pneumatic tires

Abstract

In pneumatic tires equipped with carcass cords whose extension direction changes, the reduction in fuel efficiency is suppressed. [Solution] The system comprises a tread, carcass, reinforcing layer, and sidewall, the tread having a cap tread and a base tread, the carcass including carcass cords, the base tread rubber and sidewall rubber being different from each other, the angle at which the stretching direction of the carcass cords is inclined from the tire circumferential direction at the position of the tire centerline is A1(°), the angle at which it is inclined from the tire circumferential direction at the position of the tire's maximum width is A2(°), and the loss tangent of the base tread rubber at 70° is 70°tanδ B The loss tangent of the sidewall rubber at 70°C is 70°C tanδ S A pneumatic tire that satisfies the following equation, where K is a constant. |A2-A1|>0; and |70℃ tanδ B ×70℃ tanδ S |<|A2-A1| / K (where K is 500)

Description

[Technical Field]

[0001] This invention relates to a pneumatic tire. [Background technology]

[0002] In pneumatic tires, the carcass ply forms the framework. The carcass cords that make up the carcass ply distinguish between different types of tires, such as radial tires and bias tires, depending on their direction of extension, and determine the performance of pneumatic tires, such as durability and rigidity. Patent documents 1 and 2 describe pneumatic tires in which the direction of extension of the carcass cords is controlled and the carcass cords are bent. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-84469 [Patent Document 2] International Publication No. 2021 / 123530 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, while such pneumatic tires can be given desired performance by controlling and changing the direction of extension of the carcass cords, there are concerns that energy loss due to the change in the direction of extension of the carcass cords during driving will occur, reducing the tire's fuel efficiency.

[0005] The present invention aims to suppress the decline in fuel efficiency performance in a pneumatic tire equipped with carcass cords whose stretching direction changes. [Means for solving the problem]

[0006] In other words, the present invention relates to the following tires. A pneumatic tire comprising a tread, a carcass, at least one reinforcing layer disposed radially outward of the carcass, and a sidewall, The aforementioned tread comprises a cap tread including the contact surface and a base tread located radially inward of the tire. The carcass is composed of at least one carcass ply comprising a plurality of carcass cords and a topping rubber covering the carcass cords. The reinforcing layer is composed of at least one reinforcing layer ply comprising a plurality of reinforcing layer cords and a topping rubber covering the reinforcing layer cords. Let A1(°) be the angle at which the extension direction of the carcass cord of at least one of the carcass plies is inclined from the tire circumferential direction at the position of the tire centerline, and let A2(°) be the angle at which it is inclined from the tire circumferential direction at the position of the tire's maximum width. The rubber composition constituting the base tread and the rubber composition constituting the sidewall are made of different rubber compositions. The loss loss tangent of the rubber composition constituting the base tread at 70°C is 70°C tanδ B The loss loss tangent of the rubber composition constituting the sidewall at 70°C is 70°C tanδ S When K is a constant, A1, A2, 70℃ tanδ B , 70℃ tanδ S A pneumatic tire in which K satisfies the following equations (1) and (2). (1)|A2-A1|>0 (2) | 70℃ tanδ B ×70℃ tanδ S |<|A2-A1| / K (However, K is 500) [Effects of the Invention]

[0007] According to the present invention, in a pneumatic tire equipped with carcass cords whose stretching direction changes, the decrease in fuel efficiency can be suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view of a pneumatic tire according to one embodiment of the present invention, passing through the tire rotation axis. [Figure 2] This is an example of an unfolded view showing the angle between the extension direction and the tire circumferential direction of a carcass cord constituting a carcass ply of a pneumatic tire according to one embodiment of the present invention, as viewed from the inner surface side of the tire. [Figure 3] This is a modified example of an unfolded view of a carcass cord constituting a carcass ply of a pneumatic tire according to one embodiment of the present invention, showing the angle between its stretching direction and the circumferential direction of the tire, as viewed from the inner surface side of the tire. [Figure 4] This is a schematic diagram showing a preferred range of angles between the stretching direction and the tire circumferential direction for carcass cords constituting the carcass ply of a pneumatic tire according to one embodiment of the present invention. [Modes for carrying out the invention]

[0009] Hereinafter, a pneumatic tire according to an embodiment of the present invention will be described. The pneumatic tire of the present embodiment is a pneumatic tire including a tread, a carcass, at least one reinforcing layer disposed on the outer side in the tire radial direction of the carcass, and a sidewall, wherein the tread includes a cap tread including a ground contact surface and a base tread on the inner side in the tire radial direction thereof, the carcass is composed of at least one carcass ply including a plurality of carcass cords and topping rubber covering the carcass cords, the reinforcing layer is composed of at least one reinforcing layer ply including a plurality of reinforcing layer cords and topping rubber covering the reinforcing layer cords, the extending direction of the carcass cords of at least any one of the carcass plies of the carcass ply forms an angle A1 (°) inclined from the tire circumferential direction at the position of the tire center line, and forms an angle A2 (°) inclined from the tire circumferential direction at the position of the maximum tire width, the rubber composition constituting the base tread and the rubber composition constituting the sidewall are made of different rubber compositions, the loss tangent at 70 °C of the rubber composition constituting the base tread is 70 °C tanδ B , the loss tangent at 70 °C of the rubber composition constituting the sidewall is 70 °C tanδ S , when the constant is K, A1, A2, 70 °C tanδ B , 70 °C tanδ S and K satisfy the following formulas (1) and (2), a pneumatic tire. (1) |A2 - A1| > 0 (2) |70 °C tanδ<s B × 70 °C tanδ S | < |A2 - A1| / K (where K is 500)

[0010] <0OO0193>While not intended to be constrained by theory, the following mechanisms are considered to suppress the decline in fuel efficiency performance in this invention. Specifically, in a tire in which the carcass cords are bent by controlling the direction in which they stretch, it is thought that energy loss occurs during driving due to the change in the stretching direction of the carcass cords. It is thought that energy loss can be reduced by reducing the product of the loss tangent of the rubber composition constituting the base tread and the loss tangent of the rubber composition constituting the sidewall, which are adjacent to the bent portion of the carcass cords. Furthermore, the stretching direction of the carcass cords and the loss tangent of the rubber composition constituting the base tread and the loss tangent of the rubber composition constituting the sidewall are adjusted to satisfy a predetermined relational expression. It is thought that the decline in the tire's fuel efficiency performance is suppressed by the cooperation of these factors.

[0011] In the above formula (2), the constant K is preferably 700, and more preferably 1000.

[0012] This is because it satisfies equation (2) under stricter conditions.

[0013] The rubber composition constituting the sidewall contains a rubber component, and it is preferable that the rubber component contains isoprene-based rubber.

[0014] This is because including high-strength isoprene-based rubber ensures the strength of the rubber and allows for a reduction in the amount of filler that exacerbates energy loss.

[0015] The rubber composition constituting the base tread preferably contains silica.

[0016] This is because it can suppress energy loss while maintaining the strength of the rubber, compared to other common fillers.

[0017] The rubber composition constituting the sidewall preferably contains a resin component.

[0018] In at least one of the reinforcing layer plies, the angle (°) at which the extension direction of the reinforcing layer cord is inclined from the tire circumferential direction is A RF In that case, A I and A RF It is preferable that they be different.

[0019] A I and A RF This difference is thought to mitigate the twisting of the carcass ply, which is positioned on the radially inward side of the tread to control its extension direction.

[0020] A RF The inclination direction of A1 from the tire circumferential direction is preferably in the opposite direction to the inclination direction of A1 from the tire circumferential direction.

[0021] A I and A RF It is believed that the opposing directions of their inclinations can counteract the twisting of the carcass ply, which is positioned to control its extension direction on the radially inward side of the tread.

[0022] The angle at which the extension direction of the reinforcing layer cord is inclined from the tire circumferential direction is A RF The reinforcing layer, which includes a reinforcing layer ply that is (°), is preferably composed of a single reinforcing layer ply.

[0023] It is believed that reducing the number of reinforcing plies can make the tire lighter.

[0024] The angle at which the extension direction of the reinforcing layer cord is inclined from the tire circumferential direction is A RF The reinforcing layer ply, which is (°), is preferably a belt ply.

[0025] By using a belt ply, it is possible to minimize the number of reinforcing plies required.

[0026] Preferably, the at least one reinforcing layer consists only of a belt.

[0027] This is because reducing the number of reinforcing layers makes it possible to lighten the tire.

[0028] The carcass is preferably composed of a single carcass ply.

[0029] It is believed that reducing the number of carcass plies can make the tire lighter.

[0030] A2 is preferably between +70° and +90°, or between -70° and -90°.

[0031] It is believed that the effects of the present invention can be improved by defining the range of A2 as described above.

[0032] The loss tangent 70°C tanδ of the rubber composition constituting the base tread at 70°C B However, it is preferable that it be 0.10 or less.

[0033] By setting the loss tangent of the rubber composition constituting the base tread as described above, it is believed that energy loss during tire rolling can be efficiently suppressed.

[0034] The loss tangent of the rubber composition constituting the sidewall at 70°C is 70°C tanδ. S However, it is preferable that it be 0.10 or less.

[0035] By setting the loss tangent of the rubber composition constituting the sidewall as described above, it is believed that energy loss during tire rolling can be efficiently suppressed.

[0036] <Definition> "Standard condition" refers to a state of no load where the tire is mounted on a standard rim and filled with air at the standard internal pressure. Unless otherwise specified, tires in the standard condition should be used.

[0037] Unless otherwise specified, the "dimensions of each part of the tire" refer to values ​​that are determined in the normal state for those visible on the outer surface of the tire, while those located inside the tire or on the cut surface of the tire refer to values ​​that are determined, for example, by cutting the tire in a plane including the tire's axis of rotation and holding the cut tire piece within the rim width of the normal rim.

[0038] A "standard rim" refers to the rim specified for each tire within the standards system that the tire is based on. For example, for JATMA (Japan Automobile Tire Manufacturers Association), it refers to the standard rim for the applicable size listed in the "JATMA YEAR BOOK," for ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" listed in the "STANDARDS MANUAL," and for TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "YEAR BOOK." Refer to JATMA, ETRTO, and TRA in that order, and if an applicable size is available at the time of reference, follow that standard. In the case of a tire not specified in the above standards, it refers to the narrowest rim width among the smallest diameter rims that can be mounted on that tire and that can maintain internal pressure (i.e., do not cause air leakage between the rim and tire).

[0039] "Regular internal pressure" refers to the air pressure specified for each tire in the standard system, including the standard on which the tire is based. For example, in the case of JATMA, it refers to "Maximum Air Pressure," in the case of ETRTO, it refers to "INFLATION PRESSURE," and in the case of 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 if there is an applicable size at the time of reference, follow that standard. In the case of tires not specified in the above standards, it refers to the regular internal pressure (but at least 250kPa) of another tire size (however, only those specified in the standard) that is listed with the aforementioned regular rim as the standard rim. If multiple regular internal pressures of 250kPa or higher are listed, refer to the lowest value among them.

[0040] "Regular load (kg)" refers to the load specified for each tire in the standard system that the tire is based on. For example, for JATMA it is "Maximum Load Capacity," for ETRTO it is "LOAD CAPACITY," and for TRA it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." As with regular rims and regular in-tire pressure, refer to JATMA, ETRTO, and TRA in that order, and if an applicable size is available at the time of reference, follow that standard. For tires not specified in the above standards, the maximum load capacity (kg) is calculated separately. L This is considered the normal load.

[0041] "Maximum load capacity W L The weight (kg) is calculated using the following formula: "V" is the virtual volume of the tire (mm²). 3), "Dt" is the outer diameter of the tire in the normal state (mm), "Ht" is the height of the tire's cross-section in the radial direction in a plane containing the tire's axis of rotation (mm), and "Wt" is the width of the tire's cross-section in the normal state (mm). Ht can be calculated by (Dt-R) / 2, where R is the rim diameter of the tire. Wt is the value obtained by removing any patterns or letters on the tire's sidewall. Note that the maximum load capacity is synonymous with the normal load mentioned above.

[0042]

number

[0043] The "tread section" is the part of the tire separated by the normal lines on the inner surface of the tire that pass through each tread contact edge. The "bead section" is the part of the tire that contacts the rim, maintains internal pressure, and transmits drive and braking forces. The "side section" is the part of the tire on the bead side that connects the tread section and the bead section. Each section is shown in Figure 1.

[0044] The "tread contact point" refers to the outermost edge in the tire's width direction where the tire makes contact with the ground when pressed against it. The tread contact point can be determined by mounting the tire onto a standard rim, filling it to the standard internal pressure, letting it stand at 25°C for 24 hours, then applying ink to the tire tread surface, applying a standard load (a load equal to the maximum load capacity) to the tire, pressing it perpendicularly onto cardboard (camber angle 0°), and transferring the ink.

[0045] "Tread contact width" refers to the distance along the tread surface from one tread contact edge to the other tread contact edge.

[0046] A "carcass" is a component that forms the tire's skeletal structure, and is composed of at least one carcass ply comprising multiple carcass cords and a topping rubber covering the carcass cords. Internal components exist on the radially inward side of the carcass. Examples of such internal components include an inner liner and insulation.

[0047] "Tire maximum width position" refers to the position of the maximum width within the tire's cross-section in the width direction, measured under normal conditions.

[0048] The "R1 region" refers to the region on the tire centerline where the inclination angle of the carcass cord, A1, is within a predetermined range of variation. The permissible range of variation for the inclination angle of the carcass cord in the R1 region is between -10% and 5% of the absolute value of A1 (|A1|). The R1 region straddles the tire centerline and does not include the tire's maximum width position, which is the measurement position of A2.

[0049] "A1" refers to the angle (°) at which the extension direction of the carcass cords slopes relative to the tire's circumferential direction at the tire's centerline. When viewed from the inner side of the tire, a downward slope to the right relative to the tire's circumferential direction is considered positive (+), and an upward slope to the right is considered negative (-), with the value expressed in the range of greater than -90° and less than or equal to +90°. If there are multiple applicable carcass plies, it is preferable to measure at the outermost carcass ply in the tire's radial direction. Figure 2 shows the case where A1 is positive (+). Note that the "+" symbol may be omitted when the value is positive.

[0050] "A2" refers to the angle (°) at which the extension direction of the carcass cords slopes relative to the tire's circumferential direction at the tire's maximum width. When viewed from the inner side of the tire, a downward slope to the right relative to the tire's circumferential direction is considered positive (+), and an upward slope to the right is considered negative (-), with the value expressed in the range of greater than -90° and less than or equal to +90°. If there are multiple applicable carcass plies, it is preferable to measure the outermost carcass ply in the tire's radial direction. Figure 2 shows the case where A2 is positive (+). Furthermore, if the carcass has both a main body and a winding section at the tire's maximum width, the carcass cords of the main body are the measurement target. Note that the "+" symbol may be omitted when the value is positive.

[0051] A "carcass cord whose direction of extension changes" is a carcass cord that satisfies equation (1) above, that is, |A2-A1|>0.

[0052] A "reinforcement layer" is a component provided radially outside the carcass and radially inside the tread, which has the effect of suppressing tire protrusion due to internal pressure and rotation, and receiving and mitigating input from the road surface. The reinforcement layer consists of at least one reinforcement layer ply comprising multiple reinforcement layer cords and a topping rubber covering the reinforcement layer cords. In this specification, the reinforcement layer ply that is positioned furthest in the tire radial direction among the at least one reinforcement layer ply is called the inner reinforcement layer ply. Specific examples of reinforcement layers include belts and bands.

[0053] A "belt" is one of the reinforcing layers and consists of at least one belt ply. The multiple belt cords that make up the belt ply are arranged approximately parallel to each other, and the direction of extension of the belt cords is inclined at an angle of 10° or more with respect to the tire circumferential direction. The belt has joints on the circumference of the tire. Here, "approximately parallel" means that the angle difference between the direction of extension of each belt cord and the tire circumferential direction is within ±3°.

[0054] A "band" is a reinforcing layer, consisting of at least one band ply. The band cords that make up the band ply are arranged in a spiral shape around the tire's circumference, and the direction of extension of the band cords is kept within a 5° inclination relative to the tire's circumference. The band does not have any joints around the circumference of the tire. There are two types of bands: full bands that cover the entire tread and edge bands that cover only the edges of the tread.

[0055] "A RF " is the angle (°) at which the extension direction of the reinforcing layer cord of the reinforcing layer ply is inclined relative to the tire circumferential direction. When viewed from the inner side of the tire, a downward slope to the right relative to the tire circumferential direction is considered positive (+), and an upward slope to the right is considered negative (-), and it is expressed in the range of greater than -90° and less than or equal to +90°. In Figure 2, A RF The case where the value is negative (-) is shown. Note that the "+" symbol may be omitted when the value is positive.

[0056] <Measurement method> "70℃ tanδ B " is the loss loss tangent of the rubber composition constituting the base tread at 70°C, and is measured using a dynamic viscoelasticity measuring device (e.g., GABO's Iplexer series) under the conditions of a temperature of 70°C, a frequency of 10Hz, an initial strain of 10%, a dynamic strain of ±1%, and the extension mode. The sample used for measurement is a vulcanized rubber composition with dimensions of 20mm in length, 4mm in width, and 1mm in thickness. When creating a sample by cutting it from a tire, the length direction of the sample should be aligned with the tire's circumferential direction, the thickness direction of the sample should be aligned with the tire's radial direction, and the sample should be created as close as possible to the specified dimensions described above.

[0057] "70℃ tanδ S " is the loss loss tangent of the rubber composition constituting the sidewall at 70°C, and is measured using a dynamic viscoelasticity measuring device (e.g., GABO's Iplexer series) under the conditions of a temperature of 70°C, a frequency of 10Hz, an initial strain of 10%, a dynamic strain of ±1%, and the extension mode. The sample used for measurement is a vulcanized rubber composition with dimensions of 20mm in length, 4mm in width, and 1mm in thickness. When creating a sample by cutting it from a tire, the length direction of the sample should be aligned with the tangent to the tire's circumferential direction, and the thickness direction of the sample should be aligned with the tire's width direction, and the sample should be created as close as possible to the specified dimensions described above.

[0058] The "glass transition temperature (Tg) of a rubber composition" is defined as the temperature corresponding to the maximum value (tanδ peak temperature) of the tanδ temperature distribution curve obtained using a dynamic viscoelasticity measuring device (e.g., the Iplexer series from GABO) under the conditions of a frequency of 10 Hz, initial strain of 10%, dynamic strain of ±0.5%, and heating rate of 2°C / min, within the range of -60°C to 40°C. If, in measurements within the range of -60 to 40°C, the tanδ value gradually increases or decreases with increasing temperature, the glass transition temperature of the rubber composition is considered to be 40°C or -60°C, respectively. Furthermore, if there are two or more points showing a maximum value within the range of -60°C to 40°C, the point with the lowest temperature is considered the glass transition temperature.

[0059] "A1" and "A2" are determined by averaging the angles measured using four different cords. The selection of the four cords is preferably arbitrary, and more preferably, they are four cords spaced approximately 90° apart in the circumferential direction of the tire. In this case, the cords used for measurement of A1 and A2 do not need to be the same, but it is even more preferable that the cords used for measurement of A1 and A2 are the same.

[0060] "A RF The angle is determined by averaging the angles measured with four different cords. The selection of the four cords is preferably any four, and more preferably four cords that are spaced approximately 90° apart in the circumferential direction of the tire.

[0061] The "glass transition temperature of the rubber component" refers to the static glass transition temperature of each rubber component, as determined by a differential calorimeter (for example, the Q200 manufactured by T.A. Instruments Japan Co., Ltd.).

[0062] "Styrene content" can be determined by pyrolysis gas chromatography or NMR measurement. 1 H-NMR and 13It is calculated by 13C-NMR. Unlike physical properties such as the complex modulus (E*), the amounts of components such as "styrene content" have true values ​​that do not depend on the measurement method, so it is preferable to use a measurement method that is as accurate as possible. In this specification, "pyrolysis gas chromatography" refers to a method in which a sample is heated by a pyrolysis apparatus, the individual components contained in the gas phase components produced by this heating are separated by a separation column, and each isolated component is analyzed.

[0063] "Vinyl content (amount of 1,2-bonded butadiene units)" can be determined by pyrolysis gas chromatography or NMR measurement. 1 H-NMR and 13 It is calculated using 1C-NMR. Similar to "styrene content," a true value exists for "vinyl content" that is independent of the measurement method, so it is preferable to use the most accurate measurement method possible.

[0064] "Cis content (amount of cis-1,4-bonded butadiene units)" is determined by infrared absorption spectroscopy or NMR measurement in accordance with JIS K 6239-2:2017. 1 H-NMR and 13 This value is measured by 13C-NMR and is applied, for example, to rubber components having repeating units derived from butadiene, such as BR. Similar to "styrene content," a true value exists for "cis content" that is independent of the measurement method, so it is preferable to use the most accurate measurement method possible.

[0065] The "weight-average molecular weight (Mw)" can be determined by converting the measured value using gel permeation chromatography (GPC) (for example, the GPC-8000 series manufactured by Tosoh Corporation, with a differential refractometer as the detector and TSKgel® SuperMultiporeHZ-M column manufactured by Tosoh Corporation) to a standard polystyrene equivalent. This method is applicable, for example, to SBR, BR, plasticizers, etc.

[0066] The nitrogen adsorption specific surface area (N2SA) of carbon black is measured in accordance with JIS K 6217-2:2017.

[0067] The nitrogen adsorption specific surface area (N2SA) of silica is measured by the BET method in accordance with ASTM D3037-93.

[0068] The "average primary particle diameter" is a value obtained by photographing particles with a transmission or scanning electron microscope and calculating the arithmetic mean of the particle diameters of 400 particles. If the particle is spherical, the diameter of the sphere is used as the particle diameter; if it is not spherical, the equivalent diameter of a circle (the positive square root of {4 × (particle area) / π}) is calculated from the microscope image and used as the particle diameter.

[0069] A "plasticizer" is a material that imparts plasticity to rubber components and is extracted from rubber compositions using acetone. This definition includes both liquid plasticizers at 25°C and solid plasticizers at 25°C. However, it excludes waxes and stearic acid commonly used in the tire industry.

[0070] "Plasticizer content" includes the amount of plasticizer in the rubber component that has been stretched by the plasticizer.

[0071] The "softening point of the resin component" is the temperature at which the sphere descends when the softening point specified in JIS K 6220-1:2015 7.7 is measured using a ring-type softening point measuring device.

[0072] The embodiments will be described in further detail below. However, the following description is illustrative for explaining the present invention, and the present invention is not limited to these. Drawings will be used as appropriate, but the drawings are for illustrative purposes only.

[0073] <Tires> The tire in Figure 1 consists of a tread section 1, a side section 3, and a bead section 4, and includes a cap tread 5, a base tread 6, a carcass 7, a belt 8, and a band 9. The belt 8 and band 9 constitute a reinforcing layer 10.

[0074] The carcass 7 is composed of a single carcass ply comprising multiple carcass cords and a topping rubber covering the carcass cords. The belt 8 is composed of a single belt ply comprising multiple belt cords and a topping rubber covering the belt cords. The band 9 is composed of a single band ply comprising multiple band cords and a topping rubber covering the band cords. The tire's maximum width position is indicated by P.

[0075] In the tire shown in Figure 1, the carcass 7 may be composed of multiple carcass plies, but from the viewpoint of reducing tire weight, it is preferable that it be composed of fewer carcass plies, and more preferably that it be composed of one carcass ply. The belt 8 may be composed of multiple belt plies, but from the viewpoint of reducing tire weight, it is preferable that it be composed of fewer belt plies, and more preferably that it be composed of one belt ply. The band 9 may be composed of multiple band plies, but from the viewpoint of reducing tire weight, it is preferable that it be composed of fewer band plies, and more preferably that it be composed of one band ply. The reinforcing layer 10 may be composed of multiple reinforcing layer plies, but from the viewpoint of reducing tire weight, it is preferable that it be composed of fewer reinforcing layer plies, and it is preferable that the reinforcing layer 10 is composed of one reinforcing layer ply.

[0076] In the tire of this embodiment, the reinforcing layer may include both a belt and a band, or it may consist only of a belt or a band. Of these, it is preferable that the reinforcing layer consists only of a belt.

[0077] Figure 2 shows an unfolded view of the carcass cords constituting the carcass ply, showing the angle between their extension direction and the tire circumferential direction as seen from the inner surface of the tire. In Figure 2, the left-right direction W represents the tire width direction, and the up-down direction C represents the tire circumferential direction. The carcass ply comprises multiple carcass cords and a topping rubber covering the carcass cords, and in Figure 2, these multiple carcass cords are shown as solid lines. In Figure 2, the angle at which the extension direction of the carcass cords inclins from the tire circumferential direction is A2 at one tire maximum width position P, then bends to A1 at the tire centerline position, then bends again in the opposite direction to A2 at the other tire maximum width position P. The dotted line indicates an inner reinforcing layer ply comprising multiple reinforcing layer cords and a topping rubber covering the reinforcing layer cords, specifically a belt ply.

[0078] The angle at which the carcass cord's extension direction slopes from the tire's circumferential direction at the tire's centerline is shown as A1(°), and the angle at which it slopes from the tire's circumferential direction at the tire's maximum width is shown as A2(°). Both A1 and A2 have positive (+) values ​​because they slope downward to the right with respect to the tire's circumferential direction when viewed from the inner surface of the tire. On the other hand, the angle at which the reinforcing layer cord's extension direction slopes from the tire's circumferential direction is A RF (°) is indicated. RF Because it slopes upward to the right relative to the tire's circumferential direction when viewed from the inner side of the tire, it has a negative (-) value.

[0079] Figure 3 is an unfolded view of the carcass cords constituting the carcass ply, showing the angle between their extension direction and the tire circumferential direction as seen from the inner surface of the tire. It is a modified version of Figure 2. The carcass cords in Figure 3 are shown from one maximum tire width position to the other. Their extension direction begins at an angle A2 inclined from the tire circumferential direction at one maximum tire width position P, changes smoothly along the way, and ends at an angle A2 inclined from the tire circumferential direction at the other maximum tire width position P. Otherwise, it is the same as in Figure 2.

[0080] In the tire of this embodiment, the width of the R1 region, where the inclination angle of the carcass cord A1 on the tire centerline is within a predetermined range of variation, is preferably 30% or more of the tread contact width. More preferably, the width of the R1 region is 50% or more, even more preferably 70% or more, and even more preferably 90% or more of the tread contact width. On the other hand, the width of the R1 region is preferably 100% or less of the tread contact width.

[0081] Furthermore, in the tire of this embodiment, A1 and A2 are angles in the carcass cords of at least one of the carcass plies. Preferably, A1 is the angle (°) at which the extension direction of the carcass cords of the outermost carcass ply in the tire radial direction is inclined from the tire circumferential direction at the position of the tire centerline. Also preferably, A2 is the angle (°) at which the extension direction of the carcass cords of the outermost carcass ply in the tire radial direction is inclined from the tire circumferential direction at the position of the tire width.

[0082] In other words, the pneumatic tire in this embodiment comprises a tread, a carcass, at least one reinforcing layer disposed radially outside the carcass, and a sidewall. The tread comprises a cap tread including a contact surface and a base tread located radially inside it. The carcass is composed of at least one carcass ply comprising a plurality of carcass cords and a topping rubber covering the carcass cords. The reinforcing layer is composed of at least one reinforcing layer ply comprising a plurality of reinforcing layer cords and a topping rubber covering the reinforcing layer cords. Of the carcass plies, the angle at which the extension direction of the carcass cords of the outermost carcass ply in the radial direction of the tire is inclined from the circumferential direction of the tire at the position of the tire centerline is A1(°), and the angle at which it is inclined from the circumferential direction of the tire at the position of the tire's maximum width is A2(°). The rubber composition constituting the base tread and the rubber composition constituting the sidewall are made of different rubber compositions, and the loss tangent of the rubber composition constituting the base tread at 70°C is 70°tanδ. B The loss loss tangent of the rubber composition constituting the sidewall at 70°C is 70°C tanδ S When K is a constant, A1, A2, 70℃ tanδ B , 70℃ tanδ S It is preferable that K is a pneumatic tire that satisfies the above formulas (1) and (2).

[0083] The materials of the carcass cord and reinforcing layer cord are not particularly limited and include, for example, metal cords (such as steel cords), organic fiber cords, inorganic fiber cords (excluding metal cords), etc.

[0084] The metal cord may be a single-wire monofilament cord (i.e., a cord consisting of one filament having a 1x1 structure), or it may have multiple filaments. If a single metal cord has multiple filaments, it is preferable that the metal cord has a twisted structure in which the filaments are twisted together along its longitudinal direction. The twisted structure is not particularly limited and can be, for example, a single-strand metal cord with a 1xN structure or a layered metal cord with an N+M structure.

[0085] The filaments constituting the organic fiber cord are not particularly limited, but examples include polyester fibers, nylon fibers, aramid fibers, polyketone fibers, poly(p-phenylenenium) acrylate fibers, polyacrylate fibers, rayon fibers, cellulose fibers, carbon fibers, etc., with polyester fibers being preferred. These organic fibers may be made from synthetic fibers, biomass-derived fibers, recycled / regenerated fibers, etc. These organic fibers may be used individually or in combination of two or more types. The organic fiber cord can be made by twisting together multiple yarns, each made by twisting together multiple filaments.

[0086] Examples of inorganic fiber cords other than metal cords include carbon fiber cords and glass fiber cords.

[0087] (Formula (1)) In this embodiment, the value on the right-hand side of equation (1) is greater than 0. That is, in the tire of this embodiment, A1 and A2 are at least different, so |A1-A2|>0 is satisfied. In this embodiment, there are no other particular restrictions on the value of |A1-A2| as long as it is greater than 0, but the value is usually less than 60°, may be less than 50°, may be less than 40°, may be less than 30°, may be less than 20°, or may be 10° or less. On the other hand, the value is preferably greater than 1°, more preferably greater than 3°, and even more preferably 5° or more.

[0088] Furthermore, it is preferable that A2 is between +70° and +90°, or between -70° and -90°. Figure 4 shows a schematic diagram of the preferred range of angles between the extension direction and the tire circumferential direction of the carcass cords constituting the carcass ply, as seen from the inner surface of the tire. When A2 is between +70° and +90°, or between -70° and -90°, it means that the extension direction of the carcass cords is within the range of the arc-shaped double arrows in Figure 4. It is believed that the effects of the present invention can be improved by setting the range of A2 as described above. For A2 between +70° and +90°, the lower limit is more preferably 75° or more, even more preferably 80° or more, while the upper limit is more preferably 85° or less. For A2 between -70° and -90°, the upper limit is more preferably -75° or less, even more preferably -80° or less, while the lower limit is more preferably -85° or more.

[0089] (Formula (2)) In formula (2), the value of K is preferably 520, more preferably 550, even more preferably 600, even more preferably 640, even more preferably 700, even more preferably 800, even more preferably 1000, even more preferably 1500, and even more preferably 2000.

[0090] (70℃ tanδ B ) 70°C tanδ is the loss loss tangent of the rubber composition constituting the base tread at 70°C. B The value of is not particularly limited, but is preferably less than 0.25, more preferably less than 0.20, even more preferably 0.15 or less, even more preferably 0.10 or less, and even more preferably 0.08 or less. On the other hand, the value may be, for example, 0.01 or more, more preferably 0.02 or more, even more preferably 0.03 or more, and even more preferably 0.04 or more.

[0091] (70℃ tanδ S ) 70°C tanδ is the loss loss tangent of the rubber composition constituting the sidewall at 70°C. SThe value of is not particularly limited, but is preferably less than 0.25, more preferably less than 0.20, even more preferably 0.15 or less, even more preferably 0.10 or less, and even more preferably 0.08 or less. On the other hand, the value may be, for example, 0.01 or more, more preferably 0.02 or more, even more preferably 0.03 or more, and even more preferably 0.04 or more.

[0092] 70℃ tanδ B and 70℃ tanδ S This can be appropriately adjusted depending on the type and amount of rubber components, fillers, plasticizers, etc., as described below. For example, 70℃ tanδ B and 70℃ tanδ S This can be increased by increasing the filler content in the rubber composition or by increasing the nitrogen adsorption specific surface area, and conversely, it can be decreased by decreasing these factors.

[0093] (A RF ) In at least one of the reinforcing layer plies, A is the angle at which the extension direction of the reinforcing layer cord is inclined from the tire circumferential direction. RF It is preferable that it is different from A1, and in particular A RF Preferably, the inclination direction of A1 from the tire circumferential direction is opposite to that of A1 from the tire circumferential direction. This is because it can cancel out the twisting of the carcass ply that is bias-arranged on the radially inward side of the tread.

[0094] The angle at which the extension direction of the reinforcing layer cord is inclined from the tire circumferential direction is A. RF The reinforcing layer, which includes a reinforcing layer ply of (°), is preferably composed of a single reinforcing layer ply, or is preferably a belt ply.

[0095] The pneumatic tire according to this embodiment comprises a tread and a carcass, the tread comprising a cap tread including the contact surface and a base tread on the radially inward side of the tread.

[0096] <Rubber composition that makes up the base tread> The rubber composition that makes up the base tread will be described below.

[0097] [Rubber components] The rubber composition contains a rubber component, which includes at least one of isoprene rubber (IR rubber), styrene-butadiene rubber (SBR), and butadiene rubber (BR). In this case, the rubber component may include rubber components other than IR rubber, SBR, and BR. In one embodiment, it is preferable that the rubber component includes IR rubber. In addition to IR rubber, other rubber components may be included, but it may also consist only of IR rubber. In this embodiment, it is preferable that the rubber component includes IR rubber and BR. In addition to IR rubber and BR, other rubber components may be included, but it may also consist only of IR rubber and BR. In another embodiment, it is preferable that the rubber component includes SBR. When the rubber component includes SBR, the rubber component may include rubber components other than SBR, but it may also consist only of SBR.

[0098] (Isoprene rubber) As isoprene-based rubbers, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. Natural rubber includes not only unmodified natural rubber (NR), but also modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), and grafted natural rubber. These isoprene-based rubbers may be used individually or in combination of two or more types.

[0099] NR is not particularly limited and can be any tire that is common in the tire industry, such as SIR20, RSS#3, and TSR20.

[0100] When isoprene-based rubber is included, the content of isoprene-based rubber in the rubber component is, for example, 40% by mass or more, preferably 45% by mass or more, more preferably 50% by mass or more, even more preferably 55% by mass or more, and even more preferably 60% by mass or more. Furthermore, the content is preferably less than 90% by mass, more preferably 85% by mass or less, even more preferably less than 80% by mass, and even more preferably 75% by mass or less.

[0101] (SBR) There are no particular limitations on the type of SBR used; solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR) can be used. Examples of modified SBRs include SBRs with modified terminals and / or main chains, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, branched structures, etc.). Furthermore, hydrogenated versions of these SBRs (hydrogenated SBRs) can also be used. SBRs may be used individually or in combination of two or more types.

[0102] The functional groups that the modified SBR has are preferably functional groups containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen. Examples of such functional groups include amino groups, amide groups, silyl groups, alkoxysilyl groups, isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, thiocarbonyl groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups (preferably alkoxy groups having 1 to 6 carbon atoms), hydroxyl groups, oxy groups, epoxy groups, etc., with amino groups and / or alkoxysilyl groups being preferred. As for amino groups, amino groups substituted with 1 to 2 alkyl groups having 1 to 6 carbon atoms are preferred. Specific examples of alkoxysilyls include, for example, trimethoxysilyl, triethoxysilyl, triisopropoxysilyl, dimethoxymethylsilyl, diethoxymethylsilyl, dimethylmethoxysilyl, and dimethylethoxysilyl.

[0103] For SBR, either oil-expanded or non-oil-expanded SBR can be used. Commercially available SBRs from companies such as JSR Corporation, Sumitomo Chemical Co., Ltd., UBE Corporation, Asahi Kasei Corporation, ZS Elastomer Corporation, ARLANXEO, and LG Chem can be used.

[0104] From the viewpoint of the effects of the present invention, the styrene content of SBR is preferably more than 5% by mass, more preferably more than 8% by mass, more preferably 10% by mass or more, even more preferably 15% by mass or more, and also preferably less than 50% by mass, more preferably less than 45% by mass, and even more preferably less than 40% by mass. The styrene content of SBR is measured by the measurement method described above.

[0105] From the viewpoint of the effects of the present invention, the vinyl content of SBR is preferably more than 5 mol%, more preferably more than 10 mol%, and even more preferably more than 15 mol%. Furthermore, it is preferably less than 55 mol%, more preferably less than 50 mol%, and even more preferably less than 45 mol%. The vinyl content of SBR is measured by the measurement method described above.

[0106] The weight-average molecular weight (Mw) of SBR is preferably 100,000 or more, more preferably 150,000 or more, and even more preferably 190,000 or more, from the viewpoint of low fuel consumption performance. Furthermore, from the viewpoint of crosslinking uniformity, the Mw is preferably 2,500,000 or less, and more preferably 2,000,000 or less. The Mw of SBR is measured by the measurement method described above.

[0107] When SBR is included, the SBR content in the rubber component is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, from the viewpoint of low fuel consumption performance. There is no particular upper limit to the content, and it may be 100% by mass, but it is preferably less than 90% by mass, more preferably less than 85% by mass or even more preferably less than 80% by mass.

[0108] (BR) BR is not particularly limited, and for example, BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare-earth butadiene rubber synthesized using a rare-earth element catalyst (rare-earth BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc., which are common in the tire industry, can be used. BR may be used alone or in combination of two or more types.

[0109] High-cis BR can be commercially available from companies such as Nippon Zeon Co., Ltd., UBE Corporation, and JSR Corporation. Including high-cis BR can improve low-temperature properties and wear resistance. The cis content of high-cis BR is preferably more than 90 mol%, more preferably more than 95 mol%, and even more preferably 96 mol% or more. The cis content of BR is measured by the measurement method described above.

[0110] Rare earth-based BR is synthesized using a rare earth element catalyst, and has a vinyl content of preferably less than 1.8 mol%, more preferably less than 1.5 mol%, and even more preferably less than 1.2 mol%, and a cis content of preferably more than 90 mol%, more preferably more than 95 mol%, and even more preferably 96 mol% or more. As rare earth-based BR, commercially available products from companies such as Lanxess can be used.

[0111] SPB-containing BR refers to a type in which 1,2-syndiotactic polybutadiene crystals are not simply dispersed in BR, but are chemically bonded to and dispersed in BR. Such SPB-containing BR can be commercially available from companies such as UBE Corporation.

[0112] Examples of modified BR include BR modified with functional groups similar to those described for SBR above, as well as modified butadiene rubber (modified BR) in which the terminal and / or main chain is modified with functional groups containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen.

[0113] Other modified BRs include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and in which the ends of the modified BR molecule are linked by a tin-carbon bond (tin-modified BR). Furthermore, the modified BR may be either unhydrogenated or hydrogenated.

[0114] The weight-average molecular weight (Mw) of BR is preferably greater than 300,000, more preferably greater than 350,000, and even more preferably greater than 400,000. Furthermore, from the viewpoint of crosslinking uniformity, it is preferably less than 2,000,000, more preferably less than 1,000,000, and even more preferably less than 700,000. The Mw of BR can be determined by the method described above.

[0115] The content of BR in the rubber component is not particularly limited, but is preferably more than 10% by mass, more preferably 15% by mass or more, even more preferably more than 20% by mass, and even more preferably 25% by mass or more. Furthermore, the content of BR in the rubber component is preferably less than 50% by mass, more preferably less than 45% by mass, and even more preferably less than 40% by mass.

[0116] When the rubber component includes IR-type rubber and BR, the total content of IR-type rubber and BR in 100% by mass of the rubber component is preferably more than 80% by mass, more preferably more than 90% by mass, and even more preferably more than 95% by mass, and may be 100% by mass.

[0117] (Other rubber components) In addition to the isoprene-based rubbers, SBR, and BR mentioned above, the rubber components may include other rubber components. Such rubber components may include crosslinkable rubber components commonly used in the tire industry. More specifically, examples include diene-based rubbers such as styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isobutylene-styrene block copolymer (SIBS), chloroprene rubber (CR), and acrylonitrile-butadiene rubber (NBR), as well as non-diene rubbers such as butyl rubber (IIR), ethylene propylene rubber, polynorbornene rubber, silicone rubber, polyethylene chloride rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber. These other rubber components may be used individually or in combination of two or more. Furthermore, known thermoplastic elastomers may also be included in addition to the above-mentioned rubber components.

[0118] (Rubber components synthesized from recycled and biomass-derived raw materials) Monomers, which are the constituent units of synthetic rubbers such as IR, SBR, and BR, may be derived from underground resources such as petroleum and natural gas, or they may be recycled from rubber products such as tires or non-rubber products such as polystyrene. The monomers obtained by recycling (recycled monomers) are not particularly limited, but include recycled polyisoprene, recycled butadiene, and recycled aromatic vinyl compounds. Examples of butadiene include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl compounds are not particularly limited, but include styrene. In particular, it is preferable to use recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) as raw materials.

[0119] The method for producing recycled monomer is not particularly limited, and for example, it can be synthesized from recycled naphtha obtained by decomposing rubber products such as tires. Furthermore, the method for producing recycled naphtha is not particularly limited, and for example, rubber products such as tires may be decomposed under high temperature and pressure, decomposed by microwaves, or extracted after mechanical grinding.

[0120] Furthermore, the monomers that make up polymers such as IR, SBR, and BR may be derived from biomass. In this specification, biomass refers to substances derived from natural resources such as plants. Biomass is not particularly limited, but examples include agricultural, forestry, and fishery products, sugars, wood chips, plant residues after obtaining useful components, plant-derived ethanol, and biomass naphtha.

[0121] The biomass-derived monomer (biomass monomer) is not particularly limited and includes biomass-derived butadiene and biomass-derived aromatic vinyl compounds. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. Examples of the aromatic vinyl compound are not particularly limited but include styrene. Furthermore, the method for producing the biomass monomer is not particularly limited and includes, for example, biological and / or chemical and / or physical transformations of plants and animals. Typical biological transformations include fermentation by microorganisms, while chemical and / or physical transformations include those by catalysts, high heat, high pressure, electromagnetic waves, critical liquids, and combinations thereof.

[0122] The polymer synthesized from biomass monomer components (biomass polymer) is not particularly limited, and examples include polybutadiene rubber synthesized from biomass-derived butadiene, and aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl compounds. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0123] Whether the raw materials for a polymer are biomass-derived can be determined by measuring pMC (percent Modern Carbon) according to ASTM D6866-10. pMC refers to the percentage of modern standard reference carbon. 14 Sample relative to C concentration 14 This is a ratio of C concentrations and is used as an indicator of the biomass ratio of a compound. The significance of this value is described below.

[0124] 1 mole of carbon atoms (6.02 × 10⁻¹⁰) 23 (Each) contains approximately 6.02 × 10¹⁶ atoms, which is about one trillionth of the amount of carbon atoms in a normal atom. 11 individual 14 C exists. 14 The half-life of C is 5730 years. 14 C is decreasing regularly. Therefore, in fossil fuels such as coal, oil, and natural gas, which are thought to have been fixed after more than 226,000 years have passed since atmospheric carbon dioxide was taken in and fixed by plants, etc., C was initially included in these as well. 14 All elements of C have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas are no longer viable. 14 It contains absolutely no element C. Therefore, chemical substances produced using these fossil fuels as raw materials also contain C. 14 It contains absolutely no element C.

[0125] on the other hand, 14C is continuously produced when cosmic rays undergo nuclear reactions in the atmosphere. Therefore, 14 In the Earth's atmospheric environment, carbon (C) is produced in a state where its decrease due to radioactive decay and its production through nuclear reactions are in equilibrium. 14 The amount of C is constant. Therefore, the amount of biomass resource-derived substances currently circulating in the environment 14 As mentioned above, the carbon concentration is approximately 1 × 10¹⁶ of the total carbon atoms. -12 These values ​​are approximately in mole percent. Therefore, the difference between these values ​​can be used to calculate the biomass ratio in a given compound.

[0126] this 14 C is typically measured as follows: Using accelerator mass spectrometry based on a tandem accelerator, 13 C concentration ( 13 C / 12 C), 14 C concentration ( 14 C / 12 Perform measurement C). In the measurement, 14 As a modern standard reference for the concentration of C, the amount of cyclic carbon in nature as of 1950 14 The C concentration will be used. The specific standard material will be the oxalic acid standard provided by NIST (National Institute of Standards and Technology). The specific radioactivity of carbon in this oxalic acid (per gram of carbon) will be used. 14 The radioactivity intensity of C is separated by carbon isotope, 13 The standard value is obtained by correcting C to a constant value and applying decay correction from 1950 AD to the measurement date. 14 This value is used as the C concentration value (100%). The ratio of this value to the value of the sample actually measured is the pMC value.

[0127] Therefore, if rubber is made from 100% biomass-derived materials, although there are regional differences, under normal conditions it will often not reach 100, and will show a value of approximately 110 pMC. On the other hand, regarding chemical substances derived from fossil fuels such as petroleum,14 When the C concentration is measured, it will show a value of approximately 0 pMC (for example, 0.3 pMC). This value corresponds to the aforementioned biomass ratio of 0%.

[0128] Based on the above, using materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio, in rubber compositions is preferable from an environmental protection standpoint.

[0129] [Filler] The filler preferably contains at least one selected from carbon black and silica. The carbon black may also contain recycled carbon black (rCB). The filler may also contain fillers other than carbon black and silica, such as aluminum hydroxide, calcium carbonate, alumina, clay, talc, etc., which are commonly used in the tire industry. The filler may consist only of carbon black and silica, or only of carbon black.

[0130] (Carbon Black) The carbon black used is not particularly limited and includes N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. The raw materials for carbon black may be biomass materials such as lignin and vegetable oil, or pyrolysis oil obtained by thermal decomposition of waste tires, from the perspective of life cycle assessment. The manufacturing method of carbon black may be by combustion such as the furnace process, by hydrothermal carbonization (HTC), or by thermal decomposition of methane such as the thermal black method. Commercially available products 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., Columbia Carbon Corporation, etc. Carbon black may be used alone or in combination of two or more types.

[0131] In addition to the above, from the perspective of life cycle assessment, carbon black made from biomass materials such as lignin, or recycled carbon black refined by thermal decomposition of carbon black-containing products such as tires, may also be used as carbon black.

[0132] In this specification, "recycled carbon black" refers to carbon black obtained by crushing used tires and other products containing carbon black, and calcining the crushed material, wherein, according to the thermogravimetric method compliant with JIS K 6226-2:2003, when oxidative combustion occurs by heating in air, the proportion of the mass of ash (ash content), which is the component that does not burn, is 13% by mass or more. In other words, the proportion of the mass (carbon content) lost due to the aforementioned oxidative combustion of recycled carbon black is 87% by mass or less. Recycled carbon black may also be represented as rCB.

[0133] Recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, which refers to "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, states that it can be obtained by the 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 usually lacks functional groups on its surface, as referred to in

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

[0134] Recycled carbon black may lack functional groups on its surface, or may be treated to contain functional groups on its surface. The treatment to make the surface of recycled carbon black contain functional groups can be carried out by a conventional method. For example, in European Patent Application Publication No. 3173251, carbon black obtained from a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Also, in Japanese Patent No. 6856781, carbon black obtained from a pyrolysis process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain carbon black with its surface activated. The recycled carbon black according to this embodiment also includes carbon black treated to contain functional groups on these surfaces.

[0135] Recycled carbon black commercially available from Strable Green Carbon, LD Carbon, etc. can be used.

[0136] The nitrogen adsorption specific surface area (N2SA) of carbon black is not particularly limited, but from the viewpoint of obtaining sufficient reinforcing property and good abrasion resistance, it is preferably more than 30 m 2 / g, more preferably more than 40 m 2 / g, still more preferably more than 50 m 2 / g, still more preferably more than 60 m 2 / g, still more preferably more than 70 m 2 / g. Also, regarding the upper limit of the N2SA, from the viewpoint of excellent dispersibility and difficulty in generating heat, it is preferably less than 300 m 2 / g. The N2SA of the recycled carbon black in this specification is the value measured by the above method.

[0137] From the viewpoint of reinforcing properties and crack growth resistance, the carbon black content is preferably more than 1 part by mass, more preferably more than 3 parts by mass, and even more preferably 5 parts by mass or more, per 100 parts by mass of rubber component. Furthermore, from the viewpoint of reinforcing effect, the carbon black content is preferably less than 80 parts by mass, more preferably less than 75 parts by mass, and even more preferably less than 70 parts by mass.

[0138] (silica) The rubber composition preferably contains silica as a filler. The silica is not particularly limited, and common types used in the tire industry can be used, such as silica prepared by a dry process (anhydrous silica) or silica prepared by a wet process (hydrated silica). The raw material for silica is not particularly limited, and may be a mineral-derived raw material such as quartz, or a biological-derived raw material such as rice husks (for example, silica made from biomass materials such as rice husks), or silica recycled from silica-containing products may be used. Among these, hydrated silica prepared by a wet process is preferred because it contains a large amount of silanol groups. Silica may be used alone or in combination of two or more types.

[0139] Silica derived from biomass materials can be obtained, for example, by extracting silicates from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then using these silicates to react with sulfuric acid in the same way as conventional wet silica, the precipitate of silicon dioxide is filtered, washed with water, dried, and pulverized.

[0140] The silica recycled from silica-containing products can be, for example, silica recovered from products containing silica such as semiconductors and other electronic components, tires, desiccants, and diatomaceous earth and other filter materials. The recovery method is not particularly limited and can include thermal decomposition and decomposition by electromagnetic waves. Among these, silica recovered from semiconductors and other electronic components or tires is preferred.

[0141] When silica crystallizes, it becomes insoluble in water and the silicic acid that is its component cannot be utilized. By controlling the combustion temperature and combustion time, crystallization of silica in rice husk ash can be suppressed (see, for example, Japanese Patent Application Laid-Open No. 2009-2594, Akita Prefectural University Web Journal B / 2019, vol. 6, p. 216-222, etc.).

[0142] Amorphous silica extracted from rice husks can be those commercially available from Wilmar Co., Ltd. and others.

[0143] The nitrogen adsorption specific surface area (N2SA) of silica is preferably more than 50 m 2 / g, more preferably more than 100 m 2 / g, still more preferably more than 150 m 2 / g, still more preferably more than 170 m 2 / g. Also, the upper limit of the N2SA of silica is not particularly limited, but is preferably less than 350 m 2 / g, more preferably less than 250 m 2 / g, still more preferably less than 200 m 2 / g. By being within the above range, the cut resistance tends to be improved. The N2SA of silica is a value measured by the above method.

[0144] When containing silica, the content with respect to 100 parts by mass of the rubber component is not particularly limited, but from the viewpoints of ensuring low fuel consumption and riding comfort performance, more than 1 part by mass is preferable, more than 5 parts by mass is preferable, more than 10 parts by mass is more preferable, and more than 20 parts by mass is still more preferable. Also, from the viewpoints of the dispersibility and processability of silica, less than 60 parts by mass is preferable, less than 50 parts by mass is more preferable, and less than 40 parts by mass is still more preferable.

[0145] <<Silane coupling agent>> When silica is used, it is preferable to further include a silane coupling agent. The silane coupling agent is not particularly limited and includes, for example, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl) trisulfide, bis(4-trimethoxysilylbutyl) trisulfide, bis(3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) disulfide, bis(4-trimethoxysilylbutyl) disulfide, and 3-trimethoxysilylpropyl-N,N-dimethylthiocal Examples include sulfide-based compounds such as bamoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercially available products from companies such as Evonik Industries, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Toray Dow Corning Co., Ltd. can be used. The silane coupling agent may be used alone or in combination of two or more types.

[0146] When a silane coupling agent is included, the content of the 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, per 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. Keeping the content within the above range tends to improve the dispersibility of silica.

[0147] [Other compounding agents] In addition to rubber components and fillers, the rubber composition may appropriately contain compounding agents commonly used in the tire industry, such as plasticizers, compatibilizers, processing aids, vulcanized rubber particles, waxes, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators.

[0148] (Plasticizer) A plasticizer is a material that imparts plasticity to rubber components, and the concept includes both liquid and solid plasticizers at 25°C. Examples of plasticizers include resin components, oils, liquid polymers, and ester-based plasticizers. These plasticizers may be derived from petroleum, biomass, or naphtha recycled from rubber or non-rubber products. Low molecular weight hydrocarbon components obtained by thermal decomposition and extraction of used tires or products containing various components may also be used as plasticizers. Plasticizers may be used individually or in combination of two or more types.

[0149] ≪Resin components≫ The rubber composition according to this embodiment may also contain a resin component. The resin component that can be used in this embodiment is not particularly limited, but resins commonly used in the tire industry can be used, such as C9 resins, C5 resins, C5C9 resins, dicyclopentadiene resins, aromatic vinyl resins, coumarone resins, indene resins, terpene resins, rosin resins, phenolic resins, etc. These resin components may be used individually or in combination of two or more. Each resin component may also be used individually or in combination of two or more.

[0150] ·C9 resin A "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a polymer obtained by polymerizing the C9 fraction alone, or a copolymer obtained by copolymerizing the C9 fraction with other components. For example, a resin obtained by copolymerizing dicyclopentadiene (DCPD) and a C9 fraction is called a DCPD / C9 resin. Furthermore, the C9 resin may be a hydrogenated or modified version of these resins. Examples of C9 fractions include petroleum fractions with 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene. As for C9 resins, commercially available products from companies such as BASF, Zeon Corporation, and ENEOS Corporation can be used.

[0151] ·C5 resin "C5 resins" refer to resins obtained by polymerizing C5 fractions, and may be hydrogenated or modified resins. Examples of C5 fractions other than dicyclopentadiene include petroleum fractions with 4 to 5 carbon atoms, such as cyclopentadiene, isoprene, piperylene, 2-methyl-1-butene, 2-methyl-2-butene, and 1-pentene. As C5 resins, commercially available products from companies such as Structol, Nippon Zeon Co., Ltd., and ENEOS Corporation can be used.

[0152] C5C9 resin "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be hydrogenated or modified. As C5C9 petroleum resin, commercially available products from companies such as Tosoh Corporation and LUHUA can be used.

[0153] • Dicyclopentadiene resins A "dicyclopentadiene-based resin" refers to a resin in which cyclopentadiene (CPD) and / or dicyclopentadiene (DCPD) are the most abundant monomer components, and these may be hydrogenated or modified resins. Preferred dicyclopentadiene-based resins include polymers obtained by polymerizing only dicyclopentadiene as a monomer, and copolymers (DCPD / C9 resins) obtained by copolymerizing dicyclopentadiene with the C9 fraction. Commercially available dicyclopentadiene-based resins from companies such as ExxonMobil, ENEOS Corporation, Nippon Zeon Corporation, and Maruzen Petrochemical Co., Ltd. can be used.

[0154] Aromatic vinyl resin "Aromatic vinyl resin" refers to a resin in which aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and p-chlorostyrene are the most abundant monomer components, and these may be hydrogenated or modified. As aromatic vinyl resins, α-methylstyrene or a homopolymer of styrene or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, for reasons of being economical, easy to process, and having excellent heat generation properties. As aromatic vinyl resins, commercially available products from companies such as Kraton, Eastman Chemical Company, and Mitsui Chemicals, Inc. can be used.

[0155] • Coumaron resin "Coumarone-based resin" refers to a resin containing coumarone as a monomer component, and may be hydrogenated or modified. Preferred coumarone-based resins include, for example, coumarone resin, which is a polymer with coumarone as the monomer component; coumarone-indene resin, which is a copolymer with coumarone and indene as monomer components; and coumarone-indene-styrene resin, which is a copolymer with coumarone, indene, and styrene as monomer components. As coumarone-based resins, commercially available products from companies such as Rutgers, Nippon Paint Chemical Co., Ltd., and Mitsui Chemicals, Inc. can be used.

[0156] • Indene resin "Indene-based resin" refers to a resin containing indene as a monomer component, and may be hydrogenated or modified resins. Preferred indene-based resins include, for example, coumarone-indene resin, which is a copolymer of coumarone and indene as monomer components, and coumarone-indene-styrene resin, which is a copolymer of coumarone, indene, and styrene as monomer components. Commercially available indene-based resins from companies such as Rutgers, Nippon Paint Chemical Co., Ltd., and Mitsui Chemicals, Inc. can be used.

[0157] • Terpene resins "Terpene resin" refers to a resin containing terpene compounds such as α-pinene, β-pinene, limonene, and dipentene as monomer components, and may be hydrogenated or modified. Preferred terpene resins include, for example, polyterpene resins, which are polymers in which one or more of the aforementioned terpene compounds are used as monomer components; aromatically modified terpene resins, which are copolymers in which the aforementioned terpene compounds and aromatic compounds are used as monomer components; and terpene phenol resins, which are copolymers in which the aforementioned terpene compounds and phenol compounds are used as monomer components. Examples of aromatic compounds that serve as monomer components in aromatically modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenol compounds that serve as monomer components in terpene phenol resins include phenol, bisphenol A, cresol, and xylenol. As terpene resins, commercially available products from companies such as Yasuhara Chemical Co., Ltd., Arakawa Chemical Industries, Ltd., and Nippon Terpene Chemical Co., Ltd. can be used.

[0158] • Rosin-based resin "Rosin-based resin" refers to a resin containing rosin acid compounds such as abietic acid, neoabietic acid, palastic acid, and isopimal acid, and may be hydrogenated or modified. Rosin-based resins are not particularly limited, but examples include natural resin rosin and rosin-modified resins obtained by hydrogenating, disproportionating, dimerizing, esterifying, etc. As rosin-based resins, commercially available products from companies such as Harima Chemical Industries, Ltd., Arakawa Chemical Industries, Ltd., and IREC Co., Ltd. can be used.

[0159] • Phenolic resins "Phenol-based resins" refer to resins containing phenol compounds such as phenol and cresol as monomer components, and may also be hydrogenated or modified resins. Phenolic resins are not particularly limited, but examples include phenol-formaldehyde resins, alkylphenol-formaldehyde resins, alkylphenol-acetylene resins, oil-modified phenol-formaldehyde resins, and terpene-phenol resins. Phenolic resins that are commercially available from companies such as Sumitomo Bakelite Co., Ltd., DIC Corporation, and Asahi Organic Materials Co., Ltd. can be used.

[0160] From the viewpoint of processability and improved dispersibility between the rubber component and the filler, the softening point of the resin component is preferably 60°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, while it is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. The softening point of the resin component is measured by the measurement method described above.

[0161] When a resin component is included, its content 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 2 parts by mass. On the other hand, the content is preferably less than 30 parts by mass, more preferably less than 20 parts by mass, and even more preferably less than 15 parts by mass.

[0162] ≪Oil≫ Examples of oils include mineral oil, vegetable oil, and animal oil. Furthermore, from a life cycle assessment perspective, waste oil from rubber mixers and engines, or refined waste cooking oil from restaurants, may also be used. Oils may be used individually or in combination of two or more types.

[0163] In this specification, mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. Examples of mineral oil include paraffinic oils (mineral oil), naphthenic oils, and aromatic oils. Specific examples of mineral oil include MES (Mild Extracted Solvate), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), and RAE (Residual Aromatic Extract). Furthermore, for environmental reasons, oils with a low content of polycyclic aromatic compounds (PCA) can be used. Examples of low-PCA oils include MES, TDAE, and heavy naphthenic oils. Mineral oil may be used alone or in combination of two or more types.

[0164] In this specification, vegetable oils include, for example, linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grapeseed oil, and wood wax. Furthermore, vegetable oils may also include refined oils (such as salad oil) obtained by refining the above oils, transesterified oils obtained by transesterifying the above oils, hydrogenated oils obtained by hydrogenating the above oils, thermally polymerized oils obtained by thermally polymerizing the above oils, oxidized polymerized oils obtained by oxidizing the above oils, and waste cooking oils recovered from use as edible oils. Note that vegetable oils may be liquid or solid at 25°C. Vegetable oils may be used individually or in combination of two or more types.

[0165] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably contains triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxyl group of glycerin and a fatty acid are ester-bonded. The acylglycerol is not particularly limited and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Furthermore, the acylglycerol may be a monomer, a dimer, or a polymer of three or more. Note that acylglycerols of two or more forms can be obtained by thermal polymerization, oxidative polymerization, etc. Also, the acylglycerol may be a liquid or a solid at 25°C.

[0166] The method for confirming whether the rubber composition contains the acylglycerol is not particularly limited, 1 This can be confirmed by 1H-NMR measurement. For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at 25°C for 24 hours, and after removing the rubber composition, it is measured at room temperature. 1 When 1H-NMR was measured and the tetramethylsilane (TMS) signal was set to 0.00 ppm, signals were observed around 5.26 ppm, 4.28 ppm, and 4.15 ppm. These signals are presumed to originate from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In this paragraph, "around" refers to a range of ±0.10 ppm.

[0167] The aforementioned fatty acids are not particularly limited and may be unsaturated or saturated fatty acids. 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.

[0168] In particular, it is desirable that the fatty acid contains fatty acids with few double bonds, i.e., saturated fatty acids or monounsaturated fatty acids, and oleic acid is preferred. As a vegetable oil containing such fatty acids, for example, a vegetable oil containing saturated fatty acids or monounsaturated fatty acids may be used, or a vegetable oil that has been modified by transesterification or other means may be used. Furthermore, in order to produce a vegetable oil containing such fatty acids, plants may be improved by breeding, genetic modification, genome editing, etc.

[0169] As for vegetable oils, commercially available products from companies such as Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kosan Co., Ltd., and Nisshin Oillio Group Ltd. can be used.

[0170] Examples of animal oils include fish oil, beef tallow, or oleyl alcohol which can be derived from them.

[0171] The oil content per 100 parts by mass of rubber component is preferably more than 1 part by mass, more preferably more than 2 parts by mass, and even more preferably 3 parts by mass or more. Furthermore, the content is preferably less than 20 parts by mass, more preferably less than 15 parts by mass, and even more preferably 10 parts by mass or less. Note that the oil content includes the amount of oil contained in the rubber component as an oil spreading oil, as well as the amount of oil contained in other components such as sulfur.

[0172] Liquid polymer A liquid polymer is a polymer that is liquid at 25°C, and examples include liquid diene polymers. Examples of liquid diene polymers include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), and liquid styrene-isoprene copolymer (liquid SIR). The number average molecular weight (Mn) of the liquid diene polymer, measured in polystyrene terms by gel permeation chromatography (GPC), is preferably greater than 1000, more preferably greater than 3000, while the Mn is preferably less than 100,000, and more preferably less than 15,000. The Mn of the liquid polymer is the polystyrene equivalent value measured by gel permeation chromatography (GPC). Examples of liquid diene polymers that can be used include products from Sartomer Co., Ltd., Kuraray Co., Ltd., etc. The liquid polymer may be used alone or in combination of two or more types.

[0173] Ester-based plasticizers Examples of ester-based plasticizers include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelaate (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). Ester-based plasticizers may be used individually or in combination of two or more.

[0174] (Processing aid) 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. For example, commercially available processing aids from companies such as Schill+Seilacher and Performance Additives can be used. Processing aids may be used individually or in combination of two or more.

[0175] When processing aids are included, the content per 100 parts by mass of rubber components 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 exhibiting an effect of improving processability. Furthermore, from the viewpoint of abrasion resistance and fracture strength, it 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.

[0176] (Vulcanized rubber particles) 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 viewpoint of environmental considerations and cost, recycled rubber powder produced from crushed waste tires is preferred. The vulcanized rubber particles are not particularly limited and may be unmodified or modified. Commercially available vulcanized rubber products include those from Lehigh, Muraoka Rubber Industries, and others. One type of vulcanized rubber particle may be used alone, or two or more types may be used in combination.

[0177] (wax) The wax is not particularly limited, and any wax commonly used in the tire industry can be suitably used, such as mineral waxes and plant-derived waxes. Mineral waxes refer to waxes derived from mineral resources such as oil and natural gas. Plant-derived waxes refer to waxes derived from natural resources such as plants. Among these, mineral waxes are preferred. Examples of plant-derived waxes include rice wax, carnauba wax, and candelilla wax. Examples of mineral waxes include paraffin wax, microcrystalline wax, and selected special waxes thereof, with paraffin wax being preferred. The wax according to this embodiment does not contain stearic acid. The wax can be commercially available from companies such as Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Paramelt Co., Ltd. The wax may be used alone or in combination of two or more types.

[0178] When wax is included, the content per 100 parts by mass of rubber component is preferably more than 0.3 parts by mass, more preferably more than 0.7 parts by mass, and still more preferably more than 1.0 part by mass. On the other hand, the content is preferably less than 4.0 parts by mass, more preferably less than 3.0 parts by mass, and still more preferably less than 2.5 parts by mass.

[0179] (Stearic acid) When stearic acid is included, its 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 1.0 part by mass or more, from the viewpoint of processability. On the other hand, from the viewpoint of vulcanization rate, 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.

[0180] (Zinc oxide) When zinc oxide is included, its content per 100 parts by mass of 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. On the other hand, from the viewpoint of wear resistance, 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.

[0181] (Anti-aging agent) While not particularly limited, the following are examples of anti-aging agents: naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; 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'-ditril-p-phenyl Examples include p-phenylenediamine-based antioxidants such as diamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. 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 include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., Flexis, and others. The antioxidant may be used alone or in combination of two or more.

[0182] When an anti-aging agent is included, its content per 100 parts by mass of 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. On the other hand, the content is preferably less than 7.0 parts by mass, more preferably less than 5.0 parts by mass, and even more preferably 3.0 parts by mass or less.

[0183] (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. Among these, sulfur-based vulcanizing agents are preferred. As sulfur-based vulcanizing agents, for example, sulfur, sulfur donors such as morpholine disulfide can be used. Among these, the use of sulfur is preferred. The vulcanizing agent can be used one or in combination of two or more types.

[0184] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur (oil-treated sulfur, special sulfur treated with dispersants, masterbatch-type sulfur, etc.), and insoluble sulfur (oil-treated insoluble sulfur, etc.), all of which can be suitably used. Among these, powdered sulfur is preferred. Sulfur can be used from, for example, products manufactured and sold by Tsurumi Chemical Industries, Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals, Ltd., Flexis Co., Ltd., Nippon Dry Distillation Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc.

[0185] Known organic crosslinking agents can also be used as vulcanizing agents. The organic crosslinking agents are not particularly limited as long as they can form crosslinking chains other than polysulfide bonds, but examples include alkylphenol-sulfur chloride condensates, 1,6-hexamethylene-dithiosulfate sodium dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, and dicumyl peroxide, with 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane being preferred. These organic crosslinking agents can be commercially available from companies such as Taoka Chemical Industries, Ltd., Lanxess Corporation, and Flexis.

[0186] When a vulcanizing agent is included, its content per 100 parts by mass of rubber component is preferably more than 0.4 parts by mass, more preferably 0.5 parts by mass or more, and even more preferably 1.0 part by mass or more. On the other hand, the content is preferably less than 6.0 parts by mass, more preferably less than 4.0 parts by mass, and even more preferably less than 2.0 parts by mass. When the vulcanizing agent content is within the above range, an appropriate reinforcing effect tends to be obtained. Note that if the vulcanizing agent contains components other than sulfur, such as oil-treated sulfur, the vulcanizing agent content refers to the content of the sulfur component itself.

[0187] (Vulcanization accelerator) The vulcanization accelerator is not particularly limited, and known vulcanization accelerators can be used, such as sulfenamide, thiazole, thiram, thiourea, guanidine, dithiocarbamate, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Among these, thiazole, sulfenamide, thiram, and guanidine are preferred, thiazole and sulfenamide are more preferred, and thiazole is even more preferred. For example, vulcanization accelerators manufactured and sold by Ouchi Shinko Chemical Industry Co., Ltd., Sanshin Chemical Industry Co., Ltd., etc., can be used. One or more vulcanization accelerators can be used in combination.

[0188] Examples of sulfenamide-based vulcanization accelerators include N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide (DZ). Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole (MBT) or its salts, di-2-benzothiazolyl disulfide (MBTS), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, and 2-(2,6-diethyl-4-morpholinothio)benzothiazole. Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), diortotolylguanidine, and orthotolylbiguanidine. Examples of thiram-based vulcanization accelerators include tetramethylthiram monosulfide, tetramethylthiram disulfide, and tetrabenzylthiram disulfide (TBzTD).

[0189] 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 0.5 parts by mass, and even more preferably 1.0 part by mass or more. On the other hand, the content is preferably less than 8.0 parts by mass, more preferably less than 7.0 parts by mass, and even more preferably less than 6.0 parts by mass. When the content of the vulcanization accelerator is within the above range, fracture strength and elongation tend to be ensured.

[0190] <Rubber composition constituting the sidewall> The components of the rubber composition for sidewalls will be described below.

[0191] [Rubber components] The following is an explanation of the rubber components, and the explanation for the rubber composition constituting the base tread also applies.

[0192] The rubber component comprises at least one of isoprene rubber (IR rubber) and butadiene rubber (BR). In one embodiment, it is preferable that the rubber component comprises IR rubber. In addition to IR rubber, other rubber components may be included, but it may also consist only of IR rubber. In this case, it is preferable that the rubber component comprises isoprene rubber (IR rubber) and butadiene rubber (BR). The rubber component may include rubber components other than IR rubber and BR, but it may also consist only of IR rubber and BR.

[0193] (Content) Regarding the rubber component content, the IR-based rubber content in 100% by mass of the rubber component is, for example, more than 10% by mass, preferably more than 20% by mass, more preferably more than 30% by mass, and even more preferably 35% by mass or more. On the other hand, the content is, for example, 60% by mass or less, preferably less than 55% by mass, more preferably less than 50% by mass, and even more preferably 45% by mass or less. By keeping it within the above range, the rigidity of the rubber composition increases and the amount of deformation is suppressed, which tends to suppress the decrease in fuel efficiency performance.

[0194] Furthermore, the BR content in 100% by mass of the rubber component is, for example, more than 20% by mass, preferably more than 30% by mass, and more preferably more than 40% by mass. On the other hand, the content is, for example, less than 80% by mass, preferably less than 75% by mass, more preferably less than 70% by mass, and even more preferably 65% ​​by mass or less. By keeping it within the above range, the glass transition temperature (Tg) of the rubber composition is lowered, and a reduction in the loss tangent over a wide temperature range becomes possible, which tends to suppress the decrease in fuel efficiency.

[0195] The total content of IR-based rubber and BR in 100% by mass of the rubber component is preferably more than 80% by mass, more preferably more than 90% by mass, and even more preferably more than 95% by mass, and may be 100% by mass.

[0196] [Filler] The filler may contain carbon black (CB) and silica. It is preferable that it contains carbon black. If the filler contains silica, it may further contain a silane coupling agent. The filler may further contain other fillers besides carbon black and silica. A description of each component that may constitute the filler is provided below, and the description in the section on fillers for the rubber composition constituting the base tread also applies.

[0197] (Carbon black content) When carbon black is included, the carbon black content is, for example, more than 20 parts by mass, preferably 30 parts by mass or more, more preferably 35 parts by mass or more, and even more preferably 40 parts by mass or more, per 100 parts by mass of the rubber component. On the other hand, the total content is preferably less than 60 parts by mass, more preferably less than 55 parts by mass, even more preferably less than 50 parts by mass, and even more preferably 45 parts by mass or less. When the carbon black content is within the above range, sufficient reinforcing properties, good dispersion in the rubber, and sufficient rubber strength and crack resistance tend to be obtained.

[0198] [Other compounding agents] The rubber composition constituting the sidewall may, in addition to rubber components and fillers, appropriately contain other compounding agents commonly used in the tire industry, such as plasticizers, compatibilizers, processing aids, vulcanized rubber particles, waxes, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators. Except for those described below, the same explanations given for the rubber composition constituting the base tread apply to these other compounding agents.

[0199] The rubber composition constituting the sidewall preferably contains a plasticizer, and more preferably a resin component. As the resin component, a C5C9 resin is particularly preferable. When a resin component is included, its content 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 2 parts by mass. On the other hand, the content is preferably less than 15 parts by mass, more preferably less than 10 parts by mass, and even more preferably less than 5 parts by mass.

[0200] In this specification, various materials containing carbon atoms (e.g., rubber, oil, resin components, vulcanization accelerators, antioxidants, surfactants, etc.) may be derived from atmospheric carbon dioxide. As a method for obtaining the formulations according to this embodiment 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.

[0201] <Manufacturing> The rubber composition according to this embodiment can be manufactured by known methods. For example, it can be manufactured by kneading each of the above components using a rubber kneading device such as an open roll or a closed kneader (Banbury mixer, kneader, etc.).

[0202] The mixing process includes, for example, a base mixing process in which compounding agents and additives other than the vulcanizing agent and vulcanization accelerator are mixed, and a final mixing (F mixing) process in which the vulcanizing agent and vulcanization accelerator are added to the mixture obtained in the base mixing process and mixed. Furthermore, the base mixing process can be divided into multiple processes as desired. When dividing the base mixing process, the method may be (1) a method in which some of the compounding agents and additives are mixed in advance to form a masterbatch, and then the remaining compounding agents and additives are added to the resulting masterbatch and mixed, or (2) a method in which all the compounding agents and additives to be mixed in the base mixing process are mixed at once, and then the mixture is remilled one or more times. In the method of (1) above, the number of masterbatches is not limited and may be two or more. Also, when the number of masterbatches is two or more, all the compounding agents and additives used in the base mixing process may be allocated to one of the masterbatches.

[0203] While there are no particular limitations on the mixing conditions, one example is to mix the base mixture at a discharge temperature of 150-170°C for 3-10 minutes, and then mix the final mixture at 70-110°C for 1-5 minutes.

[0204] The pneumatic tire according to this embodiment can be manufactured by conventional methods using the unvulcanized rubber composition obtained above. That is, each of the rubber compositions obtained above can be extruded at the unvulcanized stage to conform to the shape of the desired tire component, thereby forming an unvulcanized base tread and sidewall, respectively. The unvulcanized base tread and sidewall thus obtained are bonded together with other tire components on a tire molding machine by conventional methods to form an unvulcanized tire. At this time, the structure of the carcass cord is made to be predetermined. Also, if necessary, the reinforcing layer is made to be made to be predetermined. The pneumatic tire according to this embodiment can be manufactured by heating and pressurizing the thus obtained unvulcanized tire in a vulcanizing machine. The vulcanization conditions are not particularly limited, and for example, a method of vulcanization at 150 to 200°C for 10 to 40 minutes can be cited.

[0205] <Application> The pneumatic tire according to this embodiment can be used for any application, including passenger car tires, large passenger car tires, large SUV tires, racing tires, motorcycle tires, heavy-duty tires, and run-flat tires. A passenger car tire refers to a tire intended for use on a four-wheeled vehicle with a maximum load capacity of less than 1400 kg. A heavy-duty tire refers to a tire with a maximum load capacity of 1400 kg or more. Furthermore, in this specification, the tire can be used as an all-season tire, a summer tire, or a winter tire such as a studless tire. [Examples]

[0206] The following examples (case studies) are shown as preferred for implementation, but the scope of the present invention is not limited to these examples. Tires having a base tread, sidewall, and tire structure obtained using the various chemicals shown below were examined according to each table, and the results calculated based on the evaluation method described below are shown at the bottom of each table.

[0207] <Various chemicals> The various chemicals used in the examples and comparative examples are summarized below. NR:TSR20 (Natural Rubber) Styrene-butadiene rubber (SBR): SBR1502 manufactured by JSR Corporation (unmodified E-SBR, styrene content: 23.5% by mass, vinyl content: 18 mol%, Tg: -56℃, Mw: 440,000, non-oil-based) Butadiene rubber 1 (BR1): BR730 manufactured by JSR Corporation (unmodified high-cis BR, cis content: 96 mol%, Mw: 440,000) Butadiene rubber 2 (BR2): BR150B manufactured by JSR Corporation (unmodified high-cis BR, cis content: 95 mol%, Mw: 580,000) Butadiene rubber 3 (BR3): VCR617 manufactured by UBE Corporation (syndiotactic-1,2-polybutadiene crystalline dispersion; melting point of 1,2-syndiotactic polybutadiene crystals: 200°C; boiling n-hexane insoluble matter content: 17% by mass; 1,2-syndiotactic polybutadiene crystal content: 17% by mass; cis content: 98 mol%) Butadiene rubber 4 (BR4): NipolBR1250H manufactured by Nippon Zeon Co., Ltd. (Tin-modified BR, polymerized using lithium as an initiator, cis content: 42 mol%, Mw: 570,000) Carbon Black 1 (CB1): Show Black N351H (N2SA: 69m) manufactured by Cabot Japan Co., Ltd. 2 / g, average primary particle diameter: 29 nm, ash content: 1.0% by mass or less) Carbon Black 2 (CB2): Show Black N550 (N2SA: 42m) manufactured by Cabot Japan Co., Ltd. 2 / g, average primary particle diameter: 48nm, ash content: 1.0% by mass or less) Silica: UltraSil VN3 (N2SA: 175m) manufactured by Evonik Industries. 2 / g, average primary particle diameter: 17nm) Silane coupling agent: Si266 (manufactured by Evonik Industries, bis(3-triethoxysilylpropyl) disulfide) Oil: VIVATEC500 (aromatherapy process oil) by H&R. Resin: PetroTac 100V (C5C9 resin, softening point: 96℃) manufactured by Tosoh Corporation. Wax: Ozoace 0355SR manufactured by Nippon Seiro Co., Ltd. Anti-aging agent 1: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Anti-aging agent 2: Nocrack RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: Beads-derived stearic acid (manufactured by NOF Corporation) Zinc oxide: Two types of zinc oxide (manufactured by Mitsui Mining & Smelting Co., Ltd.) Sulfur: Seimi Sulfur manufactured by Nippon Dry Distillation Industry Co., Ltd. (Oil content: 10% by mass) Vulcanization accelerator 1: Noxellar CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noxellar NS (di-2-benzothiazolyl disulfide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 3: Noxellar M (2-mercaptobenzothiazole) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 4: Noxellar DPG (1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0208] <Examples and Comparative Examples> According to the formulation shown in Table 1, all chemicals except sulfur and vulcanization accelerator are mixed in a 1.7 L Banbury mixer for 5 minutes until the discharge temperature reaches 160°C to obtain a mixture. Next, sulfur and vulcanization accelerator are added to the mixture and mixed in a twin-screw open roll for 4 minutes until the temperature reaches 105°C to obtain an unvulcanized rubber composition for the base tread.

[0209] According to the formulation shown in Table 2, all chemicals except sulfur and vulcanization accelerator are mixed in a 1.7 L Banbury mixer for 5 minutes until the discharge temperature reaches 160°C to obtain a mixture. Next, sulfur and vulcanization accelerator are added to the mixture and mixed in a twin-screw open roll for 4 minutes until the temperature reaches 105°C to obtain an unvulcanized rubber composition for sidewalls.

[0210] Using an unvulcanized rubber composition for the base tread and an unvulcanized rubber composition for the sidewall, these are extruded into the shape of the base tread or sidewall, respectively, using an extruder equipped with a die of a predetermined shape. These are then bonded together with other tire components to produce an unvulcanized tire, which is then press-vulcanized for 35 minutes under conditions of 150°C to produce the test tires (tire size: 215 / 65R14) shown in Tables 3 and 4.

[0211] The tire structure in each table is explained below. In the tire in Table 3, the inclination angles of the carcass cords are A1 at +75° and A2 at +85°. Therefore, for equation (1), |A2-A1|=10°. In the tire in Table 2, the inclination angles of the carcass cords are A1 at +75° and A2 at +80°. Therefore, for equation (1), |A2-A1|=5°. Note that the carcass cords are polyester cords.

[0212] In each table, |A2-A1| / |70℃tanδ B ×70℃ tanδ S The value of | is a value that can be compared with the constant K in equation (2). That is, if the value is greater than the constant K, equation (2) is satisfied; conversely, if it is less than or equal to the constant K, equation (2) is not satisfied.

[0213] <Fuel efficiency> Using a rolling resistance tester, the rolling resistance of each test tire is measured when driven at internal pressure (210 kPa), load (5.26 kN), and speed (80 km / h). The result is expressed as an index with a baseline of 100. A higher index indicates better fuel efficiency.

[0214]

Table 1

[0215]

Table 2

[0216]

Table 3

[0217]

Table 4

[0218] <Embodiment> Examples of embodiments of the present invention are shown below.

[0219] [1] A pneumatic tire comprising a tread, a carcass, at least one reinforcing layer disposed radially outside the tire radius of the carcass, and a sidewall, The tread includes a cap tread including a ground contact surface and a base tread radially inside thereof, The carcass is composed of at least one carcass ply including a plurality of carcass cords and topping rubber covering the carcass cords, The reinforcing layer is composed of at least one reinforcing layer ply including a plurality of reinforcing layer cords and topping rubber covering the reinforcing layer cords, The extending direction of the carcass cords of at least any one of the carcass plies is preferably such that, among the carcass plies, the extending direction of the carcass cords of the outermost carcass ply in the tire radius direction forms an angle A1 (°) inclined from the tire circumferential direction at the position of the tire center line, and an angle A2 (°) inclined from the tire circumferential direction at the position of the maximum tire width, The rubber composition constituting the base tread and the rubber composition constituting the sidewall are made of different rubber compositions from each other, The loss loss tangent of the rubber composition constituting the base tread at 70°C is 70°C tanδ B The loss loss tangent of the rubber composition constituting the sidewall at 70°C is 70°C tanδ S When K is a constant, A1, A2, 70℃ tanδ B , 70℃ tanδ S A pneumatic tire in which K satisfies the following equations (1) and (2). (1)|A2-A1|>0 (2) | 70℃ tanδ B ×70℃ tanδ S |<|A2-A1| / K (However, K is 500, preferably 520, more preferably 550, even more preferably 600, and even more preferably 640.) [2] The tire according to [1] above, wherein the constant K in formula (2) is 700, preferably 800. [3] The tire according to [1] above, wherein the constant K in formula (2) is 1000, preferably 1500, and more preferably 2000. [4] The pneumatic tire according to any one of [1] to [3] above, wherein the rubber composition constituting the base tread contains a rubber component, and the rubber component contains an isoprene-based rubber. [5] A pneumatic tire according to any one of [1] to [4] above, wherein the rubber composition constituting the base tread contains silica. [6] The pneumatic tire according to any one of [1] to [5] above, wherein the rubber composition constituting the sidewall contains a rubber component, and the rubber component contains an isoprene-based rubber. [7] The pneumatic tire according to any one of [1] to [6] above, wherein the rubber composition constituting the sidewall contains a resin component. [8] In at least one of the reinforcing layer plies, the angle (°) at which the extension direction of the reinforcing layer cord is inclined from the tire circumferential direction is A RF In that case, A I and A RF A pneumatic tire that differs from any of the above [1] to [7]. [9] ARF The pneumatic tire according to [8] above, wherein the inclination direction of A1 from the tire circumferential direction is opposite to the inclination direction of A1 from the tire circumferential direction.

[10] The angle at which the extension direction of the reinforcing layer cord is inclined from the tire circumferential direction is A RF The pneumatic tire according to [8] or [9] above, wherein the reinforcing layer, which includes a reinforcing layer ply that is (°), is composed of a single reinforcing layer ply.

[11] The angle at which the extension direction of the reinforcing layer cord is inclined from the tire circumferential direction is A RF A pneumatic tire as described in any of the above [8] to

[10] , wherein the reinforcing layer ply is a belt ply.

[12] The pneumatic tire according to any one of [1] to

[11] above, wherein the at least one reinforcing layer consists only of a belt.

[13] A pneumatic tire according to any of [1] to

[12] above, wherein the carcass is composed of a single carcass ply.

[14] A pneumatic tire according to any of [1] to

[13] above, wherein A2 is +70° or more and +90° or less, preferably +75° or more and +85° or less, more preferably +80° or more and +85° or less, or -70° or less and greater than -90°, preferably -75° or less and -85° or more, more preferably -80° or less and -85° or more.

[15] The loss tangent of the rubber composition constituting the base tread at 70°C is 70°C tanδ B However, the tire is 0.10 or less, as described in any of the above [1] to

[14] .

[16] The loss tangent of the rubber composition constituting the sidewall at 70°C is 70°C tanδ S However, the tire is 0.10 or less, as described in any of the above [1] to

[15] . [Explanation of Symbols]

[0220] 1 Cap Tread 2 Base Tread 3 Carcass 4 belts 5 bands 6. Reinforcement layer CL tire centerline W (Tire width direction) C Tire circumferential direction P tire maximum width position A1 The angle at which the extension direction of the carcass cords is inclined from the tire circumferential direction at the tire centerline. At the A2 tire's widest position, the angle at which the extension direction of the carcass cords is inclined from the tire's circumferential direction. A RF The angle at which the extension direction of the reinforcing layer cord is inclined from the tire circumferential direction.

Claims

1. A pneumatic tire comprising a tread, a carcass, at least one reinforcing layer disposed radially outward of the carcass, and a sidewall, The aforementioned tread comprises a cap tread including the contact surface and a base tread located radially inward of the tire. The carcass is composed of at least one carcass ply comprising a plurality of carcass cords and a topping rubber covering the carcass cords. The reinforcing layer is composed of at least one reinforcing layer ply comprising a plurality of reinforcing layer cords and a topping rubber covering the reinforcing layer cords. The extension direction of the carcass cord of at least one of the carcass plies of the carcass ply is at an angle A that is inclined from the tire circumferential direction at the position of the tire centerline. 1 Let (°) be the angle of inclination from the circumferential direction of the tire at the position of the tire's maximum width. 2 (°) The rubber composition constituting the base tread and the rubber composition constituting the sidewall are made of different rubber compositions. The loss loss tangent of the rubber composition constituting the base tread at 70°C is 70°C tanδ B The loss loss tangent of the rubber composition constituting the sidewall at 70°C is 70°C tanδ S When K is a constant, A 1 A 2 , 70℃ tanδ B , 70℃ tanδ S A pneumatic tire in which K satisfies the following equations (1) and (2). (1)|A 2 -A 1 |>0 (2)|70℃tanδ B ×70℃tanδ S |<|A 2 -A 1 | / K (However, K is 500)

2. The tire according to claim 1, wherein the constant K in formula (2) is 700.

3. The tire according to claim 1, wherein the constant K in formula (2) is 1000.

4. The pneumatic tire according to any one of claims 1 to 3, wherein the rubber composition constituting the base tread contains a rubber component, and the rubber component contains an isoprene-based rubber.

5. The pneumatic tire according to any one of claims 1 to 3, wherein the rubber composition constituting the base tread contains silica.

6. The pneumatic tire according to any one of claims 1 to 3, wherein the rubber composition constituting the sidewall contains a rubber component, and the rubber component contains isoprene-based rubber.

7. The pneumatic tire according to any one of claims 1 to 3, wherein the rubber composition constituting the sidewall includes a resin component.

8. In at least one of the reinforcing layer plies, the angle (°) at which the extension direction of the reinforcing layer cord is inclined from the tire circumferential direction is A RF In that case, A I and A RF A pneumatic tire according to any one of claims 1 to 3, which differs from the above.

9. A RF The inclination direction from the tire circumferential direction is the A 1 The pneumatic tire according to claim 8, wherein the direction of inclination is opposite to the direction of inclination from the circumferential direction of the tire.

10. The angle at which the extension direction of the reinforcing layer cord is inclined from the tire circumferential direction is A. RF The pneumatic tire according to claim 8, wherein the reinforcing layer, which includes a reinforcing layer ply that is (°), is composed of a single reinforcing layer ply.

11. The angle at which the extension direction of the reinforcing layer cord is inclined from the tire circumferential direction is A. RF The pneumatic tire according to claim 8, wherein the reinforcing layer ply, which is (°), is a belt ply.

12. The pneumatic tire according to any one of claims 1 to 3, wherein the at least one reinforcing layer consists only of a belt.

13. The pneumatic tire according to any one of claims 1 to 3, wherein the carcass is composed of a single carcass ply.

14. A 2 A pneumatic tire according to any one of claims 1 to 3, wherein the angle is +70° or more and +90° or less, or -70° or less and greater than -90°.

15. The loss tangent of the rubber composition constituting the base tread at 70°C, 70°C tanδ B The tire according to any one of claims 1 to 3, wherein the coefficient is 0.10 or less.

16. The loss tangent of the rubber composition constituting the sidewall at 70°C, 70°C tanδ S The tire according to any one of claims 1 to 3, wherein the coefficient is 0.10 or less.

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