Tire

Abstract

A tire having a tread portion and at least one outermost surface portion other than the tread portion, wherein a rubber composition constituting the tread portion and a rubber composition constituting the at least one outermost surface portion other than the tread portion each contain a rubber component, the rubber component containing a diene rubber and a multi-component polymer containing an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit; for each individual rubber component of the rubber component constituting the tread portion, a value obtained by multiplying the mass fraction in the rubber component by the aromatic vinyl unit content (mass%) is calculated, and these values are added to calculate the aromatic vinyl unit content T Arm (mass%) in the rubber component constituting the tread portion; similarly, the aromatic vinyl unit content OMM Arm (mass%) in the rubber component constituting the at least one outermost surface portion other than the tread portion is calculated. The tire is a tire having improved crack resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to a tire having improved crack resistance. BACKGROUND

[0002] Generally, a rubber product including a tire is deteriorated by ozone or oxygen in the atmosphere, and cracks are generated on the surface thereof. Such cracks are generated due to static and dynamic stresses applied to the rubber product, thereby causing the rubber to be damaged.

[0003] Patent Document 1 discloses a pneumatic tire in which a predetermined copolymer (prepared by hydrogenating a copolymer of an aromatic vinyl compound and a conjugated diene compound) is used to improve the handling stability, fuel efficiency, and processability in a well-balanced manner.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: JP 2019-014796 A SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] An object of the present application is to provide a tire having improved crack resistance.

[0009] METHOD FOR SOLVING THE PROBLEM

[0010] Through intensive studies, the inventors have found that the above problem can be solved as follows, and have conducted further studies to complete the present application: using a rubber component including a diene-based rubber and a predetermined multi-component polymer for each of a tread portion and at least one outermost surface member other than the tread portion of the tire, and focusing on the aromatic vinyl unit content of each individual rubber component, making the aromatic vinyl unit content of the rubber component constituting the tread portion greater than the aromatic vinyl unit content of the rubber component constituting at least one outermost surface member other than the tread portion.

[0011] In other words, the present application relates to:

[0012] [1] A tire having a tread portion and at least one outermost surface member other than the tread portion, wherein,

[0013] the rubber composition constituting the tread portion includes a rubber component including a diene-based rubber and a multi-component polymer including an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit;

[0014] 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-component polymer including an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit; and

[0015] For each individual rubber component of the rubber component constituting the tread portion, a value obtained by multiplying the mass fraction in the rubber component by the aromatic vinyl unit content (mass%) is calculated, and these values are added to calculate the aromatic vinyl unit content T Arm (mass%) in the rubber component constituting the tread portion; for each individual rubber component of the rubber component constituting at least one outermost surface member other than the tread portion, a value obtained by multiplying the mass fraction in the rubber component by the aromatic vinyl unit content (mass%) is calculated, and these values are added to calculate the aromatic vinyl unit content OMM Arm (mass%) in the rubber component constituting at least one outermost surface member other than the tread portion; T Arm is greater than OMM Arm .

[0016] [2] The tire according to the above [1], wherein the content of the multi-component 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, further preferably 30 mass% or more, in 100 mass% of the rubber component; the content of the multi-component 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, further preferably 20 mass% or more, further preferably 30 mass% or more, in 100 mass% of the rubber component.

[0017] [3] The tire according to the above [1] or [2], wherein T m is 15 mass% or more, preferably 20 mass% or more, more preferably 25 mass% or more, further preferably 30 mass% or more, further preferably 33 mass% or more.

[0018] [4] The tire according to any one of the above [1] to [3], wherein the rubber composition constituting the tread contains 40 mass% or more, preferably 50 mass% or more, more preferably 60 mass% or more, further preferably 70 mass% or more, further preferably 80 mass% or more, of a filler, with respect to 100 parts by mass of the rubber component, the filler containing 50 mass% or more, more preferably 60 mass% or more, further preferably 70 mass% or more, further preferably 80 mass% or more, further preferably 83 mass% or more, further preferably 90 mass% or more, of silica;

[0019] 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, further preferably 40 parts by mass or more, further preferably 50 parts by mass or more, of a filler, relative to 100 parts by mass of a rubber component, the filler containing more than 0 mass% of silica or containing preferably 50 mass% or more, more preferably 60 mass% or more, further preferably 70 mass% or more, further preferably 80 mass% or more, further preferably 83 mass% or more, further preferably 90 mass% or more, of silica.

[0020] [5] The tire according to any one of the above [1] to [4], wherein 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, further preferably 4 to 42 parts by mass, further preferably 5 to 41 parts by mass, further preferably 5 to 40 parts by mass, further preferably 6 to 40 parts by mass, of the aromatic ring-containing resin, relative to 100 parts by mass of a rubber component.

[0021] [6] The tire according to any one of the above [1] to [5], wherein 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.

[0022] [7] The tire according to the above [6], wherein the content of the natural rubber in the tread portion is less than the content of the natural rubber in at least one outermost surface member other than the tread portion, in 100 mass% of a rubber component.

[0023] [8] The tire according to any one of the above [5] to [7], wherein the rubber composition constituting at least one outermost surface member other than the tread portion does not contain the aromatic ring-containing resin, or the parts by mass of the aromatic ring-containing resin contained in the rubber composition constituting at least one outermost surface member other than the tread portion relative to 100 parts by mass of a rubber component is less than the parts by mass of the aromatic ring-containing resin contained in the rubber composition constituting the tread portion relative to 100 parts by mass of a rubber component.

[0024] [9] The tire according to any one of the above [1] to [8], wherein 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.

[0025]

[10] The tire described in any one of [1] to [9] above, wherein, when the multi-component polymer contained in the rubber composition constituting the tread is a hydrogenated polymer of a polymer composed of aromatic vinyl units and conjugated diene units, the hydrogenation rate of the hydrogenated polymer 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%, and even more preferably 90 mol% or more and less than 100 mol%; when the multi-component polymer contained in the rubber composition constituting at least one outermost surface component other than the tread is a hydrogenated polymer of a polymer composed of aromatic vinyl units and conjugated diene units, the hydrogenation rate of the hydrogenated polymer 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%, and even more preferably 90 mol% or more and less than 100 mol%.

[0026]

[11] The tire described in any one of [1] to

[10] above, wherein at least one outermost surface component other than the tread is selected from at least one of the tire flap, tire sidewall and lap joint triangle rubber.

[0027]

[12] The tire described in any one of [1] to

[10] above, wherein at least one outermost surface component other than the tread portion is a sidewall.

[0028] Effects of the present invention

[0029] This invention enables the provision of tires with improved crack resistance. Attached Figure Description

[0030] Figure 1 An embodiment of a cross-sectional view of a tire having a tread and a sidewall.

[0031] Figure 2 An embodiment of a cross-sectional view of a tire having a tread and outermost surface components (flanges, sidewalls, and lap joint triangles). Detailed Implementation

[0032] The tire of one embodiment of the present disclosure is a tire having a tread portion and at least one outermost surface portion other than the tread portion, wherein the rubber composition constituting the tread portion contains a rubber component containing a diene rubber and a multi-component polymer containing an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit; the rubber composition constituting the at least one outermost surface portion other than the tread portion contains a rubber component containing a diene rubber and a multi-component polymer containing an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit; for each individual rubber component of the rubber component constituting the tread portion, a value obtained by multiplying the mass fraction in the rubber component by the aromatic vinyl unit content (mass%) is calculated, and these values are added to calculate the aromatic vinyl unit content T Arm (mass%) in the rubber component constituting the tread portion; for each individual rubber component of the rubber component constituting the at least one outermost surface portion other than the tread portion, a value obtained by multiplying the mass fraction in the rubber component by the aromatic vinyl unit content (mass%) is calculated, and these values are added to calculate the aromatic vinyl unit content OMM Arm (mass%) in the rubber component constituting the at least one outermost surface portion other than the tread portion; T Arm > OMM Arm .

[0033] Although not intended to be bound by theory, the mechanism of improving the crack resistance in the present disclosure can take into account the following factors. In other words, first, the multi-component polymer compounded in the diene rubber leads to the formation of an island structure, which contributes to the prevention of the propagation of cracks generated in the diene rubber due to its high crack propagation resistance. Second, the multi-component polymer compounded not only in the tread portion but also in the at least one outermost surface portion other than the tread portion makes it possible to provide the tire surface exposed to ozone or oxygen with crack propagation resistance. Third, making the aromatic vinyl unit content (T Arm ) in the rubber component constituting the tread portion greater than the aromatic vinyl unit content (OMM Arm ) in the rubber component constituting the at least one outermost surface portion other than the tread portion results in a decrease in the glass transition temperature (Tg) of the at least one outermost surface portion other than the tread portion and results in the at least one outermost surface portion other than the tread portion being softer than the tread portion, so that the at least one outermost surface portion other than the tread portion can serve as a cushioning material to absorb the impact from a stepped portion or the like, preventing cracks from occurring between the tread portion and the at least one outermost surface portion other than the tread portion. It is believed that these points described above cooperate with each other to improve the crack resistance synergistically.

[0034] The content of the multi-component 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; the content of the multi-component polymer contained in the rubber composition constituting at least one outermost surface portion other than the tread portion is preferably 2% by mass or more in 100% by mass of the rubber component. It is considered that the above contributes to exerting the effect of the crack propagation resistance of the multi-component polymer.

[0035] T Arm It is preferably 15% by mass or more. It is considered that increasing the content of the aromatic vinyl unit in the tread portion makes at least one outermost surface portion other than the tread portion easy to use as a cushioning material.

[0036] The rubber composition constituting the tread portion preferably contains 40 parts by mass or more of a filler, and the filler preferably contains 50% by mass or more of silica, in 100 parts by mass of the rubber component; the rubber composition constituting at least one outermost surface portion other than the tread portion preferably contains 10 parts by mass or more of a filler, and the filler preferably contains more than 0% by mass of silica, in 100 parts by mass of the rubber component. It is considered that, among the fillers, silica has lower rubber-binding properties than carbon black and provides a flexible rubber composition, so that it can prevent cracks between the rubber component and the filler (when an impact is applied to the rubber, stress is concentrated between the rubber component and the filler). It is considered that increasing the percentage content of silica in the tread portion and at least one outermost surface portion other than the tread portion makes it possible to further strengthen the interface between the tread and at least one outermost surface portion other than the tread portion, and also contributes to preventing cracks between the portions.

[0037] The rubber composition constituting the tread portion preferably contains 1 to 45 parts by mass of an aromatic ring-containing resin, in 100 parts by mass of the rubber component. It is considered that adding an aromatic ring-containing resin to the tread portion having a high content of aromatic vinyl units increases the interaction between the aromatic vinyl units in the rubber component and the aromatic rings of the aromatic ring-containing resin, thereby contributing to improving the reinforcing properties.

[0038] The diene rubber contained in the rubber composition constituting the tread portion preferably contains natural rubber, and the diene rubber contained in the rubber composition constituting at least one outermost surface portion other than the tread portion preferably contains natural rubber. This is because the above allows the tread portion and at least one outermost surface portion other than the tread portion to utilize the characteristics of natural rubber having high mechanical strength.

[0039] The content of natural rubber in the tread portion is preferably less than the content of natural rubber in at least one outermost surface portion other than the tread portion, in 100 parts by mass of the rubber component. It is considered that promoting a decrease in the multi-component polymer content of at least one outermost surface portion other than the tread portion results in softening of at least one outermost surface portion, making at least one outermost surface portion more easily used as a cushioning material.

[0040] Preferably, the rubber composition constituting at least one outermost surface portion other than the tread portion does not contain an aromatic ring-containing resin, or the content of an aromatic ring-containing resin contained in the rubber composition constituting at least one outermost surface portion other than the tread portion is less than the content of an aromatic ring-containing resin contained in the rubber composition constituting the tread portion, in parts by mass of the aromatic ring-containing resin with respect to 100 parts by mass of the rubber component. It is considered that increasing the relative content of the aromatic ring-containing resin in the tread portion contributes to softening of at least one outermost surface portion other than the tread portion, making at least one outermost surface portion more easily used as a cushioning material. For example, in the case where the content of the aromatic ring-containing resin in the rubber composition constituting the tread portion is 5 to 40 parts by mass (with respect to 100 parts by mass of the rubber component), the content of the aromatic ring-containing resin in the rubber composition constituting at least one outermost surface portion other than the tread portion is less than the content of the aromatic ring-containing resin in the rubber composition constituting the tread portion, and the content of the aromatic ring-containing resin in the rubber composition constituting at least one outermost surface portion other than the tread portion is preferably 0 to 10 parts by mass, more preferably 0 to 6 parts by mass, further preferably 0 to 4 parts by mass, or the aromatic ring-containing resin is not necessarily contained at all.

[0041] 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 is softer than the tread portion, so that at least one outermost surface member is more easily used 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 further preferably -20°C or higher. On the other hand, the Tg is preferably 0°C or lower, more preferably -5°C or lower, and further preferably -10°C or lower. Furthermore, 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 further preferably -40°C or higher. On the other hand, the Tg is preferably -30°C or lower, more preferably -25°C or lower, and further preferably -20°C or lower. Furthermore, in the present specification, the glass transition temperature (Tg) of the rubber composition refers to the tan δ peak temperature measured using the following method. In other words, for each test piece sample (for example, 40 mm vertical x 7 mm horizontal) of the rubber composition, a dynamic viscoelasticity evaluation device (EPLEXOR series, manufactured by GABO Qualimeter Testanlagen GmbH) is used to measure a temperature distribution curve of tan δ under 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 increasing rate of 2°C / min, and the temperature (tan δ peak temperature) corresponding to the maximum tan δ value in the obtained temperature distribution curve is set as the Tg.

[0042] In the case where the multi-component polymer contained in the rubber composition constituting the tread portion is a hydrogenated polymer of a polymer composed of an aromatic vinyl unit and a conjugated diene unit, the hydrogenation rate of the hydrogenated polymer is preferably 30 mol% or more and less than 100 mol%; and in the case where the multi-component polymer contained in the rubber composition constituting at least one outermost surface member other than the tread portion is a hydrogenated polymer of a polymer composed of an aromatic vinyl unit and a conjugated diene unit, the hydrogenation rate of the hydrogenated polymer is preferably 30 mol% or more and less than 100 mol%. It is considered that the above makes the multi-component polymer more easily exhibit crack growth resistance.

[0043] A tire as one embodiment of the present disclosure will be described below. The tire includes a tread portion composed of a rubber composition and at least one outermost surface portion other than the tread portion composed of a rubber composition. Hereinafter, unless otherwise specifically stated, the explanation of the rubber composition can be applied to the rubber composition constituting the tread portion and the rubber composition constituting at least one outermost surface portion other than the tread portion. In addition, the upper limit and lower limit numerical values with respect to "above (or higher)", "below (or lower)" and "to" are numerical values that can be arbitrarily combined, and the numerical values in the examples can be set as the upper limit and lower limit. In addition, unless otherwise specifically stated, the numerical range designated using the expression "to" should include both the numerical values at the ends.

[0044] In the present disclosure, at least one outermost surface portion other than the tread portion is not limited as long as it is a portion constituting the outermost surface of the tire, and any portion constituting the outermost surface of the tire can be applied to at least one outermost surface portion other than the tread portion, and at least one outermost surface portion other than the tread portion is not affected by its name. For example, examples of at least one outermost surface portion include Figure 2 the wing, the side wall and the lap apex, and the like shown in FIG. 1.

[0045] Therefore, at least one outermost surface portion other than the tread portion is preferably at least one portion selected from the group consisting of the wing, the side wall and the lap apex, and among these, the side wall is preferred.

[0046] In the present disclosure, in the case where a plurality of portions are applied to at least one outermost surface portion other than the tread portion, for each portion, the aromatic vinyl unit content, the multi-component polymer content, the filler content, the silica content in the filler, the content of the aromatic ring-containing resin, the natural rubber content, the glass transition temperature of the rubber composition, and (in the case where the multi-component polymer is a hydrogenated polymer of a polymer composed of an aromatic vinyl unit and a conjugated diene unit) the hydrogenation rate thereof, and the like are individually identified.

[0047] <Rubber Component>

[0048] The rubber composition constituting the tread portion and the rubber composition constituting at least one outermost surface portion other than the tread portion of the present disclosure each contain a rubber component, and the rubber component contains a diene-based rubber and a multi-component polymer.

[0049] (Multi-component Polymer)

[0050] The multi-component polymer refers to a copolymer containing an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit, can contain other monomer units, and preferably is a copolymer consisting of an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit. The copolymer can be obtained by copolymerizing monomer components containing an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit and hydrogenating it as necessary; in addition, the copolymer can also be obtained by copolymerizing monomer components containing an aromatic vinyl unit and a conjugated diene unit, preferably monomer components consisting of an aromatic vinyl unit and a conjugated diene unit, to obtain a copolymer and subsequently hydrogenating the conjugated diene unit of the above copolymer to produce a non-conjugated olefin unit. The arrangement of each unit is not particularly limited as long as it is a copolymer having an aromatic vinyl unit, a non-conjugated olefin unit, and a conjugated diene unit, and it can be a random copolymer obtained by random copolymerization or a block copolymer obtained by block copolymerization, preferably a random copolymer. One multi-component polymer can be used, or two or more of them can be used.

[0051] < aromatic vinyl unit >

[0052] The aromatic vinyl unit refers to a unit derived from an aromatic vinyl compound in the copolymer. In the present context, the aromatic vinyl compound refers to an aromatic compound substituted with at least a vinyl group, and does not include the following conjugated diene compound. Examples of the aromatic vinyl compound include, for example, styrene, a-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, and the like. These can be used alone or in combination of two or more. Among these, styrene is particularly preferable from the viewpoint of practicality (e.g., easy availability of the monomer) and for the reason that it is more suitable for obtaining the effects of the present disclosure.

[0053] < non-conjugated olefin unit >

[0054] The non-conjugated olefin unit refers to a unit derived from a non-conjugated olefin compound in the copolymer. In the present context, the non-conjugated olefin compound refers to an aliphatic unsaturated hydrocarbon, which is a non-conjugated compound having at least one carbon-carbon double bond. Examples of the non-conjugated olefin compound include, for example, a-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene; and heteroatom-substituted olefin compounds such as vinyl pivalate, 1-phenylthioethylene, N-vinylpyrrolidone, and the like. Among these, ethylene, 1-butene, and the like are preferable. These can be used alone or in combination of two or more. Among these, ethylene is more preferable from the viewpoint of practicality (e.g., easy availability of the monomer) and for the reason that it is more suitable for obtaining the effects of the present disclosure.

[0055] < conjugated diene unit >

[0056] A conjugated diene unit refers to a unit derived from a conjugated diene compound in a copolymer. Examples of the conjugated diene compound herein include, for example, 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene, and the like. These can be used alone or in combination of two or more. Among these, 1,3-butadiene or isoprene is preferred from a practical aspect (e.g., availability of monomers) and for the reason that the effects of the present disclosure are more suitably obtained, and 1,3-butadiene is more preferred.

[0057] <Multi-component polymer>

[0058] Preferred specific examples of the multi-component polymer include, for example, a hydrogenated copolymer of a copolymer of styrene and 1,3-butadiene (styrene-butadiene copolymer (SBR)). Thus, as the multi-component polymer, a hydrogenated styrene-butadiene copolymer (hydrogenated SBR) is preferred.

[0059] <Hydrogenation rate>

[0060] From the viewpoint of the effects of the present disclosure, the hydrogenation rate of the multi-component polymer (i.e., the proportion of double bonds on the conjugated diene unit being hydrogenated in the case where the multi-component polymer is a hydrogenated polymer composed of an aromatic vinyl unit and a conjugated diene unit) is preferably 30 mol% or more. The hydrogenation rate is more preferably 50 mol% or more, further preferably 70 mol% or more, further preferably 90 mol% or more. The upper limit is not particularly limited, and it can be less than 100 mol%. The hydrogenation rate can be adjusted by adjusting the hydrogen supply pressure or the reaction conditions (e.g., the reaction temperature in the hydrogenation reaction described in Manufacturing Example 2 below). Furthermore, the hydrogenation rate can be calculated from the reduction rate of the spectrum of the unsaturated bond portion in the spectrum obtained by H-NMR. 1 H-NMR.

[0061] <Modification>

[0062] As needed, the multi-component polymer can also be treated with a modifier to make a modified body in which a functional group that interacts with silica is introduced. As such a functional group, any one of those commonly used in the art can be suitably used, and examples include, for example, an alkoxysilyl group (e.g., trimethoxysilyl group, triethoxysilyl group), and the like. For example, treatment of a copolymer with chlorotriethoxysilane as a modifier after the synthesis of the copolymer but before hydrogenation thereof can obtain a modified body in which a triethoxysilyl group is introduced at the living terminal of the copolymer. Preferably, the modified multi-component polymer is used for a rubber composition that constitutes a tread portion.

[0063] <mw>

[0064] From the viewpoint of the effects of the present disclosure, the weight average molecular weight (Mw) of the multi-component polymer is preferably 50,000 or greater, more preferably 100,000 or greater, further preferably 150,000 or greater. Furthermore, from the viewpoint of the Mooney viscosity, the Mw of the multi-component polymer is preferably 2,000,000 or less, more preferably 1,000,000 or less, further preferably 700,000 or less.

[0065] <mw mn>

[0066] From the viewpoint of processability and the like, the ratio of the Mw to the number average molecular weight Mn (i.e., Mw / Mn) of the multi-component polymer is preferably 20.0 or less, more preferably 10.0 or less, and further preferably 5.0 or less. On the other hand, the lower limit of Mw / Mn is not particularly limited, and Mw / Mn can be 1.0 or more. Furthermore, in the present specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) can be measured in the form of a standard polystyrene based on the measurement values obtained by a gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M, manufactured by Tosoh Corporation).

[0067] <tg>

[0068] From the viewpoint of abrasion resistance, the glass transition temperature (Tg) of the multi-component polymer is preferably -70°C or higher, more preferably -65°C or higher, and further preferably -60°C or higher. In addition, from a similar viewpoint, the Tg of the multi-component polymer is preferably -10°C or lower, more preferably -15°C or lower, and further preferably -20°C or lower. The Tg of the multi-component polymer is measured by using a differential scanning calorimeter (Q200) manufactured by TA Instruments, Japan, while raising the temperature at a rate of 10°C / min according to JIS K 7121.

[0069] <Content of aromatic vinyl unit of multi-component polymer>

[0070] From the viewpoint of the effects of the present disclosure, the content of the aromatic vinyl unit of the multi-component polymer is preferably 5% by mass or more, more preferably 20% by mass or more, and further preferably 25% by mass or more. In addition, the content of the aromatic vinyl unit of the multi-component polymer is preferably 50% by mass or less, more preferably 45% by mass or less, and further preferably 40% by mass or less. In addition, the content of the aromatic vinyl unit of the multi-component polymer is measured by H-NMR measurement. 1 H-NMR measurement.

[0071] <Content of multi-component polymer>

[0072] From the viewpoint of the effects of the present disclosure, in the rubber composition constituting the tread portion, the content of the multi-component polymer is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 20% by mass or more, and further preferably 30% by mass or more, in 100% by mass of the rubber component. In addition, the content is preferably 100% by mass or less, more preferably 70% by mass or less, further preferably 50% by mass or less, and further preferably 40% by mass or less. In addition, from the viewpoint of the effects of the present disclosure, in the rubber composition constituting at least one outermost surface portion other than the tread portion, the content of the multi-component polymer is preferably 2% by mass or more, more preferably 8% by mass or more, more preferably 15% by mass or more, further preferably 20% by mass or more, and further preferably 30% by mass or more, in 100% by mass of the rubber component. In addition, the content is preferably 45% by mass or less, more preferably 40% by mass or less, and further preferably 35% by mass or less.

[0073] In 100% by mass of the rubber component, the multi-component polymer content constituting the tread portion of the rubber composition is preferably equal to or greater than the multi-component polymer content constituting at least one outermost surface component other than the tread portion. For example, when the multi-component polymer content (by mass%) constituting the tread portion of the rubber composition is within the above-mentioned range, the multi-component polymer content (by mass%) constituting at least one outermost surface component other than the tread portion of the rubber composition is equal to or greater than the multi-component polymer content (by weight%) constituting the tread portion of the rubber composition, or preferably is 2% or more lower than the multi-component polymer content (by weight%) constituting the tread portion of the rubber composition, more preferably 5% or more lower.

[0074] <Confirmation of Multicomponent Polymers>

[0075] Furthermore, multi-component polymers contain conjugated diene units, non-conjugated olefin units, and aromatic vinyl units, which can be detected using gel permeation chromatography (GPC). 1 H-NMR, 13 Confirmation is achieved using methods such as C-NMR. Specifically, based on gel permeation chromatography-refractive index (GPC-RI) and gel permeation chromatography-ultraviolet absorption (GPC-UV) curves, the ultraviolet absorption of aromatic rings (e.g., benzene rings) in the copolymer can be confirmed, thereby confirming the presence of a skeleton derived from aromatic vinyl compounds. Furthermore, based on... 1 H-NMR spectrum or 13 C-NMR spectroscopy confirmed the presence of units derived from each monomer component.

[0076] Furthermore, in the multicomponent polymer, the proportion of conjugated diene units present in a predetermined arrangement among all conjugated diene units can be determined using the method disclosed in WO 2018 / 092733 A (e.g., based on...). 13 This can be confirmed using C-NMR spectroscopy.

[0077] <Methods for Manufacturing Multicomponent Polymers>

[0078] For example, multicomponent polymers can be synthesized by polymerizing monomer components comprising aromatic vinyl units, non-conjugated olefin units, and conjugated diene units, followed by hydrogenation of the resulting copolymer (if necessary). Alternatively, they can be synthesized by copolymerizing monomer components comprising aromatic vinyl units and conjugated diene units to obtain a copolymer, followed by hydrogenation of the conjugated diene units of the copolymer to produce non-conjugated olefin units. Such synthesis can be carried out by conventional methods, as disclosed, for example, in JP 2018-083884 A, WO 2018 / 092733 A, etc. Modified versions of multicomponent polymers can be synthesized similarly.

[0079] (Diene-based rubber)

[0080] As the diene-based rubber, any one of rubber components (any one of which is generally used in the tire industry) other than the above-described multi-component polymer can be suitably used. Specifically, examples include, for example, isoprene-based rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR), styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isobutylene-styrene block copolymer (SIBS), chlorobutadiene rubber (CR), acrylonitrile-butadiene rubber (NBR), polynorbornene rubber, and the like. These diene-based rubber components can be used alone or in combination of two or more.

[0081] The diene-based rubber preferably contains at least one selected from the group consisting of isoprene-based rubber, SBR, and BR, and can be a rubber component containing isoprene rubber, SBR, and BR. Furthermore, the diene-based rubber can be a rubber component consisting of only isoprene-based rubber and SBR, can be a rubber component consisting of only isoprene-based rubber, SBR, and BR. Preferably, the diene-based rubber in the rubber composition constituting the tread portion contains SBR and BR, or it consists of SBR and BR. Preferably, the diene-based rubber of the rubber composition constituting at least one outermost surface member other than the tread portion contains isoprene-based rubber and BR, or it consists of isoprene-based rubber and BR.

[0082] (Isoprene-based rubber)

[0083] As the isoprene-based rubber, for example, those common in the tire industry, such as isoprene rubber (IR), natural rubber, and the like, can be used. Among these, in the natural rubber, in addition to unmodified natural rubber (NR), epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), ultra-pure natural rubber, modified natural rubber (including grafted natural rubber), and the like are included. Among these, natural rubber is preferred, and for example, NR can be suitably used. These isoprene-based rubbers can be used alone or in combination of two or more.

[0084] The NR is not particularly limited. As the NR, NRs common in the tire industry, such as SIR20, RSS#3, TSR20, and the like, can be used.

[0085] From the viewpoint of good ride comfort, the content of isoprene-based rubber in the rubber component in the rubber composition constituting the tread portion is preferably 40% by mass or less, more preferably 20% by mass or less, further preferably 10% by mass or less, or preferably the isoprene-based rubber is not contained therein. Note that, from the viewpoint of processability and durability, the content can be 1% by mass or more, 2% by mass or more, or 5% by mass or more. Furthermore, from the viewpoint of processability and durability, the content of isoprene-based rubber in the rubber component in the rubber composition constituting at least one outermost surface member other than the tread portion 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.

[0086] In 100% by mass of the rubber component, the content of isoprene-based rubber in the rubber composition constituting the tread portion is preferably less than the content of isoprene-based rubber in the rubber composition constituting at least one outermost surface member other than the tread portion. For example, in the case where the content of isoprene-based rubber (% by mass) in the rubber composition constituting at least one outermost surface member other than the tread portion is within the above range, the content of isoprene-based rubber (% by mass) in the rubber composition constituting the tread portion is 10% by mass or more, more preferably 20% by mass or more, further preferably 30% by mass or more lower than the content of isoprene-based rubber in the rubber composition constituting at least one outermost surface member other than the tread portion, or the rubber composition constituting the tread portion does not necessarily contain isoprene-based rubber at all.

[0087] (SBR)

[0088] The SBR is not particularly limited, and examples include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), modified SBRs thereof (modified S-SBR, modified E-SBR), and the like. Examples of the modified SBR include SBR modified at the terminal and / or main chain thereof, modified SBR coupled with tin, silicon compounds, or the like (condensates or modified SBRs having a branched structure, and the like), and the like. Among these, from the viewpoint of being able to improve fuel efficiency and wear resistance well, S-SBR and modified S-SBR are preferred. These SBRs can be used alone or in combination of two or more.

[0089] From the viewpoint of securing the damping and wet grip performance of the tread portion, the styrene content of the SBR is preferably 15% by mass or more, more preferably 20% by mass or more. Furthermore, from the viewpoint of temperature dependence of the grip performance and wear resistance, the content is preferably 60% by mass or less, more preferably 50% by mass or less. Furthermore, in the present specification, the styrene content of the SBR is calculated by H-NMR measurement. 1 H-NMR measurement.

[0090] From the viewpoint of ensuring reactivity with silica, rubber strength, and abrasion resistance, the amount of vinyl bonds of the SBR is preferably 10 mol% or more. In addition, from the viewpoint of preventing an increase in temperature dependence, wet grip performance, elongation at break, and abrasion resistance, the amount of vinyl bonds of the SBR is preferably 70 mol% or less. In addition, in the present specification, the amount of vinyl bonds (amount of 1,2-bond butadiene units) of the SBR is measured by infrared absorption spectroscopy.

[0091] From the viewpoint of abrasion resistance, the weight average molecular weight (Mw) of the SBR is preferably 150,000 or more, more preferably 200,000 or more, and further preferably 250,000 or more. In addition, from the viewpoint of uniformity of crosslinking and the like, the Mw is preferably 2,500,000 or less, and more preferably 2,000,000 or less. In addition, the Mw can be measured in the form of a standard polystyrene based on the measurement value of a gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPER MALTPORE HZ-M, manufactured by Tosoh Corporation).

[0092] As the SBR, an oil-extended SBR can be used, or a non-oil-extended SBR can be used. When an oil-extended SBR is used, the amount of oil extension of the SBR (i.e., the oil content of the oil extension included in the SBR) is preferably 10 to 50 parts by mass with respect to 100 parts by mass of the rubber solid content of the SBR.

[0093] As the SBR, for example, an SBR manufactured and / or sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Ube Industries, Ltd., Asahi Kasei Corporation, Zeon Corporation, ZS Elastomers Corporation, or the like can be used.

[0094] When the rubber composition constituting the tread portion contains SBR, the content of SBR in the rubber component 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, further preferably 25% by mass or more, further preferably 30% by mass or more, further preferably 35% by mass or more, from the viewpoint of ensuring the damping and wet grip properties. On the other hand, the content is preferably 85% by mass or less, more preferably 80% by mass or less, further preferably 75% by mass or less, further preferably 70% by mass or less, from the viewpoint of suppressing the improvement in durability due to heat dissipation. In addition, when the rubber composition constituting at least one of the outermost surface members other than the tread portion contains SBR, the content of SBR in the rubber component is preferably 40% by mass or less, more preferably 30% by mass or less, further preferably 20% by mass or less, further preferably 10% by mass or less, or preferably at least one of the outermost surface members other than the tread portion does not contain SBR, from the viewpoint of suppressing the improvement in durability due to heat dissipation. Note that the content can be 1% by mass or more, 2% by mass or more, or 5% by mass or more, from the viewpoint of ensuring the damping and wet grip properties.

[0095] The SBR content of the rubber composition constituting the tread portion is preferably greater than the SBR content of the rubber composition constituting at least one of the outermost surface members other than the tread portion, in 100% by mass of the rubber component. For example, the SBR content (% by mass) of the rubber composition constituting at least one of the outermost surface members other than the tread portion is preferably 10% by mass or more, more preferably 20% by mass or more, further preferably 30% by mass or more, lower than the SBR content (% by mass) of the rubber composition constituting the tread portion, or the rubber composition constituting at least one of the outermost surface members other than the tread portion does not necessarily contain SBR at all.

[0096] (BR)

[0097] The BR is not particularly limited, and those commonly used in the tire industry, such as BR having a cis content (content of cis-1,4 bonds) of less than 50% (low-cis BR), BR having a cis content of 90% or more (high-cis BR), rare-earth-based 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), and the like, can be used. These BRs can be used alone or in combination of two or more.

[0098] As the rare earth-based BR, those commonly used in the tire industry can be used. As the rare earth element-based catalyst for synthesizing (polymerizing) the rare earth-based BR, known catalysts can be used, examples of which include, for example, lanthanoid rare earth element compounds, organoaluminum compounds, aluminoxanes, halogen-containing compounds, and, if necessary, catalysts containing Lewis bases. Among these, from the viewpoint of obtaining a BR having a high cis content and a low vinyl content, the rare earth element-based catalyst is preferably a neodymium (Nd)-based catalyst using a neodymium compound as the lanthanoid rare earth element compound.

[0099] Examples of the BR containing SPB include those in which 1,2-syndiotactic polybutadiene crystals are chemically bonded to and dispersed in the BR, but exclude those in which the crystals are simply dispersed in the BR.

[0100] Examples of the modified BR include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and in which modified BR molecules are bonded at their terminals by tin-carbon bonds (tin-modified BR), butadiene rubber having an alkoxy silane condensate at the active terminal of the butadiene rubber (modified butadiene rubber for silica), and the like.

[0101] From the viewpoint of abrasion resistance, the weight average molecular weight (Mw) of the BR is preferably 300,000 or greater, more preferably 350,000 or greater, and further preferably 400,000 or greater. In addition, from the viewpoint of crosslinking uniformity and the like, the Mw is preferably 2,000,000 or less, and more preferably 1,000,000 or less. In addition, the Mw can be measured in the form of a standard polystyrene based on a measurement value of a gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPER MALTPORE HZ-M, manufactured by Tosoh Corporation).

[0102] As the BR, for example, BRs commercially available from Ube Industries, Ltd., Sumitomo Chemical Co., Ltd., JSR Corporation, Lanxess, and the like can be used.

[0103] When the rubber composition constituting the tread portion contains BR, the content of BR in the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 20% by mass or more from the viewpoint of wear resistance. In addition, the content is preferably 60% by mass or less, more preferably 50% by mass or less, and further preferably 40% by mass or less from the viewpoint of wet grip performance. In addition, when the rubber composition constituting at least one of the outermost surface portions other than the tread portion contains BR, the content of BR in the rubber component is preferably 2% by mass or more, more preferably 8% by mass or more, and further preferably 15% by mass or more from the viewpoint of wear resistance. In addition, the content is preferably 55% by mass or less, more preferably 45% by mass or less, and further preferably 35% by mass or less from the viewpoint of ride comfort.

[0104] In 100% by mass of the rubber component, the content of BR in the rubber composition constituting the tread portion is preferably equal to or greater than the content of BR in the rubber composition constituting at least one of the outermost surface portions other than the tread portion. For example, in the case where the content of BR (mass%) in the rubber composition constituting the tread portion is within the above range, the content of BR (mass%) in the rubber composition constituting at least one of the outermost surface portions other than the tread portion is the same as the content of BR in the rubber composition constituting the tread portion, or is preferably 3% by mass or more, more preferably 5% by mass or more, and further preferably 10% by mass or more lower than the content of BR in the rubber composition constituting the tread portion.

[0105] (Other Rubber Components)

[0106] As the rubber component, a rubber component other than those described above can be contained within a range not impairing the effects of the present disclosure, and examples of such a rubber component can include non-diene-based rubbers such as hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), ethylene propylene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), polyepichlorohydrin (hydrin) rubber, and the like.

[0107] (Content of Aromatic Vinyl Units in Rubber Component)

[0108] For each individual rubber component of the rubber component constituting the tread portion, a value obtained by multiplying the mass fraction in the rubber component by the content of aromatic vinyl units (mass%) is calculated, and the value obtained by adding these values is defined as the content of aromatic vinyl units T in the rubber component of the tread portion. Arm (mass %). Similarly, for each individual rubber component constituting the rubber component of the at least one outermost surface member other than the tread portion, a value obtained by multiplying the mass fraction in the rubber component by the aromatic vinyl unit content (mass %) is calculated, and a value defined by adding these values is defined as the aromatic vinyl unit content OMM in the rubber component of the at least one outermost surface member other than the tread portion Arm (mass %). In the present disclosure, T Arm is greater than OMM Arm In the present disclosure, in the case where the at least one outermost surface member other than the tread portion is a plurality of members (for example, a side wall, a wing, and a lap triangle), OMM Arm (mass %).

[0109] For example, in the case where the at least one outermost surface member other than the tread portion is a side wall, for each individual rubber component constituting the side wall, a value obtained by multiplying the mass fraction in the rubber component by the aromatic vinyl unit content (mass %) is calculated, and a value defined by adding these values is defined as the aromatic vinyl unit content SW in the rubber component of the side wall Arm (mass %).

[0110] For example, in the case where the at least one outermost surface member other than the tread portion is a side wall, for each individual rubber component constituting the side wall, a value obtained by multiplying the mass fraction in the rubber component by the aromatic vinyl unit content (mass %) is calculated, and a value defined by adding these values is defined as the aromatic vinyl unit content SW in the rubber component of the side wall Arm (mass %).

[0111] For example, in the case where the at least one outermost surface member other than the tread portion is a side wall, for each individual rubber component constituting the side wall, a value obtained by multiplying the mass fraction in the rubber component by the aromatic vinyl unit content (mass %) is calculated, and a value defined by adding these values is defined as the aromatic vinyl unit content SW in the rubber component of the side wall Arm (mass %).

[0112] From the viewpoint of the effects of the present disclosure, T Arm It is preferably 15 mass % or more, preferably 20 mass % or more, preferably 25 mass % or more, preferably 30 mass % or more, and preferably 33 mass % or more.

[0113] On the other hand, OMM Arm is less than T Arm In the case where T Arm From the viewpoint of the effects of the present disclosure, OMM Arm is less than T Arm Preferably, it is 5% or more lower by mass, more preferably 10% or more lower by mass, even more preferably 15% or more lower by mass, even more preferably 20% or more lower by mass, and even more preferably 23% or more lower by mass.

[0114] In addition, SW Arm Less than T Arm In T Arm When the above values ​​are taken, from the perspective of the effect of this disclosure, SW Arm T Arm Preferably, it is 5% or more lower by mass, more preferably 10% or more lower by mass, even more preferably 15% or more lower by mass, even more preferably 20% or more lower by mass, and even more preferably 23% or more lower by mass.

[0115] In addition, WG Arm Less than T Arm In T Arm When the above values ​​are taken, from the perspective of the effect of this disclosure, WG Arm T Arm Preferably, it is 5% or more lower by mass, more preferably 10% or more lower by mass, even more preferably 15% or more lower by mass, even more preferably 20% or more lower by mass, and even more preferably 23% or more lower by mass.

[0116] In addition, CL Arm Less than T Arm In T Arm When the above values ​​are taken, from the perspective of the effect of this disclosure, CL Arm T Arm Preferably, it is 5% or more lower by mass, more preferably 10% or more lower by mass, even more preferably 15% or more lower by mass, even more preferably 20% or more lower by mass, and even more preferably 23% or more lower by mass.

[0117] Furthermore, although no T is specified Arm OMM Arm SW Arm wG Arm and CL Arm While each of these has a specific upper limit, from the perspective of the effects of this disclosure, they each correspond to the weighted average content of aromatic vinyl units contained in each rubber component constituting the outermost surface components other than the tread and sidewalls, flanks, and tread gussets, and naturally have upper limits, which depend on the type and amount of the rubber component chosen. For example, regarding T... Arm This upper limit is approximately 50% by mass, or approximately 45% by mass, or approximately 40% by mass.

[0118] The value of the aromatic vinyl unit content of the rubber component corresponds to a weighted average value of the aromatic vinyl unit content of each of the rubber components included in the rubber component, so that, for example, the value can be increased by using more rubber components having a large aromatic vinyl unit content value, and vice versa, the value can be decreased by using more rubber components having a small aromatic vinyl unit content value.

[0119] <Filler>

[0120] The filler preferably includes carbon black and silica. In addition, the filler can consist only of carbon black and silica.

[0121] (Carbon black)

[0122] The carbon black is not particularly limited, and a carbon black commonly used in the tire industry can be used, for example, GPF, FEF, HAF, ISAF, SAF, and the like can be suitably used; or 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, and the like can be suitably used; in addition to these, an in-house synthetic product, and the like can be suitably used. These carbon blacks can be used alone or in combination of two or more.

[0123] From the viewpoint of weather resistance and reinforcing performance, the nitrogen adsorption specific surface area (N2SA) 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, further preferably 120 m 2 / g or more. In addition, from the viewpoint of dispersibility, fuel efficiency, fracture performance, and durability, the N2SA is preferably 250 m 2 / g or less, more preferably 200 m 2 / g or less, further preferably 180 m 2 / g or less. On the other hand, from the viewpoint of weather resistance and reinforcing performance, in the case of the rubber composition constituting at least one outermost surface member other than the tread portion, the N2SA is preferably 50 m 2 / g or more, more preferably 60 m 2 / g or more, further preferably 70 m 2 / g or more. In addition, from the viewpoint of dispersibility, fuel efficiency, fracture performance, and durability, the N2SA is preferably 150 m 2 / g or less, more preferably 120 m 2 / g or less, further preferably 100 m 2 / g or less. Furthermore, the N2SA of the carbon black in the present specification is a value measured according to the method A of Japanese Industrial Standard JIS K 6217-2 "Carbon black for rubber - Fundamental characteristics - Part 2: Determination of specific surface area - Nitrogen adsorption method - Single-point procedure".

[0124] When the rubber composition constituting the tread portion contains carbon black, the carbon black content in the rubber composition constituting the tread portion is preferably 1 part by mass or more, more preferably 3 parts by mass or more, further preferably 5 parts by mass or more, relative to 100 parts by mass of the rubber component, from the viewpoint of weather resistance and reinforcing properties. On the other hand, the content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, further preferably 40 parts by mass or less, from the viewpoint of improvement in durability by suppression of heat dissipation. Furthermore, when the rubber composition constituting at least one outermost surface member other than the tread portion contains carbon black, the carbon black content in the rubber composition constituting at least one outermost surface member other than the tread portion is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, further preferably 15 parts by mass or more, relative to 100 parts by mass of the rubber component, from the viewpoint of weather resistance and reinforcing properties. On the other hand, the content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, further preferably 80 parts by mass or less, from the viewpoint of improvement in durability by suppression of heat dissipation.

[0125] (Silica)

[0126] The silica is not particularly limited, and for example, a silica commonly used in the tire industry, such as a dry-process silica (anhydrous silica), a wet-process silica (hydrous silica), or the like, can be used. Among these, a hydrous silica produced by a wet process is preferred because it has many silanol groups. These silicas can be used alone or in combination of two or more.

[0127] From the viewpoint of reinforcing properties and ensuring damping, the nitrogen adsorption specific surface area (N2SA) of the silica is preferably 100 m 2 / g or more, more preferably 120 m 2 / g or more, further preferably 150 m 2 / g or more, further preferably 170 m 2 / g or more. Furthermore, from the viewpoint of heat generation and processability, the N2SA is preferably 350 m 2 / g or less, more preferably 300 m 2 / g or less, further preferably 250 m 2 / g or less. Furthermore, the N2SA of the silica in the present specification is a value measured by the BET method according to ASTM D3037-93.

[0128] When the rubber composition constituting the tread portion contains silica, from the viewpoint of securing damping and wet grip performance, the silica content in the rubber composition constituting the tread portion is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, further preferably 40 parts by mass or more, further preferably 50 parts by mass or more, further preferably 60 parts by mass or more, relative to 100 parts by mass of the rubber component. On the other hand, from the viewpoint of reducing the specific gravity of the rubber composition and achieving weight reduction, and from the viewpoint of durability improvement resulting from suppression of heat dissipation and securing of ride comfort resulting from rubber softness, the content is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, further preferably 100 parts by mass or less. Furthermore, when the rubber composition constituting at least one outermost surface member other than the tread portion contains silica, from the viewpoint of securing damping, the silica content in the rubber composition constituting at least one outermost surface member other than the tread portion is 5 parts by mass or more, 10 parts by mass or more, or 15 parts by mass or more, relative to 100 parts by mass of the rubber component, or the rubber composition constituting at least one outermost surface member does not contain silica. On the other hand, from the viewpoint of reducing the specific gravity of the rubber composition and achieving weight reduction, and from the viewpoint of durability improvement resulting from suppression of heat dissipation and securing of ride comfort resulting from rubber softness, the content is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, further preferably 80 parts by mass or less.

[0129] The silica content of the rubber composition constituting the tread portion is preferably equal to or greater than the silica content of the rubber composition constituting at least one outermost surface member other than the tread portion, in 100 parts by mass of the rubber component. For example, in the case where the silica content (parts by mass) of the rubber composition constituting the tread portion is within the above range, the silica content (parts by mass) of the rubber composition constituting at least one outermost surface member other than the tread portion is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, further preferably 15 parts by mass or more, lower than the silica content (wt%) of the rubber composition constituting the tread portion, or even in the case where at least one outermost surface member other than the tread portion does not contain silica, there is no problem.

[0130] (Other fillers)

[0131] As the filler other than silica and carbon black, those fillers commonly used in the tire industry, such as aluminum hydroxide, calcium carbonate, alumina, clay, talc, and the like, can be appropriately compounded within a range that does not impair the effects of the present disclosure.

[0132] (Filler content)

[0133] From the viewpoint of reinforcing properties and ensuring damping, the total content of the filler is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, further preferably 30 parts by mass or more, further preferably 40 parts by mass or more, further preferably 50 parts by mass or more, with respect to 100 parts by mass of the rubber component. In addition, from the viewpoint of durability improvement, the total content of the filler is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, further preferably 130 parts by mass or less, further preferably 100 parts by mass or less, further preferably 90 parts by mass or less.

[0134] In the rubber composition constituting the tread portion, the total content of the filler is first preferably 40 parts by mass or more, more preferably 50 parts by mass or more, further preferably 60 parts by mass or more, further preferably 70 parts by mass or more, further preferably 80 parts by mass or more, with respect to 100 parts by mass of the rubber component. In addition, the total content of the filler is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, further preferably 130 parts by mass or less, further preferably 120 parts by mass or less.

[0135] In the rubber composition constituting at least one outermost surface member other than the tread portion, the total content of the filler is first preferably 10 parts by mass or more, more preferably 20 parts by mass or more, further preferably 30 parts by mass or more, further preferably 40 parts by mass or more, further preferably 50 parts by mass or more, with respect to 100 parts by mass of the rubber component. In addition, the total content of the filler is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, further preferably 90 parts by mass or less.

[0136] 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, further preferably 70% by mass or more, further preferably 80% by mass or more, further preferably 83% by mass or more, further preferably 90% by mass or more. In addition, 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, further preferably 60% by mass or more, further preferably 70% by mass or more, further preferably 80% by mass or more, further preferably 83% by mass or more, further preferably 90% by mass or more.

[0137] In addition, in the case where the filler consists only of carbon black and silica, when the total content of the filler and the content of either one of carbon black and silica are measured by the above-described method, the content of the other one is naturally measured as well.

[0138] <silane coupling agent>

[0139] Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent conventionally used in combination with silica in the tire industry can be used, for example, examples include: silane coupling agents having a mercapto group; silane coupling agents having a sulfide group, such as bis(3-triethoxysilylpropyl) disulfide, bis(3-triethoxysilylpropyl) tetrasulfide, and the like; silane coupling agents having a vinyl group, such as vinyltriethoxysilane, vinyltrimethoxysilane, and the like; silane coupling agents having an amino group, such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-(2-aminoethyl) aminopropyltriethoxysilane, and the like; glycidyloxy-based silane coupling agents, such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and the like; nitro-based silane coupling agents, such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, and the like; chlorine-based silane coupling agents, such as 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, and the like. Among these, the silane coupling agent preferably includes at least one of a silane coupling agent having a sulfide group and / or a silane coupling agent having a mercapto group, and preferably includes a silane coupling agent having a sulfide group. Examples of the silane coupling agent can include, for example, those manufactured and / or sold by Momentive Performance Materials, Wacker, and / or DeGussa. These silane coupling agents can be used alone or in combination of two or more.

[0140] 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 including a binding unit A represented by the following formula (2) and a binding unit B represented by the following formula (3):

[0141] [Chemical Formula 1]

[0142]

[0143] In the formula, R 101 , R 102 , and R 103 each independently represent a group represented by C 1-12 alkyl, C 1-12 alkoxy, or -0-(R 111 -O)z-R 112 (z R 111 each independently represents C 1-30 divalent hydrocarbon group; R 112 represents C 1-30 alkyl, C 2-30 alkenyl, C 6-30 aryl, or C 7-30 aralkyl; and z represents an integer of 1 to 30; R 104 represents C 1-6 alkylene.

[0144] [Chemical Formula 2]

[0145]

[0146] [Chemical Formula 3]

[0147]

[0148] wherein x represents an integer of 0 or more; y represents an integer of 1 or more; R 201 represents a C 1-30 alkyl group, a C 2-30 alkenyl group, or a C 2-30 alkynyl group; R 202 represents a C 1-30 alkylene group, a C 2-30 alkenylene group, or a C 2-30 alkynylene group; wherein R 201 and R 202 may form a ring structure.

[0149] Examples of the compound represented by formula (1) include, for example, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and a compound represented by the following formula (4). Examples of these silane coupling agents include, for example, those manufactured by Wacker, etc. These silane coupling agents can be used alone or in combination of two or more.

[0150] [Chemical Formula 4]

[0151]

[0152] Examples of the compound containing the binding unit A represented by formula (2) and the binding unit B represented by formula (3) include, for example, those manufactured by Momentive Performance Materials, etc. They can be used alone or in combination of two or more.

[0153] When the rubber composition constituting the tread portion contains a silane coupling agent, from the viewpoint of improving the dispersibility of silica, the content of the silane coupling agent in the rubber composition constituting the tread portion is preferably 1.0 parts by mass or more, more preferably 3.0 parts by mass or more, and further preferably 5.0 parts by mass or more, relative to 100 parts by mass of silica. In addition, from the viewpoint of reducing abrasion resistance, the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 15 parts by mass or less. In addition, when the rubber composition constituting at least one outermost surface member other than the tread portion contains a silane coupling agent, the content of the silane coupling agent in the rubber composition constituting at least one outermost surface member other than the tread portion is preferably 1.0 parts by mass or more, more preferably 3.0 parts by mass or more, and further preferably 5.0 parts by mass or more, relative to 100 parts by mass of silica. In addition, from the viewpoint of preventing deterioration of abrasion resistance, the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 15 parts by mass or less.

[0154] <aromatic ring-containing resin>

[0155] In the present disclosure, the aromatic ring-containing resin generally includes a resin in which a monomer containing an aromatic ring is polymerized. Specific examples of the aromatic ring-containing resin include an aromatic vinyl resin, a C9-based petroleum resin, a C5-C9-based petroleum resin, a terpene phenol aldehyde resin, a phenol aldehyde-based resin, and the like. These aromatic ring-containing resins can be used alone or in combination of two or more.

[0156] (aromatic vinyl resin)

[0157] The aromatic vinyl resin is a polymer using an aromatic vinyl monomer (e.g., styrene) as a constituent monomer, and examples include polymers in which an aromatic vinyl monomer is polymerized as a main component (50 mass% or more, or more than 50 mass%, preferably 60 mass% or more), and the like. Specifically, examples of the aromatic vinyl resin include homopolymers in which each of a styrene-based monomer (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, a-methylstyrene, p-methoxystyrene, p-t-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and the like) is individually polymerized, copolymers of two or more styrene-based monomers, and those in which a styrene-based monomer is further combined with another monomer copolymerizable therewith so that the combination of the styrene-based monomer and the other monomer is copolymerized. As the other monomer, examples include: acrylonitrile-based monomers such as acrylonitrile, methacrylonitrile, and the like; unsaturated carbonic acids such as acrylic acid, methacrylic acid, and the like; unsaturated carbonic acid esters such as methyl acrylate, methyl methacrylate, and the like; diene-based monomers such as chloroprene, butadiene-isoprene, and the like; olefin-based monomers such as 1-butene, 1-pentene; α, β-unsaturated carbonic acids such as anhydrous maleic acid, or an acid anhydride thereof, and the like. The aromatic vinyl resin can be used alone or in combination of two or more.

[0158] As the aromatic vinyl resin, a homopolymer of a-methylstyrene or styrene, or a copolymer of a-methylstyrene and styrene is preferred, and a copolymer of a-methylstyrene and styrene is more preferred. As the aromatic vinyl resin, for example, a commercially available product manufactured by, for example, Arizona Chemical Co., Ltd., or the like can be appropriately used.

[0159] (C9 petroleum resin)

[0160] The C9 petroleum resin refers to resins obtained by polymerizing a C9 fraction obtained by refining of petroleum, and those obtained by hydrogenation or modification thereof. Examples of the C9 fraction include, for example, a petroleum fraction corresponding to 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, methylindene, and the like. Specific examples of the C9 petroleum resin include, for example, coumarone-indene resins, coumarone resins, and indene resins. The C9 petroleum resin can be used alone or in combination of two or more.

[0161] The coumarone-indene resin refers to a resin containing coumarone and indene as a main monomer component constituting a resin skeleton (main chain), and examples of a monomer component contained in the skeleton other than coumarone and indene include styrene, a-methylstyrene, methylindene, vinyltoluene, and the like. The coumarone resin refers to a resin containing coumarone as a main monomer component constituting a resin skeleton (main chain). The indene resin refers to a resin containing indene as a main monomer component constituting a resin skeleton (main chain).

[0162] (C5-C9 petroleum resin)

[0163] C5-C9 petroleum resins refer to resins obtained by copolymerizing C5 fraction and C9 fraction obtained by refining petroleum, and those obtained by hydrogenation or modification thereof. Examples of the C5 fraction include, for example, petroleum fractions corresponding to 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, isoprene, and the like. Examples of the C9 fraction include those described above. As the C5-C9 petroleum resins, for example, commercially available products of Zibo Luohua Hongjin New Material Co., Ltd., Shanghai Qilong Chemical Co., Ltd., and the like can be suitably used. The C5-C9 petroleum resins can be used alone or in combination of two or more.

[0164] (Terpene phenol resins)

[0165] Terpene phenol resins refer to resins obtained by copolymerizing terpene compounds and aromatic compounds, and those obtained by hydrogenation thereof. In the present context, examples of the terpene compounds include, for example, a-pinene, β-pinene, limonene, dipentene, and the like, and examples of the aromatic compounds include, for example, styrene, a-methylstyrene, vinyltoluene, divinyltoluene, and the like. The terpene phenol resins can be used alone or in combination of two or more.

[0166] (Phenolic resins)

[0167] Phenolic resins are resins containing a phenol skeleton in their structure, and examples include, for example, phenol formaldehyde resins, alkylphenol formaldehyde resins, alkylphenol acetylene resins, oil-modified phenol formaldehyde resins, and the like. The phenolic resins can be used alone or in combination of two or more.

[0168] (Content of aromatic ring-containing resins)

[0169] From the viewpoint of the effects of the present disclosure, the content of the aromatic ring-containing resins in the rubber composition constituting the tread portion is preferably 1 part by mass or more, more preferably 2 parts by mass or more, further preferably 3 parts by mass or more, further preferably 4 parts by mass or more, further preferably 5 parts by mass or more, further preferably 6 parts by mass or more, relative to 100 parts by mass of the rubber component. On the other hand, from a similar 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, further preferably 42 parts by mass or less, more preferably 41 parts by mass or less, more preferably 40 parts by mass or less. Furthermore, from the viewpoint of the effects of the present disclosure, the content of the aromatic ring-containing resins in the rubber composition constituting at least one outermost surface member other than the tread portion can be 1 part by mass or more, can be 2 parts by mass or more, can be 3 parts by mass or more, or can be 0 parts by mass, relative to 100 parts by mass of the rubber component. 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, further preferably 4 parts by mass or less.

[0170] The rubber composition constituting the tread portion preferably contains the aromatic ring-containing resin in the amount as described above, and the rubber composition constituting at least one of the outermost surface portions other than the tread portion contains the aromatic ring-containing resin preferably less than 2 parts by mass, more preferably less than 4 parts by mass, and even more preferably less than 6 parts by mass than the rubber composition constituting the tread portion. Alternatively, the rubber composition constituting at least one of the outermost surface portions other than the tread portion can not contain the aromatic ring-containing resin at all.

[0171] (Other resins)

[0172] The rubber composition according to the present disclosure can also contain a resin other than the above-described resins within a range not impairing the effects of the present disclosure. Examples of the resin include, for example, polyterpene resins and rosin-based resins commonly used in the tire industry. These resins can be used alone or in combination of two or more.

[0173] (Polyterpene resins)

[0174] Examples of the polyterpene resin include those composed of at least one selected from terpene raw materials (e.g., a-pinene, β-pinene, limonene, dipentene, and the like) and those obtained by further hydrogenating them. The polyterpene resin can be used alone or in combination of two or more.

[0175] (Rosin-based resins)

[0176] The rosin-based resin is a resin having rosin acid as a main component, and the rosin acid is obtained by processing rosin. Examples of the rosin-based resin include naturally produced rosin resins (polymerized rosin), such as gum rosin, wood rosin, tall oil rosin, and the like, which have resin acids (e.g., abietic acid, neoabietic acid, palustric acid, levopimaric acid, pimaric acid, isopimaric acid, dihydroabietic acid, and the like) as a main component; hydrogenated rosin resins; modified rosin resins (e.g., rosin resins modified with unsaturated carbon acids, rosin-modified phenol resins, and the like); rosin esters, such as rosin glycerin esters, rosin esters modified with unsaturated carbon acids, and the like; disproportionated rosin resins obtained by disproportionating rosin resins; and the like. The rosin-based resins can be used alone or in combination of two or more.

[0177] <Other compounding agents>

[0178] In addition to the above-described components, the rubber composition according to the present disclosure can suitably contain compounding agents commonly used in the tire industry, such as, for example, oils, waxes, antioxidants, stearic acid, zinc oxide, inorganic potassium salts, vulcanizing agents (e.g., sulfur), vulcanization accelerators, and the like.

[0179] (Oils)

[0180] Examples of the oil include, for example, process oil, vegetable fat, animal fat, and the like. Examples of the process oil include paraffin-based process oil, naphthenic-based process oil, and aromatic-based process oil, and the like. Furthermore, as an environmental measure, a process oil having a low polycyclic aromatic compound (PCA) content can be used. Examples of the process oil having a low PCA content include: treated distillate aromatic extract (TDAE), which is a re-extracted aromatic-based process oil; aromatic alternative oil, which is a mixed oil of pitch and naphthenic oil; mild extract solvate (MES); heavy naphthenic oil; and the like.

[0181] When the rubber composition constituting the tread portion contains an oil, from the viewpoint of processability, the content of the oil in the rubber composition constituting the tread portion is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and further preferably 10 parts by mass or more, relative to 100 parts by mass of the rubber component. On the other hand, from the viewpoints of fuel efficiency and durability, the content is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and further preferably 40 parts by mass or less. Furthermore, when the rubber composition constituting at least one of the outermost surface members other than the tread portion contains an oil, from the viewpoint of processability, the content of the oil in the rubber composition constituting at least one of the outermost surface members other than the tread portion is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and further preferably 3 parts by mass or more, relative to 100 parts by mass of the rubber component. On the other hand, from the viewpoints of fuel efficiency and durability, the content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and further preferably 10 parts by mass or less. Furthermore, in the present specification, the content of the oil also includes the amount of the oil contained in the oil-extended rubber.

[0182] (wax)

[0183] When the rubber composition contains a wax, from the viewpoint of weather resistance of the rubber, the content of the wax is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, relative to 100 parts by mass of the rubber component. Furthermore, from the viewpoint of preventing whitening of the tire due to blooming, the content is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0184] (antioxidant)

[0185] The antioxidant is not particularly limited, and examples include, for example, each of amine-based antioxidants, quinoline-based antioxidants, quinone-based antioxidants, phenol-based antioxidants, and imidazole-based compounds, and carbamate metal salts.

[0186] When the rubber composition contains an antioxidant, from the viewpoint of ozone cracking resistance of the rubber, the content of the antioxidant is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, relative to 100 parts by mass of the rubber component. Furthermore, from the viewpoints of wear resistance and wet grip performance, the content is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0187] (stearic acid)

[0188] As the stearic acid, any stearic acid used in the tire industry can be suitably used.

[0189] (zinc oxide)

[0190] As the zinc oxide, any zinc oxide used in the tire industry can be suitably used.

[0191] (inorganic potassium salt)

[0192] The inorganic potassium salt can be used to improve extrusion processability. Examples of the inorganic potassium salt include, for example, potassium carbonate, potassium bicarbonate, potassium tetraborate, and the like. Among these, potassium tetraborate is preferred. The inorganic potassium salt can be used alone or in combination of two or more.

[0193] (vulcanizing agent)

[0194] As the vulcanizing agent, sulfur is suitably used. As the sulfur, powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and the like can be used.

[0195] When the rubber composition constituting the tread portion contains sulfur as the vulcanizing agent, the sulfur content in the rubber composition constituting the tread portion is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and further preferably 1.0 parts by mass or more, relative to 100 parts by mass of the rubber component, from the viewpoint of ensuring sufficient vulcanization reaction. On the other hand, the content is preferably 6.0 parts by mass or less, more preferably 5.0 parts by mass or less, and further preferably 4.0 parts by mass or less, from the viewpoint of preventing deterioration. Furthermore, when the rubber composition constituting at least one outermost surface member other than the tread portion contains sulfur as the vulcanizing agent, the sulfur content in the rubber composition constituting at least one outermost surface member other than the tread portion is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and more preferably 1.2 parts by mass or more, relative to 100 parts by mass of the rubber component. On the other hand, the content is preferably 7.0 parts by mass or less, more preferably 6.0 parts by mass or less, and further preferably 5.0 parts by mass or less, from the viewpoint of preventing deterioration.

[0196] Examples of the vulcanizing agent other than sulfur include, for example, organic crosslinking agents containing a sulfur atom, such as alkylphenol-sulfur chloride condensates, 1,6-hexamethylene-bis(sodium thiosulfate anhydride), 1,6-bis(N,N'-dibenzylthiocarbamoyl disulfide)hexane, and the like; organic peroxides, such as dicumyl peroxide, and the like. As these vulcanizing agents other than sulfur, vulcanizing agents manufactured by NOKA CHEMICAL CO., LTD., FLEXSYS, LANXESS, and the like can be used.

[0197] (vulcanization accelerator)

[0198] The vulcanization accelerator is not particularly limited. Examples of the vulcanization accelerator include, for example, a sulfenamide-based vulcanization accelerator, a thiazole-based vulcanization accelerator, a thiuram-based vulcanization accelerator, a thiourea-based vulcanization accelerator, a guanidine-based vulcanization accelerator, a dithio carbamic acid-based vulcanization accelerator, an aldehyde amine or aldehyde amine-based vulcanization accelerator, an imidazoline-based vulcanization accelerator, and a xanthate-based vulcanization accelerator. Among these, from the viewpoint of more suitably obtaining a desired effect, a sulfenamide-based vulcanization accelerator and a guanidine-based vulcanization accelerator are preferable, and more preferably both are used in combination.

[0199] Examples of the sulfenamide-based vulcanization accelerator include, for example, N-cyclohexyl-2-benzothiazyl sulfenamide (CBS), N-t-butyl-2-benzothiazyl sulfenamide (TBBS), N-oxyethylene-2-benzothiazyl sulfenamide, N,N'-diisopropyl-2-benzothiazyl sulfenamide, N,N-dicyclohexyl-2-benzothiazyl sulfenamide, and the like. Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole, dibenzothiazyl disulfide, and the like. Examples of the thiuram-based vulcanization accelerator include tetramethyl thiuram monosulfide, tetramethyl thiuram disulfide, tetrabenzyl thiuram disulfide (TBzTD), and the like. Examples of the thiourea-based vulcanization accelerator include 1,3-diphenyl guanidine (DPG), di-o-tolyl guanidine, o-tolyl biguanide, and the like. These vulcanization accelerators can be used alone or in combination of two or more. For example, preferred examples of the combination include TBBS and DPG.

[0200] When the rubber composition constituting the tread portion contains a vulcanization accelerator, the content of the vulcanization accelerator in the rubber composition constituting the tread portion is preferably 1 part by mass or more, more preferably 2 parts by mass or more, with respect to 100 parts by mass of the rubber component. On the other hand, the content is preferably 8 parts by mass or less, more preferably 7 parts by mass or less, further preferably 6 parts by mass or less. Furthermore, when the rubber composition constituting at least one outermost surface member other than the tread portion contains a vulcanization accelerator, the content of the vulcanization accelerator in the rubber composition constituting at least one outermost surface member other than the tread portion is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, further preferably 1.5 parts by mass or more, with respect to 100 parts by mass of the rubber component. On the other hand, the content is preferably 6 parts by mass or less, more preferably 5 parts by mass or less, further preferably 4 parts by mass or less. When the content of the vulcanization accelerator is within the above range, the breaking strength and the elongation tend to be ensured.

[0201] < Rubber composition >

[0202] The rubber composition can be produced by a known method. For example, it can be produced by kneading the above-described components using a rubber kneading apparatus such as an open roll, a closed kneader (Banbury mixer, kneader, or the like), or the like.

[0203] For example, the kneading step includes a base kneading step of kneading the compounding agents and the additives (except for the vulcanizing agent and the vulcanization accelerator), and a final kneading (F-kneading) step of adding and kneading the vulcanizing agent and the vulcanization accelerator to the kneaded product obtained in the base kneading step. In addition, the base kneading step can be divided into a plurality of steps, if necessary. The kneading conditions are not particularly limited, and examples include a method of kneading at a discharge temperature of 150 to 170°C for 1 to 10 minutes in the base kneading step, and a method of kneading at a temperature of 70 to 110°C for 1 to 5 minutes in the final kneading step.

[0204] <tyre>

[0205] The tyre of the present disclosure includes a tread and at least one outermost surface member other than the tread portion, and the tread portion and the at least one outermost surface member other than the tread portion are composed of the above-described rubber composition, and can be used for a passenger car tyre, a truck / bus tyre, a run-flat tyre, a motorcycle tyre, and the like. In addition, it can also be used for a summer tyre, a winter tyre, and an all-season tyre.

[0206] The tyre of the present disclosure can be manufactured by a conventional method. For example, the tyre can be manufactured by extruding the tread rubber composition into a tread shape from the unvulcanized rubber composition obtained above, extruding the rubber composition for the at least one outermost surface member other than the tread portion into a shape of the at least one outermost surface member, joining them together with other tyre members on a tyre building machine, molding them to form an unvulcanized tyre by a conventional method, and then performing heat and pressure on the unvulcanized tyre in a vulcanizer. The vulcanization conditions are not particularly limited, and examples include a method of vulcanizing at 150 to 200°C for 10 to 30 minutes.

[0207] Examples

[0208] Although the present disclosure will be described based on the following examples, the present disclosure is not limited to these examples.

[0209] <various chemicals>

[0210] The various chemicals used in the examples and comparative examples are shown below:

[0211] NR: TSR20

[0212] SBR1: Modified solution polymerized SBR (styrene content: 30 mass%, vinyl bond content: 52 mol%, Mw: 250,000, non-extended product) manufactured in Manufacturing Example 1 described below

[0213] SBR2: Tufdene 4850 (unmodified S-SBR, styrene content: 40 mass%, vinyl group content: 46 mol%, Mw: 350,000, containing 50 parts by mass of an oil component (with respect to 100 parts by mass of a rubber solid content)), manufactured by Asahi Kasei Corporation

[0214] Multicomponent polymer 1: hydrogenated SBR manufactured in Manufacturing Example 2 described below

[0215] Multicomponent polymer 2: modified hydrogenated SBR manufactured in Manufacturing Example 3 described below

[0216] Multicomponent polymer 3: DYNARON (registered trademark) 2324P (hydrogenated SBR), manufactured by JSR Corporation

[0217] Multicomponent polymer 4: Tuftec (registered trademark) P1083 (SEBS), manufactured by Asahi Kasei Corporation

[0218] BR: UBEPOL BR (registered trademark) 150B (vinyl bond content: 1.5 mol%, cis 1,4-content: 97% mass%, Mw: 440,000), manufactured by Ube Industries, Ltd.

[0219] Carbon black 1: Show Black N110 (N2SA: 142 m 2 / g), manufactured by Cabot Japan K.K.

[0220] Carbon black 2: Show Black N330 (N2SA: 79 m 2 / g), manufactured by Cabot Japan K.K.

[0221] Silica: ULTRASIL (registered trademark) VN3 (N2SA: 175 m 2 / g), manufactured by Wacker Chemie AG Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl) tetrasulfide), manufactured by Wacker Chemie AG

[0222] Oil: NH-70S (aromatic oil), manufactured by Mitsui Chemicals, Inc.

[0223] Aromatic ring-containing resin: Sylvatraxx 4401 (copolymer of α-methylstyrene and styrene, softening point: 85°C), manufactured by Arizona Chemical Company

[0224] Wax: Ozoace 0355, manufactured by Nippon Seiro Co., Ltd.

[0225] Antioxidant: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine), manufactured by Sumitomo Chemical Company, Limited

[0226] Stearic acid: Stearic acid "Tsubaki", manufactured by NOF Corporation

[0227] Zinc oxide: "Ginrei R", manufactured by Toho Zinc Co., Ltd.

[0228] Inorganic potassium salt: Potassium tetraborate tetrahydrate (K2B4O7-4H2O), manufactured by Yishan Pharmaceutical Industry Co., Ltd.

[0229] Sulfur: HK-200-5 (powdered sulfur containing 5% oil), manufactured by Hosoi Chemical Industry Co., Ltd.

[0230] Vulcanization accelerator 1: Nocceler NS-G (N-tert-butyl-2-benzothiazyl sulfenamide (TBBS)), manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.

[0231] Vulcanization accelerator 2: Nocceler D (1,3-diphenylguanidine (DPG)), manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.

[0232] (Production Example 1)

[0233] Production of SBR1

[0234] Cyclohexane, tetrahydrofuran, styrene and 1,3-butadiene were charged into a nitrogen-substituted autoclave reactor. The temperature of the contents of the reactor was adjusted to 20°C, and then n-butyllithium was added to initiate polymerization. The polymerization was carried out under adiabatic conditions, and the temperature reached a maximum of 85°C. When the polymerization conversion 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 react. After the polymerization reaction was completed, 2,6-di-tert-butyl-p-cresol was added. Next, the solvent was removed by stripping, and drying was carried out by heating rollers, with the temperature adjusted to 110°C, to obtain SBR1.

[0235] (Production Example 2)

[0236] Production of hydrogenated SBR

[0237] A nitrogen gas-substituted, heat-resistant reaction vessel was charged with 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, and then stirred at 50°C for 5 hours to initiate the polymerization reaction. Next, the reaction solution was stirred for 20 minutes while supplying hydrogen gas at 0.4 MPa gauge pressure to react the unreacted polymer terminal lithium with hydrogen gas to form lithium hydride. The hydrogenation was performed using a catalyst consisting mainly of titanium dichloride at a hydrogen gas supply pressure of 0.7 MPa gauge and a reaction temperature of 90°C. Once the cumulative amount of hydrogen absorption reached an amount corresponding to the target hydrogenation rate, the reaction temperature was adjusted to room temperature, the hydrogen gas pressure was returned to normal pressure, and then the reaction solution was drawn out of the reaction vessel and introduced into water with stirring. The solvent was removed by stripping to obtain a multi-component polymer 1 (hydrogenated SBR).

[0238] (Production Example 3)

[0239] Production of modified hydrogenated SBR

[0240] The treatment as in Production Example 2 was performed to obtain a multi-component polymer 2 (modified hydrogenated SBR), except that 0.15 mol of N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane (modifier) was added to the reaction vessel after the polymerization reaction and before the hydrogenation process, and then stirred at 0°C for 1 hour, and the cumulative amount of hydrogen absorption was adjusted during the hydrogenation process to obtain the target hydrogenation rate.

[0241] The properties of the multi-component polymers are shown in Table 1 below:

[0242] [Table 1]

[0243]

[0244] Examples and Comparative Examples

[0245] According to Table 1, for each of the mixing formulations of the tread portion (Trd) and the sidewall (SW), the chemicals except for sulfur and vulcanization accelerator were kneaded for 5 minutes using a 1.7L closed Banbury mixer until the discharge temperature reached 150 to 160°C to obtain a kneaded product, and then sulfur and vulcanization accelerator were added to each of the obtained kneaded products, and the mixture was kneaded for 4 minutes until the temperature reached 105°C using a twin-screw open roll mill to obtain a corresponding unvulcanized rubber composition.

[0246] The unvulcanized rubber composition obtained from the mixing formulation of the tread portion was extruded into a tread shape, and the unvulcanized rubber composition obtained from the mixing formulation of the sidewall was extruded into a sidewall shape, and they were connected together with other tire components 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).

[0247] (Resistance to cracking)

[0248] Each test tire was fitted to a JIS standard rim 15 x 6JJ, filled with a standard air pressure, loaded with a load corresponding to the maximum load for that air pressure (according to the air pressure-load correspondence table in the JATMA YEAR BOOK), and made to travel at a speed of 80 km / h on a drum, and the travel distance until a damage that could be confirmed by visual inspection occurred at each of the tread, the sidewall, and the interface between the tread and the sidewall was measured. The travel distance of Comparative Example 1 was set to 100, and each of the tread, the sidewall, and the interface between the tread and the sidewall was expressed with an index. The greater the index, the better the resistance to cracking.

[0249]

[0250] According to the above results, the resistance to cracking was significantly improved for the tire of the present disclosure.

[0251] List of reference numerals

[0252] 1 Tire

[0253] 2 Tread portion

[0254] 3 Sidewall

[0255] 4 Lap portion

[0256] 5 Bead core

[0257] 6 Bead apex

[0258] 7 Cushion layer

[0259] 8 Rim

[0260] 9 Wing

[0261] 10 Lap apex< / tg> < / mw> < / mw>

Claims

1. A tire having a tread and at least one outermost surface component other than the tread, wherein, The rubber composition constituting the tread portion comprises a rubber component, said rubber component comprising a diene rubber and a multi-component polymer, said multi-component polymer comprising aromatic vinyl units, non-conjugated olefin units and conjugated diene units; A rubber composition constituting at least one outermost surface component other than the tread portion comprises a rubber component comprising a diene rubber and a multicomponent polymer comprising aromatic vinyl units, non-conjugated olefin units and conjugated diene units. as well as For each individual rubber component of the tread portion, the aromatic vinyl unit content T in the tread portion is calculated by multiplying the mass fraction of the rubber component by the aromatic vinyl unit content, and then summing these values. Arm For each individual rubber component constituting at least one outermost surface component other than the tread portion, the aromatic vinyl unit content (OMM) in the rubber component is calculated by multiplying the mass fraction of the rubber component by the aromatic vinyl unit content, and these values ​​are summed. Arm ;T Arm Greater than OMM Arm , The content of aromatic vinyl units is expressed in % by mass. The at least one outermost surface component other than the tread portion is the sidewall.

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

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

4. The tire according to claim 1 or 2, wherein, Relative to 100 parts by weight of the rubber component, the rubber composition constituting the tread contains 40 parts by weight or more of filler, said filler containing 50% by weight or more of silica; and Relative to 100 parts by weight of the rubber component, the rubber composition constituting at least one outermost surface component other than the tread portion contains 10 or more parts by weight of filler, said filler containing more than 0% by weight of silica.

5. The tire according to claim 1, wherein, The rubber composition constituting the tread portion comprises 1 to 45 parts by weight of an aromatic ring-containing resin relative to 100 parts by weight of the rubber component.

6. The tire according to claim 1, wherein, The diene rubbers included in the rubber composition constituting the tread portion include natural rubber; and The diene rubbers included in the rubber composition constituting at least one outermost surface component other than the tread portion include natural rubber.

7. The tire according to claim 6, wherein, In a 100% by weight rubber composition, the natural rubber content in the tread portion is less than the natural rubber content in at least one of the outermost surface components other than the tread portion.

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

9. The tire according to claim 1 or 2, wherein, The glass transition temperature of the rubber composition of the tread is higher than that of the rubber composition of at least one of the outermost surface components other than the tread portion.

10. The tire according to claim 1 or 2, wherein, In the case where the multi-component polymer contained in the rubber composition constituting the tread portion is a hydrogenated polymer of a polymer composed of aromatic vinyl units and conjugated diene units, the hydrogenation rate of the hydrogenated polymer is 30 mol% or more and less than 100 mol%. In the case where the multi-component polymer contained in the rubber composition constituting at least one outermost surface component other than the tread is a hydrogenated polymer of a polymer composed of aromatic vinyl units and conjugated diene units, the hydrogenation rate of the hydrogenated polymer is 30 mol% or more and less than 100 mol%.

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