Tire

Abstract

A tire is provided that has an improved well-balanced performance of ice and snow performance and dry-land handling stability. The tire includes a vulcanized rubber composition that satisfies formula (I) when sampled radially inward along the inner surface of the tread that is exposed by removing the tread surface with a depth of 3 mm radially inward along the tire: ΔSv ≥ 5%, where ΔSv represents the change rate of the area occupied by the depressions on the inner surface of the tread before and after impregnation under the following conditions: (impregnation conditions) the vulcanized rubber composition is completely immersed in 1000 mL of water maintained at 25°C for 3 hours.

Description

Technical Field

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

[0002] Studded tires and tire chains have been used for driving on snow and ice roads. However, since they may cause environmental problems (such as dust pollution), studless winter tires have been proposed to replace studded tires and tire chains. The materials and structural designs of studless winter tires are aimed at enabling the tires to be used on snow and ice roads that are rougher than ordinary roads. For example, rubber compositions containing diene rubber with excellent low-temperature properties, and rubber compositions containing a large amount of softening agents to enhance the softening effect have been developed (see, for example, Patent Document 1).

[0003] Another method proposed is to introduce foams or vesicles into the tread to form pores in the rubber to improve the performance on ice. However, since pores are also formed inside the tread (for example, in a sponge), the obtained tires have the disadvantage of reduced dry handling stability.

[0004] Therefore, for tires, such as studless winter tires, it is desirable to improve the snow and ice performance while ensuring dry handling stability.

[0005] Citation List

[0006] Patent Document

[0007] Patent Document 1: JP 2009-091482 A Summary of the Invention

[0008] Technical Problem

[0009] In this context, an object of the present invention is to provide an improved tire having a good balance in terms of snow and ice performance and dry handling stability.

[0010] Technical Solution

[0011] The present invention relates to a tire comprising a vulcanized rubber composition which, when sampled radially inwards along the inner surface of the tread exposed by removing the tread surface to a depth of 3 mm radially inwards along the tire, satisfies Equation (I): ΔSv ≥ 5%, where ΔSv represents the rate of change of the area occupied by the depressions on the inner surface of the tread before and after immersion under the following conditions:

[0012] (Immersion Conditions)

[0013] The vulcanized rubber composition is completely immersed in 1000 mL of water maintained at 25°C for 3 hours.

[0014] Preferably, the complex modulus (70°C E*) of the vulcanized rubber composition at 70°C satisfies Equation (II): 70°C E* ≥ 2.5 MPa.

[0015] The vulcanized rubber composition is preferably prepared from a tread rubber composition containing at least one rubber component and at least one water-soluble material.

[0016] Preferably, the tire includes a tread containing the vulcanized rubber composition, and the tread has a groove pattern in contact with the road surface, and the groove pattern is asymmetric in the tire width direction.

[0017] The tire is preferably a studless winter tire.

[0018] Advantages of the present invention

[0019] The tire of the present invention contains a vulcanized rubber composition, and when sampling is taken radially inward along the inner surface of the tread exposed by removing the tread surface with a depth of 3 mm radially inward along the tire, the vulcanized rubber composition satisfies formula (I) for ΔSv, where ΔSv represents the change rate of the area occupied by the depressions on the inner surface of the tread before and after impregnation under the conditions described above. Such a tire provides a balanced improvement in performance on ice and snow roads and dry handling stability. Description of the drawings

[0020] Figure 1 An exemplary schematic diagram showing the sampling of the vulcanized rubber composition (sample) radially inward along the inner surface of the tread exposed by removing the tread surface with a depth of 3 mm radially inward along the tire. Detailed description of the invention

[0021] The tire of the present invention contains a vulcanized rubber composition, and when sampling is taken radially inward along the inner surface of the tread exposed by removing the tread surface with a depth of 3 mm radially inward along the tire, the vulcanized rubber composition satisfies formula (I) for ΔSv, where ΔSv represents the change rate of the area occupied by the depressions on the inner surface of the tread before and after impregnation under the conditions described above.

[0022] In other words, the tire is such that when first removing a rubber composition with a predetermined thickness radially inward from the tread surface of the tire to expose the inner surface of the tread, and sampling from the exposed surface (the vulcanized rubber composition (after vulcanization)), before and after the sample is impregnated in water under predetermined conditions, the area occupied by the depressions on the inner surface of the tread of the sample (the plane formed by the inner surface of the tread of the sample) increases by at least 5%. Such a tire provides a balanced improvement in ice and snow performance and dry handling stability.

[0023] The reason for this beneficial effect is not yet clear, but it is considered to be based on the following reasons.

[0024] For example, when a tire with a dry tread that is traveling on dry ground comes into contact with a low-temperature wet road surface and turns to travel on a wetland, the number of pores formed on the tread surface increases, thereby enhancing the ability to remove the water film on a snowy or icy road, and thus obtaining excellent snow and ice grip performance. On the other hand, the inside of the tread is not affected, so good stiffness is maintained, and there is no reduction in dry handling stability as observed in foam tires where there are always voids inside the tread. Therefore, excellent handling stability is ensured. Therefore, it is considered that a tire that satisfies formula (I) provides improved snow and ice performance while maintaining good dry handling stability, thereby obtaining an improvement with a good balance of these performances.

[0025] The tire contains a vulcanized rubber composition (sample), and when sampling is taken radially inward along the inner surface of the tread exposed by removing the tread surface with a depth of 3 mm radially inward along the tire, the vulcanized rubber composition satisfies formula (I): ΔSv ≥ 5%, where ΔSv represents the rate of change of the area occupied by the depression on the inner surface of the tread after impregnation under the following conditions:

[0026] (Impregnation conditions)

[0027] The vulcanized rubber composition is completely immersed in 1000 mL of water maintained at 25°C for 3 hours.

[0028] ΔSv in formula (I) is obtained as follows: Subtract the area percentage (Svb, area %) of the depression on the inner surface of the tread before impregnation from the area percentage (Sva, area %) of the depression on the inner surface of the tread after impregnation. The "area percentage of the depression on the inner surface of the tread" refers to the percentage (area %) of the depression (pores) based on the area of the inner surface of the tread being 100%.

[0029] From the perspective of snow and ice performance, ΔSv (area %) in formula (I) preferably satisfies ΔSv ≥ 10%, more preferably ΔSv ≥ 20%, still more preferably ΔSv ≥ 30%, and particularly preferably ΔSv ≥ 35%. In addition, the lower limit can be ΔSv ≥ 22% or ΔSv ≥ 36%. There is no limit to the upper limit, but from the perspective of durability and dry handling stability, it is preferably ΔSv ≤ 70%, more preferably ΔSv ≤ 60%, still more preferably ΔSv ≤ 50%. In addition, the upper limit can be ΔSv ≤ 48%.

[0030] From the perspective of snow and ice performance, Sva preferably satisfies Sva ≥ 5%, more preferably Sva ≥ 10%, further preferably Sva ≥ 20%, further preferably Sva ≥ 30%, and particularly preferably Sva ≥ 35%. In addition, the lower limit can be Sva ≥ 22% or Sva ≥ 36%. There is no limit to the upper limit, but from the perspective of durability and dry handling stability, it is preferably Sva ≤ 70%, more preferably Sva ≤ 60%, still more preferably Sva ≤ 50%. In addition, the upper limit can be Sva ≤ 48%.

[0031] There is no limitation on Svb, but it is preferably satisfied that Svb ≤ 3%, more preferably Svb ≤ 1%. There is no limitation on the lower limit of Svb, and Svb can be 0%.

[0032] For ΔSv, Sva, and Svb, for example, a microscope can be used to photograph a predetermined area (e.g., 1 to 25 mm 2 ) on the inner surface of the tread to determine the area (%) occupied by the depression relative to 100% of the predetermined area from the photograph.

[0033] Any method that can appropriately change the area occupied by the depression on the inner surface of the tread before and after impregnation under the above conditions can be used to adjust ΔSv to the relationship of formula (I) or adjust Sva within the above range. For example, when a water-soluble material (such as the water-soluble fine particles described later) is incorporated into the tread rubber composition, a tread inner surface containing the water-soluble material can be formed before impregnation, and a tread inner surface having a depression (hole portion) generated by the dissolution of the water-soluble material can be formed after impregnation. Therefore, for example, adding a water-soluble material to the tread can cause an increase in the percentage of the area occupied by the depression on the inner surface of the tread before and after immersion. Therefore, when using such a tire, a tread surface containing a water-soluble material is provided during dry driving, and a tread surface having a depression generated by the dissolution of the water-soluble material is provided during wet driving. Therefore, during wet driving, the depression formed on the tread surface enhances the ability to remove the water film on snow or ice-covered roads, thereby obtaining excellent ice and snow grip performance, and maintaining good stiffness and excellent handling stability during dry driving.

[0034] The vulcanized rubber composition (sample) can be, for example, a vulcanized rubber composition having dimensions of 10 to 20 mm (length) × 10 to 20 mm (width) × 2 to 4 mm (thickness) (e.g., 15 mm × 15 mm × 3 mm), where the size of the surface on which the inner surface of the tread is formed is 10 to 20 mm × 10 to 20 mm, and the thickness (depth) radially inward of the tire is 2 to 4 mm.

[0035] From the perspective of dry handling stability, the vulcanized rubber composition (before impregnation) preferably has a complex modulus at 70 °C (70 °C E*) that satisfies formula (II): 70 °C E* ≥ 2.5 MPa.

[0036] From the viewpoint of dry handling stability, the complex modulus preferably satisfies E* at 70°C ≥ 3.0 MPa, more preferably E* at 70°C ≥ 3.3 MPa, and particularly preferably E* at 70°C ≥ 3.4 MPa. Further, the complex modulus may satisfy E* at 70°C ≥ 3.5 MPa, E* at 70°C ≥ 3.7 MPa, E* at 70°C ≥ 3.8 MPa, E* at 70°C ≥ 3.9 MPa, E* at 70°C ≥ 4.1 MPa, or E* at 70°C ≥ 4.3 MPa. There is no upper limit, but from the viewpoint of durability, it is preferably E* at 70°C ≤ 10.0 MPa, more preferably E* at 70°C ≤ 8.0 MPa, and still more preferably E* at 70°C ≤ 7.0 MPa. "E* at 70°C" in formula (II) means the dynamic modulus (E*, MPa) determined by viscoelastic measurement at a temperature of 70°C, a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 2%. It can be measured as described in the examples below.

[0037] E* at 70°C can be adjusted to the relationship of formula (II), for example, mainly by changing the type and amount of the rubber component, the type and amount of the reinforcing agent (filler), or the amount of the softening agent. Specifically, E* tends to be enhanced by increasing the amount of the reinforcing agent or decreasing the amount of the softening agent.

[0038] For example, a tire tread including the above-mentioned tread surface and tread inner surface can be prepared from a tread rubber composition containing one or more rubber components and one or more water-soluble materials.

[0039] (Rubber component)

[0040] The rubber component of the rubber composition suitably includes more than one isoprene-based rubber and one or more polybutadiene rubbers.

[0041] Examples of the isoprene-based rubber include natural rubber (NR), polyisoprene rubber (IR), refined NR, modified NR, and modified IR. NR and IR may be those commonly used in the tire industry, such as SIR20, RSS#3, and TSR20 of NR, and IR2200 of IR. Examples of refined NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized polyisoprene rubber, hydrogenated polyisoprene rubber, and grafted polyisoprene rubber. Each of these can be used alone, or two or more of these can be used in combination.

[0042] From the viewpoint of the balance between ice and snow performance and dry ground handling stability, based on 100% by mass of the rubber component, the amount of isoprene rubber is preferably 20% by mass or more, more preferably 30% by mass or more. The upper limit of this amount is not limited, but it is preferably 80% by mass or less, more preferably 60% by mass or less, and further preferably 50% by mass or less.

[0043] Any BR can be used, and examples include those commonly used in the tire industry, such as high-cis BR, BR containing 1,2-syndiotactic polybutadiene crystals (BR containing SPB), polybutadiene rubber synthesized using rare earth catalysts (rare earth-catalyzed BR), and tin-modified polybutadiene rubber obtained by modification with tin compounds (tin-modified BR). BR can be commercially obtained from companies such as Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Zeon Corporation. Each of these can be used alone, or two or more of these can be used in combination.

[0044] The cis content of BR is preferably 80% by mass or more, more preferably 85% by mass or more, further preferably 90% by mass or more, and particularly preferably 95% by mass or more. By using such BR, good ice and snow performance can be obtained.

[0045] In this article, the cis content is determined by infrared absorption spectroscopy.

[0046] From the viewpoint of the balance between ice and snow performance and dry ground handling stability, based on 100% by mass of the rubber component, the amount of BR is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, and particularly preferably 50% by mass or more. The upper limit of this amount is not limited, but it is preferably 90% by mass or less, more preferably 80% by mass or less, and further preferably 70% by mass or less.

[0047] BR can be unmodified or modified BR.

[0048] Modified BR can be, for example, BR having functional groups that interact with fillers such as silica. Examples include chain-end modified BR obtained by modifying at least one chain end of BR with a compound having a functional group (modifying agent) (i.e., chain-end modified BR capped with a functional group); main-chain modified BR having a functional group in the main chain; main-chain and chain-end modified BR having functional groups in both the main chain and the chain ends (e.g., main-chain and chain-end modified BR, where the main chain has a functional group and at least one chain end is modified with a modifying agent); and chain-end modified BR that has been modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule to introduce hydroxyl or epoxy groups.

[0049] Examples of functional groups include amino group, amide group, silyl group, alkoxysilyl group, isocyanate group, imino group, imidazolyl group, ureido group, ether group, carbonyl group, oxycarbonyl group, mercapto group, thioether group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazino group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group, hydroxy group, oxy group and epoxy group. These functional groups may be substituted. Among them, amino group (preferably amino group in which a hydrogen atom is substituted with a C1-C6 alkyl group), alkoxy group (preferably C1-C6 alkoxy group) and alkoxysilyl group (preferably C1-C6 alkoxysilyl group) are preferred.

[0050] The modified BR may suitably be, for example, BR modified with a compound (modifier) represented by the following formula:

[0051]

[0052] wherein R 1 , R 2 and R 3 are the same as or different from each other and each represents an alkyl group, an alkoxy group, a siloxy group, an acetal, a carboxyl group (-COOH) or a mercapto group (-SH) or a derivative thereof; R 4 and R 5 are the same as or different from each other and each represents a hydrogen atom or an alkyl group, and R 4 and R 5 may be linked together with the nitrogen atom to form a ring structure; n represents an integer.

[0053] The BR modified with the compound (modifier) of the above formula may suitably be, for example, a solution-polymerized polybutadiene rubber (BR) having a polymerization terminal (active terminal) modified with the compound of the above formula, etc.

[0054] R 1 , R 2 and R 3 may each suitably be an alkoxy group, preferably a C1-C8 alkoxy group, more preferably a C1-C4 alkoxy group. R 4 and R 5 may each suitably be an alkyl group, preferably a C1-C3 alkyl group. The symbol n is preferably from 1 to 5, more preferably from 2 to 4, still more preferably 3. When R 4 and R 5 are linked together with the nitrogen atom to form a ring structure, the ring structure is preferably a 4- to 8-membered ring. The term "alkoxy group" includes cycloalkoxy groups (e.g., cyclohexyloxy group) and aryloxy groups (e.g., phenoxy group and benzyloxy group).

[0055] Specific examples of the modifier include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane. Among them, preferred are 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropyltriethoxysilane, and 3-diethylaminopropyltrimethoxysilane. Each of these can be used alone, or two or more of these can be used in combination.

[0056] The modified BR can also be appropriately BR modified with any one of the following compounds (modifiers): including, for example, polyglycidyl ethers of polyols such as ethylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenolic groups such as diglycidylated bisphenol A; polyepoxides such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, polyepoxidized liquid polybutadiene; tertiary amines containing epoxy groups such as 4,4'-diglycidyl-diphenylmethanamine and 4,4'-diglycidyl-dibenzylmethanamine; diglycidylamino compounds such as diglycidylaniline, N,N'-diglycidyl-4-glycidylphenoxylamine, diglycidyl-o-toluidine, tetraglycidyl-m-xylenediamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, and tetraglycidyl-1,3-bis(aminomethyl)cyclohexane.

[0057] Acyl chlorides containing amino groups such as bis(1-methylpropyl)carbamoyl chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamoyl chloride, and N,N-diethylcarbamoyl chloride; silane compounds containing epoxy groups such as 1,3-bis(glycidyloxypropyl)-tetramethyldisiloxane and (3-glycidylpropoxy)-pentamethyldisiloxane;

[0058] Silane compounds containing a sulfide group, such as (trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tripropoxysilyl)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;

[0059] N-substituted aziridine compounds, such as ethyleneimine and ethyleneimine; alkoxysilanes, such as methyltriethoxysilane; (thio)benzophenone compounds containing an amino group and / or a substituted amino group, such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-tert-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; benzaldehyde compounds containing an amino group and / or a substituted amino group, such as 4-N,N-dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde, 4-N,N-divinylaminobenzaldehyde; N-substituted pyrrolidones, such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-tert-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-laurolactam, N-vinyl-ω-laurolactam, N-methyl-β-propiolactam, and N-phenyl-β-propiolactam; and

[0060] N,N-bis(2,3-epoxypropoxy)-aniline, 4,4'-methylenebis(N,N-glycidylaniline), tris(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-trione, N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylpropyleneurea, 1,3-divinyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminobenzophenone, 4-N,N-diethylaminobenzophenone, 1,3-bis(diphenylamino)-2-propanone, and 1,7-bis(methylethylamino)-4-heptanone. Among them, preferably, BR modified with an alkoxysilane is used.

[0061] Modification with any compound (modifier) can be carried out by known methods.

[0062] In the rubber composition, based on 100% by mass of the rubber component, the total amount of the isoprene rubber and BR is preferably 30% by mass or more, more preferably 60% by mass or more, still more preferably 80% by mass or more, and particularly preferably 100% by mass. A higher total amount tends to achieve a better balance between ice and snow performance and dry handling stability.

[0063] The rubber composition may contain other rubber components as long as they do not impair the beneficial effects. Examples of such other rubbers include diene rubbers such as styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR).

[0064] (Water-soluble material)

[0065] The water-soluble material can be any material soluble in water, such as water-soluble fine particles. The water-soluble fine particles can be any fine particles soluble in water. Examples include water-soluble materials having at least 1 g / 100 g of water at room temperature (20 °C).

[0066] From the perspective of the balance between ice and snow performance and dry handling stability, the median particle size (median diameter, D50) of the water-soluble fine particles is preferably 1 μm to 1 mm, more preferably 2 μm to 800 μm, still more preferably 2 μm to 500 μm. The lower limit can be 10 μm or more, and the upper limit can be 100 μm or less.

[0067] In this article, the median particle size can be measured by laser diffraction.

[0068] With respect to 100 parts by mass of the rubber component, the amount of the water-soluble material such as water-soluble fine particles is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, still more preferably 15 parts by mass or more, particularly preferably 20 parts by mass or more, and most preferably 25 parts by mass or more. The lower limit may be 30 parts by mass or more. When the amount is not less than the lower limit, good ice and snow performance tends to be obtained. The amount is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, further preferably 50 parts by mass or less, and particularly preferably 40 parts by mass or less. When the amount does not exceed the upper limit, good dry land handling stability tends to be obtained.

[0069] Examples of the water-soluble material (water-soluble fine particles) include water-soluble inorganic salts and water-soluble organic substances. Each of these can be used alone, or two or more of these can be used in combination.

[0070] Examples of the 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 disodium hydrogen phosphate and sodium dihydrogen phosphate.

[0071] Examples of the water-soluble organic substances include lignin derivatives and saccharides.

[0072] Suitable examples of the lignin derivatives include lignosulfonic acid and lignosulfonates. The lignin derivatives can be prepared by the sulfite pulping method or the sulfate pulping method.

[0073] Examples of the lignosulfonates include alkali metal salts, alkaline earth metal salts, ammonium salts, and alkanolamine salts of lignosulfonic acid. Preferred among them are alkali metal salts (such as potassium salts or sodium salts) or alkaline earth metal salts (such as calcium salts, magnesium salts, lithium salts, or barium salts) of lignosulfonic acid.

[0074] The sulfonation degree of the lignin derivatives is preferably 1.5 to 8.0 / OCH 3 . Such lignin derivatives include lignosulfonic acid and / or lignosulfonates, in which lignin and / or its degradation products are at least partially substituted by sulfonic groups (sulfonyl groups). The sulfonic groups of lignosulfonic acid may be un-ionized, or the hydrogen atoms of the sulfonic groups may be replaced by ions such as metal ions. The sulfonation degree is more preferably 3.0 to 6.0 / OCH 3 . When the sulfonation degree is within the above range, good ice and snow performance tends to be obtained, and the balance with dry land handling stability also tends to be improved.

[0075] The sulfonation degree of the lignin derivative particles (lignin derivatives forming particles) refers to the ratio of the introduced sulfonic groups, which is calculated by the following formula:

[0076] Sulfonation degree ( / OCH 3) = (S (mol) in the sulfone group in the lignin derivative) / (methoxy group (mol) of the lignin derivative).

[0077] The saccharides can be any monosaccharide, oligosaccharide or polysaccharide having any number of carbon atoms. Examples of such monosaccharides include trioses such as glyceraldehyde and dihydroxyacetone; tetroses 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 such oligosaccharides include disaccharides such as sucrose and lactose; trisaccharides such as raffinose and melezitose; tetrasaccharides such as acarbose and stachyose; and higher oligosaccharides such as xylooligosaccharide and cellooligosaccharide. Examples of such polysaccharides include glycogen, starch (amylose, amylopectin), cellulose, hemicellulose, dextrin and glucan.

[0078] (Silica)

[0079] From the viewpoint of performance balance, the rubber composition preferably contains one or more types of silica as a filler. Examples of silica include dry silica (anhydrous silica) and wet silica (hydrous silica). Among them, wet silica is preferred because it contains a large amount of silanol groups. Commercially available products from Degussa, Rhodia, Tosoh Silicone Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation, etc. can be used. Each of these can be used alone, or two or more of these can be used in combination.

[0080] With respect to 100 parts by mass of the rubber component, the amount of silica is preferably 25 parts by mass or more, more preferably 30 parts by mass or more, further preferably 50 parts by mass or more, further preferably 55 parts by mass or more, and particularly preferably 60 parts by mass or more. When the amount is not less than the lower limit, good grip performance and good handling stability tend to be obtained. The upper limit of the amount is not limited, but it is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, further preferably 170 parts by mass or less, particularly preferably 100 parts by mass or less, and most preferably 80 parts by mass or less. When the amount does not exceed the upper limit, good dispersibility tends to be obtained.

[0081] The nitrogen adsorption specific surface area (N 2 SA) of silica is preferably 70 m 2 / g or more, more preferably 140 m 2 / g or more, and further preferably 160 m 2 / g or more. N 2When the SA is not lower than the lower limit, it tends to obtain good grip performance and good tensile strength at break. The N of the silica 2 There is no limit to the upper limit of SA, but it is preferably 500 m 2 / g or less, more preferably 300 m 2 / g or less, and even more preferably 250 m 2 / g or less. N 2 When the SA is not higher than the upper limit, it tends to obtain good dispersibility.

[0082] The N of the silica 2 The SA is measured by the BET method in accordance with ASTM D3037-93.

[0083] From the perspective of the balance between ice and snow performance and dry land handling stability, based on the total amount of silica and carbon black in the rubber composition being 100% by mass, the percentage of silica is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0084] (Silane coupling agent)

[0085] The rubber composition containing silica preferably further contains one or more silane coupling agents.

[0086] Any silane coupling agent can be used, examples including: sulfide-based silane coupling agents such as 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 and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane and NXT and NXT-Z available from Momentive; vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silane coupling agents such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercially available products from companies such as Degussa, Momentive, Shin-Etsu Chemical Co., Ltd., Tokyo Chemical Industry Co., Ltd., AZmax Co., Ltd., Dow Corning Toray Co., Ltd. etc. can be used. Each of these can be used alone, or two or more of these can be used in combination.

[0087] With respect to 100 parts by mass of silica, the amount of the silane coupling agent is preferably 3 parts by mass or more, more preferably 6 parts by mass or more. When the amount is 3 parts by mass or more, good properties such as tensile strength at break tend to be obtained. The amount is also preferably 20 parts by mass or less, more preferably 15 parts by mass or less. When the amount is 20 parts by mass or less, an effect commensurate with the amount tends to be obtained.

[0088] (Carbon black)

[0089] From the viewpoint of performance balance, the rubber composition preferably contains one or more types of carbon black as a filler. Any carbon black can be used, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products obtainable from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nippon Carbon Co., Ltd., Columbian Carbon Co., Ltd., etc. can be used. Each of these can be used alone, or two or more of these can be used in combination.

[0090] With respect to 100 parts by mass of the rubber component, the amount of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more. When the amount is not less than the lower limit, it tends to obtain good ice and snow performance and good dry land handling stability. The amount is also preferably 10 parts by mass or less, more preferably 7 parts by mass or less. When the amount is not higher than the upper limit, the rubber composition tends to provide good processability.

[0091] The nitrogen adsorption specific surface area (N 2 SA) of the carbon black is preferably 50 m 2 / g or more, more preferably 80 m 2 / g or more, further preferably 100 m 2 / g or more. When N 2 SA is not less than the lower limit, it is easy to obtain good ice and snow performance and dry land handling stability. N 2 SA is also preferably 200 m 2 / g or less, more preferably 150 m 2 / g or less, still more preferably 130 m 2 / g or less. When N 2 SA does not exceed the upper limit, the carbon black tends to provide good dispersibility.

[0092] The nitrogen adsorption specific surface area of the carbon black is measured according to JIS K6217-2:2001.

[0093] From the viewpoint of the balance between ice and snow performance and dry land handling stability, with respect to 100 parts by mass of the rubber component, the total amount of silica and carbon black is preferably 50 to 120 parts by mass. The total amount is more preferably 55 parts by mass or more, further preferably 60 parts by mass or more, and preferably 100 parts by mass or less, further preferably 80 parts by mass or less.

[0094] (Liquid plasticizer)

[0095] From the viewpoints of ice and snow performance and dry land handling stability, the rubber composition suitably contains one or more liquid plasticizers.

[0096] With respect to 100 parts by mass of the rubber component, the amount of the liquid plasticizer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 15 parts by mass or more. The upper limit is not limited, but from the perspective of properties such as dry ground handling stability, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and further preferably 30 parts by mass or less.

[0097] The liquid plasticizer can be any plasticizer that is liquid at 25°C. Examples include oils, liquid resins, and liquid diene polymers. Each of these can be used alone, or two or more of these can be used in combination.

[0098] Examples of oils include processing oils and vegetable oils, and mixtures thereof. Examples of processing oils include paraffin processing oils, aromatic processing oils, and naphthenic processing oils. Examples of vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice 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 from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Nippon Energy Corporation, Olisoy, H&R, Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., etc. can be used. Among them, processing oils are preferred.

[0099] Examples of liquid resins include resins that are liquid at 25°C, such as terpene resins (including terpene phenol resins and aromatic modified terpene resins), rosin resins, styrene resins, C5 resins, C5 / C9 resins, coumarone-indene resins (including resins based only on coumarone or indene), olefin resins, polyurethane resins, and acrylic resins.

[0100] Examples of liquid diene polymers include diene polymers that are liquid at 25°C, such as liquid styrene-butadiene copolymers (liquid SBR), liquid polybutadiene polymers (liquid BR), liquid polyisoprene polymers (liquid IR), liquid styrene-isoprene copolymers (liquid SIR), liquid styrene-butadiene-styrene block copolymers (liquid SBS block polymers), and liquid styrene-isoprene-styrene block copolymers (liquid SIS block polymers). The chain ends or main chains of these polymers can be modified with polar groups.

[0101] (Resin)

[0102] The rubber composition may contain one or more resins (solid resins: resins that are solid at room temperature (25 °C)). Resins (solid resins) with a softening point of 60 °C or higher are preferred. The softening point is more preferably 70 °C or higher, still more preferably 80 °C or higher, preferably 150 °C or lower, more preferably 140 °C or lower, and still more preferably 130 °C or lower.

[0103] In this text, the softening point of the resin is measured using a ring and ball softening point measuring device in accordance with JIS K 6220-1:2001 and is defined as the temperature at which the ball drops.

[0104] Examples of the resin (solid resin) 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 from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemical Co., Ltd., BASF, Arizona Chemical Co., Ltd., Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., JX Nippon Oil & Energy Corporation, Arakawa Chemical Industries, Ltd., Tago Chemical Industry Co., Ltd., Toagosei Co., Ltd., etc. can be used. Each of these can be used alone, or two or more of these can be used in combination. Among them, aromatic vinyl polymers, coumarone-indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, and terpene resins are preferred, and among them, aromatic vinyl polymers, coumarone-indene resins, terpene resins, and rosin resins are more preferred.

[0105] The term "aromatic vinyl polymer" refers to a resin produced by polymerizing α-methylstyrene and / or styrene. Examples include styrene homopolymers (styrene resins), α-methylstyrene homopolymers (α-methylstyrene resins), copolymers of α-methylstyrene and styrene, and copolymers of styrene and other monomers.

[0106] The term "coumarone-indene resin" refers to a resin containing coumarone and indene as the main monomer components forming the resin skeleton (main chain). Examples of monomer components that can be included in the skeleton in addition to coumarone and indene include styrene, α-methylstyrene, methyl indene, and vinyl toluene.

[0107] The term "coumarone resin" refers to a resin containing coumarone as the main monomer component constituting the resin skeleton (main chain).

[0108] The term "indene resin" refers to a resin containing indene as the main monomer component constituting the resin skeleton (main chain).

[0109] Examples of phenolic resins include those prepared by reacting phenol with aldehydes such as formaldehyde, acetaldehyde or furfural using an acid or base catalyst. Among them, those prepared by reaction using an acid catalyst (e.g., novolak-type phenolic resins) are preferred.

[0110] Examples of rosin resins include rosin-based resins, such as typical natural rosin, polymerized rosin, modified rosin and their esterified compounds, as well as their hydrogenated products.

[0111] Examples of petroleum resins include C5 resins, C9 resins, C5 / C9 resins and dicyclopentadiene (DCPD) resins.

[0112] Examples of terpene resins include polyterpene resins prepared by polymerizing terpene compounds, and aromatic-modified terpene resins prepared by polymerizing terpene compounds and aromatic compounds. Hydrogenated products of the above resins can also be used.

[0113] The term "polyterpene resin" refers to a resin prepared by polymerizing terpene compounds. The term "terpene compound" refers to a hydrocarbon or its oxygen-containing derivative having a composition represented by (C 5 H 8 ) n , each having a terpene backbone and classified as, for example, monoterpene (C 10 H 16 ), sesquiterpene (C 15 H 24 ) or diterpene (C 20 H 32 ). Examples of such terpene compounds include α-pinene, β-pinene, dipentene, limonene, myrcene, allo-ocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol and γ-terpineol.

[0114] Examples of polyterpene resins include resins made from the above terpene compounds, such as pinene resin, limonene resin, dipentene resin and pinene-limonene resin, among which pinene resin is preferred. Depending on the proportion of each component in the resin, pinene resin (which usually contains two isomers, α-pinene and β-pinene) is divided into β-pinene resin mainly composed of β-pinene and α-pinene resin mainly composed of α-pinene.

[0115] Examples of the aromatic-modified terpene resins include terpene phenol resins made from the above terpene compounds and phenolic compounds, and terpene styrene resins made from the above terpene compounds and styrene compounds. Terpene phenol styrene resins made from terpene compounds, phenolic compounds, and styrene compounds can also be used. Examples of the phenolic compounds include phenol, bisphenol A, cresol, and xylenol. Examples of the styrene compounds include styrene and α-methylstyrene.

[0116] Examples of the acrylic resins include styrene acrylic resins, such as carboxyl-containing styrene acrylic resins prepared by copolymerization of an aromatic vinyl monomer component and an acrylic monomer component. In particular, solvent-free, carboxyl-containing styrene acrylic resins are applicable.

[0117] The solvent-free, carboxyl-containing styrene acrylic resin can be a (meth)acrylic resin (polymer) synthesized by high-temperature continuous polymerization (high-temperature continuous bulk polymerization, such as U.S. Patent No. 4,414,370, JP S59-6207 A, JP H5-58005B, JP H1-313522 A, U.S. Patent No. 5,010,166, and the annual research report TREND 2000, Volume 3, pages 42-45 published by Toagosei Co., Ltd.), and without using or using the minimum amount of auxiliary raw materials, such as polymerization initiators, chain transfer agents, and organic solvents. Herein, the term “(meth)acrylic acid” refers to methacrylic acid and acrylic acid.

[0118] Examples of the acrylic monomer component of the acrylic resin include (meth)acrylic acid and (meth)acrylic acid derivatives, such as (meth)acrylates (e.g., alkyl esters, aryl esters, and aralkyl esters, such as 2-ethylhexyl acrylate), (meth)acrylamides, and (meth)acrylamide derivatives. The term “(meth)acrylic acid” is a general term for acrylic acid and methacrylic acid.

[0119] Examples of the aromatic vinyl monomer component of the acrylic resin include aromatic vinyls, such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene.

[0120] In addition to (meth)acrylic acid or (meth)acrylic acid derivatives and aromatic vinyls, other monomer components can also be used as the monomer components of the acrylic resin.

[0121] From the perspective of the balance among low-temperature ice performance, high-temperature ice performance, and wet grip performance, the resin is preferably at least one selected from C5 resin, C9 resin, limonene resin, α-pinene resin, β-pinene resin, terpene phenol resin, DCPD resin, styrene resin, α-methylstyrene resin, coumarone resin, indene resin, phenolic resin, and rosin resin. From the perspective of anti-snow adhesion performance, limonene resin, α-pinene resin, β-pinene resin, terpene phenolic resin, and DCPD resin are particularly preferred.

[0122] From the perspective of the balance between ice and snow performance and dry handling stability, relative to 100 parts by mass of the rubber component, the amount of the resin is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 15 parts by mass or more. There is no limit to the upper limit, but it is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 25 parts by mass or less.

[0123] (Other materials)

[0124] From the perspectives of properties such as crack resistance and ozone resistance, the rubber composition preferably contains one or more antioxidants.

[0125] Any antioxidant can be used. Examples of antioxidants include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine, 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine-based antioxidants such as N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine; quinoline-based antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer; monophenol-based antioxidants such as 2,6-di-tert-butyl-4-methylphenol, styrenated phenol; and bisphenol-based antioxidants, triphenol-based antioxidants, or polyphenol-based antioxidants such as tetrakis[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane. Among them, p-phenylenediamine-based or quinoline-based antioxidants are preferred, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine or 2,2,4-trimethyl-1,2-dihydroquinoline polymer is more preferred. Products commercially available from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexsys, etc. can be used.

[0126] Relative to 100 parts by mass of the rubber component, the amount of the antioxidant is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more. When the amount is not less than the lower limit, sufficient ozone resistance tends to be obtained. The amount is preferably 7.0 parts by mass or less, more preferably 4.0 parts by mass or less. When the amount does not exceed the upper limit, a good tire appearance tends to be obtained.

[0127] The rubber composition preferably contains one or more types of stearic acid. From the perspective of performance balance, the amount of stearic acid is preferably 0.5 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, relative to 100 parts by mass of the rubber component.

[0128] The stearic acid can be a conventional stearic acid, for example, stearic acid obtainable from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Corporation, or Chiba Fatty Acid Co., Ltd.

[0129] The rubber composition preferably contains one or more types of zinc oxide. From the perspective of performance balance, the amount of zinc oxide is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, relative to 100 parts by mass of the rubber component.

[0130] The zinc oxide can be a conventional zinc oxide, for example, zinc oxide obtainable from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Shirakawa Technology Co., Ltd., Shoindo Chemical Industry Co., Ltd., or KAI Chemical Industry Co., Ltd.

[0131] The rubber composition may contain one or more waxes. The amount of wax is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, relative to 100 parts by mass of the rubber component.

[0132] Any wax can be used, and examples include petroleum waxes, natural waxes, and synthetic waxes prepared by purifying or chemically treating various waxes. Each of these waxes can be used alone, or two or more of these can be used in combination.

[0133] Examples of petroleum waxes include paraffin wax and microcrystalline wax. Natural waxes can be any wax from non-petroleum resources, and examples include vegetable waxes such as candelilla wax, carnauba wax, Japanese wax, rice wax, and jojoba wax; animal waxes such as beeswax, lanolin, and spermaceti; mineral waxes such as ozokerite, ceresin, and petrolatum; and purified products of the above. Products commercially available from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. can be used. The amount of wax can be appropriately selected according to ozone resistance and cost.

[0134] The rubber composition preferably contains one or more types of sulfur to moderately crosslink the polymer chains, thereby imparting well-balanced properties.

[0135] The amount of sulfur is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, still more preferably 0.7 part by mass or more, relative to 100 parts by mass of the rubber component. The amount is preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, still more preferably 3.0 parts by mass or less. When the amount is within the above range, a good balance of properties tends to be obtained.

[0136] Examples of sulfur include those commonly used in the rubber industry, such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, and soluble sulfur. Commercially available products from companies such as Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Corporation, Flexsys, Nippon Karyu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. Each of these can be used alone, or two or more of these can be used in combination.

[0137] The rubber composition preferably contains one or more vulcanization accelerators.

[0138] The amount of the vulcanization accelerator is not limited and can be arbitrarily set according to the desired curing rate or crosslink density. Relative to 100 parts by mass of the rubber component, the amount of the vulcanization accelerator is usually 0.3 to 10 parts by mass, preferably 0.5 to 7 parts by mass.

[0139] Any type of vulcanization accelerator can be used, including those commonly used. Examples of vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazole disulfide, and N-cyclohexyl-2-benzothiazole sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), tetra(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; guanidine-based vulcanization accelerators such as diphenylguanidine, di-o-tolylguanidine, and o-tolylbiguanide. Each of these can be used alone, or two or more of these can be used in combination. Among them, from the perspective of performance balance, sulfenamide-based vulcanization accelerators or guanidine-based vulcanization accelerators are preferred.

[0140] In addition to the above components, the rubber composition can appropriately contain compounding agents or materials commonly used in the tire industry, such as mold release agents.

[0141] The rubber composition can be prepared by known methods. For example, it can be prepared by kneading the respective components using a rubber kneader (e.g., an open mill or a Banbury mixer), and then vulcanizing the kneaded mixture.

[0142] The kneading conditions are as follows. In the basic kneading step of kneading additives other than vulcanizing agents and vulcanization accelerators, the kneading temperature is generally 50 to 200 °C, preferably 80 to 190 °C, and the kneading time is generally 30 seconds to 30 minutes, preferably 1 minute to 30 minutes. In the final kneading step of kneading vulcanizing agents and vulcanization accelerators, the kneading temperature is generally 100 °C or lower, preferably room temperature to 80 °C. The composition obtained after kneading vulcanizing agents and vulcanization accelerators is generally vulcanized (e.g., pressure vulcanization). The vulcanization temperature is generally 120 to 200 °C, preferably 140 to 180 °C.

[0143] The rubber composition can be applied to a tire tread, particularly to the tread (single-layer tread, or the tread running surface of a multi-layer tread) of a studless winter tire, the road surface contact area of which has a large number of drainage micro-grooves (tire grooves) each having a depth and width of about 100 μm.

[0144] (Tire)

[0145] The tire of the present invention can be produced from the above rubber composition by a conventional method. Specifically, the unvulcanized rubber composition containing the above components can be extruded into the shape of a tread (e.g., the tread running surface), and assembled with other tire components in a conventional manner in a tire building machine to form an unvulcanized tire, which can then be heated and pressurized in a vulcanizer to produce a tire. Such a tire is suitable for use as a studless winter tire for passenger cars.

[0146] The tread pattern of the tire is preferably a groove pattern (asymmetric pattern) that is asymmetric in the tire width direction to contact the road surface. The asymmetric pattern, i.e., a tread pattern that is asymmetric about the equatorial plane, will be mounted on the vehicle in a specified direction. Examples of the asymmetric pattern include a pattern having a negative ratio difference between the inner and outer sides in the vehicle mounting direction, and a pattern configured to have a different number of circumferential grooves therebetween.

[0147] A known method for improving the handling stability of a tire is to form an asymmetric tire tread pattern in the tread width direction to partially increase the stiffness of the tread blocks, thereby improving the handling stability during steering. However, on an icy road surface, due to the poor friction between the road surface and the rubber, the expected effect cannot be obtained. In the present invention, for example, water-soluble fine particles can be included in the tread rubber so that the water-soluble fine particles dissolve in the water on the road surface during driving to satisfy formula (I) and increase the area occupied by the surface depressions. Therefore, even on an icy road surface, the surface area of the tread portion can be increased to ensure sufficient friction, thereby reducing the sliding between the road and the rubber. The steering response can also be enhanced by the effect of the asymmetric pattern.

[0148] Examples

[0149] The present invention will be specifically described with reference to the exemplary embodiments, but the present invention is not limited to the embodiments.

[0150] The chemicals used in the examples and comparative examples are listed below.

[0151] Natural rubber (NR): RSS#3

[0152] Polybutadiene rubber (BR): BR150B (cis content: 95% by mass or more), from Ube Industries, Ltd.

[0153] Carbon black: Seast N220 (N 2 SA: 114m 2 / g), from Mitsubishi Chemical Corporation

[0154] Silica: Ultrasil VN3 (N 2 SA: 172m 2 / g), from Evonik Degussa

[0155] Silane coupling agent: Si266, from Evonik Degussa

[0156] Water-soluble fine particle 1: Sodium lignosulfonate (median particle diameter (median size): 10 μm), from Nippon Paper Industries Co., Ltd.

[0157] Water-soluble fine particle 2: Potassium sulfate (median particle diameter (median size): 100 μm), from Ueno Fine Chemical Industry Co., Ltd.

[0158] Water-soluble fine particle 3: MN-00 (magnesium sulfate, median particle diameter (median size): 75 μm), from Magaseika Kogyo Co., Ltd.

[0159] Water-soluble fine particle 4: USN-00 (ultrafine magnesium sulfate, median particle diameter (median size): 3 μm), from Magaseika Kogyo Co., Ltd.

[0160] Water-soluble fine particle 5: Sodium lignosulfonate (median particle diameter (median size): 100 μm), from Tokyo Chemical Industry Co., Ltd.

[0161] Water-soluble fine particle 6: MG-OK (magnesium sulfate), from Ako Kasei Co., Ltd.

[0162] Water-soluble fine particle 7: KSO (potassium sulfate), from Ueno Fine Chemical Industry Co., Ltd.

[0163] Wax: Ozoace wax, from Nippon Seiro Co., Ltd.

[0164] Antioxidant: NOCRAC 6C, from Ouchi Shinko Chemical Industrial Co., Ltd.

[0165] Oil: PS-32 (mineral oil), from Idemitsu Kosan Co., Ltd.

[0166] Stearic acid: Kiri, from NOF Corporation

[0167] Zinc oxide: Zinc oxide #2, from Mitsui Mining & Smelting Co., Ltd.

[0168] Sulfur: Powdered sulfur, from Tsurumi Chemical Industry Co., Ltd.

[0169] Vulcanization accelerator: NOCCELER NS, from Ouchi Shinko Chemical Industry Co., Ltd.

[0170] [Measurement of median particle diameter (median size) of water-soluble particles]

[0171] The median particle diameter was measured by laser diffraction using SALD-2000J of Shimadzu Corporation (using the following measurement method).

[0172] <Measurement procedure>

[0173] At room temperature, water-soluble particles were dispersed in a solution mixture of a dispersion solvent (toluene) and a dispersant (a 10 mass% solution of sodium bis(2-ethylhexyl)sulfosuccinate in toluene). The dispersion was stirred for five minutes under ultrasonic irradiation to prepare a test solution. The test solution was transferred to a batch cell and measured one minute later (refractive index: 1.70 - 0.20i).

[0174] <Examples and Comparative Examples>

[0175] Using the formulations shown in each table, natural rubber and silica, and polybutadiene rubber and silica were charged into a 1.7 L Banbury mixer. After each addition, they were kneaded at 150 °C for three minutes to obtain a kneaded mixture (masterbatch). Materials other than sulfur and vulcanization accelerator were added to the masterbatch and kneaded at 150 °C for 2 minutes to obtain a kneaded product. Then, sulfur and vulcanization accelerator were added and kneaded using a two-roll mill at 80 °C for 5 minutes to obtain an unvulcanized rubber composition.

[0176] The unvulcanized rubber compositions prepared as above were respectively formed into the shape of a tread running surface and assembled with other tire components, and then vulcanized at 170 °C for 15 minutes to prepare studless winter tires for testing (tire size: 195 / 65R15).

[0177] The studless winter tires for testing prepared as above were evaluated as described below. The table shows the results. It should be noted that Comparative Examples 1-1 and 2-1 were used as the comparative standards in Tables 1 and 2, respectively.

[0178] Samples (the size of the vulcanized rubber composition (after vulcanization) is 15 mm × 15 mm × 3 mm) as Figure 1Sampling was carried out as shown below. First, the inner surface of the tread (3 mm × 3 mm = 9 mm 2 ) of the sample (before impregnation) was photographed using a microscope (Leica DMS1000). Using this photograph, the area (mm 2 ) occupied by the depressions on the inner surface of the tread was measured to calculate the percentage (Svb, %) of the area occupied by the depressions on the inner surface of the tread before impregnation.

[0179] Subsequently, the sample (before impregnation) was completely immersed in 1000 mL of water maintained at 25°C for 3 hours.

[0180] After impregnation, the specimen was taken out and dried, and the inner surface of the tread (3 mm × 3 mm = 9 mm 2 ) of the specimen (after impregnation) was also photographed using a microscope. Using this photograph, the area (mm 2 ) occupied by the depressions on the inner surface of the tread was measured to calculate the percentage (Sva, %) of the area occupied by the depressions on the inner surface of the tread after impregnation.

[0181] Then, the change rate (ΔSv, %) of the area occupied by the depressions on the inner surface of the tread before and after the impregnation conditions was calculated using Sva (%) and Svb (%).

[0182] <Viscoelasticity test>

[0183] The dynamic modulus (70°C E*, MPa) of the sample (vulcanized rubber composition (after vulcanization)) sampled as shown below was measured using a viscoelastic spectrometer VES (Iwamoto Seisakusho Co., Ltd.). The measurement conditions were a temperature of 70°C, a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 2%. Figure 1 <Ice performance>

[0184] The ice vehicle performance of the studless winter tires for testing of each formulation example was evaluated under the following conditions. The test site was the Sumitomo Rubber Industries, Ltd. Nayoro Tire Test Field in Hokkaido, Japan. The air temperature was -5 to 0°C. A set of test tires was installed on a front-engine, rear-wheel drive car made in Japan with a displacement of 2000 cc. The distance required for the car traveling on ice to stop after braking at a speed of 30 km / h was measured and expressed as an index relative to the standard comparative example using the following formula. The higher the index, the better the ice and snow performance.

[0185] (Ice grip performance) = (Braking stop distance of the standard comparative example) / (Stop distance of each formulation example) × 100

[0186] (Ice handling stability) = (Braking stop distance of the standard comparative example) / (Stop distance of each formulation example) × 100

[0187] <Ice handling stability>

[0188] A set of test studless winter tires was installed on a front-engine, rear-wheel-drive car with a displacement of 2,000 cc made in Japan. A test driver drove the car on an icy road at a speed of 15 km / h. Then, the driver compared and evaluated the stability of the steering control. The results were expressed as an index relative to a standard comparison example. The higher the index, the better the grip performance stability (ice handling stability) on the icy road surface.

[0189] <Dry handling stability>

[0190] A set of test studless winter tires was installed on a front-engine, rear-wheel-drive car with a displacement of 2,000 cc made in Japan. A test driver drove the car on a dry asphalt test track for 10 laps. Then, the test driver compared and evaluated the stability of the steering control during the best lap time and the last lap. The results were expressed as an index relative to a standard comparison example. The higher the index, the better the grip performance stability (dry handling stability) on the dry road surface.

[0191] [Table 1]

[0192]

[0193]

[0194] [Table 2]

[0195]

[0196] As shown in the table, the embodiments with the area change rate (ΔSv) of the recesses on the inner surface of the tread satisfying the relationship of formula (I) exhibited improved ice and snow performance while maintaining good dry handling stability, thus significantly improving the balance of these characteristics. They also achieved good handling stability on ice and snow. In addition, it was also demonstrated that compared with tires having a symmetric tread pattern, tires having an asymmetric tread pattern had better comprehensive performance in terms of ice and snow performance and dry handling stability (the sum of the ice performance and dry handling stability indices) and in terms of ice and snow performance, dry handling stability, and handling stability on ice and snow (the sum of the ice performance, dry handling stability, and ice handling stability indices).

Claims

1. A tire, wherein, the tire comprises a vulcanized rubber composition which satisfies formula (I): ΔSv≥5% when sampling radially inwards along the inner surface of the tread exposed by removing the tread surface with a depth of 3 mm radially inwards along the tire, where ΔSv represents the change rate of the area occupied by the depressions on the inner surface of the tread before and after impregnation under the following conditions, the tire has a tread comprising a vulcanized rubber composition, and the tread has a groove pattern in contact with the road surface, and the groove pattern is asymmetric in the tire width direction: (Impregnation conditions) Completely immerse the vulcanized rubber composition in 1000 mL of water maintained at 25 °C for 3 hours; the vulcanized rubber composition is prepared from a tread rubber composition which comprises at least one rubber component and at least one water-soluble material; The amount of the liquid plasticizer is 15 to 30 parts by mass relative to 100 parts by mass of the rubber component.

2. The tire according to claim 1, wherein, the complex modulus (70 °C E*) of the vulcanized rubber composition at 70 °C satisfies formula (II): 70 °C E*≥2.5 MPa.

3. The tire according to claim 1 or 2, wherein, the tire is a studless winter tire.

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