tire

Abstract

This product provides a tire with improved fuel efficiency, wet grip performance, wear resistance, and wet grip performance in the later stages of wear. [Solution] A tire 1 having a tread portion 2 made of a rubber composition containing isoprene rubber and styrene-butadiene rubber, wherein the vinyl content of the styrene-butadiene rubber is greater than 26 mol%, the ash content A of the rubber composition is greater than 25%, the tread portion has two or more circumferential main grooves 8A, 8B, 8C extending in the circumferential direction of the tire, and land portions defined by the circumferential main grooves, at least one of the land portions has at least one flask-shaped circumferential groove 9A, 9B extending in the circumferential direction of the tire, and the flask-shaped circumferential groove includes a neck portion with a narrow groove width and a body portion that is located radially inward from the neck portion and has a groove width greater than the maximum groove width of the neck portion.

Description

[Technical Field]

[0001] This invention relates to a tire with significantly improved fuel efficiency, wet grip performance, wear resistance, and wet grip performance in the later stages of wear. [Background technology]

[0002] A known technique for improving the wear resistance of truck and bus tires involves micronizing or highly structuring carbon black (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-279624 [Overview of the project] [Problems that the invention aims to solve]

[0004] The methods described above for micronizing or increasing the structure of carbon black are not sufficient to improve the fuel efficiency of tires. Furthermore, the deterioration of processability due to micronization can worsen the dispersibility of carbon black, which can conversely worsen the wear resistance of tires. Therefore, there were limitations to conventional methods of improving performance through the modification of carbon black.

[0005] Furthermore, due to the impact of recent environmental regulations, there is a growing demand for truck and bus tires not only for wear resistance but also for fuel efficiency, wet grip performance, and other factors.

[0006] The present invention aims to provide a tire with significantly improved fuel efficiency, wet grip performance, wear resistance, and wet grip performance in the later stages of wear. [Means for solving the problem]

[0007] As a result of diligent research, the inventors have found that the above problems can be solved in a tire having a tread portion made of a rubber composition containing isoprene rubber and styrene-butadiene rubber with a predetermined vinyl content, by setting the ash content to a predetermined amount or more and forming predetermined flask-shaped circumferential grooves on any land portion of the tread portion. Further research has led to the completion of the present invention.

[0008] In other words, the present invention relates to the following tires. A tire having a tread portion made of a rubber composition containing rubber components including isoprene rubber and styrene-butadiene rubber, The vinyl content of the styrene-butadiene rubber is more than 26 mol%, The ash content A of the aforementioned rubber composition is greater than 25%, as defined by the following formula. The tread portion has two or more circumferential main grooves extending in the circumferential direction of the tire, and a land area defined by the circumferential main grooves, At least one of the aforementioned land portions has at least one flask-shaped circumferential groove extending in the circumferential direction of the tire, A tire in which the flask-shaped circumferential groove includes a neck portion with a narrow groove width and a body portion that is positioned inward from the neck portion in the tire radial direction and has a groove width greater than the maximum groove width of the neck portion. A = (m² / m¹) × 100 (Here, m1 is the mass of the residue obtained by immersing a test piece of the rubber composition in acetone for 72 hours in accordance with JIS K 6229 to extract the soluble components, and then heating the extracted test piece in nitrogen from room temperature to 750°C in accordance with JIS K 6226-1:2003 to thermally decompose and vaporize the organic matter; and m2 is the mass of the residue after oxidative combustion of the residue (mass m1) after thermal decomposition and vaporization by heating in air in accordance with JIS K 6226-1:2003.) [Effects of the Invention]

[0009] According to the present invention, there is provided a tire in which low fuel consumption performance, wet grip performance, wear resistance performance, and wet grip performance in the later stage of wear are well improved.

Brief Description of the Drawings

[0010] [Figure 1] It is a meridian cross-sectional view of a tire according to an embodiment of the present invention. [Figure 2] It is a developed view of the tread portion of the tire of FIG. 1. [Figure 3] It is a cross-sectional view showing an enlarged view of the flask-shaped circumferential groove of FIGS. 1 and 2. [Figure 4] It is a cross-sectional view showing an enlarged view of a modified example of the flask-shaped circumferential groove.

Modes for Carrying Out the Invention

[0011] The present invention is a tire having a tread portion composed of a rubber composition containing a rubber component containing isoprene rubber and styrene-butadiene rubber, wherein the vinyl content of the styrene-butadiene rubber is more than 26 mol%, and the ash content ratio A defined by the following formula of the rubber composition is more than 25%. The tread portion has two or more circumferential main grooves extending in the tire circumferential direction and land portions defined by the circumferential main grooves. At least one of the land portions has at least one flask-shaped circumferential groove extending in the tire circumferential direction. The flask-shaped circumferential groove includes a neck portion with a narrow groove width and a body portion disposed inside the neck portion in the tire radial direction and having a groove width larger than the maximum groove width of the neck portion. A = (m2 / m1) × 100 (Here, m1 is the mass of the residue obtained by immersing a test piece of the rubber composition in acetone for 72 hours in accordance with JIS K 6229 to extract soluble components, and then thermally decomposing and vaporizing organic substances by heating from room temperature to 750 ° C in nitrogen in accordance with JIS K 6226-1: 2003. m2 is the mass of the residue after oxidative combustion by heating in air in accordance with JIS K 6226-1: 2003 of the residue (mass m1) after the thermal decomposition and vaporization.)

[0012] While not intended to be constrained by theory, the following mechanisms are conceivable for improving the tire's fuel efficiency, wet grip performance, wear resistance, and wet grip performance in the later stages of wear in this invention.

[0013] In other words, the rubber composition constituting the tread portion of the tire of the present invention contains rubber components including isoprene rubber and styrene-butadiene rubber with a predetermined vinyl content, and the ash content is above a predetermined amount. Here, the ash content generally indicates the amount of silica in the filler. Such a rubber composition is expected to contribute to wet grip performance because (a) the inclusion of isoprene rubber and styrene-butadiene rubber in the rubber components results in a relatively high glass transition temperature (Tg) of the rubber components, (b) isoprene rubber and styrene-butadiene rubber are compatible with silica, improving silica dispersion during the mixing process and the immobilization of silica to the polymer, resulting in a smaller hysteresis loss (tanδ) in the temperature range that contributes to low fuel consumption (high temperature range such as 70°C), thus contributing to fuel efficiency, and (c) the vinyl content of the styrene-butadiene rubber is above a certain level, contributing to an improvement in the Tg of the styrene-butadiene rubber and improving the co-crosslinking properties with isoprene rubber, thus improving wear resistance. However, generally, compounding with a high silica ratio results in a lower modulus of elasticity, which may reduce the rigidity of the tire tread. For this reason, measures such as increasing the LAND / SEA ratio (i.e., reducing the proportion of SEA (grooves)) are taken to improve pattern rigidity, but a decrease in the proportion of grooves leads to a decrease in wet grip performance. This effect becomes more pronounced as the tire wears in its later stages. Therefore, (d) by adopting flask-shaped circumferential grooves (so-called flask grooves) in one of the land areas of the tread as a structure that functions similarly to grooves in the later stages of wear, it is expected that the decrease in wet grip in the later stages of wear can be compensated for.

[0014] It is believed that the combined efforts of (a) to (d) above result in significant improvements in fuel efficiency, wet grip performance, wear resistance, and wet grip performance in the later stages of wear.

[0015] The minimum groove width W1 of the neck portion is preferably 1 to 2 mm. When W1 is 1 mm or more, water flows more easily from the neck portion to the body portion during wet driving, ensuring sufficient drainage performance. On the other hand, when W1 is 2 mm or less, in the initial stages of wear, when a load is applied to the tread portion, the neck portion is more likely to close due to the ground pressure, thereby increasing the axial rigidity of the tread portion.

[0016] The maximum groove width W2 of the body is preferably 2 to 12 mm. When W2 is 2 mm or more, the groove width of the flask-shaped circumferential grooves can be easily maintained even in the final stages of wear, making it easy to ensure sufficient drainage performance. On the other hand, when W2 is 12 mm or less, the rubber volume of the tread can be easily maintained, contributing to improved wear resistance.

[0017] The maximum groove width W2 of the body is preferably 2 to 6 times the minimum groove width W1 of the neck. When W2 is twice or more than W1, the groove width of the flask-shaped circumferential grooves can be easily secured even in the final stages of wear, making it easy to ensure sufficient drainage performance. On the other hand, when W2 is six times or less than W1, the rubber volume of the tread can be easily secured, improving wear resistance.

[0018] Preferably, the depth H1 of the flask-shaped circumferential groove in the tire meridian cross-section and the distance H2 from the groove bottom to the neck portion satisfy the following relationship. When H2 / H1 is 1 / 3 or more, the groove volume of the body portion is easily secured, making it possible to easily ensure sufficient drainage performance in the final stages of wear, while when H2 / H1 is 2 / 3 or less, the rigidity of the tread portion in the tire axial direction is increased in the initial stages of wear. 1 / 3 ≤ H2 / H1 ≤ 2 / 3

[0019] Preferably, the flask-shaped circumferential groove is positioned further outward in the tire radial direction than the neck portion and includes an opening in which the groove width tapers outward toward the outside in the tire radial direction. This is because the opening in which the groove width tapers increases the volume of the flask-shaped circumferential groove in the initial stages of wear, increasing the amount of water flowing from the neck portion to the body portion, thereby improving the drainage performance of the tread portion.

[0020] The aforementioned rubber composition preferably contains silica, as this allows the effects of the present invention to be achieved.

[0021] The specific surface area of ​​silica for nitrogen adsorption is 175 m². 2 It is preferable that the value be 1 / g or more, because this is necessary for the effects of the present invention to be realized.

[0022] The aforementioned rubber composition preferably contains carbon black. This is because using carbon black in combination with silica provides a well-balanced reinforcement of the isoprene-based rubber and styrene-butadiene rubber. Furthermore, carbon black has a high capacity to absorb ultraviolet light, which can suppress the degradation of the rubber due to ultraviolet radiation.

[0023] The styrene content of the styrene-butadiene rubber is preferably 24% by mass or less. This is because increasing the Tg by increasing the vinyl content is more effective in achieving the effects of the present invention than increasing the styrene content.

[0024] The rubber composition preferably contains 0.5 to 5.0 parts by mass of zinc oxide. This is because the ash ratio more clearly indicates the proportion of silica in the filler.

[0025] The aforementioned tire is preferably designed for heavy loads, as this allows for full utilization of the effects of the present invention.

[0026] In this invention, the upper and lower numerical limits indicated by "greater than or equal to," "less than or equal to," and "~" in the description of a numerical range are numbers that can be arbitrarily combined, and in addition, the numerical values ​​in the examples can also be combined with these upper and lower limits. Furthermore, when a numerical range is specified by "~", unless otherwise specified, it means that the numerical values ​​at both ends are included. Moreover, in this invention, a numerical range indicated as including the values ​​at both ends is understood to simultaneously indicate a numerical range that does not include either of the values ​​at both ends, and even a numerical range that does not include either of the values ​​at both ends, as long as this does not contradict the spirit of this invention.

[0027] [Definition] A "standard rim" is the rim specified for each tire within the standardization system that includes the standard on which the tire is based. For example, it is called a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO.

[0028] "Regular internal pressure" refers to the air pressure specified for each tire by each standard within the tire standard system, including the standard on which the tire is based. For example, it is the "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO.

[0029] "Normal condition" refers to a state in which the tire is mounted on a normal rim, filled to the normal internal pressure, and unloaded. In this specification, unless otherwise specified, the dimensions and angles of each part of the tire are measured in the above-mentioned normal condition. If there are patterns or letters on the side of the tire, these patterns or letters are treated as if they were not present during measurement.

[0030] "Regular load" refers to the load specified for each tire by each standard within the standards system that the tire is based on. For example, it is the "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO.

[0031] The "tread contact point" refers to the outermost contact point in the tire's width direction when a tire in its normal state is subjected to a normal load, with a camber angle of 0 degrees, and making contact with a flat surface (TE1, TE2).

[0032] "Tread contact width" refers to the distance (TW) in the axial direction between the tread contact edges TE1 and TE2.

[0033] "Circumferential main grooves" refer to grooves that extend continuously in the circumferential direction of the tire and have a width of 3.0 mm or more on the tread surface.

[0034] A "flask-shaped circumferential groove" is a groove that extends in the circumferential direction of the tire, and includes a neck portion with a narrow groove width and a body portion that is located radially inward from the neck portion and has a groove width greater than the maximum groove width of the neck portion. Here, "a body portion having a groove width greater than the maximum groove width of the neck portion" means that the body portion is configured to have a portion that is wider than the maximum groove width of the neck portion. Therefore, the maximum groove width of the neck portion is smaller than the maximum groove width of the body portion, and in this sense, the groove width of the neck portion is narrow.

[0035] The term "land area" refers to the region on the tread surface defined by the circumferential main grooves. The pair of land areas located on the tread contact edge are called the "shoulder land area," and the land area inside the shoulder land area is called the "center land area."

[0036] A "lateral groove" refers to a groove carved into the surface of a tire with a width of 2.0 mm or more, where the edge component in the tire width direction is larger than the edge component in the tire circumferential direction.

[0037] A "sipe" is a groove less than 2.0 mm wide carved into the surface of a tire, in which the edge component in the tire width direction is larger than the edge component in the tire circumference direction.

[0038] [Measurement method] (ash content ratio) It is defined by the following formula. A = (m² / m¹) × 100 (Here, m1 is the mass of the residue obtained after extracting soluble components by immersing a test piece of the rubber composition in acetone for 72 hours in accordance with JIS K 6229, and then thermally decomposing and vaporizing the organic matter by heating the extracted test piece in nitrogen from room temperature to 750°C in accordance with JIS K 6226-1:2003, and m2 is the mass of the residue after oxidative combustion of the residue (mass m1) after thermal decomposition and vaporization by heating in air in accordance with JIS K 6226-1:2003.)

[0039] "Styrene content" is, 1 This value is calculated by 1H-NMR measurement and is applied, for example, to rubber components having repeating units derived from styrene, such as SBR.

[0040] "Vinyl content (amount of 1,2-bonded butadiene units)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017, and is applied to rubber components having repeating units derived from butadiene, such as SBR and BR.

[0041] "Cis content (cis-1,4-bond content)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017, and is applied, for example, to rubber components having repeating units derived from butadiene, such as BR.

[0042] "Tg" is a value determined by differential scanning calorimetry (DSC) in accordance with JIS K 7121, and is applied to SBR, for example.

[0043] The "weight-average molecular weight (Mw)" can be determined by converting the measured value using gel permeation chromatography (GPC) (for example, the GPC-8000 series from Tosoh Corporation, with a differential refractometer as the detector and TSKGEL SUPERMALTIPORE HZ-M column from Tosoh Corporation) to a standard polystyrene equivalent. This method is applicable, for example, to SBR, BR, etc.

[0044] The N2SA rating of carbon black is measured in accordance with JIS K 6217-2:2017.

[0045] The N2SA content of silica is measured by the BET method in accordance with ASTM D3037-93.

[0046] [tire] A tire, which is one embodiment of the present invention, will be described below with reference to the drawings as appropriate. However, the drawings used are merely specific examples of one embodiment, and the present invention is not limited by these drawings.

[0047] The tire of the present invention has a tread portion having two or more circumferential main grooves extending in the circumferential direction of the tire, and a land portion defined by the circumferential main grooves, wherein at least one of the land portions has at least one flask-shaped circumferential groove extending in the circumferential direction of the tire, and the flask-shaped circumferential groove includes a neck portion with a narrow groove width and a body portion that is located inward from the neck portion in the radial direction of the tire and has a groove width greater than the maximum groove width of the neck portion.

[0048] Figure 1 is a meridional cross-sectional view of the tire 1 of this embodiment, including the tire rotation axis (not shown) in its normal state. The tire 1 includes a tread portion 2, a pair of sidewall portions 3, a pair of bead portions 4, a pair of bead cores 5, a carcass layer 6, and a belt layer 7. The tread portion 2 has three circumferential main grooves 8A, 8B, and 8C and two flask-shaped circumferential grooves 9A and 9B. The distance between the tread contact edges TE1 and TE2 is the tread contact width TW.

[0049] Figure 2 shows the tread portion 2 of the tire 1 of this embodiment. The tread portion 2 has circumferential main grooves 8A, 8B, and 8C extending in the circumferential direction of the tire, as well as flask-shaped circumferential grooves 9A and 9B extending in the circumferential direction of the tire. In the land area defined by the circumferential main grooves, transverse grooves and sipes extending in the tire width direction are formed. Specifically, in the land area, a pair of shoulder land areas 20 and 50 defined by the outermost circumferential main groove (outermost circumferential main groove) 8A or 8C located in the tire width direction have shoulder sipes 21 and shoulder transverse grooves 22, and shoulder sipes 51 and shoulder transverse grooves 52, respectively. A center sipe 31 is formed in the center land area 30 defined by circumferential main grooves 8A and 8B, and a center sipe 41 is formed in the center land area 40 defined by circumferential main grooves 8B and 8C. Furthermore, a flask-shaped circumferential groove 9A is formed in the center land area 30, and a flask-shaped circumferential groove 9B is formed in the center land area 40.

[0050] In Figure 2, three circumferential main grooves, 8A, 8B, and 8C, are formed. However, in this invention, there may be two or more circumferential main grooves, four, five, or even six or more. Furthermore, in all of the circumferential main grooves 8A, 8B, and 8C, the center line in the width direction of each circumferential main groove extends in a zigzag pattern while laterally deflecting. Here, "extending in a zigzag pattern" means that the center in the width direction of the circumferential main groove extends in the tire circumferential direction while deflecting in the tire width direction. Therefore, in addition to a form in which straight grooves repeatedly bend, a form in which curved grooves repeatedly curve in a wave-like pattern is also included. However, the circumferential main grooves may be straight as well as zigzag.

[0051] In Figure 2, flask-shaped circumferential grooves 9A are formed on the center land portion 30 and 9B is formed on the center land portion 40, respectively. However, in the present invention, it is sufficient for at least one flask-shaped circumferential groove to be formed on at least one land portion. Therefore, it is sufficient for one to be formed on any one land portion, or two or more to be formed on a single land portion. Furthermore, it is sufficient for at least one land portion to have one or more flask-shaped circumferential grooves formed in this way, and there may be two or even three or more such land portions. There are no particular limitations on the land portion on which the flask-shaped circumferential groove is formed, but it is preferable for it to be formed on the center land portion sandwiched between two outermost main grooves, and in particular, it is preferable for it to be formed near the midpoint between the tire centerline and the outermost main groove. This is because the area near the tire centerline has the highest ground pressure, and it is preferable that grooves do not appear even in the later stages of wear, thus maintaining high rigidity. However, from the viewpoint of ensuring drainage performance in the later stages of wear, it is preferable for grooves to appear near the midpoint between the tire centerline and the outermost main groove in each region of the tread surface separated by the tire centerline. Furthermore, the flask-shaped circumferential grooves may be zigzag-shaped, similar to the circumferential main grooves, or they may be straight.

[0052] In Figure 2, the cross-section of the flask-shaped circumferential groove exhibits a flask shape. Due to this cross-sectional shape, even when a large load is applied to the tread portion 2, the stress on the side wall of the land portion is relieved.

[0053] In this embodiment, when the tire is new, or in the initial stages of wear of the tread portion 2, the portion of the flask-shaped circumferential groove that appears on the tread surface is the neck portion. This neck portion can be closed by the load applied to the tread portion 2, thereby increasing the rigidity of the tread portion 2 in the tire axial direction. On the other hand, as wear of the tread portion 2 progresses, the tread surface moves inward in the tire radial direction, and the opening of the flask-shaped circumferential groove shifts from the neck portion to the body portion. Therefore, as wear progresses, the width of the flask-shaped circumferential groove expands, and the drainage performance of the tread portion 2 is maintained at a high level in the later stages of wear.

[0054] In this embodiment, the tread 2 exhibits a 4-rib tread pattern when new, due to the three circumferential main grooves. In the later stages of wear, the bodies of the two flask-shaped circumferential grooves become visible on the tread surface, resulting in a 6-rib tread pattern.

[0055] Figure 3 shows a magnified view of the flask-shaped circumferential groove 9 (9A, 9B). The flask-shaped circumferential groove has a neck portion 11 and a body portion 12 that is located inward from the neck portion in the tire radial direction and has a groove width greater than the maximum groove width of the neck portion. In Figure 3, the groove width of the neck portion is fixed and constant at its minimum groove width W1, but the neck portion may have a portion with a groove width greater than W1, as long as it exhibits the effects of the present invention. Therefore, the cross-sectional shape of the neck portion may be linear as shown in Figure 3, or it may be zigzag. Here, zigzag has the same meaning as described above. One preferred embodiment is one in which the groove width of the neck portion is constant at its minimum groove width.

[0056] Furthermore, the body portion 12 has a portion with a groove width greater than the maximum groove width of the neck portion. Here, "having a portion with a groove width greater than the maximum groove width of the neck portion" means that the body portion is configured to be wider than the maximum groove width of the neck portion so that the effects of the present invention can be achieved. Therefore, the groove width of the body portion is not particularly limited as long as it includes a portion that is wider than the maximum groove width of the neck portion so that the effects of the present invention can be achieved. For example, a portion of the groove width of the body portion may be narrower than the maximum groove width of the neck portion, or the body portion may be configured to consist only of a portion with a groove width greater than the groove width of the neck portion. In Figure 3, the body portion 12 is composed only of a portion with a groove width greater than the groove width of the neck portion 11, since the groove width of the neck portion 11 is fixed at its minimum groove width W1.

[0057] The minimum groove width W1 of the neck is preferably 1 to 2 mm. When W1 is 1 mm or more, water flows more easily from the neck to the body during wet driving, making it easy to ensure sufficient drainage performance. On the other hand, when W1 is 2 mm or less, in the initial stages of wear, when a load is applied to the tread portion 2, the neck is more likely to close due to the contact pressure, increasing the rigidity of the tread portion 2 in the tire axial direction. In addition, the rubber volume of the tread portion 2 is easily ensured. As a result, the wear resistance performance of the tire 1 is improved. W1 is preferably 1.1 mm or more, more preferably 1.2 mm or more, while W1 is preferably 1.9 mm or less, and more preferably 1.8 mm or less.

[0058] The maximum groove width W2 of the body is preferably 2 to 12 mm. When the maximum groove width W2 is 2 mm or more, the width of the flask-shaped circumferential groove 9 can be easily maintained even in the final stages of wear, making it easy to ensure sufficient drainage performance. On the other hand, when the maximum groove width W2 is 12 mm or less, the rubber volume of the tread portion 2 can be easily maintained. This improves the wear resistance performance of the tire 1. W2 is preferably 3 mm or more, more preferably 4 mm or more, while W2 is preferably 11 mm or less, more preferably 10 mm or less.

[0059] The above W2 is preferably 2 to 6 times the above W1. When the above W2 is 2 times or more the above W1, the width of the flask-shaped circumferential groove 9 can be easily secured even in the final stages of wear, and sufficient drainage performance can be easily secured. When the above W2 is 6 times or less the above W1, the rubber volume of the tread portion 2 can be easily secured. This improves the wear resistance performance of the tire 1. The above W2 is preferably 2.5 times or more the above W1, more preferably 3 times or more, while the above W2 is preferably 5.5 times or less the above W1, and more preferably 5 times or less.

[0060] In the flask-shaped circumferential groove 9 of this embodiment, it is more preferable that W1 is 1 mm or more, W2 is 2 mm or more, and W2 is at least twice the size of W1. Such flask-shaped circumferential groove 9 makes it easy to ensure sufficient drainage performance even in the final stages of wear. Furthermore, in the tread portion 2, it is preferable that W1 is 2 mm or less, W2 is 12 mm or less, and W2 is at least six times the size of W1. Such flask-shaped circumferential groove 9 makes it easy to ensure sufficient rubber volume in the tread portion 2, improving the wear resistance of the tire 1.

[0061] The depth H1 of the flask-shaped circumferential groove 9 and the minimum length H2 in the radial direction of the tire from the bottom of the flask-shaped circumferential groove 9 to the neck portion preferably satisfy the following relationship. 1 / 3 ≤ H2 / H1 ≤ 2 / 3

[0062] When the above H2 / H1 ratio is 1 / 3 or more, the groove volume of the body is easily secured, making it possible to easily ensure sufficient drainage performance even in the final stages of wear. When the above H2 / H1 ratio is 2 / 3 or less, the rigidity of the tread portion 2 in the tire axial direction is increased in the initial stages of wear. In addition, the rubber volume of the tread portion 2 is easily secured. As a result, the wear resistance performance of the tire 1 is improved.

[0063] In the flask-shaped circumferential groove 9 of this embodiment, more preferably, W2 is 2 to 6 times the size of W1, and has a cross-sectional shape that satisfies the relationship 1 / 3 ≤ H2 / H1 ≤ 2 / 3. When W2 is 2 times or more the size of W1, and H2 / H1 is 1 / 3 or more, it is possible to easily ensure sufficient drainage performance at the end of wear. When W2 is 6 times or less the size of W1, and H2 / H1 is 2 / 3 or less, the rubber volume of the tread portion 2 is easily ensured, and the wear resistance performance of the tire 1 is improved.

[0064] Figure 4 shows a modified example of the flask-shaped circumferential groove. For this modified example, the configuration of the flask-shaped circumferential groove 9 described above may be adopted for parts not described below.

[0065] In Figure 4, the flask-shaped circumferential groove includes an opening (tapered section) on the radially outer side of the neck portion of the tire, where the groove width tapers. The tapered section increases the volume of the flask-shaped circumferential groove in the initial stages of wear. The tapered section also increases the amount of water flowing from the neck portion to the body portion. This improves the drainage performance of the tread portion 2.

[0066] Preferably, the maximum groove width W2 of the body is greater than the maximum groove width W3 of the tapered section. This makes it easy to secure the groove volume of the flask-shaped circumferential grooves in the body, and makes it easy to ensure sufficient drainage performance at the end of wear of the tread section 2.

[0067] [Rubber composition] The tire of the present invention has a tread portion, and the tread portion is composed of a rubber composition containing isoprene rubber and styrene-butadiene rubber, and the ash content A of the rubber composition is greater than 25%.

[0068] <Ash content ratio A> The ash content ratio A is given by the following formula: A = (m² / m¹) × 100 (Here, m1 is the mass of the residue obtained by immersing a test piece of the rubber composition in acetone for 72 hours in accordance with JIS K 6229 to extract the soluble components, and then heating the extracted test piece in nitrogen from room temperature to 750°C in accordance with JIS K 6226-1:2003 to thermally decompose and vaporize the organic matter; and m2 is the mass of the residue after oxidative combustion of the residue (mass m1) after thermal decomposition and vaporization by heating in air in accordance with JIS K 6226-1:2003.)

[0069] m1 is the mass of the residue obtained after removing acetone-soluble components by subjecting a test piece of the rubber composition to so-called acetone extraction in accordance with JIS K 6229, and then further heating the extracted test piece in nitrogen in accordance with JIS K 6226-1:2003 to thermally decompose and vaporize mainly the polymer components. m2 is the mass of the residue obtained after further heating the above residue in air in accordance with JIS K 6226-1:2003 to oxidize and burn mainly the carbon black. Therefore, under the formulation as shown in the examples herein, A generally represents the ratio (%) of the amount of silica and zinc oxide to the total amount of silica, carbon black, and zinc oxide.

[0070] From the viewpoint of the effects of the present invention, the ash content ratio A is preferably 26% or more, more preferably 29% or more, even more preferably 37% or more, even more preferably 60% or more, even more preferably 80% or more, and even more preferably 90% or more. The ash content ratio A may also be 100% by mass.

[0071] As described above, under the formulations shown in the examples of this specification, the ash content ratio A generally represents the ratio (%) of the amount of silica and zinc oxide (mass m2) to the total amount of silica, carbon black, and zinc oxide (mass m1). Therefore, it can be increased, for example, by reducing the amount of carbon black or increasing the amounts of silica and zinc oxide, and conversely, it can be decreased by increasing the amount of carbon black or decreasing the amounts of silica and zinc oxide.

[0072] <Rubber components> The rubber component contains isoprene rubber and styrene-butadiene rubber (SBR). Therefore, the rubber component may contain isoprene rubber and SBR, and may also contain other rubber components, or it may consist only of isoprene rubber and SBR.

[0073] (Isoprene rubber) As isoprene-based rubbers, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. Natural rubber includes not only unmodified natural rubber (NR), but also modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), and grafted natural rubber. These isoprene-based rubbers may be used individually or in combination of two or more types.

[0074] NR is not particularly limited and can be any tire that is common in the tire industry, such as SIR20, RSS#3, and TSR20.

[0075] In the rubber composition, the content of isoprene-based rubber in the rubber component is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 60% by mass or more, and even more preferably 65% ​​by mass or more. Since silica has good affinity with isoprene-based rubber, increasing the content of silica in the rubber component of isoprene-based rubber and dispersing silica in the isoprene-based rubber phase, which forms the marine phase, tends to improve the overall strength of the matrix, and further improve the abrasion resistance and fracture characteristics. On the other hand, from the viewpoint of wet grip performance, 95% by mass or less is preferred, 90% by mass or less is more preferred, 85% by mass or less is even more preferred, and 80% by mass or less is particularly preferred.

[0076] (SBR) There are no particular limitations on the SBR; both solution-polymerized SBR (S-SBR) and emulsion-polymerized SBR (E-SBR) can be suitably used, but S-SBR is preferred from the viewpoint of the effects of the present invention. Furthermore, modified SBRs (modified S-SBR, modified E-SBR) can be used as SBRs. Examples of modified SBRs include SBRs in which the terminals and / or main chain are modified, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, those having branched structures, etc.). These SBRs may be used individually or in combination of two or more types.

[0077] SBR exhibits excellent viscoelastic properties in the region highly correlated with wet grip performance, and its compatibility and responsiveness with silica are excellent, making it likely to be effective in improving wet grip performance and wear resistance.

[0078] The styrene content of SBR is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 9% by mass or more, from the viewpoint of wet grip performance and abrasion resistance. Furthermore, from the viewpoint of temperature dependence of grip performance and abrasion resistance, it is preferably 24% by mass or less, more preferably 18% by mass or less, and even more preferably 16% by mass or less. In this specification, the styrene content of SBR is as follows: 1 It is calculated by 1H-NMR measurement.

[0079] The vinyl content of SBR is greater than 26 mol%. If the vinyl content is less than 26 mol%, the wet grip performance and abrasion resistance cannot be fully exhibited. The vinyl content is preferably 27 mol% or more, more preferably 28 mol% or more, even more preferably 29 mol% or more, and still more preferably 30 mol% or more. Furthermore, from the viewpoint of wet grip performance and abrasion resistance, the vinyl content of SBR is preferably 45 mol% or less, more preferably 44 mol% or less, even more preferably 43 mol% or less, and still more preferably 42 mol% or less. In this specification, the vinyl content of SBR (amount of 1,2-bonded butadiene units) is measured by infrared absorption spectroscopy.

[0080] From the viewpoint of wet grip performance, the glass transition temperature (Tg) of SBR is preferably -80°C or higher, more preferably -70°C or higher, and even more preferably -65°C or higher. From the viewpoint of low fuel consumption performance, the Tg of SBR is preferably -40°C or lower, more preferably -45°C or lower, even more preferably -50°C or lower, and even more preferably -55°C or lower. In this specification, the Tg of SBR is determined in accordance with JIS K 6229, after removing the spreading oil using acetone, and the pure SBR content is determined by differential scanning calorimetry (DSC) in accordance with JIS K 7121.

[0081] The weight-average molecular weight (Mw) of SBR is preferably 100,000 or more, more preferably 150,000 or more, and even more preferably 190,000 or more, from the viewpoint of abrasion resistance. Furthermore, from the viewpoint of crosslinking uniformity, Mw is preferably 2,500,000 or less, more preferably 2,000,000 or less, and even more preferably 1,000,000 or less. Mw can be determined by converting the measured value by gel permeation chromatography (GPC) (for example, the GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation) to standard polystyrene equivalent.

[0082] When SBR is included, its content in the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and even more preferably 20% by mass or more, from the viewpoint of abrasion resistance and wet grip performance. Furthermore, from the viewpoint of abrasion resistance performance, the content is preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, and even more preferably 25% by mass or less.

[0083] (Other rubber components) The rubber component of the present invention may include rubber components other than the isoprene-based rubber and SBR mentioned above. Other rubber components that can be crosslinked are commonly used in the tire industry, and examples include butadiene rubber, styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isobutylene-styrene block copolymer (SIBS), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), ethylene propylene rubber, polynorbornene rubber, silicone rubber, polyethylene chloride rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, and the like. These other rubber components may be used individually or in combination of two or more.

[0084] BR is not particularly limited, and for example, BR with a cis content of less than 50% by mass (low-cis BR), BR with a cis content of 90% by mass or more (high-cis BR), rare-earth butadiene rubber synthesized using a rare-earth element catalyst (rare-earth BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc., which are common in the tire industry, can be used. These BRs may be used individually or in combination of two or more. The cis content of BR is a value calculated by infrared absorption spectroscopy.

[0085] When BR is included, its content in the rubber component is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and may even be 0% by mass, from the viewpoint of the effects of the present invention.

[0086] <Filler> The tread rubber composition according to the present invention preferably contains a filler comprising carbon black and / or silica. Alternatively, the filler may consist only of carbon black and silica. The filler preferably contains silica, more preferably contains carbon black and silica, or may consist only of carbon black and silica.

[0087] (silica) By incorporating silica into the tread rubber composition according to the present invention, fuel efficiency, wet grip performance, wear resistance, and other properties can be improved. The silica is not particularly limited; for example, silica prepared by a dry process (anhydrous silica) and silica prepared by a wet process (hydrated silica), which are common in the tire industry, can be used. Among these, hydrated silica prepared by a wet process is preferred because it contains a large number of silanol groups. These silicas may be used individually or in combination of two or more types.

[0088] The nitrogen adsorption specific surface area (N2SA) of silica is 130 m², from the viewpoint of wear resistance and fracture characteristics. 2Preferably, it is above / g, and 150 m 2 Preferably, it is above / g, and more preferably 170 m 2 Preferably, it is above / g, and even more preferably 175 m 2 Preferably, it is above / g, and even more preferably 185 m 2 Preferably, it is above / g, and even more preferably 195 m 2 Preferably, it is above / g. Also, from the perspective of processability, N2SA is preferably 500 m 2 / g or less, and more preferably 350 m 2 / g or less, and even more preferably 300 m 2 / g or less, and even more preferably 250 m 2 / g or less. Note that the N2SA of silica in this specification is a value measured by the BET method in accordance with ASTM D3037-93.

[0089] From the perspective of the balance between low fuel consumption performance and wet grip performance, the content of silica is preferably 8 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 12 parts by mass or more with respect to 100 parts by mass of the rubber component. Also, from the perspective of processability, the content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 80 parts by mass or less, and even more preferably 60 parts by mass or less.

[0090] (Carbon black) The carbon black is not particularly limited. For example, those commonly used in the tire industry such as GPF, FEF, HAF, ISAF, SAF, etc. can be used. These carbon blacks may be used alone or in combination of two or more.

[0091] The nitrogen adsorption specific surface area (N2SA) of the carbon black is preferably 50 m 2 / g or more from the perspective of weather resistance and reinforcement, and 80 m 2 / g or more is more preferable, and 100 m 2 / g or more is even more preferable. Also, N2SA is preferably 250 m 2 / g or less from the perspective of dispersibility, low fuel consumption performance, fracture characteristics, and durability, and 220 m 2 / g or less is more preferable, and 180 m2 More preferably less than / g, and 150m 2 A value of less than or equal to / g is even more preferable. Note that the N2SA of carbon black as used herein is the value measured according to Method A of JIS K 6217-2:2017.

[0092] From the viewpoint of weather resistance and reinforcing properties, the carbon black content per 100 parts by mass of rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more. Furthermore, from the viewpoint of low fuel consumption performance, it is preferably 60 parts by mass or less, more preferably 55 parts by mass or less, even more preferably 50 parts by mass or less, and even more preferably 45 parts by mass or less.

[0093] Other fillers besides silica and carbon black can include those commonly used in the tire industry, such as aluminum hydroxide, calcium carbonate, alumina, clay, and talc.

[0094] From the viewpoint of wear resistance, the total content of silica and carbon black per 100 parts by mass of rubber component is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more. Furthermore, from the viewpoint of suppressing a decrease in fuel efficiency and wear resistance, it is preferably 180 parts by mass or less, more preferably 130 parts by mass or less, and even more preferably 110 parts by mass or less.

[0095] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent that has conventionally been used in combination with silica in the tire industry can be used, for example: mercapto-type silane coupling agents such as 3-mercaptopropyltrimethoxysilane, Momentive's NXT-Z100, NXT-Z45, and NXT; sulfide-type silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; and thioester-type silane coupling agents such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane. Examples of coupling agents include: vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, sulfide-based silane coupling agents and / or mercapto-based silane coupling agents are preferred, and sulfide-based silane coupling agents are more preferred. These silane coupling agents may be used individually or in combination of two or more.

[0096] The content of the silane coupling agent (preferably a sulfide-based silane coupling agent) per 100 parts by mass of silica is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and still more preferably 8 parts by mass or more, from the viewpoint of improving the dispersibility of silica. Furthermore, from the viewpoint of cost and processability, it is preferably 20 parts by mass or less, more preferably 18 parts by mass or less, and even more preferably 16 parts by mass or less.

[0097] <Other compounding agents> In addition to the components mentioned above, the rubber composition according to the present invention may appropriately contain compounding agents commonly used in the tire industry, such as softeners, waxes, processing aids, antioxidants, stearic acid, zinc oxide, vulcanizing agents, and vulcanization accelerators.

[0098] Examples of softening agents include resin components, oils, and liquid rubber.

[0099] The resin components are not particularly limited, but examples include petroleum resins, terpene resins, rosin resins, phenolic resins, cresol resins, and resorcinol resins commonly used in the tire industry. Among these, one or more selected from the group consisting of phenolic resins, cresol resins, and resorcinol resins are preferred. These resin components may be used individually or in combination of two or more.

[0100] Phenolic resins are not particularly limited, but examples include phenol-formaldehyde resin, alkylphenol-formaldehyde resin, alkylphenol-acetylene resin, and oil-modified phenol-formaldehyde resin. These resin components may be used individually or in combination of two or more.

[0101] When a resin component is included, the content of the resin component per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, from the viewpoint of wet grip performance. Furthermore, from the viewpoint of suppressing heat generation, the content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 30 parts by mass or less.

[0102] Examples of oils include process oils, vegetable oils, and animal oils. Examples of process oils include paraffinic process oils, naphthenic process oils, and aromatic process oils. Furthermore, for environmental reasons, process oils with a low content of polycyclic aromatic compounds (PCA) can be used. Examples of low-PCA process oils include light extraction solvates (MES), processed distillate aromatic extracts (TDAEs), and heavy naphthenic oils. Oils may be used individually or in combination of two or more types.

[0103] When oil is included, the oil content per 100 parts by mass of rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of wear resistance, it is preferably 120 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 30 parts by mass or less. In this specification, the oil content also includes the amount of oil contained in the oil-spread rubber.

[0104] Liquid rubber is not particularly limited as long as it is a polymer that is in a liquid state at room temperature (25°C), but examples include liquid butadiene rubber (liquid BR), liquid styrene butadiene rubber (liquid SBR), liquid isoprene rubber (liquid IR), liquid styrene isoprene rubber (liquid SIR), liquid farnesene rubber, etc. These liquid rubbers may be used individually or in combination of two or more.

[0105] When liquid rubber is included, its content per 100 parts by mass of rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more. Furthermore, the liquid rubber content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 20 parts by mass or less.

[0106] When wax is included, the amount of wax per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of weather resistance of the rubber. Furthermore, from the viewpoint of preventing whitening of the tire due to bloom, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less. The wax may be used alone or in combination of two or more types.

[0107] Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. For example, commercially available processing aids from companies such as Schill+Seilacher and Performance Additives can be used. Processing aids may be used individually or in combination of two or more.

[0108] When processing aids are included, the content per 100 parts by mass of rubber components is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of exhibiting an effect of improving processability. Furthermore, from the viewpoint of abrasion resistance and fracture strength, it is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less.

[0109] While not particularly limited, examples of anti-aging agents include amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, as well as metal carbamate salts. Phenylenediamine-based anti-aging agents such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and N-cyclohexyl-N'-phenyl-p-phenylenediamine are preferred, as are quinoline-based anti-aging agents such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline. These anti-aging agents may be used individually or in combination of two or more.

[0110] When an anti-aging agent is included, the content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of the rubber's resistance to ozone cracking. Furthermore, from the viewpoint of wear resistance and wet grip performance, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0111] When stearic acid is included, its content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less.

[0112] When zinc oxide is included, its content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of wear resistance, it is preferably 5.0 parts by mass or less, more preferably 4.5 parts by mass or less, and even more preferably 4.0 parts by mass or less.

[0113] Sulfur is preferably used as a vulcanizing agent. Suitable sulfurs include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. These vulcanizing agents may be used individually or in combination of two or more.

[0114] When sulfur is included as a vulcanizing agent, the amount of sulfur per 100 parts by mass of rubber component is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, from the viewpoint of ensuring a sufficient vulcanization reaction. Furthermore, from the viewpoint of preventing deterioration, it is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less. When oil-containing sulfur is used as the vulcanizing agent, the amount of vulcanizing agent is the total amount of pure sulfur contained in the oil-containing sulfur.

[0115] Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensates, 1,6-hexamethylene-dithiosulfate sodium dihydrate, and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane). These non-sulfur vulcanizing agents can be commercially available from companies such as Taoka Chemical Industries, Ltd., Lanxess Corporation, and Flexis. These vulcanizing agents may be used individually or in combination of two or more.

[0116] Examples of vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamate, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Among these, one or more vulcanization accelerators selected from the group consisting of sulfenamide, guanidine, and thiazole vulcanization accelerators are preferred. These vulcanization accelerators may be used individually or in combination of two or more.

[0117] Examples of sulfenamide-based vulcanization accelerators include N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide (DCBS). Among these, N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS) is preferred. These vulcanization accelerators may be used individually or in combination of two or more.

[0118] Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatecholborate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine. Among these, 1,3-diphenylguanidine (DPG) is preferred. These vulcanization accelerators may be used individually or in combination of two or more.

[0119] Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, and di-2-benzothiazolyl disulfide. Among these, 2-mercaptobenzothiazole is preferred. These vulcanization accelerators may be used individually or in combination of two or more.

[0120] When a vulcanization accelerator is included, its content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, and more preferably 2 parts by mass or more. Furthermore, the content of the vulcanization accelerator per 100 parts by mass of the rubber component is preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less. By keeping the content of the vulcanization accelerator within the above range, it tends to be possible to ensure fracture strength and elongation.

[0121] [Tire manufacturing] The rubber composition according to the present invention can be manufactured by known methods. For example, it can be manufactured by kneading each of the above components using a rubber kneading device such as an open roll or a closed kneader (Banbury mixer, kneader, etc.).

[0122] The mixing process includes, for example, a base mixing process in which compounding agents and additives other than the vulcanizing agent and vulcanization accelerator are mixed, and a final mixing (F mixing) process in which the vulcanizing agent and vulcanization accelerator are added to the mixture obtained in the base mixing process and mixed. Furthermore, the base mixing process can be divided into multiple processes as desired.

[0123] There are no particular limitations on the mixing conditions, but for example, in the base mixing process, mixing is performed at a discharge temperature of 150-170°C for 3-10 minutes, and in the final mixing process, mixing is performed at 70-110°C for 1-5 minutes. There are no particular limitations on the vulcanization conditions, but for example, vulcanization is performed at 140-170°C for 10-40 minutes.

[0124] The tire of the present invention can be manufactured by conventional methods using the rubber composition described above. Specifically, an unvulcanized rubber composition, in which the above components are blended with the rubber component as needed, is extruded in an extruder equipped with a die of a predetermined shape to match the shape of the tread, bonded together with other tire components on a tire molding machine, and molded in conventional methods to form an unvulcanized tire. This unvulcanized tire is then heated and pressurized in a vulcanizer to manufacture the tire.

[0125] [Application] The tire according to the present invention can be used not only as a heavy-duty pneumatic tire, but also as a pneumatic tire for passenger cars or motorcycles, for example. Furthermore, the tire according to the present invention is not limited to pneumatic tires, but can also be applied to airless tires, for example. Of these, from the viewpoint of the effects of the present invention, it is preferable to use it as a heavy-duty pneumatic tire. A heavy-duty tire refers to a tire whose maximum load capacity is 1400 kg or more. Here, maximum load capacity has the same meaning as normal load. [Examples]

[0126] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0127] The various chemicals used in the examples and comparative examples are summarized below. NR:TSR20 SBR1: HPR840 manufactured by JSR Corporation (S-SBR, styrene content: 10% by mass, vinyl content: 42 mol%, Tg -60℃, Mw 190,000) SBR2: SLR3402 manufactured by TRINSEO (S-SBR, styrene content: 15% by mass, vinyl content: 30 mol%, Tg -62℃) SBR3: SOL R C2525 manufactured by VERSALIS (S-SBR, styrene content: 26% by mass, vinyl content: 24 mol%, Tg -50℃, Mw 600,000) SBR4: Toughden 2000R (T2000R) manufactured by Asahi Kasei Corporation (S-SBR, styrene content: 25% by mass, vinyl content: 10 mol%, Tg -66℃, Mw 450,000) CB (Carbon Black) 1: Mitsubishi Chemical Corporation's Dia Black N220 (N2SA: 115m 2 / g) CB (Carbon Black) 2: Mitsubishi Chemical Corporation's Dia Black N134 (N2SA: 148ml) 2 / g) Silica 1: Evonik Degussa's UltraSil VN3 (N2SA: 175m 2 / g, average primary particle diameter: 18nm) Silica 2: Evonik Degussa's UltraSil 9100GR (N2SA: 230m 2 / g, average primary particle diameter: 15nm) Coupling agent (silane coupling agent): Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa. Anti-aging agent: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: Beads of stearic acid manufactured by NOF Corporation Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd. Vulcanization accelerator 1: Noxellar CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noxellar D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0128] Examples and Comparative Examples According to the formulation shown in Table 1, chemicals other than sulfur and vulcanization accelerator were mixed in a 1.7 L sealed Banbury mixer for 1 to 10 minutes until the discharge temperature reached 150 to 160°C to obtain a mixture. Next, sulfur and vulcanization accelerator were added to the mixture using a twin-screw open roll mixer and mixed for 4 minutes until the temperature reached 105°C to obtain an unvulcanized rubber composition. Using the obtained unvulcanized rubber composition, it was extruded to the shape of the tread using an extruder equipped with a die of a predetermined shape, and bonded together with other tire components to produce an unvulcanized tire. Each test tire (12R22.5, truck / bus tire) was manufactured by press vulcanization at 150°C for 35 minutes. For the test tire with flask grooves, the tread pattern shown in Figure 2 was used, and for the test tire without flask grooves, the tread pattern shown in Figure 2 was used without the flask-shaped circumferential grooves 9A and 9B.

[0129] <Result> The following evaluations were performed on the obtained test tires. The results are shown in Table 1.

[0130] (Ash content ratio A) For each test tire, the ash content A (%) was determined according to the measurement method described above for the test specimens cut from the tread.

[0131] (Fuel efficiency) Using a rolling resistance tester, the rolling resistance of the test tire was measured when it was driven at a rim size of 8.25 x 22.5 mm, an internal pressure of 900 kPa, a load of 28.76 kN, and a speed of 80 km / h. The reciprocal of this value was expressed as an index, with Comparative Example 2 set to 100. A higher value indicates lower rolling resistance and superior fuel efficiency.

[0132] (Wet grip performance) Each test tire was mounted on all wheels of a truck (2-D vehicle) with a maximum load capacity of 10 tons, and the braking distance from an initial speed of 100 km / h was measured on a wet road surface. The results were expressed as an index, with Comparative Example 2 set to 100, using the following formula. A higher index indicates better wet grip performance. (Wet grip performance index) = (Braking distance of the tire in Comparative Example 2) / (Braking distance of each test tire) × 100

[0133] (Wear resistance) Each test tire was mounted on all wheels of a truck (2-D vehicle) with a maximum load capacity of 10 tons. The groove depth of the tire tread was measured after 8,000 km of driving, and the distance traveled when the tire groove depth decreased by 1 mm was determined. The results were expressed as an index using the following formula, with the distance traveled when the tire groove depth of Comparative Example 2 decreased by 1 mm set to 100. A higher index indicates better wear resistance. (Wear resistance index) = (Distance traveled when the tread of each test tire decreases by 1 mm) / (Distance traveled when the tread of the tire in Comparative Example 2 decreases by 1 mm) × 100

[0134] (Wet grip performance in the later stages of wear) For each test tire, the tire was worn down by driving it for a distance at which the cross-sectional width of the body of the flask-shaped circumferential groove of the example tire was maximized. Then, the wet grip performance in the later stages of wear was evaluated using the same method as described above for evaluating wet grip performance.

[0135] (Overall performance) For each test tire, the indices for fuel efficiency, wet grip performance, wear resistance, and wet grip performance in the later stages of wear were summed and divided by 4 to obtain the overall performance index, which was used to evaluate each test tire.

[0136] [Table 1]

[0137] The results in Table 1 show that the tire of the embodiment of the present invention is superior to the comparative example in overall evaluation of fuel efficiency, wet grip performance, wear resistance, and wet grip performance in the later stages of wear.

[0138] [Embodiment] Examples of embodiments of the present invention are shown below.

[0139] [1] A tire having a tread portion made of a rubber composition containing isoprene rubber and styrene-butadiene rubber, The vinyl content of the styrene-butadiene rubber is more than 26 mol%, preferably 27 mol% or more, more preferably 28 mol% or more, even more preferably 29 mol% or more, and even more preferably 30 mol% or more. The ash content ratio A of the rubber composition, as defined by the following formula, is greater than 25%, preferably 26% or more, more preferably 29% or more, even more preferably 37% or more, even more preferably 60% or more, even more preferably 80% or more, and even more preferably 90% or more. The tread portion has two or more circumferential main grooves extending in the circumferential direction of the tire, and a land area defined by the circumferential main grooves, At least one of the aforementioned land portions has at least one flask-shaped circumferential groove extending in the circumferential direction of the tire, A tire in which the flask-shaped circumferential groove includes a neck portion with a narrow groove width and a body portion that is positioned inward from the neck portion in the tire radial direction and has a groove width greater than the maximum groove width of the neck portion. A = (m² / m¹) × 100 (Here, m1 is the mass of the residue obtained by immersing a test piece of the rubber composition in acetone for 72 hours in accordance with JIS K 6229 to extract the soluble components, and then heating the extracted test piece in nitrogen from room temperature to 750°C in accordance with JIS K 6226-1:2003 to thermally decompose and vaporize the organic matter; and m2 is the mass of the residue after oxidative combustion of the residue (mass m1) after thermal decomposition and vaporization by heating in air in accordance with JIS K 6226-1:2003.) [2] The tire according to [1] above, wherein the minimum groove width W1 of the neck portion is 1 to 2 mm, preferably 1.1 to 1.9 mm, and more preferably 1.2 to 1.8 mm. [3] The tire according to [1] or [2] above, wherein the maximum groove width W2 of the body is 2 to 12 mm, preferably 3 to 11 mm, and more preferably 4 to 10 mm. [4] The tire according to any one of [1] to [3] above, wherein the maximum groove width W2 of the body is 2 to 6 times, preferably 2.5 to 5.5 times, and more preferably 3 to 5 times, the minimum groove width W1 of the neck. [5] The tire according to any of [1] to [4] above, wherein the depth H1 of the flask-shaped circumferential groove in the tire meridian cross section and the distance H2 from the bottom of the groove to the neck portion satisfy the following relationship. 1 / 3 ≤ H2 / H1 ≤ 2 / 3 [6] The tire according to any one of [1] to [5] above, wherein the flask-shaped circumferential groove is located further outward in the tire radial direction than the neck portion and further includes an opening in which the groove width tapers outward toward the tire radial direction. [7] The tire according to any one of [1] to [6] above, wherein the rubber composition contains silica. [8] Silica has a specific surface area of ​​175 m² for nitrogen adsorption. 2 / g or more, preferably 185m 2 / g or more, more preferably 195m 2 The tires described above [7], which are 1 / g or more. [9] The tire according to any one of [1] to [8] above, wherein the rubber composition contains carbon black.

[10] The tire according to any one of [1] to [9] above, wherein the styrene content of the styrene-butadiene rubber is 24% by mass or less, more preferably 18% by mass or less, and even more preferably 16% by mass or less.

[11] The tire according to any one of [1] to

[10] above, wherein the rubber composition contains 0.5 to 5.0 parts by mass, preferably 1.0 to 4.5 parts by mass, more preferably 1.5 to 4.0 parts by mass of zinc oxide.

[12] The tire according to any one of [1] to

[11] above, wherein the land portion having flask-shaped circumferential grooves is located in a region sandwiched between a pair of outermost circumferential main grooves located on the outermost side in the tire width direction among the two or more circumferential main grooves.

[13] A heavy-duty tire as described in any of the above [1] to

[12] . [Explanation of symbols]

[0140] 1 tire 2 Tread section 3. Sidewall section 4. Bead section 5 Bead core 6. Carcass layer 7 Belt layer 8A, 8B, 8C, 8D Circumferential main groove 9A, 9B Flask-shaped circumferential grooves TE1, TE2 tread contact patch TW Tread contact width CL tire centerline 11 Neck 12 Torso 13 Tapered section W1 Minimum groove width of the neck W2 Maximum groove width of the body W3 Maximum groove width of the tapered section H1 Depth of flask-shaped circumferential groove H2 Distance from the bottom of the groove to the neck of the circumferential groove in the rusco-shaped groove 20, 50 Shoulder Track and Field Club 21, 51 Shoulder Sipes 22, 52 Shoulder lateral groove 30, 40 Center Track and Field Club 31, 41 Center Sipes

Claims

1. A tire having a tread portion made of a rubber composition containing rubber components including isoprene rubber and styrene-butadiene rubber, The vinyl content of the styrene-butadiene rubber is more than 26 mol%, The ash content ratio A of the aforementioned rubber composition is greater than 25%, as defined by the following formula. The tread portion has two or more circumferential main grooves extending in the circumferential direction of the tire, and a land area defined by the circumferential main grooves. At least one of the aforementioned land portions has at least one flask-shaped circumferential groove extending in the circumferential direction of the tire, A tire in which the flask-shaped circumferential groove includes a neck portion with a narrow groove width and a body portion that is positioned inward from the neck portion in the tire radial direction and has a groove width greater than the maximum groove width of the neck portion. A=(m 2 / m 1 )×100 (Here, m 1 m is the mass of the residue obtained by immersing a test piece of the rubber composition in acetone for 72 hours in accordance with JIS K 6229 to extract the soluble components, and then heating the extracted test piece in nitrogen from room temperature to 750°C in accordance with JIS K 6226-1:2003 to thermally decompose and vaporize the organic matter, 2 This is the residue after thermal decomposition and vaporization (mass m 1 (This is the mass of the residue after oxidative combustion by heating in air in accordance with JIS K 6226-1:2003.)

2. A tire having a tread portion made of a rubber composition containing rubber components including isoprene rubber and styrene-butadiene rubber, The vinyl content of the styrene-butadiene rubber is more than 26 mol%, The ash content ratio A of the aforementioned rubber composition is greater than 25%, as defined by the following formula. The oil content of the rubber composition is 30 parts by mass or less per 100 parts by mass of rubber component. The tread portion has two or more circumferential main grooves extending in the circumferential direction of the tire, and a land area defined by the circumferential main grooves. At least one of the aforementioned land portions has at least one flask-shaped circumferential groove extending in the circumferential direction of the tire, A tire in which the flask-shaped circumferential groove includes a neck portion with a narrow groove width and a body portion that is positioned inward from the neck portion in the tire radial direction and has a groove width greater than the maximum groove width of the neck portion. A=(m 2 / m 1 )×100 (Here, m 1 is the mass of the residue obtained by immersing a test piece of the rubber composition in acetone for 72 hours in accordance with JIS K 6229 to extract soluble components, and then pyrolyzing and vaporizing organic substances by heating from room temperature to 750 °C in nitrogen in accordance with JIS K 6226-1:2003 for the test piece after extraction. m 2 is the mass of the residue after oxidatively burning the residue (mass m 1 ) after the pyrolysis and vaporization by heating in air in accordance with JIS K 6226-1:2003.)

3. A tire having a tread portion made of a rubber composition containing rubber components including isoprene rubber and styrene-butadiene rubber, The vinyl content of the styrene-butadiene rubber is greater than 26 mol% and 45 mol% or less. The ash content ratio A of the aforementioned rubber composition is greater than 25%, as defined by the following formula. The tread portion has two or more circumferential main grooves extending in the circumferential direction of the tire, and a land area defined by the circumferential main grooves. At least one of the aforementioned land portions has at least one flask-shaped circumferential groove extending in the circumferential direction of the tire, A tire in which the flask-shaped circumferential groove includes a neck portion with a narrow groove width and a body portion that is positioned inward from the neck portion in the tire radial direction and has a groove width greater than the maximum groove width of the neck portion. A=(m 2 / m 1 )×100 (Here, m 1 m is the mass of the residue obtained by immersing a test piece of the rubber composition in acetone for 72 hours in accordance with JIS K 6229 to extract the soluble components, and then heating the extracted test piece in nitrogen from room temperature to 750°C in accordance with JIS K 6226-1:2003 to thermally decompose and vaporize the organic matter, 2 This is the residue after thermal decomposition and vaporization (mass m 1 (This is the mass of the residue after oxidative combustion by heating in air in accordance with JIS K 6226-1:2003.)

4. A tire having a tread portion made of a rubber composition containing rubber components including isoprene rubber and styrene-butadiene rubber, The vinyl content of the styrene-butadiene rubber is more than 26 mol%, The styrene content of the styrene-butadiene rubber is 18% by mass or less. The ash content ratio A of the aforementioned rubber composition is greater than 25%, as defined by the following formula. The tread portion has two or more circumferential main grooves extending in the circumferential direction of the tire, and a land area defined by the circumferential main grooves. At least one of the aforementioned land portions has at least one flask-shaped circumferential groove extending in the circumferential direction of the tire, A tire in which the flask-shaped circumferential groove includes a neck portion with a narrow groove width and a body portion that is positioned inward from the neck portion in the tire radial direction and has a groove width greater than the maximum groove width of the neck portion. A=(m 2 / m 1 )×100 (Here, m 1 m is the mass of the residue obtained by immersing a test piece of the rubber composition in acetone for 72 hours in accordance with JIS K 6229 to extract the soluble components, and then heating the extracted test piece in nitrogen from room temperature to 750°C in accordance with JIS K 6226-1:2003 to thermally decompose and vaporize the organic matter, 2 This is the residue after thermal decomposition and vaporization (mass m 1 (This is the mass of the residue after oxidative combustion by heating in air in accordance with JIS K 6226-1:2003.)

5. The tire according to claim 2, wherein the vinyl content of the styrene-butadiene rubber is 45 mol% or less.

6. The tire according to claim 2 or 3, wherein the styrene content of the styrene-butadiene rubber is 18% by mass or less.

7. The tire according to any one of claims 1 to 3, wherein the styrene content of the styrene-butadiene rubber is 24% by mass or less.

8. A tire for heavy loads as described in any one of claims 1 to 4.

9. The tire according to any one of claims 1 to 4, wherein the minimum groove width W1 of the neck portion is 1 to 2 mm.

10. The tire according to any one of claims 1 to 4, wherein the maximum groove width W2 of the body is 2 to 12 mm.

11. The tire according to any one of claims 1 to 4, wherein the maximum groove width W2 of the body is 2 to 6 times the minimum groove width W1 of the neck.

12. The tire according to any one of claims 1 to 4, wherein the depth H1 of the flask-shaped circumferential groove in the tire meridian cross-section and the distance H2 from the bottom of the groove to the neck portion satisfy the following relationship. 1 / 3 ≤ H2 / H1 ≤ 2 / 3

13. The tire according to any one of claims 1 to 4, wherein the flask-shaped circumferential groove is positioned outside the neck portion in the tire radial direction, and further includes an opening in which the groove width tapers outward toward the outside in the tire radial direction.

14. The tire according to any one of claims 1 to 4, wherein the rubber composition contains silica.

15. The specific surface area of ​​silica for nitrogen adsorption is 175 m². 2 The tire according to claim 14, wherein the weight is 1 / g or more.

16. The tire according to any one of claims 1 to 4, wherein the rubber composition comprises carbon black.

17. The tire according to any one of claims 1 to 4, wherein the rubber composition contains 0.5 to 5.0 parts by mass of zinc oxide.

18. The tire according to any one of claims 1 to 4, wherein the land portion having flask-shaped circumferential grooves is located in a region sandwiched between a pair of outermost circumferential main grooves that are located on the outermost side in the tire width direction among the two or more circumferential main grooves.

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