Tire

Abstract

To provide a tire excellent in total performance of turning performance after a travel initial stage and a travel middle stage.SOLUTION: A tire includes a tread having a cap tread and a base tread, wherein the tread has a land ratio of 70% or more, the cap trend has an average value of a loss tangent at 30-100°C of 0.10 or more, and the base tread has an average value of the loss tangent at 30-100°C of less than 0.05.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] For the tread of a tire, from the viewpoints of safety and the environment, performances such as grip performance (such as turning performance) and wear resistance performance are required. For example, performance improvement has been carried out by methods such as devising the rubber component, filler, etc. used for the tread.

Summary of the Invention

Problems to be Solved by the Invention

[0003] An object of the present invention is to solve the above problems and provide a tire excellent in the overall performance of turning performance in the initial stage of running and after the middle stage of running.

Means for Solving the Problems

[0004] The present invention relates to a tire provided with a tread having a cap tread and a base tread, wherein the tread has a land ratio of 70% or more, the cap tread has an average value of loss tangent at 30 to 100°C of 0.10 or more, and the base tread has an average value of loss tangent at 30 to 100°C of less than 0.05.

[0005] It is preferable that the cap tread has an average value of loss tangent at 30 to 100°C of 0.12 or more.

[0006] It is more preferable that the cap tread has an average value of loss tangent at 30 to 100°C of 0.15 or more.

[0007] It is preferable that the base tread has an average value of loss tangent at 30 to 100°C of less than 0.04.

[0008] It is preferable that the base tread has an average loss tangent value at 30 to 100 °C of less than 0.03.

[0009] It is preferable that the average loss tangent value (tanδc) of the cap tread at 30 to 100 °C and the average loss tangent value (tanδb) of the base tread at 30 to 100 °C satisfy the following formula. tanδc / tanδb≧1.1

[0010] It is preferable that the average loss tangent value (tanδc) of the cap tread at 30 to 100 °C and the average loss tangent value (tanδb) of the base tread at 30 to 100 °C satisfy the following formula. tanδc / tanδb≧1.3

[0011] It is preferable that the average loss tangent value (tanδc) of the cap tread at 30 to 100 °C and the land ratio (LR (%)) satisfy the following formula. tanδc / LR×100≧0.12

[0012] It is preferable that the average loss tangent value (tanδc) of the cap tread at 30 to 100 °C and the land ratio (LR (%)) satisfy the following formula. tanδc / LR×100≧0.15

[0013] It is preferable that the average thickness (Tc) of the cap tread and the average thickness (Tb) of the base tread satisfy the following formula. Tc>Tb

[0014] It is preferable that the average thickness (Tc) of the cap tread and the average thickness (Tb) of the base tread satisfy the following formula. Tc / Tb≦ 4.0

[0015] The rubber composition for cap tread constituting the cap tread preferably contains styrene-butadiene rubber, filler, solid plasticizer, and liquid plasticizer.

[0016] The rubber composition for cap tread constituting the cap tread has a styrene-butadiene rubber content of 50% by mass or more in 100% by mass of the rubber component, a filler content of 50 parts by mass or more with respect to 100 parts by mass of the rubber component, a solid plasticizer content of 10 parts by mass or more, and a liquid plasticizer content of 5 parts by mass or more, which is preferable.

[0017] The rubber composition for base tread constituting the base tread preferably contains an isoprene-based rubber, a butadiene rubber, a filler, and a liquid plasticizer.

[0018] The rubber composition for base tread constituting the base tread has an isoprene-based rubber content of 20 to 80% by mass and a butadiene rubber content of 5 to 50% by mass in 100% by mass of the rubber component, a filler content of 10 parts by mass or more with respect to 100 parts by mass of the rubber component, and a liquid plasticizer content of 3 parts by mass or more, which is preferable.

Advantages of the Invention

[0019] According to the present invention, there is provided a tire including a tread having a cap tread and a base tread, wherein the tread has a land ratio of 70% or more, the cap tread has an average loss tangent value of 0.10 or more at 30 to 100°C, and the base tread has an average loss tangent value of less than 0.05 at 30 to 100°C. Therefore, it is possible to provide a tire having excellent comprehensive performance in cornering performance in the initial stage of running and after the middle stage of running.

Brief Description of the Drawings

[0020]

Figure 1

Modes for Carrying Out the Invention

[0021] The present invention relates to a tire provided with a tread having a cap tread and a base tread, wherein the tread has a land ratio of 70% or more, the cap tread has an average loss tangent value of 0.10 or more at 30 to 100 ° C, and the base tread has an average loss tangent value of less than 0.05 at 30 to 100 ° C. The tire is excellent in the overall performance of the turning performance in the initial stage of running and after the middle stage of running.

[0022] The reason for obtaining such an effect (mechanism) is not clear, but it is speculated as follows. For a tire with a large land ratio, after the middle stage of running when the tread surface is sufficiently warmed up, the contact area during turning is wide, so the adhesion to the road surface is enhanced, and thus the grip performance during turning after the middle stage of running is high. On the other hand, when the tread surface is not sufficiently warmed up in the initial stage of running, due to the large land ratio, that is, the small number of grooves, there are few edges caught on the road surface, and the turning performance is low. Therefore, by increasing the average loss tangent value of the cap tread in the temperature range corresponding to the tire temperature from the initial stage to the middle stage of running to 0.10 or more, even if the land ratio is large, the turning performance from the initial stage to the middle stage can be improved. In addition, a rapid temperature rise may cause the temperature rise and softening of the base tread and the accompanying destabilization. Therefore, it is considered that such a problem can be prevented by adjusting the loss tangent of the base tread to less than 0.05. It is speculated that such a mechanism improves the overall performance of the turning performance in the initial stage of running and after the middle stage of running.

[0023] Thus, in a tire provided with a tread having a cap tread and a base tread, by setting the land ratio of the tread to 70% or more, the average value of the loss tangent of the cap tread at 30 to 100°C to 0.10 or more, and the average value of the loss tangent of the base tread at 30 to 100°C to less than 0.05, the problem (objective) of improving the overall performance of the turning performance in the initial stage of running and the turning performance after the middle stage of running is solved. That is, the parameters "the tread has a land ratio of 70% or more", "the cap tread has an average loss tangent value of 0.10 or more at 30 to 100°C", and "the base tread has an average loss tangent value of less than 0.05 at 30 to 100°C" do not define the problem (objective). The problem of this application is to improve the overall performance of the turning performance in the initial stage of running and the turning performance after the middle stage of running. Therefore, the configuration satisfies the said parameters as a solution means.

[0024] In the said tire, the land ratio (LR) of the tread is 70% or more, preferably 74% or more, more preferably 76% or more, still more preferably 78% or more, and particularly preferably 80% or more. The upper limit of the said LR is preferably 90% or less, more preferably 88% or less, still more preferably 86% or less, and particularly preferably 85% or less. When it is within the above range, the effect tends to be obtained better.

[0025] In addition, in this specification, when the said tire is a pneumatic tire, the land ratio (LR) is calculated from the contact shape under the conditions of a normal rim, a normal internal pressure, and a normal load. In the case of a non-pneumatic tire, it can be measured in the same way without requiring a normal internal pressure. The "normal rim" means the rim defined for each tire in a standard system including the standard on which the tire is based. For example, in the case of JATMA, it means the standard rim; in the case of TRA, it means "Design Rim"; or in the case of ETRTO, it means "Measuring Rim". "Normal internal pressure" refers to the air pressure specified for each tire by the above-mentioned standard. For JATMA, it is the maximum air pressure; for TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; for ETRTO, it means "INFLATION PRESSURE". However, for passenger car tires, it shall be 180 kPa. "Normal load" refers to the load specified for each tire by the above-mentioned standard. For JATMA, it is the maximum load capacity; for TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; for ETRTO, it means the load obtained by multiplying "LOAD CAPACITY" by 0.88 respectively. The contact shape is obtained by assembling on a normal rim, applying the normal internal pressure, leaving it standing for 24 hours at 25°C, then painting ink on the tire tread surface, loading the normal load and pressing it against thick paper (the camber angle is 0°) to transfer it onto the paper. Rotate the tire by 72° in the circumferential direction and transfer it at 5 positions. That is, obtain the contact shape 5 times. For the 5 contact shapes, let the average value of the maximum length in the tire axial direction be L, and the average value of the length in the direction perpendicular to the axial direction be W. The land ratio (LR) is calculated by the average area of the 5 transferred contact shapes (ink parts) on the thick paper / (L × W) × 100 (%). Here, the average value of the length and area is the simple average of the 5 values.

[0026] The tread of the above-mentioned tire may be provided with grooves continuous in the tire circumferential direction and / or grooves discontinuous in the tire circumferential direction. Examples of such groove patterns include rib type, lug type, rib-lug type, and block type.

[0027] From the perspective of the comprehensive performance of the turning performance in the initial running stage and after the mid - running stage, the average value of the loss tangent (tanδc) of the cap tread at 30 - 100 °C is 0.10 or more, preferably 0.16 or more, more preferably 0.20 or more, still more preferably 0.22 or more, and particularly preferably 0.24 or more. The upper limit of the said tanδc is not particularly limited, but is preferably 0.50 or less, more preferably 0.40 or less, still more preferably 0.35 or less, and particularly preferably 0.30 or less.

[0028] From the perspective of the comprehensive performance of the turning performance in the initial running stage and after the mid - running stage, the average value of the loss tangent (tanδb) of the base tread at 30 - 100 °C is less than 0.05, preferably less than 0.04, more preferably less than 0.03, and still more preferably 0.02 or less. The lower limit of the said tanδb is not particularly limited, but is preferably 0.001 or more, more preferably 0.005 or more, and still more preferably 0.01 or more.

[0029] In the said tire, from the perspective of the comprehensive performance of the turning performance in the initial running stage and after the mid - running stage, it is preferable that the average value of the loss tangent (tanδc) of the cap tread at 30 - 100 °C and the average value of the loss tangent (tanδb) of the base tread at 30 - 100 °C satisfy the following formula. tanδc / tanδb≧1.1 tanδc / tanδb is preferably 2.5 or more, more preferably 3.0 or more, still more preferably 3.5 or more, and particularly preferably 4.0 or more. The upper limit is preferably 10.0 or less, more preferably 8.0 or less, still more preferably 7.0 or less, and particularly preferably 6.0 or less.

[0030] In the said tire, from the perspective of the comprehensive performance of the turning performance in the initial running stage and after the mid - running stage, it is preferable that the average value of the loss tangent (tanδc) of the cap tread at 30 - 100 °C and the land ratio (LR (%)) satisfy the following formula. tanδc / LR×100≧0.12 tanδc / LR×100 (=(tanδc / LR)×100) is preferably 0.20 or more, more preferably 0.24 or more, still more preferably 0.28 or more, and particularly preferably 0.30 or more. The upper limit is preferably 0.80 or less, more preferably 0.60 or less, still more preferably 0.50 or less, and particularly preferably 0.40 or less.

[0031] Here, the loss tangent (tanδ) at 30 to 100°C can be adjusted by the type and amount of chemicals (particularly rubber components, fillers, softeners, resins, sulfur, vulcanization accelerators, silane coupling agents) compounded in the rubber composition. For example, using a softener (such as resin) with low compatibility with the rubber component, increasing the amount of a plasticizer (such as solid resin) with high compatibility with the rubber component, using non-modified rubber, increasing the amount of styrene-butadiene rubber, increasing the amount of filler, increasing the amount of oil as a plasticizer, decreasing the amount of sulfur, decreasing the amount of vulcanization accelerator, or decreasing the amount of silane coupling agent tends to increase tanδ. On the other hand, using a plasticizer (such as solid resin) with high compatibility with the rubber component, using modified rubber, increasing the amount of natural rubber, decreasing the amount of styrene-butadiene rubber, decreasing the amount of filler, decreasing the amount of oil as a plasticizer, increasing the amount of sulfur, increasing the amount of vulcanization accelerator, or increasing the amount of silane coupling agent tends to decrease tanδ. Therefore, by using these methods alone or in appropriate combinations, it is possible to adjust the average value of the loss tangent (tanδc) at 30 to 100°C of the cap tread to 0.10 or more and the average value of the loss tangent (tanδb) at 30 to 100°C of the base tread to less than 0.05.

[0032] The loss tangent (tanδ) can be obtained for each of the cap tread (vulcanized rubber composition) and base tread (vulcanized rubber composition) sampled from the tire by performing a viscoelasticity test on each sample in the temperature range of 30 to 100°C, and specifically, it can be measured by the method described in the examples below.

[0033] In the tire, from the viewpoint of the overall performance of the cornering performance in the initial stage of running and after the middle stage of running, it is preferable that the average thickness (Tc (mm)) of the cap tread and the average thickness (Tb (mm)) of the base tread satisfy the following formula. Tc>Tb

[0034] Tc / Tb is preferably 9.0 or less, more preferably 6.0 or less, still more preferably 5.0 or less, and particularly preferably 4.0 or less. The lower limit of Tc / Tb is preferably 1.0 or more, more preferably 2.0 or more, still more preferably 2.5 or more, and particularly preferably 3.0 or more. When within the above range, the effect tends to be obtained more favorably.

[0035] Tc (average thickness of the cap tread (mm)) is preferably 3.0 mm or more, more preferably 3.5 mm or more, and still more preferably 4.0 mm or more. On the other hand, it is preferably 7.0 mm or less, more preferably 6.5 mm or less, and still more preferably 6.4 mm or less. When within the above range, the effect tends to be obtained more favorably.

[0036] Note that the average thicknesses (Tc (mm), Tb (mm)) of the cap tread and the base tread are the average values of the thicknesses at each point on the cap tread surface and the average values of the thicknesses at each point on the base tread surface. FIG. 1 is an enlarged cross-sectional view showing the tread portion of the tire, and shows an example of a two-layer structure tread of a cap tread 11 and a base tread 12. In FIG. 1, reference symbol Pc is a point on the cap tread surface 11c, and reference symbol Pb is a point on the base tread surface 12b. The double arrow Tc is the thickness of the cap tread 11 at the point Pc, and the double arrow Tb is the thickness of the base tread 12 at the point Pb. The thickness Tc is measured along the normal line of the cap tread surface 11c at the point Pc, and the thickness Tb is measured along the normal line of the base tread surface 12b at the point Pb.

[0037] (Chemical) Next, the chemicals that can be used in the cap tread rubber composition constituting the cap tread and the base tread rubber composition constituting the base tread will be described.

[0038] As rubber components that can be used in the rubber compositions for cap treads and base treads, isoprene rubbers (isoprene rubber (IR), epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, natural rubber (NR), deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber), butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), butyl rubbers, etc. can be mentioned.

[0039] These rubbers may be either non-modified rubbers or modified rubbers. Examples of modified rubbers include rubbers having functional groups that interact with fillers. Examples of the above functional groups include, for example, amino group, amide group, silyl group, alkoxysilyl group, isocyanate group, imino group, imidazole group, urea group, ether group, carbonyl group, oxycarbonyl group, mercapto group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazo group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group, hydroxyl group, oxy group, epoxy group, etc. Note that these functional groups may have substituents. Among them, an amino group (preferably an amino group in which the hydrogen atom of the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms), and an amide group are preferable. These rubber components may be used alone or in combination of two or more.

[0040] It is desirable that the rubber compositions for cap treads and base treads contain fillers. The fillers (reinforcing materials) that can be used in the rubber compositions for cap treads and base treads are not particularly limited, and materials known in the rubber field can be used. For example, inorganic fillers such as silica, carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, mica, etc.; poorly dispersible fillers, etc. Among them, carbon black and silica are preferred.

[0041] Examples of the carbon black that can be used in the rubber compositions for cap treads and base treads include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. These can be used alone or in combination of two or more. As commercially available products, for example, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nippon Carbon Co., Ltd., Columbian Carbon Company, etc. can be used.

[0042] Examples of the silica that can be used in the rubber compositions for cap treads and base treads include, for example, dry-process silica (anhydrous silica), wet-process silica (hydrous silica), etc. Among them, wet-process silica is preferred because it has many silanol groups.

[0043] When containing silica, it is preferable to include a silane coupling agent together with the silica. As the silane coupling agent that can be used in the rubber composition for the cap tread and the base tread, any silane coupling agent that has been conventionally used in combination with silica in the rubber industry can be used without particular limitation. For example, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, etc. sulfide-based, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercapto-based such as NXT and NXT-Z manufactured by Momentive, vinyl-based such as vinyltriethoxysilane and vinyltrimethoxysilane, amino-based such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy-based such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, nitro-based such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, chloro-based such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane, etc. can be mentioned. As commercially available products, products of companies such as Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azmax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used. These may be used alone or in combination of two or more. Among them, sulfide-based and mercapto-based are preferred.

[0044] A plasticizer may be compounded in the rubber composition for the cap tread and the base tread. The plasticizer is not particularly limited, and examples thereof include liquid plasticizers having plasticity in a liquid state at 25°C, such as oils and liquid resins, and solid plasticizers having plasticity in a solid state at 25°C, such as resins (polymers in a solid state at 25°C (solid resins)). These plasticizers may be used alone or in combination of two or more.

[0045] The oil is not particularly limited, and conventionally known oils such as paraffinic process oil, aromatic process oil, naphthenic process oil and other process oils, low PCA (polycyclic aromatic) process oils such as TDAE and MES, vegetable oils, and mixtures thereof can be used. Among them, aromatic process oil is preferable in terms of abrasion resistance and fracture properties. Specific examples of the aromatic process oil include Diana Process Oil AH series manufactured by Idemitsu Kosan Co., Ltd.

[0046] The liquid resin is not particularly limited, and examples thereof include liquid aromatic vinyl polymers, coumarone-indene resins, indene resins, terpene resins, rosin resins, and hydrogenated products thereof.

[0047] Examples of the liquid aromatic vinyl polymer include resins obtained by polymerizing α-methylstyrene and / or styrene. Specifically, liquid resins such as homopolymers of styrene, homopolymers of α-methylstyrene, and copolymers of α-methylstyrene and styrene can be mentioned.

[0048] Examples of the liquid coumarone-indene resin include resins containing coumarone and indene as main monomer components constituting the resin skeleton (main chain). Examples of monomer components that may be contained in the skeleton in addition to coumarone and indene include styrene, α-methylstyrene, methyl indene, vinyl toluene, and the like.

[0049] Examples of the liquid indene resin include liquid resins containing indene as a main monomer component constituting the resin skeleton (main chain).

[0050] Examples of the liquid terpene resin include liquid terpene resins typified by resins obtained by polymerizing terpene compounds such as α-pinene, β-pinene, camphene, and diterpene, and terpene phenols which are resins obtained using terpene compounds and phenolic compounds as raw materials.

[0051] Examples of the liquid rosin resin include liquid rosin-based resins typified by natural rosin, polymerized rosin, modified rosin, their ester compounds, or their hydrogenated products.

[0052] The resin (solid resin that is solid at 25°C) is not particularly limited. For example, solid styrene-based resins, coumarone-indene resins, terpene-based resins, p-t-butylphenol acetylene resins, acrylic-based resins, dicyclopentadiene-based resins (DCPD-based resins), C5 petroleum resins, C9 petroleum resins, C5C9 petroleum resins, etc. may be mentioned. These may be used alone or in combination of two or more.

[0053] The solid styrene resin is a solid polymer using a styrene monomer as a constituent monomer, and examples thereof include polymers obtained by polymerizing a styrene monomer as a main component (50% by mass or more). Specifically, homopolymers obtained by polymerizing styrene monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) alone, copolymers obtained by copolymerizing two or more styrene monomers, and copolymers of a styrene monomer and other monomers copolymerizable therewith are also included. Examples of other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene, butadiene and isoprene, olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride or acid anhydrides thereof; and the like.

[0054] Examples of the solid coumarone-indene resin include solid resins having the same structural units as the aforementioned liquid coumarone-indene resin.

[0055] Examples of the solid terpene resin include polyterpene, terpene phenol, and aromatic-modified terpene resin. Examples of the solid polyterpene include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene / limonene resin using terpene compounds as raw materials, and solid resins such as hydrogenated terpene resins obtained by hydrogenating the terpene resins. Examples of the solid terpene phenol include solid resins obtained by copolymerizing terpene compounds and phenolic compounds, and solid resins obtained by hydrogenating the resins, and specifically, solid resins obtained by condensing terpene compounds, phenolic compounds, and formalin. Examples of the solid aromatic-modified terpene resin include solid resins obtained by modifying terpene resins with aromatic compounds, and solid resins obtained by hydrogenating the resins.

[0056] Examples of the solid p-t-butylphenol acetylene resin include solid resins obtained by subjecting p-t-butylphenol and acetylene to a condensation reaction.

[0057] The solid acrylic resin is not particularly limited, and examples thereof include solventless acrylic solid resins. Examples of the monomer components constituting the solid acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (such as alkyl esters, aryl esters, and aralkyl esters), (meth)acrylamide, and (meth)acrylamide derivatives, i.e., (meth)acrylic acid derivatives. Further, as the monomer components constituting the solid acrylic resin, aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene may be used together with (meth)acrylic acid or (meth)acrylic acid derivatives. The solid acrylic resin may be a resin composed only of a (meth)acrylic component or a resin having components other than the (meth)acrylic component as constituent elements. Further, the solid acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

[0058] The rubber composition for the cap tread and the base tread preferably contains sulfur. Examples of the sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur, which are generally used in the rubber industry. As commercially available products, for example, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexsys, Nippon Kankyo Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0059] The rubber composition for the cap tread and the base tread preferably contains a vulcanization accelerator. As vulcanization accelerators, there can be mentioned thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyldisulfide, N-cyclohexyl-2-benzothiazylsulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-t-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine, orthotolylbiguanidine. Among them, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred.

[0060] In the rubber composition for the cap tread and the base tread, wax, antioxidant, stearic acid, zinc oxide, vulcanizing agents other than sulfur (such as organic crosslinking agents), etc. may be blended.

[0061] (Cap tread (rubber composition for cap tread)) As the rubber component of the rubber composition for the cap tread, from the viewpoint of the overall performance of the turning performance in the initial stage of running and after the mid-stage of running, the above-mentioned SBR is preferred.

[0062] In the rubber composition for the cap tread, from the viewpoint of the overall performance of the turning performance in the initial stage of running and after the mid-stage of running, the content of SBR in 100% by mass of the rubber component is preferably 50% by mass or more. The lower limit is more preferably 70% by mass or more, still more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may also be 100% by mass.

[0063] The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. can be used. As commercially available products, products of Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

[0064] The styrene content of the SBR is preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 40% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less. When within the above range, the effect tends to be obtained more favorably. In addition, the styrene content of the SBR 1 can be measured by 1H-NMR.

[0065] The vinyl content of the SBR is preferably 25% by mass or more, more preferably 35% by mass or more, still more preferably 39% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less. When within the above range, the effect tends to be obtained more favorably. In addition, the vinyl content (1,2-bonded butadiene unit content) of the SBR can be measured by infrared absorption spectrum analysis method.

[0066] As the filler for the cap tread rubber composition, from the viewpoint of the comprehensive performance of the turning performance in the initial running and after the mid-running stage, it is preferable to contain the carbon black and silica as the filler, and it is more preferable to contain carbon black.

[0067] In the cap tread rubber composition, the content of the filler is preferably 50 parts by mass or more, more preferably 80 parts by mass or more, still more preferably 110 parts by mass or more, particularly preferably 120 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 200 parts by mass or less, more preferably 170 parts by mass or less, still more preferably 150 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0068] In the rubber composition for cap treads, the carbon black content is preferably 60 parts by mass or more, more preferably 90 parts by mass or more, still more preferably 110 parts by mass or more, particularly preferably 120 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, still more preferably 130 parts by mass or less, particularly preferably 125 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0069] The nitrogen adsorption specific surface area (N 2 SA) of carbon black is preferably 30 m 2 / g or more, more preferably 50 m 2 / g or more, still more preferably 65 m 2 / g or more, particularly preferably 75 m 2 / g or more. The above N 2 SA is preferably 120 m 2 / g or less, more preferably 100 m 2 / g or less, still more preferably 90 m 2 / g or less. When within the above range, the effect tends to be obtained more favorably. In this specification, the nitrogen adsorption specific surface area of carbon black is determined according to JIS K6217-2:2001.

[0070] In the rubber composition for cap treads, the silica content is preferably 60 parts by mass or more, more preferably 80 parts by mass or more, still more preferably 85 parts by mass or more, particularly preferably 90 parts by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, still more preferably 100 parts by mass or less, particularly preferably 95 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0071] The nitrogen adsorption specific surface area (N 2 SA) of silica is preferably 120 m 2 / g or more, more preferably 150 m 2 / g or more, still more preferably 160 m 2 / g or more. The above N2 The SA is preferably less than 200 m 2 / g, more preferably less than or equal to 195 m 2 / g, still more preferably less than or equal to 185 m 2 / g. Also, the lower or upper limit of the N 2 SA of the silica may be 175 m 2 / g. In addition, in this specification, the N 2 SA of the silica is a value measured by the BET method in accordance with ASTM D3037-81.

[0072] In the rubber composition for cap tread, the content of the silane coupling agent is preferably 1 to 15 parts by mass, more preferably 3 to 10 parts by mass, based on 100 parts by mass of the silica.

[0073] The rubber composition for cap tread preferably contains a solid plasticizer having plasticity in a solid state at 25°C, and more preferably contains a solid resin such as the solid coumarone-indene resin, from the viewpoint of the overall performance of the turning performance in the initial stage of running and after the mid-stage of running.

[0074] In the rubber composition for cap tread, the content of the solid plasticizer is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 40 parts by mass or more, and particularly preferably 45 parts by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, still more preferably 50 parts by mass or less, and particularly preferably 45 parts by mass or less. When within the above range, the effect tends to be obtained better. In addition, the content of a solid resin such as a solid C5C9-based petroleum resin is preferably in the same range.

[0075] The softening point of the solid resin used in the rubber composition for cap tread is preferably 160°C or lower, more preferably 130°C or lower, still more preferably 110°C or lower, and particularly preferably 96°C or lower. The lower limit is preferably 60°C or higher, more preferably 80°C or higher, still more preferably 90°C or higher. When within the above range, the effect tends to be obtained better. In addition, in this specification, the softening point of the solid resin is the temperature at which the ball drops when measured with a ring and ball softening point measuring device according to the softening point defined in JIS K 6220-1:2001.

[0076] From the viewpoint of the overall performance of the turning performance in the initial stage of running and after the middle stage of running, it is preferable to blend a liquid plasticizer having plasticity in a liquid state at 25°C in the rubber composition for the cap tread, and it is more preferable to contain the oil.

[0077] As the oil used in the rubber composition for the cap tread, it is preferable to use a paraffinic process oil or an aromatic process oil.

[0078] In the rubber composition for the cap tread, the content of the liquid plasticizer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 50 parts by mass or less, more preferably 35 parts by mass or less, and still more preferably 25 parts by mass or less. When within the above range, the effect tends to be obtained more favorably. Note that the content of the oil is also preferably in the same range.

[0079] The rubber composition for the cap tread preferably contains sulfur. In the rubber composition for the cap tread, the content of sulfur is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, still more preferably 1.3 parts by mass or more, and particularly preferably 1.5 parts by mass or more with respect to 100 parts by mass of the rubber component. Also, the above content is preferably 7.0 parts by mass or less, more preferably 5.0 parts by mass or less, and still more preferably 3.0 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0080] The rubber composition for the cap tread preferably contains a vulcanization accelerator. In the rubber composition for cap treads, the content of the vulcanization accelerator is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, still more preferably 2.5 parts by mass or more, and particularly preferably 3.0 parts by mass or more with respect to 100 parts by mass of the rubber component. Also, the above content is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, and still more preferably 4.0 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0081] (Base tread (rubber composition for base tread)) As the rubber component of the rubber composition for base treads, from the viewpoint of the overall performance of the turning performance in the initial stage of running and after the mid-stage of running, the isoprene rubber and BR are preferable, and it is more preferable to use the isoprene rubber and BR in combination.

[0082] In the rubber composition for base treads, in 100% by mass of the rubber component, the content of the isoprene rubber is preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 60% by mass or more, and particularly preferably 70% by mass or more. The upper limit is preferably 95% by mass or less, more preferably 80% by mass or less, and still more preferably 75% by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0083] As BR, for example, high-cis polybutadiene rubber is preferable. The cis content is more preferably 97% by mass or more. As commercially available products of high-cis polybutadiene rubber, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B and BR150B manufactured by Ube Industries, Ltd. can be used. In this specification, the cis content is a value calculated by infrared absorption spectrum analysis.

[0084] As BR, for example, high-cis polybutadiene rubber is preferable. The cis content of BR is preferably 70% by mass or more, more preferably 90% by mass or more, and still more preferably 97% by mass or more.

[0085] In the rubber composition for the base tread, in 100% by mass of the rubber component, the content of BR is preferably 5% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, and particularly preferably 25% by mass or more. The upper limit is preferably 50% by mass or less, more preferably 45% by mass or less, still more preferably 35% by mass or less, and particularly preferably 30% by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0086] As the filler of the rubber composition for the base tread, from the viewpoint of the overall performance of the turning performance in the initial stage of running and after the middle stage of running, it is preferable to include the carbon black and silica as the filler, and it is more preferable to include the carbon black.

[0087] In the rubber composition for the base tread, the content of the filler is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 40 parts by mass or more, and particularly preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, still more preferably 60 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0088] In the rubber composition for the base tread, the content of the carbon black is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 40 parts by mass or more, and particularly preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, still more preferably 60 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0089] The nitrogen adsorption specific surface area (N 2 SA) of the carbon black is preferably 30 m 2 / g or more, more preferably 50 m 2 / g or more, still more preferably 65 m 2 / g or more, and particularly preferably 75 m 2 / g or more. The above N 2 SA is 120 m 2It is preferably 100 m / g or less, more preferably 90 m / g or less, and still more preferably 80 m / g or less. When it is within the above range, the effect tends to be better obtained. 2 It is more preferably 90 m / g or less, still more preferably 80 m / g or less. 2 When it is within the above range, the effect tends to be better obtained.

[0090] In the rubber composition for the base tread, the silica content is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and still more preferably 25 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and still more preferably 40 parts by mass or less. When it is within the above range, the effect tends to be better obtained.

[0091] The nitrogen adsorption specific surface area (N 2 SA) of silica is preferably 120 m / g or more, more preferably 150 m / g or more, and still more preferably 160 m / g or more. 2 The N 2 SA is preferably less than 200 m / g, more preferably less than 195 m / g, and still more preferably less than 185 m / g. 2 SA is preferably 120 m / g or more, more preferably 150 m / g or more, and still more preferably 160 m / g or more. 2 SA is preferably less than 200 m / g, more preferably less than 195 m / g, and still more preferably less than 185 m / g. 2 SA is preferably less than 200 m / g, more preferably less than 195 m / g, and still more preferably less than 185 m / g. 2 SA is preferably less than 200 m / g, more preferably less than 195 m / g, and still more preferably less than 185 m / g. 2 SA is preferably less than 200 m / g, more preferably less than 195 m / g, and still more preferably less than 185 m / g.

[0092] In the rubber composition for the base tread, the content of the silane coupling agent is preferably 1 to 15 parts by mass, more preferably 3 to 10 parts by mass with respect to 100 parts by mass of silica.

[0093] In the rubber composition for the base tread, from the viewpoint of the overall performance of the turning performance in the initial stage of running and after the middle stage of running, it is preferable to blend a liquid plasticizer having plasticity in a liquid state at 25°C, and it is more preferable to contain the oil.

[0094] As the oil used in the rubber composition for the base tread, it is preferable to use a paraffinic process oil or an aromatic process oil.

[0095] In the rubber composition for the base tread, the content of the liquid plasticizer is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 8 parts by mass or more, and particularly preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 20 parts by mass or less. When within the above range, the effect tends to be obtained more favorably. Note that the content of the oil is also desirably in a similar range.

[0096] The rubber composition for the base tread preferably contains sulfur. In the rubber composition for the base tread, the content of sulfur is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, still more preferably 1.5 parts by mass or more, and particularly preferably 2.0 parts by mass or more with respect to 100 parts by mass of the rubber component. Also, the above content is preferably 7.0 parts by mass or less, more preferably 5.0 parts by mass or less, and still more preferably 3.5 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0097] The rubber composition for the base tread preferably contains a vulcanization accelerator. In the rubber composition for the base tread, the content of the vulcanization accelerator is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, still more preferably 1.5 parts by mass or more, and particularly preferably 2.0 parts by mass or more with respect to 100 parts by mass of the rubber component. Also, the above content is preferably 7.0 parts by mass or less, more preferably 5.0 parts by mass or less, and still more preferably 3.5 parts by mass or less. When within the above range, the effect tends to be obtained more favorably.

[0098] The rubber compositions for the cap tread and the base tread are manufactured by a general method. That is, they can be manufactured by a method such as kneading the respective components with a Banbury mixer, a kneader, an open roll, etc., and then vulcanizing.

[0099] As for the kneading conditions, for additives other than vulcanizing agents and vulcanization accelerators during kneading (base kneading), the kneading temperature is usually 50 to 200 °C (preferably 80 to 190 °C), and the kneading time is usually 30 seconds to 30 minutes (preferably 1 to 30 minutes). During kneading of the vulcanizing agent and vulcanization accelerator (finish kneading), the kneading temperature is usually 100 °C or lower (preferably room temperature to 80 °C). The obtained kneaded product (unvulcanized rubber composition) is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 120 to 200 °C (preferably 140 to 180 °C).

[0100] The tire is manufactured by a normal method using the above rubber composition. That is, the rubber composition containing the above components is extruded in an unvulcanized stage according to the shapes of the cap tread and base tread, and together with other tire members, it is formed by a normal method on a tire molding machine to form an unvulcanized tire. The tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

[0101] Examples of the tire include pneumatic tires, airless (solid) tires, etc. Among them, pneumatic tires are preferred. The tire can be suitably used especially as a winter tire (such as studless tires, snow tires, studded tires, etc.). The tire can be used for passenger car tires, large passenger car tires, large SUV tires, heavy-duty tires such as trucks and buses, light truck tires, two-wheeled vehicle tires, race tires (high-performance tires), etc.

Examples

[0102] Based on the examples, the present invention will be specifically described, but the present invention is not limited only to these.

[0103] Hereinafter, various chemicals used in the examples and comparative examples will be collectively described. NR: TSR20 SBR1: HP755B (manufactured by Asahi Kasei Corporation, S-SBR, styrene content 40% by mass, vinyl content 46% by mass, oil product containing 50% by mass of oil based on 100 parts by mass of rubber solid content) SBR2: Toughden 4850 (produced by Asahi Kasei Corporation, S-SBR, containing 40% by mass of styrene and 50 parts by mass of oil per 100 parts by mass of rubber solid, an oil-extended rubber) BR: Ube Pol BR150B (produced by Ube Industries, Ltd., cis content 97% by mass or more) Carbon black: Show Black N330 (produced by Cabot Japan, Ltd., N 2 SA75m 2 / g, DBP oil absorption 102 ml / 100 g) Silica: ZEOSIL 1165MP (produced by Rhodia, N 2 SA160m 2 / g) Silane coupling agent: Si69 (produced by Evonik, bis[3-(triethoxysilyl)propyl] polysulfide) Solid resin: Petrotack 100V produced by Tosoh Corporation (C5 / C9 resin, softening point 94 °C) Oil: VIVATEC500 (produced by H&R, TDAE oil)) Zinc oxide: Zinc oxide No. 2 produced by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Stearic acid "Tsubaki" (produced by NOF Corporation) Antioxidant: Antigen 6C (produced by Sumitomo Chemical Co., Ltd., N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) Wax: Sunoc N (produced by Ouchi Shinsei Chemical Industry Co., Ltd.) Sulfur: Powder sulfur produced by Karuizawa Sulfur Co., Ltd. Vulcanization accelerator 1: Sanseler CM-G (produced by Sanshin Chemical Industry Co., Ltd., N-cyclohexyl-2-benzothiazole sulfenamide) Vulcanization accelerator 2: Nocceler ZTC (produced by Ouchi Shinsei Chemical Co., Ltd., zinc dibenzyldithiocarbamate) Vulcanization accelerator 3: Nocceler D produced by Ouchi Shinsei Chemical Industry Co., Ltd. (N,N'-diphenylguanidine)

[0104] <Method for producing rubber composition for cap tread> According to the compounding ingredients shown in Tables 1 and 4, using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd., materials other than sulfur and vulcanization accelerators were kneaded at 150°C for 5 minutes to obtain a kneaded product. Next, sulfur and vulcanization accelerators were added to the obtained kneaded product, and it was kneaded for 5 minutes at 80°C using an open roll to obtain an unvulcanized rubber composition.

[0105] <Method for manufacturing rubber composition for base tread> According to the compounding ingredients shown in Tables 2 and 5, using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd., materials other than sulfur and vulcanization accelerators were kneaded at 150°C for 5 minutes to obtain a kneaded product. Next, sulfur and vulcanization accelerators were added to the obtained kneaded product, and it was kneaded for 5 minutes at 80°C using an open roll to obtain an unvulcanized rubber composition.

[0106] <Method for manufacturing test tire> According to the specifications in Tables 3 and 6, the obtained unvulcanized rubber composition for cap tread was molded into the shape of a cap tread, and the unvulcanized rubber composition for base tread was molded into the shape of a base tread. Then, on a tire molding machine, they were laminated together with other tire members to form an unvulcanized tire, which was vulcanized at 170°C for 10 minutes to manufacture a test tire (size 205 / 70R15, passenger car tire).

[0107] [Evaluation] The test tires were evaluated by the following method, and the results are shown in Tables 3 and 6. For the reference comparative examples, Comparative Example 1-1 was used for Table 3, and Comparative Example 2-1 was used for Table 6.

[0108] (Viscoelasticity test) From the cap tread and the base tread of the tread part of each test tire, viscoelastic measurement samples with a length of 20 mm, a width of 4 mm, and a thickness of 1 mm were taken so that the tire circumferential direction was the long side, and using an Iplexer series manufactured by GABO, in the temperature range of 30 to 100 °C, at a frequency of 10 Hz, an initial strain of 10%, an amplitude of ±0.5%, and a heating rate of 2 °C / min, the temperature distribution curve of tanδ (loss tangent) was measured respectively. From the obtained temperature distribution curve of tanδc of the cap tread and the temperature distribution curve of tanδb of the base tread, the average value of the tanδ value in the temperature range of 30 to 100 °C was calculated.

[0109] (Cornering performance at the initial stage of running) The above test tires were mounted on a domestic FR car with a displacement of 2000 cc, and a 10 - lap actual vehicle running test was conducted on a dry asphalt road surface. The stability during cornering at the second lap was evaluated by 10 test drivers on a 5 - point scale from 1 to 5. The larger the score, the better the performance. The total score of the 10 scores was calculated, and taking the total score of the reference comparison example as 100, it was indexed (cornering performance index at the initial stage of running). The larger the index, the better the cornering performance at the initial stage of running.

[0110] (Cornering performance after the mid - stage of running) The above test tires were mounted on a domestic FR car with a displacement of 2000 cc, and a 10 - lap actual vehicle running test was conducted on a dry asphalt road surface. The stability during cornering at the ninth lap was evaluated by 10 test drivers on a 5 - point scale from 1 to 5. The larger the score, the better the performance. The total score of the 10 scores was calculated, and taking the total score of the reference comparison example as 100, it was indexed (cornering performance index after the mid - stage of running). The larger the index, the better the cornering performance after the mid - stage of running.

[0111]

Table 1

[0112]

Table 2

[0113]

Table 3

[0114]

Table 4

[0115]

Table 5

[0116]

Table 6

[0117]

Table 7

[0118]

Table 8

[0119] From each table, for the tires of the examples where the land ratio of the tread is 70% or more, the average value of the loss tangent at 30 to 100 °C of the cap tread is 0.10 or more, and the average value of the loss tangent at 30 to 100 °C of the base tread is less than 0.05, the overall performance of the turning performance in the initial running stage and after the mid-running stage (represented by the sum of two indexes: the turning performance in the initial running stage and the turning performance after the mid-running stage) was excellent.

Description of Signs

[0120] 11 Cap tread 11c Cap tread surface Pc Point on the cap tread surface 11c Tc Thickness of the cap tread 11 at the point Pc 12 Base tread 12b base tread surface Point on the Pb base tread surface 12b Tb Thickness of the base tread 12 at the point Pb 21 Inner liner 22 Carcass 23 Belt 23A Inner layer 23B Outer layer 24 Band

Claims

1. A tire comprising a tread having a cap tread and a base tread, wherein the tread has a land ratio of 70% or more, the cap tread has an average loss tangent value of 0.10 or more at 30 to 100°C, the base tread has an average loss tangent value of less than 0.03 at 30 to 100°C.

2. A tire comprising a tread having a cap tread and a base tread, wherein the tread has a land ratio of 70% or more, the cap tread has an average loss tangent value of 0.22 or more at 30 to 100°C, the base tread has an average loss tangent value of less than 0.05 at 30 to 100°C.

3. A tire comprising a tread having a cap tread and a base tread, wherein the tread has a land ratio of 70% or more, the cap tread has an average loss tangent value of 0.10 or more at 30 to 100°C, the base tread has an average loss tangent value of less than 0.05 at 30 to 100°C, the average loss tangent value (tanδc) of the cap tread at 30 to 100°C and the average loss tangent value (tanδb) of the base tread at 30 to 100°C satisfy the following formula. 4.0 ≤ tanδc / tanδb ≤ 6.0

4. A tire comprising a tread having a cap tread and a base tread, wherein the tread has a land ratio of 70% or more, the cap tread has an average loss tangent value of 0.10 or more at 30 to 100°C, the base tread has an average loss tangent value of less than 0.05 at 30 to 100°C, the average loss tangent value (tanδc) of the cap tread at 30 to 100°C and the land ratio (LR (%)) satisfy the following formula. tanδc / LR × 100 ≤ 0.30

5. A tire comprising a tread having a cap tread and a base tread, wherein the base tread rubber composition constituting the base tread has an isoprene rubber content of 60% by mass or more and a butadiene rubber content of 20% by mass or more and 50% by mass or less in 100% by mass of the rubber component, the tread has a land ratio of 70% or more, the cap tread has an average loss tangent value of 0.10 or more at 30 to 100°C, The base tread is a tire having an average loss tangent value at 30 to 100 °C of less than 0.

05.

6. The cap tread is the tire according to any one of claims 1, 3 to 5, wherein the average loss tangent value at 30 to 100 °C is 0.12 or more.

7. The cap tread is the tire according to any one of claims 1, 3 to 5, wherein the average loss tangent value at 30 to 100 °C is 0.15 or more.

8. The base tread is the tire according to any one of claims 2 to 5, wherein the average loss tangent value at 30 to 100 °C is less than 0.

04.

9. The base tread is the tire according to any one of claims 2 to 5, wherein the average loss tangent value at 30 to 100 °C is less than 0.

03.

10. The tire according to any one of claims 1, 2, 4, 5, wherein the average loss tangent value (tanδc) of the cap tread at 30 to 100 °C and the average loss tangent value (tanδb) of the base tread at 30 to 100 °C satisfy the following formula. tanδc / tanδb ≧ 1.1

11. The tire according to any one of claims 1, 2, 4, 5, wherein the average loss tangent value (tanδc) of the cap tread at 30 to 100 °C and the average loss tangent value (tanδb) of the base tread at 30 to 100 °C satisfy the following formula. tanδc / tanδb ≧ 1.3

12. The tire according to any one of claims 1 to 11, wherein the average loss tangent value (tanδc) of the cap tread at 30 to 100 °C and the land ratio (LR (%)) satisfy the following formula. tanδc / LR × 100 ≧ 0.12

13. The tire according to any one of claims 1 to 11, wherein the average loss tangent value (tanδc) of the cap tread at 30 to 100 °C and the land ratio (LR (%)) satisfy the following formula. tanδc / LR × 100 ≧ 0.15

14. The tire according to any one of claims 1 to 13, wherein the average thickness (Tc) of the cap tread and the average thickness (Tb) of the base tread satisfy the following formula. Tc > Tb

15. The tire according to any one of claims 1 to 14, wherein the average thickness (Tc) of the cap tread and the average thickness (Tb) of the base tread satisfy the following formula. Tc / Tb ≦ 4.0

16. The tire according to any one of claims 1 to 15, wherein the rubber composition for cap tread constituting the cap tread contains styrene-butadiene rubber, a filler, a solid plasticizer, and a liquid plasticizer.

17. The rubber composition for cap tread constituting the cap tread has a content of the styrene-butadiene rubber of 50% by mass or more in 100% by mass of the rubber component, and the tire according to claim 16, wherein the content of the filler is 50 parts by mass or more, the content of the solid plasticizer is 10 parts by mass or more, and the content of the liquid plasticizer is 5 parts by mass or more with respect to 100 parts by mass of the rubber component.

18. The tire according to any one of claims 1 to 17, wherein the rubber composition for base tread constituting the base tread contains isoprene rubber, butadiene rubber, a filler, and a liquid plasticizer.

19. The rubber composition for base tread constituting the base tread has a content of the isoprene rubber of 20 to 80% by mass and a content of the butadiene rubber of 5 to 50% by mass in 100% by mass of the rubber component, and the tire according to claim 18, wherein the content of the filler is 10 parts by mass or more and the content of the liquid plasticizer is 3 parts by mass or more with respect to 100 parts by mass of the rubber component.

Images