JP6147594B2 - Rubber composition for tire sidewall and pneumatic tire - Google Patents

Description

  The present invention relates to a rubber composition used for a sidewall portion of a pneumatic tire, a manufacturing method thereof, and a pneumatic tire using the rubber composition.

  Properties required for the sidewall rubber of pneumatic tires include low heat generation performance and tear resistance. Known methods for improving the tear resistance, which is one of the required performances, include increasing the amount of carbon black as a filler, reducing the particle size of carbon black, and adding silica. However, in these improved methods, the processability, that is, the processability deteriorates due to the increase in the viscosity of the unvulcanized rubber. Therefore, it is required to improve the tear resistance while suppressing deterioration of workability.

  By the way, Patent Documents 1 and 2 disclose blending tetrabenzylthiuram disulfide (TBzTD) as a vulcanization accelerator in a rubber composition used for a tire. However, Patent Document 1 discloses that heat-curing resistance during running on rough roads by blending a predetermined amount of TBzTD, sulfur, and a sulfenamide-based vulcanization accelerator into the cushion rubber below the belt layer of a heavy duty pneumatic tire. It improves mechanical fatigue resistance and heat resistance. Patent Document 2 realizes high grip performance and steering stability performance by blending a predetermined amount of TBzTD and sulfur into tread rubber. Therefore, these documents do not disclose the combined use of TBzTD and a benzimidazole anti-aging agent in the sidewall rubber, nor does it disclose any significant effect.

  Patent Document 3 discloses an example of an accelerator used for the use of a layer structure vulcanizate including a layer containing a hydrogenated vinyl polybutadiene and a layer containing a diene rubber for a tire sidewall or the like, and sulfur crosslinking. It is disclosed that TBzTD is used, and that mercaptobenzimidazole is used as an example of an antioxidant added to the sulfur vulcanizate. However, these TBzTD and benzimidazole anti-aging agents are described as being added to a layer containing vinyl hydride polybutadiene, and there is no specific example of using both in combination, and there is no noticeable effect of the combined use. Not mentioned.

JP 2009-114385 A JP 2002-226629 A JP-T 2009-541098

  An object of the present invention is to provide a rubber composition for a tire sidewall that can improve tear resistance without impairing processability, and a pneumatic tire using the rubber composition.

  The rubber composition for a tire sidewall according to the present invention includes 40 to 70 parts by mass of natural rubber and / or isoprene rubber and 60 to 30 parts by mass of butadiene rubber having a cis-1,4 bond content of 96% or more. 0.1 to 3 parts by mass of tetrabenzyl thiuram disulfide and 0.5 to 5 parts by mass of a benzimidazole anti-aging agent with respect to 100 parts by mass of the rubber component, and the benz with respect to the tetrabenzyl thiuram disulfide The mass ratio of the imidazole anti-aging agent is 1 to 3.

  The pneumatic tire according to the present invention is obtained by producing a sidewall portion with the rubber composition.

  The method for producing a rubber composition for a tire sidewall according to the present invention includes a first step of mixing the rubber component, the benzimidazole anti-aging agent and a filler, a mixture obtained by the first step, and the tetra A second step of mixing the benzyl thiuram disulfide and the sulfur component, and in the first step, after the temperature of the mixture during mixing reaches a certain temperature x in the range of 140-170 ° C., The temperature is maintained for 1 minute or longer within the range of x ± 5 ° C.

  According to the present invention, by adding tetrabenzyl thiuram disulfide and a benzimidazole anti-aging agent to a rubber composition used for a tire sidewall at a predetermined ratio, the tear resistance can be improved without deteriorating workability. Can do.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  The rubber composition for a tire sidewall according to the present embodiment is formed by blending a tetrabenzylthiuram disulfide and a benzimidazole anti-aging agent with a rubber component made of a diene rubber.

  Specifically, the rubber component includes (A) natural rubber and / or isoprene rubber of 40 to 70% by mass, and (B) butadiene rubber having a cis-1,4 bond content of 96% or more of 60 to 30% by mass. % Content. That is, 40-70 mass parts (A) component and 60-30 mass parts (B) component are contained in 100 mass parts of rubber components.

  The natural rubber (NR) and isoprene rubber (IR) as the component (A) are not particularly limited, and those generally used in the rubber industry can be used. The component (A) may be natural rubber alone, isoprene rubber alone, or a blend of natural rubber and isoprene rubber.

  When the content of the component (A) in the rubber component is 40 parts by mass or more, the effect of improving the low heat generation performance and the effect of improving the tear resistance can be enhanced. More preferably, it is 50 parts by mass or more. The content of the component (A) is 70 parts by mass or less, more preferably 60 parts by mass or less, because the content of the component (B) is ensured and the bending fatigue resistance is maintained.

  The butadiene rubber as the component (B) has a cis-1,4 bond content of 96% or more. By using such a butadiene rubber (BR) having a high cis content, the effect of improving the low heat generation performance is achieved. Can be increased.

Examples of the butadiene rubber having a high cis content include those synthesized using a cobalt-based catalyst and those synthesized using a rare-earth catalyst. As the rare earth element-based catalyst, a neodymium-based catalyst is preferable, and examples thereof include neodymium alone, a compound of neodymium and other metals, and an organic compound, and more specifically, NdCl ₃ , Et-NdCl _{2 and the} like are specific examples. Take as an example. Butadiene rubber synthesized with a neodymium catalyst has a microstructure with a high cis content and a low vinyl content, and further improves low heat generation performance compared to butadiene rubber synthesized with other catalysts including cobalt catalysts. can do. The microstructure of the butadiene rubber synthesized using a neodymium catalyst has a cis-1,4 bond content of 96% or more and a vinyl group (1,2-vinyl bond) content of 1.0% or less. Is preferred. Here, the cis-1,4 bond content and the vinyl group content are values calculated by the integration ratio of the ¹ HNMR spectrum.

  When the content of the component (B) in the rubber component is 30 parts by mass or more, deterioration of workability and bending fatigue resistance can be suppressed. More preferably, it is 40 parts by mass or more. The content of the component (B) is 60 parts by mass or less, more preferably, in order to secure the content of the component (A) and exhibit the effect of improving the low heat generation performance and the effect of improving the tear resistance. It is 50 parts by mass or less.

  The rubber component in the present embodiment is basically composed of a blend of the above component (A) and component (B), but other rubbers may be blended within the range in which the effect is not impaired. Other rubbers are not particularly limited. For example, diene rubbers such as styrene butadiene rubber (SBR), butadiene rubber (BR) other than component (B), acrylonitrile-butadiene rubber (NBR), and chloroprene rubber (CR). Is mentioned.

  In the rubber composition according to this embodiment, tetrabenzylthiuram disulfide (TBzTD) is blended as a vulcanization accelerator. The compounding quantity of tetrabenzyl thiuram disulfide is 0.1-3 mass parts with respect to 100 mass parts of rubber components. If the blending amount is less than 0.1 parts by mass, the effect of improving the tear resistance cannot be expected, and if it exceeds 3 parts by mass, the tear resistance may be deteriorated. The compounding amount of tetrabenzyl thiuram disulfide is more preferably 0.3 to 2 parts by mass, still more preferably 0.5 to 1.5 parts by mass with respect to 100 parts by mass of the rubber component.

  In the rubber composition according to this embodiment, tetrabenzylthiuram disulfide alone may be used as the vulcanization accelerator, but other vulcanization accelerators may be used in combination. When another vulcanization accelerator is used in combination, the blending amount is preferably 0.1 to 3 parts by mass, more preferably 0.3 to 2 parts by mass with respect to 100 parts by mass of the rubber component. More preferably, it is 0.5 to 1.5 parts by mass.

  Although it does not specifically limit as another vulcanization accelerator used together with tetrabenzyl thiuram disulfide, A sulfenamide type vulcanization accelerator is preferable. Examples of the sulfenamide vulcanization accelerator include N-cyclohexyl-2-benzothiazolylsulfenamide (CZ, JIS abbreviation: CBS), N-tert-butyl-2-benzothiazolylsulfenamide (NS , JIS abbreviation: BBS), N, N-dicyclohexyl-2-benzothiazolylsulfenamide (DZ, JIS abbreviation: DCBS), N-oxydiethylene-2-benzothiazolylsulfenamide (OBS), N, N -Diisopropyl-2-benzothiazolylsulfenamide (DPBS), N, N-di (2-ethylhexyl) -2-benzothiazolylsulfenamide, N, N-di (2-methylhexyl) -2-benzo Examples include thiazolylsulfenamide. Any one of these sulfenamide-based vulcanization accelerators may be used alone, or two or more thereof may be used in combination.

  The rubber composition according to this embodiment is blended with a benzimidazole anti-aging agent. By blending the benzimidazole anti-aging agent with the tetrabenzylthiuram disulfide in a predetermined amount at a predetermined ratio, the tear resistance can be improved without deteriorating workability. Such an effect has not been known in the past, and is an unexpected effect found for the first time by the present inventors.

  Examples of the benzimidazole anti-aging agent include 2-mercaptobenzimidazole (MBI), 2-mercaptomethylbenzimidazole, zinc salt of 2-mercaptobenzimidazole (ZnMBI) and the like. They may be used alone or in combination of two or more.

  The compounding quantity of the benzimidazole type anti-aging agent is 0.5-5 mass parts with respect to 100 mass parts of rubber components. If the blending amount is less than 0.5 parts by mass, the effect of improving the tear resistance cannot be expected, and if it exceeds 5 parts by mass, the workability and low heat generation performance may be deteriorated. The blending amount of the benzimidazole anti-aging agent is more preferably 1 to 4 parts by mass, still more preferably 1.5 to 3 parts by mass with respect to 100 parts by mass of the rubber component.

  In this embodiment, in order to improve the tear resistance without degrading the workability, the mass ratio of the benzimidazole anti-aging agent to the tetrabenzyl thiuram disulfide (that is, the benzimidazole anti-aging agent / tetrabenzyl thiuram disulfide). Is set to 1-3. The mass ratio is preferably 1.3 to 2.8, more preferably 1.5 to 2.5.

  In the rubber composition according to the present embodiment, the anti-aging agent may be a benzimidazole-based anti-aging agent alone, but other anti-aging agents may be used in combination. When using other anti-aging agent together, it is preferable that the compounding quantity is 0.5-5 mass parts with respect to 100 mass parts of rubber components, More preferably, it is 1-3 mass parts.

  The other anti-aging agent used in combination with the benzimidazole anti-aging agent is not particularly limited, and for example, an amine anti-aging agent or a phenol anti-aging agent can be used, but an amine anti-aging agent is preferable. Amine-based antioxidants include aromatic secondary amine-based antioxidants such as N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (6PPD), N-isopropyl-N. '-Phenyl-p-phenylenediamine (IPPD), N, N'-diphenyl-p-phenylenediamine (DPPD), N, N'-di-2-naphthyl-p-phenylenediamine (DNPD), N- (3 -Methacryloyloxy-2-hydroxypropyl) -N'-phenyl-p-phenylenediamine, p-phenylenediamine-based anti-aging agents such as N-cyclohexyl-N'-phenyl-p-phenylenediamine; p- (p-toluene) Sulfonylamido) diphenylamine, 4,4′-bis (α, α-dimethylbenzyl) diphenylamine (CD), o Diphenylamine-based anti-aging agents such as acetylated diphenylamine (ODPA) and styrenated diphenylamine; and naphthylamine-based anti-aging agents such as N-phenyl-1-naphthylamine (PAN) and N-phenyl-2-naphthylamine (PBN). . These can be used alone or in combination of two or more.

  Carbon rubber can be blended as a filler in the rubber composition according to this embodiment. The compounding amount of the carbon black is preferably 20 to 100 parts by mass with respect to 100 parts by mass of the rubber component, more preferably 20 to 80 parts by mass, and further preferably 30 to 50 parts by mass.

The carbon black is not particularly limited, a nitrogen absorption specific surface area _{(N 2 SA) (JIS K6217-2} ) is are preferably used those which are 35~150m ² / g, specifically, SAF grade (N100 series), ISAF class (N200 series), HAF class (N300 series), FEF class (N500 series) (both ASTM grade) are preferably used. More preferably _N 2 SA is 35~120m ² / g, more preferably 35~100m ² / g, and especially preferably from 40 to 80 m ² / g. In general, when such a carbon black having a large particle size is used, the tear resistance tends to be reduced, but in this embodiment, the combination of the tetrabenzylthiuram disulfide and the benzimidazole anti-aging agent provides a resistance to tearing. Since the tearing performance can be improved, carbon black having a large particle size can be used correspondingly to contribute to the improvement of the low heat generation performance.

In the rubber composition according to this embodiment, silica may be used in combination with carbon black as a filler. The silica is not particularly limited, but wet silica such as wet precipitation silica or wet gel silica is preferably used. BET specific surface area of the silica (measured according to BET method according to JIS K6430) is not particularly limited, is preferably 90~250m ² / g, more preferably 150~220m ² / g. The compounding quantity of a silica is not specifically limited, It is preferable that it is 50 mass parts or less with respect to 100 mass parts of rubber components, for example, 5-30 mass parts may be sufficient, and 5-20 mass parts may be sufficient.

  When silica is blended, a silane coupling agent may be used in combination in order to improve the dispersibility. It is preferable that the compounding quantity of a silane coupling agent is 5-20 mass parts with respect to 100 mass parts of silica. Although it does not specifically limit as a silane coupling agent, Sulfide silane coupling agents, such as bis (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) disulfide, are preferable.

  In addition to the above components, the rubber composition according to the present embodiment contains various additives commonly used in rubber compositions for tire sidewalls, such as zinc white, stearic acid, softener, wax, and vulcanizing agent. can do.

  Examples of the vulcanizing agent include sulfur components such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Although not particularly limited, the blending amount thereof is 100 parts by mass of the rubber component. It is preferable that it is 0.1-10 mass parts with respect to it, More preferably, it is 0.5-5 mass parts, More preferably, it is 1-3 mass parts.

  The rubber composition can be prepared by kneading according to a conventional method using a commonly used Banbury mixer, kneader, roll, or other mixer.

  A method for producing a rubber composition according to an embodiment includes a first step of mixing a rubber component, a benzimidazole anti-aging agent, and a filler, a mixture obtained by the first step, tetrabenzylthiuram disulfide, and a sulfur component. A second step of mixing.

  The first step is a kneading step generally referred to as a non-pro mixing step, in which components other than the vulcanizing agent and the vulcanization accelerator are added and mixed. That is, in the first step, an anti-aging agent containing a benzimidazole anti-aging agent is added to the rubber component together with a filler such as carbon black and / or silica, and zinc oxide, stearic acid, a softening agent, a wax are further added. Various additives such as are blended. The mixing in the first step is, for example, a known rotor including at least a stirring rotor such as a Banbury mixer, a jacket as a heating / cooling means through which a heating / cooling medium flows, and a pressure ram for adjusting the pressure inside the mixer. This can be done using a mixing device. The mixing device further includes a temperature sensor that detects the temperature of the mixture in the device, and a control unit that controls the rotational speed of the rotor.

  The second step is a final mixing step generally referred to as a pro-mixing step, and a vulcanization accelerator containing tetrabenzylthiuram disulfide and a sulfur component as a vulcanizing agent are added to the mixture obtained in the first step. And kneaded. The mixing in the second step can be performed according to a conventional method using a mixing apparatus such as an open roll or a Banbury mixer.

  In one embodiment, the first step is preferably performed by PID (Proportional Integral Differential) control. Since rubber kneading usually involves heat generation, the temperature of the mixture during mixing will continue to rise if no control is performed, but the PID control will cause the rotation speed of the mixing device rotor, the temperature of the heating and cooling medium, and the ram pressure. By controlling one or more of them, it becomes possible to continue mixing while maintaining within a certain temperature, so that the effect of improving physical properties such as tear resistance and low heat generation performance can be enhanced.

  Specifically, in the first step, after the temperature of the mixture during mixing reaches a certain temperature x within the range of 140 to 170 ° C., the temperature of the mixture is controlled within the range of x ± 5 ° C. by PID control (for example, X = 160 ° C., within the range of 155 to 165 ° C.) and mixing for 1 minute or longer. The holding temperature is preferably x = 155 to 165 ° C. The holding time is preferably 1 to 3 minutes, more preferably 1 to 2 minutes.

  The rubber composition according to the present embodiment is used as a rubber composition for a sidewall portion of a pneumatic tire, and forms a sidewall portion by vulcanization molding at, for example, 140 to 180 ° C. according to a conventional method. be able to. The pneumatic tire is not particularly limited, and examples thereof include various types of tires such as a radial tire for passenger cars and a heavy load tire used for large vehicles such as trucks and buses.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  Using a Banbury mixer, according to the blending (parts by mass) shown in Tables 1 and 2 below and the following common blending, first, in the first step (non-pro mixing step), the components excluding sulfur and the vulcanization accelerator are added and mixed ( (Discharge temperature = 160 ° C.) Then, sulfur and a vulcanization accelerator were added to and mixed with the obtained mixture in the second step (final mixing step) (discharge temperature = 100 ° C.) to obtain a rubber composition for sidewalls. Prepared.

  As shown in the table, in Example 13, PID control was performed in the first step, and in other Examples and Comparative Examples, PID control was not performed. Specifically, in the PID control of Example 13, after adding and mixing the components of the first step, the temperature of the mixture reached 160 ° C. for 1 minute at 160 ° C. (specifically, 160 ° C. ± 5 ° C. ), And then discharged. In other examples, it was discharged as it was when it reached 160 ° C.

Details of each component in Tables 1 and 2 are as follows.
・ NR: Natural rubber, RSS # 3
BR1: Low cis butadiene rubber having a cis-1,4 bond content of 33%, “D.NF35” manufactured by Asahi Kasei
BR2: butadiene rubber polymerized with a cobalt-based catalyst, cis-1,4 bond content = 96%, vinyl group content = 2%, “BR150B” manufactured by Ube Industries, Ltd.
BR3: butadiene rubber polymerized with a neodymium catalyst, cis-1,4 bond content = 97%, vinyl group content = 0.4%, “Buna CB22” manufactured by LANXESS
CB1: FEF grade carbon black, N ₂ SA = 42 m ² / g, “Seast SO” manufactured by Tokai Carbon Co., Ltd.
CB2: HAF grade carbon black, N ₂ SA = 74 m ² / g, “Seast KH” manufactured by Tokai Carbon Co., Ltd.
CB3: ISAF grade carbon black, N ₂ SA = 126 m ² / g, “Seast 7HM” manufactured by Tokai Carbon Co., Ltd.
Silica: “Nip Seal AQ” manufactured by Tosoh Silica Co., Ltd. (BET specific surface area = 205 m ² / g)
Silane coupling agent: bis (3-triethoxysilylpropyl) tetrasulfide, “Si69” manufactured by Evonik Degussa
Anti-aging agent 1: N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine, “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Anti-aging agent 2: 2-mercaptobenzimidazole, “NOCRACK MB” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Antiaging agent 3: zinc salt of 2-mercaptobenzimidazole, “NOCRACK MBZ” manufactured by Ouchi Shinsei Chemical Co., Ltd.
TBzTD: Tetrabenzylthiuram disulfide, “Sancerer TBzTD” manufactured by Sanshin Chemical Industry Co., Ltd.
Vulcanization accelerator CZ: N-cyclohexyl-2-benzothiazolylsulfenamide, “Soccinol CZ” manufactured by Sumitomo Chemical Co., Ltd.
・ Vulcanization accelerator NS: N-tert-butyl-2-benzothiazolylsulfenamide, “Noxeller NS-P” manufactured by Ouchi Shinsei Chemical Industry
・ Sulfur: “Sulfur Powder” manufactured by Tsurumi Chemical Co., Ltd.

  The common formulation is 2 parts by mass of zinc white ("Zinc Hana 1" manufactured by Mitsui Kinzoku Co., Ltd.), 2 parts by mass of stearic acid ("Lunac S-20" manufactured by Kao Corporation), relative to 100 parts by mass of the rubber component. 1 part by weight of wax (“OZOACE0355” manufactured by Nippon Seiwa Co., Ltd.) and 3 parts by weight of oil (“Process P200” manufactured by JOMO) were added in the first step.

  For each rubber composition, the processability (unvulcanized rubber viscosity) and vulcanization speed t90 are measured, and using a test piece of a predetermined shape vulcanized at 150 ° C. for 30 minutes, the tear resistance performance and the low heat generation performance are obtained. Measured and evaluated. Each measurement / evaluation method is as follows.

Workability: ML (1 + 4) value was measured according to JIS K6300 (preheating time 1 minute, rotor operating time 4 minutes, measurement temperature 100 ° C.), and the value of Comparative Example 1 was displayed as an index. The smaller the index, the lower the Mooney viscosity and the better the workability.

T90: A Mooney scorch test in accordance with JIS K6300 was performed using a rheometer (L-shaped rotor), and a t90 value (minute) at the time of measurement at a temperature of 150 ° C. for 1 minute was obtained. The smaller this value is, the faster the vulcanization rate is, and it is preferably close to Comparative Example 1 which is a control.

-Tear resistance: Tear strength was measured according to JIS K6252 (Crescent test piece), and the value was shown as an index with the value of Comparative Example 1 being 100. The larger the index, the higher the tear strength and the better the tear resistance.

Low heat generation performance: Using a spectrometer manufactured by UBM, for a test piece having a width of 5 mm, a length of 30 mm, and a thickness of 1 mm, an initial strain of 15%, a dynamic strain of ± 2.5%, a frequency of 10 Hz, Tan δ was measured under the condition of a temperature of 60 ° C., and the value was shown as an index with the value of Comparative Example 1 being 100. The smaller the index, the less heat is generated and the lower the heat generation performance (low fuel consumption performance).

  The results are as shown in Tables 1 and 2. Compared to Comparative Example 1 which is a control, Comparative Example 2 in which only TBzTD was blended improved the low heat generation performance, but the tear resistance was greatly deteriorated. In Comparative Example 3 in which only benzimidazole anti-aging agent was blended, The low heat generation performance deteriorated. In Comparative Example 4, TBzTD and a benzimidazole anti-aging agent were used in combination, but since a low cis butadiene rubber was used, the tear resistance performance was not improved and the low heat generation performance was inferior. In Comparative Example 5, the amount of the benzimidazole anti-aging agent was too large, and the processability and low heat generation performance were impaired. In Comparative Example 6, the amount of the benzimidazole anti-aging agent was small, and the effect of improving the tear resistance was insufficient. In Comparative Example 7, the amount of TBzTD was large, and the tear resistance was deteriorated. In Comparative Example 8, the mass ratio of benzimidazole anti-aging agent / TBzTD is small, so that the improvement effect of tear resistance is not obtained. In Comparative Example 9, the mass ratio is large, and the effect of improving tear resistance is not good. Insufficient and low heat generation performance was also deteriorated. In Comparative Example 10, since the rubber component was natural rubber alone, processability deteriorated. In Comparative Example 11, the content of butadiene rubber was large, and the tear resistance was deteriorated.

  On the other hand, when it is Examples 1-14 which used TBzTD and the benzimidazole series anti-aging agent together in a predetermined ratio to specific diene system rubber, tear resistance performance is improved without impairing workability practically, As for the low heat generation performance, an excellent effect equal to or greater than that of Comparative Example 1 was obtained, and a remarkable effect that was not exhibited when each was blended alone was obtained. Further, in Example 13 in which PID control was performed, a further improvement effect was obtained in tear resistance performance and low heat generation performance, and workability was improved as compared with Example 4 in which the blending coincided. In Example 14 using butadiene rubber synthesized with a neodymium catalyst, the effect of improving the low heat generation performance was high.

Claims (5)

For 100 parts by mass of a rubber component including 40 to 70 parts by mass of natural rubber and / or isoprene rubber and 60 to 30 parts by mass of butadiene rubber having a cis-1,4 bond content of 96% or more,
0.1 to 3 parts by mass of tetrabenzyl thiuram disulfide and 0.5 to 5 parts by mass of benzimidazole anti-aging agent, and the mass ratio of the benzimidazole anti-aging agent to tetrabenzyl thiuram disulfide is 1 to 3,
A rubber composition for a tire sidewall.   The rubber composition for a tire sidewall according to claim 1, wherein the butadiene rubber is synthesized using a neodymium catalyst.   The rubber composition for a tire sidewall according to claim 1 or 2, comprising 20 to 100 parts by mass of carbon black with respect to 100 parts by mass of the rubber component.   A pneumatic tire comprising a sidewall portion made of the rubber composition according to claim 1. It is a manufacturing method of the rubber composition according to any one of claims 1 to 3,
A first step of mixing the rubber component, the benzimidazole anti-aging agent and a filler, and a second step of mixing the mixture obtained in the first step, the tetrabenzylthiuram disulfide and a sulfur component. And
In the first step, after the temperature of the mixture during mixing reaches a certain temperature x within the range of 140 to 170 ° C., the temperature of the mixture is maintained within the range of x ± 5 ° C. for 1 minute or longer. A method for producing a rubber composition for a tire sidewall.