JPH01306492A - Antifreezing solution - Google Patents

Abstract

PURPOSE:To obtain an antifreezing solution free from amines and having especially excellent property to inhibit the corrosion of Al by compounding glycols with water and a corrosion-inhibitor comprising phosphoric acids, Mg compounds, nitric acid salts, etc., and adjusting the pH of the mixture to nearly neutral state. CONSTITUTION:The objective antifreezing solution is produced by compounding glycols and water with a corrosion-inhibitor consisting of (A) preferably 0.5-3.0wt.% of phosphoric acids such as ortho-phosphoric acid, (B) preferably 0.005-0.050wt.% of a magnesium compound such as magnesium oxide, (C) preferably 0.1-0.50wt.% of sodium mercaptobenzothiazole, (D) preferably 0.1-0.50wt.% of a nitric acid salt, (E) preferably 2.0-7.0wt.% of a benzoic acid salt and (F) preferably 0.1-0.5wt.% of an aromatic polybasic acid such as isophthalic acid and hemimellitic acid and adjusting the pH of the mixture to 6.5-9.0.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an antifreeze solution comprising glycols, water, and a corrosion inhibitor used for preventing freezing of cooling water of a liquid-cooled internal combustion engine. More specifically, the present invention relates to an antifreeze liquid that is used as a coolant for an automobile engine and is effective in maintaining the functions of the cooling system of an automobile engine, in addition to preventing freezing and preventing rust and corrosion.

(Prior art) Conventionally, the coolant for liquid-cooled internal combustion engines, such as automobile engines, has been made mainly of alcohols or glycols to prevent freezing in the next term, and various corrosion inhibitors have been added to this to prevent freezing. Antifreeze is used because it has both corrosion and anti-corrosion properties.

(Problems to be solved by the invention) - Methyl alcohol, ethyl alcohol, isopropyl alcohol, etc. are used as alcohols, and ethylene glycol, propylene glycol, hexylene glycol, glycerin, etc. are used alone as glycols. Or they are used in combination. Among these, antifreeze containing monoethylene glycol as a main ingredient is particularly used as a coolant in the cooling system of an automobile engine.

In the case of monoethylene glycol aqueous solution, at 30% by volume -
Antifreeze effect up to -37.0°C can be obtained with 150% by volume of 15,5'C.

Alcohols or glycols are oxidized by contact with air, producing acidic alcohol or glycol oxides. Under high temperature conditions of 50 to 100°C, the production of alcohol or glycol oxides is further promoted. These acidic alcohols or glycols significantly accelerate the corrosion of various metals constituting the cooling system of an internal combustion engine, especially an automobile engine.

Corrosion of various metals constituting the cooling system of an internal combustion engine causes a decrease in thermal conductivity due to deposition of corrosion products or blockage of the radiator pipe, causing the engine to overheat.

Antifreeze solutions containing alcohols or glycols as their main components have a corrosion inhibitor added to them because the alcohols or glycols themselves have no anticorrosion effect.

As anticorrosive agents, borax, nitrite, acid salt, nitrate, phosphate, silicate, sodium benzoate, sodium salt of mercaptobenzothiazole, benzotriazole, methylbenzotriazole, triethanolamine, jetanolamine, At least one selected from monoethanolamine, triisopropanolamine, diisopropanazine, monoisopropanazine, cyclohexylamine, ethylenediamine, hydrazine, pyridine, morpholine, etc. is used.

Representative among these are borax, triethanolamine phosphate, triethanolamine benzoate, triethanolamine nitrite, and triethanolamine sodium silicate. Borax has been widely used as an effective anti-corrosion agent for cast iron engines, but in recent years, aluminum parts have been adopted as automobile parts become lighter in order to conserve resources and energy. It has become a problem to have one.

When an aqueous ethylene glycol solution containing borax is used in the cooling system of an automobile engine, it can corrode the aluminum alloy that is the material of the engine's cylinder head and cylinder block, and the corrosion products can clog the radiator. Are known.

On the other hand, triethanolamine phosphate has excellent anticorrosion properties for iron-based and aluminum materials, and has been used as an anticorrosive agent in place of borax, but later, the coexistence of triethanolamine and nitrite produces nitrosamines. It has been reported that it is desirable to avoid the coexistence of amines and nitrites, and sodium benzoate alone cannot be expected to be effective enough to replace these anticorrosive agents.

On the other hand, sodium silicate is also effective as a corrosion inhibitor, but there is a problem in that sodium silicate tends to gel and separate during long-term storage.

That is, an object of the present invention is to provide an antifreeze solution that is a composition that does not contain amines and has particularly excellent aluminum corrosion resistance. As a result of extensive research, the present inventors found that in an antifreeze solution consisting of glycols and water, (A> phosphoric acids, (B) magnesium compound, (C) mercaptobenzothiazole soda, (D) nitrate, (E) benzoic acid, The object of the present invention could be achieved by containing an acid salt, (F) aromatic polybasic acid, and having a pH in the range of 6.5 to 9.0.

(Means for Solving the Problems) The present invention provides an antifreeze solution comprising glycols and water, (A) phosphoric acids, (B) magnesium compounds, (C) mercaptobenzothiazole soda, (D) nitrates, (E The present invention relates to an antifreeze solution containing: ) benzoate; (F) aromatic polybasic acid;

Examples of the phosphoric acids of the present invention include phosphoric acids and salts thereof. In addition to orthophosphoric acid, first to tertiary salts of alkali metals such as lithium, sodium, and potassium can be used. The amount added is 0.1 to 5.0 to the undiluted antifreeze solution.
% by weight, preferably 0.5-3.0% by weight.

Magnesium compounds of the present invention include magnesium oxide, magnesium hydroxide, magnesium permanganate, magnesium chromate, magnesium fluoride, magnesium iodide, magnesium carbonate, magnesium nitrate, magnesium sulfate, magnesium titanate, magnesium tungstate, and magnesium borate. , magnesium phosphate, magnesium dihydrogen phosphate, magnesium ammonium phosphate,
Magnesium formate, magnesium acetate, magnesium propionate, magnesium butyrate, magnesium valerate, magnesium laurate, magnesium stearate, magnesium oleate, magnesium glutamate, magnesium lactate, magnesium abate, magnesium malate, magnesium tartrate, magnesium hydrogen tartrate, Magnesium maleate, magnesium citrate, magnesium oxalate, magnesium malonate, magnesium sebacate, magnesium benzoate, magnesium phthalate, magnesium salicylate, magnesium mandelate, etc. can be used.

The amount of the magnesium compound of the present invention added is 0.001 to 0.080% by weight, preferably 0.0% by weight, based on the stock solution of antifreeze.
It ranges from 0.05 to 0.050% by weight.

The amount of sodium mercaptobenzothiazole of the present invention added is in the range of 0.05 to 0.70% by weight, preferably 0.1 to 0.50% by weight, based on the stock solution of antifreeze.

As the nitrate of the present invention, alkali metal salts such as sodium salts and potassium salts are used. The amount of nitrate added is in the range of 0.05 to 0.70% by weight, preferably 0.1 to 0.50% by weight, based on the stock solution of antifreeze.

As the benzoate of the present invention, alkali metal salts such as sodium salts and potassium salts are used. The amount of benzoate added is in the range of 1.0 to 7.0% by weight, preferably 2.0 to 7.0% by weight, based on the stock solution of the antifreeze solution.

As the aromatic polybasic acid of the present invention, benzene polycarboxyl substituted products such as phthalic acid, inphthalic acid, terephthalic acid, hemimellitic acid, trimellitic acid, trimesic acid, and pyromellitic acid can be used. Moreover, salts of these aromatic polybasic acids can also be used. The amount of aromatic polybasic acids added is 0.05 to 1.0% by weight based on the stock solution of antifreeze.
The preferred range is 0.1 to 0.5% by weight.

In addition, methylbenzotriazole, benzotriazole, etc. can be used.

Normal basic substances can be used to adjust the pH of antifreeze, but
The alkaline substance for pH adjustment is preferably lithium,
Hydroxides of alkali metals such as sodium and potassium are used. The pH adjustment range is 6.5 to 9.0, preferably 7.0 to 8.0. If P H is higher than this range, the corrosion resistance against aluminum will be poor, and if it is lower, corrosion of iron will occur, so it should be adjusted within the above range.

The antifreeze of the present invention includes silicone oil, mineral oil, alcohol,
Antifoaming agents such as higher fatty acid esters can be added.

(Example) Next, the antifreeze solution of the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Metal corrosion test method [JIS-2234 (antifreeze)] Using metal test pieces of aluminum casting, cast iron, steel, brass, solder, and copper, mixed water (sodium sulfate! 48 mg,
165 mg of sodium chloride and 13 mg of sodium bicarbonate
8mg dissolved in distilled water 11) diluted to 30% by volume with antifreeze solution, and dried air was added to 100±10ml/l.
While feeding the antifreeze at a flow rate of 88±2℃.
The temperature was maintained for 672 hours. The mass of each metal piece before and after the test was measured to determine the change in mass.

The change in mass of each metal is calculated from the following formula: 6C= (m
2-m 1)/S where: Change in Cx1i amount <mg/cd)m 1:
Mass of test piece before test (mg) m2: Mass of test piece after test (mg) S: Total surface area of test piece before test (-) Examples 1 to 6 It was dissolved in 5 parts by weight of water or 95 parts by weight of monoethylene glycol at the compounding ratio shown in Table 1, and both solutions were mixed.

The following tests and measurements were performed on each sample.

The metal corrosion test results are shown in Table-1.

Comparative Examples 1 to 5 The formulations shown in Table 1 were dissolved in 5 parts by weight of tap water or 95 parts by weight of monoethylene glycol at the blending ratio shown in Table 1, and both solutions were mixed.

The following tests and measurements were performed on the sample.

The metal corrosion test results are shown in Table-1.

(Effect of the invention) In the antifreeze solution comprising glycols and water of the present invention, (A) phosphoric acids, (B) magnesium compound, (C) mercagutobenzothiazole soda, (D) nitrate, (E) benzoate. , (F) aromatic polybasic acid, and the pH is in the range of 6.5 to 9.0, thereby significantly improving the corrosion prevention effect on aluminum and iron.

Patent applicant Nippon Shokubai Chemical Co., Ltd. Procedural amendment (
Voluntary) July kz, 1986

Claims (1)

[Claims] (1) In an antifreeze solution consisting of glycols and water, (A) phosphoric acid, (B) magnesium compound, (C) mercaptobenzothiazole soda, (D) nitrate, (E) benzoate, (F) aromatic An antifreeze solution containing a polybasic acid and having a pH in the range of 6.5 to 9.0.