Rubber composition

Abstract

To provide a rubber composition containing a phenylene diamine-based antioxidant which is excellent in quinonization prevention property and anti-aging property.SOLUTION: A rubber composition contains 100 pts.mass of diene-based rubber, 0.1 to 10 pts.mass of a phenylene diamine-based antioxidant, and a compound represented by the following formula (1), wherein a molar ratio of the compound to the phenylene diamine-based antioxidant is 0.1 to 3. In the formula (1), R1 to R3 each independently represent a hydrogen atom or a substituent. At least one of R1 and R3 is an electron-releasing group, or R2 is an electron-attractive group or an aromatic group.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition. [Background technology]

[0002] 2. Description of the Related Art Conventionally, rubber compositions containing a phenylenediamine-based antioxidant (for example, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD)) as an antioxidant have been known (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-046554 [Non-patent literature]

[0004] [Non-Patent Document 1] Science,2021,371,6525,185-189 Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, there are concerns about environmental pollution due to 6PPD quinone (see below) generated by quinonization of 6PPD (Non-Patent Document 1).

[0006] [ka]

[0007] Furthermore, in recent years, with the increasing demand for higher safety levels, there has been a demand for further improvement in the anti-aging properties of rubber products such as tires.

[0008] In view of the above circumstances, the present invention aims to provide a rubber composition containing a phenylenediamine-based antioxidant, in which the phenylenediamine-based antioxidant is unlikely to form quinones (excellent quinone formation prevention properties) and the rubber composition has excellent antiaging properties. [Means for solving the problem]

[0009] As a result of extensive investigations into the above problems, the present inventors have found that the above problems can be solved by blending a specific compound in a predetermined amount, thereby completing the present invention. That is, the present inventors have found that the above problems can be solved by the following configuration.

[0010] (1) 100 parts by mass of a diene rubber; 0.1 to 10 parts by mass of a phenylenediamine-based antioxidant; and a compound represented by formula (1) described below, A rubber composition, wherein a molar ratio of the compound to the phenylenediamine-based antioxidant is 0.1-3. (2) The rubber composition according to the above (1), wherein at least one of R1 and R3 in the above formula (1) is an electron-donating group. (3) The rubber composition according to the above (1) or (2), wherein in the above formula (1), R2 is an electron-withdrawing group or an aromatic ring. Effect of the Invention

[0011] As described below, according to the present invention, there can be provided a rubber composition containing a phenylenediamine-based antioxidant, in which the phenylenediamine-based antioxidant is unlikely to form quinones (excellent quinone formation prevention property) and the rubber composition has excellent antiaging property. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The rubber composition of the present invention will be described below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In addition, each component may be used alone or in combination of two or more. When two or more components are used in combination, the content of the components refers to the total content unless otherwise specified. In addition, excellent anti-quinonization properties and anti-aging properties and large breaking elongation are also referred to as "having excellent effects of the present invention."

[0013] The rubber composition of the present invention (hereinafter also referred to as "the composition of the present invention") is 100 parts by mass of a diene rubber; 0.1 to 10 parts by mass of a phenylenediamine-based antioxidant; Contains a compound represented by formula (1) described below (hereinafter also referred to as a "specific compound"); The molar ratio of the compound to the phenylenediamine-based antioxidant is 0.1-3 in the rubber composition.

[0014] It is believed that the composition of the present invention has such a structure and therefore solves the above-mentioned problems. The reason for this is not clear, but is thought to be roughly as follows.

[0015] Diene rubbers are known to be degraded by radicals. Here, when radicals are generated in the composition of the present invention, the phenylenediamine-based antiaging agent contained in the composition reacts with the radicals, deactivates the radicals, and is considered to suppress the deterioration of the diene rubber. On the other hand, when the phenylenediamine-based antiaging agent reacts with the radicals, it becomes a diimine by oxidation and cannot react with the radicals any more. In this case, when the amount of radicals generated is large, the suppression of the deterioration of the diene rubber may be insufficient. In contrast, the composition of the present invention contains a predetermined amount of the specific compound relative to the phenylenediamine-based antiaging agent, and it is believed that the mercapto group of the specific compound reacts with the phenylenediamine-based antiaging agent that has become a diimine, thereby regenerating hydrogen atoms for the nitrogen atoms of the diimine, thereby restoring the antiaging properties. Furthermore, it is considered that the specific compound reacts with the phenylenediamine-based antiaging agent to form a ring structure by applying energy such as heating. Specifically, the reaction proceeds as shown in the following reaction formula. In the following reaction formula, only an aromatic ring having two secondary amines as substituents is shown for the phenylenediamine-based antiaging agent. In addition, for the specific compound, R1 to R3 in formula (1) are omitted. In addition, in the following reaction formula, a five-membered ring is finally formed, but in some cases a six-membered ring may be formed.

[0016] [ka]

[0017] In this way, the specific compound reacts with the phenylenediamine-based antiaging agent to form a ring structure, and the quinone formation sites of the phenylenediamine-based antiaging agent disappear, so it is presumed that the composition of the present invention also has excellent quinone formation prevention properties.

[0018] Each component contained in the composition of the present invention will be described below.

[0019] [Diene rubber] The diene rubber contained in the composition of the present invention is not particularly limited. The compositions of the present invention may contain one or more diene rubbers.

[0020] [Specific examples] Specific examples of the diene rubber include natural rubber (NR), butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber, isoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), etc. Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene rubber (SBR), styrene-isoprene copolymer rubber, butyl rubber, etc.

[0021] [Molecular weight] The weight average molecular weight (Mw) of the diene rubber is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 100,000 to 5,000,000, more preferably 200,000 to 3,000,000, and even more preferably 300,000 to 2,000,000.

[0022] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are values ​​calculated as standard polystyrene by gel permeation chromatography (GPC).

[0023] [Phenylenediamine-based antioxidant] The phenylenediamine-based antioxidant contained in the composition of the present invention refers to an antioxidant having an aromatic ring with two secondary amines as substituents in its molecular structure.

[0024] [Specific examples] Specific examples of phenylenediamine-based antioxidants include N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD), N-phenyl-N'-(1-methylheptyl)-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, etc. Among these, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD) is preferred because it provides superior effects of the present invention.

[0025] [Content] In the composition of the present invention, the content of the phenylenediamine-based antioxidant is 0.1 to 10 parts by mass based on 100 parts by mass of the diene rubber described above. Among them, the content is preferably 1 to 4 parts by mass because the effects of the present invention are more excellent.

[0026] [Specific compound] The composition of the present invention contains a compound (specific compound) represented by the following formula (1). The specific compound is an allyl mercapto compound.

[0027] [ka] (1)

[0028] In formula (1), R1 to R3 each independently represent a hydrogen atom or a substituent, provided that at least one of R1 and R3 is an electron-donating group, or R2 is an electron-withdrawing group or an aromatic ring.

[0029] As described above, in formula (1), R1 to R3 each independently represent a hydrogen atom or a substituent (for example, a specific example described later). Among them, a hydrogen atom is preferred because the effects of the present invention are more excellent. The above-mentioned substituent may further have a substituent (for example, a specific example described later).

[0030] As described above, at least one of R1 and R3 is an electron donating group, or R2 is an electron withdrawing group or an aromatic ring. That is, the specific compound satisfies at least one of the conditions that at least one of R1 and R3 is an electron donating group (condition 1), or that R2 is an electron withdrawing group or an aromatic ring (condition 2). For reasons such as better effects of the present invention, the specific compound preferably satisfies condition 2, and more preferably satisfies both conditions 1 and 2.

[0031] [Electron-donating and electron-withdrawing groups] In this specification, the electron donating group is a group having a Hammett's substituent constant σ p The value of the Hammett substituent constant σ is 0 or less. p Refers to a group with a value greater than zero. Here, Hammett's substituent constant σ p The Hammett rule is an empirical rule proposed by LP Hammett in 1935 to quantitatively discuss the effect of substituents on the reaction or equilibrium of benzene derivatives, and is widely accepted as valid today. The substituent constants obtained by the Hammett rule include σp Value and σ m These values ​​can be found in many general textbooks, for example, "Lange's and book of Chemistry" edited by JADean, 12th edition, 1979 (McGraw-Hill) and "Chemical Domain" special edition, No. 122, pp. 96-103, 1979 (Nankodo). When the structure (group) is a polyvalent group, it is judged whether it is an electron donating group or an electron withdrawing group as a monovalent group (one in which a hydrogen atom is bonded to the other bonding position).

[0032] Specific examples of the electron donating group include an alkyl group, a halogenated alkyl group, and an alkoxy group. Among them, an alkoxy group is preferable because the effects of the present invention are more excellent. The number of carbon atoms in the electron donating group is not particularly limited, but is preferably 1 to 10 because the effects of the present invention are more excellent.

[0033] Specific examples of the electron-withdrawing group include an acid group (particularly a carboxy group), a carboxylate group (RO-CO-: R is a hydrocarbon group), a cyano group, an amide group (-CO-NR2: R is a hydrogen atom or a hydrocarbon group), a hydroxyl group, an alkoxysilyl group, an amino group, and a carbonyl group (-CO-). Among these, a carboxylate group is preferred because it provides better effects of the present invention. The number of carbon atoms in the electron-withdrawing group is not particularly limited, but is preferably 1 to 10 because it provides better effects of the present invention.

[0034] [Aromatic ring] Examples of the aromatic ring include an aromatic hydrocarbon ring and an aromatic heterocycle. Examples of the aromatic hydrocarbon ring include aromatic hydrocarbon rings having 6 to 18 carbon atoms, such as a benzene ring, a toluene ring, a xylene ring, and a naphthalene ring. Examples of the aromatic heterocycle include those containing a heteroatom such as a nitrogen atom, a sulfur atom, and an oxygen atom, and specific examples thereof include a pyridine ring and a thiophene ring. The aromatic ring is preferably an aromatic hydrocarbon ring, more preferably a benzene ring, because the effects of the present invention are more excellent. The aromatic ring may further have a substituent (for example, specific examples of which will be described later).

[0035] [Specific examples of substituents] Specific examples of the substituent in this specification include a halogeno group (halogen atom), an alkyl group (e.g., a tert-butyl group) (including a cycloalkyl group, a bicycloalkyl group, and a tricycloalkyl group), an alkenyl group (including a cycloalkenyl group and a bicycloalkenyl group), an alkynyl group, an aryl group, a heterocyclic group (which may also be called a heterocyclic group), a cyano group, a hydroxy group, a nitro group, a carboxy group, an alkoxy group, an aryloxy group, a silyloxy group, a heterocyclic oxy group, an acyloxy group, a carbamoyl group, a carbamoyloxy group, an alkoxycarbonyloxy group, an aryloxycarbonyloxy group, an amino group (including an anilino group), an ammonio group, a dialkylamino group, an acylamino group, an aminocarbonylamino group, an a Examples of the substituent include an alkoxycarbonylamino group, an aryloxycarbonylamino group, a sulfamoylamino group, an alkyl or arylsulfonylamino group, a mercapto group, an alkylthio group, an arylthio group, a heterocyclic thio group, a sulfamoyl group, a sulfo group, an alkyl or arylsulfinyl group, an alkyl or arylsulfonyl group, an acyl group, an aryloxycarbonyl group, an alkoxycarbonyl group, an aryl or heterocyclic azo group, an imido group, a phosphino group, a phosphinyl group, a phosphinyloxy group, a phosphinylamino group, a phosphono group, a silyl group, a hydrazino group, a ureido group, a boronic acid group (-B(OH)2), a phosphato group (-OPO(OH)2), a sulfato group (-OSO3H), and other known substituents.

[0036] [Molecular weight] The molecular weight of the specific compound is not particularly limited, but is preferably 50 to 1000, more preferably 80 to 500, and even more preferably 100 to 200, for reasons such as better effects of the present invention.

[0037] 〔boiling point〕 The boiling point of the specific compound is preferably 100° C. or higher, more preferably 150° C. or higher, for reasons of superior effects of the present invention and from the viewpoint of odor. The upper limit of the boiling point is not particularly limited, but is usually 300° C. or lower. In this specification, the boiling point is the value at 1 atmospheric pressure.

[0038] [Content]

[0039] <6C molar ratio> In the composition of the present invention, the molar ratio of the specific compound to the above-mentioned phenylenediamine-based antioxidant (hereinafter, also referred to as "6C molar ratio") is 0.1-3. The 6C molar ratio is preferably from 0.3 to 2, and more preferably from 0.7 to 1.5, because the effects of the present invention are more excellent.

[0040] <Parts by mass relative to 100 parts by mass of diene rubber> In the composition of the present invention, the content of the specific compound is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and even more preferably 0.5 to 3 parts by mass, relative to 100 parts by mass of the diene rubber, for reasons such as better effects of the present invention.

[0041] [Optional ingredients] The composition of the present invention may further contain other components (optional components) as necessary, provided that the effects and objects of the composition are not impaired. Examples of the optional components include various additives that are generally used in rubber compositions, such as fillers (e.g., silica, carbon black), silane coupling agents, terpene resins (e.g., aromatic modified terpene resins), thermally expandable microcapsules, zinc oxide (zinc white), stearic acid, antiaging agents other than the above-mentioned phenylenediamine-based antiaging agents, waxes, processing aids, oils, liquid polymers, thermosetting resins, vulcanizing agents (e.g., sulfur), and vulcanization accelerators.

[0042] [Carbon Black] The composition of the present invention preferably contains carbon black because the effects of the present invention are more excellent. The carbon black is not particularly limited, and various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, and FEF can be used. The nitrogen adsorption specific surface area (N2SA) of the carbon black is not particularly limited, but is preferably 50 to 200 m for the reason that the effects of the present invention are more excellent. 2 / g, and 70 to 150m 2 It is more preferable that the molecular weight is / g. Here, the nitrogen adsorption specific surface area (N2SA) is the amount of nitrogen adsorbed on the surface of carbon black measured according to JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method."

[0043] <Content> In the composition of the present invention, the content of carbon black is not particularly limited, but in order to obtain better effects of the present invention, the content is preferably 1 to 100 parts by mass, and more preferably 2 to 50 parts by mass, per 100 parts by mass of the diene rubber described above.

[0044] 〔silica〕 The composition of the present invention preferably contains silica because the effects of the present invention are more excellent. The silica is not particularly limited, and any conventionally known silica can be used. Examples of the silica include wet silica, dry silica, fumed silica, diatomaceous earth, etc. The silica may be used alone or in combination of two or more kinds.

[0045] The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of ​​the silica (hereinafter, the "CTAB adsorption specific surface area" may be simply referred to as "CTAB") is not particularly limited. However, in order to improve the effects of the present invention, it is preferred to use a silica having a cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of ​​100 to 300 m. 2 / g, and 150 to 200m 2 It is more preferable that the molecular weight is / g. Here, the CTAB adsorption specific surface area is a value obtained by measuring the amount of CTAB adsorbed on the silica surface in accordance with JIS K6217-3:2001 "Part 3: Determination of specific surface area - CTAB adsorption method."

[0046] <Content> In the composition of the present invention, the content of silica is not particularly limited, but in order to obtain better effects of the present invention, the content is preferably 10 to 150 parts by mass, and more preferably 50 to 100 parts by mass, per 100 parts by mass of the diene rubber.

[0047] [Manufacturing method] The method for producing the composition of the present invention is not particularly limited, and specific examples thereof include a method of kneading the above-mentioned components using a known method and device (e.g., a Banbury mixer, a kneader, a roll, etc.). When the composition of the present invention contains a vulcanizing agent (e.g., sulfur) and a vulcanization accelerator, it is preferable to first mix the components other than the vulcanizing agent and vulcanization accelerator at a high temperature (preferably 100 to 155°C), cool the mixture, and then mix the vulcanizing agent and vulcanization accelerator, because the effects of the present invention are more excellent for the resulting composition. The composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[0048] [Application] The composition of the present invention is preferably used as a rubber material. For example, it is preferably used for tires (particularly pneumatic tires), conveyor belts, hoses, vibration-proof materials, rubber rolls, outer covers of railway vehicles, etc. Among them, it is preferably used for tires (particularly treads). EXAMPLES

[0049] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0050] [Quinonization prevention property] The quinone-preventing properties of phenylenediamine-based antioxidants were evaluated when they reacted with specific compounds.

[0051] [Experimental Example 1] First, a phenylenediamine-based antioxidant (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) (6PPD) was oxidized with an oxidizing agent. This simulated a reaction with radicals generated in a rubber composition. Next, compound 1 (a compound represented by formula (1), in which R1 is a methoxy group, and R2 and R3 are hydrogen atoms) (corresponding to a specific compound) was mixed and reacted. The mixture was then heated (150°C).

[0052] After the reaction, 6PPD was subjected to NMR (nuclear magnetic resonance) measurement to determine the proportion of either or both of the protons at position a (see below) and the protons at position b (see below) of 6PPD remaining (6C quinone sites). As a result, the proportion of 6C quinone sites was 42%. The lower this proportion, the more difficult it is to quinone.

[0053] [ka]

[0054] [Experimental Example 2] The experiment was carried out in the same manner as in Experimental Example 1, except that compound 2 (a compound represented by formula (1), in which R1 and R3 are hydrogen atoms and R2 is a methyl ester group (CH3-O-CO-)) (corresponding to a specific compound) was used instead of compound 1. As a result, the 6C quinone site was 17%.

[0055] Comparative Experimental Example 1 An experiment was carried out in the same manner as in Experimental Example 1, except that Comparative Compound 1 (a compound represented by formula (1), in which R1 to R3 are hydrogen atoms) (not a specific compound) was used instead of Compound 1. As a result, the 6C quinone site was 80%.

[0056] [Production of rubber composition] The components in Table 1 below were mixed in the composition (parts by mass) shown in the same table. Specifically, first, the components other than sulfur and the vulcanization accelerator in Table 1 were mixed in a 1.8 L internal mixer at 130°C for 5 minutes, and a master batch was discharged. Then, sulfur and the vulcanization accelerator were added to the master batch, and the mixture was mixed at 80°C using an open roll to produce each rubber composition. In Table 1, the values ​​in parentheses for SBR are the net parts by mass of rubber (parts by mass excluding oil).

[0057] [Retention rate] Each of the obtained rubber compositions (unvulcanized) was press-vulcanized in a mold (15 cm × 15 cm × 0.2 cm) at 150°C for 30 minutes to produce a vulcanized rubber sheet. Then, in accordance with JIS K6251:2010, JIS No. 3 dumbbell-shaped test pieces (thickness 2 mm) were punched out and evaluated for breaking elongation at a temperature of 20°C and a tensile speed of 500 mm / min. In addition, the vulcanized rubber sheet prepared as described above was subjected to an aging test (left in an environment of 80°C for 168 hours (2 weeks)), and then the breaking elongation was evaluated in the same manner. Then, the breaking elongation retention rate (breaking elongation after aging test / breaking elongation before aging test×100) (%) was calculated. The results (retention rate) are shown in Table 1. From the viewpoint of anti-aging properties, the retention rate is preferably 85% or more.

[0058] [Table 1]

[0059] Details of each component in Table 1 are as follows.

[0060] ·SBR: TUFDENE E581 (SBR, oil extended product (oil extended amount: 37.5% by mass), manufactured by Asahi Kasei Chemicals) BR: Nipol BR1220 (BR, manufactured by Zeon Corporation) Silica: Zeosil 1165MP (Silica, CTAB adsorption specific surface area: 152m 2 / g, manufactured by Rhodia) Carbon black: Show Black N234 (manufactured by Showa Cabot Corporation) Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide, manufactured by Evonik Degussa) Zinc oxide: 3 types of zinc oxide (manufactured by Seido Chemical Industry Co., Ltd.) Stearic acid: Beads Stearic Acid YR (manufactured by NOF Corporation) Phenylenediamine-based antioxidant: N-phenyl-N′-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD) Anti-aging agent RD: Nonflex RD (Seiko Chemical Co., Ltd.) Process oil: Process oil Comparative Compound 1 and Compounds 1-2: Comparative Compound 1 and Compounds 1-2 described above, respectively. Sulfur: Oil-treated sulfur (Karuizawa Refinery Co., Ltd.) Vulcanization accelerator CBBS: Noccela CZ (Ouchi Shinko Chemical Industry Co., Ltd.) Vulcanization accelerator DPG: Noccela DPG (1,3-diphenylguanidine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0061] In Table 1, the column "boiling point" indicates the boiling points of the compounds used in each example (comparative compound 1, compounds 1 and 2).

[0062] In addition, in Table 1, the column "Model 3-step rate-determining activation energy" shows the maximum activation energy [kcal] obtained by quantum chemical calculation (conditions: B3LYP / 6-31G) when the phenylenediamine antioxidant (6PPD) and the compounds used in each example (comparative compound 1, compounds 1-2) react as described above ((thio)Claisen rearrangement, thiol-ene reaction) to form a 5-membered ring. The above activation energy is expressed as an index, with the above activation energy when the compound is comparative compound 1 being set to 100. It is considered that the smaller this value, the more easily the above reaction proceeds.

[0063] In addition, in Table 1, the column "6C quinone sites" indicates the value of 6C quinone sites of the corresponding experimental examples (Experimental Examples 1 to 2, Comparative Experimental Example 1). Note that the reference example does not contain compound 1, etc., so the 6C quinone sites are 100%.

[0064] As shown in the above-mentioned Experimental Examples 1 and 2 and Comparative Experimental Example 1, Experimental Examples 1 and 2 using Compounds 1 and 2 (Specific Compounds) had fewer 6C quinone conversion sites compared to Comparative Experimental Example 1 using Comparative Compound 1. From this, it can be said that, compared to Comparative Example 1 using a phenylenediamine-based antioxidant and Comparative Compound 1 in combination, Examples 1 and 2 using a phenylenediamine-based antioxidant and Compounds 1 and 2 (Specific Compounds) in combination make it difficult for the phenylenediamine-based antioxidant to undergo quinone conversion (excellent quinone conversion prevention properties).

[0065] Furthermore, as can be seen from Table 1, Examples 1 and 2, which used a phenylenediamine-based antioxidant in combination with Compounds 1 and 2 (specific compounds), showed excellent antiaging properties, compared with Reference Example, which used only a phenylenediamine-based antioxidant, and Comparative Example 1, which used a phenylenediamine-based antioxidant in combination with Comparative Compound 1. This is believed to be due to the fact that Comparative Compound 1 has a low boiling point and is therefore evaporated out of the rubber composition system during the mixing and vulcanization steps before reacting with the phenylenediamine-based antioxidant that has been oxidized to a diimine structure.

Claims

1. 100 parts by mass of a diene rubber; 0.1 to 10 parts by mass of a phenylenediamine-based antioxidant; and a compound represented by the following formula (1): A rubber composition, wherein a molar ratio of the compound to the phenylenediamine-based antioxidant is 0.1 to 3. 【Chemistry 1】 （１） In formula (1), R １ ~R ３ each independently represents a hydrogen atom or a substituent. １ and R ３ At least one of R is an electron donating group, or R ２ is an electron-withdrawing group or an aromatic ring.

2. In the formula (1), R １ and R ３ The rubber composition according to claim 1 , wherein at least one of the following groups is an electron donating group.

3. In the formula (1), R ２ The rubber composition according to claim 1 or 2, wherein is an electron-withdrawing group or an aromatic ring.

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