Rubber composition for tires and pneumatic tires

Abstract

To provide a rubber composition for tires capable of improving overall performance of wet grip performance, dry grip performance, fuel economy and wear resistance, and to provide a pneumatic tire produced using the rubber composition.SOLUTION: The present invention relates to the rubber composition for tires which contains: a rubber component in which the total content of a styrene-butadiene rubber and a butadiene rubber is 90 mass% or more; 70 pts.mass or more of silica based on 100 pts.mass of the rubber component; a mercapto-based silane coupling agent; and a styrenic resin. The rubber composition for tires satisfies the following inequalities (A) and (B): (A) α1≥20 and (B) α1 / β≤10, where α1 is the total styrene content [mass%] in the rubber component, and β is the content [pts.mass] of the styrenic resin based on 100 pts.mass of the rubber component.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rubber composition for tires and a pneumatic tire.

Background Art

[0002] Tires are required to have various performances such as wet grip performance, dry grip performance, low fuel consumption, and wear resistance, and various improvement methods have been studied (see, for example, Patent Document 1). However, in recent years, further improvements have been demanded.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to solve the above problems and provide a rubber composition for tires capable of improving the overall performance of wet grip performance, dry grip performance, low fuel consumption, and wear resistance, and a pneumatic tire produced using the rubber composition.

Means for Solving the Problems

[0005] The present invention relates to a rubber composition for tires containing a rubber component in which the total content of styrene-butadiene rubber and butadiene rubber is 90% by mass or more, silica having a content of 70 parts by mass or more based on 100 parts by mass of the rubber component, a mercapto-based silane coupling agent, and a styrene-based resin, and satisfying the following formulas (A) and (B). (A) α1 ≧ 20 (B) α1 / β ≦ 10 α1: Total styrene amount in the rubber component [mass%] β: Content of the styrene-based resin with respect to 100 parts by mass of the rubber component [parts by mass]

[0006] It is preferable that the total vinyl amount in the rubber component is 30% by mass or more.

[0007] The rubber composition preferably satisfies the following formula (C). (C) α1 + α2 ≧ 55 α1: Total styrene amount in the rubber component [% by mass] α2: Total vinyl amount in the rubber component [% by mass]

[0008] In 100% by mass of the rubber component, the content of the isoprene-based rubber is preferably 1 to 10% by mass.

[0009] The rubber composition preferably contains carbon black having a cetyltrimethylammonium bromide specific surface area of 130 m 2 / g or more.

[0010] With respect to 100 parts by mass of the rubber component, the total content of the styrene-based resin and other resins is preferably 20 parts by mass or more.

[0011] The nitrogen adsorption specific surface area of the silica is preferably 200 m 2 / g or more.

[0012] The present invention also relates to a pneumatic tire produced using the rubber composition.

Effects of the Invention

[0013] According to the present invention, since the total content of styrene-butadiene rubber and butadiene rubber is within a predetermined range, and it contains a predetermined amount of silica, a mercapto-based silane coupling agent, and a styrene-based resin, and further satisfies formulas (A) and (B), the overall performance of wet grip performance, dry grip performance, low fuel consumption, and abrasion resistance can be improved.

Modes for Carrying Out the Invention

[0014] The rubber composition for tires of the present invention contains a total content of styrene-butadiene rubber (SBR) and butadiene rubber (BR) within a predetermined range, a predetermined amount of silica, a mercapto-based silane coupling agent, and a styrene-based resin, and further satisfies the formulas (A) and (B).

[0015] The above rubber composition exhibits the aforementioned effects, which are presumed to be achieved by the following working effects. In the above rubber composition, the total content of SBR and BR and the content of silica are adjusted within a predetermined range. Further, by adjusting the total styrene amount in SBR and BR and the ratio of the total styrene amount and the content of the styrene-based resin within a predetermined range, silica and the styrene-based resin are well dispersed in the rubber composition. Thereby, it is considered that the comprehensive performance of wet grip performance, dry grip performance, low fuel consumption, and abrasion resistance is significantly improved.

[0016] In the above rubber composition, the rubber component is a component that contributes to crosslinking. Generally, the weight average molecular weight (Mw) is 10,000 or more and it is solid at normal temperature and pressure. Mw can be determined by standard polystyrene conversion based on the measured value by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0017] The above rubber composition contains SBR and / or BR as the rubber component. From the reason that the above comprehensive performance tends to be good, it is preferable to use SBR and BR in combination.

[0018] SBR is not particularly limited. For example, emulsion polymerization styrene-butadiene rubber (E-SBR), solution polymerization styrene-butadiene rubber (S-SBR), etc. can be used. SBR may be either non-modified SBR or modified SBR.

[0019] As the modified SBR, any SBR having a functional group that interacts with a filler such as silica may be used. For example, a terminal-modified SBR (a terminal-modified SBR having the above functional group at the terminal) in which at least one terminal of the SBR is modified with a compound (modifying agent) having the above functional group, a main-chain modified SBR having the above functional group in the main chain, a main-chain terminal-modified SBR having the above functional group in the main chain and at the terminal (for example, a main-chain terminal-modified SBR having the above functional group in the main chain and at least one terminal modified with the above modifying agent), a terminal-modified SBR modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or an epoxy group introduced therein, and the like can be mentioned.

[0020] Examples of the above 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, an epoxy group, and the like. These functional groups may have a substituent. Among them, 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 preferable.

[0021] As the modified SBR, an SBR modified with a compound (modifying agent) represented by the following formula is particularly preferable. [Chemical formula] (In the formula, R 1 , R 2 and R 3 are 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. R 4 and R 5represents, independently or differently, a hydrogen atom or an alkyl group. R 4 and R 5 may combine to form a ring structure together with the nitrogen atom. n represents an integer. )

[0022] As the modified SBR modified with the compound (modifying agent) represented by the above formula, among others, SBR in which the polymerization terminal (active terminal) of solution-polymerized styrene-butadiene rubber (S-SBR) is modified with the compound represented by the above formula (modified SBR described in JP-A-2010-111753, etc.) is preferably used.

[0023] R 1 、R 2 and R 3 is preferably an alkoxy group (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms). R 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 still more preferably 3. Also, when R 4 and R 5 combine to form a ring structure together with the nitrogen atom, it is preferably a 4- to 8-membered ring. Note that the alkoxy group includes a cycloalkoxy group (such as a cyclohexyloxy group) and an aryloxy group (such as a phenoxy group and a benzyloxy group).

[0024] Specific examples of the above modifying agent include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, etc. Among them, 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropyltriethoxysilane, and 3-diethylaminopropyltrimethoxysilane are preferred. These may be used alone or in combination of two or more.

[0025] As the modified SBR, modified SBR modified with the following compounds (modifying agents) can also be preferably used. Examples of the modifying agent include polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, 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, polyepoxidized liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine, 4,4'-diglycidyl-dibenzylmethylamine; diglycidylamino compounds such as diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline, diglycidyl orthotoluidine, tetraglycidyl metaxylenediamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, tetraglycidyl-1,3-bisaminomethylcyclohexane;

[0026] amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamic acid chloride, N,N-diethylcarbamic acid chloride; epoxy group-containing silane compounds such as 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane, (3-glycidyloxypropyl)-pentamethyldisiloxane;

[0027] (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, (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide and other sulfide group-containing silane compounds;

[0028] N-substituted aziridine compounds such as ethyleneimine and propyleneimine; alkoxysilanes such as methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, and N,N-bis(trimethylsilyl)aminoethyltriethoxysilane; (thio)benzophenone compounds having an amino group and / or a substituted amino group 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; benzaldehyde compounds having an amino group and / or a substituted amino group such as 4-N,N-dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde, and 4-N,N-divinylaminobenzaldehyde; N-substituted pyrrolidones such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-t-butyl-2-pyrrolidone, and N-methyl-5-methyl-2-pyrrolidone; N-substituted piperidones such as N-methyl-2-piperidone, N-vinyl-2-piperidone, and N-phenyl-2-piperidone; N-substituted lactams such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurolactam, N-vinyl-ω-laurolactam, N-methyl-β-propiolactam, and N-phenyl-β-propiolactam; and others,

[0029] 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-trione, N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethyl ethyleneurea, 1,3-divinyl ethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophenone, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone and the like can be mentioned. Among them, modified SBR modified with alkoxysilane is preferable. The modification with the above compound (modifying agent) can be carried out by a known method.

[0030] The styrene content of SBR is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more, and is preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 40% by mass or less. When it is within the above range, the above-mentioned comprehensive performance tends to be good. The styrene content can be measured by the method described in the examples below.

[0031] The vinyl content of SBR is preferably 10% by mass or more, more preferably 20% by mass or more, and is preferably 70% by mass or less, more preferably 60% by mass or less. When it is within the above range, the above-mentioned comprehensive performance tends to be good. The vinyl content (1,2-bonded butadiene unit content) can be measured by the method described in the examples below.

[0032] As SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd. and the like can be used.

[0033] When containing SBR, the content of SBR in 100% by mass of the rubber component is preferably 40% by mass or more, more preferably 60% by mass or more, still more preferably 75% by mass or more, and is preferably 90% by mass or less, more preferably 85% by mass or less. When within the above range, the above-mentioned comprehensive performance tends to be good.

[0034] BR is not particularly limited, and BR with a high cis content, BR with a low cis content, BR containing syndiotactic polybutadiene crystals, etc. can be used. BR may be either non-modified BR or modified BR, and examples of the modified BR include the modified BR into which the aforementioned functional group is introduced. These may be used alone or in combination of two or more. A cis content of 30% by mass or more is suitable for BR. Note that the cis content can be measured by infrared absorption spectrum analysis.

[0035] As BR, for example, products of Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

[0036] The vinyl content of BR is preferably 1% by mass or more, more preferably 10% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less. When within the above range, the above-mentioned comprehensive performance tends to be good. Note that the vinyl content (1,2-bonded butadiene unit amount) can be measured by the method described in the examples below.

[0037] When containing BR, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less. When within the above range, the above-mentioned comprehensive performance tends to be good.

[0038] The total content of SBR and BR in 100% by mass of the rubber component may be 90% by mass or more, preferably 95% by mass or more, and may be 100% by mass. When within the above range, the above-mentioned comprehensive performance tends to be good. When blending rubber components other than SBR and BR, the upper limit of the total content is preferably 99% by mass or less, more preferably 95% by mass or less.

[0039] Examples of rubber components that can be used in addition to SBR and BR include diene rubbers such as isoprene rubber, acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These diene rubbers can be used alone or in combination of two or more. Among them, isoprene rubber is preferred because the above-mentioned comprehensive performance tends to be good.

[0040] As the isoprene rubber, isoprene rubber (IR), natural rubber (NR), epoxidized natural rubber (ENR), etc. can be used. Also, modified NR such as deproteinized natural rubber (DPNR) and high-purity natural rubber (UPNR) can be used. These can be used alone or in combination of two or more.

[0041] When containing isoprene rubber, the content of isoprene rubber in 100% by mass of the rubber component is preferably 1% by mass or more, more preferably 3% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less. Within the above range, the above-mentioned comprehensive performance tends to be good.

[0042] The above rubber composition contains silica. Examples of silica include dry-process silica (anhydrous silicic acid), wet-process silica (hydrous silicic acid), etc. Wet-process silica is preferred because it has many silanol groups. These can be used alone or in combination of two or more.

[0043] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 150 m 2 / g or more, more preferably 200 m 2 / g or more, still more preferably 220 m 2 / g or more, and preferably 300 m 2260 m / g or less, more preferably 260 m / g or less. When within the above range, the above-mentioned comprehensive performance tends to be good. 2 When within the above range, the above-mentioned comprehensive performance tends to be good. The nitrogen adsorption specific surface area of silica is a value measured by the BET method in accordance with ASTM D3037-81.

[0044] As the silica, for example, products of Degussa, Rhodia, Tosoh Silica Corporation, Solvay Japan K.K., Tokuyama Corporation, etc. can be used.

[0045] The content of silica with respect to 100 parts by mass of the rubber component may be 70 parts by mass or more, preferably 80 parts by mass or more, more preferably 90 parts by mass or more, and preferably 120 parts by mass or less, more preferably 110 parts by mass or less. When within the above range, the above-mentioned comprehensive performance tends to be good.

[0046] The above rubber composition contains a mercapto-based silane coupling agent. The mercapto-based silane coupling agent is not particularly limited, and examples thereof include 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane. Further, as the mercapto-based silane coupling agent, in addition to compounds having a mercapto group, compounds having a structure in which the mercapto group is protected by a protecting group (for example, a compound represented by the following formula (S1)) can also be used. These may be used alone or in combination of two or more.

[0047] Particularly preferred mercapto-based silane coupling agents include a silane coupling agent represented by the following formula (S1) and a silane coupling agent containing a bonding unit A represented by the following formula (I) and a bonding unit B represented by the following formula (II).

Chemical formula

[0048] In formula (S1), R1005 , R 1006 , R 1007 and R 1008 are each independently preferably a group selected from the group consisting of linear, cyclic or branched alkyl, alkenyl, aryl and aralkyl groups having 1 to 18 carbon atoms. Also, when R 1002 is a monovalent hydrocarbon group having 1 to 18 carbon atoms, it is preferably a group selected from the group consisting of linear, cyclic or branched alkyl, alkenyl, aryl and aralkyl groups. R 1009 is preferably a linear, cyclic or branched alkylene group, particularly preferably a linear one. R 1004 can be, for example, an alkylene group having 1 to 18 carbon atoms, an alkenylene group having 2 to 18 carbon atoms, a cycloalkylene group having 5 to 18 carbon atoms, a cycloalkylalkylene group having 6 to 18 carbon atoms, an arylene group having 6 to 18 carbon atoms, an aralkylene group having 7 to 18 carbon atoms. The alkylene group and the alkenylene group may be either linear or branched, and the cycloalkylene group, the cycloalkylalkylene group, the arylene group and the aralkylene group may have a functional group such as a lower alkyl group on the ring. As this R 1004 , an alkylene group having 1 to 6 carbon atoms is preferable, and particularly preferably a linear alkylene group, for example, a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group.

[0049] In formula (S1), R 1002 , R 1005 , R 1006 , R 1007 and R 1008 Specific examples of include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group, cyclopentyl group, cyclohexyl group, vinyl group, propenyl group, allyl group, hexenyl group, octenyl group, cyclopentenyl group, cyclohexenyl group, phenyl group, tolyl group, xylyl group, naphthyl group, benzyl group, phenethyl group, naphthylmethyl group and the like. R in formula (S1) 1009 As an example of 1009 , linear alkylene groups include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, a hexylene group, etc., and branched alkylene groups include an isopropylene group, an isobutylene group, a 2-methylpropylene group, etc.

[0050] Specific examples of the silane coupling agent represented by formula (S1) include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, 3-lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthioethyltrimethoxysilane, 2-decanoylthioethyltrimethoxysilane, 2-lauroylthioethyltrimethoxysilane, etc. These may be used alone or in combination of two or more. Among them, 3-octanoylthiopropyltriethoxysilane is particularly preferred.

[0051] In the silane coupling agent containing the bonding unit A represented by formula (I) and the bonding unit B represented by formula (II), the content of the bonding unit A is preferably 30 mol% or more, more preferably 50 mol% or more, preferably 99 mol% or less, more preferably 90 mol% or less. Also, the content of the bonding unit B is preferably 1 mol% or more, more preferably 5 mol% or more, still more preferably 10 mol% or more, preferably 70 mol% or less, more preferably 65 mol% or less, still more preferably 55 mol% or less. Further, the total content of the bonding units A and B is preferably 95 mol% or more, more preferably 98 mol% or more, particularly preferably 100 mol%. Note that the contents of the linking units A and B include the amounts even when the linking units A and B are located at the terminals of the silane coupling agent. The form when the linking units A and B are located at the terminals of the silane coupling agent is not particularly limited as long as the units corresponding to the formulas (I) and (II) representing the linking units A and B are formed.

[0052] Regarding R in the formulas (I) and (II), examples of the halogen include chlorine, bromine, fluorine, etc. Examples of the branched or unbranched alkyl group having 1 to 30 carbon atoms include a methyl group, an ethyl group, etc. Examples of the branched or unbranched alkenyl group having 2 to 30 carbon atoms include a vinyl group, a 1-propenyl group, etc. Examples of the branched or unbranched alkynyl group having 2 to 30 carbon atoms include an ethynyl group, a propynyl group, etc. 11 Regarding R in the formulas (I) and (II), examples of the branched or unbranched alkylene group having 1 to 30 carbon atoms include an ethylene group, a propylene group, etc. Examples of the branched or unbranched alkenylene group having 2 to 30 carbon atoms include a vinylene group, a 1-propenylene group, etc. Examples of the branched or unbranched alkynylene group having 2 to 30 carbon atoms include an ethynylene group, a propynylene group, etc.

[0053] Regarding R in the formulas (I) and (II), 12 Regarding R in the formulas (I) and (II), examples of the branched or unbranched alkylene group having 1 to 30 carbon atoms include an ethylene group, a propylene group, etc. Examples of the branched or unbranched alkenylene group having 2 to 30 carbon atoms include a vinylene group, a 1-propenylene group, etc. Examples of the branched or unbranched alkynylene group having 2 to 30 carbon atoms include an ethynylene group, a propynylene group, etc.

[0054] In the silane coupling agent containing the linking unit A represented by the formula (I) and the linking unit B represented by the formula (II), the total number of repetitions (v + w) of the number of repetitions (v) of the linking unit A and the number of repetitions (w) of the linking unit B is preferably in the range of 3 to 300.

[0055] The content of the mercapto-based silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less with respect to 100 parts by mass of silica. When within the above range, the above-mentioned comprehensive performance tends to be good.

[0056] The above rubber composition may contain a silane coupling agent other than the mercapto-based silane coupling agent. The silane coupling agents that can be used are not particularly limited. For example, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide and other sulfide-based, vinyl-based such as vinyltriethoxysilane, vinyltrimethoxysilane, amino-based such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, glycidoxy-based such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, nitro-based such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, chloro-based such as 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, etc. These may be used alone or in combination of two or more.

[0057] The above rubber composition contains a styrene resin. Styrene resins are polymers containing styrene monomers as constituent monomers, and examples include polymers obtained by polymerizing styrene monomers as the main component (50% by mass or more). Specifically, homopolymers obtained by polymerizing each styrene monomer (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) alone, copolymers obtained by copolymerizing two or more styrene monomers, and copolymers of styrene monomers and other monomers copolymerizable therewith are also included.

[0058] Examples of other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, acrylics, unsaturated carboxylic acids such as methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, terpene compounds, conjugated dienes such as chloroprene, butadiene and isoprene, olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride or their acid anhydrides; and the like. These may be used alone or in combination of two or more.

[0059] Due to the tendency for the above-mentioned comprehensive performance to be good, styrene resins are preferably α-methylstyrene resins (α-methylstyrene homopolymers, copolymers of α-methylstyrene and styrene, etc.) and copolymers of styrene monomers and terpene compounds. Among them, α-methylstyrene resins are more preferably copolymers of α-methylstyrene and styrene.

[0060] Terpene compounds are hydrocarbons represented by the composition of (C5H8) and their oxygen-containing derivatives, including monoterpenes (C n H 10 ), sesquiterpenes (C 16 H 15 ), diterpenes (C 24 H 20 32 ​) A compound having a terpene classified as such as a basic skeleton, for example, α-pinene, β-pinene, dipentene, limonene, myrcene, allo-ocimene, ocimene, α-farnesene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, etc. can be mentioned.

[0061] The content of the styrene resin with respect to 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less. When it is within the above range, there is a tendency for the above-described comprehensive performance to be good.

[0062] The above rubber composition satisfies the following formulas (A) and (B) for the total styrene amount in the rubber component and the content of the styrene resin. (A) α1 ≧ 20 (B) α1 / β ≦ 10 α1: Total styrene amount in the rubber component [mass%] β: Content of the styrene resin with respect to 100 parts by mass of the rubber component [parts by mass]

[0063] α1 (total styrene amount in the rubber component) may be adjusted within the range that satisfies formulas (A) and (B), but is preferably 25 mass% or more, more preferably 30 mass% or more, and is preferably 50 mass% or less, more preferably 40 mass% or less. When it is within the above range, there is a tendency for the above-described comprehensive performance to be good. Here, the total styrene amount in the rubber component (total content of the styrene portions contained in the total amount of the rubber component) is Σ (content of each styrene-containing rubber × styrene amount of each styrene-containing rubber / 100). For example, when the rubber component consists of 90 mass% of SBR(A) (styrene amount 40 mass%), 5 mass% of SBR(B) (styrene amount 25 mass%), and 5 mass% of BR, the total styrene amount in the rubber component is 37.25 mass% (=(90×40 / 100 + 5×25 / 100)).

[0064] In formula (B), α1 / β is preferably 6 or less, more preferably 4 or less, and is preferably 0.5 or more, more preferably 0.8 or more. When within the above range, the above-described overall performance tends to be good.

[0065] In the above rubber composition, the total vinyl amount in the rubber component (the total content of the vinyl parts contained in the total amount of the rubber component) is preferably 30% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less. When within the above range, the above-described overall performance tends to be good. Here, the total vinyl amount in the rubber component is Σ (content of each vinyl-containing rubber × vinyl amount of each vinyl-containing rubber / 100). For example, when the rubber component consists of 90% by mass of SBR(A) (vinyl amount 20% by mass), 5% by mass of SBR(B) (vinyl amount 10% by mass), and 5% by mass of BR (vinyl amount 2% by mass), the total butadiene amount in the rubber component is 18.6% by mass (=(90×20 / 100 + 5×10 / 100 + 5×2 / 100)).

[0066] It is preferable that the total styrene amount and the total vinyl amount in the rubber component of the above rubber composition satisfy the following formula (C). (C) α1 + α2 ≧ 55 α1: Total styrene amount in the rubber component [mass%] α2: Total vinyl amount in the rubber component [mass%]

[0067] In formula (C), α1 + α2 is preferably 58 or more, more preferably 60 or more, and is preferably 85 or less, more preferably 75 or less. When within the above range, the above-described overall performance tends to be good.

[0068] The above rubber composition may contain a resin other than the styrene resin. As the resin other than the styrene resin, there is no particular limitation as long as it is widely used in the tire industry. For example, C5 resins, C9 resins, terpene resins, rosin resins, coumarone-indene resins, p-t-butylphenol acetylene resins, acrylic resins, etc. may be mentioned. These may be used alone or in combination of two or more.

[0069] As commercially available products of styrene resins and other resins, for example, products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, Nippon Paint Co., Ltd., Nippon Shokubai Co., Ltd., JXTG Energy Corporation, Arakawa Chemical Industries, Ltd., Taoka Chemical Industry Co., Ltd., ExxonMobil, CrayValley, etc. can be used.

[0070] The total content of the styrene resin and other resins is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 20 parts by mass or more, and preferably 50 parts by mass or less, more preferably 40 parts by mass or less with respect to 100 parts by mass of the rubber component. When it is within the above range, the above-mentioned comprehensive performance tends to be good. In addition, when not containing a resin other than the styrene resin, the above total content is synonymous with the styrene resin.

[0071] The above rubber composition preferably contains carbon black. There is no particular limitation on the carbon black, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. These may be used alone or in combination of two or more.

[0072] The cetyltrimethylammonium bromide (CTAB) specific surface area of the carbon black is preferably 130 m 2 / g or more, more preferably 160 m 2 / g or more, still more preferably 170 m 2 / g or more, and preferably 250 m 2200 m / g or less, more preferably 200 m / g or less. When within the above range, the above-described comprehensive performance tends to be good. 2 The CTAB specific surface area of carbon black is a value measured in accordance with JIS K6217-3:2001.

[0073]

[0074]

[0075]

[0076] The above rubber composition may contain oil. Examples of the oil include process oil, vegetable oil and fat, or a mixture thereof. As the process oil, for example, paraffinic process oil, aromatic process oil, naphthenic process oil and the like can be used. Examples of the vegetable oil and fat include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil and the like. These may be used alone or in combination of two or more. Among them, process oil is preferred.

[0077] Examples of the oil include products of Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Corporation, Oryso Co., Ltd., H&R Co., Ltd., Toyokuni Seiyu Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kogyo Co., Ltd. and the like.

[0077] When containing oil, the oil content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and preferably 40 parts by mass or less, more preferably 30 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the above-mentioned comprehensive performance tends to be good.

[0078] The above rubber composition may contain wax. The wax is not particularly limited, and examples include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant waxes and animal waxes; synthetic waxes such as polymers of ethylene, propylene, etc. These may be used alone or in combination of two or more. Among them, petroleum waxes are preferred, and paraffin wax is more preferred.

[0079] As the wax, for example, products of Ouchi Shinsei Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. can be used.

[0080] When containing wax, the wax content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the above-mentioned comprehensive performance tends to be good.

[0081] The above rubber composition may contain an anti-aging agent. Examples of the anti-aging agent include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; p-phenylenediamine-based anti-aging agents such as N-isopropyl-N′-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, and N,N′-di-2-naphthyl-p-phenylenediamine; quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; bis, tris, polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate]methane, etc. These may be used alone or in combination of two or more. Among them, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferred.

[0082] As the anti-aging agent, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., Flexsys Co., etc. can be used.

[0083] When containing the anti-aging agent, the content of the anti-aging agent is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 10 parts by mass or less, more preferably 8 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the above-mentioned comprehensive performance tends to be good.

[0084] The above rubber composition may contain stearic acid. As the stearic acid, conventionally known ones can be used. For example, products of NOF Corporation, Kao Corporation, Fuji Film Wako Pure Chemical Corporation, Chiba Fatty Acids Co., Ltd., etc. can be used.

[0085] When stearic acid is contained, the content of stearic acid is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the above-mentioned comprehensive performance tends to be good.

[0086] The above rubber composition may contain zinc oxide. As the zinc oxide, conventionally known ones can be used. For example, products of Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Shoindo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0087] When zinc oxide is contained, the content of zinc oxide is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the above-mentioned comprehensive performance tends to be good.

[0088] The above rubber composition may contain sulfur. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, soluble sulfur, etc., which are generally used in the rubber industry. These may be used alone or in combination of two or more.

[0089] As sulfur, for example, products of Tsukimi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexsys, Nippon Kankyu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0090] When sulfur is contained, the content of sulfur is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the above-mentioned comprehensive performance tends to be good.

[0091] The above rubber composition may contain a vulcanization accelerator. Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyldisulfide, and N-cyclohexyl-2-benzothiazylsulfenamide; 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, N-t-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N′-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine, and orthotolylbiguanidine. These may be used alone or in combination of two or more. Among them, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred.

[0092] As the vulcanization accelerator, for example, products manufactured by Kawaguchi Chemical Co., Ltd., Ouchi Shinsei Chemical Co., Ltd., Sanshin Chemical Industry Co., Ltd., etc. can be used.

[0093] When the vulcanization accelerator is contained, the content of the vulcanization accelerator is preferably 2 parts by mass or more, more preferably 4 parts by mass or more, and preferably 10 parts by mass or less, more preferably 8 parts by mass or less, based on 100 parts by mass of the rubber component. When within the above range, the above-mentioned comprehensive performance tends to be good.

[0094] In addition to the above components, the rubber composition may further contain additives generally used in the tire industry, such as organic peroxides; fillers such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, etc. The content of these additives is preferably 0.1 to 200 parts by mass based on 100 parts by mass of the rubber component.

[0095] The above rubber composition can be produced, for example, by kneading the respective components using a rubber kneading apparatus such as an open roll or a Banbury mixer, and then vulcanizing the kneaded mixture by a method or the like.

[0096] As the kneading conditions, in the base kneading step of kneading additives other than the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C. In the finishing kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 120°C or lower, preferably 85 to 110°C. Further, the composition kneaded with the vulcanizing agent and the vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. As the vulcanization temperature, it is usually 140 to 190°C, preferably 150 to 185°C. The vulcanization time is usually 5 to 15 minutes.

[0097] The above rubber composition is suitably used for a tread (cap tread), but can also be used for members other than the tread, such as a sidewall, a base tread, an undertread, a clinch apex, a bead apex, a breaker cushion rubber, a carcass cord coating rubber, an insulation, a chafing strip, an inner liner, etc., or for a side reinforcing layer of a run-flat tire.

[0098] The pneumatic tire of the present invention is produced by a usual method using the above rubber composition. That is, the above rubber composition is extruded in an unvulcanized state in accordance with the shape of each tire member of the tread, and together with other tire members, an unvulcanized tire is formed by molding in a usual manner on a tire molding machine. The tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

[0099] The pneumatic tire described above can be used for passenger car tires, truck and bus tires, motorcycle tires, high-performance tires, winter tires such as studless tires, run-flat tires with a side reinforcement layer, tires with a sound-absorbing member such as sponge in the tire cavity, tires with a sealing member having a sealant that can be sealed when punctured inside the tire or in the tire cavity, tires with electronic components such as sensors and wireless tags inside the tire or in the tire cavity, etc., and is suitable for passenger car tires.

Example

[0100] Based on the examples, the present invention will be specifically described, but the present invention is not limited only to these. Hereinafter, various chemicals used in the examples will be described. Isoprene rubber: TSR20 (natural rubber) SBR1: Nipol NS522 (styrene content 38% by mass, vinyl content 40% by mass) manufactured by Nippon Zeon Co., Ltd. SBR2: Modified SBR synthesized in Production Example 1 below (styrene amount: 25% by mass, vinyl amount: 60% by mass, Mw: 150,000) SBR3: Modified SBR synthesized in Production Example 2 below (styrene amount: 40% by mass, vinyl amount: 40% by mass, Mw: 750,000) SBR4: Modified SBR synthesized in Production Example 3 below (styrene amount: 25% by mass, vinyl amount: 60% by mass, Mw: 300,000) SBR5: Buna VSL5228-2 (styrene amount: 28% by mass, vinyl amount: 52% by mass) manufactured by Lanxess SBR6: Buna VSL2438-2 HM (styrene amount: 38% by mass, vinyl amount: 24% by mass) manufactured by Lanxess SBR7: Modified SBR synthesized in Production Example 4 below (styrene amount: 40% by mass, vinyl amount: 30% by mass, Mw: 950,000) BR1: N103 (vinyl amount: 12% by mass) manufactured by Asahi Kasei Chemicals Corporation BR2: BR710 (vinyl amount: 1.2% by mass) manufactured by Ube Industries, Ltd. Carbon black 1: Prototype (CTAB: 180m 2 / g, N2SA: 177 m 2 / g, IA: 188 mg / g) Carbon Black 2: N134 (CTAB: 135 m 2 / g) Carbon Black 3: N220 (CTAB: 111 m 2 / g) Silica 1: Ultrasil 9000GR manufactured by Evonik Degussa (N2SA: 240 m 2 / g) Silica 2: ZEOSIL 1115MP manufactured by Rhodia (N2SA: 115 m 2 / g) Silica 3: Ultrasil VN3 manufactured by Evonik Degussa (N2SA: 167 m 2 / g) Silane Coupling Agent 1: NXT manufactured by Momentive (3 - Octanoylthiopropyltriethoxysilane) Silane Coupling Agent 2: NXT - Z45 manufactured by Momentive (Copolymer of Bonding Unit A and Bonding Unit B (Bonding Unit A: 55 mol%, Bonding Unit B: 45 mol%)) Silane Coupling Agent 3: Si69 manufactured by Evonik Degussa (Bis(3 - triethoxysilylpropyl)tetrasulfide) Oil 1: VIVATEC500 manufactured by H&R (TDAE Oil) Oil 2: PW - 380 manufactured by Idemitsu Kosan Co., Ltd. Resin 1: Sylvatraxx4401 manufactured by Arizona Chemical (α - Methylstyrene - based resin (Copolymer of α - methylstyrene and styrene)) Resin 2: YS Resin TO125 manufactured by Yasuhara Chemical Co., Ltd. (Copolymer of styrene and terpene compound) Wax: Oz Ace 0355 manufactured by Nippon Seiro Co., Ltd. Antioxidant 1: No Crack 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N - (1,3 - Dimethylbutyl) - N’ - phenyl - p - phenylenediamine) Antioxidant 2: No Crack RD manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (Poly(2,2,4 - trimethyl - 1,2 - dihydroquinoline)) Stearic Acid: Stearic Acid "Tsubaki" manufactured by NOF Corporation Zinc oxide: Zinc white No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur manufactured by Tsurumi Chemical Co., Ltd. Vulcanization accelerator 1: Nocceler CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Nocceler D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0101] (Production Example 1) Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were charged into a nitrogen-substituted autoclave reactor. After adjusting the temperature of the reactor contents to 20°C, n-butyllithium was added to initiate polymerization. Polymerization was carried out under adiabatic conditions, and the maximum temperature reached 85°C. When the polymerization conversion rate reached 99%, 1,3-butadiene was added, and polymerization was continued for another 5 minutes. Then, 3-diethylaminopropyltrimethoxysilane was added as a modifier to carry out the reaction. After the polymerization reaction was completed, 2,6-di-tert-butyl-p-cresol was added. Subsequently, solvent was removed by steam stripping and dried with a hot roll adjusted to 110°C to obtain SBR2.

[0102] (Production Example 2) Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were charged into a nitrogen-substituted autoclave reactor. After adjusting the temperature of the reactor contents to 20°C, n-butyllithium was added to initiate polymerization. Polymerization was carried out under adiabatic conditions, and the maximum temperature reached 85°C. When the polymerization conversion rate reached 99%, 1,3-butadiene was added, and polymerization was continued for another 5 minutes. Then, 3-dimethylaminopropyltrimethoxysilane was added as a modifier to carry out the reaction. After the polymerization reaction was completed, 2,6-di-tert-butyl-p-cresol was added. Subsequently, solvent was removed by steam stripping and dried with a hot roll adjusted to 110°C to obtain SBR3.

[0103] (Production Example 3) A nitrogen-substituted autoclave reactor was charged with cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene. After adjusting the temperature of the reactor contents to 20 °C, n-butyllithium was added to initiate polymerization. Polymerization was carried out under adiabatic conditions, and the maximum temperature reached 85 °C. When the polymerization conversion reached 99%, 1,3-butadiene was added, and polymerization was continued for an additional 5 minutes. Then, N-(3-dimethylaminopropyl)acrylamide was added as a modifier to conduct the reaction. After the polymerization reaction was completed, 2,6-di-tert-butyl-p-cresol was added. Next, solvent was removed by steam stripping, and drying was performed using a hot roll adjusted to 110 °C to obtain SBR4.

[0104] (Production Example 4) A nitrogen-substituted autoclave reactor was charged with cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene. After adjusting the temperature of the reactor contents to 20 °C, n-butyllithium was added to initiate polymerization. Polymerization was carried out under adiabatic conditions, and the maximum temperature reached 85 °C. When the polymerization conversion reached 99%, 1,3-butadiene was added, and polymerization was continued for an additional 5 minutes. Then, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane was added as a modifier to conduct the reaction. After the polymerization reaction was completed, 2,6-di-tert-butyl-p-cresol was added. Next, solvent was removed by steam stripping, and drying was performed using a hot roll adjusted to 110 °C to obtain SBR7.

[0105] (Analysis of SBR) The structural identification of SBR (measurement of styrene content and vinyl content) was carried out using an apparatus of the JNM-ECA series manufactured by JEOL Ltd. The measurement was performed on a sample obtained by dissolving 0.1 g of the polymer in 15 ml of toluene, slowly pouring it into 30 ml of methanol for reprecipitation, and then measuring it after drying under reduced pressure.

[0106] (Examples and Comparative Examples) According to the compounding ingredients shown in Table 1, using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd., materials other than sulfur and vulcanization accelerators were kneaded at 150°C for 5 minutes to obtain a kneaded product. Next, sulfur and vulcanization accelerators were added to the obtained kneaded product, and it was kneaded at 80°C for 5 minutes using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was formed into the shape of a tread and bonded together with other tire members to form an unvulcanized tire, which was press-vulcanized at 150°C for 12 minutes to manufacture a test tire (size: 195 / 65R15). The following evaluations were performed using the obtained test tires, and the results are shown in Table 1. In Table 1, the rubber content in the oil-extended rubber is described in the rubber column, and the oil content in the oil-extended rubber is added to the column of Oil 1.

[0107] (Wet Grip Performance) Each test tire was mounted on all wheels of a vehicle (domestic FF2000cc), and the braking distance from an initial speed of 100 km / h on a wet asphalt road surface was determined and expressed as an index when Comparative Example 1 was set to 100 (Wet Grip Performance Index). The larger the index, the shorter the braking distance, indicating excellent wet grip performance.

[0108] (Dry Grip Performance) Each test tire was mounted on all wheels of a vehicle (domestic FF2000cc), and the braking distance from an initial speed of 100 km / h on a dry asphalt road surface was determined and expressed as an index when Comparative Example 1 was set to 100 (Dry Grip Performance Index). The larger the index, the shorter the braking distance, indicating excellent wet grip performance.

[0109] (Low Fuel Consumption) Using a rolling resistance tester, the rolling resistance of each test tire when running at a rim (15×6JJ), internal pressure (230 kPa), load (3.43 kN), and speed (80 km / h) was measured and expressed as an index when Comparative Example 1 was set to 100 (Low Fuel Consumption Index). The larger the index, the smaller the rolling resistance, indicating excellent low fuel consumption.

[0110] (Abrasion Resistance) Each test tire was mounted on all wheels of a vehicle (domestic FF 2000 cc), and the groove depth of the tire tread part was measured after a driving distance of 8000 km. The driving distance when the tire groove depth decreased by 1 mm was calculated and expressed as an index with Comparative Example 1 set to 100 (abrasion resistance index). The larger the index, the longer the driving distance, indicating excellent abrasion resistance.

[0111]

Table 1

[0112] From Table 1, it can be seen that in the Examples, compared with the Comparative Examples, the comprehensive performance (the sum of each index) of wet grip performance, dry grip performance, low fuel consumption, and abrasion resistance was improved.

Claims

1. A rubber component in which the total content of styrene-butadiene rubber and butadiene rubber is 95% by mass or more, silica having a content of 70 parts by mass or more based on 100 parts by mass of the rubber component, a mercapto-based silane coupling agent, and a styrene-based resin, wherein the total vinyl amount in the rubber component is 30% by mass or more, A rubber composition for tires satisfying the following formulas (A) and (B). (A) α1 ≧ 20 (B) α1 / β ≦ 1.32 α1: Total styrene amount in the rubber component [mass%] β: Content of the styrene-based resin with respect to 100 parts by mass of the rubber component [parts by mass]

2. The rubber composition for tires according to Claim 1, satisfying the following formula (C). (C) α1 + α2 ≧ 55 α1: Total styrene amount in the rubber component [mass%] α2: Total vinyl amount in the rubber component [mass%]

3. The rubber composition for tires according to Claim 1 or 2, wherein the content of isoprene-based rubber in 100% by mass of the rubber component is 1 to 5% by mass.

4. The rubber composition for tires according to any one of Claims 1 to 3, containing carbon black having a cetyltrimethylammonium bromide specific surface area of 130 m ２ / g or more.

5. The rubber composition for tires according to any one of Claims 1 to 4, wherein the total content of the styrene-based resin and other resins is 20 parts by mass or more with respect to 100 parts by mass of the rubber component.

6. The rubber composition for tires according to any one of Claims 1 to 5, wherein the nitrogen adsorption specific surface area of the silica is 200 m ２ / g or more.

7. A pneumatic tire produced using the rubber composition according to any one of claims 1 to 6.

Images