tire

Abstract

To provide a tire having improved ride comfort.SOLUTION: Provided is a tire comprising a sidewall, wherein the sidewall is composed of a rubber composition comprising a rubber component, and wherein, when an aromatic vinyl unit content in the rubber component is defined as S (mass%) and a thickness of a surface rubber layer at a tire maximum width position is defined as T (mm), S is 0.50 mass% or more and 5.0 mass% or less, and S / T is 0.045 or more and 3.33 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to tires. [Background technology]

[0002] The sidewall is known to have a significant impact on ride comfort. Patent Document 1 describes a tire with improved handling stability and ride comfort, which has a sidewall made of a rubber composition containing a predetermined amount of 1,2-syndiotactic polybutadiene crystals, butadiene rubber, isoprene-based rubber, and resin. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2013-1889 [Overview of the project] [Problems that the invention aims to solve]

[0004] The present invention aims to provide a tire with improved ride comfort performance. [Means for solving the problem]

[0005] After thorough investigation, it was found that the aforementioned problem can be solved by setting a predetermined relationship between the aromatic vinyl unit content in the rubber component constituting the sidewall and the thickness of the surface rubber layer at the tire's maximum width position.

[0006] In other words, the present invention relates to a tire having a sidewall, wherein the sidewall is made of a rubber composition containing a rubber component, and when the aromatic vinyl unit content in the rubber component is S (mass%) and the thickness of the surface rubber layer at the tire's maximum width position is T (mm), S is 0.50% by mass or more and 5.0% by mass or less, and S / T is 0.045 or more and 3.33 or less. Effects of the Invention

[0007] According to the present invention, a tire with improved riding comfort performance is provided. Brief Description of the Drawings

[0008] [Figure 1] It is a schematic partial cross-sectional view of a tire according to an embodiment of the present invention. [Figure 2] It is a diagram showing the tire cross-sectional width Wt, the tire cross-sectional height Ht, and the tire outer diameter Dt in the cross-section of the tire. Mode for Carrying Out the Invention

[0009] A tire according to one embodiment of the present invention is a tire provided with a sidewall, wherein the sidewall is formed of a rubber composition containing a rubber component. When the content of aromatic vinyl units in the rubber component is defined as S (% by mass), and the thickness of the surface rubber layer at the maximum tire width position is defined as T (mm), S is 0.50% by mass or more and 5.0% by mass or less, and S / T is 0.045 or more and 3.33 or less.

[0010] When the content of aromatic vinyl units in the rubber component constituting the sidewall and the thickness of the surface rubber layer at the maximum tire width position satisfy the above requirements, the riding comfort performance of the obtained tire is significantly improved. Although not intending to be bound by theory regarding the reason for this, it is considered as follows.

[0011] When a tire is rolling, it receives input from the road surface, and vibrations are transmitted from the tread surface through the sidewall surface to the vehicle. Here, the vibration of the vehicle is thought to depend on how easily the sidewall rubber converts vibration energy into heat. The tire of the present invention has the following characteristics: (1) By setting the aromatic vinyl unit content in the rubber component constituting the sidewall to a predetermined range, aromatic vinyl units aggregate to form domains within the rubber composition, and in these domains, impact is converted into thermal energy, making it easier to mitigate impact; (2) The absorption of impact in the sidewall is also thought to be affected by the amount of deflection, and deformation is less likely to occur when the thickness is thick. Therefore, by increasing the aromatic vinyl unit content as the thickness of the surface rubber layer constituting the sidewall increases, the sidewall rubber becomes more likely to convert vibration into heat in the input frequency range from the road surface, making it easier to mitigate impact. Furthermore, it is believed that these elements working together will result in a remarkable improvement in ride comfort: the aromatic vinyl unit domains will be more efficient at absorbing shocks in response to deformation in the sidewall, improving the ease of converting vibration energy into heat, and thus significantly improving ride comfort.

[0012] The rubber component preferably includes a multi-component polymer having aromatic vinyl units, non-conjugated olefin units, and conjugated diene units.

[0013] Because multi-component polymers possess high heat resistance and ozone resistance, it is believed that the above effects can be maintained for a long period of time even as tires deteriorate.

[0014] The rubber component preferably includes isoprene rubber and / or butadiene rubber. The isoprene rubber content in the rubber component is preferably 15% by mass or more and 50% by mass or less, and the butadiene rubber content is preferably 20% by mass or more and 60% by mass or less.

[0015] By incorporating these rubber components with low glass transition temperatures (Tg), it is believed that the flexibility of the sidewall rubber can be improved over an even wider temperature range, thereby mitigating input from the road surface.

[0016] The rubber composition preferably contains 35 to 70 parts by mass of a filler containing carbon black and / or silica, per 100 parts by mass of the rubber component. Furthermore, the silica content in 100% by mass of the filler is preferably 5% to 30% by mass.

[0017] It is believed that by including a predetermined amount of the aforementioned filler, energy loss due to friction between the filler and aromatic vinyl domains within the rubber can be generated, making it easier to absorb impacts. Furthermore, it is believed that by incorporating a predetermined amount of silica into the filler, the flexibility of the sidewall rubber in the micro-deformation region can be improved, thereby mitigating input from the road surface.

[0018] Tire's maximum load capacity W L Ratio of tire weight G (kg) to (kg) (G / W L ) is preferably 0.0210 or less.

[0019] Golden Week L By setting the range as described above and reducing the tire weight relative to the tire's maximum load capacity, the impact of tire weight is reduced even when loads are applied due to cargo or passengers, the impact on the entire tire can be reduced, and the deformation of the sidewall can be reduced, thus mitigating input from the road surface.

[0020] It is preferable that the tire section width Wt (mm) and tire outer diameter Dt (mm) satisfy the following formula (1). (π / 4) × (Dt 2 / Wt)≧1600 ···(1)

[0021] By setting the tire section width and tire outer diameter within the aforementioned range, the outer diameter will be made larger than a certain amount relative to the tire width, which is thought to make it easier to deform the side portion.

[0022] <Definition> "Aromatic vinyl unit content in rubber components" refers to the total amount (mass%) of aromatic vinyl units, such as styrene, contained in 100% by mass of the rubber components. For each rubber component, the value obtained by multiplying the aromatic vinyl unit content (mass%) by the mass fraction in the rubber components is calculated, and these values ​​are then summed up. Specifically, it is calculated using Σ(aromatic vinyl unit content (mass%) of each aromatic vinyl unit-containing rubber × content in the rubber components of each aromatic vinyl unit-containing rubber (mass%) / 100).

[0023] A "standard rim" is the rim specified for each tire in the standardization system that the tire is based on. For example, it is a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. In the case of tires whose size is not specified in the aforementioned standardization system, it refers to the narrowest rim with the smallest diameter that can be mounted on that tire without causing air leakage between the rim and the tire.

[0024] "Regular internal pressure" refers to the air pressure specified for each tire in the tire standard system, including the standard on which the tire is based. For example, it is the "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. For tires of sizes not specified in the aforementioned standard system, the regular internal pressure is set at 250 kPa.

[0025] "Normal condition" refers to a tire that is mounted on a normal rim, filled to the normal internal pressure, and under no load. In the case of a tire size not specified in the aforementioned standard system, it refers to a tire that is mounted on the smallest rim, filled to 250 kPa, and under no load.

[0026] "The thickness T of the surface rubber layer at the tire's maximum width position" is the distance (mm) from the sidewall surface to the carcass cord surface, measured along the normal L of the sidewall 3 at the tire's maximum width position PW. "Tire's maximum width position PW" refers to the position of the maximum width within the tire's widthwise cross-section measured under normal conditions. "Surface rubber layer" includes the sidewall rubber.

[0027] "Tire weight" is expressed in G (kg). However, G is the weight of the tire alone, excluding the weight of the rim. If sound-dampening material, sealant, sensors, etc. are attached to the inside of the tire, G will include the weight of these components.

[0028] "Maximum load capacity (W L The value of "(kg)" is calculated by the following formulas (2) and (3), where Wt (mm) is the tire section width measured in the normal state, Ht (mm) is the tire section height, and Dt (mm) is the tire outer diameter. V is the virtual volume of space occupied by the tire. The tire section width Wt is the maximum width between the outer surfaces of the sidewalls in the above state, excluding any patterns or letters on the tire sidewall. The tire section height Ht is the distance from the bottom of the bead to the outermost surface of the tread, and is half the difference between the tire outer diameter and the nominal rim diameter. V = {(Dt / 2)} 2 -(Dt / 2-Ht) 2} × π × Wt ···(2) W L = 0.000011 × V + 100 ... (3)

[0029] "Tire cross-sectional width Wt (mm)" refers to the maximum width between the outer surfaces of the sidewalls, excluding patterns or characters on the tire sidewall when such features are present, measured under normal conditions. "Tire outer diameter Dt (mm)" is the tire outer diameter measured under normal conditions.

[0030] "Recycled carbon black" refers to carbon black obtained from the pyrolysis process of used products such as waste tires containing carbon black. When subjected to oxidative combustion by heating in air via thermogravimetry in accordance with JIS K 6226-2:2003, it is carbon black in which the mass percentage of ash, which is a non-combustible component, is 13% by mass or more. That is, the mass of weight loss caused by the oxidative combustion (carbon content) is less than 87% by mass. Recycled carbon black is also referred to as recycled carbon and may be represented by rCB.

[0031] "Oil content" also includes the amount of oil contained in oil-extended rubber.

[0032] <Measurement method> "Aromatic vinyl unit content" is 1 a value calculated by 1H-NMR measurement, and is applied, for example, to rubber components having repeating units derived from aromatic vinyl compounds such as SBR and multi-component polymers. "Vinyl content (amount of 1,2-bonded butadiene units)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017, and is applied, for example, to rubber components having repeating units derived from butadiene such as SBR and BR. "Cis content (amount of cis-1,4-bonded butadiene units)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017, and is applied, for example, to rubber components having repeating units derived from butadiene such as BR.

[0033] The "weight-average molecular weight (Mw)" can be determined by converting it to standard polystyrene based on measurements obtained by gel permeation chromatography (GPC) (for example, the GPC-8000 series from Tosoh Corporation, with a differential refractometer as the detector and TSKGEL SUPERMALTIPORE HZ-M column from Tosoh Corporation). This method is applicable, for example, to SBR, BR, resin components, liquid rubber, etc.

[0034] The glass transition temperature (Tg) of a multi-component polymer is measured according to JIS K 7121, using a differential scanning calorimeter (Q200) manufactured by T.A. Instruments Japan Co., Ltd., while increasing the temperature at a heating rate of 10°C / min.

[0035] The "average primary particle size of carbon black" can be determined by observing with a transmission or scanning electron microscope, measuring 400 or more primary particles of carbon black observed within the field of view, and averaging the results. The "N2SA of carbon black" is measured in accordance with JIS K 6217-2:2017. The "average primary particle size of silica" can be determined by observing with a transmission or scanning electron microscope, measuring 400 or more primary particles of silica observed within the field of view, and averaging the results. The "N2SA of silica" is measured by the BET method in accordance with ASTM D3037-93.

[0036] The procedure for manufacturing a tire, which is one embodiment of the present invention, will be described in detail below. However, the following description is illustrative for explaining the present invention and is not intended to limit the technical scope of the present invention to this scope only. In this specification, when a numerical range is indicated using "~", it includes the numerical values ​​at both ends of the range.

[0037] <Tires> Figure 1 illustrates, but is not limited to, a tire that is an embodiment of the present invention. Figure 1 shows a portion of the cross-section of this tire perpendicular to the circumferential direction. In Figure 1, the vertical direction is the tire radial direction, the horizontal direction is the tire axial direction, and the direction perpendicular to the plane of the paper is the tire circumferential direction.

[0038] The tire according to this embodiment comprises a tread 1 that extends in the circumferential direction and forms an annular shape, a pair of sidewalls 31 arranged on both sides of the tread portion, a pair of bead portions having a bead core 21, at least one layer of carcass 33 anchored to the bead core 21, and at least one layer of belt 2 arranged on the radially outer side of the carcass 33.

[0039] In this embodiment, the bead portion of the tire is located on the inner side of the sidewall 31 in the tire axial direction. The bead portion comprises a bead core 21 and a bead apex 22 extending radially outward from the core. The bead apex 22 tapers outward in the tire radial direction.

[0040] In Figure 1, the carcass 33 is folded around the bead core 21 from the inner side in the tire axial direction outward. This folding creates a main portion and a folded portion in the carcass 33. The strip apex 25 generally extends in the radial direction of the tire. The strip apex 25 is laminated with the bead apex 22 near its radially inner end. The strip apex 25 is sandwiched between the main portion and the folded portion of the carcass 33 near its radially inner end.

[0041] In this embodiment, when the tire section width is Wt (mm) and the tire outer diameter is Dt (mm), it is preferable that Wt and Dt satisfy the following formula (1). (π / 4) × (Dt 2 / Wt)≧1600 ···(1)

[0042] Here, as Dt increases, the value of equation (1) increases, and conversely, as Dt decreases, the equivalent value decreases. On the other hand, as Wt increases, the value of equation (1) decreases, and conversely, as Wt decreases, the equivalent value increases. Focusing on this point, we can adjust Dt and Wt so that they satisfy equation (1).

[0043] The value of formula (1) is preferably 1620 or higher, more preferably 1640 or higher, and even more preferably 1660 or higher. Furthermore, the value of formula (1) is preferably 2800 or lower, more preferably 2600 or lower, even more preferably 2400 or lower, and particularly preferably 2200 or lower.

[0044] Examples of tire sizes that satisfy formula (1) include 145 / 60R18, 145 / 60R19, 155 / 55R18, 155 / 55R19, 155 / 70R17, 155 / 70R19, 165 / 55R20, 165 / 55R21, 165 / 60R19, 165 / 65R19, 165 / 70R18, 175 / 55R19, 175 / 55R20, 175 / 55R22, 175 / 60R18, 185 / 55R19, 185 / 60R20, 195 / 50R20, 195 / 55R20, 195 / 65R16, 205 / 55R17, 215 / 45R18, etc.

[0045] The tire according to this embodiment has a maximum load capacity W L Ratio of tire weight G (kg) to (kg) (G / W L From the viewpoint of the effects of the present invention, the value of ) is preferably 0.0210 or less, more preferably 0.0205 or less, even more preferably 0.0200 or less, even more preferably 0.0195 or less, even more preferably 0.0180 or less, even more preferably 0.0165 or less, and particularly preferably 0.0150 or less. On the other hand, G / W L The lower limit is not particularly limited, but for example, it can be 0.0090 or higher, 0.0100 or higher, 0.0110 or higher, or 0.0120 or higher. The tire weight G can be varied by conventional methods, that is, it can be increased by increasing the specific gravity of the tire or by increasing the thickness of each component of the tire, and vice versa.

[0046] Maximum load capacity W L (kg) is preferably 300 or more, more preferably 400 or more, even more preferably 450 or more, and particularly preferably 500 or more, from the viewpoint of better demonstrating the effects of the present invention. Also, the maximum load capacity W LThe (kg) can be, for example, 1300 or less, 1200 or less, 1100 or less, 1000 or less, 900 or less, 800 or less, 700 or less, or 650 or less, from the viewpoint of better demonstrating the effects of the present invention. L This can be increased by increasing the virtual volume V of the space occupied by the tire, and conversely, it can be decreased by increasing it.

[0047] From the viewpoint of the effects of the present invention, the thickness T (mm) of the surface rubber layer at the tire's maximum width position is preferably 0.5 mm or more, more preferably 0.8 mm or more, and even more preferably 1.0 mm or more. Furthermore, from the viewpoint of the effects of the present invention, T (mm) is preferably 12.0 mm or less, more preferably 10.0 mm or less, even more preferably 8.0 mm or less, even more preferably 6.0 mm or less, and particularly preferably 4.0 mm or less.

[0048] The ratio (S / T) of the aromatic vinyl unit content S (mass%) in the rubber component to the thickness T (mm) of the surface rubber layer at the tire's maximum width position is 0.045 or higher, preferably 0.065 or higher, more preferably 0.10 or higher, even more preferably 0.15 or higher, even more preferably 0.20 or higher, and particularly preferably 0.25 or higher. Furthermore, S / T is 3.33 or lower, preferably 3.00 or lower, more preferably 2.80 or lower, even more preferably 2.60 or lower, and particularly preferably 2.40 or lower. By setting S / T within the above range, stress tends to be more easily relieved in the styrene domain portion even when the rigidity due to the thickness of the bead portion 4 is high.

[0049] [Rubber composition] In this embodiment, the tire can more effectively improve ride comfort performance through the cooperation of the aromatic vinyl unit content in the rubber component constituting the sidewall and the thickness of the sidewall at the tire's maximum width position.

[0050] <Rubber components> The rubber composition constituting the sidewall according to this embodiment (hereinafter referred to as the rubber composition according to this embodiment unless otherwise specified) preferably contains a diene rubber and a multi-component polymer as rubber components, but may also consist only of a diene rubber and a multi-component polymer. Since multi-component polymers have high heat resistance and ozone resistance, incorporating a multi-component polymer allows the effects of the present invention to be maintained for a long time even when the tire deteriorates.

[0051] (Multi-component polymer) A multi-component polymer is a copolymer having aromatic vinyl units, non-conjugated olefin units, and conjugated diene units, and may also have other monomer units. Preferably, it is a copolymer consisting of aromatic vinyl units, non-conjugated olefin units, and conjugated diene units. This copolymer can be obtained by copolymerizing a monomer component containing aromatic vinyl units, non-conjugated olefin units, and conjugated diene units, and optionally by hydrogenation. Alternatively, it can be obtained by copolymerizing a monomer component containing aromatic vinyl units and conjugated diene units, preferably a monomer component consisting of aromatic vinyl units and conjugated diene units, to obtain a copolymer, and then hydrogenating the conjugated diene units of such copolymer to create non-conjugated olefin units. As long as the multi-component polymer is a copolymer having aromatic vinyl units, non-conjugated olefin units, and conjugated diene units, there are no particular limitations on the arrangement of each unit. It may be a random copolymer obtained by random copolymerization or a block copolymer obtained by block copolymerization, but a random copolymer is preferred. One or more types of multi-component polymers can be used.

[0052] Aromatic vinyl units An aromatic vinyl unit refers to a unit in a copolymer derived from an aromatic vinyl compound. Here, an aromatic vinyl compound refers to an aromatic compound substituted with at least a vinyl group, and does not include the conjugated diene compounds described below. Examples of aromatic vinyl compounds include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, and 2,4,6-trimethylstyrene, with styrene being preferred. These may be used individually or in combination of two or more, but among them, styrene is particularly preferred from the standpoint of practical considerations such as the availability of monomers and because it more favorably provides the effects of the present invention.

[0053] Non-conjugated olefin units A non-conjugated olefin unit refers to a unit in a copolymer derived from a non-conjugated olefin compound. Here, a non-conjugated olefin compound refers to an aliphatic unsaturated hydrocarbon that has one or more carbon-carbon double bonds and is a non-conjugated compound. Examples of non-conjugated olefin compounds include α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, or 1-octene; and heteroatom-substituted alkene compounds such as vinyl pivalate, 1-phenylthioethene, or N-vinylpyrrolidone. Among these, ethylene and 1-butene are preferred. These may be used individually or in combination of two or more, but among these, ethylene and / or 1-butene are more preferred from the standpoint of practical considerations such as the availability of monomers and because the effects of the present invention are more favorably obtained.

[0054] ≪Conjugated diene units≫ A conjugated diene unit refers to a unit in a copolymer derived from a conjugated diene compound. Examples of conjugated diene compounds include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, and 1,3-hexadiene. These may be used individually or in combination of two or more. Among these, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred, from the standpoint of practical considerations such as the availability of monomers and because the effects of the present invention are more favorably obtained.

[0055] <<Multi-component polymer>> Preferred examples of multi-component polymers include, for example, hydrogenated styrene-butadiene copolymers (SBRs) and copolymers of styrene, 1,3-butadiene, and ethylene. Therefore, hydrogenated styrene-butadiene copolymers (hydrogenated SBRs) are preferred as multi-component polymers.

[0056] ≪Hydrogenation Rate≫ When a multi-component polymer is obtained by hydrogenation, the hydrogenation rate is preferably 30 mol% or more, more preferably 50 mol% or more, even more preferably 70 mol% or more, and particularly preferably 90 mol% or more, from the viewpoint of the effects of the present invention. There is no particular upper limit to the hydrogenation rate of the multi-component polymer; it should be less than 100 mol%. The hydrogenation rate can be adjusted by adjusting reaction conditions such as hydrogen gas supply pressure and reaction temperature in the hydrogenation reaction described in Production Example 2 below. Note that the hydrogenation rate of a multi-component polymer refers to the proportion of double bonds on the conjugated diene units that are hydrogenated, in the case where the multi-component polymer is a polymer composed of aromatic vinyl units and conjugated diene units. 1 It can be calculated from the spectral reduction rate of the unsaturated bond region of the spectrum obtained by measuring 1H-NMR.

[0057] ≪Degeneration≫ The multi-component polymer can, if desired, be treated with a modifying agent to introduce a functional group that interacts with silica. Any functional group commonly used in this field can be suitably used, such as alkoxysilyl groups (e.g., trimethoxysilyl group, triethoxysilyl group). For example, if the copolymer is treated with chlorotriethoxysilane as a modifying agent before hydrogenation after synthesis, a modified polymer with a triethoxysilyl group introduced at the active end of the copolymer can be obtained.

[0058] ≪Mw≫ From the viewpoint of the effects of the present invention, the weight-average molecular weight (Mw) of the multi-component polymer is preferably 50,000 or more, more preferably 100,000 or more, and even more preferably 150,000 or more. Furthermore, from the viewpoint of processability, the Mw of the multi-component polymer is preferably 2,000,000 or less, more preferably 1,000,000 or less, and even more preferably 700,000 or less.

[0059] ≪Tg≫ From the viewpoint of wear resistance, the glass transition temperature (Tg) of the multi-component polymer is preferably -90°C or higher, more preferably -80°C or higher, even more preferably -70°C or higher, and particularly preferably -60°C or higher. Furthermore, the Tg of the multi-component polymer is preferably less than -10°C, more preferably less than -15°C, even more preferably less than -20°C, and particularly preferably less than -25°C.

[0060] ≪Aromatic vinyl unit content of multi-component polymers≫ The aromatic vinyl unit content of the multi-component polymer can be appropriately selected so that the aromatic vinyl unit content in the rubber component satisfies the range described below, but is preferably 1.0% by mass or more, more preferably 3.0% by mass or more, even more preferably 5.0% by mass or more, and particularly preferably 7.0% by mass or more. Furthermore, the aromatic vinyl unit content of the multi-component polymer is preferably 40% by mass or less, more preferably 38% by mass or less, and even more preferably 36% by mass or less. The aromatic vinyl unit content is preferably styrene content. The aromatic vinyl unit content of the multi-component polymer is measured by the measurement method described above.

[0061] ≪Content of multi-component polymers≫ The content of the multi-component polymer in the rubber component can be appropriately selected so that the aromatic vinyl unit content in the rubber component satisfies the range described below, but is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, and particularly preferably 9% by mass or more. On the other hand, the content of the multi-component polymer in the rubber component is preferably 45% by mass or less, more preferably 42% by mass or less, even more preferably 38% by mass or less, even more preferably 35% by mass or less, even more preferably 30% by mass or less, even more preferably 25% by mass or less, even more preferably 20% by mass or less, and particularly preferably 18% by mass or less.

[0062] ≪Confirmation of multi-component polymers≫ Furthermore, confirmation that it is a multi-component polymer containing conjugated diene units, non-conjugated olefin units, and aromatic vinyl units is performed by gel permeation chromatography (GPC). 1 H-NMR, 13 This can be done using techniques such as 1C-NMR. Specifically, by confirming UV absorption by aromatic rings such as benzene rings in the copolymer based on gel permeation chromatography-refractive index curves (GPC-RI curves) and gel permeation chromatography-ultraviolet absorption curves (GPC-UV curves), the presence of a skeleton derived from aromatic vinyl compounds can be confirmed. 1 H-NMR spectra and 13 Based on the 1C-NMR spectrum, the presence of units derived from each monomer component can be confirmed.

[0063] ≪Method for producing multi-component polymers≫ The above-mentioned multi-component polymer can be synthesized, for example, by polymerizing a monomer component containing aromatic vinyl units, non-conjugated olefin units, and conjugated diene units, and optionally subjecting the resulting copolymer to hydrogenation. Alternatively, it can be synthesized by copolymerizing a monomer component containing aromatic vinyl units and conjugated diene units to obtain a copolymer, and then hydrogenating the conjugated diene units of the copolymer to create non-conjugated olefin units. Such synthesis can be carried out by conventional methods, and is described, for example, in Japanese Patent Publication No. 2018-83884 and International Publication No. 2018 / 092733. The same applies to modified multi-component polymers.

[0064] (Diene-based rubber) As the diene rubber, any rubber component other than the multi-component polymers mentioned above that is commonly used in the tire industry can be suitably used. Specifically, examples include isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), etc. These diene rubbers may be used individually or in combination of two or more. The diene rubber preferably contains at least one selected from the group consisting of isoprene rubber, BR, and SBR, more preferably contains isoprene rubber, and even more preferably contains isoprene rubber and BR. Alternatively, the diene rubber may consist only of isoprene rubber and BR.

[0065] From the viewpoint of the effects of the present invention, the content of diene rubber in the rubber component is preferably 65% ​​by mass or more, more preferably 70% by mass or more, even more preferably 75% by mass or more, even more preferably 80% by mass or more, and particularly preferably 82% by mass or more. Furthermore, there is no particular upper limit to the content of diene rubber in the rubber component, and it can be, for example, 100% by mass, 97% by mass or less, 95% by mass or less, 93% by mass or less, or 91% by mass or less.

[0066] (Isoprene rubber) Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. Examples of NR include SIR20, RSS#3, and TSR20, which are commonly used in the tire industry. Examples of modified NR include deproteinized natural rubber (DPNR) and high-purity natural rubber. Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These isoprene-based rubbers may be used individually or in combination of two or more types.

[0067] The isoprene-based rubber content in the rubber component is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 25% by mass or more, and particularly preferably 30% by mass or more. On the other hand, the isoprene-based rubber content in the rubber component is preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, even more preferably 65% ​​by mass or less, even more preferably 60% by mass or less, even more preferably 55% by mass or less, and particularly preferably 50% by mass or less. By setting the isoprene-based rubber content within the above ranges, it is believed that the flexibility of the sidewall rubber can be improved over a wide temperature range, thereby mitigating input from the road surface.

[0068] (SBR) There are no particular limitations on SBR, and examples include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). Modified SBRs include SBRs in which the terminals and / or main chain are modified, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, branched structures, etc.). Among these, S-SBR and modified SBRs are preferred because they can significantly improve fuel efficiency and wear resistance. These SBRs may be used individually or in combination of two or more types.

[0069] For SBR, either oil-expanded SBR or non-oil-expanded SBR can be used. When using oil-expanded SBR, the amount of oil expanded in the SBR, that is, the amount of oil-expanding oil contained in the SBR, is preferably 10 to 50 parts by mass per 100 parts by mass of rubber solids in the SBR.

[0070] The styrene content of SBR can be appropriately selected so that the aromatic vinyl unit content in the rubber component satisfies the range described below, but is preferably 1.0% by mass or more, more preferably 3.0% by mass or more, even more preferably 5.0% by mass or more, and particularly preferably 7.0% by mass or more. Furthermore, the styrene content of SBR is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 18% by mass or less. The styrene content of SBR is measured by the method for measuring aromatic vinyl unit content described above.

[0071] The vinyl content of SBR is preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more, from the viewpoint of ensuring reactivity with silica, rubber strength, and abrasion resistance. Furthermore, the vinyl content of SBR is preferably 70 mol% or less, more preferably 65 mol% or less, and even more preferably 60 mol% or less, from the viewpoint of preventing increased temperature dependence, elongation at break, and abrasion resistance. The vinyl content of SBR is measured by the measurement method described above.

[0072] From the viewpoint of the effects of the present invention, the weight-average molecular weight (Mw) of SBR is preferably 100,000 or more, more preferably 140,000 or more, and even more preferably 180,000 or more. Furthermore, from the viewpoint of crosslinking uniformity, the weight-average molecular weight is preferably 2,000,000 or less, more preferably 1,800,000 or less, and even more preferably 1,500,000 or less. The Mw of SBR is measured by the measurement method described above.

[0073] From the viewpoint of wear resistance, the glass transition temperature (Tg) of SBR is preferably -90°C or higher, more preferably -80°C or higher, and even more preferably -70°C or higher. Furthermore, the Tg of SBR is preferably less than -10°C, more preferably less than -20°C, even more preferably less than -30°C, and particularly preferably less than -40°C.

[0074] The SBR content in the rubber component can be appropriately selected so that the aromatic vinyl unit content in the rubber component satisfies the range described below, for example, it can be 1% by mass or more, 3% by mass or more, 5% by mass or more, or 10% by mass or more. On the other hand, the SBR content in the rubber component is preferably 45% by mass or less, more preferably 42% by mass or less, even more preferably 38% by mass or less, and particularly preferably 35% by mass or less.

[0075] (BR) BR is not particularly limited, and for example, BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare-earth butadiene rubber synthesized using a rare-earth element catalyst (rare-earth BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc., which are common in the tire industry, can be used. These BRs may be used individually or in combination of two or more types.

[0076] Rare earth-based BRs can be those commonly used in the tire industry. Known rare earth element catalysts can be used for the synthesis (polymerization) of rare earth-based BRs, including, for example, lanthanum series rare earth element compounds, organoaluminum compounds, aluminoxanes, halogen-containing compounds, and catalysts containing Lewis bases as needed. Among these, Nd-based catalysts using neodymium (Nd)-containing compounds as the lanthanum series rare earth element compound are preferred from the viewpoint of obtaining BRs with high cis content and low vinyl content.

[0077] SPB-containing BR includes those in which 1,2-syndiotactic polybutadiene crystals are not simply dispersed in BR, but are chemically bonded to BR and then dispersed.

[0078] Modified BRs include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and further modified BRs in which the ends of the modified BR molecule are linked by a tin-carbon bond (tin-modified BR), and butadiene rubber having a condensed alkoxysilane compound at the active end of the butadiene rubber (modified BR for silica).

[0079] From the viewpoint of wear resistance, the weight-average molecular weight (Mw) of BR is preferably 300,000 or more, more preferably 350,000 or more, and even more preferably 400,000 or more. From the viewpoint of crosslinking uniformity, it is preferably 2,000,000 or less, and more preferably 1,000,000 or less. The Mw of BR is measured by the measurement method described above.

[0080] The BR content in the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, even more preferably 20% by mass or more, and particularly preferably 25% by mass or more. On the other hand, the BR content in the rubber component is preferably 70% by mass or less, more preferably 65% ​​by mass or less, even more preferably 60% by mass or less, even more preferably 55% by mass or less, and particularly preferably 51% by mass or less. By setting the BR content within the above range, it is believed that the flexibility of the sidewall rubber can be improved over a wide temperature range, thereby mitigating input from the road surface.

[0081] (Other rubber components) The rubber component may also include rubber components other than those mentioned above, as long as they do not impair the effects of the present invention. Examples of such rubber components include hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), halogenated butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, polyethylene chloride rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, and other non-diene rubbers. In addition to the above rubber components, known thermoplastic elastomers may or may not be included.

[0082] From the viewpoint of the effects of the present invention, the aromatic vinyl unit content in the rubber component is 0.50% by mass or more, preferably 0.60% by mass or more, more preferably 0.90% by mass or more, even more preferably 1.2% by mass or more, and particularly preferably 1.5% by mass or more. Furthermore, from the viewpoint of the effects of the present invention, the aromatic vinyl unit content in the rubber component is 5.0% by mass or less, preferably 4.9% by mass or less, more preferably 4.5% by mass or less, even more preferably 4.0% by mass or less, and particularly preferably 3.5% by mass or less.

[0083] The aromatic vinyl unit content value in a rubber component corresponds to the weighted average of the aromatic vinyl unit content of each rubber component contained in that component. Therefore, for example, it can be increased by using a large amount of rubber components with a high aromatic vinyl unit content, and conversely, it can be decreased by using a large amount of rubber components with a low aromatic vinyl unit content.

[0084] <Filler> The rubber composition according to this embodiment preferably contains carbon black and / or silica, more preferably carbon black, and even more preferably carbon black and silica. The filler may also consist solely of carbon black and silica.

[0085] (silica) The silica used is not particularly limited; for example, silica prepared by the dry process (anhydrous silica) or silica prepared by the wet process (hydrated silica), which are common in the tire industry, can be used. Furthermore, from the viewpoint of environmental impact, silica made from biomass materials (for example, amorphous silica refined from rice husks) may also be used. Among these, hydrated silica prepared by the wet process is preferred because it contains a large number of silanol groups. These silicas may be used individually or in combination of two or more types.

[0086] Silica derived from biomass materials can be obtained, for example, by extracting silicates from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then using these silicates to react with sulfuric acid in the same way as conventional wet silica, the precipitate of silicon dioxide is filtered, washed with water, dried, and pulverized.

[0087] When silica crystallizes, it becomes insoluble in water, and its component, silicic acid, cannot be utilized. By controlling the combustion temperature and combustion time, the crystallization of silica in rice husk ash can be suppressed (see Japanese Patent Publication No. 2009-2594, Akita Prefectural University Web Journal B / 2019, vol.6, pp.216-222, etc.).

[0088] Amorphous silica extracted from rice husks can be commercially available from companies such as Wilmar.

[0089] The average primary particle diameter of silica is preferably 10 nm or more, more preferably 12 nm or more, and even more preferably 14 nm or more. By setting the average primary particle diameter of silica within the above range, the number of rubber molecules bound by silica is minimized, making it easier to move flexibly, and thus it is thought that the polymer molecular chains can also relieve stress in response to input. On the other hand, from the viewpoint of facilitating shock absorption through interaction with the domains of aromatic vinyl units, the average primary particle diameter is preferably 22 nm or less, more preferably 20 nm or less, and even more preferably 18 nm or less. The average primary particle diameter of silica is measured by the measurement method described above.

[0090] The specific surface area (N2SA) of silica for nitrogen adsorption is 110 m², from the viewpoint of the effects of the present invention. 2 Preferably 140m / g or more. 2 More preferably 170m / g or more. 2 More preferably 180m / g or more. 2 A value of less than / g is particularly preferred. Furthermore, the N2SA is 350m 2 Preferably less than / g, 300m 2 More preferably less than / g, 250m 2A value of less than / g is even more preferable. The N2SA of silica is measured by the measurement method described above.

[0091] From the viewpoint of obtaining reinforcing properties, the silica content per 100 parts by mass of rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more. Furthermore, from the viewpoint of obtaining flexibility in the rubber and mitigating input from the road surface, it is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less.

[0092] (Carbon Black) The carbon black used is not particularly limited; for example, common types used in the tire industry such as GPF, FEF, HAF, ISAF, and SAF can be used. Furthermore, from an environmental perspective, recycled carbon black (rCB) obtained from the thermal decomposition of used tires may also be used. These carbon blacks may be used individually or in combination of two or more types.

[0093] Recycled carbon black is made from waste tires and contains carbon particles of various sizes. Therefore, it is thought that it can convert vibration energy into thermal energy in response to a wide range of input frequencies from the road surface, thereby improving ride comfort.

[0094] Recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, which refers to "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, states that it can be obtained by the pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (

[0027] ). Carbon black obtained from such pyrolysis processes typically lacks functional groups on its surface, as referred to in

[0004] of Patent No. 6856781 (Comparison of Surface Morphology and Chemistry of Pyrolysis Carbon Black and Commercial Carbon Black, Powder Technology 160 (2005) 190-193).

[0095] Recycled carbon black may lack functional groups on its surface, or it may be treated to include functional groups on its surface. Treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3173251, carbon black obtained from a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. In addition, in Patent No. 6856781, carbon black obtained from a pyrolysis process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain carbon black with an activated surface. The recycled carbon black according to this embodiment also includes carbon black treated to include functional groups on its surface.

[0096] Recycled carbon black can be purchased from companies such as Strable Green Carbon and LDCarbon.

[0097] The average primary particle diameter of the carbon black is preferably 40 nm or more, more preferably 45 nm or more, even more preferably 50 nm or more, and particularly preferably 55 nm or more. By setting the average primary particle diameter of the carbon black within the above range, the number of rubber molecules bound by the carbon black is minimized, making it easier to move flexibly, and thus it is thought that the polymer molecular chains can also relieve stress in response to input. On the other hand, from the viewpoint of facilitating shock absorption through interaction with the domains of aromatic vinyl units, the average primary particle diameter is preferably 120 nm or less, more preferably 110 nm or less, even more preferably 100 nm or less, and particularly preferably 90 nm or less. The average primary particle diameter of the carbon black is measured by the measurement method described above.

[0098] The nitrogen adsorption specific surface area (N2SA) of carbon black is 50 m², from the viewpoint of the effects of the present invention. 2 Preferably less than / g, 45m 2 More preferably less than / g, 42m 2 It is even more preferable that the N2SA is less than or equal to 20m 2 Preferably 25m / g or more. 2 More preferably 30m 2 A value of 1 / g or higher is even more preferable. The N2SA of carbon black is measured by the measurement method described above.

[0099] When carbon black is included, the amount of carbon black per 100 parts by mass of rubber component is preferably 25 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 35 parts by mass or more, and particularly preferably 40 parts by mass or more, from the viewpoint of obtaining reinforcing properties and preventing degradation by ultraviolet rays. Furthermore, from the viewpoint of obtaining flexibility in the rubber and mitigating input from the road surface, it is preferably 90 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 70 parts by mass or less, even more preferably 65 parts by mass or less, and particularly preferably 60 parts by mass or less.

[0100] The percentage of recycled carbon black in the total carbon black content is not particularly limited, but can be, for example, more than 1% by mass, more than 5% by mass, more than 10% by mass, more than 20% by mass, more than 25% by mass, or more than 30% by mass. On the other hand, from the viewpoint of reinforcing properties, less than 95% by mass is preferred, less than 90% by mass is more preferred, and less than 85% by mass is even more preferred.

[0101] (Other fillers) Other fillers besides silica and carbon black can be added, including aluminum hydroxide, calcium carbonate, alumina, clay, talc, and other materials commonly used in the tire industry.

[0102] From the viewpoint of the effects of the present invention, the total content of the filler per 100 parts by mass of the rubber component is preferably 30 parts by mass or more, more preferably 35 parts by mass or more, even more preferably 40 parts by mass or more, even more preferably 45 parts by mass or more, and particularly preferably 50 parts by mass or more. Furthermore, from the viewpoint of the effects of the present invention, the total content of the filler per 100 parts by mass of the rubber component is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, even more preferably 80 parts by mass or less, and particularly preferably 70 parts by mass or less.

[0103] The silica content in 100% by mass of the filler is preferably greater than 0% by mass, more preferably 3% by mass or more, even more preferably 5% by mass or more, and particularly preferably 7% by mass or more. Furthermore, the silica content in 100% by mass of the filler is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less. By setting the silica content in the filler within the above range, it is believed that the flexibility of the sidewall rubber in the micro-deformation region is improved, and input from the road surface can be mitigated.

[0104] Furthermore, if the filler consists only of carbon black and silica, the total content of the filler and the content of either carbon black or silica are determined according to the above, and the content of the other is automatically determined.

[0105] (Silane coupling agent) Silica may be used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent that has been conventionally used in combination with silica in the tire industry can be used, for example: mercapto-type silane coupling agents such as 3-mercaptopropyltrimethoxysilane, Momentive's NXT-Z100, NXT-Z45, and NXT; sulfide-type silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; and thioester-type silane coupling agents such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane. Examples of coupling agents include: vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, sulfide-based silane coupling agents and / or mercapto-based silane coupling agents are preferred, and sulfide-based silane coupling agents are more preferred. These silane coupling agents may be used individually or in combination of two or more.

[0106] When a silane coupling agent is included, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, even more preferably 2.0 parts by mass or more, and particularly preferably 4.0 parts by mass or more, from the viewpoint of improving the dispersibility of silica. Furthermore, from the viewpoint of preventing a decrease in wear resistance, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less.

[0107] When a silane coupling agent is included, the content per 100 parts by mass of silica is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 8 parts by mass or more, from the viewpoint of improving the dispersibility of silica. Furthermore, from the viewpoint of cost and processability, it is preferably 20 parts by mass or less, more preferably 18 parts by mass or less, and even more preferably 16 parts by mass or less.

[0108] <Other compounding agents> In addition to the components mentioned above, the rubber composition according to this embodiment may appropriately contain compounding agents commonly used in the tire industry, such as softeners, waxes, processing aids, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators.

[0109] Examples of softening agents include resin components, oils, and liquid rubber.

[0110] The resin components are not particularly limited, but examples include petroleum resins, terpene resins, rosin resins, and phenolic resins commonly used in the tire industry. These resin components may be used individually or in combination of two or more.

[0111] When a resin component is included, the content relative to 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more, from the viewpoint of the effects of the present invention. Furthermore, from the viewpoint of suppressing heat generation, it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 30 parts by mass or less.

[0112] Examples of oils include process oils, vegetable oils, and animal oils. Examples of process oils include paraffinic process oils, naphthenic process oils, and aromatic process oils. Furthermore, for environmental reasons, process oils with a low content of polycyclic aromatic compounds (PCA) can be used. Examples of low-PCA process oils include light extraction solvates (MES), processed distillate aromatic extracts (TDAEs), and heavy naphthenic oils.

[0113] When oil is included, the content of the oil per 100 parts by mass of rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of wear resistance, it is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 60 parts by mass or less.

[0114] Liquid rubber is not particularly limited as long as it is a polymer that is in a liquid state at room temperature (25°C), but examples include liquid butadiene rubber (liquid BR), liquid styrene butadiene rubber (liquid SBR), liquid isoprene rubber (liquid IR), liquid styrene isoprene rubber (liquid SIR), liquid farnesene rubber, etc. These liquid rubbers may be used individually or in combination of two or more.

[0115] When liquid rubber is included, its content per 100 parts by mass of rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more. Furthermore, the liquid rubber content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less.

[0116] From the viewpoint of the effects of the present invention, the total content of the softener per 100 parts by mass of rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more. Furthermore, the total content of the softener is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 60 parts by mass or less.

[0117] When wax is included, the amount of wax per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of weather resistance of the rubber. Furthermore, from the viewpoint of preventing whitening of the tire due to bloom, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0118] While not particularly limited, examples of anti-aging agents include amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, as well as metal carbamate salts. Phenylenediamine-based anti-aging agents such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and N-cyclohexyl-N'-phenyl-p-phenylenediamine, and quinoline-based anti-aging agents such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline are preferred. These anti-aging agents may be used individually or in combination of two or more.

[0119] When an anti-aging agent is included, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of the rubber's resistance to ozone cracking. Furthermore, from the viewpoint of wear resistance and wet grip performance, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0120] When stearic acid is included, its content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0121] When zinc oxide is included, its content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of wear resistance, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0122] Sulfur is preferably used as a vulcanizing agent. Suitable sulfur varieties include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

[0123] When sulfur is included as a vulcanizing agent, the amount of sulfur per 100 parts by mass of rubber component is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, from the viewpoint of ensuring a sufficient vulcanization reaction. Furthermore, from the viewpoint of preventing deterioration, it is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, even more preferably 3.0 parts by mass or less, and particularly preferably 2.5 parts by mass or less. When oil-containing sulfur is used as the vulcanizing agent, the amount of vulcanizing agent is the total amount of pure sulfur contained in the oil-containing sulfur.

[0124] Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensates, 1,6-hexamethylene-dithiosulfate sodium dihydrate, and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane. These non-sulfur vulcanizing agents can be purchased commercially from companies such as Taoka Chemical Industries, Ltd., Lanxess Corporation, and Flexis.

[0125] Examples of vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamate, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. These vulcanization accelerators may be used individually or in combination of two or more. Among these, one or more vulcanization accelerators selected from the group consisting of sulfenamide, guanidine, and thiazole vulcanization accelerators are preferred, with sulfenamide vulcanization accelerators being more preferred, as they more favorably produce the desired effect.

[0126] Examples of sulfenamide-based vulcanization accelerators include N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide (DCBS). Among these, N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS) and N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS) are preferred.

[0127] Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salts of dicatecholborate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine. Among these, 1,3-diphenylguanidine (DPG) is preferred.

[0128] Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, and di-2-benzothiazolyl disulfide. Among these, 2-mercaptobenzothiazole is preferred.

[0129] When a vulcanization accelerator is included, its content per 100 parts by mass of rubber component is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2.0 parts by mass or more. Furthermore, the content of the vulcanization accelerator per 100 parts by mass of rubber component is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, even more preferably 6.0 parts by mass or less, and particularly preferably 5.0 parts by mass or less. By keeping the content of the vulcanization accelerator within the above range, it tends to be possible to ensure fracture strength and elongation.

[0130] <Manufacturing> The rubber composition according to this embodiment can be manufactured by known methods. For example, it can be manufactured by kneading each of the above components using a rubber kneading device such as an open roll or a closed kneader (Banbury mixer, kneader, etc.).

[0131] The mixing process includes, for example, a base mixing process in which compounding agents and additives other than the vulcanizing agent and vulcanization accelerator are mixed, and a final mixing (F mixing) process in which the vulcanizing agent and vulcanization accelerator are added to the mixture obtained in the base mixing process and mixed. Furthermore, the base mixing process can be divided into multiple processes as desired.

[0132] There are no particular limitations on the mixing conditions, but for example, in the base mixing process, mixing is performed at a discharge temperature of 150-170°C for 3-10 minutes, and in the final mixing process, mixing is performed at 70-110°C for 1-5 minutes. There are no particular limitations on the vulcanization conditions, but for example, vulcanization is performed at 150-200°C for 10-30 minutes.

[0133] A tire according to this embodiment, having a sidewall made of the rubber composition described above, can be manufactured by conventional methods. That is, an unvulcanized rubber composition, in which the above components are blended with the rubber component as needed, is extruded to match the shape of the sidewall, bonded together with other tire components on a tire molding machine, and molded in a conventional method to form an unvulcanized tire. This unvulcanized tire is then heated and pressurized in a vulcanizing machine to manufacture the tire. The vulcanization conditions are not particularly limited, and for example, a method of vulcanizing at 150 to 200°C for 10 to 30 minutes can be used.

[0134] <Application> The tire according to this embodiment can be suitably used for passenger car tires, truck and bus tires, motorcycle tires, and racing tires, and is particularly preferred for use as a passenger car tire. A passenger car tire is defined as a tire intended to be mounted on a four-wheeled vehicle, with a maximum load capacity of 1000 kg or less. Furthermore, the tire according to this embodiment can be used for all-season tires, summer tires, and winter tires such as studless tires. [Examples]

[0135] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0136] The various chemicals used in the examples and comparative examples are summarized below. NR:TSR20 SBR: HPR840 (S-SBR, styrene content: 10% by mass, vinyl content: 42 mol%, Mw: 190,000, Tg: -60℃) manufactured by JSR Corporation. Multi-component polymer: Hydrogenated SBR produced in Production Example 1 described below (hydrogenation rate: 80%, styrene content: 35% by mass, Mw: 480,000, Tg: -30℃) BR: UBEPOL BR(registered trademark) 150B manufactured by Ube Industries, Ltd. (cis content: 97 mol%, Mw: 440,000) Carbon Black 1: Dia Black (registered trademark) E (FEF, N550, N2SA) manufactured by Mitsubishi Chemical Corporation: 41m 2 / g, average primary particle diameter: 81nm) Carbon Black 2: SS550 from Streble Green Carbon (carbon black obtained from the thermal decomposition process of tires) Silica 1: ULTRASIL VN3 (N2SA: 175m) manufactured by Evonik Degussa. 2 / g, average primary particle size: 18nm) Silica 2: Wilmar K185 (amorphous silica refined from rice husks) Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) manufactured by Evonik Degussa. Oil: VivaTec500 (TDAE oil) manufactured by H&R Co., Ltd. Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. Anti-aging agent 1: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Anti-aging agent 2: Nocrack RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Beads of stearic acid manufactured by NOF Corporation Sulfur: HK-200-5 (5% oil-containing powdered sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator: Noxellar CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0137] Manufacturing Example 1: Production of Hydrogenated SBR In a thoroughly nitrogen-purged heat-resistant reaction vessel, 2000 mL of n-hexane, 60 g of styrene, 140 g of butadiene, 0.93 g of THF, and 0.45 mmol of n-butyllithium were added, and the mixture was stirred at 50°C for 5 hours to carry out the polymerization reaction. Next, hydrogen gas was supplied at a pressure of 0.4 MPa-Gauge while stirring for 20 minutes to react with the unreacted lithium at the polymer ends to obtain lithium hydride. The hydrogen gas supply pressure was set to 0.7 MPa-Gauge and the reaction temperature to 90°C, and hydrogenation was carried out using a catalyst mainly composed of titanocene dichloride. When the hydrogen absorption reached the cumulative amount that would result in the desired hydrogenation rate, the reaction temperature was reduced to room temperature, the hydrogen pressure was returned to atmospheric pressure, and the reaction mixture was withdrawn from the reaction vessel. The reaction solution was then stirred into water and the solvent was removed by steam stripping to obtain hydrogenated SBR.

[0138] (Examples and Comparative Examples) According to the formulations shown in Tables 1-1, 1-2, 1-3, and 2, chemicals other than sulfur and vulcanization accelerator were mixed in a 1.7 L sealed Banbury mixer for 5 minutes until the discharge temperature reached 170°C to obtain a mixture. Next, sulfur and vulcanization accelerator were added to the mixture using a twin-screw open roll mixer and mixed for 4 minutes until the temperature reached 105°C to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was extruded into the shape of a sidewall using an extruder equipped with a die of a predetermined shape, bonded together with other tire components to form an unvulcanized tire, and then press-vulcanized at 170°C for 12 minutes to produce each test tire.

[0139] The obtained test tires were evaluated as follows. The evaluation results are shown in Tables 1-1, 1-2, 1-3, and 2.

[0140] <Ride comfort performance> Each test tire, both new and worn, was inflated to 250 kPa and mounted on all four wheels of a 2000cc front-wheel-drive passenger car. The car was then driven on a dry asphalt test course. Ride comfort was evaluated based on the test driver's perception of the feel during straight-line driving, lane changes, and acceleration / deceleration at 120 km / h. The evaluation was based on an integer score from 1 to 10, with higher scores indicating better ride comfort. The total scores of 10 test drivers were calculated. The total score of the control tire (Comparative Example 2) was converted to a baseline value (100), and the evaluation results of each test tire were indexed and displayed proportionally to the total score. A higher numerical value indicates better ride comfort.

[0141] Each test tire after wear was prepared by first wearing down the tread along the tread radius so that the depth of the deepest main groove of a new tire was 50% of that of a new tire, and then thermally degrading the tire at 80°C for 7 days.

[0142] [Table 1-1]

[0143] [Table 1-2]

[0144] [Table 1-3]

[0145] [Table 2]

[0146] The results from Tables 1-1, 1-2, 1-3, and 2 show that the tire of the present invention, in which the aromatic vinyl unit content in the rubber component constituting the sidewall and the thickness of the sidewall at the tire's maximum width position are in a predetermined relationship, shows improved overall performance in terms of ride comfort when new and after wear (average value of ride comfort index when new and ride comfort index after wear).

[0147] <Embodiment> Examples of embodiments of the present invention are shown below.

[0148] [1] A tire having a sidewall, wherein the sidewall is made of a rubber composition containing a rubber component, and when the aromatic vinyl unit content in the rubber component is S (mass%) and the thickness of the surface rubber layer at the tire's maximum width position is T (mm), S is 0.50% by mass or more and 5.0% by mass or less (preferably 0.60% by mass or more and 5.0% by mass or less, more preferably 0.90% by mass or more and 4.9% by mass or less, even more preferably 1.2% by mass or more and 4.9% by mass or less), and S / T is 0.045 or more and 3.33 or less (preferably 0.065 or more and 3.00 or less, more preferably 0.10 or more and 2.80 or less, even more preferably 0.15 or more and 2.60 or less, particularly preferably 0.20 or more and 2.40 or less). [2] The tire according to [1] above, wherein the rubber component comprises a multi-component polymer having aromatic vinyl units, non-conjugated olefin units, and conjugated diene units. [3] The tire according to [1] or [2] above, wherein the rubber component contains 15% by mass or more and 65% by mass or less (preferably 25% by mass or more and 60% by mass or less) of isoprene-based rubber. [4] The tire according to any one of [1] to [3] above, wherein the rubber component contains 20% by mass or more and 60% by mass or less (preferably 25% by mass or more and 55% by mass or less) of butadiene rubber. [5] The tire according to any one of [1] to [4] above, wherein the rubber composition contains 35 to 70 parts by mass (preferably 40 to 65 parts by mass) of a filler containing carbon black and / or silica, per 100 parts by mass of the rubber component. [6] The tire according to [5] above, wherein the silica content in 100% by mass of the filler is 5% by mass or more and 30% by mass or less (preferably 7% by mass or more and 25% by mass or less). [7] Maximum load capacity of the tire W L Ratio of tire weight G (kg) to (kg) (G / W L A tire according to any one of the above [1] to [6], wherein the ratio is 0.0210 or less (preferably 0.0180 or less, more preferably 0.0165 or less, and even more preferably 0.0150 or less). [8] A tire as described in any of [1] to [7] above, wherein the tire section width Wt (mm) and the tire outer diameter Dt (mm) satisfy the following formula (1). (π / 4) × (Dt 2 / Wt)≧1600 ···(1) [9] A tire according to any of [1] to [8] above, wherein the filler contains recycled carbon black.

[10] The tire according to any one of [1] to [9] above, wherein the filler contains silica made from biomass material (preferably amorphous silica refined from rice husks). [Explanation of symbols]

[0149] 1 tread 2 belts 3 bands 21 Bead Core 22 Bead Apex 23 Rim Cushion 24 Clinch Apex 25 Strip Apex 31 Sidewall 32 Inner Liner 33 Carcass CL Tire Equator

Claims

1. A tire with a sidewall, The sidewall is made of a rubber composition containing rubber components, The rubber component comprises a multi-component polymer having aromatic vinyl units, non-conjugated olefin units, and conjugated diene units. The total content of the filler relative to 100 parts by mass of the rubber component is 65 parts by mass or less. A tire in which, when the aromatic vinyl unit content in the rubber component is S (mass%) and the thickness of the surface rubber layer at the tire's maximum width position is T (mm), S is 0.50 mass% or more and 5.0 mass% or less, and S / T is 0.045 or more and 3.33 or less.

2. The tire according to claim 1, wherein the rubber component contains 15% by mass or more and 65% by mass or less of isoprene-based rubber.

3. The tire according to claim 1 or 2, wherein the rubber component contains 20% by mass or more and 60% by mass or less of butadiene rubber.

4. The tire according to claim 1 or 2, wherein the rubber composition contains 35 to 65 parts by mass of a filler containing carbon black and / or silica, per 100 parts by mass of the rubber component.

5. The tire according to claim 4, wherein the silica content in 100% by mass of the filler is 5% by mass or more and 30% by mass or less.

6. Tire's maximum load capacity W L Ratio of tire weight G (kg) to (kg) (G / W) L The tire according to claim 1 or 2, wherein the coefficient of

7. A tire according to claim 1 or 2, wherein the tire section width Wt (mm) and the tire outer diameter Dt (mm) satisfy the following formula (1). (π / 4)×(Dt 2 / Wt)≧1600 ・・・(1)

8. The tire according to claim 1 or 2, wherein the filler includes recycled carbon black.

9. The tire according to claim 1 or 2, wherein the filler contains silica made from biomass material.

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