JPH0542995B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an antifreeze composition used for cooling an automobile radiator, and more particularly, to an antifreeze composition suitable for a radiator made of aluminum. [Prior Art and Problems to be Solved by the Invention] In general, in order to cool automobile engines, known documents (“Antifreezes and deicing fluids” in
Encyclopedia of chemical Technology, RE
Kirk and DEOthmer Eds.Gohn Wiley and
Sons, Inc., New York, 1978, Vol.3 p79−
95), alcohol, oil,
Water and various aqueous solutions are used. Among these, an aqueous solution of ethylene glycol is widely used as an antifreeze coolant because it has a high boiling point and a low freezing point, which prevents the cooling water from freezing, and it has the advantage of being non-volatile. This is because it has However, the engine material has a weakness that causes corrosion, so in order to suppress that corrosion,
Various anti-corrosion agents are added to antifreeze coolants (Automotive Cooling Journal 26, 34).
(1983)). Substances added to antifreeze coolants as corrosion inhibitors can be broadly classified into organic substances and inorganic substances.
Examples of organic substances used include guanidine, benzenecarboxylate, triazole salt, phenol, citrate, thiocyanate, thiourea, tannin, morpholine, triethanolamine, tartrate, and nitro compounds. In addition, as inorganic substances, alkali metal sulfates, nitrates, silicates, nitrites, chromates, phosphates, borates, tagstates, molybdates, vanadates, etc. are used. Antifreeze, which is mainly made of ethylene glycol and prevents coolant from freezing, contains agents that prevent corrosion of various metals in the cooling system of automobile engines, such as aluminum, cast iron, copper, brass, and solder. It is necessary to add
This anti-corrosion agent must not cause swelling of the rubber that is the material of the radiator hose. Furthermore, there are various modes of corrosion mechanisms for these various metals, such as oxidation by air, electrochemical corrosion by potential difference, or cavitation by vapor bubbles in the fluid. Therefore,
It is known that it is more effective to use various types of corrosion inhibitors in combination than to add just one type of agent. Borates had a good anti-corrosion effect when automobile engines were made of cast iron, but with the trend toward lighter automobiles and the use of aluminum, borates have been used in aluminum engines. Silicates are known to be effective while having negative effects (U.S. Patent No.
(See Publication No. 3198820). However, silicates have poor storage stability, and if they are stored for a long time, they may form silica gel, which loses its anti-corrosion effect and may cause the inside of the radiator to become clogged. . For the purpose of preventing such gelation of silicate, embodiments are known in which various organosilicon compounds are used together with silicate (see, for example, US Pat. No. 4,485,025). On the other hand, according to US Pat. No. 4,324,675, when nitrite or nitrate is used in combination with an organic amine,
Since nitrosamines, which are carcinogens, are formed, the anti-corrosion effect can be improved by adding borax, silicates, nitrates, benzene carboxylates, triazole salts, etc. as anti-corrosion agents without using these. It is stated that good antifreeze can be produced. Also, according to U.S. Patent No. 4,426,309, borax,
It is stated that by using triazole salts and nitrates and reducing the content of silicate to 0.08% or less instead of using phosphates, it was possible to produce an antifreeze coolant without gelation problems. has been done. And it is known that in these cases, the pH of the solution should be increased to 8-11 in order to increase the solubility of the corrosion inhibitor and prevent gel formation. However, aluminum is a well-known amphoteric metal, exhibiting corrosive properties at high or low pH, but being most stable near neutrality.
In addition, in the above-mentioned literature, it is known that the borax used corrodes the aluminum material and that the corrosion products clog the radiator (Special Publication No. 1983-5509). It is known that the degree of corrosion is even more severe in test equipment. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and to provide an antifreeze composition that has a low degree of corrosion on automobile radiators and is particularly suitable for engines made of aluminum. [Means for Solving the Problems] As a result of intensive research to achieve the above object, the present inventors found that when an organic silane compound represented by the general formula () below is added to ethylene glycol,
It was possible to effectively prevent silicate gelation and obtain an antifreeze coolant with low corrosivity. That is, the antifreeze composition for automobile heat sinks of the present invention comprises (a) ethylene glycol, (b) silicate, and (c) the following formula: (In the formula, R represents an alkyl group having 4 or less carbon atoms,
R ₁

[Formula] or

trialkoxysilane represented by [Formula], R ₂ and R ₃ are the same or different and each represents a phenyl group, a cyano group, an acetyl group, or a group -CO ₂ R ₄ , and R ₄ is synonymous with R) It is characterized by containing. The organic silane of the general formula () is a new compound, and the compounds shown in Table 3 below are exemplified. The organic silane with the general formula () has the formula or expression

[Formula] or in the presence of a solvent such as THF, hexane, ether and a small amount of a base such as alkyl lithium, sodium alkoxide, alkyl magnesium chloride,

It is produced by reacting with a compound having the formula: (R, R ₂ and R ₃ are the same as above) For details, see the patent application filed by the applicant in 1983-
You can refer to No. 944710. The antifreeze cooling composition of the present invention preferably contains 92% or more ethylene glycol and 0.05 to 0.5% silicate.
Contains 0.01 to 0.55% of organic silane of general formula (), and further contains 0.07 to 0.35% of nitrate and 0.2 to 2.0 of phosphate.
%, molybdate 0.1-1.0%, vanadate
0.02-0.3%, triazole salt 0.05-0.3% and benzenecarboxylic acid 0.5-4.0%. Examples of the inorganic acid salts and organic acid salts used in the composition of the present invention include alkali metal salts such as soda salts and potassium salts. in particular,
For example, in the present invention, sodium silicate or potassium silicate is used for silicate, sodium nitrate is used for nitrate, dipotassium hydrogen phosphate is used for phosphate, and sodium benzenecarboxylate or potassium benzenecarboxylate is used for benzenecarboxylate. For molybdate, sodium molybdate can be given, and for vanadate, sodium vanadate can be given, and also,
Triazole salts include tolyltriazole soda. The antifreeze coolant of the present invention can be easily prepared by blending each component of the composition described above in a predetermined ratio. At that time, the amount of silicate added was increased to 0.5%, and an organic silane represented by the general formula () was used as a gelling inhibitor, making the liquid property of the antifreeze solution close to neutral.
It is characterized by having a pH in the range of 7.0 to 9.0. Furthermore, other additives such as antifoaming agents can be appropriately added to the antifreeze coolant of the present invention.
Furthermore, any dye can be used as long as it does not adversely affect the antifreeze, and distilled water or ion-exchanged water is suitable for the water. Hereinafter, examples of the present invention will be shown and explained in detail. Example 1 Antifreeze coolant samples 1 and 2 were manufactured by blending the compositions shown in Table 1. Samples 1 and 2 contained the following organic silanes. Sample 1: Sample 2:

[Table] Corrosion tests were conducted on each metal specimen for Samples 1 and 2 according to the ASTM D-1384 test method. The test was conducted as follows. A condenser and a thermometer were attached to a flask, a specified metal specimen was placed in the flask, and 750 ml of the test solution was added. After heating this solution at 88°C for 336 hours, a metal specimen was taken out and treated by the specimen processing method described later.
It was dried and the weight loss was measured. The corrosive solutions used in this test were sodium sulfate, sodium bicarbonate, and sodium chloride in distilled water.
It was created by dissolving 100ppm (0.1% by weight). The test solution was a 15% mixture of sample 1 or 2 in a corrosion solution. As a comparative test sample, the above corrosion solution mixed with ethylene glycol at a concentration of 15% (test sample according to ASTM D-3306) was used.
Corrosion tests were conducted on each metal specimen in the same manner as in the examples.

[Table] (1) Size of specimen Iron, copper, brass and solder: 50.8 x 25.4 x 1.59 mm Cast iron and cast aluminum: 50.8 x 25.4 x
3.18mm (2) Method for processing specimens Immediately after the test was completed, the metal specimens were taken out and rubbed very lightly with a soft-bristled brush to remove any corrosion products attached with water. In order to further remove stubbornly adhering corrosion products, each metal specimen was treated in the following manner. For iron and cast iron, sticky deposits and layers were removed with a brass scrubbing tool or brush, followed by scrubbing with a damp bristle brush and pumice stone to thoroughly clean the metal coupons. For copper and brass, 15% in concentrated hydrochloric acid (1:1)
The surface discoloration film was removed by soaking for seconds, the acid removed under running water, and then scrubbed with a damp bristle brush and pumice powder. For aluminum, 179〓 (80°C) containing 2% by weight CrO ₃ and 5% by volume H ₃ PO ₄ (85%)
for 5 minutes, rinsed with water, then rubbed very lightly with a soft bristle brush to remove the easily peelable film, and rinsed again with water. If any film remained, soak it in concentrated nitric acid for 1 minute and repeat the previous method. The results of the test are shown in Table 2.

【table】

[Table] From the above test, it can be seen that Samples 1 and 2 of the present invention have a low corrosion rate against various metals, and are particularly effective against aluminum. Example 2 The gel formation prevention effect of each sample was measured according to the gel formation prevention effect measuring method described in US Pat. No. 4,367,154. The standard sample was prepared according to the automotive engine coolant compounding ratio described in GM6038M of General Motor Company, USA. Its blending ratio is 95.795% ethylene glycol, sodium nitrate.
0.2%, sodium metaborate 1.0%, sodium silicate 0.15%, tolyltriazole soda (50%
aqueous solution) 0.20%, sodium orthophosphate 0.45%,
It contained 0.2% caustic soda, 0.005% dye and 2.0% water. To this test solution, 100 ppm of each of the organic silanes of the general formula () of the present invention were added, and
The time required for gel formation to begin was measured. The results are shown in Table 3.

[Table] [Effects of the Invention] As is clear from the above description, the antifreeze composition for automobile radiators of the present invention can significantly reduce corrosion to radiators compared to conventional antifreeze coolants. It can prevent gelation of silicate, and can have a more significant effect especially on engines made of aluminum.

Claims (1)

[Claims] 1 (a) ethylene glycol, (b) silicate, (c) the following formula: (In the formula, R represents an alkyl group having 4 or less carbon atoms,
R ₁ represents [Formula] or [Formula], R ₂ and R ₃ are the same or different and each represents a phenyl group, a cyano group, an acetyl group, or a group -CO ₂ R ₄ , and R ₄ has the same meaning as R. ) An antifreeze composition for automobile heat dissipation characterized by having a trialkoxysilane represented by: 2 Weight composition ratio: 92% ethylene glycol
Above, 0.05 to 0.5% of silicate and 0.01 to 0.55% of trialkoxysilane represented by the general formula () according to claim 1, furthermore 0.07 to 0.35% of nitrate, 0.2 to 2.0% of phosphate, and 0.1 to 0.1% of molybdate. 1.0%, vanadate 0.02~0.3% and triazole salt 0.05~
An antifreeze composition for an automatic radiator, characterized in that it contains 0.3%.