JP2008106303A - Cooling liquid composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling liquid composition having anticorrosion property to metals. <P>SOLUTION: The cooling composition comprises one or more kinds of melting point depression agent selected from a group composed of glycols and alcohols as a main component, and contains at least one kind selected from phosphoric acid and the salt thereof, and at least one kind selected from 2,6-naphthalene dicarboxylic acid and the salt thereof. By the combined use of at least one kind selected from phosphoric acid and the salt thereof and at least one kind selected from 2,6-naphthalene dicarboxylic acid and the salt thereof, its anticorrosion property particularly to magnesium, magnesium alloys, aluminum and aluminum alloys among metals improves. Thus, the cooling liquid composition is suitable for a cooling liquid flow passage in which aluminum based metals and magnesium based metals are exposed to at least a part of the surface. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a coolant composition added to cooling water of an internal combustion engine such as an automobile, and relates to a coolant composition capable of preventing metal corrosion.

  Various metals such as cast iron, steel, copper alloy, aluminum, and aluminum alloy (hereinafter referred to as “aluminum metal”) are used for a cooling system of an internal combustion engine such as an automobile engine. Therefore, the coolant composition is required to prevent corrosion regardless of the type of metal.

  Conventionally, a coolant composition containing a melting point depressant such as alcohols and glycols as a main component has been added to the coolant of an automobile engine to prevent freezing in winter. However, alcohols and glycols have no rust preventive action, and corrosion occurs in metal parts constituting the coolant flow path as they are. Therefore, various corrosion inhibitors are added to the coolant composition.

  By the way, in recent years, there is a movement to consider adopting a component made of magnesium or a magnesium alloy (hereinafter referred to as “magnesium-based metal”) for a cooling system for the purpose of saving resources and energy. Magnesium is the metal with the lowest density among practical metals and has excellent recyclability, but the standard oxidation-reduction potential is the lowest among practical metals and has low corrosion resistance. There is a need to. In order to improve the corrosion resistance of a member made of a magnesium-based metal used in the cooling system, it is conceivable that the corrosion resistance of the member itself is improved and the corrosion prevention is achieved by the cooling liquid used.

In order to impart anticorrosive properties for preventing corrosion of metals to the coolant, it is common to add a corrosion inhibitor to the coolant. For example, the cooling liquid composition containing the aromatic carboxylic acid currently disclosed by patent document 1, patent document 2, etc., the corrosion inhibitor containing the fluoride currently disclosed by patent document 3 etc. are mentioned.
US Pat. No. 4,584,119 JP-A-5-306390 Special Table 2000-527619

  The inventors of the present invention have examined the influence of each component used as a corrosion inhibitor on the metal in the coolant composition. Even if the aromatic carboxylic acid is used alone, the anticorrosion property against the magnesium-based metal is not sufficiently improved. Furthermore, in the aromatic carboxylic acid, a difference in the anticorrosion property occurs depending on the type of aromatic carboxylic acid used (number and position of carboxyl groups, type of aromatic hydrocarbon, etc.). In addition, the coolant composition containing fluorine has high anticorrosion properties against magnesium-based metals, but does not exhibit sufficient anticorrosion properties against aluminum-based metals.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the cooling fluid composition which can prevent corrosion irrespective of the kind of metal.

  The present inventors have newly shown that a coolant composition using a specific aromatic carboxylic acid in combination with other components as a corrosion inhibitor exhibits corrosion resistance against both magnesium-based metals and aluminum-based metals. It discovered and came to complete this invention.

  That is, the cooling liquid composition of the present invention is a cooling liquid composition containing as a main component one or more melting point depressants selected from the group consisting of glycols and alcohols, and includes phosphoric acid and its salts. And at least one of 2,6-naphthalenedicarboxylic acid and a salt thereof.

  When the total amount of the cooling liquid composition is 100% by weight, it is preferable that 0.12 to 3% by weight of phosphoric acid and a salt thereof are contained in terms of phosphorus element. Moreover, it is preferable that 1-10 weight% of at least 1 type of 2, 6- naphthalene dicarboxylic acid and its salt is contained when the whole cooling fluid composition is 100 weight%.

  The cooling liquid composition of the present invention is preferably used in a state containing 40 to 80% by volume of the solvent when the whole is 100% by volume in the state of use dissolved in the solvent. Here, the “use state dissolved in a solvent” means a state in which the cooling liquid composition of the present invention is used in a cooling system. That is, the coolant composition of the present invention can be appropriately diluted with a solvent such as water and used, and the absolute content cannot be defined. For this reason, it is also defined by the concentration in use.

  Since the coolant composition of the present invention contains at least one of phosphoric acid and its salt and at least one of 2,6-naphthalenedicarboxylic acid and its salt, magnesium-based metal and aluminum-based metal Corrosion protection against Further, in the coolant composition of the present invention, it is not necessary to use fluoride as a corrosion inhibitor, so there is no adverse effect on the aluminum-based metal.

  In order to describe the coolant composition of the present invention in more detail, the best mode for carrying out the present invention will be described below.

  The coolant composition of the present invention contains a melting point depressant as a main component. The melting point depressant is at least one selected from the group consisting of glycols and alcohols. Examples of glycols include ethylene glycol and propylene glycol. Examples of alcohols include methanol, ethanol, and 2-propanol. These alcohols and glycols can be used alone or in admixture of two or more. The melting point depressant as the main component is preferably contained in an amount of 20% by weight or more, and more preferably 25 to 95% by weight, when the entire coolant composition is 100% by weight.

  The coolant composition of the present invention contains at least one of phosphoric acid and its salt and at least one of 2,6-naphthalenedicarboxylic acid and its salt. As phosphoric acid, orthophosphoric acid is preferable. As the phosphate, alkali metal salts such as Na salt and K salt are preferable. Phosphorus element can greatly suppress the corrosiveness of the aluminum-based metal, and can greatly improve the anticorrosive property of the aluminum-based metal under cavitation and at high temperatures. For example, when a housing made of an aluminum-based metal is adopted for a water pump or the like, cavitation, erosion, corrosion, etc. of the water pump are effectively prevented. Moreover, the corrosion resistance of the high-temperature aluminum casting heat transfer surface is also improved.

  At least one of phosphoric acid and a salt thereof may be contained in an amount of 0.12 to 3% by weight in terms of phosphorus element when the entire coolant composition is 100% by weight. Phosphorus element exhibits corrosion resistance even outside this range, but if it is within this range, it can fully exhibit corrosion resistance against metals, improve corrosion resistance against aluminum-based metals such as under cavitation, and constitute a cooling system Reduction of adverse effects on the material (for example, magnesium-based metal) can be achieved. More desirably, the content is 0.24 to 3% by weight.

  And the cooling fluid composition of this invention contains at least 1 type of 2, 6- naphthalene dicarboxylic acid and its salt with at least 1 type of phosphoric acid and its salt. By using both in combination, the effect of preventing corrosion of magnesium-based metal and aluminum-based metal is improved. By using both in combination, it is assumed that a dense film is formed on the surface of the magnesium-based metal.

  As the 2,6-naphthalenedicarboxylate, alkali metal salts such as Na salt and K salt are preferable. At least one of 2,6-naphthalenedicarboxylic acid and a salt thereof may be contained in an amount of 1 to 10% by weight when the entire coolant composition is 100% by weight. Although corrosion resistance is exhibited even outside this range, if it is less than 1% by weight, it is not desirable because sufficient corrosion resistance may not be obtained. If it exceeds 10% by weight, the effect of addition is saturated and it is not economical. Further, the lower limit of the desirable addition amount is 2% by weight or more.

  Further, even if the content of either one of phosphoric acid and its salt and at least one of 2,6-naphthalenedicarboxylic acid and its salt is low, the other content By sufficiently increasing the amount, anticorrosive properties against magnesium-based metals are ensured. In particular, when the entire coolant composition is 100% by weight, at least one of phosphoric acid and its salt is 0.12 to 3% by weight in terms of phosphorus element, 2,6-naphthalenedicarboxylic acid and its salt. 2 to 10% by weight of at least one of them, or 0.24 to 3% by weight of at least one of phosphoric acid and its salt in terms of phosphorus element, at least of 2,6-naphthalenedicarboxylic acid and its salt By making 1 type into 1 to 10 weight%, the cooling fluid composition which shows high corrosion resistance with respect to a magnesium-type metal is obtained.

  Other common corrosion inhibitors include borates, carbonates, sulfates, nitrates, molybdates, benzoates, benzotriazoles, sodium salts of mercaptobenzothiazole, azoles such as tolyltriazole, An ethanolamine salt can be contained, and the anticorrosion property can be further improved. Of these, the addition of an organic acid-based corrosion inhibitor exhibits a higher anticorrosion effect.

  However, although fluorine has a high anticorrosive property against magnesium-based metals, it has a bad influence on aluminum-based metals, so it is preferable to suppress the content in the coolant composition of the present invention. For example, when the entire coolant composition is 100% by weight, it is preferably 0.5% by weight or less. More preferably, it does not substantially contain elemental fluorine.

  The cooling liquid composition of the present invention is used by dissolving the cooling liquid composition in a solvent such as water in a cooling system, and in a state where it is mixed with a solvent and used in the same manner as a general cooling liquid composition. Are often manufactured and distributed. That is, in the state of use in which the cooling liquid composition of the present invention is dissolved in a solvent, when the whole is 100% by volume, the solvent is contained in an amount of 40 to 80% by volume (the cooling liquid composition is contained in an amount of 20 to 60% by volume). Should be used. Even if the coolant composition of the present invention is used by being mixed with a solvent within the above range, at least one of phosphoric acid and a salt thereof, and at least one of 2,6-naphthalenedicarboxylic acid and a salt thereof are used. If the content of one kind is within the range already described, the corrosion resistance to magnesium-based metal and aluminum-based metal is effectively exhibited. Of course, use in the state of a stock solution is also possible.

  At least one of phosphoric acid and a salt thereof added to the cooling liquid composition of the present invention and at least one of 2,6-naphthalenedicarboxylic acid and a salt thereof are completely dissolved in cooling water at least when used. There is a need. Further, from the viewpoint of storage stability and handleability, it is desirable that these are completely dissolved. Therefore, sodium hydroxide, potassium hydroxide, or the like may be further added to the cooling water composition of the present invention to improve solubility. At this time, it is optimal that the pH in use is adjusted to 7-10.

  As described in detail above, the coolant composition of the present invention uses at least one of phosphoric acid and its salt and at least one of 2,6-naphthalenedicarboxylic acid and its salt in combination. Thus, it has both anticorrosive properties for magnesium-based metals and anticorrosive properties for aluminum-based metals. Therefore, it is desirable that the coolant composition of the present invention is used for a coolant channel in which an aluminum-based metal or a magnesium-based metal is exposed on at least a part of the surface. Specifically, a cooling system for an internal combustion engine such as an engine such as an engine block, a turbocharger, an exhaust gas cooler, and a fuel injector can be used.

  In the cooling liquid composition of the present invention, at least one of phosphoric acid and a salt thereof, and at least one of 2,6-naphthalenedicarboxylic acid and a salt thereof are already present in a cooling system such as an automobile. After adding the antifreeze liquid, it is possible to add each component so as to have a desired content, or by arranging these components in the cooling system in advance and then adding the existing antifreeze liquid to the cooling liquid. You may adjust so that phosphorus etc. may melt | dissolve in a composition. Each component can be added, for example, in the form of granules or tablets, or can be applied to the surface of a cooling system component as a coating composition.

  As mentioned above, although embodiment of the cooling fluid composition of this invention was described, the cooling fluid composition of this invention is not limited to the said embodiment. The coolant composition of the present invention can be implemented in various forms that have been modified or improved by those skilled in the art without departing from the scope of the present invention.

  Examples of the coolant composition of the present invention will be described below together with comparative examples.

[Examples 1 to 4]
A commercially available antifreeze mainly made of ethylene glycol (Super LLC manufactured by Toyota Motor Corporation) was diluted to 50% by weight with pure water. 2,6-naphthalenedicarboxylic acid and orthophosphoric acid are mixed at a ratio shown in Table 1 with respect to 100 parts by weight of this aqueous solution (hereinafter simply referred to as “antifreeze”), and this mixed solution is mixed with potassium hydroxide. Was adjusted to pH 7.7 to prepare a cooling liquid composition (Examples 1 to 4) in use. Table 2 shows the composition of each coolant composition. Table 3 shows the composition of the coolant composition in the state of the stock solution.

[Comparative Example 1]
The comparative example 1 was made into the coolant composition which consists of said antifreeze. The coolant composition was adjusted to pH 7.7 with potassium hydroxide.

[Comparative Examples 2 to 5]
While mixing 2,6-naphthalenedicarboxylic acid or orthophosphoric acid in the proportions shown in Table 1 with respect to the above antifreeze, the mixture was adjusted to pH 7.7 with potassium hydroxide, and Comparative Example 2 5 coolant compositions were prepared. Tables 2 and 3 show the compositions of the respective coolant compositions.

[Comparative Example 6]
While mixing 1,4-naphthalenedicarboxylic acid in the ratio of Table 1 with respect to said antifreeze, this liquid mixture was adjusted to pH 7.7 with potassium hydroxide, and the cooling fluid composition of the comparative example 6 was prepared. Prepared. The composition of the coolant composition is shown in Table 2 and Table 3.

[Comparative Example 7]
While mixing potassium fluoride with the ratio of Table 1 with respect to said antifreeze, this liquid mixture was adjusted to pH 7.7 with potassium hydroxide, and the cooling fluid composition of the comparative example 7 was prepared. The composition of the coolant composition is shown in Table 2 and Table 3.

  Table 2 shows ethylene glycol, 2,6-naphthalenedicarboxylic acid (or 1,4-naphthalenedicarboxylic acid), elemental phosphorus (or elemental fluorine) when the cooling liquid composition in use is 100% by weight, And the water content. The balance consists of corrosion inhibitor components other than the above contained in the antifreeze. Table 3 shows ethylene glycol, 2,6-naphthalenedicarboxylic acid (or 1,4-naphthalenedicarboxylic acid), and phosphorus element (or fluorine) when the coolant composition of the stock solution (not including water) is 100% by weight. In addition to the content ratio of (element), the content of water used for dilution is shown as the content ratio of water when the coolant composition in use is 100% by volume.

[Evaluation]
[Anode polarization measurement]
About each cooling fluid composition of Examples 1-4 and Comparative Examples 1-7, the passive body holding current density and the pitting corrosion potential were measured by the electrochemical test. The electrochemical test was performed by using a sample electrode using a magnesium alloy (AZ91D) plate, a reference electrode using a saturated calomel electrode (SCE), a counter electrode using a platinum plate, and a coolant filled in an electrolytic cell. It was performed by immersing in the composition. The terminal of each electrode was connected to a constant potential electrolyzer (potentiostat).

  In a state where the electrolytic cell coolant composition was maintained at 88 ° C., the potentiostat was operated to create an anodic polarization curve. From the obtained anodic polarization curve, passive substance holding current density and pitting potential (SCE standard sample) Electrode potential). The test results are shown in Table 2 together with the composition of the coolant composition. In Table 2, the ◯ mark in the pitting corrosion potential column indicates that no pitting corrosion occurred on the sample electrode (magnesium alloy plate) even when the applied voltage exceeded 500 mV in terms of the SCE standard sample electrode potential. Indicates.

[Metal corrosion test]
For each of the coolant compositions of Example 1, Comparative Example 1 and Comparative Example 7, in accordance with JIS K 2234 “Antifreeze”, an aluminum alloy corrosion test (aluminum cast heat transfer surface corrosion property: hereinafter “aluminum heat transfer”). Surface test "). The test was performed by bringing one end of a glass tube filled with each coolant composition into contact with the surface of an aluminum alloy (AC2A) plate and bringing the coolant composition into contact with the surface of the aluminum alloy plate. . At this time, the aluminum alloy plate was heated and maintained at 135 ° C. The mass change before and after the contact for 168 hours in this state was measured. The results are shown in Table 2.

According to anodic polarization measurement using a magnesium alloy plate as a sample electrode, the coolant compositions of Examples 1 to 4 containing both 2,6-naphthalenedicarboxylic acid and orthophosphoric acid had a passive state holding current density of 8 μA / cm. It was found that no pitting corrosion occurred even when the value was ² or less and exceeded 500 mV. In particular, the coolant compositions of Examples 1 to 3 contain both 2,6-naphthalenedicarboxylic acid and orthophosphoric acid, and 2.9% by weight of 2,6-naphthalenedicarboxylic acid and / or 0% of phosphorus element. More than .58 wt%, the passive state holding current density was suppressed to 6 μA / cm ² or less.

  Further, as can be seen from Comparative Example 2 and Comparative Example 3, Comparative Example 4 and Comparative Example 5 in which 2,6-naphthalenedicarboxylic acid or orthophosphoric acid is added alone, There is no significant change in the passive state holding current density even when the value is increased. However, the coolant composition of Example 4 containing both 2,6-naphthalenedicarboxylic acid and orthophosphoric acid showed the same characteristics as Comparative Example 3 and Comparative Example 5 although the addition amount was small. That is, by adding both 2,6-naphthalenedicarboxylic acid and orthophosphoric acid, the corrosion resistance to the magnesium alloy was exhibited even when the addition amount was small (Example 4). Furthermore, when the addition amount was increased, the improvement of the corrosion resistance to the magnesium alloy became remarkable (Examples 1 to 3).

  In the coolant composition of Comparative Example 6, 1,4-naphthalenedicarboxylic acid was added instead of 2,6-naphthalenedicarboxylic acid, but the corrosion resistance of the magnesium alloy was higher than that before the addition (Comparative Example 1: Antifreeze liquid). Declined. Therefore, even if 1,4-naphthalenedicarboxylic acid is added together with orthophosphoric acid, it is considered that an improvement in corrosion resistance cannot be expected.

  According to a metal corrosion test using an aluminum alloy plate, aluminum in contact with the coolant composition of Example 1 (antifreeze added with 2,6-naphthalenedicarboxylic acid and orthophosphoric acid) and Comparative Example 1 (antifreeze only) The alloy plate did not change in mass before and after the aluminum heat transfer surface test. That is, 2,6-naphthalenedicarboxylic acid and phosphorus element did not affect the corrosion of the aluminum alloy. On the other hand, although the coolant composition of Comparative Example 7 containing elemental fluorine was excellent in corrosion protection of magnesium alloy, the mass of the aluminum alloy plate was greatly reduced before and after the aluminum heat transfer surface test.

  That is, the coolant compositions of Examples 1 to 4 containing both 2,6-naphthalenedicarboxylic acid and orthophosphoric acid are coolant compositions that have both corrosion resistance against magnesium-based metals and corrosion resistance against aluminum-based metals. It was.

Claims (8)

A coolant composition comprising as a main component one or more melting point depressants selected from the group consisting of glycols and alcohols,
A coolant composition comprising at least one of phosphoric acid and a salt thereof and at least one of 2,6-naphthalenedicarboxylic acid and a salt thereof.   The coolant composition according to claim 1, comprising at least one of phosphoric acid and a salt thereof in an amount of 0.12 to 3% by weight in terms of phosphorus when the entire coolant composition is 100% by weight.   The cooling fluid composition according to claim 1, comprising 1 to 10% by weight of at least one of 2,6-naphthalenedicarboxylic acid and a salt thereof when the total cooling fluid composition is 100% by weight.   When the total amount of the cooling liquid composition is 100% by weight, at least one of phosphoric acid and its salt is 0.12 to 3% by weight in terms of phosphorus element, of 2,6-naphthalenedicarboxylic acid and its salt The cooling fluid composition according to claim 1, comprising at least 1 to 2% by weight.   When the total amount of the coolant composition is 100% by weight, at least one of phosphoric acid and its salt is 0.24 to 3% by weight in terms of phosphorus element, of 2,6-naphthalenedicarboxylic acid and its salt The coolant composition according to claim 1, comprising 1 to 10% by weight of at least one kind.   The cooling fluid composition according to any one of claims 2 to 5, which is used in a state containing 40 to 80% by volume of the solvent when the whole is 100% by volume in a use state dissolved in the solvent.   The coolant composition according to any one of claims 1 to 6, substantially free of elemental fluorine.   The coolant composition according to any one of claims 1 to 7, which is used for a coolant channel in which an aluminum-based metal and a magnesium-based metal are exposed on at least a part of the surface.