JP2005126596A - Coolant for internal combustion engine and its regeneration method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coolant for an internal combustion engine, of which the heat conductivity is as high as that of water and which has a long product life and which is capable of easily regenerating the waste coolant even after the usage. <P>SOLUTION: The coolant for the internal combustion engine is characterized in that the kind is adopted so that the predetermined anti-freezing properties are exhibited at a service temperature and in that an inorganic salt of which the amount of formulation is prescribed is included as a main component. Preferably, the inorganic salt is at least one of a molybdate and a tungstate and does not substantially contain an organic solvent as a non-freezing ingredient. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a coolant for an internal combustion engine for cooling an internal combustion engine such as an automobile engine and a method for regenerating the coolant.

  Conventionally, as a coolant for an internal combustion engine, for example, a coolant for an automobile engine, an alcohol or a glycol, for example, an organic solvent such as ethylene glycol or propylene glycol as an antifreezing component (freezing point depressant) is known. (For example, see Patent Documents 1 and 2).

Moreover, in order to prevent the corrosion of metal materials, such as aluminum castings, steel, cast iron, brass, and copper, which constitute an engine, such automobile engine coolants are generally various, such as silicates and phosphates. Corrosion inhibitors are added.
JP 2000-239658 A JP 11-349935 A

  However, the conventional automotive engine coolant has the following problems because it contains an organic solvent such as alcohols and glycols as an antifreeze component.

  That is, the conventional cooling liquid containing alcohols or glycols as an antifreeze component has a thermal conductivity much lower than that of water. If the thermal conductivity of the coolant is low, it is disadvantageous in increasing the cooling efficiency of the engine. For this reason, in order to increase the cooling efficiency, it is necessary to increase the size of a heat exchanger such as a radiator or to increase the size of the pump by increasing the circulation amount of the coolant.

  On the other hand, alcohols and glycols are oxidatively deteriorated by air, heat, etc., and thus generate a plurality of acids (formic acid, glycolic acid, etc.) as oxidative deterioration products. And since the generation of acid due to this oxidative degradation causes the pH of the cooling liquid to decrease, the corrosion prevention performance decreases, the solubility of the corrosion inhibitor decreases, and insoluble matter is generated, This will shorten the life of the coolant. In addition, since the waste cooling liquid generated by using the conventional cooling liquid contains a plurality of acids as deterioration products, it is difficult to regenerate and reuse the waste cooling liquid. Accordingly, the used cooling liquid after use is usually disposed of by incineration or the like. In addition, there is a method of regenerating the waste cooling liquid by a deionization process using an ion exchange resin or a distillation operation, but such a regeneration method is very troublesome.

  The present invention has been made in view of the above circumstances, and has a heat transfer coefficient as high as that of water, has a long life, and can easily regenerate waste coolant after use. Providing a liquid is a technical problem to be solved.

  The coolant for an internal combustion engine of the present invention that solves the above-mentioned problems is selected from the types that can exhibit the predetermined antifreezing performance at the operating temperature, and the inorganic salt whose blending amount is defined is the main active ingredient. It is characterized by including.

  In a preferred embodiment, the inorganic salt is at least one of molybdate and tungstate.

  In a preferred embodiment, the molybdate is an alkali metal salt of molybdate and the tungstate is an alkali metal salt of tungstic acid.

  In a preferred embodiment, the alkali metal salt is one of a lithium salt, a potassium salt, and a cesium salt.

  In a preferred embodiment, the inorganic salt is lithium molybdate.

  In a preferred embodiment, the coolant for an internal combustion engine of the present invention contains the inorganic salt at a blending ratio of 20 wt% or more.

  In a preferred embodiment, the internal combustion engine coolant according to the present invention has a freezing temperature of −35 ° C. or less at a concentration containing the inorganic salt in a blending ratio of 39 wt% or more.

  In a preferred embodiment, the coolant for an internal combustion engine of the present invention does not substantially contain an organic solvent such as alcohols or glycols as an antifreeze component.

  In a preferred embodiment, the internal combustion engine coolant of the present invention is used at a pH of 7 or higher.

  In a preferred embodiment, the coolant for an internal combustion engine of the present invention further includes a corrosion inhibitor capable of exhibiting a predetermined corrosion prevention performance for the metal used in the use environment.

  In a preferred embodiment, the corrosion inhibitor is a triazole.

  The method for regenerating a coolant for an internal combustion engine according to the present invention is characterized in that the waste coolant produced by using the coolant for an internal combustion engine according to claim 1 can be reused by filtration. To do.

  The coolant for an internal combustion engine of the present invention includes an inorganic salt as a main active ingredient, the kind of which is selected so that the predetermined antifreezing performance can be exhibited at the operating temperature and the blending amount thereof is defined. That is, the coolant for an internal combustion engine of the present invention contains an inorganic salt functioning as a freezing point depressant capable of exhibiting a predetermined antifreezing performance at the operating temperature as a main active ingredient.

  For this reason, the coolant for an internal combustion engine of the present invention exhibits excellent anti-freezing performance.

  Moreover, the cooling fluid for an internal combustion engine of the present invention has a thermal conductivity comparable to that of water as shown in the examples described later, and exhibits a thermal conductivity superior to that of an existing LLC (Long Life Coolant). . For this reason, it is possible to reduce the size of the heat exchanger and the size of the pump (reducing the pump load) by reducing the circulation of the coolant.

  Furthermore, the coolant for an internal combustion engine of the present invention contains the inorganic salt and water as main components, and in a preferred embodiment, does not contain any organic solvent such as alcohols and glycols. For this reason, during use as a coolant, degradation products (acids such as formic acid and glycolic acid) due to thermal and oxidative degradation such as alcohols and glycols are not generated. Accordingly, there is no possibility that the corrosion prevention performance is lowered due to a decrease in the pH of the cooling liquid caused by the deteriorated product, and an insoluble substance of the corrosion inhibitor is not produced. Therefore, the life of the coolant is extended. The waste coolant generated by using the coolant for the internal combustion engine does not contain an acid as a degradation product. Therefore, the contaminated foreign matter in use is removed by filtering the waste coolant. Then, the waste coolant can be easily regenerated and reused (reused) as it is.

  Here, the fact that the predetermined antifreezing performance can be exhibited in the use environment means that the freezing temperature of the cooling liquid for the internal combustion engine of the present invention is used for the freezing temperature due to the freezing prevention (freezing point depression) effect by the inorganic salt. Due to the fact that the temperature can be made sufficiently lower than the temperature range assumed as a possible environmental temperature (use temperature), in other words, due to the effect of freezing prevention (freezing point depression) by the inorganic salt, for the internal combustion engine of the present invention It means that the cooling liquid can be surely prevented from freezing during use.

  The kind of inorganic salt that can be used in the cooling fluid for an internal combustion engine of the present invention and the amount of the inorganic salt are not particularly limited as long as a predetermined antifreezing performance can be exhibited at the operating temperature. It is preferable that the freezing temperature of the coolant for an internal combustion engine of the present invention is −15 ° C. or lower (more preferably −35 ° C. or lower) due to the prevention (freezing point lowering) effect. Moreover, it is preferable that predetermined corrosion prevention performance can be exhibited with respect to the metal used in a use environment.

  As the inorganic salt, for example, an inorganic acid salt such as molybdate or tungstate can be suitably used. These inorganic acid salts may be used alone or in combination of two or more. On the other hand, calcium chloride, lithium bromide, etc., which are general freezing point depressants, exhibit good anti-freezing performance, but are not preferable because it is difficult to obtain sufficient metal anti-corrosion performance.

  The molybdate is preferably an alkali metal salt of molybdic acid, and the tungstate is preferably an alkali metal salt of tungstic acid. This alkali metal salt is preferably one of lithium salt, potassium salt and cesium salt. Moreover, it is also possible to use a sodium salt of molybdic acid or tungstic acid as the inorganic salt. However, sodium salts have lower solubility at low temperatures than lithium, potassium and cesium salts. For this reason, when a sodium salt is employed, insoluble substances are generated at low temperatures, so that the environmental temperature range in which the coolant for an internal combustion engine of the present invention can be used is high due to insufficient freezing prevention performance. The area that can be used is limited.

  Accordingly, preferable examples of the inorganic salt include lithium molybdate, potassium molybdate, cesium molybdate, lithium tungstate, potassium tungstate, and cesium tungstate. Among these, lithium molybdate is particularly preferable. When lithium molybdate is used as the inorganic salt, the pH of the coolant can be set to 7 by the mixing ratio of molybdenum trioxide and lithium hydroxide, and the mixing ratio as lithium molybdate is 39 wt% or more. The antifreeze temperature of the coolant prepared and prepared so as to have the concentration of −35 ° C. or lower can be set to −35 ° C. or less, and exhibits excellent antifreeze performance and anticorrosion performance for metals. In this way, when lithium molybdate is used as an inorganic salt, the excellent antifreezing performance and corrosion prevention performance can be achieved because the pH can be set in a neutral range (especially aluminum) where the metal can be protected from corrosion. This is because the solubility of lithium molybdate in the neutral range is excellent.

  And it is preferable that the cooling fluid for internal combustion engines of this invention contains the said inorganic salt in the mixture ratio of 20 wt% or more. If the blending ratio of the inorganic salt is less than 20 wt%, sufficient antifreezing performance cannot be obtained. The coolant for an internal combustion engine of the present invention can be used by diluting with water as needed depending on the usage environment such as temperature. For this reason, it is preferable to set it as the mixture ratio of the said inorganic salt in the cooling liquid at the time of using for actual use. That is, the coolant for an internal combustion engine of the present invention is preferably used at a concentration containing the inorganic acid salt at a blending ratio of 20 wt% or more.

  Moreover, it is preferable that the coolant for an internal combustion engine of the present invention has an aspect in which the freezing temperature is −35 ° C. or less at a concentration containing the inorganic salt in a blending ratio of 39 wt% or more. For example, as described above, when lithium molybdate is employed as the inorganic salt, the freezing temperature of the coolant may be set to −35 ° C. or lower by setting the blending ratio of this lithium molybdate to 39 wt% or more. it can.

  Furthermore, the coolant for an internal combustion engine of the present invention is preferably used at a pH of 7 or higher. The pH of the coolant affects the corrosion prevention performance, and if the pH is less than 7, the corrosion prevention effect on the metal cannot be sufficiently obtained.

  In addition, it is preferable that the coolant for an internal combustion engine of the present invention further includes a corrosion inhibitor capable of exhibiting predetermined corrosion prevention performance with respect to a metal used in a use environment. This corrosion inhibitor can be appropriately included as necessary depending on the use environment. For example, when the internal combustion engine coolant of the present invention is used in an environment where copper-based metal is used, it is preferable to include triazoles such as benzotriazole and tolyltriazole as a corrosion inhibitor for the copper-based metal. . The blending amount of the triazoles is preferably such that the coolant for an internal combustion engine of the present invention is used at a concentration containing the triazoles at a blending ratio of 0.005 wt% or more. When the blending ratio of triazoles is less than 0.005 wt%, sufficient corrosion prevention performance for copper-based metals cannot be expected. On the other hand, even if the blending ratio of the triazole is increased too much, the effect of the triazole is saturated, so the upper limit can be set to about 1.0 wt%.

  Examples of other corrosion inhibitors that can be included in the coolant for an internal combustion engine of the present invention include silicates, phosphates, nitrites, nitrates, and organic acid salts. In addition to the corrosion inhibitor, a colorant, an antifoaming agent, a bittering agent, and the like may be included.

  The coolant for an internal combustion engine of the present invention may be produced by dissolving the inorganic salt prepared in advance as it is in water, or by dissolving an inorganic acid and a hydroxide such as an alkali metal in water. May be. In the case of producing by dissolving an acid and an alkali in water, the pH of the coolant can be adjusted by changing the blending ratio of the acid and the alkali.

  As described above, the coolant for an internal combustion engine of the present invention does not contain an organic solvent degradation product in the used coolant after use. For this reason, the waste cooling liquid produced | generated by using the cooling fluid for internal combustion engines of this invention can be reproduced | regenerated in a reusable state by removing only the foreign material mixed during use by filtration. That is, the method of this filtration process is not specifically limited. For example, in order to effectively remove the contaminated foreign matter, it can be filtered using a mesh having a mesh width of about 5 to 50 μm. The coolant regenerated by the filtration process may be reused after appropriately adding a corrosion inhibitor or the like as necessary.

  Therefore, the coolant for an internal combustion engine of the present invention has a heat transfer rate as high as that of water, has a long life, and can easily regenerate waste coolant after use. It can be suitably used as a coolant for automobile engines.

  Sample No. consisting of an aqueous solution having the composition shown in Table 1. 1-12 were prepared. These sample Nos. Nos. 1 to 12 were prepared by dissolving an inorganic salt prepared in advance in water, or by dissolving an inorganic acid and a hydroxide such as an alkali metal in water. In the case of producing an acid and alkali dissolved in water, the pH of the cooling liquid was adjusted by changing the blending ratio of the acid and alkali.

  In addition, sample NO. 11 is the main component of the existing LLC consisting of a 50% aqueous solution of ethylene glycol.

For example, sample NO. 4, 7 and 8 are prepared by mixing molybdenum trioxide (MoO ₃ ), lithium hydroxide monohydrate (LiOH · H ₂ O) and ion-exchanged water in order to adjust the pH of the solution to 7. Produced by mixing in proportions.

Molybdenum trioxide (MoO ₃ ): 34.2 wt%
Lithium hydroxide monohydrate (LiOH.H ₂ O): 19.8 wt%
Ion exchange water: 46.0 wt%
(Evaluation of anti-freezing performance)
And sample no. About 1-12, pH and freezing temperature were investigated. The results are also shown in Table 1.

  As can be seen from Table 1, sample No. 1 was an aqueous solution of an alkali metal salt of tungstic acid and an aqueous solution of an alkali metal salt of molybdic acid (excluding sodium salt). Samples Nos. 1 to 8 each have a freezing temperature of −35 ° C. or lower and are existing LLCs. The antifreezing performance equal to or better than 11 was exhibited.

  In the case of lithium molybdate, Sample No. which is an aqueous solution of molybdic acid and lithium hydroxide. As shown in FIGS. 4, 7 and 8, the pH of the aqueous solution can be changed depending on the blending ratio of molybdenum trioxide and lithium hydroxide. The anti-freezing performance equal to or higher than 11 could be achieved.

  In addition, sample No. which consists of the aqueous solution of the sodium salt of molybdate. In No. 9, the solubility of sodium salt at low temperatures was low, and sufficient anti-freezing performance was not obtained. For this reason, from the viewpoint of anti-freezing performance, it is understood that it is not preferable to employ sodium as the alkali metal, and it is preferable to employ lithium, potassium and cesium.

  Sample No. Regarding 4, the blending ratio (concentration) as lithium molybdate was changed variously, and the relationship between the concentration and the freezing temperature was examined. On the other hand, the existing LLC sample No. Similarly, the relationship between the concentration and the freezing temperature was also examined for No. 11. As shown in FIG. 1, when the blending ratio of lithium molybdate is less than 20 wt%, the antifreezing performance is comparable to that of existing LLC, but the blending ratio of lithium molybdate is 20 wt% or more. It can be seen that the antifreezing performance superior to that of the existing LLC is exhibited. It can also be seen that when the blending ratio of lithium molybdate is 25 wt% or more, the freezing temperature is −15 ° C. or less, and when the blending ratio of lithium molybdate is 39 wt% or more, the freezing temperature is −35 ° C. or less.

(Evaluation of thermal conductivity)
Sample No. For 7, 11, 12 and ethylene glycol, the relationship between the liquid temperature and the thermal conductivity was examined by the unsteady hot wire method. The result is shown in FIG.

  As can be seen from FIG. 2, the sample NO. The thermal conductivity of No. 7 is at the same level as water, and the existing LLC sample NO. It was better than 11. In addition, sample NO. The thermal conductivity at 80 ° C. of 7, 11 and 12 was as follows.

NO. 7 (aqueous solution of lithium molybdate): 0.00168 cal / sec · deg
No. 11 (existing LLC): 0.00099 cal / sec · deg
No. 12 (ion exchange water): 0.00160 cal / sec · deg
(Evaluation of metal anticorrosion performance)
Sample Sample No. About 4, 7, 8, and 10, the corrosion prevention performance with respect to various metals was investigated by the high-temperature test (based on JIS K2234 antifreeze metal corrosiveness) of 88 degreeC x 336h. The results are also shown in Table 1. The mass change standard value of JIS K2234 is within ± 0.30 for aluminum castings and within ± 0.15 for cast iron, steel, brass and copper.

<Corrosion prevention performance for aluminum and ferrous metals>
As can be seen from Table 1, sample No. 1 was a 41% aqueous solution of lithium molybdate. 4, 7 and 8 all showed good corrosion prevention performance against aluminum-based and iron-based metals.

  On the other hand, sample no. No. 10 showed significant corrosion weight loss in aluminum castings, cast iron and steel, despite the addition of sodium molybdate which can function as an aluminum / iron-based anticorrosive.

<Corrosion prevention performance for copper-based metals>
Sample No. Sample No. 4 with benzotriazole added to No. 4 Samples Nos. 7 and 8 show good corrosion prevention performance even for copper-based metals, and in particular, sample No. 7 containing 0.005 wt% of benzotriazole was added. No. 7 showed particularly good corrosion prevention performance.

(Evaluation of long life and reusability)
Sample No. The liquid after the metal anticorrosion test for No. 4 was contaminated with 0.25 vol% foreign matter. By filtering this liquid with a 50 μm wide mesh, the foreign matter in the liquid was removed. It can be confirmed that it can be reused as it is.

It is a graph which shows the relationship between a density | concentration and freezing temperature about lithium molybdate aqueous solution and LLC. It is a graph which shows the relationship between liquid temperature and thermal conductivity about lithium molybdate aqueous solution, LLC, and ethylene glycol.

Claims (12)

  A coolant for an internal combustion engine comprising an inorganic salt whose main active ingredient is selected as its type and capable of exhibiting a predetermined anti-freezing performance at the operating temperature.   The coolant for an internal combustion engine according to claim 1, wherein the inorganic salt is at least one of molybdate and tungstate.   The coolant for an internal combustion engine according to claim 2, wherein the molybdate is an alkali metal salt of molybdic acid, and the tungstate is an alkali metal salt of tungstic acid.   The coolant for an internal combustion engine according to claim 3, wherein the alkali metal salt is one of a lithium salt, a potassium salt, and a cesium salt.   The coolant for an internal combustion engine according to claim 1, wherein the inorganic salt is lithium molybdate.   6. The coolant for an internal combustion engine according to claim 1, wherein the inorganic salt is contained at a blending ratio of 20 wt% or more.   The cooling fluid for an internal combustion engine according to claim 1, 2, 3, 4, 5 or 6, wherein the freezing temperature at a concentration containing the inorganic salt at a blending ratio of 39 wt% or more is -35 ° C or less.   The coolant for an internal combustion engine according to claim 1, 2, 3, 4, 5, 6 or 7, characterized by being substantially free of an organic solvent as an antifreeze component.   The coolant for an internal combustion engine according to claim 1, wherein the coolant is used at a pH of 7 or more.   The corrosion inhibitor according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, further comprising a corrosion inhibitor capable of exhibiting a predetermined corrosion prevention performance for a metal used in a use environment. Coolant for internal combustion engines.   The coolant for an internal combustion engine according to claim 10, wherein the corrosion inhibitor is a triazole.   12. A method for regenerating a coolant for an internal combustion engine, wherein the waste coolant generated by using the coolant for an internal combustion engine according to claim 1 can be reused by filtration.

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