Tire

Abstract

To provide a tire making both excellent wet grip performance and excellent dry grip performance compatible with each other.SOLUTION: A tire comprising a tread having at least one circumferential groove portion is provided, the circumferential groove portion is formed of a groove portion forming rubber composition, and E* (MPa) at the time when the groove portion forming rubber composition is wetted with water, E* (MPa) at the time when the composition is dried, tanδ at the time when the composition is wetted with water, tanδ at the time when the composition is dried, and a groove depth D(mm) of the circumferential groove portion satisfy the following formula (1-1) and / or the following formula (1-2) and the following formula (2): E* at the time when the composition is wetted with water / E* at the time when the composition is dried ≤0.90 (1-1); tanδ at the time when the composition is wetted with water / tanδ at the time when the composition is dried ≥1.10 (1-2); and D / (E* at the time when the composition is wetted with water / E* at the time when the composition is dried)>9.0 (2), wherein E* and tanδ are complex elastic modulus (MPa) and loss tangent at the time when 30 minutes elapse after a measurement is started, which are measured under a condition that 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 D is a groove depth (mm) of the circumferential groove portion.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, awareness of safety has been increasing as a common issue for automobiles, and further improvements in wet grip performance and handling stability are being demanded. Various studies have been conducted to improve wet grip performance, and various inventions of rubber compositions containing silica have been reported (for example, Patent Document 1). Since wet grip performance is significantly affected by the performance of the rubber composition, particularly in the tread portion that comes into contact with the road surface, technical improvements to rubber compositions for tires, such as treads, have been widely studied and put to practical use. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-285524 Summary of the Invention [Problem to be solved by the invention]

[0004] Improvements in rubber compositions for treads using silica have resulted in significant advances in the wet grip performance of tires. However, changes in grip performance when the road surface changes, such as from dry to wet or from wet to dry, remains an important technical issue and there is room for improvement. As described above, conventional technologies have room for improvement in terms of achieving both excellent wet grip performance and excellent dry grip performance. An object of the present disclosure is to solve the above-mentioned problems and to provide a tire that achieves both excellent wet grip performance and excellent dry grip performance. [Means for solving the problem]

[0005] A tire provided with a tread having at least one circumferential groove, wherein the circumferential groove is formed of a groove-forming rubber composition, and the tire satisfies the following formula (1-1) and / or the following formula (1-2) and the following formula (2) with respect to E* (MPa) when wet, E* (MPa) when dry, tanδ when wet, tanδ when dry, and the groove depth D (mm) of the circumferential groove. E* / E* when wet ≤ 0.90 (1-1) tanδ / tanδ when wet ≥ 1.10 (1-2) D / (E* / E* when wet) > 9.0 (2) (In the formula, E* and tanδ are the complex elastic modulus (MPa) and 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 elongation mode, and a measurement time of 30 minutes. D is the circumferential groove depth (mm).)

Effect of the Invention

[0006] According to the present disclosure, since the tire has the above configuration, it is possible to achieve both excellent wet grip performance and dry grip performance.

Brief Description of the Drawings

[0007] [Figure 1] It is a cross-sectional view showing a part of a pneumatic tire. [Diagram 2] It is an enlarged cross-sectional view showing the vicinity of the tread 4 of the tire 2 in FIG. 1.

Mode for Carrying Out the Invention

[0008] The present disclosure relates to a tire having a tread with at least one circumferential groove, the circumferential groove being formed from a groove-forming rubber composition, wherein the wet E* (MPa), dry E* (MPa), wet tan δ and dry tan δ of the groove-forming rubber composition, and the groove depth D (mm) of the circumferential groove satisfy the following formula (1-1) and / or formula (1-2), and the following formula (2), thereby achieving both excellent wet grip performance and dry grip performance. E* when wet / E* when dry≦0.90 (1-1) Tan δ when wet / tan δ when dry≧1.10 (1-2) D / (E* when wet / E* when dry)>9.0 (2) (In the formula, E* and tanδ are the complex modulus of elasticity (MPa) and 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 groove depth (mm) of the circumferential groove portion.)

[0009] The problem (purpose) of the present disclosure is to achieve both excellent wet grip performance and excellent dry grip performance, and the means for solving this problem is to provide a tire having a tread with at least one circumferential groove, wherein the circumferential groove is formed from a groove-forming rubber composition, and the wet E* (MPa), dry E* (MPa), wet tan δ and dry tan δ of the groove-forming rubber composition, and the groove depth D (mm) of the circumferential groove satisfy the formula (1-1) and / or the formula (1-2), and the formula (2). That is, an essential feature of the present disclosure is a tire having a tread with at least one circumferential groove, wherein the circumferential groove is formed from a groove-forming rubber composition, and the wet E* (MPa), dry E* (MPa), wet tan δ and dry tan δ of the groove-forming rubber composition, and the groove depth D (mm) of the circumferential groove satisfy the formula (1-1) and / or the formula (1-2), and the formula (2).

[0010] The reason for obtaining the above effects is not necessarily clear, but it is presumed to be due to the following mechanism. In recent years, it is not uncommon to drive on a road surface where dry and wet road surfaces are mixed due to the influence of local rainy weather. It is difficult for a driver to instantaneously judge and respond to the road surface conditions. Therefore, it is desired to stably exhibit grip performance regardless of whether the road surface is dry or wet. The groove-forming rubber composition has a complex elastic modulus that decreases by 10% or more from when it is dry to when it is water-wetted (Equation (1-1)), and / or a loss tangent that increases by 10% or more (Equation (1-2)). As a result, followability and heat generation properties can be instantaneously obtained on a wet road surface. Therefore, it is considered that, in addition to dry grip performance, excellent grip performance on a wet road surface is also exhibited. Further, the tire of the present disclosure includes a tread having at least one circumferential groove and satisfies the above Equation (2). As the groove depth D of the circumferential groove formed of the groove-forming rubber composition increases, it becomes possible to sufficiently drain the water present between the road surface and the tire on a wet road surface. Therefore, as D increases, by reducing E* / E* when dry at water-wetting and increasing the followability when wetted with water, it is considered that good grip performance can be obtained on both dry and wet road surfaces. As described above, even when driving on a road surface where dry and wet road surfaces are mixed, the state of the composition instantaneously changes and stable grip performance is exhibited. Therefore, it is presumed that the tire can achieve both excellent wet grip performance and dry grip performance.

[0011] In this specification, the complex elastic modulus (E*) and loss tangent (tanδ) of the rubber composition mean E* and tanδ of the vulcanized rubber composition. Further, E* and tanδ are values obtained by performing a viscoelasticity test on the vulcanized rubber composition.

[0012] The rubber composition satisfies the formula (1-1) and / or the formula (1-2), and the complex modulus (E*) and loss tangent (tan δ) change reversibly with water. In this specification, "the complex modulus (E*) and loss tangent (tan δ) change reversibly with water" means that the E* and tan δ of the rubber composition (after vulcanization) reversibly increase or decrease with the presence of water. Note that, for example, when changing from dry to wet to dry, it is sufficient that the E* and tan δ change reversibly. The E* and tan δ do not need to be the same in the previous drying state and the subsequent drying state, or they may be the same in the previous drying state and the subsequent drying state.

[0013] In this specification, E* and tanδ in a dry state refer to the E* and tanδ of a rubber composition in a dry state, and specifically refer to the E* and tanδ of a rubber composition dried by the method described in the examples. In this specification, E* and tanδ when wet with water refer to the E* and tanδ of a rubber composition in a state wet with water, and specifically refer to the E* and tanδ of a rubber composition wet with water by the method described in the examples.

[0014] In this specification, E* and tanδ of a rubber composition are E* and tanδ measured 30 minutes after the start of measurement 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.

[0015] The rubber composition preferably satisfies the following formula (1-1). E* when wet / E* when dry≦0.90 (1-1) (In the formula, E* is the complex modulus (MPa) 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.) E* when wet / E* when dry is preferably 0.85 or less, more preferably 0.80 or less, still more preferably 0.75 or less, and particularly preferably 0.70 or less. The lower limit of E* when wet / E* when dry is not particularly limited, but is preferably 0.10 or more, more preferably 0.20 or more, still more preferably 0.30 or more, and particularly preferably 0.35 or more. When within the above range, the effect can be preferably obtained.

[0016] The rubber composition preferably has an E* when dry of 2.5 MPa or more, more preferably 3.5 MPa or more, still more preferably 4.0 MPa or more, particularly preferably 4.5 MPa or more, and most preferably 5.0 MPa or more. The upper limit of E* when dry is not particularly limited, but is preferably 20.0 MPa or less, more preferably 15.0 MPa or less, still more preferably 13.0 MPa or less, and particularly preferably 12.0 MPa or less. When within the above range, the effect can be preferably obtained.

[0017] The rubber composition preferably satisfies the following formula (1-2). tanδ when wet / tanδ when dry ≧ 1.10 (1-2) (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 elongation mode, and a measurement time of 30 minutes.) tanδ when wet / tanδ when dry is preferably 1.15 or more, more preferably 1.20 or more, still more preferably 1.25 or more, and particularly preferably 1.30 or more. The upper limit of tanδ when wet / tanδ when dry is not particularly limited, but is preferably 1.80 or less, more preferably 1.70 or less, still more preferably 1.65 or less, and particularly preferably 1.60 or less. When within the above range, the effect can be preferably obtained.

[0018] The tanδ of the rubber composition when dry is preferably 0.15 or more, more preferably 0.20 or more, still more preferably 0.25 or more, and particularly preferably 0.30 or more. The upper limit of tanδ when dry is not particularly limited, but is preferably 6.0 or less, more preferably 5.5 or less, still more preferably 5.2 or less, and particularly preferably 5.0 or less. When within the above range, the effects can be preferably obtained.

[0019] The reversible change in E* and change in tanδ of the rubber composition due to water represented by the formula (1-1) and / or the formula (1-2) can be achieved by blending, for example, a modified rubber having at least one selected from the group consisting of carboxylic acids, sulfonic acids, and salts thereof in the molecule with at least one alkali metal salt or alkaline earth metal salt selected from the group consisting of lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, beryllium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, lithium acetate, sodium acetate, potassium acetate, rubidium acetate, cesium acetate, beryllium acetate, magnesium acetate, calcium acetate, strontium acetate, barium acetate, lithium phenoxide, sodium phenoxide, potassium phenoxide, rubidium phenoxide, cesium phenoxide, beryllium diphenoxide, magnesium diphenoxide, calcium diphenoxide, strontium diphenoxide, and barium diphenoxide. Specifically, for example, by combining a modified rubber having at least one selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof, such as carboxylic acid-modified SBR, with an alkali metal salt or alkaline earth metal salt, such as lithium acetate, the rubber composition can achieve the reversible water-induced changes in E* and tan δ represented by the formula (1-1) and / or formula (1-2). This is thought to be because, for example, an anion derived from the carboxylic acid, sulfonic acid, or salt thereof and a cation derived from the alkali metal salt or alkaline earth metal salt form an ionic bond between the modified rubber and the alkali metal salt or alkaline earth metal salt. The ionic bond is 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, and an increase in E* and / or a decrease in tan δ when dry.

[0020] The dry E* can be adjusted by the type and amount of chemicals (especially rubber components, fillers, softeners such as oils) compounded into the rubber composition. For example, the dry E* tends to increase by reducing the amount of softener or increasing the amount of filler.

[0021] The dry tan δ can be adjusted by the type and amount of chemicals (particularly rubber components, fillers, softeners, resins, sulfur, vulcanization accelerators, and silane coupling agents) compounded into the rubber composition. For example, the dry tan δ tends to increase when a softener (e.g., resin) that is poorly compatible with the rubber component is used, when an unmodified rubber is used, when the amount of filler is increased, when oil as a plasticizer is increased, when sulfur is reduced, when vulcanization accelerators are reduced, or when silane coupling agents are reduced.

[0022] Furthermore, the dry E* and tanδ can be adjusted by, for example, the acidic functional group content of the modified rubber or the content of the alkali metal salt or alkaline earth metal salt (in other words, the metal content derived from the alkali metal salt or alkaline earth metal salt). Specifically, increasing the acidic functional group content of the modified rubber or the content of the alkali metal salt or alkaline earth metal salt tends to increase the dry E* and tanδ.

[0023] When wet with water, E* and tanδ can be adjusted by, for example, using a rubber composition in which part or all of the modified rubber and the alkali metal salt or alkaline earth metal salt are crosslinked by an ionic bond, so that E* when wet with water can be decreased and / or tanδ can be increased compared to when dry, and it becomes possible to adjust E* and tanδ when dry and when wet with water. Specifically, by using the modified rubber and the alkali metal salt or alkaline earth metal salt in combination, a rubber composition crosslinked by an ionic bond is obtained, and E* when wet with water can be decreased and / or tanδ can be increased compared to when dry. Further, E* and tanδ when wet with water can be adjusted by the type and amount of chemicals compounded in the rubber composition. For example, by using the same method as the method for adjusting E* and tanδ when dry described above, the same tendency can be obtained for E* and tanδ when wet with water.

[0024] Specifically, after adjusting E* and tanδ when dry within a desired range, by using in combination a modified rubber having at least one selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof in the molecule and the alkali metal salt or alkaline earth metal salt, a reversible change in E* and / or tanδ due to water represented by the above formula (1-1) and / or the above formula (1-2) of the rubber composition can be realized.

[0025] (Rubber component) The rubber composition contains, as a rubber component, carboxylic acid (carboxylic acid group (-COOH)), sulfonic acid (sulfonic acid group (-SO3H)), and salts thereof (carboxylate ion (-COO - ) and / or sulfonate ion (-SO3 -) and preferably contains a modified rubber having at least one selected from the group consisting of salts composed of these counter cations in the molecule. The salt is not particularly limited, and examples include monovalent metal salts such as alkali metal salts (sodium salts, potassium salts, etc.), and divalent metal salts such as alkaline earth metal salts (calcium salts, strontium salts, etc.). Among them, from the viewpoint of obtaining more effects, a carboxylic acid group is preferred, a (meth)acrylic acid group and a maleic acid group are more preferred, and a methacrylic acid group and a maleic acid group are particularly preferred.

[0026] The modified rubber has at least one ionic functional group 1 selected from the group consisting of carboxylic acids, sulfonic acids, and salts thereof in the molecule. The content of the ionic functional group 1 in 100% by mass of the rubber (100% by mass of the rubber having the ionic functional group 1 in the molecule) is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, and still more preferably 1.0% by mass or more. The upper limit is not particularly limited, but preferably 40% by mass or less, and more preferably 35% by mass or less. The content of the ionic functional group 1 can be measured by performing NMR measurement and calculating the content (% by mass) based on the peak corresponding to the ionic functional group 1.

[0027] In the rubber composition, the content of the modified rubber in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 20% by mass or more, still more preferably 40% by mass or more, and particularly preferably 50% by mass or more. The upper limit is not particularly limited, but preferably 90% by mass or less, more preferably 85% by mass or less, still more preferably 80% by mass or less, and particularly preferably 75% by mass or less. When within the above range, the effects can be preferably obtained.

[0028] The rubber that constitutes the skeleton of the modified rubber is preferably composed of at least one monomer selected from the group consisting of styrene, butadiene, and isoprene as a constituent unit from the viewpoint of suitably obtaining the effects. Specific examples of the rubber include isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), and the like. The rubber component may be used alone or in combination of two or more. Among them, from the viewpoint of tire physical properties, SBR, BR, and isoprene rubber are preferable, and SBR and BR are more preferable.

[0029] SBR is not particularly limited. For example, emulsion polymerization styrene butadiene rubber (E-SBR), solution polymerization styrene butadiene rubber (S-SBR), etc. can be used. These may be used alone or in combination of two or more.

[0030] [[ID=;7]] The styrene content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more. Also, the styrene content is preferably 60% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less. When within the above range, the effects tend to be obtained more favorably. In addition, in this specification, the styrene content of SBR is 1 calculated by 1H-NMR measurement.

[0031] The vinyl content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more. The above vinyl content is preferably 75% by mass or less, more preferably 70% by mass or less. When within the above range, the effects tend to be obtained more favorably. The vinyl content (1,2-bonded butadiene unit amount) can be measured by infrared absorption spectrum analysis. [[ID=;20]]

[0032] As SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

[0033] When the rubber composition contains, as the modified rubber, a modified SBR having at least one ionic functional group 1 selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof in the molecule, the content of the modified SBR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 20% by mass or more, even more preferably 40% by mass or more, and particularly preferably 50% by mass or more. There is no particular upper limit, but it is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 75% by mass or less. Within the above range, the effects can be preferably obtained.

[0034] The BR is not particularly limited, and examples thereof include high-cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, and BR synthesized using a rare earth catalyst (rare earth BR). These may be used alone or in combination of two or more. Among these, high-cis BR with a cis content of 90% by mass or more is preferred because it improves wear resistance.

[0035] When the rubber composition contains, as the modified rubber, a modified BR having at least one ionic functional group 1 selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof in the molecule, the content of the modified BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and particularly preferably 20% by mass or more. There is no particular upper limit, but it is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 75% by mass or less. Within the above range, the effects can be preferably obtained.

[0036] Examples of the isoprene rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR, etc. As the NR, for example, those generally used in the rubber industry such as SIR20, RSS#3, TSR20, etc. can be used. The IR is not particularly limited, and for example, those generally used in the rubber industry such as IR2200, etc. can be used. Examples of the modified NR include deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc., examples of the modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc., and examples of the modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. These may be used alone or in combination of two or more.

[0037] When the rubber composition contains, as the modified rubber, a modified isoprene rubber having at least one ionic functional group 1 selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof in the molecule, the content of the modified isoprene rubber in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and particularly preferably 20% by mass or more. The upper limit is not particularly limited, but is preferably 80% by mass or less, more preferably 50% by mass or less, still more preferably 40% by mass or less, and particularly preferably 35% by mass or less. When within the above range, the effects can be preferably obtained.

[0038] Specific examples of the modified rubber include, for example, an emulsion-polymerized styrene-butadiene rubber having methacrylic acid in the molecule, which is one of the preferred embodiments of the present disclosure.

[0039] The rubber composition may contain other rubber components in addition to the modified rubber. As the other rubber components, it is preferable to contain at least one selected from the group consisting of SBR, BR, and isoprene rubber. The SBR, the BR, and the isoprene rubber may be modified rubbers other than the modified rubber or unmodified rubbers, but unmodified SBR, unmodified BR, and unmodified isoprene rubber are preferable, and unmodified BR and unmodified isoprene rubber are more preferable.

[0040] When the rubber composition contains other rubber components in addition to the modified rubber, the content of the other rubber components in 100% by mass of the rubber components is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and particularly preferably 20% by mass or more. The upper limit is not particularly limited, but is preferably 80% by mass or less, more preferably 50% by mass or less, still more preferably 40% by mass or less, and particularly preferably 35% by mass or less. When within the above range, the effects can be preferably obtained. In addition, when using a non-modified isoprene-based rubber or non-modified BR as the other rubber component, the content of the non-modified isoprene-based rubber and the content of the non-modified BR are also preferably within the same range.

[0041] (Alkali metal salt or alkaline earth metal salt) The rubber composition preferably contains at least one alkali metal salt or alkaline earth metal salt selected from the group consisting of lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, beryllium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, lithium acetate, sodium acetate, potassium acetate, rubidium acetate, cesium acetate, beryllium acetate, magnesium acetate, calcium acetate, strontium acetate, barium acetate, lithium phenoxide, sodium phenoxide, potassium phenoxide, rubidium phenoxide, cesium phenoxide, beryllium diphenoxide, magnesium diphenoxide, calcium diphenoxide, strontium diphenoxide, and barium diphenoxide. These alkali metal salts or alkaline earth metal salts may be used alone or in combination of two or more.

[0042] Among them, from the viewpoint of more preferably obtaining the effects, it is more preferable to contain at least one selected from the group consisting of potassium acetate, calcium acetate, sodium acetate, and magnesium acetate, still more preferably to contain at least one selected from the group consisting of potassium acetate, calcium acetate, and sodium acetate, and particularly preferably to contain potassium acetate and / or calcium acetate.

[0043] The reason why the above-mentioned effects are more pronounced when these alkali metal salts or alkaline earth metal salts are used is not entirely clear, but is presumed to be due to the following mechanism. When a modified rubber having a carboxylic acid or the like in its molecule is combined with a specific alkali metal salt or alkaline earth metal salt of the modified rubber, an ionic bond is formed between the carboxylic acid or the like and the metal of the alkali metal salt or alkaline earth metal salt, which exhibits water responsiveness. It is believed that the specific alkali metal salt or alkaline earth metal salt in particular has high reinforcing properties and water responsiveness. Furthermore, since the specific alkali metal salt or alkaline earth metal salt is easily dissociated by water, it is believed that the water responsiveness is further improved. Therefore, it is presumed that a rubber composition using the specific alkali metal salt or alkaline earth metal salt can achieve both better wet grip performance and better dry grip performance.

[0044] In the rubber composition, the content of the alkali metal salt or alkaline earth metal salt (total amount of the alkali metal salt or alkaline earth metal salt) 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, still more preferably 2.2 parts by mass or more, particularly preferably 5.0 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 20.0 parts by mass or less, more preferably 17.0 parts by mass or less, even more preferably 12.0 parts by mass or less, particularly preferably 10.0 parts by mass or less. Within the above ranges, the effects tend to be more favorably obtained.

[0045] The apparent specific gravity of the alkali metal salt or alkaline earth metal salt 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, better effects tend to be obtained. The apparent specific gravity of the alkali metal salt or alkaline earth metal salt is a value obtained by measuring 30 ml of the apparent volume into a 50 ml measuring cylinder and calculating from the mass.

[0046] The d50 of the alkali metal salt or alkaline earth metal salt 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. The d50 of the alkali metal salt or alkaline earth metal salt is the particle size at 50% of the integrated value in a mass-based particle size distribution curve obtained by a laser diffraction scattering method.

[0047] The nitrogen adsorption specific surface area (N2SA) of the alkali metal salt or alkaline earth metal salt 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 Within the above range, there is a tendency for the effect to be better obtained. The N2SA of the alkali metal salt or alkaline earth metal salt is a value measured by the BET method in accordance with JIS Z8830:2013.

[0048] Commercially available products of the alkali metal salts or alkaline earth metal salts include those from 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., etc.

[0049] (filler) The rubber composition preferably contains a filler. Examples of fillers that can be used include inorganic fillers such as silica, carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica; and poorly dispersible fillers, all of which are well known in the rubber field. Among these, silica and carbon black are preferred.

[0050] The silica is not particularly limited, and examples thereof include dry-process silica (anhydrous silica), wet-process silica (hydrous silica), etc. Among these, wet-process silica is preferred because it has many silanol groups.

[0051] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 30 m 2 / g or more, more preferably 100 m 2 / g or more, still more preferably 125 m 2 / g or more. Also, the N2SA of the silica is preferably 300 m 2 / g or less, more preferably 250 m 2 / g or less, still more preferably 200 m 2 / g or less. When it is within the above range, the effect can be preferably obtained. Note that the N2SA of the silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0052] As the silica, for example, products of Degussa, Rhodia, Tosoh Silica Corporation, Solvay Japan K.K., Tokuyama Corporation, etc. can be used.

[0053] In the rubber composition, the content of the silica is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, still more preferably 45 parts by mass or more, particularly preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit of the content is not particularly limited, but is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, still more preferably 90 parts by mass or less. When it is within the above range, the effect can be preferably obtained.

[0054] When the rubber composition contains silica, it is preferably further contains a silane coupling agent. The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N Examples of such compounds 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 and 2-mercaptoethyltriethoxysilane; 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 that can be used include, for example, products 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.

[0055] In the rubber composition, the content of the silane coupling agent is preferably 1.0 part by mass or more, more preferably 5.0 part by mass or more, still more preferably 8.0 part by mass or more, based on 100 parts by mass of silica. Also, the content is preferably 20.0 parts by mass or less, more preferably 15.0 parts by mass or less, still more preferably 10.0 parts by mass or less. When within the above range, the effects can be preferably obtained.

[0056] Examples of the usable carbon black include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. These may be used alone or in combination of two or more. As commercially available products, for example, products of Asahi Carbon Co., Ltd., Cabot Japan Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nippon Chemical Carbon Co., Ltd., Columbian Carbon Company, etc. can be used.

[0057] The nitrogen adsorption specific surface area (N2SA) of the carbon black is preferably 50 m 2 / g or more, more preferably 80 m 2 / g or more, still more preferably 100 m 2 / g or more. Also, the above N2SA is preferably 200 m 2 / g or less, more preferably 150 m 2 / g or less, still more preferably 130 m 2 / g or less. When within the above range, the effects tend to be obtained more favorably. Note that the nitrogen adsorption specific surface area of the carbon black is determined according to JIS K6217-2:2001.

[0058] In the rubber composition, the content of the carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, still more preferably 10 parts by mass or less. When within the above range, the effects tend to be obtained more favorably.

[0059] (Plasticizer) The rubber composition preferably contains a plasticizer, which is a material that imparts plasticity to the rubber component, and examples of the plasticizer include a liquid plasticizer (a plasticizer that is in a liquid state at room temperature (25°C)) and a resin (a resin that is in a solid state at room temperature (25°C)).

[0060] In the rubber composition, the content of the plasticizer (total amount of plasticizer) is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 25 parts by mass or more, and particularly preferably 30 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 90 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0061] Liquid plasticizers (plasticizers that are liquid at room temperature (25°C)) that can be used in the 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.

[0062] In the rubber composition, the content of the liquid plasticizer is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 8 parts by mass or more, and particularly 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 30 parts by mass or less, and even more preferably 20 parts by mass or less. Within the above range, the effect tends to be more favorably obtained. Note that the content of the liquid plasticizer also includes the amount of oil contained in the oil-extended rubber. A similar range is also preferred for the content of the oil.

[0063] Examples of the oil include process oil, vegetable oil, or a mixture thereof. As the process oil, for example, paraffinic process oil, aromatic process oil, naphthenic process oil, etc. can be used. Examples of the vegetable oil include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, etc. As commercially available products, products of Idemitsu Kosan Co., Ltd., Sankyo Oil & Chemical Industry Co., Ltd., Japan Energy Corporation, Oleoso, H&R, Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kogyo Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used. Among them, process oil (such as paraffinic process oil, aromatic process oil, naphthenic process oil, etc.) and vegetable oil are preferred.

[0064] Examples of the liquid resin 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 monomer resins), phenol resins, olefin resins, polyurethane resins, acrylic resins, etc. Also, hydrogenated products thereof can be used.

[0065] Examples of the liquid diene polymer include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer), etc. which are in a liquid state at 25°C. These may have their terminals or main chains modified with polar groups. Also, hydrogenated products thereof can be used.

[0066] Incidentally, the reversible E* change and tanδ change due to water represented by the formula (1-1) and / or the formula (1-2) of the rubber composition can also be achieved by using, instead of using the modified rubber and the alkali metal salt or alkaline earth metal salt in combination, a modified liquid diene polymer having at least one selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof in the molecule, and the alkali metal salt or alkaline earth metal salt in combination. By using the modified liquid diene polymer and the alkali metal salt or alkaline earth metal salt in combination, the same effect can be obtained by the same mechanism as in the case of using the modified rubber and the alkali metal salt or alkaline earth metal salt in combination. The modification of the modified liquid diene polymer is the same as the modification of the modified rubber.

[0067] The modified liquid diene polymer has at least one ionic functional group selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof in the molecule, and the number of functional groups per molecule is preferably 1 to 100, more preferably 2 to 50, and still more preferably 5 to 25. Incidentally, the number of functional groups per molecule can be calculated based on the peak corresponding to the functional group by performing infrared absorption spectrum analysis.

[0068] The number average molecular weight of the modified liquid diene polymer is preferably 1000 to 50000, more preferably 1500 to 40000, and still more preferably 2000 to 35000. Incidentally, the number average molecular weight can be measured by gel permeation chromatography (GPC) by conversion using a calibration curve using standard polystyrene.

[0069] When the modified liquid diene polymer is used, the modified rubber may not be used as the rubber component, but a rubber component other than the modified rubber may be used, and the modified liquid diene polymer may be used in combination with the alkali metal salt or alkaline earth metal salt. Alternatively, the modified rubber may be used as the rubber component, and the modified liquid diene polymer may be used in combination with the alkali metal salt or alkaline earth metal salt.

[0070] As the modified liquid diene polymer, from the viewpoint of obtaining the desired effect, a modified liquid IR having at least one selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof in the molecule is preferred, and a liquid IR having methacrylic acid or maleic acid in the molecule is more preferred.

[0071] When the rubber composition contains the modified liquid diene polymer, the content of the modified liquid diene polymer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 35 parts by mass or less, and particularly preferably 30 parts by mass or less. Within the above range, the effects can be suitably obtained.

[0072] Examples of liquid farnesene polymers include liquid farnesene polymers and liquid farnesene-butadiene copolymers that are liquid at 25°C. These may be modified at the ends or main chains with polar groups. Hydrogenated versions of these polymers may also be used.

[0073] Examples of the resins (resins in a solid state at room temperature (25°C)) that can be used in the rubber composition include aromatic vinyl polymers, coumarone-indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, and acrylic resins that are solid at room temperature (25°C). 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.

[0074] In the rubber composition, the content of the resin is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 60 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably 30 parts by mass or less. When it is within the above range, the effect tends to be obtained more favorably.

[0075] The softening point of the resin is preferably 50°C or higher, more preferably 55°C or higher, and still more preferably 60°C or higher. The upper limit is preferably 160°C or lower, more preferably 150°C or lower, and still more preferably 145°C or lower. When it is within the above range, the effect tends to be obtained more favorably. The softening point of the resin is measured with a ring-and-ball softening point measuring device according to the softening point defined in JIS K6220-1:2001, and is the temperature at which the ball drops.

[0076] The aromatic vinyl polymer is a polymer containing an aromatic vinyl monomer as a constituent unit. For example, resins obtained by polymerizing α-methylstyrene and / or styrene can be mentioned. Specifically, homopolymers of styrene (styrene resins), homopolymers of α-methylstyrene (α-methylstyrene resins), copolymers of α-methylstyrene and styrene, copolymers of styrene and other monomers, etc. can be mentioned.

[0077] The coumarone-indene resin is a resin containing coumarone and indene as main monomer components constituting the resin skeleton (main chain). Examples of monomer components other than coumarone and indene contained in the skeleton include styrene, α-methylstyrene, methyl indene, vinyl toluene, etc.

[0078] The coumarone resin is a resin containing coumarone as a main monomer component constituting the resin skeleton (main chain).

[0079] The indene resin is a resin containing indene as a main monomer component constituting the resin skeleton (main chain).

[0080] 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. Among these, those obtained by reacting with an acid catalyst (such as novolac phenolic resin) are preferred.

[0081] Examples of the rosin resin include rosin-based resins such as natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

[0082] 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.

[0083] 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, phenolic compounds include phenol and bisphenol A, and aromatic compounds include styrene compounds (styrene, α-methylstyrene, etc.).

[0084] The acrylic resin is a polymer containing acrylic monomers as constituent units. For example, styrene acrylic resins such as styrene acrylic resins obtained by copolymerizing an aromatic vinyl monomer component and an acrylic monomer component having a carboxyl group can be mentioned. Among them, a solventless carboxyl group-containing styrene acrylic resin can be preferably used.

[0085] As the plasticizer, for example, products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, Nippon Paint Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., Tago Chemical Industry Co., Ltd., etc. can be used.

[0086] (Other components) From the viewpoints of crack resistance, ozone resistance, etc., it is preferable that the rubber composition contains an antioxidant.

[0087] The antioxidant is not particularly limited, but examples thereof 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, N,N'-di-2-naphthyl-p-phenylenediamine, and the like. Examples of suitable antioxidants include p-phenylenediamine antioxidants such as amines; 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 antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine antioxidants and quinoline antioxidants are preferred, with polymers of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline being more preferred. Commercially available products include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and Flexis.

[0088] In the rubber composition, the content of the antioxidant is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 7.0 parts by mass or less, more preferably 4.0 parts by mass or less.

[0089] The rubber composition may contain stearic acid. The content of stearic acid in the rubber composition is preferably 0.5 to 10 parts by mass or more, and more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0090] As the stearic acid, conventionally known products can be used, for example, products available from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc.

[0091] The rubber composition may contain zinc oxide. In the rubber composition, the content of zinc oxide is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, based on 100 parts by mass of the rubber component.

[0092] As the zinc oxide, conventionally known ones can be used. For example, products of Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Sho-Doh Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0093] The rubber composition may be compounded with wax. In the rubber composition, the content of wax is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, based on 100 parts by mass of the rubber component.

[0094] The wax is not particularly limited, and examples include petroleum waxes and natural waxes. Also, synthetic waxes obtained by purifying or chemically treating a plurality of waxes can be used. These waxes may be used alone or in combination of two or more.

[0095] Examples of petroleum waxes include paraffin wax and microcrystalline wax. Natural waxes are not particularly limited as long as they are waxes derived from non-petroleum resources. For example, plant waxes such as candelilla wax, carnauba wax, wood wax, rice wax, and jojoba wax; animal waxes such as beeswax, lanolin, and spermaceti wax; mineral waxes such as ozokerite, ceresin, and petrolactam; and purified products thereof, etc. can be mentioned. As commercially available products, for example, products of Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. can be used.

[0096] The rubber composition may be compounded with sulfur in terms of forming appropriate crosslinking chains in the polymer chain and imparting a good balance of the above performance.

[0097] In the rubber composition, the sulfur content is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and even more preferably 0.7 part by mass or more, per 100 parts by mass of the rubber component, and is preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less.

[0098] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. 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., Hosoi Chemical Industry Co., Ltd., etc. These may be used alone or in combination of two or more.

[0099] The rubber composition may contain a vulcanization accelerator. In the rubber composition, the content of the vulcanization accelerator is usually 0.3 to 10 parts by mass, and preferably 0.5 to 7 parts by mass, per 100 parts by mass of the rubber component.

[0100] The type of the vulcanization accelerator is not particularly limited, and those commonly used can be used. Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyldisulfide, and N-cyclohexyl-2-benzothiazylsulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolesulfenamide, N-t-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine, and orthotolylbiguanidine. These can be used alone or in combination of two or more. Among them, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred.

[0101] Among the vulcanization accelerators, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred. The content of the sulfenamide-based vulcanization accelerator is not particularly limited, but is preferably 0.3 to 4.0 parts by mass, preferably 0.5 to 2.5 parts by mass, and more preferably 0.7 to 1.6 parts by mass with respect to 100 parts by mass of the rubber component. The content of the guanidine-based vulcanization accelerator is not particularly limited, but is preferably 0.5 to 5.0 parts by mass, preferably 0.8 to 3.0 parts by mass, and more preferably 1.0 to 2.3 parts by mass with respect to 100 parts by mass of the rubber component.

[0102] In addition to the above components, the rubber composition may be appropriately blended with ordinary additives used for their use according to the application fields such as mold release agents and pigments.

[0103] As a method for manufacturing the rubber composition, a known method can be used. For example, it can be manufactured by kneading each component using a rubber kneading device such as an open roll or a Banbury mixer, and crosslinking if necessary. The kneading conditions are such that the kneading temperature is usually 50 to 200°C, preferably 80 to 190°C, and the kneading time is usually 30 seconds to 30 minutes, preferably 1 minute to 30 minutes.

[0104] The tire of the present disclosure includes a tread having at least one circumferential groove portion, and the circumferential groove portion is formed of the groove-forming rubber composition.

[0105] Hereinafter, the present disclosure will be described in detail based on an example of a preferred embodiment with reference to the drawings as appropriate, but it is not limited to this example.

[0106] FIG. 1 shows a pneumatic tire 2. In FIG. 1, the vertical direction is the radial direction of the tire 2, the left-right direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 1, the dashed-dotted line CL represents the equatorial plane of the tire 2. The shape of this tire 2 is symmetric with respect to the equatorial plane except for the tread pattern.

[0107] This tire 2 includes a tread 4, a pair of sidewalls 6, a pair of wings 8, a pair of clinches 10, a pair of beads 12, a carcass 14, a belt 16, a band 18, an inner liner 20, and a pair of chafers 22. This tire 2 is a tubeless type. This tire 2 is mounted on a passenger car.

[0108] The tread 4 has a radially outwardly convex shape. The tread 4 forms a tread surface 24 that contacts the road surface. The tread 4 has circumferential grooves 26 engraved therein. The circumferential grooves 26 are grooves provided along the circumferential direction of the tire. The circumferential grooves 26 may be zigzag, curved, or straight as long as they communicate in the circumferential direction. The tread pattern is formed by these circumferential grooves 26. The tread 4 has a base layer 28 and a cap layer 30. The cap layer 30 is located radially outside the base layer 28. The cap layer 30 is laminated on the base layer 28.

[0109] In addition, in FIG. 1, an example of the two-layer structure tread 4 composed of the cap layer 30 and the base layer 28 is shown, but a single-layer structure tread 4 or a tread 4 having a structure of three or more layers may also be used.

[0110] In the present disclosure, among the rubber layers (layers of crosslinked rubber compositions) constituting the tread 4, at least one circumferential groove may be formed of the groove-forming rubber composition, but it is preferable that all the circumferential grooves are formed of the groove-forming rubber composition, and it is more preferable that at least the outermost surface layer among the rubber layers constituting the tread 4 is made of the groove-forming rubber composition. Specifically, in the case of a single-layer structure tread, it is the single-layer structure tread; in the case of a two-layer structure tread, it is the cap layer of the two-layer structure tread; and in the case of a tread having a structure of three or more layers, it is desirable that the cap layer (the outermost surface layer) is composed of the rubber composition.

[0111] FIG. 2 is an enlarged cross-sectional view showing the vicinity of the tread 4 of the tire 2 in FIG. 1. In FIG. 2, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2.

[0112] In the tire 2 shown in the enlarged cross-sectional view of FIG. 2, the groove depth D of the circumferential groove portion 26 is preferably 13.0 mm or less, more preferably 12.0 mm or less, still more preferably 11.5 mm or less, and is preferably 3.5 mm or more, more preferably 6.0 mm or more, still more preferably 8.0 mm or more. When within the above range, the effect tends to be obtained more favorably.

[0113] In the present specification, the groove depth of the circumferential groove portion 26 is measured along the normal line of the plane formed by extending the plane forming the ground contact surface of the tread outermost surface, and means the distance from the plane formed by extending the plane forming the ground contact surface to the deepest groove bottom. In FIG. 2, the groove depth of the circumferential groove portion 26 means the length of D.

[0114] In the tire 2 of FIG. 1, the groove depth D (mm) of the circumferential groove portion 26 and E* / E* when wet / E* when dry satisfy the following formula (2). D / (E* / E* when wet / E* when dry)> 9.0 (2) (In the formula, E* is the complex elastic modulus (MPa) 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 elongation mode, and a measurement time of 30 minutes. D is the groove depth (mm) of the circumferential groove portion 26.) D / (E* / E* when wet / E* when dry) is preferably 9.2 or more, more preferably 9.5 or more, still more preferably 10.0 or more, particularly preferably 11.0 or more. The upper limit is not particularly limited, but is preferably 16.0 or less, more preferably 15.0 or less, still more preferably 14.0 or less, particularly preferably 13.0 or less. When within the above range, the effect is preferably obtained.

[0115] In the tire 2 of FIG. 1, each sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. The radially outer portion of this sidewall 6 is joined to the tread 4. The radially inner portion of this sidewall 6 is joined to the clinch 10.

[0116] Each wing 8 is located between the tread 4 and the sidewall 6. The wing 8 is joined to each of the tread 4 and the sidewall 6.

[0117] Each clinch 10 is located substantially radially inward of the sidewall 6. The clinch 10 is located axially outside the bead 12 and the carcass 14.

[0118] Each bead 12 is located axially inside the clinch 10. The bead 12 includes a core 32 and an apex 34 extending radially outward from the core 32. The core 32 is ring-shaped and includes a wound non-stretchable wire or the like. The apex 34 tapers radially outward.

[0119] The carcass 14 includes a carcass ply 36. In this tire 2, the carcass 14 consists of one carcass ply 36, but it may be composed of two or more plies.

[0120] In this tire 2, the carcass ply 36 is stretched between the beads 12 on both sides and is along the tread 4 and the sidewall 6. The carcass ply 36 is folded back from the axially inner side to the outer side around each core 32. By this folding, a main portion 36a and a pair of folded-back portions 36b are formed in the carcass ply 36. That is, the carcass ply 36 includes the main portion 36a and the pair of folded-back portions 36b.

[0121] Although not shown, examples of the carcass ply 36 include those composed of a large number of parallel cords and topping rubber. This carcass 14 preferably has a radial structure.

[0122] The belt 16 is located radially inside the tread 4. The belt 16 is laminated with the carcass 14. The belt 16 consists of an inner layer 38 and an outer layer 40.

[0123] Although not shown, each of the inner layer 38 and the outer layer 40 may be composed of a number of parallel cords and topping rubber or the like. Each cord is inclined, for example, with respect to the equatorial plane. The inclination direction of the cords of the inner layer 38 with respect to the equatorial plane is opposite to the inclination direction of the cords of the outer layer 40 with respect to the equatorial plane.

[0124] The band 18 is located radially outside the belt 16. In the axial direction, the band 18 has the same width as the width of the belt 16. This band 18 may have a width larger than the width of this belt 16.

[0125] Although not shown, the band 18 may be composed of a cord and topping rubber or the like. The cord is wound spirally, for example.

[0126] The belt 16 and the band 18 constitute a reinforcing layer. The reinforcing layer may be constituted only by the belt 16.

[0127] The inner liner 20 is located inside the carcass 14. The inner liner 20 is joined to the inner surface of the carcass 14.

[0128] Each chafer 22 is located in the vicinity of the bead 12. In this embodiment, the chafer 22 may be composed of a cloth and rubber impregnated in the cloth or the like. This chafer 22 may be integrated with the clinch 10.

[0129] As shown in FIG. 1, a plurality of, specifically, three circumferential groove portions 26 are engraved in the tread 4 of the tire 2. These circumferential groove portions 26 are arranged at intervals in the axial direction. By engraving three circumferential groove portions 26 in this tread 4, four ribs 44 extending in the circumferential direction are formed. That is, the circumferential groove portion 26 is between the ribs 44.

[0130] Each circumferential groove portion 26 extends in the circumferential direction. The circumferential groove portions 26 are continuous without interruption in the circumferential direction.

[0131] In the manufacture of the tire 2, a plurality of rubber members are assembled to obtain a local cover (unvulcanized tire 2). This local cover is put into a mold. The outer surface of the local cover abuts against the cavity surface of the mold. The inner surface of the local cover abuts against a bladder or a core. The local cover is pressurized and heated in the mold. Due to the pressurization and heating, the polymer composition of the local cover flows. Due to the heating, the rubber undergoes a crosslinking reaction to obtain the tire 2. By using a mold having a male and female die pattern on its cavity surface, an uneven pattern is formed on the tire 2.

[0132] Examples of the tire 2 include pneumatic tires and non-pneumatic tires. Among them, pneumatic tires are preferred. For example, it can be suitably used as a summer tire (summer tire), a winter tire (such as a studless tire, a snow tire, a stud tire, etc.). The tire can be used for passenger car tires, large passenger car tires, large SUV tires, heavy load tires such as trucks and buses, light truck tires, two-wheeled vehicle tires, race tires (high-performance tires), etc.

Example

[0133] Hereinafter, examples (examples) considered to be preferable in implementation are shown, but the scope of the present disclosure is not limited to the examples.

[0134] Various chemicals used in the examples and comparative examples will be described collectively. Carboxylic acid-modified SBR: Synthesized according to the following Production Example 1 (content of carboxylic acid group: 5% by mass, styrene content: 23% by mass, butadiene content: 72% by mass) Carboxylic acid-modified BR: Synthesized according to the following Production Example 2 (content of carboxylic acid group: 5% by mass, butadiene content: 95% by mass) NR: TSR20 SBR: Nipol 1502 (E-SBR) manufactured by ZEON Corporation BR: BR730 manufactured by JSR (high cis - polybutadiene, cis content: 96% by mass) Maleic acid liquid IR: LIR - 410 manufactured by Kuraray Co., Ltd. (number of functional groups per molecule: 10, number average molecular weight: 30000) Carbon black: Diablack I manufactured by Mitsubishi Chemical Corporation (N220, N2SA: 114 m 2 / g, DBP: 114 ml / 100 g) Silica: Ultrasil VN3 manufactured by Evonik Degussa GmbH (N2SA: 175 m 2 / g) Stearic acid: Stearic acid "Tsubaki" manufactured by NOF Corporation Potassium acetate: Potassium acetate manufactured by Fujifilm Wako Pure Chemical Corporation Calcium acetate: Calcium acetate manufactured by Fujifilm Wako Pure Chemical Corporation Zinc oxide: Zinc white No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Oil: VIVATEC 400 / 500 (TDAE oil) manufactured by H&R Silane coupling agent: Si69 (bis(3 - triethoxysilylpropyl)tetrasulfide) manufactured by EVONIK - DEGUSSA Resin: SYLVARES SA85 manufactured by Arizona chemical company (copolymer of α - methylstyrene and styrene, Tg: 43°C, softening point: 85°C) Antioxidant: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd. (antioxidant, N-(1,3 - dimethylbutyl)-N’-phenyl - p - phenylenediamine) Sulfur: Powder sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator DPG: Nocceler D (1,3 - diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator NS: Nocceler NS (N - tert - butyl - 2 - benzothiazylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0135] <Production Example 1: Synthesis of Carboxylic Acid - Modified SBR> (Preparation of latex) Charge 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 regulator into a pressure reactor equipped with a stirrer. Set the reactor temperature to 5°C, and add an aqueous solution in which 1 g of 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 catalyst are dissolved to the reactor to initiate polymerization. Five hours after the start of polymerization, add 2 g of polymerization terminator to stop the reaction and obtain latex. (Preparation of Rubber) Remove unreacted monomers from the latex by steam distillation. Then, add the latex to alcohol and coagulate while adjusting the pH to 3 - 5 with a saturated aqueous sodium chloride solution or formic acid to obtain a crumb-like polymer. Dry the polymer in a vacuum dryer at 40°C to obtain a solid rubber (emulsion polymerization rubber).

[0136] (Production Example 2: Synthesis of Carboxylic Acid-Modified BR) (Preparation of Latex) Charge 2000 g of distilled water, 45 g of emulsifier (1), 1.5 g of emulsifier (2), 8 g of electrolyte, 50 g of methacrylic acid, 950 g of butadiene, and 2 g of molecular weight regulator into a pressure reactor equipped with a stirrer. Set the reactor temperature to 5°C, and add an aqueous solution in which 1 g of 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 catalyst are dissolved to the reactor to initiate polymerization. Five hours after the start of polymerization, add 2 g of polymerization terminator to stop the reaction and obtain latex. (Preparation of Rubber) Remove unreacted monomers from the latex by steam distillation. Then, add the latex to alcohol and coagulate while adjusting the pH to 3 - 5 with a saturated aqueous sodium chloride solution or formic acid to obtain a crumb-like polymer. Dry the polymer in a vacuum dryer at 40°C to obtain a solid rubber (emulsion polymerization rubber).

[0137] The materials used in Production Examples 1 and 2 are as follows. Emulsifier (1): Rosin soap manufactured by Harima Kasei Co., Ltd. Emulsifier (2): Fatty acid soap manufactured by Fujifilm Wako Pure Chemical Corporation Electrolyte: Sodium phosphate manufactured by FUJIFILM Wako Pure Chemical Corporation Styrene: Styrene manufactured by FUJIFILM Wako Pure Chemical Corporation Methacrylic acid: Methacrylic acid manufactured by FUJIFILM Wako Pure Chemical Corporation Butadiene: 1,3-Butadiene manufactured by Takachiho Chemical Industry Co., Ltd. Molecular weight regulator: tert-Dodecyl mercaptan manufactured by FUJIFILM Wako Pure Chemical Corporation Radical initiator: Paramethane hydroperoxide manufactured by NOF Corporation SFS: Sodium formaldehyde sulfoxylate manufactured by FUJIFILM Wako Pure Chemical Corporation EDTA: Sodium ethylenediaminetetraacetate manufactured by FUJIFILM Wako Pure Chemical Corporation Catalyst: Ferric sulfate manufactured by FUJIFILM Wako Pure Chemical Corporation Polymerization terminator: N,N'-Dimethyldithiocarbamate manufactured by FUJIFILM Wako Pure Chemical Corporation Alcohol: Methanol and ethanol manufactured by Kanto Chemical Co., Inc. Formic acid: Formic acid manufactured by Kanto Chemical Co., Inc. Sodium chloride: Sodium chloride manufactured by FUJIFILM Wako Pure Chemical Corporation

[0138] <NMR measurement> 1 Using 1H-NMR, calculate the content of carboxylic acid groups in the modified rubber.

[0139] (Examples and Comparative Examples) According to the compounding formulations and groove depth D shown in each table, using a 16L Banbury mixer manufactured by Kobe Steel, Ltd., knead the chemicals other than sulfur and vulcanization accelerators at 160°C for 4 minutes to obtain a kneaded product. Next, add sulfur and vulcanization accelerators to the obtained kneaded product, and knead it at 80°C for 4 minutes using an open roll to obtain an unvulcanized rubber composition. Mold the unvulcanized rubber composition into the shape of a tread, laminate it with other tire members on a tire molding machine to form an unvulcanized tire, and then vulcanize it at 170°C for 12 minutes to manufacture a test tire (size: 195 / 65R15).

[0140] Test tires obtained using compositions whose formulations were changed according to each table were examined, and the results calculated based on the following physical property measurement methods and evaluation methods are shown in each table. The reference comparative example in Table 1 is Comparative Example 1-1, and the reference comparative example in Table 2 is Comparative Example 2-1.

[0141] <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 and E* of the tread rubber were measured using a TA Instruments RSA series 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 measured value obtained 30 minutes after the start of measurement. The thickness direction of the sample is the radial direction of the tire.

[0142] <E* and tanδ when dry> The viscoelasticity measurement sample (length 40 mm × width 3 mm × thickness 0.5 mm) is dried at room temperature and normal pressure until it reaches a constant weight. The complex modulus E* and loss tangent tanδ of the dried vulcanized rubber composition (rubber piece) are measured using the viscoelasticity test method described above, and these are defined as E* and tanδ at the dry state.

[0143] <E* and tanδ when wet> Using the RSA immersion measurement jig, viscoelasticity is measured in water using the above viscoelasticity test method to determine E* and tanδ when wet with water. The water temperature is set to 30°C.

[0144] <Wet grip performance> Each test tire is mounted on all wheels of a vehicle (domestic FF 2000cc) and the braking distance from an initial speed of 100 km / h on a wet asphalt road is measured. The braking distance of the reference comparative example is set to 100, and each compound is expressed as an index. The higher the index, the better the wet grip performance.

[0145] <Dry grip performance> Each test tire is mounted on all wheels of a vehicle (domestic FF2000cc), and the braking distance from an initial speed of 100 km / h is determined on a dry asphalt road surface. Taking the braking distance of the reference comparative example as 100, each formulation is expressed as an index. The larger the index, the better the dry grip performance.

[0146]

Table 1

[0147]

Table 2

[0148] As described above, the present disclosure (1) is a tire provided with a tread having at least one circumferential groove portion, wherein the circumferential groove portion is formed of a groove-forming rubber composition, and the E* (MPa) when the groove-forming rubber composition is wet, the E* (MPa) when dry, the tanδ when wet, the tanδ when dry, and the groove depth D (mm) of the circumferential groove portion satisfy the following formula (1-1) and / or the following formula (1-2) and the following formula (2). E* / E* when dry ≤ 0.90 (1-1) tanδ / tanδ when dry ≥ 1.10 (1-2) D / (E* / E* when dry) > 9.0 (2) (In the formula, E* and tanδ are the complex elastic modulus (MPa) and 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 elongation mode, and a measurement time of 30 minutes. D is the circumferential groove depth (mm).)

[0149] The present disclosure (2) is the tire according to the present disclosure (1), wherein the groove-forming rubber composition satisfies the following formula. E* / E* when dry ≤ 0.85

[0150] This disclosure (3) is a tire according to disclosure (1) or (2) of the present disclosure, wherein the groove-forming rubber composition satisfies the following formula. tanδ at water-wet state / tanδ at dry state ≥ 1.15

[0151] This disclosure (4) is a tire according to any one of disclosures (1) to (3) of the present disclosure, wherein the groove-forming rubber composition contains a modified rubber having at least one selected from the group consisting of carboxylic acids, sulfonic acids, and salts thereof in the molecule, and at least one alkali metal salt or alkaline earth metal salt selected from the group consisting of lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, beryllium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, lithium acetate, sodium acetate, potassium acetate, rubidium acetate, cesium acetate, beryllium acetate, magnesium acetate, calcium acetate, strontium acetate, barium acetate, lithium phenoxide, sodium phenoxide, potassium phenoxide, rubidium phenoxide, cesium phenoxide, beryllium diphenoxide, magnesium diphenoxide, calcium diphenoxide, strontium diphenoxide, and barium diphenoxide.

[0152] This disclosure (5) is a tire according to disclosure (4) of the present disclosure, wherein the modified rubber having at least one selected from the group consisting of carboxylic acids, sulfonic acids, and salts thereof in the molecule is an emulsion-polymerized styrene-butadiene rubber having methacrylic acid in the molecule.

[0153] The present disclosure (6) is a tire according to any one of the present disclosures (1) to (3), wherein the groove-forming rubber composition comprises a modified liquid diene-based polymer having in its molecule at least one selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof, and at least one alkali metal salt or alkaline earth metal salt selected from the group consisting of lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, beryllium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, lithium acetate, sodium acetate, potassium acetate, rubidium acetate, cesium acetate, beryllium acetate, magnesium acetate, calcium acetate, strontium acetate, barium acetate, lithium phenoxide, sodium phenoxide, potassium phenoxide, rubidium phenoxide, cesium phenoxide, beryllium diphenoxide, magnesium diphenoxide, calcium diphenoxide, strontium diphenoxide, and barium diphenoxide.

[0154] The present disclosure (7) is the tire according to the present disclosure (6), wherein the modified liquid diene-based polymer having at least one selected from the group consisting of carboxylic acid, sulfonic acid, and salts thereof in the molecule is a liquid isoprene polymer having methacrylic acid or maleic acid in the molecule. [Explanation of symbols]

[0155] 2. Pneumatic tires 4 Tread 6 Sidewall 8 Wing 10 Clinch 12 beads 14 Carcass 16 Belt 18 bands 20 Inner liner 22 Chafer 24 Tread surface 26 Circumferential groove 27 Groove bottom 28 base layer 30 cap layers 32 cores 34 Apex 36 Carcass Ply 36a Main Part 36b Folded-back Part 38 Inner Layer 40 Outer Layer 44 Rib Equatorial Plane of CL Tire 2 D Groove Depth of Circumferential Groove Portion

Claims

1. A tire comprising a tread having at least one circumferential groove, wherein the circumferential groove is formed of a groove-forming rubber composition, and the tire satisfies the following formula (1-1) and / or the following formula (1-2), and the following formula (2), with respect to E* (MPa) when wet, E* (MPa) when dry, tanδ when wet, tanδ when dry, and the groove depth D (mm) of the circumferential groove: E* when wet / E* when dry ≤ 0.90 (1-1) tanδ when wet / tanδ when dry ≥ 1.10 (1-2) D / (E* when wet / E* when dry) > 9.0 (2) (In the formula, E* and tanδ are the complex elastic modulus (MPa) and 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 elongation mode, and a measurement time of 30 minutes. D is the circumferential groove depth (mm).)

2. The tire according to claim 1, wherein the groove-forming rubber composition satisfies the following formula: E* when wet / E* when dry ≤ 0.85

3. The tire according to claim 1 or 2, wherein the groove-forming rubber composition satisfies the following formula: tanδ when wet / tanδ when dry ≥ 1.15

4. The groove-forming rubber composition contains at least one modified rubber having at least one selected from the group consisting of carboxylic acids, sulfonic acids, and salts thereof in the molecule, and at least one alkali metal salt or alkaline earth metal salt selected from the group consisting of lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, beryllium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, lithium acetate, sodium acetate, potassium acetate, rubidium acetate, cesium acetate, beryllium acetate, magnesium acetate, calcium acetate, strontium acetate, barium acetate, lithium phenoxide, sodium phenoxide, potassium phenoxide, rubidium phenoxide, cesium phenoxide, beryllium diphenoxide, magnesium diphenoxide, calcium diphenoxide, strontium diphenoxide, and barium diphenoxide. The tire according to any one of claims 1 to 3.

5. The tire according to claim 4, wherein the modified rubber having at least one selected from the group consisting of the carboxylic acid, the sulfonic acid, and salts thereof in the molecule is an emulsion-polymerized styrene-butadiene rubber having methacrylic acid in the molecule.

6. The groove-forming rubber composition contains a modified liquid diene polymer having at least one selected from the group consisting of the carboxylic acid, the sulfonic acid, and salts thereof in the molecule, and at least one alkali metal salt or alkaline earth metal salt selected from the group consisting of lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, beryllium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, lithium acetate, sodium acetate, potassium acetate, rubidium acetate, cesium acetate, beryllium acetate, magnesium acetate, calcium acetate, strontium acetate, barium acetate, lithium phenoxide, sodium phenoxide, potassium phenoxide, rubidium phenoxide, cesium phenoxide, beryllium diphenoxide, magnesium diphenoxide, calcium diphenoxide, strontium diphenoxide, and barium diphenoxide. The tire according to any one of claims 1 to 3.

7. The tire according to claim 6, wherein the modified liquid diene polymer having at least one selected from the group consisting of the carboxylic acid, the sulfonic acid, and salts thereof in the molecule is a liquid isoprene polymer having methacrylic acid or maleic acid in the molecule.

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