JPH0228625B2 - FUTOEKI - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an antifreeze solution comprising glycols, water, and a corrosion inhibitor used to prevent freezing of cooling water of a liquid-cooled internal combustion engine. More specifically, it is used as a coolant for automobile engines to prevent freezing, as well as to prevent rust.
This relates to antifreeze that is effective in maintaining the functions of automobile engine cooling systems, such as corrosion protection. (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 during cold seasons, and various corrosion inhibitors have been added to this to prevent freezing. Antifreeze is used because it has both corrosion and anti-corrosion properties. (Problem to be Solved by the Invention) Commonly used alcohols include methyl alcohol, ethyl alcohol, isopropyl alcohol, etc., and glycols include ethylene glycol, propylene glycol, hexylene glycol, glycerin, etc. 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, the antifreeze effect can be obtained up to -15.5°C at 30% by volume and -37.0°C at 50% by volume. Alcohols or glycols are oxidized by contact with air, producing acidic alcohol or glycol oxides. 50-100
Under high temperature conditions of .degree. C., the formation of oxides of alcohols or glycols is even more accelerated. 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 radiator pipes, causing engine overheating. 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. Anticorrosive agents include borax, sodium nitrite, phosphoric acid, silicates, sodium benzoate, sodium salt of mercaptobenzothiazole, benzotriazole, methylbenzotriazole, triethanolamine, diethanolamine, monoethanolamine, triisopropanolamine. , diisopropanolamine, monoisopropanolamine, cyclohexylamine, ethylenediamine,
At least one selected from hydrazine, pyridine, morpholine, etc. is used. Representative among these are borax, triethanolamine phosphate, sodium benzoate, sodium nitrite, and 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. Having one has become a problem. When an ethylene glycol aqueous solution containing borax is used in the cooling system of an automobile engine, it corrodes the aluminum alloy that is the material of the cylinder head and cylinder block of the engine, 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 the coexistence of amines and nitrites should be avoided. Furthermore, 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) aromatic polybasic acids, (C) molybdates or tungstates, (D) Anticorrosive agent and (E) General formula (1) H(OA) _o OH...(1) (A is a _C2 - _C3 alkylene group, n
The object of the present invention could be achieved by containing a polyglycol represented by a number 2 to 10 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) aromatic polybasic acids, (C) molybdates or tungstates, ( D) Corrosion inhibitor and (E) General formula (1) H(OA) _o OH...(1) (However, A is a _C2 - _C3 alkylene group, n
The invention relates to an antifreeze solution containing a polyglycol represented by a number from 2 to 10 and having a pH in the range of 6.5 to 9.0. Examples of the phosphoric acids of the present invention include phosphoric acids and salts thereof. In addition to orthophosphoric acid, lithium,
Alkali metals such as sodium and potassium
Tertiary salts can be used. The amount added is 0.1 to 5.0% by weight, preferably 0.5 to 5.0% by weight, based on the stock solution of antifreeze.
It is 3.0% by weight. As the aromatic polybasic acids of the present invention, benzene polycarboxyl group-substituted products such as phthalic acid, isophthalic 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
0.05-1.0% by weight, preferably 0.1-0.5% by weight. As the molybdate and tungstate of the present invention, alkali metal salts such as sodium salts and potassium salts are used. The amount of molybdate and tungstate added is based on the antifreeze stock solution.
0.10-1.0% by weight, preferably 0.3-0.7% by weight. The anticorrosive agent of the present invention includes nitrites, nitrates,
At least one selected from silicate, vanadate vanadate, sodium benzoate, sodium p-tertiarybutylbenzoate, sodium mercaptobenzothiazole, methylbenzotriazole, benzotriazole, etc. is used. Representative among these are nitrates, sodium mercaptobenzothiazole, methylbenzotriazole, and sodium benzoate. The amount of the anticorrosive agent added is 0.05 to 7.0% by weight, preferably 0.1 to 5.0% by weight, based on the stock solution of antifreeze. General formula (1) of the present invention H(OA) _o OH...(1) (However, A is a _C2 - _C3 alkylene group, n
is a number from 2 to 10) Examples of polyglycols include diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (average molecular weight 200-300), tripropylene glycol, polypropylene glycol (average molecular weight 200-400), and ethylene glycol. or ethylene oxide and propylene oxide adducts of diethylene glycol (random or block) and mixtures thereof. Among these, preferred are diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (average molecular weight
200-300). General formula (1) of the present invention H(OA) _o OH...(1) (However, A is a _C2 - _C3 alkylene group, n
The amount of polyglycol added (indicated by a number from 2 to 10) is in the range of 1 to 30% by weight, preferably 5 to 15% by weight, based on the stock solution of the antifreeze solution. For adjusting the pH of the antifreeze solution, ordinary basic substances can be used, but hydroxides of alkali metals such as lithium, sodium, and potassium are preferably used. Acidic substances such as phosphoric acid can also be used if necessary. PH
The adjustment range is 6.5 to 9.0, preferably 7.0 to
It is 8.0. If the PH is higher than this range, the corrosion protection against aluminum will be poor, and if it is lower, iron will corrode, so it should be adjusted within the above range. Antifoaming agents and scale inhibitors such as silicone oil, mineral oil, alcohol, and higher fatty acid ester can be added to the antifreeze solution of the present invention. (Function) As is clear from the results of Examples and Comparative Examples described below, the antifreeze solution of the present invention contains (A) phosphoric acids, (B) aromatic polybasic acids, (C ) Molybdate or tungstate, (D) Corrosion inhibitor and (E) General formula (1) H(OA) _o OH...(1) (However, A is a _C2 - _C3 alkylene group, n
contains a polyglycol represented by a number from 2 to 10) and has a pH in the range of 6.5 to 9.0, which significantly improves the corrosion prevention effect on aluminum. As is clear from the results of the Examples and Comparative Examples described later, each of the ingredients is essential in the antifreeze solution of the present invention, which is composed of glycols and water. Each component has the following effects. (A) Phosphoric acids: Improves the corrosion resistance of aluminum and iron. (B) Aromatic polybasic acids: Can suppress the increase in PH. (C) Molybdate or tungstate: improves the corrosion resistance of aluminum and iron. (D) Corrosion inhibitor: Improves the corrosion resistance of the entire metal. (E) General formula (1) of the present invention H(OA) _o OH...(1) (However, A is a _C2 - _C3 alkylene group, n
is a number from 2 to 10): The corrosion resistance of aluminum is improved and there is no problem of pitting of iron. By setting the pH of the antifreeze 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 pitting of iron. (Example) 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)] Aluminum casting, cast iron, steel, brass, solder,
Using each metal test piece of copper, mix water (148 mg of sodium sulfate, 165 mg of sodium chloride, and 138 mg of sodium hydrogen carbonate dissolved in 1 part of distilled water) to 30%
Dry air soaked in antifreeze diluted to 100% by volume
The antifreeze temperature was maintained at 88±2° C. for 336 hours while pumping at a flow rate of ±10 ml/min. 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 (1) Test device The top surface of a disc-shaped test piece is in contact with the antifreeze liquid, and the bottom surface is heated by a heater, so that heat is transferred to the antifreeze liquid via the test piece. It was carried out using a device designed to (2) Test method: Polish the test piece with #320 water-resistant abrasive paper until it is flat. The test solution is prepared to 25% by volume with distilled or pure water. This solution contains chlorine ions.
Add sodium chloride to 100ppm. After injecting the sample into the device, 0.5Kg/ ^cm2 with air
Apply pressure to G. After the test is completed, remove any deposits from the test piece, dry it, and weigh it accurately. (3) Test conditions Test piece: Aluminum casting (AC2A) Test piece temperature: 135±1℃ Antifreeze concentration: 25% by volume aqueous solution Antifreeze liquid volume: 500ml Test time: 168 hours (continuous) (4) Test items Test piece appearance Change in mass of test piece The change in mass was determined from the following equation. C=(m2-m1)/S Where, C: Change in mass (mg/ ^cm2 ) m1: Mass of test piece before test (mg) m2: Mass of test piece after test (mg) S: Test Total surface area of previous test piece (cm ² ) Liquid phase PH after test Examples 1 to 7 The formulations in Table 1 were added to 5 parts by weight of tap water or 95 parts by weight of monoethylene glycol at the mixing ratio shown in Table 1. Dissolved and mixed both solutions. The following tests and measurements were performed on each sample. [A] Metal corrosion test [B] Heat transfer surface corrosion test The results are shown in Table-1. Comparative Examples 1 to 6 Samples prepared at the blending ratios shown in Table 1 in the same manner as Examples 1 to 7 were tested. The results were as shown in Table-1.

【table】

[Table] (Effects of the invention) In the antifreeze solution comprising glycols and water of the present invention, (A) phosphoric acids, (B) aromatic polybasic acids, (C) molybdates or tungstates, (D) Anticorrosive agent and (E) General formula (1) of the present invention H(OA) _o OH...(1) (However, A is a _C2 - _C3 alkylene group, n
contains a polyglycol represented by a number from 2 to 10) and has a pH in the range of 6.5 to 9.0, which significantly improves the corrosion prevention effect on aluminum.

Claims (1)

[Claims] 1. An antifreeze solution consisting of glycols and water, (A) phosphoric acids, (B) aromatic polybasic acids, (C) molybdate or tungstate, (D) anticorrosive and ( E) Contains polyglycol represented by general formula (1) H(OA) _o OH...(1) (where A is a _C2 - _C3 alkylene group, n is a number from 2 to 10), and has a pH of 6.5 Antifreeze characterized by a range of ~9.0.