Tire

Abstract

To provide a tire which improves total performance of chipping-resistant performance and wet grip performance.SOLUTION: A tire includes a tread part, wherein the tread part includes at least a first layer constituting a tread surface, a second layer adjacent to inside in a tire radial direction of the first layer, and a third layer existing inside in the tire radial direction of the second layer, the first layer and the second layer are composed of a rubber composition containing a rubber component containing styrene-butadiene rubber and / or an isoprene-based rubber, and silica, at least one of the rubber compositions constituting the first layer and the second layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components, and when the total styrene amount in the rubber composition constituting the first layer when the mass of the rubber component is 100 mass% is represented by S1 (mass%), and the total styrene amount in the rubber composition constituting the second layer when the mass of the rubber component is 100 mass% is represented by S2 (mass%), S2-S1 exceeds 0.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Patent Document 1 describes a rubber composition for a tire containing natural rubber and / or butadiene rubber, a norbornene polymer, and a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid, which improves handling stability and cut and chipping resistance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, Patent Document 1 still has room for improvement in the overall performance of chipping resistance and wet grip performance.

[0005] An object of the present invention is to provide a tire with improved overall performance of chipping resistance and wet grip performance.

Means for Solving the Problems

[0006] The present invention is a tire having a tread portion, wherein the tread portion includes at least a first layer constituting a tread surface, a second layer adjacent to the inner side in the tire radial direction of the first layer, and a third layer existing on the inner side in the tire radial direction of the second layer, the first layer and the second layer are composed of a rubber component containing styrene-butadiene rubber and / or isoprene-based rubber, and silica, At least one of the rubber compositions constituting the first layer and the second layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components. When the mass of the rubber component in the rubber composition constituting the first layer is 100% by mass, the total styrene amount in the rubber composition is S1 (% by mass). When the total styrene amount in the rubber composition constituting the second layer is S2 (% by mass) with the mass of the rubber component in the rubber composition being 100% by mass. Regarding a tire in which S2 - S1 is greater than 0.

Advantages of the Invention

[0007] According to the present invention, a tire is provided in which the overall performance of chipping resistance performance and wet grip performance is improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0009] A tire according to an embodiment of the present invention is a tire having a tread portion, wherein the tread portion includes at least a first layer constituting a tread surface, a second layer adjacent to the inner side in the tire radial direction of the first layer, and a third layer existing on the inner side in the tire radial direction of the second layer. The first layer and the second layer are composed of a rubber composition containing a rubber component including styrene-butadiene rubber and / or isoprene-based rubber, and silica. At least one of the rubber compositions constituting the first layer and the second layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components. When the total styrene amount in the rubber composition is set to 100% by mass of the rubber component, the total styrene amount in the rubber composition of the rubber composition constituting the first layer is S1 (mass%), and the total styrene amount in the rubber composition of the rubber composition constituting the second layer is S2 (mass%), S2 - S1 is greater than 0.

[0010] Although not intending to be bound by theory, in the tire of the present invention, as a mechanism for improving the overall performance of chipping resistance performance and wet grip performance, for example, it can be considered as follows.

[0011] First, (1) by configuring the tread portion with three or more rubber compositions, a plurality of rubber layer interfaces are formed in the tread portion. Thereby, when shear deformation occurs in the tread portion, energy loss can be caused by the friction due to the fine molecular movement of each rubber phase constituting the interface, so it is considered to contribute to the improvement of wet grip performance. And, (2) since the rubber compositions constituting the first layer and the second layer contain a rubber component including styrene-butadiene rubber and / or isoprene-based rubber, and silica, the followability to the road surface is improved by the interaction between the silanol group of silica and the moisture on the road surface, and it is considered to contribute to the improvement of wet grip performance. Furthermore, the reinforcing property by silica is also considered to contribute to the improvement of chipping resistance performance.

[0012] Further, since at least one of the rubber compositions constituting the first layer and the second layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components, the resin is bulky, and thus can impart flexibility to the rubber composition without impairing the reinforcing effect, which is considered to contribute to the improvement of wet grip performance.

[0013] And, (4) By making S2 - S1 exceed 0, since the first layer has relatively less styrene, the 30°C tanδ of the rubber composition constituting the first layer becomes small, and heat generation at the tire contact surface during vehicle running can be suppressed. Then, an effect can be expected that the fracture characteristics of the entire rubber composition constituting the tread portion are less likely to deteriorate, which is considered to contribute to the improvement of chipping resistance performance. On the other hand, since the second layer has relatively more styrene and the 30°C tanδ of the rubber composition constituting the second layer becomes large, good wet grip performance can be obtained in a situation where the tread portion is greatly distorted when the vehicle runs on a rough road. That is, by making S2 - S1 exceed 0, it is considered that heat generation due to deformation can be increased in the entire tread portion, and heat generation can be suppressed on the tread surface.

[0014] It is considered that the above (1) to (4) cooperate to achieve a remarkable effect of improving the comprehensive performance of chipping resistance performance and wet grip performance.

[0015] When the thickness of the first layer is t1 (mm), it is preferable that S1 × t1 is less than 100.0.

[0016] When S1 is large, by reducing the thickness of the first layer, the 30°C tanδ of the rubber composition constituting the first layer can be lowered, and it is considered that the wet grip performance can be further improved.

[0017] It is preferable that the rubber composition constituting the second layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components.

[0018] By containing the resin in the second layer, it is considered that the heat generation property in the tread portion is increased by the styrene component, and the wet grip performance is further improved.

[0019] It is preferable that the tanδ (tanδ1 at 30°C) of the rubber composition constituting the first layer is 0.30 or less at 30°C.

[0020] By setting tanδ1 at 30°C within the above range, it is considered that heat generation on the tread surface can be suppressed and the chipping resistance performance is further improved.

[0021] It is preferable that the complex elastic modulus (E*2 at 30°C) of the rubber composition constituting the second layer is 3.5 MPa or less at 30°C.

[0022] By setting E*2 at 30°C within the above range, it is considered that the fracture characteristics of the rubber composition in the tread portion can be reduced and the chipping resistance performance is further improved.

[0023] The rubber composition constituting the first layer preferably contains 70 parts by mass or more of silica with respect to 100 parts by mass of the rubber component.

[0024] Reinforcement by silica can be obtained, and it is considered that the chipping resistance performance is further improved.

[0025] It is preferable that S1 is more than 0 and less than 20.

[0026] By setting S1 within the above range, the followability to the road surface is improved by the interaction between the styrene group and silica, and heat generation on the tire contact surface can be suppressed. Therefore, it is considered that the chipping resistance performance and the wet grip performance are further improved.

[0027] The rubber composition constituting the second layer preferably contains 70 parts by mass or more of silica with respect to 100 parts by mass of the rubber component.

[0028] Reinforcement by silica can be obtained, and it is considered that the chipping resistance performance is further improved.

[0029] It is preferable that the modulus M2 at 200% elongation of the rubber composition constituting the second layer is 7.0 MPa or less.

[0030] By setting the modulus at 200% elongation of the rubber composition constituting the second layer within the above range, when deformation from the road surface that could not be completely absorbed by the first layer occurs, the inside of the second layer deforms flexibly, and it is considered that good wet grip performance can be obtained.

[0031] The ratio (30°C tanδ2 / 30°C tanδ3) of the tanδ (30°C tanδ2) at 30°C of the rubber composition constituting the second layer to the tanδ (30°C tanδ3) at 30°C of the rubber composition constituting the third layer is preferably more than 1.0.

[0032] By increasing the heat generation property of the second layer with respect to the heat generation property of the rubber composition constituting the third layer, better wet grip performance can be obtained in a situation where the tread portion is greatly distorted, such as when the vehicle is driving on a rough road.

[0033] The tread portion has a plurality of circumferential grooves extending continuously in the tire circumferential direction. When the thickness of the first layer is t1 (mm) and the groove depth at the deepest part of the circumferential groove is H (mm), it is preferable that t1 / H is 0.90 or less.

[0034] Since the deepest part of the circumferential groove exists on the inner side in the tire radial direction than the first layer, voids will occur after the second layer. In a situation where the tread portion is greatly distorted, such as when the vehicle is driving on a rough road, better wet grip performance can be obtained.

[0035] It is preferable that at least one groove wall of the circumferential groove is provided with a recess that is recessed outward in the groove width direction from the groove edge appearing on the tread surface of the tread portion.

[0036] By providing a recess on the groove wall of the circumferential groove, it is considered that a void can be formed inside the tread, and the absorption of impact and the suppression of propagation can be performed in the void portion.

[0037] [Definition] The "tread portion" is a member including the portion forming the ground contact surface of the tire, and in the tire radial cross-section, when it includes members forming the tire skeleton with steel or textile materials such as a belt layer, a belt reinforcing layer, and a carcass layer, it is a member disposed outside these in the tire radial direction.

[0038] The "rubber component of the rubber composition" is a component that contributes to cross-linking in the rubber composition, and generally has a weight average molecular weight (Mw) of 10,000 or more.

[0039] The "total styrene amount S in the rubber composition" is the total styrene amount (mass%) in the rubber composition when the mass of the rubber component is 100 mass%, and is the total amount of the styrene portion content in the rubber component and the styrene portion content in compounding agents other than the rubber component. The styrene portion is not particularly limited as long as it has a styrene structure, and examples include styrene, α-methylstyrene, vinyltoluene, chlorostyrene, etc.

[0040] That is, first, for each rubber component, a value obtained by multiplying the styrene content (% by mass) by the mass fraction in the rubber component is calculated for each, and the sum value (% by mass) obtained by adding these values is used. Next, for the styrene-containing compounding agents other than the rubber components contained in the rubber composition, a value obtained by multiplying the styrene content (% by mass) of each styrene-containing compounding agent by the mass fraction with respect to 100 parts by mass of the rubber component is calculated, and the sum value (% by mass) obtained by adding them is used. The total value obtained by adding the two sum values is defined as the total styrene content S (% by mass). Therefore, it is calculated by {Σ (content of styrene part in each styrene-containing rubber (% by mass) × content of each styrene-containing rubber in the rubber component (% by mass) / 100) + Σ (content of styrene part in each styrene-containing compounding agent other than the rubber component (% by mass) × compounding amount (parts by mass) of each styrene-containing compounding agent with respect to 100 parts by mass of the rubber component) / 100)}.

[0041] For example, when the rubber component consists of 30% of the first SBR (styrene content: 25% by mass), 60% of the second SBR (styrene content: 27.5% by mass), and 10% of BR, and the rubber composition further contains, in addition to the rubber component, 20 parts by mass of the first resin having a styrene part (styrene content: 5% by mass) with respect to 100 parts by mass of the rubber component and 10 parts by mass of the second resin having a styrene part (styrene content: 1% by mass) with respect to 100 parts by mass of the rubber component, the total styrene content S in the rubber composition with respect to 100% by mass of the rubber component is 25.1% by mass = {(25×30 / 100 + 27.5×60 / 100 + 0×10 / 100) + (5×20 / 100 + 1×10 / 100)}.

[0042] The "normal state" means a no-load state in which the tire is assembled on a normal rim and filled with air at a normal internal pressure.

[0043] "Normal Rim" refers to the rim defined for each tire in the standard system that includes the standards on which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Association), it refers to the standard rim for the applicable sizes described in the "JATMA YEAR BOOK"; in the case of ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" described in the "STANDARDS MANUAL"; and in the case of TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" described in the "YEAR BOOK". Refer to JATMA, ETRTO, and TRA in this order, and follow the relevant standards if there are applicable sizes during the reference. In the case of a tire not defined in the above standards, it refers to the rim with the narrowest rim width among the minimum-diameter rims that can be assembled with the tire and can maintain the internal pressure (i.e., does not cause air leakage between the rim and the tire).

[0044] "Normal Inflation Pressure" refers to the air pressure defined for each tire in the standard system that includes the standards on which the tire is based. For example, in the case of JATMA, it refers to the "Maximum Air Pressure"; in the case of ETRTO, it refers to the "INFLATION PRESSURE"; and in the case of TRA, it refers to the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". Similar to the case of the normal rim, refer to JATMA, ETRTO, and TRA in this order, and follow the relevant standards if there are applicable sizes during the reference. In the case of a tire not defined in the above standards, it refers to the normal inflation pressure (but not less than 250 kPa) of another tire size described with the normal rim as the standard rim (however, it must be defined in the standards). If there are multiple normal inflation pressures not less than 250 kPa described, it refers to the minimum value among them.

[0045] The "normal load" refers to the load specified for each tire in the standard system including the standards on which the tire is based. For example, in the case of JATMA, it is the "maximum load capacity"; in the case of ETRTO, it is "LOAD CAPACITY"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". Refer to JATMA, ETRTO, and TRA in this order, similar to the case of the normal rim and normal internal pressure. If there is an applicable size at the time of reference, follow that standard. For tires not specified in the above standards, the maximum load capacity W L calculated separately is taken as the normal load.

[0046] The "maximum load capacity W L " is calculated by the following formula. "V" is the virtual volume of the tire (mm 3 ), "Dt" is the outer diameter of the tire in the normal state (mm), "Ht" is the cross-sectional height of the tire in the radial direction of the tire in the cross-section of the tire by the plane including the tire rotation axis (mm), and "Wt" is the cross-sectional width of the tire in the normal state (mm). When the rim diameter of the tire is R, Ht can be obtained by (Dt - R) / 2. Wt is the value obtained after excluding patterns, characters, etc. on the tire sidewall. Note that the maximum load capacity is synonymous with the above normal load.

[0047]

Equation

[0048] The "dimensions of each part of the tire" are, unless otherwise specified, the values specified in the normal state for those appearing on the outer surface of the tire. On the other hand, those existing inside the tire or on the tire cut surface are, for example, the values specified in the state where the cut tire piece is held in the rim width of the normal rim by cutting the tire with a plane including the tire rotation axis.

[0049] "Loss tangent (tanδ) and complex elastic modulus E* of the rubber composition" are the tanδ and complex elastic modulus E* (MPa) under each condition measured in the elongation mode using a dynamic viscoelasticity measuring device (for example, the Implex series manufactured by GABO). The sample used for the dynamic viscoelasticity measurement is a vulcanized rubber composition with a length of 20 mm, a width of 4 mm, and a thickness of 1 mm. When cutting out a sample from a tire, if the member for creating the sample is the tread part, the length direction of the sample is made to coincide with the tire circumferential direction, and the thickness direction of the sample is made to coincide with the tire radial direction. Note that the sample is created in a state where it is as close as possible to the predetermined dimensions. The strain applied to the sample is normalized with respect to the length, and since the measured tanδ is normalized by the width and thickness of the sample, it is considered that there is no influence due to the sample size.

[0050] "Tanδ at 30°C" and "E* at 30°C" are the loss tangent (tanδ) and complex elastic modulus E* (MPa) measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of ±1%, and an elongation mode, respectively.

[0051] "Modulus at 200% elongation" is the stress at 200% elongation (MPa) when a dumbbell-shaped No. 7 test piece with a thickness of 1 mm is prepared and a tensile test is carried out at 23°C in an atmosphere under the condition of a tensile speed of 3.3 mm / second in accordance with JIS K 6251:2017.

[0052] "Groove" refers to a recessed part formed on the tread surface of the tire (extending inward in the tire radial direction) with an opening width on the tread surface of 2.0 mm or more. Those less than 2.0 mm are called "sipes".

[0053] "Circumferential groove" refers to a groove that extends continuously in the tire circumferential direction. The circumferential groove may extend linearly along the circumferential direction, or may extend in a wave shape, a sine shape, or a zigzag shape along the circumferential direction.

[0054] The "styrene content" is calculated by pyrolysis gas chromatography. In this specification, "pyrolysis gas chromatography" refers to a method in which a sample is heated by a pyrolysis apparatus, the individual components contained in the gas-phase components generated by this heating are separated by a separation column, and each isolated component is analyzed.

[0055] Similarly, the "vinyl content (1,2-bonded butadiene unit amount)" is calculated by pyrolysis gas chromatography.

[0056] The "cis content (cis-1,4-bonded butadiene unit amount)" is a value calculated by infrared absorption spectrum analysis in accordance with JIS K 6239-2:2017, and is applied to, for example, rubber components having repeating units derived from butadiene such as BR.

[0057] The "weight average molecular weight (Mw)" can be determined by standard polystyrene conversion based on the measured values by gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKgel SuperMultipore HZ-M manufactured by Tosoh Corporation). For example, it is applied to SBR, BR, plasticizers, etc.

[0058] The "nitrogen adsorption specific surface area (N2SA) of carbon black" is measured in accordance with JIS K 6217-2:2017.

[0059] The "nitrogen adsorption specific surface area (N2SA) of silica" is measured by the BET method in accordance with ASTM D3037-93.

[0060] The "average primary particle diameter" is a value obtained by photographing particles with a transmission or scanning electron microscope and calculating the arithmetic average of the particle diameters of 400 particles. When the shape of the particles is spherical, the diameter of the sphere is taken as the particle diameter, and when the shape is other than spherical, the equivalent circle diameter ({square root of 4×(area of the particle) / π}) is calculated from the microscope image and taken as the particle diameter.

[0061] "Plasticizer" refers to a material that imparts plasticity to the rubber component and is a component extracted from the rubber composition using acetone. The plasticizer includes a plasticizer that is liquid (in a liquid state) at 25°C and a plasticizer that is solid at 25°C. However, waxes and stearic acid commonly used in the tire industry are not included.

[0062] The "softening point of the resin" is the temperature at which the ball drops when measured with a ring and ball softening point measuring device in accordance with the softening point specified in JIS K 6220-1:2015 7.7.

[0063] The manufacturing procedure of the tire which is one embodiment of the present invention will be described in detail below. However, the following description is an exemplification for explaining the present invention and is not intended to limit the technical scope of the present invention only to this description range. In this specification, when a numerical range is indicated using "~", both end values are included.

[0064] <Tread portion> FIG. 1 is a cross-sectional view schematically showing a part of the tread of a tire according to an embodiment of the present invention. In FIG. 1, the vertical direction is the tire radial direction, the left-right direction is the tire width direction, and the direction perpendicular to the paper surface is the tire circumferential direction.

[0065] The tread portion according to the present embodiment has three or more rubber layers. The configuration of the rubber layers is a first layer constituting the tread surface, a second layer adjacent to the inner side in the radial direction of the first layer, and a third layer existing on the inner side in the radial direction of the second layer. There may be one or two or more additional rubber layers between the second layer and the third layer, or between the third layer and the belt layer.

[0066] When the mass of the rubber component in the rubber composition constituting the first layer is 100% by mass, the total styrene amount S1 in the rubber composition is preferably more than 0% from the viewpoint of the effects of the present invention, more preferably 5.0% by mass or more, still more preferably 8.0% by mass or more, still more preferably 10.0% by mass or more, still more preferably 11.0% by mass or more, still more preferably 12.0% by mass or more, and particularly preferably 15.0% by mass or more. Further, from the viewpoint of chipping resistance performance, S1 is preferably 40.0% by mass or less, more preferably 35.0% by mass or less, still more preferably 30.0% by mass or less, and particularly preferably less than 20.0% by mass.

[0067] When the mass of the rubber component in the rubber composition constituting the second layer is 100% by mass, the total styrene amount S2 in the rubber composition is preferably 10.0% by mass or more, more preferably 12.0% by mass or more, still more preferably 15.0% by mass or more, and particularly preferably 20.0% by mass or more from the viewpoint of wet grip performance. Further, from the viewpoint of low fuel consumption performance, S2 is preferably 40.0% by mass or less, more preferably 35.0% by mass or less, and still more preferably 30.0% by mass or less.

[0068] From the viewpoint of the effects of the present invention, S2 - S1 is more than 0% by mass, preferably more than 3.0% by mass, more preferably more than 5.0% by mass, still more preferably more than 7.0% by mass, still more preferably more than 10.0% by mass, still more preferably more than 11.0% by mass, and particularly preferably more than 12.5% by mass. Further, from the viewpoint of low fuel consumption performance, S2 - S1 is preferably less than 25.0% by mass, more preferably less than 22.0% by mass, still more preferably less than 20.0% by mass, and particularly preferably less than 18.0% by mass.

[0069] The total styrene amount S3 in the rubber composition constituting the third layer when the mass of the rubber component is 100% by mass is not particularly limited and may be, for example, 0% by mass.

[0070] Incidentally, the total styrene amount of the rubber composition can be appropriately adjusted according to the types and blending amounts of the rubber components described below. For example, the total styrene amount S can be increased by blending a styrene-butadiene rubber with a high styrene content in the styrene portion, or by blending a resin containing styrene as a monomer component. Conversely, the total styrene amount S can be reduced by reducing the blending amount of styrene-butadiene rubber, etc.

[0071] The 30°C tanδ (30°C tanδ1) of the rubber composition constituting the first layer is preferably 0.40 or less, more preferably 0.35 or less, and even more preferably 0.30 or less from the viewpoint of chipping resistance performance. Also, from the viewpoint of wet grip performance, 30°C tanδ1 is preferably 0.15 or more, more preferably 0.18 or more, and even more preferably 0.20 or more.

[0072] The 30°C tanδ (30°C tanδ2) of the rubber composition constituting the second layer is preferably 0.50 or less, more preferably 0.40 or less, and even more preferably 0.35 or less from the viewpoint of low fuel consumption performance. Also, from the viewpoint of wet grip performance, 30°C tanδ2 is preferably 0.10 or more, more preferably 0.15 or more, and even more preferably 0.18 or more.

[0073] The 30°C tanδ (30°C tanδ3) of the rubber composition constituting the third layer is preferably 0.25 or less, more preferably 0.20 or less, and even more preferably 0.15 or less from the viewpoint of low fuel consumption performance. Also, from the viewpoint of wet grip performance, 30°C tanδ2 is preferably 0.08 or more, more preferably 0.10 or more, and even more preferably 0.12 or more.

[0074] From the viewpoint of wet grip performance, 30°C tanδ2 / 30°C tanδ3 is preferably more than 1.0, more preferably more than 1.5, and even more preferably more than 1.8. Also, from the viewpoint of chipping resistance performance, 30°C tanδ2 / 30°C tanδ3 is preferably less than 2.5, more preferably less than 2.2, and even more preferably less than 2.0.

[0075] Note that the 30 tan δ of the rubber composition can be appropriately adjusted according to the types and blending amounts of the rubber components, fillers, plasticizers, etc. described below. For example, the 30°C tan can be increased by increasing the total styrene amount of the rubber composition, etc.

[0076] From the viewpoint of chipping resistance performance, the complex elastic modulus (30°C E*2) at 30°C of the rubber composition constituting the second layer is preferably 5.0 MPa or less, more preferably 4.0 MPa or less, and even more preferably 3.5 MPa or less. Also, from the viewpoint of wet grip performance, the 30°C E*2 is preferably 2.0 MPa or more, more preferably 2.3 MPa or more, and even more preferably 2.5 MPa or more.

[0077] From the viewpoint of chipping resistance performance, the complex elastic modulus (30°C E*1) at 30°C of the rubber composition constituting the first layer is preferably 6.0 MPa or less, more preferably 5.5 MPa or less, and even more preferably 5.2 MPa or less. Also, from the viewpoint of wet grip performance, the 30°C E*1 is preferably 2.5 MPa or more, more preferably 2.8 MPa or more, and even more preferably 3.0 MPa or more.

[0078] From the viewpoint of low fuel consumption performance, the complex elastic modulus (30°C E*3) of the rubber composition constituting the third layer is preferably 2.0 MPa or less, more preferably 1.8 MPa or less, and even more preferably 1.6 MPa or less. Also, from the viewpoint of wet grip performance, the 30°C E*3 is preferably 1.0 MPa or more, more preferably 1.2 MPa or more, and even more preferably 1.4 MPa or more.

[0079] From the viewpoint of the effects of the present invention, the modulus at 200% elongation (M2) of the rubber composition constituting the second layer is preferably 7.5 MPa or less, more preferably 7.0 MPa or less, and even more preferably 6.8 MPa or less. Also, from the viewpoint of chipping resistance performance, the M2 is preferably 4.5 MPa or more, more preferably 5.0 MPa or more, and even more preferably 6.0 MPa or more.

[0080] From the viewpoint of the effects of the present invention, the modulus (M1) at 200% elongation of the rubber composition constituting the first layer is preferably 10.0 MPa or less, more preferably 9.0 MPa or less, and even more preferably 8.8 MPa or less. Further, from the viewpoint of chipping resistance performance, M1 is preferably 6.5 MPa or more, more preferably 7.0 MPa or more, and even more preferably 7.5 MPa or more. The modulus (M3) at 200% elongation of the rubber composition constituting the third layer is not particularly limited.

[0081] In FIG. 1, double arrow t1 represents the thickness of the first layer 6, double arrow t2 represents the thickness of the second layer 7, and double arrow t3 represents the thickness of the third layer 8. In FIG. 1, the midpoint in the tire width direction of the land portion 2 is shown as symbol P. The straight line indicated by symbol N passes through point P and is perpendicular to the tangent plane at this point P (normal line). In this specification, the thicknesses t1, t2, and t3 are measured along the normal line N drawn from point P on the tread surface at a position where there is no groove in the cross section of FIG. 1.

[0082] From the viewpoint of chipping resistance performance, the thickness t1 of the first layer is preferably 1.5 mm or more, more preferably 1.8 mm or more, and even more preferably 2.0 mm or more. Further, from the viewpoint of wet grip performance, t1 is preferably 6.0 mm or less, more preferably 5.0 mm or less, even more preferably 5.5 mm or less, even more preferably 5.0 mm or less, and particularly preferably 4.0 mm or less.

[0083] The thickness t2 of the second layer is preferably 2.0 mm or more, more preferably 3.0 mm or more, and even more preferably 3.5 mm or more. Also, t2 is preferably 10.0 mm or less, more preferably 8.0 mm or less, and even more preferably 7.0 mm or less.

[0084] The thickness t3 of the third layer is preferably 0.5 mm or more, more preferably 1.0 mm or more, and even more preferably 1.5 mm or more. Also, t3 is preferably 5.0 mm or less, more preferably 4.5 mm or less, and even more preferably 4.0 mm or less.

[0085] From the perspective of the effects of the present invention, S1×t1 is preferably less than 110.0, more preferably less than 100.0, still more preferably less than 95.0, and even more preferably less than 90.0. Also, from the perspective of ensuring S1 and t1 to be a certain value or more, S1×t1 is preferably greater than 20.0, more preferably greater than 30.0, and even more preferably greater than 40.0.

[0086] The tread portion according to the present embodiment preferably has a plurality of circumferential grooves 1 that continuously extend in the tire circumferential direction. The circumferential grooves 1 may extend linearly along the circumferential direction or may extend in a zigzag shape along the circumferential direction. Also, the tread portion according to the present embodiment preferably has land portions 2 partitioned by the circumferential grooves 1 in the tire width direction.

[0087] The groove depth H of the deepest part of the circumferential groove 1 is obtained by the distance between the extension line 4 of the tread surface 3 and the extension line 5 of the deepest part of the groove bottom of the circumferential groove 1. Note that, for example, when there are a plurality of circumferential grooves 1, the groove depth H can be the distance between the extension line 4 of the tread surface 3 and the extension line 5 of the deepest part of the groove bottom of the circumferential groove 1 having the deepest groove depth among the plurality of circumferential grooves 1 (the left circumferential groove 1 in FIG. 1).

[0088] <Circumferential groove> FIG. 2 shows an enlarged plan view of the circumferential groove 1 according to an embodiment of the present invention. In FIG. 2, the groove edge 10 of the circumferential groove 1 is shown by a solid line, and the contour 12 of the groove wall when the tread portion is viewed in plan is shown by a broken line. Also, the recessed region (recess 11) between the groove edge 10 and the contour 12 of the groove wall of the circumferential groove 1 is represented with dots.

[0089] FIG. 3 shows a cross-sectional view taken along line A-A of the circumferential groove 1 shown in FIG. 2. As shown in FIG. 3, the circumferential groove 1 is provided with recesses 11 having a constant dent amount in the tire circumferential direction on both side groove walls. The recess 11 is configured with a flat surface 44 between the deepest part of the recess and the groove edge 10, for example, but is not limited to such a mode.

[0090] The total amount of indentation of the circumferential groove 1 is preferably 0.10 to 0.90 times, more preferably 0.15 to 0.80 times, and even more preferably 0.20 to 0.70 times the groove width W1 of the circumferential groove 1. In this specification, the "total amount of indentation of the circumferential groove" refers to c1 + c2 when the circumferential groove 1 is in the form shown in FIG. 3.

[0091] [Rubber composition] The rubber composition (hereinafter sometimes referred to as the rubber composition according to the present embodiment) constituting the first layer or the second layer of the tread portion according to the present embodiment contains a rubber component containing styrene-butadiene rubber (SBR) and / or isoprene-based rubber, and silica, and at least one of the rubber compositions constituting the first layer and the second layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components, and all can be produced using the raw materials described below. Hereinafter, the rubber composition according to the present embodiment will be described.

[0092] [Rubber component] As the rubber component, it is preferable to contain a diene-based rubber. Any of the diene-based rubbers usually used in the tire industry can be suitably used. Specifically, for example, isoprene-based rubber, butadiene rubber (BR), SBR, styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), etc. can be mentioned. These diene-based rubbers may be used alone or in combination of two or more.

[0093] The content of the diene-based rubber in the rubber component of the rubber composition according to the present embodiment is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more. The rubber component can also be composed only of a diene-based rubber component.

[0094] (SBR) The SBR is not particularly limited, and examples thereof include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). Examples of the modified SBR include SBRs having a modified terminal and / or main chain, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.). These SBRs may be used alone or in combination of two or more.

[0095] From the viewpoint of the effects of the present invention, the content of the styrene moiety in the SBR is preferably more than 18% by mass, more preferably more than 20% by mass, and still more preferably more than 25% by mass. On the other hand, the content of the styrene moiety in the SBR is preferably less than 60% by mass, more preferably less than 50% by mass, and still more preferably less than 45% by mass. When the content of the styrene moiety in the SBR exceeds 60% by mass, styrene groups are adjacent to each other, the polymer becomes too hard, crosslinking tends to be non-uniform, and there is a risk of deterioration of blowability during high-temperature driving. In addition, the temperature dependence increases, the performance change with respect to temperature change becomes large, and a stable grip performance during and after driving tends not to be obtained well. In the present specification, the content of the styrene moiety in the SBR is measured by the above-described measurement method.

[0096] The vinyl content of the SBR is preferably more than 10 mol%, more preferably more than 15 mol%, and still more preferably more than 20 mol%. Also, the vinyl content of the SBR is preferably less than 70 mol%, more preferably less than 65 mol%, and still more preferably less than 60 mol%. In the present specification, the vinyl content of the SBR is measured by the above-described measurement method.

[0097] From the perspective of wet grip performance, the glass transition temperature (Tg) of SBR is preferably -80°C or higher, more preferably -70°C or higher, and even more preferably -65°C or higher. Also, from the perspective of low fuel consumption performance, the Tg of SBR is preferably -40°C or lower, more preferably -45°C or lower, even more preferably -50°C or lower, and even more preferably -55°C or lower. Note that the Tg of SBR in this specification conforms to JIS K 6229. After removing the extender oil using acetone, the pure SBR content is determined by differential scanning calorimetry (DSC) in accordance with JIS K 7121.

[0098] The weight average molecular weight (Mw) of SBR is preferably over 200,000, more preferably over 300,000, even more preferably over 400,000, and particularly preferably over 500,000. Also, from the perspective of crosslinking uniformity, etc., Mw is preferably less than 2,000,000, more preferably less than 1,500,000, and even more preferably less than 1,000,000. Note that the Mw of SBR is measured by the above measurement method.

[0099] As SBR, oil-extended SBR can be used, or non-oil-extended SBR can be used. In this specification, as SBR, those commercially available from JSR Corporation, Sumitomo Chemical Co., Ltd., UBE Industries, Ltd., Asahi Kasei Corporation, ZS Elastomers Co., Ltd., ARLANXEO, etc. can be used.

[0100] The content of SBR in the rubber component constituting the first layer can be appropriately set so that S2 - S1 and S1×t1 are within the above ranges, but it is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, still more preferably 50% by mass or more, and particularly preferably 60% by mass or more. Also, the content of the SBR in the rubber component is preferably 90% by mass or less, and more preferably 80% by mass or less.

[0101] The content of SBR in the rubber component constituting the second layer can be appropriately set so that S2 - S1 falls within the above range, but it is preferably 25% by mass or more, more preferably 35% by mass or more, further preferably 45% by mass or more, still further preferably 55% by mass or more, still further preferably 65% by mass or more, and particularly preferably 70% by mass or more. Also, the content of the SBR in the rubber component is preferably 95% by mass or less, and more preferably 90% by mass or less.

[0102] (Isoprene rubber) As the isoprene rubber, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. Natural rubber includes, in addition to unmodified natural rubber (NR), modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. These isoprene rubbers may be used alone or in combination of two or more.

[0103] NR is not particularly limited, and those common in the tire industry can be used, for example, SIR20, RSS#3, TSR20, etc.

[0104] The content of the isoprene rubber in the rubber components constituting the first layer and the second layer is preferably 1% by mass or more, more preferably 5% by mass or more, and further preferably 10% by mass or more. Also, the content is preferably 60% by mass or less, more preferably 50% by mass or less, and further preferably 40% by mass or less.

[0105] (BR) BR is not particularly limited. For example, BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare-earth butadiene rubber synthesized using a rare-earth element-based catalyst (rare-earth-based BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc., which are common in the tire industry, can be used. These BRs may be used alone or in combination of two or more.

[0106] As the high-cis BR, for example, those commercially available from Nippon Zeon Co., Ltd., UBE Industries, Ltd., JSR Corporation, etc. can be used. By containing high-cis BR, the low-temperature properties and abrasion resistance can be improved. The cis content of the high-cis BR is preferably more than 95 mol%, more preferably more than 96 mol%, and even more preferably more than 97 mol%. The cis content of BR is measured by the above measurement method.

[0107] The rare-earth-based BR is synthesized using a rare-earth element-based catalyst, and the vinyl content is preferably less than 1.8 mol%, more preferably less than 1.6 mol%, and even more preferably 1.5 mol% or less, and the cis content is preferably more than 95 mol%, more preferably more than 96 mol%, and even more preferably 97 mol% or more. As the rare-earth-based BR, for example, those commercially available from Lanxess Co., Ltd., etc. can be used.

[0108] The SPB-containing BR is not simply a dispersion of 1,2-syndiotactic polybutadiene crystals in BR, but one in which the crystals are dispersed after being chemically bonded to BR. As such SPB-containing BR, those commercially available from UBE Industries, Ltd., etc. can be used.

[0109] Examples of the modified BR include BR modified with functional groups similar to those described for the above SBR. In addition, modified butadiene rubber (modified BR) modified with a functional group containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen in the terminal and / or main chain can also be preferably used.

[0110] Examples of other modified BRs include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and further having the terminals of the modified BR molecules bonded by tin-carbon bonds (tin-modified BR). The modified BR may be either unhydrogenated or hydrogenated.

[0111] From the viewpoint of abrasion resistance performance, the weight average molecular weight (Mw) of BR is preferably more than 300,000, more preferably more than 350,000, and still more preferably more than 400,000. From the viewpoints of crosslinking uniformity, etc., it is preferably less than 2,000,000, more preferably less than 1,000,000, and still more preferably less than 500,000. Note that Mw can be determined by the above method.

[0112] The content of BR in the rubber components constituting the first layer and the second layer is not particularly limited, but is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 20% by mass or more. Also, the content of BR in the rubber components is preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably 30% by mass or less.

[0113] (Other rubber components) The rubber component may contain a rubber component other than a diene rubber (non-diene rubber) as long as it does not affect the effects of the invention. As the non-diene rubber, rubber components generally used in the tire industry can be used. For example, butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, etc. can be mentioned. These other rubber components may be used alone or in combination of two or more. Further, in addition to the above rubber components, a known thermoplastic elastomer may or may not be contained.

[0114] (Rubber component synthesized from recycled and biomass-derived raw materials) The monomers that are structural units of synthetic rubbers such as SBR and BR may be derived from petroleum or recycled from rubber products such as tires and non-rubber products such as polystyrene. The monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled butadiene, recycled aromatic vinyl compounds, etc. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl compound is not particularly limited, and examples include styrene. Among them, it is preferable to use recycled butadiene (recycled butadiene) and / or recycled styrene (recycled styrene) as raw materials.

[0115] The production method of the recycled monomer is not particularly limited. For example, it can be synthesized from recycled naphtha obtained by decomposing rubber products such as tires. Further, the production method of recycled naphtha is not particularly limited. For example, rubber products such as tires may be decomposed under high temperature and high pressure, decomposed by microwaves, or extracted after mechanical pulverization.

[0116] Furthermore, the monomers that are the constituent units of polymers such as SBR and BR may be derived from biomass. The biomass-derived monomers (biomass monomers) are not particularly limited, and examples include biomass-derived butadiene and biomass-derived aromatic vinyl compounds. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl compound is not particularly limited, and examples include styrene. Also, the method for producing biomass monomers is not particularly limited, and examples include those by biological and / or chemical and / or physical conversion of animals and plants. Fermentation by microorganisms is typical as the biological conversion, and examples of the chemical and / or physical conversion include those by a catalyst, high heat, high pressure, electromagnetic waves, a critical liquid, and combinations thereof. Examples of the biomass sources of these monomers include sugars, wood, plant residues after obtaining useful components, plant-derived ethanol, biomass naphtha, and the like.

[0117] The polymers synthesized from biomass monomer components (biomass polymers) are not particularly limited, and examples include polybutadiene rubber synthesized from biomass-derived butadiene, and aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0118] Whether the raw material of the polymer is derived from biomass can be determined by pMC (percent Modern Carbon) measured in accordance with ASTM D6866-10. pMC is the ratio of the 14 C concentration of the sample to the 14 C concentration of the standard modern carbon (modern standard reference), and this value is used as an index indicating the biomass ratio of the compound (rubber). The significance of this value is described below.

[0119] One mole (6.02×10 23 atoms) of carbon atoms contains approximately 6.02×10 11 atoms of 14 C, which is about one trillionth of ordinary carbon atoms. 14 The half-life of 14 C is 5730 years, and 14 C decreases regularly. Therefore, in fossil fuels such as coal, oil, and natural gas, which are considered to have passed more than 226,000 years after carbon dioxide in the atmosphere was taken up and fixed by plants, etc., all of the 14 C elements have decayed at the time of fixation. Therefore, at present in the 21st century, fossil fuels such as coal, oil, and natural gas do not contain 14 any 14 C elements at all. Therefore, chemical substances produced from these fossil fuels also do not contain 14 any

[0120] On the other hand, 14 C is constantly generated by cosmic rays undergoing nuclear reactions in the atmosphere. Therefore, 14 C is in equilibrium between decrease due to radioactive decay and generation due to nuclear reactions, and in the earth's atmospheric environment, 14 the amount of 14 C is constant. Therefore, the 14 C concentration of substances derived from biomass resources that are circulating in the current environment is about 1×10 -12 mol% with respect to the total carbon atoms as described above. Therefore, by utilizing the difference between these values, the ratio (biomass ratio) of compounds derived from natural resources (compounds derived from biomass resources) in a certain compound (rubber) can be calculated.

[0121] This 14 C is generally measured as follows. Using accelerator mass spectrometry based on a tandem accelerator, 13 the 13 C concentration ( 13 C / 12 C), 14 the 14 C concentration ( 14 C / 12 C) is measured. In the measurement, 14As a modern standard reference for the concentration of C, the concentration of 14 C in the circulating carbon in nature in 1950 is adopted. As a specific reference material, the oxalic acid standard provided by NIST (National Institute of Standards and Technology) is used. The specific radioactivity of carbon in this oxalic acid (the radioactivity intensity of 14 C per gram of carbon) is separated for each carbon isotope, and 13 C is corrected to a constant value, and the value after applying the decay correction from 1950 AD to the measurement date is used as the standard 14 C concentration value (100%). The ratio of this value to the value of the sample actually measured is the pMC value.

[0122] Therefore, if the rubber is made of 100% biomass (natural-based) materials, although there are regional differences, it will show a value of approximately 110 pMC (currently, in the normal state, it often does not reach 100). On the other hand, for chemical substances derived from fossil fuels such as petroleum, when measuring the 14 C concentration, it will show a value of about 0 pMC (for example, 0.3 pMC). This value corresponds to a biomass ratio of 0% as described above.

[0123] From the above, using materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio, in the rubber composition is suitable from the perspective of environmental protection.

[0124] [Filler] The rubber composition according to this embodiment preferably contains a filler. The rubber compositions constituting the first layer and the second layer preferably contain silica, and preferably contain silica and carbon black. Also, the filler may be a filler consisting only of carbon black and silica.

[0125] [Silica] The silica is not particularly limited, and for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), etc., which are common in the tire industry, can be used. The raw material of the silica is not particularly limited, and for example, it may be a raw material derived from a mineral such as quartz, or it may be a raw material derived from a living organism such as rice husk (for example, silica using a biomass material such as rice husk as a raw material), or silica recycled from a product containing silica may be used. Among them, hydrous silica prepared by a wet method is preferable because of its large number of silanol groups. These silicas may be used alone or in combination of two or more.

[0126] Silica using a biomass material as a raw material can be obtained, for example, by extracting a silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and reacting the silicate with sulfuric acid in the same manner as conventional wet silica to precipitate silicon dioxide, followed by filtration, washing with water, drying, and pulverization.

[0127] As the silica recycled from a product containing silica, for example, silica recovered from products containing silica such as electronic components such as semiconductors, tires, desiccants, and filter materials such as diatomaceous earth can be used. The recovery method is not particularly limited, and examples include thermal decomposition and decomposition by electromagnetic waves. Among them, silica recovered from electronic components such as semiconductors or tires is preferable.

[0128] When silica crystallizes, it does not dissolve in water and the silicic acid that is its component cannot be utilized. By controlling the combustion temperature and combustion time, crystallization of silica in rice husk ash can be suppressed (see, for example, JP-A-2009-2594, Akita Prefectural University Web Journal B / 2019, vol. 6, p. 216-222, etc.). Commercially available amorphous silica extracted from rice husks, such as those from Wilmar, can be used.

[0129] From the viewpoint of ensuring reinforcing properties and grip performance, the nitrogen adsorption specific surface area (N2SA) of the silica is preferably 100 m 2 / g or more, and 120 m 2 / g or more is more preferable, and 140 m 2 / g or more is even more preferable, and 160 m 2 / g or more is even more preferable, and 170 m 2 / g or more is particularly preferable. From the viewpoint of processability, 350 m 2 / g or less is preferable, and 300 m 2 / g or less is more preferable, and 250 m 2 / g or less is even more preferable. The N2SA of silica is measured by the above measurement method.

[0130] The average primary particle diameter of silica is preferably 10 nm or more, more preferably 12 nm or more, even more preferably 14 nm or more, and particularly preferably 16 nm or more. Also, the average primary particle diameter is preferably 24 nm or less, more preferably 22 nm or less, and even more preferably 20 nm or less. The average primary particle diameter of silica is measured by the above measurement method.

[0131] The content of silica relative to 100 parts by mass of the rubber component of the rubber composition constituting the first layer is preferably more than 50 parts by mass, more preferably more than 60 parts by mass, even more preferably 70 parts by mass or more, and even more preferably more than 70 parts by mass. Also, from the viewpoint of wet grip performance, the content of silica relative to 100 parts by mass of the rubber component is preferably less than 110 parts by mass, more preferably less than 100 parts by mass, and even more preferably less than 90 parts by mass.

[0132] The content of silica relative to 100 parts by mass of the rubber component of the rubber composition constituting the second layer is preferably more than 50 parts by mass, more preferably more than 60 parts by mass, and even more preferably 70 parts by mass or more. Also, the content of silica relative to 100 parts by mass of the rubber component is preferably less than 110 parts by mass, more preferably less than 100 parts by mass, and even more preferably less than 90 parts by mass.

[0133] <Silane coupling agent> Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited. For example, sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane; vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane, etc. Among them, it is preferable to contain a sulfide-based silane coupling agent and / or a mercapto-based silane coupling agent. As the silane coupling agent, for example, those commercially available from Evonik Degussa, Momentive, etc. can be used. These silane coupling agents may be used alone or in combination of two or more.

[0134] From the viewpoint of enhancing the dispersibility of silica, the content of the silane coupling agent (the total amount when a plurality of silane coupling agents are used in combination) relative to 100 parts by mass of the rubber component is preferably more than 3.0 parts by mass, more preferably more than 5.0 parts by mass, and still more preferably 6.0 parts by mass or more. Also, from the viewpoint of preventing a decrease in wear resistance performance, it is preferably less than 15 parts by mass, more preferably less than 10 parts by mass, and still more preferably less than 9.0 parts by mass.

[0135] <Carbon black> The carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. The raw material of the carbon black may be a biomass material such as lignin or vegetable oil, or may be a pyrolysis oil obtained by thermally decomposing waste tires. Also, the manufacturing method of the carbon black may be by combustion such as the furnace method, by hydrothermal carbonization (HTC), or by thermal decomposition of methane such as the thermal black method. As commercially available products, products of Asahi Carbon Co., Ltd., Cabot Japan Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Columbian Carbon Company, etc. can be used. These may be used alone or in combination of two or more.

[0136] In addition to the above, from the viewpoint of life cycle assessment and the like, carbon black made from biomass materials such as lignin as a raw material, or recycled carbon black obtained by purifying a product containing carbon black such as a tire by thermal decomposition may also be used as the carbon black.

[0137] In this specification, "recycled carbon black" refers to carbon black obtained by pulverizing a used product such as a tire containing carbon black and firing the pulverized product, and when oxidized and burned by heating in air by a thermogravimetric method conforming to JIS K 6226-2:2003, it refers to carbon black in which the ratio of the mass of the ash content (ash amount), which is the component that does not burn, is 13% by mass or more. That is, the ratio of the mass of the weight loss (carbon amount) due to the oxidative combustion of the recycled carbon black is 87% by mass or less. Recycled carbon black may also be represented by rCB.

[0138] Recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975 refers to "Rubber Chemistry and Technology", Vol. 85, No. 3, pages 408 - 449 (2012), particularly pages 438, 440, 442, and describes that it can be obtained by pyrolysis of organic materials at 550 - 800 °C with oxygen excluded or by vacuum pyrolysis at relatively low temperatures (

[0027] ). Carbon black obtained from such a pyrolysis process usually lacks functional groups on its surface as mentioned in

[0004] of Patent No. 6856781 (Comparison of the surface morphology and chemistry of pyrolytic carbon black and commercially available carbon black, Powder Technology 160 (2005) 190 - 193).

[0139] Recycled carbon black may lack functional groups on its surface or may be treated to contain functional groups on its surface. The treatment to make the recycled carbon black contain functional groups on its surface can be carried out by conventional methods. For example, in European Patent Application Publication No. 3173251, carbon black obtained from the pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Also, in Patent No. 6856781, carbon black obtained from the pyrolysis process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain carbon black with its surface activated. The recycled carbon black according to this embodiment also includes such carbon black treated to contain functional groups on its surface.

[0140] Commercially available recycled carbon black from companies such as Strable Green Carbon and LDCarbon can be used.

[0141] The average primary particle diameter of the carbon black is preferably 15 nm or more, more preferably 18 nm or more, still more preferably 20 nm or more, and particularly preferably 22 nm or more. On the other hand, from the viewpoint of obtaining reinforcing properties, the average primary particle diameter is preferably 100 nm or less, more preferably 80 nm or less, and still more preferably 50 nm or less. The average primary particle diameter of the carbon black is measured by the above-mentioned measurement method.

[0142] The nitrogen adsorption specific surface area (N2SA) of the carbon black is preferably 200 m 2 / g or less, more preferably 180 m 2 / g or less, and still more preferably 150 m 2 / g or less from the viewpoint of the effects of the present invention. Also, the N2SA is preferably 30 m 2 / g or more, more preferably 40 m 2 / g or more, and still more preferably 45 m 2 / g or more. The N2SA of the carbon black is measured by the above-mentioned measurement method.

[0143] When the rubber composition constituting the first layer or the second layer contains carbon black, the content with respect to 100 parts by mass of the rubber component is preferably more than 3 parts by mass, more preferably more than 5 parts by mass, and still more preferably more than 9 parts by mass from the viewpoint of reinforcing properties. Also, from the viewpoint of obtaining flexibility and relaxing stress, it is preferably less than 50 parts by mass, more preferably less than 40 parts by mass, still more preferably less than 30 parts by mass, and particularly preferably less than 20 parts by mass.

[0144] <Other fillers> The filler may include other fillers other than silica and carbon black. The other fillers are not particularly limited, and for example, those generally used in the tire industry such as aluminum hydroxide, calcium carbonate, alumina, clay, talc, etc. can be blended.

[0145] [Other compounding agents] In addition to the rubber component and the filler, the rubber composition according to this embodiment may appropriately contain compounding agents generally used in the conventional tire industry, such as plasticizers, processing aids, vulcanized rubber particles, waxes, stearic acid, zinc oxide, anti-aging agents, vulcanizing agents, vulcanization accelerators, etc. At least one of the rubber compositions constituting the first layer and the second layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components, and it is preferable that the rubber composition constituting the first layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components.

[0146] <Plasticizer> A plasticizer is a material that imparts plasticity to the rubber component, and is a concept that includes both plasticizers that are liquid (liquid state) at normal temperature (25°C) and plasticizers that are solid at normal temperature (25°C). Examples of plasticizers include resins, oils, liquid polymers, ester-based plasticizers, etc. These plasticizers may be derived from petroleum, may be derived from biomass, or may be derived from naphtha recycled from rubber products or non-rubber products. Also, low-molecular-weight hydrocarbon components obtained by pyrolyzing and extracting used tires and products containing various components may be used as plasticizers. These plasticizers may be used alone or in combination of two or more.

[0147] ≪Copolymer resin containing styrene and cyclopentadiene as monomer components≫ The copolymer resin containing styrene and cyclopentadiene as monomer components is not particularly limited as long as it is a resin containing styrene and cyclopentadiene as monomer components, and may further contain the following other monomer components. Also, those obtained by hydrogenating them or modified ones may be used.

[0148] The other monomer components other than styrene and cyclopentadiene are not particularly limited, but monomer components commonly used in petroleum resins are preferable, the following C9 fraction, etc. are more preferable, and indene is even more preferable.

[0149] As the copolymer resin containing styrene and cyclopentadiene as monomer components, a copolymer resin containing styrene, cyclopentadiene and / or dicyclopentadiene, and indene as monomer components is preferable, and it may be a hydrogenated or modified copolymer resin.

[0150] As the copolymer resin containing styrene and cyclopentadiene as monomer components, for example, those commercially available from ExxonMobil, ENEOS Corporation, Nippon Zeon Co., Ltd., Maruzen Petrochemical Co., Ltd., etc. can be used. The resin may be used alone or in combination of two or more.

[0151] From the viewpoint of the effects of the present invention, the content of the styrene part in the copolymer resin containing styrene and cyclopentadiene as monomer components is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, and still more preferably 1.0% by mass or more. The upper limit of the content of the styrene part is not particularly limited, but can be, for example, less than 50% by mass, less than 40% by mass, less than 30% by mass, 10% by mass or less, 5% by mass or less, 3% by mass or less, etc.

[0152] From the viewpoint of the effects of the present invention, the softening point of the copolymer resin containing styrene and cyclopentadiene as monomer components is preferably above 70°C, more preferably above 80°C, still more preferably above 90°C, and particularly preferably above 100°C. From the viewpoints of processability and improvement of the dispersibility of the rubber component and the filler, it is preferably less than 150°C, more preferably less than 140°C, and still more preferably less than 130°C. The softening point of the resin is measured by the above measurement method.

[0153] The content of the copolymer resin containing styrene and cyclopentadiene as monomer components with respect to 100 parts by mass of the rubber component is preferably more than 5 parts by mass, more preferably more than 10 parts by mass, still more preferably more than 15 parts by mass, still more preferably more than 19 parts by mass, and particularly preferably more than 22 parts by mass. Further, from the viewpoint of processability, the content is preferably less than 100 parts by mass, more preferably less than 80 parts by mass, still more preferably less than 60 parts by mass, and particularly preferably less than 40 parts by mass.

[0154] (Other resins) The rubber composition according to the present embodiment may contain other resins other than the copolymer resin containing styrene and cyclopentadiene as monomer components. The other resins are not particularly limited, but resins commonly used in the tire industry can be used. For example, aromatic vinyl resins, dicyclopentadiene resins, C9 resins, C5 resins, C5C9 resins, terpene resins, rosin resins, phenolic resins, etc. can be mentioned. The resins may be used alone or in combination of two or more.

[0155] ≪Aromatic vinyl resin≫ In this specification, the "aromatic vinyl resin" refers to a resin containing at least one aromatic vinyl compound selected from the group consisting of styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene, etc. as a monomer component (however, excluding the copolymer resin containing styrene and cyclopentadiene as monomer components). As the aromatic vinyl resin, due to economic reasons, easy processing, and excellent heat generation properties, a homopolymer of α-methylstyrene or styrene or a copolymer of α-methylstyrene and styrene is preferable, and a copolymer of α-methylstyrene and styrene is more preferable. As the aromatic vinyl resin, for example, those commercially available from companies such as Kreton, Eastman Chemical, and Mitsui Chemicals can be used. The resins may be used alone or in combination of two or more.

[0156] ≪Dicyclopentadiene resin≫ In this specification, the "dicyclopentadiene-based resin" refers to a resin containing dicyclopentadiene as a monomer component (however, a copolymer resin containing styrene and cyclopentadiene as monomer components is excluded). As the dicyclopentadiene-based resin, for example, those commercially available from ExxonMobil, ENEOS Corporation, Nippon Zeon Co., Ltd., Maruzen Petrochemical Co., Ltd., etc. can be used. The resin may be used alone or in combination of two or more.

[0157] ≪C9-based resin≫ In this specification, the "C9-based resin" refers to a resin obtained by polymerizing a C9 fraction (however, a copolymer resin containing styrene and cyclopentadiene as monomer components is excluded), which may be a product of polymerizing the C9 fraction alone or a copolymer obtained by copolymerizing the C9 fraction with other components. Examples of the C9 fraction include at least one petroleum fraction corresponding to 8 to 10 carbon atoms selected from the group consisting of alkylstyrenes such as vinyltoluene, coumarone, indene, methylindene, etc. Specific examples of the C9-based resin include, for example, coumarone-indene resin, coumarone resin, indene resin, etc. The resin may be used alone or in combination of two or more.

[0158] ≪C5-based resin≫ In this specification, the "C5-based resin" refers to a resin obtained by polymerizing a C5 fraction other than cyclopentadiene, which may be hydrogenated or modified. Examples of the C5 fraction other than cyclopentadiene include at least one petroleum fraction corresponding to 4 to 5 carbon atoms selected from the group consisting of dicyclopentadiene, isoprene, pentane, isopentane, neopentane, pentene, pentadiene, etc. The resin may be used alone or in combination of two or more.

[0159] ≪C5C9-based resin≫ The "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified one thereof. As the C5C9 petroleum resin, for example, those commercially available from Tosoh Corporation, LUHUA Co., Ltd., etc. can be used. The resin may be used alone or in combination of two or more.

[0160] ≪Terpene resin≫ The terpene resin refers to a resin containing at least one terpene compound selected from the group consisting of α-pinene, β-pinene, limonene, dipentene, etc. as the monomer component with the highest content, preferably containing 50 mol% or more, and may be a hydrogenated or modified one thereof. Specific examples of the terpene resin include, for example, polyterpene resin containing only one or more of the above terpene compounds as monomer components; aromatic modified terpene resin containing the terpene compound and an aromatic compound as monomer components; terpene phenol resin containing the terpene compound and a phenolic compound as monomer components, etc. Examples of the aromatic compound as the monomer component of the aromatic modified terpene resin include at least one selected from the group consisting of styrene, α-methylstyrene, vinyltoluene, divinyltoluene, etc. Examples of the phenolic compound as the monomer component of the terpene phenol resin include at least one selected from the group consisting of phenol, bisphenol A, cresol, xylenol, etc. The resin may be used alone or in combination of two or more.

[0161] ≪Rosin resin≫ The rosin resin refers to a resin containing at least one rosin acid compound selected from the group consisting of abietic acid, neoabietic acid, palustric acid, isopimaric acid, etc., and may be a hydrogenated or modified one thereof. The rosin resin is not particularly limited, and examples thereof include natural resin rosin, rosin modified resin obtained by modifying it by hydrogenation, disproportionation, dimerization, esterification, etc. The resin may be used alone or in combination of two or more.

[0162] ≪Phenolic resin≫ The phenolic resin refers to a resin containing a phenolic compound such as phenol or cresol as the monomer component with the highest content, preferably containing 50 mol% or more. The phenolic resin is not particularly limited, and examples include phenol formaldehyde resin, alkylphenol formaldehyde resin, alkylphenol acetylene resin, oil-modified phenol formaldehyde resin, etc. The resin may be used alone or in combination of two or more.

[0163] ≪Softening point≫ From the viewpoint of wet grip performance, the softening point of the resin is preferably above 80 °C, more preferably above 90 °C, and even more preferably above 100 °C. Also, from the viewpoints of processability and improvement of the dispersibility of the rubber component and the filler, it is preferably less than 150 °C, more preferably less than 140 °C, and even more preferably less than 130 °C. The softening point of the resin is measured by the above measurement method.

[0164] ≪Content≫ The content of the resin (total content in the case of containing two or more) with respect to 100 parts by mass of the rubber component constituting the first layer or the second layer is preferably more than 10 parts by mass, more preferably more than 15 parts by mass, and even more preferably 20 parts by mass or more. On the other hand, from the viewpoint of low fuel consumption performance, it is preferably less than 80 parts by mass, more preferably less than 60 parts by mass, and even more preferably less than 40 parts by mass.

[0165] (Plasticizer other than resin) Oils, liquid rubbers, and ester-based plasticizers, which are plasticizers other than resin, will be described.

[0166] ≪Oil≫ Examples of oils include process oils, vegetable oils, animal oils, etc. Examples of process oils include paraffinic process oils (mineral oils), naphthenic process oils, aromatic process oils, etc. Specific examples of process oils include, for example, MES (Mild Extracted Solvate), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), RAE (Residual Aromatic Extract), etc. Also, process oils with a low content of polycyclic aromatic (PCA) compounds can be used for environmental protection. Examples of the low-PCA-content process oils include MES, TDAE, heavy naphthenic oils, etc. Further, from the perspective of life cycle assessment, it is also possible to use waste oils after being used in rubber mixers or engines, or waste cooking oils refined from those used in restaurants. The oil may be used alone or in combination of two or more kinds.

[0167] Vegetable oils include, for example, linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grape seed oil, wood rosin, etc. Further, vegetable oils include refined oils (such as salad oil) obtained by refining the above oils, transesterified oils obtained by transesterifying the above oils, hydrogenated oils obtained by hydrogenating the above oils, thermally polymerized oils obtained by thermally polymerizing the above oils, oxidative polymerized oils obtained by oxidizing the above oils, waste cooking oils recovered from those used as edible oils, etc. Note that vegetable oils may be liquid or solid at room temperature (25°C).

[0168] The vegetable oil preferably contains acylglycerol, and more preferably contains triacylglycerol. In the present specification, acylglycerol refers to a compound in which a hydroxy group of glycerin and a fatty acid are ester-bonded. The acylglycerol is not particularly limited, and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Further, the acylglycerol may be a monomer, a dimer, or a multimer of trimer or higher. The acylglycerol of dimer or higher can be obtained by thermal polymerization, oxidative polymerization, etc. Also, the acylglycerol may be liquid or solid at room temperature (25°C).

[0169] As a method for confirming whether the acylglycerol is contained in the rubber composition, it is not particularly limited, but 1 it can be confirmed by 1H-NMR measurement. For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at room temperature (25°C) for 24 hours. After removing the rubber composition, 1 1H-NMR is measured. When the signal of tetramethylsilane (TMS) is set to 0.00 ppm, signals around 5.26 ppm, around 4.28 ppm, and around 4.15 ppm are observed, and these signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In this paragraph, "around" means a range of ±0.10 ppm.

[0170] The fatty acid is not particularly limited, and may be an unsaturated fatty acid or a saturated fatty acid. Examples of the unsaturated fatty acid include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of the saturated fatty acid include butyric acid and lauric acid.

[0171] Among them, as the fatty acid, it is desirable to contain a fatty acid with few double bonds, that is, a saturated fatty acid or a monounsaturated fatty acid, and oleic acid is preferred. As the vegetable oil containing such a fatty acid, for example, a vegetable oil containing a saturated fatty acid or a monounsaturated fatty acid may be used, or a vegetable oil subjected to modification such as transesterification may be used. Further, in order to produce a vegetable oil containing such a fatty acid, plants may be improved by variety improvement, genetic recombination, genome editing, etc.

[0172] As the vegetable oil, for example, those commercially available from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., Oryz Oy, H&R, Toyokuni Oil Co., Ltd., Fuji Kogyo Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0173] Examples of the animal oil include fish oil, beef tallow, whale oil, or oleyl alcohol derived therefrom.

[0174] From the viewpoint of processability, the content with respect to 100 parts by mass of the rubber component when containing oil is preferably 8 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 20 parts by mass or more. From the viewpoint of wear resistance performance, 80 parts by mass or less is preferable, 60 parts by mass or less is more preferable, and 40 parts by mass or less is further preferable. The oil content also includes the amount of oil contained in the oil-extended rubber.

[0175] ≪Liquid Rubber≫ The liquid rubber is not particularly limited as long as it is a polymer in a liquid state at room temperature (25 ° C). For example, liquid butadiene rubber (liquid BR), liquid styrene-butadiene rubber (liquid SBR), liquid isoprene rubber (liquid IR), liquid styrene-isoprene rubber (liquid SIR), liquid farnesene rubber, etc. can be mentioned. The liquid rubber may be used alone or in combination of two or more.

[0176] When containing liquid rubber, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 5 parts by mass or more. Also, the content of the liquid rubber is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 10 parts by mass or less. The content of the liquid rubber includes the amount of the extended liquid rubber used for extending the rubber component.

[0177] ≪Ester plasticizer≫ Examples of the ester plasticizer include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), bis(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), trixylenyl phosphate (TXP), etc. The ester plasticizer may be used alone or in combination of two or more.

[0178] When containing the ester plasticizer, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 5 parts by mass or more. Also, the content of the liquid rubber is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 10 parts by mass or less. The content of the ester plasticizer includes the amount of the extended ester plasticizer used for extending the rubber component.

[0179] The content of the plasticizer (total content when containing two or more) relative to 100 parts by mass of the rubber component constituting the first layer or the second layer is preferably more than 20 parts by mass, more preferably more than 30 parts by mass, and still more preferably more than 34 parts by mass. On the other hand, from the viewpoint of low fuel consumption performance, the content is preferably less than 120 parts by mass, more preferably less than 100 parts by mass, and still more preferably less than 80 parts by mass.

[0180] (Vulcanized rubber particles) Vulcanized rubber particles are particles made of vulcanized rubber. Specifically, rubber powder etc. specified in JIS K 6316:2017 can be used. From the viewpoints of environmental consideration and cost, recycled rubber powder produced from crushed waste tires etc. is preferable. Vulcanized rubber particles may be used alone or in combination of two or more kinds.

[0181] Vulcanized rubber particles are not particularly limited, and may be non-modified vulcanized rubber particles or modified vulcanized rubber particles. As commercially available products of vulcanized rubber, for example, products of Lehigh, Murakami Rubber Industry Co., Ltd. etc. can be used.

[0182] When containing vulcanized rubber particles, the content with respect to 100 parts by mass of the rubber component can be appropriately adjusted, for example, in the range of more than 1 part by mass and less than 80 parts by mass.

[0183] (Stearic acid) When containing stearic acid, the content with respect to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1 part by mass or more, from the viewpoint of processability. Also, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0184] (Zinc oxide) When containing zinc oxide, the content with respect to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, further preferably 1.5 part by mass or more, from the viewpoint of processability. Also, from the viewpoint of abrasion resistance performance, it is preferably 5.0 parts by mass or less, more preferably 4.5 parts by mass or less, further preferably 4.0 parts by mass or less.

[0185] (Wax) The wax is not particularly limited, and any wax commonly used in the tire industry can be preferably used. For example, petroleum waxes, mineral waxes, synthetic waxes, plant-derived waxes, etc. can be mentioned. Among them, petroleum waxes and plant-derived waxes are preferred, and petroleum waxes are more preferred. Examples of plant-derived waxes include rice wax, carnauba wax, candelilla wax, etc. Examples of petroleum waxes include paraffin wax, microcrystalline wax, these selected special waxes, etc., and paraffin wax is preferred. Note that the wax according to this embodiment does not contain stearic acid. As the wax, for example, those commercially available from Ouchi Shinsei Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., etc. can be used. The wax may be used alone or in combination of two or more kinds.

[0186] When containing wax, the content based on 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1 part by mass or more, from the viewpoint of the weather resistance of the rubber. Also, from the viewpoint of preventing the whitening of the tire due to blooming, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0187] (Antioxidant) The anti-aging agent is not particularly limited, but examples include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine-based anti-aging agents such as 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), N,N'-ditoly-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; bis, tris, polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, etc. Among them, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferred, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and polymers of 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. As commercially available products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., Flexsys, etc. can be used. The anti-aging agent may be used alone or in combination of two or more kinds.

[0188] When containing the anti-aging agent, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1 part by mass or more, from the viewpoint of ozone crack resistance of the rubber. Also, from the viewpoints of abrasion resistance performance and wet grip performance, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0189] (Processing Aid) Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, and the like. As processing aids, those commercially available from, for example, Schill + Seilacher, Performance Additives, etc. can be used. The processing aids may be used alone or in combination of two or more.

[0190] When containing a processing aid, the content thereof with respect to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1 part by mass or more, from the viewpoint of exerting the effect of improving processability. Further, from the viewpoints of abrasion resistance performance and fracture strength, it is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and still more preferably 5 parts by mass or less.

[0191] (Vulcanizing agent) Sulfur is preferably used as the vulcanizing agent. As sulfur, powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, etc. can be used. The vulcanizing agent may be used alone or in combination of two or more.

[0192] When containing sulfur as the vulcanizing agent, the content thereof with respect to 100 parts by mass of the rubber component is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, and still more preferably 0.5 part by mass or more, from the viewpoint of ensuring a sufficient vulcanization reaction. Further, from the viewpoint of preventing deterioration, it is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and still more preferably 3.0 parts by mass or less. In addition, when using oil-containing sulfur as the vulcanizing agent, the content of the vulcanizing agent is the total content of pure sulfur contained in the oil-containing sulfur.

[0193] Examples of vulcanizing agents other than sulfur include alkylphenol sulfur chloride condensates, sodium 1,6 - hexamethylene - dithiolsulfate dihydrate, 1,6 - bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. Commercially available products from companies such as Tago Chemical Industry Co., Ltd., Rancess Co., Ltd., and Flexis Co., Ltd. can be used as these vulcanizing agents other than sulfur. The vulcanizing agent may be used alone or in combination of two or more kinds.

[0194] (Vulcanization accelerator) Examples of vulcanization accelerators include sulfenamide - type, thiazole - type, thiuram - type, thiourea - type, guanidine - type, dithiocarbamic acid - type, aldehyde - amine - type or aldehyde - ammonia - type, imidazoline - type, or xanthate - type vulcanization accelerators, etc. Among them, sulfenamide - type, thiazole - type, and guanidine - type vulcanization accelerators are preferred. The vulcanization accelerator may be used alone or in combination of two or more kinds.

[0195] Examples of sulfenamide - type vulcanization accelerators include N - tert - butyl - 2 - benzothiazolylsulfenamide (TBBS), N - cyclohexyl - 2 - benzothiazolylsulfenamide (CBS), N,N - dicyclohexyl - 2 - benzothiazolylsulfenamide (DCBS), etc. Among them, N - cyclohexyl - 2 - benzothiazolylsulfenamide (CBS) is preferred.

[0196] Examples of thiazole - type vulcanization accelerators include 2 - mercaptobenzothiazole, cyclohexylamine salt of 2 - mercaptobenzothiazole, di - 2 - benzothiazolyldisulfide, etc. Among them, 2 - mercaptobenzothiazole is preferred.

[0197] Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatecholborate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, and the like. Among them, 1,3-diphenylguanidine (DPG) is preferred.

[0198] When containing a vulcanization accelerator, the content thereof per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more. Also, the content of the vulcanization accelerator per 100 parts by mass of the rubber component is preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, the breaking strength and elongation tend to be ensured.

[0199] <Various materials containing carbon atoms> In this specification, various materials containing carbon atoms (such as rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from carbon dioxide in the atmosphere. As a method for obtaining the various materials from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process of synthesizing methane from carbon dioxide may be converted.

[0200] The rubber composition constituting the third layer of the tread portion can be produced by a conventional method using the above-mentioned raw materials in the same manner as the rubber composition constituting the first layer or the second layer. However, as the rubber component, it is preferably included an isoprene-based rubber, and more preferably included an isoprene-based rubber and BR.

[0201] The content of the isoprene-based rubber in the rubber component constituting the third layer of the tread portion is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 80% by mass or more. Also, the content of BR in the rubber component constituting the third layer is preferably 10% by mass or more.

[0202] The BR contained in the rubber component constituting the third layer of the tread portion is preferably low-cis BR with a cis content of less than 50 mol%, and more preferably low-cis modified BR.

[0203] In the rubber composition constituting the third layer of the tread portion, the N2SA of carbon black is preferably 80 m 2 / g or less, more preferably 70 m 2 / g or less. Also, the N2SA is preferably 30 m 2 / g or more, more preferably 50 m 2 / g or more, and even more preferably 60 m 2 / g or more.

[0204] When the rubber composition constituting the third layer contains carbon black, the content thereof per 100 parts by mass of the rubber component is preferably more than 20 parts by mass, more preferably more than 25 parts by mass, and even more preferably more than 30 parts by mass from the viewpoint of the effects of the present invention. Also, from the viewpoint of low fuel consumption performance, it is preferably less than 100 parts by mass, more preferably less than 80 parts by mass, and even more preferably less than 60 parts by mass.

[0205] The rubber composition constituting the third layer of the tread portion may or may not contain resin as a plasticizer, but preferably contains oil.

[0206] The content of the resin per 100 parts by mass of the rubber component constituting the third layer (total content when two or more kinds are contained) is not particularly limited. For example, the lower limit value can be 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, etc., and the upper limit value can be 15 parts by mass or less, 10 parts by mass or less, 8 parts by mass or less, etc.

[0207] [Manufacturing method] The rubber composition can be manufactured by a known method. For example, it can be manufactured by kneading the above-mentioned respective components using a rubber kneading device such as an open roll, a closed kneader (Banbury mixer, kneader, etc.).

[0208] The kneading process includes, for example, a base kneading process of kneading compounding agents and additives other than vulcanizing agents and vulcanization accelerators, and a final kneading (F kneading) process of adding and kneading vulcanizing agents and vulcanization accelerators to the kneaded product obtained in the base kneading process. Further, the base kneading process can be divided into a plurality of processes if desired.

[0209] The kneading conditions are not particularly limited. For example, in the base kneading process, kneading is performed at a discharge temperature of 150 to 170°C for 3 to 10 minutes, and in the final kneading process, kneading is performed at 70 to 110°C for 1 to 5 minutes.

[0210] The tire according to this embodiment can be manufactured by a normal method using the rubber composition. That is, the rubber composition in an unvulcanized state is extruded by an extruder equipped with a die of a predetermined shape to conform to the shape of the first layer, second layer, or third layer of the tread portion, and on a tire molding machine, it is bonded together with other tire members while being adjusted to have a predetermined tire structure, and an unvulcanized tire is formed by molding in a normal method. By heating and pressurizing this unvulcanized tire in a vulcanizer, a tire can be manufactured. The vulcanization conditions are not particularly limited, and for example, a method of vulcanizing at 140 to 170°C for 10 to 40 minutes can be mentioned.

[0211] [Usage] In this specification, the tire can be used for any application, whether it is a pneumatic tire or a non-pneumatic tire, 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, a run-flat tire. Note that a passenger car tire is a tire assumed to be mounted on an automobile that runs on four wheels and has a maximum load capacity of less than 1400 kg. Also, a heavy-duty tire refers to a tire with a maximum load capacity of 1400 kg or more. Further, in this specification, the tire can be used for all-season tires, summer tires, and winter tires such as studless tires.

Examples

[0212] Examples (embodiments) that are considered preferable in practice are shown below, but the scope of the present invention is not limited to the embodiments.

[0213] Tires having a tread portion produced using a rubber composition obtained by changing the formulation according to Table 1 using the various chemicals shown below were examined, and the results calculated based on the following evaluation method are shown in Tables 2 and 3. NR: TSR20 SBR1: SBR produced according to the following Production Example 1 (S-SBR, Tg: -66°C, styrene content: 19% by mass, vinyl content: 19 mol%, non-oil extended) SBR2: SBR produced according to the following Production Example 2 (S-SBR, Tg: -50°C, styrene content: 30% by mass, vinyl content: 22 mol%, non-oil extended) SBR3: HPR830E manufactured by JSR Corporation (S-SBR, Tg: -23°C, styrene content: 39.5% by mass, vinyl content: 38.5 mol%, containing 10.0% by mass of oil-extended oil per 100% by mass of rubber solids) BR1: UBEPOL BR (registered trademark) 150B manufactured by UBE Industries, Ltd. (cis content: 98 mol%, vinyl content: 1 mol%) BR2: BR1250H manufactured by Nippon Zeon Co., Ltd. (tin-modified BR, polymerized using lithium as an initiator, vinyl content: 10 - 13 mol%, cis content: 39.7 mol%) CB1: Diablack I manufactured by Mitsubishi Chemical Corporation (N220, N2SA: 114m 2 / g, average primary particle size: 22 nm) CB2: Showblack N351H manufactured by Cabot Japan, Ltd. (N2SA: 69m 2 / g, average primary particle size: 29 nm) Silica: ULTRASIL VN3 manufactured by Evonik Degussa GmbH (N2SA: 175m 2 / g, average primary particle size: 18 nm) Silane coupling agent: Si266 manufactured by Evonik Degussa GmbH (bis(3-triethoxysilylpropyl)disulfide) Oil: VivaTec500 (TDAE oil) manufactured by H&R Co., Ltd. Wax: Oz Ace 0355 manufactured by Nippon Seiro Co., Ltd. Copolymer resin: Oppera PR383 manufactured by ExxonMobil (hydrogenated DCPD-C9 resin, containing styrene and cyclopentadiene as monomer components, Mw: 770, softening point: 103°C, styrene content: 1.78% by mass) Terpene resin: YS Resin PX1150N manufactured by Yasuhara Chemical Co., Ltd. (polyt terpene resin, softening point: 115 ± 5°C) Stearic acid: Bead Stearic Acid Tsubaki manufactured by NOF Corporation Zinc oxide: Zinc White No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Antioxidant 1: No Crack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 2: No Crack RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Sulfur 1: M95 (insoluble sulfur) manufactured by Nippon Karyu Kogyo Co., Ltd. Sulfur 2: HK-200-5 (5% oil-containing powdered sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: No Celer CZ-G (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: No Celer D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 3: No Celer NS-G (N-tert-butyl-2-benzothiazolylsulfenamide (TBBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0214] (Production Example 1: Production of SBR1) Charge a nitrogen-substituted autoclave reactor with cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene. Adjust the ratio of styrene and 1,3-butadiene so that the content of the styrene part is 19% by mass. After adjusting the temperature of the contents of the reactor, add n-butyllithium to initiate polymerization. Polymerize under adiabatic conditions, pour the polymerization solution into ethanol, and recover the precipitate. Dry the precipitate by blowing air and perform vacuum drying until the loss on drying becomes 0.1% to obtain SBR1.

[0215] (Production Example 2: Production of SBR2) Charge a nitrogen-substituted autoclave reactor with cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene. Adjust the ratio of styrene and 1,3-butadiene so that the content of the styrene part is 30% by mass. After adjusting the temperature of the contents of the reactor, add n-butyllithium to initiate polymerization. Polymerize under adiabatic conditions, pour the polymerization solution into ethanol, and recover the precipitate. Dry the precipitate by blowing air and perform vacuum drying until the loss on drying becomes 0.1% to obtain SBR2.

[0216] (Examples and Comparative Examples) According to the compounding formulations shown in Table 1, using a 1.7 L sealed Banbury mixer, knead the chemicals other than sulfur and vulcanization accelerators for 1 to 10 minutes until the discharge temperature reaches 150 to 160°C to obtain a kneaded product. Next, using a twin-screw open roll, add sulfur and vulcanization accelerators to the obtained kneaded product and knead it at 105°C for 4 minutes to obtain an unvulcanized rubber composition. Mold the obtained unvulcanized rubber composition into the shapes of the first layer, second layer (thickness: 4.0 mm), and third layer (thickness: 1.0 mm) of the tread, and laminate it together with other tire members to produce an unvulcanized tire, and press vulcanize it at 150°C for 35 minutes to obtain each test tire (195 / 65R15) described in Tables 2 and 3.

[0217] (Measurement of tan δ at 30°C and E* at 30°C) From the tread portion of each test tire, rubber test pieces are prepared by cutting out a piece with a length of 20 mm, a width of 4 mm, and a thickness of 1 mm such that the tire circumferential direction is the long side and the tire radial direction is the thickness direction. For each rubber test piece, using an Iplexer series manufactured by GABO, tanδ and complex elastic modulus (E*) are measured under the conditions of a temperature of 30 °C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of ±1.0%.

[0218] <Measurement of Modulus at 200% Elongation> Regarding dumbbell-shaped No. 7 test pieces with a thickness of 1 mm cut out from the inside of the second layer of the tread portion of each test tire such that the tire circumferential direction is the tensile direction and the tire radial direction is the thickness direction, in accordance with JIS K 6251:2017, a tensile test is carried out at a tensile speed of 3.3 mm / second in an atmosphere of 23 °C, and the modulus (MPa) at 200% elongation is measured.

[0219] <Chipping Resistance Performance> Each test tire is respectively mounted on a standard rim, filled with air up to the standard internal pressure, then mounted on a vehicle and run on an uneven road at a speed of 50 km / h for 4 hours. After running, for all the cracks generated on the tire surface, the circumferential length thereof was measured, and the maximum value of the circumferential length for each tire was determined. The results are expressed exponentially with Comparative Example 1 as 100 according to the following formula. The larger the index, the smaller the crack, indicating better chipping resistance performance. (Chipping Resistance Performance Index) = (Circumferential length of the crack of the tire in Comparative Example 1) / (Circumferential length of the crack of each test tire)×100

[0220] <Wet Grip Performance> Each test tire is mounted on all the wheels of a vehicle (domestic FF2000cc), and on an uneven road, the braking distance from an initial speed of 100 km / h is determined, and the measurement results are expressed exponentially according to the following calculation formula. The larger the index, the shorter the braking distance, indicating excellent wet grip performance. In the wet grip performance index, the reference comparative example is Comparative Example 1. (Wet Grip Performance Index) = (Braking distance of Comparative Example 1) / (Braking distance of each test tire)×100

[0221] <Overall performance> The sum of the chipping resistance performance index and the wet grip performance index is displayed as the overall performance index.

[0222]

Table 1

[0223]

Table 2

[0224]

Table 3

[0225] <Embodiment> Examples of embodiments of the present invention are shown below. [1] A tire having a tread portion, The tread portion includes at least a first layer constituting a tread surface, a second layer adjacent to the inner side in the tire radial direction of the first layer, and a third layer existing on the inner side in the tire radial direction of the second layer. The first layer and the second layer are composed of a rubber composition containing a rubber component containing styrene butadiene rubber and / or isoprene, and silica. At least one of the rubber compositions constituting the first layer and the second layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components. When the mass of the rubber component in the rubber composition constituting the first layer is 100% by mass, the total styrene amount in the rubber composition is S1 (mass%). When the total styrene amount in the rubber composition when the mass of the rubber component in the rubber composition constituting the second layer is 100% by mass is S2 (mass%), A tire in which S2 - S1 is greater than 0. 〔2〕When the thickness of the first layer is t1 (mm), the tire according to 〔1〕 above, wherein S1 × t1 is less than 100.0, preferably less than 95.0, more preferably less than 90.0. 〔3〕The tire according to 〔1〕 or 〔2〕 above, wherein S2 - S1 is more than 10.0, preferably more than 11.0% by mass, more preferably more than 12.5% by mass. 〔4〕The tire according to any one of 〔1〕 to 〔3〕 above, wherein the rubber composition constituting the second layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components. 〔5〕The tire according to any one of 〔1〕 to 〔4〕 above, wherein tanδ (30 °C tanδ1) of the rubber composition constituting the first layer at 30 °C is 0.30 or less. 〔6〕The tire according to any one of 〔1〕 to 〔5〕 above, wherein the complex elastic modulus (30 °C E*2) of the rubber composition constituting the second layer at 30 °C is 3.5 MPa or less. 〔7〕The tire according to any one of 〔1〕 to 〔6〕 above, wherein the rubber composition constituting the first layer contains 70 parts by mass or more of silica with respect to 100 parts by mass of the rubber component. 〔8〕The tire according to any one of 〔1〕 to 〔7〕 above, wherein S1 is more than 0 and less than 20.0, preferably 5.0 or more and less than 20.0, more preferably 8.0 or more and less than 20.0, still more preferably 11.0 or more and less than 20.0. 〔9〕The tire according to any one of 〔1〕 to 〔8〕 above, wherein the rubber composition constituting the second layer contains 70 parts by mass or more of silica with respect to 100 parts by mass of the rubber component. 〔10〕The tire according to any one of 〔1〕 to 〔9〕 above, wherein the modulus M2 at 200% elongation of the rubber composition constituting the second layer is 7.0 MPa or less, preferably 6.8 MPa or less. 〔11〕The tire according to any one of 〔1〕 to 〔10〕 above, wherein the ratio (30 °C tanδ2 / 30 °C tanδ3) of tanδ (30 °C tanδ2) of the rubber composition constituting the second layer to tanδ (30 °C tanδ3) of the rubber composition constituting the third layer at 30 °C is more than 1.0, preferably more than 1.5, more preferably more than 1.8. 〔12〕The tread portion has a plurality of circumferential grooves extending continuously in the tire circumferential direction, A tire according to any one of the above [1] to

[11] , wherein at least one groove wall of the plurality of circumferential grooves is provided with a recess that is recessed outward in the groove width direction from a groove edge appearing on the tread surface of the tread portion.

Explanation of Signs

[0226] 1 Circumferential groove 2 Land portion 3 Tread surface 4 Extension line of the tread surface 5 Extension line of the deepest part of the groove bottom of the circumferential groove 6 First layer 7 Second layer 8 Third layer 9 Extension line of the outer surface of the second layer N Normal line to the tread surface on the tire equator P Midpoint in the tire width direction of the land portion H Groove depth of the deepest part of the circumferential groove t1 Thickness of the first layer t2 Thickness of the second layer t3 Thickness of the third layer 10 Groove edge 11 Recess 12 Contour 43 Deepest part 44 Plane W1 Opening width (groove width on the tread surface) c1 Amount of recess from the groove edge at the groove bottom c2 Amount of recess from the groove edge at the groove bottom

Claims

1. A tire having a tread portion, wherein the tread portion comprises at least a first layer constituting a tread surface, a second layer adjacent to the inner side in the tire radial direction of the first layer, and a third layer existing on the inner side in the tire radial direction of the second layer; the first layer and the second layer are composed of a rubber composition containing a rubber component containing styrene butadiene rubber and / or isoprene-based rubber and silica; at least one of the rubber compositions constituting the first layer and the second layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components; when the mass of the rubber component in the rubber composition constituting the first layer is 100% by mass, the total styrene amount in the rubber composition is S1 (% by mass); when the total styrene amount in the rubber composition constituting the second layer is S2 (% by mass) when the mass of the rubber component is 100% by mass; a tire in which S2 - S1 is greater than 0.

2. The tire according to claim 1, wherein when the thickness of the first layer is t1 (mm), S1 × t1 is less than 100.

0.

3. The tire according to claim 1 or 2, wherein S2 - S1 is greater than 10.

0.

4. The tire according to claim 1 or 2, wherein the rubber composition constituting the second layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components.

5. The tire according to claim 1 or 2, wherein the tanδ (30°C tanδ1) of the rubber composition constituting the first layer at 30°C is 0.30 or less.

6. The tire according to claim 1 or 2, wherein the complex elastic modulus (30°C E*2) of the rubber composition constituting the second layer at 30°C is 3.5 MPa or less.

7. The tire according to claim 1 or 2, wherein the rubber composition constituting the first layer contains 70 parts by mass or more of silica with respect to 100 parts by mass of the rubber component.

8. The tire according to claim 1 or 2, wherein S1 is greater than 0 and less than 20.

0.

9. The tire according to claim 1 or 2, wherein the rubber composition constituting the second layer contains 70 parts by mass or more of silica with respect to 100 parts by mass of the rubber component.

10. The tire according to claim 1 or 2, wherein the modulus M2 at 200% elongation of the rubber composition constituting the second layer is 7.0 MPa or less.

11. The ratio (30 °C tanδ2 / 30 °C tanδ3) of tanδ (30 °C tanδ2) at 30 °C of the rubber composition constituting the second layer to tanδ (30 °C tanδ3) at 30 °C of the rubber composition constituting the third layer is more than 1.0, the tire according to claim 1 or 2.

12. The tread portion has a plurality of circumferential grooves extending continuously in the tire circumferential direction, The tire according to claim 1 or 2, wherein at least one groove wall of the plurality of circumferential grooves is provided with a recess that is recessed outward in the groove width direction from a groove edge appearing on the tread surface of the tread portion.

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