JPH0737607B2 - Antifreeze for car engine - Google Patents

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, which are used to prevent freezing of cooling water in a liquid-cooled internal combustion engine. More specifically, the present invention relates to an antifreeze liquid that is effective as a cooling liquid for an automobile engine in maintaining the functions of the cooling system of the automobile engine, such as rust prevention and corrosion prevention, in addition to antifreezing. (Prior Art) Conventionally, a cooling liquid for a liquid-cooled internal combustion engine, for example, an automobile engine, is mainly composed of alcohols or glycols to prevent freezing in the cold season, and various corrosion inhibitors are added to the antifreeze. Antifreeze that has both anti-corrosive and anti-corrosive properties is used. (Problems to be Solved by the Invention) Alcohols commonly used include methyl alcohol, ethyl alcohol, isopropyl alcohol and the like, and glycols include ethylene glycol, propylene glycol, hexylene glycol, glycerin and the like alone or Used as a mixture. Among them, an antifreeze solution containing monoethylene glycol as a main component is used as a cooling solution for a cooling system of an automobile engine. -1 at 30% by volume for monoethylene glycol aqueous solution
At 5.5 ℃ and 50% by volume, antifreeze effect up to -37.0 ℃ can be obtained. Alcohols or glycols are oxidized by contact with air to form acidic alcohols or glycol oxides. The formation of alcohols or glycols is further promoted at a high temperature of 50 to 100 ° C. The acidic alcohols or glycols significantly accelerate the corrosion of various metals constituting a cooling system of an internal combustion engine, especially an automobile engine. Corrosion of various metals forming the cooling system of the internal combustion engine causes a decrease in thermal conductivity due to deposition of corrosion products or blockage of the radiator pipe, which causes engine overheating. Since the antifreeze solution containing alcohols or glycols as a main component has no anticorrosion effect on alcohols or glycols themselves, a corrosion inhibitor is added. As the anticorrosive agent, borax, sodium sulfite, phosphoric acid, silicate, sodium benzoate, sodium salt of mercaptobenzothiazole, benzotriazole, methylbenzotriazole, triethanolamine, diethanolamine, monoethanolamine, triisopropanolamine, At least one selected from diisopropanolamine, monoisopropanolamine, cyclohexylamine, ethylenediamine, hydrazine, pyridine, morpholine and the like is used. Typical of these are borax, triethanolamine phosphate,
Mention may be made of sodium benzoate, sodium nitrite and sodium silicate. Borax has been widely used as an anticorrosive agent for cast iron engines, but in recent years, aluminum parts have been adopted along with the weight reduction of automobile parts for resource saving and energy saving, and there are drawbacks in anticorrosiveness against aluminum materials. Having has become a problem. When an ethylene glycol aqueous solution containing borax is used in the cooling system of an automobile engine, it may corrode the aluminum alloy that is the material of the cylinder head and cylinder block of the engine, and the corrosion product may block the radiator. Are known. On the other hand, triethanolamine phosphate has excellent corrosion resistance against iron-based and aluminum materials, and has been used as an anticorrosive agent instead of borax, but it subsequently produces nitrosamine by the coexistence of triethanolamine and nitrite. It has been reported that it is desirable to avoid coexistence of amines and nitrite. In addition, sodium benzoate alone cannot be expected to have the effect of replacing these anticorrosive agents. On the other hand, sodium silicate is also effective as a corrosion inhibitor, but there is a problem that sodium silicate easily gels and separates during long-term storage. That is, it is an object of the present invention to provide an antifreeze solution which is particularly excellent in aluminum anticorrosion with a composition containing no amines. As a result of diligent studies, the present inventors have found that an antifreeze solution containing glycols and water contains (A) phosphoric acid, (B) aromatic polybasic acid, (C) magnesium compound, (D) anticorrosive agent. , The pH was in the range of 6.5 to 9.0, the object of the present invention could be achieved. (Means for Solving Problems) In the present invention, (A) phosphoric acid 0.1 to 5.0% by weight (B) aromatic polybasic acid 0.05 to 1.0% by weight (C) ) Magnesium compound 0.001 to 0.08% by weight (D) Anticorrosive 0.05 to 10.0% by weight and pH in the range of 6.5 to 9.0. Examples of the phosphoric acid of the present invention include phosphoric acid and salts thereof. In addition to orthophosphoric acid, first to third salts of alkali metals such as lithium, sodium and potassium can be used. The amount added is 0.1 to 5.0% by weight, preferably 0.5 to 3.0% by weight, based on the stock solution of antifreeze. As the aromatic polybasic acids of the present invention, benzene polycarboxyl-substituted compounds such as phthalic acid, isophthalic acid, terephthalic acid, hemimellitic acid, trimellitic acid, trimesic acid, and pyromellitic acid can be used. Further, salts of these aromatic polybasic acids can also be used. The amount of aromatic polybasic acid added is 0.05 to 1.0% by weight, preferably 0.1 to 0.5% by weight, based on the stock solution of antifreeze. As the magnesium compound of the present invention, magnesium oxide, magnesium hydroxide, magnesium permanganate,
Magnesium chromate, magnesium fluoride, magnesium iodide, magnesium carbonate, magnesium nitrate, magnesium sulfate, magnesium titanate, magnesium tungstate, 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 succinate, magnesium malate, magnesium tartrate, magnesium hydrogen tartrate, magnesium maleate, magnesium citrate. , Magnesium oxalate, magnesium malonate, magnesium sebacate, ammonium Kosan, magnesium phthalate, magnesium salicylate, magnesium mandelate and the like can be used. The addition amount of the magnesium compound of the present invention is in the range of 0.001 to 0.080% by weight, preferably 0.005 to 0.050% by weight, based on the stock solution of antifreeze. Examples of the anticorrosive agent of the present invention include sulfite, nitrate, silicate, molybdate, vanadate vanadate, sodium benzoate, sodium p-tert-butylbenzoate, mercaptobenzothiazole soda, methylbenzotriazole, benzo. At least one selected from triazole and the like is used. Typical of these are nitrates, molybdates, mercaptobenzothiazole soda, methylbenzotriazole, benzotriazole, and sodium benzoate. The amount of anticorrosive added is 0.05 to 10.0% by weight, preferably 0.1 to 7.0% by weight, based on the stock solution of antifreeze. For adjusting the pH of the antifreeze solution, a usual basic substance can be used, but hydroxides of alkali metals such as lithium, sodium and potassium are preferably used. If necessary, an acidic substance such as phosphoric acid can also be used. The pH adjustment range is 6.5-9.
It is 0, preferably 7.0 to 8.0. If the pH is higher than this range, the corrosion resistance to aluminum is poor, and if it is low, corrosion of iron occurs. Therefore, the pH 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 and scale inhibitors can be added. (Operation) As is clear from the results of Examples and Comparative Examples described later, the antifreeze solution of the present invention contains 0.1 to 5.0% by weight of (A) phosphoric acid and (B) aromatic polyamine in a stock solution of an antifreeze solution containing glycols and water. 0.05 to 1.0% by weight of basic acids (C) 0.001 to 0.08% by weight of magnesium compound (D) 0.05 to 10.0% by weight of anticorrosive agent, and pH in the range of 6.5 to 9.0 significantly improves the corrosion inhibition effect on aluminum. It is what is done. As is clear from the results of Examples and Comparative Examples described later, the antifreeze solution of the present invention is an antifreeze solution containing glycols and water, and each component is essential. Each component has the following action. (A) Phosphoric acid: Improves corrosion resistance of aluminum and iron. (B) Aromatic polybasic acids: An increase in pH can be suppressed. (C) Magnesium compound: improves the corrosion resistance of aluminum and iron. (D) Anticorrosion agent: improves the anticorrosion performance of the entire metal. By setting the pH of the antifreeze solution of the present invention in the range of 6.5 to 9.0, the corrosion resistance of aluminum is improved and there is no problem of iron pitting. (Examples) Next, the antifreeze solution of the present invention will be described in more detail with reference to Comparative Examples and Examples, but the present invention is not limited thereto.

[A] Metal corrosion test method [JIS-K-2234 (antifreeze), but antifreeze concentration is 15% by volume] Using aluminum cast, cast iron, steel, brass, solder, and copper metal test pieces, mixed water (sodium sulfate 148 mg , Sodium chloride 165 mg and sodium hydrogen carbonate 138 mg dissolved in distilled water 1) were soaked in an antifreeze solution diluted to 15% by volume, and the dry air was sent at a flow rate of 100 ± 10 ml / min while the antifreeze temperature was 88 ± 2 ° C. Hold for 336 hours. The mass of each metal piece before and after the test was measured to determine the change in mass.

[B] Heat Transfer Surface Corrosion Test Method Test Device The upper surface of the disc-shaped test piece was in contact with the antifreeze liquid, and the heater was heated from the lower surface so that the heat was transferred to the antifreeze liquid through the test piece. Performed on the device. Test method Test piece is ground with # 320 water resistant abrasive paper so that it becomes flat. Prepare the test solution to 20% by volume with distilled water or pure water. Sodium chloride is added to this solution so that chlorine ion becomes 100 ppm. After injecting the sample into the device, pressurize with air to 0.5 Kg / cm ² G. After completion of the test, the test piece is cleaned of adhered precipitates, dried and then precisely weighed. Test conditions Test piece: Aluminum casting (AC2A) Test piece temperature: 135 ± 1 ℃ Antifreeze concentration: 20% by volume Aqueous solution Antifreeze solution volume: 500 ml Test time: 168 hours (continuous) Test item Test piece appearance Change in test piece weight Mass Was calculated from the following equation. Here C = (m2-m1) / S, C: mass change (mg / cm ²⁾ m1: mass of specimen before test (mg) m2: mass of test piece after test (mg) S: Test Total surface area (cm ² ) of the previous test piece Liquid phase pH after the test Examples 1 to 6 The composition of Table-1 was added to 5 parts by weight of tap water or 95 parts by weight of monoethylene glycol at the composition ratio of Table-1. It melt | dissolved and both liquids were mixed. The following tests and measurements were performed on each sample.

[A] Metal corrosion test

[B] The heat transfer surface corrosion test results are shown in Table 1. Comparative Examples 1 to 5 Samples prepared with the compounding ratios in Table 1 were tested in the same manner as in Examples 1 to 6. The results are shown in Table 1. (Effect of the invention) In a stock solution of an antifreeze solution containing glycols and water, (A) phosphoric acid 0.1 to 5.0% by weight (B) aromatic polybasic acid 0.05 to 1.0% by weight (C) magnesium compound 0.001 to 0.08% by weight (D) By containing 0.05 to 10.0% by weight of an anticorrosive agent and having a pH in the range of 6.5 to 9.0, the effect of preventing corrosion on aluminum is remarkably improved. Comparative Example 1 in Table 1 shows that, in the antifreeze solution of the present invention consisting of glycols and water, the antifreeze solution containing no (A) phosphoric acid group is significantly inferior in corrosion inhibition effect. Comparative Example 2 in Table 1 shows that among the antifreeze solutions of the present invention consisting of glycols and water, the antifreeze solution containing no (B) aromatic polybasic acids has a markedly poor corrosion inhibiting effect. Comparative Example 3 in Table 1 shows that among the antifreeze solutions of the present invention consisting of glycols and water, the antifreeze solution containing no (C) magnesium compound is significantly inferior in corrosion inhibition effect. Comparative Example 4 in Table 1 shows that in the antifreeze solution comprising the glycols of the present invention and water, the antifreeze solution containing no (D) anticorrosive agent is remarkably inferior in anticorrosion effect. Comparative Example 5 in Table 1 shows that among the antifreeze solutions comprising the glycols of the present invention and water, the antifreeze solution having a pH outside the range of 6.5 to 9.0 has a markedly poor corrosion inhibiting effect.

Claims (1)

[Claims] 1. A stock solution of an antifreeze solution comprising glycols and water, wherein (A) phosphoric acid 0.1 to 5.0% by weight (B) aromatic polybasic acid 0.05 to 1.0% by weight (C) magnesium compound 0.001 to 0.08% by weight (D) An antifreeze solution for automobile engines, which contains 0.05 to 10.0% by weight of an anticorrosive agent and has a pH in the range of 6.5 to 9.0.