Pneumatic tire

Abstract

This invention provides a pneumatic tire with sufficiently suppressed changes in handling performance and sufficiently improved durability. This pneumatic tire includes a tread portion comprising a rubber layer formed of a rubber composition having a loss tangent (tanδ at 15°C) of less than 0.25 when measured under conditions such as 15°C, 10Hz frequency, 5% initial strain, and 1% dynamic strain rate. The tread portion includes a plurality of rib-shaped ground contact portions formed by circumferentially extending grooves. The tread portion has a ground contact surface divided in a meridional plane such that one ground contact area Sa and another ground contact area Sb satisfy the relationship Sa > Sb, and satisfy equations (1) and (2), where Wt (mm) is the tire's cross-sectional width, Dt (mm) is the outer diameter, and V (mm) is the cross-sectional width. 3 () is a hypothetical volume, that is, the volume of space occupied by the tire when it is mounted on a standard rim and the internal pressure is 250 kPa. 1600 ≤ (Dt) 2 ×π / 4) / Wt≤2827.4(Equation 1)[(V+1.5×10 7 ) / Wt]≤2.88×10 5 (Equation 2).

Description

Technical Field

[0001] This invention relates to an inflatable tire. Background Technology

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

[0003] Tire fuel efficiency can be evaluated by rolling resistance, and it is well known that the lower the rolling resistance, the higher the tire's fuel efficiency.

[0004] Therefore, it has been traditionally proposed to reduce rolling resistance by designing the formulation of the rubber composition that constitutes the tread portion of the tire (e.g., Patent Documents 1 to 4).

[0005] [Existing technical documents]

[0006] [Patent Literature]

[0007] [Patent Document 1] JP2018-178034A

[0008] [Patent Document 2] JP2019-089911A

[0009] [Patent Document 3] WO2018 / 186367A

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

[0011] [The problem this invention aims to solve]

[0012] However, it cannot be said that tires manufactured using the aforementioned conventional technologies exhibit minimal changes in handling characteristics between low and high speeds; the change in handling characteristics between low and high speeds needs to be suppressed. Furthermore, it cannot be said that these tires possess sufficient durability.

[0013] Therefore, one object of the present invention is to provide a pneumatic tire in which the change in handling characteristics between low-speed and high-speed driving is sufficiently suppressed and its durability is sufficiently improved.

[0014] [Problem-solving methods]

[0015] The inventors have conducted a thorough study of solutions to the above problems and discovered that the problems can be solved by the following invention, and thus completed this invention.

[0016] The invention of Implementation Method 1 is:

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

[0018] The rubber layer constituting the tread portion is formed of a rubber composition, the loss tangent (tanδ at 15°C) of which is less than 0.25 when measured under the conditions of 15°C, 10Hz frequency, 5% initial strain and 1% dynamic strain rate.

[0019] In the tread portion, multiple rib-shaped contact portions are formed by circumferential grooves that extend continuously in the circumferential direction;

[0020] When the tread portion of the ground contact surface is divided by a meridional plane, and when one ground contact area is Sa and the other is Sb, Sa > Sb; and

[0021] When the tire's cross-sectional width is Wt (mm), its outer diameter is Dt (mm), and the volume of space occupied by the tire is an imaginary volume V (mm²), 3 Furthermore, when the tire is mounted on a standardized rim and the internal pressure is 250 kPa, the tire satisfies the following equations (1) and (2).

[0022] 1600≦(Dt 2 ×π / 4) / Wt≦2827.4···(Equation 1)

[0023] [(V+1.5×10 7 ) / Wt]≦2.88×10 5 ...(Equation 2).

[0024] The invention of implementation method 2 is:

[0025] The pneumatic tire as described in Embodiment 1, wherein the tire satisfies the following (Equation 3),

[0026] [(V+2.0×10 7 ) / Wt]≦2.88×10 5 ...(Equation 3).

[0027] The invention of implementation method 3 is:

[0028] The pneumatic tire as described in Embodiment 2, wherein the tire satisfies the following (Equation 4),

[0029] [(V+2.5×10 7 ) / Wt]≦2.88×10 5 ...(Equation 4).

[0030] The invention of implementation method 4 is:

[0031] The pneumatic tire as described in any one of embodiments 1 to 3, wherein tanδ at 15°C is 0.20 or less.

[0032] The invention of implementation method 5 is:

[0033] As described in any one of embodiments 1 to 4, the pneumatic tire has an outer diameter of Dt (mm) and a cross-sectional height of Ht (mm), and when the tire is mounted on a standardized rim and the internal pressure is 250 kPa, (Dt-2×Ht) is 470 (mm) or more.

[0034] The invention of implementation method 6 is:

[0035] The pneumatic tire as described in any one of embodiments 1 to 5, wherein the length-to-width ratio is 40% or more.

[0036] The invention of implementation method 7 is:

[0037] The pneumatic tire as described in Embodiment 6 has an aspect ratio of 45% or more.

[0038] The invention of implementation method 8 is:

[0039] The pneumatic tire as described in Embodiment 7 has an aspect ratio of 47.5% or more.

[0040] The invention of implementation method 9 is:

[0041] The pneumatic tire as described in any one of embodiments 1 to 8, wherein the tire satisfies 15° tanδ×Wt≦50.

[0042] The invention of implementation method 10 is:

[0043] The pneumatic tire as described in Embodiment 9, wherein the tire satisfies 15° tanδ×Wt≦40.

[0044] The invention of implementation method 11 is:

[0045] The pneumatic tire as described in Embodiment 10, wherein the tire satisfies 15° tanδ×Wt≦30.

[0046] The invention of implementation method 12 is:

[0047] The pneumatic tire as described in any one of embodiments 1 to 11, wherein the tire satisfies Sb / Sa < 0.8.

[0048] The invention of implementation method 13 is:

[0049] The pneumatic tire as described in Embodiment 12, wherein the tire satisfies Sb / Sa < 0.75.

[0050] The invention of implementation method 14 is:

[0051] The pneumatic tire as described in Embodiment 13, wherein the tire satisfies Sb / Sa < 0.7.

[0052] The invention of implementation method 15 is:

[0053] The pneumatic tire as described in any one of embodiments 1 to 14, wherein a plurality of circumferential grooves extending continuously in the tire circumferential direction are formed in the tread portion, 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.

[0054] The invention of implementation method 16 is:

[0055] The pneumatic tire as described in any one of embodiments 1 to 15, wherein a plurality of lateral grooves extending axially in the tread portion are formed therein, and the total volume of the plurality of lateral grooves is 2.0% to 5.0% of the volume of the tread portion.

[0056] The invention of implementation method 17 is:

[0057] The pneumatic tire as described in any one of embodiments 1 to 16, wherein when the outer diameter of the tire is Dt (mm) and when the tire is mounted on a standardized rim and the internal pressure is 250 kPa, Dt is less than 685 (mm).

[0058] The invention of implementation method 18 is:

[0059] The pneumatic tire as described in any one of embodiments 1 to 17, wherein the cross-sectional width Wt (mm) is less than 205 mm.

[0060] The invention of implementation method 19 is:

[0061] The pneumatic tire as described in Embodiment 18, wherein the cross-sectional width Wt (mm) is less than 200 mm.

[0062] [Invention Effects]

[0063] According to the present invention, a pneumatic tire can be provided in which the change in handling characteristics between low-speed driving and high-speed driving is sufficiently suppressed and its durability is sufficiently improved. Detailed Implementation

[0064] [1] Features of the tire of the present invention

[0065] First, the features of the tire of the present invention will be described.

[0066] 1. Overview

[0067] The tire of the present invention is characterized firstly in that the rubber layer constituting the tread portion is formed of a rubber composition, wherein the loss tangent (tanδ at 15°C) of the rubber composition, measured under conditions of 15°C, 10 Hz frequency, 5% initial strain, and 1% dynamic strain rate, is less than 0.25.

[0068] From the perspective of shape, the tire of the present invention has the following characteristics.

[0069] In other words, in the tread portion, multiple rib-shaped contact areas are formed by circumferentially extended grooves. Therefore, when the ground contact surface of the tread portion is divided by the meridional plane, if one ground contact area is Sa and the other is Sb, then Sa > Sb.

[0070] Furthermore, when the tire's cross-sectional width is Wt (mm), its outer diameter is Dt (mm), and the volume of the space occupied by the tire is an imaginary volume V (mm²),... 3 When the tire is mounted on a standardized rim and the internal pressure is 250 kPa, the tire satisfies the following (Equation 1) and (Equation 2).

[0071] 1600≦(Dt 2 ×π / 4) / Wt≦2827.4···(Equation 1)

[0072] [(V+1.5×10 7 ) / Wt]≦2.88×10 5 ...(Equation 2)

[0073] Based on the physical properties of the rubber composition forming the tread portion and the characteristics of the tire shape described above, a pneumatic tire can be provided that not only reduces rolling resistance but also suppresses changes in handling characteristics between low-speed and high-speed driving and significantly improves durability.

[0074] In the above description, the ground contact area refers to the actual ground contact area, which does not include the tire's ground contact surface with the road surface on the entire circumference of the tire, such as grooves and crevices.

[0075] In the above description, "standardized rim" refers to a rim defined for each tire within a standard system, including the standard upon which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Association), it is a standard rim of the applicable size described in the "JATMA YEAR BOOK"; in the case of ETRO (European Tire and Rim Technology Organization), it is a "measuring rim" described in the "STANDARDS MANUAL"; and in the case of TRA (Tire and Rim Association), it is a "design rim" described in the "YEAR BOOK". For tires not specified in the standard, it refers to a rim that can be assembled and maintain internal pressure, that is, a rim that will not cause air leakage between the rim and the tire, and has the smallest rim diameter, followed by the narrowest rim width.

[0076] Furthermore, the tire's outer diameter Dt refers to the outer diameter of a tire mounted on a standardized rim with an internal pressure of 250 kPa and under no-load conditions. The tire's section width Wt (mm) refers to the width of a tire mounted on a standardized rim with an internal pressure of 250 kPa and under no-load conditions, excluding the sidewall patterns, text, etc., from the straight-line distance between the sidewalls (the total tire width).

[0077] Furthermore, specifically, under the condition that the tire is mounted on a standardized rim, with an internal pressure of 250 kPa and no load applied, the imaginary volume V (mm²) of the tire can be calculated using the following formula based on the tire outer diameter Dt (mm), tire section height (the distance from the bottom of the bead to the outermost surface of the tread, which is half the difference between the tire outer diameter and the nominal rim diameter) Ht (mm), and tire section width Wt (mm). 3 ):

[0078] V = [(Dt / 2)] 2 -{(Dt / 2)-Ht} 2 ]×π×Wt.

[0079] 2. The effect mechanism in the tire of the present invention

[0080] The mechanism by which the tire of the present invention performs well—that is, not only does it reduce rolling resistance, but it also sufficiently suppresses changes in handling characteristics at low and high speeds and sufficiently improves durability—is speculated as follows.

[0081] (1) Tire shape

[0082] As described above, in this invention, the tire's cross-sectional width Wt (mm) and outer diameter Dt (mm) are preferably satisfied that 1600 ≤ (Dt) 2×π / 4) / Wt≦2827.4(Equation 1).

[0083] When viewed from the side, the area is increased by [(Dt / 2)] relative to the tire's cross-sectional width Wt. 2 ×π)=(Dt 2 ×π / 4)], and satisfying the numerical range specified in Equation 1, the number of deformation repetitions per unit time is reduced. As a result, the time available for heat exchange is extended to improve the heat release characteristics of the side portion. The friction between the tread portion and the road surface can be reduced. Therefore, it is known that low rolling resistance and improved durability can be achieved. In (Equation 1), (Dt 2 ×π / 4) / Wt is more preferably 1700 or higher, even more preferably 1865 or higher, even more preferably 1963.5 or higher, and even more preferably 2018 or higher.

[0084] However, when viewed laterally, such tires have a large surface area, and as the outer diameter Dt increases, the centrifugal force acting on the entire tread area at high speeds also increases. Therefore, some non-uniformity is enhanced, which may lead to uneven contact pressure in the contact area.

[0085] In particular, as the driving speed increases, the centrifugal force also increases accordingly. Therefore, the handling characteristics may change significantly between low-speed and high-speed driving.

[0086] Therefore, in this invention, the imaginary volume V (mm) of the tire is... 3 The cross-sectional width Wt (mm) should ideally satisfy [(V+1.5×10 7 ) / Wt]≦2.88×10 5 (Equation 2).

[0087] Thus, it is known that by reducing the imaginary volume V of the tire by reducing the tire cross-sectional width Wt, and by reducing the volume of the tire itself, it is possible to suppress the increase in outer diameter with increasing centrifugal force, reduce rolling resistance, and reduce heat generation during high-speed driving, thereby suppressing the decrease in tread rigidity.

[0088] At this point, [(V+2.0×10] is more preferred. 7 ) / Wt]≦2.88×10 5 (Equation 3), and further preferred [(V+2.5×10 7 ) / Wt]≦2.88×10 5 (Equation 4)

[0089] Furthermore, in this invention, multiple rib-shaped contact portions are formed in the tread portion by continuously extending circumferential grooves. When the ground contact surface of the tread portion is divided by a meridian plane, with one area of ​​Sa and another of Sb, the tire strives to satisfy Sa > Sb. Thus, by forming multiple rib-shaped contact portions, the contact area of ​​the tread portion is made uneven on both sides of the meridian. Even at increased driving speeds, sudden unevenness in ground contact pressure can be suppressed, reportedly suppressing changes in handling characteristics between low and high speeds. The circumferential grooves are continuously extending grooves in the circumferential direction, and also include non-linear grooves such as herringbone or wave-shaped grooves.

[0090] Here, "ribbed ground contact portion" refers to the ground contact portion sandwiched between two circumferential grooves, excluding the ground contact portion separated by lateral grooves (block-shaped ground contact portion), the depth of which is the same as or greater than the deeper circumferential groove. In other words, it is a ground contact portion sandwiched between two circumferential grooves without any lateral grooves communicating with both circumferential grooves, or a ground contact portion with lateral grooves shallower than the deeper groove of the two circumferential grooves and communicating with both circumferential grooves.

[0091] The Sb / Sa ratio is preferably less than 0.8, more preferably less than 0.75, and even more preferably less than 0.7.

[0092] (2) Rubber composition forming the tread portion

[0093] In this invention, the tread portion is formed of a rubber composition, wherein the loss tangent (tanδ at 15°C) of the rubber composition, measured under conditions of 15°C, 10 Hz frequency, 5% initial strain, and 1% dynamic strain rate, is 0.25 or less. Thus, by reducing tanδ at 15°C to below 0.25, heat generation in the tread portion can be reduced, and tire temperature rise can be suppressed, thereby inhibiting the degradation of the durability of the rubber composition itself and the outer diameter increase caused by temperature rise, preventing tire damage, and improving durability. Tanδ at 15°C is more preferably 0.23 or less, further preferably 0.20 or less, and particularly preferably 0.18 or less.

[0094] The aforementioned 15°C tanδ measurement is performed on a piece of rubber cut radially outward from at least the bottom of the tire groove, preferably from half the depth of the deepest circumferential groove. Specifically, the measurement is performed using a viscoelasticity measuring device, such as the "Eplexor (registered trademark)" manufactured by GABO.

[0095] [2] A more preferred embodiment of the tire of the present invention

[0096] The tire of the present invention can achieve greater effects by taking the following embodiments.

[0097] 1. Aspect Ratio

[0098] The tire of the present invention preferably has an aspect ratio of 40% or more, which increases the height and area of ​​the tire sidewall portion, thereby further enhancing heat dissipation of the entire tire and suppressing the decrease in tread and sidewall rigidity. Therefore, changes in handling characteristics can be sufficiently suppressed. Furthermore, rolling resistance at high speeds can be further reduced, and tire durability can be further improved.

[0099] When the internal pressure is 250 kPa, the aspect ratio (%) can be obtained by using the tire's section height Ht (mm) and section width Wt (mm) using the following formula.

[0100] (Ht / Wt)×100(%)

[0101] The aspect ratio is more preferably 45% or more, and even more preferably 47.5% or more. Furthermore, it is even more preferably 50% or more, particularly preferably 52.5% or more, and most preferably 55% or more. There is no particular upper limit, but for example, it is 100% or less.

[0102] 2. Relationship between loss tangent (tanδ) and cross-sectional width Wt (mm)

[0103] As the cross-sectional width Wt increases, the difference between the contact pressure at the center of the tread and the contact pressure at the shoulder of the tread tends to increase, and it is assumed that heat generation becomes difficult to control. The inventors believe that as the cross-sectional width Wt increases, heat generation can be controlled by reducing tanδ, and investigated the relationship between the loss tangent at 15°C (tanδ at 15°C) and the cross-sectional width Wt (mm). The results show that if tanδ × Wt ≤ 50 at 15°C, heat generation can be controlled according to the width, further reducing rolling resistance at high speeds and further improving tire durability.

[0104] It was discovered that it is more preferable to satisfy tanδ×Wt≦40 at 15℃, and even more preferable to satisfy tanδ×Wt≦30 at 15℃.

[0105] 3. Tread grooves

[0106] In the tire of the present invention, a circumferential groove extending continuously in the tire circumferential direction is formed in the tread portion, and the groove width L is located at 80% of the maximum depth of the circumferential groove. 80 The ratio of the groove width L0 of the circumferential groove on the ground contact surface of the tread portion (L) 80The ratio (L0) is preferably 0.3 to 0.7. Therefore, movement of the entire contact portion on the bottom surface of the contact portion of the tread can be suppressed, and it is known to suppress tread cracking and improve durability. This 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] The above L0 and L 80 These refer to the straight-line distance (L0) between the edges of the grooves on the tread surface of the tire circumferential grooves, respectively, under the condition that the tire is mounted on a standardized rim, with an internal pressure of 250 kPa and no load applied, and the minimum distance (L) between the groove walls at a position where the groove depth is 80%. 80 In short, they can be obtained by compressing the bead portion of a radially cut section with a width of 2-4 cm according to the rim width.

[0108] Preferably, a plurality of circumferential grooves are formed in the tread portion, 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. It is known that this can suppress movement of the tread portion, suppress tread portion cracking, and improve durability. More preferably, it is 15% to 27%, further preferably 18% to 25%, and particularly preferably 21% to 23%.

[0109] The cross-sectional area of ​​a circumferential groove refers to the total area formed by the straight line connecting the ends of the circumferential grooves on the tread and the groove walls within a tire mounted on a standardized rim under an internal pressure of 250 kPa and without load. In short, it can be obtained by compressing a radially cut section of the bead, 2-4 cm wide, according to the rim width.

[0110] Furthermore, it is preferred that a plurality of lateral grooves extending axially in the tread portion are formed, and the total volume of the plurality of lateral grooves is 2.0-5.0% of the volume of the tread portion. It is known that this can suppress movement of the tread portion, suppress tread portion cracking, and improve durability. More preferably, it is 2.2-4.0%, further preferably 2.5-3.5%, and particularly preferably 2.7-3.0%.

[0111] The volume of the lateral grooves mentioned above refers to the total volume of a tire mounted on a standardized rim, with an internal pressure of 250 kPa and under no-load conditions, consisting of the surfaces connecting the two ends of the lateral grooves and the groove walls. In short, it can be obtained by calculating the volume of each lateral groove and multiplying it by the number of grooves, with the bead portion of a radially cut section of 2-4 cm width compressed according to the rim width. Furthermore, the volume of the tread portion can be calculated by multiplying the area excluding the lateral grooves from that section by the outer diameter, and then obtaining the difference between the calculated result and the volume of the lateral grooves.

[0112] To suppress tread chipping and further improve durability, it is preferred that the width ratio (Gw / Gd) of at least one of these lateral grooves is 0.50 to 0.80. This ratio is more preferably 0.53 to 0.77, further preferably 0.55 to 0.75, and particularly preferably 0.60 to 0.70.

[0113] The groove width and groove depth of the aforementioned lateral groove refer to the maximum length of the straight line connecting the two ends of the lateral groove tread (perpendicular to the groove direction) and the maximum depth of the lateral groove, respectively, under the condition of tire internal pressure of 250 kPa and no load applied. In short, it can be calculated by pressing the bead portion of the radially cut section with a width of 2-4 cm according to the rim width.

[0114] In the tire of the present invention, when the tire is mounted on a standardized rim and the internal pressure is 250 kPa, the specific outer diameter Dt (mm) is preferably 515 mm or more, more preferably 558 mm or more, further preferably 585 mm or more, particularly preferably 658 mm or more, and most preferably 673 mm or more. On the other hand, it is preferably less than 843 mm, more preferably less than 725 mm, further preferably less than 707 mm, particularly preferably less than 685 mm, and most preferably less than 655 mm.

[0115] Specifically, the cross-sectional width Wt (mm) is preferably 115mm or more, more preferably 130mm or more, even more preferably 150mm or more, still more preferably 170mm or more, even more preferably 185mm, and most preferably 193mm or more. On the other hand, it is preferably less than 305mm, more preferably less than 245mm, even more preferably less than 210mm, particularly preferably less than 205mm, and most preferably less than 200mm.

[0116] The specific cross-sectional height Ht (mm) is preferably 37mm or more, more preferably 87mm or more, and even more preferably 95mm or more. On the other hand, it is preferably less than 180mm, more preferably less than 112mm, and even more preferably less than 101mm.

[0117] The specific hypothetical volume V is preferably 13,000,000 mm². 3 The above, more preferably 29,000,000 mm 3 The above, or even more preferably 36,000,000 mm 3 That's all. On the other hand, it is preferably less than 66,000,000 mm. 3 More preferably less than 44,000,000 mm 3 Even more preferred is less than 38,800,000 mm 3 .

[0118] Furthermore, in this invention, considering the stability of ride comfort during driving, (Dt-2×Ht) is preferably 450 (mm) or more, more preferably 470 (mm) or more, and even more preferably 480 (mm) or more. On the other hand, considering the deformation of the tread portion, it is preferably less than 560 (mm), more preferably less than 530 (mm), and even more preferably less than 510 (mm).

[0119] [3] Implementation

[0120] The present invention will now be described in detail according to the embodiments.

[0121] 1. A rubber composition forming the tread portion

[0122] The rubber composition forming the tire tread portion of the present invention can be obtained by appropriately adjusting the types and amounts of various compounding materials, such as the rubber components, fillers, softeners, vulcanizing agents and vulcanization accelerators described below, especially the fillers and softeners.

[0123] (1) Rubber composition

[0124] In this embodiment, rubbers (polymers) commonly used in tire production, such as butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene rubber, and nitrile rubber (NBR), are used as the rubber component. Among these rubbers, butadiene rubber (BR), styrene-butadiene rubber (SBR), and isoprene rubber are preferred. Because these rubbers can entangle with each other while the individual rubber phases are separated, deformation within the rubber can be reduced.

[0125] (a)BR

[0126] In a rubber composition of 100 parts by weight, the content of BR is 1 part by weight or more and 100 parts by weight or less. Preferably, it is greater than 25 parts by weight, more preferably greater than 35 parts by weight, and particularly preferably greater than 45 parts by weight. Furthermore, it is preferred to be less than 85 parts by weight, more preferably less than 75 parts by weight, further preferably less than 65 parts by weight, and particularly preferably less than 55 parts by weight. For example, the weight-average molecular weight of BR is greater than 100,000 and less than 200,000. For example, the vinyl bond content of BR is greater than 1% by weight and less than 30% by weight. For example, the cis content of BR is greater than 1% by weight and less than 98% by weight. For example, the trans content of BR is greater than 1% by weight and less than 60% by weight. The cis content of BR can be measured by infrared absorption spectroscopy analysis.

[0127] There are no particular restrictions on BR. BR with high cis content (cis content above 90%), low cis content, or containing syndiotactic polybutadiene crystals can be used. BR can be unmodified or modified. As a modified BR, for example, BR modified with a compound (modifier) ​​represented by the following formula can be used.

[0128] [Chemical Formula 1]

[0129]

[0130] In the formula, R1, R2, and R3 represent the same or different alkyl, alkoxy, siloxy, acetal, carboxyl (-COOH), mercapto (-SH), or derivatives thereof. R4 and R5 represent the same or different hydrogen atoms or alkyl groups. R4 and R5 can combine to form a cyclic structure with a nitrogen atom. n represents an integer.

[0131] As a BR modified by the compound (modifier) ​​represented by the above formula, a BR in which the polymerization end (active end) is modified by the compound represented by the above formula can be used.

[0132] As R 1 、R 2 and R 3 Alkoxy groups are suitable (preferably alkoxy groups having 1 to 8 carbon atoms, more preferably alkoxy groups having 1 to 4 carbon atoms). As R 4 and R 5 Alkyl groups (preferably alkyl groups having 1 to 3 carbon atoms) are suitable. n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. Furthermore, when R... 4 and R 5 When combined with nitrogen atoms to form a cyclic structure, a 4- to 8-membered ring is preferred. Alkoxy groups also include cycloalkoxy groups (e.g., cyclohexyloxy) and aryloxy groups (e.g., phenoxy, benzyloxy).

[0133] Specific examples of the aforementioned modifiers include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane. These can be used alone or in combination of two or more.

[0134] In addition, modified BR can also be used as a modified BR, modified with the following compounds (modifiers). Examples of modifiers include:

[0135] Polyhydric alcohol polyglycidyl ethers, such as ethylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolethane triglycidyl ether and trimethylolpropane triglycidyl ether;

[0136] Polyglycidyl ethers of aromatic compounds having two or more phenolic groups, such as bisphenol A diglycidyl ether;

[0137] Polyepoxides, such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene and polyepoxide liquid polybutadiene;

[0138] Tertiary amines containing epoxy groups, such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine;

[0139] Diglycidyl amino compounds, such as diglycidyl aniline, N,N'-diglycidyl-4-glycidyloxyaniline, diglycidyl n-toluene, tetraglycidyl m-xylylmethylamine, tetraglycidyl amino diphenylmethane, tetraglycidyl p-phenylenediamine, diglycidyl amino methylcyclohexane, and tetraglycidyl-1,3-diaminomethylcyclohexane;

[0140] Acidic chlorides containing amino groups, such as bis(1-methylpropyl)carbamate chloride, 4-morpholine carbamate chloride, 1-pyrrolidine carbamate chloride, N,N-dimethylcarbamate chloride and N,N-diethylcarbamate chloride;

[0141] Silane compounds containing epoxy groups, such as 1,3-bis(glycidylpropyl)-tetramethyldisiloxane and (3-glycidylpropyl)-pentamethyldisiloxane;

[0142] Silane compounds containing thioether groups, such as (trimethylsilyl)[3-(trimethoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(tripropoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(methyldipropoxysilyl)propyl] sulfide, and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl] sulfide;

[0143] N-substituted aziridine compounds, such as ethyleneimine and propyleneimine;

[0144] 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;

[0145] (Thio)benzophenone compounds having an amino group and / or a substituted amino group, such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-tert-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone and N,N,N',N'-bis(tetraethylamino)benzophenone;

[0146] 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;

[0147] N-substituted pyrrolidones, such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-tert-butyl-2-pyrrolidone and N-methyl-5-methyl-2-pyrrolidone;

[0148] N-substituted piperidinones, such as N-methyl-2-piperidinone, N-vinyl-2-piperidinone and N-phenyl-2-piperidinone;

[0149] N-substituted lactams, such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurolactam, N-vinyl-ω-laurolactam, N-methyl-β-propiolactam and N-phenyl-β-propiolactam; and

[0150] 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-dimethylvinylurea, 1,3-divinylvinylurea, 1,3-diethyl-2-imidazolium ketone, 1-methyl-3-ethyl-2-imidazolium ketone, 4-N,N-dimethylaminoacetophenone, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, and 1,7-bis(methylethylamino)-4-heptanone. Modification with the above compounds (modifiers) can be carried out by known methods. These modified BRs can be used alone or in combination of two or more.

[0151] As a business partner (BR), for example, products from Sumitomo Ube Kosan Co., Ltd., JSR Corporation, Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., etc. can be used.

[0152] (b)SBR

[0153] In 100 parts by weight of rubber composition, the content of SBR is 1 part by weight or more and less than 100 parts by weight. Preferably, it is greater than 5 parts by weight, more than 15 parts by weight, and particularly preferred, greater than 25 parts by weight. Furthermore, less than 65 parts by weight is preferred, less than 55 parts by weight is more preferred, less than 45 parts by weight is further preferred, and less than 35 parts by weight is particularly preferred.

[0154] For example, the weight-average molecular weight of the SBR is greater than 100,000 and less than 2 million. The styrene content of the SBR is 5% by mass or more, particularly 8% by mass or more. Furthermore, less than 35% by mass is preferred, less than 25% by mass is more preferred, and less than 15% by mass is even more preferred. The vinyl bond content (the amount of 1,2-bonded butadiene units) of the SBR is, for example, greater than 5% by mass and less than 70% by mass. Generally, the lower the styrene content and the lower the vinyl bond content, the lower the glass transition temperature (Tg) of the rubber composition. Therefore, the rubber composition preferably has a low styrene content and a low vinyl bond content. The structural identification of the SBR (measurement of styrene content and vinyl bond content) can be performed using instruments such as the JNM-ECA series manufactured by JEOL Ltd.

[0155] There are no particular limitations on SBR; for example, emulsion-polymerized styrene-butadiene rubber (E-SBR) and solution-polymerized styrene-butadiene rubber (S-SBR) can be used. SBR can be unmodified or modified.

[0156] Modified SBR can be any SBR with functional groups that interact with fillers (such as silica). Examples include:

[0157] Terminal modified SBR (terminal modified SBR with the above-mentioned functional groups at the end), wherein at least one end of the SBR is modified by a compound (modifier) ​​having the above-mentioned functional groups.

[0158] The SBR is modified on the main chain, and its functional groups are on the main chain.

[0159] Main-chain terminal modified SBR, having functional groups in the main chain and at the terminals (e.g., a main chain terminal modified SBR having the aforementioned functional groups and at least one terminal modified with the aforementioned modifier); and

[0160] Terminally modified SBRs are modified (coupled) by using polyfunctional compounds with two or more epoxy groups in the molecule, and introducing epoxy or hydroxyl groups therein.

[0161] Examples of functional groups include amino, amide, silyl, alkoxysilyl, isocyanate, imino, imidazo, urea, ether, carbonyl, oxycarbonyl, mercapto, thioether, dithioether, sulfonyl, sulfinyl, thiocarbonyl, ammonium, imino, hydrazine, azo, diazo, carboxyl, nitrile, pyridyl, alkoxy, hydroxyl, oxygen, and epoxy. Furthermore, these functional groups may also have substituents.

[0162] Furthermore, as a modified SBR, for example, an SBR modified with a compound (modifier) ​​represented by the above formula can be used.

[0163] As an SBR (Self-Borne Batch Reactor), SBRs manufactured and sold by companies such as Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Co., Ltd., and Zeon Corporation can be used. SBRs can be used alone or in combination of two or more types.

[0164] (c) Isoprene rubber

[0165] In a rubber composition of 100 parts by weight, the content (total content) of isoprene rubber is 1 part by weight or more and less than 100 parts by weight. Preferably, it is greater than 5 parts by weight, and more than 15 parts by weight is more preferred. Furthermore, less than 55 parts by weight is preferred, less than 45 parts by weight is more preferred, less than 35 parts by weight is further preferred, and less than 25 parts by weight is particularly preferred. Examples of isoprene rubber include natural rubber (NR), isoprene rubber (IR), reconstituted NR, modified NR, and modified IR.

[0166] For example, common tire industry materials such as SIR20, RSS#3, and TSR20 can be used for natural rubber (NR). There are no particular restrictions on natural rubber (IR); for example, IR2200, also common in the tire industry, can be used. Modified NR includes deproteinized natural rubber (DPNR) and high-purity natural rubber (UPNR). Modified NR also includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Modified IR includes epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These materials can be used alone or in combination of two or more.

[0167] (d) Other rubber components

[0168] In addition, as another rubber component, it may include rubber (polymer) commonly used in tire production, such as nitrile rubber (NBR).

[0169] (2) Compound materials other than rubber components

[0170] (a) Packing

[0171] In this embodiment, the rubber composition preferably includes fillers. Specific examples of fillers include silica, carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. Silica and carbon black are preferably used as reinforcing agents. When silica is used, it is preferably used in combination with a silane coupling agent.

[0172] (a-1)Silica

[0173] The rubber composition preferably contains silica. From the perspective of obtaining good durability, the BET specific surface area of ​​silica is preferably greater than 140 m². 2 / g, more preferably greater than 160m 2 / g. On the other hand, from the perspective of obtaining good rolling resistance at high speeds, a value of less than 250m is preferred. 2 / g, more preferably less than 220m 2 / g. The BET specific surface area mentioned above is the N2SA value measured by the BET method according to ASTM D3037-93.

[0174] When silica is used as a filler and reinforcing agent, from the perspective of obtaining good durability, the silica content is preferably greater than 60 parts by weight, more preferably greater than 70 parts by weight, relative to 100 parts by weight of the rubber component. On the other hand, 200 parts by weight or less is preferred, 150 parts by weight or less is more preferred, and 130 parts by weight or less is even more preferred.

[0175] Examples of silica include dry silica (anhydrous silica) and wet silica (hydrated silica). Wet silica is preferred because it has a large number of silanol groups.

[0176] As silica, products from companies such as Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., and Tokuyama Corporation can be used.

[0177] (a-2) Silane coupling agent

[0178] 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:

[0179] 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;

[0180] Thiol-based silane coupling agents, such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z manufactured by Momentive;

[0181] Vinyl silane coupling agents, such as vinyltriethoxysilane and vinyltrimethoxysilane;

[0182] Aminosilane coupling agents, such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane;

[0183] Glycidyl ether oxysilane coupling agents, such as γ-glycidyl ether oxypropyltriethoxysilane and γ-glycidyl ether oxypropyltrimethoxysilane;

[0184] Nitrosilane coupling agents, such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and

[0185] Chlorinated silane coupling agents, such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These can be used alone or in combination of two or more.

[0186] 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.

[0187] 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.

[0188] (a-3) Carbon black

[0189] 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.

[0190] 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; channel black (channel black), such as EPC, MPC, and CC; and graphite. These can be used alone or in combination of two or more.

[0191] 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.

[0192] 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.

[0193] (a-4) Other fillers

[0194] 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. 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.

[0195] (b) Softener

[0196] The rubber composition may contain oil (including spreadable oil) or liquid rubber as a softener. The total content of these is preferably greater than 5 parts by weight, more preferably greater than 10 parts by weight, relative to 100 parts by weight of the rubber component. On the other hand, less than 70 parts by weight is preferred, less than 50 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).

[0197] 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.

[0198] 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.

[0199] 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.

[0200] 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).

[0201] Farnesene polymers can be homopolymers of farnesene (farnesene homopolymers) or copolymers of farnesene and vinyl monomers (farnesene-vinyl monomer copolymers).

[0202] 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).

[0203] 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).

[0204] 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.

[0205] As a liquid rubber, products from Kuraray Co., Ltd. and Clay Valley Co., Ltd. can be used, for example.

[0206] (c) Resin composition

[0207] In addition, 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. 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.

[0208] 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.

[0209] 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.

[0210] 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.

[0211] 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.

[0212] 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).

[0213] 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.

[0214] 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.

[0215] 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.

[0216] 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.

[0217] 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. Coumarin-indene resin, coumarin resin, indene resin, and aromatic vinyl resins are preferred as specific examples. 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.

[0218] 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.

[0219] There are no particular restrictions on acrylic resins; for example, solvent-free acrylic resins can be used.

[0220] As a solvent-free acrylic resin, (meth)acrylic resin (polymer) synthesized by high-temperature continuous polymerization (high-temperature continuous bulk polymerization: methods described in US Patent No. 4,414,370, JP 84-6207A, JP 93-58805A, JP 89-313,522A, US Patent No. 4,414,370, Toa Synthetic Research Annual Report TREND2000 No. 3, pp. 42-45, etc.), and minimizing the use of polymerization initiators, chain transfer agents, organic solvents, etc., as auxiliary materials. In this invention, (meth)acrylic acid refers to methacrylic acid and acrylic acid.

[0221] 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.

[0222] 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.

[0223] 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.

[0224] As a resin component, products from companies such as 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. can be used.

[0225] (d) Anti-aging agents

[0226] 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.

[0227] 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.

[0228] 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.

[0229] (e) Stearic acid

[0230] 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.

[0231] (f) Zinc oxide

[0232] 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.

[0233] (g) wax

[0234] 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.

[0235] There are no particular limitations on the types of waxes used; 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 like ethylene and propylene. These can be used alone or in combination of two or more.

[0236] 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.

[0237] (h) Crosslinking agents and vulcanization accelerators

[0238] 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.

[0239] 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.

[0240] 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.

[0241] 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.

[0242] 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.

[0243] Examples of vulcanization accelerators include:

[0244] Thiazole vulcanization accelerators, such as 2-mercaptobenzothiazole, di-2-benzothiazole disulfide and N-cyclohexyl-2-benzothiamide;

[0245] Thiuram-based vulcanization accelerators, such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetra(2-ethylhexyl)thiuram disulfide (TOT-N);

[0246] 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;

[0247] And guanidine vulcanization accelerators, such as diphenylguanidine, di-o-tolylguanidine and o-tolylguanidine.

[0248] These can be used individually or in combination of two or more.

[0249] (i) Other

[0250] 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, and organic peroxides. 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.

[0251] 2. Production of tread rubber composition

[0252] 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.

[0253] Mixing can be carried out using known (sealed) mixing machines, such as Banbury mixers, mixing mills, or open rolls.

[0254] 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.

[0255] 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.

[0256] 3. Tire manufacturing

[0257] The tire of the present invention is manufactured using an uncured rubber composition obtained through a refining step by conventional methods. In other words, the uncured rubber composition is extruded according to the shape of the tread and formed together with other tire components on a tire forming machine by conventional methods to produce an uncured tire.

[0258] 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 forcefully tightening the carcass to increase tread rigidity) are wound. The two ends of the carcass are fixed to two sides, and the bead portion (for securing the tire to the rim) is arranged in a ring. Then, the tread is bonded to the center of the outer periphery, and the sidewall portion is bonded to the radially outer side, thus producing an uncured tire.

[0259] 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.

[0260] 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.

[0261] At this time, multiple rib-shaped ground contact portions are formed by circumferential grooves that extend continuously in the circumferential direction; a tread portion is formed such that when the ground contact surface of the tread portion is divided by a meridional plane, with one of the divided regions being Sa and the other being Sb, Sa > Sb; and when the tire is mounted on a standardized rim and the internal pressure is 250 kPa, the tire is shaped to satisfy the above (Equation 1) and (Equation 2).

[0262] 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.

[0263] In this embodiment, a tire that can satisfy (Equation 1) and (Equation 2) is preferably used in a pneumatic tire for a passenger car, and satisfying the above equations can more advantageously solve the problem in the present invention, namely, to provide a pneumatic tire that not only sufficiently reduces the rolling resistance of the tire at high speeds, but also sufficiently improves the changes in handling characteristics and durability at low and high speeds.

[0264] Example

[0265] The present invention will now be described in more detail with reference to embodiments.

[0266] [Experiment 1]

[0267] In this experiment, tires of size 175 were prepared and evaluated.

[0268] 1. A rubber composition for use in tire treads.

[0269] First, the rubber components used in tire treads are produced.

[0270] (1) Mixed materials

[0271] First, prepare each of the following compound materials.

[0272] (a) Rubber composition

[0273] (a-1)NR:TSR20

[0274] (a-2) SBR: Modified solution-polymerized SBR produced according to the method described in the next paragraph. (Styrene content: 10% by mass, vinyl bond content: 20% by mass, Mw: 250,000)

[0275] (a-3)BR: BR150 manufactured by Ube Kosan Co., Ltd.

[0276] The SBR described above was produced according to the following procedure. First, cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were charged into a nitrogen-purged high-pressure reactor. After adjusting the temperature of the reactor contents to 20°C, n-butyllithium was added to initiate polymerization. Polymerization was carried out under adiabatic conditions, with a maximum temperature of 85°C. When the polymerization conversion reached 99%, 1,3-butadiene was added, followed by further polymerization for 5 minutes. Subsequently, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane was added as a modifier, and the reaction was carried out. After the polymerization reaction was completed, 2,6-di-tert-butyl-p-cresol was added. Then, the solvent was removed by steam stripping, and the product was dried by hot rollers adjusted to 110°C to obtain the SBR.

[0277] (b) Compound materials other than rubber components

[0278] (b-1) Carbon black: Diablack N220 manufactured by Mitsubishi Chemical Corporation

[0279] (b-2) Silica: Ultrasil VN3 (BET specific surface area: 165m²) manufactured by Evonik Co., Ltd.2 / g)

[0280] (b-3) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Degussa Co., Ltd.

[0281] (b-4) Oil: Process X-140 manufactured by Japan Energy Co., Ltd.

[0282] (b-5) Anti-aging agent: SA85 (α-methylstyrene resin) manufactured by Arizona Chemical Co., Ltd.

[0283] (b-6) Zinc oxide: White Zinc No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd.

[0284] (b-7) Stearic acid: Stearic acid "TSUBAKI" manufactured by NOF CORPORATION.

[0285] (b-8) Wax: Sunnoc wax manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0286] (b-9) Anti-aging agent-1: Nocrac6C (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0287] (b-10) Crosslinking agents and vulcanization accelerators

[0288] Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.

[0289] Vulcanization accelerator-1: NoccelerCZ-G(CBS) (N-cyclohexyl-2-benzothiazolylsulfonamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0290] Vulcanization Accelerator-2: Nocceler D(DPG)(1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0291] (2) Production of rubber compositions

[0292] Following the formulations shown in Tables 1 and 2, materials excluding sulfur and vulcanization accelerators were mixed in a Banbury mixer at 150°C for 5 minutes to obtain the mixed product. All quantities are parts by weight.

[0293] 2. Tire manufacturing

[0294] Next, sulfur and a vulcanization accelerator were added to the obtained compound, and the mixture was kneaded at 80°C with open rollers for 5 minutes to obtain a tread rubber composition. The obtained tread rubber composition was used to form a tread, which was then bonded to other tire components to form an unvulcanized tire. The tire was then pressed and vulcanized at 170°C for 10 minutes to produce various test tires with a size of 175 (Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-5).

[0295] In each of the test 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.

[0296] 3. Parameter Calculation

[0297] Subsequently, the outer diameter Dt (mm), cross-sectional width Wt (mm), cross-sectional height Ht (mm), Sb / Sa, and aspect ratio (%) of each test tire were obtained, and the hypothetical volume V (mm²) was also obtained. 3 Meanwhile, rubber test pieces measuring 20 mm in length, 4 mm in width, and 2 mm in thickness were cut from the rubber layer of the tread portion of each test tire to prepare viscoelasticity measurements, with the tire's circumference as the long side. For each rubber test piece, tanδ (tanδ at 15℃) was measured using an Eplexor series instrument manufactured by GABO Co., Ltd. under conditions of 15℃, 10 Hz frequency, 5% initial strain, and 1% dynamic strain. The thickness direction of the sample was the radial direction of the tire. The results are shown in Tables 1 and 2.

[0298] Furthermore, Sa and Sb can be obtained by mounting the tire on a standardized rim, applying standardized internal pressure, coating the tread with black ink, applying a standardized load, and pressing the tread onto thick paper (with a camber angle of 0°), thus transferring the black ink onto the paper. Specifically, the tire is rotated 72° circumferentially, and five sheets of thick paper are used to transfer ink at five different locations to obtain a transferred image. Therefore, the shape of the ground contact surface along the entire circumference of the tire can be considered obtained.

[0299] Then, when the transfer images of the five thick sheets of paper are divided by the meridional plane, Sa is obtained by summing the areas of one of the contact areas (excluding the grooves and slits, i.e., the inked area); and Sb is obtained by summing the areas of the other contact area (excluding the grooves and slits, i.e., the inked area).

[0300] Then, (Dt-2×Ht) and (Dt) were determined. 2 ×π / 4) / Wt、(V+1.5×10 7 ) / Wt、(V+2.0×10 7 ) / Wt、(V+2.5×10 7 ) / Wt and tanδ×Wt at 15℃. The results are shown in Tables 1 and 2.

[0301] 4. Performance Evaluation Test

[0302] (1) Evaluation of handling performance

[0303] Test tires were installed on all wheels of a vehicle (a domestically produced FF car with a 2000cc engine) and inflated to an internal pressure of 250 kPa. While driving on a dry road surface at speeds of 40 km / h and 120 km / h, drivers assessed the changes in handling characteristics using a five-point scale ranging from 1 (significant change) to 5 (almost no change). The total evaluation scores from 20 drivers were then calculated.

[0304] Next, the results from Comparative Examples 1-5 are set to 100, and the evaluation is indexed based on the following formula to assess handling performance. The larger the value, the better the handling performance.

[0305] Handling performance = [(Results of the test tires) / (Results of Comparative Examples 1-5)] × 100

[0306] (2) Evaluation of durability performance

[0307] 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 then driven for 10 laps at 50 km / h. Next, it was driven at 80 km / h up an uneven section of the road, and this process was repeated on a dry surface under overload conditions at the test track. 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 would experience an abnormality.

[0308] 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.

[0309] Durability = [(Results of the test tires) / (Results of Comparative Examples 1-5)] × 100

[0310] (3) Comprehensive evaluation

[0311] The combined evaluation results of (1) and (2) above are used to obtain a comprehensive evaluation.

[0312] (4) Evaluation Results

[0313] The results of each evaluation are shown in Table 1 and Table 2.

[0314] [Table 1]

[0315]

[0316]

[0317] [Table 2]

[0318]

[0319]

[0320] [Experiment 2]

[0321] In this experiment, tires of size 195 were prepared and evaluated.

[0322] After producing the test tires of Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-5 shown in Tables 3 and 4 in the same manner as in Experiment 1, the parameters were calculated using the same procedure. Performance evaluation tests were then conducted and evaluated in the same manner. In this experiment, the results of Comparative Examples 2-5 were set to 100 for evaluation. The results of each evaluation are shown in Tables 3 and 4.

[0323] [Table 3]

[0324]

[0325] [Table 4]

[0326]

[0327] [Experiment 3]

[0328] In this experiment, tires of size 225 were prepared and evaluated.

[0329] After producing 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 calculated using the same procedure. Performance evaluation tests were then conducted in the same manner and evaluated. In this experiment, the results of Comparative Examples 3-5 were set to 100 for evaluation. The results of each evaluation are shown in Tables 5 and 6.

[0330] [Table 5]

[0331]

[0332]

[0333] [Table 6]

[0334]

[0335]

[0336] [Summary of Experiments 1 to 3]

[0337] The results from Experiments 1 to 3 (Tables 1 to 6) show that for tires of any size (175, 195, 225), when Sa > Sb (Sb / Sa < 1) and the above (Equation 1) and (Equation 2) are satisfied, a pneumatic tire can be provided that not only reduces rolling resistance, but also fully suppresses changes in handling characteristics at low and high speeds, while also significantly improving durability.

[0338] Thus, it is shown that by satisfying the aforementioned embodiment 2 and subsequent embodiments, a tire with further improved handling characteristics and durability at low and high speeds can be provided.

[0339] On the other hand, when (Equation 1) or (Equation 2) is not satisfied, the changes in handling characteristics at low speeds and high speeds are not small enough, and the durability is not sufficiently improved.

[0340] [Experiment 4]

[0341] Next, three types of tires (Examples 4-1 to 4-3) were produced using the same composition, 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 the evaluations of handling characteristics and durability described above, fuel efficiency was also evaluated.

[0342] Specifically, each test tire was installed on all wheels of a vehicle (a domestically produced FF car with a 2000cc engine), inflated with air to a pressure of 250 kPa, and then driven at 100 km / h on a dry road surface. After completing one lap of 10 km, 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 of each test tire.

[0343] Next, taking the results from Examples 4-3 as 100, the results are indexed based on the following formula to evaluate fuel efficiency relatively. The larger this value, the longer the distance from releasing the accelerator to the vehicle stopping, and the smaller the rolling resistance in a steady state, indicating excellent fuel efficiency.

[0344] Fuel efficiency = [(Test tire results) / (Results of Example 4-3)] × 100

[0345] Then, as with experiments 1 through 3, the evaluation results were aggregated to make a comprehensive evaluation. The results of each evaluation are shown in Table 7.

[0346] [Table 7]

[0347]

[0348] Table 7 shows that when the relationship between the hypothetical volume V and the cross-sectional width Wt is not significantly different, as the cross-sectional width Wt decreases, such as from less than 205 mm to less than 200 mm, and as the aspect ratio increases, all handling characteristics, durability, and fuel efficiency improve. In other words, a significant effect is evident.

[0349] Although the present invention has been described above based on embodiments, the present invention is not limited to the embodiments described above. 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 rubber layer constituting the tread portion is formed of a rubber composition, the loss tangent at 15°C (tanδ) being less than 0.25 when measured under conditions of 15°C, 10Hz frequency, 5% initial strain, and 1% dynamic strain rate. In the tread portion, multiple rib-shaped contact portions are formed by circumferential grooves that extend continuously in the circumferential direction; When the ground contact surface of the tread portion is divided by a meridional plane, and when one ground contact area is Sa and the other is Sb, Sa > Sb; 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 When the tire is mounted on a standardized rim and the internal pressure is 250 kPa, the tire satisfies the following equations 1 and 2. 1600≦(Dt 2 (×π / 4) / Wt≦2827.4···Equation 1 [(V+1.5×10 7 ) / Wt]≦2.88×10 5 Equation 2; The tire satisfies the following formula 4. [(V+2.5×10 7 ) / Wt]≦2.88×10 5 ...Formula 4; 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×Ht) is 470 or more, and the hypothetical volume V mm of the tire is calculated using the following formula. 3 : V=[(Dt / 2) 2 -{(Dt / 2)-Ht} 2 ]×π×Wt; The aspect ratio is 47.5% or higher, wherein the aspect ratio is obtained by the following formula: (Ht / Wt)×100%; and When the outer diameter of the tire is Dt mm, and when the tire is mounted on a standardized rim with an internal pressure of 250 kPa, Dt is less than 685.

2. The pneumatic tire of claim 1, wherein the 15°C tanδ is less than 0.

20.

3. The pneumatic tire as claimed in claim 1, wherein the tire satisfies 15℃tanδ×Wt≦40.

4. The pneumatic tire as claimed in claim 1, wherein the tire satisfies 15℃tanδ×Wt≦30.

5. The pneumatic tire as claimed in claim 1 or 2, wherein a plurality of circumferential grooves extending continuously in the tire circumferential direction are formed in the tread portion, 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.

6. The pneumatic tire of claim 1 or 2, wherein a plurality of lateral grooves extending axially in the tread portion are formed therein, and the total volume of the plurality of lateral grooves is 2.0% to 5.0% of the volume of the tread portion.

7. The pneumatic tire of claim 1 or 2, wherein Wt is less than 205.

8. The pneumatic tire of claim 7, wherein Wt is less than 200.

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