Electric vehicle tire, evaluation method, and pm10 generation amount measuring system

Abstract

To provide a tire for an electric vehicle improved in grip performance.SOLUTION: A tire for an electric vehicle comprising a tread portion formed of a rubber composition containing a rubber component, a filler, and a plasticizer containing at least one selected from the group consisting of a resin and a liquid rubber, wherein an acetone extraction amount (mass%) of the rubber composition is defined as A E, a loss tangent at 0 °C. of the rubber composition is defined as 0 °C. tan δ, and a number concentration (pieces / cm3) of PM10 generated in a predetermined LAT abrasion test is defined as P, when an abrasion amount (cm3) of the rubber composition by the LAT abrasion test is defined as AV, the following formulas (1) and (2) are satisfied: (1) P / AV <2000 (2) AE * 0 °C. tan δ / (P / AV) * 1000> 5.0 SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a tire for an electric vehicle, an evaluation method, and a system for measuring the amount of PM10 generated. [Background technology]

[0002] There is a demand for improved grip performance in tires, and while technologies have been proposed to improve grip performance by compounding predetermined amounts of fillers such as carbon black and silica and other additives (see Patent Document 1, etc.), new technologies for improving grip performance are desired. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-187976 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims to provide a tire for electric vehicles with improved grip performance, a method for evaluating the amount of PM10 generated due to wear of the tire tread, and a system for measuring the amount of PM10 generated. [Means for solving the problem]

[0005] The present invention provides a tire for an electric vehicle having a tread portion made of a rubber composition containing a rubber component, a filler, and a plasticizer containing at least one selected from the group consisting of a resin and a liquid rubber, wherein the acetone extractable amount (mass%) of the rubber composition is defined as AE, the loss tangent of the rubber composition at 0°C is defined as 0°C tanδ, and the number concentration (particles / cm) of PM10 generated in a predetermined wear test of the rubber composition is measured under predetermined measurement conditions. 3 ) is defined as P, and the abrasion amount (cm 3) is AV, the present invention relates to a tire for an electric vehicle that satisfies the following formulas (1) and (2): (1) P / AV<2000 (2)AE×0℃tanδ / (P / AV)×1000>5.0

[0006] The present invention also relates to a method for evaluating the amount of PM10 generated by wear of a tire tread portion, and further to a system for measuring the amount of PM10 generated by a wear test. [Effects of the Invention]

[0007] The present invention provides a tire for an electric vehicle with improved grip performance, as well as a new method for evaluating the amount of PM10 generated by wear of the tire tread and a new system for measuring the amount of PM10 generated. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic diagram showing a method for cutting out a rubber sheet for evaluation. [Figure 2] FIG. 1 is a schematic diagram showing a test piece. [Figure 3] FIG. 1 is a schematic elevational view showing a test piece and a grinding wheel in an LAT wear test. [Figure 4] This is a diagram showing the configuration of a light scattering airborne particle counter used to measure PM10. [Figure 5] 1 is a cross-sectional view of a tread portion of a tire according to one embodiment of the present invention. [Figure 6] 1 is a plan view showing a tread contact surface of an embodiment of a tire for an electric vehicle. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] The tire for an electric vehicle according to an embodiment of the present invention includes a tread portion made of a rubber composition containing a rubber component, a filler, and a plasticizer selected from at least one of a resin and a liquid rubber. When the acetone extraction amount (mass%) of the rubber composition is AE, the loss tangent at 0°C of the rubber composition is 0°C tan δ, and the number concentration (number / cm 3 ) of PM10 generated in the following LAT wear test of the rubber composition is P, which is the value measured under the following measurement conditions, and the wear amount (cm 3 ) of the rubber composition by the LAT wear test is AV, the tire for an electric vehicle satisfies the following formulas (1) and (2). (1) P / AV < 2000 (2) AE × 0°C tan δ / (P / AV) × 1000 > 5.0

[0010] In this embodiment, the LAT wear test is a test conducted under the following conditions. <LAT Wear Test> Using a wear testing machine having a grinding wheel rotating in a vertical plane and a test piece rotatably supported on an axis parallel to the vertical plane, the test piece is created according to the following test piece creation method, and a wear test conforming to ISO23233 is performed by bringing the test piece into contact with the grinding wheel under the following conditions. Load applied to the test piece: 40 N Slip angle of the test piece: 6° Speed of the grinding wheel surface: 20 km / h Travel distance of the test piece: 2000 m Grinding wheel temperature: 10°C Anti-fouling sand amount: 0.2 g / min Particle size of the grinding wheel: 60 mesh

[0011] In this embodiment, the test piece used in the LAT wear test is created by the following method. <Test Piece Creation Method> An evaluation rubber sheet is cut out from the tread surface of the tire with a thickness of 2 mm ± 1 mm, and is wound along the outer peripheral surface of the roller body. The shape of the test piece after winding is made into a cylindrical shape with an outer diameter of 84 mm ± 2 mm, an inner diameter of 35 mm ± 1 mm, and an axial length (width) of 18 mm ± 1 mm, and having a through hole.

[0012] In the present embodiment, the number concentration of PM10 generated in the LAT wear test is measured under the following measurement conditions. <PM10 number concentration measurement conditions> Using an optical scattering type airborne particle counter, in accordance with ISO21501-04, measure under the following conditions. Sample air collection location: Based on the grounding center of the test piece with the grindstone disk, with the side where the grindstone disk is located as the back side, a location 25 cm vertically downward, 15 cm horizontally forward, and 10 cm horizontally to the right. Sample air suction volume: 1 L / min Measurement time: 6 minutes from the start of the LAT wear test to after 6 minutes.

[0013] While not intending to be bound by theory, the reasons why grip performance can be improved in embodiments of the present invention are thought to be as follows: (a) Even when PM10 is generated due to tread wear, if the PM10 particles adhere to each other, they will form clumps and fall, reducing the amount of airborne PM10. The generation of PM10 that adheres to each other means that the rubber composition from which it is generated has strong adhesive strength, which in turn means that the rubber composition has strong adhesive friction. Equation (1) relates to the PM10 particle concentration per amount of wear and is thought to represent the influence of adhesive friction. Rubber compositions with a value of Equation (1) smaller than a predetermined value are thought to have strong adhesive friction and contribute to improved grip performance. Furthermore, (b) rubber compositions with a large amount of acetone extractables are thought to have high adhesive strength and contribute to improved adhesive friction. Furthermore, (c) rubber compositions with a large tan δ have high hysteresis friction and are thought to contribute to improved grip performance. Furthermore, (d) since the values ​​of AE, 0°C tan δ, and P / AV are indicators of adhesive friction and hysteresis friction, as described above, a larger value of Equation (2) is thought to contribute to improved grip performance. It is believed that the above (a) to (d) work together to improve grip performance.

[0014] The right side of the formula (1) is preferably 1200, more preferably 1000.

[0015] Tires that satisfy stricter conditions of formula (1) are considered to have even better grip performance.

[0016] In this embodiment, the electric vehicle tire has a carcass cord, the fineness (dtex) of the carcass cord is F, and the maximum load capacity (kg) of the electric vehicle tire is W. L Then, F and W L It is preferable that and satisfy the following formula (3). (3)FilmWare L ≧5.6

[0017] In tires that satisfy formula (3), the fineness of the carcass cords is increased, that is, the carcass cords are thicker, and the maximum load capacity of the tire is increased, which reduces the contact area between the topping rubber and the carcass cords. As the restraint by the carcass cords is reduced, the topping rubber becomes more flexible, allowing it to respond flexibly to deformations in the tire while driving and making it easier for it to follow the road surface, which is thought to further improve grip performance.

[0018] It is preferable that F(dtex) is equal to or greater than 6000. Such a tire is thought to lead to further improvement in grip performance.

[0019] The 0° C. tan δ of the rubber composition is preferably 0.45 or more, and more preferably 0.80 or more.

[0020] A rubber composition with a large 0°C tan δ has a large hysteresis friction, and therefore satisfying the above value is thought to lead to further improvement in grip performance.

[0021] The rubber composition preferably has an acetone extractable amount AE (mass %) of 20 or more.

[0022] The amount of acetone extractables is related to the adhesiveness of the rubber composition and is therefore thought to affect the adhesive friction force. Therefore, a tire that satisfies the above value is thought to have further improved grip performance.

[0023] It is preferable that the right side of equation (2) is 8.0.

[0024] Tires that satisfy stricter conditions of formula (2) are considered to have even better grip performance.

[0025] The weight (kg) of the electric vehicle tire is G, and the maximum load capacity (kg) is W. L Then, G and W L It is preferable that the relationship of the following formula (4) is satisfied. (4) Golden Week L <0.015

[0026] Such a tire is expected to lead to further improvements in grip performance.

[0027] It is preferable that the rubber component contains styrene-butadiene rubber, the styrene content of the styrene-butadiene rubber is 30% by mass or less, and the content of the plasticizer containing at least one selected from the group consisting of the resin and the liquid rubber is 30 parts by mass or more per 100 parts by mass of the rubber component.

[0028] Such a tire is thought to have greater traction and friction, leading to further improvements in grip performance.

[0029] The rubber component preferably contains 50% by mass or more of styrene-butadiene rubber in 100% by mass of the rubber component, and the total amount of styrene in the rubber component is preferably less than 20% by mass.

[0030] It is preferable that the tread surface has three or more circumferential grooves extending in the tire circumferential direction, a pair of shoulder land portions on the outer side in the tire width direction, which are partitioned by a pair of outermost peripheral grooves located on the outermost sides in the tire width direction among the circumferential grooves, and a center land portion sandwiched between the pair of shoulder land portions, and that the negative ratio of the center land portion is greater than 0% and less than 15%.

[0031] Such tires have a larger contact area with the tread surface, which is thought to lead to further improvements in grip performance.

[0032] Another embodiment of the present invention relates to a method for evaluating the amount of PM10 generated due to wear of the tread portion of a tire, the method for evaluating the amount of PM10 generated comprising a test piece preparation step, an abrasion test step, and a step of measuring the PM10 generated in the abrasion test step, the test piece preparation step comprising a step of cutting out an evaluation rubber sheet from the tread portion of the tire, and the abrasion test step comprising a step of abrading the test piece to generate PM10.

[0033] The abrasion test step preferably includes a step of abrading the test piece by an LAT abrasion test to generate PM10, and the LAT abrasion test is preferably a method for evaluating the amount of PM10 generated, performed in accordance with ISO23233.

[0034] Another embodiment of the present invention relates to a PM10 generation amount measurement system comprising an abrasion test section and a PM10 measurement section, wherein the abrasion test section has a grinding wheel that rotates in a vertical plane and a test piece support section that can rotate on an axis parallel to the vertical plane.

[0035] The PM10 generation amount measurement system preferably comprises an abrasion test section and a PM10 measurement section in the same chamber.

[0036] The test piece is preferably cylindrical in shape with a through hole in the center, and the PM10 emission measurement system has the test piece fixed to the test piece support part.More preferably, the cylindrical shape with a through hole in the center is a cylindrical shape in which, when the axial length is taken as 1, the inner diameter of the cylinder with the through hole is 1.85 to 2.10 and the outer diameter is 4.55 to 4.70.

[0037] The PM10 measuring unit preferably includes a sample air supply unit.

[0038] <Definition> "Normal condition" means a condition in which the tire is mounted on a normal rim, inflated to the normal internal pressure, and unloaded. Unless otherwise specified, the tire will be used in the normal condition.

[0039] Unless otherwise specified, the "dimensions of each part of the tire" are values ​​that are specified when the tire appears on its outer surface in a normal state, while those that exist inside the tire or on a cut surface of the tire are values ​​that are specified when, for example, the tire is cut along a plane that includes the tire rotation axis and the cut tire piece is maintained within the rim width of a normal rim.

[0040] "Genuine rim" refers to the rim specified for each tire in 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 Organization), 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." JATMA, ETRTO, and TRA are referenced in that order, and if an applicable size is available at the time of reference, that standard is followed. In the case of a tire not specified in the above standards, it refers to the narrowest rim among the smallest diameter rims that can be mounted on the tire and can maintain internal pressure (i.e., no air leaks from between the rim and tire).

[0041] "Normal internal pressure" refers to the air pressure specified for each tire in the standard system that includes the standard on which the tire is based. For example, for JATMA, it is "maximum air pressure," for ETRTO, it is "INFLATION PRESSURE," and for TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." As with regular rims, refer to JATMA, ETRTO, and TRA in that order, and follow that standard if there is an applicable size at the time of reference. In the case of tires not specified in the above standards, it refers to the normal internal pressure (250kPa or more) of another tire size (defined in the standard) that is specified using the regular rim as the standard rim, and if there are multiple normal internal pressures of 250kPa or more listed, it refers to the smallest value among them.

[0042] "Normal load (kg)" is the load specified for each tire in the standard system including the standard on which the tire is based, for example, "Maximum Load Capacity" for JATMA, "Load Capacity" for ETRTO, and the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA. As with normal rims and normal internal pressures, JATMA, ETRTO, and TRA should be referenced in that order, and if there is an applicable size at the time of reference, that standard should be followed. For tires not specified in the above standards, the maximum load capacity W calculated separately should be used. L is the normal load.

[0043] "Maximum load capacity W L (kg)" is calculated using the following formula: "V" is the virtual volume of the tire (mm 3 ), "Dt" is the outer diameter (mm) of the tire in its normal state, "Ht" is the tire's cross-sectional height (mm) in the tire's radial direction in a cross section of the tire taken along a plane including the tire's rotation axis, and "Wt" is the tire's cross-sectional width (mm) in its normal state. Ht can be calculated by (Dt-R) / 2, where R is the tire rim diameter. Wt is the value obtained by excluding any patterns or letters on the tire sidewall. Note that maximum load capacity is synonymous with the normal load mentioned above.

[0044]

number

[0045] "Weight of tire" refers to the weight of the tire itself, excluding the weight of the rim. On the other hand, if the tire has components such as sponge or sealant, or sensor components, the weight includes these components.

[0046] The "land portion" refers to the portion of the tread that comes into contact with the ground when the tire is pressed against the ground, and is the portion of the tread that constitutes the effective contact area described below.

[0047] A "groove" is a recess formed on the tread surface of a tire (extending radially inward) with an opening width of 2.0 mm or more on the tread surface. A groove with an opening width of less than 2.0 mm is called a "sipe."

[0048] The term "circumferential groove" refers to a groove that extends continuously in the circumferential direction of the tire. The circumferential groove may extend linearly along the circumferential direction, or may extend in a wavy, sinusoidal, or zigzag pattern along the circumferential direction.

[0049] "Groove width" means the distance between groove edges on the tread surface in a cross section of the tire taken along a plane including the tire rotation axis. When the groove width varies, this refers to the maximum value.

[0050] The "tread portion" refers to a component that includes the portion that forms the tire's tread contact surface (also simply referred to as the tread surface), and in the case where the tire is equipped with components that form the tire skeleton from steel or textile materials, such as a belt layer, a belt reinforcing layer, and a carcass layer, the "tread portion" refers to a component that is located radially outward of these components in the tire radial cross section.

[0051] The "negative rate" is the ratio (%) of the groove area to the contact area of ​​a given region of the tread contact patch. The negative rate is calculated as the ratio (%) of the groove area in each land portion to the center land portion and shoulder land portion within the tread contact patch. Specifically, a tire is mounted on a standard rim, pressurized to the standard internal pressure, and left at 25°C for 24 hours. After that, ink is applied to the tire tread surface, and the tire is pressed against cardboard under a standard load (camber angle 0°). The area of ​​the contact shape of each of the center land portion and shoulder land portion is measured (this is called the area of ​​the transferred land shape). In addition, the area of ​​the shape obtained by smoothly connecting the contact shape contours of each of the center land portion and shoulder land portion is calculated, and this is considered the total area of ​​each land portion (this is called the total area of ​​the land shape obtained by connecting the transferred contours). The negative rate for each of the center land portion and shoulder land portion is calculated as [1 - (area of ​​the transferred land shape) / (total area of ​​the land shape obtained by connecting the transferred contours)] × 100 (%).

[0052] The "loss tangent of a rubber composition" is the loss tangent (tanδ) under various conditions measured in extension mode using a dynamic viscoelasticity measuring device (for example, the Iplexer series manufactured by GABO). The sample used for dynamic viscoelasticity measurement is a vulcanized rubber composition having a length of 20 mm, a width of 4 mm, and a thickness of 1 mm. When preparing a sample by cutting it out from a tire, the length direction of the sample is aligned with the tangential direction to the tire circumference, and the thickness direction of the sample is aligned with the tire width direction. In this specification, the loss tangent at 0°C, 0°C tanδ, is measured.

[0053] "0°C tan δ" is the loss tangent (tan δ) measured under the conditions of a temperature of 0°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±2.5%, and an extension mode.

[0054] "Acetone extractables (AE)" is a value calculated in accordance with JIS K 6229 by immersing each vulcanized rubber test piece in acetone at room temperature (approximately 25°C) for 72 hours to extract the soluble components, measuring the mass of each test piece before and after extraction, and then using the following formula. Acetone extractable amount (mass%) = {(mass of rubber test piece before extraction - mass of rubber test piece after extraction) / (mass of rubber test piece before extraction)} × 100

[0055] The "rubber component of the rubber composition" is a component that contributes to crosslinking within the rubber composition, and generally has a weight average molecular weight (Mw) of 10,000 or more.

[0056] "Plasticizer" is a material that imparts plasticity to rubber components and is a component that is extracted from rubber compositions using acetone. Plasticizers include those that are liquid (fluid) at 25°C and those that are solid at 25°C. However, this does not include waxes and stearic acid, which are commonly used in the tire industry.

[0057] The "plasticizer content" also includes the amount of plasticizer in the rubber component extended by the plasticizer.

[0058] The "weight average molecular weight (Mw)" can be determined by converting the measured value into standard polystyrene equivalents using gel permeation chromatography (GPC) (for example, a GPC-8000 series manufactured by Tosoh Corporation, a differential refractometer as the detector, and a TSKgel SuperMultipore HZ-M column manufactured by Tosoh Corporation). This applies to, for example, SBR, BR, plasticizers, etc.

[0059] "Styrene content" is measured by pyrolysis gas chromatography and NMR measurement ( 1 H-NMR and 13 The amount of components such as "styrene content" is calculated by C-NMR. Unlike physical property values ​​such as complex modulus (E*), the amount of components such as "styrene content" has a true value that is independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible. In this specification, "pyrolysis gas chromatography" refers to a method in which a sample is heated in a pyrolysis device, the individual components contained in the gas phase components generated by this heating are separated using a separation column, and each isolated component is analyzed.

[0060] "Vinyl content (amount of 1,2-bonded butadiene units)" can be measured by pyrolysis gas chromatography or NMR measurement ( 1 H-NMR and 13 It is calculated using C-NMR. As with the "styrene content," there is a true value for the "vinyl content" that is independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible.

[0061] "Cis content (cis-1,4-bonded butadiene unit amount)" is measured by infrared absorption spectroscopy or NMR measurement ( 1 H-NMR and 13 This is a value measured by C-NMR and is applied to rubber components that have repeating units derived from butadiene, such as BR. As with the "styrene content," there is a true value for the "cis content" that is independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible.

[0062] The "styrene content (mass%) of the rubber component" is the sum of all the values ​​calculated by multiplying the styrene content of each rubber constituting the entire rubber component (100 mass%) by its content in the entire rubber component.

[0063] "Vinyl content (mol%) of rubber component" is the sum of the values ​​calculated by multiplying the amount of vinyl bonds derived from 1,2-butadiene bonds for each rubber constituting the entire rubber component by its content in the entire rubber component. The amount of vinyl bonds (amount of 1,2-bonded butadiene units) is measured by infrared absorption spectroscopy.

[0064] The "total styrene content in the rubber component" refers to the total content (mass%) of styrene moieties in 100% by mass of the rubber component. This is calculated by multiplying the styrene content (mass%) of each rubber component by the mass fraction in the rubber component, and then adding up the resulting values. Specifically, it is calculated as Σ(styrene content (mass%) of each styrene-containing rubber × content (mass%) of each styrene-containing rubber in the rubber component / 100). For example, if the rubber component consists of 30% by mass of a first SBR (styrene content: 25% by mass), 60% by mass of a second SBR (styrene content: 27.5% by mass), and 10% by mass of BR, the total styrene content in 100% by mass of the rubber component is 24.0% by mass (= 25 × 30 / 100 + 27.5 × 60 / 100 + 0 × 10 / 100).

[0065] The "average primary particle size of carbon black" and "average primary particle size of recycled carbon black" are values ​​obtained by photographing particles with a transmission or scanning electron microscope and arithmetically averaging the particle sizes of 400 particles. If the particle shape is spherical, the particle size is the diameter of the sphere; if the particle shape is non-spherical, the particle size is calculated from the microscope image as the circle-equivalent diameter (positive square root of {4 × (particle area) / π}).

[0066] "N2SA of carbon black" is a value determined by JIS K 6217-2:2017.

[0067] "Fineness" (tex) refers to the weight (g) per 1000 m of the organic fiber cord. dtex is a unit representing one-tenth of that, corresponding to the weight (g) per 10 km of the organic fiber cord. The fineness of the carcass cord is measured in accordance with JIS L 1017. In the present embodiment, when the carcass cord is composed of two or more single yarns twisted together, the fineness F of the carcass cord refers to the total of the finenesses of each single yarn. Furthermore, the configuration (cord structure) of the carcass cord is represented in accordance with "5.2 Method of Displaying Cord Structure" of JIS L 1017. For this reason, for example, the cord structure of a carcass cord obtained by twisting two single yarns with a fineness of 1400 dtex is represented as 1400 dtex / 2. Also, in this case, the fineness F of the carcass cord is 2800 dtex, which is the total of the finenesses of each single yarn.

[0068] Hereinafter, an evaluation method for the amount of PM10 generated due to wear of the tread portion of a tire and a measurement system for the same amount according to an embodiment of the present invention will be described.

[0069] <Evaluation Method for PM10 Generation Amount> Regarding the method for measuring PM10 and the method for evaluating the amount of PM10 generated due to wear of the rubber composition constituting the tread portion of a tire in the present embodiment, it will be described with appropriate reference to the drawings. However, the drawings are merely examples for explanation.

[0070] The evaluation method for the amount of PM10 generated due to wear of the tread portion of a tire in the present embodiment includes a test piece preparation step, a wear test step, and a step of measuring PM10 generated in the wear test step. The test piece preparation step includes a step of cutting out an evaluation rubber sheet from the tread portion of the tire. The wear test step includes a step of wearing the test piece to generate PM10.

[0071] (Test Piece Preparation) FIG. 1 shows an outline of a method for cutting a rubber sheet for evaluation from a tire. The rubber sheet for evaluation S is cut out from a region of the tread portion 2 of the tire 1, including the tread contact surface. Such cutting of the rubber sheet is carried out by machining or using a cutting tool such as a knife. The shape and thickness w2 of the cut rubber sheet for evaluation are adjusted as appropriate so that it will have a predetermined shape when wrapped around a roller, but a rectangular shape is preferred. Specifically, the rubber sheet for evaluation is preferably rectangular with a width of 18 mm ± 1 mm, a length of 260 mm ± 3 mm, and a thickness of 2 mm ± 1 mm.

[0072] FIG. 2 is a perspective view of the test piece. The roller body 3 is cylindrical with a through hole at its center, and a rotation shaft is fixed to this through hole. This allows the roller body to rotate. The rubber sheet S for evaluation is firmly bonded to the outer surface of the roller body 3, for example, with an adhesive, to form the test piece 4. When the axial length w1 of the roller body is taken as 1, the test piece 4 preferably has an inner diameter d1 of 1.85 to 2.10 mm and an outer diameter d2 of 4.55 to 4.70 mm. Specifically, the test piece 4 preferably has an axial length (width) w1 of 18 mm ± 1 mm, an inner diameter d1 of 35 mm ± 1 mm, and an outer diameter d2 of 84 mm ± 2 mm. The shape and size of the roller body 3 are the same as those of the test piece 4 except for the outer diameter. However, the outer diameter of the roller body 3 can be appropriately adjusted so that when the rubber sheet S for evaluation is wound around the roller body 5, the outer diameter d2 of the test piece 4 is 84 mm ± 2 mm, and so that the rubber sheet for evaluation does not wear out completely during the abrasion test, thereby preventing damage to the roller body 3. Therefore, the outer diameter of the roller body 3 can be set to, for example, 75 to 82 mm. The thickness w2 of the rubber sheet for evaluation can also be appropriately adjusted within a predetermined range to match the outer diameter of the roller body.

[0073] (wear test) The abrasion test performed in the abrasion test step is not particularly limited, and any commonly used abrasion test method, such as the Williams test, Akron test, Lambourn test (including the modified Lambourn test), Dinh test, Taber test, NBS test, or LAT abrasion test, can be used. The abrasion test is preferably the LAT abrasion test. The LAT abrasion test is performed in accordance with ISO 23233. For example, the LAT abrasion test is performed by abrading the test piece using an LAT abrasion tester to generate PM10.

[0074] (LAT abrasion test) The LAT abrasion tester has a grinding wheel that rotates in a vertical plane and a test piece support unit that can rotate on an axis parallel to the vertical plane, and the LAT abrasion test process includes a process of bringing the test piece into contact with the grinding wheel. The test piece preparation process includes a process of cutting out a rubber sheet for evaluation from a region of the tire tread that includes the tread contact surface, and a process of wrapping the rubber sheet for evaluation around the outer circumferential surface of a roller body to prepare a test piece. The process of measuring PM10 is preferably a process of measuring the number concentration of PM10, and the PM10 number concentration can be measured, for example, using a light scattering airborne particle counter.

[0075] FIG. 3 is an elevation view showing the grinding wheel and test piece of an LAT abrasion tester according to one embodiment of the present invention. In this embodiment, the LAT abrasion tester includes a grinding wheel 6 that rotates in a vertical plane and a test piece support unit that can rotate on an axis parallel to the vertical plane. As described above, the test piece 4 is prepared by wrapping the rubber sheet S for evaluation around the outer periphery of the roller body 3 and fixed to the test piece support unit. The grinding wheel 6 is rotated by an electric motor mounted on its rear side. The grinding wheel 6 includes a disc-shaped rotating table 6a and a grinding wheel surface 6b, which is a circular ring with a fixed width and fixed to the rotating table. By bringing the test piece 4 into contact with the grinding wheel surface 6b of the rotating grinding wheel 6, the rubber sheet S for evaluation wrapped around the roller body 3 can be continuously abraded.

[0076] A plurality of abrasive grains are formed on the grindstone surface 6b. In this embodiment, the grain size of the grindstone surface 6b is set to 60 mesh. In this embodiment, the grain size of the abrasive grains is preferably 177 μm to 250 μm.

[0077] In this embodiment, the slip angle θ1 of the test piece 4 relative to the grinding wheel disk 6 is set to 6°. The slip angle θ1 is the angle of deviation between the traveling direction A1 of the test piece 4 and the rotation direction of the test piece 4 (i.e., the direction of the equatorial plane 4c of the test piece 4). The traveling direction A1 of the test piece 4 is a direction perpendicular to the line connecting the center 6c of the grinding wheel disk 6 and the ground contact center 4t of the test piece 4 (i.e., the tangential direction of the disc-shaped grinding wheel disk 6).

[0078] In this embodiment, the test piece 4 is pressed against the grinding wheel 6. At this time, a set load is applied to the test piece 4. In this embodiment, the load is set to 40 N. Then, the grinding wheel 6 is rotated around a horizontal axis, and the test piece 4 is allowed to roll freely. As a result, the evaluation rubber sheet S is worn due to friction with the grinding wheel surface 6b. In FIG. 3, the rotation direction of the grinding wheel 6 is indicated by a white arrow.

[0079] The rotation speed of the grinding wheel surface 6b is set so that the speed in the direction of travel A1 at the contact center 4t is 20 km / h, and the test piece 4 is rolled until the rolling distance reaches 2000 m.

[0080] The LAT abrasion tester is preferably equipped with a temperature control mechanism for maintaining the grinding wheel 6 at a predetermined temperature. The temperature control mechanism includes, for example, an electric heater or a heat source for heating and cooling the grinding wheel surface 6b. This includes, for example, a heat pump type heat source. In this embodiment, the grinding wheel temperature is set to 10°C.

[0081] Furthermore, the LAT abrasion test is preferably carried out while spraying antifouling sand between the test piece 4 and the grindstone surface 6b. This prevents shavings and PM10 generated when the rubber sheet S for evaluation is worn by the grindstone surface 6b from adhering to the rubber sheet S for evaluation. The antifouling sand may be, for example, a mixture of magnesium oxide and aluminum oxide. In this embodiment, the amount of antifouling sand is preferably set to 0.2 g / min.

[0082] The LAT abrasion tester may be equipped with a dust collector to remove dust generated during the test, but it is preferable to perform the test without operating the dust collector.

[0083] The LAT abrasion test is performed in accordance with ISO 23233. The LAT abrasion tester is preferably formed, for example, in a rectangular parallelepiped shape, and is provided on its front with switches for stopping the tester and a display for displaying the test status. An example of such a tester is the LAT100 (manufactured by VMI).

[0084] The wear amount AV (cm) of the rubber composition in the LAT wear test 3 ) is calculated by dividing the difference between the mass (g) of the test piece before the LAT abrasion test and the mass (g) of the test piece after the LAT abrasion test by the specific gravity (g / cm 3 ) can be calculated by dividing by the formula below. AV(cm 3 ) = {Mass of test piece before LAT abrasion test (g) - Mass of test piece after LAT abrasion test (g)} / Specific gravity of evaluation rubber sheet (g / cm 3 )

[0085] (PM10 measurement) The amount of PM10 generated in the LAT abrasion test was evaluated using a light scattering airborne particle counter to measure the number concentration of PM10 P (particles / cm 3) is preferably measured. In this case, sample air containing the PM10 is supplied from a sample air supply unit to a particle detection region, and the number concentration of PM10 in the sample air is measured in the particle detection region using a light scattering airborne particle counting method. Figure 4 is a schematic diagram of a light scattering airborne particle counter. A light scattering airborne particle counter 20 comprises a sample air supply unit 21, a light source unit 22, a light receiving unit 23, and a signal processing unit 24. Measurements are performed in accordance with ISO21501-04.

[0086] The sample air is a sample for measuring the PM10 number concentration. It is preferably suctioned at a rate of 1 L / min from a location 25 cm vertically downward, 15 cm horizontally forward, and 10 cm horizontally to the right, with the grinding wheel side facing back, relative to the center 4t of the contact point between the test piece 4 and the grinding wheel 6. In the light scattering airborne particle counter, sample air is supplied from a sample air supply unit 21 to a particle detection region 27. In the particle detection region 27, light irradiated from a light source unit 22 including a laser element 28 is scattered by PM10 in the sample air, and the scattered light is detected by a light receiving unit 23. The detected optical signal is converted into an electrical signal by a photoelectric conversion element 26 and processed by a signal processing unit 24. The particle measurement results are displayed or output to a printer, etc.

[0087] The number concentration of PM10 is preferably measured by suctioning and collecting sample air using a suction pump for 6 minutes from the start of contact between the test piece and the grinding wheel until 6 minutes have passed, and measuring the number concentration of PM10 in the sample air.

[0088] In FIG. 4, the light scattered in the particle detection region 27 is collected by the collecting lens 25 onto the photoelectric conversion element 26, but it is also possible to use a collecting mirror instead of the collecting lens 25 to collect the scattered light onto the photoelectric conversion element.

[0089] Any light scattering airborne particle counter can be used as long as it complies with ISO21501-04, but an example of a commercially available counter is the Optical Particle Sizer 3330 (manufactured by TSI).

[0090] The PM10 number concentration is preferably measured under the following conditions. Load applied to test specimen: 40N Slip angle of specimen: 6° Wheel speed: 20km / h Test piece running distance: 2000m Grindstone temperature 10℃ Antifouling sand amount: 0.2g / min Grindstone grain size: 60 mesh Sample air suction volume: 1L / min Measurement time: 6 minutes from the start of the LAT abrasion test to 6 minutes after

[0091] (PM10 emission measurement system) Furthermore, the amount of PM10 generated in the LAT abrasion test can be evaluated using a PM10 generation amount measurement system equipped with an abrasion test section and a PM10 measurement section. One embodiment of the present invention is a PM10 generation amount measurement system equipped with an abrasion test section and a PM10 measurement section.

[0092] In this system, the abrasion test unit has a grinding wheel that rotates in a vertical plane and a test piece support unit that can rotate on an axis parallel to the vertical plane. The test piece is formed by wrapping a rubber sheet for evaluation taken from the tread surface of a tire around the outer periphery of a roller body, and the test piece is brought into contact with the grinding wheel to generate PM10. The PM10 measurement unit supplies sample air containing the PM10 from a sample air supply unit to a particle detection region and measures PM10 in the particle detection region. The PM10 measurement unit is preferably a PM10 number concentration measurement unit that measures the number concentration of PM10 in the sample air using a light scattering airborne particle counting method.

[0093] The test specimen was formed by wrapping a rubber sheet for evaluation, cut out to a thickness of 2 mm ± 1 mm from the tread surface of a tire, around the outer periphery of a roller. The shape of the test specimen was a cylindrical roller having an outer diameter of 84 mm ± 2 mm, an inner diameter of 35 mm ± 1 mm, and a through hole with an axial length of 18 mm ± 1 mm.

[0094] In this embodiment, a PM10 generation amount measurement system having both an LAT abrasion test section and a PM10 measurement section in the same chamber is preferred, and a PM10 generation amount measurement system having a sample air collection section in the same chamber is more preferred. Here, the sample air is collected at a location 25 cm vertically downward, 15 cm horizontally forward, and 10 cm horizontally to the right, with the center of contact between the test piece and the grinding disk as the reference point and the side where the grinding disk is located as the back side. The sample air collection section has an opening for collecting sample air, and the sample air is sucked in by a suction pump.

[0095] The test piece used in the PM10 emission measurement system can be suitably a test piece prepared in the same manner as the test piece preparation method described above.

[0096] The grinding disk in the PM10 generation measurement system can be the same as the grinding disk used in the LAT abrasion tester. Furthermore, the contact between the grinding disk and the test piece in the PM10 generation measurement system can be performed in the same manner as described for the LAT abrasion tester.

[0097] The PM10 measurement unit is preferably a PM10 number concentration measurement unit having a configuration similar to that of the light scattering airborne particle counter. The PM10 measurement unit is also preferably equipped with a sample air supply unit, such as a pump for supplying sample air and appropriate piping. It is more preferable that the PM10 measurement unit is a PM10 number concentration measurement unit equipped with a sample air supply unit.

[0098] <Tires> Hereinafter, a tire for an electric vehicle according to one embodiment of the present invention will be described with reference to the drawings as appropriate. However, the drawings are merely examples for the purpose of explanation.

[0099] Fig. 5 is a schematic diagram showing a portion of a cross section (upper right portion of the cross section) taken along the tire meridian of a tire according to one embodiment of the present invention. In Fig. 5, the tire 1 has a tread portion 2 and a carcass 31 on the radially inner side of the tread portion.

[0100] (Regarding formula (1)) Equation (1) is the ratio of the number concentration P (particles / cm) of PM10 generated in the LAT abrasion test to the amount of abrasion AV of the evaluation rubber sheet in the LAT abrasion test. 3 The right-hand side of formula (1) is preferably 1600, more preferably 1400, even more preferably 1200, and particularly preferably 1000. On the other hand, there is no particular lower limit to the value of the left-hand side of formula (1), but it is usually about 300, or may be about 500 or about 700.

[0101] If a rubber composition with a high density is used, the value of formula (1) can be reduced, and conversely, the value of formula (1) can be increased. Also, if a rubber composition with a high viscosity is used, the number concentration of PM10 will be reduced, and the value of formula (1) can be reduced, and conversely, the value of formula (1) can be increased.

[0102] Equation (2) is the ratio of the number concentration P (particles / cm) of PM10 generated in the LAT abrasion test to the amount of abrasion AV of the evaluation rubber sheet in the LAT abrasion test. 3 The formula (2) specifies that the value obtained by multiplying the ratio of the product of the acetone extractable amount AE (mass%) of the rubber composition constituting the tread portion and 0°C tan δ (AE x 0°C tan δ) to the ratio (P / AV) of the rubber composition to the acetone extractable amount AE (mass%) of the rubber composition constituting the tread portion and 0°C tan δ by 1000 is 5.0 or more. The right-hand side of formula (2) is preferably 6.0, more preferably 8.0, even more preferably 10.0, and still more preferably 12.0. On the other hand, there is no particular upper limit to the value of the left-hand side of formula (2), but it is usually about 25, or may be about 20 or about 15.

[0103] The value of P / AV can be adjusted as described above, and the 0°C tan δ and acetone extractable amount of the rubber composition can be appropriately adjusted by the types and blending amounts of the rubber component, plasticizer, etc. The value of the left side of formula (2) can be adjusted by adjusting these.

[0104] In this embodiment, the LAT wear test is a test conducted under the following conditions. <LAT Wear Test> Using a wear testing machine having a grinding wheel disk rotating in a vertical plane and a test piece rotatably supported by an axis parallel to the vertical plane, the test piece is created according to the following test piece creation method, and the test is conducted in accordance with ISO 23233 by bringing the test piece into contact with the grinding wheel disk under the following conditions. Details of the test method are as described above. Load applied to the test piece: 40 N Slip angle of the test piece: 6° Speed of the grinding wheel surface: 20 km / h Travel distance of the test piece: 2000 m Grinding wheel temperature: 10 °C Anti-fouling sand amount: 0.2 g / min Grain size of the grinding wheel: 60 mesh

[0105] In this embodiment, the test piece used in the LAT wear test is created by the following method. Details of the creation method are as described above. <Test Piece Creation Method> An evaluation rubber sheet is cut out from the tread surface of the tire with a thickness of 2 mm ± 1 mm, and is wound along the outer peripheral surface of the roller body. The shape of the test piece after winding is made into a cylindrical shape having an outer diameter of 84 mm ± 2 mm, an inner diameter of 35 mm ± 1 mm, and an axial length (width) of 18 mm ± 1 mm, and having a through hole.

[0106] In this embodiment, the number concentration of PM10 generated in the LAT wear test is measured under the following measurement conditions. Details of the measurement method are as described above. <PM10 Number Concentration Measurement Conditions> Using an optical scattering type airborne particle counter, in accordance with ISO 21501-04, measurement is conducted under the following conditions. Sample air collection location: A location 25 cm vertically downward, 15 cm horizontally forward, and 10 cm horizontally to the right from the ground center of the test piece with respect to the grinding wheel disk, with the side where the grinding wheel disk is located being the back side. Sample air suction volume: 1 L / min Measurement time: 6 minutes from the start of the LAT wear test to 6 minutes later.

[0107] (Acetone extractable amount) From the viewpoint of the effects of the present invention, the acetone extractable amount AE of the rubber composition constituting the tread portion is 20% by mass or more, preferably 21% by mass or more, more preferably 22% by mass or more, and even more preferably 24% by mass or more. Furthermore, from the viewpoint of the effects of the present invention, the acetone extractable amount AE is, for example, 50% by mass or less, preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less. The acetone extractable amount can be adjusted by changing the type and amount of chemicals blended into the rubber composition. For example, the acetone extractable amount can be increased by increasing the content of oil or resin.

[0108] (0℃ tanδ) The 0°C tan δ of the rubber composition is, for example, 0.45 or more, preferably 0.49 or more, more preferably 0.52 or more, even more preferably 0.60 or more, and even more preferably 0.80 or more. The 0°C tan δ is, for example, 1.00 or less, preferably 0.98 or less, more preferably 0.95 or less, even more preferably 0.93 or less, and even more preferably 0.90 or less. The 0°C tan δ value can be adjusted using conventional methods in the tire industry. For example, by reducing the filler content, the 0°C tan δ value can be reduced, and conversely, by increasing the filler content, the 0°C tan δ value can be increased. Therefore, those skilled in the art can appropriately adjust the 0°C tan δ value depending on the target 0°C tan δ.

[0109] (Carcass cord and fineness) In one embodiment of the present invention, the carcass includes at least one carcass ply, and the carcass ply is composed of a plurality of carcass cords and a topping rubber covering the carcass cords. The carcass cords may be organic fiber cords that are commonly used as reinforcing materials in the tire industry. The carcass cord may be a single cord or may be formed by twisting a plurality of cords. The carcass cord testing method complies with JIS L 1017.

[0110] Examples of organic fibers used in the organic fiber cord include polyester fibers such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); nylon fibers; rayon fibers; vinylon fibers; aramid fibers; and polyurethane fibers. One or more types of organic fiber cords can be used. In this case, a hybrid cord can also be used in which multiple types of organic fiber cords are twisted together.

[0111] The carcass cord preferably has a fineness (dtex) of 5,000 or more, more preferably 6,000 or more, even more preferably 6,600 or more, and particularly preferably 7,600 or more.

[0112] (Regarding equation (3)) In the tire according to the embodiment of the present invention, the fineness (dtex) of the carcass cord is F, and the maximum load capacity (kg) of the tire is W. L When this is the case, the ratio of the fineness to the maximum load capacity shall be 5.6 or more.

[0113] The right side of formula (3) is preferably 5.8, more preferably 6.0, even more preferably 6.4, even more preferably 7.0, even more preferably 7.6, even more preferably 8.0, even more preferably 10.0, even more preferably 12.0, even more preferably 14.0.

[0114] Maximum load capacity W L is a value determined by the tire section width Wt (mm), tire section height Ht (mm), and tire outer diameter Dt (mm). It can be increased by increasing the virtual volume V of the space occupied by the tire, or conversely, it can be decreased by increasing the virtual volume V. L The value of W L can be reduced by decreasing the value of F relative to the value of W L can be increased by increasing the value of F relative to the value of

[0115] (Regarding equation (4)) Equation (4) is the maximum load capacity W of the electric vehicle tire. L The ratio of the weight G of the electric vehicle tire to the L ) is less than 0.015. The right side of formula (4) is preferably 0.014, more preferably 0.013, even more preferably 0.012, and even more preferably 0.010.

[0116] As mentioned above, the maximum load capacity W L is a value determined according to the tire section width Wt (mm), tire section height Ht (mm), and tire outer diameter Dt (mm). The tire weight can also be increased or decreased as appropriate by adjusting the rubber composition blend, cord, etc. The value of formula (4) is W L can be reduced by decreasing the value of G relative to the value of W L can be increased by increasing the value of G relative to the value of

[0117] (negative rate of tread surface) In one embodiment, the negative ratio of the center land zone is preferably more than 0% and less than 15%.

[0118] FIG. 6 shows the contact patch shape of a tire according to one embodiment of the present invention when a normal load is applied under normal conditions. The tire's tread surface includes four circumferential grooves 41 extending in the tire circumferential direction, a pair of outermost circumferential grooves 41A located on the outermost sides of the tire, and a center land portion 43 sandwiched between the shoulder land portions. In FIG. 6, the center land portion includes a crown land portion located on the tire centerline or closest to the tire centerline, and a middle land portion sandwiched between the crown land portion and the shoulder land portion. When there are two land portions closest to the centerline, both of them are considered to be the crown land portion. Also in FIG. 6, the circumferential grooves 41 include a pair of outermost circumferential grooves 41A and a pair of center circumferential grooves 41B located between the pair of outermost circumferential grooves 41A. In this embodiment, each circumferential groove 41 extends linearly parallel to the tire circumferential direction. Each circumferential groove 41 may, for example, extend in a wavy pattern. In this embodiment, one of the outermost circumferential grooves 41A has a groove width smaller than the other circumferential grooves 41, but the present invention is not limited to this.

[0119] The negative ratio of the center land portion is more than 0%, preferably more than 2%, more preferably more than 4%, and even more preferably more than 6%, and is less than 15%, preferably less than 14%, more preferably less than 13%, and even more preferably less than 12%.

[0120] The negative ratio in the shoulder land portion is preferably more than 20%, more preferably more than 23%, and even more preferably more than 25%.

[0121] (Rubber composition) In an embodiment of the present invention, the rubber composition constituting the tread portion contains a rubber component, a filler, and a plasticizer containing at least one selected from the group consisting of resins and liquid rubbers.

[0122] <Rubber component> The rubber composition constituting the tread portion preferably contains a rubber component containing at least one selected from isoprene-based rubber (IR rubber) and styrene-butadiene rubber (SBR). In this case, the rubber component may contain rubber components other than IR rubber and SBR. The rubber component may consist of only IR rubber and SBR, or may consist of only IR rubber or SBR. Each rubber that can constitute the rubber component is described below.

[0123] (Isoprene rubber) Examples of isoprene-based rubbers (IR rubbers) include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. Examples of NR include SIR20, RSS#3, TSR20, and SVR-L, which are commonly used in the rubber industry. Examples of IR include IR2200 and other commonly used rubbers. Examples of modified NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. Isoprene-based rubbers may be used alone or in combination.

[0124] The content of the IR rubber in 100% by mass of the rubber component is, for example, more than 5% by mass, preferably more than 8% by mass, and more preferably 10% by mass or more, while the content is, for example, 100% by mass or less, preferably less than 90% by mass, and more preferably less than 80% by mass.

[0125] (SBR) Styrene-butadiene rubber (SBR) is not particularly limited and includes, for example, unmodified emulsion-polymerized styrene-butadiene rubber (E-SBR) and solution-polymerized styrene-butadiene rubber (S-SBR), as well as modified SBRs such as modified emulsion-polymerized styrene-butadiene rubber (modified E-SBR) and modified solution-polymerized styrene-butadiene rubber (modified S-SBR). Examples of modified SBR include SBRs whose terminals and / or main chains are modified, and modified SBRs (condensates, branched structures, etc.) coupled with tin or silicon compounds. SBRs include oil-extended types in which flexibility is adjusted by adding extender oil, and non-oil-extended types in which no extender oil is added, and either type can be used. When oil-extended SBR is used, the amount of oil extension in SBR, i.e., the content of oil-extending oil contained in SBR, is preferably 10 to 50 parts by mass per 100 parts by mass of rubber solids of SBR. Examples of such SBR that can be used include those manufactured by JSR Corporation, Asahi Kasei Chemicals Corporation, Zeon Corporation, and ZS Elastomers Co., Ltd. They can also be produced by the methods described in the later examples. SBR can be used alone or in combination of two or more types.

[0126] The styrene content of SBR is, for example, 35% by mass or less, preferably 30% by mass or less, more preferably 28% by mass or less, and even more preferably 25% by mass or less. The styrene content of SBR is preferably more than 10% by mass, more preferably more than 12% by mass, even more preferably more than 15% by mass, and even more preferably more than 18% by mass.

[0127] The vinyl content (amount of 1,2-bonded butadiene units) of SBR can be, for example, more than 10 mol%, preferably more than 15 mol%, more preferably 20 mol% or more, and even more preferably 22 mol% or more, and is preferably less than 80 mol%, more preferably less than 70 mol%, and even more preferably less than 60 mol%.

[0128] When the rubber component contains SBR, the content of SBR in 100% by mass of the rubber component is, for example, more than 40% by mass, preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and still more preferably 80% by mass or more.On the other hand, the content is, for example, 100% by mass or less, preferably less than 97% by mass, more preferably less than 95% by mass, and still more preferably 90% by mass or less.

[0129] The total styrene amount of the rubber component is, for example, less than 30% by mass, preferably less than 25% by mass, more preferably less than 23% by mass, even more preferably less than 22% by mass, even more preferably less than 20% by mass, even more preferably 17% by mass or less, and even more preferably 16% by mass or less.

[0130] (BR) The rubber composition constituting the tread portion may contain butadiene rubber (BR) in addition to IR rubber and SBR. The BR is not particularly limited, and examples include those commonly used in the tire industry, such as BR with a high cis content, BR containing 1,2-syndiotactic polybutadiene crystals (SPB-containing BR), butadiene rubber synthesized using a rare earth catalyst (rare earth-based BR), tin-modified butadiene rubber modified with a tin compound (tin-modified BR), and other modified butadiene rubbers (modified BR). Commercially available BRs include those from UBE Corporation, JSR Corporation, Asahi Kasei Corporation, and Zeon Corporation. The modified BR may be any BR having a functional group that interacts with a filler such as silica. Examples include terminal-modified BR (terminal-modified BR having the functional group at the terminal) in which at least one terminal of the BR has been modified with a compound (modifier) ​​having the functional group, main-chain-modified BR having the functional group in the main chain, main-chain terminal-modified BR having the functional group in the main chain and at least one terminal (for example, main-chain terminal-modified BR having the functional group in the main chain and at least one terminal modified with the modifier), and terminal-modified BR modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or epoxy group introduced therein. Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an 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 the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferred.

[0131] The cis amount (cis content) of BR is preferably more than 90 mol%, more preferably more than 93 mol%, even more preferably more than 95 mol%, and even more preferably 97 mol% or more. The cis amount of BR can be measured by infrared absorption spectroscopy.

[0132] As the BR, for example, products available from UBE Corporation, JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. may be used. One type of BR may be used alone, or two or more types may be used in combination.

[0133] The BR content in 100% by mass of the rubber component is, for example, more than 5% by mass, preferably more than 7% by mass, and more preferably 10% by mass or more. On the other hand, the content is, for example, less than 90% by mass, preferably less than 80% by mass, more preferably less than 70% by mass, and even more preferably less than 60% by mass. By keeping the content within the above range, abrasion resistance tends to be improved.

[0134] (Other rubber) The other rubbers that can be used other than those mentioned above are not particularly limited, and rubbers used in the tire field can be used. Examples include diene rubbers such as acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), and styrene-isoprene-butadiene copolymer rubber (SIBR). The other rubbers may be used alone or in combination of two or more.

[0135] (Rubber components synthesized from recycled and biomass-derived raw materials) Monomers, which are structural units of synthetic rubbers such as IR rubber, SBR, and BR, may be derived from underground resources such as petroleum and natural gas, or may be recycled from rubber products such as tires or non-rubber products such as polystyrene. Monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled polyisoprene, recycled butadiene, and recycled aromatic vinyl compounds. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl compounds include, but are not limited to, styrene. Among these, recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) are preferably used as raw materials.

[0136] The method for producing the recycled monomer is not particularly limited, and examples thereof include synthesis from recycled naphtha obtained by decomposing rubber products such as tires. The method for producing recycled naphtha is also not particularly limited, and examples thereof include decomposing rubber products such as tires under high temperature and pressure, decomposing with microwaves, or mechanically crushing and then extracting.

[0137] Furthermore, the monomers that are the structural units of polymers such as IR, SBR, and BR may be derived from biomass. In this specification, biomass refers to materials derived from natural resources such as plants. Examples of biomass include, but are not limited to, agricultural, forestry, and fishery products, sugar, wood chips, plant residues after useful components have been extracted, plant-derived ethanol, and biomass naphtha.

[0138] Monomers derived from biomass (biomass monomers) are not particularly limited, and examples thereof include biomass-derived butadiene and biomass-derived aromatic vinyl compounds. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl compounds include, but are not limited to, styrene. The method for producing biomass monomers is not particularly limited, and examples include biological and / or chemical and / or physical conversion of animals and plants. A representative example of biological conversion is fermentation by microorganisms, and examples of chemical and / or physical conversion include catalytic conversion, high heat conversion, high pressure conversion, electromagnetic wave conversion, critical fluid conversion, and combinations thereof.

[0139] Polymers synthesized from biomass monomer components (biomass polymers) are not particularly limited and include polybutadiene rubber synthesized from biomass-derived butadiene, aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl compounds, etc. Examples of the aromatic vinyl / butadiene copolymers include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0140] Whether a polymer's raw material is biomass-derived can be determined by its pMC (percent modern carbon) measured in accordance with ASTM D6866-10. pMC is the modern standard reference carbon. 14 of sample against C concentration 14 This is the ratio of C concentrations and is a value used as an index of the biomass ratio of a compound. The significance of this value is explained below.

[0141] 1 mole of carbon atoms (6.02 × 10 23 ) contains approximately 6.02 × 10 atoms, which is about one trillionth of the number of ordinary carbon atoms. 11 pieces 14 C exists. 14The half-life of C is 5730 years, 14 C is decreasing regularly. Therefore, in the case of fossil fuels such as coal, oil, and natural gas, which are thought to have been absorbed and fixed by plants and other organisms more than 226,000 years ago, C was also included in these when they were first fixed. 14 All C elements have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas contain 14 Therefore, chemicals produced from these fossil fuels do not contain any C element. 14 It does not contain any C elements.

[0142] on the other hand, 14 C is constantly produced by cosmic rays undergoing nuclear reactions in the atmosphere. 14 The amount of C is balanced between radioactive decay and nuclear reaction, and in the Earth's atmospheric environment, 14 Therefore, the amount of carbon derived from biomass resources currently circulating in the environment is constant. 14 As mentioned above, the C concentration is approximately 1 × 10 -12 The value is approximately mol %. Therefore, the biomass ratio in a compound can be calculated by using the difference between these values.

[0143] this 14 C is typically measured using accelerator mass spectrometry based on a tandem accelerator. 13 C concentration ( 13 C / 12 C). 14 C concentration ( 14 C / 12 C) is measured. 14 The modern standard reference for the C concentration is the carbon circulating in nature as of 1950. 14The specific standard substance used is the oxalic acid standard provided by NIST (National Institute of Standards and Technology). The specific activity of carbon in this oxalic acid (per gram of carbon) is 14 The radioactivity of C is separated into carbon isotopes, 13 The standard value is the value corrected for decay from 1950 to the measurement date. 14 This is used as the C concentration value (100%). The ratio of this value to the value of the actually measured sample is the pMC value.

[0144] Therefore, if rubber is made from 100% biomass-derived materials, although there are regional differences, it will usually not reach 100 under normal conditions, so it will show a value of approximately 110 pMC. On the other hand, for chemical substances derived from petroleum and other fossil fuels, 14 When the carbon concentration is measured, it will show a value of about 0 pMC (for example, 0.3 pMC), which corresponds to the above-mentioned biomass ratio of 0%.

[0145] From the above, it is preferable in terms of environmental protection to use a material such as rubber having a high pMC value, that is, a material such as rubber having a high biomass ratio, in a rubber composition.

[0146] <Filler> The filler refers to a reinforcing filler, and in this embodiment, includes carbon black, silica, and other reinforcing fillers used in the tire industry. Preferably, the filler contains silica. When the filler contains silica, it may further contain a silane coupling agent.

[0147] (carbon black) The carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N660, and N762. The raw material for carbon black may be a biomass material such as lignin or vegetable oil, or pyrolysis oil obtained by pyrolysis of waste tires. Carbon black may be produced by combustion, such as in a furnace, by hydrothermal carbonization (HTC), or by pyrolysis of methane, such as in a thermal black process. Commercially available carbon blacks include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., and Columbia Carbon Co., Ltd. These may be used alone or in combination.

[0148] The average primary particle diameter of carbon black is preferably 20 nm or more, more preferably 25 nm or more, even more preferably 30 nm or more, and particularly preferably 35 nm or more. By setting the average primary particle diameter of carbon black within the above range, it is thought that the rubber molecules bound by the carbon black are minimized, allowing them to move flexibly, thereby enabling the polymer molecular chain to relieve stress in response to input. Meanwhile, the average primary particle diameter is preferably 90 nm or less, more preferably 75 nm or less, and even more preferably 60 nm or less. The average primary particle diameter of carbon black is measured by the above-mentioned measurement method.

[0149] The nitrogen adsorption specific surface area (N2SA) of the carbon black is not particularly limited, but from the viewpoint of obtaining sufficient reinforcement and good abrasion resistance, it is preferred that the N2SA be 30 m 2 / g or more is preferable, and 40m 2 / g is more preferable, and 50m 2 / g or more is more preferable, and 60m 2 / g or more is more preferable, and 70m 2 In addition, from the viewpoint of excellent dispersibility and low heat generation, the N2SA has a viscosity of 300 m / g or more. 2 / g is preferable, and 200m 2 / g is more preferable, and 150m 2 / g is more preferable, and 120m 2 / g is more preferable, and 110m 2 / g is more preferable, and 100m 2 / g is more preferable, and 90m 2 It is more preferable that the N of carbon black in this specification is less than 1 / g. 2 SA is a value measured in accordance with JIS K 6217-2:2017.

[0150] The carbon black may include recycled carbon black. Recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, citing "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, describes that recycled carbon black can be obtained by pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (

[0027] ). Carbon black obtained from such pyrolysis processes typically lacks functional groups on its surface, as mentioned in

[0004] of Japanese Patent No. 6856781 (Comparison of the Surface Morphology and Chemistry of Pyrolytic Carbon Black with Commercial Carbon Black, Powder Technology 160 (2005) pp. 190-193).

[0151] Recycled carbon black may lack functional groups on its surface, or may be treated to include functional groups on its surface. Treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, European Patent Application Publication No. 3,173,251 discloses treating carbon black obtained from a pyrolysis process with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Furthermore, Japanese Patent No. 6,856,781 discloses treating carbon black obtained from a pyrolysis process with an amino acid compound containing at least one thiol or disulfide group to obtain surface-activated carbon black. In an embodiment of the present invention, recycled carbon black also includes carbon blacks that have been treated to include functional groups on their surfaces.

[0152] (Carbon black content) The carbon black content is, for example, more than 3 parts by mass, preferably more than 4 parts by mass, and more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. On the other hand, the content is preferably less than 100 parts by mass, more preferably less than 80 parts by mass, and even more preferably less than 60 parts by mass. When the carbon black content is within the above range, sufficient reinforcement and good dispersion in the rubber are obtained, and sufficient grip performance tends to be obtained.

[0153] (silica) The silica is not particularly limited, and can be, for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrated silica), or other silica commonly used in the tire industry. The raw material for silica is also not particularly limited, and can be, for example, a mineral-derived raw material such as quartz, a biological raw material such as rice husk (for example, silica made from biomass materials such as rice husk), or silica recycled from silica-containing products. Among these, hydrated silica prepared by a wet method is preferred because it contains a large number of silanol groups. These silicas can be used alone or in combination of two or more types.

[0154] Silica made from biomass materials can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then reacting the silicate with sulfuric acid in the same manner as conventional wet-process silica to produce a silicon dioxide precipitate, which is then filtered, washed with water, dried, and pulverized.

[0155] Silica recycled from silica-containing products can be, for example, silica recovered from products containing silica, such as electronic components such as semiconductors, tires, desiccants, and filtering materials such as diatomaceous earth. The recovery method is not particularly limited, and examples include thermal decomposition and decomposition by electromagnetic waves. Among these, silica recovered from electronic components such as semiconductors or tires is preferred.

[0156] When silica crystallizes, it becomes insoluble in water, and its component, silicic acid, cannot be utilized. By controlling the combustion temperature and duration, it is possible to suppress the crystallization of silica in rice husk ash (see, for example, JP 2009-2594 A and Akita Prefectural University Web Journal B / 2019, vol. 6, pp. 216-222).

[0157] Amorphous silica extracted from rice husks may be commercially available from Wilmar Co., Ltd., etc.

[0158] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 50 m 2 / g, more preferably 100m 2 / g, more preferably 150m 2 / g, particularly preferably 170m 2 The upper limit of the N2SA of silica is not particularly limited, but is preferably 350 m 2 / g, more preferably less than 250m 2 / g, more preferably less than 200m 2 / g. By keeping it within the above range, cut resistance tends to be improved. The N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0159] (Silica content) When silica is contained, the content per 100 parts by mass of the rubber component is not particularly limited, but from the viewpoint of ensuring grip performance, it is preferably more than 10 parts by mass, more preferably more than 20 parts by mass, more preferably more than 30 parts by mass, and even more preferably more than 40 parts by mass. Also, from the viewpoints of dispersibility and processability of the silica, the content is preferably less than 150 parts by mass, more preferably less than 130 parts by mass, even more preferably less than 110 parts by mass, and even more preferably less than 100 parts by mass.

[0160] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent.Silane coupling agent is not particularly limited, but for example, sulfide-based silane coupling agent such as bis(3-triethoxysilylpropyl) disulfide, bis(3-triethoxysilylpropyl) tetrasulfide; mercapto-based silane coupling agent such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; vinyl-based silane coupling agent such as vinyltriethoxysilane, vinyltrimethoxysilane; 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane Examples of suitable silane coupling agents include amino-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, sulfide-based silane coupling agents and / or mercapto-based silane coupling agents are preferred. Examples of suitable silane coupling agents include those commercially available from Evonik Degussa GmbH and Momentive GmbH. These silane coupling agents may be used alone or in combination.

[0161] (Silane coupling agent content) When containing silane coupling agent, the content of silane coupling agent is preferably more than 1 part by mass, more preferably more than 3 parts by mass, even more preferably more than 5 parts by mass, and even more preferably more than 7 parts by mass, based on 100 parts by mass of silica.On the other hand, the content is preferably less than 20 parts by mass, more preferably less than 18 parts by mass, even more preferably less than 16 parts by mass, and even more preferably less than 14 parts by mass.By making it within the above range, the dispersibility of silica tends to improve.

[0162] (Other fillers) The other fillers are not particularly limited, and materials known in the field of the tire industry can be used, such as aluminum hydroxide, calcium carbonate, alumina, clay, talc, etc., which have been conventionally and commonly used in the tire industry. These may be used alone or in combination of two or more.

[0163] [Other compounding agents] The rubber composition contains, in addition to the rubber component and filler, a plasticizer containing at least one selected from the group consisting of resins and liquid rubbers, and may also contain, in addition to the plasticizer, compounding agents commonly used in the tire industry, such as plasticizers, processing aids, vulcanized rubber particles, wax, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators.

[0164] <Plasticizer> A plasticizer is a material that imparts plasticity to rubber components and encompasses both liquid and solid plasticizers at 25°C. Examples of plasticizers include resins, oils, liquid rubbers, and ester-based plasticizers. These plasticizers may be derived from mineral resources such as petroleum and natural gas, biomass-derived materials, or naphtha recycled from rubber and non-rubber products. Low-molecular-weight hydrocarbon components obtained by pyrolysis and extraction of used tires or products containing various components may also be used as plasticizers. Plasticizers may be used singly or in combination.

[0165] <Resin> The rubber composition contains a plasticizer containing at least one selected from the group consisting of resins and liquid rubbers. The resin is not particularly limited, but resins commonly used in the tire industry can be used, such as aromatic vinyl resins, dicyclopentadiene resins, C9 resins, C5 resins, C5C9 resins, terpene resins, rosin resins, and phenolic resins. Of these, aromatic vinyl resins, dicyclopentadiene resins, C9 resins, and terpene resins are preferred. These resins may be used alone or in combination.

[0166] <Aromatic vinyl resin> The term "aromatic vinyl resin" refers to a resin containing at least one aromatic vinyl compound selected from the group consisting of styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene, etc., as the most abundant monomer component, preferably at least 50 mol %, and may be hydrogenated or modified. As the aromatic vinyl resin, a homopolymer of α-methylstyrene or styrene or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, because they are economical, easy to process, and have excellent heat generation properties. As the aromatic vinyl resin, commercially available products available from, for example, Kraton, Eastman Chemical, Mitsui Chemicals, Inc., etc., can be used. These aromatic vinyl resins may be used alone or in combination of two or more.

[0167] <Dicyclopentadiene resin> The term "dicyclopentadiene-based resin" refers to a resin containing dicyclopentadiene (DCPD) as the monomer component with the highest content, and may be a hydrogenated or modified resin. Examples of dicyclopentadiene-based resins include DCPD / C9 resins obtained by copolymerizing dicyclopentadiene with the C9 fraction, with DCPD / C9 resins being preferred. Examples of DCPD resins that can be used include those commercially available from ExxonMobil Corporation, ENEOS Corporation, Nippon Zeon Co., Ltd., Maruzen Petrochemical Co., Ltd., and the like. These dicyclopentadiene-based resins may be used singly or in combination of two or more.

[0168] <C9 resin> The term "C9 resin" refers to a resin obtained by polymerizing a C9 fraction. It may be a C9 fraction polymerized alone or a copolymer obtained by copolymerizing a C9 fraction with other components. For example, a resin obtained by copolymerizing dicyclopentadiene (DCPD) with a C9 fraction is called a DCPD / C9 resin. These resins may also be hydrogenated or modified. Examples of C9 fractions include at least one petroleum fraction having 8 to 10 carbon atoms selected from the group consisting of vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene. Specific examples of C9 resins include coumarone-indene resin, coumarone resin, and indene resin. These C9 resins may be used alone or in combination.

[0169] <C5 resin> "C5 resin" refers to a resin obtained by polymerizing a C5 fraction other than dicyclopentadiene, and may be a hydrogenated or modified version of such a resin. Examples of C5 fractions other than dicyclopentadiene include at least one petroleum fraction having 4 to 5 carbon atoms selected from the group consisting of cyclopentadiene, isoprene, pentane, isopentane, neopentane, pentene, pentadiene, etc. These C5 resins may be used alone or in combination of two or more.

[0170] <C5C9 resin> The term "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. As the C5C9 resin, for example, commercially available resins from Tosoh Corporation, LUHUA, etc. may be used. These C5C9 resins may be used alone or in combination of two or more.

[0171] <Terpene resin> Terpene resins refer to resins containing at least one terpene compound selected from the group consisting of α-pinene, β-pinene, limonene, dipentene, etc., as the most abundant monomer component, preferably at least 50 mol %, and may be hydrogenated or modified. Specific examples of terpene resins include polyterpene resins containing only one or more of the terpene compounds as monomer components; aromatic-modified terpene resins containing the terpene compound and an aromatic compound as monomer components; and terpene phenolic resins containing the terpene compound and a phenolic compound as monomer components. Examples of aromatic compounds that serve as monomer components for aromatic-modified terpene resins include at least one selected from the group consisting of styrene, α-methylstyrene, vinyltoluene, divinyltoluene, etc. Examples of phenolic compounds that serve as monomer components for terpene phenolic resins include at least one selected from the group consisting of phenol, bisphenol A, cresol, xylenol, etc. These terpene resins may be used alone or in combination.

[0172] <Rosin-based resin> The rosin-based resin refers to a resin containing at least one rosin acid compound selected from the group consisting of abietic acid, neoabietic acid, palustric acid, isopimaric acid, etc., preferably as the monomer component with the largest content, more preferably at least 50 mol %, and may be hydrogenated or modified. The rosin-based resin is not particularly limited, but examples include natural rosin and rosin-modified resins obtained by modifying natural rosin through hydrogenation, disproportionation, dimerization, esterification, etc. These rosin-based resins may be used alone or in combination of two or more.

[0173] <Phenol-based resin> The phenolic resin refers to a resin containing a phenolic compound such as phenol or cresol as the monomer component with the largest content, preferably 50 mol% or more. Examples of the phenolic resin include, but are not limited to, phenol-formaldehyde resin, alkylphenol-formaldehyde resin, alkylphenol-acetylene resin, and oil-modified phenol-formaldehyde resin. These phenolic resins may be used alone or in combination of two or more.

[0174] <Liquid rubber> The rubber composition contains a plasticizer containing at least one selected from the group consisting of resins and liquid rubbers. The liquid rubber is not particularly limited as long as it is a polymer that is in a liquid state at 25°C, and examples thereof include liquid butadiene rubber (liquid BR), liquid styrene butadiene rubber (liquid SBR), liquid isoprene rubber (liquid IR), liquid styrene isoprene rubber (liquid SIR), and liquid farnesene rubber. One type of liquid rubber may be used alone, or two or more types may be used in combination.

[0175] <Plasticizer content> In an embodiment of the present invention, the content of the plasticizer containing at least one selected from the group consisting of a resin and a liquid rubber may be 30 parts by mass or more, preferably 31 parts by mass or more, more preferably 32 parts by mass or more, even more preferably 35 parts by mass or more, and still more preferably 40 parts by mass or more, per 100 parts by mass of the rubber component.

[0176] (Plasticizers other than resins) Plasticizers other than resins and liquid rubbers, such as oils and ester-based plasticizers, will now be described.

[0177] (oil) Examples of oils include mineral oil, vegetable oil, and animal oil. From the viewpoint of life cycle assessment, waste oils used in rubber mixers and engines, and refined waste cooking oils used in restaurants may also be used. One type of oil may be used alone, or two or more types may be used in combination.

[0178] As used herein, mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. Examples of mineral oil include paraffinic oil (mineral oil), naphthenic oil, and aromatic oil. Specific examples of mineral oil include mild extracted solvate (MES), distillate aromatic extract (DAE), treated distillate aromatic extract (TDAE), treated residual aromatic extract (TRAE), and residual aromatic extract (RAE). Furthermore, as an environmental measure, oils with a low content of polycyclic aromatic compounds (PCA) can also be used. Examples of low PCA oils include MES, TDAE, and heavy naphthenic oil.

[0179] In this specification, examples of vegetable oils include linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grapeseed oil, and Japan wax. Further examples of vegetable oils include refined oils (such as salad oil) obtained by refining the above oils, interesterified oils obtained by interesterifying the above oils, hardened oils obtained by hydrogenating the above oils, thermally polymerized oils obtained by thermally polymerizing the above oils, oxidatively polymerized oils obtained by oxidizing the above oils, and waste edible oils recovered from edible oils. Vegetable oils may be liquid or solid at 25°C.

[0180] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxyl group of glycerin is esterified with a fatty acid. The acylglycerol is not particularly limited and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Furthermore, the acylglycerol may be a monomer, a dimer, or a polymer (trimer or higher). Dimer or higher acylglycerols can be obtained by thermal polymerization, oxidative polymerization, or the like. The acylglycerol may be liquid or solid at 25°C.

[0181] The method for confirming whether the rubber composition contains the acylglycerol is not particularly limited, but may be any of the following: 1 For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at 25°C for 24 hours, and after removing the rubber composition, the 1 When H-NMR was measured, signals were observed around 5.26 ppm, 4.28 ppm, and 4.15 ppm when the signal of tetramethylsilane (TMS) was set at 0.00 ppm. These signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atoms of the ester group. In this paragraph, "around" refers to a range of ±0.10 ppm.

[0182] The fatty acid is not particularly limited and may be either an unsaturated fatty acid or a saturated fatty acid. Examples of unsaturated fatty acids include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of saturated fatty acids include butyric acid and lauric acid.

[0183] Among these, it is desirable that the fatty acid contains a fatty acid with few double bonds, i.e., saturated fatty acid or monounsaturated fatty acid, and oleic acid is preferred. As a vegetable oil containing such a fatty acid, for example, vegetable oil containing saturated fatty acid or monounsaturated fatty acid may be used, or vegetable oil modified by ester exchange or the like may be used. Furthermore, in order to produce vegetable oil containing such a fatty acid, plants may be improved by breeding, genetic modification, genome editing, or the like.

[0184] As the vegetable oil, for example, commercially available oils from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoi Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., Fuji Kosan Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0185] Examples of animal oils include fish oil, beef tallow, whale oil, and oleyl alcohol derived from these.

[0186] (ester plasticizer) Examples of ester-based plasticizers include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), and trixylenyl phosphate (TXP). One type of ester-based plasticizer may be used alone, or two or more types may be used in combination.

[0187] [Other compounding agents] In addition to the rubber component, filler, and plasticizer, the rubber composition may contain, as appropriate, compounding agents that are generally used in the tire industry, such as processing aids, vulcanized rubber particles, wax, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators.

[0188] (vulcanized rubber particles) The vulcanized rubber particles are particles made of vulcanized rubber, and specifically, rubber powder as specified in JIS K 6316:2017 can be used. From the standpoint of environmental considerations and cost, recycled rubber powder produced from crushed waste tires is preferred. One type of vulcanized rubber particle may be used alone, or two or more types may be used in combination.

[0189] The vulcanized rubber particles are not particularly limited, and may be unmodified vulcanized rubber particles or modified vulcanized rubber particles.

[0190] As commercially available vulcanized rubber, for example, products from Lehigh, Muraoka Rubber Industries, Ltd., etc. can be used.

[0191] (processing aids) Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. These processing aids may be used alone or in combination of two or more. Examples of processing aids that can be used include those commercially available from Schill + Seilacher, Performance Additives, etc.

[0192] When a processing aid is contained, the content thereof per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1 part by mass, and even more preferably more than 1.5 parts by mass from the viewpoint of improving processability, and is preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and even more preferably less than 5.0 parts by mass from the viewpoint of abrasion resistance and breaking strength.

[0193] (wax) The wax is not particularly limited, and any wax commonly used in the tire industry can be suitably used, such as petroleum wax, mineral wax, and synthetic wax. Of these, petroleum wax is preferred. Petroleum waxes include, for example, paraffin wax, microcrystalline wax, and selected special waxes thereof, and paraffin wax is preferred. Waxes that can be used include, for example, those manufactured and sold by Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., Ltd., and the like. One type of wax can be used, or two or more types can be used in combination.

[0194] When the wax is contained, the amount thereof per 100 parts by mass of the rubber component is preferably more than 0.3 parts by mass, more preferably more than 0.7 parts by mass, and even more preferably more than 1.0 part by mass, while the amount is preferably less than 4.0 parts by mass, more preferably less than 3.0 parts by mass, and even more preferably less than 2.5 parts by mass.

[0195] (stearic acid) When stearic acid is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 0.7 parts by mass, and even more preferably 1 part by mass or more, from the viewpoint of processability, while the content is preferably less than 10 parts by mass, more preferably less than 5 parts by mass, and even more preferably less than 3 parts by mass, from the viewpoint of vulcanization rate.

[0196] (zinc oxide) When zinc oxide is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 0.7 parts by mass, and even more preferably more than 1 part by mass from the viewpoint of processability, while the content is preferably 10 parts by mass or less, more preferably less than 7 parts by mass, and even more preferably 5 parts by mass or less from the viewpoint of abrasion resistance.

[0197] (anti-aging agent) The antioxidant is not particularly limited, and examples thereof 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 (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), and N,N'-ditolyl-p-phenylenediamine. p-phenylenediamine antioxidants such as N-isopropyl-N'-phenyl-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers; 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. Among these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferred, and polymers of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. Commercially available products that can be used include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and Flexis Co., Ltd. One type of antioxidant may be used alone, or two or more types may be used in combination.

[0198] When an antioxidant is contained, the content thereof per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 0.8 parts by mass, and even more preferably more than 1.0 part by mass, while the content is preferably less than 7.0 parts by mass, more preferably less than 6.0 parts by mass, and even more preferably 5.0 parts by mass or less.

[0199] (vulcanizing agent) The vulcanizing agent is not particularly limited, and known vulcanizing agents can be used, such as organic peroxides, sulfur-based vulcanizing agents, resin vulcanizing agents, and metal oxides such as magnesium oxide. Of these, sulfur-based vulcanizing agents are preferred. Examples of sulfur-based vulcanizing agents that can be used include sulfur and sulfur donors such as morpholine disulfide. Of these, sulfur is preferred. One or more types of vulcanizing agents can be used in combination.

[0200] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur (oil-treated sulfur, special sulfur treated with a dispersant, masterbatch-type sulfur, etc.), and insoluble sulfur (oil-treated insoluble sulfur, etc.), all of which are preferably used. Among these, powdered sulfur is preferred. Examples of sulfur that can be used include those manufactured and sold by Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanritsu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc.

[0201] When a vulcanizing agent is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.4 parts by mass, more preferably more than 0.8 parts by mass, even more preferably more than 1.2 parts by mass, and even more preferably 1.4 parts by mass or more. On the other hand, the content is preferably less than 6.0 parts by mass, more preferably 5.0 parts by mass or less, and even more preferably less than 4.0 parts by mass. When the content of the vulcanizing agent is within the above range, an appropriate reinforcing effect tends to be obtained, and the effects of the present invention tend to be more effectively exhibited. Note that when the vulcanizing agent contains components other than sulfur, such as oil-treated sulfur, the content of the vulcanizing agent refers to the content of the sulfur component itself.

[0202] Known organic crosslinking agents can also be used as vulcanizing agents other than sulfur. The organic crosslinking agent is not particularly limited as long as it can form crosslinked chains other than polysulfide bonds. Examples of the organic crosslinking agent include alkylphenol-sulfur chloride condensate, sodium 1,6-hexamethylene-dithiosulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, and dicumyl peroxide. 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane is preferred. These organic crosslinking agents can be commercially available from Taoka Chemical Co., Ltd., Lanxess K.K., Flexis, and other companies.

[0203] (Vulcanization accelerator) The vulcanization accelerator is not particularly limited, but examples thereof include sulfenamide vulcanization accelerators, thiazole vulcanization accelerators, guanidine vulcanization accelerators, thiuram vulcanization accelerators, thiourea vulcanization accelerators, dithiocarbamate vulcanization accelerators, aldehyde-amine vulcanization accelerators, aldehyde-ammonia vulcanization accelerators, imidazoline vulcanization accelerators, xanthate vulcanization accelerators, and caprolactam disulfide. These vulcanization accelerators may be used alone or in combination of two or more. Among them, one or more vulcanization accelerators selected from the group consisting of sulfenamide vulcanization accelerators, thiazole vulcanization accelerators, and guanidine vulcanization accelerators are preferred, as they more suitably achieve the desired effects. The vulcanization accelerators may be used alone or in combination of two or more.

[0204] Examples of sulfenamide vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), and N,N'-dicyclohexyl-2-benzothiazolylsulfenamide (DZ). Examples of thiuram vulcanization accelerators include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, and tetrabenzylthiuram disulfide (TBzTD). Examples of guanidine vulcanization accelerators include 1,3-diphenylguanidine (DPG), di-orthotolylguanidine, and orthotolylbiguanidine.

[0205] Examples of thiazole vulcanization accelerators include 2-mercaptobenzothiazole (MBT) or a salt thereof, di-2-benzothiazolyl disulfide (MBTS), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, and 2-(2,6-diethyl-4-morpholinothio)benzothiazole.

[0206] Examples of guanidine vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine.

[0207] Examples of thiuram vulcanization accelerators include tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide, tetramethylthiuram monosulfide (TMTM), dipentamethylene thiuram disulfide, and dipentamethylene thiuram tetrasulfide.

[0208] Examples of the thiourea vulcanization accelerator include thiourea compounds such as thiacarbamide, diethylthiourea, dibutylthiourea, trimethylthiourea and diorthotolylthiourea, N,N'-diphenylthiourea, trimethylthiourea and N,N'-diethylthiourea.

[0209] Examples of dithiocarbamate vulcanization accelerators include piperidinium pentamethylenedithiocarbamate (PPDC), zinc dimethyldithiocarbamate (ZnMDC), zinc diethyldithiocarbamate (ZnEDC), zinc dibutyldithiocarbamate (ZnBDC), zinc dibenzyldithiocarbamate (ZDBzC), zinc N-ethyl-N-phenyldithiocarbamate (ZnEPDC), zinc N-pentamethylenedithiocarbamate (ZnPDC), sodium dibutyldithiocarbamate (NaBDC), copper dimethyldithiocarbamate (CuMDC), iron dimethyldithiocarbamate (FeMDC), and tellurium diethyldithiocarbamate (TeEDC).

[0210] The content of the vulcanization accelerator per 100 parts by mass of the rubber component is preferably more than 0.3 parts by mass, more preferably more than 0.4 parts by mass, and even more preferably more than 0.5 parts by mass. On the other hand, the content is preferably less than 7.0 parts by mass, more preferably less than 6.0 parts by mass, and even more preferably less than 5.5 parts by mass. When the content of the vulcanization accelerator is within the above range, breaking strength and elongation tend to be ensured, and the effects of the present invention tend to be more favorably exhibited.

[0211] <Other rubber components that make up tires> The tire according to the present invention may include rubber members other than those described above. Such other rubber members are not particularly limited, and various rubber members generally used in tires may be used.

[0212] In the tire according to the present invention, various materials containing carbon atoms (for example, rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from carbon dioxide in the atmosphere. As a method for obtaining compounds from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process in which methane is synthesized from carbon dioxide may be converted.

[0213] <Application> The tire according to the present invention can be used as a pneumatic tire or a non-pneumatic tire, and can be suitably used as a pneumatic tire. The tire according to the present invention is preferably used as a tire for an electric vehicle.

[0214] <Manufacturing method> The tire according to the embodiment of the present invention can be manufactured by a known method.

[0215] (Production of rubber composition) Each of the above rubber compositions can be produced by a known method. For example, they can be produced by kneading the above components using a rubber kneading device such as an open roll or an internal kneader (e.g., a Banbury mixer or kneader). The kneading process may include, for example, a base kneading process in which compounding ingredients and additives other than the vulcanizing agent and vulcanization accelerator are kneaded, and a final kneading (F kneading) process in which the vulcanizing agent and vulcanization accelerator are added to the kneaded product obtained in the base kneading process and kneaded. Furthermore, the base kneading process can be divided into multiple processes as desired. The kneading conditions are not particularly limited, but examples include a method in which the base kneading process involves kneading for 3 to 10 minutes at a discharge temperature of 150 to 170°C, and a method in which the final kneading process involves kneading for 1 to 5 minutes at a discharge temperature of 50 to 110°C.

[0216] (tire manufacturing) Each rubber composition obtained above can be extruded in the unvulcanized state to match the shape of the desired tire component, thereby forming an unvulcanized tread component. The tire according to this embodiment can be formed into an unvulcanized tire by molding the tread thus obtained together with other tire components in a tire building machine using a conventional method. A tire can be obtained by heating and pressurizing (vulcanizing) this unvulcanized tire in a vulcanizer. The vulcanization conditions are not particularly limited, and examples include a method of vulcanizing at 150 to 200°C for 5 to 30 minutes. [Example]

[0217] The following examples (working examples) are considered to be preferable for carrying out the present invention, but the scope of the present invention is not limited to these examples. Rubber compositions and tires obtained according to the tables were examined using the various chemicals shown below, and the results calculated based on the evaluation method described below are shown as durability indices at the bottom of each table.

[0218] <Material> The materials used in the examples and comparative examples will be summarized below. Natural rubber: TSR20 SBR1: SBR produced in Production Example 1 described below (styrene content: 23.5% by mass, vinyl content: 18% by mole, Mw: 500,000) SBR2: SBR produced in Production Example 2 described below (styrene content: 25% by mass, vinyl content: 25% by mole, Mw: 1,000,000) SBR3: SBR produced in Production Example 3 described below (styrene content: 20% by mass, vinyl content: 20% by mole, Mw: 700,000) SBR4: SBR produced in Production Example 4 described below (styrene content: 30% by mass, vinyl content: 22% by mole, Mw: 1.5 million) SBR5: HPR850 (manufactured by JSR Corporation, styrene content: 27.5% by mass, vinyl content: 59% by mole, Mw: 200,000) BR: UBEPOL BR150B (UBE Corporation, unmodified BR, cis content: 97 mol%, Mw: 440,000) Carbon black: Show Black N220 (manufactured by Cabot Japan Co., Ltd., N2SA: 114m 2 / g; ash content: less than 1% by mass) Silica: Ultrasil VN3 (manufactured by Evonik Degussa, N2SA: 175 ml 2 / g) Resin: Sylvares SA85 (Kraton, copolymer of α-methylstyrene and styrene, softening point: 85°C) Silane coupling agent: Si266 (Evonik Degussa, bis(3-triethoxysilylpropyl) disulfide) Oil: Diana Process NH-70S (Idemitsu Kosan Co., Ltd., aromatic process oil) Wax: Ozoace 0355 (Nippon Seiro Co., Ltd., paraffin-based) Antioxidant 1: Nocrac 6C (Ouchi Shinko Chemical Industry Co., Ltd., N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD)) Antioxidant 2: Nocrac RD (Ouchi Shinko Chemical Industry Co., Ltd., poly(2,2,4-trimethyl-1,2-dihydroquinoline)) Stearic acid: Camellia stearate beads (NOF Corporation) Zinc oxide: Zinc oxide type 2 (manufactured by Mitsui Mining & Smelting Co., Ltd.) Sulfur: HK-200-5 (Hosoi Chemical Industry Co., Ltd., powdered sulfur, oil content: 5% by mass) Vulcanization accelerator 1: Noccela CZ (Ouchi Shinko Chemical Industry Co., Ltd., N-cyclohexyl-2-benzothiazole sulfenamide (CBS)) Vulcanization accelerator 2: Suncerer M (manufactured by Sanshin Chemical Co., Ltd., 2-mercaptobenzothiazole (MBT)) Vulcanization accelerator 3: Noccelaer D (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., 1,3-diphenylguanidine (DPG)) Carcass cord: Polyethylene terephthalate fiber, cord structure 3360dtex / 2

[0219] Production Example 1: Synthesis of SBR1 Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene are charged into a nitrogen-purged autoclave reactor. The ratio of styrene to 1,3-butadiene is adjusted so that the styrene content is 23.5% by mass. The temperature of the reactor contents is adjusted to 20°C, and n-butyllithium is added to initiate polymerization. Polymerization is carried out under adiabatic conditions. When the maximum temperature reaches 85°C and the polymerization conversion rate reaches 99%, additional 1,3-butadiene is added. After an additional 5 minutes of polymerization, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane is added as a modifier. After the polymerization reaction is complete, 2,6-di-tert-butyl-p-cresol is added. The solvent is then removed by steam stripping, and the mixture is dried on a heated roll heated to 110°C to obtain SBR1.

[0220] Production Example 2: Synthesis of SBR2 SBR2 is obtained in the same manner as in Production Example 1, except that the ratio of styrene to 1,3-butadiene is adjusted so that the styrene content is 25% by mass.

[0221] Production Example 3: Synthesis of SBR3 SBR3 is obtained in the same manner as in Production Example 1, except that the ratio of styrene to 1,3-butadiene is adjusted so that the styrene content is 20% by mass.

[0222] Production Example 4: Synthesis of SBR4 SBR4 is obtained in the same manner as in Production Example 1, except that the ratio of styrene to 1,3-butadiene is adjusted so that the styrene content is 30% by mass.

[0223] <Tires> According to the formulation shown in Table 1, all chemicals except sulfur and vulcanization accelerators were mixed in a 1.7 L internal Banbury mixer for 5 minutes until the discharge temperature reached 170°C, yielding a kneaded mixture. Next, sulfur and vulcanization accelerators were added to the mixture using a two-screw open roll mill, and the mixture was mixed for 4 minutes until the temperature reached 105°C, yielding an unvulcanized rubber composition. The unvulcanized rubber composition was extruded into a tread shape using an extruder equipped with a predetermined die, and then bonded together with other tire components to form an unvulcanized tire. The tire was press-vulcanized for 12 minutes at 170°C to produce a test tire (tire size: 235 / 70R16, maximum load capacity: 863 kg, tire weight: 11.5 kg). The carcass consisted of one carcass ply containing carcass cords (38 cords / 50 mm).

[0224] In addition, in the tire of Table 1, F is 6720dtex, W L is 863 kg and G is 11.5 kg, so for equation (3), F / W L =7.79, and for equation (4), G / W L =0.013.

[0225] [Table 1]

[0226] <Evaluation> The results of evaluation of each test tire by the following evaluation methods are shown in the corresponding columns of Table 1.

[0227] (Grip performance) The test tires were mounted on all wheels of an electric vehicle, and the vehicle was driven on a test course on a dry asphalt road surface. At that time, the test driver conducted a sensory evaluation of the control stability during steering. The evaluation was performed with integer values from 1 to 10. Based on the evaluation criteria where a higher score indicates better control stability during steering, the total scores of 10 test drivers were calculated. The total score of the reference comparison example (Comparative Example 2) was converted to a reference value (100), and the evaluation results of each test tire were indexed and displayed in proportion to the total score. A larger numerical value indicates higher grip performance.

[0228] <Embodiment> Preferred embodiments are shown below.

[0229] [1] An electric vehicle tire comprising a tread portion made of a rubber composition containing a rubber component, a filler, and a plasticizer selected from at least one of the group consisting of a resin and a liquid rubber, where the acetone extraction amount (mass %) of the rubber composition is designated as AE, and the loss tangent of the rubber composition at 0°C is designated as 0°C tan δ, the number concentration (particles / cm 3 ) of PM10 generated in the following LAT wear test of the rubber composition, measured under the following measurement conditions, is designated as P, when the wear amount (cm 3 ) of the rubber composition by the LAT wear test is designated as AV, an electric vehicle tire satisfying the following formulas (1) and (2). (1) P / AV < 2000 (2) AE × 0°C tan δ / (P / AV) × 1000 > 5.0 <LAT Wear Test> Using a wear test machine having a grindstone disk rotating in a vertical plane and a test piece rotatably supported by an axis parallel to the vertical plane, the test piece is prepared according to the following test piece preparation method, and a wear test conforming to ISO23233 is performed by bringing the test piece into contact with the grindstone disk under the following conditions. Load applied to the test piece 40 N Slip angle of the test piece 6° Speed of the grindstone surface 20 km / h Running distance of the test piece: 2000 m Grinding wheel temperature: 10 °C Anti-fouling sand amount: 0.2 g / min Grinding wheel grit size: 60 mesh <Method for preparing test piece> An evaluation rubber sheet is cut out from the tread surface of the tire with a thickness of 2 mm ± 1 mm, wound along the outer peripheral surface of the roller body, and the shape of the test piece after winding is made into a cylindrical shape with an outer diameter of 84 mm ± 2 mm, an inner diameter of 35 mm ± 1 mm, and an axial length of 18 mm ± 1 mm, having a through hole. <PM10 particle concentration measurement conditions> Using an optical scattering type airborne particle counter, in accordance with ISO21501-04, measure under the following conditions. Sampling air collection location: Based on the grounding center of the test piece with the grinding wheel disc, with the side where the grinding wheel disc is located as the back side, 25 cm vertically downward, 15 cm horizontally forward, and 10 cm horizontally to the right Sampling air suction volume: 1 L / min Measurement time: 6 minutes from the start of the LAT wear test to 6 minutes later Here, the right side of formula (1) is preferably 1600, more preferably 1400, and the right side of formula (2) is preferably 6.0. s [2] The electric vehicle tire according to [1], where the right side of formula (1) is 1200. [3] The electric vehicle tire according to [1], where the right side of formula (1) is 1000. [4] The electric vehicle tire has a carcass cord, with the fineness (dtex) of the carcass cord being F and the maximum load capacity (kg) of the electric vehicle tire being W L When doing so, F and W L Satisfy the following formula (3), and it is the electric vehicle tire according to any one of [1] to [3], (3) F / W L ≥ 5.6 Here, the right side of formula (3) is preferably 5.8, more preferably 6.0, still more preferably 6.4, still more preferably 7.0, still more preferably 7.6, still more preferably 8.0, still more preferably 10.0, still more preferably 12.0, and still more preferably 14.0. [5] The tire for an electric vehicle according to any one of [1] to [4], wherein F(dtex) is 6,000 or more, more preferably 6,600 or more, and even more preferably 7,600 or more. [6] The tire for an electric vehicle according to any one of [1] to [5], wherein the 0°C tan δ of the rubber composition is 0.45 or more, preferably 0.49 or more, more preferably 0.52 or more, and even more preferably 0.60 or more. [7] The tire for an electric vehicle according to any one of [1] to [5], wherein the rubber composition has a 0°C tan δ of 0.80 or more. [8] The tire for an electric vehicle according to any one of [1] to [7], wherein the AE of the rubber composition is 20% by mass or more, preferably 21% by mass or more, more preferably 22% by mass or more, and even more preferably 24% by mass or more. [9] The tire for an electric vehicle according to any one of [1] to [8], wherein the right side of formula (2) is 8.0, preferably 10.0, and more preferably 12.0.

[10] The weight (kg) of the electric vehicle tire is G, and the maximum load capacity (kg) is W. L Then, G and W L The tire for an electric vehicle according to any one of [1] to [9], wherein the relationship of the following formula (4) is satisfied: (4) Golden Week L <0.015 Here, the right side of formula (4) is preferably 0.014, more preferably 0.013, even more preferably 0.012, and even more preferably 0.010.

[11] The electric vehicle tire according to any one of [1] to

[10] , wherein the rubber component contains styrene-butadiene rubber, the styrene content of the styrene-butadiene rubber is 30% by mass or less, preferably 28% by mass or less, and more preferably 25% by mass or less, and the content of the plasticizer containing at least one selected from the group consisting of resins and liquid rubbers is 30 parts by mass or more, preferably 35 parts by mass or more, and more preferably 40 parts by mass or more, per 100 parts by mass of the rubber component.

[12] The electric vehicle tire according to

[11] , wherein the rubber component contains 50% by mass or more of styrene-butadiene rubber in 100% by mass of the rubber component, and the total amount of styrene in the rubber component is less than 20% by mass, preferably 17% by mass or less, and more preferably 16% by mass or less.

[13] An electric vehicle tire according to any one of [1] to

[12] , wherein the tread surface has three or more circumferential grooves extending in the tire circumferential direction, and a pair of shoulder land portions on the outer side in the tire width direction, which are partitioned by a pair of outermost peripheral grooves located on the outermost sides in the tire width direction among the circumferential grooves, and a center land portion sandwiched between the pair of shoulder land portions, and the negative ratio of the center land portion is more than 0% and less than 15%.

[14] A method for evaluating the amount of PM10 generated by wear of a tire tread, The method for evaluating the amount of PM10 generated includes a test piece preparation step, an abrasion test step, and a step of measuring PM10 generated in the abrasion test step, the test piece preparation step includes a step of cutting out a rubber sheet for evaluation from a tread portion of a tire, The method for evaluating the amount of PM10 generated, wherein the abrasion test step includes a step of abrading the test piece to generate PM10.

[15] The abrasion test step includes a step of abrading the test piece by an LAT abrasion test to generate PM10; The method for evaluating the amount of PM10 generated according to

[14] , wherein the LAT abrasion test is performed in accordance with ISO23233.

[16] A PM10 generation amount measurement system having an abrasion test section and a PM10 measurement section, The PM10 generation amount measurement system, wherein the abrasion test section has a grinding wheel that rotates in a vertical plane and a test piece support section that can rotate on an axis parallel to the vertical plane.

[17] A PM10 generation amount measurement system according to

[16] , comprising an abrasion test section and a PM10 measurement section in the same chamber.

[18] A PM10 emission measurement system according to

[16] or

[17] , wherein a cylindrical test piece having a through hole in the center is fixed to the test piece support part.

[19] The PM10 generation amount measurement system described in

[18] , wherein the cylindrical shape having a through hole in the center is a cylindrical shape in which, when the axial length is 1, the inner diameter of the cylinder having the through hole is 1.85 to 2.10 and the outer diameter is 4.55 to 4.70.

[20] The PM10 generation amount measuring system according to any one of

[16] to

[19] , wherein the PM10 measuring unit has a sample air supply unit. [Explanation of symbols]

[0230] 1 tire 2 Tread 3 Roller body 4 Test pieces 4c Equatorial plane of the specimen 4t Center of contact between grinding wheel and test piece 6 grinding wheels 6a Rotary table 6b Grindstone surface 6c Center of the grinding wheel 20 Light scattering airborne particle counter 21 Sample air supply unit 22 Light source section 23 Light receiving part 24 Signal Processing Section 25 Condenser lens 26 Photoelectric conversion element 27 Particle detection area 28 Laser Elements 31 Carcass 41 Circumferential groove 41A Outermost circumferential groove 41B Center circumferential groove 43 Center Land Division 45 Shoulder land area A1 Direction of test piece travel CL Tire centerline d1 Inner diameter of test piece d2 outer diameter of test piece S Evaluation rubber sheet w1 width of test piece w2 Thickness of the rubber sheet for evaluation

Claims

1. A tire for an electric vehicle having a tread portion made of a rubber composition containing a rubber component, a filler, and a plasticizer containing at least one selected from the group consisting of a resin and a liquid rubber, The acetone extractable amount (mass%) of the rubber composition is defined as AE, and the loss tangent of the rubber composition at 0°C is defined as 0°C tanδ. The number concentration (particles / cm) of PM10 generated in the LAT abrasion test described below for the rubber composition 3 ) is measured under the following measurement conditions, and the value is P. The amount of wear (cm) of the rubber composition in the LAT abrasion test 3 ) is AV, A tire for an electric vehicle that satisfies the following formulas (1) and (2): (1) P / AV<2000 (2) AE×0℃tanδ / (P / AV)×1000>5.0 <LAT abrasion test> An abrasion tester having a grinding wheel rotating in a vertical plane and a test piece rotatably supported on an axis parallel to the vertical plane is used, and the test piece is prepared according to the test piece preparation method described below. The test piece is brought into contact with the grinding wheel under the conditions described below, and an abrasion test in accordance with ISO 23233 is carried out. Load applied to test piece: 40N Slip angle of test piece: 6° Grinding wheel speed: 20km / h Test piece running distance: 2000m Grindstone temperature: 10℃ Antifouling sand amount: 0.2 g / min Grindstone grain size: 60 mesh <Test piece preparation method> A rubber sheet for evaluation was cut out from the tread surface of the tire to a thickness of 2 mm ± 1 mm and wrapped around the outer peripheral surface of a roller body, so that the shape of the test specimen after wrapping was a cylinder with an outer diameter of 84 mm ± 2 mm, an inner diameter of 35 mm ± 1 mm, an axial length of 18 mm ± 1 mm, and a through hole. <PM10 number concentration measurement conditions> Measurement is carried out using a light scattering airborne particle counter in accordance with ISO 21501-04 under the following conditions. Air sample collection location: Based on the center of contact between the test piece and the grinding wheel, with the side with the grinding wheel facing the back, 25 cm vertically downward, 15 cm horizontally forward, and 10 cm horizontally to the right Sample air suction volume: 1 L / min Measurement time: 6 minutes from the start of the LAT abrasion test to 6 minutes after

2. 2. The tire for an electric vehicle according to claim 1, wherein the right side of formula (1) is 1200.

3. 2. The tire for an electric vehicle according to claim 1, wherein the right side of formula (1) is 1,000.

4. The electric vehicle tire has a carcass cord, the fineness (dtex) of the carcass cord is F, and the maximum load capacity (kg) of the electric vehicle tire is W L When F and W L The tire for an electric vehicle according to any one of claims 1 to 3, wherein and satisfy the following formula (3): (3)F / W L ≧5.6

5. The tire for an electric vehicle according to any one of claims 1 to 3, wherein F(dtex) is 6000 or more.

6. The tire for an electric vehicle according to any one of claims 1 to 3, wherein the rubber composition has a 0°C tan δ of 0.45 or more.

7. The tire for an electric vehicle according to any one of claims 1 to 3, wherein the rubber composition has a 0°C tan δ of 0.80 or more.

8. The tire for an electric vehicle according to any one of claims 1 to 3, wherein the AE of the rubber composition is 20% by mass or more.

9. The tire for an electric vehicle according to any one of claims 1 to 3, wherein the right side of formula (2) is 8.

0.

10. The weight (kg) of the electric vehicle tire is G, and the maximum load capacity (kg) is W. L Then, G and W L The tire for an electric vehicle according to any one of claims 1 to 3, wherein the relationship of the following formula (4) is satisfied: (4)G / W L <0.015

11. 4. The tire for electric vehicles according to claim 1, wherein the rubber component contains styrene-butadiene rubber, the styrene-butadiene rubber has a styrene content of 30% by mass or less, and the content of the plasticizer containing at least one selected from the group consisting of resins and liquid rubbers is 30 parts by mass or more per 100 parts by mass of the rubber component.

12. The tire for an electric vehicle according to claim 11, wherein the rubber component contains 50% by mass or more of styrene-butadiene rubber in 100% by mass of the rubber component, and the total amount of styrene in the rubber component is less than 20% by mass.

13. 4. The tire for electric vehicles according to claim 1, wherein the tread surface has three or more circumferential grooves extending in the tire circumferential direction, and a pair of outermost shoulder land portions in the tire width direction, the shoulder land portions being partitioned by a pair of outermost peripheral grooves located outermost in the tire width direction among the circumferential grooves, and a center land portion sandwiched between the pair of shoulder land portions, and the negative ratio of the center land portion is greater than 0% and less than 15%.

14. A method for evaluating the amount of PM10 generated due to wear of a tire tread portion, The method for evaluating the amount of PM10 generated includes a test piece preparation step, an abrasion test step, and a step of measuring PM10 generated in the abrasion test step, the test piece preparation step includes a step of cutting out a rubber sheet for evaluation from a tread portion of a tire, The method for evaluating the amount of PM10 generated, wherein the abrasion test step includes a step of abrading the test piece to generate PM10.

15. The abrasion test step includes a step of abrading the test piece by an LAT abrasion test to generate PM10, The method for evaluating the amount of PM10 generated according to claim 14, wherein the LAT abrasion test is performed in accordance with ISO23233.

16. A PM10 generation amount measurement system including an abrasion test unit and a PM10 measurement unit, The PM10 generation amount measurement system, wherein the abrasion test section has a grinding wheel that rotates in a vertical plane and a test piece support section that can rotate on an axis parallel to the vertical plane.

17. The PM10 generation amount measurement system according to claim 16, comprising an abrasion test section and a PM10 measurement section in the same chamber.

18. The PM10 generation amount measurement system according to claim 16, wherein a cylindrical test piece having a through hole at the center is fixed to the test piece support portion.

19. The cylindrical shape having a through hole at the center has an inner diameter of 1.85 to 2.10 and an outer diameter of 4.55 to 4.70 when the axial length is 1. The PM10 generation amount measurement system according to claim 18.

20. 18. The PM10 generation amount measuring system according to claim 16, wherein the PM10 measuring unit has a sample air supply unit.

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