JPS58122946A - Antioxidant for rubber - Google Patents

Abstract

PURPOSE:To provide an antioxidant for rubber excellent in resistance to heat, ozone, and flex cracking, contg. a salt of a particular imidazole compd. and an N-phenyl-N'-alkyl-P-phenylenediamine. CONSTITUTION:An antioxidant contg. a salt of 2-mercaptobenzimidazole or 2-mercaptomethylbenzimidazole and N-phenyl-N'-alkyl-P-phenylenediamine as an effective ingredient. Said salt may be readily prepd. by separating by filtration, etc. and drying a precipitate obtained by dissolving said amine and imidazole in an org. solvent in molar ratio required for reaction, followed by heating under reflux with stirring. Rubbers to be applied include natural rubber, styrene/ butadiene copolymer rubber, polybutadiene rubber, polychloroprene rubber, etc. The amt. of antioxidant added to rubber is usually 0.1-7pts.wt. based on 100pts.wt. rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti-aging 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. I can't get the performance.

For example, 2-mercaptobenzimidazole, 2-mercaptomethylpencil dazole, N-phenyl-N'
-Alkyl-p-phenylene diamines and the like are known as anti-aging agents for rubber, but not only are they unsatisfactory in terms of performance, they are also easily extracted from rubber products by organic solvents, and furthermore, they are easily extracted from rubber products by heat. It was not possible to maintain a long service life because it sometimes volatilized from the surface.

For this reason, the present inventors have developed an anti-aging agent that has excellent heat resistance, ozone resistance, and bending resistance, and can maintain its performance even after long-term use. As a result of extensive research, we found that a specific imidazole compound and N-phenyl-N'-furkyl-p-phenylenediamine form a salt in a high-temperature organic solvent, and that this salt is an excellent anti-aging agent for rubber. We have discovered that the above two objects can be achieved, and have arrived at the present invention.

That is, the present invention provides 2-mercaptobenzimidazole or 2-mercaptomethylbenzimidazole and N
Provided is an anti-aging agent for rubber, characterized in that the active ingredient is a salt with phenyl-N'-alkyl-p-phenylenediamino (alkyl refers to an alkyl group having 8 to 8 carbon atoms). It is.

N-phenyl-N'- as a raw material used in the present invention
Alkyl-p-phenylenediamine, even if Lf
N-phenyl-N'-isopropyl-p-phenylenesiaj7, N-phenyl-N'-〇θC-butyl-p-phenylenediamine, N-phenyl-N'-1,8-dimethylbutyl-p-phenylenediamine , N-phenyl-
NZ, 4-cutyl-p-phenylenediamine, etc., and Kakaro N-phenyl-N'-alkyl-p-phenylenediamino and 2-nulkaf 1 ~ penzimidazole mol, < is 2-mercap I-methylbenzimine Dahl and O)J can be obtained as a precipitate by dissolving the amine and the binder εdazole in a suitable organic solvent at a reaction molar ratio, and heating and stirring the mixture under reflux, usually at normal pressure or under pressure. It can be easily produced by separating it by filtration etc. and drying it. In this case, the organic solvents include alcohols, ketones, benzene, tolueno,
A hydrocarbon compound such as xylene may be used.1 The anti-aging agent of the present invention containing the above-mentioned salt as an active ingredient provides rubber products with excellent heat resistance, when blended with rubber.
It has excellent performance in that it provides flexibility and ozone resistance, and its effects are maintained over a long period of time.

The anti-aging agent for rubber of the present invention can be applied 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, polychloroprene rubber, etc. It is useful for rubber, and when used, the amount added to rubber is usually 0.
The amount is 1 to 7 parts by weight, preferably 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 2-mercaptobenzimidazole 1,5f (0,01
mole) and N-phenyl-N'-isopropyl-p-
When 2.26 r of phenylene diamine (purity 98.24) is dissolved in a mixed solvent consisting of 100 td of methanol and 100 ml of acetone and heated and stirred at 90 to 100°C for 6 hours, a yellow precipitate is obtained. Filter this precipitate,
By drying, 2.41 of the salt of 2-mercaptobenzimidazole and N-phenyl-N'-isopropyl-p-7 enylenediamine was obtained.

Melting point: 300°C or higher”2 Reference Example 2 2-Mercap] Methylbenciimidazole 1.64
? (0.01 mol) and N-7 to IL/-N'
-5ec-butyl-p-V enylenediamine (purity 9
4.4%) using 2.4f (0.01 mol), Reference Example 1
Similarly, 2-mercaptomethylbenzimidazole,! :N-phenyl-N'-5ac-butyl-p-phenylenediamine salt2. B1f was obtained.

Melting point 800°C or higher Reference example 8 2-mercaptomethylbenzimidazole 1.64 ?
(0,01 mol) and N-7x = ru N'-1,
8-dimethylbutyl-p-phenylenediamine (purity 9
4,7 width) 2.68f (0.01 mol) was treated in the same manner as in Reference Example 1 to produce 2-mercaptomethylbenzimidazole and N-phenyl-N'-1,8-dimethylbutyl-p-phenylene. [2,28] with diamine was obtained.

Melting point 800'C or higher Reference example 4 2-mercaptobenzimidazole 1.57 (Q, 01
mole) and N-phenyl-N'-o))"f-lep
'Phenylene diamine (purity 96.8 width) 2.96r
(0.01 mol) and treated in the same manner as in Reference Example 1.
-Salt of mercaptomethylbenzimidazole and N-phenyl-N'-octyl-p-phenylenediamine2.
061 was obtained.

Melting point: 300°C or higher -1- The melting point of a 1:1 molar mixture of 2-mercaptobenzimidazole and N-phenyl-N'-1 sobrobyl-p-phenylenediamine (purity 98.24) is 68°C.
and 2-mercaptobenzimidazole and N-
The melting point of a mixture with -phenyl-N/-1,3-dimethylbutyl-p-phenylenediamine (pure &98.64) in a molar ratio l:1 was 43°C.3 Example 1 100 parts of natural rubber, HA 45 parts of F carbon, 5 parts of zinc white, 2.5 parts of sulfur, 1 part of stearic acid, 5N of flose oil
, 0.5 parts of N-cyclohexylbenzothiazylsulfenamide (an i-stimulating agent) and 2 parts of the anti-aging agent shown in Table 1 were rolled into 6-inch open rolls by a conventional method. A sample was prepared by blending and vulcanizing at 140°C for 80 minutes.This sample was used for heat aging, ozone aging,
A flex crack test was conducted.

Each test was conducted in accordance with JiSK-6801, and the heat aging test was conducted using a test tube heat aging machine.
After heat aging at ℃ for 48 hours, the retention rate of breaking strength was measured.

The ozone aging test was performed by measuring the time until the appearance of a rack with the naked eye in an ozone weather meter at an ozone concentration of 50 pphm, a temperature of 40° C., and a dynamic elongation rate of 20.

In the bending crack test, a scratch with an original length of 2I is made on the sample and the length of the scratch is measured after being bent 10,000 times. Further, the same test was conducted after heat treatment at 100° C. for 24 hours using a gear oven.

\ (9) Table 1 (10) Example 2 100 parts of styrene butadiene rubber, 50 parts of HAF carbon
part, process oil 5 parts, zinc white 5 parts, stearic acid 8 parts,
A formulation consisting of 2.5 parts of sulfur, 1 part of N-cyclohexylbenzothiazylsul-7enamide (vulcanization accelerator), and 2 parts of the same anti-aging agent as in Example 1 was prepared into a 6-inch open roll using a conventional method. A test was carried out in the same manner as in Example 1 using a compound that was blended at 145°C and vulcanized for 30 minutes.

The heat aging test used test pieces aged at 110° C. for 48 hours, and the ozone aging and flex crack tests used test pieces heat treated at 110° C. for 24 hours. The results are summarized in Table 2.

(11) (12)

Claims (1)

[Claims] 2-mercaptobenzimidazole or 2-mercaptomethylbenzimidazole and N-7enyl-N'-
An anti-aging agent for rubber, characterized in that the active ingredient is a salt of alkyl-p-phenylenediyl(alkyl means an alkyl group having 3 to 8 carbon atoms).