JPH0885782A - Antifreeze composition - Google Patents

Abstract

PURPOSE: To obtain an antifreeze composition that is inexpensive and excellent in corrosion suppression action. CONSTITUTION: An antifreeze composition whose major component is ethylene glycol, propylene glycol, or diethylene glycol, or a mixture of these contains 1) 0.5 to 5wt.% dodecanedioic acid or its sodium salt or potassium salt, 0.1 to 6wt.% p-tert-butylbenzoic acid or its sodium salt or potassium salt, and 0.05 to 1.0wt.% triazoles and 2) at least one selected from the group consisting of silicates, molybdates, nitrates, benzoates, and thiazole salts, and is free from 3) amine salts, phosphates, borates, and nitrites. Therefore, the antifreeze composition is excellent in an ability of suppressing corrosion of metals that are used for internal combustion engines and has an excellent corrosion suppressing power with the added amount of the dodecanedioic acid decreased in comparison with the case where dodecanedioic acid alone is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antifreeze composition mainly used as a cooling liquid for internal combustion engines such as automobile engines, and more particularly to an antifreeze composition having a function of preventing corrosion of metals constituting a cooling system.

[0002]

2. Description of the Related Art Aluminum, aluminum alloys, cast iron, steel, brass, solder, copper, etc. are used in a cooling system of an internal combustion engine such as an automobile engine, and an antifreeze composition as a cooling medium flows in the system. .

The antifreeze composition has hitherto been used as a component for lowering the freezing point of alcohols and glycols. Alcohols and glycols not only have no corrosion inhibiting effect, but they are oxidized by oxygen or the like in actual use, and the oxides corrode the constituent metals in the cooling system. Therefore, various corrosion inhibitors have been added.

Commonly used corrosion inhibitors include phosphates, borates, carbonates, sulphates, nitrates, nitrites, molybdates, benzoates, silicates, benzotriazoles, tolyltriazoles, There are triethanolamine salt and sodium salt of mercaptobenzothiazole, which are appropriately selected from these to suppress corrosion.

However, some of these corrosion inhibitors are
There are the following problems, and their use is not preferable.

[0006] For example, phosphate is an excellent pH buffering agent and serves as a corrosion inhibitor for iron and aluminum-based metals, but when water containing phosphate flows into rivers and seawater, it becomes eutrophication, Its use is severely limited today, as it negatively affects living organisms and environmental degradation is a problem.

Further, triethanolamine salt is also an excellent corrosion inhibitor for iron and aluminum metals,
When coexisting with nitrous acid, there is a problem that it reacts and has carcinogenicity. While borate is also an excellent buffer, it has the problem of corroding aluminum-based metals,
It cannot be used for the internal combustion engines of recent years where aluminum-based metals have been widely used.

In order to solve such a problem, an antifreeze solution has been developed in which two kinds of aliphatic dicarboxylic acid salts having at least 7 carbon atoms are used in combination, which is effective for corrosion of aluminum-based metals. (Japanese Patent Laid-Open No. 2-1827
82). Furthermore, an antifreeze composition containing dodecanedioic acid having a higher corrosion inhibiting effect than other aliphatic dicarboxylic acids has been developed (see JP-A-63-190184),
The corrosion of iron and aluminum-based metals was suppressed.

[0009]

However, dodecanedioic acid is expensive, and the antifreeze containing it is also expensive, and its use is limited.

Therefore, an object of the present invention is to provide an antifreeze composition containing dodecanedioic acid, which is inexpensive and has an excellent corrosion inhibiting action.

Still another object of the present invention is to provide the above antifreeze composition having a more excellent corrosion inhibiting effect than using todecanedioic acid alone.

[0012]

Means for Solving the Problems The present invention which achieves the above-mentioned object is to provide ethylene glycol, propylene glycol,
Alternatively, an antifreeze composition containing diethylene glycol or a mixture thereof as a main component, wherein 1) 0.5 to 5 wt% of one or more of dodecanedioic acid or its sodium salt or potassium salt, and p-tert-butylbenzoic acid 0.1 to 6 wt% of an acid or one or more of sodium salt or potassium salt thereof, and 0.05 to 1.0 wt% of triazoles, and 2) silicate, molybdate, nitrate. , At least one of the group consisting of benzoate and thiazole salt, and 3) free of amine salt, phosphate, borate and nitrite.

The addition amount of at least one of dodecanedioic acid or its sodium salt or potassium salt is 0.5.
The reason for this is that the addition amount of less than 0.5 wt% does not provide sufficient anticorrosion property, and the addition amount of more than 5 wt% does not improve the corrosion inhibition effect and is not economical. is there. For the same reason, the addition amounts of p-tert-butylbenzoic acid, its sodium salt and potassium salt, and the addition amounts of triazoles are set within the above ranges.

[0014]

The main component of the composition of the present invention, ethylene glycol, propylene glycol, diethylene glycol, or a mixture thereof has a function of lowering the freezing temperature of cooling water, and the dodecanedioic acid and p-ter ter contained therein are contained therein.
t-Butylbenzoic acid suppresses corrosion of iron and aluminum-based metals. In addition, triazoles suppress corrosion of copper and aluminum-based metals.

The addition of silicate or nitrate further improves the corrosion inhibiting ability of aluminum-based metals, and the addition of molybdate or benzoic acid further enhances the corrosion inhibiting ability of iron and aluminum-based metals. At this time,
The addition amount of dodecanedioic acid and p-tert-butylbenzoic acid can be suppressed while maintaining the same suppressing effect by the addition amount.

Further, the addition of thiazoles further improves the corrosion inhibiting ability of copper-based metals and solders.

As mentioned above, although it is known to utilize dodecanedioic acid in an antifreeze composition, the present inventor has found that p-tertiary is preferable to using dodecanedioic acid alone.
It was found that the combined use of t-butylbenzoic acid and the excellent inhibitory effect beyond the corrosion inhibitory effects obtained from each, and that the combined use of both simultaneously reduces the amount of expensive dodecanedioic acid. Of.

[0018]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples.
It is diluted to 0 vol% and used.

The examples are described in the following table, but the composition of the present invention is not limited thereby. In addition, unless otherwise specified,% referred to below means wt%.

Table 1 shows the configurations of Examples 1 to 6 according to the present invention. Examples 1 to 3 include dodecanedioic acid, p
-Tert-Butylbenzoic acid, benzotriazole, sodium nitrate, potassium hydroxide, ethylene glycol, but Example 4 additionally contains sodium metasilicate.
The antifreeze composition of the present invention may further contain a defoaming agent, a coloring agent and the like.

[0021]

[Table 1]

Table 2 shows the structures of Comparative Examples 1 to 6. Comparative Examples 1 and 2 are dodecanedioic acid, benzotriazole,
Comparative Examples 3 and 4 are composed of sodium nitrate, potassium hydroxide, and ethylene glycol. Comparative Examples 3 and 4 are composed of p-tert-butylbenzoic acid, benzotriazole, sodium nitrate, sodium hydroxide, and ethylene glycol. Comparative Examples 5 and 6 are It is composed of p-tert-butylbenzoic acid, azelaic acid, benzotriazole, sodium nitrate, sodium hydroxide and ethylene glycol.

[0023]

[Table 2]

A test based on JIS K2234 metal corrosiveness test was carried out for Examples 1 to 4 and Comparative Examples 1 to 6. Tables 3 and 4 show changes in mass and appearance of the test pieces after the test and changes in pH after the test.

[0025]

[Table 3]

[0026]

[Table 4]

As shown in Table 3, Examples 1 to 4 have excellent antiseptic performance against any metal such as aluminum casting, cast iron, steel, brass, solder and copper.

Further, as shown in Table 4, regarding aluminum castings, as the contents of dodecanedioic acid and p-tert-butylbenzoic acid increase, their corrosion inhibiting action increases, and therefore their amounts are increased. It is expected that the corrosion inhibitory effect will decrease if the amount is reduced.

However, as is clear from the comparison between Tables 3 and 4, when dodecanedioic acid and p-tert-butylbenzoic acid were coexisted, the dodecanedioic acid decreased in spite of the decrease in the respective contents. Acid or p-tert butylbenzoic acid alone than dodecanedioic acid and p-tert
It can be seen that the one containing both of butylbenzoic acid has a superior corrosion inhibiting action.

EP-A-242900 discloses an antifreeze solution containing an aromatic acid, preferably p-tert-butylbenzoic acid and azelaic acid, in which it is described as having excellent corrosion inhibition performance. There is. However, Comparative Examples 5 and 6
As is clear from the comparative examples of Examples 1 to 4, such a fact was not confirmed, and it was found that the combined use of dodecanoic acid and p-tert-butylbenzoic acid was superior.

[0031]

[Effect] The following effects can be obtained by the antifreeze composition of the present invention.

Since the metal used in the internal combustion engine is excellent in corrosion inhibiting power, and has a superior corrosion inhibiting power with a smaller addition amount than dodecanedioic acid alone, an inexpensive product can be provided.

Further, since it does not contain amine, phosphate and nitrite, there is no risk of pollution due to the formation of nitrosamine which is a carcinogen and eutrophication of river water.

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Claims (2)

[Claims] 1. An antifreeze composition comprising ethylene glycol, propylene glycol, diethylene glycol, or a mixture thereof as a main component, which comprises 1) one or more of dodecanedioic acid or its sodium salt or potassium salt. 5 to 5 wt% and 0.1 to 6 wt% of one or more of p-tert-butylbenzoic acid or its sodium salt or potassium salt.
And 0.05 to 1.0 wt% of triazoles, and 2) silicate, molybdate, nitrate, benzoate,
An antifreeze composition comprising at least one selected from the group consisting of thiazole salts, and 3) free of amine salts, phosphates, borates, and nitrites. 2. The triazole is benzotriazole, tolyltriazole or a mixture thereof.
The antifreeze composition according to claim 1.