tire

Abstract

This tire comprises a belt-coating rubber and a carcass-coating rubber. The belt-coating rubber contains specific amounts of a diene rubber that includes a natural rubber, a filler that comprises carbon black and silica, a cobalt salt of an organic acid, a phenolic resin, and a curing agent and has a dynamic storage modulus (Belt E') at 20°C of at least 13 MPa. The ratio (Belt E') / (Carcass E') of the dynamic storage modulus (Belt E') at 20°C of the belt-coating rubber and the dynamic storage modulus (Carcass E') at 20°C of the carcass-coating rubber is 2.5–3.5.

Description

tire

[0001] The present invention relates to a tire, and more particularly to a tire that suppresses deterioration of belt layers due to long-term use and has excellent durability and steering stability.

[0002] A pneumatic tire is primarily composed of a pair of left and right bead portions and sidewall portions, and a tread portion connected to both sidewall portions. A carcass layer is provided on the inside of the tire, and both ends of the carcass layer are folded back to encase the bead core from the inside to the outside of the tire. The carcass layer is composed of at least one carcass ply, in which carcass cords are coated with carcass coating rubber. The tread portion consists of a cap tread and an undertread, and a belt layer is disposed between the undertread and the carcass layer. The belt layer has at least one belt ply disposed as a tire reinforcing layer. Because this belt ply is subjected to strong impacts and heavy loads, steel cords are used as reinforcement materials and are coated with belt coating rubber. The belt coating rubber must have good adhesion to the steel cords. Meanwhile, with the recent trend toward longer tire usage periods, there is a problem in that the adhesion between the steel cords and the belt coating rubber decreases over time, resulting in a loss of durability. Furthermore, tires are always required to have high handling stability.

[0003] Patent Document 1 listed below discloses a rubber composition that aims to provide a rubber composition that improves adhesion performance with steel cord, the rubber composition being prepared by compounding a diene rubber containing natural rubber with 0.3 to 1.5 parts by mass of cobalt neodecanoate borate, 0.5 to 1.0 part by mass of cobalt stearate, 0.5 to 2.0 parts by mass or more of a phenolic resin, 0.5 to 5.0 parts by mass of a curing agent, and 4.0 to 8.0 parts by mass of sulfur, the rubber composition being characterized by having a dynamic storage modulus (E') of 13 MPa or more at a dynamic strain of 2% and at 20°C, a loss tangent (tan δ) of 0.20 or less at 60°C, and a number of repetitions until failure of 35,000 or more in a constant strain fatigue test at 60% strain and 400 rpm.

[0004] Patent No. 6288148

[0005] An object of the present invention is to provide a tire that suppresses deterioration of belt layers due to long-term use, has excellent durability, and maintains or improves steering stability.

[0006] As a result of extensive research, the inventors discovered that the above-mentioned problems could be solved by specifying the composition of the belt coating rubber and setting the ratio of the dynamic storage modulus of the belt coating rubber to the carcass coating rubber within a specific range, thereby completing the present invention.

[0007] That is, the present invention provides a tire comprising a belt layer in which steel cords are coated with a belt coat rubber, and a carcass ply in which carcass cords are coated with the carcass coat rubber, wherein the belt coat rubber contains a diene rubber including natural rubber, a filler consisting of carbon black and silica, an organic acid cobalt salt, a phenolic resin, and a curing agent, and the filler is contained in an amount of 50 to 70 parts by mass per 100 parts by mass of the diene rubber, the mass ratio of the amount of silica to the carbon black is 1.0 to 3.5, and a silane compound represented by the following formula (1) is contained in an amount of 2 to 10% by mass relative to the silica, the dynamic storage modulus (Belt E') at 20°C is 13 MPa or more, and the ratio (Belt E') / (Carcass E') (MPa) of the dynamic storage modulus of the belt coat rubber at 20°C of the carcass coat rubber is 13 MPa or more. E') is 2.5 to 3.5.

[0008]

[0009] (In formula (1), R １ and R ２ is a hydrocarbon group having 1 to 18 carbon atoms, and R ３ is a hydrocarbon group having 1 to 3 carbon atoms or hydrogen. １ ~R ３ may contain a heteroatom (but does not contain sulfur); n represents a number from 0 to 2.

[0010] According to the present invention, it is possible to provide a tire that is excellent in durability and steering stability by suppressing deterioration of the belt layer due to long-term use.

[0011] The tire of the present invention specifies the composition of the belt coating rubber as described above. This allows the adhesion between the steel cord and the belt coating rubber to be maintained over a long period of time, providing excellent durability. Furthermore, by specifying the ratio (Belt E') / (Carcass E') of the dynamic storage modulus at 20°C of the belt coating rubber (Belt E') (MPa) to the dynamic storage modulus at 20°C of the carcass coating rubber (Carcass E') (MPa) to be 2.5 to 3.5, excellent handling stability can also be imparted to the tire.

[0012] The present invention will be described in more detail below. First, the belt coating rubber will be described. The belt coating rubber contains a diene rubber including natural rubber, a filler consisting of carbon black and silica, an organic acid cobalt salt, a phenolic resin, and a curing agent.

[0013] (Diene Rubber) The diene rubber used in the belt coating rubber contains natural rubber (NR) as an essential component. From the viewpoint of improving the effects of the present invention, it is preferable that NR is contained in an amount of 80 parts by mass or more per 100 parts by mass of the diene rubber. Note that isoprene rubber (IR) is considered to be included in the NR referred to in the present invention. Furthermore, in the present invention, rubbers other than NR can be used as the diene rubber. Examples include butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), and ethylene-propylene-diene terpolymer (EPDM). These may be used alone or in combination of two or more. Furthermore, there are no particular limitations on the molecular weight or microstructure, and the rubber may be terminally modified with amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl, or the like, or may be epoxidized.

[0014] (Filler) The filler used in the belt coating rubber is composed of carbon black and silica. The nitrogen adsorption specific surface area (N ２SA) is 50 to 120 m from the viewpoint of improving the effect of the present invention. ２ / g, and 70 to 100m ２ From the viewpoint of improving the effects of the present invention, the CTAB specific surface area of ​​the silica is more preferably 100 to 180 m / g. ２ / g, and 130 to 170m ２ / g. From the viewpoint of the global environment, it is also preferable to use silica derived from biomass. Biomass-derived silica is commercially available, for example, Precipitated silica K160 manufactured by FengHai Rice Biotechnology Co., Ltd., and has no substantial difference in composition compared to silica not derived from biomass. In the present invention, the nitrogen adsorption specific surface area (N ２ The specific surface area (SA) is a value measured in accordance with JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method," and the CTAB specific surface area is a value measured by measuring the amount of n-hexadecyltrimethylammonium bromide adsorbed on the silica surface in accordance with JIS K6217-3:2001 "Part 3: Determination of specific surface area - CTAB adsorption method."

[0015] (Organic Acid Cobalt Salt) Examples of organic acid cobalt salts used in the belt coating rubber include cobalt naphthenate, cobalt neodecanoate, cobalt stearate, cobalt rosinate, cobalt versatate, cobalt tallate, cobalt neodecanoate borate, and cobalt acetylacetonate. Among these, boron-containing organic acid cobalt salts are preferred, and cobalt neodecanoate borate is particularly preferred.

[0016] (Phenol-based resin) To improve the effect of the belt coating rubber, it is preferable to blend a phenol-based resin. Examples of the phenol-based resin include cresol resin, resorcinol resin, alkylphenol resin, and modified phenol resin. Examples of the modified phenol resin include cashew-modified phenol resin, oil-modified phenol resin, epoxy-modified phenol resin, aniline-modified phenol resin, and melamine-modified phenol resin.

[0017] (Curing Agent) It is preferable to compound a curing agent for the phenolic resin in the belt coating rubber. Examples of curing agents include hexamethylenetetramine, hexamethoxymethylmelamine (HMMM), hexamethoxymethylolmelamine, pentamethoxymethylmelamine, hexaethoxymethylmelamine, paraformaldehyde polymers, and N-methylol derivatives of melamine. These methylene donors can be used alone or in any blend.

[0018] (Silane Compound) The belt coating rubber contains a silane compound represented by the following formula (1).

[0019]

[0020] (In formula (1), R １ and R ２ is a hydrocarbon group having 1 to 18 carbon atoms, and R ３ is a hydrocarbon group having 1 to 3 carbon atoms or hydrogen. １ ~R ３ may contain a heteroatom (but does not contain sulfur); n represents a number from 0 to 2.

[0021] When silica is used in belt coating rubber, a phenomenon is observed in which the storage modulus E' decreases compared to rubber that does not use silica when the hardness is the same, but the use of the silane compound represented by formula (1) can compensate for this decrease in storage modulus E'. Furthermore, when belt coating rubber is stored for a certain period of time before tire molding, its viscosity increases, which can impair tire moldability, but the use of the silane compound has the effect of suppressing the increase in viscosity of the rubber during storage and improving tire moldability.

[0022] From the viewpoint of improving the present invention, the silane compound represented by the formula (1) is １ and R ２ In this embodiment, n is preferably 0, and R １is preferably an alkyl group having 7 to 20 carbon atoms, specifically, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, etc., and among these, from the viewpoint of compatibility with diene rubber, an alkyl group having 8 to 10 carbon atoms is more preferred. ３ is particularly preferably an ethyl group.

[0023] (Compounding ratio of belt-coating rubber) The belt-coating rubber contains a diene rubber containing natural rubber, a filler consisting of carbon black and silica, an organic acid cobalt salt, a phenolic resin, and a curing agent, and is characterized in that the filler is contained in an amount of 50 to 70 parts by mass per 100 parts by mass of the diene rubber, the mass ratio of silica to carbon black is 1.0 to 3.5, and the silane compound represented by formula (1) is contained in an amount of 2 to 10% by mass relative to the silica. If the filler content is less than 50 parts by mass, steering stability decreases, and if it exceeds 70 parts by mass, tire durability decreases. If the silica content is less than 1.0 or exceeds 3.5, tire durability decreases. If the silane compound represented by formula (1) is added in an amount less than 2% by mass relative to the silica, the amount is too small to achieve the desired effect, and if it exceeds 10% by mass, viscosity increases during mixing, scorching worsens, and vulcanization properties deteriorate during aging.

[0024] From the viewpoint of enhancing the effects of the present invention, the content of the filler is preferably 50 to 70 parts by mass per 100 parts by mass of diene rubber, and the mass ratio of the amount of silica to the carbon black is preferably 1.0 to 3.3.

[0025] In addition, in the filler, the carbon black content is preferably 30 to 50 parts by mass per 100 parts by mass of the diene rubber, and the silica content is preferably 30 to 50 parts by mass per 100 parts by mass of the diene rubber.

[0026] Furthermore, in terms of improving the effects of the present invention, the belt coating rubber preferably contains, relative to 100 parts by mass of the diene rubber, 0.1 to 1.5 parts by mass of the organic acid cobalt salt in terms of cobalt amount, 0.5 parts by mass or more but less than 3.0 parts by mass of the phenolic resin, and 0.5 to 5.0 parts by mass of the curing agent.

[0027] The tire of the present invention is characterized in that the belt coating rubber has a dynamic storage modulus (Belt E') at 20° C. of 13 MPa or more, and the ratio (Belt E') / (Carcass E') of the dynamic storage modulus (Belt E') (MPa) of the belt coating rubber at 20° C. to the dynamic storage modulus (Carcass E') (MPa) of the carcass coating rubber at 20° C. is 2.5 to 3.5. As described above, by specifying the ratio (Belt E') / (Carcass E') of the dynamic storage modulus (Belt E') (MPa) of the belt coating rubber at 20° C. to the dynamic storage modulus (Carcass E') (MPa) of the carcass coating rubber at 20° C. to be 2.5 to 3.5, a tire with excellent steering stability can be obtained. The dynamic storage modulus is a value (MPa) measured in accordance with JIS K6394 using an elasticity spectrometer manufactured by Toyo Seiki Seisaku-sho, Ltd., under conditions of a static strain of 10%, a dynamic strain of ±2%, a frequency of 20 Hz, and a temperature of 20°C. More preferably, the (Belt E') / (Carcass E') ratio is 2.7 to 3.3. The dynamic storage modulus (Belt E') of the belt coating rubber at 20°C is preferably 15 to 20 MPa, and the dynamic storage modulus (Carcass E') of the carcass coating rubber at 20°C is preferably 4 to 8 MPa. The dynamic storage modulus value can be adjusted by changing the type and grade of the filler, the amount of sulfur, etc.

[0028] In the present invention, the composition of the carcass coat rubber is not particularly limited as long as it satisfies the range of (Belt E') / (Carcass E'). For example, NR, BR and SBR are used as diene rubbers, and it is preferable to use 30 to 50 parts by mass of carbon black per 100 parts by mass of diene rubber. The nitrogen adsorption specific surface area (N２ SA) is 70 to 100 m ２ / g is preferred.

[0029] In addition to the above-mentioned components, the belt coating rubber and carcass coating rubber may be compounded with various additives that are generally compounded in belt coating rubber or carcass coating rubber compositions, such as vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, antioxidants, plasticizers, etc. These additives can be kneaded by a general method to form a composition, which can then be used for vulcanization or crosslinking. The amounts of these additives compounded may also be conventional amounts, as long as they do not contradict the object of the present invention.

[0030] The tire of the present invention suppresses deterioration of the belt layer due to long-term use and has excellent durability and steering stability. The tire of the present invention is also preferably a pneumatic tire, which can be filled with air, an inert gas such as nitrogen, or other gases.

[0031] The present invention will be further explained below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0032] Standard Example 1, Examples 1-5, and Comparative Examples 1-6 Sample Preparation In the formulation (parts by mass) shown in Table 1, the components excluding the vulcanization system (vulcanization accelerator, sulfur) were mixed for 5 minutes in a Banbury mixer at 80°C. The temperature reached at this time was 150°C. Next, the vulcanization system was added and mixed using a roll to obtain a rubber composition. Each obtained rubber composition (unvulcanized) was press-vulcanized at 170°C for 10 minutes in a mold (15 cm x 15 cm x 0.2 cm) to prepare vulcanized rubber test pieces, which were then evaluated as follows.

[0033] Dynamic storage modulus (E'): Using the obtained test piece, measurement was performed in accordance with JIS K6394 using an elasticity spectrometer manufactured by Toyo Seiki Seisaku-sho, under conditions of static strain 10%, dynamic strain ±2%, frequency 20 Hz, and temperature 20°C (MPa).

[0034] Constant strain fatigue test: Using the obtained test specimens, dumbbell JIS No. 3 test specimens were prepared in accordance with JIS K6251, and a constant strain tensile fatigue test was carried out under the conditions of 20°C, 100% strain, and a test frequency of 6.67 Hz (rotation speed: 400 rpm) in accordance with JIS K6270, and the number of repetitions until fracture was measured.

[0035] Tire steering stability: Test tires were prepared using the obtained rubber composition for the belt coating rubber and the carcass coating rubber. Each test tire was mounted on a wheel with a rim size of 18 x 8.5J and mounted on a test vehicle. A sensory evaluation was carried out by a test driver on a test course consisting of a paved road under an air pressure of 240 kPa. The results were expressed as an index, with the measured value of Standard Example 1 being 100. The higher the index value, the better the steering stability.

[0036] Tire durability: The resulting rubber composition was used for the belt coating rubber and the carcass coating rubber to vulcanize and mold a pneumatic tire (size 295 / 35R21). The resulting tire was mounted on a rim (21 x 10.5J), filled with 100% oxygen gas, adjusted to an air pressure of 350 kPa, and left standing in an environment at 70°C for 14 days. The tire was then adjusted to an air pressure of 170 kPa and subjected to a 6,000 km running test at a speed of 60 km / h using an indoor drum tester conforming to JIS D4230 with a drum diameter of 1707 mm, increasing the load by 13% every two hours from 88% of the JATMA standard load. After the running test, the tire was disassembled and the amount of edge separation (mm) in the belt layer was measured.

[0037] The results are shown in Table 1.

[0038]

[0039] *1: NR (TSR20) *2: BR (Nipol BR1220 manufactured by Nippon Zeon Co., Ltd.) *3: SBR (Nipol 1502 manufactured by Nippon Zeon Co., Ltd.) *4: Carbon black 1 (Seast V manufactured by Tokai Carbon Co., Ltd., nitrogen adsorption specific surface area (N ２ SA) = 27 m ２ / g) *5: Carbon black 2 (SEAT 300 manufactured by Tokai Carbon Co., Ltd., nitrogen adsorption specific surface area (N ２ SA) = 84m ２ / g) *6: Silica (FengHai Rice Biotechnology Co., Ltd., Precipitated silica K160, CTAB specific surface area = 158 m ２ / g) *7: Silane coupling agent (Si75 manufactured by Evonik Degussa) *8: Silane compound (KBE-3083, octyltriethoxysilane manufactured by Shin-Etsu Chemical Co., Ltd.) *9: Zinc oxide (3 types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd.) *10: Antiaging agent (SANTOFLEX 6PPD manufactured by Flexis) *11: Cobalt neodecanoate borate (NBC-2 manufactured by DIC CORPORATION, cobalt content = 22.2 mass%, shown as the amount of organic acid cobalt in Table 1.) *12: Phenolic resin (PENACOLITE RESIN B-18-S manufactured by INDSPEC, resorcinol resin) *13: Curing agent (CYREZ964RPC, HMMM manufactured by CYTEC INDUSTRIES) *14: Sulfur (Mucron OT-20 manufactured by Shikoku Chemical Industry Co., Ltd.) *15: Vulcanization accelerator CZ (Noccela CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *16: Vulcanization accelerator DZ (Noccela DZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0040] From the results in Table 1, each Example includes a belt layer in which steel cords are coated with a belt coat rubber, and a carcass ply in which carcass cords are coated with the carcass coat rubber, the belt coat rubber contains a diene rubber including natural rubber, a filler consisting of carbon black and silica, an organic acid cobalt salt, a phenolic resin, and a curing agent, the filler is contained in an amount of 50 to 70 parts by mass per 100 parts by mass of the diene rubber, the mass ratio of the amount of silica to the carbon black (silica / carbon black ratio) is 1.0 to 3.5, the silane compound represented by formula (1) is contained in an amount of 2 to 10% by mass relative to the silica, the dynamic storage modulus (Belt E') at 20°C is 13 MPa or more, and the ratio (Belt E') / (Carcass E') (MPa) of the dynamic storage modulus of the belt coat rubber at 20°C to the dynamic storage modulus of the carcass coat rubber at 20°C is 13 MPa or more. Since the value of E') is 2.5 to 3.5, it is understood that deterioration of the belt layer due to long-term use is suppressed compared to the rubber composition of Control Example 1, and a tire excellent in durability and steering stability can be provided.

[0041] On the other hand, in Comparative Example 1, the filler content exceeded the upper limit specified in the present invention, and the silica / carbon black ratio exceeded the upper limit specified in the present invention, resulting in poor tire durability. In Comparative Example 2, the filler content was less than the lower limit specified in the present invention, and the (Belt E') / (Carcass E') ratio was also less than the lower limit specified in the present invention, resulting in poor tire handling stability. In Comparative Example 3, the silica / carbon black ratio was less than the lower limit specified in the present invention, resulting in poor tire durability. In Comparative Example 4, the dynamic storage modulus (Belt E') at 20°C of the belt coating rubber was less than the lower limit specified in the present invention, and the (Belt E') / (Carcass E') ratio was also less than the lower limit specified in the present invention, resulting in poor tire handling stability. In Comparative Example 5, a phenolic resin and a curing agent were not blended, and the dynamic storage modulus (Belt E') was less than the lower limit specified in the present invention, and the ratio (Belt E') / (Carcass E') was also less than the lower limit specified in the present invention, resulting in poor tire handling stability. In Comparative Example 6, the dynamic storage modulus (Belt E') at 20°C of the belt coating rubber was less than the lower limit specified in the present invention, and the ratio (Belt E') / (Carcass E') was also less than the lower limit specified in the present invention, resulting in poor tire handling stability.

[0042] The present invention includes the following embodiments. Embodiment 1: A tire comprising a belt layer in which steel cords are coated with a belt coat rubber, and a carcass ply in which carcass cords are coated with the carcass coat rubber, wherein the belt coat rubber contains a diene rubber including natural rubber, a filler consisting of carbon black and silica, an organic acid cobalt salt, a phenolic resin, and a curing agent, and the filler is contained in an amount of 50 to 70 parts by mass per 100 parts by mass of the diene rubber, the mass ratio of the amount of silica to the carbon black is 1.0 to 3.5, and a silane compound represented by the following formula (1) is contained in an amount of 2 to 10% by mass relative to the silica, the dynamic storage modulus (Belt E') at 20°C is 13 MPa or more, and the ratio (Belt E') / (Carcass E') (MPa) of the dynamic storage modulus of the belt coat rubber at 20°C of the carcass coat rubber is 13 MPa or more. E') is 2.5 to 3.5.

[0043]

[0044] (In formula (1), R １ and R ２ is a hydrocarbon group having 1 to 18 carbon atoms, and R ３ is a hydrocarbon group having 1 to 3 carbon atoms or hydrogen. １ ~R ３ may contain a heteroatom (but does not contain sulfur); and n represents a number from 0 to 2.) Embodiment 2: The nitrogen adsorption specific surface area (N ２ SA) is 50 to 120 m ２ / g, and the CTAB specific surface area of ​​the silica is 100 to 170 m ２ The rubber composition for a tire according to embodiment 1, wherein the nitrogen adsorption specific surface area (N ２ SA) is 70 to 100m ２ / g, and the CTAB specific surface area of ​​the silica is 130 to 170 m ２ / g. Embodiment 4: The rubber composition for a tire according to any one of embodiments 1 to 3, wherein the silica is biomass-derived silica. Embodiment 5: The tire according to any one of embodiments 1 to 4, wherein the belt coat rubber contains, per 100 parts by mass of the diene rubber, 0.3 to 1.5 parts by mass of the organic acid cobalt salt in terms of cobalt amount, 0.5 parts by mass or more but less than 3.0 parts by mass of the phenolic resin, and 0.5 to 5.0 parts by mass of the curing agent. Embodiment 6: The tire according to any one of embodiments 1 to 5, wherein the organic acid cobalt salt is cobalt neodecanoate borate. Embodiment 7: The tire according to any one of embodiments 1 to 6, wherein the proportion of natural rubber per 100 parts by mass of the diene rubber is 80 parts by mass or more. Embodiment 8: The tire according to any one of embodiments 1 to 7, wherein the (Belt E') / (Carcass E') ratio is 2.7 to 3.3. Embodiment 9: In the silane compound represented by the formula (1), n ​​is 0 and R １ is an alkyl group having 7 to 20 carbon atoms, and R ３ 9. The tire of any one of claims 1 to 8, wherein is an ethyl group.

Claims

1. A tire comprising a belt layer in which steel cords are coated with a belt coat rubber, and a carcass ply in which carcass cords are coated with the carcass coat rubber, wherein the belt coat rubber contains a diene rubber including natural rubber, a filler consisting of carbon black and silica, an organic acid cobalt salt, a phenolic resin, and a curing agent, and the filler is contained in an amount of 50 to 70 parts by mass per 100 parts by mass of the diene rubber, the mass ratio of the amount of silica to the carbon black is 1.0 to 3.5, and a silane compound represented by the following formula (1) is contained in an amount of 2 to 10% by mass relative to the silica, the dynamic storage modulus (Belt E') at 20°C is 13 MPa or more, and the ratio of the dynamic storage modulus (Belt E') (MPa) of the belt coat rubber at 20°C to the dynamic storage modulus (Carcass E') (MPa) of the carcass coat rubber at 20°C is (Belt E') / (Carcass E') E') is 2.5 to 3.

5. (In formula (1), R １ and R ２ is a hydrocarbon group having 1 to 18 carbon atoms, R ３ is a hydrocarbon group having 1 to 3 carbon atoms or hydrogen. １ ~R ３ may contain a heteroatom (but does not contain sulfur); n represents a number from 0 to 2.

2. The nitrogen adsorption specific surface area (N ２ SA) is 50 to 120m ２ / g, and the CTAB specific surface area of ​​the silica is 100 to 170 m ２ 2. The tire according to claim 1, wherein the tensile strength is 1 / g.

3. The nitrogen adsorption specific surface area (N ２ SA) is 70 to 100m ２ / g, and the CTAB specific surface area of ​​the silica is 130 to 170 m ２ 2. The tire according to claim 1, wherein the tensile strength is 1 / g.

4. The tire according to claim 1, wherein the silica is derived from biomass.

5. The tire according to claim 1, characterized in that the belt coat rubber contains, per 100 parts by mass of the diene rubber, 0.1 to 1.5 parts by mass of the organic acid cobalt salt in terms of cobalt amount, 0.5 parts by mass or more but less than 3.0 parts by mass of the phenolic resin, and 0.5 to 5.0 parts by mass of the curing agent.

6. The tire according to claim 1, wherein said organic acid cobalt salt is cobalt neodecanoate borate.

7. The tire according to claim 1, characterized in that the proportion of natural rubber is 80 parts by mass or more per 100 parts by mass of the diene rubber.

8. The tire according to claim 1, characterized in that the (Belt E') / (Carcass E') ratio is 2.7 to 3.

3.

9. In the silane compound represented by the formula (1), n ​​is 0 and R １ is an alkyl group having 7 to 20 carbon atoms, and R ３ 2. The tire according to claim 1, characterized in that: is an ethyl group.

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