Tire

Abstract

Provided is a tire having improved overall performance of eccentric wear resistance, wet grip performance, and low fuel consumption performance. A tire having a tread portion provided with at least a first layer constituting a tread surface, a second layer adjacent to the first layer on the inside in the tire radial direction, and a third layer present on the inside in the tire radial direction of the second layer, the first layer and the second layer are configured from rubber compositions containing silica and a rubber component containing a styrene butadiene rubber and / or an isoprene rubber, 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. When S1 (mass%) is the total styrene content in the rubber composition constituting the first layer when the mass of the rubber component is 100 mass%, and S2 (mass%) is the total styrene content in the rubber composition when the mass of the rubber component constituting the second layer is 100 mass%, S1-S2 is greater than 0.

Description

Technical Field

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

[0002] It is described in Patent Document 1 that the following tire can improve the uneven wear resistance: a tire having a plurality of layers of staggered belt layers and one or more circumferential belt layers, the angle of the staggered belt cords with respect to the tire width direction being 20° to 45°, and a plurality of main grooves and sub-grooves being provided on the tread surface, and the outer groove wall surface in the sub-groove being located at the tire width direction position of one or more circumferential belt layers, or being located on the inner side in the tire width direction compared to the outermost end in the tire width direction of the circumferential belt layer. [Prior Art Document] [Patent Document]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2023-88085 Summary of the Invention [Problems to be Solved by the Invention]

[0004] However, in Patent Document 1, tire performance other than uneven wear resistance is not considered.

[0005] An object of the present invention is to provide a tire with improved comprehensive performance of uneven wear resistance, wet grip performance, and low fuel consumption performance. [Means for Solving the Problems]

[0006] The present invention relates to a tire, characterized in that it is a tire having a tread portion, the tread portion includes at least a first layer constituting the tread surface, a second layer adjacent to the first layer on the inner side in the tire radial direction, 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 made of a rubber composition containing a rubber component including styrene-butadiene rubber and / or isoprene-based rubber and silica, at least any one of the rubber compositions constituting the first layer and the second layer contains a copolymer resin including styrene and cyclopentadiene as monomer components, in the rubber composition constituting the first layer, when the mass of the rubber component is set to 100% by mass, the total styrene amount in the rubber composition is set to S1 (% by mass), in the rubber composition constituting the second layer, when the mass of the rubber component is set to 100% by mass, the total styrene amount in the rubber composition is set to S2 (% by mass), S1 - S2 is greater than 0. [Advantages of the Invention]

[0007] According to the present invention, a tire with improved comprehensive performance in terms of resistance to uneven wear, wet grip performance, and low fuel consumption can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0008]

Figure 1

Figure 2

Figure 3

DESCRIPTION OF REFERENCE NUMERALS

[0009] A tire according to an embodiment of the present invention is characterized in that it is a tire having a tread surface, and the tread surface includes at least a first layer constituting the tread surface, a second layer adjacent to the first layer on the inner side in the tire radial direction, 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 made of a rubber composition containing a rubber component including styrene-butadiene rubber and / or isoprene rubber and silica. At least any one of the rubber compositions constituting the first layer and the second layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components. In the rubber composition constituting the first layer, when the mass of the rubber component is set to 100% by mass, the total styrene amount in the rubber composition is set to S1 (% by mass). In the rubber composition constituting the second layer, when the mass of the rubber component is set to 100% by mass, the total styrene amount in the rubber composition is set to S2 (% by mass), and S1 - S2 > 0.

[0010] Although it is not intended to be limited theoretically, in the tire of the present invention, as the principle of improving the comprehensive performance of uneven wear resistance, wet grip performance, and low fuel consumption performance, for example, the following speculation can be made.

[0011] First, (1) by making the tread surface composed of three or more rubber compositions, multiple rubber layer interfaces are formed on the tread surface. It is considered that, thus, when shear deformation occurs on the tread surface, energy loss can be generated due to the friction brought about by the fine molecular motion of each rubber phase constituting the interface, so it contributes to wet grip performance and low fuel consumption performance. At the same time, it is considered that (2) silica is considered to contribute to improving low fuel consumption performance and reinforces the rubber composition by chemically bonding with styrene-butadiene rubber and isoprene rubber via a silane coupling agent. Therefore, by making the first layer and the second layer contain a rubber component including styrene-butadiene rubber and / or isoprene rubber and silica, the tread surface is reinforced, which contributes to improving uneven wear resistance. Further, it is considered that (3) since the copolymer resin containing styrene and cyclopentadiene as monomer components has a large volume, by making at least any one of the rubber compositions constituting the first layer and the second layer contain this copolymer resin, flexibility can be imparted to the rubber composition without impairing the reinforcing effect, so it contributes to improving wet grip performance.

[0012] As described above, by making the rubber composition have reinforcing properties and flexibility, the entire tread surface becomes a hard and flexible state, so uneven wear of the tread surface can be suppressed.

[0013] In addition, when uneven wear occurs, (4) by making S1 - S2 > 0, if the wear progresses, the first layer with a large styrene amount becomes thinner, and in the entire tread surface, the proportion of the second layer with a styrene amount less than that of the first layer and less likely to generate heat increases. It is considered that, therefore, it helps to delay the progress of wear in the part where uneven wear occurs.

[0014] Furthermore, it can be considered that by making the first layer contain more styryl groups, the heat generation based on the styryl groups can increase the tanδ at 0°C of the first layer, thus contributing to improving the wet grip performance.

[0015] It can be considered that through the synergistic effect of the above (1) to (5), a particularly remarkable effect of improving the comprehensive performance of wear resistance, wet grip performance and low fuel consumption performance can be achieved.

[0016] When the thickness of the above first layer is set to t1 (mm), S1 × t1 is preferably less than 100.0, more preferably less than 50.0, and further preferably less than 25.0.

[0017] When S1 is large, by reducing the thickness of the first layer, it is possible to reduce the tanδ at 30°C while maintaining a high tanδ at 0°C, and both low fuel consumption performance and wet grip performance can be taken into account.

[0018] S2 is preferably greater than 0 and less than 20.

[0019] It can be considered that by setting S2 within the above range, minute styrene phase regions can be formed within the second layer, and it becomes easier to absorb external deformation based on the interface between the styrene phase regions (domin) and the surrounding rubber molecular chains.

[0020] Preferably, the rubber composition constituting the above first layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components.

[0021] It can be considered that by making the first layer contain this resin, the rubber composition on the tread surface becomes hard and flexible, so the wear resistance is further improved. In addition, it can be considered that the heat generation property at the tread surface is improved, so the wet grip performance is also further improved.

[0022] The ratio of the loss tangent (tanδ1) of the rubber composition constituting the above first layer at 70°C to the contact area ratio R (70°C tanδ1 / R) is preferably less than 0.29.

[0023] It can be considered that by setting 70°C tanδ1 / R within the above range, as the tanδ at 70°C of the first layer increases and the contact area ratio R increases, the deformation of the first layer decreases and heat generation is suppressed. It can be considered that as a result, the softening of the first layer decreases and the wear resistance is improved.

[0024] The ratio of the loss tangent (tanδ2) of the rubber composition constituting the above second layer at 70°C to the contact area ratio R (70°C tanδ2 / R) is preferably greater than 0.20.

[0025] It is considered that by setting 70°C tanδ2 / R within the above range, as the grounding area ratio R increases, the 70°C tanδ of the second layer increases, and thus the energy absorption efficiency at the second layer is improved, and the resistance to uneven wear is enhanced.

[0026] The modulus M2 of the rubber composition constituting the above-mentioned second layer at 200% elongation is preferably 9.5 MPa or less.

[0027] It is considered that by setting the modulus of the rubber composition constituting the second layer at 200% elongation within the above range, when there is deformation from the road surface that is not fully absorbed by the first layer, the second layer can deform softly and it becomes easier to absorb the deformation.

[0028] The rubber composition constituting the above-mentioned second layer preferably contains 80 parts by mass or more of silica relative to 100 parts by mass of the above-mentioned rubber component.

[0029] It is considered that the reinforcing property brought by silica can be obtained, and the resistance to uneven wear is further improved.

[0030] The ratio (70°C tanδ2 / 70°C tanδ3) of 70°C tanδ2 to the loss tangent at 70°C (70°C tanδ3) of the rubber composition constituting the above-mentioned third layer is preferably greater than 1.0.

[0031] It is considered that by increasing the heat generation property of the second layer relative to the heat generation property of the rubber composition constituting the third layer, even when there is deformation that is not fully absorbed by the first layer, the second layer can easily absorb the deformation.

[0032] The above-mentioned tread portion preferably has a plurality of circumferential grooves extending continuously in the tire circumferential direction, and on at least one groove wall of the circumferential grooves, there is a recessed portion that is recessed outward in the groove width direction compared to the groove edge of the tread surface that appears on the above-mentioned tread portion.

[0033] It is considered that by providing the recessed portion on the groove wall of the circumferential groove, a void is formed inside the tread, and the impact can be absorbed and the propagation can be suppressed in this void portion.

[0034] [Definition] The "tread portion" is a component that includes the portion forming the ground contact surface of the tire. When, in the tire radial cross-section, there are components such as a belt layer or a belt reinforcing layer, a carcass layer, etc. formed of steel or textile materials, it is a component disposed more radially outward of the tire than these components.

[0035] The "rubber component of the rubber composition" refers to the component that participates in cross-linking within the rubber composition, and is usually a component having a weight average molecular weight (Mw) of 10,000 or more.

[0036] "Total styrene content S in the rubber composition" means: when the mass of the rubber component is set to 100% by mass, the total styrene content (% by mass) in the rubber composition, which is the total of the content of the styrene moiety contained in the rubber component and the content of the styrene moiety contained in the compounding agents other than the rubber component. As the styrene moiety, there is no particular limitation as long as it is a group having a styrene structure. For example, styrene, α-methylstyrene, vinyltoluene, chlorostyrene, etc. can be cited.

[0037] That is, first, for each rubber component, the value obtained by multiplying the content (% by mass) of the styrene moiety by the mass fraction in the rubber component is calculated respectively, and the total value (% by mass) obtained by summing these values is obtained. Then, for the compounding agents other than the rubber component contained in the rubber composition and containing a styrene moiety, the value obtained by multiplying the content (% by mass) of the styrene moiety in each compounding agent containing a styrene moiety by the mass fraction relative to 100 parts by mass of the rubber component is calculated, and the total value (% by mass) obtained by summing them is obtained. The sum of these two total values is taken as the total styrene content S (% by mass). Therefore, it is calculated by {Σ(content (% by mass) of the styrene moiety of each rubber containing a styrene moiety × content (% by mass) of each rubber containing a styrene moiety in the rubber component / 100) + Σ(content (% by mass) of the styrene moiety of each compounding agent containing a styrene moiety other than the rubber component × compounding amount (parts by mass) of each compounding agent containing a styrene moiety relative to 100 parts by mass of the rubber component / 100)}.

[0038] For example, when the rubber component consists of 30% by mass of the first BR (content of the styrene moiety: 25% by mass), 60% by mass of the second SBR (content of the styrene moiety: 27.5% by mass), and 10% by mass of BR, and in the rubber composition, in addition to this rubber component, 20 parts by mass of the first resin having a styrene moiety (content of the styrene moiety: 5% by mass) and 10 parts by mass of the second resin having a styrene moiety (content of the styrene moiety: 1% by mass) are further contained relative to 100 parts by mass of the rubber component, the total styrene content S in the rubber composition relative 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)}.

[0039] "Normal state" means: the state of being assembled on a normal rim and filled with air at normal internal pressure without load.

[0040] "Normal rim" means: in the standard system including the standard on which the tire is based, the rim specified by the standard for each tire. For example, it refers to the standard rim in the applicable sizes recorded in the "JATMA YEAR BOOK" of JATMA (Japan Automobile Tire Manufacturers Association), the "Measuring Rim" recorded in the "STANDARDS MANUAL" of ETRTO (The European Tyre and Rim Technical Organisation), and the "Design Rim" recorded in the "YEAR BOOK" of TRA (The Tire and Rim Association, Inc.). Refer to them in the order of JATMA, ETRTO, and TRA, and follow the standards of the applicable sizes if any when referring. In addition, for a tire not specified in the above standards, it refers to the rim with the smallest rim width among the rims with the minimum diameter that can be assembled and maintain the internal pressure (i.e., no air leakage occurs between the rim and the tire).

[0041] "Normal internal pressure" means: in the standard system including the standard on which the tire is based, the air pressure specified by the standard for each tire. For example, it refers to the "maximum air pressure" of JATMA, the "INFLATION PRESSURE" of ETRTO, and the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" of TRA. Similar to the case of the normal rim, refer to them in the order of JATMA, ETRTO, and TRA, and follow the standards of the applicable sizes if any when referring. In addition, for a tire not specified in the above standards, it refers to the normal internal pressure (where it is 250 kPa or more) of other tire sizes (where the tire is specified in the standard) with the above normal rim as the standard rim. When there are multiple normal internal pressures of 250 kPa or more recorded, it refers to the minimum value among them.

[0042] "Normal load" refers to the load specified for each tire in the standard system that includes the standard on which the tire is based. For example, it refers to the maximum value recorded in "Maximum Load Capacity" of JATMA, "LOAD CAPACITY" of ETRTO (Load Capacity), and "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" of TRA. Similar to the case of the normal rim and normal internal pressure, it is referenced in the order of JATMA, ETRTO, and TRA, and when there are applicable dimensions during the reference, the standards thereof shall be followed. At the same time, for tires not specified in the above standards, the maximum load capacity W calculated separately shall be L set as the normal load.

[0043] "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 cross-section of the tire based on 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 set as R, Ht can be obtained by (Dt - R) / 2. When there are patterns or characters on the tire sidewall, Wt is the value obtained by removing these. In addition, the maximum load capacity has the same meaning as the above normal load.

[0044]

Mathematical formula 1

[0045] "Contact area" refers to the area of the tread obtained from the contour when the tire is pressed against the ground. It can be obtained by assembling the tire on the normal rim, applying the normal internal pressure, leaving it to stand at 25°C for 24 hours, then coating the surface of the tire tread with ink, loading the tire with the normal load (maximum load capacity) and pressing it vertically against cardboard (the camber angle is 0°) to transfer the ink. The area of the contact area refers to the total contact area. The total contact area can be calculated by rotating the tire by 72 degrees in sequence, performing the above transfer operation at a total of 5 positions, and taking the average value of the 5 obtained areas.

[0046] The "effective contact area region" is the area of the tread of the tire that comes into contact with the ground when the tire is pressed against the ground. It can be obtained by assembling the tire on a standard rim, filling it with the standard internal pressure, allowing it to stand at 25°C for 24 hours, then applying ink to the surface of the tire tread, loading the tire with the standard load (maximum load capacity), and vertically pressing it onto cardboard (camber angle is 0°) to transfer the ink. The area of the effective contact area region refers to the effective contact area. The effective contact area can be calculated by rotating the tire 72 degrees successively, performing the above transfer operation at a total of 5 positions, and taking the average of the 5 obtained areas.

[0047] The "ground contact area ratio R of the tread portion in the ground contact surface" is calculated by the following formula using the total ground contact area of the above contact area region and the effective contact area of the above effective contact area region. Ground contact area ratio R = (Effective contact area / Total ground contact area)

[0048] The "dimensions of each part of the tire" are as follows: Unless otherwise specified, the "dimensions of each part of the tire" appearing on the outer side surface of the tire are values specified in the standard state. On the other hand, for the "dimensions of each part of the tire" existing inside the tire and in the tire cross-section, for example, the tire is cut by a plane containing the tire rotation axis, and the values are specified in a state where the cut tire piece maintains the rim width of the standard rim.

[0049] The "loss tangent (tanδ) of the rubber composition" is the tanδ under each condition measured in the tensile mode using a dynamic viscoelasticity measuring device (for example, the EPLEXOR series manufactured by GABO). The sample used in the dynamic viscoelasticity measurement is a vulcanized rubber composition with a length of 20 mm × width of 4 mm × thickness of 1 mm. When cutting out and making a sample from the tire, if the part for making the sample is the tread portion, the length direction of the sample is aligned with the tire circumferential direction, and the thickness direction of the sample is aligned with the tire radial direction. In addition, the sample is made as close as possible to the specified dimensions. Since the strain applied to the sample is standardized with respect to the length and the measured tanδ is standardized with the width and thickness of the sample, it can be considered that there is no influence based on the sample size.

[0050] "Tanδ at 70°C" is the loss tangent (tanδ) measured under the conditions of a temperature of 70°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±1%, and a tensile mode.

[0051] "Tanδ at 0°C" is the loss tangent (tanδ) measured under the conditions of a temperature of 0°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±2.5%, and a tensile mode.

[0052] "Tanδ at 30°C" is the loss tangent (tanδ) 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 a tensile mode.

[0053] "Modulus at 200% elongation" is the stress (MPa) at 200% elongation when a test piece in the shape of dumbbell No. 7 with a thickness of 1 mm is produced and a tensile test is carried out at a tensile speed of 3.3 mm / second in an atmosphere of 23°C according to JIS K 6251:2017.

[0054] "Groove" means: a recess (extending radially inward of the tire) formed on the tread surface of the tire, and a recess with an opening width of 2.0 mm or more on the tread surface. A recess that is the same but less than 2.0 mm is called a "sipe".

[0055] "Circumferential groove" means: a groove extending continuously in the circumferential direction of the tire. The circumferential groove may extend linearly in the circumferential direction, or may extend in a wave shape, sine shape, or sawtooth shape in the circumferential direction.

[0056] "Content of styrene moiety" is calculated by pyrolysis gas chromatography. In addition, "pyrolysis gas chromatography" in this specification means: a method of heating a sample by a pyrolysis device, separating each component contained in the gas phase components generated by this heating through a separation column, and analyzing the separated components.

[0057] "Vinyl content (amount of 1,2-bonded butadiene units)" is similarly calculated by pyrolysis gas chromatography.

[0058] "Cis content (amount of cis-1,4-bonded butadiene units)" is a value calculated by infrared absorption spectroscopic analysis according to JIS K 6239-2:2017, and is applicable to rubber components having repeating units derived from butadiene such as BR, for example.

[0059] "Weight-average molecular weight (Mw)" can be obtained by conversion to standard polystyrene based on the measured values according to 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 applicable to SBR, BR, plasticizers, etc.

[0060] "Nitrogen adsorption specific surface area of carbon black (N2SA)" is measured according to JIS K 6217-2:2017.

[0061] "Nitrogen adsorption specific surface area of silica (N2SA)" is measured by the BET method according to ASTM D3037-93.

[0062] "Average primary particle size" is a value obtained by taking a photograph of particles with a transmission or scanning electron microscope and calculating the arithmetic average of the particle sizes of 400 particles. When the shape of the particles is spherical, the diameter of the sphere is defined as the particle size; when the shape is other than spherical, the equivalent circle diameter calculated from the microscope image (the positive square root of {4 × (particle area) / π}) is defined as the particle size.

[0063] "Plasticizer" refers to a material that imparts plasticity to the rubber component and is a component that can be extracted from the rubber composition with acetone. In addition, plasticizers include plasticizers that are liquid at 25°C (liquid state) and plasticizers that are solid at 25°C. Among them, waxes and stearic acid commonly used in the tire industry are not included.

[0064] "Softening point of resin" is the temperature at which the ball drops when measuring the softening point specified in JIS K 6220-1:2015 7.7 using a ring and ball softening point measuring device.

[0065] Regarding the manufacturing sequence of the tire according to an embodiment of the present invention, the following description is an example for explaining the present invention, and the gist thereof is not intended to limit the scope of the technology of the present invention to this description. In addition, in this specification, when using "~" to represent a numerical range, it is assumed to include the numerical values at both ends.

[0066] <Tread surface> Figure 1 It is a cross-sectional view schematically showing a part of the tread of the tire according to an embodiment of the present invention. Figure 1 In this figure, the up-down 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.

[0067] The tread surface according to this embodiment has three or more rubber layers. The structure of the rubber layer is: the first layer constituting the tread surface, the second layer adjacent to the first layer on the inner side in the radial direction, and the third layer existing on the inner side in the radial direction of the second layer. One or more rubber layers may further be provided between the second layer and the third layer, or between the third layer and the belt layer.

[0068] From the viewpoint of the effects of the present invention, in the rubber composition constituting the first layer, when the mass of the rubber component is set to 100% by mass, the total styrene amount S1 in the rubber composition is preferably 20.0% by mass or more, more preferably 21.0% by mass or more, further preferably 22.0% by mass or more, further preferably 23.0% by mass or more, further preferably 24.0% by mass or more, further preferably 25.0% by mass or more, and particularly preferably 26.0% by mass or more. In addition, from the viewpoint of low fuel consumption performance, S1 is preferably 40.0% by mass or less, more preferably 38.0% by mass or less, and further preferably 35.0% by mass or less.

[0069] From the viewpoint of the effects of the present invention, in the rubber composition constituting the second layer, when the mass of the rubber component is set to 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 14.0% by mass or more, and particularly preferably 15.0% by mass or more. Further, from the viewpoint of low fuel consumption performance, S2 is preferably 25.0% by mass or less, more preferably 20.0% by mass or less, still more preferably 18.0% by mass or less.

[0070] From the viewpoint of the effects of the present invention, S1 - S2 is preferably greater than 0% by mass, more preferably greater than 3.0% by mass, still more preferably greater than 5.0% by mass, further preferably greater than 7.0% by mass, and particularly preferably greater than 10.0% by mass. Further, from the viewpoint of forming minute styrene phase regions in the second layer and being liable to absorb external deformation based on the interfaces between the styrene phase regions and the surrounding rubber molecular chains, S1 - S2 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.

[0071] In the rubber composition constituting the third layer, there is no particular limitation on the total styrene amount S3 in the rubber composition when the mass of the rubber component is set to 100% by mass. For example, it may be 0% by mass.

[0072] In addition, the total styrene amount of the rubber composition can be appropriately adjusted by the types and compounding amounts of the following rubber components. For example, by compounding styrene - butadiene rubber having a high styrene content, resin containing styrene as a monomer component, etc., the total styrene amount S can be increased. Conversely, by reducing the compounding amount of styrene - butadiene rubber, etc., the total styrene amount S can be decreased.

[0073] From the viewpoint of the effects of the present invention, the 70°C tanδ (70°C tanδ1) of the rubber composition constituting the first layer is preferably 0.12 or more, more preferably 0.15 or more, still more preferably 0.17 or more. Further, from the viewpoint of resistance to uneven wear performance, 70°C tanδ1 is preferably 0.25 or less, more preferably 0.23 or less, still more preferably 0.20 or less.

[0074] From the viewpoint of the effects of the present invention, the 70°C tanδ (70°C tanδ2) of the rubber composition constituting the second layer is preferably 0.10 or more, more preferably 0.11 or more, still more preferably 0.12 or more. Further, from the viewpoint of resistance to uneven wear performance, 70°C tanδ2 is preferably 0.20 or less, more preferably 0.18 or less, still more preferably 0.15 or less.

[0075] From the viewpoint of the effects of the present invention, the 70°C tanδ (70°C tanδ3) of the rubber composition constituting the third layer is preferably 0.02 or more, more preferably 0.04 or more, and further preferably 0.05 or more. In addition, from the viewpoint of the resistance to uneven wear performance, 70°C tanδ3 is preferably 0.12 or less, more preferably 0.10 or less, and further preferably 0.08 or less.

[0076] 70°C tanδ2 / 70°C tanδ3 is preferably greater than 1.0, more preferably greater than 1.5, further preferably greater than 2.0, and particularly preferably greater than 2.3.

[0077] In addition, the 70 tanδ of the rubber composition can be appropriately adjusted by the types and compounding amounts of the following rubber components, fillers, plasticizers, etc. For example, 70°C tan can be increased by increasing the total styrene amount of the rubber composition.

[0078] From the viewpoint of the effects of the present invention, the modulus (M2) of the rubber composition constituting the second layer at 200% elongation is preferably 5.0 MPa or more, more preferably 6.0 MPa or more, and further preferably 8.0 MPa or more. In addition, from the viewpoint of the resistance to uneven wear performance, M2 is preferably 12.0 MPa or less, more preferably 11.0 MPa or less, further preferably 10.0 MPa or less, and particularly preferably 9.5 MPa or less.

[0079] From the viewpoint of the effects of the present invention, the modulus (M1) of the rubber composition constituting the first layer at 200% elongation is preferably 4.5 MPa or more, more preferably 5.0 MPa or more, and further preferably 6.0 MPa or more. In addition, from the viewpoint of the resistance to uneven wear performance, M1 is preferably 12.0 MPa or less, more preferably 10.0 MPa or less, and further preferably 8.0 MPa or less. In addition, the modulus (M3) of the rubber composition constituting the third layer at 200% elongation is not particularly limited.

[0080] Figure 1 Among them, the double arrow t1 is the thickness of the first layer 6, the double arrow t2 is the thickness of the second layer 7, and the double arrow t3 is the thickness of the third layer 8. Figure 1 Among them, the grounding portion 2 is represented by the symbol P at the midpoint in the tire width direction. The straight line represented by the symbol N is the straight line (normal line) passing through the point P and perpendicular to the tangent plane at that point P. In this specification, the thicknesses t1, t2, and t3 are Figure 1 in the cross-section, measured along the normal line N drawn from the point P on the tread surface at a position without grooves.

[0081] Regarding the "thickness of each rubber layer constituting the tread", when there are grooves on the tire equatorial plane, the thickness of the rubber layer in the central part of the tire width direction of the grounding part closest to the tire equatorial plane is defined as the thickness of each rubber layer constituting the tread.

[0082] From the viewpoint of low fuel consumption performance, the thickness t1 of the first layer is preferably 0.3 mm or more, more preferably 0.4 mm or more, and further preferably 0.5 mm or more. In addition, from the viewpoint of resistance to uneven wear, t1 is preferably 5.0 mm or less, more preferably 4.5 mm or less, further preferably 4.0 mm or less, further preferably 3.5 mm or less, and particularly preferably 3.0 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 further preferably 3.5 mm or more. In addition, t2 is preferably 10.0 mm or less, more preferably 8.0 mm or less, and further 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 further preferably 1.5 mm or more. In addition, t3 is preferably 5.0 mm or less, more preferably 4.5 mm or less, and further preferably 4.0 mm or less.

[0085] From the viewpoint of the effects of the present invention, S1×t1 is preferably less than 100.0, more preferably less than 70.0, further preferably less than 50.0, and particularly preferably less than 25.0. In addition, from the viewpoint of ensuring that S1 and t1 are above a certain value, S1×t1 is preferably greater than 8.0, more preferably greater than 10.0, and further preferably greater than 15.0.

[0086] The tread part according to the present embodiment preferably has a plurality of circumferential grooves 1 extending continuously in the tire circumferential direction. The circumferential grooves 1 may extend linearly in the circumferential direction or extend in a serrated shape in the circumferential direction. In addition, the tread part according to the present embodiment preferably has a grounding part 2 divided by the circumferential grooves 1 in the tire width direction.

[0087] The groove depth H of the deepest part of the circumferential groove 1 can be 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. In addition, for example, when there are a plurality of circumferential grooves 1, the groove depth H can be set as 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 with the deepest groove depth among the plurality of circumferential grooves 1 ( Figure 1 the left circumferential groove 1 in the figure).

[0088] From the viewpoint of the effects of the present invention, the contact area ratio R of the tire according to the present embodiment is preferably 0.60 or more, more preferably 0.65 or more, still more preferably 0.68 or more, and particularly preferably 0.70 or more. Further, from the viewpoint of the grip performance, the contact area ratio R is preferably 0.90 or less, more preferably 0.88 or less, still more preferably 0.85 or less.

[0089] From the viewpoint of the uneven wear resistance, the ratio of 70°C tanδ1 to the contact area ratio R of the tread portion in the contact surface (70°C tanδ1 / R) is preferably less than 0.40, more preferably less than 0.35, still more preferably less than 0.29. Further, from the viewpoint of the low fuel consumption performance, 70°C tanδ1 / R is preferably greater than 0.18, more preferably greater than 0.20, still more preferably greater than 0.22.

[0090] From the viewpoint of the uneven wear resistance, the ratio of 70°C tanδ2 to the contact area ratio R of the tread portion in the contact surface (70°C tanδ2 / R) is preferably greater than 0.17, more preferably greater than 0.20, still more preferably greater than 0.22. Further, from the viewpoint of the low fuel consumption performance, it is preferably less than 0.35, more preferably less than 0.31, still more preferably less than 0.29.

[0091] <Circumferential groove> Figure 2 shows an enlarged plan view of the circumferential groove 1 according to an embodiment of the present invention. Figure 2 In, the groove edge 10 of the circumferential groove 1 is represented by a solid line, and the contour 12 of the groove wall when viewed from above the tread portion is represented by a dashed line. Further, the recessed area (recessed portion 11) between the groove edge 10 and the contour 12 of the groove wall of the circumferential groove 1 is represented by small dots.

[0092] Figure 3 shows Figure 2 the cross-sectional view taken along the line A-A of the circumferential groove 1 shown. As Figure 3 shown, in the circumferential groove 1, recessed portions 11 having a constant recess amount in the tire circumferential direction are provided in the groove walls on both sides. The recessed portion 11 forms a plane 44 between the deepest part of the recessed portion and the groove edge 10, for example, but is not limited to such a form.

[0093] The total recess amount of the circumferential groove 1 is preferably 0.10 to 0.90 times the groove width W1 of the circumferential groove 1, more preferably 0.15 to 0.80 times, still more preferably 0.20 to 0.70 times. Further, in the present specification, when the circumferential groove 1 is Figure 3 in the form of, the "total recess amount of the circumferential groove" means c1 + c2.

[0094] [Rubber composition] The rubber composition constituting the first layer or the second layer of the tread portion according to the present embodiment (hereinafter, sometimes referred to as the rubber composition according to the present embodiment) contains a rubber component including styrene-butadiene rubber (SBR) and / or isoprene-based rubber, and silica. At least any one of the rubber compositions constituting the first layer and the second layer is a composition containing a copolymer resin including styrene and cyclopentadiene as monomer components, and any one of them can be manufactured using the raw materials described below. Hereinafter, the rubber composition according to the present embodiment will be described.

[0095] The rubber composition constituting the first layer preferably contains two or more diene rubbers selected from SBR, isoprene-based rubber, and butadiene rubber (BR), more preferably contains SBR and isoprene-based rubber, and further preferably contains SBR, isoprene-based rubber, and BR.

[0096] The rubber composition constituting the second layer preferably contains one or more diene rubbers selected from SBR, isoprene-based rubber, and BR, more preferably contains two or more diene rubbers selected from SBR, isoprene-based rubber, and BR, and further preferably contains SBR and isoprene-based rubber.

[0097] <Rubber component> As the rubber component, it is preferable to contain a diene rubber. As the diene rubber, a rubber component usually used in the tire industry can be optionally preferably used. Specifically, for example, isoprene-based rubber, BR, SBR, styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), etc. can be cited. These diene rubbers can be used alone or in combination of two or more.

[0098] The content of the diene 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 further preferably 99% by mass or more. The rubber component can also be only a diene rubber component.

[0099] (SBR) As SBR, there is no particular limitation, and solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), modified SBRs thereof (modified S-SBR, modified E-SBR), etc. can be cited. As the modified SBR, SB modified at the terminal and / or main chain; modified SBR coupled with tin, silicon compounds, etc. (condensates, substances having a branched structure, etc.) can be cited. These SBRs can be used alone or in combination of two or more.

[0100] From the viewpoint of the effects of the present invention, the styrene content of SBR is preferably greater than 18% by mass, more preferably greater than 20% by mass, and further preferably greater than 25% by mass. On the other hand, the styrene content of SBR is preferably less than 60% by mass, more preferably less than 50% by mass, and further preferably less than 45% by mass. When the styrene content of SBR is greater than 60% by mass, the styrene groups are adjacent, the polymer becomes too hard, the crosslinking easily becomes uneven, the blowout property during high-temperature driving may deteriorate, the temperature correlation increases, the property change with respect to temperature change increases, and it tends to be impossible to obtain stable grip performance during driving and in the later stage. In addition, in this specification, the styrene content of SBR is measured by the above-mentioned measurement method.

[0101] The vinyl content of SBR is preferably greater than 10 mol%, more preferably greater than 15 mol%, and further preferably greater than 20 mol%. In addition, the vinyl content of SBR is preferably less than 70 mol%, more preferably less than 65 mol%, and further preferably less than 60 mol%. In addition, in this specification, the vinyl content of SBR is measured by the above-mentioned measurement method.

[0102] From the viewpoint of wet grip performance, the glass transition temperature (Tg) of SBR is preferably -80 °C or higher, more preferably -70 °C or higher, and further preferably -65 °C or higher. In addition, from the viewpoint of low fuel consumption performance, the Tg of SBR is preferably -40 °C or lower, more preferably -45 °C or lower, further preferably -50 °C or lower, and further preferably -55 °C or lower. In addition, the Tg of SBR in this specification can be obtained by differential scanning calorimetry (DSC) according to JIS K 7121 for the pure SBR component after removing the extender oil with acetone according to JIS K 6229.

[0103] The weight average molecular weight (Mw) of SBR is preferably greater than 200,000, more preferably greater than 300,000, further preferably greater than 400,000, and particularly preferably greater than 500,000. In addition, from the viewpoints of crosslinking uniformity, etc., Mw is preferably less than 2,000,000, more preferably less than 1,500,000, and further preferably less than 1,000,000. In addition, the Mw of SBR is measured by the above-mentioned measurement method.

[0104] As SBR, oil-extended SBR or non-oil-extended SBR can be used. In this specification, as SBR, commercially available substances from JSR Corporation, Sumitomo Chemical Co., Ltd., UBE Industries, Ltd., Asahi Kasei Corporation, ZS ELASTOMERS Co., Ltd., ARLANXEO Corporation, etc. can be used.

[0105] The content of SBR in the rubber component constituting the first layer can be appropriately set in such a way that S1 - S2 and S1×t1 are within the above ranges, but it is preferably 30% by mass or more, more preferably 40% by mass or more, further preferably 50% by mass or more, further preferably 60% by mass or more, further preferably 70% by mass or more, and particularly preferably 80% by mass or more. In addition, the content of this SBR in the rubber component is preferably 95% by mass or less, more preferably 90% by mass or less.

[0106] The content of SBR in the rubber component constituting the second layer can be appropriately set in such a way that S1 - S2 is within the above range, but it is preferably 20% by mass or more, more preferably 30% by mass or more, further preferably 40% by mass or more, further preferably 50% by mass or more, further preferably 60% by mass or more, and particularly preferably 70% by mass or more. In addition, the content of this SBR in the rubber component is preferably 95% by mass or less, more preferably 90% by mass or less, and further preferably 85% by mass or less.

[0107] (Isoprene rubber) As the isoprene rubber, for example, substances commonly used in the tire industry such as isoprene rubber (IR) and natural rubber can be used. In natural rubber, in addition to non-modified 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 can also be contained. These isoprene rubbers can be used alone or in combination of two or more.

[0108] As for NR, there is no particular limitation, and substances commonly used in the tire industry can be used. For example, SIR20, RSS#3, TSR20, etc. can be cited.

[0109] The content of the isoprene rubber in the rubber components constituting the first layer and the second layer is preferably 10% by mass or more, more preferably 15% by mass or more, and further preferably 20% by mass or more. In addition, this content is preferably 70% by mass or less, more preferably 60% by mass or less, and further preferably 50% by mass or less.

[0110] (BR) As for BR, there is no particular limitation. 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 series butadiene rubber synthesized with rare-earth element-based catalysts (rare-earth series BR), BR containing syndiotactic polybutadiene crystals (BR containing SPB), modified BR (high-cis modified BR, low-cis modified BR), etc., which are commonly used in the tire industry, can be used. These BRs can be used alone or in combination of two or more.

[0111] As the high-cis BR, for example, substances commercially available from Zeon Corporation, UBE Industries, Ltd., JSR Corporation, etc. in Japan 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 greater than 95 mol%, more preferably greater than 96 mol%, and further preferably greater than 97 mol%. In addition, the cis content of BR is measured by the above-mentioned measurement method.

[0112] As the rare-earth series BR, synthesized with a rare-earth element-based catalyst, the vinyl content is preferably less than 1.8 mol%, more preferably less than 1.6 mol%, and further preferably 11.5 mol% or less, and the cis content is preferably greater than 95 mol%, more preferably greater than 96 mol%, and further preferably 97 mol% or more. As the rare-earth series BR, for example, substances commercially available from Lanxess Corporation, etc. can be used.

[0113] The BR containing SPB may be a substance in which 1,2-syndiotactic polybutadiene crystals are not simply dispersed in BR, but the crystals are dispersed by chemical bonding with BR. As such a BR containing SPB, substances commercially available from UBE Industries, Ltd., etc. can be used.

[0114] As the modified BR, in addition to BR modified with the same functional groups as those described in the above SBR, etc., modified butadiene rubber (modified BR) modified at the terminal and / or main chain with a functional group containing at least one element selected from silicon, nitrogen, and oxygen can also be preferably used.

[0115] As other modified BR, there may be mentioned modified BR (tin-modified BR) obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and further, a tin-carbon bond is bonded to the terminal of the modified BR molecule, etc. In addition, the modified BR can be either unhydrogenated modified BR or hydrogenated modified BR.

[0116] From the viewpoint of abrasion resistance, the weight-average molecular weight (Mw) of BR is preferably greater than 300,000, more preferably greater than 350,000, and further preferably greater than 400,000. In addition, from the viewpoints of crosslinking uniformity, etc., it is preferably less than 2,000,000, more preferably less than 1,000,000, and further preferably less than 500,000. In addition, Mw can be determined by the above method.

[0117] The content of BR in the rubber components constituting the first layer and the second layer is not particularly limited, and is preferably 1% by mass or more, more preferably 5% by mass or more, and further preferably 10% by mass or more. In addition, the content of this BR in the rubber component is preferably 50% by mass or less, more preferably 30% by mass or less, and further preferably 25% by mass or less.

[0118] (Other rubber components) Within the scope that does not affect the effects of the present invention, the rubber component may further contain rubber components other than diene-based rubbers (non-diene-based rubbers). As the non-diene-based rubber, rubber components commonly used in the tire industry can be used. For example, butyl-based rubbers, ethylene-propylene rubbers, polynorbornene rubbers, silicone rubbers, chlorinated polyethylene rubbers, fluororubbers (FKM), acrylic rubbers (ACM), epichlorohydrin rubbers, etc. can be cited. These other rubber components can be used alone or in combination of two or more. In addition, in addition to the above-mentioned rubber components, known thermoplastic elastomers may or may not be contained.

[0119] (Rubber components synthesized from recycled / biomass-derived raw materials) The monomers that are the constituent units of synthetic rubbers such as SBR and BR can be substances derived from petroleum or substances recycled from rubber products such as tires or non-rubber products such as polystyrene. As the monomers obtained by recycling (recycled monomers), there is no particular limitation, and recycled butadiene, recycled aromatic vinyl compounds, etc. can be cited. As the above-mentioned butadiene, 1,2-butadiene and 1,3-butadiene can be cited. As the above-mentioned aromatic vinyl compound, there is no particular limitation, and styrene, etc. can be cited. Among them, it is preferable to use recycled butadiene (recycled butadiene) and / or recycled styrene (recycled styrene) as raw materials.

[0120] As the manufacturing method of the recycled monomer, there is no particular limitation. For example, it can be cited as being synthesized from recycled naphtha obtained by cracking rubber products such as tires. In addition, as the manufacturing method of the recycled naphtha, there is no particular limitation. For example, rubber products such as tires can be cracked under high temperature and high pressure, or can be cracked with microwaves, or can be extracted after mechanical pulverization.

[0121] Furthermore, monomers that are constituent units of polymers such as SBR and BR can also be substances derived from biomass. As monomers derived from biomass (biomass monomers), there is no particular limitation, and examples include butadiene derived from biomass and aromatic vinyl compounds derived from biomass. As the above-mentioned butadiene, 1,2-butadiene and 1,3-butadiene can be cited. As the above-mentioned aromatic vinyl compounds, there is no particular limitation, and examples include styrene. In addition, the method for manufacturing monomers derived from biomass is not particularly limited. For example, substances obtained by biological and / or chemical and / or physical conversion of animals and plants can be cited. As biological conversion, fermentation based on microorganisms is representative. As chemical and / or physical conversion, conversion based on catalysts, conversion based on high heat, conversion based on high pressure, conversion based on electromagnetic waves, conversion based on supercritical fluids, and combinations thereof can be cited. As biomass sources of these monomers, those derived from sugar, wood, plant residues after obtaining useful components, ethanol of plants, biomass naphtha, etc. can be cited.

[0122] As polymers synthesized from biomass monomer components (biomass polymers), there is no particular limitation, and examples include polybutadiene rubber synthesized from butadiene derived from biomass and aromatic vinyl / butadiene copolymers synthesized from butadiene derived from biomass and / or aromatic vinyl compounds derived from biomass. As the above-mentioned aromatic vinyl / butadiene copolymers, for example, styrene-butadiene rubber synthesized from butadiene derived from biomass and / or styrene derived from biomass can be cited.

[0123] Whether the raw material of the polymer is derived from biomass can be judged by pMC (percent Modern Carbon) measured according to ASTM D6866-10. pMC means: the 14 C concentration of the sample relative to that of the 14 C in the modern standard reference, and it is a value used as an index indicating the biomass ratio of the compound. The significance of this value will be described below.

[0124] In 1 mole (6.02×10 23 pieces) of carbon atoms, there is about one trillionth of the ordinary carbon atoms, that is, about 6.02×10 11 pieces 14 C. 14 The half-life of 14 C is 5730 years, and 14All of the C elements have decayed. Therefore, in the 21st century today, fossil fuels such as coal, oil, and natural gas contain no 14 C elements. Therefore, the chemical substances produced from these fossil fuels also contain no 14 C elements.

[0125] On the other hand, 14 C is continuously generated by nuclear reactions in the atmosphere through cosmic rays. Therefore, 14 the decrease of C due to radioactive decay and the generation of C due to nuclear reactions reach equilibrium. In the atmospheric environment of the earth, 14 the amount of C is a constant. Therefore, in the current environment, the 14 C concentration of the substances derived from the biomass resources of the material cycle is, as described above, about 1×10 -12 mol% relative to all carbon atoms. Therefore, by using the difference between these values, the proportion (biomass ratio) of the compound (rubber) derived from natural resources (compound derived from biomass resources) in a certain compound can be calculated.

[0126] Generally, the 14 C is measured as follows. Using accelerator mass spectrometry based on a tandem accelerator, the 13 C concentration ( 13 C / 12 C), 14 C concentration ( 14 C / 12 C) is measured. When measuring, as the 14 C concentration reference standard modern carbon, the 14 C concentration in the circulating carbon in nature in 1950 is adopted. As a specific reference material, the oxalic acid reference material provided by NIST (National Institute of Standards and Technology) is used. The specific radioactivity of carbon in this oxalic acid (radioactivity intensity of 14 C per 1 g of carbon) is classified according to each carbon isotope, the 13 C is corrected to a fixed value, and the value applied with the decay correction from 1950 AD to the measurement date is used as the standard 14 C concentration value (100%). The ratio of the value of the actually measured sample to this value is the pMC value.

[0127] Therefore, if the rubber is made of a substance derived from 100% biomass (natural type), although there are regional differences, etc., since it is mostly not 100 under normal conditions at present, it is expected to show a value of about 110 pMC (now under normal conditions, it is generally not 100). On the other hand, for chemical substances derived from fossil fuels such as petroleum, when measuring the 14 C concentration, a value of about 0 pMC (for example, 0.3 pMC) is shown. This value corresponds to a biomass ratio of 0%.

[0128] In summary, it is preferable in terms of environmental protection to use materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio, in the rubber composition.

[0129] [Filler] The rubber composition according to this embodiment preferably contains a filler. The filler of each rubber composition constituting the first layer and the second layer contains silica, and preferably contains silica and carbon black. In addition, the filler can also be a filler composed only of carbon black and silica.

[0130] [Silica] There is no particular limitation on the silica. For example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), etc., which are commonly used in the tire industry, can be used. There is no particular limitation on the raw material of the silica. For example, it can be a raw material derived from minerals such as quartz, or a raw material derived from organisms such as rice husks (for example, silica using biomass materials such as rice husks as raw materials), and silica recovered from products containing silica can also be used. Among them, due to the large number of silanol groups, hydrous silica prepared by a wet method is preferred. These silicas can be used alone or in combination of two or more.

[0131] Silica using biomass materials as raw materials can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks with a sodium hydroxide solution, and reacting the silicate with sulfuric acid in the same way as conventional wet silica to form a silica precipitate, which is then filtered, washed, dried, and pulverized.

[0132] Silica recovered from products containing silica can be used, for example, silica recovered from products containing silica such as semiconductor and other electronic components, tires, desiccants, and filter materials such as diatomaceous earth. In addition, there is no particular limitation on the recovery method, and examples include pyrolysis based on thermal cracking, electromagnetic waves, etc. Among them, silica recovered from semiconductor and other electronic components or tires is preferred.

[0133] If silicon dioxide is crystallized, it is insoluble in water and silicic acid, which is its component, cannot be used. By managing the combustion temperature and combustion time, the crystallization of silicon dioxide in rice husk ash can be suppressed (see Japanese Patent Publication No. 2009-2594, Akita Prefectural University Online Journal B (Akita Prefectural University ウェブジャーナルB) / 2019, vol.6, p.216-222, etc.). Amorphous silicon dioxide extracted from rice husks can use commercially available substances such as Wilmar.

[0134] From the viewpoint of reinforcement and ensuring grip performance, the nitrogen adsorption specific surface area (N2SA) of silica is preferably 100 m 2 / g or more, more preferably 120m 2 / g or more, more preferably 140m 2 / g or more, more preferably 160m 2 / g or more, particularly preferably 170m 2 / g or more. In addition, from the viewpoint of heat generation and processability, 350 m 2 / g or less, more preferably 300m 2 / g or less, more preferably 250m 2 / g or less. In addition, the N2SA of silica is measured by the above-mentioned measurement method.

[0135] The average primary particle size of silicon dioxide is preferably more than 10nm, more preferably more than 12nm, further preferably more than 14nm, and particularly preferably more than 16nm. In addition, the average primary particle size is preferably less than 24nm, more preferably less than 22nm, and further preferably less than 20nm. In addition, the average primary particle size of silicon dioxide is measured by the above-mentioned determination method.

[0136] In the rubber composition constituting the first layer, the content of silica relative to 100 parts by mass of the rubber component is preferably greater than 50 parts by mass, more preferably greater than 60 parts by mass, and even more preferably greater than 70 parts by mass. In addition, from the viewpoint of reducing heat generation, 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.

[0137] In the rubber composition constituting the second layer, the content of silica relative to 100 parts by mass of the rubber component is preferably greater than 50 parts by mass, more preferably greater than 60 parts by mass, and even more preferably 80 parts by mass or more. In addition, from the viewpoint of reducing heat generation, 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.

[0138] <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 can be cited; 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, sulfide-based silane coupling agents and / or mercapto-based silane coupling agents are preferably contained. As the silane coupling agent, for example, commercially available substances from Evonik Degussa Corporation, Momentive Performance Materials Inc., etc. can be used. These silane coupling agents can be used alone or in combination of two or more.

[0139] From the viewpoint of improving the dispersibility of silica, the content of the silane coupling agent relative to 100 parts by mass of the rubber component (the total amount when multiple silane coupling agents are used in combination) is preferably greater than 3.0 parts by mass, more preferably greater than 5.0 parts by mass, and further preferably 6.0 parts by mass or more. In addition, from the viewpoint of preventing a decrease in abrasion resistance, it is preferably less than 15 parts by mass, more preferably less than 10 parts by mass, and further preferably less than 9.0 parts by mass.

[0140] <Carbon Black> The carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. The raw material of the carbon black can be biomass materials such as lignin and vegetable oil, or pyrolysis oil obtained by pyrolyzing waste tires. In addition, the manufacturing method of the carbon black can be a combustion-based method such as the furnace method, a method based on hydrothermal carbonization (HTC), or a method based on the thermal cracking of methane derived from the thermal cracking carbon black method, etc. As commercially available products, products from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Columbia Carbon Company, etc. can be used. These can be used alone or in combination of two or more.

[0141] In addition, as carbon black, in addition to the above, from the perspective of life cycle assessment, etc., carbon black made from biomass materials such as lignin, and recycled carbon black obtained by pyrolyzing and refining products containing carbon black such as tires can also be used.

[0142] In this specification, "recycled carbon black" refers to carbon black obtained by pulverizing used products such as tires containing carbon black and firing the pulverized material. Using the thermogravimetric method based on JIS K 6226-2:2003, when it is oxidized and burned by heating in air, the proportion of the non-combustible component, that is, the mass (ash content) of ash, is 13% by mass or more of carbon black. That is, the proportion of the mass (carbon content) of the reduced part based on the above oxidation combustion of recycled carbon black is 87% by mass or less. Recycled carbon black is sometimes also represented by rCB.

[0143] Recycled carbon black can be obtained by the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975 describes that in "Rubber Chemistry and Technology", Vol. 85, No. 3, pages 408-449 (2012), especially pages 438, 440, and 442 mention that it is obtained by removing oxygen and then pyrolyzing organic materials at 550-800 °C, or vacuum pyrolysis at a relatively low temperature (

[0027] ). The carbon black obtained by such a pyrolysis process is usually recycled carbon black lacking functional groups on its surface as mentioned in

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

[0144] Recycled carbon black can be carbon black lacking functional groups on its surface, or it can also be carbon black that has been treated to make its surface contain functional groups. The treatment to make the surface of the recovered carbon black contain functional groups can be carried out by conventional methods. For example, in European Patent Application Publication No. 3173251, carbon black obtained by the pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl groups and / or carboxyl groups on its surface. In addition, in Patent No. 6856781, carbon black obtained by the pyrolysis process is treated with an amino acid compound containing at least one mercapto group or disulfide group to obtain carbon black with an activated surface. The recycled carbon black involved in this embodiment includes these carbon blacks treated to make their surfaces contain functional groups.

[0145] Commercially available substances such as those from Strable Green Carbon Company and LDCarbon Company can be used as recycled carbon black.

[0146] 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 reinforcement, the average primary particle diameter is preferably 100 nm or less, more preferably 80 nm or less, still more preferably 50 nm or less. In addition, the average primary particle diameter of the carbon black is measured by the above-mentioned measurement method.

[0147] From the viewpoint of the effects of the present invention, 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, still more preferably 150 m 2 / g or less. In addition, the N2SA is preferably 30 m 2 / g or more, more preferably 40 m 2 / g or more, still more preferably 45 m 2 / g or more. In addition, the N2SA of the carbon black is measured by the above-mentioned measurement method.

[0148] When the rubber composition constituting the first layer or the second layer contains carbon black, from the viewpoint of reinforcement, its content relative 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, still more preferably more than 9 parts by mass. In addition, from the viewpoint of obtaining softness and stress relaxation, 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.

[0149] <Other fillers> The filler may also contain other fillers other than silica and carbon black. There is no particular limitation on other fillers. For example, substances commonly used in the tire industry in the past, such as aluminum hydroxide, calcium carbonate, alumina, clay, talc, etc., can be compounded.

[0150] [Other compounding agents] In the rubber composition according to the present embodiment, in addition to the rubber component and the filler, compounding agents commonly used in the tire industry in the past can be appropriately contained, such as plasticizers, processing aids, vulcanized rubber particles, waxes, stearic acid, zinc oxide, anti-aging agents, vulcanizing agents, vulcanization accelerators, etc. At least any 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 preferably the rubber composition constituting the first layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components.

[0151] <Plasticizer> A plasticizer refers to a material that imparts plasticity to a rubber component, and is a concept that includes both plasticizers that are liquid (in a liquid state) at 25°C and plasticizers that are solid at 25°C. As examples of plasticizers, resins, oils, liquid polymers, ester-based plasticizers, etc. can be cited. These plasticizers can be substances derived from petroleum, substances derived from biomass, or substances derived from naphtha recovered from rubber products or non-rubber products. In addition, low-molecular-weight hydrocarbon components obtained by thermally cracking and extracting used tires or products containing various components can also be used as plasticizers. These plasticizers can be used alone or in combination of two or more.

[0152] <<Copolymer resin containing styrene and cyclopentadiene as monomer components>> As a copolymer resin containing styrene and cyclopentadiene as monomer components, there is no particular limitation as long as it is a resin containing styrene and cyclopentadiene as monomer components, and it can also be a resin further containing other monomer components described below. In addition, it can also be a hydrogenated product or a modified product thereof.

[0153] As other monomer components other than styrene and cyclopentadiene, there is no particular limitation, and monomer components commonly used in petroleum resins are preferred, more preferably C9 fractions described below, and further preferably indene.

[0154] As a copolymer resin containing styrene and cyclopentadiene as monomer components, a copolymer resin containing styrene, cyclopentadiene and / or dicyclopentadiene, and indene as monomer components is preferred, and it can also be a hydrogenated or modified product of the copolymer resin.

[0155] As a copolymer resin containing styrene and cyclopentadiene as monomer components, for example, commercially available substances from ExxonMobil Corporation, ENEOS Corporation, Zeon Corporation, Maruzen Petrochemical Co., Ltd., etc. can be used. This resin can be used alone or in combination of two or more.

[0156] From the viewpoint of the effects of the present invention, the content of the styrene portion of 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 further preferably 1.0% by mass or more. In addition, the upper limit value of the content of this styrene portion is not particularly limited, and for example, it can be set to 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.

[0157] 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 greater than 70 °C, more preferably greater than 80 °C, still more preferably greater than 90 °C, and particularly preferably greater than 100 °C. Further, from the viewpoints of processability and improving the dispersibility of the rubber component and the filler, it is preferably less than 150 °C, more preferably less than 140 °C, still more preferably less than 130 °C. The softening point of the resin is measured by the above-mentioned measuring method.

[0158] With respect to 100 parts by mass of the rubber component, the content of the copolymer resin containing styrene and cyclopentadiene as monomer components is preferably greater than 5 parts by mass, more preferably greater than 10 parts by mass, still more preferably greater than 15 parts by mass, still more preferably greater than 19 parts by mass, and particularly preferably greater 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.

[0159] (Other resins) The rubber composition according to the present embodiment may also contain other resins other than the copolymer resin containing styrene and cyclopentadiene as monomer components. There is no particular limitation on the other resins, and 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 cited. The resins can be used alone or in combination of two or more.

[0160] <<Aromatic vinyl resin>> In this specification, the "aromatic vinyl resin" means a resin containing at least one aromatic vinyl compound selected from styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene, etc. as monomer components (wherein, the copolymer resin containing styrene and cyclopentadiene as monomer components is not included). As the aromatic vinyl resin, due to excellent economy, processability, and heat generation properties, a homopolymer of α-methylstyrene or styrene or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred. As the aromatic vinyl resin, for example, commercially available products from companies such as Kraton, Eastman Chemical, and Mitsui Chemicals can be used. The resins can be used alone or in combination of two or more.

[0161] <<Dicyclopentadiene resin>> In this specification, the "dicyclopentadiene resin" refers to a resin containing dicyclopentadiene as a monomer component (excluding copolymers containing styrene and cyclopentadiene as monomer components). As the dicyclopentadiene resin, for example, commercially available substances from ExxonMobil Corporation, ENEOS Corporation, Nippon Zeon Co., Ltd., Maruzen Petrochemical Co., Ltd., etc. can be used. This resin can be used alone or in combination of two or more.

[0162] 《C9 Resin》 In this specification, the "C9 resin" refers to a resin obtained by polymerizing C9 fractions (excluding copolymers containing styrene and cyclopentadiene as monomer components), which can be a resin obtained by homopolymerizing C9 fractions or a copolymer obtained by copolymerizing C9 fractions with other components. As C9 fractions, for example, at least one petroleum fraction having 8 to 10 carbon atoms selected from alkyl styrenes such as vinyltoluene, coumarone, indene, methyl indene, etc. can be cited. As specific examples of the C9 resin, for example, coumarone / indene resin, coumarone resin, indene resin, etc. can be cited. This resin can be used alone or in combination of two or more.

[0163] 《C5 Resin》 In this specification, the "C5 resin" refers to a resin obtained by polymerizing C5 fractions other than cyclopentadiene, which can also be their hydrogenated products or modified products. As C5 fractions other than cyclopentadiene, for example, at least one petroleum fraction having 4 to 5 carbon atoms selected from dicyclopentadiene, isoprene, pentane, isopentane, neopentane, pentene, pentadiene, etc. can be cited. This resin can be used alone or in combination of two or more.

[0164] 《C5C9 Resin》 The "C5C9 resin" refers to a resin obtained by copolymerizing the above C5 fractions with the above C9 fractions, which can also be their hydrogenated products or modified products. As the C5C9 petroleum resin, for example, commercially available substances from Tosoh Corporation, LUHUA Corporation, etc. can be cited. This resin can be used alone or in combination of two or more.

[0165] 《Terpene Resin》 "Terpene resin" means: a resin containing at least one terpene compound selected from α-pinene, β-pinene, limonene, dipentene, etc. as the monomer component with the highest content, preferably a resin containing 50 mol% or more, and may also be their hydrogenated products or modified products. As specific examples of terpene resins, for example, polyterpene resins containing only one or more of the above terpene compounds as monomer components can be cited; aromatic modified terpene resins containing the above terpene compounds and aromatic compounds as monomer components; terpene phenol resins containing the above terpene compounds and phenolic compounds as monomer components, etc. As the monomer component of the aromatic modified terpene resin, that is, the aromatic compound, for example, at least one selected from styrene, α-methylstyrene, vinyltoluene, divinyltoluene, etc. can be cited. As the monomer component of the terpene phenol resin, that is, the phenolic compound, for example, at least one selected from phenol, bisphenol A, cresol, xylenol, etc. can be cited. This resin can be used alone or in combination of two or more.

[0166] "Rosin Resin" As a rosin resin, it refers to a resin containing at least one rosin acid compound selected from abietic acid, neoabietic acid, palustric acid, isopimaric acid, etc., and may also be their hydrogenated products or modified products. As a rosin resin, there is no particular limitation, and for example, natural resin rosin, rosin modified resins obtained by hydrogenating, disproportionating, dimerizing, esterifying, etc. it can be cited. This resin can be used alone or in combination of two or more.

[0167] "Phenolic Resin" As a phenolic resin, it refers to a resin containing phenolic compounds such as phenol, cresol, etc. as the monomer component with the highest content, preferably a resin containing 50 mol% or more. As a phenolic resin, there is no particular limitation, and examples include phenol formaldehyde resin, alkylphenol formaldehyde resin, alkylphenol acetylene resin, oil-modified phenol formaldehyde resin, etc. This resin can be used alone or in combination of two or more.

[0168] "Softening Point" From the perspective of wet grip performance, the softening point of the resin is preferably greater than 80 °C, more preferably greater than 90 °C, and further preferably greater than 100 °C. In addition, from the perspectives of processability and improving the dispersibility of the rubber component and the filler, it is preferably less than 150 °C, more preferably less than 140 °C, and further preferably less than 130 °C. The softening point of the resin is measured by the above-mentioned measurement method.

[0169] "Content" The content of the resin (total content when there are two or more types) relative 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 further preferably 20 parts by mass or more. On the other hand, from the viewpoint of suppressing heat generation, the content is preferably less than 80 parts by mass, more preferably less than 60 parts by mass, and further preferably less than 40 parts by mass.

[0170] (Plasticizer other than resin) The plasticizers other than the resin, namely oils, liquid rubbers, and ester plasticizers, will be described.

[0171] 《Oil》 Examples of oils include mineral oils, vegetable oils, and animal oils. In addition, from the viewpoint of life cycle assessment, oils refined from waste oils used in rubber mixers or engines and waste cooking oils used in restaurants can also be used. Oils can be used alone or in combination of two or more.

[0172] In this specification, mineral oil refers to oils derived from mineral resources such as petroleum and natural gas. Examples of mineral oils include paraffin-based oils (mineral oil), naphthenic oils, and aromatic oils. Specific examples of mineral oils include MES (Mild Extract Solvate), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), RAE (Residual Aromatic Extract), etc. In addition, due to environmental measures, processing oils with a low content of polycyclic aromatic (polycyclic aromatic compound: PCA) compounds can also be used. Examples of the above-mentioned oils with a low PCA content include MES, TDAE, and heavy naphthenic oils. Mineral oils can be used alone or in combination of two or more.

[0173] In this specification, vegetable oil refers to, for example, linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice bran oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grape seed oil, wood wax, etc. Further, as vegetable oil, there may also be mentioned 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, heat-polymerized oils obtained by heat-polymerizing the above oils, oxidative polymerized oils obtained by oxidizing the above oils, waste cooking oils obtained by recycling the oils used as cooking oils, etc. In addition, vegetable oil can be liquid or solid at 25°C.

[0174] Vegetable oil preferably contains acylglycerol, and more preferably contains triacylglycerol. In addition, in this specification, acylglycerol refers to a compound in which the hydroxyl group of glycerol forms an ester bond with a fatty acid. As acylglycerol, there is no particular limitation, and it can be any one of 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, and triacylglycerol. Further, acylglycerol can be a monomer, a dimer, or a polymer of trimer or higher. In addition, acylglycerols of dimer or higher can be obtained by heat polymerization, oxidative polymerization, etc. In addition, acylglycerol can be liquid or solid at 25°C.

[0175] As a method for confirming whether the rubber composition contains acylglycerol, there is no particular limitation, and it can be confirmed by 1 1H-NMR measurement. For example, the rubber composition compounded with triacylglycerol is immersed in deuterated chloroform at 25°C for 24 hours, and after removing the rubber composition, 1H-NMR is measured at room temperature. 1 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 can be observed, and it is presumed that these signals are signals from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In addition, "around" in this paragraph refers to a range of ±0.10 ppm.

[0176] As the above fatty acid, there is no particular limitation, and it can be an unsaturated fatty acid or a saturated fatty acid. As unsaturated fatty acids, there may be mentioned monounsaturated fatty acids such as oleic acid or polyunsaturated fatty acids such as linoleic acid and linolenic acid. In addition, as saturated fatty acids, there may be mentioned butyric acid, lauric acid, etc.

[0177] Among them, as the above-mentioned fatty acid, it is preferably a fatty acid with fewer double bonds, that is, a saturated fatty acid or a monounsaturated fatty acid, preferably oleic acid. As such a vegetable oil containing fatty acids, for example, a vegetable oil containing a saturated fatty acid or a monounsaturated fatty acid can be used, or a modified vegetable oil such as transesterified oil can also be used. In addition, in order to produce such a vegetable oil containing fatty acids, plants can also be improved through variety improvement, genetic modification, etc.

[0178] As the vegetable oil, for example, commercially available substances from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kogyo Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0179] Examples of the animal oil include fish oil, beef tallow, whale oil, or an oil alcohol derived therefrom.

[0180] When containing oil, from the viewpoint of processability, its content relative to 100 parts by mass of the rubber component 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. In addition, from the viewpoint of wear resistance, it is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and further preferably 40 parts by mass or less. The content of the oil also includes the amount of oil contained in the oil-extended rubber.

[0181] <<Liquid Rubber>> The liquid rubber is not particularly limited as long as it is a polymer in a liquid state at normal 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 cited. The liquid rubber can be used alone or in combination of two or more.

[0182] When containing liquid rubber, its 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 further preferably 5 parts by mass or more. In addition, the content of the liquid rubber is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and further preferably 10 parts by mass or less. The content of the liquid rubber also includes the amount of the extender liquid rubber used in the increment of the rubber component.

[0183] <<Ester Plasticizer>> As ester plasticizers, for example, dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), dilauryl 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. can be cited. The ester plasticizer can be used alone or in combination of two or more.

[0184] When containing an ester plasticizer, its 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 further preferably 5 parts by mass or more. In addition, the content of the liquid rubber is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and further preferably 10 parts by mass or less. The content of the ester plasticizer also includes the amount of the incremental ester plasticizer used in the increment of the rubber component.

[0185] Relative to 100 parts by mass of the rubber component constituting the first layer or the second layer, the content of the plasticizer (total content when there are two or more) is preferably more than 20 parts by mass, more preferably more than 30 parts by mass, and further preferably more than 34 parts by mass. On the other hand, from the viewpoint of low fuel consumption performance, this content is preferably less than 120 parts by mass, more preferably less than 100 parts by mass, and further preferably less than 80 parts by mass.

[0186] (Vulcanized rubber particles) Vulcanized rubber particles are particles made of vulcanized rubber. Specifically, rubber powder specified in JIS K 6316:2017 can be used. From the viewpoints of environmental concerns and cost, recycled rubber powder made from crushed waste tires, etc. is preferred. The vulcanized rubber particles can be used alone or in combination of two or more.

[0187] As the vulcanized rubber particles, there is no particular limitation, and they can be non-modified vulcanized rubber particles or modified vulcanized rubber particles. As commercially available products of vulcanized rubber, for example, products of Lehigh Company, Murakami Rubber Industry Co., Ltd., etc. can be used.

[0188] When containing vulcanized rubber particles, its content relative 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.

[0189] (Stearic acid) When stearic acid is contained, from the viewpoint of processability, its 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. Further, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0190] (zinc oxide) When zinc oxide is contained, from the viewpoint of processability, its content relative 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, and further preferably 1.5 parts by mass or more. Further, from the viewpoint of abrasion resistance, it is preferably 5.0 parts by mass or less, more preferably 4.5 parts by mass or less, and further preferably 4.0 parts by mass or less.

[0191] (wax) The wax is not particularly limited, and any one of the substances commonly used in the tire industry can be preferably used. For example, mineral waxes, waxes derived from plants, etc. can be cited. Mineral waxes refer to waxes derived from mineral resources such as oil and natural gas. Waxes derived from plants refer to waxes derived from natural resources such as plants. Among them, mineral waxes are preferred. As waxes derived from plants, for example, rice bran wax, carnauba wax, candelilla wax, etc. can be cited. As mineral waxes, for example, paraffin wax, microcrystalline wax, selected special waxes thereof, etc. can be cited, and paraffin wax is preferred. In addition, the wax involved in this embodiment does not include stearic acid. The wax can be, for example, a commercially available substance from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., etc. The wax can be used alone or in combination of two or more.

[0192] When wax is contained, from the viewpoint of the weather resistance of the rubber, its 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. Further, from the viewpoint of preventing the whitening of the tire caused by blooming, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0193] (anti-aging agent) As the anti-aging agent, there is no particular limitation, and examples thereof include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine, 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'-dimethylxyl-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), 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-tert-butyl-4-methylphenol, styrenated phenol; bis-, tris-, and polyphenol-based anti-aging agents such as tetrakis[methylene-3-(3',5'-di-tert-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 Shinko Chemical Industrial Co., Ltd., Flexis Co., etc. can be used. The anti-aging agent can be used alone or in combination of two or more kinds.

[0194] When containing the anti-aging agent, from the viewpoint of ozone crack resistance of the rubber, its 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. In addition, from the viewpoints of abrasion resistance and wet grip performance, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0195] (Processing aid) As the processing aid, for example, 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, etc. can be cited. As the processing aid, for example, substances commercially available from companies such as Schill+Seilacher and Performance-Additives can be used. The processing aid can be used alone or in combination of two or more kinds.

[0196] When containing the processing aid, from the viewpoint of exerting the improvement effect of processability, its 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. In addition, from the viewpoints of abrasion resistance and breaking strength, it is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and further preferably 5 parts by mass or less.

[0197] (Vulcanizing agent) As the vulcanizing agent, sulfur is preferably used. As sulfur, powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, etc. can be used. The vulcanizing agent can be used alone as one kind, or two or more kinds can be used in combination.

[0198] When sulfur is contained as the vulcanizing agent, from the viewpoint of ensuring sufficient vulcanization reaction, its content relative 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 further preferably 0.5 part by mass or more. In addition, 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 further preferably 3.0 parts by mass or less. In addition, when using sulfur containing oil as the vulcanizing agent, the content of the vulcanizing agent is set as the total content of pure sulfur contained in the sulfur containing oil.

[0199] As vulcanizing agents other than sulfur, for example, alkylphenol / sulfur chloride condensates, sodium 1,6-hexamethylenedithiocarbamate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. can be cited. These vulcanizing agents other than sulfur can use commercially available substances from companies such as Taoka Chemical Industry Co., Ltd., Lanxess Co., Ltd., Flexis Co., etc. The vulcanizing agent can be used alone as one kind, or two or more kinds can be used in combination.

[0200] (Vulcanization accelerator) As the vulcanization accelerator, for example, sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamate-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, or xanthate-based vulcanization accelerators, etc. can be cited. Among them, sulfenamide-based, thiazole-based, and guanidine-based vulcanization accelerators are preferred. The vulcanization accelerator can be used alone as one kind, or two or more kinds can be used in combination.

[0201] As sulfenamide-based vulcanization accelerators, for example, N-tert-butyl-2-benzothiazolesulfenamide (TBBS), N-cyclohexyl-2-benzothiazolesulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolesulfenamide (DCBS), etc. can be cited. Among them, N-cyclohexyl-2-benzothiazolesulfenamide (CBS) is preferred.

[0202] As thiazole-based vulcanization accelerators, for example, 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazole disulfide, etc. can be cited. Among them, 2-mercaptobenzothiazole is preferred.

[0203] As a guanidine-based vulcanization accelerator, for example, 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-biphenyl guanidine, 1,3-di-o-cumenyl-2-propionylguanidine, etc. may be mentioned. Among them, 1,3-diphenylguanidine (DPG) is preferred.

[0204] When a vulcanization accelerator is contained, its content relative to 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. In addition, the content of the vulcanization accelerator relative to 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 further preferably 6 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, it tends to ensure the breaking strength and elongation at break.

[0205] <Various materials containing carbon atoms> In this specification, various materials containing carbon atoms (for example, rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may also be derived from carbon dioxide in the atmosphere. As a method for obtaining the blend according to the embodiment of the present invention from carbon dioxide, carbon dioxide can be directly converted, or methane obtained through a methanation process of synthesizing methane from carbon dioxide can be converted.

[0206] The rubber composition constituting the third layer of the tread surface 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 an isoprene-based rubber, and more preferably contains an isoprene-based rubber and BR.

[0207] The content of the isoprene-based rubber in the rubber component constituting the third layer of the tread surface is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more. In addition, the content of BR in the rubber component constituting the third layer is preferably 10% by mass or more, more preferably 20% by mass or more.

[0208] The BR contained in the rubber component constituting the third layer of the tread surface is preferably a low-cis BR having a cis content of less than 50 mol%, and more preferably a low-cis modified BR.

[0209] In the rubber composition constituting the third layer of the tread surface, the N2SA of the carbon black is preferably 80 m 2 / g or less, more preferably 70 m 2Below / g. In addition, this N2SA is preferably 30 m 2 / g or more, more preferably 50 m 2 / g or more, even more preferably 60 m 2 / g or more.

[0210] When the rubber composition constituting the third layer contains carbon black, from the viewpoint of the effects of the present invention, its content (total content when two or more are contained) relative to 100 parts by mass of the rubber component is preferably more than 20 parts by mass, more preferably more than 25 parts by mass, even more preferably more than 30 parts by mass, and even more preferably more than 40 parts by mass. In addition, 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, even more preferably less than 60 parts by mass, and particularly preferably less than 50 parts by mass.

[0211] The rubber composition constituting the third layer of the tread portion may or may not contain a resin as a plasticizer, but preferably contains oil.

[0212] The content (total content when two or more are contained) of the resin relative to 100 parts by mass of the rubber component constituting the third layer is not particularly limited. For example, the lower limit value can be set to 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 set to 15 parts by mass or less, 10 parts by mass or less, 8 parts by mass or less, etc.

[0213] [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 mill or a closed kneader (Banbury mixer, kneader, etc.).

[0214] The kneading process includes, for example, the following basic kneading process: kneading compounding agents and additives other than the vulcanizing agent and vulcanization accelerator, and a final kneading process (F kneading): adding the vulcanizing agent and vulcanization accelerator to the kneaded product obtained in the basic kneading process and kneading. Further, the above basic kneading process can also be decomposed into multiple processes as needed.

[0215] As the kneading conditions, there are no particular limitations. For example, in the basic 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.

[0216] The tire according to this embodiment can be manufactured by a conventional method using the above rubber composition. That is, the tire can be manufactured by extruding the above rubber composition in an uncured state through an extruder equipped with a die having a specified shape according to the shape of the first, second, or third layer of the tread portion, adjusting it to a specified tire structure on a tire molding machine while bonding it together with other tire components, forming an uncured tire by molding through a conventional method, and manufacturing the tire by heating and pressurizing the uncured tire in a vulcanizer. As the vulcanization conditions, there are no particular limitations. For example, a method of vulcanizing at 140 to 170 °C for 10 to 40 minutes can be cited.

[0217] [Use] In this specification, the tire, whether it is a pneumatic tire or a non-pneumatic tire, can be used for any purpose and can be used as a passenger car tire, a large passenger car tire, a large SUV tire, a racing tire, a motorcycle tire, a load-carrying tire, or a run-flat tire. In addition, a passenger car tire refers to a tire with a maximum load capacity of less than 1400 kg on the premise of being installed on a four-wheel-driving vehicle. In addition, a load-carrying tire refers to a tire with a maximum load capacity of 1400 kg or more. In addition, in this specification, the tire can be used for winter tires such as studless tires in addition to all-season tires and summer tires. [Examples]

[0218] Examples considered to be preferred in implementation are shown below (Examples), but the scope of the present invention is not limited to the Examples.

[0219] Tires having a tread portion made of a rubber composition obtained by changing the formulation according to Table 1 using various drugs shown below were studied, and the results calculated based on the following evaluation methods are shown in Tables 2 and 3. NR: TSR20 SBR1: HPR830E (S-SBR, Tg: -23 °C, styrene content: 39.5% by mass, vinyl content: 38.5 mol%, containing 10.0 parts by mass of oil extender relative to 100 parts by mass of rubber solid content) manufactured by JSR Corporation SBR2: SBR (S-SBR, Tg: -50 °C, styrene content: 30% by mass, vinyl content: 22 mol%, non-oil-extended) manufactured according to Production Example 1 below SBR3: SBR (S-SBR, Tg: -66 °C, styrene content: 19% by mass, vinyl content: 19 mol%, non-oil-extended) manufactured according to Production Example 2 below BR1: UBEPOL BR (registered trademark) 150B manufactured by UBE Industries, Ltd. (cis content: 98 mol%, vinyl content: 1 mol%) BR2: BR1250H manufactured by Zeon Corporation, Japan (tin-modified BR, polymerized using lithium as an initiator, vinyl content: 10 - 13 mol%, cis content: 39.7 mol%) CB1: DIABLACK I (N220, N2SA: 114m 2 / g, average primary particle size: 22 nm) manufactured by Mitsubishi Chemical Corporation CB2: SHOBLACK N351H (N2SA: 69m 2 / g, average primary particle size: 29 nm) manufactured by Cabot Japan Ltd. CB3: DIABLACK E (N550, N2SA: 41m 2 / g, average primary particle size: 81 nm) manufactured by Mitsubishi Chemical Corporation Silica: ULTRASIL VN3 (N2SA: 175m 2 / g, average primary particle size: 18 nm) manufactured by Evonik Degussa GmbH Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa GmbH Oil: VivaTec500 (TDAE oil) manufactured by H&R Co., Ltd. Copolymer resin: Oppera PR383 (hydrogenated DCPD-C9 resin, containing styrene and cyclopentadiene as monomer components, Mw: 770, softening point: 103 °C, styrene content: 1.78 mass%) manufactured by ExxonMobil Corporation Terpene resin: YS Resin PX1150N (polyterpene resin, softening point: 115 ± 5 °C) manufactured by Yasuhara Chemical Co., Ltd. Stearic acid: Stearic acid beads "TSUBAKI" manufactured by NOF Corporation Zinc oxide: Zinc Oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Wax: OZOACE 0355 manufactured by Nippon Seiro Co., Ltd. Antioxidant 1: NOCRAC 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. Antioxidant 2: NOCRAC RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. Sulfur 1: M95 (insoluble sulfur) manufactured by Nippon Karyukogyo Co., Ltd. Sulfur 2: Powder sulfur manufactured by Karuizawa Sulfur Co., Ltd. Vulcanization accelerator 1: NOCCELLER CZ-G (N-cyclohexyl-2-benzothiazole sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: NOCCELLER D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0220] (Production Example 1: Production of SBR2) Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were added to an autoclave reactor purged with nitrogen. The ratio of styrene and 1,3-butadiene was adjusted so that the content of the styrene portion was 30% by mass. After adjusting the temperature of the contents of the reactor, tert-butyl lithium was added to initiate polymerization. Polymerization was carried out under adiabatic conditions, and the polymerization solution was poured into ethanol to recover the precipitate. The precipitate was dried by blowing and dried under reduced pressure until the loss on drying became 0.1% to obtain SBR2.

[0221] (Production Example 2: Production of SBR3) Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were added to an autoclave reactor purged with nitrogen. The ratio of styrene and 1,3-butadiene was adjusted so that the content of the styrene portion was 19% by mass. After adjusting the temperature of the contents of the reactor, tert-butyl lithium was added to initiate polymerization. Polymerization was carried out under adiabatic conditions, and the polymerization solution was poured into ethanol to recover the precipitate. The precipitate was dried by blowing and dried under reduced pressure until the loss on drying became 0.1% to obtain SBR3.

[0222] (Examples and Comparative Examples) According to the compounding recipe shown in Table 1, using a 1.7 L closed Banbury mixer, the reagents other than sulfur and vulcanization accelerators were kneaded for 1 to 10 minutes until the discharge temperature reached 150 to 160 °C to obtain a kneaded product. Then, using a twin-screw open mill, sulfur and vulcanization accelerators were added to the kneaded product and kneaded for 4 minutes until it reached 105 °C to obtain an unvulcanized rubber composition. By shaping the obtained unvulcanized rubber composition into the shape of the first layer, second layer (thickness: 4.0 mm), and third layer (thickness: 1.0 mm) of the tread and laminating it with other tire components, an unvulcanized tire was produced. By pressurized vulcanization at 150 °C for 35 minutes, each test tire (195 / 65R15) described in Tables 2 and 3 was obtained. In addition, the groove width W1 of the circumferential groove (groove width at the tread surface) was set to 5 mm, and the total depression amount of the circumferential groove was set to 2 mm.

[0223] (Measurement of modulus at 200% elongation) For the No. 7 dumbbell-shaped test pieces cut from the inside of the second layer of the tread surface of each test tire, with the circumferential direction of the tire as the stretching direction and the radial direction of the tire as the thickness direction, and a thickness of 1 mm, a tensile test was carried out according to JIS K 6251:2017 under the conditions of an atmosphere of 23°C and a stretching speed of 3.3 mm / second, and the modulus (MPa) at 200% stretching was measured.

[0224] <Measurement of tanδ at 70°C> Rubber test pieces with a length of 20 mm × width of 4 mm × thickness of 1 mm were cut from the tread surface of each test tire, with the circumferential direction of the tire as the long side and the radial direction of the tire as the thickness direction. For each rubber test piece, using the EPLEXOR series manufactured by GABO, tanδ (tanδ at 70°C) was measured under the conditions of a temperature of 70°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±1.0%, and a tensile mode.

[0225] <Resistance to uneven wear performance> Each test tire was installed on all the wheels of a vehicle (domestic FF2000cc). After driving 1000 km on a test route on a dry asphalt road at an average speed of 80 km / h, the difference in wear amounts on both sides in the circumferential direction of the center tread blocks, intermediate tread blocks, and shoulder tread blocks of the rear wheels was measured. When measuring, for each tread block, 8 tread blocks with approximately equal intervals in the circumferential direction of the tire were used, and the average value of all the measured values was obtained. At the same time, the measurement results were expressed as an index according to the following calculation formula. The larger the index, the better the resistance to uneven wear performance. In the resistance to uneven wear performance index, Comparative Example 6 was set as the reference comparative example. (Resistance to uneven wear performance index) = (Wear amount difference of the reference comparative example) / (Wear amount difference of each test tire) × 100

[0226] <Wet grip performance> Each test tire was installed on all the tires of a vehicle (domestic FF2000cc), and the braking distance starting from an initial speed of 100 km / h on a wet asphalt road was obtained. The measurement results were expressed as an index according to the following calculation formula. The larger the index, the shorter the braking distance and the better the wet grip performance. In the wet grip performance index, Comparative Example 1 was set as the reference comparative example. (Wet grip performance index) = (Braking distance of the reference comparative example) / (Braking distance of each test tire) × 100

[0227] <Low fuel consumption performance> For each test tire, the rolling resistance coefficient (RRC) was measured in accordance with JIS D 4234:2009 (ISO 28580). For the reciprocal value of the rolling resistance coefficient, the measurement results were expressed as an exponent according to the following calculation formula. The larger the exponent, the smaller the rolling resistance and the more excellent the low fuel consumption performance. In the low fuel consumption performance index, Comparative Example 6 was set as the reference comparative example. (Low fuel consumption performance index) = (Rolling resistance coefficient of the reference comparative example) / (Rolling resistance coefficient of each test tire) × 100

[0228] <Comprehensive performance> The sum of the uneven wear resistance performance index, wet grip performance index, and low fuel consumption performance index was expressed as the comprehensive performance index.

[0229]

Table 1

[0230]

Table 2

[0231]

Table 3

[0232] <Embodiment> Examples of the embodiments of the present invention are shown below. 〔1〕A tire, characterized in that it is a tire having a tread surface the tread surface includes at least a first layer constituting the tread surface, a second layer adjacent to the first layer on the inner side in the tire radial direction, 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 any one of the rubber compositions constituting the first layer and the second layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components in the rubber composition constituting the first layer, when the mass of the rubber component is set to 100% by mass, the total styrene amount in the rubber composition is set to S1 (% by mass) in the rubber composition constituting the second layer, when the mass of the rubber component is set to 100% by mass, the total styrene amount in the rubber composition is set to S2 (% by mass) S1 - S2 > 0. 〔2〕The tire according to the above-mentioned 〔1〕, wherein when the thickness of the first layer is set to t1 (mm), S1 × t1 is less than 100.0. 〔3〕The tire according to the above-mentioned 〔2〕, wherein S1 × t1 is less than 50.0. 〔4〕The tire according to the above-mentioned 〔2〕, wherein S1 × t1 is less than 25.0. 〔5〕The tire according to any one of the above-mentioned 〔1〕 to 〔4〕, wherein S1 - S2 is greater than 7.0, preferably greater than 10.0. 〔6〕The tire according to any one of the above-mentioned 〔1〕 to 〔5〕, wherein S2 is greater than 0 and less than 20.0, preferably 10.0 or more and less than 20.0, more preferably greater than 10.0 and 18.0 or less. 〔7〕The tire according to any one of the above-mentioned 〔1〕 to 〔6〕, wherein the rubber composition constituting the first layer contains a copolymer resin containing styrene and cyclopentadiene as monomer components. 〔8〕The tire according to any one of the above-mentioned 〔1〕 to 〔7〕, wherein the ratio of the loss tangent (tanδ1) of the rubber composition constituting the first layer at 70 °C to the contact area ratio R (70 °C tanδ1 / R) is less than 0.29. 〔9〕The tire according to any one of the above-mentioned 〔1〕 to 〔8〕, wherein the ratio of the loss tangent (tanδ2) of the rubber composition constituting the second layer at 70 °C to the contact area ratio R (70 °C tanδ2 / R) is greater than 0.20, preferably greater than 0.22. 〔10〕The tire according to any one of the above-mentioned 〔1〕 to 〔9〕, wherein the modulus M2 of the rubber composition constituting the second layer at 200% elongation is 9.5 MPa or less. 〔11〕The tire according to any one of the above-mentioned 〔1〕 to 〔10〕, wherein the rubber composition constituting the second layer contains 80 parts by mass or more of silica based on 100 parts by mass of the rubber component. 〔12〕The tire according to any one of the above-mentioned 〔1〕 to 〔11〕, wherein the ratio of 70 °C tanδ2 to the loss tangent (70 °C tanδ3) of the rubber composition constituting the third layer at 70 °C (70 °C tanδ2 / 70 °C tanδ3) is greater than 1.0, preferably greater than 1.5, more preferably greater than 2.0, and further preferably greater than 2.3. 〔13〕The tire according to any one of the above-mentioned 〔1〕 to 〔12〕, wherein the tread portion has a plurality of circumferential grooves continuously extending in the tire circumferential direction, and at least one of the circumferential grooves is provided with a recessed portion recessed outward in the groove width direction compared with the groove edge of the tread surface appearing on the tread portion.

Claims

1. A tire, characterized in that: It is 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 first layer inwardly in the tire radial direction, and a third layer present inwardly 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, In the rubber composition constituting the first layer, the total amount of styrene in the rubber composition when the mass of the rubber component is 100 mass % is referred to as S1, In the rubber composition constituting the second layer, when the mass of the rubber component is 100 mass %, the total amount of styrene in the rubber composition is denoted as S2. S1-S2 is greater than 0, The unit of S1 and S2 is mass %.

2. The tire according to claim 1, wherein: When the thickness of the first layer is set to t1, S1×t1 is less than 100.0, and the unit of t1 is mm.

3. The tire according to claim 2, wherein: S1×t1 is less than 50.

0.

4. The tire according to claim 2, wherein: S1×t1 is less than 25.

0.

5. The tire according to claim 1 or 2, wherein: S1-S2 is greater than 7.

0.

6. The tire according to claim 1 or 2, wherein: S2 is greater than 0 and less than 20.

0.

7. The tire according to claim 1 or 2, wherein: The rubber composition constituting the first layer contains a copolymer resin including styrene and cyclopentadiene as monomer components.

8. The tire according to claim 1 or 2, wherein: The rubber composition constituting the first layer has a ratio of a loss tangent tan δ1 at 70°C to a contact area ratio R (70°C tan δ1 / R) of less than 0.

29.

9. The tire according to claim 1 or 2, wherein: The rubber composition constituting the second layer has a ratio of the loss tangent tan δ2 at 70°C to the contact area ratio R (70°C tan δ2 / R) of greater than 0.

20.

10. The tire according to claim 1 or 2, wherein: The modulus M2 of the rubber composition constituting the second layer at 200% elongation is 9.5 MPa or less.

11. The tire according to claim 1 or 2, wherein: The rubber composition constituting the second layer contains 80 parts by mass or more of silica based on 100 parts by mass of the rubber component.

12. The tire according to claim 1 or 2, wherein: The ratio (70°C tan δ2 / 70°C tan δ3) of 70°C tan δ2 to the loss tangent (70°C tan δ3) of the rubber composition constituting the third layer at 70°C is greater than 1.

0.

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

14. The tire according to claim 1 or 2, wherein: S1-S2 is less than 25.0.

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