Motorcycle tires

Abstract

To provide a two-wheeled vehicle tire which is excellent in low fuel consumption performance and grip performance.SOLUTION: A two-wheeled vehicle tire comprises a pair of bead parts and a pair of side wall parts, and a tread part which is continuous with both side wall parts and comprises one or more rubber layers including at least a rubber layer constituting an outermost surface, and has a tire outer diameter Dt (mm) of 580 mm or more. In the two-wheeled vehicle tire, the Dt and a tanδ value 70°Ctanδ at 70°C and a tanδ value 40°Ctanδ at 40°C of a rubber composition forming the rubber layer constituting the outermost surface of the tread part satisfy the following formula (1) : (Dt / 450)-0.50≤70°Ctanδ / 40°Ctanδ.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to motorcycle tires. [Background technology]

[0002] Since grip performance during cornering is crucial for motorcycle tires, various types of tires have been developed to meet this requirement (Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2016-222247 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, generally speaking, improving grip performance comes at the expense of fuel efficiency, and it is difficult to improve both simultaneously. Furthermore, with larger diameter tires, the contact area differs between straight-line driving and cornering, requiring performance tailored to each situation.

[0005] This disclosure aims to provide a motorcycle tire that offers excellent overall performance in terms of fuel efficiency and grip. [Means for solving the problem]

[0006] This disclosure relates to the following motorcycle tires. A motorcycle tire comprising a pair of bead portions and a pair of sidewall portions, and a tread portion consisting of one or more rubber layers, including at least one rubber layer that forms the outermost surface and is connected to both sidewall portions, and having an outer diameter Dt (mm) of 580 mm or more, A motorcycle tire in which the above-mentioned Dt and the tanδ value at 70°C (70°Ctanδ) and the tanδ value at 40°C (40°Ctanδ) of the rubber composition forming the rubber layer constituting the outermost surface of the tread portion satisfy the following equation. (Dt / 450)-0.50≦70℃tanδ / 40℃tanδ (1) [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a motorcycle tire that has excellent overall performance in terms of fuel efficiency and grip performance. [Brief explanation of the drawing]

[0008] [Figure 1] This is an example of a planar cross-sectional view of a motorcycle tire according to the present disclosure, including the tire rotation axis. [Figure 2] This is an example of an exploded view of the tread portion of a motorcycle tire according to the present disclosure. [Figure 3] This is an example of an exploded view of the tread portion of a motorcycle tire according to the present disclosure. [Modes for carrying out the invention]

[0009] While not intended to be constrained by theory, the following mechanisms are considered in this disclosure to improve the overall performance of fuel efficiency and grip performance. Specifically, in motorcycles, the crown region of the tread is heated while the shoulder region is air-cooled during straight-line driving. In large-diameter tires with an outer diameter of 580 mm or more, the temperature difference between the crown region and the shoulder region becomes larger. When the vehicle is banked by turning from this state, both the crown region and the shoulder region make contact with the ground. At this time, if the difference between the high temperature (70°C) tanδ and the low temperature (40°C) tanδ is small, grip can be obtained across the entire area in contact with the ground, thus improving overall grip performance. On the other hand, when straightening the vehicle from a banked state and driving straight, the rolling resistance of the contact area during turning, which was rapidly heated during turning, increases. At this time, if the difference between the high temperature (70°C) tanδ and the low temperature (40°C) tanδ is small, the rapid increase in rolling resistance can be suppressed, thus improving fuel efficiency. Based on the above, it is considered that the overall performance of grip performance and fuel efficiency can be improved.

[0010] It is preferable that the 70°C tanδ and the 40°C tanδ satisfy the following formula. This is because the effects of the present disclosure are more easily achieved. 70°C tanδ / 40°C tanδ ≥ 0.80 (2)

[0011] It is preferable that the 70°C tanδ satisfy the following formula. This is because the effects of the present disclosure are more easily achieved. 70°C tanδ ≥ 0.20 (3)

[0012] It is preferable that the 40°C tanδ satisfy the following formula. This is because the effects of the present disclosure are more easily achieved. 40°C tanδ ≤ 0.25 (4)

[0013] It is preferable that the rubber layer constituting the outermost surface of the tread portion is not substantially divided in the tire width direction. By not being substantially divided, the effects of the present disclosure, such as the comprehensive performance of grip performance and low fuel consumption performance, are more easily exhibited.

[0014] The rubber composition contains a gelling agent, an oil, and a resin, and it is preferable that the ratio (mass%) of the gelling agent to the total of the oil and the resin is 5.0 mass% or more. This is because the effects of the present disclosure are more easily achieved.

[0015] The rubber composition contains a filler, and it is preferable that the filler contains 40.0 mass% or more of silica. This is because the effects of the present disclosure are more easily achieved.

[0016] The rubber composition contains a rubber component, and it is preferable that the rubber component contains 70 mass% or more of styrene-butadiene rubber. This is because the effects of the present disclosure are more easily achieved.

[0017] It is preferable that the resin contains an aromatic petroleum resin. This is because the effects of the present disclosure are more easily achieved.

[0018] The rubber composition preferably contains a vulcanization accelerator, and the vulcanization accelerator preferably contains a sulfenamide-based vulcanization accelerator and a guanidine-based vulcanization accelerator, because the effects of this disclosure are more easily achieved.

[0019] The aforementioned rubber composition preferably contains sulfur, as this makes it easier to achieve the effects of this disclosure.

[0020] It is preferable that the tread surface of the tread portion has shallow grooves. This is because it promotes wear of the tread portion of a new tire, allowing it to perform at an earlier stage, and also allows for visual confirmation that the tire has worn down to the point where it can perform at its best. Furthermore, it improves drainage, and the land portion partitioned by the grooves moves easily, promoting heat generation and thus improving grip performance.

[0021] In this disclosure, the upper and lower numerical limits indicated by "greater than or equal to," "less than or equal to," and "~" in numerical range descriptions are arbitrary combinations of numbers, and in addition, the numerical values ​​in the examples can also be combined with these upper and lower limits. Furthermore, when a numerical range is specified by "~", unless otherwise specified, it means that the numerical values ​​at both ends of that range are included. Moreover, in this disclosure, a numerical range shown as including the values ​​at both ends is understood to simultaneously indicate a numerical range that does not include either of the values ​​at either end, and even a numerical range that does not include either of the values ​​at either end, unless this does not contradict the intent of this disclosure.

[0022] [Definition] Unless otherwise specified, the "dimensions of each part of the tire" refer to the values ​​specified in the standard unloaded condition, when the tire is mounted on a standard rim and filled with the standard internal pressure.

[0023] A "standard rim" refers to the rim specified for each tire within the standard system that includes the standard on which the tire is based. For example, for JATMA (Japan Automobile Tire Manufacturers Association), it refers to the standard rim for the applicable size listed in the "JATMA YEAR BOOK," for ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" listed in the "STANDARDS MANUAL," and for TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "YEAR BOOK." In the case of tires not specified in the standard, it refers to the rim with the smallest diameter and narrowest rim width among rims that can be mounted on and can maintain internal pressure, i.e., rims that do not cause air leakage between the rim and tire.

[0024] "Regular internal pressure" refers to the air pressure specified for each tire by each standard within the tire standard system, including the standard on which the tire is based. For example, it is the "maximum air pressure" for JATMA, the "maximum value" listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO.

[0025] "Regular load" refers to the load specified in the standards system, including the standard on which the tire is based. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are all regular loads.

[0026] "Tire outer diameter (Dt)" refers to the length (mm) of the tire's cross-section in its normal state.

[0027] The "crown area" refers to the region of the tread that makes contact with the ground when driving straight.

[0028] The "shoulder region" refers to the area of ​​the tread located on the outer side of the crown region in the tire width direction. There is a pair of shoulder regions on the outside of the crown region.

[0029] "The rubber layer constituting the outermost surface of the tread is not substantially divided in the tire width direction" means that the outermost surface of the tread is composed of this rubber layer in an area of ​​90% or more in the tire width direction.

[0030] [Measurement method] For the "70℃tanδ" test, a viscoelasticity measurement sample measuring 20mm in length, 4mm in width, and 1mm in thickness is taken from within the rubber layer of the tread area of ​​each test tire, with the tire circumference as the longer side. The loss tangent tan is measured using a GABO Iplexer series under the conditions of 70℃ temperature, 10% initial strain, 1% dynamic strain, 10Hz frequency, and extension mode. The thickness direction of the sample is the tire radius direction.

[0031] "40°C tanδ" is measured in the same way as 70°C tanδ, except that the measurement temperature is set to 40°C.

[0032] "Styrene content" is, 1 It is calculated by 1H-NMR measurement.

[0033] The "vinyl bond content (amount of 1,2-bonded butadiene units)" is measured according to JIS K 6239-2:2017.

[0034] The "glass transition temperature" is a value measured in accordance with JIS K 7121 using a differential scanning calorimeter (Q200) manufactured by T.A. Instruments Japan Co., Ltd., under conditions of a heating rate of 10°C / min.

[0035] The "weight-average molecular weight (Mw)" can be determined by converting the measured value obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M manufactured by Tosoh Corporation) to standard polystyrene equivalent.

[0036] The "cis content (amount of cis-1,4-bonded butadiene units)" is measured according to JIS K 6239-2:2017.

[0037] "N2SA of silica" is a value measured by the BET method in accordance with ASTM D3037-93.

[0038] The "N2SA of carbon black" is a value determined according to JIS K 6217-2:2017.

[0039] The DBP of carbon black is measured in accordance with JIS K 6217-4:2017.

[0040] The "softening point" is the temperature at which the sphere descends when the softening point specified in JIS K 6220-1:2015 is measured using a ring-type softening point measuring device.

[0041] The "SP value of a resin" refers to the solubility parameter calculated using the Hoy method based on its structure. The Hoy method is a calculation method described, for example, in KL Hoy's "Table of Solubility Parameters," Solvent and Coatings Materials Research and Development Department, Union Carbites Corp. (1985).

[0042] [Tires for motorcycles] The following describes the motorcycle tires of this disclosure. Here, motorcycle tires refer to tires intended to be mounted on motorcycles. Drawings will be used as appropriate in the explanation, but these drawings are examples of embodiments, and this disclosure should not be interpreted as being limited by these drawings.

[0043] The motorcycle tire of this disclosure comprises a pair of bead portions and a pair of sidewall portions, and a tread portion consisting of one or more rubber layers, including at least one rubber layer that is connected to both sidewall portions and constitutes the outermost surface, and has an outer diameter Dt (mm) of 580 mm or more.

[0044] Figure 1 is an example of a planar cross-sectional view of a motorcycle tire including the tire rotation axis. The motorcycle tire 1 comprises a pair of bead portions 4 and a pair of sidewall portions 3, and a tread portion 2 made of a rubber layer that is continuous with both sidewall portions and forms the outermost surface. In the above cross-section, the tread surface 2A of the tread portion 2 that contacts the road surface is convex and curves in an arc outward in the radial direction of the tire. The outer end of the tread surface 2A in the tire axial direction is the tread end 2e. Tread rubber 2B is arranged in the tread portion 2 radially outside the belt layer 5. In this embodiment, the tread rubber 2B constitutes the area from the outer surface of the belt layer 5 to the tread surface 2A. The tire outer diameter is shown as Dt.

[0045] <Tire outer diameter> The motorcycle tire disclosed herein has an outer diameter Dt (mm) of 580 mm or more. With motorcycle tires having such a large outer diameter, the contact area differs between straight-line driving and cornering, requiring performance tailored to each situation. However, this disclosure aims to improve the overall performance of fuel efficiency and grip performance even with a large tire outer diameter. The tire outer diameter is preferably 585 mm or more, more preferably 590 mm or more, even more preferably 595 mm or more, even more preferably 600 mm or more, and even more preferably 620 mm or more. On the other hand, there is no particular upper limit on the tire outer diameter in this disclosure, but it is usually around 700 mm.

[0046] <Tread section> (Formula (1)) The tread portion of the motorcycle tire of this disclosure is such that Dt (mm) and the tanδ value at 70°C (70°Ctanδ) and the tanδ value at 40°C (40°Ctanδ) of the rubber composition forming the rubber layer constituting the outermost surface of the tread portion satisfy the following equation. (Dt / 450)-0.50≦70℃tanδ / 40℃tanδ (1)

[0047] In equation (1), the value on the left side is determined by the value of Dt (mm). For example, the value on the left side of equation (1) is 0.79 when Dt is 580 mm, and 0.88 when Dt is 620 mm. Therefore, as the tire outer diameter (Dt) increases, the value on the right side of equation (1) is required to be a larger value. However, in this disclosure, it is preferable from the viewpoint of the effects of this disclosure that the difference between 70°C tanδ and 40°C tanδ becomes smaller, that is, that the value on the right side becomes a value close to 1.

[0048] The difference between 70°C tanδ and 40°C tanδ can be adjusted by conventional methods. In this disclosure, for example, this difference can be reduced by increasing the amount of gelling agent. Alternatively, the difference can also be reduced by increasing the amount of oil, increasing the amount of carbon black, or increasing the amount of resin such as petroleum resin that is incompatible with rubber components.

[0049] In the above equation (1), the difference between the right-hand side and the left-hand side is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.10 or more. A larger difference tends to result in improved grip performance.

[0050] (Formula (2)) It is preferable that the following equations are satisfied for 70°C tanδ and 40°C tanδ. 70℃tanδ / 40℃tanδ≧0.80 (2)

[0051] From the viewpoint of the effects of this disclosure, the value of 70°C tanδ / 40°C tanδ is more preferably 0.82 or higher, even more preferably 0.84 or higher, even more preferably 0.86 or higher, even more preferably 0.88 or higher, and even more preferably 0.90 or higher. On the other hand, the upper limit of this value is approximately 1.00. Here, "approximately" means that a variation of ±2% is permitted.

[0052] (Formula (3)) It is preferable that tanδ at 70°C satisfies the following equation. 70℃ tanδ≧0.20 (3)

[0053] From the viewpoint of grip performance, the 70°C tanδ value is preferably 0.21 or higher, preferably 0.22 or higher, preferably 0.23 or higher, or preferably 0.24 or higher. On the other hand, there is no particular upper limit to this value from the viewpoint of grip performance, but it is usually 0.40 or lower.

[0054] The value of 70℃ tanδ can be adjusted by conventional methods, and in this disclosure, for example, it can be increased by increasing the amount of carbon black blended or increasing the amount of petroleum resin.

[0055] (Formula (4)) It is preferable that tanδ at 40°C satisfies the following equation. 40℃ tanδ ≤ 0.25 (4)

[0056] From the viewpoint of fuel efficiency, the value of tanδ at 40°C is preferably 0.24 or less, preferably 0.23 or less, or preferably 0.22 or less. On the other hand, there is no particular lower limit to this value from the viewpoint of fuel efficiency, but it is usually 0.15 or more.

[0057] The value of 40℃ tanδ can be adjusted by conventional methods, and in this disclosure, for example, it can be reduced by increasing the amount of oil blended or increasing the blending ratio of silica in the filler.

[0058] (Rubber layer of the tread) The tread portion is not particularly limited as long as the rubber composition forming its outermost rubber layer satisfies formula (1) above. Therefore, even if the tread portion is composed of multiple rubber layers in the tire radial direction, it is sufficient that at least the outermost layer (the rubber layer constituting the outermost surface of the tread portion) satisfies formula (1), and even if the outermost rubber layer of the tread portion is substantially divided in the tire width direction, it is sufficient that all the rubber constituting the outermost rubber layer satisfies formula (1) above. Of these, in this disclosure, it is preferable that the tread portion is composed of a single rubber layer in the tire radial direction, and it is preferable that the outermost rubber layer of the tread portion is not substantially divided in the tire width direction. This is because this is an embodiment that can exert the effects of this disclosure.

[0059] (Tread surface) Shallow grooves may be formed on the tread surface of the tread portion. Here, shallow grooves refer to grooves with a width of 0.1 to 2.0 mm and a depth of 0.1 to 2.0 mm. The direction in which these shallow grooves are formed is not particularly limited and may be in the circumferential direction of the tire, the width direction of the tire, or any other direction, or in two or more different directions. Shallow grooves in the circumferential direction of the tire may be formed in an annular shape. The width of the shallow grooves may be constant or may vary in the direction of extension. On the other hand, it is preferable that the depth of the shallow grooves be constant.

[0060] In a preferred embodiment, the shallow grooves are formed in one direction, such as the circumferential direction of the tire or the width direction of the tire, and if they are formed in two or more different directions, they do not intersect with each other. Such shallow grooves promote the wear of the tread portion of a new tire, allowing it to achieve its performance sooner, and also allow for visual confirmation that the tire has worn down to the point where it can perform at its best.

[0061] In another preferred embodiment, the shallow grooves are preferably formed in two different directions in the shoulder region of the tread, with at least a portion of these shallow grooves intersecting and at least a portion of these shallow grooves opening at the tread edge. Such shallow grooves improve drainage and also improve grip performance because the land area partitioned by the grooves moves easily and promotes heat generation.

[0062] Figure 2 is an example of an unfolded view of the tread portion of a motorcycle tire according to the present disclosure. In Figure 2, an annular circumferential shallow groove 2a is formed in the circumferential direction of the tire, and a widthwise shallow groove 2b is formed in the width direction of the tire. The circumferential shallow groove 2a and the widthwise shallow groove 2b do not intersect with each other, and the widthwise shallow groove 2b does not open at the tread edge. As described above, such shallow grooves promote the wear of the tread portion of a new tire, allowing it to exhibit its performance earlier, and also allow visual confirmation that it has worn down to the point where it can exhibit its performance.

[0063] Figure 3 is an example of an unfolded view of the tread portion of a motorcycle tire according to the present disclosure. In Figure 3, a grid-like shallow groove 2c and a grid-like shallow groove 2d are formed in the shoulder region of the tread portion, extending in two different directions. These shallow grooves intersect with each other and open at the tread edge. As described above, such shallow grooves improve drainage and also improve grip performance because the land area partitioned by the grooves moves easily, promoting heat generation.

[0064] [Rubber composition] The following describes the compounding and manufacturing method of the rubber composition that forms the rubber layer constituting the outermost surface of the tread.

[0065] <Rubber components> The rubber composition preferably contains a rubber component, and the rubber component preferably contains a diene rubber. The content of the diene rubber in the rubber component is preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass.

[0066] (Diene-based rubber) Examples of diene rubbers include styrene-butadiene rubber (SBR), butadiene rubber (BR), and isoprene rubber. The diene rubber preferably contains SBR, but may consist solely of SBR.

[0067] ≪SBR≫ The type of SBR used is not particularly limited; for example, emulsion-polymerized SBR (E-SBR), solution-polymerized SBR (S-SBR), and other types commonly used in the tire industry can be used. One or more types of SBR can be used.

[0068] Furthermore, as SBR, either unmodified SBR or modified SBR can be used. Modified SBR can be any of the types commonly used in the tire industry, including those with functional groups that interact with fillers such as silica. Examples of such SBRs include terminally modified SBRs in which at least one end of the SBR is modified with a compound (modifier) ​​having the following functional group; main-chain modified SBRs in which the main chain has the following functional group; main-chain terminally modified SBRs in which the main chain and terminals have the following functional groups (for example, a main-chain terminally modified SBR in which the main chain has the following functional group and at least one end is modified with a compound (modifier) ​​having the following functional group); and terminally modified SBRs that are modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule, and in which hydroxyl groups or epoxy groups are introduced.

[0069] Examples of the above-mentioned functional groups include amino groups (preferably amino groups in which the hydrogen atoms of the amino group are substituted with C1-C6 alkyl groups), amide groups, silyl groups, alkoxysilyl groups (preferably C1-C6 alkoxysilyl groups), isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, thiocarbonyl groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups (preferably C1-C6 alkoxy groups), hydroxyl groups, oxy groups, epoxy groups, and the like. These functional groups may also have substituents. Examples of substituents include those into which functional groups such as amino groups, amide groups, alkoxysilyl groups, carboxyl groups, and hydroxyl groups have been introduced.

[0070] Furthermore, modified SBRs include those obtained by further hydrogenating, epoxidizing, or tin-modifying the above-mentioned unmodified or modified SBRs. Among these, SBR obtained by further hydrogenating the above-mentioned modified SBR (modified hydrogenated SBR) is preferred. Hydrogenated SBR is preferable from the viewpoint of the effects of this disclosure because it improves the mobility of the molecular chain by reducing the number of double bonds and increasing the number of single bonds, thereby improving the entanglement effect between polymers and tending to increase reinforcing properties.

[0071] For SBR, either oil-expanded SBR or non-oil-expanded SBR can be used. When using oil-expanded SBR, the amount of oil expanded in the SBR, that is, the amount of oil-expanding oil contained in the SBR, is preferably 10 to 50 parts by mass per 100 parts by mass of rubber solids in the SBR.

[0072] For example, SBR manufactured and sold by companies such as Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Co., Ltd. can be used.

[0073] The styrene content of SBR is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, for the reason that the effects of this disclosure are more favorably obtained. Furthermore, the styrene content is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. The styrene content of SBR is determined by the measurement method described above.

[0074] The amount of vinyl bonded to SBR (amount of 1,2-bonded butadiene units) is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 15 mol% or more, for the reasons that the effects of this disclosure are more favorably obtained. Furthermore, the amount of vinyl bonded is preferably 80 mol% or less, more preferably 60 mol% or less, and even more preferably 40 mol% or less. The amount of vinyl bonded to SBR is determined by the measurement method described above.

[0075] The glass transition temperature (Tg) of SBR is preferably -90°C or higher, more preferably -70°C or higher, and even more preferably -60°C or higher, for the reason that the effects of this disclosure are more favorably obtained. Furthermore, the Tg is preferably 0°C or lower, more preferably -10°C or lower, even more preferably -15°C or lower, even more preferably -20°C or lower, and even more preferably -25°C or lower. The glass transition temperature of SBR is determined by the measurement method described above.

[0076] The weight-average molecular weight (Mw) of SBR is preferably 200,000 or more, more preferably 300,000 or more, even more preferably 400,000 or more, and even more preferably 450,000 or more, for the reasons that the effects of this disclosure are more favorably obtained. Furthermore, the Mw is preferably 2,000,000 or less, more preferably 1,000,000 or less, even more preferably 800,000 or less, and even more preferably 700,000 or less. The weight-average molecular weight (Mw) of SBR is determined by the measurement method described above.

[0077] The SBR content in 100% by mass of the rubber component is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. Alternatively, the SBR content may be 100% by mass. In the case of oil-extracted SBR, the SBR content refers to the amount of SBR itself, excluding the oil used for oil-extraction.

[0078] ≪BR≫ The BR is not particularly limited, and for example, BR with a cis-1,4 bond content (cis content) of 90 mol% or more (high-cis BR), rare-earth butadiene rubber synthesized using a rare-earth element catalyst (rare-earth BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc., which are common in the tire industry, can be used. Of these, high-cis BR is preferred. One or more types of BR can be used.

[0079] Examples of high-cis BR include those manufactured by Nippon Zeon Co., Ltd., Ube Industries, Ltd., and JSR Corporation. The cis content of high-cis BR is preferably 95 mol% or more, more preferably 96 mol% or more, and even more preferably 97 mol% or more. The cis content of BR can be determined by the measurement method described above.

[0080] Rare earth-based BRs are synthesized using rare earth element catalysts, and the vinyl bond content (amount of 1,2-linked butadiene units) is preferably 1.8 mol% or less, more preferably 1.6 mol% or less, and even more preferably 1.2% mol or less. The cis content (cis-1,4 bond content) is preferably 95 mol% or more, more preferably 96% mol or more, and even more preferably 97 mol or more. As rare earth-based BRs, for example, those manufactured by Lanxess can be used.

[0081] SPB-containing BR refers to a type in which 1,2-syndiotactic polybutadiene crystals are not simply dispersed in BR, but are chemically bonded to and dispersed in BR. Examples of such SPB-containing BR include those manufactured by Ube Industries, Ltd.

[0082] Modified BRs include those that have undergone the same modifications as described above for SBRs. Other examples of modified BRs include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound (tin-modified BR), and butadiene rubber having a condensed alkoxysilane compound at its active end (silica-modified BR). Examples of such modified BRs include those manufactured by ZS Elastomer Co., Ltd.

[0083] The glass transition temperature (Tg) of BR is preferably -130°C or higher, more preferably -120°C or higher, and even more preferably -110°C or higher, for the reason that the effects of this disclosure are more favorably obtained. Furthermore, the Tg is preferably 0°C or lower, more preferably -40°C or lower, even more preferably -60°C or lower, even more preferably -80°C or lower, and even more preferably -90°C or lower. The glass transition temperature of BR is determined by the measurement method described above.

[0084] The BR content in 100% by mass of the rubber component is preferably 40% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less. There is no particular limit to the lower limit of the BR content; it may be 0% by mass or, for example, 5% by mass or more.

[0085] Isoprene-based rubber As isoprene-based rubbers, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. Natural rubber includes not only unmodified natural rubber (NR), but also modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. These isoprene-based rubbers may be used individually or in combination of two or more types.

[0086] NR is not particularly limited and can be any tire that is common in the tire industry, such as SIR20, RSS#3, and TSR20.

[0087] The content of isoprene-based rubber in the rubber component is preferably 40% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less. There is no particular limit to the lower limit of the isoprene-based rubber content; it may be 0% by mass or, for example, 5% by mass or more.

[0088] <<Other Diene-based Rubbers>> The rubber component may contain other diene-based rubber components other than the aforementioned SBR, BR, and isoprene-based rubbers. Other diene-based rubber components can include crosslinkable rubber components commonly used in the rubber industry, such as styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isobutylene-styrene block copolymer (SIBS), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), and polynorbornene rubber. These other rubber components may be used individually or in combination of two or more.

[0089] (Rubber components other than diene-based rubbers) The rubber component may include non-diene rubber. Examples of non-diene rubbers include butyl rubber (IIR), hydrogenated nitrile rubber (HNBR), ethylene propylene rubber, silicone rubber, polyethylene chloride rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber. Non-diene rubbers may be used alone or in combination of two or more types.

[0090] <Filler> The rubber composition preferably contains a filler. Any filler commonly used in the rubber industry can be used. Examples of such fillers include silica, carbon black, aluminum hydroxide, alumina (aluminum oxide), clay, calcium carbonate, and mica. One or more types of fillers can be used.

[0091] (silica) The silica used is not particularly limited; for example, silica prepared by a dry process (anhydrous silica) or silica prepared by a wet process (hydrated silica), which are common in the tire industry, can be used. Among these, hydrated silica prepared by a wet process is preferred because it contains a large number of silanol groups. Silica may be used alone or in combination of two or more types.

[0092] The nitrogen adsorption specific surface area (N2SA) of silica is 140 m², from the perspective of low fuel consumption and wear resistance. 2 Preferably 160m / g or more. 2 More preferably 170m / g or more, 2 A value of 350m or more is even more preferable. Furthermore, from the viewpoint of low fuel consumption and processability, 350m 2 Preferably less than / g, 300m 2 More preferably less than / g, 250m 2 A value of less than or equal to / g is even more preferable. The N2SA of silica in this specification is determined by the measurement method described above.

[0093] From the viewpoint of the effects of this disclosure, the silica content per 100 parts by mass of rubber component is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 55 parts by mass or more, and even more preferably 60 parts by mass or more. Furthermore, from the viewpoint of wear resistance performance, it 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, and even more preferably 100 parts by mass or less.

[0094] In the present disclosure, when the filler contains silica, from the perspective of the effects of the present disclosure, the filler preferably contains 40.0% by mass or more of silica, more preferably 50.0% by mass or more, still more preferably 60.0% by mass or more, still more preferably 70.0% by mass or more, still more preferably 80.0% by mass or more, still more preferably 90.0% by mass or more, still more preferably 94.0% by mass or more. The silica may be 100% by mass, or may be, for example, 97.0% by mass or less, or 95.0% by mass or less.

[0095] (Carbon black) As the carbon black, those commonly used in the rubber industry can be appropriately used, and examples thereof include GPF, FEF, HAF, ISAF, SAF, etc., or N110, N115, N120, N125, N134, N135, N219, N220, N231, N234, N293, N299, N326, N330, N339, N343, N347, N351, N356, N358, N375, N539, N550, N582, N630, N642, N650, N660, N683, N754, N762, N765, N772, N774, N787, N907, N908, N990, N991, etc. As commercially available products, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nippon Chemical Carbon Co., Ltd., Columbian Carbon Co., etc. can be used. These may be used alone or in combination of two or more.

[0096] The nitrogen adsorption specific surface area (N2SA) of the carbon black is preferably 40 m 2 / g or more, more preferably 50 m 2 / g or more, still more preferably 70 m 2 / g or more, still more preferably 100 m 2 / g or more, still more preferably 120 m 2 / g or more from the perspective of wear resistance performance, grip performance, etc. Further, the N2SA is preferably 300 m 2 / g or less, more preferably 250 m 2 / g or less, still more preferably 200 m2 More preferably less than / g, 160m 2 A value of less than / g is even more preferable. The N2SA of carbon black can be determined by the measurement method described above.

[0097] From the viewpoint of sufficient reinforcement, the dibutyl phthalate (DBP) oil absorption of carbon black is preferably 50 ml / 100g or more, and more preferably 100 ml / 100g or more. Furthermore, from the viewpoint of wet grip performance, the DBP of carbon black is preferably 200 ml / 100g or less, and more preferably 150 ml / 100g or less. The DBP of carbon black is determined by the measurement method described above.

[0098] From the viewpoint of good UV crack resistance and good abrasion resistance, the carbon black content 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, even more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, even more preferably 25 parts by mass or more, and even more preferably 30 parts by mass or more, per 100 parts by mass of rubber component. Furthermore, from the viewpoint of processability and heat generation, the content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 100 parts by mass or less, even more preferably 70 parts by mass or less, even more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less.

[0099] The total content of the filler is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, per 100 parts by mass of the rubber component, from the viewpoint of sufficient reinforcement. On the other hand, from the viewpoint of wet grip performance, the content is preferably 250 parts by mass or less, more preferably 180 parts by mass or less, and even more preferably 150 parts by mass or less.

[0100] As a filler other than silica, carbon black is preferred. Suitable fillers include, for example, those containing silica, those consisting solely of silica, those containing silica and carbon black, and those consisting solely of silica and carbon black.

[0101] (Silane coupling agent) The rubber composition preferably uses a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent conventionally used in the rubber industry can be used. Specific examples of silane coupling agents include, for example, silane coupling agents having a sulfide group such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; silane coupling agents having a mercapto group such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane; silane coupling agents having a thioester group such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane; and vinyl. Examples include silane coupling agents having vinyl groups such as triethoxysilane and vinyltrimethoxysilane; silane coupling agents having amino groups such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, silane coupling agents having sulfide groups, silane coupling agents having mercapto groups, and silane coupling agents having thioester groups are preferred, silane coupling agents having sulfide groups are more preferred, and bis(3-triethoxysilylpropyl)tetrasulfide is particularly preferred. These silane coupling agents may be used individually or in combination of two or more.

[0102] From the viewpoint of sufficient chipping resistance, the content of the silane coupling agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of silica. Furthermore, from the viewpoint of the blending effect commensurate with the content, the content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less, per 100 parts by mass of silica.

[0103] (Gelling agent) In this disclosure, the gelling agent can be used without particular limitation as long as it is a component that gels in oil at temperatures below 70°C and liquefies at temperatures above 70°C. When a gelling agent is incorporated, due to this property of the gelling agent, the tread rubber may generate less heat during straight-line driving when the tread temperature is around 60°C because the gelling agent gels in the oil, while generating more heat during cornering when the tread temperature is 80-100°C because the gelling agent liquefies in the oil. Therefore, it can contribute to reducing the difference between 40°C tanδ and 70°C tanδ.

[0104] As a gelling agent, any compound can be used regardless of the gelling mechanism, but examples include compounds in which gelling / liquefaction is switched by intermolecular interactions such as hydrogen bonding. More specifically, examples include compounds in which OH groups or COOH groups present in the molecule are responsible for these intermolecular interactions. For example, a compound having OH groups and COOH groups in its molecule will gel at low temperatures by forming a network-like higher-order structure through association of the OH groups and COOH groups. On the other hand, at high temperatures, this association will dissociate, and the compound will liquefy.

[0105] Specific examples of gelling agents include, for example, isophorone diisocyanate-2-ethylhexylamine adduct; 1,2,3,4-dibenzylidene-D-sorbitol; hydroxystearic acid such as 12-hydroxystearic acid and triglycerides of these hydroxystearic acids; N-lauroyl-L-glutamic acid-α,γ-bis-n-butylamide; spin-labeled steroids; cholesterol derivatives; aluminum dialkyl phosphate; aluminum fatty acid; phenolic cyclic oligomers; 2,3-bis-n-hexadecyloxyanthracene; and cyclic depsipeptides. Of these, 12-hydroxystearic acid and its triglycerides are preferred. One or more gelling agents can be used.

[0106] As a gelling agent, commercially available products containing the gelling agent of this disclosure, such as oil solidifying agents manufactured by Lion Hygiene Co., Ltd. and Johnson Co., Ltd., can be used.

[0107] From the viewpoint of the effects of this disclosure, the gelling agent content is preferably 2 parts by mass or more, more preferably 2.5 parts by mass or more, even more preferably 4 parts by mass or more, even more preferably 6 parts by mass or more, and even more preferably 8 parts by mass or more, per 100 parts by mass of the rubber component. On the other hand, the gelling agent content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 13 parts by mass or less.

[0108] When the rubber composition of this disclosure contains a gelling agent and an oil and / or resin, the ratio (mass%) of the gelling agent to the total amount of oil and / or resin is preferably 5.0% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and even more preferably 18% by mass or more, from the viewpoint of the effects of this disclosure. Furthermore, the same ratio (mass%) is preferably 30% by mass or less, and more preferably 25% by mass or less.

[0109] (oil) The rubber composition may contain oil. The oil is not particularly limited, and for example, process oils, vegetable oils, and mixtures thereof can be used. Examples of process oils include paraffinic process oils, naphthenic process oils, and aromatic 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 oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, safflower oil, and tung oil. Of these, aromatic process oils are preferred. The oil may be used alone or in combination of two or more types.

[0110] From the viewpoint of the effects of this disclosure, the oil content is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and even more preferably 40 parts by mass or more, per 100 parts by mass of rubber component. From the viewpoint of handling stability, the content is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, even more preferably 85 parts by mass or less, and even more preferably 80 parts by mass or less. In this specification, the oil content also includes the amount of oil contained in the oil-spreading rubber.

[0111] (resin) The rubber composition may contain a resin. The resin may be a resin component commonly used in the tire industry. Examples of such resin components include petroleum resins, terpene resins, rosin resins, phenolic resins, coumarone resins, and the like. Among these, petroleum resins are preferred from the viewpoint of the effects of this disclosure. The resin may be used alone or in combination of two or more types.

[0112] ≪Petroleum resin≫ The petroleum resin is not particularly limited, but examples include aliphatic petroleum resins, aromatic petroleum resins, and aliphatic / aromatic copolymer petroleum resins. One type may be used alone, or two or more types may be used in combination. As an aliphatic petroleum resin, a resin obtained by cationic polymerization of unsaturated monomers such as isoprene and cyclopentadiene, which are petroleum fractions with 4 to 5 carbon atoms (C5 fraction), can be used (also called C5 petroleum resin). As an aromatic petroleum resin, a resin obtained by cationic polymerization of monomers such as vinyltoluene, alkylstyrene, and indene, which are petroleum fractions with 8 to 10 carbon atoms (C9 fraction), can be used (also called C9 petroleum resin). As an aliphatic / aromatic copolymer petroleum resin, a resin obtained by copolymerizing the above C5 fraction and C9 fraction (also called C5C9 petroleum resin) is used. Hydrogenated petroleum resins may also be used. Among these, aromatic petroleum resins are preferably used. An example of an aromatic petroleum resin is α-methylstyrene resin. Examples of α-methylstyrene resins include α-methylstyrene homopolymers (poly-α-methylstyrene) and copolymers of α-methylstyrene with other compounds including aromatic compounds and phenolic compounds. Other compounds that can constitute these copolymers include styrene, methylstyrene, methoxystyrene, and divinylbenzene. α-methylstyrene resins manufactured by Kraton are preferably used.

[0113] Terpene resins Examples of terpene resins include polyterpene resins, terpene phenol resins, and terpene styrene resins. These may be used individually or in combination of two or more. Among these, terpene styrene resin is particularly suitable because it has good compatibility with both SBR and BR, and sulfur is easily dispersed within the rubber components.

[0114] Polyterpene resins are resins made from at least one terpene compound selected from α-pinene, β-pinene, limonene, dipentene, etc. Terpene phenol resins are resins made from the above terpene compounds and phenolic compounds. Terpene styrene resins are resins made from the above terpene compounds and styrene.

[0115] The terpene resin may be a hydrogenated resin (e.g., hydrogenated polyterpene resin, hydrogenated terpene styrene resin). Hydrogenation of the terpene resin can be carried out by known methods, or commercially available hydrogenated resins can be used.

[0116] In this disclosure, commercially available terpene resins may be used. Examples of such commercially available products include those manufactured and sold by Yasuhara Chemical Co., Ltd., etc.

[0117] ≪Rosin-based resin≫ The rosin-based resin is not particularly limited, but examples include natural resin rosin, and rosin-modified resins obtained by hydrogenation, disproportionation, dimerization, esterification, etc. One type may be used alone, or two or more types may be used in combination.

[0118] Phenolic resins Phenolic resins are not particularly limited, but examples include phenol-formaldehyde resin, alkylphenol-formaldehyde resin, alkylphenol-acetylene resin, oil-modified phenol-formaldehyde resin, etc. They may be used individually or in combination of two or more.

[0119] Coumaron-based resin Coumaron-based resins are resins whose main component is coumaron. Examples include coumaron resin, coumaron-indene resin, and copolymer resins whose main components are coumaron, indene, and styrene. They may be used individually or in combination of two or more types.

[0120] ≪Resin content≫ From the viewpoint of adhesive performance and grip performance, the content of the rubber component in the resin per 100 parts by mass is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more. Furthermore, from the viewpoint of abrasion resistance and grip performance, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass or less.

[0121] ≪Softening point of resin≫ From the viewpoint of grip performance, the softening point of the resin is preferably 160°C or lower, more preferably 145°C or lower, and even more preferably 130°C or lower. Furthermore, from the viewpoint of grip performance, the softening point is preferably 20°C or higher, more preferably 35°C or higher, even more preferably 50°C or higher, and even more preferably 80°C or higher. The softening point of the resin is determined by the measurement method described above.

[0122] Weight-average molecular weight of resins The weight-average molecular weight (Mw) of the resin is preferably 300 or higher, more preferably 400 or higher, and even more preferably 500 or higher, as it is less volatile and has good grip performance. Furthermore, the Mw is preferably 15,000 or lower, more preferably 10,000 or lower, and even more preferably 8,000 or lower. The Mw of the resin is the value measured by the measurement method described above.

[0123] <SP value of resin> The SP value of the resin is preferably 8.0 or higher, more preferably 8.3 or higher, even more preferably 8.6 or higher, and even more preferably 8.9 or higher, due to its excellent compatibility with rubber components (especially SBR). On the other hand, the SP value of the resin is preferably 11.0 or lower, more preferably 10.0 or lower, and even more preferably 9.5 or lower. By using a resin with an SP value within the above range, the compatibility with SBR and BR can be improved, and the wear resistance and elongation at break can be improved. The SP value of the resin is the value measured by the measurement method described above.

[0124] <Other compounding agents> In addition to the components mentioned above, the rubber composition may also appropriately contain compounding agents commonly used in the tire industry, such as waxes, processing aids, antioxidants, stearic acid, zinc oxide, inorganic potassium salts, sulfur, and other vulcanizing agents and vulcanization accelerators.

[0125] (wax) The wax used can be one that is commonly used in the tire industry. When wax is included, the amount of wax per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of weather resistance of the rubber. Furthermore, from the viewpoint of suppressing whitening of the tire due to bloom, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less. The wax may be used alone or in combination of two or more types.

[0126] (Processing aid) Processing aids can be those commonly used in the tire industry, such as fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. These may be used individually or in combination of two or more. When processing aids are included, the content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of improving processability. Furthermore, from the viewpoint of wear resistance and fracture strength, it is preferably 10 parts by mass or less, and more preferably 8 parts by mass or less.

[0127] (Anti-aging agent) Anti-aging agents that are commonly used in the tire industry can be used. Specifically, examples include amine-based, quinoline-based, quinone-based, phenol-based, imidazole-based, and phenylenediamine-based compounds, as well as metal carbamate salts. Among these, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N,N'-bis(1-methylheptyl)-p-phenylenediamine, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, and N,N'-bis(1-ethyl-3-methylpentyl) Phenylenediamine-based antioxidants such as phenyl((-p-phenylenediamine), N-4-methyl-2-pentyl-N'-phenyl-p-phenylenediamine, N,N'-diaryl-p-phenylenediamine, hindereddiaryl-p-phenylenediamine, phenylhexyl-p-phenylenediamine, and phenyloctyl-p-phenylenediamine, and quinoline-based antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline are preferred. These antioxidants may be used alone or in combination of two or more.

[0128] When an anti-aging agent is included, the content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, or even 1 part by mass or more, from the viewpoint of the rubber's resistance to ozone cracking. Furthermore, from the viewpoint of wear resistance and wet grip performance, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0129] (Stearic acid) When stearic acid is included, its content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0130] (Zinc oxide) When zinc oxide is included, its content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of wear resistance, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0131] (Inorganic potassium salts) Inorganic potassium salts that are commonly used in the tire industry can be used. Examples of inorganic potassium salts include one or more potassium salts selected from the group consisting of potassium carbonate, potassium bicarbonate, and potassium tetraborate, of which potassium tetraborate is preferred. Inorganic potassium salts may be used alone or in combination of two or more.

[0132] From the viewpoint of extrusion processability, the inorganic potassium salt content is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, per 100 parts by mass of silica. Furthermore, from the viewpoint of wear resistance, it is preferably 3 parts by mass or less, more preferably 2.5 parts by mass or less, per 100 parts by mass of silica, and even more preferably 2 parts by mass or less.

[0133] (Vulcanizing agent) Sulfur is preferably used as a vulcanizing agent. Suitable sulfurs include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. The vulcanizing agent may be used alone or in combination of two or more types.

[0134] Examples of vulcanizing agents other than sulfur include sulfur-containing vulcanizing agents such as 1,6-hexamethylene-dithiosulfate sodium dihydrate and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, as well as organic peroxides such as dicumyl peroxide. Examples of vulcanizing agents other than sulfur include those manufactured by Taoka Chemical Industries, Ltd., Flexis, and Lanxess.

[0135] When sulfur is included as a vulcanizing agent, the amount of sulfur per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 0.7 parts by mass or more, from the viewpoint of ensuring a sufficient vulcanization reaction and obtaining good grip performance and abrasion resistance. Furthermore, from the viewpoint of suppressing deterioration, it is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less.

[0136] (Vulcanization accelerator) Examples of vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamate, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. These vulcanization accelerators may be used alone or in combination of two or more. Among these, at least one of sulfenamide, guanidine, and thiazole is preferred, and the combination of sulfenamide and guanidine is more preferred.

[0137] Examples of sulfenamide-based vulcanization accelerators include N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide (DCBS). Among these, N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS) is preferred.

[0138] Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salts of dicatecholborate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine. Among these, 1,3-diphenylguanidine (DPG) is preferred.

[0139] Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, and di-2-benzothiazolyl disulfide. Among these, 2-mercaptobenzothiazole is preferred.

[0140] When a vulcanization accelerator is included, its content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, and more preferably 2 parts by mass or more. Furthermore, the content of the vulcanization accelerator per 100 parts by mass of the rubber component is preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less. By keeping the content of the vulcanization accelerator within the above range, it tends to be possible to ensure fracture strength and elongation.

[0141] [Application] The motorcycle tire disclosed herein is not particularly limited in form and may be either a pneumatic tire or a solid tire, but it is preferable to use it as a pneumatic tire. It can also be used for various applications such as on-road tires, off-road tires, and racing tires, but it is preferable to use it as a racing tire. It can also be used as both a front wheel tire and a rear wheel tire.

[0142] [Manufacturing method] <Manufacturing of rubber compositions> The rubber composition of this disclosure can be manufactured by known methods. For example, it can be manufactured by kneading each of the above components using a rubber kneading device such as an open roll or a closed kneader (Banbury mixer, kneader, etc.). The kneading process includes, for example, a base kneading step in which compounding agents and additives other than the vulcanizing agent and vulcanization accelerator are kneaded, and a final kneading (F kneading) step in which the vulcanizing agent and vulcanization accelerator are added to the kneaded product obtained in the base kneading step and kneaded. Furthermore, the base kneading step can be divided into multiple steps if desired. The kneading conditions are not particularly limited, but for example, in the base kneading step, kneading is performed at a discharge temperature of 150 to 170°C for 3 to 10 minutes, and in the final kneading step, kneading is performed at 50 to 110°C for 1 to 5 minutes.

[0143] <Tire Manufacturing> A rubber composition containing the above components can be extruded to the desired tread shape at the pre-vulcanization stage and molded together with other tire components in a conventional manner on a tire molding machine to produce an unvulcanized tire. By heating and pressurizing (vulcanizing) this unvulcanized tire in a vulcanizing machine, the motorcycle tire of this disclosure can be obtained. The vulcanization conditions are not particularly limited, and for example, a method of vulcanization at 150 to 200°C for 5 to 30 minutes can be used. [Examples]

[0144] The present disclosure will be described in detail below based on examples, but the present disclosure is not limited to these examples.

[0145] <Various chemicals> SBR1: Nipol NS522 (Available from ZS Elastomer Co., Ltd., S-SBR, Styrene content: 39% by mass, Vinyl bond content: 40 mol%, Tg: -25℃, Mw: 650,000, Contains 37.5 parts by mass of oil per 100 parts by mass of rubber component) SBR2: JSR1723 (Available from JSR Corporation, E-SBR, Styrene content: 24% by mass, Vinyl bond content: 15 mol%, Tg: -53℃, Mw: 480,000, Oil-applied rubber containing 37.5 parts by mass of oil per 100 parts by mass of rubber component) BR: Ubepol BR150B (High-cis BR synthesized using a Co-based catalyst, manufactured by Ube Industries, Ltd., cis content: 97 mol%, vinyl bond content: 1 mol%, Tg: -107℃) Carbon Black: Show Black N110 (Available from Cabot Japan Co., Ltd., N2SA: 142m) 2 / g (BET value), DBP oil absorption: 115mL / 100g) Silica: Ultrasil VN3 (available from Evonik Degussa, N2SA: 175m) 2 / g (BET value)) Silane coupling agent: Si69 (available from Evonik Degussa, bis(3-(triethoxysilyl)propyl)tetrasulfide) Oil: Diana Process NH-70S (available from Idemitsu Kosan Co., Ltd., aromatic process oil) Resin: Sylvatraxx 4401 (Available from Kraton, Aromatic petroleum resin (α-methylstyrene resin: copolymer of α-methylstyrene and styrene), Softening point 85°C, SP value: 9.1) Gelling agent: Oil-based gel (available from Lion Hygiene Co., Ltd., contains 12-hydroxystearic acid) Wax: Ozoace 0355 (available from Nippon Seiro Co., Ltd.) Anti-aging agent: Antigen 6C (available from Sumitomo Chemical Co., Ltd., N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) Stearic acid: Beads Stearic Acid "Tsubaki" (available from NOF Corporation) Zinc oxide: Ginrei R (available from Toho Zinc Co., Ltd.) Sulfur: HK-200-5 (Available from Hosoi Chemical Industry Co., Ltd., 5% oil-containing powdered sulfur) Vulcanization accelerator 1: Noxellar NS-G (available from Ouchi Shinko Chemical Industry Co., Ltd., N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS)) Vulcanization accelerator 2: Noxellar D (available from Ouchi Shinko Chemical Industry Co., Ltd., 1,3-diphenylguanidine (DPG))

[0146] <Manufacturing of test tires> According to the formulation shown in the table, all chemicals except sulfur and vulcanization accelerator were mixed for 5 minutes at a discharge temperature of 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. Next, sulfur and vulcanization accelerator were added to the resulting mixture and kneaded in an open roll for 4 minutes until it reached 105°C to obtain an unvulcanized rubber composition. According to the tire outer diameter shown in the table, the obtained unvulcanized rubber composition was molded into the shape of a tread, bonded together with other tire components to produce an unvulcanized tire, and press-vulcanized at 170°C for 12 minutes to obtain a test tire. For the test tire with an outer diameter of 580 mm, the front tire size was 90 / 90-16 and the rear tire size was 90 / 80-17. For the test tire with an outer diameter of 620 mm, the front tire size was 130 / 70ZR17 and the rear tire size was 150 / 60ZR17.

[0147] <Measurement and Evaluation> Each measurement and evaluation was performed according to the method described below. The results are shown in Table 1.

[0148] (tanδ) A 20mm long x 4mm wide x 1mm thick sample was taken from the rubber layer of the tread of each test rear tire, with the tire circumference as the longer side. The loss tangent (40°C tanδ and 70°C tanδ) was measured for each sample using a GABO Iplexer series under the conditions of initial strain 10%, dynamic strain 1%, frequency 10Hz, temperature 40°C / 70°C, and extension mode. The thickness direction of the sample was the tire radius direction.

[0149] (Rolling resistance) Each test tire was mounted on a rim, and the rolling resistance was measured using a rolling resistance tester at internal pressure (front wheel: 250kPa, rear wheel: 290kPa), load (front wheel: 1.8kN, rear wheel: 1.8kN), and speed (front wheel: 80km / h, rear wheel: 80km / h). For the test tire with an outer diameter of 580mm, the front wheel rim was MT2.15×16 and the rear wheel rim was MT2.75×17. For the test tire with an outer diameter of 620mm, the front wheel rim was MT3.50×17 and the rear wheel rim was MT4.00×17. The average value of the rolling resistance of the front wheel and the rear wheel was calculated, and the reciprocal of this average value was expressed as an index with Comparative Example 1 set to 100 (low fuel consumption performance index). The higher the number, the lower the rolling resistance and the better the fuel efficiency.

[0150] (Grip performance) Each test tire was mounted on a rim, the internal pressure (front wheel: 250kPa, rear wheel: 290kPa) was adjusted, and the tires were mounted on a 750cc motorcycle. For the 580mm outer diameter test tire, the front rim had a MT2.15×16 size, and the rear rim had a MT2.75×17 size. For the 620mm outer diameter test tire, the front rim had a MT3.50×17 size, and the rear rim had a MT4.00×17 size. The grip performance when the motorcycle was driven on a circuit was subjectively evaluated by 20 test riders on a scale of 1 to 10, and the total score was expressed as an index, with Comparative Example 1 set to 100 (Grip Performance Index). A higher number indicates better performance.

[0151] [Table 1]

[0152] The overall performance of fuel efficiency and grip performance is expressed by the sum of the fuel efficiency index and the grip performance index. From the table above, it can be seen that in the example tire for motorcycles of this disclosure, the sum of the fuel efficiency index and the grip performance index exceeds 200, indicating that the overall performance of fuel efficiency and grip performance is superior to that of the comparative example tire.

[0153] <Embodiment> Examples of embodiments of this disclosure are shown below.

[0154] [1] A motorcycle tire comprising a pair of bead portions and a pair of sidewall portions, and a tread portion consisting of one or more rubber layers, including at least one rubber layer that forms the outermost surface and is connected to both sidewall portions, wherein the tire outer diameter Dt (mm) is 580 mm or more, preferably 585 mm or more, more preferably 590 mm or more, even more preferably 595 mm or more, even more preferably 600 mm or more, and even more preferably 620 mm or more, A motorcycle tire in which the above Dt and the tanδ value at 70°C (70°Ctanδ) and the tanδ value at 40°C (40°Ctanδ) of the rubber composition forming the rubber layer constituting the outermost surface of the tread portion satisfy the following equation, or preferably the difference between the left and right sides of the following equation is 0.01 or more, more preferably 0.05 or more, and even more preferably 0.10 or more. (Dt / 450)-0.50≦70℃tanδ / 40℃tanδ (1) [2] The motorcycle tire described in [1] above, wherein the 70°C tanδ and the 40°C tanδ satisfy the following equation, preferably the value of the right-hand side of the following equation is 0.82, more preferably 0.84, even more preferably 0.86, even more preferably 0.88, and even more preferably 0.90. 70℃tanδ / 40℃tanδ≧0.80 (2) [3] The motorcycle tire according to [1] or [2] above, wherein the 70°C tanδ satisfies the following equation, preferably the value of the right-hand side of the following equation is 0.21, more preferably 0.22, even more preferably 0.23, and even more preferably 0.24 or more. 70℃ tanδ≧0.20 (3) [4] A motorcycle tire according to any of [1] to [3] above, wherein the 40°C tanδ satisfies the following equation, preferably the value of the right-hand side of the following equation is 0.24, more preferably 0.23, and even more preferably 0.22. 40℃ tanδ ≤ 0.25 (4) [5] A motorcycle tire according to any of [1] to [4] above, wherein the rubber layer constituting the outermost surface of the tread portion is not substantially divided in the tire width direction, [6] The rubber composition comprises a gelling agent, an oil, and a resin. A motorcycle tire according to any of the above [1] to [5], wherein the ratio (mass%) of the gelling agent to the total of the oil and the resin is 5.0% by mass or more, preferably 5.0 to 30% by mass, more preferably 10 to 25% by mass, even more preferably 15 to 25% by mass, and even more preferably 18 to 25% by mass. [7] A motorcycle tire according to any of [1] to [6] above, wherein the rubber composition comprises a filler, and the filler comprises 40.0% by mass or more of silica, preferably 50.0% by mass or more, more preferably 60.0% by mass or more, even more preferably 70.0% by mass or more, even more preferably 80.0% by mass or more, even more preferably 90.0% by mass or more, and even more preferably 94.0% by mass or more. [8] A motorcycle tire according to any of [1] to [7] above, wherein the rubber composition contains a rubber component, and the rubber component contains 70% by mass or more of styrene-butadiene rubber, preferably 80% by mass or more, more preferably 90% by mass or more. [9] A motorcycle tire according to any of [6] to [8] above, wherein the resin includes an aromatic petroleum resin.

[10] A motorcycle tire according to any one of [1] to [9] above, wherein the rubber composition comprises a vulcanization accelerator, and the vulcanization accelerator comprises a sulfenamide-based vulcanization accelerator and a guanidine-based vulcanization accelerator.

[11] A motorcycle tire according to any of [1] to

[10] above, wherein the rubber composition contains sulfur.

[12] A motorcycle tire according to any of [1] to

[11] above, wherein the tread surface of the tread portion has shallow grooves. [Explanation of symbols]

[0155] 1. Motorcycle tires 2 Tread section 2A Tread surface 2B Tread Rubber 2e Tread edge 3. Sidewall section 4. Bead section 5 Belt Layer C Tire centerline DT Tire Outer Diameter R Tire rotation direction TW Tread width 2a Circumferential shallow groove 2b Shallow width groove Cr Crown Region Sh shoulder region 2c lattice shallow groove 2d lattice shallow groove

Claims

1. A motorcycle tire comprising a pair of bead portions and a pair of sidewall portions, and a tread portion consisting of one or more rubber layers, including at least one rubber layer that forms the outermost surface and is connected to both sidewall portions, and having an outer diameter Dt (mm) of 580 mm or more, A motorcycle tire in which the following equations satisfy the following: Dt and the value of tanδ of the rubber composition forming the outermost surface of the tread portion, measured under the conditions of a temperature of 70°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10Hz, and extension mode, 70°C tanδ and 40°C tanδ measured under the conditions of a temperature of 40°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10Hz, and extension mode. (Dt / 450) -0.50≦70℃tanδ / 40℃tanδ (1)

2. The motorcycle tire according to claim 1, wherein the 70°C tanδ and the 40°C tanδ satisfy the following equation. 70℃tanδ / 40℃tanδ≧0.80 (2)

3. The motorcycle tire according to claim 1 or 2, wherein the 70°C tanδ satisfies the following equation. 70°C tanδ ≥ 0.20 (3)

4. A motorcycle tire according to any one of claims 1 to 3, wherein the 40°C tanδ satisfies the following equation. 40℃ tanδ ≤ 0.25 (4)

5. A motorcycle tire according to any one of claims 1 to 4, wherein the rubber layer constituting the outermost surface of the tread portion is not substantially divided in the tire width direction.

6. The rubber composition comprises a gelling agent, an oil, and a resin. A motorcycle tire according to any one of claims 1 to 5, wherein the ratio (mass%) of the gelling agent to the total of the oil and the resin is 5.0% by mass or more.

7. A motorcycle tire according to any one of claims 1 to 6, wherein the rubber composition comprises a filler, and the filler contains 40.0% by mass or more of silica.

8. The motorcycle tire according to any one of claims 1 to 7, wherein the rubber composition comprises a rubber component, and the rubber component comprises 70% by mass or more of styrene-butadiene rubber.

9. The motorcycle tire according to claim 6, wherein the resin includes an aromatic petroleum resin.

10. The motorcycle tire according to any one of claims 1 to 9, wherein the rubber composition comprises a vulcanization accelerator, and the vulcanization accelerator comprises a sulfenamide-based vulcanization accelerator and a guanidine-based vulcanization accelerator.

11. The motorcycle tire according to any one of claims 1 to 10, wherein the rubber composition contains sulfur.

12. A motorcycle tire according to any one of claims 1 to 11, wherein the tread surface of the tread portion has shallow grooves.

Images