tire

Abstract

To provide a tire that can be improved in integrated performance of low-fuel economy performance, abrasion resistance and steering stability.SOLUTION: A tire comprises a tread composed of rubber compositions that include rubber components containing isoprene rubber, butadiene rubber and styrene-butadiene rubber and a filler containing silica and carbon black. The rubber compositions satisfy the following formulas (1)-(3): contents of isoprene rubber>contents of styrene butadiene rubber (1); contents of isoprene rubber>contents of butadiene rubber (2); and contents of silica≥contents of carbon black (3), where tanδ at 30°C of the rubber compositions and a negative rate N (%) of the tread satisfy the following formulas (4) and (5): tanδ<0.10 at 30°C (4) and tanδ×N<4.0 at 30°C (5).SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In response to recent demands for improved fuel economy in tires, improvements to the tread compounding, for example, are required. Reducing the amount of filler carbon black or silica is effective for improving fuel economy. However, reducing the amount of filler reduces the strength of the tread rubber, impairing chipping resistance and abrasion resistance, and also reduces the rigidity of the tread portion, resulting in problems such as poor steering stability. Summary of the Invention [Problem to be solved by the invention]

[0003] An object of the present invention is to solve the above problems and to provide a tire that can improve the overall performance of fuel economy, wear resistance, and driving stability. [Means for solving the problem]

[0004] The present invention provides a tire having a tread made of a rubber composition including a rubber component containing an isoprene-based rubber, a butadiene rubber, and a styrene-butadiene rubber, and a filler containing silica and carbon black, The rubber composition satisfies the following formulas (1) to (3): (1) Isoprene rubber content > Styrene butadiene rubber content (2) Isoprene rubber content > Butadiene rubber content (3) Silica content ≥ Carbon black content The tan δ of the rubber composition at 30° C. and the negative rate N (%) of the tread relate to the tire which satisfy the following formulas (4) and (5). (4) tan δ at 30°C < 0.10 (5) tan δ × N at 30°C < 4.0

[0005] The silica preferably has an average primary particle size of 20 nm or less.

[0006] The rubber composition preferably contains less than 15 parts by mass of the liquid plasticizer per 100 parts by mass of the rubber component.

[0007] The rubber composition preferably contains 5 parts by mass or more of the solid plasticizer per 100 parts by mass of the rubber component.

[0008] The tire preferably comprises bead reinforcement rubber.

[0009] It is preferable that the complex modulus of elasticity E1* of the tread at 30° C. and the complex modulus of elasticity E2* of the bead reinforcing rubber at 70° C. satisfy the following formula: E2* / E1*>0.5

[0010] The tire includes an apex and a bead reinforcing rubber, It is preferable that the complex modulus of elasticity E3* of the apex at 70° C. and the complex modulus of elasticity E2* of the bead reinforcing rubber at 70° C. satisfy the following formula: E3*>E2*

[0011] The negative ratio (N) of the tread is preferably 40% or less. [Effects of the Invention]

[0012] According to the present invention, there is provided a tire having a tread made of a rubber composition containing a rubber component containing an isoprene-based rubber, a butadiene rubber, and a styrene-butadiene rubber, and a filler containing silica and carbon black, wherein the rubber composition satisfies the formulas (1) to (3), and the tan δ at 30°C of the rubber composition and the negative rate N (%) of the tread satisfy the formulas (4) to (5), thereby enabling improvement in overall performance of fuel economy, wear resistance, and handling stability. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a tire meridian cross-sectional view of a pneumatic tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view of a sidewall portion and a bead portion of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] The tire of the present invention has a tread made of a rubber composition containing a rubber component containing an isoprene-based rubber, a butadiene rubber, and a styrene-butadiene rubber, and a filler containing silica and carbon black, wherein the rubber composition satisfies the formulas (1) to (3), and the tan δ at 30°C of the rubber composition and the negative index N (%) of the tread satisfy the formulas (4) to (5). The tire is excellent in overall performance of fuel economy, wear resistance, and handling stability.

[0015] The reason why the above-mentioned effects are obtained is not entirely clear, but it is presumed to be due to the following mechanism. When the amount of isoprene-based rubber in the rubber composition constituting the tread is adjusted to a large amount that satisfies formulas (1) and (2), and the amount of silica is adjusted to be equal to or greater than the amount of carbon black (formula (3)), the large amounts of isoprene-based rubber and silica suppress the heat buildup of the tread rubber and increase the strength of the tread rubber, which is thought to impart good wear resistance and handling stability. Furthermore, by adjusting the tan δ at 30°C of the rubber composition to less than a predetermined value (formula (4)), and simultaneously adjusting the product of said tan δ and the tread's negative rate N (%) to less than a predetermined value (formula (5)), the heat buildup of the tread rubber is further suppressed, and good handling stability and wear resistance are obtained due to the small groove area ratio of the tread. It is presumed that the above mechanism achieves good wear resistance and handling stability while improving fuel economy, thereby improving these overall performances.

[0016] As described above, the present invention solves the problem (objective) of improving the overall performance of fuel economy, wear resistance, and handling stability by configuring a tire that satisfies formula (1) "content of isoprene-based rubber > content of styrene-butadiene rubber," formula (2) "content of isoprene-based rubber > content of butadiene rubber," formula (3) "content of silica ≥ content of carbon black," formula (4) "tan δ at 30°C < 0.10," and formula (5) "tan δ × N at 30°C < 4.0." In other words, the parameters of formulas (1) to (5) do not define the problem (objective); the object of the present application is to improve the overall performance of fuel economy, wear resistance, and handling stability, and the invention employs a configuration that satisfies the parameters as a means to achieve this.

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to this embodiment.

[0018] Fig. 1 is a tire meridian cross-sectional view including the tire rotation axis (not shown) of a pneumatic tire (hereinafter sometimes simply referred to as "tire") 1 according to one embodiment of the present invention in a normal state. Fig. 1 shows a preferred embodiment of a tire 1 for passenger cars that is suitable for mounting on 4WD vehicles and the like that can run not only on dry asphalt roads but also on rough road surfaces such as rubble roads and muddy ground. However, the tire 1 can also be used for heavy loads, for example.

[0019] In this specification, "normal condition" refers to a condition in which the tire 1 is mounted on a normal rim (not shown), inflated to normal internal pressure, and no load is applied. Unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal condition.

[0020] A "genuine rim" is a rim that is defined for each tire by a standard system that includes the standard on which tire 1 is based, such as a standard rim for JATMA, a "Design Rim" for TRA, or a "Measuring Rim" for ETRTO.

[0021] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard on which tire 1 is based, and is the maximum air pressure in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and "INFLATION PRESSURE" in the case of ETRTO.

[0022] The tire 1 of this embodiment includes a tread portion 2, a pair of sidewall portions 3, 3 extending radially inward from the tread portion 2, and a pair of bead portions 4, 4 continuing radially inward of the pair of sidewall portions 3, 3. An annular bead core 5 is embedded in the bead portion 4.

[0023] The tire 1 includes, for example, a tread rubber 2G that forms the tread contact surface 2a of the tread portion 2, a sidewall rubber 3G that forms the outer surface 3a of the sidewall portion 3, and a clinch rubber 4G that forms the outer surface 4a of the bead portion 4. Known embodiments are appropriately adopted for each of the sidewall rubber 3G and the clinch rubber 4G.

[0024] The tread rubber 2G is composed of a rubber composition including a rubber component containing isoprene-based rubber, butadiene rubber (BR), and styrene butadiene rubber (SBR), and a filler containing silica and carbon black.

[0025] The rubber composition constituting the tread rubber 2G contains, for example, isoprene-based rubber, BR, and SBR, but other usable rubber components include isoprene-based rubbers such as acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR), as well as diene-based rubbers other than BR and SBR.

[0026] The isoprene-based rubber and diene-based rubbers such as BR and SBR may be unmodified diene-based rubbers or modified diene-based rubbers. Examples of modified diene rubbers include diene rubbers having functional groups that interact with fillers such as silica and carbon black. Specific examples include terminal-modified diene rubbers (terminal-modified diene rubbers having the functional groups at the terminals) in which at least one terminal of the diene rubber has been modified with a compound (modifier) ​​having the functional group, main-chain-modified diene rubbers having the functional groups in the main chain, main-chain-terminal-modified diene rubbers having the functional groups in the main chain and at least one terminal (for example, main-chain-terminal-modified diene rubbers having the functional groups in the main chain and at least one terminal modified with the modifier), and terminal-modified diene rubbers modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having hydroxyl groups or epoxy groups introduced therein. These may be used alone or in combination of two or more.

[0027] Examples of the functional group include functional groups containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom. These may be used alone or in combination of two or more.

[0028] Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imido group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, and an epoxy group. These functional groups may have a substituent. Among them, an amino group (preferably an amino group in which a hydrogen atom of an amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferred because they provide a more suitable effect.

[0029] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. NRs such as SIR20, RSS#3, and TSR20 can be used, and IRs such as IR2200 can be used, which are commonly used in the tire industry. Modified NRs include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Modified NRs include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Modified IRs include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more.

[0030] The BR is not particularly limited, and examples thereof include those commonly used in the tire industry, such as BR with a high cis content, BR containing 1,2-syndiotactic polybutadiene crystals (SPB-containing BR), butadiene rubber synthesized using a rare earth catalyst (rare earth BR), and tin-modified butadiene rubber modified with a tin compound (tin-modified BR). Commercially available BRs include those from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Zeon Corporation. These may be used alone or in combination of two or more.

[0031] The BR may be either unmodified or modified. The modified BR includes BR having the above-mentioned functional groups.

[0032] From the viewpoint of performance on ice, the cis content of BR is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. In this specification, the cis content (cis-1,4-bond amount) is a value calculated from the signal intensity measured by infrared absorption spectroscopy or NMR analysis.

[0033] The SBR is not particularly limited, and examples thereof include emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. These may be used alone or in combination of two or more.

[0034] The styrene content of SBR is preferably 5.0% by mass or more, more preferably 10.0% by mass or more, even more preferably 15.0% by mass or more, and particularly preferably 20.0% by mass or more. The upper limit of the styrene content is preferably 60.0% by mass or less, more preferably 50.0% by mass or less, even more preferably 40.0% by mass or less, and particularly preferably 30.0% by mass or less. Within the above range, the effect tends to be more favorable. In this specification, the styrene content of SBR is 1 It is calculated by H-NMR measurement.

[0035] The vinyl content of the SBR is preferably 5.0% by mass or more, more preferably 10.0% by mass or more, even more preferably 12.0% by mass or more, and particularly preferably 14.0% by mass or more. The vinyl content is preferably 50.0% by mass or less, more preferably 30.0% by mass or less, even more preferably 20.0% by mass or less, and particularly preferably 18.0% by mass or less. Within the above range, the effect tends to be more favorable. The vinyl content (amount of 1,2-bonded butadiene units) can be measured by infrared absorption spectroscopy.

[0036] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

[0037] The SBR may be unmodified or modified. The modified SBR may be an SBR having the above-mentioned functional groups.

[0038] In the rubber composition constituting the tread rubber 2G, the content of the isoprene-based rubber (the content (mass%) of the isoprene-based rubber in 100% by mass of the rubber component) and the content of the styrene-butadiene rubber (the content (mass%) of the styrene-butadiene rubber in 100% by mass of the rubber component) satisfy the following formula (1). (1) Isoprene rubber content > Styrene butadiene rubber content The ratio of the isoprene rubber content to the styrene-butadiene rubber content is preferably 2.0 or more, more preferably 3.0 or more, even more preferably 3.5 or more, particularly preferably 4.0 or more, and most preferably 4.7 or more. The upper limit is preferably 8.0 or less, more preferably 7.0 or less, even more preferably 6.5 or less, and particularly preferably 6.0 or less. Within the above range, the effect tends to be more favorable.

[0039] In the rubber composition constituting the tread rubber 2G, the content of the isoprene-based rubber (the content (mass%) of the isoprene-based rubber in 100% by mass of the rubber component) and the content of the butadiene rubber (the content (mass%) of the butadiene rubber in 100% by mass of the rubber component) satisfy the following formula (2). (2) Isoprene rubber content > Butadiene rubber content The ratio of the isoprene rubber content to the butadiene rubber content is preferably 2.0 or more, more preferably 3.0 or more, even more preferably 4.0 or more, and particularly preferably 4.7 or more. The upper limit is preferably 8.0 or less, more preferably 7.0 or less, even more preferably 6.5 or less, and particularly preferably 6.0 or less. Within the above range, the effect tends to be more favorably obtained.

[0040] In the rubber composition constituting the tread rubber 2G, the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 55% by mass or more, and particularly preferably 60% by mass or more. There is no particular upper limit to the content, but it is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, and particularly preferably 70% by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0041] In the rubber composition constituting the tread rubber 2G, 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, even more preferably 15% by mass or more, and particularly preferably 20% by mass or more. The upper limit of the content is not particularly limited, but is preferably 35% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0042] In the rubber composition constituting the tread rubber 2G, the content of SBR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and particularly preferably 20% by mass or more. The upper limit of the content is not particularly limited, but is preferably 35% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0043] The rubber composition constituting the tread rubber 2G includes a filler containing silica and carbon black, and the silica content (the silica content (parts by mass) per 100 parts by mass of the rubber component) and the carbon black content (the carbon black content (parts by mass) per 100 parts by mass of the rubber component) satisfy the following formula (3). (3) Silica content ≥ Carbon black content The silica content / carbon black content ratio is preferably 1.2 or more, more preferably 1.5 or more, even more preferably 1.8 or more, and particularly preferably 2.0 or more. The upper limit is preferably 5.0 or less, more preferably 4.0 or less, even more preferably 3.5 or less, and particularly preferably 3.0 or less. Within the above range, better effects tend to be obtained.

[0044] Examples of silica include dry process silica (anhydrous silica) and wet process silica (hydrated silica). These may be used alone or in combination of two or more. Among these, wet process silica is preferred because it has a large number of silanol groups.

[0045] The average primary particle size of silica is preferably 25 nm or less, more preferably 20 nm or less, even more preferably 17 nm or less, and particularly preferably 14 nm or less. The lower limit of the average primary particle size is not particularly limited, but is preferably 3 nm or more, more preferably 5 nm or more, and even more preferably 7 nm or more. Within the above range, the effect tends to be more favorably obtained. The average primary particle size of silica can be determined by observing with a transmission or scanning electron microscope, measuring 400 or more primary particles of silica observed within the field of view, and averaging the measurements.

[0046] In the rubber composition constituting the tread rubber 2G, the content of silica is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 25 parts by mass or more, and even more preferably 30 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 100 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 40 parts by mass or less. Within the above range, the effect tends to be more suitably obtained.

[0047] As silica, for example, products from Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation, etc. can be used.

[0048] The rubber composition constituting the tread rubber 2G preferably contains a silane coupling agent. The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocalcium nitrate, Examples include sulfide-based compounds such as bamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These compounds may be used alone or in combination of two or more. Among these, sulfide-based and mercapto-based compounds are preferred because they provide better effects.

[0049] As the silane coupling agent, for example, products from Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., etc. can be used.

[0050] In the rubber composition constituting the tread rubber 2G, the content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and is preferably 25 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, relative to 100 parts by mass of silica. When the content is within the above range, the effect tends to be more favorable.

[0051] In the rubber composition constituting the tread rubber 2G, usable carbon black is not particularly limited, but examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products that can be used include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nichika Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like. These may be used alone, or two or more types may be used in combination.

[0052] The nitrogen adsorption specific surface area (N2SA) of carbon black is 50m 2 / g or more is preferable, and 70m 2 / g or more is more preferable, and 90m 2 / g or more is more preferable. 2 / g or less is preferable, and 150m 2 / g or less is more preferable, and 130m 2 Within the above range, the effect tends to be better. The nitrogen adsorption specific surface area of ​​carbon black can be determined according to JIS K6217-2:2001.

[0053] In the rubber composition constituting the tread rubber 2G, the content of carbon black is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 80 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 30 parts by mass or less. When the content is within the above range, the effect tends to be more suitably obtained.

[0054] The rubber composition constituting the tread rubber 2G may contain fillers other than silica and carbon black. The other fillers are not particularly limited, and materials known in the rubber field can be used, such as inorganic fillers such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica.

[0055] In the rubber composition constituting the tread rubber 2G, the content of the filler (total content of the filler) is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 55 parts by mass or more, and particularly preferably 60 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 90 parts by mass or less, and particularly preferably 80 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0056] In the rubber composition, the silica content in 100% by mass of the filler is preferably 40% by mass or more, preferably 50% by mass or more, more preferably 52% by mass or more, and particularly preferably 54% by mass or more. There is no particular upper limit, but it is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. Within the above range, better effects tend to be obtained.

[0057] The rubber composition constituting the tread rubber 2G may contain a plasticizer. In this specification, the plasticizer refers to a material that imparts plasticity to the rubber component, and examples thereof include liquid plasticizers (plasticizers that are liquid (liquid) at 25° C.) and solid plasticizers (plasticizers that are solid at 25° C.). These may be used alone or in combination of two or more.

[0058] In the rubber composition constituting the tread rubber 2G, the content of plasticizer (total content of liquid plasticizer and solid plasticizer) is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, particularly preferably 1 part by mass or less, per 100 parts by mass of the rubber component, and may be 0 parts by mass. The amount of plasticizer included includes the amount of oil contained in rubber (oil-extended rubber) and sulfur (oil-containing sulfur).

[0059] Examples of liquid plasticizers include oils, liquid polymers (liquid resins, liquid diene polymers, etc.), essential oils derived from natural products such as turpentine, and ester-based plasticizers. Examples of solid plasticizers include solid resins that are solid at 25°C and are commonly used in the tire industry. These may be used alone or in combination of two or more.

[0060] The oil is not particularly limited, and conventionally known oils can be used, such as process oils such as paraffinic process oil, aromatic process oil, and naphthenic process oil, low PCA (polycyclic aromatic) process oils such as TDAE and MES, vegetable oils and fats, and mixtures thereof. Examples of liquid resins include terpene resins (including terpene phenol resins and aromatic-modified terpene resins) that are liquid at 25°C, rosin resins, styrene resins, C5 resins, C5C9 resins, coumarone-indene resins (including coumarone and indene simple resins), olefin resins, polyurethane resins, and acrylic resins. Examples of liquid diene polymers include liquid styrene butadiene copolymers (liquid SBR), liquid butadiene polymers (liquid BR), liquid isoprene polymers (liquid IR), liquid styrene isoprene copolymers (liquid SIR), liquid styrene butadiene styrene block copolymers (liquid SBS block polymers), and liquid styrene isoprene styrene block copolymers (liquid SIS block polymers), all of which are liquid at 25°C.

[0061] In the rubber composition constituting the tread rubber 2G, the content of the liquid plasticizer is preferably less than 15 parts by mass, more preferably less than 10 parts by mass, even more preferably less than 5 parts by mass, particularly preferably less than 1 part by mass, and may even be 0 parts by mass, per 100 parts by mass of the rubber component. The content of the liquid plasticizer also includes the amount of oil contained in the rubber (oil-extended rubber) and sulfur (oil-containing sulfur). The content of the oil is also desirably in a similar range.

[0062] As the solid plasticizer, solid resins commonly used in tire compounds can be used. Specific examples include terpene resins, rosin resins, styrene resins, olefin resins, C5 resins, C9 resins, C5 / C9 resins, coumarone resins, indene resins, coumarone-indene resins, acrylic resins, and urethane resins. These may be used alone or in combination, or the resin itself may be a copolymer of monomer components derived from multiple sources.

[0063] In the rubber composition constituting the tread rubber 2G, the content of the solid plasticizer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is not particularly limited, but is preferably 35 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less. The content of the resin is also desirably in a similar range.

[0064] The rubber composition constituting the tread rubber 2G preferably contains sulfur. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. These may be used alone or in combination of two or more.

[0065] In the rubber composition constituting the tread rubber 2G, the sulfur content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.8 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, even more preferably 5 parts by mass or less, particularly preferably 3 parts by mass or less, and most preferably 2 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0066] The rubber composition constituting the tread rubber 2G preferably contains a vulcanization accelerator. Examples of vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide; 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-benzothiazolylsulfenamide, Nt-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-orthotolylguanidine, and orthotolylbiguanidine. These may be used alone or in combination of two or more. Among these, sulfenamide-based vulcanization accelerators are preferred.

[0067] In the rubber composition constituting the tread rubber 2G, the content of the vulcanization accelerator is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, per 100 parts by mass of the rubber component, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0068] The rubber composition constituting the tread rubber 2G preferably contains stearic acid. In the rubber composition constituting the tread rubber 2G, the content of stearic acid is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, per 100 parts by mass of the rubber component, and is preferably 5 parts by mass or less, more preferably 3 parts by mass or less.

[0069] The rubber composition constituting the tread rubber 2G may contain zinc oxide. The amount of zinc oxide per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0070] The rubber composition constituting the tread rubber 2G may contain an antioxidant. 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; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine. Examples of antioxidants include p-phenylenediamine-based antioxidants such as quinoline; 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; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. These antioxidants may be used alone or in combination of two or more. Among these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferred, and p-phenylenediamine-based antioxidants are more preferred.

[0071] In the rubber composition constituting the tread rubber 2G, the content of the antioxidant is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, per 100 parts by mass of the rubber component, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0072] The rubber composition constituting the tread rubber 2G may contain wax. The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as vegetable wax and animal wax; and synthetic waxes such as polymers of ethylene, propylene, etc. These may be used alone or in combination of two or more.

[0073] In the rubber composition constituting the tread rubber 2G, the content of the wax is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, per 100 parts by mass of the rubber component, and is preferably 10 parts by mass or less, more preferably 7 parts by mass or less.

[0074] In addition to the above components, the rubber composition constituting the tread rubber 2G can contain additives commonly used in the tire industry, such as vulcanizing agents other than sulfur (e.g., organic crosslinking agents, organic peroxides), etc. The content of each of these components is preferably 0.1 parts by mass or more and preferably 200 parts by mass or less per 100 parts by mass of the rubber component.

[0075] The rubber composition constituting the tread rubber 2G can be produced, for example, by kneading the above-mentioned components using a rubber kneading device such as an open roll or a Banbury mixer, and then vulcanizing the kneaded components.

[0076] As for kneading conditions, in the base kneading step in which additives other than the crosslinking agent (vulcanizing agent) and vulcanization accelerator are kneaded, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C. In the finish kneading step in which the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 120°C or lower, preferably 80 to 110°C. Furthermore, the composition kneaded with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 140 to 190°C, preferably 150 to 185°C.

[0077] The rubber composition constituting the tread rubber 2G has a tan δ at 30° C. that satisfies the following formula (4). (4) tan δ at 30°C < 0.10 The tan δ at 30°C is preferably 0.09 or less, more preferably 0.08 or less, even more preferably 0.07 or less, particularly preferably 0.06 or less, and most preferably 0.05 or less. There is no particular lower limit, but it is preferably 0.01 or more, more preferably 0.02 or more. Within the above range, better effects tend to be obtained.

[0078] In this specification, "tan δ at 30°C" refers to the loss tangent measured under the conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and an extension mode. The tan δ of a rubber composition at 30°C refers to the tan δ of the rubber composition after vulcanization at 30°C, and is a value obtained by conducting a viscoelasticity test on the rubber composition after vulcanization.

[0079] Tan δ at 30°C can be adjusted by the type and amount of chemicals (especially rubber components, fillers, plasticizers, sulfur, vulcanization accelerators, and silane coupling agents) compounded into the rubber composition. For example, tan δ tends to decrease by increasing the content of isoprene-based rubber, reducing the amount of fillers, or reducing the amount of liquid plasticizers.

[0080] The tan δ at 30° C. of the rubber composition constituting the tread rubber 2G and the negative ratio N (%) of the tread rubber 2G satisfy the following formula (5). (5) tan δ × N at 30°C < 4.0 Tan δ×N at 30° C. is preferably 3.6 or less, more preferably 2.8 or less, even more preferably 2.4 or less, particularly preferably 2.0 or less, and most preferably 1.8 or less. There is no particular lower limit, but it is preferably 0.5 or more, more preferably 1.0 or more, and even more preferably 1.2 or more. Within the above range, better effects tend to be obtained.

[0081] From the viewpoint of obtaining better effects, it is desirable that the negative ratio (N) of the tread rubber 2G satisfy the following formula. N≦50% N is preferably 45% or less, more preferably 40% or less, even more preferably 35% or less, and particularly preferably 30% or less. There is no particular lower limit, but it is preferably 5% or more, more preferably 15% or more, and even more preferably 20% or more. Within the above range, better effects tend to be obtained.

[0082] The negative ratio (negative ratio within the contact surface of the tread portion) is the ratio of the total groove area within the contact surface to the total area of ​​the contact surface, and is measured by the following method. In this specification, if the tire is a pneumatic tire, the negative rate is calculated from the contact shape under normal load conditions with a normal rim and normal internal pressure. In the case of a non-pneumatic tire, the negative rate can be measured in the same way without requiring normal internal pressure. "Normal rim" and "normal internal pressure" are as described above, and "normal load" is as described below. The "contact shape" is obtained by assembling the tire on a standard rim, applying the standard internal pressure, and leaving it to rest at 25°C for 24 hours. Then, ink is applied to the surface of the tire tread, and the tire is pressed against cardboard under a standard load (camber angle 0°) and transferred to the paper. The tire is rotated 72° in the circumferential direction and the pattern is transferred at five locations. In other words, the contact shape is obtained five times. For the five contact shapes, the average value of the maximum length in the tire axial direction is defined as L, and the average value of the length in the direction perpendicular to the axial direction is defined as W. The negative rate (%) is calculated as follows: [1-{average area of ​​five transferred contact shapes (ink areas) on cardboard / (L x W)}] x 100 (%). Here, the average value of the length or area is the simple average of the five values.

[0083] In this embodiment, the tire 1 includes a carcass 6 that is laid across a pair of bead portions 4, 4, and a belt layer 7 that is disposed in the tread portion 2.

[0084] The carcass 6 is configured to include at least one carcass ply, in this embodiment, a first carcass ply 6A and a second carcass ply 6B overlapping the first carcass ply 6A. In this embodiment, the first carcass ply 6A is arranged radially inward of the second carcass ply 6B. However, the first carcass ply 6A may also be arranged radially outward of the second carcass ply 6B.

[0085] In this embodiment, each of the carcass plies 6A and 6B includes a main body portion 6a and a pair of turned-up portions 6b. The main body portion 6a extends from the tread portion 2 through a pair of sidewall portions 3 to the bead cores 5 of a pair of bead portions 4. Each turned-up portion 6b is connected to the main body portion 6a and is turned around the bead core 5 from the inside to the outside in the tire axial direction. In this embodiment, each turned-up portion 6b has a radially outer end 6o that terminates at the sidewall portions 3. Each turned-up portion 6b is formed to include, for example, an inner portion 6i that slopes axially inward from the bead core 5 toward the outside in the tire radial direction, and an outer portion 6e that is connected to the inner portion 6i and slopes axially outward toward the outside in the tire radial direction. However, the configuration of each turned-up portion 6b is not limited to this.

[0086] Each of the carcass plies 6A and 6B is formed by, for example, covering a carcass cord (not shown) with a topping rubber. The carcass cords are arranged at an angle of, for example, 75 to 90 degrees to the tire. Metal fiber cords such as steel cords, and organic fiber cords such as polyester, nylon, rayon, and aramid cords can be used for the carcass cords.

[0087] The belt layer 7 is composed of at least one belt ply, and in this embodiment, two belt plies, an inner belt ply 7A and an outer belt ply 7B, arranged radially inside and outside the tire. Each of the belt plies 7A and 7B includes belt cords (not shown) arranged at an angle of, for example, 10 to 35 degrees with respect to the tire equator C. The belt plies 7A and 7B are layered such that the belt cords cross each other. For example, steel cords are suitable for the belt cords, but highly elastic organic fiber cords such as aramid or rayon can also be used.

[0088] In this embodiment, the inner belt ply 7A is formed to be wider than the outer belt ply 7B. The axial width Wa of the inner belt ply 7A is preferably 80% to 100% of the tread width TW. Note that the inner belt ply 7A may be narrower than the outer belt ply 7B, for example.

[0089] The "tread width TW" means the distance between the tread ends Te in the tire axial direction. The "tread end Te" means the axially outermost contact point of the tire when the tire 1 in the normal state is placed on a flat surface with a normal load and a camber angle of 0 degrees.

[0090] In this specification, the term "normal load" refers to the load determined for each tire by each standard in the standard system including the standard on which the tire is based, and is the "maximum load capacity" in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "LOAD CAPACITY" in the case of ETRTO.

[0091] A bead apex rubber 8 is disposed on the pair of bead portions 4, 4. Fig. 2 is an enlarged view of Fig. 1. As shown in Fig. 2, the bead apex rubber 8 of this embodiment has a two-layer structure including an apex 11 and a bead reinforcing rubber 12. The apex 11 extends radially outward from the outer surface 5a of the bead core 5 in the tire radial direction. The bead reinforcing rubber 12 is disposed axially outward of the apex 11, for example.

[0092] The tire 1 is preferably a tire equipped with a bead reinforcing rubber. The bead reinforcing rubber is a member that functions to reinforce a bead portion. In this embodiment, the apex 11 and the bead reinforcing rubber 12 are disposed with the carcass 6 sandwiched therebetween. However, the bead reinforcing rubber 12 may have a two-layer structure in which the apex 11 and the bead reinforcing rubber 12 are disposed adjacent to each other on the axially outer side of the apex 11. In this case, for example, the apex 11 and the bead reinforcing rubber 12 disposed axially outer of the apex 11 may be disposed adjacent to each other, and the carcass 6 may extend radially outside the bead reinforcing rubber 12 in the tire axial direction. Although not shown, the tire may also have a two-layer structure in which the clinch rubber 4G and the bead reinforcing rubber 12 are disposed adjacent to each other on the axially outer side of the clinch rubber 4G. The presence of the bead reinforcing rubber 12 improves wear resistance.

[0093] The reason why such an effect is obtained is not entirely clear, but it is presumed to be due to the following mechanism. As described above, satisfying formulas (1) to (5) improves the overall performance of fuel economy, wear resistance, and handling stability. Furthermore, providing bead reinforcing rubber such as bead reinforcing rubber 12 prevents excessive axial collapse of the folded-back portion 6b outward, thereby providing excellent durability. This improves wear resistance and also provides good handling stability. It is therefore expected that the overall performance of fuel economy, wear resistance, and handling stability will be significantly improved.

[0094] From the viewpoint of obtaining a better effect, it is desirable that the complex modulus E1* (MPa) of the tread rubber 2G at 30°C and the complex modulus E2* (MPa) of the bead reinforcing rubber 12 at 70°C satisfy the following formula: E2* / E1*>0.3 E2* / E1* is preferably 0.5 or more, more preferably 1.0 or more, even more preferably 1.2 or more, particularly preferably 2.0 or more, and most preferably 2.8 or more. The upper limit is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.5 or less. Within the above range, the effect tends to be better.

[0095] The complex modulus E1* of the tread rubber 2G at 30°C is preferably 2.0 MPa or more, more preferably 3.5 MPa or more, and even more preferably 4.0 MPa or more. The upper limit is preferably 15.0 MPa or less, more preferably 10.0 MPa or less, even more preferably 8.0 MPa or less, and particularly preferably 7.5 MPa or less. Within the above range, the effect tends to be more favorable.

[0096] The E2* of the bead reinforcing rubber 12 at 70°C is preferably 3.0 MPa or more, more preferably 5.0 MPa or more, even more preferably 8.0 MPa or more, and particularly preferably 10.0 MPa or more. The upper limit is preferably 30.0 MPa or less, more preferably 25.0 MPa or less, and even more preferably 20.0 MPa or less. Within the above range, better effects tend to be obtained.

[0097] In this embodiment, the apex 11 is sandwiched between each main body portion 6a and each turned-up portion 6b of both carcass plies 6A, 6B. In this embodiment, the bead reinforcing rubber 12 is disposed axially outward of each turned-up portion 6b. In this manner, both carcass plies 6A, 6B in this embodiment extend between the apex 11 and the bead reinforcing rubber 12.

[0098] It is desirable that the outer end 12e of the bead reinforcing rubber 12 in the tire radial direction be located, for example, further outward in the tire radial direction than the outer end 11e of the apex 11 in the tire radial direction.

[0099] From the viewpoint of obtaining a greater effect, it is desirable that the complex modulus of elasticity E3* of the apex 11 at 70° C. and the complex modulus of elasticity E2* of the bead reinforcing rubber 12 at 70° C. satisfy the following formula. E3*>E2* E3* / E2* is preferably 3.0 or more, more preferably 5.0 or more, even more preferably 6.0 or more, particularly preferably 7.0 or more, and most preferably 10.0 or more. The upper limit is preferably 25.0 or less, more preferably 15.0 or less, and even more preferably 13.0 or less. Within the above range, the effect tends to be better.

[0100] The complex modulus E3* of Apex 11 at 70°C is preferably 20 MPa or more, more preferably 50 MPa or more, even more preferably 60 MPa or more, and particularly preferably 65 MPa or more. The upper limit is preferably 200 MPa or less, more preferably 150 MPa or less, even more preferably 100 MPa or less, and particularly preferably 80 MPa or less. Within the above range, better effects tend to be obtained.

[0101] In this specification, "E* at 70°C" refers to the loss tangent measured under conditions of a temperature of 70°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and an extension mode, and "E* at 30°C" refers to the loss tangent measured under conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and an extension mode. The E* of a rubber composition at 70°C means the complex modulus of the rubber composition after vulcanization at 70°C, and the E* of a rubber composition at 30°C means the complex modulus of the rubber composition after vulcanization at 30°C, and these values ​​are obtained by conducting a viscoelasticity test on the rubber composition after vulcanization.

[0102] E* at 30°C and E* at 70°C can be adjusted by the type and amount of chemicals (especially rubber components, fillers, plasticizers, sulfur, and vulcanization accelerators) compounded into the rubber composition. For example, E* tends to increase by increasing the amount of fillers or resin.

[0103] The bead reinforcing rubber 12 is preferably formed to include, for example, a first portion 12A of the bead reinforcing rubber 12 whose thickness t1 in the tire axial direction gradually increases toward the tire radially outward, and a second portion 12B of the bead reinforcing rubber 12 that is continuous with the first portion 12A and whose thickness t1 gradually decreases toward the tire radially outward. In this embodiment, the first portion 12A of the bead reinforcing rubber 12 is in contact with the inner portion 6i of the turned-up portion 6b. In this embodiment, the second portion 12B of the bead reinforcing rubber 12 is in contact with the outer portion 6e of the turned-up portion 6b.

[0104] It is desirable that the inner end 12i of the bead reinforcing rubber 12 in the tire radial direction be located, for example, further outward in the tire radial direction than the outer surface 5a of the bead core 5. In addition, in this embodiment, it is desirable that the inner end 12i of the bead reinforcing rubber 12 be located further inward in the tire radial direction than the outer end 11e of the apex 11.

[0105] In this embodiment, the apex 11 has a generally triangular cross section whose axial thickness t2 gradually decreases radially outward from the outer surface 5a of the bead core 5. The outer end 11e of the apex 11 is preferably located near the radially outer end of the inner portion 6i of the turned-up portion 6b.

[0106] In this embodiment, the outer end of the turned-up portion 6b of the first carcass ply 6A and the outer end of the turned-up portion 6b of the second carcass ply 6B are spaced apart in the tire radial direction, for example.

[0107] In this embodiment, the outer end of the first carcass ply 6A and the outer end of the second carcass ply 6B are spaced apart radially inward and outward from each other across the tire maximum width position M. In this embodiment, the outer end of the second carcass ply 6B is located radially inward of the tire maximum width position M.

[0108] As shown in FIG. 2, the bead portion 4 of this embodiment is provided with a chafer rubber 20 for preventing rim slippage and a reinforcing member 21 for increasing the rigidity of the bead portion 4.

[0109] The chafer rubber 20 is preferably formed in a thin sheet shape with a thickness of about 0.5 to 1.5 mm. The chafer rubber 20 is preferably formed from, for example, a hard rubber that has excellent abrasion resistance. The chafer rubber 20 can be formed only from rubber, but it can also be reinforced by embedding, for example, a canvas cloth or an organic fiber cord arrangement in the rubber to further increase abrasion resistance.

[0110] In this embodiment, the chafer rubber 20 is formed to include a base portion 20A, an outer piece portion 20B, and an inner piece portion 20C. In this embodiment, the base portion 20A contacts a rim seat surface (not shown) of the rim and extends in the tire axial direction. In this embodiment, the outer piece portion 20B is connected to the axially outer end of the base portion 20A, extends radially outward in the tire, and terminates sandwiched between the turned-up portion 6b and the bead reinforcing rubber 12. In this embodiment, the inner piece portion 20C is connected to the axially inner end of the base portion 20A, extends radially outward in the tire along the tire cavity surface, and terminates.

[0111] In this embodiment, the outer piece portion 20B is sandwiched between the inner portion 6i and the first portion 12A of the bead reinforcing rubber 12, and terminates radially inward of the outer end 11e of the apex 11. Such an outer piece portion 20B concentrates strain during running in the vicinity of the maximum width position M of the tire.

[0112] In this embodiment, the reinforcing member 21 is connected to the apex 11 and extends radially outward of the tire. The reinforcing member 21 is sandwiched, for example, between each main body portion 6a and each folded-up portion 6b. A radially outer end 21e of the reinforcing member 21 is located radially inward of an outer end 12e of the bead reinforcing rubber 12.

[0113] The reinforcing member 21 is preferably formed to have a thickness t4 in the range of 0.5 to 3.0 mm, for example.

[0114] In the tire 1, the tread rubber 2G has main grooves 42 as the grooves 26. As shown in FIG. 1, a plurality of main grooves 42, specifically three main grooves 42, are cut in the tread rubber 2G. These main grooves 42 are arranged at intervals in the axial direction. The three main grooves 42 cut in the tread 4 form four ribs extending in the circumferential direction. Each of the main grooves 42 extends in the circumferential direction. The main grooves 42 are continuous and uninterrupted in the circumferential direction.

[0115] Examples of tires include pneumatic tires and non-pneumatic tires, with pneumatic tires being preferred. In particular, they can be suitably used as summer tires (summer tires), winter tires (studless tires, snow tires, studded tires, etc.), all-season tires, etc. Tires can be used as passenger car tires, large passenger car tires, large SUV tires, heavy-duty tires for trucks, buses, etc., light truck tires, motorcycle tires, racing tires (high-performance tires), etc. Among these, they can be suitably used as passenger car tires and light truck tires. Passenger car or light truck tires refer to tires designed to be mounted on automobiles with four or more wheels and having a maximum load capacity (normal load) of 1,400 kg or less.

[0116] A tire is manufactured using the rubber composition by a conventional method. For example, a rubber composition containing various materials is extruded in an unvulcanized state to match the shape of a tread, and molded together with other tire components in a tire building machine by a conventional method to form an unvulcanized tire, which is then heated and pressurized in a vulcanizer to manufacture the tire.

[0117] Although a tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be modified and practiced in various aspects. [Example]

[0118] The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

[0119] The various chemicals used in the examples and comparative examples will be collectively described below. NR:TSR20 SBR: Nipol 1502 (E-SBR) manufactured by ZEON Corporation BR: BR150B manufactured by Ube Industries, Ltd. Carbon black: Diablack I (N220, N2SA114m) manufactured by Mitsubishi Chemical Corporation 2 / g, DBP 114ml / 100g) Silica: Rhodia Zeosil Premium 200MP (average primary particle size 10 nm) Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) manufactured by EVONIK-DEGUSSA Resin 1: Sylvatraxx 4401 (α-methylstyrene-based resin (copolymer of α-methylstyrene and styrene)) manufactured by Arizona Chemical Co. Resin 2: Sylvatraxx 4150 manufactured by Arizona Chemical Company (β-pinene resin, β-pinene content: 98% by mass or more) Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. Antioxidant 1: Nocrac 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 2: Nocrac RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: NOF Corporation's "Tsubaki" stearic acid Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Metals Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. Vulcanization accelerator: Noccela NS (Nt-butyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0120] Examples and Comparative Examples According to the formulation shown in Table 1, chemicals other than sulfur and vulcanization accelerator were kneaded for 4 minutes at 160°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded mixture. Next, sulfur and vulcanization accelerator were added to the obtained kneaded mixture, and the mixture was kneaded for 4 minutes at 80°C using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was molded into a tread shape and laminated together with other tire components in a tire building machine to form an unvulcanized tire, which was then vulcanized for 12 minutes at 170°C to produce a test tire (size: 205 / 85R16, light truck tire) shown in Figures 1 and 2.

[0121] The test tires thus obtained were subjected to the following physical property measurements and evaluations. The results are shown in Table 1.

[0122] <Viscoelasticity test> A viscoelasticity measurement sample measuring 20 mm in length, 4 mm in width, and 1 mm in thickness was taken from the inside of the tread of each test tire, with the long side aligned in the tire circumferential direction, and the tan δ and E* of each sample (rubber composition after vulcanization) at 30°C were measured using an Eplexer series manufactured by GABO Co., Ltd. The thickness direction of the sample was the tire radial direction. In addition, using the same method, samples were taken from the bead reinforcing rubber of each test tire, and E* at 70°C was measured. Tan δ and E* at 30°C were measured under the conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and an extension mode, and E* at 70°C was measured under the conditions of a temperature of 70°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and an extension mode.

[0123] <Negative rate> The negative rate of the obtained test tires was measured by the following method (the measured negative rate is shown in Table 1). The tread contact profile of a test tire was obtained by assembling it onto a standard rim, applying standard internal pressure, and leaving it at 25°C for 24 hours. Then, ink was applied to the tire tread surface, and the tire was pressed against cardboard under a standard load (camber angle 0°) and transferred to the paper. The tire was rotated 72° circumferentially, and the transfer was performed at five locations, obtaining five contact profiles. For the five contact profiles, the average maximum length in the tire axial direction was defined as L, and the average length in the direction perpendicular to the axial direction was defined as W. The negative rate (%) was measured using the following formula. The average values ​​for length and area were calculated by simply averaging the five values. Negative rate (%) = [1-{average area of ​​five transferred contact shapes (ink areas) on cardboard / (L × W)}] × 100

[0124] <Rolling resistance> Using a rolling resistance tester, the rolling resistance was measured when the test tire was run under the following conditions, and the result was expressed as an index, with Comparative Example 1 being set at 100. The higher the index, the better (low fuel consumption). Rim: 16 x 5.5J Tire pressure: 600kPa Speed: 80km / h Load: 16.79kN

[0125] <Wear resistance> The test tires were mounted on a 3000cc, 3-ton 2-D vehicle, and the tire tread depth was measured after driving 8000km. The distance traveled when the tire tread depth decreased by 1mm was calculated and indexed using the following formula. The higher the index, the better the wear resistance. (Wear resistance index) = (travel distance when groove depth of each compound is reduced by 1 mm) / (travel distance when tire groove depth of Comparative Example 1 is reduced by 1 mm) × 100

[0126] <Handling stability> The test tires were mounted on all wheels of a 3000cc, 3-ton, 2-D vehicle. Ten test drivers evaluated the handling stability of this test vehicle on a scale of 1 to 5. A higher score indicates better performance. The scores of the 10 drivers were totaled, and the total score of the reference comparative example was set to 100, to create an index (handling stability index). A higher index indicates better handling stability.

[0127] [Table 1]

[0128] As can be seen from the table, the tires of the examples having a tread made of a rubber composition containing a rubber component containing isoprene-based rubber, butadiene rubber, and styrene-butadiene rubber, and a filler containing silica and carbon black, wherein the rubber composition satisfies the formulas (1) to (3), and the tan δ of the rubber composition at 30°C and the negative rate N (%) of the tread satisfy the formulas (4) to (5), had significantly excellent overall performance in terms of fuel economy, wear resistance, and steering stability (expressed as the sum of the three indices of fuel economy, wear resistance, and steering stability). [Explanation of symbols]

[0129] 1 tire 2 Tread section 2a Tread contact surface 2G tread rubber 3 Sidewall 3a outer surface of sidewall portion 3 3G sidewall rubber 4 Bead section 4a outer surface of bead portion 4 4G Clinch Rubber 5 bead core 5a: outer surface of the bead core 5 in the tire radial direction 6. Carcass 6A First carcass ply 6B 2nd carcass ply 6a Main body 6b Folded part 6o Outer edge of tire radius 6i The inner part of the tire that slopes inward in the axial direction 6e Outer portion inclined axially outward 7 Belt Layer 7A Inner belt ply 7B outer belt ply 8 Bead apex rubber 11. Apex 11e Apex 11 tire radial outer edge 12 Bead reinforcement rubber 12A First portion of bead reinforcement rubber 12 12B: Second portion of bead reinforcing rubber 12 12e: outer end of the bead reinforcing rubber 12 in the tire radial direction 12i: The inner end of the bead reinforcement rubber 12 in the tire radial direction 20 Chafer Rubber 20A base 20B Outer piece 20C inner piece 21 Reinforcement member 21e: outer end of the reinforcing member 21 in the tire radial direction 26 Groove 42 Main groove C Tire equator Wa Axial width of inner belt ply 7A TW tread width Te tread edge M Maximum tire width position t1 Axial thickness of the bead reinforcement rubber 12 t2 Axial thickness of Apex 11 tire t4 Thickness of reinforcing member 21

Claims

1. A tire having a tread made of a rubber composition including a rubber component containing an isoprene-based rubber, a butadiene rubber, and a styrene-butadiene rubber, and a filler containing silica and carbon black, The tire includes a bead reinforcing rubber, a complex modulus E1* of the tread at 30°C and a complex modulus E2* of the bead reinforcing rubber at 70°C satisfy the following formula, 2.8≧E2* / E1*>0.3 The rubber composition satisfies the following formulas (1) to (3): (1) Isoprene rubber content > Styrene butadiene rubber content (2) Isoprene rubber content > butadiene rubber content (3) Silica content ≧ carbon black content The tire in which the tan δ of the rubber composition at 30° C. and the negative rate N (%) of the tread satisfy the following formulas (4) and (5): (4) tan δ at 30°C < 0.10 (5) tan δ × N at 30 ° C. < 4.0

2. 2. The tire according to claim 1, wherein the silica has an average primary particle size of 20 nm or less.

3. The tire according to claim 1 or 2, wherein the rubber composition contains less than 15 parts by mass of the liquid plasticizer per 100 parts by mass of the rubber component.

4. The tire according to any one of claims 1 to 3, wherein the rubber composition contains 5 parts by mass or more of a solid plasticizer per 100 parts by mass of the rubber component.

5. The tire according to any one of claims 1 to 4, wherein a complex modulus E1* of the tread at 30°C and a complex modulus E2* of the bead reinforcing rubber at 70°C satisfy the following formula: 2.8≧E2* / E1*>0.5

6. Equipped with apex and bead reinforcement rubber, The tire according to any one of claims 1 to 5, wherein a complex modulus E3* of the apex at 70°C and a complex modulus E2* of the bead reinforcing rubber at 70°C satisfy the following formula: E3*>E2*

7. The tire according to any one of claims 1 to 6, wherein the negative ratio (N) of the tread is 40% or less.

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