Rubber composition for base tread and tire

Abstract

To enhance steering stability and low heat build-up while suppressing deterioration in durability.SOLUTION: A rubber composition for a base tread according to an embodiment includes a rubber component containing natural rubber in an amount of 70 mass% or more, a first filler that is carbon black having an N2SA of less than 60 m2 / g, a second filler that is carbon black having an N2SA of 60 m2 / g or more and / or silica, sulfur, and a sulfenamide-based vulcanization accelerator, wherein, per 100 pts.mass of the rubber component, an amount of the first filler is 10 to 45 pts.mass, an amount of the second filler is 15 to 30 pts.mass, a total amount of the first filler and the second filler is 35 to 60 pts.mass, an amount of sulfur is 1.6 to 3.0 pts.mass, and an amount of the sulfenamide-based vulcanization accelerator is 1.6 to 3.0 pts.mass.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition for a base tread and a tire using the same. [Background technology]

[0002] With the increasing demand for improved fuel economy in automobiles, rubber components with excellent low heat buildup are also desired for tires. Generally, increasing the amount of filler compounded in a rubber composition increases hardness and improves handling stability, but reduces low heat buildup. Conversely, decreasing the amount of filler tends to improve low heat buildup but reduce handling stability. Recent tires for low fuel consumption are highly required to have low heat buildup, and therefore, when a conventional rubber composition with excellent low heat buildup is used in the base tread, there is a problem of low hardness and reduced handling stability.

[0003] Patent Document 1 discloses that in a rubber composition for a base tread, carbon black and a specific sulfide compound are blended into a rubber component containing tin-modified polybutadiene rubber in order to improve fuel economy while maintaining rubber processability and handling stability.

[0004] Patent Document 2 discloses that in order to reduce rolling resistance while maintaining steering stability and durability, carbon black and silica having a specific CTAB adsorption specific surface area are blended into the rubber component of a rubber composition for a base tread, and natural rubber and a specific butadiene rubber are used in combination as the rubber component.

[0005] Patent Document 3 describes a rubber composition for a base tread, in which a rubber component containing isoprene rubber is added with a nitrogen adsorption specific surface area of ​​40 m in order to improve low heat buildup while maintaining crack resistance. 2 / g and carbon black with a nitrogen adsorption specific surface area of ​​45m 2 It is disclosed that silica is used in combination with carbon black having a porosity of 1 / g or more. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-120783 [Patent Document 2] Japanese Patent Publication No. 2022-165622 [Patent Document 3] Japanese Patent Publication No. 2022-064752 Summary of the Invention [Problem to be solved by the invention]

[0007] Conventional rubber compositions for base treads are not necessarily sufficient in terms of improving steering stability and low heat buildup while suppressing deterioration in durability, and further improvements are required.

[0008] In view of the above, an object of an embodiment of the present invention is to provide a rubber composition for a base tread that can improve steering stability and low heat buildup while suppressing deterioration in durability. [Means for solving the problem]

[0009] The present invention includes the embodiments shown below. [1] Rubber component and nitrogen adsorption specific surface area of ​​60m 2 / g and a first filler that is carbon black with a nitrogen adsorption specific surface area of ​​60 m 2 / g or more of a second filler which is carbon black and / or silica, sulfur, and a sulfenamide-based vulcanization accelerator, The rubber component contains 70% by mass or more of natural rubber, a rubber composition for a base tread, wherein, relative to 100 parts by mass of the rubber component, the amount of the first filler is 10 to 45 parts by mass, the amount of the second filler is 15 to 30 parts by mass, the total amount of the first filler and the second filler is 35 to 60 parts by mass, the amount of the sulfur is 1.6 to 3.0 parts by mass, and the amount of the sulfenamide vulcanization accelerator is 1.6 to 3.0 parts by mass. [2] The nitrogen adsorption specific surface area of ​​the carbon black of the first filler is 20 m 2 / g or more 60m 2 / g or less of the rubber composition for a base tread according to [1]. [3] The nitrogen adsorption specific surface area of ​​the carbon black of the second filler is 60 m 2 / g or more 100m 2 / g or less of the rubber composition for a base tread according to [1] or [2]. [4] The rubber composition for a base tread according to any one of [1] to [3], wherein the sulfenamide vulcanization accelerator is at least one of N-(tert-butyl)-2-benzothiazole sulfenamide and N-cyclohexyl-2-benzothiazole sulfenamide. [5] The first filler has a nitrogen adsorption specific surface area of ​​20 m 2 / g or more 40m 2 / g and carbon black with a nitrogen adsorption specific surface area of ​​40m 2 / g or more 60m 2 The rubber composition for a base tread according to any one of [1] to [4], further comprising less than 1 / g of carbon black. [6] The rubber composition for a base tread according to any one of [1] to [5], further comprising 6 parts by mass or more of a silane coupling agent per 100 parts by mass of the silica. [7] A tire having a base tread formed from the rubber composition for a base tread according to any one of [1] to [6]. [Effects of the Invention]

[0010] According to an embodiment of the present invention, it is possible to provide a rubber composition for a base tread that can improve steering stability and low heat buildup while suppressing deterioration in durability. DETAILED DESCRIPTION OF THE INVENTION

[0011] The rubber composition for a base tread according to this embodiment (hereinafter also simply referred to as "rubber composition") contains a rubber component, a first filler, a second filler, sulfur, and a sulfenamide-based vulcanization accelerator.

[0012] The rubber component contains 70% by mass or more of natural rubber (NR). That is, 100% by mass of the rubber component contains 70 to 100% by mass of natural rubber, and may be natural rubber alone. The proportion of natural rubber is preferably 75% by mass or more, and more preferably 80% by mass or more. The rubber component may contain other diene rubbers in addition to natural rubber. Examples of other diene rubbers include isoprene rubber (polyisoprene) (IR), butadiene rubber (polybutadiene) (BR), styrene-butadiene rubber (SBR), butadiene-isoprene copolymer rubber, and styrene-butadiene-isoprene copolymer rubber.

[0013] Here, diene rubber refers to rubber having repeating units corresponding to diene monomers with conjugated double bonds. Diene rubber also includes those whose terminals or main chains have been modified as needed (for example, terminal-modified BR and terminal-modified SBR).

[0014] In one embodiment, the rubber component preferably contains 70 to 100% by mass of natural rubber and 0 to 30% by mass of butadiene rubber, more preferably 75 to 100% by mass of natural rubber and 0 to 25% by mass of butadiene rubber, and even more preferably 80 to 100% by mass of natural rubber and 0 to 20% by mass of butadiene rubber. In this case, the rubber component may be natural rubber alone, i.e., 100% by mass of natural rubber and 0% by mass of butadiene rubber.

[0015] The butadiene rubber is not particularly limited and may be a modified butadiene rubber whose terminals and / or main chain are modified, or an unmodified butadiene rubber. The modified butadiene rubber is a BR modified with a functional group introduced into the terminals and / or main chain. The functional group preferably contains an oxygen atom and / or a nitrogen atom, and examples thereof include at least one selected from the group consisting of an amino group, a hydroxy group, an alkoxy group, an epoxy group, and a carboxy group.

[0016] The butadiene rubber may also be a high-cis butadiene rubber (high-cis BR) having a cis-1,4 bond content of 90% by mass or more (more preferably 95% by mass or more). Examples of high-cis BR include butadiene rubber polymerized using a cobalt catalyst or a neodymium catalyst. Here, the cis-1,4 bond content is 1 It is a value calculated from the integral ratio of the H-NMR spectrum.

[0017] The first filler has a nitrogen adsorption specific surface area (N2SA) of 60m 2 The carbon black (A) is a large particle size carbon black having a particle size larger than that of the carbon black of the second filler. The N2SA of the carbon black (A) is 20m 2 / g or more 60m 2 / g, and more preferably 20 to 50 m 2 / g, more preferably 25 to 45m 2 / g.

[0018] In this specification, the nitrogen adsorption specific surface area (N2SA) of carbon black is measured in accordance with JIS K6217-2:2017 Method A.

[0019] The first filler is N2SA 60m 2 / g, only one type of carbon black may be used, or two or more types may be used in combination. Preferably, the first filler has an N2SA of 20 m 2 / g or more 40m 2 / g or less of carbon black (A1) and N2SA is 40m 2 / g or more 60m 2 / g of carbon black (A2). By using multiple types of carbon black with different N2SA in combination, the effect of improving low heat buildup can be further enhanced.

[0020] The N2SA of the carbon black (A1) is more preferably 20 to 35 m 2 / g, and more preferably 25 to 30m 2The N2SA of the carbon black (A2) is more preferably 40 to 55 m / g. 2 / g, more preferably 40 to 50m 2 / g.

[0021] When carbon black (A1) and carbon black (A2) are used in combination as the first filler, the ratio between the two is not particularly limited, but the mass ratio (A1) / (A2) is preferably 20 / 80 to 80 / 20, more preferably 30 / 70 to 70 / 30, and even more preferably 40 / 60 to 60 / 40.

[0022] The content of the first filler is 10 to 45 parts by mass relative to 100 parts by mass of the rubber component. When the content of the first filler is 10 parts by mass or more, the effect of improving low heat buildup can be enhanced. The content of the first filler relative to 100 parts by mass of the rubber component is preferably 15 to 40 parts by mass, more preferably 20 to 35 parts by mass, and even more preferably 23 to 30 parts by mass.

[0023] The second filler has a nitrogen adsorption specific surface area (N2SA) of 60m 2 / g or more of carbon black (B) or silica, and the carbon black (B) and silica may be used in combination.

[0024] The carbon black (B) is a small particle size carbon black having a smaller particle size than the carbon black (A) of the first filler, and has better reinforcing properties. The N2SA of the carbon black (B) is 60 to 100 m 2 / g, more preferably 65 to 100m 2 / g, more preferably 70 to 95m 2 When carbon black (B) is used as the second filler, N2SA is 60m 2 / g or more of carbon black may be used alone or in combination of two or more kinds.

[0025] The silica used as the second filler is preferably wet silica such as wet precipitation silica or wet gelation silica. The nitrogen adsorption specific surface area (BET) of the silica is not particularly limited, and may be, for example, 100 to 300 m 2 / g is also acceptable, 150-250m 2 / g is also acceptable, 180-220m 2 / g is also acceptable.

[0026] In this specification, the nitrogen adsorption specific surface area of ​​silica is the BET specific surface area measured in accordance with the BET method described in JIS K6430:2008.

[0027] The content of the second filler is 15 to 30 parts by mass per 100 parts by mass of the rubber component. When the content of the second filler is 15 parts by mass or more, it is possible to increase hardness and improve handling stability. When the content of the second filler is 30 parts by mass or less, it is possible to enhance the effect of improving low heat buildup. The content of the second filler is preferably 17 to 28 parts by mass, more preferably 18 to 25 parts by mass, and even more preferably 20 to 25 parts by mass per 100 parts by mass of the rubber component.

[0028] In one embodiment, the second filler preferably contains silica, and in this case, the amount of silica in 100% by mass of the second filler may be 50 to 100% by mass, 80 to 100% by mass, or 100% by mass (i.e., silica alone).

[0029] The total content of the first filler and the second filler is 35 to 60 parts by mass per 100 parts by mass of the rubber component. When the total filler amount is 35 parts by mass or more, it is possible to suppress a decrease in hardness and improve handling stability. When the total filler amount is 60 parts by mass or less, it is possible to suppress a deterioration in low heat buildup properties. The total filler amount per 100 parts by mass of the rubber component is preferably 40 to 55 parts by mass, more preferably 42 to 53 parts by mass.

[0030] The sulfur used as a vulcanizing agent is not particularly limited, and examples thereof include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

[0031] The sulfur content is 1.6 to 3.0 parts by mass per 100 parts by mass of the rubber component. When the sulfur content is 1.6 parts by mass or more, the crosslink density can be increased, hardness can be maintained, and the effect of improving low heat buildup can be enhanced. When the sulfur content is 3.0 parts by mass or less, tear strength can be increased, and durability can be improved. The sulfur content is preferably 1.8 to 2.8 parts by mass, more preferably 2.0 to 2.6 parts by mass per 100 parts by mass of the rubber component.

[0032] Sulfenamide vulcanization accelerators are vulcanization accelerators that have a bonding group of -SN< in their chemical structure. Examples of sulfenamide vulcanization accelerators include N-(tert-butyl)-2-benzothiazole sulfenamide (TBBS), N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N-oxydiethylene-2-benzothiazole sulfenamide (MBS), and N,N-diisopropyl-2-benzothiazole sulfenamide (DIBS). Any one of these may be used alone, or two or more may be used in combination. It is preferable to use at least one of TBBS and CBS as the sulfenamide vulcanization accelerator.

[0033] The content of the sulfenamide vulcanization accelerator is 1.6 to 3.0 parts by mass per 100 parts by mass of the rubber component. When the content of the sulfenamide vulcanization accelerator is 1.6 parts by mass or more, the crosslink density can be increased, hardness can be maintained, and the effect of improving low heat buildup can be enhanced. When the content of the sulfenamide vulcanization accelerator is 3.0 parts by mass or less, tear strength can be increased, and durability can be improved. The content of the sulfenamide vulcanization accelerator is preferably 1.8 to 2.8 parts by mass, more preferably 2.0 to 2.6 parts by mass per 100 parts by mass of the rubber component.

[0034] When silica is used as the second filler, the rubber composition preferably further contains a silane coupling agent. Examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, and bis(3-triethoxysilylpropyl)tetrasulfide. Examples of suitable silane coupling agents include sulfide-based silane coupling agents such as bis(2-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide, and mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and 3-octanoylthio-1-propyltriethoxysilane. These may be used alone or in combination of two or more.

[0035] The content of the silane coupling agent is preferably 6 parts by mass or more, more preferably 6 to 20 parts by mass, and even more preferably 6 to 15 parts by mass, per 100 parts by mass of silica.

[0036] In addition to the above components, the rubber composition according to the present embodiment may contain various additives that are generally used in rubber compositions, such as wax, antioxidants, zinc oxide, stearic acid, oils, and vulcanization accelerators other than sulfenamide-based vulcanization accelerators.

[0037] The content of the wax is not particularly limited, and may be, for example, 0 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 4 parts by mass per 100 parts by mass of the rubber component.

[0038] Examples of the antioxidant include various antioxidants such as amine-ketone, aromatic secondary amine, monophenol, bisphenol, and benzimidazole antioxidants, any of which may be used alone or in combination of two or more. The content of the antioxidant is not particularly limited, and may be, for example, 0 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 4 parts by mass per 100 parts by mass of the rubber component.

[0039] The content of zinc oxide is not particularly limited, and may be, for example, 0 to 10 parts by mass, 0.5 to 7 parts by mass, or 1 to 5 parts by mass per 100 parts by mass of the rubber component.

[0040] The content of stearic acid is not particularly limited, and may be, for example, 0 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 4 parts by mass per 100 parts by mass of the rubber component.

[0041] The rubber composition according to the present embodiment can be prepared by kneading in a conventional manner using a commonly used mixer such as a Banbury mixer, kneader, roll, etc. That is, for example, in a first mixing stage, additives other than the vulcanizing agent and vulcanization accelerator are added and mixed with the rubber component, and then in a final mixing stage, the vulcanizing agent and vulcanization accelerator are added and mixed with the resulting mixture to prepare the rubber composition.

[0042] The rubber composition according to the present embodiment can be used for the base tread of a tire. Examples of the tire include pneumatic tires for various uses and sizes, such as tires for passenger cars and large tires for trucks and buses. Pneumatic tires for passenger cars are preferred.

[0043] The tire according to the present embodiment includes a base tread made using the rubber composition. The base tread is the inner layer of a tread having a multi-layer structure. In a tread having a two-layer structure consisting of a cap tread that comes into contact with the road surface and a base tread provided inside the cap tread, the base tread is the inner base tread.

[0044] The method for manufacturing the tire according to the present embodiment is not particularly limited. For example, the rubber composition is extruded into a predetermined shape according to a conventional method to obtain an unvulcanized base tread rubber member. The base tread rubber member is combined with other tire components to produce an unvulcanized tire (green tire). Thereafter, the tire can be manufactured by vulcanizing and molding at, for example, 140°C to 180°C. [Example]

[0045] Examples of the present invention will be shown below, but the present invention is not limited to these examples.

[0046] The components used in the examples and comparative examples are as follows. Natural rubber: RSS#3 Butadiene rubber 1: High cis BR (cis-1,4 bond content 95% by mass), "BR730" manufactured by ENEOS Material Corporation Butadiene rubber 2: Terminally modified BR, "Nipol BR1250H" manufactured by Nippon Zeon Co., Ltd.

[0047] Carbon black 1: N2SA=27m 2 / g, "Seast V" manufactured by Tokai Carbon Co., Ltd. Carbon Black 2: N2SA=42m 2 / g, "Seat SO" manufactured by Tokai Carbon Co., Ltd. Carbon Black 3: N2SA=84m 2 / g, "Seat 300" manufactured by Tokai Carbon Co., Ltd. Carbon Black 4: N2SA=93m 2 / g, "Seast KH" manufactured by Tokai Carbon Co., Ltd. Silica: Tosoh Silica Corporation's "Nipsil AQ" (nitrogen adsorption specific surface area 205 m 2 / g) Silane coupling agent: sulfide type, "Si75" manufactured by Evonik Japan

[0048] Wax: "OZOACE 1722" manufactured by Nippon Seiro Co., Ltd. Anti-aging agent 1: "Nocrac 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Anti-aging agent 2: "ANTIOXIDANT TMQ" manufactured by Kemai Chemical Co., Ltd. Zinc oxide: "Zinc oxide type 3" manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Kao Corporation's "Lunac S20"

[0049] Sulfur: 5% oil-treated powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator 1: TBBS, Sansera NS-G manufactured by Sanshin Chemical Industry Co., Ltd. Vulcanization accelerator 2: CBS, Sansera CM-G manufactured by Sanshin Chemical Industry Co., Ltd. Vulcanization accelerator 3:1,3-diphenylguanidine, "Soxinol DG" manufactured by Sumitomo Chemical Co., Ltd.

[0050] Using a Banbury mixer, first, in the first mixing stage, compounding ingredients excluding sulfur and vulcanization accelerator were added to the rubber component and kneaded (discharge temperature = 155°C) according to the formulation (parts by mass) shown in Tables 1 and 2. Next, in the final mixing stage, sulfur and vulcanization accelerator were added to the obtained kneaded mixture and kneaded (discharge temperature = 90°C) to prepare a rubber composition.

[0051] In Tables 1 and 2, "sulfur (net amount)" in the formulation is the amount of sulfur excluding oil.

[0052] Each rubber composition was vulcanized at 150°C for 30 minutes to prepare a vulcanized rubber sample of a predetermined shape, and the hardness, low heat buildup, and tear strength of the resulting rubber sample were evaluated using the following methods.

[0053] Hardness: The hardness of a 12.5 mm thick rubber sample was measured at 23°C in accordance with the Durometer Type A method of JIS K6253-3:2012. The higher this value, the better the handling stability.

[0054] Low heat buildup: Measured in accordance with JIS K6394:2007. Specifically, a rubber sample measuring 5 mm wide x 40 mm long x 2 mm thick was measured for loss factor tanδ using a viscoelasticity measuring device manufactured by GABO under conditions of a temperature of 60°C, static strain of 10%, dynamic strain of 1%, and frequency of 10 Hz (tensile mode), and the loss factor was expressed as an index, with the value for Comparative Example 1 being 100. A smaller index indicates a smaller tanδ, and therefore less heat buildup and better low heat buildup properties.

[0055] Tear strength: Measured in accordance with JIS K6252-1:2015. Specifically, a rubber sample (2 mm thick) was punched into a crescent shape and a 0.50±0.08 mm notch was made in the center of the indentation. Testing was carried out at a pulling rate of 500 mm / min using a tensile tester manufactured by Shimadzu Corporation. The maximum tear strength until the rubber sample broke was read and expressed as an index, with the value for Comparative Example 1 being set at 100. A higher index indicates a higher tear strength and better durability during high-speed running (high-speed durability). An index of 80 or higher can be said to have sufficient high-speed durability.

[0056] [Table 1]

[0057] [Table 2]

[0058] The results are shown in Tables 1 and 2. Examples 1 to 9 according to the present embodiment had excellent low heat build-up properties compared to Comparative Example 1, which is a conventional standard example, while maintaining sufficient high-speed durability. In addition, they had hardness of A58 or higher, which meant they had excellent handling stability.

[0059] In contrast, in Comparative Example 2, the proportion of natural rubber was low, resulting in a significant decrease in tear strength and poor high-speed durability. In Comparative Example 3, compared to Comparative Example 1, part of the carbon black was replaced with one having a smaller N2SA and the amount of vulcanization system was increased, thereby improving low heat buildup, but because the total filler amount was small, the hardness was low and handling stability was poor, just like in Comparative Example 1. In Comparative Example 4, the total filler amount was too high, resulting in poor low heat buildup.

[0060] In Comparative Example 5, the total filler amount met the specified amount, but the second filler was not blended, resulting in low hardness and poor handling stability. In Comparative Example 6, the total filler amount met the specified amount, but the first filler was not blended, resulting in poor low heat buildup. In Comparative Example 7, the sulfur amount was low, resulting in poor low heat buildup. In Comparative Example 8, the sulfur amount was too high, resulting in a significant decrease in tear strength and poor high-speed durability. In Comparative Example 9, the amount of sulfenamide vulcanization accelerator was low, resulting in poor low heat buildup. In Comparative Example 10, the amount of sulfenamide vulcanization accelerator was too high, resulting in a significant decrease in tear strength and poor high-speed durability. In Comparative Example 11, a guanidine vulcanization accelerator was used instead of a sulfenamide vulcanization accelerator, resulting in poor low heat buildup.

[0061] The various numerical ranges described in this specification can be arbitrarily combined with their upper and lower limits, and all such combinations are considered to be preferred numerical ranges described in this specification. Furthermore, a numerical range described as "X to Y" means from X to Y.

Claims

1. Rubber component and nitrogen adsorption specific surface area of ​​60m ２ / g, and a first filler that is carbon black having a nitrogen adsorption specific surface area of ​​60 m ２ / g or more of a second filler which is carbon black and / or silica, sulfur, and a sulfenamide-based vulcanization accelerator, The rubber component contains 70% by mass or more of natural rubber, the amount of the first filler is 10 to 45 parts by mass, the amount of the second filler is 15 to 30 parts by mass, the total amount of the first filler and the second filler is 35 to 60 parts by mass, the amount of the sulfur is 1.6 to 3.0 parts by mass, and the amount of the sulfenamide vulcanization accelerator is 1.6 to 3.0 parts by mass, relative to 100 parts by mass of the rubber component; Rubber composition for base tread.

2. The nitrogen adsorption specific surface area of ​​the carbon black of the first filler is 20 m ２ / g or more 60m ２ The rubber composition for a base tread according to claim 1, wherein the modulus of elasticity is less than 1 / g.

3. The nitrogen adsorption specific surface area of ​​the carbon black of the second filler is 60 m ２ / g or more 100m ２ The rubber composition for a base tread according to claim 1, wherein the modulus of elasticity is 1 / g or less.

4. 2. The rubber composition for a base tread according to claim 1, wherein the sulfenamide vulcanization accelerator is at least one of N-(tert-butyl)-2-benzothiazole sulfenamide and N-cyclohexyl-2-benzothiazole sulfenamide.

5. The first filler has a nitrogen adsorption specific surface area of ​​20 m ２ / g or more 40m ２ / g and carbon black with a nitrogen adsorption specific surface area of ​​40 m ２ / g or more 60m ２ 2. The rubber composition for a base tread according to claim 1, further comprising less than 1000 carbon black per 1000g of carbon black.

6. The rubber composition for a base tread according to claim 1, further comprising 6 parts by mass or more of a silane coupling agent relative to 100 parts by mass of the silica.

7. A tire comprising a base tread formed from the rubber composition for a base tread according to any one of claims 1 to 6.

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