Rubber composition for tires and tires

Abstract

To provide a tire rubber composition that achieves general improvement in on-ice performance and wear resistance, and a tire including the same.SOLUTION: A tire rubber composition has a rubber component, and water-soluble particles. The water-soluble particles satisfy the following formula (1) and have a particle size distribution including two or more peaks. D50<50 μm (1) (in the formula (1), D50 is a median particle size of the water-soluble particles).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition for a tire and a tire using the same. [Background technology]

[0002] Studded tires and tire chains have been used for driving on snowy and icy roads, but these pose environmental problems such as dust, so studless tires have been proposed as an alternative. Studless tires are used on snowy and icy roads, which have greater road surface irregularities than ordinary roads, so they have been designed with various materials and designs in mind, and rubber compositions have been developed that contain diene rubber, which has excellent low-temperature properties, and rubber compositions that contain a large amount of softener to enhance the softening effect (see Patent Document 1, etc.).

[0003] For example, increasing the amount of butadiene rubber is one way to improve the performance of studless tires on ice, but if the amount is increased too much, the mobility in the rubber increases, causing various chemicals to bloom, so there is a limit to how much butadiene rubber can be added.Furthermore, if the amount of butadiene rubber is increased, the proportion of natural rubber decreases, which causes the rubber to lose strength and deteriorates its wear resistance.

[0004] Other methods have been proposed, such as adding fillers such as zinc oxide whiskers (see Patent Document 2) and adding short fibers (see Patent Document 3), but there are concerns that this reduces abrasion resistance, and these methods are not sufficient for improving on-ice performance, leaving room for improvement. Thus, there is a need to improve on-ice performance while maintaining good abrasion resistance, thereby improving the overall performance of these two. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-091482 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-53977 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-249619 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide a rubber composition for tires that improves the overall performance of on-ice performance and abrasion resistance, and a tire using the same. [Means for solving the problem]

[0007] The present invention provides a rubber composition comprising a rubber component and water-soluble particles, The water-soluble particles relate to a rubber composition for a tire, which satisfies the following formula (1) and has a particle size distribution with two or more peaks: D50<50μm (1) (In formula (1), D50 represents the median particle size of the water-soluble particles.)

[0008] The particle size distribution preferably has peaks at least at particle diameters of less than 50 μm and 50 μm or more.

[0009] The content of the water-soluble particles is preferably 1 to 40 parts by mass based on 100 parts by mass of the rubber component.

[0010] The particle size distribution preferably has a peak at least at a particle diameter of 1 μm or more and less than 50 μm.

[0011] The particle size distribution preferably has a peak at least in the particle diameter range of 50 μm to 130 μm.

[0012] It is preferable that the content Ci (parts by mass) of the isoprene-based rubber and the content Cb (parts by mass) of the butadiene rubber relative to 100 parts by mass of the rubber component satisfy the following formula (2). |Ci-Cb|≦20 parts by mass (2)

[0013] The blending ratio of the water-soluble particles to the resin is preferably 30 / 70 to 95 / 5.

[0014] The present invention also relates to a tire having a tread made using the rubber composition. The tire is preferably a winter tire. [Effects of the Invention]

[0015] The present invention provides a rubber composition for tires, which comprises a rubber component and water-soluble particles, and the water-soluble particles satisfy formula (1) and have a particle size distribution with two or more peaks, thereby improving the overall performance of on-ice performance and abrasion resistance. DETAILED DESCRIPTION OF THE INVENTION

[0016] The rubber composition for a tire of the present invention contains a rubber component and water-soluble particles, and the water-soluble particles have a particle size distribution that satisfies the formula (1) and has two or more peaks, thereby improving the overall performance of on-ice performance and abrasion resistance.

[0017] The mechanism by which such an effect is obtained is not clear, but is presumed to be as follows. The use of water-soluble particles with a small D50 that satisfies formula (1) increases the edge volume of voids formed when the water-soluble particles dissolve in water on the road surface, enhancing the edge effect and water film removal effect. This improves robustness on ice and significantly improves ice performance (ice grip performance). Furthermore, the use of water-soluble particles with a small median particle size that satisfies formula (1) reduces the likelihood of water-soluble particles becoming the starting point for fracture, suppressing a decrease in abrasion resistance. Additionally, the use of water-soluble particles with a particle size distribution with two or more peaks improves ice performance on icy roads over a wide temperature range, from low to high. Therefore, it is inferred that the use of water-soluble particles with a particle size distribution that satisfies formula (1) and has two or more peaks improves ice performance while maintaining good abrasion resistance, significantly improving overall performance.

[0018] As described above, the present invention solves the problem (objective) of improving the overall performance of on-ice performance and abrasion resistance by configuring a rubber composition for a tire containing water-soluble particles that satisfy D50<50 μm and have a particle size distribution with two or more peaks. In other words, the characteristics of D50<50 μm and a particle size distribution with two or more peaks do not define the problem (objective); the object of the present application is to improve the overall performance of on-ice performance and abrasion resistance, and a composition that satisfies these characteristics is used as a means to achieve this.

[0019] (rubber component) The rubber component usable in the rubber composition is 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 overall performance on ice and abrasion resistance.

[0020] From the viewpoint of overall performance such as performance on ice and abrasion resistance, the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more. 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.

[0021] 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.

[0022] 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.

[0023] From the viewpoint of overall performance such as ice performance and abrasion resistance, the content of BR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] For example, a BR modified with a compound (modifying agent) represented by the following formula can be suitably used as the modified BR.

[0028] [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.

[0029] 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).

[0030] 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.

[0031] 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;

[0032] 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;

[0033] 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;

[0034] 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

[0035] 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.

[0036] 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.

[0037] In the rubber composition, from the viewpoint of overall performance such as ice performance and abrasion resistance, it is preferable that the content Ci (parts by mass) of isoprene-based rubber and the content Cb (parts by mass) of butadiene rubber per 100 parts by mass of the rubber component satisfy the following formula (2): |Ci-Cb|≦20 parts by mass (2) Here, |Ci-Cb|≦18 parts by mass is more preferable, and |Ci-Cb|≦15 parts by mass is even more preferable.

[0038] From the viewpoint of overall performance such as performance on ice and abrasion resistance, the total content of the isoprene-based rubber and BR in 100% by mass of the rubber component 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.

[0039] (water soluble particles) The water-soluble particles are not particularly limited as long as they are particles that are soluble in water, and for example, materials with a solubility in water at room temperature (20° C.) of 1 g / 100 g water or more can be used.

[0040] The water-soluble particles satisfy the following formula (1), that is, have a D50 (median particle size) of less than 50 μm. D50<50μm (1) (In formula (1), D50 represents the median particle size of the water-soluble particles.)

[0041] The D50 (median particle size, median diameter) of the water-soluble particles is preferably 45 μm or less, more preferably 40 μm or less, and even more preferably 35 μm or less, from the viewpoint of on-ice performance and abrasion resistance. On the other hand, although there is no particular lower limit for the D50, from the viewpoint of the overall performance of on-ice performance and abrasion resistance, it is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more.

[0042] The water-soluble particles have a particle size distribution with two or more peaks (peak tops). The number of peaks in the particle size distribution is not particularly limited as long as it has two or more peaks, and examples include cases with 2 to 10 peaks, 2 to 5 peaks, and 2 to 3 peaks.

[0043] The particle size distribution of the water-soluble particles may have two or more peaks, but preferably has at least one peak (peak top) in the region where particle diameters are less than 50 μm and another peak (peak top) in the region where particle diameters are 50 μm or more. The presence of a peak in the region where particle diameters are less than 50 μm increases the number of edges when voids are formed, improving performance on high-temperature road surfaces with a large amount of water film, while the presence of a peak in the region where particle diameters are 50 μm or more increases the flexibility of the rubber surface and increases the contact area, tending to improve ice performance at low temperatures. Therefore, the presence of these two peaks tends to achieve both ice performance on low-temperature icy road surfaces and ice performance on high-temperature icy road surfaces.

[0044] From the viewpoint of ice performance on high-temperature icy road surfaces, the peak (peak top) in the region of particle diameter less than 50 μm is preferably a peak with a particle diameter of 1 μm or more and less than 50 μm, more preferably a peak with a particle diameter of 1 μm or more and 40 μm or less, and even more preferably a peak with a particle diameter of 3 μm or more and 25 μm or less.

[0045] From the viewpoint of ice performance on low-temperature icy road surfaces, the peak (peak top) in the region of particle diameters of 50 μm or more is preferably a peak of particle diameters of 50 μm or more and 130 μm or less, more preferably a peak of particle diameters of 80 μm or more and 120 μm or less, and even more preferably a peak of particle diameters of 85 μm or more and 115 μm or less.

[0046] The particle size distribution of the water-soluble particles has two or more peaks (peak tops). From the viewpoint of achieving both low-temperature and high-temperature ice performance, it is preferable for the two or more peaks (peak tops) to have a particle size difference of 10 μm or more, more preferably 50 μm or more, and even more preferably 70 μm or more. There is no upper limit to the particle size difference, but it is preferable for the two or more peaks (peak tops) to be 300 μm or less, more preferably 200 μm or less, and even more preferably 130 μm or more. For example, if the particle size distribution has two peaks with particle sizes of 10 μm and 100 μm, it will have two peaks with a particle size difference of 90 μm (= 100 μm - 10 μm). When the particle size distribution has three peaks with particle diameters of 10 μm, 100 μm, and 200 μm, and when the particle size differences are three peaks of 90 μm (= 100 μm - 10 μm), 100 μm (= 200 μm - 100 μm), and 190 μm (= 200 μm - 10 μm), and when at least one of the peaks has a particle size difference of 10 μm or more, good ice performance can be achieved on both low-temperature icy roads and high-temperature icy roads.

[0047] In this specification, the particle size distribution (particle size distribution curve) is measured using a laser diffraction method, and the presence of two or more peaks (peak tops) can be confirmed from the obtained particle size distribution curve. Furthermore, D50 (median particle size) is the particle size at 50% of the cumulative mass value on the particle size distribution curve obtained by particle size distribution measurement using a laser diffraction method. These can be specifically measured by the method described in the Examples below.

[0048] Water-soluble particles that satisfy formula (1) and have a particle size distribution with two or more peaks can be produced, for example, by (i) a method using water-soluble particles themselves that satisfy formula (1) and have a particle size distribution with two or more peaks, or (ii) a method using a mixture of water-soluble particles A with a D50 of less than 50 μm and water-soluble particles B with a D50 of 50 μm or more (for example, a method using a mixture of water-soluble particles A with a D50 of 1 μm≦D50≦40 μm and water-soluble particles B with a D50 of 80 μm≦D50≦120 μm).

[0049] From the viewpoint of performance on ice and abrasion resistance, the aspect ratio of the water-soluble particles is preferably 1:1 to 25, more preferably 1:1 to 20, even more preferably 1:1 to 15, even more preferably 1:1 to 10, even more preferably 1:1 to 5, and particularly preferably 1:1 to 2.5. In this specification, the aspect ratio can be measured by observation using a transmission electron microscope.

[0050] The content of water-soluble particles (total amount of water-soluble particles) is preferably 1 part by mass or more, more preferably 5 parts by mass or more, even 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. By setting the content at or above the lower limit, the amount of components contributing to the edge effect increases, and good performance on ice tends to be obtained. The content is preferably 60 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less. By setting the content at or below the upper limit, good rubber physical properties such as breaking strength and abrasion resistance tend to be obtained.

[0051] In a rubber composition, when a mixture of water-soluble particles A having a D50 of less than 50 μm (for example, water-soluble particles having a D50 of 1 μm or more and 40 μm or less) and water-soluble particles B having a D50 of 50 μm or more (for example, water-soluble particles having a D50 of 80 μm or more and 120 μm or less) is blended into the rubber composition as water-soluble particles, the blending ratio of the water-soluble particles A and the water-soluble particles B (the content (parts by mass) of A relative to 100 parts by mass of the rubber component in the rubber composition / the content (parts by mass) of B relative to 100 parts by mass of the rubber component in the rubber composition) is preferably 20 / 80 to 90 / 10, more preferably 40 / 60 to 80 / 20, and even more preferably 45 / 55 to 70 / 30, from the viewpoint of overall performance on ice and abrasion resistance.

[0052] Examples of water-soluble particles include water-soluble inorganic salts and water-soluble organic substances. Among these, water-soluble inorganic salts are preferred from the viewpoint of overall performance on ice and abrasion resistance. These water-soluble particles may be used alone or in combination of two or more.

[0053] 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, phosphates such as sodium hydrogen phosphate and sodium dihydrogen phosphate, etc. Among these, from the viewpoint of overall performance on ice and abrasion resistance, metal sulfates are preferred, and magnesium sulfate is more preferred.

[0054] 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.

[0055] 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.

[0056] The lignin derivative preferably has a sulfonation degree 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.

[0057] 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

[0058] 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.

[0059] (silica) From the viewpoint of the overall performance, the rubber composition preferably contains silica as a filler. Examples of silica include dry process silica (anhydrous silica) and wet process silica (hydrated silica). Of these, wet process silica is preferred because it has a large number of silanol groups. Commercially available products include those from Evonik Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan, and Tokuyama Corporation. These may be used alone or in combination of two or more.

[0060] In the rubber composition, the compounding ratio of the water-soluble particles and the filler (content of water-soluble particles (parts by mass) / content of filler (parts by mass (total amount of filler)) is preferably 5 / 95 to 50 / 50, more preferably 15 / 85 to 40 / 60, and even more preferably 20 / 80 to 35 / 65, from the viewpoint of the overall performance on ice and abrasion resistance.

[0061] The silica content is preferably 25 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 60 parts by mass or more, per 100 parts by mass of the rubber component. By making the content above the lower limit, good abrasion resistance tends to be obtained. The upper limit of the content is not particularly limited, but is preferably 300 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 100 parts by mass or less. By making the content below the upper limit, good dispersibility tends to be obtained.

[0062] 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 more than the lower limit, good abrasion resistance and breaking strength tend to 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.

[0063] In the rubber composition, the compounding ratio of the water-soluble particles and silica (content of water-soluble particles (parts by mass) / content of silica (parts by mass)) is preferably 5 / 95 to 50 / 50, more preferably 15 / 85 to 40 / 60, and even more preferably 20 / 80 to 35 / 65, from the viewpoint of overall performance on ice and abrasion resistance.

[0064] In the rubber composition, the silica content relative to the total content of silica and carbon black (100% by mass) is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, from the viewpoint of overall performance on ice and abrasion resistance.

[0065] (Silane coupling agent) When the rubber composition contains silica, it is preferable that the rubber composition further contains 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.

[0066] 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.

[0067] (carbon black) From the viewpoint of the overall performance, the rubber composition preferably contains carbon black as a filler. 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.

[0068] The carbon black content is preferably 1 part by mass or more, more preferably 3 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, good abrasion resistance, ice performance (ice grip performance), etc. tend to be obtained. Furthermore, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less. By making the content equal to or less than the upper limit, good processability of the rubber composition tends to be obtained.

[0069] 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.

[0070] In the rubber composition, the total content of silica and carbon black is preferably 50 to 120 parts by mass per 100 parts by mass of the rubber component, from the viewpoint of overall performance on ice and abrasion resistance. The lower limit is more preferably 55 parts by mass or more, and even more preferably 60 parts by mass or more. The upper limit is more preferably 100 parts by mass or less, and even more preferably 80 parts by mass or less.

[0071] (liquid plasticizer) The rubber composition may include a liquid plasticizer. The liquid plasticizer is not particularly limited as long as it is a plasticizer that is in a liquid state at 20° C., 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] The content of the liquid plasticizer (total amount of liquid plasticizer) per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, from the viewpoint of performance on ice and abrasion resistance. The upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less, from the viewpoint of overall performance on ice and abrasion resistance.

[0076] The rubber composition may contain a resin, which is in a solid state at room temperature (25°C).

[0077] 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., JXTG Nippon Oil & 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.

[0078] 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.

[0079] 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.

[0080] A coumarone resin is a resin that contains coumarone as the main monomer component that constitutes the skeleton (main chain) of the resin.

[0081] Indene resin is a resin that contains indene as the main monomer component that constitutes the skeleton (main chain) of the resin.

[0082] 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.

[0083] Examples of rosin resins include rosin-based resins such as natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

[0084] Examples of petroleum resins include C5 resins, C9 resins, C5 / C9 resins, and dicyclopentadiene (DCPD) resins.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] Examples of aromatic vinyl monomer components constituting the acrylic resin include aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene.

[0093] 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.

[0094] In the rubber composition, the compounding ratio of the water-soluble particles and the resin (content of water-soluble particles (parts by mass) / content of resin (parts by mass)) is preferably 30 / 70 to 95 / 5, more preferably 40 / 60 to 90 / 10, and even more preferably 45 / 55 to 90 / 10, from the viewpoint of the overall performance on ice and abrasion resistance.

[0095] In the rubber composition, the total content of the resin and liquid plasticizer (total amount of the resin and liquid plasticizer) is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more per 100 parts by mass of the rubber component from the viewpoint of performance on ice. The upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less from the viewpoint of overall performance on ice and abrasion resistance.

[0096] In the rubber composition, the compounding ratio (content of water-soluble particles (parts by mass) / total amount of resin and liquid plasticizer (parts by mass)) of the water-soluble particles to the total content of resin and liquid plasticizer (total amount of resin and liquid plasticizer) is preferably 10 / 90 to 70 / 30, more preferably 15 / 85 to 60 / 40, and even more preferably 20 / 80 to 50 / 50, from the viewpoint of overall performance on ice and abrasion resistance.

[0097] (Other materials) The rubber composition preferably contains an antioxidant from the viewpoints of crack resistance, ozone resistance, and the like.

[0098] 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 Co., Ltd., and Flexis.

[0099] 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 setting the content at or above 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 setting the content at or below the upper limit, a good tire appearance tends to be obtained.

[0100] The rubber composition preferably contains stearic acid. From the viewpoint of the overall performance, 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.

[0101] 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.

[0102] The rubber composition preferably contains zinc oxide. From the viewpoint of the overall performance, 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.

[0103] 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.

[0104] Wax may be blended into the rubber composition. From the viewpoint of the overall performance, the content of 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.

[0105] 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.

[0106] It is preferable to compound sulfur into the rubber composition in order to form an appropriate amount of crosslinked chains in the polymer chains and to impart the above-mentioned good overall performance.

[0107] The sulfur content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.7 parts by mass or more, per 100 parts by mass of the rubber component. The content 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. By keeping the content within the above range, good overall performance tends to be obtained.

[0108] 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.

[0109] The rubber composition preferably contains 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.

[0110] 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.

[0111] In addition to the above components, the rubber composition may contain compounding agents generally used in the tire industry, such as materials such as a mold release agent, as appropriate.

[0112] The rubber composition can be produced by any known method, for example, by kneading the above-mentioned components using a rubber kneading device such as an open roll or a Banbury mixer, followed by vulcanization.

[0113] 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.

[0114] The rubber composition can be suitably used for various tire components such as a sidewall, a base tread, a bead apex, a clinch apex, an inner liner, an undertread, a breaker topping, a ply topping, and a tread (such as a single-layer tread or a cap tread of a multi-layer tread), and is particularly suitable for a tread.

[0115] (tire) The tire is manufactured by a conventional method using the above-mentioned rubber composition. That is, the rubber composition containing the various components is extruded in an unvulcanized state to match the shape of the various components (such as the tread), and then 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.

[0116] 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. [Example]

[0117] The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

[0118] The various chemicals used in the examples and comparative examples will be explained below. NR:RSS#3 BR: Ube Industries BR150B (Cis 95% or more by mass) Carbon black: Seast N220 (N2SA114m) manufactured by Mitsubishi Chemical Corporation 2 / g) Silica: Uratosil VN3 (N2SA172m) manufactured by Evonik Degussa 2 / g) Silane coupling agent: Si266 manufactured by Evonik Degussa Water-soluble particles A1: MN-00 manufactured by Mai Chemical Industry Co., Ltd. was sieved appropriately (magnesium sulfate, D50 (median particle size) 10 μm) Water-soluble particles A2: MN-00 manufactured by Mai Chemical Industry Co., Ltd. was sieved appropriately (magnesium sulfate, D50 (median particle size) 30 μm) Water-soluble particle A3: Sodium lignosulfonate (D50 (median particle size) 10 μm) manufactured by Tokyo Chemical Industry Co., Ltd. Water-soluble particles B1: MN-00 manufactured by Mai Chemical Industry Co., Ltd., sieved appropriately (magnesium sulfate, D50 (median particle size) 100 μm) Water-soluble particles B2: MN-00 manufactured by Mai Chemical Industry Co., Ltd., sieved appropriately (magnesium sulfate, D50 (median particle size) 110 μm) Water-soluble particles B3: MN-00 manufactured by Mai Chemical Industry Co., Ltd. was sieved appropriately (magnesium sulfate, D50 (median particle size) 200 μm) Wax: Ozoace wax manufactured by Nippon Seiro Co., Ltd. Anti-aging agent: Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Oil: Idemitsu Kosan PS-32 (paraffin-based process oil) Resin 1: Polyterpene resin (YS Resin PX1250 manufactured by Yasuhara Chemical Co., Ltd.) Resin 2: Dicyclopentadiene resin (DCPD resin) ("Quinton 1325" manufactured by Zeon Corporation) Stearic acid: Tsubaki (NOF Corporation) Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator: Noccela NS manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0119] [Measurement of water-soluble particle size distribution (particle diameter distribution) and D50 (median particle size, median diameter)] For the water-soluble particles (mixtures, etc.) used in each example and comparative example, a particle size distribution curve was obtained by laser diffraction (measurement procedure is as follows) using a SALD-2000J model manufactured by Shimadzu Corporation, and each peak (each peak top (μm)) in the curve was confirmed, and further, the particle size at 50% of the cumulative mass value of the particle size distribution curve (D50 (μm)) was measured. The results are shown in each table. <Measurement operation> Water-soluble particles were dispersed in a mixed solution of a dispersion solvent (toluene) and a dispersant (a 10% by mass solution of sodium di-2-ethylhexyl sulfosuccinate in toluene) at room temperature, and the resulting dispersion was stirred for 5 minutes while irradiating it with ultrasonic waves to obtain a test solution. The test solution was transferred to a batch cell and measured after 1 minute. (Refractive index: 1.70-0.20i)

[0120] <Examples and Comparative Examples> According to the formulations shown in each table, NR and silica, and BR and silica were added using a 1.7 L Banbury mixer, and each was mixed at 150°C for 3 minutes to obtain a kneaded product (masterbatch). Next, all materials except sulfur and vulcanization accelerator were added to the resulting masterbatch, and the mixture was mixed at 150°C for 2 minutes to obtain a kneaded product. Furthermore, sulfur and vulcanization accelerator were added, and the mixture was mixed using an open roll at 80°C for 5 minutes to obtain an unvulcanized rubber composition. The resulting unvulcanized rubber composition was press-vulcanized in a 0.5 mm thick mold at 170° C. for 12 minutes to obtain a vulcanized rubber composition.

[0121] Each of the unvulcanized rubber compositions obtained was molded into the shape of a cap tread, and the resulting mixture was laminated together with other tire components and vulcanized at 170°C for 15 minutes to produce a winter test tire (tire size: 195 / 65R15).

[0122] The vulcanized rubber compositions and winter test tires obtained were stored in a dark place at room temperature for three months, and then the following evaluations were carried out. The results are shown in the tables. The reference comparative examples in Tables 1 and 2 are Comparative Examples 1-1 and 2-1, respectively.

[0123] <Ice performance> Using winter test tires, actual vehicle performance on ice was evaluated under the following conditions. Testing was conducted at Sumitomo Rubber Industries, Ltd.'s Nayoro Test Course in Hokkaido, with evaluations conducted at temperatures of -1°C (high-temperature ice performance) and -5°C (low-temperature ice performance). The test tires were then mounted on a domestically produced 2000cc FR vehicle, and the stopping distance on ice required to stop the vehicle by applying the lock brakes at 30 km / h was measured. The stopping distance of the reference comparative example was set to 100, and the calculation was performed using the following formula. The higher the index, the better the ice performance. (Ice performance) = (braking stopping distance of standard comparison example) / (stopping distance of each formulation) × 100

[0124] <Wear resistance> The abrasion loss of the vulcanized rubber composition was measured using a Lambourn abrasion tester manufactured by Iwamoto Seisakusho Co., Ltd. under conditions of a surface rotation speed of 50 m / min, an applied load of 3.0 kg, a sand dropping rate of 15 g / min, and a slip ratio of 20%, and the reciprocal of the abrasion loss was calculated. The reciprocal of the abrasion loss of the reference comparative example was set to 100, and the reciprocal of the abrasion loss of each formulation was expressed as an index. A higher index indicates better abrasion resistance.

[0125] <Overall performance> The overall performance of ice performance (-1°C), ice performance (-5°C) and abrasion resistance was evaluated as the sum of ice performance (-1°C, index), ice performance (-5°C, index) and abrasion resistance (index).

[0126] [Table 1]

[0127] [Table 2]

[0128] From each table, it can be seen that in the examples containing a rubber component and water-soluble particles that satisfy formula (1) and have a particle size distribution with two or more peaks, the overall performance of ice performance (-1°C), ice performance (-5°C), and abrasion resistance was improved.

Claims

1. The rubber composition includes a rubber component and water-soluble particles, The water-soluble particles satisfy the following formula (1) and have a particle size distribution with two or more peaks: the particle size distribution has peaks at least in the particle diameter range of 1 μm or more and less than 50 μm and 50 μm or more and 130 μm or less, The rubber composition for tires has a content of the water-soluble particles of 1 to 40 parts by mass per 100 parts by mass of the rubber component. D50<50μm (1) (In formula (1), D50 represents the median particle size of the water-soluble particles.)

2. 2. The rubber composition for tires according to claim 1, wherein the content Ci (parts by mass) of the isoprene-based rubber and the content Cb (parts by mass) of the butadiene rubber per 100 parts by mass of the rubber component satisfy the following formula (2): |Ci-Cb|≦20 parts by mass (2)

3. 3. The rubber composition for tires according to claim 1, wherein a blending ratio of the water-soluble particles and the resin (content of water-soluble particles (parts by mass) / content of resin (parts by mass)) is 30 / 70 to 95 / 5.

4. A tire having a tread made using the rubber composition according to any one of claims 1 to 3.

5. 5. The tire of claim 4, which is a winter tire.

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