Heavy load tyre

Abstract

Provided is a heavy load tire having improved cut resistance during high load and high speed running. A heavy load tire having a sidewall formed of a sidewall rubber composition, the sidewall rubber composition containing isoprene-based rubber, butadiene rubber, and oxidized carbon black having an average particle diameter of 30 nm or less, the content of butadiene rubber in 100 mass% of the rubber component being 5 mass% or more and less than 50 mass%, wherein the content (mass%) of isoprene-based rubber and butadiene rubber in 100 mass% of the rubber component of the sidewall rubber composition satisfies the following formula (1), and the thickness (mm) at the maximum width of the sidewall and the content (mass%) of butadiene rubber in 100 mass% of the rubber component of the sidewall rubber composition satisfy the following formula (2).(1) Content of isoprene-based rubber > Content of butadiene rubber(2) Thickness at maximum width > -0.14 x Content of butadiene rubber + 10.0.

Description

Technical Field

[0001] This invention relates to tires for heavy loads. Background Technology

[0002] Heavy-duty tires installed on trucks, buses, and other vehicles are required to meet various performance requirements, including durability (cut resistance) and handling stability. In recent years, with the increasing speed of transportation, opportunities for continuous high-speed driving under high load conditions are not uncommon. Therefore, improved cut resistance under high load and high-speed driving is desired. Summary of the Invention

[0003] [The problem the invention aims to solve]

[0004] The present invention solves the above-mentioned problems and aims to provide a heavy-duty tire with improved cut resistance under high load and high speed.

[0005] [Methods used to solve problems]

[0006] The present invention relates to a heavy-duty tire having a sidewall using a sidewall rubber composition comprising isoprene rubber, butadiene rubber, and carbon black with an average particle size of 30 nm or less, wherein the butadiene rubber content in 100% by mass of the rubber composition is 5% by mass or more and less than 50% by mass, wherein the content (by mass) of the isoprene rubber and the butadiene rubber in 100% by mass of the rubber composition satisfies the following formula (1), and the thickness (mm) at the maximum width of the sidewall and the content (by mass) of the butadiene rubber in 100% by mass of the rubber composition satisfies the following formula (2).

[0007] (1) The content of isoprene rubber is greater than that of butadiene rubber.

[0008] (2) Thickness at maximum width > -0.14 × butadiene rubber content + 10.0

[0009] Preferably, the content (mass%) of the carbon black oxide and butadiene rubber in the above-mentioned sidewall rubber composition 100% by mass satisfies the following formula (3).

[0010] (3) The content of carbon black with an average particle size of less than 30 nm is greater than the content of butadiene rubber.

[0011] Preferably, the butadiene rubber comprises butadiene rubber with a cis content of 95% by mass or more.

[0012] Preferably, the above-mentioned sidewall rubber composition contains a phenylenediamine compound, and the content (mass%) of the above-mentioned isoprene rubber and the above-mentioned phenylenediamine compound in 100% by mass of the above-mentioned sidewall rubber composition satisfies the following formula (4).

[0013] (4) The ratio of isoprene rubber content to phenylenediamine compound content < 35

[0014] Preferably, the above-mentioned rubber composition for tire sidewall contains n-alkanes with 20 to 50 carbon atoms and / or isoalkanes with 20 to 50 carbon atoms, and the content (mass%) of the above-mentioned isoprene rubber in 100% by mass of the above-mentioned rubber composition for tire sidewall and the total content (mass%) of the above-mentioned n-alkanes and the above-mentioned isoalkanes satisfy the following formula (5).

[0015] (5) The total content of isoprene-based rubbers consisting of n-alkanes with 20–50 carbon atoms and isoalkanes with 20–50 carbon atoms is <100%.

[0016] Preferably, the thickness at the maximum width of the tire sidewall is 4.0 mm or more and less than 10.0 mm.

[0017] Preferably, the content of the phenylenediamine compound in the above-mentioned sidewall rubber composition is 1.5 to 4.0% by mass (100% by mass).

[0018] Preferably, the total content of n-alkanes with 20 to 50 carbon atoms and isoalkanes with 20 to 50 carbon atoms in the above-mentioned rubber composition for tire sidewalls is 0.5 to 1.0% by mass.

[0019] [Invention Effects]

[0020] The present invention relates to a heavy-duty tire having a sidewall using a sidewall rubber composition comprising isoprene rubber, butadiene rubber, and carbon black with an average particle size of 30 nm or less. The butadiene rubber content in 100% by mass of the rubber composition is 5% by mass or more and less than 50% by mass. The isoprene rubber and butadiene rubber content in 100% by mass of the rubber composition of the sidewall satisfy the above formula (1), and the thickness (mm) at the maximum width of the sidewall and the butadiene rubber content in 100% by mass of the rubber composition of the sidewall satisfy the above formula (2). Therefore, the present invention can provide a heavy-duty tire with improved cut resistance under high load and high speed. Attached Figure Description

[0021] Figure 1This is an example of a schematic diagram of a heavy-duty tire according to the present embodiment.

[0022] [Reference Signs]

[0023] 1 Tire for trucks and buses

[0024] 2 Tread surface

[0025] 3 Sidewall part

[0026] 4 Bead part

[0027] 5 Bead core

[0028] 6 Carcass

[0029] 6A Carcass ply

[0030] 6a Main body part of the ply

[0031] 6b Turn-up part of the ply

[0032] 7 Belt layer

[0033] 7A, 7B Inner and outer belt plies

[0034] 8 Apex

[0035] 10 Lap joint rubber

[0036] 11 Reinforcing cord layer

[0037] 11A Upright part (lifting part)

[0038] 11B Lower winding part (lower winding part)

[0039] 15 Sidewall Detailed Embodiment

[0040] The present invention is a heavy-duty tire having a sidewall using the following rubber composition for sidewall and satisfying the above formulas (1) and (2). The rubber composition for sidewall contains an isoprene rubber, a butadiene rubber, and carbon black having an average particle diameter of 30 nm or less in a specified formulation. Therefore, a heavy-duty tire with improved cut resistance during high load and high-speed driving can be provided.

[0041] The mechanism for obtaining such effects is not clear yet, but it is inferred as follows.

[0042] By adding more than 5% by mass and less than 50% by mass (i.e., less than half) of butadiene rubber as a rubber component, and then adding carbon black with an average particle size of less than 30 nm, the butadiene rubber layer is dispersed in the isoprene rubber layer. The carbon black reinforces each rubber layer and interface, thereby improving cut resistance. In addition, compared with ordinary carbon black, carbon black has excellent low heat generation. Therefore, it can suppress the heat generation of the tire sidewall even when driving at high speed on rough roads under high load, and can suppress the reduction of the rubber's reinforcement during tire use. Furthermore, regarding the thickness at the maximum width of the tire sidewall and the amount of butadiene rubber, by adjusting them to satisfy formula (2) "thickness at the maximum width > -0.14 × butadiene rubber content + 10.0", the thickness of the tire sidewall increases as the amount of butadiene rubber decreases, thereby mitigating surface strain and maintaining good crack growth, which is contrary to the tendency of crack development in a typical butadiene rubber formulation. Therefore, by reinforcing isoprene rubber and butadiene rubber with carbon black oxide, the strain in the sidewall portion can be optimized. Furthermore, by satisfying equation (2) and setting the thickness at the maximum width to 10.0 mm, the maximum thickness can be reduced as the amount of butadiene rubber increases, thus providing good fuel economy. Based on the above, it can be used as the sidewall rubber for heavy-duty tires that balances fuel economy with cut resistance under high loads and high speeds. Therefore, it is inferred that a heavy-duty tire with improved cut resistance under high loads and high speeds can be provided.

[0043] In this way, the above-mentioned heavy-duty tire is configured to have a sidewall using the following sidewall rubber composition and satisfy the above formulas (1) and (2). The sidewall rubber composition contains isoprene rubber, butadiene rubber and carbon black oxide with an average particle size of 30 nm or less in a specified formula, thereby solving the problem (objective) of improving cut resistance under high load and high speed. That is, the parameters of formula (1) "content of isoprene rubber > content of butadiene rubber" and formula (2) "thickness at maximum width > -0.14 × content of butadiene rubber + 10.0" are not the specified inventive object (objective). The object of this application is to improve cut resistance under high load and high speed, and a configuration that satisfies these parameters is formed as a means to solve this problem.

[0044] In the rubber composition for tire sidewalls, the content (mass%) of isoprene rubber in 100% by mass of rubber component and the content (mass%) of butadiene rubber in 100% by mass of rubber component satisfy the following formula (1).

[0045] (1) The content of isoprene rubber is greater than that of butadiene rubber.

[0046] From the viewpoint of cut resistance under high load and high speed, the content (mass%) of the aforementioned isoprene rubber and the content (mass%) of the aforementioned butadiene rubber are preferably 10% by mass or more, more preferably 20% by mass or more, further preferably 40% by mass or more, and particularly preferably 50% by mass or more. There is no particular upper limit, but it is preferably 90% by mass or less, more preferably 80% by mass or less, further preferably 70% by mass or less, and particularly preferably 60% by mass or less.

[0047] The thickness (mm) at the maximum width of the sidewall (cured sidewall rubber) of the heavy-duty tire and the butadiene rubber content (mass%) in 100% mass of the rubber component of the sidewall rubber composition satisfy the following formula (2).

[0048] (2) Thickness at maximum width > -0.14 × butadiene rubber content + 10.0

[0049] From the viewpoint of cut resistance under high load and high speed, the thickness at maximum width (thickness) - (-0.14 × butadiene rubber content + 10.0) is preferably 0.5 or more, more preferably 0.8 or more, further preferably 1.6 or more, and particularly preferably 2.0 or more. There is no particular upper limit, but it is preferably 7.0 or less, more preferably 5.0 or less, further preferably 3.6 or less, and particularly preferably 3.0 or less.

[0050] From the viewpoint of cut resistance under high load and high speed, a sidewall thickness of 4.0 mm or more and less than 10.0 mm at its maximum width is suitable. The lower limit is preferably 5.0 mm or more, more preferably 6.0 mm or more, further preferably 7.0 mm or more, and particularly preferably 7.5 mm or more. The upper limit is preferably 9.5 mm or less, more preferably 9.0 mm or less, further preferably 8.5 mm or less, and particularly preferably 8.0 mm or less.

[0051] In addition, the so-called "thickness at the maximum width (thickness at the maximum width of the tire sidewall)" refers to the thickness of the tire sidewall at the maximum width position (the outermost axial end of the tire) when the tire is filled with a specified internal pressure.

[0052] (Rubber composition)

[0053] The rubber composition for tire sidewalls contains isoprene rubber and butadiene rubber (BR). The isoprene rubber and butadiene rubber may each be composed of a single polymer or two or more polymers.

[0054] In the rubber composition for tire sidewalls, the content of isoprene-based rubber in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 50% by mass or more, further preferably 60% by mass or more, and particularly preferably 70% by mass or more. The upper limit of this content is preferably 95% by mass or less, more preferably 85% by mass or less, and further preferably 80% by mass or less. By setting this content within the above range, there is a tendency to improve cut resistance under high loads and high-speed driving.

[0055] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, altered NR, and modified IR. For example, common NRs used in the rubber industry, such as SIR20, RSS#3, and TSR20, can be used. For IR, there are no particular limitations; for example, common IRs used in the rubber industry, such as IR2200, 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 individually or in combination of two or more.

[0056] In the rubber composition for tire sidewalls, the content of BR (brane rubber) in 100% by mass of the rubber component is 5% by mass or more and less than 50% by mass. The lower limit is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more. The upper limit is preferably 45% by mass or less, more preferably 40% by mass or less, even more preferably 35% by mass or less, and particularly preferably 30% by mass or less. By setting this content within the above range, there is a tendency to improve cut resistance under high loads and high-speed driving.

[0057] From the viewpoint of cut resistance under high loads and high speeds, the cis content of BR is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 97% by mass or more. It can be considered that the higher the cis content, the more linear the molecule, and the better the balance between low heat generation and durability. Therefore, it can be inferred that heavy-duty tires with improved cut resistance under high loads and high speeds can be provided.

[0058] In addition, in this specification, the cis content (cis-1,4-binding amount) is a value calculated based on the signal intensity measured by infrared absorption spectroscopy or NMR analysis.

[0059] There are no particular limitations on BR (butadiene rubber). Examples include BR with high cis content, BR containing 1,2-meta-isotactic polybutadiene crystals (BR containing SPB), butadiene rubber synthesized using rare earth element catalysts (rare earth BR), and tin-modified butadiene rubber modified with tin compounds (tin-modified BR), which are common types of BR used in the tire industry. Regarding BR, products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Zeon Corporation, etc., can be used as commercially available products. These can be used individually or in combination of two or more.

[0060] BR can be unmodified BR or modified BR.

[0061] As a modified BR, any BR having functional groups that can interact with fillers such as silica is acceptable. Examples include end-modified BRs (end-modified BRs with the aforementioned functional groups at the end) formed by modifying at least one end of the BR with a compound (modifier) ​​having the aforementioned functional groups, main-chain modified BRs with the aforementioned functional groups in the main chain, main-chain end-modified BRs with the aforementioned functional groups in both the main chain and the end (e.g., main-chain end-modified BRs with the aforementioned functional groups in the main chain and at least one end modified by the aforementioned modifier), or modified (coupled) by a polyfunctional compound having two or more epoxy groups in the molecule, or end-modified BRs with hydroxyl or epoxy groups introduced.

[0062] Examples of the aforementioned functional groups include amino, amide, silyl, alkoxysilyl, isocyanate, imino, imidazo, urea, ether, carbonyl, oxycarbonyl, mercapto, sulfide group, disulfide group, sulfonyl, thionyl, thiocarbonyl, ammonium, imide, hydrazogroup, azo, diazo, carboxyl, nitrile, pyridyl, alkoxy, hydroxy, oxygen, and epoxy groups. Furthermore, these functional groups may have substituents. Among these, amino groups (preferably amino groups where the hydrogen atoms of the amino group are replaced by alkyl groups having 1 to 6 carbon atoms), alkoxy groups (preferably alkoxy groups having 1 to 6 carbon atoms), and alkoxysilyl groups (preferably alkoxysilyl groups having 1 to 6 carbon atoms) are preferred.

[0063] As a BR (Brandinger), products from companies such as Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Zeon Corporation can be used.

[0064] In the rubber composition for tire sidewalls, there are no particular limitations on other rubber components that can be used, and rubbers used in the tire industry can be used. Examples include diene rubbers such as styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These rubber components can be used alone or in combination of two or more.

[0065] In the rubber composition for tire sidewalls, from the viewpoint of cut resistance under high load and high speed, the total content of isoprene rubber and BR in 100% by mass of the rubber component is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and can be 100% by mass.

[0066] (Carbon black oxide)

[0067] The rubber composition for tire sidewalls contains carbon black oxide with an average particle size of 30 nm or less. From the viewpoint of cut resistance under high loads and high speeds, this average particle size is preferably 27 nm or less, more preferably 25 nm or less, even more preferably 24 nm or less, and particularly preferably 23 nm or less. While the lower limit is not particularly limited, from the viewpoint of dispersibility, it is preferably 5 nm or more, more preferably 10 nm or more, even more preferably 15 nm or more, and particularly preferably 20 nm or more.

[0068] In addition, the average particle size is the number-average particle size, which was determined by transmission electron microscopy.

[0069] The nitrogen adsorption specific surface area (N2SA) of the above-mentioned carbon black is preferably 80 m². 2 / g or more, preferably 100m 2 / g or more, more preferably 105m 2 / g or more, especially preferably 110m 2 / g or more. The preferred N2SA is 180m. 2 / g or less, more preferably 150m 2 / g or less, more preferably 130m 2 / g or less, especially preferably 120m 2 / g or less.

[0070] In addition, N2SA is obtained according to JIS K6217-2:2001.

[0071] The dibutyl phthalate (DBP) oil absorption of the aforementioned carbon black is preferably 50 ml / 100g or more, more preferably 100 ml / 100g or more, even more preferably 105 ml / 100g or more, and particularly preferably 110 ml / 100g or more. This DBP is preferably 180 ml / 100g or less, more preferably 150 ml / 100g or less, even more preferably 130 ml / 100g or less, and particularly preferably 120 ml / 100g or less.

[0072] Alternatively, DBP can be determined according to JIS-K6217-4:2001.

[0073] In the rubber composition for tire sidewalls, the content of carbon black with an average particle size of 30 nm or less relative to 100 parts by weight of the rubber component is preferably 20 parts by weight or more, more preferably 40 parts by weight or more, further preferably 50 parts by weight or more, and particularly preferably 55 parts by weight or more. There is no particular upper limit to the above content, but it is preferably 100 parts by weight or less, more preferably 80 parts by weight or less, further preferably 70 parts by weight or less, and particularly preferably 65 parts by weight or less. By setting this content within the above range, there is a tendency to improve cut resistance under high loads and high-speed driving.

[0074] Oxidized carbon black can be manufactured by oxidation using known oxidation techniques such as oxidation with ozone, dichromates, or oxidizing acids. Oxidized carbon black typically possesses functional groups such as carboxyl groups, hydroxyl groups (e.g., CHO, CO), aldehyde groups, and ketone groups (quinone groups) on the carbon black. From the viewpoint of affinity and binding with rubber components, the amount of these functional groups is preferably 0.5–7% by mass per 100g of carbon black, more preferably 1.2–5% by mass.

[0075] Specifically, for example, carbon black oxide can be produced by subjecting ordinary carbon black to hydrogen peroxide treatment or ozone treatment, thereby producing carbon black oxide with carboxyl groups and / or hydroxyl groups on its surface (see U.S. Patent Application Publication No. 2013 / 0046064, etc.).

[0076] In addition, other carbon blacks besides the aforementioned carbon black may be added to the rubber composition for tire sidewalls, provided that the effect is not adverse. There are no particular limitations on such other carbon blacks; for example, carbon blacks known in the rubber industry such as N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762 can be used. Commercially available products may 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., Columbia Carbon Co., Ltd., etc. These may be used alone or in combination of two or more.

[0077] (Other filler materials)

[0078] There are no particular limitations on filler materials other than carbon black; materials known in the rubber industry can be used, such as silica, calcium carbonate, talc, bauxite, clay, aluminum hydroxide, alumina, mica, and other inorganic fillers. Among these, silica is preferred.

[0079] Examples of usable silica include dry-process silica (anhydrous silica) and wet-process silica (hydrated silica). Wet-process silica is preferred due to its higher silanol group content. Commercially available products include those from Degussa, Rhodia, Tosoh Silicon Chemicals, Solvay Japan, and Tokuyama. These silicas can be used individually or in combination of two or more types.

[0080] 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, especially preferred is 170m 2 / g or more. Furthermore, there is no particular upper limit for the N2SA content of silica, but 350 mg / g is preferred. 2 / g or less, more preferably 250m 2 / g or less, more preferably 200m 2 / g or less. By setting the N2SA within the above range, there is a tendency for improved cut resistance under high load and high speed.

[0081] In addition, the N2SA of silica is a value determined by the BET method according to ASTM D3037-93.

[0082] When the rubber composition for the tire sidewall contains silica, the silica content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, relative to 100 parts by mass of the rubber component. The upper limit of this content is preferably 60 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. By setting this content within the above range, there is a tendency to improve cut resistance under high loads and high-speed driving.

[0083] When the rubber composition for tire sidewalls contains silica, it preferably also contains a silane coupling agent.

[0084] As a silane coupling agent, there are no particular limitations; examples include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, and bis(4-triethoxysilylbutyl)tetrasulfide. -trimethoxysilylbutyl) trisulfide, bis(3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilyl Sulfide systems include alkylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and methacrylate-3-triethoxysilylpropyl ester monosulfide; mercapto-based systems include 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z manufactured by Momentive; vinyl-based systems include vinyltriethoxysilane and vinyltrimethoxysilane; amino-based systems include 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; epoxypropoxy-based systems include γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based systems include 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chlorine-based systems include 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. As commercially available products, you can use products from Degussa, Momentive, Shin-Etsu Silicone, Tokyo Chemical Industries, Azmax, Toray Industries, Corning, and others. These can be used individually or in combination of two or more.

[0085] In the rubber composition for tire sidewalls, the content of silane coupling agent relative to 100 parts by weight of silica is preferably 0.1 parts by weight or more, more preferably 3 parts by weight or more, and even more preferably 5 parts by weight or more. The upper limit of this content is preferably 50 parts by weight or less, more preferably 20 parts by weight or less, and even more preferably 15 parts by weight or less. By setting this content within the above range, there is a tendency to improve cut resistance under high loads and high-speed driving.

[0086] In the rubber composition for tire sidewalls, the content of filler material (total filler material content) relative to 100 parts by weight of rubber component is preferably 20 parts by weight or more, more preferably 40 parts by weight or more, further preferably 50 parts by weight or more, and particularly preferably 55 parts by weight or more. The upper limit of the above-mentioned total content is not particularly limited, but is preferably 100 parts by weight or less, more preferably 80 parts by weight or less, further preferably 70 parts by weight or less, and particularly preferably 65 parts by weight or less. By setting this content within the above range, there is a tendency to improve cut resistance under high loads and high-speed driving.

[0087] In the rubber composition for tire sidewalls, from the viewpoint of cut resistance under high load and high speed, the content of carbon black with an average particle size of 30 nm or less in 100% by mass of the filler material is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and can be 100% by mass.

[0088] (Phenylenediamine compound)

[0089] From the viewpoint of cut resistance under high load and high speed, the rubber composition for tire sidewalls preferably contains a phenylenediamine compound.

[0090] In the rubber composition for tire sidewalls, the content of phenylenediamine compound relative to 100 parts by weight of rubber component is preferably 1.0 part by weight or more, more preferably 3.0 part by weight or more, even more preferably 4.0 part by weight or more, and particularly preferably 5.0 part by weight or more. There is no particular upper limit to this content, but it is preferably 10.0 parts by weight or less, more preferably 8.0 parts by weight or less, and even more preferably 6.0 parts by weight or less. By setting this content within the above range, there is a tendency to improve cut resistance under high loads and high-speed driving.

[0091] The phenylenediamine compound is not particularly limited; for example, compounds known as antioxidants in the rubber industry can be used. Specifically, examples include N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine. One of these can be used alone, or two or more can be used in combination. Among these, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) is preferred.

[0092] As an antioxidant, 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.

[0093] In rubber compositions for tire sidewalls, other antioxidants may be used in combination.

[0094] Other antioxidants are not particularly limited, but can include naphthylamine antioxidants such as phenyl-α-naphthylamine; diphenylamine antioxidants such as octyl diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; quinoline antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer; monophenol antioxidants such as 2,6-di-tert-butyl-4-methylphenol and styrylated phenol; and bisphenol, triphenol, and polyphenol antioxidants such as tetra-[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane. These can be used alone or in combination of two or more. Among them, quinoline antioxidants are preferred, and 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMQ) is more preferred.

[0095] When the rubber composition for tire sidewalls contains other antioxidants, the content of the other antioxidants is preferably 0.1 parts by weight or more, more preferably 0.5 parts by weight or more, relative to 100 parts by weight of the rubber component; furthermore, it is preferably 3.0 parts by weight or less, more preferably 2.0 parts by weight or less. By setting this content within the above range, there is a tendency to improve cut resistance under high loads and high-speed driving.

[0096] (n-alkanes, isoalkanes)

[0097] From the viewpoint of cut resistance under high load and high speed, the rubber composition for tire sidewalls preferably contains n-alkanes with 20 to 50 carbon atoms and / or isoalkanes with 20 to 50 carbon atoms.

[0098] Such n-alkanes and isoalkanes with 20 to 50 carbon atoms can be incorporated into tire sidewall rubber compositions, for example, by using waxes known in the rubber industry.

[0099] Examples of such waxes include petroleum-based waxes such as paraffin and microcrystalline wax; natural waxes such as plant-based and animal-based waxes; and synthetic waxes made from polymers of ethylene, propylene, etc. These can be used individually or in combination of two or more. Among these, petroleum-based waxes are preferred, and paraffin wax is even more preferred, considering their resistance to cuts under high loads and high speeds.

[0100] In addition, the carbon atom number distribution of wax can be determined by the following methods.

[0101] <Distribution of Carbon Atom Numbers>

[0102] The determination was performed using a capillary GC as the measuring device and an aluminum-coated capillary column as the chromatographic column. The conditions were as follows: helium as the carrier gas, a flow rate of 4 ml / min, a column temperature of 180–390 °C, and a heating rate of 15 °C / min.

[0103] In the rubber composition for tire sidewalls, the total content of n-alkanes with 20 to 50 carbon atoms and isoalkanes with 20 to 50 carbon atoms per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and even more preferably 1.0 parts by mass or more. The above content is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 2.0 parts by mass or less.

[0104] (Plasticizer)

[0105] Plasticizers may be added to the rubber composition used in tire sidewalls. Plasticizers are materials that can impart plasticity to rubber components, such as liquid plasticizers (plasticizers that are in a liquid state at room temperature (25°C)) and resins (resins that are in a solid state at room temperature (25°C)).

[0106] In the rubber composition for tire sidewalls, the content of plasticizer (total amount of plasticizer) relative to 100 parts by weight of rubber component is preferably 20.0 parts by weight or less, more preferably 10.0 parts by weight or less, even more preferably 5.0 parts by weight or less, and particularly preferably 2.0 parts by weight or less. The lower limit is not particularly limited and may be 0 parts by weight, but is preferably 0.5 parts by weight or more, more preferably 1.0 parts by weight or more. By setting this content within the above range, there is a tendency to improve cut resistance under high loads and high-speed driving.

[0107] Liquid plasticizers (plasticizers that are liquid at room temperature (25°C)) that can be used in tire sidewall rubber compositions are not particularly limited, and examples include oils, liquid polymers (liquid resins, liquid diene polymers, liquid farnesene polymers, etc.). These can be used alone or in combination of two or more.

[0108] In the rubber composition for tire sidewalls, the content of liquid plasticizer relative to 100 parts by weight of rubber component is preferably 20.0 parts by weight or less, more preferably 10.0 parts by weight or less, even more preferably 5.0 parts by weight or less, and particularly preferably 2.0 parts by weight or less. The lower limit is not particularly limited and may be 0 parts by weight, but is preferably 0.5 parts by weight or more, more preferably 1.0 parts by weight or more. By setting this content within the above range, there is a tendency to improve cut resistance under high loads and high-speed driving. Furthermore, the oil content described later is also preferably within the same range (the oil content also includes the oil contained in the oil-extended rubber).

[0109] Examples of oils include processing oils, vegetable oils, or mixtures thereof. Examples of processing oils include alkane-based processing oils, aromatic processing oils, and naphthenic processing oils. Examples of vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. Commercially available products include those from Idemitsu Kosan Co., Ltd., Sankyo Oil & Chemical Co., Ltd., Japan Energy Co., Ltd., Olisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Oil Co., Ltd., Fuji Kosan Co., Ltd., and Nissin Olivo Co., Ltd. Among them, preferred processing oils (alkane-based processing oils, aromatic processing oils, cycloalkane-based processing oils, etc.) and vegetable oils are preferred.

[0110] Examples of liquid resins include terpene resins (including terpene phenol resins and aromatic modified terpene resins), rosin resins, styrene resins, C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene (DCPD) resins, benzofuran-indene resins (including benzofuran and indene elemental resins), phenol (aldehyde) resins, olefin resins, polyurethane resins, and acrylic (ester) resins. Additionally, their hydrides can also be used.

[0111] Examples of liquid diene polymers 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), liquid styrene-isoprene-styrene block copolymers (liquid SIS block copolymers), liquid farnesene polymers, and liquid farnesene-butadiene copolymers, all of which are liquid at 25°C. The ends or main chains of these liquid diene polymers can be modified with polar groups. Additionally, their hydrides can also be used.

[0112] Examples of resins (resins that are solid at room temperature (25°C)) that can be used in tire sidewall rubber compositions include, for example, aromatic vinyl polymers, benzofuran-indene resins, benzofuran resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, and acrylic resins that are solid at room temperature (25°C). Furthermore, the resins can be hydrogenated. These resins can be used alone or in combination of two or more. From the viewpoint of cut resistance under high loads and high speeds, aromatic vinyl polymers, petroleum resins, and terpene resins are preferred.

[0113] In the rubber composition for tire sidewalls, the content of the aforementioned resin relative to 100 parts by weight of the rubber component is preferably 20.0 parts by weight or less, more preferably 10.0 parts by weight or less, even more preferably 5.0 parts by weight or less, and particularly preferably 2.0 parts by weight or less. The lower limit is not particularly limited and may be 0 parts by weight, but is preferably 0.5 parts by weight or more, more preferably 1.0 parts by weight or more. By setting this content within the above range, there is a tendency to improve cut resistance under high loads and high-speed driving.

[0114] The softening point of the aforementioned resin is preferably 60°C or higher, more preferably 70°C or higher, and even more preferably 80°C or higher. The upper limit is preferably 160°C or lower, more preferably 130°C or lower, and even more preferably 115°C or lower. By setting the softening point within the above range, there is a tendency to improve cut resistance under high loads and high-speed travel.

[0115] In addition, the softening point of the aforementioned resin refers to the softening point specified in JIS K6220-1:2001, which is the temperature at which the ball falls, as determined by a ring-and-ball softening point measuring device.

[0116] The aforementioned aromatic vinyl polymers are polymers containing aromatic vinyl monomers as constituent units. Examples include resins obtained by polymerizing α-methylstyrene and / or styrene, specifically styrene homopolymers (styrene resins), α-methylstyrene homopolymers (α-methylstyrene resins), copolymers of α-methylstyrene and styrene, and copolymers of styrene with other monomers.

[0117] The aforementioned benzofuran-indene resin is a resin containing benzofuran and indene as the main monomer components constituting the resin backbone (main chain). Other monomer components included in the backbone besides benzofuran and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

[0118] The aforementioned benzofuran resin is a resin containing benzofuran as the main monomer component constituting the resin skeleton (main chain).

[0119] The aforementioned indene resin is a resin containing indene as the main monomer component constituting the resin skeleton (main chain).

[0120] As the aforementioned phenolic resin, for example, known phenolic resins such as polymers obtained by reacting phenols with aldehydes such as formaldehyde, acetaldehyde, and furfural using an acid or base catalyst can be used. Among these, phenolic resins obtained by reacting with an acid catalyst (such as phenolic varnish (novolac) type phenolic resins) are preferred.

[0121] Examples of rosin resins include natural rosin, polymeric rosin, modified rosin, their ester compounds, and their hydrides.

[0122] Examples of the aforementioned petroleum resins include C5 series resins, C9 series resins, C5 / C9 series resins, dicyclopentadiene (DCPD) resins, and their hydrogenated derivatives. Among these, DCPD resins and hydrogenated DCPD resins are preferred.

[0123] The aforementioned terpene resins are polymers containing terpenes as constituent units. Examples include polyterpene resins obtained by polymerizing terpene compounds, and aromatic modified terpene resins obtained by polymerizing terpene compounds with aromatic compounds. As aromatic modified terpene resins, terpene-phenol resins made from terpene compounds and phenolic compounds, terpene-styrene resins made from terpene compounds and styrene compounds, or terpene-phenol-styrene resins made from terpene compounds, phenolic compounds, and styrene compounds can also be used. Furthermore, examples of terpene compounds include α-pinene and β-pinene; examples of phenolic compounds include phenol and bisphenol A; and examples of aromatic compounds include styrene compounds (styrene, α-methylstyrene, etc.).

[0124] The aforementioned acrylic (ester) resins are polymers containing acrylic monomers as constituent units. Examples include styrene acrylic resins, which have carboxyl groups and are copolymerized from aromatic vinyl monomers and acrylic (ester) monomers. Solvent-free styrene acrylic resins containing carboxyl groups are preferred.

[0125] As plasticizers, products from companies such as Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Co., Ltd., Rutgers Chemicals, BASF, Arizona Chemical Company, 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.

[0126] (Other materials)

[0127] The rubber composition for tire sidewalls preferably contains stearic acid. In the rubber composition for tire sidewalls, the content of stearic acid is preferably 0.5 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, relative to 100 parts by weight of the rubber component.

[0128] In addition, as stearic acid, conventionally known materials can be used, such as products from Nippon Oil Co., Ltd., NOF Corporation, Kao Corporation, Fujifilm and Koh Geny Co., Ltd., Chiba Fatty Acid Co., Ltd., etc.

[0129] The rubber composition for tire sidewalls preferably contains zinc oxide. In the rubber composition for tire sidewalls, the zinc oxide content is preferably 0.5 to 10 parts by weight, more preferably 1 to 5 parts by weight, relative to 100 parts by weight of the rubber component.

[0130] In addition, conventionally known zinc oxides can be used, such as those from Mitsui Metal Mining Co., Ltd., Toho Co., Ltd., HAKUSUI TECH Co., Ltd., Seido Chemical Industry Co., Ltd., and Sakai Chemical Industry Co., Ltd.

[0131] In the rubber composition for tire sidewalls, sulfur is preferably added from the viewpoint of forming appropriate crosslinked chains on the polymer chain and imparting good properties.

[0132] In the rubber composition for tire sidewalls, the sulfur content 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, relative to 100 parts by mass of the rubber component. This content is preferably 4.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 2.0 parts by mass or less.

[0133] Examples of sulfur used in the rubber industry include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, and soluble sulfur. Commercially available products include those from companies such as Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Co., Ltd., Nippon Inkyu Kogyo Co., Ltd., and Hosoi Chemical Industry Co., Ltd. These can be used individually or in combination of two or more.

[0134] The rubber composition for tire sidewalls preferably contains a vulcanization accelerator.

[0135] In the rubber composition for tire sidewalls, the content of the vulcanization accelerator is not particularly limited, and can be freely determined according to the desired vulcanization rate or crosslinking density. However, relative to 100 parts by weight of the rubber component, it is preferably 0.3 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. The upper limit is preferably 8.0 parts by weight or less, more preferably 6.0 parts by weight or less, and even more preferably 5.0 parts by weight or less.

[0136] There are no particular restrictions on the types of vulcanization accelerators; commonly used types can be used. Examples of vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazole disulfide, and N-cyclohexyl-2-benzothiazole sulfenamide; 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, N-oxoethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-o-tolylguanidine, and o-tolylbiguanidine. These can be used alone or in combination of two or more. Among them, sulfenamide-based, guanidine-based, and benzothiazole-based vulcanization accelerators are preferred.

[0137] In addition to the above-mentioned components, compounding agents commonly used in the tire industry, such as release agents, may also be appropriately added to the rubber composition for tire sidewalls.

[0138] From the viewpoint of cut resistance under high load and high speed, the content (mass%) of carbon black with an average particle size of 30 nm or less in 100% by mass of the sidewall rubber composition and the content (mass%) of butadiene rubber in 100% by mass of the sidewall rubber composition preferably satisfy the following formula (3).

[0139] (3) The content of carbon black with an average particle size of less than 30 nm is greater than the content of butadiene rubber.

[0140] Under the condition that equation (3) is satisfied, carbon black oxide can be considered to be easily distributed in isoprene rubber, thus improving its compatibility with isoprene rubber and enhancing the reinforcement provided by carbon black oxide. Therefore, it can be inferred that heavy-duty tires with improved cut resistance under high load and high speed can be provided.

[0141] The content (by mass%) of carbon black oxide with an average particle size of 30 nm or less, and the content (by mass%) of butadiene rubber, are preferably 5.0% by mass or more, more preferably 10.0% by mass or more, further preferably 15.0% by mass or more, and particularly preferably 17.0% by mass or more. There is no particular upper limit, but it is preferably 35.0% by mass or less, more preferably 30.0% by mass or less, further preferably 25.0% by mass or less, and particularly preferably 23.0% by mass or less. By setting it within the above range, there is a tendency for improved cut resistance under high loads and high-speed travel.

[0142] In the rubber composition for tire sidewalls, from the viewpoint of cut resistance under high load and high speed, the content (by mass%) of carbon black with an average particle size of 30 nm or less in 100% by mass of the rubber composition for tire sidewalls is preferably 22.0 to 40.0% by mass. The lower limit is preferably 25.0% by mass or more, more preferably 27.0% by mass or more, and even more preferably 28.0% by mass or more. The upper limit is preferably 35.0% by mass or less, more preferably 33.0% by mass or less, and even more preferably 32.0% by mass or less.

[0143] From the viewpoint of cut resistance under high load and high speed, the content of isoprene rubber in 100% by mass of the sidewall rubber composition and the content of phenylenediamine compound in 100% by mass of the sidewall rubber composition preferably satisfy the following formula (4).

[0144] (4) The ratio of isoprene rubber content to phenylenediamine compound content < 35

[0145] It can be assumed that by satisfying equation (4), the higher the proportion of isoprene-based rubber, the more phenylenediamine compounds are present. This allows for the dispersion of phenylenediamine compounds corresponding to the amount of isoprene-based rubber. Furthermore, phenylenediamine compounds near the double bonds of the isoprene-based rubber inhibit the movement of phenylenediamine compounds within the rubber phase through interaction with the surrounding carbon black oxide, thus improving crack resistance. Therefore, it is inferred that this method can prevent the progression of cracks originating from cracks on the sidewall surface, ensure the durability of the sidewall, and provide heavy-duty tires with improved cut resistance under high loads and high speeds.

[0146] The ratio of the isoprene-based rubber content to the phenylenediamine compound content is preferably 25% or less, more preferably 20% or less, even more preferably 16% or less, and particularly preferably 12% or less. The lower limit is not particularly limited, but is preferably 3% or more, more preferably 5% or more, even more preferably 7% or more, and particularly preferably 9% or more. By setting it within the above range, there is a tendency to improve cut resistance under high loads and high-speed operation.

[0147] In the rubber composition for tire sidewalls, from the viewpoint of cut resistance under high load and high speed, the content (mass%) of phenylenediamine compound in 100% by mass of the rubber composition for tire sidewalls is preferably 1.0 to 4.5% by mass. The lower limit is preferably 1.5% by mass or more, more preferably 2.0% by mass or more, further preferably 2.5% by mass or more, and particularly preferably 2.9% by mass or more. The upper limit is preferably 4.0% by mass or less, more preferably 3.5% by mass or less, further preferably 3.2% by mass or less, and particularly preferably 3.0% by mass or less.

[0148] From the viewpoint of cut resistance under high load and high speed, the content of isoprene rubber in 100% by mass of the sidewall rubber composition and the total content of n-alkanes with 20 to 50 carbon atoms and isoalkanes with 20 to 50 carbon atoms in 100% by mass of the sidewall rubber composition preferably satisfy the following formula (5).

[0149] (5) The total content of isoprene-based rubbers consisting of n-alkanes with 20–50 carbon atoms and isoalkanes with 20–50 carbon atoms is <100%.

[0150] It can be assumed that by satisfying equation (5), the higher the proportion of isoprene-based rubber, the more n-alkanes with 20-50 carbon atoms and / or isoalkanes with 20-50 carbon atoms are contained. This disperses the n-alkanes and isoalkanes corresponding to the amount of isoprene-based rubber. Furthermore, through the interaction between the n-alkanes and / or isoalkanes in the rubber phase and carbon black oxide, excessive precipitation of n-alkanes and isoalkanes onto the rubber surface can be inhibited, thus improving crack resistance. Therefore, it is inferred that this method can prevent the progression of cracks originating from cracks on the sidewall surface, ensure the durability of the sidewall, and provide heavy-duty tires with improved cut resistance under high loads and high speeds.

[0151] The content of the aforementioned isoprene-based rubber / the total content of the aforementioned n-alkanes and isoalkanes is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less. The lower limit is not particularly limited, but is preferably 40% or more, more preferably 50% or more, even more preferably 60% or more, and particularly preferably 65% ​​or more. By setting it within the above range, there is a tendency to improve cut resistance under high loads and high-speed travel.

[0152] In the rubber composition for tire sidewalls, from the viewpoint of cut resistance under high load and high speed, the total content (by mass%) of n-alkanes with 20 to 50 carbon atoms and isoalkanes with 20 to 50 carbon atoms in 100% by mass of the rubber composition for tire sidewalls is preferably 0.3 to 1.5% by mass. The lower limit is preferably 0.4% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.6% by mass or more. The upper limit is preferably 1.2% by mass or less, more preferably 1.0% by mass or less, even more preferably 0.9% by mass or less, and particularly preferably 0.8% by mass or less.

[0153] As a method for manufacturing rubber compositions for tire sidewalls, known methods can be used, such as mixing the above-mentioned components using a rubber mixing apparatus such as an open mill or a Banbury mixer, and then vulcanizing them.

[0154] As for mixing conditions, in the basic mixing process where additives other than vulcanizing agents and vulcanization accelerators are mixed, the mixing temperature is typically 50–200°C, preferably 80–190°C, and the mixing time is typically 30 seconds–30 minutes, preferably 1 minute–30 minutes. In the final mixing process where vulcanizing agents and vulcanization accelerators are mixed, the mixing temperature is typically below 100°C, preferably room temperature to 80°C. Furthermore, the composition after mixing vulcanizing agents and vulcanization accelerators is typically subjected to vulcanization treatment such as pressure vulcanization. The vulcanization temperature is typically 120–200°C, preferably 140–180°C.

[0155] Heavy-duty tires can be manufactured using conventional methods and the aforementioned sidewall rubber composition. Specifically, the sidewall rubber composition, to which the aforementioned components are added, is extruded into the shape of a sidewall during the uncured stage, and then, together with other tire components, is formed on a tire forming machine using conventional methods to create an uncured tire. This uncured tire is then heated and pressurized in a vulcanizing machine to obtain a complete tire.

[0156] Examples of tires designed for heavy-duty applications include pneumatic tires and non-pneumatic tires. Among these, pneumatic tires are preferred. Examples of heavy-duty tires include truck tires and bus tires. In addition, tires can be used for summer applications, winter applications (studless tires, snow tires, studded tires, etc.), and all-season applications.

[0157] <Structure of heavy-duty tires>

[0158] An example of a heavy-duty tire according to this embodiment is described with reference to the accompanying drawings.

[0159] Figure 1 This is an example of a schematic diagram showing a truck and bus tire 1 (hereinafter also referred to as tire 1) as an embodiment of a heavy-duty tire. As tire 1, a tire with a maximum load capacity of 2500 kg or more as specified in JIS specifications can be cited, which includes: a tire body 6 extending from the tread portion 2 through the sidewall portion 3 to the bead portion 4, and a belt layer 7 disposed inside the tread portion 2 and outside the tire body 6.

[0160] The tire carcass 6 is formed by one or more carcass ply layers 6A with carcass cords arranged at an angle of, for example, 70° to 90° relative to the tire circumference. In this example, it is formed by one carcass ply layer 6A with carcass cords arranged at 90° relative to the tire circumference. Steel cords are preferred as carcass cords in this example, but organic fiber cords such as aromatic polyamide, nylon, rayon, and polyester can also be used as required. Furthermore, the carcass ply layer 6A includes a series of ply fold-back portions 6b, which fold back from the inner side of the tire axial direction to the outer side around the bead core 5 at both ends of the ply body portion 6a spanned between the bead cores 5.

[0161] In the bead portion 4, a rigid triangular rubber 8 is disposed between the main body portion 6a of the ply layer and the ply layer fold-back portion 6b, extending radially outward from the bead core 5, to reinforce the area from the bead portion 4 to the sidewall portion 3. Symbol 10 in the figure represents an overlap rubber portion used to prevent rim slippage when forming the bead outer skin, disposed on the bottom and outer surfaces of the bead that can contact the rim. Symbol 11 represents a reinforcing cord layer using steel cord disposed between the overlap rubber 10 and the carcass ply layer 6A, formed in an L-shape: an L-shape extending from the lower end of the upright portion 11A extending along the outer surface of the ply layer fold-back portion 6b, and an L-shaped lower roll portion 11B extending along the bottom surface of the bead.

[0162] The belt layer 7 is formed by two belt ply layers 7A and 7B, which are steel belt cords (steel cords) arranged at an angle of 16 to 22° relative to the tire circumference. Each belt ply layer 7A and 7B changes the inclination direction of the cords between the cord layers, and resets the inclination direction of the cords to the radial direction so that the belt cords cross.

[0163] The sidewall 15 is disposed within the sidewall portion 3. The sidewall 15 is made of the aforementioned sidewall rubber composition, which contains isoprene rubber, butadiene rubber, and carbon black oxide with an average particle size of 30 nm or less in a specified formulation, and satisfies the above formula (1) "the content of isoprene rubber is greater than the content of butadiene rubber". The sidewall 15 satisfies the above formula (2) "the thickness at the maximum width is greater than -0.14 × the content of butadiene rubber + 10.0". Regarding the "thickness at the maximum width (thickness at the maximum width of the sidewall)" in formula (2), as described above, it is the thickness of the sidewall at the maximum width position of the tire under a specified internal pressure. Figure 1 In a tire, the thickness T is represented by the thickness at the maximum width.

[0164] [Example]

[0165] The following is a summary description of the various chemicals used in the examples and comparative examples.

[0166] NR: TSR20

[0167] BR1: BR150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass)

[0168] BR2: BR1250H (cis content: 40% by mass) manufactured by Zeon Corporation, Japan.

[0169] Carbon Black 1: DIABLACK N550 manufactured by Mitsubishi Chemical Corporation (average particle size: 48nm, N2SA: 41nm) 2 / g, DBP: 115ml / 100g)

[0170] Carbon black 1: Manufacturing example 1 below (average particle size: 48 nm, N2SA: 41 nm) 2 / g, DBP: 115ml / 100g)

[0171] Carbon Black 2: DIABLACK N220 manufactured by Mitsubishi Chemical Corporation (average particle size: 23nm, N2SA: 114nm) 2 / g, DBP: 114ml / 100g)

[0172] Carbon black 2: Manufacturing example 2 below (average particle size: 23 nm, N2SA: 114 nm) 2 / g, DBP: 114ml / 100g)

[0173] Carbon Black 3: SHOWBLACK N134 manufactured by Cabot Corporation, Japan (average particle size: 18nm, N2SA: 148nm) 2 / g, DBP absorption: 123ml / 100g)

[0174] Carbon black oxide 3: Manufacturing example 3 below (average particle size: 18 nm, N2SA: 148 nm) 2 / g, DBP absorption: 123ml / 100g)

[0175] Oil: PS-32 (mineral oil) manufactured by Idemitsu Kosan Co., Ltd.

[0176] Wax: OZOACE wax 0355 manufactured by Nippon Seika Co., Ltd. (content of n-alkanes and isoalkanes with 20-50 carbon atoms: 100% by mass)

[0177] Antioxidant: NOCRAC 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD)) manufactured by Ouchi Shinsei Chemical Co., Ltd.

[0178] Stearic acid: Tsubaki manufactured by Nippon Oil Co., Ltd.

[0179] Zinc oxide: Zinc oxide No. 2 manufactured by Mitsui Metals & Minerals Co., Ltd.

[0180] Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.

[0181] Vulcanization accelerator: Nocceler NS (N-tert-butyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.

[0182] (Manufacturing Example 1)

[0183] Weigh 200 parts by weight of sodium hypochlorite (with an effective chlorine concentration of 20% relative to carbon) relative to 100 parts by weight of carbon black 1 (DIABLACK N550), and dilute it in 4 times its volume (800 parts by weight) of purified water (0.2% aqueous solution of sodium hypochlorite) in a beaker. Then, while checking the pH, stir at room temperature for 3 hours. After the reaction is complete, filter and wash with water. For the water washing, use warm water at a volume of 10 times relative to the carbon black, and repeat the water washing and filtration at least twice. Then, dry at 130°C for 24 hours to obtain carbon black oxide 1.

[0184] (Manufacturing Example 2)

[0185] Carbon black 1 (DIABLACK N550) was replaced with carbon black 2 (DIABLACK N220), and the rest was handled in the same manner as in manufacturing example 1 to obtain carbon black 2 oxide.

[0186] (Manufacturing Example 3)

[0187] Carbon black 1 (DIABLACK N550) was replaced with carbon black 3 (SHOWBLACK N134), and the rest was handled in the same manner as in manufacturing example 1 to obtain carbon black oxide 3.

[0188] <Preparation of Rubber Compositions for Tire Sidewalls>

[0189] According to the formulations shown in the tables, the materials, excluding sulfur and vulcanization accelerator, were mixed at 150°C for 5 minutes using a 1.7L Banbury internal mixer manufactured by Kobe Steel Corporation to obtain a compound. Then, sulfur and vulcanization accelerator were added to the obtained compound, and the mixture was kneaded at 80°C for 5 minutes using a two-roll mill to obtain an unvulcanized rubber composition.

[0190] <Manufacturing of heavy-duty tires>

[0191] According to the specifications in each table (formula, thickness at the maximum width of the sidewall), the obtained uncured sidewall is shaped into the shape of the sidewall using a rubber composition, and then bonded together with other tire components on a tire forming machine to form an uncured tire. The tire is then vulcanized at 170°C for 10 minutes to manufacture a test tire (heavy-load tire).

[0192] 〔evaluate〕

[0193] The test tires were evaluated using the following methods, and the results are shown in the tables. Furthermore, each table uses Comparative Example 3 as the baseline comparative example.

[0194] <Cut resistance under high load and high speed>

[0195] The test tires were mounted on all wheels of a truck and driven for 150 km at high speed (80 km / h) on a muddy road. The sidewall surface of the tires removed from the rims was then visually inspected, and the number and size of cracks were evaluated, expressed as an index with a baseline of 100. A higher index indicates better cut resistance under high load and high speed.

[0196] Table 1

[0197]

[0198] Table 2

[0199]

[0200] Table 3

[0201]

[0202] Table 4

[0203]

[0204] Table 5

[0205]

[0206] Table 6

[0207]

[0208] According to the table, the heavy-duty tires of the embodiments that use a sidewall rubber composition containing isoprene rubber, butadiene rubber and carbon black with an average particle size of 30 nm or less in a specified formulation and satisfy the above formulas (1) and (2) have excellent cut resistance under high load and high speed.

Claims

1. A heavy-duty tire having a sidewall made of a rubber composition for the sidewall, The rubber composition for the tire sidewall contains isoprene rubber, butadiene rubber, and carbon black oxide with an average particle size of less than 30 nm. The butadiene rubber content in the rubber component (100% by mass) is 5% by mass or more and less than 50% by mass, characterized in that... In the rubber component 100% by mass of the rubber composition for the tire sidewall, the content of the isoprene rubber and the butadiene rubber, expressed as a percentage by mass, satisfies the following formula (1): (1) The content of isoprene rubber is greater than that of butadiene rubber. The thickness of the sidewall at its maximum width, expressed in mm, and the content of butadiene rubber, expressed in mass%, in 100% by mass of the rubber component in the sidewall rubber composition, satisfy the following formula (2): (2) Thickness at maximum width > -0.14 × butadiene rubber content + 10.0, The content of carbon black oxide with an average particle size of less than 30 nm is 20-100 parts by weight relative to 100 parts by weight of rubber component. The butadiene rubber has a cis content of 90% by mass or more.

2. The heavy-duty tire according to claim 1, wherein, The percentage of carbon black oxide and butadiene rubber in the 100% by mass of the rubber composition for the tire sidewall satisfies the following formula (3): (3) The content of carbon black with an average particle size of less than 30 nm is greater than the content of butadiene rubber.

3. The heavy-duty tire according to claim 1 or 2, wherein, The butadiene rubber comprises butadiene rubber with a cis content of 95% by mass or more.

4. The heavy-duty tire according to claim 1 or 2, wherein, The sidewall rubber composition contains a phenylenediamine compound, and the content of the isoprene rubber and the phenylenediamine compound in 100% by mass of the sidewall rubber composition, expressed as a percentage by mass, satisfies the following formula (4): (4) The content of isoprene rubber / the content of phenylenediamine compound < 35.

5. The heavy-duty tire according to claim 1 or 2, wherein, The sidewall rubber composition contains n-alkanes with 20 to 50 carbon atoms and / or isoalkanes with 20 to 50 carbon atoms, and the content of isoprene rubber in 100% by mass of the sidewall rubber composition, expressed as a percentage by mass, and the total content of n-alkanes and isoalkanes, expressed as a percentage by mass, satisfy the following formula (5): (5) The total content of isoprene rubbers with 20 to 50 carbon atoms of n-alkanes and 20 to 50 carbon atoms is <100%.

6. The heavy-duty tire according to claim 1 or 2, wherein, The thickness of the sidewall at its maximum width is greater than 4.0 mm and less than 10.0 mm.

7. The heavy-duty tire according to claim 4, wherein, The content of the phenylenediamine compound in the rubber composition for the tire sidewall is 1.5 to 4.0% by mass, which is 100% by mass.

8. The heavy-duty tire according to claim 1 or 2, wherein, The total content of n-alkanes with 20 to 50 carbon atoms and isoalkanes with 20 to 50 carbon atoms in the rubber composition for the tire sidewall is 0.5 to 1.0% by mass.

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