tire

Abstract

To provide a tire improved in integrated performance of wet performance and dry performance.SOLUTION: A tire comprising a tread having at least one circumferential, the circumferential groove portion is formed of a groove portion forming rubber composition including rubber components and silica, and tanδ at the time when the groove portion forming rubber composition is wetted with water, tanδ at the time when the composition is dried, and a ratio of a maximum groove depth D(mm) of the circumferential groove portion to a maximum thickness T(mm) of the tread satisfy the following formulas (1) and (2): tanδ at the time when the composition is wetted with water / tanδ at the time when the composition is dried >1.00 (1-2) and Z≥0.10, wherein tanδ is loss tangent at the time when 30 minutes elapse after measurement is started, which is measured under a condition that a temperature is 30°C, initial strain is 10%, dynamic strain is 1%, a frequency is 10 Hz, a mode is an extension mode and a measurement time is 30 minutes, and Z is D / T.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to tires. [Background technology]

[0002] Techniques such as incorporating silica into tires have been proposed to improve wet performance, but improving wet performance (performance on wet roads) tends to reduce dry performance (performance on dry roads), so it is desirable to achieve both of these performance characteristics. Summary of the Invention [Problem to be solved by the invention]

[0003] An object of the present disclosure is to provide a tire that solves the above-mentioned problems and improves overall wet and dry performance. [Means for solving the problem]

[0004] The present disclosure provides a tire having a tread with at least one circumferential groove, the circumferential groove is formed of a groove-forming rubber composition containing a rubber component and silica, The tire relates to a tire in which the tan δ when wet and the tan δ when dry of the groove-forming rubber composition, and the ratio Z of the maximum groove depth D (mm) of the circumferential groove portion to the maximum thickness T (mm) of the tread satisfy the following formulas (1) and (2): (1) Tan δ when wet / tan δ when dry > 1.00 (2) Z≧0.10 (In the formula, tanδ is the loss tangent 30 minutes after the start of measurement, measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, an extension mode, and a measurement time of 30 minutes. Z is D / T.) [Effects of the Invention]

[0005] According to the present disclosure, a tire is provided with a tread having at least one circumferential groove portion, the circumferential groove portion being formed from a groove-forming rubber composition containing a rubber component and silica, and satisfying the formulas (1) and (2), thereby improving the overall wet and dry performance. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a cross-sectional view taken along a meridian line showing a portion of a pneumatic tire according to an embodiment of the present disclosure. [Figure 2] 1 is a cross-sectional view of a tire tread portion cut along a plane including the tire axis. DETAILED DESCRIPTION OF THE INVENTION

[0007] The present disclosure relates to a tire having a tread with at least one circumferential groove, wherein the circumferential groove is formed from a groove-forming rubber composition containing a rubber component and silica, and satisfies the above formulas (1) and (2).

[0008] The mechanism by which this effect is obtained is not clear, but is presumed to be as follows. It is believed that by making the tan δ value of the rubber composition forming the circumferential grooves of the tread (groove-forming rubber composition) when wet with water exceed its tan δ value when dry (Equation (1)), the hysteresis friction with the road surface is improved, suppressing a decrease in grip performance even when the road surface changes from dry to wet, thereby obtaining excellent dry performance while maintaining good wet performance. At the same time, by adjusting the circumferential grooves formed in the tread so that Z (= the maximum groove depth D of the circumferential grooves relative to the maximum tread thickness T) is 0.1 or more (Equation (2)), the tread having circumferential grooves can obtain good drainage and ensure rigidity, thereby improving wet performance while maintaining good dry performance. From the above, it is presumed that in the present disclosure, by satisfying formulas (1) and (2), the overall wet and dry performance is significantly improved.

[0009] In this way, the tire solves the problem (objective) of improving overall wet and dry performance by configuring the rubber composition (groove-forming rubber composition) forming the circumferential grooves so that wet tan δ, dry tan δ, and Z (= maximum groove depth D (mm) of the circumferential grooves / maximum tread thickness T (mm)) satisfy the formula (1) "wet tan δ / dry tan δ > 1.00" and the formula (2) "Z ≧ 0.10". In other words, the parameters of the formula (1) "wet tan δ / dry tan δ > 1.00" and the formula (2) "Z ≧ 0.10" do not define the problem (objective); the object of the present application is to improve overall wet and dry performance, and a configuration that satisfies these parameters is used as a means to achieve this.

[0010] In this specification, tan δ of the groove-forming rubber composition means the tan δ of the groove-forming rubber composition after crosslinking if the groove-forming rubber composition is crosslinkable, and in the case of a crosslinkable rubber composition containing, for example, a diene rubber, sulfur, etc., means the tan δ of the rubber composition after vulcanization (after crosslinking). Also, tan δ is a value obtained by conducting a viscoelasticity test on the groove-forming rubber composition (in the case of a crosslinked groove-forming rubber composition, the crosslinked groove-forming rubber composition).

[0011] In this specification, dry tan δ means the tan δ of the groove-forming rubber composition in a dry state, and specifically means the tan δ of the groove-forming rubber composition (in the examples, the tread after crosslinking) dried by the method described in the examples. In this specification, tan δ when wet with water means the tan δ of a polymer composition in a state wet with water, and specifically means the tan δ of a groove-forming rubber composition wetted with water (in the example, a tread after crosslinking) by the method described in the examples.

[0012] In this specification, the tan δ of the groove-forming rubber composition is a tan δ measured under conditions of a temperature of 30° C., an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, and an extension mode.

[0013] The tire of the present disclosure includes a tread having at least one circumferential groove formed from a groove-forming rubber composition containing a rubber component and silica, and the tan δ when wet and the tan δ when dry of the groove-forming rubber composition satisfy the following formula (1): (1) Tan δ when wet / tan δ when dry > 1.00 (In the formula, tanδ is the loss tangent 30 minutes after the start of measurement, measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, an extension mode, and a measurement time of 30 minutes.)

[0014] The groove-forming rubber composition has a wet tan δ / dry tan δ ratio of preferably 1.07 or more, more preferably 1.12 or more, even more preferably 1.15 or more, and particularly preferably 1.20 or more. There are no particular limitations on the upper limit of wet tan δ / dry tan δ, but it is preferably 1.80 or less, more preferably 1.60 or less, even more preferably 1.50 or less, and particularly preferably 1.40 or less. Within the above range, the effects can be suitably obtained.

[0015] The groove-forming rubber composition has a dry tan δ of preferably 0.10 or more, more preferably 0.15 or more, even more preferably 0.16 or more, and particularly preferably 0.17 or more. There are no particular restrictions on the upper limit of dry tan δ, but it is preferably 0.50 or less, more preferably 0.40 or less, even more preferably 0.30 or less, and particularly preferably 0.25 or less. Within the above range, the effects can be suitably obtained.

[0016] The groove-forming rubber composition has a tan δ when wet with water of preferably 0.11 or more, more preferably 0.16 or more, even more preferably 0.17 or more, and particularly preferably 0.18 or more. There is no particular upper limit to the tan δ when dry, but it is preferably 0.55 or less, more preferably 0.45 or less, even more preferably 0.35 or less, and particularly preferably 0.30 or less. Within the above range, the effect can be suitably obtained.

[0017] In addition, when formula (1) satisfies tan δ when wet with water / tan δ when dry > 1.00, the loss tangent (tan δ) changes reversibly with water, but in this specification, "the loss tangent (tan δ) changes reversibly with water" means that the tan δ of the groove-forming rubber composition (after vulcanization) reversibly increases or decreases with the presence of water. Note that, for example, when changing from dry to wet to dry, it is sufficient that tan δ changes reversibly, and the tan δ does not have to be the same in the previous drying state and the subsequent drying state, or the tan δ may be the same in the previous drying state and the subsequent drying state.

[0018] The above formula (1) (such as the reversible change in tan δ due to water represented by formula (1)) of the groove-forming rubber composition (after vulcanization) can be realized, for example, by at least one component in which part or all of the crosslinking between silica and the polymer is crosslinked by an ionic bond. Specifically, by blending an ionic coupling agent with silica and polymer, it is possible to form an ionic bond between the polymer and the ionic coupling agent bonded to the silica surface. The reversibility of the ionic bond allows the crosslink between the silica and polymer to dissociate only when wet, improving the mobility of the polymer with the dissociated ionic bond. Therefore, when driving in a wet state, energy loss is likely to occur within the rubber, improving the loss coefficient tan δ. Therefore, it is believed that improving hysteresis friction with the road surface can suppress the deterioration of grip performance when changing from dry to wet roads. Meanwhile, rubber compositions containing the above materials exhibit the same behavior as conventional rubber because the silica and polymer are bonded together when dry, preventing deterioration of dry performance such as rolling resistance. It is believed that the above mechanism improves the overall wet and dry performance.

[0019] The above formula (1) can also be achieved by blending a hydrophilic modified polymer that has been modified with an acid or a base with surface-modified silica that has a metal oxide and / or basic molecules on its surface. Specifically, for example, when a modified polymer such as carboxylic acid-modified SBR is used in combination with surface-modified silica having a metal oxide and / or basic molecules on its surface, an ionic bond is formed between the modified polymer and the metal oxide and / or surface-modified silica by an anion derived from the carboxylic acid and a cation derived from the metal oxide or basic molecule. The ionic bond is then cleaved by the addition of water, and recombined by drying the water, resulting in a decrease in E* and / or an increase in tan δ when wet with water, and an increase in E* and / or a decrease in tan δ when dry. It is believed that the above mechanism also contributes to an improvement in overall wet and dry performance.

[0020] The dry tan δ can be adjusted by the type and amount of chemicals (particularly polymers, fillers, softeners, resins, sulfur, and vulcanization accelerators) compounded in the groove-forming rubber composition. For example, the dry tan δ tends to increase when a softener (e.g., resin) that is poorly compatible with the polymer is used, when an unmodified polymer is used, when the amount of filler is increased, when oil as a plasticizer is increased, when sulfur is reduced, or when the amount of vulcanization accelerator is reduced.

[0021] For example, by using the ionic coupling agent to prepare a rubber composition in which some or all of the crosslinks between the silica and the polymer are ionic-linked, or a rubber composition in which some or all of the crosslinks between the modified polymer and the metal oxide and / or surface-modified silica are ionic-linked, the tan δ when wet can be increased compared to when dry, making it possible to adjust the tan δ when wet and when dry. Specifically, by preparing a rubber composition crosslinked by ionic bonds, the tan δ when wet can be increased compared to when dry. Furthermore, the tan δ when wet can be adjusted by the type and amount of chemicals blended into the rubber composition. For example, a similar tendency can be obtained for the tan δ when wet by using a method similar to that for adjusting the dry tan δ described above.

[0022] The tire of the present disclosure includes a tread having at least one circumferential groove formed from a groove-forming rubber composition containing a rubber component and silica. The tread may be formed partially or entirely from the groove-forming rubber composition. Of these, a configuration in which the entire tread is formed from the groove-forming rubber composition is preferred.

[0023] <Groove-forming rubber composition> Regarding the tire of the present disclosure, the groove-forming rubber composition will be described below. The groove-forming rubber composition contains a rubber component and silica.

[0024] (rubber component) In the groove-forming rubber composition, the rubber component is a component that contributes to crosslinking, and is generally a polymer with a weight-average molecular weight (Mw) of 10,000 or more.

[0025] The weight average molecular weight of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more, and is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. Within the above ranges, the effect tends to be more favorably obtained.

[0026] In this specification, the weight average molecular weight (Mw) can be determined in terms of standard polystyrene based on measurements obtained using a gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M, manufactured by Tosoh Corporation).

[0027] The rubber component is not particularly limited, and any rubber known in the tire field can be used. Examples include diene rubbers such as isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These may be used alone or in combination of two or more. Among these, isoprene rubber, BR, and SBR are preferred from the viewpoint of obtaining better effects.

[0028] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. NRs such as SIR20, RSS#3, and TSR20 are commonly used in the tire industry. IRs are not particularly limited, and examples of IRs such as IR2200 are commonly used in the tire industry. Modified NRs include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Modified NRs include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Modified IRs include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more. NR is preferred.

[0029] The BR is not particularly limited, and examples thereof include BRs with a high cis content such as BR1220 manufactured by Zeon Corporation, BR150B manufactured by Ube Industries, Ltd., and BR1280 manufactured by LG Chem, BRs containing 1,2-syndiotactic polybutadiene crystals (SPB) such as VCR412 and VCR617 manufactured by Ube Industries, Ltd., and butadiene rubbers synthesized using a rare earth catalyst (rare earth BR), which are commonly used in the tire industry. These may be used alone or in combination of two or more.

[0030] The cis amount (cis content) of the BR is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, and is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less. Within the above ranges, the effect tends to be more favorably obtained. The cis content of BR can be measured by infrared absorption spectroscopy.

[0031] The SBR is not particularly limited, and examples thereof include emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. Commercially available products include those from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, and Zeon Corporation.

[0032] The styrene 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 20% by mass or more. The styrene content is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. Within the above range, the effect tends to be more favorable. In this specification, the styrene content of SBR is 1 It is calculated by H-NMR measurement.

[0033] The vinyl content of the SBR is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more. The vinyl content is preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 70 mass% or less. Within the above range, the effect tends to be more favorable. In this specification, the vinyl content (amount of 1,2-bonded butadiene units) of SBR can be measured by infrared absorption spectroscopy.

[0034] The rubber component may be oil-extended rubber. These may be used alone or in combination of two or more. Examples of oils used in oil-extended rubber include those described below. The amount of oil in the oil-extended rubber is not particularly limited, but is usually about 10 to 50 parts by mass per 100 parts by mass of rubber solids.

[0035] The rubber component may be modified to introduce a functional group that interacts with a filler such as silica. Examples of the functional group include a silicon-containing group (-SiR3 (R may be the same or different and is hydrogen, a hydroxyl group, a hydrocarbon group, an alkoxy group, or the like), an amino group, an amido group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imido group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group, or the like. These functional groups may have a substituent. Of these, a silicon-containing group is preferred, and -SiR3 (R may be the same or different and is hydrogen, a hydroxyl group, a hydrocarbon group (preferably a hydrocarbon group having 1 to 6 carbon atoms (more preferably an alkyl group having 1 to 6 carbon atoms)), or an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms)), and at least one R is a hydroxyl group) is more preferred.

[0036] Specific examples of compounds (modifiers) that introduce the above-mentioned functional groups include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane.

[0037] Modified rubber having hydrophilic properties can also be used as the rubber component of the groove-forming rubber composition. As used herein, "hydrophilic" means having a greater affinity for water compared to organic solvents. For example, the hydrophilicity of a polymer can be quantified by measuring the partition coefficient between water (or a buffered aqueous solution) and a water-immiscible organic solvent such as octanol, ethyl acetate, methylene chloride, or methyl tert-butyl ether. After equilibration, a polymer is considered to be hydrophilic if it has a higher concentration in water than in the organic solvent. The "hydrophilicity" of a modified polymer can be imparted by various methods, for example, by introducing acidic or basic functional groups, as described below, into the rubber.

[0038] Examples of hydrophilic modified rubbers include acid-modified rubbers (hereinafter also referred to as "acid-modified rubbers") and base-modified rubbers (hereinafter also referred to as "base-modified rubbers").

[0039] Examples of the acidic functional group (acidic group) in the acid-modified rubber include a carboxylic acid group (carboxy group), a sulfonic acid group, a phosphoric acid group, and a phenolic hydroxyl group. The hydrogen atom in the acidic functional group may be substituted with a metal atom or the like, or may be dissociated. Among these, from the viewpoint of obtaining a more effective effect, a carboxylic acid group (-COOH), a sulfonic acid group (-SO3H), and a phosphoric acid group (H2PO4 - ), their salts (carboxylate ions (-COO - ), sulfonate ion (-SO3 - ), phosphate ions (PO4 3- The counter cation is not particularly limited as long as it is a cation capable of forming a salt, and examples thereof include Na + , K. + etc.

[0040] The mechanism by which this effect is obtained is not clear, but is presumed to be as follows. When a modified polymer containing carboxylic acid groups is used, a more ionic bond is formed between the polymer and the ionic coupling agent bonded to the silica surface. Therefore, when the tire is wet, energy loss is more likely to occur inside the rubber, improving the loss coefficient tanδ and wet performance.

[0041] Examples of the basic functional group (basic group) in the base-modified rubber include an amino group, an imino group (=NH), an ammonium base, and a heterocyclic group having a basic nitrogen atom.

[0042] The amino group may be any of a primary amino group (-NH2), a secondary amino group (-NHR), and a tertiary amino group (-NRR').

[0043] The R and R' may be substituted or unsubstituted monovalent hydrocarbon groups, which may be linear, branched, or cyclic. The R and R' may be saturated or unsaturated hydrocarbon groups, and may contain heteroatoms such as oxygen.

[0044] The substituted or unsubstituted monovalent hydrocarbon group of R and R' preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and even more preferably 1 to 6 carbon atoms.

[0045] The substituted or unsubstituted monovalent hydrocarbon groups represented by R and R′ include substituted or unsubstituted aliphatic, alicyclic, and aromatic hydrocarbon groups which may contain a heteroatom. Specific examples include substituted or unsubstituted linear alkyl groups, branched alkyl groups, cyclic alkyl groups, aryl groups, and aralkyl groups which may contain a heteroatom.

[0046] When R and R' are substituted or unsubstituted linear or branched alkyl groups which may contain heteroatoms, the number of carbon atoms is preferably 1 to 8, more preferably 1 to 4, and even more preferably 1 to 2. When R and R' are substituted or unsubstituted cyclic alkyl groups which may contain heteroatoms, the number of carbon atoms is preferably 3 to 12. When R and R' are substituted or unsubstituted aryl groups which may contain heteroatoms, the number of carbon atoms is preferably 6 to 10. When R and R' are substituted or unsubstituted aralkyl groups which may contain heteroatoms, the number of carbon atoms is preferably 7 to 10.

[0047] Examples of the substituted or unsubstituted linear or branched alkyl group that may contain a heteroatom include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, 2-ethylhexyl, octyl, nonyl, decyl, and groups containing these heteroatoms. Examples of the substituted or unsubstituted cyclic alkyl group that may contain a heteroatom include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, adamantyl, 1-ethylcyclopentyl, and 1-ethylcyclohexyl. Examples of the substituted or unsubstituted aryl group that may contain a heteroatom include phenyl, tolyl, xylyl, biphenyl, naphthyl, anthryl, phenanthryl, and groups containing these heteroatoms. Examples of the substituted or unsubstituted aralkyl group which may contain a hetero atom include a benzyl group, a phenethyl group, and groups containing these hetero atoms.

[0048] Examples of the ammonium base include a tertiary ammonium base and a quaternary ammonium base.

[0049] Examples of the heterocyclic group having a basic nitrogen atom include nitrogen-containing heterocyclic groups such as a pyridine group, a pyrimidine group, a pyrazine group, an imidazole group, an imidazole group containing a thiol, a triazole group, and a thiazole group. In the case of a heterocyclic group, the presence of a double bond makes it easy to disperse in the rubber.

[0050] Among the basic functional groups, a pyridine group, an imidazole group, a thiazole group, and an amino group (a primary amino group, a secondary amino group, a tertiary amino group) are preferred, and an amino group is more preferred.

[0051] Examples of the polymer constituting the skeleton of the hydrophilic modified rubber include the diene rubbers mentioned above.

[0052] Among the hydrophilic modified rubbers, acid-modified SBR and acid-modified BR are preferred, carboxylic acid-modified SBR, sulfonic acid-modified SBR, carboxylic acid-modified BR, sulfonic acid-modified BR, and salts thereof are more preferred, and carboxylic acid-modified SBR, carboxylic acid-modified BR, and salts thereof are even more preferred.

[0053] When the groove-forming rubber composition contains an isoprene-based rubber (such as NR, IR, acid-modified isoprene-based rubber, or base-modified isoprene-based rubber), the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 8% by mass or more, and even more preferably 10% by mass or more, and is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. Within the above ranges, better effects tend to be obtained.

[0054] When the groove-forming rubber composition contains BR (unmodified BR, acid-modified BR, base-modified BR, etc.), the BR content, relative to 100% by mass of the rubber component, is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and particularly preferably 20% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 35% by mass or less, and particularly preferably 30% by mass or less. Within the above ranges, better effects tend to be obtained.

[0055] When the groove-forming rubber composition contains SBR (unmodified SBR, acid-modified SBR, base-modified SBR, etc.), the content of SBR in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 65% ​​by mass or more, particularly preferably 70% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, particularly preferably 80% by mass or less. Within the above ranges, better effects tend to be obtained.

[0056] When the groove-forming rubber composition contains SBR (unmodified SBR, acid-modified SBR, base-modified SBR, etc.) and BR (unmodified BR, acid-modified BR, base-modified BR, etc.), the total content of SBR and BR in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. Within the above range, better effects tend to be obtained.

[0057] (Filler) The groove-forming rubber composition contains silica. Usable silica includes dry-process silica (anhydrous silica) and wet-process silica (hydrated silica). Among these, wet-process silica is preferred because it has a large number of silanol groups. Commercially available products include those from Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan, and Tokuyama Corporation. These may be used alone or in combination of two or more.

[0058] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 100 m 2 / g or more, more preferably 150m 2 / g or more, more preferably 170m 2 / g or more, particularly preferably 200m 2 The upper limit of the N2SA of silica is not particularly limited, but is preferably 350 m 2 / g or less, more preferably 300m 2 / g or less, more preferably 250m 2 Within the above range, there is a tendency for the effect to be better obtained. The N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0059] In the groove-forming rubber composition, the content of the silica (content of unsurface-modified silica) is preferably 10 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 70 parts by mass or more, and particularly preferably 75 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 90 parts by mass or less. Within the above range, better effects tend to be obtained.

[0060] As the silica in the groove-forming rubber composition, surface-modified silica having basic molecules on the surface can also be used. The silica constituting the surface-modified silica is not particularly limited, and examples thereof include the aforementioned dry-process silica (anhydrous silica), wet-process silica (hydrated silica), etc. The N2SA of the silica constituting the surface-modified silica is also preferably in the same range as above.

[0061] The basic molecule constituting the surface-modified silica can be any molecule having basicity, and for example, a compound having a basic functional group can be suitably used. Examples of the basic functional group include the basic functional groups described above. Among the basic functional groups, pyridine groups, imidazole groups, thiazole groups, and amino groups (primary amino groups, secondary amino groups, and tertiary amino groups) are preferred, and amino groups are more preferred.

[0062] The compound having an amino group as the basic compound is not particularly limited, but for example, a compound having a primary to tertiary amino group and an alkoxysilyl group in one molecule can be suitably used.Specific examples of the compound having an amino group include compounds represented by the following formulas (I) and (II).

[0063] (R 11 O) n R 12 3-n -Si-R 13 -NR 14 R 15 (I) (In the formula, R 11 , R 12 , R 14 and R 15 R each independently represents a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group. 13 represents a substituted or unsubstituted divalent hydrocarbon group, and n represents an integer of 1 to 3.

[0064] (R 21 O) p R 22 3-p -Si-R 23 -NR 24 -R 25 -Si-(R 26 O) q R 27 3-q (II) (In the formula, R 21 , R 22 , R 24 , R 26 and R 27 R each independently represents a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group. 23 and R 25 each independently represents a substituted or unsubstituted divalent hydrocarbon group; p and q each independently represent 1 to 3.

[0065] R in formula (I) and (II) 11 ~R 15 , R 21 ~R 27 The substituted or unsubstituted monovalent and divalent hydrocarbon groups of R may be linear, branched, or cyclic. 11 ~R 15 , R 21 ~R 27 The substituted or unsubstituted monovalent and divalent hydrocarbon groups may be saturated or unsaturated hydrocarbon groups, and may contain heteroatoms such as oxygen.

[0066] R in formula (I) 11 , R 12 , R 14 and R 15 , R of formula (II) 21 , R 22 , R 24 , R 26 and R 27 The number of carbon atoms in the substituted or unsubstituted monovalent hydrocarbon group is preferably 1 to 10, more preferably 1 to 8, and even more preferably 1 to 6. 13 , R of formula (II) 23 and R 25 The substituted or unsubstituted divalent hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and even more preferably 1 to 6 carbon atoms.

[0067] R in formula (I) 11 , R 12 , R 14 and R 15 , R in formula (II) 21 , R 22 , R 24 , R 26 and R 27 Specific examples of the substituted or unsubstituted monovalent hydrocarbon group of R include the same as the substituted or unsubstituted monovalent hydrocarbon groups of R and R' described above.

[0068] R in formula (I) 13 , R in formula (II) 23 and R 25 Specific examples of the substituted or unsubstituted divalent hydrocarbon group include substituted or unsubstituted alkylene groups having 1 to 18 carbon atoms, which may contain a heteroatom, and cycloalkylene groups having 5 to 18 carbon atoms. Specific examples include a methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group, octylene group, nonylene group, decylene group, and 1,2-propylene group.

[0069] Specific examples of the compound having an amino group represented by the above formula (I) include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-[3-(trimethoxysilyl)propyl]-1-butanamine, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminobutyl)-3-aminobutyltrimethoxysilane, and N-2-(aminoethyl)-3-aminopropylmethyltrimethoxysilane.

[0070] Specific examples of the compound having an amino group represented by the above formula (II) include bis(3-trimethoxysilylpropyl)amine, bis(3-triethoxysilylpropyl)amine, bis(4-trimethoxysilylbutyl)amine, bis(triethoxysilylmethyl)amine, and bis(6-trimethoxysilylhexyl)amine.

[0071] Specific examples of compounds having an amino group other than those mentioned above include amino group-containing aromatic compounds such as N-phenyl-3-aminopropyltrimethoxysilane; amino group-containing dialkoxysilane compounds such as 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and bis(3-methyldimethoxysilylpropyl)amine; and ethylenediamine compounds such as N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine and N-(2-aminoethyl)-N'-(3-(trimethoxysilyl)propyl)ethylenediamine.

[0072] The method for producing the surface-modified silica having basic molecules on its surface (the method for treating (coating) the silica surface with basic molecules) can be any method that can bring basic molecules into contact with silica. For example, it can be prepared by mixing a basic compound and silica using a known method. Specifically, it can be produced by kneading basic molecules, silica, and other components such as a polymer using a kneading device such as an open roll or Banbury mixer, thereby generating surface-modified silica having basic molecules on its surface in the kneaded mixture. It can also be produced by mixing only a basic compound and silica using a known method.

[0073] In the groove-forming rubber composition, the content of the surface-modified silica is preferably 10 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 70 parts by mass or more, and particularly preferably 75 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 90 parts by mass or less. Within the above range, better effects tend to be obtained. The content of the surface-modified silica is the total amount of the silica and the basic molecules per 100 parts by mass of the rubber component in the groove-forming rubber composition, and includes basic molecules not attached to the silica surface. When the basic molecules are compounds having amino groups, the content of the silica having the compounds having amino groups on its surface is also preferably in the same range.

[0074] In the groove-forming rubber composition, the content of the basic molecules is preferably 2.0 parts by mass or more, more preferably 4.0 parts by mass or more, and even more preferably 6.0 parts by mass or more, per 100 parts by mass of the total silica contained in the groove-forming rubber composition. The content is preferably 30.0 parts by mass or less, more preferably 20.0 parts by mass or less, and even more preferably 15.0 parts by mass or less. Within the above range, the effects are preferably achieved.

[0075] In the groove-forming rubber composition, the total amount of silica (the total content of unsurface-modified silica and surface-modified silica such as the surface-modified silica) is preferably 10 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 70 parts by mass or more, and particularly preferably 75 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 90 parts by mass or less. Within the above range, better effects tend to be obtained.

[0076] The groove-forming rubber composition may contain fillers other than silica. In the groove-forming rubber composition, the content of the filler (total amount of silica and fillers other than silica) is preferably 10 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 70 parts by mass or more, and particularly preferably 75 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 90 parts by mass or less. Within the above range, better effects tend to be obtained.

[0077] The silica content (total content of unsurface-modified silica and surface-modified silica such as the surface-modified silica) in 100% by mass of the filler contained in the groove-forming rubber composition is preferably 60% 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. When it is within the above range, better effects tend to be obtained.

[0078] The other filler is not particularly limited, and materials known in the rubber field can be used, including, for example, inorganic fillers such as carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, mica, etc. Among these, carbon black is preferred from the viewpoint of obtaining better effects.

[0079] Carbon black that can be used in the groove-forming rubber composition is not particularly limited, but examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products that can be used include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nichika Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like. These may be used alone, or two or more types may be used in combination.

[0080] The nitrogen adsorption specific surface area (N2SA) of carbon black is 30m 2 / g or more is preferable, and 50m 2 / g or more is more preferable, and 70m 2 / g or more is more preferable. 2 / g or less is preferable, and 150m 2 / g or less is more preferable, and 130m 2 / g or less is more preferable, and 120m 2 Within the above range, the effect tends to be better.

[0081] When the groove-forming rubber composition contains carbon black, the carbon black content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above range, better effects tend to be obtained.

[0082] As other fillers in the groove-forming rubber composition, metal oxides can also be used. Examples of metal oxides include simple oxides and composite oxides of metals, such as compounds represented by MxOy (M represents a metal atom, and x and y each independently represent an integer of 1 to 6). These may be used alone or in combination of two or more. It is preferable that the metal oxide is other than zinc oxide.

[0083] Specific metal oxides include alkali metal oxides such as lithium oxide, sodium oxide, potassium oxide, rubidium oxide, and cesium oxide; alkaline earth metal oxides such as calcium oxide, strontium oxide, and barium oxide; transition metal oxides such as scandium oxide, titanium oxide, vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, yttrium oxide, zirconium oxide, niobium oxide, molybdenum oxide, technetium oxide, ruthenium oxide, rhodium oxide, palladium oxide, silver oxide, hafnium oxide, tantalum oxide, tungsten oxide, osmium oxide, iridium oxide, platinum oxide, and gold oxide; and base metal oxides such as beryllium oxide, magnesium oxide, aluminum oxide, gallium oxide, cadmium oxide, indium oxide, tin oxide, thallium oxide, lead oxide, bismuth oxide, and polonium oxide. Metal oxides can be used alone or as a mixture of two or more.

[0084] Among these, from the viewpoint of optimally obtaining the effect, it is preferable to contain at least one selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide, it is more preferable to contain at least one selected from the group consisting of beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide, and it is even more preferable to contain magnesium oxide.

[0085] In the groove-forming rubber composition, the content of the metal oxide (total amount of the metal oxide) is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, even more preferably 2.0 parts by mass or more, particularly preferably 2.2 parts by mass or more, per 100 parts by mass of the polymer component, and is preferably 10.0 parts by mass or less, more preferably 5.0 parts by mass or less, even more preferably 4.0 parts by mass or less, particularly preferably 3.0 parts by mass or less. Within the above ranges, the effects tend to be more favorably obtained. The total amount of at least one selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide, the total amount of at least one selected from the group consisting of beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide, and the content of magnesium oxide are also preferably within the same ranges.

[0086] The apparent specific gravity of the metal oxide is preferably less than 0.4 g / ml, more preferably 0.3 g / ml or less, even more preferably 0.25 g / ml or less, and is preferably 0.05 g / ml or more, more preferably 0.15 g / ml or more. Within the above ranges, the effect tends to be better. It is also preferable that the apparent specific gravity of magnesium oxide is within the same range. The apparent specific gravity of the metal oxide is a value obtained by measuring 30 ml of the apparent volume into a 50 ml measuring cylinder and calculating from the mass.

[0087] The d50 of the metal oxide is preferably less than 10 μm, more preferably 4.5 μm or less, even more preferably 1.5 μm or less, particularly preferably less than 0.75 μm, and is preferably 0.05 μm or more, more preferably 0.45 μm or more. Within the above ranges, better effects tend to be obtained. It is also preferable that the d50 of magnesium oxide is in the same range. The d50 of the metal oxide is the particle size at 50% of the integrated value in the mass-based particle size distribution curve obtained by the laser diffraction scattering method.

[0088] The nitrogen adsorption specific surface area (N2SA) of the metal oxide is preferably 100 m 2 / g or more, more preferably 115m 2 / g or more, and preferably 250m 2 / g or less, more preferably 225m 2 / g or less, more preferably 200m 2 / g or less. Within the above range, the effect tends to be better. It is also preferable that the N2SA of magnesium oxide is within the same range. The N2SA of the metal oxide is a value measured by the BET method in accordance with JIS Z8830:2013.

[0089] Commercially available metal oxides include those manufactured by Kyowa Chemical Industry Co., Ltd., Fujifilm Wako Pure Chemical Industries Co., Ltd., Kishida Chemical Co., Ltd., Kyowa Chemical Industry Co., Ltd., Tateho Chemical Industry Co., Ltd., JHE Co., Ltd., Nippon Chemical Industry Co., Ltd., Ako Kasei Co., Ltd., and the like.

[0090] When the groove-forming rubber composition contains a metal oxide, the content of the metal oxide is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above range, better effects tend to be obtained.

[0091] (coupling agent) The groove-forming rubber composition preferably contains a coupling agent. In this disclosure, a "coupling agent" is a compound that forms a bond (covalent bond, ionic bond, etc.) or an interaction with silica and a polymer (rubber component, liquid polymer, etc.). By including the coupling agent, a bond or an interaction occurs between the coupling agent and silica, and between the coupling agent and the polymer.

[0092] The total amount of the coupling agent (the total content of coupling agents such as ionic coupling agents and silane coupling agents described below) is preferably 1.0 part by mass or more, more preferably 2.5 parts by mass or more, even more preferably 4.0 parts by mass or more, and particularly preferably 5.0 parts by mass or more, relative to 100 parts by mass of silica. The upper limit of the content is preferably 50.0 parts by mass, more preferably 20.0 parts by mass or less, even more preferably 15.0 parts by mass or less, and particularly preferably 10.0 parts by mass or less. Within the above range, the effect tends to be better obtained.

[0093] As the coupling agent, any compound that bonds to or interacts with the silica and the polymer can be used, but from the viewpoint of obtaining better effects, an ionic coupling agent is preferred.

[0094] The mechanism by which this effect is obtained is not clear, but is presumed to be as follows. When an ionic coupling agent is compounded, an ionic bond is formed between the polymer and the ionic coupling agent bonded to the silica surface. As a result, due to the reversibility of the ionic bond, the crosslink between the silica and the polymer dissociates only when the tire is wetted with water, improving the mobility of the polymer whose ionic bond has dissociated. Therefore, when the tire is driven in a wet state, energy loss is likely to occur inside the rubber, improving the loss coefficient tanδ and improving wet performance.

[0095] In this disclosure, an "ionic coupling agent" is a compound that forms an ionic bond or ionic interaction with silica and a polymer (such as a rubber component or a liquid polymer). By including the ionic coupling agent, an ionic bond or ionic interaction is formed between the ionic coupling agent and silica, and between the ionic coupling agent and the polymer.

[0096] The ionic coupling agent can be any compound that forms an ionic bond or ionic interaction with each of silica and polymer (rubber component, liquid polymer, etc.). Among them, from the viewpoint of obtaining a better effect, it is desirable to include at least one selected from the group consisting of a compound represented by the following formula (1), a hydrolyzate of a compound represented by the following formula (1), and a hydrolysis condensate of a compound represented by the following formula (1).

[0097] [ka]

[0098] In formula (1), R 31 and R 32 R each independently represents a monovalent organic group. 33 and R 34 each independently represents an organic group having a group selected from the group consisting of an alkyl group, a vinyl group, an epoxy group, a styryl group, a (meth)acrylic group, an amino group, an isocyanurate group, a ureido group, a mercapto group, a sulfide group, a polyalkyleneoxyalkyl group, a carboxy group, and a quaternary ammonium group, and 34 At least one of them is an organic group having a quaternary ammonium group. Each m independently represents an integer of 0 to 2. n represents an integer. In the present disclosure, an organic group refers to a group having one or more carbon atoms.

[0099] The hydrolysate of the compound represented by formula (1) is a compound in which at least a portion of the substituents on the silicon atoms in the compound represented by formula (1) is hydrolyzed to form silanol groups. The hydrolysis condensate of the compound represented by formula (1) is a compound obtained by condensing two or more compounds selected from the group consisting of the compound represented by formula (1) and hydrolysates of the compound represented by formula (1).

[0100] In formula (1), m is preferably 1 or 2, and more preferably 2. In formula (1), n ​​is preferably an integer of 2 to 20.

[0101] R in Equation (1) 31 and R 32 The monovalent organic group preferably has 1 to 6 carbon atoms. R 31 and R3 22 The organic group having 1 to 6 carbon atoms in the formula (I) may be linear, branched, or have a ring structure. Examples of the organic group having 1 to 6 carbon atoms include alkyl groups and alkenyl groups, with alkyl groups being preferred. Examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, n-pentyl, n-hexyl, and cyclohexyl groups.

[0102] R in Equation (1) 31 and R 32 are each independently preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, further preferably a methyl group or an ethyl group, and particularly preferably a methyl group.

[0103] R in Equation (1) 33 are each independently preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, further preferably a methyl group or an ethyl group, and particularly preferably a methyl group.

[0104] R in Equation (1) 34 is an organic group having at least one quaternary ammonium group. Examples of groups having a quaternary ammonium group include groups represented by the following formula: [ka]

[0105] In the formula, R 35 ~R 37R each independently represents a monovalent organic group. 38 Y each independently represents a divalent organic group. - represents an anion. k represents an integer.

[0106] R 35 ~R 37 Examples of the monovalent organic group include monovalent hydrocarbon groups, and examples of the monovalent hydrocarbon group include alkyl groups having 1 to 12 carbon atoms and alkenyl groups having 2 to 12 carbon atoms. R 35 ~R 37 The number of carbon atoms is preferably 1 to 12, more preferably 1 to 7, still more preferably 1 to 5, and particularly preferably 1 to 3. R 35 ~R 37 The monovalent organic group is particularly preferably a methyl group or an ethyl group.

[0107] R 38 The divalent organic group includes a divalent hydrocarbon group, and examples of the divalent hydrocarbon group include an alkylene group having 1 to 12 carbon atoms and an alkenylene group having 2 to 12 carbon atoms. R 38 The number of carbon atoms is preferably 1 to 12, more preferably 1 to 7, still more preferably 1 to 5, and particularly preferably 1 to 3. R 38 The divalent organic group is particularly preferably a methylene group or an ethylene group.

[0108] k is preferably 0 to 5, more preferably 0 to 3, still more preferably 0 to 1, and particularly preferably 0.

[0109] Y - is not particularly limited, and examples thereof include halide ions such as chloride ion, bromide ion, and iodine ion; alkyl sulfate ions such as methyl sulfate ion; and ions of organic acids such as acetate ion.

[0110] Among the compounds represented by the formula (1), the hydrolysates of the compounds represented by the formula (1), and the hydrolysis condensates of the compounds represented by the formula (1), the compounds represented by the following formula (1-1) are desirable from the viewpoint of obtaining better effects.

[0111] [ka]

[0112] In formula (1-1), R 35 ~R 37 are each independently the R 35 ~R 37 R represents a group similar to 38 are each independently the R 38 represents a group similar to that represented by Y - are each independently the Y - Each k independently represents an integer similar to the above k.

[0113] In formula (1-1), R 35 ~R 37 , R 38 , Y - , and the preferred examples of k are the same as those mentioned above.

[0114] When the ionic coupling agent has a salt structure such as a quaternary ammonium salt, such as the compound represented by formula (1-1), a better effect can be obtained. The mechanism by which the effect is obtained is not clear, but is presumed to be as follows. The above -N + (R 35 )(R 36 )(R 37 )Y - When the tire has a salt structure such as this, a more ionic bond is formed between the polymer and the ionic coupling agent bonded to the silica surface. Therefore, when the tire is wet, energy loss is more likely to occur inside the rubber, which is thought to improve the loss coefficient tanδ and wet performance.

[0115] As the ionic coupling agent, commercially available products such as X-12-1126 manufactured by Shin-Etsu Chemical Co., Ltd. can be used.

[0116] The content of the ionic silane coupling agent (preferably the total amount of the compound represented by formula (1), the hydrolyzate of the compound represented by formula (1), and the hydrolysis condensate of the compound represented by formula (1)) is preferably 1.0 part by mass or more, more preferably 2.5 parts by mass or more, even more preferably 4.0 parts by mass or more, and particularly preferably 5.0 parts by mass or more, relative to 100 parts by mass of silica. The upper limit of the content is preferably 50.0 parts by mass, more preferably 20.0 parts by mass or less, even more preferably 15.0 parts by mass or less, and particularly preferably 10.0 parts by mass or less. Within the above range, better effects tend to be obtained.

[0117] The groove-forming rubber composition may contain a known silane coupling agent as a coupling agent other than the ionic coupling agent. The silane coupling agent is not particularly limited, and those known in the rubber field can be used, 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, Examples include sulfide-based compounds such as N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z manufactured by Momentive; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercially available products include those from Degussa, Momentive, Shin-Etsu Silicones Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Dow Corning Toray Co., Ltd. These may be used alone or in combination of two or more.

[0118] In the groove-forming rubber composition, the content of the silane coupling agent is preferably 0.1 parts by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more, per 100 parts by mass of silica. The upper limit of the content is preferably 50 parts by mass, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. Within the above range, better effects tend to be obtained.

[0119] (plasticizer) The groove-forming rubber composition preferably contains a plasticizer to obtain better effects. Here, the plasticizer is a material that imparts plasticity to the rubber component, and examples thereof include liquid plasticizers (plasticizers that are in a liquid state at room temperature (25°C)) and resins (resins that are in a solid state at room temperature (25°C)).

[0120] In the groove-forming rubber composition, the content of the plasticizer (total amount of plasticizer) is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. Within the above range, better effects tend to be obtained.

[0121] Liquid plasticizers (plasticizers that are liquid at room temperature (25°C)) that can be used in the groove-forming rubber composition are not particularly limited, and examples include oils, liquid polymers (liquid resins, liquid diene-based polymers, liquid farnesene-based polymers, etc.), etc. These may be used alone or in combination of two or more.

[0122] In the groove-forming rubber composition, the content of the liquid plasticizer is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. Within the above range, better effects tend to be obtained. The amount of liquid plasticizer included includes the amount of oil contained in the oil-extended rubber and the amount of oil contained in the sulfur.

[0123] Examples of oils include process oils, vegetable oils, and mixtures thereof. Examples of process oils that can be used include paraffin-based process oils, aromatic process oils, and naphthenic process oils. Examples of vegetable oils that can be used include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. Commercially available products include those from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Corporation, Oriso Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and Nisshin Oillio Group, Ltd. Among these, process oils (paraffin-based process oils, aromatic process oils, naphthenic process oils, etc.) and vegetable oils are preferred.

[0124] Examples of liquid resins include terpene resins (including terpene phenol resins and aromatic modified terpene resins), rosin resins, styrene resins, C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene (DCPD) resins, coumarone-indene resins (including coumarone and indene simple resins), phenol resins, olefin resins, polyurethane resins, acrylic resins, etc. Hydrogenated products of these resins can also be used.

[0125] Examples of liquid diene polymers include liquid styrene-butadiene copolymers, liquid butadiene polymers, liquid isoprene polymers, liquid styrene-isoprene copolymers, liquid styrene-butadiene-styrene block copolymers (liquid SBS block polymers), liquid styrene-isoprene-styrene block copolymers (liquid SIS block polymers), liquid farnesene polymers, and liquid farnesene-butadiene copolymers, which are liquid at 25°C. The terminals or main chains of these polymers may be modified with polar groups. Hydrogenated versions of these polymers can also be used.

[0126] Among liquid plasticizers that are in a liquid state at room temperature (25°C), unmodified liquid polymers and modified liquid polymers are preferred, modified liquid polymers are more preferred, and acid-modified liquid polymers are even more preferred, from the viewpoint of obtaining better effects. The unmodified liquid polymers and modified liquid polymers may be used alone or in combination of two or more.

[0127] Examples of acid-modified liquid polymers include polymers that are modified with acidic compounds and their derivatives and are in a liquid state at room temperature (25° C.).

[0128] Specifically, acid-modified liquid polymers obtained by modifying an unmodified liquid polymer with an unsaturated carboxylic acid and / or its derivatives, and acid-modified liquid polymers obtained by modifying a modified liquid polymer with an unsaturated carboxylic acid and / or its derivatives can be suitably used, and it is particularly desirable to use acid-modified liquid polymers obtained by modifying an unmodified liquid polymer with an unsaturated carboxylic acid and / or its derivatives.

[0129] The unmodified liquid polymer is an unmodified liquid polymer (liquid diene polymer) obtained by polymerizing a monomer containing a conjugated diene such as 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 2-methyl-1,3-pentadiene, 4,5-diethyl-1,3-octadiene, or 3-butyl-1,3-octadiene. Examples of unmodified liquid polymers include liquid diene polymers such as liquid polybutadiene, liquid polyisoprene, liquid styrene-butadiene random copolymer, liquid styrene-butadiene block copolymer, liquid butadiene-isoprene random copolymer, liquid butadiene-isoprene block copolymer, liquid styrene-butadiene-isoprene random copolymer, and liquid styrene-butadiene-isoprene block copolymer. Among these, from the viewpoint of obtaining better effects, liquid polybutadiene, liquid polyisoprene, liquid styrene-butadiene random copolymer, and liquid styrene-butadiene block copolymer are preferred, and liquid polybutadiene and liquid polyisoprene are more preferred. These may be used alone or in combination of two or more.

[0130] Examples of the unsaturated carboxylic acid include maleic acid, fumaric acid, itaconic acid, and (meth)acrylic acid. Examples of the unsaturated carboxylic acid derivative include unsaturated carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; unsaturated carboxylic acid esters such as maleic acid esters, fumaric acid esters, itaconic acid esters, glycidyl (meth)acrylate, and hydroxyethyl (meth)acrylate; unsaturated carboxylic acid amides such as maleic acid amides, fumaric acid amides, and itaconic acid amides; and unsaturated carboxylic acid imides such as maleic acid imide and itaconic acid imide. The unsaturated carboxylic acid or unsaturated carboxylic acid derivative may be modified with one type or two or more types.

[0131] The acid-modified liquid polymer can be produced, for example, by modifying a raw material unmodified liquid polymer with an acidic compound such as an unsaturated carboxylic acid and / or its derivative. The modification method is not particularly limited, and the polymer can be produced by a known method, for example, by adding an acidic compound such as an unsaturated carboxylic acid and / or its derivative to the raw material unmodified liquid polymer. The acid-modified liquid polymer can be used alone or in combination of two or more.

[0132] Among the above-mentioned acid-modified liquid polymers, from the viewpoint of obtaining a better effect, maleic acid-modified liquid polymers and maleic anhydride-modified liquid polymers are preferred, maleic acid-modified liquid diene-based polymers and maleic anhydride-modified liquid diene-based polymers are more preferred, and maleic acid-modified liquid polybutadiene, maleic anhydride-modified liquid polybutadiene, maleic acid-modified liquid polyisoprene and maleic anhydride-modified liquid polyisoprene are even more preferred.

[0133] The number average molecular weight (Mn) of the acid-modified liquid polymer is preferably 2,000 or more, more preferably 20,000 or more, even more preferably 25,000 or more, and particularly preferably 30,000 or more. The Mn is preferably 100,000 or less, more preferably 80,000 or less, and even more preferably 60,000 or less. The weight average molecular weight (Mw) of the acid-modified liquid polymer is also preferably within the same range. Within the above range, better effects tend to be obtained.

[0134] As the acid-modified liquid polymer, for example, products available from Kuraray Co., Ltd., Cray Valley Corporation, etc. can be used.

[0135] In the groove-forming rubber composition, the content of the acid-modified liquid polymer is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. Within the above range, better effects tend to be obtained.

[0136] Examples of the resins (resins that are solid at room temperature (25°C)) that can be used in the groove-forming rubber composition include aromatic vinyl polymers that are solid at room temperature (25°C), coumarone-indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, and acrylic resins. The resins may also be hydrogenated. These may be used alone or in combination of two or more. Of these, aromatic vinyl polymers, petroleum resins, and terpene resins are preferred.

[0137] When the groove-forming rubber composition contains the resin, the content of the resin is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. Within the above range, better effects tend to be obtained.

[0138] The softening point of the resin is preferably 50°C or higher, more preferably 55°C or higher, and even more preferably 60°C or higher. The upper limit is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 145°C or lower. Within the above range, the effect tends to be better obtained. The softening point of the resin is the temperature at which the ball drops when the softening point specified in JIS K6220-1:2001 is measured using a ring and ball softening point tester.

[0139] The aromatic vinyl polymer is a polymer containing an aromatic vinyl monomer as a constituent unit. For example, it may be a resin obtained by polymerizing α-methylstyrene and / or styrene, and specifically may be a homopolymer of styrene (styrene resin), a homopolymer of α-methylstyrene (α-methylstyrene resin), a copolymer of α-methylstyrene and styrene, or a copolymer of styrene and another monomer.

[0140] The coumarone-indene resin is a resin containing coumarone and indene as the main monomer components constituting the resin skeleton (main chain). Other monomer components contained in the skeleton besides coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0141] The coumarone resin is a resin containing coumarone as a main monomer component constituting the skeleton (main chain) of the resin.

[0142] The indene resin is a resin containing indene as a main monomer component constituting the skeleton (main chain) of the resin.

[0143] The phenolic resin may be a known polymer obtained by reacting phenol with an aldehyde such as formaldehyde, acetaldehyde, or furfural in the presence of an acid or alkali catalyst. Of these, those obtained by reacting with an acid catalyst (such as novolac phenolic resin) are preferred.

[0144] Examples of the rosin resin include rosin-based resins such as natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

[0145] Examples of the petroleum resin include C5 resin, C9 resin, C5 / C9 resin, dicyclopentadiene (DCPD) resin, and hydrogenated versions of these resins. Of these, DCPD resin and hydrogenated DCPD resin are preferred.

[0146] The terpene resin is a polymer containing terpene as a structural unit. Examples include polyterpene resins obtained by polymerizing terpene compounds and aromatic-modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds. Examples of aromatic-modified terpene resins that can be used include 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. 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.).

[0147] The acrylic resin is a polymer containing an acrylic monomer as a constituent unit. For example, a styrene-acrylic resin having a carboxyl group and obtained by copolymerizing an aromatic vinyl monomer component with an acrylic monomer component can be used. Among them, a solvent-free carboxyl-containing styrene-acrylic resin can be preferably used.

[0148] Examples of plasticizers that can be used include products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., and Taoka Chemical Co., Ltd.

[0149] (Other ingredients) The groove-forming rubber composition may contain an antioxidant. Examples of the antioxidant include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine. Examples of antioxidants include p-phenylenediamine antioxidants such as quinolone; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Commercially available products include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and Flexis. These antioxidants may be used alone or in combination of two or more.

[0150] In the groove-forming rubber composition, the content of the antioxidant is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component, and is 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. Within the above ranges, better effects tend to be obtained.

[0151] The groove-forming rubber composition may contain wax. The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; and synthetic waxes such as polymers of ethylene, propylene, etc. Commercially available products that can be used include those from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. These may be used alone or in combination of two or more.

[0152] In the groove-forming 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, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component. Within the above ranges, better effects tend to be obtained.

[0153] The groove-forming rubber composition may contain stearic acid. As the stearic acid, conventionally known ones can be used, and commercially available products that can be used include products from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. These may be used alone or in combination of two or more.

[0154] In the groove-forming rubber composition, the content of stearic acid is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and even more preferably 1.0 part by mass or more, per 100 parts by mass of the rubber component, and is preferably 10.0 parts by mass or less, and more preferably 6.0 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0155] The groove-forming rubber composition may contain zinc oxide. As the zinc oxide, conventionally known ones can be used, and commercially available products include those available from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. These may be used alone or in combination of two or more.

[0156] In the rubber composition, the content of zinc oxide is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 10.0 parts by mass or less, and more preferably 6.0 parts by mass or less. When the content is within the above range, better effects tend to be obtained.

[0157] The groove-forming rubber composition may contain sulfur. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur, which are commonly used as crosslinking agents in the rubber industry. Commercially available products include those from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., and Hosoi Chemical Industry Co., Ltd. These may be used alone or in combination of two or more.

[0158] In the groove-forming rubber composition, the sulfur content per 100 parts by mass of the rubber component is preferably at least 0.5 parts by mass, more preferably at least 0.8 parts by mass, even more preferably at least 1.0 part by mass, and is preferably at most 3.5 parts by mass, more preferably at most 3.0 parts by mass, even more preferably at most 2.8 parts by mass. Within the above ranges, better effects tend to be obtained.

[0159] The groove-forming 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-benzothiazyl sulfenamide (CBS), N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-orthotolylguanidine, and orthotolylbiguanidine. Commercially available products include those from Sumitomo Chemical Co., Ltd. and Ouchi Shinko Chemical Industry Co., Ltd. These may be used alone or in combination.

[0160] In the groove-forming rubber composition, the content of the vulcanization accelerator is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 10.0 parts by mass or less, more preferably 7.0 parts by mass or less, and even more preferably 5.0 parts by mass or less. Within the above ranges, better effects tend to be obtained.

[0161] In addition to the above components, the groove-forming rubber composition may further contain additives commonly used in the tire industry, such as organic peroxides, etc. The content of these additives is preferably 0.1 to 200 parts by mass per 100 parts by mass of the rubber component.

[0162] The groove-forming rubber composition can be produced, for example, by kneading the above-mentioned components using a rubber kneading device such as an open roll or a Banbury mixer, followed by vulcanization.

[0163] As for kneading conditions, in the base kneading step in which additives other than the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C. In the finish kneading step in which the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 120°C or lower, preferably 85 to 110°C. Furthermore, the composition kneaded with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 140 to 190°C, preferably 150 to 185°C. The vulcanization time is usually 5 to 15 minutes.

[0164] <Tires> The tire of the present disclosure has a tread having at least one circumferential groove portion, and the ratio Z (= D / T) of the maximum groove depth D (mm) of the circumferential groove portion to the maximum thickness T (mm) of the tread satisfies the following formula (2): (2) Z≧0.10 (In the formula, D is the maximum groove depth (mm) of the circumferential groove portion, T is the maximum thickness of the tread, and Z is D / T.) The lower limit of Z is preferably 0.30 or more, more preferably 0.50 or more, even more preferably 0.60 or more, and particularly preferably 0.70 or more. The upper limit is preferably 1.00 or less, more preferably 0.95 or less, even more preferably 0.90 or less, and particularly preferably 0.85 or less. Within the above range, the effect tends to be better.

[0165] In the tire of the present disclosure, the maximum groove depth D of the circumferential groove portion formed in the tread is preferably 3.0 mm or more, more preferably 6.0 mm or more, even more preferably 7.0 mm or more, and particularly preferably 8.0 mm or more. The upper limit is preferably 12.0 mm or less, more preferably 11.0 mm or less, even more preferably 10.0 mm or less, and particularly preferably 9.0 mm or less. Within the above range, better effects tend to be obtained.

[0166] In this specification, the maximum groove depth D of the circumferential groove portion is measured along the normal to the surface extending from the surface forming the contact patch on the outermost surface of the tread, and is the distance from the surface extending from the surface forming the contact patch to the deepest groove bottom, and means the maximum distance among the groove depths of the circumferential groove portions provided.

[0167] In the tire of the present disclosure, the maximum thickness T of the tread is preferably 3.0 mm or more, more preferably 5.0 mm or more, even more preferably 7.0 mm or more, and particularly preferably 9.0 mm or more. The upper limit is preferably 20.0 mm or less, more preferably 18.0 mm or less, even more preferably 16.0 mm or less, and particularly preferably 14.0 mm or less. Within the above range, the effect tends to be more favorable.

[0168] In this specification, the maximum thickness T of the tread means the maximum distance in the tire radial direction measured along the normal to the plane extending from the surface forming the contact patch on the outermost surface of the tread to the top surface of the carcass.

[0169] In the tire of the present disclosure, the negative rate S (%) of the tread is preferably 95% or less. S is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less. The negative rate is preferably 40% or more, more preferably 45% or more, and even more preferably 50% or more. Within the above range, better effects tend to be obtained.

[0170] The negative ratio (negative ratio within the contact area of ​​the tread portion) is the ratio of the total groove area within the contact area to the total area of ​​the contact area, and is measured by the following method. In this specification, if the tire is a pneumatic tire, the negative rate is calculated from the contact shape under normal load conditions with a normal rim and normal internal pressure. In the case of a non-pneumatic tire, the negative rate can be measured in the same way without requiring normal internal pressure. "Genuine rim" means a rim that is specified for each tire by the standard system that includes the standard on which the tire is based. For example, it means a standard rim in the case of JATMA, a "Design Rim" in the case of TRA, or a "Measuring Rim" in the case of ETRTO. "Normal internal pressure" refers to the air pressure specified for each tire by the above standards. In the case of JATMA, it means the maximum air pressure, in the case of TRA, it means the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it means "INFLATION PRESSURE". In the case of passenger car tires, it is 180kPa. "Normal load" refers to the load specified for each tire by the above standards, and means the load obtained by multiplying the maximum load capacity in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "LOAD CAPACITY" in the case of ETRTO, by 0.88. The contact shape is obtained by assembling the tire on a standard rim, applying the standard internal pressure, and leaving it to stand at 25°C for 24 hours. Then, ink is applied to the surface of the tire tread, and the tire is pressed against cardboard under a standard load (camber angle 0°) and transferred to the paper. The tire is rotated 72° in the circumferential direction and the pattern is transferred at five locations. In other words, the contact shape is obtained five times. For the five contact shapes, the average value of the maximum length in the tire axial direction is defined as L, and the average value of the length in the direction perpendicular to the axial direction is defined as W. The negative rate (%) is calculated as follows: [1-{average area of ​​five transferred contact shapes (ink areas) on cardboard / (L x W)}] x 100 (%). Here, the average value of the length or area is the simple average of the five values.

[0171] The tire of the present disclosure has a tread having at least one circumferential groove, the circumferential groove being formed from a groove-forming rubber composition containing a rubber component and silica. From the viewpoint of obtaining better effects, it is desirable that the tan δ of the groove-forming rubber composition when wet with water and the tan δ when dry, and the ratio Z (= D / T) of the maximum groove depth D (mm) of the circumferential groove to the maximum thickness T (mm) of the tread satisfy the following formula: (tan δ when wet / tan δ when dry) × Z≧0.10 (In the formula, tanδ is the loss tangent 30 minutes after the start of measurement, measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, an extension mode, and a measurement time of 30 minutes. D is the maximum groove depth (mm) of the circumferential groove portion. T is the maximum thickness of the tread. Z is D / T.) (tan δ when wet / tan δ when dry) × Z is preferably 0.30 or more, more preferably 0.50 or more, even more preferably 0.80 or more, particularly preferably 0.90 or more, and most preferably 1.00 or more. The upper limit is preferably 1.71 or less, more preferably 1.50 or less, even more preferably 1.20 or less, and particularly preferably 1.10 or less. Within the above range, better effects tend to be obtained.

[0172] The tire of the present disclosure has a tread having at least one circumferential groove formed from a groove-forming rubber composition containing a rubber component and silica. From the viewpoint of obtaining better effects, it is desirable that the tan δ of the groove-forming rubber composition when wet with water and the negative rate S (%) of the tread satisfy the following formula: Tan δ / S when wet ≧ 0.0018 (In the formula, tanδ is the loss tangent 30 minutes after the start of measurement, measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, an extension mode, and a measurement time of 30 minutes. S is the negative ratio of the tread.) The tan δ / S when wetted with water is preferably 0.0020 or more, more preferably 0.0023 or more, even more preferably 0.0024 or more, and particularly preferably 0.0026 or more. The upper limit is preferably 0.0086 or less, more preferably 0.0050 or less, even more preferably 0.0037 or less, and particularly preferably 0.0033 or less. Within the above range, the effect tends to be more favorable.

[0173] 1 is a cross-sectional view taken along a meridian line, showing a portion of a pneumatic tire 1 according to an embodiment of the present disclosure. Note that the tire according to the present disclosure is not limited to the following configuration.

[0174] In Fig. 1, the up-down direction is the tire radial direction (hereinafter also simply referred to as the radial direction), the left-right direction is the tire axial direction (hereinafter also simply referred to as the axial direction), and the direction perpendicular to the paper surface is the tire circumferential direction (hereinafter also simply referred to as the circumferential direction). This tire 1 has a shape that is approximately symmetrical with respect to a crown center (center line CL) 17 in Fig. 1. This center line CL is also called a tread center line and represents the equatorial plane EQ of the tire 1.

[0175] The tire 1 includes a tread 2, a sidewall 3, a bead 4, a carcass 5, and a belt 6. The tire 1 is a tubeless type.

[0176] The tread 2 has a tread surface 7. In a cross section of the tire 1 cut in the meridian direction, the tread surface 7 has a shape that is convex radially outward. This tread surface 7 comes into contact with the road surface. A plurality of grooves 8 extending circumferentially are cut into the tread surface 7. These grooves 8 form a tread pattern. The outer portions of the tread 2 in the tire axial direction (tire width direction) are called shoulder portions 15. The sidewalls 3 extend substantially radially inward from the ends of the tread 2. These sidewalls 3 are made of cross-linked rubber or the like.

[0177] As shown in FIG. 1, the bead 4 is located approximately radially inward of the sidewall 3. The bead 4 includes a core 10 and an apex 11 extending radially outward from the core 10. The core 10 has a ring shape along the circumferential direction of the tire. The core 10 is formed by winding an inelastic wire. Typically, a steel wire is used for the core 10. The apex 11 tapers radially outward. The apex 11 is made of a high-hardness crosslinked rubber or the like.

[0178] In this embodiment, the carcass 5 is made up of a carcass ply 12. The carcass ply 12 is laid between the beads 4 on both sides and runs along the inside of the tread 2 and the sidewall 3. The carcass ply 12 is folded around the core 10 from the inside to the outside in the tire axial direction. Although not shown, the carcass ply 12 is made up of a large number of cords arranged in parallel and a topping rubber. The absolute value of the angle that each cord makes with respect to the equatorial plane EQ (CL) is usually 70° to 90°. In other words, the carcass 5 has a radial structure.

[0179] In this embodiment, the belt 6 is located radially outside the carcass 5. The belt 6 is laminated on the carcass 5. The belt 6 reinforces the carcass 5. The belt 6 may be composed of an inner layer belt 13 and an outer layer belt 14. In this embodiment, the widths of the two belts 13 and 14 are different.

[0180] Although not shown, each of the inner layer belt 13 and the outer layer belt 14 typically consists of a large number of parallel cords and a topping rubber. Each cord is preferably inclined with respect to the equatorial plane EQ. The inclination direction of the cords of the inner layer belt 13 is preferably opposite to the inclination direction of the cords of the outer layer belt.

[0181] Although not shown, a band may be laminated on the radially outer side of the belt 6. The width of this band is larger than that of the belt 6. This band may be made of a cord and a topping rubber. The cord is wound spirally. The belt is restrained by this cord, thereby suppressing lifting of the belt 6. The cord is preferably made of organic fiber. Examples of preferred organic fibers include nylon fiber, polyester fiber, rayon fiber, polyethylene naphthalate fiber, and aramid fiber.

[0182] Although not shown, an edge band may be disposed radially outward of the belt 6 and near the widthwise end (edge ​​portion) of the belt 6. This edge band may be formed of cords and a topping rubber, similar to the above-mentioned band. One example of the edge band is one layered on the upper surface of the step 20 portion of the wide inner layer belt 13. The cords of this edge band may be inclined in the same direction as the cords of the narrow outer layer belt 14 and biased relative to the cords of the wide inner layer belt 13.

[0183] Although not shown, a cushion rubber layer may be laminated on the carcass 5 near the width direction end of the belt 6. The cushion layer may be made of a soft crosslinked rubber. The cushion layer absorbs stress at the end of the belt.

[0184] FIG. 2 shows a cross section of the tread 2 of the tire 1 taken along a plane including the tire axis. In tire 1, the tread rubber composition (rubber composition after vulcanization) that constitutes tread 2 is composed of the groove-forming rubber composition described above, and the tan δ when wet with water and the tan δ when dry of the tread rubber composition (rubber composition after vulcanization) satisfy the formula (1).

[0185] The tread 2 of the tire 1 is provided with circumferential grooves 8. In the tire 1, the maximum groove depth D of the circumferential grooves 8 is the distance in the normal direction from an extension of the surface that forms the contact patch of the tread surface 7 to the deepest groove bottom, and refers to the depth of the deepest groove formed among the multiple circumferential grooves 8. In the tire 1, the maximum thickness T of the tread 2 refers to the maximum distance in the tire radial direction from an extension of the surface that forms the contact patch of the tread surface 7 to the upper surface of the carcass 5. Z, which is expressed by the maximum groove depth D / maximum thickness T, satisfies the above formula (2). [Example]

[0186] Below, examples (embodiments) that are considered preferable for implementation will be shown, but the scope of the present disclosure is not limited to the embodiments.

[0187] The compositions obtained by varying the formulation according to Table 1 using the various chemicals shown below and the tire specifications shown in Table 1 were examined, and the results calculated based on the evaluation method below are shown in Table 1. SBR: Nipol 1502 (E-SBR) manufactured by ZEON Corporation BR: JSR BR730 (high cis polybutadiene (cis content 96% by mass)) NR:TSR20 Carboxylic acid-modified SBR: synthesized according to Production Example 1 below (carboxylic acid group content: 5% by mass, styrene content: 23% by mass, butadiene content: 72% by mass) Carbon black: Diablack I (N220, N2SA114m) manufactured by Mitsubishi Chemical Corporation 2 / g, DBP 114ml / 100g) Silica: Ultrasil VN3 (N2SA175m) manufactured by Evonik Degussa 2 / g) Ionic coupling agent: X-12-1126 (quaternary ammonium salt) manufactured by Shin-Etsu Chemical Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) manufactured by EVONIK-DEGUSSA Maleic acid modified liquid polyisoprene: Kuraray LIR-410 (Mw 30000) Maleic anhydride modified liquid polyisoprene: Kuraray LIR-403 (Mn34000) Unmodified liquid polyisoprene: Kuraray LIR-50 (Mw 54000) Magnesium oxide: Kyowamag 150 manufactured by Kyowa Chemical Industry Co., Ltd. (apparent specific gravity: 0.36 g / ml, d50: 4.46 μm, N2SA: 145 m 2 / g) Basic molecule: Shin-Etsu Chemical's KBE-903 (3-aminopropyltriethoxysilane) Stearic acid: Tsubaki (NOF Corporation) Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Oil: H&R VIVATEC 400 / 500 (TDAE oil) Resin: SYLVARES SA85 (copolymer of α-methylstyrene and styrene, Tg 43°C, softening point 85°C) manufactured by Arizona Chemical Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. Anti-aging agent: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator DPG: Noccela D (diphenyl guanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator NS: Noccela NS (N-tert-butyl-2-benzothiazylsulfenamide (TBBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0188] <Production Example 1: Synthesis of Carboxylic Acid-Modified SBR> (Latex Preparation) A pressure-resistant reactor equipped with a stirrer is charged with 2000 g of distilled water, 45 g of emulsifier (1), 1.5 g of emulsifier (2), 8 g of electrolyte, 250 g of styrene, 50 g of methacrylic acid, 700 g of butadiene, and 2 g of molecular weight modifier. The reactor temperature is set to 5°C, and an aqueous solution in which 1 g of a radical initiator and 1.5 g of SFS are dissolved, and an aqueous solution in which 0.7 g of EDTA and 0.5 g of a catalyst are dissolved, are added to the reactor to initiate polymerization. Five hours after the start of polymerization, 2 g of a polymerization terminator is added to terminate the reaction, thereby obtaining a latex. (Rubber Preparation) Unreacted monomers are removed from the latex by steam distillation. Thereafter, the latex is added to alcohol and coagulated while adjusting the pH to 3 to 5 with a saturated aqueous sodium chloride solution or formic acid, to obtain a crumb-like polymer. The polymer is dried in a vacuum dryer at 40°C to obtain a solid rubber (emulsion polymerized rubber).

[0189] The materials used in Production Example 1 are as follows: Emulsifier (1): Rosin acid soap manufactured by Harima Chemical Co., Ltd. Emulsifier (2): Fatty acid soap manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Electrolyte: Sodium phosphate manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Styrene: Styrene manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Methacrylic acid: methacrylic acid manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Butadiene: 1,3-butadiene manufactured by Takachiho Chemical Industry Co., Ltd. Molecular weight modifier: tert-dodecyl mercaptan manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Radical initiator: Paramenthane hydroperoxide manufactured by NOF Corporation SFS: Sodium formaldehyde sulfoxylate manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. EDTA: Sodium ethylenediaminetetraacetate manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Catalyst: Ferric sulfate manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Polymerization terminator: N,N'-dimethyldithiocarbamate manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Alcohol: Methanol and ethanol manufactured by Kanto Chemical Co., Ltd. Formic acid: Formic acid manufactured by Kanto Chemical Co., Ltd. Sodium chloride: Sodium chloride manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0190] Examples and Comparative Examples According to the formulation shown in Table 1, chemicals other than sulfur and vulcanization accelerator are kneaded for 4 minutes at 160°C using a 16L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded mixture. Next, sulfur and a vulcanization accelerator are added to the kneaded mixture, and the mixture is kneaded using an open roll at 80° C. for 4 minutes to obtain an unvulcanized polymer composition. The unvulcanized polymer composition is molded into a tread shape, and is laminated together with other tire components on a tire building machine to form an unvulcanized tire. Thereafter, the tire is vulcanized at 170°C for 12 minutes to produce a test tire (specifications: Table 1, size: 195 / 65R15).

[0191] The materials used (carboxylic acid-modified SBR, surface-modified silica) and the test tires produced are subjected to the following property measurements and evaluations. The reference comparative example in Table 1 is Comparative Example 1.

[0192] <Reaction rate of basic molecules> By the following method, unreacted basic molecules of each surface-modified silica are eluted into water, and the reaction rate of the basic molecules is calculated by titration. (1) Prepare a calibration curve for basic molecules. (2) The surface-modified silica is dispersed in water, unreacted basic molecules are eluted, and titration is performed. (3) The amount of unreacted basic molecules is calculated using the titration value and the calibration curve formula. (4) The reaction rate is calculated from the amount of basic molecules used in the synthesis.

[0193] <Carboxylic acid group content> The content of carboxylic acid groups in the carboxylic acid-modified SBR is 1Calculated using H-NMR.

[0194] <Negative rate> The negative rate of the test tire is measured by the following method. The tread contact shape of the test tire is obtained by assembling it on a standard rim, applying standard internal pressure, and leaving it at 25°C for 24 hours, then applying ink to the surface of the tire tread, applying a standard load and pressing it against cardboard (camber angle 0°), and transferring it to the paper. The tire is rotated 72° in a circumferential direction and the print is made at five locations, obtaining five contact patterns. For the five contact shapes, the average value of the maximum length in the tire axial direction is defined as L, and the average value of the length in the direction perpendicular to the axial direction is defined as W, and the negative rate (%) is calculated using the following formula. The average value of length or area is calculated by taking the simple average of the five values. Negative rate (%) = [1-{average area of ​​five transferred contact shapes (ink areas) on cardboard / (L × W)}] × 100

[0195] <Viscoelasticity test> A viscoelasticity measurement sample measuring 40 mm in length, 3 mm in width, and 0.5 mm in thickness was taken from inside the rubber layer of the tread of each test tire, with the long side in the tire circumferential direction. The tan δ of the tread rubber was measured using an RSA series instrument manufactured by TA Instruments under the following conditions: temperature 30°C, initial strain 10%, dynamic strain 1%, frequency 10 Hz, extension mode, and measurement time 30 minutes, with the measurement value obtained 30 minutes after the start of measurement. The thickness direction of the sample is the radial direction of the tire.

[0196] <tan δ when dry> The viscoelasticity measurement sample (length 40 mm x width 3 mm x thickness 0.5 mm) is dried at room temperature and atmospheric pressure until it reaches a constant weight. The loss tangent tan δ of the resulting dry vulcanized polymer composition (rubber pieces) is measured by the above-mentioned method and is defined as dry tan δ.

[0197] <tan δ when wet> The above-mentioned viscoelasticity measurement sample (length 40 mm×width 3 mm×thickness 0.5 mm) is immersed in 100 ml of water at 23° C. for 2 hours to obtain a vulcanized polymer composition when wet with water. The loss tangent tanδ of the resulting vulcanized polymer composition (rubber piece) when wet with water is measured for viscoelasticity in water by the above-mentioned method using an RSA immersion measuring jig, and this is taken as tanδ when wet with water. The water temperature is set to 30°C.

[0198] <Dry grip performance> Each test tire is fitted to all wheels of a vehicle (domestic FF 2000cc) and driven 10 laps around a course on dry roads. The braking performance on dry roads is then evaluated and calculated by 20 test drivers on a 5-point scale from 1 to 5. The higher the score, the better the performance. The total score of the 20 people's ratings was calculated, and the total score of the reference comparative example was set to 100, and the total score was indexed. The higher the index, the better the dry grip performance.

[0199] <Wet grip performance> Each test tire is fitted to all wheels of a vehicle (domestic FF 2000cc) and driven 10 laps around a course on a wet road surface. The braking performance on the wet road surface is then evaluated and calculated by 20 test drivers on a 5-point scale from 1 to 5. The higher the score, the better the performance. The total score of the 20 people's ratings was calculated, and the total score of the reference comparative example was set to 100, and the total score was indexed. The higher the index, the better the wet grip performance.

[0200] <Overall performance> The overall wet and dry performance (expressed as the sum of two indices for wet grip performance and dry grip performance) is evaluated.

[0201] [Table 1]

[0202] The present disclosure (1) provides a tire having a tread with at least one circumferential groove, the circumferential groove is formed of a groove-forming rubber composition containing a rubber component and silica, In the tire, the tan δ when wet and the tan δ when dry of the groove-forming rubber composition, and the ratio Z of the maximum groove depth D (mm) of the circumferential groove to the maximum thickness T (mm) of the tread satisfy the following formulas (1) and (2): (1) Tan δ when wet / tan δ when dry > 1.00 (2) Z≧0.10 (In the formula, tanδ is the loss tangent 30 minutes after the start of measurement, measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, an extension mode, and a measurement time of 30 minutes. Z is D / T.)

[0203] The present disclosure (2) is the tire according to the present disclosure (1), in which the groove-forming rubber composition contains a modified polymer.

[0204] The present disclosure (3) is the tire according to the present disclosure (1) or (2), in which the groove-forming rubber composition contains an ionic coupling agent.

[0205] The present disclosure (4) is the tire according to the present disclosure (3), in which the ionic coupling agent has a salt structure.

[0206] The present disclosure (5) is the tire according to the present disclosure (4), wherein the salt is a quaternary ammonium salt.

[0207] The present disclosure (6) is a tire according to any one of the present disclosures (2) to (4), wherein the modified polymer has at least one group selected from the group consisting of a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, and salts thereof in the molecule.

[0208] The present disclosure (7) is the tire according to any one of the present disclosures (1) to (7), wherein Z satisfies the following formula: Z≧0.70 (Wherein, Z is D / T.)

[0209] The present disclosure (8) is the tire according to any one of the present disclosures (1) to (7), wherein the negative rate S (%) of the tread is 75% or less.

[0210] The present disclosure (9) is the tire according to any one of the present disclosures (1) to (8), wherein the wet tan δ and dry tan δ of the groove-forming rubber composition and the Z satisfy the following formulas: (tan δ when wet / tan δ when dry) × Z≧0.90 (In the formula, tanδ is the loss tangent 30 minutes after the start of measurement, measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, an extension mode, and a measurement time of 30 minutes. Z is D / T.)

[0211] The present disclosure (10) is the tire according to the present disclosure (8) or (9), in which the tan δ of the groove-forming rubber composition when wet with water and the S satisfy the following formula: Tan δ / S when wet ≧ 0.0024 (In the formula, tanδ is the loss tangent 30 minutes after the start of measurement, measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, an extension mode, and a measurement time of 30 minutes. S is the negative ratio of the tread.) [Explanation of symbols]

[0212] 1 tire 2 Tread 3 Sidewall 4 beads 5. Carcass 6 Belt 7 Tread surface 8 Groove 10 cores 11 Apex 12 Carcass ply 13 Inner belt 14 outer belt 15 Shoulder section 17 Crown center (tread centerline CL, tire 1 equatorial plane EQ) 20 steps D Maximum groove depth of circumferential groove T Maximum tread thickness

Claims

1. A tire having a tread with at least one circumferential groove, the circumferential groove is formed of a groove-forming rubber composition containing a rubber component and silica, A tire in which the tan δ when wet and the tan δ when dry of the groove-forming rubber composition, and the ratio Z of the maximum groove depth D (mm) of the circumferential groove portion to the maximum thickness T (mm) of the tread satisfy the following formulas (1) to (3): (1) tan δ when wet with water / tan δ when dry > 1.00 (2) Z≧0.10 (3) (tan δ when wet with water / tan δ when dry) × Z ≧ 0.90 (In the formula, tanδ is the loss tangent 30 minutes after the start of measurement, measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, an extension mode, and a measurement time of 30 minutes. Z is D / T.)

2. A tire having a tread with at least one circumferential groove, the circumferential groove is formed of a groove-forming rubber composition containing a rubber component and silica, the tan δ when wet and the tan δ when dry of the groove-forming rubber composition, and the ratio Z of the maximum groove depth D (mm) of the circumferential groove portion to the maximum thickness T (mm) of the tread satisfy the following formulas (1) and (2), The tire wherein the groove-forming rubber composition contains an ionic coupling agent. (1) tan δ when wet with water / tan δ when dry > 1.00 (2) Z≧0.10 (In the formula, tanδ is the loss tangent 30 minutes after the start of measurement, measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, an extension mode, and a measurement time of 30 minutes. Z is D / T.)

3. A tire having a tread with at least one circumferential groove, the circumferential groove is formed of a groove-forming rubber composition containing a rubber component and silica, the tan δ when wet and the tan δ when dry of the groove-forming rubber composition, and the ratio Z of the maximum groove depth D (mm) of the circumferential groove portion to the maximum thickness T (mm) of the tread satisfy the following formulas (1) and (2), the groove-forming rubber composition contains a modified polymer, The modified polymer has at least one group selected from the group consisting of a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, and salts thereof in the molecule. (1) tan δ when wet with water / tan δ when dry > 1.00 (2) Z≧0.10 (In the formula, tanδ is the loss tangent 30 minutes after the start of measurement, measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, an extension mode, and a measurement time of 30 minutes. Z is D / T.)

4. The tire according to claim 1 or 2, wherein the groove-forming rubber composition contains a modified polymer.

5. The tire according to claim 1 or 3, wherein the groove-forming rubber composition contains an ionic coupling agent.

6. 6. The tire according to claim 2 or 5, wherein the ionic coupling agent has a salt structure.

7. 7. The tire of claim 6, wherein said salt is a quaternary ammonium salt.

8. The tire according to claim 4, wherein the modified polymer has at least one group selected from the group consisting of a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, and salts thereof in the molecule.

9. The tire according to any one of claims 1 to 8, wherein Z satisfies the following formula: Z≧0.70 (Wherein Z is D / T.)

10. The tire according to any one of claims 1 to 9, wherein the negative rate S (%) of the tread is 75% or less.

11. The tire according to any one of claims 2 to 10, wherein the tan δ when wet and the tan δ when dry of the groove-forming rubber composition, and Z, satisfy the following formulas: (tan δ when wet with water / tan δ when dry)×Z≧0.90 (In the formula, tanδ is the loss tangent 30 minutes after the start of measurement, measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, an extension mode, and a measurement time of 30 minutes. Z is D / T.)

12. The tire according to claim 10 or 11, wherein tan δ of the groove-forming rubber composition when wet with water and the S satisfy the following formula: Tan δ / S when wet with water ≧0.0024 (In the formula, tan δ is the loss tangent 30 minutes after the start of measurement, measured under the conditions of a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, an extension mode, and a measurement time of 30 minutes. S is the negative rate of the tread.)

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