Pneumatic radial tires for passenger cars

Abstract

The present invention provides a pneumatic radial tire for a passenger car, which has both riding comfort at low temperatures and handling stability when driving at high speeds. The present invention is a pneumatic radial tire for a passenger car, wherein: a carcass and a tread are provided; the tread is assembled in a standard wheel rim; when the internal pressure is the standard internal pressure, the cross-sectional width Wt (mm) and the outer diameter Dt (mm) of the tire satisfy 1963.4≤(Dt 2 ×π / 4) / Wt≤2827.4; the tread includes at least one main groove extending along the circumferential direction of the tread on the tread running surface; and the land-sea ratio in the tread running surface is greater than 55% and less than 85%; when measured at a frequency of 10 Hz, an initial strain of 2% and a dynamic strain rate of 1%, the loss tangent (tanδ) of the rubber composition forming the tread is such that |20℃tanδ-50℃tanδ| is at least 0.01 and less than 0.15, and |5℃tanδ-20℃tanδ| is greater than 0.15 and less than 0.70.

Description

Technical Field

[0001] The invention relates to a pneumatic radial tire for a passenger car, in particular to a radial tire for a passenger car having both riding comfort at low temperatures and handling stability during high-speed driving. Background Art

[0002] As the weight and speed of passenger cars increase, radial tires (hereinafter also simply referred to as "tire") are often used as pneumatic tires for passenger cars.

[0003] The radial tire generally includes a carcass having radially arranged cords that spans a pair of bead portions in a toroidal shape and a tread provided on the tire radially outer side of the carcass. The radial tire is molded in consideration of fuel efficiency and vehicle interior comfort during driving.

[0004] With respect to such radial tires, there is an increasing demand for achieving both comfortable riding and stable handling performance (handling stability) in passenger cars equipped with the tires in view of recent environmental issues and safety measures.

[0005] Therefore, in order to meet these requirements, the composition of the rubber composition constituting the tread (for example, Patent Documents 1 and 2) and the tread pattern (for example, Patent Documents 3 and 4) have been studied.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: JP2012-229285A

[0009] Patent Document 2: JP2013-107989A

[0010] Patent Document 3: JP2014-177238A

[0011] Patent Document 4: JP2015-147543A Summary of the invention

[0012] Problems to be solved by the invention

[0013] However, the above conventional technologies are not sufficient in terms of ride comfort and handling stability. In particular, a radial tire is required that has both ride comfort at low temperatures and handling stability at high speeds.

[0014] Therefore, an object of the present invention is to provide a pneumatic radial tire for a passenger vehicle which combines ride comfort at low temperatures with handling stability at high speeds.

[0015] Means for solving problems

[0016] The present inventors have conducted intensive research on solutions to the above problems and have found that the above problems can be solved by the following invention, thereby completing the present invention.

[0017] (1) The invention is:

[0018] A pneumatic radial tire for a passenger car, the pneumatic radial tire comprising a carcass and a tread, the carcass having radially arranged cords and spanning a pair of bead portions in a ring shape, and the tread being arranged on the tire radial outer side of the carcass, wherein:

[0019] When the tire is mounted on a standard rim and the internal pressure is the standard internal pressure, the cross-sectional width of the tire is Wt (mm) and the outer diameter is Dt (mm), the tread satisfies 1963.4≤(Dt 2 ×π / 4) / Wt≤2827, and

[0020] The tread running surface has at least one main groove extending in the circumferential direction of the tread.

[0021] The land-to-sea ratio in the tread running surface is greater than 55% and less than 85%; and

[0022] For the loss tangent (tan δ) of the rubber composition forming the tread measured under the conditions of a frequency of 10 Hz, an initial strain of 2% and a dynamic strain rate of 1%,

[0023] |20℃tanδ-50℃tanδ| is 0.01 or more and less than 0.15, and

[0024] |5℃tanδ-20℃tanδ| is greater than 0.1 and less than 0.70.

[0025] (2) The invention is:

[0026] The pneumatic radial tire for a passenger car according to (1), wherein |20°C tan δ - 50°C tan δ| is greater than 0.08 and less than 0.12.

[0027] (3) The invention is:

[0028] The pneumatic radial tire for a passenger car according to (1) or (2), wherein |5°C tan δ - 20°C tan δ| is greater than 0.30 and less than 0.40.

[0029] (4) The invention is:

[0030] The pneumatic radial tire for a passenger vehicle according to any one of (1) to (3), wherein:

[0031] The tread is divided into four or more areas in the tire axial direction by three or more main grooves and a pair of ground contact ends, and

[0032] In each of the four or more regions, a difference in average tread area per unit length in the tire circumferential direction is 15% or less.

[0033] (5) The invention is:

[0034] The pneumatic radial tire for a passenger vehicle according to any one of (1) to (4), wherein:

[0035] The tread is divided into a central land region and two shoulder land regions by a pair of shoulder main grooves extending continuously in the tire circumferential direction across a center line passing through the axis of the tread pattern.

[0036] The width of the shoulder main groove is greater than 4 mm and less than 20 mm, and the center of the groove width is located at the center side of the 25% width position from the tread ground contact end; and

[0037] The central land portion area accounts for more than 40% of the entire land portion area of ​​the tire contact patch.

[0038] (6) The invention is:

[0039] The pneumatic radial tire for a passenger vehicle according to any one of (1) to (5), wherein:

[0040] The tread is composed of a cap rubber layer constituting the running surface of the tread and a base rubber layer located inside the cap rubber layer.

[0041] The cap rubber layer has a higher hardness than the base rubber layer, and a JIS A hardness of greater than 45 and less than 75.

[0042] (7) The invention is:

[0043] The pneumatic radial tire for a passenger vehicle according to any one of (1) to (6), wherein the rubber composition forming the tread contains 35% by mass or more of a diene rubber as a rubber component; and

[0044] The rubber component contains 35 parts by mass or more of a rubber having a BET specific surface area greater than 140 m 2 / g and less than 250m 2 / g of silica.

[0045] (8) The invention is:

[0046] The pneumatic radial tire for a passenger vehicle according to any one of (1) to (7), wherein the central land region is provided with lateral grooves and / or lateral sipes extending in a direction across the land region.

[0047] (9) The invention is:

[0048] The pneumatic radial tire for a passenger vehicle according to any one of (1) to (8), wherein:

[0049] When the tire is mounted on a standard rim and the internal pressure is 250 kPa, when the outer diameter of the tire is Dt (mm) and the cross-sectional height of the tire is Ht (mm), (Dt-2×Ht) is 470 (mm) or more.

[0050] (10) The invention is:

[0051] The pneumatic radial tire for a passenger vehicle according to any one of (1) to (9), wherein the aspect ratio is 40% or more.

[0052] (11) The invention is:

[0053] The pneumatic radial tire for a passenger vehicle according to (10), wherein the aspect ratio is 45% or more.

[0054] (12) The invention is:

[0055] The pneumatic radial tire for a passenger vehicle according to (6), wherein the aspect ratio is 47.5% or more.

[0056] (13) The invention is:

[0057] The pneumatic radial tire for a passenger vehicle according to (12), wherein the aspect ratio is 50% or more.

[0058] (14) The invention is:

[0059] The pneumatic radial tire for a passenger vehicle according to any one of (1) to (13), wherein:

[0060] The groove width L at a depth of 80% of the maximum depth of the main groove extending in the circumferential direction of the tread is 80 The ratio of the width L0 of the main groove on the ground contact surface (L 80 / L0) is 0.3 to 0.7.

[0061] (15) The invention is:

[0062] The pneumatic radial tire for a passenger vehicle according to any one of (1) to (14), wherein:

[0063] The tread is divided into a central land area and two shoulder land areas by a pair of shoulder main grooves extending continuously along the circumferential direction of the tire across a center line passing through the axis of the tread pattern, and has a plurality of lateral grooves extending along the axial direction of the tire, and the total volume of the plurality of lateral grooves is 2.0% to 5.0% of the volume of the tread.

[0064] (16) The invention is:

[0065] The pneumatic radial tire for a passenger vehicle according to (15), wherein at least one of the lateral grooves is a lateral groove having a groove width / groove depth of 0.50 to 0.80.

[0066] (17) The invention is:

[0067] The pneumatic radial tire for a passenger vehicle according to any one of (1) to (16), wherein:

[0068] When the tire is mounted on a standard rim and the internal pressure is 250 kPa, when the outer diameter of the tire is Dt (mm), Dt is less than 685 (mm).

[0069] (18) The invention is:

[0070] The pneumatic radial tire for a passenger vehicle according to any one of (1) to (17), wherein the cross-sectional width Wt (mm) is less than 205 mm.

[0071] (19) The invention is:

[0072] The pneumatic radial tire for a passenger vehicle according to (18), wherein the cross-sectional width Wt (mm) is less than 200 mm.

[0073] Effects of the Invention

[0074] According to the present invention, a pneumatic radial tire for a passenger car which has both riding comfort at low temperatures and handling stability during high-speed running can be provided. DETAILED DESCRIPTION

[0075] Hereinafter, the present invention will be described in detail based on embodiments.

[0076] [1] Features of the tire of the present invention

[0077] First, the features of the tire according to the present invention are described.

[0078] The inventors of the present invention believe that the shape of the tread and the physical properties of the rubber are related to both the ride comfort at low temperatures and the handling stability at high speeds, and that they need to meet certain conditions. After conducting various experiments and studies, it was found that in order to solve the above problems, the tread needs to have the shape and rubber physical properties shown below, and the present invention was completed.

[0079] Specifically, first, regarding the shape of the tread, it was found that when the tire is mounted on a standard rim and the internal pressure is the standard internal pressure, when the cross-sectional width of the tire is Wt (mm) and the outer diameter is Dt (mm), 1963.4≤(Dt 2 ×π / 4) / Wt≤2827.4, there must be at least one main groove extending along the circumferential direction of the tread on the tread running surface, and the tread running surface must be molded so that the land-sea ratio is greater than 55% and less than 85%.

[0080] Secondly, regarding the rubber properties of the tread, for the loss tangent (tanδ) measured under the conditions of frequency 10 Hz, initial strain 2%, and dynamic strain rate 1%, it is necessary that |20℃tanδ-50℃tanδ| is greater than 0.01 and less than 0.15, and |5℃tanδ-℃tanδ| is greater than 0.15 and less than 0.70, and it was found that it is necessary to use a rubber composition formulated to exhibit such rubber properties.

[0081] As described above, since the tread has an appropriate shape and rubber properties, it is possible to provide a tire that has both riding comfort at low temperatures and handling stability at high speeds.

[0082] That is, by forming the tread into the above-mentioned shape, a sufficient tire contact area can be ensured. On the other hand, since the tread has the rubber properties as described above, the hardness of the tread rubber can be appropriately maintained, and the change of the tread shape during driving can be fully suppressed. In the tire according to the present invention, the effects based on the tread shape and the effects based on the physical properties of the tread rubber are synergistically exerted, so that the optimized tread contact shape can be maintained even when driving at high speeds or at low temperatures, and the ride comfort at low temperatures and the handling stability during high-speed driving can be achieved at the same time.

[0083] [2] Embodiments of the present invention

[0084] Hereinafter, the present invention will be described in detail based on embodiments.

[0085] 1. Tread shape

[0086] As described above, the tire of the present embodiment is a pneumatic radial tire for a passenger car, which first has a carcass having radially arranged cords toroidally spanning a pair of bead portions, and a tread provided on the tire radially outer side of the carcass.

[0087] In the present embodiment, the passenger car tire refers to a tire installed on a four-wheel vehicle and having a maximum load capacity of 1000 kg or less. Here, the maximum load capacity is the maximum load capacity specified for each tire in the standard system including the standard to which the tire is based. For example, in the case of the JATMA standard (Japan Automobile Tire Association standard), it is the maximum load capacity based on the load index (LI); in the case of TRA (Tire and Rim Association, Inc.), it is the maximum value recorded in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; in the case of ETRTO, it is "INFLATION PRESSURE".

[0088] When the cross-sectional width of the tire is Wt (mm) and the outer diameter is Dt (mm), when the tire of this embodiment is mounted on a standard rim and the internal pressure is the standard internal pressure, 1963.4≤(Dt 2 ×π / 4) / Wt≤2827.4.

[0089] The above formula shows that, relative to the tire's cross-sectional width Wt, the tire area viewed from the lateral direction [(Dt / 2) 2 ×π)=(Dt 2 ×π / 4)] is larger than that of conventional tires. By satisfying the numerical range specified by the formula, the moment of inertia of the tire when rolling becomes larger, which can improve handling stability.

[0090] In the above description, the "standard rim" is a rim specified for each tire in the standard system including the standard on which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Association Standard), it is a standard rim of applicable size described in the "JATMA YEAR BOOK". In the case of "ETRTO (The European Tire and Rim Technical Organization)", it is the "Measuring Rim" described in the "STANDARDS MANUAL". In the case of TRA (Tire and Rim Association, Inc.), it is the "Design Rim" described in the "YEAR BOOK". If the tire is not specified in the standard, it refers to a rim that can be assembled and can maintain the internal pressure, that is, a rim with no air leakage between the rim and the tire, the smallest rim diameter, and then the narrowest rim width.

[0091] "Standard internal pressure" is the air pressure specified by the standard for each tire. In the case of JATMA, it is the maximum air pressure; in the case of TRA, it is the maximum value recorded in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table; in the case of ETRTO, it is "INFLATION PRESSURE".

[0092] The outer diameter Dt of the tire is the outer diameter of the tire when the tire is assembled on a standard rim, the internal pressure is 250 kPa (the standard internal pressure of a passenger car tire), and no load is applied. The cross-sectional width Wt (mm) of the tire is the tire width obtained by subtracting the pattern, letters, etc. on the side of the tire from the straight-line distance between the sidewalls including all patterns, letters, etc. on the side of the tire (the total width of the tire) when the tire is assembled on a standard rim, the internal pressure is 250 kPa (the standard internal pressure of a passenger car tire), and no load is applied.

[0093] Furthermore, in the present embodiment, the cap tread has at least one main groove (circumferential main groove) extending in the circumferential direction of the tread.

[0094] By providing such circumferential main grooves on the tread surface, a stable running quality can be ensured while a sufficient contact area of ​​the tire is ensured.

[0095] In the above description, "tread surface" refers to the outer peripheral surface of the tire that contacts the road surface when the tire is assembled on a standard rim, a standard internal pressure is applied, and the tire rolls under a standard load. "Standard load" is the load specified for each tire in each standard system including the standards to which the tire is based, and refers to the maximum mass that can be loaded on the tire. In the case of JATMA, it is the maximum load capacity; in the case of TRA, it is the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; in the case of ETRTO, it is "LOAD CAPACITY".

[0096] The "circumferential main groove" refers to the cross-sectional area of ​​the tire width direction of 10mm 2 The circumferential main groove formed in the center of the tread width direction is called the crown main groove, and the circumferential main groove formed at the end of the tread width direction is called the shoulder main groove.

[0097] In addition, in the present embodiment, the tread is molded so that the land-sea ratio of the tread running surface is greater than 55% and less than 85%. The "land-sea ratio" is the ratio of the land area (the total surface area of ​​the contact portion) to the sea area (the area of ​​the entire groove bottom surface) on the tread running surface.

[0098] By providing the above-mentioned circumferential main groove and controlling the land-sea ratio on the tread running surface within the above-mentioned range, it is possible to ensure a sufficient tire contact area and ensure stable riding comfort.

[0099] 2. Tread rubber composition

[0100] Next, in the tire of the present embodiment, the tread is formed by a rubber composition, which is mixed in the following manner: for the loss tangent (tanδ) measured under the conditions of a frequency of 10 Hz, an initial strain of 2%, and a dynamic strain rate of 1%, |20℃tanδ-50℃tanδ| is greater than 0.01 and less than 0.15, and |5℃tanδ-20℃tanδ| is greater than 0.15 and less than 0.70.

[0101] In the above, tan δ is the loss tangent measured at 5°C, 20°C, and 50°C, for example, using an "Iplexer (registered trademark)" viscoelasticity measuring apparatus manufactured by GABO under the conditions of a frequency of 10 Hz, an initial strain of 2%, and a dynamic strain rate of 1%.

[0102] The above-mentioned |20°C tan δ-50°C tan δ| is more preferably greater than 0.08 and less than 0.12, and |5°C tan δ-20°C tan δ| is more preferably greater than 0.30 and less than 40.

[0103] By using a tire having a tread having the above-described shape and rubber properties, the tread contact shape of the tire at low temperatures or when running at high speeds can be optimized, and riding comfort at low temperatures and handling stability at high speeds can be achieved at a high level.

[0104] 3. Optimal selection of tread

[0105] In the present embodiment, it is more preferable that the tread is formed as follows.

[0106] (1) First, the tread is divided into four or more regions in the axial direction of the tire by three or more main grooves and a pair of ground contact edges, and the difference in average tread area per unit length (10 cm) in the circumferential direction of the tire is preferably 15% or less. As a result, the ground contact surface of the tread can be brought into more complete contact with the road surface, thereby achieving a higher level of ride comfort at low temperatures and handling stability at high speeds.

[0107] Specifically, first, the tread is divided into four or more regions along the tire axial direction by three or more main grooves. Since the regions are regions divided along the tire axial direction, each region is formed along the circumferential direction.

[0108] Then, focusing on the area formed in a certain circumferential direction, the average tread area per unit length (10 cm) in the tire circumferential direction is measured from a certain position, and then the average tread area per unit length (10 cm) in the tire circumferential direction is measured from another position, and the two measurement results are compared, and the difference between the two is set to be 15% or less. The above content is established regardless of the measurement position, and the difference in the average tread area per unit length is 15% or less regardless of the measurement position.

[0109] The same as described above is true not only in one circumferential region but also in each of four or more regions.

[0110] (2) Then, in the present embodiment, the tread is divided into a central land area and two shoulder land areas by a pair of extended shoulder main grooves extending continuously in the tire circumferential direction across the center of the tread pattern in the tire axial direction (i.e., the center line passing through the tire axial center of the tread pattern). Preferably, the groove width of the shoulder main groove is greater than 4 mm and less than 20 mm, and is located on the central side of the 25% width position of the ground contact width from the tread ground contact end, and the central land area accounts for more than 40% of the entire land area of ​​the tire ground contact area. As a result, the ground contact surface of the tread can be brought into contact with the road surface more fully, thereby achieving a higher level of ride comfort at low temperatures and handling stability at high speeds.

[0111] Here, the "ground contact end" refers to the outer end of the tire axially in the "tread ground contact width", and the "tread ground contact width" refers to the maximum straight-line distance in the axial direction of the tire on the contact surface with the flat plate when the tire is mounted on a "standard rim" and filled with the "standard internal pressure", and the tire is placed statically in a vertical position on a flat plate and a load corresponding to the "standard load" is applied.

[0112] (3) In addition, in the present embodiment, the tread is composed of a cap rubber layer constituting the tread running surface and a base rubber layer located inside the cap rubber layer, and the hardness of the cap rubber layer is preferably higher than the hardness of the base rubber layer, preferably with a JIS A hardness greater than 45 and less than 75.

[0113] Thus, when the tread is formed into a two-layer structure of a cap rubber layer and a base rubber layer, the hardness of the cap rubber layer is higher than that of the base rubber layer, and the JIS A hardness of the cap rubber layer is greater than 45 and less than 75, the hard cap rubber layer can ensure stability at high speeds while the soft base rubber layer absorbs impact. As a result, a higher level of ride comfort at low temperatures and handling stability at high speeds can be achieved.

[0114] (4) In the present embodiment, it is preferred that lateral grooves and / or lateral sipes extending in a direction intersecting the land portion are provided in the central land portion region of the tread.

[0115] By providing such lateral grooves and / or lateral sipes, it is possible to maintain the wear resistance of the tread center land region and improve the durability of the tire.

[0116] In this embodiment, considering the stability of ride comfort during driving, the outer diameter Dt (mm) of the tire and the tire cross-sectional height Ht (mm) (the distance from the bead bottom to the tread top, which is 1 / 2 of the difference between the outer diameter of the tire and the nominal rim diameter) of the tire preferably satisfy (Dt-2×Ht) of 450 (mm) or more, more preferably 470 (mm) or more, and further preferably 480 (mm) or more when the internal pressure is 250 kPa and the tire is unloaded. On the other hand, considering the deformation of the tread portion, it is preferably less than 560 (mm), more preferably less than 530 (mm), and even more preferably less than 510 (mm).

[0117] In consideration of tire durability, the aspect ratio of the tire of the present embodiment is preferably 40% or more.

[0118] The above aspect ratio (%) can be obtained by the following formula using the cross-sectional height Ht (mm) and the cross-sectional width Wt (mm) of the tire when the internal pressure is 250 kPa.

[0119] (Ht / Wt)×100(%)

[0120] The aspect ratio is more preferably 45% or more, further preferably 47.5% or more, still more preferably 50% or more, particularly preferably 52.5% or more, and most preferably 55% or more.

[0121] In addition, the groove width L at 80% of the maximum depth of the main groove in the ground contact area of ​​the main groove is 80 The ratio of the width L0 of the main groove (L 80 / L0) is preferably 0.3 to 0.7. As a result, the movement of the entire land portion can be suppressed at the bottom surface of the land portion of the tread portion, and the stability of the ride comfort can be improved. The ratio is more preferably 0.35 to 0.65, further preferably 0.40 to 0.60, and particularly preferably 0.45 to 0.55.

[0122] The above L0 and L 80 They refer to the straight-line distance (L0) between the groove edges on the tread surface of the main groove in the tread direction of the tire when the tire is mounted on a standard rim, the internal pressure is 250 kPa, and there is no load, and the minimum distance between the groove walls at 80% of the main groove depth (L 80). In short, it can be obtained by placing a bead portion cut out in the radial direction and having a width of 2 cm to 4 cm in a pressed state according to the rim width.

[0123] In addition, in the present embodiment, the tread is divided into a central land area and two shoulder land areas by a pair of shoulder main grooves extending continuously in the tire circumferential direction with the center line passing through the central part of the tire axial direction of the tread pattern, and has a plurality of lateral grooves extending in the tire axial direction. The total volume of the plurality of lateral grooves is preferably 2.0% to 5.0% of the tread volume. As a result, the movement of the tread portion can be suppressed and ride comfort and handling stability can be achieved. It is more preferably 2.2% to 4.0%, further preferably 2.5% to 3.5%, and particularly preferably 2.7% to 3.0%.

[0124] The volume of the lateral grooves is the total volume of the surface consisting of the ends of the lateral grooves and the groove walls in a tire mounted on a standard rim, with an internal pressure of 250 kPa and in an unloaded state. In simple terms, it can be obtained by calculating the volume of each lateral groove and multiplying it by the number of grooves when the bead portion cut out in the radial direction and having a width of 2 cm to 4 cm is pressed according to the rim width. In addition, the volume of the tread portion can be calculated by calculating the area of ​​the tread portion excluding the lateral grooves from the above portion and multiplying it by the outer diameter, and then obtaining the difference between the calculated result and the volume of the lateral grooves.

[0125] From the viewpoint of suppressing uneven wear of the tread and improving durability, the groove width ratio (Gw / Gd), i.e., the ratio of the groove width Gw to the groove depth Gd, of at least one of the lateral grooves is preferably 0.50 to 0.80, more preferably 0.53 to 0.77, further preferably 0.55 to 0.75, and particularly preferably 0.60 to 0.70.

[0126] The width and depth of the lateral grooves are the maximum length of a straight line connecting the tread ends of the lateral grooves and perpendicular to the groove direction, and the maximum depth of the lateral grooves, respectively, in a tire with an internal pressure of 250 kPa and no load. In simple terms, it can be calculated by placing a bead portion with a width of 2 cm to 4 cm cut out in the radial direction in a pressed state according to the rim width.

[0127] In the tire according to the present invention, when the tire is assembled into a standard rim and the internal pressure is 250 kPa, the specific outer diameter Dt (mm) is, for example, preferably 515 mm or more. More preferably, it is 558 mm or more, further preferably, it is 585 mm or more, particularly preferably, it is 658 mm or more, and most preferably, it is 673 mm or more. On the other hand, it is preferably less than 843 mm, more preferably less than 725 mm, further preferably, less than 707 mm, particularly preferably, less than 685 mm, and most preferably, less than 675 mm.

[0128] The specific cross-sectional width Wt (mm) is, for example, preferably 115 mm or more, more preferably 130 mm or more, further preferably 150 mm or more, further preferably 170 mm or more, even more preferably 185 mm or more, and most preferably 193 mm or more. On the other hand, it is preferably less than 305 mm, more preferably less than 245 mm, further preferably less than 210 mm, particularly preferably less than 205 mm, and most preferably less than 200 mm.

[0129] The specific cross-sectional height Ht (mm) is, for example, preferably 37 mm or more, more preferably 87 mm or more, and further preferably 95 mm or more. On the other hand, it is preferably less than 180 mm, more preferably less than 112 mm, and even more preferably less than 101 mm.

[0130] 4. Tread rubber

[0131] As described above, in the tread rubber of the tire of the present embodiment, the tread is formed using a rubber composition, and the rubber composition is mixed so that for the loss tangent (tanδ) of the rubber composition forming the tread measured under the conditions of a frequency of 10 Hz, an initial strain of 2% and a dynamic strain rate of 1%, |20℃tanδ-50℃tanδ| is greater than 0.01 and less than 0.15, and |5℃tanδ-20℃tanδ| is greater than 0.15 and less than 0.70.

[0132] (1) Tread rubber composition

[0133] The rubber composition having such rubber properties can be obtained from the following rubber components and other compounding materials. In particular, by adjusting the type and amount of the rubber component, the type and amount of silica, the type and amount of carbon black, the type and amount of the plasticizer, and the amount of sulfur, the desired rubber properties can be easily achieved.

[0134] (A) Rubber component

[0135] As the rubber component, it is preferred to contain 35% by mass or more of diene rubber. Specific examples of diene rubber include natural rubber (NR), isoprene-based rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR) and styrene-isoprene-butadiene copolymer rubber (SIBR). These can be used alone or in combination of two or more.

[0136] (B) Isoprene rubber

[0137] When the rubber composition contains isoprene-based rubber, the content (total content) of the isoprene-based rubber in 100% by mass of the rubber component is, for example, greater than 5% by mass and less than 100% by mass. Examples of the isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), reformed NR, modified NR, and modified IR.

[0138] As NR, for example, SIR20, RSS#3, TSR20, etc. commonly used in the tire industry can be used. IR is not particularly limited, for example, IR2200 commonly used in the tire industry can be used. Reformed NR includes deproteinized natural rubber (DPNR), high purity natural rubber (UPNR), etc. Modified natural rubber includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Modified IR includes epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. These can be used alone or in combination of two or more.

[0139] (B)SBR

[0140] When the rubber composition contains SBR, the content of SBR in 100% by mass of the rubber component is, for example, greater than 5% by mass and less than 100% by mass. The weight average molecular weight of SBR is, for example, greater than 100,000 and less than 2,000,000. The amount of styrene in SBR is, for example, greater than 5% by mass and less than 50% by mass. The vinyl amount (1,2-bonded butadiene unit amount) of SBR is, for example, greater than 5% by mass and less than 70% by mass.

[0141] The structural identification of SBR (measurement of the styrene content and the vinyl content) can be performed using, for example, a JNM-ECA series apparatus manufactured by JEOL Ltd. (JEOL Ltd.).

[0142] The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR) and solution-polymerized styrene-butadiene rubber (S-SBR) can be used. The SBR may be unmodified SBR or modified SBR.

[0143] The modified SBR can be any SBR having functional groups that interact with fillers such as silica. Examples include:

[0144] Terminal-modified SBR (terminal-modified SBR having the above-mentioned functional group at the terminal), wherein at least one terminal of the SBR is modified by a compound (modifying agent) having the above-mentioned functional group;

[0145] Main chain modified SBR having the above functional groups on the main chain;

[0146] A main chain terminal modified SBR having the above functional groups in the main chain and at the terminal (e.g., a main chain terminal modified SBR having the above functional groups in the main chain and having at least one terminal modified by the above modifier; and

[0147] Terminally modified SBR is modified (coupled) with a multifunctional compound having two or more epoxy groups in the molecule to introduce epoxy groups or hydroxyl groups.

[0148] Examples of the above functional groups include amino, amide, silyl, alkoxysilyl, isocyanate, imino, imidazolyl, urea, ether, carbonyl, oxycarbonyl, sulfhydryl, sulfhydryl, disulfide, sulfonyl, sulfinyl, thiocarbonyl, ammonium, imido, hydrazine, azo, diazo, carboxyl, nitrile, pyridyl, alkoxy, hydroxyl, oxy and epoxy. In addition, these functional groups may have substituents.

[0149] Furthermore, as the modified SBR, for example, SBR modified with a compound (modifying agent) represented by the following formula may be used.

[0150] [Chemical formula 1]

[0151]

[0152] In the formula, R1, R2 and R3 are the same or different and represent an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (-COOH), a mercapto group (-SH) or a derivative thereof. R4 and R5 are the same or different and represent a hydrogen atom or an alkyl group. R4 and R5 may be combined with a nitrogen atom to form a ring structure. n represents an integer.

[0153] As the modified SBR modified by the compound (modifier) ​​represented by the above formula, there can be used SBR in which the polymerization end (active end) of solution-polymerized styrene-butadiene rubber (S-SBR) is modified by the compound represented by the above formula (for example, the modified SBR described in JP-A-2010-111753).

[0154] As R1, R2 and R3, alkoxy groups are suitable (preferably alkoxy groups having 1 to 8 carbon atoms, more preferably alkoxy groups having 1 to 4 carbon atoms). As R4 and R5, alkyl groups (preferably alkyl groups having 1 to 3 carbon atoms) are suitable. n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. In addition, when R4 and R5 are combined with the nitrogen atom to form a cyclic structure, it is preferably a 4- to 8-membered ring. Alkoxy groups also include cycloalkoxy groups (cyclohexyloxy, etc.) and aryloxy groups (phenoxy, benzyloxy, etc.).

[0155] Specific examples of the above-mentioned modifiers include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane and diethylaminopropyltriethoxysilane. These can be used alone or in combination of two or more.

[0156] In addition, as the modified SBR, a modified SBR modified with the following compounds (modifiers) can also be used. Examples of the modifiers include:

[0157] Polyglycidyl ethers of polyols, for example ethylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolethane triglycidyl ether, trimethylolpropane triglycidyl ether;

[0158] Polyglycidyl ethers of aromatic compounds having two or more phenolic groups, such as diglycidyl bisphenol A;

[0159] Polyepoxides, such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, polyepoxidized liquid polybutadiene;

[0160] Epoxy-containing tertiary amines, such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine;

[0161] diglycidylamino compounds, for example diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline, diglycidyl-o-toluidine, tetraglycidylmethyleneoxydiphenylamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane and tetraglycidyl-1,3-bisaminomethylcyclohexane;

[0162] Acid chlorides containing amino groups, for example bis-(1-methylpropyl)carbamate chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylurea chloride, N,N-diethylurea chloride;

[0163] Silane compounds containing epoxy groups, such as 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane and (3-glycidyloxypropyl)-pentamethyldisiloxane;

[0164] Silane compounds containing a sulfide group, such as (trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tripropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldipropoxysilyl)propyl]sulfide, and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide;

[0165] N-substituted aziridine compounds, such as ethyleneimine and propyleneimine;

[0166] Alkoxysilanes, for example methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane and N,N-bis(trimethylsilyl)aminoethyltriethoxysilane;

[0167] (Thio)benzophenone compounds having an amino group and / or a substituted amino group, for example, 4-N,N-dimethylaminobenzophenone, 4-N,N-di-tert-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone, and N,N,N',N'-bis-(tetraethylamino)benzophenone;

[0168] Benzaldehyde compounds having an amino group and / or a substituted amino group, such as 4-N,N-dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde, 4-N,N-divinylaminobenzaldehyde;

[0169] N-substituted pyrrolidones, for example N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-tert-butyl-2-pyrrolidone and N-methyl-5-methyl-2-pyrrolidone;

[0170] N-substituted piperidones, such as methyl-2-piperidone, N-vinyl-2-piperidone and N-phenyl-2-piperidone;

[0171] N-substituted lactams, such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurolactam, N-vinyl-ω-laurolactam, N-methyl-β-propiolactam and N-phenyl-β-propiolactam; and

[0172] N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), tris-(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-trione, N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophenone, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone and 1,7-bis(methylethylamino)-4-heptanone. The above compounds (modifiers) can be modified by known methods.

[0173] As SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Co., Ltd., Zeon Corporation, etc. can be used. SBR can be used alone or in combination of two or more.

[0174] (C)BR

[0175] When the rubber composition contains BR, the content of BR in 100% by mass of the rubber component is, for example, greater than 5% by mass and less than 100% by mass. The weight average molecular weight of BR is, for example, greater than 100,000 and less than 2,000,000. The amount of vinyl in BR is, for example, greater than 1% by mass and less than 30% by mass. The amount of cis in BR is, for example, greater than 1% by mass and less than 98% by mass. The amount of trans in BR is, for example, greater than 1% by mass and less than 60% by mass.

[0176] BR is not particularly limited, and BR with a high cis content (90% or more of cis content), BR with a low cis content, BR containing syndiotactic polybutadiene crystals, etc. can be used. BR can be unmodified BR or modified BR, and examples of modified BR include modified BR introduced with the above-mentioned functional groups. These can be used alone or in combination of two or more. The cis content can be determined by infrared absorption spectroscopy analysis.

[0177] As BR, for example, products of Ube Kosan Co., Ltd., JSR Corporation, Asahi Kasei Co., Ltd., Nippon Zeon Corporation, etc. can be used.

[0178] (B) Compounding materials other than rubber components

[0179] (A) Silica

[0180] The rubber composition preferably contains silica as a filler reinforcing agent. From the viewpoint of obtaining good durability, the BET specific surface area of ​​silica is preferably greater than 140 m 2 / g, more preferably greater than 160m 2 On the other hand, from the viewpoint of obtaining good rolling resistance during high-speed running, it is preferably less than 250 m 2 / g, more preferably less than 220m 2 The above BET specific surface area is the N2SA value measured by the BET method according to ASTM D3037-93.

[0181] When silica is used as a filler reinforcing agent, the content of silica is preferably 35 parts by mass or more, more preferably 40 parts by mass or more, relative to 100 parts by mass of the rubber component. On the other hand, it is preferably 200 parts by mass or less, more preferably 100 parts by mass or less, and further preferably 60 parts by mass or less.

[0182] Examples of silica include dry silica (anhydrous silica) and wet silica (hydrated silica). Among them, wet silica is preferred because it has a large number of silanol groups.

[0183] As silica, for example, products of Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation, etc. can be used.

[0184] (B) Silane coupling agent

[0185] The rubber composition preferably contains silica and a silane coupling agent. The silane coupling agent is not particularly limited. Examples of the silane coupling agent include:

[0186] Sulfides, such as bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide bis(trimethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide and 3-triethoxysilylpropyl methacrylate monosulfide;

[0187] Mercapto groups, such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z manufactured by Momentive;

[0188] Vinyls, such as vinyltriethoxysilane, vinyltrimethoxysilane;

[0189] Amino groups, such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane;

[0190] Glycidoxy groups, such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane;

[0191] Nitro groups, such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane; and

[0192] Chlorinated compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These may be used alone or in combination of two or more.

[0193] As the silane coupling agent, for example, products manufactured by Degussa, Momentive, Shinetsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used.

[0194] The content of the silane coupling agent is, for example, greater than 3 parts by mass and less than 25 parts by mass relative to 100 parts by mass of silica.

[0195] (C) Carbon black

[0196] The rubber composition preferably contains carbon black. The content of the carbon black is, for example, 1 part by mass or more and 200 parts by mass or less relative to 100 parts by mass of the rubber component.

[0197] The carbon black is not particularly limited, and examples thereof include furnace blacks such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene blacks; thermal blacks such as FT and MT; and channel blacks such as EPC, MPC, and CC. These may be used alone or in combination of two or more.

[0198] The nitrogen adsorption specific surface area (N2SA) of carbon black is, for example, greater than 30 m 2 / g and less than 250m 2 / g. The amount of dibutyl phthalate (DBP) adsorbed by carbon black is, for example, greater than 50 ml / 100 g and less than 250 ml / 100 g. The nitrogen adsorption specific surface area of ​​carbon black is measured according to ASTM D4820-93, and the amount of adsorbed DBP is measured according to ASTM D2414-93.

[0199] The specific carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products include, for example, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nikka Carbon Co., Ltd., and Columbia Carbon Co., Ltd. These may be used alone or in combination of two or more.

[0200] (D) Polymer component

[0201] The rubber composition may contain a polymer component other than the rubber component, such as a liquid polymer or a solid polymer.

[0202] The liquid polymer is a polymer that is liquid at room temperature (25° C.), and the solid polymer is a polymer that is solid at room temperature (25° C.). Examples of the liquid polymer and the solid polymer include farnesene polymers, liquid diene polymers, styrene resins, coumarone-indene resins, terpene resins, p-tert-butylphenol acetylene resins, phenol resins, C5 resins, C9 resins, C5C9 resins, and acrylic resins.

[0203] Farnesene polymers are polymers obtained by polymerizing farnesene and have a farnesene-based structural unit. Farnesene includes isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecatriene).

[0204] The farnesene polymer may be a homopolymer of farnesene (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer).

[0205] Examples of vinyl monomers include:

[0206] Aromatic vinyl compounds such as styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, 5-tert-butyl-2-methylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethylether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-tert-butylstyrene, 3-tert-butylstyrene, 4-tert-butylstyrene, vinylxylene, vinylnaphthalene, vinyltoluene, vinylpyridine, diphenylethylene, and diphenylethylene containing a tertiary amino group; and

[0207] Conjugated diene compounds, such as butadiene and isoprene.

[0208] These can be used alone or in combination of two or more.

[0209] As the farnesene polymer, a liquid farnesene polymer may be used. The liquid farnesene polymer is a farnesene polymer that is liquid at room temperature (25° C.) and has a weight average molecular weight (Mw) greater than 3,000 and less than 300,000.

[0210] The glass transition temperature (Tg) of the farnesene polymer is, for example, higher than -100° C. and lower than -10° C. Tg is a value measured at a temperature increase rate of 10° C. / min using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan, Inc. in accordance with JIS-K7121:1987.

[0211] The melt viscosity of the farnesene polymer is, for example, greater than 0.1 Pa·s and less than 500 Pa·s. The melt viscosity is a value measured at 38° C. using a Brookfield viscometer (manufactured by BROOKFIELD ENGINEERING LABS INC.).

[0212] In the farnesene-vinyl monomer copolymer, the copolymerization ratio of farnesene to vinyl monomer (farnesene / vinyl monomer) by mass is, for example, 40 / 60 to 90 / 10.

[0213] The content of the farnesene polymer is, for example, greater than 1.0 part by mass and less than 50.0 parts by mass relative to 100 parts by mass of the rubber component.

[0214] As the farnesene polymer, for example, products produced by Kuraray Co., Ltd., etc. can be used.

[0215] Examples of the liquid diene polymer include liquid styrene-butadiene copolymers (liquid SBR), liquid butadiene polymers (liquid BR), liquid isoprene polymers (liquid IR), liquid styrene isoprene copolymers (liquid SIR).

[0216] The weight average molecular weight (Mw) of the liquid diene polymer in terms of polystyrene equivalent (measured by gel permeation chromatography (GPC)) is, for example, greater than 1.0×10 3 And less than 2.0×10 5 In this specification, the Mw of the liquid diene polymer is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0217] The content of the liquid polymer (the total content of the liquid farnesene polymer, the liquid diene polymer, etc.) relative to 100 parts by mass of the rubber component is, for example, greater than 1 part by mass and less than 100 parts by mass.

[0218] The coumarone-indene resin is a resin containing coumarone and indene as monomer components constituting the resin skeleton (main chain). Examples of monomer components other than coumarone and indene contained in the skeleton include styrene, α-methylstyrene, methylindene, and vinyltoluene.

[0219] The content of the coumarone-indene resin is, for example, greater than 1.0 part by mass and less than 50.0 parts by mass relative to 100 parts by mass of the rubber component.

[0220] The hydroxyl value (OH value) of the coumarone-indene resin is, for example, greater than 15 mgKOH / g and less than 150 mgKOH / g. The OH value is the amount of potassium hydroxide required to neutralize acetic acid bonded to the hydroxyl group when 1 g of the resin is acetylated, and is expressed in milligrams. It is measured by potentiometric titration (JIS K0070: 1992).

[0221] The softening point of the coumarone-indene resin is, for example, higher than 30° C. and lower than 160° C. The softening point is the temperature at which a ball falls when the softening point specified in JIS K6220-1:2001 is reached, as measured using a ring-ball softening point tester.

[0222] The styrene resin is a polymer having a styrene monomer as a constituent monomer, and examples thereof include polymers obtained by polymerizing a styrene monomer as a main component (50% by mass or more). Specifically, it includes homopolymers obtained by polymerizing a styrene monomer (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) alone, copolymers obtained by copolymerizing two or more styrene monomers, and copolymers obtained by copolymerizing a styrene monomer and other monomers copolymerizable with the styrene monomer.

[0223] Examples of other monomers include: acrylonitriles such as acrylonitrile and methacrylate; unsaturated carboxylic acids such as acrylic acid and methacrylic acid; unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate; dienes such as chloroprene, butadiene, isoprene; olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride and its anhydride.

[0224] Examples of terpene resins include polyterpenes, terpene phenols, and aromatic modified terpene resins. Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are resins having (C5H8) n Hydrocarbons or their oxygen-containing derivatives, which are classified as monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32) as a basic skeleton. Examples thereof include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, diterpenes, α-terpinene, α-terpinene, γ-terpinene, terpinene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

[0225] Examples of polyterpenes include terpene resins, such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin and β-pinene / limonene resin made from the above-mentioned terpene compounds, and terpene resins obtained by hydrogenating terpene resins. Examples of terpene phenols include resins obtained by copolymerizing the above-mentioned terpenoid compounds and phenolic compounds, and resins obtained by hydrogenating the above-mentioned resins. Specifically, resins formed by condensing the above-mentioned terpene compounds, phenolic compounds and formalin can be cited. Examples of phenolic compounds include phenol, bisphenol A, cresol and xylenol.

[0226] Examples of aromatic modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating the above resins. The above aromatic compounds are not particularly limited as long as they are compounds having an aromatic ring, and examples thereof include: phenol compounds such as phenol, alkylphenol, alkoxyphenol, and phenol containing an unsaturated hydrocarbon group; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, and naphthol containing an unsaturated hydrocarbon group; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and styrene containing an unsaturated hydrocarbon group; coumarone and indene.

[0227] The acrylic resin is not particularly limited, and for example, an acrylic resin containing no solvent may be used.

[0228] As a solvent-free acrylic resin, a (meth) acrylic resin (polymer) is synthesized by a high temperature continuous polymerization method (high temperature continuous block polymerization method: methods described in U.S. Pat. No. 4414370, JP 84-6207A, JP 93-58805A, JP 89-313522A, U.S. Pat. No. 5010166, Toa Synthetic Research Annual Report TREND 2000 No. 3, pp. 42-45, etc.) without using a polymerization initiator, a chain transfer agent, an organic solvent, etc. as auxiliary raw materials as much as possible. In the present invention, (meth) acrylic refers to methacrylic and acrylic.

[0229] Examples of the monomer component constituting the acrylic resin include (meth)acrylic acid and (meth)acrylic acid derivatives such as (meth)acrylic acid esters (alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylamide derivatives.

[0230] In addition, as the monomer component constituting the acrylic resin, an aromatic vinyl compound such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, divinylnaphthalene and the like can be used together with (meth)acrylic acid or a (meth)acrylic acid derivative.

[0231] The acrylic resin may be a resin composed only of a (meth)acrylic component or may be a resin further containing components other than the (meth)acrylic component. In addition, the acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

[0232] The content of the solid polymer (the total content of the solid coumarone-indene resin and the like) is, for example, greater than 1.0 part by mass and less than 100.0 parts by mass relative to 100 parts by mass of the rubber component.

[0233] Examples of polymer components such as liquid polymers and solid polymers include products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Toso Co., Ltd., Rutgers Chemicals Co., Ltd., BASF Co., Ltd., Arizona Chemical Co., Ltd., Nitto Chemical Co., Ltd., Nippon Catalyst Co., Ltd., JX Energy Co., Ltd., Arakawa Chemical Industry Co., Ltd., Taoka Chemical Industry Co., Ltd., and the like.

[0234] (E) Oil

[0235] The rubber composition may contain oil. The content of the oil is, for example, greater than 1.0 part by mass and less than 100.0 parts by mass. The content of the oil also includes the amount of oil contained in the rubber (oil-coated rubber).

[0236] Examples of oils include process oils, vegetable oils and mixtures thereof. As process oils, for example, paraffin process oils, aromatic process oils, naphthenic process oils, etc. can be used. Examples of vegetable oils include castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, beni flower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia oil and tung oil. These can be used alone or in combination of two or more.

[0237] Examples of oils that can be used include products of Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Seiyu Co., Ltd., Showa Shell Sekiyu Co., Ltd., and Fuji Kosan Co., Ltd.

[0238] (F) Low temperature plasticizer

[0239] The rubber composition may contain a low temperature plasticizer. Examples of low temperature plasticizers include liquid components such as dioctyl phthalate (DOP), dibutyl phthalate (DBP), tris(2-ethylhexyl) phosphate (TOP) and di(2-ethylhexyl) sebacate (DOS). When the low temperature plasticizer is included, the content relative to 100 parts by mass of the rubber component is, for example, greater than 1 part by mass and less than 60 parts by mass.

[0240] (G) Wax

[0241] The rubber composition preferably contains wax. The content of the wax is, for example, greater than 0.5 parts by mass and less than 20 parts by mass relative to 100 parts by mass of the rubber component.

[0242] The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax, natural waxes such as vegetable wax and animal wax, and synthetic waxes such as polymers of ethylene and propylene, etc. These may be used alone or in combination of two or more.

[0243] As the wax, for example, products of Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Kagaku Co., Ltd. can be used.

[0244] (H) Anti-aging agent

[0245] The rubber composition preferably contains an antioxidant. The content of the antioxidant is, for example, greater than 1 part by mass and less than 10 parts by mass relative to 100 parts by mass of the rubber component.

[0246] Examples of antioxidants include: naphthylamine antioxidants, such as phenyl-α-naphthylamine; diphenylamine antioxidants, such as octylated diphenylamine, 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine antioxidants, such as N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine; quinoline antioxidants, such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants, such as 2,6-di-tert-butyl-4-methylphenol, styrenated phenol; bisphenol antioxidants, triphenol antioxidants, polyphenol antioxidants, such as tetrakis-[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane. These can be used alone or in combination of two or more.

[0247] As the antioxidant, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo Co., Ltd., Flexis Co., Ltd., etc. can be used.

[0248] (I) Stearic acid

[0249] The rubber composition may contain stearic acid. The content of stearic acid is, for example, greater than 0.5 parts by mass and less than 10.0 parts by mass relative to 100 parts by mass of the rubber component.

[0250] As stearic acid, conventionally known stearic acid can be used, for example, products of NOF Corporation, NOF Corporation, Kao Corporation, Fuji Film Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc.

[0251] (J) Zinc Oxide

[0252] The rubber composition may contain zinc oxide. The content of zinc is, for example, greater than 0.5 parts by mass and less than 10 parts by mass relative to 100 parts by mass of the rubber component. As zinc oxide, conventionally known zinc oxide may be used, for example, products of Mitsui Metal Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc.

[0253] (K) Cross-linking agent and vulcanization accelerator

[0254] The rubber composition preferably contains a crosslinking agent such as sulfur. The content of the crosslinking agent is, for example, greater than 0.1 parts by mass and less than 10.0 parts by mass relative to 100 parts by mass of the rubber component.

[0255] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur commonly used in the rubber industry. These may be used alone or in combination of two or more.

[0256] As sulfur, for example, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Corporation, Flexis Co., Ltd., Nippon Kanryo Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0257] Examples of cross-linking agents other than sulfur include: Tackilol V200 manufactured by Taoka Chemical Industry Co., Ltd., DURALINK HTS (1,6-sodium hexamethylene dithiosulfate dihydrate) manufactured by Flexis, KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyl disulfide)hexane) manufactured by Lanxess; and organic peroxides such as diisopropyl peroxide.

[0258] The rubber composition preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, greater than 0.3 parts by mass and less than 10.0 parts by mass relative to 100 parts by mass of the rubber component.

[0259] Examples of vulcanization accelerators include:

[0260] Thiazole vulcanization accelerators, such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide and N-cyclohexyl-2-benzothiazolyl sulfenamide;

[0261] Thiuram vulcanization accelerators, such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N);

[0262] Sulfenamide vulcanization accelerators, such as N-cyclohexyl-2-benzothiazolesulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide and N,N'-diisopropyl-2-benzothiazolesulfenamide; and

[0263] Guanidine vulcanization accelerators such as diphenylguanidine, di-o-triguanidine and di-o-tolylguanidine.

[0264] These can be used alone or in combination of two or more.

[0265] (L) Other

[0266] In addition to the above ingredients, the rubber composition may contain additives commonly used in the tire industry, such as fillers such as organic peroxides, calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, graphite, etc. The content of these additives is, for example, greater than 0.1 parts by mass and less than 200 parts by mass relative to 100 parts by mass of the rubber component.

[0267] (2) Production of tread rubber composition

[0268] The rubber composition is produced by a general method, for example, a production method including a base kneading step of kneading a rubber component with a filler such as silica or carbon black and a final kneading step of kneading the kneaded product obtained in the base kneading step with a crosslinking agent.

[0269] Kneading can be performed using a known (closed) kneading machine such as a Banbury mixer, a kneader, or an open roll.

[0270] The mixing temperature of the base mixing step is, for example, higher than 50° C. and lower than 200° C., and the mixing time is, for example, greater than 30 seconds and less than 30 minutes. In the base mixing process, in addition to the above ingredients, compounding agents commonly used in the rubber industry, such as softeners such as oil, stearic acid, zinc oxide, anti-aging agents, wax, vulcanization accelerators, etc., can be appropriately added and mixed as needed.

[0271] In the final kneading step, the kneaded product obtained in the base kneading step is kneaded with a crosslinking agent. The kneading temperature in the final kneading step is, for example, room temperature or higher and lower than 80° C., and the kneading time is, for example, greater than 1 minute and less than 15 minutes. In the final kneading step, in addition to the above-mentioned components, a vulcanization accelerator, zinc oxide, etc. may be appropriately added and kneaded as needed.

[0272] 5. Tire manufacturing

[0273] The tire of the present invention is manufactured by a conventional method using the unvulcanized rubber composition obtained in the final mixing step. That is, the unvulcanized rubber composition is extruded according to the shape of each tire component of the tread, and molded together with other tire components on a tire molding machine by a conventional method to manufacture an unvulcanized tire.

[0274] Specifically, the inner liner (as a member to ensure the airtightness of the tire), the carcass (as a member to bear the load, impact and inflation pressure of the tire), and the belt (as a member to strongly tighten the carcass to increase the rigidity of the tread) are wound on the forming drum, and the two ends of the carcass are fixed to the edges on both sides, and the bead portion (as a member for fixing the tire to the rim) is arranged and formed into a ring shape. Then the tread is attached to the center of the outer circumference, and the sidewall portion (a member to protect the carcass and bear bending) is attached to the radial outside to manufacture an unvulcanized tire.

[0275] In this embodiment, it is preferred to provide an inclined belt layer extending at an angle greater than 55° and less than 75° relative to the tire circumferential direction as the belt layer. As a result, the durability of the tire can be ensured while the rigidity of the tread can be sufficiently maintained.

[0276] Then, the manufactured unvulcanized tire is heated and pressed in a vulcanizer to obtain a tire. The vulcanization step can be performed by applying a known vulcanization method. The vulcanization temperature is, for example, higher than 120° C. and lower than 200° C., and the vulcanization time is, for example, greater than 5 minutes and less than 15 minutes.

[0277] Example

[0278] Hereinafter, the present invention will be described in more detail with reference to Examples.

[0279] [1] Experiment 1

[0280] First, tires with different land-to-sea ratios and tread rubber properties were manufactured and mounted on passenger cars. Then, driving tests were conducted to evaluate ride comfort at low temperatures and handling stability at high speeds.

[0281] 1. Production of rubber composition for tread

[0282] First, a rubber composition for a tread is produced.

[0283] (1) Mixed materials

[0284] First, the following mixed materials are prepared.

[0285] (a) Rubber component

[0286] (A)NR:TSR20

[0287] (B-1) SBR1: T3830 manufactured by Asahi Kasei Corporation (S-SBR, oil-extended product)

[0288] (B-2) SBR2: SBR1723 (E-SBR) manufactured by JSR Corporation

[0289] (B-3) SBR3: Nipol NS522 (oil-filled product) manufactured by Nippon Zeon Co., Ltd.

[0290] (B-4) SBR4: SLR6430 (S-SBR, oil-extended product) manufactured by Dow Chemical Co., Ltd.

[0291] (B-5) SBR5: SYNTION 3041 manufactured by Synthos (oil-filled product)

[0292] (B-6) SBR6: modified SBR produced according to the method described in the next paragraph (styrene content: 25% by mass, vinyl bond content: 60% by mass, Mw: 400,000)

[0293] (B-7) SBR7: T4850 manufactured by Asahi Kasei Corporation

[0294] (C-1) BR1: BR150 manufactured by Ube Kosan Co., Ltd.

[0295] (C-2) BR2: BR360 manufactured by Ube Kosan Co., Ltd.

[0296] (C-3) BR3: BR730 manufactured by Ube Kosan Co., Ltd.

[0297] SBR6 is manufactured according to the procedure shown below. First, cyclohexane, tetrahydrofuran, styrene and 1,3-butadiene are loaded into an autoclave reactor after nitrogen substitution. After the temperature of the reactor contents is adjusted to 20°C, n-butyl lithium is added to initiate polymerization. The polymerization is carried out under adiabatic conditions, and the maximum temperature reaches 85°C. When the polymerization conversion rate reaches 99%, 1,3-butadiene is added, and then the polymerization is further carried out for 5 minutes. Then, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane is added as a modifier for reaction. After the polymerization 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 SBR6.

[0298] (b) Compounding materials other than rubber components

[0299] (A-1) Silica 1: ZEOSIL 1115MP manufactured by Rhodia (BET specific surface area: 115 m 2 / g)

[0300] (A-2) Silica 2: Ultrasil VN3 manufactured by Degussa (BET specific surface area: 167 m 2 / g)

[0301] (B-1) Silane coupling agent 1: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Degussa

[0302] (B-2) Silane coupling agent 2: NXT (3-octanoylthiopropyltriethoxysilane) manufactured by Momentive

[0303] (C) Carbon black: Diamond Black N220 manufactured by Mitsubishi Chemical Corporation

[0304] (D) Oil: ProcessX-140 manufactured by Japan Energy Co., Ltd.

[0305] (E) Resin: YSPolystar U130 (terpene phenol resin) manufactured by Yasuhara Chemical Co., Ltd.

[0306] (F) Wax: Ozoace0355 manufactured by Nippon Seiro Co., Ltd.

[0307] (G) Antiaging agent: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Kagaku Co., Ltd.

[0308] (H) Stearic acid: "TSUBAKI" stearic acid manufactured by NOF CORPORATION

[0309] (I) Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd.

[0310] (J) Crosslinking agent and vulcanization accelerator sulfur:

[0311] Sulfur: Sulfur powder manufactured by Tsurumi Chemical Industry Co., Ltd.

[0312] Vulcanization accelerator 1: Noxeller NS / CZ (N-tert-butyl-2-benzothiazolylsulfonamide / N-cyclohexyl-2-benzothiazolylsulfonamide) manufactured by Ouchi Shinko Kagaku Co., Ltd.

[0313] Vulcanization accelerator 2: Noxeller DPG (1,3-diphenylguanidine) manufactured by Ouchi Shinko Kagaku Co., Ltd.

[0314] (2) Production of rubber composition

[0315] According to the formulation shown in Table 1, materials other than sulfur and the vulcanization accelerator were kneaded at 150° C. for 5 minutes using a Banbury mixer to obtain a kneaded product. The amounts of each compounding are parts by mass.

[0316] [Table 1]

[0317]

[0318] 2. Tire manufacturing

[0319] Next, sulfur and a vulcanization accelerator were added to the obtained rubber composition for tread, and kneaded for 5 minutes at 80°C using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was molded into a tread in a manner having the respective land-sea ratios shown in Tables 2 and 3, and then bonded together with other tire components to form an unvulcanized tire. The formed unvulcanized tire was pressed at 170°C for 10 minutes and then vulcanized to produce a test tire (size: 175 / 80R16 91S, section width Wt: 175mm, outer diameter Dt: 689mm, (Dt 2 ×π / 4) / Wt=2130.5). The number of the circumferential main grooves is set to four.

[0320] 3. Performance evaluation test

[0321] (1) Physical properties of the tread

[0322] From the inner side of the rubber layer of the tread portion of each test tire, a viscoelasticity measurement sample with a length of 20 mm, a width of 4 mm, and a thickness of 1 mm was collected with the tire circumferential direction as the long side. Using the "Iplexer (registered trademark)" manufactured by GABO, the loss tangent (tanδ) at 5°C, 20°C, or 50°C was measured under the conditions of a frequency of 10 Hz, an initial strain of 2%, and a dynamic strain rate of 1%. The results are shown in Table 1. The thickness direction of the sample is the radial direction of the tire, and each measurement result is the average value of the values ​​measured from each sample with the same composition.

[0323] (2) Ride comfort evaluation test at low temperature

[0324] Each test tire was installed on all wheels of a vehicle (a Japanese FF car with a displacement of 2000cc) and driven on a test route on a dry asphalt surface at a speed of 40km / h in an environment of 5°C. The driver made a sensory evaluation of the ride comfort at this time. In terms of evaluation, the sum of the five-level evaluations of 10 drivers (from 1 to 5 points, the higher the score, the better) was calculated and evaluated by indexing using the following formula. The higher the number, the better the ride comfort at low temperatures.

[0325] Ride comfort at low temperature = [(total evaluation value of the test tire) / (total evaluation value of Comparative Example 1)] × 100

[0326] (3) High-speed driving handling stability evaluation test

[0327] Each test tire is mounted on all wheels of a vehicle (Japanese FF car, displacement 2000cc), and the vehicle is driven at a speed of 80 km / h on a dry asphalt test route to measure the lap time for evaluation. Based on the difference in lap time with a separately prepared reference tire, the following formula is used for indexation and evaluation. The larger the value, the better the handling characteristics and the better the handling stability.

[0328] Handling stability = [(lap time of test tire - lap time of reference tire) / (lap time of comparative example 1 - lap time of reference tire)] × 100

[0329] (4) Evaluation results

[0330] The results of the low-temperature ride comfort and high-temperature handling stability evaluation tests are shown in Tables 2 and 3. A comprehensive evaluation was then performed based on the sum of the two indices.

[0331] [Table 2-1]

[0332]

[0333] and

[0334] [Table 2-2]

[0335]

[0336] [Table 3]

[0337]

[0338] As can be seen from Tables 2 and 3, when the land-sea ratio is greater than 55% and less than 85%, and when |20℃tanδ-50℃tanδ| in the tread rubber composition is greater than 0.01 and less than 0.15, and |5℃tanδ-20℃tanδ| is greater than 0.15 and less than 0.70, both the ride comfort at low temperatures and the handling stability at high speeds exceed the index of 100, and the comprehensive evaluation results show that a tire having both ride comfort at low temperatures and handling stability at high speeds can be provided. When |20℃tanδ-50℃tanδ| is greater than 0.08 and less than 0.12, and |5℃tanδ-20℃tanδ| is greater than 0.30 and less than 0.40, it is shown that a tire having both ride comfort at low temperatures and handling stability at high speeds can be provided.

[0339] [2] Experiment 2

[0340] 1. Experimental Methods

[0341] Tires were manufactured and evaluated in the same manner as in Experiment 1, except that the number of circumferential main grooves was set to 1, 2, 3, or 4, and the difference in the average value of the ground contact area per unit length in the tire circumferential direction of the regions divided by the circumferential main grooves (average tread area) was changed to the value shown in Table 4. The tread rubber used was a rubber composition of Formulation 2, and the land-sea ratio was fixed to 80%.

[0342] 2. Evaluation results

[0343] The evaluation results are shown in Table 4. In this experiment, the evaluation was performed with the results of the tire of Example 16 as a reference (evaluation value: 100), unlike Experiment 1 in which the evaluation results were evaluated with the results of the tire of Comparative Example 1 as a reference.

[0344] [Table 4]

[0345]

[0346] As can be seen from Table 4, if the number of circumferential main grooves is one or more, ride comfort at low temperatures and handling stability at high speeds can be achieved. In addition, when the number is three or more and the difference in average tread area is 15% or less, a higher level of ride comfort at low temperatures and handling stability at high speeds can be achieved.

[0347] [3] Experiment 3

[0348] 1. Experimental Methods

[0349] Next, tires were produced and evaluated in the same manner except that four circumferential main grooves (two central main grooves and two shoulder main grooves) were provided, and the groove width of the shoulder main grooves, the position of the groove width center (the ratio of the distance from the tread contact edge to the contact width), and the area ratio of the central land area to the entire land area of ​​the tire contact area were changed to those shown in Table 5. Formulation 5 was used for the tread rubber.

[0350] 2. Evaluation results

[0351] The evaluation results are shown in Table 5. In this experiment, the evaluation was performed using the results of the tire of Example 26 as a reference (evaluation value: 100); unlike Experiment 1 in which the evaluation was performed using the results of the tire of Comparative Example 1 as a reference.

[0352] [Table 5]

[0353]

[0354] It can be seen from Table 5 that when the groove width of the shoulder main groove is greater than 4 mm and less than 20 mm, the center of the groove width is located on the central side of the 25% width position from the ground contact end of the tread, and the area ratio of the central land area is greater than 40%, a higher level of ride comfort at low temperatures and handling stability during high-speed driving can be achieved.

[0355] [4] Experiment 4

[0356] 1. Experimental Methods

[0357] Next, tires having a two-layer tread structure (wherein the cap rubber layer and the base rubber layer have different formulations) were manufactured and evaluated in the same manner as shown in Table 6. The number of circumferential main grooves was 4, and the land-sea ratio was 80%.

[0358] 2. Evaluation results

[0359] The evaluation results are shown in Table 6. In Table 6, rubber hardness (JIS A hardness) is also shown, which is measured by pressing an A-type durometer on the sample from the contact surface side at 23° C. in accordance with JIS K6253 using hardness measurement samples cut from the cap rubber layer and the base rubber layer. In this experiment, the evaluation was performed using the results of the tire of Example 28 as a reference (evaluation value: 100); this is different from Experiment 1 in which the evaluation results of the tire of Comparative Example 1 were used as a reference for evaluation.

[0360] [Table 6]

[0361]

[0362] It can be seen from Table 6 that when the tread surface is composed of a cap rubber layer and a base rubber layer, the hardness of the cap rubber layer is higher than the hardness of the base rubber layer, and the JIS A hardness is greater than 45 and less than 75, a higher level of ride comfort at low temperatures and handling stability during high-speed driving can be achieved.

[0363] [5] Experiment 5

[0364] 1. Experimental Methods

[0365] In the above experiments 1 to 4, the tire size was fixed to 175 / 80R16 and the experiments were performed. 2 ×π / 4) / Wt, and the evaluation was performed in the same manner. The tread rubber used was a rubber composition of recipe 2, the number of circumferential main grooves was fixed at 4, the land-sea ratio was fixed at 80%, and the average tread area difference was fixed at 20%. In addition, in each test tire, the above (L 80 / L0) is set to 0.5, and the total volume of the lateral grooves including the lateral grooves having a groove width / groove depth of 0.65 is set to 3.5% of the volume of the tread portion.

[0366] 2. Evaluation results

[0367] The evaluation results are shown in Table 7. In this experiment, the evaluation was performed using the results of the tire of Comparative Example 8 as a reference (evaluation value: 100); unlike Experiment 1 in which the evaluation was performed using the evaluation results of the tire of Comparative Example 1 as a reference.

[0368] [Table 7]

[0369]

[0370] It can be seen from Table 7 that when the land-sea ratio is greater than 55% and less than 85% and the number of circumferential main grooves is more than one, when 1963.4≦(Dt 2 ×π / 4) / Wt≦2827.4, indicating that riding comfort at low temperatures and handling stability at high speeds can be achieved. At this time, when (Dt-2×Ht) is 470 (mm) or more, a higher level of riding comfort at low temperatures and handling stability at high speeds can be achieved.

[0371] Although the present invention has been described above based on the embodiment, the present invention is not limited to the above-mentioned embodiment. Various modifications can be made to the above-mentioned embodiment within the scope of the same and equivalent to the present invention.

Claims

1. A pneumatic radial tire for a passenger vehicle, the pneumatic radial tire comprising a carcass and a tread, the carcass having radially arranged cords and spanning a pair of bead portions in a ring shape, and the tread being arranged on the tire radial outer side of the carcass, wherein: When the tire is mounted on a standard rim and the internal pressure is the standard internal pressure, the cross-sectional width of the tire is Wt (mm) and the outer diameter is Dt (mm), the tread satisfies 1963.4≤(Dt 2 ×π / 4) / Wt≤2827, and The tread running surface has at least one main groove extending in the circumferential direction of the tread. The land-to-sea ratio in the tread surface is greater than 55% and less than 85%, wherein the land-to-sea ratio is the ratio of the total surface area of ​​the contact portion on the tread surface to the area of ​​the entire groove bottom surface; and For the loss tangent (tan δ) of the rubber composition forming the tread measured under the conditions of a frequency of 10 Hz, an initial strain of 2% and a dynamic strain rate of 1%, |20℃tanδ-50℃tanδ| is greater than 0.08 and less than 0.12, |5℃tanδ-20℃tanδ| is greater than 0.30 and less than 0.40, and The tread is divided into a central land area and two shoulder land areas by a pair of shoulder main grooves extending continuously in the circumferential direction of the tire across a center line passing through the axis of the tread pattern, and has a plurality of lateral grooves extending axially along the tire, and the total volume of the plurality of lateral grooves is 2.0% to 5.0% of the volume of the tread.

2. The pneumatic radial tire for a passenger vehicle according to claim 1, wherein: The tread is divided into four or more regions in the tire axial direction by three or more main grooves and a pair of ground contact ends, and In each of the four or more regions, a difference in average tread area per unit length in the tire circumferential direction is 15% or less.

3. The pneumatic radial tire for a passenger vehicle according to claim 1 or 2, wherein: The tread is divided into a central land region and two shoulder land regions by a pair of shoulder main grooves extending continuously in the tire circumferential direction across a center line passing through the axis of the tread pattern. The width of the shoulder main groove is greater than 4 mm and less than 20 mm, and the center of the groove width is located at the center side of the 25% width position from the tread ground contact end; and The central land portion area accounts for more than 40% of the entire land portion area of ​​the tire contact patch.

4. The pneumatic radial tire for a passenger vehicle according to claim 1 or 2, wherein: The tread is composed of a cap rubber layer constituting the running surface of the tread and a base rubber layer located inside the cap rubber layer. The cap rubber layer has a higher hardness than the base rubber layer, and a JIS A hardness of greater than 45 and less than 75.

5. The pneumatic radial tire for a passenger vehicle according to claim 1 or 2, wherein: The rubber composition forming the tread contains 35% by mass or more of a diene rubber as a rubber component; and The rubber component contains 35 parts by mass or more of a rubber having a BET specific surface area greater than 140 m 2 / g and less than 250m 2 / g of silica.

6. The pneumatic radial tire for a passenger vehicle according to claim 1 or 2, wherein: The central land region is provided with lateral grooves and / or lateral sipes extending in a direction across the land region.

7. The pneumatic radial tire for a passenger vehicle according to claim 1 or 2, wherein: When the outer diameter of the tire is Dt (mm) and the cross-sectional height of the tire is Ht (mm), and the tire is mounted on a standard rim and the internal pressure is 250 kPa, (Dt-2×Ht) is 470 (mm) or more.

8. The pneumatic radial tire for a passenger vehicle according to claim 1 or 2, wherein: The aspect ratio is 40% or more.

9. The pneumatic radial tire for a passenger vehicle according to claim 8, wherein: The aspect ratio is 45% or more.

10. The pneumatic radial tire for a passenger vehicle according to claim 9, wherein: The aspect ratio is 47.5% or more.

11. The pneumatic radial tire for a passenger vehicle according to claim 10, wherein: The aspect ratio is 50% or more.

12. The pneumatic radial tire for a passenger vehicle according to claim 1 or 2, wherein: The groove width L at a depth of 80% of the maximum depth of the main groove extending in the circumferential direction of the tread is 80 The ratio of the width L0 of the main groove on the ground contact surface (L 80 / L0) is 0.3 to 0.

7.

13. The pneumatic radial tire for a passenger vehicle according to claim 1, wherein: At least one of the lateral grooves has a groove width / groove depth of 0.50 to 0.

80.

14. The pneumatic radial tire for a passenger vehicle according to claim 1 or 2, wherein: When the tire is mounted on a standard rim and the internal pressure is 250 kPa, when the outer diameter of the tire is Dt (mm), Dt is less than 685 (mm).

15. The pneumatic radial tire for a passenger vehicle according to claim 1 or 2, wherein: The cross-sectional width Wt (mm) is less than 205 mm.

16. The pneumatic radial tire for a passenger vehicle according to claim 15, wherein: The cross-sectional width Wt (mm) is less than 200 mm.

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