Tire

Abstract

Provided is a tire comprising a belt layer capable of maintaining excellent noise performance, ride comfort performance, and durability performance and improving low fuel consumption performance.　Provided is a tire 1 in which a belt layer 7 is arranged inside of a tread part 2. The belt layer 7 includes at least one belt ply 7A, 7B. The belt ply 7A, 7B includes a belt cord 9 comprising a steel single wire 9A having a flat cross section and topping rubber 10 covering the belt cord 9. The topping rubber 10 has a complex elastic modulus ES* of 8.0-20.0 MPa at 70 °C and a loss tangent tanδ of 0.04-0.16 at 70 °C. The ratio (tanδ / ES*) between the loss tangent tanδ and the complex elastic modulus ES* (MPa) of the topping rubber 10 is 0.002-0.017.

Description

Technical Field

[0001] The present invention relates to a tire having a belt layer in a tread portion.

Background Art

[0002] Conventionally, a tire using a belt cord made of a steel single wire having a flat cross-sectional shape in a belt layer is known. For example, Patent Document 1 below proposes a pneumatic tire including a belt layer in which a belt cord made of a steel single wire having a specific major axis and minor axis is coated with a cord topping rubber having a specific complex elastic modulus.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The tire of Patent Document 1 is expected to improve the low fuel consumption performance, noise performance, and riding comfort performance due to weight reduction in a well-balanced manner. However, in recent years, the demand for low fuel consumption performance has increased, and further improvement has been expected even in the tire of Patent Document 1.

[0005] The present invention has been devised in view of the above actual situation, and the main object is to provide a tire having a belt layer that can improve low fuel consumption performance while maintaining good noise performance, riding comfort performance, and durability performance.

Means for Solving the Problems

[0006] The present invention relates to a tire in which a belt layer is disposed inside a tread portion. The belt layer includes at least one belt ply. The belt ply includes a belt cord made of a steel single wire having a flat cross-sectional shape, and a topping rubber that covers the belt cord. The topping rubber has a complex elastic modulus ES* at 70°C of 8.0 to 20.0 MPa, and a loss tangent tanδ at 70°C of 0.04 to 0.16, and a ratio (tanδ / ES*) of the loss tangent tanδ to the complex elastic modulus ES* (MPa) of the topping rubber is 0.002 to 0.017.

[0007] In the tire of the present invention, it is desirable that the topping rubber has a loss tangent tanδ at 70°C of 0.04 to 0.09.

[0008] In the tire of the present invention, it is more desirable that the topping rubber has a loss tangent tanδ at 70°C of 0.04 to 0.06.

[0009] In the tire of the present invention, it is desirable that the topping rubber has a complex elastic modulus ES* at 70°C of 14.0 to 20.0 MPa.

[0010] In the tire of the present invention, it is desirable that the steel single wire has a ratio (LD / SD) of the major axis LD to the minor axis SD in the cross-sectional shape of 1.05 to 1.35, and the major axis LD is 0.30 to 0.50 mm.

[0011] In the tire of the present invention, the steel single wire is corrugated in at least one of the major axis direction and the minor axis direction in the cross-sectional shape. It is desirable that the corrugation pitch P of the steel single wire is 3.0 to 10.0 mm, and the corrugation height H of the steel single wire is 0.05 to 0.15 mm.

[0012] In the tire of the present invention, it is desirable that the belt cord is disposed in the topping rubber such that the minor axis direction of the steel single wire is along the thickness direction of the belt ply.

[0013] In the tire of the present invention, the topping rubber contains cobalt elements, and the ratio (c / L) of the concentration c (ppm) of the cobalt elements to the outer peripheral length L (mm) in the cross-sectional shape of the steel single wire is desirably 350 to 1000 ppm / mm.

Advantages of the Invention

[0014] In the tire of the present invention, the belt ply includes a belt cord made of steel single wires having a cross-sectionally flat shape and a topping rubber that coats the belt cord. The topping rubber has a complex elastic modulus ES* at 70°C of 8.0 to 20.0 MPa and a loss tangent tanδ at 70°C of 0.04 to 0.16, and the ratio (tanδ / ES*) of the loss tangent tanδ of the topping rubber to the complex elastic modulus ES* (MPa) is 0.002 to 0.017.

[0015] Such a topping rubber can suppress heat generation during running and improve the low fuel consumption performance of the tire without affecting the noise performance, ride comfort performance, and durability performance of the tire. Therefore, the tire of the present invention can improve the low fuel consumption performance while maintaining good noise performance, ride comfort performance, and durability performance.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0017] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a tire meridian cross-sectional view including the rotation axis of the tire 1 in the normal state of the present embodiment. The tire 1 of the present embodiment is preferably used as a pneumatic rubber tire mounted on a passenger car or the like. Note that the tire 1 is not limited to a pneumatic rubber tire for a passenger car, and can be applied to various tires such as a pneumatic tire for heavy loads, a pneumatic tire made of resin, and a non-pneumatic tire in which the inside of the tire is not filled with pressurized air.

[0018] Here, the "normal state" means that when the tire 1 is a pneumatic rubber tire, the tire 1 is rim-mounted on a normal rim and is in a no-load state adjusted to the normal internal pressure. Hereinafter, unless otherwise specified, the dimensions and the like of each part of the tire 1 are values measured in this normal state.

[0019] The "normal rim" is a rim defined for each tire in a standard system including the standard on which the tire 1 is based. For example, in JATMA, it is the "standard rim", in TRA, it is the "Design Rim", and in ETRTO, it is the "Measuring Rim".

[0020] The "normal internal pressure" is the air pressure defined for each tire in a standard system including the standard on which the tire 1 is based. In JATMA, it is the "maximum air pressure", in TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in ETRTO, it is the "INFLATION PRESSURE".

[0021] As shown in FIG. 1, the tire 1 of the present embodiment includes an annular tread portion 2, a pair of sidewall portions 3 extending on both sides of the tread portion 2, and a pair of bead portions 4 extending continuously with the sidewall portions 3. The tire 1 of the present embodiment has a toroidal carcass 6 extending across the bead cores 5 of the pair of bead portions 4, and a belt layer 7 disposed on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2.

[0022] The carcass 6 includes at least one, in this embodiment, one carcass ply 6A. The carcass ply 6A includes, for example, carcass cords (not shown) arranged at an angle of 75 to 90° with respect to the tire circumferential direction. As the carcass cords, for example, organic fiber cords such as aromatic polyamide and rayon can be adopted.

[0023] The carcass ply 6A includes, for example, a main body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a folded-back portion 6b that is continuous with the main body portion 6a and is folded back from the inner side to the outer side of the tire axial direction around the bead core 5. Between the main body portion 6a and the folded-back portion 6b of the carcass ply 6A, for example, a bead apex rubber 8 extending radially outward of the tire from the bead core 5 is arranged.

[0024] The belt layer 7 includes at least one, in this embodiment, two belt plies 7A and 7B. The two belt plies 7A and 7B include, for example, a first belt ply 7A located on the inner side in the tire radial direction and a second belt ply 7B located outside the first belt ply 7A. Such a belt layer 7 can increase the rigidity of the tread portion 2 and improve the durability performance of the tire 1.

[0025] FIG. 2 is an enlarged cross-sectional view of the belt ply 7A. In FIG. 2, the belt ply 7A is illustrated, but the belt ply 7B can also adopt a similar structure. As shown in FIG. 2, at least one of the belt plies 7A and 7B of this embodiment includes a belt cord 9 made of a flat-section steel single wire 9A and a topping rubber 10 covering the belt cord 9.

[0026] The topping rubber 10 preferably has a complex elastic modulus ES* at 70°C of 8.0 to 20.0 MPa and a loss tangent tanδ at 70°C of 0.04 to 0.16. Such topping rubber 10 can suppress heat generation during driving and improve the low fuel consumption performance of the tire 1 without affecting the noise performance, ride comfort performance, and durability performance. Therefore, the tire 1 of the present embodiment can improve the low fuel consumption performance while maintaining good noise performance, ride comfort performance, and durability performance.

[0027] Here, the complex elastic modulus ES* and loss tangent tanδ of the topping rubber 10 at 70°C are values measured using a dynamic viscoelasticity measuring device (Implex series) manufactured by GABO in accordance with the provisions of JIS-K6394 under the following conditions. Initial strain: 10% Amplitude of dynamic strain: ±1% Frequency: 10 Hz Deformation mode: Tension Measurement temperature: 70°C

[0028] The complex elastic modulus ES* of the topping rubber 10 at 70°C is more preferably 14.0 to 20.0 MPa. Such topping rubber 10 can suppress the deformation of the belt layer 7 and improve the durability performance of the tire 1. On the other hand, when the complex elastic modulus ES* of the topping rubber 10 is 8.0 to 14.0 MPa at 70°C, the noise performance and ride comfort performance can be improved.

[0029] The loss tangent tanδ of the topping rubber 10 at 70°C is more preferably 0.04 to 0.14, still more preferably 0.04 to 0.09, and most preferably 0.04 to 0.06. Such topping rubber 10 can further suppress heat generation during driving and more improve the low fuel consumption performance of the tire 1 without affecting the noise performance, ride comfort performance, and durability performance.

[0030] The ratio (tanδ / ES*) of the loss tangent tanδ to the complex elastic modulus ES* (MPa) of the topping rubber 10 is preferably 0.002 to 0.017. Such topping rubber 10 can suppress heat generation during driving and improve the low fuel consumption performance of the tire 1 without affecting the noise performance, ride comfort performance, and durability performance. Therefore, the tire 1 of this embodiment can improve the low fuel consumption performance while maintaining good noise performance, ride comfort performance, and durability performance.

[0031] Examples of the rubber component used for the topping rubber 10 include isoprene rubbers such as natural rubber (NR) and isoprene rubber (IR), diene rubbers such as butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), chloroprene rubber (CR), and acrylonitrile-butadiene rubber (NBR). From the viewpoint of durability performance, it is preferable that the topping rubber 10 uses natural rubber (NR) or a combination of natural rubber (NR) and isoprene rubber (IR).

[0032] It is desirable that the topping rubber 10 contains cobalt element in the rubber. Examples of the compound containing cobalt element include organic acid cobalt salts such as cobalt stearate, cobalt naphthenate, cobalt neodecanoate, and cobalt boron trineodecanoate. Such topping rubber 10 can promote crosslinking with the belt cord 9 by the cobalt element during vulcanization molding and improve the adhesiveness with the belt cord 9.

[0033] The topping rubber 10 preferably contains carbon black. From the viewpoint of durability performance, the content of carbon black is preferably 10 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. On the other hand, from the viewpoint of heat generation property, the upper limit of the content of carbon black is preferably 100 parts by mass or less, and more preferably 70 parts by mass or less.

[0034] The carbon black is not particularly limited, and examples include furnace black (furnace carbon black) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black (acetylene carbon black); thermal black (thermal carbon black) such as FT and MT; channel black (channel carbon black) such as EPC, MPC, and CC; graphite, and the like. These may be used alone or in combination of two or more.

[0035] The nitrogen adsorption specific surface area (N2SA) of the carbon black is, for example, more than 30 m 2 / g and less than 250 m 2 / g. The dibutyl phthalate (DBP) absorption amount of the carbon black is, for example, more than 50 ml / 100 g and less than 250 ml / 100 g. The nitrogen adsorption specific surface area of the carbon black is measured according to ASTM D4820-93, and the DBP absorption amount is measured according to ASTM D2414-93.

[0036] Specific carbon blacks are not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, and the like. As commercially available products, for example, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nippon Chemical Co., Ltd., Columbian Carbon Company, and the like can be used. These may be used alone or in combination of two or more.

[0037] Topping rubber 10 preferably further contains silica as needed. From the viewpoint of obtaining good durability performance, the BET specific surface area of the silica is preferably more than 140 m 2 / g, more preferably more than 160 m 2 / g. On the other hand, from the viewpoint of obtaining good low fuel consumption performance, the upper limit of the BET specific surface area of the silica is preferably less than 250 m 2 / g, preferably less than 220 m 2It is more preferably less than / g. This BET specific surface area is the value of N 2 SA measured by the BET method in accordance with ASTM D3037-93.

[0038] When not used in combination with a silane coupling agent, the content of silica based on 100 parts by mass of the rubber component is preferably 3 parts by mass or more, and more preferably 5 parts by mass or more. On the other hand, as the upper limit of the content of silica when not used in combination with a silane coupling agent, it is preferably 25 parts by mass or less, and more preferably 15 parts by mass or less. When used in combination with a silane coupling agent, 25 parts by mass or more is preferable. On the other hand, as the upper limit of the content of silica when used in combination with a silane coupling agent, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably 30 parts by mass or less.

[0039] Examples of the silica include dry-process silica (anhydrous silica), wet-process silica (hydrous silica), etc. Among these, wet-process silica is preferable because it has many silanol groups.

[0040] As the silica, for example, products of companies such as Degussa, Rhodia, Tosoh Silica Corporation, Solvay Japan K.K., Tokuyama Corporation, etc. can be used.

[0041] As described above, when using silica, it is also possible to use a silane coupling agent in combination. The silane coupling agent is not particularly limited. For example, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide and other sulfide-based, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, NXT, NXT-Z manufactured by Momentive and other mercapto-based, vinyltriethoxysilane, vinyltrimethoxysilane and other vinyl-based, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane and other amino-based, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane and other glycidoxy-based, 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane and other nitro-based, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane and other chloro-based, etc. can be mentioned. These may be used alone or in combination of two or more.

[0042] As the silane coupling agent, for example, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azmax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used.

[0043] The content of the silane coupling agent is, for example, more than 3 parts by mass and less than 15 parts by mass with respect to 100 parts by mass of silica.

[0044] In addition to carbon black and silica, the topping rubber 10 may further contain fillers generally used in the tire industry, such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, etc. These contents are, for example, more than 0.1 part by mass and less than 200 parts by mass with respect to 100 parts by mass of the rubber component.

[0045] The topping rubber 10 preferably contains a curable resin component such as a modified resorcinol resin or a modified phenol resin. Thereby, the adhesiveness with the steel cord can be improved without significantly deteriorating the heat generation property and the elongation at break.

[0046] The content of the curable resin component is preferably, for example, 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of the rubber component. On the other hand, the upper limit of the content of the curable resin component is preferably 10 parts by mass or less, more preferably 8 parts by mass or less.

[0047] Specific examples of the modified resorcinol resin include Sumikanol 620 (modified resorcinol resin) manufactured by Tago Chemical Industry Co., Ltd., and examples of the modified phenol resin include PR12686 (cashew oil modified phenol resin) manufactured by Sumitomo Bakelite Co., Ltd.

[0048] When using the modified resorcinol resin, it is preferably contained together with a methylene donor as a curing agent. Examples of the methylene donor include hexamethylenetetramine (HMT), hexamethoxymethylol melamine (HMMM), and hexamethylol melamine pentamethyl ether (HMMPME). It is preferably contained in an amount of 5 parts by mass or more, for example, about 15 parts by mass with respect to 100 parts by mass of the curable resin component.

[0049] As a specific methylene donor, for example, Sumikanol 507 manufactured by Taoka Chemical Industry Co., Ltd. can be used.

[0050] From the viewpoint of processability (providing adhesiveness), the topping rubber 10 preferably contains a softening agent such as oil or a resin component as needed. The total content of these is preferably more than 0.5 part by mass and less than 10 parts by mass with respect to 100 parts by mass of the rubber component.

[0051] Examples of the oil include mineral oil (generally referred to as process oil), vegetable oil and fat, or a mixture thereof. As the mineral oil (process oil), for example, paraffinic process oil, aromatic process oil, naphthenic process oil, etc. can be used. Examples of the vegetable oil and fat 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, tung oil, etc. These may be used alone or in combination of two or more.

[0052] As specific process oil (mineral oil), for example, products of Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Corporation, Oleo GmbH, H&R AG, Toyokuni Oil Co., Ltd., Showa Shell Sekiyu KK, Fuji Kogyo Co., Ltd., etc. can be used.

[0053] The resin component may be solid or liquid at normal temperature. Specific examples of the resin component include resins such as rosin-based resins, styrene-based resins, coumarone-based resins, terpene-based resins, C5 resins, C9 resins, C5C9 resins, acrylic resins, etc., and two or more of them may be used in combination. The content of the resin component is preferably more than 2 parts by mass and less than 45 parts by mass, more preferably less than 30 parts by mass with respect to 100 parts by mass of the rubber component.

[0054] Rosin-based resins are resins mainly composed of rosin acids obtained by processing pine resin. These rosin-based resins (rosins) can be classified according to the presence or absence of modification, and can be classified into unmodified rosin (non-modified rosin) and rosin derivatives. Examples of unmodified rosin include tall rosin (also known as tall oil rosin), gum rosin, wood rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, and other chemically modified rosins. Rosin derivatives are derivatives of unmodified rosin, and examples include rosin esters, unsaturated carboxylic acid-modified rosins, unsaturated carboxylic acid-modified rosin esters, amide compounds of rosin, amine salts of rosin, etc.

[0055] Styrene-based resins are polymers using styrene-based monomers as constituent monomers, and examples include polymers polymerized with styrene-based monomers as the main component (50% by mass or more). Specific styrene-based resins include homopolymers obtained by polymerizing each styrene-based monomer (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) alone, copolymers obtained by copolymerizing two or more styrene-based monomers, and copolymers of styrene-based monomers and other monomers copolymerizable therewith.

[0056] Examples of other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, acrylics, unsaturated carboxylic acids such as methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene and butadiene isoprene, olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride or their acid anhydrides; etc.

[0057] Among the coumarone resins, coumarone-indene resins are preferred. Coumarone-indene resins are resins that contain coumarone and indene as monomer components that constitute the resin skeleton (main chain). Other monomer components contained in the skeleton besides coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0058] The content of the coumarone-indene resin is, for example, 1.0 mass parts per 100 mass parts of the rubber component. More than 50.0 parts by mass and less than 50.0 parts by mass.

[0059] The hydroxyl value (OH value) of the coumarone-indene resin is, for example, more than 15 mgKOH / g and less than 150 mgKOH / g. The OH value is the amount of potassium hydroxide required to neutralize acetic acid bonded to hydroxyl groups when acetylating 1 g of the resin, expressed in milligrams, and is a value measured by potentiometric titration (JIS K 0070:1992).

[0060] The softening point of the coumarone-indene resin is, for example, more than 30° C. and less than 160° C. The softening point is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point tester.

[0061] Examples of terpene resins include polyterpene, terpene phenol, and aromatic modified terpene resins. Polyterpene is a resin obtained by polymerizing a terpene compound and a hydrogenated product thereof. Terpene compounds are (C 5 H 8 ) n The hydrocarbons and their oxygen-containing derivatives represented by the composition: monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32) Compounds having a terpene as the basic skeleton and classified into, for example, α-pinene, β-pinene, dipentene, limonene, myrcene, allo-ocimene, ocimene, α-farnesene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, etc.

[0062] Examples of polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, β-pinene / limonene resin, etc. which use the above-mentioned terpene compounds as raw materials, and hydrogenated terpene resins obtained by hydrogenating the terpene resins. Examples of terpene phenols include resins obtained by copolymerizing terpene compounds and phenolic compounds, and resins obtained by hydrogenating such resins. Specific examples of terpene phenols include resins obtained by condensing terpene compounds, phenolic compounds and formalin. Examples of phenolic compounds include phenol, bisphenol A, cresol, xylenol, etc. Examples of aromatic-modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating such resins. The aromatic compound is not particularly limited as long as it has an aromatic ring, and examples include phenolic compounds such as phenol, alkylphenol, alkoxyphenol, phenolic compounds containing an unsaturated hydrocarbon group; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, naphthol compounds containing an unsaturated hydrocarbon group; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, styrene derivatives containing an unsaturated hydrocarbon group; coumarone, indene, etc.

[0063] "C5 resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of the C5 fraction include petroleum fractions corresponding to 4 to 5 carbon atoms such as cyclopentadiene, pentene, pentadiene, isoprene, etc. As the C5-based petroleum resin, dicyclopentadiene resin (DCPD resin) is preferably used.

[0064] "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, which may be hydrogenated or modified. Examples of the C9 fraction include petroleum fractions corresponding to 8 to 10 carbon atoms such as vinyltoluene, alkylstyrene, indene, and methylindene. As specific examples, for instance, coumarone-indene resin, coumarone resin, indene resin, and aromatic vinyl-based resins are preferably used. Among the aromatic vinyl-based resins, due to economic reasons, ease of processing, and excellent heat generation properties, a homopolymer of α-methylstyrene or styrene, or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred. As the aromatic vinyl-based resins, those commercially available from companies such as Kraton Corporation and Eastman Chemical Company can be used.

[0065] "C5C9 resin" refers to a resin obtained by copolymerizing a C5 fraction and a C9 fraction, which may be hydrogenated or modified. Examples of the C5 fraction and the C9 fraction include the above-mentioned petroleum fractions. As the C5C9 resin, for example, those commercially available from Tosoh Corporation, LUHUA, etc. can be used.

[0066] The acrylic resin is not particularly limited, and for example, a solventless acrylic resin can be used.

[0067] The solventless acrylic resin is a (meth)acrylic resin (polymer) synthesized by a high-temperature continuous polymerization method (high-temperature continuous bulk polymerization method) (the methods described in U.S. Patent No. 4,414,370, JP-A-59-6207, JP-B-5-58005, JP-A-1-313522, U.S. Patent No. 5,010,166, Annual Report of Toagosei Research TREND2000 No. 3 p42-45, etc.) without using a polymerization initiator, chain transfer agent, organic solvent, etc. as auxiliary raw materials as much as possible. In the present invention, "(meth)acrylic" means methacrylic and acrylic.

[0068] Examples of monomer components constituting the acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (such as alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylic acid derivatives such as (meth)acrylamide derivatives.

[0069] In addition, as monomer components constituting the acrylic resin, aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene may be used together with (meth)acrylic acid or (meth)acrylic acid derivatives.

[0070] The acrylic resin may be a resin composed only of the (meth)acrylic component or a resin having components other than the (meth)acrylic component as constituent elements. Further, the acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, etc.

[0071] Examples of resin components that can be used include products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, Nippon Paint Co., Ltd., Nippon Catalyst Co., Ltd., JX Energy Co., Ltd., Arakawa Chemical Industries, Ltd., and Tago Chemical Industries, Ltd.

[0072] Topping rubber 10 preferably contains an anti-aging agent. The content of the anti-aging agent is, for example, more than 1 part by mass and less than 10 parts by mass with respect to 100 parts by mass of the rubber component.

[0073] Examples of the anti-aging agent include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; p-phenylenediamine-based anti-aging agents 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 anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; bis, tris, polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate]methane, etc. These may be used alone or in combination of two or more.

[0074] Examples of the anti-aging agent include products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., Flexsys Co., etc. that can be used.

[0075] Topping rubber 10 may contain stearic acid. The content of stearic acid is, for example, more than 0.5 part by mass and less than 10.0 parts by mass with respect to 100 parts by mass of the rubber component. As the stearic acid, conventionally known ones can be used, for example, products of NOF Corporation, Kao Corporation, Fuji Film Wako Pure Chemical Corporation, Chiba Fatty Acids Co., Ltd., etc. can be used.

[0076] Topping rubber 10 may contain zinc oxide. The content of zinc oxide is, for example, more than 0.5 part by mass and less than 15 parts by mass with respect to 100 parts by mass of the rubber component. As the zinc oxide, conventionally known ones can be used, for example, products of Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusuitech Co., Ltd., Sho Do Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0077] Topping rubber 10 preferably contains a crosslinking agent such as sulfur. The content of the crosslinking agent is, for example, more than 0.1 part by mass and less than 10.0 parts by mass with respect to 100 parts by mass of the rubber component.

[0078] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, soluble sulfur, etc., which are generally used in the rubber industry. These may be used alone or in combination of two or more.

[0079] In addition, as sulfur, for example, products of companies such as Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexsys, Nippon Kankyu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0080] Examples of crosslinking agents other than sulfur include vulcanization accelerators containing sulfur atoms such as Tackiol V200 manufactured by Tago Chemical Industry Co., Ltd., Duralink HTS (sodium 1,6 - hexamethylene - dithiolsulfate dihydrate) manufactured by Flexsys, KA9188 (1,6 - bis(N,N’ - dibenzylthiocarbamoyldithio)hexane) manufactured by Rancess, and organic peroxides such as dicumyl peroxide.

[0081] Topping rubber 10 preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, more than 0.3 part by mass and less than 10.0 parts by mass with respect to 100 parts by mass of the rubber component.

[0082] As vulcanization accelerators, there can be mentioned thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyldisulfide, N-cyclohexyl-2-benzothiazylsulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-t-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine, orthotolylbiguanidine. These may be used alone or in combination of two or more.

[0083] The rubber composition for the belt used in the topping rubber 10 may, in addition to these components, further contain additives generally used in the tire industry, such as fatty acid metal salts, carboxylic acid metal salts, organic peroxides, etc. The content of these additives is, for example, more than 0.1 part by mass and less than 200 parts by mass with respect to 100 parts by mass of the rubber component.

[0084] The ratio (c / L) of the concentration c (ppm) of the above cobalt element to the outer peripheral length L (mm) in the cross-sectional shape of the steel single wire 9A is preferably 350 to 1000 ppm / mm. When the ratio (c / L) is 350 ppm / mm or more, the adhesiveness to the belt cord 9 can be improved, and the durability performance of the tire 1 can be improved. When the ratio (c / L) is 1000 ppm / mm or less, it is possible to suppress the embrittlement of the adhesive layer with the belt cord 9, and even when repeated deformation due to the rotation of the tire 1 acts, peeling is suppressed, and the durability performance of the tire 1 can be improved. From such a viewpoint, the ratio (c / L) is more preferably 400 to 740 ppm / mm.

[0085] In the belt cord 9 of the present embodiment, the minor axis direction of the steel single wire 9A is arranged in the topping rubber 10 so as to be along the thickness direction of the belt plies 7A and 7B. Such a belt cord 9 can maintain the rigidity of the tread portion 2 while reducing the thickness of the belt plies 7A and 7B, which helps to achieve both low fuel consumption performance and durability performance associated with the weight reduction of the tire 1.

[0086] The steel single wire 9A preferably has a ratio (LD / SD) of the major axis LD to the minor axis SD in the cross-sectional shape of 1.05 to 1.35. If the ratio (LD / SD) of the steel single wire 9A is less than 1.05, the rigidity of the belt layer 7 may become excessively high, and the noise performance and ride comfort performance of the tire 1 may not be improved. If the ratio (LD / SD) of the steel single wire 9A is greater than 1.35, the strength of the steel single wire 9A may decrease, which may affect the durability performance of the tire 1.

[0087] The steel single wire 9A preferably has a major axis LD in the cross-sectional shape of 0.30 to 0.50 mm. If the major axis LD of the steel single wire 9A is less than 0.30 mm, the strength of the steel single wire 9A may decrease, which may affect the durability performance of the tire 1. If the major axis LD of the steel single wire 9A is greater than 0.50 mm, the rigidity of the belt layer 7 may become excessively high, which may affect the noise performance and ride comfort performance of the tire 1.

[0088] FIG. 3 is a schematic view seen from the major axis direction of the steel single wire 9A. As shown in FIG. 3, the steel single wire 9A is corrugated in at least one, and in this embodiment, both, of the major axis direction and the minor axis direction in the cross-sectional shape. Such a steel single wire 9A can moderately relax the rigidity of the belt layer 7 and improve the noise performance and ride comfort performance of the tire 1.

[0089] The corrugation pitch P of the steel single wire 9A is preferably 3.0 to 10.0 mm. Here, the corrugation pitch P is the length of one pitch in the longitudinal direction of the corrugated steel single wire 9A. If the corrugation pitch P of the steel single wire 9A is less than 3.0 mm, the effect of improving the noise performance and riding comfort performance of the tire 1 may be reduced. If the corrugation pitch P of the steel single wire 9A is greater than 10.0 mm, the strength of the steel single wire 9A may decrease, which may affect the durability performance of the tire 1.

[0090] The corrugation pitch P of the steel single wire 9A in this embodiment is substantially constant along the longitudinal direction of the steel single wire 9A. The corrugation pitch P of the steel single wire 9A may vary in length along the longitudinal direction of the steel single wire 9A, for example.

[0091] The corrugation height H of the steel single wire 9A is preferably 0.05 to 0.15 mm. If the corrugation height H of the steel single wire 9A is less than 0.05 mm, the effect of improving the noise performance and riding comfort performance of the tire 1 may be reduced. If the corrugation height H of the steel single wire 9A is greater than 0.15 mm, the strength of the steel single wire 9A may decrease, which may affect the durability performance of the tire 1.

[0092] As shown in FIG. 1, the tread portion 2 of this embodiment includes a tread rubber 2A that forms a tread contact surface 2a. The tread rubber 2A preferably has a complex elastic modulus ET* of 4.5 to 10.0 MPa at 70°C and a loss tangent tanδ of 0.08 to 0.15 at 70°C.

[0093] Here, the complex elastic modulus ET* and loss tangent tanδ of the tread rubber 2A at 70°C are values measured using a dynamic viscoelasticity measuring device (Implex series) manufactured by GABO in accordance with the provisions of JIS-K6394 under the following conditions, similar to the above-mentioned topping rubber 10. Initial strain: 10% Amplitude of dynamic strain: ±1% Frequency: 10 Hz Deformation mode: Tension Measured temperature: 70°C

[0094] Such tread rubber 2A can suppress heat generation during driving and further improve the low fuel consumption performance of tire 1 without affecting the noise performance, ride comfort performance, and durability performance. Therefore, tire 1 of this embodiment can further improve the low fuel consumption performance while maintaining good noise performance, ride comfort performance, and durability performance.

[0095] The ratio (ET* / ES*) of the complex elastic modulus ET* of tread rubber 2A to the complex elastic modulus ES* of topping rubber 10 is preferably 1.3 or less. Such a tread portion 2 helps to improve the noise performance, ride comfort performance, durability performance, and low fuel consumption performance of tire 1 in a well-balanced manner.

[0096] As described above, particularly preferred embodiments of the present invention have been described in detail. However, the present invention is not limited to the above-described embodiments and can be implemented in various forms with modifications.

Examples

[0097] A tire of size 175 / 70R13 having the tire meridian cross-section of FIG. 1 was prototyped based on the following specifications. Using the prototyped tire, the tire strength, noise performance, ride comfort performance, durability performance, and low fuel consumption performance were evaluated. The manufacturing method and the test method for each prototyped tire are as follows.

[0098] <Manufacture of Belt Rubber Composition> First, the manufacture of the belt rubber composition used for the topping rubber was carried out.

[0099] (1) Compounding Materials First, the following compounding materials were prepared.

[0100] (a) Rubber Components NR: RSS3

[0101] (b) Compounding Materials Other than Rubber Components (A) Carbon Black - 1: Show Black N326 manufactured by Cabot Japan Ltd. (N 2 SA: 78 m 2 / g) (B) Carbon Black - 2: Show Black N550 manufactured by Cabot Japan Ltd. (N 2 SA: 42 m 2 / g) (C) Curable Resin Component - 1: PR12686 manufactured by Sumitomo Bakelite Co., Ltd. (Cashew Oil Modified Phenolic Resin) (D) Curable Resin Component - 2: Sumicanol 620 manufactured by Taoka Chemical Industry Co., Ltd. (Modified Resorcinol Resin) (E) Curing Agent: Sumicanol 507 manufactured by Taoka Chemical Industry Co., Ltd. (Methylene Donor / Resin Curing Agent) (F) Cobalt Organic Acid - 1: COST manufactured by DIC Corporation (Cobalt Content: 9.5 mass%) (G) Cobalt Organic Acid - 2: DICNATE NBC - 2 manufactured by DIC Corporation (Cobalt Neodecanoate Boron, Cobalt Content 22.5 mass%) (H) Zinc Oxide: Zinc White No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. (I) Antioxidant - 1: No Crack 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N - Phenyl - N' - (1,3 - dimethylbutyl) - p - phenylenediamine) (J) Antioxidant - 2: Antage RD manufactured by Kawaguchi Chemical Industry Co., Ltd. (2,2,4 - Trimethyl - 1,2 - dihydroquinoline) (K) Oil: Process X - 140 manufactured by Japan Energy Corporation (L) Crosslinking Agent, Vulcanization Accelerator and Crosslinking Aid Sulfur: Cristex HSOT20 manufactured by Flexsys Japan Ltd. (Insoluble Sulfur Containing 80 Mass% Sulfur and 20 Mass% Oil) Vulcanization Accelerator: Noxeller DZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N,N-Dicyclohexyl-2-benzothiazolylsulfenamide) Crosslinking aid: Duralink HTS manufactured by Flexsys

[0102] (2) Production of rubber composition According to the respective compounding contents shown in Table 1, using a Banbury mixer, materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes under the condition of 150 °C to obtain a kneaded product. Each compounding amount is in parts by mass.

[0103] The compounding of the topping rubber is shown in Table 1.

Table 1

[0104] Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and it was kneaded for 5 minutes under the condition of 80 °C using an open roll to obtain a rubber composition for a belt.

[0105] <Manufacture of tire> The steel wires shown in Table 2 and Table 3 were drawn out and arranged, and using the obtained rubber composition for a belt, it was topped so that the total thickness became 0.95 mm above and below, and after vulcanization, it was cut out so that the steel cord became 24° with respect to the tire circumferential direction to obtain a belt member.

[0106] Thereafter, together with other tire members, the belt members were laminated in two layers so as to cross each other to form an unvulcanized tire, and it was press-vulcanized at 170 °C for 10 minutes to manufacture a test tire.

[0107] <Tire strength> The energy until the prototype tire was punctured by a protrusion and the tire burst was measured. The results are expressed as an index with Comparative Example 1 as 100, and the larger the numerical value, the greater the energy and the higher the tire strength.

[0108] <Noise performance> A test driver got into a test vehicle, a front-wheel drive compact passenger car with prototype tires mounted on all wheels, and drove on a road for measuring road noise, and the noise was measured. The results are represented by an index with Comparative Example 1 taken as 100. The larger the numerical value, the smaller the noise, indicating excellent noise performance.

[0109] <Ride comfort performance> Vibration was applied to the prototype tire with a vibrator, and the time until the vibration converged after the application of vibration was measured. The results are represented by an index with Comparative Example 1 taken as 100. The larger the numerical value, the better the vibration convergence, indicating excellent ride comfort performance.

[0110] <Durability performance> The prototype tire was mounted on a bench durability tester, and the driving distance until the tire was damaged was measured. The results are represented by an index with Comparative Example 1 taken as 100. The larger the numerical value, the longer the driving distance, indicating excellent durability performance.

[0111] <Low fuel consumption performance> The prototype tire was mounted on a rolling resistance tester, and the rolling resistance when driving under a load condition was measured. The results are represented by an index with Comparative Example 1 taken as 100. The larger the numerical value, the smaller the rolling resistance, indicating excellent low fuel consumption performance.

[0112] The test results are shown in Tables 2 and 3.

Table 2

Table 3

[0113] As a result of the test, it was confirmed that the tires of the examples can improve the low fuel consumption performance while maintaining good noise performance, ride comfort performance and durability performance.

Explanation of symbols

[0114] 1 Tire 2 Tread part 7 belt layers 7A, 7B belt plies 9 belt cords 9A steel single wires 10 topping rubbers

Claims

1. A tire having a belt layer disposed inside a tread portion, wherein the belt layer includes at least one belt ply, the belt ply includes a belt cord made of a steel single wire having a flat cross-sectional shape and a topping rubber covering the belt cord, the topping rubber has a complex elastic modulus ES* at 70°C of 14.0 to 20.0 MPa and a loss tangent tanδ at 70°C of 0.04 to 0.06, a ratio (tanδ / ES*) of the loss tangent tanδ to the complex elastic modulus ES* (MPa) of the topping rubber is 0.002 to 0.017, the tread portion includes a tread rubber forming a tread contact surface, the tread rubber has a complex elastic modulus ET* at 70°C of 4.5 to 10.0 MPa and a loss tangent tanδ at 70°C of 0.08 to 0.15, a tire.

2. The tire according to claim 1, wherein a ratio (LD / SD) of a major diameter LD to a minor diameter SD in a cross-sectional shape of the steel single wire is 1.05 to 1.35 and the major diameter LD is 0.30 to 0.50 mm.

3. The steel single wire is corrugated in at least one of a major diameter direction and a minor diameter direction in a cross-sectional shape, a corrugation pitch P of the steel single wire is 3.0 to 10.0 mm, a corrugation height H of the steel single wire is 0.05 to 0.15 mm, and the tire according to claim 1 or 2.

4. The tire according to any one of claims 1 to 3, wherein the belt cord is disposed in the topping rubber such that a minor diameter direction of the steel single wire is along a thickness direction of the belt ply.

5. The topping rubber contains a cobalt element, a ratio (c / L) of a concentration c (ppm) of the cobalt element to an outer peripheral length L (mm) in a cross-sectional shape of the steel single wire is 350 to 1000 ppm / mm, and the tire according to any one of claims 1 to 4.

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