Load-bearing tire

Abstract

This invention provides a heavy-duty tire with excellent durability. A heavy-duty tire is a tire with a bead triangle rubber, the bead triangle rubber having an inner triangle rubber portion and an outer triangle rubber portion, at least one of the inner triangle rubber portion and the outer triangle rubber portion comprising isoprene rubber, carbon black, and a modified rubber material functionalized with thiuram sulfide compounds, the complex elastic modulus (Ei*) of the inner triangle rubber portion and the complex elastic modulus (Eo*) of the outer triangle rubber portion satisfying the following formulas (1) to (2), wherein Ei* and Eo* are complex elastic moduli measured under the conditions of a temperature of 70°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10Hz, and a tensile mode, (1) Ei* > Eo*, (2) Ei* / Eo* ≤ 7.0.

Description

Technical Field

[0001] This invention relates to heavy-duty tires. Background Technology

[0002] Truck tires require the same performance characteristics as other tires, but durability is particularly important. Summary of the Invention

[0003] The problem that the invention aims to solve

[0004] The purpose of this invention is to provide a heavy-duty tire that solves the above-mentioned problems and provides excellent durability.

[0005] Methods for solving problems

[0006] This invention relates to a heavy-duty truck tire, which is a heavy-duty truck tire with a bead triangle rubber rubber having an inner triangle rubber portion and an outer triangle rubber portion.

[0007] The material selected from at least one of the inner triangular rubber portion and the outer triangular rubber portion comprises isoprene-based rubber, carbon black, and a modified rubber material functionalized with thiuram sulfide compounds.

[0008] The complex elastic modulus (Ei*) of the inner triangular rubber portion and the complex elastic modulus (Eo*) of the outer triangular rubber portion satisfy the following formulas (1) to (2).

[0009] (1) Ei*>Eo*

[0010] (2) Ei* / Eo*≤7.0

[0011] (Ei* and Eo* are the complex elastic moduli measured under the conditions of 70℃ temperature, 5% initial strain, 1% dynamic strain, 10Hz frequency, and tensile mode). Attached Figure Description

[0012] Figure 1 This is a cross-sectional view illustrating one embodiment of the heavy-duty tire of the present invention.

[0013] Figure 2 It is an enlarged cross-sectional view of the tire bead. Detailed Implementation

[0014] This invention relates to a heavy-duty tire comprising a bead tread rubber having an inner tread rubber portion and an outer tread rubber portion, wherein at least one of the inner tread rubber portion and the outer tread rubber portion comprises isoprene rubber, carbon black, and a modified rubber material functionalized with a thiuram sulfide compound, and satisfies formulas (1) to (2). The heavy-duty tire exhibits excellent durability.

[0015] The mechanism (reason) for achieving this effect is still unclear, but the following are speculations.

[0016] From a life cycle assessment (LCA) perspective, it is desirable to use recycled materials in large heavy-duty tires used in trucks, buses, and other vehicles. Because heavy-duty tires bear a higher load than regular tires, research is underway to soften the two-layer structure of the bead tread rubber's front end. However, there are concerns that insufficient interfacial adhesion exists when both the inner (lower) and outer (upper) portions of the bead tread rubber are made of rubber powder, potentially leading to interfacial damage under high loads. Therefore, it is believed that by dispersing modified recycled rubber in isoprene-based rubber and combining it with portions functionalized with thiuram sulfide compounds, the adhesion of the bead tread rubber interface can be ensured, and crack propagation from the interface can be suppressed, while simultaneously inhibiting rubber strength reduction. Furthermore, it is believed that by adjusting the complex elastic modulus (Ei*, Eo*) of the inner (lower) and outer (upper) portions of the bead rubber to satisfy equations (1) to (2), and by setting the difference in complex elastic modulus below a specified value, strain generated at the interface between the inner (lower) and outer (upper) portions can be suppressed, thereby suppressing damage from the interface. Therefore, it is speculated that this imparts excellent durability to the aforementioned heavy-duty tire.

[0017] As described above, the bead triangle rubber having an inner triangular rubber portion and an outer triangular rubber portion, by setting it to satisfy Equation (1) "Ei*>Eo*" and Equation (2) "Ei* / Eo*≤7.0", solves the problem (objective) of imparting excellent durability to the bead triangle rubber. At least one of the inner triangular rubber portion and the outer triangular rubber portion comprises isoprene-based rubber, carbon black, and a modified rubber material functionalized with thiuram sulfide compounds. That is, the parameters of Equation (1) "Ei*>Eo*" and Equation (2) "Ei* / Eo*≤7.0" are not the parameters that define the problem (objective). The problem of this application is to impart excellent durability, and as a solution, it is configured to satisfy these parameters.

[0018] Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

[0019] Figure 1 This is a cross-sectional view of the present invention's heavy-duty tire, as an example, when used as a tubeless tire for trucks, buses, etc., under a standard internal pressure of 5%. Figure 2 It is a magnified cross-sectional view of the tire bead section.

[0020] exist Figure 1 In this tire, the heavy-duty tire 1 has a tire body 6 that extends from the tread portion 2 through the sidewall portion 3 to the bead portion 4, and a belt layer 7 disposed on the outer side of the tire body 6 in the radial direction and on the inner side of the tread portion 2.

[0021] exist Figure 1 In this example, the belt layer 7 is formed from three or more beltply sheets using belt cords. In this example, the belt layer 7 is shown as a four-layer structure consisting of a first beltply 7A, with the belt cords arranged at an angle of, for example, 60 ± 15° relative to the tire circumference, on the innermost radial direction; and second to fourth beltply sheets 7B to 7D, arranged at small angles of, for example, 10° to 35° relative to the tire circumference. These belt layers 7A to 7D are overlapped at the points where the belt cords intersect, improving belt rigidity and providing a hoop effect to strengthen the tread portion 2. Alternatively, a belt reinforcement layer can be formed on the outer radial direction of the belt layer 7, with the cords arranged at an angle of ±10° relative to the tire circumference.

[0022] In this example, the carcass 6 is formed from a single carcass ply 6A, which is formed by carcass cords arranged at an angle of 70 to 90 degrees relative to the tire circumference. Steel cords are preferred as carcass cords, but organic fiber cords such as nylon, rayon, polyester, or aromatic polyamide can be used as needed. The carcass ply 6A has a series of ply fold-back portions 6b on both sides of the ply body portion 6a spanning between the bead cores 5, 5, which fold back from the axial inside to the outer side around the bead core 5.

[0023] The bead core 5 is, for example, a ring formed by winding steel bead wire in multiple stages and rows. In this example, a flat hexagonal bead core with a transversely elongated cross-section is shown. The bead core 5 increases the engagement force with the rim J over a wide range by having its lower surface in the radial direction approximately parallel to the rim piece J1 of the standard rim J. In this example, the standard rim J is a 15° tapered rim for tubeless use; therefore, the lower surface of the bead core 5 in the radial direction is inclined at a 15° angle relative to the tire axis. The cross-sectional shape of the bead core 5 can be a regular hexagon, rectangle, or circle, depending on the desired effect.

[0024] Next, as Figure 2 As shown, the bead portion 4 is provided with a reinforcing cord layer 9. The reinforcing cord layer 9 passes between the main cord portion 6a and the cord layer folding portion 6b of the tire carcass 6, and is surrounded in a U-shape around the bead core 5 by the bead triangle rubber 8 and the tire carcass 6. The bead triangle rubber 8 extends outward from the bead core 5 in the radial direction of the tire with a tapering tip.

[0025] The reinforcing cord layer 9 is formed with an inner piece 9a extending along the inner surface of the cord body 6a, and an outer piece 9b extending radially outward along the outer surface of the cord fold-back portion 6b, passing radially inward from the inner side of the bead core 5. In this example, the reinforcing cord layer 9 exemplifies a single-layer cord fabric layer formed by arranging steel reinforcing cords at an angle of 10 to 60° relative to the tire circumference.

[0026] Next, the bead triangle rubber 8 has an inner triangle rubber portion 8A and an outer triangle rubber portion 8B. In this example, the inner triangle rubber portion 8A is formed of hard rubber with a small triangular cross-section having a slope, the slope being outward in the radial direction of the tire and inclined inward from the axial direction of the tire. The outer triangle rubber portion 8B is formed of soft rubber extending outward in the radial direction of the tire from the bottom surface in contact with the slope. The bead triangle rubber 8 is formed as a two-layer structure consisting of the inner triangle rubber portion 8A and the outer triangle rubber portion 8B.

[0027] The complex elastic modulus (Ei*) of the inner triangular rubber portion 8A and the complex elastic modulus (Eo*) of the outer triangular rubber portion 8B satisfy the following formulas (1) to (2).

[0028] (1) Ei*>Eo*

[0029] (2) Ei* / Eo*≤7.0

[0030] (Ei* and Eo* are the complex elastic moduli measured under the conditions of 70℃ temperature, 5% initial strain, 1% dynamic strain, 10Hz frequency, and tensile mode).

[0031] Ei* / Eo* is preferably 6.0 or less, more preferably 5.0 or less, even more preferably 4.5 or less, and particularly preferably 4.0 or less. The lower limit is not particularly limited, but is preferably 2.0 or more, more preferably 3.0 or more, even more preferably 3.5 or more, and particularly preferably 3.8 or more. Within the above ranges, better results are tended to be obtained.

[0032] Ei* is preferably 13.0 MPa or higher, more preferably 15.0 MPa or higher, even more preferably 18.0 MPa or higher, and particularly preferably 20.0 MPa or higher. There is no particular upper limit, but it is preferably 30.0 MPa or lower, more preferably 26.0 MPa or lower, even more preferably 24.0 MPa or lower, and particularly preferably 22.0 MPa or lower. Within the above range, better results are tended to be obtained.

[0033] The mechanism (reason) for achieving the aforementioned effect is not yet clear, but it is speculated as follows: It is believed that setting the complex elastic modulus of the inner triangular rubber portion to a specified value or higher can suppress deformation in the bead triangular rubber. Therefore, it is speculated that this imparts excellent durability to the aforementioned heavy-duty tire.

[0034] Eo* is preferably 2.0 MPa or higher, more preferably 3.0 MPa or higher, even more preferably 3.5 MPa or higher, and particularly preferably 4.0 MPa or higher. There is no particular upper limit, but it is preferably 7.0 MPa or lower, more preferably 6.0 MPa or lower, even more preferably 5.5 MPa or lower, and particularly preferably 5.0 MPa or lower. Within the above range, better results are tended to be obtained.

[0035] The complex modulus of elasticity (E*) can be adjusted, for example, by modifying the proportions of isoprene-based rubbers, modified rubber materials functionalized with thiuram vulcanizates, carbon black, other fillers, vulcanizing agents, and vulcanization accelerators. Specifically, E* tends to increase when mixing isoprene-based rubbers, or modified rubber materials functionalized with thiuram vulcanizates, or when increasing the amount of fillers, the amount of carbon black, or decreasing the carbon black particle size.

[0036] It should be noted that Ei* and Eo* are the complex moduli of elasticity measured under the conditions of 70℃, initial strain of 5%, dynamic strain of 1%, frequency of 10Hz, and tensile mode. Ei* and Eo* are the values ​​of the vulcanized rubber composition.

[0037] The inner triangular rubber portion 8A and the outer triangular rubber portion 8B are respectively composed of a rubber composition for the inner triangular rubber portion and a rubber composition for the outer triangular rubber portion. At least one of the rubber compositions for the inner and outer triangular rubber portions contains isoprene-based rubber, carbon black, and a modified rubber material functionalized with thiuram sulfide compounds. From the viewpoint of obtaining better results, it is preferable that both the rubber composition for the inner and outer triangular rubber portions are compositions containing these components.

[0038] Examples of isoprene-based rubbers that can be used in rubber compositions for the inner and outer triangular rubber portions include natural rubber (NR), isoprene rubber (IR), modified NR, altered NR, and modified IR. For example, NR commonly used in the rubber industry, such as SIR20, RSS#3, and TSR20, can be used. There are no particular limitations on IR; for example, IR2200, which is speculated to be used in the rubber industry, can be used. Examples of modified NR include deproteinized natural rubber (DPNR) and high-purity natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These can be used alone or in combination of two or more.

[0039] When the rubber composition for the inner triangular rubber portion contains isoprene-based rubber, the content of isoprene-based rubber in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, and particularly preferably 80% by mass or more. There is no particular upper limit, and it can be 100% by mass, 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. Within the above range, better results are tended to be obtained.

[0040] When the rubber composition for the outer triangular rubber portion contains isoprene-based rubber, the content of isoprene-based rubber in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and can be 100% by mass. Within the above ranges, better results are tended to be obtained.

[0041] The rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion may contain rubber components other than isoprene-based rubbers. Other diene-based rubbers can be used, for example. Examples of other diene-based rubbers include butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), ethylene propylene rubber (EPDM), chloroprene rubber (CR), and nitrile rubber (NBR). Butyl rubbers and fluororubbers can also be used. They can be used alone or in combination of two or more. From the viewpoint of obtaining better results, it is preferable that the rubber composition for the inner triangular rubber portion contains SBR and the rubber composition for the outer triangular rubber portion contains BR.

[0042] There are no particular limitations on SBR; for example, emulsion-polymerized styrene-butadiene rubber (E-SBR) and solution-polymerized styrene-butadiene rubber (S-SBR) can be used. These can be used alone or in combination of two or more.

[0043] The styrene content of the SBR is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. Furthermore, the styrene content is preferably 60% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less. Better results are tended to be obtained within the above ranges. It should be noted that the styrene content of the SBR is determined by… 1 Calculated by H-NMR measurements.

[0044] The vinyl content in the butadiene portion of the SBR is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. This vinyl content is preferably 80% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less. Better results are tended to be obtained when it is within the above range. It should be noted that the vinyl content of the SBR can be determined by infrared absorption spectroscopy.

[0045] As an SBR, for example, SBR manufactured and sold by companies such as Sumitomo Chemical Co., Ltd., JSR Co., Ltd., Asahi Kasei Corporation, and Zeon Corporation can be used.

[0046] SBRs can be either unmodified or modified. As a modified SBR, any SBR possessing functional groups that interact with fillers such as silica is acceptable. Examples include SBRs obtained by modifying at least one end of an SBR with a compound (modifier) ​​possessing the aforementioned functional groups (end-modified SBR with the aforementioned functional groups at the end), main-chain modified SBRs possessing the aforementioned functional groups in the main chain, main-chain end-modified SBRs possessing the aforementioned functional groups in both the main chain and at the end (e.g., main-chain end-modified SBRs obtained by having the aforementioned functional groups on the main chain and at least one end modified with the aforementioned modifier), and end-modified SBRs by introducing hydroxyl or epoxy groups through modification (coupling) with a polyfunctional compound having two or more epoxy groups in the molecule.

[0047] Examples of functional groups include amino, amide, silyl, alkoxysilyl, isocyanate, imino, imidazo, urea, ether, carbonyl, oxycarbonyl, mercapto, thioether, dithioether, sulfonyl, sulfinyl, thiocarbonyl, ammonium, imide, hydrazine, azo, diazo, carboxyl, nitrile, pyridinyl, alkoxy, hydroxy, oxygen, and epoxy groups. It should be noted that these functional groups may have substituents. Among them, amino (preferably an amino group where the hydrogen atom is replaced by an alkyl group having 1 to 6 carbon atoms), alkoxy (preferably an alkoxy group having 1 to 6 carbon atoms), and alkoxysilyl (preferably an alkoxysilyl group having 1 to 6 carbon atoms).

[0048] There are no particular limitations on BR (Brane Brewery). For example, high-cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, and BR synthesized using rare-earth catalysts (rare-earth BR) can be used. These can be used alone or in combination. Among them, high-cis BR with a cis content of 90% by mass or more is preferred for the purpose of improving wear resistance. These can be used alone or in combination.

[0049] Furthermore, BR can be either unmodified or modified. Examples of modified BRs include those with the same functional groups as modified SBRs.

[0050] As a BR (Brandinger), products from companies such as Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Zeon Corporation can be used.

[0051] When the rubber composition used in the inner triangular rubber portion contains SBR, the SBR content in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass, and particularly preferably 20% by mass or more. There is no particular upper limit, but it is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. Within the above ranges, better results are tended to be obtained.

[0052] When the outer triangular rubber composition contains BR, the BR content in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and particularly preferably 20% by mass or more. There is no particular upper limit, but it is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. Within the above ranges, better results are tended to be obtained.

[0053] Carbon blacks that can be used in rubber compositions for the inner and outer triangular rubber parts include GPF, FEF, HAF, ISAF, and SAF, but are not particularly limited. Commercially available products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Corporation, Shin-Nippon Chemical Carbon Co., Ltd., and Colombia Carbon Co., Ltd. These can be used alone or in combination of two or more.

[0054] In the rubber composition for the inner triangular rubber section, the nitrogen adsorption specific surface area (N2SA) of carbon black is preferably 20 m². 2 / g or more, preferably 50m 2 / g or more, further preferably 70m 2 / g or more. There is no particular upper limit for carbon black N2SA, but 150 μg is preferred. 2 / g or less, more preferably 100m 2 / g or less, more preferably 90m 2 Below / g. If it is within the above range, better results are tended to be obtained.

[0055] In the rubber composition for the inner triangular rubber portion, the carbon black content relative to 100 parts by weight is preferably 30 parts by weight or more, more preferably 50 parts by weight or more, further preferably 65 parts by weight or more, and particularly preferably 70 parts by weight or more. Furthermore, the carbon black content is preferably 150 parts by weight or less, more preferably 120 parts by weight or less, further preferably 100 parts by weight or less, and particularly preferably 90 parts by weight or less. Within the above ranges, better results are tended to be obtained.

[0056] In the rubber composition for the outer triangular rubber portion, the nitrogen adsorption specific surface area (N2SA) of carbon black is preferably 20 m². 2 / g or more, preferably 30m 2 / g or more, further preferably 40m 2 / g or more. There is no particular upper limit for carbon black N2SA, but 150 μg is preferred. 2 / g or less, more preferably 100m 2 / g or less, more preferably 80m 2 / g or less, especially preferably 60m 2 Below / g. If it is within the above range, better results are tended to be obtained.

[0057] The nitrogen adsorption specific surface area of ​​carbon black was determined according to method A of JIS K6217.

[0058] In the rubber composition for the outer triangular rubber portion, the carbon black content relative to 100 parts by weight of the rubber component is preferably 20 parts by weight or more, more preferably 30 parts by weight or more, even more preferably 35 parts by weight or more, and particularly preferably 40 parts by weight or more. Furthermore, the carbon black content is preferably 100 parts by weight or less, more preferably 80 parts by weight or less, even more preferably 70 parts by weight or less, and particularly preferably 60 parts by weight or less. Within the above ranges, better results are tended to be obtained.

[0059] Examples of fillers other than carbon black that can be used in rubber compositions for the inner and outer triangular rubber parts include silica, calcium carbonate, talc, bauxite, clay, aluminum hydroxide, alumina, mica, and other substances known in the rubber industry. Among these, silica is preferred.

[0060] Examples of silica that can be used in rubber compositions for inner and outer triangular rubber parts include dry silica (anhydrous silica) and wet silica (hydrated silica). Among these, wet silica is preferred because it contains more silanol groups.

[0061] When the rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion contain silica, the silica content relative to 100 parts by weight of the rubber component is preferably 50 parts by weight or less, more preferably 20 parts by weight or less, even more preferably 10 parts by weight or less, and particularly preferably 5 parts by weight or less. The lower limit is not particularly limited, but is preferably 3 parts by weight or more, more preferably 5 parts by weight or more. If the upper limit of this content is within the above range, better results are tended to be obtained.

[0062] The nitrogen adsorption specific surface area (N2SA) of silica is preferably 50 m² / s. 2 / g or more, preferably 100m 2 / g or more, further preferably 150m 2 / g or more. Furthermore, the N2SA of silica is preferably 250m. 2 / g or less, more preferably 220m 2 / g or less, more preferably 200m 2 Below / g. If within the above range, better results are generally obtained. It should be noted that the N2SA of silica is determined using the BET method based on ASTM D3037-93.

[0063] Products from companies such as Degussa, Rhodia, Tosoh Silicon Chemicals, Solvay Japan, and Tokuyama Corporation can be used as silica.

[0064] The tread rubber composition preferably contains a silane coupling agent along with silica. There are no particular limitations on the silane coupling agent; examples include sulfide systems such as bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, and bis(3-trimethoxysilylpropyl)tetrasulfide; thiol-based systems such as 3-mercaptopropyltrimethoxysilane; vinyl-based systems such as vinyltriethoxysilane; amino-based systems such as 3-aminopropyltriethoxysilane; epoxypropoxy-based systems such as γ-epoxypropoxypropyltriethoxysilane; nitro-based systems such as 3-nitropropyltrimethoxysilane; and chlorine-based systems such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, sulfide systems are preferred from the viewpoint of achieving better results.

[0065] As silane coupling agents, products from companies such as Degussa, Momentive, Shin-Tsu Silicon Co., Ltd., Tokyo Chemical Industry Co., Ltd., AZmax Co., Ltd., and Toray Dow Corning Co., Ltd. can be used.

[0066] When the rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion contain a silane coupling agent, the content of the silane coupling agent relative to 100 parts by weight of silicon dioxide is preferably 3 parts by weight or more, more preferably 5 parts by weight or more, and even more preferably 8 parts by weight or more. Furthermore, it is preferably 25 parts by weight or less, more preferably 20 parts by weight or less, and even more preferably 15 parts by weight or less. Within the above ranges, better results are tended to be obtained.

[0067] The modified rubber material functionalized with thiuram sulfide compounds, which can be used in rubber compositions for the inner and outer triangular rubber parts, is not particularly limited, and any rubber material modified with thiuram sulfide compounds can be used. It should be noted that, in this invention, the modified rubber material functionalized with thiuram sulfide compounds is a rubber material that does not belong to the aforementioned rubber components.

[0068] As a thiuram sulfide compound, there are no particular limitations; examples include alkyl thiuram sulfides, aryl thiuram sulfides, heterocyclic thiuram sulfides, thiuram disulfides, thiuram polysulfides, tetrabenzyl thiuram disulfides, tetraalkyl thiuram disulfides, tetramethyl thiuram disulfides, tetraethyl thiuram disulfides, and di(pentamethyl)thiuram monosulfides. These can be used alone or in combination of two or more.

[0069] There are no particular limitations on rubbers that can be functionalized with thiuram sulfide compounds (rubbers that form a skeleton), such as the rubber components mentioned above.

[0070] From a life cycle assessment (LCA) perspective, modified recycled rubber is preferred as a modified rubber material functionalized with the aforementioned thiuram vulcanizates. In this specification, "modified recycled rubber" refers to a rubber material obtained by pulverizing a portion of used rubber products (waste rubber products) such as tires, subjecting them to desulfurization, and then further functionalizing them with thiuram vulcanizates. Using modified recycled rubber functionalized with thiuram vulcanizates tends to yield better results.

[0071] Modified reclaimed rubber, due to the cleavage of some of the cross-linked structures in the rubber through desulfurization and functionalization, has increased reactivity. Therefore, it is advantageous for improving problems such as reduced reinforcement that may occur when using recycled materials. For example, it is produced by functionalizing rubber with functional groups capable of acting on uncured diene rubber (introducing a modifying compound) in reclaimed rubber or vulcanized rubber powder (powdered rubber). Here, reclaimed rubber is not particularly limited, and examples include pulverized rubber mechanically ground at room temperature or under frozen conditions, desulfurized rubber that has undergone further desulfurization, reclaimed rubber obtained by regenerating rubber used in automobile tires, inner tubes, and other rubber products as specified in JIS K6313, and reclaimed rubber having the same properties as reclaimed rubber.

[0072] It should be noted that modified recycled rubber can use products from companies such as Lehigh.

[0073] Regarding the rubber composition for the inner triangular rubber portion, the content of the modified rubber material functionalized with thiuram sulfide compounds is preferably 3 parts by mass or more, more preferably 6 parts by mass or more, further preferably 8 parts by mass or more, and particularly preferably 10 parts by mass or more, relative to 100 parts by mass of the rubber component. Furthermore, this content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, further preferably 15 parts by mass or less, and particularly preferably 13 parts by mass or less. Within the above ranges, better results are tended to be obtained.

[0074] Regarding the rubber composition for the outer triangular rubber portion, the content of the modified rubber material functionalized with thiuram sulfide compounds is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, further preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more, relative to 100 parts by mass of the rubber component. Furthermore, this content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, further preferably 30 parts by mass or less, and particularly preferably 25 parts by mass or less. Within the above ranges, better results are tended to be obtained.

[0075] From the viewpoint of achieving better results, in at least one of the rubber compositions for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion, the content ratio of the modified rubber material functionalized with a thiuram sulfide compound to the isoprene-based rubber (content of the modified rubber material in the rubber composition (parts by mass) / content of the isoprene-based rubber in the rubber composition (parts by mass)) is preferably 0.33 or less, more preferably 0.25 or less, further preferably 0.22 or less, and particularly preferably 0.20 or less. The lower limit of this content ratio is not particularly limited, but it is preferably 0.10 or more, more preferably 0.12 or more, further preferably 0.14 or more, and particularly preferably 0.16 or more. Better results are tended to be obtained within the above range. Preferably, both the rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion satisfy the above relationship.

[0076] The mechanism (reason) for achieving the effects described above is not yet clear, but it is speculated as follows.

[0077] It is believed that when the ratio of modified rubber material to isoprene-based rubber, especially the ratio of modified reclaimed rubber to isoprene-based rubber, increases, the contribution of modified reclaimed rubber in the rubber becomes greater, potentially reducing interfacial adhesion and compromising durability. This possibility decreases when the ratio is below a specified range, particularly below 0.25. Therefore, it is speculated that this will impart excellent durability to the aforementioned heavy-duty tires.

[0078] From the viewpoint of achieving better results, in at least one of the rubber compositions for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion, the content ratio of carbon black to modified rubber material functionalized with thiuram sulfide compounds (content of carbon black in the rubber composition (parts by mass) / content of the modified rubber material in the rubber composition (parts by mass)) is preferably 1.5 or more, more preferably 2.0 or more, further preferably 2.5 or more, and particularly preferably 3.0 or more. There is no particular upper limit to this content ratio, but it is preferably 5.0 or less, more preferably 4.5 or less, further preferably 4.0 or less, and particularly preferably 3.5 or less. Better results are tended to be obtained when the content is within the above range. Preferably, both the rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion satisfy the above relationship.

[0079] The mechanism (reason) for achieving the effects described above is not yet clear, but the following is a speculation.

[0080] It is believed that by dispersing carbon black around modified rubber materials, especially modified reclaimed rubber, the overall structure of the rubber can be strengthened, and crack growth from the interface can be suppressed. Therefore, it is speculated that this imparts excellent durability to the aforementioned heavy-duty tires.

[0081] Powdered reclaimed rubber can be mixed into the rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion. "Powdered reclaimed rubber" refers to reclaimed rubber obtained by mechanically pulverizing rubber at room temperature or under frozen conditions, desulfurized rubber that has undergone further desulfurization, rubber used in automobile tires, inner tubes and other rubber products as specified in JIS K6313, and reclaimed rubber with the same properties as reclaimed rubber, but which is a material that has not undergone desulfurization treatment, functionalization or other modification treatment.

[0082] It should be noted that, in this invention specification, powdered recycled rubber is not considered a rubber component.

[0083] When the rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion contain powdered reclaimed rubber, the content of the powdered reclaimed rubber relative to 100 parts by weight of the rubber component is preferably 3 parts by weight or more, more preferably 6 parts by weight or more, further preferably 8 parts by weight or more, and particularly preferably 10 parts by weight or more. Furthermore, this content is preferably 50 parts by weight or less, more preferably 30 parts by weight or less, further preferably 15 parts by weight or less, and particularly preferably 13 parts by weight or less.

[0084] The rubber composition for the inner triangular rubber part and the rubber composition for the outer triangular rubber part may contain plasticizers.

[0085] In this specification, plasticizer refers to a material that imparts plasticity to rubber components, and includes both liquid plasticizers (plasticizers that are liquid at 25°C) and solid plasticizers (plasticizers that are solid at 25°C). Specifically, it includes components such as those extracted from rubber compositions using acetone. These can be used alone or in combination of two or more.

[0086] In the rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion, the total content of plasticizer (the total content of liquid plasticizer and solid plasticizer) relative to 100 parts by weight of rubber component is preferably 10.0 parts by weight or less, more preferably 5.0 parts by weight or less, even more preferably 3.0 parts by weight or less, and particularly preferably 2.0 parts by weight or less. Within the above range, better results are tended to be obtained.

[0087] It should be noted that the content of plasticizer includes the amount of oil contained in rubber (oil-extended rubber) and sulfur (oil-containing sulfur).

[0088] Examples of liquid plasticizers include oils, liquid polymers (diene-based, olefin-based, ester-based, etc.), liquid resins, essential oils derived from natural sources such as turpentine, and ester-based plasticizers. Examples of solid plasticizers include solid resins that are solid at 25°C and are commonly used in the tire industry. These can be used alone or in combination of two or more. Among them, as a liquid plasticizer, at least one selected from the group consisting of oils, liquid polymers, and liquid resins is preferred, oil is more preferred, and processing oil is even more preferred.

[0089] The aforementioned oils are not particularly limited and can include paraffinic processing oils, aromatic processing oils, naphthenic processing oils, low-PCA (polycyclic aromatic) processing oils such as TDAE and MES, vegetable oils, and mixtures thereof, as well as other currently known oils. These can be used alone or in combination of two or more. Among them, paraffinic processing oils are preferred.

[0090] As an oil, products from companies such as Idemitsu Kosan Co., Ltd., Sankyo Oil & Chemical Co., Ltd., Nippon Energy Co., Ltd., Olisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Oil Co., Ltd., and Fuji Kosan Co., Ltd. can be used.

[0091] Examples of liquid resins include terpene resins (including terpene phenol resins and aromatic modified terpene resins), rosin resins, styrene resins, C5 resins, C5C9 resins, benzofuran-indene resins (including benzofuran and indene single resins), olefin resins, polyurethane resins, and acrylic resins, which are liquid at 25°C.

[0092] For example, products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Co., Ltd., Rutgers Chemicals Co., Ltd., BASF Corporation, Arizona Chemical Co., Ltd., Nippon Paint Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Co., Ltd., Arakawa Chemical Industry Co., Ltd., Taoka Chemical Industry Co., Ltd., etc. can be used as the liquid resin mentioned above.

[0093] As liquid diene polymers, examples include liquid styrene-butadiene copolymers (liquid SBR), liquid butadiene polymers (liquid BR), liquid isoprene polymers (liquid IR), liquid styrene-isoprene copolymers (liquid SIR), liquid styrene-butadiene-styrene block copolymers (liquid SBS block copolymers), and liquid styrene-isoprene-styrene block copolymers (liquid SIS block copolymers), which are liquid at 25°C. Their ends or main chains can be modified with polar groups.

[0094] As a liquid diene polymer, products from companies such as Sattoma Corporation and Kuraray Corporation can be used.

[0095] In the rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion, the content of liquid plasticizer (preferably oil) relative to 100 parts by weight of the rubber component is preferably 10.0 parts by weight or less, more preferably 5.0 parts by weight or less, even more preferably 3.0 parts by weight or less, and particularly preferably 2.0 parts by weight or less. Within the above ranges, better results are tended to be obtained.

[0096] It should be noted that the content of plasticizers also includes the amount of oil contained in rubber (oil-extended rubber) and sulfur (oil-containing sulfur).

[0097] As solid plasticizers for tire compounds, commonly used solid resins can be used. Specifically, examples include terpene resins, rosin resins, styrene resins, olefin resins, C5 resins, C9 resins, C5 / C9 resins, benzofuran resins, indene resins, benzofuran-indene resins, acrylic resins, and polyurethane resins. These can be one or a mixture of two or more, and the resin itself can be a copolymer derived from multiple monomer components.

[0098] As solid plasticizers, products from companies such as Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Co., Ltd., Rutgers Chemicals Co., Ltd., BASF Corporation, Arizona Chemical Co., Ltd., Nippon Paint Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Co., Ltd., Arakawa Chemical Industry Co., Ltd., and Taoka Chemical Industry Co., Ltd. can be used.

[0099] The softening point of the solid plasticizer is preferably 30°C or higher, more preferably 50°C or higher, even more preferably 80°C or higher, preferably 200°C or lower, more preferably 160°C or lower, even more preferably 140°C or lower, and particularly preferably 120°C or lower. By setting it within the above range, the more desirable effect is tended to be obtained.

[0100] It should be noted that, in the specification of this invention, the softening point of the solid plasticizer is the softening point specified in JIS K 6220-1:2001, which is determined by a sphere-type softening point measuring device, and is the temperature at which the sphere falls.

[0101] In the rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion, the content of solid plasticizer (preferably resin) is preferably 10.0 parts by weight or less, more preferably 5.0 parts by weight or less, even more preferably 3.0 parts by weight or less, and particularly preferably 2.0 parts by weight or less, relative to 100 parts by weight of the rubber component. Better results are tended to be obtained within the above ranges.

[0102] The rubber composition for the inner triangular rubber part and the rubber composition for the outer triangular rubber part preferably contain sulfur.

[0103] Examples of sulfur used in the rubber industry include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, and soluble sulfur. These can be used individually or in combination of two or more.

[0104] As sulfur, for example, products of companies such as Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Co., Ltd., Nippon Kanryu Kogyo Co., Ltd., and Hosoi Chemical Industry Co., Ltd.

[0105] In the rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion, the sulfur content relative to 100 parts by weight of the rubber component is preferably 0.1 parts by weight or more, more preferably 0.5 parts by weight or more, and even more preferably 0.8 parts by weight or more. Furthermore, the above content is preferably 10.0 parts by weight or less, more preferably 7.0 parts by weight or less, even more preferably 5.5 parts by weight or less, and particularly preferably 4.0 parts by weight or less. Within the above range, better results are tended to be obtained.

[0106] The rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion preferably contain a vulcanization accelerator. Examples of vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazole disulfide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetra(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide, N-oxoethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-o-toluidine, and o-toluidine diguanidine. These can be used alone or in combination of two or more. Sulfenamide-based vulcanization accelerators are preferred.

[0107] As a vulcanization accelerator, products from companies such as Kawaguchi Chemical Co., Ltd., Ouchi Shinsei Chemical Co., Ltd., and Rhein Chemie Co., Ltd. can be used.

[0108] In the rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion, the content of the vulcanization accelerator relative to 100 parts by weight of the rubber component is preferably 0.5 parts by weight or more, more preferably 1.0 parts by weight or more, and further preferably 10.0 parts by weight or less, more preferably 5.0 parts by weight or less. Better results are tended to be obtained when the content is within the above range.

[0109] The rubber composition for the inner triangular rubber part and the rubber composition for the outer triangular rubber part preferably contain stearic acid.

[0110] As stearic acid, currently known stearic acid can be used, such as products from Nippon Oil Co., Ltd., Kao Corporation, Fujifilm and Koko Pure Chemical Co., Ltd., Chiba Fatty Acid Co., Ltd., etc.

[0111] In the rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion, the content of stearic acid relative to 100 parts by weight of the rubber component is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more. Furthermore, the above content is preferably 5 parts by weight or less, more preferably 3 parts by weight or less. Better results are tended to be obtained when the content is within the above range.

[0112] The rubber composition for the inner triangular rubber part and the rubber composition for the outer triangular rubber part may contain zinc oxide.

[0113] As zinc oxide, currently known zinc oxides can be used, such as those from Mitsui Metal Mining Co., Ltd., Toho Co., Ltd., Hakusui Chemicals Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc.

[0114] In the rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion, the zinc oxide content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and further preferably 10 parts by mass or less, more preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component. Better results are tended to be obtained when the content is within the above range.

[0115] The rubber composition for the inner triangular rubber part and the rubber composition for the outer triangular rubber part may contain antioxidants. Examples of antioxidants include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octyl diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine-based antioxidants such as N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine; quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based antioxidants such as 2,6-di-tert-butyl-4-methylphenol and styreneated phenol; and bisphenol, triphenol, and polyphenol-based antioxidants such as tetra[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenol)propionate]methane. These can be used alone or in combination of two or more. Among them, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferred, with p-phenylenediamine-based antioxidants being more preferred.

[0116] As an anti-aging agent, products from companies such as Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Co., Ltd., and Flexis Co., Ltd. can be used.

[0117] In the rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion, the content of the antioxidant is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and further preferably 10 parts by mass or less, more preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component. Better results are tended to be obtained when the content is within the above range.

[0118] The rubber composition used for the inner triangular rubber portion and the rubber composition used for the outer triangular rubber portion may contain wax. There are no particular limitations on the type of wax; examples include petroleum-based waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant-based waxes and animal-based waxes; and synthetic waxes such as polymers of ethylene and propylene. These can be used alone or in combination of two or more.

[0119] As a wax, for example, products from companies such as Ouchi Shinshin Chemical Industry Co., Ltd., Nippon Seiwa Co., Ltd., and Seiko Chemical Co., Ltd. can be used.

[0120] In the rubber composition for the inner triangular rubber portion and the rubber composition for the outer triangular rubber portion, the wax content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, relative to 100 parts by mass of the rubber component. Furthermore, the above content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. Within the above range, better results are tended to be obtained.

[0121] In addition to the aforementioned components, the rubber compositions for the inner and outer triangular rubber portions may contain additives commonly used in the tire industry, such as vulcanizing agents other than sulfur (e.g., organic crosslinking agents, organic peroxides, etc.). The content of each of these components is preferably 0.1 parts by weight or more, and more preferably 200 parts by weight or less, relative to 100 parts by weight of the rubber component.

[0122] Relative to 100 parts by mass of the rubber component in the rubber composition for the outer triangular rubber part, the carbon black content (Cao) (parts by mass) and the Ei* / Eo* preferably satisfy the following formula.

[0123] Cao / (Ei* / Eo*)≥4.0

[0124] The ratio of Cao / (Ei* / Eo*) is more preferably 6.0 or higher, further preferably 7.0 or higher, and particularly preferably 8.0 or higher. The upper limit is preferably 20.0 or lower, more preferably 17.0 or lower, further preferably 15.0 or lower, and particularly preferably 12.0 or lower. Within the above ranges, better results are tended to be obtained.

[0125] The carbon black content (Cai) (parts by mass) and the Ei* / Eo* satisfy the following formula relative to 100 parts by mass of the rubber component in the rubber composition for the inner triangular rubber part.

[0126] Cai / (Ei* / Eo*)≥9.0

[0127] Cai / (Ei* / Eo*) is more preferably 11.0 or higher, further preferably 13.0 or higher, and particularly preferably 15.0 or higher. The upper limit is preferably 30.0 or lower, more preferably 25.0 or lower, further preferably 20.0 or lower, and particularly preferably 18.0 or lower. Within the above ranges, better results are tended to be obtained.

[0128] The aforementioned rubber composition can be manufactured, for example, by mixing the components using a rubber mixing apparatus such as an open-roll mill or a Banbury mixer, followed by vulcanization.

[0129] As for the mixing conditions, in the basic kneading process involving additives other than the crosslinking agent (vulcanizing agent) and vulcanization accelerator, the mixing temperature is typically 100–180°C, preferably 120–170°C. In the refining mixing process involving the vulcanizing agent and vulcanization accelerator, the mixing temperature is typically below 120°C, preferably 80–110°C. Furthermore, the composition obtained from mixing the vulcanizing agent and vulcanization accelerator is typically subjected to vulcanization treatments such as pressure vulcanization. The vulcanization temperature is typically 140–190°C, preferably 150–185°C.

[0130] Heavy-duty tires are manufactured using the aforementioned rubber composition by conventional methods. That is, a rubber composition is obtained by mixing various additives as needed, the inner and outer triangular rubber portions are mixed in the uncured stage, extruded, shaped on a tire forming machine by conventional methods, and bonded together with other tire components to form an uncured tire. Then, the tire can be manufactured by heating and pressurizing in a vulcanizing machine.

[0131] There are no particular limitations on tires used for heavy-duty transport; examples include pneumatic tires, solid tires, and airless tires. Among these, pneumatic tires are preferred.

[0132] Figure 1 The heavy-duty tire 1 can be used for various types of tires, such as pneumatic tires for heavy-duty use and non-air tires whose interior is not filled with air.

[0133] As for heavy-duty tires 1, examples include truck tires, bus tires, etc.

[0134] In addition, heavy-duty tires refer to tires with a maximum load capacity of 1400 kg or more. Here, maximum load capacity refers to the maximum load capacity specified by the standard system that includes the standard on which the tire is based. For example, if it is the JATMA standard (Japan Automobile Tire Association standard), it is the maximum load capacity based on the Load Index (LI); if it is TRA, it is the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and if it is ETRTO, it is "LOAD CAPACITY".

[0135] The above describes in detail the particularly preferred embodiments of the present invention, but the present invention is not limited to the embodiments shown in the figures and can be implemented in various ways.

[0136] [Example]

[0137] The present invention will be specifically described based on the embodiments, but the present invention is not limited thereto.

[0138] The following describes the various reagents used in the examples and comparative examples.

[0139] NR: TSR20

[0140] SBR: SBR1502 (styrene content 23.5% by mass) manufactured by Sumitomo Chemical Industries, Ltd.

[0141] BR: BR150B (cis content 98% by mass) manufactured by Ube Industries, Ltd.

[0142] Carbon Black 1: Cabot Nippon Co., Ltd.'s N550 (N2SA41m) 2 / g)

[0143] Carbon Black 2: Cabot Japan Co., Ltd.'s N330 (N2SA75m) 2 / g)

[0144] Modified rubber material: EkoDyne (a modified reclaimed rubber functionalized with thiuram sulfide compounds) manufactured by Lehigh.

[0145] Reclaimed rubber (unmodified): GF-80 REPROCESSED GROUND RUBBER (powdered reclaimed rubber, 80 mesh) manufactured by Lehigh.

[0146] Resin: PR12686 (cashew oil modified phenolic resin) manufactured by Sumitomo Bakelite Co., Ltd.

[0147] Oil: DIANAPROCESS NH-70S (aromatic processing oil) manufactured by Idemitsu Kosan Co., Ltd.

[0148] Antioxidant: NOCRAC RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinsei Chemical Co., Ltd.

[0149] Stearic acid: "Kiri" manufactured by Nippon Oil Co., Ltd.

[0150] Zinc oxide: Zinc oxide No. 2 manufactured by Mitsui Metals & Minerals Co., Ltd.

[0151] Sulfur 1: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.

[0152] Sulfur 2: Crystex (oil-treated insoluble sulfur, containing 80% insoluble sulfur and 20% oil, the total amount of oil-treated insoluble sulfur is listed in the table) manufactured by Flexsys.

[0153] Vulcanization accelerator 1: NOCRAC NS (N-tert-butyl-2-benzothiophene sulfenamide (TBBS)) manufactured by Ouchi Shinsei Chemical Co., Ltd.

[0154] Vulcanization accelerator 2: NOCRAC D (N,N'-diphenylguanidine (DPG)) manufactured by Ouchi Shinsei Chemical Co., Ltd.

[0155] Vulcanization accelerator 3: NOCRAC H (hexamethylenetetramine (HMT)) manufactured by Ouchi Shinsei Chemical Co., Ltd.

[0156] (Examples and Comparative Examples)

[0157] According to the formulations shown in Tables 1 and 2, using a 1.7L Banbury internal mixer manufactured by Kobe Steel Corporation, sulfur and reagents other than the vulcanization accelerator were mixed for 5 minutes at 150°C to obtain a compound. Next, sulfur and the vulcanization accelerator were added to the obtained compound, and the mixture was mixed for 5 minutes at 80°C using an open-roll mill to obtain unvulcanized rubber compositions for the outer triangular rubber portion and for the inner triangular rubber portion.

[0158] The obtained unvulcanized rubber composition for the outer triangular rubber portion and the unvulcanized rubber composition for the inner triangular rubber portion were formed into a two-layer structure of bead triangular rubber, consisting of an outer triangular rubber portion and an inner triangular rubber portion, according to the specifications in Table 3. The bead triangular rubber was then bonded together with other tire components to prepare an unvulcanized tire. The tire was then vulcanized under pressure at 150°C for 30 minutes to obtain a test tire (load-bearing tire, size: 11R22.5).

[0159] The obtained test tires were evaluated as follows. The results are shown in Table 3.

[0160] <Viscoelasticity Test>

[0161] Viscoelasticity test samples (vulcanized rubber) measuring 20 mm in length, 4 mm in width, and 1 mm in thickness were taken from the outer and inner triangular portions of the bead rubber of each test tire, with the tire circumference as the long side. Using a GABO EPLEXOR series instrument, the complex elastic modulus Eo* (outer triangular portion) and Ei* (inner triangular portion) of each sample were measured under the conditions of 70°C, 5% initial strain, 1% dynamic strain, 10 Hz frequency, and tensile mode. The thickness direction of the sample is the tire radius direction.

[0162] <Durability>

[0163] Using a drum tester, the test tire was driven at 20 km / h under the conditions of rim (8.25×22.5), internal pressure (700 kPa), and load (26.72 kN×2.5). The driving time until the bead broke was expressed as an index with Comparative Example 1 set to 100. The higher the value, the better the durability.

[0164] [Table 1]

[0165]

[0166] [Table 2]

[0167]

[0168] [Table 3]

[0169]

[0170] The tires in the table that have bead rubber having an inner triangular rubber portion and an outer triangular rubber portion, and that are selected from at least one of the inner triangular rubber portion and the outer triangular rubber portion and include isoprene rubber, carbon black and modified rubber material functionalized with thiuram sulfide compounds, and that satisfy the embodiments of formulas (1) to (2) above, have excellent durability.

[0171] In this invention (1), a load-bearing tire is provided with a bead rubber having an inner triangular rubber portion and an outer triangular rubber portion. At least one of the inner triangular rubber portion and the outer triangular rubber portion is selected from the group consisting of isoprene rubber, carbon black, and a modified rubber material functionalized with a thiuram sulfide compound. The complex elastic modulus (Ei*) of the inner triangular rubber portion and the complex elastic modulus (Eo*) of the outer triangular rubber portion satisfy the following formulas (1) to (2).

[0172] (1) Ei*>Eo*

[0173] (2) Ei* / Eo*≤7.0

[0174] (Ei* and Eo* are the complex elastic moduli measured under the conditions of 70℃ temperature, 5% initial strain, 1% dynamic strain, 10Hz frequency, and tensile mode).

[0175] In the present invention (2), in the heavy-duty tire according to the present invention (1), at least one of the inner triangular rubber portion and the outer triangular rubber portion is selected, and the content ratio of the modified rubber material to the isoprene rubber, i.e., the content of the modified rubber material / the content of the isoprene rubber, is 0.25 or less.

[0176] In the present invention (3), in the heavy-duty tire according to the present invention (1) or (2), in at least one of the group consisting of the inner triangular rubber portion and the outer triangular rubber portion, the content ratio of the carbon black to the modified rubber material, i.e., the content of the carbon black / the content of the modified rubber material, is 2.0 or more.

[0177] In the present invention (4), the load-bearing tire according to any one of the present invention (1) to (3) has an Ei* of 15.0 MPa or more.

[0178] In this invention (5), the load-bearing tire according to any one of (1) to (4) of the present invention, the content (Cao) of carbon black in 100 parts by mass of the rubber component in the outer triangular rubber portion and the Ei* / Eo* satisfy the following formula,

[0179] Cao / (Ei* / Eo*)≥6.0.

[0180] In this invention (6), in the heavy-duty tire according to any one of (1) to (5), the content (Cai) of carbon black in the inner triangular rubber portion relative to 100 parts by mass of the rubber component and the Ei* / Eo* satisfy the following formula:

[0181] Cai / (Ei* / Eo*)≥11.0.

[0182] Figure Labels

[0183] 2nd pregnancy face

[0184] 3. Sidewall

[0185] 4. Bead area

[0186] 5. Bead core

[0187] 6. Fetal body

[0188] 6A tire carcass cord

[0189] 6a Main body of the curtain

[0190] 6b Curtain folding section

[0191] 8. Bead triangle rubber

[0192] 8A Inner triangular rubber part

[0193] 8B Outer triangular rubber part

[0194] 9. Strengthen the cord layer

[0195] 9a inner film

[0196] 9b (outer film).

Claims

1. A heavy-duty tire, comprising a bead rubber portion having an inner triangular portion and an outer triangular portion. The material selected from at least one of the inner triangular rubber portion and the outer triangular rubber portion comprises isoprene-based rubber, carbon black, and a modified rubber material functionalized with thiuram sulfide compounds. The complex elastic modulus Ei* of the inner triangular rubber part and the complex elastic modulus Eo* of the outer triangular rubber part satisfy the following formulas (1) to (2). (1) Ei*>Eo* (2) 2.0 ≤ Ei* / Eo* ≤ 7.0 in, Ei* and Eo* are the complex elastic moduli measured under the conditions of 70℃ temperature, 5% initial strain, 1% dynamic strain, 10Hz frequency, and tensile mode. The carbon black content Ca in the outer triangular rubber portion relative to 100 parts by mass of the rubber component and the Ei* / Eo* satisfy the following formula. 20.0≥Cao / (Ei* / Eo*)≥6.0, The carbon black content Cai in the inner triangular rubber portion relative to 100 parts by mass of the rubber component and the Ei* / Eo* satisfy the following formula. 30.0≥Cai / (Ei* / Eo*)≥11.

0.

2. The heavy-duty tire according to claim 1, wherein, selected from at least one of the inner triangular rubber portion and the outer triangular rubber portion, the content ratio of the modified rubber material to the isoprene rubber, i.e., the content of the modified rubber material / the content of the isoprene rubber, is 0.25 or less.

3. The heavy-duty tire according to claim 1 or 2, wherein, selected from at least one of the inner triangular rubber portion and the outer triangular rubber portion, the content ratio of carbon black to the modified rubber material, i.e., the content of carbon black / content of the modified rubber material, is 2.0 or more.

4. The load-bearing tire according to claim 1 or 2, wherein Ei* is 15.0 MPa or higher.

5. The heavy-duty tire according to claim 4, wherein Ei* is 30.0 MPa or less.

6. The load-bearing tire according to claim 1 or 2, wherein Eo* is 2.0 MPa or more and 7.0 MPa or less.

Images