JPH0128108B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention particularly relates to a rust preventive agent represented by the following general formula that is effective against a wide range of metals such as iron-based, copper-based, and aluminum-based metals. [In the formula, R represents any one of an amino acid, a methyl group, or a hydroxyl group, and n represents an integer of 0 to 2. X represents a C ₀ -C ₅ linear or branched saturated or unsaturated aliphatic divalent group or a C ₆ -C ₁₀ aromatic divalent group. Y is a hydrogen atom, an alkali metal, an alkaline earth metal, or a quaternary ammonium group, and m represents the same integer as the valence of Y. ] Conventionally used iron-based rust inhibitors include sodium nitrite, phosphorus-based compounds, and chromium-based compounds. However, these rust inhibitors, for example,
Sodium nitrite has the problem of carcinogenicity due to nitroso compounds produced by reaction with amines.
Chromium-based materials have drawbacks such as the toxicity of chromium ions, and phosphorus-based materials have drawbacks such as eutrophication due to phosphorus compounds, so their use is becoming restricted. Nevertheless, a water-soluble rust inhibitor for iron-based rust that is as effective as sodium nitrite has not yet been available, so it is widely used. However, this sodium nitrite cannot be said to be an effective rust inhibitor for copper-based metals, especially iron-based metals and copper-based metals.
Alternatively, the combination of copper-based metal and aluminum-based metal is disadvantageous, and in terms of sustainability, it is susceptible to decomposition by microorganisms and has a short lifespan. Similarly, aliphatic carboxylic acids and aliphatic dicarboxylic acids are well known as iron-based rust preventive agents, but they are not widely used because they are inferior in terms of effectiveness. In addition, as effective rust inhibitors for copper-based metals, benzotriazole and its derivatives, and 2-
There are mercaptobenzothiazole salts and the like, but their drawback is that they are not effective against iron-based metals. In view of these drawbacks of conventional products, the present inventors
As a result of intensive research, we have developed a rust preventive agent that is extremely effective against metals such as iron, copper, and aluminum, and has a stable effect. In other words, it is a compound consisting of a carboxylic acid having a benzothiazole ring, or its alkali metal or alkaline earth metal salt, or ammonium salt or amine salt, and although it is the same carboxylic acid type, it is a conventionally known carboxylic acid. It is surprising that it exhibits a much stronger rust-preventing power than acids, and that it can also exhibit extremely stable rust-preventing power against aluminum-based and copper-based metals. The product of the present invention is a highly stable compound synthesized from the sodium salt of 2-mercaptobenzothiazole or the sodium salt of nuclear-substituted 2-mercaptobenzothiazole and a halogenated alkylcarboxylic acid or a halogenated arylcarboxylic acid. It is a compound. Examples include 2-benzothiadylthioacetic acid, 4-methyl-2-benzothiadylthioacetic acid, 6-amino-2-benzothiadylthioacetic acid, 6-hydroxy-2-benzothiadylthioacetic acid, 2- Benzothiazylthioformic acid, 3-(2
-benzothiadylthio)-propionic acid, 3-(4
-Methyl-2-benzothiadylthio)-propionic acid, 3-(6-amino-2-benzothiadylthio)-propionic acid, 3-(6-hydroxy-2-
Benzothiazylthio)-propionic acid, 3-(4,
6-dimethyl-2-benzothiadylthio)-propionic acid, 2-(2-benzothiadylthio)-propionic acid, 2-(4-methyl-2-benzothiadylthio)-propionic acid, 5-( 2-benzothiadylthio)-valeric acid, 3-(2-benzothiadylthio)-valeric acid, 5-(5,6-dihydroxy-2-
benzothiadylthio)-valeric acid, 5-(4-methyl-2-benzothiadylthio)-valeric acid, 3-(2-
benzothiadylthio)-acrylic acid, 3-(4-methyl-2-benzothiadylthio)-acrylic acid,
4-(2-benzothiadylthio)-butyric acid, 4-(4
-Methyl-2-benzothiadylthio)-butyric acid, 4
-(6-amino-2-benzothiadylthio)-butyric acid, 2-(2-benzothiadylthio)-benzoic acid,
Examples include 2-(4-methyl-2-benzothiadylthio)-benzoic acid. The product of the present invention may be an alkali metal salt or an alkaline earth metal salt of these carboxylic acids. Examples of the alkali metal include lithium, sodium, and potassium, and examples of the alkaline earth metal include magnesium, calcium, and strontium. etc. In particular, sodium and potassium salts are effective in improving water solubility. By introducing a quaternary ammonium group into the product of the present invention in addition to these metals, the effect can be enhanced due to improved water solubility and the antirust action of the ammonium group. Examples include -H.Z, where Z is ammonia and alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine, monoethylamine,
Aliphatic amines such as diethylamine and tributylamine, alicyclic amines such as dicyclohexylamine and cyclohexylamine, heterocyclic amines such as morpholine and pyridine, and polyethylene polyamines such as diethylenetriamine, triethylenetetramine, and tetraethylenepentamine. can be mentioned. The rust preventive agent of the present invention can be used in cooling water systems or heating systems in chemical plants that come into contact with water, antifreeze for vehicles, heat transfer systems in solar systems, rust preventive oils,
It is effective in paints, rust preventive agents for concrete, high water content hydraulic fluids, antifreeze for vehicles used in places where many combinations of various metals are used, and heat transfer systems in solar systems. Naturally, the use of the product of the present invention is not limited to this. In addition, the effect can be further improved by using the rust preventive agent of the present invention together with a known rust preventive agent. This will be explained below by giving synthesis examples and examples. Synthesis Example Add and dissolve 20 parts of 2-mercaptobenzothiazole sodium salt in 200 parts of methanol, heat to 40°C and stir. Separately, add a solution of 14 parts of β-chloropropionate sodium salt in methanol.
Add dropwise over 30 minutes, and after completion of the dropwise addition, heat to reflux to complete the reaction. Next, methanol was distilled off, the resulting crystalline substance was dissolved in water again to make it acidic, and then cooled.
The obtained crystalline substance was washed with sufficient cold water and dried to obtain 23 parts of white crystalline substance [3-(2-benzothiadylthio)propionic acid] with a melting point of 141-143°C (yield 93%).
get. (Literature value: 142-143°C) The obtained product was reacted with an equivalent amount of sodium hydroxide, and used in Examples as 3-(2-benzothiadylthio)-propionate sodium salt. The compounds of Examples 2 to 12 below were also obtained by the same method, and each was used as a sodium salt, potassium salt, or amine salt in the Examples. As a comparative example, additive-free, sodium nitrite,
2-mercaptobenzothiazole sodium salt,
Benzotriazole, triethanolamine, sebacic acid sodium salt and triethanolamine salt were used. The test liquid used was city water with the following water quality.
Pour 350 ml of the specified chemical (product of the present invention) into 500 ml of Kolben, and prepare a test piece (SPCC steel plate, 50 φ x 1 mm, copper plate) with a 5φ hole in the center.
TCuPl, 50φ x 1mm) was polished with waterproof abrasive paper #320 in advance, degreased with 10% NaOH, washed with water, degreased with acetone again, dried, mounted on a stirring rod equipped with a stirring motor, and placed in the center of the Kolben liquid section. let me,
The test piece is kept at 50℃ in a constant temperature bath and tested for one week while rotating at 120rpm. During this period, water was replenished to maintain a constant liquid level. The degree of corrosion (mdd) is calculated from the corrosion weight loss of the test piece after one week. Corrosion degree (mdd) = Corrosion loss (mg) / Number of test days (day) / Test piece surface area (dm ² ) The obtained test results are shown in the table.

【table】

【table】

[Table] From the examples, it was found that carboxylic acid salts having a benzothiazole ring are extremely effective rust inhibitors for iron-based, copper-based metals, and the like.

Claims (1)

[Claims] 1. General formula [In the formula, R represents any one of an amino group, a methyl group, and a hydroxyl group, and n represents an integer of 0 to 2. X represents a C ₀ -C ₅ linear or branched saturated or unsaturated aliphatic divalent group or a C ₆ -C ₁₀ aromatic divalent group. Y is a hydrogen atom, an alkali metal, an alkaline earth metal, or a quaternary ammonium group, and m represents the same integer as the valence of Y. ] Rust preventive agent.