Heavy-duty tires

Abstract

To provide a heavy-duty tire that can improve wet grip performance after long-distance driving. [Solution] A heavy-duty tire comprising a tread, a carcass, and a belt layer, wherein the tread is composed of a rubber composition containing a rubber component including isoprene rubber, and a copolymer resin containing styrene and cyclopentadiene as monomer components, and when the total amount of styrene in the rubber composition constituting the tread is defined as S (mass%), the content of isoprene rubber in the rubber composition constituting the tread is C1 (mass%), the total thickness of the tread is T1 (mm), the average content of isoprene rubber in the topping rubber covering the belt layer is C2 (mass%), and the total thickness of the belt layer is defined as T2 (mm), and when a = C1 / T1 and b = C2 / T2, S / (a / b) is greater than 7.0.

Description

[Technical Field]

[0001] This invention relates to a heavy-duty tire. [Background technology]

[0002] Heavy-duty tires require particularly high resistance to fracture, but fracture resistance and fuel efficiency are inversely related. Furthermore, in recent years, due to increased safety concerns, there has been a growing demand for wet grip performance in heavy-duty tires, but wet grip performance and fuel efficiency are inversely related. Therefore, there is a need for a method to improve fuel efficiency, fracture resistance, and wet grip performance in a balanced manner. Patent Document 1 describes a heavy-duty tire that maintains fuel efficiency and fracture resistance while also exhibiting excellent wet grip performance. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-109935 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The present invention aims to provide a heavy-duty tire that can improve wet grip performance after long-distance driving. [Means for solving the problem]

[0005] The present invention relates to a heavy-duty tire including a tread, a carcass, and a belt layer, wherein the tread is composed of a rubber composition containing a rubber component including isoprene rubber and a copolymer resin containing styrene and cyclopentadiene as monomer components, the carcass includes a metal cord, the belt layer is provided between the tread and the carcass, and each of the plurality of belt plies constituting the belt layer is composed of a metal cord and a belt topping rubber including isoprene rubber. When the mass of the rubber composition constituting the tread is 100% by mass, the total styrene amount in the rubber composition constituting the tread is S (% by mass), the content of isoprene rubber in the rubber composition constituting the tread is C1 (% by mass), the total thickness of the tread is T1 (mm), the average content of isoprene rubber in the belt topping rubber is C2 (% by mass) when the mass of the belt topping rubber is 100% by mass, and the total thickness of the belt layer is T2 (mm), the present invention relates to a heavy-duty tire in which S / (a / b) is more than 7.0, where a = C1 / T1 and b = C2 / T2.

Advantages of the Invention

[0006] According to the present invention, there is provided a heavy-duty tire capable of improving wet grip performance after long-distance driving.

Brief Description of the Drawings

[0007] [Figure 1] It is a cross-sectional view of a heavy-duty tire according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view showing a part of a circumferential groove according to this embodiment. [Figure 3] It is a cross-sectional view showing a part of another circumferential groove according to this embodiment. [Figure 4] It is a view schematically showing a belt ply.

Embodiments for Carrying Out the Invention

[0008] A tire according to one embodiment of the present invention is a heavy-duty tire comprising a tread, a carcass, and a belt layer, wherein the tread is composed of a rubber composition containing a rubber component including isoprene rubber and a copolymer resin containing styrene and cyclopentadiene as monomer components, the carcass includes metal cords, the belt layer is provided between the tread and the carcass, and each of the plurality of belt plies constituting the belt layer consists of a metal cord and a belt topping rubber containing isoprene rubber, and the mass of the rubber composition constituting the tread is 100% by mass When a = C1 / T1 and b = C2 / T2, the total amount of styrene in the rubber composition constituting the tread is S (mass%), the amount of isoprene-based rubber in the rubber composition constituting the tread is C1 (mass%) when the mass of the rubber composition constituting the tread is 100% by mass, the total thickness of the tread is T1 (mm), the average amount of isoprene-based rubber in the belt topping rubber when the mass of the belt topping rubber is 100% by mass is C2 (mass%), and the total thickness of the belt layer is T2 (mm), then a = C1 / T1 and b = C2 / T2, and the result is a heavy-duty tire where S / (a / b) is greater than 7.0.

[0009] While not intended to be constrained by theory, the following is one possible mechanism for maintaining high wet grip performance even after long-distance driving in the heavy-duty tire of the present invention.

[0010] (1) By incorporating a copolymer resin containing styrene and cyclopentadiene as monomer components into the tread, the wet grip performance in the initial stages of use can be improved.

[0011] However, because styrene has low compatibility with isoprene-based rubber, in treads containing isoprene-based rubber, there is a concern that the copolymer resin will migrate from the tread surface to the radially inward side of the tire during driving, reducing the sustainability of wet grip performance. Therefore, it is thought that by reducing (2)a / b and making the isoprene-based rubber content per unit thickness of the belt layer installed radially inward from the tread relatively larger than the isoprene-based rubber content per unit thickness of the tread, the migration of the copolymer resin can be suppressed.

[0012] Furthermore, by increasing the ratio of S to a / b (3), it is believed that a remarkable effect can be achieved: the ability to maintain high wet grip performance for a long period of time.

[0013] The belt layer preferably includes high-angle belt plies with an absolute value of 10 degrees or more of the cord angle with respect to the tire circumferential direction, and low-angle belt plies with an absolute value of 5 degrees or less of the cord angle with respect to the tire circumferential direction.

[0014] The belt layer preferably comprises two or more high-angle belt plies and one or more low-angle belt plies, wherein the low-angle belt plies are provided between the two high-angle belt plies.

[0015] Preferably, the tread has grooves that have recesses that are recessed outward in the groove width direction from the groove edges that appear on the tread surface.

[0016] As the tread wears down, the groove width expands, which is thought to improve drainage and make it easier to improve wet grip performance after tire wear.

[0017] From the viewpoint of the effects of the present invention, it is preferable that a is less than 3.0.

[0018] From the viewpoint of the effects of the present invention, the metal cord included in the belt ply preferably has a 1x1 structure.

[0019] From the viewpoint of the effects of the present invention, the content of the copolymer resin in the rubber composition constituting the tread relative to 100 parts by mass of the rubber component is preferably 5 parts by mass or more.

[0020] Preferably, the rubber component constituting the tread further contains styrene-butadiene rubber. It is believed that the inclusion of styrene-butadiene rubber in the rubber component constituting the tread allows the tread, which conforms to the road surface, to generate heat efficiently.

[0021] The rubber composition constituting the tread preferably contains 10 parts by mass or more of silica per 100 parts by mass of the rubber component. It is believed that the inclusion of 10 parts by mass or more of silica 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] <Definition> The "tread" is a component that includes the part that forms the contact surface of the tire, and in the cross-section of the tire, which is a plane containing the tire's axis of rotation, it is a component that is positioned radially outward from other components such as the reinforcing layer and the carcass.

[0023] The "belt layer" is a layer located radially outward from the carcass layer. It includes multiple working layers in which the internal reinforcing material is tilted at an angle of approximately 18 to 30 degrees relative 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 degrees relative to the tire's circumferential direction.

[0024] "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.

[0025] 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.

[0026] 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).

[0027] "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.

[0028] "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.

[0029] "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.

[0030]

number

[0031] "Total tread thickness" refers to the overall thickness of the tread on the tire's equatorial plane when the tire is cut across a plane containing the tire's axis of rotation. In cases where the tire has circumferential grooves on its equatorial plane, it refers to the overall thickness of the tread from the point where a straight line connecting the tire's widthwise ends on the tire's equatorial plane intersects with the tire's equatorial plane.

[0032] "Total belt layer thickness" refers to the total thickness of the belt layer on the tire's equatorial plane when the tire is cut in a cross-section along the plane containing the tire's rotation axis.

[0033] "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.

[0034] A "plasticizer" is a material that imparts plasticity to rubber components and is extracted from rubber compositions using acetone. Plasticizers include those that are liquid at 25°C and those that are solid at 25°C. However, waxes and stearic acid commonly used in the tire industry are excluded.

[0035] "Plasticizer content" also includes the amount of plasticizer contained in the stretched rubber component previously stretched by a plasticizer such as oil, resin component, liquid rubber component, etc. The same applies to the content of oil, resin component, and liquid rubber. For example, when the stretching component is oil, the stretched oil is included in the oil content.

[0036] <Measurement method> "Styrene content" is calculated by pyrolysis gas chromatography or NMR measurement ( 1 1H-NMR and 13 13C-NMR). Component amounts such as "styrene content" are different from physical property values such as complex elastic modulus (E*). Since there is a true value that does not depend on the measurement method, it is preferable to use a measurement method with as high precision as possible. In this specification, "pyrolysis gas chromatography" refers to a method in which a sample is heated by a pyrolysis device, the individual components contained in the gas-phase components generated by this heating are separated by a separation column, and each isolated component is analyzed. Styrene content is applied to, for example, rubber components having repeating units (styrene units) derived from styrene such as SBR.

[0037] "Vinyl content (amount of 1,2-bonded butadiene units)" is calculated by pyrolysis gas chromatography or NMR measurement ( 1 1H-NMR and 13 13C-NMR). Similar to the "styrene content", since there is a true value for the "vinyl content" that does not depend on the measurement method, it is preferable to use a measurement method with as high precision as possible. Vinyl content is applied to, for example, rubber components having repeating units derived from butadiene such as SBR and BR.

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

[0039] "Total styrene content S in the rubber composition" refers to the total amount of styrene (mass%) in the rubber composition when the mass of the rubber composition is set to 100% by mass, and is the sum of the amount of styrene contained in the rubber component and the amount of styrene contained in compounding agents other than the rubber component.

[0040] The aforementioned "styrene portion" is not particularly limited as long as it is a group having a styrene structure, but examples include styrene, α-methylstyrene, vinyltoluene, chlorostyrene, etc. In this specification, when the "styrene portion" is styrene (for example, when the styrene portion-containing rubber is styrene-butadiene rubber), the "styrene portion content" may be expressed as "styrene content".

[0041] The "total amount of styrene S (mass%) in the rubber composition" can be calculated by multiplying the total amount of styrene (mass%) in the rubber composition, assuming the mass of the rubber component is 100% by mass, by the mass of the rubber component relative to the total mass of the rubber composition.

[0042] The "total amount of styrene (mass%) in the rubber composition when the mass of the rubber component is 100% by mass" is determined by first calculating the value obtained by multiplying the styrene content (mass%) of each rubber component by its mass fraction in the rubber component, and then summing these values ​​together. Next, for each styrene-containing compounding agent other than the rubber component contained in the rubber composition, the value obtained by multiplying the styrene content (mass%) of each styrene-containing compounding agent by its mass fraction relative to 100 parts by mass of the rubber component, and then summing these values ​​together. The total amount of styrene in the rubber composition is then calculated by adding these two sums together.

[0043] 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, and the total mass of the rubber composition per 100 parts by mass of the rubber component is 186 parts by mass, then the total amount of styrene S in the rubber composition per 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)} × 100 / 186 = 13.5 (by mass).

[0044] 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 manufactured by Tosoh Corporation, with a differential refractometer as the detector and TSKgel® SuperMultiporeHZ-M column manufactured by Tosoh Corporation) to a standard polystyrene equivalent. This method is applicable, for example, to SBR, BR, plasticizers, etc.

[0045] The nitrogen adsorption specific surface area (N2SA) of carbon black is measured in accordance with JIS K 6217-2:2017.

[0046] The nitrogen adsorption specific surface area (N2SA) of silica is measured by the BET method in accordance with ASTM D3037-93.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] [tire] The heavy-duty tire according to this embodiment is a heavy-duty tire comprising a tread and a carcass, wherein the tread is composed of the rubber composition described below, the carcass includes metal cords, a belt layer is provided between the tread and the carcass, and each of the plurality of belt plies constituting the belt layer consists of metal cords and a belt topping rubber containing isoprene rubber, and the total amount of the rubber composition constituting the tread when the mass of the rubber composition constituting the tread is 100% by mass. When the amount of ethylene is S (mass%), the amount of isoprene-based rubber in the rubber composition constituting the tread is C1 (mass%) when the mass of the rubber composition constituting the tread is 100% by mass, the total thickness of the tread is T1 (mm), the average amount of isoprene-based rubber in the belt topping rubber when the mass of the belt topping rubber is 100% by mass is C2 (mass%), and the total thickness of the belt layer is T2 (mm), and a = C1 / T1 and b = C2 / T2 are defined, then S / (a / b) is greater than 7.0. The following describes a tire according to one embodiment of the present invention with reference to the drawings, but the drawings are for illustrative purposes only. Furthermore, the embodiments shown below are merely examples.

[0051] Figure 1 is a cross-sectional view showing a part of a heavy-duty tire according to this embodiment. In Figure 1, the vertical direction is the radial direction of the heavy-duty tire 1, the horizontal direction is the tire width direction of the heavy-duty tire 1, and the direction perpendicular to the plane of the paper is the circumferential direction of the heavy-duty tire 1. In Figure 1, the tire centerline CL of the heavy-duty tire 1 also represents the equatorial plane EQ of the heavy-duty tire 1. The shape of this heavy-duty tire 1 is symmetrical with respect to the equatorial plane EQ, except for the tread pattern.

[0052] This heavy-duty tire 1 comprises a tread 3, a belt layer 6, a sidewall 7, an inner liner 15, and a carcass 16. The inner liner 15 is located inside the carcass 16. The tread 3 forms a tread surface 2 that contacts the road surface. The tread surface 2 has circumferential grooves 8 that extend continuously in the circumferential direction of the tire.

[0053] <Tread> The tread 3 may be a tread consisting of a single rubber layer, or it may be a tread 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.

[0054] In Figure 1, the tread 3 comprises a cap rubber layer 4 and a base rubber layer 5, with the outer surface of the cap rubber layer 4 forming the tread surface 2, and the base rubber layer 5 adjacent to the inner side of the cap rubber layer 4 in the tire radial direction. Furthermore, there may be one or more additional rubber layers between the base rubber layer 5 and the belt layer 6, as long as the effects of the present invention are achieved.

[0055] In this specification, "rubber composition constituting the tread" refers to the rubber composition constituting the cap rubber layer when the tread consists of two or more layers.

[0056] The total tread thickness T1 is preferably 8.0 mm or more, more preferably 10.0 mm or more, even more preferably 12.0 mm or more, and particularly preferably 14.0 mm or more. On the other hand, T1 is preferably 22.0 mm or less, more preferably 20.0 mm or less, even more preferably 18.0 mm or less, even more preferably 17.0 mm or less, and particularly preferably 16.0 mm or less.

[0057] The tread preferably has grooves with recesses that are recessed outward in the groove width direction from the groove edges that are visible on the tread surface. There are no particular limitations on the grooves with such recesses, but circumferential grooves are preferred.

[0058] Figure 2 is a cross-sectional view showing a portion of the circumferential groove according to this embodiment. In Figure 2, the vertical direction is the radial direction of the tire, the horizontal direction is the axial direction of the tire, and the direction perpendicular to the plane of the paper is the circumferential direction of the tire. In Figure 2, the groove wall 10 of the circumferential groove 8 is provided with a recess that is recessed outward in the groove width direction from the groove edge 12 that appears on the tread surface of the tire. In Figure 2, the groove width gradually increases from the end on the tire surface side toward the radial side of the tire, but the embodiment is not limited to this configuration.

[0059] Figure 3 is a cross-sectional view showing a portion of another circumferential groove according to this embodiment. In Figure 3, the circumferential groove 8 has a constant groove width in a range of distance L from the tread surface 2, and from there the groove width gradually increases toward the radially inward direction of the tire, then gradually decreases to form a recess 9.

[0060] The total recess amount of the circumferential groove 8 (c1 + c2 in Figures 2 and 3) is preferably 0.10 to 5.00 times the groove width W1 of the circumferential groove 8, more preferably 0.20 to 3.00 times, and even more preferably 0.30 to 1.00 times. If there are multiple circumferential grooves having such recesses, it is sufficient that the total recess amount of any one of the circumferential grooves satisfies the above relationship, and it is also acceptable for all grooves having recesses to satisfy the above relationship.

[0061] From the viewpoint of the effects of the present invention, the groove depth H of the circumferential groove is preferably greater than 5 mm, more preferably greater than 8 mm, even more preferably greater than 10 mm, and particularly preferably greater than 12 mm. On the other hand, H is preferably less than 26 mm, more preferably less than 24 mm, even more preferably less than 22 mm, and particularly preferably less than 20 mm.

[0062] <Belt layer and carcass> The belt layer 6 extends in the tire width direction and is located on the radially inner side of the tread 3. The belt layer 6 is also located on the radially outer side of the carcass 16 and reinforces the carcass 16.

[0063] In Figure 1, the belt layer 6 is formed of four belt plies, including a first belt ply 6a, a second belt ply 6b, a third belt ply 6c, and a fourth belt ply 6d, which are stacked in order from the inside in the radial direction of the tire. The first belt ply 6a is stacked on the carcass 16. In Figure 1, in the tire rotation axis direction, the second belt ply 6b has the largest width among the four layers, and the fourth belt ply 6d has the smallest width among the four layers, but the configuration is not limited to this.

[0064] Each of the multiple belt plies constituting the belt layer 6 consists of a metal cord and a belt topping rubber containing isoprene-based rubber. Figure 4 shows a cross-sectional view of the metal cord 21 in a plane perpendicular to the longitudinal direction. Each belt ply constituting the belt layer 6 has multiple metal cords 21 and a 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 the topping rubber 22. The metal cords 21 are embedded in the topping rubber 22.

[0065] The metal cord according to this embodiment has one or more 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 or more filaments. Preferably, the metal cord according to this embodiment is composed of one to four filaments.

[0066] When a single metal cord has two or more filaments, it is preferable that the metal cord has a twisted structure in which the 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.

[0067] 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 a 1×2 structure, a 1×3 structure, a 1×4 structure, and so on.

[0068] 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.

[0069] 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 steel 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.

[0070] The outer diameter D of the metal cord filament is preferably 0.37 mm or more, more preferably 0.39 mm or more, and even more preferably 0.41 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 0.49 mm or less, more preferably 0.47 mm or less, and even more preferably 0.45 mm or less.

[0071] The metal cord according to this embodiment may be plated by a known method. A metal cord having a plated layer exhibits high moisture-resistant heat adhesion 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 plated layer can be applied to the surface of each filament.

[0072] 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.

[0073] 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.

[0074] The belt layer 6 preferably includes high-angle belt plies with an absolute value of 10 degrees or more (preferably 10 degrees or more and 70 degrees or less, more preferably 12 degrees or more and 60 degrees or less, and even more preferably 15 degrees or more and 50 degrees or less) of the cord angle with respect to the tire circumferential direction, and low-angle belt plies with an absolute value of 5 degrees or less (preferably 4 degrees or less, more preferably 3 degrees or less, and even more preferably 2 degrees or less) of the cord angle with respect to the tire circumferential direction.

[0075] In this specification, the code angle is the angle relative to the tire circumferential direction when the tire is viewed in a plan view in the tire radial direction, and is the angle at any position in the tire circumferential direction. If there are multiple code angles at that tire circumferential position, it is at least one of them. The sign of the code angle is positive if the metal code extends away from the tire centerline CL to the right, and negative if it extends away from the tire centerline CL to the left.

[0076] The belt layer 6 includes two or more high-angle belt plies and one or more low-angle belt plies, and it is preferable that the low-angle belt plies are provided between the two high-angle belt plies. For example, the first belt ply 6a and the fourth belt ply 6d can be high-angle belt plies, and the second belt ply 6b and / or the third belt ply 6c can be low-angle belt plies.

[0077] The total thickness T2 of the belt layer is preferably 1.0 mm or more, more preferably 1.5 mm or more, even more preferably 2.0 mm or more, and particularly preferably 2.5 mm or more. On the other hand, T2 is preferably 5.0 mm or less, more preferably 4.5 mm or less, even more preferably 4.0 mm or less, and particularly preferably 3.5 mm or less.

[0078] In Figure 1, the carcass 16 is formed from a single carcass ply, but the invention is not limited to this configuration and may be formed from two or more carcass plies. The carcass 16 includes a metal cord, which is covered with a topping rubber. The metal cord and topping rubber constituting the carcass ply can be the same as those constituting the belt ply.

[0079] The absolute value of the cord angle of the metal cords contained in the carcass 16 with respect to the tire circumferential direction is not particularly limited, but is preferably 70 degrees or more and 90 degrees or less.

[0080] In the rubber composition constituting the tread, the total amount of styrene S in the rubber composition, when the mass of the rubber composition is 100% by mass, is preferably 0.50% by mass or more, more preferably 0.70% by mass or more, even more preferably 0.90% by mass or more, and particularly preferably 1.10% by mass or more, from the viewpoint of the effects of the present invention. On the other hand, there is no particular upper limit to S, but from the viewpoint of low fuel consumption performance, it is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5.0% by mass or less.

[0081] 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.

[0082] In the rubber composition constituting the tread, the isoprene-based rubber content C1 in the rubber composition, when the mass of the rubber composition is 100% by mass, is preferably 15% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, even more preferably 30% by mass or more, even more preferably 35% by mass or more, and particularly preferably 40% by mass or more. On the other hand, C1 is preferably 60% by mass or less, more preferably 55% by mass or less, even more preferably 50% by mass or less, and particularly preferably 47% by mass or less.

[0083] The value of 'a' determined by C1 / T1 is an index representing the isoprene-based rubber content per unit thickness in the rubber composition constituting the tread. 'a' is preferably 1.0 or higher, more preferably 1.5 or higher, even more preferably 2.0 or higher, and particularly preferably 2.5 or higher. On the other hand, 'a' is preferably 7.0 or lower, more preferably 6.0 or lower, even more preferably 5.0 or lower, and particularly preferably 4.0 or lower.

[0084] As the rubber composition constituting the belt topping rubber, a standard composition used in the tire industry for covering metal cords can be used.

[0085] The rubber components that can be used for belt topping rubber are not particularly limited, and include natural rubber (NR), isoprene-based rubbers such as isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), and the like. The rubber components preferably contain 50% by mass or more of isoprene-based rubber, more preferably 60% by mass or more, and even more preferably 70% by mass or more.

[0086] In the rubber composition constituting the belt topping rubber, there are no particular limitations on the components other than the rubber component, but for example, the following can be used in the following amounts per 100 parts by mass of the rubber component.

[0087] [Table 1]

[0088] In the rubber composition constituting the belt topping rubber, when the mass of the rubber composition is 100% by mass, the isoprene-based rubber content C2 in the rubber composition is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, even more preferably 50% by mass or more, and particularly preferably 52% by mass or more. On the other hand, C2 is preferably 66% by mass or less, more preferably 64% by mass or less, even more preferably 62% by mass or less, and particularly preferably 60% by mass or less.

[0089] The value of b, determined by C2 / T2, is an index representing the isoprene-based rubber content per unit thickness in the rubber composition constituting the belt topping rubber. A value of b of 6.0 or higher is preferred, more preferably 9.0 or higher, even more preferably 12.0 or higher, and particularly preferred 15.0 or higher. On the other hand, a value of b of 60.0 or lower is preferred, more preferably 50.0 or lower, even more preferably 40.0 or lower, and particularly preferred 30.0 or lower.

[0090] From the viewpoint of the effects of the present invention, a / b is preferably less than 1.0, more preferably less than 0.80, even more preferably less than 0.60, even more preferably less than 0.40, even more preferably less than 0.30, and particularly preferably less than 0.25. On the other hand, a / b is preferably greater than 0.05, more preferably greater than 0.07, even more preferably greater than 0.09, even more preferably greater than 0.11, and particularly preferably greater than 0.13.

[0091] From the viewpoint of the effects of the present invention, S / (a / b) is greater than 7.0, preferably greater than 7.2, more preferably greater than 7.4, and still preferably greater than 7.5. On the other hand, there is no particular upper limit to S / (a / b), but it is preferably less than 200, more preferably less than 150, still preferably less than 100, still preferably less than 50, still preferably less than 40, still still preferably less than 30, and particularly preferably less than 20.

[0092] [Rubber composition that makes up the tread] The rubber composition constituting the tread according to this embodiment (hereinafter referred to as the rubber composition according to this embodiment) comprises a rubber component containing isoprene 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.

[0093] <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.

[0094] 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.

[0095] The rubber component according to this embodiment includes isoprene as an essential component. The rubber component preferably includes isoprene rubber and SBR, and may consist only of isoprene rubber and SBR.

[0096] (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. These isoprene-based rubbers may be used individually or in combination of two or more types.

[0097] NR is not particularly limited and can use any tire that is common in the tire industry, such as SIR20, RSS#3, and TSR20.

[0098] From the viewpoint of the effects of the present invention, the content of isoprene-based rubber in the rubber component is preferably 30% by mass or more, more preferably 45% by mass or more, even more preferably 60% 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 it is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.

[0099] (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 versions of these SBRs (hydrogenated SBRs) can also be used. These SBRs may be used individually or in combination of two or more types.

[0100] 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.

[0101] 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.

[0102] The styrene content of SBR can be appropriately set so that S / (a / b) falls within the above range, but is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more. On the other hand, the styrene content of SBR is preferably less than 40% by mass, more preferably less than 35% by mass, even more preferably less than 30% by mass, and particularly preferably less than 25% by mass. In this specification, the styrene content of SBR is measured by the measurement method described above.

[0103] 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.

[0104] 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.

[0105] The weight-average molecular weight (Mw) of SBR is preferably greater than 100,000, more preferably greater than 150,000, and even more preferably greater than 200,000. Furthermore, from the viewpoint of crosslinking uniformity, the Mw is preferably less than 2,000,000, more preferably less than 1,500,000, and even more preferably less than 1,000,000. The Mw of SBR is measured by the measurement method described above.

[0106] 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.

[0107] The SBR content in the rubber component can be appropriately set so that S / (a / b) falls within the above range, but is preferably 5% by mass or more, more preferably 7% by mass or more, even more preferably 10% by mass or more, even more preferably 12% by mass or more, even more preferably 15% by mass or more, and particularly preferably 18% by mass or more. Furthermore, the SBR content in the rubber component is preferably 70% by mass or less, more preferably 55% by mass or less, even more preferably 40% by mass or less, and particularly preferably 25% by mass or less.

[0108] (BR) While there are no particular limitations on the type of BR used, common types used in the tire industry can be used, such as BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare-earth butadiene rubber synthesized using a rare-earth element catalyst (rare-earth BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), and modified BR (high-cis modified BR, low-cis modified BR). These BRs may be used individually or in combination of two or more types.

[0109] 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.

[0110] From the viewpoint of the effects of the present invention, the BR content in the rubber component is preferably less than 30% by mass, more preferably less than 20% by mass, even more preferably less than 10% by mass, and particularly preferably less than 5% by mass. 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.

[0111] (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.

[0112] (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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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 concentration14 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.

[0118] 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.

[0119] on the other hand, 14 C is continuously produced by cosmic rays undergoing 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.

[0120] 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 value obtained by correcting C to a constant value and applying decay correction from 1950 AD to the measurement date is the standard value. 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.

[0121] 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%.

[0122] Based on the 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. <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.

[0123] (silica) The silica used is not particularly limited, and common types 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. These silicas may be used individually or in combination of two or more types.

[0124] 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.

[0125] 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.

[0126] 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.).

[0127] Amorphous silica extracted from rice husks can be commercially available from companies such as Wilmar.

[0128] The specific surface area (N2SA) of silica for nitrogen adsorption is 110 m², from the viewpoint of the effects of the present invention. 2Preferably more than / g, 130m 2 More preferably than / g, 150m 2 More preferably than / g, 170m 2 More preferably than / g, 190m 2 More preferably than / g, 210m 2 A value exceeding / g is particularly preferred. Furthermore, the N2SA is 350m 2 Preferably less than / g, 320m 2 Less than / g is more preferable, 280m 2 A value of less than / g is even more preferable. The N2SA of silica is measured by the measurement method described above.

[0129] The average primary particle diameter of silica is preferably 24 nm or less, more preferably 22 nm or less, even more preferably 20 nm or less, and particularly preferably 18 nm or less. 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.

[0130] From the viewpoint of the effects of the present invention, the silica content per 100 parts by mass of rubber component is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more. Furthermore, the silica content is preferably 100 parts by mass or less, more preferably 800 parts by mass or less, even more preferably 600 parts by mass or less, and particularly preferably 40 parts by mass or less.

[0131] (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 the 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 the 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. These carbon blacks may be used individually or in combination of two or more types.

[0132] 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.

[0133] 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).

[0134] 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.

[0135] Recycled carbon black can be purchased from companies such as Strable Green Carbon and LD Carbon.

[0136] The nitrogen adsorption specific surface area (N2SA) of carbon black is 30m² from the perspective of reinforcement. 2 Preferably 50m2 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 / g or less is more preferable, 120m 2 A value of less than or equal to / g is even more preferable.

[0137] 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.

[0138] When carbon black is included, the 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, even more preferably 30 parts by mass or more, and particularly preferably 35 parts by mass or more, from the viewpoint of reinforcing properties. Furthermore, from the viewpoint of suppressing heat generation, it is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 60 parts by mass or less, and particularly preferably 50 parts by mass or less.

[0139] (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.

[0140] 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 50 parts by mass or more, more preferably 55 parts by mass or more, even more preferably 60 parts by mass or more, and particularly preferably 65 parts by mass or more. Furthermore, the content is preferably 140 parts by mass or less, more preferably 130 parts by mass or less, and even more preferably 120 parts by mass or less.

[0141] The silica content in the filler is preferably 25% by mass or more, more preferably 30% by mass or more, even more preferably 35% by mass or more, and particularly preferably 40% by mass or more. Furthermore, the silica content in the filler is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 80% by mass or less, and particularly preferably 70% by mass or less.

[0142] (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. These silane coupling agents may be used individually or in combination of two or more.

[0143] 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.

[0144] <Plasticizer> The rubber composition according to this embodiment contains a copolymer resin (hereinafter simply referred to as "copolymer resin") containing styrene and cyclopentadiene as monomer components as a plasticizer, and may also contain other plasticizers besides the copolymer resin. Examples of other plasticizers include resin components other than the copolymer resin, oils, liquid polymers, ester-based plasticizers, etc. These plasticizers may be derived from mineral resources such as petroleum and natural gas, from biomass, or from 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.

[0145] (Resin components) The rubber composition according to this embodiment includes a copolymer resin containing styrene and cyclopentadiene as monomer components as a resin component, and other resin components may be used in combination. The resin components that can be used in this embodiment are not particularly limited, but resins commonly used in the tire industry can be used, such as C9 resins, C5 resins, C5C9 resins, dicyclopentadiene resins, aromatic vinyl resins, coumarone resins, indene resins, terpene resins, rosin resins, phenolic resins, etc. These 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.

[0146] ≪Copolymer resin≫ 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.

[0147] 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.

[0148] The copolymer resin is preferably a DCPD-C9 resin, which is a copolymer of cyclopentadiene and / or dicyclopentadiene with the C9 fraction described below. Alternatively, the DCPD-C9 resin may be hydrogenated or modified.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] The copolymer resin content 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. 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.

[0153] The resin components other than the copolymer resin are not particularly limited, but resins commonly used in the tire industry can be used, such as C9 resins, C5 resins, C5C9 resins, aromatic vinyl resins, coumarone resins, indene resins, terpene resins, rosin resins, phenolic resins, etc. These 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.

[0154] ≪C9 series resin≫ 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.

[0155] ≪C5 series resin≫ "C5 resins" refer to resins obtained by polymerizing C5 fractions, and may be hydrogenated or modified versions of these resins. 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. As C5 resins, commercially available products from companies such as Structol, Nippon Zeon Co., Ltd., and ENEOS Corporation can be used.

[0156] ≪C5C9 resin≫ "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.

[0157] Aromatic vinyl resin "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.

[0158] Coumaron-based resin "Coumarone-based resin" refers to a resin containing coumarone as a monomer component, and may be hydrogenated or modified. Preferred coumarone-based resins include, for example, coumarone resin, which is a polymer with coumarone as the monomer component; coumarone-indene resin, which is a copolymer with coumarone and indene as monomer components; and coumarone-indene-styrene resin, which is a copolymer with coumarone, indene, and styrene as monomer components. As coumarone-based resins, commercially available products from companies such as Rutgers, Nippon Paint Chemical Co., Ltd., and Mitsui Chemicals, Inc. can be used.

[0159] Indene resin "Indene-based resin" refers to a resin containing indene as a monomer component, and may be hydrogenated or modified resins. Preferred indene-based resins include, for example, coumarone-indene resin, which is a copolymer of coumarone and indene as monomer components, and coumarone-indene-styrene resin, which is a copolymer of coumarone, indene, and styrene as monomer components. Commercially available indene-based resins from companies such as Rutgers, Nippon Paint Chemical Co., Ltd., and Mitsui Chemicals, Inc. can be used.

[0160] Terpene resins "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.

[0161] ≪Rosin-based resin≫ "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.

[0162] Phenolic resins "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.

[0163] The content of resin components (total amount when multiple resin components are used in combination) per 100 parts by mass of rubber components 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. 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.

[0164] (oil) 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.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] Examples of animal oils include fish oil, beef tallow, whale oil, or oleyl alcohol which can be derived from them.

[0173] When oil is included, the content of oil per 100 parts by mass of rubber component (total amount if multiple oils are used in combination) 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. Furthermore, the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less.

[0174] (Liquid polymer) The liquid polymer is not particularly limited as long as it is a polymer that is in a liquid state at 25°C, but examples include liquid rubbers such as liquid butadiene rubber (liquid BR), liquid styrene butadiene rubber (liquid SBR), liquid isoprene rubber (liquid IR), liquid styrene isoprene rubber (liquid SIR), and liquid farnesene rubber. These liquid polymers may be used individually or in combination of two or more.

[0175] The weight-average molecular weight (Mw) of the liquid polymer is usually less than 10,000, preferably 9,000 or less, more preferably 6,000 or less, and even more preferably 4,500 or less. The Mw of the liquid rubber is preferably 100 or more, more preferably 500 or more, even more preferably 1,000 or more, even more preferably 1,500 or more, and particularly preferably 2,000 or more. When the Mw of the liquid polymer is within the above range, the effects of the present invention tend to be better obtained. Note that in this specification, the liquid polymer is not included in the rubber component described above.

[0176] (Ester-based plasticizers) 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.

[0177] From the viewpoint of the effects of the present invention, the content of plasticizer per 100 parts by mass of rubber component (total amount if multiple plasticizers are used in combination) 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. 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.

[0178] <Other compounding agents> In addition to the components mentioned above, the rubber composition according to this embodiment may appropriately contain compounding agents commonly used in the tire industry, such as vulcanized rubber particles (rubber powder), antioxidants, waxes, processing aids, stearic acid, zinc oxide, vulcanizing agents, and vulcanization accelerators.

[0179] 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.

[0180] The vulcanized rubber particles are not particularly limited and may be either unmodified vulcanized rubber particles or modified vulcanized rubber particles.

[0181] Commercially available vulcanized rubber products can be used, such as those from Lehigh, Muraoka Rubber Industries, and others.

[0182] 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 companies such as Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis. These antioxidants may be used individually or in combination of two or more.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. For example, commercially available processing aids from companies such as Schill+Seilacher and Performance Additives can be used. These processing aids may be used individually or in combination of two or more.

[0187] When a processing aid is included, the 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 exhibiting an effect of improving processability. Furthermore, from the viewpoint of abrasion resistance and fracture strength, it is preferably less than 10 parts by mass, more preferably 8.0 parts by mass or less, and even more preferably 5.0 parts by mass or less.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] 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.

[0192] 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, hexamethylene-1,6-bisthiosulfate 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.

[0193] 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. These vulcanization accelerators may be used individually 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.

[0194] 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).

[0195] 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.

[0196] Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salts of dicatecholborate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine.

[0197] When a vulcanization accelerator is included, the content per 100 parts by mass of the rubber component (total amount if multiple vulcanization accelerators are used in combination) is preferably 0.5 parts by mass or more, more preferably 0.7 parts by mass or more, and even more preferably 1.0 part 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 7.0 parts by mass or less.

[0198] 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.

[0199] [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.).

[0200] 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.

[0201] 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.

[0202] 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 obtained by the above method is molded to match the shape of the tread. 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.

[0203] [Tire Uses] The tire according to this embodiment can be suitably used as a heavy-duty tire. A heavy-duty tire is a tire intended to be mounted on a four-wheeled vehicle and has a maximum load capacity of 1000 kg or more. The maximum load capacity of a heavy-duty tire is preferably 1200 kg or more, and more preferably 1400 kg or more. [Examples]

[0204] 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 investigated tires having the basic structure of Figure 1 and the tread obtained according to the formulation in Table 2, and the belt layer described in Table 1, and the results calculated based on the evaluation method below are shown in Table 1.

[0205] The various chemicals used in the examples and comparative examples are summarized below. IR-type rubber: TSR20(NR) SBR: HPR840 manufactured by JSR Corporation (S-SBR, styrene content: 10% by mass, vinyl content: 42 mol%, Tg: -60℃, Mw: 190,000, non-stretchable) Carbon Black: Show Black N220 (N2SA: 115m) manufactured by Cabot Japan Co., Ltd. 2 / g, average primary particle diameter: 22nm) Silica: UltraSil VN3 (N2SA: 175m) manufactured by Evonik Industries. 2 / g, average primary particle diameter: 18nm) 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) Wax: Sunnock N (paraffin wax) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Anti-aging agent: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical 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.

[0206] (Making a belt ply) Using an unvulcanized rubber composition corresponding to the belt topping rubber, a 1×1 structure (monofilament) steel cord is coated to obtain a belt ply constituting the belt layer as a steel cord-rubber composite. The average isoprene-based rubber content C2 (mass%) in the belt topping rubber and the total thickness T2 (mm) of the belt layer, when the mass of the belt topping rubber is 100% by mass, are as shown in Table 1.

[0207] (Tire manufacturing) According to the formulation shown in Table 2, chemicals other than sulfur and vulcanization accelerator are mixed in a 1.7 L closed Banbury mixer for 5 minutes until the discharge temperature reaches 160°C to obtain a mixture. Next, using a twin-screw open roll mixer, the vulcanizing agent and vulcanization accelerator are added to the obtained mixture and mixed for 4 minutes until the temperature reaches 105°C to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition is molded to the shape of the tread and bonded together with the belt ply, carcass, and other tire components to produce an unvulcanized tire. The tire is vulcanized at 170°C to obtain the test tires (size: 295 / 70R22.5) listed in Table 2, having the basic structure shown in Figure 1. The code angle of the first belt ply 6a is -45 degrees, the code angle of the second belt ply 6b is less than ±1 degree, the code angle of the third belt ply 6c is -15 degrees, the code angle of the fourth belt ply 6d is +15 degrees, and the groove depth H of the circumferential groove is 18 mm.

[0208] <Wet grip performance after long-distance driving> Each test tire is mounted on all wheels of a truck, and after 10,000 km of driving, the braking distance from an initial speed of 50 km / h on a wet asphalt surface is measured and expressed as an index using the following formula. A higher index indicates a shorter braking distance and better wet grip performance. (Wet grip performance index) = (Braking distance of the tire in Comparative Example 2) / (Braking distance of each test tire) × 100

[0209] [Table 2]

[0210] <Embodiment> Examples of embodiments of the present invention are shown below.

[0211] [1] A heavy-duty tire comprising a tread, a carcass, and a belt layer, wherein the tread is composed of a rubber composition containing a rubber component including isoprene rubber and a copolymer resin containing styrene and cyclopentadiene as monomer components, the carcass includes metal cords, the belt layer is provided between the tread and the carcass, and each of the multiple belt plies constituting the belt layer consists of a metal cord and a belt topping rubber containing isoprene rubber, and when the mass of the rubber composition constituting the tread is 100% by mass... A heavy-duty tire in which, when S (mass%) is the total amount of styrene in the rubber composition constituting the tread, C1 (mass%) is the content of isoprene-based rubber in the rubber composition constituting the tread when the mass of the rubber composition constituting the tread is 100% by mass, T1 (mm) is the total thickness of the tread, C2 (mass%) is the average content of isoprene-based rubber in the belt topping rubber when the mass of the belt topping rubber is 100% by mass, and T2 (mm) is the total thickness of the belt layer, and when a = C1 / T1 and b = C2 / T2 is defined, S / (a / b) is greater than 7.0. [2] The heavy-duty tire according to [1] above, wherein the belt layer includes high-angle belt plies with an absolute value of 10 degrees or more of the cord angle with respect to the tire circumferential direction, and low-angle belt plies with an absolute value of 5 degrees or less of the cord angle with respect to the tire circumferential direction. [3] The heavy-duty tire according to [1] or [2] above, wherein the belt layer comprises two or more high-angle belt plies and one or more low-angle belt plies, and the low-angle belt plies are provided between the two high-angle belt plies. [4] The heavy-duty tire according to any one of [1] to [3] above, wherein the tread has grooves in which recesses are provided that are recessed outward in the groove width direction from the groove edge that appears on the tread surface. [5] A heavy-duty tire as described in any of [1] to [4] above, wherein a is less than 3.0. [6] A heavy-duty tire according to any one of [1] to [5] above, wherein the metal cord included in the belt ply has a 1x1 structure. [7] A heavy-duty tire according to any one of [1] to [6] above, wherein the content of the copolymer resin in the rubber composition constituting the tread is 5 parts by mass or more per 100 parts by mass of the rubber component. [8] The heavy-duty tire according to any one of [1] to [7] above, wherein the rubber component constituting the tread further contains styrene-butadiene rubber. [9] The heavy-duty tire according to any one of [1] to [8] above, wherein the rubber composition constituting the tread contains 10 parts by mass or more of silica per 100 parts by mass of the rubber component. [Explanation of symbols]

[0212] 1. Heavy-duty tires 2 Tread surface 3 tread 4. Cap rubber layer 5. Base rubber layer 6 Belt Layer 7 Sidewall 8 Circumferential groove 9 recesses 10 trench wall 12 groove edge 15 Inner Liner 16 Carcass 21 Metal cord 22 Topping Rubber H Groove depth of circumferential groove T1 tread total thickness Total thickness of the T2 belt layer CL tire centerline

Claims

1. A heavy-duty tire comprising a tread, carcass, and belt layer, The tread is composed of a rubber composition containing a rubber component including isoprene rubber, and a copolymer resin containing styrene and cyclopentadiene as monomer components. The carcass includes metal cords, The belt layer is provided between the tread and the carcass. Each of the multiple belt plies constituting the belt layer consists of a metal cord and a belt topping rubber containing isoprene-based rubber. S (mass%) is the total amount of styrene in the rubber composition constituting the tread when the mass of the rubber composition constituting the tread is 100% by mass, and C is the content of isoprene-based rubber in the rubber composition constituting the tread when the mass of the rubber composition constituting the tread is 100% by mass. 1 (mass %), the total thickness of the tread is T 1 (mm), the average content of isoprene-based rubber in the belt topping rubber when the mass of the belt topping rubber is 100% by mass is C 2 (mass%), the total thickness of the belt layer is T 2 (mm) a=C 1 / T 1 b=C 2 / T 2 If defined as follows, Heavy-duty tires with an S / (a / b) ratio greater than 7.

0.

2. The heavy-duty tire according to claim 1, wherein the belt layer includes high-angle belt plies with an absolute value of the cord angle with respect to the tire circumferential direction of 10 degrees or more, and low-angle belt plies with an absolute value of the cord angle with respect to the tire circumferential direction of 5 degrees or less.

3. The belt layer includes two or more high-angle belt plies and one or more low-angle belt plies. The heavy-duty tire according to claim 2, wherein the low-angle belt ply is provided between two of the high-angle belt plies.

4. The heavy-duty tire according to any one of claims 1 to 3, wherein the tread has grooves in which recesses are provided that are recessed outward in the groove width direction from the groove edge that appears on the tread surface.

5. A heavy-duty tire according to any one of claims 1 to 3, wherein a is less than 3.

0.

6. The heavy-duty tire according to any one of claims 1 to 3, wherein the metal cord included in the belt ply has a 1x1 structure.

7. A heavy-duty tire according to any one of claims 1 to 3, wherein the content of the copolymer resin in the rubber composition constituting the tread is 5 parts by mass or more relative to 100 parts by mass of the rubber component.

8. The heavy-duty tire according to any one of claims 1 to 3, wherein the rubber component constituting the tread further comprises styrene-butadiene rubber.

9. The heavy-duty tire according to any one of claims 1 to 3, wherein the rubber composition constituting the tread contains 10 parts by mass or more of silica per 100 parts by mass of the rubber component.

Images