Tire rubber composition and tire

Abstract

To provide a tire rubber composition and a tire each having excellent durability.SOLUTION: The present invention relates to a tire rubber composition that contains a rubber component and a copolymer of a (meth)acrylate ester A and a (meth)acrylate ester B, wherein an ester moiety of the (meth)acrylate ester A and an ester moiety of the (meth)acrylate ester B have different numbers of carbon atoms from each other.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Conventionally, various methods for improving various tire performances have been studied, and improvements such as durability performance have been demanded (Patent Document 1, etc.).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to solve the above problems and provide a rubber composition for tires and a tire having excellent durability performance.

Means for Solving the Problems

[0005] The present invention is a rubber composition for tires containing a rubber component and a copolymer of (meth)acrylic acid ester A and (meth)acrylic acid ester B, wherein the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester A is different from the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester B.

Effects of the Invention

[0006] ​The present invention relates to a rubber composition for tires, which comprises a rubber component and a copolymer of (meth)acrylic acid ester A and (meth)acrylic acid ester B, wherein the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester A is different from the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester B. Since it is such a rubber composition for tires, the durability performance can be improved.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0008] The above rubber composition for tires contains a rubber component and a copolymer of (meth)acrylic acid ester A and (meth)acrylic acid ester B, and the copolymer is such that the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester A is different from the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester B.

[0009] The mechanism by which the above-mentioned effects are obtained with the rubber composition for tires is not necessarily clear, but it is presumed as follows. The -COO- part of (meth)acrylic acid ester A and the -COO- of (meth)acrylic acid ester B having an ester part with a carbon number different from that of the ester part of the (meth)acrylic acid ester A approach each other and cause an attracting effect. When the carbon number of R in the -COO-R part of (meth)acrylic acid ester A is different from the carbon number of R in the -COO-R part of (meth)acrylic acid ester B, the -COO-R part of (meth)acrylic acid ester A and the -COO-R part of (meth)acrylic acid ester B can mesh alternately with each other between polymer chains. When stress is applied to the rubber, the meshed parts can come apart to disperse energy. Thus, it is considered that the -COO-R part of (meth)acrylic acid ester A and the -COO-R part of (meth)acrylic acid ester B act as sacrificial bonds. Therefore, it is presumed that the durability performance is improved by the above rubber composition for tires.

[0010] The above rubber composition for tires contains a rubber component. In this specification, the above 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 above rubber component is in a solid state at 25°C.

[0011] The weight average molecular weight of the above 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 it is within the above range, the effect tends to be obtained more favorably.

[0012] 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).

[0013] The above rubber component 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 (a terminal-modified rubber having the above functional group at the terminal) in which at least one terminal 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 terminal 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.

[0014] Examples of the above 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 a substituent. Among them, an amino group (preferably an amino group in which a hydrogen atom of the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferred.

[0015] Examples of the rubber component include diene rubbers. Examples of the diene rubbers include isoprene rubbers, 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. Examples of the rubber component also include butyl rubbers, fluororubbers, etc. These rubber components may be subjected to modification treatment or hydrogenation treatment, and extended rubbers extended with oils, resins, liquid rubber components, etc. may also be used. These may be used alone or in combination of two or more. Among them, it is preferable to contain at least one of isoprene rubbers, BR, and SBR, more preferably to contain at least one of isoprene rubbers and BR, and still more preferably to contain at least isoprene rubbers and BR.

[0016] Examples of the isoprene rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, denatured NR, denatured IR, etc. As for NR, for example, those common in the rubber industry such as SIR20, RSS#3, TSR20, etc. can be used. IR is not particularly limited, and for example, those common in the rubber industry such as IR2200, etc. can be used. Examples of the modified NR include deproteinized natural rubber (DPNR), high-purity natural rubber, etc., examples of the denatured NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc., and examples of the denatured IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. These may be used alone or in combination of two or more.

[0017] BR is not particularly limited. For example, high-cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, BR synthesized using a rare earth catalyst (rare earth BR), etc. can be used. These may be used alone or in combination of two or more. Among them, BR preferably contains high-cis BR with a cis content of 90% by mass or more. The cis content is more preferably 95% by mass or more. The cis content can be measured by infrared absorption spectroscopy analysis.

[0018] When there is one type of BR, the cis amount of BR means the cis amount of that BR. When there are multiple types, it means the average cis amount. The average cis amount of BR can be calculated by {Σ(content of each BR × cis amount of each BR)} / total content of all BR. For example, in 100% by mass of the rubber component, if BR with a cis amount of 90% by mass is 20% by mass and BR with a cis amount of 40% by mass is 10% by mass, the average cis amount of BR is 73.3% by mass (=(20×90 + 10×40) / (20 + 10)).

[0019] As BR, either non-modified BR or modified BR can be used. Examples of modified BR include modified BR into which functional groups similar to those of modified rubber are introduced. Also, as BR, hydrogenated butadiene polymer (hydrogenated BR) can be used.

[0020] As BR, for example, products of Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

[0021] 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.

[0022] The styrene content of SBR is preferably 5% by mass or more, more preferably 20% by mass or more, still more preferably 24% 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 it is within the above range, the effect tends to be obtained more favorably. In the present specification, the styrene content can be measured by 1 1H-NMR measurement.

[0023] When there is one type of SBR, the styrene amount of the SBR means the styrene amount of the SBR, and when there are multiple types, it means the average styrene amount. The average styrene amount of SBR can be calculated by {Σ(content of each SBR × styrene amount of each SBR)} / total content of all SBRs. For example, when 85% by mass of SBR with a styrene amount of 40% by mass and 5% by mass of SBR with a styrene amount of 25% by mass are present in 100% by mass of the rubber component, the average styrene amount of SBR is 39.2% by mass (=(85×40 + 5×25) / (85 + 5)).

[0024] The vinyl bond amount of SBR is preferably 3% by mass or more, more preferably 10% by mass or more, still more preferably 17% by mass or more. The vinyl bond amount is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less. When it is within the above range, the effect tends to be obtained more favorably. In the present specification, the vinyl bond amount (1,2-bonded butadiene unit amount) can be measured by infrared absorption spectrum analysis.

[0025] The vinyl amount (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 the SBR, and when there are multiple types, it means the average vinyl amount. The average vinyl content of SBR can be calculated by Σ{content of each SBR × (100 [mass%] - styrene content of each SBR [mass%]) × vinyl content of each SBR [mass%]} / Σ{content of each SBR × (100 [mass%] - styrene content of each SBR [mass%])}. For example, in 100 parts by mass of the rubber component, if there are 75 parts by mass of SBR with a styrene content of 40 mass% and a vinyl content of 30 mass%, 15 parts by mass of SBR with a styrene content of 25 mass% and a vinyl content of 20 mass%, and the remaining 10 parts by mass are other than SBR, the average vinyl content of SBR is 28 mass% (={75×(100 [mass%]-40 [mass%])×30 [mass%]+15×(100 [mass%]-25 [mass%])×20 [mass%])} / {75×(100 [mass%]-40 [mass%])+15×(100 [mass%]-25 [mass%])}).

[0026] As SBR, either non-modified SBR or modified SBR can be used. Examples of modified SBR include those with functional groups similar to modified rubber introduced. Also, as SBR, hydrogenated styrene-butadiene copolymer (hydrogenated SBR) can be used.

[0027] 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.

[0028] The raw materials (monomers) for synthetic rubbers such as IR, SBR, and BR may be derived from underground resources such as petroleum and natural gas, or may be recycled from rubber products such as tires and non-rubber products such as polystyrene. The monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled polyisoprene, 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 polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) as raw materials.

[0029] The method for producing recycled monomers is not particularly limited, and examples include being synthesized from recycled naphtha obtained by decomposing rubber products such as tires. Also, the method for producing recycled naphtha is not particularly limited, and for example, rubber products such as tires may be decomposed under high temperature and high pressure, decomposed by microwaves, or extracted after mechanical pulverization.

[0030] Furthermore, the raw materials (monomers) for synthetic rubbers such as IR, SBR, and BR may be derived from biomass. In this specification, biomass refers to substances derived from natural resources such as plants. Biomass is not particularly limited, and examples include agricultural and forestry products, sugars, wood chips, plant residues after obtaining useful components, plant-derived ethanol, biomass naphtha, and the like.

[0031] The biomass-derived monomers (biomass monomers) are not particularly limited, and examples include biomass-derived butadiene and biomass-derived aromatic vinyls. 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 the 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 as the biological conversion, and examples of the chemical and / or physical conversion include those by a catalyst, high heat, high pressure, electromagnetic waves, a critical liquid, and combinations thereof.

[0032] The polymers synthesized from the biomass monomer components (biomass polymers) are not particularly limited, and examples include polybutadiene rubber synthesized from biomass-derived butadiene and aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyls. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

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

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

[0035] In one mole (6.02×10 23 pieces) of carbon atoms, there are about 6.02×10 11 pieces, which is about one trillionth of ordinary carbon atoms, of 14C exists. 14 C is called a radioactive isotope, and its half-life is 5730 years, decreasing regularly. It takes 226,000 years for all of them to decay. Therefore, after carbon dioxide in the atmosphere is taken up and fixed by plants, etc., in fossil fuels such as coal, oil, and natural gas, where more than 226,000 years are considered to have passed, at the beginning of fixation, it was also included in these. 14 All of the C element has decayed. Therefore, at present in the 21st century, fossil fuels such as coal, oil, and natural gas 14 contain no C element at all. Therefore, chemical substances produced using these fossil fuels as raw materials 14 also contain no C element at all.

[0036] On the other hand, 14 C is constantly generated by cosmic rays undergoing nuclear reactions in the atmosphere, and is in balance with the decrease due to radioactive decay. In the earth's atmospheric environment, 14 the amount of C is a certain amount. Therefore, for substances derived from biomass resources circulating in the current environment 14 the C concentration 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 biomass ratio of a certain compound can be calculated.

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

[0038] C concentration value (100%). The ratio of this value to the value of the actually measured sample is the pMC value. 14 Therefore, if the rubber is made of 100% biomass-derived substances, although there are regional differences and the like, currently in the normal state, it often does not reach 100, so it will show a value of about 110 pMC. On the other hand, for chemical substances derived from fossil fuels such as petroleum, when measuring this

[0039] C concentration, it will show a value of about 0 pMC (for example, 0.3 pMC). This value corresponds to a biomass ratio of 0% mentioned above.

[0040] When the rubber composition for tires contains isoprene rubber as a rubber component, the content of isoprene rubber in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 40% by mass or more, still more preferably 45% by mass or more, and preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0041] When the rubber composition for tires contains BR, the content of BR in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 45% by mass or more, still more preferably 55% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less, still more preferably 70% by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0042] When the rubber composition for tires contains SBR, the content of SBR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and is preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0043] The rubber composition for tires is a copolymer of (meth)acrylic acid ester A and (meth)acrylic acid ester B, and includes a copolymer in which the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester A is different from the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester B. The copolymer may be used alone or in combination of two or more. In the present specification, “(meth)acrylic” means “acrylic” or “methacrylic”. That is, (meth)acrylic acid ester refers to acrylic acid ester or methacrylic acid ester.

[0044] In the above copolymer, the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester A is preferably 1 or more, and is preferably 3 or less, more preferably 2 or less. When it is within the above range, the effect tends to be obtained more favorably.

[0045] In the above copolymer, the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester B is preferably 2 or more, more preferably 3 or more, still more preferably 4 or more, and is preferably 10 or less, more preferably 8 or less, still more preferably 7 or less. When it is within the above range, the effect tends to be obtained more favorably.

[0046] In the above copolymer, the difference in the number of carbon atoms in the ester moiety of the above (meth)acrylic acid ester B and the number of carbon atoms in the ester moiety of the above (meth)acrylic acid ester A ((the number of carbon atoms in the ester moiety of (meth)acrylic acid ester B - the number of carbon atoms in the ester moiety of (meth)acrylic acid ester A)) is preferably 1 or more, more preferably 2 or more, still more preferably 3 or more. The upper limit is preferably 10 or less, more preferably 8 or less, still more preferably 7 or less. When within the above range, the effect tends to be obtained more favorably.

[0047] The ester group of the above (meth)acrylic acid ester A and the ester group of the above (meth)acrylic acid ester B may be a group in any shape of linear, branched, or cyclic, but from the viewpoint that the effect tends to be obtained more favorably, a linear hydrocarbon group is desirable. The ester group may have a substituent. Examples of the substituent include known groups such as a hydroxyl group.

[0048] Specific examples of the above (meth)acrylic acid ester A and the above (meth)acrylic acid ester B include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate (n-butyl, sec-butyl, iso-butyl or tert-butyl), pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, stearyl (meth)acrylate, ethylene oxide adduct of (meth)acrylic acid, and the like. These may be used alone or in combination of two or more. Among them, from the viewpoint that the above (meth)acrylic acid ester A tends to give better effects, methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate are preferable, methyl acrylate and methyl methacrylate are more preferable, and methyl methacrylate is particularly preferable. Among them, from the viewpoint that the above (meth)acrylic acid ester B tends to give better effects, butyl (meth)acrylate, pentyl (meth)acrylate, and hexyl (meth)acrylate are preferable, butyl acrylate, pentyl acrylate, and hexyl acrylate are more preferable, and butyl acrylate is particularly preferable.

[0049] In the above copolymer, the molar ratio (S) of the above (meth)acrylic acid ester A to the above (meth)acrylic acid ester B, that is, (the proportion of (meth)acrylic acid ester A units in the copolymer) / (the proportion of (meth)acrylic acid ester B units in the copolymer) S is preferably 0.40 or more, more preferably 0.50 or more, still more preferably 0.65 or more, and is preferably 2.5 or less, more preferably 2.0 or less, still more preferably 1.5 or less. When it is within the above range, the effects tend to be obtained more favorably. (Measurement method) In the present specification, the above molar ratio is 1 a value measured by 1H-NMR measurement. For example, in the case of a copolymer of methyl methacrylate and butyl acrylate, it is immersed in deuterated chloroform at 25°C for 24 hours, and at room temperature 1 1H-NMR is measured. When the signal of tetramethylsilane (TMS) is set to 0.00 ppm, signals around 3.60 ppm and around 4.00 ppm are observed, and these signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In this paragraph, "around" means a range of ±0.10 ppm.

[0050] Although the mechanism by which more effects can be obtained by adjusting to the molar ratio within the specified range is not clear, it is considered that by setting the molar ratio within the specified range, the above sacrificial bonds are sufficiently introduced into the rubber component, thereby improving the durability performance.

[0051] The chain structure of the above copolymer is not particularly limited, and examples include block copolymers, random copolymers, tapered copolymers in which a random copolymer and a block copolymer are mixed, and alternating copolymers. These may be used alone or in combination of two or more. Among them, from the viewpoint that the effect tends to be obtained more favorably, an alternating copolymer is preferable.

[0052] The glass transition temperature (Tg) of the above copolymer is preferably -40°C or higher, more preferably -30°C or higher, still more preferably -20°C or higher, and is preferably 40°C or lower, more preferably 30°C or lower, still more preferably 20°C or lower. When it is within the above range, the effect tends to be obtained more favorably. In this specification, Tg is a value measured by performing differential scanning calorimetry (DSC) under the condition of a heating rate of 10°C / min in accordance with JIS K7121.

[0053] The weight average molecular weight (Mw) of the above copolymer is preferably 5000 or more, more preferably 10,000 or more, still more preferably 20,000 or more, and is preferably 1,000,000 or less, more preferably 500,000 or less, still more preferably 200,000 or less. When it is within the above range, the effect tends to be obtained more favorably.

[0054] The above copolymer can be prepared by copolymerizing the above (meth)acrylic acid ester A and the above (meth)acrylic acid ester B by a known method.

[0055] In the above rubber composition for tires, the content of the above copolymer (total amount of the above copolymer) is preferably 1 part by mass or more, more preferably 5 parts by mass or more, still more preferably 15 parts by mass or more, and preferably less than 100 parts by mass, more preferably less than 75 parts by mass, still more preferably less than 50 parts by mass, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0056] Although the mechanism by which a more effective result is obtained by adjusting the content of the above copolymer within a predetermined range is not clear, it is considered that the above sacrificial bond is favorably formed by setting it within the predetermined range, thereby improving the durability performance.

[0057] The above rubber composition for tires preferably contains a filler. The above filler is not particularly limited, and materials known in the rubber field can be used. For example, inorganic fillers such as carbon black, silica, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, mica, bio char (BIO CHAR); poorly dispersible fillers, etc. can be mentioned. Among them, carbon black and silica are preferred from the viewpoint of obtaining a more effective result.

[0058] In the above rubber composition for tires, the content of the filler (total amount of fillers such as carbon black and silica) is preferably 5 parts by mass or more, more preferably 40 parts by mass or more, still more preferably 50 parts by mass or more, and preferably 200 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 100 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the effect tends to be obtained more favorably.

[0059] The available carbon blacks are not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. The raw material of the carbon black may be a biomass material such as lignin or vegetable oil, or may be a pyrolysis oil obtained by pyrolyzing waste tires. Further, the manufacturing method of the carbon black may be by combustion such as the furnace method, may be by hydrothermal carbonization (HTC), or may be by thermal decomposition of methane such as the thermal black method. As commercially available products, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Columbian Carbon Co., etc. can be used. These may be used alone or in combination of two or more.

[0060] The nitrogen adsorption specific surface area (N2SA) of the carbon black is preferably 5 m 2 / g or more, more preferably 30 m 2 / g or more, and still more preferably 50 m 2 / g or more. Further, the above N2SA is preferably 200 m 2 / g or less, more preferably 100 m 2 / g or less, and still more preferably 90 m 2 / g or less. When within the above range, the effect tends to be obtained more favorably. The nitrogen adsorption specific surface area of the carbon black is determined according to JIS K6217-2:2001.

[0061] In the above rubber composition for tires, the content of the carbon black is preferably 5 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 37 parts by mass or more, based on 100 parts by mass of the rubber component, and is preferably 150 parts by mass or less, more preferably 80 parts by mass or less, still more preferably 70 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0062] In the above rubber composition for tires, 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.

[0063] Silica using biomass materials as raw materials can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and reacting the silicate with sulfuric acid in the same manner as conventional wet silica to precipitate silicon dioxide, followed by filtration, washing with water, drying, and pulverization.

[0064] Silica recycled from products containing silica can be used, for example, silica recovered from products containing silica such as electronic components such as semiconductors, tires, desiccants, and filter materials such as diatomaceous earth. The recovery method is not particularly limited, and examples include thermal decomposition and decomposition by electromagnetic waves. Among them, silica recovered from electronic components such as semiconductors or tires is preferred.

[0065] When silica crystallizes, it is insoluble in water and the silicic acid that is its component cannot be utilized. By controlling the combustion temperature and combustion time, the crystallization of silica in rice husk ash can be suppressed (see, for example, Japanese Patent Laid-Open No. 2009-2594, Akita Prefectural University Web Journal B / 2019, vol. 6, p. 216-222, etc.).

[0066] Amorphous silica extracted from rice husks can be those commercially available from Wilmar Co., Ltd. and the like.

[0067] In the above rubber composition for tires, the silica content is, based on 100 parts by mass of the rubber component, Good preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and preferably 150 parts by mass or less, more preferably 50 parts by mass or less, still more preferably 20 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0068] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 50 m 2 / g or more, more preferably 70 m 2 / g or more, still more preferably 80 m 2 / g or more. Also, the upper limit of the N2SA of the 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 the silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0069] Examples of the hardly dispersible filler include microfibrillated plant fibers, short fibrous cellulose, gel-like compounds, etc. Among them, microfibrillated plant fibers are preferred.

[0070] As the above microfibrillated plant fibers, cellulose microfibrils are preferred from the viewpoint of obtaining good reinforcing properties. The cellulose microfibrils are not particularly limited as long as they are derived from natural products. For example, resource biomasses such as fruits, grains, and root vegetables, wood, bamboo, hemp, jute, kenaf, and pulp, paper, cloth, agricultural crop residues, food wastes, and sewage sludge obtained from these as raw materials, waste biomasses such as rice straw, wheat straw, and thinned wood, and those derived from cellulose produced by tunicates, acetic acid bacteria, etc. may be mentioned. These microfibrillated plant fibers may be used alone or in combination of two or more.

[0071] 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, more typically a cellulose fiber having a microstructure with an average fiber diameter of 500 nm or less formed by an aggregate of cellulose molecules. A typical cellulose microfibril is formed, for example, as an aggregate of cellulose fibers having the average fiber diameter as described above.

[0072] When the above rubber composition for tires contains a poorly dispersible filler, the content of the poorly 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.

[0073] When the above rubber composition for tires contains silica, it is preferable to further contain a silane coupling agent. The silane coupling agent is not particularly limited, and those known in the rubber field can be used. For example, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, etc. of the sulfide series, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercapto series such as NXT and NXT-Z manufactured by Momentive, vinyl series such as vinyltriethoxysilane and vinyltrimethoxysilane, amino series such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy series such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, nitro series such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, chloro series 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.

[0074] In the above rubber composition for tires, the content of the silane coupling agent is preferably 0.1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more with respect to 100 parts by mass of silica. The upper limit of the content is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0075] The above rubber composition for tires may contain a plasticizer. In this specification, a plasticizer is a material that imparts plasticity to a rubber component, and is a concept including both a plasticizer that is liquid at 25°C and a plasticizer that is solid at 25°C. Examples of plasticizers include resin components, oils, liquid polymers, ester-based plasticizers, etc. These plasticizers may be derived from mineral resources such as petroleum and natural gas, may be derived from biomass, or may be derived from naphtha recycled from rubber products or non-rubber products. Also, a low-molecular-weight hydrocarbon component obtained by thermally decomposing and extracting a used tire or a product containing various components may be used as a plasticizer. These plasticizers may be used alone or in combination of two or more.

[0076] Specific examples of the above plasticizer include oils, other liquid polymers, resins, etc. These may be used alone or in combination of two or more.

[0077] Examples of oils include mineral oils, vegetable oils, animal oils, etc. Also, from the perspective of life cycle assessment, waste oils used in rubber mixers or engines, or refined waste cooking oils used in restaurants may be used.

[0078] In this specification, mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. Examples of mineral oil include paraffinic oil (mineral oil), naphthenic oil, aromatic oil, etc. Specific examples of mineral oil include, for example, MES (Mild Extract Solvated), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), RAE (Residual Aromatic Extract), etc. Also, oil with a low content of polycyclic aromatic (PCA) compounds can be used for environmental protection. Examples of the low-PCA-content oil include MES, TDAE, heavy naphthenic oil, etc.

[0079] In this specification, vegetable oil refers to, for example, linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grape seed oil, wood rosin, etc. Furthermore, vegetable oil includes refined oil (such as salad oil) obtained by refining the above oil, transesterified oil obtained by transesterifying the above oil, hydrogenated oil obtained by hydrogenating the above oil, thermally polymerized oil obtained by thermally polymerizing the above oil, oxidatively polymerized oil obtained by oxidizing the above oil, waste cooking oil recovered from those used as edible oil, etc. Note that vegetable oil may be liquid or solid at 25°C. These vegetable oils may be used alone or in combination of two or more.

[0080] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably contains triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxy group of glycerin and a fatty acid are ester-bonded. The acylglycerol is not particularly limited, and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Further, the acylglycerol may be a monomer, a dimer, or a multimer of trimer or more. Note that acylglycerols of dimer or more can be obtained by thermal polymerization, oxidative polymerization, or the like. Also, the acylglycerol may be liquid or solid at 25°C.

[0081] As a method for confirming whether the acylglycerol is contained in the rubber composition, it is not particularly limited, but 1 it can be confirmed by 1H-NMR measurement. For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at 25°C for 24 hours. After removing the rubber composition, 1 1H-NMR is measured. When the signal of tetramethylsilane (TMS) is set to 0.00 ppm, signals are observed at around 5.26 ppm, around 4.28 ppm, and around 4.15 ppm. These signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In this paragraph, "around" means a range of ±0.10 ppm.

[0082] The fatty acid is not particularly limited, and may be an unsaturated fatty acid or a saturated fatty acid. Examples of the unsaturated fatty acid include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of the saturated fatty acid include butyric acid and lauric acid.

[0083] Among these, as the fatty acid, it is desirable to contain a fatty acid with few double bonds, that is, a saturated fatty acid or a monounsaturated fatty acid, and oleic acid is preferred. As the vegetable oil containing such a fatty acid, for example, a vegetable oil containing a saturated fatty acid or a monounsaturated fatty acid may be used, or a vegetable oil subjected to modification such as transesterification may be used. Further, in order to produce a vegetable oil containing such a fatty acid, plants may be improved by varietal improvement, genetic recombination, genome editing, etc.

[0084] As the oil, for example, those commercially available from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., Oryzoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kogyo Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0085] Examples of the liquid polymer include a liquid diene polymer (liquid rubber) and a liquid farnesene polymer at 25°C. Examples of the liquid rubber include a liquid styrene-butadiene copolymer (liquid SBR), a liquid butadiene polymer (liquid BR), a liquid isoprene polymer (liquid IR), a liquid styrene-isoprene copolymer (liquid SIR), a liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), a liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer), etc. These may have their terminals or main chains modified with polar groups. Also, hydrogenated products thereof can be used.

[0086] The weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) of the liquid diene polymer is preferably 1.0×10 3 ~5.0×10 4 and more preferably 3.0×10 3 ~1.5×10 4 The lower limit or upper limit of Mw of the liquid diene polymer may also be 4500 or 8500. In this specification, the Mw of the liquid diene polymer is a polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0087] As the above liquid diene polymer, for example, products of Sartomer Co., Kuraray Co., Ltd. etc. can be used.

[0088] As the above resin, as a tire compounding, a resin (resin) usually used can be used, and it may be liquid or solid at 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. Further, the resin itself may be a copolymer of monomer components from a plurality of sources. Among them, aromatic vinyl polymers, petroleum resins, terpene resins, and hydrogenated resins thereof are desirable.

[0089] When using a resin that is solid at 25°C as the above 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. Further, it is preferably 160°C or lower, more preferably 150°C or lower, still more preferably 140°C or lower, and particularly preferably 100°C or lower. When within the above range, the effect tends to be obtained better. When the resin is liquid at 25°C, 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. Incidentally, the softening point of the above resin is measured by a ring and ball softening point measuring device for the softening point defined in JIS K6220-1:2001, and is the temperature at which the ball drops.

[0090] The above aromatic vinyl polymer is a polymer containing an aromatic vinyl monomer as a constituent unit. For example, resins obtained by polymerizing α-methylstyrene and / or styrene can be mentioned. Specifically, a homopolymer of styrene (styrene resin), a homopolymer of α-methylstyrene (α-methylstyrene resin), a copolymer of α-methylstyrene and styrene, a copolymer of styrene and other monomers, etc. can be mentioned.

[0091] The above coumarone-indene resin is a resin containing coumarone and indene as the main monomer components constituting the resin skeleton (main chain). As monomer components contained in the skeleton other than coumarone and indene, styrene, α-methylstyrene, methyl indene, vinyl toluene, etc. can be mentioned.

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

[0093] The above indene resin is a resin containing indene as the main monomer component constituting the resin skeleton (main chain).

[0094] As the above phenol resin, for example, known ones such as polymers obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde, and furfural in the presence of an acid or alkali catalyst can be used. Among them, those obtained by reacting with an acid catalyst (such as novolak-type phenol resins) are preferred.

[0095] As the above rosin resin, rosin-based resins represented by natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof can be mentioned.

[0096] As the above petroleum resin, C5-based resins, C9-based resins, C5 / C9-based resins, dicyclopentadiene (DCPD) resins, C9 / DCPD resins, hydrogenated products thereof, etc. can be mentioned. Among them, DCPD resins, hydrogenated DCPD resins, C9 / DCPD resins, and C9 / hydrogenated DCPD resins are preferred.

[0097] The above terpene resin is a polymer containing terpenes as constituent units. For example, there are polyterpene resins obtained by polymerizing terpene compounds, aromatic modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds, and the like. Examples of aromatic modified terpene resins include terpene phenol resins using terpene compounds and phenolic compounds as raw materials, terpene styrene resins using terpene compounds and styrene compounds as raw materials, and terpene phenol styrene resins using terpene compounds, phenolic compounds and styrene compounds as raw materials. As the terpene compound, α-pinene, β-pinene, etc. can be mentioned. As the phenolic compound, phenol, bisphenol A, etc. can be mentioned. As the aromatic compound, styrene compounds (styrene, α-methylstyrene, etc.) can be mentioned. Among them, aromatic modified terpene resins are preferred.

[0098] 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.

[0099] 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 Shokubai Co., Ltd., ENEOS Co., Ltd., Arakawa Chemical Industries, Ltd., Tago Chemical Industry Co., Ltd., etc. can be used.

[0100] 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.

[0101] 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]

[0102] 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.

[0103] 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.

[0104] 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.

[0105] Farnesene-based polymers with a weight average molecular weight (Mw) of 3000 or more and 300,000 or less can be preferably used. The Mw of the farnesene-based polymer is preferably 8000 or more, more preferably 10,000 or more, and preferably 100,000 or less, more preferably 60,000 or less, and even more preferably 50,000 or less. When within the above range, the effects tend to be more preferably obtained.

[0106] The farnesene-based polymer may be in a liquid state or a solid state at 25°C. Among them, a liquid farnesene-based polymer in a liquid state at 25°C is desirable.

[0107] In the above rubber composition for tires, the content of the plasticizer (total amount of the plasticizer) is preferably 1 part by mass or more, more preferably 5 parts by mass or more, still more preferably 8 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 30 parts by mass or less, still more preferably 25 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.

[0108] In the above rubber composition for tires, the content of the solid plasticizer in the solid state at 25°C is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 4 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0109] In the above rubber composition for tires, the content of the above resin in the solid state at 25°C is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 4 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0110] In the above rubber composition for tires, the content of the liquid plasticizer in the liquid state at 25°C is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 4 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 10 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.

[0111] In the above rubber composition for tires, the oil content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 4 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less. When within the above range, the effect tends to be obtained more favorably. Note that the oil content also includes the amount of oil contained in the oil-extended rubber.

[0112] The above rubber composition for tires may further contain vulcanized rubber particles. The vulcanized rubber particles are particles made of vulcanized rubber. Specifically, rubber powder etc. specified in JIS K 6316:2017 can be used. From the viewpoints of environmental consideration and cost, recycled rubber powder produced from crushed waste tires etc. is preferable. These may be used alone or in combination of two or more.

[0113] The vulcanized rubber particles are not particularly limited, and may be non-modified vulcanized rubber particles or modified vulcanized rubber particles.

[0114] As commercially available products of vulcanized rubber particles, for example, products of Lehigh, Murakami Rubber Industry Co., Ltd. etc. can be used.

[0115] In the above rubber composition for tires, the content of vulcanized rubber particles is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, still more preferably 10 parts by mass or more, based on 100 parts by mass of the rubber component, and is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 15 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0116] From the viewpoints of crack resistance, ozone resistance etc., the above rubber composition for tires preferably contains an anti-aging agent.

[0117] The anti-aging agent is not particularly limited, but examples include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine-based anti-aging agents such as N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditoly-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; bis, tris, polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among them, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferred, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and polymers of 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. As commercial products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., Flexsys Co., etc. can be used.

[0118] In the above rubber composition for tires, the content of the anti-aging agent is preferably 0.2 parts by mass or more, more preferably 2.0 parts by mass or more, and still more preferably 3.4 parts by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 10.0 parts by mass or less, and more preferably 6.0 parts by mass or less.

[0119] The above rubber composition for tires preferably contains stearic acid. In the above rubber composition for tread, the content of stearic acid is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, still 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.

[0120] 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.

[0121] The above rubber composition for tire preferably contains zinc oxide. In the above rubber composition for tread, the content of zinc oxide is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, still more preferably 2.0 parts by mass or more, and preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, based on 100 parts by mass of the rubber component.

[0122] 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.

[0123] The above rubber composition for tire may be compounded with wax. In the above rubber composition for tire, the content of wax is preferably 0.5 parts by mass or more, more preferably 1.6 parts by mass or more, and preferably 8.0 parts by mass or less, more preferably 5.0 parts by mass or less, based on 100 parts by mass of the rubber component.

[0124] The wax is not particularly limited, and any wax commonly used in the tire industry can be preferably used. For example, mineral waxes, plant-derived waxes, etc. can be mentioned. Mineral waxes refer to waxes derived from mineral resources such as oil and natural gas. Plant-derived waxes refer to waxes derived from natural resources such as plants. Among them, mineral waxes are preferred. Examples of plant-derived waxes include rice wax, carnauba wax, candelilla wax, etc. Examples of mineral waxes include paraffin wax, microcrystalline wax, these 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 Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., etc. can be used. These waxes may be used alone or in combination of two or more.

[0125] In the above rubber composition for tires, it is preferable to compound sulfur as a crosslinking agent in terms of forming appropriate crosslinking chains in the polymer chain and imparting good performance.

[0126] The above rubber composition for tires preferably contains sulfur. In the above rubber composition for tires, the sulfur content is 1.0 part by mass or more, preferably 2.0 parts by mass or more, more preferably 2.5 parts by mass or more, based on 100 parts by mass of the rubber component. The sulfur content is preferably 7.0 parts by mass or less, more preferably 5.0 parts by mass or less, still more preferably 4.0 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0127] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. As commercially available products, products of Tsuruami Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexsys 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.

[0128] The above rubber composition for tires preferably contains a vulcanization accelerator. In the above rubber composition for tires, the content of the vulcanization accelerator is not particularly limited and may be freely determined according to the desired vulcanization rate and crosslink density. However, based on 100 parts by mass of the rubber component, it is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and still more preferably 1.0 parts by mass or more. The upper limit is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, and still more preferably 5.0 parts by mass or less.

[0129] 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-benzothiazolesulfenamide, N-t-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine, and orthotolylbiguanidine. These may be used alone or in combination of two or more. Among them, sulfenamide-based, guanidine-based, and benzothiazole-based vulcanization accelerators are preferred.

[0130] In addition to the above components, the above rubber composition for tires may be appropriately blended with compounding agents generally used in the tire industry, such as materials such as mold release agents.

[0131] In this specification, various materials containing carbon atoms (such as rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from carbon dioxide in the atmosphere. As a method for obtaining the above-mentioned composition 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.

[0132] The rubber composition for tires is kneaded using a rubber kneading device such as an open roll or a Banbury mixer for each of the above components, and then a crosslinked rubber composition is obtained by a method such as crosslinking.

[0133] As the kneading conditions, in the base kneading step of kneading additives other than the vulcanizing agent and the vulcanization accelerator, the kneading temperature is preferably 50°C or higher, more preferably 80°C or higher, and preferably 200°C or lower, more preferably 190°C or lower. The kneading time is preferably 30 seconds or longer, more preferably 1 minute or longer, and preferably 30 minutes or shorter. In the finishing kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is preferably 20°C or higher, and preferably 100°C or lower, more preferably 80°C or lower. The composition kneaded with the vulcanizing agent and the vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is preferably 120°C or higher, more preferably 140°C or higher, and preferably 200°C or lower, more preferably 180°C or lower.

[0134] From the viewpoint that the effects are more likely to be obtained satisfactorily, it is desirable that the phase of the copolymer exists in the rubber component in the rubber composition for tires after the above crosslinking or vulcanization.

[0135] When the phase of the copolymer exists in the rubber component, the domain diameter P of the copolymer in the rubber component is desirably 10 nm or more and less than 2000 nm. The domain diameter is preferably 20 nm or more, more preferably 50 nm or more, and preferably less than 1000 nm, more preferably less than 500 nm. When within the above range, the effects tend to be obtained more satisfactorily.

[0136] In this specification, the domain diameter can be measured by observation with a scanning electron microscope (SEM). Specifically, it can be determined as the average value of any 100 in the field of view, respectively.

[0137] Although the mechanism by which more effects can be obtained by having a domain diameter within a predetermined range is not clear, it is considered that by setting the domain diameter within a predetermined range, the above sacrificial bond is uniformly introduced into the rubber composition, thereby improving the durability performance.

[0138] Regarding the domain diameter of the copolymer in the above rubber component, the domain diameter tends to increase by increasing the content of the copolymer, shortening the kneading time, and decreasing the content of the filler. On the other hand, the domain diameter tends to decrease by decreasing the content of the copolymer, lengthening the kneading time, and increasing the content of the filler.

[0139] The tire member to which the above rubber composition for tires is applied is not particularly limited, and examples include tread, sidewall, wing, base tread, undertread, bead apex, clinch, inner liner, etc.

[0140] Among the above tire members, from the viewpoint of obtaining more effects, it is desirable to apply it to the sidewall. In this case, the above rubber composition for tires is used as a rubber composition for sidewalls.

[0141] Although the mechanism by which more effects can be obtained by applying it to the sidewall is not clear, it is considered that the deterioration of the sidewall due to vibrations of the tire or the like is suppressed by the above sacrificial bond, thereby improving the durability performance.

[0142] The above tire is manufactured by a conventional method using the above rubber composition for tires. That is, a composition blended with various additives as required is extruded into the shape of various tire members such as sidewalls at the uncrosslinked or unvulcanized stage, formed 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.

[0143] The above tire is not particularly limited, and examples include pneumatic tires, solid tires, airless tires, etc. Among them, pneumatic tires are preferred.

[0144] The above tire is suitably used as a passenger car tire, a large passenger car tire, a large SUV tire, a truck and bus tire, a two-wheeler tire, a racing tire, a winter tire (a studless tire, a snow tire, a stud tire), an all-season tire, a run-flat tire, an aircraft tire, a mining tire, etc.

[0145] In a tire having a tire member composed of the above rubber composition for tires, the tire member has a maximum thickness T (mm) in the tire member. In this specification, the maximum thickness T of the tire member means the maximum value of the thicknesses of the respective tire members constituting each rubber layer. The thickness at each point on the surface of each tire member is a value measured along the normal line of the surface of each tire member at that point, and the maximum thickness T of each tire member is the maximum value of the thicknesses at each point. When the tire member is composed of two or more rubber layers, the maximum thickness T of the tire member refers to the maximum value of the total thickness of the two or more rubber layers.

[0146] In the above tire, the maximum thickness T (mm) of the above tire member is preferably 2.0 mm or more, more preferably 2.5 mm or more, and still more preferably 2.8 mm or more. The upper limit is preferably 15.0 mm or less, more preferably 10.0 mm or less, and still more preferably 6.0 mm or less. When within the above range, the effect tends to be obtained more favorably.

[0147] Although it is not clear what mechanism can achieve more effective results by adjusting the maximum thickness T of the tire member within a specified range, it is considered that by setting the maximum thickness of the tire member within a specified range, rubber strength can be ensured, thereby improving durability performance.

[0148] When the above tire member is a sidewall, the sidewall has a predetermined maximum thickness Ts (mm). In this specification, the maximum thickness Ts of the above sidewall means the maximum value of the sidewall thickness. The thickness at each point on the sidewall surface is a value measured along the normal line of the sidewall surface at that point, and the maximum thickness Ts of the sidewall is the maximum value of the thickness at each point.

[0149] In the above tire, the maximum thickness Ts (mm) of the sidewall is preferably 2.0 mm or more, more preferably 2.5 mm or more, and still more preferably 2.8 mm or more. The upper limit is preferably 6.0 mm or less, more preferably 5.0 mm or less, and still more preferably 4.0 mm or less. When within the above range, there is a tendency to obtain better effects.

[0150] In this specification, dimensions such as thickness are values measured in the normal state. The "normal state" refers to a state where the tire is mounted on a normal rim, filled with the normal internal pressure, and is unloaded. Here, the "normal rim" is the rim defined for each tire in the standard system including the standard on which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Association), it is the standard rim in the applicable size described in the "JATMA YEAR BOOK"; in the case of ETRTO (The European Tyre and Rim Technical Organisation), it is the "Measuring Rim" described in the "STANDARDS MANUAL"; in the case of TRA (The Tire and Rim Association, Inc.), it is the "Design Rim" described in the "YEAR BOOK". Refer to JATMA, ETRTO, and TRA in this order, and follow the standard if there is an applicable size during the reference. In the case of a tire not defined in the standard, it refers to the rim with the smallest rim diameter and then the narrowest rim width among the rims that can be mounted on the tire and can hold the internal pressure, that is, the rim that does not cause air leakage between the rim / tire. Also, the "normal internal pressure" refers to the air pressure defined for each tire in the standard system including the standard on which the tire is based. In the case of JATMA, it is the "maximum air pressure"; in the case of ETRTO, it is the "INFLATION PRESSURE"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". Refer to JATMA, ETRTO, and TRA in this order, and follow the standard if there is an applicable size during the reference. In the case of a tire not defined in the standard, it refers to the normal internal pressure (however, 250 KPa or more) of another tire size (defined in the standard) with the normal rim described as the standard rim. In the case where there are multiple normal internal pressures of 250 KPa or more described, it refers to the minimum value among them.

[0151] In the above tire, it is desirable that the product (P×T) of the domain diameter P of the copolymer present in the rubber component of the rubber composition for the tire constituting the tire member and the maximum thickness T (mm) of the tire member exceeds 20. The above P×T preferably exceeds 50, more preferably exceeds 140, and still more preferably exceeds 350. The upper limit of the above P×T is not particularly limited, but is preferably less than 10000, more preferably less than 5000, still more preferably less than 2000, and particularly preferably less than 500. When within the above range, the effect tends to be obtained more favorably.

[0152] Although the mechanism by which a more effective result is obtained by adjusting to a predetermined P×T is not clear, it is considered that by setting the maximum thickness of the tire member within a predetermined range, the rigidity effect due to the thickness of the tire member and the effect of forming the above sacrificial bond favorably are exhibited. Therefore, it is considered that the durability performance is improved.

[0153] In the above tire, it is desirable that the product (P×Ts) of the domain diameter P of the copolymer present in the rubber component of the rubber composition for the sidewall constituting the sidewall and the maximum thickness Ts (mm) of the sidewall exceeds 20. The above P×Ts preferably exceeds 50, more preferably exceeds 140, and still more preferably exceeds 380. The upper limit of the above P×Ts is not particularly limited, but is preferably less than 2000, more preferably less than 500, and still more preferably less than 450. When within the above range, the effect tends to be obtained more favorably. When within the above range, the effect tends to be obtained more favorably.

[0154] In the above tire, it is desirable that the product (S×T) of the (ratio of the (meth)acrylate A unit in the copolymer) / (ratio of the (meth)acrylate B unit in the copolymer) S (the above molar ratio S) of the copolymer in the rubber composition for the tire constituting the tire member and the maximum thickness T (mm) of the tire member exceeds 0.8. The above S×T is preferably more than 2.2, more preferably more than 3.0, and still more preferably more than 3.5. The upper limit of the above S×T is not particularly limited, but is preferably less than 12.0, more preferably less than 10.0, and still more preferably less than 7.5. When within the above range, the effect tends to be obtained more favorably.

[0155] Although the mechanism by which more effects can be obtained by adjusting to a predetermined S×T is not clear, it is considered that the rigidity effect by adjusting the maximum thickness of the tire member to a predetermined range and the introduction effect of the above sacrificial bond by adjusting the molar ratio to a predetermined range are exerted. Therefore, it is considered that the durability performance is improved.

[0156] In the above tire, it is desirable that the product (the ratio of the (meth)acrylate A unit in the copolymer to the copolymer) / (the ratio of the (meth)acrylate B unit in the copolymer) S (the above molar ratio S) of the above copolymer in the sidewall rubber composition constituting the sidewall and the maximum thickness Ts (mm) of the above sidewall exceeds 1.2. The above S×T is preferably more than 2.4, more preferably more than 3.0, and still more preferably more than 3.5. The upper limit of the above S×T is not particularly limited, but is preferably less than 10.0, more preferably less than 8.0, and still more preferably less than 7.5. When within the above range, the effect tends to be obtained more favorably.

[0157] The tire having a tread preferably has a predetermined tread groove depth. The tread groove depth is the tire radial distance to the deepest part of the groove extending in an arbitrary direction defining various tread patterns formed on the tread surface of the vulcanized tire. In this specification, the tread groove depth D means the distance measured along the normal line of the plane obtained by extending the plane forming the ground contact surface of the outermost tread surface in the circumferential groove, from the plane obtained by extending the plane 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.

[0158] 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 8.0 mm or more, and is preferably 20.0 mm or less, more preferably 15.0 mm or less, still more preferably 10.0 mm or less. When it is within the above range, the effect tends to be obtained more favorably.

[0159] In the case of the groove depth D within a predetermined range, the mechanism by which a more effective result is obtained is not clear, but it is considered that by adjusting to the groove depth within a predetermined range, rubber strength is ensured, and thereby the durability performance is improved.

[0160] In a tire having a tread and a sidewall, it is desirable that the product (P×D) of the domain diameter P (nm) of the above copolymer present in the rubber component of the sidewall rubber composition constituting the sidewall (using the above rubber composition for the tire as the sidewall rubber composition) and the groove depth D (mm) of the circumferential groove formed in the above tread exceeds 50. The above P×D preferably exceeds 120, more preferably exceeds 400, still more preferably exceeds 800. The upper limit of the above P×D is not particularly limited, but is preferably less than 20000, more preferably less than 7500, still more preferably less than 5000. When it is within the above range, the effect tends to be obtained more favorably. When it is within the above range, the effect tends to be obtained more favorably.

[0161] The mechanism by which a more effective result is obtained by adjusting to a predetermined P×D is not clear, but the effect of the rubber strength adjusted to the groove depth within a predetermined range and the effect of the above sacrificial bond being favorably formed are exhibited. Therefore, it is considered that the durability performance is improved.

[0162] In a tire having a tread and a sidewall, it is desirable that the product (S×D) of the ratio of the (meth)acrylate A unit in the copolymer to the ratio of the (meth)acrylate B unit in the copolymer (the molar ratio S) in the sidewall rubber composition constituting the sidewall (using the above tire rubber composition as the sidewall rubber composition) and the groove depth D (mm) of the circumferential groove formed in the tread exceeds 2.0. The above S×D preferably exceeds 3.0, more preferably exceeds 5.0, and still more preferably exceeds 6.0. The upper limit of the above S×D is not particularly limited, but is preferably less than 12.0, more preferably less than 10.0, and still more preferably less than 9.0. When within the above range, the effect tends to be obtained more favorably. When within the above range, the effect tends to be obtained more favorably.

[0163] Although the mechanism by which more effects can be obtained by adjusting to a predetermined S×D is not clear, it is considered that the effect of rubber strength adjusted to a groove depth within a predetermined range and the effect of introducing the above sacrificial bond by adjusting the molar ratio to a predetermined range are exerted. Therefore, it is considered that the durability performance is improved.

[0164] Hereinafter, an example of the above tire will be described with reference to the drawings, but it is not limited to such a form.

[0165] In FIG. 1, the vertical direction is the radial direction of the tire 2, the left - right direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. The tire 2 is symmetric about the left - right. The tread 4 is a single - layer structure tread.

[0166] In addition, in FIG. 1, an example of the single - layer structure tread 4 is shown, but a two - layer structure tread composed of a cap tread and a base tread, or a tread having a structure of three or more layers may also be used.

[0167] In tire 2, each sidewall 6 extends substantially radially inward from the edge of tread 4. The radially outer portion of this sidewall 6 is joined to tread 4. The radially inner portion of this sidewall 6 is joined to bead 10. This sidewall 6 can prevent damage to carcass 14.

[0168] In the tire 2 of FIG. 1, the sidewall 6 is made of the above rubber composition for tires. That is, the sidewall 6 is composed of a rubber component and a copolymer of (meth)acrylic acid ester A and (meth)acrylic acid ester B having an ester moiety with a carbon number different from that of the ester moiety of (meth)acrylic acid ester A, which is a rubber composition for sidewalls.

[0169] In the tire 2 of FIG. 1, the maximum thickness Ts of the sidewall 6 is the maximum dimension among the thicknesses of each sidewall at each point on the surface of the sidewall 6, and in the example of FIG. 1, it is indicated by Ts.

[0170] Each wing 8 in FIG. 1 is located between tread 4 and sidewall 6. Wing 8 is joined to each of tread 4 and sidewall 6.

[0171] Each bead 10 is located substantially radially inside the sidewall 6 and has a portion that contacts the rim at least at one place or more.

[0172] Carcass 14 includes carcass ply 36. In this tire 2, carcass 14 consists of one carcass ply 36, but it may also be composed of two or more plies.

[0173] In this tire 2, the carcass ply 36 is stretched between the bead cores 32 on both sides and runs along the tread 4 and the sidewall 6. The carcass ply 36 is folded back from the axial inner side to the outer side around each bead core 32. Due to this folding, a main part 36a and a pair of folded parts 36b are formed on the carcass ply 36. That is, the carcass ply 36 includes a main part 36a and a pair of folded parts 36b.

[0174] Each bead core 32 is provided with a bead apex 34 that extends radially outward from the 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.

[0175] 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 between 75° and 90°. In other words, this carcass 14 preferably has a radial structure.

[0176] The belt layer 16 in FIG. 1 is located radially inside the tread 4. The belt layer 16 is laminated with the carcass 14. The belt layer 16 reinforces the carcass 14. In the tire 2 of FIG. 1, the belt layer 16 consists of an inner layer 38 and an outer layer 40. As is clear from FIG. 1, in the axial direction, it is desirable that the width of the inner layer 38 is slightly larger than the width of the outer layer 40. In this tire 2, the axial width of the belt layer 16 is preferably not less than 0.6 times and not more than 0.9 times the cross-sectional width of the tire 2.

[0177] Each of the inner layer 38 and the outer layer 40 preferably consists of a number of parallel single-wire steel cords (steel monofilaments) and topping rubber (coating rubber). In other words, the belt layer 16 includes a number of parallel steel monofilaments.

[0178] Band 18 in FIG. 1 is located radially outside the belt layer 16. In the axial direction, band 18 has the same width as the width of belt layer 16. This band 18 may have a width larger than the width of this belt layer 16.

[0179] Although not shown, band 18 preferably consists of cords and topping rubber. The cords are wound spirally. This band 18 has a so-called jointless structure. The cords extend substantially in the circumferential direction. The angle of the cords with respect to the circumferential direction is preferably 5° or less, more preferably 2° or less. Since the belt layer 16 is constrained by these cords, lifting of the belt layer 16 is suppressed.

[0180] The belt layer 16 and band 18 in FIG. 1 constitute a reinforcing layer. The reinforcing layer may be constituted by only the belt layer 16.

[0181] FIG. 2 is an enlarged view near the tread 4 of FIG. 1. The tire of FIG. 2 is a tire 2 having a groove 26 on the tire equatorial plane (on the CL).

[0182] 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.

[0183] Each chafer 22 is located near the bead 12. In this embodiment, chafer 22 preferably consists of cloth and rubber impregnated in this cloth. This chafer 22 may be integrated with the clinch 10.

[0184] 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 grooves 42 are located between the ribs 44 and the ribs 44.

[0185] Each main groove 42 extends in the circumferential direction. The main groove 42 is continuous without interruption in the circumferential direction. The main groove 42 promotes the drainage of water existing between the road surface and the tire 2, for example, in rainy weather. Therefore, even when the road surface is wet, the tire 2 can come into sufficient contact with the road surface.

[0186] D in FIG. 2 indicates the groove depth of the circumferential main groove 42 formed in the tread 4.

[0187] In the tire 2, the number of carbon atoms in the ester moiety of the (meth)acrylate A of the copolymer in the sidewall rubber composition constituting the sidewall 6, the number of carbon atoms in the ester moiety of the (meth)acrylate B of the copolymer, the domain diameter P of the copolymer present in the rubber component, the content of the copolymer in the sidewall rubber composition, (the ratio of (meth)acrylate A units in the copolymer) / (the ratio of (meth)acrylate B units in the copolymer) S, the maximum thickness Ts of the sidewall 6, and the groove depth D of the circumferential groove formed in the tread 4 are desirably within the aforementioned ranges. Also, P×Ts, S×T, P×D, and S×D are desirably within the aforementioned ranges.

Example

[0188] Hereinafter, various chemicals used in the manufacture of the tire will be collectively described. The chemicals are purified according to established methods as necessary.

[0189] Hereinafter, various chemicals used in the manufacture of the tire will be collectively described. The chemicals are purified according to established methods as necessary. NR:TSR20 BR: BR150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass) Carbon black: Diablack N550 manufactured by Mitsubishi Chemical Corporation (N2SA: 40 m 2 / g) Silica: Ultrasil VN3 (manufactured by Evonik Industries AG, N2SA: 175 m 2 / g) Oil: Diana Process NH-70S (aromatic process oil) manufactured by Idemitsu Kosan Co., Ltd. Resin: YS Resin PX300N (terpene resin with a softening point of 30 °C) manufactured by Yasuhara Chemical Co., Ltd. Wax: Oz Ace 0355 (manufactured by Nippon Seiro Co., Ltd.) Antioxidant 1: Nocrack 6C (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 2: Nocrack 224 (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: manufactured by NOF Corporation Zinc oxide: Zinc oxide No. 3 (manufactured by Hakusuitech Co., Ltd.) Copolymer 1: Production Example 1 below Copolymer 2: Production Example 2 below Sulfur: Powdered sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd.) Vulcanization accelerator: Noxeller CZ-G (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0190] (Production Example 1 Production of Copolymer 1) Into a glass flask equipped with a heating, cooling, and stirring device, a reflux condenser, and a nitrogen inlet tube, 39.4 g of methyl methacrylate, 50.5 g of butyl acrylate, and 55.0 g of toluene are placed. Further, 0.09 g of 2,2'-azobis(isobutyronitrile) is added, and the reaction is carried out at 80 °C for 6 hours under a nitrogen atmosphere. Subsequently, hexane is added to stop the reaction, and copolymer 1 (copolymer of methyl methacrylate and butyl acrylate (methyl methacrylate / butyl acrylate = 1.0, alternating copolymer, Tg: 27 °C, Mw: 254,000) is obtained by reprecipitation purification.

[0191] (Production Example 2: Production of Copolymer 2) Into a glass flask equipped with a heating, cooling, and stirring device, a reflux condenser, and a nitrogen inlet tube, 25.0 g of methyl methacrylate, 96.1 g of butyl acrylate, and 110 g of toluene are placed. Further, 0.60 g of 2,2'-azobis(isobutyronitrile) is added, and the reaction is carried out at 80°C for 6 hours under a nitrogen atmosphere. Subsequently, hexane is added to stop the reaction, and by reprecipitation purification, Copolymer 2 (a copolymer of methyl methacrylate and butyl acrylate (methyl methacrylate / butyl acrylate = 0.33, alternating copolymer, Tg: -45°C, Mw: 111,000) is obtained.

[0192] <Preparation of Test Tires> According to the formulation shown in Table 1, using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd., materials other than sulfur and vulcanization accelerators are kneaded at 150°C for 5 minutes to obtain a kneaded product. Sulfur and vulcanization accelerators are added to the kneaded product, and it is kneaded at 80°C for 5 minutes using an open roll to obtain an unvulcanized rubber composition. The unvulcanized rubber composition is formed into the shape of a sidewall, 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).

[0193] 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

[0194] <Durability Performance> Regarding the test tire, using a drum tester, under the conditions of a standard rim (6.0J), an internal pressure (260 kPa), a load (4.56 kN), and an ambient temperature of 25°C, on the drum, with a speed of 230 km / h, measure the running time until damage occurs. The results are expressed as an index with the reference comparative example set to 100. The larger the index, the better the durability performance.

[0195]

Table 1

[0196] The present invention (1) is a rubber composition for tires containing a rubber component and a copolymer of (meth)acrylic acid ester A and (meth)acrylic acid ester B, wherein the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester A is different from the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester B, and it is a rubber composition for tires.

[0197] The present invention (2) is the rubber composition for tires according to the present invention (1), wherein the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester A is 1 or more and 3 or less, and the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester B is 2 or more and 10 or less.

[0198] The present invention (3) is the rubber composition for tires according to the present invention (1) or (2), wherein a phase of the copolymer exists in the rubber component, and the domain diameter P of the copolymer in the rubber component is 10 nm or more and less than 2000 nm.

[0199] The present invention (4) is a rubber composition for tires in any combination of the present inventions (1) to (3), wherein the content of the copolymer with respect to 100 parts by mass of the rubber component is 5 parts by mass or more and less than 50 parts by mass.

[0200] The present invention (5) is a rubber composition for tires in any combination with any one of the present inventions (1) to (4), wherein the copolymer has a ratio S of (the proportion of (meth)acrylic acid ester A units in the copolymer) / (the proportion of (meth)acrylic acid ester B units in the copolymer) of 0.40 or more and 2.5 or less.

[0201] The present invention (6) is a tire having a tire member composed of a rubber composition for tires in any combination with any one of the present inventions (1) to (5).

[0202] The present invention (7) is the tire according to the present invention (6), wherein the product (P × T) of the domain diameter P of the copolymer present in the rubber component of the rubber composition for tires constituting the tire member and the maximum thickness T (mm) of the tire member exceeds 20 and is less than 2000.

[0203] The present invention (8) is the tire according to the present invention (7), wherein P × T exceeds 350.

[0204] The present invention (9) is a tire in any combination with any one of the present inventions (6) to (8), wherein the maximum thickness T (mm) of the tire member is 2.0 mm or more and 6.0 mm or less.

[0205] The present invention (10) is a tire in any combination with any one of the present inventions (6) to (9), wherein the product (S × T) of the ratio S of (the proportion of (meth)acrylic acid ester A units in the copolymer) / (the proportion of (meth)acrylic acid ester B units in the copolymer) of the copolymer in the rubber composition for tires constituting the tire member and the maximum thickness T (mm) of the tire member exceeds 3.0.

[0206] The present invention (11) is a tire in any combination with any one of the present inventions (6) to (10), wherein the tire member is a sidewall.

[0207] The present invention (12) has a tread, A tire according to any combination of the present inventions (6) to (11), wherein the groove depth D of the circumferential groove formed in the tread is 5.0 mm or more and 20 mm or less.

[0208] The present invention (13) has a tread and a sidewall composed of the rubber composition for a tire. A tire according to any combination of the present inventions (6) to (12), wherein the product (P×D) of the domain diameter P (nm) of the copolymer present in the rubber component of the rubber composition for a tire constituting the sidewall and the groove depth D (mm) of the circumferential groove formed in the tread is more than 120 and less than 20000.

[0209] The present invention (14) has a tread and a sidewall composed of the rubber composition for a tire. A tire according to any combination of the present inventions (6) to (13), wherein the product (S×D) of the ratio of the (meth)acrylate ester A unit in the copolymer to the ratio of the (meth)acrylate ester B unit in the copolymer (S) in the rubber composition for a tire constituting the sidewall and the groove depth D (mm) of the circumferential groove formed in the tread is more than 3.0.

Explanation of Signs

[0210] 2 Tire 4 Tread 6 Sidewall 8 Wing 10 Crimp 12 Bead 14 Carcass 16 Belt layer 18 Band 20 Inner liner 22 Chafer 24 Tread surface 26 Groove 32 Bead core 34 Bead apex 36 Carcass ply 36a Main part 36b Turn-up part 38 Inner layer 40 Outer layer 42 Main groove 44 Rib Equatorial plane of CL tire Ts Maximum thickness of sidewall D Main groove depth of circumferential main groove formed in tread

Claims

1. A rubber composition for a tire comprising a rubber component and a copolymer of (meth)acrylic acid ester A and (meth)acrylic acid ester B, wherein the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester A is different from the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester B. A rubber composition for a tire characterized by this.

2. The rubber composition for a tire according to claim 1, wherein the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester A is 1 or more and 3 or less, and the number of carbon atoms in the ester moiety of the (meth)acrylic acid ester B is 2 or more and 10 or less.

3. A phase of the copolymer is present in the rubber component, The rubber composition for a tire according to claim 1, wherein the domain diameter P of the copolymer in the rubber component is 10 nm or more and less than 2000 nm.

4. The rubber composition for a tire according to claim 1, wherein the content of the copolymer with respect to 100 parts by mass of the rubber component is 5 parts by mass or more and less than 50 parts by mass.

5. The rubber composition for a tire according to claim 1, wherein the copolymer has (the ratio of (meth)acrylic acid ester A units in the copolymer) / (the ratio of (meth)acrylic acid ester B units in the copolymer) S of 0.40 or more and 2.5 or less.

6. A tire having a tire member composed of the rubber composition for a tire according to claim 1.

7. The tire according to claim 6, wherein the product (P×T) of the domain diameter P of the copolymer present in the rubber component of the rubber composition for a tire constituting the tire member and the maximum thickness T (mm) of the tire member exceeds 20 and is less than 2000.

8. The tire according to claim 7, wherein P×T exceeds 350.

9. The tire according to claim 6, wherein the maximum thickness T (mm) of the tire member is 2.0 mm or more and 6.0 mm or less.

10. The tire according to claim 6, wherein the product (S×T) of (the ratio of (meth)acrylic acid ester A units in the copolymer) / (the ratio of (meth)acrylic acid ester B units in the copolymer) S of the copolymer in the rubber composition for a tire constituting the tire member and the maximum thickness T (mm) of the tire member exceeds 3.

0.

11. The tire according to claim 6, wherein the tire member is a sidewall.

12. Having a tread, The tire according to claim 6, wherein the groove depth D of the circumferential groove formed in the tread is 5.0 mm or more and 20.0 mm or less.

13. It has a tread and a sidewall composed of the rubber composition for a tire, The tire according to claim 6, wherein the product (P × D) of the domain diameter P (nm) of the copolymer present in the rubber component of the rubber composition for a tire constituting the sidewall and the groove depth D (mm) of the circumferential groove formed in the tread is more than 120 and less than 20,000.

14. It has a tread and a sidewall composed of the rubber composition for a tire, The tire according to claim 6, wherein the product (S × D) of S, which is (the ratio of the (meth)acrylate ester A unit in the copolymer) / (the ratio of the (meth)acrylate ester B unit in the copolymer) in the copolymer in the rubber composition for a tire constituting the sidewall, and the groove depth D (mm) of the circumferential groove formed in the tread is more than 3.0.

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