JPH032896B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an antiaging agent for rubber that has excellent heat resistance, ozone resistance, and flex crack resistance. It is well known that natural rubber or synthetic rubber products tend to age due to heat, ozone, and repeated bending, making them unusable. Various methods have been proposed to prevent aging, most of which involve the use of various anti-aging agents. However, especially in recent years, there is a strong desire to maintain a long lifespan under conditions where rubber products tend to age more easily, such as the shift to radial tires and faster belt conveyors, and conventional anti-aging agents may not be sufficient. Performance could not be obtained. For example, 2-mercaptobenzimidazole,
2-Mercaptomethylbenzimidazole, N-
Phenyl-N'-alkyl-p-phenylenediamine and the like are known as anti-aging agents for rubber, but not only are they unsatisfactory in terms of performance, but they are also easily extracted from rubber products by organic solvents. Moreover, it could not maintain a long service life because it could volatilize from the rubber surface due to heat. For this reason, the present inventors are working diligently to develop an anti-aging agent that has excellent performance in heat resistance, ozone resistance, and flex resistance, and that can maintain its performance even after long-term use. As a result of the study, certain imidazole compounds and N-phenyl-N'-
It was discovered that alkyl-p-phenylenediamine forms a salt in a high-temperature organic solvent, and that this salt has an excellent effect as an anti-aging agent for rubber, and that the above object can be achieved. This led to an invention. That is, the present invention provides 2-mercaptobenzimidazole or 2-mercaptomethylbenzimidazole and N-phenyl-N'-alkyl-p
- Provides an anti-aging agent for rubber, characterized in that it contains a salt with phenylenediamine (alkyl means an alkyl group having 3 to 8 carbon atoms) as an active ingredient. N-phenyl-N'-alkyl-p-phenylenediamine as a raw material used in the present invention is:
For example, N-phenyl-N'-isopropyl-p
-phenylenediamine, N-phenyl-N'-sec
-Butyl-p-phenylenediamine, N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine, N-phenyl-N'-octyl-p-
phenylenediamine, and such N-phenyl-N'-alkyl-p-phenylenediamine and 2-mercaptobenzimidazole or 2-mercaptobenzimidazole.
-Salts with mercaptomethylbenzimidal are
The amine and the imidazole are dissolved in a suitable organic solvent in a reaction molar ratio, and heated and stirred under reflux, usually at normal pressure or under pressure, to obtain a precipitate, which is separated by filtration etc. and dried. It can be easily manufactured by In this case, the organic solvents include alcohols, ketones,
Hydrocarbon compounds such as benzene, toluene, and xylene are used. The anti-aging agent of the present invention containing the above-mentioned salt as an active ingredient imparts excellent heat resistance, flexibility resistance, and ozone resistance to rubber products when it is blended with rubber.
Furthermore, it has excellent performance in that its effects are maintained over a long period of time. The anti-aging agent for rubber of the present invention is applicable not only to natural rubber but also to synthetic rubbers such as styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, ethylene-propylene copolymer rubber, polybutadiene rubber, polyisoprene rubber, and polychloroprene rubber. It is useful, and when used, the amount added to rubber is usually 0.1 to 7 parts by weight, preferably 0.5 to 4 parts by weight, per 100 parts by weight of rubber. Further, when using the anti-aging agent for rubber of the present invention, other anti-aging agents and other additives may be used in combination, if necessary. The present invention will be explained below with reference to Examples. Reference example 1 2-mercaptobenzimidazole 1.5g
(0.01 mol) and N-phenyl-N'-isopropyl-p-phenylenediamine (purity 93.2%)
When 2.26 g of the solution is dissolved in a mixed solvent of 100 ml of methanol and 100 ml of acetone and heated and stirred at 90-100°C for 6 hours, a yellow precipitate is obtained. This precipitate was filtered and dried to obtain 2.4 g of a salt of 2-mercaptobenzimidazole and N-phenyl-N'-isopropyl-p-phenylenediamine.
I got it. Melting point 300℃ or higher Reference example 2 2-Mercaptomethylbenzimidazole 1.64
g (0.01 mol) and N-phenyl-N'-sec-
Butyl-p-phenylenediamine (purity 94.4%)
Using 2.4 g (0.01 mol), 2-mercaptomethylbenzimidazole and N
2.31 g of a salt with -phenyl-N'-sec-butyl-p-phenylenediamine was obtained. Melting point 300℃ or higher Reference example 3 2-Mercaptomethylbenzimidazole 1.64
g (0.01 mol) and N-phenyl-N'-1.3-
Dimethylbutyl-p-phenylenediamine (purity
94.7%) and treated in the same manner as in Reference Example 1 to combine 2-mercaptomethylbenzimidazole and N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine. salt 2.28
I got g. Melting point: 300°C or higher Reference example 4 2-mercaptobenzimidazole 1.5g
(0.01 mol) and 2.96 g of N-phenyl-N'-octyl-p-phenylenediamine (purity 96.3%)
(0.01 mol) and treated in the same manner as in Reference Example 1 to produce 2-mercaptomethylbenzimidazole and N-
2.06 g of a salt with phenyl-N'-octyl-p-phenylenediamine was obtained. Melting point: 300℃ or higher In addition, 2-mercaptobenzimidazole and N-
The melting point of a mixture of phenyl-N'-isopropyl-p-phenylenediamine (purity 93.2%) in a molar ratio of 1:1 is 68°C, and that of 2-mercaptobenzimidazole and N-phenyl-N'-1, 3-
Dimethylbutyl-p-phenylenediamine (purity
98.6%) in a molar ratio of 1:1, the melting point is 43°C.
It was hot. Example 1 100 parts of natural rubber, 45 parts of HAF carbon, 5 parts of zinc white
2.5 parts of sulfur, 1 part of stearic acid, 5 parts of process oil, 0.5 part of N-cyclohexylbenzothiazyl sulfenamide (vulcanization accelerator) and 2 parts of the anti-aging agent shown in Table 1. A sample was prepared by compounding the mixture using a 6-inch diameter open roll and vulcanizing it at 140°C for 80 minutes. Heat aging, ozone aging, and flex cracking tests were conducted using this sample. Each test was conducted in accordance with JIS K-6301, and the heat aging test was performed using a test tube heat aging machine at 100℃ for 48 hours, after which the retention rate (%) of breaking strength was measured. did. The ozone aging test was conducted in an ozone weather meter at an ozone concentration of 50pphm, a temperature of 40℃, and a dynamic elongation rate of 20%.
The time until a crack that can be measured with the naked eye occurs was measured. For the flex crack test, a scratch with an original length of 2 mm is made on the sample.
The length of the scratch was measured after bending 10,000 times. A similar test was also conducted after heat treatment at 100°C for 24 hours using gear open.

【table】

[Table] Example 2 100 parts of styrene-butadiene rubber, HAF carbon
50 parts, process oil 5 parts, zinc white 5 parts, stearic acid 3 parts, sulfur 2.5 parts, N-cyclohexylbenzothiazyl sulfenamide (vulcanization accelerator) 1 part, and anti-aging agent 2 similar to Example 1. The test was carried out in the same manner as in Example 1, using a 6-inch diameter open roll and vulcanizing the mixture at 145° C. for 30 minutes. The heat aging test used test pieces aged at 110°C for 48 hours, and the ozone aging and flex cracking tests used test pieces heat treated at 110°C for 24 hours. The results are summarized in Table 2.

【table】

【table】

Claims (1)

[Claims] 1 2-mercaptobenzimidazole or 2-mercaptomethylbenzimidazole and N-
An anti-aging agent for rubber, characterized in that the active ingredient is a salt with phenyl-N'-alkyl-p-phenylenediamine (alkyl refers to an alkyl group having 3 to 8 carbon atoms).