Phenothiazine derivative compound

Abstract

By using a phenothiazine-based derivative compound represented by a general formula (R1 is a monovalent aliphatic hydrocarbon group having 1-10 carbon atoms, R2 is a divalent aliphatic hydrocarbon group having 1-5 carbon atoms, and n is 0 or an integer between 1 and 6) as an antioxidant, it is possible to prevent problems such as appearance defects caused by migration of the antioxidant to a surface, contamination of other members that come into contact with a molding member, volatilization or elution of the antioxidant into an external environment, and extraction by liquid media such as oils / fats and organic solvents, and enable safe use and a longer working life of rubber molded members in a variety of usage environments.

Description

Phenothiazine derivative compounds

[0001] The present invention relates to a phenothiazine derivative compound, and more particularly to a phenothiazine derivative compound suitable as an antioxidant for elastomeric polymer materials.

[0002] A wide variety of synthetic rubbers, produced from natural rubber and fossil resources, are processed into various forms depending on their intended use. They have permeated every corner of society and economy, bringing great convenience and benefits to our lives.

[0003] For example, natural rubber and diene-based synthetic rubbers, such as styrene-butadiene copolymer rubber (SBR), offer an excellent balance of properties such as strength, abrasion resistance, elasticity, and low-temperature performance, and are relatively inexpensive, making them suitable for a wide range of applications, including automobile tires. However, due to the unsaturated bonds present in their molecular chains, natural rubber and diene-based synthetic rubbers are susceptible to oxidative degradation caused by heat, light, oxygen, ozone, etc., and can lose their original properties and functionality over time. To prevent this, antioxidants are added during the manufacturing and molding processes.

[0004] As antioxidants, non-staining phenolic antioxidants are used in the manufacturing process, and aromatic amine antioxidants, which have excellent effects in preventing oxidative degradation, tend to be used frequently in the molding and processing stage. From these, an aromatic amine antioxidant suitable for the application and the environment in which it is used is appropriately selected.

[0005] The following points must be kept in mind when using aromatic amine antioxidants: - Antioxidants that pose a risk to human health require occupational safety and health measures to prevent exposure. - In rubber molded parts, migration of the antioxidant to the surface can lead to poor appearance and contamination of other parts, and the antioxidant can volatilize to the outside due to heat, or be extracted by water, oils, solvents, etc., resulting in a loss of the initial expected antioxidant effect. - When rubber molded parts come into direct contact with drinking water or food, or when used in medical parts, care must be taken to ensure that the amount of antioxidant leaching is acceptable from a health perspective. - In the case of large molded parts such as automobile tires, there is a risk of large amounts of antioxidant volatilizing or leaching into the external environment.

[0006] In particular, in relation to the recent issue of tire-road wear particles (TRWP), there are concerns about the impact of antioxidants released from automobile tires or their wear particles on the ecosystem. Under these circumstances, there is a movement to select new antioxidants with less environmental impact from the existing group of additive-type antioxidants.

[0007] However, although the above measures may reduce the impact on the external environment, they do not essentially solve the problem of outflow. Therefore, in order to essentially solve this problem, the development of a non-leaching antioxidant is an urgent issue.

[0008] Japanese Patent Laid-Open No. 4-264106 Japanese Patent Laid-Open No. 5-230132 Japanese Patent Laid-Open No. 2009-209268 Japanese Patent Laid-Open No. 2000-103794

[0009] Rubber Chem. Technol., Vol. 45, p. 204 (1972) Rubber Chem. Technol., Vol. 46, p. 106 (1973) Rubber Chem. Technol., Vol. 52, p. 883 (1979)

[0010] From this perspective, attempts have been made to chemically bond antioxidant components to rubber molecules to prevent the antioxidant from eluting or volatilizing to the outside.

[0011] For example, the nitrosoaniline method (Non-Patent Document 1), the hydroformylation method (Patent Document 1), and the maleic anhydride modification method (Patent Document 2) are known. However, these methods require an additional rubber modification step or reaction step, and are therefore not practical in terms of production costs.

[0012] Also known is a method of copolymerizing an antioxidant having a polymerizable unsaturated group when producing synthetic rubber (Non-Patent Documents 2 and 3, Patent Document 3). However, it is difficult to say that the antioxidants having a polymerizable unsaturated group described in these documents are versatile.

[0013] In order to solve the above problems, the present inventors have proposed a compound represented by the general formula: (where R 1 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, and R 2 is a divalent aliphatic hydrocarbon group having 1 to 5 carbon atoms, and n is 0 or an integer of 1 to 6).

[0014] In such compounds, the phenothiazine moiety, which is the antioxidant component, chemically bonds to the rubber molecules when the elastomeric polymer material is crosslinked. This prevents problems such as poor appearance due to migration of the antioxidant to the surface, contamination of other components in contact with the molded part, volatilization or elution of the antioxidant component into the external environment, and extraction by liquid media such as oils and organic solvents. As a result, this enables the safe use and long life of diene rubber molded parts in a variety of usage environments.

[0015] Furthermore, in the case of large molded parts such as automobile tires, it is possible to reduce the volatilization and elution of antioxidant components from their surfaces into the external environment, making this technology useful from the perspective of environmental conservation.

[0016] The phenothiazine derivative compound according to the present invention has the general formula (where R 1 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, and R 2 is a divalent aliphatic hydrocarbon group having 1 to 5 carbon atoms, and n is 0 or an integer of 1 to 6).

[0017] R 1 Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, a 2-ethylhexyl group, an n-nonyl group, an isopropyl group, a 2-butyl group, a 2-pentyl group, a 3-pentyl group, a 2-hexyl group, a 3-hexyl group, a 2-heptyl group, a 3-heptyl group, a 4-heptyl group, a 2-octyl group, a 3-octyl group, a 4-octyl group, a tertiary butyl group, and a 1,1-dimethyl-1 1-propyl group, 1,1-dimethyl-1-butyl group, 1,1-dimethyl-1-pentyl group, 1,1-dimethyl-1-hexyl group, 3-methyl-3-pentyl group, 3-ethyl-3-pentyl group, 3-methyl-3-hexyl group, etc., or cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, 1-methyl-1-cyclopentyl group, 1-methyl-1-cyclohexyl group, 1-adamantyl group, etc.

[0018] R 2 Specific examples include a methylene group, an ethylene group, a 1,3-propylene group, a 2-propylidene group, a 1-butylidene group, and a 2-butylidene group.

[0019] Specific examples of the phenothiazine derivative compound [I] include bis[(10-methyl-10H-phenothiazine-2-yl)methyl] disulfide, bis[(10-methyl-10H-phenothiazine-2-yl)methyl] trisulfide, bis[(10-methyl-10H-phenothiazine-2-yl)methyl] tetrasulfide, bis[(10-methyl-10H-phenothiazine-2-yl)methyl] pentasulfide, bis[(10-methyl-10H-phenothiazine-2-yl)methyl] Examples of such sulfur compounds include hexasulfide, bis[(10-methyl-10H-phenothiazin-3-yl)methyl]disulfide, bis[(10-methyl-10H-phenothiazin-3-yl)methyl]trisulfide, bis[(10-methyl-10H-phenothiazin-3-yl)methyl]tetrasulfide, bis[(10-methyl-10H-phenothiazin-3-yl)methyl]pentasulfide, and bis[(10-methyl-10H-phenothiazin-3-yl)methyl]hexasulfide.

[0020] There is no particular limitation on the method for producing the phenothiazine derivative compound [I]. For example, it can be produced by using inexpensive diphenylamine or 10H-phenothiazine as a starting material, and by reacting the compound represented by the general formula (where R 1 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, and R 2 It can be easily produced by reacting a phenothiazine derivative compound represented by the formula (wherein X is a divalent aliphatic hydrocarbon group having 1 to 5 carbon atoms, and X is a halogen atom) with sodium polysulfide. A specific example is the production of bis[(10-methyl-10H-phenothiazin-3-yl)methyl] polysulfide from 3-chloromethyl-10-methyl-10H-phenothiazine.

[0021] As the sodium polysulfide, hydrous sodium polysulfide or anhydrous sodium polysulfide can be used. For example, hydrous sodium polysulfide can be produced by reacting sodium sulfide with sulfur. Anhydrous sodium polysulfide can be produced by the method described in Patent Document 4.

[0022] The phenothiazine derivative compound according to the present invention can be suitably used as an antioxidant for elastomeric polymer materials.

[0023] The phenothiazine derivative compound [I] is used in an amount of about 0.01 to 2.0 parts by weight, preferably about 0.1 to 1.0 part by weight, per 100 parts by weight of the elastomeric polymer material. If it is used in a proportion less than this, a sufficient antioxidant effect cannot be expected, while if it is used in a proportion greater than this, further improvement in the antioxidant effect cannot be expected, which is uneconomical.

[0024] If necessary, an antioxidant may be added in addition to the phenothiazine derivative compound of the present invention. Examples of such antioxidants include amine-based antioxidants, phenol-based antioxidants, and wax-based antioxidants.

[0025] The elastomeric polymer material in which the phenothiazine derivative compound [I] of the present invention can be used is not particularly limited, but sulfur-crosslinkable elastomeric polymer material is preferred. Specific examples include diene rubbers. Examples of diene rubbers include natural rubber (NR) and synthetic diene rubbers, the latter of which include isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), and chloroprene rubber (CR). These diene rubbers may be used alone or in combination of two or more. Sulfur-crosslinkable acrylic rubbers may also be used.

[0026] The polymerization form of the diene synthetic rubber may be either a homopolymer or a copolymer of two or more polymerizable unsaturated monomers, and the polymerization form of the copolymer may be any of a random copolymer, a block copolymer, an alternating polymer, and a graft copolymer.

[0027] Diene synthetic rubbers are produced by a polymerization method suited to the type and application of each synthetic rubber, and are used as appropriate by a polymerization method suitable for each type and application. Examples of methods that can be used include radical polymerization, anionic polymerization, cationic polymerization, and coordination polymerization, from the viewpoint of the active species in the polymerization reaction, and solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, and gas phase polymerization, from the viewpoint of the phase state of the polymerization reaction.

[0028] Examples of crosslinking methods for diene rubbers include sulfur crosslinking, organic peroxide crosslinking, quinone dioxime crosslinking, metal oxide crosslinking, and thiourea crosslinking. A crosslinking method is used depending on the type of diene rubber and its application, and sulfur crosslinking is preferably used.

[0029] The sulfur used for sulfur crosslinking may be powdered sulfur produced by pulverizing lump sulfur, precipitated sulfur, or the like.

[0030] Examples of crosslinking accelerators include aldehydes / ammonias, aldehydes / amines, guanidines, thioureas, thiazoles, sulfenamides, thiurams, dithiocarbamic acid salts, xanthogenates, etc., and an appropriate one is selected from these depending on the type of diene rubber, processing conditions, and properties of the final product. In this case, the above compounds may be used alone or in combination of two or more.

[0031] As the crosslinking promoter, a metal oxide such as zinc oxide or a fatty acid such as stearic acid is used, and each of them may be used alone or in combination of two or more.

[0032] The rubber composition containing the phenothiazine derivative compound [I] may contain fillers such as carbon black and silica, softeners, synthetic plasticizers, tackifiers, lubricants, peptizers, pigments, etc. as appropriate.

[0033] The rubber composition is prepared by blending the phenothiazine derivative compound [I], a crosslinking agent, a crosslinking accelerator, and other compounding ingredients used as needed with rubber, and mixing them using a Banbury mixer, a pressure kneader, an open roll, etc. The crosslinking of the obtained rubber composition is carried out by primary crosslinking at about 120 to 200°C for about 1 to 60 minutes, and, if necessary, oven crosslinking (secondary crosslinking) at about 120 to 200°C for about 1 to 20 hours.

[0034] The present invention will now be described in detail with reference to examples, although the present invention, including its effects, is not limited to these examples.

[0035] Example 1 A 1-L five-neck flask equipped with a stirrer, thermometer, reflux condenser, nitrogen gas inlet, and outlet tube was charged with 0.3 L of thoroughly dehydrated dimethoxyethane, followed by 32.6 g (1.0 mol) of powdered sulfur and 11.5 g (0.50 mol) of metallic sodium. The temperature of the contents was slowly raised to 65°C and maintained at that temperature for 30 minutes, after which the reaction was continued at 70°C for another 30 minutes. Next, 130.9 g (0.50 mol) of 3-chloromethyl-10-methyl-10H-phenothiazine was added, and the reaction was continued at 85°C for 5 hours. The reaction mixture was cooled to room temperature, and the insoluble matter was filtered off. Activated carbon (Shirasagi A, an Osaka Gas Chemicals product) was added to the brown filtrate, and the mixture was left for several hours, after which the activated carbon was filtered off. The volatile components were then removed from the filtrate by distillation under reduced pressure to give 130.7 g (90% yield) of bis[(10-methyl-10H-phenothiazin-3-yl)methyl]tetrasulfide as a yellow solid. The average number of sulfur atoms per molecule was 4. 1 H NMR (400MHz, Acetone d6, δ ppm): 3.3 (s, 3H, N-CH3) 3.5-4.1 (m, 2H, -CH2S-) 6.7-7.0 (m, 3H, Ar) 7.1-7.3 (m, 4H, Ar)

[0036] Reference Example: After the interior of a 1000 ml four-neck flask equipped with a magnetic stirrer, thermometer, reflux tube, nitrogen gas inlet, and outlet tube was purged with nitrogen gas, 200 g of a 15% toluene solution of 1,3-butadiene (a product of Tokyo Chemical Industry Co., Ltd.), 10 g of styrene, and 2.0 ml of tetrahydrofuran were sequentially added. Next, while introducing nitrogen gas into the vessel, 0.50 ml of n-butyllithium hexane solution (1.6 mol / L) was added to initiate the polymerization reaction. As the polymerization progressed, the temperature of the reaction solution rose from 20°C to a maximum of 80°C. 40 minutes after the start of polymerization, 0.8 ml of methanol was added to terminate the polymerization. The resulting reaction solution was poured into 500 ml of methanol to precipitate a styrene-butadiene copolymer. This was then dried under reduced pressure at 100°C for 2 hours, yielding 40 g of styrene-butadiene copolymer. 1H-NMR confirmed that the bound styrene content was 224% and the vinyl bond content was 55%. Furthermore, the molecular weight was measured using gel permeation chromatography (Shimadzu Corporation HPLC System 20A) under the following measurement conditions, and the number average molecular weight (Mn) was 230,000, the weight average molecular weight (Mw) was 269,000 (both values ​​converted to polystyrene), and the Mw / Mn was 1.17. Column: Shodex GPC KF-807L x 4 Detector: RID-20A Measurement temperature: 40°C Sample concentration: 0.2% THF solution Carrier (THF) flow rate: 1.0 ml / min

[0037] Example 2 Styrene-butadiene copolymer obtained in Reference Example 100 parts by weight FEF carbon black (Tokai Carbon's Seast GSO) 50 parts by weight Stearic acid (Miyoshi Oil & Fats' TST) 2.0 parts by weight Sulfur (Hosoi Chemical Industry's precipitated sulfur) 1.5 parts by weight Zinc oxide (Sakai Chemical Industry's zinc oxide No. 2) 3.0 parts by weight Crosslinking accelerator CBS (Ouchi Shinko Chemical Industry's Noccela CZ-G) 1.8 parts by weight Crosslinking accelerator DPG (Ouchi Shinko Chemical Industry's Noccela D) 1.5 parts by weight Phenothiazine derivative compound of Example 1 0.5 parts by weight The above components were mixed using an open roll to obtain a diene-based rubber composition. This was subjected to primary crosslinking for 20 minutes at 160°C using a 100-ton press molding machine, yielding a sheet-like crosslinked product with a thickness of approximately 2 mm.

[0038] Comparative Example In Example 2, no phenothiazine derivative compound was used.

[0039] The crosslinking characteristics of the diene rubber composition and the physical properties of the crosslinked product were measured as follows: Mooney scorch test: Based on JIS K6300-1 (125°C), which corresponds to ISO 289-1. Minimum Mooney viscosity (ML min) and scorch time (t5) were measured using a Mooney Viscometer AM-3 manufactured by Toyo Seiki Seisakusho. Physical properties at room temperature: Based on JIS K6251, which corresponds to ISO 37, and JIS K6253, which corresponds to ISO 7619-1. Air heating aging test: Based on JIS K6257, which corresponds to ISO 188 (100°C, 250 hours).

[0040] The results obtained in Example 2 and Comparative Example are shown in the following table. Table Measurement Results Actual 2 Ratio Mooney scorch test (125°C) ML min (pts) 30 32 t5 (min) 13.0 12.5 Physical properties at normal state Hardness (Duro A) 68 69 100% modulus (MPa) 3.5 3.4 Strength at break (MPa) 16.5 17.0 Elongation at break (%) 400 390 Heat aging test (100°C, 250 hours) Change in hardness (Duro A) +10 +7 100% modulus change rate +80 +100 Strength at break change rate (%) +2 -5 Elongation at break change rate (%) -40 -50

[0041] From the above results, it is clear that there is almost no difference in the normal physical properties regardless of whether or not a phenothiazine derivative compound is added, but the addition of a phenothiazine derivative compound improves the heat aging resistance.

Claims

1. General formula (where R 1 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, and R 2 is a divalent aliphatic hydrocarbon group having 1 to 5 carbon atoms, and n is 0 or an integer of 1 to 6.

2. General formula (where R 1 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, and R 2 2. The method for producing a phenothiazine derivative compound according to claim 1, comprising reacting a phenothiazine derivative compound represented by the formula (I) with sodium polysulfide.

3. A rubber composition comprising 0.01 to 2.0 parts by weight of the phenothiazine derivative compound [I] according to claim 1 per 100 parts by weight of an elastomeric polymer material.

4. The rubber composition according to claim 3, wherein the elastomeric polymer material is natural rubber or diene-based synthetic rubber.