JP2772578B2 - antifreeze - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an antifreeze mainly used as a coolant for an internal combustion engine, and more particularly, to an excellent anti-corrosion function of metal of a cooling system and high hardness. It relates to an antifreeze which is extremely stable even in hard water.

2. Description of the Related Art Conventionally, an antifreeze mainly used as a coolant for an internal combustion engine mainly contains glycols, and various kinds of corrosion inhibitors having a function of preventing corrosion of metals in the cooling system are mixed with the antifreeze. It consisted of

A typical antifreeze is British Standard BS3150, which is based on ethylene glycol and contains amine phosphate and sodium salt of mercaptobenzothiazole as corrosion inhibitors.

However, in this case, the amine salt employed as a corrosion inhibitor has a disadvantage that it easily reacts with nitrite to form nitrosamine, which is a carcinogenic substance.

In view of the above disadvantages, phosphates, silicates, borates, and nitrites have been employed as corrosion inhibitors other than amine salts, but conventional ones employing these are carcinogenic substances. Although the disadvantage of producing nitrosamines is eliminated, there are the following disadvantages.

First, when phosphates flow into rivers, eutrophication promotes the growth of algae, causing pollution such as water bloom and red tide.

Reacts with the hard water component contained in the cooling liquid and the like to form a precipitate. Therefore, not only does the function of the corrosion inhibitor deteriorate, but also the accumulation of the precipitate causes a blockage in the circulation path of the cooling system, causing trouble.

Secondly, silicate is inferior in stability in a liquid, easily gels when heat or pH changes, or when other salts coexist, thereby deteriorating the function of the corrosion inhibitor.

Borates in turn tend to corrode aluminum or its alloys in particular.

And since nitrite is consumed quickly, the corrosion prevention function is reduced quickly.

In addition, among the above-mentioned conventional drawbacks, the problem of lack of stability with respect to hard water, which is particularly cited, is that as shown in the figure, hard water having a high hardness (ppm) is used worldwide as dilution water for antifreeze. The situation was significant given the large number of countries.

In order to improve the stability against hard water, JP-A No. 2-182782 discloses that "a heating medium containing a dicarboxylic acid mixture as a corrosion inhibitor" contains two kinds of dicarboxylic acids having 7 to 14 carbon atoms. Has been proposed.

(Problems to be Solved by the Invention) However, the “heating medium liquid containing a dicarboxylic acid mixture as a corrosion inhibitor” described in JP-A-2-1822782 is
Although the stability to hard water is improved to some extent, it is insufficient for hard water having high hardness.

The present invention was devised in view of the above circumstances, and the object of the present invention is to use a conventional corrosion inhibitor consisting of a phosphate, an amine salt, a silicate, a borate, and a nitrite, and Another object of the present invention is to provide an antifreeze which is excellent in the function of preventing corrosion of metal in a cooling system and which is extremely stable against hard water having high hardness.

(Means for Solving the Problems) Means taken by the present invention to achieve the above object will be described below.

That is, the composition of the antifreeze according to the present invention is: "An antifreeze containing glycols as a main component and containing no phosphate, amine salt, silicate, borate and nitrite in the components, comprising sebacic acid or 0.5 to 4.0 wt% of at least one of the alkali metal salts, 0.5 to 3.0 wt% of p-tert-butylbenzoic acid or at least one of the alkali metal salts thereof, and 0.05 to 1.0 wt% of triazoles. Antifreeze, characterized by the fact that

(Operation of the Invention) By the above means, regarding the antifreeze according to the present invention, first, the glycol as the main component lowers the freezing point of the cooling liquid or the like.

Next, sebacic acid or an alkali metal salt thereof prevents corrosion of metals in the cooling system, particularly metals containing iron or aluminum as a component. Further, since the hard water component contained in the cooling liquid or the like is dissolved, the formation of a precipitate due to the hard water component and the component contained in the antifreeze solution is suppressed.

The reason why the content of at least one of the sebacic acid or the alkali metal salt thereof is limited to the range of 0.5 to 4.0 wt% is as follows.

In other words, if the content is less than 0.5 wt%, a sufficient corrosion prevention function cannot be obtained, and if the content exceeds 4.0 wt%, not only does the corrosion prevention function not improve much, but may adversely affect the stability against hard water. Because there is.

Next, by coexisting only a small amount of p-tertbutyl benzoic acid or its alkali metal salt with sebacic acid or its alkali metal salt, corrosion is significantly prevented as compared with the case where sebacic acid or its alkali metal salt is used alone. The function is improved and the formation of a precipitate with the hard water component is extremely effectively suppressed.

The reason why the content of at least one of the above-mentioned p-tertbutylbenzoic acid or its alkali metal salt is limited to the range of 0.5 to 3.0 wt% is as follows.

That is, if it is less than 0.5 wt%, the content of coexisting sebacic acid or its alkali metal salt cannot be reduced so much, which is inconvenient in terms of stability against hard water. Further, the effective content of the coexisting sebacic acid or its alkali metal salt for the corrosion prevention function is determined as described above, so that the content of p-tertbutyl benzoic acid or its alkali metal salt exceeds 3.0 wt%. This is because not only can the content of sebacic acid or its alkali metal salt be reduced to less, but also economically wasteful.

Although sebacic acid and p-tert-butylbenzoic acid alone each have a metal corrosion preventing function, these alkali metal salts also have that function. Accordingly, the antifreeze component may contain in advance the respective alkali metal salts of sebacic acid and p-tertbutylbenzoic acid. Alternatively, it is naturally predicted that sebacic acid and p-tertbutyl benzoic acid generate each alkali metal salt in the presence of an alkali metal component such as Na, K, and Li. Sebacic acid and p-tertbutyl benzoic acid may be contained in the presence of the component.

Then, the triazoles prevent corrosion of metals in the cooling system, particularly metals containing copper and aluminum as components.

The content of the triazole is limited to the range of 0.05 to 1.0 wt% for the following reason.

That is, if the content is less than 0.05 wt%, a sufficient corrosion prevention function cannot be exhibited, and if the content exceeds 1.0 wt%, the corrosion prevention function is not so much improved, and it is economically useless.

Further, since the antifreeze according to the present invention does not contain an amine salt and a nitrite, it does not generate nitrosamine which is a carcinogenic substance.

Next, since it does not contain phosphate, there is no fear of pollution due to the occurrence of blue moss and red tide when flowing into a river or the like, and no precipitate due to hard water components contained in the coolant or the like is generated.

Next, since it does not contain a silicate, it does not gel even if other salts coexist.

And since it does not contain borate, it does not corrode the aluminum component of the cooling system.

(Example) Hereinafter, the present example will be described in detail with reference to Tables 1, 3, 5, and 7, but this is a typical example, and the present invention is not limited by the present example. .

First, examples according to the present invention are 1 to 6, and the configuration is shown in Table 1.

Examples 1 and 2 in Table 1 are composed of ethylene glycol, sebacic acid, p-tertbutylbenzoic acid, benzotriazole, potassium hydroxide, and water. Next, Example 3
Is ethylene glycol, sebacic acid, p-tertbutyl benzoic acid, sodium benzoate, benzotriazole,
It is composed of caustic potash and water. Next, Example 4 describes ethylene glycol, sebacic acid, p-tertbutyl benzoic acid,
It is composed of tolyltriazole, potassium hydroxide, and water.
Next, in Example 5, ethylene glycol, sebacic acid, p-
It is composed of tert-butylbenzoic acid, benzotriazole, sodium nitrate, potassium hydroxide, and water. And Example 6
Is composed of ethylene glycol, sebacic acid, p-tertbutyl benzoic acid, sodium benzoate, benzotriazole, sodium nitrate, sodium molybdate, potassium hydroxide, and water.

The antifreeze according to the present invention may contain an antifoaming agent, a coloring agent, and the like in addition to the above-described components, or may be used in combination with other conventionally known corrosion inhibitors such as tungstate and sulfate. May be.

Next, Comparative Examples 7 to 9 and Conventional Examples 10 to 13 are shown in Table 2.

Comparative Examples 7 and 8 were composed of ethylene glycol, sebacic acid, p-tertbutylbenzoic acid, benzotriazole, potassium hydroxide, and water. Comparative Example 9 was composed of ethylene glycol, sodium sebacate, p-tertbutylbenzoic acid, benzotriazole, caustic potash, and water.

Conventional Example 10 is composed of ethylene glycol, sebacic acid, dodecanedioic acid, benzotriazole, potassium hydroxide, and water. Next, Conventional Example 11 is composed of ethylene glycol, sodium sebacate, benzotriazole, and water. Next, Conventional Example 12 is composed of ethylene glycol, sodium nitrate, triethanolamine, orthophosphoric acid, mercaptobenzothiazole sodium salt, and water. Conventional Example 13 is composed of ethylene glycol, sodium benzoate, tolyltriazole, sodium nitrate, sodium metasilicate (9-hydrate), sodium nitrite, borax (10-hydrate), and water.

Examples 1 to 6 and Comparative Examples 7 to thus obtained.
9 and Conventional Examples 10 to 13 were subjected to the following Tests A to C. Table 3 and Table 4 for Test A, Tables 5 and 6 for Test B, and Tables 7 and 8 for Test C. Were obtained respectively.

 However, for this test, the following method was adopted.

First, the test A is a test for confirming the stability to hard water. Each antifreeze solution used in this test is hard water (CaCO _{2) obtained} by adding CaCl ₂ to ion-exchanged water so that Ca ²⁺ becomes 400 ppm. 50vo by ₃ )
Diluted to 1%.

The diluted solution is left at room temperature for 24 hours in the dark,
vol% was measured.

Next, test B is a test for confirming the corrosion prevention function for aluminum, and is a test performed by ASTM D4340-84 (Corrosion
of Cast Aluminum Alloys in Engine Coolants Under
Heat-Rejecti-ng Conditions) were performed by an aluminum alloy heat-exchange surface corrosion test specified. In this test B, the test conditions shown in Table 9 were adopted.

Next, test C is a test for confirming the corrosion prevention function for metals specified in paragraph 7.4 of JISK2234-1987 (antifreeze). The antifreeze used for the test was prepared water (1 l).
148 mg of Na ₂ SO ₄ , 165 mg of NaCl, and 138 mg of NaHCO ₃ ) were diluted to 30 vol% in water, and the metals to be tested were aluminum casting, cast iron,
Test pieces of steel, brass, solder, and copper were used, respectively.

As is clear from Table 3, Examples 1 to 6 are extremely excellent in stability against hard water having high hardness, and as is clear from Table 7, aluminum casting, cast iron, steel, brass,
Excellent corrosion prevention function for both metals, solder and copper. Furthermore, as is clear from Table 5, the corrosion rate is slow,
It turns out that it is excellent in the corrosion prevention function with respect to aluminum.

In comparison, Comparative Example 7 was excellent in stability against hard water, as evident from Table 4, but was inferior in corrosion prevention function, as evident from Tables 6 and 8, and particularly in the case of aluminum castings, the appearance of test specimens. , Corrosion was partially confirmed and the mass change was remarkable. This is considered to be due to Comparative Example 7 having a low sebacic acid content. Next, Comparative Example 8 is excellent in stability against hard water as evident from Table 4, but is inferior in corrosion prevention function as evident from Tables 6 and 8, and in particular, changes in mass of brass, solder and copper test pieces. Is remarkable. This is because Comparative Example 8
Next, it is considered that Comparative Example 9 has a somewhat excellent corrosion prevention function as evident from Tables 6 and 8, but has a poor stability to hard water as evident from Table 4. It turns out that it is inferior. This is considered to be due to Comparative Example 9 having a high sebacic acid content and a low p-tertbutylbenzoic acid content.

Next, Conventional Example 10 is excellent in the corrosion prevention function as evident from Tables 6 and 8, but is insufficient in stability against hard water as evident from Table 4. Next, Conventional Example 11 and
As shown in Tables 6 and 8, Sample No. 12 has an excellent corrosion prevention function, but as shown in Table 4, is extremely poor in stability against hard water. And conventional example 13
Is excellent in hard water stability as evident from Table 4, but inferior in corrosion prevention function as evident from Table 6.

(Effect of the Invention) As described above, when the antifreeze according to the present invention is adopted,
The following effects are obtained.

That is, the antifreeze according to the present invention comprises: "0.5 to 4.0 wt% of at least one of sebacic acid or an alkali metal salt thereof, 0.5 to 3.0 wt% of at least one of p-tertbutylbenzoic acid or an alkali metal salt thereof, triazole Liquid containing 0.05 to 1.0 wt%
It has excellent metal corrosion prevention function and is extremely stable against hard water with high hardness. Therefore, it is particularly effective in countries where hard water having a high hardness must be used as dilution water for antifreeze.

By coexisting at least one of p-tertbutylbenzoic acid or an alkali metal salt thereof in a small amount with sebacic acid or an alkali metal salt thereof, the content of expensive sebacic acid or an alkali metal salt thereof can be reduced. Can,
Therefore, it can be provided at low cost.

Further, since the antifreeze according to the present invention does not contain phosphate, amine salt, silicate, borate and nitrite in the components, there is no fear of producing nitrosamine which is a carcinogenic substance.

Even if the antifreeze component flows into rivers, etc., there is little concern about pollution due to the occurrence of blue water and red tide, and hard water components and precipitates are not generated, so that when used in a cooling system, the circulation path etc. will be blocked. There is no need to worry.

Even if other salts coexist, they do not gel, and there is no fear that the corrosion prevention function is reduced by the gelation.

Does not corrode aluminum or its alloys.

[Brief description of the drawings]

The figure is a graph showing the total hardness of water in North America, Europe, Australia, the Middle East, Asian countries, and Japan.

Claims (1)

(57) [Claims] 1. An antifreeze containing glycols as a main component and containing no phosphate, amine salt, silicate, borate or nitrite in the component, wherein at least one of sebacic acid and an alkali metal salt thereof is used. 1
Liquid containing 0.5 to 4.0% by weight of p-tert-butylbenzoic acid or at least one of its alkali metal salts and 0.05 to 1.0% by weight of triazoles. .