JP2011201953A - Coolant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coolant which can absorb the heat of a secondary cell and a capacitor to be mounted on an automobile and the like, can be circulated through piping or be circulated by convection within a predetermined space, can release heat, and has sufficient insulation performance.SOLUTION: The coolant has a density at 15°C of not higher than 0.84 g/cm, a kinematic viscosity at 40°C of not higher than 20 mm/s, a flash point of not lower than 190°C, and a conductivity of not higher than 10 pS/m. The coolant further contains at least one additive out of an amine based antioxidant, a phenolic antioxidant, a corrosion inhibitor, and a pour point depressant.

Description

  The present invention relates to a coolant that suppresses the temperature rise of a secondary battery or a capacitor that is mounted on an automobile, a construction machine, an agricultural machine (such as a tractor), and the like and is repeatedly used by charging.

  In recent years, environmental issues have been regarded as important. Electric vehicles that do not emit carbon dioxide, a greenhouse gas, have attracted attention. However, their use has been limited to experimental ones, leading to full-fledged popularization. There is no actual situation.

  One of the reasons why electric vehicles are not so popular is that the performance of the battery has not yet met the requirements. One problem with battery performance is battery heat generation. Lithium ion batteries currently used for electric vehicles generate heat when used or charged, but if the temperature rises, they will deteriorate and break down, so it is necessary to keep them at an appropriate temperature. Therefore, if it is in use (during travel), it is necessary to take measures to cool it against the air. Further, for charging, it is considered to take measures disclosed in Japanese Patent Application Laid-Open No. 10-290535, for example. Specifically, at the time of charging, when the temperature becomes higher than a predetermined temperature, the charging is temporarily stopped, and the charging is resumed after the temperature is lowered. However, in order to perform sufficient air cooling during traveling, there is a problem that the installation location and shape are limited, and temporary suspension during charging delays completion of charging.

  As a technique for solving such a problem, a method of forcibly cooling the battery with a liquid can be considered. And as the liquid to be used, water or oil can be considered, but the idea of cooling electrical components with oil has been widely adopted so far. For example, capacitor cooling is one of them. And various lubricating oil and insulating oil which can be used for the use are proposed.

  For example, Japanese translations of PCT publication No. 2008-544458 discloses an insulating oil blend having sufficient characteristics for various uses. This insulating oil blend can also be used in a transformer, and in that case, it also functions as a cooling oil that suppresses the temperature rise of the transformer by natural convection.

  Japanese Unexamined Patent Application Publication No. 2009-161604 and Japanese Unexamined Patent Application Publication No. 2009-2425477 disclose a transmission oil composition for automobiles in consideration of cooling performance.

Japanese Patent Laid-Open No. 10-290535 Special table 2008-544458 gazette JP 2009-161604 A JP 2009-242547 A

  However, conventional lubricating oils and insulating oils have not been designed for cooling secondary batteries mounted on automobiles, and none of them has the performance required as a cooling liquid for secondary batteries. . That is, none of the functions that efficiently absorb the heat generated from the object to be cooled, smoothly circulate in the piping, and dissipate heat are not considered.

  In addition, the function to absorb heat and dissipate heat is required not only for the secondary battery but also for the capacitor. Capacitor cooling uses natural convection of the coolant, but the capacitor coolant also takes into account the ease of convection in addition to the ability to absorb and dissipate heat. There was no.

  On the other hand, when the coolant leaks due to an accident or the like, in order to prevent a secondary disaster due to a short circuit of the secondary battery or the capacitor, it is necessary that the conductivity is low, that is, the insulating property is excellent. Therefore, the present invention absorbs heat from a secondary battery or a capacitor mounted on an automobile or the like, circulates in a pipe, or convects in a predetermined space to dissipate heat and has sufficient insulation performance. An object is to provide a coolant.

The coolant according to the present invention has a density at 15 ° C. of 0.84 g / cm ³ or less, a kinematic viscosity at 40 ° C. of 20 mm ² / s or less, a flash point of 190 ° C. or more, and a conductivity of 10 pS / m or less.

  The density at 15 ° C. is the density according to JIS K 2249 “Crude oil and petroleum products—density test method and density / mass / volume conversion table”. When this value is increased, the specific heat capacity and the thermal conductivity are lowered, and therefore, sufficient cooling performance is not obtained.

The kinematic viscosity at 40 ° C. is a kinematic viscosity obtained by JIS K 2283 “Crude oil and petroleum products—Kinematic viscosity test method and viscosity index calculation method”. If this value is higher than 20 mm ² / s, it cannot be sufficiently circulated in a temperature environment where the secondary battery or capacitor is used. The circulation includes forced circulation due to an external force applied by a motor or the like and natural convection due to a density difference caused by a temperature difference. Capacitor cooling is usually due to natural convection, but if the kinematic viscosity is high in this case, the convection speed is lowered and the cooling efficiency is deteriorated. In addition, it is preferable to employ forced circulation for the secondary battery of an automobile. However, if the kinematic viscosity is high in this case, the pipe resistance increases and the cooling efficiency deteriorates. For these reasons, the kinematic viscosity at 40 ° C. is preferably small, and more preferably 13 mm ² / s or less.

  The flash point is a flash point obtained by JIS K 2265-4 “How to obtain a flash point—Part 4: Cleveland Opening Method”. If this value is less than 190 ° C., there is a risk of fire if there is a leak from a pipe provided for the coolant due to an accident or the like, which causes a problem in safety. In addition, most of the lubricating oils including hydraulic fluids are classified into the third and fourth petroleums of the fourth class of dangerous goods under the Fire Service Act. In addition, the fourth and third petroleums have a flash point of 70 ° C. or higher and lower than 200 ° C., and the fourth and fourth petroleums have a flash point of 200 ° C. or higher. Therefore, in view of the safety assumed by law, the flash point is preferably 200 ° C. or higher.

  The electrical conductivity is the electrical conductivity obtained by JIS K 2276 “Petroleum product-aviation fuel oil test method”. If this value is large, a secondary disaster due to a short circuit of the secondary battery or the capacitor may occur, which causes a problem in safety.

  Since the coolant according to the present invention is preferably composed of hydrocarbons, the coolant is specified by the density of 15 ° C., kinematic viscosity of 40 ° C., and flash point used for specifying the properties of crude oil and petroleum products. However, the configuration need not be limited to hydrocarbons. For example, an organic compound such as silicone oil or fluorine oil, or other composition may be used as long as the above properties are satisfied.

この熱浸透率を決める要素の一つである密度は、動粘度にも影響を与えるため、使用される温度領域での動粘度と熱浸透率の密度を介したバランスを考慮する必要がある。ところが、従来の潤滑油や絶縁油等では、自動車等に搭載される二次電池やキャパシタが使用される温度領域での動粘度と熱浸透率のバランスを考慮したものはなかった。更に、自動車等に搭載される二次電池やキャパシタの冷却用であれば、引火点及び導電率についても、安全性を考慮する必要がある。そこで、本発明者は、自動車等の二次電池やキャパシタを冷却するために必要となる性状を、潤滑油等の一般的な基油の利用を主として検討したところ、特定の性状を所定の範囲とすることにより、理論上、それらを満たすことができる事実を見出した。本発明は、この新たな知見に基づくものである。 ADVANTAGE OF THE INVENTION According to this invention, a cooling fluid can be provided for the cooling of the secondary battery mounted in a motor vehicle or a capacitor. Conventional lubricants and insulating oils are assumed to be used in a high temperature range (for example, 60 to 80 ° C.), and are used in cooling a secondary battery or a capacitor, that is, a low temperature range. The kinematic viscosity becomes high in a temperature range of about 40 ° C., and there is a problem that it is difficult to circulate the inside of a pipe provided for cooling liquid in a limited space such as in an automobile. Moreover, although it is assumed that it is used in a low temperature region such as a cold region, although the kinematic viscosity in the low temperature region is low, the flash point is low, there is a problem in safety. In addition, as an index indicating the cooling performance, there is a heat penetration rate represented by the following formula (1).

The density, which is one of the factors that determine the thermal permeability, also affects the kinematic viscosity. Therefore, it is necessary to consider the balance between the kinematic viscosity and the thermal permeability in the temperature range to be used. However, there is no conventional lubricating oil or insulating oil that takes into consideration the balance between kinematic viscosity and heat permeability in the temperature range where secondary batteries and capacitors mounted on automobiles and the like are used. Furthermore, if it is for the cooling of the secondary battery and capacitor which are mounted in a motor vehicle etc., it is necessary to consider safety also about a flash point and electrical conductivity. Therefore, the present inventor mainly examined the use of general base oils such as lubricating oil for properties necessary for cooling secondary batteries and capacitors such as automobiles. And found the fact that they can be satisfied in theory. The present invention is based on this new knowledge.

  The cooling fluid according to the present invention can be produced with a common base oil such as a lubricating oil. For example, it is possible to use a highly refined oil which is a mineral oil or a synthetic oil used for a normal lubricating oil and has a sulfur content of about 0.3% by mass or less. In particular, API (American Petroleum Institute, US Petroleum) Association) Base oils belonging to group 2, group 3, group 4, etc. in the base oil category can be used alone or as a mixture. Of the base oils belonging to Group 2, those having only an excellent viscosity index are referred to as Group 2 Plus. However, Group 2 Plus can be obtained by a production method substantially similar to that of Group 3. Accordingly, in the following description, group 2 plus is included in group 3.

For Group 2 base oils, for example, paraffinic mineral oil obtained by appropriately combining refining means such as hydrocracking and dewaxing for lubricating oil fractions obtained by atmospheric distillation of crude oil GTL (Gas Liquid Liquid) synthesized by the Fischer-Tropsch method of natural gas liquid fuel technology and the base purified by the ISODEWAX process that converts and dewaxes wax produced in the dewaxing process into isoparaffin There is oil. Group 2 base oils refined by hydrorefining methods such as the Gulf Company method have a total sulfur content of less than 10 ppm and an aroma content of 5% or less, which is suitable for the present invention. However, the viscosity needs to be in a range in which the kinematic viscosity at 40 ° C. of the cooling oil to be the product is 20 mm ² / s or less. The total sulfur content should be less than 700 ppm, preferably less than 500 ppm, more preferably less than 10 ppm. The total nitrogen content is also less than 10 ppm, preferably less than 1 ppm. Furthermore, the aniline point should be 80 to 150 ° C, preferably 100 to 135 ° C. A viscosity index of 80 or more and less than 120 is suitable. Preferably it is 100 or more and less than 120.

Group 3 base oils include, for example, paraffinic mineral oil produced by advanced hydrorefining of lubricating oil fractions obtained by atmospheric distillation of crude oil, and Fischer Tropu, a natural gas liquid fuel technology. Base oil refined by ISODEWAX process which converts and dewaxes wax produced by GTL (Gas Liquid Liquid) and dewaxing process to isoparaffin, and group refined by Mobil WAX isomerization process Oil is also suitable. However, the viscosity needs to be in a range in which the kinematic viscosity at 40 ° C. of the cooling oil to be the product is 20 mm ² / s or less. The total sulfur content is 0 to 100 ppm, preferably less than 10 ppm. The total nitrogen content is also less than 10 ppm, preferably less than 1 ppm. Furthermore, it is good to use an aniline point of 80-150 degreeC, Preferably it is 110-135 degreeC. A viscosity index of 120 or more is suitable. Preferably it is 120 or more and less than 160.

  Examples of the synthetic oil include polyolefin, alkylbenzene, alkylnaphthalene, ester, polyoxyalkylene glycol, polyphenyl ether, dialkyldiphenyl ether, fluorine-containing compounds (perfluoropolyether, fluorinated polyolefin, etc.), silicone oil and the like.

The polyolefin includes polymers of various olefins or hydrides thereof. Any olefin may be used, and examples thereof include ethylene, propylene, butene, and α-olefins having 5 or more carbon atoms. In the production of polyolefin, one of the above olefins may be used alone, or two or more may be used in combination. Particularly preferred are polyolefins called polyalphaolefins (PAO), which are Group 4 base oils. As described above, the viscosity of these synthetic base oils also needs to be within a range in which the kinematic viscosity of the cooling oil to be the product is 20 mm ² / s or less.

GTL (Gas Liquid) synthesized by the Fischer-Tropsch method, which is a natural gas liquid fuel technology, has an extremely low sulfur content and aromatic content compared to mineral oil base oil refined from crude oil. Is extremely high, so that it has excellent oxidation stability and very low evaporation loss, and is therefore suitable as the base oil of the present invention. Typically, the total sulfur content is less than 10 ppm and the total nitrogen content is less than 1 ppm. An example of such a GTL base oil product is SHELL XHVI®. However, as described above, it is necessary to select the viscosity of the cooling oil to be the product at which the kinematic viscosity at 40 ° C. is 20 mm ² / s or less, as described above.

  The sulfur content in the base oil component of the cooling oil that is the cooling liquid according to the present invention is 0.3% by mass or less, preferably 1000 ppm or less, more preferably 100 ppm or less, and even more preferably 10 ppm or less. The content of the base oil in the cooling oil according to the present invention is not particularly limited, but is 60% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass based on the total amount of the cooling oil. % Or more.

  The cooling oil which is the cooling liquid according to the present invention may be one to which a known additive is added as necessary. Examples of the additive include the following.

As the antioxidant, generally used phenol-based and amine-based antioxidants shown below can be used.
Examples of the phenolic antioxidant include octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 4,4′-methylenebis (2,6-di-t-butylphenol); 4,4′-bis (2,6-di-t-butylphenol); 4,4′-bis (2-methyl-6-t-butylphenol); 2,2′-methylenebis (4-ethyl-6-t) -Butylphenol); 2,2'-methylenebis (4-methyl-6-tert-butylphenol); 4,4'-butylidenebis (3-methyl-6-tert-butylphenol); 4,4'-isopropylidenebis (2 , 6-di-t-butylphenol); 2,2′-methylenebis (4-methyl-6-nonylphenol); 2,2′-isobutylidenebis (4,6-dimethylphenol); 2'-methylenebis (4-methyl-6-cyclohexylphenol); 2,6-di-t-butyl-4-methylphenol; 2,6-di-t-butyl-4-ethylphenol; 2,4-dimethyl -6-tert-butylphenol; 2,6-di-tert-amyl-p-cresol; 2,6-di-tert-butyl-4- (N, N'-dimethylaminomethylphenol);4,4'- Thiobis (2-methyl-6-tert-butylphenol); 4,4′-thiobis (3-methyl-6-tert-butylphenol); 2,2′-thiobis (4-methyl-6-tert-butylphenol); bis (3-methyl-4-hydroxy-5-t-butylbenzyl) sulfide; bis (3,5-di-t-butyl-4-hydroxybenzyl) sulfide; n-octyl-3- (4-hydroxy-3, 5 Di-t-butylphenyl) propionate, n-octadecyl-3- (4-hydroxy-3,5-di-t-butylphenyl) propionate; 2,2′-thio [diethyl-bis-3- (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate], 2,4-di-t-butylphenol and the like.
Among these, bisphenol-based and ester group-containing phenol-based ones are particularly preferable.

Examples of amine antioxidants include p, p′-dioctyl-diphenylamine, p, p′-di-α-methylbenzyl-diphenylamine, Np-butylphenyl-Np′-octylphenylamine, mono Alkyldiphenylamines such as t-butyldiphenylamine and monooctyldiphenylamine, or styrenated diphenylamine, 4,4′-bis (α, α-dimethylbenzyl) diphenylamine, and methylphenyl-1-naphthylamine, ethylphenyl-1- Phenyl-α-naphthylamines such as naphthylamine, butylphenyl-1-naphthylamine, hexylphenyl-1-naphthylamine, octylphenyl-1-naphthylamine, Nt-dodecylphenyl-1-naphthylamine, di (2,4-diethylphenyl) Bis) amine, bis (dialkylphenyl) amines such as di (2-ethyl-4-nonylphenyl) amine, 1-naphthylamine, phenyl-1-naphthylamine, phenyl-2-naphthylamine, N-hexylphenyl-2-naphthylamine , Aryl-naphthylamines such as N-octylphenyl-2-naphthylamine, phenylenediamines such as N, N′-diisopropyl-p-phenylenediamine, N, N′-diphenyl-p-phenylenediamine, phenothiazine, 3,7 -Phenothiazines such as dioctylphenothiazine and the like.
Of these, phenyl-α-naphthylamine and alkyldiphenylamine are preferably used alone or in combination of two, and dioctyldiphenylamine and N- (p-octylphenyl) -1-naphthylamine are used in combination. Is particularly preferable from the viewpoint of oxidation stability.

  The antioxidant is preferably blended so as to be 0.01 to 5% by mass based on the total amount of the cooling oil. When the blending amount is in the range of 5% by mass or less, the solubility in the cooling oil, the economy, and the antioxidant performance are harmonized. A more preferable blending amount is 0.05 to 4% by mass, particularly preferably 0.1 to 3% by mass, based on the total amount of the cooling oil.

As the corrosion inhibitor (metal deactivator), a benzotriazole-based compound is preferable. By using the benzotriazole-based compound in combination with the base oil component, or the base oil component and the antioxidant, it is possible to further improve the effect of preventing corrosion to metal elements, particularly Cu, Al, Ni and the like. Examples of the benzotriazole compounds used here include benzotriazoles represented by the following general formula (I) and derivatives thereof. The derivatives include alkylbenzotriazoles represented by the following general formula (II), N-alkylbenzotriazoles represented by the general formula (III), and N- (alkyls represented by the general formula (IV). ) Those containing aminoalkylbenzotriazole. In the formula, a, b, and c are each 0, 1, 2, or 3, and R3 in the formula is a structure represented by the general formula (V). R1, R2, and R4 are linear or branched C1-C4 alkyl groups, R5 is a methylene or ethylene group, R6 and R7 are hydrogen, or the same or different, linear or branched carbon atoms 1-18. An alkyl group, preferably a branched alkyl group having 1 to 12 carbon atoms, and R8 and R9 are the same or different alkyl groups having 3 to 15 carbon atoms.

  Specific examples of benzotriazole and its derivatives include the following. First, 4-alkyl-benzotriazoles such as benzotriazole, 4-methyl-benzotriazole, 4-ethyl-benzotriazole, 5-alkyl-benzotriazoles such as 5-methyl-benzotriazole, 5-ethyl-benzotriazole, 1-alkyl-benzotriazoles such as 1-dioctylaminomethyl-2,3-benzotriazole, benzotriazole derivatives such as 1-alkyl-toltriazoles such as 1-dioctylaminomethyl-2,3-tolutriazole, benzo 2- (alkyldithio) -benzimidazoles such as imidazole, 2- (octyldithio) -benzimidazole, 2- (decyldithio) -benzimidazole, 2- (dodecyldithio) -benzimidazole, 2- (octyldithio) ) - torr imidazole, 2- (Deshirujichio) - torr imidazole, 2- (dodecyldithio) - torr imidazole such as 2- (alkyldithio) - there is a benzimidazole derivative of the torque imidazoles.

  Indazole derivatives such as tolindazoles such as indazole, 4-alkyl-indazole, 5-alkyl-indazole, benzothiazole, 2-mercaptobenzothiazole derivative (manufactured by Chiyoda Chemical Co., Ltd .: Thiolite B-3100), 2- (hexyl) 2- (Alkyldithio) benzothiazoles such as dithio) benzothiazole, 2- (octyldithio) benzothiazole, 2- (alkyldithio) such as 2- (hexyldithio) tolthiazole, 2- (octyldithio) tolthiazole Tolthiazoles, 2- (N, N-diethyldithiocarbamyl) benzothiazole, 2- (N, N-dibutyldithiocarbamyl) -benzothiazole, 2- (N, N-dihexyldithiocarbamyl) -benzothiazole 2- (N, N-dia Kirdithiocarbamyl) benzothiazoles, 2- (N, N-diethyldithiocarbamyl) tolthiazole, 2- (N, N-dibutyldithiocarbamyl) tolthiazole, 2- (N, N-dihexyldithiocarbamyl) ) There are benzothiazole derivatives such as 2- (N, N-dialkyldithiocarbamyl) -torzothiazoles such as tolthiazole.

  Furthermore, 2- (alkyldithio) -benzoxazoles such as 2- (octyldithio) benzoxazole, 2- (decyldithio) benzoxazole, 2- (dodecyldithio) benzoxazole, 2- (octyldithio) toluoxazole, 2 Benzoxazole derivatives such as 2- (alkyldithio) toluazoles such as-(decyldithio) toluxazole and 2- (dodecyldithio) toluxazole, 2,5-bis (heptyldithio) -1,3,4-thiadiazole, 2 , 5-bis (nonyldithio) -1,3,4-thiadiazole, 2,5-bis (dodecyldithio) -1,3,4-thiadiazole, 2,5-bis (octadecyldithio) -1,3,4 2,5-bis (alkyldithio) -1,3,4-thio such as thiadiazole Diazoles, 2,5-bis (N, N-diethyldithiocarbamyl) -1,3,4-thiadiazole, 2,5-bis (N, N-dibutyldithiocarbamyl) -1,3,4-thiadiazole 2,5-bis (N, N-dialkyldithiocarbamyl) -1,3,4-thiadiazoles such as 2,5-bis (N, N-dioctyldithiocarbamyl) -1,3,4-thiadiazole 2-N, N-dibutyldithiocarbamyl-5-mercapto-1,3,4-thiadiazole, 2-N, N-dioctyldithiocarbamyl-5-mercapto-1,3,4-thiadiazole Thiadiazole derivatives such as N, N-dialkyldithiocarbamyl-5-mercapto-1,3,4-thiadiazoles, 1-di-octylaminomethyl-2,4-triazol Like 1-alkyl-2,4-triazole derivative of triazoles such like.

  Pour point depressants include, for example, polyalkyl methacrylate, polybutene, polyalkyl styrene, polyvinyl acetate, polyalkyl acrylate, ethylene-vinyl acetate copolymer, ethylene-alkyl acrylate copolymer, chlorinated polyethylene, alkenyl succinic acid amide. System compounds and the like. One of these pour point depressants may be used alone, or two or more thereof may be used in combination. The blending amount of the pour point depressant is preferably 0.01 to 2.0 mass%, more preferably 0.05 to 1.0 mass%, based on the total amount of cooling oil.

  In addition to the additives described above, additives such as an antifoaming agent and a viscosity index improver can be used.

The cooling oil was adjusted using the following mineral oil as the base oil. Table 1 shows the properties of the obtained cooling oil. Table 1 also shows properties of commercially available heat medium oil as a reference example.
<Base oil 1>
GTL base oil synthesized by the Fischer-Tropsch method and classified as Group 2 (Gp2) by API (American Petroleum Institute) base oil classification. (Characteristics: Kinematic viscosity at 100 ° C .; 2.64 mm ² / s, kinematic viscosity at 40 ° C .; 9.34 mm ² / s, viscosity index; 119, sulfur content (sulfur element equivalent value); less than 10 mass ppm, Nitrogen content (nitrogen element conversion value); less than 1 mass ppm, aniline point; 113 ° C., 15 ° C. density; 0.807 g / cm ³ , 20 ° C. density: 0.803 g / cm ³ , 20 ° C. refractive index: 1 .449, flash point: 202 ° C.)
<Base oil 2>
GTL base oil synthesized by the Fischer-Tropsch method and classified as Group 3 (Gp3) by API (American Petroleum Institute) base oil classification. (Characteristics: kinematic viscosity at 100 ° C., a kinematic viscosity at ^{3.98mm 2 / s, 40 ℃;} 17.2mm 2 / s, viscosity index; 131, sulfur content (sulfur metal basis); less than 10 mass ppm, Nitrogen content (nitrogen element equivalent); less than 1 ppm by mass, aniline point; 121 ° C., 15 ° C. density; 0.817 g / cm ³ , 20 ° C. density: 0.813 g / cm ³ , 20 ° C. refractive index: 1 .454, flash point: 226 ° C)
<Base oil 3>
A paraffinic mineral oil obtained by appropriately combining refining means such as hydrocracking and hydrodewaxing to a lubricating oil fraction obtained by atmospheric distillation of crude oil. Association) Those classified as Group 2 (Gp2) by base oil classification. (Characteristics: Kinematic viscosity at 100 ° C .; 3.08 mm ² / s, kinematic viscosity at 40 ° C .; 12.2 mm ² / s, viscosity index; 111, sulfur content (sulfur element equivalent value); less than 10 mass ppm, Nitrogen content (nitrogen element conversion value); less than 1 ppm by mass, aniline point; 108 ° C., 15 ° C. density; 0.833 g / cm ³ , 20 ° C. density: 0.830 g / cm ³ , 20 ° C. refractive index: 1 .459, flash point: 194 ° C)
<Base oil 4>
A paraffinic mineral oil obtained by appropriately combining refining means such as hydrocracking and hydrodewaxing to a lubricating oil fraction obtained by atmospheric distillation of crude oil. Association) Those classified as Group 3 (Gp3) by base oil classification. (Characteristics: kinematic viscosity at 100 ° C., a kinematic viscosity at ^{4.25mm 2 / s, 40 ℃;} 19.5mm 2 / s, viscosity index; 125, sulfur content (sulfur metal basis); less than 10 mass ppm, Nitrogen content (nitrogen element conversion value); less than 1 ppm by mass, aniline point; 116 ° C., 15 ° C. density; 0.835 g / cm ³ , 20 ° C. density: 0.832 g / cm ³ , 20 ° C. refractive index: 1 .461, flash point: 224 ° C)
<Base oil 5>
A paraffinic mineral oil obtained by applying a suitable combination of refining means such as dewaxing to lubricating oil fractions obtained by atmospheric distillation of crude oil, according to API (American Petroleum Institute) base oil classification Those classified as Group 1 (Gp1). (Characteristics: Kinematic viscosity at 100 ° C .; 4.59 mm ² / s, kinematic viscosity at 40 ° C .; 24.3 mm ² / s, viscosity index; 103, sulfur content (sulfur element equivalent value); 4500 mass ppm, nitrogen Minute content (nitrogen element conversion value); 20 mass ppm, aniline point; 100 ° C., 15 ° C. density; 0.864 g / cm ³ , 20 ° C. density: 0.861 g / cm ³ , 20 ° C. Refractive index: 1.475 Flash point: 218 ° C)
<Base oil 6>
A naphthenic mineral oil obtained by applying a suitable combination of refining means such as dewaxing to a lubricating oil fraction obtained by atmospheric distillation of crude oil, according to API (American Petroleum Institute) base oil classification Those classified as Group 5 (Gp5). (Characteristics: Kinematic viscosity at 100 ° C .; 2.25 mm ² / s, kinematic viscosity at 40 ° C .; 8.70 mm ² / s, viscosity index; 49, 15 ° C. density; 0.884 g / cm ³ , aniline point; 77 ° C. , Flash point 148 ℃)

＜アニリン点＞
J I S K ２２５６「石油製品−アニリン点及び混合アニリン点試験方法」によって得られるアニリン点。
＜導電率＞
ＪＩＳ Ｋ ２２７６「石油製品−航空燃料油試験方法」により得られる導電率。 In addition, the measuring method of each property shown in Table 1 is as follows.
<Kinematic viscosity (@ 40 ° C.), Kinematic viscosity (@ 100 ° C.), Viscosity index>
Kinematic viscosity and viscosity index obtained by JIS K 2283 "Crude oil and petroleum products-kinematic viscosity test method and viscosity index calculation method".
<Density (@ 15 ℃)>
It is a density according to JIS K 2249 “Crude oil and petroleum products—density test method and density / mass / volume conversion table”. In addition, the numerical value in a table | surface is displayed by the unit kg / m < ³ > of the said Formula (1).
<Flash point>
Flash point obtained by JIS K 2265-4 “How to determine flash point-Part 4: Cleveland Opening Method”.
<Pour point>
Pour point obtained by JIS K 2269 “Pour point of crude oil and petroleum products and cloud point test method of petroleum products”.
<Heat penetration rate>
Based on the density, the specific heat capacity was calculated from the following formula (2), the thermal conductivity was calculated from the formula (3), and the thermal permeability was calculated from the above-described formula (1). In addition, the temperature t in Formula (2) and Formula (3) was calculated as 15 degreeC.

<Aniline point>
Aniline point obtained by JISK 2256 "Petroleum products-Test method for aniline point and mixed aniline point".
<Conductivity>
Electrical conductivity obtained by JIS K 2276 “Petroleum products-Aviation fuel oil test method”.

  As shown in Table 1, Examples 1 to 4 have lower kinematic viscosity at 40 ° C. than Comparative Examples 1 and 2, but the heat permeability does not change, and use of secondary batteries and capacitors mounted on automobiles and the like. It is assumed that the heat carrying capacity in the temperature environment is high. That is, it can be said that it is suitable for cooling oil for secondary batteries and capacitors mounted in automobiles and the like. And these cooling oils can be manufactured using a common base oil, and it has confirmed that GTL wax was especially preferable as a base oil. On the other hand, from the results of Comparative Examples 1 and 2, the base oil 5 belonging to the group 1 of the API base oil category adopted as the base oil of the conventional insulating oil and the same base oil used as the base oil of the conventional lubricating oil. It was confirmed that the base oil 6 belonging to Group 5 is not suitable as the base oil of the cooling oil according to the present invention. The heat medium oil of the reference example has the same heat permeability as the cooling oil of the example, and is a numerical value that satisfies safety in both flash point and conductivity, but it is used in a high temperature range. Therefore, the kinematic viscosity at 40 ° C. is high, and it is not suitable for cooling a secondary battery or a capacitor mounted on an automobile or the like.

＜酸化防止剤Ｂ＞
以下の一般式（ＶＩＩ）に示す構造をもつ、２，２’−メチレンビス（４−エチル，６−ｔ−ブチルフェノール）で構成されるフェノール系酸化防止剤。

＜酸化防止剤C＞
２，４−ジ−ｔ−ブチルフェノールで構成されるフェノール系酸化防止剤。
＜腐食防止剤＞
以下の一般式（ＶＩＩＩ）に示す構造をもつ、N,N-ビス(2-エチルヘキシル)-(4又は5)-メチル-1H-ベンゾトリアゾール-1-メチルアミンで構成される腐食防止剤。なお、構造式のRは２-エチルヘキシルである。

＜流動点降下剤＞
以下の性状のポリメタクリレート。
Ｍｎ（数平均分子量） ３２４３４ （標準物質 ポリスチレン）
Ｍｗ（重量平均分子量） ６００９３ （標準物質 ポリスチレン）
Ｍｗ／Ｍｎ １．８５２７９ （標準物質 ポリスチレン）
なお、分子量の測定条件は以下の通りである。
クロマト Shodex GPC101
カラム Shodex GPC KF-805L ×２
温度 ４０℃
流量 １ｍｌ/min
キャリアー ＴＨＦ
検出器 ＲＩ Next, the following commercially available corrosion inhibitors, phenolic antioxidants, and pour point depressants were added to the base oils 1 to 6 to prepare the cooling oils shown in Table 2. Further, in Table 3, Comparative Example 10 of the heat medium oil listed as Reference Example in Table 1 as Comparative Example 5, Commercial Insulating Oil as Comparative Examples 6, 7, and 8, and Commercial Lubricating Oil as Comparative Example 9 Shows the properties of commercially available ATF.
<Antioxidant A>
Phenolic antioxidants comprising benzenepropanoic acid 3,5-bis (1,1-dimethyl-ethyl) -4-hydroxy-C7-C9 side chain alkyl ester having the structure shown in the following general formula (VI) Agent. In the structural formula, R is C7 to C9.

<Antioxidant B>
A phenolic antioxidant composed of 2,2′-methylenebis (4-ethyl, 6-t-butylphenol) having a structure represented by the following general formula (VII).

<Antioxidant C>
A phenolic antioxidant composed of 2,4-di-t-butylphenol.
<Corrosion inhibitor>
A corrosion inhibitor comprising N, N-bis (2-ethylhexyl)-(4 or 5) -methyl-1H-benzotriazole-1-methylamine having a structure represented by the following general formula (VIII): In the structural formula, R is 2-ethylhexyl.

<Pour point depressant>
Polymethacrylate with the following properties.
Mn (number average molecular weight) 32434 (standard material polystyrene)
Mw (weight average molecular weight) 60093 (standard material polystyrene)
Mw / Mn 1.85279 (standard material polystyrene)
The molecular weight measurement conditions are as follows.
Chromatography Shodex GPC101
Column Shodex GPC KF-805L x 2
Temperature 40 ℃
Flow rate 1ml / min
Carrier THF
Detector RI

  As shown in Table 2, the deterioration of heat permeability and kinematic viscosity at 40 ° C. due to the addition of normally used additives in the normal range is not confirmed, and the use of the additive does not affect the cooling performance. I was able to confirm. In addition, it was confirmed that there is no influence on the flash point and conductivity, and that there is no influence on safety when circulating inside an automobile or the like.

Claims (6)

A coolant having a density of 15 ° C. of 0.84 g / cm ³ or less, a kinematic viscosity of 40 ° C. of 20 mm ² / s or less, a flash point of 190 ° C. or more, and a conductivity of 10 pS / m or less. The coolant according to claim 1, wherein the density at 15 ° C. is 0.81 g / cm ³ or less.   The cooling liquid according to claim 1 or 2 whose flash point is 200 ° C or more. The cooling liquid according to claim 1, wherein the kinematic viscosity at 40 ° C. is 13 mm ² / s or less. The coolant according to claim 1, wherein the kinematic viscosity at 40 ° C. is 13 to ²⁰ mm ² / s. Furthermore, the cooling fluid of Claims 1-5 containing any one or more additives of an amine antioxidant, a phenolic antioxidant, a corrosion inhibitor, or a pour point depressant.