Cooling liquid for immersion cooling system

Abstract

To provide a cooling liquid for an immersion cooling system in which the influence on an electronic device to be immersed is further suppressed.SOLUTION: A cooling liquid for a liquid immersion cooling system is contained in a liquid immersion tank of a liquid immersion cooling system as a cooling liquid. The cooling liquid contains a hydrocarbon oil and one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants. The hydrocarbon oil is contained in an amount of 50 mass% or more with respect to the total amount of the cooling liquid for an immersion cooling system. A 5% distillation temperature of the cooling liquid for an immersion cooling system is 320°C or higher, a %CN is 30.0 or less, and a kinematic viscosity at 40°C is 11.5 mm2 / s or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a coolant for an immersion cooling system. This application claims priority based on Japanese Patent Application No. 2022-113248, filed on July 14, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] With the rapid increase in data transmission and reception, the load on supercomputers and data servers is increasing, and the amount of heat generated by these electronic devices is also increasing. Until now, air cooling has been the mainstream method for cooling these electronic devices, but as air cooling has limitations in its cooling efficiency, attention has been focused on liquid immersion cooling, which has higher cooling efficiency.

[0003] Figure 1 shows an example of the basic configuration of an immersion cooling system. The immersion cooling system 10 includes an immersion tank 1, a heat exchanger 3, a pump 5, and a cooling device 7. The immersion tank 1 is filled with a cooling liquid for the immersion cooling system. The electronic devices are cooled in the immersion bath 1. The coolant for the immersion cooling system, which has been warmed by the exhaust heat from the electronic devices, is pumped up by a pump 5 and undergoes heat exchange with cold water produced by a cooling device 7 in a heat exchanger 3. The coolant for the immersion cooling system, which has been cooled by the heat exchange, is circulated back into the immersion bath 1. By using the immersion cooling system 10, it is possible to maintain a safe and constant temperature even when the electronic device is continuously used under high load conditions.

[0004] Specifically, Patent Document 1 discloses an immersion cooling system that includes (a) an electronic hardware device and (b) a liquid cooling medium. The liquid cooling medium is disclosed to be (i) a mixture of a synthetic ester and a saturated medium-chain triglyceride, wherein the synthetic ester has a viscosity of 28-38 cSt at 40°C, as determined in accordance with ASTM D445, or (ii) a polyalkylene glycol, wherein if the liquid cooling medium comprises a polyalkylene glycol, the polyalkylene glycol constitutes at least 70% by weight of the liquid cooling medium. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6282289 Summary of the Invention [Problem to be solved by the invention]

[0006] It is also important that the coolant for the immersion cooling system does not adversely affect the electronic devices that are immersed in. Specifically, it is required to suppress swelling of the insulating materials in the electronic devices and elution of metals from the electronic devices. The liquid cooling medium described in Patent Document 1 takes into consideration the balance between flash point and viscosity, but does not consider the effects on electronic devices that are immersed in it. The ester contained in the liquid cooling medium described in Patent Document 1 generates acid upon hydrolysis, which may cause problems with the elution of metals from electronic devices. Furthermore, a coolant for an immersion cooling system is also required to have high thermal stability.

[0007] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a coolant for an immersion cooling system that has high thermal stability and that further reduces the impact on electronic devices in which it is immersed. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention employs the following configuration. [1] A coolant for an immersion cooling system, which is filled as a coolant in an immersion tank of the immersion cooling system, contains a hydrocarbon oil and one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants, and the hydrocarbon oil is contained in an amount of 50 mass% or more based on the total amount of the coolant for the immersion cooling system, and the coolant for the immersion cooling system has a 5% distillation temperature of 320°C or higher, and %C N is 30.0 or less, and the kinematic viscosity at 40°C is 11.5mm 2 / s or more for use in immersion cooling systems. [2] The coolant for an immersion cooling system according to [1], having a 95% distillation temperature of 430°C or higher. [3] The coolant for an immersion cooling system according to [1] or [2], wherein the content of the antioxidant is 0.01 mass % or more and 5 mass % or less with respect to the total amount of the coolant for an immersion cooling system. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a coolant for an immersion cooling system that has high thermal stability and that has less adverse effects on electronic devices in which it is immersed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of an immersion cooling system. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Coolant for immersion cooling systems) The coolant for an immersion cooling system of this embodiment is a coolant for an immersion cooling system that is filled into an immersion tank of the immersion cooling system. The coolant for the immersion cooling system of this embodiment is used to cool electronic devices. Such electronic equipment includes computer servers, server motherboards, microprocessors, capacitors, and other heat-generating electronic devices.

[0012] The coolant for an immersion cooling system of this embodiment contains a hydrocarbon oil and one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants, and the hydrocarbon oil is contained in an amount of 50 mass% or more based on the total amount of the coolant for an immersion cooling system. The coolant for an immersion cooling system has a 5% distillation temperature of 320°C or higher and a %C N is 30.0 or less, and the kinematic viscosity at 40°C is 11.5mm 2 / s or more.

[0013] The coolant for the immersion cooling system of this embodiment has a kinematic viscosity of 11.5 mm at 40°C. 2 / s or more, 15.0 mm 2 / s or more is preferable, and 20.0 mm 2 / s or more is more preferable, and 25.0 mm 2 / s or more is more preferable. The coolant for the immersion cooling system of this embodiment has a kinematic viscosity of 70.0 mm at 40°C. 2 / s or less is preferable, and 60.0 mm 2 / s or less is more preferable, and 50.0 mm 2 / s or less is even more preferable.

[0014] The coolant for the immersion cooling system of this embodiment has a kinematic viscosity of 11.5 mm at 40°C. 2 / s or more, swelling of the insulating material of the electronic device can be suppressed. This is presumably because high-viscosity components (e.g., compounds with long carbon chains) are less likely to be incorporated into the resin of the insulating material of the electronic device. If the kinetic viscosity at 40°C of the coolant for an immersion cooling system of this embodiment is equal to or greater than the above-mentioned preferable lower limit, swelling of the insulating material of the electronic device can be further suppressed. When the kinetic viscosity at 40°C of the coolant for the immersion cooling system of this embodiment is equal to or less than the above-mentioned preferable upper limit, the flowability of the coolant for the immersion cooling system of this embodiment is improved, and the coolant circulates more easily, improving the cooling performance. In addition, the load on the pump that pumps the coolant in the immersion cooling system can be reduced.

[0015] For example, the coolant for the immersion cooling system of this embodiment has a kinematic viscosity of 11.5 mm at 40°C. 2 / s or more 70.0mm 2 / s or less is preferable, and 15.0 mm 2 / s or more 60.0mm 2 / s or less is more preferable, and 20.0 mm 2 / s or more 60.0mm 2 / s or less is more preferable, and 25.0 mm 2 / s or more 50.0mm 2 It is particularly preferable that the ratio is 1 / s or less.

[0016] The coolant for the immersion cooling system of this embodiment has a kinematic viscosity of 3.5 mm at 80°C. 2 / s or more 30.0mm 2 / s or less is preferable, and 4.5 mm 2 / s or more 27.5mm 2 / s or less is more preferable, and 6.0 mm 2 / s or more 25.0mm 2 / s or less is even more preferable.

[0017] The coolant for the immersion cooling system of this embodiment has a kinematic viscosity of 2.5 mm at 100°C. 2 / s or more 20.0mm 2 / s or less is preferable, and 3.0 mm 2 / s or more 17.5mm 2 / s or less is more preferable, and 4.0 mm 2 / s or more 15.0mm 2 / s or less is even more preferable.

[0018] In this specification, the kinematic viscosities at 40°C, 80°C, and 100°C refer to the kinematic viscosities at 40°C, 80°C, and 100°C measured in accordance with JIS K2283:2000.

[0019] The 5% distillation temperature of the coolant for the immersion cooling system of this embodiment is 320°C or higher, preferably 330°C or higher, more preferably 350°C or higher, and even more preferably 370°C or higher. Furthermore, the 5% distillation temperature of the coolant for the immersion cooling system is preferably 600°C or lower, more preferably 550°C or lower, and even more preferably 520°C or lower.

[0020] By ensuring that the 5% distillation temperature of the coolant for an immersion cooling system is 320°C or higher, swelling of the insulating material of electronic devices can be suppressed. This is presumably because high-boiling point components are less likely to be incorporated into resins such as insulating materials of electronic devices. If the 5% distillation temperature of the coolant for an immersion cooling system is equal to or higher than the above-mentioned preferable lower limit, swelling of the insulating material of electronic devices can be further suppressed. When the 5% distillation temperature of the coolant for the immersion cooling system is equal to or lower than the above-mentioned preferable upper limit, the fluidity of the coolant for the immersion cooling system is improved, and circulation is facilitated, thereby improving cooling performance. In addition, the load on the pump that delivers the coolant in the immersion cooling system can be reduced.

[0021] For example, the 5% distillation temperature of the coolant for the immersion cooling system of this embodiment is preferably 320°C or higher and 600°C or lower, more preferably 330°C or higher and 550°C or lower, even more preferably 350°C or higher and 550°C or lower, and particularly preferably 370°C or higher and 520°C or lower.

[0022] The 95% distillation temperature of the coolant for the immersion cooling system of this embodiment is preferably 430°C or higher, more preferably 450°C or higher, and even more preferably 500°C or higher. Furthermore, the 95% distillation temperature of the coolant for the immersion cooling system is preferably 800°C or lower, more preferably 750°C or lower, and even more preferably 700°C or lower.

[0023] If the 95% distillation temperature of the coolant for the immersion cooling system is equal to or higher than the above-mentioned preferable lower limit, swelling of the insulating material of the electronic device can be further suppressed. When the 95% distillation temperature of the coolant for the immersion cooling system is equal to or lower than the above-mentioned preferable upper limit, the fluidity of the coolant for the immersion cooling system is improved, and circulation is facilitated, thereby improving cooling performance. In addition, the load on the pump that delivers the coolant in the immersion cooling system can be reduced.

[0024] For example, the 95% distillation temperature of the coolant for the immersion cooling system of this embodiment is preferably 430°C or higher and 800°C or lower, more preferably 450°C or higher and 750°C or lower, and even more preferably 500°C or higher and 700°C or lower.

[0025] For example, among the above, the coolant for the immersion cooling system of this embodiment preferably has a 5% distillation temperature of 320°C or higher and 600°C or lower and a 95% distillation temperature of 430°C or higher and 800°C or lower; more preferably a 5% distillation temperature of 330°C or higher and 550°C or lower and a 95% distillation temperature of 450°C or higher and 750°C or lower; even more preferably a 5% distillation temperature of 350°C or higher and 550°C or lower and a 95% distillation temperature of 450°C or higher and 750°C or lower; and particularly preferably a 5% distillation temperature of 370°C or higher and 520°C or lower and a 95% distillation temperature of 500°C or higher and 700°C or lower. If the 5% distillation temperature and 95% distillation temperature of the coolant for an immersion cooling system of this embodiment are within the above-mentioned preferred ranges, the cooling performance can be improved while further suppressing swelling of the insulating material of the electronic device.

[0026] In this specification, the 5% distillation temperature and the 95% distillation temperature refer to values ​​measured by gas chromatographic distillation in accordance with JIS K2254:2018.

[0027] The measurement conditions for gas chromatographic distillation in this specification are as follows. (1) When the end point (100% distillation temperature) is 600°C or higher Equipment: Shimadzu GC-2030 Column: UA-1HT (30m x 0.5mm I.D. x 0.10μm) Carrier gas: Helium 15mL / min Detector: FID Detector temperature: 400℃ Inlet temperature: PTV 40~380℃ Column temperature: 40 to 380°C (6 min) Heating rate: 10℃ / min Injection volume: 0.5 μL (carbon disulfide solution) (2) When the end point (100% distillation temperature) is less than 600°C Equipment: Shimadzu GC-2010plus Column: UA-1HT (30m x 0.5mm I.D. x 0.10μm) Carrier gas: Helium 15mL / min Detector: FID Detector temperature: 360℃ Inlet temperature: PTV 40~380℃ Column temperature: 40 to 350°C (6 min) Heating rate: 10℃ / min Injection volume: 0.5 μL (carbon disulfide solution)

[0028] %C of the coolant for the liquid immersion cooling system of this embodiment N is 30.0 or less, preferably 27.5 or less, and more preferably 25.0 or less. Also, the %C of the coolant for the immersion cooling system N is preferably 0.5 or more, more preferably 1.5 or more, and even more preferably 2.5 or more.

[0029] %C of coolant for immersion cooling system N If the value is 30.0 or less, swelling of the insulating material in the electronic device can be suppressed. If the value is equal to or less than the above-mentioned preferable upper limit, swelling of the insulating material in the electronic device can be further suppressed. %C of coolant for immersion cooling system N When is equal to or greater than the above-mentioned preferable lower limit, the solubility of the additive is improved.

[0030] For example, the %C of the coolant for the immersion cooling system of this embodiment N is preferably 0.5 or more and 30.0 or less, more preferably 1.5 or more and 27.5 or less, and even more preferably 2.5 or more and 25.0 or less.

[0031] %C of the coolant for the liquid immersion cooling system of this embodiment P is preferably 99.5 or less, more preferably 98.5 or less, and even more preferably 97.5 or less. Also, the %C of the coolant for the immersion cooling system P is preferably 70.0 or more, more preferably 72.5 or more, and even more preferably 75.0 or more.

[0032] %C of coolant for immersion cooling system P When is equal to or less than the above-mentioned preferable upper limit, the solubility of the additive is further improved. %C of coolant for immersion cooling system P When the value is equal to or greater than the above-mentioned preferable lower limit, swelling of the insulating material of the electronic device can be further suppressed.

[0033] For example, the %C of the coolant for the immersion cooling system of this embodiment P is preferably 70.0 or more and 99.5 or less, more preferably 72.5 or more and 98.5 or less, and even more preferably 75.0 or more and 97.5 or less.

[0034] %C of the coolant for the liquid immersion cooling system of this embodiment A is preferably 5.0 or less, more preferably 3.0 or less, and even more preferably 0.

[0035] %C of coolant for immersion cooling system A If is equal to or less than the above-mentioned preferable upper limit, electronic devices are less likely to be affected.

[0036] In this specification, %C N , %CP and %C A are each determined by a method (ndM ring analysis) in accordance with ASTM D 3238-85. %C N %C means the percentage (mass proportion) of naphthenic carbon atoms relative to the total carbon atoms. P %C means the percentage (mass ratio) of the number of carbon atoms in paraffins to the total number of carbon atoms. A means the percentage of the number of aromatic carbon atoms relative to the total number of carbon atoms. The above mentioned %C N , %C P and %C A The preferred range of %C is based on the value determined by the above method. For example, even in the case of a mineral base oil that does not contain naphthene, the %C determined by the above method is N can have a value greater than 0.

[0037] <Hydrocarbon oil> The coolant for the immersion cooling system of this embodiment contains hydrocarbon oil. Examples of hydrocarbon oils include saturated aliphatic hydrocarbon oils, unsaturated aliphatic hydrocarbon oils (olefinic hydrocarbons), alicyclic hydrocarbon oils (naphthenic hydrocarbons), and aromatic hydrocarbon oils. The aliphatic saturated hydrocarbon oil may be a straight-chain saturated hydrocarbon oil (normal paraffin hydrocarbon) or a branched-chain saturated hydrocarbon oil (isoparaffin hydrocarbon). Specific examples of hydrocarbon oils in the coolant for the immersion cooling system of this embodiment include mineral oils and synthetic oils.

[0038] <Mineral oil> As the mineral oil, a distillate obtained by atmospheric distillation of crude oil can be used. In addition, a lubricating oil fraction obtained by further vacuum distillation of the distillate obtained by the atmospheric distillation and then refining the distillate through various refining processes can also be used. The refining process may be a suitable combination of hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, clay treatment, etc. Mineral oil can be obtained by combining these refining processes in a suitable order. Mineral oil also includes wax isomerate oil. Wax isomerate oil is a hydrocarbon obtained by hydrocracking and hydroisomerization of GTL wax or CTL wax synthesized by the Fischer-Tropsch process (FT process), or slack wax obtained by solvent dewaxing, to produce a lubricating oil fraction. GTL wax is wax synthesized by the FT process using natural gas as a feedstock, and CTL wax is wax synthesized by the FT process using coal as a feedstock. Hydrocarbons obtained by hydrocracking and isomerization of these waxes to produce a lubricating oil fraction are generally referred to as GTL or CTL. As the mineral oil, a mixture of a plurality of refined oils with different properties obtained by subjecting different crude oils or distillate oils to a combination of different refining processes, as well as a mixture with GTL, etc. may be used.

[0039] As the mineral oil, API base oil classification Group I base oil (hereinafter referred to as "API Group I base oil"), Group II base oil (hereinafter referred to as "API Group II base oil"), or Group III base oil (hereinafter referred to as "API Group III base oil"), or a mixture thereof, can be used. API Group I base oils are mineral base oils having a sulfur content greater than 0.03 wt.% and / or a saturates content less than 90 wt.% and a viscosity index greater than or equal to 80 and less than 120. API Group II base oils are mineral base oils having a sulfur content of 0.03% by weight or less, a saturates content of 90% by weight or more, and a viscosity index of 80 or greater but less than 120. API Group III base oils are mineral base oils having a sulfur content of 0.03% by weight or less, a saturates content of 90% by weight or more, and a viscosity index of 120 or greater.

[0040] The hydrocarbon oil may consist of one mineral oil or may be a mixed base oil containing two or more mineral oils, the API classifications of which may be the same or different from each other. The mineral oil in the coolant for an immersion cooling system of this embodiment preferably contains an API Group III base oil, from the viewpoint of further suppressing the effects on electronic devices.

[0041] ≪Synthetic oil≫ Examples of synthetic oils include polyolefins and alkylbenzenes.

[0042] Polyolefin Examples of polyolefins include homopolymers or copolymers of olefin monomers having 2 to 16 carbon atoms, preferably 2 to 12 carbon atoms, and hydrogenated polymers thereof. The olefin monomers may be any of α-olefins, internal olefins, linear olefins, and branched olefins. Specific examples of such olefin monomers include ethylene, propylene, 1-butene, 2-butene, isobutene, pentene, hexene, heptene, octene, nonene, decene, undecene, dodecene, tridecene, tetradecene, pentadecene, hexadecene, and mixtures thereof. Among the above polyolefins, poly-α-olefins (PAOs) are preferred from the viewpoints of viscosity characteristics and oxidation stability.

[0043] The polyolefins can be produced by known methods. For example, they can be produced by a thermal reaction without a catalyst, or the target polyolefins can be produced by homopolymerizing or copolymerizing the olefins using known catalysts such as organic peroxide catalysts such as benzoyl peroxide; Friedel-Crafts catalysts such as aluminum chloride, aluminum chloride-polyhydric alcohol catalysts, aluminum chloride-titanium chloride catalysts, aluminum chloride-alkyltin halide catalysts, and boron fluoride catalysts; Ziegler catalysts such as organic aluminum chloride-titanium chloride catalysts and organic aluminum-titanium tetrachloride catalysts; metallocene catalysts such as aluminoxane-zirconocene catalysts and ionic compound-zirconocene catalysts; and Lewis acid complex catalysts such as aluminum chloride-base catalysts and boron fluoride-base catalysts.

[0044] Alkylbenzene The alkylbenzene is preferably one having 1 to 4 alkyl groups each having 1 to 40 carbon atoms in the molecule. The alkyl group of the alkylbenzene may be linear or branched, but branched alkyl groups are preferred from the standpoints of stability, viscosity characteristics, etc., and branched alkyl groups derived from olefin oligomers such as propylene, butene, and isobutylene are more preferred from the standpoint of easy availability.

[0045] Among the alkylbenzenes mentioned above, the alkylbenzene in this embodiment is most preferably an alkylbenzene having one or two alkyl groups, i.e., a monoalkylbenzene, a dialkylbenzene, or a mixture thereof, from the viewpoints of stability and availability. Furthermore, the alkylbenzene may be not only an alkylbenzene having a single structure, but also a mixture of alkylbenzenes having different structures.

[0046] The alkylbenzene can be produced by a known method, for example, by using an aromatic compound as a raw material and an alkylating agent and an alkylation catalyst. Specific examples of aromatic compounds used as raw materials include benzene, toluene, xylene, ethylbenzene, methylethylbenzene, diethylbenzene, and mixtures thereof. Specific examples of the alkylating agent include linear or branched olefins having 6 to 40 carbon atoms obtained by polymerization of lower monoolefins such as ethylene, propylene, butene, and isobutylene, preferably propylene; linear or branched olefins having 6 to 40 carbon atoms obtained by thermal cracking of wax, heavy oil, petroleum fractions, polyethylene, polypropylene, and the like; linear olefins having 9 to 40 carbon atoms obtained by separating n-paraffins from petroleum fractions such as kerosene and diesel and olefinating them using a catalyst; and mixtures thereof. Examples of alkylation catalysts that can be used in the alkylation include known catalysts such as Friedel-Crafts catalysts such as aluminum chloride and zinc chloride; and acidic catalysts such as sulfuric acid, phosphoric acid, tungstosilicic acid, hydrofluoric acid, and activated clay.

[0047] The hydrocarbon oil in the coolant for an immersion cooling system of this embodiment may contain hydrocarbon oil having carbon derived from biomass. Specific examples of hydrocarbon oils having carbon derived from biomass include base oils synthesized from vegetable oils such as palm oil, coconut oil, soybean oil, rapeseed oil, and mixtures thereof.

[0048] Examples of commercially available hydrocarbon oils containing biomass-derived carbon include SynNova TM 4 Base Oil (Novvi) and SynNova TM 9 Base Oil (manufactured by Novvi), etc.

[0049] The hydrocarbon oil in the coolant for an immersion cooling system of this embodiment may be mineral oil alone, synthetic oil alone, or a mixture of mineral oil and synthetic oil. Among these, API Group III base oil or poly-α-olefin is preferred.

[0050] The 5% distillation temperature of the hydrocarbon oil in the coolant for an immersion cooling system of this embodiment is preferably 320°C or higher, more preferably 330°C or higher, and even more preferably 350°C or higher. The 5% distillation temperature of the hydrocarbon oil is preferably 600°C or lower, more preferably 550°C or lower, and even more preferably 520°C or lower.

[0051] If the 5% distillation temperature of the hydrocarbon oil is equal to or higher than the above-mentioned preferable lower limit, swelling of insulating materials in electronic devices can be further suppressed. When the 5% distillation temperature of the hydrocarbon oil is equal to or lower than the above-mentioned preferable upper limit, the fluidity of the coolant for the immersion cooling system of this embodiment is improved, circulating more easily, thereby improving cooling performance and further reducing the load on the pump that pumps the coolant in the immersion cooling system.

[0052] For example, the 5% distillation temperature of the hydrocarbon oil in the coolant for the immersion cooling system of this embodiment is preferably 320°C or higher and 600°C or lower, more preferably 330°C or higher and 550°C or lower, and even more preferably 350°C or higher and 520°C or lower.

[0053] The hydrocarbon oil in the coolant for an immersion cooling system of this embodiment preferably has a 95% hydrocarbon oil distillation temperature of 430°C or higher, more preferably 450°C or higher, and even more preferably 500°C or higher. The 95% distillation temperature of the hydrocarbon oil is preferably 800°C or lower, more preferably 750°C or lower, and even more preferably 700°C or lower.

[0054] If the 95% distillation temperature of the hydrocarbon oil is equal to or higher than the above-mentioned preferable lower limit, swelling of insulating materials in electronic devices can be further suppressed. When the 95% distillation temperature of the hydrocarbon oil is equal to or lower than the above-mentioned preferable upper limit, the fluidity of the coolant for the immersion cooling system of this embodiment is improved, circulating more easily, thereby improving cooling performance and further reducing the load on the pump that pumps the coolant in the immersion cooling system.

[0055] For example, the 95% distillation temperature of the hydrocarbon oil in the coolant for the immersion cooling system of this embodiment is preferably 430°C or higher and 800°C or lower, more preferably 450°C or higher and 750°C or lower, and even more preferably 500°C or higher and 700°C or lower.

[0056] For example, among the above, the hydrocarbon oil in the coolant for the immersion cooling system of this embodiment preferably has a 5% distillation temperature of 320°C or more and 600°C or less and a 95% distillation temperature of 430°C or more and 800°C or less, more preferably a 5% distillation temperature of 330°C or more and 550°C or less and a 95% distillation temperature of 450°C or more and 750°C or less, and even more preferably a 5% distillation temperature of 350°C or more and 550°C or less and a 95% distillation temperature of 500°C or more and 700°C or less. When the 5% distillation temperature and the 95% distillation temperature of the hydrocarbon oil in the coolant for the immersion cooling system of this embodiment are within the above-mentioned preferred ranges, the cooling performance can be improved while further suppressing swelling of the insulating material of the electronic device.

[0057] The hydrocarbon oil in the coolant for an immersion cooling system of this embodiment may be used alone or in combination of two or more types. When the coolant for an immersion cooling system of this embodiment contains two or more hydrocarbon oils, the above-mentioned "5% distillation temperature" and "95% distillation temperature" refer to values ​​measured by gas chromatographic distillation for a mixture of two or more hydrocarbon oils.

[0058] <Antioxidants> The coolant for an immersion cooling system of this embodiment contains one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants. The antioxidants may be used alone or in combination of two or more.

[0059] Amine antioxidants Examples of the amine-based antioxidant include aromatic amine-based antioxidants and hindered amine-based antioxidants. Examples of aromatic amine antioxidants include primary aromatic amine compounds such as alkylated α-naphthylamine; and secondary aromatic amine compounds such as alkylated diphenylamine, phenyl-α-naphthylamine, alkylated phenyl-α-naphthylamine, and phenyl-β-naphthylamine.

[0060] Among the above, the aromatic amine antioxidant is preferably alkylated diphenylamine, alkylated phenyl-α-naphthylamine, or a combination thereof.

[0061] Examples of the hindered amine antioxidant include compounds having a 2,2,6,6-tetraalkylpiperidine skeleton (2,2,6,6-tetraalkylpiperidine derivatives). The 2,2,6,6-tetraalkylpiperidine derivative is preferably a 2,2,6,6-tetraalkylpiperidine derivative having a substituent at the 4-position. Two 2,2,6,6-tetraalkylpiperidine skeletons may be bonded via the substituent at each 4-position. The N-position of the 2,2,6,6-tetraalkylpiperidine skeleton may be unsubstituted or may be substituted with an alkyl group having 1 to 4 carbon atoms at the N-position. The 2,2,6,6-tetraalkylpiperidine skeleton is preferably a 2,2,6,6-tetramethylpiperidine skeleton.

[0062] The substituent at the 4-position of the 2,2,6,6-tetraalkylpiperidine skeleton is an acyloxy group (R 1 COO-), alkoxy group (R 1 O-), alkylamino group (R 1 NH-), acylamino group (R 1 CONH-) and others. R 1 is preferably a hydrocarbon group having 1 to 30 carbon atoms, more preferably 1 to 24 carbon atoms, and even more preferably 1 to 20 carbon atoms. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, an alkylcycloalkyl group, an aryl group, an alkylaryl group, and an arylalkyl group.

[0063] When two 2,2,6,6-tetraalkylpiperidine skeletons are bonded via a substituent at each 4-position, the substituent may be a hydrocarbylene bis(carbonyloxy) group (-OOC-R 2 -COO-), hydrocarbylenediamino group (-HN-R 2 -NH-), hydrocarbylene bis(carbonylamino) group (-HNCO-R 2 -CONH-) etc. 2 is preferably a hydrocarbylene group having 1 to 30 carbon atoms, and more preferably an alkylene group.

[0064] The substituent at the 4-position of the 2,2,6,6-tetraalkylpiperidine skeleton is preferably an acyloxy group. Examples of compounds having an acyloxy group at the 4-position of the 2,2,6,6-tetraalkylpiperidine skeleton include esters of 2,2,6,6-tetramethyl-4-piperidinol and carboxylic acids. Examples of the carboxylic acid include linear or branched aliphatic carboxylic acids having 8 to 20 carbon atoms.

[0065] Phenolic antioxidants Phenolic antioxidants include 4,4'-methylenebis(2,6-di-tert-butylphenol); 4,4'-bis(2,6-di-tert-butylphenol); 4,4'-bis(2-methyl-6-tert-butylphenol); 2,2'-methylenebis(4-ethyl-6-tert-butylphenol); 2,2'-methylenebis(4-methyl-6-tert-butylphenol); 4,4'-butylidenebis(3-methyl-6-tert-butylphenol); 4,4'-isopropylidenebis(2,6-di-tert-butylphenol); 2,2'-methylenebis(4-methyl-6-nonylphenol); 2,2'-isobutylidenebis(4,6-dimethylphenol); 2,2'-methylenebis(4-methyl-6-cyclohexylphenol); 2,6-di-tert-butyl-4-methylphenol; 2,6 Examples of the phenol compounds include hindered phenol compounds and bisphenol compounds such as 2,4-di-tert-butyl-4-ethylphenol; 2,4-dimethyl-6-tert-butylphenol; 2,6-di-tert-butyl-4-(N,N'-dimethylaminomethyl)phenol; 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-tert-butylbenzyl)sulfide; bis(3,5-di-tert-butyl-4-hydroxybenzyl)sulfide; 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid esters; and 3-methyl-5-tert-butyl-4-hydroxyphenol fatty acid esters.

[0066] Of the above, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid esters are preferred as the phenolic antioxidant.

[0067] 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid esters include octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; decyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; dodecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; tetradecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; hexadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; pentaerythritol-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; 2,2'-thio-diethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and the like, with octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate being preferred.

[0068] <Optional ingredients> The coolant for an immersion cooling system of this embodiment may contain optional components other than the hydrocarbon oil, amine-based antioxidant, and phenol-based antioxidant described above, such as antioxidants other than the amine-based antioxidants and phenol-based antioxidants, metal deactivators, rust inhibitors, antifoaming agents, metal detergents, antiwear agents, viscosity index improvers, pour point depressants, mist inhibitors, and demulsifiers.

[0069] <Other antioxidants> Specific examples of antioxidants other than amine-based antioxidants and phenol-based antioxidants include peroxide decomposers such as sulfur-based antioxidants and sulfur-phosphorus-based antioxidants.

[0070] The content of other antioxidants is, for example, preferably 1.0% by mass or less, more preferably 0.1% by mass or less, and even more preferably no other antioxidants are contained.

[0071] ≪Metal deactivator≫ Examples of metal deactivators include benzotriazole-based compounds, tolyltriazole-based compounds, thiadiazole-based compounds, and imidazole-based compounds.

[0072] <Antifoaming agent> Examples of the antifoaming agent include silicone-based antifoaming agents.

[0073] Viscosity index improver Examples of viscosity index improvers include non-dispersant or dispersant poly(meth)acrylate viscosity index improvers, non-dispersant or dispersant olefin-(meth)acrylate copolymer viscosity index improvers, styrene-maleic anhydride copolymer viscosity index improvers, and mixtures thereof.

[0074] Pour point depressants Examples of pour point depressants include the above-mentioned polymethacrylate polymers that are compatible with hydrocarbon oils.

[0075] <Mist suppressant> Examples of mist suppressants include ethylene-propylene copolymers, polymethacrylate, polyisobutylene, polybutene, etc. The average molecular weight of these compounds as mist suppressants is usually 10,000 to 8,000,000.

[0076] The content of hydrocarbon oil in the coolant for an immersion cooling system of this embodiment is preferably 95 mass% or more, more preferably 97 mass% or more, and even more preferably 98.5 mass% or more, based on the total amount of the coolant for an immersion cooling system. The content of hydrocarbon oil is preferably 99.99 mass % or less, more preferably 99.95 mass % or less, and even more preferably 99.92 mass % or less, based on the total amount of the coolant for the immersion cooling system. For example, the content of hydrocarbon oil is preferably 95% by mass or more and 99.99% by mass or less, more preferably 97% by mass or more and 99.95% by mass or less, and even more preferably 98.5% by mass or more and 99.92% by mass or less, based on the total amount of the coolant for the immersion cooling system.

[0077] The content of one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants in the coolant for an immersion cooling system is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and even more preferably 0.08 mass% or more, relative to the total amount of the coolant for an immersion cooling system. Furthermore, the content of one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1.5% by mass or less, based on the total amount of the coolant for the immersion cooling system. For example, the content of one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.05% by mass or more and 3% by mass or less, and even more preferably 0.08% by mass or more and 1.5% by mass or less, relative to the total amount of the coolant for the immersion cooling system. When the content of one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants in the coolant for an immersion cooling system is within the above-mentioned preferred range, the thermal stability can be further improved while the influence on electronic devices is further suppressed.

[0078] The content of one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants in the coolant for an immersion cooling system is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.08 parts by mass or more, per 100 parts by mass of the hydrocarbon oil. The content of one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 1.5 parts by mass or less, per 100 parts by mass of the hydrocarbon oil. For example, the content of one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants is preferably 0.01 parts by mass or more and 5 parts by mass or less, more preferably 0.05 parts by mass or more and 3 parts by mass or less, and even more preferably 0.08 parts by mass or more and 1.5 parts by mass or less, relative to 100 parts by mass of the hydrocarbon oil.

[0079] The coolant for the immersion cooling system may contain the optional components described above. When the coolant for an immersion cooling system contains optional components, the content of the optional components is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, relative to the total amount of the coolant for an immersion cooling system.

[0080] In one embodiment, the coolant for an immersion cooling system is a coolant for an immersion cooling system consisting only of the above-mentioned hydrocarbon oil and one or more antioxidants selected from the group consisting of phenolic antioxidants and amine-based antioxidants.

[0081] The coolant for the immersion cooling system of this embodiment preferably has an acid value of 0.1 mgKOH / g or less, and more preferably 0.05 mgKOH / g or less. When the acid value of the coolant for an immersion cooling system of this embodiment is equal to or less than the above-mentioned preferable upper limit, corrosion prevention properties for metals used in electronic devices to be immersed are further improved. The acid value refers to the total acid value measured in accordance with JIS K 2501 "Petroleum products and lubricants - Test method for neutralization number." [Example]

[0082] The effects of the present invention will be described in detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0083] <Coolant formulation for immersion cooling systems> Coolants for immersion cooling systems of Examples 1 to 10 and Comparative Examples 1 to 14 were produced with the blending ratios shown in Tables 1 to 5. The values ​​in Tables 1 to 5 represent mass % based on the total amount of the coolant for the immersion cooling system.

[0084] Details of each component contained in the coolant for the immersion cooling system are as follows. <Hydrocarbon oil> (A-1): Mineral oil (40°C kinematic viscosity: 11.9 mm 2 / s, 5% distillation temperature: 329℃, 95% distillation temperature: 432℃, %C P :72.9, %C N :27.1, %C A :0) (A-2): Mineral oil (40℃ kinematic viscosity: 34.8mm 2 / s, 5% distillation temperature: 413℃, 95% distillation temperature: 528℃, %C P :84.3, %C N :15.7, %C A :0) (A-3): Mineral oil (40°C kinematic viscosity: 44.9 mm 2 / s, 5% distillation temperature: 412℃, 95% distillation temperature: 554℃, %C P :80.4, %C N :19.6, %C A :0) (A-4): Poly-α-olefin (40°C kinematic viscosity: 45.8 mm 2 / s, 5% distillation temperature: 463℃, 95% distillation temperature: 581℃, %C P :91.6, %C N :8.4, %C A :0) (A-5): Poly-α-olefin (40°C kinematic viscosity: 48.0 mm 2 / s, 5% distillation temperature: 426℃, 95% distillation temperature: 593℃, %C P :90.9, %C N :9.1, %CA :0) (A-6): ポリ-α-オレフィン (40℃ kinematic viscosity: 17.4mm 2 / s, 5% reserve temperature: 412℃, 95% reserve temperature: 487℃, %C P :91.4%,%C N :8.6,%C A :0) (A-7): Mineral oil (40℃ dynamic viscosity: 33.4mm 2 / s, 5% reserve temperature: 408℃, 95% reserve temperature: 528℃, %C P :80.4%,%C N :19.6,%C A :0) (A-8): Mineral oil (40℃ dynamic viscosity: 42.4mm 2 / s, 5% reserve temperature: 377℃, 95% reserve temperature: 511℃, %C P :67.0,%C N :27.0,%C A :6.0) (A-9): Mineral oil (40℃ dynamic viscosity: 37.8mm 2 / s, 5% reserve temperature: 377℃, 95% reserve temperature: 520℃, %C P :71.0,%C N :29.0,%C A :0) (A-10): 100% plant-derived carbonized hydrogen oil (product name "SynNova 4 Base Oils", manufactured by Novvi Co., Ltd., 40°C dynamic viscosity: 19.7mm 2 / s, 5% reserve temperature: 425℃, 95% reserve temperature: 461℃, %C P :93.1,%C N :6.9,%C A :0) (A-11): Mineral oil (40℃ dynamic viscosity: 35.1mm 2 / s, 5% reserve temperature: 424℃, 95% reserve temperature: 522℃, %C P :85.7%,%C N :14.3%,%C A :0)

[0085] (a-1): Mineral oil (40℃ dynamic viscosity: 8.7mm 2 / s, 5% reserve temperature: 271℃, 95% reserve temperature: 418℃, %C P:65.3, %C N :34.7, %C A :0) (a-2): Ester oil (a 78:22 mixture of trade names "Unistar (registered trademark) H-281R" and "Unistar (registered trademark) H-381R", both manufactured by NOF Corporation) (kinematic viscosity at 40°C: 28.6 mm 2 / s, 5% distillation temperature: 408℃, 95% distillation temperature: 615℃, %C P :31.6, %C N :68.4, %C A :0) (a-3): Mineral oil (40℃ kinematic viscosity: 54.8mm 2 / s, 5% distillation temperature: 319℃, 95% distillation temperature: 438℃, %C P :38.3, %C N :49.6, %C A :12.2) (a-4): Poly-α-olefin (40°C kinematic viscosity: 5.0 mm 2 / s, 5% distillation temperature: 308℃, 95% distillation temperature: 322℃, %C P :85.5, %C N :12.5, %C A :2)

[0086] <Antioxidants> (B-1): Phenolic antioxidant (compound name: octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (B-2): Amine antioxidant (compound name: monobutylphenyl monooctylphenylamine) (B-3): Amine antioxidant (compound name: N-dodecylphenyl-1-naphthylamine) (b-1) Sulfur-phosphorus antioxidant (compound name: zinc bis(2-ethylhexyl)dithiophosphate)

[0087] [Evaluation of impact on electronic devices] 50 mL of the coolant for the immersion cooling system of each example was poured into a 100 mL beaker, and two capacitors (AVX, SCCR20B335PRBLE) with their coatings removed and their terminals cut off were immersed. The length (mm) of the insulation of the capacitors immersed at 80°C for one week was measured to evaluate the impact (swelling) on ​​electronic devices. The average measured length and the results of evaluation based on the following criteria are shown in Tables 1 to 5. <Immersion test criteria> A: The capacitor insulation swells and stretches to a length of less than 0.29 mm. B: The length of the capacitor's insulating material that has swelled and stretched is 0.29 mm or more but less than 0.39 mm. C: The length of the capacitor insulation that has swelled and stretched is 0.39 mm or more.

[0088] [Evaluation of dynamic viscosity] Tables 1 to 5 show the kinematic viscosities of the coolants for the immersion cooling system of each example at 40°C, 80°C, and 100°C measured in accordance with JIS K2283:2000.

[0089] [Evaluation of distillation properties] Tables 1 to 5 show the 5% distillation temperature and 95% distillation temperature of the coolant for the immersion cooling system of each example, measured under the following conditions in accordance with JIS K2254:2018. <Measurement conditions> (1) When the end point (100% distillation temperature) is 600°C or higher Equipment: Shimadzu GC-2030 Column: UA-1HT (30m x 0.5mm I.D. x 0.10μm) Carrier gas: Helium 15mL / min Detector: FID Detector temperature: 400℃ Inlet temperature: PTV 40~380℃ Column temperature: 40 to 380°C (6 min) Heating rate: 10℃ / min Injection volume: 0.5 μL (carbon disulfide solution) (2) When the end point (100% distillation temperature) is less than 600°C Equipment: Shimadzu GC-2010plus Column: UA-1HT (30m x 0.5mm I.D. x 0.10μm) Carrier gas: Helium 15mL / min Detector: FID Detector temperature: 360℃ Inlet temperature: PTV 40~380℃ Column temperature: 40 to 350°C (6 min) Heating rate: 10℃ / min Injection volume: 0.5 μL (carbon disulfide solution)

[0090] [Evaluation of acid value] Tables 1 to 5 show the acid values ​​of the coolants for the immersion cooling system of each example, measured in accordance with JIS K2501:2003. From the perspective of further suppressing metal elution, a value of 0.1 or less was deemed acceptable.

[0091] [Evaluation of thermal stability] 50 mL of the coolant for the immersion cooling system of each example was added to a 100 mL beaker, and one catalyst cut to 38.5 ± 1 cm after preparation in accordance with JIS K2514-2 (section 6.2) was immersed in it. After leaving the coolant in a constant temperature bath at 100°C for one week, the acid value of the coolant was measured to evaluate its thermal stability. The results are shown in Tables 1 to 5.

[0092] [Table 1]

[0093] [Table 2]

[0094] [Table 3]

[0095] [Table 4]

[0096] [Table 5]

[0097] As shown in Tables 1 to 5, the coolants for immersion cooling systems of the Examples caused less swelling of the capacitor insulating material and had higher thermal stability than the coolants for immersion cooling systems of the Comparative Examples, and therefore maintained a low acid value for a long period of time. Therefore, it was confirmed that the influence on the electronic device in which it is immersed can be further suppressed.

[0098] 5% distillation temperature is 320℃ or higher, %C N is 30.0 or less, and the kinematic viscosity at 40°C is 11.5mm 2 The coolant for the immersion cooling system of the embodiment has a 5% distillation temperature of less than 320°C and a %C N Comparative Example 10, in which the 5% distillation temperature is less than 320°C and the kinematic viscosity at 40°C is 11.5mm 2 Compared with the coolants for immersion cooling systems of Comparative Examples 13 and 14, which had a flow rate of less than 1 / s, swelling of the insulating material of the capacitor was suppressed. Therefore, it was confirmed that the cooling liquid for the liquid immersion cooling system of the example has less influence on the electronic device in which it is immersed. The coolant for the immersion cooling system in Comparative Example 9 used ester oil instead of hydrocarbon oil, and therefore the acid value of the new oil was high, and the acid value remained high even in the deteriorated oil after thermal stabilization. Therefore, it is presumed that the coolant for an immersion cooling system of Comparative Example 9 is more likely to elute metals from electronic devices over a long period of time than the coolant for an immersion cooling system of the Examples.

[0099] The coolants for immersion cooling systems of the examples, which contained one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants, had lower acid values ​​after thermal stability tests than the coolants for immersion cooling systems of Comparative Examples 1 to 14, which did not contain one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants, and Comparative Example 15, which did not contain one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants and contained a sulfur-phosphorus-based antioxidant. Therefore, it is presumed that the coolants for immersion cooling systems of the examples will suppress metal elution from electronic devices for a long period of time, compared to the coolants for immersion cooling systems of the comparative examples. [Explanation of symbols]

[0100] 10: Immersion cooling system, 1: Immersion tank, 3: Heat exchanger, 5: Pump, 7: Cooling device

Claims

1. A coolant for an immersion cooling system, which is filled as a coolant in an immersion tank of the immersion cooling system, A hydrocarbon oil; and one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants, The coolant for the immersion cooling system contains the hydrocarbon oil in an amount of 50 mass% or more based on the total amount of the coolant for the immersion cooling system, The cooling liquid for the immersion cooling system has a 5% distillation temperature of 320°C or higher, and Ｎ is 0.5 or more and 30.0 or less, and the kinematic viscosity at 40°C is 11.5 mm ２ / s or more.

2. A coolant for an immersion cooling system, which is filled as a coolant in an immersion tank of the immersion cooling system, A hydrocarbon oil; and one or more antioxidants selected from the group consisting of amine-based antioxidants and phenol-based antioxidants, The coolant for the immersion cooling system contains the hydrocarbon oil in an amount of 50 mass% or more based on the total amount of the coolant for the immersion cooling system, The cooling liquid for the immersion cooling system has a 5% distillation temperature of 320°C or higher, and Ｎ The kinematic viscosity at 40°C is 11.5 mm ２ / s or more (provided that the density at 15°C is 0.84 g / cm ３ Below, the kinematic viscosity at 40 ° C is 20 mm ２ / s or less, flash point of 190°C or more, evaporation amount of 4.0 mg or less, and conductivity of 10 pS / m or less, excluding coolants for immersion cooling systems.

3. 3. The coolant for an immersion cooling system according to claim 1 or 2, comprising: (a) a non-conductive, non-aqueous, and water-immiscible oil component; and (b) 0.001 to 1 wt. % of a polymer additive component, measured on an oil-free basis, excluding compositions comprising one or more polyolefin polymers having a number average molecular weight of at least about 20,000 (gel permeation chromatography, polystyrene standard).

4. % C Ｎ The coolant for an immersion cooling system according to claim 2 , wherein the value of the σ is 0.5 or more and 30.0 or less.

5. Kinematic viscosity at 40°C is 25 mm ２ The coolant for an immersion cooling system according to claim 2, wherein the coolant has a viscosity of 1000 psi or more.

6. 3. The coolant for an immersion cooling system according to claim 1, wherein the hydrocarbon oil is a poly-α-olefin.

7. The coolant for an immersion cooling system according to claim 1 or 2, wherein the hydrocarbon oil is a hydrocarbon oil having carbon derived from biomass.

8. 3. The coolant for an immersion cooling system according to claim 1 or 2, which is used to fill an immersion tank of an immersion cooling system as a coolant, and which comes into direct contact with an insulating material of an electronic device including an insulating material in the immersion cooling system.

9. 3. The coolant for an immersion cooling system according to claim 1 or 2, wherein the coolant is used in an immersion cooling system, the immersion cooling system including an immersion tank filled with the coolant for an immersion cooling system and cooling an electronic device, a heat exchanger that cools the coolant for the immersion cooling system, and a pump that circulates the coolant for the immersion cooling system through the immersion tank and the heat exchanger.

10. The coolant for use in an immersion cooling system according to claim 8 or 9, wherein the electronic device is a computer server, a server motherboard, or a microprocessor.

11. The coolant for an immersion cooling system according to claim 1 or 2, wherein the antioxidant is an amine-based antioxidant.

Images