Pneumatic tire

Abstract

Provided is a pneumatic tire in which the rolling resistance at high speed is sufficiently reduced, and in which durability is also sufficiently improved. The pneumatic tire has a side portion, at the maximum width of the tire, the thickness S (mm) of the rubber layer radially outside the carcass of the side portion is 3 mm or less, the loss tangent (70°C tan δ) of the rubber layer measured at 70°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is 0.15 or less, and when the tire is mounted on a standard rim, the inner pressure is 250 kPa, the cross-sectional width of the tire is Wt (mm), the outer diameter is Dt (mm), the volume of the space occupied by the tire is a virtual volume V (mm 3 ), the tire satisfies the following (Formula 1) and (Formula 2): 1700 ≦ (Dt 2 × π / 4) / Wt ≦ 2827.4 (Formula 1) [(V + 1.5 × 10 7 ) / Wt] ≦ 2.88 × 10 5 (Formula 2).

Description

TECHNICAL FIELD

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

[0002] In recent years, from the viewpoint of increasing concern for environmental problems and economic efficiency, the requirement for fuel efficiency of automobiles is becoming higher, and there is a strong demand for improving the fuel efficiency of pneumatic tires (hereinafter referred to as "tires") mounted 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, in the past, a proposal has been made to reduce the rolling resistance by studying the formulation of a rubber composition constituting the tread portion of a tire (for example, Patent Documents 1 to 4).

[0005] PRIOR 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, it cannot be said that the rolling resistance of a tire manufactured by the above conventional technology is sufficiently reduced at the time of high-speed running, and further reduction is required. Also, it cannot be said that such a tire has sufficient durability.

[0013] Therefore, one object of the present disclosure is to provide a pneumatic tire whose rolling resistance at the time of high-speed running is sufficiently reduced, and whose durability is also sufficiently improved.

[0014] MEANS FOR SOLVING THE PROBLEM

[0015] The present inventors have earnestly studied a solution to the above problem, and found that the above problem can be solved by the disclosure described below, and completed the present disclosure.

[0016] The present disclosure is:

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

[0018] The thickness S (mm) of the rubber layer radially outside the carcass of the side portion at the maximum width of the tire is 3 mm or less; the loss tangent (70°C tan δ) of the rubber layer measured at 70°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is 0.15 or less; and

[0019] When the cross-sectional width of the tire in a state where the tire is mounted on a standard rim and the internal pressure is 250 kPa is Wt (mm), the outer diameter is Dt (mm), and the volume of the space occupied by the tire is a virtual volume V (mm 3 ), the tire satisfies the following (Formula 1) and (Formula 2):

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

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

[0022] Technical effects of the present application

[0023] According to the present disclosure, it is possible to provide a pneumatic tire in which the rolling resistance at high speed is sufficiently reduced, and the durability is sufficiently improved. DETAILED DESCRIPTION

[0024] 1) Features of the tire of the present disclosure

[0025] First, the features of the tire according to the present disclosure will be described.

[0026] 1. SUMMARY

[0027] The tire according to the present disclosure is characterized in that the thickness S (mm) of the rubber layer radially outside the carcass of the side portion at the maximum width of the tire is 3 mm or less, and the loss tangent (70°C tan δ) of the rubber layer measured at 70°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is 0.15 or less.

[0028] The tire according to the present disclosure is further characterized in that when the cross-sectional width of the tire in a state where the tire is mounted on a standard rim and the internal pressure is 250 kPa is Wt (mm), the outer diameter is Dt (mm), and the volume of the space occupied by the tire is a virtual volume V (mm 3 ), the tire satisfies the following (Formula 1) and (Formula 2):

[0029] 1700 ≦ (Dt 2 × π / 4) / Wt ≦ 2827.4 (Formula 1)

[0030] [(V + 1.5 × 107 ) / Wt]≦2.88x10 5 (Formula 2).

[0031] The rubber layer forming the side portion and the shape of the tire have the above-described characteristics, and thus a tire in which the rolling resistance is sufficiently reduced and the durability is sufficiently improved at high speed running can be provided.

[0032] In the above description, the "standard rim" is a rim defined for each tire in a standard system including the standard on which the tire is based. 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 YEARBOOK"; 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". If the tire is not specified in the standard, it refers to a rim that can be assembled and can maintain the internal pressure, i.e., does not cause air leakage between the rim and the tire, and has the minimum rim diameter and the narrowest rim width.

[0033] Further, the outer diameter Dt of the tire refers to the outer diameter of the tire in the state of being mounted on the standard rim, having an internal pressure of 250 kPa, and being in an unloaded state. The cross-sectional width Wt (mm) of the tire refers to the width of the tire in the state of being mounted on the standard rim, having an internal pressure of 250 kPa, and being in an unloaded state, and refers to the distance from the straight line between the sidewall of the tire including all patterns, letters, etc. on the tire side surface (total width of the tire) excluding the distance of the patterns, letters, etc. on the tire side surface.

[0034] Further, the virtual volume V (mm 3 , specifically, can be calculated based on the outer diameter Dt (mm) of the tire, the cross-sectional height (distance from the bead bottom to the outermost side of the tread; 1 / 2 of the difference between the outer diameter of the tire and the nominal diameter of the rim) Ht (mm), and the cross-sectional width Wt (mm) of the tire in the state of being mounted on the standard rim, having an internal pressure of 250 kPa, and not being subjected to a load, by the following formula:

[0035] V = [(Dt / 2) 2 - {(Dt / 2) - Ht} 2 ] x π x Wt.

[0036] 2. Mechanism of the effect exhibited by the tire according to the present disclosure

[0037] The mechanism of the effect exhibited by the tire according to the present disclosure, i.e., the mechanism in which the rolling resistance is sufficiently reduced and the durability is sufficiently improved at high speed running, is presumed as follows.

[0038] (1) Tire shape

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

[0040] By increasing the area of the tire when viewed from the side with respect to the cross-sectional width Wt of the tire [(Dt / 2 2 × π) = (Dt 2 × π / 4)], and satisfying the numerical range specified in (Formula 1), the number of repetitions of deformation per unit time is reduced, as a result, the time available for heat exchange is increased, thereby improving the heat dissipation performance of the side portion, and the friction between the tread portion and the road surface can be reduced, it is believed that the durability and low rolling resistance of the tire can be improved.

[0041] In (Formula 1), (Dt 2 × π / 4) / Wt is more preferably 1735 or more, still more preferably 1737 or more, still more preferably 1749 or more, still more preferably 1751 or more, still more preferably 1753 or more, still more preferably 1758 or more, still more preferably 1760 or more, still more preferably 1787 or more, still more preferably 1801 or more, still more preferably 1818 or more, still more preferably 1853 or more, still more preferably 1856 or more, still more preferably 1864 or more, still more preferably 1865 or more, still more preferably 1963.4 or more, still more preferably 2004 or more, still more preferably 2018 or more, still more preferably 2027 or more, still more preferably 2030 or more, still more preferably 2033 or more, still more preferably 2113 or more.

[0042] However, since the centrifugal force of such a tire increases during rolling, the radius of the tire greatly increases during rolling, and the tread portion becomes correspondingly thinner, and thus, when an impact is applied to the tread portion, damage can occur. In addition, since the outer diameter increases due to the centrifugal force, the amount of deformation of the side portion also increases, and thus, there is room for improvement in terms of rolling resistance during high-speed travel.

[0043] Therefore, in the present disclosure, the virtual volume V (mm 3 ) and the cross-sectional width Wt (mm) of the tire are sought to satisfy [(V + 1.5 × 10 7 ) / Wt] ≦ 2.88 × 10 5 (Formula 2).

[0044] In this case, it is considered that the virtual volume V of the tire is reduced in accordance with the reduction of the tire cross-sectional width Wt, and the volume of the tire itself is reduced, the rate of increase in the outer diameter caused by centrifugal force can be reduced, and the damage resistance of the tread portion when an impact is applied to the tread portion can be improved. In addition, it is considered that the amount of deformation of the side portion can be reduced by suppressing the increase in the outer diameter of the tire.

[0045] [(V + 1.5 x 10 7 ) / Wt] is more preferably 2.87 x 10 5 The following is also preferably 2.86 x 10 5 The following is also preferably 2.77 x 10 5 The following is also preferably 2.60 x 10 5 The following is also preferably 2.58 x 10 5 The following is also preferably 2.54 x 10 5 The following is also preferably 2.50 x 10 5 The following is also preferably 2.42 x 10 5 The following is also preferably 2.26 x 10 5 The following is also preferably 2.25 x 10 5 The following is also preferably 2.24 x 10 5 The following is also preferably 2.21 x 10 5 The following is also preferably 2.20 x 10 5 The following is also preferably 2.19 x 10 5 The following is also preferably 2.16 x 10 5 The following is also preferably 2.16 x 10

[0046] At this time, more preferably [(V + 2.0 x 10 7 ) / Wt] ≦ 2.88 x 10 5 (Formula 3), further preferably [(V + 2.5 x 10 7 ) / Wt] ≦ 2.88 x 10 5 (Formula 4).

[0047] The above [(V + 2.0 x 10 7 ) / Wt] is also preferably 2.83 x 10 5 The following is also preferably 2.79 x 10 5 The following is also preferably 2.77 x 10 5 The following is also preferably 2.64 x 10 5 The following is also preferably 2.49 x 10 5 The following is also preferably 2.47 x 10 5 The following is also preferably 2.46 x 10 5 The following is also preferably 2.45 x 10 5 The following is also preferably 2.44 x 105 the following.

[0048] Furthermore, [(V+2.5×10⁷) / Wt] is preferably 2.86×10⁷. 5 The following is also preferred: 2.77 × 10⁻⁶ 5 The following is also preferred: 2.76 × 10⁻⁶ 5 The following is also preferred: 2.72 × 10⁻⁶ 5 The following is also preferred: 2.71 × 10⁻⁶ 5 The following is also preferred: 2.70 × 10 5 The following is also preferred: 2.69 × 10⁻⁶ 5 The preferred value is 2.68 × 10⁻⁶. 5 the following.

[0049] (2) Rubber composition forming the tread area

[0050] In this disclosure, the thickness S (mm) of the rubber layer forming the tread portion on the radially outer side of the tire carcass at the maximum width of the tire is 3 mm or less, and the loss tangent (70°C tanδ) measured under the conditions of 70°C, 10 Hz frequency, 5% initial strain, and 1% dynamic strain rate is 0.15 or less.

[0051] Therefore, heat generation in the sidewalls can be reduced, and the heat dissipation performance of the sidewalls can be further improved. This can suppress the increase in tire outer diameter due to air expansion inside the tire, and it is believed that this can further improve durability and low rolling resistance at high speeds. tanδ at 70°C is more preferably 0.11 or less, and even more preferably 0.07 or less.

[0052] The aforementioned 70°C tanδ measurement is performed on a piece of rubber cut at least radially outward from the bottom of the tire groove (preferably radially outward from half the depth of the deepest circumferential groove). Specifically, it is measured using a viscoelasticity measuring device, such as the "Eplexor (registered trademark)" manufactured by GABO. When the rubber layer forming the side is formed of multiple layers, the 70°C tanδ of one of the layers should be less than 0.15.

[0053] 2) A more preferred embodiment of the tire according to this disclosure.

[0054] The tire according to this disclosure can achieve more significant technical effects by adopting the following embodiments.

[0055] 1. Flatness

[0056] The tire disclosed herein preferably has an aspect ratio of 40% or more, thereby increasing the side surface area, further improving heat dissipation performance, further reducing rolling resistance at high speeds, and further improving tire durability.

[0057] When the internal pressure is 250 kPa, the above-mentioned flatness (%) can be obtained by the following equation using the cross-sectional height Ht (mm) and the cross-sectional width Wt (mm) of the tire.

[0058] (Ht / Wt) x 100 (%)

[0059] The flatness is more preferably 45% or more, further preferably 47.5% or more, further preferably 49% or more, further preferably 50% or more, further preferably 51% or more, further preferably 52.5% or more, further preferably 53% or more, further preferably 55% or more, and further preferably 58% or more. There is no specific upper limit, but for example, it is 100% or less.

[0060] 2. Side rubber layer

[0061] When the side portion is thick and has a large area, the amount of heat generated can be greater than the amount of heat released from the side portion. Therefore, the relationship between (V / Wt) x S (an index related to the volume of the side portion) and the 70°C tan δ (an index related to heat generation) was investigated. As a result, it was found that if 70°C tan δ x (V / Wt) x S ≦ 80000 (Equation 5) is satisfied, the generation of heat can be appropriately controlled, the rolling resistance at high speed can be further reduced, and the durability of the tire can be further improved.

[0062] More preferably, 70°C tan δ x (V / Wt) x S ≦ 60000 (Equation 6). Further preferably, 70°C tan δ x (V / Wt) x S ≦ 40000 (Equation 7) and 70°C tan δ x (V / Wt) x S ≦ 35000 (Equation 8).

[0063] More specifically, 70°C tan δ x (V / Wt) x S is more preferably 72750 or less, further preferably 69624 or less, further preferably 63398 or less, further preferably 59631 or less, further preferably 54900 or less, further preferably 52171 or less, further preferably 47994 or less, further preferably 44385 or less, further preferably 33673 or less, further preferably 31884 or less, further preferably 30104 or less, further preferably 29515 or less, further preferably 27847 or less, further preferably 27519 or less, further preferably 16626 or less, further preferably 15078 or less, and further preferably 13725 or less.

[0064] 3. Tire shape

[0065] In the tire according to the present disclosure, the specific outer diameter Dt (mm) is preferably, for example, 515 mm or more, more preferably 558 mm or more, further preferably 585 mm or more, further preferably 649 mm or more, further preferably 658 mm or more, further preferably 663 mm or more, further preferably 664 mm or more, further preferably 665 mm or more, further preferably 672 mm or more, and most preferably 673 mm or more, when the tire is mounted on a standard rim and the internal pressure is 250 kPa.

[0066] On the other hand, the outer diameter Dt (mm) is preferably less than 843 mm, more preferably 734 mm or less, further preferably less than 725 mm, further preferably 718 mm or less, further preferably 717 mm or less, further preferably 716 mm or less, further preferably 713 mm or less, further preferably 710 mm or less, further preferably less than 707 mm, further preferably 692 mm or less, further preferably 691 mm or less, further preferably less than 685 mm, further preferably 684 mm or less, further preferably 680 mm or less, further preferably 679 mm or less, and further most preferably 674 mm or less.

[0067] The specific cross-sectional width Wt (mm) is preferably, for example, 115 mm or more, more preferably 130 mm or more, further preferably 150 mm or more, further preferably 170 mm or more, still more preferably 175 mm or more, still more preferably 176 mm or more, still more preferably 177 mm or more, still more preferably 178 mm or more, still more preferably 181 mm or more, still more preferably 182 mm or more, even more preferably 185 mm, and most preferably 193 mm or more.

[0068] On the other hand, the cross-sectional width Wt (mm) is preferably less than 305 mm, more preferably less than 245 mm, further preferably 231 mm or less, further preferably 229 mm or less, further preferably 228 mm or less, further preferably 227 mm or less, further preferably 226 mm or less, further preferably 225 mm or less, further preferably less than 210 mm, further preferably less than 205 mm, further preferably 202 mm or less, further preferably 201 mm or less, further preferably 200 mm or less, further preferably 199 mm or less, further preferably 198 mm or less, and further most preferably 196 mm or less.

[0069] The specific cross-sectional height Ht (mm) is preferably, for example, 37 mm or more, more preferably 69 mm or more, further preferably 70 mm or more, further preferably 71 mm or more, further preferably 78 mm or more, further preferably 79 mm or more, further preferably 80 mm or more, further preferably 87 mm or more, further preferably 89 mm or more, further preferably 90 mm or more, further preferably 95 mm or more, further preferably 96 mm or more, further preferably 98 mm or more, and further most preferably 99 mm or more.

[0070] On the other hand, the cross-sectional height Ht (mm) is preferably less than 180 mm, more preferably 117 mm or less, further preferably 113 mm or less, further preferably less than 112 mm, further preferably 104 mm or less, and further preferably 101 mm or less.

[0071] The specific virtual volume V is preferably 13000000 mm 3 More preferably, the above is 23136067 mm 3 Further preferably, the above is 23206160 mm 3 Further preferably, the above is 23672177 mm 3 Further preferably, the above is 28431992 mm 3 Further preferably, the above is 28526824 mm 3 Further preferably, the above is 29000000 mm 3 Further preferably, the above is 29087378 mm 3 Further preferably, the above is 30111710 mm 3 Further preferably, the above is 30354118 mm 3 Further preferably, the above is 34196412 mm 3 Further preferably, the above is 35417448 mm 3 Further preferably, the above is 35785417 mm 3 Further preferably, the above is 35954077 mm 3 Further preferably, the above is 36000000 mm 3 Further preferably, the above is 36203610 mm 3 Further preferably, the above is 37040131 mm 3 Further preferably, the above is 37040131 mm

[0072] On the other hand, the virtual volume V is preferably less than 66000000 mm 3 More preferably, the above is 50043281 mm 3 Further preferably, the above is less than 44000000 mm 3 Further preferably, the above is 43478150 mm 3 Further preferably, the above is 42618582 mm 3 Further preferably, the above is 40161995 mm 3 Further preferably, the above is less than 38800000 mm 3 .

[0073] Further, in the present disclosure, in consideration of stability of driving comfort during travel, (Dt - 2 x Ht) is preferably 450 mm or more, more preferably 457 mm or more, further preferably 470 mm or more, further preferably 480 mm or more, further preferably 482 mm or more, and further preferably 484 mm or more.

[0074] On the other hand, in view of the deformation of the tread portion, (Dt - 2 x Ht) is preferably less than 560 mm, more preferably 559 mm or less, further preferably 558 mm or less, further preferably 534 mm or less, further preferably 533 mm or less, further preferably 532 mm or less, further preferably less than 530 mm, further preferably less than 510 mm, further preferably 508 mm or less, further preferably 507 mm or less, and further preferably 506 mm or less.

[0075] 3) Embodiments

[0076] Hereinafter, the present disclosure will be specifically described according to embodiments.

[0077] 1. Rubber composition forming the side portion

[0078] The rubber composition forming the side portion of the tire according to the present disclosure can be obtained by appropriately adjusting the types and amounts of various compounding materials, such as the rubber component, filler, softener, vulcanizing agent, and vulcanization accelerator described below.

[0079] (1) Rubber component

[0080] 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 them, butadiene rubber (BR) and isoprene-based rubber are preferably used.

[0081] (a) BR

[0082] From the viewpoint of abrasion resistance, the content of BR is, for example, preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more, in 100 parts by mass of the rubber component. On the other hand, from the viewpoint of maintaining the rolling resistance at the time of high-speed running, the content is preferably 75 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 65 parts by mass or less.

[0083] The weight average molecular weight of the BR is, for example, greater than 100,000 and less than 2 million. The vinyl bond content of the BR is, for example, greater than 1 mass% and less than 30 mass%. The cis content of the BR is, for example, greater than 1 mass% and less than 98 mass%. The trans content of the BR is, for example, greater than 1 mass% and less than 60 mass%. The cis content can be measured by infrared absorption spectroscopy.

[0084] 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 syndiotactic polybutadiene crystals, or the like can be used. The BR can be an unmodified BR, or can be a modified BR. For the modified BR, for example, a BR modified with a compound (modifier) represented by the following formula can be used.

[0085] [Chemical 1]

[0086]

[0087] in the formula, R 1 , R 2 , and R 3 represent the same or different alkyl group, alkoxy group, siloxy group, acetal group, carboxyl group (-COOH), mercapto group (-SH), or derivative thereof. R 4 , and R 5 represent the same or different hydrogen atom or alkyl group. R 4 , and R 5 may combine to form a cyclic structure having a nitrogen atom. n represents an integer.

[0088] As the modified BR modified with the compound (modifier) represented by the above formula, a BR whose polymer terminal (active terminal) has been modified with the compound represented by the above formula can be used.

[0089] As R 1 , R 2 , and R 3 , an alkoxy group (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms) is preferred. As R 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. Further, when R 4 , and R 5 form a cyclic structure in combination with the 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).

[0090] 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 two or more thereof can be used in combination.

[0091] Further, for the modified BR, a modified BR modified with the following compounds (modifiers) can also be used. Examples of the modifiers include:

[0092] Polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylol ethane triglycidyl ether, and trimethylol propane triglycidyl ether;

[0093] Polyglycidyl ethers of aromatic compounds having two or more phenolic groups such as diglycidylated bisphenol A;

[0094] Polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene;

[0095] Epoxy group-containing tertiary amines such as 4,4'-diglycidyl diphenylmethylamine, and 4,4'-diglycidyl dibenzylmethylamine;

[0096] Diglycidyl amino compounds such as diglycidyl aniline, N,N'-diglycidyl-4-glycidoxyaniline, diglycidyl n-o-toluidine, tetraglycidyl-m-xylene diamine, tetraglycidyl aminodiphenylmethane, tetraglycidyl p-phenylenediamine, diglycidyl aminomethylcyclohexane, and tetraglycidyl-1,3-diaminomethylcyclohexane;

[0097] Amino group-containing acid chlorides such as bis(1-methylpropyl)carbamoyl chloride, 4-morpholinocarbonyl chloride, 1-pyrrolidinocarbonyl chloride, N,N-dimethylcarbamoyl chloride, and N,N-diethylcarbamoyl chloride;

[0098] Epoxy group-containing silane compounds such as 1,3-bis(glycidyloxypropyl)-tetramethyldisiloxane and (3-glycidyloxypropyl)-pentamethyldisiloxane;

[0099] Sulfide group-containing silane compounds 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;

[0100] N-substituted aziridine compounds such as ethyleneimine and propyleneimine;

[0101] alkoxysilanes such as methyltriethoxysilane, N,N-bis(trimethylsilyl)-3- aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, and N,N-bis(trimethylsilyl)aminoethyltriethoxysilane;

[0102] (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;

[0103] 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-diethylaminobenzaldehyde;

[0104] 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;

[0105] N-substituted piperidones such as N-methyl-2-piperidone, N-vinyl-2-piperidone, and N-phenyl-2-piperidone;

[0106] 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;

[0107] and N,N-bis(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis(N,N-glycidyl aniline), tris-(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-trione, N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethyl ethylene urea, 1,3-divinyl ethylene urea, 1,3-diethyl-2-imidazolinone, 1-methyl-3-ethyl-2-imidazolinone, 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.

[0108] For BR, for example, products of Ube Industries, Ltd., JSR Corporation, Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., and the like can be used.

[0109] (b) isoprene rubber

[0110] From the viewpoint of obtaining good low heat generation and durability at high speed running, the content (total content) of the isoprene rubber is preferably 25 parts by mass or more, more preferably 30 parts by mass or more, and further preferably 35 parts by mass or more, in 100 parts by mass of the rubber component. On the other hand, the content is preferably 55 parts by mass or less, more preferably 50 parts by mass or less, and further preferably 45 parts by mass or less.

[0111] Examples of the isoprene rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. Among them, NR is preferred from the viewpoint of excellent strength.

[0112] For NR, for example, SIR20, RSS#3, TSR20, and the like, which are common in the tire industry, can be used. IR is not particularly limited, and for example, IR2200, which is common in the tire industry, and the like can be used. Modified NR includes deproteinized natural rubber (DPNR), high purity natural rubber (UPNR), and the like. Modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, and the like. 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.

[0113] (c) SBR

[0114] The rubber component can contain SBR as needed. In this case, the content of SBR is, for example, 1 part by mass or more and less than 100 parts by mass, in 100 parts by mass of the rubber component. The content is more preferably greater than 5 parts by mass, further preferably greater than 15 parts by mass, and particularly preferably greater than 25 parts by mass. On the other hand, the content is preferably less than 65 parts by mass, more preferably less than 55 parts by mass, further preferably less than 45 parts by mass, and particularly preferably less than 35 parts by mass.

[0115] The weight average molecular weight of the SBR is, for example, greater than 100,000 and less than 2 million. The styrene content of the SBR is, for example, preferably greater than 5 mass% and less than 50 mass%, more preferably greater than 10 mass% and less than 40 mass%, and further preferably greater than 20 mass% and less than 35 mass%. The vinyl bond content (amount of 1,2-bound butadiene units) of the SBR is, for example, greater than 5 mass% and less than 70 mass%. The structure identification of the SBR (measurement of the styrene content and the vinyl bond content) can be performed using, for example, a JNM-ECA series instrument manufactured by JEOL Ltd.

[0116] 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 unmodified SBR or modified SBR, and these can be used alone or in combination of two or more.

[0117] The modified SBR can be any SBR having a functional group capable of interacting with a filler such as silica. Examples thereof include:

[0118] a terminal-modified SBR (terminal-modified SBR having the above-described functional group at the terminal) in which at least one terminal of the SBR is modified with a compound (modifier) having the above-described functional group;

[0119] a main chain-modified SBR having the functional group on the main chain;

[0120] a main chain-terminal-modified SBR (for example, a main chain-terminal-modified SBR having the above-described functional group on the main chain and at least one terminal modified with the above-described modifier) having the functional group on both the main chain and the terminal; and

[0121] a terminal-modified SBR modified (coupled) with a multifunctional compound having two or more epoxy groups in the molecule and having an epoxy group or a hydroxyl group introduced therein.

[0122] For the SBR, for example, SBRs produced and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., or the like can be used. The SBR can be used alone or in combination of two or more.

[0123] (d) Other Rubber Components

[0124] Further, for another rubber component, the rubber composition can contain a rubber (polymer) generally used for producing a tire, such as nitrile rubber (NBR).

[0125] 2) Extending materials other than rubber components

[0126] (a) Fillers

[0127] In the present embodiment, the rubber composition preferably contains a filler. Specific examples of the filler include silica, carbon black, graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. Among them, carbon black can be preferably used as a reinforcing agent. If necessary, silica is also preferably used as a reinforcing agent. In this case, it is preferable to use it in combination with a silane coupling agent.

[0128] (a-1) Carbon black

[0129] The content of carbon black is, for example, preferably 10 parts by mass or more and 100 parts by mass or less, more preferably 30 parts by mass or more and 70 parts by mass or less, and further preferably 40 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the rubber component. This can improve the crack growth resistance, durability, ultraviolet light degradation resistance, and the like of the tire.

[0130] The nitrogen adsorption specific surface area (N2SA) of the carbon black is, for example, greater than 30 m 2 / g and less than 250 m 2 / g. The amount of dibutyl phthalate (DBP) absorbed by the carbon black is, for example, greater than 50 mL / 100 g and less than 250 mL / 100 g. The nitrogen adsorption specific surface area of the carbon black is measured according to ASTM D4820-93, and the amount of DBP absorbed is measured according to ASTM D2414-93.

[0131] The carbon black is not particularly limited, and examples thereof include furnace black (furnace carbon black) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black (acetylene carbon black); thermal black (thermal carbon black) such as FT and MT; and channel black (channel carbon black) such as EPC, MPC, and CC.

[0132] Commercially available products include, for example, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nikka Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like. These can be used alone or in combination of two or more.

[0133] (a-2) Silica

[0134] If necessary, the rubber composition preferably contains silica. From the viewpoint of obtaining good durability, the BET specific surface area of the silica is preferably greater than 140 m 2 / g, more preferably greater than 160 m 2 / g. On the other hand, from the viewpoint of obtaining good rolling resistance at high speed running, the BET specific surface area of the silica is preferably less than 250 m 2 / g, more preferably less than 220 m 2 / g. Further, from the viewpoint of obtaining good durability, the content of the silica is preferably greater than 35 parts by mass, more preferably greater than 40 parts by mass, further preferably greater than 45 parts by mass, with respect to 100 parts by mass of the rubber component. On the other hand, from the viewpoint of obtaining good rolling resistance at high speed running, the content of the silica is preferably less than 70 parts by mass, more preferably less than 65 parts by mass, further preferably less than 60 parts by mass. The above BET specific surface area is the value of N2SA measured according to the BET method of ASTM D3037-93.

[0135] Examples of the silica include dry silica (anhydrous silica) and wet silica (hydrous silica). Among them, wet silica is preferred because it contains a large amount of silanol groups.

[0136] For the silica, for example, products of Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation, and the like can be used.

[0137] (a-3) Silane Coupling Agent

[0138] As described above, the rubber composition preferably contains a silane coupling agent together with the silica. The silane coupling agent is not particularly limited. Examples of the silane coupling agent include:

[0139] sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl) tetrasulfide, bis(2-triethoxysilyl ethyl) tetrasulfide, bis(4-triethoxysilylbutyl) tetrasulfide, bis(3-trimethoxysilylpropyl) tetrasulfide, bis(2-trimethoxysilyl ethyl) tetrasulfide, bis(2-triethoxysilyl ethyl) trisulfide, bis(4-trimethoxysilylbutyl) trisulfide, bis(3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilyl ethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilyl ethyl) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilyl ethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silane coupling agents such as 3-mercaptopropyl trimethoxysilane, 2-mercaptoethyl triethoxysilane, and NXT and NXT-Z produced by Momentive; vinyl-based silane coupling agents such as vinyl triethoxysilane and vinyl trimethoxysilane; amino-based silane coupling agents such as 3-aminopropyl triethoxysilane and 3-aminopropyl trimethoxysilane; glycidyl ether oxy-based silane coupling agents such as γ-glycidyl ether oxypropyl triethoxysilane and γ-glycidyl ether oxypropyl trimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyl trimethoxysilane and 3-nitropropyl triethoxysilane; and chloro-based silane coupling agents such as 3-chloropropyl trimethoxysilane and 3-chloropropyl triethoxysilane. These can be used alone or in combination of two or more.

[0140] As the silane coupling agent, for example, products of Degussa, Momentive, Shinetsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., and the like can be used.

[0141] The content of the silane coupling agent is, for example, greater than 3 parts by mass and less than 15 parts by mass with respect to 100 parts by mass of the silica.

[0142] (a-4) Other fillers

[0143] The rubber composition can contain, in addition to the above-mentioned carbon black and silica, fillers commonly used in the tire industry such as graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. For example, the content of these is greater than 0.1 parts by mass and less than 200 parts by mass with respect to 100 parts by mass of the rubber component.

[0144] (b) Softener

[0145] The rubber composition can contain an oil (including a filling oil), a liquid rubber, or the like as a softener. The total content of these is preferably greater than 5 parts by mass, more preferably greater than 10 parts by mass, and still more preferably greater than 12 parts by mass with respect to 100 parts by mass of the rubber component. On the other hand, it is preferably less than 30 parts by mass, more preferably less than 20 parts by mass, and still more preferably less than 17 parts by mass. The oil content also includes the oil content in the rubber (oil-extended rubber).

[0146] Examples of the oil include mineral oils, generally referred to as process oils, vegetable fats and mixtures thereof. For the mineral oil (process oil), for example, a paraffin-based process oil, an aromatic-based process oil, and a naphthenic-based process oil can be used. Examples of the vegetable fats include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, pine rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower 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.

[0147] Examples of the process oil (mineral oil) include products of Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo K.K., Japan Energy Corporation, Olisoy Co., H & R Co., Toyokuni Seiyu Co., Ltd., Showa Shell Sekiyu Co., Ltd., Fuji Kosan Co., Ltd., and the like.

[0148] The liquid rubber as a softener is a polymer in a liquid state at room temperature (25°C) and is a polymer having a monomer similar to solid rubber as a constituent element. Examples of the liquid rubber include farnesene-based polymers, liquid diene-based polymers, and hydrogenated additives thereof.

[0149] Farnesene-based polymers are polymers having a structural unit based on farnesene obtained by polymerizing farnesene. Farnesene includes isomers such as a-farnesene ((3E,7E)-3, 11-trimethyl-1, 3, 6, 10-dodecatriene) and β-farnesene (7, 11-dimethyl-3-methylene-1, 6, 10-dodecatriene).

[0150] The farnesene-based polymer can be a homopolymer of farnesene (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer).

[0151] Examples of the liquid diene polymer include a liquid styrene-butadiene copolymer (liquid SBR), a liquid butadiene polymer (liquid BR), a liquid isoprene polymer (liquid IR), and a liquid styrene-isoprene copolymer (liquid SIR).

[0152] The weight average molecular weight (Mw) of the polystyrene equivalent of the liquid diene polymer is measured by gel permeation chromatography (GPC), for example, greater than 1.0 x 10 3 and less than 2.0 x 10 5 In the present specification, the Mw of the liquid diene polymer is a converted value of polystyrene measured by gel permeation chromatography (GPC).

[0153] For the liquid rubber, for example, products of Kuraray Co., Ltd. and Clay Valley Co., Ltd. can be used.

[0154] (c) Resin component

[0155] If necessary, the rubber composition preferably contains a resin component. The resin component can be solid or liquid at room temperature, and examples of the specific resin component include a styrene resin, a coumarone resin, a terpene resin, a C5 resin, a C9 resin, a C5 / C9 resin, an acrylic resin, and the like. Two or more resin components can be used in combination. The content of the resin component is preferably greater than 2 parts by mass and less than 45 parts by mass, more preferably less than 30 parts by mass, with respect to 100 parts by mass of the rubber component.

[0156] A styrene resin is a polymer using a styrene monomer as a constituent monomer, examples of which include a polymer obtained by polymerization with a styrene monomer as a main component (50 mass% or more). Specifically, it includes a homopolymer obtained by polymerizing a styrene monomer alone (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, a-methylstyrene, p-methoxystyrene, p-t-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and the like), a copolymer obtained by copolymerizing two or more kinds of styrene monomers, and further, a copolymer obtained by copolymerizing a styrene monomer and another monomer copolymerizable with the styrene monomer.

[0157] Examples of the other monomer include acrylonitrile-based monomers such as acrylonitrile and methacrylate; unsaturated carboxylic acids such as acrylic acid and methacrylic acid; unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate; dienes such as chloroprene, butadiene, and isoprene; olefins such as 1-butene and 1-pentene; and a, β-unsaturated carboxylic acids such as maleic anhydride and anhydrides thereof.

[0158] For the coumarone-based resin, a coumarone-indene resin is preferably used. The coumarone-indene resin is a resin containing coumarone and indene as monomer components constituting the skeleton (main chain) of the resin. Examples of the monomer component other than coumarone and indene contained in the skeleton include styrene, a-methylstyrene, methylindene, and vinyltoluene.

[0159] The content of the coumarone-indene resin is, for example, greater than 1.0 mass part and less than 50.0 mass part with respect to 100 mass parts of the rubber component.

[0160] The coumarone-indene resin has a hydroxyl value (OH value) of, for example, greater than 15 mgKOH / g and less than 150 mgKOH / g. The OH value refers to the amount of potassium hydroxide required to neutralize the acetic acid combined with the hydroxyl group when 1 g of the resin is acetylated, expressed in mg. It is a value measured by potentiometric titration (JIS K 0070:1992).

[0161] The coumarone-indene resin has a softening point of, for example, greater than 30°C and less than 160°C. The softening point refers to the temperature at which the ball falls when the softening point defined in JIS K 6220-1:2001 is measured with a ring-and-ball type softening point measuring device.

[0162] Examples of the terpene resin include polyterpenes, terpene phenols, and aromatic modified terpene resins. Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are hydrocarbons having a composition represented by (C5H8)n or oxygen-containing derivatives thereof, which are classified into monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H24 ), diterpenes (C 20 H 32 ) and the like. Examples thereof include α-pinene, β-pinene, dipentene, limonene, myrcene, allo-ocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol and γ-terpineol.

[0163] Examples of polyterpenes include terpene resins made from the above-mentioned terpene compounds, such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin and β-pinene / limonene resin, and hydrogenated terpene resins obtained by hydrogenating the above-mentioned terpene resins. Examples of terpene phenol include resins obtained by copolymerizing the above-mentioned terpene compounds and phenol compounds, and resins obtained by hydrogenating the above-mentioned resins. Specifically, mention can be made of resins obtained by condensing the above-mentioned terpene compounds, phenol compounds and formalin. Examples of phenol compounds include phenol, bisphenol A, cresol and xylene. Examples of aromatic-modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating the above-mentioned resins. The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and examples thereof include phenol compounds such as phenol, alkylphenol, alkoxyphenol and phenol having an unsaturated hydrocarbon group; naphthol compounds such as naphthol, alkyl naphthol, alkoxy naphthol and naphthol having an unsaturated hydrocarbon group; styrene derivatives such as styrene, alkyl styrene, alkoxy styrene, styrene having an unsaturated hydrocarbon group; coumarone and indene.

[0164] C5 resin refers to a resin obtained by polymerizing a C5 fraction. Examples of the C5 fraction include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene and isoprene. For the C5 petroleum resin, dicyclopentadiene resin (DCPD resin) is preferably used.

[0165] C9 resin refers to a resin obtained by polymerizing a C9 fraction, which can be hydrogenated or modified. Examples of the C9 fraction include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkyl styrene, indene and methyl indene. For specific examples, coumarone-indene resin, coumarone resin, indene resin and aromatic vinyl-based resin are preferably used. For the aromatic vinyl-based resin, a homopolymer of α-methyl styrene or styrene or a copolymer of α-methyl styrene and styrene is preferable because it is economical, easy to process and has good heat generation performance. A copolymer of α-methyl styrene and styrene is more preferable. For the aromatic vinyl-based resin, for example, those commercially available from Clayton, Eastman Chemical and the like can be used.

[0166] The C5 / C9 resin refers to a resin obtained by copolymerizing a C5 fraction and a C9 fraction, and can be hydrogenated or modified. Examples of the C5 fraction and the C9 fraction include the above-described petroleum fractions. For the C5 / C9 resin, for example, those commercially available from Tosoh Corporation, LUHUA Corporation, and the like can be used.

[0167] The acrylic resin is not particularly limited, but for example, a solventless acrylic resin can be used.

[0168] For the solventless acrylic resin, a (meth)acrylic resin (polymer) can be mentioned, which is polymerized by a high-temperature continuous polymerization method (a high-temperature continuous block polymerization method (a method described in US 4414370 B, JP 59-6207 A, JP 5-58005 B, JP 1-313522 A, US 5010166 B, Toa Synthetic Research Annual Report TREND 2000 No. 3 p42-45, and the like)) with as little use as possible of a polymerization initiator, a chain transfer agent, an organic solvent, and the like auxiliary raw materials. In the present disclosure, (meth)acrylic acid refers to methacrylic acid and acrylic acid.

[0169] Examples of the monomer component constituting the acrylic resin include (meth)acrylic acid, and (meth)acrylic acid derivatives such as (meth)acrylate (alkyl ester, aryl ester, aralkyl ester, and the like), (meth)acrylamide, and (meth)acrylamide derivatives.

[0170] Further, for the monomer component constituting the acrylic resin, an aromatic vinyl compound such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, divinyl naphthalene, and the like can be used together with (meth)acrylic acid or (meth)acrylic acid derivatives.

[0171] The acrylic resin can be a resin consisting only of a (meth)acrylic acid component, or also a resin having a component other than the (meth)acrylic acid component. Further, the acrylic resin can have a hydroxyl group, a carboxyl group, a silanol group, and the like.

[0172] For the resin component, for example, products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Toso Co., Ltd., Rutgers Chemicals Co., Ltd., BASF Co., Ltd., Arizona Chemical Co., Ltd., Nitto Chemical Co., Co., Ltd., Nippon Catalyst Co., Ltd., JX Energy Co., Ltd., Arakawa Chemical Industry Co., Ltd., Taoka Chemical Industry Co., Ltd., and the like can be used.

[0173] (d) Anti-aging agent

[0174] The rubber composition preferably contains an anti-aging agent. The content of the anti-aging agent is, for example, greater than 1 part by mass and less than 10 parts by mass, and more preferably 6.5 parts by mass or greater, with respect to 100 parts by mass of the rubber component.

[0175] Examples of the anti-aging agent include naphthylamine-based anti-aging agents such as phenyl-a-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(a,a'-dimethylbenzyl)diphenylamine; p-phenylenediamine-based 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-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-tert-butyl-4-methylphenol, styrenated phenol; bisphenol-based, triphenol-based, and polyphenol-based anti-aging agents such as tetra-[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane. These can be used alone or in combination of two or more.

[0176] For the anti-aging agent, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexsys, and the like can be used.

[0177] (e) stearic acid

[0178] The rubber composition can contain stearic acid. The content of stearic acid is, for example, greater than 0.5 parts by mass and less than 10.0 parts by mass, more preferably 3 parts by mass or greater, with respect to 100 parts by mass of the rubber component. For the stearic acid, conventionally known stearic acids, for example, products of NOF Corporation, NOF Corporation, Kao Corporation, Fuji film Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., and the like can be used.

[0179] (f) zinc oxide

[0180] The rubber composition can contain zinc oxide. The content of zinc oxide is, for example, greater than 0.5 parts by mass and less than 10 parts by mass, more preferably 4.5 parts by mass or greater, with respect to 100 parts by mass of the rubber component. For the zinc oxide, conventionally known zinc oxides, for example, products of Mitsui Metal Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., and the like can be used.

[0181] (g) wax

[0182] The rubber composition preferably contains wax. The content of wax is, for example, 0.5 to 20 parts by mass, preferably 1.0 to 15 parts by mass, more preferably 1.5 to 10.0 parts by mass, with respect to 100 parts by mass of the rubber component. The content of wax is further preferably 2.0 parts by mass or greater.

[0183] The wax is not particularly limited, and examples thereof include petroleum-based waxes such as paraffin wax 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.

[0184] For the wax, for example, products of Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Kagaku Co., Ltd. can be used.

[0185] (h) Cross-linking agent and vulcanization accelerator

[0186] The rubber composition preferably contains a cross-linking agent such as sulfur. The content of the cross-linking agent is, for example, greater than 0.1 parts by mass and less than 10.0 parts by mass, and more preferably 2 parts by mass or greater, with respect to 100 parts by mass of the rubber component.

[0187] Examples of the sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur, which are commonly used in the rubber industry. These can be used alone or in combination of two or more.

[0188] For the sulfur, for example, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Corporation, Flexsys, Nippon Kanryu Kogyo Co., Ltd., and Hosoi Chemical Industry Co., Ltd., and the like can be used.

[0189] Examples of the cross-linking agent other than sulfur include vulcanizing agents containing a sulfur atom such as Tackirol V200 produced by Taoka Chemical Industry Co., Ltd., DURALINK HTS (sodium 1,6-hexamethylenedithiodithioate dihydrate) produced by Flexsys, and KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoylthio)hexane) produced by Lanxess, and organic peroxides such as dicumyl peroxide.

[0190] The rubber composition preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, 0.3 parts by mass or more and 10.0 parts by mass or less, more preferably 1 part by mass or more, and further preferably 1.5 parts by mass or more, with respect to 100 parts by mass of the rubber component.

[0191] Examples of the vulcanization accelerator include:

[0192] Thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2- benzothiazole disulfide, and N-cyclohexyl-2-benzothiazole sulfenamide;

[0193] Thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetra(2-ethylhexyl)thiuram disulfide (TOT-N);

[0194] Sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-o-tolylguanidine, and o-tolylbiguanide. These can be used alone or in combination of two or more.

[0195] (i) Other

[0196] In addition to the above-mentioned components, the rubber composition can contain additives commonly used in the tire industry, such as fatty acid metal salts, carboxylic acid metal salts, and organic peroxides. The content of these additives is, for example, greater than 0.1 parts by mass and less than 200 parts by mass, with respect to 100 parts by mass of the rubber component.

[0197] 2. Production of rubber composition for forming side portions

[0198] The rubber composition can be produced by a conventional method, for example, a manufacturing method including a base kneading step (kneading the rubber component with a filler such as carbon black) and a final kneading step (kneading the kneaded product obtained in the base kneading step with a crosslinking agent).

[0199] Kneading can be performed using a known (closed) kneader such as a Banbury mixer, a kneader, or an open roll mill.

[0200] In the base kneading step, the kneading temperature is, for example, greater than 50°C and less than 200°C, and the kneading time is, for example, greater than 30 seconds and less than 30 minutes. In the base kneading step, in addition to the above-mentioned components, a compounding agent commonly used in the rubber industry, such as a softener such as an oil, stearic acid, zinc oxide, an anti-aging agent, a wax, and a vulcanization accelerator, etc., can be appropriately added as needed and kneaded.

[0201] In the final kneading step, the kneaded product obtained in the base kneading step is kneaded with a crosslinking agent. In the final kneading step, the kneading temperature is, for example, higher than room temperature and lower than 80°C, and the kneading time is, for example, greater than 1 min and less than 15 min. In the final kneading step, in addition to the above-mentioned components, a vulcanization accelerator, zinc oxide, and the like can be appropriately added as needed, and kneading is performed.

[0202] 3. Tire production

[0203] The tire of the present disclosure is produced by a conventional method using the unvulcanized rubber composition obtained by the final kneading step. That is, the unvulcanized rubber composition is extruded according to the shape of the sidewall, and molded by a conventional method on a tire building machine in combination with other tire components to produce an unvulcanized tire.

[0204] Specifically, on a building drum, an inner liner (as a component to ensure the air tightness of the tire), a carcass (as a component to bear the load, impact, and inflation pressure received by the tire), a belt (as a component to strongly tighten the carcass to increase the rigidity of the tread), and the like are wound, both ends of the carcass are fixed to both side edges, a bead portion (as a component to fix the tire to a rim) is arranged and molded into a ring shape. Then, a tread is pasted at the center of the outer circumference, and a sidewall portion is pasted at the radially outer side to form a side portion, thereby producing an unvulcanized tire.

[0205] In the present embodiment, it is preferable to provide an inclined belt layer extending at an angle of 15° to 30° with respect to the tire circumferential direction as a belt. Thus, the durability of the tire is ensured while the rigidity of the tread can be sufficiently maintained. Further, since it can be restrained in the circumferential direction, it becomes easy to suppress the increase in the outer diameter.

[0206] Then, the produced unvulcanized tire is heated and pressurized in a curing press to obtain a tire. The curing step can be performed by applying a known curing means. The curing temperature is, for example, greater than 120°C and less than 200°C, and the curing time is, for example, greater than 5 min and less than 15 min.

[0207] At this time, the tire is mounted on a standard rim, and the internal pressure is set to 250 kPa, and the tire is formed into a shape satisfying the above (Formula 1) and (Formula 2).

[0208] Specific tires that can satisfy the above (Formula 1) and (Formula 2) include tires of the following size symbols: 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, and the like.

[0209] In the present embodiment, the tire that can satisfy (Formula 1) and (Formula 2) is preferably applied to a pneumatic tire for a passenger car, and satisfying the above formulas can more effectively solve the technical problem of the present disclosure, i.e., providing a pneumatic tire with reduced rolling resistance at high speed and excellent durability.

[0210] Examples

[0211] Hereinafter, the present disclosure will be described more specifically with reference to examples.

[0212] [Experiment 1]

[0213] In the present experiment, a tire of 175 size was manufactured and evaluated.

[0214] 1. Production of rubber composition for forming a side portion

[0215] A rubber composition for forming a side portion was produced.

[0216] (1) Blended materials

[0217] First, each of the blended materials shown below was prepared.

[0218] (a) Rubber component

[0219] (a-1) NR: TSR20

[0220] (a-2) BR-1: UBEPOL-BR150B, manufactured by Ube Industries, Ltd. (cis content: 97 mass%)

[0221] (a-3) BR-2: Nipol-BR1250H, manufactured by Nippon Zeon Co., Ltd. (tin end-modified BR, cis content: 40 mass%)

[0222] (a-4) BR-3: UBEPOL VCR617, manufactured by Ube Industries, Ltd. (cis content: 98 mass%)

[0223] (b) Mixing materials other than rubber components

[0224] (b-1) Carbon black: Show Black N550, manufactured by Cabot Japan Co., Ltd. (N2SA: 42 m 2 / g)

[0225] (b-2) Oil: Process X-140, manufactured by Japan Energy Co., Ltd.

[0226] (b-3) Stearic acid: Stearic acid "Tsubaki", manufactured by NOF Corporation

[0227] (b-5) Wax: Sannok wax, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0228] (b-6) Anti-aging agent-1: Nocrac 6C (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine), manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0229] (b-7) Anti-aging agent-2: Antage RD (2,2,4-trimethyl-1,2-dihydroquinoline), manufactured by Kawaguchi Chemical Industry Co., Ltd.

[0230] (b-8) Cross-linking agent and vulcanization accelerator

[0231] Sulfur: powdered sulfur, manufactured by Tsurumi Chemical Industry Co., Ltd.

[0232] Vulcanization accelerator: Nocceler NS (N-tert-butyl-2-benzothiazolesulfenamide), manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0233] 2) Production of rubber composition for forming side portion

[0234] According to the formulations shown in Tables 1 and 2, materials except sulfur and vulcanization accelerator were kneaded at 150°C for 5 min with a Banbury mixer to obtain a kneaded product. Each compounding amount was parts by mass.

[0235] Next, sulfur and vulcanization accelerator were added to the obtained kneaded product, and the mixture was kneaded at 80°C for 5 min using an open roll mill to obtain a rubber composition for forming a side portion.

[0236] 2. Tire production

[0237] Using the obtained rubber composition, a side portion member having a thickness S (mm) shown in Tables 1 and 2 was formed, and was bonded with other tire members to form an unvulcanized tire, and then was press-vulcanized at 170°C for 10 min to produce each test tire having a size of 175 type (Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-5).

[0238] 3. Parameter calculation

[0239] Thereafter, the outer diameter Dt (mm), the cross-sectional width Wt (mm), the cross-sectional height Ht (mm), and the flatness (%) of each test tire were obtained, and the virtual volume V (mm 3 ) was calculated. At the same time, a rubber test piece of 20 mm in length, 4 mm in width, and 1 mm in thickness was cut from the rubber layer of the side portion of each test tire (with the tire circumferential direction being the long side) to produce a rubber test piece for viscoelasticity measurement. For each rubber test piece, tan δ (70°C tan δ) was measured at 70°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1% using an Eplexor series manufactured by GABO Co., Ltd. The results are shown in Tables 1 and 2.

[0240] Then, (Dt-2xHt), (Dt2xπ / 4) / Wt, (V+1.5x10 7 ) / Wt, (V+2.0x10 7 ) / Wt, (V+2.5x10 7 ) / Wt, and 70°C tan δxWt were measured. The results are shown in Tables 1 and 2.

[0241] 5. Performance evaluation test

[0242] (1) Evaluation of rolling resistance at high speed

[0243] Each test tire was mounted on all wheels of a vehicle (Japanese FF car, displacement 2000 cc), inflated to an internal pressure of 250 kPa, and then driven at a speed of 100 km / h on a test course of a dry road surface. After completing one lap of 10 km, the throttle was released, and the distance from the throttle-off to the stop of the vehicle was measured as the rolling resistance at high speed.

[0244] Next, the results in Comparative Examples 1 to 5 were set to 100, and the results were index-converted to relatively evaluate the rolling resistance at high speed according to the following formula. The larger the value, the longer the distance from the throttle-off to the stop of the vehicle, the smaller the rolling resistance in a steady state, and the better the fuel efficiency.

[0245] Rolling resistance = [(result of test tire) / (result of Comparative Example 1 to 5)] x 100

[0246] (2) Evaluation of durability

[0247] Each test tire was mounted on all wheels of a vehicle (Japanese FF car, displacement 2000 cc), inflated to an internal pressure of 250 kPa, and then driven at a speed of 50 km / h for 10 laps on a test course of a dry road surface under an overload state, and then driven to climb over unevenness provided on the road surface at a speed of 80 km / h, and the process was repeated. Thereafter, one lap was driven at a speed of 50 km / h, and then the speed at which the driver felt an abnormality was measured while the speed was gradually increased.

[0248] Next, the results in Comparative Examples 1 to 5 were set to 100, and the results were index-converted to relatively evaluate the durability according to the following formula. The larger the value, the better the durability.

[0249] Durability = [(result of test tire) / (result of Comparative Example 1 to 5)] x 100

[0250] (3) Comprehensive evaluation

[0251] The evaluation results of the above (1) and (2) were integrated to obtain a comprehensive evaluation.

[0252] (4) Evaluation results

[0253] The results of each evaluation are shown in Tables 1 and 2.

[0254] [Table 1]

[0255]

[0256]

[0257] [Table 2]

[0258]

[0259]

[0260] [Experiment 2]

[0261] In this experiment, tires of 195 size were manufactured and evaluated.

[0262] 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, each parameter was calculated by performing the same steps. Then, in the same manner, performance evaluation tests were performed and evaluated. In this experiment, the results of Comparative Example 2-5 were set to 100 for evaluation. The results of each evaluation are shown in Tables 3 and 4.

[0263] [Table 3]

[0264]

[0265]

[0266] [Table 4]

[0267]

[0268]

[0269] [Experiment 3]

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

[0271] After producing the test tires of Examples 3-1 to 3-5 and Comparative Examples 3-1 to 3-5 shown in Tables 5 and 6 in the same manner as in Experiment 1, each parameter was calculated by performing the same steps. Then, in the same manner, performance evaluation tests were performed and evaluated. In this experiment, the results of Comparative Example 3-5 were set to 100 for evaluation. The results of each evaluation are shown in Tables 5 and 6.

[0272] [Table 5]

[0273]

[0274]

[0275] [Table 6]

[0276]

[0277]

[0278] [Summary of Experiments 1 to 3]

[0279] From the results of Experiments 1 to 3 (Tables 1 to 6), it was found that for any size, 175 size, 195 size, and 225 size tires, when the above (Formula 1) and (Formula 2) were satisfied, a pneumatic tire could be provided in which the rolling resistance at high speed running was sufficiently reduced and the durability was sufficiently improved.

[0280] Then, it was found that by satisfying each of the requirements of the present disclosure (2) and thereafter, a tire in which the rolling resistance and durability at high speed running were further improved could be provided.

[0281] On the other hand, when (Formula 1) or (Formula 2) was not satisfied, the rolling resistance at high speed running could not be sufficiently reduced, and the durability could not be sufficiently improved.

[0282] [Experiment 4]

[0283] Next, three types of tires (Examples 4-1 to 4-3) were produced with the same formulation in which there was no significant difference in the relationship between the virtual volume V and the cross-sectional width Wt, and were evaluated in the same manner. Here, in addition to the rolling resistance and durability at high speed running, the driving comfort was also evaluated.

[0284] Specifically, each test tire was mounted on all the wheels of a vehicle (Japanese FF car, displacement 2000 cc), was inflated so that the internal pressure was 250 kPa, and then was driven on a dry road test course. After the vehicle was driven at a speed of 100 km / h for 10 km, the driving comfort was evaluated by 20 drivers by sensory test on a 5-point scale. After adding up the evaluations of the 20 drivers, the evaluations were indexed according to the following formula, in which the total score of Example 4-3 was taken as 100 points, and the driving comfort was evaluated relatively. The larger the value, the better the driving comfort.

[0285] Driving Comfort = [(Total Score of Evaluation of Test Tire) / (Total Score of Evaluation of Example 4-3)] x 100

[0286] Then, as in Experiments 1 to 3, each evaluation result was added up to obtain a comprehensive evaluation. Table 7 shows the results of each evaluation.

[0287] [Table 7]

[0288]

[0289]

[0290] Table 7 shows that when there is no large difference between the relationship of the virtual volume V and the cross-sectional width Wt, as the cross-sectional width Wt becomes smaller (e.g., from less than 205 mm to less than 200 mm), and the flatness increases, the rolling resistance and durability at high speed are improved. It was also found that the driving comfort was also improved.

[0291] Although the present disclosure has been described above based on the embodiments, the present disclosure is not limited to the above-described embodiments. Various modifications can be made to the above-described embodiments within the same and equivalent scope of the present disclosure.

[0292] The present disclosure (1) is:

[0293] A pneumatic tire having a side portion, wherein

[0294] At the maximum width of the tire, the thickness S (mm) of the rubber layer radially outside the carcass of the side portion is 3 mm or less; the loss tangent (70°C tan δ) of the rubber layer measured at 70°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is 0.15 or less; and

[0295] When the cross-sectional width of the tire is Wt (mm), the outer diameter is Dt (mm), and the volume of the space occupied by the tire is the virtual volume V (mm 3 ) in a state where the tire is mounted on a standard rim and the internal pressure is 250 kPa, the tire satisfies the following (Formula 1) and (Formula 2):

[0296] 1700 ≦ (Dt 2 × π / 4) / Wt ≦ 2827.4 (Formula 1)

[0297] [(V + 1.5 × 10 7 ) / Wt] ≦ 2.88 × 10 5 (Formula 2).

[0298] The present disclosure (2) is the pneumatic tire according to the present disclosure (1), wherein the following (Formula 3) is satisfied:

[0299] [(V + 2.0 × 10 7 ) / Wt] ≦ 2.88 × 10 5 (Formula 3).

[0300] The present disclosure (3) is the pneumatic tire according to the present disclosure (2), wherein the following (Formula 4) is satisfied:

[0301] [(V + 2.5 × 10 7 ) / Wt] ≦ 2.88 × 10 5 (Formula 4).

[0302] The present disclosure (4) is a pneumatic tire according to any combination of the present disclosure (1) to (3), in which, when an outer diameter of the tire in a state where the tire is mounted on a standard rim and an inner pressure is 250 kPa is Dt (mm) and a cross-sectional height of the tire is Ht (mm), (Dt - 2 x Ht) is 470 (mm) or greater.

[0303] The present disclosure (5) is a pneumatic tire according to any combination of the present disclosure (1) to (4), in which a flatness is 40% or greater.

[0304] The present disclosure (6) is a pneumatic tire according to the present disclosure (5), in which the flatness is 45% or greater.

[0305] The present disclosure (7) is a pneumatic tire according to the present disclosure (6), in which the flatness is 47.5% or greater.

[0306] The present disclosure (8) is a pneumatic tire according to the present disclosure (7), in which the flatness is 50% or greater.

[0307] The present disclosure (9) is a pneumatic tire according to any combination of the present disclosure (1) to (8), in which the following (Formula 5) is satisfied:

[0308] 70°C tan δ x (V / Wt) x S ≦ 80000 (Formula 5).

[0309] The present disclosure (10) is a pneumatic tire according to the present disclosure (9), in which the following (Formula 6) is satisfied:

[0310] 70°C tan δ x (V / Wt) x S ≦ 60000 (Formula 6).

[0311] The present disclosure (11) is a pneumatic tire according to the present disclosure (10), in which the following (Formula 7) is satisfied:

[0312] 70°C tan δ x (V / Wt) x S ≦ 40000 (Formula 7).

[0313] The present disclosure (12) is a pneumatic tire according to the present disclosure (11), in which the following (Formula 8) is satisfied:

[0314] 70°C tan δ x (V / Wt) x S ≦ 35000 (Formula 8).

[0315] The present disclosure (13) is a pneumatic tire according to any combination of the present disclosure (1) to (12), in which Dt is less than 685 (mm), where Dt (mm) is an outer diameter of the tire when the tire is mounted on a standard rim and an inner pressure is 250 kPa.

[0316] The present disclosure (14) is a pneumatic tire according to any combination of the present disclosure (1) to (13), in which the cross-sectional width Wt (mm) is less than 205 mm.

[0317] The present disclosure (15) is a pneumatic tire according to the present disclosure (14), in which the cross-sectional width Wt (mm) is less than 200 mm.

[0318] The present disclosure (16) is a pneumatic tire according to any combination of the present disclosure (1) to (15), in which the pneumatic tire is a pneumatic tire for a passenger vehicle.

Claims

1. A pneumatic tire having a side portion, characterized in that, the thickness S mm of a rubber layer radially outside the carcass of the side portion at the maximum width of the tire is 3 mm or less; the loss tangent tan δ of the rubber layer at 70°C measured under conditions of a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is 0.15 or less; and When a tire is mounted on a standard rim and the cross-sectional width of the tire in a state where the internal pressure is 250 kPa is Wt mm, the outer diameter is Dt mm, and the volume of the space occupied by the tire is a virtual volume V mm 3 , the cross-sectional width Wt mm is 170 mm or greater, and the tire satisfies the following equation: 1700 ≦ (Dt 2 x π / 4) / Wt ≦ 2827.4 (Equation 1) [(V + 2.5 x 10 7 ) / Wt] ≦ 2.88 x 10 5 (Formula 4) 70°C tan δ x (V / Wt) x S ≦ 72750 (Formula 5).

2. The pneumatic tire of claim 1, wherein, the pneumatic tire satisfies the following (Formula 3): [(V + 2.0 x 10 7 ) / Wt] < 2.49 x 10 5 (Formula 3).

3. The pneumatic tire of claim 1, wherein, the pneumatic tire satisfies the following (Formula 4): [(V + 2.5 x 10 7 ) / Wt] ≦ 2.76 x 10 5 (Form 4).

4. The pneumatic tire of any of claims 1-3, wherein, (Dt - 2 x Ht) is 470 mm or more when the outer diameter of the tire is Dt mm and the cross-sectional height of the tire is Ht mm in a state where the tire is mounted on a standard rim and the internal pressure is 250 kPa.

5. The pneumatic tire of any of claims 1-4, wherein, the flat ratio of the pneumatic tire is 40% or more.

6. The pneumatic tire of claim 5, wherein, the flat ratio of the pneumatic tire is 45% or more.

7. The pneumatic tire of claim 6, wherein, the flat ratio of the pneumatic tire is 47.5% or more.

8. The pneumatic tire of claim 7, wherein, the flat ratio of the pneumatic tire is 50% or more.

9. The pneumatic tire of claim 1, wherein, the pneumatic tire satisfies the following (Formula 6): 70°C tan δ x (V / Wt) x S ≦ 60000 (Formula 6).

10. The pneumatic tire of claim 9, wherein, the pneumatic tire satisfies the following (Formula 7): 70°C tan δ x (V / Wt) x S ≦ 40000 (Formula 7).

11. The pneumatic tire of claim 10, wherein, the pneumatic tire satisfies the following (Formula 8): 70°C tan δ x (V / Wt) x S ≦ 35000 (Formula 8).

12. The pneumatic tire of any of claims 1-11, wherein, the Dt is less than 685 mm, where Dt mm is the outer diameter of the tire when the tire is mounted on a standard rim and the internal pressure is 250 kPa.

13. The pneumatic tire of any of claims 1-12, wherein, the cross-sectional width Wt mm is less than 205 mm.

14. The pneumatic tire of claim 13, wherein, the cross-sectional width Wt mm is less than 200 mm.

15. The pneumatic tire of any of claims 1-14, wherein, the pneumatic tire is a pneumatic tire for a passenger vehicle.

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