tire

Abstract

To provide a tire having improved crack growth resistance of sidewalls while increasing a use ratio of recycled rubber or powder rubber.SOLUTION: A tire includes sidewalls each formed from a rubber composition containing a modified rubber crumb and having elongation at break at 23°C of 500% or more, and satisfies a following formula (1): (cross-section height) / (cross-section width)×100≥50%.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] In recent years, there has been a demand for recycling waste materials from the viewpoints of environmental issues and resource conservation, and this is also being demanded for tires. Waste tires are used for various purposes after undergoing various treatments, such as crushing them into small pieces using a crusher to remove fibers and steel, and then reusing them as rubber powder.

[0003] In particular, so-called material recycling, which is a circulation type in which waste tires are reused as tires, is considered to be very important, and for example, Patent Documents 1 and 2 disclose a method of converting waste tires into recycled rubber and powdered rubber and reusing them as tires. However, recycled rubber and powdered rubber have problems such as high heat generation performance and reduced abrasion resistance, and therefore their usage rate is decreasing year by year, and improvements are desired. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2002-338743 A [Patent Document 2] JP 2005-2140 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above-mentioned current situation, and has an object to provide a tire in which the crack growth resistance of the sidewall is improved while increasing the proportion of recycled rubber and powdered rubber used. [Means for solving the problem]

[0006] The present invention relates to a tire having a sidewall made of a rubber composition that contains modified rubber crumb and has an elongation at break of 500% or more at 23° C., and that satisfies the following formula (1): Section height / section width × 100 ≧ 50% (1)

[0007] The rubber composition preferably contains an isoprene-based rubber and a butadiene rubber. The rubber composition preferably contains 1.4 parts by mass or more of sulfur per 100 parts by mass of the rubber component.

[0008] The rubber composition has a nitrogen adsorption specific surface area of ​​100 to 150 m 2 / g Carbon Black A and nitrogen adsorption specific surface area 10-80m 2 It is preferable that the carbon black B contains 100% by weight of carbon black B.

[0009] The modified rubber crumb is preferably rubber crumb functionalized with a thiuram sulfide compound. It is preferable that the sidewall has a thickness of 1.5 mm or more. Effect of the Invention

[0010] The present invention relates to a tire having a sidewall made of a rubber composition that contains modified rubber crumb and has an elongation at break of 500% or more at 23°C, and that satisfies the above formula (1). Therefore, the crack growth resistance of the sidewall can be improved while increasing the proportion of recycled rubber or powdered rubber used. [Brief description of the drawings]

[0011] [Figure 1] 1 is a tire meridian cross-sectional view showing an example of a pneumatic tire 1 in a normal state according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The tire of the present invention has a sidewall made of a rubber composition that contains modified rubber crumb and has an elongation at break of 500% or more at 23°C, and satisfies the above formula (1). This makes it possible to improve the crack growth resistance of the sidewall while increasing the usage ratio of reclaimed rubber and powdered rubber.

[0013] The mechanism by which such an effect is obtained is not clear, but is presumed to be as follows. Generally, recycled rubber and powdered rubber have a drawback that they are poorly reactive during vulcanization and become the starting point of fracture when rubber is deformed. When they are included, problems such as deterioration of crack growth resistance arise. In contrast, the tire uses modified rubber crumbs and has a sidewall (vulcanized rubber composition) with an elongation at break (EB) of 500% or more. Therefore, it is possible to increase the proportion of recycled rubber or powdered rubber used, impart high rubber strength, and improve crack growth resistance and strength against tensile fracture. Furthermore, since the tire size satisfies formula (1), the strain due to rolling is small, stress concentration is alleviated, and durability such as good crack growth resistance can be imparted. Therefore, it is presumed that by using a tire that contains modified rubber crumbs, has a sidewall with an elongation at break of 500% or more, and satisfies formula (1), it is possible to increase the proportion of recycled rubber or powdered rubber used and improve the crack growth resistance of the sidewall.

[0014] For example, when highly reactive modified rubber crumbs are used as the modified rubber, they are less likely to become the starting point of fracture, the elongation at break is increased, and rubber strength such as crack growth resistance and strength against tensile fracture is significantly improved. Rubber strength such as crack growth resistance and strength against tensile fracture can also be ensured by blending highly reinforcing carbon black as the carbon black. Furthermore, by making a tire satisfying formula (1), stress concentration can be alleviated and durability such as good crack growth resistance can be imparted. Therefore, it is presumed that the tire can improve the crack growth resistance of the sidewall while increasing the proportion of recycled rubber and powdered rubber used.

[0015] In this way, the tire has a sidewall made of a rubber composition containing modified rubber crumbs and having an elongation at break of 500% or more at 23° C., and is configured to satisfy formula (1), thereby solving the problem (objective) of improving the crack growth resistance of the sidewall while increasing the proportion of recycled rubber and powdered rubber used. In other words, the parameters of elongation at break of 500% or more at 23° C. and section height / section width×100≧50% do not define the problem (objective), but the problem of the present application is to improve the crack growth resistance of the sidewall while increasing the proportion of recycled rubber and powdered rubber used, and a configuration that satisfies the parameters is used as a means to achieve this.

[0016] Here, methods for achieving a rubber composition (rubber composition after vulcanization) with an elongation at break of 500% or more at 23°C include (a) a method using highly reactive modified rubber crumb, (b) a method of blending two or more types of rubber with different hardness (for example, a mixed rubber containing isoprene-based rubber, butadiene rubber, etc.), (c) a method of compounding highly reinforcing carbon black, (d) a method of blending two or more types of carbon black with small and large particle sizes, (e) optimizing the vulcanization accelerator ratio, and (f) a method of using a high molecular weight polymer, which may be used alone or in combination as appropriate.

[0017] [Rubber composition (rubber composition after vulcanization)] The rubber composition (rubber composition after vulcanization) constituting the sidewall of the tire has an elongation at break at 23°C (EB(23°C)) of 500% or more. From the viewpoint of rubber strength (crack growth resistance, strength against tensile breakage, etc.), EB(23°C) is preferably 540% or more, more preferably 560% or more, even more preferably 570% or more, and particularly preferably 580% or more. The upper limit of EB(23°C) is not particularly limited, but is preferably 800% or less, more preferably 750% or less, and even more preferably 700% or less, because the broken rubber is appropriately cut from the rubber surface and a good wear appearance is obtained. The EB(23°C) is a value according to JIS K6251, and specifically, can be measured by the method described in the examples described later.

[0018] (Modified rubber crumb) The rubber composition (rubber composition after vulcanization) that constitutes the sidewall contains modified rubber crumb. The modified rubber crumb has its crosslinked structure in the rubber partially broken by devulcanization and functionalization, increasing its reactivity, improving problems such as reduced hardness, worsening heat generation, and increased viscosity of unvulcanized rubber.

[0019] Here, the reclaimed rubber is not particularly limited, and examples thereof include crushed rubber mechanically crushed at room temperature or in a frozen state, devulcanized rubber further devulcanized, recycled rubber from used rubber of automobile tires, tubes and other rubber products as specified in JIS K6313, and reclaimed rubber having properties equivalent thereto. Examples of the "modified rubber crumb" include rubber materials obtained by functionalizing (introducing a modifying compound) reclaimed rubber or vulcanized rubber powder (powdered rubber) that has a functional group capable of acting on unvulcanized diene rubber with a modifying compound.

[0020] As a modifying compound usable for the functionalization treatment, for example, from the viewpoint of elongation at break, crack growth resistance, etc., thiuram sulfide compounds and the like can be preferably used. The modifying compound may be used alone or in combination of two or more. Examples of thiuram sulfide compounds include alkyl thiuram sulfide, aryl thiuram sulfide, heterocyclic thiuram sulfide, thiuram disulfide, thiuram polysulfide, tetrabenzyl thiuram disulfide, tetraalkyl thiuram disulfide, tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, dipentamethyl thiuram monosulfide, etc.

[0021] The content of the modified rubber crumb is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 9 parts by mass or more, based on 100 parts by mass of the rubber component, from the viewpoint of improving the overall performance of low heat buildup, processability, and rubber strength. From the viewpoint of the physical properties of the rubber composition (viscosity, hardness, breaking properties, heat buildup, etc.), the content is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less.

[0022] The rubber composition (rubber composition after vulcanization) may further contain powdered reclaimed rubber. When modified rubber crumbs or reclaimed rubber that has been subjected to devulcanization is used alone, there is a concern that the breaking energy may decrease, but by using powdered reclaimed rubber in combination, the decrease can be suppressed.

[0023] "Powdered regenerated rubber" refers to rubber that has been mechanically pulverized at room temperature or in a frozen state, devulcanized rubber that has been further devulcanized, used rubber from automobile tires, tubes, and other rubber products as specified in JIS K6313, and regenerated rubber with equivalent properties, but which has not been modified by devulcanization or functionalization. By using powdered regenerated rubber and modified rubber crumbs in combination, even rubber compositions containing regenerated rubber tend to have improved processability and vulcanization properties. In the rubber composition, modified rubber crumbs, powdered regenerated rubber, and other regenerated rubbers are materials that do not fall under the category of rubber components.

[0024] The content of the reclaimed rubber powder is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 9 parts by mass or more, per 100 parts by mass of the rubber component, from the viewpoints of elongation at break, crack growth resistance, etc. From the viewpoints of the physical properties of the rubber composition (viscosity, hardness, physical properties at break, heat generation, etc.), the content is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less.

[0025] In addition, for regenerated rubber such as modified rubber crumb and powdered regenerated rubber, products from Lehigh Rubber Co., Ltd., Muraoka Rubber Industry Co., Ltd., Asahi Regenerated Rubber Co., Ltd., etc. can be used.

[0026] (Rubber component) The rubber component usable in the rubber composition is not particularly limited, and rubbers used in the tire field can be used. For example, 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) can be mentioned. Among them, isoprene rubber and BR are preferable. From the viewpoint of crack growth resistance, it is preferable to use a blend of two or more kinds of rubbers having different hardness such as isoprene rubber and BR, and it is more preferable to use isoprene rubber and BR in combination. These rubber components may be used alone or in combination of two or more kinds.

[0027] The content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 25% by mass or more, and even more preferably 40% by mass or more, from the viewpoints of low heat buildup and rubber strength. The upper limit of the content is not particularly limited and may be 100% by mass, but is preferably 90% by mass or less, more preferably 75% by mass or less, and even more preferably 60% by mass or less.

[0028] Examples of isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. NR can be SIR20, RSS♯3, TSR20, and the like, and IR can be IR2200, and the like, which are common in the tire industry. Modified NR can be deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), and the like. Modified NR can be epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, and the like. Modified IR can be epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, and the like. These may be used alone or in combination of two or more.

[0029] When BR is compounded, 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 content is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. By keeping the content within the above range, a sidewall having good rubber properties tends to be obtained.

[0030] The cis content of BR is preferably 80% by mass or more, more preferably 85% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more, from the viewpoint of crack growth resistance, etc. In this specification, the cis content (cis-1,4-bond amount) is a value calculated from the signal intensity measured by infrared absorption spectrum analysis or NMR analysis.

[0031] 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 products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, and the like. These may be used alone or in combination of two or more.

[0032] 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 of the modified BR include terminally modified BR (terminally 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 having a functional group (modifying agent), 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 terminal (for example, main-chain terminal BR having a functional group in the main chain and at least one terminal modified with a modifying agent), and terminally 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.

[0033] 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 imide 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 them, an amino group (preferably an amino group in which a hydrogen atom of an 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.

[0034] For example, the modified BR may be a BR modified with a compound (modifying agent) represented by the following formula:

[0035] [ka] (In the formula, R 1 , R 2 and R 3 R may be the same or different and represents 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 5 R may be the same or different and represents a hydrogen atom or an alkyl group. 4 and R 5 may be bonded to form a ring structure together with the nitrogen atom, and n represents an integer.

[0036] 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 5is 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 further preferably 3. In addition, R 4 and R 5 When the nitrogen atom and the nitrogen atom are bonded to each other to form a ring structure, 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 and a benzyloxy group).

[0037] Specific examples of the compound (modifier) ​​represented by the formula include 2-dimethylaminoethyl trimethoxysilane, 3-dimethylaminopropyl trimethoxysilane, 2-dimethylaminoethyl triethoxysilane, 3-dimethylaminopropyl triethoxysilane, 2-diethylaminoethyl trimethoxysilane, 3-diethylaminopropyl trimethoxysilane, 2-diethylaminoethyl triethoxysilane, 3-diethylaminopropyl triethoxysilane, etc. Among them, 3-dimethylaminopropyl trimethoxysilane, 3-dimethylaminopropyl triethoxysilane, and 3-diethylaminopropyl trimethoxysilane are preferred. These may be used alone or in combination of two or more.

[0038] The modified BR may be 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; diglycidyl amino compounds such as diglycidyl aniline, N,N'-diglycidyl-4-glycidyloxyaniline, diglycidyl orthotoluidine, tetraglycidyl meta-xylylenediamine, tetraglycidyl aminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidyl aminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane;

[0039] 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;

[0040] Sulfide group-containing silane compounds 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;

[0041] 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 others.

[0042] Examples of the BR 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 BR modified with alkoxysilane is preferred.

[0043] As the modified BR modified with the compound (modifier) ​​represented by the above formula, for example, BR modified at the polymerization end (active end) of solution-polymerized butadiene rubber with the compound represented by the above formula is preferably used. The modification with the compound (modifier) ​​can be carried out by a known method.

[0044] (Carbon Black) From the viewpoint of crack growth resistance, it is preferable to compound carbon black in the rubber composition. Carbon black may be used alone or in combination of two or more kinds. As carbon black, products of 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., etc. can be used.

[0045] The carbon black content (total amount of carbon black) is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 35 parts by mass or more, based on 100 parts by mass of the rubber component. By making it equal to or more than the lower limit, sufficient reinforcement tends to be obtained. In addition, the upper limit of the content is not particularly limited, but is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 60 parts by mass or less. By making it equal to or less than the upper limit, good low heat build-up tends to be obtained.

[0046] The carbon black is not particularly limited, but for example, it is preferable to use carbon black having a nitrogen adsorption specific surface area (NSA) of 100 to 150 m 2 / g of carbon black (hereinafter also referred to as carbon black A), with a nitrogen adsorption specific surface area (NSA) of 10 to 80 m 2 / g of carbon black (hereinafter also referred to as carbon black B), etc. can be suitably used.

[0047] Carbon Black A (N2SA100~150m 2 / g of carbon black), the lower limit of the N2SA is set to 105 m from the viewpoint of rubber strength such as crack growth resistance and strength against tensile breakage. 2 / g or more is more preferable, and 110m 2 The upper limit is 140 m / g or more from the viewpoint of dispersibility. 2 / g or less is more preferable, and 130m 2 / g or less is more preferable.

[0048] When carbon black A is compounded, its content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, based on 100 parts by mass of the rubber component. By making it equal to or more than the lower limit, good crack growth resistance, rubber strength such as strength against tensile breakage, etc. tend to be obtained. In addition, the upper limit of the content is not particularly limited, but is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less. By making it equal to or less than the upper limit, good low heat build-up properties tend to be obtained.

[0049] Carbon Black B (N2SA10~80m 2 / g of carbon black), the lower limit of the N2SA is set to 20m from the viewpoint of rubber strength such as crack growth resistance and strength against tensile breakage. 2 / g or more is more preferable, and 30m 2 The upper limit is preferably 60 m / g or more from the viewpoint of dispersibility. 2 / g or less is more preferable, and 50m 2 / g or less is more preferable.

[0050] When carbon black B is compounded, its content is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more, based on 100 parts by mass of the rubber component. By making it equal to or more than the lower limit, good crack growth resistance, rubber strength such as strength against tensile breakage, etc. tend to be obtained. In addition, the upper limit of the content is not particularly limited, but is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 60 parts by mass or less. By making it equal to or less than the upper limit, good low heat build-up properties tend to be obtained.

[0051] (silica) Silica may be compounded in the rubber composition. Examples of silica include dry process silica (anhydrous silica) and wet process silica (hydrated silica). Among them, wet process silica is preferred because it has a large number of silanol groups. Commercially available products include those from Degussa, Rhodia, Tosoh Silica, Solvay Japan, and Tokuyama. These may be used alone or in combination of two or more.

[0052] When silica is compounded, the content thereof is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 60 parts by mass or less.

[0053] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 70 m 2 / g or more, more preferably 140m2 / g or more, more preferably 160m 2 / g or more. There is a warning that a good breaking strength can be obtained by making it above the lower limit. In addition, the upper limit of N2SA of silica is not particularly limited, 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.

[0054] (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-dimethylthiocarbamate, Examples of such silanes include sulfide-based silanes such as bamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silanes such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z; vinyl-based silanes such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silanes such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based silanes such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silanes such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silanes such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercially available products include those manufactured by Degussa, Momentive, Shin-Etsu Silicones, Tokyo Chemical Industry, Azumax, and Dow Corning Toray Co., Ltd. These may be used alone or in combination of two or more.

[0055] The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 6 parts by mass or more, based on 100 parts by mass of silica. If it is above the lower limit, good breaking strength tends 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, the effect corresponding to the amount of the compounding tends to be obtained.

[0056] (Liquid plasticizer) From the viewpoints of low heat generation, processability, and rubber strength, it is preferable to compound a liquid plasticizer in the rubber composition. 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, and liquid diene-based polymer. These may be used alone or in combination of two or more kinds.

[0057] Examples of the oil include process oil, vegetable oil, or a mixture thereof. Examples of the process oil include paraffin-based process oil, aromatic process oil, and naphthenic process oil. Examples of the vegetable oil 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. Examples of commercially available products include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Mill Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and Nisshin Oillio Group Co., Ltd.

[0058] 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.

[0059] 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, liquid farnesene butadiene copolymers, etc., which may be modified at the ends or main chains with polar groups.

[0060] The content of the liquid plasticizer (total amount of the liquid plasticizer) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. By keeping the content within the above range, the overall performance of low heat build-up, processability, and rubber strength tends to be improved.

[0061] (Resin) The rubber composition may contain a resin (solid resin: a resin that is in a solid state at room temperature (25° C.)).

[0062] Examples of resins (solid resins) include aromatic vinyl polymers, coumarone-indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, acrylic resins, etc. 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 Co., Ltd., Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., JXTG Nippon Oil & Energy Co., Ltd., Arakawa Chemical Industries Co., Ltd., Taoka Chemical Co., Ltd., Toagosei Co., Ltd., etc. These may be used alone or in combination of two or more.

[0063] 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.

[0064] Coumarone-indene resin is a resin that contains 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, vinyltoluene, etc.

[0065] A coumarone resin is a resin that contains coumarone as the main monomer component that constitutes the resin skeleton (main chain).

[0066] An indene resin is a resin that contains indene as the main monomer component that constitutes the resin skeleton (main chain).

[0067] 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.

[0068] Examples of rosin resins include rosin-based resins such as natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

[0069] Examples of petroleum resins include C5 resins, C9 resins, C5 / C9 resins, and dicyclopentadiene (DCPD) resins.

[0070] As the terpene resin, a polyterpene resin obtained by polymerizing a terpene compound, an aromatic modified terpene resin obtained by polymerizing a terpene compound and an aromatic compound, etc. can be used. Hydrogenated products of these resins can also be used.

[0071] Polyterpene resin is a resin obtained by polymerizing a terpene compound. The terpene compound is (C5H8) n The hydrocarbons and their oxygen-containing derivatives represented by the composition 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.

[0072] Examples of polyterpene resins include pinene resin, limonene resin, dipentene resin, pinene / limonene resin, etc., which are made from the above-mentioned terpene compounds. Among them, pinene resin is preferred because it is easy to polymerize and is inexpensive because it is made from natural rosin. 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.

[0073] Examples of 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 the above 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.

[0074] As the acrylic resin, a styrene-acrylic resin having a carboxyl group and obtained by copolymerizing an aromatic vinyl monomer component with an acrylic monomer component, such as a styrene-acrylic resin, can be used. Among them, a solvent-free carboxyl group-containing styrene-acrylic resin can be preferably used.

[0075] 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-59-6207, JP-B-5-58005, JP-A-1-313522, U.S. Pat. No. 5,010,166, Toa Gosei Kenkyuu Nenpo TREND 2000 Vol. 3, p. 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 means methacryl and acrylic.

[0076] Examples of acrylic monomer components constituting the acrylic resin 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.

[0077] Examples of aromatic vinyl monomer components constituting the acrylic resin include aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene.

[0078] As a monomer component constituting the acrylic resin, other monomer components may be used in addition to (meth)acrylic acid, a (meth)acrylic acid derivative, and aromatic vinyl.

[0079] The total content of the resin (solid resin) and the liquid plasticizer (total amount of the resin and the liquid plasticizer) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more. The upper limit is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less. By keeping it within the above range, the overall performance of low heat buildup, processability, and rubber strength tends to be improved.

[0080] (Other materials) The rubber composition may contain a compound represented by the following formula (I). The compound strengthens the bond between carbon black and polymer, which tends to improve fracture properties and low heat buildup. In addition, when the reinforcing properties are sufficient, the low heat buildup properties tend to be further improved by reducing the amount of carbon black.

[0081] [ka] (In the formula, R 1 , R 2 are the same or different and each is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, or an alkynyl group having 1 to 20 carbon atoms. M r+ represents a metal ion, and r represents its valence.)

[0082] R 1 , R 2 Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group. R 1 , R 2 Examples of the alkenyl group of R include a vinyl group, an allyl group, a 1-propenyl group, and a 1-methylethenyl group. 1 , R 2 Examples of the alkynyl group include an ethynyl group and a propargyl group.

[0083] R 1 , R 2 is preferably a hydrogen atom or an alkyl group, more preferably a hydrogen atom or a methyl group, and further preferably a hydrogen atom. That is, the compound represented by the above formula (I) is preferably a compound represented by the following formula (I-1), (I-2) or (I-3), and more preferably a compound represented by the following formula (I-1). [ka] [ka] [ka]

[0084] In the above formulas (I), (I-1), (I-2) and (I-3), examples of the metal ion include a sodium ion, a potassium ion and a lithium ion, with a sodium ion being preferred.

[0085] The content of the compound represented by formula (I) is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, based on 100 parts by mass of carbon black. The content is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less. By keeping the content within the above range, the breaking characteristics and low heat generation property tend to be improved.

[0086] From the viewpoints of crack resistance, ozone resistance, and the like, it is preferable to compound an antioxidant in the rubber composition.

[0087] The antiaging agent is not particularly limited, and examples thereof include naphthylamine-based antiaging agents such as phenyl-α-naphthylamine; diphenylamine-based antiaging agents 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, Examples of the antioxidant include p-phenylenediamine antioxidants such as amines; quinoline antioxidants such as polymerized 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, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and polymerized 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. Commercially available products include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis Co., Ltd.

[0088] The content of the antioxidant is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, based on 100 parts by mass of the rubber component. By making the content equal to or more than the lower limit, sufficient ozone resistance tends to be obtained. The content is preferably 7.0 parts by mass or less, more preferably 4.0 parts by mass or less. By making the content equal to or less than the upper limit, good tire appearance tends to be obtained.

[0089] The rubber composition preferably contains stearic acid in an amount of preferably 0.5 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the rubber component.

[0090] As the stearic acid, any known stearic acid can be used, for example, products available from NOF Corporation, NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., and the like.

[0091] The rubber composition preferably contains zinc oxide in an amount of preferably 0.5 to 10.0 parts by mass, and more preferably 1.0 to 5.0 parts by mass, based on 100 parts by mass of the rubber component.

[0092] As the zinc oxide, any known zinc oxide can be used, for example, products available 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.

[0093] The rubber composition may contain wax. The content of the wax is preferably 0.1 to 5.0 parts by mass, and more preferably 0.5 to 3.0 parts by mass, based on 100 parts by mass of the rubber component.

[0094] The wax is not particularly limited, and examples thereof include petroleum wax and natural wax. In addition, synthetic wax obtained by refining or chemically treating a plurality of waxes can also be used. These waxes may be used alone or in combination of two or more kinds. Examples of petroleum wax include paraffin wax and microcrystalline wax. The natural wax is not particularly limited as long as it is derived from a resource other than petroleum, and examples thereof include vegetable waxes such as candelilla wax, carnauba wax, Japan wax, rice wax, and jojoba wax; animal waxes such as beeswax, lanolin, and spermaceti; mineral waxes such as ozokerite, ceresin, and petrolactam; and refined products thereof. Examples of commercially available products include products from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Chemical Co., Ltd. The wax content may be appropriately set in terms of ozone resistance and cost.

[0095] It is preferable to compound sulfur in the rubber composition, in order to form an appropriate amount of crosslinked chains in the polymer chains and to impart physical properties such as good crack growth resistance.

[0096] From the viewpoint of physical properties such as crack growth resistance, the sulfur content is preferably 1.2 parts by mass or more, more preferably 1.4 parts by mass or more, even more preferably 1.6 parts by mass or more, and particularly preferably 1.8 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit of the content is not particularly limited, but 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.

[0097] 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 kinds.

[0098] 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 from the viewpoint of improving the overall performance of low heat buildup, processability, and rubber strength, it is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.6 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 3.0 parts by mass or less, more preferably 1.6 parts by mass or less, and even more preferably 1.3 parts by mass or less.

[0099] The type of vulcanization accelerator is not particularly limited, and commonly used ones 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, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-orthotolyl guanidine, and orthotolyl biguanidine. These may be used alone or in combination of two or more. Among them, sulfenamide vulcanization accelerators and guanidine vulcanization accelerators are preferred.

[0100] 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.

[0101] 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.

[0102] As for the kneading conditions, in the base kneading step in which additives other than the vulcanizing agent and the 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 the 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 the 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.

[0103] 〔tire〕 The tire is manufactured by a normal method using the above-mentioned rubber composition. That is, the rubber composition containing each component is extruded in an unvulcanized state to match the shape of the sidewall, and molded together with other tire components in a tire building machine by a normal method to form an unvulcanized tire. The unvulcanized tire is heated and pressurized in the vulcanizer to obtain a tire.

[0104] The tire may be a pneumatic tire, a solid tire, or other airless tire, among which a pneumatic tire is preferred. The tire may be used as a passenger car tire, a large passenger car tire, a large SUV tire, a heavy load tire such as a truck or a bus tire, a light truck tire, a two-wheeled vehicle tire, a high performance tire such as a racing tire, or the like. The tire may also be used as an all-season tire, a summer tire, a winter tire such as a studless tire, or the like.

[0105] The tire satisfies the following formula (1). Section height (H) / section width (W) × 100 ≧ 50% (1) From the viewpoint of mitigating stress concentration and imparting good crack growth resistance, etc., H / W×100≧55% is preferable, and H / W×100≧60% is more preferable. There is no particular upper limit, and it is 100% or less. The cross-sectional height is the distance from the bead base line to the radial outer end of the tire, and the cross-sectional width is the distance between the left and right axial outer ends of the tire, and are represented by H and W in the tire in FIG. 1 described later.

[0106] From the viewpoint of reducing stress concentration and imparting good crack growth resistance, the tire preferably has a sidewall thickness of 1.5 mm or more. The thickness is more preferably 2.0 mm or more, even more preferably 2.3 mm or more, and particularly preferably 2.5 mm or more. There is no particular upper limit, but the thickness is preferably 5.0 mm or less, more preferably 4.7 mm or less, and even more preferably 4.5 mm or less. Note that this is the distance in the tire axial direction from the left and right axial outer ends (sidewall surfaces) of the tire to the carcass cord surface (including the carcass cord covering rubber), and is represented by Wsw in the tire in FIG. 1 described later.

[0107] 1 is a tire meridian cross-sectional view showing an example of a normal pneumatic tire 1 according to the present embodiment. In FIG. 1, the up-down direction is the radial direction of the tire 1, the left-right direction is the axial direction of the tire 1, and the direction perpendicular to the paper surface is the circumferential direction of the tire 1.

[0108] 1, the dashed dotted line CL represents the equatorial plane of the tire 1. The dotted line BBL extending in the axial direction is the bead base line. This bead base line is a line that defines the rim diameter of the rim R (see JATMA, etc.).

[0109] The symbol PE is the intersection point between the outer surface of the tire 1 and the equatorial plane. This intersection point PE is also called the equator. This intersection point PE is also the radially outer end of the tire 1. The double-headed arrow H is the section height of the tire 1 (see JATMA). This section height H is represented by the radial distance from the bead base line to the equator PE (the distance from the bead base line to the radially outer end of the tire 1). The symbol PW is the axially outer end of the tire 1. In other words, this outer end PW is the position on the outer surface of the tire 1 where the tire 1 shows the maximum width in the axial direction. The double-headed arrow W is the section width of the tire 1 (see JATMA). This section width W is represented by the axial distance from one outer end PW to the other outer end PW (the distance between the left and right axially outer ends of the tire 1). The tire 1 satisfies the formula (1) "section height H / section width W×100≧50%".

[0110] In Fig. 1, a tire 1 is mounted on a rim R. This rim R is a regular rim. Air is filled inside the tire 1. As a result, the internal pressure of the tire 1 is adjusted to the regular internal pressure.

[0111] In this specification, unless otherwise specified, the dimensions (dimensions such as section width, section height, sidewall thickness, etc.) and angles of each component of the tire 1 are measured when the tire 1 is mounted on a regular rim and filled with air to achieve a regular internal pressure (also referred to as a regular state). No load is applied to the tire 1 during measurement. In the case of a passenger car tire 1, the dimensions and angles are measured when the internal pressure is 180 kPa.

[0112] A regular rim means a rim specified in the standard on which the tire 1 is based. A "standard rim" in the JATMA standard, a "design rim" in the TRA standard, and a "measuring rim" in the ETRTO standard are regular rims. Regular internal pressure means an internal pressure specified in the standard on which the tire 1 is based. The "maximum air pressure" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are regular internal pressures.

[0113] The tire 1 includes a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and a belt layer 7 disposed on the outside of the carcass 6 in the tire radial direction and in the tread portion 2.

[0114] The carcass 6 is composed of at least one carcass ply 6A, 6B, two in this embodiment. Each carcass ply 6A, 6B has carcass cords (not shown) arranged at an angle of, for example, 75 to 90 degrees with respect to the tire circumferential direction. As the carcass cord, for example, an organic fiber cord such as aromatic polyamide or rayon can be used.

[0115] Each carcass ply 6A, 6B in this embodiment includes a main body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a turned-up portion 6b continuing to the main body portion 6a and turned back from the axially inner side to the outer side around the bead core 5. Between the main body portion 6a and the turned-up portion 6b of each carcass ply 6A, 6B, a bead apex rubber 8 extending from the bead core 5 to the radially outer side of the tire is disposed.

[0116] The belt layer 7 includes at least one belt ply 7A, 7B, in this embodiment, two belt plies. The belt plies 7A, 7B are formed, for example, from an inner belt ply 7A arranged on the carcass 6 side and an outer belt ply 7B arranged on the tire radial direction outer side of the inner belt ply 7A. In each of the belt plies 7A, 7B, belt cords (not shown) are arranged inclined at an angle of preferably 10 to 35 degrees with respect to the tire circumferential direction. The inner belt ply 7A and the outer belt ply 7B in this embodiment are overlapped with the belt cords crossing each other.

[0117] As the belt cord, for example, steel, aromatic polyamide, rayon, etc. can be suitably adopted. Although the belt layer 7 of the present embodiment is composed of two belt plies 7A and 7B, it may be composed of three or more belt plies. In this case, the outer belt ply 7B is the one disposed on the outermost side in the tire radial direction among the multiple belt plies.

[0118] The sidewall 11 of the sidewall portion 3 is located axially outboard of the carcass 6. The thickness Wsw of the sidewall 11 is represented by the distance in the tire axial direction from the outer end PW (sidewall surface) to the surface of the carcass cord (not shown) in the carcass 6 (the distance Wsw in the tire axial direction from the left and right axial outer ends (sidewall surfaces) of the tire to the carcass cord surface). EXAMPLES

[0119] Below is a description of the various chemicals used in the examples and comparisons. NR:TSR20 BR: BR150B (cis content 97% by mass) manufactured by Ube Industries, Ltd. Carbon black (ISAF): Diablack I (N2SA114m) manufactured by Mitsubishi Chemical Corporation 2 / g) Carbon black (FEF): Diablack E (N2SA41m) manufactured by Mitsubishi Chemical Corporation 2 / g) Reclaimed rubber: Lehigh GF-80 REPROCESSED GROUND RUBBER (powdered reclaimed rubber, 80 mesh particle size) Modified rubber crumb: Lehigh's EkoDyne Oil: Diana Process NH-70S (aromatic process oil) manufactured by Idemitsu Kosan Co., Ltd. Wax: Ozoace OZ0355 by Nippon Seiro Co., Ltd. Antioxidant 6C: Nocrac 6C (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Anti-aging agent RD: Nocrac 224 (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: NOF Corporation's "Tsubaki" stearic acid Zinc oxide: Zinc oxide type 2 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Insoluble sulfur containing 10% oil (Seimisulfur manufactured by Nippon Kanretsu Kogyo Co., Ltd. (insoluble sulfur containing 60% or more of insoluble matter due to carbon disulfide, 10% oil content) Vulcanization accelerator NS: Noccela NS (N-tert-butyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0120] The crack growth resistance was calculated assuming that the above-mentioned various chemicals would be used on the sidewalls of various tires according to the respective tables and the following manufacturing and test conditions. The results are shown in the evaluation column of each table.

[0121] (Manufacturing conditions) Using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd., chemicals other than sulfur and vulcanization accelerator are kneaded at 150°C for 4 minutes, then sulfur and vulcanization accelerator are added, and the mixture is kneaded using an open roll at 80°C for 5 minutes, after which an unvulcanized rubber composition is prepared. The unvulcanized rubber composition is then molded into the shape of a sidewall, laminated together with other tire components on a tire building machine, and press-vulcanized for 20 minutes under conditions of 170°C to produce test tires (tire sizes: 215 / 65R17, 215 / 60R17, 215 / 55R17, 215 / 40R17).

[0122] (Test conditions for elongation at break) A vulcanized rubber sheet (rubber composition after vulcanization) is prepared (collected) from the sidewall of the test tire. Next, a No. 3 dumbbell-shaped test piece made of the collected vulcanized rubber sheet (rubber composition after vulcanization) is used to carry out a tensile test at a temperature of 23°C in accordance with JIS K6251:2010 "Vulcanized rubber and thermoplastic rubber - Determination of tensile properties" to measure the elongation at break at 23°C (EB(23°C)). The larger the EB(23°C), the better the strength against tensile break.

[0123] (Test conditions for crack growth resistance test) The test tire buttress portion is cut with a cutter in three places around the circumference, each 5 mm long and 1 mm deep, and the tire is run at 100 km / h under a load of 80% of LIMAX. After a certain distance is run, the average crack growth distance at the three places is measured. The standard comparative example 1 is set to 100, and each test tire is expressed as an index. The higher the index, the better the crack growth resistance.

[0124] [Table 1]

[0125] [Table 2]

[0126] The tire of the embodiment uses modified rubber crumbs and has a sidewall (vulcanized rubber composition) with an elongation at break (EB) of 500% or more, so it is possible to increase the proportion of recycled rubber or powdered rubber used, impart high rubber strength, and improve crack growth resistance and strength against tensile fracture, and further, because the tire size satisfies formula (1), the strain due to rolling is small, stress concentration is alleviated, and durability such as good crack growth resistance can be imparted. Therefore, by using the tire of the embodiment that contains modified rubber crumbs, has a sidewall with an elongation at break of 500% or more, and satisfies formula (1), it is possible to improve the crack growth resistance of the sidewall while increasing the proportion of recycled rubber or powdered rubber used. [Explanation of symbols]

[0127] 1. Pneumatic tires 2 Tread section 3 Sidewall 4 Bead section 5 Bead Core 6. Carcass 6A, 6B Carcass ply 6a Main body 6b Folded part 7 Belt layer 7A, 7B Belt ply 8 Bead apex rubber 11 Sidewall CL Equatorial plane of tire 1 BBL Bead Base Line PE Intersection of the outer surface of tire 1 and the equatorial plane (equator) H Section height of tire 1 PW Axial outer end of tire 1 W Section width of tire 1 Wsw Sidewall 11 Thickness

Claims

1. A rubber composition comprising a rubber component and modified rubber crumb, The content of the modified rubber crumb is 5 to 10 parts by mass based on 100 parts by mass of the rubber component, The tire has a sidewall made of a rubber composition having an elongation at break of 500% or more at 23°C, and A tire that satisfies the following formula (1): Section height / section width × 100 ≧ 50% (1)

2. The tire of claim 1 , wherein the rubber composition comprises an isoprene-based rubber and a butadiene rubber.

3. The tire according to claim 1 or 2, wherein the rubber composition contains 1.4 parts by mass or more of sulfur per 100 parts by mass of the rubber component.

4. The rubber composition has a nitrogen adsorption specific surface area of ​​100 to 150 m ２ / g of carbon black A and a nitrogen adsorption specific surface area of ​​10 to 80 m ２ The tire according to any one of claims 1 to 3, comprising carbon black B in an amount of 0.1 to 0.2 g / g.

5. 5. The tire according to claim 1, wherein the modified rubber crumb is a rubber crumb functionalized with a thiuram sulfide compound.

6. The tire according to any one of claims 1 to 5, wherein the sidewall has a thickness of 1.5 mm or more.

7. The tire according to any one of claims 1 to 6, wherein the rubber composition contains 5 to 80 parts by mass of reclaimed rubber powder per 100 parts by mass of the rubber component.

8. The tire according to any one of claims 1 to 7, wherein the rubber composition contains 1 to 30 parts by mass of a liquid plasticizer based on 100 parts by mass of a rubber component.

9. The tire according to any one of claims 1 to 8, wherein the rubber composition contains 0.2 to 7.0 parts by mass of an antioxidant per 100 parts by mass of the rubber component.

10. The tire according to any one of claims 1 to 9, wherein the rubber composition contains 0.5 to 10 parts by mass of stearic acid per 100 parts by mass of the rubber component.

11. The tire according to any one of claims 1 to 10, wherein the rubber composition contains 0.1 to 5.0 parts by mass of wax per 100 parts by mass of the rubber component.

12. The tire according to any one of claims 1 to 11, wherein the rubber composition contains 0.3 to 3.0 parts by mass of a vulcanization accelerator per 100 parts by mass of the rubber component.

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