tire

Abstract

To provide a tire that is improved in steering stability during high-speed running.SOLUTION: A tire comprises a tread. The tread is constituted by rubber compositions that include rubber components containing isoprene rubber and styrene-butadiene rubber, silica and carbon blacks. In the rubber compositions, contents of the silica are above 80 mass parts with respect to 100 parts by mass of the rubber components. The rubber compositions satisfy the following formulas (1)-(2). Contents A (mass parts) of silica in the rubber compositions, a maximum thickness B (mm) of the tread, a land ratio C (%) of the tread and a glass transfer temperature D (°C) of the rubber compositions satisfy the following formulas (3)-(4): (1) contents of isoprene rubber - total styrene amounts in the rubber components>0; (2) contents of carbon blacks - total styrene amounts in the rubber components>0; (3) A / B>8; (4) C / D>2.00.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to tires. [Background technology]

[0002] A key performance requirement for tires is handling stability, which allows the vehicle to drive smoothly and precisely as the driver intends. For example, it has been described that handling stability can be improved by incorporating a polymer containing structural units derived from 1,3,7-octatriene, which includes 3,4-bonding units, into a rubber composition (see Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-007425 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, with improvements in vehicle performance and the development of expressways, long-distance travel at high speeds is no longer uncommon these days, and it is thought that further improvements in handling stability at high speeds are desired. The present invention aims to solve the aforementioned problems and improve handling stability during high-speed driving. [Means for solving the problem]

[0005] The present invention relates to a tire having a tread, wherein the tread is composed of a rubber composition comprising a rubber component containing isoprene rubber and styrene-butadiene rubber, silica, and carbon black, wherein the content of silica in the rubber composition is 80 parts by mass or more per 100 parts by mass of the rubber component, the rubber composition satisfies the following formulas (1) to (2), and the silica content A (parts by mass) in the rubber composition, the maximum thickness B (mm) of the tread, the land ratio C (%) of the tread, and the glass transition temperature D (°C) of the rubber composition satisfy the following formulas (3) to (4). (1) Isoprene rubber content - Total styrene content in rubber components > 0 (2) Carbon black content - Total styrene content in rubber component > 0 (3) A / B > 8 (4)|C / D|>2.00 [Effects of the Invention]

[0006] The present invention relates to a tire equipped with a tread, wherein the tread is composed of a rubber composition comprising a rubber component containing isoprene rubber and styrene-butadiene rubber, silica, and carbon black, wherein the content of silica in the rubber composition is 80 parts by mass or more per 100 parts by mass of the rubber component, the rubber composition satisfies the above formulas (1) to (2), and the silica content A (parts by mass) in the rubber composition, the maximum thickness B (mm) of the tread, the land ratio C (%) of the tread, and the glass transition temperature D (°C) of the rubber composition satisfy the above formulas (3) to (4), thereby improving handling stability during high-speed driving. [Modes for carrying out the invention]

[0007] The present invention provides a tire with a tread, wherein the tread is composed of a rubber composition comprising a rubber component containing isoprene rubber and styrene-butadiene rubber, silica, and carbon black, wherein the content of silica in the rubber composition is 80 parts by mass or more per 100 parts by mass of the rubber component, the rubber composition satisfies the above formulas (1) to (2), and the silica content A (parts by mass) in the rubber composition, the maximum thickness B (mm) of the tread, the land ratio C (%) of the tread, and the glass transition temperature D (°C) of the rubber composition satisfy the above formulas (3) to (4). The tire can improve handling stability during high-speed driving.

[0008] The reason why the aforementioned effects are obtained is not entirely clear, but it is presumed to be due to the following mechanism. [1] It is believed that a microphase separation structure is formed within the rubber phase by the rubber component of the rubber composition constituting the tread containing isoprene rubber and styrene-butadiene rubber. Furthermore, it is believed that by making the isoprene rubber content greater than the total amount of styrene in the rubber component so as to satisfy formula (1) above, styrene domains formed by the aggregation of the styrene portion of styrene-butadiene rubber can be formed within the rubber phase. It is believed that these styrene domains create a scratching effect between the tread surface and the road surface, and also cause friction with surrounding rubber molecular chains, thereby improving the grip of the tread surface. [2] Furthermore, it is believed that by incorporating more carbon black than the total amount of styrene in the rubber component, that is, by satisfying the above equation (2) between the carbon black content and the total amount of styrene in the rubber component, the highly heat-generating carbon black interacts with the styrene portion of the styrene-butadiene rubber, thereby further improving the grip of the tread surface. [3] It is thought that by incorporating a sufficiently large amount of silica relative to the maximum thickness of the tread, such that the silica content and the maximum thickness of the tread satisfy equation (3) above, the friction on the tread surface can be more easily transmitted to the inside of the tire by the silica. In particular, unlike carbon black, silica has little energy loss due to friction with the surrounding rubber molecular chains, so it is thought that it can easily transmit deformation caused by friction on the tread surface to the inside of the tire and instantly generate a reaction force in response to it. [4] Furthermore, it is thought that the lower the glass transition temperature of the rubber composition, the lower the rigidity and the less reaction force is generated at high speeds. Therefore, it is thought that the reaction force generated on the tread surface can be increased by making the land ratio of the tread and the glass transition temperature of the rubber composition sufficiently large relative to the glass transition temperature of the rubber composition so that the above equation (4) is satisfied. As described above [1] to [4], the grip of the tread surface is improved, and the deformation caused by friction on the tread surface is instantly transmitted to the inside of the tire, making it more responsive. Therefore, it is thought that this can improve handling stability at high speeds. Based on the above effects, it is presumed that this can improve handling stability during high-speed driving.

[0009] Thus, the present invention is a tire provided with a tread, wherein the tread is composed of a rubber composition containing an isoprene rubber and a styrene-butadiene rubber as a rubber component, silica, and carbon black. The rubber composition has a silica content of 80 parts by mass or more with respect to 100 parts by mass of the rubber component. The rubber composition satisfies the formula (1) "content of isoprene rubber - total styrene amount in the rubber component > 0" and the formula (2) "content of carbon black - total styrene amount in the rubber component > 0". The silica content A (parts by mass) in the rubber composition, the maximum thickness B (mm) of the tread, the land ratio C (%) of the tread, and the glass transition temperature D (°C) of the rubber composition satisfy the formula (3) "A / B > 8" and the formula (4) "|C / D| > 2.00", thereby solving the problem (objective) of improving the handling stability during high-speed driving. That is, the parameters of the formulas (1) to (4) do not define the problem (objective). The problem of the present application is to improve the handling stability during high-speed driving, and the solution means therefor is configured to satisfy the above parameters.

[0010] The tire of the present invention is a tire provided with a tread, wherein the tread is composed of a rubber composition containing an isoprene rubber and a styrene-butadiene rubber as a rubber component, silica, and carbon black.

[0011] In this specification, the rubber component has a weight average molecular weight (Mw) of 150,000 or more and is a component contributing to crosslinking.

[0012] The weight average molecular weight of the above rubber component is preferably 170,000 or more, more preferably 200,000 or more, still more preferably 250,000 or more, and preferably 2,000,000 or less, more preferably 1,500,000 or less, still more preferably 1,000,000 or less. When it is within the above range, the effect tends to be obtained more favorably.

[0013] In addition, in this specification, the weight average molecular weight (Mw) can be determined by conversion to standard polystyrene based on the measurement value by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0014] In the above rubber composition, the total styrene amount (mass%) in the rubber component is preferably 5.0 mass% or more, more preferably 7.0 mass% or more, still more preferably 10.0 mass% or more, particularly preferably 12.0 mass% or more, and the upper limit is preferably 60.0 mass% or less, more preferably 50.0 mass% or less, still more preferably 40.0 mass% or less, even more preferably 35.0 mass% or less, particularly preferably 30.0 mass% or less. When it is within the above range, the effect tends to be obtained more favorably.

[0015] Here, the total styrene amount in the rubber component is the total content (unit: mass%) of the styrene part contained in the total amount of the rubber component, and can be calculated by Σ (content of each rubber component × styrene amount in each rubber component / 100). For example, in 100 mass% of the rubber component, if SBR with a styrene amount of 40 mass% is 85 mass%, SBR with a styrene amount of 25 mass% is 5 mass%, and BR with a styrene amount of 0 mass% is 10 mass%, the total styrene amount in the rubber component is 35.25 mass% (= 85 × 40 / 100 + 5 × 25 / 100 + 10 × 0 / 100).

[0016] In addition, the styrene amount in each rubber component can be measured by nuclear magnetic resonance (NMR) method. Regarding the total styrene amount in the rubber component, in the examples of this specification, it is calculated according to the above calculation formula, but for example, it may also be analyzed from the tire by a thermal decomposition gas chromatograph mass spectrometer (Py-GC / MS) or the like.

[0017] The above rubber composition contains a rubber component containing an isoprene rubber and a styrene butadiene rubber (SBR).

[0018] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. For NR, examples include SIR20, RSS#3, TSR20, etc., which are commonly used in the tire industry. For IR, there are no particular limitations; examples include IR2200, etc., which are commonly used in the tire industry. Examples of modified NR include deproteinized natural rubber (DPNR) and high-purity natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used individually or in combination of two or more. Among these, NR is preferred.

[0019] The SBR is not particularly limited; for example, emulsion polymerized styrene-butadiene rubber (E-SBR) and solution polymerized styrene-butadiene rubber (S-SBR) can be used. However, emulsion polymerized styrene-butadiene rubber is preferred from the viewpoint of obtaining better effects. These may be used individually or in combination of two or more types.

[0020] The styrene content of SBR is preferably 5% by mass or more, more preferably 7% by mass or more, even more preferably 10% by mass or more, and also preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less. Within the above range, a better effect tends to be obtained.

[0021] The vinyl content of SBR 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 30% by mass or more. It is also preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, and particularly preferably 35% by mass or less. When the content is within the above range, a better effect tends to be obtained. In this specification, the amount of vinyl in the rubber component is: 1 It is calculated by 1H-NMR measurement.

[0022] For example, SBR manufactured and sold by companies such as Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Co., Ltd. can be used. Alternatively, SBR synthesized by known methods can also be used.

[0023] The styrene content of SBR mentioned above refers to the styrene content of a single type of SBR if that type is used, and to the average styrene content if there are multiple types of SBR. The average styrene content of SBR can be calculated using the formula {Σ(content of each SBR × styrene content of each SBR)} / total content of all SBR. For example, if 85% of the rubber component is SBR with 40% styrene content and 5% is SBR with 25% styrene content, the average styrene content of the SBR is 39.2% (=(85 × 40 + 5 × 25) / (85 + 5)).

[0024] Furthermore, the vinyl content of SBR mentioned above is the ratio of vinyl bonds when the total mass of the butadiene portion in the SBR is set to 100 (unit: mass%), where vinyl content [mass%] + cis content [mass%] + trans content [mass%] = 100 [mass%]. If there is only one type of SBR, it refers to the vinyl content of that SBR; if there are multiple types, it refers to the average vinyl content. The average vinyl content of SBR can be calculated using the formula: Σ{Content of each SBR × (100 [mass%] - Styrene content of each SBR [mass%]) × Vinyl content of each SBR [mass%]} / Σ{Content of each SBR × (100 [mass%] - Styrene content of each SBR [mass%])}. For example, if 100 parts by mass of rubber component, 75 parts by mass of SBR contain 40% by mass of styrene and 30% by mass of vinyl, and 25% by mass of vinyl, If 15 parts by mass of SBR have a 20% vinyl content and the remaining 10 parts by mass are other than SBR, the average vinyl content of the SBR is 28% by mass (= {75 × (100 [mass%] - 40 [mass%]) × 30 [mass%] + 15 × (100 [mass%] - 25 [mass%]) × 20 [mass%])} / {75 × (100 [mass%] - 40 [mass%]) + 15 × (100 [mass%] - 25 [mass%])}.

[0025] SBR can be either unmodified SBR or modified SBR. Modified SBRs can be any SBR having a functional group that interacts with a packing material such as silica or carbon black. Examples include terminally modified SBRs (terminally modified SBRs having the functional group at the terminal) in which at least one end of the SBR is modified with a compound having the functional group (modifying agent), main-chain modified SBRs having the functional group in the main chain, main-chain terminally modified SBRs having the functional group in both the main chain and the terminal (for example, main-chain terminally modified SBRs having the functional group in the main chain and at least one end modified with the modifying agent), and terminally modified SBRs that are modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule, and in which hydroxyl groups or epoxy groups are introduced. These may be used individually or in combination of two or more types.

[0026] Examples of the above-mentioned functional groups include functional groups containing at least one atom selected from the group consisting of nitrogen atoms, oxygen atoms, and silicon atoms. These may be used individually or in combination of two or more.

[0027] Examples of the above-mentioned functional groups include amino groups, amide groups, silyl groups, alkoxysilyl groups, isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, thiocarbonyl groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, and the like. These functional groups may have substituents. Among these, amino groups (preferably amino groups in which the hydrogen atoms of the amino group are substituted with C1-C6 alkyl groups), alkoxy groups (preferably alkoxy groups having C1-C6), and alkoxysilyl groups (preferably alkoxysilyl groups having C1-C6) are preferred because they provide a more favorable effect.

[0028] Furthermore, hydrogenated SBR can also be used as the SBR, and from the viewpoint of obtaining better effects, it is preferable to use hydrogenated SBR.

[0029] The hydrogenation rate of the above-mentioned hydrogenated SBR (the percentage of hydrogenated material relative to the butadiene portion of SBR) is preferably 75 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and particularly preferably 93 mol% or more. Furthermore, 99 mol% or less is preferred, and 98 mol% or less is more preferred. When the hydrogenation rate is within the above range, the effect tends to be better. The hydrogenation rate is 1 It can be calculated from the spectral reduction rate of the unsaturated bond region of the spectrum obtained by measuring 1H-NMR.

[0030] The method and reaction conditions for producing the above-mentioned hydrogenated SBR are not particularly limited, and hydrogenation of SBR can be carried out using known methods and conditions. Typically, this is done at 20-150°C, under a hydrogen pressure of 0.1-10 MPa, and in the presence of a hydrogenation catalyst. The hydrogenation rate can be arbitrarily selected by changing the amount of hydrogenation catalyst, the hydrogen pressure during the hydrogenation reaction, the reaction time, etc. Typically, a compound containing any of the metals from Groups 4 to 11 of the periodic table can be used as the hydrogenation catalyst. For example, compounds containing Ti, V, Co, Ni, Zr, Ru, Rh, Pd, Hf, Re, and Pt atoms can be used as hydrogenation catalysts. More specific examples of hydrogenation catalysts include metallocene compounds such as Ti, Zr, Hf, Co, Ni, Pd, Pt, Ru, Rh, and Re; supported heterogeneous catalysts in which metals such as Pd, Ni, Pt, Rh, and Ru are supported on carriers such as carbon, silica, alumina, and diatomaceous earth; homogeneous Ziegler-type catalysts combining organic salts or acetylacetone salts of metal elements such as Ni and Co with reducing agents such as organoaluminum; organometallic compounds or complexes such as Ru and Rh; and hydrogen-adsorbed fullerenes and carbon nanotubes.

[0031] Of these, metallocene compounds containing any of Ti, Zr, Hf, Co, or Ni are preferred because they can undergo hydrogenation in a homogeneous system in an inert organic solvent. Furthermore, metallocene compounds containing any of Ti, Zr, or Hf are preferred. In particular, hydrogenation catalysts obtained by reacting titanocene compounds with alkyllithium are preferred because they are inexpensive and industrially particularly useful catalysts. Specific examples include the hydrogenation catalysts described in Japanese Patent Publication No. 1-275605, 5-271326, 5-271325, 5-222115, 11-292924, 2000-37632, 59-133203, 63-5401, 62-218403, 7-90017, 43-19960, and 47-40473. These hydrogenation catalysts can be used individually or in combination of two or more. Furthermore, as hydrogenated SBR, a product obtained by copolymerizing styrene with one or more of ethylene or monobutene and optionally butadiene as monomers may also be used.

[0032] The total content of isoprene-based rubber and SBR in 100% by mass of the rubber component is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, and may be 100% by mass. Within the above range, better effects tend to be obtained.

[0033] The isoprene-based rubber content in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. Furthermore, it is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less. Within these ranges, a better effect tends to be obtained.

[0034] The SBR content in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more. Furthermore, it is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. Within these ranges, a better effect tends to be obtained.

[0035] The above rubber composition may also contain other rubber components besides isoprene-based rubber and SBR. Other rubber components include, for example, butadiene rubber (BR), styrene-isoprene butadiene rubber (SIBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR). Other rubber components include butyl rubber and fluororubber. These may be used individually or in combination of two or more. Among these, BR is preferred.

[0036] BR is not particularly limited; for example, high-cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, and BR synthesized using rare-earth catalysts (rare-earth BR) can be used. These may be used individually or in combination of two or more.

[0037] The cis content of BR is preferably 20% by mass or more, more preferably 40% by mass or more, even more preferably 60% by mass or more, particularly preferably 80% by mass or more, and most preferably 90% by mass or more, with no particular upper limit. Within the above range, a better effect tends to be obtained. In this specification, the cis content of the rubber component can be measured by infrared absorption spectroscopy.

[0038] The cis amount of BR mentioned above refers to the cis amount of a single type of BR if there is only one type, and to the average cis amount if there are multiple types. The average cis content of BR can be calculated using the formula {Σ(content of each BR × cis content of each BR)} / total BR content. For example, if 20% of BR has a cis content of 90% and 10% has a cis content of 40% out of 100% of rubber components, the average cis content of BR is 73.3% (=(20 × 90 + 10 × 40) / (20 + 10)).

[0039] Furthermore, BR may be undenatured or modified. Modified BR can be modified BR in which functional groups similar to those of modified SBR have been introduced.

[0040] For example, BR products from companies such as Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Corporation can be used.

[0041] The BR content in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, and also preferably 40% by mass or less, more preferably 30% by mass or less. Within this range, a better effect tends to be obtained.

[0042] The rubber component may be oil-stretched rubber or resin-stretched rubber. These may be used individually or in combination of two or more types. The oil used in oil-extracted rubber and the resin used in resin-extracted rubber are the same as those described later in the section on plasticizers. Furthermore, while the oil content in oil-extracted rubber and the resin content in resin-extracted rubber are not particularly limited, they are typically around 10 to 50 parts by mass per 100 parts by mass of rubber solids.

[0043] The above rubber composition contains silica. The silica used is not particularly limited; for example, dry-process silica (anhydrous silicic acid) and wet-process silica (hydrated silicic acid) can be used. These may be used individually or in combination of two or more types. Among these, wet-process silica is preferred because it contains a large number of silanol groups. Biomass silica made from biomass materials such as rice husks may also be used as appropriate.

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

[0045] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 80 m 2 / g or more, more preferably 100 m 2 / g or more, still more preferably 120 m 2 / g or more, particularly preferably 150 m 2 / g or more. Also, the N2SA is preferably 300 m 2 / g or less, more preferably 250 m 2 / g or less, still more preferably 200 m 2 / g or less, particularly preferably 180 m 2 / g or less. When within the above range, the effect tends to be obtained more favorably. Note that the N2SA of the silica can be measured in accordance with ASTM D3037 - 81.

[0046] The content of silica with respect to 100 parts by mass of the rubber component is 80 parts by mass or more, preferably 85 parts by mass or more, more preferably 90 parts by mass or more, still more preferably 95 parts by mass or more, particularly preferably 100 parts by mass or more, and is also preferably 200 parts by mass or less, more preferably 180 parts by mass or less, still more preferably 150 parts by mass or less, particularly preferably 120 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0047] When the above rubber composition contains silica, it is preferable to contain a silane coupling agent together with the silica. The silane coupling agent is not particularly limited and includes, for example, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl) trisulfide, bis(4-trimethoxysilylbutyl) trisulfide, bis(3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) disulfide, bis(4-trimethoxysilylbutyl) disulfide, and 3-trimethoxysilylpropyl-N,N-dimethylthiocal Examples include sulfide compounds such as bamoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z; vinyl compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These may be used individually or in combination of two or more. Among these, sulfide-based and mercapto-based compounds are preferred because they provide better efficacy.

[0048] Examples of silane coupling agents that can be used include products from Evonik Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Toray Dow Corning Co., Ltd.

[0049] The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 8 parts by mass or more, and 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, per 100 parts by mass of silica. When the content is within the above range, a better effect tends to be obtained.

[0050] The above rubber composition contains carbon black. Examples of carbon black include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Recycled carbon black obtained by thermal decomposition of plastic products or rubber products containing carbon black, such as tires, may also be used. These may be used individually or in combination of two or more types.

[0051] The specific surface area (N2SA) of carbon black for nitrogen adsorption is 50 m². 2 Preferably 100m / g or more 2 More preferably 114m / g or more 2 More preferably 120m / g or more. 2 More preferably 135m / g or more. 2 A value of 1 / g or more is particularly preferred. Furthermore, the above N2SA is 250m 2 Preferably less than / g, 200m 2 More preferably less than / g, 160m 2 More preferably less than / g, and 150m 2 A value of less than / g is particularly preferable. Within this range, better effects tend to be obtained. The specific surface area for nitrogen adsorption of carbon black is determined according to JIS K6217-2:2001.

[0052] The dibutyl phthalate oil absorption (DBP oil absorption) of carbon black is preferably 80 ml / 100g or more, more preferably 90 ml / 100g or more, even more preferably 100 ml / 100g or more, particularly preferably 110 ml / 100g or more, and most preferably 114 ml / 100g or more. Furthermore, the DBP oil absorption is preferably 200 ml / 100g or less, more preferably 170 ml / 100g or less, even more preferably 150 ml / 100g or less, and particularly preferably 125 ml / 100g or less. When the absorption is within the above range, a better effect tends to be obtained. The amount of dibutyl phthalate absorbed by carbon black is determined in accordance with JIS K6217-4:2001.

[0053] For carbon black, products from companies such as Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nippon Chemical Carbon Co., Ltd., and Columbia Carbon can be used.

[0054] The carbon black content per 100 parts by mass of rubber component is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, and also preferably 100 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 30 parts by mass or less. Within the above range, a better effect tends to be obtained.

[0055] The above rubber composition may contain other fillers besides silica and carbon black. Other fillers may include materials known in the rubber field, such as inorganic fillers like calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica; and poorly dispersible fillers.

[0056] The total amount of filler (total filler content) per 100 parts by mass of rubber component is preferably 90 parts by mass or more, more preferably 100 parts by mass or more, even more preferably 110 parts by mass or more, and particularly preferably 120 parts by mass or more. It is also preferably 300 parts by mass or less, more preferably 250 parts by mass or less, even more preferably 200 parts by mass or less, and particularly preferably 150 parts by mass or less. When the amount is within the above range, a better effect tends to be obtained.

[0057] In the above 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 60% by mass or more, and particularly preferably 70% by mass or more. There is no upper limit, but it is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less. When it is within the above range, the effect tends to be better obtained.

[0058] The above rubber composition may contain a plasticizer. In this specification, a plasticizer is a material that imparts plasticity to a rubber component, and may be a liquid or a solid at room temperature (25°C). These may be used individually or in combination of two or more.

[0059] In the above rubber composition, the plasticizer content (total amount of plasticizer) is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 50 parts by mass or more, even more preferably 55 parts by mass or more, even more preferably 60 parts by mass or more, particularly preferably 65 parts by mass or more, most preferably 70 parts by mass or more, and also preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 90 parts by mass or less. When the content is within the above range, the effect tends to be better obtained. Furthermore, the plasticizer content includes the amount of oil and resin contained in rubber (oil-expandable rubber, resin-expandable rubber) and sulfur (oil-containing sulfur).

[0060] Examples of plasticizers include oils, liquid polymers, and resins. These may be used individually or in combination of two or more.

[0061] The above-mentioned oils are not particularly limited and can be conventionally known oils such as paraffinic process oils, aromatic process oils, naphthenic process oils, low PCA (polycyclic aromatic) process oils such as TDAE and MES, vegetable oils, and mixtures thereof. These may be used individually or in combination of two or more types. Furthermore, from the perspective of life cycle analysis, lubricating oils used in rubber mixing mixers or automobile engines, or waste cooking oil may be used as appropriate.

[0062] Examples of the above-mentioned vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil.

[0063] Examples of oils that can be used include those from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoy Inc., H&R Inc., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., Nisshin Oillio Group Ltd., and others.

[0064] Examples of the above-mentioned liquid polymers include liquid diene polymers (liquid rubber) and liquid farnesene polymers at 25°C. Examples of liquid rubbers include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), and liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer). These polymers may have polar groups attached to their ends or main chains. Hydrogenated versions of these polymers can also be used.

[0065] The above liquid diene polymer has a weight-average molecular weight (Mw) on a polystyrene basis, measured by gel permeation chromatography (GPC), of 1.0 × 10⁻⁶. 3 ~5.0×10 4 Preferably, 3.0 × 10 3 ~1.5×10 4 It is more preferable that this is the case. Furthermore, the lower or upper limit of Mw for the liquid diene polymer may be 4500 or 8500. In this specification, the Mw of liquid diene polymers is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0066] Examples of liquid diene polymers that can be used include products from companies such as Sartomer and Kuraray.

[0067] The above-mentioned resin can be any resin commonly used in tire compounding, and may be either liquid or solid at room temperature (25°C). Examples include aromatic vinyl polymers, coumarone indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, and acrylic resins. The resin may also be hydrogenated. These may be used individually or in combination of two or more. The resin itself may also be a copolymer of monomer components of multiple origins. Among these, aromatic vinyl polymers, petroleum resins, and terpene resins are preferred from the viewpoint of obtaining better effects, and aromatic vinyl polymers are particularly preferred.

[0068] In the above rubber composition, the resin content is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 25 parts by mass or more, particularly preferably 40 parts by mass or more, most preferably 50 parts by mass or more, and also preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less, based on 100 parts by mass of the rubber component. When the content is within the above range, a better effect tends to be obtained.

[0069] The softening point of the above-mentioned resin is preferably 50°C or higher, more preferably 55°C or higher, even more preferably 60°C or higher, and particularly preferably 85°C or higher, when using a resin that is solid at room temperature. Furthermore, it is preferably 160°C or lower, more preferably 150°C or lower, even more preferably 140°C or lower, and particularly preferably 100°C or lower. When the softening point is within the above range, the effect tends to be better. When the resin is liquid at room temperature, the softening point is preferably 20°C or lower, preferably 10°C or lower, and preferably 0°C or lower. The softening point of the above resin is determined by measuring the softening point specified in JIS K6220-1:2001 using a ring-type softening point measuring device, and the temperature at which the sphere descends is the softening point.

[0070] The above-mentioned aromatic vinyl polymer is a polymer containing aromatic vinyl monomers as constituent units. Examples include resins obtained by polymerizing α-methylstyrene and / or styrene, specifically, homopolymers of styrene (styrene resin), homopolymers of α-methylstyrene (α-methylstyrene resin), copolymers of α-methylstyrene and styrene, copolymers of styrene and other monomers.

[0071] The above-mentioned coumarone-indene resin is a resin that contains coumarone and indene as the main monomer components that constitute the resin's backbone (main chain). Other monomer components that may be included in the backbone besides coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

[0072] The coumarone resin described above is a resin that contains coumarone as the main monomer component that constitutes the resin's backbone (main chain).

[0073] The above-mentioned indene resin is a resin that contains indene as the main monomer component that constitutes the resin's backbone (main chain).

[0074] As the phenolic resin mentioned above, known polymers such as those obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde, and furfural using an acid or alkali catalyst can be used. Among these, those obtained by reaction with an acid catalyst (such as novolac-type phenolic resins) are preferred.

[0075] Examples of the rosin resins mentioned above include natural rosin, polymerized rosin, modified rosin, their ester compounds, and rosin-based resins represented by their hydrogenated products.

[0076] Examples of the above petroleum resins include C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene (DCPD) resins, C9 / DCPD resins, and hydrogenated versions thereof. Among these, DCPD resins, hydrogenated DCPD resins, C9 / DCPD resins, and C9 / hydrogenated DCPD resins are preferred.

[0077] The above-mentioned terpene resins are polymers containing terpenes as constituent units. Examples include polyterpene resins obtained by polymerizing terpene compounds, and aromatically modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds. As aromatically modified terpene resins, terpene-phenol resins made from terpene compounds and phenolic compounds, terpene-styrene resins made from terpene compounds and styrene compounds, and terpene-phenol-styrene resins made from terpene compounds, phenolic compounds, and styrene compounds can also be used. Examples of terpene compounds include α-pinene and β-pinene, examples of phenolic compounds include phenol and bisphenol A, and examples of aromatic compounds include styrene compounds (styrene, α-methylstyrene, etc.).

[0078] The above-mentioned acrylic resin is a polymer containing acrylic monomers as constituent units. Examples include styrene-acrylic resins such as styrene-acrylic resin, which have carboxyl groups and are obtained by copolymerizing an aromatic vinyl monomer component with an acrylic monomer component. Among these, solvent-free carboxyl group-containing styrene-acrylic resins can be suitably used.

[0079] Examples of resins that can be used include those from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, ExxonMobil, Kraton, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., Taoka Chemical Industries, Ltd., and others.

[0080] The above rubber composition may contain an anti-aging agent. Examples of anti-aging agents include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; N-isopropyl-N′-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, and N,N′-di-2-naphthyl-p-phenylenediamine. Examples of anti-aging agents include p-phenylenediamine-based anti-aging agents such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers; monophenol-based anti-aging agents such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate]methane. Commercially available products include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis Co., Ltd. These may be used individually or in combination of two or more.

[0081] In the above rubber composition, the content of the anti-aging agent is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, even more preferably 1.0 part by mass or more, and also preferably 10.0 parts by mass or less, more preferably 6.0 parts by mass or less, and even more preferably 4.0 parts by mass or less, per 100 parts by mass of the rubber component. When the content is within the above range, a better effect tends to be obtained.

[0082] The above rubber composition may contain wax. The wax is not particularly limited and can be any petroleum-based wax such as paraffin wax or microcrystalline wax; a natural wax such as plant-based wax or animal-based wax; or a synthetic wax such as polymers of ethylene or propylene. Commercially available products from companies such as Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Chemical Co., Ltd. can be used. These can be used individually or in combination of two or more types.

[0083] In the above rubber composition, the wax content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, and more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component. When the content is within the above range, a better effect tends to be obtained.

[0084] The above rubber composition may contain stearic acid. Conventional known stearic acid can be used, and commercially available products from companies such as NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries Ltd., and Chiba Fatty Acid Co., Ltd. can be used. These may be used individually or in combination of two or more types.

[0085] In the above rubber composition, the stearic acid content is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, even more preferably 3.0 parts by mass or more, and preferably 10.0 parts by mass or less, and more preferably 6.0 parts by mass or less, per 100 parts by mass of the rubber component. When the content is within the above range, the effect tends to be better obtained.

[0086] The above rubber composition may contain zinc oxide. Conventional known zinc oxides can be used, and commercially available products from companies such as Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., and Sakai Chemical Industry Co., Ltd. can be used. These may be used individually or in combination of two or more types.

[0087] In the above rubber composition, the zinc oxide content is preferably 1.0 part by mass or more, more preferably 2.5 parts by mass or more, even more preferably 3.5 parts by mass or more, and preferably 10.0 parts by mass or less, and more preferably 6.0 parts by mass or less, per 100 parts by mass of the rubber component. When the content is within the above range, the effect tends to be better obtained.

[0088] The above rubber composition may contain sulfur. Examples of sulfur commonly used as a crosslinking agent in the rubber industry include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur. Commercially available products from companies such as Tsurumi Chemical Industries, Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Co., Ltd., Flexis Co., Ltd., Nippon Dry Distillation Co., Ltd., and Hosoi Chemical Industry Co., Ltd. can be used. These may be used individually or in combination of two or more types.

[0089] In the above rubber composition, the sulfur content is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, even more preferably 1.8 parts by mass or more, and also preferably 3.5 parts by mass or less, more preferably 2.8 parts by mass or less, and even more preferably 2.5 parts by mass or less, per 100 parts by mass of the rubber component. When the content is within the above range, a better effect tends to be obtained.

[0090] The above rubber composition may contain 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) and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiadylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-oxyethylene-2-benzothiazolesulfenamide, and N,N′-diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, dioltotolylguanidine, and orthotolylbiguanidine. Commercially available products include those from Sumitomo Chemical Co., Ltd. and Ouchi Shinko Chemical Co., Ltd. These may be used individually or in combination of two or more.

[0091] In the above rubber composition, the content of the vulcanization accelerator is preferably 1.5 parts by mass or more, more preferably 2.5 parts by mass or more, even more preferably 3.5 parts by mass or more, per 100 parts by mass of the rubber component, and also preferably 10.0 parts by mass or less, more preferably 8.0 parts by mass or less, and even more preferably 7.0 parts by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0092] In addition to the above components, the above rubber composition may further contain additives commonly used in the tire industry, such as organic peroxides. The content of these additives is preferably 0.1 to 200 parts by mass per 100 parts by mass of the rubber component.

[0093] The above rubber composition satisfies the following formula (1) in terms of the isoprene rubber content (content of isoprene rubber in 100% by mass of rubber components (by mass%)) and the total styrene content in the rubber components (by mass%). (1) Isoprene rubber content - Total styrene content in rubber components > 0 The right-hand side of formula (1) above is preferably 1, more preferably 2, even more preferably 5, and particularly preferably 8. In formula (1) above, the ratio of "isoprene rubber content - total styrene content in rubber components" is preferably less than 100, more preferably less than 70, even more preferably less than 50, even more preferably less than 45, even more preferably less than 40, particularly preferably less than 30, and most preferably less than 20. When the ratio is within the above range, a better effect tends to be obtained.

[0094] The above rubber composition satisfies the following formula (2) in terms of carbon black content (carbon black content per 100 parts by mass of rubber component (parts by mass)) and total styrene content (by mass) in the rubber component. (2) Carbon black content - Total styrene content in rubber component > 0 The right-hand side of formula (2) above is preferably 1, more preferably 2, even more preferably 3, and particularly preferably 5. Also, in formula (2) above, "carbon black content - total styrene content in rubber component" is preferably less than 50, more preferably less than 40, even more preferably less than 30, even more preferably less than 20, even more preferably less than 15, and particularly preferably less than 10. When it is within the above range, a better effect tends to be obtained.

[0095] The glass transition temperature (tanδ peak temperature) of the above rubber composition (after vulcanization) is preferably -45°C or higher, more preferably -40°C or higher, even more preferably -35°C or higher, and particularly preferably -30°C or higher. It is also preferably 0°C or lower, more preferably -5°C or lower, even more preferably -10°C or lower, and particularly preferably -15°C or lower. Within this range, a better effect tends to be obtained. The glass transition temperature can be measured by viscoelastic thermal dispersion measurement using the method described in the examples below.

[0096] The above rubber composition can be produced, for example, by kneading each of the above components using a rubber kneading device such as an open roll or Banbury mixer, and then vulcanizing it.

[0097] Regarding the mixing conditions, in the base mixing step where additives other than the vulcanizing agent and vulcanization accelerator are mixed, the mixing temperature is usually 100°C to 180°C, preferably 120°C to 170°C. In the finish mixing step where the vulcanizing agent and vulcanization accelerator are mixed, the mixing temperature is usually 120°C or lower, preferably 80°C to 110°C. Furthermore, the composition mixed with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 140°C to 190°C, preferably 150°C to 185°C. The vulcanization time is usually 5 minutes to 15 minutes.

[0098] The above rubber composition is used in the tread (especially the part that comes into contact with the road surface during driving (cap tread)).

[0099] From the viewpoint of obtaining better results, it is preferable that the rubber cut from the above tread satisfies the following formula (5) within 180 days after vulcanization. (5) Hso / Hsa × 100 ≥ 93.0 (In formula (5) above, Hso represents the hardness at room temperature. Hsa represents the hardness at room temperature after heat treatment at 80°C for 168 hours.)

[0100] The following are possible reasons why such effects can be obtained. The tread surface becomes hot due to friction with the road surface during high-speed driving. Therefore, by minimizing the change in hardness of the tread rubber during thermal degradation, it is possible to improve the tread rubber surface's ability to follow the road surface and the scratching effect created by domains with different hardness levels, thereby improving handling stability.

[0101] The right-hand side of equation (5) above is preferably 93.2, more preferably 93.4, and even more preferably 93.8. In addition, the upper limit of "Hso / Hsa × 100" in equation (5) above is not particularly limited and may be 100, but for example, it is preferably 99.0 or less, more preferably 98.0 or less, and even more preferably 97.0 or less. When it is within the above range, a better effect tends to be obtained. Hso and Hsa can be measured by the method described in the examples below.

[0102] Hso can be adjusted as appropriate within the range that satisfies formula (5) above, but is preferably 70 or less, more preferably 65 or less, and also preferably 45 or more, more preferably 50 or more. Similarly, Hsa is preferably 75 or less, more preferably 70 or less, also preferably 55 or more, more preferably 60 or more, and particularly preferably 62 or more. When within the above ranges, a better effect tends to be obtained.

[0103] While there are no particular limitations on how Hso and Hsa are adjusted, Hso can be increased by methods such as increasing the amount of reinforcing agent, decreasing the amount of softener, increasing the amount of sulfur, or increasing the amount of vulcanization accelerator. Conversely, it can be lowered by methods such as decreasing the amount of reinforcing agent, increasing the amount of softener, decreasing the amount of sulfur, or decreasing the amount of vulcanization accelerator. Hsa can be lowered by methods such as using a (co)polymer with fewer conjugated diene units as the rubber component, lowering Hso, decreasing the amount of sulfur and increasing the amount of vulcanization accelerator, increasing the amount of zinc oxide and stearic acid, incorporating a plasticizer with an iodine value of 100-150 g / 100 g, or increasing the amount of heat applied during vulcanization (longer time / higher temperature). Hsa can also be increased by methods such as raising Hso, increasing the amount of sulfur and decreasing the amount of vulcanization accelerator, decreasing the amount of zinc oxide and stearic acid, or decreasing the amount of heat applied during vulcanization.

[0104] From the viewpoint of obtaining a better effect, it is preferable that the rubber cut from the tread satisfies the following formula (6). (6) Rupture energy of rubber (MPa·%) = Elongation at break of rubber (%) × Rupture strength of rubber (MPa) × 1 / 2 ≥ 5000

[0105] The following are possible reasons why such effects can be obtained. It is believed that the greater the wear energy, the less likely the rubber is to tear. Therefore, it is thought that this can suppress tearing of the tread surface due to friction with the road surface when driving at high speeds, and suppress the reduction in the actual contact area, thereby improving handling stability at high speeds.

[0106] The right-hand side of equation (6) above is preferably 5100, more preferably 5500, even more preferably 6000, and particularly preferably 6500. Furthermore, in equation (6) above, there is no particular upper limit to the fracture energy of the rubber; the larger the value, the better, but for example, 100,000 or less is preferred, 50,000 or less is more preferred, and 10,000 or less is even more preferred. When the value is within the above range, a better effect tends to be obtained.

[0107] In this specification, the fracture energy (MPa·%) of rubber is the value of TB × EB / 2, calculated from the elongation EB (%) and fracture strength TB (MPa) of rubber at 23°C, measured in accordance with JIS K6251:2010. Specifically, it can be measured by the method described in the examples below.

[0108] EB (elongation at break) can be adjusted mainly by the amount of reinforcing and softening agents added, while TB (strength at break) can be adjusted mainly by the type and amount of reinforcing and rubber components added.

[0109] The tire of the present invention is manufactured by conventional methods using the above-mentioned rubber composition. Specifically, the rubber composition is extruded to match the shape of the tread at the unvulcanized stage, and then molded together with other tire components in a conventional manner on a tire molding machine to form an unvulcanized tire. This unvulcanized tire is then heated and pressurized in a vulcanizing machine to obtain a tire.

[0110] The above tire comprises a tread made from a rubber composition containing isoprene rubber and styrene-butadiene rubber, silica, and carbon black, wherein the silica content A (silica content per 100 parts by mass of rubber component (parts by mass)) and the maximum thickness B (mm) of the tread satisfy the following formula (3). (3) A / B > 8 The right-hand side of equation (3) above is preferably 9, more preferably 10, even more preferably 11, and particularly preferably 13. Also, in equation (3) above, "A / B" is preferably less than 30, more preferably less than 25, even more preferably less than 20, and particularly preferably less than 15. When it is within the above range, a better effect tends to be obtained.

[0111] In this specification, the maximum tread thickness (B) refers to the thickness of the tread before use (new), and means the radial thickness of the tire from the tread surface (outer surface of the tire) on the equatorial plane to the outer surface of the reinforcing layer such as the band layer in the radial cross-section of the tire. If the tire has grooves on the equatorial plane, it refers to the radial distance from the intersection of the straight line connecting the radially outer ends of the grooves with the tire's equatorial plane to the outer surface of the reinforcing layer such as the band layer.

[0112] The maximum tread thickness (maximum tread thickness) B (mm) is preferably 5.0 mm or more, more preferably 5.5 mm or more, even more preferably 6.0 mm or more, particularly preferably 7.0 mm or more, and also preferably 10.0 mm or less, more preferably 9.5 mm or less, even more preferably 9.0 mm or less, particularly preferably 8.5 mm or less. Within the above range, a better effect tends to be obtained.

[0113] The above tire comprises a tread made from a rubber composition containing isoprene rubber and styrene-butadiene rubber, silica, and carbon black, wherein the land ratio C (%) of the tread and the glass transition temperature D (°C) of the rubber composition satisfy the following formula (4). (4)|C / D|>2.00 The right-hand side of equation (4) above is preferably 2.10, more preferably 2.50, even more preferably 3.00, and particularly preferably 3.40. Also, in equation (4) above, "|C / D|" is preferably less than 7.00, more preferably less than 6.50, even more preferably less than 6.00, even more preferably less than 5.50, even more preferably less than 5.00, and particularly preferably less than 4.50. When it is within the above range, a better effect tends to be obtained.

[0114] In this specification, if the tire is a pneumatic tire, the land ratio (C) is calculated from the contact patch shape under normal rim, normal internal pressure, and normal load conditions. In the case of a non-pneumatic tire, it can be measured similarly without requiring normal internal pressure.

[0115] A "standard rim" refers to the rim specified for each tire within the standards system that the tire is based on. For example, for JATMA (Japan Automobile Tire Manufacturers Association), it refers to the standard rim for the applicable size listed in the "JATMA YEAR BOOK," for ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" listed in the "STANDARDS MANUAL," and for TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "YEAR BOOK." Refer to JATMA, ETRTO, and TRA in that order, and if an applicable size is available at the time of reference, follow that standard. In the case of tires not specified in the standards, it refers to the rim with the smallest diameter and the narrowest rim width among rims that can be mounted on and can maintain internal pressure, i.e., rims that do not cause air leakage between the rim and tire.

[0116] "Regular internal pressure" refers to the air pressure specified for each tire by the aforementioned standards. For JATMA, it is the maximum air pressure; for ETRTO, it is "INFLATION PRESSURE"; and for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." Similar to the case of "regular rim," refer to JATMA, ETRTO, and TRA in that order and follow the respective standards. In the case of tires not specified in the standards, it refers to the regular internal pressure (but 250 kPa or higher) of another tire size (specified in the standards) that uses the aforementioned regular rim as the standard rim. If multiple regular internal pressures of 250 kPa or higher are listed, refer to the lowest value among them.

[0117] "Regular load" refers to the load specified for each tire in the standards system, including the standard on which the aforementioned tire is based, and represents the maximum mass that the tire is allowed to be loaded with. For JATMA, it refers to the maximum load capacity; for ETRTO, it refers to "LOAD CAPACITY"; and for TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". As with the "regular rim" and "regular internal pressure" mentioned above, refer to JATMA, ETRTO, and TRA in that order and follow their respective standards. For tires not specified in any standard, the regular load WL is determined by the following calculation. V={(Dt / 2)2-(Dt / 2-Ht)2}×π×Wt WL = 0.000011 × V + 175 WL: Regular load (kg) V: Virtual volume of the tire (mm²) 3 ) Dt: Tire outer diameter (mm) Ht: Tire section height (mm) Wt: Tire section width (mm)

[0118] The contact patch shape can be obtained by mounting the tire onto a standard rim, applying standard internal pressure, letting it stand at 25°C for 24 hours, then applying ink to the tire tread surface, applying standard load, pressing it onto cardboard (camber angle 0°), and transferring the shape to the paper. Therefore, the tire is rotated 72° in the circumferential direction, and the transfer is performed at 5 locations. In other words, the contact patch shape is obtained 5 times. At this time, for the 5 contact patch shapes, the parts that are interrupted by grooves in the contour are smoothly connected, and the resulting shape is considered the virtual contact surface.

[0119] The land ratio (C) is calculated as: average area of ​​the five contact shapes (inked areas) transferred to the cardboard / (average area of ​​the virtual contact surface from the five contact shapes) × 100 (%).

[0120] The land ratio (ratio of land area to total contact area) C(%) of the above tread is preferably 60% or more, more preferably 65% ​​or more, and also preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less. When it is within the above range, a better effect tends to be obtained.

[0121] The above-mentioned tires include pneumatic tires and non-pneumatic tires, but pneumatic tires are preferred. They are particularly suitable for use as summer tires, winter tires (studless tires, snow tires, studless tires, etc.), all-season tires, etc. The tires can be used for passenger cars, large passenger cars, large SUVs, heavy-duty trucks and buses, light trucks, motorcycles, and racing tires (high-performance tires). Passenger car tires refer to tires intended for use on vehicles with four or more wheels, with a maximum load capacity (regular load) of 1400 kg or less. [Examples]

[0122] The following examples (implementations) are considered preferable for implementation, but the scope of the present invention is not limited to these examples.

[0123] The following tables show the results of examining tires obtained by varying the formulations and other factors using the various chemicals listed below. The results are calculated based on the evaluation method described below.

[0124] NR:TSR20 SBR1: SBR produced in the following manufacturing example 1 (styrene content: 30% by mass, vinyl content: 30% by mass) Hydrogenated SBR: Hydrogenated SBR produced in the following manufacturing example 2 (styrene content: 30% by mass, vinyl content: 31% by mass) SBR2: SLR6430 (manufactured by Trinseo, styrene content: 40% by mass, vinyl content: 25% by mass) BR: BR150B manufactured by Ube Industries, Ltd. (Cystic content: 97% by mass) Carbon black: Dia Black I (N220, N2SA) manufactured by Mitsubishi Chemical Corporation: 114ml 2 / g, DBP oil absorption: 114ml / 100g) Silica: Evonik De Gussa's UltraSil VN3 (N2SA: 175m 2 / g) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik DeGussa. Resin 1: SYLVARES SA85 (manufactured by Arizona Chemicals, copolymer of α-methylstyrene and styrene, softening point: 85°C) Resin 2: Oppera PR395 (manufactured by ExxonMobil, C9 / hydrogenated DCPD resin, softening point: 115℃) Resin 3: Sylvatraxx 4150 (manufactured by Kraton, polyterpene resin, softening point: 150°C) Oil: H&R VIVATEC 400 / 500 (TDAE oil) Stearic acid: Stearic acid "Tsubaki" (manufactured by NOF Corporation) Zinc Oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Anti-aging agent: Antigen 6C (manufactured by Sumitomo Chemical Co., Ltd., N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) Wax: Sunnock N (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Sulfur: Powdered sulfur (manufactured by Karuizawa Sulfur Co., Ltd.) Vulcanization accelerator CZ: Noxellar CZ (manufactured by Ouchi Shinko Chemical Co., Ltd., N-cyclohexyl-2-benzothiazolyl sulfenamide) Vulcanization accelerator DPG: Noxellar D (manufactured by Ouchi Shinko Chemical Co., Ltd., 1,3-diphenylguanidine)

[0125] (Manufacturing Example 1) In a thoroughly nitrogen-purged heat-resistant reaction vessel, 2000 ml of n-hexane, 60 g of styrene, 140 g of butadiene, 0.93 g of TMEDA, and 0.45 mmol of n-butyllithium were added, and the mixture was stirred at 50°C for 5 hours to carry out the polymerization reaction. Then, 20 ml of methanol was added, and the unreacted reaction vessel was withdrawn. The reaction solution was then added to water with stirring, and the solvent was removed by steam stripping to obtain SBR. The weight-average molecular weight (Mw) of the obtained SBR was 480,000. The styrene content was 30% by mass, and the vinyl content was 30% by mass.

[0126] (Manufacturing example 2) In a thoroughly nitrogen-purged heat-resistant reaction vessel, 2000 ml of n-hexane, 60 g of styrene, 140 g of butadiene, 0.93 g of TMEDA, and 0.45 mmol of n-butyllithium were added, and the mixture was stirred at 50°C for 5 hours to carry out the polymerization reaction. Next, hydrogen gas was supplied at a pressure of 0.4 MPa-Gauge while stirring for 20 minutes to react with the unreacted lithium at the polymer ends to form lithium hydride. The hydrogen gas supply pressure was set to 0.7 MPa-Gauge and the reaction temperature to 90°C, and hydrogenation was carried out using a catalyst mainly composed of titanocene dichloride. When the hydrogen absorption reached the cumulative amount that would result in the desired hydrogenation rate, the reaction temperature was reduced to room temperature, the hydrogen pressure was returned to atmospheric pressure, and the mixture was withdrawn from the reaction vessel. The reaction solution was then stirred into water and the solvent was removed by steam stripping to obtain hydrogenated SBR. The hydrogenation rate of the obtained hydrogenated SBR was 80 mol%, and the weight-average molecular weight (Mw) was 480,000. Furthermore, the styrene content was 30% by mass, and the vinyl content was 31% by mass.

[0127] <Manufacturing of test tires> According to the formulation shown in Table 1, the chemicals other than sulfur and vulcanization accelerator were mixed for 4 minutes at 160°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a mixture. Next, sulfur and vulcanization accelerator were added to the mixture and mixed for 4 minutes at 80°C using an open roll to obtain an unvulcanized rubber composition. The resulting unvulcanized rubber composition is molded into a tread shape and bonded together with other tire components on a tire molding machine to form an unvulcanized tire. Then, it is vulcanized at 170°C for 12 minutes to produce a test tire (size: 195 / 65R15).

[0128] Table 1 shows the results calculated based on the evaluation method described below, assuming vulcanized rubber compositions obtained from compositions with varying formulations according to Table 1, and test tires. The evaluation criteria for handling stability will be those of Comparative Example 3.

[0129] (Viscoelastic temperature dispersion measurement test) Using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., a temperature distribution curve of the tanδ of the vulcanized rubber composition was created under the conditions of a frequency of 10 Hz, initial strain of 10%, amplitude of ±0.20%, and heating rate of 2 °C / min. The temperature corresponding to the largest tanδ value in the obtained temperature distribution curve was defined as the tanδ peak temperature (Tg (°C)). The tanδ peak temperature corresponds to the glass transition temperature (compounding Tg (°C)) of the rubber composition (after vulcanization).

[0130] (hardness) The hardness (JIS-A hardness) at room temperature (25°C) is measured (Hso) using a Type A durometer in accordance with JIS K6253-3 (2012) "Vulcanized rubber and thermoplastic rubber - Method for determining hardness - Part 3: Durometer hardness". After measurement, the test specimen is heat-treated at 80°C for 168 hours under conditions of 20% oxygen concentration, and then the hardness at room temperature is measured (Hsa) using the same method.

[0131] (Destructive energy) For test specimens cut from the tread (cap tread) of the above-mentioned test tire, a tensile test will be conducted at a temperature of 23°C in accordance with JIS K6251:2010 "Vulcanized rubber and thermoplastic rubber - Method for determining tensile properties". The elongation at break EB [%] (23°C) and the strength at break TB [MPa] (23°C) will be measured, and the fracture energy (fracture E [MPa·%]) (=TB × EB / 2) will be calculated. (Conditions for tensile testing) Environmental temperature=23℃ Testing machine = "Strograph" product name, manufactured by Toyo Seiki Seisakusho Co., Ltd. Tensile speed = 500 mm / min

[0132] <Handling Stability> Each test tire is mounted on a vehicle, and its handling performance is subjectively evaluated on a 5-point scale (out of 5) while driving on a dry road surface at an average speed of 120 km / h. The evaluation is conducted by 10 test drivers, and the total score is expressed as an index with a baseline of 100. A higher number indicates better handling stability at high speeds.

[0133] [Table 1]

[0134] The present invention (1) is a tire having a tread, The tread is composed of a rubber composition containing isoprene rubber and styrene-butadiene rubber, silica, and carbon black. The rubber composition has a silica content of 80 parts by mass or more per 100 parts by mass of the rubber component. The rubber composition satisfies the following formulas (1) to (2): The tire is one in which the silica content A (parts by mass) of the rubber composition, the maximum thickness B (mm) of the tread, the land ratio C (%) of the tread, and the glass transition temperature D (°C) of the rubber composition satisfy the following formulas (3) to (4). (1) Isoprene rubber content - Total styrene content in rubber components > 0 (2) Carbon black content - Total styrene content in rubber component > 0 (3) A / B > 8 (4)|C / D|>2.00

[0135] The present invention (2) is a tire according to the present invention (1) in which the rubber cut from the tread satisfies the following formula (5) within 180 days after vulcanization. (5) Hso / Hsa × 100 ≥ 93.0 (In formula (5) above, Hso represents the hardness at room temperature. Hsa represents the hardness at room temperature after heat treatment at 80°C for 168 hours.)

[0136] The present invention (3) is a tire according to the present invention (1) or (2) in which the rubber cut from the tread satisfies the following formula (6). (6) Rupture energy of rubber (MPa·%) = Elongation at break of rubber (%) × Rupture strength of rubber (MPa) × 1 / 2 ≥ 5000

[0137] The present invention (4) is a tire according to any one of the present inventions (1) to (3), wherein the rubber composition satisfies the following formula. 50 > Isoprene rubber content - Total styrene content in rubber components > 8

[0138] The present invention (5) is a tire according to any one of the present inventions (1) to (4), wherein the rubber composition satisfies the following formula. 50 > Carbon black content - Total styrene content in rubber components > 5

[0139] The present invention (6) is a tire according to any one of the present inventions (1) to (5), wherein the rubber composition contains 10 to 70% by mass of isoprene-based rubber in 100% by mass of the rubber component.

[0140] The present invention (7) is a tire according to any one of the present inventions (1) to (6), wherein the rubber composition contains 10 to 100 parts by mass of carbon black per 100 parts by mass of the rubber component.

[0141] The present invention (8) is a tire according to any one of the present inventions (1) to (7), wherein the total amount of styrene in the rubber component is 5.0 to 60.0% by mass.

[0142] The present invention (9) is a tire according to any one of the present inventions (1) to (8), wherein the silica content A (parts by mass) in the rubber composition and the maximum thickness B (mm) of the tread satisfy the following formula. 30 > A / B > 10

[0143] The present invention (10) is a tire according to any one of the present inventions (1) to (9) wherein the land ratio C (%) of the tread and the glass transition temperature D (°C) of the rubber composition satisfy the following formula. 5.50 > |C / D| > 2.50

[0144] The present invention (11) is a tire according to any one of the present inventions (1) to (10), wherein the rubber composition contains 90 to 200 parts by mass of silica per 100 parts by mass of the rubber component.

[0145] The present invention (12) is a tire according to any one of the present inventions (1) to (11), wherein the maximum thickness of the tread is 5.0 to 10.0 mm.

[0146] The present invention (13) is a tire according to any one of the present inventions (1) to (12), wherein the land ratio of the tread is 60 to 95%.

[0147] The present invention (14) is a tire according to any one of the present inventions (1) to (13), wherein the glass transition temperature of the rubber composition is -45°C to 0°C.

[0148] The present invention (15) is a tire according to any of the present inventions (1) to (14) in which the rubber cut from the tread satisfies the following formula within 180 days after vulcanization. 70≧Hso≧45 (In the above formula, Hso represents the hardness at room temperature.)

Claims

1. A tire having a tread, The tread is composed of a rubber composition containing isoprene rubber and styrene-butadiene rubber, silica, and carbon black. The rubber composition has a silica content of 80 parts by mass or more per 100 parts by mass of the rubber component. The rubber composition satisfies the following formulas (1) to (2): A tire in which the silica content A (parts by mass) of the rubber composition, the maximum thickness B (mm) of the tread, the land ratio C (%) of the tread, and the glass transition temperature D (°C) of the rubber composition satisfy the following formulas (3) to (4). (1) Isoprene rubber content - Total styrene content in rubber components > 0 (2) Carbon black content - Total styrene content in rubber components > 0 (3) A / B > 8 (4) |C / D|>2.00

2. The tire according to claim 1, wherein the rubber cut from the tread satisfies the following formula (5) within 180 days after vulcanization. (5) Hso / Hsa×100≧93.0 (In formula (5) above, Hso represents the hardness at room temperature. Hsa represents the hardness at room temperature after heat treatment at 80°C for 168 hours.)

3. The tire according to claim 1 or 2, wherein the rubber cut from the tread satisfies the following formula (6). (6) Rupture energy of rubber (MPa·%) = Elongation of rubber at break (%) × Rupture strength of rubber (MPa) × 1 / 2 ≥ 5000

4. The tire according to claim 1 or 2, wherein the rubber composition satisfies the following formula. 50 > Isoprene rubber content - Total styrene content in rubber components > 8

5. The tire according to claim 1 or 2, wherein the rubber composition satisfies the following formula. 50 > Carbon black content - Total styrene content in rubber components > 5

6. The tire according to claim 1 or 2, wherein the rubber composition comprises 10 to 70% by mass of isoprene-based rubber in 100% by mass of the rubber component.

7. The tire according to claim 1 or 2, wherein the rubber composition comprises 10 to 100 parts by mass of carbon black with respect to 100 parts by mass of the rubber component.

8. The tire according to claim 1 or 2, wherein the total amount of styrene in the rubber component is 5.0 to 60.0% by mass.

9. The tire according to claim 1 or 2, wherein the silica content A (parts by mass) in the rubber composition and the maximum tread thickness B (mm) satisfy the following formula. 30 > A / B > 10

10. The tire according to claim 1 or 2, wherein the land ratio C (%) of the tread and the glass transition temperature D (°C) of the rubber composition satisfy the following formula. 5.50>|C / D|>2.50

11. The tire according to claim 1 or 2, wherein the rubber composition contains 90 to 200 parts by mass of silica per 100 parts by mass of the rubber component.

12. The tire according to claim 1 or 2, wherein the maximum thickness of the tread is 5.0 to 10.0 mm.

13. The tire according to claim 1 or 2, wherein the land ratio of the tread is 60 to 95%.

14. The tire according to claim 1 or 2, wherein the glass transition temperature of the rubber composition is -45°C to 0°C.

15. The tire according to claim 1 or 2, wherein the rubber cut from the tread satisfies the following formula within 180 days after vulcanization. 70 ≥ Hso ≥ 45 (In the above formula, Hso represents the hardness at room temperature.)

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