Rubber composition for tires and tires

Abstract

To provide a rubber composition for tires that has excellent damage resistance performance, and a tire that comprises a tire member composed of the rubber composition for tires.SOLUTION: Provided is a rubber composition for tires that contains a rubber component including an epoxidated diene rubber, an imidazole compound, and a divalent or higher carboxylic acid compound. When the elongation at break EB (%) and breaking strength TB (MPa) are measured in accordance with JIS K6251 using a 2-mm thick dumbbell-shaped test piece in compliance with ASTM D638 Type V, the EB repair rate (%) RREB and the TB repair rate (%) RRTB respectively satisfy (1) TB≥0.40, (2) RREB≥20 and (3) RRTB≥20, where RREB is a value defined by (EB (%) of a repaired test piece / EB (%) of an annealed test piece)×100, and RRTB is a value defined by (TB (MPa) of a repaired test piece / TB (MPa) of an annealed test piece)×100.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rubber composition for tires and a tire.

Background Art

[0002] In recent years, due to environmental considerations, as the demand for reducing the fuel consumption of vehicles has increased, in the case of tires as well, weight reduction of tires has been studied from the viewpoint of reducing rolling resistance. However, reducing the volume of rubber such as the tread and sidewall in order to reduce the weight can be a factor in reducing the cut resistance performance of the tire.

[0003] Patent Document 1 describes a tire having a reinforcing layer made of urethane to enhance the cut resistance of the sidewall.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a rubber composition for tires having excellent cut resistance performance and a tire provided with a tire member made of the rubber composition for tires.

Means for Solving the Problems

[0006] The present invention relates to a rubber composition for tires as follows. A rubber component containing an epoxidized diene rubber, an imidazole compound, and a divalent or higher carboxylic acid compound, When measuring the elongation at break EB (%) and fracture strength TB (MPa) of a 2mm thick dumbbell-shaped test specimen conforming to ASTM D638 Type V according to JIS K 6251, the TB and the EB repair rate (%) RR defined below are used. EB , and the TB repair rate (%) RR as defined below. TB However, each of these is a rubber composition for tires that satisfies formulas (1) to (3). TB≧0.40 (1) RR EB ≥20 (2) RR TB ≥20 (3) (RR EB This value is defined as EB (%) of the repaired specimen / EB (%) of the annealed specimen × 100. TB This value is defined as TB (MPa) of the repaired specimen / TB (MPa) of the annealed specimen × 100. Here, a repaired specimen is a specimen that has been cut in the thickness direction at the center of its long side, the cut surfaces immediately bonded together, and then heat-treated at 80°C for 24 hours. An annealed specimen is a specimen that has been heat-treated at 80°C for 24 hours. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a tire rubber composition with excellent resistance to external damage and a tire equipped with a tire component made of the tire rubber composition. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view of a tire according to one embodiment of the present invention, with the view passing through the tire's rotation axis. [Modes for carrying out the invention]

[0009] The rubber composition for tires of the present invention contains a rubber component including an epoxidized diene rubber, an imidazole compound, and a divalent or higher carboxylic acid compound. When measuring the elongation at break EB (%) and the breaking strength TB (MPa) in accordance with JIS K 6251 for a dumbbell-shaped test piece having a thickness of 2 mm and conforming to ASTM D638 Type V, the TB, the EB recovery rate (%) RR defined below EB , and the TB recovery rate (%) RR defined below TB are rubber compositions for tires that satisfy the formulas (1) to (3), respectively. TB ≧ 0.4 0 (1) RR EB ≧ 20 (2) RR TB ≧ 20 (3) (RR EB is a value defined as EB (%) of the repaired test piece / EB (%) of the annealed test piece × 100. RR TB is a value defined as TB (MPa) of the repaired test piece / TB (MPa) of the annealed test piece × 100. Here, the repaired test piece is a test piece obtained by cutting the test piece in the thickness direction at the center of its long side, immediately bonding the cut surfaces, and then heat-treating at 80°C for 24 hours. The annealed test piece is a test piece heat-treated at 80°C for 24 hours.)

[0010] The rubber composition for tires of the present invention contains an epoxidized diene rubber, an imidazole compound, and a divalent or higher carboxylic acid compound, and thus has self-healing ability, and is considered to exhibit excellent cut resistance performance. Although not intending to be bound by theory, the following is considered as the mechanism. That is, when the rubber is damaged, the damaged part is in a state where chemical bonds, that is, covalent bonds, ionic bonds, etc. are broken at the molecular level. However, in the rubber composition for tires of the present invention, it is considered that an ionic scaffold is formed at the damaged part by the reaction of the epoxy group of the epoxidized diene rubber and the imidazole moiety of the imidazole compound. And then, a divalent or higher carboxylic acid compoundIt is believed that the reaction forms ionic bonds, regenerating the network between polymers. As a result, the tire rubber composition of the present invention is thought to exhibit self-healing properties.

[0011] The right-hand side of equation (1) is preferably 0.50.

[0012] A higher breaking strength is considered to benefit the effects of the present invention.

[0013] The right-hand side of formula (2) is preferably 45, more preferably 60, and even more preferably 72, and the right-hand side of formula (3) is preferably 50, more preferably 60, and even more preferably 72.

[0014] A higher individual repair rate is considered to benefit the effects of the present invention.

[0015] The aforementioned rubber composition for tires contains a filler, the filler content of which is preferably less than 45 parts by mass, more preferably less than 20 parts by mass, and even more preferably less than 5 parts by mass, per 100 parts by mass of the rubber component, or the composition may not contain a filler at all.

[0016] Another aspect of the present invention is a tire having a tire member made of a rubber composition for tires.

[0017] The rubber composition for tires of the present invention, which has self-healing properties and improved resistance to trauma, can be suitably used as a tire component.

[0018] The aforementioned tire member is preferably a tire surface layer member. This is an embodiment that facilitates the demonstration of the effects of the present invention.

[0019] The tire surface layer member is preferably at least one selected from the group consisting of a tread, sidewall, wing, and clinch.

[0020] This is an embodiment that facilitates the demonstration of the effects of the present invention.

[0021] The tire surface member is a sidewall, and the sidewall is an outer layer sidewall. When the thickness (mm) of the outer layer sidewall is W, it is preferable that W satisfies equation (4). W≧1.0 (4)

[0022] Having an outer sidewall of a certain thickness or more makes it easier to achieve the self-healing effect.

[0023] The aforementioned W and the aforementioned RR TB It is preferable that the conditions satisfy equation (5). W×S TB >50 (5)

[0024] It is believed that the required trauma resistance can be achieved when the product of the thickness of the outer sidewall and the repair rate is above a certain value.

[0025] <Definition> A "standard rim" refers to the rim specified for each tire within the standard system that includes the standard on which the tire is based. For example, for JATMA (Japan Automobile Tire Manufacturers Association), it refers to the standard rim for the applicable size listed in the "JATMA YEAR BOOK," for ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" listed in the "STANDARDS MANUAL," and for TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "YEAR BOOK." In the case of tires not specified in the standard, it refers to the rim with the smallest diameter and narrowest rim width among rims that can be mounted on and can maintain internal pressure, i.e., rims that do not cause air leakage from between the rim and tire.

[0026] "Tire surface components" refer to the components that make up the outer surface of a tire. Examples include, but are not limited to, the tread, sidewall, wing, and clinch.

[0027] "Outer sidewall thickness (W)" refers to the thickness (mm) of the outer sidewall at the tire's widest point. This thickness W is measured with the tire, cut along a plane passing through the tire's axis of rotation, and held on the standard rim.

[0028] <Measurement method> "Epoxylation rate" is the ratio (mol%) of the number of epoxidized double bonds to the total number of double bonds in the rubber before epoxylation for epoxydiene rubbers, and is measured using an NMR spectrometer of the JNM-ECA series manufactured by JEOL Ltd.

[0029] "Elongation at break EB (%)" and "Breaking strength TB (MPa)" are measured by conducting a tensile test on a 2 mm thick dumbbell-shaped test specimen conforming to ASTM D638 Type V, in accordance with JIS K 6251 "Vulcanized rubber and thermoplastic rubber - Determination of tensile test properties", under conditions of a tensile speed of 3.3 mm / second in a 23°C atmosphere.

[0030] “EB repair rate (%) RR EB The value is defined as "EB(%) of the repaired specimen / EB(%) of the annealed specimen × 100". Here, the repaired specimen is a specimen prepared by cutting a specimen used to measure elongation at break EB(%) in the thickness direction at the center of its long side, immediately bonding the cut surfaces together, and then heat-treating it at 80°C for 24 hours. The annealed specimen is a specimen prepared by heat-treating a specimen used to measure elongation at break EB(%) at 80°C for 24 hours.

[0031] “TB repair rate (%) RR TB The value is defined as "TB (MPa) of the repaired specimen / TB (MPa) of the annealed specimen × 100". Here, the repaired specimen is a specimen used to measure the fracture strength TB (MPa), which is cut in the thickness direction at the center of its long side, the cut surfaces are immediately bonded together, and then heat-treated at 80°C for 24 hours. The annealed specimen is a specimen used to measure the fracture strength TB (MPa), which is heat-treated at 80°C for 24 hours.

[0032] The N2SA content of silica is measured by the BET method in accordance with ASTM D3037-93.

[0033] The N2SA rating of carbon black is measured in accordance with JIS K 6217-2:2017.

[0034] The "average primary particle diameter" can be determined by observing with a transmission or scanning electron microscope, measuring 400 or more primary particles observed within the field of view, and averaging the results. This method is applied to materials such as carbon black and silica.

[0035] <Rubber composition for tires> The rubber composition for tires of the present invention comprises a rubber component including an epoxidized diene rubber, an imidazole compound, and a divalent or higher carboxylic acid compound.

[0036] (Rubber component) The epoxidized diene rubber is not particularly limited and examples include epoxidized natural rubber (ENR), epoxidized isoprene rubber, epoxidized butadiene rubber, epoxidized butadiene acrylonitrile rubber, epoxidized styrene-butadiene rubber, and epoxidized isoprene-butadiene rubber. The epoxidized diene rubber may be used alone or in combination of two or more types.

[0037] The epoxidized diene rubber is not particularly limited; commercially available products or diene rubber that has been epoxidized may be used. The epoxidization of diene rubber can be carried out in accordance with the epoxidization of natural rubber.

[0038] Methods for epoxidizing natural rubber include, for example, the chlorhydrin method, direct oxidation method, hydrogen peroxide method, alkyl hydroperoxide method, and peracid method (Japanese Patent Publication No. 4-26617, Japanese Patent Application Publication No. 2-110182, British Patent No. 2113692, etc.). Examples of peracid methods include reacting natural rubber with organic peracids such as peracetic acid or performic acid. By adjusting the amount of organic peracid and the reaction time, epoxidized natural rubber with various epoxidation rates can be prepared. The natural rubber to be epoxidized is not particularly limited; for example, SIR20, RSS#3, TSR20, deproteinized natural rubber (DPNR), and high-purity natural rubber (HPNR), which are common in the tire industry, can be used.

[0039] From a practical standpoint, such as ease of availability, ENR and epoxidized butadiene rubber are preferred as epoxidized diene rubbers, with ENR being more preferred.

[0040] The epoxidation rate of the epoxidized diene rubber is preferably more than 15 mol%, more preferably more than 20 mol%, and even more preferably 25 mol% or more. On the other hand, from the viewpoint of fracture properties, the epoxidation rate is preferably 75 mol% or less, more preferably less than 60 mol%, and even more preferably 50 mol% or less. The epoxidation rate is the value measured by the method described above.

[0041] The content of epoxidized diene rubber in 100% by mass of the rubber component is preferably more than 70% by mass, more preferably more than 80% by mass, even more preferably more than 90% by mass, and even more preferably more than 95% by mass, with 100% by mass being the most preferable.

[0042] The rubber component may contain other rubber components besides the epoxidized diene rubbers mentioned above. Other rubber components that can be crosslinked are those commonly used in the tire industry. Examples include unepoxidized diene rubbers such as natural rubber (NR), isoprene rubber (IR) and isoprene rubber (IR rubber), styrene-butadiene rubber (SBR), butadiene rubber (BR), styrene-isoprene-butadiene copolymer rubber (SIBR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), and polynorbornene rubber, as well as non-diene rubbers such as butyl rubber (IIR), hydrogenated nitrile rubber (HNBR), ethylene propylene rubber, silicone rubber, polyethylene chloride rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber. These other rubber components may be used individually or in combination of two or more.

[0043] (Carboxylic acid compounds with two or more valent values) Divalent or higher valent carvones acid A compound is a compound that has two or more carboxyl groups. acid The compound is not particularly limited as long as it can form an ionic bond with the ionic scaffold generated by the reaction of the epoxy group of the epoxidized diene rubber with the imidazole compound, and various compounds can be used. The divalent or higher carboxylic acid compound may be any aliphatic carboxylic acid compound, alicyclic carboxylic acid compound, or aromatic carboxylic acid compound. acid The compound may have substituents. Divalent or more carboxylated carboxylates. acid Examples of substituents on the compound include hydroxyl groups, alkoxy groups, and amino groups. The number of substituents may be one or two or more. Furthermore, the types of substituents may be one or two or more.

[0044] Divalent or higher valent carvones acidExamples of compounds include divalent carboxylic acid compounds such as maleic acid, fumaric acid, phthalic acid, malic acid, tartaric acid, and suberic acid; trivalent carboxylic acid compounds such as citric acid; tetravalent carboxylic acid compounds such as pyromellitic acid; and hexavalent carboxylic acid compounds such as melitic acid.

[0045] Divalent or higher valent carvones acid The compounds may be used individually or in combination of two or more.

[0046] Divalent or higher valent carvones acid A preferred example of the compound is a divalent carboxylic acid compound. A compound represented by the following formula (I) can be suitably used as the divalent carboxylic acid compound. Because this compound has carboxyl groups at both ends, it is possible to form a strong network between the polymers. HOOC-A-COOH (I) (In the formula, A is a divalent hydrocarbon group having 1 to 10 carbon atoms, and may have substituents.)

[0047] The hydrocarbon group of A may be aliphatic, alicyclic, or aromatic. Of the hydrocarbon groups of A, the aliphatic and alicyclic hydrocarbon groups may be saturated or unsaturated. Of the hydrocarbon groups of A, the alicyclic and aromatic hydrocarbon groups may have their hydrogen atoms substituted with alkyl groups. Of the hydrocarbon groups of A, the aliphatic hydrocarbon group may be linear or branched. The number of carbon atoms in the hydrocarbon group of A is preferably 2 or more, preferably 12 or less, more preferably 10 or less, even more preferably 8 or less, and even more preferably 6 or less.

[0048] Specific examples of hydrocarbon groups in A include alkylene groups, alkenylene groups, cycloalkylene groups, and arylene groups, with alkylene groups being preferred. Examples of alkylene groups include linear alkylene groups such as methylene groups, ethylene groups, n-propylene groups, n-butylene groups, and n-hexylene groups, and branched alkylene groups such as isopropylene groups, isobutylene groups, and 2-methylpropylene groups. Of these, linear alkylene groups are preferred, ethylene groups, n-propylene groups, and n-hexylene groups are more preferred, and n-hexylene groups are even more preferred.

[0049] The hydrocarbon group A may have substituents. Examples of substituents include hydroxyl groups, alkoxy groups, amino groups, etc. The number of substituents may be one or two or more. Furthermore, the types of substituents may be one or two or more.

[0050] Divalent or greater carboxylic acids compound From the viewpoint of the effects of the present invention, the content of is preferably more than 0.5 parts by mass, more preferably more than 0.6 parts by mass, even more preferably more than 0.7 parts by mass, even more preferably more than 0.8 parts by mass, and even more preferably more than 0.9 parts by mass, per 100 parts by mass of epoxidized diene rubber. Furthermore, the content is preferably less than 20 parts by mass, more preferably less than 10 parts by mass, and even more preferably less than 5 parts by mass.

[0051] (Imidazole compounds) An imidazole compound is a compound having an imidazole ring. The imidazole compound is not particularly limited as long as it can react with the epoxy group of an epoxidized diene rubber to form an ionic scaffold.

[0052] Various imidazole compounds can be used, and for example, compounds represented by the following formula (II) are preferred.

[0053] [ka] (In the formula, R1 , R 2 , R 3 , R 4 R represents a hydrogen atom or a hydrocarbon group, either identical or different. 3 , R 4 (These may be bonded to each other to form a ring structure.)

[0054] R 1 , R 2 , R 3 , R 4 Examples of hydrocarbon groups include alkyl groups having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms; cycloalkyl groups having 5 to 24 carbon atoms, preferably 5 to 12 carbon atoms, more preferably 5 to 8 carbon atoms; aryl groups having 6 to 30 carbon atoms, preferably 6 to 24 carbon atoms, more preferably 6 to 12 carbon atoms; and aralkyl groups having 7 to 25 carbon atoms, preferably 7 to 13 carbon atoms, more preferably 7 to 10 carbon atoms.

[0055] Also, R 3 , R 4 When R is bonded to form a ring structure, 3 , R 4 Examples of ring structures formed by the carbon atoms of the imidazole ring include aromatic rings, heterocycles, and aliphatic rings having 5 to 12 carbon atoms.

[0056] From the viewpoint of the effects of the present invention, R 1 , R 2 , R 3 , R 4 Preferably, at least one of them is an alkyl group, R 1 , R 2 , R 3 , R 4 It is more preferable that two of them are alkyl groups and the other two are hydrogen atoms, R 1 and R 2 and are alkyl groups, R 3 and R 4 It is even more preferable that the atoms are hydrogen atoms.

[0057] Specific examples of imidazole compounds include imidazole, 1-methylimidazole, 1-butylimidazole, 1-propylimidazole, 1-ethylimidazole, 1,2-dimethylimidazole, 1-decyl-2-methylimidazole, 1-benzyl-2-methylimidazole, and benzimidazole. Imidazole compounds may be used individually or in combination of two or more.

[0058] Among these, 1,2-dimethylimidazole, 1-methylimidazole, and 1-benzyl-2-methylimidazole are preferred.

[0059] As imidazole compounds, for example, products from Shikoku Chemicals Co., Ltd. and others can be used.

[0060] The imidazole compound content is preferably more than 0.05 molar equivalents, more preferably more than 0.15 molar equivalents, and even more preferably more than 0.25 molar equivalents, relative to the carboxyl group in the divalent or higher carboxylic acid compound, and also preferably less than 3 molar equivalents, more preferably less than 2 molar equivalents, and even more preferably less than 1 molar equivalent. Being within the above range tends to be preferable from the viewpoint of the effects of the present invention.

[0061] (Other ingredients) The rubber composition for tires of the present invention may contain, in addition to the above-mentioned components, various compounding agents and additives commonly used in the tire industry, such as fillers like carbon black and silica, silane coupling agents, plasticizers including resins and oils, stearic acid, zinc oxide, vulcanizing agents, and vulcanization accelerators.

[0062] (Filler) The rubber composition for tires of the present invention may contain fillers, but the amount of fillers is preferably less than 45 parts by mass, more preferably less than 20 parts by mass, and even more preferably less than 5 parts by mass, per 100 parts by mass of the rubber component, or it may not contain any fillers at all. The amount of fillers refers to the total amount of fillers, and if only one type of filler is included, it refers to the amount of that one type of filler.

[0063] As fillers, silica and carbon black can be used, as well as fillers commonly used in the tire industry, such as aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, magnesium sulfate, talc, and clay. Fillers may be used individually or in combination of two or more types.

[0064] Silica The silica used is not particularly limited, and common types used in the tire industry can be used, such as silica prepared by the dry method (anhydrous silica) or silica prepared by the wet method (hydrated silica). Among these, hydrated silica prepared by the wet method is preferred because it contains a large number of silanol groups. Silica may be used alone or in combination of two or more types.

[0065] The nitrogen adsorption specific surface area (N2SA) of silica is 140 m², from the perspective of low fuel consumption and wear resistance. 2 Preferably more than / g, 150m 2 More preferably than / g, 160m 2 More preferably than / g, 175m 2 A value of 350m or more is particularly preferred. Furthermore, from the viewpoint of low fuel consumption and processability, 350m 2 Less than / g is preferable, 300m 2 Less than / g is more preferable, 250m 2 A value of less than / g is even more preferable. The N2SA of silica is measured by the measurement method described above.

[0066] The average primary particle diameter of silica is preferably less than 25 nm, more preferably less than 22 nm, and even more preferably less than 20 nm. The lower limit of the average primary particle diameter is not particularly limited, but is preferably greater than 1 nm, more preferably greater than 3 nm, and even more preferably greater than 5 nm. The average primary particle diameter can be determined by the method described above.

[0067] Carbon Black The carbon black used is not particularly limited and can be any that is common in the tire industry, such as GPF, FEF, HAF, ISAF, SAF, etc. Specifically, N110, N115, N120, N125, N134, N135, N219, N220, N231, N234, N293, N299, N326, N330, N339, N343, N347, N351, N356, N358, N375, N539, N550, N582, N630, N642, N650, N660, N683, N754, N762, N765, N772, N774, N787, N907, N908, N990, N991, etc. can be suitably used, as can other proprietary synthetic products. These can be used individually or in combination of two or more types.

[0068] The nitrogen adsorption specific surface area (N2SA) of carbon black is 10 m² from the perspective of reinforcing properties. 2 Preferably 20m / g or more. 2 More preferably 35m 2 More preferably 50m 2 A value of 200m or more is particularly preferred. Furthermore, from the viewpoint of low fuel consumption and processability, 200m 2 Preferably less than / g, 150m 2 More preferably less than / g, 130m 2 A value of less than / g is even more preferable. The N2SA of carbon black is measured by the measurement method described above.

[0069] The average primary particle diameter of carbon black is preferably less than 30 nm, more preferably less than 26 nm, even more preferably less than 23 nm, and even more preferably 22 nm or less. The lower limit of the average primary particle diameter is not particularly limited, but is preferably greater than 1 nm, more preferably greater than 3 nm, and even more preferably greater than 5 nm. The average primary particle diameter can be determined by the method described above.

[0070] ≪Silane coupling agents≫ Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent that has conventionally been used in combination with silica in the tire industry can be used, for example: mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane. Examples include thioester silane coupling agents such as lan; vinyl silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. In particular, it is preferable to contain a sulfide silane coupling agent and / or a mercapto silane coupling agent. As silane coupling agents, for example, those commercially available from Momentive, etc., can be used. Silane coupling agents may be used alone or in combination of two or more.

[0071] The silane coupling agent content is preferably more than 1.0 part by mass, more preferably more than 3.0 parts by mass, and even more preferably more than 5.0 parts by mass, per 100 parts by mass of silica, from the viewpoint of improving silica dispersibility. Furthermore, from the viewpoint of cost and processability, it is preferably less than 30 parts by mass, more preferably less than 20 parts by mass, and even more preferably less than 15 parts by mass.

[0072] <Physical properties of rubber compositions for tires> The rubber composition for tires of the present invention satisfies the above formulas (1) to (3).

[0073] (Formula (1)) The above formula (1) specifies the fracture strength TB (MPa) as follows: TB≧0.40 (1)

[0074] The right-hand side of equation (1) is preferably 0.50, more preferably 0.60, and even more preferably 0.70. While there are no particular restrictions on the upper limit of TB from the viewpoint of the effects of the present invention, it is typically, for example, less than 5.00.

[0075] In the above, the fracture strength TB can be increased by lowering the heating and pressurizing temperature, etc. Conversely, it can be decreased by raising the heating and pressurizing temperature, etc.

[0076] (Formula (2)) Equation (2) above is the EB repair rate RR EB The following provisions apply to this matter. RR EB ≥20 (2)

[0077] The right-hand side of equation (2) is preferably 45, more preferably 60, and even more preferably 72. EB Regarding the upper limit, there are no particular restrictions from the viewpoint of the effects of the present invention, but it is usually, for example, less than 90.

[0078] In the above, the EB repair rate RR EBThis can be increased by lowering the heating and pressurizing temperature, etc. Conversely, it can be decreased by raising the heating and pressurizing temperature, etc.

[0079] (Formula (3)) Equation (3) above is the TB repair rate RR TB The following provisions apply to this matter. RR TB ≥20 (3)

[0080] The right-hand side of equation (3) is preferably 50, more preferably 60, and even more preferably 72. TB Regarding the upper limit, there are no particular restrictions from the viewpoint of the effects of the present invention, but it is usually, for example, less than 90.

[0081] In the above, the TB repair rate RR TB This can be increased by lowering the heating and pressurizing temperature, etc. Conversely, it can be decreased by raising the heating and pressurizing temperature, etc.

[0082] <Tires> The tire of the present invention will be described with reference to Figure 1. However, the tire of the present invention is not limited to the drawings.

[0083] Figure 1 is a cross-sectional view of a tire with respect to a plane passing through the tire's axis of rotation, showing the upper half to the right of the tire's centerline C. The tire 1 in Figure 1 comprises a tread 2 having a tread surface that contacts the ground, a sidewall 3, a wing 4 which is a surface member sandwiched between the tread 2 and the sidewall 3, a clinch 5 extending from one end of the sidewall to the rim, a band 6 positioned radially inward of the tread, a breaker 7 positioned further radially inward of the band, a carcass 8 positioned further radially inward of the breaker, and an inner liner 9 positioned further radially inward of the carcass. The tread 2 consists of a cap tread 2a and a base tread 2b, and the sidewall 3 consists of an outer sidewall 3a and an inner sidewall 3b.

[0084] The tire of the present invention is a tire that uses the self-healing rubber composition of the present invention in any of its tire components. For example, the tire of the present invention is a tire that uses the rubber composition of the present invention in at least one of the tire components shown in Figure 1, or a tire that uses it in all of the tire components shown in Figure 1.

[0085] In particular, the tire of the present invention is preferably a tire in which the self-healing rubber composition for tires of the present invention is used in tire surface components that are susceptible to damage, such as the tread, sidewall, wing, and clinch. Furthermore, among these tire surface components, for example, if the sidewall consists of an outer sidewall and an inner sidewall, the rubber composition for tires of the present invention can be used in either, but a tire in which it is used in the outer sidewall is particularly preferred. Furthermore, among these tire surface components, for example, if the tread consists of a cap tread and a base tread, the rubber composition for tires of the present invention can be used in either, but a tire in which it is used in the cap tread is particularly preferred.

[0086] (Formula (4)) In the tire of the present invention, when the thickness (mm) of the outer sidewall is W, it is preferable that W satisfies formula (4). W≧1.0 (4)

[0087] The right-hand side of equation (4) above is preferably 1.2, more preferably 1.4, and even more preferably 1.5. Furthermore, there is no particular upper limit to the value of W, as increased thickness improves trauma resistance; however, the thickness of the outer sidewall is typically 30 mm.

[0088] (Formula (5)) The tire of the present invention comprises the W and the RR TB It is preferable that the two satisfy equation (5). W×S TB >50 (5)

[0089] The right-hand side of equation (5) above is preferably 60, more preferably 70, even more preferably 75, even more preferably 90, and even more preferably 100. Also, W × RR TB The higher the value, the better the trauma resistance, so there is no particular upper limit, but it is usually around 290. <Manufacturing> (Manufacturing of rubber compositions) The rubber composition for tires of the present invention can be manufactured by known methods. For example, it can be manufactured by kneading each of the above components using a rubber kneading device such as an open roll or closed kneader (Banbury mixer, kneader, etc.). The kneading process can be, for example, a method of kneading at a discharge temperature of 150 to 170°C for 3 to 10 minutes. This kneading process can be carried out in multiple stages if desired. The conditions for each stage of kneading can be appropriately set by those skilled in the art.

[0090] (Tire manufacturing) The tires obtained above for The rubber composition can be extruded to the desired shape of the tire component while still in its uncured state, and then molded together with other tire components in a conventional manner on a tire molding machine to produce an uncured tire. The tire of the present invention can be obtained by heating and pressurizing this uncured tire in a vulcanizing machine. The heating and pressurizing conditions are not particularly limited, but for example, a method of heating and pressurizing at 140 to 200°C for 30 to 180 minutes can be used.

[0091] <Application> A tire having a tire component made from the rubber composition for tires of the present invention can be used for any type of tire, whether pneumatic or non-pneumatic, but it is preferably used as a pneumatic tire. Furthermore, the tire of the present invention can be used for a variety of applications, such as passenger car tires, heavy-duty tires for trucks and buses, motorcycle tires, and high-performance tires for racing. [Examples]

[0092] Hereinafter, examples (embodiments) that are considered preferable in implementation are shown, but the scope of the present invention is not limited to the embodiments. Rubber compositions obtained according to Table 1 using various chemicals shown below are examined, and the results calculated based on the following evaluation methods are shown in Table 1.

[0093] <Various Chemicals> ENR (Epoxidized Natural Rubber) 1: ENR25 (epoxidation rate 25 mol%) manufactured by Kumpulan Guthrie Sdn. Bhd. ENR (Epoxidized Natural Rubber) 2: ENR50 (epoxidation rate: 50 mol%) manufactured by Kumpulan Guthrie Sdn. Bhd. NR (Natural Rubber): TSR20 Imidazole compound: 1,2 - Dimethylimidazole (manufactured by Shikoku Chemicals Corporation) Carboxylic acid compound: Suberic acid (dicarboxylic acid, manufactured by Tokyo Chemical Industry Co., Ltd.)

[0094] Embodiments and Comparative Examples According to the formulation shown in Table 1, using a 1.7L closed Banbury mixer, various chemicals are kneaded at 150°C for 5 minutes to obtain a kneaded product.

[0095] The unvulcanized rubber compositions obtained above are heated and pressurized under the conditions described in Table 1 to obtain test rubber compositions.

[0096] <Tensile Test> From each test rubber composition, dumbbell-shaped test pieces conforming to ASTM D638 Type V with a thickness of 2 mm are prepared, and in accordance with JIS K 6251 "Vulcanized Rubber and Thermoplastic Rubber - Method for Determining Tensile Test Properties", a tensile test is carried out at a tensile speed of 3.3 mm / second in an atmosphere of 23°C, and the elongation at break EB (%) and the tensile strength TB (MPa) are measured.

[0097] <TB Index> Taking the value of TB (MPa) of the reference example as 100, the value of TB in each example is indexed. The larger the index value, the greater the tensile strength.

[0098] <EB repair rate (RR EB )(%), EB repair rate index> RR EB is a value defined by the following formula for the EB (%) of the repair test piece and the EB (%) of the anneal test piece. Here, the repair test piece is a test piece obtained by cutting a test piece in the thickness direction at the center of its long side, immediately bonding the cut surfaces, and then heat-treating at 80°C for 24 hours. The anneal test piece is a test piece heat-treated at 80°C for 24 hours. Taking the value of the EB repair rate (%) of the reference example as 100, the value of the EB repair rate in each example is indexed. The larger the index value, the larger the EB repair rate. RR EB = EB (%) of the repair test piece / EB (%) of the anneal test piece × 100

[0099] <TB repair rate (RR TB )(%), TB repair rate index> RR TB is a value defined by the following formula for the TB (MPa) of the repair test piece and the TB (MPa) of the anneal test piece. The repair test piece and the anneal test piece are as described above. Taking the value of the TB repair rate (%) of the reference example as 100, the value of the TB repair rate in each example is indexed. The larger the index value, the larger the TB repair rate. RR TB = TB (MPa) of the repair test piece / TB (MPa) of the anneal test piece × 100

[0100] <Abrasion resistance performance> The average value of the TB index, EB repair rate index, and TB repair rate index is taken as the abrasion resistance performance index.

[0101]

Table 1

[0102] <Embodiment> Preferred embodiments are shown below.

[0103] [1] A rubber component containing an epoxidized diene rubber, an imidazole compound, and a divalent or higher carboxylic acid compound, When measuring the elongation at break EB (%) and fracture strength TB (MPa) of a 2mm thick dumbbell-shaped test specimen conforming to ASTM D638 Type V according to JIS K 6251, the TB and the EB repair rate (%) RR defined below are used. EB , and the TB repair rate (%) RR as defined below. TB However, each of these is a rubber composition for tires that satisfies formulas (1) to (3). TB≧0.40 (1) RR EB ≥20 (2) RR TB ≥20 (3) (RR EB This value is defined as EB (%) of the repaired specimen / EB (%) of the annealed specimen × 100. TB This value is defined as TB (MPa) of the repaired specimen / TB (MPa) of the annealed specimen × 100. Here, a repaired specimen is a specimen that has been cut in the thickness direction at the center of its long side, the cut surfaces immediately bonded together, and then heat-treated at 80°C for 24 hours. An annealed specimen is a specimen that has been heat-treated at 80°C for 24 hours. [2] The tire rubber composition according to [1], wherein the right-hand side of formula (1) is 0.50, preferably 0.60, and more preferably 0.70. [3] The tire rubber composition according to [1] or [2] above, wherein the right-hand side of formula (2) is 45 and the right-hand side of formula (3) is 50. [4] The tire rubber composition according to [1] or [2] above, wherein the right-hand side of formula (2) is 60 and the right-hand side of formula (3) is 60. [5] The tire rubber composition according to [1] or [2] above, wherein the right-hand side of formula (2) is 72 and the right-hand side of formula (3) is 72. [6] The tire rubber composition contains a filler, The content of the filler is less than 45 parts by mass, preferably less than 20 parts by mass, and more preferably less than 5 parts by mass, per 100 parts by mass of the rubber component, or The tire rubber composition according to any one of the above [1] to [5], wherein the tire rubber composition does not contain a filler. [7] A tire having a tire member made of a tire rubber composition described in any one of the above items [1] to [6]. [8] The tire according to [7] above, wherein the tire member is a tire surface member. [9] The tire according to [8] above, wherein the tire surface member is at least one selected from the group consisting of a tread, a sidewall, a wing, and a clinch.

[10] The tire surface member is the sidewall, The aforementioned sidewall is an outer layer sidewall, The tire according to [9] above, wherein when the thickness (mm) of the outer layer sidewall is W, W satisfies equation (4), preferably the right-hand side of equation (4) is 1.2, more preferably 1.4, and even more preferably 1.5. W≧1.0 (4)

[11] The W and the RR TB The tire according to

[10] above, wherein the right-hand side of equation (5) is preferably 60, more preferably 70, even more preferably 75, even more preferably 90, and even more preferably 100. W×S TB >50 (5) [Explanation of Symbols]

[0104] 1 tire 2 tread 2a Cap Tread 2b Base tread 3 Sidewall 3a Outer sidewall 3b Inner sidewall 4 Wing 5. Clinch 6 bands 7. Circuit breaker 8 Carcass 9 Inner Liner R Rim W: Thickness of the outer sidewall at the point of maximum tire width C Tire centerline

Claims

1. A tire having a tire component made of a tire rubber composition comprising a rubber component containing an epoxidized diene rubber, an imidazole compound, and a divalent or higher carboxylic acid compound, The content of the aforementioned epoxidized diene rubber in 100% by mass of the rubber component is more than 70% by mass. The imidazole compound is a compound represented by the following formula (II): 【Chemistry 1】 (In formula (II), R 1 , R 2 , R 3 , R 4 R represents a hydrogen atom or a hydrocarbon group, either identical or different. 3 , R 4 (These may be bonded to each other to form a ring structure.) The aforementioned divalent or greater carboxylic acid compound is a divalent carboxylic acid compound represented by the following formula (I), The divalent carboxylic acid compound may or may not have substituents. HOOC-A-COOH (I) (In formula (I), A is a divalent hydrocarbon group having 1 to 6 carbon atoms, with or without substituents.) The aforementioned rubber composition for tires does not contain a filler, or the filler content is less than 45 parts by mass per 100 parts by mass of the rubber component. When measuring the elongation at break EB (%) and fracture strength TB (MPa) of a dumbbell-shaped test specimen conforming to ASTM D638 Type V with a thickness of 2 mm in accordance with JIS K 6251, the TB and the EB repair rate (%) RR defined below are used. EB , and the TB repair rate (%) RR as defined below TB However, each satisfies equations (1) to (3), When the tire member is an outer sidewall and the thickness (mm) of the outer sidewall is W, W satisfies the following equation (4): A tire in which W and RR TB satisfy the following formula (5). TB ≥ 0.40 (1) RR EB ≧20 (2) RR TB ≧20 (3) W ≥ 1.0 (4) W×RR TB >50 (5) (RR EB This value is defined as EB (%) of the repaired specimen / EB (%) of the annealed specimen × 100. RR TB This value is defined as TB (MPa) of the repaired specimen / TB (MPa) of the annealed specimen × 100. Here, a repaired specimen is a specimen that has been cut in the thickness direction at the center of its long side, the cut surfaces immediately bonded together, and then heat-treated at 80°C for 24 hours. An annealed specimen is a specimen that has been heat-treated at 80°C for 24 hours.

2. The tire according to claim 1, wherein the right-hand side of formula (1) is 0.

50.

3. The tire according to claim 1, wherein the right-hand side of equation (2) is 45 and the right-hand side of equation (3) is 50.

4. The tire according to claim 1, wherein the right-hand side of equation (2) is 60 and the right-hand side of equation (3) is 60.

5. The tire according to claim 1, wherein the right-hand side of equation (2) is 72 and the right-hand side of equation (3) is 72.

6. The aforementioned tire rubber composition contains a filler, The tire according to any one of claims 1 to 5, wherein the content of the filler is less than 45 parts by mass per 100 parts by mass of the rubber component.

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