tire

Abstract

To provide a tire which can improve total performance of low fuel consumption performance and abrasion resistance performance.SOLUTION: A tire includes a tread part having at least one rubber layer, wherein a ratio (G / WL) of tire weight G (kg) to maximum load capacity WL(kg) of the tire is 0.0160 or less, the cross-section width Wt of the tire is 200 mm or more, a first layer constituting the tread surface is composed of a rubber composition containing a rubber component and a filler, the thickness t1 of the first layer exceeds 3.0 mm, and when a complex elastic modulus at 30°C of the rubber composition is represented by 30°CE*(MPa), and a land ratio on the ground surface of the tread part is represented by R, 30°CE* exceeds 8.0 MPa, and the product (R×30°CE*) of R and 30°CE* exceeds 5.0.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] In addition to low fuel consumption performance (rolling resistance characteristics), the tread of a tire is required to have performance such as wear resistance and wet skid resistance. Performance improvement has been carried out by devising the rubber component, filler, etc. used in the tread part (for example, Patent Documents 1 and 2), but there is still room for improvement in the point of improving these performances in a well-balanced manner.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a tire capable of improving the overall performance of low fuel consumption performance and wear resistance.

Means for Solving the Problems

[0005] In recent years, tires have been made lighter in order to reduce the rolling resistance of the tires. In order to reduce the weight of the tire, it is conceivable to reduce the thickness of the tread part, but there is a concern that the life of the tire will be shortened due to wear. In addition, since low fuel consumption rubber generates less heat, it deforms immediately when it receives an impact, and there is a tendency for rubber destruction to progress easily.

[0006] The present invention is a tire provided with a tread part having at least one rubber layer, and the maximum load capacity W of the tire LThe ratio (G / W L ) of the tire weight G (kg) to the maximum load capacity W

Advantages of the Invention

[0007] According to the present invention, there is provided a tire capable of improving the overall performance of low fuel consumption performance and wear resistance performance.

Brief Description of the Drawings

[0008]

Figure 1

Embodiments for Carrying Out the Invention

[0009] A tire according to an embodiment of the present invention is a tire provided with a tread portion having at least one rubber layer, wherein the ratio (G / W L ) of the tire weight G (kg) to the maximum load capacity W L ) of the tire is 0.0160 or less, the cross-sectional width Wt of the tire is 200 mm or more, the first layer constituting the tread surface is composed of a rubber composition containing a rubber component and a filler, the thickness t1 of the first layer is more than 3.0 mm, when the complex elastic modulus of the rubber composition at 30°C is 30°C E* (MPa) and the land ratio at the ground contact surface of the tread portion is R, 30°C E* is more than 8.0 MPa, and the product (R × 30°C E*) of R and 30°C E* is more than 5.0.

[0010] Although not intending to be bound by theory, the reasons for the improvement in the overall performance of the fuel efficiency and wear resistance of the tire of the present invention are considered as follows.

[0011] When the tire cross-sectional width Wt is increased, the maximum load capacity W L increases, so it is considered that the fuel efficiency effect due to reducing G / W L to 0.0160 or less and reducing the weight of the tire becomes greater.

[0012] Also, by making the 30°C E* of the first layer exceed 8.0 MPa, the rubber becomes harder and the amount of rubber deformation is suppressed. Furthermore, by increasing the land ratio, it is considered that the force applied per unit area of the rubber becomes smaller and the amount of rubber deformation is suppressed. From this, it is considered that by making the product of these a certain value or more, the deformation of the rubber can be suppressed.

[0013] And by applying the above requirements to a tire with a tire cross-sectional width Wt of 200 mm or more and a thickness t1 of the first layer exceeding 3.0 mm, it is considered that these cooperate to contribute to the improvement of the overall performance of the fuel efficiency and wear resistance of the tire.

[0014] The tanδ (30°C tanδ) of the rubber composition at 30°C is preferably less than 0.25.

[0015] By setting 30°C tanδ within the above range, it is considered that the fuel efficiency performance can be improved.

[0016] The product of 30°C tanδ, 30°C E*, and t1 (30°C tanδ × 30°C E* × t1) is preferably less than 8.25.

[0017] By setting 30°C tanδ × 30°C E* × t1 within the above range, it is considered that both the fuel efficiency performance and the hardness of the rubber can be achieved.

[0018] From the viewpoints of abrasion resistance performance and wet grip performance, the rubber composition preferably contains silica having an average primary particle diameter of 16 nm or less.

[0019] From the viewpoints of abrasion resistance performance and low fuel consumption performance, the rubber composition preferably contains a mercapto-based silane coupling agent.

[0020] The acetone extraction amount of the rubber composition is preferably 20% by mass or less.

[0021] By setting the acetone extraction amount within the above range, it is considered that the hardness of the rubber can be maintained and the abrasion resistance performance can be improved.

[0022] From the viewpoint of the effects of the present invention, the rubber component preferably includes an isoprene-based rubber.

[0023] From the viewpoint of the effects of the present invention, the rubber component preferably includes a styrene-butadiene rubber having a styrene content of 30% by mass or less.

[0024] S / 30°C E* is preferably 2.5 or less.

[0025] When 30°C E* is small, the deformation of the tread rubber becomes large. On the other hand, by reducing the total styrene amount S in the rubber component, the heat generation during the deformation of the tread rubber can be suppressed. From this, it is considered that by reducing the total styrene amount S as 30°C E* becomes smaller, the low fuel consumption performance and the breaking strength of the tread rubber are further improved. Also, from the viewpoint of the effects of the present invention, the total styrene amount S in the rubber component is preferably 25% by mass or less.

[0026] The product of R and S (R×S) is preferably 15.0 or less.

[0027] By setting R×S within the above range, it is considered that both low fuel consumption performance and abrasion resistance performance can be achieved.

[0028] Let the modulus at 200% elongation of the rubber composition be M 200 (MPa). When M of the rubber composition 200 , 30°C E*, and 30°C tanδ satisfy the relational expression M 200 × 30°C E* / 30°C tanδ ≧ 200, it is preferable.

[0029] M 200 × 30°C E* / 30°C tan within the above range is considered to be able to improve the low fuel consumption performance and wear resistance performance in a well - balanced manner.

[0030] From the viewpoint of the difficulty of oil migration, the rubber composition preferably contains vegetable oil.

[0031] From the viewpoint of constructing a sustainable society, the filler preferably contains silica made from biomass materials as a raw material.

[0032] <Definition> The "tread portion" is the portion that forms the contact surface of the tire. In the radial cross - section of the tire, when the tire skeleton is formed by members such as steel or textile materials such as the belt layer, belt reinforcing layer, and carcass layer, it is a member outside these in the radial direction of the tire.

[0033] The "normal state" is a no - load state in which the tire is assembled on a normal rim and filled with air at normal internal pressure.

[0034] The "dimensions of each part of the tire" are, unless otherwise specified, values specified in the normal state for those appearing on the outer surface of the tire, while those existing inside the tire or on the tire cross - section are, for example, values specified in a state where the tire is cut by a plane including the tire rotation axis and the cut tire piece is held in the rim width of the normal rim.

[0035] "Normal Rim" refers to the rim defined for each tire in a standard system that includes the standards on which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Association), it refers to the standard rim in the applicable sizes described in the "JATMA YEAR BOOK"; in the case of ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" described in the "STANDARDS MANUAL"; and in the case of TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" described in the "YEAR BOOK". Refer to JATMA, ETRTO, and TRA in that order, and follow the relevant standards if there are applicable sizes during the reference. In the case of a tire not defined in the above standards, it refers to the rim with the narrowest width among the rims with the minimum diameter that can be assembled with the tire and can maintain the internal pressure (i.e., does not cause air leakage between the rim and the tire).

[0036] "Normal Inflation Pressure" refers to the air pressure defined for each tire in a standard system that includes the standards on which the tire is based. For example, in the case of JATMA, it refers to the "Maximum Air Pressure"; in the case of ETRTO, it refers to the "INFLATION PRESSURE"; and in the case of TRA, it refers to the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". Similar to the case of the normal rim, refer to JATMA, ETRTO, and TRA in that order, and follow the relevant standards if there are applicable sizes during the reference. In the case of a tire not defined in the above standards, it refers to the normal inflation pressure (but not less than 250 kPa) of another tire size described with the normal rim as the standard rim (however, as defined in the standards). If there are multiple normal inflation pressures not less than 250 kPa described, it refers to the minimum value among them.

[0037] The "normal load" refers to the load defined for each tire in a standard system including the standards on which the tire is based. For example, in the case of JATMA, it is the "maximum load capacity"; in the case of ETRTO, it is "LOAD CAPACITY"; and in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". When referring, in the order of JATMA, ETRTO, and TRA, as in the case of the normal rim and normal internal pressure, if there is an applicable size at the time of reference, follow that standard. For tires not defined in the above standards, the maximum load capacity W L calculated separately is taken as the normal load.

[0038] The "maximum load capacity W L " is calculated by the following formula. "V" is the virtual volume of the tire (mm 3 ), "Dt" is the outer diameter of the tire in the normal state (mm), "Ht" is the cross-sectional height of the tire in the radial direction of the tire in the cross-section of the tire by a plane including the tire rotation axis (mm), and "Wt" is the cross-sectional width of the tire in the normal state (mm). When R is the rim diameter of the tire, Ht can be obtained by (Dt - R) / 2. Wt is the value obtained excluding patterns or characters etc. on the tire sidewall. Note that the maximum load capacity is synonymous with the above normal load.

[0039]

Equation

[0040] The "tire weight G (kg)" refers to the weight of the tire alone excluding the weight of the rim. On the other hand, when the tire inner cavity is equipped with a sound insulation material, a sealant, a sensor, etc., G is the weight including these.

[0041] The "groove", including circumferential grooves and transverse grooves, refers to a recess with a width greater than at least 2.0 mm.

[0042] The "contact area" is the area of the tread obtained from the contour when the tire is pressed against the ground. After assembling the tire on the standard rim, applying the standard internal pressure, and leaving it stationary at 25°C for 24 hours, ink is applied to the tire tread surface. Then, the tire is loaded with the standard load (maximum load capacity) and pressed vertically against thick paper (the camber angle is 0°), and the ink is transferred to obtain it. The area of the contact area is called the total contact area. The total contact area can be calculated as the average value of the five areas obtained by performing the above transfer operation while rotating the tire by 72° each time and doing this for a total of five locations.

[0043] The "effective contact area" is the area of the tread where the tire contacts the ground when the tire is pressed against the ground. After assembling the tire on the standard rim, applying the standard internal pressure, and leaving it stationary at 25°C for 24 hours, ink is applied to the tire tread surface. Then, the tire is loaded with the standard load (maximum load capacity) and pressed vertically against thick paper (the camber angle is 0°), and the ink is transferred to obtain it. The area of the effective contact area is called the effective contact area. The effective contact area can be calculated as the average value of the five areas obtained by performing the above transfer operation while rotating the tire by 72° each time and doing this for a total of five locations.

[0044] The "land ratio R" is calculated by the following formula from the total contact area for the contact area and the effective contact area for the effective contact area. (Land ratio) = (Effective contact area / Total contact area)

[0045] The "overall thickness of the tread portion" refers to the overall thickness of the tread portion on the tire equatorial plane in the cross-section obtained by cutting the tire with a plane including the tire rotation axis. Note that the inner end in the tire radius direction of the overall thickness of the tread portion is the inner interface in the tire radius direction of the rubber composition constituting the tread portion. When the tire is provided with a belt reinforcing layer, a belt layer, and a carcass layer, among these, it is the total thickness of the rubber layer outside the outermost layer in the tire radius direction in the tire radius direction. Note that when there are circumferential grooves on the tire equatorial plane, the overall thickness of the tread portion is measured with the grooves filled.

[0046] The "thickness of each rubber layer constituting the tread portion" is the thickness of each rubber layer on the tire equatorial plane in a cross-section obtained by cutting the tire with a plane including the tire rotation axis, and is the average value of the thicknesses of the tread portion obtained at five positions by rotating the tire by 72° in the circumferential direction. For example, the thickness of the first layer refers to the linear distance in the tire radial direction from the outermost surface of the tread to the inner interface of the first layer in the tire radial direction on the tire equatorial plane. When there are circumferential grooves on the tire equatorial plane, the thickness of each rubber layer constituting the tread portion shall be the thickness of each rubber layer at the center in the tire width direction of the land portion closest to the tire equatorial plane. The "land portion closest to the tire equatorial plane" refers to the land portion having the groove edge closest to the tire equatorial plane among the circumferential grooves existing on the tire equatorial plane. When such land portions exist on both sides in the tire width direction, the thickness of each rubber layer constituting the tread portion shall be the average value of the thicknesses of each rubber layer at the center in the tire width direction of the two land portions. Also, when there are current-carrying members or the like on the land portion on the tire equatorial plane and the interface is unclear, the interface blocked by the current-carrying members or the like shall be virtually joined and measured.

[0047] The "plasticizer" is a material that imparts plasticity to the rubber component and is a component extracted from the rubber composition using acetone. The plasticizer includes plasticizers that are liquid (liquid state) at 25°C and plasticizers that are solid at 25°C. However, waxes and stearic acid commonly used in the tire industry are not included.

[0048] The "content of plasticizer" also includes the amount of plasticizer contained in the extended rubber component previously extended by plasticizers such as oil, resin component, and liquid rubber component. The same applies to the content of oil, the content of resin component, and the content of liquid rubber. For example, when the extended component is oil, the extended oil is included in the content of oil.

[0049] <Measurement method> The "thickness of each rubber layer constituting the tread portion" is measured with the tire cut by a plane including the tire rotation axis and the width of the bead portion adjusted to match the width of the standard rim.

[0050] "30°C tan δ" is the loss tangent measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of ±1%, and an elongation mode using a dynamic viscoelasticity measuring device (for example, the Implex series manufactured by GABO). The sample for loss tangent measurement is a vulcanized rubber composition with a length of 20 mm × width of 4 mm × thickness of 1 mm. When preparing by cutting from a tire, it is cut from the tread part of the tire such that the tire circumferential direction is the long side and the tire radial direction is the thickness direction.

[0051] "30°C E*" is the complex elastic modulus measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of ±1%, and an elongation mode using a dynamic viscoelasticity measuring device (for example, the Implex series manufactured by GABO). The sample for this measurement is prepared in the same manner as in the case of 30°C tan δ.

[0052] "Modulus at 200% elongation (M 200 )" is the tensile stress (MPa) at 200% elongation in the columnar direction (the rolling direction when forming a rubber sheet by extrusion or shearing) measured in accordance with JIS K 6251:2017 under the condition of a tensile speed of 3.3 mm / second in an atmosphere of 23°C. The sample for M 200 measurement is a dumbbell-shaped No. 7 vulcanized rubber test piece with a thickness of 1 mm. When preparing by cutting from a tire, it is cut from the tread part of the tire such that the tire circumferential direction is the tensile direction and the tire radial direction is the thickness direction.

[0053] "Acetone extraction amount" can be obtained by immersing each vulcanized rubber test piece in acetone for 72 hours in accordance with JIS K 6229:2015 to extract soluble components, measuring the mass of each test piece before and after extraction, and using the following formula. When preparing by cutting from a tire, it is cut from the tread part of the tire such that the tire circumferential direction is the long side and the tire radial direction is the thickness direction. (Acetone extraction amount (mass%)) = {(mass of rubber test piece before extraction - mass of rubber test piece after extraction) / (mass of rubber test piece before extraction)} × 100

[0054] "Styrene content" is a value calculated by pyrolysis gas chromatography and is applied, for example, to rubber components having repeating units derived from styrene such as SBR. In this specification, "pyrolysis gas chromatography" refers to a method in which a sample is heated by a pyrolysis device, individual components contained in the gas-phase components generated by this heating are separated by a separation column, and each isolated component is analyzed.

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

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

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

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

[0059] The "nitrogen adsorption specific surface area (N2SA) of carbon black" is measured in accordance with JIS K 6217-2:2017. The "nitrogen adsorption specific surface area (N2SA) of silica" is measured by the BET method in accordance with ASTM D3037-93.

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

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

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

[0063] [Tire] In the tire according to this embodiment, the ratio (G / W L )(kg) of the tire weight G (kg) to the maximum load capacity W L is 0.0160 or less from the viewpoint of the effect of the present invention, preferably 0.0155 or less, more preferably 0.0150 or less, still more preferably 0.0145 or less, and particularly preferably 0.0140 or less. The lower limit value of the G / W L is not particularly limited from the viewpoint of the effect of the present invention, but can be, for example, 0.0120 or more, 0.0125 or more, 0.0130 or more. Note that the tire weight G can be varied by a conventional method, that is, it can be increased by increasing the specific gravity of the tire or increasing the thickness of each member of the tire, and conversely, it can be decreased.

[0064] 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 from the viewpoint of more favorably exhibiting the effects of the present invention. Also, the maximum load capacity W L (kg) can be, for example, 1300 or less, 1200 or less, 1100 or less, 1000 or less, 900 or less, 800 or less, 700 or less from the viewpoint of more favorably exhibiting the effects of the present invention. Note that the maximum load capacity W L can be increased by increasing the virtual volume V of the space occupied by the tire, and conversely, can also be decreased.

[0065] In the tire according to the present embodiment, the tire section width Wt (mm) is 200 or more, preferably 205 or more, and more preferably 210 or more from the viewpoint of the effects of the present invention. Also, Wt is not particularly limited from the viewpoint of the effects of the present invention, but is preferably 270 or less, preferably 260 or less, and still more preferably 250 or less.

[0066] The land ratio R on the ground contact surface of the tread portion is preferably 0.50 or more, more preferably 0.55 or more, and still more preferably 0.60 or more. Also, the land ratio R is preferably 0.85 or less, more preferably 0.80 or less, and still more preferably 0.75 or less.

[0067] The tread portion according to the present embodiment has at least one rubber layer. The tread portion according to the present embodiment may be a tread portion composed of a single rubber layer, or may be a tread portion having a first layer whose outer surface constitutes the tread surface and one or more rubber layers (inner rubber layers) existing between the first layer and the belt layer.

[0068] The thickness of the first layer constituting the tread surface with respect to the thickness of the entire tread portion can be, for example, 30% or more, 50% or more, 70% or more, 90% or more, and the tread portion may be composed only of the first layer constituting the tread surface.

[0069] The thickness t1 of the first layer is more than 3.0 mm, preferably 3.5 mm or more, more preferably 4.0 mm or more, and even more preferably 4.5 mm or more, from the viewpoints of durability and the effects of the present invention. Further, the thickness t1 of the first layer is preferably 12.0 mm or less, more preferably 11.0 mm or less, and even more preferably 10.0 mm or less.

[0070] The specific gravity of the rubber composition constituting the first layer is preferably 1.270 or less, more preferably 1.260 or less, even more preferably 1.250 or less, still more preferably 1.240 or less, and particularly preferably 1.230 or less, from the viewpoint of the effects of the present invention. On the other hand, the lower limit value of the specific gravity is not particularly limited from the viewpoint of the effects of the present invention, but is preferably 1.150 or more, more preferably 1.160 or more, and even more preferably 1.170 or more. The specific gravity can be increased, for example, by increasing the content of silica, and conversely, can be decreased by decreasing the content of silica. In the present specification, the specific gravity of the rubber composition means the specific gravity of the vulcanized rubber composition and is measured based on JIS K 2249-4:2011.

[0071] The 30°C E* of the rubber composition constituting the first layer is more than 8.0 MPa, preferably more than 8.2 MPa, more preferably more than 8.4 MPa, even more preferably more than 8.6 MPa, and particularly preferably more than 8.8 MPa, from the viewpoint of the effects of the present invention. Further, the 30°C E* of the rubber composition is preferably less than 15.0 MPa, more preferably less than 14.0 MPa, even more preferably less than 13.0 MPa, and particularly preferably less than 12.0 MPa. The 30°C E* of the rubber composition can be appropriately adjusted by the types and blending amounts of the rubber component, vulcanized rubber particles, resin component, oil, etc. described later.

[0072] From the perspective of the effects of the present invention, the 30°C tanδ of the rubber composition constituting the first layer is preferably less than 0.25, more preferably less than 0.24, still more preferably less than 0.23, still more preferably less than 0.22, and particularly preferably less than 0.21. Also, the 30°C tanδ of the rubber composition is preferably more than 0.06, more preferably more than 0.08, and still more preferably more than 0.10. Note that the 30°C tanδ of the rubber composition can be appropriately adjusted according to the types and blending amounts of the rubber component, vulcanized rubber particles, resin component, oil, etc. described later.

[0073] The M of the rubber composition constituting the first layer 200 From the perspective of the effects of the present invention, is preferably 4.0 MPa or more, more preferably 5.0 MPa or more, still more preferably 6.0 MPa or more, and particularly preferably 7.0 MPa or more. Also, the M of the rubber composition 200 is preferably 15.0 MPa or less, more preferably 13.0 MPa or less, and still more preferably 11.0 MPa or less. Note that the M of the rubber composition 200 can be appropriately adjusted according to the types and blending amounts of the rubber component, vulcanized rubber particles, resin component, oil, etc. described later.

[0074] The product (R × 30°C E*) of the land ratio R and the 30°C E* (MPa) of the rubber composition constituting the first layer is more than 5.0, preferably more than 5.2, more preferably more than 5.4, still more preferably more than 5.6, and particularly preferably more than 5.8. On the other hand, the upper limit value of R × 30°C E* is not particularly limited, but is preferably less than 12.0, more preferably less than 10.0, still more preferably less than 9.0, and particularly preferably less than 8.0.

[0075] The ratio (S / 30°C E*) of the total styrene amount S (mass%) in the rubber component to the 30°C E* of the rubber composition constituting the first layer is preferably 3.0 or less, more preferably 2.7 or less, still more preferably 2.5 or less, and particularly preferably 2.3 or less. Also, the lower limit value of S / 30°C E* is not particularly limited from the perspective of the effects of the present invention, but is preferably more than 0, more preferably 0.4 or more, still more preferably 0.8 or more, and particularly preferably 1.2 or more.

[0076] The acetone extraction amount of the rubber composition constituting the first layer is preferably 22% by mass or less, more preferably 20% by mass or less, still more preferably 18% by mass or less, and particularly preferably 16% by mass or less. Also, the acetone extraction amount of the rubber composition constituting the first layer is preferably 3% by mass or more, more preferably 4% by mass or more, still more preferably 5% by mass or more, and particularly preferably 6% by mass or more.

[0077] The product (R×S) of the land ratio R and the total styrene amount S (mass%) in the rubber component is preferably 20.0 or less, more preferably 18.0 or less, still more preferably 15.0 or less, and particularly preferably 14.0 or less. On the other hand, the lower limit value of R×S is not particularly limited, but is preferably more than 0, more preferably 1.0 or more, still more preferably 3.0 or more, and particularly preferably 5.0 or more.

[0078] The product (30°C tanδ × 30°C E* × t1) of 30°C tanδ, 30°C E*, and t1 is preferably less than 12.0, more preferably less than 11.0, and still more preferably less than 10.0. On the other hand, 30°C tanδ × 30°C E* × t1 is preferably more than 5.0, more preferably more than 6.0.

[0079] M 200 × 30°C E* / 30°C tanδ is preferably 200 or more, more preferably 250 or more, and still more preferably 300 or more. On the other hand, the upper limit value of M 200 × 30°C E* / 30°C tanδ is not particularly limited, but is preferably 800 or less, more preferably 750 or less, and still more preferably 700 or less.

[0080] [Rubber composition] The tire according to this embodiment can more effectively improve the comprehensive performance of low fuel consumption performance and wear resistance performance by the cooperation of the configuration of the tire and the tread part described above and the physical properties of the rubber composition constituting the tread part. Hereinafter, the rubber composition constituting the first layer will be described.

[0081] [Rubber component] In the rubber composition according to this embodiment, a diene rubber is preferably used as the rubber component. Examples of the diene rubber include isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), and the like. These diene rubbers may be modified rubbers treated with a modifying group capable of interacting with a filler such as carbon black or silica, or may be hydrogenated rubbers in which a part of the unsaturated bonds is hydrogenated. The diene rubber may be used alone or in combination of two or more. Further, as the diene rubber, an extended rubber preliminarily extended using a plasticizer described later may be used.

[0082] The content of the diene rubber in the rubber component is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. Further, the rubber component may consist only of the diene rubber.

[0083] As the diene rubber component, at least one selected from the group consisting of isoprene rubber, styrene-butadiene rubber (SBR), and butadiene rubber (BR) is preferably used. The rubber component preferably contains SBR, more preferably contains SBR and isoprene rubber and / or BR, still more preferably contains isoprene rubber, BR, and SBR, and may consist only of isoprene rubber, SBR, and BR as the rubber component.

[0084] (Isoprene rubber) The isoprene rubber is not particularly limited, and examples thereof include natural rubber (NR), isoprene rubber (IR), modified natural rubber, etc. Examples of NR include SIR20, RSS#3, TSR20, etc. Examples of IR include IR2200, etc. Examples of modified natural rubber include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, grafted natural rubber, etc. These isoprene rubbers may be used alone or in combination of two or more.

[0085] From the viewpoint of the effects of the present invention, the content of the isoprene rubber in the rubber component is preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 40% by mass or less, and particularly preferably 30% by mass or less. The lower limit of the content is not particularly limited, and for example, it can be 1% by mass or more, 3% by mass or more, 5% by mass or more, 7% by mass or more, 10% by mass or more.

[0086] (BR) BR is not particularly limited, and for example, BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare-earth-based butadiene rubber synthesized using a rare-earth element-based catalyst (rare-earth-based BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc., which are common in the tire industry, can be used. These BRs may be used alone or in combination of two or more.

[0087] As high-cis BR, for example, those commercially available from Zeon Corporation, UBE Industries, Ltd., JSR Corporation, etc. can be used. By containing high-cis BR, the abrasion resistance performance can be improved. The cis content of high-cis BR is preferably 95 mol% or more, more preferably 96 mol% or more, and still more preferably 97 mol% or more. The cis content of BR is measured by the above measurement method.

[0088] As the modified BR, a modified butadiene rubber (modified BR) modified with a functional group containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen at the terminal and / or main chain is preferably used.

[0089] As other modified BRs, those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and in which the terminal of the modified BR molecule is bonded by a tin-carbon bond (tin-modified BR), etc. can be mentioned. Further, the modified BR may be either an unhydrogenated one or a hydrogenated one.

[0090] From the viewpoint of wear resistance performance, the weight average molecular weight (Mw) of BR is preferably 300,000 or more, more preferably 350,000 or more, and even more preferably 400,000 or more. Also, from the viewpoints such as crosslinking uniformity, etc., it is preferably 2,000,000 or less, and more preferably 1,000,000 or less. The Mw of BR is measured by the above measurement method.

[0091] 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, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less. Also, the lower limit value of the content is not particularly limited, but for example, it can be 1% by mass or more, 3% by mass or more, 5% by mass or more, 7% by mass or more, 10% by mass or more.

[0092] (SBR) SBR is not particularly limited, and examples thereof include unmodified solution polymerization SBR (S-SBR), emulsion polymerization SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR), etc. As the modified SBR, SBR modified at the terminal and / or main chain, modified SBR coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.), etc. can be mentioned. Further, hydrogenated products of these SBRs (hydrogenated SBR) can also be used. These SBRs may be used alone or in combination of two or more.

[0093] As the SBR according to this embodiment, extended SBR can be used, or non-extended SBR can also be used. When using extended SBR, the amount of extension of 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 content of the SBR.

[0094] The SBR listed above may be used alone or in combination of two or more. As the SBR listed above, for example, those commercially available from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., ZS Elastomer Co., Ltd., etc. can be used.

[0095] The styrene content of the SBR can be appropriately selected so that the total styrene amount S in the rubber component satisfies the following range, but is preferably 40% by mass or less, more preferably 37% by mass or less, still more preferably 34% by mass or less, and particularly preferably 30% by mass or less. Also, the styrene content of the SBR is preferably 5% by mass or more, more preferably 7% by mass or more, still more preferably 10% by mass or more, and particularly preferably 12% by mass or more. Note that the styrene content of the SBR is measured by the above measurement method.

[0096] From the viewpoints of ensuring reactivity with silica and wear resistance performance, the vinyl content of the SBR is preferably 5 mol% or more, more preferably 10 mol% or more, and still more preferably 15 mol% or more. Also, from the viewpoints of elongation at break and wear resistance performance, the vinyl content of the SBR is preferably 50 mol% or less, more preferably 40 mol% or less, and still more preferably 35 mol% or less. Note that in this specification, the vinyl content of the SBR is measured by the above measurement method.

[0097] From the viewpoint of the effects of the present invention, the weight average molecular weight (Mw) of the SBR is preferably 100,000 or more, more preferably 200,000 or more, and still more preferably 300,000 or more. Also, from the viewpoint of crosslinking uniformity, the weight average molecular weight is preferably 2,000,000 or less, more preferably 1,800,000 or less, and still more preferably 1,500,000 or less. Note that the weight average molecular weight of the SBR is measured by the above measurement method.

[0098] The content of SBR in the rubber component can be appropriately selected so that the total styrene amount S in the rubber component satisfies the range described below. However, 20% by mass or more is preferable, 30% by mass or more is more preferable, 40% by mass or more is further preferable, 50% by mass or more is further preferable, and 60% by mass or more is particularly preferable. 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.

[0099] From the viewpoint of the effects of the present invention, the total styrene amount S in the rubber component is preferably 30% by mass or less, more preferably 27% by mass or less, further preferably 25% by mass or less, and particularly preferably 22% by mass or less. Also, the lower limit of the total styrene amount S in the rubber component is not particularly limited, but 1% by mass or more is preferable, 3% by mass or more is more preferable, 5% by mass or more is further preferable, and 7% by mass or more is particularly preferable.

[0100] (Other rubber components) The rubber component may contain a rubber component other than the diene-based rubber (non-diene-based rubber) as long as it does not affect the effects of the present invention. As the non-diene-based rubber, rubber components generally used in the tire industry can be used. For example, butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, etc. can be mentioned. These other rubber components may be used alone or in combination of two or more. Also, in addition to the above rubber components, a known thermoplastic elastomer may or may not be contained.

[0101] (Rubber components synthesized from recycled and biomass-derived raw materials) Monomers, which are the constituent units of synthetic rubbers such as IR, BR, and SBR, may be derived from underground resources such as petroleum and natural gas, or may be recycled from rubber products such as tires and non-rubber products such as polystyrene. The monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled polyisoprene, recycled butadiene, and recycled aromatic vinyl compounds. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl compound is not particularly limited, and examples include styrene. Among them, it is preferable to use recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and recycled styrene (recycled styrene) as raw materials.

[0102] The method for producing recycled monomers is not particularly limited, and examples include being synthesized from recycled naphtha obtained by decomposing rubber products such as tires. Also, the method for producing recycled naphtha is not particularly limited, and for example, rubber products such as tires may be decomposed under high temperature and high pressure, decomposed by microwaves, or extracted after mechanical pulverization.

[0103] Furthermore, monomers, which are the constituent units of synthetic rubbers such as IR, BR, and SBR, may be derived from biomass. In this specification, biomass refers to substances derived from natural resources such as plants. The biomass is not particularly limited, and examples include agricultural and forestry products, sugar, wood chips, plant residues after obtaining useful components, ethanol derived from plants, and biomass naphtha.

[0104] The biomass-derived monomers (biomass monomers) are not particularly limited, and examples include biomass-derived butadiene and biomass-derived aromatic vinyl compounds. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl compound is not particularly limited, and examples include styrene. Further, the method for producing the biomass monomer is not particularly limited, and examples include those by biological and / or chemical and / or physical conversion of animals and plants. Fermentation by microorganisms is typical as the biological conversion, and examples of the chemical and / or physical conversion include those by a catalyst, high heat, high pressure, electromagnetic waves, a critical liquid, and combinations thereof.

[0105] The polymers synthesized from the biomass monomer components (biomass polymers) are not particularly limited, and examples include polybutadiene rubber synthesized from biomass-derived butadiene, and aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl compounds. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0106] Whether the raw material of the polymer is derived from biomass can be determined by pMC (percent Modern Carbon) measured in accordance with ASTM D6866-10.

[0107] pMC is the ratio of the 14 C concentration of the sample to the 14 C concentration of the standard modern carbon (modern standard reference), and is a value used as an index indicating the biomass ratio of the compound. The significance of this value is described below.

[0108] In one mole (6.02 × 10 23 pieces) of carbon atoms, about 6.02 × 10, which is about one trillionth of ordinary carbon atoms11 There is 14 carbon C. 14 The half-life of C is 5730 years, and 14 C decreases regularly. It takes 226,000 years for all of these to decay. Therefore, in fossil fuels such as coal, oil, and natural gas, for which more than 226,000 years are considered to have passed after carbon dioxide in the atmosphere and the like were taken up and fixed by plants and the like, the 14 element C has all decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas do not contain 14 any element C. Therefore, chemical substances produced using these fossil fuels as raw materials also do not contain 14 any element C.

[0109] On the other hand, 14 C is constantly generated by nuclear reactions of cosmic rays in the atmosphere. From this, 14 C is in equilibrium between reduction by radioactive decay and generation by nuclear reactions, and in the atmospheric environment of the Earth, 14 the amount of C is constant. Therefore, the 14 C concentration of substances derived from biomass resources that circulate in the current environment is about 1×10 -12 mol% with respect to the entire carbon atoms as described above. Therefore, by utilizing the difference between these values, the biomass ratio in a certain compound can be calculated.

[0110] This 14 C is generally measured as follows. Using accelerator mass spectrometry based on a tandem accelerator, 13 the C concentration ( 13 C / 12 C), 14 the C concentration ( 14 C / 12 C) is measured. In the measurement, 14 as a modern standard reference for the concentration of C, the 14The C concentration is adopted. As a specific reference material, the oxalic acid standard provided by NIST (National Institute of Standards and Technology) is used. The specific activity of carbon in this oxalic acid (the radioactivity intensity of 14 C per 1 g of carbon) is separated for each carbon isotope, 13 and for 14 C, it is corrected to a fixed value, and the value after applying the decay correction from 1950 AD to the measurement date is used as the standard

[0111] C concentration value (100%). The ratio of this value to the value of the actually measured sample is the pMC value. 14 Therefore, if the rubber is made of 100% biomass-derived substances, although there are regional differences and the like, it often does not reach 100 under normal current conditions, so it will show a value of approximately 110 pMC. On the other hand, for chemical substances derived from fossil fuels such as petroleum, when measuring this

[0112] C concentration, it will show a value of about 0 pMC (for example, 0.3 pMC). This value corresponds to a biomass ratio of 0% mentioned above.

[0113] <Filler> The rubber composition according to this embodiment contains a filler. The filler according to this embodiment preferably contains silica, more preferably contains carbon black and silica, and may also be a filler consisting only of carbon black and silica.

[0114] (Silica) The silica is not particularly limited, and for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), etc., which are common in the tire industry, can be used. The raw material of the silica is not particularly limited, and for example, it may be a raw material derived from a mineral such as quartz, or it may be a raw material derived from a living organism such as rice husk (for example, silica using a biomass material such as rice husk as a raw material), or silica recycled from a product containing silica may be used. Among them, hydrous silica prepared by a wet method is preferred because of its large number of silanol groups. These silicas may be used alone or in combination of two or more.

[0115] Silica using a biomass material as a raw material can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husk using a sodium hydroxide solution, and reacting the silicate with sulfuric acid in the same manner as conventional wet silica to precipitate silicon dioxide, followed by filtration, washing with water, drying, and pulverization.

[0116] As the silica recycled from a product containing silica, for example, silica recovered from products containing silica such as electronic components such as semiconductors, tires, desiccants, and filter media such as diatomaceous earth can be used. The recovery method is not particularly limited, and examples include pyrolysis and decomposition by electromagnetic waves. Among them, silica recovered from electronic components such as semiconductors or tires is preferred.

[0117] When silica crystallizes, it is insoluble in water and the silicic acid that is its component cannot be utilized. By controlling the combustion temperature and combustion time, crystallization of silica in rice husk ash can be suppressed (see, for example, JP-A-2009-2594, Akita Prefectural University Web Journal B / 2019, vol. 6, p. 216-222, etc.).

[0118] Amorphous silica extracted from rice husk can be a commercially available product from Wilmar Co., Ltd. or the like.

[0119] The nitrogen adsorption specific surface area (N2SA) of the silica is 110 m from the viewpoint of ensuring reinforcement and attenuation in the tread portion.2 Preferably more than / g, 140m 2 More preferably more than / g, 170m 2 Even more preferably more than / g, 200m 2 Particularly preferably more than / g. Also, from the viewpoints of heat generation property and processability, 350m 2 Preferably not more than / g, 300m 2 More preferably not more than / g, 250m 2 Even more preferably not more than / g. The N2SA of silica is measured by the above measurement method.

[0120] From the viewpoint of increasing the specific surface area of silica, increasing the interaction with the rubber component, suppressing the movement of molecular chains, and suppressing heat generation, the average primary particle diameter of silica is preferably 20 nm or less, more preferably 18 nm or less, and even more preferably 16 nm or less. The lower limit value of the average primary particle diameter is not particularly limited, but from the viewpoint of the dispersibility of silica, it is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm or more. The average primary particle diameter of silica is measured by the above measurement method.

[0121] From the viewpoints of ensuring reinforcement and attenuation in the tread part, the content of silica relative to 100 parts by mass of the rubber component is preferably 40 parts by mass or more, more preferably 55 parts by mass or more, even more preferably 70 parts by mass or more, and particularly preferably 80 parts by mass or more. Also, from the viewpoint of reducing the specific gravity of the rubber and achieving weight reduction, it is preferably 140 parts by mass or less, more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 95 parts by mass or less.

[0122] (Carbon black) The carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. The raw material of the carbon black may be a biomass material such as lignin or vegetable oil, or may be a pyrolysis oil obtained by pyrolyzing waste tires. Also, the manufacturing method of the carbon black may be by combustion such as the furnace method, by hydrothermal carbonization (HTC), or by thermal decomposition of methane such as the thermal black method. As commercial products, products of Asahi Carbon Co., Ltd., Cabot Japan Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Columbian Carbon Company, etc. can be used. These carbon blacks may be used alone or in combination of two or more.

[0123] In addition to the above, from the perspective of life cycle assessment and others, carbon black made from biomass materials such as lignin and vegetable oil as raw materials, or recycled carbon black obtained by pyrolyzing and purifying products containing carbon black such as tires may also be used as the carbon black.

[0124] In this specification, "recycled carbon black" refers to carbon black obtained by pulverizing used products such as tires containing carbon black and firing the pulverized material, and when oxidized and burned by heating in air using a thermogravimetric measurement method conforming to JIS K 6226-2:2003, it refers to carbon black in which the ratio of the mass of the component that does not burn (ash content) is 13% by mass or more. That is, the ratio of the mass of the weight loss amount (carbon amount) due to the oxidative combustion of the recycled carbon black is 87% by mass or less. Recycled carbon black may also be represented by rCB.

[0125] Recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975 refers to "Rubber Chemistry and Technology", Vol. 85, No. 3, pages 408 - 449 (2012), especially pages 438, 440, 442, and describes that it can be obtained by pyrolysis of organic materials at 550 - 800 °C with oxygen excluded or by vacuum pyrolysis at relatively low temperatures (

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

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

[0126] Recycled carbon black may lack functional groups on its surface, or may be treated to contain functional groups on its surface. The treatment to make recycled carbon black contain functional groups on its surface can be carried out by conventional methods. For example, in European Patent Application Publication No. 3173251, carbon black obtained from a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Also, in Patent No. 6856781, carbon black obtained from a pyrolysis process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain carbon black with an activated surface. The recycled carbon black according to this embodiment also includes such carbon black treated to contain functional groups on its surface.

[0127] Commercially available recycled carbon black from companies such as Strable Green Carbon and LDCarbon can be used.

[0128] From the perspective of weather resistance and reinforcement, the nitrogen adsorption specific surface area (N2SA) of carbon black is preferably 50 m 2 / g or more, and 80 m2 More preferably, it is 100 m 2 / g or more, and even more preferably. Also, from the viewpoints of dispersibility, low fuel consumption performance, fracture characteristics, and durability performance, 250 m 2 / g or less is preferable, and 220 m 2 / g or less is more preferable. Note that the N2SA of carbon black is measured by the above measurement method.

[0129] When containing carbon black, the content with respect to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more from the viewpoints of weather resistance and reinforcing property. Also, from the viewpoint of low fuel consumption performance, 30 parts by mass or less is preferable, 25 parts by mass or less is more preferable, 20 parts by mass or less is even more preferable, and 15 parts by mass or less is particularly preferable.

[0130] (Other fillers) Fillers other than silica and carbon black are not particularly limited, and for example, aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, magnesium sulfate, talc, clay, biochar, etc., which have been conventionally commonly used in the tire industry, can be blended. These other fillers may be used alone or in combination of two or more.

[0131] The ratio of the content of carbon black to the content of silica is preferably 0.40 or less, more preferably 0.30 or less, even more preferably 0.21 or less, even more preferably 0.17 or less, even more preferably 0.13 or less, and particularly preferably 0.10 or less. By setting the ratio of the content of carbon black to the content of silica within the above range, the low fuel consumption performance can be further improved. On the other hand, the lower limit value of the ratio of the content of carbon black to the content of silica is not particularly limited, and for example, it can be 0.01 or more, 0.02 or more, 0.05 or more, and it may also be a filler that does not contain carbon black.

[0132] From the viewpoint of ensuring reinforcement and damping properties in the tread portion, the total filler content relative to 100 parts by mass of the rubber component is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, still more preferably 70 parts by mass or more, and particularly preferably 80 parts by mass or more. From the viewpoint of the effects of the present invention, it is preferably 140 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.

[0133] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and in the tire industry, any silane coupling agent conventionally used in combination with silica can be used. However, from the viewpoint of more suitably obtaining the desired effects, one or more silane coupling agents selected from the group consisting of sulfide-based silane coupling agents and mercapto-based silane coupling agents are preferred, and mercapto-based silane coupling agents are more preferred.

[0134] Examples of the sulfide-based silane coupling agent include bis(3-triethoxysilylpropyl)disulfide, bis(3-triethoxysilylpropyl)tetrasulfide, and the like. These sulfide-based silane coupling agents may be used alone or in combination of two or more.

[0135] As used herein, the mercapto-based silane coupling agent refers to a silane coupling agent having a mercapto group and a silane coupling agent having a structure in which the mercapto group is protected by a protecting group. The mercapto-based silane coupling agent is not particularly limited. For example, it includes a compound having a mercapto group represented by the following formula (2), a compound in which the mercapto group is protected by an ester represented by the following formula (3), and a compound containing a bonding unit A represented by the following formula (4) and / or a bonding unit B represented by the following formula (5). Among them, a compound represented by the following formula (3), or a compound containing a bonding unit A represented by the following formula (4) and / or a bonding unit B represented by the following formula (5) is preferable, and a compound represented by the following formula (3) is more preferable, because the effects of the present invention can be exhibited more favorably. These mercapto-based silane coupling agents may be used alone or in combination of two or more.

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0136] Examples of the compound represented by the formula (2) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and the compound represented by the following formula (6) (Si363 manufactured by Evonik Degussa). Among them, the compound represented by the following formula (6) can be preferably used. These may be used alone or in combination of two or more. [Chemical formula]

[0137] Examples of the compound represented by the formula (3) include 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, 3-octanoylthio-1-propyltrimethoxysilane, and the like.

[0138] The compound containing the bonding unit A represented by the formula (4) and / or the bonding unit B represented by the formula (5) suppresses the increase in viscosity during processing compared to sulfide-based silane coupling agents such as bis-(3-triethoxysilylpropyl)tetrasulfide. Therefore, it is considered that the dispersibility of silica becomes better, and the low fuel consumption performance, wet grip performance, and elongation at break are further improved. This is probably because the sulfide moiety of the bonding unit A is a C-S-C bond, which is thermally more stable than tetrasulfide or disulfide, resulting in less increase in Mooney viscosity.

[0139] From the perspective of suppressing the increase in viscosity during processing, the content of the bonding unit A is preferably 30 to 99 mol%, more preferably 50 to 90 mol%. Further, the content of the bonding unit B is preferably 1 to 70 mol%, more preferably 5 to 65 mol%, and even more preferably 10 to 55 mol%. Also, the total content of the bonding units A and B is preferably 95 mol% or more, more preferably 98 mol% or more, and particularly preferably 100 mol%. Note that the contents of the bonding units A and B are amounts including the case where the bonding units A and B are located at the ends of the silane coupling agent. The form when the bonding units A and B are located at the ends of the silane coupling agent is not particularly limited as long as it forms units corresponding to the formulas (4) and (5) representing the bonding units A and B.

[0140] In a compound containing the bonding unit A represented by the formula (4) and the bonding unit B represented by the formula (5), the total number of repetitions (x + y) of the number of repetitions (x) of the bonding unit A and the number of repetitions (y) of the bonding unit B is preferably in the range of 3 to 300. When within this range, the mercaptosilane of the bonding unit B can cover -C7H of the bonding unit A, so that it is possible to suppress the shortening of the scorch time and ensure good reactivity with silica or a rubber component. 15

[0141] Examples of the compound containing the bonding unit A represented by the formula (4) and / or the bonding unit B represented by the formula (5) include NXT-Z30, NXT-Z45, NXT-Z60, NXT-Z100, etc. manufactured by Momentive. These may be used alone or in combination of two or more.

[0142] ​Silane coupling agents other than sulfide-based silane coupling agents and mercapto-based silane coupling agents are not particularly limited. For example, 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; and the like. These other silane coupling agents may be used alone or in combination of two or more. As the silane coupling agents listed above, for example, silane coupling agents manufactured and sold by Momentive, Evonik Degussa, etc. can be used.

[0143] From the viewpoint of enhancing the dispersibility of silica, the content of the silane coupling agent relative to 100 parts by mass of silica is preferably 1.0 part by mass or more, more preferably 3.0 parts by mass or more, and even more preferably 5.0 parts by mass or more. Also, 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 even more preferably 12 parts by mass or less.

[0144] <Other compounding agents> In addition to the above components, the rubber composition according to this embodiment may appropriately contain compounding agents generally used in the conventional tire industry, such as plasticizers, vulcanized rubber particles, processing aids, waxes, anti-aging agents, stearic acid, zinc oxide, vulcanizing agents, vulcanization accelerators, and the like.

[0145] A plasticizer is a material that imparts plasticity to a rubber component, and is a concept that includes both plasticizers that are liquid at 25°C and plasticizers that are solid at normal temperature (25°C). Examples of plasticizers include resin components, oils, liquid rubbers, ester-based plasticizers, etc. These plasticizers may be derived from mineral resources such as petroleum and natural gas, may be derived from biomass, or may be derived from naphtha recycled from rubber products or non-rubber products. Also, low-molecular-weight hydrocarbon components obtained by pyrolyzing and extracting used tires and products containing various components may be used as plasticizers. These plasticizers may be used alone or in combination of two or more.

[0146] (Resin component) The resin component is not particularly limited as long as it is a resin component commonly used in the tire industry. For example, tackifying resins such as dicyclopentadiene-based resins, aromatic vinyl resins, C9 resins, C5 resins, C5C9 resins, terpene resins, rosin resins, and phenolic resins can be mentioned. These resin components may be used alone or in combination of two or more.

[0147] The "dicyclopentadiene-based resin" refers to a resin containing cyclopentadiene (CPD) or dicyclopentadiene (DCPD) as a monomer component, and may be hydrogenated or modified thereof. Examples of dicyclopentadiene-based resins include DCPD / C9 resins containing dicyclopentadiene and the C9 fraction described below as monomer components (the DCPD / C9 resin may be hydrogenated or modified thereof), and DCPD / C9 resins containing dicyclopentadiene and styrene as monomer components are preferred. As dicyclopentadiene-based resins, for example, those commercially available from ExxonMobil, ENEOS Corporation, Nippon Zeon Co., Ltd., Maruzen Petrochemical Co., Ltd., etc. can be used. These dicyclopentadiene-based resins may be used alone or in combination of two or more.

[0148] The term "aromatic vinyl resin" refers to a resin containing aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene, etc. as the monomer component with the highest content, and those obtained by hydrogenating or modifying them may also be used. As the aromatic vinyl resin, due to economic reasons, easy processing, and excellent heat generation properties, a homopolymer of α-methylstyrene or styrene, or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred. As the aromatic vinyl resin, for example, those commercially available from companies such as Kreton, Eastman Chemical, and Mitsui Chemicals, Inc. can be used. These aromatic vinyl resins may be used alone or in combination of two or more.

[0149] The term "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, which may be a homopolymer of the C9 fraction alone or a copolymer obtained by copolymerizing the C9 fraction with other components. For example, a resin obtained by copolymerizing dicyclopentadiene (DCPD) and a C9 fraction is called a DCPD / C9 resin. Also, those obtained by hydrogenating or modifying them may be used. Examples of the C9 fraction include petroleum fractions corresponding to 8 to 10 carbon atoms such as vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene. These C9 resins may be used alone or in combination of two or more.

[0150] The term "C5 resin" refers to a resin obtained by polymerizing a C5 fraction, and those obtained by hydrogenating or modifying them may also be used. Examples of the C5 fraction include petroleum fractions corresponding to 4 to 5 carbon atoms such as cyclopentadiene, isoprene, pentane, isopentane, neopentane, pentene, and pentadiene. These C5 resins may be used alone or in combination of two or more.

[0151] The "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and it may be hydrogenated or modified. As the C5C9 petroleum resin, for example, those commercially available from Tosoh Corporation, LUHUA Co., Ltd., etc. can be used. These C5C9 resins may be used alone or in combination of two or more.

[0152] The "terpene resin" refers to a resin containing terpene compounds such as α-pinene, β-pinene, limonene, dipentene, etc. as the monomer component with the highest content, and it may be hydrogenated or modified. Specific examples of terpene resins include, for example, polyterpene resins containing only one or more of the above terpene compounds as monomer components; aromatic modified terpene resins containing the terpene compounds and aromatic compounds as monomer components; terpene phenol resins containing the terpene compounds and phenolic compounds as monomer components, etc. Examples of aromatic compounds serving as monomer components of aromatic modified terpene resins include styrene, α-methylstyrene, vinyltoluene, divinyltoluene, etc. Examples of phenolic compounds serving as monomer components of terpene phenol resins include phenol, bisphenol A, cresol, xylenol, etc. These terpene resins may be used alone or in combination of two or more.

[0153] The "rosin resin" refers to a resin containing rosin acid compounds such as abietic acid, neoabietic acid, palustric acid, isopimaric acid, etc., and it may be hydrogenated or modified. The rosin resin is not particularly limited, and examples include natural resin rosin, rosin modified resins obtained by modifying it by hydrogenation, disproportionation, dimerization, esterification, etc. These rosin resins may be used alone or in combination of two or more.

[0154] "Phenolic resin" refers to a resin containing a phenolic compound such as phenol or cresol as the monomer component with the highest content. The phenolic resin is not particularly limited, and examples include phenol formaldehyde resin, alkylphenol formaldehyde resin, alkylphenol acetylene resin, oil-modified phenol formaldehyde resin, etc. These phenolic resins may be used alone or in combination of two or more.

[0155] From the perspective of grip performance, the softening point of the resin component is preferably 60 °C or higher, more preferably 70 °C or higher, and even more preferably 80 °C or higher. Also, from the perspectives of processability and improvement of the dispersibility of the rubber component and the filler, it is preferably 150 °C or lower, more preferably 140 °C or lower, and even more preferably 130 °C or lower. The softening point of the resin component is measured by the above-mentioned measurement method.

[0156] When containing a resin component, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more. Also, from the perspective of suppressing heat generation, it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 30 parts by mass or less.

[0157] (Oil) Examples of the oil include mineral oil, vegetable oil, animal oil, etc. Also, from the perspective of life cycle assessment, waste oil after being used in a rubber mixer or an engine, or refined waste cooking oil used in a restaurant may be used.

[0158] In this specification, mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. Examples of mineral oil include paraffinic oil (mineral oil), naphthenic oil, aromatic oil, etc. Specific examples of mineral oil include, for example, MES (Mild Extracted Solvate), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), RAE (Residual Aromatic Extract), etc. Also, oils with a low content of polycyclic aromatic (PCA) compounds can be used for environmental protection. Examples of the low-PCA-content oils include MES, TDAE, and heavy naphthenic oil.

[0159] 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 oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grape seed oil, wood rosin, etc. Furthermore, vegetable oils include refined oils (such as salad oil) obtained by refining the above oils, transesterified oils obtained by transesterifying the above oils, hydrogenated oils obtained by hydrogenating the above oils, thermally polymerized oils obtained by thermally polymerizing the above oils, oxidatively polymerized oils obtained by oxidizing the above oils, and waste cooking oils recovered from those used as edible oils, etc. Note that vegetable oil may be liquid or solid at room temperature (25°C). These vegetable oils may be used alone or in combination of two or more.

[0160] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably contains triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxy group of glycerin and a fatty acid are ester-bonded. The acylglycerol is not particularly limited, and may be any of 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, and triacylglycerol. Further, the acylglycerol may be a monomer, a dimer, or a multimer of trimer or higher. Note that acylglycerols of dimer or higher can be obtained by thermal polymerization, oxidative polymerization, or the like. Also, the acylglycerol may be liquid or solid at normal temperature (25°C).

[0161] As a method for confirming whether the acylglycerol is contained in the rubber composition, it is not particularly limited. For example, the following 1 can be confirmed by 1H-NMR measurement. Specifically, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at normal temperature (25°C) for 24 hours. After removing the rubber composition, 1 1H-NMR is measured. When the signal of tetramethylsilane (TMS) is set to 0.00 ppm, signals are observed around 5.26 ppm, around 4.28 ppm, and around 4.15 ppm. These signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In this paragraph, "around" means a range of ±0.10 ppm.

[0162] The fatty acid is not particularly limited, and may be an unsaturated fatty acid or a saturated fatty acid. Examples of the unsaturated fatty acid include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of the saturated fatty acid include butyric acid and lauric acid.

[0163] Among them, as the fatty acid, it is desirable to contain a fatty acid with few double bonds, that is, a saturated fatty acid or a monounsaturated fatty acid, and oleic acid is preferred. As the vegetable oil containing such a fatty acid, for example, a vegetable oil containing a saturated fatty acid or a monounsaturated fatty acid may be used, or a vegetable oil subjected to modification such as transesterification may be used. Further, in order to produce such a vegetable oil containing a fatty acid, plants may be improved by varietal improvement, genetic recombination, etc.

[0164] As the vegetable oil, for example, those commercially available from Idemitsu Kosan Co., Ltd., Sankyo Oil Chemical Co., Ltd., ENEOS Co., Ltd., Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kogyo Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0165] Examples of the animal oil include fish oil, beef tallow, or oleyl alcohol that can be derived therefrom.

[0166] The content of the unsaturated fatty acid contained in the constituent fatty acids of the vegetable oil is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, still more preferably 75% by mass or more, still more preferably 80% by mass or more, and particularly preferably 85% by mass or more.

[0167] From the viewpoint of processability, the content of the vegetable oil with respect to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 5 parts by mass or more. Further, from the viewpoint of the hardness of the rubber, it is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and still more preferably 30 parts by mass or less.

[0168] From the viewpoint of processability, the content of the oil with respect to 100 parts by mass of the rubber component (the total amount of all when using a plurality of oils in combination) 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 the hardness of the rubber, it is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and still more preferably 30 parts by mass or less.

[0169] 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. may be mentioned. These liquid rubbers may be used alone or in combination of two or more.

[0170] Examples of the ester plasticizer include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), bis(2-ethylhexyl) azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), etc. These ester plasticizers may be used alone or in combination of two or more.

[0171] The content of the plasticizer with respect to 100 parts by mass of the rubber component (the total amount of all when using a plurality of plasticizers in combination) is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, further preferably 30 parts by mass or more, and particularly preferably 35 parts by mass or more. Also, the content is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, further preferably 60 parts by mass or less, and particularly preferably 50 parts by mass or less.

[0172] The vulcanized rubber particles are particles made of vulcanized rubber. Specifically, rubber powder etc. specified in JIS K 6316:2017 can be used. From the viewpoints of environmental consideration and cost, recycled rubber powder produced from crushed waste tires etc. is preferable. These may be used alone or in combination of two or more.

[0173] The vulcanized rubber particles are not particularly limited and may be non-modified vulcanized rubber particles or modified vulcanized rubber particles. As commercially available products of vulcanized rubber, for example, products of Lehigh, Murakami Rubber Industry Co., Ltd., etc. can be used.

[0174] When containing vulcanized rubber particles, the content relative to 100 parts by mass of the rubber component can be appropriately adjusted, for example, in the range of more than 1 part by mass and less than 80 parts by mass.

[0175] Examples of the processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, etc. As the processing aids, for example, those commercially available from Schill+Seilacher, Performance Additives, etc. can be used. These processing aids may be used alone or in combination of two or more.

[0176] When containing the processing aids, from the viewpoint of exerting the effect of improving processability, the 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 even more preferably more than 1.5 parts by mass. Also, from the viewpoints of abrasion resistance and fracture strength, it is preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and even more preferably less than 5.0 parts by mass.

[0177] The wax is not particularly limited, and any wax commonly used in the tire industry can be preferably used. Examples include mineral waxes, plant-derived waxes, etc. Mineral waxes refer to waxes derived from mineral resources such as oil and natural gas. Plant-derived waxes refer to waxes derived from natural resources such as plants. Among them, mineral waxes are preferred. Examples of plant-derived waxes include rice wax, carnauba wax, candelilla wax, etc. Examples of mineral waxes include paraffin wax, microcrystalline wax, and their selected special waxes, etc., and paraffin wax is preferred. Note that the wax according to this embodiment does not contain stearic acid. As the wax, for example, those commercially available from Ouchi Shinsei Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., etc. can be used. These waxes may be used alone or in combination of two or more.

[0178] When containing wax, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and still more preferably 1.5 part by mass or more from the viewpoint of the weather resistance of the rubber. Also, from the viewpoint of preventing the whitening of the tire due to blooming, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0179] The anti-aging agent is not particularly limited, and examples thereof include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine-based anti-aging agents such as N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditoly-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; bis, tris, and polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among them, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferred, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and polymers of 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. As commercially available products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., Flexsys Co., etc. can be used. These anti-aging agents may be used alone or in combination of two or more.

[0180] When containing an anti-aging agent, the content thereof with respect to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 part by mass or more from the viewpoint of ozone crack resistance of the rubber. Also, from the viewpoints of abrasion resistance performance and wet grip performance, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0181] When containing stearic acid, the content based on 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and still more preferably 1.5 part by mass or more from the viewpoint of processability. Also, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

[0182] When containing zinc oxide, the content based on 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and still more preferably 1.5 part by mass or more from the viewpoint of processability. Also, from the viewpoint of abrasion resistance performance, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

[0183] Sulfur is preferably used as the vulcanizing agent. As sulfur, powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, etc. can be used.

[0184] When containing sulfur as the vulcanizing agent, the content based on 100 parts by mass of the rubber component is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and still more preferably 1.0 part by mass or more from the viewpoint of ensuring a sufficient vulcanization reaction. Also, from the viewpoint of deterioration prevention, it is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and still more preferably 3.5 parts by mass or less. In addition, when using oil-containing sulfur as the vulcanizing agent, the content of the vulcanizing agent is the total content of pure sulfur contained in the oil-containing sulfur.

[0185] Examples of vulcanizing agents other than sulfur include alkylphenol sulfur chloride condensates, sodium 1,6 - hexamethylene - dithiolsulfate dihydrate, 1,6 - bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. Commercially available products from companies such as Taoka Chemical Co., Ltd., Rancess Co., Ltd., Flexsys Co., etc. can be used as these vulcanizing agents other than sulfur.

[0186] Examples of the vulcanization accelerator include sulfenamide - type vulcanization accelerators, thiazole - type vulcanization accelerators, guanidine - type vulcanization accelerators, thiuram - type vulcanization accelerators, dithiocarbamate - type vulcanization accelerators, caprolactam disulfide, and the like. These vulcanization accelerators may be used alone or in combination of two or more. Among them, from the viewpoint of more preferably obtaining the desired effect, one or more vulcanization accelerators selected from the group consisting of sulfenamide - type vulcanization accelerators, thiazole - type vulcanization accelerators, and guanidine - type vulcanization accelerators are preferred, and it is more preferred to use a combination of sulfenamide - type vulcanization accelerators and guanidine - type vulcanization accelerators.

[0187] Examples of the sulfenamide - type vulcanization accelerator include N - tert - butyl - 2 - benzothiazolylsulfenamide (TBBS), N - cyclohexyl - 2 - benzothiazolylsulfenamide (CBS), N,N - dicyclohexyl - 2 - benzothiazolylsulfenamide (DCBS), and the like. Among them, TBBS and CBS are preferred.

[0188] Examples of the thiazole - type vulcanization accelerator include 2 - mercaptobenzothiazole (MBT) or its salts, di - 2 - benzothiazolyldisulfide (MBTS), 2 - (2,4 - dinitrophenyl) mercaptobenzothiazole, 2 - (2,6 - diethyl - 4 - morpholinothio) benzothiazole, and the like. Among them, MBTS and MBT are preferred, and MBTS is more preferred.

[0189] Examples of the guanidine - type vulcanization accelerator include 1,3 - diphenylguanidine (DPG), 1,3 - di - o - tolguanidine, 1 - o - tolbiguanide, di - o - tolguanidine salt of dicatechol borate, 1,3 - di - o - cumenylguanidine, 1,3 - di - o - biphenylguanidine, 1,3 - di - o - cumenyl - 2 - propionylguanidine, and the like. Among them, DPG is preferred.

[0190] When contained, the content of the vulcanization accelerator relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and still more preferably 1.5 part by mass or more. Further, the content of the vulcanization accelerator relative to 100 parts by mass of the rubber component is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, and still more preferably 4.0 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, the breaking strength and elongation tend to be ensured.

[0191] [Manufacture of Rubber Composition and Tire] The rubber composition according to the present embodiment can be manufactured by a known method. For example, it can be manufactured by kneading each of the above components using a rubber kneading device such as an open roll, a closed kneader (Banbury mixer, kneader, etc.).

[0192] The kneading process includes, for example, a base kneading process of kneading compounding agents and additives other than the vulcanizing agent and the vulcanization accelerator, and a final kneading (F kneading) process of adding and kneading the vulcanizing agent and the vulcanization accelerator to the kneaded product obtained in the base kneading process. Further, the base kneading process can be divided into a plurality of processes if desired.

[0193] The kneading conditions are not particularly limited. For example, in the base kneading process, kneading is performed at a discharge temperature of 150 to 170°C for 3 to 10 minutes, and in the final kneading process, kneading is performed at 70 to 110°C for 1 to 5 minutes. The vulcanization conditions are not particularly limited, and for example, a method of vulcanizing at 150 to 200°C for 10 to 30 minutes can be mentioned.

[0194] A tire provided with a tread portion composed of the rubber composition can be manufactured by a conventional method. That is, an unvulcanized rubber composition in which each of the above components is blended with the rubber component as necessary is extruded according to the shape of the first layer of the tread portion, and is bonded together with the inner rubber layer of the tread portion and other tire members on a tire molding machine, and is molded by a conventional method to form an unvulcanized tire. The tire can be manufactured by heating and pressurizing this unvulcanized tire in a vulcanizer. The vulcanization conditions are not particularly limited, and for example, a method of vulcanizing at 150 to 200 ° C for 10 to 30 minutes can be mentioned.

[0195] [Use of the tire] The tire according to the present embodiment can be suitably used for passenger car tires, truck / bus tires, motorcycle tires, and racing tires, and among them, it is preferably used for passenger car tires. The passenger car tire is a tire assumed to be mounted on an automobile running on four wheels, and refers to a tire having a maximum load capacity of 1000 kg or less.

Example

[0196] Hereinafter, examples (Examples) considered to be preferable in carrying out the invention will be shown, but the scope of the present invention is not limited to the examples. Using the various chemicals shown below, tires having the first layer of the tread portion obtained according to the formulations in Tables 1 to 4 were examined, and the results calculated based on the following evaluation methods are shown in Tables 1 to 4.

[0197] Hereinafter, various chemicals used in Examples and Comparative Examples will be summarized. NR: TSR20 SBR: EUROPRENE (registered trademark) SOL R C2525 manufactured by Versalis (styrene content: 26% by mass, vinyl content: 24% by mass, Mw: 600,000, non-oil product) BR: CB24 manufactured by Lanxess Co., Ltd. (BR synthesized using a Nd-based catalyst, cis content: 96 mol%, Mw: 500,000) Carbon black: SHOW BLACK N220 manufactured by Cabot Japan Co., Ltd. (N2SA: 111m 2 / g) Silica 1: ULTRASIL® VN3 manufactured by Evonik Degussa (N2SA: 175 m 2 / g, average primary particle size: 17 nm) Silica 2: ULTRASIL® 9100GR manufactured by Evonik Degussa (N2SA: 230 m 2 / g, average primary particle size: 15 nm) Silica 3: Rice husk-derived silica obtained by the following production example (N2SA: 175 m 2 / g, average primary particle size: 18 nm) Silane coupling agent 1: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa Silane coupling agent 2: NXT-Z45 manufactured by Momentive (mercapto group-based silane coupling agent, copolymer of bonding unit A and bonding unit B (bonding unit A: 55 mol%, bonding unit B: 45 mol%)) Oil 1: VivaTec500 (TDAE oil) manufactured by H&R Oil 2: Sunflower oil manufactured by Nisshin Oillio Group, Ltd. (content of oleic acid contained in constituent fatty acids: 55% by mass, total content of polyunsaturated fatty acids contained in constituent fatty acids: 8% by mass) Resin component: Oppera PR395 (hydrogenated DCPD / C9 resin, softening point: 118°C) manufactured by ExxonMobil Wax: Oz Ace 0355 (paraffin wax) of Nippon Seiro Co., Ltd. Antioxidant: No Crack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Zinc oxide: Zinc white No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Bead stearic acid camellia of NOF Corporation Sulfur: HK-200-5 (5% oil-containing powdered sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator: Nocceler CZ (N-cyclohexyl-2-benzothiazolylsulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0198] (Production example of Silica 3) Add rice husk ash to an aqueous sodium hydroxide solution and heat and stir with a stirring rod. Then, let it return to room temperature, centrifuge to precipitate the carbon content, and filter the supernatant through a Kiriyama funnel. Further, add water to the precipitate, stir, then centrifuge again, filter the supernatant through a Kiriyama funnel, and mix this filtrate with the previous filtrate. Then, dilute this mixed filtrate with water to obtain an aqueous sodium silicate solution.

[0199] Take out a part of the aqueous sodium silicate solution, dilute it with pure water, then adjust the pH to 2 - 4 by adding 1 mol / L sulfuric acid, and then heat. Next, add the remaining part of the aqueous sodium silicate solution to adjust the pH to 8 - 10, heat further, and dilute this with pure water to obtain a seed solution.

[0200] Heat and stir the seed solution, and simultaneously dropwise add the remaining aqueous sodium silicate solution and 1 mol / L sulfuric acid thereto, and stir while adjusting the pH to the range of 8 - 11. After the dropping of the aqueous sodium silicate solution is completed, continue dropping only 1 mol / L sulfuric acid at the same rate and finish the dropping at a predetermined pH (1.5 - 6). Filter the white precipitate formed after the dropping is completed through a Kiriyama funnel, and wash the filtrate with water. Repeat this once again, dry the filtrate, and obtain silica 3.

[0201] (Examples and Comparative Examples) According to the compounding formulations shown in Tables 1 - 4, using a 1.7 L sealed Banbury mixer, knead the chemicals other than sulfur and vulcanization accelerators for 1 - 10 minutes until the discharge temperature reaches 150 - 160°C to obtain a kneaded product. Next, using a twin - screw open roll, add sulfur and vulcanization accelerators to the kneaded product, knead for 4 minutes until it reaches 105°C to obtain an unvulcanized rubber composition. Using this unvulcanized rubber composition, extrude and mold it according to the shape of the first layer (thickness: 5.0 mm) of the tread part with an extruder equipped with a die of a predetermined shape, laminate it together with the second layer (thickness: 1.0 mm) of the tread part and other tire members to produce an unvulcanized tire, and press - vulcanize it at 170°C for 12 minutes to obtain each test tire described in Tables 1 - 4.

[0202] <Measurement of tanδ at 30°C and E* at 30°C> For each vulcanized rubber test piece prepared by cutting out from the inside of the first layer of the tread part of each test tire, with the tire circumferential direction as the long side and the tire radial direction as the thickness direction, having a length of 20 mm × width of 4 mm × thickness of 1 mm, using a dynamic viscoelasticity measuring device (Implex series manufactured by GABO), at a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of ±1%, and under the conditions of the elongation mode, the loss tangent tanδ and the complex elastic modulus E* are measured.

[0203] <Tensile test> For the dumbbell-shaped No. 7 test pieces cut out with a thickness of 1 mm from the inside of the first and second layers of the tread part of each test tire, with the tire circumferential direction as the tensile direction and the tire radial direction as the thickness direction, in accordance with JIS K 6251:2017, in an atmosphere of 23°C, a tensile test is carried out under the condition of a tensile speed of 3.3 mm / second, and the modulus (M 200 )(MPa) at 200% elongation is measured.

[0204] <Measurement of acetone extraction amount (AE amount)> For each vulcanized rubber test piece prepared by cutting out from each rubber layer of the tread part of each test tire, the AE amount is measured respectively. The AE amount is obtained by immersing each vulcanized rubber test piece in acetone for 24 hours, extracting the soluble components, measuring the mass of each test piece before and after extraction, and using the following formula. Acetone extraction amount (mass%) = {(mass of the vulcanized rubber test piece before extraction - mass of the vulcanized rubber test piece after extraction) / (mass of the rubber test piece before extraction)} × 100

[0205] <Low fuel consumption performance> Using a rolling resistance tester, when each test tire is run at an internal pressure (230 kPa), a load (3.43 kN), and a speed (80 km / h), the rolling resistance is measured and is expressed as an index with the reference comparative example (Comparative Example 2 in Table 1, Comparative Example 10 in Table 2, Comparative Example 19 in Table 3, Comparative Example 29 in Table 4) taken as 100. The larger the index, the smaller the rolling resistance, indicating excellent low fuel consumption performance.

[0206] <Abrasion resistance performance> Each test tire was mounted on a domestic FF vehicle, the groove depth of the tread part was measured after a driving distance of 8000 km, the driving distance when the tire groove depth decreased by 1 mm was calculated, and it was expressed as an index with the reference comparative example (Comparative Example 2 in Table 1, Comparative Example 10 in Table 2, Comparative Example 19 in Table 3, Comparative Example 29 in Table 4) set to 100. The larger the index, the better the abrasion resistance performance.

[0207] <Comprehensive performance> The total value of the above fuel efficiency index and abrasion resistance performance index is shown as the comprehensive performance index.

[0208]

Table 1

[0209]

Table 2

[0210]

Table 3

[0211]

Table 4

[0212] <Embodiment> Examples of embodiments of the present invention are shown below.

[0213] 〔1〕A tire provided with a tread part having at least one rubber layer, wherein the ratio of the tire weight G (kg) to the maximum load capacity W L (kg) of the tire (G / W L) is 0.0160 or less, the cross-sectional width Wt of the tire is 200 mm or more, the first layer constituting the tread surface is composed of a rubber composition containing a rubber component and a filler, the thickness t1 of the first layer is more than 3.0 mm, when the complex elastic modulus of the rubber composition at 30 °C is 30 °C E* (MPa) and the land ratio on the grounding surface of the tread portion is R, 30 °C E* is more than 8.0 MPa, and the product (R × 30 °C E*) of R and 30 °C E* is more than 5.0. 〔2〕The tire according to the above 〔1〕, wherein R × 30 °C E* is more than 6.0 (preferably more than 6.0 and less than 12.0). 〔3〕The tire according to the above 〔1〕 or 〔2〕, wherein tan δ (30 °C tan δ) of the rubber composition at 30 °C is less than 0.25. 〔4〕The tire according to any one of the above 〔1〕 to 〔3〕, wherein the product (30 °C tan δ × 30 °C E* × t1) of 30 °C tan δ, 30 °C E*, and t1 is less than 12.0 (preferably more than 5.0 and less than 11.0). 〔5〕The tire according to any one of the above 〔1〕 to 〔4〕, wherein the rubber composition contains silica having an average primary particle diameter of 16 nm or less. 〔6〕The tire according to any one of the above 〔1〕 to 〔5〕, wherein the rubber composition contains a mercapto-based silane coupling agent. 〔7〕The tire according to any one of the above 〔1〕 to 〔6〕, wherein the acetone extraction amount of the rubber composition is 20% by mass or less. 〔8〕The tire according to any one of the above 〔1〕 to 〔7〕, wherein the rubber component contains an isoprene-based rubber. 〔9〕The tire according to any one of the above 〔1〕 to 〔8〕, wherein the rubber component contains a styrene-butadiene rubber having a styrene content of 30% by mass or less. 〔10〕The tire according to any one of the above 〔1〕 to 〔9〕, wherein the total styrene amount S in the rubber component is 25% by mass or less. 〔11〕The tire according to the above 〔10〕, wherein S / 30 °C E* is 2.5 or less. 〔12〕The tire according to the above 〔10〕 or 〔11〕, wherein the product (R × S) of R and S is 15.0 or less. 〔13〕The modulus at 200% elongation of the rubber composition is M200 When it is (MPa), M of the rubber composition 200 , 30 °C E*, and 30 °C tanδ satisfy the following formula (1), the tire according to any one of the above [1] to

[12] . M 200 × 30 °C E* / 30 °C tanδ ≥ 200 ··· (1)

[14] The tire according to any one of the above [1] to

[13] , wherein the rubber composition contains vegetable oil.

[15] The tire according to any one of the above [1] to

[14] , wherein the filler contains silica made from a biomass material as a raw material.

Claims

1. A tire comprising a tread portion having at least one rubber layer, Ratio (G / W) of tire weight G (kg) to maximum load capacity W of tire L (kg) is 0.0160 or less, and L ​ wherein the cross-sectional width Wt of the tire is 200 mm or more, the first layer constituting the tread surface is composed of a rubber composition containing a rubber component and a filler, the thickness t1 of the first layer is more than 3.0 mm, when the complex elastic modulus of the rubber composition at 30°C is 30°C E* (MPa) and the land ratio at the ground contact surface of the tread portion is R, 30°C E* is more than 8.0 MPa, and the product (R × 30°C E*) of R and 30°C E* is more than 5.

0.

2. The tire according to claim 1, wherein R × 30°C E* is more than 6.

0.

3. The tire according to claim 1, wherein tanδ (30°C tanδ) of the rubber composition at 30°C is less than 0.

25.

4. The tire according to claim 3, wherein the product (30°C tanδ × 30°C E* × t1) of 30°C tanδ, 30°C E*, and t1 is less than 12.

0.

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

6. The tire according to any one of claims 1 to 4, wherein the rubber composition contains a mercapto-based silane coupling agent.

7. The tire according to any one of claims 1 to 4, wherein the acetone extraction amount of the rubber composition is 20% by mass or less.

8. The tire according to any one of claims 1 to 4, wherein the rubber component includes an isoprene-based rubber.

9. The tire according to any one of claims 1 to 4, wherein the rubber component includes a styrene-butadiene rubber having a styrene content of 30% by mass or less.

10. The tire according to any one of claims 1 to 4, wherein the total styrene amount S in the rubber component is 25% by mass or less.

11. The tire according to claim 10, wherein S / 30°C E* is 2.5 or less.

12. The tire according to claim 10, wherein the product (R × S) of R and S is 15.0 or less.

13. Let the modulus at 200% elongation of the rubber composition be M 200 (MPa), then the M of the rubber composition 200 , 30°C E*, and 30°C tan δ satisfy the following formula (1). The tire according to any one of claims 1 to 4 M 200 M×tanδ at 30°C E* / tanδ at 30°C ≥ 200...(1)

14. The tire according to any one of claims 1 to 4, wherein the rubber composition contains vegetable oil.

15. The tire according to any one of claims 1 to 4, wherein the filler includes silica made from a biomass material as a raw material.

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