tire

Abstract

To provide a tire that can improve the overall performance of handling stability and wet grip performance. [Solution] A tire comprising a tread portion and a belt layer, wherein the tread portion is composed of a rubber composition containing a rubber component including styrene-butadiene rubber and / or isoprene-based rubber, and a copolymer resin containing styrene and cyclopentadiene as monomer components, and the belt layer has metal cords consisting of one to four filaments, the outer diameter of the filaments being D (mm), and the total amount of styrene in the rubber composition when the mass of the rubber component is 100% by mass being S (mass%), wherein D × S is greater than 2.0.

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Hitherto, various methods for improving handling stability and wet grip performance have been studied (see, for example, Patent Documents 1 and 2). However, in recent years, further improvement in these performances has been demanded.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a tire capable of improving the overall performance of handling stability and wet grip performance.

Means for Solving the Problems

[0005] The present invention relates to a tire including a tread portion and a belt layer, wherein the tread portion is composed of a rubber composition containing a rubber component containing styrene-butadiene rubber and / or isoprene rubber, and a copolymer resin containing styrene and cyclopentadiene as monomer components, the belt layer has a metal cord composed of one or more and four or less filaments, and when the outer diameter of the filament is D (mm) and the total styrene amount in the rubber composition is S (mass%) when the mass of the rubber component in the rubber composition is 100 mass%, a tire in which D×S is more than 2.0.

Effects of the Invention

[0006] According to the present invention, there is provided a tire capable of improving the overall performance of handling stability performance and wet grip performance.

Brief Description of the Drawings

[0007] [Figure 1] It is a cross-sectional view of a tire according to an embodiment of the present invention. [Figure 2] It is a diagram schematically showing a belt layer. [Figure 3] It is an explanatory diagram of a configuration example of a single-twist metal cord.

Mode for Carrying Out the Invention

[0008] A tire according to an embodiment of the present invention is a tire provided with a tread portion and a belt layer, wherein the tread portion is composed of a rubber composition containing a rubber component containing styrene-butadiene rubber and / or isoprene-based rubber, and a copolymer resin containing styrene and cyclopentadiene as monomer components, and the belt layer has a metal cord composed of one or more and four or less filaments. When the outer diameter of the filament is D (mm) and the total styrene amount in the rubber composition is S (mass%) when the mass of the rubber component in the rubber composition is 100 mass%, it is a tire in which D × S is more than 2.0.

[0009] Although not intended to be bound by theory, in the tire of the present invention, as a mechanism for improving the overall performance of handling stability performance and wet grip performance, for example, it can be considered as follows.

[0010] (1) It is considered that a scraping effect on the road surface is obtained because the rubber composition constituting the tread portion contains a domain derived from the styrene portion.

[0011] (2) Copolymer resins containing styrene and cyclopentadiene as monomer components have high compatibility with styrene-butadiene rubber and isoprene-based rubber, and are bulky. Therefore, rubber compositions containing these resins are given flexibility without impairing the reinforcing effect. For this reason, tires using this resin in the tread can continue to generate energy loss even when repeatedly starting and stopping, and are therefore thought to contribute to improved wet grip performance.

[0012] (3) By using metal cords with a large outer diameter filament in the belt layer, the shear stiffness of the tire is increased, and the response to lateral forces is improved. From this, it is thought that by making the product of the outer diameter D of the filament and the total amount of styrene S in the rubber composition (D × S) larger than a predetermined value, it is possible to improve handling stability while exhibiting high wet grip performance.

[0013] It is believed that the combined efforts of (1), (2), and (3) above will achieve a remarkable effect: a synergistic improvement in handling stability and wet grip performance.

[0014] The aforementioned metal cord is preferably made of a single filament because the cord is easily deformed.

[0015] When Y (parts by mass) is the silica content in the rubber composition relative to 100 parts by mass of the rubber component, it is preferable that D × Y is greater than 16. It is believed that setting D × Y within the above range improves the balance between handling stability and wet grip performance.

[0016] From the viewpoint of the effects of the present invention, the content of the copolymer resin in the rubber composition relative to 100 parts by mass of the rubber component is preferably 10 parts by mass or more.

[0017] From the viewpoint of the effects of the present invention, the rubber component preferably includes styrene-butadiene rubber and isoprene-based rubber.

[0018] The total styrene content S in the rubber composition is preferably 8.0% by mass or more. By setting S within the above range, it is believed that the tread portion that follows the road surface generates heat efficiently.

[0019] From the viewpoint of the effects of the present invention, the rubber component preferably contains 40% by mass or more of styrene-butadiene rubber.

[0020] From the viewpoint of the effects of the present invention, the average primary particle size of the silica contained in the rubber composition is preferably less than 17 nm.

[0021] The silica content Y in the rubber composition is preferably 80 parts by mass or more per 100 parts by mass of the rubber component. It is believed that the silica content of 80 parts by mass or more improves road surface conformability through interaction between the silanol groups of silica and moisture on the road surface, thereby contributing to improved wet grip performance.

[0022] From the viewpoint of reinforcing properties and heat generation, the rubber composition preferably contains 1 to 25 parts by mass of carbon black per 100 parts by mass of the rubber component.

[0023] <Definition> The "tread portion" is a component that includes the part that forms the contact surface of the tire, and in a cross-section of the tire with a plane including the tire rotation axis, if the tire has components that form the tire skeleton using steel or textile materials such as belt layers, belt reinforcement layers, and carcasses, the tread portion is a component that is positioned radially outward from these components.

[0024] The "belt layer" is a layer located radially outside the carcass of the tire. It includes multiple working layers in which the internal reinforcing material is tilted at an angle of approximately 18-30° with respect to the tire's circumferential direction and overlaps in opposite directions, as well as circumferential belt layers in which the internal reinforcing material is oriented at an angle of ±10° with respect to the tire's circumferential direction.

[0025] "Standard condition" refers to a state of no load where the tire is mounted on a standard rim and filled with air at the standard internal pressure. Unless otherwise specified, tires in the standard condition should be used.

[0026] Unless otherwise specified, the "dimensions of each part of the tire" refer to values ​​that are determined in the normal state for those visible on the outer surface of the tire, while those located inside the tire or on the cut surface of the tire refer to values ​​that are determined, for example, by cutting the tire in a plane including the tire's axis of rotation and holding the cut tire piece within the rim width of the normal rim.

[0027] A "standard rim" refers to the rim specified for each tire within the standards system that the tire is based on. 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 Organisation), 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." Refer to JATMA, ETRTO, and TRA in that order, and if an applicable size is available at the time of reference, follow that standard. In the case of a tire not specified in the above standards, it refers to the narrowest rim width among the smallest diameter rims that can be mounted on that tire and that can maintain internal pressure (i.e., do not cause air leakage between the rim and tire).

[0028] "Regular internal pressure" refers to the air pressure specified for each tire in the standards system, including the standard on which the tire is based. For example, for JATMA it refers to "maximum air pressure," for ETRTO it refers to "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 if there is an applicable size at the time of reference, follow that standard. In the case of tires not specified in the above standards, it refers to the regular internal pressure (but at least 250kPa) of another tire size (but specified in the standard) that is listed with the aforementioned regular rim as the standard rim. If multiple regular internal pressures of 250kPa or higher are listed, refer to the lowest value among them.

[0029] "Regular load (kg)" refers to the load specified for each tire in the standard system that the tire is based on. For example, for JATMA it is "Maximum Load Capacity," for ETRTO it is "LOAD CAPACITY," and for TRA it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." As with regular rims and regular in-tire pressure, refer to JATMA, ETRTO, and TRA in that order, and if an applicable size is available at the time of reference, follow that standard. For tires not specified in the above standards, the maximum load capacity (kg) is calculated separately. L This is considered the normal load.

[0030] "Maximum load capacity W L The weight (kg) is calculated using the following formula: "V" is the virtual volume of the tire (mm²). 3), "Dt" is the outer diameter of the tire in the normal state (mm), "Ht" is the height of the tire's cross-section in the radial direction in a plane containing the tire's axis of rotation (mm), and "Wt" is the width of the tire's cross-section in the normal state (mm). Ht can be calculated by (Dt-R) / 2, where R is the rim diameter of the tire. Wt is the value obtained by removing any patterns or letters on the tire's sidewall. Note that the maximum load capacity is synonymous with the normal load mentioned above.

number

[0031] "Rubber components of a rubber composition" refer to components that contribute to crosslinking within a rubber composition, and generally have a weight-average molecular weight (Mw) of 10,000 or more.

[0032] A "plasticizer" is a material that imparts plasticity to rubber components and is extracted from rubber compositions using acetone. This definition includes both liquid plasticizers at 25°C and solid plasticizers at 25°C. However, it excludes waxes and stearic acid commonly used in the tire industry.

[0033] "Plasticizer content" includes the amount of plasticizer contained in the extensible rubber component that has been pre-stretched with plasticizers such as oil, resin components, and liquid rubber components. The same applies to the oil content, resin component content, and liquid rubber content; for example, if the extensible component is oil, the extensible oil is included in the oil content.

[0034] <Measurement method> "Styrene content" can be determined by pyrolysis gas chromatography or NMR measurement. 1 H-NMR and 13It is calculated by (13)C-NMR. Component amounts such as "styrene content" are different from physical property values such as complex elastic modulus (E*), and there are true values that do not depend on the measurement method. Therefore, it is preferable to use a measurement method with as high precision as possible. In this specification, "thermal decomposition gas chromatography" refers to a method in which a sample is heated by a thermal decomposition device, individual components contained in the gas-phase components generated by this heating are separated by a separation column, and each isolated component is analyzed. The styrene content is applied, for example, to rubber components having repeating units (styrene units) derived from styrene such as SBR.

[0035] The "vinyl content (amount of 1,2-bonded butadiene units)" is determined by thermal decomposition gas chromatography or NMR measurement ( 1 1H-NMR and 13 13C-NMR). Similar to the "styrene content", since there is a true value that does not depend on the measurement method for the "vinyl content", it is preferable to use a measurement method with as high precision as possible. The vinyl content is applied, for example, to rubber components having repeating units derived from butadiene such as SBR and BR.

[0036] The "cis content (amount of cis-1,4-bonded butadiene units)" is a value measured by infrared absorption spectrometry or NMR measurement ( 1 1H-NMR and 13 13C-NMR) in accordance with JIS K 6239-2:2017, and is applied, for example, to rubber components having repeating units derived from butadiene such as BR. Similar to the "styrene content", since there is a true value that does not depend on the measurement method for the "cis content", it is preferable to use a measurement method with as high precision as possible.

[0037] The "total styrene amount S in the rubber composition" is the total styrene amount (mass %) in the rubber composition when the mass of the rubber component is 100 mass %, and is the total amount of the styrene portion contained in the rubber component and the styrene portion contained in the compounding agent other than the rubber component. The styrene portion is not particularly limited as long as it is a group having a styrene structure, and examples thereof include styrene, α-methylstyrene, vinyltoluene, chlorostyrene, and the like.

[0038] Specifically, first, for each rubber component, a value is calculated by multiplying the styrene content (mass%) by the mass fraction in the rubber component, and these values ​​are added together to obtain a total value (mass%). Next, for each styrene-containing compounding agent other than the rubber component contained in the rubber composition, a value is calculated by multiplying the styrene content (mass%) of each styrene-containing compounding agent by the mass fraction relative to 100 mass parts of the rubber component, and these values ​​are added together to obtain a total value (mass%). The sum of these two total values ​​is then defined as the total styrene amount S (mass%). Therefore, it is calculated using {Σ(styrene content (mass%) of each styrene-containing rubber × styrene content in the rubber component of each styrene-containing rubber (mass%) / 100) + Σ(styrene content (mass%) of each styrene-containing compounding agent other than the rubber component × amount of each styrene-containing compounding agent relative to 100 mass parts of the rubber component (mass parts) / 100)}. In this specification, if the "styrene portion" is styrene (for example, if the styrene portion-containing rubber is styrene-butadiene rubber), the "styrene portion content" may be expressed as "styrene content."

[0039] For example, if the rubber component consists of 30% by mass of a first SBR (styrene content: 25% by mass), 60% by mass of a second SBR (styrene content: 27.5% by mass), and 10% by mass of BR, and the rubber composition further contains, in addition to the rubber component, 20 parts by mass of a first resin having a styrene portion (styrene content: 5% by mass) per 100 parts by mass of the rubber component, and 10 parts by mass of a second resin having a styrene portion (styrene content: 1% by mass) per 100 parts by mass of the rubber component, then the total amount of styrene S in the rubber composition relative to 100% by mass of the rubber component is 25.1% by mass = {(25 × 30 / 100 + 27.5 × 60 / 100 + 0 × 10 / 100) + (5 × 20 / 100 + 1 × 10 / 100)}.

[0040] The "weight-average molecular weight (Mw)" can be determined by converting the measured value using gel permeation chromatography (GPC) (for example, the GPC-8000 series from Tosoh Corporation, with a differential refractometer as the detector and TSKgel SuperMultipore HZ-M column from Tosoh Corporation) to a standard polystyrene equivalent. This method is applicable, for example, to 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] The "average primary particle diameter" is a value determined by photographing particles with a transmission or scanning electron microscope and taking the arithmetic mean of the particle diameters of 400 particles. If the particle is spherical, the diameter of the sphere is used as the particle diameter; if it is not spherical, the equivalent diameter of a circle (the positive square root of {4 × (particle area) / π}) is calculated from the microscope image and used as the particle diameter. The average primary particle diameter is applied to silica, carbon black, and other materials.

[0044] The "softening point of the resin component" is the temperature at which the sphere descends when the softening point specified in JIS K 6220-1:2015 7.7 is measured using a ring-type softening point measuring device.

[0045] The "average thickness of the plating layer" is measured in accordance with JIS H 8501:1999.

[0046] The procedure for manufacturing a tire, which is one embodiment of the present invention, will be described in detail below. However, the following description is illustrative for explaining the present invention and is not intended to limit the technical scope of the present invention to this scope only.

[0047] [tire] A tire according to one embodiment of the present invention will be described below with reference to the drawings.

[0048] Figure 1 shows a cross-sectional view of the tire 11 according to this embodiment, in a plane passing through the tire rotation axis. Although Figure 1 shows only the portion to the left of the CL (center line), the tire has a similar structure continuously to the right of the CL, with the CL as the axis of symmetry. As shown in Figure 1, the tire 11 comprises 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 arbitrarily selected.

[0049] The tread portion 12 may be a tread portion consisting of a single rubber layer, or it may be a tread portion having a cap rubber layer that constitutes the tread surface, and one or more rubber layers existing between the cap rubber layer and the belt layer 17.

[0050] In this specification, "rubber composition constituting the tread portion" refers to the rubber composition constituting the cap rubber layer when the tread portion consists of two or more layers.

[0051] <Belt layer and metal cord> Figure 2 shows a cross-sectional view of the metal cord 21 in a plane perpendicular to the longitudinal direction. The ply forming the belt layer 17 has multiple metal cords 21 and topping rubber 22. The multiple metal cords 21 are arranged in a row in parallel. The topping rubber 22 covers the metal cords 21, and the entire circumference of each individual metal cord is covered with topping rubber 22. The metal cords 21 are embedded in the topping rubber 22.

[0052] The metal cord 21 may or may not be inclined with respect to the tire circumferential direction. The inclination angle of the metal cord 21 with respect to the tire circumferential direction is not particularly limited, but is set in the range of 0° to 60°, preferably 5° to 45°, and more preferably 10° to 30°.

[0053] The metal cord according to this embodiment has one to four steel strands, also called filaments. That is, the metal cord may be a single-strand monofilament cord (i.e., a cord consisting of one filament having a 1x1 structure), or it may have two to four filaments.

[0054] When a single metal cord has 2 to 4 filaments, it is preferable that the metal cord has a twisted structure in which these filaments are twisted together along its longitudinal direction. The twisted structure is not particularly limited and can be, for example, a single-strand metal cord with a 1×N structure or a layered metal cord with an N+M structure.

[0055] A single-strand structure can be expressed as, for example, a 1×N structure. A 1×N structure means a structure in which N filaments are twisted together to form a single layer. A single layer means a structure in which, in a cross-section perpendicular to the longitudinal direction of the metal cord, the filaments are arranged to form a single layer along the circumference of a circle. Examples of single-strand structures in this embodiment include 1×2 structures, 1×3 structures, and 1×4 structures.

[0056] Figure 3 is a perspective view of a metal cord having a 1x2 structure. The metal cord 50 shown in Figure 3 has two filaments 51 twisted together spirally along the longitudinal direction to form a single layer.

[0057] A layered twisted structure has a structure in which multiple filaments are wound in layers sequentially from the center outwards in a cross section perpendicular to the longitudinal direction of the metal cord, and can be represented, for example, as an N+M structure. An N+M structure means a structure having a core in which N filaments are twisted together in a spiral along their longitudinal direction, and an outer sheath in which M filaments are twisted together in a spiral along the longitudinal direction of the core to cover the outer circumference of the core. An example of a layered twisted structure in this embodiment is a 2+2 structure.

[0058] The metal constituting the metal cord 21 is not particularly limited, but steel cord is preferably used from the viewpoint of high strength and flexibility. The material of the steel filaments constituting the steel cord is not particularly limited, and HT (High Tensile), SHT (Super High Tensile), UHT (Ultra High Tensile), etc. can be used. Recycled iron obtained by melting used iron products may also be used. When using a metal cord made by twisting multiple steel filaments together, steel filaments that have been pre-curled in the longitudinal direction may be used from the viewpoint of improving durability by making it easier for the topping rubber to penetrate inside the steel cord.

[0059] The filament diameter D of the metal cord 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, even more preferably 0.22 mm or more, and particularly preferably 0.25 mm or more, from the viewpoint of ensuring the durability of the metal cord against impact. Furthermore, from the viewpoint of the tread's ability to follow the road surface, D is preferably 0.55 mm or less, more preferably 0.51 mm or less, even more preferably 0.48 mm or less, and particularly preferably 0.45 mm or less.

[0060] The metal cord according to this embodiment may be coated with a plating layer. A metal cord having a plating layer exhibits high moisture-resistant heat bonding performance even under harsh conditions of high temperature and humidity, thereby preventing delamination between the topping rubber and the metal cord and improving the durability of the tire under humid and hot conditions. If the metal cord has multiple filaments, a plating layer can be applied to the surface of each filament.

[0061] The composition 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, metal cords having a ternary plating layer consisting of copper (Cu), zinc (Zn), and cobalt (Co) exhibit high moisture-resistant thermal bonding performance even under harsh conditions of high temperature and humidity, thereby preventing delamination between the topping rubber and the metal cord and improving the durability of the tire under humid and hot conditions.

[0062] From the viewpoint of suppressing excessive copper reaction, 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. Furthermore, from the viewpoint of suppressing adhesion reduction due to the formation of excessive zinc oxide, it is preferably 44% by mass or less, more preferably 40% by mass or less, even more preferably 36% by mass or less, and particularly preferably 32% by mass or less.

[0063] 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. Furthermore, from the viewpoint of preventing rubber deterioration due to copper leaching in a humid and hot environment, it is preferably 78% by mass or less, more preferably 75% by mass or less, and even more preferably 72% by mass or less.

[0064] From the viewpoint of thermal and humid adhesion, 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. Furthermore, from the viewpoint of preventing crack formation during wire drawing, it 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.

[0065] The plating layer can be formed by plating copper, zinc, and cobalt layers onto the filament before wire drawing, and then diffusing the metals of each layer formed on the filament surface by heat treatment. The order in which the layers are formed on the filament to create the plating layer is not particularly limited.

[0066] Next, the heat-treated material can be drawn to a desired filament diameter to form a filament with a plating layer. If the metal cord consists of a single filament, it can be used as is after drawing. If the metal cord has multiple filaments, after drawing, the resulting filaments can be twisted together, for example, to form a desired twisted structure, thereby creating a metal cord with a plating layer.

[0067] From the viewpoint of initial adhesion, 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. Furthermore, from the viewpoint of suppressing excessive adhesion reaction, it is preferably 0.40 μm or less, more preferably 0.35 μm or less, and even more preferably 0.30 μm or less.

[0068] The number of metal cords E (also called ends) per 50 mm width in the direction perpendicular to the longitudinal direction of the metal cord is not particularly limited, but is preferably 20 or more, more preferably 25 or more, even more preferably 30 or more, even more preferably 35 or more, and particularly preferably 40 or more. Furthermore, E is preferably 90 or less, more preferably 80 or less, even more preferably 70 or less, even more preferably 60 or less, and particularly preferably 55 or less.

[0069] <Total styrene content S> In the rubber composition constituting the tread portion, the total amount of styrene S in the rubber composition, when the mass of the rubber component is 100% by mass, is preferably 7.5% by mass or more, more preferably 8.0% by mass or more, and even more preferably 8.5% by mass or more, from the viewpoint of the effects of the present invention. Furthermore, the total amount of styrene S in the rubber composition, when the mass of the rubber component is 100% by mass, is preferably 35% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, and particularly preferably 20% by mass or less, from the viewpoint of low fuel consumption performance.

[0070] The total amount of styrene in the rubber composition can be adjusted as appropriate by the type and amount of rubber components described below. For example, the total amount of styrene S can be increased by increasing the amount of styrene-butadiene rubber, incorporating styrene-butadiene rubber with a high styrene content, or incorporating a resin component that contains styrene as a monomer component. Conversely, the total amount of styrene S can be reduced by decreasing the amount of styrene-butadiene rubber.

[0071] <D×S> From the viewpoint of the effects of the present invention, D×S is greater than 2.0, preferably greater than 2.6, more preferably greater than 3.3, even more preferably greater than 3.9, and particularly preferably greater than 4.4. On the other hand, from the viewpoint of low fuel consumption performance, D×S is less than 20.0, more preferably less than 16.0, even more preferably less than 12.0, even more preferably less than 10.0, and particularly preferably less than 8.0.

[0072] <D×Y> In the rubber composition constituting the tread portion, when Y (parts by mass) is the silica content per 100 parts by mass of rubber components in the rubber composition, D×Y is preferably greater than 16, more preferably greater than 19, even more preferably greater than 21, and particularly preferably greater than 23, from the viewpoint of the effects of the present invention. On the other hand, there is no particular upper limit to D×Y, but from the viewpoint of low fuel consumption performance, it is preferably less than 55, more preferably less than 52, even more preferably less than 50, even more preferably less than 48, even more preferably less than 45, even more preferably less than 42, and particularly preferably less than 39. The silica content Y (parts by mass) per 100 parts by mass of rubber components in the rubber composition will be described later.

[0073] [Rubber composition that makes up the tread] The rubber composition constituting the tread portion according to this embodiment (hereinafter referred to as the rubber composition according to this embodiment) comprises a rubber component containing styrene-butadiene rubber and / or isoprene-based rubber, and a copolymer resin containing styrene and cyclopentadiene as monomer components, both of which can be manufactured using the raw materials described below. The rubber composition according to this embodiment will be described below.

[0074] <Rubber components> In the rubber composition according to this embodiment, diene rubber is preferably used as the rubber component. Examples of diene rubber 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 that can interact with fillers such as carbon black or silica, or they may be hydrogenated rubbers in which some of the unsaturated bonds have been hydrogenated. One type of diene rubber may be used alone, or two or more types may be used in combination. In addition, as the diene rubber, stretched rubber that has been pre-stretched using a plasticizer described later may be used.

[0075] The content of 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. Alternatively, the rubber component may consist solely of diene rubber.

[0076] The rubber component according to this embodiment contains styrene-butadiene rubber and / or isoprene-based rubber as essential components. The rubber component preferably contains SBR, more preferably contains SBR and isoprene-based rubber and / or BR, even more preferably contains SBR and isoprene-based rubber, and particularly preferably contains SBR, BR, and isoprene-based rubber. Alternatively, the rubber component may consist only of SBR, BR, and isoprene-based rubber.

[0077] (SBR) 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 with modified terminals and / or main chains, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, branched structures, etc.). Furthermore, hydrogenated SBRs (hydrogenated SBRs) can also be used. SBRs may be used alone or in combination of two or more types.

[0078] In this embodiment, stretchable SBR can be used, or non-stretchable SBR can be used. When stretchable SBR is used, the amount of stretch of the SBR, that is, the amount of stretchable plasticizer contained in the SBR, is preferably 10 to 50 parts by mass per 100 parts by mass of rubber solids of the SBR.

[0079] As for the SBRs listed above, commercially available products from companies such as Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, and ZS Elastomer Co., Ltd. can be used.

[0080] From the viewpoint of the effects of the present invention, the styrene content of SBR is preferably 10% by mass or more, more preferably 13% by mass or more, even more preferably 16% by mass or more, and particularly preferably 20% by mass or more. On the other hand, the styrene content of SBR is preferably less than 60% by mass, more preferably less than 50% by mass, and even more preferably less than 45% by mass. In this specification, the styrene content of SBR is measured by the measurement method described above.

[0081] The vinyl content of SBR is preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more. Furthermore, the vinyl content of SBR is preferably 60 mol% or less, more preferably 50 mol% or less, and even more preferably 45 mol% or less. In this specification, the vinyl content of SBR is measured by the measurement method described above.

[0082] From the viewpoint of wet grip performance, the glass transition temperature (Tg) of SBR is preferably -75°C or higher, more preferably -70°C or higher, and even more preferably -65°C or higher. Furthermore, from the viewpoint of low fuel consumption performance, the Tg of SBR is preferably -40°C or lower, more preferably -45°C or lower, even more preferably -50°C or lower, and particularly preferably -55°C or lower.

[0083] The weight-average molecular weight (Mw) of SBR is preferably greater than 150,000, more preferably greater than 200,000, and even more preferably greater than 300,000. Furthermore, from the viewpoint of crosslinking uniformity, the Mw is preferably less than 2 million, more preferably less than 1.5 million, and even more preferably less than 1 million. The Mw of SBR is measured by the measurement method described above.

[0084] As the SBR, either oil-expanded SBR or non-oil-expanded SBR can be used. In this specification, as the SBR, commercially available products from JSR Corporation, Sumitomo Chemical Co., Ltd., UBE Corporation, Asahi Kasei Corporation, ZS Elastomer Corporation, ARLANXEO, etc. can be used.

[0085] The SBR content in the rubber component can be appropriately set so that D×S falls within the above range, but it is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, even more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 75% by mass or more. On the other hand, there is no particular upper limit to the content, but for example it can be 99% by mass or less, 95% by mass or less, 90% by mass or less, or 85% by mass or less.

[0086] (Isoprene rubber) As isoprene-based rubbers, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. Natural rubber includes not only unmodified natural rubber (NR), but also modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. Isoprene-based rubbers may be used alone or in combination of two or more types.

[0087] NR is not particularly limited and can be any that is common in the tire industry, such as SIR20, RSS#3, TSR20, etc.

[0088] From the viewpoint of the effects of the present invention, the content of isoprene-based rubber in the rubber component is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more. On the other hand, there is no particular upper limit to the content, but it is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 30% by mass or less.

[0089] (BR) BR is not particularly limited, and for example, BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare-earth butadiene rubber synthesized using a rare-earth element catalyst (rare-earth BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc., which are common in the tire industry, can be used. BR may be used alone or in combination of two or more types.

[0090] High-cis BR can be commercially available from companies such as Nippon Zeon Co., Ltd., UBE Corporation, and JSR Corporation. The inclusion of high-cis BR improves wear resistance. The cis content of 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 measurement method described above.

[0091] From the viewpoint of the effects of the present invention, the BR content 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, even 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, but for example, it can be 1% by mass or more, 3% by mass or more, or 5% by mass or more.

[0092] (Other rubber components) The rubber component may contain other rubber components besides diene rubber, as long as they do not affect the effects of the present invention. Other rubber components besides diene rubber can 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, polyethylene chloride rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber. In addition to the above rubber components, known thermoplastic elastomers may or may not be included. Other rubber components may be used individually or in combination of two or more.

[0093] (Rubber components synthesized from recycled and biomass-derived raw materials) Monomers, which are the constituent units of synthetic rubbers such as IR, SBR, and BR, may be derived from underground resources such as petroleum and natural gas, or they may be recycled from rubber products such as tires or non-rubber products such as polystyrene. The monomers obtained by recycling (recycled monomers) are not particularly limited, but include recycled polyisoprene, recycled butadiene, and recycled aromatic vinyl compounds. Examples of butadiene include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl compounds are not particularly limited, but include styrene. In particular, it is preferable to use recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) as raw materials.

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

[0095] Furthermore, the monomers that make up polymers such as IR, SBR, and BR may be derived from biomass. In this specification, biomass refers to substances derived from natural resources such as plants. Biomass is not particularly limited, but examples include agricultural, forestry, and fishery products, sugars, wood chips, plant residues after obtaining useful components, plant-derived ethanol, and biomass naphtha.

[0096] The biomass-derived monomer (biomass monomer) is not particularly limited and includes biomass-derived butadiene and biomass-derived aromatic vinyl compounds. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. Examples of the aromatic vinyl compound are not particularly limited but include styrene. Furthermore, the method for producing the biomass monomer is not particularly limited and includes, for example, biological and / or chemical and / or physical transformations of plants and animals. Typical biological transformations include fermentation by microorganisms, while chemical and / or physical transformations include those by catalysts, high heat, high pressure, electromagnetic waves, critical liquids, and combinations thereof.

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

[0098] Whether the raw materials for a polymer are biomass-derived can be determined by measuring pMC (percent Modern Carbon) according to ASTM D6866-10. pMC refers to the percentage of modern standard reference carbon. 14 Sample relative to C concentration 14 This is a ratio of C concentrations and is used as an indicator of the biomass ratio of a compound. The significance of this value is described below.

[0099] 1 mole of carbon atoms (6.02 × 10⁻¹⁰) 23 (Each) contains approximately 6.02 × 10¹⁶ atoms, which is about one trillionth of the amount of carbon atoms in a normal atom. 11 individual 14 C exists. 14 The half-life of C is 5730 years. 14 C is decreasing regularly. Therefore, in fossil fuels such as coal, oil, and natural gas, which are thought to have been fixed after more than 226,000 years have passed since atmospheric carbon dioxide was taken in and fixed by plants, etc., C was initially included in these as well. 14 All elements of C have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas are no longer viable. 14 It contains absolutely no element C. Therefore, chemical substances produced using these fossil fuels as raw materials also contain C. 14 It contains absolutely no element C.

[0100] on the other hand, 14C is continuously produced when cosmic rays undergo nuclear reactions in the atmosphere. Therefore, 14 In the Earth's atmospheric environment, carbon (C) is produced in a state where its decrease due to radioactive decay and its production through nuclear reactions are in equilibrium. 14 The amount of C is constant. Therefore, the amount of biomass resource-derived substances currently circulating in the environment 14 As mentioned above, the carbon concentration is approximately 1 × 10¹⁶ of the total carbon atoms. -12 These values ​​are approximately in mole percent. Therefore, the difference between these values ​​can be used to calculate the biomass ratio in a given compound.

[0101] this 14 C is typically measured as follows: Using accelerator mass spectrometry based on a tandem accelerator, 13 C concentration ( 13 C / 12 C), 14 C concentration ( 14 C / 12 Perform measurement C). In the measurement, 14 As a modern standard reference for the concentration of C, the amount of cyclic carbon in nature as of 1950 14 The C concentration will be used. The specific standard material will be the oxalic acid standard provided by NIST (National Institute of Standards and Technology). The specific radioactivity of carbon in this oxalic acid (per gram of carbon) will be used. 14 The radioactivity intensity of C is separated by carbon isotope, 13 The standard value is obtained by correcting C to a constant value and applying decay correction from 1950 AD to the measurement date. 14 This value is used as the C concentration value (100%). The ratio of this value to the value of the sample actually measured is the pMC value.

[0102] Therefore, if rubber is made from 100% biomass-derived materials, although there are regional differences, under normal conditions it will often not reach 100, and will show a value of approximately 110 pMC. On the other hand, regarding chemical substances derived from fossil fuels such as petroleum,14 When the C concentration is measured, it will show a value of approximately 0 pMC (for example, 0.3 pMC). This value corresponds to the aforementioned biomass ratio of 0%.

[0103] For the reasons stated above, using materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio, in rubber compositions is preferable from an environmental protection standpoint.

[0104] <Filler> The rubber composition according to this embodiment preferably contains silica as a filler, and more preferably contains silica and carbon black. Alternatively, the filler may consist only of silica and carbon black.

[0105] (silica) The silica used is not particularly limited, and common silica used in the tire industry can be used, such as silica prepared by a dry process (anhydrous silica) or silica prepared by a wet process (hydrated silica). The raw material for silica is not particularly limited, and may be a mineral-derived raw material such as quartz, or a biological-derived raw material such as rice husks (for example, silica made from biomass materials such as rice husks), or silica recycled from silica-containing products may be used. Among these, hydrated silica prepared by a wet process is preferred because it contains a large number of silanol groups. Silica may be used alone or in combination of two or more types.

[0106] Silica derived from biomass materials can be obtained, for example, by extracting silicates from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then using these silicates to react with sulfuric acid in the same way as conventional wet silica, the precipitate of silicon dioxide is filtered, washed with water, dried, and pulverized.

[0107] The silica recycled from silica-containing products can be, for example, silica recovered from products containing silica such as semiconductors and other electronic components, tires, desiccants, and diatomaceous earth and other filter materials. The recovery method is not particularly limited and can include thermal decomposition and decomposition by electromagnetic waves. Among these, silica recovered from semiconductors and other electronic components or tires is preferred.

[0108] When silica crystallizes, it becomes insoluble in water, and its component, silicic acid, cannot be utilized. By controlling the combustion temperature and combustion time, the crystallization of silica in rice husk ash can be suppressed (see Japanese Patent Publication No. 2009-2594, Akita Prefectural University Web Journal B / 2019, vol.6, pp.216-222, etc.). Amorphous silica extracted from rice husks can be commercially available from companies such as Wilmar.

[0109] The nitrogen adsorption specific surface area (N2SA) of silica is 110 m², which is considered to be the optimal value in terms of wear resistance and elongation at break. 2 Preferably 130m / g or more. 2 More preferably 150m / g or more, 2 More preferably 170m / g or more. 2 More preferably 190m / g or more. 2 A value of 1 / g or more is particularly preferred. Furthermore, from the viewpoint of heat generation and processability, 350m 2 Preferably less than / g, 300m 2 More preferably less than / g, 250m 2 A value of less than / g is even more preferable. The N2SA of silica is measured by the measurement method described above.

[0110] The average primary particle diameter of silica is preferably less than 26 nm, more preferably less than 20 nm, even more preferably less than 18 nm, even more preferably less than 17 nm, and particularly preferably less than 16 nm. The lower limit of the average primary particle diameter is not particularly limited, but from the viewpoint of silica dispersibility, it is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm or more. The average primary particle diameter of silica is measured by the measurement method described above.

[0111] From the viewpoint of the effects of the present invention, the silica content Y per 100 parts by mass of rubber component is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, even more preferably 70 parts by mass or more, and particularly preferably 80 parts by mass or more. Furthermore, 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.

[0112] (Carbon Black) The carbon black used is not particularly limited and includes N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. The raw materials for carbon black may be biomass materials such as lignin and vegetable oil, or pyrolysis oil obtained by thermal decomposition of waste tires. The manufacturing method for carbon black may be combustion such as the furnace method, hydrothermal carbonization (HTC), or thermal decomposition of methane such as the thermal black method. Commercially available products 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., Columbia Carbon Corporation, etc. Carbon black may be used alone or in combination of two or more types.

[0113] In addition to the above, from the perspective of life cycle assessment, carbon black made from biomass materials such as lignin, or recycled carbon black refined by thermal decomposition of carbon black-containing products such as tires, may also be used as carbon black.

[0114] In this specification, "recycled carbon black" refers to carbon black obtained by crushing used tires and other products containing carbon black, and calcining the crushed material, wherein, according to the thermogravimetric method compliant with JIS K 6226-2:2003, when oxidative combustion occurs by heating in air, the proportion of the mass of ash (ash content), which is the component that does not burn, is 13% by mass or more. In other words, the proportion of the mass (carbon content) lost due to the aforementioned oxidative combustion of recycled carbon black is 87% by mass or less. Recycled carbon black may also be represented as rCB.

[0115] Recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, which refers to "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, states that it can be obtained by the 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 usually lacks functional groups on its surface, as referred to in

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

[0116] Recycled carbon black may lack functional groups on its surface, or it 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. 3173251, carbon black obtained from a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. In addition, in Japanese Patent Publication No. 6856781, carbon black obtained from a pyrolysis process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain carbon black with an activated surface. The recycled carbon black according to this embodiment also includes carbon black treated to include functional groups on its surface.

[0117] Recycled carbon black can be purchased from companies such as Strable Green Carbon and LD Carbon.

[0118] The nitrogen adsorption specific surface area (N2SA) of carbon black is 30m² from the perspective of reinforcement. 2 Preferably 50m / g or more. 2 More preferably 70m 2 More preferably 90m / g or more. 2 A value of 200m or more is particularly preferred. Furthermore, from the viewpoint of low fuel consumption and processability, 200m 2 Preferably less than / g, 150m 2 Less than / g is more preferable, 120m 2 A value of less than / g is even more preferable.

[0119] The average primary particle diameter 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. The lower limit of the average primary particle diameter is not particularly limited, but is preferably 5 nm or more, more preferably 8 nm or more, and even more preferably 10 nm or more.

[0120] When carbon black is included, the amount of carbon black per 100 parts by mass of rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, from the viewpoint of reinforcing properties. Furthermore, from the viewpoint of suppressing heat generation, it is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less.

[0121] (Other fillers) Other fillers besides silica and carbon black are not particularly limited and may include those commonly used in the tire industry, such as aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, magnesium sulfate, talc, clay, and biochar. These other fillers may be used individually or in combination of two or more.

[0122] From the viewpoint of the effects of the present invention, the total content of filler per 100 parts by mass of rubber component is preferably 55 parts by mass or more, more preferably 65 parts by mass or more, even more preferably 75 parts by mass or more, and particularly preferably 85 parts by mass or more. Furthermore, 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.

[0123] The silica content in the filler is preferably 65% ​​by mass or more, more preferably 70% by mass or more, even more preferably 75% by mass or more, even more preferably 80% by mass or more, and particularly preferably 85% by mass or more. Furthermore, the silica content in the filler is preferably 99% by mass or less, and more preferably 97% by mass or less.

[0124] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent used in combination with silica in the tire industry can be used, but examples include mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; and 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane. Examples include thioester-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. In particular, it is preferable to contain a sulfide-based silane coupling agent and / or a mercapto-based silane coupling agent. As silane coupling agents, for example, those commercially available from Evonik Industries, Momentive, etc., can be used. The silane coupling agent may be used alone or in combination of two or more types.

[0125] When a silane coupling agent is included, 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, 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 silica dispersibility. Furthermore, from the viewpoint of preventing a decrease in wear resistance, the content 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.

[0126] <Copolymer resin> The rubber composition according to this embodiment includes a copolymer resin (hereinafter simply referred to as "copolymer resin") containing styrene and cyclopentadiene as monomer components as a resin component.

[0127] The copolymer resin is not particularly limited as long as it contains styrene and cyclopentadiene as monomer components, and may further contain other monomer components. Furthermore, it may be a hydrogenated or modified version of the resin.

[0128] The "styrene" constituting the monomer component may be any compound having a styrene structure other than styrene, such as styrene, α-methylstyrene, vinyltoluene, and chlorostyrene. Styrene monomers such as vinyltoluene (methylstyrene) are included in the C9 fraction, for example. Other monomer components are not particularly limited, but monomer components commonly used in petroleum resins are preferred, such as the C9 fraction other than monomers having a styrene structure. Examples of the C9 fraction other than monomers having a styrene structure include at least one selected from the group consisting of coumarone, indene, methylindene, etc.

[0129] The copolymer resin is preferably a DCPD-C9 resin, which is a copolymer of cyclopentadiene and / or dicyclopentadiene with a C9 fraction. Alternatively, the DCPD-C9 resin may be hydrogenated or modified.

[0130] Copolymer resins containing styrene and cyclopentadiene as monomer components can be commercially available from companies such as ExxonMobil, ENEOS Corporation, Zeon Corporation, and Maruzen Petrochemical Co., Ltd. Co., Ltd. The copolymer resin may be used alone or in combination of two or more types.

[0131] From the viewpoint of the effects of the present invention, the styrene content in the copolymer resin is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, even more preferably 1.0% by mass or more, even more preferably 2.0% by mass or more, even more preferably 3.0% by mass or more, even more preferably 4.0% by mass or more, and particularly preferably 5.0% by mass or more. Furthermore, there is no particular upper limit to the styrene content, but for example, it can be less than 50% by mass, less than 40% by mass, less than 30% by mass, less than 20% by mass, or less than 10% by mass.

[0132] From the viewpoint of the effects of the present invention, the softening point of the copolymer resin is preferably above 70°C, more preferably above 80°C, even more preferably above 90°C, and particularly preferably above 100°C. Furthermore, from the viewpoint of processability and improved dispersibility between the rubber component and the filler, it is preferably below 150°C, more preferably below 140°C, and even more preferably below 130°C. The softening point of the copolymer resin is measured by the measurement method described above.

[0133] The copolymer resin content per 100 parts by mass of rubber component is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more. Furthermore, from the viewpoint of suppressing heat generation, it is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, even more preferably 80 parts by mass or less, and particularly preferably 70 parts by mass or less.

[0134] <Other compounding agents> In addition to the components mentioned above, the rubber composition according to this embodiment may also contain, as appropriate, compounding agents commonly 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.

[0135] In this specification, "plasticizer" refers to a material that imparts plasticity to rubber components, and is a concept that includes both liquid plasticizers at 25°C and solid plasticizers at 25°C. Examples of plasticizers include resin components, oils, liquid rubber, and ester-based plasticizers. These plasticizers may be derived from petroleum, biomass, or naphtha recycled from rubber or non-rubber products. In addition, low molecular weight hydrocarbon components obtained by thermal decomposition and extraction of used tires or products containing various components may be used as plasticizers. These plasticizers may be used individually or in combination of two or more types.

[0136] (Resin components) The rubber composition according to this embodiment may contain other resin components besides the copolymer resin. The other resin components are not particularly limited, but resins commonly used in the tire industry can be used, such as aromatic vinyl resins, dicyclopentadiene resins, C9 resins, C5 resins, C5C9 resins, terpene resins, rosin resins, phenolic resins, etc. The other resin components may be used individually or in combination of two or more. Each resin component may also be used individually or in combination of two or more.

[0137] "Aromatic vinyl resin" refers to a resin in which aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and p-chlorostyrene are the most abundant monomer components, and these may be hydrogenated or modified. As aromatic vinyl resins, α-methylstyrene or a homopolymer of styrene or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, for reasons of being economical, easy to process, and having excellent heat generation properties. As aromatic vinyl resins, commercially available products from companies such as Kraton, Eastman Chemical Company, and Mitsui Chemicals, Inc. can be used.

[0138] A "dicyclopentadiene-based resin" refers to a resin containing dicyclopentadiene as a monomer component. Examples of dicyclopentadiene-based resins that can be used are those commercially available from companies such as ExxonMobil, ENEOS Corporation, Zeon Corporation, and Maruzen Petrochemical Co., Ltd. These dicyclopentadiene-based resins may be used individually or in combination of two or more types.

[0139] A "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a polymer obtained by polymerizing the C9 fraction alone, or a copolymer obtained by copolymerizing the C9 fraction with other components. For example, a resin obtained by copolymerizing dicyclopentadiene (DCPD) and a C9 fraction is called a DCPD / C9 resin. Furthermore, the C9 resin may be a hydrogenated or modified version of these resins. Examples of C9 fractions include petroleum fractions with 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene. As for C9 resins, commercially available products from companies such as BASF, Zeon Corporation, and ENEOS Corporation can be used.

[0140] "C5 resins" refer to resins obtained by polymerizing C5 fractions other than cyclopentadiene, and may be hydrogenated or modified versions of these fractions. Examples of C5 fractions other than dicyclopentadiene include petroleum fractions with 4 to 5 carbon atoms, such as cyclopentadiene, isoprene, piperylene, 2-methyl-1-butene, 2-methyl-2-butene, and 1-pentene. Commercially available C5 resins from companies such as Structol, Nippon Zeon Co., Ltd., and ENEOS Corporation can be used.

[0141] "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be hydrogenated or modified. As C5C9 petroleum resin, commercially available products from companies such as Tosoh Corporation and LUHUA can be used.

[0142] "Terpene resin" refers to a resin containing terpene compounds such as α-pinene, β-pinene, limonene, and dipentene as monomer components, and may be hydrogenated or modified. Preferred terpene resins include, for example, polyterpene resins, which are polymers in which one or more of the aforementioned terpene compounds are used as monomer components; aromatically modified terpene resins, which are copolymers in which the aforementioned terpene compounds and aromatic compounds are used as monomer components; and terpene phenol resins, which are copolymers in which the aforementioned terpene compounds and phenol compounds are used as monomer components. Examples of aromatic compounds that serve as monomer components in aromatically modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenol compounds that serve as monomer components in terpene phenol resins include phenol, bisphenol A, cresol, and xylenol. As terpene resins, commercially available products from companies such as Yasuhara Chemical Co., Ltd., Arakawa Chemical Industries, Ltd., and Nippon Terpene Chemical Co., Ltd. can be used.

[0143] "Rosin-based resin" refers to a resin containing rosin acid compounds such as abietic acid, neoabietic acid, palastic acid, and isopimal acid, and may be hydrogenated or modified. Rosin-based resins are not particularly limited, but examples include natural resin rosin and rosin-modified resins obtained by hydrogenating, disproportionating, dimerizing, esterifying, etc. As rosin-based resins, commercially available products from companies such as Harima Chemical Industries, Ltd., Arakawa Chemical Industries, Ltd., and IREC Co., Ltd. can be used.

[0144] "Phenol-based resins" refer to resins containing phenol compounds such as phenol and cresol as monomer components, and may also be hydrogenated or modified resins. Phenolic resins are not particularly limited, but examples include phenol-formaldehyde resins, alkylphenol-formaldehyde resins, alkylphenol-acetylene resins, oil-modified phenol-formaldehyde resins, and terpene-phenol resins. Phenolic resins that are commercially available from companies such as Sumitomo Bakelite Co., Ltd., DIC Corporation, and Asahi Organic Materials Co., Ltd. can be used.

[0145] From the viewpoint of the effects of the present invention, the total content of the resin component (including the copolymer resin) per 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more. Furthermore, from the viewpoint of suppressing heat generation, it is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, even more preferably 80 parts by mass or less, and particularly preferably 70 parts by mass or less.

[0146] From the viewpoint of the effects of the present invention, the content of resin components other than the copolymer resin (total amount when multiple resin components are used in combination) per 100 parts by mass of rubber component is preferably less than 30 parts by mass, more preferably less than 20 parts by mass, even more preferably less than 10 parts by mass, even more preferably less than 5 parts by mass, or may not be included at all.

[0147] Examples of oils include mineral oil, vegetable oil, and animal oil. Furthermore, from a life cycle assessment perspective, waste oil from rubber mixers and engines, or refined waste cooking oil from restaurants, may also be used. Oils may be used individually or in combination of two or more types.

[0148] In this specification, mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. Examples of mineral oil include paraffinic oils (mineral oil), naphthenic oils, and aromatic oils. Specific examples of mineral oil include MES (Mild Extracted Solvate), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), and RAE (Residual Aromatic Extract). Furthermore, for environmental reasons, oils with a low content of polycyclic aromatic compounds (PCA) can be used. Examples of low-PCA oils include MES, TDAE, and heavy naphthenic oils. Mineral oil may be used alone or in combination of two or more types.

[0149] In this specification, vegetable oils include, for example, 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 wood wax. Furthermore, vegetable oils may also include refined oils (such as salad oil) obtained by refining the above oils, transesterified oils obtained by transesterifying the above oils, hydrogenated oils obtained by hydrogenating the above oils, thermally polymerized oils obtained by thermally polymerizing the above oils, oxidized polymerized oils obtained by oxidizing the above oils, and waste cooking oils recovered from use as edible oils. Note that vegetable oils may be liquid or solid at 25°C. Vegetable oils may be used individually or in combination of two or more types.

[0150] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably contains triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxyl group of glycerin and a fatty acid are ester-bonded. The acylglycerol is not particularly limited and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Furthermore, the acylglycerol may be a monomer, a dimer, or a polymer of three or more. Note that acylglycerols of two or more forms can be obtained by thermal polymerization, oxidative polymerization, etc. Also, the acylglycerol may be a liquid or a solid at 25°C.

[0151] The method for confirming whether the rubber composition contains the acylglycerol is not particularly limited, 1 This can be confirmed by 1H-NMR measurement. For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at 25°C for 24 hours, and after removing the rubber composition, it is measured at room temperature. 1 When 1H-NMR was measured and the tetramethylsilane (TMS) signal was set to 0.00 ppm, signals were observed around 5.26 ppm, 4.28 ppm, and 4.15 ppm. These signals are presumed to originate from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In this paragraph, "around" refers to a range of ±0.10 ppm.

[0152] The aforementioned fatty acids are not particularly limited and may be unsaturated or saturated fatty acids. 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.

[0153] In particular, it is desirable that the fatty acid contains fatty acids with few double bonds, i.e., saturated fatty acids or monounsaturated fatty acids, and oleic acid is preferred. As a vegetable oil containing such fatty acids, for example, a vegetable oil containing saturated fatty acids or monounsaturated fatty acids may be used, or a vegetable oil that has been modified by transesterification or other means may be used. Furthermore, in order to produce a vegetable oil containing such fatty acids, plants may be improved by breeding, genetic modification, genome editing, etc.

[0154] As for vegetable oils, commercially available products from companies such as Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kosan Co., Ltd., and Nisshin Oillio Group Ltd. can be used.

[0155] Examples of animal oils include fish oil, beef tallow, whale oil, or oleyl alcohol which can be derived from them.

[0156] When oil is included, the content of oil per 100 parts by mass of 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, even more preferably 7 parts by mass or more, and particularly preferably 10 parts by mass or more, from the viewpoint of the effects of the present invention. Furthermore, the content is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 40 parts by mass or less.

[0157] The liquid rubber is not particularly limited as long as it is a polymer that is in a liquid state at 25°C, but examples 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. The liquid rubber may be used alone or in combination of two or more types.

[0158] The weight-average molecular weight (Mw) of 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. Furthermore, the Mw of 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 liquid rubber is within the above range, the effects of the present invention tend to be better obtained. Note that in this specification, liquid rubber is not included in the above rubber components.

[0159] When liquid rubber is included, the content of the rubber component per 100 parts by mass 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, even more preferably 7 parts by mass or more, and particularly preferably 10 parts by mass or more, from the viewpoint of the effects of the present invention. Furthermore, the content is 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.

[0160] Examples of ester-based plasticizers include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelaate (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). Ester-based plasticizers may be used individually or in combination of two or more.

[0161] From the viewpoint of the effects of the present invention, the content of plasticizers per 100 parts by mass of rubber components (total amount if multiple plasticizers are used in combination) is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more. Furthermore, the content 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.

[0162] 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 viewpoint 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.

[0163] The vulcanized rubber particles are not particularly limited and may be either unmodified vulcanized rubber particles or modified vulcanized rubber particles.

[0164] Commercially available vulcanized rubber products can be used, such as those from Lehigh, Muraoka Rubber Industries, and others.

[0165] While not particularly limited, examples of anti-aging agents include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; 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'-ditril-p-phenylenediamine. Examples include p-phenylenediamine-based antioxidants such as methyl amine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based 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 Co., Ltd., Flexis, and others. The antioxidant may be used alone or in combination of two or more.

[0166] When an anti-aging agent is included, 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 the rubber's resistance to ozone cracking. Furthermore, from the viewpoint of wear resistance, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0167] 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. The wax can be commercially available from companies such as Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Paramelt Co., Ltd. The wax may be used alone or in combination of two or more types.

[0168] When wax is included, the amount of wax per 100 parts by mass of 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 weather resistance of the rubber. Furthermore, from the viewpoint of preventing whitening of the tire due to bloom, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0169] Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. Processing aids may be used individually or in combination of two or more. Examples of processing aids that can be used are those commercially available from companies such as Schill+Seilacher and Performance Additives.

[0170] When stearic acid is included, its content per 100 parts by mass of 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 processability. Furthermore, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0171] When zinc oxide is included, its content per 100 parts by mass of 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 processability. Furthermore, from the viewpoint of wear resistance, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0172] Sulfur is preferably used as a vulcanizing agent. Suitable sulfur varieties include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

[0173] When sulfur is included as a vulcanizing agent, the amount of sulfur per 100 parts by mass of 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, it 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 amount of vulcanizing agent is the total amount of pure sulfur contained in the oil-containing sulfur.

[0174] As a vulcanizing agent other than sulfur, known organic crosslinking agents can also be used. The organic crosslinking agent is not particularly limited as long as it can form crosslinking chains other than polysulfide bonds, but examples include alkylphenol-sulfur chloride condensates, 1,6-hexamethylene-dithiosulfate sodium dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, and dicumyl peroxide. These organic crosslinking agents can be commercially available from companies such as Taoka Chemical Industries, Ltd., Lanxess Corporation, and Flexis.

[0175] The vulcanization accelerator is not particularly limited, but examples include sulfenamide-based vulcanization accelerators, thiazole-based vulcanization accelerators, guanidine-based vulcanization accelerators, thiram-based vulcanization accelerators, thiourea-based vulcanization accelerators, dithiocarbamate-based vulcanization accelerators, aldehyde-amine-based vulcanization accelerators, aldehyde-ammonia-based vulcanization accelerators, imidazoline-based vulcanization accelerators, xanthate-based vulcanization accelerators, caprolactam disulfide, and the like. The vulcanization accelerator may be used alone or in combination of two or more. Among these, one or more vulcanization accelerators selected from the group consisting of sulfenamide-based vulcanization accelerators, thiazole-based vulcanization accelerators, and guanidine-based vulcanization accelerators are preferred because they more favorably produce the desired effect. The vulcanization accelerator may be used alone or in combination of two or more.

[0176] Examples of sulfenamide-based vulcanization accelerators include N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide (DCBS).

[0177] Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole (MBT) or its salts, di-2-benzothiazolyl disulfide (MBTS), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, and 2-(2,6-diethyl-4-morpholinothio)benzothiazole. Of these, MBTS and MBT are preferred, with MBTS being more preferred.

[0178] Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatecholborate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 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 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, even more preferably 0.1 parts by mass or less, and particularly preferably no guanidine-based vulcanization accelerator is contained, from the viewpoint of the effects of the present invention.

[0179] When a vulcanization accelerator is included, its 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 ensuring a sufficient vulcanization rate. Furthermore, from the viewpoint of suppressing blooming, the content of the vulcanization accelerator is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0180] In this specification, various materials containing carbon atoms (e.g., rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from atmospheric carbon dioxide. Methods for obtaining these materials from carbon dioxide include directly converting carbon dioxide, or converting methane obtained through a methanation process in which methane is synthesized from carbon dioxide.

[0181] [Manufacturing of rubber compositions and tires] The rubber composition according to this embodiment can be manufactured by known methods. For example, it can be manufactured by kneading each of the above components using a rubber kneading device such as an open roll or a closed kneader (Banbury mixer, kneader, etc.).

[0182] The mixing process includes, for example, a base mixing process in which compounding agents and additives other than the vulcanizing agent and vulcanization accelerator are mixed, and a final mixing (F mixing) process in which the vulcanizing agent and vulcanization accelerator are added to the mixture obtained in the base mixing process and mixed. Furthermore, the base mixing process can be divided into multiple processes as desired.

[0183] While there are no particular limitations on the mixing conditions, one example is to mix the base mixture at a discharge temperature of 150-170°C for 3-10 minutes, and then mix the final mixture at 70-110°C for 1-5 minutes.

[0184] The tires according to this embodiment can be manufactured by conventional methods using the corresponding rubber compositions. Specifically, a metal cord is coated with an unvulcanized rubber composition corresponding to the belt topping rubber to obtain a ply that forms the belt layer as a metal cord-rubber composite. Furthermore, the unvulcanized rubber composition corresponding to the tread portion obtained by the above method is molded to match the shape of the tread portion. These are then bonded together with other tire components on a tire molding machine and molded in a conventional method to form an unvulcanized tire, and this unvulcanized tire is heated and pressurized in a vulcanizing machine to manufacture the tire. The vulcanization conditions are not particularly limited, but for example, a method of vulcanization at 150 to 200°C for 10 to 30 minutes can be used.

[0185] [Tire Uses] The tire according to this embodiment can be a general-purpose tire such as a passenger car tire, a truck / bus tire, or a motorcycle tire, or it can be a racing tire. A passenger car tire refers to a tire intended for use on a four-wheeled vehicle, with a maximum load capacity of 1000 kg or less. The type of tire is not particularly limited and may be either a pneumatic tire or a solid tire. Furthermore, the tire according to this embodiment can be used as an all-season tire, a summer tire, or a winter tire such as a studless tire. [Examples]

[0186] The following examples (examples) are shown as preferred for implementation, but the scope of the present invention is not limited to these examples. Using the various chemicals shown below, we examined a tire having a tread portion obtained according to the formulation in Table 1 and a belt layer having steel cords as described in Table 1, and the results calculated based on the evaluation method below are shown in Table 1.

[0187] The various chemicals used in the examples and comparative examples are summarized below. IR-type rubber: NR (TSR20) SBR: SBR produced by the following manufacturing example 1 (S-SBR, styrene content: 20% by mass, vinyl content: 20 mol%, Tg: -60℃, Mw: 700,000, non-oil-based) BR: UBEPOL BR (registered trademark) 150B manufactured by UBE Corporation (unmodified BR, cis content: 97 mol%, Mw: 440,000) Carbon Black: Show Black N220 (N2SA: 115m) manufactured by Cabot Japan Co., Ltd. 2 / g, average primary particle diameter: 22nm) Silica: UltraSil 9100GR (N2SA: 230m) manufactured by Evonik Industries 2 / g, average primary particle diameter: 15nm) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Industries. Copolymer resin: ExxonMobil Oppera PR383 (hydrogenated DCPD-C9 resin, containing styrene and cyclopentadiene as monomer components, styrene content: 1.78% by mass, softening point: 103°C, Mw: 770) Terpene resin: SYLVATARAXX4150 (polyterpene resin, softening point: 115°C) manufactured by Kraton Corporation. Oil: H&R VivaTec500 (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: Beads of stearic acid manufactured by NOF Corporation Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd. (5% oil-containing powdered sulfur) Vulcanization accelerator: Noxellar CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0188] (Manufacturing example 1: Manufacturing of SBR1) Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene are charged into a nitrogen-purged autoclave reactor. The ratio of styrene to 1,3-butadiene is adjusted so that the styrene content is 20% by mass. After adjusting the temperature of the reactor contents to 20°C, n-butyllithium is added to start polymerization. Polymerization is carried out under adiabatic conditions, reaching a maximum temperature of 80°C. After confirming the formation of polymers with an Mw of 700,000 by GPC, the polymerization solution is poured into 4 L of ethanol and the precipitate is collected. The obtained precipitate is air-dried, and then dried under reduced pressure at 80°C / 10 Pa or less until the drying loss is 0.1% to obtain SBR1.

[0189] (Preparation of the belt layer) The steel cords described in Table 1 are coated with an unvulcanized rubber composition corresponding to the belt topping rubber to obtain a steel cord-rubber composite that forms the belt layer.

[0190] (Tire manufacturing) According to the formulation shown in Table 1, chemicals other than sulfur and vulcanization accelerator were mixed in a 1.7 L closed Banbury mixer for 5 minutes until the discharge temperature reached 160°C to obtain a mixture. Next, using a twin-screw open roll mixer, the vulcanizing agent and vulcanization accelerator were added to the obtained mixture and mixed for 4 minutes until the temperature reached 105°C to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was molded to the shape of the tread section and bonded together with the belt ply and other tire components to produce an unvulcanized tire, which was then vulcanized at 170°C to obtain each test tire (size: 155 / 70R19).

[0191] <Handling Stability Performance> Each test tire is mounted on one of the four wheels of a front-wheel-drive (FF) passenger car, and the vehicle is driven on a dry asphalt test course. The handling characteristics are evaluated based on the feeling of the test driver during straight driving, lane changes, and acceleration / deceleration at 100 km / h. The evaluation is given as an integer value from 1 to 5 points, with higher scores indicating better handling characteristics. The total score of 10 test drivers is calculated. The total score of the tires in Comparative Example 3 is converted to a baseline value (100), and the evaluation results of each test tire are indexed and displayed in proportion to the total score.

[0192] <Wet grip performance> Each test tire is mounted on one of the four wheels of a front-wheel-drive passenger car, and the braking distance from an initial speed of 100 km / h is measured on a wet asphalt surface. The measurement results are expressed as an index using the following formula. A higher index indicates a shorter braking distance and superior wet grip performance. (Wet grip performance index) = (Braking distance of the tire in Comparative Example 3) / (Braking distance of each test tire) × 100

[0193] <Overall Performance> The sum of the above handling stability performance index and wet grip performance index is displayed as the overall performance index.

[0194] [Table 1]

[0195] <Embodiment> Examples of embodiments of the present invention are shown below.

[0196] [1] A tire comprising a tread portion and a belt layer, wherein the tread portion is composed of a rubber composition comprising a rubber component including styrene-butadiene rubber and / or isoprene-based rubber, and a copolymer resin containing styrene and cyclopentadiene as monomer components, and the belt layer has metal cords consisting of one to four filaments, wherein the outer diameter of the filaments is D (mm), and the total amount of styrene in the rubber composition when the mass of the rubber component is 100% by mass is S (mass%), and D × S is greater than 2.0. [2] The tire according to [1] above, wherein the metal cord consists of a single filament. [3] A tire as described in [1] or [2] above, wherein D×S is greater than 3.3. [4] The tire according to any one of [1] to [3] above, wherein when the silica content in the rubber composition is Y (parts by mass) relative to 100 parts by mass of the rubber component, D × Y is greater than 16, preferably greater than 19, and more preferably greater than 21. [5] The tire according to any one of [1] to [4] above, wherein the content of the copolymer resin in the rubber composition is 10 parts by mass or more, preferably 20 parts by mass or more, and more preferably 30 parts by mass or more, relative to 100 parts by mass of the rubber component. [6] The tire according to any one of [1] to [5] above, wherein the rubber component comprises styrene-butadiene rubber and isoprene-based rubber. [7] A tire as described in any of [1] to [6] above, with an S value of 8.0 or higher. [8] The tire according to any one of [1] to [7] above, wherein the rubber component contains 40% by mass or more, preferably 50% by mass or more, and more preferably 60% by mass or more, styrene-butadiene rubber. [9] The tire according to any one of [1] to [8] above, wherein the average primary particle size of the silica contained in the rubber composition is less than 17 nm.

[10] The tire according to any one of [1] to [9] above, wherein the silica content Y in the rubber composition is 80 parts by mass or more per 100 parts by mass of the rubber component.

[11] The tire according to any one of [1] to

[10] above, wherein the rubber composition contains 1 to 25 parts by mass of carbon black per 100 parts by mass of the rubber component. [Explanation of symbols]

[0197] 11... Tires 12...Tread section 13. Sidewall section 14. Bead section 15. Inner Liner 16.. Carcass 17. Belt layer 18. Bead core 21, 50... Metal cord 22. Topping rubber 51...Filament CL... Center Line

Claims

1. A tire comprising a tread section and a belt layer, The tread portion is composed of a rubber composition containing a rubber component including styrene-butadiene rubber and / or isoprene-based rubber, and a copolymer resin containing styrene and cyclopentadiene as monomer components. The belt layer has a metal cord consisting of one to four filaments. When the outer diameter of the filament is D (mm), and the total amount of styrene in the rubber composition is S (mass%) when the mass of the rubber component is 100% by mass, Tires with a DxS rating of over 2.

0.

2. The tire according to claim 1, wherein the metal cord consists of a single filament.

3. The tire according to claim 1 or 2, wherein D×S is greater than 3.

3.

4. The tire according to claim 1 or 2, wherein when the silica content in the rubber composition is Y (parts by mass) relative to 100 parts by mass of the rubber component, D × Y is greater than 16.

5. The tire according to claim 1 or 2, wherein the content of the copolymer resin in the rubber composition is 10 parts by mass or more relative to 100 parts by mass of the rubber component.

6. The tire according to claim 1 or 2, wherein the rubber component comprises styrene-butadiene rubber and isoprene-based rubber.

7. The tire according to claim 1 or 2, wherein S is 8.0 or greater.

8. The tire according to claim 1 or 2, wherein the rubber component contains 40% by mass or more of styrene-butadiene rubber.

9. The tire according to claim 1 or 2, wherein the average primary particle size of the silica contained in the rubber composition is less than 17 nm.

10. The tire according to claim 1 or 2, wherein the silica content Y in the rubber composition is 80 parts by mass or more per 100 parts by mass of the rubber component.

11. The tire according to claim 1 or 2, wherein the rubber composition contains 1 to 25 parts by mass of carbon black per 100 parts by mass of the rubber component.

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