tire

Abstract

To provide a tire configured so that wet grip performance can be improved after the tire is worn.SOLUTION: The tire comprises a tread part and at least one belt layer. The tread part comprises at least a first rubber layer at an outermost side in a tire radial direction and a second rubber layer made adjacent to the inside in the tire radial direction of the first rubber layer. The first rubber layer is constituted of rubber constituents including styrene-butadiene rubber and first rubber compositions including silica, and the second rubber layer is constituted of the rubber constituents including styrene-butadiene rubber and second rubber compositions including silica. The tread part has two or more circumferential main grooves extending in a tire circumferential direction and a land part defined by the circumferential main grooves. At least one circumferential main groove of the circumferential main grooves is formed so that a deepest part of a groove bottom thereof is positioned closer to the inside in the tire radial direction than an outermost part of the second rubber layer in the land part arranged adjacent to the circumferential main groove. When contents (mass parts) of silica with respect to 100 mass parts of the rubber constituents in the first rubber compositions are defined as A1SIL, and contents (mass parts) of silica with respect to 100 mass parts of the rubber constituents in the second rubber compositions are defined as A2SIL, and when a cross sectional width (mm) of the tire at the time when a normal load is applied to the tread in a normal state to push the tread on a plane is defined as Wt and a width (mm) of a belt layer with a largest width of belt layers is defined as Wb, A1SIL, A2SIL, Wt and Wb satisfy the following relational expression: (1) A2SIL / A1SIL>1.05 and (2) A2SIL / (Wt-Wb)>1.00.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Since there is a trade-off between grip performance and fuel economy, for example, Patent Document 1 describes a tire tread having a two-layer structure (a so-called cap / base structure) of a base rubber located on the radially inner side of the tire and a cap rubber located on the radially outer side of the base rubber, and using a rubber composition with a small loss tangent (tan δ) for the base rubber, in order to improve the steering stability and fuel economy of the tire. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3213127 Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of such a tire, the loss tangent tanδ of the cap rubber layer is high, so that the wet grip performance is high when the tire is new. However, as the tire is driven repeatedly, the cap rubber layer undergoes thermal degradation due to the effect of self-heating and becomes hard, so that the rigidity of the tread contact surface increases, and the tire loses its ability to follow the road surface, which may result in a decrease in wet grip performance.

[0005] An object of the present invention is to provide a tire having improved wet grip performance after wear. [Means for solving the problem]

[0006] The present invention relates to the following tire. A tire having a tread portion and at least one belt layer, The tread portion includes at least a first rubber layer that is an outermost layer in the radial direction of the tire, and a second rubber layer that is adjacent to the inner side of the first rubber layer in the radial direction of the tire, the first rubber layer is composed of a rubber component including a styrene-butadiene rubber and a first rubber composition including silica, the second rubber layer is composed of a rubber component including a styrene-butadiene rubber and a second rubber composition including silica, The tread portion has two or more circumferential main grooves extending in a tire circumferential direction and a land portion defined by the circumferential main grooves, At least one of the circumferential main grooves is formed such that a deepest portion of a groove bottom is located radially inward of an outermost portion of the second rubber layer in a land portion adjacent to the circumferential main groove, The content (parts by mass) of silica relative to 100 parts by mass of the rubber component in the first rubber composition is A1 SIL The content (parts by mass) of silica relative to 100 parts by mass of the rubber component in the second rubber composition is A2 SIL When the normal load is applied to the tread in a normal state and pressed against a flat surface, the cross-sectional width (mm) of the tire is Wt, and the width (mm) of the widest belt layer among the belt layers is Wb. A1 SIL , A2 SIL , Wt and Wb satisfy the following relationship. (1) A2 SIL / A1 SIL >1.05 (2) A2 SIL / (Wt-Wb)>1.00 Effect of the Invention

[0007] According to the present invention, it is possible to provide a tire having improved wet grip performance after wear. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing the tire section width Wt, the tire outer diameter Dt, and the width Wb of the widest belt layer in a tire cross section taken along a plane passing through the tire rotation axis. [Diagram 2] FIG. 2 is a development view of a portion of the tread of a tire. [Diagram 3] 1 is a cross-sectional view of a portion of a tire tread taken along a plane passing through the tire rotation axis. [Figure 4] FIG. 2 is a development view of a portion of a tread of a tire having widened circumferential narrow grooves in the land portion closest to the tire centerline. [Diagram 5] 5 is a diagram showing a cross section of the widened circumferential narrow groove of FIG. 4 taken along a plane passing through the tire rotation axis. [Figure 6] 1 is an exploded view of a portion of a tire tread having a perforation in a shoulder region. [Figure 7] FIG. 2 is a development view of a portion of a tread of a tire having circumferential narrow grooves in shoulder regions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A tire according to an embodiment of the present invention is a tire having a tread portion and at least one belt layer, the tread portion including at least a first rubber layer that is outermost in the radial direction of the tire, and a second rubber layer adjacent to the first rubber layer on the inner side in the radial direction of the tire, the first rubber layer being composed of a first rubber composition containing a rubber component including styrene-butadiene rubber and silica, the second rubber layer being composed of a rubber component including styrene-butadiene rubber and a second rubber composition containing silica, the tread portion having two or more circumferential main grooves extending in the circumferential direction of the tire and a land portion defined by the circumferential main grooves, at least one of the circumferential main grooves being formed such that a deepest portion of a groove bottom is located radially inward of an outermost portion of the second rubber layer in the land portion adjacent to the circumferential main groove, and a content (parts by mass) of silica relative to 100 parts by mass of the rubber component in the first rubber composition is A1 SIL The content (parts by mass) of silica relative to 100 parts by mass of the rubber component in the second rubber composition is A2 SIL When the normal load is applied to the tire in a normal state and the tread is pressed against a flat surface, the cross-sectional width (mm) of the tire is Wt, and the width (mm) of the widest belt layer among the belt layers is Wb. A1 SIL , A2SIL , Wt and Wb satisfy the following relationship: (1) A2 SIL / A1 SIL >1.05 (2) A2 SIL / (Wt-Wb)>1.00

[0010] Although not intending to be bound by theory, the mechanism by which wet grip performance after wear is improved in the present invention is believed to be as follows.

[0011] That is, (1) in the tire of the present invention, which uses at least two different layers of tread rubber and has a predetermined circumferential main groove, when the rubber of the first layer on the surface wears, the second layer of tread rubber is exposed to the surface, and the first layer of tread rubber remains on the edge of the land portion. In this case, by using a rubber with a large silica content for the second layer of rubber, the effect of improving wet grip performance after wear can be obtained. In addition, (2) the first layer of rubber tread has a smaller silica content than the second layer, so it is softer. Therefore, the first layer of rubber remaining on the edge of the land portion exhibits road surface following properties, and the wet grip effect of the second layer of rubber can be enhanced. Furthermore, (3) the contact area with the ground becomes larger as the tire wears, which has the effect of improving wet grip performance after wear. And it is considered that the wet grip performance after wear is improved by the cooperation of (1) to (3).

[0012] When the glass transition temperature (°C) of the second rubber composition is Tg2, Tg2 is preferably higher than -30°C.

[0013] It is believed that by increasing the glass transition temperature of the second rubber layer, the heat generation property of the second rubber layer can be increased, and friction can be easily generated in the center of the land portion after wear.

[0014] When tan δ of the first rubber composition at 30° C. is taken as 30° C. tan δ1, 30° C. tan δ1 is preferably less than 0.30.

[0015] It is believed that by suppressing the 30°C tan δ of the first rubber layer, the phase difference between the input and response of the first rubber layer can be reduced, making it easier to generate a reaction force.

[0016] When the total styrene amount (mass%) of the rubber component contained in the first rubber composition is St1 and the total styrene amount (mass%) of the rubber component contained in the second rubber composition is St2, it is preferable that at least one of St1 and St2 is less than 25.0.

[0017] It is believed that by reducing the total styrene content of the rubber components contained in the rubber composition constituting the first rubber layer and the second rubber layer, the formation of domains (styrene domains) due to the styrene moiety in the rubber composition of the first rubber layer is suppressed, heat generation between the styrene domains and the surrounding rubber molecular chains is suppressed, and responsiveness can be improved. It is also believed that the second rubber layer can easily follow the minute responses of the road surface.

[0018] The rubber component contained in the second rubber composition preferably contains at least one of a butadiene rubber and an isoprene-based rubber.

[0019] At least one of the rubber component contained in the first rubber composition and the rubber component contained in the second rubber composition preferably contains a butadiene rubber.

[0020] It is preferable that the rubber component contained in the first rubber composition and the rubber component contained in the second rubber composition each contain a butadiene rubber.

[0021] The tread portion preferably has a widening circumferential groove whose groove width is wider on the inner side in the tire radial direction.

[0022] After wear, the widened circumferential grooves increase in width, which is believed to improve drainage and wet grip performance.

[0023] The widened circumferential groove is preferably present in a land portion located on the tire centerline, or in a land portion closest to the tire centerline when a circumferential main groove is present on the tire centerline.

[0024] After wear, the groove width of the widened circumferential groove increases, which is thought to improve drainage in the center portion in the tire width direction and improve wet grip performance.

[0025] When a pair of land portions located at the outermost sides in the tire width direction among the land portions are defined as shoulder land portions, the shoulder land portions have an opening area of ​​more than 0.1 mm and less than 15 mm 2 It is preferable that the substrate has one or more small holes.

[0026] The small holes contribute to improved drainage, which is thought to improve drainage in the shoulder land areas and improve wet grip performance.

[0027] When a pair of land portions located on the outermost sides in the tire width direction among the land portions are defined as shoulder land portions, it is preferable that the shoulder land portions have at least one circumferential narrow groove.

[0028] The circumferential narrow grooves contribute to improving drainage, which is believed to improve drainage in the shoulder land areas and thus wet grip performance.

[0029] [Definition] "Normal condition" refers to a condition where the tire is mounted on a normal rim, inflated to normal internal pressure, and unloaded. "Dimensions, etc. of each part of the tire" are values ​​specified in the normal condition, unless otherwise specified.

[0030] "Genuine rim" refers to a rim that is specified for each tire by the standard system that includes the standard on which the tire is based, for example, the standard rim for the applicable size listed in the "JATMA YEAR BOOK" for JATMA (Japan Automobile Tire Manufacturers Association), the "Measuring Rim" listed in the "STANDARDS MANUAL" for ETRTO (The European Tyre and Rim Technical Organisation), and the "Design Rim" listed in the "YEAR BOOK" for TRA (The Tire and Rim Association, Inc.), referring to JATMA, ETRTO, and TRA in that order, and following the standard if there is an applicable size at the time of reference. And, for tires not specified in the standard, it refers to a rim that can be assembled to a rim and can hold internal pressure, that is, a rim that does not leak air from between the rim and tire, with the smallest rim diameter and the next narrowest rim width.

[0031] "Regular internal pressure" refers to the air pressure set for each tire by each standard in the standard system including the standard on which the tire is based. For JATMA, it is the "maximum air pressure", for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and for ETRTO, it is "INFLATION PRESSURE". As with regular rims, refer to JATMA, ETRTO, and TRA in that order, and follow the standard if there is an applicable size at the time of reference. In the case of a tire not specified in the standard, it refers to the regular internal pressure (250KPa or more) of another tire size (specified in the standard) that is specified with the regular rim as the standard rim. Note that if multiple regular internal pressures of 250KPa or more are listed, it refers to the smallest value among them.

[0032] "Normal load" means the load specified in the standard system including the standard on which the tire is based. It is the "maximum value" and "normal load" listed in "Maximum load capacity" in the JATMA standard, "LOAD CAPACITY" in the ETRTO standard, and "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard. As with the normal rim and normal internal pressure, refer to JATMA, ETRTO, and TRA in that order, and follow the standard if there is an applicable size at the time of reference. For tires not specified in the standard, the normal load WL (kg) is calculated as follows. WL=0.000011×V+175 V = {(Dt / 2) 2 -(Dt / 2-Ht) 2}×π×Wt V: Virtual volume of the tire (mm 3 ) Dt: Tire outer diameter Dt (mm) Ht: Section height of the tire (mm) Wt: tire section width (mm)

[0033] The tire section width Wt is the maximum width between the outer sidewall surfaces of the tire in a normal state, excluding any patterns or letters on the sidewalls. The tire section height Ht is the distance from the bottom surface of the bead to the outermost surface of the tread, and is half the difference between the tire outer diameter Dt and the nominal rim diameter.

[0034] The "belt layer" refers to a layer disposed adjacent to the tread on the radially inner side of the tread, mainly in radial tires, and serves to strongly tighten the carcass and increase the rigidity of the tread. The belt layer includes cords forming the framework and rubber covering the cords. In the present invention, the belt layer is a belt layer that is commonly used in the tire industry.

[0035] "Circumferential main groove" refers to a groove that extends continuously in the circumferential direction of the tire and has a groove width of 4 mm or more in the tire width direction on the tread surface. The circumferential main groove may extend linearly along the circumferential direction, or may extend in a wavy, sinusoidal, or zigzag shape along the circumferential direction. However, this does not include the widening circumferential groove described below.

[0036] "Circumferential narrow groove" refers to a groove that extends continuously in the circumferential direction of the tire and has a groove width in the tire width direction on the tread surface of less than 4 mm. The circumferential narrow groove may extend linearly along the circumferential direction, or may extend in a wavy, sinusoidal, or zigzag shape along the circumferential direction. However, it does not include the widened circumferential groove described below.

[0037] The "widening circumferential groove" refers to a groove that extends continuously in the tire circumferential direction, has a groove width in the tire width direction that is smallest on the tread surface and is configured to widen on the tire radially inward side. The widening circumferential groove may extend linearly in the circumferential direction, or may extend in a wavy, sinusoidal, or zigzag shape in the circumferential direction.

[0038] "Total styrene content (mass%) of the rubber component" is calculated by multiplying the styrene content of each rubber that constitutes the entire rubber component (100 mass%) by its styrene content in the entire rubber component, and adding up all of these values.

[0039] The "small hole" is a small hole on the tread surface that extends from the inside of the tread and opens to the tread surface. The small holes exist independently and are not connected to the circumferential grooves, lateral grooves, etc.

[0040] [Measurement method] "30℃ tan δ" is the loss tangent measured using a GABO Iplexer series under the following conditions: temperature 30℃, initial strain 5%, dynamic strain 1%, frequency 10Hz, and elongation mode. When cutting out a sample for loss tangent measurement from the tread of a tire, cut out a piece from inside the rubber layer of interest to a size of 20mm length x 4mm width x 1mm thickness, with the long side in the tire circumferential direction and the thickness in the tire radial direction.

[0041] The "glass transition temperature (Tg) (°C) of the rubber composition" is the temperature (tan δ peak temperature) corresponding to the maximum value in the temperature distribution curve obtained by measuring the temperature distribution curve of the loss tangent tan δ in the range of -60 to 40°C under the conditions of a frequency of 10Hz, an initial strain of 10%, an amplitude of ±0.5%, and a temperature rise rate of 2°C / min using a dynamic viscoelasticity measuring device (for example, an Iplexer series manufactured by GABO Co., Ltd.). In addition, in the case where the tan δ value continues to gradually increase or decrease with increasing temperature in the measurement in the range of -60 to 40°C, the glass transition temperature of the rubber composition is 40°C or -60°C, respectively. In addition, in the case where there are two or more temperatures at which the tan δ value is maximum in the range of -60 to 40°C, the temperature corresponding to the lowest temperature point among these is regarded as the glass transition temperature of the rubber composition. The measurement sample is prepared in the same manner as in the case of 0°C tan δ.

[0042] "Styrene content (mass%)" is 1 It is calculated by H-NMR measurement.

[0043] "Vinyl content (amount of 1,2-bonded butadiene units) (mol%)" is calculated by infrared absorption spectrum analysis in accordance with JIS K 6239-2:2017.

[0044] "Cis content (cis-1,4-bonded butadiene unit amount) (mol%)" is calculated by infrared absorption spectrum analysis in accordance with JIS K 6239-2:2017.

[0045] The "glass transition temperature (Tg) (°C)" is measured in accordance with JIS K 7121 using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan, Inc., while increasing the temperature at a rate of 10°C / min. In the present invention, the Tg of styrene-butadiene rubber is particularly measured.

[0046] The "weight average molecular weight (Mw)" can be determined based on a measurement value obtained by gel permeation chromatography (GPC) (e.g., GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation) in terms of standard polystyrene.

[0047] "N2SA of carbon black" is measured in accordance with JIS K 6217-2:2017.

[0048] "N2SA of Silica" is measured by the BET method in accordance with ASTM D3037-93.

[0049] The "average primary particle size" can be determined by observing with a transmission or scanning electron microscope, measuring 400 or more primary particles observed within the field of view, and averaging the measurements. If the particle shape is spherical, the diameter of the sphere is used as the particle size, and if the particle shape is non-spherical, the circle equivalent diameter (positive square root of {4 x (particle area) ÷ π}) is calculated from the transmission electron microscope image to determine the particle size. This applies to carbon black, silica, etc.

[0050] The "softening point" is defined as the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point measuring apparatus.

[0051] The "plasticizer content" includes the amount of plasticizer in the rubber component extended by the plasticizer. Similarly, the "oil content" includes the amount of oil in the oil-extended rubber.

[0052] [tire] The tire of the present invention will be described below with reference to the drawings as appropriate. However, the drawings are merely examples, and the present invention should not be interpreted as being limited based on the drawings.

[0053] The tire of the present invention is a tire having a tread portion and at least one belt layer, wherein the tread portion comprises at least a first rubber layer which is radially outermost in the tire direction, and a second rubber layer which is adjacent to the radially inward side of the first rubber layer, and the tread portion has two or more circumferential main grooves extending in the tire circumferential direction, and a land portion defined by the circumferential main grooves, and the deepest portion of the groove bottom of at least one of the circumferential main grooves is formed so as to be located radially inward of the outermost portion of the second rubber layer within the land portion adjacent to that circumferential main groove.

[0054] FIG. 1 is a cross-sectional view of a tire according to an embodiment of the present invention taken along a plane passing through the tire rotation axis. In the tire of FIG. 1, the tire section width is indicated by Wt. The tread portion of the tire includes a first rubber layer on the outermost side in the tire radial direction, and a second rubber layer adjacent to the tire radially inward side of the first rubber layer, and includes two or more circumferential main grooves extending in the tire circumferential direction, and a land portion defined by the circumferential main grooves, but this is not shown in FIG. 1. In FIG. 1, a belt layer 11 and a belt layer 12 are provided on the tire radially inner side of the tread portion. Of these, the belt layer 11 is the widest belt layer, and its width is indicated by Wb. The tire section width is indicated by Wt. Dt is the tire outer diameter.

[0055] Fig. 2 is a development view of the tread surface of a tire according to one embodiment of the present invention. The direction of the arrow W is the tread width direction, and the direction of the arrow C is the tire circumferential direction. CL indicates the tire center line, and Te indicates the tread edge. In Fig. 2, the tread surface is divided into four land portions 3 by three circumferential main grooves 2.

[0056] Fig. 3 shows a part of a cross section of a tire according to an embodiment of the present invention, taken along a plane passing through the tire rotation axis. In Fig. 3, the tread portion includes a first rubber layer 4 on the outermost side in the tire radial direction, and a second rubber layer 5 adjacent to the first rubber layer on the inner side in the tire radial direction. Here, the deepest part of the groove bottom of the circumferential main groove 2 (the lower end at depth D in Fig. 3) is formed to be located radially inward of the outermost part of the second rubber layer 5 of the land portion 3 adjacent to the circumferential main groove 2 (the upper end at thickness H2 of the second rubber layer in Fig. 3). Note that the tread portion only needs to include at least the first rubber layer and the second rubber layer adjacent thereto, and may further include other rubber layers between the belt layer.

[0057] In the tire of the present invention, it is preferable that the length in the tire width direction of the land portion located on the tire centerline, or the land portion closest to the tire centerline when a circumferential main groove is present on the tire centerline, increases from the outer side toward the inner side in the tire radial direction. After wear, the first rubber layer plays a role in supporting the ends of the land portions, and it is considered that the above-mentioned configuration makes it easier for the first rubber layer to support the ends of the land portions.

[0058] <Equation (1), Equation (2)> In the tire of the present invention, the content (parts by mass) of silica relative to 100 parts by mass of the rubber component in the first rubber composition is A1 SIL The content (parts by mass) of silica relative to 100 parts by mass of the rubber component in the second rubber composition is A2 SIL When the normal load is applied under normal conditions and the tread is pressed against a flat surface, the tire cross-sectional width (mm) is Wt and the width (mm) of the widest belt layer among the belt layers is Wb. A1 SIL , A2 SIL , Wt and Wb satisfy the predetermined relationship shown in the above formula (1) and formula (2).

[0059] (Formula (1), A2 SIL / A1 SIL ) Equation (1) is as follows. (1) A2 SIL / A1 SIL >1.05

[0060] The right side of formula (1) is preferably 1.06, more preferably 1.07, even more preferably 1.10, even more preferably 1.20, even more preferably 1.30, even more preferably 1.40, even more preferably 1.50. On the other hand, there is no particular upper limit for the value of the left side of formula (1), but it may be, for example, 3.00, 2.50, 2.00, or 1.70.

[0061] The value of the left side of formula (1) can be adjusted by adjusting the amount of silica blended into the first rubber composition constituting the first rubber layer and the amount of silica blended into the second rubber composition constituting the second rubber layer.

[0062] (Formula (2), A2 SIL / (Wt-Wb) Equation (2) is as follows. (2) A2 SIL / (Wt-Wb)>1.00

[0063] The right side of formula (2) is preferably 1.08, more preferably 1.10, even more preferably 1.20, even more preferably 1.25, even more preferably 1.30, even more preferably 1.40, even more preferably 1.50. On the other hand, there is no particular upper limit for the value of the left side of formula (2), but it may be, for example, 3.00, 2.50, 2.00, or 1.70.

[0064] The value of the left side of formula (2) can be adjusted by adjusting the amount of silica blended in the second rubber composition constituting the second rubber layer, as well as the tire cross-sectional width and the width of the widest belt layer.

[0065] <tg> (Tg2) In the tire of the present invention, when the glass transition temperature (°C) of the second rubber composition is Tg2, Tg2 is preferably higher than -30°C.

[0066] From the viewpoint of wet grip performance, Tg2 is preferably higher than −25° C., more preferably higher than −20° C. On the other hand, the upper limit of Tg2 is not particularly limited, but may be, for example, lower than 15° C., or lower than 5° C., or lower than 0° C.

[0067] (Tg1) In the tire of the present invention, when the glass transition temperature (°C) of the first rubber composition is Tg1, Tg1 is preferably higher than -50°C and lower than -10°C.

[0068] Furthermore, Tg1 is more preferably above -47°C, even more preferably above -45°C, while it is more preferably below -13°C, even more preferably below -15°C.

[0069] Tg2 and Tg1 can be appropriately adjusted by the type and amount of the rubber component constituting the rubber composition, and the type and amount of additives other than the rubber component.

[0070] <30℃ tanδ> (30℃ tanδ1) In the tire of the present invention, when tan δ at 30° C. of the first rubber composition is taken as 30° C. tan δ1, 30° C. tan δ1 is preferably less than 0.30.

[0071] From the viewpoint of wet grip performance, 30°C tan δ1 is preferably less than 0.26, more preferably less than 0.24, and even more preferably less than 0.20. On the other hand, there is no particular restriction on the lower limit of 30°C tan δ1, but it may be, for example, more than 0.10, or more than 0.12.

[0072] (30℃ tanδ2) In the tire of the present invention, when tan δ of the second rubber composition at 30° C. is taken as 30° C. tan δ2, 30° C. tan δ2 is preferably less than 0.50 and more than 0.10.

[0073] Furthermore, 30° C. tan δ2 is more preferably less than 0.48, and even more preferably 0.46 or less, while it is more preferably greater than 0.12, and even more preferably greater than 0.15.

[0074] The 30° C. tan δ1 and 30° C. tan δ2 can be appropriately adjusted by the type and amount of the rubber component constituting the rubber composition, and the type and amount of the additives other than the rubber component.

[0075] <St1、St2> In the tire of the present invention, when the total styrene amount (mass%) of the rubber components contained in the first rubber composition is St1 and the total styrene amount (mass%) of the rubber components contained in the second rubber composition is St2, it is preferable that at least one of St1 and St2 is less than 25.0, and it is more preferable that both St1 and St2 are less than 25.0.

[0076] St1 is preferably less than 20.0, more preferably less than 19.0, even more preferably less than 18.0, and even more preferably less than 17.0. St2 is preferably less than 20.0, more preferably less than 19.0, even more preferably less than 18.0, and even more preferably less than 17.0.

[0077] The value of St1 can be adjusted by adjusting the styrene content of each of the rubber components blended in the first rubber composition. Similarly, the value of St2 can be adjusted by adjusting the styrene content of each of the rubber components blended in the second rubber composition.

[0078] <Wide circumferential groove> In the tire of the present invention, it is preferable that the tread portion has a widening circumferential groove whose groove width is wider on the radially inner side of the tire. This is because, after wear, the widening circumferential groove has a wider groove width, which improves drainage and wet grip performance.

[0079] In Fig. 4, a linear widening circumferential groove 6 is formed on each of two land portions 3 adjacent to a circumferential main groove 2 passing on the tire centerline. The widening circumferential groove may extend, for example, in a wavy, sinusoidal, or zigzag shape along the circumferential direction. There are no particular limitations on the land portion in which the widening circumferential groove is formed, but it is preferable that the widening circumferential groove is formed on a land portion located on the tire centerline, or, when a circumferential main groove exists on the tire centerline, it is preferable that the widening circumferential groove is formed on the land portion closest to the tire centerline, as in the widening circumferential groove 6 in Fig. 4.

[0080] FIG. 5 shows a cross section of the widened circumferential groove 6. In FIG. 5, the groove width of the widened circumferential groove increases uniformly toward the inside in the tire radial direction, but the increase in the groove width is not limited to this mode, and may increase while repeating small increases and decreases in a curved or stepped manner, for example. The same applies to the ratio of the tire width direction length of the opening to the tire width direction length of the groove bottom, and FIG. 5 is one example and is not limited thereto, and the ratio may be appropriately increased or decreased within a range less than 1. Note that in FIG. 5, the display of each layer constituting the tread portion is omitted.

[0081] <Small hole> In the tire of the present invention, when a pair of land portions located on the outermost sides in the tire width direction are shoulder land portions, the shoulder land portions have an opening area of ​​more than 0.1 mm and less than 15 mm 2 In FIG. 6, small holes 7 are formed on a pair of shoulder land portions 3 on the tread surface. The small holes contribute to improving drainage, which improves drainage in the shoulder land portions and contributes to improving wet grip performance. For example, in actual use, even if one side of the shoulder land portion or the center land portion wears preferentially and the remaining shoulder land portion hardens over time, it is believed that the small holes ensure drainage and make it easier to improve wet grip performance after wear. The opening area of ​​the small holes on the tread surface is 0.1 mm 2 More than 0.5mm is preferable 2 More than 1.0mm is more preferable. 2 More preferably, 1.5 mm 2 The opening area of ​​the small holes on the tread surface is preferably 15 mm or less. 2 Less than 10mm is preferable 2 Less than 7.0mm is preferable. 2 Less than 5.0 mm is more preferable. 2 It is particularly preferable that the depth of the deepest portion of the small hole is 3% or more, and more preferably 5% or more, of the depth of the deepest portion of the circumferential main groove. Also, it is preferable that the depth of the deepest portion of the small hole is 80% or less, and more preferably 60% or less, and even more preferably 40% or less, of the depth of the deepest portion of the circumferential main groove.

[0082] <Circumferential narrow groove> In the tire of the present invention, when a pair of land portions located on the outermost sides in the tire width direction are shoulder land portions, the shoulder land portions preferably have at least one circumferential narrow groove. In Fig. 7, a circumferential narrow groove 8 is formed on a pair of shoulder land portions 3 on the tread surface. The circumferential narrow groove contributes to improving drainage, which improves drainage in the shoulder region and contributes to improving wet grip performance.

[0083] [Rubber composition] Hereinafter, the rubber composition according to the tire of the present invention, that is, the first rubber composition constituting the first rubber layer of the tread portion and the second rubber composition constituting the second rubber layer will be described. The following description can be applied to both the first rubber composition and the second rubber composition unless otherwise specified. Therefore, when simply referring to the rubber composition, it is meant to include both the first rubber composition and the second rubber composition.

[0084] The rubber compositions according to the present invention, that is, the first rubber composition and the second rubber composition each contain a rubber component and silica.

[0085] <Rubber component> The rubber compositions according to the present invention, that is, the first rubber composition and the second rubber composition, each contain a styrene-butadiene rubber as a rubber component.

[0086] The rubber component contained in the second rubber composition preferably contains at least one of a butadiene rubber and an isoprene-based rubber.

[0087] At least one of the rubber components contained in the first rubber composition and the rubber components contained in the second rubber composition preferably contains a butadiene rubber. It is preferable that both of the rubber components contained in the first rubber composition and the rubber components contained in the second rubber composition contain a butadiene rubber.

[0088] These rubber components can be used in combination with other rubber components described below. They can be modified to obtain an interaction with a filler, or a portion of the double bonds can be hydrogenated to suppress deterioration. They can also be extended with a plasticizer described below to form an extended rubber.

[0089] (SBR) There are no particular limitations on the SBR, and examples thereof include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). Modified SBRs include SBRs whose ends and / or main chains are modified, and modified SBRs (condensates, those having a branched structure, etc.) coupled with tin or silicon compounds. Of these, S-SBR and modified SBR are preferred. Furthermore, hydrogenated products of these SBRs (hydrogenated SBR), etc. can also be used. These SBRs may be used alone or in combination of two or more.

[0090] Examples of S-SBR that can be used in the present invention include S-SBR manufactured and sold by JSR Corporation, Sumitomo Chemical Co., Ltd., Ube Industries, Ltd., Asahi Kasei Corporation, ZS Elastomers Co., Ltd., and the like.

[0091] 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 blow resistance, the styrene content is preferably less than 60% by mass, more preferably less than 55% by mass, and even more preferably less than 50% by mass. In this specification, the styrene content of SBR is calculated by the above-mentioned method.

[0092] The vinyl content of SBR is preferably more than 10 mol%, more preferably more than 13 mol%, and even more preferably more than 15 mol%, from the viewpoints of ensuring reactivity with silica, wet grip performance, rubber strength, and abrasion resistance. Also, the vinyl content of SBR is preferably less than 70 mol%, more preferably less than 65 mol%, and even more preferably less than 60 mol%, from the viewpoints of preventing an increase in temperature dependency, breaking elongation, and abrasion resistance. In this specification, the vinyl content of SBR (amount of 1,2-bonded butadiene units) is measured by the above-mentioned method.

[0093] From the viewpoint of wet grip performance, the weight average molecular weight (Mw) of SBR is preferably more than 200,000, more preferably more than 250,000, and even more preferably more than 300,000. From the viewpoint of crosslinking uniformity, the weight average molecular weight is preferably less than 2,000,000, more preferably less than 1,800,000, and even more preferably less than 1,500,000. In this specification, the weight average molecular weight of SBR can be determined by the above-mentioned method.

[0094] From the viewpoint of wet grip performance, the content of SBR in the rubber component is preferably more than 45% by mass, more preferably more than 50% by mass, even more preferably more than 55% by mass, and even more preferably 60% by mass or more. On the other hand, the upper limit of the content of SBR in the rubber component is not particularly limited and may be 100% by mass.

[0095] (BR) The BR is not particularly limited, and can be one that is 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 more than 90 mol% (high cis BR), rare earth butadiene rubber (rare earth BR) synthesized using a rare earth catalyst, BR containing syndiotactic polybutadiene crystals (SPB-containing BR), and modified BR (high cis modified BR, low cis modified BR). Modified BR can be BR modified with the same functional groups as those described above for SBR. These BRs can be used alone or in combination of two or more.

[0096] As the high cis BR, for example, those commercially available from Zeon Corporation, Ube Industries, Ltd., JSR Corporation, etc. can be used. By containing high cis BR, it is possible to improve low temperature properties and wear resistance. The cis content is preferably more than 95 mol%, more preferably more than 96 mol%, and even more preferably 97 mol% or more. In this specification, the cis content (amount of cis-1,4-bonded butadiene units) is a value calculated by the above method.

[0097] 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 1.6 mol%, and even more preferably 1.5% or less, and a cis content of preferably more than 95 mol%, more preferably more than 96 mol%, and even more preferably 97 mol% or more. As the rare earth BR, for example, commercially available products from LANXESS LTD. can be used.

[0098] The SPB-containing BR is not one in which 1,2-syndiotactic polybutadiene crystals are simply dispersed in the BR, but one in which the 1,2-syndiotactic polybutadiene crystals are dispersed after being chemically bonded to the BR. As such an SPB-containing BR, commercially available products from Ube Industries, Ltd. can be used.

[0099] As the modified BR, a modified butadiene rubber (modified BR) in which the terminals and / or the main chain are modified with a functional group containing at least one element selected from the group consisting of silicon, nitrogen and oxygen is preferably used.

[0100] Other modified BRs include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and further having the terminals of the modified BR molecule bonded with tin-carbon bonds (tin-modified BR), etc. The modified BR may be either non-hydrogenated or hydrogenated.

[0101] 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 crosslinking uniformity, etc., it is preferably less than 2,000,000, more preferably less than 1,000,000, and even more preferably less than 500,000. Mw can be determined by the above-mentioned method.

[0102] When BR is contained, the content in the rubber component is preferably less than 50% by mass, more preferably less than 45% by mass, and even more preferably 40% by mass or less, from the viewpoint of wet grip performance. On the other hand, the lower limit of the content of BR in the rubber component is not particularly limited and may be 0% by mass, but may also be, for example, more than 1% by mass, more than 5% by mass, more than 10% by mass, or 15% by mass or more.

[0103] (Isoprene rubber) As the isoprene-based rubber, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. In addition to unmodified natural rubber (NR), natural rubber also includes modified natural rubber such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. These isoprene-based rubbers may be used alone or in combination of two or more.

[0104] The NR is not particularly limited, and any NR commonly used in the tire industry can be used, such as SIR20, RSS#3, and TSR20.

[0105] When an isoprene-based rubber is contained, the content in the rubber component is preferably less than 50% by mass, more preferably less than 40% by mass, and even more preferably less than 30% by mass, from the viewpoint of wet grip performance. On the other hand, the lower limit of the content of the isoprene-based rubber in the rubber component is not particularly limited and may be 0% by mass, but may also be, for example, more than 1% by mass, more than 5% by mass, more than 10% by mass, more than 20% by mass, or 25% by mass or more.

[0106] (Other rubber components) The rubber component according to the present invention may contain rubber components other than the isoprene-based rubber, SBR, and BR. As the other rubber components, crosslinkable rubber components generally used in the tire industry can be used, such as styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isobutylene-styrene block copolymer (SIBS), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, etc. These other rubber components may be used alone or in combination of two or more.

[0107] <Filler> The rubber composition according to the present invention, i.e., the first rubber composition and the second rubber composition, both contain silica. The rubber composition according to the present invention preferably further contains carbon black. The rubber composition according to the present invention may further contain other fillers other than silica and carbon black as a filler. The rubber composition according to the present invention may not contain the other fillers.

[0108] The other fillers are not particularly limited, and any fillers that have been generally used in the tire industry can be used, such as aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, magnesium sulfate, talc, clay, biochar, etc. These fillers may be used alone or in combination of two or more.

[0109] (silica) The silica is not particularly limited, and may 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. From the viewpoint of environmental load, silica made from biomass materials (for example, amorphous silica purified from rice husks) may be used. Among them, hydrated silica prepared by a wet method is preferred because it contains a large number of silanol groups. These silicas may be used alone or in combination of two or more.

[0110] 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 silica to produce a precipitate of silicon dioxide, which can be obtained by filtering, washing with water, drying, and pulverizing. When silica crystallizes, it does not dissolve in water, and its component silicic acid cannot be used. By controlling the combustion temperature and combustion time, the crystallization of silica in rice husk ash can be suppressed (see JP 2009-2594 A, Akita Prefectural University Web Journal B / 2019, vol. 6, p. 216-222, etc.). Amorphous silica extracted from rice husks can be commercially available from Wilmar Co., Ltd., etc.

[0111] The nitrogen adsorption specific surface area (N2SA) of silica is set at 140m from the viewpoints of fuel efficiency and wear resistance. 2 / g or more is preferable, and 150m 2 / g is more preferable, and 160m 2 More preferably, 175m 2 From the viewpoints of fuel efficiency and processability, it is more preferable that the tensile strength is 350 m 2 / g is preferable, and 300m 2 / g is more preferable, and 250m 2 / g or less is more preferable. In this specification, the N2SA of silica is a value measured by the above-mentioned method.

[0112] The average primary particle size of silica is preferably more than 10 nm, more preferably more than 12 nm, and even more preferably more than 14 nm. The average primary particle size is preferably less than 26 nm, more preferably less than 24 nm, and even more preferably 22 nm or less. The average primary particle size of silica is measured by the above-mentioned measuring method.

[0113] When silica is contained, the content per 100 parts by mass of the rubber component is preferably more than 20 parts by mass, more preferably more than 30 parts by mass, even more preferably more than 40 parts by mass, and even more preferably more than 45 parts by mass from the viewpoint of wet grip performance, and is preferably less than 130 parts by mass, more preferably less than 110 parts by mass, even more preferably less than 100 parts by mass, and even more preferably less than 90 parts by mass from the viewpoint of abrasion resistance.

[0114] (Carbon Black) The carbon black can be any carbon black commonly used in the tire industry, and examples thereof include GPF, FEF, HAF, ISAF, SAF, and the like. More specific examples thereof include N110, N115, N120, N125, N134, N135, N219, N220, N231, N234, N293, N299, N326, N330, N339, N343, N347, N351, N356, N358, N375, N539, N550, N582, N630, N642, N650, N660, N683, N754, N762, N765, N772, N774, N787, N907, N908, N990, N991, and the like. From the viewpoint of life cycle assessment, in addition to the above carbon blacks, carbon blacks made from lignin as a raw material and recycled carbon blacks obtained by pyrolysis or the like from products containing carbon black such as tires may be used. These carbon blacks may be used alone or in combination of two or more kinds.

[0115] From the perspective of reinforcement, the nitrogen adsorption specific surface area (N2SA) of carbon black is 10m 2 / g or more is preferable, and 30m 2 More preferably, 50m 2 From the viewpoints of fuel efficiency and processability, it is more preferable that the tensile strength is more than 200 m 2 / g or less is preferable, and 175m 2 / g is more preferable, and 150m 2 The N2SA of carbon black is measured by the above-mentioned method.

[0116] The average primary particle size of carbon black is preferably more than 10 nm, more preferably more than 12 nm, and even more preferably more than 14 nm. The average primary particle size is preferably less than 26 nm, more preferably less than 24 nm, and even more preferably 22 nm or less. The average primary particle size of carbon black is measured by the above-mentioned measurement method.

[0117] When carbon black is contained, the content per 100 parts by mass of the rubber component is preferably more than 1 part by mass, more preferably more than 3 parts by mass, and even more preferably 5 parts by mass or more, from the viewpoint of abrasion resistance and wet grip performance, and is preferably less than 50 parts by mass, more preferably less than 40 parts by mass, and even more preferably 35 parts by mass or less, from the viewpoint of fuel economy.

[0118] (Filler content) The total content of the filler 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 more than 60 parts by mass from the viewpoint of abrasion resistance, and is preferably less than 200 parts by mass, more preferably less than 150 parts by mass, and even more preferably less than 120 parts by mass from the viewpoint of fuel economy and elongation at break.

[0119] When the filler contains both silica and carbon black, the content of silica is preferably greater than the content of carbon black from the viewpoint of the balance of fuel economy, wet grip performance, and abrasion resistance. The ratio of silica to the total content of silica and carbon black is preferably more than 60 mass%, more preferably more than 70 mass%, even more preferably more than 80 mass%, and even more preferably more than 90 mass%.

[0120] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent.Silane coupling agent is not particularly limited, and can be used any silane coupling agent that is conventionally used in combination with silica in the tire industry, such as thioester-based silane coupling agents such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, 3-octanoylthio-1-propyltrimethoxysilane; mercapto-based silane coupling agents such as those shown in the following chemical formula; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide, bis(3-triethoxysilylpropyl) tetrasulfide; vinyltriethoxysilane, Examples of the silane coupling agents include vinyl trimethoxysilane and the like; amino silane coupling agents such as 3-aminopropyl triethoxysilane, 3-aminopropyl trimethoxysilane, and 3-(2-aminoethyl) aminopropyl triethoxysilane; glycidoxy silane coupling agents such as γ-glycidoxypropyl triethoxysilane and γ-glycidoxypropyl trimethoxysilane; nitro silane coupling agents such as 3-nitropropyl trimethoxysilane and 3-nitropropyl triethoxysilane; chloro silane coupling agents such as 3-chloropropyl trimethoxysilane and 3-chloropropyl triethoxysilane. Among these, thioester silane coupling agents and / or sulfide silane coupling agents are preferred. These silane coupling agents may be used alone or in combination of two or more.

[0121] The mercapto-based silane coupling agent is preferably a compound represented by the following chemical formula (1) and / or a compound containing a bonding unit A represented by the following chemical formula (2) and a bonding unit B represented by the following chemical formula (3).

[0122] [ka]

[0123] (In the formula, R 101 , R 102 , and R 103 are each independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or -O-(R 111 -O) z -R 112 (z R 111 each independently represents a divalent hydrocarbon group having 1 to 30 carbon atoms; R 112 represents an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group having 7 to 30 carbon atoms; z represents an integer of 1 to 30; 104 represents an alkylene having 1 to 6 carbon atoms.

[0124] [ka]

[0125] [ka]

[0126] (wherein x represents an integer of 0 or more; y represents an integer of 1 or more; R 201 represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, or an alkynyl group having 2 to 30 carbon atoms, which may be substituted by a hydroxyl or carboxyl group; R 202 represents an alkylene having 1 to 30 carbon atoms, an alkenylene having 2 to 30 carbon atoms, or an alkynylene having 2 to 30 carbon atoms; 201 and R 202 may form a ring structure.)

[0127] Examples of the compound represented by formula (1) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and the compound represented by the following chemical formula (4) (Si363 manufactured by Evonik Degussa), and the compound represented by the following chemical formula (4) can be preferably used. These may be used alone or in combination of two or more.

[0128] [ka]

[0129] Examples of compounds containing a bond unit A represented by chemical formula (2) and a bond unit B represented by chemical formula (3) include those manufactured and sold by Momentive, Inc. These may be used alone or in combination of two or more.

[0130] When a silane coupling agent is contained, the content (total amount when multiple silane coupling agents are used) per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1.0 parts by mass, even more preferably more than 2.0 parts by mass, and even more preferably more than 4.0 parts by mass from the viewpoint of improving the dispersibility of silica. Also, from the viewpoint of preventing a decrease in abrasion resistance, the content is preferably less than 20 parts by mass, more preferably less than 12 parts by mass, even more preferably less than 10 parts by mass, and even more preferably less than 9.0 parts by mass.

[0131] The content of the silane coupling agent with respect to 100 parts by mass of silica is preferably more than 1.0 parts by mass, more preferably more than 3.0 parts by mass, and even more preferably more than 5.0 parts by mass, from the viewpoint of increasing the dispersibility of silica.Furthermore, from the viewpoint of cost and processability, it is preferably less than 20 parts by mass, more preferably less than 15 parts by mass, and even more preferably less than 12 parts by mass.

[0132] <Plasticizer> The rubber composition according to the present invention preferably contains a plasticizer, such as a resin, an oil, a liquid rubber, or an ester-based plasticizer.

[0133] (resin) The resin is not particularly limited, but examples thereof include petroleum resins, terpene resins, rosin resins, phenol resins, etc., which are commonly used in the tire industry. These resins may be used alone or in combination of two or more. Among them, petroleum resins are preferred.

[0134] <Petroleum resin> As the petroleum resin, C5 petroleum resin, aromatic petroleum resin, C5C9 petroleum resin, etc. These resins may be used alone or in combination of two or more.

[0135] C5 petroleum resin refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. As a C5 petroleum resin, dicyclopentadiene resin (DCPD resin) is preferably used.

[0136] Aromatic petroleum resin refers to a resin obtained by polymerizing a C9 fraction, and may be a hydrogenated or modified resin. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of aromatic petroleum resins that are preferably used include coumarone-indene resins, coumarone resins, indene resins, and aromatic vinyl resins.

[0137] 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, for example, commercially available products from Kraton, Eastman Chemical, etc. can be used.

[0138] The C5C9 petroleum resin refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. Examples of the C5 fraction and the C9 fraction include the petroleum fractions mentioned above. As the C5C9 petroleum resin, for example, those commercially available from Tosoh Corporation, LUHUA, etc. can be used.

[0139] <Terpene resin> Examples of the terpene resin include polyterpene resins consisting of at least one selected from terpene compounds such as α-pinene, β-pinene, limonene, and dipentene; aromatic modified terpene resins made from the terpene compounds and aromatic compounds; terpene phenolic resins made from terpene compounds and phenolic compounds; and those obtained by subjecting these terpene resins to hydrogenation treatment (hydrogenated terpene resins). Examples of aromatic compounds that are raw materials for aromatic modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenolic compounds that are raw materials for terpene phenolic resins include phenol, bisphenol A, cresol, and xylenol. These resins may be used alone or in combination of two or more.

[0140] <Rosin-based resin> The rosin-based resin is not particularly limited, but examples thereof include natural resin rosin, and rosin-modified resins obtained by modifying natural resin rosin through hydrogenation, disproportionation, dimerization, esterification, etc. These resins may be used alone or in combination of two or more kinds.

[0141] <Phenol-based resin> The phenol-based resin is not particularly limited, but examples thereof include phenol formaldehyde resin, alkylphenol formaldehyde resin, alkylphenol acetylene resin, oil-modified phenol formaldehyde resin, etc. These resins may be used alone or in combination of two or more kinds.

[0142] ≪Softening point≫ From the viewpoint of wet grip performance, the softening point of the resin is preferably more than 60° C., more preferably more than 70° C., and even more preferably more than 80° C. From the viewpoint of processability and improving the dispersibility of the rubber component and the filler, the softening point is preferably less than 150° C., more preferably less than 140° C., and even more preferably less than 130° C. In this specification, the softening point is obtained by the above-mentioned method.

[0143] ≪Content≫ When a resin is contained, the content per 100 parts by mass of the rubber component is preferably more than 1 part by mass, more preferably more than 3 parts by mass, and even more preferably more than 5 parts by mass from the viewpoint of wet grip performance, and is preferably less than 60 parts by mass, more preferably less than 40 parts by mass, even more preferably less than 30 parts by mass, and even more preferably less than 20 parts by mass from the viewpoint of suppressing heat buildup.

[0144] (oil) Examples of the oil include process oil, vegetable oil, and animal oil. Examples of the process oil include paraffin-based process oil, naphthenic process oil, and aromatic process oil. In addition, as an environmental measure, process oil with a low content of polycyclic aromatic compound (PCA) compounds can be used. Examples of the low PCA content process oil include light extract solvate (MES), treated distillate aromatic extract (TDAE), and heavy naphthenic oil.

[0145] When oil is contained, the content per 100 parts by mass of the rubber component is preferably more than 3 parts by mass, more preferably more than 5 parts by mass, and even more preferably more than 7 parts by mass from the viewpoint of processability. Also, from the viewpoint of abrasion resistance, the content is preferably less than 120 parts by mass, more preferably less than 80 parts by mass, and even more preferably less than 40 parts by mass. In this specification, the content of oil includes the amount of oil contained in the oil-extended rubber.

[0146] (Liquid Rubber) The liquid rubber is not particularly limited as long as it is a polymer that is in a liquid state at room temperature (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. These liquid rubbers may be used alone or in combination of two or more kinds.

[0147] When the liquid rubber is contained, the content per 100 parts by mass of the rubber component is preferably more than 1 part by mass, more preferably more than 2 parts by mass, even more preferably more than 3 parts by mass, and even more preferably more than 5 parts by mass. The content of the liquid rubber is preferably less than 50 parts by mass, more preferably less than 40 parts by mass, and even more preferably less than 20 parts by mass.

[0148] (Ester plasticizer) 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), trixylenyl phosphate (TXP), etc. These ester-based plasticizers may be used alone or in combination of two or more.

[0149] The content of the plasticizer per 100 parts by mass of the rubber component is preferably more than 5 parts by mass, more preferably more than 10 parts by mass, and even more preferably more than 15 parts by mass from the viewpoint of wet grip performance, and is preferably less than 120 parts by mass, more preferably less than 80 parts by mass, and even more preferably less than 40 parts by mass from the viewpoint of processability.

[0150] <Other compounding agents> In addition to the above-mentioned components, the rubber composition according to the present invention may appropriately contain compounding agents generally used in the tire industry, such as wax, processing aids, antioxidants, stearic acid, zinc oxide, vulcanizing agents, and vulcanization accelerators.

[0151] (wax) Any wax commonly used in the tire industry can be used. The wax may be used alone or in combination of two or more. When the wax is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1.0 parts by mass, and even more preferably 1.5 parts by mass or more, from the viewpoint of weather resistance of the rubber. Also, from the viewpoint of preventing whitening of the tire due to bloom, the content is preferably less than 10 parts by mass, more preferably less than 7.0 parts by mass, and even more preferably less than 5.0 parts by mass.

[0152] (Processing aids) Examples of the processing aid include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, etc. These processing aids may be used alone or in combination of two or more. Examples of the processing aids that can be used include those commercially available from Schill+Seilacher, Performance Additives, etc.

[0153] When the processing aid is contained, the content thereof per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1 part by mass, and even more preferably more than 1.5 parts by mass from the viewpoint of improving processability, and is preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and even more preferably less than 5.0 parts by mass from the viewpoints of abrasion resistance and breaking strength.

[0154] (Anti-aging agent) The antiaging agent is not particularly limited, but examples thereof include amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, and carbamic acid metal salts, and the like. Phenylenediamine-based antiaging agents such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and N-cyclohexyl-N'-phenyl-p-phenylenediamine, and quinoline-based antiaging agents such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline are preferred. These antiaging agents may be used alone or in combination of two or more.

[0155] When an antioxidant is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1.0 parts by mass, and even more preferably more than 1.5 parts by mass from the viewpoint of ozone crack resistance of the rubber, and is preferably less than 10 parts by mass, more preferably less than 7 parts by mass, and even more preferably less than 5 parts by mass from the viewpoint of abrasion resistance and wet grip performance.

[0156] (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 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less from the viewpoint of vulcanization speed.

[0157] (Zinc Oxide) When zinc oxide is contained, the content per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1.0 parts by mass, and even more preferably more than 1.5 parts by mass from the viewpoint of processability, and is preferably less than 10 parts by mass, more preferably less than 7 parts by mass, and even more preferably less than 5 parts by mass from the viewpoint of abrasion resistance.

[0158] (Vulcanizing agent) As the vulcanizing agent, sulfur is preferably used. As the sulfur, powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, etc. can be used. The vulcanizing agent may be used alone or in combination of two or more kinds.

[0159] When sulfur is contained as a vulcanizing agent, the content per 100 parts by mass of the rubber component is preferably more than 0.1 parts by mass, more preferably more than 0.3 parts by mass, and even more preferably more than 0.5 parts by mass, from the viewpoint of ensuring sufficient vulcanization reaction. Also, from the viewpoint of preventing deterioration, it is preferably less than 5.0 parts by mass, more preferably less than 4.0 parts by mass, and even more preferably less than 3.0 parts by mass. Note that, when oil-containing sulfur is used as a vulcanizing agent, the content of the vulcanizing agent is the total content of the pure sulfur contained in the oil-containing sulfur.

[0160] Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensates, sodium 1,6-hexamethylene-dithiosulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. As these vulcanizing agents other than sulfur, commercially available products from Taoka Chemical Co., Ltd., Lanxess Co., Ltd., Flexis, etc. can be used.

[0161] (Vulcanization accelerator) Examples of the vulcanization accelerator include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, or xanthate-based vulcanization accelerators, etc. These vulcanization accelerators may be used alone or in combination of two or more.

[0162] Among them, it is preferable that the rubber composition contains one or more vulcanization accelerators selected from the group consisting of sulfenamide-based, guanidine-based, and thiazole-based vulcanization accelerators, and it is more preferable that the rubber composition contains a sulfenamide-based vulcanization accelerator and a guanidine-based vulcanization accelerator.

[0163] 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 them, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) is preferred.

[0164] Examples of the guanidine vulcanization accelerator 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 them, 1,3-diphenylguanidine (DPG) is preferable.

[0165] Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, etc. Among these, 2-mercaptobenzothiazole is preferred.

[0166] When a vulcanization accelerator is contained, the content per 100 parts by mass of the rubber component is preferably more than 1 part by mass, more preferably more than 1.5 parts by mass, and even more preferably more than 2 parts by mass. The content per 100 parts by mass of the rubber component is preferably less than 8 parts by mass, more preferably less than 7 parts by mass, and even more preferably less than 6 parts by mass. By setting the content of the vulcanization accelerator within the above range, breaking strength and elongation tend to be ensured.

[0167] [Belt layer] In the tire of the present invention, the belt layer may be a belt layer commonly used in the tire industry. The belt layer includes a cord forming the framework thereof and a rubber coating the cord. As the cord, in addition to a steel cord, other cords such as an organic fiber cord may be used.

[0168] In the tire of the present invention, the belt layer may be a single layer or may be a multi-layer of two or more layers, and is preferably a multi-layer of two or more layers. In addition, when the width (mm) of the widest belt layer among the belt layers is Wb, the tire cross-sectional width (mm) Wt and the silica content (parts by mass) A2 relative to 100 parts by mass of the rubber component in the second rubber composition are expressed as SIL The relationship of the above formula (2) is satisfied between these values. Here, the value of Wb can be appropriately adjusted by increasing or decreasing the width of the mold.

[0169] [Manufacturing] (Production of Rubber Composition) The rubber composition according to the present invention, i.e., the first rubber composition constituting the first rubber layer and the second rubber composition constituting the second rubber layer, can both 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 (Banbury mixer, kneader, etc.).

[0170] The kneading step includes, for example, a base kneading step in which compounding ingredients and additives other than the vulcanizing agent and the vulcanization accelerator are kneaded, and a final kneading (F kneading) step in which the vulcanizing agent and the 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 a plurality of steps as desired.

[0171] The kneading conditions are not particularly limited, but examples include a method in which in the base kneading step, kneading is performed for 3 to 10 minutes at a discharge temperature of 150 to 170°C, and in the final kneading step, kneading is performed for 1 to 5 minutes at 70 to 110°C.

[0172] (Tire manufacturing) The tire of the present invention can be manufactured by a normal method using the first rubber composition, the second rubber composition, and the belt layer with the widest belt layer having a predetermined width. That is, the tire of the present invention can be manufactured by extruding the unvulcanized first rubber composition and the second rubber composition in an extruder equipped with a die of a predetermined shape according to the shape of the first rubber layer and the second rubber layer, laminating them together with the belt layer according to the present invention and other tire components on a tire building machine, molding them by a normal method to form an unvulcanized tire, and heating and pressurizing the unvulcanized tire in a vulcanizer. The vulcanization conditions are not particularly limited, and examples thereof include a method of vulcanizing at 150 to 200°C for 10 to 30 minutes.

[0173] [Application] The tire of the present invention can be used for any purpose, regardless of whether it is a pneumatic tire or a non-pneumatic tire. It can also be used as a racing tire, a passenger car tire, a large passenger car tire, a large SUV tire, or a motorcycle tire. Among these, a passenger car tire is preferable. Here, a passenger car tire is a tire that is intended to be mounted on a four-wheeled vehicle, and has a maximum load capacity of 1000 kg or less according to the JATMA standard.

[0174] Moreover, the tire of the present invention can be used as a summer tire, a winter tire, or a studless tire for each of the above tires. EXAMPLES

[0175] The present invention will be described based on examples, but the present invention is not limited to only the examples.

[0176] The various chemicals used in the examples and comparative examples are listed below. SBR1: Styrene-butadiene rubber synthesized in Production Example 1 below (modified S-SBR, styrene content: 25% by mass, vinyl content: 25% by mole, Tg: -55°C, non-oil extended product) SBR2: HPR850 manufactured by JSR Corporation (styrene content: 27.5% by mass, vinyl content: 59% by mole, Tg: -24°C) SBR3: Styrene-butadiene rubber synthesized in Production Example 2 below (modified S-SBR, styrene content: 33 mass%, vinyl content: 46 mol%, Tg: -22°C, non-oil extended product) SBR4: JSR0122 manufactured by JSR Corporation (E-SBR, styrene content: 38% by mass, vinyl content: 16 mol%, Tg: -37°C, 100 parts by mass of rubber solids extended with 34 parts by mass of oil) SBR5: SBR1502 manufactured by JSR Corporation (E-SBR, styrene content: 23.5% by mass, vinyl content: 18% by mole, Tg: -51°C) BR: UBEPOL BR (registered trademark) 150B manufactured by Ube Industries, Ltd. (vinyl content: 1.5 mol%, cis content: 97 mol%, Mw: 440,000) NR:TSR20 CB (Carbon Black) 1: Show Black N134 (N2SA: 148m) manufactured by Cabot Japan Co., Ltd. 2 / g, average primary particle diameter: 18nm) CB (Carbon Black) 2: N220 (N2SA: 115m) manufactured by Birla Carbon Brasil Ltda 2 / g, average primary particle diameter: 22nm) Silica: ULTRASIL® VN3 (N2SA: 175 ml) manufactured by Evonik Degussa 2 / g, average primary particle diameter: 18nm) Coupling agent (silane coupling agent) 1: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa Coupling agent (silane coupling agent) 2: NXT (3-octanoylthiopropyltriethoxysilane) manufactured by Momentive Oil: H&R VivaTec500 (TDAE oil) Resin 1: Sylvares SA85 manufactured by Kraton (a copolymer of α-methylstyrene and styrene, softening point: 85°C) Resin 2: NOVARES C90 (coumarone-indene resin, softening point: 90°C) manufactured by Rutgers Chemicals Wax: Sannock N manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Anti-aging agent 1: Antigen 6C (6PPD, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Antioxidant 2: Nocrac 224 (TMQ, 2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: Beads of stearic acid camellia manufactured by NOF Corporation Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd. Vulcanization accelerator 1: Noccela CZ (CBS, N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccelaer D (DPG, 1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0177] Preparation Example 1: Synthesis of SBR1 The ratio of styrene and 1,3-butadiene is adjusted so that the styrene content in the target product is 25% by mass. Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene are charged into a nitrogen-substituted autoclave reactor. After adjusting the temperature of the reactor contents to 20°C, n-butyllithium is added to initiate polymerization. Polymerization is carried out under adiabatic conditions, and when the polymerization conversion rate reaches 99%, 1,3-butadiene is added and further polymerized, and then methyltriethoxysilane is added as a modifier to carry out a modification reaction. After the reaction is completed, 2,6-di-tert-butyl-p-cresol is added. Next, the solvent is removed by steam stripping, and the mixture is dried with a heated roll adjusted to 110°C to obtain SBR1.

[0178] Production Example 2: Synthesis of SBR3 The ratio of styrene and 1,3-butadiene is adjusted so that the styrene content in the target product is 33% by mass. Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene are charged into a nitrogen-substituted autoclave reactor. After adjusting the temperature of the reactor contents to 20°C, n-butyllithium is added to start polymerization. Polymerization is carried out under adiabatic conditions, and when the polymerization conversion rate reaches 99%, 1,3-butadiene is added, and after further polymerization, 3-[bis-(trimethylsilyl)amino]propyltriethoxysilane is added as a modifier to carry out a modification reaction. After the reaction is completed, 2,6-di-tert-butyl-p-cresol is added. Next, the solvent is removed by steam stripping, and the mixture is dried with a heated roll adjusted to 110°C to obtain SBR3.

[0179] [Examples and Comparative Examples] According to the compounding recipe shown in Table 1, the chemicals other than sulfur and vulcanization accelerator are kneaded for 1 to 10 minutes using a 1.7 L closed type Banbury mixer until the discharge temperature reaches 150 to 160 ° C. to obtain a kneaded product. Next, sulfur and vulcanization accelerator are added to the kneaded product obtained using a two-axis open roll, and kneaded for 4 minutes until the temperature reaches 105 ° C. to obtain an unvulcanized rubber composition. The unvulcanized rubber composition obtained is molded according to the shape of the first layer (4 mm) and second layer (6 mm) of the tread, and is laminated together with the belt layer and other tire components to prepare an unvulcanized tire, which is vulcanized at 170 ° C. to obtain each test tire (Tire 1: 225 / 45R17, Tire 2: 205 / 55R16, Tire 3: 195 / 45R16).

[0180] The belt layer is disposed adjacent to the tread on the inner side in the tire radial direction, and two layers of the belt layer are disposed adjacent to the tread. Of the two belt layers, the belt layer disposed on the inner side in the tire radial direction is the widest belt layer.

[0181] On the tread surface of each test tire, three straight circumferential main grooves are provided, one of which passes along the tire centerline, and the remaining two are provided at equal intervals on the outer side in the tire width direction from the main groove passing along the tire centerline. The groove depth (deepest point) of each of these circumferential main grooves is 6.5 mm.

[0182] <Properties of rubber layer> The properties of each rubber layer constituting the tire are measured by the following methods. The results are shown in the corresponding column of Table 1 for the rubber composition constituting each rubber layer.

[0183] (30℃ tan δ) A viscoelasticity measurement sample having a length of 20 mm, a width of 4 mm, and a thickness of 1 mm is taken from inside a specified rubber layer (first rubber layer) in the tread portion of each test tire, with the long side in the tire circumferential direction and the thickness in the tire radial direction. The loss tangent tan δ is measured using an Iplexer series manufactured by GABO under the following conditions: temperature 30°C, initial strain 5%, dynamic strain 1%, frequency 10 Hz, and extension mode.

[0184] (Glass transition temperature (Tg) of rubber composition) For each rubber test piece cut from the inside of a predetermined rubber layer (second rubber layer) of the tread portion of each test tire, a length of 20 mm, a width of 4 mm, and a thickness of 1 mm are cut out so that the tire circumferential direction is the long side and the tire radial direction is the thickness. A temperature distribution curve of the loss tangent tanδ is measured in the range of -60 to 40°C using an Iplexer series manufactured by GABO under the conditions of a frequency of 10 Hz, an initial strain of 10%, an amplitude of ±0.5%, and a heating rate of 2°C / min. The temperature (tanδ peak temperature) corresponding to the maximum value in the obtained temperature distribution curve is taken as the glass transition temperature (Tg). In the measurement in the range of -60 to 40°C, if the tanδ value continues to gradually increase or decrease with increasing temperature, the glass transition temperature of the rubber composition is taken as 40°C or -60°C, respectively. In addition, if there are two or more temperatures at which the tanδ value is maximum in the range of -60 to 40°C, the temperature corresponding to the lowest temperature point among these is taken as the glass transition temperature of the rubber composition.

[0185] <Wet grip performance after wear> Each test tire is thermally aged at 80°C for 7 days, and then uniformly worn along the tire radius when new so that the tire wears 4.5 mm on the tire equator, and then mounted on all wheels of a vehicle. The vehicle is driven at a speed of 100 km / h on a wet asphalt road surface, and the braking distance from the point where the brakes are applied is measured. The wet grip performance of each tire after wear is expressed as an index using the following calculation formula, so that the braking distance of the test tire of the reference comparative example is 100. The higher the index, the better the wet grip performance. (Wet grip performance index after wear) = (braking distance after wear of the reference comparative tire) / (braking distance after wear of each test tire)×100

[0186] [Table 1]

[0187] [Table 2]

[0188] [Table 3]

[0189] [Table 4]

[0190] In the above Tables 2 to 4, "◯" means that the given conditions are met, and "×" means that the conditions are not met.

[0191] <Embodiment> The following are preferred embodiments.

[0192] [1] A tire having a tread portion and at least one belt layer, The tread portion includes at least a first rubber layer that is an outermost layer in the radial direction of the tire, and a second rubber layer that is adjacent to the inner side of the first rubber layer in the radial direction of the tire, the first rubber layer is composed of a rubber component including a styrene-butadiene rubber and a first rubber composition including silica, the second rubber layer is composed of a rubber component including a styrene-butadiene rubber and a second rubber composition including silica, The tread portion has two or more circumferential main grooves extending in a tire circumferential direction and a land portion defined by the circumferential main grooves, At least one of the circumferential main grooves is formed such that a deepest portion of a groove bottom is located radially inward of an outermost portion of the second rubber layer in a land portion adjacent to the circumferential main groove, The content (parts by mass) of silica relative to 100 parts by mass of the rubber component in the first rubber composition is A1 SIL The content (parts by mass) of silica relative to 100 parts by mass of the rubber component in the second rubber composition is A2 SIL When the normal load is applied to the tread in a normal state and pressed against a flat surface, the cross-sectional width (mm) of the tire is Wt, and the width (mm) of the widest belt layer among the belt layers is Wb. A1 SIL , A2 SIL , Wt and Wb satisfy the following relationship, and the right side of formula (1) is preferably 1.06, more preferably 1.07, and the right side of formula (2) is preferably 1.08, more preferably 1.10, and even more preferably 1.20. (1) A2 SIL / A1 SIL >1.05 (2) A2 SIL / (Wt-Wb)>1.00 [2] The tire according to the above [1], wherein the glass transition temperature (°C) of the second rubber composition is Tg2, and Tg2 is higher than -30°C, preferably higher than -25°C, and more preferably higher than -20°C. [3] The tire according to the above [1] or [2], wherein when tan δ at 30° C. of the first rubber composition is 30° C. tan δ1, 30° C. tan δ1 is less than 0.30, preferably less than 0.26, more preferably less than 0.24, and even more preferably less than 0.20. [4] The tire according to any one of the items [1] to [3], wherein when the total styrene amount (mass%) of the rubber component contained in the first rubber composition is St1 and the total styrene amount (mass%) of the rubber component contained in the second rubber composition is St2, at least one of St1 and St2 is less than 25.0, preferably less than 20.0, more preferably less than 19.0, even more preferably less than 18.0, and still more preferably less than 17.0. [5] The tire according to any one of the above [1] to [4], wherein the rubber component contained in the second rubber composition contains at least one of a butadiene rubber and an isoprene-based rubber. [6] The tire according to any one of the above [1] to [5], wherein at least one of the rubber component contained in the first rubber composition and the rubber component contained in the second rubber composition contains a butadiene rubber. [7] The tire according to any one of the above [1] to [5], wherein the rubber component contained in the first rubber composition and the rubber component contained in the second rubber composition both contain butadiene rubber. [8] The tire according to any one of the items [1] to [7] above, wherein the right side of formula (1) is 1.10, preferably 1.20, more preferably 1.30, even more preferably 1.40, and still more preferably 1.50. [9] The tire according to any one of the items [1] to [8], wherein the right side of formula (2) is 1.25, preferably 1.30, more preferably 1.40, and even more preferably 1.50.

[10] The tire according to any one of the above [1] to [9], wherein the tread portion has a widening circumferential groove whose groove width is wider on the radially inner side of the tire.

[11] The tire according to

[10] above, wherein the widened circumferential groove is present in a land portion located on the tire centerline, or in the case where a circumferential main groove is present on the tire centerline, in the land portion closest to the tire centerline.

[12] When a pair of land portions located at the outermost sides in the tire width direction among the land portions are defined as shoulder land portions, the shoulder land portions have an opening area of ​​more than 0.1 mm but less than 15 mm 2 , preferably more than 0.5 and less than 10 mm 2 , more preferably more than 1.0 and less than 7.0 mm 2 , and more preferably more than 1.5 and less than 7.0 mm 2 The tire according to any one of the above [1] to

[11] , having one or more small holes.

[13] The tire according to any one of the items [1] to

[11] , wherein a pair of land portions located at the outermost sides in the tire width direction among the land portions are defined as shoulder land portions, and the shoulder land portions have at least one circumferential narrow groove. [Explanation of symbols]

[0193] Dt: Tire outer diameter Wt Tire section width Wb: Width of the widest belt layer W: Tire width direction C Tire circumferential direction CL··Tire center line Te Tread Edge H1: Thickness of the first rubber layer H2: Thickness of the second rubber layer D Groove depth 11. Belt layer 12. Belt layer 2... Circumferential main groove 3... land department 4. First rubber layer 5. Second rubber layer 6. Widened circumferential groove 7...Small hole 8... Circumferential narrow groove< / tg>

Claims

1. A tire having a tread portion and at least one belt layer, The tread portion includes at least a first rubber layer that is an outermost layer in a radial direction of the tire, and a second rubber layer that is adjacent to the inner side of the first rubber layer in the radial direction of the tire, the first rubber layer is composed of a rubber component including a styrene-butadiene rubber and a first rubber composition including silica, the second rubber layer is composed of a rubber component including a styrene-butadiene rubber and a second rubber composition including silica, The tread portion has two or more circumferential main grooves extending in a tire circumferential direction and a land portion defined by the circumferential main grooves, At least one of the circumferential main grooves is formed such that a deepest portion of a groove bottom is located radially inward of an outermost portion of the second rubber layer in a land portion adjacent to the circumferential main groove, The content (parts by mass) of silica relative to 100 parts by mass of the rubber component in the first rubber composition is A1 SIL The content (parts by mass) of silica relative to 100 parts by mass of the rubber component in the second rubber composition is A2 SIL When a normal load is applied in a normal state and the tread is pressed against a flat surface, the cross-sectional width (mm) of the tire is Wt, and the width (mm) of the widest belt layer among the belt layers is Wb. A1 SIL , A2 SIL , Wt and Wb satisfy the following relationship: <h2 style=";text-align:left;direction:ltr">(1) 2<h2 style=";text-align:left;direction:ltr"> SIL <h2 style=";text-align:left;direction:ltr"> / A1<h2 style=";text-align:left;direction:ltr"> SIL <h2 style=";text-align:left;direction:ltr"> 51555 <h2 style=";text-align:left;direction:ltr">(2) 2<h2 style=";text-align:left;direction:ltr"> SIL <h2 style=";text-align:left;direction:ltr"> / (Wt-Wb)>1.00

2. The tire according to claim 1, wherein the glass transition temperature (° C.) of the second rubber composition is Tg2, and Tg2 is higher than −30° C.

3. The tire according to claim 1 or 2, wherein when tan δ at 30° C. of the first rubber composition is taken as 30° C. tan δ1, 30° C. tan δ1 is less than 0.

30.

4. 3. The tire according to claim 1 or 2, wherein a total styrene amount (mass%) of the rubber component contained in the first rubber composition is St1 and a total styrene amount (mass%) of the rubber component contained in the second rubber composition is St2, and at least one of St1 and St2 is less than 25.

0.

5. 3. The tire according to claim 1, wherein the rubber component contained in the second rubber composition includes at least one of a butadiene rubber and an isoprene-based rubber.

6. The tire according to claim 1 or 2, wherein at least one of the rubber component contained in the first rubber composition and the rubber component contained in the second rubber composition contains a butadiene rubber.

7. The tire according to claim 1 or 2, wherein the rubber component contained in the first rubber composition and the rubber component contained in the second rubber composition each contain a butadiene rubber.

8. The tire according to claim 1 or 2, wherein the right side of formula (1) is 1.

10.

9. The tire according to claim 1 or 2, wherein the right side of formula (2) is 1.

25.

10. The tire according to claim 1 or 2, wherein the tread portion has a widening circumferential groove whose groove width is wider on the inner side in the tire radial direction.

11. The tire according to claim 10, wherein the widened circumferential groove is present in a land portion located on a tire centerline, or in a land portion closest to the tire centerline when a circumferential main groove is present on the tire centerline.

12. When a pair of land portions located at the outermost sides in the tire width direction among the land portions are defined as shoulder land portions, the shoulder land portions have an opening area of ​​more than 0.1 mm and less than 15 mm 2 3. A tire according to claim 1 or 2, having one or more small holes of

13. The tire according to claim 1 or 2, wherein a pair of land portions located outermost in the tire width direction among the land portions are defined as shoulder land portions, and the shoulder land portions have at least one circumferential narrow groove.

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