tire

Abstract

To provide a tire enabling suppression of deterioration in on-ice gripping performance due to market traveling.SOLUTION: A tire is provided, comprising: a cord layer; and a tread rubber layer arranged in the outside, in a tire radial direction, of the cord layer. The tread rubber layer includes at least: a surface side tread rubber layer arranged on a surface side of the tire; and an inner tread rubber layer arranged adjacently to inside in the tire radial direction, of the surface side tread rubber layer. In the tire, both the surface side tread rubber layer and the inner tread rubber layer include water-soluble material and satisfy the formula (1) below. [Formula 1].SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a tire. [Background technology]

[0002] From a safety standpoint, studless tires are required to have good grip on surfaces covered with ice or thin ice. It is known that the coefficient of friction on the road surface is at its lowest when the pressure of the tires melts the ice, creating a thin layer of water on the surface, increasing the risk of injury. Another factor that can worsen grip on ice is the hardening of the cap rubber placed on the road surface. Generally, hardening of rubber occurs due to the evaporation and migration of plasticizer components contained in the rubber.

[0003] To improve grip on ice when a thin film of water forms, a method has been developed in which water-soluble fillers are incorporated into the rubber, which dissolves in the water film to create irregularities on the surface and remove the water film. However, it has been difficult to fully prevent the rubber from hardening and the deterioration of grip on ice due to driving in the field. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made in view of the above-mentioned current situation, and has an object to provide a tire that can suppress deterioration of grip performance on ice due to use in the market. [Means for solving the problem]

[0005] The present invention relates to a tire including a cord layer and a tread rubber layer disposed radially outward of the cord layer, wherein the tread rubber layer has at least a surface-side tread rubber layer disposed on the surface side of the tire, and an inner tread rubber layer disposed adjacent to and radially inward of the surface-side tread rubber layer, and both the surface-side tread rubber layer and the inner tread rubber layer contain a water-soluble material, and satisfy the following formula (1):

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[0006] In any meridian cross section of the tire, at least a part of the inner tread rubber layer is preferably located radially outward of the groove bottom located most radially inward of the tire.

[0007] It is preferable that the following formula (2) is satisfied.

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[0008] It is preferable that the thickness of the inner tread rubber layer accounts for 60% or more of the total thickness of the tread rubber layer.

[0009] It is preferable that the following formula (3) is satisfied.

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[0010] It is preferable that the following formula (4) is satisfied.

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[0011] It is preferable that the following formula (5) is satisfied.

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[0012] It is preferable that the following formula (6) is satisfied.

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[0013] It is preferable that the following formula (7) is satisfied.

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[0014] It is preferable that the following formula (8) is satisfied.

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[0015] It is preferable that the following formula (9) is satisfied.

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[0016] It is preferable that the following formula (10) is satisfied.

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[0017] It is preferable that the following formula (11) is satisfied.

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[0018] The present invention is a tire comprising a cord layer and a tread rubber layer arranged radially outward of the cord layer, wherein the tread rubber layer has at least a surface-side tread rubber layer arranged on the surface side of the tire, and an inner tread rubber layer arranged adjacent to and radially inward of the surface-side tread rubber layer, and both the surface-side tread rubber layer and the inner tread rubber layer contain a water-soluble material, and the tire satisfies formula (1), thereby making it possible to suppress deterioration of grip performance on ice due to on-road driving. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view showing a portion of a passenger vehicle tire according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention provides a tire having a cord layer and a tread rubber layer disposed radially outward of the cord layer, wherein the tread rubber layer has at least a surface-side tread rubber layer disposed on the surface side of the tire and an inner tread rubber layer disposed radially inward of the surface-side tread rubber layer, and both the surface-side tread rubber layer and the inner tread rubber layer contain a water-soluble material and satisfy formula (1), thereby suppressing a decrease in grip on ice due to on-road driving.

[0021] The mechanism by which such an effect is obtained is not clear, but is presumed to be as follows. Tires have a problem in that rubber hardens during use in the field, resulting in a decline in ice grip performance. To address this issue, the tire incorporates a water-soluble material into both the surface tread rubber layer disposed on the surface side of the tire and the inner tread rubber layer disposed inward of the surface tread rubber layer, with a larger amount of water-soluble material incorporated into the inner tread rubber layer than the surface tread rubber layer. As a result, good ice grip performance is achieved at the beginning of use due to the rubber hardness and water-soluble material suited to ice grip performance. Furthermore, when the rubber hardens at the end of wear, the inner tread rubber layer is exposed, and the water-soluble material incorporated in a larger amount than the surface tread rubber layer increases the amount of edge voids formed by dissolution with water on the road surface, enhancing the edge effect and water film removal effect, resulting in good ice grip performance even at the end of wear. Therefore, it is presumed that the tire inhibits the decline in ice grip performance during use in the field.

[0022] In this way, the present invention solves the problem (objective) of suppressing the deterioration of grip performance on ice due to on-the-road driving by configuring a tire that satisfies the above formula (1). In other words, the above formula (1) does not define the problem (objective); the object of the present application is to suppress the deterioration of grip performance on ice due to on-the-road driving, and the configuration that satisfies the above formula (1) is used as a means to solve this problem.

[0023] The tire includes a cord layer and a tread rubber layer disposed radially outward of the cord layer. The cords used in the cord layer are not particularly limited as long as they are used in tires, and examples include carcass cords (case cords), breaker cords, and band cords. "Radially outward of the cord layer" refers to the radially outward direction of the tire from the cord layer.

[0024] The tread rubber layer has at least a surface-side tread rubber layer disposed on the surface side of the tire, and an inner tread rubber layer disposed adjacent to and on the radially inward side of the surface-side tread rubber layer. Any multi-layer structure tread can be used as the tread rubber layer disposed on the radially outer side of the cord layer, including a two-layer structure tread, a three-layer structure tread, and a tread with a structure of four or more layers. In the multi-layer structure tread, it is preferable that the surface-side tread rubber layer constitutes the outermost rubber layer of the multi-layer structure tread, and the inner tread rubber layer is a rubber layer disposed adjacent to and on the radially inward side of the outermost rubber layer.

[0025] In the tire, both the surface tread rubber layer and the inner tread rubber layer contain a water-soluble material. The water-soluble material is not particularly limited as long as it is a material that is soluble in water, and for example, a material that has a solubility in water at room temperature (20°C) of 1 g / 100 g water or more can be used.

[0026] Examples of the water-soluble material include water-soluble inorganic salts, water-soluble organic substances, etc. These may be used alone or in combination of two or more.

[0027] Examples of water-soluble inorganic salts include metal sulfates such as magnesium sulfate and potassium sulfate; metal chlorides such as potassium chloride, sodium chloride, calcium chloride and magnesium chloride; metal hydroxides such as potassium hydroxide and sodium hydroxide; carbonates such as potassium carbonate and sodium carbonate; and phosphates such as sodium hydrogen phosphate and sodium dihydrogen phosphate.

[0028] Examples of water-soluble organic substances include lignin derivatives and sugars. Suitable lignin derivatives include lignin sulfonic acid, lignin sulfonate, etc. The lignin derivative may be obtained by either the sulfite pulp method or the kraft pulp method.

[0029] Examples of lignin sulfonates include alkali metal salts, alkaline earth metal salts, ammonium salts, and alcoholamine salts of lignin sulfonic acid. Of these, alkali metal salts (potassium salt, sodium salt, etc.) and alkaline earth metal salts (calcium salt, magnesium salt, lithium salt, barium salt, etc.) of lignin sulfonic acid are preferred.

[0030] The lignin derivative preferably has a degree of sulfonation of 1.5 to 8.0 / OCH3. In this case, the lignin derivative contains lignosulfonic acid and / or lignosulfonate in which at least a portion of lignin and / or its decomposition products is substituted with a sulfo group (sulfone group), and the sulfo group of the lignosulfonic acid may be in an ionized state or the hydrogen of the sulfo group may be substituted with an ion such as a metal ion. The sulfonation degree is more preferably 3.0 to 6.0 / OCH3. By keeping the sulfonation degree within the above range, good performance on ice and snow can be obtained, and the balance between this and steering stability on dry roads tends to be improved.

[0031] The degree of sulfonation of the lignin derivative particles (the lignin derivative constituting the particles) is the introduction rate of sulfo groups, and is calculated by the following formula. Sulfonation degree ( / OCH3) = S (mol) in sulfonic groups in lignin derivatives / Methoxyl groups (mol) in lignin derivatives

[0032] The number of carbon atoms constituting the sugars is not particularly limited, and they may be monosaccharides, oligosaccharides, or polysaccharides. Examples of monosaccharides include trioses such as aldotriose and ketotriose; tetraoses such as erythrose and threose; pentoses such as xylose and ribose; hexoses such as mannose, allose, altrose, and glucose; and heptoses such as sedoheptulose. Examples of oligosaccharides include disaccharides such as sucrose and lactose; trisaccharides such as raffinose and melezitose; tetrasaccharides such as acarbose and stachyose; and oligosaccharides such as xylooligosaccharides and cellooligosaccharides. Examples of polysaccharides include glycogen, starch (amylose, amylopectin), cellulose, hemicellulose, dextrin, and glucan.

[0033] From the viewpoint of grip performance on ice, the water-soluble material preferably has a median particle size (median diameter, D50) of 1 μm to 1 mm. More preferably, it is 2 μm to 800 μm, and even more preferably, it is 2 μm to 500 μm. The lower limit may be 10 μm or more, and the upper limit may be 100 μm or less. In this specification, the median particle size can be measured by laser diffraction.

[0034] The tire satisfies the following formula (1).

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[0035] The content of the water-soluble material in the surface tread rubber layer is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 15 parts by mass or more, per 100 parts by mass of the rubber component in the surface tread rubber layer. The content is preferably 70 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 30 parts by mass or less. By keeping the content within the above range, deterioration of grip performance on ice due to market driving tends to be suppressed.

[0036] The content of the water-soluble material in the inner tread rubber layer is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more, per 100 parts by mass of the rubber component in the inner tread rubber layer. The content is preferably 100 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 40 parts by mass or less. By keeping the content within the above range, deterioration of grip performance on ice due to market driving tends to be suppressed.

[0037] The rubber components that can be used in the rubber composition for the surface tread rubber layer and the rubber composition for the inner tread rubber layer that constitute the surface tread rubber layer and the inner tread rubber layer are not particularly limited, and rubbers used in the tire field can be used. Examples include diene rubbers such as isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). Among these, isoprene rubber and BR are preferred from the viewpoint of grip performance on ice.

[0038] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. NRs such as SIR20, RSS#3, and TSR20 can be used, and IRs such as IR2200 can be used, which are commonly used in the tire industry. Modified NRs include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Modified NRs include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Modified IRs include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more.

[0039] From the viewpoint of performance on ice, the cis content of BR is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. In this specification, the cis content (cis-1,4-bond amount) is a value calculated from the signal intensity measured by infrared absorption spectroscopy or NMR analysis.

[0040] The BR is not particularly limited, and examples thereof include those commonly used in the tire industry, such as BR with a high cis content, BR containing 1,2-syndiotactic polybutadiene crystals (SPB-containing BR), butadiene rubber synthesized using a rare earth catalyst (rare earth BR), and tin-modified butadiene rubber modified with a tin compound (tin-modified BR). Commercially available BRs include those from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Zeon Corporation. These may be used alone or in combination of two or more.

[0041] The BR may be either unmodified or modified. The modified BR may be a modified BR having a functional group that interacts with a filler such as silica. Examples include terminal-modified BR (terminal-modified BR having a functional group at the terminal) in which at least one terminal of the modified BR has been modified with a compound (modifier) ​​having a functional group, main-chain-modified BR having a functional group in the main chain, main-chain-terminal-modified BR having functional groups in the main chain and at the terminals (for example, main-chain-terminal BR having a functional group in the main chain and at least one terminal modified with a modifier), and terminal-modified BR modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or epoxy group introduced therein.

[0042] Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imido group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, and an epoxy group. These functional groups may have a substituent. Among these, an amino group (preferably an amino group in which a hydrogen atom of the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferred.

[0043] For example, a BR modified with a compound (modifying agent) represented by the following formula can be suitably used as the modified BR.

[0044] [ka] (In the formula, R 1 , R 2 and R 3 R may be the same or different and represent an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (-COOH), a mercapto group (-SH), or a derivative thereof. 4 and R 5are the same or different and represent a hydrogen atom or an alkyl group. 4 and R 5 may bond to form a ring structure together with the nitrogen atom, and n represents an integer.

[0045] R 1 , R 2 and R 3 R is preferably an alkoxy group (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms). 4 and R 5 is preferably an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. In addition, R 4 and R 5 When the groups bond to form a ring structure together with the nitrogen atom, the ring is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (such as a cyclohexyloxy group) and an aryloxy group (such as a phenoxy group or a benzyloxy group).

[0046] Specific examples of compounds (modifiers) represented by the above formula include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane. Among these, 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropyltriethoxysilane, and 3-diethylaminopropyltrimethoxysilane are preferred. These may be used alone or in combination of two or more.

[0047] The modified BR may be preferably modified with the following compounds (modifiers): Examples of the modifiers include polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenol groups, such as diglycidylated bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; and 4,4'- Epoxy group-containing tertiary amines such as diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylamino compounds such as diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline, diglycidyl orthotoluidine, tetraglycidyl meta-xylenediamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane;

[0048] Amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamic acid chloride, and N,N-diethylcarbamic acid chloride; epoxy group-containing silane compounds such as 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane and (3-glycidyloxypropyl)-pentamethyldisiloxane;

[0049] sulfide group-containing silane compounds such as (trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(trippropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldipropoxysilyl)propyl]sulfide, and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide;

[0050] N-substituted aziridine compounds such as ethyleneimine and propyleneimine; alkoxysilanes such as methyltriethoxysilane; (thio)benzophenone compounds having amino groups and / or substituted amino groups such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-t-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone, and N,N,N',N'-bis-(tetraethylamino)benzophenone; 4-N,N-dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde, 4-N benzaldehyde compounds having an amino group and / or a substituted amino group, such as N-divinylaminobenzaldehyde; N-substituted pyrrolidones such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, Nt-butyl-2-pyrrolidone, and N-methyl-5-methyl-2-pyrrolidone; N-substituted piperidones such as N-methyl-2-piperidone, N-vinyl-2-piperidone, and N-phenyl-2-piperidone; N-substituted lactams such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurylolactam, N-vinyl-ω-laurylolactam, N-methyl-β-propiolactam, and N-phenyl-β-propiolactam; and

[0051] Examples of suitable BRs include N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), tris-(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-triones, N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophene, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, and 1,7-bis(methylethylamino)-4-heptanone. Among these, modified BRs modified with alkoxysilanes are preferred.

[0052] The modified BR modified with the compound (modifier) ​​represented by the above formula is preferably, for example, a BR in which the polymerization terminal (active terminal) of a solution-polymerized butadiene rubber is modified with the compound represented by the above formula. The modification with the compound (modifier) ​​can be carried out by a known method.

[0053] In the rubber composition for the surface side tread rubber layer, the content of the isoprene-based rubber in 100% by mass of the rubber component contained in the rubber composition for the surface side tread rubber layer is preferably 20% by mass or more, more preferably 30% by mass or more, from the viewpoint of suppressing deterioration of grip performance on ice due to market driving. The upper limit of the content is not particularly limited, but is preferably 80% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less.

[0054] In the rubber composition for the inner tread rubber layer, the content of the isoprene-based rubber in 100% by mass of the rubber component contained in the rubber composition for the inner tread rubber layer is preferably 20% by mass or more, more preferably 30% by mass or more, from the viewpoint of initial grip performance on ice. The upper limit of the content is not particularly limited, but is preferably 80% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less.

[0055] In the rubber composition for the surface side tread rubber layer, the content of BR in 100% by mass of the rubber component contained in the rubber composition for the surface side tread rubber layer is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, from the viewpoint of initial grip performance on ice. The upper limit of the content is not particularly limited, but is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less.

[0056] In the rubber composition for the inner tread rubber layer, the content of BR in 100% by mass of the rubber component contained in the rubber composition for the inner tread rubber layer is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, from the viewpoint of suppressing deterioration of grip performance on ice due to market driving. The upper limit of the content is not particularly limited, but is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less.

[0057] From the viewpoint of suppressing deterioration of grip performance on ice due to road use in the market, the total content of the isoprene-based rubber and the BR in 100% by mass of the rubber component in each of the rubber composition for the surface side tread rubber layer and the rubber composition for the inner tread rubber layer is preferably 30% by mass or more, more preferably 60% by mass or more, still more preferably 80% by mass or more, and may be 100% by mass.

[0058] The rubber composition for the surface tread rubber layer and the rubber composition for the inner tread rubber layer preferably contain silica. Examples of silica that can be used in the rubber composition for the surface tread rubber layer and the rubber composition for the inner tread rubber layer include dry process silica (anhydrous silica) and wet process silica (hydrated silica). Of these, wet process silica is preferred because it contains a large number of silanol groups. Commercially available products that can be used include those from Degussa, Rhodia, Tosoh Silica Corporation, Solvay Japan, and Tokuyama Corporation. These may be used alone or in combination of two or more.

[0059] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 70 m 2 / g or more, more preferably 140m 2 / g or more, more preferably 160m 2 / g or more. By making it equal to or greater than the lower limit, good abrasion resistance and breaking strength can be obtained. In addition, there is no particular restriction on the upper limit of N2SA of silica, but it is preferably 500 m 2 / g or less, more preferably 300m 2 / g or less, more preferably 250m 2 By setting the content to the upper limit or less, good dispersibility tends to be obtained. The N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0060] The content of silica contained in the rubber composition for the surface tread rubber layer is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 40 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is not particularly limited, but is preferably 300 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 75 parts by mass or less. By keeping the content within the above range, initial grip performance on ice tends to be high.

[0061] The content of silica contained in the rubber composition for the inner tread rubber layer is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is not particularly limited, but is preferably 200 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 50 parts by mass or less. By keeping the content within the above range, deterioration of grip performance on ice due to market driving tends to be suppressed.

[0062] From the viewpoint of suppressing deterioration of grip performance on ice due to running in the market, it is preferable that the rubber composition for the surface side tread rubber layer and the rubber composition for the inner tread rubber layer satisfy the following formula.

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[0063] When the rubber composition for the surface side tread rubber layer and the rubber composition for the inner tread rubber layer contain silica, it is preferable that they further contain a silane coupling agent. The silane coupling agent is not particularly limited, and examples thereof 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, 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-dimethylthiocalcium nitrate, Examples include sulfide-based compounds such as bamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z manufactured by Momentive; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercially available products include those from Degussa, Momentive, Shin-Etsu Silicones Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Dow Corning Toray Co., Ltd. These may be used alone or in combination of two or more.

[0064] The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 6 parts by mass or more, per 100 parts by mass of silica. If it is above the lower limit, good breaking strength and the like tend to be obtained. Also, the content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. If it is below the upper limit, an effect commensurate with the amount blended tends to be obtained.

[0065] The rubber composition for the surface tread rubber layer and the rubber composition for the inner tread rubber layer preferably contain carbon black for the purpose of suppressing ultraviolet degradation. Examples of carbon black include, but are not limited to, N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available carbon blacks available from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nichika Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like, may be used. These carbon blacks may be used alone or in combination of two or more.

[0066] The nitrogen adsorption specific surface area (N2SA) of carbon black is 50m 2 / g or more is preferable, and 80m 2 / g or more is more preferable, and 100m 2 / g or more is more preferable. By making it equal to or more than the lower limit, good abrasion resistance and performance on ice tend to be obtained. 2 / g or less is preferable, and 150m 2 / g or less is more preferable, and 130m 2 By setting the content to the upper limit or less, good dispersibility of the carbon black tends to be obtained. The nitrogen adsorption specific surface area of ​​carbon black can be determined according to JIS K6217-2:2001.

[0067] The content of carbon black contained in the rubber composition for the surface tread rubber layer is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 4 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is not particularly limited, but is preferably 30 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 8 parts by mass or less. By keeping the content within the above range, it tends to be possible to improve grip performance on ice while suppressing ultraviolet degradation.

[0068] The content of carbon black contained in the rubber composition for the inner tread rubber layer is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is not particularly limited, but is preferably 100 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 35 parts by mass or less. By keeping the content within the above range, ultraviolet degradation in the final stage of wear can be suppressed.

[0069] From the viewpoint of optimizing tire production costs and ensuring steering stability, the rubber composition for the surface side tread rubber layer and the rubber composition for the inner tread rubber layer preferably satisfy the following formula.

number

[0070] The rubber composition for the surface tread rubber layer and the rubber composition for the inner tread rubber layer preferably contain a liquid plasticizer (a plasticizer that is in a liquid state at 25°C), a resin, etc. The resin refers to a resin that is in a solid state at room temperature (25°C).

[0071] The liquid plasticizer is not particularly limited, and examples thereof include oil, liquid resin, liquid diene polymer, etc. These may be used alone or in combination of two or more kinds.

[0072] Examples of oils include process oils, vegetable oils, and mixtures thereof. Examples of process oils that can be used include paraffin-based process oils, aromatic process oils, and naphthenic process oils. Examples of vegetable oils that can be used 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 Yuka Kogyo Co., Ltd., Japan Energy Corporation, Oriso Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and Nisshin Oillio Group, Ltd.

[0073] Examples of liquid resins include terpene resins (including terpene phenol resins and aromatic modified terpene resins) that are liquid at 20°C, rosin resins, styrene resins, C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene (DCPD) resins, coumarone-indene resins (including coumarone and indene simple resins), phenol resins, olefin resins, polyurethane resins, and acrylic resins.

[0074] 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 polymers), liquid styrene isoprene styrene block copolymers (liquid SIS block polymers), liquid farnesene polymers, and liquid farnesene butadiene copolymers, which are liquid at 20° C. The terminals or main chains of these polymers may be modified with polar groups.

[0075] Examples of resins include aromatic vinyl polymers, coumarone-indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, and acrylic resins. Commercially available products include those from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., JX Nippon Energy Corporation, Arakawa Chemical Industries, Ltd., Taoka Chemical Co., Ltd., and Toagosei Co., Ltd. These may be used alone or in combination of two or more.

[0076] An aromatic vinyl polymer is a resin obtained by polymerizing α-methylstyrene and / or styrene, and examples thereof include a homopolymer of styrene (styrene resin), a homopolymer of α-methylstyrene (α-methylstyrene resin), a copolymer of α-methylstyrene and styrene, and a copolymer of styrene and another monomer.

[0077] Coumarone-indene resin is a resin containing coumarone and indene as the main monomer components that make up the resin skeleton (main chain). Other monomer components contained in the skeleton besides coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

[0078] A coumarone resin is a resin that contains coumarone as the main monomer component that constitutes the skeleton (main chain) of the resin.

[0079] Indene resin is a resin that contains indene as the main monomer component that constitutes the skeleton (main chain) of the resin.

[0080] Examples of phenolic resins include those obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde, and furfural in the presence of an acid or alkali catalyst. Among these, those obtained by reacting with an acid catalyst (such as novolac-type phenolic resins) are preferred.

[0081] Examples of rosin resins include rosin-based resins such as natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

[0082] Examples of petroleum resins include C5 resins, C9 resins, C5 / C9 resins, and dicyclopentadiene (DCPD) resins.

[0083] Examples of terpene resins that can be used include polyterpene resins obtained by polymerizing a terpene compound and aromatic modified terpene resins obtained by polymerizing a terpene compound and an aromatic compound. Hydrogenated products of these resins can also be used.

[0084] Polyterpene resins are resins obtained by polymerizing terpene compounds. The terpene compounds are (C5H8) n The hydrocarbons and their oxygen-containing derivatives are represented by the following composition: monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32 ), and examples thereof include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

[0085] Examples of polyterpene resins include pinene resin, limonene resin, dipentene resin, and pinene / limonene resin, which are made from the above-mentioned terpene compounds. Among these, pinene resin is preferred because it is easy to polymerize and is inexpensive because it is made from natural pine resin. Pinene resins usually contain both α-pinene and β-pinene, which are isomers, but are classified into β-pinene resins containing β-pinene as the main component and α-pinene resins containing α-pinene as the main component, depending on the components contained.

[0086] Examples of aromatic modified terpene resins include terpene phenol resins made from the above-mentioned terpene compounds and phenolic compounds, and terpene styrene resins made from the above-mentioned terpene compounds and styrene compounds. Terpene phenol styrene resins made from the above-mentioned terpene compounds, phenolic compounds, and styrene compounds can also be used. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol. Examples of styrene compounds include styrene and α-methylstyrene.

[0087] Examples of the acrylic resin include styrene-acrylic resins such as styrene-acrylic resins that have a carboxyl group and are obtained by copolymerizing an aromatic vinyl monomer component with an acrylic monomer component. Among these, solvent-free carboxyl-containing styrene-acrylic resins are preferred.

[0088] The solvent-free carboxyl group-containing styrene-acrylic resin is a (meth)acrylic resin (polymer) synthesized by a high-temperature continuous polymerization method (high-temperature continuous bulk polymerization method) (methods described in U.S. Pat. No. 4,414,370, JP-A Nos. 59-6207, JP-B Nos. 5-58005, 1-313522, U.S. Pat. No. 5,010,166, and Toa Gosei Kenkyusho Annual Report TREND 2000, Vol. 3, pp. 42-45, etc.), with minimal use of auxiliary raw materials such as polymerization initiators, chain transfer agents, and organic solvents. In this specification, (meth)acrylic refers to both methacrylic and acrylic.

[0089] Examples of acrylic monomer components constituting acrylic resins include (meth)acrylic acid, (meth)acrylic acid esters (alkyl esters such as 2-ethylhexyl acrylate, aryl esters, aralkyl esters, etc.), (meth)acrylamide, (meth)acrylic acid derivatives such as (meth)acrylamide derivatives, etc. (Meth)acrylic acid is a general term for acrylic acid and methacrylic acid.

[0090] Examples of aromatic vinyl monomer components constituting the acrylic resin include aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene.

[0091] As the monomer component constituting the acrylic resin, other monomer components may be used in addition to (meth)acrylic acid, (meth)acrylic acid derivatives, and aromatic vinyl.

[0092] The softening point of the resin is preferably 50° C. or higher, more preferably 70° C. or higher, and particularly preferably 80° C. or higher. The softening point is preferably 200° C. or lower, more preferably 160° C. or lower. If the softening point is within the above range, deterioration of grip performance on ice due to on-road driving tends to be suppressed. The softening point of the resin 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.

[0093] From the viewpoint of suppressing deterioration of grip performance on ice due to road use, it is preferable that the resin content and the liquid plasticizer content per 100 parts by mass of the rubber component contained in the surface tread rubber layer satisfy the following formula.

number

[0094] From the viewpoint of suppressing deterioration of grip performance on ice due to driving in the market, it is preferable that the resin content and the liquid plasticizer content per 100 parts by mass of the rubber component contained in the inner tread rubber layer satisfy the following formula.

number

[0095] The content of the liquid plasticizer in the rubber composition for the surface tread rubber layer 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, per 100 parts by mass of the rubber component. The upper limit of the content is not particularly limited, but is preferably 70 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less. By keeping the content within the above range, deterioration of grip performance on ice due to market driving tends to be suppressed.

[0096] The content of the liquid plasticizer in the rubber composition for the inner tread rubber layer 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, per 100 parts by mass of the rubber component. The upper limit of the content is not particularly limited, but is preferably 70 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less. By keeping the content within the above range, deterioration of grip performance on ice due to market driving tends to be suppressed.

[0097] The content of the resin contained in the rubber composition for the surface tread rubber layer is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 7 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is not particularly limited, but is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. By keeping the content within the above range, deterioration of grip performance on ice due to on-road driving tends to be suppressed.

[0098] The content of the resin contained in the rubber composition for the inner tread rubber layer is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 7 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is not particularly limited, but is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. By keeping the content within the above range, deterioration of grip performance on ice due to market driving tends to be suppressed.

[0099] From the viewpoint of suppressing deterioration of grip performance on ice due to running in the market, the tire preferably satisfies the following formula (6).

number

[0100] From the viewpoint of suppressing deterioration of grip performance on ice due to running in the market, the tire preferably satisfies the following formula (7):

number

[0101] From the viewpoint of suppressing deterioration of grip performance on ice due to running in the market, the tire preferably satisfies the following formula (9).

number

[0102] From the viewpoint of suppressing deterioration of grip performance on ice due to running in the market, the tire preferably satisfies the following formula (11):

number

[0103] The rubber composition for the surface side tread rubber layer and the rubber composition for the inner tread rubber layer preferably contain an antioxidant from the viewpoints of crack resistance, ozone resistance, and the like.

[0104] The antioxidant is not particularly limited, but examples thereof include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and the like. Examples of suitable antioxidants include p-phenylenediamine antioxidants such as amines; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine antioxidants and quinoline antioxidants are preferred, with polymers of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline being more preferred. Commercially available products include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and Flexis.

[0105] In the rubber composition for the surface tread rubber layer and the rubber composition for the inner tread rubber layer, the content of the antioxidant is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, per 100 parts by mass of the rubber component. By making the content equal to or greater than the lower limit, sufficient ozone resistance tends to be obtained. The content is preferably 7.0 parts by mass or less, more preferably 4.0 parts by mass or less. By making the content equal to or less than the upper limit, a good tire appearance tends to be obtained.

[0106] The rubber composition for the surface tread rubber layer and the rubber composition for the inner tread rubber layer preferably contain stearic acid. The content of stearic acid is preferably 0.5 to 10 parts by mass or more, more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0107] As the stearic acid, conventionally known products can be used, such as products from NOF Corporation, NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., and the like.

[0108] The rubber composition for the surface tread rubber layer and the rubber composition for the inner tread rubber layer preferably contain zinc oxide. The content of zinc oxide is preferably 0.5 to 10.0 parts by mass, more preferably 1.0 to 5.0 parts by mass, per 100 parts by mass of the rubber component.

[0109] As the zinc oxide, conventionally known products can be used, for example, products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0110] The rubber composition for the surface tread rubber layer and the rubber composition for the inner tread rubber layer may contain wax. The content of the wax is preferably 0.1 to 5.0 parts by mass, more preferably 0.5 to 3.0 parts by mass, per 100 parts by mass of the rubber component.

[0111] The wax is not particularly limited, and examples thereof include petroleum-based waxes and natural waxes. Synthetic waxes obtained by refining or chemically processing multiple waxes can also be used. These waxes can be used alone or in combination of two or more. Petroleum-based waxes include paraffin wax and microcrystalline wax. Natural waxes are not particularly limited as long as they are derived from non-petroleum resources, and examples include plant-based waxes such as candelilla wax, carnauba wax, Japan wax, rice wax, and jojoba wax; animal-based waxes such as beeswax, lanolin, and spermaceti; mineral-based waxes such as ozokerite, ceresin, and petrolactam; and refined products thereof. Commercially available products include those from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Chemical Co., Ltd. The wax content can be appropriately determined based on ozone resistance and cost.

[0112] It is preferable to compound sulfur into the rubber composition for the surface side tread rubber layer and the rubber composition for the inner tread rubber layer in order to form an appropriate amount of crosslinked chains in polymer chains.

[0113] The amount of sulfur per 100 parts by mass of the rubber component is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and even more preferably 0.7 part by mass or more, and is preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less.

[0114] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. Commercially available products include those from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. These may be used alone or in combination of two or more.

[0115] The rubber composition for the surface side tread rubber layer and the rubber composition for the inner tread rubber layer preferably contain a vulcanization accelerator. The content of the vulcanization accelerator is not particularly limited and may be freely determined according to the desired vulcanization speed and crosslink density, but is usually 0.3 to 10 parts by mass, preferably 0.5 to 7 parts by mass, per 100 parts by mass of the rubber component.

[0116] The type of vulcanization accelerator is not particularly limited, and any commonly used accelerator can be used. Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenyl guanidine, di-orthotolyl guanidine, and orthotolyl biguanidine. These may be used alone or in combination of two or more. Among these, sulfenamide vulcanization accelerators and guanidine vulcanization accelerators are preferred.

[0117] In addition to the above components, the rubber composition for the surface side tread rubber layer and the rubber composition for the inner tread rubber layer may appropriately contain compounding agents that are generally used in the tire industry, such as materials such as a mold release agent.

[0118] As a method for producing the rubber composition for the surface side tread rubber layer and the rubber composition for the inner tread rubber layer, a known method can be used. For example, they can be produced by kneading the components using a rubber kneading device such as an open roll or a Banbury mixer, followed by vulcanization.

[0119] As for kneading conditions, in the base kneading step in which additives other than the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 50 to 200°C, preferably 80 to 190°C, and the kneading time is usually 30 seconds to 30 minutes, preferably 1 minute to 30 minutes. In the finish kneading step in which the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 100°C or lower, preferably room temperature to 80°C. Furthermore, the composition kneaded with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 120 to 200°C, preferably 140 to 180°C.

[0120] The tire is manufactured by a conventional method using the rubber composition for the surface tread rubber layer and the rubber composition for the inner tread rubber layer described above. That is, the rubber composition for the surface tread rubber layer and the rubber composition for the inner tread rubber layer, each containing each component, are extruded in an unvulcanized state to match the shapes of the respective components, and molded together with other tire components in a tire building machine by a conventional method to form an unvulcanized tire. The unvulcanized tire is then heated and pressurized in the vulcanizer to obtain a tire.

[0121] Examples of tires include pneumatic tires and airless (solid) tires, with pneumatic tires being preferred. They are particularly suitable for use as winter tires (studless tires, snow tires, studded tires, etc.). Tires can be used as passenger car tires, large passenger car tires, large SUV tires, heavy-duty tires for trucks and buses, light truck tires, motorcycle tires, racing tires (high-performance tires), etc.

[0122] In order to suppress deterioration of grip performance on ice due to running in the market, it is preferable that the thicknesses of the surface side tread rubber layer and the inner tread rubber layer of the tire satisfy the following formula (2).

number

[0123] The thickness of the surface-side tread rubber layer is the maximum dimension among the thicknesses of the surface-side tread rubber layer at each point on the surface of the surface-side tread rubber layer. The thickness of the inner tread rubber layer is the maximum dimension among the thicknesses of the inner tread rubber layer at each point on the surface of the inner tread rubber layer. The thicknesses of the surface-side tread rubber layer and the inner tread rubber layer at each point are measured along the normal to the surface of the surface-side tread rubber layer at each point and the normal to the surface of the inner tread rubber layer at each point, respectively.

[0124] From the viewpoint of preventing deterioration of grip performance on ice due to running in the market, the thickness of the inner tread rubber layer of the tire preferably accounts for 50% or more of the total thickness of the tread rubber layer, more preferably 55% or more, and even more preferably 60% or more. There is no particular upper limit, but it is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less.

[0125] The thickness of the tread rubber layer (the thickness of the tread rubber layer disposed radially outward of the cord layer) is the thickness from the surface of the cord layer to the surface-side tread rubber layer, and is the maximum dimension among the thicknesses of the tread rubber layer from each point on the surface of the surface-side tread rubber layer to the surface of the cord layer. The thickness of the tread rubber layer at each point (the thickness of the tread rubber layer from each point on the surface of the surface-side tread rubber layer to the surface of the cord layer) is measured along the normal to the surface of the surface-side tread rubber layer at each point.

[0126] From the viewpoint of preventing deterioration of ice grip performance due to on-road driving, it is preferable that the tire has at least a portion of the inner tread rubber layer located radially outward of the radially innermost groove bottom in any meridian cross section of the tire, thereby achieving good ice grip performance even in the final stages of wear due to the edge effect of voids formed by dissolution of a large amount of water-soluble material and the effect of removing water film.

[0127] From the viewpoint of suppressing deterioration of grip performance on ice due to running in the market, the tire preferably satisfies the following formula (3):

number

[0128] From the viewpoint of suppressing deterioration of grip performance on ice due to running in the market, the tire preferably satisfies the following formula (4):

number

[0129] From the viewpoint of suppressing deterioration of grip performance on ice due to running in the market, the tire preferably satisfies the following formula (5).

number

[0130] From the viewpoint of suppressing deterioration of grip performance on ice due to running in the market, the tire preferably satisfies the following formula (8).

number

[0131] From the viewpoint of suppressing deterioration of grip performance on ice due to running in the market, the tire preferably satisfies the following formula (10):

number

[0132] Hereinafter, an example of a preferred embodiment of the tire of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view showing a portion of a passenger car tire according to one embodiment of the present invention. Note that Fig. 1 illustrates a passenger car tire, but the pneumatic tire of the present invention can also be used for other purposes, such as a heavy load tire.

[0133] 1, the up-down direction is the tire radial direction, the left-right direction is the tire axial direction, and the direction perpendicular to the plane of the page is the tire circumferential direction. A passenger vehicle tire 1 includes a tread portion 7, a pair of sidewall portions 8 extending radially inward from both ends of the tread portion 7, bead portions 3 located at the inner ends of each sidewall portion 8, and chafers 2 located on the top of the rim. A carcass 10 is spanned between the bead portions 3 on both sides, and a breaker portion 9 is disposed on the radially outer side of this carcass 10.

[0134] The carcass 10 is formed from one or more carcass plies in which carcass cords are arranged. The carcass ply passes from the tread portion 7 through the sidewall portion 8, and is folded back from the inside to the outside in the tire axial direction around the bead cores 4 and the bead apexes 5 that extend from the upper ends of the bead cores 4 toward the sidewalls, and is secured thereto. The breaker portion 9 is made up of two or more breaker plies in which breaker cords are arranged, and the breaker cords are arranged in different directions so that they cross between the breaker plies. A band 6 is arranged above the breaker portion 9 to protect the breaker portion 9.

[0135] The tread portion 7 is composed of a surface-side tread rubber layer 7c, which is arranged on the side that comes into contact with the road surface out of the surface-side tread rubber layer and the inner tread rubber layer, and an inner tread rubber layer 7b, which is arranged radially inward of the surface-side tread rubber layer 7c. Both the surface-side tread rubber layer 7c and the inner tread rubber layer 7b contain the water-soluble material and satisfy the formula (1). It is also preferable that the contents of the resin and liquid plasticizer contained in the surface-side tread rubber layer 7c and the inner tread rubber layer 7b satisfy the formulas (2) and (3).

[0136] It is preferable that the thicknesses of the surface-side tread rubber layer 7c and the inner tread rubber layer 7b satisfy the above-mentioned formula (4). In this case, in Fig. 1, symbol P1 indicates a point on the surface of the surface-side tread rubber layer 7c, and symbol P2 indicates a point on the surface of the inner tread rubber layer 7b. The double-headed arrow T1 indicates the thickness of the surface-side tread rubber layer 7c at point P1, and the double-headed arrow T2 indicates the thickness of the inner tread rubber layer 7b at point P2. These thicknesses T1 and T2 are measured along the normal to the surface of the surface-side tread rubber layer at point P1 and the normal to the surface of the inner tread rubber layer at point P2, respectively. The thickness of the surface-side tread rubber layer 7c is the maximum dimension among the thicknesses of the surface-side tread rubber layer at each point on the surface of the surface-side tread rubber layer 7c, and the thickness of the inner tread rubber layer 7b is the maximum dimension among the thicknesses of the inner tread rubber layer at each point on the surface of the inner tread rubber layer 7b.

[0137] It is preferable that the thickness of the inner tread rubber layer 7b account for 50% or more of the total thickness of the tread rubber layer. In Figure 1, symbol P3 indicates a point on the surface of the surface-side tread rubber layer 7c. The double-headed arrow T3 indicates the thickness of the tread rubber layer disposed on the radially outer side of the band 6 (cord layer) at point P3. This thickness T3 is measured along the normal to the surface of the surface-side tread rubber layer at point P3. The thickness of the tread rubber layer (a tread rubber layer consisting of the surface-side tread rubber layer 7c and the inner tread rubber layer 7b) is the maximum dimension among the thicknesses of the tread rubber layer at each point on the surface of the surface-side tread rubber layer 7c.

[0138] In the tire meridian cross section of Figure 1, at least a portion of the inner tread rubber layer 7b of the tire 1 is located at a location that is radially outward of the groove bottom 26a (the groove bottom of the groove 26 that is radially inward of the tire) that is radially inward of the tire. [Example]

[0139] The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

[0140] The various chemicals used in the examples and comparative examples will be explained below. NR:RSS#3 BR: Ubepol BR150B manufactured by Ube Industries, Ltd. (high cis BR synthesized using a Co-based catalyst, cis content 95% by mass or more) Carbon black: Cabot Japan's Show Black N220 (N2SA112m 2 / g) Silica: Uratosil VN3 (N2SA175m) manufactured by Evonik Degussa 2 / g) Silane coupling agent: Si69 manufactured by Evonik Degussa Water-soluble particle 1: MN-00 (magnesium sulfate, median particle size: 75 μm) manufactured by Mai Chemical Industry Co., Ltd. Water-soluble particle 2: USN-00 (ultrafine magnesium sulfate, median particle size: 3 μm) manufactured by Mai Chemical Industry Co., Ltd. Water-soluble particles 3: Sodium lignosulfonate (median particle size: 10 μm) manufactured by Nippon Paper Industries Co., Ltd. Oil: NH-60 manufactured by Idemitsu Kosan Co., Ltd. Resin 1: Sylvatraxx 4150 (β-pinene resin, softening point 70-80°C) manufactured by Arizona Chemical Company Resin 2: Sylvatraxx 4401 (copolymer of α-methylstyrene and styrene, softening point 85°C) manufactured by Arizona Chemical Company Resin 3: YS Resin TO125 (aromatic modified terpene resin, softening point 125°C) manufactured by Yasuhara Chemical Co., Ltd. Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. Anti-aging agent: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Stearic acid: NOF Corporation's "Tsubaki" stearic acid Zinc oxide: Ginrei R manufactured by Toho Zinc Co., Ltd. Sulfur: HK-200-5 (powdered sulfur containing 5% oil) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccelaer D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0141] <Examples and Comparative Examples> (tire manufacturing) The rubber compositions for the surface tread rubber layer and the inner tread rubber layer shown in Table 1 were kneaded in a Banbury mixer to obtain the respective kneaded products. The resulting unvulcanized rubber compositions were molded into the shapes of the surface tread rubber layer and the inner tread rubber layer, which were then laminated together with other tire components on a tire building machine and press-vulcanized at 150°C for 30 minutes to obtain test tires (tire size 195 / 65R15).

[0142] The test tires were subjected to the following evaluations, and the results are shown in Table 1.

[0143] <Grip performance on ice after wear> After buffing the test tires, tires that had been driven 12,000 km were mounted on the tires, and braking performance (stopping distance on ice) was measured by applying the lock brakes at 30 km / h to stop the vehicle on ice. The stopping distance was expressed as an index using the following formula, with the new Comparative Example 1 being set at 100. The higher the index, the better the grip performance on ice after wear. (Ice grip performance index) = (Stopping distance when new for Comparative Example 1) / (Stopping distance after wear for each formulation) × 100

[0144] [Table 1]

[0145] Table 1 reveals that a tire having a surface tread rubber layer and an inner tread rubber layer, both of which contain a water-soluble material, and which satisfies formula (1) above, has excellent grip performance on ice even after wear, and can suppress deterioration of grip performance on ice due to field driving. [Explanation of symbols]

[0146] 1 Passenger car tires 2 Chafer 3 Bead section 4 bead core 5 Bead Apex 6 bands 7 Tread section 7c Surface tread rubber layer 7b Inner tread rubber layer 8 Sidewall 9 Breaker section 10 Carcass 26 Groove 26a groove bottom

Claims

1. A tire comprising a cord layer and a tread rubber layer disposed radially outward of the cord layer, the tread rubber layer has at least a surface side tread rubber layer disposed on a surface side of the tire, and an inner tread rubber layer disposed adjacent to and on the inner side in the tire radial direction of the surface side tread rubber layer, A tire in which the surface side tread rubber layer and the inner tread rubber layer both contain a water-soluble material and satisfy the following formula (1), [Equation 1] A tire in which the thickness of the inner tread rubber layer accounts for 60% or more of the total thickness of the tread rubber layer.

2. A tire comprising a cord layer and a tread rubber layer disposed radially outward of the cord layer, the tread rubber layer has at least a surface side tread rubber layer disposed on a surface side of the tire, and an inner tread rubber layer disposed adjacent to and on the inner side in the tire radial direction of the surface side tread rubber layer, A tire in which the surface side tread rubber layer and the inner tread rubber layer both contain a water-soluble material and satisfy the following formula (1), [Equation 2] A tire that satisfies the following formula (3): [Equation 3]

3. A tire comprising a cord layer and a tread rubber layer disposed radially outward of the cord layer, the tread rubber layer has at least a surface side tread rubber layer disposed on a surface side of the tire, and an inner tread rubber layer disposed adjacent to and on the inner side in the tire radial direction of the surface side tread rubber layer, A tire in which the surface side tread rubber layer and the inner tread rubber layer both contain a water-soluble material and satisfy the following formula (1), [Equation 4] A tire that satisfies the following formula (4): [Equation 5]

4. A tire comprising a cord layer and a tread rubber layer disposed radially outward of the cord layer, the tread rubber layer has at least a surface side tread rubber layer disposed on a surface side of the tire, and an inner tread rubber layer disposed adjacent to and on the inner side in the tire radial direction of the surface side tread rubber layer, A tire in which the surface side tread rubber layer and the inner tread rubber layer both contain a water-soluble material and satisfy the following formula (1), [Equation 6] A tire that satisfies the following formula (5): [Equation 7]

5. A tire comprising a cord layer and a tread rubber layer disposed radially outward of the cord layer, the tread rubber layer has at least a surface side tread rubber layer disposed on a surface side of the tire, and an inner tread rubber layer disposed adjacent to and on the inner side in the tire radial direction of the surface side tread rubber layer, A tire in which the surface side tread rubber layer and the inner tread rubber layer both contain a water-soluble material and satisfy the following formula (1), [Equation 8] A tire that satisfies the following formula (6): [Equation 9]

6. A tire comprising a cord layer and a tread rubber layer disposed radially outward of the cord layer, the tread rubber layer has at least a surface side tread rubber layer disposed on a surface side of the tire, and an inner tread rubber layer disposed adjacent to and on the inner side in the tire radial direction of the surface side tread rubber layer, A tire in which the surface side tread rubber layer and the inner tread rubber layer both contain a water-soluble material and satisfy the following formula (1), [Equation 10] A tire that satisfies the following formula (7): [0011]

7. A tire comprising a cord layer and a tread rubber layer disposed radially outward of the cord layer, the tread rubber layer has at least a surface side tread rubber layer disposed on a surface side of the tire, and an inner tread rubber layer disposed adjacent to and on the inner side in the tire radial direction of the surface side tread rubber layer, A tire in which the surface side tread rubber layer and the inner tread rubber layer both contain a water-soluble material and satisfy the following formula (1), [0012] A tire that satisfies the following formula (8): [0013]

8. A tire comprising a cord layer and a tread rubber layer disposed radially outward of the cord layer, the tread rubber layer has at least a surface side tread rubber layer disposed on a surface side of the tire, and an inner tread rubber layer disposed adjacent to and on the inner side in the tire radial direction of the surface side tread rubber layer, A tire in which the surface side tread rubber layer and the inner tread rubber layer both contain a water-soluble material and satisfy the following formula (1), [0014] A tire that satisfies the following formula (9): [Equation 15]

9. A tire comprising a cord layer and a tread rubber layer disposed radially outward of the cord layer, the tread rubber layer has at least a surface side tread rubber layer disposed on a surface side of the tire, and an inner tread rubber layer disposed adjacent to and on the inner side in the tire radial direction of the surface side tread rubber layer, A tire in which the surface side tread rubber layer and the inner tread rubber layer both contain a water-soluble material and satisfy the following formula (1), [0016] A tire that satisfies the following formula (10): [Equation 17]

10. A tire comprising a cord layer and a tread rubber layer disposed radially outward of the cord layer, the tread rubber layer has at least a surface side tread rubber layer disposed on a surface side of the tire, and an inner tread rubber layer disposed adjacent to and on the inner side in the tire radial direction of the surface side tread rubber layer, A tire in which the surface side tread rubber layer and the inner tread rubber layer both contain a water-soluble material and satisfy the following formula (1), [Equation 18] A tire that satisfies the following formula (11): [Equation 19]

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