Pneumatic tire

Abstract

To suppress deterioration of fuel economy in a pneumatic tire having a carcass cord changing in an extending direction.SOLUTION: A tire circumferential inclination angle A1 (°) on a tire center line in a carcass ply cord extending direction, a tire circumferential inclination angle A2 (°) at a tire maximum-width position, a thickness (mm) Ta from a tread outer surface to a tread inner surface on the tire center line, a cap tread thickness (mm) Tca on the tire center line, a cap tread thickness (mm) Tcb on a tire inner surface normal line passing through a tire widthwise end portion of the inner reinforcing layer ply, a thickness (mm) Tb from the tread outer surface to the tread inner surface on the normal line, a 70 °C. loss tangent 70 °C. tan δ b of the rubber composition of the base tread, and a constant K satisfy the following formula (1): A pneumatic tire satisfying (2) and (3): (1) A2-A1> 0 (2) Tca / Ta-Tcb / Tb> 0 (3) 70 °C tan δ b <A2-A1 * (Tca / Ta-Tcb / Tb) / K (where K is 3.2) SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] In a pneumatic tire, the carcass ply forms the framework. The carcass cords that make up the carcass ply determine the type of tire, such as a radial tire or a bias tire, depending on the direction in which they extend, and also determine the performance of the pneumatic tire, such as durability and rigidity. Patent Documents 1 and 2 describe pneumatic tires in which the direction in which the carcass cords extend is controlled to bend the carcass cords. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2023-84469 [Patent Document 2] International Publication No. 2021 / 123530 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in such pneumatic tires, while it is possible to impart desired performance to the pneumatic tire by controlling and changing the extension direction of the carcass cords, there is a concern that energy loss occurs due to the change in the extension direction of the carcass cords during driving, resulting in a decrease in the fuel efficiency of the tire.

[0005] The present invention aims to suppress a decrease in fuel economy in a pneumatic tire having carcass cords whose extension direction changes. [Means for solving the problem]

[0006] That is, the present invention relates to the following tire. A pneumatic tire comprising a tread, a carcass, and at least one reinforcing layer disposed radially outward of the carcass, The tread includes a cap tread including a tread contact surface and a base tread located radially inward of the cap tread, The carcass is composed of at least one carcass ply including 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 including a plurality of reinforcing layer cords and a topping rubber covering the reinforcing layer cords; Among the at least one reinforcing layer ply, the reinforcing layer ply arranged most inward in the tire radial direction is defined as an inner reinforcing layer ply, The angle at which the extending direction of the carcass cord of the carcass ply that is outermost in the tire radial direction is inclined from the tire circumferential direction at the tire center line is defined as A1 (°), and the angle at which the extending direction of the carcass cord of the carcass ply that is outermost in the tire radial direction is inclined from the tire circumferential direction at the tire maximum width position is defined as A2 (°), The thickness (mm) from the outer surface of the tread to the inner surface of the tread on the tire centerline is Ta, the thickness (mm) of the cap tread on the tire centerline is Tca, the thickness (mm) of the cap tread on the normal line to the tire inner surface passing through the tire width direction end of the inner reinforcing layer ply is Tcb, the thickness (mm) from the outer surface of the tread to the inner surface of the tread on the normal line is Tb, and the loss tangent at 70°C of the rubber composition constituting the base tread is 70°C tanδ b , where K is the constant, A1, A2, Ta, Tca, Tb, Tcb, 70℃ tanδ b and K satisfies the following formulas (1), (2), and (3): (1)|A2-A1|>0 (2) Tca / Ta - Tcb / Tb>0 (3) 70℃ tanδ b <|A2-A1|×(Tca / Ta-Tcb / Tb) / K (where K is 3.2) [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress a decrease in fuel economy in a pneumatic tire having carcass cords whose extension direction changes. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a pneumatic tire according to one embodiment of the present invention, taken along a plane passing through a tire rotation axis. [Figure 2] 1 is an example of a developed view illustrating an angle formed by the extending direction of a carcass cord constituting a carcass ply of a pneumatic tire according to one embodiment of the present invention and the tire circumferential direction. [Figure 3] 10 is a modified development view showing the angle formed by the extending direction of a carcass cord constituting a carcass ply of a pneumatic tire according to one embodiment of the present invention and the tire circumferential direction. [Figure 4] 1 is a schematic diagram illustrating a preferred range of an angle formed between the extension direction of a carcass cord constituting a carcass ply of a pneumatic tire according to one embodiment of the present invention and the tire circumferential direction. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] A pneumatic tire according to one embodiment of the present invention will be described below. The pneumatic tire of this embodiment is a pneumatic tire including a tread, a carcass, and at least one reinforcing layer disposed radially outward of the carcass, the tread including a cap tread including a tread contact surface and a base tread disposed radially inward of the cap tread, the carcass including at least one carcass ply including a plurality of carcass cords and a topping rubber covering the carcass cords, the reinforcing layer including at least one reinforcing layer ply including a plurality of reinforcing layer cords and a topping rubber covering the reinforcing layer cords, the reinforcing layer ply disposed radially inward of the at least one reinforcing layer ply is an inner reinforcing layer ply, and the carcass The angle at which the extending direction of the carcass cord of the carcass ply that is outermost in the tire radial direction among the carcass plies inclines from the tire circumferential direction at the tire center line is defined as A1 (°), the angle at which the extending direction of the carcass cord of the carcass ply that is outermost in the tire radial direction inclines from the tire circumferential direction at the tire center line is defined as A2 (°), the thickness (mm) from the outer surface of the tread to the inner surface of the tread on the tire center line is defined as Ta, the thickness (mm) of the cap tread on the tire center line is defined as Tca, the thickness (mm) of the cap tread on the normal line to the tire inner surface passing through the end of the inner reinforcing layer ply in the tire width direction is defined as Tcb, the thickness (mm) from the outer surface of the tread to the inner surface of the tread on the normal line is defined as Tb, and the loss tangent at 70°C of the rubber composition constituting the base tread is defined as 70°C tanδ. b , where K is the constant, A1, A2, Ta, Tca, Tb, Tcb, 70℃ tanδ b and K satisfy the following formulas (1), (2), and (3): (1)|A2-A1|>0 (2) Tca / Ta - Tcb / Tb>0 (3) 70℃ tanδ b <|A2-A1|×(Tca / Ta-Tcb / Tb) / K (where K is 3.2)

[0010] While not intending to be bound by theory, the mechanism by which the present invention suppresses a decrease in fuel economy performance is believed to be as follows. That is, in the present invention, the angle at which the extension direction of the carcass cords inclines from the tire circumferential direction is different between the angle at the tire centerline and the angle at the maximum tire width is different. In response to this, the thickness ratio of the cap tread at the tire widthwise end of the inner reinforcing layer ply is reduced compared to that at the tire centerline to ensure the thickness of the base tread. The difference in the angle at which the extension direction of the carcass cords inclines from the tire circumferential direction, the difference in the thickness ratio of the cap tread, and the loss tangent of the rubber composition constituting the base tread are adjusted to satisfy a predetermined relationship. It is believed that this suppresses a decrease in fuel economy performance of the tire.

[0011] Preferably, K is 4.0, and more preferably 5.5.

[0012] This is because it satisfies equation (3) under stricter conditions.

[0013] It is preferable that the rubber composition constituting the base tread contains a rubber component, and that the rubber component contains an isoprene-based rubber.

[0014] This is because the inclusion of isoprene-based rubber, which has low heat buildup, can suppress a decrease in fuel economy of the tire.

[0015] It is preferable that Tca and Tcb further satisfy the formula (4). (4) Tca>Tcb

[0016] By making the thickness Tca of the cap tread on the tire centerline larger than the thickness Tcb of the cap tread on the normal to the tire inner surface passing through the tire widthwise end of the inner reinforcing layer ply, the thickness of the base tread at the tire widthwise end of the inner reinforcing layer ply can be secured and a decrease in the fuel efficiency of the tire can be suppressed, which is thought to further improve the fuel efficiency of the tire.

[0017] It is preferable that A1, A2, Ta, Tb, Tca, and Tcb further satisfy formula (5). (5)(Tca / Ta-Tcb / Tb) / |A2-A1|>0.003

[0018] (a) The ratio of the cap tread thickness Tca to the thickness Ta from the outer surface of the tread to the inner surface of the tread at the tire centerline, and (b) the ratio of the cap tread thickness Tcb to the thickness Tb from the outer surface of the tread to the inner surface of the tread on a normal to the tire inner surface passing through the tire width direction end of the inner reinforcing layer ply. By adjusting the difference between (a) and (b) and the difference in the angle at which the extension direction of the carcass cords is inclined from the tire circumferential direction, an appropriate difference in the base tread thickness can be set in terms of heat buildup depending on the difference in the extension direction of the carcass cords, which is thought to further improve the fuel efficiency of the tire.

[0019] In at least one of the reinforcing layer plies, the angle (°) at which the extending direction of the reinforcing layer cord is inclined from the tire circumferential direction is defined as A RF In this case, A1 and A RF It is preferable that it is different from

[0020] A1 and A RF It is believed that the difference between the above makes it possible to mitigate twisting of the carcass ply, which is arranged by controlling the extending direction of the carcass ply on the radially inner side of the tread portion of the tire.

[0021] The above A RF The direction of inclination of the grooves A1 from the tire circumferential direction is preferably opposite to the direction of inclination of the grooves A2 from the tire circumferential direction.

[0022] A1 and A RF It is believed that by having the inclination directions of the plies opposite to each other, it is possible to cancel out the twist of the carcass ply arranged by controlling the extension direction on the radially inner side of the tread portion of the tire.

[0023] The angle at which the extending direction of the reinforcing layer cord is inclined from the tire circumferential direction is ARF The reinforcing layer including the reinforcing layer ply (°) is preferably composed of one reinforcing layer ply.

[0024] It is believed that reducing the number of reinforcing layer plies can reduce the weight of the tire.

[0025] The angle at which the extending direction of the reinforcing layer cord is inclined from the tire circumferential direction is A RF It is preferable that the reinforcing layer ply (°) is a belt ply.

[0026] It is believed that the use of a belt ply makes it possible to minimize the number of reinforcing layer plies.

[0027] Preferably, the at least one reinforcing layer consists of a belt only.

[0028] It is believed that reducing the number of types of reinforcing layers can make the tire lighter.

[0029] The carcass is preferably made up of one carcass ply.

[0030] It is believed that reducing the number of carcass plies can reduce the weight of the tire.

[0031] It is preferable that A2 is +70° or more and +90° or less, or -70° or less and more than -90°.

[0032] By setting A2 in the above range, the effects of the present invention can be improved.

[0033] <Definition> "Normal condition" means that the tire is mounted on a normal rim, inflated to the normal internal pressure, and unloaded. Unless otherwise specified, the tire must be in normal condition.

[0034] Unless otherwise specified, the "dimensions of each part of the tire" are values ​​that are specified when the tire appears on its outer surface in a normal state, while those that exist inside the tire or on a cut surface of the tire are values ​​that are specified when, for example, the tire is cut along a plane that includes the tire rotation axis and the cut tire piece is maintained within the rim width of a normal rim.

[0035] "Genuine rim" refers to the rim specified for each tire in the standard system that includes the standard on which the tire is based. For example, for JATMA (Japan Automobile Tire Manufacturers Association), it refers to the standard rim for the applicable size listed in the "JATMA YEAR BOOK," for ETRTO (The European Tyre and Rim Technical Organization), it refers to the "Measuring Rim" listed in the "STANDARDS MANUAL," and for TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "YEAR BOOK." JATMA, ETRTO, and TRA are referenced in that order, and if an applicable size is available at the time of reference, that standard is followed. In the case of a tire not specified in the above standards, it refers to the narrowest rim among the smallest diameter rims that can be mounted on the tire and can maintain internal pressure (i.e., no air leaks from between the rim and tire).

[0036] "Normal internal pressure" refers to the air pressure specified for each tire in the standard system that includes the standard on which the tire is based. For example, for JATMA, it is "maximum air pressure," for ETRTO, it is "INFLATION PRESSURE," and for TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." As with regular rims, refer to JATMA, ETRTO, and TRA in that order, and follow that standard if there is an applicable size at the time of reference. In the case of tires not specified in the above standards, it refers to the normal internal pressure (250kPa or more) of another tire size (defined in the standard) that is specified using the regular rim as the standard rim, and if there are multiple normal internal pressures of 250kPa or more listed, it refers to the smallest value among them.

[0037] "Normal load (kg)" is the load specified for each tire in the standard system including the standard on which the tire is based, for example, "Maximum Load Capacity" for JATMA, "Load Capacity" for ETRTO, and the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA. As with normal rims and normal internal pressures, JATMA, ETRTO, and TRA should be referenced in that order, and if there is an applicable size at the time of reference, that standard should be followed. For tires not specified in the above standards, the maximum load capacity W calculated separately should be used. L is the normal load.

[0038] "Maximum load capacity W L (kg)" is calculated using the following formula: "V" is the virtual volume of the tire (mm 3), "Dt" is the outer diameter (mm) of the tire in its normal state, "Ht" is the tire's cross-sectional height (mm) in the tire's radial direction in a cross section of the tire taken along a plane including the tire's rotation axis, and "Wt" is the tire's cross-sectional width (mm) in its normal state. Ht can be calculated by (Dt-R) / 2, where R is the tire rim diameter. Wt is the value obtained by excluding any patterns or letters on the tire sidewall. Note that maximum load capacity is synonymous with the normal load mentioned above.

[0039]

number

[0040] The "tread portion" refers to a component that includes the part that forms the contact surface of the tire, and when it includes components such as a reinforcing layer or a carcass, it is a component that is located radially outward of those components in the cross section of the tire taken along a plane that includes the tire rotation axis.

[0041] "Tread edge" refers to the outermost edge in the tire width direction that comes into contact with the ground when the tire is pressed against the ground. The tread edge can be determined by mounting the tire on a standard rim, inflating it to the standard internal pressure, leaving it to stand at 25°C for 24 hours, applying ink to the tire tread surface, applying a standard load (a load equal to the maximum load capacity) to the tire, pressing it vertically against cardboard (camber angle 0°), and transferring the ink.

[0042] "Tread contact width" means the distance along the tread surface from one tread contact edge to the other tread contact edge.

[0043] The "carcass" is a component that forms the tire framework and is composed of at least one carcass ply that includes multiple carcass cords and a topping rubber covering the carcass cords. An inner component is located radially inward of the carcass. Examples of the inner component include an inner liner and insulation.

[0044] "Tire maximum width position" refers to the maximum width position in a cross section in the tire width direction measured under normal conditions. In each drawing, this position is indicated by P.

[0045] The "R1 region" refers to the region on the tire centerline where the carcass cord inclination angle A1 is within a predetermined variation range. The allowable variation range of the carcass cord inclination angle 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 maximum tire width position, which is the measurement position for A2.

[0046] "A1" is the angle (°) at which the extending direction of the carcass cord is inclined from the tire circumferential direction at the tire centerline. When viewed from the inside of the tire, an angle that slopes downward to the right with respect to the tire circumferential direction is considered positive (+), and an angle that slopes upward to the right is considered negative (-), and is expressed in the range of more than -90° and up to +90°. If there are multiple carcass plies, the measurement is made on the carcass ply that is outermost in the tire radial direction. Figure 2 shows the case where A1 is positive (+). Note that if the value is positive, the "+" sign can be omitted.

[0047] "A2" is the angle (°) at which the extending direction of the carcass cord is inclined from the tire circumferential direction at the tire's widest position. When viewed from the inside of the tire, an angle that slopes downward to the right with respect to the tire circumferential direction is considered positive (+), and an angle that slopes upward to the right is considered negative (-), and is expressed in the range of more than -90° and up to +90°. Figure 2 shows the case where A2 is positive (+). Note that if the value is positive, the "+" sign may be omitted. When there are multiple carcass plies, it is preferable to measure the carcass ply that is outermost in the tire's radial direction.

[0048] The carcass ply, which is the subject of A2 measurement, extends from the tire centerline to both sides in the tire width direction, with at least one side extending beyond the tire's maximum width position. In this case, the other side may or may not extend beyond the tire's maximum width position. If the carcass ply has a main body portion and a turned-up portion at the tire's maximum width position, A2 is measured at the carcass cord of the main body portion. There are also cases where the turned-up portion of the carcass ply is not present at the tire's maximum width position at all, or is present only on one side in the tire width direction. In these cases, A2 is also measured at the carcass cord of the main body portion.

[0049] Regarding the main body portion and the turned-up portion of the carcass ply, for example, the following cases are assumed. a: When the rolled-up parts are on both sides of the main body in the tire width direction b: The main body of the carcass ply extends to the maximum width position on both sides in the tire width direction, and the turned-up portion exists only on one side of the main body in the tire width direction (there is no turned-up portion on the other side of the main body in the tire width direction). c: The main body portion of the carcass ply does not extend to the maximum width position on one side in the tire width direction, and the turned-up portion does not exist on only one side of the main body portion in the tire width direction (the main body portion does not extend to the maximum width position on the other side in the tire width direction, and no turned-up portion exists on the other side in the tire width direction). d: When the main body of the carcass ply extends to the maximum width position on both sides in the tire width direction, and the turned-up portion does not exist on either side of the main body in the tire width direction e: When the main body of the carcass ply extends only to the maximum width position on one side in the tire width direction, and the turned-up portion does not exist on either side of the main body in the tire width direction

[0050] In the above cases a to e, A2 is measured as follows. That is, in the cases of a, b, and d, A2 is measured at two locations on the main body. At least one of these A2s must meet the specified requirements. On the other hand, in the cases of c and e, A2 is measured at one location on the main body. That A2 must meet the specified requirements.

[0051] The "carcass cord whose drawing direction changes" is a carcass cord that satisfies the above formula (1), that is, |A2-A1|>0.

[0052] The "reinforcing layer" is a component located radially outward of the carcass and radially inward of the tread, and is responsible for preventing tire protrusion due to internal pressure and rotation, as well as for receiving and absorbing input from the road surface. The reinforcing layer is composed of at least one reinforcing layer ply having a plurality of reinforcing layer cords and a topping rubber covering the reinforcing layer cords. Of the at least one reinforcing layer ply, the reinforcing layer ply located radially inward is called the inner reinforcing layer ply. Specific examples of reinforcing layers include belts and bands.

[0053] A "belt" is one of the reinforcing layers and is composed of at least one belt ply. The belt ply is made up of multiple belt cords arranged approximately parallel to one another, with the extension direction of the belt cords inclined at an angle of 10 degrees or more with respect to the tire circumferential direction. The belt has a joint portion on the circumference of the tire. Here, "approximately parallel" means that the angle difference between the extension direction of each belt cord and the tire circumferential direction is within ±3 degrees.

[0054] A "band" is one of the reinforcing layers and is composed of at least one band ply. The band cords that make up the band ply are arranged in a spirally wound state in the circumferential direction of the tire, and the extension direction of the band cords is inclined at an angle of 5° or less relative to the circumferential direction of the tire. The band does not have any joints on 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 edge of the tread.

[0055] "A RF " is the angle (°) at which the extending direction of the reinforcing layer cords of the reinforcing layer ply is inclined from the tire circumferential direction, and when viewed from the inside of the tire, a positive (+) is used when the reinforcing layer cords are inclined downward to the right with respect to the tire circumferential direction, and a negative (-) is used when the reinforcing layer cords are inclined upward to the right with respect to the tire circumferential direction, and is expressed in the range of more than -90° and up to +90°. In Figure 2, A RFThe case where the value is positive (+) is shown. Note that if the value is positive, the "+" sign can be omitted.

[0056] "Ta" is the thickness (mm) from the outer surface of the tread to the inner surface of the tread on the tire centerline, "Tca" is the thickness (mm) of the cap tread on the tire centerline, "Tcb" is the thickness (mm) of the cap tread on a line normal to the tire inner surface passing through the tire width direction end of the inner reinforcing layer ply, and "Tb" is the thickness (mm) from the outer surface of the tread to the inner surface of the tread on the same line normal.

[0057] <Measurement method> "70℃ tanδ b " is the loss tangent at 70°C of the rubber composition constituting the base tread, and is measured using a dynamic viscoelasticity measuring device (for example, the Iplexer series manufactured by GABO) under conditions of a temperature of 70°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±1%, and an extension mode. The sample used for the measurement is a vulcanized rubber composition having a length of 20 mm, a width of 4 mm, and a thickness of 1 mm. When cutting a sample from a tire, the length direction of the sample is aligned with the tire circumferential direction, and the thickness direction of the sample is aligned with the tire radial direction, and the sample is prepared as close to the above-mentioned specified dimensions as possible.

[0058] "A1, A2" are each determined as the average of angles measured on four different cords. The four cords are preferably selected from any four cords, and more preferably four cords spaced at equal intervals of approximately 90° around the tire circumferential direction. In this case, the measurement targets for A1 and A2 do not need to be the same cord, but it is more preferable that the measurement targets for A1 and A2 be the same cord.

[0059] "A RF " is determined as the average of angles measured for four different cords. The four cords are preferably selected from any four cords, and more preferably, are selected to be four cords spaced at equal intervals of approximately 90° around the tire circumferential direction.

[0060] The "glass transition temperature of the rubber component" refers to the static glass transition temperature of each rubber component determined by a differential scanning calorimeter (for example, Q200 manufactured by TA Instruments Japan Co., Ltd.).

[0061] "Styrene content" is measured by pyrolysis gas chromatography and NMR measurement ( 1 H-NMR and 13 The amount of components such as "styrene content" is calculated by C-NMR. Unlike physical property values ​​such as complex modulus (E*), the amount of components such as "styrene content" has a true value that is independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible. In this specification, "pyrolysis gas chromatography" refers to a method in which a sample is heated in a pyrolysis device, the individual components contained in the gas phase components generated by this heating are separated using a separation column, and each isolated component is analyzed.

[0062] "Vinyl content (amount of 1,2-bonded butadiene units)" can be measured by pyrolysis gas chromatography or NMR measurement ( 1 H-NMR and 13 It is calculated using C-NMR. As with the "styrene content," there is a true value for the "vinyl content" that is independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible.

[0063] "Cis content (cis-1,4-bonded butadiene unit amount)" is measured by infrared absorption spectroscopy or NMR measurement ( 1 H-NMR and 13 This is a value measured by C-NMR and is applied to rubber components that have repeating units derived from butadiene, such as BR. As with the "styrene content," the "cis content" also has a true value that is independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible.

[0064] The "weight average molecular weight (Mw)" can be determined by converting the measured value into standard polystyrene equivalents using gel permeation chromatography (GPC) (for example, a GPC-8000 series manufactured by Tosoh Corporation, a differential refractometer as the detector, and a TSKgel (registered trademark) SuperMultiporeHZ-M column manufactured by Tosoh Corporation). This applies to, for example, SBR, BR, plasticizers, etc.

[0065] The "nitrogen adsorption specific surface area (N2SA) of carbon black" is measured in accordance with JIS K 6217-2:2017.

[0066] The "nitrogen adsorption specific surface area (N2SA) of silica" is measured by the BET method in accordance with ASTM D3037-93.

[0067] The "average primary particle size" is a value obtained by photographing particles with a transmission or scanning electron microscope and calculating the arithmetic mean of the particle sizes of 400 particles. If the particle shape is spherical, the particle size is the diameter of the sphere, and if the particle shape is non-spherical, the particle size is calculated from the microscope image as the circle-equivalent diameter (positive square root of {4 × (particle area) / π}).

[0068] "Plasticizer" is a material that imparts plasticity to rubber components and is a component that is extracted from rubber compositions using acetone. Plasticizers include those that are liquid (fluid) at 25°C and those that are solid at 25°C. However, this does not include waxes and stearic acid, which are commonly used in the tire industry.

[0069] The "plasticizer content" also includes the amount of plasticizer in the rubber component extended by the plasticizer.

[0070] The "softening point of the resin" is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2015 7.7 is measured using a ring and ball softening point tester.

[0071] The following describes the embodiments in more detail. However, the following description is merely an example for explaining the present invention, and the present invention is not limited thereto. Furthermore, although the description will be made using drawings as appropriate, the drawings are merely examples.

[0072] <Tires> The tire of FIG. 1 includes a cap tread 1, a base tread 2, a carcass 3, a belt 4, and a band 5. The belt 4 and the band 5 constitute a reinforcing layer 6.

[0073] The carcass 3 is composed of one carcass ply including a plurality of carcass cords and a topping rubber covering the carcass cords. The belt 4 is composed of one belt ply including a plurality of belt cords and a topping rubber covering the belt cords. The band 5 is composed of one band ply including a plurality of band cords and a topping rubber covering the band cords. In this tire, the belt ply constituting the belt 4 is the inner reinforcing layer ply. The thickness from the outer surface of the tread to the inner surface of the tread on the tire centerline is indicated by Ta (mm), and the thickness of the cap tread is indicated by Tca (mm). Furthermore, the thickness from the outer surface of the tread to the inner surface of the tread on a normal line L of the tire inner surface passing through the tire width direction end of the inner reinforcing layer ply is indicated by Tb (mm), and the thickness of the cap tread on the normal line L is indicated by Tcb (mm). The tire maximum width position is indicated by P.

[0074] In the tire of FIG. 1 , the carcass 3 may be composed of multiple carcass plies, but from the viewpoint of reducing the tire weight, it is preferably composed of fewer carcass plies, and more preferably composed of a single carcass ply. The belt 4 may be composed of multiple belt plies, but from the viewpoint of reducing the tire weight, it is preferably composed of fewer belt plies, and more preferably composed of a single belt ply. The band 5 may be composed of multiple band plies, but from the viewpoint of reducing the tire weight, it is preferably composed of fewer band plies, and more preferably composed of a single band ply. The reinforcing layer 6 may be composed of multiple reinforcing layer plies, but from the viewpoint of reducing the tire weight, it is preferably composed of fewer reinforcing layer plies, and more preferably composed of a single reinforcing layer ply.

[0075] In the tire of the present embodiment, the reinforcing layer may include both the belt and the band, or may consist of only the belt or the band. Of these, it is preferable that the reinforcing layer consists of only the belt.

[0076] FIG. 2 is a developed view of the carcass cords constituting the carcass ply, showing the angle between the extension direction of the carcass cords and the tire circumferential direction. In FIG. 2, the left-right direction W represents the tire width direction, the up-down direction C represents the tire circumferential direction, and the direction perpendicular to the paper surface represents the tire radial direction. FIG. 2 shows the appearance from the inside of the tire. The carcass ply includes multiple carcass cords and topping rubber covering the carcass cords, and the multiple carcass cords are shown in FIG. 2 with solid lines. The extension direction of the carcass cord in FIG. 2 is inclined at an angle A2 from the tire circumferential direction at one tire maximum width position P, then bends to A1 at the tire centerline position, and then bends again in the opposite direction to A2 at the other tire maximum width position P. The double-dashed line shows an inner reinforcing layer ply, specifically a belt ply, including multiple reinforcing layer cords and topping rubber covering the reinforcing layer cords.

[0077] The angle at which the extending direction of the carcass cords is inclined from the tire circumferential direction at the tire centerline is indicated by A1 (°), and the angle at which the extending direction of the carcass cords is inclined from the tire circumferential direction at the tire's maximum width is indicated by A2 (°). Both A1 and A2 are inclined downward to the right with respect to the tire circumferential direction when viewed from the tire's inner surface, so they have a positive (+) value. On the other hand, the angle at which the extending direction of the reinforcing layer cords is inclined from the tire circumferential direction is indicated by A RF (°). A RF is inclined upward to the right with respect to the tire circumferential direction when viewed from the tire inner surface side, and therefore has a negative (-) value.

[0078] FIG. 3 is a development view showing the angle that the extension direction of the carcass cords constituting the carcass ply makes with the tire circumferential direction, and is a modification of FIG. 2. FIG. 3 also shows the state from the inside surface of the tire. The extension direction of the carcass cord in FIG. 3 has an inclination angle from the tire circumferential direction of the tire at one tire maximum width position P, which then changes smoothly to A1 at the tire center line position, and then changes smoothly in the opposite direction to A2 at the other tire maximum width position P. In FIG. 3, the inclination angle from the tire circumferential direction of the tangent to the carcass cord at the tire center line CL is indicated as A1 (°), and the inclination angle from the tire circumferential direction of the tangent to the carcass cord at the tire maximum width position P is indicated as A2 (°). The rest is the same as in FIG. 2.

[0079] In the tire of this embodiment, the width of the R1 region, where the inclination angle of the carcass cords, A1 on the tire centerline, is within a predetermined range of variation, is preferably 30% or more of the tread width. The width of the R1 region is more preferably 50% or more, even more preferably 70% or more, and even more preferably 90% or more of the tread width. On the other hand, the width of the R1 region is preferably 100% or less of the tread width.

[0080] The material of the carcass cords and the reinforcing layer cords is not particularly limited, and examples thereof include metal cords (such as steel cords), organic fiber cords, and inorganic fiber cords (excluding metal cords).

[0081] The metal cord may be a single monofilament cord (i.e., a cord having a 1x1 structure and consisting of one filament), or may have multiple filaments. When a single metal cord has multiple filaments, the metal cord preferably has a twisted structure in which the filaments are twisted together along its longitudinal direction. The twisted structure is not particularly limited, and may be, for example, a single-twisted metal cord having a 1xN structure or a multi-layer twisted metal cord having an N+M structure.

[0082] The filaments constituting the organic fiber cord are not particularly limited, but examples thereof include polyester fibers, nylon fibers, aramid fibers, polyketone fibers, polyparaphenylene acrylate fibers, polyacrylate fibers, rayon fibers, cellulose fibers, and carbon fibers, with polyester fibers being preferred. These organic fibers may be formed from synthetic fibers, biomass-derived fibers, recycled / regenerated fibers, and the like. These organic fibers may be used alone or in combination of two or more. The organic fiber cord may be formed by twisting together multiple yarns, each of which is formed by twisting together multiple filaments.

[0083] Examples of inorganic fiber cords other than metal cords include carbon fiber cords and glass fiber cords.

[0084] (Formula (1)) In this embodiment, the value of the right side of formula (1) is a value greater than 0. That is, in the tire of this embodiment, A1 and A2 are at least different, and therefore |A2-A1|>0 is satisfied. In this embodiment, the value of |A2-A1| is not particularly limited as long as it is greater than 0, but this value is usually less than 60°, and may be less than 50°, less than 40°, less than 30°, less than 20°, less than 15°, or 10° or less. On the other hand, this value is preferably greater than 1°, more preferably greater than 3°, and even more preferably greater than 5°.

[0085] Furthermore, A2 is preferably +70° or more and +90° or less, or -70° or less and exceeding -90°. FIG. 4 is a schematic diagram showing preferred ranges of the angle between the extension direction of the carcass cords constituting the carcass ply and the tire circumferential direction, viewed from the tire inner surface side. A2 of +70° or more and +90° or less, or -70° or less and exceeding -90° means that the extension direction of the carcass cords is within the range indicated by the arc-shaped double arrow in FIG. 4. By setting A2 within the above range, the effects of the present invention can be improved. For A2 of +70° or more and +90° or less, the lower limit is more preferably +75° or more, and even more preferably +80° or more, while the upper limit is more preferably +85° or less. For A2 of -70° or less and exceeding -90°, the upper limit is more preferably -75° or less, and even more preferably -80° or less, while the lower limit is more preferably -85° or more.

[0086] (Formula (2)) From the viewpoint of the effects of the invention, the value of the right side of formula (2) is preferably 0.02, more preferably 0.04, even more preferably 0.06, and even more preferably 0.07. On the other hand, there is no particular upper limit on the value of the left side of formula (2), but from the viewpoint of tire balance, it is usually 0.50 or less, preferably 0.30 or less, more preferably 0.20 or less, and even more preferably 0.10 or less.

[0087] The thickness Ta from the outer surface of the tread to the inner surface of the tread along the tire centerline varies depending on the tire size, but is preferably 6.0 mm or more, more preferably 7.0 mm or more, and even more preferably 8.0 mm or more. On the other hand, Ta is preferably 15.0 mm or less, more preferably 13.0 mm or less, and even more preferably 11.0 mm or less. The thickness Tca of the cap tread along the tire centerline is preferably 4.8 mm or more, more preferably 5.6 mm or more, and even more preferably 6.4 mm or more. On the other hand, Tca is preferably 12.0 mm or less, more preferably 10.4 mm or less, and even more preferably 8.8 mm or less. The thickness Tb from the outer surface of the tread to the inner surface of the tread along a line normal to the tire inner surface passing through the tire widthwise end of the inner reinforcing layer ply is preferably 4.2 mm or more, more preferably 4.9 mm or more, and even more preferably 5.6 mm or more. On the other hand, Tb is preferably 10.5 mm or less, more preferably 9.1 mm or less, and even more preferably 7.7 mm or less. Furthermore, the thickness Tcb of the cap tread on a line normal to the tire inner surface passing through the tire width direction end of the inner reinforcing layer ply is preferably 2.9 mm or more, more preferably 3.4 mm or more, and even more preferably 3.9 mm or more. On the other hand, Tcb is preferably 7.4 mm or less, more preferably 6.4 mm or less, and even more preferably 5.4 mm or less.

[0088] (Formula (3)) In formula (3), the value of K is preferably 3.8, more preferably 4.0, even more preferably 5.0, even more preferably 5.5, even more preferably 6.0, even more preferably 6.5, and even more preferably 7.0. On the other hand, there is no particular upper limit to the value of K, but it is usually about 50.0, about 25.0, or about 15.0.

[0089] (70℃ tanδ b ) 70°C tanδ, which is the loss tangent at 70°C of the rubber composition constituting the base tread bAlthough the value of is not particularly limited, it is preferably more than 0.02, more preferably more than 0.03, even more preferably more than 0.04, and even more preferably 0.05 or more. On the other hand, the value is preferably less than 0.19, more preferably less than 0.15, even more preferably less than 0.13, and even more preferably 0.12 or less.

[0090] 70℃ tanδ b can be appropriately adjusted by the types and amounts of rubber components, fillers, plasticizers, etc., which will be described later. b can be increased by using a rubber component with a high glass transition temperature, by increasing the content of a filler in the rubber composition, by increasing the amount of a resin component as a plasticizer component, or the like, and can be decreased by the opposite means.

[0091] (Formula (4)) Equation (4) specifies that Tca is greater than Tcb. In other words, it specifies that the difference between Tca and Tcb (Tca - Tcb) is greater than 0. In this embodiment, there is no particular limitation as long as the difference between Tca and Tcb is greater than 0, but the difference is preferably greater than 0.5 mm, more preferably greater than 1.0 mm, even more preferably greater than 2.0 mm, and even more preferably greater than 2.5 mm. On the other hand, the difference between Tca and Tcb is usually less than 5.0 mm, preferably less than 4.5 mm, more preferably less than 4.0 mm, and even more preferably less than 3.5 mm.

[0092] (Formula (5)) From the viewpoint of the effects of the invention, the value of the right side of formula (5) is preferably 0.004, more preferably 0.006, even more preferably 0.008, even more preferably 0.010, and even more preferably 0.015. On the other hand, there is no particular restriction on the upper limit of this value, but from the viewpoint of tread balance, it is usually 0.100 or less, preferably 0.075 or less, more preferably 0.050 or less, and even more preferably 0.025 or less.

[0093] (A RF ) In at least one of the reinforcing layer plies, the extending direction of the reinforcing layer cord is inclined from the tire circumferential direction by an angle A RF is preferably different from A1, and in particular A RF The direction of inclination of from the tire circumferential direction is preferably opposite to the direction of inclination of A1 from the tire circumferential direction, because this can cancel out the twist of the carcass ply bias-arranged on the radially inner side of the tread.

[0094] The angle at which the stretching direction of the reinforcing layer cord is inclined from the tire circumferential direction is A RF The reinforcing layer including the reinforcing layer ply (°) is preferably composed of one reinforcing layer ply or is preferably a belt ply. When there are multiple reinforcing layer plies, A RF The reinforcing layer ply for which the value of the reinforcing layer thickness is measured is preferably the innermost reinforcing layer ply in the radial direction of the tire.

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

[0096] <Rubber composition constituting the base tread> The rubber composition constituting the base tread will be described.

[0097] [Rubber component] The rubber composition includes a rubber component, and the rubber component includes at least one of an isoprene-based rubber (IR rubber), a styrene-butadiene rubber (SBR), and a butadiene rubber (BR). In this case, the rubber component may include a rubber component other than the IR rubber, the SBR, and the BR.

[0098] The rubber component preferably contains an IR rubber. In this case, the rubber component may consist of only the IR rubber, but preferably contains a rubber component other than the IR rubber, and preferably contains an IR rubber and a BR. The rubber component may consist of only the IR rubber and a BR.

[0099] In another embodiment, the rubber component preferably contains SBR. In this case, the rubber component may contain rubber components other than SBR, but may also consist solely of SBR.

[0100] (Isoprene rubber) Examples of isoprene-based rubbers that can be used include those commonly used in the tire industry, such as isoprene rubber (IR) and natural rubber. Natural rubber includes unmodified natural rubber (NR) as well as modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), highly purified natural rubber (UPNR), and grafted natural rubber. These isoprene-based rubbers may be used alone or in combination of two or more.

[0101] The NR is not particularly limited, and those commonly used in the tire industry can be used, such as SIR20, RSS#3, and TSR20.

[0102] The content of the 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 still more preferably 6% by mass or more, and preferably less than 80% by mass, more preferably 75% by mass or less, even more preferably less than 70% by mass, and still more preferably less than 65% by mass.

[0103] (SBR) The SBR is not particularly limited, and solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR) can be used. Modified SBRs include SBRs whose ends and / or main chains are modified, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.). Furthermore, hydrogenated products of these SBRs (hydrogenated SBRs) can also be used. One type of SBR may be used alone, or two or more types may be used in combination.

[0104] The functional group contained in the modified SBR is preferably a functional group containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen. Examples of such functional groups include amino, amido, silyl, alkoxysilyl, isocyanate, imino, imidazole, urea, ether, carbonyl, oxycarbonyl, mercapto, sulfide, disulfide, sulfonyl, sulfinyl, thiocarbonyl, ammonium, imido, hydrazo, azo, diazo, carboxyl, nitrile, pyridyl, alkoxy (preferably C1-C6 alkoxy), hydroxyl, oxy, and epoxy groups. Of these, amino and / or alkoxysilyl groups are preferred. The amino group is preferably an amino group substituted with one or two C1-C6 alkyl groups. Specific examples of the alkoxysilyl include trimethoxysilyl, triethoxysilyl, triisopropoxysilyl, dimethoxymethylsilyl, diethoxymethylsilyl, dimethylmethoxysilyl, and dimethylethoxysilyl.

[0105] As the SBR, either oil-extended or non-oil-extended SBR can be used. SBR commercially available from JSR Corporation, Sumitomo Chemical Co., Ltd., UBE Corporation, Asahi Kasei Corporation, ZS Elastomers Co., Ltd., ARLANXEO, LG Chem, etc. can be used.

[0106] 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, even more preferably 10% by mass or more, and even more preferably 15% by mass or more, and is 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 above-mentioned measurement method.

[0107] 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%. Also, 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 above-mentioned measurement method.

[0108] 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 fuel economy. Furthermore, from the viewpoint of crosslink uniformity, etc., Mw is preferably 2.5 million or less, and more preferably 2 million or less. Mw of SBR is measured by the above-mentioned measurement method.

[0109] From the viewpoint of fuel economy, the content of SBR in the rubber component is preferably 30% by mass or more, more preferably more than 40% by mass, and even more preferably 50% by mass or more. 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, and even more preferably less than 80% by mass.

[0110] (BR) The BR is not particularly limited, and can be one commonly used in the tire industry, such as 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 (rare earth BR) synthesized using a rare earth catalyst, BR containing syndiotactic polybutadiene crystals (SPB-containing BR), or modified BR (high-cis modified BR, low-cis modified BR). One type of BR may be used alone, or two or more types may be used in combination.

[0111] As the high-cis BR, for example, commercially available products from Zeon Corporation, UBE Corporation, JSR Corporation, etc. can be used. The inclusion of high-cis BR can improve low-temperature properties and wear resistance. The cis content of the 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 above-mentioned measurement method.

[0112] The rare earth BR is synthesized using a rare earth 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 the rare earth BR, for example, commercially available products from LANXESS K.K. can be used.

[0113] The SPB-containing BR is not simply 1,2-syndiotactic polybutadiene crystals dispersed in the BR, but is dispersed after being chemically bonded to the BR. As such SPB-containing BR, commercially available products from UBE Corporation and the like can be used.

[0114] Examples of modified BR include BR modified with functional groups similar to those described above for SBR, and also preferably used are modified butadiene rubbers (modified BRs) whose terminals and / or main chains are modified with functional groups containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen.

[0115] Other examples of modified BR include tin-modified BR, which is obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and in which the terminals of the modified BR molecule are further bonded with a tin-carbon bond (tin-modified BR).Modified BR may be either non-hydrogenated or hydrogenated.

[0116] The weight-average molecular weight (Mw) of the BR is preferably more than 300,000, more preferably more than 350,000, and even more preferably more than 400,000. From the viewpoint of crosslink 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 the BR can be determined by the above-mentioned method.

[0117] The content of BR in the rubber component is not particularly limited, but is preferably more than 20% by mass, more preferably 25% by mass or more, even more preferably more than 30% by mass, and even more preferably more than 35% by mass. 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.

[0118] (Other rubber components) The rubber component may contain other rubber components in addition to the above-mentioned isoprene-based rubber, SBR, and BR. Examples of such rubber components 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-based rubbers such as butyl rubber (IIR), ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber. These other rubber components may be used alone or in combination of two or more. In addition to the above-mentioned rubber components, known thermoplastic elastomers may also be contained.

[0119] (Rubber components synthesized from recycled and biomass-derived raw materials) Monomers, which are structural units of synthetic rubbers such as IR, SBR, and BR, may be derived from underground resources such as petroleum and natural gas, or may be recycled from rubber products such as tires or non-rubber products such as polystyrene. Monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled polyisoprene, recycled butadiene, and recycled aromatic vinyl compounds. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl compounds include, but are not limited to, styrene. Among these, recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) are preferably used as raw materials.

[0120] The method for producing the recycled monomer is not particularly limited, and examples thereof include synthesis from recycled naphtha obtained by decomposing rubber products such as tires. The method for producing recycled naphtha is also not particularly limited, and examples thereof include decomposing rubber products such as tires under high temperature and pressure, decomposing with microwaves, or mechanically crushing and then extracting.

[0121] Furthermore, the monomers that are the structural units of polymers such as IR, SBR, and BR may be derived from biomass. In this specification, biomass refers to materials derived from natural resources such as plants. Examples of biomass include, but are not limited to, agricultural, forestry, and fishery products, sugar, wood chips, plant residues after useful components have been extracted, plant-derived ethanol, and biomass naphtha.

[0122] Monomers derived from biomass (biomass monomers) are not particularly limited, and examples thereof include biomass-derived butadiene and biomass-derived aromatic vinyl compounds. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl compounds include, but are not limited to, styrene. The method for producing biomass monomers is not particularly limited, and examples include biological and / or chemical and / or physical conversion of animals and plants. A representative example of biological conversion is fermentation by microorganisms, and examples of chemical and / or physical conversion include catalytic conversion, high heat conversion, high pressure conversion, electromagnetic wave conversion, critical fluid conversion, and combinations thereof.

[0123] Polymers synthesized from biomass monomer components (biomass polymers) are not particularly limited and include polybutadiene rubber synthesized from biomass-derived butadiene, aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl compounds, etc. Examples of the aromatic vinyl / butadiene copolymers include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0124] Whether a polymer's raw material is biomass-derived can be determined by its percent modern carbon (pMC) measured in accordance with ASTM D6866-10. pMC is the modern standard reference carbon. 14 of sample against C concentration 14 This is the ratio of the carbon concentration, and this value is used as an index showing the biomass ratio of the compound (rubber). The significance of this value is explained below.

[0125] 1 mole of carbon atoms (6.02 × 10 23 ) contains approximately 6.02 × 10 atoms, which is about one trillionth of the number of ordinary carbon atoms. 11 pieces 14 C exists. 14The half-life of C is 5730 years, 14 C is decreasing regularly. Therefore, in the case of fossil fuels such as coal, oil, and natural gas, which are thought to have been absorbed and fixed by plants and other organisms more than 226,000 years ago, C was also included in these when they were first fixed. 14 All C elements have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas contain 14 Therefore, chemicals produced from these fossil fuels do not contain any C element. 14 It does not contain any C elements.

[0126] on the other hand, 14 C is constantly produced by cosmic rays undergoing nuclear reactions in the atmosphere. 14 The amount of C is balanced between radioactive decay and nuclear reaction, and in the Earth's atmospheric environment, 14 Therefore, the amount of carbon derived from biomass resources currently circulating in the environment is constant. 14 As mentioned above, the C concentration is approximately 1 × 10 -12 The value is approximately mol %. Therefore, the biomass ratio in a compound can be calculated by using the difference between these values.

[0127] this 14 C is typically measured using accelerator mass spectrometry based on a tandem accelerator. 13 C concentration ( 13 C / 12 C). 14 C concentration ( 14 C / 12 C) is measured. 14 The modern standard reference for the C concentration is the carbon circulating in nature as of 1950. 14The specific standard substance used is the oxalic acid standard provided by NIST (National Institute of Standards and Technology). The specific activity of carbon in this oxalic acid (per gram of carbon) is 14 The radioactivity of C is separated into carbon isotopes, 13 The standard value is the value corrected for decay from 1950 to the measurement date. 14 This is used as the C concentration value (100%). The ratio of this value to the value of the actually measured sample is the pMC value.

[0128] Therefore, if rubber is made from 100% biomass-derived materials, although there are regional differences, it will usually not reach 100 under normal conditions, so it will show a value of approximately 110 pMC. On the other hand, for chemical substances derived from petroleum and other fossil fuels, 14 When the carbon concentration is measured, it will show a value of about 0 pMC (for example, 0.3 pMC), which corresponds to the above-mentioned biomass ratio of 0%.

[0129] From the above, it is preferable in terms of environmental protection to use a material such as rubber having a high pMC value, that is, a material such as rubber having a high biomass ratio, in a rubber composition.

[0130] [Filler] The filler includes carbon black. The carbon black includes recycled carbon black (rCB). The filler may also include fillers other than carbon black. Examples of such fillers include silica, aluminum hydroxide, calcium carbonate, alumina, clay, and talc, which have been commonly used in the tire industry. The filler may contain carbon black and silica, may consist of only carbon black and silica, or may consist of only carbon black.

[0131] (carbon black) Carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. From the perspective of life cycle assessment, the raw material for carbon black may be a biomass material such as lignin or vegetable oil. Furthermore, carbon black may be produced by combustion, such as in a furnace, by hydrothermal carbonization (HTC), or by thermal decomposition of methane, such as in a thermal black process. Commercially available carbon black 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., and Columbia Carbon Co., Ltd. One type of carbon black may be used alone, or two or more types may be used in combination.

[0132] In addition to the above, from the viewpoint of life cycle assessment, carbon black may be made from a biomass material such as lignin, or recycled carbon black obtained by pyrolysis and purification of a product containing carbon black, such as a tire.

[0133] As used herein, "recycled carbon black" refers to carbon black obtained by crushing used tires or other products containing carbon black and calcining the crushed material, and refers to carbon black in which, when subjected to oxidative combustion by heating in air as measured by thermogravimetry in accordance with JIS K 6226-2:2003, the proportion of the mass of ash (ash content), which is the non-combustible component, is 13% by mass or more. In other words, the proportion of the mass (carbon content) of the recycled carbon black lost due to oxidative combustion is 87% by mass or less. Recycled carbon black is sometimes expressed as rCB.

[0134] Recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, citing "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, describes the carbon black as being obtained by pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (

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

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

[0135] Recycled carbon black may lack functional groups on its surface, or may be treated to include functional groups on its surface. The treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3,173,251, carbon black obtained by a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Furthermore, in Japanese Patent Publication No. 6,856,781, carbon black obtained by a pyrolysis process is treated with an amino acid compound containing at least one thiol or disulfide group to obtain surface-activated carbon black. The recycled carbon black of this embodiment also includes carbon blacks treated to include functional groups on their surfaces.

[0136] As the recycled carbon black, commercially available products from Strable Green Carbon, LD Carbon, etc. can be used.

[0137] The nitrogen adsorption specific surface area (N2SA) of the carbon black is not particularly limited, but from the viewpoint of obtaining sufficient reinforcement and good abrasion resistance, it is preferred that the N2SA be 30 m2 / g or more is preferable, and 40m 2 / g is more preferable, and 50m 2 / g or more is more preferable, and 60m 2 / g or more is more preferable, and 70m 2 The upper limit of the N2SA is preferably 300 m / g from the viewpoint of excellent dispersibility and low heat generation. 2 The N2SA of the recycled carbon black in this specification is the value measured by the above method.

[0138] The amount of carbon black is preferably more than 20 parts by mass, more preferably more than 25 parts by mass, even more preferably more than 30 parts by mass, and still more preferably more than 35 parts by mass, per 100 parts by mass of the rubber component, from the viewpoint of reinforcement. Also, from the viewpoint of processability, the amount of carbon black is preferably less than 75 parts by mass, more preferably less than 70 parts by mass, even more preferably less than 65 parts by mass, and still more preferably 60 parts by mass or less.

[0139] (silica) The silica is not particularly limited, and can be, for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrated silica), or other silica commonly used in the tire industry. The raw material for silica is not particularly limited, and can be, for example, a mineral-derived raw material such as quartz, a biological raw material such as rice husk (for example, silica made from biomass materials such as rice husk), or silica recycled from a silica-containing product. Among these, hydrated silica prepared by a wet method is preferred because it contains a large number of silanol groups. Silica can be used alone or in combination of two or more types.

[0140] Silica made from biomass materials can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then reacting the silicate with sulfuric acid in the same manner as conventional wet-process silica to produce a silicon dioxide precipitate, which is then filtered, washed with water, dried, and pulverized.

[0141] Silica recycled from silica-containing products can be, for example, silica recovered from products containing silica, such as electronic components such as semiconductors, tires, desiccants, and filtering materials such as diatomaceous earth. The recovery method is not particularly limited, and examples include thermal decomposition and decomposition by electromagnetic waves. Among these, silica recovered from electronic components such as semiconductors or tires is preferred.

[0142] When silica crystallizes, it becomes insoluble in water, and its component, silicic acid, cannot be utilized. By controlling the combustion temperature and duration, it is possible to suppress the crystallization of silica in rice husk ash (see, for example, JP 2009-2594 A and Akita Prefectural University Web Journal B / 2019, vol. 6, pp. 216-222).

[0143] Amorphous silica extracted from rice husks may be commercially available from Wilmar Co., Ltd., etc.

[0144] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 50 m 2 / g, more preferably 100m 2 / g, more preferably 150m 2 / g, more preferably 170m 2 The upper limit of the N2SA of silica is not particularly limited, but is preferably 350 m 2 / g, more preferably less than 250m 2 / g, more preferably less than 200m 2 / g. By setting it within the above range, cut resistance tends to be improved. The N2SA of silica is measured by the above-mentioned measurement method.

[0145] From the viewpoint of reinforcing properties, the average primary particle diameter of silica is preferably more than 10 nm, more preferably more than 12 nm, and even more preferably more than 15 nm. The average primary particle diameter is preferably less than 25 nm, and more preferably less than 20 nm. The average primary particle diameter of silica is measured by the above-mentioned measurement method.

[0146] When silica is contained, the content per 100 parts by mass of the rubber component is not particularly limited, but from the viewpoint of fuel economy, it is preferably more than 10 parts by mass, more preferably more than 15 parts by mass, more preferably more than 20 parts by mass, and even more preferably 25 parts by mass or more. Also, from the viewpoints of dispersibility and processability of silica, the content is preferably less than 60 parts by mass, more preferably less than 50 parts by mass, and even more preferably less than 40 parts by mass.

[0147] (Silane coupling agent) When silica is used, it is preferable to further contain a silane coupling agent. The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthio Examples of suitable silanes include sulfide-based silanes such as carbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silanes such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z; vinyl-based silanes such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silanes such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based silanes such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silanes such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silanes such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercially available products that can be used include those manufactured by Evonik Industries, Momentive, Shin-Etsu Silicones Co., Ltd., Tokyo Chemical Industry Co., Ltd., AZMAX Co., Ltd., and Dow Corning Toray Co., Ltd. The silane coupling agents may be used alone or in combination of two or more.

[0148] When containing silane coupling agent, the content of silane coupling agent is preferably more than 1 part by mass, more preferably more than 3 parts by mass, even more preferably more than 5 parts by mass, and even more preferably more than 7 parts by mass, based on 100 parts by mass of silica.On the other hand, the content is preferably less than 20 parts by mass, more preferably less than 18 parts by mass, even more preferably less than 16 parts by mass, and even more preferably less than 14 parts by mass.By making it within the above range, the dispersibility of silica tends to improve.

[0149] [Other compounding agents] In addition to the rubber component and filler, the rubber composition may contain, as appropriate, compounding agents that are conventionally commonly used in the tire industry, such as plasticizers, compatibilizers, processing aids, vulcanized rubber particles, wax, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators.

[0150] (plasticizer) A plasticizer is a material that imparts plasticity to rubber components and encompasses both liquid and solid plasticizers at 25°C. Examples of plasticizers include resins, oils, liquid polymers, and ester-based plasticizers. These plasticizers may be derived from mineral resources such as petroleum and natural gas, biomass-derived materials, or naphtha recycled from rubber and non-rubber products. Low-molecular-weight hydrocarbon components obtained by pyrolysis and extraction of used tires and other products containing various components may also be used as plasticizers. Plasticizers may be used singly or in combination.

[0151] <Resin> The rubber composition according to the present embodiment may contain a resin in combination. Resins that can be used in the present embodiment are not particularly limited, but include resins commonly used in the tire industry, such as C9 resins, C5 resins, C5C9 resins, dicyclopentadiene resins, aromatic vinyl resins, coumarone resins, indene resins, terpene resins, rosin resins, and phenolic resins. These resins may be used alone or in combination of two or more. Each resin may also be used alone or in combination of two or more.

[0152] ·C9 resin The term "C9 resin" refers to a resin obtained by polymerizing a C9 fraction. It may be a polymer obtained by polymerizing a C9 fraction alone, or a copolymer obtained by copolymerizing a C9 fraction with other components. For example, a resin obtained by copolymerizing dicyclopentadiene (DCPD) with a C9 fraction is called a DCPD / C9 resin. The C9 resin may also be a hydrogenated or modified version of the above. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene. Examples of C9 resins that can be used include commercially available C9 resins from BASF, Zeon Corporation, ENEOS Corporation, and the like.

[0153] ·C5 resin "C5 resin" refers to a resin obtained by polymerizing a C5 fraction, and may be a hydrogenated or modified C5 resin. Examples of C5 fractions other than dicyclopentadiene include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, isoprene, piperylene, 2-methyl-1-butene, 2-methyl-2-butene, and 1-pentene. Examples of C5 resins that can be used include those commercially available from Struktol, Nippon Zeon Corporation, ENEOS Corporation, and the like.

[0154] C5C9 resin The term "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. Examples of C5C9 petroleum resins that can be used include those commercially available from Tosoh Corporation, Luhua, and the like.

[0155] Dicyclopentadiene resin The term "dicyclopentadiene-based resin" refers to a resin containing cyclopentadiene (CPD) and / or dicyclopentadiene (DCPD) as the monomer component with the highest content, and may be a hydrogenated or modified resin. Preferred examples of dicyclopentadiene-based resins include polymers obtained by polymerizing only dicyclopentadiene as a monomer, and copolymers obtained by copolymerizing dicyclopentadiene with the C9 fraction (DCPD / C9 resin). Examples of dicyclopentadiene-based resins that can be used include commercially available products from ExxonMobil Corporation, ENEOS Corporation, Nippon Zeon Co., Ltd., Maruzen Petrochemical Co., Ltd., and the like.

[0156] Aromatic vinyl resin The term "aromatic vinyl resin" refers to a resin containing an aromatic vinyl compound such as styrene, α-methylstyrene, vinyltoluene, or p-chlorostyrene as the monomer component with the highest content, and may be a hydrogenated or modified version of such a resin. As the aromatic vinyl resin, a homopolymer of α-methylstyrene or styrene or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, because they are economical, easy to process, and have excellent heat generation properties. As the aromatic vinyl resin, commercially available products available from Kraton, Eastman Chemical, Mitsui Chemicals, Inc., etc., can be used.

[0157] Coumarone resin "Cumarone resin" refers to a resin containing coumarone as a monomer component, and may be hydrogenated or modified. Examples of preferred coumarone resins include coumarone resins, which are polymers containing only coumarone as a monomer component; coumarone-indene resins, which are copolymers containing coumarone and indene as monomer components; and coumarone-indene-styrene resins, which are copolymers containing coumarone, indene, and styrene as monomer components. Commercially available coumarone resins available from Rutgers, Nippon Paint Chemicals, Inc., Mitsui Chemicals, Inc., and other companies can be used.

[0158] Indene resin "Indene-based resin" refers to a resin containing indene as a monomer component, and may be hydrogenated or modified. Examples of preferred indene-based resins include coumarone-indene resins, which are copolymers of coumarone and indene as monomer components, and coumarone-indene-styrene resins, which are copolymers of coumarone, indene, and styrene as monomer components. Commercially available indene-based resins available from Rutgers, Nippon Paint Chemicals, and Mitsui Chemicals, Inc., for example, can be used.

[0159] Terpene resin The term "terpene resin" refers to a resin containing a terpene compound such as α-pinene, β-pinene, limonene, or dipentene as a monomer component, and may be hydrogenated or modified. Examples of preferred terpene resins include polyterpene resins, which are polymers containing only one or more of the terpene compounds as monomer components; aromatic-modified terpene resins, which are copolymers containing the terpene compound and an aromatic compound as monomer components; and terpene phenolic resins, which are copolymers containing the terpene compound and a phenolic compound as monomer components. Examples of aromatic compounds that serve as monomer components for aromatic-modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenolic compounds that serve as monomer components for terpene phenolic resins include phenol, bisphenol A, cresol, and xylenol. Examples of commercially available terpene resins include those available from Yasuhara Chemical Co., Ltd., Arakawa Chemical Industries, Ltd., and Nippon Terpene Chemical Co., Ltd.

[0160] Rosin-based resin The term "rosin-based resin" refers to a resin containing a rosin acid compound such as abietic acid, neoabietic acid, palustric acid, or isopimaric acid, and may be hydrogenated or modified. Examples of rosin-based resins include, but are not limited to, natural rosin resins and rosin-modified resins obtained by modifying natural rosin resins by hydrogenation, disproportionation, dimerization, esterification, or the like. Examples of rosin-based resins that can be used include commercially available rosin resins from Harima Chemical Industries, Ltd., Arakawa Chemical Industries, Ltd., and Airec Corporation.

[0161] Phenolic resin The term "phenolic resin" refers to a resin containing a phenolic compound such as phenol or cresol as a monomer component, and may be hydrogenated or modified. Examples of phenolic resins include, but are not limited to, phenol-formaldehyde resin, alkylphenol-formaldehyde resin, alkylphenol-acetylene resin, oil-modified phenol-formaldehyde resin, and terpene-phenol resin. Examples of phenolic resins that can be used include commercially available resins from Sumitomo Bakelite Co., Ltd., DIC Corporation, Asahi Organic Materials Co., Ltd., and the like.

[0162] ·Softening point From the viewpoints of processability and improving the dispersibility of the rubber component and the filler, the softening point of the resin is preferably 60° C. or higher, more preferably 70° C. or higher, and even more preferably 80° C. or higher. On the other hand, 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 is measured by the above-mentioned measurement method.

[0163] ·Content When a resin is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1 part by mass, and even more preferably more than 2 parts by mass, while 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.

[0164] <Oil> Examples of oils include mineral oil, vegetable oil, and animal oil. From the viewpoint of life cycle assessment, waste oils used in rubber mixers and engines, and refined waste cooking oils used in restaurants may also be used. One type of oil may be used alone, or two or more types may be used in combination.

[0165] As used herein, mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. Examples of mineral oil include paraffinic oil (mineral oil), naphthenic oil, and aromatic oil. Specific examples of mineral oil include mild extracted solvate (MES), distillate aromatic extract (DAE), treated distillate aromatic extract (TDAE), treated residual aromatic extract (TRAE), and residual aromatic extract (RAE). Furthermore, oils with a low content of polycyclic aromatic compounds (PCA) can also be used as an environmentally friendly measure. Examples of low PCA oils include MES, TDAE, and heavy naphthenic oil. Mineral oils may be used singly or in combination.

[0166] As used herein, examples of vegetable oils include linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grapeseed oil, and Japan wax. Further examples of vegetable oils include refined oils (such as salad oil) obtained by refining the above oils, interesterified oils obtained by interesterifying the above oils, hardened oils obtained by hydrogenating the above oils, thermally polymerized oils obtained by thermally polymerizing the above oils, oxidatively polymerized oils obtained by oxidizing the above oils, and waste edible oils recovered from edible oils and the like. Vegetable oils may be liquid or solid at 25°C. One vegetable oil may be used alone, or two or more may be used in combination.

[0167] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxyl group of glycerin is esterified with a fatty acid. The acylglycerol is not particularly limited and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Furthermore, the acylglycerol may be a monomer, a dimer, or a polymer (trimer or higher). Dimer or higher acylglycerols can be obtained by thermal polymerization, oxidative polymerization, or the like. The acylglycerol may be liquid or solid at 25°C.

[0168] The method for confirming whether the rubber composition contains the acylglycerol is not particularly limited, but may be any of the following: 1 For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at 25°C for 24 hours, and after removing the rubber composition, the 1 When H-NMR was measured, signals were observed around 5.26 ppm, 4.28 ppm, and 4.15 ppm when the signal of tetramethylsilane (TMS) was set at 0.00 ppm. These signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atoms of the ester group. In this paragraph, "around" refers to a range of ±0.10 ppm.

[0169] The fatty acid is not particularly limited and may be either an unsaturated fatty acid or a saturated fatty acid. Examples of unsaturated fatty acids include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of saturated fatty acids include butyric acid and lauric acid.

[0170] Among these, it is desirable that the fatty acid contains a fatty acid with few double bonds, i.e., saturated fatty acid or monounsaturated fatty acid, and oleic acid is preferred. As a vegetable oil containing such a fatty acid, for example, vegetable oil containing saturated fatty acid or monounsaturated fatty acid may be used, or vegetable oil modified by ester exchange or the like may be used. Furthermore, in order to produce vegetable oil containing such a fatty acid, plants may be improved by breeding, genetic modification, genome editing, or the like.

[0171] As the vegetable oil, for example, commercially available products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoi Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., Fuji Kosan Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0172] Examples of animal oils include fish oil, beef tallow, and oleyl alcohol derived from these.

[0173] The oil content per 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more. The content is preferably less than 30 parts by mass, more preferably less than 25 parts by mass, and even more preferably less than 20 parts by mass. The oil content includes the amount of oil contained in the rubber component as an extender oil and the amount of oil contained in other components such as sulfur.

[0174] <Liquid polymer> Liquid polymers are polymers that are liquid at 25°C, and examples thereof include liquid diene polymers. Examples of liquid diene polymers include liquid styrene-butadiene copolymers (liquid SBR), liquid butadiene polymers (liquid BR), liquid isoprene polymers (liquid IR), and liquid styrene-isoprene copolymers (liquid SIR). The liquid diene polymers preferably have a polystyrene-equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC) of more than 1,000, more preferably more than 3,000, while the Mn is preferably less than 100,000, more preferably less than 15,000. The Mn of the liquid polymer is a polystyrene-equivalent value measured by gel permeation chromatography (GPC). Examples of liquid diene polymers that can be used include products from Sartomer Corporation and Kuraray Co., Ltd. One type of liquid polymer may be used alone, or two or more types may be used in combination.

[0175] <Ester-based plasticizers> Examples of ester-based plasticizers include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), and trixylenyl phosphate (TXP). One type of ester-based plasticizer may be used alone, or two or more types may be used in combination.

[0176] (processing aids) Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. Examples of processing aids that can be used include those commercially available from Schill + Seilacher, Performance Additives, etc. One type of processing aid may be used alone, or two or more types may be used in combination.

[0177] When a processing aid is contained, the content thereof per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1 part by mass, and even more preferably more than 1.5 parts by mass from the viewpoint of improving processability, and is preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and even more preferably less than 5.0 parts by mass from the viewpoint of abrasion resistance and breaking strength.

[0178] (vulcanized rubber particles) The vulcanized rubber particles are particles made of vulcanized rubber, and specifically, rubber powder as specified in JIS K 6316:2017 can be used. From the standpoint of environmental considerations and cost, recycled rubber powder produced from crushed waste tires is preferred. The vulcanized rubber particles are not particularly limited, and may be unmodified vulcanized rubber particles or modified vulcanized rubber particles. Commercially available vulcanized rubber products include products from Lehigh and Muraoka Rubber Industries Co., Ltd. One type of vulcanized rubber particle may be used alone, or two or more types may be used in combination.

[0179] (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. Waxes commercially available from, for example, Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., Ltd., etc. can be used. One type of wax may be used alone, or two or more types may be used in combination.

[0180] When the wax is contained, the amount thereof per 100 parts by mass of the rubber component is preferably more than 0.3 parts by mass, more preferably more than 0.7 parts by mass, and even more preferably more than 1.0 part by mass, while the amount is preferably less than 4.0 parts by mass, more preferably less than 3.0 parts by mass, and even more preferably less than 2.5 parts by mass.

[0181] (stearic acid) When stearic acid is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 0.7 parts by mass, and even more preferably 1.0 part by mass or more from the viewpoint of processability, while the content is preferably less than 10 parts by mass, more preferably less than 5 parts by mass, and even more preferably less than 3 parts by mass from the viewpoint of vulcanization rate.

[0182] (zinc oxide) When zinc oxide is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 0.7 parts by mass, and even more preferably 1 part by mass or more, from the viewpoint of processability, while the content is preferably less than 10 parts by mass, more preferably less than 5 parts by mass, and even more preferably less than 3 parts by mass, from the viewpoint of abrasion resistance.

[0183] (anti-aging agent) The antioxidant is not particularly limited, but examples thereof include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), and N,N'-ditolyl-p-phenylenediamine. p-phenylenediamine-based antioxidants such as diphenyl ether diphenyl ether (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers; 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 that can be used include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and Flexis Co., Ltd. One type of antioxidant may be used alone, or two or more types may be used in combination.

[0184] When an antioxidant is contained, the content thereof per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 0.8 parts by mass, and even more preferably more than 1.0 part by mass, while the content is preferably less than 7.0 parts by mass, more preferably less than 5.0 parts by mass, and even more preferably 3.0 parts by mass or less.

[0185] (vulcanizing agent) The vulcanizing agent is not particularly limited, and known vulcanizing agents can be used, such as organic peroxides, sulfur-based vulcanizing agents, resin vulcanizing agents, and metal oxides such as magnesium oxide. Of these, sulfur-based vulcanizing agents are preferred. Examples of sulfur-based vulcanizing agents that can be used include sulfur and sulfur donors such as morpholine disulfide. Of these, sulfur is preferred. One or more types of vulcanizing agents can be used in combination.

[0186] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur (oil-treated sulfur, special sulfur treated with a dispersant, masterbatch-type sulfur, etc.), and insoluble sulfur (oil-treated insoluble sulfur, etc.), all of which are preferably used. Among these, powdered sulfur is preferred. Examples of sulfur that can be used include those manufactured and sold by Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanritsu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc.

[0187] Known organic crosslinking agents can also be used as the vulcanizing agent. The organic crosslinking agent is not particularly limited as long as it can form crosslinked chains other than polysulfide bonds. Examples of the organic crosslinking agent include alkylphenol-sulfur chloride condensate, sodium 1,6-hexamethylene-dithiosulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, and dicumyl peroxide. 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane is preferred. These organic crosslinking agents can be commercially available from Taoka Chemical Co., Ltd., Lanxess K.K., Flexis, and other companies.

[0188] When a vulcanizing agent is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.4 parts by mass, more preferably 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 content of the vulcanizing agent is within the above range, an appropriate reinforcing effect tends to be obtained. Note that when the vulcanizing agent contains components other than sulfur, such as oil-treated sulfur, the content of the vulcanizing agent refers to the content of the sulfur component itself.

[0189] (Vulcanization accelerator) The vulcanization accelerator is not particularly limited, and known vulcanization accelerators can be used. Examples include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, and xanthate-based vulcanization accelerators. Among these, thiazole-based, sulfenamide-based, thiuram-based, and guanidine-based accelerators are preferred, thiazole-based and sulfenamide-based accelerators are more preferred, and thiazole-based accelerators are even more preferred. Examples of vulcanization accelerators that can be used include those manufactured and sold by Ouchi Shinko Chemical Industry Co., Ltd., Sanshin Chemical Industry Co., Ltd., etc. One or more vulcanization accelerators can be used in combination.

[0190] Examples of sulfenamide vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), and N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DZ). Examples of thiazole vulcanization accelerators include 2-mercaptobenzothiazole (MBT) or its salt, di-2-benzothiazolyl disulfide (MBTS), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, and 2-(2,6-diethyl-4-morpholinothio)benzothiazole. Examples of guanidine vulcanization accelerators include 1,3-diphenylguanidine (DPG), di-orthotolylguanidine, and orthotolylbiguanidine. Examples of thiuram vulcanization accelerators include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, and tetrabenzylthiuram disulfide (TBzTD).

[0191] 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, breaking strength and elongation tend to be ensured.

[0192] In this specification, various materials containing carbon atoms (e.g., rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from atmospheric carbon dioxide. As a method for obtaining the compound according to the present embodiment from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process for synthesizing methane from carbon dioxide may be converted.

[0193] <Manufacturing> The rubber composition according to the present embodiment can be produced by a known method, for example, by kneading the above-described components using a rubber kneading device such as an open roll or an internal kneader (such as a Banbury mixer or kneader).

[0194] The kneading process may include, for example, a base kneading process in which compounding ingredients and additives other than the vulcanizing agent and vulcanization accelerator are kneaded, and a final kneading (F kneading) process in which the vulcanizing agent and vulcanization accelerator are added to the kneaded product obtained in the base kneading process and kneaded. Furthermore, the base kneading process may be divided into multiple processes as desired. When the base kneading process is divided, the method may be (1) a method in which some of the compounding ingredients and additives are pre-mixed to form a masterbatch, and then the remaining compounding ingredients and additives are added to the resulting masterbatch and kneaded, or (2) a method in which all of the compounding ingredients and additives to be kneaded in the base kneading process are kneaded at once, and then the kneaded product is remilled one or more times. In the above method (1), the number of masterbatches is not limited and may be two or more. Furthermore, when the number of masterbatches is two or more, all of the compounding ingredients and additives used in the base kneading process may be allocated to one of the masterbatches.

[0195] The kneading conditions are not particularly limited, but examples include a method in which the base kneading step involves kneading for 3 to 10 minutes at a discharge temperature of 150 to 170°C, and in the final kneading step, kneading for 1 to 5 minutes at 70 to 110°C.

[0196] The pneumatic tire according to the present embodiment can be manufactured by a conventional method using the unvulcanized rubber composition obtained above. Specifically, the unvulcanized rubber composition is first extruded to match the shape of a base tread, and the resulting unvulcanized base tread is then bonded together with other tire components in a tire building machine by a conventional method to form an unvulcanized tire. During this process, the thickness of the cap tread, the thickness from the outer surface to the inner surface of the tread, and the structure of the carcass cord are all set to predetermined values. Furthermore, if necessary, the reinforcing layer is also set to a predetermined structure. The unvulcanized tire thus obtained is heated and pressurized in a vulcanizer to manufacture the pneumatic tire according to the present embodiment. The vulcanization conditions are not particularly limited, and examples include a method of vulcanizing at 150 to 200°C for 10 to 40 minutes.

[0197] <Application> The pneumatic tire according to the present embodiment can be used for any purpose, and can be used as a passenger car tire, a large passenger car tire, a large SUV tire, a racing tire, a motorcycle tire, a heavy-duty tire, or a run-flat tire. Passenger car tires are tires designed to be mounted on four-wheeled vehicles and have a maximum load capacity of less than 1,400 kg. Heavy-duty tires are tires with a maximum load capacity of 1,400 kg or more. In this specification, the term "tire" can be used as an all-season tire, a summer tire, or a winter tire such as a studless tire. [Example]

[0198] Below, examples (working examples) that are considered preferable for carrying out the present invention are shown, but the scope of the present invention is not limited to the working examples. In accordance with each table, inner liners obtained using the various chemicals shown below and tires having the tire structures were examined, and the results calculated based on the evaluation methods below are shown at the bottom of each table.

[0199] <Various chemicals> The various chemicals used in the examples and comparative examples are listed below. NR:TSR20 SBR: SBR1502 manufactured by JSR Corporation (unmodified E-SBR, styrene content: 23.5% by mass, vinyl content: 18% by mole, Tg: -56°C, Mw: 440,000, non-oil extended) Butadiene rubber 1: BR730 manufactured by JSR Corporation (BR synthesized using a Nd-based catalyst, cis content: 96 mol%, vinyl content: 0.9 mol%) Butadiene rubber 2: BR1250H manufactured by Zeon Corporation (tin-modified BR, polymerized using lithium as an initiator, cis content: 42 mol%, vinyl content: 10 to 13 mol%, Mw: 570,000) Butadiene rubber 3: VCR617 manufactured by UBE Corporation (syndiotactic 1,2-polybutadiene crystal content: 17% by mass, 1,2-syndiotactic polybutadiene crystal melting point: 200°C, cis-1,4 bond content: 92%) Carbon black: 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) Silica: TOKUSIL USG-A (N2SA: 175 m) manufactured by OSC Siam Silica Co., Ltd. 2 / g) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Industries Resin: SI Group SP-1068 (octylphenol / formaldehyde resin) Oil: Sankyo Yuka Kogyo Co., Ltd. A / O Mix (a mixture of naphthenic asphalt and naphthenic base oil) Wax: Ozoace 0355SR manufactured by Nippon Seiro Co., Ltd. Stearic acid: Camellia stearic acid beads manufactured by NOF Corporation Antioxidant 1: Nocrac 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 2: Nocrac RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Processing aid 1: Activator 73A (a mixture of zinc salts of aliphatic and aromatic carboxylic acids) manufactured by Struktol Processing aid 2: Aflux 16 manufactured by Rhein Chemie (a mixture of fatty acid calcium salt and fatty acid amide ester, calcium content: 6.2%) Zinc oxide: Zinc oxide type 2 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Seimisulfur manufactured by Nippon Kanretsu Kogyo Co., Ltd. (oil content: 10% by mass) Vulcanization accelerator 1: Noccela CZ-G (N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccela M (2-mercaptobenzothiazole) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 3: Noccela NS (di-2-benzothiazolyl disulfide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 4: Noccela DPG (1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0200] <Examples and Comparative Examples> According to the compounding recipes shown in each table, all chemicals except sulfur and vulcanization accelerators are mixed in a 1.7 L Banbury mixer for 5 minutes until the discharge temperature reaches 160°C to obtain a kneaded mixture. Next, sulfur and vulcanization accelerators are added to the resulting kneaded mixture, and the mixture is 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.

[0201] The resulting unvulcanized rubber composition is extruded to match the shape of the base tread using an extruder equipped with a die of a predetermined shape. The thickness of the cap tread, the thickness of the tread, the structure of the carcass cord, and other tire components are adjusted to the predetermined values, and the unvulcanized tire is then laminated together with other tire components to produce an unvulcanized tire. Each test tire (tire size: 215 / 55R17) is manufactured by press-vulcanizing the tire at 150°C for 35 minutes.

[0202] In the tire in Table 1, the inclination angles of the carcass cords are A1 +75° and A2 +85°. The thickness Ta from the outer surface of the tread to the inner surface of the tread on the tire centerline is 10.0 mm, and the thickness Tca of the cap tread is 8.0 mm. The thickness Tcb of the cap tread on a line normal to the tire inner surface passing through the tire width direction end of the inner reinforcing layer ply is 5.4 mm, and the thickness Tb from the outer surface of the tread to the inner surface of the tread on the same line is 7.2 mm. Therefore, for equation (1), |A2 - A1| = 10°, and for equation (2), Tca / Ta = 0.8, Tcb / Tb = 0.75, and Tca / Ta - Tcb / Tb = 0.05. Furthermore, in equation (4), Tca=8.0 mm>Tcb=5.4 mm, and in equation (5), (Tca / Ta-Tcb / Tb) / |A2-A1|=0.005.

[0203] In addition, in the tire in Table 2, the inclination angles of the carcass cords are A1 +75° and A2 +80°. The thickness Ta from the outer surface of the tread to the inner surface of the tread on the tire centerline is 10.0 mm, and the thickness Tca of the cap tread is 8.0 mm. The thickness Tcb of the cap tread on a line normal to the tire inner surface passing through the tire width direction end of the inner reinforcing layer ply is 5.4 mm, and the thickness Tb from the outer surface of the tread to the inner surface of the tread on the same line normal is 7.5 mm. Therefore, in equation (1), |A2 - A1| = 5°, and in equation (2), Tca / Ta = 0.8, Tcb / Tb = 0.72, and Tca / Ta - Tcb / Tb = 0.08. Furthermore, in equation (4), Tca=8.0 mm>Tcb=5.4 mm, and in equation (5), (Tca / Ta-Tcb / Tb) / |A2-A1|=0.016.

[0204] In each table, |A2-A1| × (Tca / Ta-Tcb / Tb) / 70℃ tanδ according to formula (3) b The value of is a value that can be compared with the constant K. That is, if the value is greater than the constant K, then equation (3) is satisfied, and conversely, if the value is equal to or less than the constant K, then equation (3) is not satisfied.

[0205] <Low fuel consumption performance> Using a rolling resistance tester, the rolling resistance of each test tire is measured when it is run under an internal pressure of 210 kPa, a load of 5.25 kN, and a speed of 80 km / h, and the result is displayed as an index with the reference example being 100. The higher the index, the better the fuel efficiency.

[0206] [Table 1]

[0207] [Table 2]

[0208] <Embodiment> Examples of embodiments of the present invention are given below.

[0209] [1] A pneumatic tire comprising a tread, a carcass, and at least one reinforcing layer disposed radially outward of the carcass, The tread includes a cap tread including a tread contact surface and a base tread located radially inward of the cap tread, The carcass is composed of at least one carcass ply including 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 including a plurality of reinforcing layer cords and a topping rubber covering the reinforcing layer cords; Among the at least one reinforcing layer ply, the reinforcing layer ply arranged most inward in the tire radial direction is defined as an inner reinforcing layer ply, The angle at which the extending direction of the carcass cord of the carcass ply that is outermost in the tire radial direction is inclined from the tire circumferential direction at the tire center line is defined as A1 (°), and the angle at which the extending direction of the carcass cord of the carcass ply that is outermost in the tire radial direction is inclined from the tire circumferential direction at the tire maximum width position is defined as A2 (°), The thickness (mm) from the outer surface of the tread to the inner surface of the tread on the tire centerline is Ta, the thickness (mm) of the cap tread on the tire centerline is Tca, the thickness (mm) of the cap tread on the normal line to the tire inner surface passing through the tire width direction end of the inner reinforcing layer ply is Tcb, the thickness (mm) from the outer surface of the tread to the inner surface of the tread on the normal line is Tb, and the loss tangent at 70°C of the rubber composition constituting the base tread is 70°C tanδ b , where K is the constant, A1, A2, Ta, Tca, Tb, Tcb, 70℃ tanδ b and K satisfy the following formulas (1), (2), and (3), the value of the right-hand side of formula (2) is preferably 0.02, more preferably 0.04, even more preferably 0.06, and still more preferably 0.07, and the value of K in formula (3) is preferably 3.8. (1)|A2-A1|>0 (2) Tca / Ta - Tcb / Tb>0 (3) 70℃ tanδ b <|A2-A1|×(Tca / Ta-Tcb / Tb) / K (where K is 3.2) [2] The pneumatic tire according to [1], wherein K is 4.0, preferably 5.0. [3] The pneumatic tire according to [1], wherein K is 5.5, preferably 6.0, more preferably 6.5, and even more preferably 7.0. [4] The pneumatic tire according to any one of [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 [1] to [4], wherein Tca and Tcb further satisfy formula (4). (4) Tca>Tcb [6] The pneumatic tire according to any one of [1] to [5], wherein A1, A2, Ta, Tb, Tca, and Tcb further satisfy formula (5), and the right-hand side of formula (5) is preferably 0.004, more preferably 0.006, even more preferably 0.008, even more preferably 0.010, and even more preferably 0.015. (5)(Tca / Ta-Tcb / Tb) / |A2-A1|>0.003 [7] In at least one of the reinforcing layer plies, the angle (°) at which the extending direction of the reinforcing layer cord is inclined from the tire circumferential direction is defined as A RF In this case, A1 and A RF The pneumatic tire according to any one of [1] to [6], wherein [8] A RF The pneumatic tire according to [7], wherein the inclination direction of said grooves A1 from the tire circumferential direction is opposite to the inclination direction of said grooves A2 from the tire circumferential direction. [9] The angle at which the extending direction of the reinforcing layer cord is inclined from the tire circumferential direction is A RF The pneumatic tire according to [7] or [8], wherein the reinforcing layer including the reinforcing layer ply of (°) is composed of one reinforcing layer ply.

[10] The angle at which the extending direction of the reinforcing layer cord is inclined from the tire circumferential direction is A RF The pneumatic tire according to any one of [7] to [9], wherein the reinforcing layer ply (°) is a belt ply.

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

[10] , wherein the carcass is composed of one carcass ply.

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

[11] , 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 more than -90°, preferably -75° or less and -85° or more, more preferably -80° or less and -85° or more. [Explanation of symbols]

[0210] 1 Cap Tread 2 Base Tread 3. Carcass 4 Belt 5 bands 6 Reinforcement layer L: Normal line on the inner surface of the tire passing through the tire width direction end of the inner reinforcing layer ply Ta: Thickness from the outer surface of the tread to the inner surface of the tread on the tire centerline Tb Thickness from the outer surface of the tread to the inner surface of the tread on the normal line L Tca Cap tread thickness at tire centerline Tcb: Thickness from the outer surface of the tread to the inner surface of the tread on the normal line L CL Tire centerline W Tire width direction C Circumferential direction of tire P Maximum tire width position A1: The angle at which the extending direction of the carcass cord is inclined from the tire circumferential direction at the tire center line position A2 The angle at which the extending direction of the carcass cord is inclined from the tire circumferential direction at the tire's maximum width position A RF The angle at which the stretching direction of the reinforcing layer cord is inclined from the tire circumferential direction

Claims

1. A pneumatic tire comprising a tread, a carcass, and at least one reinforcing layer disposed radially outward of the carcass, The tread includes a cap tread including a tread contact surface and a base tread located radially inward of the cap tread, The carcass is composed of at least one carcass ply including 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 including a plurality of reinforcing layer cords and a topping rubber covering the reinforcing layer cords; Among the at least one reinforcing layer ply, the reinforcing layer ply arranged most inward in the tire radial direction is defined as an inner reinforcing layer ply, The angle at which the extending direction of the carcass cord of the outermost carcass ply in the tire radial direction is inclined from the tire circumferential direction at the tire center line position is defined as A. 1 (°), and the angle of inclination from the tire circumferential direction at the position of the maximum tire width is A. 2 (°), The thickness (mm) from the outer surface of the tread to the inner surface of the tread on the tire centerline is Ta, the thickness (mm) of the cap tread on the tire centerline is Tca, the thickness (mm) of the cap tread on the normal line to the tire inner surface passing through the tire width direction end of the inner reinforcing layer ply is Tcb, the thickness (mm) from the outer surface of the tread to the inner surface of the tread on the normal line is Tb, and the loss tangent at 70°C of the rubber composition constituting the base tread is 70°C tanδ. b , where K is a constant, A 1 , A 2 , Ta, Tca, Tb, Tcb, 70°C tan δ b and K satisfy the following formulas (1), (2), and (3): (1)|A 2 -A 1 |>0 (2) Tca / Ta-Tcb / Tb>0 (3)700δ b 99 2 9. The 1 9×(SYSYS)3 (where K is 3.2)

2. 2. The pneumatic tire of claim 1, wherein K is 4.

0.

3. 2. The pneumatic tire of claim 1, wherein K is 5.

5.

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 Tca and Tcb further satisfy formula (4). (4) Tca>Tcb

6. A 1 , A 2 4. The pneumatic tire according to claim 1, wherein Ta, Tb, Tca, and Tcb further satisfy formula (5). (5)(THE THIS THIS) IS 2 9. The 1 90003

7. In at least one of the reinforcing layer plies, the angle (°) at which the extending direction of the reinforcing layer cord is inclined from the tire circumferential direction is defined as A. RF In this case, the above A 1 and A RF The pneumatic tire according to any one of claims 1 to 3, wherein

8. The above A RF The inclination direction from the tire circumferential direction is 1 8. The pneumatic tire according to claim 7, wherein the direction of inclination of the grooves is opposite to the direction of inclination of the grooves from the circumferential direction of the tire.

9. The stretching direction of the reinforcing layer cord is inclined at an angle A from the tire circumferential direction. RF 8. The pneumatic tire according to claim 7, wherein the reinforcing layer including the reinforcing layer ply having a flexural modulus of 0.5° is constituted by one reinforcing layer ply.

10. The stretching direction of the reinforcing layer cord is inclined at an angle A from the tire circumferential direction. RF 8. The pneumatic tire according to claim 7, wherein the reinforcing layer ply having a thickness of 0.5 mm is a belt ply.

11. The pneumatic tire according to any one of claims 1 to 3, wherein the carcass is constituted by one carcass ply.

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

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