Tire

Abstract

The invention provides a tire capable of improving wet grip performance during high-speed driving. The tire is provided with a tread portion having at least one rubber layer, the ratio (G / WL) of the tire weight G (kg) to the maximum load capacity WL (kg) of the tire is 0.0140 or less, and the first layer constituting the tread surface is configured from a rubber composition containing a rubber component and a filler. When the total styrene content in the rubber component is S (mass%) and the ground contact area ratio in 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 greater than 0 and 15 or less.

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 enhancing the adhesion on a wet road surface, for example, a method of compounding a plasticizer such as resin into tread rubber is known (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Problems to be Solved by the Invention

[0004] With the construction of highways and the high - performance of vehicles, the opportunity to drive at high speeds on wet road surfaces has increased. Therefore, in the tire market, there is a particularly strong demand for wet grip performance during high - speed driving.

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

Means for Solving the Problems

[0006] The present invention relates to a tire having a tread portion with at least one rubber layer, wherein the ratio (G / W L ) of the tire weight G (kg) to the maximum load capacity W L (kg) 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 contact area ratio in the contact surface of the tread portion is R, S is 20 or less, and the product (R × S) of R and S is greater than 0 and 15 or less.

Advantages of the Invention

[0007] According to the present invention, a tire that achieves improved wet grip performance during high - speed driving is provided. Brief Description of the Drawings

[0008]

Figure 1

[0009] A tire according to an embodiment of the present invention is a tire having a tread portion with at least one rubber layer, wherein the ratio (G / W L ) of the tire weight G (kg) to the maximum load capacity 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 set as S (mass %), and the grounding area ratio in the grounding surface of the tread portion is set as R, S is 20 or less, and the product of R and S (R×S) is greater than 0 and 15 or less.

[0010] Regarding the reason for the improvement of the wet grip performance of the tire of the present invention during high-speed driving, although it is not intended to be limited theoretically, the following speculation can be made.

[0011] It can be considered that the ratio of the tire weight G (kg) to the maximum load capacity W L (kg) (G / W L ) is smaller, the density when looking at the entire tire becomes smaller, and the natural vibration frequency is more likely to become high-frequency than in the normal case. In addition, it can be considered that on a wet road surface, since it is easy to slip between the tire and the road surface during high-speed driving, the entire tire is likely to absorb the input generated by this slip and easily convert the kinetic energy into heat. Further, it can be considered that by having a styrene portion in the tread rubber, a scraping effect brought about by the styrene phase region (domin) can be obtained.

[0012] On the other hand, the styrene phase region is a hard phase region. When it exists in excess relative to the grounding area ratio, the rubber component of the tread rubber becomes difficult to move, and it is difficult to generate grounding property and energy loss at the tread portion. It can be considered that, thereby, by setting the ratio of the styrene amount to the grounding area ratio to a certain value or less, the mobility of the rubber in the tread portion can also be ensured.

[0013] At the same time, it can be considered that: based on the coordinated action of these, it is easy to absorb the input caused by the slip when the entire tire travels at high speed on a wet road surface, and it is easy to obtain the scraping effect brought about by the styrene phase region and the accompanying deformation (energy loss) on the tread surface. Therefore, it is possible to improve the wet grip performance during high-speed driving.

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

[0015] By reducing the tanδ of the tread rubber at normal temperature, the phase difference between the input from the road surface and the response can be reduced. It can be considered that, therefore, the force can be instantaneously exerted in the tread rubber, and it becomes further easier to improve the wet grip performance during high-speed driving.

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

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

[0018] It is considered that by compounding a dicyclopentadiene resin into the rubber composition, the water repellency of the tread rubber can be improved, and the wet grip performance at high speeds can be improved.

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

[0020] It is considered that the greater the tire weight G, the easier it is for the inertia during rotation to increase. In addition, it is considered that when the total styrene amount S in the rubber component is large, as described above, the ground contact property of the tread surface decreases, and it becomes difficult to improve the wet grip performance at high speeds. It is considered that therefore, by setting the product of them (G×S) within the above range, the wet grip performance at high speeds can be improved.

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

[0022] It is considered that by setting the glass transition temperature of the rubber composition to -15°C or lower, the tread portion can deform softly with respect to the high-frequency deformation corresponding to high-speed driving, the ground contact property is improved, and the wet grip performance at high speeds becomes easy to improve.

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

[0024] It is considered that by setting 0°C tanδ / 0°C E* within the above range, after removing water, good followability and heat generation property of the tread portion in contact with the road surface can be exhibited, and the wet grip performance at high speeds is improved.

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

[0026] It is considered that by compounding vulcanized rubber particles into the rubber composition, a phase region of vulcanized rubber particles is formed, heat is generated due to friction at the interface between the vulcanized rubber particles and the rubber matrix, and the pulling effect brought by the vulcanized rubber particles can be obtained. Therefore, the frictional property with respect to the road surface at the tread surface is improved, and the wet grip performance at high speeds is improved.

[0027] <Definition> The "tread portion" is the portion that forms the ground contact surface of the tire. When there are components such as a belt layer or a belt reinforcing layer and a carcass layer formed of steel or textile materials in the tire radial cross-section, it is a component located more outside the tire in the radial direction than these components.

[0028] "Normal state" means: a state without load where the tire is assembled on a normal rim and filled with air at normal internal pressure.

[0029] "Dimensions of each part of the tire": Unless otherwise specified, the "dimensions of each part of the tire" appearing on the outer side of the tire are values specified in the normal state. On the other hand, for the "dimensions of each part of the tire" inside the tire and in the tire cross-section, for example, they are values specified in a state where the tire slice obtained by cutting the tire with a plane containing the tire rotation axis is held at the rim width of the normal rim.

[0030] "Normal rim" means: In the standard system including the standard on which the tire is based, the rim specified for each tire by the standard. For example, it refers to the standard rim in the applicable dimensions recorded in the "JATMA YEAR BOOK" of JATMA (Japan Automobile Tire Manufacturers Association), the "Measuring Rim" recorded in the "STANDARDS MANUAL" of ETRTO (The European Tyre and Rim Technical Organisation), and the "Design Rim" recorded in the "YEAR BOOK" of TRA (The Tire and Rim Association, Inc.). Refer in the order of JATMA, ETRTO, and TRA, and follow the standard if there is an applicable dimension during reference. In addition, for a tire not specified in the above standards, it means the rim with the smallest rim width among the rims with the smallest diameter that can assemble the tire and maintain the internal pressure (i.e., no air leakage occurs between the rim and the tire).

[0031] "Normal internal pressure" means: In the standard system including the standard on which the tire is based, the air pressure specified for each tire by the standard. For example, it refers to the "maximum air pressure" of JATMA, the "INFLATION PRESSURE" of ETRTO, and the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" of TRA. Similar to the case of the normal rim, refer in the order of JATMA, ETRTO, and TRA, and follow the standard if there is an applicable dimension during reference. In addition, for a tire not specified in the above standards, it means the normal internal pressure (where it is 250 kPa or more) of other tire sizes (where the tire is specified in the standard) with the above normal rim as the standard rim. When there are multiple normal internal pressures of 250 kPa or more recorded, it refers to the minimum value among them.

[0032] "Normal load" refers to the load specified for each tire in the standard system that includes the standard on which the tire is based. For example, it refers to the maximum value recorded in the "Maximum Load Capacity" of JATMA, the "LOAD CAPACITY" of ETRTO, and the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" of TRA. Similar to the case of the normal rim and normal internal pressure, it is referenced in the order of JATMA, ETRTO, and TRA, and when there are applicable dimensions during the reference, the standards thereof are followed. At the same time, for tires not specified in the above standards, the maximum load capacity W calculated separately is set as the normal load. L It is set as the normal load.

[0033] "Maximum load capacity W" L " is calculated by the following calculation formula. "V" is the virtual volume of the tire (mm 3 ), "Dt" is the outer diameter of the tire in the normal state (mm), "Ht" is the cross-sectional height of the tire in the tire diameter direction in the cross-section of the tire based on the plane including the tire rotation axis (mm), and "Wt" is the cross-sectional width of the tire in the normal state (mm). When the rim diameter of the tire is set as R, Ht can be obtained by (Dt - R) / 2. When there are patterns or characters, etc. on the tire sidewall, Wt is the value obtained by removing these. In addition, the maximum load capacity has the same meaning as the above normal load.

[0034]

Mathematical formula 1

[0035] "Tire weight G (kg)" refers to the weight of the tire alone without the weight of the rim. On the other hand, when the tire inner cavity part has sound insulation materials, seals, sensors, etc., G is the weight including these.

[0036] The "groove" including the circumferential groove and the transverse groove refers to: a recessed part with a width of at least more than 2.0 mm.

[0037] The "contact area" is the area of the tread obtained from the contour when the tire is pressed on the ground. It can be obtained by assembling the tire on the normal rim, applying the normal internal pressure, leaving it standing at 25°C for 24 hours, then coating the surface of the tire tread with ink, loading the tire with the normal load (maximum load capacity) and pressing it vertically on the cardboard (the camber angle is 0°) to transfer the ink. The area of the contact area refers to the total contact area. The total contact area can be calculated by rotating the tire 72 degrees in sequence, performing the above transfer operation at a total of 5 places, and taking the average value of the 5 obtained areas.

[0038] The "effective contact area region" is the region of the tread of the tire that comes into contact with the ground when the tire is pressed against the ground. It can be obtained by assembling the tire on a standard rim, filling it with the standard internal pressure, leaving it standing at 25°C for 24 hours, then applying ink to the surface of the tire tread, loading the tire with the standard load (maximum load capacity), and vertically pressing it onto cardboard (camber angle is 0°) to transfer the ink. The area of the effective contact area region refers to the effective contact area. The effective contact area can be calculated by rotating the tire by 72 degrees in sequence at a total of 5 positions for the above-mentioned transfer operation and taking the average of the 5 obtained areas.

[0039] The "contact area ratio R" is calculated by the following formula from the total contact area of the above-mentioned contact area region and the effective contact area of the above-mentioned effective contact area region. (Contact area ratio) = (Effective contact area / Total contact area)

[0040] The "thickness of the entire tread portion" means: in the cross-section obtained by cutting the tire along a plane including the tire rotation axis, the thickness of the entire tread portion in the tire equatorial plane. In addition, in the thickness of the entire tread portion, the radially inner end of the tire is the radially inner interface of the rubber composition constituting the tread portion. When the tire has a belt reinforcing layer, a belt layer, and a carcass layer, it is the thickness of the entire rubber layer located radially outside the radially outermost layer among these. In addition, when there is a circumferential groove in the tire equatorial plane, the groove is regarded as a filled groove when measuring the thickness of the entire tread portion.

[0041] The "thickness of each rubber layer constituting the tread portion" is: in the cross-section obtained by cutting the tire along a plane including the tire rotation axis, the thickness of each rubber layer in the tire equatorial plane, and the average value of the thicknesses of each rubber layer constituting the tread portion obtained by rotating the tire by 72° along the circumferential direction in sequence at 5 positions. For example, the thickness of the first layer means: the straight radial distance from the outermost surface of the tread to the radially inner interface of the first layer in the tire equatorial plane. In addition, when there is a circumferential groove in the tire equatorial plane, the thickness of each rubber layer constituting the tread portion is taken as the thickness of each rubber layer at the center in the tire width direction of the grounding portion closest to the tire equatorial plane. The "grounding portion closest to the tire equatorial plane" means: the grounding portion having the groove edge closest to the tire equatorial plane in the circumferential groove existing in the tire equatorial plane. When such grounding portions exist on both sides in the tire width direction, the thickness of each rubber layer constituting the tread portion is taken as the average value of the thicknesses of each rubber layer at the center in the tire width direction of these 2 grounding portions. In addition, when the grounding portion on the tire equatorial plane exists in an energized component or the like and the interface is not clear, the value measured by virtually connecting the interfaces blocked by the energized component or the like is taken.

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

[0043] "The content of plasticizer" also includes the amount of plasticizer contained in the rubber component with increased plasticizer, such as pre-increased by oil, resin component, liquid rubber component, etc. In addition, the same applies to the content of oil, resin component, and liquid rubber. For example, when the increment component is oil, the increment oil is included in the content of oil.

[0044] <Measurement method> "The thickness of each rubber layer constituting the tread portion" is measured in a cross-section obtained by cutting the tire along a plane including the tire rotation axis, with the width of the bead portion being the same as the width of the regular rim.

[0045] "30°C tanδ" is the tangent of the loss angle measured using a dynamic viscoelasticity measurement device (e.g., the EPLEXOR series manufactured by GABO) under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of ±1%, and a tensile mode. The sample for measuring the tangent of the loss angle is a vulcanized rubber composition with a length of 20 mm × a width of 4 mm × a thickness of 1 mm. When cutting out and manufacturing from the tire, it is cut out from the tread portion of the tire with the circumferential direction of the tire as the long side and the radial direction of the tire as the thickness direction.

[0046] "0°C tanδ" is the tangent of the loss angle measured using a dynamic viscoelasticity measurement device (e.g., the EPLEXOR series manufactured by GABO) under the conditions of a temperature of 0°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±2.5%, and a tensile mode. The sample for this measurement is manufactured in the same way as in the case of 30°C tanδ.

[0047] "0°C E*" is the complex elastic modulus measured using a dynamic viscoelasticity measurement device (e.g., the EPLEXOR series manufactured by GABO) under the conditions of a temperature of 0°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±2.5%, and a tensile mode. The sample for this measurement is manufactured in the same way as in the case of 30°C tanδ.

[0048] "The glass transition temperature (Tg) of the rubber composition" is measured using a dynamic viscoelasticity measuring device (e.g., the EPLEXOR 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 heating rate of 2°C / min to obtain the temperature distribution curve of tanδ in the range from -60°C to 40°C. The temperature (tanδ peak temperature) corresponding to the maximum tanδ value in the obtained temperature distribution curve is determined as Tg. When there are two maximum values of tanδ in the range from -60°C to 40°C, the point with the lower temperature is taken as Tg. In addition, when a temperature distribution curve in which tanδ gradually decreases as the temperature rises is obtained in the range from -60°C to 40°C, according to the above definition, Tg is taken as -60°C. The sample for this measurement is prepared in the same manner as in the case of tanδ at 0°C.

[0049] "Styrene content" is a value calculated by pyrolysis gas chromatography and is applicable to rubber components having repeating units derived from styrene such as SBR, for example. In addition, "pyrolysis gas chromatography" in this specification means a method of heating a sample with a pyrolysis device, separating each component contained in the gas phase components generated by this heating through a separation column, and analyzing the separated components.

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

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

[0052] "Total styrene amount in the rubber component" means the total content (mass%) of styrene units contained in 100 mass% of the rubber component. For each rubber component, the value obtained by multiplying the styrene content (mass%) by the mass fraction in the rubber component is calculated, and these values are summed up. Specifically, it is calculated by Σ (styrene content (mass%) of each rubber containing styrene units × content (mass%) of each rubber containing styrene units in the rubber component / 100).

[0053] "The 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 according to JIS K 7121 and is applicable to SBR, BR, etc., for example.

[0054] "Weight-average molecular weight (Mw)" can be obtained by conversion with standard polystyrene based on the measured values according to gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKgel SuperMultipore HZ-M manufactured by Tosoh Corporation). For example, it is applicable to SBR, BR, plasticizers, etc.

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

[0056] "Average primary particle size" is obtained by taking pictures of particles with a transmission or scanning electron microscope and calculating the arithmetic average of the particle sizes of 400 particles. For the particle size, when the shape of the particle is approximately circular, the diameter of the circle is set as the particle size; when it is needle-shaped or rod-shaped, the minor axis is set as the particle size; in other cases, the equivalent circle diameter calculated from the electron microscope image is set as the particle size. The equivalent circle diameter can be obtained as the positive square root of "[4×(area of the particle) / π]". The average primary particle size is applicable to silica, carbon black, etc.

[0057] "Softening point of the resin component" is the temperature at which the ball drops when measuring the softening point specified in JIS K 6220-1:2015 7.7 using a ring-and-ball softening point measuring device.

[0058] The manufacturing sequence of the tire according to an embodiment of the present invention will be described in detail below. Herein, the following description is an example for explaining the present invention, and the gist of the present invention is not limited to the scope of this description.

[0059] [Tire] In the tire according to this embodiment, from the viewpoint of the effects of the present invention, the ratio (G / W L (kg)) of the tire weight G (kg) to the maximum load capacity W L is 0.0140 or less, preferably 0.0137 or less, more preferably 0.0135 or less, and further preferably 0.0133 or less. On the other hand, from the viewpoint of the effects of the present invention, the lower limit value of this G / W L is not particularly limited. For example, it can be set to 0.0110 or more, 0.0115 or more, 0.0120 or more, 0.0125 or more. In addition, the tire weight G can be changed by conventional methods, that is, by increasing the specific gravity of the tire or increasing the thickness of each component of the tire, or it can be reduced by the opposite operation.

[0060] From the viewpoint of better exerting the effects of the present invention, the maximum load capacity W L (kg) is preferably 300 or more, more preferably 400 or more, still more preferably 450 or more, and particularly preferably 500 or more. In addition, from the viewpoint of better exerting the effects of the present invention, the maximum load capacity W L (kg) can be set to, 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. In addition, the maximum load capacity W L can be increased by increasing the virtual volume V of the space occupied by the above-mentioned tire, or can be decreased by the opposite operation.

[0061] The ground contact area ratio R in the ground contact surface of the tread portion is preferably 0.50 or more, more preferably 0.55 or more, still more preferably 0.60 or more. In addition, the ground contact area ratio R is preferably 0.85 or less, more preferably 0.80 or less, still 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 constituting the 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 can be set to, for example, 30% or more, 50% or more, 70% or more, 90% or more with respect to the thickness of the entire tread portion, or may be a tread portion composed 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, still more preferably 5.0 mm or more. In addition, the thickness t1 of the first layer is preferably 13.0 mm or less, more preferably 12.0 mm or less, still 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, still more preferably 0.17 or less, and particularly preferably 0.15 or less. In addition, the 0°C tanδ of the rubber composition is preferably 0.06 or more, more preferably 0.08 or more, still more preferably 0.10 or more. In addition, the 0°C tanδ of the rubber composition can be appropriately adjusted according to the types and compounding amounts of the following rubber components, vulcanized rubber particles, resin components, oils, etc.

[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, still more preferably 0.50 or more, and particularly preferably 0.60 or more. In addition, the 0°C tanδ of the rubber composition is preferably 1.00 or less, more preferably 0.95 or less, still more preferably 0.90 or less. In addition, the 0°C tanδ of the rubber composition can be appropriately adjusted by the types and compounding amounts of the following rubber components, vulcanized rubber particles, resin components, oils, etc.

[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, still 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 become good. In addition, the 0°C E* of the rubber composition is preferably 4.0 MPa or more, more preferably 5.0 MPa or more, still more preferably 6.0 MPa or more. In addition, the 0°C E* of the rubber composition can be appropriately adjusted by the types and compounding amounts of the following rubber components, vulcanized rubber particles, resin components, oils, etc.

[0068] The Tg of the rubber composition constituting the first layer is preferably -13°C or less, more preferably -15°C or less, still more preferably -17°C or less. In addition, the Tg of the rubber composition is preferably -40°C or more, more preferably -35°C or more, still more preferably -30°C or more. In addition, the Tg of the rubber composition can be appropriately adjusted by the types and compounding amounts of the following rubber components, vulcanized rubber particles, resin components, oils, etc.

[0069] 0°C tanδ / 0°C E* is preferably 0.035 or more, more preferably 0.040 or more, still more preferably 0.044 or more. It is considered that by setting within the above range, after water removal, good followability and heat generation of the tread surface in contact with the road surface can be exhibited, and the wet grip performance during high-speed driving can be improved. In addition, 0°C tanδ / 0°C E* is preferably 0.060 or less, more preferably 0.055 or less, still more preferably 0.050 or less.

[0070] The product (R×S) of the contact area ratio R and the total styrene content S (mass%) in the rubber component is 15 or less, preferably 13 or less, more preferably 12 or less, still more preferably 10 or less, and particularly preferably 8 or less. On the other hand, R×S is greater than 0, preferably 1 or more, more preferably 2 or more, still 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, further 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, preferably 20 or more, more preferably 30 or more, further preferably 40 or more, and particularly preferably 50 or more.

[0072] [Rubber composition] The tire according to this embodiment can more effectively improve the wet grip performance during high-speed driving through the synergistic effects of the above-mentioned constitution of the tire and the tread surface and the above-mentioned physical properties of the rubber composition constituting the tread surface. Hereinafter, the rubber composition constituting the first layer will be described.

[0073] [Rubber component] In the rubber composition according to this embodiment, a diene rubber can be 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 can be modified rubbers treated with a modifying group capable of interacting with fillers such as carbon black and silica, or hydrogenated rubbers in which a part of the unsaturated bonds are hydrogenated. The diene rubber can be used alone or in combination of two or more. In addition, as the diene rubber, an oil-extended rubber obtained by previously adding the following plasticizer can also be used. In addition, the rubber component according to this embodiment does not contain the component of the following vulcanized rubber particles.

[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, further preferably 90% by mass or more, and particularly preferably 95% by mass or more. In addition, a rubber component composed only of a diene rubber can also be used.

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

[0076] [Isoprene rubber] As the isoprene rubber, there is no particular limitation. For example, natural rubber (NR), isoprene rubber (IR), modified natural rubber, etc. can be cited. As NR, for example, SIR20, RSS#3, TSR20, etc. can be cited. As IR, for example, IR2200, etc. can be cited. As modified natural rubber, for example, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, grafted natural rubber, etc. can be cited. These isoprene rubbers can be used alone or in combination of two or more.

[0077] From the viewpoint of the effects of the present invention, the content of the isoprene rubber in the rubber component is preferably 50% by mass or less, more preferably 40% by mass or less, further preferably 30% by mass or less, and particularly preferably 25% by mass or less. In addition, the lower limit value of this content is not particularly limited. For example, it can be set to 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) As BR, there is no particular limitation. For example, BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare-earth-based butadiene rubber synthesized with a rare-earth element-based catalyst (rare-earth-based BR), BR containing syndiotactic polybutadiene crystals (BR containing SPB), modified BR (high-cis modified BR, low-cis modified BR), etc., which are commonly used in the tire industry, can be used. These BRs can be used alone or in combination of two or more.

[0079] As high-cis BR, for example, commercially available substances from Zeon Corporation, UBE Corporation, JSR Corporation, etc. in Japan can be used. By containing high-cis BR, the abrasion resistance can be improved. The cis content of high-cis BR is preferably 95 mol% or more, more preferably 96 mol% or more, and further preferably 97 mol% or more. In addition, the cis content of BR is measured by the above-mentioned measurement method.

[0080] As modified BR, modified butadiene rubber (modified BR) in which the terminal and / or main chain is modified with a functional group containing at least one element selected from silicon, nitrogen, and oxygen can be 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 further, modified BRs in which a tin-carbon bond is bonded to the terminal of the modified BR molecule (tin-modified BR), etc. can be cited. In addition, the modified BR can be either an unhydrogenated modified BR or a hydrogenated modified BR.

[0082] From the viewpoint of abrasion resistance, the weight-average molecular weight (Mw) of BR is preferably 300,000 or more, more preferably 350,000 or more, and further preferably 400,000 or more. In addition, from the viewpoints of crosslinking uniformity and the like, it is preferably 2,000,000 or less, more preferably 1,000,000 or less. In addition, the Mw of BR is measured by the above-described measurement method.

[0083] From the viewpoint of the effects of the present invention, the content of BR in the rubber component is preferably 50% by mass or less, more preferably 40% by mass or less, further preferably 30% by mass or less, and particularly preferably 25% by mass or less. In addition, the lower limit value of this content is not particularly limited. For example, it may be set to 1% by mass or more, 3% by mass or more, 5% by mass or more, 7% by mass or more, or 10% by mass or more.

[0084] (SBR) As the SBR, there is no particular limitation. For example, unmodified solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), modified SBRs thereof (modified S-SBR, modified E-SBR), etc. may be mentioned. As the modified SBR, SBR modified at the terminal and / or main chain; modified SBR coupled with tin, silicon compounds, etc. (condensates, substances having a branched structure, etc.) may be mentioned. Further, hydrides of these SBRs (hydrogenated SBR) etc. may also be used. These SBRs may be used alone or in combination of two or more.

[0085] As the SBR according to the present embodiment, oil-extended SBR and non-oil-extended SBR may be used. When using oil-extended SBR, the amount of oil extended in the SBR, that is, the content of the extender plasticizer contained in the SBR is preferably 10 to 50 parts by mass with respect to 100 parts by mass of the rubber solid component 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, commercially available substances from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., ZSELASTOMERS Co., Ltd., etc. may be used.

[0087] The styrene content of the SBR may be appropriately selected on the premise that the total styrene amount S in the rubber component satisfies the following range, and is preferably 40% by mass or less, more preferably 37% by mass or less, further preferably 34% by mass or less, and particularly preferably 30% by mass or less. In addition, the styrene content of the SBR is preferably 5% by mass or more, more preferably 7% by mass or more, further preferably 10% by mass or more, and particularly preferably 12% by mass or more. In addition, the styrene content of the SBR is measured by the above-described measurement method.

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

[0089] From the viewpoint of the effects of the present invention, the weight average molecular weight (Mw) of SBR is preferably 100,000 or more, more preferably 200,000 or more, and further preferably 300,000 or more. In addition, 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 further preferably 1,500,000 or less. In addition, the weight average molecular weight of SBR is measured by the above-mentioned measurement method.

[0090] The content of SBR in the rubber component can be appropriately selected on the premise that the total styrene amount S in the rubber component satisfies the following range, and is preferably 20% by mass or more, more preferably 30% by mass or more, further preferably 40% by mass or more, further preferably 50% by mass or more, 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, further preferably 90% by mass or less, and particularly preferably 85% by mass or less.

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

[0092] (Other rubber components) Within the range that does not affect the effects of the present invention, the rubber component may also contain rubber components other than diene-based rubbers (non-diene-based rubbers). As the non-diene-based rubber, rubber components commonly used in the tire industry can be used. For example, butyl-based rubbers, ethylene-propylene rubbers, polynorbornene rubbers, silicone rubbers, chlorinated polyethylene rubbers, fluororubbers (FKM), acrylic rubbers (ACM), epichlorohydrin rubbers, etc. can be cited. These other rubber components can be used alone or in combination of two or more. In addition, in addition to the above-mentioned rubber components, known thermoplastic elastomers may or may not be contained.

[0093] (Rubber components synthesized from recycled / biomass-derived raw materials) The monomers that are the constituent units of synthetic rubbers such as IR, SBR, and BR can be substances derived from underground resources such as petroleum and natural gas, or substances recycled from rubber products such as tires or non-rubber products such as polystyrene. As the monomers obtained by recycling (recycled monomers), there is no particular limitation, and examples include recycled polyisoprene, recycled butadiene, recycled aromatic vinyl compounds, etc. As the above butadiene, 1,2-butadiene and 1,3-butadiene can be cited. As the above aromatic vinyl compound, there is no particular limitation, and styrene, etc. can be cited. Among them, it is preferable to use recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and recycled styrene (recycled styrene) as raw materials.

[0094] As the method for producing recycled monomers, there is no particular limitation. For example, it can be cited as being synthesized from recycled naphtha obtained by pyrolyzing rubber products such as tires. In addition, as the method for producing recycled naphtha, there is no particular limitation. For example, rubber products such as tires can be pyrolyzed under high temperature and high pressure, or pyrolyzed by microwave, or extracted after mechanical pulverization.

[0095] Furthermore, the monomers that are the constituent units of polymers such as IR, SBR, and BR can also be biomass-derived substances. In this specification, biomass refers to substances derived from natural resources such as plants. As biomass, there is no particular limitation, and examples include substances derived from agricultural, forestry, and fishery products or sugars, wood chips, plant residues after obtaining useful components, ethanol from plants, biomass naphtha, etc.

[0096] As the biomass-derived monomers (biomass monomers), there is no particular limitation, and examples include biomass-derived butadiene, biomass-derived aromatic vinyl compounds, etc. As the above butadiene, 1,2-butadiene and 1,3-butadiene can be cited. As the above aromatic vinyl compound, there is no particular limitation, and styrene, etc. can be cited. In addition, the method for producing biomass-derived monomers is not particularly limited. For example, substances obtained by biological and / or chemical and / or physical conversion of animals and plants can be cited. As biological conversion, fermentation based on microorganisms is representative. As chemical and / or physical conversion, conversion based on catalysts, conversion based on high heat, conversion based on high pressure, conversion based on electromagnetic waves, conversion based on supercritical fluids, and combinations thereof can be cited.

[0097] As a polymer synthesized from biomass monomer components (biomass polymer), there is no particular limitation, and examples thereof include polybutadiene rubber synthesized from biomass-derived butadiene, aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl compounds, and the like. As the above-mentioned aromatic vinyl / butadiene copolymer, for example, styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene can be mentioned.

[0098] Whether the raw material of the polymer is derived from biomass can be judged by pMC (percent Modern Carbon) measured according to ASTM D6866-10.

[0099] pMC refers to: the 14 C concentration of the sample relative to that of the 14 modern standard reference of C, which is a value used as an index indicating the biomass ratio of a compound. The meaning of this value will be described below.

[0100] In 1 mole (6.02×10 23 ), there is about one trillionth of the normal carbon atoms, that is, about 6.02×10 11 atoms 14 of 14 C. The half-life of 14 C is 5730 years, and 14 C decreases regularly. It takes 226,000 years for all of these to decay. Therefore, it can be considered that after carbon dioxide in the atmosphere and the like are absorbed and immobilized by plants and the like, in fossil fuels such as coal, oil, and natural gas that have experienced more than 226,000 years, all of the 14 C elements contained therein at the time of initial immobilization have decayed. Therefore, in the 21st century today, fossil fuels such as coal, oil, and natural gas contain no 14 C elements at all. Therefore, chemical substances produced using these fossil fuels as raw materials also contain no

[0101] On the other hand, 14 C is continuously generated by nuclear reactions in the atmosphere by cosmic rays. Therefore, 14 the decrease of 14 C due to radioactive decay and the generation due to nuclear reactions reach equilibrium, and in the atmospheric environment of the earth, 14 the -12Values around mol%. Therefore, by using the difference between these values, the biomass ratio in a certain compound can be calculated.

[0102] Generally, the 14 C is measured as described below. Using accelerator mass spectrometry based on a tandem accelerator, 13 C concentration ([[]] 13 C / [[[]] 12 C), [[[]] 14 C concentration ([[]] 14 C / [[[]] 12 C) is measured. During the measurement, as the standard modern carbon for the benchmark of the [[[]] 14 C concentration, the [[[]] 14 C concentration in the circulating carbon in nature in 1950 is adopted. As a specific reference material, the oxalic acid standard provided by NIST (National Institute of Standards and Technology) is used. The specific radioactivity of carbon in this oxalic acid (the radioactivity intensity of [[[]] 14 C per 1 g of carbon) is classified according to each carbon isotope, the [[[]] 13 C is corrected to a fixed value, and the value applied with the decay correction from 1950 AD to the measurement date is used as the standard [[[]] 14 C concentration value (100%). The ratio of the value of the actually measured sample to this value is the pMC value.

[0103] Therefore, if the rubber is made of 100% substances derived from biomass, although there are regional differences, etc., since it is mostly not 100 under normal conditions now, it is expected to show a value of about 110 pMC. On the other hand, for chemical substances derived from fossil fuels such as petroleum, when measuring the [[[]] 14 C concentration, a value of about 0 pMC (for example, 0.3 pMC) is shown. This value corresponds to the above-mentioned biomass ratio of 0%.

[0104] In summary, it is preferable in terms of environmental protection to use materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio, in the rubber composition.

[0105] <Vulcanized rubber particles> "Vulcanized rubber particles" refers to: a rubber composition obtained by a process different from the rubber base constituting the rubber composition of the present embodiment, and through image analysis such as SEM, a phase region different from the rubber matrix constituting the rubber composition of the present embodiment is formed. Generally, it is the following recycled rubber, rubber powder, etc., but not limited thereto. Depending on the use, a rubber composition different from the rubber composition of the present embodiment can be prepared and pulverized to obtain it. Vulcanized rubber particles can be used alone or in combination of two or more.

[0106] "Recycled rubber" means rubber obtained by recycling used rubber such as automotive tires, inner tubes (tubes), and other rubber products specified in JIS K 6313:2012, and rubber having the same properties. In addition, powdered rubber is not included. In addition, desulfurization treatment can be applied to recycled rubber.

[0107] The type of recycled rubber can be any one of inner tube recycled rubber, tire recycled rubber, and other recycled rubber, or a combination of multiple types. Among them, tire recycled rubber is preferred.

[0108] Recycled rubber can use rubber obtained by known manufacturing methods. For example, the most common steam method (oil method) has been developed, as well as methods based on Banbury mixers / twin-screw reactive extruders, microwave-based methods, ultrasonic-based methods, electron beam irradiation-based methods, etc. It can also be rubber manufactured by any method. In addition, commercially available recycled rubber can also be used. As one specific example for manufacturing recycled rubber, a method can be cited in which vulcanized rubber powder is put into a closed mixer or extruder, heated to 100 - 250 °C, and treated for 5 - 50 minutes while applying mechanical shear force for desulfurization and then recycled. As commercially available products, for example, substances manufactured and sold by Murakami Rubber Industry Co., Ltd., ASAHI Recycled Rubber Co., Ltd., etc. can be used.

[0109] Recycled rubber can be used alone or in combination of two or more types.

[0110] "Rubber powder" means vulcanized rubber powder obtained by recycling waste rubber products. As the raw material of rubber powder, that is, waste rubber, from the viewpoints of environmental concerns and cost, it is preferred to use overflow rubber (spew) / burrs (burr) cut from the tread rubber of used tires (crushed products of used tires). In addition, the type of rubber of the waste rubber is not particularly limited, and diene rubbers such as NR, SBR, BR, IR, etc. can be cited. In addition, as rubber powder, materials passing through a 30-mesh sieve, 40-mesh sieve, etc. in a Tyler mesh can be used. Rubber powder can be used alone or in combination of two or more types.

[0111] The average particle size of the rubber powder 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. In addition, the average particle size of the rubber powder in this specification is the average particle size based on mass calculated from the particle size distribution measured according to JIS Z 8815:1994.

[0112] As the rubber powder, for example, substances manufactured and sold by Murakami Rubber Industry Co., Ltd., ASAHI Recycling Rubber Co., Ltd., Lehigh Technologies, etc. can be used.

[0113] In the rubber component of the vulcanized rubber particles, the content ratio of natural rubber is preferably 40% by mass or more, more preferably 50% by mass or more, and further preferably 60% by mass or more. When the content ratio of natural rubber is within the above range, it tends to obtain excellent elongation at break. The content ratio of natural rubber can be determined by measurement using pyrolysis gas chromatography (PyGC).

[0114] The content of the vulcanized rubber particles relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and further preferably 5 parts by mass or more. On the other hand, this content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, further 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. In addition, the filler may also be a filler composed only of carbon black and silica.

[0116] (Silica) There is no particular limitation on the silica. For example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), etc., which are commonly used in the tire industry, can be used. There is no particular limitation on the raw material of the silica. For example, it may be a raw material derived from minerals such as quartz, or a raw material derived from organisms such as rice husks (for example, silica using biomass materials such as rice husks as raw materials), and silica recovered from products containing silica can also be used. Among them, due to the large number of silanol groups, hydrous silica prepared by a wet method is preferred. These silicas can be used alone or in combination of two or more.

[0117] For silica using biomass materials as raw materials, for example, silicate can be extracted from rice husk ash obtained by burning rice husks with a sodium hydroxide solution, and the silicate is reacted with sulfuric acid in the same way as conventional wet silica to form a silica precipitate, which is then filtered, washed with water, dried, and pulverized.

[0118] Silica recovered from products containing silica, for example, silica recovered from products containing silica such as electronic components such as semiconductors, tires, desiccants, diatomaceous earth and other filter materials can be used. In addition, the recovery method is not particularly limited, and thermal cracking, electromagnetic wave cracking and the like can be cited. Among them, silica recovered from electronic components such as semiconductors or tires is preferred.

[0119] If silicon dioxide is crystallized, it will not dissolve in water, and the silicic acid as a component cannot be used. By controlling the combustion temperature and combustion time, the crystallization of silicon dioxide in rice husk ash can be suppressed (see Japanese Patent Publication No. 2009-2594, Akita Prefectural University Online Journal B (Akita Prefectural University ウェブジャーナルB) / 2019, vol. 6, p. 216-222, etc.).

[0120] Amorphous silica extracted from rice husks and commercially available products such as Wilmar can be used.

[0121] From the viewpoint of reinforcement and ensuring the damping property in the tread portion, the nitrogen adsorption specific surface area (N2SA) of silica is preferably 110 m 2 / g or more, more preferably 140m 2 / g or more, more preferably 170m 2 / g or more, particularly preferably 200m 2 / g or more. In addition, from the viewpoint of heat generation and processability, 350 m 2 / g or less, more preferably 300m 2 / g or less, more preferably 250m 2 / g or less. In addition, the N2SA of silica is measured by the above-mentioned measurement method.

[0122] From the viewpoint of increasing the specific surface area of ​​silica, increasing the interaction with the rubber component to inhibit the activity of the molecular chain and inhibiting the heat generation, the average primary particle size of silica is preferably less than 20nm, more preferably less than 18nm, and more preferably less than 16nm. The lower limit of the average primary particle size is not particularly limited, and from the viewpoint of the dispersibility of silica, it is preferably more than 1nm, more preferably more than 3nm, and more preferably more than 5nm. In addition, the average primary particle size of silica is measured by the above-mentioned determination method.

[0123] From the viewpoint of ensuring damping properties and wet grip performance at the tread surface, 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, still more preferably 50 parts by mass or more, and particularly preferably 55 parts by mass or more. Further, from the viewpoint of reducing the specific gravity of the rubber to achieve weight reduction, it is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, still more preferably 95 parts by mass or less, and particularly preferably 90 parts by mass or less.

[0124] (Carbon black) There is no particular limitation on the carbon black, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762 and the like. 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. In addition, the manufacturing method of the carbon black may be a combustion-based method such as a furnace method, a method based on hydrothermal carbonization (HTC), or a method based on thermal pyrolysis of methane derived from a thermal cracking carbon 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., Columbia Carbon Company, etc. can be used. These can be used alone or in combination of two or more.

[0125] In addition, as the carbon black, in addition to the above, from the viewpoint of life cycle assessment, etc., carbon black using biomass materials such as lignin and vegetable oil as raw materials, and recycled carbon black obtained by pyrolyzing and refining products containing carbon black such as tires can also be used.

[0126] In this specification, "recycled carbon black" means carbon black obtained by pulverizing products such as used tires containing carbon black and firing the pulverized product, and when oxidized and burned by heating in air using a thermogravimetric method based on JIS K 6226-2:2003, the proportion of the non-combustible component, that is, the mass (ash content) of ash is 13% by mass or more. That is, the proportion of the mass (carbon content) of the reduced amount based on the above oxidation combustion of the recycled carbon black is 87% by mass or less. Recycled carbon black is sometimes also 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 describes that in "Rubber Chemistry and Technology", Vol. 85, No. 3, pages 408 - 449 (2012), especially pages 438, 440, and 442, it is mentioned that pyrolysis of organic materials is carried out at 550 - 800 °C after removing oxygen, or vacuum pyrolysis at a relatively low temperature (

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

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

[0128] Recycled carbon black can be carbon black lacking functional groups on its surface, or it can also be carbon black that has been treated to have functional groups on its surface. The treatment to make the surface of the recycled carbon black contain functional groups can be carried out by conventional methods. For example, in European Patent Application Publication No. 3173251, carbon black obtained by a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl groups and / or carboxyl groups on its surface. In addition, in Patent No. 6856781, carbon black obtained by a pyrolysis process is treated with an amino acid compound containing at least one mercapto group or disulfide group to obtain carbon black with an activated surface. The recycled carbon black involved in this embodiment includes such carbon black treated to have functional groups on its surface.

[0129] Commercially available substances such as those from Strable Green Carbon and LDCarbon can be used as recycled carbon black.

[0130] From the viewpoints of weather resistance and reinforcing properties, the nitrogen adsorption specific surface area (N2SA) of carbon black is preferably 50 m 2 / g or more, more preferably 80 m 2 / g or more, and further preferably 100 m 2 / g or more. In addition, from the viewpoints of dispersibility, low fuel consumption performance, fracture characteristics, and durability performance, it is preferably 250 m 2 / g or less, more preferably 220 m 2 / g or less. In addition, the N2SA of carbon black is measured by the above-mentioned measurement method.

[0131] When carbon black is contained, from the viewpoints of weather resistance and reinforcement, its content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 5 parts by mass or more. Further, from the viewpoint of low fuel consumption performance, it is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, still more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less.

[0132] (Other fillers) The fillers other than silica and carbon black are not particularly limited. For example, aluminum hydroxide, alumina, calcium carbonate, magnesium sulfate, talc, clay, biochar, etc., which are commonly used in the tire industry, can be compounded. These other fillers can 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, still more preferably 0.21 or less, still more preferably 0.17 or less, still 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. For example, it can be 0.01 or more, 0.02 or more, 0.05 or more, or a filler containing no carbon black can also be used.

[0134] From the viewpoints of ensuring reinforcement and damping at the tread portion, the total content of the fillers 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. There is no particular limitation on the silane coupling agent, and any silane coupling agent that has been conventionally used in combination with silica in the tire industry can be used. For example, mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane can be cited; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; thioester-based silane coupling agents such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane; vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane, etc. Among them, a sulfide-based silane coupling agent and / or a mercapto-based silane coupling agent are preferably contained. As the silane coupling agent, for example, commercially available substances from Momentive Performance Materials Inc. and others can be used. These silane coupling agents can be used alone or in combination of two or more.

[0136] From the viewpoint of improving 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 part by mass or more, and further preferably 5.0 part by mass or more. In addition, from the viewpoints of cost and processability, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and further preferably 12 parts by mass or less.

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

[0138] A plasticizer refers to a material that imparts plasticity to rubber components, and is a concept that includes both plasticizers that are liquid at 25°C and plasticizers that are solid at normal temperature (25°C). As examples of plasticizers, resin components, oils, liquid rubbers, ester-based plasticizers, etc. can be cited. These plasticizers can be substances derived from mineral resources such as petroleum and natural gas, substances derived from biomass, or substances derived from naphtha recovered from rubber products and non-rubber products. In addition, low-molecular-weight hydrocarbon components obtained by thermally cracking and extracting used tires and products containing various components can also be used as plasticizers. These plasticizers can be used alone or in combination of two or more.

[0139] (Resin component) As the resin component, there is no particular limitation as long as it is a resin component commonly used in the tire industry. For example, adhesive 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 phenolic resins can be cited. These resin components can be used alone or in combination of two or more.

[0140] "Dicyclopentadiene-based resin" refers to a resin containing cyclopentadiene (CPD) or dicyclopentadiene (DCPD), and can also be their hydrogenated products or modified products. As dicyclopentadiene-based resins, for example, DCPD / C9 resins containing dicyclopentadiene and the following C9 fraction as monomer components (this DCPD / C9 resin can also be their hydrogenated products or modified products) can be cited, and DCPD / C9 resins containing dicyclopentadiene and styrene as monomer components are preferred. As dicyclopentadiene-based resins, for example, commercially available substances from ExxonMobil Corporation, ENEOS Corporation, Zeon Corporation, Maruzen Petrochemical Co., Ltd., etc. can be used. These dicyclopentadiene-based resins can be used alone or in combination of two or more.

[0141] "Aromatic vinyl-based resin" refers to a resin containing aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and p-chlorostyrene as the monomer component with the highest content, and can also be their hydrogenated products or modified products. As aromatic vinyl-based resins, due to economic efficiency, easy processing, and excellent heat generation properties, homopolymers of α-methylstyrene or styrene or copolymers of α-methylstyrene and styrene are preferred, and copolymers of α-methylstyrene and styrene are more preferred. As aromatic vinyl-based resins, for example, commercially available substances from Kraton Corporation, Eastman Chemical Company, Mitsui Chemicals, Inc., etc. can be used. These aromatic vinyl-based resins can be used alone or in combination of two or more.

[0142] "C9 resin" refers to: a resin obtained by polymerizing C9 fractions, which can be a resin obtained by homopolymerizing C9 fractions or a copolymer obtained by copolymerizing C9 fractions with other components. For example, a resin obtained by copolymerizing dicyclopentadiene (DCPD) with C9 fractions is called DCPD / C9 resin. In addition, it can also be their hydrogenated products or modified products. As C9 fractions, for example, petroleum fractions equivalent to 8 to 10 carbon atoms such as vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene can be cited. These C9 resins can be used alone or in combination of two or more.

[0143] "C5 resin" refers to: a resin obtained by polymerizing C5 fractions, which can also be their hydrogenated products or modified products. As C5 fractions, for example, petroleum fractions equivalent to 4 to 5 carbon atoms such as cyclopentadiene, isoprene, pentane, isopentane, neopentane, pentene, and pentadiene can be cited. These C5 resins can be used alone or in combination of two or more.

[0144] "C5C9 resin" refers to: a resin obtained by copolymerizing the above C5 fractions with the above C9 fractions, which can also be their hydrogenated products or modified products. As C5C9 petroleum resins, for example, commercially available substances from Tosoh Corporation, LUHUA Corporation, etc. These C5C9 resins can be used alone or in combination of two or more.

[0145] "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, which can also be their hydrogenated products or modified products. As specific examples of terpene resins, for example, polyterpene resins containing only one or more of the above terpene compounds as monomer components can be cited; aromatic modified terpene resins containing the above terpene compounds and aromatic compounds as monomer components; terpene phenol resins containing the above terpene compounds and phenolic compounds as monomer components, etc. As aromatic compounds constituting the monomer components of aromatic modified terpene resins, for example, styrene, α-methylstyrene, vinyltoluene, divinyltoluene, etc. can be cited. As phenolic compounds constituting the monomer components of terpene phenol resins, for example, phenol, bisphenol A, cresol, xylenol, etc. can be cited. These terpene resins can be used alone or in combination of two or more.

[0146] "Rosin-based resin" refers to a resin that contains rosin acid compounds such as abietic acid, neoabietic acid, palustric acid, and isopimaric acid as the monomer component with the highest content, and may also be their hydrogenated products or modified products. As the rosin-based resin, there is no particular limitation. For example, natural resin rosin, rosin modified resins obtained by hydrogenating, disproportionating, dimerizing, esterifying, etc. of rosin can be cited. These rosin-based resins can be used alone or in combination of two or more.

[0147] "Phenolic resin" refers to a resin that contains phenolic compounds such as phenol and cresol as the monomer component with the highest content. As the phenolic resin, there is no particular limitation. Phenol formaldehyde resin, alkylphenol formaldehyde resin, alkylphenol acetylene resin, oil-modified phenol formaldehyde resin, etc. can be cited. These phenolic resins can 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 further preferably 80 °C or higher. In addition, from the viewpoints of processability and improving the dispersibility of the rubber component and the filler, it is preferably 150 °C or lower, more preferably 140 °C or lower, and further preferably 130 °C or lower. In addition, the softening point of the resin component is measured by the above-mentioned measurement method.

[0149] When a resin component is contained, its 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, further preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more. In addition, from the viewpoint of suppressing heat generation, it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and further preferably 40 parts by mass or less.

[0150] (Oil) As the oil, for example, mineral oil, vegetable oil, animal oil, etc. can be cited. In addition, from the viewpoint of life cycle assessment, oil refined from waste oil after use in a rubber mixer or an engine, or waste cooking oil used in a restaurant can also be used.

[0151] In this specification, mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. As mineral oil, paraffin-based oil (mineral oil), naphthenic oil, aromatic oil, etc. can be cited. As specific examples of mineral oil, for example, MES (Mild Extract Solvate), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), RAE (Residual Aromatic Extract), etc. can be cited. In addition, due to environmental measures, oil with a low content of polycyclic aromatic (polycyclic aromatic compound: PCA) compounds can also be used. As the oil with a low PCA content, MES, TDAE, heavy naphthenic oil, etc. can be cited.

[0152] In this specification, "vegetable oil" refers to, for example, linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice bran oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grape seed oil, wood wax, etc. Further, as vegetable oil, refined oil (such as salad oil) obtained by refining the above oil, transesterified oil obtained by transesterifying the above oil, hydrogenated oil obtained by hydrogenating the above oil, thermally polymerized oil obtained by thermally polymerizing the above oil, oxidatively polymerized oil obtained by oxidizing the above oil, waste cooking oil obtained by recovering the oil used as edible oil, etc. can also be cited. In addition, vegetable oil can be liquid or solid at normal temperature (25°C). These vegetable oils can be used alone or in combination of two or more.

[0153] The vegetable oil involved in this embodiment preferably contains acylglycerol, and more preferably contains triacylglycerol. In addition, in this specification, acylglycerol refers to a compound in which the hydroxyl group of glycerol forms an ester bond with a fatty acid. As acylglycerol, there is no particular limitation, and it can be any one of 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, and triacylglycerol. Further, acylglycerol can be a monomer, a dimer, or a polymer of trimer or higher. In addition, acylglycerol of dimer or higher can be obtained by thermal polymerization, oxidative polymerization, etc. In addition, acylglycerol can be liquid or solid at normal temperature (25°C).

[0154] The method for confirming whether or not the rubber composition contains acylglycerols is not particularly limited, and for example, the following method can be used. 1 Specifically, a rubber composition containing triacylglycerol was immersed in deuterated chloroform at room temperature (25°C) for 24 hours, and after removing the rubber composition, the rubber composition was measured at room temperature. 1 H-NMR, when the signal of tetramethylsilane (TMS) is set to 0.00ppm, signals near 5.26ppm, 4.28ppm, and 4.15ppm can be observed, and it is speculated that these signals are signals from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In addition, "nearby" in this paragraph refers to the range of ±0.10ppm.

[0155] As the above-mentioned fatty acid, there is no particular limitation, and it can be an unsaturated fatty acid or a saturated fatty acid. As the unsaturated fatty acid, monounsaturated fatty acids such as oleic acid or polyunsaturated fatty acids such as linoleic acid and linolenic acid can be listed. In addition, as the saturated fatty acid, butyric acid, lauric acid, etc. can be listed.

[0156] Among them, as the above-mentioned fatty acid, preferably a fatty acid containing less double bonds, i.e. a saturated fatty acid or a monounsaturated fatty acid, preferably oleic acid. As such a vegetable oil containing fatty acids, for example, a vegetable oil containing a saturated fatty acid or a monounsaturated fatty acid can be used, and a vegetable oil modified by transesterification can also be used. In addition, in order to produce a vegetable oil containing such fatty acids, plants can also be improved by variety improvement, genetic modification, etc.

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

[0158] Examples of the animal oil include fish oil, beef tallow, and oleyl alcohol derived therefrom.

[0159] When oil is contained, the content thereof is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and further preferably 5 parts by mass or more relative to 100 parts by mass of the rubber component from the viewpoint of processability. In addition, from the viewpoint of wear resistance, the content is preferably 90 parts by mass or less, more preferably 70 parts by mass or less, further 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 cited. These liquid rubbers can be used alone, or two or more of them can be used in combination.

[0161] As the ester plasticizer, for example, dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), dilauryl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), etc. can be cited. The ester plasticizer can be used alone, or two or more of them can be used in combination.

[0162] Relative to 100 parts by mass of the rubber component, the content of the plasticizer (when multiple plasticizers are used in combination, it is 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. In addition, this 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] As the processing aid, for example, fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, etc. can be cited. As the processing aid, for example, commercially available substances from companies such as Schill+Seilacher and Performance-Additives can be used. These processing aids can be used alone or two or more of them can be used in combination.

[0164] When the processing aid is contained, from the viewpoint of exerting the improvement effect of processability, its content relative to 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 further preferably more than 1.5 parts by mass. In addition, from the viewpoints of abrasion resistance and breaking strength, it is preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and further preferably less than 5.0 parts by mass.

[0165] As the wax, there is no particular limitation, and any one of the substances commonly used in the tire industry can be preferably used. For example, mineral waxes, waxes derived from plants, etc. can be cited. Mineral waxes refer to waxes derived from mineral resources such as oil and natural gas. Waxes derived from plants refer to waxes derived from natural resources such as plants. Among them, mineral waxes are preferred. As waxes derived from plants, for example, rice bran wax, carnauba wax, candelilla wax, etc. can be cited. As mineral waxes, for example, paraffin wax, microcrystalline wax, selected special waxes of these, etc. can be cited, and paraffin wax is preferred. In addition, the wax involved in this embodiment does not contain stearic acid. The wax, for example, can use substances commercially available from Ouchi Shinsei Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., etc. These waxes can be used alone or in combination of two or more.

[0166] When containing wax, from the viewpoint of the weather resistance of the rubber, its content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and further preferably 1.5 part by mass or more. In addition, from the viewpoint of preventing the whitening of the tire caused by blooming, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

[0167] As the anti-aging agent, there is no particular limitation, and naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine can be cited; diphenylamine-based anti-aging agents 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'-dimethylxyl-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N,N'-di-2-naphthyl-p-phenylenediamine (DNPD), etc. p-phenylenediamine-based anti-aging agents; quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-tert-butyl-4-methylphenol and styrenated phenol; bis-, tris-, polyphenol-based anti-aging agents such as tetrakis[methylene-3-(3,5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane, etc. Among them, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferred, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and polymers of 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. As commercially available products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., Flexis Co., etc. can be used. These anti-aging agents can be used alone or in combination of two or more.

[0168] When an antioxidant is contained, from the viewpoint of the ozone crack resistance of the rubber, its content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and further preferably 1.5 part by mass or more. In addition, from the viewpoints of abrasion resistance and wet grip performance, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

[0169] When stearic acid is contained, from the viewpoint of processability, its content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and further preferably 1.5 part by mass or more. In addition, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

[0170] When zinc oxide is contained, from the viewpoint of processability, its content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and further preferably 1.5 part by mass or more. In addition, from the viewpoint of abrasion resistance, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

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

[0172] When sulfur is contained, from the viewpoint of ensuring a sufficient vulcanization reaction, its content relative to 100 parts by mass of the rubber component is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and further preferably 1.0 part by mass or more. In addition, from the viewpoint of preventing deterioration, it is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and further preferably 3.5 parts by mass or less. In addition, when using sulfur containing oil as the vulcanizing agent, the content of the vulcanizing agent is set to the total content of the pure sulfur component contained in the sulfur containing oil.

[0173] As vulcanizing agents other than sulfur, for example, alkylphenol / sulfur chloride condensates, sodium 1,6 - hexamethylenedithiocarbamate dihydrate, 1,6 - bis(N,N'-dibenzylthiocarbamoyl disulfide) hexane, etc. can be cited. These vulcanizing agents other than sulfur can use commercially available substances from companies such as Taoka Chemical Industry Co., Ltd., Lanxess AG, and Flexis.

[0174] As vulcanization accelerators, for example, sulfenamide-based vulcanization accelerators, thiazole-based vulcanization accelerators, guanidine-based vulcanization accelerators, thiuram-based vulcanization accelerators, dithiocarbamate-based vulcanization accelerators, caprolactam disulfide, etc. can be cited. These vulcanization accelerators can be used alone or in combination of two or more. Among them, from the viewpoint of better obtaining the desired effects, one or more vulcanization accelerators selected from sulfenamide-based vulcanization accelerators, thiazole-based vulcanization accelerators, and guanidine-based vulcanization accelerators are preferred, and more preferably, a sulfenamide-based vulcanization accelerator and a guanidine-based vulcanization accelerator are used in combination.

[0175] As sulfenamide-based vulcanization accelerators, for example, N-tert-butyl-2-benzothiazole sulfenamide (TBBS), N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazole sulfenamide (DCBS), etc. can be cited. Among them, TBBS and CBS are preferred.

[0176] As thiazole-based vulcanization accelerators, for example, 2-mercaptobenzothiazole (MBT) or its salts, di-2-benzothiazole disulfide (MBTS), 2-(2,4-dinitrophenyl) mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio) benzothiazole, etc. can be cited. Among them, MBTS and MBT are preferred, and more preferably MBTS.

[0177] As guanidine-based vulcanization accelerators, for example, 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatecholborate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenyl guanidine, 1,3-di-o-cumenyl-2-propionylguanidine, etc. can be cited. Among them, DPG is preferred.

[0178] When a vulcanization accelerator is contained, its content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and further preferably 1.5 part by mass or more. In addition, the content of the vulcanization accelerator relative to 100 parts by mass of the rubber component is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, and further preferably 4.0 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, it tends to ensure the breaking strength and elongation at break.

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

[0180] The kneading process, for example, includes the following basic kneading process: kneading compounding agents and additives other than the vulcanizing agent and vulcanization accelerator, and a final kneading process (F kneading): adding the vulcanizing agent and vulcanization accelerator to the kneaded product obtained in the basic kneading process and kneading. Further, the above basic kneading process can also be decomposed into multiple processes as needed.

[0181] As the kneading conditions, there are no particular limitations. For example, in the basic kneading process, 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 cited. As the vulcanization conditions, there are no particular limitations. For example, a method of vulcanizing at 150 to 200 °C for 10 to 30 minutes can be cited.

[0182] A tire having a tread portion composed of the above rubber composition can be manufactured by a conventional method. That is, for this tire, the above respective components can be compounded to the rubber component as needed, the prepared unvulcanized rubber composition is extruded and processed according to the shape of the first layer of the tread portion, the obtained tread portion is bonded together with the inner rubber layer of the tread portion and other tire components on a tire molding machine, and an unvulcanized tire is formed by a conventional method, and the obtained unvulcanized tire is heated and pressurized in a vulcanizer for manufacturing. As the vulcanization conditions, there are no particular limitations. For example, a method of vulcanizing at 150 to 200 °C for 10 to 30 minutes can be cited.

[0183] [Use of the tire] The tire according to this embodiment can be preferably used for passenger car tires, truck / bus tires, two-wheeler tires, and racing tires, and among them, it is preferably used for passenger car tires. In addition, a passenger car tire means a tire premised on being installed on an automobile traveling on four wheels and having a maximum load capacity of 1000 kg or less. [Examples]

[0184] The following shows examples (examples) considered to be preferred during implementation, but the scope of the present invention is not limited to the examples. Tires having a first layer of the tread portion obtained by compounding using various reagents shown below according to the compounding in Table 1 were studied, and the results calculated based on the following evaluation methods are shown in Tables 2 and 3.

[0185] The following summarizes various reagents used in the examples and comparative examples. 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 (S-SBR, styrene content: 10% by mass, Tg: -60°C, Mw: 190,000, non-oil-extended) manufactured by JSR Corporation SBR4: HPR850 (S-SBR, styrene content: 27.5% by mass, Tg: -24°C, Mw: 200,000, non-oil-extended) manufactured by JSR Corporation BR: UBEPOL BR (registered trademark) 150B manufactured by UBE Industries, Ltd. (unmodified BR, cis content: 97 mol%, Mw: 440,000) Carbon black: SHOBLACK N220 (N2SA: 111 m 2 / g) manufactured by Cabot Japan Ltd. Silica: ULTRASIL (registered trademark) VN3 (N2SA: 175 m 2 / g, average primary particle size: 17 nm) manufactured by Evonik Degussa GmbH 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 (copolymer of α-methylstyrene and styrene, softening point: 85°C) manufactured by Kraton Wax: OZOACE 0355 (paraffin wax) of Nippon Seiro Co., Ltd. Antioxidant: NOCRAC 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. Zinc oxide: Zinc Oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Stearic acid beads "TSUBAKI" manufactured by NOF Corporation Sulfur: HK-200-5 (powdered sulfur containing 5% oil) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator: NOCCELLER CZ (N-cyclohexyl-2-benzothiazole sulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0186] (Examples and Comparative Examples) According to the compounding recipe shown in Table 1, using a 1.7L closed Banbury mixer, knead the reagents other than sulfur and vulcanization accelerator for 1 - 10 minutes until the discharge temperature reaches 150 - 160°C to obtain a kneaded product. Then, using a twin-screw open mill, add sulfur and vulcanization accelerator to this kneaded product and knead for 4 minutes until it reaches 105°C to obtain an unvulcanized rubber composition. By using this unvulcanized rubber composition, extrude and form it according to the shape of the tread surface (thickness: 11mm) on an extruder equipped with a die of a specified shape, bond it together with other tire components to produce an unvulcanized tire, and carry out pressure vulcanization at 170°C for 12 minutes to obtain each test tire (size: 215 / 55R18) recorded in Tables 2 and 3.

[0187] (Measurement of tanδ at 30°C) For each vulcanized rubber test piece with a length of 20mm × width of 4mm × thickness of 1mm, cut out and made from the inside of the first layer of the tread surface of each test tire, with the tire circumferential direction as the long side and the tire radial direction as the thickness direction, use a dynamic viscoelasticity measuring device (EPLEXOR series manufactured by GABO) to measure the loss tangent tanδ under the conditions of a temperature of 30°C, a frequency of 10Hz, an initial strain of 5%, a dynamic strain of ±1%, and a tensile mode.

[0188] (Measurement of tanδ at 0°C and E* at 0°C) For each vulcanized rubber test piece with a length of 20mm × width of 4mm × thickness of 1mm, cut out and made from the inside of the first layer of the tread surface of each test tire, with the tire circumferential direction as the long side and the tire radial direction as the thickness direction, use a dynamic viscoelasticity measuring device (EPLEXOR series manufactured by GABO) to measure the loss tangent tanδ and the complex elastic modulus E* under the conditions of a temperature of 0°C, a frequency of 10Hz, an initial strain of 10%, a dynamic strain of ±2.5%, and a tensile mode.

[0189] (Measurement of glass transition temperature (Tg)) For each vulcanized rubber test piece cut out and produced from the inside of the first layer of the tread surface of each test tire, with the tire circumferential direction as the long side and the tire radial direction as the thickness direction, having dimensions of 20 mm in length × 4 mm in width × 1 mm in thickness, using a dynamic viscoelasticity measuring device (EPLEXOR 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 heating rate of 2 °C / min, the temperature distribution curve of tanδ in the range of the length from -60 °C to 40 °C is obtained, and the temperature (tanδ peak temperature) corresponding to the maximum tanδ value in the obtained temperature distribution curve is determined as the Tg of the rubber composition.

[0190] <Wet grip performance> Air at 250 kPa is filled into each test tire, and it is installed on all the wheels of an automobile with a displacement of 2000 cc. On a wet asphalt road surface, the braking distance when braking with an initial speed of 100 km / h is measured. For the reciprocal value of the braking distance, the braking distance of Comparative Example 3 is set to 100 and expressed as an index. The larger the index, the more excellent the wet grip performance during high-speed driving.

[0191]

Table 1

[0192]

Table 2

[0193]

Table 3

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

[0195] 〔1〕A tire, characterized in that it is a tire having a tread surface with 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 set to S (mass %), and the grounding area ratio in the grounding surface of the tread portion is set to R, S is 20 or less, and the product (R × S) of R and S is greater than 0 and 15 or less (preferably 1 or more and 13 or less, more preferably 2 or more and 12 or less). 〔2〕The tire according to the above 〔1〕, wherein G / W L is 0.0135 or less. 〔3〕The tire according to the above-mentioned 〔1〕 or 〔2〕, wherein S is 15 or less. 〔4〕The tire according to the above-mentioned 〔3〕, wherein S is 12 or less. 〔5〕The tire according to any one of the above-mentioned 〔1〕 to 〔4〕, wherein the tanδ (30 °C tanδ) of the rubber composition at 30 °C is 0.15 or less. 〔6〕The tire according to any one of the above-mentioned 〔1〕 to 〔5〕, 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 the above-mentioned 〔1〕 to 〔6〕, wherein the rubber composition contains a dicyclopentadiene-based resin. 〔8〕The tire according to any one of the above-mentioned 〔1〕 to 〔7〕, wherein 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). 〔9〕The tire according to any one of the above-mentioned 〔1〕 to 〔8〕, wherein the glass transition temperature of the rubber composition is -15 °C or less. 〔10〕The tire according to any one of the above-mentioned 〔1〕 to 〔9〕, wherein the ratio of the tanδ (0 °C tanδ) of the rubber composition at 0 °C to the complex elastic modulus (MPa) (0 °C E*) at 0 °C (0 °C tanδ / 0 °C E*) is 0.044 or more. 〔11〕The tire according to any one of the above-mentioned 〔1〕 to 〔10〕, wherein the rubber composition contains vulcanized rubber particles.

Claims

1. A tire, characterized in that: The tire has a tread portion having at least one rubber layer. Tire weight G relative to the tire's maximum load capacity W L Ratio G / W L Below 0.0140, G and W L The unit is kg. The first layer constituting the tread surface is composed of a rubber composition containing a rubber component and a filler. When the total amount of styrene in the rubber component is S and the contact area ratio in the contact surface of the tread portion is R, S is 20 or less, and the product of R and S (R×S) is greater than 0 and less than 15, The unit of S is mass %.

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

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: The rubber composition has a tan δ at 30° C., that is, tan δ at 30° C. of 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 size 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 less than 150.

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

10. The tire according to any one of claims 1 to 4, wherein The rubber composition has a ratio of tan δ at 0°C, 0°C tan δ, to a complex elastic modulus 0°C E* at 0°C, 0°C tan δ / 0°C E*, of 0.044 or more, where the unit of the complex elastic modulus is MPa.

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

12. The tire according to any one of claims 1 to 4, wherein G / W L It is above 0.0110.

13. The tire according to any one of claims 1 to 4, wherein: S is 1.0 or more.

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