Propylene carbonate-based thermal conductive fluid

Abstract

Alkene carbonate-based anhydrous cooling fluids have low toxicity and electrical conductivity, and high heat capacity. The fluids provide corrosion protection to cooling systems and remain liquid below -30°C. Furthermore, the fluids exhibit low viscosity at low temperatures. Some formulations contain dehydrating orthoesters.

Description

[Technical Field]

[0001] Cross-reference to prior applications This application is based on U.S. Provisional Patent Application No. 63 / 521,326, filed on 15 June 2023, and claims priority and interest therein.

[0002] Support from the U.S. government Not applicable

[0003] Technical field This invention relates to thermally conductive fluids, and more specifically, to low-conductivity liquids with high heat capacity. [Background technology]

[0004] Fuel cell and / or battery systems for mobile applications, particularly for automobiles, must be able to operate even in ambient temperatures as low as approximately -40°C. Therefore, freeze protection coolant circuits are essential. Furthermore, temperatures can exceed 100°C during rapid battery charging and electric motor operation; therefore, heat released during battery charging must be removed to avoid damage to the battery and other components. Consequently, direct cooling of batteries using dielectric, low-electrical-conductivity coolants is currently being actively researched as a more efficient and safer method than indirect cooling with water (see, for example, International Publication No. 2020 / 264154). Low-conductivity dielectric coolants also enable direct cooling of electric motors and associated motor electronics.

[0005] Conventional aqueous antifreezes based on monoalkylene glycols (particularly monoethylene glycol), used in internal combustion engines and, as needed, in combination with other glycols, cannot be used as direct coolants in fuel cells, batteries, or electronic systems unless the coolant circuit is completely electrically insulated. Aqueous thermal conductive fluids have high electrical conductivity due to salts and ionizable compounds present as corrosion inhibitors in the fluid. High electrical conductivity can cause short circuits, adversely affecting the function of fuel cell and battery systems. Furthermore, in the event of an accident causing battery leakage, there is a risk of short circuits between the positive and negative electrodes and / or the generation of hydrogen gas due to electrolysis by the aqueous thermal conductive fluid. The risks of short circuits and hydrogen generation can be minimized by using low-conductivity aqueous coolants (see, for example, German Patent Application Publication No. 10063951, U.S. Patent No. 7,4196,17 and U.S. Published Patent Application No. 2013 / 0092870); however, damage to the battery cell carries the risk of dangerous hydrogen fluoride and other reaction products being generated when the aqueous coolant comes into contact with the electrolyte and lithium hexafluoride phosphate (LiPF6), a battery electrolyte frequently used as a protic coolant, reacts. This risk is further increased by the presence of moisture, for example, due to the hygroscopic nature of the coolant.

[0006] Heat removal is not only necessary for automotive fuel cells, batteries, and electronic systems, but is also a common challenge in modern server farms to prevent overheating of electronic devices. In data centers and communication systems, heat generation increases as computing power increases. While there is a strong desire for increased processing and storage density in data centers, thermal challenges remain a significant obstacle. Therefore, there is a need for efficient, low-power devices to cool server systems, thereby facilitating increased processing and storage density. The use of liquid cooling is becoming increasingly prevalent in such devices, replacing air cooling in many heat transfer processes to improve energy efficiency. Because water or water-based systems exhibit significant electrical conductivity, which can cause electrical short circuits through direct contact with electrical components or, in the case of indirect cooling, through leakage of the coolant loop, fluorinated organic liquids are typically used in such heat transfer systems. Fluorinated organic liquids are usually non-flammable, but they are not ideal due to environmental concerns such as their potential to deplete the ozone layer and contribute to global warming.

[0007] Thermally conductive fluids typically need to maintain their initial low electrical conductivity and dielectric properties over long periods, and should not exhibit an increase in conductivity due to various decomposition processes, often through ion formation by oxidation or corrosion, or water absorption over time.

[0008] Monoethylene glycol (EG) boils at 197°C under standard pressure, and therefore monoethylene glycol-containing compositions have a significant vapor pressure above approximately 170°C, limiting their use as thermal conductive fluids at high temperatures. The same applies to monopropylene glycol (PG), which has a boiling point of 188°C under standard pressure. Furthermore, PG compositions are solid or have very high viscosity at low temperatures (-30°C), limiting their use as anhydrous thermal conductive fluids. However, both glycols are used as standard coolants in internal combustion engines after being diluted with water. Propylene carbonate has been reported as a fluid substitute in aqueous (U.S. Patent No. 3,607,756) and anhydrous (German Patent Application Publication No. 102007016738, U.S. Patent No. 11,108,102) thermal conductive applications.

[0009] Recently, driving factors such as product safety, environmental impact, and the proportion of natural ingredients have become the focus of scientific research and product development. Indeed, efforts to raise awareness of environmental impact are a universal concern recognized by many government agencies. Carbon dioxide emissions have been identified as the largest contributor to greenhouse gas emissions into the atmosphere and are a cause of global warming. While biodegradability is an important element in environmental protection, the biodegradation of glycols derived from fossil fuels inevitably results in the release of carbon dioxide that has been fixed into the atmosphere. Bio-based materials (e.g., fermentation-derived) are organic materials derived from carbon sources in which carbon dioxide from the atmosphere is fixed using solar energy. Renewable glycols, in which carbon is derived from new carbon sources, can reduce carbon dioxide emissions into the atmosphere to virtually zero during biodegradation (U.S. Published Patent Application 2007 / 0200088).

[0010] When conducting heat transfer at a relatively high temperature, is it necessary to make the cooling system at a higher pressure, or is it necessary to rely on oils such as mineral oil, silicone oil, synthetic oil or fatty acid ester, or fluorinated hydrocarbons as the heat transfer fluid? The former is technically complex, and the cooling system is usually of the air-release type. In the latter cooling method, these compounds have a low heat capacity, and due to the openness of the cooling system, when water is mixed in, there is a drawback that they separate into two layers due to their low miscibility with water. Therefore, an object of the present invention is to provide a non-aqueous heat transfer fluid that can be used for electronic components.

[0011] The strategy of using organic molecules as dehydrating agents is still a relatively overlooked approach. However, organic molecules with well-understood dehydration characteristics such as orthoesters, acetals, hemiacetals, ketals and hemiketals are excellent starting points in the development and optimization of novel functional fluid dehydrating agents. Orthoesters are highly reactive due to the electron-deficient central carbon atom. The reaction between orthoester and water is irreversible, and water is either removed or pseudo-captured within the carboxylic acid ester. Orthoesters react very specifically with water. In the absence of water, orthoesters are stable base stock components. Orthoesters are catalytically hydrolyzed by Bronsted acids, ammonium salts of strong Bronsted acids or Lewis acids.

Summary of the Invention

[0012] The main requirements for the heat transfer fluid are as follows. · Non-toxic or minimally toxic · Environmentally friendly · Heat resistance up to 200 °C · Non-flammable or very high flash point · Liquid up to -30 °C or below · Low viscosity at low temperatures enabling pumpability · Corrosion resistance <​​​​The most frequently used heat transfer systems today are based on aqueous solutions of ethylene glycol or propylene glycol. Propylene glycol is preferred when toxicity is a concern. The disadvantages of currently used water-glycol-based fluids are: Due to its high water content, the material becomes highly compressed above 100°C, potentially reaching 2-4 bar above 200°C, thus requiring special material requirements and technically appropriate countermeasures. • Decomposes at high temperatures • Decomposition of glycol increases conductivity and corrosion. • Dissolves ionic species, leading to increased corrosion potential and electrical conductivity. That is the case.

[0014] Prior art has addressed these problems by using non-aqueous fluids, such as mineral oil-based fluids. While such non-aqueous thermal conductive fluids can be heated above 240°C, they often become highly viscous at low temperatures. Furthermore, mineral oil-based fluids are water pollutants and / or have high melting points. Mineral oil-based thermal conductive fluids are also not always desirable because their miscibility with water can make complete removal difficult.

[0015] Therefore, the object of the present invention is to provide novel non-aqueous heat-conducting fluids useful for fuel cells and for direct cooling of battery systems, electric motors, and electrical systems in general. These fluids can be used at relatively high temperatures, have high heat capacity, are suitable for use in open cooling systems, and exhibit compatibility with water. Ideal coolants should further exhibit low conductivity dielectric properties and maintain these properties during use. The inventors have identified four groups of compounds useful for this invention, namely components A1, A2, A3, and A4. Component A1 is an alkene carbonate and is essential to the compositions of the present invention. Component A2 enhances the effect of component A1 and is combined with the A1 compound in many preferred embodiments. Component A3 enhances certain compositions and may be included in the formulation as needed, with or without component A2. Component A4 is a dehydrating orthoester and may be included in the formulation with or without components A2 and A3. Component A4 is preferably included in the formulation when it is necessary to maintain a dry (e.g., anhydrous) state.

[0016] A1 Essential component A1 is one or more of formulas (I) [ka] (In the formula, R is hydrogen or a C1-C4 alkyl group, preferably hydrogen or methyl, most preferably methyl, and n is 1-3, most preferably 1) It is an alkylene carbonate derivative represented by [formula].

[0017] A2 The heat-conducting fluid is given by equation (II) [ka] (In the formula, R 1 R is hydrogen or C1-C4 alkyl, preferably hydrogen, methyl or ethyl, more preferably hydrogen or methyl, most preferably hydrogen, 2 (The C1-C6 alkyl group is preferably methyl, ethyl, or n-butyl, more preferably methyl or n-butyl, and most preferably methyl or n-butyl.) The A2 compound, which is a derivative represented by R, may also be included. 2 R may be an aryl group, most preferably a phenyl group. 3 R is hydrogen or methyl, and n is an arithmetic mean of 3.0 to 4.0, which represents the value resulting from the ethoxylation reaction. 2 When n is an aryl group, n is 1 to 2 by its arithmetic mean, and particularly preferably 1.

[0018] Component A2 is preferably a substantially pure compound represented by formula (II) with n=3, or a mixture of compounds represented by formula (II) with n=3 and n=4. In the compound represented by formula (II) in the mixture, n is preferably 3.0 to 3.6, particularly preferably 3.0 to 3.5, more preferably 3.05 to 3.4, extremely preferably 3.1 to 3.3, and most preferably 3.15 to 3.2 in arithmetic mean terms.

[0019] The purity of the compound represented by formula (II) with n=3 is generally 80% by weight or more, preferably 85% by weight or more, more preferably 90% by weight or more, with 95% by weight, and most preferably 97.5% by weight or more. The remainder consists mainly of compounds represented by formula (II) with n=2 and n=4. On the other hand, in the case of the compound represented by formula (II) with n=4, the purity is 50% by weight or more, preferably 55% by weight or more, more preferably 60% by weight or more. The remainder preferably consists of the compound represented by formula (II) with n=3 and, in a smaller proportion, the compound represented by formula (II) with n=5.

[0020] A preferred A2 component, which contains a substantially pure compound, Triethylene glycol monomethyl ether, • Tripropylene glycol monomethyl ether, Triethylene glycol monoethyl ether That is the case.

[0021] A preferred component A2, which includes a mixture of compounds represented by formula (II) where n=3 and n=4, · A mixture of tetraethylene glycol monomethyl ether and triethylene glycol monomethyl ether, · A mixture of tetraethylene glycol monoethyl ether and triethylene glycol monoethyl ether, and · A mixture of tetrapropylene glycol monomethyl ether and tripropylene glycol monomethyl ether is used.

[0022] Generally not necessarily preferred, but mixtures of compounds represented by formula (II) with n = 3 and n = 4 having different R 2 groups can also be used. Such mixtures are · A mixture of tetraethylene glycol monoethyl ether and triethylene glycol monomethyl ether, · A mixture of tetraethylene glycol monomethyl ether and triethylene glycol monoethyl ether is used.

[0023] Not necessarily preferred, but mixed alkylene glycol derivatives of formula (II) (where n R 3 are independently of each other, may be the same or different), for example, tri- and tetra-alkylene glycol derivatives represented by formula (II) or mixtures of ethylene oxide and propylene oxide can also be used. In the case of mixtures of compounds represented by formula (II) with n = 3 and n = 4, the weight ratio is preferably 100:0 to 40:60, more preferably 95:5 to 50:50, most preferably 90:10 to 60:40, and 85:15 to 70:30 is more preferred, and 85:15 to 75:25 is most preferred. R 2 is phenyl, R 3 are each hydrogen or methyl, and derivatives represented by formula (II) such as phenoxyethanol and phenoxypropanol with n = 1 can also be used.

[0024] U.S. Published Patent Application No. 2021 / 0403782 discloses a fuel cell coolant containing component A2, the composition containing up to 50% by weight of deionized water relative to the total aqueous mixture, and having an electrical conductivity of 50 μS / cm or less at 25°C. Conversely, congeners of component A2 with n greater than 5 and high molecular weight congeners of component A2 increase the viscosity of the composition, hindering its pumpability. High viscosity increases the power consumption of the pump, leading to increased energy consumption by the pump. Furthermore, congeners of component A2, especially those with n greater than 5, have high melting points and are at risk of precipitation at low temperatures. Conversely, congeners of component A2 with n of 1 or 2 have undesirably low boiling points, excessively reducing the viscosity of the composition. In certain applications, excessively low viscosity may be undesirable because low viscosity liquids easily penetrate seals and cause leaks. Leaks can also occur due to excessive swelling or shrinkage of rubber or polymer materials. The swelling of the polymer is controlled by selecting an A2 compound with the desired polarity. The polarity is R 1 Convert hydrogen to C1~C4, R 2 From methyl to C2~C6, and R 3 The amount decreases by changing hydrogen to methyl. Highly polar A2 compounds are R 1 is hydrogen, R 2 It is represented by methyl or hydrogen.

[0025] A3 Component A3 consists of alkylene glycol, polyalkylene oxide, polyhydric alcohol, glycerin, or a mixture of two or more of these compounds. More preferably, component A3 is selected from the group consisting of monoethylene glycol, monopropylene glycol (1,2-propanediol), 1,3-propanediol, 1,4-butanediol, glycerin, and mixtures thereof. 1,3-propanediol and 1,4-butanediol are environmentally friendly and have high boiling points. 1,3-propanediol and 1,4-butanediol can also be produced by biological pathways using genetically modified organisms. Component A3 can be selected to adjust polarity as needed, and therefore to fine-tune compatibility with rubber and elastomers.

[0026] A4 Component A4 is formula (IV) or formula (IVb) R 1 -C(OR 4 )3 formula (IV), R 1 -C(OR 4 )2-YC(OR 4 )2-R 1 Formula (IVb) (In the formula, R 1 R is hydrogen or C1-C6 alkyl, preferably hydrogen, methyl or ethyl, particularly preferably hydrogen or methyl, and most preferably methyl. 4 The following structure [ka] (Here, R 2 R is a C1-C6 alkyl group, preferably methyl, ethyl, or n-butyl, and particularly preferably methyl. 3 (The organic group is represented as follows: is hydrogen or methyl, preferably hydrogen, n is 0 to 3, and Y is -CH2-CH2-O-CH2-CH2- or -CH2-CH2-S-CH2-CH2-) Orthoester derivatives represented by formula (V) and (Vb) [ka] (In the formula, R 1 and R 3 R is independently selected from substituted or unsubstituted, branched or linear C1-C6 alkyl or alkyl ether groups, 2 and R 4 (where is independently selected from substituted or unsubstituted, linear or branched C1-C6 alkyl groups, Y is independently a substituted or unsubstituted alkyl group, y is an integer from 1 to 3, and z is an integer from 2 to 6) It consists of a cyclic orthoester represented by .

[0027] Bis(2-hydroxyethyl) sulfide and 2,2-thiodipropionic acid derivatives are industrially used, often in ester form, as synergistic secondary antioxidants in conjunction with phenolic and amine antioxidants. When Y in formula (IVb) is -CH2-CH2-S-CH2-CH2-, the dehydrating and antioxidant properties of the orthoester can be combined. This is particularly advantageous because the coexistence of moisture and oxygen can expose functional fluids to severe corrosive conditions.

[0028] R 1 and R 3 CH3-, CH3CH2-, CH3O(CH2) n -(where n is an integer from 1 to 5) may be selected. 3 It can also be a -CH2CH2- group and can function as a linker. 2 and R 4 The linker may be independently selected from -CH3, -CH2CH3, CH2CH2CH3, -CH2CH(CH3)2, and -CH2C(CH3)3. Y is the linker between the two oxygen atoms. This may be independently, for example, -CH- or -CH(CH3)-. Y may be an integer from 1 to 3. Thus, the two oxygen atoms may be linked by, for example, -CH2-, -CH2CH2-, or -CH2CH2CH2-, and Y is usually 2. Z may be an integer from 2 to 6, usually 2 or 3.

[0029] The base stocks of components A1, A2, A3, and A4 can be mixed in any ratio.

[0030] Additional additives Those skilled in the art will recognize that a good cooling fluid may require the addition of well-known additives. The suitability and compatibility of the additives with the mixture of components A1, A2, A3 and / or A4 should be confirmed. The compositions of the present invention may, if necessary, • Antioxidants, • Corrosion inhibitors, • Wear-resistant additives, • Extreme pressure additives, • Friction modifier, • Surfactants, • Dispersant, • Antifoaming agent, • Buffering agent, • Dyes, and ·emulsifier It may also contain one or more additives selected from the group consisting of the following.

[0031] Such additives are optional in any case, and the amount of each additive may be independently 0 to 5.0% by weight, preferably 0.001 to 3.5% by weight, and more preferably 0.002 to 2.5% by weight, in the composition of the present invention. In order to achieve the low electrical conductivity required by the present invention, it is preferable to remove compounds in salt (ionic) form and compounds that dissociate easily, especially acids, when selecting the components to be used. Therefore, a preferred embodiment includes using the above additional additives in substantially nonionic form under the conditions of use.

[0032] Detailed description of the invention The following description is provided to enable those skilled in the art to manufacture and use this invention and describes the best mode that the inventors have conceived for carrying out the invention. However, since the general principle of the invention is specifically defined in the specification to provide a low-conductivity thermal fluid with high heat capacity, those skilled in the art can easily conceive of various modifications.

[0033] Propylene carbonate (4-methyl-1,3-dioxolan-2-one) has the following advantageous properties, making it highly suitable as a thermal conductive fluid for fuel cells, as well as for direct cooling (immersion cooling) of batteries, electrical systems, and electric motors.

[0034] ·Non-toxic, • Environmentally friendly and biodegradable. Melting point at -48℃, • Boiling point of approximately 242°C • High flash point of 132℃, • High self-ignition temperature of 455℃, • Low viscosity at low temperatures, • Low conductivity of less than 1 μS / cm Non-corrosive, • Do not decompose at high temperatures. • Miscibility with water (240 g / L at 20°C) ·Non-hygroscopic, • Not classified as a VOC (Volatile Organic Compound), and • It must be readily available and inexpensive.

[0035] However, in the presence of acids, bases, metal oxides, or salts, propylene carbonate may decompose and release CO2. In aqueous solution, the decomposition products are propylene glycol and CO2.

[0036] Propylene carbonate is an extremely versatile reagent. It possesses the properties of a polar aprotic solvent with a high molecular dipole moment. Propylene carbonate is used as a solvent in various applications and systems, including resins, paints and paint strippers, polymers (e.g., polyacrylates, nylon), as an extraction solvent, a pharmaceutical solvent, a gas absorbent, and many other applications. Due to its high dielectric constant, propylene carbonate is used as an electrolyte in lithium batteries, forming an effective solvation shell around lithium and other alkali metal ions.

[0037] Tests have shown that propylene carbonate (PC) does not induce significant toxic effects or catabolic toxicity at concentrations up to 5000 mg / kg / day, and therefore is substantially non-toxic. Emissions from propylene carbonate do not pose a danger to workers or residents, and due to its rapid biodegradability (80% in 10 days), PC has very low aquatic toxicity and environmental impact. Propylene carbonate is not classified as a DOT hazardous material, and the National Fire Protection Association (NFPA) has a health hazard rating of 1, a flammability rating of 1, and a reactivity rating of 0. It is stable under fire exposure conditions and does not react with water (EPA / 600 / R-98 / 068: Environmental profile of propylene carbonate).

[0038] Both ethylene carbonate and propylene carbonate are prepared by carbonation of epoxide, ethylene, or propylene oxide, respectively. CHRCH2O + CO2 → RC2H3O2CO This synthesis of alkylene carbonates is particularly attractive because the production of these epoxides consumes carbon dioxide and exhibits a very appealing CO2 balance, with propylene carbonate being a good example of an environmentally friendly method (Demirel, Yasar. J. Chem. Eng. Process Technol, vol. 6, no. 3, 2015). Propylene carbonate can also be produced from urea and propylene glycol. This synthetic route allows the use of recycled propylene as a raw material, expanding the range of environmentally friendly production methods. When propylene carbonate is produced from renewable-based propylene oxide, PC may be able to achieve a negative carbon dioxide balance.

[0039] The compositions of the present invention are subject to the following provisions. The composition of the present invention contains less than 0.5% by weight of water, preferably less than 0.3%, more preferably less than 0.25%, and most preferably less than 0.20%, with less than 0.15%, and most preferably less than 0.1% by weight. • If the water content is higher, the boiling point of the composition containing component A1 is limited to approximately 150°C or lower. Therefore, the low water content of the present invention, through the combination of components A1 and A2, raises the boiling point. Even a small amount of water significantly lowers the boiling point of the composition and increases its conductivity.

[0040] The compositions of the present invention preferably have a specific heat capacity of 1.8 kJ / kg·K or more, more preferably 1.9 or more, very preferably 2.0 or more, and most preferably 2.1 kJ / kg·K or more at 50°C. The compositions of the present invention preferably have a thermal conductivity of 0.15 W / m·K or more. The specific heat capacity of propylene carbonate-based thermal conductive fluids can be increased by the addition of organic solvents. Surprisingly, it has been found that the heat capacity of propylene carbonate-based thermal conductive fluids can be increased by the addition of glycol ethers compared to propylene carbonate alone. Formulations K and M (Table III below) have higher heat capacities than ordinary aqueous thermal conductive fluids. As examples, triethylene glycol monomethyl ether (MTG), triethylene glycol mono-n-butyl ether (BTG), tripropylene glycol monomethyl ether, phenoxypropanol, and phenoxyethanol were selected.

[0041] The compositions of the present invention preferably have a boiling point of 200°C or higher, preferably 210°C or higher, more preferably 220°C or higher, and most preferably 230°C or higher at 1013.25 hPa (standard atmospheric pressure). This ensures that the composition remains liquid even at high ambient temperatures, and can function as a heat-conducting fluid without excessive increases in vapor pressure at the top of the composition. Therefore, the compositions of the present invention may be used in open systems even at high temperatures. When using orthoesters as dehydrating agents, oligomeric orthoesters represented by formulas (Ib) and (IIb) are preferred due to their high boiling points. The orthoester of RC(OR')3 is a functional group containing three alkoxy groups bonded to a carbon atom. Due to their structural similarity and polarity, orthoesters are ideal candidates for use in propylene carbonate-based functional fluids.

[0042] [Table 1]

[0043] [Table 2]

[0044] [Table 3]

[0045] The viscosity of the composition of the present invention is advantageous as it is neither too low nor too high. The kinematic viscosity at 100°C according to ASTM D445 is preferably 4 mm². 2 / s or less, more preferably 3 or less, and most preferably 2 mm 2 It is less than or equal to / s. Furthermore, the kinematic viscosity at -40°C in accordance with ASTM D445 is preferably 600 mm². 2 / s or less, preferably 500 or less, more preferably 400 or less, most preferably 350 mm 2 The viscosity is less than or equal to / s. An advantage of the composition of the present invention is that, over a wide temperature range, preferably -40°C to +100°C, it has lower viscosity than conventional coolants based on water and monoethylene glycol, and also exhibits less change in viscosity. Therefore, in the composition according to this disclosure, the change in kinematic viscosity from -40°C to +100°C is approximately 500 mm. 2 The conductivity is less than / s, and the degree of change is smaller than that of a mixture of water and monoethylene glycol. As a result, the cooling system may use a pump with low transport power, and less energy is required to transport the coolant within the cooling system. The conductivity of all formulations is less than 2 μS / cm.

[0046] In sensitive applications, water absorption can be a significant problem and potentially lead to failure. Formulations K and M were evaluated using the wet equilibrium reflux boiling point (Wet ERBP) according to FMVSS 116 section S6.2 (CFR Title 49, chapter V, part 571, standard No. 116), and their hygroscopicity was compared to that of triethylene glycol monomethyl ether (MTG). The following results indicate that the hygroscopicity of propylene carbonate formulations containing different glycol ethers is lower than that of standard polar glycol ethers. After the hygroscopicity test, both formulations K and M were single-phase mixtures. Orthoesters can react almost quantitatively with trace amounts (<0.2%) of water at room temperature, and do not require stoichiometric amounts of orthoester for complete water removal. These properties make orthoesters suitable for water removal. The oligomeric orthoesters represented by formulas (Ib) and (IIb) are preferred because they have the ability to capture a greater weight of water than high molecular weight monomer orthoesters (improving atom economy). In certain cases, a Lewis or Brønsted acid catalyst is required. The catalyst can also be provided on a solid support, such as a strongly acidic ion exchange resin (SAC).

[0047] [Table 4]

[0048] [Table 5]

[0049] Composition K was prepared and evaluated under the conditions described in ASTM D1384 (modified as described below). ASTM D1384 is a standard test method for general corrosion of various metals typical in cooling and / or heating systems of internal combustion engines. ASTM D1384 was modified to evaluate metals used in fuel cell assemblies. Such metals include stainless steel, aluminum alloys, and copper. ASTM D1384 was further modified so that test formulation K is not diluted with "corrosive water".

[0050] According to ASTM D1384, metal test specimens were immersed in a thermal conductive composition for 336 hours, maintained at 88°C with an airflow rate of 100 mL / min. The weight change of the metal test specimens was then measured. To pass ASTM D1384, the maximum acceptable weight loss is 10 mg for stainless steel and 30 mg for aluminum and copper.

[0051] The thermal conductive composition of the present invention exhibits general corrosion inhibition for aluminum, stainless steel, and copper. For example, in formulation K, the loss of stainless steel was 0.2 mg / piece, and the losses of aluminum and copper were 0.3 and 2.4 mg / piece, respectively. The physical parameters of the fluid did not change after the test. The water content after the modified ASTM corrosion test was 650 ppm.

[0052] After the completion of the modified ASTM D1384 test, the electrical resistance of formulation K was measured. The compositions of the present invention exhibit high electrical resistance even after exposure to different metal surfaces over a long test period. The electrical conductivity after testing was less than 2 μS / cm. Anhydrous thermal conductive fluids using the components disclosed in the specification have a much lower tendency to dissolve ionic species and inorganic salts compared to standard glycol / water-based thermal conductive fluids, so that the thermal conductive system retains low conductivity even when contaminated with flux during radiator manufacturing, for example, or exposed to high temperatures for a certain period. The heat resistance and ion elution of formulations K and L at ambient and high temperatures were evaluated. An aqueous monoethylene glycol solution was used as a reference substance. The heat resistance conditions were as follows: 100 mL of the solution was stored at 110°C for 3.5 days, and the electrical conductivity was measured after the test. The ion elution test was performed using a 0.1% flux solution at 25°C and 120°C, respectively. The solution was stirred at a constant temperature for 2 hours. Since pH is defined only in aqueous solutions, pH values ​​in non-aqueous solutions are not reported.

[0053] [Table 6]

[0054] The following claims are understood to include those specifically illustrated and described herein, those that are obviously replaceable, and those that encompass the essential idea of ​​the invention. Those skilled in the art will understand that various adaptations and modifications of the preferred embodiments described herein are possible without departing the scope of the invention. The embodiments described herein are for illustrative purposes only and should not be construed as limiting the invention. Therefore, it is understood that within the scope of the claims, the invention may be implemented in ways other than those specifically described herein.

Claims

1. A ready-to-use heat conductive fluid for directly cooling electrical systems, It contains component A1 and at least one of components A2 and A3, The aforementioned A1 component is one or more formulas 【Chemistry 1】 (In the formula, R is hydrogen or a C1-C4 alkyl group, and n is 1-3.) It is an alkylene carbonate derivative represented by The aforementioned A2 component is one or more equations (II) 【Chemistry 2】 (In the formula, R １ R is hydrogen or C1-C6 alkyl, ２ is C1-C6 alkyl or aryl, R ３ (where is hydrogen or methyl, and n is between 3.0 and 4.0) The derivative of the formula is an alkylene glycol ether derivative represented by , or the derivative of the formula may be phenoxyethanol and / or phenoxypropanol. The aforementioned component A3 is selected from the group consisting of monoethylene glycol, monopropylene glycol, 1,3-propanediol, 1,4-butanediol, glycerin, and mixtures thereof. A heat-conducting fluid that can be used as is.

2. Formula (IV) or formula (IVb) R １ -C(OR ４ ) ３ Formula (IV), R １ -C(OR ４ ) ２ -Y-C(OR ４ ) ２ -R １ Formula (IVb) (In the formula, R １ R is hydrogen or C1-C6 alkyl, ４ The following organic groups 【Transformation 3】 (Here, R ２ is C1-C6 alkyl, R ３ is hydrogen or methyl, and Y is -CH ２ -CH ２ -O-CH ２ -CH ２ - or -CH ２ -CH ２ -S-CH ２ -CH ２ - where n is between 0 and 3) Component A4 is an orthoester derivative represented by formula (II) and (IIb) 【Chemistry 4】 (In the formula, R １ and R ３ R is independently selected from substituted or unsubstituted, branched or linear C1-C6 alkyl or alkyl ether groups, ２ and R ４ (where is independently selected from substituted or unsubstituted, linear or branched C1-C6 alkyl groups, Y is independently a substituted or unsubstituted alkyl group, y is an integer from 1 to 3, and z is an integer from 2 to 6) The ready-to-use thermal conductive fluid according to claim 1, further comprising a cyclic orthoester represented by .

3. The ready-to-use thermal conductive fluid according to claim 1, wherein the hygroscopic properties are controlled by the addition of a nonpolar alkylene glycol ether which is a derivative represented by the formula of component A2.

4. The ready-to-use thermal conductive fluid according to claim 1, further comprising one or more additives selected from the group consisting of antioxidants, corrosion inhibitors, wear-resistant additives, extreme pressure additives, friction modifiers, surfactants, dispersants, defoamers, buffers, and dyes.

5. The ready-to-use thermal conductive fluid according to claim 1, wherein the composition has an electrical conductivity of 5 μS / cm or less at 25°C.

6. The ready-to-use thermal conductive fluid according to claim 1, wherein the boiling point of the composition at 1013 hPa is 200°C or higher.

7. The kinematic viscosity of the composition at 100°C, according to ASTM D445, is 4 mmHg. ２ A ready-to-use heat conductive fluid according to claim 1, wherein the coefficient of thermal conductivity is less than or equal to / s.

8. The kinematic viscosity of the composition at -40°C, according to ASTM D445, is 600 mmHg. ２ A ready-to-use heat conductive fluid according to claim 1, wherein the coefficient of thermal conductivity is less than or equal to / s.

9. The ready-to-use heat conductive fluid according to claim 1, wherein the specific heat capacity of the fluid at 50°C is 2.0 kJ / kg·K or more.

10. The ready-to-use thermal conductive fluid according to claim 9, wherein the specific heat capacity is increased by the addition of an alkylene glycol ether represented by formula (II).

11. A system comprising at least one heating device using the ready-to-use heat conductive fluid described in claim 1, wherein the fluid circulates within a thermal management system.

12. The system according to claim 11, wherein the heating device is selected from a fuel cell, a battery, an electrical system, an electric motor, a power control semiconductor, a circuit board, a multi-chip module, a semiconductor device, a semiconductor integrated circuit, a server, and a data center.

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