JPH0336851B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an antiaging agent for rubber that has excellent heat resistance and flex cracking resistance. It is well known that natural rubber or synthetic rubber products generally age due to heat and repeated bending and become unusable. Various methods have been proposed to prevent such aging, and most of them involve the use of various anti-aging agents. However, especially in recent years, there has been a strong desire for rubber products to maintain a long service life under conditions where they are more prone to aging, such as the shift to radial tires and faster belt conveyors, and conventional anti-aging agents are not sufficient. However, the performance could not be achieved. For example, 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole,
2,2,4-trimethyl-1,2-dihydroquinoline polymers and the like are known as anti-aging agents for rubber. It was easily extracted from the soil and could not maintain its lifespan over a long period of time. For this reason, the inventors particularly focused on heat resistance,
As a result of intensive research to develop an anti-aging agent that provides excellent flexibility and maintains its performance even after long-term use, we found that a specific imidazole compound and 2,2,4-trimethyl-1 , 2-dihydroquinoline polymer forms a salt in a high-temperature organic solvent, and it was discovered that this salt has an extremely excellent effect as an anti-aging agent for rubber, and can achieve the above object, and the present invention Completed the invention. That is, the present invention provides 2-mercaptobenzimidazole or 2-mercaptomethylbenzimidazole and 2,2,4-trimethyl-1,2-
The present invention provides an anti-aging agent for rubber containing a salt with a dihydroquinoline polymer as an active ingredient. 2,2,4- as a raw material used in the present invention
Trimethyl-1,2-dihydroquinoline polymers are described, for example, in "Handbook of Rubber and Plastic Compounded Chemicals [Revised Board]" (Rubber Digest Co., Ltd., 1972).
As described on page 89 of the issue published on October 15th, it is known as an anti-aging agent for rubber and is commercially available. In the present invention, such commercially available products can usually be used as they are. It is produced, for example, by the condensation of aniline with acetone, diacetone alcohol or mesityl oxide under an acidic catalyst, and generally has the formula The main structure is as shown in , but the bonding positions of dimers and above are not necessarily constant, and
It may also contain partially bound aniline or acetone. This quinoline polymer is said to have a degree of polymerization (the value of n in the above formula) that is distributed approximately from 1 to 7, has a softening point of 70°C or higher, and is an amber to brown resinous powder. . 2-Mercaptobenzimidazole or 2
-mercaptomethylbenzimidazole and 2,
A salt with a 2,4-trimethyl-1,2-dihydroquinoline polymer is prepared by dissolving the imidazole and quinoline polymer in, for example, a suitable organic solvent, and generally heating and stirring the mixture under reflux under normal pressure or increased pressure. It is obtained as a precipitate by doing this, and it can be easily produced by separating this by filtration and drying. In this case, alcohols, ketones, or hydrocarbon compounds such as benzene, toluene, and xylene are used as the organic solvent. Furthermore, it has the excellent performance of imparting excellent heat resistance and bending resistance to rubber products and retaining these effects 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. When used, the amount added to rubber is usually 0.1 to 7 parts by weight per 100 parts by weight of rubber.
Preferably it is 0.5 to 4 parts by weight. 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 1.5 g of 2-mercaptobenzimidazole and 1.73 g of 2,2,4-trimethyl-1,2-dihydroquinoline polymer (dimer content 18.8% by weight)
was dissolved in a mixed solvent consisting of 100 ml of methanol and 100 ml of acetone, and heated at 90 to 100°C for 6 hours.
A yellow precipitate is obtained upon stirring. This precipitate was filtered and dried to obtain 2.1 g of a salt of 2-mercaptobenzimidazole and 2,2,4-trimethyl-1,2-dihydroquinoline polymer. Melting point: 300°C or higher Reference example 2 1.6 g of 2-mercaptobenzimidazole and 1.73 g of 2,2,4-trimethyl-1,2-dihydroquinoline polymer (dimer content 29.5% by weight)
was treated in the same manner as in Reference Example 1 to obtain 2.25 g of a salt of 2-mercaptobenzimidazole and 2,2,4-trimethyl-1,2-dihydroquinoline polymer.
I got it. Melting point: 300°C or higher Reference Example 3 Using 1.5 g of 2-mercaptobenzimidazole and 1.73 g of 2,2,4-trimethyl-1,2-dihydroquinoline polymer (dimer content 38% by weight), the same procedure as in Reference Example 1 was carried out. 2-mercaptobenzimidazole and 2,2,4-trimethyl-
2.05 g of a salt with a 1,2-dihydroquinoline polymer was obtained. Melting point: 300°C or higher The melting points of a simple mixture of both raw materials in the combinations of raw materials in Reference Examples 1 to 3 were 81°C, 78°C, and 75°C, respectively. Example 1 100 parts of natural rubber, 45 parts of HAF carbon, 5 parts of zinc white
1 part 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. By method, 6″〓Mixed in open roll, 40cm at 140℃
Samples were prepared by vulcanization for minutes. A heat aging test and a flex crack test were conducted using this sample. The heat aging test was conducted in accordance with JISK-6301, and the retention rate (%) of breaking strength was measured after heat aging at 100°C for 48 hours using a test tube heat aging machine. The bending crack test was conducted in accordance with JISK-6301, by making a scratch with an original length of 2 mm on the sample, and measuring the length of the scratch after being bent 10,000 times. In addition, a similar test was conducted on a sample that had been heat aged in a gear oven at 100°C for 24 hours. The results are summarized in Table 2.

【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-cyclohexyl-benzothiazyl sulfenamide (vulcanization accelerator) 1
A heat aging test was carried out in the same manner as in Example 1 for a compound consisting of 1 part and 2 parts of the anti-aging agent shown in Table 1, which was compounded using a 6-inch φ open roll in a conventional manner and vulcanized at 145°C for 30 minutes. A flex crack test was conducted. The heat aging test was performed at 110°C for 24 hours, and the bending crack test was performed by measuring the length after being bent 5,000 times. The results are summarized in Table 2.

【table】

Claims (1)

[Claims] 1 2-mercaptobenzimidazole or 2-mercaptomethylbenzimidazole and 2,
An anti-aging agent for rubber, characterized in that the active ingredient is a salt with a 2,4-trimethyl-1,2-dihydroquinoline polymer.