TIRES

Abstract

The invention relates to a tire comprising: a tread section; and a belt layer (11, 12), wherein the tread section comprises a first rubber layer (4) and a second rubber layer (5) radially adhering to the first rubber layer (4), the first and second rubber layers (4, 5) being composed of a first and second rubber composition respectively, each containing a rubber component that includes SBR and SiO2, the tread section comprising two or more main circumferential grooves (2), and rib sections (3) defined by the main circumferential grooves (2), at least one of the main circumferential grooves (2) being formed such that a lowest section of a groove bottom is located radially inward with respect to an outermost section of the second rubber layer (5) in the rib section (3) adhering to the main circumferential groove (2), and if a content A1 SIL(Mass parts) of silicon dioxide in phr of the first rubber composition and an A2 content SIL (Mass fractions) of SiO2 in phr of the second rubber composition and a cross-sectional width Wt (mm) of the tire and a width Wb (mm) of a widest belt layer (11, 12) when a tread is pressed against a plane in a normal condition under a normal load, A1 SIL , A2 SIL , Wt and Wb satisfy the following relationship, A2 SIL / A1 SIL > 1.05, and A2 SIL / (Wt − Wb) > 1.00.

Description

BACKGROUND OF THE INVENTIONField of the invention

[0001] The present invention relates to a tire. Description of the state of the art

[0002] Since grip performance and low fuel consumption performance are at a trade-off, for example, Japanese Patent No. 3213127 discloses that a tread portion of a tire has a two-layer structure (so-called cap / base structure) of a base rubber located on an inner side in a tire radial direction and a cap rubber located on an outer side in the tire radial direction, and a rubber composition having a small loss tangent (tanδ) is applied to the base rubber to improve steering stability performance and low fuel consumption performance of the tire. SUMMARY OF THE INVENTION

[0003] In the case of the tire described above, the loss tangent tanδ of a rubber cover layer is high, so wet grip performance is high in a new product. However, the rubber cover layer thermally deteriorates and hardens due to the influence of self-heating during repeated driving. Therefore, there are concerns that the stiffness of a tread ground contact area increases, tracking ability with respect to a road surface is lost, and wet grip performance deteriorates.

[0004] An object of the present invention is to provide a tire having improved wet grip performance after abrasion.

[0005] The present invention relates to a tire. A tire comprises: a tread portion; and at least one belt layer, wherein the tread portion includes at least a first rubber layer located on an outermost side in a tire radial direction and a second rubber layer adjacent to an inner side of the first rubber layer in the tire radial direction. The first rubber layer is composed of a first rubber composition containing a rubber component containing styrene-butadiene rubber and silica. The second rubber layer is composed of a second rubber composition containing a rubber component containing styrene-butadiene rubber and silica. The tread portion includes two or more circumferential main grooves extending in a tire circumferential direction and land portions defined by the circumferential main grooves.at least one of the main circumferential grooves is formed such that a deepest portion of a groove bottom is located inward in the tire radial direction with respect to an outermost portion of the second rubber layer in the land portion abutting the main circumferential groove, and when a content (parts by mass) of the silica with respect to 100 parts by mass of the rubber component in the first rubber composition is specified as A1, SIL and a content (parts by mass) of the silicon dioxide with respect to 100 parts by mass of the rubber component in the second rubber composition is referred to as A2 SIL and a section width (mm) of the tire is referred to as Wt and a width (mm) of a widest belt layer among the belt layers is referred to as Wb when a tread in a normal state is pressed against a plane under a normal load, A1 SIL , A2 SIL , Wt and Wb satisfy the following relationship, A2SIL / A1SIL>1.05, and A2SIL / (Wt−Wb)>1.00.

[0006] According to the present invention, it is possible to provide a tire having improved wet grip performance after abrasion. SHORT DESCRIPTION OF THE CHARACTERS Fig. 1 is a view showing a tire section width Wt, a tire outer diameter Dt, and a width Wb of a widest belt layer in a cross section of a tire taken along a plane passing through a tire rotational axis. Fig. 2 is a developed view of a part of a tread of the tire. Fig. 3 is a view showing a cross-section of a part of the tread of the tire along the plane passing through the tire rotation axis. Fig.4 is a developed view of a portion of the tread of the tire having a widened fine circumferential groove at a land portion closest to a tire centerline. Fig. 5 is a view showing a cross section of the widened fine circumferential groove of Fig. 4 along the plane passing the tire rotation axis. Fig. 6 is a developed view of a portion of the tread of the tire with a small hole in a shoulder area. Fig. 7 is a developed view of a portion of the tread of the tire having a fine circumferential groove in the shoulder region. DETAILED DESCRIPTION OF THE INVENTION

[0007] A tire according to an embodiment of the present invention includes: a tread portion; and at least one belt layer, wherein the tread portion includes at least a first rubber layer located on an outermost side in a tire radial direction and a second rubber layer adjacent to an inner side of the first rubber layer in the tire radial direction, the first rubber layer being composed of a first rubber composition containing a rubber component containing styrene-butadiene rubber and silica, the second rubber layer being composed of a second rubber composition containing a rubber component containing styrene-butadiene rubber and silica, the tread portion including two or more circumferential main grooves extending in a tire circumferential direction and land portions defined by the circumferential main grooves,at least one of the main circumferential grooves is formed such that a deepest portion of a groove bottom is located inward in the tire radial direction with respect to an outermost portion of the second rubber layer in the land portion abutting the main circumferential groove, and when a content (parts by mass) of the silica with respect to 100 parts by mass of the rubber component in the first rubber composition is specified as A1, SIL and a content (parts by mass) of the silicon dioxide with respect to 100 parts by mass of the rubber component in the second rubber composition is referred to as A2 SIL and a section width (mm) of the tire is referred to as Wt and a width (mm) of a widest belt layer among the belt layers is referred to as Wb when a tread in a normal state is pressed against a plane under a normal load, A1 SIL , A2 SIL , Wt and Wb satisfy the following relationship, A2SIL / A1SIL<1.05, and A2SIL / (Wt−Wb)>1.00.

[0008] Although not intended to be limited by theory, in the present invention, the following can be assumed as a mechanism in which wet grip performance is improved after abrasion.

[0009] That is, (1) in the tire of the present invention using at least two layers of different tread rubbers and having a predetermined circumferential main groove, when the rubber of a surface layer of a first layer is abraded, the tread rubber of a second layer is exposed on a surface, and the tread rubber of the first layer remains at an edge portion of the land portion. In this case, an effect of improving wet grip performance after abrasion can be obtained by using a rubber containing a large amount of silica for the second layer rubber. Furthermore, (2) the tread rubber of the first layer is softer than that of the second layer because the amount of silica is less than that of the second layer.Therefore, the first-layer rubber remaining at the edge portion of the land portion exhibits road surface following ability, and the wet grip effect of the second-layer rubber can be enhanced. Furthermore, (3) abrasion increases the contact area with the ground compared to before abrasion, so that the effect of improving wet grip performance after abrasion can be obtained. Thus, it is believed that the wet grip performance after abrasion is improved by a combination of (1) to (3).

[0010] It is preferable that when a glass transition temperature (°C) of the second rubber composition is referred to as Tg2, Tg2 is higher than -30 °C.

[0011] It is believed that by increasing the glass transition temperature of the second rubber layer, it is possible to increase exothermicity of the second rubber layer and easily generate friction at a center of the land portion after abrasion.

[0012] It is preferable that when tanδ of the first rubber composition at 30 °C is referred to as 30 °C-tanδ1, 30 °C-tanδ1 is less than 0.30.

[0013] It is believed that by suppressing the 30 °C tanδ of the first rubber layer, it is possible to reduce a phase difference between a force input and a reaction of the first rubber layer and easily generate a reaction force.

[0014] It is preferable that when a total styrene amount (mass %) of the rubber component contained in the first rubber composition is referred to as St1 and a total styrene amount (mass %) of the rubber component contained in the second rubber composition is referred to as St2, at least one of St1 and St2 is less than 25.0.

[0015] It is believed that by reducing the total amount of styrene in the rubber component contained in the rubber composition constituting the first rubber layer and the second rubber layer, it is possible to suppress the formation of a domain (styrene segment domain) by a styrene segment in the first rubber layer, suppress the exothermic reaction between rubber molecular chains around the styrene segment domain, and slightly improve the reactivity. Furthermore, it is believed that the second rubber layer can easily follow the minute reaction of the road surface.

[0016] It is preferable that the rubber component contained in the second rubber composition contains at least one of butadiene rubber and isoprene-based rubber.

[0017] It is preferable that at least one of the rubber component contained in the first rubber composition and the rubber component contained in the second rubber composition contains butadiene rubber.

[0018] It is preferable that the rubber component contained in the first rubber composition and the rubber component contained in the second rubber composition both contain butadiene rubber.

[0019] It is preferable that the tread portion has a widened circumferential groove whose groove width is widened on an inner side in the tire radial direction.

[0020] It is believed that the groove width of the widened circumferential groove is increased after abrasion, so that drainage ability is improved and wet grip performance is improved.

[0021] It is preferable that the widened circumferential groove is provided in the land portion located on a tire center line, or in a case where the main circumferential groove is provided on the tire center line, in the land portion closest to the tire center line.

[0022] It is believed that the groove width of the widened circumferential groove is increased after abrasion, so that the drainage ability at a center portion in a tire width direction is improved and the wet grip performance is improved.

[0023] It is preferable that, when a pair of land portions located on an outermost side in a tire width direction are defined as shoulder land portions among the land portions, the shoulder land portions have one or more small holes having an opening area of ​​greater than 0.1 mm 2 and smaller than 15 mm 2 have.

[0024] It is believed that the small hole contributes to improving drainage ability, so that the drainage ability in the shoulder land sections is improved and the wet grip performance is improved.

[0025] It is preferable that, when a pair of land portions located on an outermost side in a tire width direction are defined as shoulder land portions among the land portions, the shoulder land portions have at least one or more circumferential fine grooves.

[0026] It is believed that the fine circumferential groove contributes to improving the drainage ability, so that the drainage ability in the shoulder land sections is improved and the wet grip performance is improved. [Definitions]

[0027] The "normal condition" is a condition in which the tire is mounted on a normal rim, with normal internal pressure applied, and no load applied. A "dimension of each part of the tire" is a value specified in the normal condition unless otherwise stated.

[0028] The “normal rim” is a rim specified for each tire by a standard on which the tire is based, in a standards system that includes the standard. For example, in a case of The Japan Automobile Tire Manufacturers Association, Inc. (JATMA), it refers to a standard rim with respect to an applicable size described in “JATMA YEAR BOOK,” in a case of The European Tire and Rim Technical Organization (ETRTO), it refers to “Measuring Rim” described in “STANDARDS MANUAL,” and in a case of The Tire and Rim Association, Inc. (TRA), it refers to “Design Rim” described in “YEAR BOOK.” Here, JATMA, ETRTO, and TRA are referred to in that order, and in a case of the existence of an applicable size at the time of reference, a standard with respect to the applicable size is followed.In a case of a tire not specified in the standard, the "normal rim" refers to a rim with a smallest rim diameter followed by a rim with a narrowest rim width among rims that can be rim-mounted on the tire and can maintain internal pressure, that is, rims that do not cause air leakage between the rim and the tire.

[0029] The "normal internal pressure" is an air pressure specified for each tire by a standard on which the tire is based, in a standards system that includes the standard. It refers to "the maximum air pressure" in the case of JATMA, refers to the maximum value described in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table in the case of TRA, and refers to "INFLATION PRESSURE" in the case of ETRTO. Here, as with the normal rim, JATMA, ETRTO, and TRA are referred to in that order, and in the case of the existence of an applicable size at the time of reference, a standard is followed with respect to the applicable size.In the case of a tire not specified in the standard, the "normal internal pressure" refers to a normal internal pressure (250 kPa or more) for a different tire size (specified in the standard) specified for the normal rim as a standard rim. In a case where multiple normal internal pressures of 250 kPa or more are specified, the "normal internal pressure" refers to the minimum value.

[0030] The "normal load" means a load specified in a standard system that includes a standard on which the tire is based. It is "maximum load capacity" in the JATMA standard, "LOAD CAPACITY" in the ETRTO standard, and "maximum value" and "normal load" described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard. Here, as with the normal rim and normal internal pressure, JATMA, ETRTO, and TRA are referred to in that order, and in the case of the existence of an applicable size at the time of reference, a standard related to the applicable size is followed. In the case of a tire not specified in the standard, a normal load W L (kg) by the following calculation. WL=0.000011×V+175 V=[(Dt / 2)2−(Dt / 2−Ht)2]×π×Wt

[0031] V is a virtual volume (mm 3) of the tire, Dt is a tire outer diameter (mm), Ht is a section height (mm) of the tire, and Wt is a section width (mm) of the tire.

[0032] The tire section width Wt is the maximum width between the outer surfaces of the sidewalls in the normal state, excluding any patterns or letters on the tire sidewall. The tire section height Ht is the distance from the bead portion bottom surface to the outermost tread surface and is 1 / 2 of the difference between the tire outer diameter Dt and the nominal rim diameter.

[0033] The "belt layer" is a layer arranged mainly on an inner side of the tread in a radial tire, adjacent to the tread in the tire radial direction. It plays the role of strongly tightening a carcass to increase the rigidity of the tread. The belt layer includes a cord forming its skeleton and a rubber covering the cord. In the present invention, a belt layer commonly used in the tire industry is used as the belt layer.

[0034] The "circumferential main groove" refers to a groove that extends continuously in the tire circumferential direction and has a groove width of 4 mm or more in the tire width direction on a tread surface. The circumferential main groove may extend linearly along the circumferential direction, or may extend in a wave shape, a sinusoidal shape, or a zigzag shape along the circumferential direction. Note that the following widened circumferential groove is not included.

[0035] A "fine circumferential groove" refers to a groove that extends continuously in the tire circumferential direction and has a groove width of less than 4 mm in the tire width direction on the tread surface. The fine circumferential groove may extend linearly along the circumferential direction or may extend in a wave shape, a sinusoidal shape, or a zigzag shape along the circumferential direction. Note that the following widened circumferential groove is not included.

[0036] The "widened circumferential groove" is a groove that extends continuously in the tire circumferential direction and is configured such that the groove width is minimal in the tire width direction at the tread surface and increases on the inner side in the tire radial direction. The widened circumferential groove may extend linearly along the circumferential direction or may extend in a wave shape, a sinusoidal shape, or a zigzag shape along the circumferential direction.

[0037] The “total styrene amount (mass %) of the rubber component” is obtained by calculating values ​​obtained by multiplying the styrene content of each rubber constituting the total rubber component (100 mass %) by a percentage of the styrene content in the total rubber component and adding all the values.

[0038] A "pinhole" is a small hole located on the tread surface, extending from the inner side of the tread and open to the tread surface. These pinholes are independent of each other and do not communicate with the circumferential groove, a lateral groove, or the like. [Measurement method]

[0039] The "30°C tanδ" is a loss tangent measured using the Eplexor series manufactured by GABO under conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and a strain mode. In a case where a sample for measuring the loss tangent is prepared by cutting it from the tread portion of the tire, the sample is prepared by cutting it from an inner side of the target rubber layer to a size of 20 mm long, 4 mm wide, and 1 mm thick such that the tire circumferential direction is a long side and the tire radial direction is a thickness.

[0040] Regarding the "glass transition temperature (Tg) (°C) of the rubber composition," a temperature distribution curve of a loss tangent tanδ is measured in a range of -60°C to 40°C using a dynamic viscoelasticity measuring device (e.g., Eplexor series, manufactured by GABO) under conditions of a frequency of 10 Hz, an initial strain of 10%, an amplitude of ±0.5%, and a temperature rise rate of 2°C / min. A temperature (tanδ peak temperature) corresponding to the maximum value in the obtained temperature distribution curve is set as the glass transition temperature. In a case where the tanδ value continues to gradually increase or decrease with a temperature rise in the measurement in the range of -60°C to 40°C, the glass transition temperature of the rubber composition is set to 40°C or -60°C.Furthermore, in a case where there are two or more points where the temperature at which the tanδ value is maximized is in the range of -60 °C to 40 °C, a temperature corresponding to the lowest temperature point among the points is set as the glass transition temperature of the rubber composition. A sample for measurement is prepared in the same way as in the case of 30 °C-tanδ.

[0041] The “styrene content (mass %)” is determined by 1 H-NMR measurement calculated.

[0042] A “Vinyl content (1,2-bonded butadiene unit amount) (mol%)” is calculated by infrared absorption spectral analysis in accordance with JIS K 6239-2:2017.

[0043] A “cis content (cis-1,4-bonded butadiene unit amount) (mol%)” is calculated by infrared absorption spectral analysis in accordance with JIS K 6239-2:2017.

[0044] 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 Ltd. by measuring while raising the temperature at a temperature rise rate of 10 °C / min. Specifically, the Tg of the styrene-butadiene rubber is measured in the present invention.

[0045] A “weight-average molecular weight (Mw)” can be obtained with respect to standard polystyrene based on a measured value obtained by gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation).

[0046] An “N2SA of soot” is measured in accordance with JIS K 6217-2:2017.

[0047] An “N2SA of silica” is measured by a BET method in accordance with ASTM D3037-93.

[0048] An "average primary particle diameter" can be observed with a transmission electron microscope or a scanning electron microscope and can be obtained by measuring 400 or more primary particles observed in a field of view and averaging the measured values. In a case where a particle shape is spherical, a diameter of the sphere is used as the particle diameter. In a case where the particle shape is non-spherical, a circle-equivalent diameter (positive square root of {4 × (area of ​​particle) ÷ π}) is calculated from a transmission electron microscope image and used as the particle diameter. The carbon black or the like is applied to the silica or the like.

[0049] A “softening point” is defined as a temperature at which a ball falls in a case where a softening point defined in JIS K 6220-1:2001 is measured with a ring-and-ball type softening point measuring device.

[0050] A "plasticizer content" also includes the amount of a plasticizer in the rubber component extended by the plasticizer. Similarly, an "oil content" also includes the amount of oil contained in oil-extended rubber. [Tires]

[0051] The tire of the present invention will be described below with reference to the drawings. It should be noted that the drawings are merely examples, and the present invention should not be interpreted as limited based on the drawings.

[0052] The tire of the present invention is a tire comprising: a tread portion; and at least one belt layer, wherein the tread portion includes at least a first rubber layer located on an outermost side in a tire radial direction and a second rubber layer abutting against an inner side of the first rubber layer in the tire radial direction, the tread portion includes two or more circumferential main grooves extending in a tire circumferential direction and land portions defined by the circumferential main grooves, and a deepest portion of a groove bottom of at least one of the circumferential main grooves is formed to be inward in the tire radial direction with respect to an outermost portion of the second rubber layer in the land portion abutting against the circumferential main groove.

[0053] Fig.1 is a cross-sectional view of the tire according to an embodiment of the present invention taken along a plane passing through a tire rotational axis. In the tire of Fig. 1, a tire section width is indicated by Wt. The tread portion of the tire includes the first rubber layer located on the outermost side in the tire radial direction and the second rubber layer adjacent to the inner side of the first rubber layer in the tire radial direction, and includes the two or more circumferential main grooves extending in the tire circumferential direction and the land portions defined by the circumferential main grooves; however, this point is in Fig. 1 not shown. In Fig.1, a belt layer 11 and a belt layer 12 are provided on the inner side of the tread portion in the tire radial direction. Among them, the belt layer 11 is a widest belt layer, and its width is indicated by Wb. A tire section width is indicated by Wt. Dt is a tire outer diameter.

[0054] Fig. Figure 2 is a development view of the tread surface of the tire according to an embodiment of the present invention. A direction of an arrow from W is a tread width direction, and a direction of an arrow from C is a tire circumferential direction. CL indicates a tire center line, and Te indicates a tread end. Fig. 2, the tread surface is divided into four web sections 3 by three main circumferential grooves 2.

[0055] Fig.Figure 3 shows a part of a cross-section of the tire according to an embodiment of the present invention along the plane passing through the tire rotation axis. Fig. 3, the tread portion includes a first rubber layer 4 located on the outermost side in the tire radial direction, and a second rubber layer 5 adjacent to the inner side of the first rubber layer in the tire radial direction. Here, a deepest portion of a groove bottom of the circumferential main groove 2 (a lower end at a depth D in Fig. 3) formed so as to be in a plane with respect to an outermost portion (an upper end at a thickness H2 of the second rubber layer in Fig.3) the second rubber layer 5 of the land portion 3, which abuts the circumferential main groove 2, is located inward in the tire radial direction. The tread portion only needs to include at least the first rubber layer and the second rubber layer abutting the first rubber layer, and it may further include another rubber layer in a space with the belt layer.

[0056] In the tire of the present invention, among the land portions, a tire width-direction length of a land portion located on the tire center line, or, in a case where the circumferential main groove is present on the tire center line, a land portion closest to the tire center line, is preferably increased from the outer side to the inner side in the tire radial direction. Since the first rubber layer plays a role of supporting an end portion of the land portion after abrasion, it is believed that the first rubber layer supports the end portion of the land portion more easily by adopting the above-described configuration. <Ausdrücke (1) und (2)>

[0057] In the tire of the present invention, when the content (parts by mass) of the silica with respect to 100 parts by mass of the rubber component in the first rubber composition as A1 SILand the content (parts by mass) of the silicon dioxide with respect to 100 parts by mass of the rubber component in the second rubber composition is referred to as A2 SIL and the section width (mm) of the tyre is referred to as Wt and the width (mm) of a widest belt layer among the belt layers is referred to as Wb when the tread is pressed against the plane in the normal state under a normal load, A1 SIL , A2 SIL , Wt and Wb have a predetermined relationship shown in expressions (1) and (2). (Expression (1), A2 SIL / A1 SIL )

[0058] Expression (1) is as follows. A2SIL / A1SIL>1.05

[0059] A right side of Expression (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, and even more preferably 1.50. Moreover, there is no particular upper limit for a value on a left side of Expression (1), and for example, the value may be 3.00, 2.50, 2.00, or 1.70.

[0060] The value on the left side of Expression (1) can be adjusted by adding or subtracting the amount of silica blended into the first rubber composition constituting the first rubber layer and the amount of silica blended in the second rubber composition constituting the second rubber layer. (Expression (2), A2 SIL / (Wt - Wb))

[0061] Expression (2) is as follows. A2SIL / (Wt−Wb)>1.00

[0062] A right side of Expression (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, and even more preferably 1.50. Moreover, there is no particular upper limit for a value on a left side of Expression (2), and for example, the value may be 3.00, 2.50, 2.00, or 1.70.

[0063] The value on the left side of expression (2) can be adjusted by adding or subtracting the amount of silica blended into the second rubber composition constituting the second rubber layer and the tire section width and the width of the widest belt layer. <tg>(Tg2)

[0064] In the tire of the present invention, when the glass transition temperature (°C) of the second rubber composition is referred to as Tg2, Tg2 is preferably higher than -30 °C.

[0065] From the perspective of wet grip performance, Tg2 is preferably higher than -25 °C and more preferably higher than -20 °C. Furthermore, an upper limit of Tg2 is not particularly restricted, but may be, for example, lower than 15 °C, lower than 5 °C, or lower than 0 °C. (Tg1)

[0066] In the tire of the present invention, when the glass transition temperature (°C) of the first rubber composition is referred to as Tg1, Tg1 is preferably higher than -50 °C and more preferably lower than -10 °C.

[0067] Furthermore, Tg1 is more preferably higher than -47°C and even more preferably higher than -45°C. Furthermore, Tg1 is more preferably lower than -13°C and even more preferably lower than -15°C.

[0068] Tg2 and Tg1 can be appropriately adjusted depending on types and blending amounts of the rubber component constituting the rubber composition and types and blending amounts of additives other than the rubber component. <30 °C-tanδ>(30 °C-tanδ1)

[0069] In the tire of the present invention, when tanδ of the first rubber composition at 30 °C is referred to as 30 °C-tanδ1, 30 °C-tanδ1 is preferably less than 0.30.

[0070] From the perspective of wet grip performance, 30°C-tanδ1 is preferably less than 0.26, more preferably less than 0.24, and even more preferably less than 0.20. Furthermore, there is no particular restriction on the lower limit of 30°C-tanδ1, and for example, the lower limit may be greater than 0.10 or greater than 0.12. (30 °C-tanδ2)

[0071] In the tire of the present invention, when tanδ of the second rubber composition at 30 °C is referred to as 30 °C-tanδ2, 30 °C-tanδ2 is preferably less than 0.50 and greater than 0.10.

[0072] Furthermore, 30°C-tan δ2 is more preferably less than 0.48, and even more preferably 0.46 or less. Furthermore, 30°C-tan δ2 is more preferably more than 0.12, and even more preferably more than 0.15.

[0073] 30 °C-tanδ1 and 30 °C-tanδ2 can be appropriately adjusted depending on types and blending amounts of the rubber component constituting the rubber composition and types and blending amounts of additives other than the rubber component. <St1, St2>

[0074] In the tire of the present invention, when the total styrene amount (mass %) of the rubber component contained in the first rubber composition is referred to as St1 and the total styrene amount (mass %) of the rubber component contained in the second rubber composition is referred to as St2, it is preferable that at least one of St1 and St2 is less than 25.0, and it is further preferable that both St1 and St2 are less than 25.0.

[0075] 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.

[0076] The value of St1 can be adjusted by adding or subtracting the styrene content of each rubber component blended into the first rubber composition. The value of St2 can also be adjusted by adding or subtracting the styrene content of each rubber component blended into the second rubber composition. <Verbreiterte Umfangsrille>

[0077] In the tire of the present invention, the tread portion preferably has a widened circumferential groove whose groove width is widened on an inner side in the tire radial direction. This is because the groove width of the widened circumferential groove is increased after abrasion, which improves drainage ability and wet grip performance.

[0078] In Fig. 4, a widened circumferential groove 6 having a linear shape is formed on each of two land portions 3 adjacent to the circumferential main groove 2 passing the tire centerline. The widened circumferential groove may extend, for example, in a wave shape, a sinusoidal shape, or a zigzag shape along the circumferential direction. Furthermore, there is no particular limitation on the land portion at which the widened circumferential groove is formed, but it is preferable that the widened circumferential groove be formed on the land portion located on the tire centerline, or in a case where the circumferential main groove is present on the tire centerline, it is preferable that the widened circumferential groove be formed on the land portion closest to the tire centerline, as in the widened circumferential groove 6 in Fig. 4.

[0079] 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 inner side in the tire radial direction, but the increase in the groove width is not limited to such an aspect, and, for example, the groove width may increase with repeated slight increases and decreases in a curved shape or a step shape. Also, a ratio of a tire width direction length of an opening portion to a tire width direction length of the groove bottom is the same, and Fig. 5 is an example and is not limited to this. The ratio is appropriately increased or decreased within a range of less than 1. In Fig. 5, each layer forming the tread portion is not shown. <Kleines Loch>

[0080] In the tire of the present invention, when a pair of land portions located on the outermost side in the tire width direction are defined as shoulder land portions, the shoulder land portions preferably have one or more small holes having an opening area of ​​greater than 0.1 mm 2 and smaller than 15 mm 2 up. In Fig. 6, small holes 7 are formed on a pair of shoulder land portions 3 of the tread surface. It is believed that the small hole contributes to improving the drainage ability, so that the drainage ability in the shoulder land portions is improved, which contributes to improving wet grip performance. For example, it is believed that in actual use, even in a case where a shoulder land portion or a middle land portion is excellently abraded and the remaining shoulder land portion is hardened over time, the drainage ability can be ensured by the small hole, and the wet grip performance after abrasion can be slightly improved. An opening area of ​​the small hole to the tread surface is preferably greater than 0.1 mm 2 , more preferably larger than 0.5 mm 2 , even more preferably greater than 1.0 mm 2 and particularly preferably larger than 1.5 mm 2 . In addition, the opening area of ​​the small hole to the tread surface is preferably less than 15 mm 2 , more preferably less than 10 mm 2 , even more preferably less than 7.0 mm 2 and particularly preferably less than 5.0 mm 2 A depth of a deepest portion of the small hole is preferably 3% or more, and more preferably 5% or more, of the deepest portion of the circumferential main groove. Furthermore, the depth of the deepest portion of the small hole is preferably 80% or less, more preferably 60% or less, and even more preferably 40% or less, of the deepest portion of the circumferential main groove. <Feine Umfangsrille>

[0081] In the tire of the present invention, when the pair of land portions located on the outermost side in the tire width direction are defined as shoulder land portions, the shoulder land portions preferably have at least one or more fine circumferential grooves. Fig. 7, a fine circumferential groove 8 is formed on the pair of shoulder land portions 3 of the tread surface. Since the fine circumferential groove contributes to improving the drainage ability, the drainage ability in a shoulder region is improved, which contributes to improving the wet grip performance. [Rubber composition]

[0082] The following describes 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 of the tread portion. The following description applies to both the first rubber composition and the second rubber composition unless otherwise specified. Therefore, when simply referring to the rubber composition, it means that the rubber composition includes both the first rubber composition and the second rubber composition.

[0083] 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. <kautschukkomponente>

[0084] The rubber compositions according to the present invention, that is, the first rubber composition and the second rubber composition, each contain styrene-butadiene rubber as the rubber component.

[0085] It is preferable that the rubber component contained in the second rubber composition contains at least one of butadiene rubber and isoprene-based rubber.

[0086] It is preferable that at least one of the rubber component contained in the first rubber composition and the rubber component contained in the second rubber composition contains butadiene rubber. It is preferable that the rubber component contained in the first rubber composition and the rubber component contained in the second rubber composition both contain butadiene rubber.

[0087] These rubber components can also be used in combination with other rubber components to be described below, and, in addition to being modified for the purpose of obtaining interaction with a filler or subjected to hydrogenation of a part of a double bond portion from the viewpoint of suppressing deterioration, they can also be used as an extended rubber extended by a plasticizer to be described below. (SBR)

[0088] The SBR is not particularly limited, and examples thereof include a solution-polymerized SBR (S-SBR), an emulsion-polymerized SBR (E-SBR), and a modified SBR (modified S-SBR, modified E-SBR). Examples of the modified SBR include an SBR whose terminal and / or main chain is modified, and a modified SBR coupled with tin, a silicon compound, or the like (a condensate, a compound having a branched structure, or the like). Among them, an S-SBR and a modified SBR are preferable. Furthermore, hydrogenated substances of the SBRs (hydrogenated SBR) can also be used. The SBRs can be used alone or in combinations of two or more.

[0089] Examples of the S-SBR that can be used in the present invention include S-SBRs manufactured and sold by JSR Co., Ltd., Sumitomo Chemical Co., Ltd., UBE Corporation, Asahi Kasei Co., Ltd., and ZS Elastomers Co., Ltd.

[0090] From the viewpoint of wet grip performance and abrasion resistance performance, the styrene content of the SBR is preferably more than 10 mass%, more preferably more than 15 mass%, and even more preferably more than 20 mass%. Furthermore, from the viewpoint of temperature dependence of wet grip performance and impact resistance performance, the styrene content is preferably less than 60 mass%, more preferably less than 55 mass%, and even more preferably less than 50 mass%. In the present specification, the styrene content of the SBR is calculated by the method described above.

[0091] The vinyl content of the SBR is preferably more than 10 mol%, more preferably more than 13 mol%, and even more preferably more than 15 mol% from the viewpoint of ensuring reactivity with silica, wet grip performance, rubber strength, and abrasion resistance performance. Furthermore, from the viewpoint of preventing an increase in temperature dependence, elongation at break, and abrasion resistance performance, the vinyl content of the SBR is preferably less than 70 mol%, more preferably less than 65 mol%, and even more preferably less than 60 mol%. In the present specification, the vinyl content (1,2-bonded butadiene unit amount) of the SBR is measured by the method described above.

[0092] The weight-average molecular weight (Mw) of the 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 wet grip performance. Furthermore, from the viewpoint of crosslinking uniformity, the weight-average molecular weight is preferably less than 2 million, more preferably less than 1.8 million, and even more preferably less than 1.5 million. In the present specification, the weight-average molecular weight of the SBR can be obtained by the method described above.

[0093] From the perspective of wet grip performance, the content of SBR in the rubber component is preferably more than 45 mass%, more preferably more than 50 mass%, even more preferably more than 55 mass%, and even more preferably 60 mass% or more. Furthermore, the upper limit of the content of SBR in the rubber component is not particularly limited and may be 100 mass%. (BR)

[0094] The BR is not particularly limited. For example, a BR with a cis content of less than 50 mol% (low-cis BR), a BR with a cis content of more than 90 mol% (rich-cis BR), a rare earth element-based butadiene rubber (rare earth-based BR) synthesized using a rare earth element-based catalyst, a BR (SPB-containing BR) containing syndiotactic polybutadiene crystals, a modified BR (rich-cis modified BR, low-cis modified BR), and the like commonly used in the tire industry can be used. Examples of the modified BR include the BR modified with the same functional groups as those described in the SBR. The BR can be used alone or in combinations of two or more.

[0095] As the cis-rich BR, for example, those commercially available from Zeon Co., Ltd., UBE Corporation, and JSR Co., Ltd. can be used. By containing the cis-rich BR, low-temperature properties and abrasion resistance performance can be improved. The cis content is preferably more than 95 mol%, more preferably more than 96 mol%, and even more preferably 97 mol% or more. In the present specification, the cis content (unit amount of cis-1,4-bonded butadiene) is a value calculated by the method described above.

[0096] The rare earth-based BR is synthesized using the rare earth element-based catalyst, and the vinyl content is preferably less than 1.8 mol%, more preferably less than 1.6 mol%, and even more preferably 1.5 mol% or less, and the cis content is preferably more than 95 mol%, more preferably more than 96 mol%, and even more preferably 97 mol% or more. For the rare earth-based BR, for example, those commercially available from LANXESS AG can be used.

[0097] Examples of SPB-containing BR include those in which 1,2-syndiotactic polybutadiene crystals are not simply dispersed in the BR, but are chemically bonded to the BR and then dispersed. As such SPB-containing BR, those commercially available from UBE Corporation can be used.

[0098] As the modified BR, a modified butadiene rubber (modified BR) whose terminal and / or main chain is modified with a functional group containing at least one element selected from the group consisting of silicon, nitrogen and oxygen is suitably used.

[0099] Other modified BRs used include tin-modified BR, which is obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound to the polymerization product. One end of a modified BR molecule is bonded with a tin-carbon bond. Furthermore, the modified BR can be either non-hydrogenated or hydrogenated.

[0100] The weight-average molecular weight (Mw) of the BR is preferably more than 300,000, more preferably more than 350,000 or more, and even more preferably more than 400,000 from the viewpoint of abrasion resistance performance. Furthermore, from the viewpoint of crosslinking uniformity and the like, the weight-average molecular weight is preferably less than 2 million, more preferably less than 1 million, and even more preferably less than 500,000 million. The Mw can be obtained by the method described above.

[0101] In a case where the BR is included, the content of the BR in the rubber component is preferably less than 50 mass%, more preferably less than 45 mass%, and even more preferably 40 mass% or less from the viewpoint of wet grip performance. Furthermore, a lower limit of the content of the BR in the rubber component is not particularly limited and may be 0 mass%, but it may be, for example, more than 1 mass%, more than 5 mass%, more than 10 mass%, or 15 mass% or more. (Isoprene-based rubber)

[0102] Isoprene-based rubbers include, for example, isoprene rubber (IR), natural rubber, and the like, which are commonly used in the tire industry. In addition to unreformulated natural rubber (NR), natural rubber also includes reformulated natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. These isoprene-based rubbers can be used alone or in combinations of two or more.

[0103] The NR is not particularly restricted, and any NR commonly used in the tire industry can be used. Examples include SIR20, RSS#3, and TSR20.

[0104] In a case where the isoprene-based rubber is included, the content of the isoprene-based rubber in the rubber component is preferably less than 50 mass%, more preferably less than 40 mass%, and even more preferably less than 30 mass% from the viewpoint of wet grip performance. Furthermore, a lower limit of the content of the isoprene-based rubber in the rubber component is not particularly limited and may be 0 mass%, but it may be, for example, more than 1 mass%, more than 5 mass%, more than 10 mass%, more than 20 mass%, or 25 mass% or more. (Other rubber components)

[0105] As the rubber component according to the present invention, a rubber component other than isoprene-based rubber, SBR, and BR may be included. As the other rubber component, a crosslinkable rubber component commonly used in the tire industry may be used. Examples thereof include 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), and hydrin rubber. These other rubber components may be used alone or in combinations of two or more. <Füllstoff>

[0106] The rubber compositions according to the present invention, that is, 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 a filler other than silica and carbon black as a filler. The rubber composition according to the present invention may not contain the other filler.

[0107] The other fillers are not particularly limited, and for example, any filler conventionally used in the tire industry can be used, such as aluminum hydroxide, alumina, calcium carbonate, magnesium sulfate, talc, clay, and biochar (BIO_CHAR). These fillers can be used alone or in combinations of two or more. (silicon dioxide)

[0108] The silica is not particularly limited, and for example, silica produced by a dry process (anhydrous silica) or silica produced by a wet process (hydrous silica), which is commonly used in the tire industry, can be used. Furthermore, from the viewpoint of environmental impact, silica (for example, amorphous silica refined from rice husk) using a biomass material as a raw material can be used. Among them, hydrous silica produced by the wet process is preferred because silanol groups are abundant. These types of silica can be used alone or in combinations of two or more.

[0109] For example, silica using a biomass material as a raw material can be obtained by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and filtering, washing, drying, and pulverizing a silica precipitate produced by reacting the silicate with sulfuric acid in the same manner as in the case of wet silica in the prior art. When silica crystallizes, it does not dissolve in water, and one component thereof, i.e., silicic acid, cannot be used. By controlling the combustion temperature and combustion time, it is possible to suppress the crystallization of silica in the rice husk ash (see Japanese Unexamined Patent Publication No. 2009-2594, Akita Prefectural University Web Journal B / 2019, vol. 6, pp. 216 to 222, and the like).As the amorphous silicon dioxide extracted from rice husks, those commercially available from Wilmar can be used.

[0110] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably greater than 140 m from the viewpoint of low fuel consumption and abrasion resistance performance. 2 / g, more preferably greater than 150 m 2 / g, even more preferably greater than 160 m 2 / g and even more preferably greater than 175 m 2 / g. In addition, from the point of view of performance in terms of low fuel consumption and process efficiency, the specific nitrogen adsorption surface is preferably less than 350 m 2 / g, more preferably less than 300 m 2 / g and even more preferably less than 250 m 2 / g. The N2SA of the silicon dioxide in the present specification is a value measured by the method described above.

[0111] The average primary particle diameter of the silicon dioxide is preferably greater than 10 nm, more preferably greater than 12 nm, and even more preferably greater than 14 nm. Furthermore, the average primary particle diameter is preferably less than 26 nm, more preferably less than 24 nm, and even more preferably 22 nm or less. The average primary particle diameter of the silicon dioxide is measured by the measurement method described above.

[0112] In a case where silica is contained, the content of silica, relative to 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. Furthermore, from the viewpoint of abrasion resistance performance, the content 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. (Soot)

[0113] As the carbon black, a carbon black commonly used in the tire industry can be suitably used. Examples thereof include GPF, FEF, HAF, ISAF, and SAF, and more specifically, 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, and N991 can be used. Furthermore, from the perspective of environmental performance, in addition to the above carbon black, carbon black using lignin as a raw material or reclaimed carbon black obtained by thermal decomposition of a product containing carbon black, such as a tire, can be used. These types of carbon black can be used alone or in combinations of two or more.

[0114] The specific nitrogen adsorption surface (N2SA) of the soot is preferably greater than 10 m from the point of view of reinforcement 2 / g, more preferably larger than 30 m 2 / g and even more preferably greater than 50 m 2 / g. In addition, from the point of view of performance in terms of low fuel consumption and process efficiency, the specific nitrogen adsorption surface is preferably less than 200 m 2 / g, more preferably less than 175 m 2 / g and even more preferably less than 150 m 2 / g. The N2SA of soot is measured using the method described above.

[0115] The average primary particle diameter of the carbon black is preferably greater than 10 nm, more preferably greater than 12 nm, and even more preferably greater than 14 nm. Furthermore, the average primary particle diameter is preferably less than 26 nm, more preferably less than 24 nm, and even more preferably 22 nm or less. The average primary particle diameter of the carbon black is measured by the measurement method described above.

[0116] In a case where carbon black is contained, the content of carbon black relative to 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 performance and wet grip performance. Furthermore, from the viewpoint of low fuel consumption performance, the content 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. (Filler content)

[0117] The total content of the filler relative to 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 performance. Furthermore, from the viewpoint of low fuel consumption performance and elongation at break, the total content 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.

[0118] In a case where the filler contains both silica and carbon black, the content of silica is preferably higher than the content of carbon black from the viewpoint of balancing low fuel consumption performance, wet grip performance, and abrasion resistance performance. 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%. (silane coupling agent)

[0119] It is preferable to use silica in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent that has been conventionally used in combination with silica in the tire industry can be used. Examples thereof include a thioester-based silane coupling agent such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane; a mercapto-based silane coupling agent such as those shown by the following chemical formula; a sulfide-based silane coupling agent such as bis(3-triethoxysilylpropyl)disulfide and bis(3-triethoxysilylpropyl)tetrasulfide; a vinyl-based silane coupling agent such as vinyltriethoxysilane and vinyltrimethoxysilane.an amino-based silane coupling agent such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; a glycidoxy-based silane coupling agent such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; a nitro-based silane coupling agent such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and a chlorine-based silane coupling agent such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, it is preferable to contain a thioester-based silane coupling agent and / or a sulfide-based silane coupling agent. These silane coupling agents can be used alone or in combinations of two or more.

[0120] The mercapto-based silane coupling agent is preferably a compound represented by chemical formula (1) and / or a compound containing a bonding unit A represented by chemical formula (2) and a bonding unit B represented by chemical formula (3).

[0121] (In the formula, R 101 , R 102 and R 103 each independently of one another is alkyl having 1 to 12 carbon atoms, alkoxy having 1 to 12 carbon atoms or a group which is substituted by -O-(R 111 -O) z -R 112 is represented (e.g. pieces of R 111 each independently represents a divalent hydrocarbon group having 1 to 30 carbon atoms; R 112 represents alkyl having 1 to 30 carbon atoms, alkenyl having 2 to 30 carbon atoms, aryl having 6 to 30 carbon atoms or aralkyl having 7 to 30 carbon atoms; z represents an integer from 1 to 30); and R 104 represents alkylene with 1 to 6 carbon atoms.)

[0122] (In the formula, x represents an integer of 0 or more; y represents an integer of 1 or more; R 201 represents alkyl having 1 to 30 carbon atoms, alkenyl having 2 to 30 carbon atoms or alkynyl having 2 to 30 carbon atoms, which may optionally be replaced by a hydrogen atom, a halogen atom, hydroxyl or carboxyl; and R 202 represents alkylene having 1 to 30 carbon atoms, alkenylene having 2 to 30 carbon atoms or alkynylene having 2 to 30 carbon atoms; where R 201 and R 202 a ring structure can be formed.)

[0123] As the compound represented by formula (1), for example, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, or a compound represented by formula (4) (Si363, manufactured by Evonik Degussa GmbH) can be used, and the compound represented by formula (4) can be used appropriately. These can be used alone or in combinations of two or more.

[0124] Examples of the compound containing the bonding unit A represented by Chemical Formula 2 and the bonding unit B represented by Chemical Formula 3 include those manufactured and sold by Momentive Performance Materials Inc. These can be used alone or in combinations of two or more.

[0125] In a case where the silane coupling agent is contained, the content of the silane coupling agent (the total amount of all the silane coupling agents in a case of using a plurality of silane coupling agents in combination) with respect to 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 silica dispersibility. Moreover, from the viewpoint of preventing a decrease in abrasion resistance performance, 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.

[0126] The content of the silane coupling agent relative 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 improving the dispersibility of silica. Furthermore, from the viewpoint of cost and process efficiency, the content 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. <weichmacher>

[0127] The rubber composition according to the present invention preferably contains a plasticizer. Examples of the plasticizer include a resin, an oil, a liquid rubber, and an ester-based plasticizer. (Resin)

[0128] The resin is not particularly limited, and examples include a petroleum resin, a terpene resin, a rosin resin, or a phenolic resin commonly used in the tire industry. These resins can be used alone or in combinations of two or more. Among them, a petroleum resin is preferred. <<Erdölharz> >

[0129] As the petroleum resin, a C5 petroleum resin, an aromatic petroleum resin, a C5C9 petroleum resin, or the like can be used. These resins can be used alone or in combinations of two or more.

[0130] C5 petroleum resin refers to a resin obtained by polymerizing a C5 fraction. Examples of the C5 fraction include petroleum fractions equivalent to those containing 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. Dicyclopentadiene resin (DCPD resin) is suitably used as the C5 petroleum resin.

[0131] The aromatic petroleum resin refers to a resin obtained by polymerizing a C9 fraction and may be a hydrogenated or modified product thereof. Examples of the C9 fraction include petroleum fractions equivalent to those having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. As a specific example of the aromatic petroleum resin, for example, a coumarone-indene resin, a coumarone resin, an indene resin, and an aromatic vinyl-based resin are suitably used.

[0132] The aromatic vinyl-based resin is preferably a homopolymer of α-methylstyrene or styrene or a copolymer of α-methylstyrene and styrene, and more preferably a copolymer of α-methylstyrene and styrene, because it is economical, easy to process, and exothermic. For example, those commercially available from Kraton Corporation and Eastman Chemical Company can be used as the aromatic vinyl-based resin.

[0133] C5C9 petroleum resin refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified product thereof. Examples of the C5 fraction and the C9 fraction include the petroleum fractions described above. For example, those commercially available from Tosoh Corporation and LUHUA can be used as the C5C9 petroleum resin. < <terpenharz>>

[0134] Examples of the terpene resin include a polyterpene resin formed from at least one selected from terpene compounds such as α-pinene, β-pinene, limonene, and dipentene; an aromatic-modified terpene resin using the terpene compound and an aromatic compound as a raw material; a terpene-phenolic resin using the terpene compound and a phenolic compound as a raw material; and a hydrogenated product of these terpene resins (hydrogenated terpene resin). Examples of the aromatic compound serving as the raw material of the aromatic-modified terpene resin include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of the phenolic compound serving as the raw material of the terpene-phenolic resin include phenol, bisphenol A, cresol, and xylenol. These resins can be used alone or in combinations of two or more. < <kolophoniumharz>>

[0135] The rosin resin is not particularly limited, and examples thereof include natural resin rosin and rosin-modified resins obtained by modifying natural resin rosin through hydrogenation, disproportionation, dimerization, esterification, or the like. These resins can be used alone or in combinations of two or more. < <phenolharz>>

[0136] The phenolic resin is not particularly limited, and examples include a phenol-formaldehyde resin, an alkylphenol-formaldehyde resin, an alkylphenol-acetylene resin, and an oil-modified phenol-formaldehyde resin. These resins can be used alone or in combinations of two or more. < <erweichungspunkt>>

[0137] A softening point of the resin is preferably higher than 60°C, more preferably higher than 70°C, and even more preferably higher than 80°C from the viewpoint of wet grip performance. Furthermore, from the viewpoint of improving the process efficiency and dispersibility of the rubber component and the filler, the softening point is preferably lower than 150°C, more preferably lower than 140°C, and even more preferably lower than 130°C. In the present specification, the softening point is obtained by the method described above. < <gehalt>>

[0138] In a case where the resin is contained, the content of the resin relative to 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. Furthermore, from the viewpoint of suppressing exothermicity, the content 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. (Oil)

[0139] Examples of the oil include a process oil, a vegetable oil, and an animal oil. Examples of the process oil include a paraffinic process oil, a naphthenic process oil, and an aromatic process oil. In addition, a process oil with a low polycyclic aromatic compound (PCA) content can be used for environmental protection measures. Examples of the low PCA content process oil include an MES (mild extraction solvent), a TDAE (treated distillate aromatic extract), and a heavy naphthenic oil.

[0140] In a case where the oil is contained, the content of the oil with respect to 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 process efficiency. Furthermore, from the viewpoint of abrasion resistance performance, 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 the present specification, the content of the oil includes the amount of oil contained in the oil-extended rubber. (liquid rubber)

[0141] The liquid rubber is not particularly limited as long as it is a polymer in a liquid state at room temperature (25°C). Examples include liquid butadiene rubber (liquid BR), liquid styrene-butadiene rubber (liquid SBR), liquid isoprene rubber (liquid IR), liquid styrene-isoprene rubber (liquid SIR), and liquid farnesene rubber. These liquid rubbers can be used alone or in combinations of two or more.

[0142] In a case where the liquid rubber is included, the content of the liquid rubber relative to 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. Furthermore, 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. (Ester-based plasticizer)

[0143] Examples of ester-based plasticizers include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di(2-ethylhexyl)azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), and trixylenyl phosphate (TXP). These ester-based plasticizers can be used alone or in combinations of two or more.

[0144] The content of the plasticizer relative to 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. Furthermore, from the viewpoint of process efficiency, 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. <Andere Mischmittel>

[0145] In addition to the components described above, the rubber composition according to the present invention may suitably contain a mixing agent conventionally used in the tire industry, such as wax, a processing aid, an antioxidant, stearic acid, zinc oxide, a vulcanizing agent or a vulcanization accelerator. (Wax)

[0146] Any wax commonly used in the tire industry can be used as the wax. The wax can be used alone or in combinations of two or more. In a case where the wax is contained, the content of the wax with respect to 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. Furthermore, from the viewpoint of preventing tire whitening due to blooming, 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. (processing aids)

[0147] Examples of the processing aid include a fatty acid metal salt, a fatty acid amide, an amide ester, a silica surface activator, a fatty acid ester, a mixture of a fatty acid metal salt and an amide ester, and a mixture of a fatty acid metal salt and a fatty acid amide. These processing aids can be used alone or in combinations of two or more. For example, those commercially available from Schill + Seilacher GmbH and Performance Additives, Inc. can be used as the processing aid.

[0148] In a case where the processing aid is included, the content of the processing aid, relative to 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 exhibiting an improvement effect on process efficiency. Furthermore, from the viewpoint of abrasion resistance and fracture toughness, the content is preferably less than 10 parts by mass, more preferably less than 8 parts by mass, and even more preferably less than 5 parts by mass. (antioxidant)

[0149] The antioxidant is not particularly limited, and examples thereof include antioxidants such as amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, and carbamic acid metal salts. A phenylenediamine-based antioxidant 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 a quinoline-based antioxidant such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline are preferred. These antioxidants can be used alone or in combinations of two or more.

[0150] In a case where the antioxidant is contained, the content of the antioxidant, relative to 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 cracking resistance of the rubber. Furthermore, from the viewpoint of abrasion resistance performance and wet grip performance, the content 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. (Stearic acid)

[0151] In a case where stearic acid is contained, the content of stearic acid relative to 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 process efficiency. Furthermore, from the viewpoint of vulcanization rate, the content is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less. (Zinc oxide)

[0152] In a case where zinc oxide is contained, the content of zinc oxide relative to 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 process efficiency. Furthermore, from the viewpoint of abrasion resistance performance, the content 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. (vulcanizing agent)

[0153] Sulfur is preferably used as the vulcanizing agent. Sulfur powder, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, and the like can be used as the sulfur. These vulcanizing agents can be used alone or in combinations of two or more.

[0154] In a case where sulfur is contained as the vulcanizing agent, the content of sulfur with respect to 100 parts by mass of the rubber component is preferably more than 0.1 part 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. Moreover, from the viewpoint of preventing deterioration, the content 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. In a case where oily sulfur is used as the vulcanizing agent, the content of the vulcanizing agent is the total content of pure sulfur contained in the oily sulfur.

[0155] Examples of vulcanizing agents other than sulfur include alkylphenol sulfur chloride condensates, 1,6-hexamethylene sodium dithiosulfate dihydrate, and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane. These vulcanizing agents other than sulfur can be used as those commercially available from Taoka Chemical Co., Ltd., LANXESS AG, and FLEXSYS. (vulcanization accelerator)

[0156] Examples of the vulcanization accelerator include a sulfenamide-based vulcanization accelerator, a thiazole-based vulcanization accelerator, a thiuram-based vulcanization accelerator, a thiourea-based vulcanization accelerator, a guanidine-based vulcanization accelerator, a dithiocarbamic acid-based vulcanization accelerator, an aldehyde-amine-based or aldehyde-ammonia-based vulcanization accelerator, an imidazoline-based vulcanization accelerator, and a xanthate-based vulcanization accelerator. These vulcanization accelerators can be used alone or in combination of two or more.

[0157] Among them, it is preferable to contain one or more vulcanization accelerators selected from the group consisting of the sulfenamide-based vulcanization accelerator, the guanidine-based vulcanization accelerator, and the thiazole-based vulcanization accelerator, and it is further preferable to contain the sulfenamide-based vulcanization accelerator and the guanidine-based vulcanization accelerator.

[0158] Examples of the sulfenamide-based vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), and N,N'-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS). Among them, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) is preferred.

[0159] Examples of the guanidine-based vulcanization accelerator include 1,3-diphenylguanidine (DPG), 1,3-diotolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicachol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine. Among these, 1,3-diphenylguanidine (DPG) is preferred.

[0160] Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole, a cyclohexylamine salt of 2-mercaptobenzothiazole, and di-2-benzothiazolyl disulfide. Among them, 2-mercaptobenzothiazole is preferred.

[0161] In a case where the vulcanization accelerator is included, the content of the vulcanization accelerator with respect to 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. Moreover, the content of the vulcanization accelerator with respect to 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. When the content of the vulcanization accelerator is within the above range, there is a tendency that breaking strength and elongation can be ensured. [Belt layer]

[0162] In the tire of the present invention, a belt layer commonly used in the tire industry can be used as the belt layer. The belt layer includes a cord forming its skeleton and a rubber covering the cord. In addition to a steel cord, other cords, such as an organic fiber cord, can be used as the cord.

[0163] In the tire of the present invention, the belt layer may be a single layer or may be a multilayer of two or more layers, and it is preferably a multilayer of two or more layers. Furthermore, when a width (mm) of a widest belt layer among the belt layers is denoted as Wb, the relationship of Expression (2) between the tire section width (mm) Wt and the content (parts by mass) A2 SIL of the silica with respect to 100 parts by mass of the rubber component in the second rubber composition. Here, the value of Wb can be appropriately adjusted by increasing or decreasing a width of a mold. [Manufacture](Manufacture of rubber composition)

[0164] The rubber compositions according to the present invention, that is, both 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, the rubber composition can be produced by kneading each of the above components using a rubber kneading device such as an open roll, a closed-type kneader (Banbury mixer, kneader, or the like).

[0165] For example, the kneading step includes a basic kneading process of kneading a mixing agent and an additive other than the vulcanizing agent and vulcanization accelerator, and a final kneading process (F-kneading) of adding the vulcanizing agent and vulcanization accelerator to the kneaded product obtained in the basic kneading process and kneading the mixed product. Furthermore, the basic kneading process can be divided into multiple processes as needed.

[0166] Kneading conditions are not particularly limited. For example, in the initial kneading process, kneading is carried out at a discharge temperature of 150°C to 170°C for 3 to 10 minutes, and in the final kneading process, kneading is carried out at a temperature of 70°C to 110°C for 1 to 5 minutes. (Tire manufacturing)

[0167] The tire of the present invention can be manufactured by a conventional method using the first rubber composition, the second rubber composition, and the widest belt layer having a predetermined width. That is, the tire of the present invention can be manufactured by extruding the unvulcanized first and second rubber compositions into the first rubber layer and the second rubber layer shapes with an extruder including a base having a predetermined shape, bonding them on a tire molding machine together with the belt layer according to the present invention and other tire elements, and molding them via a conventional method to form an unvulcanized tire, followed by heating and pressurizing this unvulcanized tire in a vulcanizing machine. Vulcanization conditions are not particularly limited.For example, vulcanization is carried out at a temperature of 150 °C to 200 °C for 10 to 30 minutes. [Use]

[0168] The tire of the present invention can be used for any application, whether it is a pneumatic tire or a pneumatic tire. Furthermore, the tire can be used as a racing tire, a passenger car tire, a large passenger car tire, a large SUV tire, and a motorcycle tire. Among them, a passenger car tire is preferred. Here, a passenger car tire is a tire intended to be installed on an automobile traveling on four wheels and refers to a tire having a maximum load capacity of 1000 kg or less in the JATMA standard.

[0169] Furthermore, the tire of the present invention can be used as a summer tire, a winter tire, and a studless tire of each of the tires described above. [Examples]

[0170] The present invention will be described based on examples, but the present invention is not limited to examples.

[0171] Below, various chemicals used in examples and comparative examples are shown collectively. SBR1: Styrene-butadiene rubber (modified S-SBR, styrene content: 25 mass%, vinyl content: 25 mol%, Tg: -55°C, non-oil-extended product) synthesized in Production Example 1 SBR2: HPR850 (styrene content: 27.5 mass%, vinyl content: 59 mol%, Tg: -24°C) manufactured by JSR Co., Ltd. SBR3: Styrene-butadiene rubber (modified S-SBR, styrene content: 33 mass%, vinyl content: 46 mol%, Tg: -22 °C, non-oil-extended product), synthesized in Preparation Example 2 SBR4: JSR0122 (E-SBR, styrene content: 38 mass%, vinyl content: 16 mol%, Tg: -37°C, 100 parts by mass of rubber solid content, extended with 34 parts by mass of oil), manufactured by JSR Co., Ltd. SBR5: SBR1502 (E-SBR, styrene content: 23.5 mass%, vinyl content: 18 mol%, Tg: -51 °C), manufactured by JSR Co., Ltd. BR: UBEPOL BR (registered trademark) 150B (vinyl content: 1.5 mol%, cis content: 97 mol%, Mw: 440,000), manufactured by UBE Corporation No.: TSR20 Soot (CB) 1: SHOBLACK N134 (N2SA: 148 m 2 / g, average primary particle diameter: 18 nm), manufactured by Cabot Japan KK Soot (CB) 2: N220 (N2SA: 115 m 2 / g, average primary particle diameter: 22 nm), manufactured by Birla Carbon Brasil Ltda. Silicon dioxide: ULTRASIL (registered trademark) VN3 (N2SA: 175 m 2 / g, average Primary particle diameter: 18 nm), manufactured by Evonik Degussa GmbH Coupling agent (silane coupling agent) 1: Si266 (bis(3-triethoxysilylpropyl)disulfide), manufactured by Evonik Degussa GmbH Coupling agent (silane coupling agent) 2: NXT (3-octanoylthiopropyltriethoxysilane), manufactured by Momentive Performance Materials Inc. Oil: VivaTec500 (TDAE oil), manufactured by H&R Group Resin 1: Sylvares SA85 (copolymer of α-methylstyrene and styrene, softening point: 85 °C), manufactured by Kraton Corporation Resin 2: NOVARES C90 (coumarone-indene resin, softening point: 90 °C), manufactured by Rutgers Chemicals GmbH Wax: SUNNOC N, manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. Antioxidant 1: Antigen 6C (6PPD, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine), manufactured by Sumitomo Chemical Co., Ltd. Antioxidant 2: NOKLAK 224 (TMQ, 2,2,4-trimethyl-1,2-dihydroquinoline polymer), manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. Stearic acid: Pearl-shaped stearic acid Tsubaki, 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: NOCCELER CZ (CBS, N-cyclohexyl-2-benzothiazolylsulfenamide), manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. Vulcanization accelerator 2: NOCCELER D (DPG, 1,3-diphenylguanidine (DPG)), manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. Preparation Example 1: Synthesis of SBR1

[0172] The ratio of styrene to 1,3-butadiene is adjusted so that the target styrene content is 25 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. The polymerization is carried out under adiabatic conditions. When the polymerization conversion rate reaches 99%, 1,3-butadiene is added, and the polymerization is further carried out. Then, methyltriethoxysilane is added as a modifier to conduct a modification reaction. After the reaction is complete, 2,6-di-tert-butyl-p-cresol is added. Next, the obtained solution is subjected to solvent removal by steam stripping and dried with a heat roller temperature-adjusted to 110 °C to obtain SBR1. Preparation Example 2: Synthesis of SBR3

[0173] The ratio of styrene to 1,3-butadiene is adjusted so that the target styrene content is 33 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. The polymerization is carried out under adiabatic conditions. When the polymerization conversion rate reaches 99%, 1,3-butadiene is added, and the polymerization is further carried out. Then, 3-[bis(trimethylsilyl)amino]propyltriethoxysilane is added as a modifier to conduct a modification reaction. After the reaction is complete, 2,6-di-tert-butyl-p-cresol is added. Next, the obtained solution is subjected to solvent removal by steam stripping and dried with a heat roller temperature-adjusted to 110 °C to obtain SBR3. [Examples and comparative examples]

[0174] According to the mixture shown in Table 1, using a 1.7-liter closed-type Banbury mixer, chemicals other than sulfur and a vulcanization accelerator were kneaded for 1 to 10 minutes until a discharge temperature reached 150°C to 160°C to obtain a kneaded product. Next, using a double-axis open roll, sulfur and a vulcanization accelerator were added to the resulting kneaded product and kneaded for 4 minutes until the temperature reached 105°C to obtain an unvulcanized rubber composition.The obtained unvulcanized rubber composition is molded into the shapes of the first layer (4 mm) and the second layer (6 mm) of the tread and bonded together with the belt layer and other tire elements to prepare an unvulcanized tire, followed by vulcanization at 170 °C, thereby obtaining each of test tires (Tire 1: 225 / 45R17, Tire 2: 205 / 55R16, Tire 3: 195 / 45R16).

[0175] Two belt layers are arranged adjacent to the tread on the inside of the tire's radial direction. Of the two belt layers, the belt layer located on the inside of the tire's radial direction is the widest.

[0176] On the tread surface of each test tire, the circumferential main grooves consist of three linear main grooves, one of which passes the tire centerline. The remaining two are installed at equally spaced positions on the outer side in the tire width direction relative to the main groove passing the tire centerline. The groove depth (deepest portion) of each circumferential main groove is set to 6.5 mm. <Physikalische Eigenschaften von Kautschukschicht>

[0177] The physical properties of each rubber layer constituting the tire are measured by the following method. The results are described in the corresponding columns of Table 1 for the rubber compositions constituting each rubber layer. (30 °C-tanδ)

[0178] A viscoelasticity measurement sample having a length of 20 mm, a width of 4 mm, and a thickness of 1 mm is taken from the inside of a predetermined rubber layer (first rubber layer) of the tread portion of each test tire such that the tire circumferential direction is a long side and the tire radial direction is a thickness, and a loss tangent tanδ is measured using Eplexor series manufactured by GABO under conditions of a temperature of 30 °C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and a strain mode. (Glass transition temperature (Tg) of rubber composition)

[0179] For each rubber test piece prepared by cutting out from the inner side of a predetermined rubber layer (second rubber layer) of the tread portion of each test tire to have a length of 20 mm, a width of 4 mm, and a thickness of 1 mm such that the tire circumferential direction is a long side and the tire radial direction is a thickness, a temperature distribution curve of the loss tangent tanδ is measured in a range of -60 °C to 40 °C using Eplexor series manufactured by GABO under conditions of a frequency of 10 Hz, an initial strain of 10%, an amplitude of ±0.5%, and a temperature rise rate of 2 °C / min, and a temperature (tanδ peak temperature) corresponding to the maximum value of the obtained temperature distribution curve is set as the glass transition temperature (Tg).In a case where the tanδ value continues to gradually increase or decrease with a temperature increase during measurement in the range of -60 °C to 40 °C, the glass transition temperature of the rubber composition is set to 40 °C or -60 °C. Moreover, in a case where there are two or more points at which a temperature at which the tanδ value is maximized is in the range of -60 °C to 40 °C, a temperature corresponding to the lowest temperature point among the points is set as the glass transition temperature of the rubber composition. <Nasshaftungsleistung nach Abrieb>

[0180] Each test tire is thermally deteriorated at 80°C for 7 days and is further abraded evenly along a tire radius in a new product such that the tire is abraded by 4.5 mm on a tire equator, and then installed on all wheels of a vehicle. The vehicle travels at a speed of 100 km / h on a wet asphalt road surface, and a braking distance from a point where a brake is applied is measured. The wet grip performance of each tire after abrasion is expressed as an index by the following calculation expression such that a braking distance of the test tire of a reference comparative example is 100. The larger the index, the better the (Wet grip performance index after abrasion) = (Braking distance after abrasion of tires of reference comparison example) / (Braking distance after abrasion of each test tire) × 100 [Table 1] Table 1 Rubber composition A B C D E F G H Mixed quantity (parts by mass) SBR1 60 0 40 30 60 0 0 60 SBR2 0 60 60 30 0 0 0 0 SBR3 0 0 0 0 0 60 0 0 SBR4 0 0 0 0 0 0 20,1 0 SBR5 0 0 0 0 0 0 70 0 BR 15 15 0 40 40 40 0 15 NR 25 25 0 0 0 0 15 25 (extending oil) (0) (0) (0) (0) (0) (0) (5,1) (0) CB1 0 0 30 10 30 0 0 0 CB2 5 5 0 0 0 10 35 55 Silicon dioxide 72 72 46 63 47 73 78 49 Coupling agent 1 0 0 0 0 5 8 8 0 Coupling agent 2 8 8 5 7 0 0 0 5 Öl 15 0 10 7,5 15 12 0 15 Resin 1 6 6 0 0 0 0 0 0 Resin 2 0 0 15 15 15 0 0 0 wax 1,5 1,5 1,5 1,5 1,5 1,5 1,5 1,5 Antioxidant 1 2 2 2 2 2 2 2 2 Antioxidants 2 1 1 1 1 1 1 1 1 Stearic acid 2 2 2 2 2 2 2 2 zinc oxide 2 2 2 2 2 2 2 2 sulfur 1,4 1,4 1,4 1,4 1,4 1,4 1,4 1,4 Vulcanization accelerator 1 2, 3 2, 3 2, 3 2, 3 2, 3 2, 3 2, 3 2,3 Vulcanization accelerator 2 1,5 1,5 1,5 1,5 1,5 1,5 1,5 1,5 Physical properties 30 °C-tanδ 0,17 0,19 0,23 0,21 0,25 0,29 0,46 0,31 Tg (°C) 36,9 18,5 17,2 31,4 39,7 30,5 -37,7 44,5 Total styrene amount (mass-%) 18,8 16,5 29,0 17,6 18,8 23,8 24,1 18,8 [Table 2] Table 2 (225 / 45R17) Examples Comparison examples 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-1 1-2 1-3 1-4 1-5 1-6 Tires First rubber layer C A B H C H E C A F B H C Second rubber layer H G G A D B B H D C D H C Amount of silicon dioxide from the first layer (A1 SIL ) 46 72 72 49 46 49 47 46 72 73 72 49 46 Amount of silicon dioxide from second layer (A2 SIL ) 49 78 78 72 63 72 72 49 63 46 63 49 46 Width of widest belt layer (Wb) 185 190 190 190 190 190 190 180 190 190 190 190 190 Tire section width (Wt) 230 240 240 240 240 240 240 230 240 240 240 240 240 Total styrene amount (mass%) of rubber component of first layer (St1) 29,0 18,8 16,5 18,8 29,0 18,8 18,8 29,0 18,8 23,8 16,5 18,8 29,0 Total styrene amount (mass%) of rubber component of second layer (St2) 18,8 24,1 24,1 18,8 17,6 16,5 16,5 18,8 17,6 29,0 17,6 18,8 29,0 Characteristics Expression (1) A2 SIL / A1 SIL 1,07 1,08 1,8 1,47 1,37 1,47 1,53 1,07 0,88 0,63 0,88 1,00 1,00 Expression (2) A2 SIL / (Wt - Wb) 1,09 1,56 1,56 1,44 1,26 1,44 1,44 0, 98 1,26 0,92 1,26 0, 98 0, 92 Tg (°C) of second layer (Tg2) - 44,5 - 37,7 - 37,7 - 36,9 - 31,4 - 18,5 - 18,5 - 44, 5 - 31,4 - 17,2 - 31,4 - 4, 5 - 17,2 30 °C-tanδ of first layer (30 °C-tanδ1) 0, 23 0, 17 0, 19 0,31 0,23 0,31 0,25 0,23 0, 17 0, 29 0, 19 0,31 0,23 At least one of St1 and St2 is less than 25.0 ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ × Evaluation Performance index of wet grip after abrasion 110 120 120 130 140 138 150 90 90 100 100 70 70 [Table 3] Table 3 (205 / 55R16) Examples Comparison examples 2-1 2-2 2-3 2-4 2-5 2-1 2-2 2-3 Tires First rubber layer C H C H E C B H Second rubber layer H A D B B H D H Amount of silicon dioxide from the first layer (A1 SIL ) 46 49 46 49 47 46 72 49 Amount of silicon dioxide from second layer (A2 SIL ) 49 72 63 72 72 49 63 49 Width of widest belt layer (Wb) 160 160 160 160 160 155 160 160 Tire section width (Wt) 206 210 210 210 210 206 210 210 Total styrene amount (mass%) of rubber component of first layer (St1) 29,0 18,8 29,0 18,8 18,8 29,0 16,5 18,8 Total styrene amount (mass%) of rubber component of second layer (St2) 18,8 18,8 17, 6 16,5 16, 5 18,8 17, 6 18,8 Characteristics Expression (1) A2 SIL / A1 SIL 1,07 1,47 1,37 1,47 1,53 1,07 0,88 1,00 Expression (2) A2 SIL / (Wt - Wb) 1,07 1, 44 1,26 1,44 1,44 0,96 1,26 0,98 Tg (°C) of second layer (Tg2) - 44,5 - 36, 9 - 31,4 - 18,5 - 18,5 - 44,5 - 31,4 - 44,5 30 °C-tanδ of first layer (30 °C-tanδ1) 0,23 0,31 0,23 0,31 0,25 0,23 0,19 0,31 At least one of St1 and St2 is less than 25.0 ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Evaluation Performance index of wet grip after abrasion 105 120 128 125 135 85 70 75 [Table 4] Table 4 (195 / 45R16) Examples Comparison examples 3-1 3-2 3-3 3-4 3-5 3-1 3-2 3-3 Tires First rubber layer C H C H E C B H Second rubber layer H A D B B H D H Amount of silicon dioxide from the first layer (A1 SIL ) 46 49 46 49 47 46 72 49 Amount of silicon dioxide from second layer (A2 SIL ) 49 72 63 72 72 49 63 49 Width of widest belt layer (Wb) 150 150 150 150 150 145 150 150 Tire section width (Wt) 195 200 200 200 200 195 200 200 Total styrene amount (mass%) of rubber component of first layer (St1) 29,0 18,8 29,0 18,8 18,8 29,0 16,5 18,8 Total styrene amount (mass%) of rubber component of second layer (St2) 18,8 18,8 17, 6 16, 5 16, 5 18,8 17, 6 18,8 Characteristics Expression (1) A2 SIL / A1 SIL 1,07 1, 47 1,37 1,47 1,53 1,07 0,88 1,00 Expression (2) A2 SIL / (Wt - Wb) 1,09 1, 44 1,26 1,44 1,44 0, 98 1,26 0, 98 Tg (°C) of second layer (Tg2) -44,5 -36, 9 -31,4 -18,5 -18,5 -44,5 -31,4 -44,5 30 °C-tanδ of first layer (30 °C-tanδ1) 0,23 0,31 0,23 0,31 0,25 0,23 0,19 0,31 At least one of St1 and St2 is less than 25.0 ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Evaluation Performance index of wet grip after abrasion 102 115 123 120 130 83 68 73

[0181] In Tables 2 to 4, "0" means that the given condition is met, and "×" means that the given condition is not met. <Ausführungsform>

[0182] A preferred embodiment is shown below. [1] A tire comprising: a tread portion; and at least one belt layer, wherein the tread portion includes at least a first rubber layer located on an outermost side in a tire radial direction and a second rubber layer adjacent to an inner side of the first rubber layer in the tire radial direction, the first rubber layer being composed of a first rubber composition containing a rubber component containing styrene-butadiene rubber and silica, the second rubber layer being composed of a second rubber composition containing a rubber component containing styrene-butadiene rubber and silica, the tread portion including two or more circumferential main grooves extending in a tire circumferential direction and land portions defined by the circumferential main grooves, at least one of the circumferential main grooves being formed so,that a deepest portion of a groove bottom is located inward in the tire radial direction with respect to an outermost portion of the second rubber layer in the land portion adjacent to the main circumferential groove when a content (parts by mass) of the silica with respect to 100 parts by mass of the rubber component in the first rubber composition is set as A1, SIL and a content (parts by mass) of the silicon dioxide with respect to 100 parts by mass of the rubber component in the second rubber composition is referred to as A2 SIL and a section width (mm) of the tire is referred to as Wt and a width (mm) of a widest belt layer among the belt layers is referred to as Wb when a tread in a normal state is pressed against a plane under a normal load, A1 SIL , A2 SIL , Wt and Wb satisfy the following relationship, a right side of expression (1) is preferably 1.06 and more preferably 1.07 and a right side of expression (2) is preferably 1.08, more preferably 1.10 and even more preferably 1.20, A2SIL / A1SIL>1.05, and A2SIL / (Wt−Wb)>1.00. [2] The tire according to [1], wherein when a glass transition temperature (°C) of the second rubber composition is referred to as Tg2, Tg2 is higher than -30 °C, preferably higher than -25 °C, and more preferably higher than -20 °C. [3] The tire according to [1] or [2], wherein, when tanδ of the first rubber composition at 30 °C is referred to as 30 °C-tanδ1, 30 °C-tanδ1 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 [1] to [3], wherein, when a total styrene amount (mass %) of the rubber component contained in the first rubber composition is referred to as St1 and a total styrene amount (mass %) of the rubber component contained in the second rubber composition is referred to as 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 even more preferably less than 17.0. [5] The tire according to any one of [1] to [4], wherein the rubber component contained in the second rubber composition contains at least one of butadiene rubber and isoprene-based rubber. [6] The tire according to any one of [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 butadiene rubber. [7] The tire according to any one of [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 [1] to [7], wherein the right side of expression (1) is 1.10, preferably 1.20, more preferably 1.30, even more preferably 1.40, and even more preferably 1.50. [9] The tire according to any one of [1] to [8], wherein the right side of expression (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 [1] to [9], wherein the tread portion has a widened circumferential groove whose groove width is widened on an inner side in the tire radial direction.

[11] The tire according to

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

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

[11] , wherein, when a pair of land portions located on an outermost side in a tire width direction are defined among the land portions as shoulder land portions, the shoulder land portions have one or more small holes having an opening area of ​​greater than 0.1 mm 2 and smaller than 15 mm 2 , preferably larger than 0.5 mm 2 and smaller than 10 mm 2 , more preferably greater than 1.0 mm 2 and less than 7.0 mm 2 and even more preferably larger than 1.5 mm 2 and less than 7.0 mm 2 have.

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

[11] , wherein, when a pair of land portions located on an outermost side in a tire width direction among the land portions are defined as shoulder land portions, the shoulder land portions have at least one or more circumferential fine grooves. Brief description of the reference symbols Dt tire outer diameter Wt tire section width Wb Width of widest belt layer W Tire width direction C Tire circumferential direction CL tire centerline The tread end H1 Thickness of first rubber layer H2 Thickness of second rubber layer D Groove depth 11 Belt layer 12 belt layer 2 main circumferential grooves 3 bridge section 4 first rubber layer 5 second rubber layer 6 widened circumferential groove 7 small hole 8 fine circumferential grooves QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 3213127

[0002] JP 2009-2594

[0109] Cited non-patent literature

[0000] Akita Prefectural University Web Journal B / 2019, vol. 6, pp. 216 to 222

[0109] < / gehalt> < / erweichungspunkt> < / phenolharz> < / kolophoniumharz> < / terpenharz> < / weichmacher> < / kautschukkomponente> < / tg>

Claims

[1] Tires, comprising: a tread section; and at least one belt layer (11, 12), wherein the tread portion includes at least a first rubber layer (4) located on an outermost side in a tire radial direction and a second rubber layer (5) adjacent to an inner side of the first rubber layer (4) in the tire radial direction, the first rubber layer (4) is composed of a first rubber composition containing a rubber component containing styrene-butadiene rubber and silicon dioxide, the second rubber layer (5) is composed of a second rubber composition containing a rubber component containing styrene-butadiene rubber and silicon dioxide, the tread portion includes two or more main circumferential grooves (2) extending in a tire circumferential direction and land portions (3) defined by the main circumferential grooves (2), at least one of the main circumferential grooves (2) is formed such that a deepest portion of a groove bottom is located inward in the tire radial direction with respect to an outermost portion of the second rubber layer (5) in the land portion (3) abutting the main circumferential groove (2), and when a content (parts by mass) of the silicon dioxide with respect to 100 parts by mass of the rubber component in the first rubber composition is specified as A1 SIL and a content (parts by mass) of the silicon dioxide with respect to 100 parts by mass of the rubber component in the second rubber composition is referred to as A2 SILand a section width (mm) of the tyre is referred to as Wt and a width (mm) of a widest belt layer (11, 12) among the belt layers (11, 12) is referred to as Wb when a tread in a normal state is pressed against a plane under a normal load, A1 SIL , A2 SIL , Wt and Wb satisfy the following relationship, A2SIL / A1SIL>1.05, and A2SIL / (Wt−Wb)>1.

00. [2] Tire according to claim 1, wherein, when a glass transition temperature (°C) of the second rubber composition is referred to as Tg2, Tg2 is higher than -30 °C. [3] Tire according to claim 1 or 2, where, when tanδ of the first rubber composition at 30 °C is referred to as 30 °C-tanδ1, 30 °C-tanδ1 is less than 0.

30. [4] Tire according to one of claims 1 to 3, wherein, when a total styrene amount (mass %) of the rubber component contained in the first rubber composition is referred to as St1 and a total styrene amount (mass %) of the rubber component contained in the second rubber composition is referred to as St2, at least one of St1 and St2 is less than 25.

0. [5] Tire according to one of claims 1 to 4, wherein the rubber component contained in the second rubber composition contains at least one of butadiene rubber and isoprene-based rubber. [6] Tire according to one of claims 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 butadiene rubber. [7] Tire according to one of claims 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] Tire according to one of claims 1 to 7, where a right side of expression (1) is 1.

10. [9] Tire according to one of claims 1 to 8, where a right-hand side of expression (2) is 1.

25. [10] Tire according to one of claims 1 to 9, wherein the tread portion has a widened circumferential groove (6) whose groove width is widened on an inner side in the tire radial direction. [11] Tire according to claim 10, wherein the widened circumferential groove (6) is provided in the land portion (3) located on a tire center line (CL), or in a case where the main circumferential groove (2) is provided on the tire center line (CL), in the land portion (3) closest to the tire center line (CL). [12] Tire according to one of claims 1 to 11, wherein, when a pair of land portions (3) located on an outermost side in a tire width direction are defined among the land portions (3) as shoulder land portions (3), the shoulder land portions (3) have one or more small holes (7) having an opening area of ​​greater than 0.1 mm 2 and smaller than 15 mm 2 have. [13] Tyre according to one of claims 1 to 11, wherein, when a pair of land portions (3) located on an outermost side in a tire width direction are defined as shoulder land portions (3) among the land portions (3), the shoulder land portions (3) have at least one or more fine circumferential grooves (8).

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