Tire

Abstract

Provided is a tire including a tread section and at least one outermost member other than the tread section. A rubber composition that composes the tread section and a rubber composition that composes the at least one outermost member other than the tread section each include a rubber component containing a diene rubber and a multi-component polymer. The multi-component polymer has an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit. For each rubber component that constitutes the rubber component of the tread section, the value obtained by multiplying the aromatic-vinyl-unit content (mass%) by the mass fraction in the rubber component is calculated, and these obtained values are summed to calculate the aromatic-vinyl-unit content TArm (mass%) in the rubber component of the tread section. Meanwhile, the aromatic-vinyl-unit content OMMArm (mass%) in the rubber component of the at least one outermost member other than the tread section is similarly calculated. At this time, TArm is greater than OMMArm. The tire is a tire in which crack resistance has been improved.

Description

Technical Field

[0001] The present invention relates to a tire with improved crack resistance performance.

Background Art

[0002] Generally, rubber products including tires are deteriorated by ozone and oxygen in the atmosphere, and cracks are generated on the surface. These cracks progress due to static and dynamic stresses applied to the rubber products, and as a result, the rubber reaches destruction.

[0003] Patent Document 1 describes providing a pneumatic tire in which handling stability, low fuel consumption, and processability are well-balanced by using a predetermined copolymer obtained by hydrogenating a copolymer of an aromatic vinyl compound and a conjugated diene compound.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a tire with improved crack resistance performance.

Means for Solving the Problems

[0006] As a result of intensive studies, the present inventor has found that by using a rubber component containing a diene rubber and a predetermined multi-polymer for each of the tread portion of the tire and at least one outermost surface member other than the tread portion, and paying attention to the aromatic vinyl unit content of each rubber component, the above problems can be solved by making the aromatic vinyl unit content of the rubber component constituting the tread portion larger than that of the rubber component constituting at least one outermost surface member other than the tread portion. Further studies have been repeated to complete the present invention.

[0007] That is, the present invention is [1] A tire including a tread portion and at least one outermost surface member other than the tread portion, The rubber composition constituting the tread portion contains a rubber component including a diene rubber and a multi-polymer, The multi-polymer has an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit, The rubber composition constituting at least one outermost surface member other than the tread portion contains a rubber component including a diene rubber and a multi-polymer, The multi-polymer has an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit, For each rubber component constituting the rubber component of the tread portion, a value obtained by multiplying the aromatic vinyl unit content (mass%) by the mass fraction in the rubber component is calculated, and the sum of these values is used to calculate the aromatic vinyl unit content T Arm (mass%) of the rubber component of the tread portion. On the other hand, for each rubber component constituting the rubber component of at least one outermost surface member other than the tread portion, a value obtained by multiplying the aromatic vinyl unit content (mass%) by the mass fraction in the rubber component is calculated, and the sum of these values is used to calculate the aromatic vinyl unit content OMM Arm (mass%) of the rubber component of at least one outermost surface member other than the tread portion. When calculating, T Arm is greater than OMM Arm A tire, [2] The content of the multi-polymer contained in the rubber composition constituting the tread portion is 5 mass% or more, preferably 10 mass% or more, more preferably 20 mass% or more, still more preferably 30 mass% or more in 100 mass% of the rubber component, The content of the multi-polymer contained in the rubber composition constituting at least one outermost surface member other than the tread portion is 2 mass% or more, preferably 8 mass% or more, more preferably 15 mass% or more, still more preferably 20 mass% or more, still more preferably 30 mass% or more in 100 mass% of the rubber component. The tire according to [1] above, [3] The above TArm is 15% by mass or more, preferably 20% by mass or more, more preferably 25% by mass or more, still more preferably 30% by mass or more, still more preferably 33% by mass or more, of the tire according to [1] or [2] above, [4] The rubber composition constituting the tread contains 40 parts by mass or more, preferably 50 parts by mass or more, more preferably 60 parts by mass or more, still more preferably 70 parts by mass or more, still more preferably 80 parts by mass or more, of a filler based on 100 parts by mass of the rubber component, and the filler contains 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 83% by mass or more, still more preferably 90% by mass or more of silica, The rubber composition constituting at least one outermost surface member other than the tread portion contains 10 parts by mass or more, preferably 20 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 40 parts by mass or more, still more preferably 50 parts by mass or more, of a filler based on 100 parts by mass of the rubber component, and the filler contains more than 0% by mass of silica, preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 83% by mass or more, still more preferably 90% by mass or more, of the tire according to any one of [1] to [3] above, [5] The rubber composition constituting the tread portion contains 1 to 45 parts by mass, preferably 2 to 44 parts by mass, more preferably 3 to 43 parts by mass, still more preferably 4 to 42 parts by mass, still more preferably 5 to 41 parts by mass, still more preferably 5 to 40 parts by mass, still more preferably 6 to 40 parts by mass, of an aromatic ring-containing resin based on 100 parts by mass of the rubber component, of the tire according to any one of [1] to [4] above, [6] The diene rubber contained in the rubber composition constituting the tread portion contains natural rubber, and the diene rubber contained in the rubber composition constituting at least one outermost surface member other than the tread portion contains natural rubber, of the tire according to any one of [1] to [5] above, [7] The content of natural rubber in the tread portion in 100% by mass of the rubber component is less than the content of natural rubber in at least one outermost surface member other than the tread portion in 100% by mass of the rubber component. The tire according to [6] above, [8] The rubber composition constituting at least one outermost surface member other than the tread portion does not contain an aromatic ring-containing resin, or the mass part of the aromatic ring-containing resin with respect to 100 mass parts of the rubber component contained in the rubber composition constituting at least one outermost surface member other than the tread portion is less than the mass part of the aromatic ring-containing resin with respect to 100 mass parts of the rubber component contained in the rubber composition constituting the tread portion. The tire according to any one of [5] to [7] above, [9] The glass transition temperature of the rubber composition constituting the tread is higher than the glass transition temperature of the rubber composition constituting at least one outermost surface member other than the tread portion. The tire according to any one of [1] to [8] above,

[10] When the multi-polymer contained in the rubber composition constituting the tread portion is a hydrogenated polymer composed of an aromatic vinyl unit and a conjugated diene unit, the hydrogenation rate is 30 mol% or more and less than 100 mol%, preferably 50 mol% or more and less than 100 mol%, more preferably 70 mol% or more and less than 100 mol%, still more preferably 90 mol% or more and less than 100 mol%. When the multi-polymer contained in the rubber composition constituting at least one outermost surface member other than the tread portion is a hydrogenated polymer composed of an aromatic vinyl unit and a conjugated diene unit, the hydrogenation rate is 30 mol% or more and less than 100 mol%, preferably 50 mol% or more and less than 100 mol%, more preferably 70 mol% or more and less than 100 mol%, still more preferably 90 mol% or more and less than 100 mol%. The tire according to any one of [1] to [9] above,

[11] At least one outermost surface member other than the tread portion is at least one selected from the group consisting of a wing, a sidewall, and a clinch apex. The tire according to any one of [1] to

[10] above,

[12] At least one outermost surface member other than the tread portion is a sidewall. The tire according to any one of [1] to

[10] above, relates to.

Advantages of the Invention

[0008] According to the present invention, it is possible to provide a tire with improved crack resistance performance.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0010] A tire according to an embodiment of the present disclosure is a tire including a tread portion and at least one outermost surface member other than the tread portion, wherein a rubber composition constituting the tread portion includes a rubber component including a diene rubber and a multi-polymer, the multi-polymer has an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit, a rubber composition constituting at least one outermost surface member other than the tread portion includes a rubber component including a diene rubber and a multi-polymer, the multi-polymer has an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit, and for each rubber component constituting the rubber component of the tread portion, a value obtained by multiplying the aromatic vinyl unit content (mass%) by the mass fraction in the rubber component is calculated and the sum of these values is used to calculate the aromatic vinyl unit content T Arm (mass%) of the rubber component in the tread portion, while for each rubber component constituting the rubber component of at least one outermost surface member other than the tread portion, a value obtained by multiplying the aromatic vinyl unit content (mass%) by the mass fraction in the rubber component is calculated and the sum of these values is used to calculate the aromatic vinyl unit content OMM Arm (mass%) of the rubber component of at least one outermost surface member other than the tread portion, when calculating, T Arm is OMM ArmIt is a larger tire.

[0011] Although not intended to be restricted by theory, in the present disclosure, the following mechanisms are considered as those capable of improving crack resistance performance. That is, first, when the multi-polymer is compounded in the diene rubber, it forms a sea-island structure and contributes to preventing the progress of cracks generated in the diene rubber due to its high crack growth resistance. Second, by compounding the multi-polymer not only in the tread portion but also in at least one outermost surface member other than the tread portion, crack growth resistance can be imparted to the surface of the tire exposed to ozone and oxygen. Third, by increasing the aromatic vinyl unit content (T Arm ) in the rubber component constituting the tread portion compared to the aromatic vinyl unit content (OMM Arm ) in the rubber component constituting at least one outermost surface member other than the tread portion, the glass transition temperature (Tg) of at least one outermost surface member other than the tread portion decreases and becomes softer than the tread portion. Therefore, at least one outermost surface member other than the tread portion functions as a buffer material that absorbs impacts from steps and the like, and the generation of cracks between the tread portion and at least one outermost surface member other than the tread portion can be prevented. It is considered that the above points cooperate with each other to synergistically improve the crack resistance performance.

[0012] The content of the multi-polymer contained in the rubber composition constituting the tread portion is preferably 5% by mass or more in 100% by mass of the rubber component. On the other hand, the content of the multi-polymer contained in the rubber composition constituting at least one outermost surface member other than the tread portion is preferably 2% by mass or more in 100% by mass of the rubber component. It is considered to contribute to bringing out the crack growth resistance effect by the multi-polymer.

[0013] The T Arm is preferably 15% by mass or more. By increasing the aromatic vinyl unit content of the tread portion, it is considered that at least one outermost surface member other than the tread portion is more likely to function as a buffer material.

[0014] The rubber composition constituting the tread preferably contains 40 parts by mass or more of a filler with respect to 100 parts by mass of the rubber component, and the filler preferably contains 50% by mass or more of silica. On the other hand, the rubber composition constituting at least one outermost surface member other than the tread portion preferably contains 10 parts by mass or more of a filler with respect to 100 parts by mass of the rubber component, and the filler preferably contains more than 0% by mass of silica. Among the fillers, silica has lower rubber binding properties than carbon black and results in a flexible rubber composition, so it is considered useful for preventing crack generation between the rubber component and the filler where stress concentrates when an impact is applied to the rubber. By increasing the content ratio of such silica in both the tread portion and at least one outermost surface member other than the tread portion, it is also considered useful for reinforcing the interface between the tread and at least one outermost surface member other than the tread portion and preventing crack generation between the members.

[0015] The rubber composition constituting the tread portion preferably contains 1 to 45 parts by mass of an aromatic ring-containing resin with respect to 100 parts by mass of the rubber component. By adding an aromatic ring-containing resin to the tread portion with a high content of aromatic vinyl units, it is considered to contribute to increasing the interaction between the aromatic vinyl units in the rubber component and the aromatic rings of the aromatic ring-containing resin and enhancing the reinforcing property.

[0016] The diene rubber contained in the rubber composition constituting the tread portion preferably includes natural rubber. On the other hand, the diene rubber contained in the rubber composition constituting at least one outermost surface member other than the tread portion preferably includes natural rubber. This is because it is possible to form the tread portion and at least one outermost surface member other than the tread portion that utilize the characteristics of natural rubber with high mechanical strength.

[0017] The content of natural rubber in the tread portion in 100% by mass of the rubber component is preferably less than the content of natural rubber in at least one outermost surface member other than the tread portion in 100% by mass of the rubber component. As a result of promoting a decrease in the content of the multi-polymer in at least one outermost surface member other than the tread portion, it is considered that the outermost surface member becomes softer and functions more easily as a cushioning material.

[0018] The rubber composition constituting at least one outermost surface member other than the tread portion does not contain an aromatic ring-containing resin, or the mass part of the aromatic ring-containing resin with respect to 100 mass parts of the rubber component contained in the rubber composition constituting at least one outermost surface member other than the tread portion is less than the mass part of the aromatic ring-containing resin with respect to 100 mass parts of the rubber component contained in the rubber composition constituting the tread portion. By relatively increasing the content of the aromatic ring-containing resin in the tread portion, it is considered that at least one outermost surface member other than the tread portion becomes softer and functions more easily as a cushioning material. The content of the aromatic ring-containing resin with respect to 100 mass parts of the rubber component is, for example, when it is 5 to 40 mass parts in the rubber composition constituting the tread portion, in the rubber composition constituting at least one outermost surface member other than the tread portion, it is less than the content of the aromatic ring-containing resin in the rubber composition constituting the tread portion, and is preferably 0 to 10 mass parts, more preferably 0 to 6 mass parts, still more preferably 0 to 4 mass parts, and may not be contained at all.

[0019] The glass transition temperature (Tg) of the rubber composition constituting the tread portion is preferably higher than the glass transition temperature of the rubber composition constituting at least one outermost surface member other than the tread portion. It is considered that at least one outermost surface member other than the tread portion becomes softer than the tread portion and is more likely to function as a cushioning material. The Tg of the rubber composition constituting the tread portion is preferably -60°C or higher, more preferably -40°C or higher, and still more preferably -20°C or higher. On the other hand, the Tg is preferably 0°C or lower, more preferably -5°C or lower, and still more preferably -10°C or lower. Also, the Tg of the rubber composition constituting at least one outermost surface member other than the tread portion is preferably -70°C or higher, more preferably -55°C or higher, and still more preferably -40°C or higher. On the other hand, the Tg is preferably -30°C or lower, more preferably -25°C or lower, and still more preferably -20°C or lower. In the present specification, the glass transition temperature (Tg) of the rubber composition refers to the tanδ peak temperature measured by the following method. That is, for a test piece sample of the rubber composition (for example, 40 mm long × 7 mm wide), using a dynamic viscoelasticity evaluation apparatus (EPLEXOR series manufactured by GABO), under the conditions of a frequency of 10 Hz, an initial strain of 10%, an amplitude of ±0.5%, a dynamic strain of 1.0%, and a temperature increase rate of 2°C / min, the temperature distribution curve of tanδ was measured, and the temperature (tanδ peak temperature) corresponding to the largest tanδ value in the obtained temperature distribution curve was taken as Tg.

[0020] When the multi-polymer contained in the rubber composition constituting the tread portion is a hydrogenated polymer composed of an aromatic vinyl unit and a conjugated diene unit, the hydrogenation rate is preferably 30 mol% or more and less than 100 mol%. On the other hand, when the multi-polymer contained in the rubber composition constituting at least one outermost surface member other than the tread portion is a hydrogenated polymer composed of an aromatic vinyl unit and a conjugated diene unit, the hydrogenation rate is preferably 30 mol% or more and less than 100 mol%. It is considered that the crack growth resistance of the multi-polymer is likely to be exhibited.

[0021] Hereinafter, a tire according to an embodiment of the present disclosure will be described. The tire includes a tread portion composed of a rubber composition and at least one outermost surface member other than the tread portion composed of a rubber composition. Hereinafter, the description of the rubber composition is applicable to the rubber composition constituting the tread portion and the rubber composition constituting at least one outermost surface member other than the tread portion, unless otherwise specified. Note that the upper and lower limit values related to the description of the numerical range, such as "above", "below", and "~", are numerical values that can be arbitrarily combined, and the numerical values in the examples can also be used as the upper and lower limits. Further, when specifying a numerical range by "~", unless otherwise specified, it means that the numerical values at both ends are also included.

[0022] In the present disclosure, at least one outermost surface member other than the tread portion is not particularly limited as long as it is a member constituting the outermost surface of the tire, and any of them may be applicable, and it is not affected by its name. Examples of the outermost surface member include the wing, sidewall, and clinch apex shown in FIG. 2.

[0023] Therefore, it is preferable that at least one outermost surface member other than the tread portion is at least one selected from the group consisting of a wing, a sidewall, and a clinch apex, and among them, a sidewall is preferable.

[0024] In the present disclosure, when a plurality of members correspond to at least one outermost surface member other than the tread portion, for each member, the content of aromatic vinyl units, the content of the multi-polymer, the content of the filler, the content of silica in the filler, the content of the aromatic ring-containing resin, the content of natural rubber, the glass transition temperature of the rubber composition, and the hydrogenation rate in the case where the multi-polymer is a hydrogenated polymer composed of aromatic vinyl units and conjugated diene units are recognized.

[0025] <Rubber component> The rubber composition constituting the tread portion of the present disclosure and the rubber composition constituting at least one outermost surface member other than the tread portion both contain a rubber component including a diene rubber and a multi-polymer.

[0026] (Multi-polymer) The multi-polymer is a copolymer having an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit, and may have other monomer units. Preferably, it is a copolymer composed of an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit. This copolymer can be obtained by copolymerizing a monomer component containing an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit and hydrogenating it if desired. Alternatively, a copolymer can be obtained by copolymerizing a monomer component containing an aromatic vinyl unit and a conjugated diene unit, preferably a monomer component composed of an aromatic vinyl unit and a conjugated diene unit, and then hydrogenating the conjugated diene unit of the copolymer to create a non-conjugated olefin unit. As long as the multi-polymer is a copolymer having an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit, there is no particular limitation on the sequence of each unit, and it may be a random copolymer obtained by random copolymerization or a block copolymer obtained by block copolymerization, but a random copolymer is preferred. One or more kinds of multi-polymers can be used.

[0027] ≪Aromatic vinyl unit≫ The aromatic vinyl unit refers to a unit derived from an aromatic vinyl compound in the copolymer. Here, the aromatic vinyl compound refers to an aromatic compound substituted with at least a vinyl group and does not include the conjugated diene compounds described later. Examples of the aromatic vinyl compound include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, and the like. These may be used alone or in combination of two or more. Among these, styrene is particularly preferred from the viewpoint of practical aspects such as the availability of the monomer and the reason that the effects of the present disclosure can be more preferably obtained.

[0028] ≪Non-conjugated olefin unit≫ The non-conjugated olefin unit refers to a unit derived from a non-conjugated olefin compound in the copolymer. Here, the non-conjugated olefin compound refers to an aliphatic unsaturated hydrocarbon that is a non-conjugated compound having one or more carbon-carbon double bonds. Examples of the non-conjugated olefin compound include α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, or 1-octene; heteroatom-substituted alkene compounds such as vinyl pivalate, 1-phenylthioethene, or N-vinylpyrrolidone. Among these, ethylene, 1-butene, etc. are preferred. These may be used alone or in combination of two or more. Among these, ethylene is more preferred from the viewpoint of practical aspects such as the availability of the monomer and the reason that the effects of the present disclosure can be more preferably obtained.

[0029] ≪Conjugated diene unit≫ The conjugated diene unit refers to a unit derived from a conjugated diene compound in a copolymer. Here, examples of the conjugated diene compound include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene, etc. These may be used alone or in combination of two or more. Among these, from the perspective of practical aspects such as the availability of monomers and the reason that the effects of the present disclosure can be more preferably obtained, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred.

[0030] ≪Multicomponent polymer≫ Preferred specific examples of the multicomponent polymer include, for example, a hydrogenated copolymer of styrene and 1,3-butadiene (styrene-butadiene copolymer (SBR)). Therefore, as the multicomponent polymer, a hydrogenated styrene-butadiene copolymer (hydrogenated SBR) is preferred.

[0031] ≪Hydrogenation rate≫ The hydrogenation rate of the multicomponent polymer (when the multicomponent polymer is a hydrogenated polymer composed of an aromatic vinyl unit and a conjugated diene unit, it is the ratio of the double bonds on the conjugated diene unit that are hydrogenated.) is preferably 30 mol% or more from the perspective of the effects of the present disclosure. The hydrogenation rate is more preferably 50 mol% or more, still more preferably 70 mol% or more, and still more preferably 90 mol% or more. The upper limit is not particularly limited as long as it is less than 100 mol%. The hydrogenation rate can be adjusted by adjusting reaction conditions such as the hydrogen gas supply pressure and reaction temperature in the hydrogenation reaction as described in Production Example 2 below. Incidentally, the hydrogenation rate can be calculated from the spectrum reduction rate of the unsaturated bond part of the spectrum obtained by measuring 1H-NMR. 1 It can be calculated from the spectrum reduction rate of the unsaturated bond part of the spectrum obtained by measuring 1H-NMR.

[0032] ≪Modification≫ The multi-polymer can, if desired, be treated with a modifier to obtain a modified product having a functional group that interacts with silica. Any of the functional groups commonly used in this field can be preferably used, and examples thereof include alkoxysilyl groups (e.g., trimethoxysilyl group, triethoxysilyl group). For example, if the copolymer is treated with chlorotriethoxysilane as a modifier before hydrogenation treatment after synthesis, a modified product in which a triethoxysilyl group is introduced at the active end of the copolymer can be obtained. The modified multi-polymer is preferably used in the rubber composition constituting the tread portion.

[0033] ≪Mw≫ From the viewpoint of the effects of the present disclosure, the weight average molecular weight (Mw) of the multi-polymer is preferably 50,000 or more, more preferably 100,000 or more, and still more preferably 150,000 or more. Further, the Mw of the multi-polymer is preferably 2,000,000 or less, and from the viewpoint of Mooney viscosity, more preferably 1,000,000 or less, and still more preferably 700,000 or less.

[0034] ≪Mw / Mn≫ From the viewpoint of processability and the like, the ratio of Mw to the number average molecular weight (Mn) of the multi-polymer, that is, the preferred range of Mw / Mn is preferably 20.0 or less, more preferably 10.0 or less, and still more preferably 5.0 or less. On the other hand, there is no particular limitation on the lower limit value of Mw / Mn, and there is no particular problem at 1.0 or more. In the present specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) can be determined by standard polystyrene conversion based on the measured values by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0035] ≪Tg≫ From the viewpoint of abrasion resistance, the glass transition temperature (Tg) of the multi-polymer is preferably -70°C or higher, more preferably -65°C or higher, and even more preferably -60°C or higher. Also, from the same viewpoint, the Tg of the multi-polymer is preferably less than -10°C, more preferably less than -15°C, and even more preferably less than -20°C. The Tg of the multi-polymer is measured in accordance with JIS K 7121 by heating at a rate of 10°C / min using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan Co., Ltd. while increasing the temperature.

[0036] ≪Aromatic vinyl unit content of the multi-polymer≫ From the viewpoint of the effects of the present disclosure, the aromatic vinyl unit content of the multi-polymer is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more. Also, the aromatic vinyl unit content of the multi-polymer is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. The aromatic vinyl unit content of the multi-polymer is measured by 1H-NMR measurement. 1 Measured by 1H-NMR measurement.

[0037] ≪Content of the multi-polymer≫ From the viewpoint of the effects of the present disclosure, in the rubber composition constituting the tread portion, the content of the multi-polymer is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, and even more preferably 30% by mass or more per 100% by mass of the rubber component. Also, the content is preferably 100% by mass or less, more preferably 70% by mass or less, even more preferably 50% by mass or less, and even more preferably 40% by mass or less. Further, from the viewpoint of the effects of the present disclosure, in the rubber composition constituting at least one outermost surface member other than the tread portion, the content of the multi-polymer is preferably 2% by mass or more, more preferably 8% by mass or more, even more preferably 15% by mass or more, and even more preferably 20% by mass or more, and even more preferably 30% by mass or more per 100% by mass of the rubber component. Also, the content is preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less.

[0038] The content of the multi-polymer in 100% by mass of the rubber component of the rubber composition constituting the tread portion is preferably the same as or more than the content of the multi-polymer in 100% by mass of the rubber component of the rubber composition constituting at least one outermost surface member other than the tread portion. For example, when the content (% by mass) of the multi-polymer in the rubber composition constituting the tread portion is within the above range, the content (% by mass) of the multi-polymer in the rubber composition constituting at least one outermost surface member other than the tread portion is preferably the same as that or 2% by mass or more lower, and more preferably 5% by mass or more lower.

[0039] ≪Confirmation of multi-polymer≫ In addition, the confirmation that it is a multi-polymer containing a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit is carried out by using methods such as gel permeation chromatography (GPC), 1 H-NMR, 13 C-NMR, etc. Specifically, based on the gel permeation chromatography-refractive index curve (GPC-RI curve) and the gel permeation chromatography-ultraviolet absorption curve (GPC-UV curve), the UV absorption by aromatic rings such as benzene rings in the copolymer can be confirmed, and the presence of the skeleton derived from the aromatic vinyl compound can be confirmed. Also, 1 Based on the H-NMR spectrum and 13 the C-NMR spectrum, the presence of units derived from each monomer component can be confirmed.

[0040] Also, among the total conjugated diene units in the multi-polymer, the ratio of the conjugated diene units present in a predetermined sequence can be confirmed based on the 13 C-NMR spectrum, for example, by the method described in International Publication No. 2018 / 092733.

[0041] ≪Manufacturing method of multi-polymer≫ The above-mentioned multi-polymer can be synthesized, for example, by polymerizing monomer components containing aromatic vinyl units, non-conjugated olefin units, and conjugated diene units to obtain a copolymer and optionally subjecting the copolymer to a hydrogenation treatment. Alternatively, after copolymerizing monomer components containing aromatic vinyl units and conjugated diene units to obtain a copolymer, the conjugated diene units of the copolymer can be hydrogenated to create non-conjugated olefin units, thereby also synthesizing the multi-polymer. Such synthesis can be carried out by conventional methods, for example, as described in JP-A-2018-83884 and WO2018 / 092733. The same applies to modified forms of the multi-polymer.

[0042] (Diene rubber) As the diene rubber, any rubber component other than the above-mentioned multi-polymer that is commonly used in the tire industry can be preferably used. Specifically, for example, isoprene rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR), styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isobutylene-styrene block copolymer (SIBS), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), polynorbornene rubber, etc. can be mentioned. The diene rubber component may be used alone or in combination of two or more.

[0043] The diene rubber preferably contains at least one selected from the group consisting of isoprene rubber, SBR, and BR, and may also be a rubber component containing isoprene rubber, SBR, and BR. Further, the diene rubber may be a rubber component consisting only of isoprene rubber and SBR, or a rubber component consisting only of isoprene rubber, SBR, and BR. The diene rubber of the rubber composition constituting the tread portion preferably contains SBR and BR, or consists of SBR and BR. The diene rubber of the rubber composition constituting at least one outermost surface member other than the tread portion preferably contains isoprene rubber and BR, or consists of isoprene rubber and BR.

[0044] (Isoprene rubber) As the isoprene rubber, for example, general ones in the tire industry such as isoprene rubber (IR) and natural rubber can be used. Among these, natural rubber includes, in addition to unmodified natural rubber (NR), modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. Among them, natural rubber is preferred, and for example, NR can be preferably used. These isoprene rubbers may be used alone or in combination of two or more.

[0045] NR is not particularly limited, and general ones in the tire industry can be used, and examples include SIR20, RSS#3, TSR20, etc.

[0046] In the rubber composition constituting the tread portion, the content of the isoprene rubber in the rubber component is preferably 40% by mass or less, more preferably 20% by mass or less, further preferably 10% by mass or less, or preferably does not contain isoprene rubber, from the viewpoint of good ride comfort. However, from the viewpoints of processability and durability performance, the content may be 1% by mass or more, 2% by mass or more, or 5% by mass or more. Also, in the rubber composition constituting at least one outermost surface member other than the tread portion, from the viewpoints of processability and durability performance, the content of the isoprene rubber in the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, further preferably 30% by mass or more. On the other hand, from the viewpoint of good ride comfort, the content is preferably 70% by mass or less, more preferably 60% by mass or less, further preferably 50% by mass or less.

[0047] The content of isoprene rubber in 100% by mass of the rubber component of the rubber composition constituting the tread portion is preferably less than the content of isoprene rubber in 100% by mass of the rubber component of the rubber composition constituting at least one outermost surface member other than the tread portion. For example, when the content (mass%) of isoprene rubber in the rubber composition constituting at least one outermost surface member other than the tread portion is within the above range, the content (mass%) of isoprene rubber in the rubber composition constituting the tread portion is preferably 10% by mass or more lower than that, more preferably 20% by mass or more lower, still more preferably 30% by mass or more lower, and it may not contain any isoprene rubber at all.

[0048] (SBR) There is no particular limitation on SBR, and examples include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). Examples of modified SBRs include SBRs with modified terminals and / or main chains, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.). Among them, S-SBR and modified SBR are preferred from the viewpoint of being able to improve low fuel consumption performance and wear resistance performance well. These SBRs may be used alone or in combination of two or more.

[0049] From the viewpoints of ensuring damping properties and wet grip performance in the tread portion, the styrene content of SBR is preferably 15% by mass or more, more preferably 20% by mass or more. Also, from the viewpoints of temperature dependence of grip performance and wear resistance performance, it is preferably 60% by mass or less, more preferably 50% by mass or less. In this specification, the styrene content of SBR is 1 calculated by 1H-NMR measurement.

[0050] The vinyl bond content of SBR is preferably 10 mol% or more from the viewpoint of ensuring reactivity with silica and from the viewpoints of rubber strength and abrasion resistance performance. Also, the vinyl bond content of SBR is preferably 70 mol% or less from the viewpoints of preventing an increase in temperature dependence, wet grip performance, elongation at break, and abrasion resistance performance. In this specification, the vinyl bond content (1,2-bond butadiene unit amount) of SBR is measured by infrared absorption spectroscopy analysis.

[0051] The weight average molecular weight (Mw) of SBR is preferably 150,000 or more, more preferably 200,000 or more, and even more preferably 250,000 or more from the viewpoint of abrasion resistance performance. Also, Mw is preferably 2,500,000 or less, more preferably 2,000,000 or less from the viewpoints of crosslinking uniformity and the like. Note that Mw can be determined by standard polystyrene conversion based on the measured value by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M manufactured by Tosoh Corporation).

[0052] As SBR, oil-extended SBR can be used, or non-oil-extended SBR can be used. When using oil-extended SBR, the oil extension amount of SBR, that is, the content of the oil-extended oil contained in SBR, is preferably 10 to 50 parts by mass with respect to 100 parts by mass of the rubber solid content of SBR.

[0053] As SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Ube Industries, Ltd., Asahi Kasei Corporation, Nippon Zeon Co., Ltd., ZS Elastomer Co., Ltd., etc. can be used.

[0054] When contained in the rubber component, the content in the rubber composition constituting the tread portion is preferably 10% by mass or more, more preferably 15% by mass or more, further preferably 20% by mass or more, still further preferably 25% by mass or more, still further preferably 30% by mass or more, and still further preferably 35% by mass or more from the viewpoints of ensuring damping properties and wet grip performance. On the other hand, from the viewpoint of improving durability performance by suppressing heat generation, the content is preferably 85% by mass or less, more preferably 80% by mass or less, further preferably 75% by mass or less, and still further preferably 70% by mass or less. Further, when contained in the rubber component, the content in the rubber composition constituting at least one outermost surface member other than the tread portion is preferably 40% by mass or less, more preferably 30% by mass or less, further preferably 20% by mass or less, still further preferably 10% by mass or less, or preferably does not contain SBR from the viewpoint of improving durability performance by suppressing heat generation. However, from the viewpoints of ensuring damping properties and wet grip performance, the content may be 1% by mass or more, 2% by mass or more, or 5% by mass or more.

[0055] The content of SBR in 100% by mass of the rubber component of the rubber composition constituting the tread portion is preferably more than the content of SBR in 100% by mass of the rubber component of the rubber composition constituting at least one outermost surface member other than the tread portion. For example, the content (% by mass) of SBR in the rubber composition constituting at least one outermost surface member other than the tread portion is preferably 10% by mass or more lower than the content (% by mass) of SBR in the rubber composition constituting the tread portion, more preferably 20% by mass or more lower, still further preferably 30% by mass or more lower, or may not contain any SBR at all.

[0056] (BR) BR is not particularly limited. For example, BR with a cis content (cis-1,4 bond content) of less than 50% (low-cis BR), BR with a cis content of 90% or more (high-cis BR), rare earth butadiene rubber synthesized using a rare earth element-based catalyst (rare earth-based BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc., which are common in the tire industry, can be used. BR can be used alone or in combination of two or more.

[0057] As the rare earth-based BR, those generally used in the tire industry can be used. As the rare earth element-based catalyst used for the synthesis (polymerization) of the rare earth-based BR, known catalysts can be used. For example, catalysts containing lanthanum series rare earth element compounds, organoaluminum compounds, aluminoxane, halogen-containing compounds, and optionally Lewis bases can be mentioned. Among them, from the viewpoint of obtaining BR with a high cis content and a low vinyl content, a Nd-based catalyst using a neodymium (Nd)-containing compound as the lanthanum series rare earth element compound is preferable.

[0058] The SPB-containing BR includes those in which the 1,2-syndiotactic polybutadiene crystals are not simply dispersed in BR but are dispersed after being chemically bonded to BR.

[0059] As the modified BR, those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and in which the ends of the modified BR molecules are bonded by tin-carbon bonds (tin-modified BR), butadiene rubber having a condensed alkoxysilane compound at the active end of the butadiene rubber (modified BR for silica), etc. can be mentioned.

[0060] The weight average molecular weight (Mw) of BR is preferably 300,000 or more, more preferably 350,000 or more, and even more preferably 400,000 or more from the viewpoint of wear resistance performance. Further, from the viewpoints of crosslinking uniformity and the like, it is preferably 2,000,000 or less, and more preferably 1,000,000 or less. Note that Mw can be determined by standard polystyrene conversion based on the measured value by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M manufactured by Tosoh Corporation).

[0061] As the BR, for example, those commercially available from Ube Industries, Ltd., Sumitomo Chemical Co., Ltd., JSR Corporation, LANXESS Corporation, etc. can be used.

[0062] When contained in the rubber component, the content in the rubber composition constituting the tread portion is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more from the viewpoint of wear resistance performance. Further, from the viewpoint of wet grip performance, it is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. Also, when contained in the rubber component, the content in the rubber composition constituting at least one outermost surface member other than the tread portion is preferably 2% by mass or more, more preferably 8% by mass or more, and even more preferably 15% by mass or more from the viewpoint of wear resistance performance. Further, from the viewpoint of riding comfort, it is preferably 55% by mass or less, more preferably 45% by mass or less, and even more preferably 35% by mass or less.

[0063] The content of BR in 100% by mass of the rubber component of the rubber composition constituting the tread portion is preferably the same as or more than the content of BR in 100% by mass of the rubber component of the rubber composition constituting at least one outermost surface member other than the tread portion. For example, when the content (% by mass) of BR in the rubber composition constituting the tread portion is within the above range, the content (% by mass) of BR in the rubber composition constituting at least one outermost surface member other than the tread portion is preferably the same as that or 3% by mass or more lower, more preferably 5% by mass or more lower, and even more preferably 10% by mass or more lower.

[0064] (Other rubber components) The rubber component may contain rubber components other than the above as long as the effects of the present disclosure are not impaired. Examples of such rubber components include non-diene rubbers such as hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), ethylene propylene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber.

[0065] (Aromatic vinyl unit content of rubber component) For each rubber component constituting the rubber component of the tread portion, a value obtained by multiplying the aromatic vinyl unit content (% by mass) by the mass fraction in the rubber component is calculated, and the sum of these values is defined as the aromatic vinyl unit content T Arm (% by mass) of the rubber component of the tread portion. Similarly, for each rubber component constituting the rubber component of at least one outermost surface member other than the tread portion, a value obtained by multiplying the aromatic vinyl unit content (% by mass) by the mass fraction in the rubber component is calculated, and the sum of these values is defined as the aromatic vinyl unit content OMM Arm (% by mass) of the rubber component of at least one outermost surface member other than the tread portion. In the present disclosure, T Arm is larger than OMM Arm . Here, OMM Arm(Mass %) is calculated for each of at least one outermost surface member other than the tread portion, when there are a plurality such as sidewalls, wings, clinch apexes, etc.

[0066] For example, when at least one outermost surface member other than the tread portion is a sidewall, for each rubber component constituting the rubber component of the sidewall, a value obtained by multiplying the aromatic vinyl unit content (mass %) by the mass fraction in the rubber component is calculated for each, and the sum of those values is defined as the aromatic vinyl unit content SW Arm (Mass %) in the rubber component of the sidewall.

[0067] When at least one outermost surface member other than the tread portion is a wing, for each rubber component constituting the rubber component of the wing, a value obtained by multiplying the aromatic vinyl unit content (mass %) by the mass fraction in the rubber component is calculated for each, and the sum of those values is defined as the aromatic vinyl unit content WG Arm (Mass %) in the rubber component of the wing.

[0068] When at least one outermost surface member other than the tread portion is a clinch apex, for each rubber component constituting the rubber component of the clinch apex, a value obtained by multiplying the aromatic vinyl unit content (mass %) by the mass fraction in the rubber component is calculated for each, and the sum of those values is defined as the aromatic vinyl unit content CL Arm (Mass %) in the rubber component of the clinch apex.

[0069] T Arm From the viewpoint of the effects of the present disclosure, it is preferably 15 mass % or more, preferably 20 mass % or more, preferably 25 mass % or more, preferably 30 mass % or more, preferably 33 mass % or more.

[0070] On the other hand, OMM Arm is smaller than T Arm OMM Arm From the viewpoint of the effects of the present disclosure, OMM ArmWhen taking the above value, the T Arm is preferably 5 mass% or more smaller than that, more preferably 10 mass% or more smaller, still more preferably 15 mass% or more smaller, still more preferably 20 mass% or more smaller, and still more preferably 23 mass% or more smaller.

[0071] Also, SW Arm is smaller than T Arm . SW Arm is, from the viewpoint of the effects of the present disclosure, when T Arm takes the above value, preferably 5 mass% or more smaller than that T Arm is preferably 5 mass% or more smaller than that, more preferably 10 mass% or more smaller, still more preferably 15 mass% or more smaller, still more preferably 20 mass% or more smaller, and still more preferably 23 mass% or more smaller.

[0072] Also, WG Arm is smaller than T Arm . WG Arm is, from the viewpoint of the effects of the present disclosure, when T Arm takes the above value, preferably 5 mass% or more smaller than that T Arm is preferably 5 mass% or more smaller than that, more preferably 10 mass% or more smaller, still more preferably 15 mass% or more smaller, still more preferably 20 mass% or more smaller, and still more preferably 23 mass% or more smaller.

[0073] Also, CL Arm is smaller than T Arm . CL Arm is, from the viewpoint of the effects of the present disclosure, when T Arm takes the above value, preferably 5 mass% or more smaller than that T Arm is preferably 5 mass% or more smaller than that, more preferably 10 mass% or more smaller, still more preferably 15 mass% or more smaller, still more preferably 20 mass% or more smaller, and still more preferably 23 mass% or more smaller.

[0074] Note that T Arm , and also OMM Arm , SW Arm , WGArm and CL Arm From the perspective of the effects of the present disclosure, neither of them is particularly limited in terms of the upper limit. However, since each corresponds to the weighted average value of the aromatic vinyl unit content of each rubber component that constitutes each of the tread portion, the sidewall, which is the outermost surface member other than the tread portion, the wing, the clinch apex, etc., there is naturally an upper limit depending on the type and amount of the rubber components to be selected. Such upper limit values are, for example, about 50% by mass, or about 45% by mass, or about 40% by mass for T Arm Regarding [it], it is about 50% by mass, or about 45% by mass, or about 40% by mass.

[0075] Since the value of the aromatic vinyl unit content of the rubber component corresponds to the weighted average value of the aromatic vinyl unit content of each rubber component contained in the rubber component, for example, it can be increased by using a large amount of a rubber component having a large value of the aromatic vinyl unit content, and conversely, it can be decreased by using a large amount of a rubber component having a small value of the aromatic vinyl unit content.

[0076] <Filler> As the filler, it is preferable to contain carbon black and silica. Also, the filler may consist only of carbon black and silica.

[0077] (Carbon Black) The carbon black is not particularly limited, and those commonly used in the tire industry such as GPF, FEF, HAF, ISAF, SAF, etc. can be used. Specifically, N110, N115, N120, N125, N134, N135, N219, N220, N231, N234, N293, N299, N326, N330, N339, N343, N347, N351, N356, N358, N375, N539, N550, N582, N630, N642, N650, N660, N683, N754, N762, N765, N772, N774, N787, N907, N908, N990, N991, etc. can be preferably used. In addition to these, self-made synthetic products, etc. can also be preferably used. These carbon blacks may be used alone or in combination of two or more.

[0078] The nitrogen adsorption specific surface area (N 2 SA) of the carbon black used in the rubber composition constituting the tread portion is preferably 100 m 2 / g or more, more preferably 110 m 2 / g or more, and even more preferably 120 m 2 / g or more, from the viewpoints of weather resistance and reinforcement. Also, the N 2 SA is preferably 250 m 2 / g or less, more preferably 200 m 2 / g or less, and even more preferably 180 m 2 / g or less, from the viewpoints of dispersibility, low fuel consumption performance, fracture characteristics, and durability. On the other hand, the N 2 SA of the rubber composition constituting at least one outermost surface member other than the tread portion is preferably 50 m 2 / g or more, more preferably 60 m 2 / g or more, and even more preferably 70 m 2 / g or more, from the viewpoints of weather resistance and reinforcement. Also, the N 2 SA is preferably 150 m 2 / g or less, more preferably 120 m 2 / g or less, and even more preferably 100 m 2 / g or less, from the viewpoints of dispersibility, low fuel consumption performance, fracture characteristics, and durability. The N 2 SA of the carbon black in this specification is a value measured in accordance with Method A of JIS K 6217-2 "Basic characteristics of carbon black for rubber - Part 2: Method for determining specific surface area - Nitrogen adsorption method - Single point method".

[0079] When carbon black is contained, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and still more preferably 5 parts by mass or more from the viewpoints of weather resistance and reinforcing property in the rubber composition constituting the tread portion. On the other hand, from the viewpoint of improving durability performance by suppressing heat generation, the content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and still more preferably 40 parts by mass or less. Further, when carbon black is contained, the content relative to 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 15 parts by mass or more from the viewpoints of weather resistance and reinforcing property in the rubber composition constituting at least one outermost surface member other than the tread portion. On the other hand, from the viewpoint of improving durability performance by suppressing heat generation, the content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 80 parts by mass or less.

[0080] (Silica) The silica is not particularly limited, and for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), etc., which are common in the tire industry, can be used. Among them, hydrous silica prepared by a wet method is preferable because of its large number of silanol groups. These silicas may be used alone or in combination of two or more.

[0081] The nitrogen adsorption specific surface area (N 2 SA) of the silica is preferably 100 m 2 / g or more, more preferably 120 m 2 / g or more, still more preferably 150 m 2 / g or more, and still more preferably 170 m 2 / g or more from the viewpoints of ensuring reinforcing property and damping property. Further, from the viewpoints of heat generation property and processability, it is preferably 350 m 2 / g or less, more preferably 300 m 2 / g or less, and still more preferably 250 m 2 / g or less. The N 2 SA of the silica in this specification is a value measured by the BET method in accordance with ASTM D3037-93.

[0082] When contained, the content with respect to 100 parts by mass of the rubber component in the rubber composition constituting the tread portion is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 40 parts by mass or more, still more preferably 50 parts by mass or more, and still more preferably 60 parts by mass or more from the viewpoints of ensuring damping properties and wet grip performance. On the other hand, from the viewpoints of reducing the specific gravity of the rubber composition to achieve weight reduction, improving durability performance by suppressing heat generation, and ensuring riding comfort performance due to the softness of the rubber, the content is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and still more preferably 100 parts by mass or less. Further, when contained, the content with respect to 100 parts by mass of the rubber component in the rubber composition constituting at least one outermost surface member other than the tread portion may contain 5 parts by mass or more, may contain 10 parts by mass or more, or may contain 15 parts by mass or more from the viewpoint of ensuring damping properties, but it may not be contained as the rubber composition constituting the outermost surface member. On the other hand, from the viewpoints of reducing the specific gravity of the rubber composition to achieve weight reduction, improving durability performance by suppressing heat generation, and ensuring riding comfort performance due to the softness of the rubber, the content is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 80 parts by mass or less.

[0083] The content of silica with respect to 100 parts by mass of the rubber component in the rubber composition constituting the tread portion is preferably the same as or more than the content of silica with respect to 100 parts by mass of the rubber component in the rubber composition constituting at least one outermost surface member other than the tread portion. For example, when the content of silica (parts by mass) in the rubber composition constituting the tread portion is within the above range, the content of silica (parts by mass) in the rubber composition constituting at least one outermost surface member other than the tread portion is preferably 5 parts by mass or less lower than that, more preferably 10 parts by mass or less lower than that, still more preferably 15 parts by mass or less lower than that, or may not contain silica at all.

[0084] (Other fillers) As fillers other than silica and carbon black, those generally used in the tire industry, such as aluminum hydroxide, calcium carbonate, alumina, clay, talc, etc., can be appropriately blended within the range that does not impair the effects of the present disclosure.

[0085] (Content of filler) From the viewpoint of ensuring reinforcement and damping properties, the total content of the filler relative to 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, further preferably 30 parts by mass or more, still further preferably 40 parts by mass or more, and even further preferably 50 parts by mass or more. Also, from the viewpoint of improving durability, etc., the total content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, further preferably 130 parts by mass or less, still further preferably 100 parts by mass or less, and even further preferably 90 parts by mass or less.

[0086] In the rubber composition constituting the tread portion, the total content of the filler relative to 100 parts by mass of the rubber component is particularly preferably 40 parts by mass or more, more preferably 50 parts by mass or more, further preferably 60 parts by mass or more, still further preferably 70 parts by mass or more, and even further preferably 80 parts by mass or more. Also, the total content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, further preferably 130 parts by mass or less, and still further preferably 120 parts by mass or less.

[0087] In the rubber composition constituting at least one outermost surface member other than the tread portion, the total content of the filler relative to 100 parts by mass of the rubber component is particularly preferably 10 parts by mass or more, 20 quality parts by mass or more is more preferable, 30 parts by mass or more is further preferable, 40 parts by mass or more is still further preferable, and 50 parts by mass or more is even further preferable. Also, the total content is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, and further preferably 90 parts by mass or less.

[0088] In the rubber composition constituting the tread portion, the content of silica in 100% by mass of the filler is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 83% by mass or more, and still more preferably 90% by mass or more. Further, in the rubber composition constituting at least one outermost surface member other than the tread portion, the content of silica in 100% by mass of the filler is preferably more than 0% by mass, more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 83% by mass or more, and still more preferably 90% by mass or more.

[0089] In addition, when the filler consists only of carbon black and silica, if the total content of the filler and the content of either carbon black or silica are determined according to the above, the content of the remaining other will be determined automatically.

[0090] <Silane coupling agent> Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and in the tire industry, any silane coupling agent conventionally used in combination with silica can be used. For example, a silane coupling agent having a mercapto group as described below; a silane coupling agent having a sulfide group such as bis(3-triethoxysilylpropyl)disulfide and bis(3-triethoxysilylpropyl)tetrasulfide; a silane coupling agent having a vinyl group such as vinyltriethoxysilane and vinyltrimethoxysilane; a silane coupling agent having an amino group such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; a glycidoxy-based silane coupling agent such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; a nitro-based silane coupling agent such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; a chloro-based silane coupling agent such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane; and the like. Among them, it is preferable to contain at least one of a silane coupling agent having a sulfide group and a silane coupling agent having a mercapto group, and it is more preferable to contain a silane coupling agent having a sulfide group. Examples of the silane coupling agent include those manufactured and sold by Momentive and Evonik Degussa. These silane coupling agents may be used alone or in combination of two or more.

[0091] The silane coupling agent having a mercapto group is preferably at least one of a compound represented by the following formula (1) and a compound containing a bonding unit A represented by the following formula (2) and a bonding unit B represented by the following formula (3).

Chemical formula

Chemical formula

Chemical formula

[0092] Examples of the compound represented by the formula (1) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and compounds represented by the following formula (4). Examples of these silane coupling agents include those manufactured by Evonik Degussa. These silane coupling agents may be used alone or in combination of two or more.

Chemical formula

[0093] Examples of the compound containing the bonding unit A represented by the formula (2) and the bonding unit B represented by the formula (3) include those manufactured by Momentive Performance Materials Inc. These may be used alone or in combination of two or more.

[0094] When containing a silane coupling agent, the content relative to 100 parts by mass of silica is preferably 1.0 part by mass or more, more preferably 3.0 parts by mass or more, and still more preferably 5.0 parts by mass or more from the viewpoint of enhancing the dispersibility of silica in the rubber composition constituting the tread portion. Also, from the viewpoint of preventing a decrease in wear resistance performance, it is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and still more preferably 15 parts by mass or less. When containing a silane coupling agent, the content relative to 100 parts by mass of silica is preferably 1.0 part by mass or more, more preferably 3.0 parts by mass or more, and still more preferably 5.0 parts by mass or more from the viewpoint of enhancing the dispersibility of silica in the rubber composition constituting at least one outermost surface member other than the tread portion. Also, from the viewpoint of preventing a decrease in wear resistance performance, it is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and still more preferably 15 parts by mass or less.

[0095] <Aromatic ring-containing resin> In the present disclosure, the aromatic ring-containing resin typically includes a resin obtained by polymerizing a monomer containing an aromatic ring. Specific examples of the aromatic ring-containing resin include, for example, aromatic vinyl resins, C9 petroleum resins, C5C9 petroleum resins, terpene phenol resins, phenolic resins, and the like. One or more aromatic ring-containing resins can be used.

[0096] (Aromatic vinyl resin) An aromatic vinyl resin is a polymer using an aromatic vinyl monomer such as styrene as a constituent monomer, and examples include polymers polymerized with an aromatic vinyl monomer as a main component (50% by mass or more, or more than 50% by mass, preferably 60% by mass or more). Specifically, styrene-based monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) are each homopolymers polymerized alone, copolymers copolymerized with two or more styrene-based monomers, and those copolymerized by further combining a styrene-based monomer with other monomers copolymerizable therewith. Examples of the other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene, butadiene and isoprene, olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride or acid anhydrides thereof; etc. The aromatic vinyl resin may be used alone or in combination of two or more. acid Unsaturated carboxylic acid esters such as acrylic acid and methacrylic acid, dienes such as chloroprene, butadiene and isoprene, olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride or acid anhydrides thereof; etc. can be exemplified. The aromatic vinyl resin may be used alone or in combination of two or more.

[0097] As the aromatic vinyl resin, a homopolymer of α-methylstyrene or styrene or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred. As the aromatic vinyl resin, for example, commercially available products such as those manufactured by Arizona Chemical Company can be preferably used.

[0098] (C9 petroleum resin) C9 petroleum resins are resins obtained by polymerizing C9 fractions obtained in petroleum refining, hydrogenated products thereof, and modified products thereof. Examples of C9 fractions include petroleum fractions corresponding to 8 to 10 carbon atoms such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of C9 petroleum resins include, for example, coumarone-indene resins, coumarone resins, and indene resins. One or more C9 resins can be used.

[0099] The above-mentioned coumarone-indene resin is a resin containing coumarone and indene as the main monomer components constituting the resin skeleton (main chain). Monomer components contained in the skeleton other than coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc. The coumarone resin is a resin containing coumarone as the main monomer component constituting the resin skeleton (main chain). The above-mentioned indene resin is a resin containing indene as the main monomer component constituting the resin skeleton (main chain).

[0100] (C5C9 petroleum resin) C5C9 petroleum resins are, for example, resins obtained by copolymerizing the C5 fraction obtained in petroleum refining and the above-mentioned C9 fraction, hydrogenated products thereof, and modified products thereof. Examples of C5 fractions include petroleum fractions corresponding to 4 to 5 carbon atoms such as cyclopentadiene, pentene, pentadiene, and isoprene. Examples of C9 fractions are those mentioned above. As C5C9 petroleum resins, commercially available products such as those manufactured by LUHUA, Qilong, and Tosoh Corporation are preferably used. One or more C5C9 petroleum resins can be used.

[0101] (Terpene phenol resin) Terpene phenol resins are resins obtained by copolymerizing terpene compounds and aromatic compounds, or their hydrogenated products. Here, examples of terpene compounds include α-pinene, β-pinene, limonene, dipentene, etc., and examples of aromatic compounds include styrene, α-methylstyrene, vinyltoluene, divinyltoluene, etc. One or more terpene phenol resins can be used.

[0102] (Phenolic resin) Phenolic resins are resins containing a phenol skeleton in their structure, and examples include phenol formaldehyde resins, alkylphenol formaldehyde resins, alkylphenol acetylene resins, oil-modified phenol formaldehyde resins, etc. One or more phenolic resins can be used.

[0103] (Content of aromatic ring-containing resin) In the rubber composition constituting the tread portion, from the viewpoint of the effects of the present disclosure, the content of the aromatic ring-containing resin with respect to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, further preferably 3 parts by mass or more, still further preferably 4 parts by mass or more, still further preferably 5 parts by mass or more, and still further preferably 6 parts by mass or more. On the other hand, from the same viewpoint, the content is preferably 45 parts by mass or less, more preferably 44 parts by mass or less, further preferably 43 parts by mass or less, still further preferably 42 parts by mass or less, still further preferably 41 parts by mass or less, and still further preferably 40 parts by mass or less. Also, in the rubber composition constituting at least one outermost surface member other than the tread portion, from the viewpoint of the effects of the present disclosure, the content of the aromatic ring-containing resin with respect to 100 parts by mass of the rubber component may be 1 part by mass or more, may be 2 parts by mass or more, may be 3 parts by mass or more, or may be 0 parts by mass. On the other hand, from the viewpoint of the effects of the present disclosure, the content is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, and further preferably 4 parts by mass or less.

[0104] The rubber composition constituting the tread portion preferably contains an aromatic ring-containing resin in the content as described above. However, the rubber composition constituting at least one outermost surface member other than the tread portion preferably contains less aromatic ring-containing resin than the rubber composition constituting the tread portion as described above. For example, it preferably contains at least 2 parts by mass less, more preferably at least 4 parts by mass less, and even more preferably at least 6 parts by mass less. Alternatively, the rubber composition constituting at least one outermost surface member other than the tread portion may contain no aromatic ring-containing resin at all.

[0105] (Other resins) The rubber composition according to the present disclosure can also contain resins other than those described above as long as the effects of the present disclosure are not impaired. Examples of such resins include polyterpene resins and rosin resins commonly used in the tire industry. These resins may be used alone or in combination of two or more.

[0106] (Polyterpene resin) Examples of the polyterpene resin include those composed of at least one selected from terpene raw materials such as α-pinene, β-pinene, limonene, and dipentene, and these may be further hydrogenated. One or more polyterpene petroleum resins can be used.

[0107] (Rosin resin) The rosin resin is a resin mainly composed of rosin acid obtained by processing rosin. Rosin resins include natural rosin resins (polymerized rosin) such as gum rosin, wood rosin, and tall oil rosin mainly composed of resin acids such as abietic acid, neoabietic acid, palustric acid, levopimaric acid, pimaric acid, isopimaric acid, and dehydroabietic acid, as well as hydrogenated rosin resins, unsaturated carboxylic acid-modified rosin resins, modified rosin resins such as rosin-modified phenol resins, rosin glycerin esters, unsaturated carboxylic acid-modified rosin esters, and disproportionated rosin resins obtained by disproportionating rosin resins. Rosin system treeOne or more kinds of fats can be used.

[0108] <Other compounding agents> In addition to the above components, the rubber composition according to the present disclosure may appropriately contain compounding agents generally used in the conventional tire industry, such as oils, waxes, anti-aging agents, stearic acid, zinc oxide, inorganic potassium salts, vulcanizing agents such as sulfur, vulcanization accelerators, and the like.

[0109] (Oil) Examples of the oil include process oil, vegetable oil, animal oil, etc. Examples of the process oil include paraffinic process oil, naphthenic process oil, aromatic process oil, etc. Also, a process oil with a low content of polycyclic aromatic compound (PCA) for environmental measures can be mentioned. Examples of the low-PCA-content process oil include Treated Distillate Aromatic Extract (TDAE) obtained by re-extracting aromatic process oil, aromatic alternative oil which is a mixed oil of asphalt and naphthenic oil, mild extraction solvates (MES), and heavy naphthenic oil, etc.

[0110] When contained, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and still more preferably 10 parts by mass or more from the viewpoint of processability in the rubber composition constituting the tread portion. On the other hand, from the viewpoints of low fuel consumption performance and durability performance, the content is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and still more preferably 40 parts by mass or less. Further, when contained, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and still more preferably 3 parts by mass or more from the viewpoint of processability in the rubber composition constituting at least one outermost surface member other than the tread portion. On the other hand, from the viewpoints of low fuel consumption performance and durability performance, the content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 10 parts by mass or less. In the present specification, the oil content also includes the amount of oil contained in the oil-extended rubber.

[0111] (Wax) When contained, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1 part by mass or more from the viewpoint of the weather resistance of the rubber. Further, from the viewpoint of preventing whitening of the tire due to blooming, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0112] (Antioxidant) The antioxidant is not particularly limited, and examples thereof include antioxidants such as amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, and metal carbamates.

[0113] When contained, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1 part by mass or more from the viewpoint of ozone crack resistance of the rubber. Further, from the viewpoints of abrasion resistance performance and wet grip performance, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0114] (Stearic acid) As the stearic acid, any stearic acid used in the tire industry can be preferably used.

[0115] (Zinc oxide) As the zinc oxide, any zinc oxide used in the tire industry can be preferably used.

[0116] (Inorganic potassium salt) The inorganic potassium salt can be used to improve the extrusion processability. Examples of the inorganic potassium salt include potassium carbonate, potassium hydrogen carbonate, potassium tetraborate, etc. Among these, potassium tetraborate is preferable. One or more kinds of inorganic potassium salts can be used.

[0117] (Vulcanizing agent) Sulfur is preferably used as the vulcanizing agent. As the sulfur, powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, etc. can be used.

[0118] When the vulcanizing agent contains sulfur, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 0.8 part by mass or more, and still more preferably 1.0 part by mass or more from the viewpoint of ensuring a sufficient vulcanization reaction in the rubber composition constituting the tread portion. On the other hand, from the viewpoint of preventing deterioration, the content is preferably 6.0 parts by mass or less, more preferably 5.0 parts by mass or less, and still more preferably 4.0 parts by mass or less. Further, when the vulcanizing agent contains sulfur, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 0.8 part by mass or more, and still more preferably 1.2 part by mass or more from the viewpoint of ensuring a sufficient vulcanization reaction in the rubber composition constituting at least one outermost surface member other than the tread portion. On the other hand, from the viewpoint of preventing deterioration, the content is preferably 7.0 parts by mass or less, more preferably 6.0 parts by mass or less, and still more preferably 5.0 parts by mass or less.

[0119] Examples of vulcanizing agents other than sulfur include organic crosslinking agents containing sulfur atoms such as alkylphenol sulfur chloride condensates, sodium 1,6 - hexamethylene - dithiolsulfate dihydrate, 1,6 - bis(N,N'-dibenzylthiocarbamoyldithio)hexane, and organic peroxides such as dicumyl peroxide. Examples of these vulcanizing agents other than sulfur include those manufactured by Taoka Chemical Industry Co., Ltd., Flexsys, and Rancess Co., Ltd.

[0120] (Vulcanization accelerator) The vulcanization accelerator is not particularly limited. For example, it includes sulfenamide - based, thiazole - based, thiuram - based, thiourea - based, guanidine - based, dithiocarbamic acid - based, aldehyde - amine - based or aldehyde - ammonia - based, imidazoline - based, and xanthate - based vulcanization accelerators. Among them, sulfenamide - based vulcanization accelerators and guanidine - based vulcanization accelerators are preferred from the viewpoint of more suitably obtaining the desired effects, and it is more preferred to use these two types in combination.

[0121] Examples of sulfenamide - based vulcanization accelerators include N - cyclohexyl - 2 - benzothiazolylsulfenamide (CBS), N - t - butyl - 2 - benzothiazolylsulfenamide (TBBS), N - oxyethylene - 2 - benzothiazolylsulfenamide, N,N'-diisopropyl - 2 - benzothiazolylsulfenamide, N,N - dicyclohexyl - 2 - benzothiazolylsulfenamide, etc. Examples of thiazole - based vulcanization accelerators include 2 - mercaptobenzothiazole, dibenzothiazolyl disulfide, etc. Examples of thiuram - based vulcanization accelerators include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetrabenzylthiuram disulfide (TBzTD), etc. Examples of guanidine - based vulcanization accelerators include 1,3 - diphenylguanidine (DPG), diorthotolylguanidine, orthotolylbiguanidine, etc. These vulcanization accelerators may be used alone or in combination of two or more. Preferred combinations include, for example, TBBS and DPG.

[0122] When contained, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, in the rubber composition constituting the tread portion. On the other hand, the content is preferably 8 parts by mass or less, more preferably 7 parts by mass or less, still more preferably 6 parts by mass or less. Further, when contained, the content relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1 part by mass or more, still more preferably 1.5 parts by mass or more, in the rubber composition constituting at least one outermost surface member other than the tread portion. On the other hand, the content is preferably 6 parts by mass or less, more preferably 5 parts by mass or less, still more preferably 4 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, the breaking strength and elongation tend to be ensured.

[0123] <Rubber composition> The rubber composition can be produced by a known method. For example, it can be produced by kneading the above-mentioned respective components using a rubber kneading device such as an open roll, a closed kneader (Banbury mixer, kneader, etc.).

[0124] The kneading process includes, for example, a base kneading process of kneading compounding agents and additives other than the vulcanizing agent and the vulcanization accelerator, and a final kneading (F kneading) process of adding the vulcanizing agent and the vulcanization accelerator to the kneaded product obtained in the base kneading process and kneading them. Further, the base kneading process can be divided into a plurality of processes if desired. The kneading conditions are not particularly limited, but for example, in the base kneading process, kneading is performed at a discharge temperature of 150 to 170°C for 1 to 10 minutes, and in the final kneading process, kneading is performed at 70 to 110°C for 1 to 5 minutes.

[0125] <Tire> The tire according to the present disclosure includes a tread and at least one outermost surface member other than the tread portion, which are constituted by the above rubber composition, and can be used for passenger car tires, truck / bus tires, run-flat tires, motorcycle tires, etc. Further, it can be used for summer tires, winter tires, all-season tires.

[0126] The tire of the present disclosure can be manufactured by a conventional method. For example, among the unvulcanized rubber compositions obtained above, the one for the tread is extruded according to the shape of the tread, and the one for at least one outermost surface member other than the tread part is extruded according to the shape of the outermost surface member, and then bonded together with other tire members on a tire molding machine and molded by a conventional method to form an unvulcanized tire. By heating and pressurizing this unvulcanized tire in a vulcanizer, a tire can be manufactured. The vulcanization conditions are not particularly limited. For example, a method of vulcanizing at 150 to 200 ° C for 10 to 30 minutes can be mentioned.

Examples

[0127] Hereinafter, the present disclosure will be described based on examples, but the present disclosure is not limited only to these examples.

[0128] <Various chemicals> Hereinafter, various chemicals used in the examples and comparative examples are collectively shown. NR: TSR20 SBR1: Modified solution-polymerized SBR manufactured in Production Example 1 described below (styrene content: 30% by mass, vinyl bond amount: 52 mol%, Mw: 250,000, non-oil product) SBR2: Toughden 4850 manufactured by Asahi Kasei Corporation (unmodified S-SBR, styrene content: 40% by mass, vinyl content: 46 mol%, Mw: 350,000, containing 50 parts by mass of oil per 100 parts by mass of rubber solid content) Multicomponent polymer 1: Hydrogenated SBR manufactured in Production Example 2 described below Multicomponent polymer 2: Hydrogenated modified SBR manufactured in Production Example 3 described below Multicomponent polymer 3: DYNARON (registered trademark) 2324P (hydrogenated SBR) manufactured by JSR Corporation Multicomponent polymer 4: Toughtec (registered trademark) P1083 (SEBS) manufactured by Asahi Kasei Corporation BR: UBEPOL BR (registered trademark) 150B manufactured by Ube Industries, Ltd. (vinyl bond amount: 1.5 mol%, cis 1,4-content: 97%, Mw: 440,000) Carbon black 1: Show Black N110 (N manufactured by Cabot Japan Co., Ltd.) 2 SA: 142 m 2 / g) Carbon black 2: Show Black N330 (N manufactured by Cabot Japan Co., Ltd.) 2 SA: 79 m 2 / g) Silica: ULTRASIL (registered trademark) VN3 (N manufactured by Evonik Degussa GmbH) 2 SA: 175 m 2 / g) Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) manufactured by Evonik Degussa GmbH Oil: NH-70S (aromatic oil) manufactured by Idemitsu Kosan Co., Ltd. Aromatic ring-containing resin: Sylvatraxx 4401 (copolymer of α-methylstyrene and styrene, softening point: 85°C) manufactured by Arizona Chemical Wax: Ozoace0355 manufactured by Nippon Seiro Co., Ltd. Antioxidant: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Stearic acid: Stearic acid "Tsubaki" manufactured by NOF Corporation Zinc oxide: Ginrei R manufactured by Toho Zinc Co., Ltd. Inorganic potassium salt : US Potassium tetraborate tetrahydrate (K 2 B 4 O 7 ·4H 2 O) manufactured by Yamamoto Chemical Industry Co., Ltd. Sulfur: HK-200-5 (5% oil-containing powdered sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Nocceler NS-G (N-tert-butyl-2-benzothiazolylsulfenamide (TBBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Nocceler D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0129] (Production Example 1) Manufacture of SBR1 A nitrogen-substituted autoclave reactor was charged with cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene. After adjusting the temperature of the reactor contents to 20 °C, n-butyllithium was added to initiate polymerization. Polymerization was carried out under adiabatic conditions, and the maximum temperature reached 85 °C. When the polymerization conversion rate reached 99%, 1,3-butadiene was added, and after further polymerization for 5 minutes, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane was added as a modifier to conduct the reaction. After the polymerization reaction was completed, 2,6-di-tert-butyl-p-cresol was added. Then, solvent removal was performed by steam stripping, and drying was carried out using a hot roll adjusted to 110 °C to obtain SBR1.

[0130] (Production Example 2) Production of Hydrogenated SBR 2000 ml of n-hexane, 68 g of styrene, 132 g of butadiene, 2.5 g of THF, and 0.45 mmol of n-butyllithium were added to a heat-resistant reaction vessel sufficiently purged with nitrogen, and the mixture was stirred at 50 °C for 5 hours to conduct a polymerization reaction. Then, while supplying hydrogen gas at a pressure of 0.4 MPa-Gauge, the mixture was stirred for 20 minutes to react with unreacted polymer terminal lithium to form lithium hydride. The hydrogen gas supply pressure was set to 0.7 MPa-Gauge, the reaction temperature was set to 90 °C, and hydrogenation was carried out using a catalyst mainly composed of titanocene dichloride. When the integrated amount of hydrogen absorption reached the target hydrogenation rate, the reaction temperature was returned to room temperature, the hydrogen pressure was returned to normal pressure, and the mixture was withdrawn from the reaction vessel. The reaction solution was stirred and poured into water, and the solvent was removed by steam stripping to obtain a multi-polymer 1 (hydrogenated SBR).

[0131] (Production Example 3) Production of Hydrogenated Modified SBR After the polymerization reaction and before the hydrogenation step, 0.15 mol of N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane (modifier) was added, and the mixture was stirred at 0 °C for 1 hour. And, in the hydrogenation step, the integrated amount of hydrogen absorption harvest was adjusted to the target hydrogenation rate, and the treatment was carried out in the same manner as in Production Example 2 to obtain a multi-polymer 2 (hydrogenated modified SBR).

[0132] The characteristics of the multi-polymer are shown in Table 1 below.

[0133]

Table 1

[0134] <Examples and Comparative Examples> According to Table 1, for each of the compounding formulations of the tread part (Trd) and the sidewall part (SW), chemicals other than sulfur and vulcanization accelerators were kneaded for 5 minutes using a 1.7 L sealed Banbury mixer until the discharge temperature reached 150 - 160 °C to obtain kneaded materials. Then, sulfur and vulcanization accelerators were added to the obtained kneaded materials respectively, and they were kneaded using a twin-screw open roll for 4 minutes until the temperature reached 105 °C to obtain each unvulcanized rubber composition.

[0135] The unvulcanized rubber composition obtained from the compounding formulation of the tread part was molded into the shape of the tread, and the unvulcanized rubber composition obtained from the compounding formulation of the sidewall part was molded into the shape of the sidewall. These were bonded together with other tire members to produce an unvulcanized tire. The unvulcanized tire was press-vulcanized at 170 °C for 12 minutes to produce a test tire (195 / 65R15 91V).

[0136] (Crack resistance performance) Each test tire was assembled on a JIS standard rim 15×6JJ, filled with the normal air pressure, and loaded with the maximum load corresponding to this air pressure according to the air pressure - load capacity correspondence table. It was run on a drum at a speed of 80 km / h, and the running distance at the time when damage visible by visual inspection occurred at the tread, sidewall, and the interface between the tread and the sidewall was determined respectively. Regarding the tread, sidewall, and the interface between the tread and the sidewall, the running distance of Comparative Example 1 was set to 100 and shown as an index respectively. The larger the index, the better the crack resistance.

[0137]

Table 2

[0138] From the above results, it can be seen that the crack resistance performance of the tire of the present disclosure is improved.

Explanation of symbols

[0139] 1 Tire 2 Tread portion 3 Sidewall 4 Clinch portion 5 Bead core 6 Bead apex 7 Breaker 8 Rim 9 Wing 10 Clinch apex

Claims

1. A tire comprising a tread portion and at least one outermost surface member other than the tread portion, wherein at least one outermost surface member other than the tread portion is at least one selected from the group consisting of a wing and a sidewall, the rubber composition constituting the tread portion contains a rubber component including a diene rubber and a multi-polymer, the multi-polymer has an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit, the rubber composition constituting at least one outermost surface member other than the tread portion contains a rubber component including a diene rubber and a multi-polymer, the multi-polymer has an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit, For each rubber component constituting the rubber component of the tread portion, a value obtained by multiplying the aromatic vinyl unit content (mass %) by the mass fraction in the rubber component is calculated, and these values are summed to obtain the aromatic vinyl unit content T Arm (mass %) in the rubber component of the tread portion. On the other hand, for each rubber component constituting the rubber component of at least one outermost surface member other than the tread portion, a value obtained by multiplying the aromatic vinyl unit content (mass %) by the mass fraction in the rubber component is calculated, and these values are summed to obtain the aromatic vinyl unit content OMM Arm (mass %) in the rubber component of at least one outermost surface member other than the tread portion. When calculating, T Arm is greater than OMM Arm , the tire.

2. the content of the multi-polymer contained in the rubber composition constituting the tread portion is 5% by mass or more in 100% by mass of the rubber component, the content of the multi-polymer contained in the rubber composition constituting at least one outermost surface member other than the tread portion is 2% by mass or more in 100% by mass of the rubber component. The tire according to claim 1.

3. The above-mentioned T Arm The tire according to claim 1 or 2, wherein the above-mentioned T is 15% by mass or more.

4. the rubber composition constituting the tread portion contains 40 parts by mass or more of a filler with respect to 100 parts by mass of the rubber component, and the filler contains 50% by mass or more of silica, the rubber composition constituting at least one outermost surface member other than the tread portion contains 10 parts by mass or more of a filler with respect to 100 parts by mass of the rubber component, and the filler contains more than 0% by mass of silica. The tire according to any one of claims 1 to 3.

5. the rubber composition constituting the tread portion contains 1 to 45 parts by mass of an aromatic ring-containing resin with respect to 100 parts by mass of the rubber component. The tire according to any one of claims 1 to 4.

6. the diene rubber contained in the rubber composition constituting the tread portion contains natural rubber, and the diene rubber contained in the rubber composition constituting at least one outermost surface member other than the tread portion contains natural rubber. The tire according to any one of claims 1 to 5.

7. the content of natural rubber in 100% by mass of the rubber component in the tread portion is less than the content of natural rubber in 100% by mass of the rubber component in at least one outermost surface member other than the tread portion. The tire according to claim 6.

8. The rubber composition constituting at least one outermost surface member other than the tread portion does not contain an aromatic ring-containing resin, or the amount of the aromatic ring-containing resin per 100 parts by mass of the rubber component contained in the rubber composition constituting at least one outermost surface member other than the tread portion is less than the amount of the aromatic ring-containing resin per 100 parts by mass of the rubber component contained in the rubber composition constituting the tread portion. The tire according to any one of claims 5 to 7.

9. The glass transition temperature of the rubber composition constituting the tread portion is higher than the glass transition temperature of the rubber composition constituting at least one outermost surface member other than the tread portion. The tire according to any one of claims 1 to 8.

10. When the multi-polymer contained in the rubber composition constituting the tread portion is a hydrogenated polymer composed of an aromatic vinyl unit and a conjugated diene unit, the hydrogenation rate is 30 mol% or more and less than 100 mol%. When the multi-polymer contained in the rubber composition constituting at least one outermost surface member other than the tread portion is a hydrogenated polymer composed of an aromatic vinyl unit and a conjugated diene unit, the hydrogenation rate is 30 mol% or more and less than 100 mol%. The tire according to any one of claims 1 to 9.

11. At least one outermost surface member other than the tread portion is a sidewall. The tire according to any one of claims 1 to 10.

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