tire

Abstract

To provide a tire that is excellent in integrated performance of abrasion resistance and wet grip performance.SOLUTION: A tire comprises a cap tread including rubber components, silica and reformed vegetable oil. In the cap tread, a content Tc of isoprene rubber in 100 mass% of the rubber components are 50 mass% or more, a content Sc of silica with respect to 100 parts by mass of the rubber components are 50 parts by mass or more and 150 parts by mass or less, and a content Vc of the reformed vegetable oil are 1 part by mass or more and 50 parts by mass or less. In the cap tread, a fracture elongation EB is 550% or more, and a loss tangent tanδ at 0°C is 0.37 or more. The Ic, the Sc, the Vc, the EB and an acetone extraction amount AE of the cap tread satisfy the following formula (1): (1) Ic / 50+Sc / 50+AE / 20+EB / 550≥4.3.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] The wear resistance and wet grip performance of a tire are conflicting performances, and it is generally difficult to achieve both.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In particular, due to the recent demand for reducing fossil fuels, there is an increasing demand to use isoprene rubber such as natural rubber instead of existing synthetic polymers, but it is desired to improve the wet grip performance while ensuring the wear resistance.

[0004] An object of the present invention is to solve the above problems and provide a tire having excellent comprehensive performance of wear resistance and wet grip performance.

Means for Solving the Problems

[0005] The present invention is a tire provided with a cap tread containing a rubber component, silica, and a modified vegetable oil, wherein the cap tread the content Ic of isoprene rubber in 100% by mass of the rubber component is 50% by mass or more, the content Sc of the silica with respect to 100 parts by mass of the rubber component is 50 parts by mass or more and 150 parts by mass or less, and the content Vc of the modified vegetable oil is 1 part by mass or more and 50 parts by mass or less, the cap tread has an elongation at break EB of 550% or more and a loss tangent tanδ at 0 ° C of 0.37 or more, the present invention relates to a tire in which the Ic, the Sc, the Vc, the EB, and the acetone extraction amount AE of the cap tread satisfy the following formula (1). (1) Ic / 50 + Sc / 50 + AE / 20 + EB / 550 ≧ 4.3

Effects of the Invention

[0006] The present invention relates to a tire having a cap tread containing a rubber component, silica, and a modified vegetable oil, wherein the cap tread has a content Ic of isoprene rubber in 100% by mass of the rubber component of 50% by mass or more, a content Sc of the silica of 50 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the rubber component, a content Vc of the modified vegetable oil of 1 part by mass or more and 50 parts by mass or less, the cap tread has an elongation at break EB of 550% or more and a loss tangent tanδ at 0 °C of 0.37 or more, and the Ic, the Sc, the Vc, the EB, and an acetone extraction amount AE of the cap tread satisfy the above formula (1). Therefore, it is possible to provide a tire having excellent comprehensive performance in terms of abrasion resistance and wet grip performance.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0008] The above tire includes a cap tread containing a rubber component, silica, and a modified vegetable oil, and the cap tread has a content Ic of isoprene rubber in 100% by mass of the rubber component of 50% by mass or more, a content Sc of the silica of 50 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the rubber component, a content Vc of the modified vegetable oil of 1 part by mass or more and 50 parts by mass or less, an elongation at break EB of 550% or more, and a loss tangent tanδ at 0 °C of 0.37 or more. Further, Ic, Sc, Vc, EB, and an acetone extraction amount AE of the cap tread satisfy the formula (1) "Ic / 50 + Sc / 50 + AE / 20 + EB / 550 ≥ 4.3".

[0009] The reason for obtaining the above-described effect by the above tire is not necessarily clear, but it is presumed as follows. Since it contains isoprene rubber such as natural rubber, silica, and modified vegetable oil, the hydrophobicity of silica is improved by the interaction between silica and the modified vegetable oil, and the dispersibility in the isoprene rubber is improved. As a result, the hysteresis loss is improved, and an effect of improving the wet grip performance can be obtained. In addition, the double bond sites present in the modified vegetable oil bind to isoprene rubber such as natural rubber via sulfur, so that a high-strength formulation can be obtained without impairing the breaking strength of the isoprene rubber itself. Furthermore, by satisfying a breaking elongation at break of a predetermined value or more, tanδ(0°C), and formula (1), while ensuring good breaking strength, an effect of improving the wet grip performance by the modified vegetable oil can be obtained. Therefore, it is presumed that the overall performance of wear resistance and wet grip performance is improved by the above tire.

[0010] In this way, the above tire solves the problem (objective) of improving the overall performance of wear resistance and wet grip performance by adopting a configuration that satisfies the relationship of "Ic / 50 + Sc / 50 + AE / 20 + EB / 550 ≥ 4.3". That is, the parameter of "Ic / 50 + Sc / 50 + AE / 20 + EB / 550 ≥ 4.3" does not define the problem (objective). The problem of the present application is to improve the overall performance of wear resistance and wet grip performance, and as a solution means therefor, a configuration that satisfies the parameter is adopted.

[0011] The rubber composition for the cap tread contains a rubber component. Here, the rubber component is a component that contributes to crosslinking. Generally, a polymer having a weight average molecular weight (Mw) of 10,000 or more and a polymer component that is not extracted by acetone corresponds to the rubber component. The elastomer component is in a solid state at normal temperature (25°C).

[0012] 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, particularly preferably 270,000 or more, and 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.

[0013] In this 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). Also, in the case of a polymer having a modifying group, since the modifying group and the silica gel of the column interact and accurate Mw and Mn cannot be obtained, usually, Mw and Mn are measured before the modification treatment is carried out.

[0014] The rubber component that can be used in the above rubber composition for cap tread may be an unmodified rubber or a modified rubber. Examples of the modified rubber include rubbers having a functional group that interacts with a filler such as silica. For example, a terminal-modified rubber (terminal-modified rubber having the above functional group at the terminal) in which at least one end of the rubber is modified with a compound (modifying agent) having the above functional group, a main-chain modified rubber having the above functional group in the main chain, a main-chain terminal-modified rubber having the above functional group in the main chain and at the terminal (for example, a main-chain terminal-modified rubber having the above functional group in the main chain and at least one end modified with the above modifying agent), and a terminal-modified rubber modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or an epoxy group introduced therein, etc. are mentioned.

[0015] Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an 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.

[0016] The rubber composition for cap tread contains an isoprene rubber as a rubber component.

[0017] In the rubber composition for cap tread, the content Ic (total amount of non-modified isoprene rubber and modified isoprene rubber) of the isoprene rubber in 100% by mass of the rubber component is 50% by mass or more, preferably 55% by mass or more, more preferably 58% by mass or more, still more preferably 60% by mass or more. The upper limit is not particularly limited and may be 100% by mass, but is preferably 90% by mass or less, more preferably 85% by mass or less, still more preferably 80% by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0018] Examples of isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. Examples of NR include SIR20, RSS♯3, TSR20, and other rubber industry-standard rubbers. Examples of IR include IR2200 and other rubber industry-standard rubbers. Examples of modified NR include deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), and other rubbers. Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more.

[0019] Among these, it is preferable that NR is contained since the above-mentioned effects can be obtained more effectively. In order to improve wet grip performance, it is generally effective to incorporate a large amount of silica as a filler, but it is difficult to introduce functional groups that interact with silica into NR, as in styrene-butadiene rubber, and there are tendencies to have issues with the dispersibility of silica and the reinforcing properties of silica. Therefore, in a formulation that mainly uses NR, even if silica is incorporated, the expected improvement in wet grip performance cannot be obtained, and abrasion resistance also tends to deteriorate due to insufficient reinforcing properties. In contrast, in the above tire, as described above, an interaction occurs between the silica and the modified vegetable oil, improving the hydrophobicity of the silica, improving its dispersibility in NR, and improving the wet grip performance. In addition, the double bond site of the modified vegetable oil bonds with NR via sulfur, resulting in a compound with high strength without impairing the breaking strength of the NR itself. Therefore, it is assumed that even in a compound that mainly contains NR, it is possible to improve the overall performance of abrasion resistance and wet grip performance.

[0020] In the above rubber composition for cap tread, the content of NR in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 55% by mass or more, still more preferably 60% by mass or more. The upper limit is not particularly limited and may be 100% by mass, but is preferably 90% by mass or less, more preferably 85% by mass or less, still more preferably 80% by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0021] In the above rubber composition for cap tread, a rubber component other than the above isoprene rubber may be included. Examples of such rubber components include diene rubbers. Examples of diene rubbers include butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), etc. In addition, examples of rubber components include butyl rubber, fluororubber, etc. These may be used alone or in combination of two or more. Further, these rubber components may be subjected to modification treatment or hydrogenation treatment, and extended rubber extended with an oil, a resin, a liquid rubber component, etc. may also be used. Among them, it is preferable to contain at least one of BR and SBR.

[0022] BR is not particularly limited, and 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 spectrometry.

[0023] 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 content of BR can be calculated by {Σ(content of each BR × cis content of each BR)} / total content of all BRs. For example, in 100% by mass of the rubber component, when the BR with a cis content of 90% by mass is 20% by mass and the BR with a cis content of 40% by mass is 10% by mass, the average cis content of BR is 73.3% by mass (=(20×90 + 10×40) / (20 + 10)).

[0024] Also, either non-modified BR or modified BR can be used for BR. Examples of modified BR include modified BRs into which functional groups similar to those of modified rubbers are introduced. Further, hydrogenated butadiene polymers (hydrogenated BRs) can also be used for BR.

[0025] As BR, for example, products of Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

[0026] In the above rubber composition for cap tread, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 8% by mass or more, still more preferably 10% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0027] SBR is not particularly limited. 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.

[0028] The styrene content of SBR is preferably 5% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more. The styrene content is preferably 60% by mass or less, more preferably 40% by mass or less, still more preferably 35% by mass or less. When within the above range, the effect tends to be obtained more favorably. In the present specification, the styrene content 1 can be measured by 1H-NMR measurement.

[0029] When there is one type of SBR, the styrene content of the SBR means the styrene content of that SBR. When there are multiple types, it means the average styrene content. The average styrene content of SBR can be calculated by {Σ(content of each SBR × styrene content of each SBR)} / total content of all SBRs. For example, in 100% by mass of the rubber component, when 85% by mass of SBR has a styrene content of 40% by mass and 5% by mass of SBR has a styrene content of 25% by mass, the average styrene content of SBR is 39.2% by mass (=(85×40 + 5×25) / (85 + 5)).

[0030] The vinyl bond content of SBR is preferably 30% by mass or more, more preferably 40% by mass or more, and still more preferably 50% by mass or more. When the vinyl bond content is within the range of preferably 70% by mass or less, more preferably 65% by mass or less, and still more preferably 60% by mass or less, the effect tends to be obtained more favorably. In addition, in this specification, the vinyl bond content (1,2-bonded butadiene unit amount) can be measured by infrared absorption spectroscopy.

[0031] The vinyl bond content (1,2-bonded butadiene unit amount) of SBR is the ratio of vinyl bonds when the total mass of the butadiene part in SBR is set to 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 that SBR. 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 [% by mass] - styrene content of each SBR [% by mass]) × vinyl content of each SBR [% by mass]} / Σ{content of each SBR × (100 [% by mass] - styrene content of each SBR [% by 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% by mass and a vinyl content of 30% by mass, 15 parts by mass of SBR with a styrene content of 25% by mass and a vinyl content of 20% by mass, and the remaining 10 parts by mass are other than SBR, the average vinyl content of SBR is 28% by mass (= {75 × (100 [% by mass] - 40 [% by mass]) × 30 [% by mass] + 15 × (100 [% by mass] - 25 [% by mass]) × 20 [% by mass]}) / {75 × (100 [% by mass] - 40 [% by mass]) + 15 × (100 [% by mass] - 25 [% by mass])}.

[0032] As SBR, either non-modified SBR or modified SBR can be used. Examples of the modified SBR include those with functional groups similar to the modified rubber introduced. Also, as SBR, hydrogenated styrene-butadiene copolymer (hydrogenated SBR) can be used.

[0033] As SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used. Also, those synthesized by known methods can be used.

[0034] In the above rubber composition for cap tread, the content of SBR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, and preferably 50% by mass or less, more preferably 45% by mass or less, still more preferably 40% by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0035] Incidentally, the raw materials (monomers) of synthetic rubbers such as SBR and BR may be derived from petroleum or recycled from rubber products such as tires and non-rubber products such as polystyrene. The monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled butadiene and recycled aromatic vinyl. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl is not particularly limited, and examples include styrene. Among them, it is preferable to use recycled butadiene (recycled butadiene) and / or recycled styrene (recycled styrene) as raw materials.

[0036] The method for producing recycled monomers is not particularly limited. For example, it may be synthesized from recycled naphtha obtained by decomposing rubber products such as tires. 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.

[0037] Furthermore, the raw materials (monomers) of synthetic rubbers such as SBR and BR may be derived from biomass. The monomers derived from biomass (biomass monomers) are not particularly limited, and examples include biomass-derived butadiene and biomass-derived aromatic vinyl. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl is not particularly limited, and examples include styrene. The method for producing biomass monomers is not particularly limited, and examples include those by biological and / or chemical and / or physical conversion of animals and plants. Fermentation by microorganisms is typical of biological conversion, and examples of chemical and / or physical conversion include those by catalysts, high heat, high pressure, electromagnetic waves, supercritical fluids, and combinations thereof. Examples of the biomass sources of these monomers include sugars, wood, plant residues after obtaining useful components, plant-derived ethanol, biomass naphtha, and the like.

[0038] The polymers synthesized from biomass monomer components (biomass polymers) are not particularly limited, and examples include polybutadiene rubber synthesized from biomass-derived butadiene, aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl, and the like. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0039] 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.

[0040] pMC is the ratio of the 14 C concentration of the sample to the 14 C concentration of the modern standard reference, and this value is used as an index indicating the biomass ratio of the compound (rubber). The significance of this value is described below.

[0041] In one mole (6.02×10 23 pieces) of carbon atoms, there are approximately 6.02×10 11 pieces of 14 C, which is about one trillionth of the normal carbon atoms. 14 14 14 14 14 14 14 C is called a radioactive isotope, and its half-life is 5730 years and it decreases regularly. It takes 226,000 years for all of these to decay. Therefore, in fossil fuels such as coal, oil, and natural gas, which are considered to have passed more than 226,000 years after carbon dioxide in the atmosphere was taken up and fixed by plants, etc., all of the

[0042] On the one hand, 14 C undergoes nuclear reactions in the atmosphere by cosmic rays, is continuously generated, and is balanced with the decrease due to radioactive decay. In the Earth's atmospheric environment, 14 the amount of C is a certain amount. Therefore, the 14 C concentration of substances derived from biomass resources circulating in the current environment is about 1×10 -12 mol% with respect to the entire C atoms as described above. Therefore, by utilizing the difference between these values, the ratio (biomass ratio) of the compound (biomass resource-derived compound) derived from natural resources in a certain compound (rubber) can be calculated.

[0043] 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 (the radioactivity intensity of 13 C per gram of carbon) is separated for each carbon isotope, 14 C is corrected to a certain value, and the value after applying the decay correction from 1950 AD to the measurement date is used as the standard

[0044] Therefore, if the rubber is made of a 100% biomass (natural) - derived substance, although there are regional differences, it will show a value of approximately 110 pMC (currently, in the normal state, it often does not reach 100). On the other hand, for chemical substances derived from fossil fuels such as petroleum, when measuring the 14 C concentration, it will show almost 0 pMC (for example, 0.3 pMC). This value corresponds to a biomass ratio of 0% mentioned above.

[0045] From the above, using materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio, in the rubber composition is suitable from the perspective of environmental protection.

[0046] The above rubber composition for cap tread contains silica as a filler. The silica that can be used is not particularly limited. For example, silica prepared by the dry method (anhydrous silica), silica prepared by the wet method (hydrous silica), etc., which are common in the tire industry, can be used. The raw material of silica is not particularly limited. For example, it may be a raw material derived from minerals such as quartz, or a raw material derived from organisms such as rice husks (for example, silica using biomass materials such as rice husks as raw materials), or silica recycled from products containing silica may 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.

[0047] Silica using biomass materials as raw materials can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and reacting the silicate with sulfuric acid in the same way as conventional wet silica to precipitate silicon dioxide, followed by filtration, washing with water, drying, and pulverization.

[0048] Silica recycled from products containing silica can be, for example, silica recovered from products containing silica such as electronic components such as semiconductors, tires, desiccants, and filter materials such as diatomaceous earth. Further, the recovery method is not particularly limited, and examples thereof include thermal decomposition and decomposition by electromagnetic waves. Among these, silica recovered from electronic components such as semiconductors or tires is preferable.

[0049] When silica crystallizes, it becomes insoluble in water and the silicic acid that is its component cannot be utilized. By controlling the combustion temperature and combustion time, crystallization of silica in rice husk ash can be suppressed (see, for example, Japanese Patent Application Laid-Open No. 2009-2594, Akita Prefectural University Web Journal B / 2019, vol. 6, p. 216-222, etc.).

[0050] Amorphous silica extracted from rice husks can be those commercially available from companies such as Wilmar.

[0051] 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.

[0052] In the above rubber composition for cap treads, the content Sc of silica with respect to 100 parts by mass of the rubber component is 50 parts by mass or more, preferably 70 parts by mass or more, more preferably 90 parts by mass or more, still more preferably 100 parts by mass or more. The upper limit is 150 parts by mass or less, preferably 140 parts by mass or less, more preferably 130 parts by mass or less, still more preferably 120 parts by mass or less. When within the above range, the effect tends to be obtained more favorably. In addition, it is desirable that the content of the above plant-derived silica and the content of the above rice husk silica are also in the same range.

[0053] When silica is contained in a predetermined amount or more, particularly 70 parts by mass or more, the mechanism by which more effects can be obtained is not clear. However, even with a large amount of silica, due to the interaction between silica and the modified vegetable oil, silica is highly dispersed in the isoprene rubber, and the hysteresis loss is improved, so that the wet grip performance is greatly improved. Therefore, it is considered that the overall performance of wear resistance and wet grip performance is improved.

[0054] The rubber composition for the cap 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); difficult-to-disperse fillers, etc. may be mentioned. Among them, from the viewpoint of obtaining more effects, carbon-derived fillers (carbon-containing fillers) such as carbon black are preferable. The fillers may be used alone or in combination of two or more.

[0055] In the above rubber composition for the cap tread, the carbon black that can be used is not particularly limited, and 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 Co., 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 may be appropriately used in an equivalent substitution with the above carbon black.

[0056] 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. Further, 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 it is within the above range, the effect tends to be obtained more favorably. Incidentally, the nitrogen adsorption specific surface area of carbon black is determined according to JIS K6217-2:2001.

[0057] The dibutyl phthalate oil absorption amount (DBP) of carbon black is preferably 40 ml / 100 g or more, more preferably 60 ml / 100 g or more, and still more preferably 70 ml / 100 g or more. Further, the above DBP is preferably 200 ml / 100 g or less, more preferably 150 ml / 100 g or less, and still more preferably 100 ml / 100 g or less. When it is within the above range, the effect tends to be obtained more favorably. Incidentally, the DBP of carbon black is determined according to the measurement method of JIS K6217-4:2001.

[0058] In the above rubber composition for cap treads, the content of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and 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, and still more preferably 10 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0059] Examples of the hardly dispersible filler include microfibrillated vegetable fibers, short fibrous cellulose, gel-like compounds, etc. Among them, microfibrillated vegetable fibers are preferred.

[0060] As the microfibrillated plant fiber, cellulose microfibril is preferable in terms of obtaining good reinforcing properties. The cellulose microfibril is not particularly limited as long as it is derived from natural products. For example, resource biomass such as fruits, grains, and root vegetables, wood, bamboo, hemp, jute, kenaf, and pulp, paper, cloth, agricultural crop residues, food waste, and waste biomass such as sewage sludge obtained from these as raw materials, unused biomass such as rice straw, wheat straw, and thinned wood, and those derived from cellulose produced by tunicates, acetic acid bacteria, etc. These microfibrillated plant fibers may be used alone or in combination of two or more.

[0061] In the present specification, the cellulose microfibril typically means a cellulose fiber having an average fiber diameter within the range of 10 μm or less, and more typically a cellulose fiber having a micro-structure with an average fiber diameter of 500 nm or less formed by an aggregation of cellulose molecules. A typical cellulose microfibril is formed, for example, as an aggregate of cellulose fibers having the above-mentioned average fiber diameter.

[0062] When the rubber composition for the cap tread contains a hardly dispersible filler, the content of the hardly dispersible filler is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit of the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0063] In the above rubber composition for cap tread, the content of the filler (total amount of fillers such as silica and carbon black) is preferably 55 parts by mass or more, more preferably 75 parts by mass or more, still more preferably 95 parts by mass or more, particularly preferably 105 parts by mass or more, and preferably 155 parts by mass or less, more preferably 145 parts by mass or less, still more preferably 135 parts by mass or less, particularly preferably 125 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0064] In the above rubber composition for cap tread, the silica content rate in the filler (100% by mass) is preferably 91% by mass or more, more preferably 93% by mass or more, still more preferably 96% by mass or more. The upper limit is not particularly limited and may be 100% by mass, but is preferably 99% by mass or less, more preferably 98% by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0065] When the silica in the filler is a predetermined amount or more, particularly 93% by mass or more, the mechanism by which more effects are obtained is not clear. However, even with a large amount of silica, due to the interaction between silica and the modified vegetable oil, the silica is highly dispersed in the isoprene rubber, and the hysteresis loss is improved, thereby greatly improving the wet grip performance. Therefore, it is considered that the comprehensive performance of abrasion resistance and wet grip performance is improved.

[0066] The above rubber composition for cap 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, vinyl type such as vinyltriethoxysilane and vinyltrimethoxysilane, amino type such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy type such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, nitro type such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, chloro type such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane, etc. can be mentioned. As commercially available products, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Admax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used. These may be used alone or in combination of two or more kinds.

[0067] In the above rubber composition for cap 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 within the above range, the effect tends to be obtained more favorably.

[0068] The above rubber composition for cap tread contains a modified vegetable oil as a plasticizer. The modified vegetable oil may be used alone or in combination of two or more.

[0069] In the present specification, the modified vegetable oil refers to one having a lower content of carbon-carbon double bonds than before modification (a vegetable oil having a lower content of carbon-carbon double bonds than the vegetable oil before modification), and means a vegetable oil whose carbon-carbon double bond amount has decreased by modifying the vegetable oil.

[0070] Examples of the above modified vegetable oil include vegetable oils that have been modified in some way in the carbon-carbon double bonds of the vegetable oil and have a lower carbon-carbon double bond amount than before modification. For example, vegetable oils in which the carbon-carbon double bonds in the molecule have been modified by various modifiers, oxidized vegetable oils (such as lubricating oils and waste cooking oils after use in a rubber mixing mixer or an automobile engine), and vegetable oils in which vegetable oils are bonded to each other using the carbon-carbon double bonds in the molecule are exemplified.

[0071] In the above rubber composition for cap tread, the content Vc of the above modified vegetable oil with respect to 100 parts by mass of the rubber component is 1 part by mass or more, preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and still more preferably 20 parts by mass or more. The upper limit of the content is 50 parts by mass or less, preferably 45 parts by mass or less, more preferably 42 parts by mass or less, and still more preferably 40 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0072] Among the above-mentioned modified vegetable oils, from the viewpoint of obtaining more effects, vegetable oils in which the carbon-carbon double bonds in the molecule are modified with various modifiers are preferred, and among them, epoxidized vegetable oils are more preferred.

[0073] The above-mentioned epoxidized vegetable oil is a compound obtained by epoxidizing the unsaturated bond portion of the fatty acid of the vegetable oil. As the above-mentioned vegetable oil, usually, vegetable oils extracted from plant seeds, fruits, etc. can be used.

[0074] Examples of the above-mentioned vegetable oil (plant-derived oil) include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, other polyunsaturated vegetable oils, mixtures thereof, etc. In addition, monoglycerides and diglycerides of unsaturated fatty acids derived from vegetable oils can also be used for the preparation of epoxidized vegetable oils. These may be used alone or in combination of two or more. Generally, vegetable oils mainly contain unsaturated fatty acids such as linoleic acid, linolenic acid, and oleic acid.

[0075] Among the above-mentioned vegetable oils, from the viewpoint of obtaining more effects, epoxidized soybean oil, epoxidized linseed oil, and epoxidized castor oil are preferred, and epoxidized soybean oil and epoxidized linseed oil are more preferred.

[0076] As the above-mentioned epoxidized vegetable oil, commercially available products such as those manufactured by Sanwa Chemical Co., Ltd., Takemoto Yushi Co., Ltd., ADEKA Corporation, Daicel Ornex Co., Ltd., and MIWON can be used.

[0077] In the above rubber composition for cap treads, the content of the epoxidized vegetable oil (total amount of epoxidized soybean oil, epoxidized linseed oil, epoxidized castor oil, etc.) is preferably 1 part by mass or more, more preferably 10 parts by mass or more, still more preferably 20 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit of the content is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, still more preferably 40 parts by mass or less. When within the above range, the effect tends to be obtained more favorably. In addition, the content of epoxidized soybean oil, epoxidized linseed oil, or the content of epoxidized castor oil alone is also preferably in the same range.

[0078] The above rubber composition for cap treads may contain a plasticizer other than the modified vegetable oil. In this specification, a plasticizer is a material that imparts plasticity to the rubber component, and it may be liquid or solid at normal temperature (25°C). These may be used alone or in combination of two or more.

[0079] Examples of the plasticizer include oils other than the modified vegetable oil, liquid polymers, resins, etc. These may be used alone or in combination of two or more.

[0080] The above oil is not particularly limited, and conventional oils such as paraffinic process oil, aromatic process oil, naphthenic process oil, etc., low PCA (polycyclic aromatic) process oil such as TDAE, MES, the vegetable oils described in the above modified vegetable oil, and mixtures thereof can be used. These may be used alone or in combination of two or more.

[0081] As the above oil, for example, products of Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Corporation, Orisoy Co., H&R Co., Toyokuni Seiyu Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kogyo Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0082] 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), and the like. These may have a polar group-modified terminal or main chain. Further, hydrogenated products thereof can also be used.

[0083] The above liquid diene polymer preferably has a polystyrene-reduced weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) of 1.0×10 3 ~5.0×10 4 and more preferably 3.0×10 3 ~1.5×10 4 . Further, the lower limit or upper limit of Mw of the liquid diene polymer may be 4500 or 8500. In the present specification, Mw of the liquid diene polymer is a polystyrene-reduced value measured by gel permeation chromatography (GPC).

[0084] Examples of the liquid diene polymer include products of Sartomer Company and Kuraray Co., Ltd.

[0085] From the viewpoint of obtaining more effects, it is desirable that the rubber composition for cap tread contains the above resin.

[0086] When the above resin is contained, the mechanism by which more effects are obtained is not clear, but it is considered that the resin improves the hysteresis loss, thereby improving the wet grip performance, and thereby improving the overall performance of wear resistance and wet grip performance.

[0087] As the above-mentioned resin, as a tire formulation, resins (resins) commonly used can be used, and they may be liquid or solid at normal temperature (25°C). For example, aromatic vinyl polymers, coumarone-indene resins, coumarone resins, indene resins, 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 derived from a plurality of sources. Among them, from the viewpoint of obtaining more effects, aromatic vinyl polymers, petroleum resins, terpene resins, and hydrogenated resins thereof are desirable.

[0088] When using a resin that is solid at normal temperature as the above-mentioned resin, the softening point is preferably 50°C or higher, more preferably 55°C or higher, still more preferably 60°C or higher, and particularly preferably 85°C or higher. Also, it is preferably 160°C or lower, more preferably 150°C or lower, still more preferably 140°C or lower, and particularly preferably 100°C or lower. When within the above range, there is a tendency to obtain better effects. When the resin is liquid at normal temperature, the softening point is preferably 20°C or lower, preferably 10°C or lower, and preferably 0°C or lower. In the case of a hydrogenated resin, it is desirable that the softening point is the same as above. Note that the softening point of the above-mentioned resin is the temperature at which the ball drops when measured with a ring and ball softening point measuring device according to the softening point defined in JIS K6220-1:2001.

[0089] The above-mentioned aromatic vinyl polymer is a polymer containing an aromatic vinyl monomer as a structural 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.

[0090] The above-mentioned coumarone-indene resin is a resin containing coumarone and indene as the main monomer components constituting the resin skeleton (main chain). Examples of monomer components other than coumarone and indene contained in the skeleton include styrene, α-methylstyrene, methyl indene, vinyl toluene, and the like.

[0091] The above-mentioned coumarone resin is a resin containing coumarone as the main monomer component constituting the resin skeleton (main chain).

[0092] The above-mentioned indene resin is a resin containing indene as the main monomer component constituting the resin skeleton (main chain).

[0093] As the above-mentioned phenol resin, for example, known polymers such as those obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde, and furfural in the presence of an acid or alkali catalyst can be used. Among them, those obtained by reacting with an acid catalyst (such as novolak-type phenol resin) are preferred.

[0094] Examples of the above-mentioned rosin resin include rosin-based resins typified by natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

[0095] Examples of the above-mentioned petroleum resin include C5 resin, C9 resin, C5 / C9 resin, dicyclopentadiene (DCPD) resin, C9 / DCPD resin, and hydrogenated products thereof. Among them, DCPD resin, hydrogenated DCPD resin, C9 / DCPD resin, and C9 / hydrogenated DCPD resin are preferred.

[0096] The above terpene resin is a polymer containing terpenes as constituent units. For example, there are polyt terpene 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.

[0097] 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 and having a carboxyl group. Among them, a solventless carboxyl group-containing styrene acrylic resin can be preferably used.

[0098] As the above resin, for example, products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, ExxonMobil, KRATON, Nippon Paint Co., Ltd., Nippon Catalyst Co., Ltd., ENEOS Co., Ltd., Arakawa Chemical Industries, Ltd., Tago Chemical Industry Co., Ltd., etc. can be used.

[0099] 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 plasticizer.

[0100] 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]

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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 10000 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.

[0105] The farnesene-based polymer may be in a liquid state or a solid state at normal temperature (25°C). Among them, a liquid farnesene-based polymer in a liquid state at normal temperature (25°C) is desirable.

[0106] In the rubber composition for cap tread, the content of the plasticizer (total amount of plasticizers) is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, still more preferably 50 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, still more preferably 50 parts by mass or less. When within the above range, the effect tends to be obtained more favorably. Note that the content of the plasticizer includes the amount of oil and resin contained in the oil-extended rubber and resin-extended rubber.

[0107] In the rubber composition for cap tread, the content of the solid plasticizer in a solid state at normal temperature (25 °C) is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less. When within the above range, the effect tends to be obtained more favorably. Note that the content of the above resin in a solid state at normal temperature (25 °C) and the content of the above aromatic vinyl polymer in a solid state at normal temperature (25 °C) are also preferably in the same range.

[0108] In the above rubber composition, the content of the liquid plasticizer in a liquid state at normal temperature (25 °C) is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less. When 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) (total amount of the modified vegetable oil, other oils, and the amount of oil contained in the oil-extended rubber) is also preferably in the same range.

[0109] The above rubber composition for cap tread preferably contains an anti-aging agent from the viewpoints of crack resistance, ozone resistance, etc.

[0110] 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.

[0111] In the above rubber composition for cap tread, the content of the anti-aging agent is preferably 0.5 part by mass or more, more preferably 1.5 part by mass or more, still more preferably 2.5 part by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 7.0 parts by mass or less, more preferably 5.0 parts by mass or less.

[0112] The rubber composition for cap tread preferably contains stearic acid. In the rubber composition for cap tread, the content of stearic acid is preferably 0.5 part by mass or more, more preferably 2.0 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component.

[0113] 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.

[0114] The rubber composition for cap tread preferably contains zinc oxide. In the rubber composition for cap tread, the content of zinc oxide is preferably 0.5 part by mass or more, more preferably 2.0 parts by mass or more, and preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, based on 100 parts by mass of the rubber component.

[0115] 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.

[0116] The rubber composition for cap tread may be blended with wax. In the rubber composition for cap 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.

[0117] The wax is not particularly limited, and any wax commonly used in the tire industry can be preferably used. For example, petroleum waxes, mineral waxes, synthetic waxes, plant-derived waxes, etc. can be mentioned. Among them, petroleum waxes and plant-derived waxes are preferred, and petroleum waxes are more preferred. Examples of plant-derived waxes include rice wax, carnauba wax, candelilla wax, etc. Examples of petroleum waxes include paraffin wax, microcrystalline wax, and their selected special waxes, etc., and paraffin wax is preferred. Note that the wax according to this embodiment does not contain stearic acid. As the wax, for example, those commercially available from Ouchi Shinsei Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., etc. can be used. These waxes may be used alone or in combination of two or more.

[0118] The rubber composition for the cap tread contains sulfur. In the rubber composition for the cap tread, the sulfur content is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, still more preferably 1.2 part by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 2.5 parts by mass or less, more preferably 2.0 parts by mass or less, still more preferably 1.5 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0119] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, soluble sulfur, etc., which are generally used in the rubber industry. As commercially available products, products of Tsuruami Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis Co., Ltd., Nippon Karyu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

[0120] The rubber composition for the cap tread preferably contains a vulcanization accelerator. In the above rubber composition for cap treads, the content of the vulcanization accelerator is not particularly limited and may be freely determined according to the desired vulcanization rate and crosslink density. However, it is preferably 1.0 part by mass or more, more preferably 3.0 part by mass or more, still more preferably 3.9 part by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, still more preferably 6.0 parts by mass or less.

[0121] 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. As commercially available products, products of Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., etc. can be used. 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.

[0122] In addition to the above components, the above rubber composition for cap treads may be appropriately blended with compounding agents generally used in the tire industry, such as materials for release agents.

[0123] In this specification, various materials containing carbon atoms (for example, 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.

[0124] The rubber composition for the cap tread can be produced, for example, by kneading the above components using a rubber kneading device such as an open roll or a Banbury mixer, and then vulcanizing.

[0125] 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.

[0126] The rubber composition for the cap tread (vulcanized rubber composition) has an elongation at break EB of 550% or more. EB is preferably 560% or more, more preferably 570% or more, still more preferably 580% or more. The upper limit of EB is not particularly limited, but is preferably 740% or less, more preferably 700% or less, still more preferably 680% or less. When within the above range, the effect can be preferably obtained. In this specification, the elongation at break EB is the value of the elongation at break EB at 23 °C measured according to JIS K6251:2010.

[0127] EB (elongation at break) can be mainly adjusted by the blending amounts of the reinforcing agent and the softening agent.

[0128] The above rubber composition for cap tread (vulcanized rubber composition) has a loss tangent tanδ at 0°C of 0.37 or more. The tanδ at 0°C is preferably 0.40 or more, more preferably 0.42 or more, still more preferably 0.44 or more, and particularly preferably 0.45 or more. The upper limit of tanδ at 0°C is not particularly limited, but is preferably 0.80 or less, more preferably 0.75 or less, and still more preferably 0.70 or less. When within the above range, the effects can be preferably obtained. In this specification, the tanδ at 0°C is the loss tangent measured under the conditions of a temperature of 0°C, an initial strain of 10%, a dynamic strain of 2.5%, a frequency of 10 Hz, and an elongation mode.

[0129] The tanδ at 0°C can be adjusted, for example, by adjusting the amount of filler, the amount of carbon black, blending a liquid resin or a liquid polymer, blending silica or aluminum hydroxide, blending a filler with a small particle size, or reducing the particle size of the filler. Specifically, when increasing the amount of filler or carbon black, blending a liquid resin, a liquid polymer, silica or aluminum hydroxide, or blending a filler with a small particle size, the tanδ at 0°C tends to increase.

[0130] The acetone extraction amount AE (mass%) of the above rubber composition for cap tread (vulcanized rubber composition) is preferably 18 mass% or more, more preferably 22 mass% or more, and still more preferably 23 mass% or more. The upper limit of AE is preferably 30 mass% or less, more preferably 28 mass% or less, and still more preferably 26 mass% or less. When within the above range, the effects tend to be preferably obtained.

[0131] When the acetone extraction amount is a predetermined amount or more, particularly 22 mass% or more, the mechanism by which more effects are obtained is not clear, but when the acetone extraction amount is large, the hydrophobicity of silica is improved, and the dispersibility in the isoprene rubber is improved. Therefore, it is considered that the hysteresis loss is improved, the wet grip performance is improved, and as a result, the comprehensive performance of abrasion resistance and wet grip performance is improved.

[0132] In this specification, the acetone extraction amount (AE) is a value measured by the measurement method of the acetone extraction amount conforming to JIS K 6229:2015.

[0133] As a method for adjusting AE, a method known to those skilled in the art can be adopted. For example, when the amount of plasticizer such as various oils in the rubber composition increases, it tends to increase.

[0134] The content Ic (mass %) of the isoprene rubber in 100 mass % of the rubber component of the rubber composition for cap tread, the content Sc (parts by mass) of the silica with respect to 100 parts by mass of the rubber component of the rubber composition for cap tread, the content Vc (parts by mass) of the modified vegetable oil with respect to 100 parts by mass of the rubber component of the rubber composition for cap tread, the elongation at break EB of the rubber composition for cap tread (vulcanized rubber composition), and the acetone extraction amount AE (mass %) of the rubber composition for cap tread (vulcanized rubber composition) satisfy the following formula (1). (1) Ic / 50 + Sc / 50 + AE / 20 + EB / 550 ≥ 4.3 The right side of formula (1) is preferably 4.5, more preferably 5.3, and still more preferably 5.8. The upper limit of Ic / 50 + Sc / 50 + AE / 20 + EB / 550 is not particularly limited, but is preferably 7.0 or less, more preferably 6.7 or less, and still more preferably 6.5 or less. When within the above range, the effect tends to be preferably obtained.

[0135] The rubber composition for cap tread is used for the cap tread of a tire member.

[0136] The above tire is manufactured by a conventional method using the above rubber composition for the cap tread. That is, a composition blended with various additives as required is extruded into the shape of various tire members such as the cap tread at the unvulcanized stage, molded by a conventional 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.

[0137] The above tire is not particularly limited, and examples include pneumatic tires, solid tires, airless tires, etc. Among them, pneumatic tires are preferred.

[0138] The above tire is preferably used as a passenger car tire, a large passenger car tire, a large SUV tire, a truck / bus tire, a two-wheeler tire, a racing tire, a winter tire (a studless tire, a snow tire, a studded tire), an all-season tire, a run-flat tire, an aircraft tire, a mining tire, etc.

[0139] In the above tire, the thickness T (mm) of the cap tread is preferably 7.0 mm or more, more preferably 7.5 mm or more, and still more preferably 8.0 mm or more. The upper limit of the thickness T of the cap tread is preferably 12.0 mm or less, more preferably 11.0 mm or less, and still more preferably 10.5 mm or less. Also, when within the above range, the effect tends to be preferably obtained.

[0140] In this specification, the thickness T of the cap tread refers to the thickness of the cap tread on the tire equatorial plane in the radial cross-section of the tire, and in the radial cross-section of the tire, it is the straight-line distance from the tread surface (the surface of the cap tread) to the inner surface of the cap tread in the radial direction of the tire.

[0141] The thickness of the cap tread on the tire equatorial plane is a value measured along the tire equatorial plane from the outermost surface of the cap 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 cap tread in the tire radial direction.

[0142] For the above tire, it is desirable 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 rubber composition for the cap tread and the thickness T (mm) of the cap tread is 4 or more. Sc / T is preferably 5 or more, more preferably 6 or more, still more preferably 7 or more. Also, the upper limit of Sc / T is preferably 16 or less, more preferably 14 or less, still more preferably 12 or less. When within the above range, the effect tends to be obtained more favorably.

[0143] When Sc / T is adjusted to be a predetermined value or more, particularly 5 or more, the mechanism by which a more effect is obtained is not clear, but by containing a sufficient amount of silica with respect to the thickness of the cap tread, a large amount of silica is highly dispersed in the isoprene-based rubber, and thereby the hysteresis loss is improved, so that the wet grip performance is improved. Therefore, it is presumed that the comprehensive performance of wear resistance and wet grip performance is improved.

[0144] For the above tire, it is desirable that the ratio (Vc / T) of the content Vc (parts by mass) of the above modified vegetable oil to 100 parts by mass of the rubber component of the rubber composition for the cap tread and the thickness T (mm) of the cap tread is 0.4 or more. Vc / T is preferably 0.5 or more, more preferably 1.0 or more, still more preferably 1.5 or more. Also, the upper limit of Vc / T is preferably 6.0 or less, more preferably 5.0 or less, still more preferably 4.0 or less. When within the above range, the effect tends to be obtained more favorably.

[0145] When Vc / T is at a predetermined value or more, particularly 0.5 or more, the mechanism by which more effects can be obtained is not clear. However, by including a sufficient amount of modified vegetable oil with respect to the thickness of the cap tread, the hydrophobicity of silica is improved, and the dispersibility in isoprene rubber is improved. Therefore, it is considered that the hysteresis loss is improved, the wet grip performance is improved, and as a result, the overall performance of wear resistance and wet grip performance is improved.

[0146] In the above tire, the groove depth D (mm) of the circumferential groove formed in the tread is preferably 5.0 mm or more, more preferably 6.0 mm or more, still more preferably 6.5 mm or more, and is preferably 10.0 mm or less, more preferably 9.5 mm or less, still more preferably 9.0 mm or less. When it is within the above range, there is a tendency that better effects can be obtained.

[0147] When the groove depth D of the circumferential groove formed in the tread is adjusted to a predetermined range, the mechanism by which more effects can be obtained is not clear. However, by adjusting the groove depth, the grip performance and elongation are adjusted in a well-balanced manner, and as a result, it is considered that the overall performance of wear resistance and wet grip performance is improved.

[0148] In this specification, the groove depth D of the circumferential groove means the distance measured along the normal line of the surface obtained by extending the surface forming the ground contact surface of the tread outermost surface, from the surface obtained by extending the surface forming the ground contact surface to the deepest groove bottom, and refers to the maximum distance among the groove depths of the provided circumferential grooves.

[0149] 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 and the groove depth D (mm) of the circumferential groove formed in the tread is 5.0 or more and 17.5 or less. Sc / D is preferably 6.0 or more, more preferably 7.0 or more, still more preferably 8.0 or more. Also, the upper limit of Sc / D is preferably 15.0 or less, more preferably 14.0 or less, still more preferably 13.0 or less. When it is within the above range, there is a tendency that better effects can be obtained.

[0150] When Sc / D is adjusted within a predetermined range, particularly 6.0 or more and 15.0 or less, the mechanism by which more effects can be obtained is not clear. However, by adjusting the groove depth, the grip performance and elongation are well balanced, and by containing a sufficient amount of silica, a large amount of silica is highly dispersed in the isoprene rubber, thereby improving the hysteresis loss and improving the wet grip performance. Therefore, it is presumed that the overall performance of abrasion resistance and wet grip performance is improved.

[0151] It is desirable that the ratio (Vc / D) of the content Vc (parts by mass) of the modified vegetable oil to 100 parts by mass of the rubber component and the groove depth D (mm) of the circumferential groove formed in the tread is 0.4 or more and 6.3 or less. Vc / D is preferably 0.5 or more, more preferably 1.0 or more, and still more preferably 2.0 or more. Also, the upper limit of Vc / D is preferably 5.0 or less, more preferably 4.5 or less, and still more preferably 4.0 or less. When within the above range, there is a tendency for better effects to be obtained.

[0152] When Vc / D is adjusted within a predetermined range, particularly 0.5 or more and 5.0 or less, the mechanism by which more effects can be obtained is not clear. However, by adjusting the groove depth, the grip performance and elongation are well balanced, and by containing a sufficient amount of modified vegetable oil, the hydrophobicity of silica is improved and the dispersibility in the isoprene rubber is improved. Therefore, the hysteresis loss is improved and the wet grip performance is improved, and as a result, it is considered that the overall performance of abrasion resistance and wet grip performance is improved.

[0153] In this specification, dimensions such as thickness are measured with the bead portion of the tire adjusted to the normal rim width. At the time of measurement, the tire is cut out in the tire radial direction, and both bead ends of the sample are fixed in a state where they are adjusted to the width of the normal rim.

[0154] In this specification, unless otherwise specified, the dimensions of each part of the tire are the values measured in the normal state. The "normal state" refers to a state where the tire is mounted on a standard rim, filled with the standard internal pressure, and is in an unloaded condition. Here, the "standard rim" is the rim defined for each tire in the standard system including the standard to which the tire conforms. For example, in the case of JATMA (Japan Automobile Tire Manufacturers Association), it is the standard rim in the applicable sizes 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 that order, and follow the relevant standard if there is an applicable size at the time of reference. For a tire not defined by a 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 to which the tire conforms. 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 that order, and follow the relevant standard if there is an applicable size at the time of reference. For a tire not defined by a standard, it refers to the standard internal pressure (however, 250 KPa or more) of another tire size (defined by a standard) with the standard rim described as the standard rim. In the case where there are multiple standard internal pressures of 250 KPa or more, it refers to the minimum value among them.

[0155] Hereinafter, an example of the above tire will be described with reference to the drawings, but it is not limited to such a form.

[0156] 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 direction. The tread 4 includes a cap layer 30 (cap tread) and a base layer 28 (base tread).

[0157] Note that in FIG. 1, an example of a two-layer structure tread 4 composed of the cap layer 30 and the 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.

[0158] In the tire 2 of FIG. 1, the cap layer 30 is composed of the rubber composition for the cap tread. The cap layer 30 contains a rubber component, silica, and a modified vegetable oil, and the content Ic of the isoprene-based rubber in 100% by mass of the rubber component is 50% by mass or more, the content Sc of silica with respect to 100 parts by mass of the rubber component is 50 parts by mass or more and 150 parts by mass or less, the content Vc of the modified vegetable oil with respect to 100 parts by mass of the rubber component is 1 part by mass or more and 50 parts by mass or less, the elongation at break EB is 550% or more, and the loss tangent tan δ at 0°C is 0.40 or more. Further, in the cap layer 30, the above Ic, the above Sc, the above Vc, the above EB, and the acetone extraction amount AE of the cap tread satisfy the formula (1) "Ic / 50 + Sc / 50 + AE / 20 + EB / 550 ≧ 4.4".

[0159] In the tire 2, each sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. The outer portion in the radial direction of the sidewall 6 is joined to the tread 4. The inner portion in the radial direction of the sidewall 6 is joined to the clinch 10. The sidewall 6 can prevent damage to the carcass 14.

[0160] 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.

[0161] Each clinch 10 is located substantially radially inward of the sidewall 6 and has a portion that contacts the rim at at least one location.

[0162] The carcass 14 includes a carcass ply 36. In this tire 2, the carcass 14 consists of a single carcass ply 36, but it may also be composed of two or more plies.

[0163] 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 to the outer side around each bead core 32. Due to this folding, a main portion 36a and a pair of folded-back portions 36b are formed in the carcass ply 36. That is, the carcass ply 36 includes a main portion 36a and a pair of folded-back portions 36b.

[0164] Each bead core 32 includes a bead apex 34 that extends radially outward from this bead core 32. The bead core 32 is ring-shaped and preferably includes a wound non-stretchable wire. The bead apex 34 tapers radially outward.

[0165] 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.

[0166] The belt layer 16 in FIG. 1 is located radially inward of the tread 4. The belt layer 16 is laminated with the carcass 14. The belt layer 16 reinforces the carcass 14. In the tire 2 of FIG. 1, the belt layer 16 consists of an inner layer 38 and an outer layer 40. As is clear from FIG. 1, in the axial direction, it is desirable that the width of the inner layer 38 is slightly larger than the width of the outer layer 40. In this tire 2, the axial width of the belt layer 16 is preferably not less than 0.6 times and not more than 0.9 times the cross-sectional width of the tire 2.

[0167] Each of the inner layer 38 and the outer layer 40 preferably comprises a number of parallel single-wire steel cords (steel monofilaments) and topping rubber (coating rubber). In other words, the belt layer 16 includes a number of parallel steel monofilaments.

[0168] The band 18 in FIG. 1 is located radially outside the belt layer 16. In the axial direction, the band 18 has a width equal to the width of the belt layer 16. This band 18 may have a width larger than the width of this belt layer 16.

[0169] Although not shown, the band 18 preferably consists of a cord and topping rubber. The cord is wound in a spiral. This band 18 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is preferably 5° or less, more preferably 2° or less. Since the belt layer 16 is constrained by this cord, lifting of the belt layer 16 is suppressed.

[0170] 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.

[0171] 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 (on the CL). In this case, the cap 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 surface of the cap layer 30 (cap tread), specifically, the straight-line distance in the normal direction from the outer surface of the cap layer 30 in the tire radial direction to the interface on the outermost surface side of the tire of the base layer 28.

[0172] 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.

[0173] 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 this cloth. This chafer 22 may be integrated with the clinch 10.

[0174] 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.

[0175] 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.

[0176] In the tire 2, regarding the content Sc of silica and the content Vc of modified vegetable oil with respect to 100 parts by mass of the rubber component of the cap layer 30, the thickness T of the cap layer 30, and the groove depth D of the circumferential groove formed in the tread 4, it is desirable that Sc / T, Vc / T, Sc / D, Vc / D, T, and D are within the aforementioned ranges.

Examples

[0177] Hereinafter, examples (embodiments) considered preferable for implementation are shown, but the scope of the present disclosure is not limited to the embodiments.

[0178] The following is a summary description of various chemicals used in the manufacture of tires. The chemicals are purified according to established methods as necessary.

[0179] NR: RSS#3 SBR: HPR850 manufactured by JSR Corporation (styrene content: 27.5% by mass, vinyl bond content: 59.0% by mass) BR: BR150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass) Carbon black: Diablack I manufactured by Mitsubishi Chemical Corporation (N220, N2SA: 114 m 2 / g, DBP oil absorption: 114 ml / 100 g) Silica: Ultrasil VN3 manufactured by Evonik Degussa GmbH (N2SA: 175 m 2 / g) Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) manufactured by Evonik Degussa GmbH Modified soybean oil: Chemizer SE-100 (epoxidized soybean oil) manufactured by Sanwa Synthetic Chemical Co., Ltd. Modified linseed oil: Chemizer ELS-100 (epoxidized linseed oil) manufactured by Sanwa Synthetic Chemical Co., Ltd. Soybean oil: Industrial soybean oil manufactured by Kaneda Co., Ltd. Resin: SYLVATRAXX 4401 manufactured by Arizona Chemical Company (copolymer of α-methylstyrene and styrene, softening point: 85°C) Antioxidant: Nocrack 6C (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. Stearic acid: Stearic acid "Tsubaki" (manufactured by NOF Corporation) Zinc oxide: Zinc oxide No. 2 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur (manufactured by Karuizawa Sulfur Co., Ltd.) Vulcanization accelerator 1: Sunseller NS (N-tert-butylbenzothiazyl-2-sulfenamide) manufactured by Sanshin Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noxeller D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Co., Ltd.

[0180] <Preparation of Test Tires> According to the compounding content shown in Table 1, using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd., materials other than sulfur and vulcanization accelerators are kneaded at 150°C for 5 minutes to obtain a kneaded product. Sulfur and vulcanization accelerators are added to the kneaded product, and it is kneaded using an open roll at 80°C for 5 minutes to obtain an unvulcanized rubber composition. The unvulcanized rubber composition for the cap tread is formed into the shape of a cap tread, and on a tire molding machine, it is bonded together with other tire members to form an unvulcanized tire, which is vulcanized at 170°C for 10 minutes to manufacture a test tire (size 205 / 55R16, passenger car tire).

[0181] Assuming test tires obtained from compositions with formulations and specifications changed according to Table 1, the results calculated based on the following evaluation methods are shown in Table 1. Note that the reference comparative example is as follows. Table 1: Comparative Example 1

[0182] <Elongation at Break (EB)> A vulcanized rubber sheet (vulcanized rubber composition) is prepared (sampled) from inside the cap tread of the test tire. Then, using a No. 3 dumbbell-shaped test piece made of the vulcanized rubber sheet (vulcanized rubber composition), a tensile test is carried out under the condition of a temperature of 23°C in accordance with JIS K6251:2010 "Vulcanized Rubber and Thermoplastic Rubber - Method for Determining Tensile Properties", and the elongation at break at 23°C (EB(23°C)) (%) is measured.

[0183] <Viscoelasticity Test> A viscoelasticity measurement sample with a length of 20 mm, a width of 4 mm, and a thickness of 1 mm is sampled from inside the cap tread of the test tire such that the tire circumferential direction is the long side. The loss tangent tanδ of the viscoelasticity measurement sample is measured using an Iplexer series manufactured by GABO under the conditions of a temperature of 0°C, an initial strain of 10%, a dynamic strain of 2.5%, a frequency of 10 Hz, and an elongation mode (loss tangent tanδ at 0°C). Note that the thickness direction of the sample is the tire radial direction.

[0184] <Acetone extraction amount (AE)> Collect a rubber test piece from inside the cap tread of the test tire. In accordance with the measurement method of the acetone extraction amount conforming to JIS K 6229, measure the amount of the substance extracted by acetone contained in the rubber test piece. Acetone extraction amount AE (mass %) = (mass of the sample before extraction - mass of the sample after extraction) / mass of the sample before extraction × 100

[0185] <Wet grip performance> Mount the test tire on all wheels of a vehicle (domestic FF 2000 cc), and determine the braking distance from an initial speed of 100 km / h on a wet asphalt road surface. Set the reference comparative example as an index of 100 and express it as an index. The larger the numerical value, the better the wet grip performance.

[0186] <Wear resistance> Mount the test tire on a vehicle (domestic FF 2000 cc). After driving 15,000 km on a paved road surface, calculate the driving distance when the cap tread wears 1 mm, and derive the driving distance until the grooves of the tread wear out. Compare the derived driving distances, set the reference comparative example as 100, and express it as an index according to the following formula. The larger the index, the better the wear resistance. (Wear resistance index) = (driving distance of each example or each comparative example) / (driving distance of the reference comparative example) × 100

[0187] <Comprehensive performance> Evaluate the sum of the index of the wet grip performance and the index of the wear resistance as the comprehensive performance. The larger the index, the better the comprehensive performance of the wear resistance and the wet grip performance.

[0188]

Table 1

[0189] The tire of the present invention (1) is a tire provided with a cap tread containing a rubber component, silica and a modified vegetable oil, The cap tread is, The content Ic of isoprene rubber in 100% by mass of the rubber component is 50% by mass or more, the content Sc of the silica with respect to 100 parts by mass of the rubber component is 50 parts by mass or more and 150 parts by mass or less, and the content Vc of the modified vegetable oil is 1 part by mass or more and 50 parts by mass or less, the cap tread has an elongation at break EB of 550% or more and a loss tangent tanδ at 0°C of 0.37 or more, the tire is such that the Ic, the Sc, the Vc, the EB, and the acetone extraction amount AE of the cap tread satisfy the following formula (1). (1) Ic / 50 + Sc / 50 + AE / 20 + EB / 550 ≥ 4.3

[0190] The tire according to the present invention (2) is the tire according to the present invention (1), wherein the modified vegetable oil has a lower content of carbon-carbon double bonds than before modification.

[0191] The tire according to the present invention (3) is the tire according to the present invention (1) or (2) that satisfies the following formula. Ic / 50 + Sc / 50 + AE / 20 + EB / 550 ≥ 5.3

[0192] The tire according to 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 in the cap tread is 70 parts by mass or more.

[0193] The tire according to the present invention (5) is a tire in any combination with any one of the present inventions (1) to (4), wherein the silica content rate in the filler of the cap tread is 93% by mass or more.

[0194] The tire according to the present invention (6) is a tire in any combination with any one of the present inventions (1) to (5), wherein the cap tread contains a resin.

[0195] The tire according to the present invention (7) is a tire in any combination with any one of the present inventions (1) to (6), wherein the acetone extraction amount AE of the cap tread is 22% by mass or more.

[0196] The tire of the present invention (8) is a tire in any combination with any one of the present inventions (1) to (7) where the thickness T of the cap tread is 7 mm or more and 12 mm or less.

[0197] The tire of the present invention (9) is a tire in any combination with any one of the present inventions (1) to (8) where the ratio (Sc / T) of the content Sc (parts by mass) of silica to 100 parts by mass of the rubber component and the thickness T (mm) of the cap tread is 5 or more.

[0198] The tire of the present invention (10) is a tire in any combination with any one of the present inventions (1) to (9) where the ratio (Vc / T) of the content Vc (parts by mass) of the modified vegetable oil to 100 parts by mass of the rubber component and the thickness T (mm) of the cap tread is 0.5 or more.

[0199] The tire of the present invention (11) is a tire in any combination with any one of the present inventions (1) to (10) where the groove depth D of the circumferential groove formed in the tread is 5.0 mm or more and 10.0 mm or less.

[0200] The tire of the present invention (12) is a tire in any combination with any one of the present inventions (1) to (11) where 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 6.0 or more and 15.0 or less.

[0201] The tire of the present invention (13) is a tire in any combination with any one of the present inventions (1) to (12) where the ratio (Vc / D) of the content Vc (parts by mass) of the modified vegetable oil to 100 parts by mass of the rubber component and the groove depth D (mm) of the circumferential groove formed in the tread is 0.5 or more and 5.0 or less.

Explanation of Signs

[0202] 2 Tire 4 Tread 6 Sidewall 8 Wing 10 Clinch 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 Bead core 34 Bead 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 cap tread D Depth of the main groove of the circumferential main groove formed in the tread

Claims

1. A tire comprising a cap tread containing a rubber component, silica, and a modified vegetable oil, wherein the cap tread, the content Ic of isoprene rubber in 100% by mass of the rubber component is 50% by mass or more, the content Sc of the silica with respect to 100 parts by mass of the rubber component is 50 parts by mass or more and 150 parts by mass or less, and the content Vc of the modified vegetable oil is 1 part by mass or more and 50 parts by mass or less, the cap tread has an elongation at break EB of 550% or more and a loss tangent tanδ at 0 °C of 0.37 or more, the tire in which the Ic, the Sc, the Vc, the EB, and the acetone extraction amount AE of the cap tread satisfy the following formula (1). (1) Ic / 50 + Sc / 50 + AE / 20 + EB / 550 ≥ 4.3

2. The tire according to claim 1, wherein the modified vegetable oil has a lower content of carbon-carbon double bonds than before modification.

3. The tire according to claim 1, which satisfies the following formula. Ic / 50 + Sc / 50 + AE / 20 + EB / 550 ≥ 5.3

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 70 parts by mass or more.

5. The tire according to claim 1, wherein the silica content rate in the filler is 93% by mass or more.

6. The tire according to claim 1, wherein the cap tread contains a resin.

7. The tire according to claim 1, wherein the acetone extraction amount AE is 22% by mass or more.

8. The tire according to claim 1, wherein the thickness T of the cap tread is 7 mm or more and 12 mm or less.

9. The tire according to claim 1, wherein the ratio (Sc / T) of the content Sc (parts by mass) of silica to 100 parts by mass of the rubber component and the thickness T (mm) of the tread is 5 or more.

10. The tire according to claim 1, wherein the ratio (Vc / T) of the content Vc (parts by mass) of the modified vegetable oil to 100 parts by mass of the rubber component and the thickness T (mm) of the tread is 0.5 or more.

11. The tire according to claim 1, wherein the groove depth D of the circumferential groove formed in the tread is 5.0 mm or more and 10.0 mm or less.

12. 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 6.0 or more and 15.0 or less.

13. The tire according to claim 1, wherein the ratio (Vc / D) of the content Vc (parts by mass) of the above-mentioned modified vegetable oil to 100 parts by mass of the rubber component and the groove depth D (mm) of the circumferential groove formed in the tread is 0.5 or more and 5.0 or less.

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