Tire

Abstract

A tire has a tread portion and at least one belt layer, the tread portion is provided with: a tread portion; first rubber layer on the outermost side in the radial direction of the tire comprising a first rubber composition containing a rubber component containing styrene butadiene rubber and silica, and second rubber layer adjacent to the inner side in the radial direction of the tire comprising a second rubber composition containing a rubber component containing styrene butadiene rubber and silica The tire includes a second rubber layer, two or more circumferential main grooves extending in the circumferential direction of the tire, and land portions partitioned by the circumferential main grooves, the deepest portion of the groove bottom of at least one of the circumferential main grooves being closer to the inside in the radial direction of the tire than the outermost portion of the second rubber layer. The content A1SIL of silicon dioxide in the first rubber composition, the content A2SIL of silicon dioxide in the second rubber composition, the section width Wt of the tire and the width Wb of the belted layer meet A2SIL / A1SILgt; 1.05, A < 2 > SIL / (W < t >-W ) < gt >; and 1.00.

Description

Technical Field

[0001] The present invention relates to tires. Background Art

[0002] Since there is a trade-off between grip performance and fuel efficiency, for example, Patent Document 1 discloses that the tread portion of a tire is configured as a two-layer structure (so-called cap rubber / base structure) of a base rubber located radially inside the tire and a cap rubber located radially outside the base rubber, and that a rubber composition having a small loss tangent (tan δ) is used for the base rubber, thereby improving the handling stability and fuel efficiency of the tire. [Prior art literature] [Patent Document]

[0003] Patent Document 1: Japanese Patent No. 3213127 Summary of the invention [Problems to be solved by the invention]

[0004] In the case of the above tire, the loss tangent tanδ of the running surface rubber layer is high, so the wet grip performance is high when it is new. However, there is a concern that with repeated running, the running surface rubber layer will be thermally degraded and hardened due to the influence of self-heating, so the rigidity of the tread surface will increase, the road tracking performance will be lost, and the wet grip performance will be reduced.

[0005] An object of the present invention is to provide a tire having improved wet grip performance after wear. [Methods used to solve the problem]

[0006] The present invention relates to the following tire. A tire having a tread portion and at least one belt layer, wherein: The tread portion includes at least a first rubber layer on the outermost side in the tire radial direction and a second rubber layer adjacent to the first rubber layer on the inner side in the tire radial direction. The first rubber layer is composed of a first rubber composition including a rubber component containing styrene butadiene rubber and silica. The second rubber layer is composed of a second rubber composition including a rubber component containing styrene butadiene rubber and silica. The tread portion includes: two or more circumferential main grooves extending in the tire circumferential direction and a land portion divided by the circumferential main grooves; The deepest part of the groove bottom of at least one of the circumferential main grooves is formed to be located further inward in the tire radial direction than the outermost part of the second rubber layer in the land portion adjacent to the circumferential main groove. The content (in parts by mass) of silica in the first rubber composition relative to 100 parts by mass of the rubber component is denoted by A1. SIL The content (in parts by mass) of silica in the second rubber composition relative to 100 parts by mass of the rubber component is A2 SIL , when a normal load is applied under normal conditions and the tread is pressed on a plane, the cross-sectional width (mm) of the tire is Wt, and the width (mm) of the widest belt layer among the belt layers is Wb, A1 SIL 、A2 SIL , Wt and Wb satisfy the following relationship. (1)A2 SIL / A1 SIL >1.05 (2)A2 SIL / (Wt-Wb)>1.00 [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a tire having improved wet grip performance after wear. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] [ Figure 1 ] is a diagram showing the tire cross-sectional width Wt, the tire outer diameter Dt, and the width Wb of the widest belt layer in a cross section of the tire on a plane passing through the tire rotation axis. [ Figure 2 ] is an expanded view of a portion of the tire tread. [ Figure 3 ] is a diagram showing a cross-section of a portion of the tread of a tire on a plane passing through the tire rotation axis. [ Figure 4 ] is a developed view of a portion of the tread of a tire having widened circumferential fine grooves in the land portion closest to the tire centerline. [ Figure 5 ] is to indicate Figure 4 A cross-section of a widened circumferential fine groove in a plane passing through the axis of rotation of the tire. [ Figure 6 ] is an expanded view of a portion of the tread of a tire having small holes in the shoulder area. [ Figure 7 ] is a developed view of a portion of the tread of a tire having circumferential fine grooves in the shoulder area. [Explanation of symbols] Dt: tire outer diameter Wt: tire section width Wb: Width of the widest belt layer W: Tire width direction C: Tire circumference CL: tire center line Te: tread end H1: Thickness of the first rubber layer H2: Thickness of the second rubber layer D: Groove depth 11: Belt 12: Belt 2: Circumferential main groove 3: Land Department 4: First rubber layer 5: Second rubber layer 6: Widen the circumferential groove 7: Small hole 8: Circumferential fine groove DETAILED DESCRIPTION

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

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

[0011] That is, (1) in the tire of the present invention which uses at least two layers of different tread rubber and has a predetermined circumferential main groove, when the rubber of the surface layer of the first layer is worn, it becomes the following form: the tread rubber of the second layer is exposed on the surface, and the tread rubber of the first layer remains at the edge of the land portion. At this time, by using rubber with a large amount of silica in the rubber of the second layer, the effect of improving the wet grip performance after wear can be obtained. In addition, (2) since the silica content of the tread rubber of the first layer is less than that of the second layer, it is correspondingly softer. Therefore, the first layer of rubber remaining at the edge of the land portion exerts road surface following properties and can strengthen the wet grip effect based on the second layer of rubber. In addition, (3) due to wear, the contact area with the ground is larger than before wear, thereby achieving the effect of improving the wet grip performance after wear. Moreover, through the synergistic effect of (1) to (3), the wet grip performance after wear is improved.

[0012] Preferably, when the glass transition temperature (°C) of the second rubber composition is Tg2, Tg2 is greater than -30°C.

[0013] By increasing the glass transition temperature of the second rubber layer, the heat generation property of the second rubber layer can be increased, and friction can be easily generated at the center of the worn land portion.

[0014] Preferably, when tan δ of the first rubber composition at 30°C is tan δ1 at 30°C, tan δ1 at 30°C is less than 0.30.

[0015] By controlling the 30°C tanδ of the first rubber layer, the phase difference between input and response of the first rubber layer can be reduced, and the reaction force can be easily generated.

[0016] Preferably, when the total styrene amount (mass %) of the rubber components contained in the first rubber composition is St1 and the total styrene amount (mass %) of the rubber components contained in the second rubber composition is St2, at least one of St1 and St2 is less than 25.0.

[0017] By reducing the total styrene content of the rubber components contained in the rubber composition constituting the first rubber layer and the second rubber layer, the formation of a domain (styrene domain) based on the styrene portion in the rubber composition can be suppressed in the first rubber layer, and the heat generation between the styrene domain and the surrounding rubber molecular chains can be suppressed, and the responsiveness can be easily improved. In addition, the second rubber layer can easily follow the subtle response of the road surface.

[0018] Preferably, the rubber component contained in the second rubber composition includes at least one of butadiene rubber and isoprene rubber.

[0019] Preferably, 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.

[0020] Preferably, both the rubber component contained in the first rubber composition and the rubber component contained in the second rubber composition contain butadiene rubber.

[0021] Preferably, the tread portion has: an expanded circumferential groove whose groove width increases toward the inner side in the tire radial direction.

[0022] As the groove width of the widened circumferential groove increases after wear, drainage is improved, thereby improving wet grip performance.

[0023] Preferably, the widened circumferential groove exists in a land portion located on the tire centerline, or in a land portion closest to the tire centerline when a circumferential main groove exists on the tire centerline.

[0024] Since the groove width of the widened circumferential groove increases after wear, drainage of the central portion in the tire width direction is improved, thereby improving wet grip performance.

[0025] Preferably, when a pair of land portions located at the outermost sides in the tire width direction among the land portions are shoulder land portions, the shoulder land portions have at least one opening area greater than 0.1 mm 2 And less than 15mm 2 of small holes.

[0026] Since the small holes contribute to the improvement of drainage, the drainage at the shoulder land portion is improved, and the wet grip performance is improved.

[0027] Preferably, when a pair of land portions located outermost in the tire width direction among the land portions are shoulder land portions, the shoulder land portions have at least one circumferential narrow groove.

[0028] Since the circumferential narrow grooves contribute to the improvement of drainage, the drainage of the shoulder land portion is improved, and the wet grip performance is improved.

[0029] [definition] The "normal state" is an unloaded state in which the rim is assembled on a normal rim and filled with a normal internal pressure. Unless otherwise specified, the "dimensions of each part of the tire" are values ​​specified in the normal state.

[0030] "Regular rim" refers to the rim specified for each tire in the specification system that includes the specifications on which the tire is based. For example, in JATMA (Japan Motor Vehicle Tire Association), it refers to the standard rim in the applicable size recorded in the "JATMA Yearbook", in ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" recorded in the "STANDARDS MANUAL", and in TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" recorded in the "Yearbook". Reference is made to JATMA, ETRTO, and TRA in this order. If there is an applicable size when referring, then that specification shall be followed. Furthermore, in the case of tires not specified in the specifications, it refers to a rim that can be assembled on a rim and can maintain internal pressure, that is, a rim that does not cause air leakage between the rim and the tire, and has the smallest rim diameter and the narrowest rim width.

[0031] "Normal internal pressure" refers to the air pressure specified for each tire in each specification in the specification system including the specifications on which the tire is based. In JATMA, it refers to the "maximum air pressure", in TRA, it refers to the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in ETRTO, it refers to the "INFLATION PRESSURE". As with regular rims, reference is made in the order of JATMA, ETRTO, and TRA. If there is an applicable size when referring, the specification is followed. In addition, in the case of tires not specified in the specifications, it refers to the normal internal pressure (of which 250 kPa or more) of other tire sizes (tire sizes specified in the specifications) recorded with the regular rim as the standard rim. It should be noted that when there are multiple normal internal pressures of 250 kPa or more, it refers to the minimum value among them.

[0032] "Normal load" refers to the load specified in the specification system including the specifications on which the tire is based. The maximum value recorded in the "Maximum load capacity" in the JATMA specification, the "Load capacity (LOAD CAPACITY)" in the ETRTO specification, and the "Tire load limits (TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES)" in the TRA specification is the "Normal load". Like the normal rim and normal internal pressure, refer to JATMA, ETRTO, and TRA in this order. If there is an applicable size when referring, follow the specification. In addition, in the case of a tire not specified in the specification, the normal load WL (kg) is calculated by the following calculation. WL=0.000011×V+175 V = {(Dt / 2) 2 -(Dt / 2-Ht) 2}×π×Wt V: Imaginary volume of the tire (mm 3 ) Dt: Tire outer diameter Dt (mm) Ht: Tire section height (mm) Wt: tire section width (mm)

[0033] The tire cross-sectional width Wt is, in a normal state, the maximum width between the outer surfaces of the sidewalls excluding the patterns, characters, etc., when there are patterns or characters on the side of the tire. The tire cross-sectional height Ht is the distance from the bottom surface of the bead portion to the outermost surface of the tread, which is 1 / 2 of the difference between the outer diameter Dt of the tire and the nominal rim diameter.

[0034] The term "belt layer" refers to a layer disposed adjacent to the tread on the inner side of the tread in the radial direction of the tire, mainly in a radial tire, and plays a role in strongly fastening the carcass and improving the rigidity of the tread. The belt layer includes: cords forming the skeleton of the belt layer and rubber covering the cords. In the present invention, the belt layer uses a belt layer commonly used in the tire industry.

[0035] "Circumferential main groove" refers to a groove that extends continuously in the circumferential direction of the tire, and has a groove width of 4 mm or more in the tire width direction at the tread surface. The circumferential main groove may extend in a straight line along the circumferential direction, or may extend in a wavy, sinusoidal or zigzag shape along the circumferential direction. It does not include the widened circumferential groove described later.

[0036] "Circumferential fine grooves" refer to grooves that extend continuously in the circumferential direction of the tire and have a groove width of less than 4 mm in the tire width direction at the tread surface. Circumferential fine grooves may extend in a straight line along the circumferential direction, or may extend in a wavy, sinusoidal or zigzag shape along the circumferential direction. However, the widened circumferential grooves described later are not included.

[0037] "Expanded circumferential groove" refers to a groove that extends continuously in the circumferential direction of the tire, and is configured such that the groove width in the tire width direction is the smallest at the tread surface and expands inwardly in the tire radial direction. The expanded circumferential groove may extend in a straight line along the circumferential direction, or may extend in a wavy, sinusoidal or zigzag shape along the circumferential direction.

[0038] “Total styrene content of rubber component (mass %)” refers to the value obtained by multiplying the styrene content of each rubber constituting the entire rubber component (100 mass %) by the content ratio in the entire rubber component and adding them together.

[0039] "Small holes" refer to small holes existing on the tread surface, extending from the inside of the tread and opening on the tread surface. The small holes exist independently and are not connected to the circumferential grooves, lateral grooves, etc.

[0040] [Measurement method] "30°C tanδ" is the loss tangent measured using the EPLEXOR series manufactured by GABO under the conditions of temperature 30°C, initial strain 5%, dynamic strain 1%, frequency 10 Hz, and elongation mode. The sample for loss tangent measurement is prepared by the following method: when cutting out from the tread portion of the tire, a sample of 20 mm in length × 4 mm in width × 1 mm in thickness is cut out from the inside of the rubber layer to be tested, with the tire circumferential direction as the long side and the tire radial direction as the thickness.

[0041] The "glass transition temperature (Tg) (°C) of the rubber composition" is set as follows: using a dynamic viscoelasticity measuring device (e.g., EPLEXOR series manufactured by GABO), under the conditions of a frequency of 10 Hz, an initial strain of 10%, an amplitude of ±0.5%, and a heating rate of 2°C / min, the temperature distribution curve of the loss tangent tanδ in the range of -60°C to 40°C is measured, and the temperature corresponding to the maximum value in the obtained temperature distribution curve (tanδ peak temperature). It should be noted that in the measurement in the range of -60°C to 40°C, when the tanδ value continues to gradually increase or gradually decrease as the temperature rises, the glass transition temperature of the rubber composition is set to 40°C or -60°C, respectively. In addition, in the range of -60°C to 40°C, when there are two or more temperatures with the maximum tanδ value, the temperature corresponding to the lowest point among these temperatures is taken as the glass transition temperature of the rubber composition. The sample for measurement is prepared in the same way as the case of 30°C tanδ.

[0042] "Styrene content (mass %)" by 1 H-NMR measurement and calculation.

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

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

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

[0046] The “weight average molecular weight (Mw)” can be determined based on the value measured by gel permeation chromatography (GPC) (e.g., GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGELSUPERMULTIPORE HZ-M manufactured by Tosoh Corporation) and converted to standard polystyrene.

[0047] “N2SA of carbon black” is measured according to JIS K 6217-2:2017.

[0048] "N2SA of silica" is measured by the BET method according to ASTM D3037-93.

[0049] The "average primary particle size" can be obtained by measuring 400 or more primary particles observed in the field of view through a transmission or scanning electron microscope. It should be noted that when the shape of the particles is spherical, the diameter of the sphere is used as the particle size. When the particles are not spherical, the equivalent circle diameter (the positive square root of {4×(area of ​​the particle)÷π}) is calculated from the transmission electron microscope image as the particle size. It can be applied to carbon black, silica, etc.

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

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

[0052] [tire] Below, please refer to the attached Figure 1 However, the drawings are merely illustrative, and the present invention should not be construed as being limited to the drawings.

[0053] The tire of the present invention is a tire having a tread portion and at least one belt layer, wherein the tread portion at least comprises: a first rubber layer at the outermost side in the tire radial direction and a second rubber layer adjacent to the first rubber layer at the inner side in the tire radial direction, and the tread portion comprises: two or more circumferential main grooves extending in the tire circumferential direction and a land portion divided by the circumferential main grooves, wherein the deepest portion of the groove bottom of at least one of the circumferential main grooves is formed so as to be located closer to the tire radial direction than the outermost portion of the second rubber layer in the land portion adjacent to the circumferential main groove.

[0054] Figure 1 : is a cross-sectional view of a tire according to one embodiment of the present invention on a plane passing through the tire rotation axis. Figure 1 In the tire, the tire cross-sectional width is represented by Wt. The tread portion of the tire includes a first rubber layer on the outermost side in the tire radial direction and a second rubber layer adjacent to the first rubber layer on the inner side in the tire radial direction, and has two or more circumferential main grooves extending in the tire circumferential direction, and a land portion divided by the circumferential main grooves, but Figure 1 This is not shown in Figure 1 In the tire, 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 the widest belt layer, and its width is represented by Wb. The tire cross-sectional width is represented by Wt. Dt is the tire outer diameter.

[0055] Figure 2 : is an expanded view of the tread surface of a tire according to one embodiment of the present invention. The arrow direction of W is the tread width direction, and the arrow direction of C is the tire circumferential direction. CL represents the tire centerline, and Te represents the tread end. Figure 2 In the tread, the tread surface is divided into four land portions 3 by three circumferential main grooves 2 .

[0056] Figure 3 FIG. 4 shows a part of a cross section of a tire according to one embodiment of the present invention, taken on a plane passing through the tire rotation axis. Figure 3 In the embodiment, the tread portion includes: a first rubber layer 4 on the outermost side in the tire radial direction, and a second rubber layer 5 adjacent to the first rubber layer on the inner side in the tire radial direction. Figure 3 The lower end of the depth D is formed as follows: the outermost portion of the second rubber layer 5 in the land portion 3 adjacent to the circumferential main groove 2 ( Figure 3In the embodiment, the thickness H2 of the second rubber layer (the upper end) is closer to the inner side of the tire radial direction. It should be noted that the tread portion only needs to have at least the first rubber layer and the second rubber layer adjacent to the first rubber layer, and can further have other rubber layers between it and the belt layer.

[0057] In the tire of the present invention, preferably, the tire width direction length of the land portion located on the tire center line or the land portion closest to the tire center line when there is a circumferential main groove on the tire center line increases from the tire radial direction outer side toward the inner side. After wear, the first rubber layer plays a role of supporting the end of the land portion, and by adopting the above structure, the first rubber layer can more easily support the end of the land portion.

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

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

[0060] The right side of formula (1) is preferably 1.06, more preferably 1.07, further preferably 1.10, further preferably 1.20, further preferably 1.30, further preferably 1.40, further preferably 1.50. On the other hand, the upper limit of the value of the left side of formula (1) is not particularly limited, and may be, for example, 3.00, or 2.50, or 2.00, or 1.70.

[0061] The value of the left side of the formula (1) can be adjusted by increasing or decreasing the amount of silica compounded in the first rubber composition constituting the first rubber layer and the amount of silica compounded in the second rubber composition constituting the second rubber layer.

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

[0063] The right side of formula (2) is preferably 1.08, more preferably 1.10, further preferably 1.20, further preferably 1.25, further preferably 1.30, further preferably 1.40, further preferably 1.50. On the other hand, the upper limit of the value of the left side of formula (2) is not particularly limited, and may be, for example, 3.00, or 2.50, or 2.00, or 1.70.

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

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

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

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

[0068] Furthermore, Tg1 is more preferably higher than -47°C, and further preferably higher than -45°C. On the other hand, it is more preferably lower than -13°C, and further preferably lower than -15°C.

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

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

[0071] From the viewpoint of wet grip performance, tan δ1 at 30°C is preferably less than 0.26, more preferably less than 0.24, and further preferably less than 0.20. On the other hand, the lower limit of tan δ1 at 30°C is not particularly limited, and may be, for example, greater than 0.10 or greater than 0.12.

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

[0073] Furthermore, tan δ2 at 30°C is more preferably less than 0.48, and further preferably not more than 0.46. On the other hand, it is more preferably greater than 0.12, and further preferably greater than 0.15.

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

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

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

[0077] The value of St1 can be adjusted by increasing or decreasing the styrene content of each rubber component blended in the first rubber composition. The value of St2 can also be adjusted by increasing or decreasing the styrene content of each rubber component blended in the second rubber composition.

[0078] <Wide Circumferential Groove> In the tire of the present invention, the tread portion preferably has an expanded circumferential groove whose width increases radially inwardly of the tire. This is because after wear, the expanded circumferential groove has a larger width, thereby improving drainage and wet grip performance.

[0079] exist Figure 4 In the embodiment, a straight widened circumferential groove 6 is formed on each of two land portions 3 adjacent to the circumferential main groove 2 passing through the tire center line. The widened circumferential groove may extend in a wavy, sinusoidal, or sawtooth shape along the circumferential direction, for example. In addition, there is no particular limitation on the land portion where the widened circumferential groove is formed, but it is preferably formed on the land portion located on the tire center line, or, when there is a circumferential main groove on the tire center line, it is preferably formed as follows: Figure 4 As shown in the widened circumferential groove 6, it is formed on the land portion closest to the tire centerline.

[0080] Figure 5 denoting the cross section of the widened circumferential groove 6. Figure 5 In the embodiment, the width of the widened circumferential groove increases uniformly toward the inner side of the tire radial direction, but the increase of the groove width is not limited to this method, and it can be increased while repeatedly increasing and decreasing slightly in a curved or stepped manner. The same is true for the ratio of the tire width length of the opening to the tire width length of the groove bottom. Figure 5 is an example and is not limited thereto. The ratio can be appropriately increased or decreased within a range less than 1. Figure 5 In the figure, the representation of each layer constituting the tread portion is omitted.

[0081] <Small hole> In the tire of the present invention, preferably, when the pair of land portions located at the outermost sides in the tire width direction are shoulder land portions, the shoulder land portions have at least one opening area greater than 0.1 mm 2 And less than 15mm 2 In Figure 6 In the embodiment of the present invention, small holes 7 are formed on a pair of shoulder land portions 3 on the tread surface. Since the small holes contribute to the improvement of drainage, the drainage in the shoulder land portion is improved, which contributes to the improvement of wet grip performance. For example, in actual use, even if the shoulder land portion or the central land portion on one side is worn first and the remaining shoulder land portion hardens over time, the small holes can ensure drainage and can easily improve the wet grip performance after wear. The opening area of ​​the small holes toward the tread surface is preferably greater than 0.1 mm. 2 , more preferably greater than 0.5 mm 2 , further preferably greater than 1.0 mm 2 , especially preferably greater than 1.5 mm 2 In addition, the opening area of ​​the small hole toward the tread surface is preferably less than 15 mm 2 , preferably less than 10 mm 2 , further preferably less than 7.0 mm 2 , particularly preferably less than 5.0 mm 2 The depth of the deepest part of the small hole is preferably 3% or more of the deepest part of the circumferential main groove, more preferably 5% or more. In addition, the depth of the deepest part of the small hole is preferably 80% or less of the deepest part of the circumferential main groove, more preferably 60% or less, and further preferably 40% or less.

[0082] <Circumferential fine groove> In the tire of the present invention, preferably, when the pair of land portions located at the outermost sides in the tire width direction are shoulder land portions, the shoulder land portions have at least one circumferential narrow groove. Figure 7 In the tire, a pair of shoulder land portions 3 on the tread surface are formed with circumferential narrow grooves 8. Since the circumferential narrow grooves contribute to the improvement of drainage, the drainage in the shoulder region is improved, which contributes to the improvement of wet grip performance.

[0083] [Rubber composition] Hereinafter, the rubber composition of the tire of the present invention, that is, the first rubber composition constituting the first rubber layer of the tread portion and the second rubber composition constituting the second rubber layer will be described. Unless otherwise specifically stated, the following description can be applied to the first rubber composition and the second rubber composition. Therefore, when referred to as a rubber composition, it means that both the first rubber composition and the second rubber composition are included.

[0084] The rubber composition of the present invention, that is, the first rubber composition and the second rubber composition, respectively contain a rubber component and silica.

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

[0086] Preferably, the rubber component contained in the second rubber composition contains at least one of butadiene rubber and isoprene-based rubber.

[0087] Preferably, 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. Preferably, both the rubber component contained in the first rubber composition and the rubber component contained in the second rubber composition contain butadiene rubber.

[0088] These rubber components may be used in combination with other rubber components described below. From the perspective of modification for the purpose of interaction with fillers and suppression of degradation, in addition to hydrogenation of a portion of the double bond portion, they may be made into filled rubbers filled with plasticizers described below.

[0089] (SBR) As SBR, there is no particular limitation, and solution polymerization SBR (S-SBR), emulsion polymerization SBR (E-SBR), their modified SBR (modified S-SBR, modified E-SBR) etc. can be cited. As modified SBR, SBR with modified terminal and / or main chain, modified SBR (condensate, modified SBR with branched structure etc.) coupled with tin, silicon compound etc. etc. can be cited. Among them, S-SBR and modified SBR are preferred. Further, hydrides (hydrogenated SBR) etc. of these SBRs can also be used. These SBRs can be used alone or in combination of two or more.

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

[0091] From the perspective of wet grip performance and abrasion resistance, the styrene content of SBR is preferably greater than 10% by mass, more preferably greater than 15% by mass, and further preferably greater than 20% by mass. In addition, from the perspective of temperature dependence of grip performance and blow molding resistance, it is preferably less than 60% by mass, more preferably less than 55% by mass, and further preferably less than 50% by mass. It should be noted that in this specification, the styrene content of SBR can be calculated by the method described.

[0092] From the perspective of ensuring reactivity with silica, wet grip performance, rubber strength and wear resistance, the vinyl content of SBR is preferably greater than 10 mol%, more preferably greater than 13 mol%, and further preferably greater than 15 mol%. In addition, from the perspective of preventing the increase in temperature dependence of grip performance, elongation at break and wear resistance, the vinyl content of SBR is preferably less than 70 mol%, more preferably less than 65 mol%, and further preferably less than 60 mol%. It should be noted that in this specification, the vinyl content (1,2-bound butadiene unit amount) of SBR can be determined by the method described.

[0093] From the perspective of wet grip performance, the weight average molecular weight (Mw) of SBR is preferably greater than 200,000, more preferably greater than 250,000, and further preferably greater than 300,000. In addition, from the perspective of crosslinking uniformity, the weight average molecular weight is preferably less than 2 million, more preferably less than 1.8 million, and further preferably less than 1.5 million. It should be noted that in this specification, the weight average molecular weight of SBR can be obtained by the method described above.

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

[0095] (BR) There are no particular limitations on the BR, and examples thereof include BR having a cis content of less than 50 mol% (low cis BR), BR having a cis content of more than 90 mol% (high cis BR), rare earth-based butadiene rubber synthesized using a rare earth element catalyst (rare earth-based BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), and modified BR (high cis-modified BR, low cis-modified BR), which are commonly used in the tire industry. Examples of the modified BR include BR modified with the same functional groups as those described in the above SBR. These BRs may be used alone or in combination of two or more.

[0096] As high cis BR, commercial products of, for example, Japan Zeon Co., Ltd., Ube Industries, Ltd., JSR Corporation, etc. can be used. By containing high cis BR, low temperature characteristics and wear resistance can be improved. The cis content is preferably greater than 95 mol%, more preferably greater than 96 mol%, and further preferably greater than 97 mol%. It should be noted that in this specification, the cis content (cis-1,4-bonded butadiene unit amount) is a value calculated by the method described above.

[0097] The rare earth BR is synthesized using a rare earth element catalyst, and the vinyl content is preferably less than 1.8 mol%, more preferably less than 1.6 mol%, and further preferably less than 1.5 mol%, and the cis content is preferably greater than 95 mol%, more preferably greater than 96 mol%, and further preferably greater than 97 mol%. As the rare earth BR, for example, commercially available products from LANXESS Co., Ltd. can be used.

[0098] Examples of SPB-containing BR include BR in which 1,2-syndiotactic polybutadiene crystals are chemically bonded to BR and then dispersed, rather than simply dispersing 1,2-syndiotactic polybutadiene crystals in BR. As such SPB-containing BR, commercially available products from Ube Industries, Ltd. and the like can be used.

[0099] As the modified BR, it is preferable to use a modified butadiene rubber (modified BR) in which the terminal and / or the main chain is modified with a functional group containing at least one element selected from silicon, nitrogen and oxygen.

[0100] Other modified BRs include BR obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and further modifying the BR molecule by bonding the ends with tin-carbon bonds (tin-modified BR). The modified BR may be either unhydrogenated modified BR or hydrogenated modified BR.

[0101] From the perspective of wear resistance, the weight average molecular weight (Mw) of BR is preferably greater than 300,000, more preferably greater than 350,000, and further preferably greater than 400,000. In addition, from the perspective of crosslinking uniformity, it is preferably less than 2 million, more preferably less than 1 million, and further preferably less than 500,000. It should be noted that Mw can be obtained by the above method.

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

[0103] (Isoprene rubber) As the isoprene rubber, for example, isoprene rubber (IR) and natural rubber commonly used in the tire industry can be used. Natural rubber includes, in addition to unmodified natural rubber (NR), epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, grafted natural rubber and other modified natural rubbers. These isoprene rubbers can be used alone or in combination of two or more.

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

[0105] From the perspective of wet grip performance, when isoprene rubber is contained, the content of isoprene rubber in the rubber component is preferably less than 50% by mass, more preferably less than 40% by mass, and further preferably less than 30% by mass. On the other hand, the lower limit of the content of isoprene rubber in the rubber component is not particularly limited and may be 0% by mass, but may also be set to, for example, greater than 1% by mass, greater than 5% by mass, greater than 10% by mass, greater than 20% by mass, or 25% by mass or more.

[0106] (Other rubber components) As the rubber component of the present invention, other rubber components other than the isoprene-based rubber, SBR and BR described above may be contained. As other rubber components, crosslinkable rubber components commonly used in the tire industry may be used, for example, 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), epichlorohydrin rubber, etc. These other rubber components may be used alone, or two or more thereof may be used in combination.

[0107] <Packing> The rubber composition of the present invention, i.e., the first rubber composition and the second rubber composition, both contain silica. Preferably, the rubber composition of the present invention further contains carbon black. In the rubber composition of the present invention, as a filler, other fillers other than silica and carbon black may be further contained. The rubber composition of the present invention may not contain the other filler.

[0108] There are no particular limitations on other fillers, and any of the fillers commonly used in the tire industry, such as aluminum hydroxide, alumina, calcium carbonate, magnesium sulfate, talc, clay, and biochar, can be used. These fillers can be used alone or in combination of two or more.

[0109] (Silicon Dioxide) As silicon dioxide, there is no particular limitation, for example, silicon dioxide (anhydrous silicon dioxide) modulated by a dry method, silicon dioxide (hydrous silicon dioxide) modulated by a wet method, and other silicon dioxide commonly used in tire industry can be used. In addition, from the perspective of environmental load, silicon dioxide (for example, amorphous silicon dioxide refined from rice husk) using biomass materials as raw materials can be used. Among them, from the reason of many silanol groups, hydrous silicon dioxide modulated by a wet method is preferably used. These silicon dioxides can be used alone or in combination of two or more.

[0110] Silicon dioxide made from biomass materials can be obtained, for example, by the following method: using sodium hydroxide solution, extracting silicate from rice husk ash obtained by burning rice husks, using the silicate, reacting it with sulfuric acid in the same way as conventional wet silica to generate a precipitate of silicon dioxide, and filtering, washing, drying, and crushing the resulting precipitate of silicon dioxide. When silicon dioxide crystallizes, it is insoluble in water, and its component silicic acid cannot be used. By managing the combustion temperature and combustion time, the crystallization of silicon dioxide in rice husk ash can be suppressed (see JP Patent Publication No. 2009-2594, Akita Prefectural University Online Journal B / 2019, Volume 6, Pages 216-222, etc.). Amorphous silicon dioxide extracted from rice husks can use commercial products such as Wilmar.

[0111] From the perspective of low fuel consumption and wear resistance, the nitrogen adsorption specific surface area (N2SA) of silica is preferably greater than 140 m 2 / g, more preferably greater than 150m 2 / g, more preferably greater than 160m 2 / g, more preferably 175m 2 In addition, from the perspective of low fuel consumption and processability, it is preferably less than 350 m 2 / g, more preferably less than 300m 2 / g, more preferably less than 250m 2 It should be noted that the N2SA of silica in this specification is a value measured by the above method.

[0112] The average primary particle size of silicon dioxide is preferably greater than 10 nm, more preferably greater than 12 nm, and further preferably greater than 14 nm. In addition, the average primary particle size is preferably less than 26 nm, more preferably less than 24 nm, and further preferably less than 22 nm. It should be noted that the average primary particle size of silicon dioxide is measured by the measurement method.

[0113] From the perspective of wet grip performance, when silica is contained, the content of silica is preferably greater than 20 parts by mass, more preferably greater than 30 parts by mass, further preferably greater than 40 parts by mass, and further preferably greater than 45 parts by mass, relative to 100 parts by mass of the rubber component. In addition, from the perspective of wear resistance, the content is preferably less than 130 parts by mass, more preferably less than 110 parts by mass, further preferably less than 100 parts by mass, and further preferably less than 90 parts by mass.

[0114] (Carbon Black) As the carbon black, carbon black commonly used in the tire industry can be appropriately used, for example, GPF, FEF, HAF, ISAF, SAF, etc., 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, N991, etc. Furthermore, from the perspective of life cycle assessment, in addition to the above-mentioned carbon black, carbon black made from lignin as a raw material, recycled carbon black obtained by thermal decomposition of products containing carbon black such as tires, etc., can also be used. These carbon blacks can be used alone or in combination of two or more.

[0115] From the perspective of reinforcement, the nitrogen adsorption specific surface area (N2SA) of carbon black is preferably greater than 10 m 2 / g, more preferably greater than 30m 2 / g, more preferably greater than 50m 2 / g. In addition, from the perspective of low fuel consumption performance and processability, it is preferably less than 200m 2 / g, more preferably less than 175m 2 / g, more preferably less than 150m 2 / g. It should be noted that the N2SA of carbon black is measured by the above method.

[0116] The average primary particle size of carbon black is preferably greater than 10 nm, more preferably greater than 12 nm, and further preferably greater than 14 nm. In addition, the average primary particle size is preferably less than 26 nm, more preferably less than 24 nm, and further preferably less than 22 nm. It should be noted that the average primary particle size of carbon black is measured by the above-mentioned measurement method.

[0117] From the perspective of wear resistance and wet grip performance, when carbon black is contained, the content of carbon black is preferably greater than 1 part by mass, more preferably greater than 3 parts by mass, and further preferably greater than 5 parts by mass, relative to 100 parts by mass of the rubber component. In addition, from the perspective of low fuel consumption performance, it is preferably less than 50 parts by mass, more preferably less than 40 parts by mass, and further preferably less than 35 parts by mass.

[0118] (Content of filler) From the perspective of wear resistance, the total content of fillers is preferably greater than 40 parts by mass, more preferably greater than 50 parts by mass, and further preferably greater than 60 parts by mass relative to 100 parts by mass of the rubber component. In addition, from the perspective of low fuel consumption performance and elongation at break, it is preferably less than 200 parts by mass, more preferably less than 150 parts by mass, and further preferably less than 120 parts by mass.

[0119] When the filler contains both silica and carbon black, the content of silica is preferably greater than the content of carbon black from the perspective of balancing low fuel consumption performance, wet grip performance and wear resistance. The ratio of silica to the total content of silica and carbon black is preferably greater than 60% by mass, more preferably greater than 70% by mass, further preferably greater than 80% by mass, and further preferably greater than 90% by mass.

[0120] (Silane coupling agent) Preferably, silica is used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent that has been used in combination with silica in the rubber industry can be used, for example: 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, 3-octanoylthio-1-propyltrimethoxysilane and other thioester-based silane coupling agents; mercapto-based silane coupling agents such as compounds represented by the following chemical formula; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; Vinyl silane coupling agents such as vinyl triethoxysilane and vinyl trimethoxysilane; amino silane coupling agents such as 3-aminopropyl triethoxysilane, 3-aminopropyl trimethoxysilane, and 3-(2-aminoethyl)aminopropyl triethoxysilane; glycidoxy silane coupling agents such as γ-glycidoxypropyl triethoxysilane and γ-glycidoxypropyl trimethoxysilane; nitro silane coupling agents such as 3-nitropropyl trimethoxysilane and 3-nitropropyl triethoxysilane; chlorine silane coupling agents such as 3-chloropropyl trimethoxysilane and 3-chloropropyl triethoxysilane, etc. Among them, thioester silane coupling agents and / or sulfide silane coupling agents are preferred. These silane coupling agents can be used alone or in combination of two or more.

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

[0122]

Chemical formula 1

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

[0124]

Chemical formula 2

[0125]

Chemical formula 3

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

[0127] As the compound represented by formula (1), for example, 3-mercaptopropyl trimethoxysilane, 3-mercaptopropyl triethoxysilane, 2-mercaptoethyl trimethoxysilane, 2-mercaptoethyl triethoxysilane, a compound represented by the following chemical formula (4) (Si363 manufactured by Evonik Degussa), etc. can be mentioned, and the compound represented by the following chemical formula (4) can be suitably used. They can be used alone, or two or more can be used in combination.

[0128]

Chemical formula 4

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

[0130] From the perspective of improving the dispersibility of silica, when a silane coupling agent is contained, the content of the silane coupling agent (the total amount when multiple silane coupling agents are used) is preferably greater than 0.5 parts by mass, more preferably greater than 1.0 parts by mass, further preferably greater than 2.0 parts by mass, and further preferably greater than 4.0 parts by mass, relative to 100 parts by mass of the rubber component. In addition, from the perspective of preventing a decrease in wear resistance, it is preferably less than 20 parts by mass, more preferably less than 12 parts by mass, further preferably less than 10 parts by mass, and further preferably less than 9.0 parts by mass.

[0131] From the perspective of improving the dispersibility of silica, the content of the silane coupling agent is preferably greater than 1.0 mass parts, more preferably greater than 3.0 mass parts, and further preferably greater than 5.0 mass parts relative to 100 mass parts of silica. In addition, from the perspective of cost and processability, it is preferably less than 20 mass parts, more preferably less than 15 mass parts, and further preferably less than 12 mass parts.

[0132] <Plasticizer> The rubber composition of the present invention preferably contains a plasticizer. Examples of the plasticizer include resins, oils, liquid rubbers, and ester plasticizers.

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

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

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

[0136] Aromatic petroleum resins refer to resins obtained by polymerizing C9 fractions, and may be obtained by hydrogenating or modifying them. Examples of C9 fractions include petroleum fractions corresponding to 8 to 10 carbon atoms, such as vinyl toluene, alkyl styrene, indene, and methyl indene. Specific examples of aromatic petroleum resins include preferably coumarone-indene resins, coumarone resins, indene resins, and aromatic vinyl resins.

[0137] As the aromatic vinyl resin, α-methylstyrene or a homopolymer of styrene, or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, based on the reasons of economical efficiency, easy processing, and excellent heat generation. As the aromatic vinyl resin, commercial products of Kraton, Eastman Chemical, etc. can be used, for example.

[0138] C5C9 petroleum resin refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be obtained by hydrogenating them or modifying them. As the C5 fraction and the C9 fraction, the petroleum fractions may be cited. As the C5C9 petroleum resin, commercial products of Tosoh Corporation, LUHUA Corporation, etc. may be used, for example.

[0139] 《Terpene resin》 As terpene resins, there can be mentioned polyterpene resins formed from at least one of terpene compounds selected from α-pinene, β-pinene, limonene and dipentene; aromatic modified terpene resins using the terpene compounds and aromatic compounds as raw materials; terpene phenol resins using terpene compounds and phenol compounds as raw materials; and those obtained by hydrogenating these terpene resins (hydrogenated terpene resins). As aromatic compounds that are raw materials for aromatic modified terpene resins, for example, styrene, α-methylstyrene, vinyltoluene, divinyltoluene, etc. can be mentioned. As phenolic compounds that are raw materials for terpene phenol resins, for example, phenol, bisphenol A, cresol, xylenol, etc. can be mentioned. These resins can be used alone or in combination of two or more.

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

[0141] 《Phenolic resin》 The phenolic resin is not particularly limited, and examples thereof include phenolic resins, alkylphenolic resins, alkylphenolacetylene resins, oil-modified phenolic resins, etc. These resins may be used alone or in combination of two or more.

[0142] Softening Point From the perspective of wet grip performance, the softening point of the resin is preferably greater than 60° C., more preferably greater than 70° C., and further preferably greater than 80° C. In addition, from the perspective of improving processability and the dispersibility of rubber components and fillers, it is preferably less than 150° C., more preferably less than 140° C., and further preferably less than 130° C. It should be noted that in this specification, the softening point can be obtained by the above method.

[0143] "content" From the viewpoint of wet grip performance, when a resin is contained, the content of the resin is preferably greater than 1 part by mass, more preferably greater than 3 parts by mass, and further preferably greater than 5 parts by mass relative to 100 parts by mass of the rubber component. From the viewpoint of suppressing heat generation, the content is preferably less than 60 parts by mass, more preferably less than 40 parts by mass, further preferably less than 30 parts by mass, and further preferably less than 20 parts by mass.

[0144] (Oil) Examples of the oil include process oil, vegetable oil, animal oil, and the like. Examples of the process oil include paraffinic process oil, cycloparaffinic process oil, and aromatic process oil. In addition, in terms of environmental measures, process oils with low polycyclic aromatic compound (PCA) content may also be used. Examples of the process oils with low PCA content include mild extraction solvates (MES), treated distillate aromatic extracts (TDAE), and heavy naphthenic oils.

[0145] From the viewpoint of processability, when oil is contained, the content of oil is preferably greater than 3 parts by mass, more preferably greater than 5 parts by mass, and further preferably greater than 7 parts by mass, relative to 100 parts by mass of the rubber component. From the viewpoint of wear resistance, it is preferably less than 120 parts by mass, more preferably less than 80 parts by mass, and further preferably less than 40 parts by mass. It should be noted that in this specification, the content of oil also includes the amount of oil contained in the oil-extended rubber.

[0146] (Liquid Rubber) The liquid rubber is not particularly limited as long as it is a polymer that is in a liquid state at room temperature (25° C.), and examples thereof include liquid butadiene rubber (liquid BR), liquid styrene butadiene rubber (liquid SBR), liquid isoprene rubber (liquid IR), liquid styrene isoprene rubber (liquid SIR), liquid farnesene rubber, etc. These liquid rubbers may be used alone or in combination of two or more.

[0147] When liquid rubber is contained, the content of liquid rubber is preferably greater than 1 part by mass, more preferably greater than 2 parts by mass, further preferably greater than 3 parts by mass, further preferably greater than 5 parts by mass, relative to 100 parts by mass of the rubber component. In addition, the content of liquid rubber is preferably less than 50 parts by mass, more preferably less than 40 parts by mass, further preferably less than 20 parts by mass.

[0148] (Ester plasticizer) As ester plasticizers, for example, 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), tricresyl phosphate (TXP), etc. These ester plasticizers may be used alone or in combination of two or more.

[0149] From the viewpoint of wet grip performance, the content of the plasticizer is preferably greater than 5 parts by mass, more preferably greater than 10 parts by mass, and further preferably greater than 15 parts by mass, relative to 100 parts by mass of the rubber component. From the viewpoint of processability, the content is preferably less than 120 parts by mass, more preferably less than 80 parts by mass, and further preferably less than 40 parts by mass.

[0150] <Other compounding agents> The rubber composition of the present invention may appropriately contain compounding agents commonly used in the tire industry, such as wax, processing aid, antioxidant, stearic acid, zinc oxide, vulcanizing agent, vulcanization accelerator, etc., in addition to the above-mentioned components.

[0151] (wax) As the wax, any wax commonly used in the tire industry can be used. One wax can be used alone, or two or more waxes can be used in combination. From the perspective of weather resistance of the rubber, when the wax is contained, the content of the wax is preferably greater than 0.5 parts by mass, more preferably greater than 1.0 parts by mass, and further preferably greater than 1.5 parts by mass relative to 100 parts by mass of the rubber component. In addition, from the perspective of preventing the whitening of the tire caused by blooming, it is preferably less than 10 parts by mass, more preferably less than 7.0 parts by mass, and further preferably less than 5.0 parts by mass.

[0152] (Processing Aids) As processing aids, for example, fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, etc. can be cited. These processing aids can be used alone or in combination of two or more. As processing aids, for example, commercial products of Schill+Seilacher, Performance Additives, etc. can be used.

[0153] From the perspective of improving processability, when a processing aid is contained, the content of the processing aid is preferably greater than 0.5 parts by mass, more preferably greater than 1 part by mass, and further preferably greater than 1.5 parts by mass relative to 100 parts by mass of the rubber component. From the perspective of wear resistance and breaking strength, the content is preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and further preferably less than 5.0 parts by mass.

[0154] (Antioxidant) As antioxidant, there is no particular limitation, for example, antioxidants such as amine, quinoline, quinone, phenol, and imidazole compounds, and metal carbamates can be cited, preferably 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, N-cyclohexyl-N'-phenyl-p-phenylenediamine and other phenylenediamine antioxidants, and quinoline antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline. These antioxidants can be used alone or in combination of two or more.

[0155] From the perspective of the ozone cracking resistance of the rubber, when an antioxidant is contained, the content of the antioxidant is preferably greater than 0.5 parts by mass, more preferably greater than 1.0 parts by mass, and further preferably greater than 1.5 parts by mass relative to 100 parts by mass of the rubber component. In addition, from the perspective of wear resistance and wet grip performance, it is preferably less than 10 parts by mass, more preferably less than 7 parts by mass, and further preferably less than 5 parts by mass.

[0156] (Stearic Acid) From the viewpoint of processability, when stearic acid is contained, the content of stearic acid is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and further preferably 1.5 parts by mass or more, relative to 100 parts by mass of the rubber component. In addition, from the viewpoint of vulcanization speed, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0157] (Zinc Oxide) From the viewpoint of processability, when zinc oxide is contained, the content of zinc oxide is preferably greater than 0.5 parts by mass, more preferably greater than 1.0 parts by mass, and further preferably greater than 1.5 parts by mass, relative to 100 parts by mass of the rubber component. From the viewpoint of wear resistance, the content is preferably less than 10 parts by mass, more preferably less than 7 parts by mass, and further preferably less than 5 parts by mass.

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

[0159] From the perspective of ensuring a sufficient vulcanization reaction, when sulfur is contained as a vulcanizing agent, the content of sulfur is preferably greater than 0.1 parts by mass, more preferably greater than 0.3 parts by mass, and further preferably greater than 0.5 parts by mass relative to 100 parts by mass of the rubber component. In addition, from the perspective of preventing deterioration, it is preferably less than 5.0 parts by mass, more preferably less than 4.0 parts by mass, and further preferably less than 3.0 parts by mass. It should be noted that the content of the vulcanizing agent when oil-containing sulfur is used as a vulcanizing agent is the total content of pure sulfur components contained in the oil-containing sulfur.

[0160] Examples of the vulcanizing agent other than sulfur include alkylphenol-sulfur chloride condensate, 1,6-hexamethylene-sodium dithiosulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. As these vulcanizing agents other than sulfur, commercial products of Taoka Chemical Industry Co., Ltd., LANXESS Co., Ltd., Flexsys Co., Ltd., etc. can be used.

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

[0162] Among them, the case where one or more vulcanization accelerators selected from the group consisting of sulfenamide-based, guanidine-based and thiazole-based vulcanization accelerators are contained is preferred, and the case where the vulcanization accelerator is composed of a sulfenamide-based vulcanization accelerator and a guanidine-based vulcanization accelerator is more preferred.

[0163] Examples of the sulfenamide 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.

[0164] Examples of the guanidine vulcanization accelerator include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatecholate borate, 1,3-di-o-isopropylphenylguanidine, 1,3-di-o-biphenylguanidine, and 1,3-di-o-isopropylphenyl-2-propionylguanidine. Among them, 1,3-diphenylguanidine (DPG) is preferred.

[0165] Examples of the thiazole vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, and di(2-benzothiazolyl)disulfide. Among them, 2-mercaptobenzothiazole is preferred.

[0166] When a vulcanization accelerator is contained, the content of the vulcanization accelerator is preferably greater than 1 part by mass, more preferably greater than 1.5 parts by mass, and further preferably greater than 2 parts by mass, relative to 100 parts by mass of the rubber component. In addition, the content of the vulcanization accelerator is preferably less than 8 parts by mass, more preferably less than 7 parts by mass, and further preferably less than 6 parts by mass, relative to 100 parts by mass of the rubber component. By setting the content of the vulcanization accelerator within the above range, there is a tendency that the breaking strength and elongation can be ensured.

[0167] [Belt] In the tire of the present invention, the belt layer can use the belt layer commonly used in the tire industry. The belt layer includes cords forming the skeleton of the belt layer and rubber covering the cords. As the cord, in addition to steel cords, other cords such as organic fiber cords can also be used.

[0168] In the tire of the present invention, the belt layer may be a single layer or a plurality of layers, preferably a plurality of layers. In addition, when the width (mm) of the widest belt layer among the belt layers is Wb, the cross-sectional width (mm) Wt of the tire and the content (mass parts) of silica in the second rubber composition relative to 100 parts by mass of the rubber component A2 are SIL Here, the value of Wb can be appropriately adjusted by increasing or decreasing the width of the mold.

[0169] [manufacture] (Manufacturing of rubber composition) The rubber composition of the present invention (i.e., the first rubber composition constituting the first rubber layer and the second rubber composition constituting the second rubber layer) can be manufactured by a known method. For example, it can be manufactured by mixing the above-mentioned components using a rubber mixing device such as an open roll or a closed mixer (Banbury mixer, kneader, etc.).

[0170] The kneading process includes, for example, a basic kneading process: kneading the compounding agents and additives other than the vulcanizing agent and the vulcanization accelerator; and a final kneading (F kneading) process: adding the vulcanizing agent and the vulcanization accelerator to the kneaded product obtained in the basic kneading process and kneading. In addition, the basic kneading process may also need to be divided into a plurality of processes.

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

[0172] (Manufacturing of tires) The tire of the present invention can be manufactured by a common method using the first rubber composition, the second rubber composition, and the belt layer with the widest width being a belt layer of a specified width. That is, the tire of the present invention can be manufactured by the following method: using an extruder with a die of a specified shape, the unvulcanized first rubber composition and the second rubber composition are extruded into the shape of the first rubber layer and the second rubber layer, and the unvulcanized first rubber composition and the second rubber composition are laminated together with the belt layer of the present invention and other tire components on a tire molding machine, and molded by a common method to form an unvulcanized tire, and the unvulcanized tire is heated and pressurized in a vulcanizer. The vulcanization conditions are not particularly limited, and for example, a method of vulcanizing at 150 to 200° C. for 10 to 30 minutes can be cited.

[0173] [use] The tire of the present invention can be used for any purpose, whether it is a pneumatic tire or a non-pneumatic tire. In addition, it can be used as a racing tire, a passenger car tire, a large passenger car tire, a large SUV tire, or a motorcycle tire. Among them, a passenger car tire is preferred. Here, a passenger car tire refers to a tire that is installed on a four-wheeled motor vehicle as a prerequisite, and the maximum load capacity in the JATMA specification is a tire of less than 1000 kg.

[0174] Furthermore, the tire of the present invention can be used as a summer tire, a winter tire, or a studless tire of the above-mentioned tires. [Example]

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

[0176] Various chemicals used in Examples and Comparative Examples are summarized below. SBR1: Styrene butadiene rubber synthesized in the following Production Example 1 (modified S-SBR, styrene content: 25% by mass, vinyl content: 25 mol%, Tg: -55°C, non-oil-extended product) SBR2: HPR850 manufactured by JSR Corporation (styrene content: 27.5% by mass, vinyl content: 59 mol%, Tg: -24°C) SBR3: Styrene butadiene rubber synthesized in the following Preparation Example 2 (modified S-SBR, styrene content: 33% by mass, vinyl content: 46 mol%, Tg: -22°C, non-oil-extended product) SBR4: JSR0122 manufactured by JSR Corporation (E-SBR, styrene content: 38% by mass, vinyl content: 16 mol%, Tg: -37°C, 100 parts by mass of rubber solids filled with 34 parts by mass of oil) SBR5: SBR1502 manufactured by JSR Corporation (E-SBR, styrene content: 23.5% by mass, vinyl content: 18 mol%, Tg: -51°C) BR: UBEPOL BR (registered trademark) 150B manufactured by Ube Industries, Ltd. (vinyl content: 1.5 mol%, cis content: 97 mol%, Mw: 440,000) NR:TSR20 CB (Carbon Black) 1: Showblack N134 (N2SA: 148m 2 / g, average primary particle size: 18nm) CB (Carbon Black) 2: N220 (N2SA: 115m 2 / g, average primary particle size: 22nm) Silicon dioxide: ULTRASIL (registered trademark) VN3 (N2SA: 175m 2 / g, average primary particle size: 18nm) Coupling agent (silane coupling agent) 1: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa Coupling agent (silane coupling agent) 2: NXT (3-octanoylthiopropyltriethoxysilane) manufactured by Momentive Performance Materials Oil: VivaTec500 (TDAE oil) manufactured by H&R Resin 1: Sylvares SA85 manufactured by Kraton (copolymer of α-methylstyrene and styrene, softening point: 85°C) Resin 2: NOVARES C90 manufactured by Rutgers Chemicals (benzofuran-indene resin, softening point: 90°C) Wax: Sunnoc N manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 1: Antigen 6C (6PPD, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Antioxidant 2: NOCRAC 224 (TMQ, 2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: Camellia stearic acid beads manufactured by NOF Corporation Zinc oxide: Zinc oxide No. 2 manufactured by Mitsui Mining and 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 Industry Co., Ltd. Vulcanization accelerator 2: Nocceler D (DPG, 1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

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

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

[0179] [Examples and Comparative Examples] According to the formulation shown in Table 1, chemicals other than sulfur and vulcanization accelerator were kneaded for 1 to 10 minutes using a 1.7L closed Banbury mixer until the discharge temperature reached 150 to 160°C to obtain a kneaded product. Then, sulfur and vulcanization accelerator were added to the obtained kneaded product using a biaxial open mill, and kneaded for 4 minutes until the temperature reached 105°C to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was formed into the shape of the first layer (4 mm) and the second layer (6 mm) of the tread, and laminated with the belt layer and other tire components to produce an unvulcanized tire, which was vulcanized at 170°C to obtain various test tires (tire 1: 225 / 45R17, tire 2: 205 / 55R16, tire 3: 195 / 45R16).

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

[0181] On the tread surface of each test tire, the circumferential main grooves are set as three straight main grooves, one of which passes through the tire centerline, and the remaining two are respectively set at positions equidistant from the main groove passing through the tire centerline on the outside of the tire width direction. The groove depth (deepest part) of these circumferential main grooves is set to 6.5mm.

[0182] <Physical Properties of Rubber Layer> The physical properties of each rubber layer constituting the tire were measured by the following methods. The results are described in the corresponding columns of Table 1 regarding the rubber composition constituting each rubber layer.

[0183] (30℃tanδ) A viscoelasticity measurement sample of 20 mm in length × 4 mm in width × 1 mm in thickness was collected from the inside of the specified rubber layer (first rubber layer) of the tread portion of each test tire so that the tire circumferential direction became the long side and the tire radial direction became the thickness. The loss tangent tanδ was measured using the EPLEXOR series manufactured by GABO under the conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and an elongation mode.

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

[0185] <Wet grip performance after wear> Each test tire was heat-degraded at 80°C for 7 days, and then each test tire was evenly worn along the tire radius when it was new so that the tire equator was worn 4.5 mm, and then installed on all wheels of the vehicle. The vehicle was driven at a speed of 100 km / h on a wet asphalt road surface, and the braking distance from the braking point was measured. The wet grip performance of each tire after wear is represented by an index using the following calculation formula, where the braking distance of the test tire of the benchmark comparative example is set to 100. The larger the index, the better the wet grip performance. (Wet grip performance index after wear) = (Braking distance after wear of the tire of the reference comparative example) / (Braking distance after wear of each test tire)×100

[0186] [Table 1] Table 1

[0187] [Table 2]

[0188] [Table 3]

[0189] [Table 4]

[0190] In the above Tables 2 to 4, "○" means that a given condition is satisfied, and "×" means that a given condition is not satisfied.

[0191] <Implementation Method> Preferred embodiments are described below.

[0192] [1] A tire comprising a tread portion and at least one belt layer, wherein: The tread portion includes at least a first rubber layer on the outermost side in the tire radial direction and a second rubber layer adjacent to the first rubber layer on the inner side in the tire radial direction. The first rubber layer is composed of a first rubber composition including a rubber component containing styrene butadiene rubber and silica. The second rubber layer is composed of a second rubber composition including a rubber component containing styrene butadiene rubber and silica. The tread portion includes: two or more circumferential main grooves extending in the tire circumferential direction and a land portion divided by the circumferential main grooves; The deepest part of the groove bottom of at least one of the circumferential main grooves is formed to be located further inward in the tire radial direction than the outermost part of the second rubber layer in the land portion adjacent to the circumferential main groove. The content (in parts by mass) of silica in the first rubber composition relative to 100 parts by mass of the rubber component is denoted by A1. SIL The content (in parts by mass) of silica in the second rubber composition relative to 100 parts by mass of the rubber component is A2 SIL , when a normal load is applied under normal conditions and the tread is pressed on a plane, the cross-sectional width (mm) of the tire is Wt, and the width (mm) of the widest belt layer among the belt layers is Wb, A1 SIL 、A2 SIL , Wt and Wb satisfy the following relationship. Preferably, the right side of formula (1) is 1.06, more preferably 1.07. Preferably, the right side of formula (2) is 1.08, more preferably 1.10, and further preferably 1.20. (1)A2 SIL / A1 SIL >1.05 (2)A2 SIL / (Wt-Wb)>1.00 [2] The tire according to [1] above, wherein, when the glass transition temperature (°C) of the second rubber composition is Tg2, Tg2 is greater than -30°C, preferably greater than -25°C, and more preferably greater than -20°C. [3] The tire according to [1] or [2], wherein, when tan δ of the first rubber composition at 30°C is tan δ1 at 30°C, tan δ1 at 30°C 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] A tire according to any one of [1] to [3] above, wherein, when the total amount of styrene (mass %) of the rubber components contained in the first rubber composition is St1 and the total amount of styrene (mass %) of the rubber components contained in the second rubber composition is St2, at least one of St1 and St2 is less than 25.0, preferably less than 20.0, more preferably less than 19.0, further preferably less than 18.0, and further preferably less than 17.0. [5] The tire according to any one of [1] to [4] above, wherein the rubber component contained in the second rubber composition includes at least one of butadiene rubber and isoprene rubber. [6] The tire according to any one of [1] to [5] above, wherein at least one of the rubber component contained in the first rubber composition and the rubber component contained in the second rubber composition comprises butadiene rubber. [7] The tire according to any one of [1] to [5] above, wherein both the rubber component contained in the first rubber composition and the rubber component contained in the second rubber composition contain butadiene rubber. [8] The tire according to any one of [1] to [7] above, wherein the right side of the formula (1) is 1.10, preferably 1.20, more preferably 1.30, further preferably 1.40, and further preferably 1.50. [9] The tire according to any one of [1] to [8] above, wherein the right side of formula (2) is 1.25, preferably 1.30, more preferably 1.40, and even more preferably 1.50.

[10] The tire according to any one of [1] to [9] above, wherein the tread portion has an expanded circumferential groove whose groove width increases toward the inner side in the tire radial direction.

[11] The tire according to

[10] above, wherein the widened circumferential groove exists on a land portion located on the tire center line, or exists on a land portion closest to the tire center line when a circumferential main groove exists on the tire center line.

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

[11] , wherein when the pair of land portions located most outer in the tire width direction among the land portions are shoulder land portions, the shoulder land portions have one or more small holes, and the opening area of ​​the small holes is greater than 0.1 mm 2 And less than 15mm 2 , preferably greater than 0.5 mm 2 And less than 10mm 2 , more preferably greater than 1.0 mm 2 And less than 7.0mm 2 , further preferably greater than 1.5 mm 2 And less than 7.0mm 2 .

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

[11] above, wherein when a pair of land portions located outermost in the tire width direction among the land portions are shoulder land portions, the shoulder land portions have at least one circumferential narrow groove.< / tg>

Claims

1. A tire, characterized in that: The tire has a tread portion and at least one belt layer, The tread portion includes at least a first rubber layer on the outermost side in the tire radial direction and a second rubber layer adjacent to the first rubber layer on the inner side in the tire radial direction. The first rubber layer is composed of a first rubber composition including a rubber component containing styrene butadiene rubber and silica. The second rubber layer is composed of a second rubber composition including a rubber component containing styrene butadiene rubber and silica. The tread portion includes: two or more circumferential main grooves extending in the tire circumferential direction and a land portion divided by the circumferential main grooves; The deepest part of the groove bottom of at least one of the circumferential main grooves is formed to be located further inward in the tire radial direction than the outermost part of the second rubber layer in the land portion adjacent to the circumferential main groove. The content of silica in the first rubber composition relative to 100 parts by mass of the rubber component is denoted by A1. SIL The content of silica in the second rubber composition relative to 100 parts by mass of the rubber component is A2 SIL , when a normal load is applied in a normal state and the tread is pressed on a plane, the cross-sectional width of the tire is Wt, and the width of the widest belt layer among the belt layers is Wb, A1 SIL 、A2 SIL , Wt and Wb satisfy the following relationship: <h2 style=";text-align:left;direction:ltr">(1)A2<h2 style=";text-align:left;direction:ltr"> SIL <h2 style=";text-align:left;direction:ltr"> / A1<h2 style=";text-align:left;direction:ltr"> SIL <h2 style=";text-align:left;direction:ltr"> >1.05, <h2 style=";text-align:left;direction:ltr">(2)A2<h2 style=";text-align:left;direction:ltr"> SIL <h2 style=";text-align:left;direction:ltr"> / (Wt-Wb)>1.00, Among them, A1 SIL and A2 SIL The unit of is parts by mass, and the unit of Wt and Wb is mm.

2. The tire according to claim 1, wherein: When the glass transition temperature of the second rubber composition is Tg2, Tg2 is greater than -30°C, and the unit of Tg2 is °C.

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

30.

4. The tire according to claim 1 or 2, wherein: When the total styrene amount of the rubber components contained in the first rubber composition is St1 and the total styrene amount of the rubber components contained in the second rubber composition is St2, at least one of St1 and St2 is less than 25.0, and the units of St1 and St2 are mass %.

5. The tire according to claim 1 or 2, wherein: The rubber component contained in the second rubber composition includes at least one of butadiene rubber and isoprene rubber.

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

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

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

10.

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

25.

10. The tire according to claim 1 or 2, wherein: The tread portion has an expanded circumferential groove whose groove width increases toward the inner side in the tire radial direction.

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

12. The tire according to claim 1 or 2, wherein: When a pair of land portions located at the outermost sides in the tire width direction among the land portions are shoulder land portions, the shoulder land portions have at least one opening area greater than 0.1 mm 2 And less than 15mm 2 of small holes.

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

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