Coolant composition and concentrated coolant composition

Abstract

The present invention relates to a coolant composition containing the following substances: a) an alcohol; b) water; c1) a triazole compound; c2) an imidazole compound; d) phosphate ions; and e) metasilicate.

Description

Background of the Invention 1. Technical Field

[0002] The present disclosure relates to coolant compositions and concentrated coolant compositions, and particularly to coolant compositions for motor vehicles having a battery. 2. Background Art

[0004] In motor vehicles, a coolant is used to cool an engine, etc., and in a motor vehicle having a battery, the coolant is also used to cool a battery, etc. The coolant for cooling a battery needs to have various properties such as, for example, low electric conductivity and high corrosion prevention. However, a rust inhibitor for improving corrosion prevention generally increases the electric conductivity of the coolant, and thus it is difficult to achieve both low electric conductivity and high corrosion prevention in the coolant. In addition, when the corrosion prevention of aluminum in the coolant (corrosion prevention with respect to aluminum) is insufficient, hydrogen is generated due to aluminum corrosion, which may cause an increase in the hydrogen concentration and a decrease in the liquid level in the storage tank.

[0005] Coolant compositions containing various components are known. For example, Japanese Unexamined Patent Application Publication No. 7-278855 and Japanese Unexamined Patent Application Publication No. 2006-510168 (translation of PCT application) disclose coolant compositions containing azoles such as triazole and imidazole. Japanese Unexamined Patent Application Publication No. 2001-72967 discloses a coolant composition containing phosphoric acid or an alkali metal salt thereof. Japanese Unexamined Patent Application Publication No. 2011-79712 discloses that hydrogen production can be terminated by adding phosphoric acid to a hydrogen production system.

[0006] However, the above coolant compositions all have room for improvement in terms of satisfying all of low electric conductivity, high corrosion prevention, and low hydrogen production property. Summary of the Invention

[0007] As described above, the above coolant compositions all have room for improvement in terms of satisfying all of low electric conductivity, high corrosion prevention, and low hydrogen production property. Therefore, one aspect of the present disclosure provides a coolant composition having low electric conductivity, high corrosion prevention, and low hydrogen production property.

[0008] The inventors have found that a coolant composition has all of low electric conductivity, high corrosion prevention, and low hydrogen production property due to a combination of a triazole compound, an imidazole compound, and a phosphate ion.

[0009] (1) A first aspect of the present disclosure relates to a coolant composition containing the following substances:

[0010] a) an alcohol;

[0011] b) water;

[0012] c1) a triazole compound;

[0013] c2) an imidazole compound;

[0014] d) phosphate ions; and

[0015] e) metasilicate.

[0016] (2) The ratio of the content of the imidazole compound to the content of the triazole compound may be less than 0.1.

[0017] (3) The pH of the coolant composition may be from 5.5 to 9.0.

[0018] (4) The composition may be used in a cooling circuit including a battery.

[0019] (5) The electrical conductivity of the coolant composition may be 200 μS / cm or less at 25 °C.

[0020] (6) A second aspect of the present disclosure relates to a concentrated coolant composition for obtaining the coolant composition of the first aspect, which is used after dilution with water.

[0021] (7) A third aspect of the present disclosure relates to a concentrated coolant composition comprising:

[0022] alcohol;

[0023] triazole compound;

[0024] imidazole compound; and

[0025] phosphate ions.

[0026] Aspects of the present disclosure enable it to provide a coolant composition having low electrical conductivity, high corrosion protection, and low hydrogen generation properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Hereinafter, the features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described with reference to the drawings, in which like reference numerals denote like elements, and in which:

[0028] Figure 1 An instrument for hydrogen generation property testing in the examples is shown. DETAILED DESCRIPTION

[0029] Hereinafter, preferred embodiments of the present invention will be described in detail.

[0030] The coolant composition of the embodiment of the present invention contains the following substances: a) alcohol; b) water; c1) triazole compound; c2) imidazole compound; d) phosphate ions; and e) metasilicate. In the coolant composition of this embodiment, due to the combination of the triazole compound, imidazole compound, and phosphate ions, high metal corrosion protection (high corrosion protection regarding metals) and low hydrogen generation properties can be achieved simultaneously while maintaining low electrical conductivity.

[0031] In the coolant composition of the present embodiment, an alcohol (component a)) and water (component b)) are used as base materials.

[0032] The alcohol acts as a freezing point depressant and has anti-freezing properties. The alcohol may be, for example, at least one alcohol selected from the group consisting of monohydric alcohols, dihydric alcohols, trihydric alcohols, and glycol monoalkyl ethers.

[0033] The monohydric alcohol may be, for example, one or a mixture of two or more selected from methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, and octanol.

[0034] The dihydric alcohol may be, for example, one or a mixture of two or more selected from ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3 - propanediol, 1,4 - butanediol, 1,3 - butanediol, 1,5 - pentanediol, and hexanediol.

[0035] The trihydric alcohol may be, for example, one or a mixture of two or more selected from glycerol, trimethylolethane, trimethylolpropane, 5 - methyl - 1,2,4 - heptanetriol, and 1,2,6 - hexanetriol.

[0036] The glycol monoalkyl ether may be, for example, one or a mixture of two or more selected from ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and tetraethylene glycol monobutyl ether.

[0037] Among the above - mentioned alcohols, from the viewpoints of handleability, cost, and availability, ethylene glycol, propylene glycol, and 1,3 - propanediol are preferred, and ethylene glycol is more preferred.

[0038] Considering the anti - freezing properties, based on the mass of the base materials, the alcohol content is preferably 20% by mass to 80% by mass, more preferably 30% by mass to 70% by mass, and particularly preferably 40% by mass to 60% by mass.

[0039] As for water, for example, ion - exchanged water and distilled water can be used. Based on the mass of the base materials, the water content is preferably 20% by mass to 80% by mass, more preferably 30% by mass to 70% by mass, and particularly preferably 40% by mass to 60% by mass.

[0040] The coolant composition of the present embodiment contains a triazole compound (component c1)). Due to the triazole compound contained in the coolant composition, metal corrosion prevention (especially aluminum corrosion prevention and steel corrosion prevention) is improved, and the hydrogen generation property is also reduced.

[0041] There is no particular limitation on the triazole compound; for example, an aromatic triazole or an alkyl-substituted aromatic triazole can be used, and benzotriazole and tolyltriazole are preferred.

[0042] In the coolant composition of the present embodiment, the content of the triazole compound is preferably 0.05% by mass to 1.0% by mass, and more preferably 0.05% by mass to 0.5% by mass, based on 100% by mass of the base material. When the content of the triazole compound is within this range, high aluminum corrosion prevention, high steel corrosion prevention, and low hydrogen generation properties are achieved while maintaining low conductivity.

[0043] The coolant composition of the present embodiment contains an imidazole compound (component c2)). Due to the imidazole compound contained in the coolant composition, metal corrosion prevention (especially steel corrosion prevention) is improved.

[0044] There is no particular limitation on the imidazole compound; for example, imidazole, an alkyl- or aryl-substituted imidazole, and a condensed imidazole can be used, imidazole, an alkyl-substituted imidazole, and benzimidazole are preferred, and an alkyl-substituted imidazole is more preferred, and 1-methylimidazole is particularly preferred.

[0045] In the coolant composition of the present embodiment, the content of the imidazole compound is preferably 0.0005% by mass to 0.09% by mass, and more preferably 0.0005% by mass to 0.04% by mass, based on 100% by mass of the base material. When the content of the imidazole compound is within this range, sufficiently low conductivity and high steel corrosion prevention are achieved.

[0046] In the coolant composition of the present embodiment, the ratio of the content of the imidazole compound to the content of the triazole compound (c2 / c1) is preferably less than 0.1, more preferably 0.01 or more and less than 0.1, further preferably 0.04 or more and less than 0.1, particularly preferably 0.06 or more and less than 0.1, and most preferably 0.08 or more and less than 0.1. When c2 / c1 is less than 0.1, the conductivity of the coolant composition is significantly reduced while maintaining high metal corrosion prevention.

[0047] The coolant composition of the present embodiment contains phosphate ions (component d)). Due to the phosphate ions contained in the coolant composition, hydrogen generation from aluminum can be inhibited.

[0048] Regarding the coolant composition of the present embodiment, there is no particular limitation on the compound that generates phosphate ions, and examples include phosphoric acid and its salts. The compound that generates phosphate ions is preferably phosphoric acid and its alkali metal salts, and more preferably phosphoric acid.

[0049] In the coolant composition of the present embodiment, the content of phosphate ions (content calculated as P) is preferably from 0.0005% by mass to 0.01% by mass, and more preferably from 0.0005% by mass to 0.005% by mass, with the base material being 100% by mass. When the content of phosphate ions is within this range, low electrical conductivity and high metal corrosion prevention (especially aluminum corrosion prevention) are achieved.

[0050] The coolant composition of the present embodiment contains metasilicate (component (e)). In the coolant composition of the present embodiment, metasilicate is used as a pH regulator. Due to the metasilicate used as a pH regulator, the electrical conductivity of the coolant composition can be lower than that obtained when commonly used potassium hydroxide or the like is used.

[0051] There is no particular limitation on the metasilicate, and it may be an alkali metal salt or alkaline earth metal salt of metasilicic acid, and preferably an alkali metal salt of metasilicic acid, more preferably sodium metasilicate.

[0052] In the coolant composition of the present embodiment, the content of metasilicate (content calculated as acid anhydride) can be such that the pH of the coolant composition can be adjusted to a predetermined range, and is generally from 0.0005% by mass to 0.05% by mass, with the base material being 100% by mass.

[0053] In addition to the above components (a) to (e)), as long as the effects of the present invention are not impaired, the coolant composition of the present embodiment may contain one or more additional additives as needed. There is no particular limitation on the additional additives, and examples include metal corrosion inhibitors (carboxylic acids, nitrates, nitrites, thiazoles, molybdates, and borates), dyes, bittering agents, and defoamers. In the coolant composition of the present embodiment, the additional additives and their contents are selected such that the electrical conductivity of the coolant composition does not exceed 200 μS / cm. Based on the coolant composition, the total content of the additional additives is generally 10% by mass or less, and preferably 5% by mass or less.

[0054] The coolant composition of the present embodiment preferably does not contain a C5-C 16 aliphatic monocarboxylic acid or its alkali metal salt, ammonium salt, or amine salt. Examples of the C5-C 16 aliphatic monocarboxylic acid include heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, and mixtures thereof. In one embodiment, the coolant composition of the present embodiment does not contain octanoic acid and 2-ethylhexanoic acid and their alkali metal salts, ammonium salts, and amine salts.

[0055] The pH of the coolant composition of the present embodiment is preferably from 5.5 to 9.0 and more preferably from 6.0 to 8.0 at 20°C. The pH of the coolant composition can be measured in accordance with JIS K 2234 8.4 pH value.

[0056] The coolant composition of the present embodiment has a sufficiently low conductivity, and the conductivity is preferably 200 μS / cm or less, more preferably 150 μS / cm or less at 25°C. The conductivity of the coolant composition can be measured using a personal SC meter SC72 and a detector SC72SN-11 (for pure water) manufactured by Yokogawa Electric Corporation.

[0057] The coolant composition of the present embodiment has sufficiently high metal corrosion prevention, and for example, aluminum corrosion prevention, steel corrosion prevention, and brass corrosion prevention are all -0.15 mg / cm 2 or greater. According to JIS K 2234 8.6 metal corrosion prevention, the corrosion prevention of the coolant composition can be directly measured using the coolant composition as a test solution.

[0058] In the present embodiment, as long as the effects of the present invention are obtained, there is no particular limitation on the method for preparing the coolant composition, and common methods for producing the coolant composition can be used. For example, by mixing components a) to d) and additional additives as needed, uniformly stirring the mixture, and adjusting the pH to a predetermined level using metasilicate, the coolant composition can be prepared.

[0059] The present embodiment also includes a concentrated coolant composition for obtaining the above coolant composition. The concentrated coolant composition of the present embodiment contains components a), c1), c2), and d) of the above coolant composition, and may contain water (component b)), a metasilicate pH regulator (component e)), and additional additives as needed. The concentrated coolant composition of the present embodiment can be used to obtain the coolant composition containing components a) to e) of the present embodiment by diluting it with water by, for example, 1.1 mass times or more and 5 mass times or less. Therefore, the concentrated coolant composition of the present embodiment may contain water (component b)) or may not contain water (component b)). When the concentrated coolant composition of the present embodiment contains water, its content is less than the water content in the coolant composition.

[0060] The coolant composition of the present embodiment can generally be used as a coolant. Since the coolant composition of the present embodiment achieves both low conductivity and high corrosion prevention, the coolant composition of the present embodiment is preferably used as a coolant for HEV, PHEV, EV, and FCV, and more preferably as a coolant for a cooling circuit including a battery in an EV or FCV. Therefore, in a preferred embodiment, the coolant composition of the present embodiment is a coolant composition for a cooling circuit including a battery.

[0061] Hereinafter, the present invention will be described more specifically by way of examples. However, the technical scope of the present invention is not limited to these examples.

[0062] Example 1

[0063] As a base material, 50.0% by mass of ethylene glycol and 50.0% by mass of ion-exchanged water were used, and 0.05% by mass of benzotriazole, 0.0045% by mass of 1-methylimidazole, and 0.0005% by mass of phosphoric acid (calculated as P) were added thereto. The pH of the resulting mixture was adjusted to 7.0 with sodium metasilicate, thereby obtaining the coolant composition of Example 1.

[0064] Example 2

[0065] As a base material, 50.0% by mass of ethylene glycol and 50.0% by mass of ion-exchanged water were used, and 1.0% by mass of tolyltriazole, 0.09% by mass of 1-methylimidazole, and 0.01% by mass of phosphoric acid (calculated as P) were added thereto. The pH of the resulting mixture was adjusted to 7.0 with sodium metasilicate, thereby obtaining the coolant composition of Example 2.

[0066] Example 3

[0067] As a base material, 50.0% by mass of ethylene glycol and 50.0% by mass of ion-exchanged water were used, and 0.18% by mass of tolyltriazole, 0.01% by mass of 1-methylimidazole, and 0.004% by mass of phosphoric acid (calculated as P) were added thereto. The pH of the resulting mixture was adjusted to 7.0 with sodium metasilicate, thereby obtaining the coolant composition of Example 3.

[0068] Example 4

[0069] The coolant composition of Example 4 was obtained in the same manner as in Example 1, except that the amount of 1-methylimidazole added was changed to 0.0005% by mass.

[0070] Example 5

[0071] The coolant composition of Example 5 was obtained in the same manner as in Example 1, except that the amount of benzotriazole added was changed to 0.1% by mass.

[0072] Examples 6 - 8

[0073] The coolant compositions of Examples 6, 7, and 8 were obtained in the same manner as in Example 2, except that the amounts of 1-methylimidazole added were changed to 0.01% by mass, 0.04% by mass, and 0.08% by mass, respectively, and the pH was adjusted to 6.5.

[0074] Examples 9 and 10

[0075] The amounts of phosphoric acid added were changed to 0.0005% by mass and 0.005% by mass, respectively, and the pH was adjusted to 6.5. Except for this, coolant compositions of Examples 9 and 10 were obtained in the same manner as in Example 2.

[0076] Comparative Example 1

[0077] Using 50.0% by mass of ethylene glycol and 50.0% by mass of ion-exchanged water as the base materials, and adding 0.2% by mass of benzotriazole thereto, a coolant composition of Comparative Example 1 was obtained.

[0078] Comparative Example 2

[0079] Using 50.0% by mass of ethylene glycol and 50.0% by mass of ion-exchanged water as the base materials, and adding 0.2% by mass of tolyltriazole thereto, a coolant composition of Comparative Example 2 was obtained.

[0080] Comparative Example 3

[0081] Using 50.0% by mass of ethylene glycol and 50.0% by mass of ion-exchanged water as the base materials, and adding 0.2% by mass of 1-methylimidazole thereto, a coolant composition of Comparative Example 3 was obtained.

[0082] Comparative Example 4

[0083] Tolyltriazole was not used, and the pH was adjusted to 7.2. Except for this, a coolant composition of Comparative Example 4 was obtained in the same manner as in Example 3.

[0084] Comparative Example 5

[0085] Except for not using phosphoric acid or the pH regulator sodium metasilicate, a coolant composition of Comparative Example 5 was obtained in the same manner as in Example 3.

[0086] Comparative Example 6

[0087] Except for not using 1-methylimidazole, a coolant composition of Comparative Example 6 was obtained in the same manner as in Example 3.

[0088] Comparative Example 7

[0089] Using 50.0% by mass of ethylene glycol and 50.0% by mass of ion-exchanged water as the base materials, adding 0.0005% by mass of phosphoric acid (calculated as P) thereto, and adjusting the pH of the resulting mixture to 7.2 with sodium metasilicate, a coolant composition of Comparative Example 7 was obtained.

[0090] Comparative Example 8

[0091] Using 50.0% by mass of ethylene glycol and 50.0% by mass of ion-exchanged water as the base materials, 0.004% by mass of phosphoric acid (calculated as P) was added thereto, and the pH of the resulting mixture was adjusted to 7.0 with sodium metasilicate, thereby obtaining the coolant composition of Comparative Example 8.

[0092] Comparative Example 9

[0093] The coolant composition of Comparative Example 9 was obtained in the same manner as in Comparative Example 8, except that potassium hydroxide was used instead of the sodium metasilicate pH regulator.

[0094] The conductivity, pH, metal corrosion prevention, and hydrogen generation property of aluminum of the coolant compositions of Examples 1 to 10 and Comparative Examples 1 to 9 were evaluated by the following methods.

[0095] Conductivity

[0096] The conductivity was measured at 25 °C using a personal SC meter SC72 and a detector SC72SN-11 (for pure water) manufactured by Yokogawa Electric Corporation.

[0097] pH

[0098] The pH was measured at 20 °C in accordance with JIS K 2234 8.4.

[0099] Corrosion prevention

[0100] The corrosion prevention was measured in accordance with JIS K 2234 8.6 metal corrosion prevention. However, the metals were limited to aluminum, steel, and brass, and each coolant composition was directly used as the test solution without using a conditioned solution. In each case, when it was -0.15 mg / cm 2 or greater, the corrosion prevention with respect to aluminum, steel, and brass was considered favorable.

[0101] Hydrogen generation property

[0102] Figure 1 The instrument shown in was used for visual inspection of the amount of gas generated. Specifically, in the instrument shown in Figure 1 the test tube was filled with the coolant composition, the test piece cut from the aluminum heat dissipation tube was placed in the lower part and left standing at 45 °C for 120 hours, and the amount of gas generated by the aluminum test piece in the graduated test tube filled with the coolant composition was visually inspected. The gas generated was confirmed to be hydrogen by gas chromatography analysis.

[0103] Tables 1 to 4 show the formulations and evaluation results of the coolant compositions of Examples 1 to 10 and Comparative Examples 1 to 9.

[0104] Table 1

[0105]

[0106] Table 2

[0107]

[0108] Table 3

[0109]

[0110] Table 4

[0111]

[0112] As shown in Tables 1 to 4, the coolant compositions of Examples 1 to 10 containing triazole compounds, imidazole compounds, and phosphate ions have high metal corrosion prevention and low hydrogen generation while having low conductivity.

[0113] According to Comparative Examples 1 and 2, when a triazole compound was added alone to the base material, the steel corrosion prevention was poor and hydrogen was generated in the hydrogen generation test. According to Comparative Example 3, when an imidazole compound was added alone to the base material, the aluminum corrosion prevention and the steel corrosion prevention were poor and hydrogen was generated in the hydrogen generation test. According to Comparative Examples 7 and 8, when phosphoric acid was added to the base material and the pH was adjusted with sodium metasilicate, the steel corrosion prevention and the brass corrosion prevention were poor and hydrogen was generated in the hydrogen generation test. The comparison between Comparative Examples 8 and 9 revealed that the conductivity increased by changing the pH regulator from sodium metasilicate to potassium hydroxide.

[0114] Furthermore, the comparison between Example 3 and Comparative Example 4 revealed that due to the triazole compound contained in the coolant composition, the aluminum corrosion prevention and the steel corrosion prevention were improved and the generation of hydrogen was suppressed in the hydrogen generation test. The comparison between Example 3 and Comparative Example 5 revealed that due to the phosphate ions contained in the coolant composition, the generation of hydrogen was suppressed in the hydrogen generation test. The comparison between Example 3 and Comparative Example 6 revealed that due to the imidazole compound contained in the coolant composition, the steel corrosion prevention was improved.

[0115] According to Example 2 and Examples 6 to 8, a smaller ratio (c2 / c1) of the imidazole compound content to the triazole compound content tended to result in a lower conductivity of the coolant composition, and a c2 / c1 ratio of less than 0.1 resulted in a significantly lower conductivity, which was more preferable.

Claims

1. A coolant composition, characterized in that, It contains: alcohol; water; a triazole compound; an imidazole compound; phosphate ions; and metasilicate, wherein the alcohol and water are used as base materials, the content of the alcohol is 20% by mass to 80% by mass, based on the mass of the base materials, the content of the water is 20% by mass to 80% by mass, based on the mass of the base materials, the content of the triazole compound is 0.05% by mass to 1.0% by mass, where the base materials are 100% by mass, the content of the imidazole compound is 0.0005% by mass to 0.09% by mass, where the base materials are 100% by mass, the content of the phosphate ions is 0.0005% by mass to 0.01% by mass in terms of P, where the base materials are 100% by mass, the content of the metasilicate is 0.0005% by mass to 0.05% by mass in terms of acid anhydride, where the base materials are 100% by mass.

2. The coolant composition according to claim 1, characterized in that, The ratio of the content of the imidazole compound to the content of the triazole compound is less than 0.

1.

3. The coolant composition according to claim 1 or 2, characterized in that, The pH of the coolant composition is 5.5 to 9.

0.

4. The coolant composition according to claim 1 or 2, characterized in that, The coolant composition is used for a cooling circuit including a battery.

5. The coolant composition according to claim 1 or 2, characterized in that, The conductivity of the coolant composition is 200 μS / cm or less at 25°C.

6. A concentrated coolant composition for obtaining the coolant composition according to claim 1 or 2, characterized in that, The concentrated coolant composition is used after dilution with water.

Images