tire

Abstract

To provide a tire which can improve wet grip performance during high speed travelling.SOLUTION: A tire includes a tread part having at least one rubber layer, wherein a ratio (G / WL) of tire weight G (kg) to maximum load capacity WL(kg) of the tire is 0.0140 or less, a first layer constituting the tread surface is composed of a rubber composition containing a rubber component and a filler, and when the total styrene amount in the rubber component is represented by S (mass%), and a land ratio on the ground surface of the tread part is represented by R, S is 20 or less, and the product (R×S) of R and S is more than 0 and 15 or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] As a method for improving the wet grip performance of a tire by improving the adhesiveness on a wet road surface, for example, a method of blending a plasticizer such as resin into tread rubber is known (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] With the improvement of highways and the high performance of vehicles, the opportunities to drive on wet road surfaces at high speeds are increasing. Therefore, in the tire market, particularly the wet grip performance during high-speed driving is strongly required.

[0005] An object of the present invention is to provide a tire capable of improving the wet grip performance during high-speed driving.

Means for Solving the Problems

[0006] The present invention is a tire provided with a tread portion having at least one rubber layer, wherein the ratio (G / W L (kg)) of the tire weight G (kg) to the maximum load capacity W L ) of the tire is 0.0140 or less, the first layer constituting the tread surface is composed of a rubber composition containing a rubber component and a filler, when the total styrene amount in the rubber component is S (mass %), and the land ratio on the ground contact surface of the tread portion is R, S is 20 or less, and the product (R × S) of R and S is more than 0 and 15 or less.

Advantages of the Invention

[0007] According to the present invention, there is provided a tire capable of improving wet grip performance during high-speed driving.

Brief Description of the Drawings

[0008]

Figure 1

Embodiments for Carrying Out the Invention

[0009] A tire according to an embodiment of the present invention is a tire provided with a tread portion having at least one rubber layer, and the ratio (G / W L )(kg) of the tire weight G (kg) to the maximum load capacity W of the tire L is 0.0140 or less, the first layer constituting the tread surface is composed of a rubber composition containing a rubber component and a filler, when the total styrene amount in the rubber component is S (mass %), and the land ratio at the ground contact surface of the tread portion is R, S is 20 or less, and the product (R×S) of R and S is more than 0 and 15 or less.

[0010] Regarding the reason why the wet grip performance of the tire of the present invention during high-speed driving is improved, although not intended to be restricted by theory, it is considered as follows.

[0011] The smaller the ratio (G / W L )(kg) of the tire weight G (kg) to the maximum load capacity W of the tire L , the smaller the density when viewed as a whole tire, and it is considered that the natural frequency is more likely to be higher than usual. Also, on a wet road surface, since slipping is likely to occur between the tire and the road surface during high-speed driving, it is considered that the whole tire is likely to absorb the input generated by this slipping and is likely to convert kinetic energy into heat. Furthermore, it is considered that the styrene domain can obtain a scraping effect due to the presence of the styrene part in the tread rubber.

[0012] On the one hand, the styrene domain is a hard domain. If it exists in excess with respect to the land ratio, the rubber component of the tread rubber becomes less mobile, and it becomes difficult to cause grounding and energy loss in the tread portion. Therefore, it is considered that the mobility of the rubber in the tread portion can be ensured by making the product of the styrene amount and the land ratio equal to or less than a certain value.

[0013] And when these cooperate, it absorbs the input due to slippage when driving on a wet road surface at high speed throughout the tire, and on the tread surface, it becomes easier to obtain the scraping effect by the styrene domain and the accompanying deformation (energy loss). Therefore, it is considered that the wet grip performance during high-speed driving can be improved.

[0014] The tanδ (tanδ at 30 °C) of the rubber composition at 30 °C is preferably 0.15 or less.

[0015] By reducing the tanδ of the tread rubber at room temperature, the phase difference between the input from the road surface and the response can be reduced. Therefore, it is considered that it becomes easier to instantaneously exert force in the tread rubber, and the wet grip performance during high-speed driving is more likely to be improved.

[0016] From the viewpoint of increasing the specific surface area of silica, increasing the interaction with the rubber component, suppressing the movement of molecular chains, and suppressing heat generation, the rubber composition preferably contains silica having an average primary particle diameter of 16 nm or less.

[0017] The rubber composition preferably contains a dicyclopentadiene-based resin.

[0018] By blending a dicyclopentadiene-based resin into the rubber composition, it is considered that the water repellency of the tread rubber can be improved and the wet grip performance during high-speed driving can be improved.

[0019] The product (G×S) of G and S is preferably 150 or less.

[0020] It is considered that the larger the tire weight G is, the more likely the inertia during rolling is to increase. Also, as described above, when the total styrene amount S in the rubber component is large, the ground contact property of the tread surface decreases, and it is considered that it becomes difficult to improve the wet grip performance during high-speed driving. Therefore, it is considered that by setting these products (G×S) within the above range, the wet grip performance during high-speed driving can be improved.

[0021] The glass transition temperature of the rubber composition is preferably -15°C or lower.

[0022] By setting the glass transition temperature of the rubber composition to -15°C or lower, the tread portion can be deformed flexibly even with respect to the high-frequency deformation corresponding to high-speed driving, the ground contact property is improved, and it is considered that the wet grip performance during high-speed driving can be easily improved.

[0023] The ratio (0°C tanδ / 0°C E*) of tanδ (0°C tanδ) at 0°C to the complex elastic modulus (MPa) (0°C E*) at 0°C of the rubber composition is preferably 0.044 or more.

[0024] By setting 0°C tanδ / 0°C E* within the above range, after the water is removed, the tread portion in contact with the road surface can exhibit good followability and heat generation properties, so it is considered that the wet grip performance during high-speed driving is improved.

[0025] The rubber composition preferably contains vulcanized rubber particles.

[0026] By blending vulcanized rubber particles into the rubber composition, domains of vulcanized rubber particles are formed, heat is generated by friction at the interface between the vulcanized rubber particles and the rubber matrix, and the effect of snagging by the vulcanized rubber particles is obtained. Therefore, the frictional property with respect to the road surface at the tread surface is improved, and it is considered that the wet grip performance during high-speed driving is improved.

[0027] <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 the tire skeleton is formed by members such as a belt layer, a belt reinforcing layer, and a carcass layer made of steel or textile materials, it is a member located outside these members in the radial direction of the tire.

[0028] The "normal state" means a no-load state in which the tire is mounted on a normal rim and filled with air at the normal internal pressure.

[0029] 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.

[0030] The "normal rim" is the rim defined for each tire in the standard system including the standard 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 size 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"; 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 standard if there is an applicable size at the time of reference. In the case of a tire not defined in the above standards, it refers to the rim with the narrowest rim width among the rims with the smallest diameter that can be mounted on the tire and can hold the internal pressure (i.e., does not cause air leakage between the rim / tire).

[0031] "Normal internal pressure" refers to the air pressure specified for each tire in the standard system including the standards on which the tire is based. For example, in the case of JATMA, it is the "maximum air pressure"; in the case of ETRTO, it is "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 normal rims, refer to JATMA, ETRTO, and TRA in this order, and follow the relevant standard if there is an applicable size during the reference. In the case of a tire not specified in the above standards, it refers to the normal internal pressure (however, not less than 250 kPa) of another tire size described with the normal rim as the standard rim (however, as specified in the standard). If there are multiple normal internal pressures not less than 250 kPa described, the minimum value among them shall be referred to.

[0032] "Normal load" refers to the load specified for each tire in the standard system including the standards on which the tire is based. For example, in the case of JATMA, it is the "maximum load capacity"; in the case of ETRTO, it is "LOAD CAPACITY"; and in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". Similar to the case of normal rims and normal internal pressures, refer to JATMA, ETRTO, and TRA in this order, and follow the relevant standard if there is an applicable size during the reference. In the case of a tire not specified in the above standards, the maximum load capacity W L calculated separately shall be taken as the normal load.

[0033] "Maximum load capacity W L " is calculated according to the following formula. "V" is the virtual volume of the tire (mm 3) "Dt" is the outer diameter of the tire (mm) in the normal state, "Ht" is the cross-sectional height of the tire in the cross-section of the tire by the plane including the tire rotation axis (mm) in the tire radial direction, and "Wt" is the cross-sectional width of the tire (mm) in the normal state. When the rim diameter of the tire is R, Ht can be obtained by (Dt - R) / 2. Wt is the value obtained by excluding patterns, characters, etc. on the tire sidewall. Note that the maximum load capacity is synonymous with the above normal load.

[0034]

Number

[0035] "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 a sound insulation material, a sealant, a sensor, etc., G is the weight including these.

[0036] "Groove", including circumferential grooves and transverse grooves, refers to a recess with a width greater than at least 2.0 mm.

[0037] "Contact area" is the area of the tread obtained from the contour when the tire is pressed against the ground. After assembling the tire on the normal rim, applying the normal internal pressure, standing for 24 hours at 25°C, painting ink on the tire tread surface, loading the tire with the normal load (maximum load capacity) and pressing it vertically against cardboard (the camber angle is 0°), it is obtained by transferring the ink. The area of the contact area is called the total contact area. The total contact area can be calculated as the average value of the five areas obtained by performing the above transfer operation while rotating the tire by 72° each time for a total of five locations.

[0038] The "effective contact area" is the area of the tread that comes into contact with the ground when the tire is pressed against the ground. It is obtained by assembling the tire on a standard rim, applying the standard internal pressure, allowing it to stand for 24 hours at 25°C, then painting ink on the tire tread surface, loading the tire with the standard load (maximum load capacity), pressing it vertically against thick paper (the camber angle is 0°), and transferring the ink. The area of the effective contact area is referred to as the effective contact area. The effective contact area can be calculated as the average value of the five areas obtained by performing the above transfer operation while rotating the tire by 72° each time and performing the operation at a total of five locations.

[0039] The "land ratio R" is calculated by the following formula from the total contact area of the contact area and the effective contact area of the effective contact area. (Land ratio) = (Effective contact area / Total contact area)

[0040] The "overall thickness of the tread portion" refers to the overall thickness of the tread portion on the tire equatorial plane in a cross-section obtained by cutting the tire with a plane including the tire rotation axis. Note that the inner end in the tire radial direction of the overall thickness of the tread portion is the inner interface of the rubber composition constituting the tread portion. When the tire is provided with a belt reinforcing layer, a belt layer, and a carcass layer, among these, it is the total thickness of the rubber layer outside the outermost layer in the tire radial direction in the tire radial direction. Note that when there are circumferential grooves on the tire equatorial plane, the overall thickness of the tread portion is measured with the grooves filled.

[0041] "The thickness of each rubber layer constituting the tread portion" is the thickness of each rubber layer on the tire equatorial plane in a cross-section obtained by cutting the tire with a plane including the tire rotation axis, and is the average value of the thicknesses of the tread portion measured at five positions by rotating the tire by 72° in the circumferential direction. For example, the thickness of the first layer refers to the linear distance in the tire radial direction from the outermost surface of the tread to the inner interface of the first layer in the tire radial direction on the tire equatorial plane. When the tire has circumferential grooves on the tire equatorial plane, the thickness of each rubber layer constituting the tread portion shall be the thickness of each rubber layer at the center in the tire width direction of the land portion closest to the tire equatorial plane. The "land portion closest to the tire equatorial plane" refers to the land portion having the groove edge closest to the tire equatorial plane among the circumferential grooves existing on the tire equatorial plane. When such land portions exist on both sides in the tire width direction, the thickness of each rubber layer constituting the tread portion shall be the average value of the thicknesses of each rubber layer at the center in the tire width direction of the two land portions. Also, when there are current-carrying members or the like on the land portion on the tire equatorial plane and the interface is unclear, the interface blocked by the current-carrying members or the like shall be virtually connected and measured.

[0042] "Plasticizer" is a material that imparts plasticity to the rubber component and is a component extracted from the rubber composition using acetone. Plasticizers include plasticizers that are liquid (liquid state) at 25°C and plasticizers that are solid at 25°C. However, waxes and stearic acid commonly used in the tire industry are not included.

[0043] "The content of the plasticizer" also includes the amount of the plasticizer contained in the extended rubber component previously extended by the plasticizer such as oil, resin component, and liquid rubber component. The same applies to the content of oil, the content of resin component, and the content of liquid rubber. For example, when the extended component is oil, the extended oil is included in the content of oil.

[0044] <Measurement method> "The thickness of each rubber layer constituting the tread portion" is measured with the tire cut by a plane including the tire rotation axis and the width of the bead portion adjusted to match the width of the standard rim.

[0045] "30°C tanδ" 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 loss tangent measurement is a vulcanized rubber composition with a length of 20 mm × width of 4 mm × thickness of 1 mm. When produced by cutting out from a tire, it is cut out from the tread portion of the tire such that the circumferential direction of the tire is the long side and the radial direction of the tire is the thickness direction.

[0046] "0°C tanδ" 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 produced in the same manner as in the case of 30°C tanδ.

[0047] "0°C E*" is the complex elastic modulus 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 produced in the same manner as in the case of 30°C tanδ.

[0048] "The glass transition temperature (Tg) of the rubber composition" is measured by using a dynamic viscoelasticity measuring device (for example, the Implex series manufactured by GABO) to measure the temperature distribution curve of tanδ in the range from -60°C to 40°C under the conditions of a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±0.5%, and a heating rate of 2°C / min, and determining the temperature (tanδ peak temperature) corresponding to the largest tanδ value in the obtained temperature distribution curve as Tg. When there are two points with the maximum value of tanδ within the range from -60°C to 40°C, the lower temperature side is taken as Tg. Also, when a temperature distribution curve in which tanδ gradually decreases with an increase in temperature is obtained in the range from -60°C to 40°C, Tg is taken as -60°C according to the above definition. The sample for this measurement is produced in the same manner as in the case of 0°C tanδ.

[0049] "Styrene content" is a value calculated by pyrolysis gas chromatography and is applied, for example, to rubber components having repeating units derived from styrene such as SBR. In this specification, "pyrolysis gas chromatography" refers to a method in which a sample is heated by a pyrolysis apparatus, individual components contained in the gas-phase components generated by this heating are separated by a separation column, and each isolated component is analyzed.

[0050] "Vinyl content (1,2-bonded butadiene unit amount)" is a value calculated by infrared absorption spectrum analysis in accordance with JIS K 6239-2:2017 and is applied, for example, to rubber components having repeating units derived from butadiene such as SBR and BR.

[0051] "Cis content (cis-1,4-bonded butadiene unit amount)" is a value calculated by infrared absorption spectrum analysis in accordance with JIS K 6239-2:2017 and is applied, for example, to rubber components having repeating units derived from butadiene such as BR.

[0052] "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 is the total. 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).

[0053] "Glass transition temperature (Tg) of the rubber component" is a value measured by differential scanning calorimetry (DSC) under the condition of a heating rate of 10 °C / min in accordance with JIS K 7121 and is applied, for example, to SBR, BR, etc.

[0054] 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 applicable to SBR, BR, plasticizers, etc.

[0055] The "nitrogen adsorption specific surface area (N2SA) of carbon black" is measured in accordance with JIS K 6217-2:2017. The "nitrogen adsorption specific surface area (N2SA) of silica" is measured by the BET method in accordance with ASTM D3037-93.

[0056] The "average primary particle diameter" is obtained by photographing the 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 it 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.

[0057] The "softening point of the resin component" is measured with a ring and ball softening point measuring device according to the softening point defined in JIS K 6220-1:2015 7.7, and it is the temperature at which the ball drops.

[0058] The manufacturing procedure of the tire which is one embodiment of the present invention will be described in detail below. However, the following description is an exemplification for explaining the present invention, and is not intended to limit the technical scope of the present invention only to this description range.

[0059] [Tire] In the tire according to this embodiment, the ratio (G / W L (kg) of the tire weight G (kg) to the maximum load capacity W L) is, from the viewpoint of the effects of the present invention, 0.0140 or less, preferably 0.0137 or less, more preferably 0.0135 or less, and even more preferably 0.0133 or less. On the other hand, the G / W L The lower limit value of is not particularly limited from the viewpoint of the effects of the present invention. For example, it can be 0.0110 or more, 0.0115 or more, 0.0120, 0.0125 or more. Note that the tire weight G 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.

[0060] The maximum load capacity W L (kg) is preferably 300 or more, more preferably 400 or more, even more preferably 450 or more, and particularly preferably 500 or more from the viewpoint of more favorably exhibiting the effects of the present invention. Also, the maximum load capacity W L (kg) can be, for example, 1300 or less, 1200 or less, 1100 or less, 1000 or less, 900 or less, 800 or less, 700 or less, 650 or less from the viewpoint of more favorably exhibiting the effects of the present invention. Note that the maximum load capacity W L can be increased by increasing the virtual volume V of the space occupied by the tire, and conversely, it can be decreased.

[0061] The land ratio R on the ground contact surface of the tread portion is preferably 0.50 or more, more preferably 0.55 or more, and even more preferably 0.60 or more. Also, the land ratio R is preferably 0.85 or less, more preferably 0.80 or less, and even more preferably 0.75 or less.

[0062] The tread portion according to the present embodiment has at least one rubber layer. The tread portion according to the present embodiment may be a tread portion composed of a single rubber layer, or may be a tread portion having a first layer whose outer surface constitutes a tread surface and one or more rubber layers (inner rubber layers) existing between the first layer and the belt layer.

[0063] The thickness of the first layer constituting the tread surface with respect to the overall thickness of the tread portion can be, for example, 30% or more, 50% or more, 70% or more, 90% or more, and the tread portion may consist only of the first layer constituting the tread surface.

[0064] The thickness t1 of the first layer is preferably 3.0 mm or more, more preferably 4.0 mm or more, and even more preferably 5.0 mm or more. Also, the thickness t1 of the first layer is preferably 13.0 mm or less, more preferably 12.0 mm or less, and even more preferably 11.0 mm or less.

[0065] The 30°C tanδ of the rubber composition constituting the first layer is preferably 0.25 or less, more preferably 0.20 or less, even more preferably 0.17 or less, and particularly preferably 0.15 or less. Also, the 0°C tanδ of the rubber composition is preferably 0.06 or more, more preferably 0.08 or more, and even more preferably 0.10 or more. Note that the 0°C tanδ of the rubber composition can be appropriately adjusted according to the types and blending amounts of the rubber component, vulcanized rubber particles, resin component, oil, etc. described below.

[0066] From the viewpoint of the effects of the present invention, the 0°C tanδ of the rubber composition constituting the first layer is preferably 0.25 or more, more preferably 0.30 or more, even more preferably 0.50 or more, and particularly preferably 0.60 or more. Also, the 0°C tanδ of the rubber composition is preferably 1.00 or less, more preferably 0.95 or less, and even more preferably 0.90 or less. Note that the 0°C tanδ of the rubber composition can be appropriately adjusted according to the types and blending amounts of the rubber component, vulcanized rubber particles, resin component, oil, etc. described below.

[0067] The 0°C E* of the rubber composition constituting the first layer is preferably 11.0 MPa or less, more preferably 10.0 MPa or less, and even more preferably 9.5 MPa or less. By setting the 0°C E* of the rubber composition within the above range, the wet grip performance tends to be good. Also, the 0°C E* of the rubber composition is preferably 4.0 MPa or more, more preferably 5.0 MPa or more, and even more preferably 6.0 MPa or more. Note that the 0°C E* of the rubber composition can be appropriately adjusted according to the types and compounding amounts of the rubber component, vulcanized rubber particles, resin component, oil, etc. described later.

[0068] The Tg of the rubber composition constituting the first layer is preferably -13°C or less, more preferably -15°C or less, and even more preferably -17°C or less. Also, the Tg of the rubber composition is preferably -40°C or more, more preferably -35°C or more, and even more preferably -30°C or more. Note that the Tg of the rubber composition can be appropriately adjusted according to the types and compounding amounts of the rubber component, vulcanized rubber particles, resin component, oil, etc. described later.

[0069] 0°C tanδ / 0°C E* is preferably 0.035 or more, more preferably 0.040 or more, and even more preferably 0.044 or more. By setting it within the above range, after water removal, the tread portion in contact with the road surface can exhibit good followability and heat generation properties, so it is considered that the wet grip performance during high-speed driving is improved. Also, 0°C tanδ / 0°C E* is preferably 0.060 or less, more preferably 0.055 or less, and even more preferably 0.050 or less.

[0070] The product (R×S) of the land ratio R and the total styrene amount S (mass%) in the rubber component is 15 or less, preferably 13 or less, more preferably 12 or less, even more preferably 10 or less, and particularly preferably 8 or less. On the other hand, R×S is more than 0, preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, and particularly preferably 4 or more.

[0071] The product (G × S) of the tire weight G (kg) and the total styrene amount S (mass %) in the rubber component is preferably 170 or less, more preferably 150 or less, still more preferably 130 or less, and particularly preferably 110 or less. On the other hand, the lower limit value of G × S is not particularly limited, but is preferably 20 or more, more preferably 30 or more, still more preferably 40 or more, and particularly preferably 50 or more.

[0072] [Rubber composition] The tire according to the present embodiment can more effectively improve the wet grip performance during high-speed driving by the cooperation of the configurations of the tire and the tread portion described above and the physical properties of the rubber composition constituting the tread portion. Hereinafter, the rubber composition constituting the first layer will be described.

[0073] <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), and the like. These diene rubbers may be modified rubbers treated with a modifying group capable of interacting with fillers such as carbon black and silica, or may be hydrogenated rubbers in which a part of the unsaturated bonds 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 plasticizer described later may be used. Note that the rubber component according to the present embodiment does not include the vulcanized rubber particles described later.

[0074] The content of the 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, a rubber component composed only of the diene rubber may be used.

[0075] As the diene rubber component, at least one selected from the group consisting of isoprene rubber, styrene-butadiene rubber (SBR), and butadiene rubber (BR) is preferably used. The rubber component preferably contains SBR, more preferably contains SBR and isoprene rubber and / or BR, still more preferably contains isoprene rubber, BR, and SBR, and may also be a rubber component consisting only of isoprene rubber, SBR, and BR.

[0076] (Isoprene rubber) The isoprene rubber is not particularly limited, and examples thereof include natural rubber (NR), isoprene rubber (IR), modified natural rubber, etc. Examples of NR include SIR20, RSS#3, TSR20, etc. Examples of IR include IR2200, etc. Examples of modified natural rubber include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, grafted natural rubber, etc. These isoprene rubbers may be used alone or in combination of two or more.

[0077] From the viewpoint of the effects of the present invention, the content of isoprene rubber in the rubber component is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, and particularly preferably 25% by mass or less. The lower limit of the content is not particularly limited, and for example, it can be 1% by mass or more, 3% by mass or more, 5% by mass or more, 7% by mass or more, 10% by mass or more.

[0078] (BR) BR is not particularly limited, and for example, BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare-earth-based 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.

[0079] 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 the high-cis BR, the wear 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 the BR is measured by the above-mentioned measurement method.

[0080] As the modified BR, a modified butadiene rubber (modified BR) modified with a functional group containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen in the terminal and / or main chain is preferably used.

[0081] As other modified BRs, those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and having the terminals of the modified BR molecules bonded by a tin-carbon bond (tin-modified BR), etc. can be mentioned. Also, the modified BR may be either non-hydrogenated or hydrogenated.

[0082] From the viewpoint of wear resistance performance, the weight average molecular weight (Mw) of the BR is preferably 300,000 or more, more preferably 350,000 or more, and even more preferably 400,000 or more. From the viewpoints of crosslinking uniformity, etc., it is preferably 2,000,000 or less, more preferably 1,000,000 or less. The Mw of the BR is measured by the above-mentioned measurement method.

[0083] From the viewpoint of the effects of the present invention, the content of the BR in the rubber component is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less. The lower limit value of the content is not particularly limited, but for example, it can be 1% by mass or more, 3% by mass or more, 5% by mass or more, 7% by mass or more, 10% by mass or more.

[0084] (SBR) The SBR is not particularly limited, and examples thereof include unmodified solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). Examples of the modified SBR include SBRs with modified terminals and / or main chains, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.). Furthermore, hydrogenated products of these SBRs (hydrogenated SBR) can also be used. These SBRs may be used alone or in combination of two or more.

[0085] In this embodiment, either extended SBR or non-extended SBR can be used as the SBR. When using extended SBR, the amount of extension of the SBR, that is, the content of the extendable plasticizer 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.

[0086] The SBRs listed above may be used alone or in combination of two or more. As the SBRs 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.

[0087] The styrene content of the SBR can be appropriately selected so that the total amount of styrene S in the rubber component satisfies the following range, but is preferably 40% by mass or less, more preferably 37% by mass or less, still more preferably 34% by mass or less, and particularly preferably 30% 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. Note that the styrene content of the SBR is measured by the above measurement method.

[0088] The glass transition temperature (Tg) of SBR is preferably -35°C or lower, more preferably -40°C or lower, still more preferably -45°C or lower, and particularly preferably -50°C or lower, from the viewpoint of facilitating deformation of the rubber composition even at high frequencies corresponding to high-speed driving. On the other hand, the lower limit value of the Tg is not particularly limited, but from the viewpoint of abrasion resistance, it is preferably -100°C or higher, more preferably -90°C or higher, and still more preferably -85°C or higher. The glass transition temperature (Tg) of SBR is measured by the above-mentioned measuring method.

[0089] 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, from the viewpoint of the effects of the present invention. Also, 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. The weight average molecular weight of SBR is measured by the above-mentioned measuring method.

[0090] The content of SBR in the rubber component can be appropriately selected so that the total styrene amount S in the rubber component satisfies the following range, but is preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 40% by mass or more, still more preferably 50% by mass or more, and particularly preferably 60% by mass or more. On the other hand, the content of SBR in the rubber component is preferably 99% by mass or less, more preferably 95% by mass or less, still more preferably 90% by mass or less, and particularly preferably 85% by mass or less.

[0091] The total styrene amount S (mass%) in the rubber component is 20 or less, preferably 16 or less, more preferably 13 or less, still more preferably 11 or less, still more preferably 10 or less, and particularly preferably 9.0 or less, from the viewpoint of the effects of the present invention. Also, the total styrene amount S (mass%) in the rubber component is more than 0, preferably 1.0 or more, more preferably 2.0 or more, still more preferably 3.0 or more, and particularly preferably 4.0 or more, from the viewpoint of the effects of the present invention.

[0092] (Other rubber components) The rubber component may contain a rubber component other than the diene rubber (non-diene rubber) as long as it does not affect the effects of the present invention. As the non-diene rubber, rubber components generally used in the tire industry can be used. For example, butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, etc. can be mentioned. These other rubber components may be used alone or in combination of two or more. In addition to the above rubber components, a known thermoplastic elastomer may or may not be contained.

[0093] (Rubber component synthesized from recycled and biomass-derived raw materials) The monomers that are the constituent units of synthetic rubbers such as IR, BR, and SBR may be derived from underground resources such as petroleum and natural gas, or may be 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 polyisoprene, 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 polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and recycled styrene (recycled styrene) as raw materials.

[0094] The method for producing the recycled monomer is not particularly limited. For example, it can be synthesized from recycled naphtha obtained by decomposing rubber products such as tires. Further, the method for producing recycled naphtha is not particularly limited. For example, rubber products such as tires may be decomposed under high temperature and high pressure, decomposed by microwaves, or extracted after mechanical pulverization.

[0095] Furthermore, the monomers that are the constituent units of synthetic rubbers such as IR, BR, and SBR may be derived from biomass. In this specification, biomass refers to substances derived from natural resources such as plants. Biomass is not particularly limited, and examples include agricultural and forestry products, sugars, wood chips, plant residues after obtaining useful components, ethanol derived from plants, biomass naphtha, and the like.

[0096] The monomers derived from biomass (biomass monomers) are not particularly limited, and examples include butadiene derived from biomass and aromatic vinyl compounds derived from biomass. 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.

[0097] The polymers synthesized from biomass monomer components (biomass polymers) are not particularly limited, and examples include polybutadiene rubber synthesized from butadiene derived from biomass and aromatic vinyl / butadiene copolymers synthesized from butadiene derived from biomass and / or aromatic vinyl compounds derived from biomass. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from butadiene derived from biomass and / or styrene derived from biomass.

[0098] 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.

[0099] pMC refers to that of modern standard reference14 The ratio of the sample to the C concentration 14 is the ratio of the C concentration and is a value used as an index indicating the biomass ratio of the compound. The significance of this value is described below.

[0100] In one mole (6.02×10 23 pieces) of carbon atoms, there are approximately 6.02×10 11 pieces, which is about one trillionth of normal carbon atoms. 14 14C exists. 14 The half-life of 14C is 5730 years, and 14 14C is decreasing regularly. It takes 226,000 years for all of these to decay. Therefore, in fossil fuels such as coal, oil, and natural gas, which are considered to have passed more than 226,000 years after carbon dioxide in the atmosphere was taken up and fixed by plants, etc., all of the 14 14C elements contained in them at the time of fixation have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas do not contain any 14 14C elements. Therefore, chemical substances produced from these fossil fuels also do not contain any 14 14C elements.

[0101] On the other hand, 14 14C is constantly generated by cosmic rays undergoing nuclear reactions in the atmosphere. From this, 14 14C 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 14C is constant. Therefore, the 14 14C concentration of substances derived from biomass resources circulating in the current environment is about 1×10 -12 mol% with respect to the entire carbon atoms as described above. Therefore, by utilizing the difference between these values, the biomass ratio in a certain compound can be calculated.

[0102] This 14 14C is generally measured as follows. Using accelerator mass spectrometry based on a tandem accelerator, 13 the 14C concentration ( 13 14C / 12 C), 14 C concentration ( 14 C / 12 C) is measured. In the measurement, 14 As a modern standard reference for the C concentration, the 14 C concentration in the circulating carbon in nature as of 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 radioactivity intensity of 14 C per gram of carbon) is separated for each carbon isotope, 13 For 14 C, it is corrected to a constant value, and the value obtained by applying the decay correction from 1950 AD to the measurement date is used as the value of the standard

[0103] Therefore, if the rubber is made of 100% biomass-derived substances, although there are regional differences and the like, it usually does not reach 100 in the normal state at present, so it will show a value of about 110 pMC. On the other hand, for chemical substances derived from fossil fuels such as petroleum, when the 14 C concentration is measured, it will show a value of about 0 pMC (for example, 0.3 pMC). This value corresponds to a biomass ratio of 0% mentioned above.

[0104] From the above, using materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio, in the rubber composition is suitable from the perspective of environmental protection.

[0105] <Vulcanized rubber particles> The "vulcanized rubber particles" are rubber compositions obtained by a process different from the rubber matrix constituting the rubber composition according to the present embodiment, and form domains distinguishable from the rubber matrix constituting the rubber composition according to the present embodiment by image analysis such as SEM. Generally, they are recycled rubber and powdered rubber described later, etc., but are not limited thereto, and depending on the application, a rubber composition different from the rubber composition according to the present embodiment may be prepared and obtained by pulverization. The vulcanized rubber particles may be used alone or in combination of two or more.

[0106] The "recycled rubber" is obtained by recycling used rubber such as tires, tubes, and other rubber products specified in JIS K 6313:2012 and those having properties equivalent thereto. However, it excludes powdered ones. Further, the recycled rubber is subjected to a devulcanization treatment.

[0107] The type of recycled rubber may be any of tube recycled rubber, tire recycled rubber, and other recycled rubbers, and a plurality of types may be combined. Among these, tire recycled rubber is preferred.

[0108] As the recycled rubber, those obtained by known production methods can be used. For example, starting from the most common pan method (oil method), methods using a Banbury mixer, a twin-screw reactive extruder, a microwave method, an ultrasonic method, an electron beam irradiation method, etc. have been developed, but it may be produced by any method. Also, commercially available recycled rubber may be used. As one specific example for manufacturing recycled rubber, there is a method of putting vulcanized rubber powder into a closed mixer or an extruder, heating it to 100 to 250°C, and subjecting it to a treatment for 5 to 50 minutes while applying mechanical shear force to devulcanize and recycle it. As commercially available products, for example, those manufactured and sold by Murakami Rubber Industry Co., Ltd., Asahi Recycling Rubber Co., Ltd., etc. can be used.

[0109] The recycled rubber may be used alone or in combination of two or more.

[0110] "Powdered rubber" refers to vulcanized powdered rubber recycled from waste rubber products. From the perspectives of environmental consideration and cost, it is preferable to use, as the waste rubber serving as the raw material for powdered rubber, ground tread rubber of used tires, cut sprues and burrs, etc. (ground materials of waste tires). Further, the rubber type of the waste rubber is not particularly limited, and examples thereof include diene rubbers such as NR, SBR, BR, and IR. Note that, as the powdered rubber, 30-mesh pass products, 40-mesh pass products, etc. in a Tyler mesh can be used. The powdered rubber may be used alone or in combination of two or more.

[0111] The average particle size of the powdered rubber is preferably 70 μm or more, more preferably 100 μm or more. The average particle size is preferably 1 mm or less, more preferably 750 μm or less. Note that the average particle size of the powdered rubber in this specification is the mass-based average particle size calculated from the particle size distribution measured in accordance with JIS Z 8815:1994.

[0112] As the powdered rubber, for example, those manufactured and sold by Murakami Rubber Industries Co., Ltd., Asahi Recycling Rubber Co., Ltd., Lehigh Technologies, etc. can be used.

[0113] The rubber component in the vulcanized rubber particles preferably has a natural rubber content ratio of 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more. When the natural rubber content ratio is within the above range, excellent elongation at break tends to be obtained. The content ratio of natural rubber is determined by measurement by pyrolysis gas chromatography (PyGC).

[0114] The content of the vulcanized rubber particles 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, still more preferably 5 parts by mass or more. On the other hand, the content 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 20 parts by mass or less.

[0115] <Filler> The rubber composition according to this embodiment preferably contains silica as a filler, and more preferably contains carbon black and silica. Further, the filler may be a filler consisting only of carbon black and silica.

[0116] (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 a raw material derived from a living organism such as rice husk (for example, silica using a biomass material such as rice husk as a raw material), or silica recycled from a product containing silica may be used. Among them, hydrous silica prepared by a wet method is preferred because it has many silanol groups. These silicas may be used alone or in combination of two or more.

[0117] Silica using a biomass material as a raw material can be obtained, for example, by extracting a silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and reacting the silicate with sulfuric acid in the same manner as conventional wet silica to precipitate silicon dioxide, followed by filtration, washing with water, drying, and pulverization.

[0118] As the silica recycled from a product containing silica, for example, silica recovered from products containing silica such as electronic components such as semiconductors, tires, desiccants, and filter materials such as diatomaceous earth can be used. The recovery method is not particularly limited, and examples include thermal decomposition and decomposition by electromagnetic waves. Among them, silica recovered from electronic components such as semiconductors or tires is preferred.

[0119] When silica crystallizes, it does not dissolve in water and the silicic acid that is its component cannot be utilized. By controlling the combustion temperature and combustion time, crystallization of silica in rice husk ash can be suppressed (see, for example, JP-A-2009-2594, Akita Prefectural University Web Journal B / 2019, vol. 6, p. 216-222, etc.).

[0120] Amorphous silica extracted from rice husks can be those commercially available from Wilmar Co., Ltd. or the like.

[0121] From the viewpoint of ensuring reinforcement and attenuation in the tread part, the nitrogen adsorption specific surface area (N2SA) of silica is preferably 110 m 2 / g or more, more preferably 140 m 2 / g or more, even more preferably 170 m 2 / g or more, particularly preferably 200 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, even more preferably 250 m 2 / g or less. The N2SA of silica is measured by the above-mentioned measurement method.

[0122] From the viewpoint of increasing the specific surface area of silica, increasing the interaction with the rubber component, suppressing the movement of molecular chains, and suppressing heat generation, the average primary particle diameter of silica is preferably 20 nm or less, more preferably 18 nm or less, and even more preferably 16 nm or less. The lower limit value 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 even more preferably 5 nm or more. The average primary particle diameter of silica is measured by the above-mentioned measurement method.

[0123] From the viewpoint of ensuring attenuation in the tread part and wet grip performance, the content of silica relative to 100 parts by mass of the rubber component is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 50 parts by mass or more, and particularly preferably 55 parts by mass or more. Also, from the viewpoint of reducing the specific gravity of the rubber and achieving weight reduction, it is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 95 parts by mass or less, and particularly preferably 90 parts by mass or less.

[0124] (Carbon black) The carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. The raw material of the carbon black may be a biomass material such as lignin or vegetable oil, or may be a pyrolysis oil obtained by pyrolyzing waste tires. Also, the method for producing carbon black may be by combustion such as the furnace method, by hydrothermal carbonization (HTC), or by thermal decomposition of methane such as the thermal black method. As commercially available products, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Columbian Carbon Company, etc. can be used. These carbon blacks may be used alone or in combination of two or more.

[0125] In addition to the above, from the perspective of life cycle assessment, etc., carbon black made from biomass materials such as lignin and vegetable oil as raw materials, or recycled carbon black obtained by pyrolyzing and purifying products containing carbon black such as tires may also be used as the carbon black.

[0126] In this specification, "recycled carbon black" refers to carbon black obtained by pulverizing used products such as tires containing carbon black and firing the pulverized product, and when oxidized and burned by heating in air by a thermogravimetric method conforming to JIS K 6226-2:2003, it refers to carbon black in which the ratio of the mass of the ash content (ash amount), which is the component that does not burn, is 13% by mass or more. That is, the ratio of the mass of the weight loss amount (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.

[0127] 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), especially pages 438, 440, 442, and describes that it can be obtained by pyrolysis of organic materials at 550 - 800 °C with oxygen excluded, or by vacuum pyrolysis at relatively low temperatures (

[0027] ). Carbon black obtained from such pyrolysis processes 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).

[0128] Recycled carbon black may lack functional groups on its surface, or may be treated to contain functional groups on its surface. The treatment to make the recycled carbon black contain functional groups on its surface can be carried out by conventional methods. For example, in European Patent Application Publication No. 3173251, carbon black obtained from the pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Also, in Patent No. 6856781, carbon black obtained from the pyrolysis process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain carbon black with an activated surface. The recycled carbon black according to this embodiment also includes carbon black treated to contain functional groups on its surface.

[0129] Recycled carbon black commercially available from companies such as Strable Green Carbon and LDCarbon can be used.

[0130] From the viewpoints of weather resistance and reinforcement, the nitrogen adsorption specific surface area (N2SA) of carbon black is preferably 50 m 2 / g or more, and 80 m2 More preferably 100 m 2 / g or more is even more preferable. Also, from the viewpoints of dispersibility, low fuel consumption performance, fracture characteristics, and durability performance, 250 m 2 / g or less is preferable, and 220 m 2 / g or less is more preferable. Note that the N2SA of carbon black is measured by the above measurement method.

[0131] When containing carbon black, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more from the viewpoints of weather resistance and reinforcing property. Also, from the viewpoint of low fuel consumption performance, 30 parts by mass or less is preferable, 25 parts by mass or less is more preferable, 20 parts by mass or less is even more preferable, and 15 parts by mass or less is particularly preferable.

[0132] (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 have been conventionally commonly used in the tire industry, can be blended. These other fillers may be used alone or in combination of two or more.

[0133] The ratio of the content of carbon black to the content of silica is preferably 0.40 or less, more preferably 0.30 or less, even more preferably 0.21 or less, even more preferably 0.17 or less, even more preferably 0.13 or less, and particularly preferably 0.10 or less. By setting the ratio of the content of carbon black to the content of silica within the above range, the wet grip performance can be further improved. On the other hand, the lower limit value of the ratio of the content of carbon black to the content of silica is not particularly limited, and for example, it can be 0.01 or more, 0.02 or more, 0.05 or more, and it may also be a filler that does not contain carbon black.

[0134] From the viewpoint of ensuring reinforcement and damping properties in the tread portion, the total filler content relative to 100 parts by mass of the rubber component is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, still more preferably 60 parts by mass or more, and particularly preferably 70 parts by mass or more. From the viewpoint of the effects of the present invention, it is preferably 160 parts by mass or less, more preferably 120 parts by mass or less, still more preferably 100 parts by mass or less, and particularly preferably 95 parts by mass or less.

[0135] (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 that has been 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. are included. 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 Co., Ltd. etc. can be used. These silane coupling agents may be used alone or in combination of two or more.

[0136] From the perspective of enhancing the dispersibility of silica, the content of the silane coupling agent relative to 100 parts by mass of silica is preferably 1.0 part by mass or more, more preferably 3.0 parts by mass or more, and even more preferably 5.0 parts by mass or more. From the perspectives of cost and processability, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less.

[0137] <Other compounding agents> In addition to the above components, the rubber composition according to this embodiment may appropriately contain compounding agents generally used in the conventional tire industry, such as plasticizers, processing aids, waxes, anti-aging agents, stearic acid, zinc oxide, vulcanizing agents, vulcanization accelerators, etc.

[0138] A plasticizer is a material that imparts plasticity to the rubber component, and is a concept that includes both plasticizers that are liquid at 25°C and plasticizers that are solid at normal temperature (25°C). Examples of plasticizers include resin components, oils, liquid rubbers, ester-based plasticizers, etc. These plasticizers may be derived from mineral resources such as petroleum and natural gas, may be derived from biomass, or may be derived from naphtha recycled from rubber products or non-rubber products. Also, low-molecular-weight hydrocarbon components obtained by pyrolyzing and extracting used tires and products containing various components may be used as plasticizers. These plasticizers may be used alone or in combination of two or more.

[0139] (Resin component) The resin component is not particularly limited as long as it is a resin component commonly used in the tire industry. For example, tackifying resins such as dicyclopentadiene-based resins, aromatic vinyl resins, C9-based resins, C5-based resins, C5C9-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.

[0140] The term "dicyclopentadiene-based resin" refers to a resin containing cyclopentadiene (CPD) or dicyclopentadiene (DCPD) as monomer components, which may be hydrogenated or modified ones. Examples of dicyclopentadiene-based resins include DCPD / C9 resins containing dicyclopentadiene and the C9 fraction described below as monomer components (the DCPD / C9 resins may be hydrogenated or modified ones), and DCPD / C9 resins containing dicyclopentadiene and styrene as monomer components are preferred. As dicyclopentadiene-based resins, for example, those commercially available from ExxonMobil, ENEOS Corporation, Nippon Zeon Co., Ltd., Maruzen Petrochemical Co., Ltd., etc. can be used. These dicyclopentadiene-based resins may be used alone or in combination of two or more.

[0141] The term "aromatic vinyl-based resin" refers to a resin containing an aromatic vinyl compound such as styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene, etc. as the monomer component with the highest content, which may be hydrogenated or modified ones. As aromatic vinyl-based resins, 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 aromatic vinyl-based resins, for example, those commercially available from Crayton, Eastman Chemical, Mitsui Chemicals, Inc., etc. can be used. These aromatic vinyl-based resins may be used alone or in combination of two or more.

[0142] "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, which may be a polymer of 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 resins may be used alone or in combination of two or more.

[0143] "C5 resin" refers to a resin obtained by polymerizing a C5 fraction, which may be 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 resins may be used alone or in combination of two or more.

[0144] "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, which may be obtained by hydrogenating or modifying them. 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.

[0145] The "terpene resin" refers to a resin containing terpene compounds such as α-pinene, β-pinene, limonene, dipentene, etc. as the monomer component with the highest content, 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.

[0146] The "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. The rosin resin is not particularly limited, and examples thereof 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.

[0147] The "phenolic resin" refers to a resin containing phenolic compounds such as phenol, cresol, etc. as the monomer component with the highest content. The phenolic resin is not particularly limited, and examples thereof include phenol-formaldehyde resin, alkylphenol-formaldehyde resin, alkylphenol-acetylene resin, oil-modified phenol-formaldehyde resin, etc. These phenolic resins may be used alone or in combination of two or more.

[0148] From the viewpoint of grip performance, the softening point of the resin component is preferably 60°C or higher, more preferably 70°C or higher, and even more preferably 80°C or higher. Further, from the viewpoints of processability and improvement of 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 resin component is measured by the above-described measuring method.

[0149] When containing a resin component, the content relative to 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more. Further, from the viewpoint of suppressing heat generation, it is preferably 60 parts by mass or lower, more preferably 50 parts by mass or lower, and even more preferably 40 parts by mass or lower.

[0150] (Oil) Examples of the oil include mineral oil, vegetable oil, animal oil, etc. Further, from the viewpoint of life cycle assessment, it is also possible to use waste oil after being used in a rubber mixer or an engine, or refined waste cooking oil used in a cooking shop.

[0151] In this specification, the mineral oil refers to an oil derived from mineral resources such as petroleum and natural gas. Examples of the mineral oil include paraffinic oil (mineral oil), naphthenic oil, aromatic oil, etc. Specific examples of the mineral oil include, for example, MES (Mild Extracted Solvate), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), RAE (Residual Aromatic Extract), etc. Further, it is also possible to use an oil with a low content of polycyclic aromatic (PCA) compounds for environmental measures. Examples of the low PCA content oil include MES, TDAE, heavy naphthenic oil, etc.

[0152] In this specification, "vegetable oil" includes, for example, linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice bran oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grapeseed oil, wood wax, etc. Further, as vegetable oils, there may be mentioned refined oils (such as salad oil) obtained by refining the above oils, transesterified oils obtained by transesterifying the above oils, hydrogenated oils obtained by hydrogenating the above oils, thermally polymerized oils obtained by thermally polymerizing the above oils, oxidative polymerized oils obtained by oxidizing the above oils, waste edible oils recovered from those used as edible oils, etc. Note that the vegetable oil may be liquid or solid at normal temperature (25°C). These vegetable oils may be used alone or in combination of two or more.

[0153] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably contains triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxy group of glycerin and a fatty acid are ester-bonded. The acylglycerol is not particularly limited, and may be any of 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, and triacylglycerol. Further, the acylglycerol may be a monomer, a dimer, or a multimer of trimer or higher. Note that acylglycerols of dimer or higher can be obtained by thermal polymerization, oxidative polymerization, etc. Also, the acylglycerol may be liquid or solid at normal temperature (25°C).

[0154] The method for confirming whether the above acylglycerol is contained in the rubber composition is not particularly limited. For example, the following 1 can be confirmed by 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 were 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.

[0155] 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.

[0156] Among them, it is desirable that the fatty acid contains 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. In addition, in order to produce a vegetable oil containing such a fatty acid, plants may be improved by variety improvement, genetic recombination, etc.

[0157] As the vegetable oil, for example, those commercially available from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kogyo Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0158] Examples of animal oils include fish oil, beef tallow, or oleyl alcohol that can be derived from them.

[0159] From the viewpoint of processability, the content of the oil based on 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 5 parts by mass or more. From the viewpoint of wear resistance performance, it is preferably 90 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, and particularly preferably 30 parts by mass or less.

[0160] The liquid rubber is not particularly limited as long as it is a polymer in a liquid state at normal temperature (25°C). For example, liquid butadiene rubber (liquid BR), liquid styrene-butadiene rubber (liquid SBR), liquid isoprene rubber (liquid IR), liquid styrene-isoprene rubber (liquid SIR), liquid farnesene rubber, etc. can be mentioned. These liquid rubbers may be used alone or in combination of two or more.

[0161] Examples of the ester plasticizer include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), bis(2-ethylhexyl) azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), etc. These ester plasticizers may be used alone or in combination of two or more.

[0162] The content of the plasticizer with respect to 100 parts by mass of the rubber component (when a plurality of plasticizers are used in combination, the total amount of all) is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, further preferably 30 parts by mass or more, and particularly preferably 35 parts by mass or more. Also, the content is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, further preferably 60 parts by mass or less, and particularly preferably 50 parts by mass or less.

[0163] Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, and the like. As the processing aids, those commercially available from, for example, Schill+Seilacher, Performance Additives, etc. can be used. These processing aids may be used alone or in combination of two or more.

[0164] When containing a processing aid, the content thereof per 100 parts by mass of the rubber component is preferably more than 0.5 part by mass, more preferably more than 1 part by mass, and still more preferably more than 1.5 part by mass from the viewpoint of exerting the effect of improving processability. Further, from the viewpoints of abrasion resistance and fracture strength, it is preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and still more preferably less than 5.0 parts by mass.

[0165] The wax is not particularly limited, and any of those usually used in the tire industry can be preferably used. Examples thereof include mineral waxes and plant-derived waxes. Mineral waxes refer to waxes derived from mineral resources such as oils and natural gases. Plant-derived waxes refer to waxes derived from natural resources such as plants. Among them, mineral waxes are preferred. Examples of plant-derived waxes include rice wax, carnauba wax, candelilla wax, and the like. Examples of mineral waxes include paraffin wax, microcrystalline wax, and these selected special waxes, and paraffin wax is preferred. Note that the wax according to the present embodiment does not contain stearic acid. As the wax, those commercially available from, for example, Ouchi Shinko 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.

[0166] When contained, 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 still more preferably 1.5 part by mass or more from the viewpoint of the weather resistance of the rubber. Further, from the viewpoint of preventing whitening of the tire due to blooming, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0167] The antioxidant is not particularly limited, but naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditoly-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N,N'-di-2-naphthyl-p-phenylenediamine (DNPD) and other p-phenylenediamine-based antioxidants; quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; bis, tris, polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane and the like. Among them, p-phenylenediamine-based antioxidants and quinoline-based antioxidants 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., Ltd. and the like can be used. These antioxidants may be used alone or in combination of two or more.

[0168] When contained, the content of the anti-aging agent 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 still more preferably 1.5 part by mass or more from the viewpoint of ozone crack resistance of the rubber. Further, from the viewpoints of abrasion resistance performance and wet grip performance, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0169] When contained, the content of stearic acid 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 still more preferably 1.5 part by mass or more from the viewpoint of processability. Further, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0170] When contained, the content of zinc oxide 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 still more preferably 1.5 part by mass or more from the viewpoint of processability. Further, from the viewpoint of abrasion resistance performance, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0171] Sulfur is preferably used as the vulcanizing agent. As sulfur, powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, etc. can be used.

[0172] When the vulcanizing agent contains sulfur, 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 still more preferably 1.0 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 3.5 parts by mass or less. In addition, when oil-containing sulfur is used as the vulcanizing agent, the content of the vulcanizing agent is the total content of pure sulfur contained in the oil-containing sulfur.

[0173] Examples of vulcanizing agents other than sulfur include alkylphenol sulfur chloride condensates, sodium 1,6 - hexamethylene - dithiolsulfate dihydrate, 1,6 - bis(N,N'-dibenzylthiocarbamoyldithio)hexane, and the like. As these vulcanizing agents other than sulfur, those commercially available from companies such as Taoka Chemical Industry Co., Ltd., Rancess Co., Ltd., and Flexsys can be used.

[0174] Examples of vulcanization accelerators include sulfenamide - type vulcanization accelerators, thiazole - type vulcanization accelerators, guanidine - type vulcanization accelerators, thiuram - type vulcanization accelerators, dithiocarbamate - type vulcanization accelerators, caprolactam disulfide, and the like. These vulcanization accelerators may be used alone or in combination of two or more. Among them, from the viewpoint of more preferably obtaining the desired effect, one or more vulcanization accelerators selected from the group consisting of sulfenamide - type vulcanization accelerators, thiazole - type vulcanization accelerators, and guanidine - type vulcanization accelerators are preferred, and it is more preferred to use a combination of sulfenamide - type vulcanization accelerators and guanidine - type vulcanization accelerators.

[0175] Examples of sulfenamide - type vulcanization accelerators include N - tert - butyl - 2 - benzothiazolylsulfenamide (TBBS), N - cyclohexyl - 2 - benzothiazolylsulfenamide (CBS), N,N - dicyclohexyl - 2 - benzothiazolylsulfenamide (DCBS), and the like. Among them, TBBS and CBS are preferred.

[0176] Examples of thiazole - type 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.

[0177] Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, the 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.

[0178] When containing a vulcanization accelerator, 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 still more preferably 1.5 part by mass or more. Also, the content of the vulcanization accelerator relative to 100 parts by mass of the rubber component is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, and still more preferably 4.0 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, the breaking strength and elongation tend to be ensured.

[0179] [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.).

[0180] 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 the vulcanizing agent and the vulcanization accelerator to the kneaded product obtained in the base kneading process and kneading them. Further, the base kneading process can be divided into a plurality of processes if desired.

[0181] The kneading conditions are not particularly limited. For example, in the base kneading process, a method of kneading at a discharge temperature of 150 to 170°C for 3 to 10 minutes, and in the final kneading process, kneading at 70 to 110°C for 1 to 5 minutes can be mentioned. 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.

[0182] A tire having a tread portion composed of the rubber composition can be manufactured by a conventional method. That is, an unvulcanized rubber composition in which each of the above components is blended with the rubber component as necessary is extruded according to the shape of the first layer of the tread portion, and is bonded together with the inner rubber layer of the tread portion and other tire members on a tire molding machine, and molded by a conventional method to form an unvulcanized tire. By heating and pressurizing this unvulcanized tire in a vulcanizer, a tire can be manufactured. The vulcanization conditions are not particularly limited, and for example, a method of vulcanizing at 150 to 200 ° C for 10 to 30 minutes can be mentioned.

[0183] [Use of the tire] The tire according to the present embodiment can be suitably used for passenger car tires, truck / bus tires, motorcycle tires, and racing tires, and among them, it is preferably used for passenger car tires. The passenger car tire is a tire assumed to be mounted on an automobile that runs on four wheels, and refers to a tire having a maximum load capacity of 1000 kg or less.

Examples

[0184] Hereinafter, examples (Examples) considered to be preferable in practice are shown, but the scope of the present invention is not limited to the examples. Using the various chemicals shown below, tires having the first layer of the tread portion obtained according to the formulation in Table 1 were examined, and the results calculated based on the following evaluation method are shown in Tables 2 and 3.

[0185] Hereinafter, various chemicals used in Examples and Comparative Examples are collectively shown. NR: TSR20 SBR1: SBR1502 manufactured by JSR Corporation (unmodified E-SBR, styrene content: 23.5% by mass, Tg: -56 ° C, Mw: 440,000, non-oil extended) SBR2: SPRINTAN (registered trademark) SLR3402 manufactured by TRINSEO (modified S-SBR, styrene content: 15% by mass, Tg: -60 ° C, non-oil extended) SBR3: HPR840 manufactured by JSR Corporation (S-SBR, styrene content: 10% by mass, Tg: -60 °C, Mw: 190,000, non-oil extended) SBR4: HPR850 manufactured by JSR Corporation (S-SBR, styrene content: 27.5% by mass, Tg: -24 °C, Mw: 200,000, non-oil extended) BR: UBEPOL BR (registered trademark) 150B manufactured by UBE Industries, Ltd. (unmodified BR, cis content: 97 mol%, Mw: 440,000) Carbon black: Showblack N220 manufactured by Cabot Japan Limited (N2SA: 111 m 2 / g) Silica: ULTRASIL (registered trademark) VN3 manufactured by Evonik Degussa GmbH (N2SA: 175 m 2 / g, average primary particle diameter: 17 nm) Silane coupling agent 1: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa GmbH Silane coupling agent 2: NXT (3-octanoylthiopropyltriethoxysilane) manufactured by Evonik Degussa GmbH Oil: VivaTec400 (TDAE oil) manufactured by H&R Resin component: Sylvatraxx (registered trademark) 4401 manufactured by Clayton (copolymer of α-methylstyrene and styrene, softening point: 85 °C) Wax: Oz Ace 0355 (paraffin wax) of Nippon Seiro Co., Ltd. Antioxidant: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Zinc oxide: Zinc white No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Tsubaki Bead Stearic Acid manufactured by NOF Corporation Sulfur: HK-200-5 (5% oil-containing powdered sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator: Nocceler CZ (N-cyclohexyl-2-benzothiazolylsulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0186] (Examples and Comparative Examples) According to the formulation shown in Table 1, using a 1.7 L sealed Banbury mixer, chemicals other than sulfur and vulcanization accelerators are kneaded for 1 to 10 minutes until the discharge temperature reaches 150 to 160 °C to obtain a kneaded product. Next, using a twin-screw open roll, sulfur and vulcanization accelerators are added to the kneaded product and kneaded for 4 minutes until the temperature reaches 105 °C to obtain an unvulcanized rubber composition. Using the unvulcanized rubber composition, it is extruded into the shape of the tread part (thickness: 11 mm) using an extruder equipped with a die of a predetermined shape and bonded together with other tire members to produce an unvulcanized tire, and press-vulcanized at 170 °C for 12 minutes to obtain each test tire (size: 215 / 55R18) described in Tables 2 and 3.

[0187] <Measurement of tanδ at 30 °C> For each vulcanized rubber test piece prepared by cutting out from the inside of the first layer of the tread part 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 is 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.

[0188] <Measurement of tanδ and E* at 0 °C> For each vulcanized rubber test piece prepared by cutting out from the inside of the first layer of the tread part 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 0 °C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±2.5%, and an elongation mode.

[0189] <Measurement of glass transition temperature (Tg)> For each vulcanized rubber test piece prepared by cutting out from the inside of the first 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), under the conditions of a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±0.5%, and a temperature rising rate of 2°C / min, the temperature distribution curve of tanδ in the range from -60°C to 40°C is measured, and the temperature (tanδ peak temperature) corresponding to the largest tanδ value in the obtained temperature distribution curve is determined as the Tg of the rubber composition.

[0190] <Wet Grip Performance> Each test tire is filled with air at 250 kPa and mounted on all four wheels of an automobile with an exhaust volume of 2000 cc. While driving on a wet asphalt road surface at an initial speed of 100 km / h, the brake is depressed and the braking distance is measured. Regarding the value of the reciprocal of the braking distance, the braking distance of Comparative Example 3 is set to 100 and expressed exponentially. The larger the exponent, the better the wet grip performance during high-speed driving.

[0191]

Table 1

[0192]

Table 2

[0193]

Table 3

[0194] <Embodiment> Examples of embodiments of the present invention are shown below.

[0195] 〔1〕A tire provided with a tread portion having at least one rubber layer, wherein the ratio of the tire weight G (kg) to the maximum load capacity W L (kg) of the tire (G / W L) is 0.0140 or less, the first layer constituting the tread surface is composed of a rubber composition containing a rubber component and a filler, when the total styrene amount in the rubber component is S (mass %), and the land ratio on the grounding surface of the tread portion is R, S is 20 or less, and the product of R and S (R×S) is more than 0 and 15 or less (preferably 1 or more and 13 or less, more preferably 2 or more and 12 or less) tire. 〔2〕G / W L is 0.0135 or less, the tire according to the above 〔1〕. 〔3〕S is 15 or less, the tire according to the above 〔1〕 or 〔2〕. 〔4〕S is 12 or less, the tire according to the above 〔3〕. 〔5〕The tanδ (30 °C tanδ) of the rubber composition at 30 °C is 0.15 or less, the tire according to any one of the above 〔1〕~〔4〕. 〔6〕The rubber composition contains silica having an average primary particle diameter of 16 nm or less, the tire according to any one of the above 〔1〕~〔5〕. 〔7〕The rubber composition contains a dicyclopentadiene-based resin, the tire according to any one of the above 〔1〕~〔6〕. 〔8〕The product of G and S (G×S) is 150 or less (preferably 20 or more and 150 or less, more preferably 30 or more and 130 or less), the tire according to any one of the above 〔1〕~〔7〕. 〔9〕The glass transition temperature of the rubber composition is -15 °C or less, the tire according to any one of the above 〔1〕~〔8〕. 〔10〕The ratio (0 °C tanδ / 0 °C E*) of tanδ (0 °C tanδ) at 0 °C to the complex elastic modulus (MPa) (0 °C E*) at 0 °C of the rubber composition is 0.044 or more, the tire according to any one of the above 〔1〕~〔9〕. 〔11〕The rubber composition contains vulcanized rubber particles, the tire according to any one of the above 〔1〕~〔10〕.

Claims

1. A tire comprising a tread portion having at least one rubber layer, Ratio (G / W) of tire weight G (kg) to maximum load capacity W of tire L (kg) is 0.0140 or less, L and wherein a first layer constituting the tread surface is composed of a rubber composition containing a rubber component and a filler, when the total styrene amount in the rubber component is S (mass %) and the land ratio on the grounding surface of the tread portion is R, S is 20 or less, and the product of R and S (R×S) is more than 0 and 15 or less.

2. G / W L The tire according to claim 1, wherein G / W is 0.0135 or less.

3. The tire according to claim 1, wherein S is 15 or less.

4. The tire according to claim 3, wherein S is 12 or less.

5. The tire according to any one of claims 1 to 4, wherein tanδ (30°C tanδ) of the rubber composition at 30°C is 0.15 or less.

6. The tire according to any one of claims 1 to 4, wherein the rubber composition contains silica having an average primary particle diameter of 16 nm or less.

7. The tire according to any one of claims 1 to 4, wherein the rubber composition contains a dicyclopentadiene-based resin.

8. The tire according to any one of claims 1 to 4, wherein the product of G and S (G×S) is 150 or less.

9. The tire according to any one of claims 1 to 4, wherein the glass transition temperature of the rubber composition is -15°C or less.

10. The tire according to any one of claims 1 to 4, wherein the ratio of tanδ (0°C tanδ) to the complex elastic modulus (MPa) (0°C E*) at 0°C of the rubber composition (0°C tanδ / 0°C E*) is 0.044 or more.

11. The tire according to any one of claims 1 to 4, wherein the rubber composition contains vulcanized rubber particles.

Images