Additive for coolant or method for producing coolant, and additive for coolant

Abstract

Provided is a coolant additive that can be used in the production of a non-phosphate coolant. This method for producing a coolant additive includes a reaction step for mixing and reacting water, an alcohol, a silicate, and a metal coupling agent.

Description

[Technical Field]

[0001] The present invention relates to a coolant additive or a method for producing a coolant, and to a coolant additive. [Background technology]

[0002] Coolants containing phosphoric acid compounds, which have excellent rust-preventing properties for iron or aluminum, are commonly used as engine coolants and other coolants. However, when hard water is used to dilute the coolant, a chemical reaction between phosphoric acid and minerals occurs, resulting in precipitation and a decrease in the rust-preventing properties of the engine coolant. Furthermore, there is a growing trend to reduce the use of phosphoric acid, which can cause eutrophication, and the development of non-phosphate-based coolants is desirable.

[0003] For example, Patent Document 1 discloses a coolant composition containing alcohol, silicate, and a calcium compound. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 7-70558 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the composition of Patent Document 1 is used as a coolant, the coolant is prone to gelling and becoming unstable due to the silicate contained in the composition. Therefore, there is a need for the development of a non-phosphate-based coolant that is less susceptible to gelling.

[0006] SUMMARY OF THE INVENTION It is therefore an object of one aspect of the present invention to provide a coolant additive that can be used to produce non-phosphate based coolants. [Means for solving the problem]

[0007] To achieve the above object, the inventors conducted extensive research and discovered that a coolant additive produced by mixing and reacting specific components can be used to produce a coolant that is less prone to gelling and is highly stable. They also discovered that the coolant has the same rust prevention properties as phosphoric acid-based coolants, leading to the completion of the present invention.

[0008] That is, the present invention comprises the following configurations. A method for producing a coolant additive, comprising a reaction step of mixing and reacting water, an alcohol, a silicate, and a metal coupling agent. A coolant additive comprising a mixture of water, an alcohol, a silicate, a metal coupling agent, and a partial reaction product of these components. [Effects of the Invention]

[0009] Advantageous Effects of Invention According to one aspect of the present invention, it is possible to provide a coolant additive that can be used to produce a non-phosphate-based coolant. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 shows the results of the stability test in Evaluation Example 1. [Figure 2] FIG. 10 is a graph showing the results of the aluminum casting heat transfer surface corrosion test of Evaluation Example 4. [Figure 3] FIG. 10 is a diagram showing the results of a metal corrosivity test in Evaluation Example 4. [Figure 4] FIG. 10 is a diagram showing the results of a metal corrosivity test in Evaluation Example 5. [Figure 5] FIG. 10 is a graph showing the results of the hard water stability test in Evaluation Example 6. [Figure 6] FIG. 10 is a diagram showing the evaluation results of Evaluation Example 8. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to these, and various modifications are possible within the scope of the description. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. Unless otherwise specified in this specification, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B."

[0012] 1. Manufacturing method of coolant additives A method for producing a coolant additive according to one aspect of the present invention includes a reaction step of mixing and reacting water, an alcohol, a silicate, and a metal coupling agent.

[0013] In this specification, the term "metal coupling agent" refers to a compound having two or more different reactive groups (e.g., an epoxy group and an alkoxysilyl group), but is not limited to compounds that serve to bond two or more different substances. In addition, when a compound has three or more reactive groups, it is sufficient that at least two of the reactive groups are different.

[0014] The reaction step can produce a coolant additive containing a reactant formed by reacting at least water, silicate, or a metal coupling agent, as described below.

[0015] (water) The water used in the method for producing a coolant additive according to one aspect of the present invention may be purified water such as ultrapure water, pure water, or distilled water.

[0016] (alcohol) The alcohol used in the method for producing a coolant additive according to one embodiment of the present invention may be a monohydric alcohol or a polyhydric alcohol. Furthermore, the alcohol may be a primary alcohol, a secondary alcohol, or a tertiary alcohol. The alcohol is preferably a polyhydric alcohol, more preferably an aliphatic polyhydric alcohol, and even more preferably a primary aliphatic polyhydric alcohol. From the viewpoint of suppressing gelation and freezing of the coolant, the alcohol is preferably a glycol or glycol ether. From the viewpoint of suppressing gelation of the coolant, the lower limit of the carbon number of the alcohol is preferably 2 or more. Furthermore, from the viewpoint of suppressing gelation of the coolant, the upper limit of the carbon number of the alcohol is preferably 10 or less, more preferably 5 or less.

[0017] Examples of preferred alcohols include ethylene glycol, propylene glycol, diethylene glycol, glycerin, and 1,3-propanediol. Among these alcohols, ethylene glycol or propylene glycol are more preferred, and ethylene glycol is even more preferred, in terms of preventing the coolant from gelling and freezing. Use of ethylene glycol improves the rust prevention properties for aluminum.

[0018] (silicate) The silicate used in the method for producing a coolant additive according to one embodiment of the present invention is preferably a silicate containing an element of Group 1 or Group 2 of the periodic table, in terms of improving rust prevention properties.

[0019] An example of the composition formula of a silicate containing an element from Group 1 or Group 2 of the periodic table is a substance represented by nX2O·mSiO2. X can be, for example, an alkali metal or alkaline earth metal such as potassium, sodium, lithium, magnesium, or calcium. n and m are preferably 0.1 to 10. The structure of the silicate may be ortho-, meta-, or pyro-, etc. Among silicates containing alkali metals or alkaline earth metals, alkali metal silicates are more preferred in terms of improving rust prevention, and potassium silicate, represented by the compound name, is even more preferred.

[0020] (Metal Coupling Agent) The metal coupling agent used in the method for producing a coolant additive according to one embodiment of the present invention refers to a coupling agent containing a metal element such as titanium, zirconium, aluminum, silicon, etc. Among them, a silane coupling agent is preferred from the viewpoint of suppressing gel formation in the coolant.

[0021] Examples of titanium coupling agents include titanium alkoxides, etc. Examples of zirconium coupling agents include zirconium alkoxides, etc. Examples of aluminum coupling agents include aluminum alkoxides, etc.

[0022] Examples of silane coupling agents include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-ureidopropyltrialkoxysilane, 3-isocyanatepropyltriethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, and 3-mercaptopropyltrimethoxysilane. Examples of organic functional groups associated with silane coupling agents include vinyl groups, epoxy groups, styryl groups, methacrylic groups, acrylic groups, amino groups, ureido groups, isocyanate groups, isocyanurate groups, mercapto groups, and methylene groups. The number of hydroxyl groups associated with the silanol groups is preferably between one and three. Silane coupling agents having epoxy groups are more preferred, and 3-glycidoxypropyltrimethoxysilane (hereinafter sometimes referred to as "3-GPTMS") is even more preferred, as they suppress the formation of gel in the coolant and do not have an unpleasant odor.

[0023] (Reaction process conditions) In the reaction step, water, alcohol, silicate, and a metal coupling agent are mixed to prepare a mixture.

[0024] The lower limit of the amount of the metal coupling agent is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, based on 100% by mass of the mixture. The upper limit of the amount of the metal coupling agent is preferably 35% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less. When the amount of the metal coupling agent is within the above range, the reaction proceeds efficiently. Furthermore, even when the coolant composition is mixed with ethylene glycol, water, or the like to produce a coolant, gelation is further suppressed, resulting in a stabilized coolant.

[0025] The lower limit of the amount of silicate is preferably 12.5% ​​by mass or more, more preferably 15% by mass or more, and even more preferably 17.5% by mass or more, based on 100% by mass of the mixture. The upper limit of the amount of silicate is preferably 25% by mass or less, more preferably 22.5% by mass or less, and even more preferably 20% by mass or less. When the amount of silicate is within the above range, the reaction proceeds efficiently, and the resulting coolant exhibits good rust prevention properties.

[0026] The lower limit of the amount of alcohol may be 0.1% by mass or more, 1% by mass or more, 2% by mass or more, or 5% by mass or more, based on 100% by mass of the mixture. The upper limit of the amount of alcohol may be 50% by mass or less, 40% by mass or less, 30% by mass or less, or 20% by mass or less. When the amount of alcohol is within the above range, the reaction proceeds efficiently. Furthermore, by reacting an alcohol within the above range with a mixture containing a silicate and a metal coupling agent, the corrosion resistance of aluminum is improved.

[0027] The lower limit of the amount of water is preferably 22.5% by mass or more, more preferably 35% by mass or more, based on 100% by mass of the mixture. The upper limit of the amount of water is preferably 75% by mass or less, more preferably 60% by mass or less. When the amount of water is within the above range, the reaction proceeds efficiently. In one embodiment, from the viewpoint of facilitating the preparation of a coolant containing a coolant additive, the amount of water blended is preferably greater than the amounts of the metal coupling agent, silicate, and alcohol blended.

[0028] When preparing the mixture, the order of mixing is not particularly limited, but from the viewpoint of the stability of the coolant additive, it is preferable to mix water and silicate and then mix the metal coupling agent. The mixture may be prepared by a known method such as stirring.

[0029] The reaction temperature is usually 20° C. to 80° C., preferably 25° C. to 60° C., because evaporation of components during the reaction step is minimal and the production equipment can be simplified. In addition, to stabilize the quality, the reaction time is usually 3 hours to 100 hours, preferably 5 hours to 80 hours.

[0030] After preparing the mixture, it is preferable to react the mixture for a time that satisfies the following formula (A) or longer, in order to promote the synthesis of the compound described below. During the reaction step, the mixture may be left to stand or may be fluidized by stirring or the like. y≧7.58x-22.9 (A) In formula (A), x=1000 / (273.14+T), y=ln(h), T represents the temperature (unit: °C) that satisfies 0≦T≦100, h represents time (unit: hours).

[0031] Furthermore, after preparing the mixture, it is more preferable to leave the mixture standing or stirring it for a time period that satisfies the following formula (B) or longer, in order to promote the synthesis of the compound described below. y≧7.58x-21.1 (B) In formula (B), x=1000 / (273.14+T), y=ln(h), T represents the temperature (unit: °C) that satisfies 0≦T≦100, h represents time (unit: hours).

[0032] The lower limit of T in formulas (A) and (B) is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher. The upper limit of T is preferably 100°C or lower, more preferably 85°C or lower, and even more preferably 70°C or lower. When T is within the above range, evaporation of components is reduced, which allows for simplification of the coolant additive manufacturing equipment. Furthermore, when T is within the above range, the stability of the coolant additive or a coolant containing the coolant additive is improved.

[0033] The lower limit of h in formulas (A) and (B) may be 1 hour or more, 7 hours or more, 14 hours or more, 24 hours or more, 48 hours or more, or 72 hours or more. The upper limit of h may be 1000 hours or less, 360 hours or less, 120 hours or less, or 96 hours or less. When h is within the above range, the stability of the coolant additive or the coolant containing the coolant additive is improved. From the viewpoints of simplifying the equipment and stabilizing the quality, it is desirable to carry out the reaction at 30 to 40°C for 70 hours or more.

[0034] The coolant additive produced by the method for producing a coolant additive according to one aspect of the present invention described above is also included in one aspect of the present invention.

[0035] 2. Coolant manufacturing method The method for producing a coolant according to one aspect of the present invention may include a step of producing a coolant additive by the method for producing a coolant additive according to one aspect of the present invention.

[0036] In a method for producing a coolant according to one embodiment of the present invention, a coolant is produced by adding water such as ion-exchanged water, a solvent such as ethylene glycol, an organic acid, a neutralizing agent (pH adjuster), a colorant, an antifoaming agent, etc. to the coolant additive produced by the method for producing a coolant additive according to one embodiment of the present invention described above.

[0037] The amount of the coolant additive in the coolant according to one embodiment of the present invention can be adjusted appropriately depending on the application, but the lower limit of the amount of the coolant additive is preferably 0.05% by mass or more, and more preferably 0.1% by mass or more, based on 100% by mass of the coolant. The upper limit of the amount of the coolant additive is preferably 3% by mass or less, and more preferably 1% by mass or less. When the amount of the coolant additive is within the above range, the rust prevention and stability of the coolant are further improved. Furthermore, when the amount of the coolant additive is within the above range, the coolant exhibits sufficient rust prevention properties for metals.

[0038] [3. Coolant Additives and Coolants] A coolant additive according to one embodiment of the present invention includes a mixture of water, an alcohol, a silicate, and a metal coupling agent, and a partial reaction product obtained by reacting these components. The term "partial reaction product" refers to a reaction product formed by the reaction of at least two components contained in the liquid, or a reaction product formed by the reaction of the same components. Examples include a reaction product of a metal coupling agent and water, a reaction product of a metal coupling agent and a silicate, a reaction product of a metal coupling agent, a silicate, and water, a reaction product of a silicate and a silicate, or a reaction product of water, a silicate, and / or a metal coupling agent and an alcohol. Another embodiment of the present invention also includes a coolant additive produced by the method for producing a coolant additive according to one embodiment of the present invention.

[0039] A coolant according to one aspect of the present invention includes the coolant additive. Also included in one aspect of the present invention is a coolant produced by the coolant production method according to one aspect of the present invention.

[0040] The coolant according to one aspect of the present invention has high stability. Furthermore, the coolant according to one aspect of the present invention is a non-phosphate-based coolant, but has the same rust prevention properties as a phosphate-based coolant. Furthermore, the coolant according to one aspect of the present invention is a non-phosphate-based coolant, and has excellent hard water stability.

[0041] The coolant may be used as a coolant or antifreeze for internal combustion engines such as diesel engines and gasoline engines, batteries such as fuel cells and secondary batteries, heat pipes, motors, etc. In particular, it can be suitably used as a coolant for internal combustion engines.

[0042] [4. Coolant Additives] A coolant additive according to one embodiment of the present invention contains a compound represented by the following formula (1) as a partial reaction product. [ka] In formula (1), R1 to R3 each independently represent a hydroxyl group, an alkyl group having an ether bond, or an amide group, and any two of R1 to R3 may be bonded to each other, and the bonded group may be a ketone group; R4 is an alkyl group having 1 to 10 carbon atoms, -(CH2) Z1 -CO-NH-(CH2) Z2 - or -(CH2) Z3 -SH2-(CH2) Z4 -, 1≦Z1+Z2≦10, and 1≦Z3+Z4≦10; R5 is an alkyl group having 1 to 10 carbon atoms, an isopropyl group, a vinyl group, a styryl group, an acryl group, an amino group, a carboxyl group, a ureido group, a mercapto group, an isocyanate group, a silanol group, a hydroxy group, an aldehyde group, a carbonyl group, a nitro group, a sulfone group, a phenyl group, a naphthyl group, a cyano group, a fluoro group, a chloro group, a bromo group, an iodo group, a triazole group, an epoxy group, a hydrocarbon ring group, or a heterocyclic group; The compound of formula (1) may form a dimer or higher polymer with at least one of R1 to R3 as a linking group, and the linking group has an ether bond.

[0043] The coolant additive according to one aspect of the present invention preferably contains, as a partial reaction product, any of the compounds represented by the following formulas (2) to (9), more preferably any of the compounds represented by the following formulas (2), (3), (6) or (7), and even more preferably a compound represented by the following formula (2) or (6). [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0044] Methods for identifying the structure of the compound contained in the coolant additive according to one embodiment of the present invention include identification by analysis using mass spectrometry (MS), nuclear magnetic resonance (NMR), or the like.

[0045] The coolant according to one embodiment of the present invention has an excellent anti-rust effect on metals even though it does not contain phosphoric acid. Use of the coolant according to one embodiment of the present invention can prevent and reduce water pollution caused by eutrophication in lakes, marshes, inland seas, etc., thereby contributing to the achievement of the Sustainable Development Goals (SDGs).

[0046] 〔summary〕 An embodiment of the present invention includes the following configuration. [1] A method for producing a coolant additive, comprising a reaction step of mixing and reacting water, alcohol, silicate, and a metal coupling agent. [2] The method for producing a coolant additive according to [1], wherein the metal coupling agent is at least one coupling agent selected from a titanium coupling agent, a zirconium coupling agent, an aluminum coupling agent, and a silane coupling agent. [3] The method for producing a coolant additive according to [1] or [2], wherein the metal coupling agent is 3-glycidoxypropyltrimethoxysilane. [4] The method for producing a coolant additive according to any one of [1] to [3], wherein in the reaction step, the water and the silicate are mixed, and then the metal coupling agent is added. [5] A method for producing a coolant, comprising a step of producing a coolant additive by the method for producing a coolant additive according to any one of [1] to [4]. [6] A coolant additive comprising a mixture of water, an alcohol, a silicate, and a metal coupling agent, and a partial reaction product of these components. [7] The coolant additive according to [6], wherein the partial reaction product is at least one selected from the group consisting of a reaction product of the metal coupling agent and the water, a reaction product of the metal coupling agent and the silicate, and a reaction product of the metal coupling agent, the silicate, and the water. [Example]

[0047] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, % represents % by mass unless otherwise specified. Although dropwise addition is performed in the preparation examples, dropwise addition is not necessary. Furthermore, although the mixture is allowed to stand in the reaction step in the preparation examples, the mixture may be continuously or intermittently flowed by stirring or the like.

[0048] (Preparation Example 1) Preparation of coolant additive and coolant In a beaker, 34% ultrapure water, 38% 50% potassium silicate aqueous solution (1K potassium silicate manufactured by Nippon Chemical Industry Co., Ltd.) (i.e., 19% potassium silicate, 19% water), 22% 3-GPTMS, and 6% ethylene glycol (hereinafter sometimes abbreviated as "EG") were added dropwise and stirred in this order. The mixture obtained by dropwise addition and stirring was then left to stand in a thermostatic bath at 0°C or 30°C for 1, 2, or 3 days under the reaction conditions listed in Table 1 to prepare coolant additives. The obtained coolant additives 1 to 6 were mixed with ethylene glycol containing an organic acid and a neutralizing agent in the coolant formulation ratios listed in Table 1 to prepare coolants 1 to 6, which were then evaluated. Note that the organic acid and neutralizing agent are additives commonly found in coolants and do not affect the stability of the coolant, and the neutralizing agent does not contribute to corrosion prevention.

[0049] (Preparation Example 2) Preparation of coolant additive and coolant In a beaker, 34% ultrapure water, 38% 50% potassium silicate aqueous solution, 22% 3-GPTMS, and 6% EG were added dropwise and stirred in this order. The mixture obtained after dropwise addition and stirring without standing to heat was designated as coolant additive 7. This was mixed with ethylene glycol containing an organic acid and a neutralizer in the coolant formulation ratios shown in Table 1 to prepare coolant 7, which was then evaluated.

[0050] (Evaluation example 1) Coolant stability test The coolants 1 to 7 obtained in Preparation Examples 1 and 2 were left to stand in a thermostatic bath at 60° C. for 1 hour to evaluate the stability of the coolants. The evaluation results are shown in Table 1.

[0051] [Table 1]

[0052] Coolants 3 and 7 after being left standing in a thermostatic bath at 60°C for 1 hour are shown in Figure 1. In Figure 1, the coolant (50% diluted solution) is a coolant obtained by diluting it with ultrapure water.

[0053] As shown in Table 1, coolants 1 to 3 containing coolant additives obtained by setting the standing temperature to 30°C and standing for one day or more were stable, did not become cloudy or produce precipitates, and gelation of the coolant was suppressed. Also, as shown in Figure 1, coolant 3 was transparent and had good properties. The stability of the coolant was maintained even when coolant 3 was mixed with ultrapure water and diluted to a coolant concentration of 50%. Coolants 1 and 2 also showed similar results to coolant 3.

[0054] Coolants 4 to 6 containing the coolant additives at a standing temperature of 0°C became cloudy and were unstable. On the other hand, although not shown in Table 1, no precipitation or cloudiness occurred in the coolant containing the coolant additives obtained by standing at 0°C for 37 days. This result suggests that in the manufacture of coolant additives, if the standing time is extended when the standing temperature is low, gelation of the coolant may be suppressed, but it is difficult to reliably ensure the stability of the coolant.

[0055] As shown in Table 1 and Figure 1, coolant 7, which was prepared without allowing time for the mixture to react, was cloudy and unstable. Even when coolant 7 was mixed with ultrapure water and diluted to a 50% coolant concentration, the coolant remained cloudy and unstable. This is thought to be because coolant 7 was prepared by diluting coolant additive 7, which had a low reaction rate because no reaction time was allowed. These results suggest that the coolant can be stabilized by chemically reacting the mixture at a constant temperature and time and producing a coolant using a coolant additive with a high reaction rate.

[0056] (Evaluation Example 2) Examination of the proportion of each component in a coolant additive Next, the change in coolant performance was evaluated by varying the blend ratio of 3-GPTMS without changing the blend amounts of potassium silicate and EG. Ultrapure water, 38% 50% potassium silicate aqueous solution, 6% EG, and 3-GPTMS were added dropwise and stirred in a beaker in this order. The 3-GPTMS ratios were set to 12%, 17%, 22%, 27%, and 32%, and water was added to make the mixture 100%. The resulting mixture was left standing at 30°C for 3 days to prepare a coolant additive. 0.4% of the resulting coolant additive was mixed with ethylene glycol containing an organic acid and a neutralizer in the same ratio as the coolant formulation listed in Table 1 to prepare a coolant and evaluate it.

[0057] The change in coolant performance was also evaluated by varying the blend ratio of potassium silicate. Ultrapure water, a 50% potassium silicate aqueous solution, 22% 3-GPTMS, and 6% EG were added dropwise to a beaker in this order and stirred. The ratios of the 50% potassium silicate aqueous solution were set to 28%, 33%, 38%, 43%, and 48%, and water was added to make the mixture 100%. The resulting mixture was left to stand at 30°C for three days to prepare a coolant additive. The resulting coolant additive was mixed with ethylene glycol containing an organic acid and a neutralizer in the same ratio as the coolant formulation listed in Table 1 to prepare a coolant and evaluate it.

[0058] Metal corrosion tests were conducted on the coolants prepared above. These tests were conducted in accordance with JIS K2234:2018 Antifreeze. The evaluation results are shown in Tables 2 and 3.

[0059] [Table 2]

[0060] [Table 3]

[0061] As shown in Table 2, even when the blending ratio of 3-GPTMS was 12 to 32%, the components contained in the mixture reacted, and the coolant exhibited good rust prevention properties.

[0062] As shown in Table 3, even when the blending ratio of potassium silicate was 14 to 24%, the components contained in the mixture reacted, and the coolant exhibited good rust prevention properties.

[0063] (Evaluation Example 3) Test to examine the timing of adding each component of a coolant additive Next, the stability of the coolant additives was evaluated by changing the timing of addition of each component when preparing the coolant additives. Coolant additives 9 to 12 were prepared by adding the components dropwise to a beaker and stirring in the order shown in Table 4. The amounts of each component used when preparing the coolant additives were 34% ultrapure water, 38% 50% potassium silicate aqueous solution, 22% 3-GPTMS, and 6% EG.

[0064] [Table 4]

[0065] As shown in Table 4, no clouding occurred during the preparation of Coolant Additives 9 and 11. In the preparation of Coolant Additive 10, clouding (gelation) occurred after the addition of the potassium silicate aqueous solution. On the other hand, the coolant additive became transparent after all the components were added dropwise and stirred, and then allowed to stand in a 30°C thermostatic bath for several days. Although Coolant Additive 10 was usable, it took longer to prepare Coolant Additive 10 than Coolant Additives 9 and 11 in order to eliminate the cloudiness.

[0066] Furthermore, in the preparation of coolant additive 12, cloudiness occurred after adding water, but disappeared when the potassium silicate aqueous solution was added. The cloudiness disappeared after all the components were mixed, so this is acceptable, but for stable preparation, it is preferable that cloudiness does not occur even during preparation.

[0067] From these results, it was found that it is preferable to add 3-GPTMS after mixing water and the potassium silicate aqueous solution to prevent cloudiness during preparation of the coolant additive.

[0068] (Evaluation Example 4) Engine Coolant Evaluation Test The coolant additive 3 prepared in Preparation Example 1 was mixed with ethylene glycol containing an organic acid and a neutralizing agent to prepare an engine coolant (containing 0.2 to 10% of the coolant additive). The prepared engine coolant was subjected to an aluminum cast heat transfer surface corrosion test and a metal corrosion test. These tests were conducted in accordance with JIS K2234:2018 Antifreeze. An aqueous solution with a volume fraction of 30% was prepared from the engine coolant, and the results of the aluminum cast heat transfer surface corrosion test are shown in Figure 2, and the results of the metal corrosion test are shown in Figure 3.

[0069] 2 and 3, it was confirmed that engine coolants containing 0.3 to 4% of coolant additive 3 have rust prevention properties. In Evaluation Example 4, the results of the JIS test showed that the optimum content of the coolant additive prepared in Preparation Example 1 in the coolant is 0.4%. Note that the optimum content of the coolant additive in the coolant varies depending on the blending amounts of each component of the coolant additive.

[0070] (Evaluation Example 5) Evaluation test of the rust prevention properties of coolant Metal corrosion tests (based on JIS K2234:2018 antifreeze) were conducted on samples a to d shown below to evaluate their rust prevention effects. The coolant was diluted with water, and the metal corrosion test was conducted using a 30% aqueous solution, while the aluminum heat transfer surface test was conducted using a 25% aqueous solution. The evaluation results for the rust prevention properties of each coolant are shown in Figure 4. Sample a: Coolant 3 prepared in Preparation Example 1 Sample b: Commercially available phosphoric acid-based coolant Sample c: Commercially available silica-based coolant Sample d: Commercially available organic acid-based coolant

[0071] As shown in FIG. 4, it was confirmed that sample a had the same rust prevention properties as samples b to d of commercially available coolants.

[0072] (Evaluation Example 6) Hard water stability test of coolant The presence or absence of precipitation when samples a and b of Evaluation Example 5 were diluted with hard water was evaluated. Specifically, the above samples a and b were evaluated under the following conditions 1 to 4. The evaluation results are shown in FIG. <Condition 1> 100 mL of the sample and 100 mL of hard water (containing 10 ppm of Ca) were stirred and then allowed to stand in a dark place for 24 hours. <Condition 2> 100 mL of the sample and 100 mL of hard water (containing 100 ppm of Ca) were stirred and then allowed to stand in a dark place for 24 hours. <Condition 3> 100 mL of the sample and 100 mL of hard water (containing 10 ppm of Ca) were stirred, heated to 80°C, and allowed to stand in a dark place for 24 hours. <Condition 4> 100 mL of the sample and 100 mL of hard water (containing 100 ppm of Ca) were stirred, heated to 80°C, and allowed to stand in a dark place for 24 hours.

[0073] As shown in Figure 5, precipitation occurred in sample b under all conditions 1 to 4, but no precipitation was observed in sample a. Phosphate-based coolants tend to react with mineral components and cause precipitation, but sample a did not cause precipitation, demonstrating its excellent hard water stability.

[0074] (Evaluation Example 7) Analytical test of coolant additives In the coolant additive prepared in the above evaluation example, it is presumed that the chemical reaction is accelerated by mixing the components and then leaving them at a constant temperature, thereby imparting stability and rust prevention to the coolant. It is also presumed that the reactants produced by the chemical reaction contribute to the stability and rust prevention of the coolant. Therefore, analytical tests were conducted on the components contained in the coolant additive.

[0075] The coolant additive 3 prepared in Preparation Example 1 was analyzed by LC-MS. The sample to be subjected to LC-MS was prepared by dissolving the coolant additive in a mixed solution of 10 mM aqueous ammonium bicarbonate solution and acetonitrile (mixing ratio = 1:1). The sample to be subjected to LC-MS was not subjected to vacuum concentration, heating, etc.

[0076] The analytical conditions by LC-MS are shown below. Instrument (LC): Agilent 1100 Series manufactured by Agilent Technologies Instrument (MS): Bruker Daltonics micrOTOF focus type Column: Unison UK-C8 (3 μm, 4.6 × 150 mm) Mobile phase: 10 mM ammonium bicarbonate aqueous solution / acetonitrile = 1 / 5 Flow rate: 1mL / min Column temperature (LC section): 40°C Mass spectrometry temperature (MS part): 190℃ Detection method: ESI (negative mode) Injection volume: 10μL

[0077] Analysis revealed that the coolant additive contained the following two compounds, which are believed to have been produced during the reaction process used to prepare the coolant additive. [ka] [ka]

[0078] Furthermore, based on the results of LC-MS analysis (molecular weight), the following two compounds were also suggested to be included in the coolant additives. [ka] [ka]

[0079] In addition to LC-MS, 1 The coolant additives were also analyzed by H-NMR. The NMR analysis results suggested that the following four compounds were also present in the coolant additives: [ka] [ka] [ka] [ka]

[0080] The compounds of the above formulas (2) to (9) are presumed to correspond to the reaction products of a metal coupling agent and water. Note that the above analysis results were obtained when a silane coupling agent was used as the metal coupling agent.

[0081] Although not confirmed by LC-MS and NMR analysis, the following compound may have been produced based on the structure of the components (water, 3-GPTMS, EG, and potassium silicate) used to prepare the coolant additive. [ka] [ka] [ka] [ka]

[0082] The above four compounds are presumed to correspond to the reaction products of a metal coupling agent, water, silicate, and alcohol, or the reaction products of a metal coupling agent, water, and alcohol, and the above compounds use a silane coupling agent as the metal coupling agent.

[0083] (Evaluation Example 8) Examination of reaction temperature and reaction time In a beaker, 34% ultrapure water, 38% 50% potassium silicate aqueous solution, 22% 3-GPTMS, and 6% EG were added dropwise and stirred in this order. The reaction temperatures of the mixture obtained by dropwise stirring were 10°C, 20°C, 30°C, 60°C, and 70°C. Table 5 shows the reaction times at which the reaction of the metal coupling agent was confirmed when the reaction temperatures of the mixture obtained by dropwise stirring were 10°C, 20°C, 30°C, 60°C, and 70°C. Table 6 also shows the reaction times at which gelation in the mixture was inhibited when the reaction temperatures of the mixture obtained by dropwise stirring were 10°C, 20°C, 30°C, 60°C, and 70°C.

[0084] [Table 5]

[0085] [Table 6]

[0086] As shown in Table 5, it was found that when the reaction temperature was low, the metal coupling agent reacted by extending the reaction time. From the results of Evaluation Examples 1 to 7, it is presumed that the reaction product functions as a coolant additive at any reaction temperature examined in Evaluation Example 8, but production efficiency is poor when the reaction temperature is low.

[0087] Furthermore, based on the results in Tables 5 and 6, an equation showing the correlation between reaction temperature and reaction time was derived. The graph created to derive the equation is shown in Figure 6. The circled plots in Figure 6 are plots obtained by reflecting the data in Table 6, and the following equation (A1) was derived. y≧7.58x-22.889 (A1) In formula (A1), x=1000 / (273.14+T), y=ln(h), T represents the temperature (unit: °C) that satisfies 0≦T≦100, h represents time (unit: hours).

[0088] The plots indicated by triangles in FIG. 6 were obtained by reflecting the data in Table 5, and the following formula (B1) was derived. y≧7.58x-21.089 (B1) In formula (B1), x=1000 / (273.14+T), y=ln(h), T represents the temperature (unit: °C) that satisfies 0≦T≦100, h represents time (unit: hours).

[0089] The reaction temperatures and reaction times in Table 5 satisfy the above formulas (A1) and (B1). When the reaction was continued for a time sufficient to satisfy formula (B1), almost no unreacted metal coupling agent was detected, and the reaction product was produced without waste. The reaction temperature and reaction time can be determined appropriately, but if the reaction rate is low, the stability of the coolant additive and the coolant will be insufficient.

[0090] (Evaluation Example 9) Examination of the timing of adding alcohol A coolant additive was prepared by adding ultrapure water, a 50% potassium silicate aqueous solution, 3-GPTMS, and EG to a beaker in the amounts and according to the procedure shown in Table 7. The prepared coolant additive was used to conduct various tests, and the results are shown in Table 7. The stability test was conducted under the same test conditions and blending conditions as in Evaluation Example 1, the metal corrosivity test was conducted under the same conditions as in Evaluation Example 2, and the hard water stability test was conducted under the same test conditions and blending conditions as in Evaluation Example 6.

[0091] As shown in Table 7, Coolant Additive 13 lacks antifreeze properties due to the absence of EG. Coolant Additives 3, 13, and 14 all performed well in stability, metal corrosion, and hard water stability tests. This indicates that the reaction of water, silicate, and metal coupling agent produces partial reaction products. The presence of these partial reaction products indicates that these coolant additives exhibit excellent stability and rust prevention.

[0092] The aluminum rust prevention test was conducted by immersing the entire aluminum test piece (AC2A) in a solution containing 1% of each cooling additive, 1% sodium hypochlorite, and 98% water, and then leaving it in a constant temperature bath at 60°C for 96 hours, after which the change in weight of the aluminum test piece was evaluated.

[0093] Coolant Additive 3, produced by mixing alcohol, silicate, water, and a metal coupling agent and leaving it to stand at 30°C for three days, had high rust prevention properties. However, Coolant Additive 13, which did not contain alcohol, and Coolant Additive 14, which was produced by mixing silicate, water, and a metal coupling agent and leaving it to stand at 30°C for three days before adding alcohol, had inferior rust prevention properties to Coolant Additive 3. These results demonstrate that a coolant additive with excellent rust prevention effects can be obtained by mixing and reacting alcohol, water, silicate, and a metal coupling agent with a coolant additive. It is believed that in Coolant Additive 3, a reaction product is produced by the reaction of water, silicate, and / or a metal coupling agent with alcohol.

[0094] From the above results, in one embodiment of the reaction step of the present invention, water, silicate, and metal coupling agent may be mixed for a predetermined time (for example, several hours to several days), and then alcohol may be added.

[0095] [Table 7] [Industrial Applicability]

[0096] The present invention can be used in coolant additives, coolants for cooling engines or batteries, rust inhibitor compositions for rust prevention, metal working compositions for metal working, and the like.

Claims

1. A method for producing a coolant additive, comprising a reaction step of mixing and reacting water, an alcohol, a silicate, and a silane coupling agent having an epoxy group.

2. The method for producing a coolant additive according to claim 1 , wherein the amount of water blended is greater than the amount of alcohol blended.

3. 3. The method for producing a coolant additive according to claim 1, wherein the silane coupling agent having an epoxy group is 3-glycidoxypropyltrimethoxysilane.

4. 3. The method for producing a coolant additive according to claim 1, wherein in the reaction step, the water and the silicate are mixed together, and then the silane coupling agent having an epoxy group is added.

5. A method for producing a coolant, comprising the step of producing a coolant additive by the method for producing a coolant additive according to claim 1 or 2.

6. A coolant additive comprising a mixture of water, an alcohol, a silicate, and a silane coupling agent having an epoxy group, and a partial reaction product of these components.

7. 7. The coolant additive according to claim 6, wherein the partial reaction product is at least one selected from the group consisting of a reaction product of the silane coupling agent having an epoxy group and the water, a reaction product of the silane coupling agent having an epoxy group and the silicate, and a reaction product of the silane coupling agent having an epoxy group, the silicate, and the water.

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