Tire

Abstract

To provide a tire that provides improved overall performance in terms of low fuel consumption performance and crack resistance.SOLUTION: A tire includes: a pair of sidewalls in a side portion; and a pair of clinch apexes located on an inner side of the sidewalls in a radial direction and in contact with a rim. A rubber composition constituting the clinch apex contains recycled carbon black, and has a loss tangent 70°C tanδC at 70°C of less than 0.25, a length of a contact portion between the clinch apex and the sidewall is 5 mm or more and 30 mm or less in a tire meridian cross-section including a tire rotation axis, and a complex modulus of elasticity 70°C E*S at 70°C of the rubber composition constituting the sidewall is 2.0 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In response to demands for longer tire life, studies are being conducted to extend the life of each component that makes up a tire. Patent Document 1 describes an improvement in crack resistance by examining the total amount of styrene in the rubber component that makes up the clinch apex and its thickness. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-60806 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a tire that has improved overall performance in terms of fuel economy and crack resistance. [Means for solving the problem]

[0005] The present invention provides a tire having a pair of sidewalls in a side portion, and a pair of clinch apexes located radially inside the sidewalls and in contact with a rim, The rubber composition constituting the clinch apex contains recycled carbon black and has a loss tangent at 70°C (70°C tanδ C is less than 0.25, In a tire meridian cross section including the tire rotation axis, the length of the contact portion between the clinch apex and the sidewall is 5 mm or more and 30 mm or less, The complex modulus (MPa) 70°C E* of the rubber composition constituting the sidewall at 70°C S is 2.0 or more. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a tire that has improved overall performance in terms of fuel economy and crack resistance. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic view showing a portion of a cross section (upper right portion of the cross section) taken along the tire meridian for a tire according to one embodiment of the present invention. [Figure 2] 1 is a schematic diagram of the outer surface of a sidewall on which a plurality of columnar micro-ridges are formed. [Figure 3] 1 is a schematic diagram of the outer surface of a sidewall on which a plurality of small protuberances in the shape of a truncated square pyramid are formed. [Figure 4] XX cross-sectional view of FIG. 3. [Figure 5] 1 is a schematic diagram of the outer surface of a sidewall having a plurality of rib-like micro-ridges formed thereon. [Figure 6] FIG. 6 is a cross-sectional view of FIG. 5 taken along the line Y-Y. DETAILED DESCRIPTION OF THE INVENTION

[0008] A tire according to one embodiment of the present invention has a pair of sidewalls in a side portion, and a pair of clinch apexes located radially inside the sidewalls and in contact with a rim, wherein a rubber composition constituting the clinch apexes contains recycled carbon black and has a loss tangent at 70°C (70°C tanδ C ) is less than 0.25, and in a tire meridian cross section including the tire rotation axis, the length (mm) of the contact portion between the clinch apex and the sidewall is 5 to 30, and the complex modulus of elasticity (MPa) at 70°C (70°CE*) of the rubber composition constituting the sidewall is S ) is 2 or more.

[0009] While not intending to be bound by theory, the reasons why the overall performance of fuel economy and crack resistance can be improved in the embodiments of the present invention are believed to be as follows: (1) It is believed that fuel economy is ensured by setting the 70°C tan δ of the clinch apex below a predetermined value. Furthermore, (2) It is believed that by setting the complex modulus E* of the sidewall rubber to a predetermined value or more, the difference in rigidity between the sidewall and the clinch apex is reduced, and the difference in strain during running is also reduced, thereby making it less likely that energy loss will occur. Furthermore, (3) It is believed that by setting the length of the contact portion between the sidewall and the clinch apex to a predetermined value or less, strain applied to the tire during running is dispersed, thereby suppressing cracks. It is believed that the above (1) to (3) working together provide the remarkable effect of improving the overall performance of fuel economy and crack resistance.

[0010] It is preferable that the length of the contact portion between the clinch apex and the sidewall is 10 mm or more and 20 mm or less.

[0011] This ensures a sufficient contact area between the sidewall and the clinch apex, which is thought to distribute the strain on the tire during driving and prevent cracks.

[0012] The 70°C tanδ C is preferably less than 0.20.

[0013] It is believed that setting the loss tangent to such a value will result in greater fuel efficiency.

[0014] 70℃E* S (MPa) is preferably 3.0 or more, and more preferably 4.5 or more.

[0015] Complex modulus E* S By making the value equal to or greater than such a predetermined value, it is believed that the difference in rigidity between the sidewall and the clinch apex and the difference in strain during running can be further reduced.

[0016] The 70°C tanδ C is 0.10 or less, and S (MPa) is preferably 5.0 or more.

[0017] It is believed that such a tire will eliminate the difference in rigidity between the clinch apex and the sidewall, reduce distortion, and improve fuel economy.

[0018] The amount of the recycled carbon black is preferably less than 20 parts by mass based on 100 parts by mass of the rubber component.

[0019] Recycled carbon black is obtained by pyrolysis of waste tires and the like, and the surface is incinerated. When recycled carbon black is incorporated into a rubber composition, the recycled carbon black bonds weaker to the surrounding rubber polymers than other carbon blacks, etc., and it is thought that rubber compositions containing recycled carbon black have improved elongation and increased flexibility. As a result, the rubber composition can flexibly respond to tire deformation during driving, and crack resistance is improved.

[0020] When the rubber composition constituting the clinch apex includes a rubber component containing more than 20% by mass of isoprene-based rubber and the content of the isoprene-based rubber in the rubber component is less than 100% by mass, it is preferable that the rubber component includes at least one of butadiene rubber and styrene-butadiene rubber.

[0021] Such a tire is believed to have reduced flex crack growth.

[0022] The rubber composition constituting the sidewall preferably contains more than 40% by mass of butadiene rubber.

[0023] Such a tire is believed to have reduced flex crack growth.

[0024] The sidewall preferably has a micro-ridge formation portion in which a plurality of micro-ridges are formed on the outer surface.

[0025] The presence of the micro-ridge formation portion is believed to contribute to improving crack resistance since it is possible to suppress stress concentration on the outer surface of the sidewall.

[0026] The shape of the micro-protrusions is preferably columnar, frustum or rib-like.

[0027] By making the micro-ridges have these predetermined shapes, stress concentration on the outer surface of the sidewall can be suppressed, which is thought to contribute to improving crack resistance.

[0028] The micro-ridges have a height of 0.03 mm or more and 0.50 mm or less, and are formed in at least one direction at intervals of 0.50 mm or less, with 20 or more micro-ridges formed, and the micro-ridge-forming portion is 10 mm 2 It is preferable that the area is equal to or larger than this.

[0029] By keeping the size of the micro-protrusions within these predetermined ranges, stress concentration on the outer surface of the sidewall can be suppressed, which is thought to contribute to improving crack resistance.

[0030] The maximum width of the micro-protuberances is preferably 0.03 mm or more and 5.0 mm or less.

[0031] By keeping the maximum width of the micro-ridges within a predetermined range, stress concentration on the outer surface of the sidewall can be suppressed, which is thought to contribute to improving crack resistance.

[0032] It is preferable that the height of the minute protuberances gradually increase from the maximum tire width position toward the outer side in the tire radial direction, and also gradually increase from the maximum tire width position toward the inner side in the tire radial direction.

[0033] Relatively large distortion occurs near the tire's widest point on the sidewall, but by making the height of the micro-bumps lower on the side closer to the tire's widest point, it is thought that this reduces the unevenness in rubber volume around the tire at points where large distortion occurs, avoids stress concentration near the micro-bumps, and contributes to improved crack resistance.

[0034] When the thickness of the sidewall (mm) is T, the 70℃ tanδ of the clinch apex C It is preferable that the relationship of formula (1) is satisfied. (1) T×70℃ tanδ C <0.80

[0035] Such a tire is expected to have excellent fuel economy.

[0036] When the carbon black content (parts by mass) of the sidewall is W and the length (mm) of the contact area between the clinch apex and the sidewall is L, the relationship between W, L and 70°C tanδ C It is preferable that the relationship of formula (2) is satisfied. (2) W×L / 70℃ tanδ C >5000

[0037] Such a tire is thought to be less susceptible to strain accumulation between the sidewall and the clinch apex, resulting in a tire with excellent fuel efficiency.

[0038] <Definition> "Normal condition" refers to a condition in which the tire is mounted on a normal rim and filled with air at normal internal pressure, with no load applied.

[0039] Unless otherwise specified, the dimensions of each part of the tire that appear on the outer surface are values ​​specified in a normal state, while the dimensions of the interior of the tire or on a cut surface of the tire are values ​​specified when, for example, the tire is cut along a plane including the tire rotation axis and the cut tire piece is maintained at the rim width of a normal rim.

[0040] "Weight of tire" refers to the weight of the tire itself, excluding the weight of the rim. On the other hand, if the tire has components such as sponge or sealant, or sensor components, the weight includes these components.

[0041] "Genuine rim" refers to the rim specified for each tire in the standard system that includes the standard on which the tire is based. 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 Organization), 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." JATMA, ETRTO, and TRA are referenced in that order, and if an applicable size is available at the time of reference, that standard is followed. In the case of a tire not specified in the above standards, it refers to the narrowest rim among the smallest diameter rims that can be mounted on the tire and can maintain internal pressure (i.e., no air leaks from between the rim and tire).

[0042] "Normal internal pressure" refers to the air pressure specified for each tire in the standard system that includes the standard on which the tire is based. For example, for JATMA, it is "maximum air pressure," for ETRTO, it is "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 follow that standard if there is an applicable size at the time of reference. In the case of tires not specified in the above standards, it refers to the normal internal pressure (250kPa or more) of another tire size (defined in the standard) that is specified using the regular rim as the standard rim, and if there are multiple normal internal pressures of 250kPa or more listed, it refers to the smallest value among them.

[0043] "Normal load" refers to the load specified for each tire in the standard system that includes the standard on which the tire is based. 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 normal rims and normal internal pressures, JATMA, ETRTO, and TRA should be referenced in that order, and if there is an applicable size at the time of reference, that standard should be followed. For tires not specified in the above standards, the maximum load capacity W calculated separately should be used. L is the normal load.

[0044] "Maximum load capacity W L " is calculated using the following formula: "V" is the virtual volume of the tire (mm 3 ), "Dt" is the outer diameter (mm) of the tire in its normal state, "Ht" is the tire's cross-sectional height (mm) in the tire's radial direction in a cross section of the tire taken along a plane including the tire's rotation axis, and "Wt" is the tire's cross-sectional width (mm) in its normal state. Ht can be calculated by (Dt-R) / 2, where R is the tire rim diameter. Wt is the value obtained by excluding any patterns or letters on the tire sidewall. Note that maximum load capacity is synonymous with the normal load mentioned above.

[0045]

number

[0046] "Recycled carbon black" refers to carbon black obtained from the thermal decomposition process of used tires and other products containing carbon black, and is carbon black in which, when subjected to oxidative combustion by heating in air using a thermogravimetric method in accordance with JIS K 6226-2:2003, the proportion of ash (the mass of the non-combustible component) is 13% by mass or more. In other words, the mass of the weight loss due to the oxidative combustion (carbon amount) is 87% by mass or less. Recycled carbon black is also called recycled carbon or recycled carbon black, and is sometimes expressed as rCB.

[0047] "Sidewall thickness (T)" is the thickness in the tire width direction of the rubber layer that forms the sidewall at the point where the distance between the outer surface of the sidewall in the tire width direction is the longest on a cross section of the tire taken along a plane including the tire's rotation axis. "Sidewall thickness" is the average of the values ​​measured at five points when the tire is rotated 72 degrees each time. Measurements can be performed by creating a cross section of the tire taken along a plane including the tire's rotation axis and holding it with the bead spacing aligned to the standard rim width.

[0048] The "length of the contact area between the clinch apex and the sidewall" is the length (mm) of the interface between the clinch apex and the sidewall, measured by cutting the tire on a plane including the tire rotation axis and holding it on a regular rim. For example, this corresponds to L in Figure 1.

[0049] The term "micro-bump" refers to a convex protrusion formed on the outer surface of the sidewall, with a height of 0.03 mm to 0.50 mm. The maximum width of the micro-bump is preferably 0.03 mm to 0.50 mm.

[0050] The "micro-ridge formation portion" refers to the portion on the outer surface of the sidewall where the micro-ridges are formed.

[0051] The "loss tangent and complex modulus of a rubber composition" are the loss tangent (tanδ) and complex modulus E* (MPa) measured under various conditions in extension mode using a dynamic viscoelasticity measuring device (e.g., the Iplexer series manufactured by GABO). The sample used for dynamic viscoelasticity measurement is a vulcanized rubber composition having a length of 20 mm, a width of 4 mm, and a thickness of 1 mm. When cutting a sample from a tire, the length direction of the sample is aligned with the tangential direction to the tire circumference, and the thickness direction of the sample is aligned with the tire width direction.

[0052] "70°C tanδ" and "70°C E*" are the loss tangent (tanδ) and the complex modulus E* (MPa), respectively, measured under the conditions of a temperature of 70°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±1%, and an extension mode.

[0053] <Measurement method> "Styrene content" is measured by pyrolysis gas chromatography and NMR measurement ( 1 H-NMR and 13 The amount of components such as "styrene content" is calculated by C-NMR. Unlike physical property values ​​such as complex modulus (E*), the amount of components such as "styrene content" has a true value that is independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible. In this specification, "pyrolysis gas chromatography" refers to a method in which a sample is heated in a pyrolysis device, the individual components contained in the gas phase components generated by this heating are separated using a separation column, and each isolated component is analyzed.

[0054] "Vinyl content (amount of 1,2-bonded butadiene units)" can be measured by pyrolysis gas chromatography or NMR measurement ( 1 H-NMR and 13 It is calculated using C-NMR. As with the "styrene content," there is a true value for the "vinyl content" that is independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible.

[0055] "Cis content (cis-1,4-bonded butadiene unit amount)" is measured by infrared absorption spectroscopy or NMR measurement ( 1H-NMR and 13 This is a value measured by C-NMR and is applied to rubber components that have repeating units derived from butadiene, such as BR. As with the "styrene content," the "cis content" also has a true value that is independent of the measurement method, so it is preferable to use a measurement method with as high accuracy as possible.

[0056] The "ash content of carbon black" and the "ash content of recycled carbon black" are measured by the thermogravimetric method of JIS K 6226-2:2003.

[0057] "N2SA of carbon black" and "N2SA of recycled carbon black" are values ​​determined according to JIS K 6217-2:2017.

[0058] The "average primary particle size of carbon black" and "average primary particle size of recycled carbon black" are values ​​obtained by photographing particles with a transmission or scanning electron microscope and arithmetically averaging the particle sizes of 400 particles. If the particle shape is spherical, the particle size is the diameter of the sphere; if the particle shape is non-spherical, the particle size is calculated from the microscope image as the circle-equivalent diameter (positive square root of {4 × (particle area) / π}).

[0059] "N2SA of silica" is a value measured by the BET method in accordance with ASTM D3037-93.

[0060] <Tires> Hereinafter, a tire according to one embodiment of the present invention will be described with reference to the drawings as appropriate. However, the drawings are merely examples for the purpose of explanation.

[0061] Fig. 1 is a schematic diagram showing a portion of a cross section (upper right portion of the cross section) taken along the tire meridian of a tire according to one embodiment of the present invention. In Fig. 1, the tire 1 includes a pair of sidewalls 2 arranged on both sides and a clinch apex 3 arranged on the inner end of each sidewall in the tire radial direction. The length of the contact area between the sidewall and the clinch apex is indicated by L, and the thickness of the sidewall is indicated by T.

[0062] 70℃ tanδ of rubber composition for clinch apex C is less than 0.25, preferably less than 0.20, more preferably less than 0.15, even more preferably 0.10 or less, even more preferably less than 0.10, and even more preferably 0.07 or less.

[0063] 70℃ tanδ C can be appropriately adjusted by changing the types and amounts of components constituting the rubber composition described below. For example, the 70°C tanδ can be adjusted by increasing the amount of filler, decreasing its particle size, decreasing the amounts of vulcanizing agent and vulcanization accelerator, etc. C The reverse operation can increase the 70℃ tanδ C There is a tendency to be able to reduce

[0064] 70°C E* of sidewall rubber composition S is 2.0 or more, preferably 4.5 or more, more preferably 5.0 or more, and even more preferably 6.0 or more.

[0065] 70°C E* S can be appropriately adjusted by changing the types and amounts of the components constituting the rubber composition described below. For example, by increasing the amount of filler, decreasing its particle size, reducing the total amount of plasticizer, and increasing the amounts of vulcanizing agent and vulcanization accelerator, the 70°C E* S The reverse operation also tends to increase the 70℃E* S There is a tendency to be able to reduce

[0066] In a tire meridian cross section including the tire rotation axis, the length L (mm) of the contact portion between the clinch apex and the sidewall is 5 mm or more and 30 mm or less, preferably 8 mm or more, more preferably 10 mm or more, and even more preferably 12 mm or more, and is preferably 25 mm or less, more preferably 20 mm or less.

[0067] (Formula (1)) The relationship satisfied by equation (1) is as follows: (1) T×70℃ tanδ C <0.80 The right side of formula (1) is preferably 0.75, more preferably 0.70, even more preferably 0.65, even more preferably 0.60, and even more preferably 0.55.

[0068] By reducing the thickness of the sidewall, C By reducing , the value of the left side of equation (1) can be reduced, and by doing the opposite, it can be increased. C The value of can be adjusted as described above. The thickness T (mm) of the sidewall is not particularly limited as long as it is within the range of thicknesses that can be normally adopted. For example, in the case of a passenger car tire, T is greater than 1.5 mm, preferably greater than 2.0 mm, more preferably greater than 2.3 mm, and even more preferably greater than 2.5 mm. On the other hand, T is, for example, less than 10.0 mm, preferably less than 9.0 mm, more preferably less than 8.0 mm, and even more preferably less than 7.0 mm.

[0069] (Formula (2)) The relationship satisfied by equation (2) is as follows: (2) W×L / 70℃ tanδ C >5000 The right side of formula (2) is preferably 5,200, more preferably 5,400, even more preferably 5,600, even more preferably 6,000, and even more preferably 10,000.

[0070] The carbon black content W of the rubber composition for sidewalls is, for example, more than 30 parts by mass, preferably more than 40 parts by mass, more preferably 50 parts by mass or more, and even more preferably 60 parts by mass or more, per 100 parts by mass of the rubber component, while it is preferably less than 150 parts by mass, more preferably less than 110 parts by mass, and even more preferably less than 80 parts by mass.

[0071] For example, the carbon black content of the rubber composition for the sidewall may be reduced, the length of the contact area between the sidewall and the clinch apex may be reduced, or the 70°C tan δ C By increasing , the value of the left side of equation (2) can be reduced, and by doing the opposite, the value of the left side of equation (2) can be increased. C The adjustment of the value of is as described above.

[0072] (Micro-ridge forming part) The tire of the present invention preferably has a micro-ridge-forming portion in which a plurality of micro-ridges are formed on the outer surface of at least one of the pair of sidewalls.

[0073] In the microridge formation portion, the microridges may be arranged in a single row in the tire radial direction or in multiple rows. Here, "single row in the tire radial direction" means that there are no more than two microridges lined up in the tire radial direction. Also, the microridges may be arranged in a single row in the tire circumferential direction or in multiple rows. Here, "single row in the tire circumferential direction" means that there are no more than two microridges lined up in the tire circumferential direction. It is preferable that the microridges be provided in multiple rows in the tire radial direction and multiple rows in the tire circumferential direction.

[0074] The area of ​​the micro-ridge formation is the area defined by the line surrounding the outermost part of the multiple micro-ridges arranged at intervals of 0.50 mm or less when viewed from a direction perpendicular to the tire surface. The area of ​​the micro-ridge formation is 10 mm 2 It is preferable that the above ratio is satisfied. This is because stress concentration on the outer surface of the sidewall can be suppressed, contributing to improving the crack resistance of the sidewall. Furthermore, in the microridge formation portion, the group of microridges may be continuous or divided. Here, divided means that the spacing between the microridges is greater than 1.0 mm. Therefore, it is sufficient for there to be at least one microridge formation portion on the outer surface of at least one of the pair of sidewalls, and there may be multiple microridge formation portions.

[0075] (minor elevation) The shape of the micro-ridges is not particularly limited as long as it suppresses stress concentration on the outer surface of the sidewall and contributes to improving the crack resistance of the sidewall, and specific examples include a columnar shape, a frustum shape, a rib shape (stripe shape), etc. Examples of columnar shapes include cylindrical shapes and polygonal prism shapes such as triangular prisms, square prisms, and pentagonal prisms. Examples of frustum shapes include circular frustum shapes and polygonal frustum shapes such as triangular frustum shapes, square frustum shapes, and pentagonal frustum shapes. Examples of rib shapes include the shape of a cross section perpendicular to the longitudinal direction of the rib-shaped micro-ridges, and any shape may be included. Examples of the cross-sectional shape include a rectangle or a trapezoid.

[0076] FIG. 2 shows a portion of a microridge-formed portion in which cylindrical microridges 12 are formed on the sidewall outer surface 11. FIG. 3 shows a portion of a microridge-formed portion in which square-pyramid-shaped microridges 13 are formed on the sidewall outer surface 11. FIG. 4 is a cross-sectional view taken along line XX of FIG. 3, in which the microridges are viewed from a direction perpendicular to a plane including a normal to the sidewall outer surface. FIG. 4 shows the height h of the microridges 13, the maximum width w of the microridges 13, and the spacing d between the microridges 13. FIG. 5 shows a portion of a microridge-formed portion in which rib-shaped microridges 14 are formed on the sidewall outer surface 11. FIG. 6 is a cross-sectional view taken along line YY of FIG. 5, in which the microridges are viewed from a direction perpendicular to a plane including a normal to the sidewall outer surface. FIG. 6 shows the height h of the microridges 14, the maximum width w of the microridges 14, and the spacing d between the microridges 14.

[0077] Here, with respect to the microbumps, "height" refers to the maximum height of the microbump measured along a normal line erected on the outer surface of the sidewall, "maximum width" refers to the maximum width of the microbumps on the outer surface of the sidewall measured in one direction in which the microbumps are arranged, and "spacing" refers to the minimum spacing between the microbumps on the outer surface of the sidewall measured in one direction in which the microbumps are arranged. Note that the height, maximum width, and spacing of the microbumps are all measured with the outer surface of the sidewall laid out on a plane.

[0078] The height of the microbumps at the tire's widest point is preferably 0.03 mm or more, and may be 0.05 mm or more, or 0.10 mm or more, while the height is preferably 0.50 mm or less, and may be 0.45 mm or less, or 0.40 mm or less. The maximum width of the microbumps is preferably 0.03 mm or more, and may be 0.05 mm or more, or 0.10 mm or more, while the maximum width is preferably 5.00 mm or less, and may be 3.00 mm or less, 1.00 mm or less, or 0.50 mm or less. Furthermore, the spacing between the microbumps is preferably 1.00 mm or less, and may be 0.70 mm or less, or 0.50 mm or less. The spacing between the microbumps may be at least about half the maximum width, or may be about the same as the maximum width. The density of the microbumps (units / cm 2 ) can be roughly calculated from the maximum width and spacing of the micro-protuberances. For example, in the example described below, it is about 700 / cm 2 is.

[0079] It is preferable that 20 or more micro-ridges are formed in at least one direction, and the micro-ridge formation portion is 10 mm 2 It is preferable that the area be equal to or larger than this, because this can suppress stress concentration on the outer surface of the sidewall and contribute to improving the crack resistance of the sidewall.

[0080] The height of the micro-ridges preferably increases gradually from the tire's maximum width position toward the tire's radially outer side and from the tire's maximum width position toward the tire's radially inner side. This is because, although relatively large strain occurs near the tire's maximum width position on the sidewall, decreasing the height of the micro-ridges closer to the tire's maximum width position is thought to reduce non-uniformity in rubber volume in the tire circumferential direction at positions where large strain occurs, avoid stress concentration near the micro-ridges, and contribute to improving the sidewall's crack resistance.

[0081] The micro-ridges preferably have arc-shaped depressions on their outermost surfaces, such as micro-ridge 14 shown in Fig. 5. This configuration can prevent air from accumulating in the arc-shaped depressions, thereby preventing the micro-ridges from having poor appearance.

[0082] <Rubber composition> The rubber composition for the clinch apex and the rubber composition for the sidewall will be described below.

[0083] [Rubber composition for clinch apex] Each component of the rubber composition for the clinch apex will be described below: The rubber composition constituting the clinch apex contains recycled carbon black.

[0084] <Rubber component> The rubber composition constituting the clinch apex contains a rubber component containing isoprene rubber (IR rubber) and butadiene rubber (BR). In this case, the rubber component may contain rubber components other than IR rubber and BR, but may also consist of only IR rubber and BR. Each rubber that can constitute the rubber component is described below.

[0085] (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, TSR20, and SVR-L, which are commonly used in the rubber industry. Examples of IR include IR2200 and other commonly used rubber products. Examples of modified NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). 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. Isoprene-based rubbers may be used alone or in combination of two or more.

[0086] The content of the IR rubber in 100% by mass of the rubber component is, for example, more than 15% by mass, preferably more than 20% by mass, more preferably more than 25% by mass, even more preferably more than 35% by mass, and still more preferably more than 45% by mass. On the other hand, the content is, for example, 100% by mass or less, preferably less than 90% by mass, and more preferably less than 80% by mass. By keeping the content within the above range, processability during rubber kneading tends to be improved.

[0087] (BR) The BR is not particularly limited, and examples thereof include those commonly used in the tire industry, such as BR with a high cis content, BR containing 1,2-syndiotactic polybutadiene crystals (SPB-containing BR), butadiene rubber synthesized using a rare earth catalyst (rare earth-based BR), tin-modified butadiene rubber modified with a tin compound (tin-modified BR), and other modified butadiene rubbers (modified BR).Commercially available BRs include those from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Zeon Corporation. The modified BR may be any BR having a functional group that interacts with a filler such as silica. Examples include terminal-modified BR (terminal-modified BR having the functional group at the terminal) in which at least one terminal of the BR has been modified with a compound (modifier) ​​having the functional group, main-chain-modified BR having the functional group in the main chain, main-chain terminal-modified BR having the functional group in the main chain and at least one terminal (for example, main-chain terminal-modified BR having the functional group in the main chain and at least one terminal modified with the modifier), and terminal-modified BR modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or epoxy group introduced therein. Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imido group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, and an epoxy group. These functional groups may have a substituent. Among these, an amino group (preferably an amino group in which a hydrogen atom of the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferred.

[0088] The cis amount (cis content) of the BR is preferably more than 90% by mass, more preferably more than 93% by mass, even more preferably more than 95% by mass, and still more preferably 97% by mass or more. The cis amount of the BR can be measured by infrared absorption spectroscopy.

[0089] As the BR, for example, products of Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used. The BR may be used alone or in combination of two or more types.

[0090] The BR content in 100% by mass of the rubber component is, for example, more than 25% by mass, preferably more than 35% by mass, more preferably more than 45% by mass, and even more preferably 50% by mass or more. On the other hand, the content is, for example, less than 90% by mass, preferably less than 80% by mass, and more preferably less than 70% by mass. By keeping the content within the above range, flex crack growth resistance tends to be improved.

[0091] The total content of the IR rubber and BR in 100% by mass of the rubber component is preferably more than 80% by mass, more preferably more than 90% by mass, and even more preferably more than 95% by mass, and may be 100% by mass.

[0092] (Other rubber) The other rubbers that can be used other than those mentioned above are not particularly limited, and rubbers used in the tire field can be used. Examples include diene rubbers such as styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), and styrene-isoprene-butadiene copolymer rubber (SIBR). The other rubbers can be used alone or in combination of two or more.

[0093] (SBR) The styrene-butadiene rubber (SBR) is not particularly limited, and examples thereof include unmodified emulsion-polymerized styrene-butadiene rubber (E-SBR) and solution-polymerized styrene-butadiene rubber (S-SBR), as well as modified SBRs such as modified emulsion-polymerized styrene-butadiene rubber (modified E-SBR) and modified solution-polymerized styrene-butadiene rubber (modified S-SBR). Examples of modified SBRs include SBRs whose terminals and / or main chains are modified, and modified SBRs (condensates, branched structures, etc.) coupled with tin or silicon compounds. SBRs include oil-extended types in which flexibility is adjusted by adding an extender oil, and non-oil-extended types in which no extender oil is added, and either type can be used. Examples of such SBRs include those manufactured by JSR Corporation, Asahi Kasei Chemicals Corporation, Nippon Zeon Corporation, and ZS Elastomers Co., Ltd. One or more types of SBR can be used in combination.

[0094] The styrene content of SBR is preferably more than 15% by mass, more preferably more than 20% by mass, and even more preferably more than 23% by mass. From the viewpoint of fuel economy, the styrene content is preferably less than 40% by mass, more preferably less than 30% by mass, and even more preferably less than 25% by mass. The styrene content of SBR is a value calculated by the above-mentioned measurement method.

[0095] The vinyl content (amount of 1,2-bonded butadiene units) of SBR is preferably more than 10% by mass, more preferably more than 15% by mass, and more preferably more than 20% by mass. The vinyl content is preferably less than 80% by mass, preferably less than 50% by mass, and more preferably less than 30% by mass. The vinyl content of SBR is a value measured by the above-mentioned measurement method.

[0096] The content of the SBR rubber in 100% by mass of the rubber component is, for example, more than 10% by mass, preferably more than 20% by mass, and more preferably more than 40% by mass, while the content is, for example, 100% by mass or less, preferably less than 90% by mass, and more preferably less than 80% by mass.

[0097] (Rubber components synthesized from recycled and biomass-derived raw materials) The raw materials (monomers) of synthetic rubbers such as SBR and BR may be derived from petroleum or may be recycled from rubber products such as tires or non-rubber products such as polystyrene. Monomers obtained by recycling (recycled monomers) are not particularly limited, and examples thereof include recycled butadiene and recycled aromatic vinyl. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyls include, but are not particularly limited to, styrene. Among these, it is preferable to use recycled butadiene (recycled butadiene) and / or recycled styrene (recycled styrene) as raw materials.

[0098] The method for producing the recycled monomer is not particularly limited, and examples thereof include synthesis from recycled naphtha obtained by decomposing rubber products such as tires. The method for producing recycled naphtha is also not particularly limited, and examples thereof include decomposing rubber products such as tires under high temperature and pressure, decomposing with microwaves, or mechanically crushing and then extracting.

[0099] Furthermore, the raw materials (monomers) of synthetic rubbers such as SBR and BR may be derived from biomass. Examples of biomass-derived monomers (biomass monomers) include, but are not limited to, biomass-derived butadiene and biomass-derived aromatic vinyl. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl include, but are not limited to, styrene. Furthermore, methods for producing biomass monomers are also not limited, including, for example, biological and / or chemical and / or physical conversion of animals and plants. A typical example of biological conversion is fermentation using microorganisms, while examples of chemical and / or physical conversion include catalytic, high-temperature, high-pressure, electromagnetic, and critical fluid conversion, as well as combinations thereof. Biomass sources for these monomers include sugar, wood, plant residues after useful components have been extracted, plant-derived ethanol, and biomass naphtha.

[0100] Polymers synthesized from biomass monomer components (biomass polymers) are not particularly limited and include polybutadiene rubber synthesized from biomass-derived butadiene, aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl compounds, etc. Examples of the aromatic vinyl / butadiene copolymers include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0101] Whether the raw material for a polymer is biomass-derived can be determined by the pMC (percent modern carbon) measured in accordance with ASTM D6866-10.

[0102] pMC is the modern standard reference 14 of sample against C concentration 14 This is the ratio of C concentrations and is a value used as an index of the biomass ratio of a compound. The significance of this value is explained below.

[0103] 1 mole of carbon atoms (6.02 × 10 23 ) contains approximately 6.02 × 10 atoms, which is about one trillionth of the number of ordinary carbon atoms. 11 pieces 14 C exists. 14 The half-life of C is 5730 years, 14 Therefore, in the case of fossil fuels such as coal, oil, and natural gas, which are thought to have been absorbed and fixed by plants and other organisms more than 226,000 years ago, carbon dioxide was included in these when they were first fixed. 14 All C elements have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas contain 14 Therefore, chemicals produced from these fossil fuels do not contain any C element. 14 It does not contain any C elements.

[0104] on the other hand, 14 C is constantly produced by cosmic rays undergoing nuclear reactions in the atmosphere. 14 The amount of C is balanced between radioactive decay and nuclear reaction, and in the Earth's atmospheric environment, 14 Therefore, the amount of carbon derived from biomass resources currently circulating in the environment is constant. 14 As mentioned above, the C concentration is approximately 1 × 10 -12 The value is approximately mol %. Therefore, the biomass ratio in a compound can be calculated by using the difference between these values.

[0105] this 14 C is typically measured using accelerator mass spectrometry based on a tandem accelerator. 13 C concentration ( 13 C / 12 C). 14 C concentration ( 14 C / 12 C) is measured. 14The modern standard reference for the C concentration is the carbon circulating in nature as of 1950. 14 The specific standard substance used is the oxalic acid standard provided by NIST (National Institute of Standards and Technology). The specific activity of carbon in this oxalic acid (per gram of carbon) is 14 The radioactivity of C is separated into carbon isotopes, 13 The standard value is the value corrected for decay from 1950 to the measurement date. 14 This is used as the C concentration value (100%). The ratio of this value to the value of the actually measured sample is the pMC value.

[0106] Therefore, if rubber is made from 100% biomass-derived materials, although there are regional differences, it will usually not reach 100 under normal conditions, so it will show a value of approximately 110 pMC. On the other hand, for chemical substances derived from petroleum and other fossil fuels, 14 When the carbon concentration is measured, it will show a value of about 0 pMC (for example, 0.3 pMC), which corresponds to the above-mentioned biomass ratio of 0%.

[0107] From the above, it is preferable in terms of environmental protection to use a material such as rubber having a high pMC value, that is, a material such as rubber having a high biomass ratio, in a rubber composition.

[0108] <Filler> The filler includes recycled carbon black (rCB). In addition to recycled carbon black, the filler can also include regular carbon black, silica, and other reinforcing fillers used in the tire industry. When the filler includes silica, it may further include a silane coupling agent. The filler preferably includes recycled carbon black and a carbon black other than recycled carbon black.

[0109] (recycled carbon black) In the present invention, recycled carbon black refers to carbon black obtained from the pyrolysis process of used tires or other products containing carbon black, and which, when subjected to oxidative combustion by heating in air as measured by thermogravimetry in accordance with JIS K 6226-2:2003, has a mass ratio of ash (i.e., the mass of the non-combustible component) of 5% by mass or more. The ash content of recycled carbon black is preferably 7% by mass or more, more preferably 9% by mass or more, even more preferably 11% by mass or more, and even more preferably 13% by mass or more. The ash content is preferably less than 30% by mass, more preferably less than 27% by mass, and even more preferably less than 25% by mass.

[0110] Recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, citing "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, describes the carbon black as being obtained by 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 mentioned in

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

[0111] Recycled carbon black may lack functional groups on its surface, or may be treated to include functional groups on its surface. The treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, European Patent Application Publication No. 3,173,251 discloses that 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. Japanese Patent Publication No. 6,856,781 also discloses that carbon black obtained from a pyrolysis process is treated with an amino acid compound containing at least one thiol or disulfide group to obtain surface-activated carbon black. In one embodiment of the present invention, recycled carbon black also includes carbon blacks that have been treated to include functional groups on their surfaces.

[0112] The average primary particle diameter of recycled carbon black is preferably 20 nm or more, more preferably 25 nm or more, even more preferably 30 nm or more, and particularly preferably 35 nm or more. By setting the average primary particle diameter of carbon black within the above range, it is thought that the rubber molecules bound by the carbon black are minimized, allowing them to move flexibly, thereby enabling the polymer molecular chain to relieve stress in response to input force. On the other hand, the average primary particle diameter is preferably 90 nm or less, more preferably 75 nm or less, and even more preferably 60 nm or less. The average primary particle diameter of carbon black is measured by the above-mentioned measurement method.

[0113] The nitrogen adsorption specific surface area (N2SA) of the recycled carbon black is not particularly limited, but from the viewpoint of obtaining sufficient reinforcement and good abrasion resistance, it is preferred that the N2SA be 30 m 2 / g or more is preferable, and 40m 2 / g is more preferable, and 50m 2 / g or more is more preferable, and 60m 2 / g or more is more preferable, and 70m 2 In addition, from the viewpoint of excellent dispersibility and low heat generation, the N2SA has a viscosity of 300 m / g or more. 2 / g is preferable, and 200m 2 / g is more preferable, and 150m 2 / g is more preferable, and 120m 2 / g is more preferable, and 110m 2 / g is more preferable, and 100m 2 / g is more preferable, and 90m 2 / g or less is more preferable. Note that the N2SA of the recycled carbon black in this specification is a value measured in accordance with JIS K 6217-2:2017.

[0114] From the viewpoint of reinforcement, the amount of recycled carbon black is, for example, more than 3 parts by mass, preferably more than 5 parts by mass, more preferably more than 6 parts by mass, and even more preferably more than 7 parts by mass, per 100 parts by mass of the rubber component. On the other hand, the amount of recycled carbon black may be less than 50 parts by mass, preferably less than 40 parts by mass, more preferably less than 30 parts by mass, even more preferably less than 20 parts by mass, even more preferably less than 10 parts by mass, and even more preferably 8 parts by mass or less.

[0115] (Carbon black other than rCB) Carbon black other than recycled carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. The raw material for carbon black may be a biomass material such as lignin or vegetable oil, or pyrolysis oil obtained by pyrolysis of waste tires. Carbon black may be produced by combustion, such as in a furnace process, by hydrothermal carbonization (HTC), or by pyrolysis of methane, such as in a thermal black process. Commercially available carbon blacks 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., and Columbia Carbon Co., Ltd. These may be used alone or in combination.

[0116] The average primary particle diameter of carbon black is preferably 20 nm or more, more preferably 25 nm or more, even more preferably 30 nm or more, and particularly preferably 35 nm or more. By setting the average primary particle diameter of carbon black within the above range, the rubber molecules bound by the carbon black are minimized, allowing them to move flexibly, which is thought to enable the polymer molecular chain to relieve stress in response to input. Meanwhile, the average primary particle diameter is preferably 90 nm or less, more preferably 75 nm or less, and even more preferably 60 nm or less. The average primary particle diameter of carbon black is measured by the above-mentioned measurement method.

[0117] The nitrogen adsorption specific surface area (N2SA) of the carbon black is not particularly limited, but from the viewpoint of obtaining sufficient reinforcement and good abrasion resistance, it is preferred that the N2SA be 30 m 2 / g or more is preferable, and 40m 2 / g is more preferable, and 50m 2 / g or more is more preferable, and 60m 2 / g or more is more preferable, and 70m 2 In addition, from the viewpoint of excellent dispersibility and low heat generation, the N2SA has a viscosity of 300 m / g or more. 2 / g is preferable, and 200m 2 / g is more preferable, and 150m 2 / g is more preferable, and 120m 2 / g is more preferable, and 110m 2 / g is more preferable, and 100m 2 / g is more preferable, and 90m 2 / g or less is more preferable. In this specification, the N2SA of carbon black is a value measured in accordance with JIS K 6217-2:2017.

[0118] When carbon black other than recycled carbon black is contained, the amount of the carbon black relative to 100 parts by mass of the rubber component is, for example, more than 25 parts by mass, preferably more than 35 parts by mass, more preferably more than 45 parts by mass, and even more preferably 50 parts by mass or more. On the other hand, the amount is preferably less than 90 parts by mass, more preferably less than 80 parts by mass, and even more preferably less than 70 parts by mass.

[0119] From the viewpoint of reinforcement, the total carbon black content (the sum of the recycled carbon black content and the carbon black other than recycled carbon black) is preferably more than 30 parts by mass, more preferably more than 40 parts by mass, and even more preferably more than 50 parts by mass, per 100 parts by mass of the rubber component. On the other hand, from the viewpoint of fuel economy, it is preferably less than 80 parts by mass, more preferably less than 75 parts by mass, even more preferably less than 70 parts by mass, even more preferably less than 65 parts by mass, and even more preferably less than 60 parts by mass. When the carbon black content is within the above range, sufficient reinforcement and good dispersion in the rubber are obtained, and sufficient rubber strength and crack resistance tend to be obtained.

[0120] (silica) The silica is not particularly limited, and can be, for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrated silica), or other silica commonly used in the tire industry. The raw material for silica is not particularly limited, and can be, for example, a mineral-derived raw material such as quartz, a biological raw material such as rice husk (for example, silica made from biomass materials such as rice husk), or silica recycled from a silica-containing product. Among these, hydrated silica prepared by a wet method is preferred because it contains a large number of silanol groups. Silica can be used alone or in combination of two or more types.

[0121] Silica made from biomass materials can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then reacting the silicate with sulfuric acid in the same manner as conventional wet-process silica to produce a silicon dioxide precipitate, which is then filtered, washed with water, dried, and pulverized.

[0122] Silica recycled from silica-containing products can be, for example, silica recovered from products containing silica, such as electronic components such as semiconductors, tires, desiccants, and filtering materials such as diatomaceous earth. The recovery method is not particularly limited, and examples include thermal decomposition and decomposition by electromagnetic waves. Among these, silica recovered from electronic components such as semiconductors or tires is preferred.

[0123] When silica crystallizes, it becomes insoluble in water, and its component, silicic acid, cannot be utilized. By controlling the combustion temperature and duration, it is possible to suppress the crystallization of silica in rice husk ash (see, for example, JP 2009-2594 A and Akita Prefectural University Web Journal B / 2019, vol. 6, pp. 216-222).

[0124] Amorphous silica extracted from rice husks may be commercially available from Wilmar Co., Ltd., etc.

[0125] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 50 m 2 / g, more preferably 100m 2 / g, more preferably 150m 2 / g, particularly preferably 170m 2 The upper limit of the N2SA of silica is not particularly limited, but is preferably 350 m 2 / g, more preferably less than 250m 2 / g, more preferably less than 200m 2 The N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0126] (Silica content) When silica is contained, the content per 100 parts by mass of the rubber component is not particularly limited, but from the viewpoint of the effects of the present invention, it is preferably more than 1 part by mass, more preferably more than 5 parts by mass, more preferably more than 10 parts by mass, and even more preferably more than 20 parts by mass. Also, from the viewpoints of dispersibility and processability of silica, the content is preferably less than 150 parts by mass, more preferably less than 100 parts by mass, even more preferably less than 50 parts by mass, and even more preferably less than 30 parts by mass.

[0127] (Silane coupling agent) When silica is used as the filler, it is preferable to further contain a silane coupling agent. The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, and 3-trimethoxysilylpropyl-N,N-dimethyl Examples of such compounds include sulfide-based compounds such as thiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z manufactured by Momentive; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercially available products include those from Evonik Degussa, Momentive, Shin-Etsu Silicones Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Dow Corning Toray Co., Ltd. These may be used alone or in combination of two or more.

[0128] (Silane coupling agent content) When containing silane coupling agent, the content of silane coupling agent is preferably more than 1 part by mass, more preferably more than 3 parts by mass, even more preferably more than 5 parts by mass, and even more preferably more than 7 parts by mass, based on 100 parts by mass of silica.On the other hand, the content is preferably less than 20 parts by mass, more preferably less than 18 parts by mass, even more preferably less than 16 parts by mass, and even more preferably less than 14 parts by mass.By making it within the above range, the dispersibility of silica tends to improve.

[0129] (Other fillers) The other fillers are not particularly limited, and materials known in the field of the tire industry can be used, such as inorganic fillers such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, mica, etc. These may be used alone or in combination of two or more.

[0130] <Other compounding agents> In addition to the rubber component and filler, the rubber composition may contain, as appropriate, compounding agents that are generally used in the tire industry, such as plasticizers, processing aids, vulcanized rubber particles, wax, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators.

[0131] (plasticizer) A plasticizer is a material that imparts plasticity to rubber components and encompasses both liquid (liquid) plasticizers at room temperature and solid plasticizers at room temperature. Examples of plasticizers include resins, oils, liquid polymers, and ester-based plasticizers. These plasticizers may be derived from petroleum, biomass, or naphtha recycled from rubber or non-rubber products. Low-molecular-weight hydrocarbon components obtained by pyrolysis and extraction of used tires or products containing various components may also be used as plasticizers. Plasticizers may be used singly or in combination.

[0132] <Oil> The oil is not particularly limited, and any oil commonly used in the tire industry can be suitably used, such as process oil, vegetable oil, and animal oil. Examples of process oil include paraffinic process oil (mineral oil), naphthenic process oil, and aromatic process oil. Specific examples of process oil include mild extracted solvate (MES), distillate aromatic extract (DAE), treated distillate aromatic extract (TDAE), treated residual aromatic extract (TRAE), and residual aromatic extract (RAE). Furthermore, as an environmental measure, process oil with a low content of polycyclic aromatic compounds (PCA) can also be used. Examples of low-PCA process oils include MES, TDAE, and heavy naphthenic oil. Furthermore, from the perspective of life cycle assessment, refined waste oil from rubber mixers and engines, or waste cooking oil from restaurants, can also be used. Among these, aromatic process oils are preferred, and TDAE oil is more preferred. The oils that can be used include those manufactured and sold by, for example, H&R, JXTG Nippon Oil & Energy Corporation, Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd. One type of oil can be used, or two or more types can be used in combination.

[0133] As used herein, examples of vegetable oils include 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 Japan wax. Further examples of vegetable oils include refined oils (such as salad oils) obtained by refining the above-mentioned oils, interesterified oils obtained by interesterifying the above-mentioned oils, hardened oils obtained by hydrogenating the above-mentioned oils, thermally polymerized oils obtained by thermally polymerizing the above-mentioned oils, oxidatively polymerized oils obtained by oxidizing the above-mentioned oils, and waste edible oils recovered from edible oils and the like. Vegetable oils may be liquid or solid at room temperature. These vegetable oils may be used alone or in combination of two or more.

[0134] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxyl group of glycerin is ester-bonded to a fatty acid. 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 (trimer or higher). Dimer or higher acylglycerols can be obtained by thermal polymerization, oxidative polymerization, or the like. Furthermore, the acylglycerol may be liquid or solid at room temperature.

[0135] The method for confirming whether the rubber composition contains the acylglycerol is not particularly limited, but may be any of the following: 1 For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at room temperature for 24 hours, and after removing the rubber composition, the 1When H-NMR was measured, signals were observed around 5.26 ppm, 4.28 ppm, and 4.15 ppm when the signal of tetramethylsilane (TMS) was set at 0.00 ppm. These signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atoms of the ester group. In this paragraph, "around" refers to a range of ±0.10 ppm.

[0136] The fatty acid is not particularly limited and may be either an unsaturated fatty acid or a saturated fatty acid. 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.

[0137] Among these, it is desirable that the fatty acid contains a fatty acid with few double bonds, i.e., saturated fatty acid or monounsaturated fatty acid, and oleic acid is preferred. As a vegetable oil containing such a fatty acid, for example, vegetable oil containing saturated fatty acid or monounsaturated fatty acid may be used, or vegetable oil modified by ester exchange or the like may be used. Furthermore, in order to produce vegetable oil containing such a fatty acid, plants may be improved by breeding, genetic modification, genome editing, or the like.

[0138] As the vegetable oil, for example, commercially available products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoi Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., Fuji Kosan Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0139] The oil content per 100 parts by mass of the rubber component is preferably more than 1 part by mass, more preferably more than 3 parts by mass, and even more preferably more than 5 parts by mass. The content is preferably less than 20 parts by mass, more preferably less than 15 parts by mass, and even more preferably less than 10 parts by mass. The oil content includes the amount of oil contained in the rubber component as an extender oil and the amount of oil contained in other components such as sulfur.

[0140] <Liquid polymer> Liquid polymers are polymers that are liquid at room temperature, and examples thereof include liquid diene polymers. Examples of liquid diene polymers include liquid styrene-butadiene copolymers (liquid SBR), liquid butadiene polymers (liquid BR), liquid isoprene polymers (liquid IR), and liquid styrene-isoprene copolymers (liquid SIR). The liquid diene polymers preferably have a polystyrene-equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC) of more than 1,000, more preferably more than 3,000, while the Mn is preferably less than 100,000, more preferably less than 15,000. The Mn of the liquid polymer is a polystyrene-equivalent value measured by gel permeation chromatography (GPC). Examples of liquid diene polymers that can be used include products from Sartomer Corporation and Kuraray Co., Ltd. The liquid polymers may be used alone or in combination of two or more.

[0141] (resin) The rubber composition according to the present embodiment may contain a resin in combination. Resins that can be used in the present embodiment are not particularly limited, and resins commonly used in the tire industry can be used. Examples of such resins include adhesive resins such as C9 resins, C5 resins, C5C9 resins, aromatic vinyl resins, dicyclopentadiene resins, terpene resins, rosin resins, and phenol resins. These resins may be used alone or in combination of two or more.

[0142] "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a copolymer obtained by polymerizing a C9 fraction alone or a copolymer obtained by copolymerizing a C9 fraction with other components. For example, a resin obtained by copolymerizing dicyclopentadiene (DCPD) with a C9 fraction is called a DCPD / C9 resin. These resins may also be hydrogenated or modified. Examples of C9 fractions include petroleum fractions with 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene.

[0143] "C5 resin" refers to a resin obtained by polymerizing a C5 fraction, and may be a hydrogenated or modified C5 resin. Examples of C5 fractions other than dicyclopentadiene include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, isoprene, pentane, isopentane, neopentane, pentene, and pentadiene.

[0144] The term "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. Examples of C5C9 resins that can be used include those commercially available from Tosoh Corporation, Luhua, and the like.

[0145] <Dicyclopentadiene resin> "Dicyclopentadiene resin" refers to a resin containing dicyclopentadiene (DCPD) as the monomer component with the largest content, and may be a hydrogenated or modified resin. Examples of dicyclopentadiene resins include DCPD / C9 resins obtained by copolymerizing dicyclopentadiene with the C9 fraction, with DCPD / C9 resins being preferred. Examples of DCPD resins that can be used include those commercially available from ExxonMobil Corporation, ENEOS Corporation, Nippon Zeon Co., Ltd., Maruzen Petrochemical Co., Ltd., and the like.

[0146] <Aromatic vinyl resin> The term "aromatic vinyl resin" refers to a resin containing an aromatic vinyl compound such as styrene, α-methylstyrene, vinyltoluene, or p-chlorostyrene as the monomer component with the highest content, and may be a hydrogenated or modified version of such a compound. As the aromatic vinyl resin, a homopolymer of α-methylstyrene or styrene or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, because they are economical, easy to process, and have excellent heat generation properties. As the aromatic vinyl resin, commercially available products from Kraton, Eastman Chemical, Mitsui Chemicals, Inc., etc., can be used.

[0147] <Cumarone resin> Coumarone resins refer to resins containing coumarone as a monomer component, and may be hydrogenated or modified. Examples of coumarone resins include coumarone-indene resins, which contain coumarone and indene as monomer components, and coumarone-indene-styrene resins, which contain coumarone, indene, and styrene as monomer components.

[0148] <Indene-based resin> Indene resins are resins containing indene as a monomer component, and may be hydrogenated or modified. Examples of coumarone resins include coumarone-indene resins, which contain coumarone and indene as monomer components, and coumarone-indene-styrene resins, which contain coumarone, indene, and styrene as monomer components.

[0149] <Terpene resin> Terpene resins refer to resins containing terpene compounds such as α-pinene, β-pinene, limonene, and dipentene as the most abundant monomer component, and may be hydrogenated or modified. Specific examples of terpene resins include polyterpene resins containing only one or more of the terpene compounds as monomer components; aromatic-modified terpene resins containing the terpene compound and an aromatic compound as monomer components; and terpene phenolic resins containing the terpene compound and a phenolic compound as monomer components. Examples of aromatic compounds that serve as monomer components for aromatic-modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenolic compounds that serve as monomer components for terpene phenolic resins include phenol, bisphenol A, cresol, and xylenol.

[0150] <Rosin-based resin> The rosin-based resin refers to a resin containing a rosin acid compound such as abietic acid, neoabietic acid, palustric acid, or isopimaric acid, and may be a hydrogenated or modified version of such a resin. The rosin-based resin is not particularly limited, but examples thereof include natural rosin resin and rosin-modified resins obtained by modifying rosin by hydrogenation, disproportionation, dimerization, esterification, or the like.

[0151] <Phenol-based resin> The phenolic resin refers to a resin that contains phenolic compounds such as phenol and cresol as the monomer component with the largest content. The phenolic resin is not particularly limited, but examples thereof include phenol formaldehyde resin, alkylphenol formaldehyde resin, alkylphenol acetylene resin, and oil-modified phenol formaldehyde resin.

[0152] When a resin is contained, the content per 100 parts by mass of the rubber component is preferably more than 2 parts by mass, more preferably more than 3 parts by mass, and even more preferably more than 4 parts by mass, while the content is preferably less than 20 parts by mass, more preferably less than 15 parts by mass, and even more preferably less than 10 parts by mass.

[0153] <Ester-based plasticizers> Examples of ester-based plasticizers include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelate (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). One type of ester-based plasticizer may be used alone, or two or more types may be used in combination.

[0154] (anti-aging agent) The antioxidant is not particularly limited, but examples thereof include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), and N,N'-ditolyl-p-phenylenediamine. p-phenylenediamine-based antioxidants such as diisopropyl-N'-phenyl-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers; 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 that can be used include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis, etc.

[0155] When an antioxidant is contained, the content thereof per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 0.8 parts by mass, and even more preferably more than 1.0 part by mass, while the content is preferably less than 7.0 parts by mass, more preferably less than 5.0 parts by mass, and even more preferably 3.0 parts by mass or less.

[0156] (vulcanized rubber particles) The 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 standpoint of environmental considerations and cost, recycled rubber powder produced from crushed waste tires is preferred. These may be used alone or in combination of two or more types.

[0157] The vulcanized rubber particles are not particularly limited, and may be unmodified vulcanized rubber particles or modified vulcanized rubber particles.

[0158] As commercially available vulcanized rubber, for example, products from Lehigh, Muraoka Rubber Industries, Ltd., etc. can be used.

[0159] (processing aids) Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, 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 alone or in combination of two or more. Examples of processing aids that can be used include those commercially available from Schill + Seilacher, Performance Additives, etc.

[0160] When a processing aid is contained, the content thereof per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1 part by mass, and even more preferably more than 1.5 parts by mass from the viewpoint of improving processability, and is preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and even more preferably less than 5.0 parts by mass from the viewpoint of abrasion resistance and breaking strength.

[0161] (wax) The wax is not particularly limited, and any wax commonly used in the tire industry can be suitably used, such as petroleum wax, mineral wax, and synthetic wax. Of these, petroleum wax is preferred. Petroleum waxes include, for example, paraffin wax, microcrystalline wax, and selected special waxes thereof, and paraffin wax is preferred. Waxes that can be used include, for example, those manufactured and sold by Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., Ltd., and the like. One type of wax can be used, or two or more types can be used in combination.

[0162] When the wax is contained, the amount thereof per 100 parts by mass of the rubber component is preferably more than 0.3 parts by mass, more preferably more than 0.7 parts by mass, and even more preferably more than 1.0 part by mass, while the amount is preferably less than 4.0 parts by mass, more preferably less than 3.0 parts by mass, and even more preferably less than 2.5 parts by mass.

[0163] (stearic acid) When stearic acid is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 0.7 parts by mass, and even more preferably 1.0 part by mass or more from the viewpoint of processability, while the content is preferably less than 10 parts by mass, more preferably less than 5 parts by mass, and even more preferably less than 3 parts by mass from the viewpoint of vulcanization rate.

[0164] (zinc oxide) When zinc oxide is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 0.7 parts by mass, and even more preferably more than 1 part by mass from the viewpoint of processability, while the content is preferably 10 parts by mass or less, more preferably less than 7 parts by mass, and even more preferably 5 parts by mass or less from the viewpoint of abrasion resistance.

[0165] (vulcanizing agent) The vulcanizing agent is not particularly limited, and known vulcanizing agents can be used, such as organic peroxides, sulfur-based vulcanizing agents, resin vulcanizing agents, and metal oxides such as magnesium oxide. Of these, sulfur-based vulcanizing agents are preferred. Examples of sulfur-based vulcanizing agents that can be used include sulfur and sulfur donors such as morpholine disulfide. Of these, sulfur is preferred. One or more types of vulcanizing agents can be used in combination.

[0166] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur (oil-treated sulfur, special sulfur treated with a dispersant, masterbatch-type sulfur, etc.), and insoluble sulfur (oil-treated insoluble sulfur, etc.), all of which are preferably used. Among these, powdered sulfur is preferred. Examples of sulfur that can be used include those manufactured and sold by Tsurumi Chemical Industry Co., Ltd., Karuizawa Iso Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanritsu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc.

[0167] When a vulcanizing agent is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.4 parts by mass, more preferably more than 0.5 parts by mass, even more preferably more than 1.0 part by mass, and even more preferably more than 1.5 parts by mass. On the other hand, the content is preferably less than 6.0 parts by mass, more preferably 5.0 parts by mass or less, and even more preferably less than 4.0 parts by mass. When the content of the vulcanizing agent is within the above range, an appropriate reinforcing effect tends to be obtained. Note that when the vulcanizing agent contains components other than sulfur, such as oil-treated sulfur, the content of the vulcanizing agent refers to the content of the sulfur component itself.

[0168] (Vulcanization accelerator) The vulcanization accelerator is not particularly limited, and known vulcanization accelerators can be used. Examples include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, and xanthate-based vulcanization accelerators. Among these, sulfenamide-based, thiuram-based, and guanidine-based accelerators are preferred, and sulfenamide-based accelerators are more preferred. Examples of vulcanization accelerators that can be used include those manufactured and sold by Ouchi Shinko Chemical Industry Co., Ltd., Sanshin Chemical Industry Co., Ltd., etc. These vulcanization accelerators can be used alone or in combination of two or more.

[0169] Examples of sulfenamide vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), and N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS). Examples of thiuram vulcanization accelerators include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, and tetrabenzylthiuram disulfide (TBzTD). Examples of guanidine vulcanization accelerators include 1,3-diphenylguanidine (DPG), di-orthotolylguanidine, and orthotolylbiguanidine.

[0170] The content of the vulcanization accelerator per 100 parts by mass of the rubber component is preferably more than 0.3 parts by mass, more preferably more than 0.4 parts by mass, and even more preferably more than 0.5 parts by mass. On the other hand, the content is preferably less than 4.0 parts by mass, more preferably less than 3.0 parts by mass, and even more preferably less than 2.0 parts by mass. When the content of the vulcanization accelerator is within the above range, breaking strength and elongation tend to be ensured. [Sidewall rubber composition] Each component of the rubber composition for a sidewall will be described.

[0171] (rubber component) The rubber component is as described below and as described above for the rubber composition for the clinch apex. The rubber component contains a rubber selected from IR rubber and BR, and may contain rubber components other than IR rubber and BR. The rubber component may also consist solely of a rubber selected from IR rubber and BR.

[0172] <IR rubber content> The rubber component is as described in the section on the rubber composition for clinch apex, and the content of the IR rubber in 100% by mass of the rubber component is, for example, more than 15% by mass, preferably more than 25% by mass, more preferably more than 35% by mass, even more preferably 40% by mass or more, and even more preferably 45% by mass or more. Meanwhile, the content is, for example, 100% by mass or less, preferably less than 90% by mass, and more preferably less than 80% by mass. By keeping the content within the above range, processability during rubber kneading tends to be improved.

[0173] The BR content in 100% by mass of the rubber component is, for example, more than 30% by mass, preferably more than 40% by mass, more preferably more than 50% by mass, even more preferably 55% by mass or more, and still more preferably 60% by mass or more. On the other hand, the content is, for example, less than 90% by mass, preferably less than 80% by mass, and more preferably less than 70% by mass. By keeping the content within the above range, flex crack growth tends to be improved.

[0174] The total content of the IR rubber and BR in 100% by mass of the rubber component is preferably more than 80% by mass, more preferably more than 90% by mass, and even more preferably more than 95% by mass, and may be 100% by mass.

[0175] (filler) The filler may include carbon black (including recycled carbon black), silica, and other fillers. When the filler includes silica, it may further include a silane coupling agent. The components that may constitute the filler are as described in the section on the rubber composition for the clinch apex. The filler preferably includes carbon black.

[0176] <Carbon black> For carbon black (including recycled carbon black), the explanation given for the rubber composition for the clinch apex can be similarly applied.

[0177] ≪Content≫ When carbon black is contained, the total amount of carbon black including recycled carbon black is, for example, more than 30 parts by mass, preferably more than 40 parts by mass, more preferably 50 parts by mass or more, and even more preferably 60 parts by mass or more, per 100 parts by mass of the rubber component. On the other hand, the total amount is preferably less than 150 parts by mass, more preferably less than 110 parts by mass, and even more preferably less than 80 parts by mass. When the carbon black content is within the above range, sufficient reinforcement and good dispersion in the rubber are obtained, and sufficient rubber strength and crack resistance tend to be obtained.

[0178] (Other compounding agents) For other details than those mentioned above, the explanation given for the rubber composition for the clinch apex is similarly applicable.

[0179] <Other rubber components that make up tires> In this specification, the tire may include other rubber components in addition to those described above. Such other rubber components are not particularly limited, and various rubber components generally used in tires may be used.

[0180] 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. As a method for obtaining the compound according to the embodiment of the present invention from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process for synthesizing methane from carbon dioxide may be converted.

[0181] <Application> In this specification, the term "tire" refers to either a pneumatic tire or a non-pneumatic tire, but can be suitably used as a pneumatic tire. Furthermore, in this specification, the term "tire" refers to a tire that can be used for various purposes, such as a passenger car tire, a heavy-duty tire for trucks and buses, a motorcycle tire, and a high-performance tire.

[0182] <Manufacturing method> The tire according to this embodiment can be manufactured by a known method.

[0183] (Production of rubber composition) Each of the above rubber compositions can be produced by a known method. For example, they can be produced by kneading the above components using a rubber kneading device such as an open roll or an internal kneader (e.g., a Banbury mixer or kneader). The kneading process may include, for example, a base kneading process in which compounding ingredients and additives other than the vulcanizing agent and vulcanization accelerator are kneaded, and a final kneading (F kneading) process in which the vulcanizing agent and vulcanization accelerator are added to the kneaded product obtained in the base kneading process and kneaded. Furthermore, the base kneading process can be divided into multiple processes as desired. The kneading conditions are not particularly limited, but examples include a method in which the base kneading process involves kneading for 3 to 10 minutes at a discharge temperature of 150 to 170°C, and a method in which the final kneading process involves kneading for 1 to 5 minutes at a discharge temperature of 50 to 110°C.

[0184] (tire manufacturing) Each rubber composition obtained above can be extruded in the unvulcanized state to match the shape of the desired tire component, respectively, to form an unvulcanized clinch apex and sidewall. The tire according to this embodiment can be made into an unvulcanized tire by molding the thus obtained clinch apex and sidewall together with other tire components in a tire building machine using a conventional method. A tire can be obtained by heating and pressurizing (vulcanizing) this unvulcanized tire in a vulcanizer. The vulcanization conditions are not particularly limited, and examples include a method of vulcanizing at 150 to 200°C for 5 to 30 minutes. [Example]

[0185] Examples (working examples) that are considered preferable for carrying out the present invention are shown below, but the scope of the present invention is not limited to these working examples. Rubber compositions and tires obtained according to the tables were examined using the various chemicals shown below, and the results calculated based on the evaluation methods described below are shown as indices at the bottom of each table.

[0186] <Material> The materials used in the examples and comparative examples will be summarized below. Natural rubber: SVR-L BR: BR150B (Ube Industries, Ltd., unmodified high-cis BR, vinyl content: 1 mol%, cis content: 97 mol%, Mw: 440,000) Carbon black (CB) 1: Show Black N550 (manufactured by Cabot Japan Co., Ltd., N2SA: 42m 2 / g; ash content: less than 1% by mass) Carbon black (CB) 2: Show Black N220 (manufactured by Cabot Japan Co., Ltd., N2SA: 114m 2 / g; Ash content: less than 1% by mass (mass%) Recycled carbon black (rCB): Carbon black obtained from the pyrolysis process of tires (ash content: 17% by mass) Antioxidant: Nocrac 6C (Ouchi Shinko Chemical Industry Co., Ltd., N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) Stearic acid: Camellia stearate beads (NOF Corporation) Zinc oxide: Zinc oxide type 2 (manufactured by Mitsui Mining & Smelting Co., Ltd.) Oil: PS-32 (mineral oil, manufactured by Idemitsu Kosan Co., Ltd.) Sulfur: HK-200-5 (Hosoi Chemical Industry Co., Ltd., powdered sulfur, oil content: 5% by mass) Vulcanization accelerator 1: Noccela CZ (Ouchi Shinko Chemical Industry Co., Ltd., N-cyclohexyl-2-benzothiazole sulfenamide) Vulcanization accelerator 2: Noccela NS (Ouchi Shinko Chemical Industry Co., Ltd., N-tert-butyl-2-benzothiazylsulfenamide)

[0187] <Rubber composition for clinch apex> According to the compounding recipes shown in Tables 1 and 2, chemicals other than sulfur and vulcanization accelerators are mixed for 5 minutes at a discharge temperature of 150°C using a 1.7 L internal Banbury mixer. Next, sulfur and vulcanization accelerators are added to the resulting mixture, which is then mixed with an open roll for 4 minutes until the temperature reaches 100°C, to obtain an unvulcanized rubber composition for clinch apex.

[0188] <Sidewall rubber composition> According to the compounding recipes shown in Tables 1 and 2, the chemicals other than sulfur and the vulcanization accelerator are mixed in a 1.7 L closed-type Banbury mixer for 5 minutes until the discharge temperature reaches 150°C, to obtain a kneaded mixture. Next, using a two-screw open roll, sulfur and the vulcanization accelerator are added to the resulting kneaded mixture, and the mixture is mixed for 4 minutes until the temperature reaches 100°C, to obtain an unvulcanized rubber composition for sidewalls.

[0189] <Tires> According to the descriptions in Tables 2 and 3, the unvulcanized rubber composition for the clinch apex and the unvulcanized rubber composition for the sidewall were molded into the shape of the clinch apex and the shape of the sidewall, respectively, and then bonded together with other components to form an unvulcanized tire. Each test tire (size: 215 / 60R16, sidewall thickness T: 5.0 mm) was manufactured by press-vulcanizing the tire at 170°C for 12 minutes.

[0190] Furthermore, the microbumps on the outer surface of the sidewall are formed during press vulcanization using a mold equipped with side plates on which a marking for forming the microbumps is engraved on the surface facing the microbump-forming portion. The shapes of microbumps A and B are as follows: Height h (mm) is the height of the microbump at the tire's maximum width position, height h1 (mm) is the height of the microbump at the tire's radially outermost position, and height h2 (mm) is the height of the microbump at the tire's radially innermost position. When the value of h1 is greater than h, the height of the microbump gradually increases from the tire's maximum width position toward the tire's radially outer side, and when the value of h2 is greater than h, the height of the microbump gradually increases from the tire's maximum width position toward the tire's radially inner side.

[0191] [Table 1]

[0192] <Evaluation> The results of evaluation of each test tire by the evaluation methods described below are shown in the corresponding columns of Tables 2 and 3 below.

[0193] <Fuel efficiency index> Using a rolling resistance tester, the rolling resistance of each test tire was measured when it was run under an internal pressure of 230 kPa, a load of 3.43 kN, and a speed of 80 km / h, and the reciprocal of the measured value was expressed as an index, with the reference comparative example (Comparative Example 3) being set at 100. A larger value indicates lower rolling resistance and better fuel economy.

[0194] <Crack resistance performance index> Each test tire is mounted on a standard rim, inflated to the standard air pressure, and the maximum load corresponding to this air pressure is applied according to the air pressure-load capacity correspondence table in the JATMA Year Book. Using a drum-type tire testing machine, the tire is run on the drum at a speed of 80 km / h. The distance traveled is determined when visually noticeable damage occurs. The results are expressed as an index, with the distance traveled for the reference comparative example (Comparative Example 3) being set at 100. A higher index indicates better crack resistance.

[0195] The overall performance index is the sum of the fuel efficiency performance index and the crack resistance performance index.

[0196] [Table 2]

[0197] [Table 3]

[0198] <Embodiment> The following describes a preferred embodiment.

[0199] [1] A tire having a pair of sidewalls on a side portion and a pair of clinch apexes located radially inside the sidewalls and in contact with the rim, The rubber composition constituting the clinch apex contains recycled carbon black, and the amount of recycled carbon black is less than 50 parts by mass, preferably less than 40 parts by mass, and more preferably less than 30 parts by mass, per 100 parts by mass of the rubber component, and the loss tangent at 70°C (70°C tanδ) C is less than 0.25, In a tire meridian cross section including the tire rotation axis, the length of the contact portion between the clinch apex and the sidewall is 5 mm or more and 30 mm or less, preferably 8 mm or more and 30 mm or less, more preferably 8 mm or more and 25 mm or less, even more preferably 8 mm or more and 20 mm or less, and still more preferably 10 mm or more and 25 mm or less, The complex modulus (MPa) 70°C E* of the rubber composition constituting the sidewall at 70°C S is 2.0 or higher, tires. [2] The tire according to [1], wherein the length of the contact portion between the clinch apex and the sidewall is 10 mm or more and 20 mm or less, preferably 12 mm or more and 20 mm or less. [3] 70℃ tanδ C The tire according to [1] or [2], wherein the value is less than 0.20, preferably less than 0.15, more preferably 0.10 or less, even more preferably less than 0.10, and even more preferably 0.07 or less. [4] 70℃E* S The tire according to any one of [1] to [3], wherein the σ is 4.5 or more, preferably 5.0 or more, and more preferably 6.0 or more. [5] 70℃ tanδ C is 0.10 or less, and S is 5.0 or more, preferably, the 70°C tan δ C is 0.07 or less, and S The tire according to any one of [1] to [4], wherein the value is 6.0 or more. [6] The tire according to any one of [1] to [5], wherein the content of the recycled carbon black is less than 20 parts by mass, preferably less than 10 parts by mass, and more preferably 8 parts by mass or less, per 100 parts by mass of the rubber component. [7] The rubber composition constituting the clinch apex contains a rubber component containing more than 20% by mass, preferably more than 25% by mass, more preferably more than 35% by mass, even more preferably more than 45% by mass, and still more preferably 50% by mass or more of isoprene-based rubber, based on 100% by mass of the rubber component; The tire according to any one of [1] to [6], wherein when the content of the isoprene-based rubber in the rubber component is less than 100% by mass, the rubber component contains at least one of a butadiene rubber and a styrene-butadiene rubber, the content of BR is more than 25% by mass, preferably more than 35% by mass, more preferably more than 45% by mass, and even more preferably 50% by mass or more, and the content of SBR-based rubber is more than 10% by mass, preferably more than 20% by mass, and more preferably more than 40% by mass. [8] The tire according to any one of [1] to [7], wherein the rubber composition constituting the sidewall contains more than 30% by mass, preferably more than 40% by mass, more preferably more than 50% by mass, even more preferably 55% by mass or more, and still more preferably 60% by mass or more of butadiene rubber per 100% by mass of the rubber component. [9] The tire according to any one of [1] to [8], wherein the sidewall has a micro-ridge formation portion in which a plurality of micro-ridges are formed on the outer surface.

[10] The tire according to [9], wherein the shape of the micro-protrusions is columnar, frustum or rib-like.

[11] The height of the micro-ridges is 0.03 mm or more, and may be 0.05 mm or more, or 0.10 mm or more, and the height is 0.50 mm or less, or may be 0.45 mm or less, or may be 0.40 mm or less, and 20 or more are formed at intervals of 0.50 mm or less in at least one direction, and the micro-ridge formation portion is 10 mm 2 The tire according to [9] or

[10] , having an area of ​​at least 100 mm.

[12] The tire according to any one of [9] to

[11] , wherein the maximum width of the micro-bumps is 0.03 mm or more, optionally 0.05 mm or more, or optionally 0.10 mm or more, and the maximum width is 5.0 mm or less, optionally 3.00 mm or less, optionally 1.00 mm or less, or optionally 0.50 mm or less.

[13] A tire according to any one of [9] to

[12] , wherein the height of the micro-protrusions gradually increases from the maximum tire width position toward the outer side in the tire radial direction, and gradually increases from the maximum tire width position toward the inner side in the tire radial direction.

[14] When the thickness of the sidewall (mm) is T, T and 70℃ tanδ C The tire according to any one of [1] to

[13] , wherein the relationship of formula (1) is satisfied, A tire in which the right side of formula (1) is preferably 0.75, more preferably 0.70, even more preferably 0.65, even more preferably 0.60, and even more preferably 0.55. (1) T×70℃ tanδ C <0.80

[15] When the carbon black content (parts by mass) of the rubber composition for sidewall is W and the length (mm) of the contact area between the clinch apex and the sidewall is L, the relationship between W, L and 70°C tanδ C The tire according to any one of [1] to

[14] , wherein and satisfy the relationship of formula (2), A tire in which the right side of formula (2) is preferably 5200, more preferably 5400, even more preferably 5600, even more preferably 6000, and even more preferably 10000. (2) W×L / 70℃ tanδ C >5000 [Explanation of symbols]

[0200] 1 tire 2 Sidewall 3 Clinch Apex CL Tire equatorial plane L Length of contact area between sidewall and clinch apex R rim T Sidewall Thickness 11 Sidewall outer surface 12 Microprotuberance 13 Microprotuberance 14 Microprotuberance w Maximum width of the micro-ridge d Spacing of micro-ridges h Micro-ridge height

Claims

1. A tire having a pair of sidewalls on a side portion and a pair of clinch apexes located radially inside the sidewalls and in contact with a rim, The rubber composition constituting the clinch apex contains recycled carbon black and has a loss tangent (70°C tanδ) at 70°C. C is less than 0.25, In a tire meridian cross section including the tire rotation axis, the length of a contact portion between the clinch apex and the sidewall is 5 mm or more and 30 mm or less, Complex modulus of elasticity (MPa) 70°C E* of the rubber composition constituting the sidewall S A tire having a tread area of ​​2.0 or greater.

2. The tire according to claim 1, wherein a length of a contact portion between the clinch apex and the sidewall is 10 mm or more and 20 mm or less.

3. The 70°C tan δ C 3. The tire of claim 1 or 2, wherein the ρ is less than 0.

20.

4. The 70°C E* S 3. The tire according to claim 1, wherein the tread width is 4.5 or more.

5. The 70°C tan δ C is 0.10 or less, and the 70°C E* S 3. The tire according to claim 1, wherein the tread width is 5.0 or more.

6. The tire according to claim 1 or 2, wherein an amount of the recycled carbon black is less than 20 parts by mass per 100 parts by mass of the rubber component.

7. the rubber composition constituting the clinch apex includes a rubber component containing more than 20% by mass of an isoprene-based rubber based on 100% by mass of the rubber component, The tire according to claim 1 or 2, wherein when the content of the isoprene-based rubber in the rubber component is less than 100% by mass, the rubber component contains at least one of a butadiene rubber and a styrene-butadiene rubber.

8. The tire according to claim 1 or 2, wherein the rubber composition constituting the sidewall contains more than 40% by mass of butadiene rubber based on 100% by mass of the rubber component.

9. The tire according to claim 1 or 2, wherein the sidewall has a micro-ridge formation portion in which a plurality of micro-ridges are formed on an outer surface.

10. 10. The tire of claim 9, wherein the micro-ridges have a pillar-like, frustum-like or rib-like shape.

11. The micro-ridges have a height of 0.03 mm or more and 0.50 mm or less, and 20 or more are formed at intervals of 0.50 mm or less in at least one direction, and the micro-ridge formation portion is 10 mm 2 10. The tire of claim 9, having an area of ​​at least

12. The tire of claim 9, wherein the maximum width of the micro-bumps is 0.03 mm or greater and 5.0 mm or less.

13. 10. The tire of claim 9, wherein the height of the micro-bumps gradually increases from the maximum tire width location toward the tire radially outward and gradually increases from the maximum tire width location toward the tire radially inward.

14. When the thickness of the sidewall (mm) is T, the difference between T and 70°C tan δ C The tire according to claim 1 or 2, wherein the relationship of formula (1) is satisfied. (1) T×70℃tanδ C <0.80

15. When the carbon black content (parts by mass) of the rubber composition for the sidewall is W and the length (mm) of the contact portion between the clinch apex and the sidewall is L, the relationship between W and L at 70°C tan δ is C The tire according to claim 1 or 2, wherein and satisfy the relationship of formula (2). (2) W×L / 70℃tanδ C >5000

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