Rubber composition and tire

Abstract

To provide a rubber composition and a tire that are capable of improving grip performance on a wet road surface right after travel on a dry road surface.SOLUTION: The rubber composition contains a compound represented by the formula (1) in the figure.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to rubber compositions and tires. [Background technology]

[0002] Conventionally, various methods for improving the grip performance of rubber compositions have been investigated (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-188563 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of investigations by the present inventors, it has been found that there is room for improvement in conventional technology in terms of improving grip performance on a wet road surface immediately after driving on a dry road surface. The present disclosure aims to solve the above-mentioned problems and to provide a rubber composition and a tire that can improve grip performance on a wet road surface immediately after driving on a dry road surface. [Means for solving the problem]

[0005] The present disclosure relates to a rubber composition containing a compound represented by the following formula (1): [ka] [In formula (1), R 1 are the same or different and represent a divalent hydrocarbon group; R 2 are the same or different and represent a hydrogen atom or a monovalent hydrocarbon group, n is an integer of 0 to 10, and m is the number of repetitions. [Effects of the Invention]

[0006] The present disclosure relates to a rubber composition containing the compound represented by formula (1) above, and therefore can improve grip performance on a wet road surface immediately after driving on a dry road surface. DETAILED DESCRIPTION OF THE INVENTION

[0007] The rubber composition of the present disclosure contains a compound represented by the following formula (1), which can improve grip performance on a wet road surface immediately after driving on a dry road surface. [ka] [In formula (1), R 1 are the same or different and represent a divalent hydrocarbon group; R 2 are the same or different and represent a hydrogen atom or a monovalent hydrocarbon group, n is an integer of 0 to 10, and m is the number of repetitions.

[0008] The reason why the above-mentioned effects can be obtained with the above rubber composition is presumed to be as follows. As described above, the present inventors' investigations revealed that conventional technologies leave room for improvement in terms of improving grip performance on wet roads immediately after driving on dry roads. The present inventors further investigated the newly discovered problem, noting that the surface temperature of dry roads is approximately 40°C and that of wet roads is approximately 10°C. They then came up with the idea of incorporating a temperature-responsive material, a material whose hydrophilicity and hydrophobicity change depending on temperature, into the rubber composition. Poly(N-isopropylacrylamide) (PNIPAM) is a well-known temperature-responsive material, and although PNIPAM was incorporated into the rubber composition, the performance improvement effect was insufficient. After further investigation into this result, they speculated that because PNIPAM has amide terminals, when the rubber composition comes into contact with a wet road and becomes hydrophilic, the repulsion between the polar group and the rubber increases, resulting in its detachment from the rubber composition during repeated driving.

[0009] Therefore, the present inventors conducted extensive research based on the idea that it is possible to reduce the polarity of the terminals by using a compound that has a temperature-responsive group and is composed of oxygen atoms, carbon atoms, and hydrogen atoms. As a result, they found that the compound represented by the above formula (1) has a temperature-responsive group and low polarity at the terminals, and therefore can suppress detachment from the rubber composition, and that compounding the compound represented by the above formula (1) can improve grip performance on wet roads immediately after driving on dry roads.

[0010] As described above, by compounding the compound represented by the above formula (1), detachment from the rubber composition is suppressed, and the hydrophilicity and hydrophobicity change in response to changes in road surface temperature, so it is presumed that grip performance on wet roads immediately after driving on dry roads can be improved. In addition, the above rubber composition contains the compound represented by the above formula (1), but the compound is not bonded to the rubber component, which is the matrix component of the rubber composition, that is, it exists in a state where it can move freely within the rubber composition, and therefore it is presumed that the above effect can be more suitably obtained.

[0011] The rubber composition contains a rubber component. Here, the rubber component is a component that constitutes the matrix of the rubber composition and cannot be removed from the vulcanized rubber by an organic solvent such as acetone, and generally has a weight-average molecular weight (Mw) of 100,000 or more (solid state at 25°C).

[0012] The weight average molecular weight of the rubber component is preferably 100,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more, and is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. Within the above ranges, the effect tends to be more favorably obtained.

[0013] In this specification, the weight average molecular weight (Mw) can be determined in terms of standard polystyrene based on measurements obtained using a gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M, manufactured by Tosoh Corporation).

[0014] Usable rubber components include diene rubbers such as styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber, acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These may be used alone or in combination of two or more. Of these, SBR, BR, and isoprene rubber are preferred, SBR and BR are more preferred, and a combination of SBR and BR is even more preferred.

[0015] The rubber component may be modified to introduce a functional group that interacts with a filler such as silica. Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, and an epoxy group. These functional groups may have a substituent. Among these, a carboxyl group, an amino group (preferably an amino group in which a hydrogen atom of the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferred.

[0016] Specific examples of compounds (modifiers) having the above functional groups include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane.

[0017] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. NRs such as SIR20, RSS#3, and TSR20 are commonly used in the tire industry. IRs are not particularly limited, and examples of IRs such as IR2200 are commonly used in the tire industry. Modified NRs include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Modified NRs include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Modified IRs include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more. NR is preferred.

[0018] The content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 80% by mass or less, more preferably 30% by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0019] The BR is not particularly limited, and can be a high-cis BR, a low-cis BR, a BR containing syndiotactic polybutadiene crystals, etc. Commercially available products include those from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Zeon Corporation. These can be used alone or in combination of two or more.

[0020] The cis amount (cis content) of the BR is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, most preferably 90% by mass or more, and most preferably 95% by mass or more, with no particular upper limit. Within the above range, better effects tend to be obtained. The cis content of BR can be measured by infrared absorption spectroscopy.

[0021] The BR content in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, and is preferably 80% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less. Within the above ranges, the effects tend to be more favorably obtained.

[0022] The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. Commercially available products include those from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. These may be used alone or in combination of two or more.

[0023] The styrene content of the SBR is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, particularly preferably 20% by mass or more, and most preferably 25% by mass or more. The styrene content is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 35% by mass or less. Within the above range, the effect tends to be more favorable. In this specification, the styrene content of SBR is 1 It is calculated by H-NMR measurement.

[0024] The amount of SBR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0025] In 100% by mass of the rubber component, the total content of BR and SBR is preferably 40% by mass or more, more preferably 60% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass. When it is within the above range, the effect tends to be more favorably obtained.

[0026] In the rubber composition, it is preferable that some or all of the crosslinks between rubber molecules in the rubber component are crosslinked by ionic bonds. When ionic bonds are included in the crosslinks in the polymer component (rubber component), the E* can be reduced only when wetted with water due to the reversibility of the non-covalent ionic bonds. By reducing E* and making the rubber hydrophilic, the rubber conforms well to the road surface and the contact area can be increased, making it easier to instantly respond to wet road surfaces. The compound represented by formula (1) can be blended to easily achieve instantaneous changes in hydrophilicity and hydrophobicity in response to changes in road surface temperature, further improving grip performance on wet roads immediately after driving on a dry road. Furthermore, because ionic bonds are the strongest of all non-covalent bonds, sufficient bonding strength can be maintained when dry.

[0027] In the rubber composition, the proportion of crosslinks formed by ionic bonds out of 100% of all crosslinks is preferably 0.1% or more, more preferably 0.5% or more, and even more preferably 1% or more. The upper limit is not particularly limited and may be 100%. The upper limit is not particularly limited and may be 100%, but is preferably 10% or less, more preferably 5% or less. Within the above range, better effects tend to be obtained. The proportion of crosslinks formed by ionic bonds can be measured by the method described in the Examples below.

[0028] The ionic bond between rubber molecules is not particularly limited, and examples thereof include an ionic bond in which the cation side of the ionic bond is derived from at least one selected from the group consisting of a metal element, a metalloid element, and a nitrogen element, and the anion side is derived from at least one selected from the group consisting of a carboxylic acid-modified SBR and a carboxylic acid-modified BR.

[0029] Examples of the metal element on the cation side include alkali metals (lithium, sodium, potassium, etc.), alkaline earth metals (magnesium, calcium, strontium, etc.), etc.; and examples of the metalloid element include silicon, boron, germanium, etc. These may be used alone or in combination of two or more.

[0030] As a compound capable of supplying a metal element, a metalloid element, and a nitrogen element on the cation side of an ionic bond, a compound having at least one element selected from the group consisting of a metal element, a metalloid element, and a nitrogen element can be suitably used. In this case, the metal element, the metalloid element, or the nitrogen element in the compound constitutes the cation side of the ionic bond. These elements may be used alone or in combination of two or more. Among these, a compound having a nitrogen element is preferred, and examples thereof include nitrogen-containing compounds (ammonia, amines, etc.) that can form cations such as quaternary ammonium salts.

[0031] Specific examples of nitrogen-containing compounds (compounds having a nitrogen element) include 1,2-dimethylimidazole, N-butylimidazole, N-(trimethylsilyl)imidazole, N-decyl-2-methylimidazole, N-hydroxyethylimidazole, N-(3-trimethoxysilylpropyl)imidazole, N-vinylimidazole, 1-butylbenzimidazole; trimethylamine, triethylamine, triisopropylamine, tri-n-butylamine, trimethylphosphine, triethylphosphine, triisopropylphosphine, tri-n-butylphosphine, triphenylphosphine; and the like. These may be used alone or in combination of two or more. Among these, imidazole compounds such as N-butylimidazole are preferred.

[0032] The content of the "compound having at least one selected from the group consisting of metal elements, metalloid elements, and nitrogen elements" is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 30 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 7 parts by mass or less. Within the above ranges, the effects tend to be favorably obtained.

[0033] Examples of the carboxylic acid-modified SBR and carboxylic acid-modified BR on the anion side of the ionic bond include SBR having a carboxylic acid group (carboxyl group) and BR having a carboxylic acid group (carboxyl group). In this case, the carboxylic acid group of the carboxylic acid-modified SBR and carboxylic acid-modified BR constitutes the anion side of the ionic bond. These may be used alone or in combination of two or more. Of these, carboxylic acid-modified SBR is preferred.

[0034] The carboxylic acid-modified SBR and carboxylic acid-modified BR may be any SBR and BR having a carboxylic acid group (carboxyl group), and examples thereof include terminal-modified SBR and BR in which at least one terminal of SBR or BR has been modified with a compound (modifier) having a carboxylic acid group (terminal-modified SBR and BR having a carboxylic acid group at the terminal), main-chain-modified SBR and BR having a carboxylic acid group in the main chain, and main-chain terminal-modified SBR and BR having carboxylic acid groups in the main chain and at the terminals (for example, main-chain terminal-modified SBR and BR having a carboxylic acid group in the main chain and at least one terminal modified with a modifier). These may be used alone or in combination of two or more.

[0035] The content of "a rubber component having at least one selected from the group consisting of carboxylic acid-modified SBR and carboxylic acid-modified BR" in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more. There is no particular upper limit, and it may be 100% by mass. Within the above range, good effects tend to be obtained.

[0036] The rubber composition contains a compound (polymer) represented by the following formula (1): The compound represented by the following formula (1) may be used alone or in combination of two or more kinds. The compound represented by the following formula (1) is a temperature-responsive polymer. Temperature-responsive polymers are materials that undergo reversible conformational changes in polymer chains associated with hydration and dehydration in response to temperature changes, and whose hydrophilicity and hydrophobicity change reversibly with temperature changes. This reversible change is known to be due to the molecular structure of a molecule that contains hydrophilic groups capable of hydrogen bonding and hydrophobic groups that are not compatible with water. The present inventors have discovered that the hydrophilicity and hydrophobicity of temperature-responsive polymers change reversibly with changes in temperature not only in water but also in antifreeze (i.e., at low temperatures) and in compositions containing resins and / or elastomers. [ka] [In formula (1), R 1 are the same or different and represent a divalent hydrocarbon group; R 2 are the same or different and represent a hydrogen atom or a monovalent hydrocarbon group, n is an integer of 0 to 10, and m is the number of repetitions.

[0037] R 1 Examples of the divalent hydrocarbon group include a branched or linear alkylene group having 1 to 30 carbon atoms, a branched or linear alkenylene group having 2 to 30 carbon atoms, a branched or linear alkynylene group having 2 to 30 carbon atoms, and an arylene group having 6 to 30 carbon atoms. The group may also be a group in which at least two of these groups are bonded together. Of these, a branched or linear alkylene group having 1 to 30 carbon atoms is preferred. R 1 The number of carbon atoms in the divalent hydrocarbon group is preferably 1 or more, more preferably 2 or more, and is preferably 30 or less, more preferably 15 or less, even more preferably 10 or less, and particularly preferably 5 or less. When the number is within the above range, good effects tend to be obtained.

[0038] R 1 Examples of the branched or linear alkylene group having 1 to 30 carbon atoms (preferably 2 or more, and preferably 15 or less, more preferably 10 or less, and even more preferably 5 or less) include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, an undecylene group, a dodecylene group, a tridecylene group, a tetradecylene group, a pentadecylene group, a hexadecylene group, a heptadecylene group, an octadecylene group, an ethylidene group, a propylidene group, an isopropylidene group, etc. Among these, from the viewpoint of obtaining a better effect, a methylene group, an ethylene group, a propylene group, a butylene group, and a pentylene group are preferred, an ethylene group, a propylene group, a butylene group, and a pentylene group are more preferred, and an ethylene group, a propylene group, and a butylene group are even more preferred.

[0039] The alkylene group may be an alkylene group containing an alicyclic structure. As the alkylene group containing an alicyclic structure, an alkylene group having a monocyclic alicyclic structure is preferable, and an alkylene group having a 5- or 6-membered alicyclic structure is more preferable, and specific examples thereof include a 1,2-cyclopentylene group, a 1,3-cyclopentylene group, a 1,2-cyclohexylene group, a 1,3-cyclohexylene group, a 1,4-cyclohexylene group, a 1,2-cyclopentanedimethylene group, a 1,3-cyclopentanedimethylene group, a 1,2-cyclohexanedimethylene group, a 1,3-cyclohexanedimethylene group, and a 1,4-cyclohexanedimethylene group.

[0040] R 1 Examples of the branched or linear alkenylene group having 2 to 30 carbon atoms (preferably 2 or more, and preferably 15 or less, more preferably 10 or less, and even more preferably 5 or less) include a vinylene group, a 1-propenylene group, a 2-propenylene group, a 1-butenylene group, a 2-butenylene group, a 1-pentenylene group, a 2-pentenylene group, a 1-hexenylene group, a 2-hexenylene group, and a 1-octenylene group.

[0041] R 1Examples of the branched or linear alkynylene group having 2 to 30 carbon atoms (preferably 2 or more, and preferably 15 or less, more preferably 10 or less, and even more preferably 5 or less) include an ethynylene group, a propynylene group, a butynylene group, a pentynylene group, a hexynylene group, a heptynylene group, an octynylene group, a nonynylene group, a decynylene group, an undecynylene group, and a dodecynylene group.

[0042] R 1 Examples of the arylene group having 6 to 30 carbon atoms (preferably 6 to 15 carbon atoms) include a phenylene group, a tolylene group, a xylylene group, and a naphthylene group.

[0043] R 2 The monovalent hydrocarbon group may be linear, branched, or cyclic, and examples thereof include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. It may also be a group in which at least two of these groups are bonded together. Of these, an aliphatic hydrocarbon group is preferred, and a linear aliphatic hydrocarbon group is more preferred. The number of carbon atoms in the hydrocarbon group is preferably 1 or more, more preferably 2 or more, and is preferably 20 or less, more preferably 15 or less, even more preferably 10 or less, particularly preferably 5 or less, and most preferably 3 or less. When the number of carbon atoms is within the above range, good effects tend to be obtained.

[0044] R 2 The number of carbon atoms in the aliphatic hydrocarbon group is preferably 1 or more, more preferably 2 or more, and is preferably 20 or less, more preferably 15 or less, even more preferably 10 or less, particularly preferably 5 or less, and most preferably 3 or less. When the number of carbon atoms is within the above range, good effects tend to be obtained. Preferred examples include alkyl groups having the above carbon numbers, and specific examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, 2-ethylhexyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, octadecyl, etc. Among these, from the viewpoint of obtaining better effects, methyl, ethyl, n-propyl, and isopropyl are preferred, methyl, ethyl, and n-propyl are more preferred, methyl and ethyl are even more preferred, and ethyl is particularly preferred.

[0045] R 2 The alicyclic hydrocarbon group preferably has 3 to 8 carbon atoms, and specific examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclopropenyl group, a cyclobutenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a cyclooctenyl group, a cyclohexylmethyl group, and a 2-cyclohexylethyl group. Also, R 2 The alicyclic hydrocarbon group is a tricyclodecanyl group, a 1-adamantyl group, a bicyclo[2.2.1]heptyl group, a tricyclo[5.2.1.0 2,6 ] may be a polycyclic alicyclic alkyl group such as a decanyl group or a decahydronaphthyl group.

[0046] R 2 The aromatic hydrocarbon group preferably has 6 to 10 carbon atoms, and specific examples thereof include a phenyl group, a benzyl group, a phenethyl group, a tolyl group, a xylyl group, a naphthyl group, etc. In the tolyl group and the xylyl group, the substitution position of the methyl group on the benzene ring may be any of the ortho-, meta-, and para-positions.

[0047] R 2are the same or different and are preferably a hydrogen atom or an aliphatic hydrocarbon group (particularly, an alkyl group having 1 to 3 carbon atoms), more preferably an aliphatic hydrocarbon group (particularly, an alkyl group having 1 to 3 carbon atoms), whereby better effects can be obtained.

[0048] n is an integer of 0 to 10, and is preferably 8 or less, more preferably 6 or less, even more preferably 4 or less, particularly preferably 2 or less, and most preferably 1 or less. When it is within the above range, good effects tend to be obtained.

[0049] m is the number of repeating units and is not particularly limited, and it is desirable that the weight-average molecular weight of the compound represented by formula (1) be within the following range, for example, an integer of 1 to 1000, preferably 3 or more, more preferably 5 or more, even more preferably 10 or more, particularly preferably 20 or more, and preferably 500 or less, more preferably 300 or less, even more preferably 150 or less, particularly preferably 80 or less, most preferably 40 or less, and most preferably 30 or less. When it is within the above range, better effects tend to be obtained.

[0050] The weight average molecular weight (Mw) of the compound represented by the above formula (1) is preferably 50 or more, more preferably 500 or more, even more preferably 1000 or more, and particularly preferably 1500 or more, and is preferably 60000 or less, more preferably 40000 or less, even more preferably 20000 or less, particularly preferably 10000 or less, most preferably 5000 or less, and most preferably 3500 or less. When it is within the above range, the effect tends to be better obtained.

[0051] The repeating units of the compound represented by the formula (1) may be the same or different. That is, the compound represented by the formula (1) may be a homopolymer or a copolymer. When the compound represented by the formula (1) is a copolymer, the copolymer may be either a block copolymer or a random copolymer. In particular, the compound represented by the formula (1) is preferably a homopolymer.

[0052] The lower critical solution temperature (LCST) of the compound represented by formula (1) is preferably −20° C. or higher, more preferably −10° C. or higher, even more preferably 0° C. or higher, particularly preferably 2° C. or higher, and most preferably 5° C. or higher, and is preferably 75° C. or lower, more preferably 70° C. or lower, even more preferably 60° C. or lower, particularly preferably 50° C. or lower, most preferably 40° C. or lower, more preferably 30° C. or lower, more preferably 20° C. or lower, more preferably 18° C. or lower, and more preferably 15° C. or lower. Within the above ranges, the effect tends to be better obtained. In this specification, the lower critical solution temperature (LCST) can be easily measured by preparing a 1 mass % polymer / antifreeze solution using a 90 v / v % aqueous methanol solution (antifreeze), storing the solution in a freezer (e.g., −20° C.) or refrigerator (e.g., +5° C.) at a predetermined temperature for at least one hour, and checking the turbidity at each temperature. The 90 v / v % aqueous methanol solution is a liquid consisting of methanol and water, and is obtained by adding 9 times the volume of methanol to water and mixing at 25°C for 30 minutes.

[0053] Specific examples of the compound represented by the above formula (1) include poly(methyl vinyl ether) (PMVE), poly(ethyl vinyl ether) (PEVE), poly(2-hydroxyethyl vinyl ether) (PHEVE), poly(2-hydroxybutyl vinyl ether) (PHBVE), poly(2-methoxyethyl vinyl ether) (PMOVE), poly(3-hydroxypropyl vinyl ether), poly(4-hydroxybutyl vinyl ether), poly(diethylene glycol monovinyl ether), poly(2-ethoxyethyl vinyl ether), ), poly(2-(2-methoxyethoxy)ethyl vinyl ether), poly(2-(2-ethoxyethoxy)ethyl vinyl ether), poly(2-(2-(2-ethoxyethoxy)ethoxy)ethyl vinyl ether), poly(2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl vinyl ether), poly(2-(2-(2-(2-ethoxyethoxy)ethoxy)ethoxy)ethyl vinyl ether), poly(propylene glycol monovinyl ether), poly(1-hydroxypropan-2-yl vinyl ether), poly(dipropylene pyrene glycol monovinyl ether), poly(triethylene glycol monovinyl ether), poly(4-hydroxycyclohexyl vinyl ether), poly(1,4-cyclohexanedimethanol monovinyl ether), poly(hydroxymethyl vinyl ether), poly(1-hydroxyethyl vinyl ether), poly(5-hydroxypentyl vinyl ether), poly(1-hydroxypropyl vinyl ether), poly(2-hydroxypropyl vinyl ether), poly(2-hydroxy-1-methylethyl vinyl ether), poly(1-hydroxybutyl vinyl ether), poly(2-hydroxybutyl vinyl ether), poly(3-hydroxybutyl vinyl ether), poly(3-hydroxy-1-methylpropyl vinyl ether), poly(3-hydroxy-2-methylpropyl vinyl ether), poly(2-hydroxy-2-methylpropyl vinyl ether), poly(2-hydroxy-1-methylpropyl vinyl ether), poly(1-hydroxymethylpropyl vinyl ether), poly(2-hydroxy-1,1-dimethylethyl vinyl ether), poly(1-hydroxy-2-methylpropyl vinyl ether), poly(4-hydroxyamyl vinyl ether), poly(3-hydroxyamyl vinyl ether), poly(2-hydroxyamyl vinyl ether), poly(4-hydroxy-3-methylbutyl vinyl ether), poly(3-hydroxy-3-methylbutyl ether), poly(2-hydroxycyclopentyl vinyl ether), poly(3-hydroxycyclopentyl vinyl ether), poly(2-hydroxycyclohexyl vinyl ether), poly(3-hydroxycyclohexyl vinyl ether), poly Poly(4-hydroxycyclohexyl vinyl ether), poly(4-(hydroxymethyl)cyclohexyl vinyl ether), poly(4-(2-hydroxyethyl)cyclohexyl vinyl ether), poly(2-hydroxycycloheptyl vinyl ether), poly(2-hydroxycyclooctyl vinyl ether), poly(4-hydroxycyclooctyl vinyl ether), poly(2-hydroxycyclodecanyl vinyl ether), poly(3-hydroxy-1-vinyloxyadamantane), poly(bicyclo[2.2.1]heptanediol monovinyl ether), poly(tricyclo[5.2.1.0, 2,6 ]decanediol monovinyl ether), poly(decalindiol monovinyl ether), poly(3-methoxypropyl vinyl ether), poly(3-ethoxypropyl vinyl ether), poly(3-ethoxybutyl vinyl ether), poly(methyldiethylene glycol vinyl ether), poly(ethyldiethylene glycol vinyl ether), poly(methyltriethylene glycol vinyl ether), poly(methyltetraethylene glycol vinyl ether), poly(methylpentaethylene glycol vinyl ether), etc. These may be used alone or in combination of two or more. Compounds where n=0 include poly(ethyl vinyl ether), poly(propyl vinyl ether), poly(n-butyl vinyl ether), poly(n-pentyl vinyl ether), poly(n-hexyl vinyl ether), poly(n-heptyl vinyl ether), poly(n-octyl vinyl ether), poly(n-nonyl vinyl ether), poly(n-decyl vinyl ether), poly(n-undecyl vinyl ether), poly(n-dodecyl vinyl ether), poly(n-tridecyl vinyl ether), poly(n-tetradecyl vinyl ether), poly(n-pentadecyl vinyl ether), poly(n-hexadecyl vinyl ether), poly(n-heptadecyl vinyl ether), poly(n-octadecyl vinyl ether), poly(n-eicosyl vinyl ether), poly(isopropyl vinyl ether), poly(sec-butyl vinyl ether), poly(tert-butyl vinyl ether), poly(isobutyl vinyl ether), and poly(isoamyl vinyl ether). vinyl ether), poly(isohexyl vinyl ether), poly(isoheptyl vinyl ether), poly(isooctyl vinyl ether), poly(1,2-dimethylpropyl vinyl ether), poly(1,3-dimethylbutyl vinyl ether), poly(2-ethylbutyl vinyl ether), poly(2-ethylhexyl vinyl ether), poly(1-methylheptyl vinyl ether), poly(2-methyloctyl vinyl ether), poly(1-pentylhexyl vinyl ether), poly(4-ethyl-1-methyloctyl vinyl ether), poly(cyclopentyl vinyl ether), poly(cyclohexyl vinyl ether), poly(cycloheptyl vinyl ether), poly(cyclooctyl vinyl ether), poly(4-methylcyclohexyl vinyl ether), poly(4-ethylcyclohexyl vinyl ether), poly(1-adamantyl vinyl ether), poly(bicyclo[2.2.1]heptyl vinyl ether), poly(tricyclo[5.2.1.0]heptyl vinyl ether) 2,6 ]decanyl vinyl ether), etc. These may be used alone or in combination of two or more. Among these, poly(methyl vinyl ether) (PMVE), poly(ethyl vinyl ether) (PEVE), poly(2-hydroxyethyl vinyl ether) (PHEVE), poly(2-hydroxybutyl vinyl ether) (PHBVE), poly(2-methoxyethyl vinyl ether) (PMOVE), 2-methoxybutyl vinyl ether, 2-methoxypropyl vinyl ether, 2-ethoxyethyl vinyl ether, 2-ethoxybutyl vinyl ether, and 2-ethoxypropyl vinyl ether are preferred, and poly(methyl vinyl ether) (PMVE), poly(ethyl vinyl ether) (PEVE), poly(2-hydroxyethyl vinyl ether) (PHEVE), poly(2-hydroxybutyl vinyl ether) (PHBVE), and poly(2-methoxyethyl vinyl ether) (PMOVE) are more preferred.

[0054] The compound represented by the formula (1) may be a commercially available product or may be synthesized according to a known method. For example, the compound represented by the formula (1) may be synthesized according to the methods described in JP-A-2013-166829, JP-A-2017-14438, JP-A-2019-44050, JP-A-2018-111776, or the like.

[0055] The content of the compound represented by the formula (1) is preferably at least 1 part by mass, more preferably at least 3 parts by mass, even more preferably at least 5 parts by mass, particularly preferably at least 10 parts by mass, and most preferably at least 15 parts by mass, per 100 parts by mass of the rubber component, and is preferably at most 80 parts by mass, more preferably at most 60 parts by mass, even more preferably at most 40 parts by mass, particularly preferably at most 30 parts by mass, and most preferably at most 20 parts by mass. Within the above ranges, the effect tends to be better obtained.

[0056] The rubber composition preferably contains a resin. Examples of resins include terpene resins (including rosin resins), aromatic resins, C5 resins, C9 resins, C5 / C9 resins, coumarone-indene resins (including coumarone and indene simple resins), olefin resins, cyclopentadiene resins, polyurethane resins, and acrylic resins. These may be used alone or in combination of two or more. They may also be hydrogenated (hydrogenated resins). It is also preferable that the resin is modified with a polar functional group that interacts with silica. As the polar functional group that interacts with silica, the same groups as the functional groups that interact with fillers such as silica described above are used in the same preferred embodiments.

[0057] Among these, at least one resin selected from the group consisting of terpene resins (including rosin resins), aromatic resins, C5 resins, C9 resins, C5 / C9 resins, coumarone-indene resins (including simple coumarone and indene resins), and olefin resins is preferred, more preferably at least one resin selected from the group consisting of terpene resins (including rosin resins), aromatic resins, C5 resins, C9 resins, and C5 / C9 resins, even more preferably at least one resin selected from the group consisting of aromatic resins, C5 resins, C9 resins, and C5 / C9 resins, particularly preferably at least one resin selected from the group consisting of C5 resins, C9 resins, and C5 / C9 resins, with C5 / C9 resins being the most preferred. It is presumed that compounding a resin with a high Tg increases the Tg of the rubber composition, increasing the 0°C tan δ and thereby more suitably achieving the effects.

[0058] Examples of terpene resins that can be used include polyterpene resins obtained by polymerizing terpene compounds and aromatic modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds. Hydrogenated versions of these resins can also be used. These resins can be used alone or in combination of two or more.

[0059] Polyterpene resin is a resin obtained by polymerizing terpene compounds. Terpene compounds are (C5H8)n The hydrocarbons and their oxygen-containing derivatives are represented by the following composition: monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32 ), and examples thereof include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, etc. These may be used alone or in combination of two or more.

[0060] Examples of polyterpene resins include pinene resins, limonene resins, dipentene resins, and pinene / limonene resins, which are made from the above-mentioned terpene compounds. These may be used alone or in combination of two or more. Among these, pinene resins are preferred. Pinene resins usually contain both α-pinene and β-pinene, which are isomers, but are classified into β-pinene resins containing β-pinene as the main component and α-pinene resins containing α-pinene as the main component, depending on the components contained.

[0061] Examples of aromatic modified terpene resins include terpene phenol resins made from terpene compounds and phenolic compounds, and terpene styrene resins made from terpene compounds and styrene compounds. Terpene phenol styrene resins made from terpene compounds, phenolic compounds, and styrene compounds can also be used. These may be used alone or in combination of two or more. In this specification, polymers containing terpene compounds and phenolic compounds as constituent monomers, such as aromatic modified terpene resins, are treated as terpene resins rather than aromatic resins.

[0062] Examples of rosin-based resins include gum rosin, which is obtained by processing pine resin and contains as its main component resin acids such as abietic acid and pimaric acid, natural rosin resins (polymerized rosins) such as wood rosin and tall oil rosin, hydrogenated rosin resin, maleic acid-modified rosin resin, rosin-modified phenolic resin, rosin glycerin ester, disproportionated rosin resin, etc. These may be used alone or in combination of two or more. In this specification, rosin-based resins are included in terpene-based resins.

[0063] As the terpene resin, polyterpene resin is preferred, and β-pinene resin is more preferred, because better effects tend to be obtained.

[0064] Aromatic resins are polymers containing aromatic monomers as constituent monomers, and examples thereof include homopolymers obtained by polymerizing one type of aromatic monomer alone, copolymers obtained by copolymerizing two or more types of aromatic monomers, and copolymers of an aromatic monomer and another monomer copolymerizable therewith. These may be used alone or in combination of two or more types.

[0065] Examples of aromatic monomers include styrene-based monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene; phenol-based monomers such as phenol, alkylphenol, and alkoxyphenol; and naphthol-based monomers such as naphthol, alkylnaphthol, and alkoxynaphthol. These may be used alone or in combination of two or more. Among these, styrene-based monomers are preferred, and styrene and α-methylstyrene are more preferred.

[0066] The aromatic resin is preferably a polymer containing α-methylstyrene as a constituent monomer (α-methylstyrene resin), and more preferably a copolymer of α-methylstyrene and styrene, because these tend to produce better effects.

[0067] C5 resins are polymers containing structural units of hydrocarbons having 5 carbon atoms and their polymers (dimers, etc.). Examples of hydrocarbons having 5 carbon atoms and their polymers include isoprene, pentane, and cyclopentadiene. Specific examples of C5 resins include copolymers of isoprene and pentane. C5 resins also include aliphatic petroleum resins obtained by (co)polymerizing C5 fractions obtained by thermal cracking of naphtha in the petrochemical industry. C5 fractions include olefinic hydrocarbons such as 1-pentene, 2-pentene, and 2-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, and 1,3-pentadiene. These may be used alone or in combination of two or more. In this specification, a polymer containing cyclopentadiene as a constituent monomer is referred to as a cyclopentadiene-based resin.

[0068] A C9 resin is a polymer containing structural units of a hydrocarbon having 9 carbon atoms and its polymers (dimers, etc.). Examples of the hydrocarbon having 9 carbon atoms and its polymers (dimers, etc.) include indene, methylstyrene, vinyltoluene, etc. Specific examples of C9 resins include solid polymers obtained by (co)polymerizing a C9 fraction using a Friedel-Crafts catalyst or the like, such as a copolymer containing indene as the main component, a copolymer containing methylindene as the main component, a copolymer containing α-methylstyrene as the main component, and a copolymer containing vinyltoluene as the main component. These may be used alone or in combination of two or more types. In this specification, a polymer containing methylstyrene as a constituent monomer is considered to be an aromatic resin.

[0069] Examples of the C5 / C9 resin include a mixture of the C5 resin and the C9 resin, a copolymer of a C5 fraction and a C9 fraction, etc. These may be used alone or in combination of two or more. The C5 resin is preferably an aliphatic resin, and the C9 resin is preferably an alicyclic resin.

[0070] Examples of coumarone-indene resins (including coumarone and indene simple resins) include resins containing coumarone and / or indene as the main monomer component constituting the resin skeleton (main chain). These may be used alone or in combination of two or more. Examples of monomer components that may be contained in the skeleton other than coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0071] Examples of olefin-based resins include polyethylene-based resins such as polyethylene, ethylene-propylene copolymer, ethylene-propylene-non-conjugated diene copolymer, ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-ethyl acrylate copolymer, and chlorinated polyethylene, polypropylene-based resins such as polypropylene, propylene-ethylene random copolymer, propylene-ethylene block copolymer, and chlorinated polypropylene, polybutene, polyisobutylene, polymethylpentene, and cyclic olefin copolymers. These may be used alone or in combination of two or more.

[0072] The softening point of the resin is preferably 30° C. or higher, more preferably 60° C. or higher, and even more preferably 80° C. or higher, and is preferably 160° C. or lower, and more preferably 140° C. or lower. Within the above ranges, the effect tends to be more favorably obtained. In this specification, the softening point of a polymer (resin, polymer, etc.) is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point tester.

[0073] Commercially available resins include those manufactured by Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., Taoka Chemical Co., Ltd., and ExxonMobil Corporation.

[0074] The amount of the resin, relative to 100 parts by mass of the rubber component, is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 60 parts by mass or less, particularly preferably 40 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0075] The rubber composition preferably contains carbon black. The carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products that can be used include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nichika Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like. These may be used alone, or two or more types may be used in combination.

[0076] The nitrogen adsorption specific surface area (N2SA) of carbon black is 50m 2 / g or more is preferable, and 70m 2 / g or more is more preferable, and 90m 2 / g or more is more preferable. 2 / g or less is preferable, and 150m 2 / g or less is more preferable, and 130m 2 Within the above range, the effect tends to be better. The nitrogen adsorption specific surface area of carbon black can be determined according to JIS K6217-2:2001.

[0077] The amount of carbon black is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 20 parts by mass or less, based on 100 parts by mass of the rubber component. When the amount is within the above range, better effects tend to be obtained.

[0078] The composition preferably contains silica, which is a hydrophilic material having a hydroxyl group, and therefore water is preferably incorporated into the composition, allowing the compound represented by formula (1) to more preferably change its hydrophilicity due to temperature change or the like, and the effect tends to be more preferably obtained. Examples of silica include dry-process silica (anhydrous silica) and wet-process silica (hydrated silica). Among these, wet-process silica is preferred because it has a large number of silanol groups. Commercially available products include those from Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan, and Tokuyama Corporation. These may be used alone or in combination of two or more.

[0079] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 50 m 2 / g or more, more preferably 100m 2 / g or more, more preferably 150m 2 The upper limit of the N2SA of silica is not particularly limited, but is preferably 350 m 2 / g or less, more preferably 250m 2 / g or less, more preferably 200m 2 Within the above range, there is a tendency for the effect to be better obtained. The N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0080] The content of silica, relative to 100 parts by mass of the rubber component, is preferably 5 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 50 parts by mass or more, particularly preferably 65 parts by mass or more, and is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 120 parts by mass or less, particularly preferably 100 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0081] The content of silica in 100% by mass of the filler is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more, and may be 100% by mass, but is preferably 95% by mass or less. When it is within the above range, the effect tends to be better.

[0082] When silica is contained, it is preferable to use the silica in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and examples thereof include 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, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl sulfide-based compounds such as propyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercially available products that can be used include, for example, products from Degussa, Momentive, Shin-Etsu Silicones Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Dow Corning Toray Co., Ltd. These may be used alone or in combination of two or more.

[0083] The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 6 parts by mass or more, and even more preferably 8 parts by mass or more, relative to 100 parts by mass of silica, and is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above range, the effect tends to be more favorable.

[0084] In order for the compound represented by formula (1) to more effectively change its hydrophilicity in response to temperature changes, the presence of water is preferred. Therefore, the composition preferably contains a water-absorbing material such as a water-absorbing fiber, a water-absorbing elastomer, and / or a water-absorbing resin. This allows water to be efficiently incorporated into the composition, allowing the compound represented by formula (1) to more effectively change its hydrophilicity in response to temperature changes. Furthermore, by incorporating a water-absorbing material in addition to the compound represented by formula (1), moisture absorption is enhanced, which facilitates a decrease in the rubber temperature when wetted with water, thereby facilitating the temperature response of the compound represented by formula (1), and it is presumed that this effect can be more effectively achieved. These water-absorbent materials may be used alone or in combination of two or more. Among them, water-absorbent fibers are preferred. Examples of water-absorbent materials include materials containing heteroatoms (fibers, elastomers, resins).

[0085] The heteroatom refers to an atom other than a carbon atom or a hydrogen atom, and is not particularly limited as long as it can form a reversible molecular bond with water, such as a hydrogen bond or an ionic bond. However, it is preferably at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom, a phosphorus atom, and a halogen atom, more preferably an oxygen atom, a nitrogen atom, or a silicon atom, and even more preferably an oxygen atom.

[0086] Examples of structures and groups containing an oxygen atom include an ether group, an ester group, a carboxy group, a carbonyl group, an alkoxy group, a hydroxy group, etc. Among these, an ether group is preferred, and an oxyalkylene group is more preferred. Examples of structures and groups containing a nitrogen atom include amino groups (primary amino groups, secondary amino groups, tertiary amino groups), amide groups, nitrile groups, nitro groups, etc. Among these, amino groups are preferred, and tertiary amino groups are more preferred. Examples of structures and groups containing silicon atoms include silyl groups, alkoxysilyl groups, silanol groups, etc. Among these, silyl groups are preferred, and alkoxysilyl groups are more preferred. Examples of the structure or group containing a sulfur atom include a sulfide group, a sulfate group, a sulfate ester, and a sulfo group. Examples of structures and groups containing a phosphorus atom include a phosphate group and a phosphate ester. Examples of structures and groups containing a halogen atom include halogeno groups such as a fluoro group, a chloro group, a bromo group, and an iodo group.

[0087] For example, cellulose fibers have hydroxyl groups, and therefore, cellulose fibers are an example of water-absorbent fibers. The cellulose fiber is preferably cellulose microfibrils. The cellulose microfibrils are not particularly limited as long as they are derived from natural products, and examples thereof include those derived from resource biomass such as fruits, grains, and root vegetables, wood, bamboo, hemp, jute, and kenaf, as well as pulp, paper, cloth, agricultural waste, waste biomass such as food waste and sewage sludge obtained from these as raw materials, unused biomass such as rice straw, wheat straw, and thinned wood, as well as cellulose produced by sea squirts, acetic acid bacteria, etc. These may be used alone or in combination of two or more types.

[0088] Examples of water-absorbent elastomers include elastomers having oxyalkylene groups. Examples of such elastomers include epoxide-allyl glycidyl ether copolymers, amine-allyl glycidyl ether copolymers, and silyl-allyl glycidyl ether copolymers. These may be used alone or in combination of two or more.

[0089] Examples of water-absorbent resins include polyvinyl alcohol, polyurethane, polyvinyl acetate, epoxy resin, cellulose resin, polyethylene glycol, sodium polyacrylate, etc. These may be used alone or in combination of two or more.

[0090] The content of the water-absorbent fiber, water-absorbent elastomer, and / or water-absorbent resin per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and is preferably 25 parts by mass or less, more preferably 23 parts by mass or less, and even more preferably 20 parts by mass or less. Within the above ranges, better effects tend to be obtained. When two or more types of water-absorbent fibers, water-absorbent elastomers, and / or water-absorbent resins are used in combination, the above content means the total content.

[0091] The rubber composition preferably contains a liquid plasticizer (a plasticizer that is in a liquid state at room temperature (25° C.)). Liquid plasticizers (plasticizers that are liquid at room temperature (25°C)) are not particularly limited, and examples include oils and liquid polymers (liquid diene polymers, etc.). These may be used alone or in combination of two or more. Of these, oils are preferred.

[0092] The content of the liquid plasticizer is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit of the content is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 25 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0093] Examples of oils include process oils, vegetable oils, and mixtures thereof. Examples of process oils that can be used include paraffin-based process oils, aromatic process oils, and naphthenic process oils. Examples of vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. Commercially available products include those from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Corporation, Oriso, H&R, Toyokuni Oil Mills, Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and Nisshin Oillio Group, Ltd. These oils may be used alone or in combination. Among these, process oils (paraffin-based process oils, aromatic process oils, naphthenic process oils, etc.) and vegetable oils are preferred, and aromatic process oils are more preferred.

[0094] The oil content is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the oil content is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 25 parts by mass or less. Within the above range, better effects tend to be obtained. The oil content includes oil contained in the oil extender.

[0095] Examples of liquid diene polymers include liquid styrene-butadiene copolymers (liquid SBR), liquid butadiene polymers (liquid BR), liquid isoprene polymers (liquid IR), liquid styrene-isoprene copolymers (liquid SIR), liquid styrene-butadiene-styrene block copolymers (liquid SBS block polymers), liquid styrene-isoprene-styrene block copolymers (liquid SIS block polymers), liquid farnesene polymers, and liquid farnesene-butadiene copolymers, which are liquid at 25°C. These may be modified at the ends or main chains with polar groups. Hydrogenated versions of these polymers can also be used. These may be used alone or in combination. In this specification, a liquid polymer is a component that functions primarily as a plasticizer and can be partially eliminated from vulcanized rubber by an organic solvent such as acetone, and generally has a weight-average molecular weight (Mw) of less than 100,000 (liquid state at 25°C).

[0096] The content of the liquid diene polymer is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit of the content is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 25 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0097] The rubber composition may contain an antioxidant. Examples of the antioxidant include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine. Examples of suitable antioxidants include p-phenylenediamine-based antioxidants such as quinoline; quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Commercially available products include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and Flexis. These antioxidants may be used alone or in combination. Among these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferred, with p-phenylenediamine-based antioxidants being more preferred.

[0098] The content of the antioxidant is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 12 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0099] The rubber composition may contain a wax. The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as vegetable wax and animal wax; and synthetic waxes such as polymers of ethylene, propylene, etc. Commercially available products include those from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. These may be used alone or in combination of two or more.

[0100] The amount of wax per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0101] The rubber composition may contain zinc oxide. As the zinc oxide, conventionally known ones can be used, and commercially available products include those available from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. These may be used alone or in combination of two or more.

[0102] The amount of zinc oxide per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0103] The rubber composition may contain stearic acid. As the stearic acid, conventionally known ones can be used, and commercially available products that can be used include products from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. These may be used alone or in combination of two or more.

[0104] The content of stearic acid is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, based on 100 parts by mass of the rubber component. When the content is within the above range, better effects tend to be obtained.

[0105] The rubber composition contains sulfur, and most of the sulfur is bonded to the rubber component in the vulcanized rubber composition. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur, which are commonly used as crosslinking agents in the rubber industry. Commercially available products include those from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., and Hosoi Chemical Industry Co., Ltd. These may be used alone or in combination of two or more.

[0106] The amount of sulfur per 100 parts by mass of the rubber component is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, and is preferably 3.5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2.5 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0107] The rubber composition may contain a vulcanization accelerator. Examples of vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD) and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazyl sulfenamide (CBS), N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-orthotolylguanidine, and orthotolylbiguanidine. Commercially available products include those from Sumitomo Chemical Co., Ltd. and Ouchi Shinko Chemical Industry Co., Ltd. These may be used alone or in combination. Of these, sulfenamide vulcanization accelerators are preferred.

[0108] The content of the vulcanization accelerator is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and is preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 3 parts by mass or less, based on 100 parts by mass of the rubber component. When the content is within the above range, better effects tend to be obtained.

[0109] In addition to the above components, the rubber composition may further contain additives commonly used in the tire industry, such as organic peroxides, etc. The content of these additives is preferably 0.1 to 200 parts by mass per 100 parts by mass of the rubber component.

[0110] The rubber composition can be produced, for example, by kneading the above components using a rubber kneading device such as an open roll or a Banbury mixer, followed by vulcanization.

[0111] As for kneading conditions, in the base kneading step in which additives other than the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C. In the finish kneading step in which the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 120°C or lower, preferably 80 to 110°C. Furthermore, the composition kneaded with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 140 to 190°C, preferably 150 to 185°C. The vulcanization time is usually 5 to 15 minutes.

[0112] The above rubber composition (vulcanized rubber composition) preferably satisfies the following formula (A), and more preferably has a complex modulus E* that reversibly changes with water and satisfies the following formula (A). Formula (A) Complex modulus of elasticity E* when wetted with water / Complex modulus of elasticity E* before wetted with water × 100<95 (In the formula, E* is the E* of the rubber composition at 23°C.)

[0113] The above formula (A) means that the E* of the rubber composition when wetted with water is reduced to less than 95% of the E* (100%) of the rubber composition before wetting with water (the rubber composition when initially dried before wetting with water). This means that the complex modulus (E*) when swollen with water is smaller than the complex modulus (E*) when initially dried before wetting with water. Therefore, when the road surface changes from dry to wet, the rubber composition is wetted by water, the complex modulus E* of the rubber composition decreases, the deterioration of wet grip performance is suppressed, and good wet performance is obtained. This is presumably because, since wet roads are prone to slippage, sufficient grip performance cannot be obtained if E* remains at a level suitable for dry roads, but as E* decreases, the contact area with the road surface increases, the deterioration of wet grip performance can be suppressed, and good wet performance (wet grip performance, etc.) can be obtained. On the other hand, when the road surface changes from wet to dry, the rubber composition moistened with water dries, causing the E* of the rubber composition to increase (return), maintaining rolling resistance when driving on dry roads and ensuring good fuel economy. Furthermore, the decrease in dry grip performance can be suppressed, resulting in good dry grip performance. This is presumably because, since the tire is less likely to slip on dry roads, sufficient grip performance cannot be obtained with an E* that is suitable for wet roads. However, by increasing E*, the tire becomes suitable for dry roads, suppressing the decrease in dry grip performance and achieving good dry grip performance. In this way, the complex modulus E* changes reversibly with water, and by satisfying the above formula (A), an appropriate complex modulus (E*) can be obtained according to the road surface condition (wet road surface, dry road surface), thereby achieving a more suitable effect. Furthermore, when the rubber comes into contact with water, it becomes more likely to be cooled by water and become hydrophilic, and it is presumed that the hydrophilicity increases the actual contact area with the road surface, causing adhesion, thereby improving wet grip performance.

[0114] In this specification, the complex modulus (E*) of a rubber composition means the E* of the rubber composition after vulcanization.

[0115] In this specification, "the complex modulus E* changes reversibly due to water" means that the complex modulus E* of the rubber composition (after vulcanization) reversibly increases or decreases in the presence of water. Note that, for example, when changing from dry to wet to dry, the complex modulus E* only needs to change reversibly, and the complex modulus E* does not need to be the same in the earlier drying state and the later drying state, or it may be the same in the earlier drying state and the later drying state.

[0116] In this specification, the complex modulus E* before wetting with water means the complex modulus E* of a rubber composition (after vulcanization) that has been dried before wetting with water, and specifically means the complex modulus E* of a rubber composition (after vulcanization) that has been dried before wetting with water by the method described in the examples. In this specification, the complex modulus E* when wet with water means the complex modulus E* of a rubber composition (after vulcanization) in a state wet with water, and specifically means the complex modulus E* of a rubber composition (after vulcanization) wetted with water by the method described in the examples.

[0117] In this specification, the complex modulus E* of a rubber composition (after vulcanization) is measured on a test vulcanized rubber sheet using an RSA-GII manufactured by TA Instruments under conditions of a strain of 0.25%, a frequency of 10 Hz, and a temperature of 23°C.

[0118] As shown in the above formula (A), the complex modulus E* when wet with water / the complex modulus E* before wet with water × 100 (E* of the rubber composition (after vulcanization) when wet with water / E* of the rubber composition (after vulcanization) before wet with water × 100) is less than 95, and is preferably 94 or less, more preferably 93 or less, even more preferably 91 or less, particularly preferably 89 or less, most preferably 87 or less, even most preferably 86 or less, still most preferably 85 or less, and particularly most preferably 84 or less. By making it equal to or greater than the lower limit, the contact area with the road surface is improved, and therefore deterioration of grip performance tends to be suppressed. The lower limit is not particularly limited, but is preferably 50 or more, more preferably 70 or more, and even more preferably 75 or more. Within the above range, the effect tends to be more suitably obtained.

[0119] The complex modulus E* (MPa) before wetting with water is preferably 4.0 MPa or more, more preferably 4.5 MPa or more, and even more preferably 5.0 MPa or more. There is no particular upper limit, but it is preferably 20.0 MPa or less, more preferably 17.0 MPa or less, and even more preferably 15.0 MPa or less. Within the above range, better effects tend to be obtained.

[0120] The change in the complex modulus E* of a rubber composition expressed by the above formula (A) and the reversible change in the complex modulus E* due to water can be achieved, for example, by blending a substance that can reversibly cleave and recombine ionic bonds between rubber molecules by adding water and drying. Specifically, the change in the complex modulus E* of a rubber composition expressed by the above formula (A) and the reversible change in the complex modulus E* due to water can be achieved by combining a modified BR or modified SBR, such as a carboxylic acid-modified BR or carboxylic acid-modified SBR, with a compound containing a metal, a metalloid, or nitrogen. This combination forms ionic bonds between rubber molecules between cations derived from the metal, metalloid, or nitrogen and anions derived from the carboxylic acid. The ionic bonds between the rubber molecules are cleaved by adding water and recombined by drying the water. As a result, E* decreases when the rubber is wet with water and increases when the rubber is dried (before wetting with water and after re-drying).

[0121] The E* value when dry (before wetting with water and after re-drying) can be adjusted by the type and amount of chemicals (especially rubber components, fillers, and softeners such as oil) compounded in the rubber composition; for example, reducing the amount of softener tends to increase the E* value when dry, and increasing the amount of filler tends to increase the E* value when dry. Furthermore, the E* value when dry can be adjusted by the carboxylic acid modification rate (carboxylic acid group content) of modified BR or modified SBR, such as carboxylic acid-modified BR or carboxylic acid-modified SBR; increasing the carboxylic acid group content tends to increase the E* value when dry.

[0122] For example, by forming a rubber composition in which some or all of the rubber molecules in the rubber component are crosslinked by ionic bonds, the E* value when wet can be lowered compared to the dry state, making it possible to adjust the E* values when wet and dry. Specifically, by using a modified BR or modified SBR, such as a carboxylic acid-modified BR or carboxylic acid-modified SBR, in combination with a metal, metalloid, or nitrogen-containing compound, a rubber composition crosslinked by ionic bonds is obtained, making it possible to lower the E* value when wet compared to the dry state. Furthermore, the E* value can be adjusted by the type and amount of chemicals (especially rubber components, fillers, and softeners such as oils) blended into the rubber composition. For example, increasing the amount of filler tends to increase the E* value when wet, while decreasing the amount of softener tends to increase the E* value when wet.

[0123] Specifically, by adjusting the E* value in the dry state (before wetting with water and after re-drying) to within a desired range and then using a modified BR or modified SBR such as a carboxylic acid-modified BR or carboxylic acid-modified SBR in combination with a metal, metalloid, or nitrogen-containing compound, the rubber composition can achieve the E* change represented by the above formula (A) and the reversible E* change due to water. The E* value before wetting with water can also be achieved.

[0124] The rubber composition can be used (as a rubber composition for tires) for tire components such as tread (cap tread, i.e., the outermost rubber layer in the tread), sidewall, base tread, undertread, shoulder, clinch, bead apex, breaker cushion rubber, carcass cord covering rubber, insulation, chafer, inner liner, etc., as well as side reinforcing rubber and bead reinforcing rubber of run-flat tires. Among these, it is preferably used for tread (cap tread) and base tread, and more preferably for tread (cap tread).

[0125] The tire (pneumatic tire, etc.) of the present disclosure is manufactured by a conventional method using the above rubber composition. That is, the rubber composition, to which various additives are optionally blended, is extruded in an unvulcanized state to match the shapes of the tire components (particularly the tread (cap tread)), molded in a conventional method on a tire building machine, and laminated together with other tire components to form an unvulcanized tire, which is then heated and pressurized in a vulcanizer to manufacture the tire.

[0126] It is sufficient that at least a part of the tire component (for example, the tread) of the tire is made of the rubber composition, and the entire tire component may be made of the rubber composition.

[0127] The above-mentioned tires are suitably used as tires for passenger cars, large passenger cars, large SUVs, trucks and buses, motorcycles, racing tires, run-flat tires, aircraft tires, mining tires, etc. The tire can be suitably used as a summer tire, a winter tire (studless tire, snow tire, studded tire), or an all-season tire. [Example]

[0128] The present disclosure will be specifically described based on examples, but the present disclosure is not limited to these examples.

[0129] The various chemicals used during synthesis and polymerization were purified according to standard methods as necessary.

[0130] The methods for evaluating the obtained polymers will be summarized below.

[0131] (Measurement of weight average molecular weight (Mw)) The weight average molecular weight (Mw) of the polymer was determined by converting it into standard polystyrene based on the measured value obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0132] (LCST measurement) Each polymer was added to an antifreeze solution (a liquid consisting of methanol and water, obtained by adding 9 times the volume of methanol to the water and mixing at 25°C for 30 minutes) so that the concentration was 1% by mass, and the solution was gradually heated from -20°C to +80°C. After storing the solution at each temperature for 2 hours, it was observed whether the solution became clear or cloudy, and the temperature at which the solution changed from clear to cloudy was taken as the lower critical solution temperature (LCST).

[0133] (Polymer structure identification) The structure of the polymer was identified by measurement using a JNM-ECA series NMR device manufactured by JEOL Ltd.

[0134] (Production Example 1) (Polymerization of poly(ethyl vinyl ether) (PEVE)) A glass flask purged with inert gas was charged with 1 g of aluminum chloride and 200 g of toluene. While maintaining the internal temperature at -20°C to -5°C, an ethyl vinyl ether / toluene solution (20.3 g of ethyl vinyl ether (EVE monomer), 100 g of toluene) was added dropwise. A sample of the reaction mixture was taken and analyzed by GPC. The weight-average molecular weight (Mw) was 2201, the number-average molecular weight (Mn) was 1202, and the molecular weight distribution (MD) was 1.8. The reaction mixture was stirred at room temperature, and when the internal temperature reached 0°C or higher, 60 g of water was added to the mixture to terminate the reaction. The aqueous layer was removed by separation, and the addition of water and separation were repeated until the pH of the aqueous layer reached 4 or higher. The organic layer obtained by separation was blown dry to volatilize the toluene, and then dried under reduced pressure at 80°C / <10 Pa or less until a constant weight was reached, yielding PEVE. The yield was nearly 100%, and GPC analysis revealed a weight-average molecular weight (Mw) of 2205 and an LCST of 0°C.

[0135] (Production Example 2) (Polymerization of poly(methyl vinyl ether) (PMVE)) A polymer was synthesized in the same manner as in Production Example 1, except that methyl vinyl ether was used instead of ethyl vinyl ether, to obtain PMVE. The yield was nearly 100%, and analysis revealed that the LCST was 35°C.

[0136] (Production Example 3) (Polymerization of poly(2-hydroxyethyl vinyl ether) (PHEVE)) A polymer was synthesized in the same manner as in Production Example 1, except that 2-hydroxyethyl vinyl ether was used instead of ethyl vinyl ether, to obtain PHEVE. The yield was nearly 100%, and analysis revealed that the LCST was 60°C.

[0137] (Production Example 4) (Polymerization of poly(2-hydroxybutyl vinyl ether) (PHBVE)) A polymer was synthesized in the same manner as in Production Example 1, except that 2-hydroxybutyl vinyl ether was used instead of ethyl vinyl ether, to obtain PHBVE. The yield was nearly 100%, and analysis revealed that the LCST was 50°C.

[0138] (Production Example 5) (Polymerization of poly(2-methoxyethyl vinyl ether) (PMOVE)) PMOVE was synthesized in the same manner as in Production Example 1, except that 2-methoxyethyl vinyl ether was used instead of ethyl vinyl ether. The yield was nearly 100%, and analysis revealed that the LCST was 70°C.

[0139] (Production Example 6) (Polymerization of poly(N-isopropylacrylamide) (PNIPAM)) PNIPAM was obtained by synthesizing a polymer in the same manner as in Production Example 1, except that N-isopropylacrylamide was used instead of ethyl vinyl ether. The yield was nearly 100%, and analysis revealed that the LCST was 32°C.

[0140] The various chemicals used in the examples and comparative examples will be explained below. SBR: JSR HPR850 (S-SBR, styrene content: 27.5% by mass) manufactured by JSR Corporation Carboxylic acid-modified SBR: Nipol LX426 (styrene-butadiene latex, rubber solids 50%) manufactured by Nippon Zeon Co., Ltd. The carboxylic acid-modified SBR used was coagulated rubber made by subjecting Nipol LX426 to the following process. Weigh out 12 kg of Equinene (a mixed solvent with alcohol as the main ingredient) into a 1.25 L bucket and stir mechanically. 2. Weigh out 6.5 kg of emulsion (Nipol LX426) and pour into 1. 3. Weigh out 1.5 kg of 0.5% aqueous sulfuric acid solution and pour it into 2. 4. Filter through a colander (approximately 6.5 kg of WET polymer). 5. Blow dry in a walk-in draft. 6. Dry in a vacuum oven until the loss on drying is 0.5% (approximately 3.1 kg of dry polymer). BR: BR150B (cis content: 97% by mass) manufactured by Ube Industries, Ltd. Carbon black: Diablack N220 (N2SA: 111m) manufactured by Mitsubishi Chemical Corporation 2 / g) Silica: Ultrasil VN3 (N2SA: 175 ml) manufactured by Evonik Degussa 2 / g) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa 1,2-Dimethylimidazole: Curesol 1.2DMZ manufactured by Shikoku Chemicals Co., Ltd. 1-Butylimidazole: commercially available Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. Antioxidant: Nocrac 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Oil: Diana Process AH-24 (aromatic process oil) manufactured by Idemitsu Kosan Co., Ltd. PMVE: Poly(methyl vinyl ether) (PMVE) (in formula (1), R 2 : methyl group, n: 0) PEVE: Poly(ethyl vinyl ether) (PEVE) (in formula (1), R 2 : ethyl group, n: 0) PHEVE: Poly(2-hydroxyethyl vinyl ether) (PHEVE) (in formula (1), R 1 : ethylene group, R 2 : hydrogen atom, n: 1) PHBVE: Poly(2-hydroxybutyl vinyl ether) (PHBVE) (in formula (1), R 1 : butylene group, R 2 : hydrogen atom, n: 1) PMOVE: Poly(2-methoxyethyl vinyl ether) (PMOVE) (in formula (1), R 1 : ethylene group, R 2 : methyl group, n: 1) PNIPAM: Poly(N-isopropylacrylamide) (PNIPAM) synthesized in the above production example Resin 1: Sylvatraxx 4150 manufactured by Arizona Chemical Company (β-pinene resin, β-pinene content: 98% by mass or more, softening point: 116°C) Resin 2: Sylvatraxx 4401 (α-methylstyrene resin (copolymer of α-methylstyrene and styrene), softening point: 82°C) manufactured by Arizona Chemical Company Resin 3: ECR-373 manufactured by ExxonMobil Corporation (a copolymer of C5 fraction and C9 fraction (C5 / C9 resin), softening point: 86°C) Cellulose fiber: Biomass nanofiber manufactured by Sugino Machine Co., Ltd. (product name: "BiNFi-s Cellulose", microfibrillated cellulose fiber) Stearic acid: NOF Corporation's "Tsubaki" stearic acid Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: HK-200-5 (powdered sulfur containing 5% oil by mass) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0141] Examples and Comparative Examples According to the formulation shown in Table 1, chemicals other than sulfur and vulcanization accelerator were kneaded for 4 minutes at 160°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded mixture. Next, sulfur and vulcanization accelerator were added to the obtained kneaded mixture, and the mixture was kneaded for 4 minutes at 80°C using an open roll to obtain an unvulcanized rubber composition. The resulting unvulcanized rubber composition was press-vulcanized at 170°C for 12 minutes to obtain a vulcanized rubber composition. The obtained unvulcanized rubber composition was molded into a tread shape, and then laminated together with other tire components on a tire building machine to form an unvulcanized tire. After that, the tire was vulcanized at 170°C for 12 minutes to produce a test tire (size: 195 / 65R15).

[0142] The vulcanized rubber compositions and test tires obtained were evaluated as follows, and the results are shown in Table 1.

[0143] <Complex elastic modulus E* measurement> The complex modulus E* of the rubber piece (vulcanized rubber composition) was measured using RSA-GII manufactured by TA Instruments (the value of E* is the average value of five measurements). (Measurement conditions) Measurement mode: Extension Frequency: 10Hz Distortion: 0.25% ·Temperature: 23℃ Sample size: L 10 mm x W 3 mm x T 0.5 mm (L is the distance between the chucks)

[0144] (Complex modulus E* before wetting with water) The vulcanized rubber composition of the above sample size was dried at room temperature and normal pressure until it reached a constant weight. The complex modulus E* of the obtained vulcanized rubber composition (rubber piece) before wetting with water was measured by the above method and defined as E* before wetting with water.

[0145] (Complex modulus of elasticity E* when wet with water) A vulcanized rubber composition when wet with water was obtained by immersing the vulcanized rubber composition of the above sample size in 100 ml of water at 23° C. for 2 hours. The complex modulus E* of the obtained vulcanized rubber composition when wet with water (rubber piece) was measured by the above method and was defined as E* when wet with water.

[0146] (Ionic bond ratio (ratio of crosslinks consisting of ionic bonds)) This was determined based on the amount of each ingredient mixed.

[0147] (Grip performance on wet roads immediately after driving on dry roads) Each test tire was fitted to all wheels of a vehicle (domestic FF 2000cc) and driven 10 laps on a course that alternated between wet and dry road surfaces. The grip performance on the first and tenth laps was evaluated on a 5-point scale from 1 to 5 based on the driver's sense of touch. Similar tests were conducted for 20 drivers, and the evaluation results for the first and tenth laps were added together. The wet / dry grip performance maintenance of each test tire was calculated by dividing the score for the tenth lap by the score for the first lap, and indexed based on Comparative Example 3 being 100. The larger the index, the better the grip performance on alternating wet and dry road surfaces until the latter part of the journey, and the better the grip performance on wet road surfaces immediately after driving on dry road surfaces.

[0148] [Table 1]

[0149] From Table 1, it was found that the examples containing the compound represented by the above formula (1) were able to improve the grip performance on a wet road surface immediately after driving on a dry road surface.

[0150] The present disclosure (1) relates to a rubber composition containing a compound represented by the following formula (1): [ka] [In formula (1), R 1 are the same or different and represent a divalent hydrocarbon group; R 2 are the same or different and represent a hydrogen atom or a monovalent hydrocarbon group, n is an integer of 0 to 10, and m is the number of repetitions.

[0151] The present disclosure (2) is the rubber composition according to the present disclosure (1), wherein the lower critical solution temperature (LCST) of the compound represented by the formula (1) is 0°C to 20°C.

[0152] The present disclosure (3) is the rubber composition according to the present disclosure (1) or (2), which satisfies the following formula (A): Formula (A) Complex modulus of elasticity E* when wetted with water / Complex modulus of elasticity E* before wetted with water × 100<95 (In the formula, E* is the E* of the rubber composition at 23°C.)

[0153] The present disclosure (4) is a rubber composition according to any one of the present disclosures (1) to (3), wherein the rubber composition contains 5 to 20 parts by mass of the compound represented by formula (1) per 100 parts by mass of the rubber component.

[0154] The present disclosure (5) is a rubber composition according to any one of the present disclosures (1) to (4), wherein the rubber composition contains at least one resin selected from the group consisting of terpene-based resins, aromatic-based resins, C5-based resins, C9-based resins, C5 / C9-based resins, coumarone-indene-based resins, and olefin-based resins.

[0155] The present disclosure (6) is the rubber composition according to any one of the present disclosures (1) to (5), wherein the crosslinks between rubber molecules of the rubber component are partially or entirely crosslinked by ionic bonds.

[0156] The present disclosure (7) is the rubber composition according to any one of the present disclosures (1) to (6), which contains water-absorbent fibers, elastomer, and / or resin.

[0157] The present disclosure (8) is the rubber composition according to any one of the present disclosures (1) to (7), which is for use in a tire tread.

[0158] The present disclosure (9) also relates to a tire having a tire component using the rubber composition according to any one of the present disclosures (1) to (8).

[0159] The present disclosure (10) is the tire according to the present disclosure (9), wherein the tire component is a tread.

Claims

1. A rubber composition comprising a diene rubber and a compound represented by the following formula (1): 【Chemical 1】 [In formula (1), R １ are the same or different and represent a divalent hydrocarbon group; R ２ are the same or different and represent a hydrogen atom or a monovalent hydrocarbon group, n is an integer of 0 to 10, and m is the number of repetitions. A rubber composition that satisfies the following formula (A): Formula (A) Complex modulus of elasticity E* when wetted with water / Complex modulus of elasticity E* before wetted with water × 100<95 (In the formula, E* is the E* of the rubber composition at 23°C.)

2. 2. The rubber composition according to claim 1, wherein the compound represented by formula (1) has a lower critical solution temperature (LCST) of 0 to 20°C.

3. The rubber composition according to claim 1 or 2, which satisfies the following formula (A): Formula (A) Complex modulus of elasticity E* when wetted with water / Complex modulus of elasticity E* before wetted with water × 100<95 (In the formula, E* is the E* of the rubber composition at 23°C.)

4. The rubber composition according to any one of claims 1 to 3, comprising 5 to 20 parts by mass of the compound represented by formula (1) per 100 parts by mass of the rubber component.

5. The rubber composition according to any one of claims 1 to 4, comprising at least one resin selected from the group consisting of terpene resins, aromatic resins, C5 resins, C9 resins, C5 / C9 resins, coumarone-indene resins, and olefin resins.

6. 6. The rubber composition according to claim 1, wherein a part or all of the crosslinks between rubber molecules of the rubber component are formed by ionic bonds.

7. The rubber composition according to any one of claims 1 to 6, further comprising a water-absorbent fiber, an elastomer, and / or a resin.

8. The rubber composition according to any one of claims 1 to 7, which is for use in a tire tread.

9. A tire having tire components made using the rubber composition according to any one of claims 1 to 8.

10. 10. The tire of claim 9, wherein the tire component is a tread.

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