Pneumatic tire

Abstract

The present application provides a pneumatic tire having sufficiently improved grip and durability at high speed, whereby the pneumatic tire can exhibit excellent grip at high speed and superior durability. The pneumatic tire has a tread, and is characterized in that a ground contact surface of the tread is formed of at least two kinds of rubber compositions having different thermal conductivities, and satisfies the following formulas (1) and (2), where Wt (mm) is a cross-sectional width, Dt (mm) is an outer diameter of the tire when mounted on a standard rim and inflated to an internal pressure of 250 kPa, V (mm3) is an imaginary volume of a space occupied by the tire. 3 1700 ≦ (Dt 2 × π / 4) / Wt ≦ 2827.4 ··· (1) [(V + 1.5 x 10 7 ) / Wt] ≦ 2.88 x 10 5 ··· (2)

Description

TECHNICAL FIELD

[0001] The present application relates to a pneumatic tire. BACKGROUND

[0002] In recent years, from the viewpoint of environmental problems and economic efficiency, the demand for fuel efficiency of automobiles has been increasing, and there is a strong demand for improving the fuel efficiency of pneumatic tires (hereinafter referred to as "tires") installed on automobiles.

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

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

[0005] [Related Art Documents]

[0006] [Patent Documents]

[0007] [Patent Document 1] JP 2018-178034 A

[0008] [Patent Document 2] JP 2019-089911 A

[0009] [Patent Document 3] WO 2018 / 186367 A

[0010] [Patent Document 4] JP 2019-206643 A SUMMARY

[0011] [Problems to be Solved by the Invention]

[0012] However, although the tire manufactured with the above conventional technique can reduce the rolling resistance, it cannot be said that the grip performance and the durability at high speed running are sufficient.

[0013] Therefore, an object of the present application is to provide a pneumatic tire whose grip performance and durability at high speed running are sufficiently improved, and which can exhibit excellent grip performance and excellent durability at high speed running.

[0014] [Means for Solving the Problems]

[0015] The present inventors have earnestly studied a solution to the above problems, and found that the above problems can be solved by the following invention, and completed the present application.

[0016] The invention of Embodiment 1 is:

[0017] A pneumatic tire having a tread portion, in which

[0018] the tread portion has a ground contact surface made of at least two rubber compositions having different thermal conductivities,

[0019] 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 an imaginary volume V (mm 3 ) and when the tire is mounted on a standardized rim and the internal pressure is 250 kPa, the tire satisfies the following (Formula 1) and (Formula 2):

[0020] 1700 ≦ (Dt 2 x π / 4) / Wt ≦ 2827.4 ··· (Formula 1)

[0021] [(V + 1.5 x 10 7 ) / Wt] ≦ 2.88 x 10 5 ··· (Formula 2).

[0022] The invention of Embodiment 2 is the pneumatic tire according to Embodiment 1, wherein the following (Formula 3) is satisfied:

[0023] 1718 ≦ (Dt 2 x π / 4) / Wt ≦ 2827.4 ··· (Formula 3).

[0024] The invention of Embodiment 3 is the pneumatic tire according to Embodiment 1 or 2, wherein the following (Formula 4) is satisfied:

[0025] [(V + 2.0 x 10 7 ) / Wt] ≦ 2.88 x 10 5 ··· (Formula 4).

[0026] The invention of Embodiment 4 is the pneumatic tire according to Embodiment 3, wherein the following (Formula 5) is satisfied:

[0027] [(V + 2.5 x 10 7 ) / Wt] ≦ 2.88 x 10 5 ··· (Formula 5).

[0028] The invention of Embodiment 5 is the pneumatic tire according to any one of Embodiments 1 to 4, wherein when the outer diameter of the tire is Dt (mm) and the cross-sectional height of the tire is Ht (mm), and when the tire is mounted on a standardized rim and the internal pressure is 250 kPa, (Dt - 2 x Ht) is 470 (mm) or more.

[0029] The invention of Embodiment 6 is the pneumatic tire according to any one of Embodiments 1 to 5, which has an aspect ratio of 40% or more.

[0030] The invention of Embodiment 7 is the pneumatic tire according to Embodiment 6, which has an aspect ratio of 45% or more.

[0031] The invention of Embodiment 8 is the pneumatic tire according to Embodiment 7, which has an aspect ratio of 47.5% or more.

[0032] The invention of Embodiment 9 is the pneumatic tire according to Embodiment 8, which has an aspect ratio of 50% or more.

[0033] The invention of Embodiment 10 is the pneumatic tire according to any one of Embodiments 1 to 9, wherein, in the at least two rubber compositions having different thermal conductivities, when the thermal conductivity of the rubber composition having the highest thermal conductivity is Ka (W / m·K) and the thermal conductivity of the rubber composition having the lowest thermal conductivity is Kb (W / m·K), the following (Formula 6) is satisfied:

[0034] Ka - Kb > 0.01 ··· (Formula 6).

[0035] The invention of Embodiment 11 is the pneumatic tire according to Embodiment 10, wherein the following (Formula 7) is satisfied:

[0036] Ka - Kb > 0.05 ··· (Formula 7).

[0037] The invention of Embodiment 12 is the pneumatic tire according to any one of Embodiments 1 to 11, wherein, in the tread portion, in the at least two rubber compositions having different thermal conductivities, when the thermal conductivity of the rubber composition having the highest thermal conductivity is Ka (W / m·K) and the thermal conductivity of the rubber composition having the lowest thermal conductivity is Kb (W / m·K), the ratio Sb (%) of the contact area of the contact portion formed of the rubber composition having the thermal conductivity Kb to the total contact area is larger than the ratio Sa (%) of the contact area of the contact portion formed of the rubber composition having the thermal conductivity Ka to the total contact area, and (Sb - Sa) x Wt < 3.00 x 10 4 .

[0038] The invention of Embodiment 13 is the pneumatic tire according to Embodiment 12, wherein (Sb - Sa) x Wt < 2.50 x 10 4 .

[0039] The invention of Embodiment 14 is the pneumatic tire according to any one of Embodiments 1 to 13, wherein, in the at least two rubber compositions having different thermal conductivities, the loss tangent (30°C tan δ) measured for the rubber composition having the lowest thermal conductivity is 0.16 or less at 30°C, at a frequency of 10 Hz, at an initial strain of 5%, and at a dynamic strain of 1%.

[0040] The invention of Embodiment 15 is the pneumatic tire according to Embodiment 14, wherein the 30°C tan δ is 0.14 or less.

[0041] The invention of Embodiment 16 is the pneumatic tire according to any one of Embodiments 1 to 15, wherein the following (Formula 8) is satisfied when Td (mm) is the thickness of the tread portion:

[0042] 30°C tan δ x Td ≧ 1.5 ··· (Formula 8).

[0043] The invention of Embodiment 17 is the pneumatic tire according to Embodiment 16, wherein the following (Formula 9) is satisfied:

[0044] 30°C tan δ x Td ≧ 1.8 ··· (Formula 9).

[0045] The invention of Embodiment 18 is the pneumatic tire according to any one of Embodiments 1 to 17, wherein the tread portion has a plurality of circumferential grooves that extend continuously 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 portion.

[0046] The invention of Embodiment 19 is the pneumatic tire according to any one of Embodiments 1 to 18, wherein the tread portion has a plurality of lateral grooves that extend 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.

[0047] The invention of Embodiment 20 is the pneumatic tire according to any one of Embodiments 1 to 19, wherein Dt is less than 685 (mm), where Dt (mm) is the outer diameter of the tire when the tire is mounted on a standardized rim and the internal pressure is 250 kPa.

[0048] The invention of Embodiment 21 is the pneumatic tire according to any one of Embodiments 1 to 20, wherein the cross-sectional width Wt (mm) is less than 205 mm.

[0049] The invention of Embodiment 22 is the pneumatic tire according to Embodiment 21, wherein the cross-sectional width Wt (mm) is less than 200 mm.

[0050] The invention of Embodiment 23 is the pneumatic tire according to any one of Embodiments 1 to 22, which is a pneumatic tire for a passenger vehicle.

[0051] [Effects of the Invention]

[0052] According to the present application, it is possible to provide a pneumatic tire in which the grip performance and durability at high speed are sufficiently improved, and which can exhibit excellent grip performance and excellent durability at high speed. DETAILED DESCRIPTION

[0053] [1] Features of the tire of the present application

[0054] First, the features of the tire of the present application will be described.

[0055] 1. SUMMARY

[0056] The tire of the present application is characterized in that the ground contact surface is formed of at least two rubber compositions having different thermal conductivities.

[0057] The tire of the present application is further characterized in that, 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 an imaginary volume V (mm 3 ) and when the tire is mounted on a standardized rim and the internal pressure is 250 kPa, the tire satisfies the following (Formula 1) and (Formula 2):

[0058] 1700 ≦ (Dt 2 x π / 4) / Wt ≦ 2827.4 ··· (Formula 1)

[0059] [(V + 1.5 x 10 7 ) / Wt] ≦ 2.88 x 10 5 ··· (Formula 2).

[0060] By providing these characteristics, a pneumatic tire having excellent grip performance and durability at high speed running can be provided.

[0061] In the above description, "the ground contact surface is formed of at least two rubber compositions having different thermal conductivities" does not necessarily mean that the tread is formed of each rubber composition over the entire circumference of the contact surface of the tread portion. The tread can be formed of each rubber composition anywhere over the entire circumference. However, formation over the entire circumference is preferred.

[0062] The term "ground contact surface" means the contact surface of the tread portion when the tire is mounted on a standard rim and the internal pressure is 250 kPa, and a load of the maximum load capacity or close to that is applied.

[0063] In the above description, the "standardized rim" means the rim defined for each tire in the standard system, including the standard to which the tire conforms. For example, in the case of JATMA (Japan Automobile Tire and Rim Association), it is the standard rim of the applicable size described in the "JATMA YEAR BOOK", in the case of ETRTO (European Tyre and Rim Technical Organization), it is the "Measuring Rim" described in the "STANDARDS MANUAL", and in the case of TRA (Tire and Rim Association, Inc.), it is the "Design Rim" described in the "YEAR BOOK". For a tire for which no provision is made in the standard, it means the rim that can be assembled and can hold the internal pressure, that is, the rim that does not cause air leakage between the rim and the tire, and has the smallest rim diameter, and then the narrowest rim width.

[0064] Further, the outer diameter Dt of the tire means the outer diameter of the tire mounted on the standardized rim, with an internal pressure of 250 kPa and in a no-load state. The cross-sectional width Wt (mm) of the tire means the width of the tire mounted on the standardized rim, with an internal pressure of 250 kPa and in a no-load state, and is the distance between the tire beads excluding the patterns, letters, etc. of the sidewall from the straight-line distance (total width of the tire) including all patterns, letters, etc. of the sidewall.

[0065] Further, specifically, the imaginary volume V (mm3) of the tire can be calculated based on the outer diameter Dt (mm) of the tire, the cross-sectional height (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, in a state where the tire is mounted on the standardized rim, with an internal pressure of 250 kPa and without applying a load, by the following formula: 3 ):

[0066] V = [(Dt / 2) 2 - {(Dt / 2) - Ht} 2 ] x π x Wt.

[0067] 2. Effect manifestation mechanism in the tire of the present application

[0068] The effect manifestation mechanism of the tire of the present application, that is, the mechanism in which the grip performance and the durability performance are sufficiently exhibited at high speed, is presumed as follows.

[0069] As described above, in the present application, the cross-sectional width Wt (mm) and the outer diameter Dt (mm) of the tire are made to satisfy 1700 ≦ (Dt 2 x π / 4) / Wt ≦ 2827.4 (Formula 1) as much as possible. It is preferable to satisfy 1718 ≦ (Dt 2(Dt x π / 4) / Wt≦2827.4 (Formula 3).(Dt 2 (Dt x π / 4) is more preferably 1865 or more, further preferably 1963.5 or more, even more preferably 2018 or more.

[0070] In (Formula 1), (Dt 2 (Dt x π / 4) / Wt is more preferably 1728 or more, further preferably 1731 or more, further preferably 1745 or more, further preferably 1747 or more, further preferably 1751 or more, further preferably 1753 or more, further preferably 1763 or more, further preferably 1805 or more, further preferably 1811 or more, further preferably 1829 or more, further preferably 1833 or more, further preferably 1860 or more, further preferably 2004 or more, further preferably 2019 or more, further preferably 2021 or more, further preferably 2039 or more, and further preferably 2131 or more.

[0071] When the tire is viewed from the lateral direction, by increasing [(Dt / 2 2 (Dt x π) = (Dt 2 (Dt x π / 4)] with respect to the cross-sectional width Wt of the tire, and satisfying the numerical range specified in Formula 1, the number of repetitions of deformation per unit time decreases, and as a result, the time available for heat exchange increases, thereby improving the heat release performance of the side portion, and improving durability and low rolling resistance.

[0072] However, such a tire has a large centrifugal force during rolling, so the radius of the tire increases significantly during rolling, which can cause unevenness in the contact pressure. In particular, as the running speed increases, the centrifugal force further increases, which can cause further unevenness in the contact pressure, thereby causing a decrease in the grip performance.

[0073] Therefore, in the present application, the imaginary volume V (mm 3 ) and the cross-sectional width Wt (mm) of the tire satisfy [(V + 1.5 x 10 7 ) / Wt]≦2.88 x 10 5 (Formula 2).

[0074] Thus, by reducing the imaginary volume V of the tire according to the reduction in the cross-sectional width Wt of the tire and reducing the volume of the tire itself, the speed of the outer diameter increase due to the centrifugal force can be reduced, and it is known that uneven ground contact pressure can be suppressed.

[0075] [(V + 1.5 x 10 7 ) / Wt] is more preferably 2.87 x 10 5 Further preferably 2.85 x 10 5 Further preferably 2.80 x 105 Further preferably, 2.59 x 10 5 Further preferably, 2.55 x 10 5 Further preferably, 2.54 x 10 5 Further preferably, 2.51 x 10 5 Further preferably, 2.48 x 10 5 Further preferably, 2.41 x 10 5 Further preferably, 2.25 x 10 5 Further preferably, 2.23 x 10 5 Further preferably, 2.21 x 10 5 Further preferably, 2.20 x 10 5 Further preferably, 2.19 x 10 5 Further preferably, 2.18 x 10 5 Further preferably, 2.16 x 10 5 Further preferably, 2.15 x 10

[0076] In the present application, the contact surface of the tread portion is made of at least two rubber compositions having different thermal conductivities. Therefore, thermal flow occurs in the tread portion, so it is known that the deformation of the entire tread can be suppressed.

[0077] Based on these results, it is known that the decrease in the grip performance at high speed running can be sufficiently suppressed.

[0078] At this time, more preferably, [(V + 2.0 x 10 7 ) / Wt] < 2.88 x 10 5 (Formula 4), further preferably, [(V + 2.5 x 10 7 ) / Wt] < 2.88 x 10 5 (Formula 5).

[0079] The above [(V + 2.0 x 10 7 ) / Wt] is further preferably 2.81 x 10 5 Further preferably, 2.80 x 10 5 Further preferably, 2.79 x 10 5 Further preferably, 2.75 x 10 5 Further preferably, 2.63 x 10 5 Further preferably, 2.48 x 10 5 Further preferably, 2.47 x 10 5 Further preferably, 2.46 x 10 5 Further preferably, 2.45 x 10 5 Further preferably, 2.44 x 105 Further preferably 2.43 x 10 5 Further preferably 2.43 x 10

[0080] Further preferably 2.43 x 10 7 Further preferably 2.85 x 10 5 Further preferably 2.77 x 10 5 Further preferably 2.75 x 10 5 Further preferably 2.73 x 10 5 Further preferably 2.71 x 10 5 Further preferably 2.69 x 10 5 Further preferably 2.68 x 10 5 Further preferably 2.67 x 10 5 Further preferably 2.67 x 10

[0081] [2] More preferable embodiments of the tire of the present application

[0082] The tire of the present application can achieve greater effects by adopting the following embodiments.

[0083] 1. Aspect ratio

[0084] The tire of the present application is preferably a tire having an aspect ratio of 40% or more. Thus, the area of the side portion can be increased, the heat release performance of the entire tire can be further improved, the rigidity of the tread and the side portion can be suppressed from decreasing, and the decrease in the grip performance at high speed can be further suppressed.

[0085] When the internal pressure is 250 kPa, the aspect ratio (%) described above can be obtained using the cross-sectional height Ht (mm) and the cross-sectional width Wt (mm) of the tire by the following formula.

[0086] (Ht / Wt) x 100 (%)

[0087] 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 53% or more, further preferably 55% or more, further preferably 58% or more, and further preferably 59% or more. There is no specific upper limit, but for example, it is 100% or less.

[0088] 2. Thermal conductivity

[0089] As described above, by forming the contact surface of the tread portion with at least two kinds of rubber compositions having different thermal conductivities, heat flow can be generated within the tread portion and the deformation of the entire tread can be suppressed.

[0090] At this time, in the at least two rubber compositions having different thermal conductivities, when the thermal conductivity of the rubber composition having the highest thermal conductivity is Ka (W / m K) and the thermal conductivity of the rubber composition having the lowest thermal conductivity is Kb (W / m K), the greater (Ka - Kb) is, the more the heat flow of the contact surface of the tread portion, which is preferable because the heat dissipation can be enhanced. Specifically, Ka - Kb > 0.01 is preferable, Ka - Kb > 0.02 is more preferable, Ka - Kb > 0.05 is further preferable, Ka - Kb > 0.08 is further preferable, Ka - Kb > 0.10 is further preferable, Ka - Kb > 0.11 is further preferable, and Ka - Kb > 0.24 is further preferable. Although the upper limit of (Ka - Kb) is not particularly defined, it is preferably about 0.80.

[0091] Specifically, Ka is preferably 0.3 to 0.9 W / m K, and Kb is preferably 0.1 to 0.7 W / m K.

[0092] The thermal conductivity K (W / m K) is a value measured according to the hot wire method (measurement temperature: 23°C) prescribed in JIS R 2616. Specifically, a rapid heat meter (such as "kemtherm QTM-500" manufactured by Kyoto Electronics Industry Co., Ltd.) or a thermal conductivity measuring device (such as "TCM1001" manufactured by Lesca Corporation) can be used for the measurement.

[0093] The thermal conductivity can be adjusted by adjusting the compounding ratio of carbon black, silica, or the like in the compounding material described later. In addition, it can also be adjusted by newly compounding graphene, graphite, carbon nanofiber, or the like.

[0094] 3. Contact area of each rubber composition

[0095] It is known that the wider the tire width, the greater the contact pressure of the center portion of the tread, and the greater the difference from the contact pressure of the shoulder portion of the tread. In this case, the shoulder region of the tread can be made of a rubber composition having the highest thermal conductivity Ka. In view of the effective heat dissipation by landing, it is preferable that the center region of the tread be widely formed of a rubber composition having the thermal conductivity Ka, and the wider the tire, the more preferable it is to make the center region wider.

[0096] However, when the ratio of the contact area of the ground portion formed from the rubber composition having the highest thermal conductivity Ka to the total ground area is Sa(%) and the ratio of the contact area of the ground portion formed from the rubber composition Kb having the lowest thermal conductivity to the total ground area is Sb(%) and when S increases, it is difficult to concentrate heat, and efficient heat dissipation cannot be achieved. Sa must be smaller than Sb (about 0.1% to 30%).

[0097] More specifically, Sb-Sa is more preferably 88% or more, further preferably 90% or more, further preferably 92% or more, and further preferably 94% or more.

[0098] Therefore, when the relationship between Sa and Sb and Wt is specifically examined, it is found that (Sb-Sa) x Wt < 3.00 x 10 4 is preferred, (Sb-Sa) x Wt < 2.50 x 10 4 is more preferred, (Sb-Sa) x Wt < 2.19 x 10 4 is further preferred, (Sb-Sa) x Wt < 2.18 x 10 4 is further preferred, (Sb-Sa) x Wt < 2.17 x 10 4 is further preferred, (Sb-Sa) x Wt < 2.11 x 10 4 is further preferred, and (Sb-Sa) x Wt < 2.04 x 10 4 is further preferred.

[0099] (Sb-Sa) x Wt < 2.00 x 10 4 is further preferred, (Sb-Sa) x Wt < 1.89 x 10 4 is further preferred, (Sb-Sa) x Wt < 1.88 x 10 4 is further preferred, (Sb-Sa) x Wt < 1.85 x 10 4 is further preferred, (Sb-Sa) x Wt < 1.80 x 10 4 is further preferred, (Sb-Sa) x Wt < 1.76 x 10 4 is further preferred, (Sb-Sa) x Wt < 1.72 x 10 4 is further preferred, (Sb-Sa) x Wt < 1.67 x 10 4 is further preferred, (Sb-Sa) x Wt < 1.63 x 10 4 is further preferred, (Sb-Sa) x Wt < 1.62 x 10 4 is further preferred, and (Sb-Sa) x Wt < 1.54 x 10 4 is further preferred.

[0100] The above formulae should be satisfied when measured at any point on the circumference of the tread. It is preferable that this be satisfied throughout the circumference.

[0101] 4. Tan Delta (tan δ) of Rubber Composition

[0102] In the tire of the present application, the tan delta (30°C tan δ) measured for the rubber composition having the lowest thermal conductivity among at least two rubber compositions having different thermal conductivities, for example, is preferably 0.1 or more and 0.7 or less, and more preferably 0.16 or less, under the conditions of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1%.

[0103] Therefore, when the 30°C tan δ of the rubber composition having the lowest thermal conductivity is reduced to 0.16 or less, the heat generation of the tread portion can be reduced, and the temperature rise of the tire is suppressed. Therefore, the deterioration of the durability of the rubber composition itself and the outer diameter growth due to the temperature rise are suppressed, and the tire is prevented from being damaged, and the durability is improved. Further, it is more preferably 0.14 or less. The measurement of the 30°C tan δ is performed on the rubber cut from at least the radially outer side of the tire groove bottom, preferably from the radially outer side of half the depth of the deepest circumferential groove. Specifically, for example, a viscoelasticity measuring device of "Eplexor (registered trademark)" manufactured by GABO can be used for the measurement.

[0104] Further, when the thickness of the tread portion is Td (mm), it is preferable that 30°C tan δ x Td satisfy Formula 8, more preferably that 30°C tan δ x Td satisfy Formula 9, and further preferably that 30°C tan δ x Td satisfy 2.0. By satisfying such a formula, the effect of the present application can be more sufficiently exhibited. The thickness Td of the tread portion refers to the distance (mm) from the outermost surface of the center portion of the tread to the cord layer, and specifically, for example, is 4 mm or more and 25 mm or less.

[0105] 5. Tread Groove

[0106] The tire of the present application has a circumferential groove extending continuously in the tire circumferential direction in the tread portion. The groove width L at 80% of the maximum depth of the circumferential groove 80 The ratio (L 80 / L0) of the groove width L at 80% of the maximum depth of the circumferential groove to the groove width L0 on the ground contact surface of the tread portion is preferably 0.3 to 0.7. Therefore, 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 collapse 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.

[0107] L0 and L 80 respectively, are the linear distance between the edges of the circumferential groove on the surface of the tread of the tire at the state where the tire is mounted on a standardized rim, the internal pressure is 250 kPa, and no load is applied, and the minimum distance between the walls of the groove at the position where the groove depth is 80% (L 80 ), respectively. In brief, they can be obtained by compressing the bead portion of the section cut in the radial direction with a width of 2-4 cm in the state according to the rim width.

[0108] It is preferable that the tread portion have a plurality of circumferential grooves, and the total cross-sectional area of the plurality of circumferential grooves be 10 to 30% of the cross-sectional area of the tread portion. It is known that this makes it possible to suppress movement of the tread portion and suppress the occurrence of chipping in the tread portion. It is more preferable that it be 15 to 27%, it is further preferable that it be 18 to 25%, and it is particularly preferable that it be 21 to 23%. The circumferential grooves can be grooves that extend continuously in the tire circumferential direction, and non-linear grooves such as herringbone grooves and wavy grooves are also included in the circumferential grooves.

[0109] The cross-sectional area of the circumferential groove is the total value of the area composed of the straight line connecting the ends of the circumferential groove and the walls of the groove in the tire mounted on a standardized rim, at an internal pressure of 250 kPa and in a no-load state. In brief, they can be obtained by compressing the bead portion of the section cut in the radial direction with a width of 2-4 cm in the state according to the rim width.

[0110] Further, it is preferable that a plurality of lateral grooves extending in the tire axial direction be formed in the tread portion, and the total volume of the plurality of lateral grooves be 2.0-5.0% of the volume of the tread portion. It is known that this makes it possible to suppress movement of the tread portion and suppress the occurrence of chipping in the tread portion. It is more preferable that it be 2.2 to 4.0%, it is further preferable that it be 2.5 to 3.5%, and it is particularly preferable that it be 2.7 to 3.0%.

[0111] The volume of the above-mentioned lateral groove is the total volume of the volume composed of the surfaces connecting the ends of the lateral groove and the walls of the groove in the tire mounted on a standardized rim, at an internal pressure of 250 kPa and in a no-load state. In brief, by compressing the bead portion of the section cut in the radial direction with a width of 2-4 cm in the state according to the rim width, it can be obtained by calculating the volume of each lateral groove and multiplying the number of grooves. Further, the area of the portion excluding the lateral groove from the section is calculated and multiplied by the outside diameter, and then the difference between the calculation result and the volume of the lateral groove is obtained, whereby the volume of the tread portion can be calculated.

[0112] In order to suppress the chipping in the tread portion and further improve the durability, it is preferable that these lateral grooves contain grooves having a width ratio (Gw / Gd) (i.e., the ratio of the groove width Gw to the groove depth Gd) of 0.50 to 0.80. The ratio is more preferably 0.53 to 0.77, further preferably 0.55 to 0.75, particularly preferably 0.60 to 0.70.

[0113] The groove width and the groove depth of the above lateral grooves each refer to the maximum length of a straight line (which is perpendicular to the groove direction) connecting both ends of the lateral groove tread, and the maximum depth of the lateral groove, respectively, in a state where the internal pressure of the tire is 250 kPa and no load is applied. In short, it can be calculated by compressing the bead portion of a section cut in the radial direction with a width of 2 to 4 cm in a state where the bead portion is compressed according to the rim width.

[0114] 6. Tire shape

[0115] In the tire of the present application, when the tire is mounted on a standardized rim and the internal pressure is 250 kPa, the specific outer diameter Dt (mm) is, for example, preferably 515 mm or more, more preferably 558 mm or more, further preferably 585 mm or more, further preferably 650 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.

[0116] On the other hand, it is preferably less than 843 mm, more preferably 735 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 709 mm or less, further preferably less than 707 mm, further preferably 693 mm or less, further preferably 690 mm or less, further preferably less than 685 mm, further preferably 684 mm or less, further preferably 679 mm or less, further preferably 678 mm or less, and further preferably 674 mm or less.

[0117] The specific cross-sectional width Wt (mm) is preferably 115 mm or more, more preferably 130 mm or more, further preferably 150 mm or more, still more preferably 170 mm or more, yet more preferably 175 mm or more, yet more preferably 176 mm or more, yet more preferably 177 mm or more, yet more preferably 181 mm or more, and yet more preferably 182 mm, particularly preferably 185 mm or more, and most preferably 193 mm or more.

[0118] On the other hand, it is preferably less than 305 mm, more preferably less than 245 mm, further preferably 232 mm or less, further preferably 231 mm or less, further preferably 230 mm or less, further preferably 229 mm or less, further preferably 226 mm or less, further preferably less than 210 mm, further preferably less than 205 mm, further preferably 201 mm or less, further preferably 200 mm or less, further preferably less than 200 mm, and further preferably 199 mm or less.

[0119] A specific cross-sectional height Ht (mm) is, for example, preferably 37 mm or more, more preferably 69 mm or more, further preferably 70 mm or more, further preferably 71 mm or more, further preferably 77 mm or more, further preferably 78 mm or more, further preferably 79 mm or more, further preferably 80 mm or more, further preferably 81 mm or more, further preferably 87 mm or more, further preferably 91 mm or more, further preferably 95 mm or more, further preferably 97 mm or more, further preferably 98 mm or more, and further preferably 99 mm or more.

[0120] On the other hand, it is preferably less than 180 mm, more preferably 116 mm or less, further preferably 114 mm or less, further preferably less than 112 mm, further preferably 106 mm or less, further preferably less than 101 mm, and further preferably 100 mm or less.

[0121] A specific imaginary volume V is preferably 13,000,000 mm 3 or more, more preferably 23,225,099 mm 3 or more, further preferably 23,279,803 mm 3 or more, more preferably 23,332,669 mm 3 or more, more preferably 28,653,292 mm 3 or more, more preferably 28,719,183 mm 3 or more, more preferably 28,783,303 mm 3 or more, further preferably 29,000,000 mm 3 or more, more preferably 29,988,186 mm 3 or more, more preferably 30,346,008 mm 3 or more, more preferably 34,384,955 mm 3 or more, more preferably 35,622,714 mm 3 or more, more preferably 35,835,871 mm 3 or more, further preferably 36,000,000 mm 3 or more, further preferably 36,200,312 mm3 , further preferably 36,300,653 mm 3 above, and further preferably 36,878,037 mm 3 above.

[0122] On the other hand, it is preferably less than 66,000,000 mm 3 , more preferably 51,413,226 mm 3 below, further preferably less than 44,000,000 mm 3 , further preferably 43,419,514 mm 3 below, further preferably 42,160,723 mm 3 below, further preferably 40,613,053 mm 3 below, and further preferably less than 38,800,000 mm 3 .

[0123] Further, in the present application, in view of stability of ride comfort during running, (Dt - 2 x Ht) is preferably 450 (mm) or more, more preferably 456 (mm) or more, further preferably 458 (mm) or more, further preferably 470 (mm) or more, further preferably 480 (mm) or more, further preferably 481 (mm) or more, and further preferably 482 (mm) or more.

[0124] On the other hand, in view of deformation of the tread portion, it is preferably less than 560 (mm), more preferably 559 (mm) or less, further preferably 556 (mm) or less, further preferably 534 (mm) or less, further preferably 531 (mm) or less, further preferably less than 530 (mm), further preferably 510 (mm) or less, further preferably less than 510 (mm), further preferably 509 (mm) or less, further preferably 507 (mm) or less, and further preferably 506 (mm) or less.

[0125] [3] Embodiment

[0126] Hereinafter, the present application will be specifically described according to an embodiment.

[0127] 1. Rubber composition forming a tread portion

[0128] The rubber composition forming the tire tread portion according to the present application can be obtained by appropriately adjusting the kinds and amounts of various compounding materials, such as the rubber ingredient, the filler, the softener, the vulcanizing agent, and the vulcanization accelerator, particularly the filler and the softener, as described below.

[0129] (1) Rubber ingredient

[0130] In the present embodiment, as the rubber component, a rubber (polymer) generally used for producing a tire, such as butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene-based rubber, and nitrile rubber (NBR), can be used. Among these rubbers, isoprene-based rubber, butadiene rubber (BR), and styrene-butadiene rubber (SBR) are preferably used.

[0131] (a) Isoprene-based rubber

[0132] The content (total content) of isoprene-based rubber in 100 parts by mass of the rubber component is preferably 25 parts by mass or more, more preferably 35 parts by mass or more, and further preferably 45 parts by mass or more. On the other hand, it is preferably 75 parts by mass or less, more preferably 65 parts by mass or less, and further preferably 55 parts by mass or less.

[0133] Examples of the isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), reconstituted NR, modified NR, and modified IR. From the viewpoint of excellent strength, NR is preferred.

[0134] As the NR, for example, SIR20, RSS#3, TSR20, and the like, which are common in the tire industry, can be used. The IR is not particularly limited, and for example, IR2200 and the like, which are common in the tire industry, can be used. The modified NR includes deproteinized natural rubber (DPNR), ultra-pure natural rubber (UPNR), and the like. The modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, and the like. The modified IR includes epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, and the like. These materials can be used alone or in combination of two or more.

[0135] (b) BR

[0136] The content of BR in 100 parts by mass of the rubber component is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and further preferably 35 parts by mass or more. On the other hand, it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and further preferably 45 parts by mass or less.

[0137] The weight average molecular weight of BR is, for example, greater than 100,000 and less than 2,000,000. The vinyl bond amount of BR is, for example, greater than 1% by mass and less than 30% by mass. The cis content of BR is, for example, greater than 1% by mass and less than 98% by mass. The trans content of BR is, for example, greater than 1% by mass and less than 60% by mass. The cis content can be measured by infrared absorption spectroscopy.

[0138] The BR is not particularly limited, and a BR having a high cis content (cis content of 90% or more), a BR having a low cis content, a BR containing a syndiotactic polybutadiene crystal, or the like can be used. The BR can be an unmodified BR or a modified BR. As the modified BR, for example, a BR modified with a compound (modifier) represented by the following formula can be used.

[0139] [Chemical Formula 1]

[0140]

[0141] In the formula, R1, R2, and R3 represent the same or different alkyl group, alkoxy group, siloxy group, acetal group, carboxyl group (-COOH), mercapto group (-SH), or derivative thereof. R4 and R5 represent the same or different hydrogen atom or alkyl group. R4 and R5 can combine to form a cyclic structure with a nitrogen atom. n represents an integer.

[0142] As the BR modified with the compound (modifier) represented by the above formula, a BR in which the polymerization terminal (active terminal) is modified with the compound represented by the above formula can be used.

[0143] As R 1 , R 2 , and R 3 , an alkoxy group is preferred (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms). As R 4 , and R 5 , an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms) is preferred. n is preferably 1 to 5, more preferably 2 to 4, even more preferably 3. Furthermore, when R 4 , and R 5 combine to form a cyclic structure with a nitrogen atom, a 4- to 8-membered ring is preferred. The alkoxy group also includes a cycloalkoxy group (for example, a cyclohexyloxy group) and an aryloxy group (for example, a phenoxy group, a benzyloxy group).

[0144] Specific examples of the above modifier 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.

[0145] Furthermore, as the modified BR, a modified BR modified with the following compound (modifier) can also be used. Examples of the modifier include:

[0146] Polyglycidyl ethers of polyols such as ethylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylol ethane triglycidyl ether, and trimethylol propane triglycidyl ether;

[0147] Polyglycidyl ethers of aromatic compounds having two or more phenolic groups such as bisphenol A diglycidyl ether;

[0148] Polyepoxy compounds such as 1,4-diglycidyl benzene, 1,3,5-triglycidyl benzene, and polyepoxidized liquid polybutadiene;

[0149] Epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethane and 4,4'-diglycidyl-dibenzylmethane;

[0150] Diglycidyl amino compounds such as diglycidyl aniline, N,N'-diglycidyl-4-glycidoxyaniline, diglycidyl n-toluidine, tetraglycidyl-m-xylidyl amine, tetraglycidyl-aminodi- phenylmethane, tetraglycidyl-p-phenylenediamine, diglycidyl aminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane;

[0151] Amino group-containing acid chlorides such as bis(1-methylpropyl)aminoformic acid chloride, 4-morpholinocarbonyl chloride, 1-pyrrolidinocarbonyl chloride, N,N-dimethylcarbonyl amide chloride, and N,N-diethylcarbonyl amide acid chloride;

[0152] Epoxy group-containing silane compounds such as 1,3-bis(glycidylpropyl)-tetramethyldisiloxane and (3-glycidylpropyl)-pentamethyldisiloxane;

[0153] Silane compounds containing a thioether group such as (trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tripropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldipropoxysilyl)propyl]sulfide, and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide;

[0154] N-substituted aziridine compounds such as ethyleneimine and propyleneimine;

[0155] alkoxysilanes such as methyltriethoxysilane, N,N-bis(trimethylsilyl)-3- aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, and N,N-bis(trimethylsilyl)aminoethyltriethoxysilane;

[0156] (thio)benzophenone compounds having an amino group and / or a substituted amino group such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-t-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'-tetrakis(ethylamino)benzophenone;

[0157] 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;

[0158] N-substituted pyrrolidones such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-t-butyl-2-pyrrolidone, and N-methyl-5-methyl-2-pyrrolidone;

[0159] N-substituted piperidones such as N-methyl-2-piperidone, N-vinyl-2-piperidone, and N-phenyl-2-piperidone;

[0160] N-substituted lactams such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-lauryllactam, N-vinyl-ω-lauryllactam, N-methyl-β-propiolactam, and N-phenyl-β-propiolactam; and

[0161] N,N-bis(2,3-epoxypropyl)-aniline, 4,4-methylenebis(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-dimethylurea, 1,3-divinylurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminophenylacetone, 4-N,N-diethylaminophenylacetone, 1,3-bis(diphenylamino)-2-propanone, and 1,7-bis(methylethylamino)-4-heptanone. The modification with the above compounds (modifiers) can be carried out by known methods.

[0162] As the BR, for example, products of Sumitomo Ube Industries, Ltd., JSR Corporation, Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., and the like can be used.

[0163] (c) SBR

[0164] The content of the SBR is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, in 100 parts by mass of the rubber component. On the other hand, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less.

[0165] The weight average molecular weight of the SBR is, for example, greater than 100,000 and less than 2,000,000. The styrene content of the SBR is 5 mass% or more, in particular at least 8 mass% or more. In addition, it is preferably less than 35 mass%, more preferably less than 25 mass%, and further preferably less than 15 mass%. The vinyl bond amount (1,2-bonded butadiene unit content) of the SBR is, for example, greater than 5 mass% and less than 70 mass%. The structure identification (measurement of the styrene content and the vinyl bond amount) of the SBR can be performed using, for example, a JNM-ECA series device manufactured by JEOL Ltd.

[0166] The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), or the like can be used. The SBR can be a non-modified SBR or a modified SBR. These can be used alone or two or more.

[0167] The modified SBR can be any SBR having a functional group that interacts with a filler such as silica. Examples thereof include:

[0168] a terminal-modified SBR (a terminal-modified SBR in which at least one end of the SBR is modified with a compound (a modifier) having the above-described functional group);

[0169] a main chain-modified SBR in which the functional group is on the main chain;

[0170] a main chain-terminal-modified SBR having the functional group on the main chain and the terminal (for example, a main chain-terminal-modified SBR in which the main chain has the above-described functional group and at least one terminal is modified with the above-described modifier); and

[0171] a terminal-modified SBR modified (coupled) with a multifunctional compound having two or more epoxy groups in the molecule and in which an epoxy group or a hydroxyl group is introduced.

[0172] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Co., Ltd., Nippon Zeon Corporation, and the like can be used. The SBR can be used alone or in combination of two or more.

[0173] (d) Other Rubber Component

[0174] In the present embodiment, as the other rubber component, the rubber composition can contain a rubber (polymer) generally used for producing a tire, such as nitrile rubber (NBR), as described above.

[0175] (2) Blending Material Other than Rubber Component

[0176] (a) Filler

[0177] In the present embodiment, the rubber composition preferably contains a filler. Specific examples of the filler include silica, carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. Among them, silica and carbon black can be preferably used as a reinforcing agent. When silica is used, it is preferably used in combination with a silane coupling agent.

[0178] (a-1) Silica

[0179] The rubber composition preferably contains silica as a filler reinforcing agent. From the viewpoint of obtaining good durability, the BET specific surface area of the silica is preferably greater than 140 m 2 / g, and more preferably greater than 160 m 2 / g. On the other hand, from the viewpoint of obtaining good rolling resistance at high speed running, it is preferably less than 250 m 2 / g, and more preferably less than 220 m 2 / g. The above BET specific surface area is the N2SA value measured by the BET method according to ASTM D3037-93.

[0180] When silica is used as a filler reinforcing agent, the content of silica is preferably greater than 35 parts by mass, and more preferably greater than 40 parts by mass, with respect to 100 parts by mass of the rubber component. On the other hand, it is preferably 200 parts by mass or less, more preferably 100 parts by mass or less, and further preferably 60 parts by mass or less.

[0181] Examples of the silica include dry-process silica (anhydrous silica) and wet-process silica (hydrous silica). Among them, the wet-process silica is preferred because it has a large number of silanol groups.

[0182] As silica, products from companies such as Evonik, Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., and Tokuyama Corporation can be used.

[0183] (a-2) Silane coupling agent

[0184] The rubber composition preferably contains a silane coupling agent and silica. There are no particular limitations on the silane coupling agent. Examples of silane coupling agents include:

[0185] Sulfide-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)tetrasulfide, etc. Silyl ethyl) disulfide, bis(4-triethoxysilyl butyl) disulfide, bis(3-trimethoxysilyl propyl) disulfide, bis(2-triethoxysilyl ethyl) disulfide, bis(4-trimethoxysilyl butyl) disulfide, 3-trimethoxysilyl propyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilyl ethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-trimethoxysilyl propyl methacrylate monosulfide;

[0186] Thiol-based silane coupling agents, such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z manufactured by Momentive;

[0187] Vinyl silane coupling agents, such as vinyltriethoxysilane and vinyltrimethoxysilane;

[0188] Aminosilane coupling agents, such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane;

[0189] Glycidyl ether oxysilane coupling agents, such as γ-glycidyl ether oxypropyltriethoxysilane and γ-glycidyl ether oxypropyltrimethoxysilane;

[0190] Nitrosilane coupling agents, such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and

[0191] Chlorinated silane coupling agents, such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These can be used alone or in combination of two or more.

[0192] As silane coupling agents, products from companies such as Degussa, Momentive, Shinetsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Toray Dow Corning Co., Ltd. can be used.

[0193] For example, the content of silane coupling agent is greater than 3 parts by mass and less than 25 parts by mass relative to 100 parts by mass of silicon dioxide.

[0194] (a-3) Carbon black

[0195] The rubber composition preferably contains carbon black. For example, the carbon black content is greater than 200 parts by weight and less than 100 parts by weight of the rubber component.

[0196] There are no particular limitations on carbon black, and examples include furnace black (furnace black), such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black; thermal cracking black (thermal cracking black), such as FT and MT; and channel black (channel black), such as EPC, MPC, and CC. These can be used alone or in combination of two or more.

[0197] The nitrogen adsorption specific surface area (N2SA) of carbon black is, for example, greater than 30 m². 2 / g and less than 250m 2 / g. The amount of dibutyl phthalate (DBP) absorbed by carbon black is, for example, greater than 50 ml / 100g and less than 250 ml / 100g. The nitrogen adsorption specific surface area of ​​carbon black is measured according to ASTM D4820-93, and the amount of DBP absorbed is measured according to ASTM D2414-93.

[0198] There are no particular limitations on the specific carbon black used; examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products include those from companies such as Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nikka Carbon Co., Ltd., and Columbia Carbon Co., Ltd. These can be used alone or in combination of two or more.

[0199] (a-4) Other fillers

[0200] In addition to carbon black and silica, the rubber composition may also contain fillers commonly used in the tire industry, such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. As fillers for adjusting the thermal conductivity of the rubber composition, graphene, graphite, carbon nanofibers, etc., are also preferred. For example, these contents are greater than 0.1 parts by weight and less than 200 parts by weight relative to 100 parts by weight of the rubber component.

[0201] (b) Softener

[0202] The rubber composition may contain oil (including spreadable oil) or liquid rubber as a softener. The total content of these components is preferably greater than 1 part by weight, more preferably greater than 8 parts by weight, and even more preferably greater than 10 parts by weight, relative to 100 parts by weight of the rubber component. On the other hand, less than 100 parts by weight is preferred, less than 40 parts by weight is more preferred, and less than 30 parts by weight is even more preferred. The oil content also includes the amount of oil contained in the rubber (oil-diffused rubber).

[0203] Examples of oils include mineral oils (generally referred to as processed oils), vegetable oils, and fats, or mixtures thereof. Examples of mineral oils (processed oils) include paraffinic processed oils, aromatic processed oils, naphthenic processed oils, etc. 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 bran oil, beni flower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These can be used alone or in combination of two or more.

[0204] Specific examples of processed oils (mineral oils) include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Olisoy Co., Ltd., H&R Co., Ltd., Toyokuni Seiyu Co., Ltd., Showa Shell Sekiyu Co., Ltd., and Fuji Kosan Co., Ltd.

[0205] Liquid rubber, mentioned as a softener, is a polymer that exists in a liquid state at room temperature (25°C) and is a polymer with monomers similar to those in solid rubber as constituent elements. Examples of liquid rubber include farnesene polymers, liquid diene polymers, and their hydrogenated additives.

[0206] Farnesene polymers are polymers obtained by polymerizing farnesenes and have farnesene-based structural units. Farnesenes include isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodecathetene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecathetene).

[0207] Farnesene polymers can be homopolymers of farnesene (farnesene homopolymers) or copolymers of farnesene and vinyl monomers (farnesene-vinyl monomer copolymers).

[0208] Examples of liquid diene polymers include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), and liquid styrene-isoprene copolymer (liquid SIR).

[0209] The polystyrene equivalent weight-average molecular weight (Mw) of the liquid diene polymer, as determined by gel permeation chromatography (GPC), is, for example, greater than 1.0 × 10⁻⁶. 3 And less than 2.0 × 10 5 In this specification, the Mw of the liquid diene polymer is the polystyrene conversion value determined by gel permeation chromatography (GPC).

[0210] The content of liquid rubber (total content of liquid farnesene polymers, liquid diene polymers, etc.) is, for example, greater than 1 part by mass and less than 100 parts by mass relative to 100 parts by mass of rubber component.

[0211] As a liquid rubber, products from Kuraray Co., Ltd. and Clay Valley Co., Ltd. can be used, for example.

[0212] (c) Resin composition

[0213] Furthermore, if necessary, the rubber composition preferably contains a resin component. The resin component can be solid or liquid at room temperature, and specific resin components include styrene resin, coumarone resin, terpene resin, C5 resin, C9 resin, C5C9 resin, and acrylic resin, etc. Two or more types of resin components can be used in combination. The content of the resin component relative to 100 parts by weight of the rubber composition is preferably greater than 2 parts by weight and less than 45 parts by weight, more preferably less than 30 parts by weight.

[0214] (Styrene resin)

[0215] Styrene resins are polymers that use styrene monomers as constituent monomers. Examples include polymers obtained by polymerizing styrene monomers as a major component (more than 50% by mass). Specifically, they include homopolymers obtained by polymerizing styrene monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) individually, copolymers obtained by copolymerizing two or more styrene monomers, and copolymers obtained by copolymerizing styrene monomers with other monomers that can be copolymerized with styrene monomers.

[0216] Other examples of monomers include acrylonitriles, such as acrylonitrile and methacrylates; unsaturated carboxylic acids, such as acrylic acid and methacrylates; unsaturated carboxylic acid esters, such as methyl acrylate and methyl methacrylate; dienes, such as chloroprene, butadiene, and isoprene; alkenes, such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids (such as maleic anhydride) and their anhydrides.

[0217] (Coumarone resins)

[0218] Coumarin-indene resin is preferred as a coumarone-based resin. Coumarin-indene resin is a resin containing coumarone and indene as monomeric components constituting the resin backbone (main chain). Examples of monomeric components in the backbone other than coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

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

[0220] The hydroxyl value (OH value) of coumarone-indene resin is, for example, greater than 15 mg KOH / g and less than 150 mg KOH / g. The OH value, expressed in milligrams, refers to the amount of potassium hydroxide required to neutralize the acetic acid bound to the hydroxyl group when 1 g of resin is acetylated. It is measured by potentiometric titration (JIS K 0070:1992).

[0221] The softening point of coumarone-indene resin is, for example, above 30°C and below 160°C. The softening point is the temperature at which the ball falls when measuring the softening point as defined in JIS K 6220-1:2001 using a ring-ball softening point measuring device.

[0222] (terpene resin)

[0223] Examples of terpene resins include polyterpenes, terpene phenols, and aromatically modified terpene resins. Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenation products. Terpene compounds are compounds with the structure (C5H8). n Hydrocarbons that make up the composition of or their oxygen-containing derivatives, which are classified as monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32 Compounds with terpenes as their basic skeleton include α-pinene, β-pinene, dipentene, limonene, myrcene, allociperene, osimene, α-phellandrene, α-terpinene, γ-terpinene, terpinene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

[0224] Examples of polyterpenes include terpene resins made from the aforementioned terpene compounds, such as α-pinene resins, β-pinene resins, limonene resins, dipentene resins, and β-pinene / limonene resins, as well as hydrogenated terpene resins obtained by hydrogenating terpene resins. Examples of terpene phenols include resins obtained by copolymerizing the aforementioned terpene compounds and phenolic compounds, as well as resins obtained by hydrogenating the aforementioned resins. Specifically, resins obtained by condensing the aforementioned terpene compounds, phenolic compounds, and formalin are mentioned. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol. Examples of aromatically modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, as well as resins obtained by hydrogenating the aforementioned resins. There are no particular restrictions on aromatic compounds, as long as they are compounds with an aromatic ring. Examples include phenolic compounds, such as phenol, alkylphenol, alkoxyphenol and phenols containing unsaturated hydrocarbon groups; naphthol compounds, such as naphthol, alkylnaphthol, alkoxynaphthol and naphthols containing unsaturated hydrocarbon groups; styrene derivatives, such as styrene, alkylstyrene, alkoxystyrene and styrene containing unsaturated hydrocarbon groups; coumarone and indene.

[0225] (C5 resin, C9 resin, C5C9 resin)

[0226] "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. Dicyclopentadiene resin (DCPD resin) is preferred as a C5-based petroleum resin.

[0227] "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, which can be hydrogenated or modified. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. As specific examples, coumarone-indene resins, coumarone resins, indene resins, and aromatic vinyl resins are preferred. As aromatic vinyl resins, homopolymers of α-methylstyrene or styrene, or copolymers of α-methylstyrene and styrene, are preferred because they are economical, easy to process, and have excellent heat dissipation properties. Copolymers of α-methylstyrene and styrene are more preferred. For example, commercially available resins from Clayton, Eastman Chemical, etc., can be used as aromatic vinyl resins.

[0228] "C5C9" resin refers to a resin obtained by copolymerizing C5 and C9 fractions, and it can be hydrogenated or modified. Examples of C5 and C9 fractions include the petroleum fractions mentioned above. Commercially available resins from companies such as Tosoh Corporation and LUHUA can be used as C5C9 resins.

[0229] (Acrylic resin)

[0230] There are no particular restrictions on acrylic resins; for example, solvent-free acrylic resins can be used.

[0231] As a solvent-free acrylic resin, (meth)acrylic resin (polymer) synthesized by high-temperature continuous polymerization (high-temperature continuous bulk polymerization: US4,414,370B, JP 84-6207A, JP 93-58805A, JP 89-313522A, US 5,010,166B, Toa Synthetic Research Annual Report TREND2000 No.3p42-45, etc.) can be mentioned, and polymerization initiators, chain transfer agents, organic solvents, etc., are used as auxiliary raw materials as much as possible. In this invention, (meth)acrylic acid refers to methacrylic acid and acrylic acid.

[0232] Examples of monomeric components constituting acrylic resins include (meth)acrylic acid and (meth)acrylic acid derivatives, such as (meth)acrylates (alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylamide derivatives.

[0233] In addition, as a monomeric component constituting acrylic resins, aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, divinylnaphthalene, etc., can be used together with (meth)acrylic acid or (meth)acrylic acid derivatives.

[0234] Acrylic resins can be resins composed solely of (meth)acrylic acid, or resins containing components other than (meth)acrylic acid. Furthermore, acrylic resins can contain hydroxyl, carboxyl, or silanol groups, etc.

[0235] Polymer components used as resin components may include, for example, products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Toso Co., Ltd., Rutgers Chemicals Co., Ltd., BASF Co., Ltd., Arizona Chemical Co., Ltd., Nitto Chemical Co., Ltd., Nippon Catalyst Co., Ltd., JX Energy Co., Ltd., Arakawa Chemical Industry Co., Ltd., and Taoka Chemical Industry Co., Ltd.

[0236] (d) Anti-aging agents

[0237] The rubber composition preferably contains an anti-aging agent. For example, the content of the anti-aging agent is greater than 1 part by weight and less than 10 parts by weight relative to 100 parts by weight of the rubber component.

[0238] Examples of anti-aging agents include naphthylamine anti-aging agents, such as phenyl-α-naphthylamine; diphenylamine anti-aging agents, such as octyl diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine anti-aging agents, 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 anti-aging agents, such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenolic anti-aging agents, such as 2,6-di-tert-butyl-4-methylphenol and styreneated phenol; and bis, tri, and polyphenolic anti-aging agents, such as tetrakis[3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate methane]. These can be used alone or in combination of two or more.

[0239] As an anti-aging agent, products from companies such as Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexsys Co., Ltd., etc. can be used.

[0240] (e) Stearic acid

[0241] The rubber composition may contain stearic acid. For example, the stearic acid content is greater than 0.5 parts by weight and less than 10.0 parts by weight relative to 100 parts by weight of the rubber component. As stearic acid, conventionally known stearic acids can be used, such as products from NOF Corporation, Kao Corporation, Fuji Film Wako Pure Chemical Industries, Ltd., and Chiba Fatty Acid Co., Ltd.

[0242] (f) Zinc oxide

[0243] The rubber composition may contain zinc oxide. For example, the zinc oxide content is greater than 0.5 parts by weight and less than 10 parts by weight relative to 100 parts by weight of the rubber component. Conventionally known zinc oxides can be used as the zinc oxide, such as products from Mitsui Metal Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc.

[0244] (g) wax

[0245] The rubber composition preferably contains wax. For example, the wax content is 0.5 to 20 parts by weight, preferably 1.5 to 15 parts by weight, and more preferably 3.0 to 10.0 parts by weight, relative to 100 parts by weight of the rubber component.

[0246] There are no particular limitations on the types of waxes used, and examples include petroleum waxes such as paraffin and microcrystalline wax; natural waxes such as plant waxes and animal waxes; and synthetic waxes such as polymers of ethylene or propylene. These can be used alone or in combination of two or more.

[0247] As a wax, for example, products from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Kagaku Co., Ltd. can be used.

[0248] (h) Crosslinking agents and vulcanization accelerators

[0249] The rubber composition preferably contains a crosslinking agent, such as sulfur. For example, the crosslinking agent content is greater than 0.1 parts by weight and less than 10.0 parts by weight relative to 100 parts by weight of the rubber component.

[0250] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, and soluble sulfur, which are commonly used in the rubber industry. These can be used alone or in combination of two or more.

[0251] For example, products from companies such as Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Corporation, Flexsys Co., Ltd., Nippon Kanryu Kogyo Co., Ltd., and Hosoi Chemical Industry Co., Ltd. can be used as sulfur.

[0252] Examples of crosslinking agents other than sulfur include sulfur-containing vulcanizing agents, such as Tackirol V200 manufactured by Taoka Chemical Industry Co., Ltd., DURALINK HTS (1,6-hexamethylene-sodium dithiosulfate dihydrate) manufactured by Flexsys, and KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane) manufactured by Lanxess; and organic peroxides, such as dicumyl peroxide.

[0253] The rubber composition preferably contains a vulcanization accelerator. For example, the content of the vulcanization accelerator is greater than 0.3 parts by weight and less than 10.0 parts by weight relative to 100 parts by weight of the rubber component.

[0254] Examples of vulcanization accelerators include:

[0255] Thiazole vulcanization accelerators, such as 2-mercaptobenzothiazole, di-2-benzothiazole disulfide and N-cyclohexyl-2-benzothiamide;

[0256] Thiuram-based vulcanization accelerators, such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetra(2-ethylhexyl)thiuram disulfide (TOT-N);

[0257] Sulfimide-based vulcanization accelerators, such as N-cyclohexyl-2-benzothiazole sulfinamide, N-tert-butyl-2-benzothiazole sulfinamide, N-oxyethylidene-2-benzothiazole sulfinamide, N-oxyethylidene-2-benzothiazole sulfinamide and N,N'-diisopropyl-2-benzothiazole sulfinamide;

[0258] And guanidine vulcanization accelerators, such as diphenylguanidine, di-o-tolylguanidine and o-tolylguanidine.

[0259] These can be used individually or in combination of two or more.

[0260] (i) Other

[0261] In addition to the components mentioned above, the rubber composition may also contain additives commonly used in the tire industry, such as fatty acid metal salts, carboxylic acid metal salts, organic peroxides, and graphite. For example, the content of these additives is greater than 0.1 parts by weight and less than 200 parts by weight relative to 100 parts by weight of the rubber composition.

[0262] 2. Production of rubber compositions

[0263] The rubber composition is produced by a conventional method, for example, a manufacturing method comprising the following steps: a basic mixing step in which the rubber component is mixed with a filler (such as silica or carbon black), and a fine mixing step in which the mixed product obtained in the basic mixing step is mixed with a crosslinking agent.

[0264] Mixing can be carried out using known (sealed) mixing machines, such as Banbury mixers, mixing mills, or open rolls.

[0265] The mixing temperature in the basic mixing step is, for example, above 50°C and below 200°C, and the mixing time is, for example, greater than 30 seconds and less than 30 minutes. In addition to the above-mentioned components, in the basic mixing process, compounding agents commonly used in the rubber industry, such as softeners (e.g., oils, stearic acid, zinc oxide), anti-aging agents, waxes, and vulcanization accelerators, may be added and mixed as needed.

[0266] In the fine mixing step, the compounded product obtained in the basic mixing step and the crosslinking agent are mixed. The mixing temperature in the fine mixing step is, for example, above room temperature and below 80°C, and the mixing time is, for example, greater than 1 minute and less than 15 minutes. In addition to the above components, vulcanization accelerators, zinc oxide, etc., may be added and mixed appropriately as needed in the fine mixing step.

[0267] As mentioned above, the thermal conductivity of the rubber composition can be adjusted by changing the mixing ratio of carbon black, silica, etc., or by mixing graphene, graphite, carbon nanofibers, etc. in this mixing operation.

[0268] 3. Tire manufacturing

[0269] The tire of the present invention is manufactured using an uncured rubber composition obtained through a fine mixing step by a conventional method. Specifically, firstly, the uncured rubber composition is extruded according to the shape of each tire component of the tread. At this time, by simultaneously extruding rubber compositions with different thermal conductivity, tread regions with different thermal conductivity can be obtained.

[0270] Next, the tread is formed together with other tire components on a tire forming machine using conventional methods to produce an uncured tire.

[0271] Specifically, on a molded roller, an inner liner (ensuring tire airtightness), a tire carcass (bearing the load, impact, and inflation pressure), and a belt (for tightening the carcass to increase tread rigidity) are wound. The two ends of the carcass are fixed to two sides, and bead portions (for securing the tire to the rim) are arranged in a ring. Then, the tread is bonded to the center of the outer periphery, and the sidewall portions (protecting the carcass and resisting bending) are bonded to the radially outer side, thus producing an uncured tire.

[0272] In this embodiment, it is preferable that the belt is provided as an inclined belt layer extending at an angle of 15° to 30° relative to the tire circumferential direction. Therefore, tire durability is ensured while maintaining sufficient tread rigidity. Furthermore, since it can be constrained in the circumferential direction, it is easy to suppress the growth of the outer diameter.

[0273] The uncured tires are then heated and pressed in a vulcanizing machine to obtain a tire. The vulcanization step can be carried out using known vulcanization methods. The vulcanization temperature is, for example, above 120°C and below 200°C, and the vulcanization time is, for example, greater than 5 minutes and less than 15 minutes.

[0274] At this point, when the tire is mounted on a standardized rim and the internal pressure is set to 250 kPa, the tire is formed into a shape that satisfies the above (Equation 1) and (Equation 2).

[0275] Specific tires that can meet the requirements of Formula 1 and Formula 2 above include tires with sizes marked 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, 195 / 55R20, etc.

[0276] In this embodiment, tires that satisfy (Equation 1) and (Equation 2) are preferably used in pneumatic tires for passenger vehicles. Satisfying the above equations can more advantageously solve the problem in this invention, namely, providing pneumatic tires that not only have low rolling resistance and high fuel efficiency, but also have improved grip and durability at high speeds, thus exhibiting excellent grip and durability at high speeds.

[0277] The pneumatic tires for passenger cars referred to here are tires installed on four-wheeled vehicles with a maximum load capacity of 1000 kg or less. Here, maximum load capacity refers to the maximum load capacity defined for each tire within the standard system upon which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Association standard), it is the maximum load capacity based on the load index (LI); in the case of TRA (The Tire and Rim Association, Inc.), it is the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFRATION PRESSURES"; and in the case of ETRTO, it is "INFRATION PRESSURES".

[0278] There is no particular limitation on the maximum load capacity, as long as it is below 1000 kg. However, generally speaking, as the maximum load capacity increases, the tire weight tends to increase, and the braking distance also increases accordingly due to inertia. Therefore, the maximum load capacity is preferably below 900 kg, more preferably below 800 kg, and even more preferably below 700 kg.

[0279] From the perspective of braking distance due to inertia, the tire weight is preferably 20 kg or less, more preferably 15 kg or less, and even more preferably 12 kg or less, 10 kg or less, and 8 kg or less. The tire of the present invention can be equipped with electronic components; in this case, the tire weight referred to herein includes the weight of the electronic components and the electronic component mounting components. If sealants, sponges, etc., are provided in the cavity, the tire weight includes them.

[0280] Example

[0281] The present invention will now be described in more detail with reference to embodiments. In the following description, two rubber compositions with different thermal conductivity are used as the rubber compositions (tread rubber compositions) forming the tread portion.

[0282] [Experiment 1]

[0283] In this experiment, tires of size 175 were prepared and evaluated.

[0284] 1. A rubber composition for use in tire treads.

[0285] First, the rubber components used in tire treads are produced.

[0286] (1) Mixed materials

[0287] First, prepare the various mixtures shown below.

[0288] (a) Rubber composition

[0289] (a-1)NR:TSR20

[0290] (a-2)BR: UBEPOL-BR150 manufactured by Ube Kosan Co., Ltd. (cis content: 97% by mass, trans content: 2% by mass, vinyl bond content: 1% by mass)

[0291] (a-3)SBR: Europrene SOL R C2525 manufactured by Versalis (styrene content: 26% by mass, vinyl bond content: 24% by mass)

[0292] (b) Compound materials other than rubber components

[0293] (b-1) Carbon Black-1: Seast F manufactured by Tokai Carbon Co., Ltd.

[0294] (b-2) Carbon Black-2: Ketjen Black EC300J manufactured by Ketjen Black International Co., Ltd.

[0295] (b-3) Silica: Ultrasil VN3 manufactured by Evonik Co., Ltd.

[0296] (b-4) Silane coupling agent: Si363 manufactured by Degussa Co., Ltd.

[0297] (b-5) Oil: Process oil A / OMIX manufactured by Sankyo Yuka Kogyo Co., Ltd.

[0298] (b-6) Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd.

[0299] (b-7) Stearic acid: Stearic acid "TSUBAKI" manufactured by NOF CORPORATION.

[0300] (b-8) Zinc oxide: White Zinc No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd.

[0301] (b-9) Anti-aging agent-1: Nocrac6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0302] (b-10) Crosslinking agents and vulcanization accelerators

[0303] Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.

[0304] Vulcanization accelerator-1: NoccelerCZ-G(CBS) (N-cyclohexyl-2-benzothiazolylsulfonamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0305] Vulcanization Accelerator-2: Nocceler D(DPG)(1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0306] (2) Manufacturing a rubber composition for tire tread

[0307] (a) Producing rubber compositions with low thermal conductivity

[0308] First, using the above-mentioned compounding materials, a basic and fine compounding was performed using a composition of 50 parts by mass of NR, 40 parts by mass of BR, 10 parts by mass of SBR, 5 parts by mass of carbon black-1, 0.1 parts by mass of carbon black-2, 50 parts by mass of silica, 4 parts by mass of silane coupling agent, 15 parts by mass of oil, 1.5 parts by mass of wax, 2 parts by mass of stearic acid, 3 parts by mass of zinc oxide, 3 parts by mass of antioxidant, 1.5 parts by mass of sulfur, 1 part by mass of vulcanization accelerator-1, and 0.5 parts by mass of vulcanization accelerator-2 to obtain a rubber composition with low thermal conductivity (Kb: 0.30 W / m·K). Using the Eplexor series manufactured by GABO, the loss tangent (tanδ at 30°C) of this rubber composition was measured at 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1%, which was 0.14.

[0309] (b) Producing rubber compositions with high thermal conductivity

[0310] Next, using the same compounding materials, but with appropriately increased amounts of carbon black-1, carbon black-2, and silica, basic and fine compounding were performed using the same compounding method to obtain four rubber compositions with high thermal conductivity, from A to D. The specific thermal conductivity Ka of rubber compositions A to D is as follows: rubber composition A is 0.32 W / m·K, rubber composition B is 0.41 W / m·K, rubber composition C is 0.54 W / m·K, and rubber composition D is 0.38 W / m·K.

[0311] 2. Tire manufacturing

[0312] Next, biaxial extrusion molding was performed using a rubber composition with low thermal conductivity and a rubber composition with high thermal conductivity to obtain the tread, wherein the difference (Sb-Sa) between the region Sb of the low thermal conductivity rubber composition and the region Sa of the high thermal conductivity rubber composition is shown in Tables 1 and 2. The obtained tread was bonded together with other tire components to form an uncured tire, and then vulcanized under pressure at 170°C for 10 minutes to produce test tires of size 175 (Examples 1-1 to 1-5 and Comparative Examples 1-3 to 1-5). The thickness Td of the tread portion was set to 13 mm (tanδ × Td = 1.82 at 30°C).

[0313] In addition, two types of test tires (Comparative Example 1-1 and Comparative Example 1-2) were manufactured using treads formed from only one type of rubber composition.

[0314] Among the tested tires, the above (L) 80 The ratio of L0) is 0.5, the total cross-sectional area of ​​the circumferential groove is 22% of the cross-sectional area of ​​the tread portion, and the total volume of the lateral groove, including the lateral groove with a groove width / groove depth of 0.65, is set to 3.5% of the volume of the tread portion.

[0315] 3. Parameter Calculation

[0316] Subsequently, the outer diameter Dt (mm), cross-sectional width Wt (mm), cross-sectional height Ht (mm), and aspect ratio (%) of each test tire were obtained, and the hypothetical volume V (mm²) was also obtained. 3 At this point, (Ka-Kb) is determined. The results are shown in Tables 1 and 2.

[0317] Then, (Dt-2×Ht) and (Dt) were calculated. 2 ×π / 4) / Wt、(V+1.5×10 7 ) / Wt、(V+2.0×10 7 ) / Wt、(V+2.5×10 7 (Sb-Sa)×Wt. The results are shown in Tables 1 and 2.

[0318] 4. Performance Evaluation Test

[0319] (1) Evaluation of grip at high speed

[0320] Each test tire was mounted on all wheels of a vehicle (a domestically produced front-wheel-drive car with a 2000cc engine), inflated to an internal pressure of 250 kPa, and then driven at 100 km / h on a dry test track. The lap times were measured and evaluated. For evaluation, the difference in lap times compared to a separately prepared reference tire was obtained. The time difference in Comparative Examples 1-5 was set to 100, exponentialized based on the following formula, and the grip at high speeds was evaluated relatively. A higher value indicates better grip during high-speed driving.

[0321] Grip force at high speed = [(Loop time of test tire - lap time of reference tire) / (Loop time of comparison examples 1-5 - lap time of reference tire)] × 100

[0322] (2) Evaluation of durability performance

[0323] All test tires were installed on all wheels of the vehicle (a domestically produced FF car with a 2000cc engine), and air was inflated to a pressure of 250 kPa. The vehicle was driven for 10 laps at 50 km / h, followed by a climb up an uneven section of the road at 80 km / h. This process was repeated on a dry road surface under overload conditions. Afterward, the vehicle was driven for one lap again at 50 km / h, and then the speed was gradually increased to measure the speed at which the driver experienced any abnormalities.

[0324] Next, the results from Comparative Examples 1-5 are set to 100, and the durability performance is evaluated relatively by exponentialization based on the following formula. The larger the value, the better the durability.

[0325] Durability = [(Test results of tires) / (Results of comparative examples 1-5)] × 100

[0326] (3) Comprehensive evaluation

[0327] The combined evaluation results of (1) and (2) above are used to obtain a comprehensive evaluation.

[0328] (4) Evaluation Results

[0329] The results of each evaluation are shown in Tables 1 and 2. In Comparative Examples 1-1 and 1-2, since the values ​​of (Ka-Kb) and (Sb-Sa) could not be calculated, the relevant results are indicated by "-".

[0330] [Table 1]

[0331]

[0332] [Table 2]

[0333]

[0334] [Experiment 2]

[0335] In this experiment, tires of size 195 were prepared and evaluated.

[0336] After manufacturing the test tires of Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-5 as shown in Tables 3 and 4 in the same manner as in Experiment 1, the parameters were obtained. Then, similarly, performance evaluation tests were conducted and evaluated. In this experiment, the results in Comparative Examples 2-5 were set to 100 for evaluation. The results of each evaluation are shown in Tables 3 and 4.

[0337] [Table 3]

[0338]

[0339] [Table 4]

[0340]

[0341] [Experiment 3]

[0342] In this experiment, tires of size 225 were prepared and evaluated.

[0343] After manufacturing the test tires of Examples 3-1 to 3-5 and Comparative Examples 3-1 to 3-5 as shown in Tables 5 and 6 in the same manner as in Experiment 1, the parameters were obtained. Then, similarly, performance evaluation tests were conducted and evaluated. In this experiment, the results in Comparative Examples 3-5 were set to 100 for evaluation. The results of each evaluation are shown in Tables 5 and 6.

[0344] [Table 5]

[0345]

[0346] [Table 6]

[0347]

[0348] [Summary of Experiments 1 to 3]

[0349] The results of Experiments 1 to 3 (Tables 1 to 6) show that when any of the tire sizes of 175, 195 and 225 meets the above (Equation 1) and (Equation 2), a pneumatic tire with significantly improved grip and durability at high speeds can be provided.

[0350] Thus, it is shown that by meeting the requirements of Embodiment 2 and thereafter, tires with further improved grip and durability at high speeds can be provided.

[0351] On the other hand, it shows that when (Equation 1) or (Equation 2) is not satisfied, the grip and durability at high speeds cannot be adequately improved.

[0352] [Experiment 4]

[0353] Next, three types of tires (Examples 4-1 to 4-3) were produced using the same formula, with no significant difference in the relationship between the hypothetical volume V and the cross-sectional width Wt, and were evaluated in the same manner. Here, in addition to evaluating grip and durability at high speeds, fuel efficiency was also evaluated.

[0354] Specifically, all test tires were mounted on all wheels of a vehicle (a domestically produced FF car with a 2000cc engine). After being inflated to an internal pressure of 250 kPa, the tires were driven on a dry road test track. After completing 10 km at 100 km / h, the accelerator was released, and the distance from when the accelerator was released to when the vehicle came to a stop was measured as the rolling resistance at high speed. The higher this value, the longer the distance from when the accelerator is released to when the vehicle comes to a stop, and the lower the rolling resistance under steady-state conditions.

[0355] Next, the results from Examples 4-3 are used as 100 and exponentialized based on the following formula to evaluate fuel efficiency. The larger this value, the smaller the rolling resistance in steady state, and the better the fuel efficiency. The evaluation results are shown in Table 7.

[0356] Fuel efficiency = [(Measurement results of the test tire) / (Measurement results of Example 4-3)] × 100

[0357] Then, as with experiments 1 to 3, the evaluation results were summed to obtain a comprehensive evaluation. The results of each evaluation are shown in Table 7.

[0358] [Table 7]

[0359]

[0360] According to Table 7, when there is no significant difference in the relationship between the hypothetical volume V and the cross-sectional width Wt, as the cross-sectional width Wt decreases, such as from less than 205 mm to less than 200 mm, and as the length-to-width ratio increases, it is found that the grip, durability and fuel efficiency at high speeds are improved, showing a significant effect.

[0361] Although the present invention has been described above according to embodiments, the present invention 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 invention.

Claims

1. A pneumatic tire having a tread portion, wherein the tread portion has a ground contact surface made of at least two kinds of rubber compositions having different thermal conductivities, 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 an imaginary volume V (mm 3 ), and when the tire is mounted on a standardized rim and the internal pressure is 250 kPa, the tire satisfies the following (Formula 1) and (Formula 2): 1700 ≦ (Dt 2 x π / 4) / Wt ≦ 2827.4... (Equation 1) [(V + 1.5 x 10 7 ) / Wt] ≦ 2.88 x 10 5 ... (Equation 2), and in the at least two kinds of rubber compositions having different thermal conductivities, when the thermal conductivity of the rubber composition having the highest thermal conductivity is Ka (W / m-K) and the thermal conductivity of the rubber composition having the lowest thermal conductivity is Kb (W / m-K), 0.11 ≦ Ka - Kb ≦ 0.

24.

2. The pneumatic tire of claim 1, wherein, the following (Formula 3) is satisfied: 1718 ≦ (Dt 2 x π / 4) / Wt ≦ 2827.4... (Equation 3) 3. The pneumatic tire of claim 1 or 2, wherein, the following (Formula 4) is satisfied: [(V + 2.0 x 10 7 ) / Wt] < 2.88 x 10 5 · · · (Equation 4).

4. The pneumatic tire of claim 3, wherein, the following (Formula 5) is satisfied: [(V + 2.5 x 10 7 ) / Wt] < 2.88 x 10 5 · · · (Equation 5).

5. The pneumatic tire of either claim 1 or 2, wherein, when an outer diameter of the tire is Dt (mm) and a cross-sectional height of the tire is Ht (mm), and when the tire is mounted on a standardized rim and an internal pressure is 250 kPa, (Dt - 2 x Ht) is 470 (mm) or more.

6. The pneumatic tire according to claim 1 or 2, having an aspect ratio of 40% or more.

7. The pneumatic tire according to claim 6, having an aspect ratio of 45% or more.

8. The pneumatic tire according to claim 7, having an aspect ratio of 47.5% or more.

9. The pneumatic tire according to claim 8, having an aspect ratio of 50% or more.

10. The pneumatic tire of either claim 1 or 2, wherein, In the tread portion, in the at least two rubber compositions having different thermal conductivities, when the thermal conductivity of the rubber composition having the highest thermal conductivity is Ka (W / m K) and the thermal conductivity of the rubber composition having the lowest thermal conductivity is Kb (W / m K), the ratio Sb (%) of the contact area of the contact portion formed of the rubber composition having the thermal conductivity Kb to the total contact area is greater than the ratio Sa (%) of the contact area of the contact portion formed of the rubber composition having the thermal conductivity Ka to the total contact area, and (Sb - Sa) x Wt < 3.00 x 10-3 is satisfied. 4 .

11. The pneumatic tire of claim 10, wherein, Sb-Sa) x Wt < 2.50 x 10 4 .

12. The pneumatic tire of either claim 1 or 2, wherein, in the at least two kinds of rubber compositions having different thermal conductivities, a loss tangent (30°C tan δ) measured for the rubber composition having the lowest thermal conductivity is 0.16 or less under conditions of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1%.

13. The pneumatic tire according to claim 12, wherein the 30°C tan δ is 0.14 or less.

14. The pneumatic tire of either claim 1 or 2, wherein, when Td (mm) is a thickness of the tread portion, the following (Formula 8) is satisfied: 30°C tan δ x Td ≧ 1.5 ··· (Formula 8).

15. The pneumatic tire of claim 14, wherein, the following (Formula 9) is satisfied: 30°C tan δ x Td ≧ 1.8 ··· (Formula 9).

16. The pneumatic tire of either claim 1 or 2, wherein, the tread portion has a plurality of circumferential grooves extending continuously in a tire circumferential direction, and a total cross-sectional area of the plurality of circumferential grooves is 10% to 30% of a cross-sectional area of the tread portion.

17. The pneumatic tire of either claim 1 or 2, wherein, the tread portion has a plurality of lateral grooves extending in a tire axial direction, and a total volume of the plurality of lateral grooves is 2.0% to 5.0% of a volume of the tread portion.

18. The pneumatic tire of either claim 1 or 2, wherein, Dt is less than 685 (mm), where Dt (mm) is an outer diameter of the tire when the tire is mounted on a standardized rim and an internal pressure is 250 kPa.

19. The pneumatic tire of either claim 1 or 2, wherein, the cross-sectional width Wt (mm) is less than 205 mm.

20. The pneumatic tire of claim 19, wherein, the cross-sectional width Wt (mm) is less than 200 mm.

21. The pneumatic tire according to claim 1 or 2, which is a pneumatic tire for a passenger vehicle.

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