Pneumatic tire

Abstract

The present invention provides a pneumatic tire in which the rolling resistance is sufficiently reduced during high-speed driving, while having sufficiently improved chipping resistance (anti-chipping property). A pneumatic tire having a tread portion, at least one rubber layer forming the tread portion contains a rubber component and carbon black, the rubber component contains isoprene rubber, styrene-butadiene rubber and butadiene rubber, and relative to 100 parts by mass of the rubber component, the carbon black is more than 5 parts by mass and 25 parts by mass or less; when the cross-sectional width of the tire is Wt (mm), the outer diameter is Dt (mm) and the volume of the space occupied by the tire is the virtual volume V (mm 3 ) in the state where the tire is mounted on a standard rim and the internal pressure is 250 kPa, the tire satisfies the following (Equation 1) and (Equation 2): 1700 ≦ (Dt 2 × π / 4) / Wt ≦ 2827.4 (Equation 1).

Description

Technical Field

[0001] The present disclosure relates to pneumatic tires. Background Art

[0002] In recent years, from the viewpoint of growing concerns about environmental issues and economic efficiency, the demand for automotive fuel efficiency has been increasing, and there is also a strong demand for improving the fuel efficiency of pneumatic tires (hereinafter simply referred to as "tires") installed in automobiles.

[0003] The fuel efficiency of a tire can be evaluated by rolling resistance, and it is known that the smaller the rolling resistance, the better the fuel efficiency of the tire.

[0004] Therefore, conventionally, it has been proposed to reduce the rolling resistance by designing the formulation of the rubber composition constituting the tread portion of the tire (for example, Patent Documents 1 to 4).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: JP2018-178034A

[0008] Patent Document 2: JP2019-089911A

[0009] Patent Document 3: WO2018 / 186367A

[0010] Patent Document 4: JP2019-206643A Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] However, it cannot be said that the rolling resistance of the tires manufactured by the above conventional techniques is sufficiently reduced during high-speed driving, and further reduction is still required. Moreover, it cannot be said that these tires have sufficient chipping resistance.

[0013] Therefore, an object of the present disclosure is to provide a pneumatic tire in which the rolling resistance during high-speed driving is sufficiently reduced and its chipping resistance is sufficiently improved.

[0014] Means for Solving the Problems

[0015] The inventors of the present invention conducted intensive studies to solve the above problems, found that the above problems can be solved by the following-described solution, and thus completed the present invention.

[0016] The solution of the present invention is as follows:

[0017] A pneumatic tire having a tread portion, wherein

[0018] At least one of the rubber layers forming the tread surface portion contains a rubber component and carbon black. The rubber component includes an isoprene rubber, a styrene-butadiene rubber, and a butadiene rubber. With respect to 100 parts by mass of the rubber component, the carbon black is more than 5 parts by mass and 25 parts by mass or less; and when the sectional width of the tire is Wt (mm), the outer diameter is Dt (m), and the volume of the space occupied by the tire is a virtual volume V (mm 3 ), and the tire is mounted on a standard rim and the internal pressure is 250 kPa, the tire satisfies the following (Equation 1) and (Equation 2):

[0019] 1700 ≦ (Dt 2 × π / 4) / Wt ≦ 2827.4 (Equation 1)

[0020] [(V + 1.5 × 10 7 ) / Wt] ≦ 2.88 × 10 5 (Equation 2)

[0021] Effects of the present invention

[0022] According to the present disclosure, a pneumatic tire can be provided which has a sufficiently reduced rolling resistance during high-speed driving and a sufficiently improved crack resistance. Detailed embodiments

[0023] [1] Features of the tire of the present disclosure

[0024] First, the features of the tire of the present disclosure will be described.

[0025] 1. Overview

[0026] The tire of the present disclosure is characterized in that at least one of the rubber layers forming the tread surface portion is formed of a rubber composition containing a rubber component and carbon black. The rubber component includes an isoprene rubber, a styrene-butadiene rubber, and a butadiene rubber. With respect to 100 parts by mass of the rubber component, the carbon black is more than 5 parts by mass and 25 parts by mass or less.

[0027] The tire of the present disclosure is further characterized in that when the sectional width of the tire is Wt (mm), the outer diameter is Dt (m), and the volume of the space occupied by the tire is a virtual volume V (mm 3 ), and the tire is mounted on a standard rim and the internal pressure is 250 kPa, the tire satisfies the following (Equation 1) and (Equation 2):

[0028] 1700 ≦ (Dt 2 × π / 4) / Wt ≦ 2827.4 (Equation 1)

[0029] [(V + 1.5 × 10 7 ) / Wt] ≦ 2.88 × 105 (Formula 2)

[0030] The physical properties of the rubber composition forming the tread portion and the shape of the tire have the above characteristics, so that a tire can be provided which has a sufficiently reduced rolling resistance during high-speed driving and a sufficiently improved resistance to chunking and tearing.

[0031] In the above description, the "standard rim" is the rim defined 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), it is the standard rim of the applicable size described in the "JATMA YEARBOOK"; 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 (The Tire and Rim Association, Inc.), it is the "Design Rim" described in the "YEAR BOOK". For tires not specified in the standard, it refers to the rim that can be assembled and maintain the internal pressure, that is, the rim that will not cause air leakage between the rim and the tire, has the smallest rim diameter, and then the narrowest rim width.

[0032] In addition, the outer diameter Dt of the tire is the outer diameter of the tire mounted on the standard rim, having an internal pressure of 250 kPa and in an unloaded state. The cross-sectional width Wt (mm) of the tire is the width of the tire mounted on the standardized rim, having an internal pressure of 250 kPa and in an unloaded state, and is the distance obtained by removing the patterns and letters etc. on the tire side from the linear distance (total width of the tire) between the sidewalls including all the patterns and letters etc. on the tire side.

[0033] In addition, the virtual area V (mm 3 ) of the tire can be specifically calculated by the following formula:

[0034] V = [(Dt / 2) 2 - {(Dt / 2) - Ht} 2 × π × Wt

[0035] wherein, the outer diameter Dt (mm) of the tire, the cross-sectional height of the tire (the distance from the bottom of the bead to the outermost surface of the tread; 1 / 2 of the difference between the outer diameter of the tire and the nominal rim diameter) Ht (mm), and the cross-sectional width Wt (mm) of the tire are the corresponding parameters of the tire in the state where the tire is mounted on the standard rim, the internal pressure is 250 kPa and no load is applied.

[0036] 2. Effect manifestation mechanism in the tire of the present disclosure

[0037] The effect manifestation mechanism in the tire of the present disclosure, that is, the mechanism for sufficiently reducing the rolling resistance and sufficiently improving the durability during high-speed driving, is speculated as follows.

[0038] (1) Tire shape

[0039] As described above, in the present disclosure, the sectional width Wt (mm) and the outer diameter Dt (mm) of the tire are set to satisfy 1700 ≦ (Dt 2 × π / 4) / Wt ≦ 2827.4 (Equation 1).

[0040] Relative to the sectional width Wt of the tire, by increasing [(Dt / 2) 2 × π) = (Dt 2 × π / 4)], that is, the area when observing the tire from the side, to satisfy the numerical range specified in Equation 1, the repeated deformation per unit time is reduced. As a result, the time available for heat exchange increases, thereby improving the heat release performance of the side portion, and the friction between the tread portion and the road surface can be reduced, and thus it is considered that low rolling resistance can be achieved. In (Equation 1), (Dt 2 × π / 4) / Wt is further preferably 1735 or more, further preferably 1737 or more, further preferably 1749 or more, further preferably 1751 or more, further preferably 1753 or more, further preferably 1758 or more, further preferably 1760 or more, further preferably 1787 or more, further preferably 1801 or more, further preferably 1818 or more, further preferably 1853 or more, further preferably 1856 or more, further preferably 1864 or more, further preferably 1865 or more, further preferably 1963.5 or more, further preferably 2008 or more, further preferably 2010 or more, further preferably 2015 or more, further preferably 2016 or more, further preferably 2018 or more, and further preferably 2131 or more.

[0041] However, if the tread portion of such a tire slips on a rough road surface such as sand, the force applied to the tread surface becomes more severe than before, and cracking may occur.

[0042] In addition, since the centrifugal force during rolling increases during high-speed driving, there is a risk that the tire radius will increase significantly during rolling, and the force applied to the tread when slipping will become more severe. In addition, in such a high-speed driving state, the tread portion becomes round and the amount of deformation increases, so there is room for further improvement in reducing the rolling resistance during high-speed driving.

[0043] Therefore, in the present disclosure, the virtual area V (mm 3) and the cross-sectional width Wt (mm) satisfy [(V + 1.5×10 7 ) / Wt] ≦ 2.88×10 5 (Equation 2).

[0044] Thus, the virtual area V of the tire is reduced according to the reduction of the cross-sectional width of the tire, the volume of the tire itself is reduced, thereby reducing the increase in the outer diameter caused by centrifugal force, suppressing the increase in the outer diameter during rolling, and the force applied to the tread during sliding can be reduced, and thus it is considered that the occurrence of cracking can be suppressed. In addition, when driving at high speed, the deformation of the tread portion into a circular shape is suppressed, and the rolling resistance during high-speed driving is also improved. In addition, by suppressing the increase in the outer diameter, the weakening of the tread portion can be suppressed, and the damage resistance of the tread portion can be improved.

[0045] [(V + 1.5×10 7 ) / Wt] is further preferably 2.87×10 5 or less, more preferably 2.86×10 5 or less, more preferably 2.79×10 5 or less, more preferably 2.60×10 5 or less, more preferably 2.58×10 5 or less, more preferably 2.54×10 5 or less, more preferably 2.50×10 5 or less, more preferably 2.47×10 5 or less, more preferably 2.42×10 5 or less, more preferably 2.26×10 5 or less, more preferably 2.25×10 5 or less, more preferably 2.24×10 5 or less, more preferably 2.21×10 5 or less, more preferably 2.20×10 5 or less, more preferably 2.19×10 5 or less, more preferably 2.18×10 5 or less, and more preferably 2.16×10 5 or less.

[0046] At this time, it is more preferably [(V + 2.0×10 7 ) / Wt] ≦ 2.88×10 5 (Equation 3), and further preferably [(V + 2.5×10 7 ) / Wt] ≦ 2.88×10 5 (Equation 4).

[0047] The above [(V + 2.0×107 ) / Wt] is further preferably 2.83×10 5 Hereinafter, it is further preferably 2.79×10 5 Hereinafter, it is further preferably 2.77×10 5 Hereinafter, it is further preferably 2.75×10 5 Hereinafter, it is further preferably 2.64×10 5 Hereinafter, it is further preferably 2.47×10 5 Hereinafter, it is further preferably 2.46×10 5 Hereinafter, it is further preferably 2.45×10 5 Hereinafter, and it is further preferably 2.44×10 5 Hereinafter.

[0048] Furthermore, [(V + 2.5×10 7 ) / Wt] is further preferably 2.86×10 5 Hereinafter, it is further preferably 2.75×10 5 Hereinafter, it is further preferably 2.74×10 5 Hereinafter, it is further preferably 2.73×10 5 Hereinafter, it is further preferably 2.71×10 5 Hereinafter, it is further preferably 2.70×10 5 Hereinafter, it is further preferably 2.69×10 5 Hereinafter, and it is further preferably 2.68×10 5 Hereinafter.

[0049] (2) Rubber composition for forming tread portion

[0050] In the present disclosure, at least one of the rubber layers forming the tread portion is made of a rubber composition containing isoprene rubber, styrene-butadiene rubber, and butadiene rubber as rubber components. As a result, any of the three rubber layers can form an island-phase microstructure, and thus it is considered that the force inside the tread can be reduced.

[0051] Furthermore, in the rubber composition of the tread portion, the content of carbon black is more than 5 parts by mass and 25 parts by mass or less, that is, 1 / 4 or less of the rubber components. As a result, it is possible to prevent carbon in the rubber layer from forming a three-dimensional network, and like the island phase, it is possible to slow down the entry of external force, and at the same time, sufficient reinforcement can be obtained.

[0052] As a result, it is considered that rolling resistance and chipping resistance can be achieved simultaneously on rough roads without deteriorating heat generation.

[0053] [2] More preferred embodiments of the tire of the present disclosure.

[0054] By adopting the following embodiments, the tires of the present disclosure can achieve greater effects.

[0055] 1. Aspect ratio

[0056] The tires of the present disclosure are preferably tires having an aspect ratio of 40% or more. Thus, it is considered that slippage on rough roads can be reduced because the contact area increases due to flexure when the tire contacts the ground. In addition, by reducing the heat generation contribution in the tread portion, the deformation of the tire can be generated uniformly throughout the tire, sufficiently reducing the total heat generated by the tire. As a result, the rolling resistance during high-speed driving can be further reduced.

[0057] When the internal pressure is 250 kPa, the above aspect ratio (%) can be obtained using the sectional height Ht (mm) and sectional width Wt (mm) of the tire by the following formula.

[0058] (Ht / Wt)×100 (%)

[0059] The aspect ratio is more preferably 44% or more, further preferably 45% or more, further preferably 47.5% or more, further preferably 48% or more, further preferably 49% or more, further preferably 50% or more, further preferably 52.5% or more, further preferably 55% or more, further preferably 57% or more, and further preferably 59% or more. There is no specific upper limit. However, for example, it is 100% or less.

[0060] 2. Relationship between carbon black content and sectional width

[0061] As the sectional width Wt becomes smaller, the force applied per unit area to the tread portion during rolling becomes larger, and chipping is likely to occur. Then, the present inventors considered that if the compounding amount of carbon black increases with the size of the sectional width Wt and the product of the sectional width Wt and the compounding amount of carbon black is maintained above a certain level, the reinforcing property of the tread portion is enhanced according to the sectional width Wt, and the chipping resistance is improved. Examining the relationship between the compounding amount (parts by mass) of carbon black CB and the sectional width Wt of the tire, it was found that if CB×Wt≥900 (Equation 5) is satisfied, the chipping resistance can be controlled according to the width.

[0062] The above CB×Wt is more preferably 1056 or more, further preferably 1062 or more, further preferably 1098 or more, further preferably 1176 or more, further preferably 1200 or more, further preferably 1212 or more, further preferably 1362 or more, further preferably 1368 or more, further preferably 1374 or more, further preferably 1456 or more, further preferably 1500 or more, further preferably 1608 or more. Further preferably 1800 or more, further preferably 2655 or more, further preferably 2985 or more, further preferably 3465 or more, further preferably 4425 or more, further preferably 4950 or more, and further preferably 5650 or more.

[0063] 3. Tread groove

[0064] The tire of the present disclosure has a circumferential groove that continuously extends in the circumferential direction of the tire in the tread portion. The ratio (L 80 / L0) of the groove width L80 at a depth of 80% of the maximum depth of the circumferential groove to the groove width L0 of the circumferential groove on the ground contact surface of the tread portion is preferably 0.3 to 0.7. As a result, the movement of the entire land portion on the bottom surface of the land portion of the tread portion can be suppressed, and thus it is considered that the occurrence of cracking of the tread portion can be suppressed. 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. The circumferential groove may be a groove that continuously extends in the circumferential direction of the tire, and non-linear grooves such as serrated grooves and wavy grooves are also included in the circumferential groove.

[0065] In a state where the tire is mounted on a standard rim, the internal pressure is 250 kPa, and no load is applied, the above L0 and L80 respectively refer to the straight-line distance (L0) between the groove edges on the tread surface portion of the circumferential groove of the tire and the minimum distance (L 80 ) between the groove wall portions at a position where the groove depth is 80%.

[0066] Simply put, they can be obtained by pressing the bead portion of a cross-section with a width of 2 to 4 cm cut out in the radial direction according to the rim width.

[0067] Preferably, the tread portion has a plurality of circumferential grooves, and the total cross-sectional area of the plurality of circumferential grooves is 10% to 30% of the cross-sectional area of the tread portion. This is considered to be able to suppress the movement of the tread portion and suppress the occurrence of cracking of the tread portion. It is more preferably 15 to 27%, further preferably 18 to 25%, and particularly preferably 21 to 23%.

[0068] The cross-sectional area of the circumferential grooves refers to the total area formed by the straight line connecting the ends of the circumferential grooves on the tread and the groove walls in a tire mounted on a standard rim, having an internal pressure of 250 kPa and in an unloaded state. Simply put, they can be obtained by squeezing the bead portion of a cross-section with a width of 2 to 4 cm cut radially according to the rim width.

[0069] In addition, the tread portion preferably has a plurality of lateral grooves extending in the tire axial direction, and the total volume of the plurality of lateral grooves is 2.0 to 5.0% of the volume of the tread portion. This is considered to suppress the movement of the tread portion and suppress the occurrence of tread cracking. It is more preferably 2.2 to 4.0%, further preferably 2.5 to 3.5%, and particularly preferably 2.7 to 3.0%.

[0070] The volume of the above-mentioned lateral grooves refers to the total volume formed by the surface connecting the ends of the lateral grooves and the groove walls in a tire mounted on a standard rim, having an internal pressure of 250 kPa and in an unloaded state. Simply put, it can be obtained by calculating the volume of each lateral groove and multiplying it by the number of grooves in a state where the bead portion of a cross-section with a width of 2 to 4 cm cut radially is squeezed according to the rim width.

[0071] In addition, the volume of the tread portion can be calculated by calculating the area obtained by removing the lateral groove portion from the above cross-section, multiplying it by the outer diameter, and then obtaining the difference between the result of the above calculation and the volume of the lateral grooves.

[0072] In order to suppress the occurrence of tread cracking and further improve durability, it is preferable that the groove width ratio (Gw / Gd), that is, the ratio of the groove width Gw to the groove depth Gd, of at least one of these lateral grooves is 0.50 to 0.80. This ratio is more preferably 0.53 to 0.77, further preferably 0.55 to 0.75, and particularly preferably 0.60 to 0.70.

[0073] The groove width and groove depth of the above-mentioned lateral grooves refer to the maximum length of the straight line connecting the tread ends of the lateral grooves in a state where the tire internal pressure is 250 kPa and no load is applied, and the straight line is perpendicular to the groove direction and the maximum depth of the lateral grooves respectively. Simply put, it can be calculated in a state where the bead portion of a cross-section with a width of 2 to 4 cm cut in the radial direction is squeezed according to the rim width.

[0074] 4. Tire Shape

[0075] In the tire of the present disclosure, when the tire is mounted on a standard rim and the internal pressure is 250 kPa, the specific outer diameter Dt (mm) is preferably, for example, 515 mm or more, more preferably 558 mm or more, further preferably 585 mm or more, further preferably 649 mm or more, further preferably 658 mm or more, further preferably 663 mm or more, further preferably 664 mm or more, further preferably 665 mm or more, further preferably 672 mm or more, and most preferably 673 mm or more.

[0076] On the other hand, it is preferably less than 843 mm, more preferably 734 mm or less, further preferably less than 725 mm, further preferably 718 mm or less, further preferably 717 mm or less, further preferably 716 mm or less, further preferably 713 mm or less, further preferably 710 mm or less, further preferably less than 707 mm, further preferably 693 mm or less, further preferably 691 mm or less, further preferably less than 685 mm, further preferably 684 mm or less, further preferably 680 mm or less, further preferably 679 mm or less, and further preferably 674 mm or less.

[0077] 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, still more preferably 176 mm or more, still more preferably 177 mm or more, still more preferably 182 mm or more, still more preferably 183 mm or more, and even more preferably 185 mm, and most preferably 193 mm or more in terms of volume.

[0078] On the other hand, it is preferably less than 305 mm, more preferably less than 245 mm, further preferably 231 mm or less, further preferably 229 mm or less, further preferably 228 mm or less, further preferably 227 mm or less, further preferably 226 mm or less, further preferably 225 mm or less, further preferably less than 210 mm, further preferably less than 205 mm, further preferably 202 mm or less, further preferably 201 mm or less, further preferably 200 mm or less, further preferably less than 200 mm, further preferably 199 mm or less, further preferably 198 mm or less, and further preferably 196 mm or less.

[0079] Specific cross-sectional height Ht (mm) is preferably, for example, 37 mm or more, more preferably 69 mm or more, further preferably 70 mm or more, further preferably 78 mm or more, further preferably 79 mm or more, further preferably 80 mm or more, further preferably 87 mm or more, further preferably 88 mm or more, further preferably 90 mm or more, further preferably 95 mm or more, further preferably 96 mm or more, further preferably 98 mm or more, and further preferably 99 mm or more.

[0080] On the other hand, it is preferably less than 180 mm, more preferably 117 mm or less, further preferably 113 mm or less, further preferably less than 112 mm, further preferably 105 mm or less, further preferably 101 mm or less, and further preferably less than 101 mm.

[0081] Specific virtual area V is preferably, for example, 13,000,000 mm 3 or more, more preferably 23,005,355 mm 3 or more, further preferably 23,471,373 mm 3 or more, further preferably 23,510,297 mm 3 or more, further preferably 28,431,992 mm 3 or more, further preferably 28,526,824 mm 3 or more, further preferably 29,000,000 mm 3 or more, further preferably 29,087,378 mm 3 or more, further preferably 30,152,956 mm 3 or more, further preferably 30,354,118 mm 3 or more, further preferably 34,331,262 mm 3 or more, further preferably 35,417,448 mm 3 or more, further preferably 35,785,417 mm 3 or more, further preferably 36,000,000 mm 3 or more, further preferably 36,015,050 mm 3 or more, further preferably 36,203,610 mm 3 or more, and further preferably 37,040,131 mm 3 or more.

[0082] On the other hand, it is preferably less than 66,000,000 mm 3 , more preferably 50,043,281 mm 3Hereinafter, it is further preferably less than 44,000,000 mm 3 , and it is further preferably 43,478,150 mm 3 Hereinafter, it is further preferably 42,618,582 mm 3 Hereinafter, it is further preferably 40,161,995 mm 3 Hereinafter, and it is further preferably less than 38,800,000 mm 3 .

[0083] Furthermore, in the present disclosure, considering the stability of riding comfort during driving, (Dt - 2×Ht) is preferably 450 mm or more, more preferably 457 mm or more, further preferably 470 mm or more, further preferably 480 mm or more, further preferably 482 mm or more, and further preferably 483 mm or more.

[0084] On the other hand, considering the deformation of the tread surface, it is preferably less than 560 mm, more preferably 559 mm or less, further preferably 558 mm or less, further preferably 534 mm or less, further preferably 533 mm or less, further preferably less than 530 mm, further preferably less than 510 mm, further preferably 508 mm or less, and further preferably 507 mm or less.

[0085] 5. Tan delta

[0086] In addition, in the tire of the present disclosure, the tan delta (30°C tanδ) of the tread rubber layer measured under the conditions of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is preferably less than 0.150, more preferably 0.147 or less. As a result, heat generation of the tread surface can be reduced, and a remarkable effect is exhibited in reducing the rolling resistance during high-speed driving.

[0087] The 30°C tanδ preferably satisfies (30°C tanδ / Td)×100≥2.00 (Equation 7), where Td (mm) is the rubber layer thickness of the tread layer in the radial direction of the tire. More preferably, it satisfies (30°C tanδ / Td)×100≥2.50 (Equation 8), and further preferably satisfies (30°C tanδ / Td)×100≥3.00 (Equation 9).

[0088] More specifically, (30°C tanδ / Td)×100 is more preferably 2.24 or more, further preferably 2.41 or more, further preferably 2.47 or more, further preferably 2.50 or more, further preferably 2.53 or more, further preferably 2.63 or more, further preferably 2.68 or more, further preferably 3.11 or more, further preferably 3.15 or more, further preferably 3.16 or more, further preferably 3.27 or more, further preferably 3.74 or more, further preferably 3.75 or more, and further preferably 4.30 or more.

[0089] By maintaining the 30°C tanδ relative to the tread thickness Td at a value above a certain level in this manner, the force applied to the tread portion from the road surface can be reduced, thereby improving the crack resistance.

[0090] The measurement of the above-mentioned 30°C tanδ is performed on the rubber cut from at least the radially outer side of the bottom of the groove of the tire, preferably from the radially outer side at half the depth of the deepest circumferential groove. Specifically, for example, it is measured using the "Eplexor (registered trademark)" viscoelastic measurement device manufactured by GABO.

[0091] When the tread portion is formed of a plurality of rubber layers, with the innermost layer being the base rubber layer and the other layers being the cap rubber layers, this rubber composition can be used as the cap rubber layer. In the cap rubber layer, it is particularly preferred to use it as the outermost rubber layer.

[0092] [3] Embodiments

[0093] Hereinafter, the present disclosure will be specifically described based on the embodiments.

[0094] 1. Rubber composition for forming the tread portion

[0095] The rubber composition for forming the tread portion of the tire of the present disclosure can be obtained by appropriately adjusting the types and amounts of various additive materials, such as the rubber component, filler, softener, vulcanizing agent, and vulcanization accelerator described below.

[0096] (1) Rubber component

[0097] In the present embodiment, the rubber component can use a composition containing isoprene rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR), and nitrile rubber (NBR). By making the rubber component a three-component system in this way, a microstructure in which any one of the three rubber phases is the above-mentioned island phase can be formed.

[0098] (a) Isoprene rubber

[0099] From the viewpoint of obtaining good low heat build-up property and durability during high-speed driving, the content (total content) of the isoprene rubber in 100 parts by mass of the rubber component is preferably more than 5 parts by mass, more preferably more than 7.5 parts by mass. On the other hand, from the viewpoint of wet grip performance, it is preferably less than 20 parts by mass, more preferably less than 15 parts by mass. The isoprene rubber includes natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR, etc.

[0100] For NR, for example, SIR20, RSS#3, TSR20, etc., which are common in the tire industry, can be used. IR is not particularly limited, and for example, IR 2200, etc., which are common in the tire industry, can be used. The modified NR includes deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc. The modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber, etc. The modified IR includes epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber, etc. These can be used alone or in combination of two or more.

[0101] (b) SBR

[0102] From the viewpoint of wet grip performance, the content of SBR in 100 parts by mass of the rubber component is, for example, preferably more than 30 parts by mass, more preferably more than 35 parts by mass. On the other hand, from the viewpoint of heat build-up during high-speed driving, it is preferably less than 55 parts by mass, more preferably less than 50 parts by mass. The weight-average molecular weight of SBR is, for example, more than 100,000 and less than 2 million. From the viewpoint of obtaining good wet grip performance, the styrene content of SBR is, for example, preferably more than 5 mass%, more preferably more than 10 mass%, and particularly preferably more than 20 mass%. On the other hand, from the viewpoints of heat build-up and durability during high-speed driving, it is preferably less than 50 mass%, more preferably less than 40 mass%, and particularly preferably less than 35 mass%. The vinyl bonding amount (1,2-bonded butadiene unit amount) of SBR is, for example, more than 5 mass% and less than 70 mass%. The structure identification (measurement of styrene content and vinyl bonding amount) of SBR can be carried out using, for example, the JNM-ECA series equipment produced by JEOL Ltd.

[0103] SBR is not particularly limited, and for example, emulsion polymerization styrene-butadiene rubber (E-SBR) and solution polymerization styrene-butadiene rubber (S-SBR), etc., can be used. SBR can be unmodified SBR or modified SBR.

[0104] The modified SBR can be any SBR having functional groups that interact with fillers such as silica. Examples thereof include end-modified SBR (end-modified SBR having the above functional groups at the ends), wherein at least one end of the SBR is modified with a compound having the above functional groups (modifying agent); backbone-modified SBR having the above functional groups in the backbone, backbone-end-modified SBR having the above functional groups in the backbone and at the ends (for example, backbone-end-modified SBR having the above functional groups in the backbone and having at least one end modified with the above modifying agent); and end-modified SBR modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and introducing epoxy groups or hydroxyl groups.

[0105] Examples of the functional groups include amino group, amide group, silyl group, alkoxysilyl group, isocyanate group, imino group, imidazole group, ureido group, ether group, carbonyl group, oxycarbonyl group, mercapto group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazino group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group, hydroxyl group, oxy group, and epoxy group. In addition, these functional groups may have substituents.

[0106] In addition, for the modified SBR, for example, SBR modified with a compound (modifying agent) represented by the following formula can be used.

[0107] [Chemical formula 1]

[0108]

[0109] In the formula, R 1 , R 2 and R 3 represent the same or different alkyl groups, alkoxy groups, silanyloxy groups, acetal groups, carboxyl groups (-COOH), mercapto groups (-SH) or their derivatives. R 4 and R 5 are the same or different and represent a hydrogen atom or an alkyl group. R 4 and R 5 may combine to form a ring structure having a nitrogen atom. n represents an integer.

[0110] For the modified SBR modified with the compound represented by the above formula (modifying agent), solution-polymerized styrene-butadiene rubber (S-SBR) modified with the compound represented by the above formula at the polymerization terminal (active terminal) can be used (for example, the modified SBR described in JP-A-2010-111753).

[0111] As R 1 , R 2 and R 3 , an alkoxy group (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms) is preferred. As R 4and R 5 , preferably an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms). n is preferably from 1 to 5, more preferably from 2 to 4, and particularly preferably 3. Further, when R 4 and R 5 combine with the nitrogen atom to form a ring structure, a 4- to 8-membered ring is preferred. The alkoxy group also includes cycloalkoxy groups (e.g., cyclohexyloxy) and aryloxy groups (e.g., phenoxy and benzyloxy).

[0112] Specific examples of the above modifiers include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane. These can be used alone or in combination of two or more.

[0113] In addition, as the modified SBR, modified SBR modified with the following compounds (modifiers) can also be used. Examples of the modifiers include polyglycidyl ethers of polyhydric alcohols, such as ethylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenolic groups, such as diglycidylated bisphenol A; polyepoxides, such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxy liquid polybutadiene; tertiary amines containing epoxy groups, such as 4,4'-diglycidyl-diphenylmethanamine, and 4,4'-diglycidyl-dibenzylmethanamine; diglycidylamino compounds, such as diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline, diglycidyl-o-toluidine, tetraglycidyl-m-xylidine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, and tetraglycidyl-1,3-bis(aminomethyl)cyclohexane; acyl chlorides containing amino groups, such as bis-(1-methylpropyl)carbamic acid hydrochloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamyl chloride, and N,N-diethylcarbamic acid hydrochloride; silane compounds containing epoxy groups, such as 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane, and (3-glycidyloxypropyl)-pentamethyldisiloxane; silane compounds containing sulfide groups, 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; N-substituted aziridine compounds, such as ethyleneimine and propyleneimine; alkoxysilanes, such as methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, and N,N-bis(trimethylsilyl)aminoethyltriethoxysilane;(Thio)benzophenone compounds having an amino group and / or a substituted amino group, such as 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; benzaldehyde compounds having an amino group and / or a substituted amino group, such as 4-N,N-dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde, and 4-N,N-divinylaminobenzaldehyde; N-substituted pyrrolidones, such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-tert-butyl-2-pyrrolidone, and N-methyl-5-methyl-2-pyrrolidone; N-substituted piperidones, such as N-methyl-2-piperidone, N-vinyl-2-piperidone, and N-phenyl-2-piperidone; 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 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-dimethylvinylurea, 1,3-divinylurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophenone, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-acetone, and 1,7-bis(methylethylamino)-4-heptanone. The above compounds (modifiers) can be used for modification by known methods.;

[0114] For SBR, for example, SBR produced and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used. SBR can be used alone or in combination of two or more kinds.

[0115] (c) BR

[0116] From the viewpoint of abrasion resistance, the content of BR in 100 parts by mass of the rubber component is, for example, preferably more than 35 parts by mass, more preferably more than 40 parts by mass. On the other hand, from the viewpoint of rolling resistance during high-speed driving, the content is preferably less than 55 parts by mass, more preferably less than 50 parts by mass. The weight-average molecular weight of BR is, for example, more than 100,000 and less than 2,000,000. The vinyl bond content of BR is, for example, more than 1% and less than 30%. The cis content of BR is, for example, more than 1% and less than 98%. The trans content of BR is, for example, more than 1% and less than 60%.

[0117] BR is not particularly limited, and BR with a high cis content (more than 90% of the 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 the modified BR includes modified BR into which the above functional groups are introduced. These can be used alone or in combination of two or more. The cis content can be measured by infrared absorption spectrometry.

[0118] For BR, for example, products of UBE Corporation, JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used.

[0119] (d) Other rubber components

[0120] In addition, as another rubber component, the rubber composition may contain rubbers (polymers) commonly used in tire production, such as nitrile rubber (NBR).

[0121] (2) Composite materials other than rubber components

[0122] (a) Filler

[0123] In the present embodiment, the rubber composition preferably contains a filler. The specific filler in the present embodiment is carbon black, and if necessary, it may contain silica, graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, etc. When using silica, it is preferably used together with a silane coupling agent.

[0124] (a-1) Carbon black

[0125] In the present embodiment, relative to 100 parts by mass of the rubber component, the rubber composition contains more than 5 parts by mass and 25 parts by mass or less of carbon black. The content of carbon black is more preferably 6 parts by mass or more, more preferably more than 10 parts by mass, and particularly preferably 15 parts by mass or more. Thus, as described above, the formation of a three-dimensional network of carbon in the rubber layer can be prevented, and the force applied to the tread surface can be reduced in the same manner as the island phase formed by the rubber component, while sufficient reinforcement can be obtained.

[0126] The nitrogen adsorption specific surface area (N2SA) of the carbon black is, for example, greater than 30 m 2 / g and less than 250 m 2 / g. The dibutyl phthalate (DBP) absorption of the 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 the carbon black is measured according to ASTM D4820-93, and the DBP absorption is measured according to ASTM D2414-93.

[0127] The carbon black is not particularly limited, and examples thereof include furnace black (furnace carbon black), such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black (acetylene carbon black); thermal black (thermal carbon black), such as FT and MT; and channel black (channel carbon black), such as EPC, MPC, and CC. These may be used alone or in combination of two or more.

[0128] The specific carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercial products include, for example, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsui Chemicals, Inc., Lion Corporation, Shin Nikka Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like. These may be used alone or in combination of two or more.

[0129] (a-2) Silica

[0130] If necessary, the rubber composition preferably contains silica. From the viewpoint of obtaining good durability performance, the BET specific surface area of the silica is preferably greater than 140 m 2 / g, more preferably greater than 160 m 2 / g. On the other hand, from the viewpoint of obtaining good rolling resistance during high-speed driving, it is preferably less than 250 m 2 / g, and more preferably less than 220 m 2 / g. Further, from the viewpoint of obtaining good durability performance, the content of silica is preferably more than 35 parts by mass, more preferably more than 40 parts by mass, still more preferably more than 45 parts by mass, still more preferably 47 parts by mass or more, and still more preferably 49 parts by mass or more, relative to 100 parts by mass of the rubber component. On the other hand, from the viewpoint of obtaining good rolling resistance during high-speed driving, it is preferably less than 85 parts by mass, more preferably 84 parts by mass or less, still more preferably 82 parts by mass or less, still more preferably 69 parts by mass or less, and still more preferably 67 parts by mass. The above BET specific surface area is the N2SA value measured by the BET method according to ASTM D3037-93.

[0131] Examples of silica include dry silica (anhydrous silica) and wet silica (hydrous silica). Among them, wet silica is preferred because it has a large number of silanol groups.

[0132] For silica, for example, products of Degussa, Rhodia, Tosoh silicone Corporation, Solvay Japan Co., Ltd., Tokuyama Corporation, etc. can be used.

[0133] (a-3) Silane coupling agent

[0134] The rubber composition preferably contains a silane coupling agent and silica. The silane coupling agent is not particularly limited. Examples of the silane coupling agent include sulfur-based silane coupling agents 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)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-dimethylthio tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide;

[0135] Mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z produced by Momentive;

[0136] Vinyl-based silane coupling agents, such as vinyltriethoxysilane and vinyltrimethoxysilane;

[0137] Amino-based silane coupling agents, such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane;

[0138] Glycidyl-based silane coupling agents, such as γ-glycidylpropyltriethoxysilane and γ-glycidylpropyltrimethoxysilane;

[0139] Nitro-based silane coupling agents, such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and

[0140] Chlorine-containing silane coupling agents, such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These can be used alone or in combination of two or more.

[0141] For silane coupling agents, for example, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Toray Dow Corning Co., Ltd. etc. can be used.

[0142] Relative to 100 parts by mass of silica, the content of the silane coupling agent is, for example, more than 3 parts by mass and less than 25 parts by mass, more preferably 10 parts by mass or more.

[0143] (a-4) Other fillers

[0144] In addition to the above carbon black and silica, the rubber composition may further contain fillers commonly used in the tire industry, such as graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide and mica. Relative to 100 parts by mass of the rubber component, these contents are, for example, more than 0.1 part by mass and less than 200 parts by mass.

[0145] (b) Plasticizer

[0146] The rubber composition may contain oil (including filled oil) and liquid rubber etc. as plasticizers. Relative to 100 parts by mass of the rubber component, the content of the plasticizer is preferably more than 10 parts by mass, more preferably more than 20 parts by mass, further preferably more than 25 parts by mass. On the other hand, it is preferably less than 50 parts by mass, more preferably less than 40 parts by mass, further preferably less than 35 parts by mass. The content of the oil also includes the amount of oil contained in the oil-extended rubber.

[0147] Examples of oils include mineral oils (commonly referred to as processing oils), vegetable oils and fats, or mixtures thereof. For mineral oils (processing oils), for example, paraffin processing oils, aromatic processing oils, naphthenic processing oils, etc. can be used. Examples of vegetable oils and fats include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, benihana 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.

[0148] Examples of processing oils (mineral oils) include products of Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Nippon Energy Corporation, Olisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., and Fuji Kogyo Co., Ltd.

[0149] Liquid rubber as a softener is a polymer that is liquid at room temperature (25 °C) and is a polymer composed of monomers similar to solid rubber. Examples of liquid rubbers include farnesene-based polymers, liquid diene-based polymers, and their hydrides.

[0150] Farnesene-based polymers are polymers obtained by polymerizing farnesene and have farnesene-based structural units. Farnesene includes its 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).

[0151] Farnesene-based polymers can be homopolymers of farnesene (farnesene homopolymers) or copolymers of farnesene and vinyl monomers (farnesene-vinyl monomer copolymers).

[0152] Examples of liquid diene polymers include liquid styrene-butadiene copolymers (liquid SBR), liquid butadiene polymers (liquid BR), liquid isoprene polymers (liquid IR), and liquid styrene-isoprene copolymers (liquid SIR).

[0153] The weight-average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) of liquid diene polymers is, for example, greater than 1.0×10 3 and less than 2.0×10 5 . In this specification, the Mw of liquid diene polymers is the polystyrene conversion value measured by gel permeation chromatography (GPC).

[0154] For liquid rubber, for example, products of Kuraray Co., Ltd. and Clay Valley Co., Ltd. can be used.

[0155] (c) Resin component

[0156] In addition, the rubber composition preferably contains a resin component. The resin component can be solid or liquid at room temperature. Specific resin components include styrene resins, coumarone resins, terpene resins, C5 resins, C9 resins, C5C9 resins, and acrylic resins, etc. Two or more resin components can be used in combination. With respect to 100 parts by mass of the rubber component, the content of the resin component is preferably more than 2 parts by mass, more preferably 5 parts by mass or more. On the other hand, it is preferably less than 10 parts by mass, more preferably less than 6 parts by mass.

[0157] A styrene resin is a polymer using styrene monomer as a constituent monomer. Examples thereof include polymers obtained by polymerizing styrene monomer as a main component (50% by mass or more). Specifically, it includes homopolymers obtained by polymerizing styrene monomer alone (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene, etc.), copolymers obtained by copolymerizing two or more styrene monomers, and in addition, copolymers obtained by copolymerizing styrene monomer and other monomers copolymerizable with styrene monomer.

[0158] Examples of other monomers include acrylonitrile, 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, and isoprene; olefins, such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids, such as maleic anhydride and its acid anhydride.

[0159] For coumarone resins, coumarone-indene resins are preferably used. Coumarone-indene resins are resins containing coumarone and indene as monomer components constituting the resin skeleton (main chain). In addition to coumarone and indene, examples of monomer components contained in the skeleton include styrene, α-methylstyrene, methyl indene, and vinyltoluene.

[0160] With respect to 100 parts by mass of the rubber component, the content of the coumarone-indene resin is, for example, more than 1.0 part by mass and less than 50.0 parts by mass.

[0161] The hydroxyl value (OH value) of the coumarin-indene resin is, for example, greater than 15 mg KOH / g and less than 150 mg KOH / g. The OH value is the amount of potassium hydroxide, expressed in milligrams, required to neutralize the acetic acid combined with the hydroxyl groups when 1 g of the resin is acetylated. The OH value is a value measured by potentiometric titration (JIS K 0070:1992).

[0162] The softening point of the coumarin-indene resin is, for example, higher than 30 °C and lower than 160 °C. The softening point refers to the temperature at which the ball drops when the softening point defined in JIS K 6220-1:2001 is measured using a ring and ball softening point measuring device.

[0163] 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 hydrocarbons having the composition (C5H8) or their oxygen-containing derivatives, which are compounds having a basic skeleton classified as monoterpenes (C n H 10 ), sesquiterpenes (C 16 H 15 ), diterpenes (C 24 H 20 ), etc. Examples of terpene compounds include α-pinene, β-pinane, dipentene, limonene, myrcene, isolongifolene, octene, α-phellandrene, α-terpinene, γ-terpinene, turpentine, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol. 32 ) etc. Examples of polyterpenes include terpene resins made from the above terpene compounds, such as α-pinene resin, β-pinane resin, limonene resin, dipentene resin, and β-pinene / limonene resin, and hydrogenated terpenes obtained by hydrogenating terpene resins. Examples of terpene phenols include resins obtained by copolymerizing the above terpene compounds and phenolic compounds, and resins obtained by hydrogenating the above resins. Specifically, resins obtained by condensing the above terpene compounds, phenol compounds, and formalin can be mentioned. Examples of phenol compounds include phenol, bisphenol A, cresol, and xylenol. 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 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, alkylphenols, alkoxyphenols, and phenols containing unsaturated hydrocarbon groups; naphthol compounds such as naphthol, alkylnaphthols, alkoxynaphthols, and naphthols containing unsaturated hydrocarbon groups; styrene derivatives such as styrene, alkylstyrenes, alkoxystyrenes, and styrenes containing unsaturated hydrocarbon groups; coumarin and indene.

[0164]

[0165] ​C5 resin refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. For C5-based petroleum resins, dicyclopentadiene resin (DCPD resin) is preferably used.

[0166] C9 resin refers to the resin obtained by polymerizing C9 fraction, which can be hydrogenated or modified. The example of C9 fraction includes petroleum fractions with 8 to 10 carbon atoms, such as vinyl toluene, alkyl styrene, indene and methyl indene. For specific examples, coumarin-indene resin, coumarin resin, indene resin and aromatic vinyl resin are preferably used. For aromatic vinyl resin, preferably alpha-methylstyrene or homopolymer of styrene or copolymer of alpha-methylstyrene and styrene, because it is economical, easy to process and excellent in heating. More preferably, copolymer of alpha-methylstyrene and styrene. As aromatic vinyl resin, for example, products purchased from Clayton and Eastman (Eastman) Chemical, etc. can be used.

[0167] C5C9 resin refers to a resin obtained by copolymerizing C5 fraction and C9 fraction, and may be hydrogenated or modified. C5 fraction and C9 fraction include the above-mentioned petroleum fraction. For C5C9 fraction, for example, those purchased from Tosoh Co., Ltd. and LUHUA, etc., can be used.

[0168] The acrylic resin is not particularly limited, and for example, a solvent-free acrylic resin can be used.

[0169] As for the solvent-free acrylic resin, there can be mentioned (meth)acrylic resin (polymer) synthesized by high temperature continuous polymerization (high temperature continuous block polymerization: US 4414370B, JP 84-6207A, JP 93-58805A, JP 89-313522A, US 5010166B, Toa Synthetic Research Annual Report TREND 2000, Vol. 3, pp. 42-45, etc.), and polymerization initiator, chain transfer agent, organic solvent, etc. are not used as auxiliary raw materials as much as possible. In the present invention, (meth)acrylic acid refers to methacrylic acid and acrylic acid.

[0170] Examples of the monomer components 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.

[0171] In addition, as the monomer components constituting the acrylic resin, aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene can be used together with (meth)acrylic acid or (meth)acrylic acid derivatives.

[0172] The acrylic resin may be a resin composed only of (meth)acrylic acid components, or a resin having components other than (meth)acrylic acid components. In addition, the acrylic resin may have hydroxyl groups, carboxyl groups, silanol groups, etc.

[0173] For the resin components, for example, 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., Co., Ltd., Nippon Catalyst Co., Ltd., JX Energy Co., Ltd., Arakawa Chemical Industry Co., Ltd., and Tago Chemical Industry Co., Ltd. can be used.

[0174] (d) Antioxidant

[0175] 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, more preferably 3 parts by mass or more, relative to 100 parts by mass of the rubber component.

[0176] Examples of the antioxidant include naphthylamine-based antioxidants such as naphthyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine-based antioxidants such as N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine; quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based antioxidants such as 2,6-di-tert-butyl-4-methylphenol and styrenated phenol; bis-, tris-, and polyphenol-based 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.

[0177] For the antioxidant, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., and Flexsys Co., Ltd. can be used.

[0178] (e) Stearic acid

[0179] The rubber composition may contain stearic acid. With respect to 100 parts by mass of the rubber component, the content of stearic acid is, for example, more than 0.5 part by mass and less than 10.0 parts by mass. For stearic acid, conventionally known stearic acid can be used, and, for example, products of NOF Corporation, NOF Corporation, Kao Corporation, FUJIFILM Wako Pure Chemical Corporation, and Chiba Fatty Acid Co., Ltd. etc. can be used.

[0180] (f) Zinc oxide

[0181] The rubber composition may contain zinc oxide. With respect to 100 parts by mass of the rubber component, the content of zinc oxide is, for example, more than 0.5 part by mass and less than 10 parts by mass. For zinc oxide, conventionally known zinc oxide can be used, for example, products of Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Shirakawa Tech Co., Ltd., Shoindo Chemical Industry Co., Ltd., and Sakai Chemical Industry Co., Ltd. etc. can be used.

[0182] (g) Wax

[0183] The rubber composition preferably contains wax. With respect to 100 parts by mass of the rubber component, the content of wax is, for example, 0.5 to 20 parts by mass, preferably 1.0 to 15 parts by mass, more preferably 1.5 to 10.0 parts by mass.

[0184] The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant wax and animal wax; and synthetic waxes such as polymers of ethylene or propylene. These can be used alone or in combination of two or more.

[0185] For wax, for example, products of Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Moritomo Chemical Co., Ltd. can be used.

[0186] (h) Crosslinking agent and vulcanization accelerator

[0187] The rubber composition preferably contains a crosslinking agent such as sulfur. With respect to 100 parts by mass of the rubber component, the content of the crosslinking agent is, for example, more than 0.1 part by mass and less than 10.0 parts by mass, more preferably 1.5 parts by mass or more.

[0188] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, and soluble sulfur commonly used in the rubber industry. These can be used alone or in combination of two or more.

[0189] For sulfur, for example, products from Karizawa Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Corporation, Flexsys Co., Ltd., Nippon Karyu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0190] Examples of crosslinking agents other than sulfur include sulfur-containing vulcanizing agents such as Tackirol V200 produced by Taoka Chemical Industry Co., Ltd., DURALINK HTS (1,6 - hexamethylene - disodium dithiocarbamate dihydrate) produced by Flexsys, and KA9188 (1,6 - bis(N,N'-dibenzylthiocarbamoyl disulfide)) produced by Lanxess; and organic peroxides such as dicumyl peroxide.

[0191] 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, more preferably 3 parts by mass or more, relative to 100 parts by mass of the rubber component.

[0192] Examples of vulcanization accelerators include

[0193] Thiazole - based vulcanization accelerators such as 2 - mercaptobenzothiazole, di - 2 - benzothiazolyl disulfide, and N - cyclohexyl - 2 - benzothiazole sulfenamide;

[0194] Thiuram - based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetra(2 - ethylhexyl)thiuram disulfide (TOT - N);

[0195] Sulfenamide - based vulcanization accelerators such as N - cyclohexyl - 2 - benzothiazole sulfenamide, N - tert - butyl - 2 - benzothiazole sulfenamide, N - oxyethylene - 2 - benzothiazole sulfenamide, N - oxyethylene - 2 - benzothiazole sulfenamide, and N,N'-diisopropyl - 2 - benzothiazole sulfenamide; and guanidine - based vulcanization accelerators such as diphenylguanidine, di - o - tolylguanidine, and o - tolylbiguanide. These can be used alone or in combination of two or more.

[0196] (i) Others

[0197] In addition to the above components, the rubber composition may further contain additives commonly used in the tire industry, such as fatty acid metal salts, carboxylic acid metal salts, and organic peroxides. 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.

[0198] 2. Preparation of tread rubber composition

[0199] A rubber composition is produced by a conventional method. For example, the manufacturing method includes a basic 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 basic kneading step with a crosslinking agent.

[0200] Kneading can be carried out using a known (sealed) kneader, such as a Banbury mixer, a kneader or an open roll.

[0201] The kneading temperature in the basic kneading step is, for example, higher than 50 °C and lower than 200 °C, and the kneading time is, for example, longer than 30 seconds and shorter than 30 minutes. In the basic kneading step, in addition to the above components, compounding agents commonly used in the rubber industry can be appropriately added and kneaded as needed, such as softeners like oil, stearic acid, zinc oxide, anti-aging agents, waxes and vulcanization accelerators.

[0202] In the final kneading step, the kneaded product obtained in the basic kneading step and the crosslinking agent are kneaded. The kneading temperature in the final kneading step is, for example, higher than room temperature and lower than 80 °C, and the kneading time is, for example, longer than 1 minute and shorter than 15 minutes. In the final kneading step, in addition to the above components, vulcanization accelerators and zinc oxide etc. can be appropriately added and kneaded as needed.

[0203] 3. Tire manufacturing

[0204] The tire of the present invention is made of the unvulcanized rubber composition obtained from the final kneading step by a conventional method. That is, the unvulcanized rubber composition is extruded according to the shape of the tread and formed together with other tire members on a tire molding machine by a conventional method to produce an unvulcanized tire.

[0205] Specifically, on a forming drum, an inner liner (as a member for ensuring the airtightness of the tire), a carcass (as a member for bearing the load and impact on the tire), and a belt (as a member for strongly tightening the carcass to increase the tread rigidity) etc. are wound, the two ends of the carcass are fixed to the both side edge portions, and a bead portion (as a member for fixing the tire to a rim) is arranged to form a ring shape. Then the tread is pasted on the center of the outer circumference, and a sidewall portion (as a member for protecting the carcass and resisting bending) is pasted on the radially outer side to produce an unvulcanized tire.

[0206] In the present embodiment, as the belt, an inclined belt layer extending at an angle of 15° to 30° with respect to the tire circumferential direction is preferably provided. Thereby, the durability of the tire can be ensured, and at the same time, the rigidity of the tread can be sufficiently maintained. In addition, since the tire is restricted in the circumferential direction, it is easy to suppress the growth of the outer diameter.

[0207] Then, the unvulcanized tire produced is heated and pressurized in a vulcanizer to obtain a tire. The vulcanization step can be carried out 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.

[0208] At this time, the tire is formed into a shape that satisfies the above (Equation 1) and (Equation 2) when mounted on a standard rim and the internal pressure is set to the standardized internal pressure.

[0209] Specific tires that can satisfy the above (Equation 1) and (Equation 2) include tires with size symbols such as 145 / 60R18, 145 / 60R19, 155 / 55R18, 155 / 55R19, 155 / 70R17, 155 / 70R19, 165 / 55R20, 165 / 55R21, 165 / 60R19, 165 / 65R19, 165 / 70R18, 175 / 55R19, 175 / 55R20, 175 / 55R22, 175 / 60R18, 185 / 55R19, 185 / 60R20, 195 / 50R20, and 195 / 55R20.

[0210] In the present embodiment, the tire that can satisfy (Equation 1) and (Equation 2) is preferably applicable to a pneumatic tire for a passenger car. Satisfying the above various equations can be more conducive to solving the problem of the present disclosure, that is, providing a pneumatic tire with a sufficiently reduced rolling resistance during high-speed driving and a sufficiently improved resistance to cracking (resistance to chunking).

[0211] Examples

[0212] Hereinafter, the present disclosure will be described more specifically with reference to examples.

[0213] [Experiment 1]

[0214] In this experiment, tires of size 175 were prepared and evaluated.

[0215] 1. Manufacture of rubber composition for tread

[0216] First, a rubber composition for tread was produced. 1) Compounding agents

[0217] First, various compounding agents shown below were prepared.

[0218] (a) Rubber components

[0219] (a-1) NR: TSR20

[0220] (a-2) SBR: Modified solution-polymerized SBR was produced according to the method described in the next paragraph (styrene content: 30% by mass, vinyl bond content: 52% by mass, Mw: 250,000)

[0221] (a-3)BR-1: UBEPOL-BR360B manufactured by Ube Industries, Ltd. (cis content: 98% by mass)

[0222] (a-4)BR-2: N103 manufactured by Asahi Kasei Chemicals Corporation (cis content: 35% by mass)

[0223] The above SBR is produced according to the following steps. First, cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene are charged into a high-pressure autoclave reactor purged with nitrogen. After adjusting the temperature of the reactor contents to 20°C, n-butyllithium is added to initiate polymerization. Polymerization is carried out under adiabatic conditions, and the maximum temperature reaches 85°C. When the polymerization conversion rate reaches 99%, 1,3-butadiene is added, and then polymerization is further carried out for 5 minutes. Thereafter, 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 through a heating roll adjusted to 110°C to obtain SBR.

[0224] (b) Additive materials other than rubber components

[0225] (b-1) Carbon black: Show Black N134 (N2SA: 134 m 2 / g) manufactured by Cabot Japan Co., Ltd.

[0226] (b-2) Silica: Ultrasil VN3 (BET specific surface area: 165 m 2 / g) manufactured by Evonik

[0227] (b-3) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Degussa

[0228] (b-4) Oil: Process X-140 manufactured by Japan Energy Corporation

[0229] (b-5) Resin: SYLVATRAXX 4401 (α-methylstyrene resin) manufactured by Arizona Chemical Co.

[0230] (b-6) Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd.

[0231] (b-7) Anti-aging agent-1: Nocrac 6C (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0232] (b-8) Anti-aging agent - 2: Nocrac 224 (2,2,4-trimethyl-1,2-dihydroquinoline polymer) produced by Ouchi Shinsei Chemical Industry Co., Ltd.

[0233] (b-9) Crosslinking agent and vulcanization accelerator

[0234] Sulfur: Powder sulfur produced by Tsurumi Chemical Industry Co., Ltd.

[0235] Vulcanization accelerator - 1: Nocceler NS (N-tert-butyl-2-benzothiazolesulfenamide) produced by Ouchi Shinsei Chemical Industry Co., Ltd.

[0236] Vulcanization accelerator - 2: Nocceler DPG (1,3-diphenylguanidine) produced by Ouchi Shinsei Chemical Industry Co., Ltd.

[0237] (2) Preparation of rubber composition

[0238] According to the formulations shown in Table 1 and Table 2, materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 150 °C using a Banbury mixer to obtain a kneaded product. Each compounding amount is in parts by mass.

[0239] 2. Tire manufacturing

[0240] Next, sulfur and vulcanization accelerator were added to the obtained kneaded material, and the mixture was kneaded for 5 minutes at 80 °C using an open roll to obtain a tread rubber composition. The obtained tread rubber composition was used to form a tread, which was bonded to other tire components to form an unvulcanized tire, and then it was pressure-vulcanized at 170 °C for 10 minutes to fabricate each test tire of size 175 (Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-7).

[0241] 3. Parameter calculation

[0242] After that, for each test tire, the thickness Td (mm), outer diameter Dt (mm), cross-sectional width Wt (mm), cross-sectional height Ht (mm) and flatness ratio (%) of the rubber layer of the tread portion, as well as the virtual area V (mm 3 ) were obtained.

[0243] Meanwhile, a rubber test piece for viscoelasticity measurement was fabricated by cutting out a piece with a length of 20 mm × width of 4 mm × thickness of 2 mm from the rubber layer of the tread portion of each test tire, with the circumferential direction of the tire as the long side. For each rubber test piece, tanδ (tanδ at 30 °C) was measured at 30 °C, a frequency of 10 Hz, an initial strain of 5% and a dynamic strain rate of 1% using the Eplexor series produced by GABO Co., Ltd. For test tires with the same composition, the average value of each measured value was used.

[0244] Then, calculate (Dt - 2×Ht), (Dt 2 ×π / 4) / Wt, (V + 1.5×10 7 ) / Wt, (V + 2.0×10 7 ) / Wt, (V + 2.5×10 7 ) / Wt, CB×Wt, and (30℃ tanδ / Td)×100. The results are shown in Table 1 and Table 2.

[0245] 4. Performance Evaluation Test

[0246] (1) Evaluation of Rolling Resistance during High-Speed Driving

[0247] Install each test tire on all the wheels of a vehicle (a Japanese FF vehicle with a displacement of 2000 cc), inflate the air to make the internal pressure reach 250 kPa, and then drive at a speed of 100 km / h on the test route of a dry road surface. After running one lap of 10 km, release the throttle and measure the distance from closing the throttle to the vehicle stopping as the rolling resistance during high-speed driving.

[0248] Next, set the results in Comparative Examples 1 - 5 as 100, and index the results based on the following formula to relatively evaluate the rolling resistance during high-speed driving. The larger this value is, the longer the distance from closing the throttle to the vehicle stopping, the smaller the rolling resistance in the steady state, indicating excellent fuel efficiency.

[0249] Rolling Resistance = [(Result of Test Tire) / (Result of Comparative Examples 1 - 5)]×100

[0250] (2) Evaluation of Resistance to Cracking

[0251] Install each test tire on all the wheels of a vehicle (a Japanese FF vehicle with a displacement of 2000 cc), inflate the air to make the internal pressure reach 250 kPa, and then drive at a speed of 100 km / h on the test route of a dry road surface. After running one lap of 10 km, similarly run laps on the sandy route. After finishing the laps, accumulate the number and size of the cracked blocks on the tire tread surface and calculate its reciprocal.

[0252] Then, set the calculation results in Comparative Examples 1 - 7 as 100, and relatively evaluate the durability through indexing based on the following formula. The larger the value, the smaller the number of cracked blocks and the smaller the size of the cracks, indicating excellent resistance to cracking.

[0253] Resistance to Cracking = [(Calculation Result of Test Tire) / (Calculation Result of Comparative Examples 1 - 7)]×100

[0254] (3) Comprehensive Evaluation

[0255] Add the evaluation results of (1) and (2) above to obtain a comprehensive evaluation.

[0256] (4) Evaluation results

[0257] Tables 1 and 2 list the results of each evaluation.

[0258] [Table 1]

[0259]

[0260] [Table 2]

[0261]

[0262] [Experiment 2]

[0263] In this experiment, tires of size 95 were manufactured and evaluated.

[0264] After manufacturing the test tires of Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-7 shown in Tables 3 and 4 in the same manner as in Experiment 1, the respective parameters were calculated by adopting the same procedure. Then, the performance evaluation tests were carried out and evaluated in the same manner. In this experiment, when evaluating the rolling resistance during high-speed driving, the result of Comparative Example 2-5 was set to 100, and when evaluating the crack resistance, the result of Comparative Example 2-7 was set to 100. The results of each evaluation are shown in Tables 3 and 4.

[0265] [Table 3]

[0266]

[0267] [Table 4]

[0268]

[0269] [Experiment 3]

[0270] In this experiment, tires of size 225 were manufactured and evaluated.

[0271] After manufacturing the test tires of Examples 3-1 to 3-5 and Comparative Examples 3-1 to 3-7 shown in Tables 5 and 6 in the same manner as in Experiment 1, the respective parameters were calculated by adopting the same procedure. Then, the performance evaluation tests were carried out and evaluated in the same manner. In this experiment, when evaluating the rolling resistance during high-speed driving, the result of Comparative Example 3-5 was set to 100, and when evaluating the crack resistance, the result of Comparative Example 3-7 was set to 100. The results of each evaluation are shown in Tables 5 and 6.

[0272] [Table 5]

[0273]

[0274] [Table 6]

[0275]

[0276] [Summary of Experiments 1 to 3]

[0277] From the results of Experiments 1 to 3 (Tables 1 to 6), it can be seen that for tires of any one of the sizes 175, 195, and 225, when the above (Equation 1) and (Equation 2) are satisfied, a pneumatic tire with a sufficiently reduced rolling resistance and improved crack resistance during high-speed driving can be provided.

[0278] Moreover, it can be seen that by satisfying each requirement specified in Claim 2 and subsequent claims, a tire with further improved rolling resistance and crack resistance during high-speed driving can be provided.

[0279] On the other hand, when (Equation 1) or (Equation 2) is not satisfied, the rolling resistance during high-speed driving cannot be sufficiently reduced, and the crack resistance cannot be sufficiently improved.

[0280] [Experiment 4]

[0281] Next, three tires (Examples 4-1 to 4-3) with no significant difference in the relationship between the virtual volume V and the cross-sectional width Wt were manufactured using the same formulation and evaluated in the same manner. Here, in addition to evaluating the rolling resistance and crack resistance during high-speed driving, the riding comfort was also evaluated.

[0282] Specifically, each test tire was mounted on all the wheels of a vehicle (a Japanese FF vehicle with a displacement of 2000 cc), and air was filled to make the internal pressure 250 kPa, and then it was driven on a dry road test route. The driver's sensory test evaluated the riding comfort when driving 10 laps at a speed of 100 km / h, and the score was 5 points. After summarizing the evaluations of 20 drivers, the evaluations were indexed according to the following formula. The total score in Example 4-3 was 100, and the riding comfort was relatively evaluated. The larger the value, the better the riding comfort.

[0283] Riding comfort = [(Total evaluation score of the test tire) / (Total evaluation score of Example 4-3)] × 100

[0284] Then, as in Experiments 1 to 3, the respective evaluation results were added up to obtain a comprehensive evaluation. The results of each evaluation are shown in Table 7.

[0285] [Table 7]

[0286]

[0287] Table 7 shows that when there is no significant difference in the relationship between the virtual volume V and the cross-sectional width Wt, as the cross-sectional width Wt changes from less than 205 mm to less than 200 mm and as the aspect ratio increases, both the rolling resistance and durability during high-speed driving are improved. That is to say, significant effects can be seen.

[0288] The present disclosure has been described based on the embodiments, but the present disclosure is not limited to the above embodiments. Various modifications can be made to the above embodiments within the same and equivalent scope as the present disclosure.

[0289] The present disclosure (1) is:

[0290] A pneumatic tire having a tread surface, wherein,

[0291] At least one of the rubber layers forming the tread surface contains a rubber component and carbon black, the rubber component contains isoprene rubber, styrene-butadiene rubber, and butadiene rubber, and the carbon black is greater than 5 parts by mass and 25 parts by mass or less relative to 100 parts by mass of the rubber component; when the tire is mounted on a standard rim and the internal pressure is 250 kPa, the cross-sectional width of the tire is Wt (mm), the outer diameter is Dt (m), and the volume of the space occupied by the tire is the virtual volume V (mm 3 ), the tire satisfies the following (Equation 1) and (Equation 2):

[0292] 1700≦(Dt 2 ×π / 4) / Wt≦2827.4 (Equation 1)

[0293] [(V + 1.5×10 7 ) / Wt]≦2.88×10 5 (Equation 2).

[0294] The present disclosure (2) is the tire according to the present disclosure (1), wherein the tire satisfies the following (Equation 3):

[0295] [(V + 2.0×10 7 ) / Wt]≦2.88×10 5 (Equation 3).

[0296] The present disclosure (3) is the tire according to the present disclosure (2), wherein the tire satisfies the following (Equation 4):

[0297] [(V + 2.5×10 7 ) / Wt]≦2.88×10 5 (Equation 4).

[0298] The present disclosure (4) is the pneumatic tire as described in any combination of the present disclosure (1) to (3), wherein when the outer diameter of the tire is Dt (mm) and the sectional height of the tire is Ht (mm), when the tire is mounted on a standard rim and the internal pressure is 250 kPa, (Dt - 2×Ht) is 470 (mm) or more.

[0299] The present disclosure (5) is the pneumatic tire as described in any combination of the present disclosure (1) to (4), and its aspect ratio is 40% or more.

[0300] The present disclosure (6) is the pneumatic tire as described in the present disclosure (5), and its aspect ratio is 45% or more.

[0301] The present disclosure (7) is the pneumatic tire as described in the present disclosure (6), and its aspect ratio is 47.5% or more.

[0302] The present disclosure (8) is the pneumatic tire as described in the present disclosure (7), and its aspect ratio is 50% or more.

[0303] The present disclosure (9) is the pneumatic tire as described in any combination of the present disclosure (1) to (8), wherein the loss tangent (tanδ at 30°C) of the tread rubber layer measured under the conditions of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is less than 0.15.

[0304] The present disclosure (10) is the pneumatic tire as described in any combination of the present disclosure (1) to (9), wherein the amount (parts by mass) of carbon black CB and the sectional width Wt (mm) of the tire satisfy the following (Equation 5):

[0305] CB × Wt ≥ 900 (Equation 5).

[0306] The present disclosure (11) is the pneumatic tire as described in the present disclosure (10), wherein the tire satisfies the following (Equation 6):

[0307] CB × Wt ≥ 1500 (Equation 6).

[0308] The present disclosure (12) is the pneumatic tire as described in any combination of the present disclosure (1) to (11), wherein the tread portion has a circumferential groove that continuously extends along the tire circumference, and the groove width L at a depth of 80% of the maximum depth of the circumferential groove 80 The ratio (L 80 / L0) to the groove width L0 of the circumferential groove on the ground contact surface of the tread portion is 0.3 to 0.7.

[0309] The present disclosure (13) is the pneumatic tire as described in any combination of the present disclosure (1) to (12), wherein the tread portion has a plurality of circumferential grooves that continuously extend along the tire circumference, and the total sectional area of the plurality of circumferential grooves is 10% to 30% of the sectional area of the tread portion.

[0310] The present disclosure (14) is the pneumatic tire as described in any combination of the present disclosures (1) to (13), wherein the tread surface has a plurality of transverse grooves extending in the tire axial direction, and the total volume of the plurality of transverse grooves is 2.0 to 5.0% of the volume of the tread surface.

[0311] The present disclosure (15) is the pneumatic tire as described in the present disclosure (14), wherein at least one of the transverse grooves is a transverse groove having a groove width / groove depth of 0.50 to 0.80.

[0312] The present disclosure (16) is the pneumatic tire as described in any combination of the present disclosures (1) to (15), wherein when the outer diameter of the tire is Dt (mm) in a state where the tire is mounted on a standard rim and the internal pressure is 250 kPa, Dt is less than 685 (mm).

[0313] The present disclosure (17) is the pneumatic tire as described in any combination of the present disclosures (1) to (16), wherein the sectional width Wt (mm) is less than 205 mm.

[0314] The present disclosure (18) is the pneumatic tire as described in the present disclosure (17), wherein the sectional width Wt (mm) is less than 200 mm.

[0315] The present disclosure (19) is the pneumatic tire as described in the present disclosure (18), wherein when the thickness of the rubber layer of the tread layer in the tire radial direction is Td (mm), and the loss tangent of the rubber layer measured under the conditions of 30 °C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is 30 °C tanδ, the following (Equation 7) is satisfied:

[0316] (30 °C tanδ / Td) × 100 ≥ 2.00 (Equation 7).

[0317] The present disclosure (20) is the pneumatic tire as described in the present disclosure (19), wherein the tire satisfies the following (Equation 8):

[0318] (30 °C tanδ / Td) × 100 ≥ 2.50 (Equation 8).

[0319] The present disclosure (21) is the pneumatic tire as described in the present disclosure (20), wherein the tire satisfies the following (Equation 9):

[0320] (30 °C tanδ / Td) × 100 ≥ 3.00 (Equation 9).

[0321] The present disclosure (22) is the pneumatic tire as described in any combination of the present disclosures (1) to (21), wherein the tread surface is formed of a plurality of rubber layers, and the rubber composition is used in the tread running surface rubber layer.

[0322] The present disclosure (23) is the pneumatic tire described in any combination of the present disclosures (1) to (22), which is a pneumatic tire for a passenger car.

Claims

1. An inflated tire having a tread surface, wherein, at least one of the rubber layers forming the tread surface contains a rubber composition, the rubber composition contains a rubber component and carbon black, the rubber component contains isoprene rubber, styrene-butadiene rubber and butadiene rubber, and relative to 100 parts by mass of the rubber component, the carbon black is more than 10 parts by mass and 25 parts by mass or less; and, When the cross-sectional width of the tire is Wt mm, the outer diameter is Dt mm, and the volume of the space occupied by the tire is the virtual volume V mm in the state where the tire is mounted on a standard rim and the internal pressure is 250 kPa. 3 The tire satisfies (Equation 1), (Equation 3), and (Equation 4): 1700 ≦ (Dt 2 × π / 4) / Wt ≦ 2827.4 (Equation 1) [(V + 2.0×10 7 ) / Wt] ≦ 2.44×10 5 (Equation 3) [(V + 2.5×10 7 ) / Wt] ≦ 2.88×10 5 (Equation 4); the cross-sectional width Wt mm is 176 mm or more; when the cross-sectional height of the tire is Ht mm in a state where the tire is mounted on a standard rim and the internal pressure is 250 kPa, (Dt - 2×Ht) is 470 or more; The virtual volume V mm of the tire 3 is calculated by the following formula: V = [(Dt / 2) 2 -{(Dt / 2)-Ht} 2 ×π×Wt; where the outer diameter Dt mm, the section height Ht mm, and the section width Wt mm of the tire are the corresponding parameters of the tire in the state where the tire is mounted on a standard rim, the internal pressure is 250 kPa, and no load is applied.

2. The pneumatic tire according to claim 1, wherein, the aspect ratio is 40% or more.

3. The pneumatic tire according to claim 2, wherein, the aspect ratio is 45% or more.

4. The pneumatic tire according to claim 3, wherein, the aspect ratio is 47.5% or more.

5. The pneumatic tire according to claim 4, wherein, the aspect ratio is 50% or more.

6. The inflated tire according to any one of claims 1 to 5, wherein, the loss tangent 30°C tanδ of the tread rubber layer measured under the conditions of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is less than 0.

15.

7. The inflated tire according to any one of claims 1 to 5, wherein, the amount of carbon black CB parts by mass and the cross-sectional width Wt mm of the tire satisfy the following (Equation 5): CB×Wt≧900 (Equation 5).

8. The pneumatic tire according to claim 7, wherein, The inflated tire satisfies the following (Equation 6): CB×Wt≧1500 (Equation 6).

9. The inflated tire according to any one of claims 1 to 5, wherein, The tread surface has a circumferential groove that extends continuously along the tire circumference. The groove width L at a depth of 80% of the maximum depth of the circumferential groove 80 and the ratio L 80 / L0 of the groove width L of the circumferential groove on the ground contact surface of the tread surface is 0.3 to 0.

7.

10. The inflated tire according to any one of claims 1 to 5, wherein, the tread surface has a plurality of circumferential grooves continuously extending in the tire circumferential direction, and the total cross-sectional area of the plurality of circumferential grooves is 10% to 30% of the cross-sectional area of the tread surface.

11. The inflated tire according to any one of claims 1 to 5, wherein, the tread surface has a plurality of lateral grooves extending in the tire axial direction, and the total volume of the plurality of lateral grooves is 2.0% to 5.0% of the volume of the tread surface.

12. The pneumatic tire according to claim 11, wherein, At least one of the lateral grooves is a lateral groove with a groove width / groove depth of 0.50 to 0.

80.

13. The inflated tire according to any one of claims 1 to 5, wherein, when the outer diameter of the tire is Dt mm in a state where the tire is mounted on a standard rim and the internal pressure is 250 kPa, Dt is less than 685.

14. The pneumatic tire according to any one of claims 1 to 5, wherein, The cross-sectional width Wtmm is less than 205 mm.

15. The pneumatic tire according to claim 14, wherein, The cross-sectional width Wt mm is less than 200 mm.

16. The inflated tire according to any one of claims 1 to 5, wherein, when the thickness of the rubber layer of the tread surface in the tire radial direction is Td mm and the loss tangent of the rubber layer measured under the conditions of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is 30°C tanδ, the following (Equation 7) is satisfied: (30°C tanδ / Td)×100≧2.00 (Equation 7).

17. The pneumatic tire according to claim 16, wherein, The tire satisfies the following (Equation 8): (30°C tanδ / Td)×100≧2.50 (Equation 8).

18. The pneumatic tire according to claim 17, wherein, The tire satisfies the following (Equation 9): (30°C tanδ / Td)×100≧3.00 (Equation 9).

19. The pneumatic tire according to any one of claims 1 to 5, wherein, The tread surface portion is formed of a plurality of rubber layers, and the rubber composition is used in the tread rubber layer of the tread surface portion.

20. The pneumatic tire according to any one of claims 1 to 5, wherein, The pneumatic tire is a pneumatic tire for a passenger car.

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