Rubber composition and tire

Abstract

The purpose of the present invention is to provide a rubber composition and a tire which are capable of improving the overall performance of wet grip performance and dry grip performance. The present invention pertains to a rubber composition in which the hardness is reversibly changed by water, and which satisfies expressions (1) and (2) below. (1) [(Hardness when dry) - (Hardness when wet from water)] ≥ 1 (In the expression, hardness is defined as the JIS-A hardness of the rubber composition at 25℃.) (2) (tanδ at 70℃ when dry) ≥ 0.18 (In the expression, tanδ at 70℃ is defined as the loss tangent measured under the conditions of 70℃, an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz.)

Description

[Technical Field]

[0001] The present invention relates to a rubber composition and a tire. [Background technology]

[0002] In recent years, awareness of safety has been increasing as a common issue for automobiles, and further improvements in wet grip performance are required. Various studies have been conducted to improve wet grip performance, and many inventions of rubber compositions containing silica have been reported (for example, Patent Document 1). Since wet grip performance is significantly affected by the performance of the rubber composition, particularly in the tread portion that comes into contact with the road surface, technical improvements to rubber compositions for tires, such as treads, have been widely studied and put into practical use. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-285524 Summary of the Invention [Problem to be solved by the invention]

[0004] As a result of intensive research by the present inventors, it has been found that while significant progress has been made in the wet grip performance of tires due to technological improvements in rubber compositions for treads that use silica, the change in grip performance when the road surface changes from dry to wet or from wet to dry remains an important technical issue and there is room for improvement. As a result of extensive research by the inventors into this point, it was found that conventional rubber either does not change in hardness when it changes from a dry state (not wet with water) to a wet state (so-called wet state), or it has the property of becoming hard when cooled by water, which reduces the contact area with the road surface, and as a result, wet grip performance tends to be lower than dry grip performance. As described above, it has been found that there is room for improvement in the conventional technology in terms of improving the overall wet grip performance and dry grip performance. An object of the present invention is to provide a rubber composition and a tire that can solve the above problems and improve the overall wet grip performance and dry grip performance. [Means for solving the problem]

[0005] The present invention relates to a rubber composition whose hardness is reversibly changed by water and which satisfies the following formulas (1) and (2): Dry hardness - wet hardness ≥ 1 (1) (In the formula, the hardness is the JIS-A hardness of the rubber composition at 25°C.) Tan δ at 70°C when dry ≧ 0.18 (2) (In the formula, tan δ at 70°C is the loss tangent measured under the conditions of 70°C, initial strain 10%, dynamic strain 2%, and frequency 10 Hz.)

[0006] In the above formula (1), the value of dry hardness minus wet hardness is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more.

[0007] In the above formula (2), tan δ at 70° C. in a dry state is preferably 0.19 or more, more preferably 0.20 or more, and even more preferably 0.21 or more.

[0008] The rubber composition preferably contains a hydrophilic material.

[0009] The rubber composition preferably contains a diene rubber and a polymer having a carbon-carbon double bond and a heteroatom.

[0010] The heteroatom 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.

[0011] It is preferable that the insoluble content of the polymer is 5% by mass or more when 1 g of the polymer is suspended in 10 mL of water.

[0012] It is preferable that the insoluble content of the polymer is 5% by mass or more when 1 g of the polymer is suspended in 10 mL of tetrahydrofuran.

[0013] The rubber composition preferably contains 5 parts by mass or more of the polymer per 100 parts by mass of the rubber component.

[0014] The rubber composition preferably contains an isoprene-based rubber.

[0015] The rubber composition preferably contains butadiene rubber.

[0016] The rubber composition preferably contains 95% by mass or less of styrene-butadiene rubber in 100% by mass of the rubber component.

[0017] It is preferable to satisfy the relationship: content of styrene butadiene rubber in 100% by mass of the rubber component>50% by mass>content of butadiene rubber in 100% by mass of the rubber component>content of isoprene-based rubber in 100% by mass of the rubber component.

[0018] It is preferable that the silica and carbon black are each contained in an amount of 20 parts by mass or more per 100 parts by mass of the rubber component.

[0019] It is preferable that the resin contains a petroleum-based resin.

[0020] The rubber composition is preferably a rubber composition for a tread.

[0021] The present invention also relates to a tire having a tire component at least partially constituted by the above rubber composition.

[0022] The tire component is preferably a tread.

[0023] It is preferable that the tire component is a tread, and that the thickness of the tread is 4 mm or more.

[0024] It is preferable that the tire component is a tread, and that the land ratio of the tread is 30% or more.

[0025] It is preferable that the tire component is a tread and that the tire component is provided with grooves that are continuous in the tire circumferential direction and / or grooves that are discontinuous in the tire circumferential direction. [Effects of the Invention]

[0026] According to the present invention, the rubber composition has a hardness that changes reversibly with water and satisfies the above formulas (1) and (2), and therefore can improve the overall wet grip performance and dry grip performance. DETAILED DESCRIPTION OF THE INVENTION

[0027] The rubber composition of the present invention has a hardness that reversibly changes with water and satisfies the following formulas (1) and (2), thereby improving the overall wet grip performance and dry grip performance. Dry hardness - wet hardness ≥ 1 (1) (In the formula, the hardness is the JIS-A hardness of the rubber composition at 25°C.) Tan δ at 70°C when dry ≧ 0.18 (2) (In the formula, tan δ at 70°C is the loss tangent measured under the conditions of 70°C, initial strain 10%, dynamic strain 2%, and frequency 10 Hz.)

[0028] The rubber composition provides the above-mentioned effects, and although the reason why such effects are obtained is not entirely clear, it is presumed as follows. The rubber composition of the present invention has a hardness that reversibly changes with water and satisfies the above formula (1). Here, the above formula (1) means that the hardness when wet with water is smaller than the hardness when dry. That is, the rubber composition of the present invention has a hardness that reversibly changes with water and satisfies the above formula (1), which means that the hardness when wet with water is smaller than the hardness when dry, and the hardness changes reversibly in the presence of water. Therefore, when the road surface changes from dry to wet, the rubber composition is wetted with water, the hardness of the rubber composition decreases, and the decrease in grip performance (wet grip performance) can be suppressed, resulting in good grip performance (wet grip performance). This is presumably because wet roads are prone to slippage, and sufficient grip performance cannot be obtained if the hardness remains appropriate for dry roads, but by reducing the hardness, the contact area with the road surface increases, the decrease in grip performance (wet grip performance) can be suppressed, and good grip performance (wet grip performance) can be obtained. On the other hand, when the road surface changes from wet to dry, the rubber composition moistened with water dries and the hardness of the rubber composition increases, preventing a decrease in grip performance (dry grip performance) and providing good grip performance (dry grip performance). This is because, since the tire is less likely to slip on dry roads, sufficient grip performance cannot be obtained if the hardness remains at a level suitable for wet roads, but by increasing the hardness, the tire becomes suitable for dry roads, preventing a decrease in grip performance (dry grip performance), and providing good grip performance (dry grip performance). In this way, the hardness changes reversibly depending on the water, and by satisfying the above formula (1), an appropriate hardness can be obtained depending on the water condition on the road surface (wet road surface, dry road surface), thereby improving the overall wet grip performance and dry grip performance. Furthermore, the rubber composition of the present invention satisfies the above formula (2), thereby achieving better wet grip performance and dry grip performance. Therefore, the rubber composition of the present invention has a hardness that reversibly changes with water, and by satisfying the above formulas (1) and (2), the overall wet grip performance and dry grip performance can be improved. As described above, the present invention solves the problem (objective) of improving the overall performance of wet grip performance and dry grip performance by configuring a rubber composition that satisfies the parameters of the above formulas (1) and (2). In other words, the parameters do not define the problem (objective); the object of the present application is to improve the overall performance of wet grip performance and dry grip performance, and as a means of solving this problem, the rubber composition is configured to satisfy the parameters of the above formulas (1) and (2). In other words, satisfying the parameters of the above formulas (1) and (2) is an essential constituent requirement. In this specification, the hardness tan δ of a rubber composition means the hardness tan δ of the rubber composition after vulcanization. Also, tan δ is a value obtained by conducting a viscoelasticity test on the rubber composition after vulcanization.

[0029] In this specification, "the hardness changes reversibly with water" means that the hardness 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 hardness only needs to change reversibly, and the hardness does not have to be the same in the first drying state and the second drying state, or may be the same in the first drying state and the second drying state.

[0030] In this specification, the term "dry hardness" means the hardness of a rubber composition (after vulcanization) in a dry state, and specifically means the hardness of a rubber composition (after vulcanization) dried by the method described in the examples. In this specification, the hardness when wet with water means the hardness of a rubber composition (after vulcanization) in a state wet with water, and specifically means the hardness of a rubber composition (after vulcanization) wetted with water by the method described in the examples.

[0031] In this specification, the hardness (JIS-A hardness) of a rubber composition (after vulcanization) is measured at 25°C using a type A durometer in accordance with JIS K6253-3 (2012) "Vulcanized rubber and thermoplastic rubber - Determination of hardness - Part 3: Durometer hardness."

[0032] In this specification, tan δ at 70°C in a dry state means tan δ at 70°C of a rubber composition (after vulcanization) in a dry state, and specifically means tan δ at 70°C of a rubber composition (after vulcanization) dried by the method described in the examples.

[0033] In this specification, the 70°C tan δ of a rubber composition (after vulcanization) is a loss tangent measured under conditions of 70°C, initial strain of 10%, dynamic strain of 2%, and frequency of 10 Hz.

[0034] As shown in the above formula (1), (dry hardness - wet hardness (dry rubber composition (after vulcanization) hardness - wet rubber composition (after vulcanization) hardness)) is 1 or more, preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, particularly preferably 5 or more, most preferably 6 or more, more preferably 8 or more, more preferably 9 or more, more preferably 10 or more, more preferably 11 or more, more preferably 13 or more, more preferably 15 or more, more preferably 18 or more, more preferably 21 or more, more preferably 24 or more, and although the upper limit is not particularly limited, it is preferably 50 or less, more preferably 40 or less, even more preferably 30 or less, particularly preferably 28 or less, most preferably 26 or less. Within the above range, the effect can be more suitably obtained.

[0035] The dry hardness (hardness of the rubber composition (after vulcanization) when dried) can be adjusted as appropriate within the range that satisfies the above formula (1), but is preferably 20 or more, more preferably 25 or more, even more preferably 30 or more, particularly preferably 40 or more, most preferably 50 or more, more preferably 55 or more, more preferably 58 or more, more preferably 62 or more, more preferably 64 or more, and is preferably 95 or less, more preferably 90 or less, even more preferably 85 or less, particularly preferably 75 or less, most preferably 70 or less, more preferably 66 or less, more preferably 65 or less. When the hardness is within the above range, the effect can be more suitably obtained.

[0036] The hardness when wet with water (hardness of the rubber composition (after vulcanization) when wet with water) can be adjusted appropriately within the range satisfying the above formula (1), but is preferably 20 or more, more preferably 25 or more, even more preferably 30 or more, particularly preferably 35 or more, most preferably 40 or more, more preferably 43 or more, more preferably 45 or more, more preferably 46 or more, more preferably 49 or more, more preferably 50 or more, more preferably 51 or more, more preferably 53 or more, more preferably 55 or more, and also preferably 80 or less, more preferably 70 or less, even more preferably 65 or less, even more preferably 62 or less, particularly preferably 61 or less, most preferably 60 or less, more preferably 59 or less, more preferably 56 or less. When the hardness is within the above range, the effect can be more suitably obtained.

[0037] As shown in the above formula (2), the tan δ at 70°C in a dry state (tan δ at 70°C of the rubber composition (after vulcanization) in a dry state) is 0.18 or more, preferably 0.19 or more, more preferably 0.20 or more, even more preferably 0.21 or more, particularly preferably 0.22 or more, and most preferably 0.23 or more, and although there is no particular upper limit, it is preferably 0.60 or less, more preferably 0.40 or less, even more preferably 0.30 or less, and particularly preferably 0.25 or less. Within the above range, the effect can be more suitably obtained.

[0038] The hardness change of the rubber composition represented by the above formula (1), the reversible hardness change caused by water, can be achieved by compounding a hydrophilic material, i.e., a compound capable of forming reversible molecular bonds with water, such as hydrogen bonds or ionic bonds. The hydrophilic material is not particularly limited as long as it is a compound that can form a reversible molecular bond with water, such as a hydrogen bond or an ionic bond, and examples thereof include compounds having heteroatoms. To explain the manufacturing guidelines for satisfying the above parameters in more detail, by using a rubber component containing a diene rubber in combination with a polymer having a carbon-carbon double bond and a heteroatom, it is possible to achieve the hardness change of the rubber composition represented by the above formula (1), as well as the reversible hardness change caused by water. This is because heteroatoms can form reversible molecular bonds, such as hydrogen bonds and ionic bonds, with water in the rubber composition, and as a result of the formation of these molecular bonds, the hardness of the rubber composition decreases when wet with water. Furthermore, by using the above-mentioned combination, the polymer is crosslinked to the rubber component by the carbon-carbon double bonds during vulcanization and fixed to the rubber component, thereby preventing the polymer from being released from the rubber component and preventing the polymer from precipitating on the rubber surface, and also preventing a decrease in grip performance (wet grip performance, dry grip performance).

[0039] In addition, the tan δ at 70°C when dry can be adjusted by the type and amount of chemicals (especially rubber components, fillers, softeners, resins, sulfur, vulcanization accelerators, and silane coupling agents) compounded into the rubber composition. For example, the tan δ at 70°C tends to increase when a softener (e.g., resin) that is poorly compatible with the rubber components is used, when an unmodified rubber is used, when the amount of filler is increased, when oil as a plasticizer is increased, when sulfur is reduced, when vulcanization accelerators are reduced, or when silane coupling agents are reduced.

[0040] Furthermore, the dry hardness can be adjusted by the type and amount of chemicals (especially softeners such as rubber components, fillers, oils, and resins) compounded into the rubber composition. For example, increasing the amount of softener tends to decrease the dry hardness, increasing the amount of filler tends to increase the dry hardness, and decreasing the amount of sulfur tends to decrease the dry hardness. The dry hardness can also be adjusted by adjusting the amounts of sulfur and vulcanization accelerator compounded. More specifically, increasing the amount of sulfur tends to increase the dry hardness, and increasing the amount of vulcanization accelerator tends to increase the dry hardness.

[0041] More specifically, by adjusting the dry hardness to within a desired range and then blending a hydrophilic material, or more preferably by using a rubber component containing a diene rubber in combination with a polymer having a carbon-carbon double bond and a heteroatom, the hardness change of the rubber composition represented by the above formula (1), reversible hardness change due to water, can be achieved, and the dry tan δ at 70°C can also be adjusted to within a desired range. Furthermore, the amount of filler can be increased in order to increase the dry tan δ at 70°C.

[0042] Another means for achieving the hardness change of the rubber composition represented by the above formula (1) and the reversible hardness change caused by water is to use a rubber component containing a diene rubber in combination with a polymer having a carbon-carbon double bond and a heteroatom. This crosslinks the polymer to the rubber component via the carbon-carbon double bond during vulcanization and fixes it to the rubber component, thereby preventing the polymer from being released from the rubber component, thereby achieving the hardness change of the rubber composition represented by the above formula (1) and the reversible hardness change caused by water. If the rubber composition does not have a carbon-carbon double bond, it may be liberated into water when it comes into contact with water, and a reversible change in hardness may not be obtained.

[0043] Another method for achieving the hardness change of a rubber composition represented by the above formula (1) and the reversible hardness change caused by water is, for example, a method in which the ionic bonds between rubber molecules are reversibly broken and rebonded by adding water and drying. More specifically, the hardness change of a rubber composition represented by the above formula (1) and the reversible hardness change caused by water can be achieved by using a rubber containing a halogen or oxygen in combination with a compound containing a metal, metalloid, or nitrogen. This is because the combination forms ionic bonds between rubber molecules between cations derived from the metal, metalloid, or nitrogen and anions derived from the halogen or oxygen. The ionic bonds between the rubber molecules are broken by adding water and rebonded by drying the water, resulting in a decrease in hardness when wet with water and an increase in hardness when dry.

[0044] The following describes the chemicals that can be used.

[0045] Examples of rubber components include diene rubbers such as isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), and butyl rubber (IIR). The rubber components may be used alone or in combination of two or more. Among these, diene rubbers are preferred, with isoprene rubber, BR, and SBR being more preferred, and SBR being even more preferred. A combination of isoprene rubber and SBR, a combination of BR and SBR, or a combination of isoprene rubber, BR, and SBR is also preferred.

[0046] Here, the rubber component is a rubber having a weight average molecular weight (Mw) of preferably 150,000 or more, more preferably 350,000 or more. There is no particular upper limit for Mw, but it is preferably 4,000,000 or less, more preferably 3,000,000 or less.

[0047] The content of the diene rubber in 100% by mass of the rubber component is preferably 20% 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, and most preferably 90% by mass or more, and may be 100% by mass. When it is within the above range, the effect tends to be better obtained.

[0048] The SBR is not particularly limited, and can be, for example, emulsion-polymerized SBR (E-SBR), solution-polymerized SBR (S-SBR), or other commonly used SBRs in the tire industry. These may be used alone or in combination of two or more.

[0049] The styrene content of the SBR is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. Within the above ranges, the effects tend to be more favorably obtained.

[0050] The vinyl content of the SBR is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, particularly preferably 40% by mass or more, and most preferably 50% by mass or more, and is preferably 75% by mass or less, more preferably 65% ​​by mass or less. Within the above range, compatibility with the BR is improved, and the effect tends to be more suitably obtained.

[0051] The SBR may be unmodified or modified. The modified SBR may be any SBR having a functional group that interacts with a filler such as silica, and examples thereof include terminal-modified SBR in which at least one terminal of the SBR has been modified with a compound (modifier) ​​having the above functional group (terminal-modified SBR having the above functional group at the terminal), main-chain-modified SBR in which the main chain has the above functional group, main-chain-terminal-modified SBR in which the main chain and terminals have the above functional group (for example, main-chain-terminal-modified SBR in which the main chain has the above functional group and at least one terminal has been modified with the above modifier), and terminal-modified SBR modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and into which hydroxyl groups or epoxy groups have been introduced. These may be used alone or in combination of two or more.

[0052] Examples of the functional group include an amino group, an amido 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 imido 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, an amino group (preferably an amino group in which a hydrogen atom of an 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), an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms), and an amide group are preferred.

[0053] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

[0054] The amount of SBR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less. Within the above ranges, the effects tend to be more favorably obtained.

[0055] The BR is not particularly limited, and any BR commonly used in the tire industry can be used. These may be used alone or in combination of two or more.

[0056] The cis content of BR is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 97% by mass or more. There is no particular upper limit, and it may be 100% by mass. When it is within the above range, the effect tends to be more suitably obtained.

[0057] The BR may be either unmodified or modified. Modified BR includes modified BR having the aforementioned functional groups introduced therein. Preferred embodiments are the same as those for modified SBR.

[0058] As the BR, for example, products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used.

[0059] The BR content 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 70% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. Within the above ranges, the effects tend to be more suitably obtained.

[0060] 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.

[0061] The content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 3% by mass or more, more preferably 5% by mass or more, and is preferably 60% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. Within the above ranges, the effects tend to be more suitably obtained.

[0062] It is preferable to satisfy the relationship of: content of styrene-butadiene rubber in 100% by mass of the rubber component > 50% by mass > content of butadiene rubber in 100% by mass of the rubber component > content of isoprene-based rubber in 100% by mass of the rubber component, which tends to produce more favorable effects.

[0063] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) 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). The cis content (cis-1,4-bonded butadiene unit content) and vinyl content (1,2-bonded butadiene unit content) can be measured by infrared absorption spectroscopy, and the styrene content can be measured by 1 It can be measured by H-NMR measurement.

[0064] The rubber composition preferably contains a hydrophilic material. As described above, the hydrophilic material is not particularly limited as long as it is a compound capable of forming a reversible molecular bond with water, such as a hydrogen bond or an ionic bond, and examples thereof include compounds having heteroatoms. Among these, compounds having a carbon-carbon double bond and a heteroatom are preferred, and polymers having a carbon-carbon double bond and a heteroatom are more preferred.

[0065] The carbon-carbon double bonds are necessary for crosslinking with the diene rubber, and the number thereof is not particularly limited.

[0066] The heteroatom refers to an atom other than carbon and hydrogen atoms, 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, but 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. The heteroatom is preferably present in the main chain (skeleton) of the polymer, and more preferably in the repeating unit of the polymer.

[0067] 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.

[0068] An oxyalkylene group is a group represented by -(AO)-, and -(AO) n A group represented by - (n is the number of repeating units) is preferred. The number of carbon atoms in the alkylene group A in the oxyalkylene group AO is preferably 1 or more, more preferably 2 or more, and preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. Within the above ranges, the effect tends to be more suitably obtained.

[0069] The alkylene group A in the oxyalkylene group AO may be either linear or branched, but is preferably branched because it results in a bulkier structure and the effect can be more suitably obtained. For the reason that the effect can be more suitably obtained, AO is preferably an oxyalkylene group having 2 to 3 carbon atoms (oxyethylene group (EO), oxypropylene group (PO)), an oxyalkylene group having 2 to 3 carbon atoms and a branched chain R 4 (R 4 represents a hydrocarbon group which may have a heteroatom.) is preferably bonded to an oxyalkylene group having 2 to 3 carbon atoms, a branched chain R 4 It is more preferable to use a group having a branched chain R bonded thereto. 4 is preferably bonded to the carbon atom adjacent to the oxygen atom.

[0070] R 4 The hydrocarbon group, which may have a heteroatom, is not particularly limited. The number of carbon atoms in the hydrocarbon group is preferably 1 or more, more preferably 2 or more, and preferably 10 or less, more preferably 6 or less, and even more preferably 4 or less. When the number of carbon atoms is within the above range, the effect tends to be more suitably obtained. R 4 As the hydrocarbon group which may have a hetero atom, a group represented by the following formula is preferred. [ka]

[0071] The group represented by -(AO)- is more preferably a group represented by the following formula (B), and particularly preferably a group represented by the following formulas (A) to (B), and can also be used in combination with a group represented by the following formula (C). [ka]

[0072] When the polymer contains two or more types of oxyalkylene groups, the arrangement of the oxyalkylene groups may be block or random.

[0073] The polymer is preferably a polymer containing a group (structural unit) represented by the formula (B) above, and more preferably a polymer consisting of groups (structural units) represented by the formulas (A) and (B) above. The content of the group (structural unit) represented by the above formula (B) in 100 mol% of the above polymer is preferably 2 mol% or more, more preferably 5 mol% or more, and preferably 50 mol% or less, more preferably 40 mol% or less, even more preferably 30 mol% or less, and particularly preferably 20 mol% or less.

[0074] The weight average molecular weight (Mw) of the polymer is preferably 10,000 or more, more preferably 50,000 or more, even more preferably 100,000 or more, and particularly preferably 500,000 or more, and is preferably 3,000,000 or less, more preferably 2,500,000 or less, even more preferably 2,000,000 or less, particularly preferably 1,500,000 or less, and most preferably 1,000,000 or less.

[0075] The polymer preferably has an insoluble content (water-insoluble content) of 5% by mass or more when 1 g of the polymer is suspended in 10 mL of water, more preferably 10% by mass or more, even more preferably 30% by mass or more, particularly preferably 50% by mass or more, most preferably 70% by mass or more, even most preferably 80% by mass or more, and even most preferably 90% by mass or more, with no particular upper limit. The insoluble matter can be measured by the method described in the Examples. The greater the insoluble content, the more the amount of the polymer that dissolves in water when the rubber is wetted with water can be reduced, and the more suitably the reversible hardness change can be achieved.

[0076] The polymer preferably has an insoluble content (THF insoluble content) of 5% by mass or more when 1 g of the polymer is suspended in 10 mL of tetrahydrofuran, more preferably 10% by mass or more, even more preferably 30% by mass or more, particularly preferably 50% by mass or more, most preferably 70% by mass or more, and most preferably 90% by mass or more, with no particular upper limit. The insoluble matter can be measured by the method described in the Examples. Since diene rubbers are soluble in tetrahydrofuran, the greater the amount of the polymer that is insoluble in tetrahydrofuran, the less compatible it is with the diene rubber, and the more likely it is that the effect of reducing hardness when wet with water will be sufficiently obtained.

[0077] The polymer may be a commercially available product, or may be produced by preparing a polymer from a monomer having a hetero atom. The monomer having a hetero atom is not particularly limited, but examples of the monomer having an oxygen atom include ethers such as vinyl ether, alkoxystyrene, allyl glycidyl ether, ethylene oxide, propylene oxide, and tetrahydrofuran, (meth)acrylic acid and esters thereof, and acid anhydrides; monomers having a nitrogen atom include acrylonitrile, N-vinylcarbazole, carbamic acid, and caprolactam; and monomers having a silicon atom include alkoxysilylstyrene and alkoxysilylvinyls. When the monomer having a heteroatom does not contain an unsaturated bond, a monomer having a carbon-carbon double bond (for example, a conjugated diene monomer such as butadiene or isoprene, or a vinyl polymer such as styrene) may be polymerized together with the monomer having a heteroatom. The polymerization method is not particularly limited, and can be carried out by a known method.

[0078] The content of the polymer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, particularly preferably 30 parts by mass or more, most preferably 40 parts by mass or more, still most preferably 50 parts by mass or more, even most preferably 60 parts by mass or more, particularly most preferably 70 parts by mass or more, more preferably 80 parts by mass or more, more preferably 90 parts by mass or more, more preferably 100 parts by mass or more, and preferably 150 parts by mass or less, more preferably 120 parts by mass or less, per 100 parts by mass of the rubber component. Within the above ranges, the effect tends to be better obtained.

[0079] The rubber composition may contain silica. Examples of silica include dry-process silica (silicic anhydride) and wet-process silica (hydrated silicic acid), but wet-process silica is preferred because it contains a large number of silanol groups. These may be used alone or in combination of two or more.

[0080] The nitrogen adsorption specific surface area (N2SA) of silica is 40m 2 / g or more, preferably 60m 2 / g or more, more preferably 80m 2 / g or more, more preferably 160m 2 / g or more. In addition, the N2SA is preferably 600m 2 / g or less, more preferably 300m 2 / g or less, more preferably 250m 2 / g or less, particularly preferably 200m 2 Within the above range, the effect tends to be more favorably obtained. The N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-81.

[0081] As silica, for example, products from Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation, etc. can be used.

[0082] The amount of silica per 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, particularly preferably 20 parts by mass or more, most preferably 30 parts by mass or more, more preferably 50 parts by mass or more, more preferably 60 parts by mass or more, more preferably 70 parts by mass or more, and is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, even more preferably 120 parts by mass or less, particularly preferably 100 parts by mass or less, most preferably 90 parts by mass or less. Within the above ranges, the effect tends to be better obtained.

[0083] In the rubber composition, the content of silica in 100% by mass of the filler (reinforcing filler) is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, and although there is no particular upper limit, it is preferably 90% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. Within the above range, the effect tends to be more suitably obtained.

[0084] When the rubber composition contains silica, it is preferable that the rubber composition further contains 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, 3-trimethoxysilylpropyl-N Examples of such compounds include sulfide-based compounds such as 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.Among these, sulfide-based silane coupling agents and mercapto-based silane coupling agents are preferred because they tend to produce better effects, and disulfide-based silane coupling agents having a disulfide bond, such as bis(3-triethoxysilylpropyl) disulfide, are more preferred.

[0085] The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, relative to 100 parts by mass of silica. When the content is within the above range, better effects tend to be obtained.

[0086] The rubber composition may contain 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. These may be used alone or in combination of two or more.

[0087] The nitrogen adsorption specific surface area (N2SA) of the carbon black is preferably 80 m 2 / g or more, more preferably 100m 2 / g or more, and preferably 150m 2 / g or less, more preferably 130m 2 Within the above range, there is a tendency for the effect to be better obtained. In this specification, the N2SA of carbon black is a value measured in accordance with JIS K6217-2:2001.

[0088] As carbon black, for example, products manufactured by Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nichika Carbon Co., Ltd., Columbia Carbon Company, etc. can be used.

[0089] The amount of carbon black is, per 100 parts by mass of the rubber component, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, particularly preferably 30 parts by mass or more, and is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 80 parts by mass or less, particularly preferably 60 parts by mass or less, and most preferably 50 parts by mass or less. Within the above ranges, the effect tends to be better obtained.

[0090] The silica and carbon black are each preferably contained in an amount of 20 parts by mass or more per 100 parts by mass of the rubber component, and more preferably contained in an amount of 30 parts by mass or more per 100 parts by mass of the rubber component. Within the above ranges, better effects tend to be obtained.

[0091] The rubber composition may contain oil. 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. These may be used alone or in combination of two or more. Among these, process oils are preferred because they provide better effects, and aromatic process oils are more preferred.

[0092] As the oil, for example, products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu KK, Fuji Kosan Co., Ltd., etc. can be used.

[0093] The oil content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 50 parts by mass or less, and more preferably 35 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained. The oil content also includes the amount of oil contained in the rubber (oil-extended rubber).

[0094] The rubber composition may contain a resin. The resin is not particularly limited as long as it is one commonly used in the tire industry, and examples thereof include rosin-based resins, coumarone-indene resins, α-methylstyrene-based resins, terpene-based resins, pt-butylphenol acetylene resins, acrylic resins, C5 resins, and C9 resins. Commercially available products include those from 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., JXTG Nippon Oil & Energy Corporation, Arakawa Chemical Industries, Ltd., Taoka Chemical Co., Ltd., and Toagosei Co., Ltd. These resins may be used alone or in combination of two or more. Among these, petroleum-based resins such as coumarone-indene resins, α-methylstyrene-based resins, pt-butylphenol acetylene resins, C5 resins, and C9 resins are preferred, with coumarone-indene resins being more preferred.

[0095] The softening point of the resin is preferably 30° C. or higher, more preferably 60° C. or higher, even more preferably 80° C. or higher, and is preferably 200° C. or lower, more preferably 160° C. or lower, even more preferably 140° C. or lower, and particularly preferably 120° C. or lower. By keeping the softening point within the above range, the above-mentioned effects tend to be more suitably obtained. In this specification, the softening point of a resin 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.

[0096] The resin content, relative to 100 parts by mass of the rubber component, is preferably 1 part by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, particularly preferably 20 parts by mass or more, most preferably 30 parts by mass or more, and most preferably 40 parts by mass or more, and is preferably 80 parts by mass or less, more preferably 60 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0097] The rubber composition may contain 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. These may be used alone or in combination of two or more. Of these, petroleum waxes are preferred, and paraffin wax is more preferred.

[0098] As the wax, for example, products from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. can be used.

[0099] The amount of wax 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 is preferably 20 parts by mass or less, more preferably 10 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0100] 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 antioxidants include p-phenylenediamine antioxidants such as quinoline; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. These antioxidants may be used alone or in combination of two or more. Among these, p-phenylenediamine antioxidants and quinoline antioxidants are preferred.

[0101] As the antioxidant, for example, products available from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis, etc. can be used.

[0102] The content of the antioxidant 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 5 parts by mass or less, per 100 parts by mass of the rubber component. Within the above ranges, the effect tends to be more favorable.

[0103] The rubber composition may contain stearic acid. As the stearic acid, conventionally known ones can be used, for example, products available from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc.

[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 5 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 may contain zinc oxide. As the zinc oxide, conventionally known products can be used, for example, products 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. can be used.

[0106] 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 5 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0107] The rubber composition may contain sulfur. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. These may be used alone or in combination of two or more.

[0108] As sulfur, for example, products from Tsurumi Chemical Industry Co., Ltd., Karuizawa Iso Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanritsu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0109] The amount of sulfur per 100 parts by mass of the rubber component is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0110] The rubber composition may contain a vulcanization accelerator. Examples of vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-orthotolylguanidine, and orthotolylbiguanidine. These may be used alone or in combination of two or more. Among these, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred because they provide more suitable effects.

[0111] As the vulcanization accelerator, for example, products manufactured by Kawaguchi Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., etc. can be used.

[0112] The content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, more preferably 7 parts by mass or less, based on 100 parts by mass of the rubber component. When the content is within the above range, the effect tends to be more favorable.

[0113] In addition to the above components, the rubber composition may further contain additives commonly used in the tire industry, such as organic peroxides, fillers such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, etc. The content of these additives is preferably 0.1 to 200 parts by mass per 100 parts by mass of the rubber component.

[0114] The rubber composition can be produced, for example, by kneading the components using a rubber kneading device such as an open roll or a Banbury mixer, followed by vulcanization.

[0115] 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.

[0116] The rubber composition can be used (as a rubber composition for tires) in tire components such as tread (cap tread), sidewall, base tread, undertread, shoulder, clinch, bead apex, breaker cushion rubber, carcass cord covering rubber, insulation, chafer, inner liner, etc., and side reinforcing layer of run-flat tires. Among these, it is preferably used in components that may come into contact with water (tread, sidewall, shoulder), and more preferably in the tread. In the case of a tread composed of a cap tread and a base tread, it can be preferably used in the cap tread. Examples of components that may come into contact with water include components (tread, sidewall, shoulder) that are located on the outermost surface of a tire when new or during running when the tire is worn.

[0117] The tire (pneumatic tire, etc.) of the present invention 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.

[0118] 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.

[0119] The above-mentioned tires are suitable for use as passenger car tires, large passenger car tires, large SUV tires, truck and bus tires, motorcycle tires, racing tires, winter tires (studless tires, snow tires, studded tires), all-season tires, run-flat tires, aircraft tires, mining tires, etc.

[0120] In the tire, the tread thickness is preferably 4 mm or more, more preferably 6 mm or more, even more preferably 8 mm or more, and particularly preferably 11 mm or more. Within the above range, the effect tends to be better. There is no particular upper limit, but it is preferably 35 mm or less, more preferably 25 mm or less, even more preferably 20 mm or less, and particularly preferably 15 mm or less.

[0121] In the above tires, the tread groove depth (the radial distance of the tire to the deepest part of the groove) is usually around 70% of the tread thickness, and is correlated with the tread thickness.

[0122] The tire preferably has a tread made of a rubber composition whose hardness changes reversibly with water and satisfies the above formulas (1) and (2), and the tread thickness is 4 mm or more, thereby enabling more favorable improvement in the overall wet grip performance and dry grip performance.

[0123] The above-mentioned tire provides the above-mentioned effects, and although the reason why such effects are obtained is not entirely clear, it is presumed as follows. As described above, the hardness changes reversibly with water, and by satisfying the above formula (1), an appropriate hardness can be obtained depending on the water condition on the road surface (wet road surface, dry road surface), thereby improving the overall wet grip performance and dry grip performance.Furthermore, by satisfying the above formula (2), the rubber composition of the present invention can obtain even better wet grip performance and dry grip performance. There is a correlation between tread thickness and groove depth, and as thickness increases, groove depth tends to also increase. Therefore, from the perspective of tread thickness, increasing the tread groove depth, i.e., increasing the tread thickness, can improve wet grip performance. As described above, the wet grip performance of the tread is improved by increasing its thickness, but the tire can more suitably improve the overall performance of dry grip performance and wet grip performance by ensuring that the thickness of the tread made from the rubber composition is within a specified range. Therefore, in the tire, the rubber composition constituting the tread has a hardness that changes reversibly with water, satisfies the above formulas (1) and (2), and further, the thickness of the tread is within a predetermined range, thereby enabling more optimal improvement in the overall performance of wet grip performance and dry grip performance. Furthermore, by using rubber whose hardness changes reversibly with water, it is possible to obtain grip performance that suits the road surface conditions, and the range of hardness of rubber that can be used in the tread is expanded, thereby improving the freedom of tread design.

[0124] In this specification, the thickness of a tread is the radial length of the part of the tread layer where the radial width of the tread layer is at its maximum when the tread is composed of one layer, and is the radial length of the part of the tread layer where the radial width of the cap tread located on the surface layer is at its maximum when the tread is composed of two layers, such as a cap tread and a base tread, which is a multi-layer tread.

[0125] In the tire, the land ratio of the tread is preferably 30% or more, more preferably 40% or more, more preferably 50% or more, and even more preferably 75% or more from the viewpoint of dry grip performance, and the upper limit is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less from the viewpoint of wet grip performance.

[0126] The tire preferably has a tread made of a rubber composition whose hardness changes reversibly with water and satisfies the above formulas (1) and (2), and the land ratio of the tread is preferably 30% or more, thereby enabling more favorable improvement in the overall wet grip performance and dry grip performance.

[0127] The above-mentioned tire provides the above-mentioned effects, and although the reason why such effects are obtained is not entirely clear, it is presumed as follows. As described above, the hardness changes reversibly with water, and by satisfying the above formula (1), an appropriate hardness can be obtained depending on the water condition on the road surface (wet road surface, dry road surface), thereby improving the overall wet grip performance and dry grip performance.Furthermore, by satisfying the above formula (2), the rubber composition of the present invention can obtain even better wet grip performance and dry grip performance. Furthermore, the dry grip performance of the tread is improved by increasing the land ratio, and the wet grip performance is improved by decreasing the land ratio. However, in the tire, the overall performance of the dry grip performance and the wet grip performance can be more suitably improved by ensuring that the land ratio of the tread made from the rubber composition is within a predetermined range. Therefore, in the tire, the rubber composition constituting the tread has a hardness that reversibly changes depending on water, satisfies the above formulas (1) and (2), and further, the land ratio of the tread is within a predetermined range, thereby enabling more optimal improvement in the overall wet grip performance and dry grip performance. Furthermore, by using rubber whose hardness changes reversibly with water, it is possible to obtain grip performance that suits the road surface conditions, and the range of hardness of rubber that can be used in the tread is expanded, thereby improving the freedom of tread design.

[0128] In this specification, if the tire is a pneumatic tire, the land ratio is calculated from the contact shape under normal load conditions with a normal rim and normal internal pressure. In the case of a non-pneumatic tire, the land ratio can be measured in the same way without requiring normal internal pressure. "Genuine rim" means a rim that is specified for each tire by the standard system that includes the standard on which the tire is based. For example, it means a standard rim in the case of JATMA, a "Design Rim" in the case of TRA, or a "Measuring Rim" in the case of ETRTO. "Normal internal pressure" refers to the air pressure specified for each tire by the above standards. In the case of JATMA, this means the maximum air pressure, in the case of TRA, it means the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it means "INFLATION PRESSURE". In the case of passenger car tires, it is 180kPa. "Normal load" refers to the load specified for each tire by the above standards, and means the load obtained by multiplying the maximum load capacity in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "LOAD CAPACITY" in the case of ETRTO by 0.88. The contact shape is obtained by assembling the tire on a standard rim, applying the standard internal pressure, and leaving it to stand at 25°C for 24 hours. Then, ink is applied to the surface of the tire tread, and the tire is pressed against cardboard under a standard load (camber angle 0°) and transferred to the paper. The tire is rotated 72° in the circumferential direction and the pattern is transferred at five locations. In other words, the contact shape is obtained five times. For the five contact shapes, the average value of the maximum length in the tire axial direction is defined as L, and the average value of the length in the direction perpendicular to the axial direction is defined as W. The land ratio is calculated as the average area of ​​the five contact shapes (ink areas) transferred onto the cardboard / (L x W) x 100 (%). Here, the average value of the length or area is the simple average of the five values.

[0129] The tread of the tire may have circumferentially continuous grooves and / or circumferentially discontinuous grooves. Examples of patterns having such grooves include rib, lug, rib-lug, and block types. [Example]

[0130] The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

[0131] (Production Example 1) Hexane, 1,3-butadiene, styrene, tetrahydrofuran, and ethylene glycol diethyl ether were charged into a nitrogen-purged autoclave reactor, followed by the addition of bis(diethylamino)methylvinylsilane and n-butyllithium as a cyclohexane solution and n-hexane solution, respectively, to initiate polymerization. The copolymerization of 1,3-butadiene and styrene was carried out for 3 hours with the stirring speed set to 130 rpm and the reactor temperature set to 65°C while continuously feeding the monomers into the reactor. The resulting polymer solution was then stirred at 130 rpm, N-(3-dimethylaminopropyl)acrylamide was added, and the reaction was carried out for 15 minutes. After the polymerization reaction was completed, 2,6-di-tert-butyl-p-cresol was added. The solvent was then removed by steam stripping, and the mixture was dried on a heated roll heated to 110°C to obtain modified styrene-butadiene rubber (SBR).

[0132] (Production Example 2) Synthesis of Polymer 1 (Epoxide-Allyl Glycidyl Ether Copolymer) 500 mL of diethyl ether was added to a nitrogen-purged glass flask, and the flask was cooled to an internal temperature of 0°C or below. 10 mL of a 0.55 mol / L triisobutylaluminum / hexane solution was then added, followed by dropwise addition of a 0.55 mol / L ethanol / diethyl ether solution so that the internal temperature did not exceed 10°C. Next, a solution prepared by mixing ethylene oxide and allyl glycidyl ether in a molar ratio of 9 / 1 to a total weight of 200 g was added dropwise so that the internal temperature did not exceed 10°C, and the mixture was stirred for 8 hours. Next, the solvent was distilled off under reduced pressure at an external temperature of 50°C / internal pressure of 1.0 kPa or less, and the remaining residue was suspended in water and filtered. The filtered residue was washed with THF and then dried under reduced pressure at 50°C / 1 kPa or less until a constant weight was reached, thereby obtaining polymer 1 in an 80% yield (infrared absorption spectrum, peaks of an ether group derived from formula (A) above and carbon-carbon peaks derived from formula (B) above were confirmed. The weight-average molecular weight (Mw) was 780,000, and the content of the group (structural unit) represented by formula (B) above in 100 mol% of the polymer was 8 mol%).

[0133] (Production Example 3) Synthesis of Polymer 2 (Amine-Allyl Glycidyl Ether Copolymer) Except for changing ethylene oxide to triglycidylamine, the same procedure as in Production Example 2 was carried out to obtain a polymer 2 of triglycidylamine and allyl glycidyl ether in an 80% yield (analysis was carried out in the same manner as in Production Example 2 to confirm the absorption of amine and peaks derived from carbon-carbon double bonds, the weight-average molecular weight was 980,000, and the content of the group (structural unit) represented by the above formula (B) in 100 mol % of the polymer was 8 mol %).

[0134] (Production Example 4) Synthesis of Polymer 3 (Silyl-Allyl Glycidyl Ether Copolymer) Except for changing ethylene oxide to triethoxysilyl glycidyl ether, the operation was carried out in the same manner as in Production Example 2 to obtain a polymer 3 of triethoxysilyl glycidyl ether and allyl glycidyl ether in a yield of 80% (the same analysis as in Production Example 2 was performed to confirm the absorption of silanol and the peak derived from the carbon-carbon double bond, the weight average molecular weight was 640,000, and the content of the group (structural unit) represented by the above formula (B) in 100 mol% of the polymer was 8 mol%).

[0135] In addition, the following evaluations were performed on the obtained polymers 1 to 3.

[0136] <Measurement of water-insoluble content> Weighed 1 g of the polymer into a glass flask, poured 10 mL of water, stirred at an internal temperature of 66 °C for 10 minutes, then continued stirring until the internal temperature reached 25 °C or lower, filtered with a filter paper made of cellulose with a mesh size of 5C, dried the residue remaining on the filter paper at a temperature of 80 °C and an internal pressure of 0.1 kPa or lower for 8 hours, measured the weight, and calculated the water-insoluble content according to the following formula. Water-insoluble content (mass%) = dry weight of residue (g) / initial weight of polymer (g) x 100

[0137] <Measurement of THF-insoluble content> Weighed 1 g of the polymer into a glass flask, poured 10 mL of tetrahydrofuran, stirred at an internal temperature of 66 °C for 10 minutes, then continued stirring until the internal temperature reached 25 °C or lower, filtered with a filter paper made of cellulose with a mesh size of 5C, dried the residue remaining on the filter paper at a temperature of 80 °C and an internal pressure of 0.1 kPa or lower for 8 hours, measured the weight, and calculated the THF-insoluble content according to the following formula. THF-insoluble content (mass%) = dry weight of residue (g) / initial weight of polymer (g) x 100

[0138] Hereinafter, various chemicals used in the examples and comparative examples will be collectively described. SBR: SBR synthesized by the above method (modified S-SBR, styrene content: 25 mass%, vinyl content: 59 mol%, non-oil product) BR: BR150B manufactured by Ube Industries, Ltd. (cis content: 97 mass%) NR:TSR20 Polymer 1: Polymer 1 synthesized by the above method (water insoluble: 96% by mass, THF insoluble: 96% by mass) Polymer 2: Polymer 2 synthesized by the above method (water insoluble: 82% by mass, THF insoluble: 96% by mass) Polymer 3: Polymer 3 synthesized by the above method (water insoluble: 92% by mass, THF insoluble: 92% by mass) Silica: ZEOSIL 1165MP (N2SA: 160m) manufactured by Rhodesia 2 / g) Carbon black: SEAT 9H (DBP oil absorption 115 ml / 100 g, N2SA: 110 m) manufactured by Tokai Carbon Co., Ltd. 2 / g) Silane coupling agent: Si75 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa Oil: Process X-140 (aromatic process oil) manufactured by Japan Energy Co., Ltd. Resin: G90 (coumarone-indene resin, softening point: 90°C) manufactured by Nitto Chemical Co., Ltd. Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. Antioxidant: Santoflex 13 (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD)) manufactured by Flexis Co., Ltd. Stearic acid: NOF Corporation's "Tsubaki" stearic acid Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Noccela NS (N-tert-butyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccelaer D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0139] 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.

[0140] The vulcanized rubber compositions thus obtained were evaluated as follows, and the results are shown in Table 1.

[0141] (Hardness of vulcanized rubber (Hs)) The Shore hardness (Hs) of the vulcanized rubber composition (test piece) was measured using a Type A durometer (JIS-A hardness) in accordance with JIS K6253-3 (2012) "Vulcanized rubber and thermoplastic rubber - Determination of hardness - Part 3: Durometer hardness." The measurement was carried out at 25°C.

[0142] (Hardness when wet with water) A vulcanized rubber composition (cuboid shape of 30 mm × 30 mm × 4 mm) was immersed in 20 ml of water at 25° C. for 6 hours to obtain a vulcanized rubber composition after wetting with water. The hardness of the obtained vulcanized rubber composition after wetting with water was measured by the above-mentioned method and was defined as the hardness when wet with water.

[0143] (Hardness when dry) The vulcanized rubber composition after wetting with water was dried under reduced pressure at 80°C and 1 kPa or less until it reached a constant weight, thereby obtaining a dried vulcanized rubber composition. The temperature of the obtained dried vulcanized rubber composition was returned to 25°C, and the hardness of the dried vulcanized rubber composition was measured by the above method and recorded as the dry hardness.

[0144] (Hardness when rehydrated) The dried vulcanized rubber composition (cuboid shape of 30 mm × 30 mm × 4 mm) was immersed in 20 ml of water at 25° C. for 6 hours to obtain a vulcanized rubber composition after rewetting with water. The hardness of the obtained vulcanized rubber composition after rewetting with water was measured by the above-mentioned method and was defined as the hardness after rewetting with water.

[0145] (tan δ when dry) The 70°C tan δ of the dried vulcanized rubber composition was measured using a viscoelasticity spectrometer VES manufactured by Iwamoto Seisakusho Co., Ltd. The measurement conditions were as follows: Measurement temperature 70℃, initial strain 10%, dynamic strain 2%, frequency 10Hz

[0146] (Wet grip performance index) The resulting unvulcanized rubber composition sheet was molded into a tread shape, laminated with other tire components, and press-vulcanized at 150°C for 15 minutes to produce a kart tire (tire size: 11 x 1.10-5). The kart tire was mounted on a kart and driven eight laps around a 2km test course on a pre-watered road surface, and the grip performance was evaluated by a test driver on a scale of 100 to 200, with Comparative Example 1 being assigned 100.

[0147] (Dry grip performance index) The resulting unvulcanized rubber composition sheet was molded into a tread shape, laminated with other tire components, and press-vulcanized at 150°C for 15 minutes to produce a kart tire (tire size: 11 x 1.10-5). The kart tire was mounted on a kart and driven eight laps around a 2-km test course on a dry road surface, and the test driver evaluated the grip performance on a scale of 100 to 200, with Comparative Example 1 being assigned a score of 100.

[0148] [Table 1]

[0149] From Table 1, it can be seen that the hardness changes reversibly with water, and the examples that satisfy the above formulas (1) and (2) can improve the overall performance of wet grip performance and dry grip performance (expressed as the sum of the two indexes of wet grip performance and dry grip performance).

[0150] (Tire manufacturing) The obtained unvulcanized rubber composition was molded into a tread shape (tread thickness shown in Table 2), laminated with other tire components, and press-vulcanized at 170°C / 12 minutes to produce a test tire (size: 195 / 65R15).

[0151] (Wet grip performance index) The test tire was mounted on a vehicle, and the vehicle was driven eight times around a 2 km test course on which water had been sprinkled on the road surface beforehand. The test driver evaluated the grip performance on a scale of 100 to 200, with Example 2-1 being set at 100. The evaluation results are shown in Table 2.

[0152] (Dry grip performance index) The test tire was mounted on a vehicle, which ran eight laps around a test course with a lap length of 2 km on a dry road surface, and the test driver evaluated the grip performance on a scale of 100 to 200, with Example 2-1 being set at 100. The evaluation results are shown in Table 2.

[0153] [Table 2]

[0154] From Table 2, it can be seen that a tire having a tread made of a rubber composition whose hardness changes reversibly with water and which satisfies the above formulas (1) and (2), and whose tread thickness is 4 mm or more, can more suitably improve the overall performance of wet grip performance and dry grip performance (expressed as the sum of the two indexes of wet grip performance and dry grip performance).

[0155] (Tire manufacturing) The obtained unvulcanized rubber composition was molded into a tread shape (land ratio shown in Table 3), laminated with other tire components, and press-vulcanized at 170°C / 12 minutes to produce a test tire (size: 195 / 65R15).

[0156] (Land ratio measurement) The land ratio (%) was measured using the JATMA standard according to the method for measuring the land ratio described in this specification. The measurement results are shown in Table 3.

[0157] (Wet grip performance index) The test tire was mounted on a vehicle, and the vehicle was driven eight times around a 2 km test course on which water had been sprinkled on the road surface beforehand. The test driver evaluated the grip performance on a scale of 100 to 200, with Example 3-1 being set at 100. The evaluation results are shown in Table 3.

[0158] (Dry grip performance index) The test tire was mounted on a vehicle, which ran eight laps around a test course with a lap length of 2 km on a dry road surface, and the test driver evaluated the grip performance on a scale of 100 to 200, with Example 3-1 being set at 100. The evaluation results are shown in Table 3.

[0159] [Table 3]

[0160] From Table 3, it can be seen that a tire having a tread made of a rubber composition whose hardness changes reversibly with water and which satisfies the above formulas (1) and (2), and whose tread has a land ratio of 30% or more, can more suitably improve the overall wet grip performance and dry grip performance (expressed as the sum of the two indexes of wet grip performance and dry grip performance).

Claims

1. a rubber component containing an isoprene-based rubber, a butadiene rubber, and a styrene-butadiene rubber; a polymer having a carbon-carbon double bond and an oxygen atom, A rubber composition whose hardness changes reversibly with water and satisfies the following formulas (1) and (2): Hardness when dry - Hardness when wet with water ≧ 1 (1) (In the formula, the hardness is the JIS-A hardness of the rubber composition at 25°C.) tanδ at 70 ° C. when dry ≧ 0.18 (2) (In the formula, tan δ at 70°C is the loss tangent measured under the conditions of 70°C, initial strain of 10%, dynamic strain of 2%, and frequency of 10 Hz.)

2. Petroleum-based resins, A diene rubber, a polymer having a carbon-carbon double bond and an oxygen atom, A rubber composition whose hardness changes reversibly with water and satisfies the following formulas (1) and (2): Hardness when dry - Hardness when wet with water ≧ 1 (1) (In the formula, the hardness is the JIS-A hardness of the rubber composition at 25°C.) tanδ at 70 ° C. when dry ≧ 0.18 (2) (In the formula, tan δ at 70°C is the loss tangent measured under the conditions of 70°C, initial strain of 10%, dynamic strain of 2%, and frequency of 10 Hz.)

3. 3. The rubber composition according to claim 1, wherein in the formula (1), the value of dry hardness minus wet hardness is 4 or more.

4. 4. The rubber composition according to claim 1, wherein in the formula (2), tan δ at 70° C. in a dry state is 0.21 or more.

5. The rubber composition according to any one of claims 1 to 4, further comprising a hydrophilic material.

6. The rubber composition according to any one of claims 1 to 5, wherein the content of the styrene-butadiene rubber in 100% by mass of the rubber component is 95% by mass or less.

7. The rubber composition according to any one of claims 1 to 6, wherein the relationship of the content of the styrene-butadiene rubber in 100% by mass of the rubber component > 50% by mass > the content of the butadiene rubber in 100% by mass of the rubber component > the content of the isoprene-based rubber in 100% by mass of the rubber component is satisfied.

8. 8. The rubber composition according to claim 1, further comprising 20 parts by mass or more of silica and carbon black, each of which is 20 parts by mass or more per 100 parts by mass of the rubber component.

9. The rubber composition according to any one of claims 1 to 8, which is a rubber composition for a tread.

10. A tire having a tire component at least partly constituted by the rubber composition according to any one of claims 1 to 9.

11. The tire according to claim 10, wherein the tire component is a tread, and the tread has a thickness of 4 mm or more.

12. The tire according to claim 10 or 11, wherein the tire component is a tread, and the land ratio of the tread is 30% or more.

13. The tire according to any one of claims 10 to 12, wherein the tire component is a tread, and the tire has a groove that is continuous in the tire circumferential direction and / or a groove that is discontinuous in the tire circumferential direction.

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