tire

Abstract

To provide a tire for solving the problem in which: as a use period of tires tends to be long in recent years, the adhesiveness between a steel cord and a belt coating rubber is lowered with long-term use and thus tire durability is impaired; and high steering stability is always required for tires.SOLUTION: The above problem is solved by a tire comprising a belt coating rubber and a carcass coating rubber, wherein the belt coating rubber contains specific amounts of a diene rubber including a natural rubber, a filler including carbon black and silica, an organic acid cobalt salt, a phenolic resin, and a curing agent, and has a dynamic storage elastic modulus (Belt E') at 20°C of 13 MPa or more, and a ratio (Belt E') / (Carcass E') of a dynamic storage elastic modulus (Belt E') of the belt coating rubber at 20°C to a dynamic storage elastic modulus (Carcass E') of the carcass coating rubber at 20°C is 2.5 to 3.5.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] A pneumatic tire is mainly composed of a pair of bead portions and sidewall portions on the left and right, 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 so as to envelop the bead cores from the inside to the outside of the tire. The carcass layer is composed of at least one carcass ply in which the carcass cords are coated with carcass coating rubber. The tread portion is composed 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. Since the belt ply is subjected to strong impacts and large loads, a steel cord is used as a reinforcing material, and the steel cord is coated with a belt coat rubber. The belt coat rubber is required to have good adhesion to the steel cord. On the other hand, in recent years, there has been a trend for tires to be used for longer periods, which has led to problems such as the deterioration of the adhesion between the steel cord and the belt coating rubber over long periods of use, resulting in a loss of durability. In addition, high driving stability is always required for tires.

[0003] Patent Document 1 below discloses a rubber composition that aims to provide a rubber composition that improves adhesion performance with steel cord, the rubber composition being obtained 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 parts 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 in that the dynamic storage modulus (E') at 2% dynamic strain and 20°C is 13 MPa or more, the loss tangent (tan δ) at 60°C is 0.20 or less, and the number of repetitions until failure in a constant strain fatigue test at 60% strain and 400 rpm is 35,000 or more. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6288148 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a tire in which deterioration of belt layers due to long-term use is suppressed, durability is excellent, and driving stability is maintained or improved. [Means for solving the problem]

[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 coat rubber and setting the ratio of the dynamic storage modulus of the belt coat rubber to the carcass coat rubber within a specific range, thereby completing the present invention.

[0007] That is, the present invention provides a belt layer in which a steel cord is coated with a belt coat rubber, a carcass ply in which a carcass cord is coated with a carcass coat rubber, In a tire comprising: The rubber for belt coating contains a diene rubber including natural rubber, a filler including 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 relative to 100 parts by mass of the diene rubber, the mass ratio of the silica to the carbon black is 1.0 to 3.5; The silica contains a silane compound represented by the following formula (1) in an amount of 2 to 10% by mass based on the silica, The dynamic storage modulus (Belt E') at 20°C is 13 MPa or more, and The ratio (Belt E') / (Carcass E') of the dynamic storage modulus (Belt E') (MPa) at 20°C of the belt coat rubber to the dynamic storage modulus (Carcass E') (MPa) at 20°C of the carcass coat rubber is 2.5 to 3.5. The present invention provides a tire characterized by the above-mentioned.

[0008] [ka]

[0009] (In formula (1), R 1 and R 2 is a hydrocarbon group having 1 to 18 carbon atoms, R 3 R 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 is a number from 0 to 2. Effect of the Invention

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

[0011] In the tire of the present invention, the composition of the belt coat rubber is specified as above. This allows the adhesion between the steel cord and the belt coat rubber to be maintained for a long period of time, providing excellent durability. In addition, by specifying the ratio (Belt E') / (Carcass E') of the dynamic storage modulus (Belt E') at 20°C (MPa) of the belt coat rubber to the dynamic storage modulus (Carcass E') at 20°C (MPa) of the carcass coat rubber to be 2.5 to 3.5, excellent steering stability can be imparted to the tire. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will be described in more detail below. First, the belt coat rubber will be described. 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.

[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 in 100 parts by mass of the diene rubber. Note that isoprene rubber (IR) is included in the NR referred to in the present invention. In the present invention, the diene rubber may be any rubber other than NR, such as butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), ethylene-propylene-diene terpolymer (EPDM), etc. These may be used alone or in combination of two or more. 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, etc., or epoxidized.

[0014] (Filler) The filler used in the rubber for belt coating is composed of carbon black and silica. The nitrogen adsorption specific surface area (N2SA) of the carbon black is set to 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 effect of the present invention, the CTAB specific surface area of ​​the silica is more preferably 100 to 180 m 2 / g, and 130 to 170m 2 / g is more preferable. From the viewpoint of the global environment, it is also preferable to use silica derived from biomass. Note that 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 other than that derived from biomass. In the present invention, the nitrogen adsorption specific surface area (N2SA) is a value measured according to 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 according to JIS K6217-3:2001 "Part 3: Determination of specific surface area - CTAB adsorption method".

[0015] (Organic acid cobalt salts) Examples of the organic acid cobalt salt 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, the organic acid cobalt salts containing boron are preferred, and cobalt neodecanoate borate is particularly preferred.

[0016] (Phenol Resin) In order to improve the effect, it is preferable to compound a phenolic resin in the belt coating rubber. Examples of the phenolic resin include cresol resin, resorcinol resin, alkylphenol resin, and modified phenol resin. Examples of the modified phenolic resin include cashew-modified phenolic resin, oil-modified phenolic resin, epoxy-modified phenolic resin, aniline-modified phenolic resin, and melamine-modified phenolic resin.

[0017] (hardening agent) It is preferable that a hardener for the phenolic resin is blended into the belt coating rubber. The hardeners include, for example, hexamethylenetetramine, hexamethoxymethylmelamine (HMMM), hexamethoxymethylolmelamine, pentamethoxymethylmelamine, hexaethoxymethylmelamine, polymers of para-formaldehyde, N-methylol derivatives of melamine, etc. These methylene donors can be used alone or in any blend.

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

[0019] [ka]

[0020] (In formula (1), R 1 and R 2 is a hydrocarbon group having 1 to 18 carbon atoms, R 3 R 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 is a number from 0 to 2.

[0021] When silica is used in rubber for belt coating, the storage modulus E' decreases compared to rubber not using silica when the hardness is the same, but the use of the silane compound represented by the formula (1) can compensate for the decrease in the storage modulus E'. In addition, when rubber for belt coating is stored for a certain period of time before tire molding, the viscosity increases, which may 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 1 is 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 preferable. 3 is particularly preferably an ethyl group.

[0023] (Rubber blend ratio for belt coating) The rubber for belt coating 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 is characterized in that it contains 50 to 70 parts by mass of the filler per 100 parts by mass of the diene rubber, the amount of silica to the carbon black is a mass ratio of 1.0 to 3.5, and it contains 2 to 10% by mass of the silane compound represented by formula (1) relative to the silica. If the content of the filler is less than 50 parts by mass, the steering stability decreases, whereas if it exceeds 70 parts by mass, the durability of the tire decreases. If the amount of silica to carbon black is less than 1.0 or exceeds 3.5 in terms of mass ratio, the durability of the tire decreases. When the amount of the silane compound represented by the formula (1) is less than 2% by mass relative to the silica, the amount is too small to produce the desired effect, whereas when the amount is more than 10% by mass, the viscosity increases during mixing, scorching worsens, and the vulcanization properties during aging deteriorate.

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

[0025] 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] From the viewpoint of improving the effects of the present invention, the rubber for belt coating 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 and 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 dynamic storage modulus (Belt E') of the belt coat rubber at 20°C is 13 MPa or more, and the ratio (Belt E') / (Carcass E') 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 2.5 to 3.5. As described above, by specifying the ratio (Belt E') / (Carcass E') of the dynamic storage modulus (Belt E') (MPa) at 20°C of the belt coat rubber to the dynamic storage modulus (Carcass E') (MPa) at 20°C of the carcass coat rubber 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 according to JIS K6394 using an elasticity spectrometer manufactured by Toyo Seiki Seisakusho 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 of the belt coat rubber at 20° C. (Belt E') is preferably 15 to 20 MPa, and the dynamic storage modulus of the carcass coat rubber at 20° C. (Carcass E') is preferably 4 to 8 MPa. The dynamic storage modulus can be adjusted by changing the type or grade of the filler, the amount of sulfur, or the like.

[0028] In the present invention, the composition of the carcass coat rubber is not particularly limited as long as it satisfies the above range of (Belt E') / (Carcass E'), but 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 (N2SA) of carbon black is 70 to 100 m 2 / g is preferred.

[0029] In addition to the above-mentioned components, the rubber for belt coating and the rubber for carcass coating may contain various additives that are generally compounded in rubber compositions for belt coating or rubber compositions for carcass coating, such as vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, antiaging agents, and plasticizers, and these additives can be kneaded in a general manner to form a composition, which can be used for vulcanization or crosslinking. The amounts of these additives may be conventional amounts, so long as they do not go against 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 preferably a pneumatic tire, and can be filled with air, an inert gas such as nitrogen, or other gases. EXAMPLES

[0031] The present invention will be further described 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 to 5, and Comparative Examples 1 to 6 Sample preparation In the formulation (parts by mass) shown in Table 1, the components other than the vulcanization system (vulcanization accelerator, sulfur) were mixed for 5 minutes in a Banbury mixer at 80°C. The temperature reached at that time was 150°C. Next, the vulcanization system was added and mixed using a roll to obtain a rubber composition. Each of the obtained rubber compositions (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 evaluated as follows.

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

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

[0035] Tire steering stability: Test tires were made using the obtained rubber composition for the belt coat rubber and the carcass coat rubber. Each test tire was mounted on a wheel with a rim size of 18 x 8.5J and mounted on a test vehicle, and a sensory evaluation was carried out by a test driver on a test course consisting of a paved road under the condition of 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 more excellent the steering stability.

[0036] Tire durability: The obtained rubber composition was used for the belt coat rubber and the carcass coat rubber to vulcanize and mold a pneumatic tire (size 295 / 35R21). The obtained tire was mounted on a rim (21×10.5J), filled with gas with an oxygen concentration of 100%, and the air pressure was set to 350 kPa, and the tire was left standing in an environment at a temperature of 70° C. for 14 days. The air pressure was then adjusted to 170 kPa, and the tire was subjected to a running test of 6,000 km at a speed of 60 km / h, with the load being increased by 13% every 2 hours from 88% of the JATMA-specified load, using an indoor drum tester conforming to JIS D4230 with a drum diameter of 1707 mm. After the running test, the tire was disassembled to measure the amount (mm) of edge separation in the belt layer.

[0037] The results are shown in Table 1.

[0038] [Table 1]

[0039] *1:NR(TSR20) *2: BR (Nipol BR1220 manufactured by Zeon Corporation) *3: SBR (Nipol 1502 manufactured by Zeon Corporation) *4: Carbon black 1 (Tokai Carbon Co., Ltd., Seast V, nitrogen adsorption specific surface area (N2SA) = 27 m 2 / g) *5: Carbon black 2 (Tokai Carbon Co., Ltd., Seast 300, nitrogen adsorption specific surface area (N2SA) = 84 m 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: Anti-aging agent (Flexis SANTOFLEX 6PPD) *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:Phenol-based resin (INDSPEC PENACOLITE RESIN B-18-S, resorcinol resin) *13: Hardener (CYREZ964RPC, HMMM, manufactured by CYTEC INDUSTRIES) *14: Sulfur (Mu-Cron OT-20 manufactured by Shikoku Chemical Industries 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 a steel cord is coated with a belt coat rubber, and a carcass ply in which a carcass cord is coated with a 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 belt coat rubber contains 50 to 70 parts by mass of the filler per 100 parts by mass of the diene rubber, the amount of silica to the carbon black is a mass ratio (silica / carbon black ratio) of 1.0 to 3.5, the silane compound represented by the 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 rubber composition 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 Reference Example 1, and a tire excellent in durability and driving stability can be provided.

[0041] On the other hand, in Comparative Example 1, the filler content exceeded the upper limit stipulated in the present invention, and the silica / carbon black ratio exceeded the upper limit stipulated in the present invention, resulting in poor tire durability. In Comparative Example 2, the content of the filler was below the lower limit specified in the present invention, and (Belt E') / (Carcass E') was also below the lower limit specified in the present invention, resulting in poor tire handling stability. In Comparative Example 3, the silica / carbon black ratio was below the lower limit specified in the present invention, and therefore the tire durability was poor. In Comparative Example 4, the dynamic storage modulus (Belt E') of the belt coat rubber at 20°C was less than the lower limit specified in the present invention, and (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 5, no phenolic resin or curing agent was blended, and the dynamic storage modulus (Belt E') 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 6, the dynamic storage modulus (Belt E') of the belt coat rubber at 20°C was less than the lower limit specified in the present invention, and (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 belt layer in which a steel cord is coated with a belt coat rubber, and a carcass ply in which a carcass cord is coated with a carcass coat rubber, In a tire comprising: The rubber for belt coating contains a diene rubber including natural rubber, a filler including 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 relative to 100 parts by mass of the diene rubber, the mass ratio of the silica to the carbon black is 1.0 to 3.5; The silica contains a silane compound represented by the following formula (1) in an amount of 2 to 10% by mass based on the silica, The dynamic storage modulus (Belt E') at 20°C is 13 MPa or more, and The ratio (Belt E') / (Carcass E') of the dynamic storage modulus (Belt E') (MPa) at 20°C of the belt coat rubber to the dynamic storage modulus (Carcass E') (MPa) at 20°C of the carcass coat rubber is 2.5 to 3.5. A tire characterized by:

[0043] [ka]

[0044] (In formula (1), R 1 and R 2 is a hydrocarbon group having 1 to 18 carbon atoms, R 3 R 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 is a number from 0 to 2. Embodiment 2: The nitrogen adsorption specific surface area (N2SA) of the carbon black is 50 to 120 m 2 / g, and the CTAB specific surface area of ​​the silica is 100 to 170 m 2 / g of the rubber composition for tires according to embodiment 1. Embodiment 3: 3. The rubber composition for tires according to embodiment 1 or 2, wherein the silica is biomass-derived silica. Embodiment 4: The tire according to any one of embodiments 1 to 3, characterized in that the belt coat rubber contains, relative to 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 and 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 5: 5. The tire according to any one of embodiments 1 to 4, wherein the organic acid cobalt salt is cobalt neodecanoate borate.

Claims

1. A belt layer in which a steel cord is coated with a belt coat rubber, and a carcass ply in which a carcass cord is coated with a carcass coat rubber, In a tire comprising: The rubber for belt coating contains a diene rubber including natural rubber, a filler including 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 silica to the carbon black is 1.0 to 3.5; The silica contains a silane compound represented by the following formula (1) in an amount of 2 to 10% by mass based on the silica, The dynamic storage modulus (Belt E') at 20°C is 13 MPa or more, and A ratio (Belt E') / (Carcass E') 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 2.5 to 3.

5. A tire characterized by: 【Chemistry 1】 (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 heteroatoms (but not 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. 2. The tire according to claim 1, wherein the silica is biomass-derived silica.

4. The tire according to claim 1, characterized in that the belt coat rubber 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 and less than 3.0 parts by mass of the phenolic resin, and 0.5 to 5.0 parts by mass of the curing agent.

5. 2. The tire according to claim 1, wherein the organic acid cobalt salt is cobalt neodecanoate borate.

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