tire

Abstract

The aim is to improve the overall performance of tires, including their resistance to flexural crack growth when new and their resistance to flexural crack growth after thermal degradation. [Solution] A tire having a sidewall, wherein the sidewall is made of a rubber composition containing rubber components and fillers, the sulfur content in the rubber composition is less than 0.65% by mass, the ratio V of the crosslink density of monosulfide bonds to the total crosslink density of the rubber composition is 0.10 or more, the thickness of the surface rubber layer at the tire's maximum width position is D (mm), and the maximum load capacity of the tire is W. L (kg), where G (kg) is the tire weight, K = G / W L If defined as such, a tire where K is 0.018 or less and V / (K×D) is 1.00 or greater.

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] There is a need for a tire in which cracks are less likely to occur due to stress during driving and the progression of cracks is less likely to occur. Patent Document 1 describes a rubber composition for a sidewall having excellent crack resistance and a pneumatic tire using the rubber composition for the sidewall.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a tire capable of improving the overall performance of the crack growth resistance performance during bending at the time of a new tire and the crack growth resistance performance during bending after heat deterioration.

Means for Solving the Problems

[0005] The present invention is a tire provided with a sidewall, wherein the sidewall is composed of a rubber composition containing a rubber component and a filler, the amount of sulfur in the rubber composition is less than 0.65% by mass, and the ratio V of the crosslink density of monosulfide bonds to the total crosslink density of the rubber composition is 0.10 or more. When the thickness of the surface rubber layer at the maximum width position of the tire is D (mm), the maximum load capacity of the tire is W L (kg), and the tire weight is G (kg), and K = G / W L is defined, the present invention relates to a tire in which K is 0.018 or less and V / (K×D) is 1.00 or more.

Effects of the Invention

[0006] According to the present invention, it is possible to improve the overall performance of flexural crack growth resistance when the tire is new and flexural crack growth resistance after thermal degradation. [Brief explanation of the drawing]

[0007] [Figure 1] This is a cross-sectional view of an example of a tire, which is one embodiment of the present invention. [Modes for carrying out the invention]

[0008] One embodiment of the present invention is a tire having a sidewall, wherein the sidewall is made of a rubber composition containing rubber components and fillers, the sulfur content in the rubber composition is less than 0.65% by mass, the ratio V of the crosslink density of monosulfide bonds to the total crosslink density of the rubber composition is 0.10 or more, the thickness of the surface rubber layer at the tire's maximum width position is D (mm), and the maximum load capacity of the tire is W. L (kg), where G (kg) is the tire weight, K = G / W L If defined as such, it is a tire where K is 0.018 or less and V / (K×D) is 1.00 or more.

[0009] While not intended to be constrained by theory, the mechanism by which the overall performance of the tire of the present invention improves, both in terms of resistance to flexural crack growth when the tire is new and after thermal degradation, can be considered as follows, for example.

[0010] (1) Tires are generally manufactured by crosslinking unvulcanized tires made using various tire components with sulfur. The crosslinking forms are classified into monosulfide bonds, in which only one sulfur molecule is interposed, and polysulfide bonds, in which two or more sulfur molecules are interposed between the crosslinking points. Polysulfide bonds are weak because multiple sulfur molecules are interposed between the crosslinking points. On the other hand, monosulfide bonds have only one sulfur molecule interposed between the crosslinking points, and the crosslinking chain is not easily broken. Therefore, by setting the ratio V of the crosslinking density of monosulfide bonds to the total crosslinking density of the rubber composition within the above range, it is thought that the decrease in flexural crack growth performance after thermal degradation can be suppressed.

[0011] (2) Furthermore, by setting the ratio K of tire weight to maximum load capacity of the tire within the aforementioned range, the dynamic load (amount of strain) applied to the sidewall is reduced, which is thought to suppress the growth of bending cracks.

[0012] (3) Furthermore, by setting the relation V / (K×D) within the aforementioned range and adjusting the ratio V and ratio K according to the size of the thickness D of the surface rubber layer at the tire's widest position, which contributes to the flexural crack growth resistance, it is considered possible to improve the overall performance of the flexural crack growth resistance when the tire is new and the flexural crack growth resistance after thermal degradation in a well-balanced manner.

[0013] It is believed that the combined efforts of (1), (2), and (3) above will achieve a remarkable effect: an improvement in the overall performance of the tire, both in terms of resistance to flexural crack growth when new and after thermal degradation.

[0014] From the viewpoint of the effects of the present invention, the aforementioned rubber component preferably contains 35% by mass or more of isoprene-based rubber.

[0015] From the viewpoint of the effects of the present invention, the total content of butadiene rubber and styrene-butadiene rubber relative to the content of isoprene-based rubber in the aforementioned rubber component is preferably 0.15 or more.

[0016] From the viewpoint of the effects of the present invention, the carbon black content in the filler is preferably 80% by mass or more.

[0017] From the viewpoint of the effects of the present invention, the total content of filler in the rubber composition relative to 100 parts by mass of the rubber component is preferably 40 parts by mass or more.

[0018] From the viewpoint of ensuring an appropriate ratio V of the crosslink density of monosulfide bonds to the total crosslink density of the rubber composition, the sulfur content in the rubber composition per 100 parts by mass is preferably 0.1 parts by mass or more and less than 1.0 part by mass.

[0019] The rubber component preferably includes hydrogenated styrene-butadiene rubber.

[0020] Because hydrogenated styrene-butadiene rubber has high heat resistance and ozone resistance, it is believed that it can maintain its resistance to flexural crack growth for a long period of time even as tires deteriorate.

[0021] <Definition> "Standard condition" refers to a state of no load where the tire is mounted on a standard rim and filled with air at the standard internal pressure. Unless otherwise specified, tires in the standard condition should be used.

[0022] Unless otherwise specified, the "dimensions of each part of the tire" refer to values ​​that are determined in the normal state for those visible on the outer surface of the tire, while those located inside the tire or on the cut surface of the tire refer to values ​​that are determined, for example, by cutting the tire in a plane including the tire's axis of rotation and holding the cut tire piece within the rim width of the normal rim.

[0023] A "standard rim" refers to the rim specified for each tire within the standards system that the tire is based on. For example, for JATMA (Japan Automobile Tire Manufacturers Association), it refers to the standard rim for the applicable size listed in the "JATMA YEAR BOOK," for ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" listed in the "STANDARDS MANUAL," and for TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "YEAR BOOK." Refer to JATMA, ETRTO, and TRA in that order, and if an applicable size is available at the time of reference, follow that standard. In the case of a tire not specified in the above standards, it refers to the narrowest rim width among the smallest diameter rims that can be mounted on that tire and that can maintain internal pressure (i.e., do not cause air leakage between the rim and tire).

[0024] "Regular internal pressure" refers to the air pressure specified for each tire in the standards system, including the standard on which the tire is based. For example, for JATMA it refers to "maximum air pressure," for ETRTO it refers to "INFLATION PRESSURE," and for TRA it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." As with regular rims, refer to JATMA, ETRTO, and TRA in that order, and if there is an applicable size at the time of reference, follow that standard. In the case of tires not specified in the above standards, it refers to the regular internal pressure (but at least 250kPa) of another tire size (but specified in the standard) that is listed with the aforementioned regular rim as the standard rim. If multiple regular internal pressures of 250kPa or higher are listed, refer to the lowest value among them.

[0025] "Regular load (kg)" refers to the load specified for each tire in the standard system that the tire is based on. For example, for JATMA it is "Maximum Load Capacity," for ETRTO it is "LOAD CAPACITY," and for TRA it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." As with regular rims and regular in-tire pressure, refer to JATMA, ETRTO, and TRA in that order, and if an applicable size is available at the time of reference, follow that standard. For tires not specified in the above standards, the maximum load capacity (kg) is calculated separately. L This is considered the normal load.

[0026] "Maximum load capacity W L The weight (kg) is calculated using the following formula: "V" is the virtual volume of the tire (mm²). 3 ), "Dt" is the outer diameter of the tire in the normal state (mm), "Ht" is the height of the tire's cross-section in the radial direction in a plane containing the tire's axis of rotation (mm), and "Wt" is the width of the tire's cross-section in the normal state (mm). Ht can be calculated by (Dt-R) / 2, where R is the rim diameter of the tire. Wt is the value obtained by removing any patterns or letters on the tire's sidewall. Note that the maximum load capacity is synonymous with the normal load mentioned above.

[0027]

number

[0028] "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.

[0029] "The thickness D 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 maximum width in the tire width direction on a plane passing through the tire's axis of rotation. "Surface rubber layer" includes the sidewall rubber.

[0030] "Rubber components of a rubber composition" refer to components that contribute to crosslinking within a rubber composition, and generally have a weight-average molecular weight (Mw) of 10,000 or more.

[0031] A "plasticizer" is a material that imparts plasticity to rubber components and is extracted from rubber compositions using acetone. This definition includes both liquid plasticizers at 25°C and solid plasticizers at 25°C. However, it excludes waxes and stearic acid commonly used in the tire industry.

[0032] "Plasticizer content" includes the amount of plasticizer contained in the extensible rubber component that has been pre-stretched with plasticizers such as oil, resin components, and liquid rubber components. The same applies to the oil content, resin component content, and liquid rubber content; for example, if the extensible component is oil, the extensible oil is included in the oil content.

[0033] <Measurement method> "Sulfur content Ts in the rubber composition" is the amount of sulfur (mass%) measured by the oxygen combustion flask method in accordance with JIS K 6233:2016.

[0034] The "total crosslink density of the rubber composition" is measured according to a known swelling and compression method. Specifically, for example, a vulcanized rubber test piece measuring 20 mm in length, 20 mm in width, and 1 mm in thickness is immersed in a tetrahydrofuran:toluene mixed solution = 1:1 for 24 hours to prepare a swollen sample. The degree of swelling and compression of this swollen sample is measured using a thermomechanical analyzer, and the total crosslink density of the rubber composition (mol / cm³) is calculated using the Flory-Rehner formula. 3Calculate

[0035] The "crosslink density of monosulfide bonds in the rubber composition" is measured in accordance with a known swelling compression method. Specifically, for example, a vulcanized rubber test piece with a length of 20 mm × width of 20 mm × thickness of 1 mm is immersed in a mixed solution of tetrahydrofuran:toluene = 1:1 saturated with lithium aluminum hydride (LiAlH4) for 24 hours to prepare a swollen sample in which polysulfide bonds are cleaved. For this swollen sample, the swelling compression degree is measured using a thermomechanical analyzer, and using the Flory-Rehner equation, the crosslink density (mol / cm 3 ) of the monosulfide bonds in the rubber composition is calculated. When the vulcanized rubber test piece is prepared by cutting it out from a tire, when the tire member is a sidewall, it is cut out from the sidewall such that the thickness direction of the sidewall becomes the thickness direction.

[0036] The "ratio V of the crosslink density of monosulfide bonds to the total crosslink density of the rubber composition" is obtained by "(crosslink density of monosulfide bonds in the rubber composition) / (total crosslink density of the rubber composition)".

[0037] The "styrene content" is calculated by pyrolysis gas chromatography or NMR measurement ( 1 1H-NMR and 13 13C-NMR). Component amounts such as the "styrene content" are different from physical property values such as the complex elastic modulus (E * ), and since there is a true value that does not depend on the measurement method, it is preferable to use a measurement method with as high precision as possible. In this specification, "pyrolysis gas chromatography" refers to a method in which a sample is heated by a pyrolysis apparatus, the individual components contained in the gas-phase components generated by this heating are separated by a separation column, and each isolated component is analyzed. The styrene content is applied, for example, to rubber components having repeating units (styrene units) derived from styrene such as SBR.

[0038] "Vinyl content (amount of 1,2-bonded butadiene units)" can be determined by pyrolysis gas chromatography or NMR measurement. 1 H-NMR and 13 It is calculated by 13C-NMR. Similar to "styrene content," a true value exists for "vinyl content" that is independent of the measurement method, so it is preferable to use a measurement method that is as accurate as possible. Vinyl content is applied to rubber components having repeating units derived from butadiene, such as SBR and BR.

[0039] "Cis content (amount of cis-1,4-bonded butadiene units)" is determined by infrared absorption spectroscopy or NMR measurement in accordance with JIS K 6239-2:2017. 1 H-NMR and 13 This value is measured by 13C-NMR and is applied, for example, to rubber components having repeating units derived from butadiene, such as BR. Similar to "styrene content," a true value exists for "cis content" that is independent of the measurement method, so it is preferable to use the most accurate measurement method possible.

[0040] The "weight-average molecular weight (Mw)" can be determined by converting the measured value using gel permeation chromatography (GPC) (for example, the GPC-8000 series manufactured by Tosoh Corporation, with a differential refractometer as the detector and TSKgel® SuperMultipore HZ-M column manufactured by Tosoh Corporation) to a standard polystyrene equivalent. This method is applied, for example, to SBR, BR, plasticizers, etc.

[0041] The glass transition temperature (Tg) of SBR is determined in accordance with JIS K 6229:2015 by removing the spreading oil using acetone, and then determining the pure SBR content by differential scanning calorimetry (DSC) in accordance with JIS K 7121:2012.

[0042] The nitrogen adsorption specific surface area (N2SA) of carbon black is measured in accordance with JIS K 6217-2:2017.

[0043] The nitrogen adsorption specific surface area (N2SA) of silica is measured by the BET method in accordance with ASTM D3037-93.

[0044] The "average primary particle diameter" is a value obtained by photographing particles with a transmission or scanning electron microscope and taking the arithmetic mean of the particle diameters of 400 particles. If the particle shape is spherical, the diameter of the sphere is used as the particle diameter; if it is not spherical, the equivalent diameter of a circle (the positive square root of {4 × (particle area) / π}) is calculated from the microscope image and used as the particle diameter. The average primary particle diameter is applied to silica, carbon black, and other materials.

[0045] 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.

[0046] <Tires> The tire according to this embodiment includes a sidewall made of the rubber composition described below. A tire according to one embodiment of the present invention will be described below with reference to the drawings, but the drawings are for illustrative purposes only. Furthermore, the embodiments described below are merely examples.

[0047] Figure 1 is a cross-sectional view of a tire as shown by a plane passing through the tire's axis of rotation, showing only the right side as it is divided by the tire's centerline CL. The tire in Figure 1 comprises a tread 1, a pair of sidewalls 31 arranged on both sides of the tread, an inner liner 32, a pair of bead portions having a bead core 21, at least one layer of carcass 33 anchored to the bead core 21, at least one layer of belt 2 arranged radially outward of the carcass 33, and a band 3 covering the belt 2.

[0048] The tire weight G is preferably 5.5 kg or more, more preferably 6.0 kg or more, even more preferably 6.5 kg or more, and particularly preferably 7.0 kg or more. There is no particular upper limit to the tire weight G, but it is usually 100 kg or less, and can be, for example, 80 kg or less, 60 kg or less, 40 kg or less, 20 kg or less, 15 kg or less, or 10 kg or less.

[0049] The tire weight G can be increased, for example, by increasing the specific gravity of the tire or by increasing the thickness of each component of the tire, and conversely, it can also be decreased. Also, the maximum load capacity W L This can be increased, for example, by increasing the virtual volume V of the space occupied by the tire, and conversely, it can be decreased.

[0050] Tire's 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 exhibiting the effects of the present invention. L From the viewpoint of better exhibiting the effects of the present invention, the (kg) can be, for example, 1300 or less, 1200 or less, 1100 or less, 1000 or less, 900 or less, or 800 or less.

[0051] K = G / W L When defined as such, K is 0.018 or less from the viewpoint of the effects of the present invention, preferably 0.017 or less, more preferably 0.016 or less, and even more preferably 0.015 or less. On the other hand, the lower limit of K is not particularly limited, but can be, for example, 0.009 or more, 0.010 or more, 0.011 or more, or 0.012 or more.

[0052] From the viewpoint of the effects of the present invention, the thickness D of the surface rubber layer at the tire's maximum width position is preferably 1.0 mm or more, more preferably 2.0 mm or more, even more preferably 3.0 mm or more, and particularly preferably 3.5 mm or more. Furthermore, from the viewpoint of the effects of the present invention, D is preferably 10.0 mm or less, more preferably 9.0 mm or less, even more preferably 8.0 mm or less, and particularly preferably 7.0 mm or less.

[0053] The amount of sulfur in the rubber composition constituting the sidewall is less than 0.65% by mass, preferably less than 0.62% by mass, preferably less than 0.59% by mass, and particularly preferably less than 0.56% by mass, from the viewpoint of the effects of the present invention. On the other hand, the amount of sulfur in the rubber composition constituting the sidewall is more than 0.40% by mass, more preferably more than 0.45% by mass, and even more preferably more than 0.50% by mass, from the viewpoint of increasing the crosslinking points of the polymer and ensuring the elongation of the sidewall rubber. The amount of sulfur in the rubber composition can be appropriately adjusted by the amount of sulfur and vulcanization accelerator blended as described below.

[0054] The ratio V of the crosslink density of monosulfide bonds to the total crosslink density of the rubber composition constituting the sidewall is preferably 0.10 or higher, more preferably 0.15 or higher, more preferably 0.20 or higher, even more preferably 0.25 or higher, and particularly preferably 0.30 or higher, from the viewpoint of the effects of the present invention. On the other hand, V is preferably 0.70 or lower, more preferably 0.60 or lower, even more preferably 0.50 or lower, and particularly preferably 0.45 or lower, from the viewpoint of maintaining the flexural crack growth resistance performance when the tire is new. Note that V can be appropriately adjusted by the type and content of sulfur and vulcanization accelerator, and their mass content ratio, and tends to increase by increasing the ratio of the vulcanization accelerator content to sulfur, for example.

[0055] From the viewpoint of the effects of the present invention, V / (K×D) is 1.00 or more, preferably 1.50 or more, more preferably 2.00 or more, still preferably 2.50 or more, still preferably 3.00 or more, and particularly preferably 3.50 or more. On the other hand, there is no particular upper limit to V / (K×D), but it is preferably 15.0 or less, more preferably 10.0 or less, still preferably 8.00 or less, still preferably 7.00 or less, still preferably 6.50 or less, and particularly preferably 6.00 or less.

[0056] [Rubber composition] The rubber composition constituting the sidewall according to this embodiment (hereinafter referred to as the rubber composition according to this embodiment) contains rubber components, fillers, and sulfur, all of which can be manufactured using the raw materials described below. The rubber composition according to this embodiment will be described below.

[0057] <Rubber components> The rubber component according to this embodiment preferably includes a diene rubber. Furthermore, the rubber component preferably includes an isoprene rubber, more preferably includes an isoprene rubber and butadiene rubber and / or styrene-butadiene rubber, and even more preferably includes an isoprene rubber and butadiene rubber. The rubber component may also consist only of isoprene rubber and butadiene rubber, or only of isoprene rubber and styrene-butadiene rubber.

[0058] Examples of diene rubbers include isoprene rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR), styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber (SIBR), chloroprene rubber (CR), and acrylonitrile-butadiene rubber (NBR). These diene rubbers may be modified rubbers treated with modifying groups that can interact with fillers such as carbon black or silica, or they may be hydrogenated rubbers in which some of the unsaturated bonds have been hydrogenated. Diene rubbers may be used individually or in combination of two or more. In addition, as the diene rubber, stretchable rubber that has been pre-stretched using a plasticizer described later may be used.

[0059] The content of diene rubber in the rubber component is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. Alternatively, the rubber component may consist solely of diene rubber.

[0060] (Isoprene rubber) As isoprene-based rubbers, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. Natural rubber includes not only unmodified natural rubber (NR), but also modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. These isoprene-based rubbers may be used individually or in combination of two or more types.

[0061] NR is not particularly limited and can be any that is common in the tire industry, such as SIR20, RSS#3, TSR20, etc.

[0062] From the viewpoint of the effects of the present invention, the content of isoprene-based rubber in the rubber component is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, even more preferably 35% by mass or more, and particularly preferably 40% by mass or more. On the other hand, there is no particular upper limit to the content, but it is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, even more preferably 60% by mass or less, and particularly preferably 50% by mass or less.

[0063] (BR) While there are no particular limitations on the type of BR used, common types used in the tire industry can be used, such as 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), and modified BR (high-cis modified BR, low-cis modified BR). These BRs may be used individually or in combination of two or more types.

[0064] High-cis BR can be commercially available from companies such as Nippon Zeon Co., Ltd., UBE Corporation, and JSR Corporation. Including high-cis BR can improve low-temperature properties and wear resistance. The cis content of high-cis BR is preferably more than 95 mol%, more preferably more than 96 mol%, and even more preferably more than 97 mol%. The cis content of BR is measured by the measurement method described above.

[0065] 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.

[0066] When the rubber component contains BR, the content of BR in the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and particularly preferably 50% by mass or more, from the viewpoint of the effects of the present invention. On the other hand, there is no particular upper limit to the content, but it is preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, and particularly preferably 65% ​​by mass or less.

[0067] (SBR) SBR is not particularly limited, but examples include unmodified solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). Modified SBRs include SBRs with modified terminals and / or main chains, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, branched structures, etc.). Furthermore, hydrogenated versions of these SBRs (hydrogenated SBRs) can also be used. These SBRs may be used individually or in combination of two or more types.

[0068] From the viewpoint of the effects of the present invention, the hydrogenation rate of hydrogenated SBR is preferably more than 30 mol%, more preferably more than 50 mol%, and even more preferably more than 70 mol%. On the other hand, there is no particular upper limit to the hydrogenation rate, and it is sufficient if it is less than 100 mol%. The hydrogenation rate can be adjusted by adjusting the reaction conditions such as the hydrogen gas supply pressure and reaction temperature in the hydrogenation reaction as described in Production Example 1 below. Note that the hydrogenation rate of a multi-component polymer refers to the proportion of double bonds on the conjugated diene units that have been hydrogenated, in the case where the multi-component polymer is a polymer consisting of aromatic vinyl units and conjugated diene units that has been hydrogenated. 1 It can be calculated from the spectral reduction rate of the unsaturated bond region of the spectrum obtained by measuring 1H-NMR.

[0069] As for SBR, oil-expanded SBR can be used, or non-oil-expanded SBR can be used. When oil-expanded SBR is used, 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] Examples of SBRs that can be used in this embodiment include those commercially available from companies such as JSR Corporation, Sumitomo Chemical Co., Ltd., UBE Corporation, Asahi Kasei Corporation, ZS Elastomers Co., Ltd., and ARLANXEO.

[0071] From the viewpoint of the effects of the present invention, the styrene content of SBR is preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more. On the other hand, the styrene content of SBR is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. The styrene content of SBR is measured by the measurement method described above.

[0072] From the viewpoint of the effects of the present invention, the vinyl content of SBR is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more. Furthermore, the vinyl content of SBR is preferably 80 mol% or less, more preferably 70 mol% or less, and even more preferably 60 mol% or less. The vinyl content of SBR is measured by the measurement method described above.

[0073] From the viewpoint of the effects of the present invention, the glass transition temperature (Tg) of SBR is preferably -50°C or higher, more preferably -40°C or higher, and even more preferably -35°C or higher. Furthermore, the Tg of SBR is preferably 0°C or lower, more preferably -10°C or lower, and even more preferably -20°C or lower. The Tg of SBR is measured by the measurement method described above.

[0074] From the viewpoint of grip performance, the weight-average molecular weight (Mw) of SBR is preferably 200,000 or more, more preferably 250,000 or more, and even more preferably 300,000 or more. Furthermore, from the viewpoint of crosslinking uniformity, the Mw of SBR 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.

[0075] When the rubber component contains SBR, the content of SBR in the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, and particularly preferably 30% by mass or more, from the viewpoint of the effects of the present invention. On the other hand, there is no particular upper limit to the content, but it is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, and particularly preferably 60% by mass or less.

[0076] From the viewpoint of the effects of the present invention, the total content of BR and SBR relative to the isoprene-based rubber content in the rubber component is preferably 0.15 or more, more preferably 0.33 or more, even more preferably 0.50 or more, even more preferably 0.75 or more, even more preferably 1.0 or more, and particularly preferably 1.1 or more. On the other hand, the total content of BR and SBR relative to the isoprene-based rubber content in the rubber component is preferably 4.0 or less, more preferably 3.0 or less, even more preferably 2.5 or less, even more preferably 2.0 or less, and particularly preferably 1.7 or less.

[0077] (Other rubber components) The rubber component may contain other rubber components besides diene rubber, as long as they do not affect the effects of the present invention. Other rubber components besides diene rubber can include crosslinkable rubber components commonly used in the tire industry, such as butyl rubber (IIR), halogenated butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, polyethylene chloride rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber. In addition to the above rubber components, known thermoplastic elastomers may or may not be included. Other rubber components may be used individually or in combination of two or more.

[0078] (Rubber components synthesized from recycled and biomass-derived raw materials) Monomers, which are the constituent units of synthetic rubbers such as IR, SBR, and BR, may be derived from underground resources such as petroleum and natural gas, or they may be recycled from rubber products such as tires or non-rubber products such as polystyrene. The monomers obtained by recycling (recycled monomers) are not particularly limited, but include recycled polyisoprene, recycled butadiene, and recycled aromatic vinyl compounds. Examples of butadiene include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl compounds are not particularly limited, but include styrene. In particular, it is preferable to use recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) as raw materials.

[0079] The method for producing recycled monomer is not particularly limited, and for example, it can be synthesized from recycled naphtha obtained by decomposing rubber products such as tires. Furthermore, the method for producing recycled naphtha is not particularly limited, and for example, rubber products such as tires may be decomposed under high temperature and pressure, decomposed by microwaves, or extracted after mechanical grinding.

[0080] Furthermore, the monomers that make up polymers such as IR, SBR, and BR may be derived from biomass. In this specification, biomass refers to substances derived from natural resources such as plants. Biomass is not particularly limited, but examples include agricultural, forestry, and fishery products, sugars, wood chips, plant residues after obtaining useful components, plant-derived ethanol, and biomass naphtha.

[0081] The biomass-derived monomer (biomass monomer) is not particularly limited and includes biomass-derived butadiene and biomass-derived aromatic vinyl compounds. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. Examples of the aromatic vinyl compound are not particularly limited but include styrene. Furthermore, the method for producing the biomass monomer is not particularly limited and includes, for example, biological and / or chemical and / or physical transformations of plants and animals. Typical biological transformations include fermentation by microorganisms, while chemical and / or physical transformations include those by catalysts, high heat, high pressure, electromagnetic waves, critical liquids, and combinations thereof.

[0082] The polymer synthesized from biomass monomer components (biomass polymer) is not particularly limited, and examples include polybutadiene rubber synthesized from biomass-derived butadiene, and aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl compounds. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0083] Whether the raw materials for a polymer are biomass-derived can be determined by measuring pMC (percent Modern Carbon) according to ASTM D6866-10. pMC refers to the percentage of modern standard reference carbon. 14 Sample relative to C concentration14 This is a ratio of C concentrations and is used as an indicator of the biomass ratio of a compound. The significance of this value is described below.

[0084] 1 mole of carbon atoms (6.02 × 10⁻¹⁰) 23 (Each) contains approximately 6.02 × 10¹⁶ atoms, which is about one trillionth of the amount of carbon atoms in a normal atom. 11 individual 14 C exists. 14 The half-life of C is 5730 years. 14 C is decreasing regularly. Therefore, in fossil fuels such as coal, oil, and natural gas, which are thought to have been fixed after more than 226,000 years have passed since atmospheric carbon dioxide was taken in and fixed by plants, etc., C was initially included in these as well. 14 All elements of C have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas are no longer viable. 14 It contains absolutely no element C. Therefore, chemical substances produced using these fossil fuels as raw materials also contain C. 14 It contains absolutely no element C.

[0085] on the other hand, 14 C is continuously produced when cosmic rays undergo nuclear reactions in the atmosphere. Therefore, 14 In the Earth's atmospheric environment, carbon (C) is produced in a state where its decrease due to radioactive decay and its production through nuclear reactions are in equilibrium. 14 The amount of C is constant. Therefore, the amount of biomass resource-derived substances currently circulating in the environment 14 As mentioned above, the carbon concentration is approximately 1 × 10¹⁶ of the total carbon atoms. -12 These values ​​are approximately in mole percent. Therefore, the difference between these values ​​can be used to calculate the biomass ratio in a given compound.

[0086] this 14 C is typically measured as follows: Using accelerator mass spectrometry based on a tandem accelerator, 13 C concentration ( 13 C / 12 C), 14 C concentration ( 14 C / 12 Perform measurement C). In the measurement, 14 As a modern standard reference for the concentration of C, the amount of cyclic carbon in nature as of 1950 14 The C concentration will be used. The specific standard material will be the oxalic acid standard provided by NIST (National Institute of Standards and Technology). The specific radioactivity of carbon in this oxalic acid (per gram of carbon) will be used. 14 The radioactivity intensity of C is separated by carbon isotope, 13 The standard value is obtained by correcting C to a constant value and applying decay correction from 1950 AD to the measurement date. 14 This value is used as the C concentration value (100%). The ratio of this value to the value of the sample actually measured is the pMC value.

[0087] Therefore, if rubber is made from 100% biomass-derived materials, although there are regional differences, under normal conditions it will often not reach 100, and will show a value of approximately 110 pMC. On the other hand, regarding chemical substances derived from fossil fuels such as petroleum, 14 When the C concentration is measured, it will show a value of approximately 0 pMC (for example, 0.3 pMC). This value corresponds to the aforementioned biomass ratio of 0%.

[0088] Based on the above, using materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio, in rubber compositions is preferable from an environmental protection standpoint.

[0089] <Filler> The rubber composition according to this embodiment includes a filler. The filler preferably contains carbon black, and may further contain other fillers such as silica. Alternatively, the filler may consist solely of carbon black.

[0090] The carbon black used is not particularly limited and includes N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. The raw materials for the carbon black may be biomass materials such as lignin and vegetable oil, or pyrolysis oil obtained by thermal decomposition of waste tires. The manufacturing method for the carbon black may be combustion such as the furnace method, hydrothermal carbonization (HTC), or thermal decomposition of methane such as the thermal black method. Commercially available products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Columbia Carbon Corporation, etc. These carbon blacks may be used individually or in combination of two or more types.

[0091] In addition to the above, from the perspective of life cycle assessment, carbon black made from biomass materials such as lignin, or recycled carbon black refined by thermal decomposition of carbon black-containing products such as tires, may also be used as carbon black.

[0092] In this specification, "recycled carbon black" refers to carbon black obtained by crushing used tires and other products containing carbon black, and calcining the crushed material, wherein, according to the thermogravimetric method compliant with JIS K 6226-2:2003, when oxidative combustion occurs by heating in air, the proportion of the mass of ash (ash content), which is the component that does not burn, is 13% by mass or more. In other words, the proportion of the mass (carbon content) lost due to the aforementioned oxidative combustion of recycled carbon black is 87% by mass or less. Recycled carbon black may also be represented as rCB.

[0093] 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 usually lacks functional groups on its surface, as referred to in

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

[0094] 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 Japanese Patent Publication 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.

[0095] Recycled carbon black can be purchased from companies such as Strable Green Carbon and LD Carbon.

[0096] The nitrogen adsorption specific surface area (N2SA) of carbon black is 10 m² from the perspective of reinforcing properties. 2 Preferably more than / g, 20m2 More preferably than / g, 30m 2 More preferably than / g, 40m 2 A value exceeding / g is particularly preferred. Furthermore, from the viewpoint of heat generation and processability, 200m 2 Less than / g is preferable, 150m 2 Less than / g is more preferable, 120m 2 A value of less than / g is even more preferable. The N2SA of carbon black is measured by the measurement method described above.

[0097] The average primary particle diameter of carbon black is preferably 95 nm or less, more preferably 80 nm or less, and even more preferably 85 nm or less. The lower limit of the average primary particle diameter is not particularly limited, but is preferably 10 nm or more, more preferably 20 nm or more, even more preferably 30 nm or more, and particularly preferably 40 nm or more.

[0098] From the viewpoint of the effects of the present invention, the carbon black content per 100 parts by mass of rubber component is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and particularly preferably 50 parts by mass or more. Furthermore, the content is preferably 110 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 90 parts by mass or less, and particularly preferably 80 parts by mass or less.

[0099] (silica) The silica used is not particularly limited, and common types used in the tire industry can be used, such as silica prepared by a dry process (anhydrous silica) or silica prepared by a wet process (hydrated silica). The raw material for silica is not particularly limited, and may be a mineral-derived raw material such as quartz, or a biological-derived raw material such as rice husks (for example, silica made from biomass materials such as rice husks), or silica recycled from silica-containing products may be used. Among these, hydrated silica prepared by a 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.

[0100] 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.

[0101] The silica recycled from silica-containing products can be, for example, silica recovered from products containing silica such as semiconductors and other electronic components, tires, desiccants, and diatomaceous earth and other filter materials. The recovery method is not particularly limited and can include thermal decomposition and decomposition by electromagnetic waves. Among these, silica recovered from semiconductors and other electronic components or tires is preferred.

[0102] 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.). Amorphous silica extracted from rice husks can be commercially available from companies such as Wilmar.

[0103] The nitrogen adsorption specific surface area (N2SA) of silica is 110 m², from the perspective of low fuel consumption and wear resistance. 2 Preferably 130m / g or more. 2 More preferably 150m / g or more, 2 More preferably 170m / g or more. 2 A value of 350m or more is particularly preferable. Furthermore, from the viewpoint of low fuel consumption and processability, 350m 2 Preferably less than / g, 300m 2 More preferably less than / g, 250m 2 A value of less than / g is even more preferable. The N2SA of silica is measured by the measurement method described above.

[0104] The average primary particle diameter of silica is preferably 24 nm or less, more preferably 22 nm or less, even more preferably 20 nm or less, and particularly preferably 18 nm or less. The lower limit of the average primary particle diameter is not particularly limited, but from the viewpoint of silica dispersibility, it is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm or more. The average primary particle diameter of silica is measured by the measurement method described above.

[0105] When silica is included, its content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, from the viewpoint of the effects of the present invention. Furthermore, the content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 20 parts by mass or less.

[0106] (Other fillers) Other fillers besides silica and carbon black are not particularly limited and may include those commonly used in the tire industry, such as aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, magnesium sulfate, talc, and clay. These other fillers may be used individually or in combination of two or more.

[0107] From the viewpoint of the effects of the present invention, the total content of filler per 100 parts by mass of rubber component is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and particularly preferably 50 parts by mass or more. Furthermore, from the viewpoint of low fuel consumption performance and elongation at break, it is preferably 110 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 90 parts by mass or less, and particularly preferably 80 parts by mass or less.

[0108] The carbon black content in the filler is preferably 65% ​​by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may also be 100% by mass.

[0109] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent used in combination with silica in the tire industry can be used, but examples include mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; and 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane. Examples include thioester-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. In particular, it is preferable to contain a sulfide-based silane coupling agent and / or a mercapto-based silane coupling agent. As silane coupling agents, for example, those commercially available from Evonik Industries, Momentive, etc., can be used. The silane coupling agent may be used alone or in combination of two or more types.

[0110] From the viewpoint of improving silica dispersibility, the content of the silane coupling agent per 100 parts by mass of silica is preferably 1.0 part by mass or more, more preferably 3.0 parts by mass or more, and even more preferably 5.0 parts by mass or more. Furthermore, from the viewpoint of cost and processability, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less.

[0111] <Plasticizer> The rubber composition according to this embodiment preferably contains a plasticizer. This plasticizer is a material that imparts plasticity to the rubber component and is a concept that includes both liquid plasticizers at 25°C and solid plasticizers at 25°C. Examples of plasticizers include resin components, oils, liquid rubber, ester-based plasticizers, etc. These plasticizers may be derived from mineral resources such as petroleum and natural gas, from biomass, or from naphtha recycled from rubber or non-rubber products. In addition, low molecular weight hydrocarbon components obtained by thermal decomposition and extraction of used tires or products containing various components may be used as plasticizers. These plasticizers may be used individually or in combination of two or more.

[0112] (Resin components) The rubber composition according to this embodiment may also contain a resin component. The resin component that can be used in this embodiment is not particularly limited, but resins commonly used in the tire industry can be used, such as C9 resins, C5 resins, C5C9 resins, dicyclopentadiene resins, aromatic vinyl resins, coumarone resins, indene resins, terpene resins, rosin resins, phenolic resins, etc. These resin components may be used individually or in combination of two or more. Each resin component may also be used individually or in combination of two or more.

[0113] ≪C9 series resin≫ A "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a polymer obtained by polymerizing the C9 fraction alone, or a copolymer obtained by copolymerizing the C9 fraction with other components. For example, a resin obtained by copolymerizing dicyclopentadiene (DCPD) and a C9 fraction is called a DCPD / C9 resin. Furthermore, the C9 resin may be a hydrogenated or modified version of these resins. Examples of C9 fractions include petroleum fractions with 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene. As for C9 resins, commercially available products from companies such as BASF, Zeon Corporation, and ENEOS Corporation can be used.

[0114] ≪C5 series resin≫ "C5 resins" refer to resins obtained by polymerizing C5 fractions, and may be hydrogenated or modified resins. Examples of C5 fractions other than dicyclopentadiene include petroleum fractions with 4 to 5 carbon atoms, such as cyclopentadiene, isoprene, piperylene, 2-methyl-1-butene, 2-methyl-2-butene, and 1-pentene. As C5 resins, commercially available products from companies such as Structol, Nippon Zeon Co., Ltd., and ENEOS Corporation can be used.

[0115] ≪C5C9 resin≫ "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be hydrogenated or modified. As C5C9 petroleum resin, commercially available products from companies such as Tosoh Corporation and LUHUA can be used.

[0116] <Dicyclopentadiene resins> A "dicyclopentadiene-based resin" refers to a resin in which cyclopentadiene (CPD) and / or dicyclopentadiene (DCPD) are the most abundant monomer components, and these may be hydrogenated or modified resins. Preferred dicyclopentadiene-based resins include polymers obtained by polymerizing only dicyclopentadiene as a monomer, and copolymers (DCPD / C9 resins) obtained by copolymerizing dicyclopentadiene with the C9 fraction. Commercially available dicyclopentadiene-based resins from companies such as ExxonMobil, ENEOS Corporation, Nippon Zeon Corporation, and Maruzen Petrochemical Co., Ltd. can be used.

[0117] Aromatic vinyl resin "Aromatic vinyl resin" refers to a resin in which aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and p-chlorostyrene are the most abundant monomer components, and these may be hydrogenated or modified. As aromatic vinyl resins, α-methylstyrene or a homopolymer of styrene or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, for reasons of being economical, easy to process, and having excellent heat generation properties. As aromatic vinyl resins, commercially available products from companies such as Kraton, Eastman Chemical Company, and Mitsui Chemicals, Inc. can be used.

[0118] Coumaron-based resin "Coumarone-based resin" refers to a resin containing coumarone as a monomer component, and may be hydrogenated or modified. Preferred coumarone-based resins include, for example, coumarone resin, which is a polymer with coumarone as the monomer component; coumarone-indene resin, which is a copolymer with coumarone and indene as monomer components; and coumarone-indene-styrene resin, which is a copolymer with coumarone, indene, and styrene as monomer components. As coumarone-based resins, commercially available products from companies such as Rutgers, Nippon Paint Chemical Co., Ltd., and Mitsui Chemicals, Inc. can be used.

[0119] Indene resin "Indene-based resin" refers to a resin containing indene as a monomer component, and may be hydrogenated or modified resins. Preferred indene-based resins include, for example, coumarone-indene resin, which is a copolymer of coumarone and indene as monomer components, and coumarone-indene-styrene resin, which is a copolymer of coumarone, indene, and styrene as monomer components. Commercially available indene-based resins from companies such as Rutgers, Nippon Paint Chemical Co., Ltd., and Mitsui Chemicals, Inc. can be used.

[0120] Terpene resins "Terpene resin" refers to a resin containing terpene compounds such as α-pinene, β-pinene, limonene, and dipentene as monomer components, and may be hydrogenated or modified. Preferred terpene resins include, for example, polyterpene resins, which are polymers in which one or more of the aforementioned terpene compounds are used as monomer components; aromatically modified terpene resins, which are copolymers in which the aforementioned terpene compounds and aromatic compounds are used as monomer components; and terpene phenol resins, which are copolymers in which the aforementioned terpene compounds and phenol compounds are used as monomer components. Examples of aromatic compounds that serve as monomer components in aromatically modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenol compounds that serve as monomer components in terpene phenol resins include phenol, bisphenol A, cresol, and xylenol. As terpene resins, commercially available products from companies such as Yasuhara Chemical Co., Ltd., Arakawa Chemical Industries, Ltd., and Nippon Terpene Chemical Co., Ltd. can be used.

[0121] ≪Rosin-based resin≫ "Rosin-based resin" refers to a resin containing rosin acid compounds such as abietic acid, neoabietic acid, palastic acid, and isopimal acid, and may be hydrogenated or modified. Rosin-based resins are not particularly limited, but examples include natural resin rosin and rosin-modified resins obtained by hydrogenating, disproportionating, dimerizing, esterifying, etc. As rosin-based resins, commercially available products from companies such as Harima Chemical Industries, Ltd., Arakawa Chemical Industries, Ltd., and IREC Co., Ltd. can be used.

[0122] Phenolic resins "Phenol-based resins" refer to resins containing phenol compounds such as phenol and cresol as monomer components, and may also be hydrogenated or modified resins. Phenolic resins are not particularly limited, but examples include phenol-formaldehyde resins, alkylphenol-formaldehyde resins, alkylphenol-acetylene resins, oil-modified phenol-formaldehyde resins, and terpene-phenol resins. Phenolic resins that are commercially available from companies such as Sumitomo Bakelite Co., Ltd., DIC Corporation, and Asahi Organic Materials Co., Ltd. can be used.

[0123] (oil) Examples of oils include mineral oil, vegetable oil, and animal oil. Furthermore, from a life cycle assessment perspective, waste oil from rubber mixers and engines, or refined waste cooking oil from restaurants, may also be used. Oils may be used individually or in combination of two or more types.

[0124] In this specification, mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. Examples of mineral oil include paraffinic oils (mineral oil), naphthenic oils, and aromatic oils. Specific examples of mineral oil include MES (Mild Extracted Solvate), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), and RAE (Residual Aromatic Extract). Furthermore, for environmental reasons, oils with a low content of polycyclic aromatic compounds (PCA) can be used. Examples of low-PCA oils include MES, TDAE, and heavy naphthenic oils. Mineral oil may be used alone or in combination of two or more types.

[0125] In this specification, vegetable oils include, for example, linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grapeseed oil, and wood wax. Furthermore, vegetable oils may also include refined oils (such as salad oil) obtained by refining the above oils, transesterified oils obtained by transesterifying the above oils, hydrogenated oils obtained by hydrogenating the above oils, thermally polymerized oils obtained by thermally polymerizing the above oils, oxidized polymerized oils obtained by oxidizing the above oils, and waste cooking oils recovered from use as edible oils. Note that vegetable oils may be liquid or solid at 25°C. Vegetable oils may be used individually or in combination of two or more types.

[0126] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably contains triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxyl group of glycerin and a fatty acid are ester-bonded. The acylglycerol is not particularly limited and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Furthermore, the acylglycerol may be a monomer, a dimer, or a polymer of three or more. Note that acylglycerols of two or more forms can be obtained by thermal polymerization, oxidative polymerization, etc. Also, the acylglycerol may be a liquid or a solid at 25°C.

[0127] The method for confirming whether the rubber composition contains the acylglycerol is not particularly limited, 1 This can be confirmed by 1H-NMR measurement. For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at 25°C for 24 hours, and after removing the rubber composition, it is measured at room temperature. 1 When 1H-NMR was measured and the tetramethylsilane (TMS) signal was set to 0.00 ppm, signals were observed around 5.26 ppm, 4.28 ppm, and 4.15 ppm. These signals are presumed to originate from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In this paragraph, "around" refers to a range of ±0.10 ppm.

[0128] The aforementioned fatty acids are not particularly limited and may be unsaturated or saturated fatty acids. Examples of unsaturated fatty acids include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of saturated fatty acids include butyric acid and lauric acid.

[0129] In particular, it is desirable that the fatty acid contains fatty acids with few double bonds, i.e., saturated fatty acids or monounsaturated fatty acids, and oleic acid is preferred. As a vegetable oil containing such fatty acids, for example, a vegetable oil containing saturated fatty acids or monounsaturated fatty acids may be used, or a vegetable oil that has been modified by transesterification or other means may be used. Furthermore, in order to produce a vegetable oil containing such fatty acids, plants may be improved by breeding, genetic modification, genome editing, etc.

[0130] As for vegetable oils, commercially available products from companies such as Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kosan Co., Ltd., and Nisshin Oillio Group Ltd. can be used.

[0131] Examples of animal oils include fish oil, beef tallow, whale oil, or oleyl alcohol which can be derived from them.

[0132] When oil is included, its 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, and even more preferably 5 parts by mass or more. Furthermore, the content is preferably less than 35 parts by mass, more preferably less than 25 parts by mass, and even more preferably less than 15 parts by mass.

[0133] (Liquid rubber) Liquid rubber is not particularly limited as long as it is a polymer that is in a liquid state at 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), and liquid farnesene rubber. These liquid rubbers may be used individually or in combination of two or more.

[0134] (Ester-based plasticizers) Examples of ester-based plasticizers include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelaate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), and trixylenyl phosphate (TXP). Ester-based plasticizers may be used individually or in combination of two or more.

[0135] From the viewpoint of the effects of the present invention, the content of plasticizer per 100 parts by mass of rubber component (total amount if multiple plasticizers are used in combination) is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more. Furthermore, the content is preferably less than 35 parts by mass, more preferably less than 25 parts by mass, and even more preferably less than 15 parts by mass.

[0136] <Other compounding agents> In addition to rubber components, fillers, and plasticizers, the rubber composition according to this embodiment may appropriately contain compounding agents commonly used in the tire industry, such as vulcanized rubber particles, processing aids, waxes, antioxidants, stearic acid, zinc oxide, vulcanizing agents, and vulcanization accelerators.

[0137] Vulcanized rubber particles are particles made of vulcanized rubber, and specifically, rubber powder as specified in JIS K 6316:2017 can be used. From the viewpoint of environmental considerations and cost, recycled rubber powder produced from crushed waste tires is preferred. One type of vulcanized rubber particle may be used alone, or two or more types may be used in combination.

[0138] The vulcanized rubber particles are not particularly limited and may be either unmodified or modified vulcanized rubber particles. Commercially available vulcanized rubber products can be used, for example, those from Lehigh, Muraoka Rubber Industries, and others.

[0139] When vulcanized rubber particles are included, the content per 100 parts by mass of the rubber component can be appropriately adjusted, for example, within a range of more than 1 part by mass and less than 80 parts by mass.

[0140] Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. These processing aids may be used individually or in combination of two or more. Examples of processing aids that can be used are those commercially available from companies such as Schill+Seilacher and Performance Additives.

[0141] The wax is not particularly limited, and any wax commonly used in the tire industry can be suitably used, such as mineral waxes and plant-derived waxes. Mineral waxes refer to waxes derived from mineral resources such as oil and natural gas. Plant-derived waxes refer to waxes derived from natural resources such as plants. Among these, mineral waxes are preferred. Examples of plant-derived waxes include rice wax, carnauba wax, and candelilla wax. Examples of mineral waxes include paraffin wax, microcrystalline wax, and selected special waxes thereof, with paraffin wax being preferred. The wax according to this embodiment does not contain stearic acid. The wax can be commercially available from companies such as Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Paramelt Co., Ltd. These waxes may be used individually or in combination of two or more types.

[0142] When wax is included, the amount of wax per 100 parts by mass of rubber component is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1.0 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 5.0 parts by mass or less.

[0143] While not particularly limited, examples of anti-aging agents include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), and N,N'-ditril-p-phenylenediamine. Examples include p-phenylenediamine-based antioxidants such as methyl amine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferred, and polymers of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. Commercially available products include those from companies such as Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis. These antioxidants may be used individually or in combination of two or more.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] Sulfur is preferably used as a vulcanizing agent. Suitable sulfurs include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. These sulfurs may be used individually or in combination of two or more.

[0148] From the viewpoint of ensuring a sufficient vulcanization reaction, the sulfur content per 100 parts by mass of rubber component is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and even more preferably 0.3 parts by mass or more. Furthermore, from the viewpoint of the effects of the present invention, the content is preferably less than 1.5 parts by mass, more preferably less than 1.1 parts by mass, even more preferably less than 1.0 part by mass, even more preferably less than 0.8 parts by mass, and particularly preferably less than 0.6 parts by mass. When oil-containing sulfur is used as the vulcanizing agent, the content of the vulcanizing agent shall be the total content of pure sulfur contained in the oil-containing sulfur.

[0149] 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 commercially available from companies such as Taoka Chemical Industries, Ltd., Lanxess Corporation, and Flexis. These vulcanizing agents may be used individually or in combination of two or more.

[0150] The vulcanization accelerator is not particularly limited, but examples include sulfenamide-based vulcanization accelerators, thiazole-based vulcanization accelerators, guanidine-based vulcanization accelerators, thiram-based vulcanization accelerators, thiourea-based vulcanization accelerators, dithiocarbamate-based vulcanization accelerators, aldehyde-amine-based vulcanization accelerators, aldehyde-ammonia-based vulcanization accelerators, imidazoline-based vulcanization accelerators, xanthate-based vulcanization accelerators, caprolactam disulfide, and the like. 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-based vulcanization accelerators, thiazole-based vulcanization accelerators, and guanidine-based vulcanization accelerators are preferred because they more favorably produce the desired effect.

[0151] 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, TBBS and CBS are preferred.

[0152] Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole (MBT) or its salts, di-2-benzothiazolyl disulfide (MBTS), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, and 2-(2,6-diethyl-4-morpholinothio)benzothiazole. Among these, MBTS and MBT are preferred.

[0153] 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, DPG is preferred.

[0154] When a vulcanization accelerator is included, its 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 ensuring a sufficient vulcanization rate. Furthermore, from the viewpoint of suppressing blooming, the content of the vulcanization accelerator is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0155] In this specification, various materials containing carbon atoms (e.g., rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from atmospheric carbon dioxide. Methods for obtaining these materials from carbon dioxide include directly converting carbon dioxide, or converting methane obtained through a methanation process in which methane is synthesized from carbon dioxide.

[0156] [Manufacturing of rubber compositions and tires] 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.). The kneading process includes, for example, a base kneading step in which compounding agents and additives other than the vulcanizing agent and vulcanization accelerator are kneaded, and a final kneading (F kneading) step in which the vulcanizing agent and vulcanization accelerator are added to the kneaded product obtained in the base kneading step and kneaded. Furthermore, the base kneading step can be divided into multiple steps if desired.

[0157] 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.

[0158] A tire according to this embodiment, having a sidewall made of the aforementioned rubber composition, can be manufactured by conventional methods. That is, an unvulcanized rubber composition corresponding to the sidewall obtained by the aforementioned method 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 can then be heated and pressurized in a vulcanizing machine to manufacture the tire according to this embodiment. 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.

[0159] <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]

[0160] The following examples (case studies) are shown as preferred for implementation, but the scope of the present invention is not limited to these examples. Using the various chemicals shown below, we examined tires having sidewalls obtained according to the formulations in Tables 1, 2, and 3, and the results calculated based on the evaluation method below are shown in Tables 1, 2, and 3.

[0161] The various chemicals used in the examples and comparative examples are summarized below. NR:TSR20 BR: UBEPOL BR (registered trademark) 150B manufactured by UBE Corporation (cis content: 97 mol%, Mw: 440,000) SBR: Hydrogenated SBR produced in the manufacturing example described below (hydrogenation rate: 80%, styrene content: 35% by mass, Mw: 480,000, Tg: -30℃) Carbon Black: Dia Black (registered trademark) E (FEF, N550, N2SA) manufactured by Mitsubishi Chemical Corporation: 41m 2 / g, average primary particle diameter: 81nm) Silica: ULTRASIL VN3 (N2SA: 175m) manufactured by Evonik Industries. 2 / g, average primary particle diameter: 18nm) Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) manufactured by Evonik Industries. 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. Stearic acid: Beads of stearic acid manufactured by NOF Corporation Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. 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.

[0162] 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 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 unreacted lithium at the polymer terminals to form 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 cumulative amount of hydrogen absorption reached the desired hydrogenation rate, the reaction temperature was reduced to room temperature, the hydrogen pressure was returned to atmospheric pressure, and the reaction vessel was withdrawn. The reaction solution was then stirred into water and the solvent was removed by steam stripping to obtain hydrogenated SBR.

[0163] (Examples and Comparative Examples) According to the formulations shown in Tables 1, 2, and 3, the chemicals other than sulfur and vulcanization accelerator were mixed in a 1.7 L sealed Banbury mixer at 150°C for 5 minutes to obtain a mixture. Next, sulfur and vulcanization accelerator were added to the mixture and mixed in an open roll at 80°C for 5 minutes to obtain an unvulcanized rubber composition. The unvulcanized rubber composition was molded to the shape of the sidewall and bonded together with other tire components to form an unvulcanized tire, which was then press-vulcanized at 170°C for 12 minutes to obtain each test tire listed in Table 1 (tire size: 245 / 35ZR20, maximum load capacity WL: 580 kg).

[0164] <Measurement of sulfur content> For each vulcanized rubber test piece, which is cut from the tread of each test tire, the sulfur content is measured using the oxygen combustion flask method in accordance with JIS K 6233:2016.

[0165] <Measurement of crosslinking density> Each test specimen, measuring 20 mm in length, 20 mm in width, and 1 mm in thickness, is cut from the sidewall of each test tire, ensuring the thickness direction of the sidewall is aligned with the thickness direction. These specimens are then immersed in a tetrahydrofuran:toluene = 1:1 mixed solution for 24 hours to allow them to swell. The degree of swelling and compression of these swollen samples is measured using a thermomechanical analyzer (TMA-50, Shimadzu Corporation), and the total crosslink density (mol / cm³) of the rubber composition is calculated using the Flory-Rehner formula. 3 The crosslinking density (mol / cm³) of the monosulfide bonds in the rubber composition is calculated. In addition, each test piece, which is cut from the sidewall of each test tire, is immersed for 24 hours in a tetrahydrofuran:toluene = 1:1 mixed solution saturated with lithium aluminum hydride (LiAlH4) to prepare a swollen sample in which the polysulfide bonds have been broken. The degree of swelling and compression of this swollen sample is measured in the same manner as above, and the crosslinking density (mol / cm³) of the monosulfide bonds in the rubber composition is calculated using the Flory-Rehner formula. 3 The ratio V of the crosslink density of monosulfide bonds to the total crosslink density of the rubber composition is calculated.

[0166] <Flexural crack growth resistance performance of new tires> Each test tire is mounted on a rim, inflated with air, mounted on a vehicle, and driven for 40,000 km. After the run, the condition of the cracks in the sidewall of each test tire (depth, number, and length) is evaluated and expressed as an index, with the index of the control tire (Comparative Example 3) set to 100. A higher index indicates better resistance to flexural crack growth.

[0167] <Flexural crack growth resistance after thermal degradation> Each test tire is mounted on a rim, inflated with air, and subjected to thermal degradation at 80°C for three weeks. These tires are then mounted on a vehicle, and after 40,000 km of driving, the condition of the cracks in the sidewall of each test tire (depth, number, and length) is evaluated and expressed as an index, with the index of the control tire (Comparative Example 3) set to 100. A higher index indicates better resistance to flexural crack growth.

[0168] <Overall Performance> The sum of the flexural crack growth resistance index for new tires and the flexural crack growth resistance index after thermal degradation is shown as the overall performance index.

[0169] [Table 1]

[0170] [Table 2]

[0171] [Table 3]

[0172] <Embodiment> Examples of embodiments of the present invention are shown below.

[0173] [1] A tire having a sidewall, wherein the sidewall is made of a rubber composition containing rubber components and fillers, the sulfur content in the rubber composition is less than 0.65% by mass, preferably less than 0.60% by mass, the ratio V of the crosslink density of monosulfide bonds to the total crosslink density of the rubber composition is 0.10 or more, the thickness of the surface rubber layer at the tire's maximum width position is D (mm), and the maximum load capacity of the tire is W. L (kg), where G (kg) is the tire weight, K = G / W L If defined as such, a tire where K is 0.018 or less and V / (K×D) is 1.00 or greater. [2] The tire described in [1] above, wherein V / (K×D) is 2.00 or greater. [3] A tire as described in [1] or [2] above, wherein K is 0.017 or less. [4] A tire as described in any of [1] to [3] above, with a V of 0.30 or higher. [5] The tire according to any one of [1] to [4] above, wherein the rubber component contains 35% by mass or more, preferably 40% by mass or more and 80% by mass or less, isoprene-based rubber. [6] The tire according to any one of [1] to [5] above, wherein the total content of butadiene rubber and styrene-butadiene rubber relative to the content of isoprene-based rubber in the rubber component is 0.15 or more, preferably 0.50 or more, and more preferably 0.75 or more and 4.0 or less. [7] A tire according to any of [1] to [6] above, wherein the carbon black content in the filler is 80% by mass or more. [8] The tire according to any one of [1] to [7] above, wherein the total content of filler in the rubber composition is 40 parts by mass or more, preferably 45 parts by mass or more, relative to 100 parts by mass of the rubber component. [9] The tire according to any one of [1] to [8] above, wherein the sulfur content in the rubber composition is 0.1 parts by mass or more and less than 1.0 part by mass per 100 parts by mass of the rubber component.

[10] The tire according to any one of [1] to [9] above, wherein the rubber component includes hydrogenated styrene-butadiene rubber. [Explanation of symbols]

[0174] 1 tread 2 belts 3 bands 21 Bead Core 31 Sidewall 32 Inner Liner 33 Carcass CL tire centerline PW tire maximum width position D. Thickness of the surface rubber layer at the tire's widest point.

Claims

1. A tire with a sidewall, The sidewall is made of a rubber composition containing rubber components and fillers. The amount of sulfur in the rubber composition is less than 0.65% by mass. The ratio V of the crosslink density of monosulfide bonds to the total crosslink density of the rubber composition is 0.10 or more. D (mm) is the thickness of the surface rubber layer at the tire's widest point, and W is the tire's maximum load capacity. L (kg), with the tire weight being G (kg), K=G / W L If defined as follows, A tire in which K is 0.018 or less and V / (K×D) is 1.00 or more.

2. The tire according to claim 1, wherein V / (K×D) is 2.00 or greater.

3. The tire according to claim 1 or 2, wherein K is 0.017 or less.

4. The tire according to claim 1 or 2, wherein V is 0.30 or greater.

5. The tire according to claim 1 or 2, wherein the rubber component contains 35% by mass or more of isoprene-based rubber.

6. The tire according to claim 1 or 2, wherein the total content of butadiene rubber and styrene-butadiene rubber relative to the content of isoprene-based rubber in the rubber component is 0.15 or more.

7. The tire according to claim 1 or 2, wherein the carbon black content in the filler is 80% by mass or more.

8. The tire according to claim 1 or 2, wherein the total content of filler in the rubber composition is 40 parts by mass or more relative to 100 parts by mass of the rubber component.

9. The tire according to claim 1 or 2, wherein the sulfur content in the rubber composition is 0.1 parts by mass or more and less than 1.0 part by mass per 100 parts by mass of the rubber component.

10. The tire according to claim 1 or 2, wherein the rubber component comprises hydrogenated styrene-butadiene rubber.

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