tire

Abstract

To provide a tire which can improve durability performance.SOLUTION: A tire comprises: a tread part; and a belt layer. The tread part includes at least one rubber layer, and the belt layer includes a steel cord and a topping rubber which coats the steel cord. A cap rubber layer constituting the tread surface of the tread part and the topping rubber are respectively constituted by a rubber composition respectively containing a rubber constituent and filler. When the complex elastic modulus (70°CE*1) of the topping rubber at 70°C is 15.0 MPa or less, the maximum load capacity of the tire is WL(kg), and tanδ of the topping rubber at 70°C is 70°Ctanδ1, WL and 70°Ctanδ1 satisfy the following expression (1): 9.33×10-5×WL-70°Ctanδ1>0.023 ...(1).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] There is a demand for a tire with excellent durability that can suppress the frequency of tire replacement and be used for a longer period. Patent Document 1 discloses a steel element for reinforcing a rubber product, the steel element being covered with a coating of a ternary or quaternary alloy of copper - M - zinc, and a reinforced rubber article containing the steel element and a rubber compound.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, the specific degree of durability when the rubber article is used as a tire is not clear, and there is room for improvement.

[0005] An object of the present invention is to improve the durability performance of a tire.

Means for Solving the Problems

[0006] The present invention is a tire provided with a tread portion and a belt layer, wherein the tread portion has at least one rubber layer, the belt layer has steel cords and topping rubber covering the steel cords, the cap rubber layer constituting the tread surface of the tread portion and the topping rubber are each composed of a rubber composition containing a rubber component and a filler, the complex elastic modulus (70°C E*1) of the topping rubber at 70°C is 15.0 MPa or less, and the maximum load capacity of the tire is W L(kg), when the tanδ of the topping rubber at 70 °C is defined as 70 °C tanδ1, W L and a tire in which 70 °C tanδ1 satisfies the following formula (1). 9.33×10 -5 ×W L -70 °C tanδ1 > 0.023 ···(1)

Advantages of the Invention

[0007] According to the present invention, the durability performance of the tire can be improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0009] A tire according to an embodiment of the present invention is a tire including a tread portion and a belt layer, wherein the tread portion has at least one rubber layer, the belt layer has a steel cord and a topping rubber covering the steel cord, a cap rubber layer constituting a tread surface of the tread portion and the topping rubber are each composed of a rubber composition containing a rubber component and a filler, a complex elastic modulus (70 °C E*1) of the topping rubber at 70 °C is 15.0 MPa or less, a maximum load capacity of the tire is W L (kg), when the tanδ of the topping rubber at 70 °C is defined as 70 °C tanδ1, W L and a tire in which 70 °C tanδ1 satisfies the following formula (1). 9.33×10 -5 ×W L -70 °C tanδ1 > 0.023 ···(1)

[0010] Although not intending to be bound by theory, the reasons for the improved durability performance of the tire of the present invention are considered as follows.

[0011] When the virtual volume (air capacity) of the tire increases, the maximum load capacity W of the tire L is considered to increase, and the amount of deformation of the tread portion and the belt layer can be suppressed. Therefore, when W L is small, the deformation in the belt layer becomes relatively large. Therefore, by making the heat generation property (70°C tanδ1) of the topping rubber covering the belt layer smaller, it is considered that the durability performance of the tire can be easily improved. On the other hand, when the heat generation property (70°C tanδ1) of the topping rubber is high, by increasing W L and suppressing the amount of deformation of the tread portion and the belt layer, it is considered that the durability performance of the tire can be easily improved.

[0012] Also, by setting the complex elastic modulus (70°C E*1) of the topping rubber at 70°C to 15.0 MPa or less, it is considered that the generation of strain concentration in the belt layer due to extremely high rigidity of the belt layer can be suppressed.

[0013] By the above cooperation, it is considered that the remarkable effect of more effectively improving the durability performance of the tire is achieved.

[0014] The filler contained in the rubber composition constituting the topping rubber preferably contains silica.

[0015] By blending silica into the topping rubber, the rigidity in the micro-deformation region of the topping rubber can be reduced. Therefore, the adhesion to the steel cord topping rubber is improved, and it is considered that the durability performance of the tire is further improved.

[0016] The filler contained in the rubber composition constituting the topping rubber preferably contains recycled carbon black.

[0017] Recycled carbon black has a wider particle size distribution than ordinary carbon black. Therefore, compared with the case of compounding ordinary carbon black, it can suppress the movement of the polymer against a wide range of frequencies of input from the road surface, and can suppress the heat generation of the topping rubber. Thus, it is considered that the durability performance of the tire is further improved.

[0018] The content of carbon black with respect to 100 parts by mass of the rubber component of the rubber composition constituting the cap rubber layer is preferably 20 parts by mass or less. Further, the tanδ (30°C tanδ2) at 30°C of the cap rubber layer is preferably 0.16 or less.

[0019] By reducing the heat generation property of the cap rubber layer, such as by reducing the content of carbon black in the cap rubber layer, the temperature of the tire surface can be kept relatively low. And by suppressing the heat generation of the surface member, the heat generated in the tire internal members such as the belt layer can escape more easily, and it is considered that the durability performance of the tire is further improved.

[0020] When the tanδ at 30°C of the cap rubber layer is 30°C tanδ2 and the tanδ at 0°C of the cap rubber layer is 0°C tanδ2, 0°C tanδ2 / 30°C tanδ2 is preferably more than 2.3.

[0021] By setting 0°C tanδ2 / 30°C tanδ2 within the above range, the cap rubber layer can be kept in a flexible state up to a low temperature range. Therefore, in a wide temperature range, the concentration of strain on the tire internal members due to the deformation caused by rolling can be suppressed. As a result, the mechanical fatigue deterioration due to the deformation of the topping rubber is suppressed, and it is considered that the durability performance of the tire is further improved.

[0022] The total styrene amount in the rubber component constituting the cap rubber layer is preferably 15% by mass or less.

[0023] By setting the total styrene content in the rubber component constituting the cap rubber layer within the above range, even when a styrene-butadiene rubber, which generally has a higher glass transition temperature compared to isoprene rubber or butadiene rubber, is blended, the complex elastic modulus can be reduced in a wide temperature range, particularly in the low temperature range. Therefore, it is considered that the cap rubber layer can be maintained in a flexible state.

[0024] W L From the viewpoint of facilitating the exhibition of the effects of the present invention, it is preferably 400 or more.

[0025] The steel cord is preferably a single-wire monofilament cord.

[0026] By using a non-twisted monofilament cord as the steel cord and increasing the rigidity of the steel cord, it is considered that the amount of deformation of the belt layer can be suppressed.

[0027] When the cross-sectional area of the steel cord is S (mm 2 ), and the number of the steel cords per 50 mm width in the direction orthogonal to the longitudinal direction of the steel cord is E, from the viewpoint of the effects of the present invention, S×E is preferably 1.0 or more and 25 or less.

[0028] When the silica content in 100 parts by mass of the rubber component of the rubber composition constituting the topping rubber is Y (parts by mass), Y / (S×E) is preferably 0.10 or more.

[0029] By blending silica into the topping rubber, the rubber becomes more acidic, and the zinc oxide film on the plated surface of the steel cord is likely to peel off, so it is considered that an adhesive layer can be efficiently formed. Here, by setting Y / (S×E) within the above range, the advantage of adhesive layer formation due to acidification exceeds the thickening of the adhesive layer due to copper precipitation, and it is considered that good adhesive performance can be obtained.

[0030] The steel cord preferably has a ternary plating layer composed of copper, zinc, and cobalt.

[0031] By adopting ternary plating, cobalt, which has a greater ionization tendency than copper, preferentially elutes. Therefore, it is considered that the thickening of the adhesive layer due to the elution of copper after damp heat deterioration can be suppressed, and the adhesive strength can be maintained at a high level.

[0032] When the weight of the tire is G (kg), G / W L is preferably 0.060 or less.

[0033] G / W L By setting G / W within the above range, by reducing the amount of rubber in the entire tire, while suppressing the total heat generation due to deformation, and by ensuring sufficient air capacity with respect to the load, the total heat generation due to deformation can be synergistically suppressed. Therefore, it is considered that high durability performance and low fuel consumption performance can be achieved simultaneously.

[0034] <Definition> The "tread portion" is the portion that forms the ground contact surface of the tire. In the radial cross-section of the tire, when it includes members that form the tire skeleton with steel or textile materials such as the belt layer, belt reinforcing layer, carcass layer, etc., it is the member outside these in the radial direction of the tire.

[0035] The "belt layer" is a layer provided outside the carcass layer in the radial direction of the tire. The internal reinforcing material is inclined about 18 to 30° with respect to the circumferential direction of the tire and overlaps in the opposite direction, and a plurality of working layers, or a circumferential belt layer in which the internal reinforcing material is oriented at an angle of ±10° with respect to the circumferential direction of the tire, etc. are applicable.

[0036] The "normal state" is a no-load state in which the tire is mounted on a normal rim and filled with air at normal internal pressure.

[0037] The "dimensions of each part of the tire" are, unless otherwise specified, values specified in the normal state for those appearing on the outer surface of the tire. On the other hand, those existing inside the tire or on the tire cut surface are, for example, values specified in a state where the tire is cut by a plane including the tire rotation axis and the cut tire piece is held at the rim width of the normal rim.

[0038] A "regular rim" is a rim defined for each tire in a standard system that includes the standards on which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Association), it refers to the "standard rim" in the applicable sizes described in the "Jatma Year Book"; in the case of ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" described in the "STANDARDS MANUAL"; and in the case of TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" described in the "YEAR BOOK". Refer to JATMA, ETRTO, and TRA in that order, and follow the relevant standards if there are applicable sizes during the reference. In the case of a tire not defined in the above standards, it refers to the rim with the narrowest width among the rims with the smallest diameter that can be assembled with the tire and can maintain the internal pressure (i.e., does not cause air leakage between the rim and the tire).

[0039] A "regular internal pressure" is the air pressure defined for each tire in a standard system that includes the standards on which the tire is based. For example, in the case of JATMA, it refers to the "maximum air pressure"; in the case of ETRTO, it refers to the "INFLATION PRESSURE"; and in the case of TRA, it refers to the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". Similar to the case of the regular rim, refer to JATMA, ETRTO, and TRA in that order, and follow the relevant standards if there are applicable sizes during the reference. In the case of a tire not defined in the above standards, it refers to the regular internal pressure (but not less than 250 kPa) of another tire size described with the regular rim as the standard rim (provided that it is defined in the standards). If there are multiple regular internal pressures not less than 250 kPa described, it refers to the minimum value among them.

[0040] "Tire weight G (kg)" refers to the weight of the tire alone without including the weight of the rim. On the other hand, when the tire inner cavity is equipped with sound insulation materials, sealants, sensors, etc., G shall be the weight including these components.

[0041] "Maximum load capacity (W L )(kg)" is the value calculated by the following formula when the tire cross-sectional width measured in the normal state is Wt (mm), the tire cross-sectional height is Ht (mm), and the tire outer diameter is Dt (mm), and is different from the "maximum load capacity" based on the load index defined in the JATMA standard. V is the virtual volume of the space occupied by the tire.

[0042]

Equation

[0043] "Tire outer diameter Dt" refers to the outer diameter of the tire in the normal state.

[0044] "Tire cross-sectional width Wt" refers to the maximum width between the outer surfaces of the sidewalls in the normal state (excluding patterns or characters on the tire sidewall if any).

[0045] "Tire cross-sectional height Ht" refers to the height in the tire radial direction in the cross-section of the tire including the tire rotation axis. When the rim diameter of the tire is R, it can be obtained by (Dt - R) / 2.

[0046] "Cross-sectional area of steel cord" is the cross-sectional area of the steel cord when cut along a plane perpendicular to the longitudinal direction of the steel cord.

[0047] "Softening agent" is a material that imparts plasticity to the rubber component and is a component extracted from the rubber composition using acetone. The softening agent includes softening agents that are liquid at 25°C (liquid) and softening agents that are solid at 25°C. However, waxes and stearic acid commonly used in the tire industry are excluded.

[0048] "Content of softening agent" also includes the amount of softening agent contained in the stretched rubber component previously stretched by a softening agent such as oil, resin component, liquid rubber component, etc. The same applies to the content of oil, resin component, and liquid rubber. For example, when the stretching component is oil, the stretched oil is included in the content of oil.

[0049] <Measurement method> "E* at 70°C" is the complex elastic modulus 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 an elongation mode using a dynamic viscoelasticity measuring device (for example, the Implex series manufactured by GABO). The sample for measuring E* at 70°C is a vulcanized rubber composition with a length of 20 mm × width of 4 mm × thickness of 1 mm. When it is cut out from a tire, it is cut out from the topping rubber such that the circumferential direction of the tire is the long side and the radial direction of the tire is the thickness direction.

[0050] "tanδ at 70°C" is the loss tangent 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 an elongation mode using a dynamic viscoelasticity measuring device (for example, the Implex series manufactured by GABO). The sample for this measurement is prepared in the same manner as in the case of E* at 70°C.

[0051] "tanδ at 30°C" is the loss tangent measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of ±1%, and an elongation mode using a dynamic viscoelasticity measuring device (for example, the Implex series manufactured by GABO). The sample for measuring tanδ at 30°C is a vulcanized rubber composition with a length of 20 mm × width of 4 mm × thickness of 1 mm. When it is cut out from a tire, it is cut out from the tread part such that the circumferential direction of the tire is the long side and the radial direction of the tire is the thickness direction.

[0052] "tanδ at 0°C" is the loss tangent measured under the conditions of a temperature of 0°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±2.5%, and an elongation mode using a dynamic viscoelasticity measuring device (for example, the Implex series manufactured by GABO). The sample for this measurement is prepared in the same manner as in the case of tanδ at 30°C.

[0053] The "average thickness of the plating layer" is measured in accordance with JIS H 8501:1999.

[0054] The "styrene content" is 1 a value calculated by 1H-NMR measurement, and is applied to, for example, rubber components having repeating units derived from styrene such as SBR.

[0055] The "vinyl content (amount of 1,2-bonded butadiene units)" is a value calculated by infrared absorption spectrum analysis in accordance with JIS K 6239-2:2017, and is applied to, for example, rubber components having repeating units derived from butadiene such as SBR and BR.

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

[0057] The "total styrene amount in the rubber component" is the total content (% by mass) of styrene units contained in 100% by mass of the rubber component. For each rubber component, a value obtained by multiplying the styrene content (% by mass) by the mass fraction in the rubber component is calculated, and the sum of these values. Specifically, it is calculated by Σ (styrene content (% by mass) of each rubber containing styrene units × content (% by mass) of each rubber containing styrene units in the rubber component / 100).

[0058] The "weight average molecular weight (Mw)" can be determined by standard polystyrene conversion based on the measured value by gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation). For example, it is applied to SBR, BR, etc.

[0059] The "nitrogen adsorption specific surface area of carbon black (N 2The "nitrogen adsorption specific surface area of silica (N 2 SA)" is measured according to ASTM D3037-93 by the BET method.

[0060] The "average primary particle diameter" is obtained by photographing particles with a transmission or scanning electron microscope and calculating the arithmetic mean of 400 particle diameters. When the shape of the particle is approximately circular, the diameter of the circle is taken as the particle diameter; when the particle is needle-shaped or rod-shaped, the minor axis is taken as the particle diameter; in other cases, the equivalent circle diameter is calculated from the electron microscope image and taken as the particle diameter. The equivalent circle diameter is obtained as the positive square root of [4 × (area of the particle) / π]. The average primary particle diameter is applicable to silica, carbon black, etc.

[0061] The "softening point of the resin component" is measured with a ring and ball softening point measuring device according to the softening point specified in JIS K 6220-1:2015 7.7, and is the temperature at which the ball drops.

[0062] The manufacturing procedure of the tire, which is one embodiment of the present invention, will be described in detail below. However, the following description is an exemplification for explaining the present invention, and is not intended to limit the technical scope of the present invention only to this description scope.

[0063] <Tire> Hereinafter, a tire according to an embodiment of the present invention will be described with reference to the drawings.

[0064] FIG. 1 shows a cross-sectional view of the tire 11 according to this embodiment in a plane passing through the tire rotation axis. In FIG. 1, only the left side portion of the CL (center line) is shown, but with CL as the axis of symmetry, the same structure is continuously provided on the right side of the CL. As shown in FIG. 1, the tire 11 includes a tread portion 12, a sidewall portion 13, a bead portion 14, an inner liner 15, a carcass 16, a belt layer 17, and a bead wire 18. The belt layer 17 has two layers, but the number of layers is not particularly limited and can be arbitrarily selected.

[0065] Figure 2 shows a cross-sectional view taken along a plane perpendicular to the longitudinal direction of the steel cord 21. Each belt layer 17 has a plurality of steel cords 21 and topping rubber 22. The plurality of steel cords 21 are arranged in parallel in a row. Further, the topping rubber 22 covers the steel cord 21, and the entire circumference of each individual steel cord is covered with the topping rubber 22. The steel cord 21 is embedded in the topping rubber 22.

[0066] The steel cord 21 may or may not be inclined with respect to the tire circumferential direction. The inclination angle of the steel cord 21 with respect to the tire circumferential direction is not particularly limited, but is set, for example, in the range of 0° to 60°, preferably 5° to 45°, and more preferably 10° to 30°.

[0067] (Steel cord) The steel cord according to the present embodiment has one or more steel filaments also called filaments. The steel cord may be a single-wire monofilament cord (that is, a cord composed of one filament having a 1×1 structure), or may have a plurality of filaments, but a monofilament cord is mentioned as a preferred embodiment.

[0068] By making the steel cord a non-twisted monofilament cord and increasing the rigidity of the steel cord, it is considered that the amount of deformation of the belt layer can be suppressed.

[0069] When one steel cord has a plurality of filaments, the steel cord preferably has a twisted structure in which the plurality of filaments are twisted along its longitudinal direction. The twisted structure in the case where the steel cord has a plurality of filaments is not particularly limited, and for example, it can be a single-twisted steel cord having a 1×N structure or a layer-twisted steel cord having an N+M structure.

[0070] The single-twist structure can be expressed, for example, as a 1×N structure. The 1×N structure means a structure in which N filaments are twisted together to form a single layer (one layer). The single layer means a structure in which, in a cross section perpendicular to the longitudinal direction of the steel cord, the filaments are arranged along the circumferential direction of a single circle in a single layer (one layer). In the single-twist structure, N is preferably 6 or less, more preferably 4 or less, and particularly preferably 2.

[0071] Figure 3 is a perspective view of a steel cord having a 1×2 structure. The steel cord 50 shown in Figure 3 spirally twists two filaments 51 along the longitudinal direction so as to form a single layer.

[0072] The layer-twist structure has a structure in which, in a cross section perpendicular to the longitudinal direction of the steel cord, a plurality of filaments are wound in a plurality of layers in order from the center, and can be expressed, for example, as an N+M structure. The N+M structure means a structure having a core in which N filaments are twisted together in a spiral shape along the longitudinal direction thereof, and an outer sheath in which M filaments are twisted together in a spiral shape along the longitudinal direction of the core so as to cover the outer periphery of the core.

[0073] The material of the steel filament is not particularly limited, and HT material (High Tensile), SHT material (Super High Tensile), UHT material (Ultra High Tensile), etc. can be used. Also, recycled iron obtained by melting used iron products may be used. When using a steel cord in which a plurality of steel filaments are twisted together, from the viewpoint of improving the durability performance by making it easier for the topping rubber to enter the inside of the steel cord, steel filaments pre-bent in the longitudinal direction may be used.

[0074] The filament diameter of the steel cord is not particularly limited and can be arbitrarily selected according to required characteristics and the like. However, from the viewpoint of ensuring the durability of the steel cord against impact, 0.10 mm or more is preferable, 0.13 mm or more is more preferable, 0.16 mm or more is further preferable, 0.19 mm or more is further preferable, 0.22 mm or more is further preferable, 0.25 mm or more is further preferable, and 0.28 mm or more is particularly preferable. Also, from the viewpoint of sufficiently absorbing impact and improving the riding comfort performance, 0.70 mm or less is preferable, 0.60 mm or less is more preferable, 0.50 mm or less is further preferable, 0.45 mm or less is further preferable, 0.40 mm or less is further preferable, and 0.35 mm or less is particularly preferable.

[0075] The steel cord according to this embodiment may be provided with a plating layer. Since the steel cord having a plating layer exhibits high moisture and heat resistance adhesion performance even under severe conditions of high temperature and high humidity, peeling between the topping rubber and the steel cord can be prevented, and the durability of the tire under moisture and heat conditions can be improved. When the steel cord has a plurality of filaments, a plating layer can be provided on the surface of each filament.

[0076] The configuration of the plating layer is not particularly limited, but a plating layer containing a copper layer and a zinc layer is preferable, and a plating layer containing a copper layer, a zinc layer, and a cobalt layer is more preferable. In particular, a steel cord having a ternary plating layer composed of copper (Cu), zinc (Zn), and cobalt (Co) exhibits high moisture and heat resistance adhesion performance even under severe conditions of high temperature and high humidity, so peeling between the topping rubber and the steel cord can be prevented, and the durability of the tire under moisture and heat conditions can be improved.

[0077] From the perspective of suppressing the excessive reaction of copper, the zinc content in the plating layer is preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more. Further, from the perspective of suppressing the decrease in adhesion due to the generation of excessive zinc oxide, it is preferably 44% by mass or less, more preferably 40% by mass or less, even more preferably 36% by mass or less, and particularly preferably 32% by mass or less.

[0078] From the perspective of adhesiveness, the copper content in the plating layer is preferably 55% by mass or more, more preferably 58% by mass or more, and even more preferably 61% by mass or more. Further, from the perspective of preventing rubber deterioration due to the elution of copper in a humid heat environment, it is preferably 78% by mass or less, more preferably 75% by mass or less, even more preferably 72% by mass or less.

[0079] From the perspective of thermo-humid adhesiveness, the cobalt content in the plating layer is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and even more preferably 3.0% by mass or more. Further, from the perspective of preventing crack generation during wire drawing, it is preferably 8.0% by mass or less, more preferably 7.0% by mass or less, even more preferably 6.0% by mass or less.

[0080] The plating layer can be formed by plating a copper layer, a zinc layer, a cobalt layer, etc. on a filament before wire drawing, and then performing heat treatment to diffuse the metals of the respective layers formed on the surface of the filament. Note that the lamination order formed on the filament for forming the plating layer is not particularly limited.

[0081] Next, a filament having a plating layer can be formed by wire-drawing the heat-treated material to a desired filament diameter. When the steel cord is composed of a single filament, it can be used as it is after wire drawing. Further, when the steel cord has a plurality of filaments, after wire drawing, the obtained filaments can be twisted, for example, into a desired twist structure to form a steel cord having a plating layer.

[0082] From the perspective of initial adhesiveness, the average thickness of the plating layer is preferably 0.10 μm or more, more preferably 0.13 μm or more, and even more preferably 0.16 μm or more. Also, from the perspective of suppressing excessive adhesion reaction, it is preferably 0.40 μm or less, more preferably 0.35 μm or less, and even more preferably 0.30 μm or less.

[0083] The cross-sectional area S of the steel cord is preferably 0.04 mm 2 or more, more preferably 0.05 mm 2 or more, even more preferably 0.06 mm 2 or more, particularly preferably 0.07 mm 2 or more. Also, the cross-sectional area S of the steel cord is preferably 0.80 mm 2 or less, more preferably 0.60 mm 2 or less, even more preferably 0.40 mm 2 or less, even more preferably 0.30 mm 2 or less, even more preferably 0.25 mm 2 or less, even more preferably 0.20 mm 2 or less, particularly preferably 0.20 mm or less.

[0084] The number E (also called ends) of steel cords per 50 mm width in the direction perpendicular to the longitudinal direction of the steel cord is not particularly limited, but is preferably 20 or more, more preferably 25 or more, even more preferably 30 or more, even more preferably 35 or more, and particularly preferably 40 or more. Also, E is preferably 90 or less, more preferably 80 or less, even more preferably 70 or less, and particularly preferably 60 or less.

[0085] The product (S × E) of S and E is preferably 1.0 or more, more preferably 2.0 or more, even more preferably 3.0 or more, even more preferably 4.0 or more, even more preferably 5.0 or more, and particularly preferably 5.5 or more. Also, the product of S and E is preferably 25 or less, more preferably 20 or less, even more preferably 15 or less, even more preferably 12 or less, even more preferably 10 or less, and particularly preferably 8.0 or less. Note that the product of S and E is an index representing the amount of steel cord per unit cross-sectional area.

[0086] When the content of silica with respect to 100 parts by mass of the rubber component of the rubber composition constituting the topping rubber is Y (parts by mass), Y / (S×E) is preferably 0.10 or more, more preferably 0.30 or more, still more preferably 0.50 or more, still more preferably 0.75 or more, still more preferably 1.0 or more, and particularly preferably 1.2 or more. By blending silica into the topping rubber, the rubber becomes more acidic, and the zinc oxide film on the plated surface of the steel cord is likely to peel off, so that an adhesive layer can be efficiently formed. Here, by setting Y / (S×E) within the above range, it is considered that the advantage of adhesive layer formation due to acidification exceeds the thickening of the adhesive layer due to copper precipitation, and good adhesive performance can be obtained. On the other hand, the upper limit value of Y / (S×E) is not particularly limited, but is preferably 20 or less, more preferably 10 or less, still more preferably 5.0 or less, and particularly preferably 2.5 or less.

[0087] The maximum load capacity W of the tire L (kg) is preferably 400 or more, more preferably 500 or more, still more preferably 600 or more, still more preferably 700 or more, and particularly preferably 800 or more from the viewpoint of more favorably exhibiting the effects of the present invention. Also, W L (kg) is preferably 1300 or less, more preferably 1200 or less, and still more preferably 1100 or less. Note that W L can be increased by increasing the virtual volume V of the space occupied by the tire, and conversely can be decreased.

[0088] When the weight of the tire is G (kg), G / W L is preferably 0.060 or less, more preferably 0.040 or less, still more preferably 0.025 or less, and particularly preferably 0.020 or less from the viewpoint of the effects of the present invention. On the other hand, G / W LThe lower limit is not particularly limited, and for example, it can be 0.012 or more, 0.013 or more, 0.014 or more. The weight G of the tire can be varied by a conventional method, that is, it can be increased by increasing the specific gravity of the tire or increasing the thickness of each member of the tire, and conversely, it can be decreased.

[0089] The complex elastic modulus (70°C E*1) of the topping rubber at 70°C is 15.0 MPa or less from the viewpoint of the effects of the present invention, preferably 14.0 MPa or less, more preferably 12.0 MPa or less, further preferably 10.0 MPa or less, still further preferably 9.0 MPa or less, still further preferably 8.0 MPa or less, and particularly preferably 7.0 MPa or less. On the other hand, the lower limit of 70°C E*1 is not particularly limited, but preferably 2.0 MPa or more, more preferably 3.0 MPa or more, and further preferably 4.0 MPa or more.

[0090] The tanδ (70°C tanδ1) of the topping rubber at 70°C is preferably 0.079 or less, more preferably 0.065 or less, further preferably 0.052 or less, still further preferably 0.046 or less, still further preferably 0.040 or less, still further preferably 0.036 or less, and particularly preferably 0.033 or less from the viewpoint of the effects of the present invention. On the other hand, the lower limit of 70°C tanδ1 is not particularly limited, but preferably 0.020 or more, more preferably 0.023 or more, and further preferably 0.026 or more.

[0091] The tire according to this embodiment is W L and 70°C tanδ1 satisfies the following formula (1). 9.33×10 -5 ×W L -70°C tanδ1 > 0.023 ···(1)

[0092] 9.33×10 -5 ×W L-70 °C tan δ1 is preferably greater than 0.024, more preferably greater than 0.030, still more preferably greater than 0.035, and particularly preferably greater than 0.040 from the viewpoint of the effects of the present invention. On the other hand, 9.33×10 -5 ×W L The upper limit of -70 °C tan δ1 is not particularly limited, but is preferably less than 0.090, more preferably less than 0.085, still more preferably less than 0.080, and particularly preferably less than 0.075.

[0093] Tan δ at 30 °C (30 °C tan δ2) of the cap rubber layer is preferably 0.25 or less, more preferably 0.23 or less, still more preferably 0.20 or less, still more preferably 0.18 or less, still more preferably 0.16 or less, still more preferably 0.15 or less, and particularly preferably 0.14 or less from the viewpoint of heat generation. On the other hand, 30 °C tan δ2 is preferably 0.03 or more, more preferably 0.05 or more, still more preferably 0.07 or more, and particularly preferably 0.09 or more from the viewpoint of riding comfort performance.

[0094] Tan δ at 0 °C (0 °C tan δ2) of the cap rubber layer is preferably 0.42 or less, more preferably 0.40 or less, still more preferably 0.38 or less, still more preferably 0.36 or less, and particularly preferably 0.34 or less from the viewpoint of low fuel consumption performance at low temperatures. On the other hand, 0 °C tan δ2 is preferably 0.07 or more, more preferably 0.10 or more, still more preferably 0.12 or more, still more preferably 0.15 or more, and particularly preferably 0.18 or more from the viewpoint of wet grip performance.

[0095] The 0°C tanδ2 / 30°C tanδ2 is preferably greater than 1.4, more preferably greater than 1.5, still more preferably greater than 1.7, still more preferably greater than 1.9, still more preferably greater than 2.1, and particularly preferably greater than 2.3. By setting the 0°C tanδ2 / 30°C tanδ2 within the above range, the cap rubber layer can be maintained in a flexible state even in a low temperature range, so that in a wide temperature range, the concentration of strain on the tire internal members due to deformation by rolling can be suppressed. As a result, it is considered that the mechanical fatigue deterioration due to the deformation of the topping rubber is suppressed, and the durability performance of the tire is further improved. On the other hand, although the upper limit value of 0°C tanδ2 / 30°C tanδ2 is not particularly limited, it is preferably less than 3.0, more preferably less than 2.8.

[0096] [Rubber composition] The rubber composition constituting the topping rubber of the tire according to the present embodiment and the rubber composition constituting the tread portion (hereinafter referred to as the rubber composition according to the present embodiment) contain a rubber component and a filler, and both can be manufactured using the raw materials described below. Hereinafter, the rubber composition according to the present embodiment will be described, but unless otherwise specified, it is applicable to both the rubber composition constituting the tread portion and the rubber composition constituting the topping rubber.

[0097] <Rubber component> In the rubber composition according to the present embodiment, a diene rubber is preferably used as the rubber component. Examples of the diene rubber include isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), etc. These diene rubbers may be modified rubbers treated with a modifying group capable of interacting with a filler such as carbon black or silica, or may be hydrogenated rubbers in which a part of the unsaturated bond is hydrogenated. The diene rubber may be used alone or in combination of two or more. Further, as the diene rubber, an extended rubber preliminarily extended using a softening agent described later may be used.

[0098] The content of diene rubber in the rubber component is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. Further, the rubber component may be composed of only diene rubber.

[0099] As the diene rubber component, at least one selected from the group consisting of isoprene rubber, SBR, and BR is preferably used. The diene rubber component preferably contains isoprene rubber, more preferably contains isoprene rubber and SBR and / or BR, still more preferably contains isoprene rubber and SBR, and particularly preferably contains isoprene rubber, BR, and SBR.

[0100] (Isoprene rubber) As the isoprene rubber, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. Natural rubber includes, in addition to unmodified natural rubber (NR), modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. These isoprene rubbers may be used alone or in combination of two or more.

[0101] NR is not particularly limited, and those common in the tire industry can be used. For example, SIR20, RSS#3, TSR20, etc. can be mentioned.

[0102] From the viewpoint of the effects of the present invention, the content of isoprene rubber in the rubber component constituting the topping rubber is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and particularly preferably 90% by mass or more. On the other hand, the upper limit value of the content is not particularly limited and may be 100% by mass.

[0103] From the viewpoint of the effects of the present invention, the content of the isoprene rubber in the rubber component constituting the cap rubber layer is preferably 70% by mass or less, more preferably 60% by mass or less, still more preferably 50% by mass or less, and particularly preferably 45% by mass or less. On the other hand, the lower limit of the content is not particularly limited, but can be 1% by mass or more, 5% by mass or more, 10% by mass or more, or 15% by mass or more.

[0104] (SBR) There is no particular limitation on the SBR. Examples include unmodified solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBR (modified S-SBR, modified E-SBR). Examples of the modified SBR include SBR with a modified terminal and / or main chain, and modified SBR coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.). Among them, S-SBR and modified SBR are preferred. Furthermore, hydrogenated products (hydrogenated SBR) of these SBRs can also be used. These SBRs can be used alone or in combination of two or more.

[0105] In this embodiment, either extended SBR or non-extended SBR can be used as the SBR. When using extended SBR, the extension amount of the SBR, that is, the content of the extension softener contained in the SBR, is preferably 10 to 50 parts by mass with respect to 100 parts by mass of the rubber solid content of the SBR.

[0106] As the SBR listed above, for example, those commercially available from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., ZS Elastomer Co., Ltd., etc. can be used.

[0107] The styrene content of the SBR is preferably 40% by mass or less, more preferably 36% by mass or less, still more preferably 32% by mass or less, and particularly preferably 28% by mass or less. Also, the styrene content of the SBR is preferably 5% by mass or more, more preferably 7% by mass or more, still more preferably 10% by mass or more, and particularly preferably 12% by mass or more. The styrene content of the SBR is measured by the above measurement method.

[0108] From the viewpoints of ensuring reactivity with silica and abrasion resistance performance, the vinyl content of SBR is preferably 5 mol% or more, more preferably 10 mol% or more, and still more preferably 15 mol% or more. Further, from the viewpoints of elongation at break and abrasion resistance performance, the vinyl content of SBR is preferably 45 mol% or less, more preferably 40 mol% or less, and still more preferably 35 mol% or less. Note that the vinyl content of SBR is measured by the above measurement method.

[0109] From the viewpoint of the effects of the present invention, the weight average molecular weight (Mw) of SBR is preferably 100,000 or more, more preferably 200,000 or more, and still more preferably 300,000 or more. Further, from the viewpoint of crosslinking uniformity, the weight average molecular weight is preferably 2,000,000 or less, more preferably 1,800,000 or less, and still more preferably 1,500,000 or less. Note that the weight average molecular weight of SBR is measured by the above measurement method.

[0110] The content of SBR in the rubber component constituting the topping rubber is not particularly limited, but is preferably 40% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, and particularly preferably 5% by mass or less.

[0111] The content of SBR in the rubber component constituting the cap rubber layer can be appropriately selected, for example, so that the total styrene amount in the rubber component constituting the cap rubber layer satisfies the following range, but is preferably 85% by mass or less, more preferably 80% by mass or less, still more preferably 75% by mass or less, and particularly preferably 70% by mass or less. On the other hand, the lower limit value of the content is not particularly limited, but can be 1% by mass or more, 5% by mass or more, 10% by mass or more, 15% by mass or more.

[0112] (BR) BR is not particularly limited. For example, BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare-earth butadiene rubber synthesized using a rare-earth element-based catalyst (rare-earth-based BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc., which are common in the tire industry, can be used. These BRs may be used alone or in combination of two or more.

[0113] As the high-cis BR, for example, those commercially available from Nippon Zeon Co., Ltd., Ube Industries, Ltd., JSR Corporation, etc. can be used. By containing high-cis BR, the abrasion resistance performance can be improved. The cis content of the high-cis BR is preferably 95 mol% or more, more preferably 96 mol% or more, and even more preferably 97 mol% or more. The cis content of BR is measured by the above measurement method.

[0114] The content of BR in the rubber component constituting the topping rubber is not particularly limited, but is preferably 40% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less.

[0115] From the viewpoint of the effects of the present invention, the content of BR in the rubber component constituting the cap rubber layer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 30 parts by mass or more. Also, the content is preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, and particularly preferably 45% by mass or less.

[0116] From the viewpoint of the effects of the present invention, the total styrene amount in the rubber component constituting the cap rubber layer is preferably 25% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and particularly preferably 13% by mass or less. Also, the lower limit value of the total styrene amount in the rubber component is not particularly limited, but is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and particularly preferably 7% by mass or more.

[0117] (Other rubber components) The rubber component may contain other rubber components other than the diene rubber as long as the effects of the present invention are not affected. As the other rubber components other than the diene rubber, crosslinkable rubber components generally used in the tire industry can be used. For example, butyl rubber (IIR), halogenated butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber and other non-diene rubbers can be mentioned. In addition to the above rubber components, known thermoplastic elastomers may or may not be contained. The other rubber components may be used alone or in combination of two or more.

[0118] (Rubber components synthesized from recycled and biomass-derived raw materials) The monomers that are the constituent units of synthetic rubbers such as SBR and BR may be derived from petroleum or recycled from rubber products such as tires and non-rubber products such as polystyrene. The monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled butadiene and recycled aromatic vinyl compounds. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl compound is not particularly limited, and examples include styrene. Among them, it is preferable to use recycled butadiene (recycled butadiene) and / or recycled styrene (recycled styrene) as raw materials.

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

[0120] Furthermore, monomers that are constituent units of polymers such as SBR and BR may be derived from biomass. The biomass-derived monomers (biomass monomers) are not particularly limited, and examples include biomass-derived butadiene and biomass-derived aromatic vinyl compounds. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl compound is not particularly limited, and examples include styrene. Also, the method for producing biomass monomers is not particularly limited, and examples include those by biological and / or chemical and / or physical conversion of animals and plants. Fermentation by microorganisms is typical of biological conversion, and examples of chemical and / or physical conversion include those by catalysts, high heat, high pressure, electromagnetic waves, supercritical fluids, and combinations thereof. Examples of the biomass sources of these monomers include sugars, wood, plant residues after obtaining useful components, plant-derived ethanol, biomass naphtha, and the like.

[0121] The polymers synthesized from biomass monomer components (biomass polymers) are not particularly limited, and examples include polybutadiene rubber synthesized from biomass-derived butadiene, and aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0122] Whether the raw material of the polymer is derived from biomass can be determined by pMC (percent Modern Carbon) measured in accordance with ASTM D6866-10. pMC is the ratio of the 14 C concentration of the sample to the 14 C concentration of the standard modern carbon (modern standard reference), and this value is used as an index indicating the biomass ratio of the compound (rubber). The significance of this value will be described below.

[0123] One mole (6.02×10 23 atoms) of carbon atoms contains approximately 6.02×10 11 atoms of 14 C, which is about one trillionth of ordinary carbon atoms. 14 The half-life of 14 C is 5730 years, and 14 C decreases regularly. Therefore, after carbon dioxide in the atmosphere is taken up and fixed by plants, etc., in fossil fuels such as coal, oil, and natural gas, which are thought to have passed more than 226,000 years since fixation, all of the 14 C element has decayed at the time of current fixation. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas do not contain 14 any 14 C element at all. Therefore, chemical substances produced from these fossil fuels as raw materials also do not contain

[0124] On the other hand, 14 C is constantly generated by cosmic rays undergoing nuclear reactions in the atmosphere. Therefore, 14 C is in equilibrium between the decrease due to radioactive decay and the generation due to nuclear reactions, and in the earth's atmospheric environment, 14 the amount of 14 C is constant. Therefore, the 14 C concentration of substances derived from biomass resources that are circulating in the current environment is about 1×10 -12 mol% with respect to the total number of -12 C atoms as described above. Therefore, by utilizing the difference between these values, the ratio (biomass ratio) of compounds derived from natural resources (compounds derived from biomass resources) in a certain compound (rubber) can be calculated.

[0125] This 14 C is generally measured as follows. Using accelerator mass spectrometry based on a tandem accelerator, 13 the C concentration ( 13 12 C / 14 C) and 14 the C concentration ( 14 C / 12 C) are measured. In the measurement, 14As a modern standard reference for the concentration of C, the 14 C concentration in the circulating carbon in nature in 1950 is adopted. As a specific standard substance, the oxalic acid standard provided by NIST (National Institute of Standards and Technology) is used. The specific radioactivity of carbon in this oxalic acid (the 14 radioactivity intensity of 13 C per gram of carbon) is fractionated for each carbon isotope, and for 14 C, it is corrected to a constant value, and the value after applying the decay correction from 1950 AD to the measurement date is used as the standard

[0126] C concentration value (100%). The ratio of this value to the value of the actually measured sample is the pMC value. 14 Therefore, if the rubber is made of a 100% biomass (natural system) - derived substance, although there are regional differences, it will show a value of approximately 110 pMC (currently, in the normal state, it often does not reach 100). On the other hand, for chemical substances derived from fossil fuels such as petroleum, when measuring this

[0127] C concentration, it will show almost 0 pMC (for example, 0.3 pMC). This value corresponds to a biomass ratio of 0% mentioned above.

[0128] <Filler> The rubber composition according to this embodiment preferably contains silica as a filler, and preferably contains silica and carbon black. Also, it may be a filler consisting only of silica and carbon black.

[0129] (Silica) The silica is not particularly limited, and for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), etc., which are common in the tire industry, can be used. The raw material of the silica is not particularly limited, and for example, it may be a raw material derived from a mineral such as quartz, or it may be a raw material derived from a living organism such as rice husk (for example, silica using a biomass material such as rice husk as a raw material), or silica recycled from a product containing silica may also be used. Among them, hydrous silica prepared by a wet method is preferred because it has many silanol groups. These silicas may be used alone or in combination of two or more.

[0130] Silica using a biomass material as a raw material can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husk using a sodium hydroxide solution, and reacting the silicate with sulfuric acid in the same manner as conventional wet silica to precipitate silicon dioxide, followed by filtration, washing with water, drying, and pulverization.

[0131] As the silica recycled from a product containing silica, for example, silica recovered from products containing silica such as electronic components such as semiconductors, tires, desiccants, and filter media such as diatomaceous earth can be used. The recovery method is not particularly limited, and examples include pyrolysis and decomposition by electromagnetic waves. Among them, silica recovered from electronic components such as semiconductors or tires is preferred.

[0132] When silica crystallizes, it does not dissolve in water and the silicic acid as its component cannot be utilized. By controlling the combustion temperature and combustion time, the crystallization of silica in rice husk ash can be suppressed (see, for example, JP-A-2009-2594, Akita Prefectural University Web Journal B / 2019, vol. 6, p. 216-222, etc.).

[0133] Amorphous silica extracted from rice husk can be those commercially available from Wilmar Co., Ltd. and the like.

[0134] The nitrogen adsorption specific surface area of silica (N 2SA) is preferably 100 m 2 / g or more from the viewpoint of wear resistance and elongation at break, more preferably 120 m 2 / g or more, still more preferably 140 m 2 / g or more, particularly preferably 160 m 2 / g or more. Also, from the viewpoints of heat generation and processability, it is preferably 350 m 2 / g or less, more preferably 300 m 2 / g or less, still more preferably 250 m 2 / g or less. The N 2 SA of silica is measured by the above measurement method.

[0135] The average primary particle diameter of silica is preferably 20 nm or less, more preferably 18 nm or less, still more preferably 17 nm or less, and particularly preferably 16 nm or less. The lower limit of the average primary particle diameter is not particularly limited, but from the viewpoint of the dispersibility of silica, it is preferably 1 nm or more, more preferably 3 nm or more, and still more preferably 5 nm or more. The average primary particle diameter of silica is measured by the above measurement method.

[0136] The content Y (parts by mass) of silica with respect to 100 parts by mass of the rubber component of the rubber composition constituting the topping rubber is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more from the viewpoint of the effects of the present invention. Also, from the viewpoint of tire strength, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass or less.

[0137] The content of silica with respect to 100 parts by mass of the rubber component of the rubber composition constituting the cap rubber is preferably 1 part by mass or more, more preferably 4 parts by mass or more, still more preferably 7 parts by mass or more, and particularly preferably 10 parts by mass or more from the viewpoint of the effects of the present invention. Also, the content is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, still more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less.

[0138] (Carbon black) The carbon black is not particularly limited, and those commonly used in the tire industry such as GPF, FEF, HAF, ISAF, SAF, etc. can be used. Specifically, N110, N115, N120, N125, N134, N135, N219, N220, N231, N234, N293, N299, N326, N330, N339, N343, N347, N351, N356, N358, N375, N539, N550, N582, N630, N642, N650, N660, N683, N754, N762, N765, N772, N774, N787, N907, N908, N990, N991, etc. can be preferably used. In addition, self-made products, etc. can also be preferably used. The raw material of the carbon black may be a biomass material such as lignin or vegetable oil, or may be a pyrolysis oil obtained by pyrolyzing waste tires. Further, the manufacturing method of the carbon black may be by combustion such as the furnace method, may be by hydrothermal carbonization (HTC), or may be by thermal decomposition of methane such as the thermal black method. As commercially available products, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nippon Carbon Co., Ltd., Columbian Carbon Company, etc. can be used. These carbon blacks may be used alone or in combination of two or more.

[0139] In this specification, the "recycled carbon black" refers to carbon black obtained by pulverizing used products such as tires containing carbon black and firing the pulverized product, and in the thermogravimetric measurement method conforming to JIS K 6226-2:2003, when oxidized and burned by heating in air, it refers to carbon black in which the ratio of the mass of the ash content (ash amount), which is the component that does not burn, is 13% by mass or more. That is, the ratio of the mass of the weight loss (carbon amount) due to the oxidative combustion of the recycled carbon black is 87% by mass or less. Recycled carbon black may also be represented by rCB.

[0140] Recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975 refers to "Rubber Chemistry and Technology", Vol. 85, No. 3, pages 408-449 (2012), particularly pages 438, 440, and 442, and describes that it can be obtained by pyrolysis of organic materials at 550-800 °C with oxygen excluded or vacuum pyrolysis at relatively low temperatures (

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

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

[0141] Recycled carbon black may lack functional groups on its surface, or may be treated to contain functional groups on its surface. The treatment to make the surface of recycled carbon black contain functional groups can be carried out by conventional methods. For example, in European Patent Application Publication No. 3173251, carbon black obtained from a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Also, in Patent No. 6856781, carbon black obtained from a pyrolysis process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain carbon black with an activated surface. The recycled carbon black according to this embodiment also includes carbon black treated to contain functional groups on its surface as described above.

[0142] Commercially available recycled carbon black from companies such as Strable Green Carbon and LDCarbon can be used.

[0143] The filler contained in the rubber composition constituting the topping rubber preferably contains recycled carbon black. Recycled carbon black has a wider particle size distribution than ordinary carbon black. Therefore, compared with the case of blending ordinary carbon black, the movement of the polymer can be suppressed against a wide variety of input frequencies from the road surface, and the heat generation of the topping rubber can be suppressed, so it is considered that the durability performance of the tire is further improved.

[0144] The nitrogen adsorption specific surface area (N 2 SA) of the carbon black contained in the rubber composition constituting the topping rubber is preferably 20 m 2 / g or more, more preferably 40 m 2 / g or more, still more preferably 50 m 2 / g or more, particularly preferably 60 m 2 / g or more. Also, from the viewpoints of low fuel consumption performance and processability, it is preferably 200 m 2 / g or less, more preferably 150 m 2 / g or less, still more preferably 120 m 2 / g or less. The N 2 SA of the carbon black is measured by the above measurement method.

[0145] The average primary particle diameter of the carbon black contained in the rubber composition constituting the topping rubber is preferably 45 nm or less, more preferably 40 nm or less, still more preferably 35 nm or less, and particularly preferably 32 nm or less. The lower limit of the average primary particle diameter is not particularly limited, but is preferably 5 nm or more, more preferably 8 nm or more, and still more preferably 10 nm or more. The average primary particle diameter of the carbon black is measured by the above measurement method.

[0146] The nitrogen adsorption specific surface area (N 2 SA) of the carbon black contained in the rubber composition constituting the cap rubber is preferably 30 m 2 / g or more from the viewpoint of reinforcement, more preferably 50 m 2 / g or more, still more preferably 70 m 2 / g or more, still more preferably 90 m2 Above / g is particularly preferred. Also, from the viewpoints of low fuel consumption performance and processability, 200 m 2 / g or less is preferred, 150 m 2 / g or less is more preferred, 120 m 2 / g or less is even more preferred.

[0147] The average primary particle diameter of the carbon black contained in the rubber composition constituting the topping rubber is preferably 36 nm or less, more preferably 32 nm or less, even more preferably 28 nm or less, and particularly preferably 24 nm or less. The lower limit of the average primary particle diameter is not particularly limited, but 5 nm or more is preferred, 8 nm or more is more preferred, and 10 nm or more is even more preferred.

[0148] The content of carbon black with respect to 100 parts by mass of the rubber component in the rubber composition constituting the topping rubber is preferably 10 parts by mass or more, more preferably 13 parts by mass or more, even more preferably 16 parts by mass or more, still more preferably 19 parts by mass or more, and particularly preferably 22 parts by mass or more from the viewpoint of elongation at break. Also, from the viewpoint of suppressing heat generation, 50 parts by mass or less is preferred, 45 parts by mass or less is more preferred, 40 parts by mass or less is even more preferred, and 35 parts by mass or less is particularly preferred.

[0149] When the rubber composition constituting the topping rubber contains recycled carbon black, the content with respect 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, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more from the viewpoint of the effects of the present invention. Also, from the viewpoint of suppressing heat generation, 50 parts by mass or less is preferred, 45 parts by mass or less is more preferred, 40 parts by mass or less is even more preferred, and 35 parts by mass or less is particularly preferred.

[0150] From the viewpoint of reinforcement, the content of carbon black relative to 100 parts by mass of the rubber component constituting the cap rubber layer is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, still more preferably 7 parts by mass or more, and particularly preferably 10 parts by mass or more. From the viewpoint of suppressing heat generation, it is preferably 35 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 27 parts by mass or less, still more preferably 23 parts by mass or less, and particularly preferably 20 parts by mass or less.

[0151] (Other fillers) Fillers other than silica and carbon black are not particularly limited, and for example, aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, magnesium sulfate, talc, clay, biochar, etc., which are generally used in the tire industry, can be blended. These other fillers may be used alone or in combination of two or more.

[0152] From the viewpoint of the effects of the present invention, the total content of fillers relative to 100 parts by mass of the rubber component is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, still more preferably 30 parts by mass or more, and particularly preferably 35 parts by mass or more. From the viewpoint of suppressing heat generation, it is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, still more preferably 50 parts by mass or less, and particularly preferably 45 parts by mass or less.

[0153] The ratio of silica to the total content of silica and carbon black in the rubber composition constituting the topping rubber is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, still more preferably 20% by mass or more, and particularly preferably 25% by mass or more. Also, the ratio of silica to the total content of silica and carbon black in the rubber composition constituting the topping rubber is preferably 75% by mass or less, more preferably 65% by mass or less, still more preferably 55% by mass or less, and particularly preferably 45% by mass or less.

[0154] The ratio of silica to the total content of silica and carbon black in the rubber composition constituting the cap rubber layer is preferably 20% by mass or more, more preferably 25% by mass or more, still more preferably 30% by mass or more, and particularly preferably 33% by mass or more. Further, the ratio of silica to the total content of silica and carbon black in the rubber composition constituting the cap rubber layer is preferably 99% by mass or less, more preferably 90% by mass or less, still more preferably 80% by mass or less, and particularly preferably 70% by mass or less.

[0155] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and in the tire industry, any silane coupling agent conventionally used in combination with silica can be used. For example, mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl)disulfide and bis(3-triethoxysilylpropyl)tetrasulfide; thioester-based silane coupling agents such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane; vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane; etc. Among them, it is preferable to contain a sulfide-based silane coupling agent and / or a mercapto-based silane coupling agent. As the silane coupling agent, for example, those commercially available from Momentive and other companies can be used. These silane coupling agents may be used alone or in combination of two or more.

[0156] When containing a silane coupling agent, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, still more preferably 2.0 parts by mass or more, and particularly preferably 4.0 parts by mass or more from the viewpoint of enhancing the dispersibility of silica. Further, from the viewpoint of preventing a decrease in wear resistance performance, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 12 parts by mass or less.

[0157] <Thermosetting resin> The rubber composition constituting the topping rubber preferably contains a thermosetting resin. Here, the thermosetting resin refers to a resin that polymerizes by heating to form a polymer having a network structure and hardens and does not return to its original state.

[0158] The thermosetting resin is not particularly limited, and examples thereof include resorcinol resin, modified resorcinol resin, cresol resin, modified cresol resin, phenol resin, modified phenol resin, etc. These thermosetting resins may be used alone or in combination of two or more. By blending these thermosetting resins, the adhesiveness to the cord, the elongation at break, and the complex elastic modulus can be improved. Among them, resorcinol resin, modified resorcinol resin, and modified cresol resin are preferred, and modified resorcinol resin is more preferred.

[0159] Examples of the resorcinol resin include resorcinol·formaldehyde condensates. Examples of the modified resorcinol resin include those obtained by alkylating a part of the repeating units of the resorcinol resin.

[0160] Examples of the cresol resin include cresol·formaldehyde condensates. Examples of the modified cresol resin include those obtained by modifying the terminal methyl group of the cresol resin into a hydroxyl group and those obtained by alkylating a part of the repeating units of the cresol resin.

[0161] Examples of phenolic resins include those obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde, and furfural in the presence of an acid or alkali catalyst. Among them, those obtained by reacting with an acid catalyst (such as novolak-type phenolic resins) are preferred. Examples of modified phenolic resins include resins obtained by modifying phenolic resins with cashew oil, tall oil, linseed oil, various animal and vegetable oils, unsaturated fatty acids, rosin, alkylbenzene resins, aniline, melamine, and the like.

[0162] When the rubber composition constituting the topping rubber contains a thermosetting resin, the content thereof per 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 still more preferably 1.5 part by mass or more from the viewpoints of adhesiveness and durability performance. Further, from the viewpoint of suppressing the adhesion reaction during vulcanization and preventing a decrease in durability after wet heat deterioration, it is preferably 6.0 parts by mass or less, more preferably 5.0 parts by mass or less, still more preferably 4.5 parts by mass or less, and particularly preferably 4.0 parts by mass or less.

[0163] <Curing agent> The rubber composition constituting the topping rubber preferably contains a curing agent for curing the above-mentioned thermosetting resin. The curing agent is not particularly limited, and examples thereof include hexamethoxymethylmelamine (HMMM), modified etherified methylolmelamine resin, hexamethylenetetramine (HMT), pentakis(methoxymethyl)methylolmelamine, and tetrakis(methoxymethyl)dimethylolmelamine. A modified etherified methylolmelamine resin is preferred. These curing agents may be used alone or in combination of two or more.

[0164] When the rubber composition constituting the topping rubber contains a curing agent, the content thereof with respect to 100 parts by mass of the rubber component is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, still more preferably 0.5 part by mass or more, and particularly preferably 0.7 part by mass or more from the viewpoint of the effects of the present invention. Further, the content is preferably 3.0 parts by mass or less, more preferably 2.5 parts by mass or less, and still more preferably 2.0 parts by mass or less.

[0165] <Cobalt compound> The rubber composition constituting the topping rubber preferably contains a cobalt compound. By containing a cobalt compound, the adhesive force between the steel cord and the topping rubber can be increased, and a tire excellent in durability can be obtained. Examples of the cobalt compound include cobalt alone, cobalt chloride, cobalt organic acid, cobalt inorganic acid, etc., and cobalt organic acid is preferred. These cobalt compounds may be used alone or in combination of two or more.

[0166] Cobalt organic acid is preferably used to promote the adhesion between the plating layer of the steel cord and the rubber composition and to prevent the plating component from flowing out into the rubber composition during hygrothermal deterioration. The number of carbon atoms of the organic acid constituting the cobalt organic acid is preferably 12 or more and 24 or less, and more preferably 14 or more and 22 or less. Specific examples of the cobalt organic acid salt include, for example, cobalt stearate, cobalt naphthenate, cobalt neodecanoate, cobalt rosinate, cobalt versatate, cobalt tallate, cobalt oleate, cobalt linoleate, cobalt linolenate, cobalt palmitate, etc. Further, the cobalt organic acid may be a complex salt in which a part of the organic acid is replaced with boric acid (for example, cobalt boron trineodecanoate).

[0167] Examples of the cobalt inorganic acid include cobalt sulfate, cobalt nitrate, cobalt phosphate, cobalt chromate, etc.

[0168] When the rubber composition constituting the topping rubber contains a cobalt compound, the content thereof per 100 parts by mass of the rubber component is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, and still more preferably 0.5 part by mass or more from the viewpoint of adhesiveness. Further, the content is preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less, and still more preferably 1.5 parts by mass or less.

[0169] <Other compounding agents> In addition to the above components, the rubber composition according to the present embodiment may appropriately contain compounding agents generally used in the conventional tire industry, such as softeners, vulcanized rubber particles (rubber powder), anti-aging agents, waxes, processing aids, stearic acid, zinc oxide, vulcanizing agents, vulcanization accelerators, and the like.

[0170] As used herein, the "softener" is a material that imparts plasticity to the rubber component, and is a concept including both softeners that are liquid (liquid state) at room temperature (25°C) and softeners that are solid at room temperature (25°C). Examples of softeners include resin components, oils, liquid polymers, ester plasticizers, and the like. These softeners may be derived from petroleum, may be derived from biomass, or may be derived from naphtha recycled from rubber products or non-rubber products. Further, low-molecular-weight hydrocarbon components obtained by thermally decomposing and extracting used tires and products containing various components may be used as softeners. These softeners may be used alone or in combination of two or more.

[0171] (Resin component) The resin component is not particularly limited, but resin components commonly used in the tire industry can be used. For example, tacky resins such as C9-based resins, C5-based resins, C5C9-based resins, dicyclopentadiene-based resins, aromatic vinyl-based resins, terpene-based resins, rosin-based resins, and phenol-based resins can be mentioned. These resin components may be used alone or in combination of two or more. The rubber composition according to the present embodiment preferably contains one or more resin components selected from the group consisting of terpene-based resins, dicyclopentadiene-based resins, and aromatic vinyl-based resins, and more preferably contains a resin component containing dicyclopentadiene, styrene, and indene as monomer components.

[0172] The "C9-based resin" refers to a resin obtained by polymerizing a C9 fraction, which may be a resin obtained by polymerizing the C9 fraction alone or a copolymer obtained by copolymerizing the C9 fraction with other components. For example, a resin obtained by copolymerizing dicyclopentadiene (DCPD) and a C9 fraction is called a DCPD / C9 resin. Also, those obtained by hydrogenating or modifying them may be used. Examples of the C9 fraction include petroleum fractions corresponding to 8 to 10 carbon atoms such as vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene. These C9-based resins may be used alone or in combination of two or more.

[0173] The "C5-based resin" refers to a resin obtained by polymerizing a C5 fraction, which may be a resin obtained by hydrogenating or modifying them. Examples of the C5 fraction include petroleum fractions corresponding to 4 to 5 carbon atoms such as cyclopentadiene, isoprene, pentane, isopentane, neopentane, pentene, and pentadiene. These C5-based resins may be used alone or in combination of two or more.

[0174] The "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and it may be hydrogenated or modified. As the C5C9 petroleum resin, for example, those commercially available from Tosoh Corporation, LUHUA Co., Ltd., etc. can be used. These C5C9 resins may be used alone or in combination of two or more.

[0175] The "dicyclopentadiene resin" refers to a resin containing cyclopentadiene (CPD) or dicyclopentadiene (DCPD), and it may be hydrogenated or modified. As the dicyclopentadiene resin, for example, DCPD / C9 resins containing dicyclopentadiene and the C9 fraction as monomer components (the DCPD / C9 resins may be hydrogenated or modified) can be mentioned, and DCPD / C9 resins containing dicyclopentadiene, styrene, and indene as monomer components are preferred. As the dicyclopentadiene resin, for example, those commercially available from ExxonMobil Corporation, ENEOS Corporation, Nippon Zeon Co., Ltd., Maruzen Petrochemical Co., Ltd., etc. can be used. These dicyclopentadiene resins may be used alone or in combination of two or more.

[0176] The "aromatic vinyl resin" refers to a resin containing aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene, etc. as the monomer component with the highest content, and it may be hydrogenated or modified. As the aromatic vinyl resin, due to economic reasons, ease of processing, and excellent 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, those commercially available from Creighton Corporation, Eastman Chemical Company, Mitsui Chemicals, Inc., etc. can be used. These aromatic vinyl resins may be used alone or in combination of two or more.

[0177] The term "terpene resin" refers to a resin containing terpene compounds such as α-pinene, β-pinene, limonene, dipentene, etc. as monomer components, and those obtained by hydrogenating or modifying them may also be used. Specific examples of terpene resins include, for example, polyterpene resins containing only one or more of the above terpene compounds as monomer components; aromatic-modified terpene resins containing the terpene compounds and aromatic compounds as monomer components; terpene phenol resins containing the terpene compounds and phenolic compounds as monomer components, and the like. Examples of aromatic compounds serving as monomer components of aromatic-modified terpene resins include styrene, α-methylstyrene, vinyltoluene, divinyltoluene, etc. Examples of phenolic compounds serving as monomer components of terpene phenol resins include phenol, bisphenol A, cresol, xylenol, etc. These terpene resins may be used alone or in combination of two or more.

[0178] The term "rosin resin" refers to a resin containing rosin acid compounds such as abietic acid, neoabietic acid, palustric acid, isopimaric acid, etc., and those obtained by hydrogenating or modifying them may also be used. Rosin resins are not particularly limited, and examples include natural resin rosin, rosin-modified resins obtained by modifying it by hydrogenation, disproportionation, dimerization, esterification, etc. These rosin resins may be used alone or in combination of two or more.

[0179] The term "phenolic resin" refers to a resin containing phenolic compounds such as phenol, cresol, etc. as the monomer component with the highest content, and those obtained by hydrogenating or modifying them may also be used. Phenolic resins are not particularly limited, and examples include phenol formaldehyde resins, alkylphenol formaldehyde resins, alkylphenol acetylene resins, oil-modified phenol formaldehyde resins, etc. These phenolic resins may be used alone or in combination of two or more.

[0180] The softening point of the pressure-sensitive adhesive resin is preferably 35°C or higher, more preferably 50°C or higher, and even more preferably 65°C or higher. Further, from the viewpoints of processability and improvement in the dispersibility of the rubber component and the filler, it is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. The softening point of the pressure-sensitive adhesive resin is measured by the above-described measuring method.

[0181] When the rubber composition constituting the cap rubber layer contains a pressure-sensitive adhesive resin, the content thereof with respect 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 even more preferably 5 parts by mass or more. Further, from the viewpoint of suppressing heat generation, it is preferably less than 40 parts by mass, more preferably less than 30 parts by mass, even more preferably less than 20 parts by mass, and particularly preferably 15 parts by mass or less. The content of the pressure-sensitive adhesive resin with respect to 100 parts by mass of the rubber component of the rubber composition constituting the topping rubber is not particularly limited, but is preferably less than 30 parts by mass, more preferably less than 20 parts by mass, and even more preferably less than 10 parts by mass.

[0182] Examples of the oil include process oil, vegetable oil, animal oil, and the like. Examples of the process oil include paraffinic process oil (mineral oil), naphthenic process oil, aromatic process oil, and the like. Specific examples of the process oil include, for example, MES (Mild Extract Solvated), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), RAE (Residual Aromatic Extract), and the like. Further, a process oil having a low content of polycyclic aromatic (PCA) compounds can also be used for environmental measures. Examples of the low-PCA-content process oil include MES, TDAE, and heavy naphthenic oil. Further, from the viewpoint of life cycle assessment, waste oil used in a rubber mixer or an engine, or refined waste cooking oil used in a cooking shop may be used.

[0183] Examples of vegetable oils include 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 oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grape seed oil, and wood rosin. Further, examples of vegetable oils include refined oils (such as salad oil) obtained by refining the above oils, transesterified oils obtained by transesterifying the above oils, hydrogenated oils obtained by hydrogenating the above oils, thermally polymerized oils obtained by thermally polymerizing the above oils, oxidation polymerized oils obtained by oxidizing the above oils, and waste cooking oils recovered from those used as edible oils and the like. Note that the vegetable oil may be liquid or solid at normal temperature (25°C). The vegetable oil may be used alone or in combination of two or more.

[0184] The vegetable oil preferably contains acylglycerol, and more preferably contains triacylglycerol. In the present specification, acylglycerol refers to a compound in which a hydroxy group of glycerin and a fatty acid are ester-bonded. The acylglycerol is not particularly limited, and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Further, the acylglycerol may be a monomer, a dimer, or a multimer of three or more. Note that acylglycerols of two or more can be obtained by thermal polymerization, oxidation polymerization, or the like. Also, the acylglycerol may be liquid or solid at normal temperature (25°C).

[0185] The method for confirming whether the acylglycerol is contained in the rubber composition is not particularly limited. For example, it can be confirmed by the following 1 1H-NMR measurement. Specifically, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at normal temperature (25°C) for 24 hours. After removing the rubber composition, at room temperature 1When measuring 1H-NMR and setting the signal of tetramethylsilane (TMS) to 0.00 ppm, signals around 5.26 ppm, around 4.28 ppm, and around 4.15 ppm were observed, and these signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In this paragraph, "around" means a range of ±0.10 ppm.

[0186] The fatty acid is not particularly limited and may be an unsaturated fatty acid or a saturated fatty acid. Examples of unsaturated fatty acids include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of saturated fatty acids include butyric acid and lauric acid.

[0187] Among them, as the fatty acid, it is desirable to contain a fatty acid with few double bonds, that is, a saturated fatty acid or a monounsaturated fatty acid, and oleic acid is preferred. As the vegetable oil containing such a fatty acid, for example, a vegetable oil containing a saturated fatty acid or a monounsaturated fatty acid may be used, or a vegetable oil subjected to modification such as transesterification may be used. Further, in order to produce a vegetable oil containing such a fatty acid, plants may be improved by variety improvement, genetic recombination, or the like.

[0188] As the vegetable oil, for example, those commercially available from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., Oriso Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kogyo Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0189] Examples of animal oils include fish oil, beef tallow, or oleyl alcohol that can be derived therefrom.

[0190] From the viewpoint of the effects of the present invention, the content with respect to 100 parts by mass of the rubber component when containing oil is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and further preferably 3 parts by mass or more. Also, the content is preferably less than 30 parts by mass, more preferably less than 20 parts by mass, further preferably less than 15 parts by mass, and particularly preferably 10 parts by mass or less.

[0191] The liquid polymer is not particularly limited as long as it is a polymer in a liquid state at normal temperature (25°C). For example, liquid butadiene polymers (liquid BR), liquid isoprene rubber polymers (liquid IR), liquid styrene-butadiene copolymers (liquid SBR), liquid styrene-isoprene rubber copolymers (liquid SIR), polymers containing myrcene and farnesene, etc. can be mentioned. These liquid polymers may be used alone or in combination of two or more.

[0192] When containing a liquid polymer, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and still more preferably 3 parts by mass or more. Also, the content is preferably less than 30 parts by mass, more preferably less than 20 parts by mass, and still more preferably 10 parts by mass or less.

[0193] Examples of ester plasticizers include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), bis(2-ethylhexyl) azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), etc. The ester plasticizers may be used alone or in combination of two or more.

[0194] From the viewpoint of the effects of the present invention, the content of the softener relative to 100 parts by mass of the rubber component (the total amount of all when a plurality of softeners are used in combination) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and still more preferably 3 parts by mass or more. Also, the content is preferably 70 parts by mass or less, more preferably 50 parts by mass or less, still more preferably 35 parts by mass or less, and particularly preferably 25 parts by mass or less.

[0195] The anti-aging agent is not particularly limited, but examples include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine-based anti-aging agents such as N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditoly-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; bis, tris, polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, etc. Among them, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferred, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and polymers of 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. As commercial products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., Flexsys Co., etc. can be used. These anti-aging agents may be used alone or in combination of two or more.

[0196] When containing an anti-aging agent, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 part by mass or more from the viewpoint of ozone crack resistance of the rubber. Also, from the viewpoint of abrasion resistance performance, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

[0197] The wax is not particularly limited, and any wax commonly used in the tire industry can be preferably used. For example, petroleum waxes, mineral waxes, synthetic waxes, waxes derived from plants, etc. can be mentioned. Among them, petroleum waxes and waxes derived from plants are preferable, and petroleum waxes are more preferable. Examples of waxes derived from plants include rice wax, carnauba wax, candelilla wax, etc. Examples of petroleum waxes include paraffin wax, microcrystalline wax, these selected special waxes, etc., and paraffin wax is preferable. Note that the wax according to this embodiment does not contain stearic acid. As the wax, for example, those commercially available from Ouchi Shinsei Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., etc. can be used. These waxes may be used alone or in combination of two or more.

[0198] When containing wax, the content with respect to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 0.8 part by mass or more, from the viewpoint of the weather resistance of the rubber. Also, from the viewpoint of preventing whitening of the tire due to blooming, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

[0199] Examples of the processing aid include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, etc. As the processing aid, for example, those commercially available from Schill+Seilacher, Performance Additives, etc. can be used. These processing aids may be used alone or in combination of two or more.

[0200] When containing stearic acid, the content with respect to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, further preferably 1.5 part by mass or more, from the viewpoint of processability. Also, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

[0201] When the rubber composition constituting the topping rubber contains zinc oxide, the content per 100 parts by mass of the rubber component is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, still more preferably 3.0 parts by mass or more, and particularly preferably 4.0 parts by mass or more from the viewpoint of the effects of the present invention. Further, from the viewpoint of wear resistance performance, it is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and still more preferably 9 parts by mass or less.

[0202] When the rubber composition constituting the cap rubber layer contains zinc oxide, the content per 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 from the viewpoint of processability. Further, from the viewpoint of wear resistance performance, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

[0203] Sulfur is preferably used as the vulcanizing agent. As the sulfur, powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, etc. can be used.

[0204] When the rubber composition constituting the topping rubber contains sulfur, the content per 100 parts by mass of the rubber component is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, still more preferably 3.0 parts by mass or more, further preferably 4.0 parts by mass or more, and particularly preferably 5.0 parts by mass or more from the viewpoint of the effects of the present invention. Further, from the viewpoint of deterioration prevention, it is preferably 10.0 parts by mass or less, more preferably 9.0 parts by mass or less, and still more preferably 8.0 parts by mass or less. In addition, when using oil-containing sulfur as the crosslinking agent, the content of the vulcanizing agent is the total content of pure sulfur contained in the oil-containing sulfur.

[0205] When the rubber composition constituting the cap rubber layer contains sulfur, the content per 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, still more preferably 0.5 part by mass or more from the viewpoint of ensuring a sufficient vulcanization reaction. Further, from the viewpoint of deterioration prevention, it is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and still more preferably 3.0 parts by mass or less.

[0206] As a vulcanizing agent other than sulfur, known organic crosslinking agents can also be used. The organic crosslinking agent is not particularly limited as long as it can form a crosslinking chain other than a polysulfide bond. For example, alkylphenol-sulfur chloride condensates, hexamethylene-1,6-bis(sodium thiosulfate) dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, dicumyl peroxide, etc. can be mentioned, and hexamethylene-1,6-bis(sodium thiosulfate) dihydrate is preferred. These organic crosslinking agents can be those commercially available from Tago Chemical Industry Co., Ltd., Rancy Co., Ltd., Flexsys Co., etc.

[0207] When the rubber composition constituting the topping rubber contains a vulcanizing agent other than sulfur (preferably hexamethylene-1,6-bis(sodium thiosulfate) dihydrate), the content relative to 100 parts by mass of the rubber component is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and even more preferably 1.0 part by mass or more from the viewpoint of the effects of the present invention. On the other hand, the content is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less.

[0208] The vulcanization accelerator is not particularly limited. For example, sulfenamide-based vulcanization accelerators, thiazole-based vulcanization accelerators, guanidine-based vulcanization accelerators, thiuram-based vulcanization accelerators, thiourea-based vulcanization accelerators, dithiocarbamate-based vulcanization accelerators, aldehyde-amine-based vulcanization accelerators, aldehyde-ammonia-based vulcanization accelerators, imidazoline-based vulcanization accelerators, xanthate-based vulcanization accelerators, caprolactam disulfide, etc. can be mentioned. These vulcanization accelerators may be used alone or in combination of two or more. Among them, from the viewpoint that the desired effects can be more preferably obtained, one or more vulcanization accelerators selected from the group consisting of sulfenamide-based vulcanization accelerators, thiazole-based vulcanization accelerators, and guanidine-based vulcanization accelerators are preferred.

[0209] Examples of sulfenamide vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), and the like.

[0210] Examples of thiazole vulcanization accelerators include 2-mercaptobenzothiazole (MBT) or its salts, di-2-benzothiazolyldisulfide (MBTS), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio)benzothiazole, and the like. Among them, MBTS and MBT are preferred, and MBTS is more preferred.

[0211] Examples of guanidine vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatecholborate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, and the like. Among them, DPG is preferred. However, when the rubber composition constituting the topping rubber contains a guanidine vulcanization accelerator, the content thereof with respect to 100 parts by mass of the rubber component is preferably 0.5 part by mass or less, more preferably 0.3 part by mass or less, still more preferably 0.1 part by mass or less, and particularly preferably not containing a guanidine vulcanization accelerator, from the viewpoint of the effects of the present invention.

[0212] When containing a vulcanization accelerator, the content thereof with respect to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, still more preferably 1.5 part by mass or more, from the viewpoint of ensuring a sufficient vulcanization rate. Further, the content of the vulcanization accelerator is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, from the viewpoint of suppressing blooming.

[0213] In this specification, various materials containing carbon atoms (such as rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from carbon dioxide in the atmosphere. As a method for obtaining the various materials from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process of synthesizing methane from carbon dioxide may be converted.

[0214] [Manufacture of Rubber Composition and Tire] The rubber composition according to this embodiment can be manufactured by a known method. For example, it can be manufactured by kneading the above-mentioned respective components using a rubber kneading device such as an open roll, a closed kneader (Banbury mixer, kneader, etc.).

[0215] The kneading process includes, for example, a base kneading process of kneading compounding agents and additives other than the vulcanizing agent and the vulcanization accelerator, and a final kneading (F kneading) process of adding and kneading the vulcanizing agent and the vulcanization accelerator to the kneaded product obtained in the base kneading process. Further, the base kneading process can be divided into a plurality of processes if desired.

[0216] The kneading conditions are not particularly limited. For example, in the base kneading process, kneading is performed at a discharge temperature of 150 to 170°C for 3 to 10 minutes, and in the final kneading process, kneading is performed at 70 to 110°C for 1 to 5 minutes.

[0217] The tire according to this embodiment, which includes a topping rubber and a cap rubber layer composed of the rubber composition, can be manufactured by a normal method using the corresponding rubber composition for each. That is, a steel cord is coated with an unvulcanized rubber composition corresponding to the topping rubber to obtain a steel cord-rubber composite. Then, the unvulcanized rubber composition corresponding to the cap rubber layer is extruded into the shape of the cap rubber layer using an extruder equipped with a die of a predetermined shape, and is bonded together with other tire members on a tire molding machine and molded by a normal method to form an unvulcanized tire. The tire can be manufactured by heating and pressurizing this unvulcanized tire in a vulcanizer. The vulcanization conditions are not particularly limited, and for example, a method of vulcanizing at 150 to 200 °C for 10 to 30 minutes can be mentioned.

[0218] <Use> The tire according to this embodiment can be a general-purpose tire such as a passenger car tire, a truck / bus tire, or a motorcycle tire, or a racing tire. Note that a passenger car tire is a tire assumed to be mounted on a four-wheeled automobile, and refers to one with a maximum load capacity of 1000 kg or less. Further, the tire according to this embodiment can be used for all-season tires, summer tires, winter tires such as studless tires, etc.

Example

[0219] Hereinafter, examples (Examples) considered to be preferable when implementing are shown, but the scope of the present invention is not limited to the Examples. Using the various chemicals shown below, a tire having a steel cord coated with a topping rubber obtained according to the formulation in Table 1 and a cap rubber layer obtained according to the formulation in Table 2 was examined, and the results calculated based on the following evaluation method are shown in Tables 3 to 7.

[0220] Hereinafter, the various chemicals used in the Examples and Comparative Examples are collectively shown. NR: TSR20 BR: UBEPOL BR (registered trademark) 150B manufactured by Ube Industries, Ltd. (unmodified BR, cis content: 97% by mass, Mw: 440,000) SBR: SBR1502 manufactured by JSR Corporation (unmodified E-SBR, styrene content: 23.5% by mass, vinyl content: 18 mol%, Mw: 420,000) Carbon Black 1: Cabot Japan Ltd.'s Show Black N330 (N 2 SA: 75m 2 / g, average primary particle diameter: 30 nm) Carbon Black 2: Cabot Japan Ltd.'s Show Black N220 (N 2 SA: 115m 2 / g, average primary particle diameter: 22 nm) Carbon Black 3: SS550 manufactured by Streble Green Carbon (recycled carbon black obtained by the thermal decomposition process of tires) Silica: Evonik Degussa's ULTRASIL VN3 (N 2 SA: 175m 2 / g) Silane coupling agent: Evonik Degussa's Si266 (bis(3-triethoxysilylpropyl) disulfide) Thermosetting resin: Sumitomo Bakelite Co., Ltd.'s Sumilite Resin PR-12686E (cashew oil-modified phenol resin, softening point: 100 °C) Hardening agent: Tago Chemical Industry Co., Ltd.'s Sumicanol 507AP (modified etherified methylol melamine resin) Oil: Idemitsu Kosan Co., Ltd.'s Diana Process NH-70S (aromatic process oil) Adhesive resin 1: SYLVATARAXX 4150 manufactured by Clayton (politerpene resin, softening point: 115 °C) Adhesive resin 2: ExxonMobil's Oppera PR-395 (hydrogenated DCPD / C9 resin, softening point: 118 °C) Zinc oxide: Mitsui Mining & Smelting Co., Ltd.'s No. 1 zinc white Antioxidant 1: Nocrack 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) Antioxidant 2: Nocrack FR manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (2,2,4-trimethyl-1,2-dihydroquinoline polymer) Cobalt compound: Cost-F (cobalt stearate) manufactured by DIC Corporation Stearic acid: Bead stearic acid camellia manufactured by NOF Corporation Wax: Oz Ace 0355 of Nippon Seiro Co., Ltd. Vulcanizing agent 1: M95 (insoluble sulfur) manufactured by Nippon Carbonization Industry Co., Ltd. Vulcanizing agent 2: DURALINK HTS (sodium hexamethylene-1,6-bisthiosulfate dihydrate) manufactured by Flexsys Vulcanizing agent 3: Powder sulfur (5% oil-containing powder sulfur) manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Nocceler DZ (N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Nocceler CZ (N-cyclohexyl-2-benzothiazolylsulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 3: Nocceler D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0221] (Examples and Comparative Examples) According to the formulations shown in Table 1 and Table 2, using a 1.7 L sealed Banbury mixer, chemicals other than sulfur and vulcanization accelerators are kneaded for 5 minutes until the discharge temperature reaches 160 °C to obtain a kneaded product. Next, using a twin-screw open roll, a vulcanizing agent and a vulcanization accelerator are added to the obtained kneaded product, and kneaded for 4 minutes until the temperature reaches 105 °C to obtain an unvulcanized rubber composition. Using the obtained unvulcanized rubber composition of Table 1, a steel cord (filament diameter: 0.30 mm) is coated to obtain a steel cord-rubber composite. Then, the unvulcanized rubber composition of Table 2 is extruded using an extruder equipped with a die of a predetermined shape to match the shape of the cap rubber layer, and laminated together with other tire members on a tire molding machine to produce an unvulcanized tire, and vulcanized at 170 °C to obtain each test tire described in Tables 3 to 7. Here, for the binary-plated steel cord, the average thickness of the plating layer is 0.24 μm, and the composition of the plating layer is 63% by mass of Cu and 37% by mass of Zn. For the ternary-plated steel cord, the average thickness of the plating layer is 0.19 μm, and the composition of the plating layer is 68% by mass of Cu, 28% by mass of Zn, and 4% by mass of Co. In addition, in the configuration of the steel cord in the table, "1×2 40e" means that there are 40 steel cords of 1×2 structure per 50 mm in the width direction orthogonal to the longitudinal direction of the steel cord (40 ends), and "1×1 80e" means that there are 80 monofilament steel cords of 1×1 structure per 50 mm in the width direction orthogonal to the longitudinal direction of the steel cord (80 ends).

[0222] <Measurement of tanδ1 at 70 °C and E*1 at 70 °C> For each vulcanized rubber test piece prepared by cutting out from the topping rubber coating the steel cord of each test tire with a length of 20 mm × width of 4 mm × thickness of 1 mm such that the tire circumferential direction is the long side and the tire radial direction is the thickness direction, using a dynamic viscoelasticity measuring device (Implex series manufactured by GABO), the loss tangent tanδ and the complex elastic modulus E* are 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 an elongation mode.

[0223] <Measurement of tanδ2 at 30 °C and tanδ2 at 0 °C> For each vulcanized rubber test piece prepared by cutting out from the inside of the cap rubber layer of the tread portion of each test tire with a length of 20 mm × width of 4 mm × thickness of 1 mm such that the tire circumferential direction is the long side and the tire radial direction is the thickness direction, using a dynamic viscoelasticity measuring device (Implex series manufactured by GABO), measure the loss tangent tanδ under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of ±1%, and an elongation mode. Also, measure the loss tangent tanδ under the conditions of a temperature of 0°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±2.5%, and an elongation mode.

[0224] <Peel test> Cut out the belt layer including the tire equator portion as a sample piece with a width of 25 mm in the tire axial direction. Further, leave the sample piece in an oven at a temperature of 80°C and a relative humidity of 90% for one week to cause hydrothermal deterioration. Using a peel tester, measure the peel resistance when peeling from one end side of the obtained sample piece along between the belt plies at a speed of 50 mm / min. Then, display the results as "durability performance" in terms of an index with the peel resistance of each of the reference comparative examples (Comparative Example 4 in Table 3, Comparative Example 8 in Table 4, Comparative Example 13 in Table 5, Comparative Example 17 in Table 6, Comparative Example 21 in Table 7) set to 100.

[0225]

Table 1

[0226]

Table 2

[0227]

Table 3

[0228]

Table 4

[0229]

Table 5

[0230]

Table 6

[0231]

Table 7

[0232] <Embodiment> Examples of embodiments of the present invention are shown below.

[0233] 〔1〕A tire comprising a tread portion and a belt layer, wherein the tread portion has at least one rubber layer, the belt layer has a steel cord and a topping rubber covering the steel cord, and a cap rubber layer and the topping rubber constituting the tread surface of the tread portion are each composed of a rubber composition containing a rubber component and a filler, the complex elastic modulus (70°C E*1) of the topping rubber at 70°C is 15.0 MPa or less, preferably 12.0 MPa or less, more preferably 12.0 MPa or less, and still more preferably 8.0 MPa or less, and the maximum load capacity of the tire is W L (kg), when the tanδ of the topping rubber at 70°C is 70°C tanδ1, W L and a tire in which 70°C tanδ1 satisfies the following formula (1). 9.33×10 -5 ×W L -70°C tanδ1 > 0.023 ···(1) 〔2〕The tire according to 〔1〕 above, wherein the filler contained in the rubber composition constituting the topping rubber contains silica. 〔3〕The tire according to 〔1〕 or 〔2〕 above, wherein the filler contained in the rubber composition constituting the topping rubber contains recycled carbon black. 〔4〕The content of carbon black with respect to 100 parts by mass of the rubber component of the rubber composition constituting the cap rubber layer is 20 parts by mass or less, the tire according to any one of 〔1〕 to 〔3〕 above. 〔5〕The tanδ (30 °C tanδ2) of the cap rubber layer at 30 °C is 0.16 or less, the tire according to any one of 〔1〕 to 〔4〕 above. 〔6〕When the tanδ of the cap rubber layer at 30 °C is 30 °C tanδ2 and the tanδ of the cap rubber layer at 0 °C is 0 °C tanδ2, 0 °C tanδ2 / 30 °C tanδ2 is more than 2.3, the tire according to any one of 〔1〕 to 〔5〕 above. 〔7〕The total styrene amount in the rubber component constituting the cap rubber layer is 15% by mass or less, preferably 13% by mass or less, the tire according to any one of 〔1〕 to 〔6〕 above. 〔8〕W L is 400 or more, preferably 500 or more, more preferably 600 or more, still more preferably 700 or more, the tire according to any one of 〔1〕 to 〔7〕 above. 〔9〕The steel cord is a single - wire monofilament cord, the tire according to any one of 〔1〕 to 〔8〕 above. 〔10〕When the cross - sectional area of the steel cord is S (mm 2 ) and the number of the steel cords per 50 mm width in the direction orthogonal to the longitudinal direction of the steel cord is E, S×E is 1.0 or more and 25 or less, preferably 2.0 or more and 20 or less, more preferably 3.0 or more and 15 or less, still more preferably 4.0 or more and 10 or less, the tire according to any one of 〔1〕 to 〔9〕 above. 〔11〕When the content of silica with respect to 100 parts by mass of the rubber component of the rubber composition constituting the topping rubber is Y (parts by mass), Y / (S×E) is 0.10 or more, preferably 0.50 or more, more preferably 1.0 or more, the tire according to 〔10〕 above. 〔12〕The steel cord has a ternary plating layer composed of copper, zinc, and cobalt, the tire according to any one of 〔1〕 to 〔11〕 above. 〔13〕When the weight of the tire is G (kg), G / W LThe tire according to any one of the above [1] to

[12] , wherein the value is 0.060 or less, preferably 0.025 or less, more preferably 0.020 or less.

Explanation of symbols

[0234] 11 ··· Tire 12 ··· Tread portion 13 ··· Sidewall portion 14 ··· Bead portion 15 ··· Inner liner 16 ··· Carcass 17 ··· Belt layer 18 ··· Bead wire 21, 50 ··· Steel cord 22 ··· Topping rubber 51 ··· Filament CL ··· Center line

Claims

1. A tire having a tread portion and a belt layer, wherein the tread portion has at least one rubber layer, the belt layer has a steel cord and a topping rubber covering the steel cord, the cap rubber layer constituting the tread surface of the tread portion and the topping rubber are each composed of a rubber composition containing a rubber component and a filler, the complex elastic modulus (70°C E*1) of the topping rubber at 70°C is 15.0 MPa or less, Let the maximum load capacity of the tire be W L (kg), and when the tanδ of the topping rubber at 70°C is 70°C tanδ1, W L and a tire in which 70°C tanδ1 satisfies the following formula (1). 9.33×10 -5 ×W L −70 °C tan δ1 > 0.023... (1)

2. The tire according to claim 1, wherein the filler contained in the rubber composition constituting the topping rubber contains silica.

3. The tire according to claim 1 or 2, wherein the filler contained in the rubber composition constituting the topping rubber contains recycled carbon black.

4. The tire according to claim 1 or 2, wherein the content of carbon black relative to 100 parts by mass of the rubber component of the rubber composition constituting the cap rubber layer is 20 parts by mass or less.

5. The tire according to claim 1 or 2, wherein tanδ (30°C tanδ2) of the cap rubber layer at 30°C is 0.16 or less.

6. The tire according to claim 1 or 2, when tanδ at 30°C of the cap rubber layer is 30°C tanδ2 and tanδ at 0°C of the cap rubber layer is 0°C tanδ2, 0°C tanδ2 / 30°C tanδ2 is more than 2.

3.

7. The tire according to claim 1 or 2, wherein the total styrene amount in the rubber component constituting the cap rubber layer is 15% by mass or less.

8. W L The tire according to claim 1 or 2, wherein W is 400 or more.

9. The tire according to claim 1 or 2, wherein the steel cord is a single-wire monofilament cord.

10. Let the cross-sectional area of the steel cord be S (mm 2 ), and when the number of the steel cords per 50 mm width in the direction orthogonal to the longitudinal direction of the steel cord is E, the tire according to claim 1 or 2, wherein S×E is 1.0 or more and 25 or less.

11. The tire according to claim 10, when the content of silica relative to 100 parts by mass of the rubber component of the rubber composition constituting the topping rubber is Y (parts by mass), Y / (S × E) is 0.10 or more.

12. The tire according to claim 1 or 2, wherein the steel cord has a ternary plating layer composed of copper, zinc, and cobalt.

13. When the weight of the tire is G (kg), G / W L is 0.060 or less. The tire according to claim 1 or 2.

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