JP2011074181A - Coolant composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coolant composition which suppresses corrosion of various metals, precipitation of a dimer (DM) of thiazole, and deterioration of rubber. <P>SOLUTION: The coolant composition includes 1.0-5.0 mass% aliphatic dibasic acid, 0.05-0.5 mass% phosphoric acid in terms of metallic phosphorus, and 0.1-0.3 mass% thiazoles. The pH of the coolant composition is adjusted to 7.0-8.0 with sodium hydroxide. The corrosion of metals can be suppressed by the aliphatic dibasic acid and the phosphoric acid, and the precipitation of the DM and the deterioration of rubber can be suppressed by the thiazoles and the sodium hydroxide. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a coolant composition which is mixed in cooling water of an internal combustion engine such as an automobile and prevents cooling water from freezing.

  Conventionally, a cooling liquid mainly composed of a melting point depressant such as alcohols or glycols is added to the cooling water of an automobile engine to prevent freezing in winter. However, alcohols and glycols are not only rust-proof, but also oxidized when they come into contact with oxygen during circulation at high temperatures, and the resulting oxide promotes corrosion of the metals that make up the cooling water flow path. There is.

  Therefore, the coolant is generally phosphate, borate, carbonate, sulfate, nitrate, molybdate, benzoate, silicate, benzotriazole, sodium salt of mercaptobenzothiazole, tolyltriazole, triethanol. A rust inhibitor selected from amine salts and the like is added. In this way, a predetermined amount of the cooling liquid to which the rust inhibitor is added is mixed with the cooling water to prevent corrosion of the metal during use.

  It is known that phosphoric acid or an alkali metal salt thereof greatly contributes to the inhibition of corrosion of aluminum and aluminum alloys, and greatly improves the aluminum corrosion resistance under cavitation. However, phosphate has a problem that it reacts with a hard water component to form a precipitate.

  Therefore, the re-published patent WO2005 / 033362 includes phosphoric acid, P-tert-butylbenzoic acid (PTBBA), magnesium nitrate, 2-phosphonobutane-1,2,4 tricarboxylic acid, and tolyltriazole. Discloses a coolant composition neutralized with potassium hydroxide to a pH value of 8.0. In the re-published patent WO2005 / 037951, phosphoric acid, P-tert-butylbenzoic acid, sebacic acid, sodium molybdate, strontium nitrate, 2-phosphonobutane-1,2,4 tricarboxylic acid, A coolant composition comprising tolyltriazole and 2-mercaptobenzothiazole soda and neutralized with potassium hydroxide is disclosed.

  According to these cooling liquid compositions, not only is the aluminum alloy highly resistant to corrosion at high temperatures, but it does not react with the hard water component to produce precipitates.

International Publication No. 2005/033362 International Publication No. 2005/037951

  However, in the conventional coolant composition, although the corrosion inhibitory effect on iron, aluminum alloy, etc. is high, when a large amount of thiazole, which is one of rust preventives for copper-based metals, is blended, the coolant becomes sunlight (ultraviolet). When exposed, a precipitate of thiazole dimer (DM) forms. For example, when this precipitate is generated in the reserve tank, problems such as poor visibility and clogging of the hose occur. On the other hand, if the amount of thiazole is reduced excessively to avoid this problem, the compatibility with rubber parts such as radiator hoses may be deteriorated. This is because thiazole functions as a rust preventive for copper-based metals, and also has an effect of suppressing deterioration of rubber.

  The present invention has been made in view of such circumstances, and it is intended to provide a coolant composition that can suppress corrosion of various metals such as iron and aluminum alloys, and can suppress deterioration of rubber and precipitation of DM. It is a problem to be solved.

  A feature of the cooling liquid composition of the present invention that can solve the above problems is a cooling liquid composition mainly composed of a melting point depressant selected from alcohols and glycols, and 1.0 to 5.0 per 100% by mass of the composition. Contains 0.05% by weight of aliphatic dibasic acid, 0.05-0.5% by weight of phosphoric acid in terms of metal phosphorus, and 0.1-0.3% by weight of thiazoles, and adjusted to pH 7.0-8.0 with sodium hydroxide It is characterized by being made.

  According to the cooling liquid composition of the present invention, corrosion of various metals such as iron and aluminum alloys can be suppressed, rubber deterioration and DM deposition can be suppressed.

  Alcohols and glycols that are melting point depressants include methanol, ethanol, 2-propanol, monoethylene glycol, propylene glycol, 1,3 butylene glycol, hexylene glycol, diethylene glycol, glycerin, etc. alone or in combination of two or more. It can be used by mixing.

  Examples of aliphatic dibasic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, piperic acid, suberic acid, sebacic acid, azelaic acid, brassylic acid, taptic acid, undecanedioic acid, and dodecanedioic acid. Illustrated. Those having 9 to 12 carbon atoms are preferred, and sebacic acid having excellent solubility and anticorrosion properties is particularly preferred. When the aliphatic dibasic acid having less than 9 carbon atoms is used, the anticorrosion property against iron is lowered. When the carbon number is 13 or more, the solubility is low and the storage stability is lowered.

  The addition amount of the aliphatic dibasic acid is 1.0 to 5.0% by mass per 100% by mass of the composition. If it is less than 1.0% by mass, it becomes difficult to suppress corrosion of iron, steel, brass and solder, and even if added over 5.0% by mass, the effect becomes saturated and expensive.

  Examples of phosphoric acid include orthophosphoric acid, pyrophosphoric acid, trimetaphosphoric acid, and tetrametaphosphoric acid. This phosphoric acid greatly contributes to the inhibition of corrosion of aluminum and aluminum alloys, and greatly improves the aluminum corrosion resistance under cavitation. Phosphoric acid is contained in an amount of 0.05 to 0.5% by mass in terms of metallic phosphorus per 100% by mass of the composition. If it is less than 0.05% by mass in terms of metal phosphorus, the corrosion resistance of aluminum and iron becomes insufficient, and if it exceeds 0.5% by mass, the corrosion resistance against brass decreases.

  Thiazoles mainly suppress the deterioration of rubber. Examples of thiazoles include benzothiazole, polybenzothiazole, sodium salt of mercaptobenzothiazole, and benzothiazolylthiopropionic acid. The amount of thiazole added is 0.1 to 0.3% by mass per 100% by mass of the composition. If the amount of thiazole added is less than 0.1% by mass, it will be difficult to suppress the deterioration of the rubber. If it exceeds 0.3% by mass, a large amount of DM will precipitate when exposed to sunlight (ultraviolet rays). To do. For example, when this precipitate is generated in the reserve tank, problems such as poor visibility and clogging of the hose occur.

  The greatest feature of the present invention resides in that at least phosphoric acid and aliphatic dibasic acid are neutralized with sodium hydroxide. When neutralized with potassium hydroxide or lithium hydroxide, unless more thiazole is blended, the deterioration of the rubber cannot be suppressed, and as a contradiction, a large amount of DM may be precipitated. The pH value for neutralization is 7.0 to 8.0. When the pH value is less than 7.0, the effect of inhibiting corrosion of various metals decreases, and when the pH value exceeds 8.0, the corrosion resistance of aluminum and aluminum alloy decreases. By being neutralized, the various drugs to be added are completely dissolved.

  The coolant composition of the present invention preferably further contains 1.0 to 5.0% by mass of alkylbenzoic acid per 100% by mass of the composition. By adding alkylbenzoic acid, corrosion of iron and solder can be further suppressed. Examples of the alkyl benzoic acid include p-toluic acid, p-ethyl benzoic acid, p-propyl benzoic acid, p-isopropyl benzoic acid, p-tert butyl benzoic acid and the like. It is not preferable to add it as an alkali metal salt other than sodium such as potassium or lithium, and it is preferable to add it as an alkylbenzoic acid and neutralize it with the above-mentioned sodium hydroxide to obtain a sodium salt.

  If the amount of alkylbenzoic acid added is less than 1.0% by mass, the added effect cannot be obtained, and if it exceeds 5.0% by mass, the effect is saturated and the amount of other components added is not preferred. In addition, the addition amount of an aliphatic benzoic acid can reduce the addition amount of an aliphatic dibasic acid, and can reduce cost. Moreover, the anticorrosion property of iron further improves by using together with the molybdate mentioned later.

  The coolant composition of the present invention preferably further contains 0.05 to 1.0% by mass of triazole per 100% by mass of the composition. Addition of triazoles can further suppress copper corrosion. Examples of triazoles include benzotriazole, tolyltriazole, 4-phenyl-1,2,3-triazole, 2-naphthotriazole, 4-nitrobenzotriazole and the like. If the addition amount of the triazole is less than 0.05% by mass, the added effect cannot be obtained, and if the addition amount exceeds 1.0% by mass, the effect is saturated and the addition amount of the other components is not preferable.

  The coolant composition of the present invention preferably contains 0.05 to 1.0% by mass of nitrate per 100% by mass of the composition. By adding nitrate, pitting corrosion of aluminum and aluminum alloy can be further suppressed. As this nitrate, salts of alkali metals other than sodium such as potassium and lithium are not preferable, and sodium nitrate is particularly preferable. If the addition amount of the nitrate is less than 0.05% by mass, the added effect cannot be obtained, and if the addition amount exceeds 1.0% by mass, the effect is saturated and the addition amount of the other components is not preferable.

  The coolant composition of the present invention preferably contains 0.1 to 0.2% by mass of molybdate per 100% by mass of the composition. Addition of molybdate can further suppress iron corrosion. As the molybdate, salts of alkali metals other than sodium such as potassium and lithium are not preferable, and sodium salts are particularly preferable. If the addition amount of the molybdate is less than 0.1% by mass, the added effect cannot be obtained, and if the addition amount exceeds 0.2% by mass, the effect is saturated and the addition amount of other components is not preferable.

  The coolant composition of the present invention preferably contains 0.0001 to 0.1% by mass of an alkaline earth metal compound in terms of metal per 100% by mass of the composition. Alkaline earth metal compounds have the effect of greatly suppressing corrosion of aluminum and aluminum alloys at high temperatures. Accordingly, cavitation, erosion, and corrosion of the water pump with respect to the aluminum housing are prevented, and the high-temperature aluminum casting heat transfer surface corrosion resistance is further improved.

  Alkaline earth metal compounds include oxides, hydroxides, permanganates, chromates, fluorides, iodides, carbonates, nitrates, sulfates, titanates, tungstates, borates, Phosphate, dihydrogen phosphate, formate, acetate, propionate, butyrate, valerate, laurate, stearate, oleate, glutamate, lactate, succinate, apple Acid salts, tartrate salts, maleates, citrates, oxalates, malonates, sebacates, benzoates, phthalates, salicylates, mandelates, and the like can be used.

  As the alkaline earth metal compound, it is desirable to use at least one of a calcium compound and a magnesium compound. Only one of the calcium compound and the magnesium compound may be blended, or both may be blended together. However, since the calcium compound has a greater anticorrosive effect than the magnesium compound, it is desirable to blend at least the calcium compound. . In the case of combined use, the mixing ratio of the calcium compound and the magnesium compound is preferably calcium compound / magnesium compound = 1/2 in terms of a metal-converted mass ratio.

  If the addition amount of the alkaline earth metal compound is less than 0.0001% by mass in terms of metal, the added effect cannot be obtained, and if the addition amount exceeds 0.1% by mass, the effect is saturated and the addition amount of other components is limited. It is not preferable.

  The cooling liquid composition of the present invention preferably contains 0.01 to 1.0% by mass of 2-phosphonobutane-1,2,4 tricarboxylic acid as a sequestering agent per 100% by mass of the composition. By containing 2-phosphonobutane-1,2,4 tricarboxylic acid, the corrosion resistance of the aluminum casting heat transfer surface is further improved. If the addition amount of 2-phosphonobutane-1,2,4tricarboxylic acid is less than 0.01% by mass, the added effect cannot be obtained, and if it exceeds 1.0% by mass, the effect is saturated and the addition amount of other components is limited. Therefore, it is not preferable. 2-phosphonobutane-1,2,4 tricarboxylic acid is not preferably added as a salt of an alkali metal other than sodium such as potassium or lithium, and is preferably added as a sodium salt.

  By the way, the addition of the alkaline earth metal compound may form a scale-like deposit in the cooling water flow path. In this case, even if 2-phosphonobutane-1,2,4 tricarboxylic acid is added to reduce the addition amount of the alkaline earth metal compound, it is equivalent to the case where the addition amount of the alkaline earth metal compound is large. The above anticorrosion performance can be obtained, and the formation of deposits can be prevented.

  The cooling liquid composition of the present invention is usually used by mixing 20 to 60% by volume in cooling water. Therefore, from the viewpoint of storage stability and handleability, each drug must be completely dissolved in the stock solution state of the coolant composition, and the coolant composition of the present invention is completely dissolved in both the stock solution state and the diluted state. It is in a uniform state.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The following “%” means “% by mass”.

  As shown in Table 1, sebacic acid is 4.0%, phosphoric acid is 0.15% in terms of metallic phosphorus, thiazole 0.2%, sodium nitrate 0.3%, triazole 0.5%, water 4.0%, and ethylene glycol remainder, sodium hydroxide The pH value was adjusted to 7.7 to obtain the coolant composition of Example 1.

  The same as Example 1 except that the addition amount of sebacic acid was 1.0%.

The same as Example 1 except that the addition amount of sebacic acid was 5.0%.
(Comparative Example 1)
The same as Example 1 except that the addition amount of sebacic acid was 0.5%.
<Test and evaluation>
The coolant compositions of Examples 1 and 2 and Comparative Example 1 were subjected to a high temperature metal corrosion test in accordance with the metal corrosion test specified in JIS K2234. However, the liquid temperature was set to 120 ° C., and air was passed in a pressurized airtight container without venting. The results are shown in Table 1. The table below also shows the acceptable range of weight increase / decrease for each metal specified in JIS K2234.

  From Table 1, it can be seen that Comparative Example 1 has a greater weight reduction of cast iron, steel, brass, and solder than each Example. Moreover, according to visual observation of the test piece, in Comparative Example 1, the aluminum was blackened and the solder was rough. Therefore, it is clear that the addition amount of the aliphatic dibasic acid (sebacic acid) is preferably 1.0 to 5.0% by mass.

  The same as Example 1 except that the addition amount of phosphoric acid was 0.50% in terms of metal phosphorus.

The same as Example 1 except that the addition amount of phosphoric acid was 0.05% in terms of metal phosphorus.
(Comparative Example 2)
The same as Example 1 except that the addition amount of phosphoric acid was 0.60% in terms of metal phosphorus.
(Comparative Example 3)
The same as Example 1 except that the addition amount of phosphoric acid was 0.01% in terms of metal phosphorus.
<Test and evaluation>
The coolant compositions of Examples 4 and 5 and Comparative Examples 2 and 3 were subjected to a high temperature metal corrosion test in accordance with a metal corrosion test specified in JIS K2234. However, the liquid temperature was set to 120 ° C., and air was passed in a pressurized airtight container without venting. The results are shown in Table 2 together with the results of Example 1.

  From Table 2, it can be seen that the weight loss of brass is larger in Comparative Example 2 than in Examples 4 and 5, and that in Comparative Example 3 is greater in weight loss of cast iron, steel, brass, and solder. Further, according to the visual observation of the test piece, in Comparative Examples 2 and 3, the aluminum turned black and the solder was rough. Moreover, in Example 4, discoloration was recognized by the brass. Therefore, it is clear that the addition amount of phosphoric acid is preferably 0.05 to 0.5 mass.

  The same as Example 1 except that the addition amount of thiazole was 0.1%.

The same as Example 1 except that the amount of thiazole added was 0.3%.
(Comparative Example 4)
Same as Example 1 except that no thiazole was added.
(Comparative Example 5)
The same as Example 1 except that the addition amount of thiazole was 0.5%.
(Comparative Example 6)
The same as Example 1, except that the amount of thiazole added was 0.3% and the pH was adjusted to 7.7 using potassium hydroxide instead of sodium hydroxide.
(Comparative Example 7)
The same as Example 1, except that the amount of thiazole added was 0.3% and the pH was adjusted to 7.7 using lithium hydroxide instead of sodium hydroxide.
<Test and evaluation>
The cooling liquid compositions of Example 1, Examples 6, 7 and Comparative Examples 4-7 were tested for action on rubber. Each cooling liquid composition was diluted with ion-exchanged water to a concentration of 50% by volume and placed in a sealed container, and a rubber material made of EPDM was immersed for 1200 hours while maintaining the liquid temperature at 120 ° C. Thereafter, the rubber material was taken out, the rubber hardness specified in JIS K6253 was measured, and the difference from the rubber hardness before immersion was calculated. Table 3 shows that the hardness change is less than +10 points, and the hardness change is +10 points or more.

  Further, each cooling liquid composition was diluted with ion-exchanged water to a concentration of 30% by volume, and 100 ml each was put into an unemployed transparent glass 100 ml measuring cylinder. These were placed in a place exposed to sunlight in the room and allowed to stand at room temperature for 7 days. The state of each subsequent cooling liquid composition was visually observed, and the DM precipitation amount of less than 10% by volume was evaluated as ◯, the DM precipitation amount of 10% by volume or more was evaluated as ×, The results are shown in Table 3.

  In Comparative Examples 4, 6, and 7, it was recognized that the rubber was cured. In Comparative Example 5, precipitation was observed in the coolant composition. Therefore, it is clear that addition of thiazole can prevent rubber deterioration, and the addition amount of thiazole is preferably 0.1 to 0.3% by mass. From the comparison between Example 6 and Comparative Examples 6 and 7, when neutralized with potassium hydroxide or lithium hydroxide, the addition of thiazole does not prevent the rubber from being deteriorated, but neutralized with sodium hydroxide. It is clear that the deterioration of the rubber can be surely prevented by the cooperation with thiazole.

  The same as Example 1 except that 2.0% of alkylbenzoic acid (PTBBA) was further added to the coolant composition before neutralization with sodium hydroxide.

  The same as Example 1, except that 5.0% of alkylbenzoic acid (PTBBA) was further added to the coolant composition before neutralization with sodium hydroxide.

  The same as Example 1 except that 1.0% of alkylbenzoic acid (PTBBA) was further added to the coolant composition before neutralization with sodium hydroxide.

The same as Example 1 except that 0.5% of alkylbenzoic acid (PTBBA) was further added to the coolant composition before neutralization with sodium hydroxide.
<Test and evaluation>
The coolant composition of Example 8-11 was subjected to a high temperature metal corrosion test based on the metal corrosion test defined in JIS K2234. However, the liquid temperature was set to 120 ° C., and air was passed in a pressurized airtight container without venting. The results are shown in Table 4 together with the results of Example 1.

  From Table 4, it can be seen that the addition of alkylbenzoic acid (PTBBA) to the coolant composition of Example 1 further improves the corrosion resistance of the solder. This effect increases as the amount of alkyl benzoic acid added increases. However, when the amount of alkyl benzoic acid added is 0.5% as in Example 11, this effect is almost the same as in Example 1. Therefore, addition of alkyl benzoic acid is effective. The amount is preferably 1.0 to 5.0% by mass.

  In addition, from Table 1, although the anticorrosion property with respect to solder is improving even if sebacic acid is added, since sebacic acid is expensive, cost reduction is aimed at by substituting a part of sebacic acid with alkylbenzoic acid. be able to.

  Further, the same as Example 1 except that 0.2% of sodium molybdate was added.

Example 1 except that in the coolant composition before neutralization with sodium hydroxide, the amount of sebacic acid added was reduced to 2.0%, 2.0% alkyl benzoic acid was added, and 0.2% sodium molybdate was added. It is the same.
<Test and evaluation>
The coolant composition of Examples 12-13 was subjected to a high temperature metal corrosion test based on the metal corrosion test defined in JIS K2234. However, the liquid temperature was set to 120 ° C., and air was passed in a pressurized airtight container without venting. The results are shown in Table 5 together with the results of Example 1.

  According to the coolant compositions of Examples 12 and 13, the amount of increase / decrease in the weight of each metal is extremely small compared to Example 1. Further, by visual inspection of the test piece, it was confirmed that the gloss of cast iron was maintained in Examples 12 and 13 as compared with Example 1 even after the test. Furthermore, in Example 13, although it was excellent in anticorrosion property, although the addition amount of expensive sebacic acid was reduced, it is an inexpensive cooling liquid composition.

Claims (9)

A coolant composition comprising as a main component a melting point depressant selected from alcohols and glycols,
1.0 to 5.0% by weight of an aliphatic dibasic acid per 100% by weight of the composition;
0.05 to 0.5% by mass of phosphoric acid in terms of metal phosphorus,
0.1 to 0.3% by mass of thiazoles,
A coolant composition having a pH value adjusted to 7.0 to 8.0 with sodium hydroxide.   The coolant composition according to claim 1, which does not contain a potassium salt or a lithium salt.   The cooling fluid composition according to claim 1 or 2, comprising 1.0 to 5.0% by mass of alkylbenzoic acid per 100% by mass of the composition.   The coolant composition according to any one of claims 1 to 3, comprising 0.05 to 1.0 mass% of triazole per 100 mass% of the composition.   The cooling fluid composition according to any one of claims 1 to 4, comprising 0.05 to 1.0% by mass of nitrate per 100% by mass of the composition.   The coolant composition according to any one of claims 1 to 5, comprising 0.05 to 1.0% by mass of molybdate per 100% by mass of the composition.   The coolant composition according to any one of claims 1 to 6, comprising 0.0001 to 0.1% by mass of an alkaline earth metal compound in terms of metal per 100% by mass of the composition.   The coolant composition according to any one of claims 1 to 7, comprising 0.01 to 1.0% by mass of 2-phosphonobutane-1,2,4 tricarboxylic acid per 100% by mass of the composition.   The coolant composition according to any one of claims 1 to 8, wherein the aliphatic dibasic acid is an aliphatic dibasic acid having 9 to 12 carbon atoms.