass of the rubber component exceeds 50% by mass, and the content of the modified isoprene-based rubber is less than 40% by mass, the ratio (S / Ic) of the total styrene amount S (% by mass) in the rubber component to the content Ic (% by mass) of the modified isoprene-based rubber is less than 1.00, and a tire in which the ratio (Sc / T) of the content Sc (parts by mass) of the silica to the thickness T (mm) of the tread with respect to 100 parts by mass of the rubber component exceeds 10.

0.

2. The tire according to claim 1, wherein S / Ic is 0.80 or less.

3. The tire according to claim 1, wherein Sc / T is 11.5 or more.

4. The tire according to claim 1, wherein the content Sc of silica with respect to 100 parts by mass of the rubber component is 80 parts by mass or more.

5. The tire according to claim 1, wherein the ratio (Mc / T) of the total content Mc (% by mass) of styrene-butadiene rubber and butadiene rubber in 100% by mass of the rubber component to the thickness T (mm) of the tread is 11.5 or more.

6. The tire according to claim 1, wherein the ratio (Ic / T) of the content Ic (% by mass) of the modified isoprene-based rubber to the thickness T (mm) of the tread with respect to 100 parts by mass of the rubber component is 2.8 or more.

7. The tire according to claim 1, wherein the thickness T (mm) of the tread is 5.5 mm or more.

8. The tire according to claim 1, wherein the groove depth D of the circumferential groove formed in the tread is 2.0 mm or more and 8.0 mm or less.

9. The tire according to claim 1, wherein the ratio (Sc / D) of the content Sc (parts by mass) of silica to 100 parts by mass of the rubber component and the groove depth D (mm) of the circumferential groove formed in the tread is 10.0 or more and 50.0 or less.

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