Heavy-duty tire

Abstract

To provide a heavy-duty tire which is excellent in overall performance of low fuel consumption performance and abrasion resistance performance.SOLUTION: There is provided a heavy-duty tire comprising a tread part. The tread part comprises a rubber layer which comprises a tread surface and is composed of a rubber composition comprising: a rubber component comprising isoprene-based rubber; and a filler comprising silica. A content of the isoprene-based rubber in the rubber component is greater than 85 mass%. A content of the silica in the filler is greater than 60 mass%. The tread surface of the tread part comprises two or more circumferential main grooves extending continuously in a tire circumferential direction, and a groove depth of a deepest part in the circumferential main grooves is less than 16 mm. When AIR represents the content (mass%) of the isoprene-based rubber in the rubber component, ASIL represents the content (mass%) of the silica in the filler, and DCG represents the groove depth (mm) of the deepest part in the circumferential main grooves, AIR, ASIL, and DLG satisfy the following expression (1): (1) AIR×ASIL / DCG>340.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In the case of large vehicles such as trucks and buses, there is an increasing demand for fuel-efficient heavy-duty tires to be used in response to environmental regulations, the introduction of labeling systems, and carbon-neutral initiatives. For example, Patent Document 1 describes that fuel-efficient heavy-duty pneumatic tires can be improved by having a tread portion made up of a cap rubber layer and a base rubber layer that satisfy predetermined conditions such as modulus. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-114651 Summary of the Invention [Problem to be solved by the invention]

[0004] However, since a formulation that emphasizes fuel efficiency is at odds with wear resistance, it is important to achieve both fuel efficiency and wear resistance. Furthermore, from a sustainability perspective, there is growing attention on the use of natural and recyclable materials.

[0005] An object of the present invention is to provide a heavy-duty tire that is excellent in overall performance in terms of fuel economy and wear resistance. [Means for solving the problem]

[0006] The present invention relates to the following heavy duty tire. A heavy-duty tire having a tread portion, the tread portion has a rubber layer including a tread surface, which is composed of a rubber composition including a rubber component containing an isoprene-based rubber and a filler containing silica, the content of the isoprene-based rubber in the rubber component is more than 85% by mass, The content of the silica in the filler is more than 60% by mass, The tread surface of the tread portion has two or more circumferential main grooves that extend continuously in the tire circumferential direction, and the groove depth of the deepest part of the circumferential main groove is less than 16 mm, The content (mass%) of the isoprene rubber in the rubber component is A IR The content (mass%) of the silica in the filler is A SIL , the groove depth (mm) of the deepest part of the circumferential main groove is D CG In the case where A IR , A SIL and D LG A heavy-duty tire that satisfies the following formula (1). (1) A IR ×A SIL / D CG >340 [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a heavy-duty tire that is excellent in overall performance in terms of fuel economy and wear resistance. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a heavy duty tire according to one embodiment of the present invention, taken along a plane including a tire rotation axis. [Figure 2] FIG. 2 is a development view of the tread portion of the tire of FIG. 1. [Figure 3] FIG. 3 is a cross-sectional view taken along line C1-C1 in FIG. 2. [Figure 4] FIG. 3 is a cross-sectional view taken along line C2-C2 in FIG. 2. [Figure 5] FIG. 2 is a conceptual diagram showing the configuration of a reinforcing layer with the tread surface facing forward. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a heavy-duty tire according to one embodiment of the present invention will be described. The heavy-duty tire according to this embodiment is a tire having a tread portion, the tread portion having a rubber layer including a tread surface, which is made of a rubber composition including a rubber component containing an isoprene-based rubber and a filler containing silica, the content of the isoprene-based rubber in the rubber component being more than 85% by mass, the content of the silica in the filler being more than 60% by mass, the tread surface of the tread portion having two or more circumferential main grooves extending continuously in the tire circumferential direction, the depth of the deepest part of the circumferential main grooves being less than 16 mm, and the content (mass %) of the isoprene-based rubber in the rubber component being A IR The content (mass%) of the silica in the filler is A SIL , the groove depth (mm) of the deepest part of the circumferential main groove is D CG In the case where A IR , A SIL and D LG is a heavy-duty tire that satisfies the following formula (1). (1) A IR ×A SIL / D CG >340

[0010] While not intending to be bound by theory, the following is believed to be the mechanism by which the overall performance of fuel economy and wear resistance is improved in the present invention. Specifically, (A) by increasing the isoprene-based rubber content to more than 85% by mass, it is believed that this contributes to ensuring sufficient rubber strength for a heavy-duty tire and reducing heat generation in the rubber component. (B) Because silica has low heat generation among fillers, increasing the silica content in the filler to more than 60% by mass is believed to contribute to reducing heat generation in the rubber. (C) Because the molecules of isoprene-based rubber are larger than those of synthetic rubber, the spaces within the rubber are larger and the density is lower. Therefore, the more isoprene-based rubber there is, the easier it is for the rubber component to incorporate silica, widening the area in which silica can disperse, which is believed to contribute to reducing heat generation in the rubber. (D) By reducing the groove depth of the deepest part of the circumferential main groove to less than 16 mm, the block rigidity of the tread pattern is increased, which is believed to contribute to reducing rolling resistance and improving wear resistance. It is believed that by balancing the content of isoprene-based rubber, the content of silica in the filler, and the depth of the deepest part of the circumferential main groove so as to satisfy formula (1), the above factors (1) to (4) work together to improve heat generation performance and wear resistance in a balanced manner.

[0011] The right side of the formula (1) is preferably 400, more preferably 500. It is believed that by satisfying the formula (1) under stricter conditions, the effect of the present invention, that is, improving heat generation performance and wear resistance in a balanced manner, can be more effectively achieved.

[0012] The hardness of the rubber composition is preferably 64 or more and 80 or less. A higher hardness is more effective in suppressing deformation of the rubber, leading to reduced rolling resistance, so a hardness of 64 or more is preferable, while a hardness of 80 or more makes it difficult for the rubber to elongate, which is disadvantageous in terms of chipping and breakage, so a hardness of 80 or less is preferable.

[0013] The average primary particle size of the silica is preferably less than 16 nm. It is believed that the use of silica with a small particle size can improve the abrasion resistance while suppressing the heat buildup of the rubber.

[0014] ASIL is preferably greater than 70, more preferably greater than 80, and even more preferably greater than 90. It is believed that an increase in the silica content in the filler contributes to further suppressing heat buildup in the rubber.

[0015] A IR It is preferable that the value exceeds 90. It is believed that an increase in the content of isoprene-based rubber contributes to ensuring a rubber strength satisfactory for a heavy-duty tire and reducing heat generation of the rubber component.

[0016] D CG is preferably less than 13, and more preferably less than 10. This is thought to contribute to a reduction in rolling resistance and an improvement in wear resistance because the block rigidity of the tread pattern is increased.

[0017] The tread surface of the tread portion preferably has at least one flask-shaped circumferential groove extending in the tire circumferential direction, and the flask-shaped circumferential groove preferably includes a neck portion with a narrow groove width and a body portion disposed radially inward of the neck portion and having a groove width greater than the maximum groove width of the neck portion. When new, the groove walls close together when the tire comes into contact with the ground, which is thought to suppress a decrease in tread rigidity and to be advantageous for fuel economy and wear resistance. Meanwhile, as wear progresses, the groove width increases, which suppresses an excessive increase in tread rigidity due to a decrease in remaining groove depth. This is thought to enable fuel economy and wear resistance to be maintained while minimizing the impact on other performances.

[0018] The tread surface of the tread portion preferably has at least one flask-shaped widthwise sipe extending in the tire width direction, and the flask-shaped widthwise sipe preferably includes a neck portion with a narrow groove width and a body portion disposed radially inward of the neck portion and having a groove width greater than the maximum groove width of the neck portion. When new, the groove walls close together when the tire contacts the ground, which is believed to suppress a decrease in tread rigidity and to be advantageous for fuel economy and wear resistance. Meanwhile, as wear progresses, the groove width increases, which suppresses an excessive increase in tread rigidity due to a decrease in remaining groove depth. This is believed to enable fuel economy and wear resistance to be maintained while minimizing the impact on other performances.

[0019] The tread surface of the tread portion preferably has at least one flask-shaped circumferential groove extending in the tire circumferential direction and at least one flask-shaped widthwise sipe extending in the tire width direction, each of the flask-shaped circumferential groove and the flask-shaped widthwise sipe including a neck portion with a narrow groove width and a body portion disposed radially inward of the neck portion and having a groove width greater than the maximum groove width of the neck portion, and when a pair of the two or more circumferential main grooves positioned outermost in the tire width direction is defined as an outermost main groove, and a region on the tread surface on the inner side in the tire width direction, bounded by the pair of outermost main grooves, is defined as a center region, at least one of the flask-shaped circumferential groove and the flask-shaped widthwise sipe is preferably located in the center region. Because the center region of the tread surface experiences high ground contact pressure, it is believed that the contributions of the flask-shaped circumferential groove and the flask-shaped widthwise sipe to fuel economy and wear resistance can be more easily achieved.

[0020] The heavy-duty tire preferably includes a reinforcing layer on the radially inner side of the tread portion, the reinforcing layer preferably including a band ply including a spirally wound band cord. By suppressing the dimensional growth of the tire, it is possible to reduce ground pressure, which is thought to be advantageous for fuel economy and wear resistance.

[0021] Preferably, the reinforcing layer includes a plurality of belt plies each including a large number of parallel belt cords, and at least one of the belt plies is disposed radially inward of the band ply. By disposing at least one belt ply radially inward of the band ply, the carcass, whose cords have an inclination angle of approximately 90° relative to the tire equatorial plane, does not come into direct contact with the band ply, whose cords have an inclination angle of approximately 0°, thereby reducing the influence of distortion due to the difference in cord angles. This is believed to be advantageous not only in terms of durability but also in terms of fuel economy.

[0022] In this specification, the upper and lower limit values ​​of "greater than or equal to," "less than or equal to," and "to" used to describe a numerical range can be arbitrarily combined, and in addition, the numerical values ​​in the examples can also be combined with the upper and lower limit values. Furthermore, when a numerical range is specified by "to," it means that both end values ​​are included unless otherwise specified. Furthermore, in this specification, a numerical range indicated as including both end values ​​is understood to simultaneously indicate a numerical range that does not include either end value, or even a numerical range that does not include both end values, as long as it does not contradict the spirit of the present invention.

[0023] [Definition] The "tread portion" refers to a component that includes the portion that forms the tread surface of the tire, and in the case where components that reinforce and form the tire frame, such as a reinforcing layer or carcass, are provided on the tire radially inner side in the tire cross section, the "tread portion" refers to a component that is located on the tire radially outer side of these components.

[0024] "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.

[0025] Unless otherwise specified, the "dimensions of each part of the tire" are values ​​that are specified when the tire appears on its outer surface in a normal state, while those that exist inside the tire or on a cut surface of the tire are values ​​that are specified when, for example, the tire is cut along a plane that includes the tire rotation axis and the cut tire piece is maintained within the rim width of a normal rim.

[0026] "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).

[0027] "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.

[0028] "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.

[0029] "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.

[0030]

number

[0031] Isoprene rubber content in rubber component (mass%) A IR " is the content of isoprene-based rubber present in the rubber component.

[0032] Silica content in filler (mass%) A SIL " is the content of silica present in the filler.

[0033] The "tread contact edge" refers to the outermost contact position in the tire width direction when a normal load is applied to a tire in a normal state and the tire contacts a flat surface with a camber angle of 0 degrees (Te1, Te2).

[0034] A "circumferential main groove" refers to a groove that extends continuously in the circumferential direction of the tire, and in a new tire, the maximum groove width (W3 in Figure 2) perpendicular to the extension direction exceeds 2.0% of the tread contact width TW.

[0035] Depth D of deepest part of circumferential main groove CG " refers to the depth (mm) of the deepest circumferential main groove, for example, D in Figure 1 CG The distance is indicated by

[0036] A "flask-shaped circumferential groove" is a groove extending in the tire circumferential direction, including a neck portion with a narrow groove width and a body portion disposed radially inward of the neck portion and having a portion with a groove width greater than the maximum groove width of the neck portion. Here, "body portion with a portion with a groove width greater than the maximum groove width of the neck portion" means that the body portion is configured to have a portion 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. The groove width of the neck portion of the flask-shaped circumferential groove, when the tire is new, is a groove width (W11 in FIG. 3) perpendicular to the extension direction of the neck portion that is 2.0% or less of the tread contact width TW.

[0037] "Lug groove" means a groove-shaped body that extends at least in the tire width direction and has a groove width perpendicular to the extending direction of the tire of 1.5 mm or more when the tire is new.

[0038] "Sipe" means a notch-like body that extends at least in the tire width direction and has a width perpendicular to the extending direction of less than 1.5 mm when the tire is new.

[0039] A "flask-shaped lateral sipe" is a sipe extending in the tire width direction, including a neck portion with a narrow groove width and a body portion disposed radially inward of the neck portion and having a portion with a groove width greater than the maximum groove width of the neck portion. The meaning of "body portion with a portion with a groove width greater than the maximum groove width of the neck portion" is as described in the preceding paragraph. The groove width of the neck portion of the flask-shaped lateral sipe, in a new tire, is less than 1.5 mm in the direction perpendicular to the extension direction (W21 in FIG. 4).

[0040] "Land portion" refers to the area on the tread surface defined by the circumferential main grooves, and the pair of land portions on the tread ground contact edge side are called "shoulder land portions," and the land portion inside the shoulder land portions is called "center land portion."

[0041] The "reinforcing layer" is a layer provided on the radially inner side of the tread to reinforce the tire structure, and is typically composed of a belt ply, band ply, etc. Here, the "belt ply" refers to a tire component in which a belt cord is covered with a belt covering rubber, and the "band ply" refers to a tire component in which a band cord is covered with a band covering rubber. The reinforcing layer is disposed on the radially outer side of the carcass that forms the tire skeleton.

[0042] A "softener" is a material that imparts plasticity to the rubber component, and is a concept that includes both softeners that are liquid (fluid) at 25°C and softeners that are solid at 25°C. Examples of softeners include resins, oils, liquid rubbers, and ester-based plasticizers. The "softener content" also includes the amount of softener in the rubber component that has been extended by the softener.

[0043] [Measurement method] The "hardness of the rubber composition" is the Shore hardness (Hs) measured at a temperature of 23°C using a Type A durometer in accordance with JIS K 6253-3:2012. When a measurement sample is prepared from a tire tread, the tread rubber is cut out from the surface side that forms the tire's contact surface so that the tire radial direction is the thickness direction, and the Type A durometer is pressed against the sample from the contact surface side to measure.

[0044] The "styrene content" is calculated by pyrolysis gas chromatography. In this specification, "pyrolysis gas chromatography" refers to a method in which a sample is heated in a pyrolysis apparatus, 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.

[0045] The "vinyl content (amount of 1,2-bonded butadiene units)" is also calculated by pyrolysis gas chromatography.

[0046] The "cis content (cis-1,4-bond content)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017, and applies to rubber components having repeating units derived from butadiene, such as BR.

[0047] The "glass transition temperature Tg" is a value determined by differential scanning calorimetry (DSC) in accordance with JIS K 7121, and is applied to, for example, SBR. For example, when the SBR contains an extender oil, the glass transition temperature Tg is measured in accordance with JIS K 6229 on a sample after removing the extender oil with acetone.

[0048] The "weight average molecular weight (Mw)" can be determined by converting the measured value into standard polystyrene equivalents using gel permeation chromatography (GPC) (for example, a GPC-8000 series manufactured by Tosoh Corporation, a differential refractometer as the detector, and a TSKgel SuperMultipore HZ-M column manufactured by Tosoh Corporation). This applies to, for example, SBR, BR, etc.

[0049] "N2SA of carbon black" is measured in accordance with JIS K 6217-2:2017.

[0050] "N2SA of silica" is measured by the BET method in accordance with ASTM D3037-93.

[0051] The "average primary particle size" is calculated by photographing particles with a transmission or scanning electron microscope and taking the arithmetic average of the particle sizes of 400 particles. If the particle shape is nearly circular, the diameter of the circle is used as the particle size; if it is needle-like or rod-like, the minor axis is used as the particle size; otherwise, the equivalent circle diameter is calculated from the electron microscope image. The equivalent circle diameter is calculated as the positive square root of [4 x (particle area) / π]. The average primary particle size applies to silica, carbon black, etc.

[0052] The "softening point of the resin" is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2015 7.7 is measured using a ring and ball softening point tester.

[0053] [tire] A heavy-duty tire according to one embodiment of the present invention will be described below with reference to the accompanying drawings. However, the drawings used merely specifically illustrate one embodiment, and the present invention is not limited to these drawings.

[0054] The heavy-duty tire according to the present embodiment is a tire having a tread portion having a rubber layer including a tread surface made of a predetermined rubber composition, and the content (mass %) of the isoprene-based rubber in the rubber component is A IR , the silica content (mass%) in the filler is A SIL , the deepest groove depth of the circumferential main groove (mm) is D CG In the case where A IR , A SIL and D LG is a heavy-duty tire that satisfies the following formula (1). (1) A IR ×A SIL / D CG >340

[0055] FIG. 1 is a cross-sectional view of a tire 1, a heavy-duty tire according to this embodiment, taken along a plane including the tire rotation axis. The tire 1 includes a tread portion 3 including a tread surface 2, a reinforcing layer 6 disposed radially inward of the tread portion 3, and a pair of bead portions 10 that contact the rim. The tread portion 3 is composed of a cap rubber layer 4 and a base rubber layer 5, and the reinforcing layer 6 includes two belt plies 7a and 7b, a band ply 8 sandwiched between the belt plies 7a and 7b, and covering rubber 9 disposed on both ends of the band ply. The bead portions 10 include a bead core 11 and a bead filler 12. Two circumferential main grooves 13 (only one groove located in the right half of the tire is shown in FIG. 1) extending continuously in the tire circumferential direction and one flask-shaped circumferential groove 14 are formed in the tread surface 2. CL represents the tire centerline. D CG is the depth of the deepest part of the circumferential main groove.

[0056] In FIG. 1, the tread portion 3 is made up of two layers, a cap rubber layer and a base rubber layer, but the tread portion may be made up of three or four or more rubber layers. For example, if the tread portion 3 is made up of three rubber layers, the rubber layer located in the middle may be of a type belonging to the cap rubber layer or a type belonging to the base rubber layer. In the reinforcing layer 6, the number of belt plies 7 is not limited to two, but may be one, or three or more. The number of band plies 8 is not limited to one, but may be two or more. Covering rubber 9 can be added as needed to cover the ends of the belt plies and band plies.

[0057] Figure 2 is a development view of the tread surface 2 of the tire in Figure 1. The tread surface 2 is formed with two circumferential main grooves 13 extending in the tire circumferential direction and one flask-shaped circumferential groove 14 extending in the tire circumferential direction. A pair of shoulder land portions 15 is formed by the circumferential main grooves 13 and the tread edge Te, and a center land portion 16 is formed in the area sandwiched between the pair of shoulder land portions 15. The center land portion 16 is divided in two by the flask-shaped circumferential groove 14 located at the center of the tread surface 2. Lug grooves 17 connecting the circumferential main grooves 13 and the tread edge Te are formed in the shoulder land portions 15, and flask-shaped widthwise sipes 18 connecting the circumferential main groove 13 and the flask-shaped circumferential groove 14 are formed in the center land portion 16. W3 indicates the maximum groove width of the circumferential main groove 13 perpendicular to the extension direction.

[0058] In FIG. 2, two circumferential main grooves 13 are formed, but the number may be three, four, or more. Furthermore, the circumferential main grooves 13 extend in a zigzag pattern with their widthwise centerlines swaying laterally, but they may also be linear or zigzag. Here, "extending in a zigzag pattern" means that the widthwise center of the circumferential main groove extends in the tire circumferential direction while swaying in the tire width direction. Therefore, this includes not only a configuration in which a linear groove repeatedly bends, but also a configuration in which a curved groove repeatedly curves in a wave-like pattern. Furthermore, in FIG. 2, many lug grooves 17 are formed, but the configuration and number of lug grooves 17 are not particularly limited in this embodiment.

[0059] <Formula (1)> The value of the right side of formula (1) is preferably 360, more preferably 380, even more preferably 400, even more preferably 450, even more preferably 460, even more preferably 500, even more preferably 510, even more preferably 520, even more preferably 600. IR ×A SIL / D CG There is no particular upper limit to the value of , but it can usually be assumed to be around 1000.

[0060] Regarding formula (1), A IR and ASIL can be adjusted by increasing or decreasing the amount of isoprene rubber in the rubber component and the amount of silica in the filler. CG can be adjusted by increasing or decreasing the depth of the deepest part of the circumferential main groove, thereby adjusting the value of the right side of formula (1).

[0061] A IR and A SIL The preferred range of D is as described below. CG From the viewpoint of wear resistance, the distance D is preferably 15.0 mm or less, more preferably 14.8 mm or less, even more preferably 14.6 mm or less, even more preferably 14.4 mm or less, even more preferably 14.2 mm or less, and even more preferably 14.0 mm or less. CG It is preferable that the thickness is a predetermined value or more from the viewpoint of drainage properties, etc., but normally, a thickness of 10.0 mm or more is acceptable.

[0062] <Flask-shaped circumferential groove> In the heavy-duty tire of this embodiment, it is preferable that the tread surface of the tread portion has at least one flask-shaped circumferential groove extending in the tire circumferential direction, and that the flask-shaped circumferential groove includes a neck portion with a narrow groove width, and a body portion that is positioned radially inward of the neck portion in the tire radial direction and has a portion with a groove width larger than the maximum groove width of the neck portion.

[0063] In FIG. 2 , the flask-shaped circumferential groove 14 is formed on the tire centerline so as to bisect the center land portion 16. However, in this embodiment, it is sufficient that at least one flask-shaped circumferential groove is formed in at least one land portion. Therefore, one flask-shaped circumferential groove may be formed in any one land portion, and two or more flask-shaped circumferential grooves may be formed in one land portion. Furthermore, it is sufficient that there is at least one land portion with one or more flask-shaped circumferential grooves, and there may be two or three or more such land portions. There are no particular limitations on the land portion in which the flask-shaped circumferential groove is formed, but it is preferable that it be formed in the center land portion. This is because the area near the tire centerline is the area with the highest ground contact pressure, and therefore it is believed that the flask-shaped circumferential groove's contribution to fuel economy and wear resistance is easily achieved. Furthermore, like the circumferential main groove, the flask-shaped circumferential groove may be zigzag or linear.

[0064] 3 is a cross-sectional view of the flask-shaped circumferential groove 14 taken along line C1-C1 in FIG. 2. The flask-shaped circumferential groove has a neck portion 19 and a body portion 20 that is located radially inward of the neck portion and has a portion with a groove width greater than the maximum groove width of the neck portion. In FIG. 3, the groove width of the neck portion is fixed and constant at its minimum groove width W11, but the neck portion may have a portion with a groove width greater than W11 as long as the effects of the present invention are achieved. Therefore, the cross-sectional shape of the neck portion may be linear as shown in FIG. 3, or may be zigzag. Here, zigzag has the same meaning as above. In one preferred embodiment, the groove width of the neck portion is constant at its minimum groove width.

[0065] Furthermore, the body 20 has a portion with a groove width larger than the maximum groove width of the neck. Here, "having a portion with a groove width larger than the maximum groove width of the neck" means that the body is configured to be wider than the maximum groove width of the neck so as to achieve the effects of the present invention. Therefore, the groove width of the body is not particularly limited as long as it includes a portion larger than the maximum groove width of the neck so as to achieve the effects of the present invention. For example, the body may have a portion with a groove width narrower than the maximum groove width of the neck, or the body may be configured so that only the portion with a groove width larger than the groove width of the neck. In FIG. 3, the groove width of the neck 19 is fixed at its minimum groove width W11, so the body 20 is configured only with a portion with a groove width larger than the groove width of the neck 19.

[0066] The minimum groove width W11 of the neck portion is preferably 0.5 mm or more and 2.0 mm or less. When W11 is 0.5 mm or more, water can easily flow from the neck portion to the body portion, for example, when driving on wet roads, making it possible to easily ensure sufficient drainage performance. On the other hand, when W11 is 2.0 mm or less, when a load is applied to the tread portion 3 in the early stages of wear, the neck portion is easily closed by ground contact pressure, thereby increasing the axial rigidity of the tread portion 3. In addition, the rubber volume of the tread portion 3 is easily ensured. This improves the wear resistance of the tire 1. W11 is more preferably 0.7 mm or more, even more preferably 0.9 mm or more, and even more preferably 1.1 mm or more. On the other hand, W11 is more preferably 1.8 mm or less, even more preferably 1.6 mm or less, even more preferably 1.4 mm or less, and even more preferably 1.2 mm or less.

[0067] The maximum groove width W12 of the body portion is preferably 2.0 mm or more and 12.0 mm or less. When the maximum groove width W12 is 2.0 mm or more, the width of the flask-shaped circumferential groove 14 is easily ensured, and input from the road surface can be reduced. On the other hand, when the maximum groove width W12 is 12.0 mm or less, the rubber volume of the tread portion 3 is easily ensured, and the wear resistance of the tire 1 is improved. W12 is more preferably 3.0 mm or more, even more preferably 4.0 mm or more, even more preferably 5.0 mm or more, and even more preferably 6.0 mm or more. On the other hand, W12 is more preferably 11.0 mm or less, even more preferably 10.0 mm or less, and even more preferably 8.0 mm or less.

[0068] The above W12 is preferably 2.0 to 8.0 times the above W11. When the above W12 is 2.0 times or more the above W11, the width of the flask-shaped circumferential groove 14 can be easily ensured, and input from the road surface can be reduced. When the above W12 is 8.0 times or less the above W11, the rubber volume of the tread portion 3 can be easily ensured, and the wear resistance of the tire 1 can be improved. The above W12 is preferably 2.5 times or more the above W11, and more preferably 3.0 times or more, while the above W12 is preferably 7.0 times or less the above W11, more preferably 6.0 times or less, and even more preferably 5.0 times or less.

[0069] In the flask-shaped circumferential groove 14 of this embodiment, it is more preferable that W11 is 0.5 mm or more, W12 is 2.0 mm or more, and W12 is 2.0 times or more of W11. Such a flask-shaped circumferential groove 14 can reduce input from the road surface. Moreover, in the flask-shaped circumferential groove 14 of this embodiment, it is preferable that W11 is 2.0 mm or less, W12 is 12.0 mm or less, and W12 is 8.0 times or less of W11. Such a flask-shaped circumferential groove 14 easily ensures the rubber volume of the tread portion 3, and improves the wear resistance of the tire 1.

[0070] It is preferable that the depth H11 of the flask-shaped circumferential groove 14 and the minimum length H12 in the tire radial direction from the groove bottom to the neck of the flask-shaped circumferential groove 14 satisfy the following relationship. 1 / 4≦H12 / H11≦3 / 4

[0071] By making the H12 / H11 ratio 1 / 4 or more, the groove volume of the body portion can be easily secured, and input from the road surface can be reduced. By making the H12 / H11 ratio 3 / 4 or less, the rigidity of the tread portion 3 in the tire axial direction can be increased. Also, the rubber volume of the tread portion 3 can be easily secured. This improves the wear resistance of the tire 1. It is more preferable that the H12 / H11 ratio be 1 / 3 or more. On the other hand, it is more preferable that the H12 / H11 ratio be 2 / 3 or less.

[0072] In the flask-shaped circumferential groove 14 of this embodiment, more preferably, W12 is 2.0 to 8.0 times W11 and has a cross-sectional shape that satisfies 1 / 4≦H12 / H11≦3 / 4. When W12 is at least twice W11 and H12 / H11 is at least 1 / 4, input from the road surface can be reduced. When W12 is at most 8.0 times W11 and H12 / H11 is at most 3 / 4, the rubber volume of the tread portion 3 can be easily ensured, and the wear resistance of the tire 1 can be improved.

[0073] <Flask-shaped widthwise sipes> In the heavy-duty tire of this embodiment, it is preferable that the tread surface of the tread portion has at least one flask-shaped widthwise sipe extending in the tire width direction, and that the flask-shaped widthwise sipe includes a neck portion with a narrow groove width and a body portion that is positioned radially inward of the neck portion in the tire radial direction and has a portion with a groove width larger than the maximum groove width of the neck portion.

[0074] 2, a large number of flask-shaped widthwise sipes 18 are formed on the center land portion 16 so as to connect the circumferential main groove 13 to the flask-shaped circumferential groove in the tire width direction, but in this embodiment, it is sufficient that at least one flask-shaped widthwise sipe is formed in at least one land portion, or two or more flask-shaped widthwise sipes may be formed in one land portion, or it is sufficient that there is at least one land portion with one or more flask-shaped widthwise sipes formed therein, and the number of such land portions may be two, three or more. In addition, the flask-shaped widthwise sipes do not need to connect adjacent circumferential grooves, and may connect adjacent circumferential grooves as shown in FIG. 2, or may open to only one of the circumferential grooves, or may not open to any of the circumferential grooves.

[0075] Figure 4 is a cross-sectional view of the flask-shaped widthwise sipe 18 taken along line C2-C2 in Figure 2. The flask-shaped widthwise sipe differs from the flask-shaped circumferential groove in that the flask-shaped widthwise sipe is formed on the tread surface 2 and extends in the tire width direction within the land portion, but the shape in the cross-section is the same as the flask-shaped circumferential groove, and the description of the flask-shaped circumferential groove applies. However, the following description applies to the size of the flask-shaped widthwise sipe.

[0076] The minimum groove width W21 of the neck portion is preferably 0.3 mm or more and 1.5 mm or less. When W21 is 0.3 mm or more, water can easily flow from the neck portion to the body portion during wet driving, for example, and sufficient drainage performance can be easily ensured. On the other hand, when W21 is 1.5 mm or less, when a load is applied to the tread portion 3 in the early stages of wear, the neck portion is easily closed by ground contact pressure, and the rigidity of the tread portion 3 in the tire circumferential direction is increased. In addition, the rubber volume of the tread portion 3 is easily ensured. This improves the wear resistance of the tire 1. W21 is more preferably 0.4 mm or more, and even more preferably 0.5 mm or more. On the other hand, W21 is more preferably 1.2 mm or less, even more preferably 1.0 mm or less, even more preferably 0.8 mm or less, and even more preferably 0.6 mm or less.

[0077] The maximum groove width W22 of the body portion is preferably 1.5 mm or more and 8.0 mm or less. When the maximum groove width W22 is 1.5 mm or more, the width of the flask-shaped widthwise sipes 18 can be easily ensured, and input from the road surface can be reduced. On the other hand, when the maximum groove width W22 is 8.0 mm or less, the rubber volume of the tread portion 3 can be easily ensured, and the wear resistance of the tire 1 can be improved. W22 is more preferably 2.0 mm or more, even more preferably 2.5 mm or more, and even more preferably 3.0 mm or more. On the other hand, W22 is more preferably 7.0 mm or less, even more preferably 6.0 mm or less, even more preferably 5.0 mm or less, and even more preferably 4.0 mm or less.

[0078] The W22 is preferably 4.0 to 13.0 times the W21. When the W22 is 4.0 or more times the W21, the width of the flask-shaped widthwise sipes 18 can be easily ensured, and input from the road surface can be reduced. When the W22 is 13.0 or less times the W21, the rubber volume of the tread portion 3 can be easily ensured, and the wear resistance of the tire 1 can be improved. The W22 is more preferably 5.0 or more times the W21, and even more preferably 6.0 or more times the W21, while the W22 is preferably 11.0 or less times the W21, more preferably 9.0 or less times the W21, and even more preferably 7.0 or less times the W21.

[0079] In the flask-shaped widthwise sipes 18 of this embodiment, it is more preferable that W21 is 0.3 mm or more, W22 is 1.5 mm or more, and W22 is 4.0 times or more of W21. Such flask-shaped widthwise sipes 18 can reduce input from the road surface. Furthermore, in the flask-shaped widthwise sipes 18 of this embodiment, it is preferable that W21 is 1.5 mm or less, W22 is 8.0 mm or less, and W22 is 13.0 times or less of W21. Such flask-shaped widthwise sipes 18 easily ensure rubber volume in the tread portion 3, improving the wear resistance of the tire 1.

[0080] It is preferable that the depth H21 of the flask-shaped widthwise sipe 18 and the minimum length H22 in the tire radial direction from the groove bottom to the neck of the flask-shaped widthwise sipe 18 satisfy the following relationship. January 5th or less than H22 / H21 or less than March 5th

[0081] By setting the H22 / H21 ratio to 1 / 5 or more, the groove volume of the body portion can be easily ensured, and input from the road surface can be reduced. By setting the H22 / H21 ratio to 3 / 5 or less, the rigidity of the tread portion 3 in the tire axial direction can be increased. Also, the rubber volume of the tread portion 3 can be easily ensured. This improves the wear resistance of the tire 1. The H22 / H21 ratio is more preferably 1 / 4 or more, and even more preferably 1 / 3 or more. On the other hand, the H22 / H21 ratio is more preferably 1 / 2 or less, and even more preferably 2 / 5 or less.

[0082] In the flask-shaped widthwise sipe 18 of this embodiment, more preferably, W22 is 4.0 to 13.0 times W21 and has a cross-sectional shape that satisfies 1 / 5≦H22 / H21≦3 / 5. When W22 is 4.0 times or more W21 and H22 / H21 is 1 / 5 or more, input from the road surface can be reduced. When W22 is 13.0 times or less W21 and H22 / H21 is 3 / 5 or less, the rubber volume of the tread portion 3 is easily ensured, and the wear resistance of the tire 1 is improved.

[0083] (W12 / W11×A SIL ) In the heavy duty tire of this embodiment, the content A of the W12 / W11 and silica in the filler SIL The product of (W12 / W11×A SIL ) is preferably greater than 140, as this contributes to improving the overall performance of fuel economy and wear resistance. The value of W12 / W11×A is more preferably greater than 160, and even more preferably greater than 180. SIL Although there is no particular upper limit to the value, it is usually preferable that the value be less than 800.

[0084] <Reinforcing layer> The heavy-duty tire of this embodiment preferably includes a reinforcing layer on the radially inner side of the tread portion, the reinforcing layer including a band ply including a band cord wound in a spiral shape. The band ply preferably has a so-called full band configuration in which both ends are arranged opposite each other across the equatorial plane.

[0085] Preferably, the reinforcing layer further includes a plurality of belt plies each including a large number of parallel belt cords, with at least one belt ply disposed radially inward of the band ply. In a radial tire, a carcass including carcass cords forming the tire framework is disposed with the carcass cords at an angle of approximately 90° (i.e., an inclination angle of approximately 90°) relative to the tire equatorial plane, while the inclination angle of the band ply is approximately 0°. Therefore, disposing the band ply directly on the carcass would result in distortion due to the angle difference between the carcass cords and the band cords. In contrast, the inclination angle of the belt cords constituting the belt ply is greater than 0° and less than 90°. Therefore, disposing at least one belt ply radially inward of the band ply, as described above, reduces the effect of distortion due to the angle difference between the cords between the plies. This is believed to be advantageous not only in terms of durability but also in terms of fuel economy.

[0086] A specific example of the configuration of the reinforcing layer is an example in which an inner belt ply, a band ply, and an outer belt ply are arranged in this order from the inner side to the outer side in the tire radial direction. Here, the band ply is preferably in the form of a full band. The inner belt ply may be made of a single belt ply, or may be made of two belt plies with different inclination angles, or may be made of three or more layers. The outer belt ply may be made of a single belt ply, or may be made of two belt plies with different inclination angles, or may be made of three or more layers. Furthermore, a pair of band plies in the form of so-called edge bands may be arranged further outward in the tire radial direction from the outer belt ply to reinforce the outer portion in the tire width direction.

[0087] Fig. 5 shows an example of the configuration of the reinforcing layer 6. In Fig. 5, the left-right direction is the axial direction of the tire 1, and the up-down direction is the circumferential direction of the tire 1. The direction perpendicular to the paper surface is the radial direction of the tire 1. The front side of the paper surface is the radially outer side, and the back side is the radially inner side.

[0088] In FIG. 5, the reinforcing layer 6 is composed of a belt 7 consisting of two belt plies 7a and 7b, and a band ply 8. The two belt plies 7a and 7b are arranged in this order from the inside to the outside in the radial direction. Each belt ply is arranged so that both ends face each other across the equatorial plane. While this configuration is one preferred embodiment, the tire of this embodiment is not limited to this configuration. For example, the total number of belt plies may be one, or three or more. In FIG. 5, the belt ply 7a has a wide axial width, and the belt ply 7b has a narrow axial width. Although this configuration is one preferred embodiment, the tire of this embodiment is not limited to this configuration.

[0089] In Fig. 5, the band ply 8 is disposed between the belt plies 7a and 7b. The band ply 8 has a so-called full band configuration in which both ends are disposed opposite each other across the equator. Band plies also include those with so-called edge bands that reinforce the outer portions of the tire in the width direction, and edge bands can be added as needed.

[0090] Each belt ply includes a large number of belt cords arranged in parallel. In FIG. 5, the belt cords are represented by solid lines for ease of explanation, but are covered with belt-covering rubber. In the tire of this embodiment, the belt cords are preferably steel cords. In each belt ply, the belt cords are inclined with respect to the circumferential direction. In FIG. 5, angle θ1 is the inclination angle (hereinafter referred to as the first inclination angle θ1) of the belt cords included in belt ply 7a with respect to the tire equatorial plane. Angle θ2 is the inclination angle (hereinafter referred to as the second inclination angle θ2) of the belt cords included in belt ply 7b with respect to the equatorial plane. The first inclination angle θ1 and the second inclination angle θ2 are preferably 10° or more and 60° or less. From the viewpoint of effectively restricting tire movement and ensuring a stable contact shape, the first inclination angle θ1 is preferably 10° or more and 30° or less. The second inclination angle θ2 is preferably 10° or more and 30° or less.

[0091] In Figure 5, the band ply 8 includes a spirally wound band cord. In Figure 5, the band cord is represented by a solid line for ease of explanation, but is covered with a band covering rubber. In the tire of this embodiment, the band cord may be either a steel cord or an organic fiber cord, but a steel cord is preferred. Examples of the organic fiber include nylon fiber, polyester fiber, rayon fiber, and aramid fiber. In the band ply 8, the angle that the band cord forms with the circumferential direction is preferably 5° or less, more preferably 2° or less. The band cord of the band ply 8 extends substantially in the circumferential direction.

[0092] In FIG. 5, the belt ply 7a is disposed radially inward of the band ply 8. This belt ply 7a has a width in the tire width direction wider than the band ply 8, which contributes to suppressing tension fluctuations in the band cord. Therefore, the band ply 8 can effectively suppress dimensional growth of the tire and reduce ground contact pressure, which is advantageous for fuel economy and wear resistance. From this perspective, it is preferable that at least one belt ply of the multiple belt plies constituting the belt is positioned radially inward of the band ply 8. Furthermore, it is preferable that at least one belt ply positioned inside the band ply 8 has a width wider than the band ply 8.

[0093] [Rubber composition] The rubber composition constituting the rubber layer including the tread surface of the heavy duty tire according to this embodiment will be described below. The rubber composition contains a rubber component including an isoprene-based rubber and a filler including silica.

[0094] <Rubber component> The rubber component may contain other rubber components in addition to the isoprene-based rubber. Examples of such rubber components include crosslinkable rubber components commonly used in the tire industry, such as diene-based rubbers (e.g., styrene-butadiene rubber (SBR), butadiene rubber (BR), styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isobutylene-styrene block copolymer (SIBS), chloroprene rubber (CR), and acrylonitrile-butadiene rubber (NBR), as well as non-diene-based rubbers (e.g., hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber. These rubber components may be used alone or in combination.

[0095] The rubber component preferably contains at least one of SBR and BR in addition to the isoprene-based rubber, and may contain both SBR and BR. The rubber component may also consist of the isoprene-based rubber, SBR and BR, or may consist of only the isoprene-based rubber.

[0096] (Isoprene rubber) Examples of isoprene-based rubbers that can be used include those commonly used in the tire industry, such as isoprene rubber (IR) and natural rubber. Natural rubber includes unmodified natural rubber (NR) as well as modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), highly purified natural rubber (UPNR), and grafted natural rubber. These isoprene-based rubbers may be used alone or in combination of two or more.

[0097] The NR is not particularly limited, and those commonly used in the tire industry can be used, such as SIR20, RSS#3, and TSR20.

[0098] <A IR ≫ The content of the isoprene-based rubber in the rubber component is more than 85% by mass, preferably more than 90% by mass, more preferably more than 92% by mass, even more preferably more than 95% by mass, and may be 100% by mass.

[0099] (SBR) There are no particular limitations on the SBR, and either solution-polymerized SBR (S-SBR) or emulsion-polymerized SBR (E-SBR) can be suitably used, but from the viewpoint of the effects of the present invention, S-SBR is preferred. Furthermore, modified SBRs (modified S-SBR, modified E-SBR) can also be used. Examples of modified SBRs include SBRs whose terminals and / or main chains are modified, and modified SBRs (condensates, those with branched structures, etc.) coupled with tin, silicon compounds, etc. One type of SBR may be used alone, or two or more types may be used in combination.

[0100] As the SBR, either oil-extended or non-oil-extended SBR can be used. As the SBR, commercially available SBRs from JSR Corporation, Sumitomo Chemical Co., Ltd., UBE Corporation, Asahi Kasei Corporation, ZS Elastomers Co., Ltd., ARLANXEO, etc. can be used.

[0101] From the viewpoints of wet grip performance and abrasion resistance, the styrene content of SBR is preferably more than 10% by mass, more preferably more than 15% by mass, and even more preferably more than 20% by mass. From the viewpoints of temperature dependency of grip performance and abrasion resistance, the styrene content is preferably less than 40% by mass, more preferably less than 35% by mass, and even more preferably less than 30% by mass. The styrene content of SBR is measured by the above-mentioned measurement method.

[0102] From the viewpoints of wet grip performance and abrasion resistance, the vinyl content of SBR is preferably more than 10 mol%, more preferably more than 15 mol%, and even more preferably more than 20 mol%. Also, from the viewpoints of wet grip performance and abrasion resistance, the vinyl content of SBR is preferably less than 40 mol%, more preferably less than 35 mol%, and even more preferably less than 30 mol%. The vinyl content of SBR (amount of 1,2-bonded butadiene units) is measured by the above-mentioned measurement method.

[0103] From the viewpoint of wet grip performance, the glass transition point (Tg) of SBR is preferably above −80° C., more preferably above −70° C., and even more preferably above −65° C. From the viewpoint of fuel economy performance, the Tg of SBR is preferably below −30° C., more preferably below −35° C., and even more preferably below −40° C. The Tg of SBR is measured by the above-mentioned measurement method.

[0104] 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 crosslink uniformity, etc., Mw is preferably 2.5 million or less, more preferably 2 million or less, and even more preferably 1 million or less. Mw of SBR is measured by the above-mentioned measurement method.

[0105] When SBR is contained, the content in the rubber component is preferably more than 1 mass%, more preferably more than 3 mass%, and even more preferably more than 5 mass%, from the viewpoints of abrasion resistance and wet grip performance, and the content is preferably less than 10 mass%, more preferably less than 8 mass%, and even more preferably less than 7 mass%, from the viewpoint of abrasion resistance.

[0106] (BR) The BR is not particularly limited, and can be one commonly used in the tire industry, such as BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare earth butadiene rubber (rare earth BR) synthesized using a rare earth catalyst, BR containing syndiotactic polybutadiene crystals (SPB-containing BR), or modified BR (high-cis modified BR, low-cis modified BR). One type of BR may be used alone, or two or more types may be used in combination.

[0107] As the high-cis BR, for example, commercially available products from Zeon Corporation, UBE Corporation, JSR Corporation, etc. can be used. The inclusion of high-cis BR can improve low-temperature properties and wear resistance. The cis content of the high-cis BR is preferably more than 90 mol%, more preferably more than 95 mol%, and even more preferably 96 mol% or more. The cis content of BR is measured by the above-mentioned measurement method.

[0108] The rare earth BR is synthesized using a rare earth catalyst and has a vinyl content of preferably less than 1.8 mol%, more preferably less than 1.5 mol%, and even more preferably less than 1.2 mol%, and a cis content of preferably more than 90 mol%, more preferably more than 95 mol%, and even more preferably 96 mol% or more. As the rare earth BR, for example, commercially available products from LANXESS K.K. can be used.

[0109] The SPB-containing BR is not simply 1,2-syndiotactic polybutadiene crystals dispersed in the BR, but is dispersed after being chemically bonded to the BR. As such SPB-containing BR, commercially available products from UBE Corporation and the like can be used.

[0110] Examples of modified BR include BR modified with functional groups similar to those described above for SBR, and also preferably used are modified butadiene rubbers (modified BRs) whose terminals and / or main chains are modified with functional groups containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen.

[0111] Other examples of modified BR include tin-modified BR, which is obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and in which the terminals of the modified BR molecule are further bonded with a tin-carbon bond (tin-modified BR).Modified BR may be either non-hydrogenated or hydrogenated.

[0112] From the viewpoint of abrasion resistance, the weight-average molecular weight (Mw) of BR is preferably more than 300,000, more preferably more than 350,000, and even more preferably more than 400,000. From the viewpoint of crosslink uniformity, etc., it is preferably less than 2,000,000, more preferably less than 1,000,000, and even more preferably less than 700,000. The Mw of BR can be determined by the above-mentioned method.

[0113] The content of BR in the rubber component is not particularly limited, but is preferably more than 1% by mass, more preferably more than 3% by mass, and even more preferably more than 5% by mass. The content of BR in the rubber component is also preferably less than 15% by mass, more preferably less than 12% by mass, and even more preferably less than 9% by mass.

[0114] (Rubber components synthesized from recycled and biomass-derived raw materials) Monomers, which are structural units of synthetic rubbers such as IR, SBR, and BR, may be derived from underground resources such as petroleum and natural gas, 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 include recycled polyisoprene, recycled butadiene, and recycled aromatic vinyl compounds. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl compounds include, but are not limited to, styrene. Among these, recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) are preferably used as raw materials.

[0115] 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.

[0116] Furthermore, the monomers that are the structural units of polymers such as IR, SBR, and BR may be derived from biomass. In this specification, biomass refers to materials derived from natural resources such as plants. Examples of biomass include, but are not limited to, agricultural, forestry, and fishery products, sugar, wood chips, plant residues after useful components have been extracted, plant-derived ethanol, and biomass naphtha.

[0117] Monomers derived from biomass (biomass monomers) are not particularly limited, and examples thereof include biomass-derived butadiene and biomass-derived aromatic vinyl compounds. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl compounds include, but are not limited to, styrene. The method for producing biomass monomers is not particularly limited, and examples include biological and / or chemical and / or physical conversion of animals and plants. A representative example of biological conversion is fermentation by microorganisms, and examples of chemical and / or physical conversion include catalytic conversion, high heat conversion, high pressure conversion, electromagnetic wave conversion, critical fluid conversion, and combinations thereof.

[0118] 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.

[0119] Whether a polymer's raw material is biomass-derived can be determined by its pMC (percent modern carbon) measured in accordance with ASTM D 6866-10. pMC is the modern standard reference carbon. 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.

[0120] 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. 14The 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.

[0121] 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.

[0122] 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. 14 The modern standard reference for the C concentration is the carbon circulating in nature as of 1950. 14The 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.

[0123] 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 biomass ratio of 0% mentioned above.

[0124] 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.

[0125] <Filler> The filler contains silica. Preferably, the filler further contains carbon black. The filler may contain fillers other than silica and carbon black, but may also be a filler consisting only of carbon black and silica.

[0126] The fillers other than silica and carbon black are not particularly limited, but may include, for example, aluminum hydroxide, calcium carbonate, alumina, clay, talc, and the like, which have been conventionally used in the tire industry.

[0127] The filler may be used alone or in combination of two or more kinds.

[0128] (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.

[0129] 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.

[0130] 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.

[0131] 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).

[0132] Amorphous silica extracted from rice husks may be commercially available from Wilmar Co., Ltd., etc.

[0133] The nitrogen adsorption specific surface area (N2SA) of silica is 130m from the viewpoint of wear resistance and fracture characteristics. 2 / g or more is preferable, and 150m 2 / g is more preferable, and 170m 2 / g or more is more preferable, and 175m 2 / g or more is more preferable, and 185m 2 / g or more is more preferable, and 195m 2 / g. In addition, from the viewpoint of processability, N2SA is more preferably 500m 2 / g or less is preferable, and 350m 2 / g is more preferable, and 300m 2 / g is more preferable, and 250m 2 / g or less is more preferable. The N2SA of silica is a value measured by the above-mentioned measurement method.

[0134] From the viewpoint of the effects of the present invention, the average primary particle diameter of silica is preferably less than 18 nm, more preferably less than 17 nm, and even more preferably less than 16 nm. Also, from the viewpoint of processability, the average primary particle diameter is preferably greater than 12 nm, more preferably greater than 13 nm, and even more preferably greater than 14 nm. The average primary particle diameter of silica is measured by the above-mentioned measurement method.

[0135] From the viewpoint of a balance between fuel economy and wet grip performance, the content of silica is preferably more than 25 parts by mass, more preferably more than 30 parts by mass, and even more preferably 35 parts by mass or more, per 100 parts by mass of the rubber component. From the viewpoint of processability, the content is preferably less than 150 parts by mass, more preferably less than 100 parts by mass, even more preferably less than 80 parts by mass, and even more preferably less than 60 parts by mass.

[0136] <A SIL ≫ The silica content in the filler is more than 60% by mass. From the viewpoint of the effects of the present invention, the content is preferably more than 63% by mass, more preferably more than 70% by mass, even more preferably more than 80% by mass, and even more preferably more than 90% by mass. On the other hand, the content is usually less than 95% by mass, but may be 100% by mass.

[0137] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent.Silane coupling agent is not particularly limited, but for example, sulfide-based silane coupling agent such as bis(3-triethoxysilylpropyl) disulfide, bis(3-triethoxysilylpropyl) tetrasulfide; mercapto-based silane coupling agent such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; vinyl-based silane coupling agent such as vinyltriethoxysilane, vinyltrimethoxysilane; 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane Examples of suitable silane coupling agents include amino-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. Examples of suitable silane coupling agents include those commercially available from Evonik Degussa GmbH and Momentive GmbH. These silane coupling agents may be used alone or in combination.

[0138] The content of the silane coupling agent relative to 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 even more preferably 8 parts by mass or more, from the viewpoint of improving the dispersibility of silica. Also, 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.

[0139] (carbon black) 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 black products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., and Columbia Carbon Co., Ltd. These carbon blacks may be used alone or in combination.

[0140] In addition to the above, from the viewpoint of life cycle assessment, recycled carbon black obtained by pyrolyzing and purifying products containing carbon black, such as tires, may also be used as the carbon black.

[0141] "Recycled carbon black" refers to carbon black obtained by crushing used tires or other products containing carbon black and calcining the crushed material, and refers to carbon black in which, when subjected to oxidative combustion by heating in air as measured by thermogravimetry 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 proportion of the mass of the recycled carbon black lost due to oxidative combustion (carbon mass) is 87% by mass or less. Recycled carbon black is also called recovered carbon black and is sometimes expressed as rCB.

[0142] 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).

[0143] Recycled carbon black may lack functional groups on its surface, or may be treated to include functional groups on its surface. Treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, 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. The recycled carbon black of this embodiment also includes carbon blacks that have been treated to include functional groups on their surfaces.

[0144] As the recycled carbon black, commercially available products from Strable Green Carbon, LD Carbon, etc. can be used.

[0145] The nitrogen adsorption specific surface area (N2SA) of carbon black is 50m from the viewpoint of weather resistance and reinforcement. 2 / g or more is preferable, and 80m2 / g is more preferable, and 100m 2 In addition, N2SA is more preferably 250m / g or more in terms of dispersibility, fuel efficiency, breakage characteristics and durability. 2 / g or less is preferable, and 220m 2 / g is more preferable, and 180m 2 / g is more preferable, and 150m 2 The N2SA of carbon black is measured by the above-mentioned measurement method.

[0146] From the viewpoints of weather resistance and reinforcing properties, the average primary particle diameter of carbon black is preferably greater than 12 nm, more preferably greater than 15 nm, and even more preferably greater than 17 nm. Furthermore, from the viewpoints of dispersibility, fuel economy, breakage characteristics, and durability, the average primary particle diameter is preferably less than 25 nm, more preferably less than 22 nm, and even more preferably less than 20 nm. The average primary particle diameter of carbon black is measured by the above-mentioned measurement method.

[0147] The total content of carbon black 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 5 parts by mass or more, from the viewpoint of weather resistance and reinforcement, and is preferably less than 40 parts by mass, more preferably less than 30 parts by mass, and even more preferably 20 parts by mass or less, from the viewpoint of fuel economy.

[0148] The total content of silica and carbon black per 100 parts by mass of the rubber component is preferably more than 40 parts by mass, more preferably more than 50 parts by mass, and even more preferably 55 parts by mass or more, from the viewpoint of abrasion resistance. Also, from the viewpoint of suppressing deterioration in fuel economy and abrasion resistance, the total content is preferably less than 180 parts by mass, more preferably less than 130 parts by mass, and even more preferably less than 110 parts by mass.

[0149] <Other compounding agents> In addition to the above components, the rubber composition may contain, as appropriate, compounding agents that are conventionally commonly used in the tire industry, such as softeners, vulcanized rubber particles (rubber powder), antioxidants, waxes, processing aids, stearic acid, zinc oxide, vulcanizing agents, and vulcanization accelerators.

[0150] Examples of softeners include resins, oils, liquid rubbers, and ester-based plasticizers. These softeners may be derived from mineral resources such as petroleum and natural gas, biomass-derived materials, 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 softeners. One type of softener may be used alone, or two or more types may be used in combination.

[0151] (resin) Among the other compounding ingredients, the rubber composition preferably contains a resin. Examples of the resin include, but are not limited to, adhesive resins commonly used in the tire industry, such as dicyclopentadiene resins, aromatic vinyl resins, C9 resins, C5 resins, C5C9 resins, coumarone resins, indene resins, terpene resins, rosin resins, and phenol resins. One type of resin may be used alone, or two or more types may be used in combination.

[0152] <Dicyclopentadiene resin> The term "dicyclopentadiene-based resin" refers to a resin containing cyclopentadiene (CPD) or dicyclopentadiene (DCPD) as a monomer component, and may be hydrogenated or modified. Examples of dicyclopentadiene-based resins include DCPD / C9 resins containing dicyclopentadiene and a C9 fraction (described below) as monomer components (the DCPD / C9 resins may be hydrogenated or modified). DCPD / C9 resins containing dicyclopentadiene and styrene as monomer components are preferred, and DCPD / C9 resins containing dicyclopentadiene, styrene, and indene as monomer components are particularly preferred. Examples of dicyclopentadiene-based 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. These dicyclopentadiene-based resins may be used alone or in combination.

[0153] <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 available from Kraton, Eastman Chemical Company, Mitsui Chemicals, Inc., etc., can be used. These aromatic vinyl resins may be used alone or in combination of two or more.

[0154] <C9 resin> "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a polymer 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 having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene. These C9 resins may be used alone or in combination.

[0155] <C5 resin> "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 include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, isoprene, pentane, isopentane, neopentane, pentene, and pentadiene. These C5 resins may be used alone or in combination of two or more.

[0156] <C5C9 resin> 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. As the C5C9 resin, for example, commercially available resins from Tosoh Corporation, LUHUA, etc. may be used. These C5C9 resins may be used alone or in combination of two or more.

[0157] <Cumarone resin> "Cumarone resin" refers to a resin containing coumarone as a monomer component, and may be hydrogenated or modified. Examples of coumarone resins include coumarone-indene resins containing coumarone and indene as monomer components, and coumarone-indene-styrene resins containing coumarone, indene, and styrene as monomer components. These coumarone resins may be used alone or in combination of two or more.

[0158] <Indene-based resin> "Indene resin" refers to a resin containing indene as a monomer component, and may be hydrogenated or modified. Examples of indene resins include coumarone-indene resins containing coumarone and indene as monomer components, and coumarone-indene-styrene resins containing coumarone, indene, and styrene as monomer components. These indene resins may be used alone or in combination of two or more.

[0159] <Terpene resin> The term "terpene resin" refers to a resin 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. These terpene resins may be used alone or in combination.

[0160] <Rosin-based resin> The term "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 hydrogenated or modified. Examples of rosin-based resins include, but are not limited to, natural rosin and rosin-modified resins obtained by modifying rosin through hydrogenation, disproportionation, dimerization, esterification, or the like. These rosin-based resins may be used singly or in combination of two or more.

[0161] <Phenol-based resin> "Phenol-based resin" refers to a resin that contains a phenolic compound such as phenol or cresol as the monomer component with the largest content. Examples of phenol-based resins include, but are not limited to, phenol-formaldehyde resins, alkylphenol-formaldehyde resins, alkylphenol-acetylene resins, and oil-modified phenol-formaldehyde resins. These phenol-based resins may be used alone or in combination of two or more.

[0162] ≪Softening point≫ From the viewpoint of wet grip performance, the softening point of the resin is preferably above 80° C., more preferably above 90° C., and even more preferably above 100° C. Furthermore, from the viewpoint of processability and improving the dispersibility of the rubber component and the filler, the softening point is preferably below 150° C., more preferably below 140° C., and even more preferably below 130° C. The softening point of the resin is measured by the above-mentioned measurement method.

[0163] ≪Content≫ The amount of resin per 100 parts by mass of the rubber component is preferably more than 1 part by mass, more preferably more than 5 parts by mass, and even more preferably 5 parts by mass or more, while from the viewpoint of suppressing heat buildup, the amount is preferably less than 60 parts by mass, more preferably less than 30 parts by mass, and even more preferably less than 20 parts by mass.

[0164] (Softeners other than resin) Softeners other than resins, such as oil, liquid rubber, and ester-based plasticizers, will now be explained.

[0165] <Oil> Examples of oils include mineral oil, vegetable oil, and animal oil. From the viewpoint of life cycle assessment, waste oils used in rubber mixers and engines, and refined waste cooking oils used in restaurants may also be used. One type of oil may be used alone, or two or more types may be used in combination.

[0166] Mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. Examples of mineral oil include paraffinic oil (mineral oil), naphthenic oil, and aromatic oil. Specific examples of mineral 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, oils with a low content of polycyclic aromatic compounds (PCA) can also be used. Examples of low PCA oils include MES, TDAE, and heavy naphthenic oil.

[0167] 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 oil) obtained by refining the above oils, interesterified oils obtained by interesterifying the above oils, hardened oils obtained by hydrogenating the above oils, thermally polymerized oils obtained by thermally polymerizing the above oils, oxidatively polymerized oils obtained by oxidizing the above oils, and waste edible oils recovered from edible oils. Vegetable oils may be liquid or solid at 25°C.

[0168] The vegetable oil preferably contains acylglycerol, and more preferably triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxyl group of glycerin is esterified with 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 25°C.

[0169] 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 25°C for 24 hours, and after removing the rubber composition, the 1 When 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.

[0170] 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.

[0171] 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.

[0172] 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.

[0173] Examples of animal oils include fish oil, beef tallow, and oleyl alcohol derived from these.

[0174] When oil is contained, the content per 100 parts by mass of the 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 abrasion resistance, the content 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. The oil content includes the amount of oil contained in the oil-extended rubber.

[0175] <Liquid rubber> The liquid rubber is not particularly limited as long as it is a polymer that is in a liquid state at 25° C., and examples thereof 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. One type of liquid rubber may be used alone, or two or more types may be used in combination.

[0176] When liquid rubber is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more. The content of liquid rubber is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 10 parts by mass or less. The content of liquid rubber includes the amount of extended liquid rubber used to extend the rubber component.

[0177] <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.

[0178] When an ester plasticizer is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more. The content of the liquid rubber is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 10 parts by mass or less. The content of the ester plasticizer includes the amount of the extending ester plasticizer used to extend the rubber component.

[0179] (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. One type of vulcanized rubber particle may be used alone, or two or more types may be used in combination.

[0180] The vulcanized rubber particles are not particularly limited, and may be unmodified or modified. Commercially available vulcanized rubber products include those from Lehigh Industries, Muraoka Rubber Industries, and the like.

[0181] When vulcanized rubber particles are contained, the content thereof relative to 100 parts by mass of the rubber component can be appropriately adjusted, for example, within the range of more than 1 part by mass and less than 80 parts by mass.

[0182] (anti-aging agent) The antioxidant is not particularly limited, and 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 antioxidants such as N-isopropyl-N'-phenyl-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol 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., and Flexis Co., Ltd. One type of antioxidant may be used alone, or two or more types may be used in combination.

[0183] When an antioxidant is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of ozone crack resistance of the rubber, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, from the viewpoint of abrasion resistance and wet grip performance.

[0184] (wax) The wax is not particularly limited, and any wax commonly used in the tire industry can be suitably used, such as mineral waxes and plant-derived waxes. Mineral waxes refer to waxes derived from mineral resources such as oil and natural gas. Plant-derived waxes refer to waxes derived from natural resources such as plants. Among these, mineral waxes are preferred. Examples of plant-derived waxes include rice wax, carnauba wax, and candelilla wax. Examples of mineral waxes include paraffin wax, microcrystalline wax, and selected special waxes thereof, with paraffin wax being preferred. The wax according to this embodiment does not contain stearic acid. Waxes that can be used include those commercially available from, for example, Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., Ltd., etc. One type of wax may be used alone, or two or more types may be used in combination.

[0185] When wax is contained, the 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 weather resistance of the rubber, and is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, from the viewpoint of preventing whitening of the tire due to bloom.

[0186] (processing aids) 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. Examples of processing aids that can be used include those commercially available from Schill + Seilacher, Performance Additives, etc. One type of processing aid may be used alone, or two or more types may be used in combination.

[0187] When a processing aid is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of improving processability, and 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, from the viewpoint of abrasion resistance and breaking strength.

[0188] (stearic acid) When stearic acid is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, from the viewpoint of vulcanization rate.

[0189] (zinc oxide) When zinc oxide is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more from the viewpoint of processability, and 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 from the viewpoint of abrasion resistance.

[0190] (vulcanizing agent) Sulfur is preferably used as the vulcanizing agent. Examples of sulfur that can be used include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. The vulcanizing agent may be used alone or in combination of two or more.

[0191] When sulfur is contained as a vulcanizing agent, the content per 100 parts by mass of the 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, the content 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 content of the vulcanizing agent is the total content of pure sulfur contained in the oil-containing sulfur.

[0192] Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensate, sodium 1,6-hexamethylene-dithiosulfate dihydrate, and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane. These vulcanizing agents other than sulfur are commercially available from Taoka Chemical Co., Ltd., Lanxess K.K., Flexis, and the like. One vulcanizing agent may be used alone, or two or more may be used in combination.

[0193] (Vulcanization accelerator) Examples of vulcanization accelerators 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, thiazole-based, and guanidine-based vulcanization accelerators are preferred. One type of vulcanization accelerator may be used alone, or two or more types may be used in combination.

[0194] Examples of sulfenamide vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), etc. Among these, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) is preferred.

[0195] Examples of the thiazole vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, etc. Among these, 2-mercaptobenzothiazole is preferred.

[0196] Examples of guanidine vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, etc. Among these, 1,3-diphenylguanidine (DPG) is preferred.

[0197] When a vulcanization accelerator is contained, the content thereof per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more. The content thereof 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 setting the content of the vulcanization accelerator within the above range, breaking strength and elongation tend to be ensured.

[0198] <Various materials containing carbon atoms> In this specification, various materials containing carbon atoms (for example, rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from atmospheric carbon dioxide. The various materials may be obtained from carbon dioxide by directly converting carbon dioxide or by converting methane obtained through a methanation process in which methane is synthesized from carbon dioxide.

[0199] <Hardness of rubber composition> The hardness of the rubber composition is preferably 64 or more and 80 or less. From the viewpoint of ride comfort performance, the hardness is preferably 65 or more, more preferably 66 or more, and even more preferably 67 or more. On the other hand, from the viewpoint of maintaining flexibility as rubber, the hardness is preferably 75 or less, more preferably 70 or less, and even more preferably 68 or less. The hardness of the rubber composition is a value measured by the above-mentioned measurement method.

[0200] The hardness of a rubber composition can be adjusted by the types and amounts of components blended into the rubber composition. For example, increasing the amount of softener tends to decrease the hardness, while decreasing the amount of softener tends to increase the hardness; increasing the amount of filler tends to increase the hardness, while decreasing the amount of filler tends to decrease the hardness; decreasing the amount of sulfur or vulcanization accelerator tends to decrease the hardness, while increasing the amount of sulfur or vulcanization accelerator tends to increase the hardness.

[0201] [Manufacturing method] The rubber composition can be produced by a known method, for example, by kneading the above-mentioned components using a rubber kneading device such as an open roll or an internal kneader (such as a Banbury mixer or kneader).

[0202] The kneading step includes, for example, a base kneading step in which compounding ingredients and additives other than the vulcanizing agent and vulcanization accelerator are kneaded, and a final kneading (F kneading) step in which the vulcanizing agent and vulcanization accelerator are added to the kneaded product obtained in the base kneading step and kneaded. Furthermore, the base kneading step can be divided into multiple steps as desired.

[0203] The kneading conditions are not particularly limited, but examples include a method in which the base kneading step involves kneading for 3 to 10 minutes at a discharge temperature of 150 to 170°C, and in the final kneading step, kneading for 1 to 5 minutes at 70 to 110°C.

[0204] The heavy-duty tire according to the present embodiment can be manufactured by a conventional method using the rubber composition. That is, the unvulcanized rubber composition is extruded to match the shape of the tread using an extruder equipped with a die of a predetermined shape, and then laminated together with other tire components in a tire building machine while adjusting to obtain a predetermined tire structure, and molded by a conventional method to form an unvulcanized tire. The unvulcanized tire is then heated and pressurized in a vulcanizer, whereby a tire can be manufactured. The vulcanization conditions are not particularly limited, and examples thereof include a method of vulcanizing at 140 to 170°C for 10 to 40 minutes.

[0205] [Application] The tire according to the present embodiment can also be used as a heavy-duty tire. The tire according to the present embodiment is not limited to a pneumatic tire and can also be used as an airless tire, for example, but is preferably used as a pneumatic tire. Here, a heavy-duty tire is a tire that is used not only for large trucks and buses but also for small trucks, buses, vans, etc., and has a maximum load capacity of more than 1000 kg. When the tire according to the present embodiment is applied to large trucks or buses, its maximum load capacity is preferably 1400 kg or more. [Example]

[0206] Below, examples (working examples) that are considered preferable for carrying out the present invention are shown, but the scope of the present invention is not limited to these working examples. According to each table, rubber layers including tread surfaces obtained using the various chemicals shown below, and tires having tire structures were examined, and the results calculated based on the evaluation methods below are shown at the bottom of each table.

[0207] [Various medicines] The various chemicals used in the examples and comparative examples are listed below. NR:TSR20 SBR: SOL® C2525 manufactured by Versalis (S-SBR, styrene content: 26% by mass, vinyl content: 24% by mole, Tg: -50°C, Mw: 600,000) BR: BUNA CB24 manufactured by ARLANXEO (butadiene rubber synthesized using a neodymium catalyst, cis content: 96 mol%, vinyl content: 0.7 mol%, Mw: 500,000) CB (carbon black): Mitsubishi Chemical Corporation's Diablack N134 (N2SA:148m 2 / g, average primary particle diameter: 18nm) Silica 1: Ultrasil VN3 (N2SA: 175 ml) manufactured by Evonik Degussa 2 / g, average primary particle diameter: 18nm) Silica 2: Ultrasil 9100GR (N2SA: 230 ml) manufactured by Evonik Degussa 2 / g, average primary particle diameter: 15nm) Coupling agent (silane coupling agent): Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa Antioxidant: Nocrac 6C (6PPD) (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Wax: Ozoace 0355 (paraffin wax) manufactured by Nippon Seiro Co., Ltd. Stearic acid: Camellia stearic acid beads manufactured by NOF Corporation Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: HK-200-5 (powdered sulfur containing 5% oil) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0208] [Examples and Comparative Examples] According to the formulation shown in each table, all chemicals except sulfur and vulcanization accelerators were mixed in a 1.7 L closed-type Banbury mixer for 1 to 10 minutes until the discharge temperature reached 150-160°C. A kneaded mixture was obtained. Next, sulfur and vulcanization accelerators were added to the resulting mixture using a two-screw open roll mill, and the mixture was mixed for 4 minutes until the temperature reached 105°C, yielding an unvulcanized rubber composition. The resulting unvulcanized rubber composition was extruded using an extruder equipped with a predetermined die to conform to the shape of the rubber layer, including the tread surface. The resulting unvulcanized rubber composition was then bonded with other tire components while adjusting to achieve the desired tire structure. The unvulcanized tires were then press-vulcanized at 150°C for 35 minutes to produce test tires (tire size: 275 / 80R22.5, truck and bus tires).

[0209] In each table, if a flask-shaped circumferential groove is present, the flask-shaped circumferential groove is arranged on the tire centerline as shown in Figure 2. If a flask-shaped circumferential groove is not present, a non-flask-shaped regular circumferential groove is arranged according to the minimum groove width of the neck of the flask-shaped circumferential groove and the depth of the deepest part. If a flask-shaped widthwise sipe is present, the flask-shaped widthwise sipe is arranged on the center land portion as shown in Figure 2. If a flask-shaped widthwise sipe is not present, a non-flask-shaped regular widthwise sipe is arranged according to the minimum groove width of the neck of the flask-shaped widthwise sipe and the depth of the deepest part. A reinforcing layer including a belt ply and a band ply is arranged on the radially inner side of the tread as shown in Figure 5. The band ply has a so-called full band configuration, in which both ends are arranged opposite each other across the equatorial plane. In this case, the position of the band ply being "1 / 2" means that the band ply is positioned between the first and second belt plies from the inside in the tire radial direction out of a total of two belt plies, and "2 / 2" means that the band ply is positioned on the outside in the tire radial direction out of a total of two belt plies.

[0210] [evaluation] The results of measurements for each test tire by the following methods are recorded in the corresponding columns of the table below. Unless otherwise specified, each test tire is used after being brought into normal condition.

[0211] <Hardness of rubber composition> A tread portion forming the contact surface of the test tire is cut out so that the thickness direction is in the tire radial direction to prepare a hardness measurement sample, and the hardness of the rubber composition is measured at 23°C by pressing a Type A durometer against the sample from the contact surface side in accordance with JIS K 6253-3:2012.

[0212] <Low fuel consumption performance> For each test tire, a rolling resistance tester is used to measure the rolling resistance coefficient (RRC) when the tire is run on a drum at a speed of 80 km / h under the following conditions. The results are expressed as an index, with the reference comparative example being set at 100. The higher the value, the lower the rolling resistance of the tire. Rim: 22.5 x 8.25 Internal pressure: 900kPa Vertical load: 28.76kN

[0213] <Wear resistance> Each test tire was fitted to all wheels of a test vehicle, and the tire tread depth was measured after 8,000 km of travel. The distance traveled when the tire tread depth decreased by 1 mm was calculated. The results were expressed as an index, with the distance traveled when the tire tread depth of the reference comparative tire decreased by 1 mm being set at 100. The higher the index, the better the wear resistance.

[0214] [Table 1]

[0215] [Table 2]

[0216] [Embodiment] Examples of embodiments of the present invention are given below.

[0217] [1] A heavy-duty tire having a tread portion, the tread portion has a rubber layer including a tread surface, which is composed of a rubber composition including a rubber component containing an isoprene-based rubber and a filler containing silica, the content of the isoprene-based rubber in the rubber component is more than 85% by mass, The silica content in the filler is greater than 60% by mass, preferably greater than 63% by mass; The tread surface of the tread portion has two or more circumferential main grooves extending continuously in the tire circumferential direction, and the groove depth of the deepest portion of the circumferential main groove is less than 16 mm, preferably 15 mm or less, and more preferably less than 14 mm, The content (mass%) of the isoprene rubber in the rubber component is A IR The content (mass%) of the silica in the filler is A SIL , the groove depth (mm) of the deepest part of the circumferential main groove is D CG In the case where AIR , A SIL and D LG satisfies the following formula (1), and the right-hand side of the following formula (1) is preferably 360, more preferably 380. (1) A IR ×A SIL / D CG >340 [2] The heavy duty tire according to the above [1], wherein the right side of the formula (1) is 400, preferably 450, and more preferably 460. [3] The heavy duty tire according to the above [1], wherein the right side of the formula (1) is 500, preferably 510, more preferably 520, and even more preferably 600. [4] The heavy-duty tire according to any one of [1] to [3] above, wherein the hardness of the rubber composition is 64 or more and 80 or less, preferably 65 or more and 75 or less, more preferably 66 or more and 70 or less, and even more preferably 67 or more and 68 or less. [5] The heavy-duty tire according to any one of [1] to [4] above, wherein the average primary particle size of the silica is less than 18 nm, preferably less than 17 nm, more preferably less than 16 nm, even more preferably more than 12 nm and less than 16 nm, even more preferably more than 13 nm and less than 16 nm, and even more preferably more than 14 nm and less than 16 nm. [6]A SIL The heavy-duty tire according to any one of the above [1] to [5], wherein the tensile strength is greater than 70. [7]A SIL The heavy-duty tire according to any one of the above [1] to [5], wherein the value of the tensile strength is greater than 80. [8]A SIL The heavy-duty tire according to any one of the above [1] to [5], wherein the tensile strength is greater than 90. [9]A IR The heavy-duty tire according to any one of the above [1] to [8], wherein the % by mass of the saturation modulus is more than 90%, preferably more than 92% by mass, and more preferably more than 95% by mass.

[10] D CGThe heavy-duty tire according to any one of the above [1] to [9], wherein the σ is 15.0 or less, preferably 14.8 or less, more preferably 14.6 or less, even more preferably 14.4 or less, and still more preferably 14.2 or less.

[11] D CG The heavy-duty tire according to any one of the above [1] to [9], wherein the value of the flexural modulus is 14.0 or less.

[12] A heavy-duty tire according to any one of [1] to

[11] above, wherein the tread surface of the tread portion has at least one flask-shaped circumferential groove extending in the tire circumferential direction, and the flask-shaped circumferential groove includes a neck portion with a narrow groove width, and a body portion that is positioned radially inward of the neck portion and has a portion with a groove width larger than the maximum groove width of the neck portion.

[13] A heavy-duty tire according to any one of [1] to

[12] above, wherein the tread surface of the tread portion has at least one flask-shaped widthwise sipe extending in the tire width direction, and the flask-shaped widthwise sipe includes a neck portion having a narrow groove width, and a body portion that is positioned radially inward of the neck portion and has a portion with a groove width larger than the maximum groove width of the neck portion.

[14] The tread surface of the tread portion has at least one flask-shaped circumferential groove extending in the tire circumferential direction and at least one flask-shaped widthwise sipe extending in the tire width direction, and the flask-shaped circumferential groove and the flask-shaped widthwise sipe each include a neck portion having a narrow groove width and a body portion that is located more inward in the tire radial direction than the neck portion and has a portion with a groove width larger than the maximum groove width of the neck portion,

[11] above, wherein, among the two or more circumferential main grooves, a pair located outermost in the tire width direction is defined as an outermost circumferential main groove, and an area on the tread surface on the inner side in the tire width direction partitioned by the pair of outermost circumferential main grooves is defined as a center area, and at least one of the flask-shaped circumferential groove and the flask-shaped widthwise sipe is present in the center area.

[15] The heavy-duty tire includes a reinforcing layer on the radially inner side of the tread portion, The heavy-duty tire according to any one of the above [1] to

[14] , wherein the reinforcing layer is provided with a band ply including a spirally wound band cord.

[16] The reinforcing layer includes a plurality of belt plies including a large number of parallel belt cords, The heavy-duty tire according to

[15] above, wherein at least one belt ply is disposed radially inward of the band ply. [Explanation of symbols]

[0218] 1 Heavy duty tires 2 Tread surface 3 Tread section 4 Cap rubber layer 5 Base rubber layer 6 Reinforcement layer 7 Belt 7a, 7b belt plies 8 band ply 9 Covering rubber 10 Bead section 11 Bead core 12 Apex 13 Circumferential main groove 14 Flask-shaped circumferential groove 15 Shoulder land area 16 Center Land Division 17 Lug groove 18 Flask-shaped widthwise sipes 19 Neck 20 Torso CL Tire centerline (equator) DCG: Depth of deepest part of circumferential main groove W Tire width direction TW tread width Te tread edge W11, W21 Minimum groove width of neck W12, W22 Maximum groove width of the body W3 Maximum width of circumferential main groove perpendicular to the extension direction H11, H21 Depth of flask-shaped circumferential groove H12, H22 Distance from the bottom of the flask-shaped circumferential groove to the neck θ1 First tilt angle θ2 Second tilt angle

Claims

1. A heavy-duty tire having a tread portion, the tread portion has a rubber layer including a tread surface, which is composed of a rubber composition including a rubber component containing an isoprene-based rubber and a filler containing silica, the content of the isoprene-based rubber in the rubber component is more than 85% by mass, The content of the silica in the filler is more than 60% by mass, The tread surface of the tread portion has two or more circumferential main grooves extending continuously in the tire circumferential direction, and the groove depth of the deepest portion of the circumferential main grooves is less than 16 mm, The content (mass%) of the isoprene-based rubber in the rubber component is A IR The content (mass%) of the silica in the filler is A SIL , the groove depth (mm) of the deepest part of the circumferential main groove is D CG In the case where A IR , A SIL and D LG A heavy-duty tire that satisfies the following formula (1). (1) A IR ×A SIL / D CG >340

2. 2. The heavy duty tire according to claim 1, wherein the right side of formula (1) is 400.

3. 2. The heavy duty tire according to claim 1, wherein the right side of formula (1) is 500.

4. 2. The heavy duty tire according to claim 1, wherein the hardness of the rubber composition is 64 or more and 80 or less.

5. 5. The heavy duty tire according to claim 1, wherein the silica has an average primary particle size of less than 16 nm.

6. A SIL The heavy duty tire according to claim 1 or 4, wherein the tensile strength is greater than 70.

7. A SIL The heavy duty tire according to claim 1 or 4, wherein the tensile strength is greater than 80.

8. A SIL The heavy duty tire according to claim 1 or 4, wherein the tensile strength is greater than 90.

9. A IR The heavy duty tire according to claim 1 or 4, wherein the tensile strength is greater than 90.

10. D CG 5. The heavy duty tire according to claim 1, wherein the tread width is 15.0 or less.

11. D CG 5. The heavy duty tire according to claim 1, wherein the tread width is 14.0 or less.

12. 5. The heavy-duty tire according to claim 1, wherein a tread surface of the tread portion has at least one flask-shaped circumferential groove extending in the tire circumferential direction, the flask-shaped circumferential groove including a neck portion having a narrow groove width and a body portion disposed radially inward of the neck portion and having a groove width greater than the maximum groove width of the neck portion.

13. 5. The heavy-duty tire according to claim 1, wherein the tread surface of the tread portion has at least one flask-shaped widthwise sipe extending in the tire width direction, and the flask-shaped widthwise sipe includes a neck portion having a narrow groove width, and a body portion disposed radially inward of the neck portion and having a portion with a groove width larger than the maximum groove width of the neck portion.

14. a tread surface of the tread portion having at least one flask-shaped circumferential groove extending in the tire circumferential direction and at least one flask-shaped widthwise sipe extending in the tire widthwise direction, the flask-shaped circumferential groove and the flask-shaped widthwise sipe each including a neck portion having a narrow groove width and a body portion that is disposed more inward in the tire radial direction than the neck portion and has a portion with a groove width larger than the maximum groove width of the neck portion, 5. The heavy-duty tire according to claim 1, wherein, among the two or more circumferential main grooves, a pair located outermost in the tire width direction is defined as an outermost circumferential main groove, and an area on the tread surface on the inner side in the tire width direction partitioned by the pair of outermost circumferential main grooves is defined as a center region, and at least one of the flask-shaped circumferential groove and the flask-shaped widthwise sipe is present in the center region.

15. The heavy-duty tire includes a reinforcing layer on the radially inner side of the tread portion, 5. The heavy-duty tire according to claim 1, wherein the reinforcing layer comprises a band ply including a spirally wound band cord.

16. the reinforcing layer includes a plurality of belt plies including a large number of belt cords arranged in parallel, The heavy-duty tire according to claim 15, wherein at least one belt ply is disposed radially inward of the band ply.

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