tire

Abstract

To provide a tire capable of improving grip performance during cornering. [Solution] A tire having a tread portion and a belt layer, wherein the tread portion has at least one rubber layer, and a cap rubber layer that forms the tread surface of the tread portion is made of a rubber composition containing a rubber component, liquid rubber, and a terpene-based resin, and the belt layer has a steel cord consisting of 1 to 4 filaments, and the outer diameter D of the filaments is 0.45 mm or less, and when Y=A / P is defined as A (mass%) and P (mass%), Y is 0.50 or more and Y / D is 1.6 or more.

Description

[Technical Field]

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

[0002] Pneumatic tires are required to have both good grip performance when traveling straight and when cornering. Patent Document 1 discloses a rubber composition for tire treads that contains a specific carbon black and has excellent grip performance from the initial stage of driving and peak grip performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-158662 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a tire that can improve grip performance during cornering. [Means for solving the problem]

[0005] The present invention relates to a tire having a tread portion and a belt layer, wherein the tread portion has at least one rubber layer, a cap rubber layer that forms the tread surface of the tread portion is made of a rubber composition containing a rubber component, liquid rubber, and a terpene resin, the belt layer has steel cords consisting of 1 to 4 filaments, the outer diameter D of the filaments is 0.45 mm or less, and when Y=A / P is defined as A (mass%) and P (mass%), Y is 0.50 or more and Y / D is 1.6 or more. [Effects of the Invention]

[0006] According to the present invention, a tire is provided that can improve grip performance during cornering. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view of a tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is a diagram schematically illustrating a belt layer. [Figure 3] FIG. 1 is an explanatory diagram of an example of the configuration of a single-twist steel cord. DETAILED DESCRIPTION OF THE INVENTION

[0008] One embodiment of the present invention relates to a tire having a tread portion and a belt layer, wherein the tread portion has at least one rubber layer, and a cap rubber layer that forms the tread surface of the tread portion is made of a rubber composition containing a rubber component, liquid rubber, and a terpene resin, and the belt layer has steel cords consisting of 1 to 4 filaments, and the outer diameter D of the filaments is 0.45 mm or less, and when Y=A / P is defined as A (mass%) and P (mass%), Y is 0.50 or more and Y / D is 1.6 or more.

[0009] While not intending to be bound by theory, the reason why the cornering grip performance of the tire of the present invention is improved is believed to be as follows.

[0010] The rubber composition constituting the cap rubber layer of the present invention (1) contains a liquid rubber, which is a low-molecular-weight polymer, so that the molecular chain ends of the liquid rubber contribute to improving heat buildup, and (2) by using a terpene resin in combination, the liquid rubber is easily dispersed uniformly in the cap rubber layer due to its compatibility with the terpene resin.

[0011] Furthermore, (3) by reducing the filament diameter of the steel cord, the circumferential rigidity of the steel cord is reduced, which is thought to make the steel cord more likely to deform along the unevenness of the road surface. And (4) by increasing the amount of acetone extractables from the rubber composition that constitutes the cap rubber layer, the flexibility of the tread rubber is improved. Furthermore, by adjusting the amount of acetone extractables from the rubber composition that constitutes the cap rubber layer according to the filament diameter of the steel cord, the road-following ability of the tread rubber is improved, and the molecular chain ends of the liquid rubber are thought to be more likely to generate heat.

[0012] It is believed that the cooperation of the above (1) to (4) will achieve a remarkable effect of synergistically improving grip performance during cornering.

[0013] From the viewpoint of grip performance, the rubber component preferably contains 50% by mass or more of styrene-butadiene rubber.

[0014] From the viewpoint of abrasion resistance, the rubber composition preferably contains 80 parts by mass or more of silica per 100 parts by mass of the rubber component.

[0015] The rubber composition preferably contains silica having an average primary particle size of 20 nm or less. By setting the average primary particle size of silica within this range, it is believed that the balance between grip performance and abrasion resistance is improved.

[0016] The total amount of styrene in the rubber component is preferably 20% by mass or more. By setting the total amount of styrene in the rubber component within this range, it is believed that the cap rubber that conforms to the road surface will efficiently generate heat.

[0017] The steel cord can be suitably used in a 1x1 structure or a 1x4 structure, with the 1x1 structure being particularly preferred because the cord is easily deformed.

[0018] From the viewpoint of the effects of the present invention, the number of the steel cords arranged per 50 mm in the tire width direction is preferably 20 or more and 60 or less.

[0019] The steel cord preferably has a ternary plating layer made of copper, zinc, and cobalt. By adopting the ternary plating, cobalt, which has a higher ionization tendency than copper, is preferentially eluted, which is thought to suppress thickening of the adhesive layer due to elution of copper after moist heat degradation, maintain high adhesive strength, and improve steering stability and durability.

[0020] The groove area ratio of the contact surface of the inner tread, which forms the inner edge of the vehicle centered on the tire equator, is S in (%), the groove area ratio of the outer tread part on the contact surface of the vehicle's outer edge is S оut (%), |S in -S оut | / (Y / D) is preferably greater than 0 and less than 5.0. in -S оut It is believed that by setting | / (Y / D) in the above range, grip performance can be improved.

[0021] <Definition> The "tread portion" refers to a component that includes the portion that forms the tire's contact surface, and in a cross section of the tire taken along a plane including the tire rotation axis, if the tire is equipped with components that form the tire skeleton using steel or textile materials, such as a belt layer, a belt reinforcing layer, and a carcass, the "tread portion" refers to a component that is located radially outward of these components.

[0022] The "belt layer" is a layer located radially outward of the carcass, and includes multiple working layers in which the internal reinforcing material is inclined at an angle of approximately 18 to 30 degrees relative to the tire circumferential direction and overlaps in the opposite direction, and a circumferential belt layer in which the internal reinforcing material is oriented at an angle of ±10 degrees relative to the tire circumferential direction.

[0023] "Normal condition" means that the tire is mounted on a normal rim, inflated to the normal internal pressure, and unloaded. Unless otherwise specified, the tire must be in its normal condition.

[0024] Unless otherwise specified, the "dimensions of each part of the tire" are values ​​that are specified when the tire appears on its outer surface in a normal state, while those that exist inside the tire or on a cut surface of the tire are values ​​that are specified when, for example, the tire is cut along a plane that includes the tire rotation axis and the cut tire piece is maintained within the rim width of a normal rim.

[0025] "Genuine rim" refers to the rim specified for each tire in the standard system that includes the standard on which the tire is based. For example, for JATMA (Japan Automobile Tire Manufacturers Association), it refers to the standard rim for the applicable size listed in the "JATMA YEAR BOOK," for ETRTO (The European Tyre and Rim Technical Organization), it refers to the "Measuring Rim" listed in the "STANDARDS MANUAL," and for TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "YEAR BOOK." JATMA, ETRTO, and TRA are referenced in that order, and if an applicable size is available at the time of reference, that standard is followed. In the case of a tire not specified in the above standards, it refers to the narrowest rim among the smallest diameter rims that can be mounted on the tire and can maintain internal pressure (i.e., no air leaks from between the rim and tire).

[0026] "Normal internal pressure" refers to the air pressure specified for each tire in the standard system that includes the standard on which the tire is based. For example, for JATMA, it is "maximum air pressure," for ETRTO, it is "INFLATION PRESSURE," and for TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." As with regular rims, refer to JATMA, ETRTO, and TRA in that order, and follow that standard if there is an applicable size at the time of reference. In the case of tires not specified in the above standards, it refers to the normal internal pressure (250kPa or more) of another tire size (defined in the standard) that is specified using the regular rim as the standard rim, and if there are multiple normal internal pressures of 250kPa or more listed, it refers to the smallest value among them.

[0027] "Normal load (kg)" is the load specified for each tire in the standard system including the standard on which the tire is based, for example, "Maximum Load Capacity" for JATMA, "Load Capacity" for ETRTO, and the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA. As with normal rims and normal internal pressures, JATMA, ETRTO, and TRA should be referenced in that order, and if there is an applicable size at the time of reference, that standard should be followed. For tires not specified in the above standards, the maximum load capacity W calculated separately should be used. L is the normal load.

[0028] "Maximum load capacity W L (kg)" is calculated using the following formula: "V" is the virtual volume of the tire (mm 3), "Dt" is the outer diameter (mm) of the tire in its normal state, "Ht" is the tire's cross-sectional height (mm) in the tire's radial direction in a cross section of the tire taken along a plane including the tire's rotation axis, and "Wt" is the tire's cross-sectional width (mm) in its normal state. Ht can be calculated by (Dt-R) / 2, where R is the tire rim diameter. Wt is the value obtained by excluding any patterns or letters on the tire sidewall. Note that maximum load capacity is synonymous with the normal load mentioned above.

number

[0029] The "groove area ratio" is calculated from the contact shape when the tread is pressed against a flat surface under a normal load under normal conditions. The contact shape is obtained by, for example, mounting a tire on a normal rim and maintaining the normal internal pressure, applying ink to the tread, pressing the tire perpendicularly against cardboard or the like under a normal load (camber angle 0°), and transferring the ink applied to the tread. The obtained contact shape is then divided around the tire equator, allowing the groove area ratios of the contact surface of the inner tread, which forms the vehicle's inner edge, and the contact surface of the outer tread, which forms the vehicle's outer edge, to be determined.

[0030] The "rubber component of the rubber composition" refers to a component that contributes to crosslinking within the rubber composition, and typically has a weight average molecular weight (Mw) of 10,000 or more. The Mw of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more. The Mw of the rubber component is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less.

[0031] "Plasticizer" is a material that imparts plasticity to the rubber component and is a component that is extracted from the rubber composition using acetone. Plasticizers include plasticizers that are liquid (fluid) at 25°C and plasticizers that are solid at 25°C. However, this does not include wax and stearic acid that are commonly used in the tire industry.

[0032] The "plasticizer content" includes the amount of plasticizer contained in an extended rubber component that has been previously extended with a plasticizer such as oil, a resin component, or a liquid rubber component. The same applies to the oil content, the resin component content, and the liquid rubber content. For example, if the extended component is oil, the extended oil is included in the oil content.

[0033] <Measurement method> The "acetone extractable amount" can be calculated in accordance with JIS K 6229:2015 by immersing each rubber test piece in acetone for 72 hours to extract the soluble components, measuring the mass of each rubber test piece before and after extraction, and then using the following formula. (Amount of acetone extracted (mass%)) = {(mass of rubber test piece before extraction - mass of rubber test piece after extraction) / (mass of rubber test piece before extraction)} × 100

[0034] The "polymer amount (mass %)" in a rubber composition indicates the ratio of the total mass of the rubber components in the rubber composition to the total mass of the rubber composition, and can be calculated by the following formula, where the rubber test pieces after the acetone extraction are heated in a nitrogen stream from room temperature to 750°C at a rate of 10°C / min by thermogravimetry in accordance with JIS K 6226-1:2003, and subjected to thermal decomposition, and the masses of each rubber test piece before and after thermal decomposition are measured. (Polymer amount (mass%)) = {(mass of rubber test piece before pyrolysis - mass of rubber test piece after pyrolysis) / (mass of rubber test piece before pyrolysis)} × 100

[0035] The "average thickness of the plating layer" is measured in accordance with JIS H 8501:1999.

[0036] "Styrene content" is measured by pyrolysis gas chromatography and NMR measurement ( 1 H-NMR and 13It is calculated by C-NMR. Unlike physical properties such as complex modulus (E*), component amounts such as "styrene content" have true values ​​that are independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible. In this specification, "pyrolysis gas chromatography" refers to a method in which a sample is heated in a pyrolysis device, the individual components contained in the gas phase components generated by this heating are separated using a separation column, and each isolated component is analyzed. The styrene content is applied to rubber components that have repeating units (styrene units) derived from styrene, such as SBR.

[0037] "Vinyl content (amount of 1,2-bonded butadiene units)" can be measured by pyrolysis gas chromatography or NMR measurement ( 1 H-NMR and 13 It is calculated by C-NMR. As with the "styrene content," there is a true value for the "vinyl content" that is independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible. The vinyl content is applied to rubber components that contain repeating units derived from butadiene, such as SBR and BR.

[0038] "Cis content (cis-1,4-bonded butadiene unit amount)" is measured by infrared absorption spectroscopy or NMR measurement ( 1 H-NMR and 13 This is a value measured by C-NMR and is applied to rubber components that have repeating units derived from butadiene, such as BR. As with the "styrene content," there is a true value for the "cis content" that is independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible.

[0039] The "total styrene content in the rubber component" refers to the total content (mass%) of styrene units in 100% by mass of the rubber component. This is calculated by multiplying the styrene content (mass%) of each rubber component by the mass fraction in the rubber component, and then adding up the resulting values. Specifically, it is calculated as Σ(styrene content (mass%) of each styrene unit-containing rubber × content (mass%) of each styrene unit-containing rubber in the rubber component / 100). For example, if the rubber component consists of 20% by mass of a first SBR (styrene content: 25% by mass), 30% by mass of a second SBR (styrene content: 27.5% by mass), and 50% by mass of BR, the total styrene content in the rubber component is approximately 13.3% by mass (=(25 × 20 / 100) + (27.5 × 30 / 100) + (0 × 10 / 100)).

[0040] The "weight average molecular weight (Mw)" can be determined by converting the measured value into standard polystyrene equivalents using gel permeation chromatography (GPC) (for example, a GPC-8000 series manufactured by Tosoh Corporation, a differential refractometer as the detector, and a TSKgel SuperMultipore HZ-M column manufactured by Tosoh Corporation). This applies to, for example, SBR, BR, plasticizers, etc.

[0041] The "nitrogen adsorption specific surface area (N2SA) of carbon black" is measured in accordance with JIS K 6217-2:2017.

[0042] The "nitrogen adsorption specific surface area (N2SA) of silica" is measured by the BET method in accordance with ASTM D3037-93.

[0043] "Average primary particle size" is a value determined by photographing particles with a transmission or scanning electron microscope and taking the arithmetic average of the particle sizes of 400 particles. If the particle shape is spherical, the particle size is the diameter of the sphere, and if the particle shape is non-spherical, the particle size is calculated from the microscope image as the circle-equivalent diameter (positive square root of {4 x (particle area) / π}). The average primary particle size applies to silica, carbon black, etc.

[0044] The "softening point of the resin component" is the softening point specified in JIS K 6220-1:2015 7.7 measured using a ring and ball softening point tester, and is the temperature at which the ball drops.

[0045] A procedure for producing a tire according to one embodiment of the present invention will be described in detail below. However, the following description is merely an example for explaining the present invention, and is not intended to limit the technical scope of the present invention to the scope of the description.

[0046] <Tires> Hereinafter, a tire according to one embodiment of the present invention will be described with reference to the drawings.

[0047] FIG. 1 shows a cross-sectional view of a tire 11 according to this embodiment taken along a plane passing through the tire rotation axis. While FIG. 1 shows only the portion to the left of the center line (CL), the tire has a similar structure that continues to the right of the CL, with the CL as the axis of symmetry. As shown in FIG. 1, the tire 11 includes a tread portion 12, a sidewall portion 13, a bead portion 14, an inner liner 15, a carcass 16, a belt layer 17, and a bead core 18. The belt layer 17 has two layers, but the number of layers is not particularly limited and can be selected as desired.

[0048] The tread portion 12 may be a tread portion consisting of a single rubber layer, or may be a tread portion having a cap rubber layer that forms the tread surface and one or more rubber layers that exist between the cap rubber layer and the belt layer 17.

[0049] <Belt layer and steel cord> 2 shows a cross section of the steel cord 21 taken along a plane perpendicular to the longitudinal direction. The ply forming the belt layer 17 has a plurality of steel cords 21 and a topping rubber 22. The plurality of steel cords 21 are arranged in a row. The topping rubber 22 covers the steel cords 21, and the entire circumference of each steel cord is covered with the topping rubber 22. The steel cords 21 are embedded in the topping rubber 22.

[0050] The steel cords 21 may or may not be inclined with respect to the tire circumferential direction. The inclination angle of the steel cords 21 with respect to the tire circumferential direction is not particularly limited, but is set, for example, in the range of 0° to 60°, preferably 5° to 45°, and more preferably 10° to 30°.

[0051] The steel cord according to this embodiment has 1 to 4 steel wires, also called filaments. That is, the steel cord may be a monofilament cord (i.e., a cord having a 1x1 structure and consisting of one filament), or may have 2 to 4 filaments.

[0052] When one steel cord has two to four filaments, the steel cord preferably has a twisted structure in which the filaments are twisted together in the longitudinal direction. The twisted structure is not particularly limited, and may be, for example, a single-twisted steel cord with a 1×N structure or a multi-layered steel cord with an N+M structure.

[0053] The single twist structure can be expressed, for example, as a 1xN structure. The 1xN structure means a structure in which N filaments are twisted together to form a single layer (one layer). The single layer means a structure in which, in a cross section perpendicular to the longitudinal direction of the steel cord, the filaments are arranged in a single layer (one layer) along the circumferential direction of a circle. Examples of single twist structures in this embodiment include a 1x2 structure, a 1x3 structure, and a 1x4 structure.

[0054] Fig. 3 is a perspective view of a steel cord having a 1 x 2 structure. The steel cord 50 shown in Fig. 3 has two filaments 51 twisted together in a spiral shape along the longitudinal direction to form a single layer.

[0055] The layered twisted structure has a structure in which a plurality of filaments are wound in layers in order from the center in a cross section perpendicular to the longitudinal direction of the steel cord, and can be expressed as an N+M structure, for example. The N+M structure means a structure having a core in which N filaments are twisted together in a spiral along the longitudinal direction of the core, and an outer sheath in which M filaments are twisted together in a spiral along the longitudinal direction of the core so as to cover the outer periphery of the core. An example of the layered twisted structure in this embodiment is a 2+2 structure.

[0056] The material of the steel filaments is not particularly limited, and may be high tensile (HT), super high tensile (SHT), ultra high tensile (UHT), or the like. Recycled iron obtained by melting used iron products may also be used. When using a steel cord made by twisting together multiple steel filaments, steel filaments that have been pre-formed in the longitudinal direction may be used to improve durability by making it easier for the topping rubber to penetrate into the steel cord.

[0057] From the viewpoint of the road surface conformability of the tread rubber, the filament diameter D of the steel cord is 0.45 mm or less, preferably 0.42 mm or less, more preferably 0.40 mm or less, even more preferably 0.38 mm or less, and particularly preferably 0.35 mm or less. Also, from the viewpoint of ensuring the durability of the steel cord against impact, the filament diameter D is preferably 0.10 mm or more, more preferably 0.13 mm or more, even more preferably 0.16 mm or more, even more preferably 0.19 mm or more, still more preferably 0.22 mm or more, and particularly preferably 0.25 mm or more.

[0058] The steel cord according to the present embodiment may be provided with a plated layer. A steel cord having a plated layer exhibits high moisture-heat resistant adhesion performance even under harsh conditions of high temperature and humidity, thereby preventing peeling between the topping rubber and the steel cord and improving the durability of the tire under moist and hot conditions. When the steel cord has multiple filaments, a plated layer can be provided on the surface of each filament.

[0059] The configuration of the plating layer is not particularly limited, but a plating layer containing a copper layer and a zinc layer is preferred, and a plating layer containing a copper layer, a zinc layer, and a cobalt layer is more preferred. In particular, a steel cord having a ternary plating layer consisting of copper (Cu), zinc (Zn), and cobalt (Co) exhibits high moisture-heat resistant adhesion performance even under harsh conditions of high temperature and humidity, and can prevent peeling between the topping rubber and the steel cord, thereby improving the durability of the tire under moist and hot conditions.

[0060] The zinc content in the plating layer is preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more from the viewpoint of suppressing excessive copper reaction, and is preferably 44% by mass or less, more preferably 40% by mass or less, even more preferably 36% by mass or less, and particularly preferably 32% by mass or less from the viewpoint of suppressing adhesion deterioration due to excess zinc oxide generation.

[0061] From the viewpoint of adhesion, the copper content in the plating layer is preferably 55% by mass or more, more preferably 58% by mass or more, and even more preferably 61% by mass or more, and from the viewpoint of preventing rubber deterioration due to copper elution in a humid and hot environment, the copper content is preferably 78% by mass or less, more preferably 75% by mass or less, and even more preferably 72% by mass or less.

[0062] The cobalt content in the plating layer is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and even more preferably 3.0% by mass or more from the viewpoint of hot and moist adhesion, and is preferably 8.0% by mass or less, more preferably 7.0% by mass or less, and even more preferably 6.0% by mass or less from the viewpoint of preventing cracks during wire drawing.

[0063] The plating layer can be formed by plating a copper layer, a zinc layer, a cobalt layer, or the like on the filament before wire drawing, and then diffusing the metals of each layer formed on the surface of the filament by heat treatment. Note that the order of layers formed on the filament to form the plating layer is not particularly limited.

[0064] Next, the heat-treated material is drawn to a desired filament diameter to form a filament having a plated layer. When the steel cord is composed of a single filament, it can be used as is after drawing. When the steel cord has multiple filaments, it can be made into a steel cord having a plated layer by, for example, twisting the resulting filaments together to form a desired twist structure after drawing.

[0065] The average thickness of the plating layer is preferably 0.10 μm or more, more preferably 0.13 μm or more, and even more preferably 0.16 μm or more from the viewpoint of initial adhesion, and is preferably 0.40 μm or less, more preferably 0.35 μm or less, and even more preferably 0.30 μm or less from the viewpoint of suppressing excessive adhesion reaction.

[0066] The number E of steel cords per 50 mm width in a direction perpendicular to the longitudinal direction of the steel cord (also called ends) is not particularly limited, but is preferably 20 or more, more preferably 25 or more, even more preferably 30 or more, still more preferably 35 or more, and particularly preferably 40 or more. E is also preferably 90 or less, more preferably 80 or less, still more preferably 70 or less, still more preferably 60 or less, and particularly preferably 55 or less.

[0067] The groove area ratio of the contact surface of the inner tread, which forms the inner edge of the vehicle centered on the tire equator, is S in (%), the groove area ratio of the outer tread part on the contact surface of the vehicle's outer edge is S оut (%), |S in -S оut is preferably 2% or more, more preferably 3% or more, and even more preferably 4% or more. in -S оut is preferably 10% or less, more preferably 9% or less, and even more preferably 8% or less. in -S оut It is believed that by setting | within the above range, it is possible to improve grip performance.

[0068] S in is preferably 8% or more, more preferably 12% or more, and even more preferably 18% or more. in is preferably 45% or less, more preferably 42% or less, and even more preferably 39% or less.

[0069] S оut is preferably 5% or more, more preferably 10% or more, and even more preferably 15% or more. оut is preferably 40% or less, more preferably 37% or less, and even more preferably 34% or less.

[0070] S in is S оut Larger is preferable. S in S оut By increasing the value, the rigidity toward the outside of the vehicle becomes greater than that toward the inside of the vehicle, and the cornering force ratio (CF ratio) of the rear to the front increases, which is thought to improve linearity and grip performance.

[0071] From the viewpoint of road conformity and heat buildup of the tread rubber, the acetone extractable amount A of the rubber composition is preferably 4% by mass or more, more preferably 7% by mass or more, even more preferably 10% by mass or more, still more preferably 13% by mass or more, even more preferably 16% by mass or more, and particularly preferably 18% by mass or more. From the viewpoint of abrasion resistance, it is preferably 35% by mass or less, more preferably 33% by mass or less, even more preferably 31% by mass or less, still more preferably 29% by mass or less, and particularly preferably 27% by mass or less.

[0072] The polymer content P in the rubber composition is preferably 24% by mass or more, more preferably 26% by mass or more, even more preferably 28% by mass or more, and particularly preferably 30% by mass or more. The polymer content P in the rubber composition is preferably 37% by mass or less, more preferably 36% by mass or less, even more preferably 35% by mass or less, and particularly preferably 34% by mass or more.

[0073] Y calculated by A / P is an index representing the content of plasticizer in the rubber composition. Y is 0.50 or more, preferably 0.53 or more, more preferably 0.56 or more, and even more preferably 0.59 or more. On the other hand, the upper limit of Y is not particularly limited, but is preferably 1.0 or less, more preferably 0.95 or less, even more preferably 0.90 or less, still more preferably 0.85 or less, and particularly preferably 0.80 or less.

[0074] From the viewpoint of the effects of the present invention, Y / D is 1.6 or more, preferably 1.7 or more, more preferably 1.8 or more, even more preferably 1.9 or more, and particularly preferably 2.0 or more. On the other hand, the upper limit of Y / D is not particularly limited, but is preferably 8.0 or less, more preferably 6.0 or less, even more preferably 4.0 or less, and particularly preferably 3.0 or less.

[0075] |S in -S оut | / (Y / D) is preferably less than 5.0, more preferably less than 4.6, even more preferably less than 4.2, and particularly preferably less than 3.8. in -S оutIt is believed that by setting | / (Y / D) in the above range, the grip performance can be further improved. in -S оut | / (Y / D) is preferably greater than 0, more preferably greater than 1.0, even more preferably greater than 1.5, and particularly preferably greater than 2.0.

[0076] [Rubber composition] The rubber composition constituting the cap rubber layer according to this embodiment (hereinafter referred to as the rubber composition according to this embodiment) contains a rubber component, a liquid rubber, and a terpene resin, and can be produced using the raw materials described below. The rubber composition according to this embodiment will be described below.

[0077] <Rubber component> In the rubber composition according to the present embodiment, a diene rubber is preferably used as the rubber component. Examples of diene rubbers include isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene rubber (SIR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR). These diene rubbers may be modified rubbers treated with modifying groups capable of interacting with fillers such as carbon black and silica, or may be hydrogenated rubbers in which some of the unsaturated bonds have been hydrogenated. The diene rubbers may be used alone or in combination of two or more. Furthermore, extended rubbers that have been previously extended using a plasticizer, as described below, may also be used as the diene rubber.

[0078] The content of the diene rubber in the rubber component is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The rubber component may also consist solely of the diene rubber.

[0079] The diene rubber component is preferably at least one selected from the group consisting of isoprene rubber, SBR, and BR. The diene rubber component preferably contains SBR, and more preferably contains SBR and isoprene rubber and / or BR. The rubber component may be composed only of SBR, or may be composed only of SBR and BR, or may be composed only of SBR, BR, and isoprene rubber.

[0080] (Isoprene rubber) Examples of isoprene-based rubbers that can be used include those commonly used in the tire industry, such as isoprene rubber (IR) and natural rubber. Natural rubber includes unmodified natural rubber (NR) as well as modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), highly purified natural rubber, and grafted natural rubber. These isoprene-based rubbers may be used alone or in combination of two or more.

[0081] The NR is not particularly limited, and those commonly used in the tire industry can be used, such as SIR20, RSS#3, and TSR20.

[0082] From the viewpoint of the effects of the present invention, the content of the isoprene-based rubber 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, still more preferably 20% by mass or less, and particularly preferably 15% by mass or less. On the other hand, the lower limit of the content is not particularly limited, and can be, for example, 1% by mass or more, 3% by mass or more, or 5% by mass or more.

[0083] (SBR) The SBR is not particularly limited, but examples include unmodified solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). Modified SBRs include SBRs whose ends and / or main chains are modified, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.). Furthermore, hydrogenated products of these SBRs (hydrogenated SBRs) can also be used. These SBRs may be used alone or in combination of two or more.

[0084] The SBR according to the present embodiment may be either an extended SBR or a non-extended SBR. When an extended SBR is used, the amount of extension of the SBR, i.e., the content of the extended plasticizer contained in the SBR, is preferably 10 to 50 parts by mass per 100 parts by mass of the rubber solid content of the SBR.

[0085] As the SBR listed above, for example, commercially available products from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., ZS Elastomers Co., Ltd., etc. can be used.

[0086] The styrene content of SBR is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more. The styrene content of SBR is preferably 54% by mass or less, more preferably 52% by mass or less, even more preferably 50% by mass or less, still more preferably 46% by mass or less, and particularly preferably 42% by mass or less. The styrene content of SBR is measured by the above-mentioned measurement method.

[0087] The vinyl content of SBR is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 15 mol% or more, from the viewpoints of ensuring reactivity with silica and abrasion resistance. Furthermore, the vinyl content of SBR is preferably 45 mol% or less, more preferably 40 mol% or less, and even more preferably 35 mol% or less, from the viewpoints of breaking elongation and abrasion resistance. The vinyl content of SBR is measured by the above-mentioned measurement method.

[0088] From the viewpoint of the effects of the present invention, the weight average molecular weight (Mw) of SBR is preferably 100,000 or more, more preferably 200,000 or more, and even more preferably 300,000 or more. 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 even more preferably 1,500,000 or less. The weight average molecular weight of SBR is measured by the above-mentioned measurement method.

[0089] The content of SBR in the rubber component can be appropriately selected so that the total styrene content in the rubber component satisfies the range described below, but is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, still more preferably 70% by mass or more, and particularly preferably 75% by mass or more. On the other hand, the upper limit of the content is not particularly limited, but can be 100% by mass, 99% by mass or less, 95% by mass or less, or 90% by mass or less.

[0090] (BR) The BR is not particularly limited, and examples of the BR that can be used include those commonly used in the tire industry, such as BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare earth butadiene rubber (rare earth BR) synthesized using a rare earth catalyst, BR containing syndiotactic polybutadiene crystals (SPB-containing BR), and modified BR (high-cis modified BR, low-cis modified BR). These BRs may be used alone or in combination of two or more.

[0091] As the high-cis BR, for example, commercially available products from Zeon Corporation, UBE Corporation, JSR Corporation, etc. can be used. The inclusion of high-cis BR can improve abrasion resistance. The cis content of the high-cis BR is preferably 95 mol% or more, more preferably 96 mol% or more, and even more preferably 97 mol% or more. The cis content of BR is measured by the above-mentioned measurement method.

[0092] 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. On the other hand, the lower limit of the content is not particularly limited, and can be, for example, 1% by mass or more, 3% by mass or more, or 5% by mass or more.

[0093] From the viewpoint of the effects of the present invention, the total styrene content in the rubber component is preferably 6% by mass or more, more preferably 10% by mass or more, even more preferably 14% by mass or more, still more preferably 18% by mass or more, and particularly preferably 20% by mass or more. Also, the total styrene content in the rubber component is preferably 54% by mass or less, more preferably 52% by mass or less, even more preferably 50% by mass or less, still more preferably 46% by mass or less, and particularly preferably 42% by mass or less.

[0094] (Other rubber components) The rubber component may contain other rubber components besides the diene rubber, as long as the effects of the present invention are not affected. Examples of rubber components other than the diene rubber include crosslinkable rubber components commonly used in the tire industry, such as butyl rubber (IIR), halogenated butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber. In addition to the above rubber components, a known thermoplastic elastomer may or may not be contained. The other rubber components may be used alone, or two or more may be used in combination.

[0095] (Rubber components synthesized from recycled and biomass-derived raw materials) Monomers, which are structural units of synthetic rubbers such as IR, SBR, and BR, may be derived from underground resources such as petroleum and natural gas, or may be recycled from rubber products such as tires or non-rubber products such as polystyrene. Monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled polyisoprene, recycled butadiene, and recycled aromatic vinyl compounds. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl compounds include, but are not limited to, styrene. Among these, recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) are preferably used as raw materials.

[0096] The method for producing the recycled monomer is not particularly limited, and examples thereof include synthesis from recycled naphtha obtained by decomposing rubber products such as tires. The method for producing recycled naphtha is also not particularly limited, and examples thereof include decomposing rubber products such as tires under high temperature and pressure, decomposing with microwaves, or mechanically crushing and then extracting.

[0097] Furthermore, the monomers that are the structural units of polymers such as IR, SBR, and BR may be derived from biomass. In this specification, biomass refers to materials derived from natural resources such as plants. Examples of biomass include, but are not limited to, agricultural, forestry, and fishery products, sugar, wood chips, plant residues after useful components have been extracted, plant-derived ethanol, and biomass naphtha.

[0098] Monomers derived from biomass (biomass monomers) are not particularly limited, and examples thereof include biomass-derived butadiene and biomass-derived aromatic vinyl compounds. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl compounds include, but are not limited to, styrene. The method for producing biomass monomers is not particularly limited, and examples include biological and / or chemical and / or physical conversion of animals and plants. A representative example of biological conversion is fermentation by microorganisms, and examples of chemical and / or physical conversion include catalytic conversion, high heat conversion, high pressure conversion, electromagnetic wave conversion, critical fluid conversion, and combinations thereof.

[0099] Polymers synthesized from biomass monomer components (biomass polymers) are not particularly limited and include polybutadiene rubber synthesized from biomass-derived butadiene, aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl compounds, etc. Examples of the aromatic vinyl / butadiene copolymers include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0100] Whether a polymer's raw material is biomass-derived can be determined by its percent modern carbon (pMC) measured in accordance with ASTM D6866-10. pMC is the modern standard reference carbon. 14 of sample against C concentration 14 This is the ratio of C concentrations and is a value used as an index of the biomass ratio of a compound. The significance of this value is explained below.

[0101] 1 mole of carbon atoms (6.02 × 10 23 ) contains approximately 6.02 × 10 atoms, which is about one trillionth of the number of ordinary carbon atoms. 11 pieces 14 C exists. 14The half-life of C is 5730 years, 14 Therefore, in the case of fossil fuels such as coal, oil, and natural gas, which are thought to have been absorbed and fixed by plants and other organisms more than 226,000 years ago, carbon dioxide was included in these when they were first fixed. 14 All C elements have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas contain 14 Therefore, chemicals produced from these fossil fuels do not contain any C element. 14 It does not contain any C elements.

[0102] on the other hand, 14 C is constantly produced by cosmic rays undergoing nuclear reactions in the atmosphere. 14 The amount of C is balanced between radioactive decay and nuclear reaction, and in the Earth's atmospheric environment, 14 Therefore, the amount of carbon derived from biomass resources currently circulating in the environment is constant. 14 As mentioned above, the C concentration is approximately 1 × 10 -12 The value is approximately mol %. Therefore, the biomass ratio in a compound can be calculated by using the difference between these values.

[0103] this 14 C is typically measured using accelerator mass spectrometry based on a tandem accelerator. 13 C concentration ( 13 C / 12 C). 14 C concentration ( 14 C / 12 C) is measured. 14 The modern standard reference for the C concentration is the carbon circulating in nature as of 1950. 14The specific standard substance used is the oxalic acid standard provided by NIST (National Institute of Standards and Technology). The specific activity of carbon in this oxalic acid (per gram of carbon) is 14 The radioactivity of C is separated into carbon isotopes, 13 The standard value is the value corrected for decay from 1950 to the measurement date. 14 This is used as the C concentration value (100%). The ratio of this value to the value of the actually measured sample is the pMC value.

[0104] Therefore, if rubber is made from 100% biomass-derived materials, although there are regional differences, it will usually not reach 100 under normal conditions, so it will show a value of approximately 110 pMC. On the other hand, for chemical substances derived from petroleum and other fossil fuels, 14 When the carbon concentration is measured, it will show a value of about 0 pMC (for example, 0.3 pMC), which corresponds to the above-mentioned biomass ratio of 0%.

[0105] From the above, it is preferable in terms of environmental protection to use a material such as rubber having a high pMC value, that is, a material such as rubber having a high biomass ratio, in a rubber composition.

[0106] <Filler> The rubber composition according to the present embodiment preferably contains silica as a filler, more preferably contains silica and carbon black, and may also contain a filler consisting of only silica and carbon black.

[0107] (silica) The silica is not particularly limited, and can be, for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrated silica), or other silica commonly used in the tire industry. The raw material for silica is also not particularly limited, and can be, for example, a mineral-derived raw material such as quartz, a biological raw material such as rice husk (for example, silica made from biomass materials such as rice husk), or silica recycled from silica-containing products. Among these, hydrated silica prepared by a wet method is preferred because it contains a large number of silanol groups. These silicas can be used alone or in combination of two or more types.

[0108] Silica made from biomass materials can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then reacting the silicate with sulfuric acid in the same manner as conventional wet-process silica to produce a silicon dioxide precipitate, which is then filtered, washed with water, dried, and pulverized.

[0109] Silica recycled from silica-containing products can be, for example, silica recovered from products containing silica, such as electronic components such as semiconductors, tires, desiccants, and filtering materials such as diatomaceous earth. The recovery method is not particularly limited, and examples include thermal decomposition and decomposition by electromagnetic waves. Among these, silica recovered from electronic components such as semiconductors or tires is preferred.

[0110] When silica crystallizes, it becomes insoluble in water, and its component, silicic acid, cannot be utilized. By controlling the combustion temperature and duration, the crystallization of silica in rice husk ash can be suppressed (see, for example, JP 2009-2594 A, Akita Prefectural University Web Journal B / 2019, vol. 6, pp. 216-222). Amorphous silica extracted from rice husks can be commercially available from Wilmar, Inc.

[0111] The nitrogen adsorption specific surface area (N2SA) of silica is 90m from the viewpoint of wear resistance and elongation at break. 2 / g or more is preferable, and 100m 2 / g or more is more preferable, and 110m 2 From the viewpoint of heat buildup and processability, it is more preferable that the tensile strength is 350 m / g or more. 2 / g or less is preferable, and 300m 2 / g or less is more preferable, and 250m 2 / g or less is more preferable. The N2SA of silica is measured by the above-mentioned measuring method.

[0112] The average primary particle size of silica is preferably 26 nm or less, more preferably 24 nm or less, even more preferably 22 nm or less, and particularly preferably 20 nm or less.The lower limit of the average primary particle size 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 size of silica is measured by the above-mentioned measuring method.

[0113] When silica is contained, the content per 100 parts by mass of the rubber component is, from the viewpoint of the effects of the present invention, preferably 50 parts by mass or more, more preferably 70 parts by mass or more, even more preferably 80 parts by mass or more, still more preferably 90 parts by mass or more, particularly preferably 100 parts by mass or more, and is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, and even more preferably 130 parts by mass or less.

[0114] (carbon black) Carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. The raw material for carbon black may be a biomass material such as lignin or vegetable oil, or pyrolysis oil obtained by pyrolysis of waste tires. Carbon black may be produced by combustion, such as in a furnace process, by hydrothermal carbonization (HTC), or by pyrolysis of methane, such as in a thermal black process. Commercially available carbon blacks include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., and Columbia Carbon Co., Ltd. These carbon blacks may be used alone or in combination.

[0115] As used herein, "recycled carbon black" refers to carbon black obtained by crushing used tires or other products containing carbon black and calcining the crushed material, and refers to carbon black in which, when subjected to oxidative combustion by heating in air as measured by thermogravimetry in accordance with JIS K 6226-2:2003, the proportion of the mass of ash (ash content), which is the non-combustible component, is 13% by mass or more. In other words, the proportion of the mass (carbon content) of the recycled carbon black lost due to oxidative combustion is 87% by mass or less. Recycled carbon black is sometimes expressed as rCB.

[0116] Recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, citing "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, describes the carbon black as being obtained by pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (

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

[0004] of Japanese Patent Publication No. 6856781 (Comparison of the Surface Morphology and Chemistry of Pyrolytic Carbon Black with Commercial Carbon Black, Powder Technology 160 (2005) pp. 190-193).

[0117] Recycled carbon black may lack functional groups on its surface, or may be treated to include functional groups on its surface. Treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3,173,251, 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. Furthermore, in Japanese Patent Publication No. 6,856,781, carbon black obtained from a pyrolysis process is treated with an amino acid compound containing at least one thiol or disulfide group to obtain surface-activated carbon black. The recycled carbon black of this embodiment also includes carbon blacks treated to include functional groups on their surfaces.

[0118] As the recycled carbon black, commercially available products from Strable Green Carbon, LD Carbon, etc. can be used.

[0119] The nitrogen adsorption specific surface area (N2SA) of carbon black is 30m from the viewpoint of reinforcement. 2 / g or more is preferable, and 50m2 / g or more is more preferable, and 70m 2 / g or more is more preferable, and 90m 2 / g or more is particularly preferable. From the viewpoint of fuel economy and processability, 200m 2 / g or less is preferable, and 150m 2 / g or less is more preferable, and 120m 2 / g or less is more preferable.

[0120] The average primary particle size of carbon black is preferably 36 nm or less, more preferably 32 nm or less, even more preferably 28 nm or less, and particularly preferably 24 nm or less. There is no particular lower limit to the average primary particle size, but it is preferably 5 nm or more, more preferably 8 nm or more, and even more preferably 10 nm or more.

[0121] When carbon black is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, still more preferably 30 parts by mass or more, and particularly preferably 50 parts by mass or more, from the viewpoint of reinforcement. Also, from the viewpoint of suppressing heat buildup, the content is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, and even more preferably 130 parts by mass or less.

[0122] (Other fillers) The filler other than silica and carbon black is not particularly limited, and may be one commonly used in the tire industry, such as aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, magnesium sulfate, talc, clay, biochar, etc. These other fillers may be used alone or in combination of two or more.

[0123] From the viewpoint of the effects of the present invention, the total amount of fillers per 100 parts by mass of the rubber component is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, even more preferably 90 parts by mass or more, and particularly preferably 100 parts by mass or more, and is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, and even more preferably 130 parts by mass or less.

[0124] (Silane coupling agent) Silica is preferably used in combination with silane coupling agent.Silane coupling agent is not particularly limited, and can use any silane coupling agent that is used in combination with silica in tire industry, for example, mercapto-based silane coupling agent such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; sulfide-based silane coupling agent such as bis(3-triethoxysilylpropyl)disulfide, bis(3-triethoxysilylpropyl)tetrasulfide; 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, 3-octanoylthio-1-propyltrimethoxysilane Examples of suitable silane coupling agents include thioester-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; 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; and chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, sulfide-based silane coupling agents and / or mercapto-based silane coupling agents are preferred. Examples of suitable silane coupling agents include those commercially available from Momentive, Inc. These silane coupling agents may be used alone or in combination.

[0125] When a silane coupling agent is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, even more preferably 2.0 parts by mass or more, and particularly preferably 4.0 parts by mass or more, from the viewpoint of improving the dispersibility of silica, and 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, from the viewpoint of preventing a decrease in abrasion resistance.

[0126] <Other compounding agents> In addition to the above components, the rubber composition according to the present embodiment may contain, as appropriate, compounding agents that are generally used in the tire industry, such as plasticizers, vulcanized rubber particles (rubber powder), antioxidants, waxes, processing aids, stearic acid, zinc oxide, vulcanizing agents, and vulcanization accelerators.

[0127] In this specification, the term "plasticizer" refers to a material that imparts plasticity to a rubber component, and is a concept that includes both plasticizers that are liquid (fluid state) at 25°C and plasticizers that are solid at 25°C. Examples of plasticizers include resin components, oils, liquid rubbers, and ester-based plasticizers. These plasticizers may be derived from petroleum, biomass, or naphtha recycled from rubber or non-rubber products. Low-molecular-weight hydrocarbon components obtained by pyrolysis and extraction of used tires or products containing various components may also be used as plasticizers. These plasticizers may be used alone or in combination.

[0128] The rubber composition according to the present embodiment is characterized by containing a liquid rubber and a terpene resin as plasticizers. By using the liquid rubber and the terpene resin in combination, the compatibility of the terpene resin can make it easier to improve the dispersibility of the liquid rubber in the rubber composition.

[0129] (resin component) The rubber composition according to the present embodiment contains a terpene resin as a resin component, and may be used in combination with other resin components.

[0130] The term "terpene resin" refers to a resin containing a terpene compound, such as α-pinene, β-pinene, limonene, or dipentene, as a monomer component, and may be hydrogenated or modified. Examples of preferred terpene resins include polyterpene resins, which are polymers containing only one or more of the terpene compounds as monomer components; aromatic-modified terpene resins, which are copolymers containing the terpene compound and an aromatic compound as monomer components; and terpene phenolic resins, which are copolymers containing the terpene compound and a phenolic compound as monomer components. Examples of aromatic compounds that serve as monomer components for aromatic-modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenolic compounds that serve as monomer components for terpene phenolic resins include phenol, bisphenol A, cresol, and xylenol. Examples of commercially available terpene resins available from Yasuhara Chemical Co., Ltd., Arakawa Chemical Industries, Ltd., and Nippon Terpene Chemical Co., Ltd. may be used. These terpene resins may be used alone or in combination.

[0131] The resin components other than the terpene resin are not particularly limited, but resin components commonly used in the tire industry can be used, such as adhesive resins such as dicyclopentadiene resins, aromatic vinyl resins, C9 resins, C5 resins, C5C9 resins, rosin resins, and phenolic resins. These resin components may be used alone or in combination of two or more. Each resin component may also be used alone or in combination of two or more.

[0132] The term "dicyclopentadiene-based resin" refers to a resin containing cyclopentadiene (CPD) and / or dicyclopentadiene (DCPD) as the monomer component with the highest content, and may be a hydrogenated or modified resin. Preferred examples of dicyclopentadiene-based resins include polymers obtained by polymerizing only dicyclopentadiene as a monomer, and copolymers obtained by copolymerizing dicyclopentadiene with the C9 fraction (DCPD / C9 resin). Examples of dicyclopentadiene-based resins that can be used include commercially available products from ExxonMobil Corporation, ENEOS Corporation, Nippon Zeon Co., Ltd., Maruzen Petrochemical Co., Ltd., and the like.

[0133] The term "C9 resin" refers to a resin obtained by polymerizing a C9 fraction. It may be a polymer obtained by polymerizing a C9 fraction alone, or a copolymer obtained by copolymerizing a C9 fraction with other components. For example, a resin obtained by copolymerizing dicyclopentadiene (DCPD) with a C9 fraction is called a DCPD / C9 resin. The C9 resin may also be a hydrogenated or modified version of the above. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene. Examples of C9 resins that can be used include commercially available C9 resins from BASF, Zeon Corporation, ENEOS Corporation, and the like.

[0134] "C5 resin" refers to a resin obtained by polymerizing a C5 fraction, and may be a hydrogenated or modified C5 resin. Examples of C5 fractions other than dicyclopentadiene include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, isoprene, piperylene, 2-methyl-1-butene, 2-methyl-2-butene, and 1-pentene. As the C5 resin, commercially available products from, for example, Struktol Corporation, Zeon Corporation, and ENEOS Corporation can be used.

[0135] The term "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. Examples of C5C9 petroleum resins that can be used include those commercially available from Tosoh Corporation, Luhua, and the like.

[0136] The term "aromatic vinyl resin" refers to a resin containing an aromatic vinyl compound such as styrene, α-methylstyrene, vinyltoluene, or p-chlorostyrene as the monomer component with the highest content, and may be a hydrogenated or modified version of such a resin. As the aromatic vinyl resin, 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, because they are economical, easy to process, and have excellent heat generation properties. As the aromatic vinyl resin, commercially available products available from Kraton, Eastman Chemical, Mitsui Chemicals, Inc., etc., can be used.

[0137] The term "rosin-based resin" refers to a resin containing a rosin acid compound such as abietic acid, neoabietic acid, palustric acid, or isopimaric acid, and may be hydrogenated or modified. Examples of rosin-based resins include, but are not limited to, natural rosin resins and rosin-modified resins obtained by modifying natural rosin resins by hydrogenation, disproportionation, dimerization, esterification, or the like. Examples of rosin-based resins that can be used include commercially available rosin resins from Harima Chemical Industries, Ltd., Arakawa Chemical Industries, Ltd., and Airec Corporation.

[0138] The term "phenolic resin" refers to a resin containing a phenolic compound such as phenol or cresol as a monomer component, and may be hydrogenated or modified. Examples of phenolic resins include, but are not limited to, phenol-formaldehyde resin, alkylphenol-formaldehyde resin, alkylphenol-acetylene resin, oil-modified phenol-formaldehyde resin, and terpene-phenol resin. Examples of phenolic resins that can be used include commercially available resins from Sumitomo Bakelite Co., Ltd., DIC Corporation, Asahi Organic Materials Co., Ltd., and the like.

[0139] The softening point of the resin component is preferably 35° C. or higher, more preferably 50° C. or higher, and even more preferably 65° C. or higher. From the viewpoint of processability and improving the dispersibility of the rubber component and the filler, the softening point 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 adhesive resin is measured by the above-mentioned measurement method.

[0140] The amount of the terpene resin per 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more. From the viewpoint of suppressing heat buildup, the amount 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 35 parts by mass or less.

[0141] From the viewpoint of the effects of the present invention, the total content of the resin components per 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more. From the viewpoint of suppressing heat buildup, the total content 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 35 parts by mass or less.

[0142] The liquid rubber is not particularly limited as long as it is a polymer that is in a liquid state at 25° C., and examples thereof include 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. These liquid rubbers may be used alone or in combination of two or more.

[0143] The weight average molecular weight (Mw) of the liquid rubber is usually less than 10,000, preferably 9,000 or less, more preferably 6,000 or less, and even more preferably 4,500 or less. The Mw of the liquid rubber is preferably 100 or more, more preferably 500 or more, even more preferably 1,000 or more, and particularly preferably 2,000 or more. When the Mw of the liquid rubber is within the above range, the effects of the present invention tend to be more favorably obtained. In this specification, the liquid rubber is not included in the above rubber component.

[0144] From the viewpoint of the effects of the present invention, the content of the liquid rubber per 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, still more preferably 7 parts by mass or more, and particularly preferably 10 parts by mass or more. The content is also preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass or less.

[0145] The proportion of the liquid rubber relative to the total content of the liquid rubber and the terpene resin in the rubber composition is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and particularly preferably 20% by mass or more. The proportion of the liquid rubber relative to the total content of the liquid rubber and the terpene resin in the rubber composition is preferably 80% by mass or less, more preferably 67% by mass or less, even more preferably 55% by mass or less, even more preferably 50% by mass or less, and particularly preferably 45% by mass or less.

[0146] Examples of oils include mineral oil, vegetable oil, and animal oil. From the viewpoint of life cycle assessment, waste oils used in rubber mixers and engines, and refined waste cooking oils used in restaurants may also be used. One type of oil may be used alone, or two or more types may be used in combination.

[0147] As used herein, 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, and aromatic oil. Specific examples of mineral oil include mild extracted solvate (MES), distillate aromatic extract (DAE), treated distillate aromatic extract (TDAE), treated residual aromatic extract (TRAE), and residual aromatic extract (RAE). Furthermore, oils with a low content of polycyclic aromatic compounds (PCA) can also be used as an environmentally friendly measure. Examples of low PCA oils include MES, TDAE, and heavy naphthenic oil. Mineral oils may be used singly or in combination.

[0148] As used herein, examples of vegetable oils include linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grapeseed oil, and Japan wax. Further examples of vegetable oils include refined oils (such as salad oil) obtained by refining the above oils, interesterified oils obtained by interesterifying the above oils, hardened 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 edible oils recovered from edible oils and the like. Vegetable oils may be liquid or solid at 25°C. One vegetable oil may be used alone, or two or more may be used in combination.

[0149] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxyl group of glycerin is esterified with a fatty acid. The acylglycerol is not particularly limited and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Furthermore, the acylglycerol may be a monomer, a dimer, or a polymer (trimer or higher). Dimer or higher acylglycerols can be obtained by thermal polymerization, oxidative polymerization, or the like. The acylglycerol may be liquid or solid at 25°C.

[0150] The method for confirming whether the rubber composition contains the acylglycerol is not particularly limited, but may be any of the following: 1 For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at 25°C for 24 hours, and after removing the rubber composition, the 1 When H-NMR was measured, signals were observed around 5.26 ppm, 4.28 ppm, and 4.15 ppm when the signal of tetramethylsilane (TMS) was set at 0.00 ppm. These signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atoms of the ester group. In this paragraph, "around" refers to a range of ±0.10 ppm.

[0151] The fatty acid is not particularly limited and may be either an unsaturated fatty acid or a saturated fatty acid. Examples of unsaturated fatty acids include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of saturated fatty acids include butyric acid and lauric acid.

[0152] Among these, it is desirable that the fatty acid contains a fatty acid with few double bonds, i.e., saturated fatty acid or monounsaturated fatty acid, and oleic acid is preferred. As a vegetable oil containing such a fatty acid, for example, vegetable oil containing saturated fatty acid or monounsaturated fatty acid may be used, or vegetable oil modified by ester exchange or the like may be used. Furthermore, in order to produce vegetable oil containing such a fatty acid, plants may be improved by breeding, genetic modification, genome editing, or the like.

[0153] As the vegetable oil, for example, commercially available products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoi Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., Fuji Kosan Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0154] Examples of animal oils include fish oil, beef tallow, whale oil, and oleyl alcohol derived from these.

[0155] When oil is contained, the content per 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 30 parts by mass or more, from the viewpoint of the effects of the present invention. The content is preferably 90 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 70 parts by mass or less, and particularly preferably 60 parts by mass or less.

[0156] Examples of ester-based plasticizers include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), 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), and trixylenyl phosphate (TXP). One type of ester-based plasticizer may be used alone, or two or more types may be used in combination.

[0157] The amount of plasticizer per 100 parts by mass of the rubber component (the total amount when multiple plasticizers are used in combination) is, from the viewpoint of the effects of the present invention, preferably 30 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 50 parts by mass or more, and particularly preferably 60 parts by mass or more. The amount is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and even more preferably 80 parts by mass or less.

[0158] The vulcanized rubber particles are particles made of vulcanized rubber, and specifically, rubber powder as specified in JIS K 6316:2017 can be used. From the standpoint of environmental considerations and cost, recycled rubber powder produced from crushed waste tires is preferred. One type of vulcanized rubber particle may be used alone, or two or more types may be used in combination.

[0159] The vulcanized rubber particles are not particularly limited, and may be unmodified vulcanized rubber particles or modified vulcanized rubber particles.

[0160] As commercially available vulcanized rubber, for example, products from Lehigh, Muraoka Rubber Industries, Ltd., etc. can be used.

[0161] The antioxidant is not particularly limited, and examples thereof include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), and N,N'-ditolyl-p-phenylenediamine. p-phenylenediamine antioxidants such as N-isopropyl-N'-phenyl-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferred, and polymers of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. Commercially available products include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis, and the like. These antioxidants may be used alone or in combination of two or more.

[0162] When an antioxidant is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of ozone crack resistance of the rubber, and is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, from the viewpoint of abrasion resistance.

[0163] The wax is not particularly limited, and any wax commonly used in the tire industry can be suitably used, such as mineral waxes and plant-derived waxes. 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 these, mineral waxes are preferred. Examples of plant-derived waxes include rice wax, carnauba wax, and candelilla wax. Examples of mineral waxes include paraffin wax, microcrystalline wax, and selected special waxes thereof, with paraffin wax being preferred. The wax according to this embodiment does not contain stearic acid. Waxes commercially available from, for example, Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., Ltd., etc. can be used. One type of wax may be used alone, or two or more types may be used in combination.

[0164] When the wax is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, and more preferably 0.8 parts by mass or more, from the viewpoint of weather resistance of the rubber, and is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less, from the viewpoint of preventing whitening of the tire due to bloom.

[0165] Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. Examples of processing aids that can be used include those commercially available from Schill + Seilacher, Performance Additives, etc. These processing aids may be used alone or in combination of two or more.

[0166] When stearic acid is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less from the viewpoint of vulcanization rate.

[0167] When zinc oxide is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, from the viewpoint of abrasion resistance.

[0168] As the vulcanizing agent, sulfur is preferably used, and examples of sulfur that can be used include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

[0169] When sulfur is contained as a vulcanizing agent, the content per 100 parts by mass of the rubber component is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, from the viewpoint of ensuring a sufficient vulcanization reaction. Furthermore, from the viewpoint of preventing deterioration, the content is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, even more preferably 3.0 parts by mass or less, and particularly preferably 2.5 parts by mass or less. When oil-containing sulfur is used as the vulcanizing agent, the content of the vulcanizing agent is the total content of pure sulfur contained in the oil-containing sulfur.

[0170] Known organic crosslinking agents can also be used as vulcanizing agents other than sulfur. The organic crosslinking agent is not particularly limited as long as it can form crosslinked chains other than polysulfide bonds. Examples of the organic crosslinking agent include alkylphenol-sulfur chloride condensate, sodium hexamethylene-1,6-bisthiosulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, and dicumyl peroxide. These organic crosslinking agents can be commercially available from Taoka Chemical Co., Ltd., Lanxess K.K., Flexis, and other companies.

[0171] The vulcanization accelerator is not particularly limited, but examples thereof include sulfenamide vulcanization accelerators, thiazole vulcanization accelerators, guanidine vulcanization accelerators, thiuram vulcanization accelerators, thiourea vulcanization accelerators, dithiocarbamate vulcanization accelerators, aldehyde-amine vulcanization accelerators, aldehyde-ammonia vulcanization accelerators, imidazoline vulcanization accelerators, xanthate vulcanization accelerators, and caprolactam disulfide. These vulcanization accelerators may be used alone or in combination of two or more. Among them, one or more vulcanization accelerators selected from the group consisting of sulfenamide vulcanization accelerators, thiazole vulcanization accelerators, and guanidine vulcanization accelerators are preferred, as they more suitably achieve the desired effects.

[0172] Examples of sulfenamide vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), and N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS).

[0173] Examples of thiazole vulcanization accelerators include 2-mercaptobenzothiazole (MBT) or its salt, di-2-benzothiazolyl disulfide (MBTS), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio)benzothiazole, etc. Among these, MBTS and MBT are preferred, and MBTS is more preferred.

[0174] Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine. Among these, DPG is preferred. However, when the rubber composition constituting the topping rubber contains a guanidine-based vulcanization accelerator, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or less, more preferably 0.3 parts by mass or less, and even more preferably 0.1 parts by mass or less, from the viewpoint of the effects of the present invention. It is particularly preferred that the rubber composition does not contain a guanidine-based vulcanization accelerator.

[0175] When a vulcanization accelerator is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of ensuring a sufficient vulcanization rate. Moreover, the content of the vulcanization accelerator is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, from the viewpoint of suppressing blooming.

[0176] In this specification, various materials containing carbon atoms (for example, rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from atmospheric carbon dioxide. As a method for obtaining such various materials from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process in which methane is synthesized from carbon dioxide may be converted.

[0177] [Production of rubber composition and tire] The rubber composition according to the present embodiment can be produced by a known method, for example, by kneading the above-described components using a rubber kneading device such as an open roll or an internal kneader (such as a Banbury mixer or a kneader).

[0178] The kneading step includes, for example, a base kneading step in which compounding ingredients and additives other than the vulcanizing agent and vulcanization accelerator are kneaded, and a final kneading (F kneading) step in which the vulcanizing agent and vulcanization accelerator are added to the kneaded product obtained in the base kneading step and kneaded. Furthermore, the base kneading step can be divided into multiple steps as desired.

[0179] The kneading conditions are not particularly limited, but examples include a method in which the base kneading step involves kneading for 3 to 10 minutes at a discharge temperature of 150 to 170°C, and in the final kneading step, kneading for 1 to 5 minutes at 70 to 110°C.

[0180] The tires according to the present embodiment can be manufactured by a conventional method using the corresponding rubber compositions. That is, a steel cord is coated with an unvulcanized rubber composition corresponding to the belt topping rubber, and the ply forming the belt layer is obtained as a steel cord-rubber composite. The unvulcanized rubber composition corresponding to the cap rubber layer obtained by the above method is molded to match the shape of the cap rubber layer. These are laminated together with other tire components on a tire building machine and molded by a conventional method to form an unvulcanized tire. A tire can be manufactured by heating and pressurizing this unvulcanized tire in a vulcanizer. The vulcanization conditions are not particularly limited, and examples include a method of vulcanizing at 150 to 200°C for 10 to 30 minutes.

[0181] <Application> The tire according to the present embodiment can be a general-purpose tire such as a passenger car tire, a truck / bus tire, or a motorcycle tire, or can be a racing tire. Passenger car tires are tires designed to be mounted on four-wheeled vehicles and have a maximum load capacity of 1000 kg or less. The type of tire is not particularly limited, and can be either a pneumatic tire or a solid tire. The tire according to the present embodiment can also be used as an all-season tire, a summer tire, or a winter tire such as a studless tire. [Example]

[0182] The following examples (working examples) are considered to be preferable for carrying out the present invention, but the scope of the present invention is not limited to these examples. Using the various chemicals shown below, tires having a cap layer obtained according to the formulations shown in Tables 1 and 2 and a belt layer having steel cords shown in Tables 1 and 2 were examined, and the results calculated based on the following evaluation method are shown in Tables 1 and 2.

[0183] The various chemicals used in the examples and comparative examples are listed below. NR:TSR20 SBR1: SBR1502 manufactured by JSR Corporation (unmodified E-SBR, styrene content: 23.5% by mass, vinyl content: 18% by mole, Mw: 420,000) SBR2: SLR6430 manufactured by TRINSEO (S-SBR, styrene content: 40% by mass, vinyl content: 24% by mole, Mw: 1.01 million, oil-extended product containing 37.5 parts by weight of oil per 100 parts by weight of rubber component) BR: UBEPOL BR (registered trademark) 150B (unmodified BR, cis content: 97 mol%, Mw: 440,000) manufactured by UBE Corporation Carbon black 1: Show Black N330 (N2SA: 75 ml) manufactured by Cabot Japan Co., Ltd. 2 / g, average primary particle diameter: 30nm) Carbon black 2: Show Black N220 (N2SA: 115m) manufactured by Cabot Japan Co., Ltd. 2 / g, average primary particle diameter: 22nm) Silica 1: Zeosil 1115MP (N2SA:115m) manufactured by Solvay 2 / g, average primary particle diameter: 24nm) Silica 2: ZEOSIL 115GR (N2SA:115m) manufactured by Solvay 2 / g, average primary particle diameter: 20nm) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Industries Liquid rubber 1: Ricon 142 (liquid BR) manufactured by Cray Valley Liquid rubber 2: Ricon 100 (liquid SBR) manufactured by Cray Valley Resin component 1: YS Resin TO-125 (aromatic modified terpene resin, softening point: 125°C) manufactured by Yasuhara Chemical Co., Ltd. Resin component 2: Sylvares SA85 manufactured by Kraton (copolymer of α-methylstyrene and styrene, softening point: 85°C) Oil: H&R VivaTec 500 (TDAE oil) Anti-aging agent: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Wax: Sunnock N (paraffin wax) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: Camellia stearic acid beads manufactured by NOF Corporation Zinc oxide: Zinc oxide type 2 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd. (5% oil-containing powdered sulfur) Vulcanization accelerator 1: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccelaer D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0184] (Production of belt layer) The steel cords shown in Tables 1 and 2 are coated with an unvulcanized rubber composition corresponding to the belt topping rubber, and a ply forming a belt layer is obtained as a steel cord-rubber composite.

[0185] (Tire manufacturing) According to the compounding recipes shown in Tables 1 and 2, a 1.7 L closed-type Banbury mixer is used to knead the chemicals other than sulfur and vulcanization accelerator for 5 minutes until the discharge temperature reaches 160°C, and a kneaded mixture is obtained. Next, a vulcanizing agent and vulcanization accelerator are added to the kneaded mixture using a two-screw open roll, and the mixture is kneaded for 4 minutes until the temperature reaches 105°C, and an unvulcanized rubber composition is obtained. The unvulcanized rubber composition obtained is molded to fit the shape of the cap rubber layer, and laminated together with the belt ply and other tire components to prepare an unvulcanized tire, which is then vulcanized at 170°C to prepare each test tire (size: 205 / 65R15, rim: 15x6JJ, internal pressure: 230 kPa, S in :38%, S оut :31%). Here, the steel cords used in the belt layer are ternary plated steel cords with an average plating layer thickness of 0.19 μm and a plating layer composition of 68 mass % Cu, 28 mass % Zn, and 4 mass % Co. In the steel cord configuration in the table, "1x2 45e" means that there are 45 1x2 structure steel cords per 50 mm width in the direction perpendicular to the longitudinal direction of the steel cord (45 ends).

[0186] <Measurement of acetone extractables (AE amount)> The AE amount is measured for each rubber test piece cut out from the cap rubber layer of each test tire. In accordance with JIS K 6229:2015, each rubber test piece is immersed in acetone for 72 hours to extract the soluble components, and the mass of each rubber test piece is measured before and after extraction, and the AE amount is calculated using the following formula. (Amount of acetone extracted (mass%)) = {(mass of rubber test piece before extraction - mass of rubber test piece after extraction) / (mass of rubber test piece before extraction)} × 100

[0187] <Measurement of polymer amount> The rubber test pieces after the acetone extraction are subjected to thermal decomposition in a nitrogen stream by heating from room temperature to 750°C at a rate of 10°C / min using a thermogravimetric method in accordance with JIS K 6226-1:2003, and the masses of the rubber test pieces before and after thermal decomposition are measured, and the polymer amount is calculated using the following formula. (Polymer amount (mass%)) = {(mass of rubber test piece before pyrolysis - mass of rubber test piece after pyrolysis) / (mass of rubber test piece before pyrolysis)} × 100

[0188] <Grip performance when cornering> The test tires were fitted to all wheels of a domestically produced FR vehicle (2000cc), and the vehicle was driven 10 laps on a test course with a dry asphalt surface. While driving in a straight line at 100 km / h, the test driver sensorily evaluated the stability of control when braking and entering a corner. The evaluation was performed using an integer value of 1 to 5, with a higher score indicating better control stability during steering. The total score of the 20 test drivers was calculated based on this evaluation standard. The total score of each reference and comparative example was converted to a reference value (100), and the evaluation results of each test tire were displayed as an index proportional to the total score. A higher value indicates better grip performance during cornering.

[0189] [Table 1]

[0190] [Table 2]

[0191] <Embodiment> Examples of embodiments of the present invention are given below.

[0192] [1] A tire having a tread portion and a belt layer, wherein the tread portion has at least one rubber layer, and a cap rubber layer constituting the tread surface of the tread portion is made of a rubber composition containing a rubber component, a liquid rubber, and a terpene-based resin, and the belt layer has a steel cord consisting of 1 to 4 filaments, and the outer diameter D of the filament is 0.45 mm or less (preferably 0.10 mm or more and 0.42 mm or less), and when Y=A / P is defined as A (mass%) and P (mass%), where A is the amount of acetone extractable from the rubber composition and P is the amount of polymer in the rubber composition, Y is 0.50 or more (preferably 0.53 or more, more preferably 0.56 or more and 1.0 or less), and Y / D is 1.6 or more (preferably 2.0 or more and 8.0 or less). [2] The tire according to the above [1], wherein the rubber component contains 50% by mass or more (preferably 60% by mass or more, more preferably 70% by mass or more) of styrene-butadiene rubber. [3] The tire according to the above [1] or [2], wherein the rubber composition contains 80 parts by mass or more (preferably 100 parts by mass or more) of silica per 100 parts by mass of the rubber component. [4] The tire according to any one of the above [1] to [3], wherein the rubber composition contains silica having an average primary particle diameter of 20 nm or less. [5] The tire according to any one of the above [1] to [4], wherein the total amount of styrene in the rubber component is 20% by mass or more. [6] The tire according to any one of the above [1] to [5], wherein the steel cord has a 1x1 structure. [7] The tire according to any one of the above [1] to [5], wherein the steel cord has a 1x4 structure. [8] The tire according to any one of the above [1] to [7], wherein the number of the steel cords arranged per 50 mm in the tire width direction is 20 or more and 60 or less (preferably 25 or more and 55 or less). [9] The tire according to any one of the above [1] to [8], wherein the steel cord has a ternary plating layer made of copper, zinc, and cobalt.

[10] The groove area ratio of the contact surface of the inner tread portion, which forms the inner end side of the vehicle centered on the tire equator, is Sin (%), the groove area ratio of the outer tread part on the contact surface of the vehicle's outer edge is S оut (%), |S in -S оut The tire according to any one of the above [1] to [9], wherein | / (Y / D) is greater than 0 and less than 5.0 (preferably greater than 1.0 and less than 4.6). [Explanation of symbols]

[0193] 11. Tires 12 Tread section 13 Sidewall 14 Bead section 15···Inner liner 16. Carcass 17. Belt layer 18 Bead core 21, 50... Steel cord 22 Topping rubber 51... Filament CL···Center Line

Claims

1. A tire having a tread portion and a belt layer, The tread portion has at least one rubber layer, a cap rubber layer constituting a tread surface of the tread portion is made of a rubber composition containing a rubber component, a liquid rubber, and a terpene resin; The belt layer has a steel cord consisting of 1 to 4 filaments, The outer diameter D of the filament is 0.45 mm or less, The amount of acetone extractable from the rubber composition is A (mass%), and the amount of polymer in the rubber composition is P (mass%). Y = A / P When we define A tire in which Y is 0.50 or more and Y / D is 1.6 or more.

2. The tire according to claim 1, wherein the rubber component contains 50% by mass or more of styrene-butadiene rubber.

3. The tire according to claim 1 or 2, wherein the rubber composition contains 80 parts by mass or more of silica per 100 parts by mass of the rubber component.

4. The tire according to claim 1 or 2, wherein the rubber composition contains silica having an average primary particle diameter of 20 nm or less.

5. The tire according to claim 1 or 2, wherein the total amount of styrene in the rubber component is 20% by mass or more.

6. 3. The tire of claim 1, wherein the steel cords have a 1x1 construction.

7. 3. The tire of claim 1, wherein the steel cords have a 1x4 construction.

8. The tire according to claim 1 or 2, wherein the number of the steel cords arranged per 50 mm in the tire width direction is 20 or more and 60 or less.

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

10. The groove area ratio of the contact surface of the inner tread portion that forms the vehicle inner end side centered on the tire equator is S in (%), and the groove area ratio of the contact surface of the outer tread portion that constitutes the outer end side of the vehicle is S оut (%), |S in -S оut The tire according to claim 1 or 2, wherein | / (Y / D) is greater than 0 and less than 5.0.

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