Pneumatic tire

Abstract

Provided is a pneumatic tire having sufficiently improved wet traction performance in a low-temperature environment compared to conventional products.　A pneumatic tire comprising a tread in which at least two circumferential main grooves continuously extending in the circumferential direction of the tire are formed, wherein the tread has a plurality of transverse grooves that are wider at a center portion thereof than at an end portion thereof and are each formed in a land section delimited in the width direction of the tire by adjacent two of the circumferential main grooves, at least one of rubber layers forming the tread contains, as rubber components, an isoprene rubber and a styrene-butadiene rubber which has a styrene content of at most 30 mass% and in which the vinyl linked amount in the butadiene portion is at most 40 mass%, and a local maximum (peak) of the loss tangent (tanδ) is present in the range of -20°C to 0°C, as measured at a frequency of 10 Hz, an initial strain of 2%, and a dynamic strain rate of 1%.

Description

Technical Field

[0001] The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having excellent wet grip performance in a low-temperature environment.

Background Art

[0002] With the progress of vehicle speed increase in recent years, in pneumatic tires (hereinafter also simply referred to as "tires"), there has been an increasing demand for improving wet grip performance, particularly in a low-temperature environment, specifically, in a low-temperature environment below 10°C.

[0003] Under such circumstances, in order to improve wet grip performance, studies have been conducted on tread rubber (Patent Documents 1 and 2), tread shape (Patent Documents 3 and 4), and the like.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the above-described conventional technologies, the wet grip performance in a low-temperature environment has not yet been sufficiently improved, and further improvement is required.

[0006] Therefore, an object of the present invention is to provide a pneumatic tire having a wet grip performance under a low temperature environment that is sufficiently improved as compared with the prior art.

Means for Solving the Problems

[0007] The inventor of the present invention has intensively studied the solution to the above problems, and has found that the above problems can be solved by the invention described below, and has completed the present invention.

[0008] The invention according to claim 1 is a pneumatic tire including a tread in which two or more circumferential main grooves continuously extending in the tire circumferential direction are formed, wherein the tread a plurality of lateral grooves are formed in the land portion partitioned in the tire width direction by two adjacent circumferential main grooves, and the lateral grooves are formed in a shape that is wider on the central portion side than on the end portion side, at least one layer of the rubber layer forming the tread contains a styrene-butadiene rubber having a styrene content of 30% by mass or less and a vinyl bond content in the butadiene portion of 40% by mass or less and an isoprene rubber as rubber components, and has a loss tangent (tan δ) measured under the conditions of a frequency of 10 Hz, an initial strain of 2%, and a dynamic strain rate of 1% showing a maximum value (peak) within the range of -20°C or higher and 0°C or lower, and is a pneumatic tire characterized by being formed of a rubber composition.

[0009] The invention according to claim 2 is the pneumatic tire according to claim 1, wherein in the rubber composition, the amount of the isoprene rubber in 100 parts by mass of the rubber components is 10 parts by mass or more and 60 parts by mass or less.

[0010] The invention according to claim 3 is the pneumatic tire according to claim 2, wherein in the rubber composition, the amount of the isoprene rubber in 100 parts by mass of the rubber components is 20 parts by mass or more and 40 parts by mass or less.

[0011] The invention according to claim 4 is in the rubber composition, the amount of styrene-butadiene rubber in 100 parts by mass of the rubber component is 30 not less than [mass part] and not more than 60 parts by mass, and is a pneumatic tire according to any one of claims 1 to 3.

[0012] The invention according to claim 5 is in the rubber composition, a butadiene rubber is further added to the rubber component, and the amount of butadiene rubber in 100 parts by mass of the rubber component is not less than 10 parts by mass and not more than 30 parts by mass, and is a pneumatic tire according to any one of claims 1 to 4.

[0013] The invention according to claim 6 is the rubber composition contains a resin component in an amount exceeding 5 parts by mass and less than 40 parts by mass with respect to 100 parts by mass of the rubber component, and is a pneumatic tire according to any one of claims 1 to 5.

[0014] The invention according to claim 7 is the resin component is a terpene resin, and is a pneumatic tire according to claim 6.

[0015] The invention according to claim 8 is the rubber composition contains 40 parts by mass or more and 200 parts by mass or less of silica with respect to 100 parts by mass of the rubber component, and is a pneumatic tire according to any one of claims 1 to 7.

[0016] The invention according to claim 9 is the silica is silica having a nitrogen adsorption specific surface area of 150 m 2 / g or more, and is a pneumatic tire according to claim 8.

[0017] The invention according to claim 10 is The pneumatic tire according to claim 8 or claim 9, wherein the rubber composition contains a silane coupling agent.

[0018] The invention according to claim 11 is The pneumatic tire according to claim 10, wherein the content of the silane coupling agent in the rubber composition is 3.0 parts by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0019] The invention according to claim 12 is The content of the silane coupling agent in the rubber composition is 4.5 parts by mass or more with respect to 100 parts by mass of the rubber component, 8.0 The pneumatic tire according to claim 11, wherein the content is parts by mass or less.

[0020] The invention according to claim 13 is The pneumatic tire according to any one of claims 10 to 12, wherein the rubber composition contains a mercapto-based silane coupling agent as the silane coupling agent.

[0021] The invention according to claim 14 is The pneumatic tire according to any one of claims 1 to 13, wherein the rubber composition has a loss tangent (tanδ) measured under the conditions of a frequency of 10 Hz, an initial strain of 2%, and a dynamic strain rate of 1% and exhibits a maximum value (peak) in the range of -15°C or higher and 0°C or lower.

[0022] The invention according to claim 15 is The tread is formed of a plurality of rubber layers, The pneumatic tire according to any one of claims 1 to 14, wherein the rubber composition is used for the cap rubber layer of the tread.

[0023] The invention according to claim 16 is When the width on the main groove end side in the circumferential direction of the transverse groove is A (mm) and the width on the central part side is B (mm), 1.0 < B / A ≤ 40.0 An air-filled tire according to any one of claims 1 to 15, characterized in that

[0024] The invention according to claim 17 is An air-filled tire according to claim 16, characterized in that 5.0 ≦ B / A ≦ 35.0.

[0025] The invention according to claim 18 is When incorporated into a standard rim and the internal pressure is the standard internal pressure, if the cross-sectional width of the tire is Wt (mm) and the outer diameter is Dt (mm), an air-filled tire according to any one of claims 1 to 17, characterized in that 1963.4 ≦ (Dt 2 × π / 4) / Wt ≦ 2827.4 is satisfied.

[0026] The invention according to claim 19 is An air-filled tire according to any one of claims 1 to 18, characterized in that it is an air-filled tire for a passenger car.

Advantages of the Invention

[0027] According to the present invention, it is possible to provide an air-filled tire in which the wet grip performance in a low-temperature environment is sufficiently improved compared with the prior art.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Best Mode for Carrying Out the Invention

[0029] Hereinafter, the present invention will be specifically described based on embodiments.

[0030] [1] Regarding the characteristics of the tire of the present invention First, the characteristics of the tire according to the present invention will be described.

[0031] The inventor considered that in order to improve the wet grip performance in a low-temperature environment, instead of separately examining the tread shape and the tread rubber, each needs to satisfy certain conditions, and conducted various experiments and studies, resulting in the completion of the present invention.

[0032] That is, in the tire according to the present invention, first, regarding the tread shape, two or more circumferential main grooves continuously extending in the tire circumferential direction are formed, and on the land portion partitioned in the tire width direction by two adjacent circumferential main grooves, a plurality of lateral grooves are formed in a shape that is wider on the central portion side than on the end portion side.

[0033] Next, regarding the tread rubber, at least one rubber layer forming the tread contains styrene-butadiene rubber with a styrene content of 30% by mass or less and a vinyl bond content in the butadiene portion of 40% by mass or less and isoprene rubber as rubber components, and the loss tangent (tanδ) measured under the conditions of a frequency of 10 Hz, an initial strain of 2%, and a dynamic strain rate of 1% exhibits a maximum value (peak) within the range of -20°C or higher and 0°C or lower, and is formed of a rubber composition.

[0034] By adopting such a tread shape and tread rubber, it is possible to provide a pneumatic tire in which the wet grip performance in a low-temperature environment is sufficiently improved by their mutual cooperation.

[0035] In addition, when the tread is formed of a plurality of rubber layers such as a cap rubber layer and a base rubber layer, this rubber composition is preferably used for the cap rubber layer.

[0036] [2] Embodiments of the present invention Hereinafter, the present invention will be specifically described based on embodiments.

[0037] 1. Tread shape As described above, the tire of the present embodiment includes a tread in which two or more circumferential main grooves continuously extending in the tire circumferential direction are formed, and a land portion partitioned in the tire width direction by two adjacent circumferential main grooves has a plurality of lateral grooves formed in a shape that is wider on the central portion side than on the end portion side.

[0038] The rubber component constituting the rubber composition of the tread has a low glass transition temperature (Tg). When traveling in a low-temperature environment, the difference between the hardness of the rubber component and the hardness of other components becomes large, and stress is likely to concentrate at the interface. Then, due to this stress concentration, a defect occurs in the land portion of the tread on the ground contact surface, leading to a decrease in the ground contact area, so there is a risk of deterioration of the wet braking performance. This defect is particularly likely to occur on the end portion side close to the circumferential main groove.

[0039] Therefore, in the present embodiment, the lateral grooves are formed in a shape that is wider on the central portion side than on the end portion side. As a result, since the ground contact area on the end portion side close to the circumferential main groove becomes large, the occurrence of defects on the end portion side of the land portion on the ground contact surface can be suppressed, and the wet braking performance in a low-temperature environment can be sufficiently exhibited.

[0040] Specifically, FIGS. 1 and 2 are each an example of a schematic development view showing the form of the ground contact surface of the tread of the pneumatic tire according to the present embodiment. And FIG. 3 is an example of a schematic development view showing the form of the ground contact surface of the tread of a conventional tire. In FIGS. 1 to 3, 3 is the circumferential main groove, 4 is the land portion, and 5 is the lateral groove. And CL is the center line showing the center of the tread. Also, c indicates the central portion side of the lateral groove 5, and e indicates the end portion side of the lateral groove 5.

[0041] As shown in FIGS. 1 to 3, each tire includes a tread in which two or more (three in FIGS. 1 to 3) circumferential main grooves 3 extending continuously in the tire circumferential direction are formed, and a land portion 4 is defined in the tire width direction by two adjacent circumferential main grooves. And a plurality of lateral grooves 5 are formed in the land portion 4.

[0042] In the present embodiment, as shown in FIGS. 1 and 2, the lateral groove 5 is formed in a shape that becomes wider on the central portion side c than on the end portion side e. By forming the lateral groove 5 in such a shape, the contact area on the end portion side e close to the circumferential main groove 3 becomes large, so that the occurrence of chipping on the end portion side e can be suppressed, and the wet braking performance in a low temperature environment can be sufficiently exhibited.

[0043] This is because, in the case of the lateral groove 5 that is wider on the central portion side c than on the end portion side e, the contact area increases and the stress is also dispersed to the wide central portion side c, so that the concentration of stress on the end portion side e is alleviated and the occurrence of chipping is suppressed.

[0044] On the other hand, in a conventional tire, as shown in FIG. 3, since the shape of the lateral groove 5 is not formed in a shape that becomes wider on the central portion side c than on the end portion side e, chipping is likely to occur on the end portion side e in a low temperature environment.

[0045] In the present embodiment, the lateral groove 5 may be in a complete state within the land portion 4 as shown in FIG. 1, that is, in a state not connected to the circumferential main groove 3, or may be connected to the circumferential main groove 3 as shown in FIG. 2. And, as shown in FIG. 4, the lateral groove 5 and the circumferential main groove 3 may be connected via a branch groove 10. Also, as the direction in which the lateral groove 5 is provided, it may be an oblique direction with respect to the circumferential main groove 3 as shown in FIGS. 1 and 2, or may be an orthogonal direction.

[0046] And, in the present embodiment, when the width of the lateral groove on the end portion side is A (mm) and the width on the central portion side is B (mm), B / A is 1.0 UltraWhen it is formed so as to be 40.0 or less, more preferably 5.0 or more and 35 or less, a sufficient large ground contact area on the end portion side can be ensured. In the case where the width of the lateral groove gradually decreases toward the end portion in the width direction and the width of the end portion becomes 0, the "width on the end portion side" refers to the width of the lateral groove at a position 10% inside from the end of the circumferential main groove in the tire width direction of the lateral groove.

[0047] In the above, the "circumferential main groove" refers to a groove having a cross-sectional area in the tire width direction of 10 mm 2 or more.

[0048] And the "ground contact surface" refers to the outer peripheral surface over the entire circumference of the tire that contacts the road surface when the tire is assembled to a standard rim, filled with a standard internal pressure, and rolled under a state of applying a standard load. Specifically, for example, it can be obtained by assembling the tire to a standard rim, applying a standard internal pressure, allowing it to stand at 25 ° C for 24 hours, then applying ink to the surface of the tread, applying a standard load, and pressing it against thick paper for transfer.

[0049] Here, the "standard rim" is a rim defined for each tire in a standard system including the standard on which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Association), it is the standard rim in the applicable size described in the "JATMA YEAR BOOK", in the case of ETRTO (The European Tyre and Rim Technical Organisation), it is the "Measuring Rim" described in the "STANDARDS MANUAL", and in the case of TRA (The Tire and Rim Association, Inc.), it is the "Design Rim" described in the "YEAR BOOK". In the case of a tire not defined in the standard, it refers to a rim that can be assembled with the tire and can hold the internal pressure, that is, among the rims that do not cause air leakage between the rim / tire, the one with the smallest rim diameter and then the narrowest rim width.

[0050] The "normal internal pressure" is the air pressure defined for each tire by the above-mentioned standard. For JATMA, it is the maximum air pressure; for TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and for ETRTO, it refers to "INFLATION PRESSURE".

[0051] The "normal load" is the load defined for each tire by each standard in the standard system including the standard on which the above-mentioned tire is based, and refers to the maximum mass that can be allowed to be loaded on the tire. For JATMA, it is the maximum load capacity; for TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and for ETRTO, it is "LOAD CAPACITY".

[0052] In this embodiment, the groove width of the lateral groove refers to the widthwise distance perpendicular to the center line of the lateral groove on the contact surface obtained when the tire in the normal state is pressed with the normal load at a camber angle of 0 degrees.

[0053] 2. Tread Rubber Next, as described above, in the tire of this embodiment, at least one layer of the rubber layer forming the tread contains styrene-butadiene rubber with a styrene content of 30% by mass or less and a vinyl bond content in the butadiene part of 40% by mass or less, and isoprene rubber as rubber components, and is formed of a rubber composition that shows a maximum value (peak) within the range of -20°C or higher and 0°C or lower in the loss tangent (tanδ) measured under the conditions of a frequency of 10 Hz, an initial strain of 2%, and a dynamic strain rate of 1%.

[0054] Styrene-butadiene rubbers such as SBR with a styrene content of 30% by mass or less and a vinyl bond content in the butadiene part of 40% by mass or less have low polarity and thus excellent compatibility with isoprene rubbers such as natural rubber (NR). By blending such rubbers with good compatibility to form a rubber component, both the followability to the road surface and the frictional properties with the road surface can be achieved simultaneously.

[0055] Furthermore, by designing the tread rubber so that the loss tangent (tanδ) exhibits a maximum value (peak) within the range of -20°C or higher and 0°C or lower, that is, by designing a high glass transition temperature Tg, the rigidity of the rubber during braking can be increased, and thus good wet braking performance can be obtained even in a low-temperature environment.

[0056] In this embodiment, tanδ can be measured, for example, using a viscoelasticity measuring device "IPLEXER (registered trademark)" manufactured by GABO Co., Ltd. And the peak temperature of tanδ described above is more preferably within the range of -15°C or higher and 0°C or lower.

[0057] (1) Compounding materials of the rubber composition Such a rubber composition can be obtained from the rubber component described below and other compounding materials.

[0058] (a) Rubber component The rubber component preferably contains a diene rubber. Specific diene rubbers include isoprene rubbers (IR), butadiene rubbers (BR), styrene-butadiene rubbers (SBR), acrylonitrile-butadiene rubbers (NBR), chloroprene rubbers (CR), butyl rubbers (IIR), styrene-isoprene-butadiene copolymer rubbers (SIBR), and other rubbers. These may be used alone or in combination of two or more.

[0059] (i) Isoprene rubber When the rubber composition contains an isoprene rubber, the content (total content) of the isoprene rubber in 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, as the lower limit. Further, the upper limit is preferably 60 parts by mass or less, more preferably 40 parts by mass or less. By setting the content in this way, the SBR phase and the isoprene rubber phase form a co-continuous structure, and other compounding agents can be retained in each other's phases, so that the occurrence of the above-mentioned defects can be sufficiently suppressed.

[0060] Specific examples of the isoprene rubber include natural rubber (NR), isoprene rubber (IR), modified NR, denatured NR, denatured IR, and the like.

[0061] As NR, for example, those generally used in the tire industry such as SIR20, RSS#3, TSR20, etc. can be used. IR is not particularly limited, and for example, those generally used in the tire industry such as IR2200, etc. can be used. Examples of the modified NR include deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc. Examples of the denatured NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Examples of the denatured IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. These may be used alone or in combination of two or more.

[0062] (b) SBR When the rubber composition contains SBR, the content of SBR in 100 parts by mass of the rubber component is preferably 30 parts by mass or more as the lower limit and preferably 60 parts by mass or less as the upper limit. The weight average molecular weight of SBR is, for example, 100,000 or more and 2,000,000 or less as the lower and upper limits. In the SBR used in this embodiment, the styrene content is 30% by mass or less, and the vinyl bond content (1,2-bond butadiene unit amount) in the butadiene part is 40% by mass or less. The structure identification of SBR (measurement of styrene content and vinyl bond content) can be performed using, for example, an apparatus of the JNM-ECA series manufactured by JEOL Ltd.

[0063] The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. can be used. The SBR may be either unmodified SBR or modified SBR.

[0064] 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 (terminal-modified SBR having the above functional group at the terminal) in which at least one terminal of 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, etc. may be mentioned.

[0065] 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, etc. Note that these functional groups may have substituents.

[0066] Further, as the modified SBR, for example, an SBR modified with a compound (modifying agent) represented by the following (Formula 1) can be used.

[0067]

Chemical formula

[0068] In the formula, R1, R2, and R3 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. R4 and R5 are the same or different and represent a hydrogen atom or an alkyl group. R4 and R5 may combine to form a ring structure together with the nitrogen atom. n represents an integer.

[0069] As the modified SBR modified by the compound (modifying agent) represented by the above formula, SBR in which the polymerization terminal (active terminal) of solution-polymerized styrene-butadiene rubber (S-SBR) is modified by the compound represented by the above formula (modified SBR described in JP-A-2010-111753, etc.) can be used.

[0070] As R1, R2, and R3, an alkoxy group is preferable (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms). As R4 and R5, an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms) is preferable. n is preferably 1 to 5, more preferably 2 to 4, and still more preferably 3. When R4 and R5 combine to form a ring structure together with the nitrogen atom, a 4- to 8-membered ring is preferable. 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).

[0071] 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. These may be used alone or in combination of two or more.

[0072] In addition, as the modified SBR, modified SBR modified with the following compounds (modifying agents) can also be 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; 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;(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; 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, 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, 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, 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, N-methyl-5-methyl-2-pyrrolidone; N-substituted piperidones such as N-methyl-2-piperidone, N-vinyl-2-piperidone, 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, N-phenyl-β-propiolactam; in addition, 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. The modification with the above compound (modifying agent) can be carried out by a known method.;

[0073] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., Versalis and the like can be used. The SBR may be used alone or in combination of two or more kinds.;

[0074] (C) BR The rubber composition may contain a butadiene rubber (BR) as necessary. When BR is included, the content of BR in 100 parts by mass of the rubber component is, for example, 10 parts by mass or more and 30 parts by mass or less. The weight average molecular weight of BR is, for example, 100,000 or more and 2,000,000 or less. The vinyl bond amount of BR is, for example, 1% by mass or more and 30% by mass or less. The cis content of BR is, for example, 1% by mass or more and 98% by mass or less. The trans content of BR is, for example, 1% by mass or more and 60% by mass or less.;

[0075] BR is not particularly limited, and BR with a high cis content (cis content of 90% or more), BR with a low cis content, BR containing syndiotactic polybutadiene crystals, etc. can be used. BR may be either unmodified BR or modified BR, and examples of the modified BR include the modified BR into which the aforementioned functional groups are introduced. These may be used alone or in combination of two or more. The cis content can be measured by infrared absorption spectroscopy.

[0076] As BR, for example, products of Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

[0077] (b) Compounding materials other than the rubber component (i) Silica The rubber composition preferably contains silica. Specifically, silica having a nitrogen adsorption specific surface area (N 2 SA) of 150 m 2 / g or more and 250 m 2 / g or less is preferable, and more preferably 190 m 2 / g or more and 220 m 2 / g or less. The N 2 SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0078] The content based on 100 parts by mass of the rubber component is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more as the lower limit. Also, as the upper limit, it is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 120 parts by mass or less, and particularly preferably 100 parts by mass or less.

[0079] The content of silica is preferably 40 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the rubber component, and it is preferable to make the content of silica larger than the styrene and vinyl bond amounts in SBR. Thereby, since silica can be evenly dispersed throughout the rubber matrix, the hardness is made uniform even at low temperatures, the followability of the tire to the road surface is improved, and the occurrence of defects can be suppressed.

[0080] Specific silicas include, for example, dry-process silica (anhydrous silica), wet-process silica (hydrous silica), etc. Among them, wet-process silica is preferred because of its large number of silanol groups. For example, products of Degussa, Rhodia, Tosoh Silica Corporation, Solvay Japan, Tokuyama Corporation, etc. can be used.

[0081] (b) Silane coupling agent The rubber composition preferably contains a silane coupling agent together with silica. 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-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, etc. sulfide-based, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercapto-based such as NXT and NXT-Z manufactured by Momentive, vinyl-based such as vinyltriethoxysilane and vinyltrimethoxysilane, amino-based such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy-based such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, nitro-based such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, chloro-based such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These may be used alone or in combination of two or more.

[0082] The preferable content of the silane coupling agent is, for example, 3.0 parts by mass or more and 20.0 parts by mass or less, more preferably 4.5 parts by mass or more, 10 parts by mass or less, and even more preferably 8.0 parts by mass or less with respect to 100 parts by mass of silica. As specific silane coupling agents, for example, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azmax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used.

[0083] Among them, a highly reactive mercapto-based silane coupling agent is particularly preferable because it can improve the dispersion of silica, reinforce both the SBR phase and the NR phase, and suppress the occurrence of defects.

[0084] (C) Carbon black The rubber composition preferably contains carbon black. The content of carbon black is, for example, 1 part by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0085] The carbon black is not particularly limited, and examples include furnace black (furnace carbon black) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black (acetylene carbon black); thermal black (thermal carbon black) such as FT and MT; channel black (channel carbon black) such as EPC, MPC, and CC; graphite, etc. These may be used alone or in combination of two or more.

[0086] The nitrogen adsorption specific surface area (N 2 SA) of the carbon black is, for example, 30 m 2 / g or more and 250 m 2is below / g. The dibutyl phthalate (DBP) absorption of carbon black is, for example, 50 ml / 100 g or more and 250 ml / 100 g or less. The nitrogen adsorption specific surface area of carbon black is measured in accordance with ASTM D4820-93, and the DBP absorption is measured in accordance with ASTM D2414-93.

[0087] Specific carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. As commercial products, for example, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nippon Chemical Carbon Co., Ltd., Columbia Carbon Company, etc. can be used. These may be used alone or in combination of two or more.

[0088] (ii) Resin component The rubber composition preferably contains a resin component, whereby the Tg can be designed to be high. The content with respect to 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably more than 25 parts by mass as the lower limit. Also, as the upper limit, it is preferably less than 40 parts by mass, more preferably less than 30 parts by mass. By containing the resin component in an amount less than the styrene-vinyl bond amount in such a range, the formation of minute domains of the resin due to the interaction with SBR in the matrix can be prevented.

[0089] From the viewpoint of wet grip performance, the softening point of the resin component is preferably 60°C or higher, more preferably 65°C or higher. Also, from the viewpoint of wet grip performance at low temperatures, it is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. The softening point of the resin component is measured with a ring and ball softening point measuring device in accordance with JIS K 6220-1:2001 and is defined as the temperature at which the ball drops.

[0090] The resin component is not particularly limited, and examples thereof include petroleum resins, terpene resins, rosin resins, phenolic resins, etc. that are commonly used in the tire industry. These resin components may be used alone or in combination of two or more. Among these, it is preferable to use a terpene resin, and it may be used in combination with other resins.

[0091] Terpene resins have good compatibility with isoprene rubber and are difficult to form minute domains in the system. Therefore, stress concentration is easily alleviated, and abrasion resistance at low temperatures can be improved. Further, due to the good compatibility of terpene resins with isoprene rubber, the system becomes uniform, so that the peak temperature of tanδ can be increased, and heat generation when input at high frequency can be improved.

[0092] Examples of terpene resins include polyterpenes, terpene phenols, aromatic-modified terpene resins, etc. Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are hydrocarbons represented by the composition of (C 5 H 8 ) n and their oxygen-containing derivatives, and are compounds having a terpene as a basic skeleton, which are classified into monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32 ), etc. Examples thereof include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-felandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, etc.

[0093] Examples of polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene / limonene resin, which are made from the above-mentioned terpene compounds as raw materials, as well as hydrogenated terpene resins obtained by hydrogenating the terpene resins. Examples of terpene phenols include resins obtained by copolymerizing the above-mentioned terpene compounds and phenolic compounds, and resins obtained by hydrogenating such resins. Specifically, examples include resins obtained by condensing the above-mentioned terpene compounds, phenolic compounds, and formalin. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol. Examples of aromatic-modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating such resins. The aromatic compound is not particularly limited as long as it has an aromatic ring. Examples include phenolic compounds such as phenol, alkylphenol, alkoxyphenol, and unsaturated hydrocarbon group-containing phenol; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, and unsaturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and unsaturated hydrocarbon group-containing styrene; and coumarone and indene.

[0094] As commercially available terpene resins, for example, products of Yasuhara Chemical Co., Ltd. can be used, and they may be used alone or in combination of two or more.

[0095] Examples of petroleum resins include C5-based petroleum resins, aromatic-based petroleum resins, and C5C9-based petroleum resins.

[0096] The "C5-based petroleum resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of the C5 fraction include petroleum fractions corresponding to 4 to 5 carbon atoms such as cyclopentadiene, pentene, pentadiene, and isoprene. As the C5-based petroleum resin, dicyclopentadiene resin (DCPD resin) is preferably used.

[0097] "Aromatic petroleum resin" refers to a resin obtained by polymerizing a C9 fraction, which may be hydrogenated or modified. Examples of the C9 fraction include petroleum fractions corresponding to 8 to 10 carbon atoms such as vinyltoluene, alkylstyrene, indene, and methylindene. As specific examples of the aromatic petroleum resin, for example, coumarone-indene resin, coumarone resin, indene resin, and aromatic vinyl resin are preferably used. As the aromatic vinyl resin, due to economic reasons, ease of processing, and excellent heat generation properties, a homopolymer of α-methylstyrene or styrene or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred. As the aromatic vinyl resin, for example, those commercially available from companies such as Crayton and Eastman Chemical can be used.

[0098] "C5C9 petroleum resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, which may be hydrogenated or modified. Examples of the C5 fraction and the C9 fraction include the above-mentioned petroleum fractions. As the C5C9 petroleum resin, for example, those commercially available from Tosoh Corporation, LUHUA, etc. can be used.

[0099] The rosin resin is not particularly limited, and examples thereof include natural resin rosin, rosin-modified resins obtained by modifying it by hydrogenation, disproportionation, dimerization, esterification, etc.

[0100] The phenolic resin is not particularly limited, and examples thereof include phenol formaldehyde resin, alkylphenol formaldehyde resin, alkylphenol acetylene resin, oil-modified phenol formaldehyde resin, etc.

[0101] (H)oil The rubber composition may contain oil. The oil content is preferably at least 3 parts by mass, more preferably at least 5 parts by mass, and even more preferably at least 10 parts by mass, based on 100 parts by mass of the rubber component. The upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. Note that the oil content includes the amount of oil contained in the rubber (oil-extended rubber).

[0102] 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, etc. 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, etc. These may be used alone or in combination of two or more.

[0103] Examples of the oil include products of Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Corporation, Oleos SA, H&R AG, Toyokuni Oil Co., Ltd., Showa Shell Sekiyu KK, Fuji Kogyo Co., Ltd., etc., which can be used.

[0104] (f) Wax The rubber composition preferably contains wax. The wax content is, for example, 0.5 parts by mass or more and 20 parts by mass or less based on 100 parts by mass of the rubber component.

[0105] The wax is not particularly limited, and examples include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as vegetable waxes and animal waxes; and synthetic waxes such as polymers of ethylene, propylene, etc. These may be used alone or in combination of two or more.

[0106] 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.

[0107] (B) Antioxidant The rubber composition preferably contains an antioxidant. The content of the antioxidant is, for example, 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0108] Examples of the antioxidant include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; p-phenylenediamine-based antioxidants such as N-isopropyl-N′-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, and N,N′-di-2-naphthyl-p-phenylenediamine; quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; bis, tris, polyphenol-based antioxidants 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.

[0109] As the antioxidant, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., Flexsys, etc. can be used.

[0110] (E) Stearic acid The rubber composition may contain stearic acid. The content of stearic acid is, for example, 0.5 part by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the rubber component. 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.

[0111] (Li) Zinc oxide The rubber composition may contain zinc oxide. The content of zinc oxide is, for example, 0.5 parts by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the rubber component. 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., Sho Do Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0112] (Nu) Crosslinking agent and vulcanization accelerator The rubber composition preferably contains a crosslinking agent such as sulfur. The content of the crosslinking agent is, for example, 0.1 parts by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0113] 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.

[0114] As the sulfur, for example, products of Tsurumi 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.

[0115] Examples of crosslinking agents other than sulfur include sulfur-containing vulcanizing agents such as Tackiol V200 manufactured by Tago Chemical Industry Co., Ltd., DURALINK HTS (sodium 1,6 - hexamethylene - dithiolsulfate dihydrate) manufactured by Flexsys, KA9188 (1,6 - bis(N,N’ - dibenzylthiocarbamoyldithio)hexane) manufactured by Rancess, etc., and organic peroxides such as dicumyl peroxide.

[0116] The rubber composition preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, 0.3 parts by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0117] Examples of vulcanization accelerators 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.

[0118] (Le) Others In addition to the above components, the rubber composition may further contain additives commonly 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, for example, 0.1 part by mass or more and 200 parts by mass or less based on 100 parts by mass of the rubber component.

[0119] (2) Preparation of rubber composition The rubber composition is prepared by a production method including a base kneading step of kneading a rubber component and a filler such as silica or carbon black, and a finishing kneading step of kneading the kneaded product obtained in the base kneading step and a crosslinking agent, by a general method.

[0120] Kneading can be carried out using a known (closed type) kneader such as a Banbury mixer, a kneader, or an open roll.

[0121] The kneading temperature in the base kneading step is, for example, 50°C or higher and 200°C or lower, and the kneading time is, for example, 30 seconds or longer and 30 minutes or shorter. In the base kneading step, in addition to the above components, compounding agents used in the conventional rubber industry, such as softening agents like oil, stearic acid, zinc oxide, anti-aging agents, wax, vulcanization accelerators, etc., may be appropriately added and kneaded as needed.

[0122] In the finishing kneading step, the kneaded product obtained in the base kneading step and a crosslinking agent are kneaded. The kneading temperature in the finishing kneading step is, for example, room temperature or higher and 80°C or lower, and the kneading time is, for example, 1 minute or longer and 15 minutes or shorter. In the finishing kneading step, in addition to the above components, vulcanization accelerators, zinc oxide, etc. may be appropriately added and kneaded as needed.

[0123] 3. Tire Manufacturing The tire of the present invention is manufactured by a usual method using the unvulcanized rubber composition obtained through the above finishing kneading step. That is, the unvulcanized rubber composition is extruded according to the shape of each tire member of the tread, and together with other tire members, it is molded by a usual method on a tire molding machine to first produce an unvulcanized tire.

[0124] Specifically, on a forming drum, an inner liner as a member for ensuring the airtightness of the tire, a carcass as a member for withstanding the load, impact, and inflation air pressure received by the tire, a belt as a member for strongly clamping the carcass to increase the rigidity of the tread, etc. are wound, both ends of the carcass are fixed to both side edges, and a bead portion as a member for fixing the tire to a rim is arranged, and after forming it into a toroidal shape, a tread is attached to the central portion of the outer periphery, and a sidewall portion as a member for protecting the carcass and withstanding bending is bonded to the radially outer side to produce an unvulcanized tire.

[0125] Thereafter, the produced unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire. The vulcanization step can be carried out by applying known vulcanization means. The vulcanization temperature is, for example, 120°C or higher and 200°C or lower, and the vulcanization time is, for example, 5 minutes or longer and 15 minutes or shorter.

[0126] In this embodiment, when the tire is mounted on a standard rim and the internal pressure is the standard internal pressure, if the cross-sectional width of the tire is Wt (mm) and the outer diameter is Dt (mm), it is preferable that 1963.4 ≦ (Dt 2 × π / 4) / Wt ≦ 2827.4 is satisfied. That is, with respect to the cross-sectional width Wt of the tire, the area [(Dt / 2) 2 × π) = (Dt 2 × π / 4)] from the lateral direction of the tire is preferably a tire larger than the conventional one. By satisfying the above formula, the moment of inertia during the rolling of the tire can be sufficiently ensured. In addition, by increasing the outer diameter more than the conventional one, the time when it does not contact the ground during braking can be extended. Therefore, heat generation and air cooling during contact with the ground can be efficiently repeated, and good heat generation performance can be obtained in the tread portion during braking. As a result, further improvement in wet grip performance in a low-temperature environment can be achieved.

[0127] Note that the outer diameter Dt of the tire in the above formula is the outer diameter of the tire in a state where the tire is mounted on a standard rim and the internal pressure is the standard internal pressure (for example, 250 kPa for a passenger car tire) and it is unloaded. And the cross-sectional width Wt of the tire is the straight-line distance between the sidewalls including all the patterns and characters on the side surface of the tire in a state where the tire is mounted on a standard rim and the internal pressure is the standard internal pressure and it is unloaded, that is, the width obtained by removing the patterns, characters, etc. on the side surface of the tire from the total width of the tire.

[0128] Specific tires that can satisfy the above formula include tires with size notations such as 145 / 60R18, 145 / 60R19, 155 / 55R18, 155 / 55R19, 155 / 70R17, 155 / 70R19, 165 / 55R20, 165 / 55R21, 165 / 60R19, 165 / 65R19, 165 / 70R18, 175 / 55R19, 175 / 55R20, 175 / 55R22, 175 / 60R18, 185 / 55R19, 185 / 60R20, 195 / 50R20, 195 / 55R20, etc.

[0129] Then, the tires satisfying the above formulas are preferably applied to pneumatic tires for passenger cars, and by satisfying the above formulas, they can more preferably contribute to the solution of the problems in the present invention.

[0130] The pneumatic tire for passenger cars mentioned here refers to a tire mounted on an automobile running on four wheels, and a tire with a maximum load capacity of 1000 Kg or less.

[0131] The maximum load capacity is not particularly limited as long as it is 1000 Kg or less. Generally, as the maximum load capacity increases, the tire weight tends to increase, and accordingly, the braking distance also becomes longer due to inertia. Therefore, it is preferably 900 Kg or less, more preferably 800 Kg or less, and still more preferably 700 Kg or less.

[0132] From the viewpoint of the braking distance due to inertia as described above, the tire weight is preferably 20 Kg or less, more preferably 15 Kg or less, and still more preferably 12 Kg or less, 10 Kg or less, 8 Kg or less. Note that the tire of the present invention may be provided with electronic components. In this case, the tire weight mentioned here is the tire weight including the weight of the electronic components and the electronic component mounting members. Also, when a sealant, sponge, etc. are provided in the inner cavity portion, it is the tire weight including them.

Examples

[0133] Hereinafter, the present invention will be described more specifically with reference to examples.

[0134] 1. Manufacture of rubber composition First, the rubber composition was manufactured.

[0135] (1) Compounding materials First, the following compounding materials were prepared.

[0136] (a) Rubber component (i) NR: TSR20 (ii) SBR1: Europrene SOL R C3737 manufactured by Versalis (Styrene content: 37% by mass, vinyl bond content: 37% by mass) (iii) SBR2: Europrene SOL R C2525 manufactured by Versalis (Styrene content: 25% by mass, vinyl bond content: 25% by mass) (iv) SBR3: Modified S-SBR prepared according to the method described in the following paragraph (Styrene content: 28% by mass, vinyl bond content: 56% by mass) (v) BR: BR150B manufactured by Ube Industries, Ltd.

[0137] The above SBR3 was prepared according to the procedure shown below. First, 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 after further polymerization for 5 minutes, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane was added as a modifier to carry out the reaction. After completion of the polymerization reaction, 2,6-di-tert-butyl-p-cresol was added. Then, solvent was removed by steam stripping and dried with a hot roll adjusted to 110°C to obtain SBR3.

[0138] (b) Compounding materials other than the rubber component (i) Silica: Ultrasil VN3 (N manufactured by Evonik Industries AG 2 SA: 175 m 2 / g) (ii) Silane coupling agent 1: Si266 manufactured by Evonik Industries AG (Bis(3-triethoxysilylpropyl) disulfide) (iii) Silane coupling agent 2: NXT-Z45 manufactured by Momentive (Mercapto-based silane coupling agent) (iv) Carbon black: Diablack N220 manufactured by Mitsubishi Chemical Corporation (Ho) Oil: Diana Process AH-24 (aromatic type) manufactured by Idemitsu Kosan Co., Ltd. (He) Resin 1: SYLVARES SA 85 manufactured by Clayton (Aromatic vinyl resin) (To) Resin 2: TO125 manufactured by Yasuhara Chemical Co., Ltd. (Aromatic modified terpene resin) (Chi) Wax: Sannox Wax manufactured by Ouchi Shinsei Chemical Co., Ltd. (Ri) Antioxidant: No Crack 6C manufactured by Ouchi Shinsei Chemical Co., Ltd. (Nu) Stearic acid: Bead Stearic Acid "Tsubaki" manufactured by NOF Corporation (Ru) Zinc oxide: Zinc White No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. (Nu) Crosslinking agent and vulcanization accelerator Sulfur: Powder sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator: Nocceler NS manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

[0139] (2) Production of rubber composition According to the formulation shown in Table 1, using a Banbury mixer, materials other than sulfur and vulcanization accelerator were kneaded at 150 °C for 5 minutes to obtain a kneaded product. Each formulation amount is in parts by mass.

[0140]

Table 1

[0141] 2. Tire production Next, sulfur and a vulcanization accelerator were added to the obtained tread rubber composition, and it was kneaded using an open roll at 80 °C for 5 minutes to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was molded into a tread having the groove pattern shapes shown in Table 2 and Table 3, and bonded together with other tire members to form an unvulcanized tire, which was press-vulcanized at 170 °C for 10 minutes to manufacture each test tire (size: 175 / 80R16).

[0142] In Tables 2 and 3, Pattern 1 of the transverse grooves refers to the pattern of the transverse grooves shown in Fig. 3, Pattern 2 of the transverse grooves refers to the pattern of the transverse grooves shown in Fig. 1, and Pattern 3 of the transverse grooves refers to the pattern of the transverse grooves shown in Fig. 2. In Patterns 2 and 3 of the transverse grooves, when the width on the end side is A (mm) and the width on the central part side is B (mm), the transverse grooves were formed such that B / A is 3.0 for Pattern 2 and 6.0 for Pattern 3.

[0143] 3. Evaluation Test (1) Measurement of Loss Tangent (tanδ) From the rubber layer of the tread part of each test tire, viscoelastic measurement samples with a size of 20 mm in length × 4 mm in width × 1 mm in thickness were collected with the tire circumferential direction as the long side. Using an Iplexer series manufactured by GABO, under the conditions of a frequency of 10 Hz, an initial strain of 2%, an amplitude of ±1%, and a heating rate of 2°C / min, the temperature was changed from -50°C to 5°C to measure tanδ, and the temperature distribution curve was created. Then, the temperature (tanδ peak temperature) corresponding to the largest tanδ value in the obtained temperature distribution curve was defined as the glass transition temperature (Tg). The results are shown together in Table 1.

[0144] (2) Low-Temperature Wet Grip Performance Evaluation Test Each test tire was mounted on all four wheels of a vehicle (a domestic FF vehicle with a displacement of 2000 cc), and after driving 8000 km at a speed of 80 km / h on a test course of a wet asphalt road surface (temperature less than 20°C), the brakes were applied and the braking distance was measured. The evaluation was carried out by indexing according to the following formula with the braking distance measured when the test tire of Comparative Example 1 was new set as 100. The larger the numerical value, the better the wet grip performance at low temperatures. The results are shown together in Tables 2 and 3. Wet Grip Performance =[(Braking Distance of Comparative Example 1 / Braking Distance of Test Tire)] × 100

[0145] (3) Evaluation of Wear Performance In addition, the wear performance was evaluated.

[0146] Specifically, for each test tire that had traveled 8,000 km in the above low-temperature wet grip performance evaluation test, the depth of the circumferential main groove near the equator of the tire was measured, and the change rate (decrease rate) with respect to the groove depth measured before the test was determined. The evaluation was performed by indexing according to the following formula based on the change rate in Comparative Example 8 and the change rate in each test tire. The larger the numerical value, the less the groove wears and the better the wear performance. The results are shown together in Tables 2 and 3. Wear performance = [(Change rate of groove depth in Comparative Example 8 / Change rate of groove depth in test tire)] × 100

[0147]

Table 2

[0148]

Table 3

[0149] From Tables 2 and 3, it can be seen that when a tread is formed of a rubber composition containing a styrene-butadiene rubber having a styrene content of 30% by mass or less and a vinyl bond content in the butadiene portion of 40% by mass or less and an isoprene rubber as rubber components, and the loss tangent (tanδ) measured under the conditions of a frequency of 10 Hz, an initial strain of 2%, and a dynamic strain rate of 1% shows a peak in the range of -20°C or higher and 0°C or lower, and a lateral groove having a shape that becomes wider on the central side than on the end side is formed, the wet grip performance in a low-temperature environment is improved.

[0150] And when the amount of the isoprene rubber in 100 parts by mass of the rubber components is 20 parts by mass or more and 60 parts by mass or less, and the peak temperature of tanδ is -15°C or higher and 0°C or lower, etc., it can be seen that the wet grip performance in a low-temperature environment is further improved. Also, when the compounding materials are appropriately selected as shown in Claims 2 to 12, it can be seen that the wet grip performance in a low-temperature environment is further improved.

[0151] Although the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above embodiments within the same and equivalent scope of the present invention.

Explanation of Reference Signs

[0152] 3 Circumferential Main Groove 4 Land Portion 5 Cross Groove 10 Branch Groove CL Center Line c Central Portion Side e End Portion Side

Claims

1. A pneumatic tire comprising a tread in which two or more circumferential main grooves continuously extending in the circumferential direction of the tire are formed, wherein the tread, a plurality of lateral grooves are formed in the land portion partitioned in the tire width direction by two adjacent circumferential main grooves, and the lateral grooves are wider on the central portion side than on the end portion side, at least one layer of the rubber layer forming the tread, contains styrene-butadiene rubber having a styrene content of 30% by mass or less and a vinyl bond content in the butadiene portion of 40% by mass or less and isoprene rubber as rubber components, and has a loss tangent (tanδ) measured under the conditions of a frequency of 10 Hz, an initial strain of 2%, and a dynamic strain rate of 1% showing a maximum value (peak) within the range of -20°C or higher and 0°C or lower, and is formed of a rubber composition, and is characterized by a pneumatic tire.

2. The pneumatic tire according to claim 1, wherein the amount of isoprene rubber in 100 parts by mass of the rubber components is 10 parts by mass or more and 60 parts by mass or less.

3. The pneumatic tire according to claim 2, wherein the amount of isoprene rubber in 100 parts by mass of the rubber components is 20 parts by mass or more and 40 parts by mass or less.

4. The pneumatic tire according to any one of claims 1 to 3, wherein the amount of styrene-butadiene rubber in 100 parts by mass of the rubber components is 30 parts by mass or more and 60 parts by mass or less.

5. In the rubber composition, butadiene rubber is further added to the rubber components, The pneumatic tire according to any one of claims 1 to 4, wherein the amount of butadiene rubber in 100 parts by mass of the rubber components is 10 parts by mass or more and 30 parts by mass or less.

6. The pneumatic tire according to any one of claims 1 to 5, wherein the rubber composition contains a resin component exceeding 5 parts by mass and less than 40 parts by mass with respect to 100 parts by mass of the rubber components.

7. The pneumatic tire according to claim 6, wherein the resin component is a terpene resin.

8. The pneumatic tire according to any one of claims 1 to 7, wherein the rubber composition contains 40 parts by mass or more and 200 parts by mass or less of silica with respect to 100 parts by mass of the rubber components.

9. The silica has a nitrogen adsorption specific surface area of 150 m ２ / g or more, and the pneumatic tire according to claim 8, characterized in that.

10. The pneumatic tire according to claim 8 or claim 9, wherein the rubber composition contains a silane coupling agent.

11. The pneumatic tire according to claim 10, wherein the content of the silane coupling agent in the rubber composition is 3.0 parts by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the rubber component.

12. The pneumatic tire according to claim 11, wherein the content of the silane coupling agent in the rubber composition is 4.5 parts by mass or more and 8.0 parts by mass or less with respect to 100 parts by mass of the rubber component.

13. The pneumatic tire according to any one of claims 10 to 12, wherein the rubber composition contains a mercapto-based silane coupling agent as the silane coupling agent.

14. The pneumatic tire according to any one of claims 1 to 13, wherein the rubber composition shows a maximum value (peak) within the range of -15°C or higher and 0°C or lower in the loss tangent (tanδ) measured under the conditions of a frequency of 10 Hz, an initial strain of 2%, and a dynamic strain rate of 1%.

15. The tread is formed of a plurality of rubber layers, The pneumatic tire according to any one of claims 1 to 14, wherein the rubber composition is used for the cap rubber layer of the tread.

16. The pneumatic tire according to any one of claims 1 to 15, wherein when the width on the side of the circumferential main groove end of the lateral groove is A (mm) and the width on the central side is B (mm), 1.0 < B / A ≤ 40.

0.

17. The pneumatic tire according to claim 16, wherein 5.0 ≤ B / A ≤ 35.

0.

18. When incorporated into a standard rim and the cross-sectional width of the tire is Wt (mm) and the outer diameter is Dt (mm) with the internal pressure being the standard internal pressure, 1963.4 ≦ (Dt ２ × π / 4) / Wt ≦ 2827.4, and the pneumatic tire according to any one of claims 1 to 17, characterized in that it satisfies the above condition.

19. The pneumatic tire according to any one of claims 1 to 18, which is a pneumatic tire for a passenger car.

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