Rubber composition and tires

Abstract

The phenylenediamine-based antioxidant is used as a substitute for 6PPD, while improving scorch resistance and heat aging resistance. [Solution] The rubber composition according to the embodiment comprises a rubber component, a phenylenediamine-based antioxidant represented by the following formula (1), and a thiuram disulfide-based vulcanization accelerator. In formula (1), R 1 and R 2 Each of these independently represents a hydrocarbon group having 6 or more carbon atoms, however, R 1 and R 2 Except when it is a combination of a phenyl group and a 1,3-dimethylbutyl group. [Formula 1] JPEG2026103949000010.jpg42129

Description

Technical Field

[0001] The present invention relates to a rubber composition and a tire using the same.

Background Art

[0002] Tires are deteriorated by the influence of the external environment such as ozone, so an anti-aging agent is blended in the rubber composition for tires. Conventionally, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) has been generally used as the anti-aging agent to be blended in tires. However, since 6PPD may have an impact on the environment, it is desirable not to use 6PPD.

[0003] In Patent Documents 1 and 2, in order to provide a rubber composition excellent in ozone resistance and aging resistance without using 6PPD, it has been proposed to use bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD) in combination with a quinoline-based anti-aging agent.

[0004] Patent Document 3 discloses that when 77PD is used, scorch (early vulcanization) occurs, and in order to suppress the scorch, a specific vulcanization retarder is combined with 77PD.

Prior Art Documents

Patent Documents

[0005] [[ID=3i]]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] As mentioned above, certain amine-based antioxidants, including 77PD as a substitute for 6PPD, raise concerns about scorching and deterioration of processability. Furthermore, there is room for improvement in heat aging resistance.

[0007] Furthermore, Patent Document 4 discloses that in a silica-containing rubber composition, the Mooney scorch value can be increased by using thiuram disulfide instead of diphenylguanidine as a vulcanization accelerator. However, it does not disclose the combined use of thiuram disulfide with a phenylenediamine-based antioxidant as a substitute for 6PPD, nor does it disclose that this improves scorch and enhances heat aging resistance.

[0008] In view of the above, embodiments of the present invention aim to provide a rubber composition that can improve scorch resistance and heat aging resistance while using a phenylenediamine-based antioxidant as a substitute for 6PPD, and a tire using the same. [Means for solving the problem]

[0009] The present invention includes embodiments shown below. [1] A rubber component, a phenylenediamine-based antioxidant represented by the following general formula (1), and a thiuram disulfide-based vulcanization accelerator, [ka] In formula (1), R 1 and R 2 Each of these independently represents a hydrocarbon group having 6 or more carbon atoms, however, R 1 and R 2 A rubber composition, except in which the combination is a phenyl group and a 1,3-dimethylbutyl group. [2] The thiuram disulfide-based vulcanization accelerator is represented by the following general formula (2): [ka] In formula (2), R 3 , R4 , R 5 and R 6 are each independently a hydrocarbon group having 30 or less carbon atoms, which may optionally contain one or more heteroatoms, R 3 and R 4 , and / or, R 5 and R 6 may together with the nitrogen atom to which they are attached form a heterocyclic group, the rubber composition according to [1]. [3] In the formula (2), R 3 , R 4 , R 5 and R 6 except when all are methyl groups, the rubber composition according to [2]. [4] The rubber composition according to any one of [1] to [3], further comprising a quinoline-based antioxidant. [5] The rubber composition according to any one of [1] to [4], which is a rubber composition for tires. [6] A tire comprising a rubber part produced from the rubber composition according to any one of [1] to [5]. [Advantages of the Invention]

[0010] According to an embodiment of the present invention, scorch resistance and heat aging resistance can be improved while using a phenylene diamine-based antioxidant as an alternative to 6PPD. [Embodiments for Carrying out the Invention]

[0011] The rubber composition according to the present embodiment includes a rubber component, a specific phenylene diamine-based antioxidant, and a thiuram disulfide-based vulcanization accelerator.

[0012] The rubber component is not particularly limited, and various diene-based rubbers generally used in rubber compositions can be used. A diene-based rubber refers to a rubber having a repeating unit corresponding to a diene monomer having a conjugated double bond, and the polymer main chain contains a carbon-carbon double bond. The content of the diene-based rubber in the rubber component is preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass.

[0013] Specific examples of diene rubbers include natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), chloroprene rubber (CR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, and styrene-isoprene-butadiene copolymer rubber. Any one of these may be used, or two or more may be used in combination. These diene rubbers also include those with modified ends or main chains as needed (e.g., modified SBR, modified BR) or those modified to impart desired properties (e.g., modified NR). Among these, at least one diene rubber selected from the group consisting of natural rubber, synthetic isoprene rubber, butadiene rubber, and styrene-butadiene rubber is preferred.

[0014] The styrene-butadiene rubber may be solution-polymerized styrene-butadiene rubber (SSBR) or emulsion-polymerized styrene-butadiene rubber (ESBR). The styrene-butadiene rubber may also be modified styrene-butadiene rubber (modified SBR) which is modified by introducing functional groups to the terminals and / or main chain, or it may be unmodified styrene-butadiene rubber (unmodified SBR) which is not modified, or modified SBR and unmodified SBR may be used in combination.

[0015] The functional groups introduced into the modified rubber are preferably those that interact with silica, and preferably include at least one selected from the group consisting of oxygen atoms, nitrogen atoms, and silicon atoms, and more preferably include oxygen atoms and / or nitrogen atoms. Specific examples of functional groups include at least one selected from the group consisting of amino groups, hydroxyl groups, alkoxy groups, silyl groups, alkoxysilyl groups, epoxy groups, and carboxyl groups.

[0016] In one embodiment, the 100 parts by mass of the rubber component preferably contains 50 to 90 parts by mass of SBR (preferably modified SBR, more preferably modified SSBR) and 10 to 50 parts by mass of BR, for example in a silica-containing rubber composition, and more preferably contains 60 to 80 parts by mass of SBR and 20 to 40 parts by mass of BR.

[0017] In one embodiment, the 100 parts by mass of the rubber component preferably contains 50 to 90 parts by mass of isoprene rubber and 10 to 50 parts by mass of BR, for example in a rubber composition containing carbon black, and more preferably contains 60 to 80 parts by mass of isoprene rubber and 20 to 40 parts by mass of BR. Here, isoprene rubber refers to natural rubber and / or synthetic isoprene rubber, and is preferably natural rubber.

[0018] The rubber composition according to this embodiment contains a phenylenediamine-based antioxidant represented by the following general formula (1) (hereinafter referred to as phenylenediamine (1)) as an antioxidant. [ka]

[0019] In formula (1), R 1 and R 2 Each of these independently represents a hydrocarbon group with 6 or more carbon atoms. However, R 1 and R 2 Cases where the combination is a phenyl group and a 1,3-dimethylbutyl group are excluded. That is, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) is not included in phenylenediamine (1).

[0020] For details, see R 1 and R 2 The number of carbon atoms in the hydrocarbon group represented by is preferably 6 to 20, more preferably 6 to 10. The hydrocarbon group may be linear or branched, may contain a cyclic hydrocarbon group (e.g., an alicyclic hydrocarbon group or an aryl group), may be saturated or unsaturated.

[0021] In one embodiment, R 1 and R 2 Each of these groups is preferably independently a monovalent saturated hydrocarbon group or an aryl group, and more preferably an alkyl group, a cycloalkyl group, or an aryl group. Specific examples of alkyl groups include linear or branched hexyl groups (e.g., n-hexyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 1-methylpentyl group), linear or branched heptyl groups (e.g., n-heptyl group, 1,2-dimethylpentyl group, 1,3-dimethylpentyl group, 1,4-dimethylpentyl group, 1-methylhexyl group), linear or branched octyl groups (e.g., n-octyl group, 1-methylheptyl, 1-ethyl-3-methylpentyl group), linear or branched nonyl groups, linear or branched decyl groups, linear or branched dodecyl groups, etc. Cycloalkyl groups may have alkyl groups as substituents. Specific examples of cycloalkyl groups include cyclohexyl groups, methylcyclopentyl groups, cycloheptyl groups, methylcyclohexyl groups, etc. Specific examples of aryl groups include phenyl, tolyl, and xylyl groups.

[0022] In one embodiment, R 1 and R 2 Each of these is an aryl group or an alkyl group having 7 or more carbon atoms, and at least one of them may be an alkyl group having 7 or more carbon atoms, or each of these is a phenyl group or an alkyl group having 7 to 20 carbon atoms, and at least one of them may be an alkyl group having 7 to 20 carbon atoms.

[0023] Specific examples of phenylenediamine (1) include N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N-(1-methylheptyl)-N'-phenyl-p-phenylenediamine (8PPD), N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, and N-(1,4-dimethylpentyl)-N'-phenyl-p-phenylenediamine (7PPD). Any one of these may be used, or two or more may be used in combination.

[0024] The content of phenylenediamine (1) is not particularly limited, and may be 0.1 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 rubber component.

[0025] The anti-aging agent may be phenylenediamine (1) alone, or it may be used in combination with other anti-aging agents. Examples of other anti-aging agents include quinoline-based anti-aging agents, monophenol-based anti-aging agents, bisphenol-based anti-aging agents, and benzimidazole-based anti-aging agents.

[0026] In one embodiment, the rubber composition preferably contains a quinoline-based antioxidant along with phenylenediamine (1) as an antioxidant, which can further improve heat resistance to aging. Examples of quinoline-based antioxidants include 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMQ), 6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline (ETMQ), and 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline. Any one of these may be used, or two or more may be used in combination.

[0027] When phenylenediamine (1) and a quinoline-based antioxidant are used in combination, the amount of the quinoline-based antioxidant is not particularly limited, but may be 0.05 to 5 parts by mass, 0.1 to 2 parts by mass, or 0.3 to 1 part by mass per 100 parts by mass of the rubber component. The mass ratio of phenylenediamine (1) to the amount of the quinoline-based antioxidant is not particularly limited, for example, phenylenediamine (1) / quinoline-based antioxidant may be 2 / 1 to 10 / 1 or 3 / 1 to 6 / 1.

[0028] The rubber composition according to this embodiment contains a thiuram disulfide-based vulcanization accelerator as a vulcanization accelerator. By incorporating a thiuram disulfide-based vulcanization accelerator, it is possible to improve scorching when phenylenediamine (1) is used as a substitute for 6PPD, and to improve heat aging resistance.

[0029] As a thiuram disulfide-based vulcanization accelerator, a compound represented by the following general formula (2) (hereinafter referred to as thiuram disulfide (2)) is preferably used. [ka]

[0030] In formula (2), R 3 , R 4 , R 5 and R 6 Each of these is an independent hydrocarbon group having 30 or fewer carbon atoms (i.e., 1 to 30 carbon atoms), which may optionally contain one or more heteroatoms. 3 and R 4 , and / or, R 5 and R 6 These may each form a heterocyclic group with the nitrogen atom to which they are bonded.

[0031] R 3 , R 4 , R 5 and R 6 The hydrocarbon group represented by may be linear or branched, may contain cyclic hydrocarbon groups (e.g., alicyclic hydrocarbon groups or aryl groups), may contain heterocyclic groups, may be saturated or unsaturated. Examples of the heteroatoms include oxygen atoms and nitrogen atoms, which may be included as substituents or may be included in the main chain as ether bonds, ester bonds, or amide bonds. The number of carbon atoms in the hydrocarbon group is preferably 1 to 24, more preferably 4 to 22, more preferably 6 to 20, and even more preferably 8 to 20. Since a larger number of carbon atoms tends to result in a better improvement in heat aging resistance, the number of carbon atoms is even more preferably 12 to 20.

[0032] R 3 and R 4 They may form a heterocyclic group together with the nitrogen atom to which they are bonded, R 5 and R 6These may form a heterocyclic group together with the nitrogen atom to which they are bonded. When such a heterocyclic group is formed, the number of carbon atoms is R 3 and R 4 The sum of R 5 and R 6 It is the sum of R 3 and R 4 The total number is between 2 and 60, R 5 and R 6 The total number of these groups is between 2 and 60. Specific examples of heterocyclic groups include pyrrolidine rings, pyrrole rings, and piperidine rings, and one or more hydrocarbon groups may be bonded to these heterocyclic groups as substituents.

[0033] In one embodiment, R 3 , R 4 , R 5 and R 6 Preferably, each of these groups is independently a methyl group, an ethyl group, a linear or branched propyl group, a linear or branched butyl group, a linear or branched pentyl group, a linear or branched hexyl group, a linear or branched octyl group, a linear or branched nonyl group, a linear or branched decyl group, a linear or branched dodecyl group, a linear or branched tridecyl group, a linear or branched tetradecyl group, a linear or branched pentadecyl group, a linear or branched hexadecyl group, a linear or branched heptadecyl group, a linear or branched octadecyl group, a linear or branched nonadecyl group, a cyclohexyl group, a phenyl group, or a benzyl group. 3 , R 4 , R 5 and R 6 Each of these may independently be a monovalent saturated hydrocarbon group having the above number of carbon atoms, or an alkyl group having the above number of carbon atoms.

[0034] Specific examples of thiuram disulfide (2) include tetramethyl thiuram disulfide, tetrabutyl thiuram disulfide, tetrabenzyl thiuram disulfide, tetrakis(2-ethylhexyl) thiuram disulfide, tetradodecyl thiuram disulfide, and tetraoctadecyl thiuram disulfide. Furthermore, from a nitrosamine-free and sustainable standpoint, SI group's thiuram disulfide "NAUGARD BIO-XL" is also a preferred example.

[0035] In one embodiment, from the viewpoint of improving scorch resistance and heat aging resistance, it is preferable that tetramethylthiuram disulfide is not included in thiuram disulfide (2). That is, in formula (2), R 3 , R 4 , R 5 and R 6 If all of them are methyl groups, it is preferable to remove them.

[0036] The content of thiuram disulfide (2) is not particularly limited, and may be 0.05 to 6 parts by mass, 0.1 to 5 parts by mass, or 0.2 to 4 parts by mass per 100 parts by mass of rubber component.

[0037] The vulcanization accelerator may be thiuram disulfide (2) alone, or it may be used in combination with other vulcanization accelerators. Examples of other vulcanization accelerators include sulfenamide-based vulcanization accelerators, guanidine-based vulcanization accelerators, and thiazole-based vulcanization accelerators.

[0038] In one embodiment, the vulcanization accelerator preferably comprises thiuram disulfide (2) and a sulfenamide-based vulcanization accelerator. Examples of sulfenamide-based vulcanization accelerators include N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N-oxydiethylene-2-benzothiazole sulfenamide (MBS), N-(tert-butyl)-2-benzothiazole sulfenamide (TBBS), and N,N-diisopropyl-2-benzothiazole sulfenamide (DIBS), of which one or more may be used in combination.

[0039] When a sulfenamide-based vulcanization accelerator is used in combination, its content is not particularly limited. For example, it may be 0.2 to 6 parts by mass, 0.5 to 5 parts by mass, or 1 to 3 parts by mass per 100 parts by mass of the rubber component. The mass ratio of the thiuram disulfide (2) content to the sulfenamide-based vulcanization accelerator content is not particularly limited. For example, the ratio of thiuram disulfide (2) to sulfenamide-based vulcanization accelerator may be 1 / 30 to 1 / 4, 1 / 20 to 1 / 3, or 1 / 10 to 1 / 2.

[0040] In addition to the above-mentioned components, the rubber composition according to this embodiment may also contain various additives commonly used in rubber compositions, such as fillers, silane coupling agents, oils, zinc oxide, stearic acid, waxes, and vulcanizing agents.

[0041] Silica and / or carbon black are preferred as fillers. The filler content is not particularly limited and may be 20 to 200 parts by mass, 30 to 150 parts by mass, or 40 to 120 parts by mass per 100 parts by mass of rubber component.

[0042] As silica, it is preferable to use wet silica, such as wet sedimentation silica or wet gelation silica. The specific surface area of ​​the silica for nitrogen adsorption is not particularly limited, for example, 100 to 300 m². 2 / g is also acceptable, 150-250m 2 / g is also acceptable, 180-220m 2 / g is also acceptable. The nitrogen adsorption specific surface area of ​​silica is the BET specific surface area measured according to the BET method described in JIS K6430:2008.

[0043] Various known grades of carbon black can be used. Specifically, these include SAF grade (N100 series), ISAF grade (N200 series), HAF grade (N300 series), FEF grade (N500 series), and GPF grade (N600 series) (all ASTM grades). One or more of these grades of carbon black can be used.

[0044] In one embodiment, when silica is the main component of the filler, the silica content is not particularly limited, but may be 40 to 180 parts by mass, 60 to 150 parts by mass, or 80 to 120 parts by mass per 100 parts by mass of rubber component. In this case, the carbon black content may be, for example, 3 to 10 parts by mass per 100 parts by mass of rubber component. Here, "silica as the main component" means that the ratio of silica in the filler is 60% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more (the same applies when carbon black is the main component).

[0045] In one embodiment, when carbon black is used as the main component of the filler, the carbon black content is not particularly limited, but may be 20 to 100 parts by mass, 30 to 80 parts by mass, or 40 to 60 parts by mass per 100 parts by mass of rubber component.

[0046] When the rubber composition contains silica as a filler, it is preferable to include a silane coupling agent. Examples of silane coupling agents include sulfide silane coupling agents such as bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)disulfide, 3-mercaptopropyltrimethoxysilane, and 3-mercaptopropyl Examples of mercaptosilane coupling agents include pyrtriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyldimethylmethoxysilane, and mercaptoethyltriethoxysilane, as well as thioester group-containing silane coupling agents such as 3-octanoylthio-1-propyltriethoxysilane, 3-propionylthiopropyltrimethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane. These can be used individually or in combination of two or more.

[0047] The content of the silane coupling agent is not particularly limited, but is preferably 2 to 25% by mass of the silica amount, that is, 2 to 25 parts by mass per 100 parts by mass of silica. More preferably, the content of the silane coupling agent is 5 to 20% by mass of the silica amount.

[0048] The oil content is not particularly limited; for example, it may be 0 to 40 parts by mass, 3 to 30 parts by mass, or 5 to 25 parts by mass per 100 parts by mass of rubber component.

[0049] The zinc oxide content is not particularly limited; for example, it may be 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 rubber component.

[0050] The stearic acid content is not particularly limited; for example, it may be 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 rubber component.

[0051] The wax content is not particularly limited; for example, it may be 0 to 10 parts by mass, 0.3 to 5 parts by mass, or 0.5 to 3 parts by mass per 100 parts by mass of rubber component.

[0052] Sulfur is preferably used as the vulcanizing agent. The content of the vulcanizing agent is not particularly limited, but is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and even more preferably 1 to 3 parts by mass, per 100 parts by mass of rubber component.

[0053] The rubber composition according to this embodiment can be prepared by kneading in accordance with conventional methods using a commonly used mixer such as a Banbury mixer, kneader, or roll. That is, for example, in the first mixing stage, other additives excluding the vulcanizing agent and vulcanization accelerator can be added and mixed with the rubber component, and then, in the final mixing stage, the vulcanizing agent and vulcanization accelerator can be added and mixed with the resulting mixture to prepare the rubber composition.

[0054] The rubber composition according to this embodiment can be used in various rubber components such as tires, vibration-damping rubber, and conveyor belts. Preferably, it is for tires. Examples of tires include passenger car tires, large truck and bus tires, and pneumatic tires of various sizes and applications. In tires, it can be applied to various parts such as the tread, sidewall, and bead.

[0055] In one embodiment, a tire including rubber parts (e.g., tread rubber, sidewall rubber, etc.) made from the above rubber composition is manufactured as follows: The rubber composition is molded into a predetermined shape by conventional methods, for example, by extrusion. The resulting molded product is combined with other parts to produce a green tire. A pneumatic tire can be manufactured by vulcanizing the green tire at, for example, 140 to 180°C.

[0056] A tire according to one embodiment includes a tread rubber made using the above-mentioned rubber composition. The tread rubber of the tire may have a two-layer structure consisting of a cap rubber and a base rubber, or a single-layer structure in which both are integrated. In the case of a single-layer structure, it is preferable that the tread rubber is made of the above-mentioned rubber composition. In the case of a two-layer structure, it is preferable that the outer cap rubber that contacts the road surface is made of the above-mentioned rubber composition, but both the cap rubber and the base rubber may be made of the above-mentioned rubber composition. [Examples]

[0057] The following are examples of the present invention, but the present invention is not limited to these examples.

[0058] The components used in the examples and comparative examples are as follows: • SBR: Alkoxy and amino-terminated SSBR, manufactured by ENEOS Material Co., Ltd., "HPR350" • BR: "UBEPOL BR150B" manufactured by UBE Elastomer Co., Ltd. • NR: RSS#3

[0059] • Carbon Black: "Seast KH" manufactured by Tokai Carbon Co., Ltd. • Silica: Tosoh Silica Co., Ltd.'s "Nip Seal AQ" (nitrogen adsorption specific surface area 205 m²) 2 / g) • Coupling agent: Sulfidosilane coupling agent, "Si69" manufactured by Evonik Industries. • Oil: ENEOS Corporation "Process NC140" • Zinc oxide: "Zinc Oxide No. 3" manufactured by Mitsui Mining & Smelting Co., Ltd. • Stearic acid: "Lunaq S-20" manufactured by Kao Corporation

[0060] • Anti-aging agent 1: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), manufactured by Ouchi Shinko Chemical Industry Co., Ltd., "Nocrac 6C" • Anti-aging agent 2: Bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), manufactured by Lanxess, "VULKANOX 4030" • Anti-aging agent 3: N-(1-methylheptyl)-N'-phenyl-p-phenylenediamine (8PPD), manufactured by Seiko Chemical Co., Ltd. as "Ozonon 35" • Anti-aging agent 4: 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMQ) Kawaguchi Chemical Industry Co., Ltd. "Antage RD"

[0061] • Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industries, Ltd. • Vulcanization accelerator 1: N-cyclohexyl-2-benzothiazole sulfenamide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., "Noxellar CZ-G" • Vulcanization accelerator 2: Diphenylguanidine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., "Noxellar D" • Vulcanization accelerator 3: N-(tert-butyl)-2-benzothiazole sulfenamide, Sanshin Chemical Industry Co., Ltd. "Sunceller NS-G" • Vulcanization accelerator 4: Tetramethylthiuram monosulfide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., "Noxellar TS" • Vulcanization accelerator 5: Tetramethylthiuram disulfide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., "Noxellar TT-P" • Vulcanization accelerator 6: Tetrabenzyl thiuram disulfide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., "Noxellar TBZTD" • Vulcanization accelerator 7: Tetrakis(2-ethylhexyl)thiuram disulfide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., "Noxellar TOT-N" • Vulcanization accelerator 8: Tetrabutylthiuram disulfide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., "Noxellar TBT-N"

[0062] • Sulfurization accelerator 9: Tetraoctadecyl thiuram disulfide obtained by the synthesis example 1 below (in formula (2), R 3 ~R 6 =CH3(CH2) 16 CH2-) Synthesis Example 1: A solution was prepared by dissolving 52.20 g of dioctadoxylamine in 500 ml of THF, and a solution of 18.75 g of potassium hydroxide dissolved in 18.75 ml of water was added dropwise to this solution. After the addition of potassium hydroxide, 18.13 ml of carbon disulfide was added to the solution and the mixture was stirred at room temperature. Saturated iodine-methanol solution was added dropwise to the reaction mixture until the color of the reaction mixture no longer faded. The reaction mixture was then filtered, and the residue was purified by silica gel column chromatography to obtain the desired purified product. The yield was 85% by mass. Regarding the purified reaction product, 13 13C-NMR analysis and mass spectrometry were performed to confirm that tetraoctadecyl thiuram disulfide was obtained.

[0063] The evaluation methods in the examples and comparative examples are as follows.

[0064] (1) Scorch resistance In accordance with JIS K6300-1:2013, a rotaryless Mooney meter manufactured by Toyo Seiki Seisakusho Co., Ltd. was used to preheat the unvulcanized rubber composition at 125°C for 1 minute. The time t5 required for the viscosity to rise by 5 Mooney units from the minimum viscosity Vm was measured, and the values ​​were expressed as an index, with the value of Comparative Example 1-1 set to 100 in the first experimental example and the value of Comparative Example 2-1 set to 100 in the second experimental example. A larger index indicates a longer scorch time and superior scorch resistance.

[0065] (2) Heat aging resistance A 2.0 mm thick test specimen was prepared by vulcanizing the rubber composition at 160°C for 20 minutes. Tensile tests were performed on both the unaged and aged specimens (aged in a gear oven at 90°C for 96 hours) in accordance with JIS K6251:2017 (using a No. 3 dumbbell), and the elongation at break and stress at break were measured. The calculated values ​​after aging were determined as a percentage of the calculated values ​​for the unaged specimen, and this was defined as the retention rate of elongation at break and stress at break. In the first experimental example, the retention rates of elongation at break and stress at break for Comparative Example 1-1 were set to 100, and in the second experimental example, the retention rates of elongation at break and stress at break for Comparative Example 2-1 were set to 100. The retention rates of elongation at break and stress at break for each example and comparative example are expressed as indices. A higher value indicates a higher retention rate and superior heat aging resistance.

[0066] [First Experimental Example] Using a Banbury mixer, according to the formulations (parts by mass) shown in Tables 1 and 2 below, first, in the first mixing stage, compounding agents excluding sulfur and vulcanization accelerator were added to the rubber component and kneaded (discharge temperature = 155°C). Next, in the final mixing stage, sulfur and vulcanization accelerator were added to the resulting mixture and kneaded (discharge temperature = 90°C) to prepare the rubber composition. In the first experimental example, Comparative Example 1-1 was used as the standard formulation, and the amount of vulcanization accelerator added was adjusted to achieve approximately the same hardness as the standard formulation.

[0067] The scorch resistance and heat aging resistance of each obtained rubber composition were evaluated. The results are shown in Tables 1 and 2.

[0068] [Table 1]

[0069] [Table 2]

[0070] Comparative Example 1-1 is a standard formulation using 6PPD as an antioxidant. Comparative Examples 1-2 and 1-3 used 77PD and 8PPD, respectively, as substitutes for 6PPD, and showed shorter scorch times and inferior scorch resistance compared to Comparative Example 1-1. In Comparative Example 1-4, thiram monosulfide was used instead of the guanidine-based vulcanization accelerator compared to Comparative Example 1-2, but the improvement in scorch resistance was insufficient. Similarly, in Comparative Example 1-5, thiram monosulfide was used instead of the guanidine-based vulcanization accelerator compared to Comparative Example 1-3, but the improvement in scorch resistance was insufficient.

[0071] In contrast, in Examples 1-1 to 1-10, the combination of phenylenediamine (1) as a substitute for 6PPD and thiuram disulfide (2) improved scorch resistance compared to Comparative Examples 1-2 and 1-3. Furthermore, the scorch resistance index remained within -10% of the standard formulation of Comparative Example 1-1, maintaining processability. In particular, in Examples 1-3 to 1-9, which used vulcanization accelerators 6 to 9, the scorch resistance was equivalent to that of Comparative Example 1-1, demonstrating a significant improvement in scorch resistance. In addition, in Examples 1-1 to 1-10, the combined use of phenylenediamine (1) and thiuram disulfide (2) also improved heat aging resistance compared to Comparative Example 1-1.

[0072] [Second Experimental Example] A rubber composition was prepared according to the formulation (parts by mass) shown in Table 3 below, with the rest being the same as in the first experimental example. The obtained rubber composition was used to evaluate scorch resistance and heat aging resistance in the same manner as in the first experimental example. The results are shown in Table 3. In the second experimental example, Comparative Example 2-1 was used as the standard formulation, and the amount of vulcanization accelerator added was adjusted to achieve approximately the same hardness as the standard formulation.

[0073] [Table 3]

[0074] While the first experimental example used an SBR-based silica compound, the second experimental example used an NR-based carbon black compound. In the second experimental example, as in the first experimental example, the deterioration of scorch resistance caused by using phenylenediamine (1) as a substitute for 6PPD was improved by using phenylenediamine (1) and thiuram disulfide (2) in combination, and heat aging resistance was also improved.

[0075] Furthermore, the various numerical ranges described in this specification can be any combination of their upper and lower limits, and all such combinations are described herein as preferred numerical ranges. Also, the description of a numerical range as "X~Y" means X or greater and Y or less.

Claims

1. The product contains a rubber component, a phenylenediamine-based antioxidant represented by the following general formula (1), and a thiuram disulfide-based vulcanization accelerator. 【Chemistry 1】 In formula (1), R １ and R ２ Each of these independently represents a hydrocarbon group having 6 or more carbon atoms, however, R １ and R ２ Except when it is a combination of a phenyl group and a 1,3-dimethylbutyl group, Rubber composition.

2. The thiuram disulfide-based vulcanization accelerator is represented by the following general formula (2): 【Chemistry 2】 In formula (2), R ３ , R ４ , R ５ and R ６ are each independently a hydrocarbon group having 30 or fewer carbon atoms, which may optionally contain one or more heteroatoms, and R ３ and R ４ , and / or R ５ and R ６ may together with the nitrogen atom to which they are attached form a heterocyclic group. The rubber composition according to claim 1.

3. In the above formula (2), R ３ , R ４ , R ５ and R ６ The rubber composition according to claim 2, except in the case where all of them are methyl groups.

4. The rubber composition according to claim 1, further comprising a quinoline-based anti-aging agent.

5. A rubber composition for tires, according to any one of claims 1 to 4.

6. A tire comprising a rubber portion made from the rubber composition described in any one of claims 1 to 4.

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