Use of monoesters and diesters as insulating coolants.

Abstract

The present invention relates to the use of a combination consisting essentially of a monoalcohol fatty acid ester and a diester as a liquid insulating coolant.

Description

[Technical field]

[0001] The present invention relates to the use of a composition comprising a combination of a monoester and a diester as a liquid insulating coolant.

[0002] Liquid insulating coolants are non-conductive liquids used to reduce the temperature of and insulate electrical devices. This type of coolant is suitable for direct immersion cooling of electrical devices, in which the electrical devices are in direct contact with the liquid insulating coolant. [Background technology]

[0003] Immersion cooling is an efficient way to reduce temperatures because the thermal conductivity of liquids is higher than that of air, the traditional cooling method.

[0004] A variety of compounds exist, among which several esters have been described.

[0005] WO2020252235 discloses the use of an insulating oil-based heat transfer fluid for cooling electrical components. The insulating oil-based heat transfer fluid can be a certain type of isoparaffin, ester oil or ether oil. Esters suitable for use as the insulating oil-based heat transfer fluid include, in particular, esters of monocarboxylic acids and monohydric alcohols; diesters of diols and monocarboxylic acids and diesters of dicarboxylic acids and monohydric alcohols; polyol esters of monocarboxylic acids and polyesters of monohydric alcohols and polycarboxylic acids; and mixtures thereof.

[0006] WO2020182718 discloses the use of at least one ester for cooling the drive system of an electric or hybrid vehicle. The ester according to the invention is advantageously a monoester, a diester or a triester. Preferably, the ester is a monoester or a diester. The monoester is preferably obtained from a carboxylic acid which at least comprises a hydrocarbon chain having 3 to 14 carbon atoms. The diester is formed between a dicarboxylic acid having a linear, saturated or unsaturated hydrocarbon chain, preferably a dicarboxylic acid having a linear, saturated or unsaturated hydrocarbon chain having 3 to 14 carbon atoms, and a monohydric alcohol having a linear or branched, saturated or unsaturated hydrocarbon chain, preferably a monohydric alcohol having a linear or branched, saturated or unsaturated hydrocarbon chain, interrupted by at least one heteroatom, preferably an oxygen atom, having 2 to 14 carbon atoms.

[0007] However, a need remains for liquid insulating coolants having improved material compatibility properties.

[0008] Indeed, since the liquid insulating coolant is in direct contact with the material(s) constituting the electrical equipment and possibly with other material(s) in the cooling system, it must exhibit good compatibility with the material(s) present on, in and / or around the electrical equipment.

[0009] "Material compatibility with insulating coolant" means that after immersion of the material in the insulating coolant at 80°C for 168 hours, preferably according to the method described in Example 2, the material exhibits a volume change of 20% or less, preferably 15% or less, more preferably 10% or less.

[0010] By "submerged the material in the insulating coolant" it is meant that the entire material is surrounded by the insulating coolant.

[0011] This volume change indicates the potential for swelling or shrinkage of the material and thus chemical interactions between the material and the insulating coolant. Summary of the Invention [Problem to be solved by the invention]

[0012] The need to control heat as new, high-performance batteries and power electronics are developed necessitates more efficient cooling systems, including liquid insulating coolants that are compatible with the materials that make up these batteries and power electronics.

[0013] Therefore, there remains a need for new liquid insulating coolants for managing the temperature of electrical devices, particularly in the field of electric vehicles and information appliances, such as servers, which exhibit, together with good material compatibility, one or more, preferably all of the following properties: - Dielectric breakdown of at least 30 kV, measured according to standard ASTM D877; - Electrical resistivity of at least 200 MΩ·m at 20 °C, measured according to standard ASTM 1169; - Thermal conductivity of at least 0.1300 W / (m·°C) at 20°C, measured according to standard ASTM 7896; - 10mm at 40°C, measured according to standard ASTM D445 2 Kinematic viscosity less than / s; - 3mm at 100°C, measured according to standard ASTM D445 2 Kinematic viscosity less than / s; - At most 950 kg / m at 20°C, measured according to standard ASTM 7042 3 density; - a flash point of at least 130 ° C, measured according to standard ASTM D92; - low pour point of at most -30 °C, measured according to standard ASTM D97; - Oxidative stability of at least 600 minutes, measured according to standard ASTM D 2272. [Means for solving the problem]

[0014] The present inventors have surprisingly found that certain combinations of monoesters and diesters not only exhibit one or more of the above properties, but also exhibit good materials compatibility.

[0015] Accordingly, the present invention relates to the use of a combination consisting essentially of a monoalcohol fatty acid ester and a diester as a liquid insulating coolant, wherein the monoalcohol fatty acid ester / diester mass ratio is between 15 / 85 and 55 / 45. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] In this patent application, the term "consisting essentially of" is intended to include, inter alia, the impurity(s) of the compound under consideration, the presence of which is indicated by a purity of the compound under consideration of less than 100%.

[0017] In this application, all value ranges used should be understood to be inclusive of the upper and lower limits, unless otherwise stated.

[0018] A combination essentially consisting of a monoalcohol fatty acid ester and a diester, with a monoalcohol fatty acid ester / diester mass ratio of 15 / 85 to 55 / 45, exhibits low electrical conductivity, good thermal conductivity, and low viscosity, which make the combination suitable for use as an insulating coolant. In particular, this combination exhibits all the above-mentioned properties.

[0019] Moreover, the combination has the advantage that it also has good material compatibility.

[0020] Preferably, the material is selected from the group consisting of copper; sealants; coatings, such as epoxies; polymers, especially thermoplastic polymers, such as polyvinyl chloride (PVC), polycarbonate (PC) and polylactic acid (PLA), or thermosetting polymers, such as polyurethane and polyimide.

[0021] More preferably, the material is selected from the group consisting of polymers, even more preferably from the group consisting of thermoplastic polymers, in particular the material is VC, PLA and / or PC.

[0022] Monoalcohol fatty acid esters are monoesters resulting from the esterification of a monoalcohol with a fatty acid.

[0023] A monoalcohol is a hydrocarbon chain that contains only one hydroxyl functional group.

[0024] Preferably, the monoalcohol contains from 4 to 18 carbon atoms, more preferably from 5 to 8 carbon atoms.

[0025] Diesters result from the esterification of a diol with a fatty acid or from the esterification of a monoalcohol with a dicarboxylic acid.

[0026] A diol is a hydrocarbon chain that contains two hydroxyl functional groups.

[0027] Preferably, the diol contains 3 to 18 carbon atoms, more preferably 3 to 8 carbon atoms.

[0028] Preferably, the dicarboxylic acid contains from 4 to 12 carbon atoms, more preferably from 6 to 10 carbon atoms.

[0029] Preferably, the fatty acid of the monoalcohol fatty acid ester and the fatty acid of the diester each independently contain from 6 to 22 carbon atoms, more preferably from 8 to 18 carbon atoms.

[0030] Preferably, the fatty acid of the monoalcohol fatty acid ester and the fatty acid of the diester are different.

[0031] In particular, the fatty acid of the monoalcohol fatty acid ester contains 12 to 18 carbon atoms.

[0032] In particular, the fatty acids of the diesters contain 8 to 10 carbon atoms.

[0033] Preferably, the diester contains from 16 to 28 carbon atoms, more preferably from 19 to 26 carbon atoms.

[0034] Preferably, the monoalcohol fatty acid ester contains from 16 to 26 carbon atoms, more preferably from 17 to 23 carbon atoms.

[0035] Advantageously, in the use according to the invention, - monoalcohol fatty acid esters are obtained from the esterification of monoalcohols containing 5 to 8 carbon atoms with fatty acids containing 12 to 18 carbon atoms; - Diesters are obtained from the esterification of diols with fatty acids or of monoalcohols with dicarboxylic acids, the diesters containing from 19 to 26 carbon atoms.

[0036] Advantageously, in the use according to the invention, the monoalcohol is selected from the group consisting of isoamyl alcohol and 2-ethylhexyl alcohol; the fatty acids are selected from the group consisting of caprylic acid, capric acid, lauric acid, isostearic acid, and mixtures thereof;

[0037] Advantageously, in the use according to the invention, the diol is propylene glycol.

[0038] Advantageously, in the use according to the invention, the dicarboxylic acid is sebacic acid.

[0039] Advantageously, in the use according to the invention, the monoalcohol fatty acid ester is selected from the group consisting of isoamyl isostearate, isoamyl laurate and 2-ethylhexyl laurate.

[0040] Advantageously, in the use according to the invention, the diester is selected from the group consisting of propylene glycol di-caprate / caprylate and di-2-ethylhexyl sebacate.

[0041] Advantageously, in the use according to the invention, said combination consists essentially of: - Isoamyl isostearate and propylene glycol di-caprate / caprylate; - Isoamyl laurate and propylene glycol dicaprate / caprylate; or - 2-Ethylhexyl Laurate and Di-2-Ethylhexyl Sebacate.

[0042] Advantageously, in the use according to the invention, the monoalcohol fatty acid ester / diester weight ratio is between 20 / 80 and 55 / 45.

[0043] Preferably, the mass ratio of monoalcohol fatty acid ester / diester is 20 / 80 to 50 / 50.

[0044] The present invention also relates to a combination consisting essentially of a monoalcohol fatty acid ester and a diester, wherein the weight ratio of the monoalcohol fatty acid ester / diester is 15 / 85 to 55 / 45, and the combination of the monoalcohol fatty acid ester and the diester is as follows: - Isoamyl Isostearate and Propylene Glycol Di-Caprate / Caprylate, - Isoamyl laurate and propylene glycol dicaprate / caprylate, or - 2-Ethylhexyl Laurate and Di-2-Ethylhexyl Sebacate.

[0045] The mass ratio of monoalcohol fatty acid ester / diester is preferably 20 / 80 to 55 / 45, and more preferably 20 / 80 to 50 / 50.

[0046] The combination according to the invention shows particularly good compatibility with materials, especially PVC, PC and PLA, as shown in Example 2.

[0047] The present invention also relates to a composition comprising a combination according to the invention and an antioxidant and / or a metal deactivator.

[0048] Preferably, the amount of said combination is at least 75% by weight, more preferably at least 80% by weight, based on the weight of the composition.

[0049] Preferably, the amount of antioxidant is at least 0.05% by weight, more preferably at least 0.1% by weight, based on the weight of the composition.

[0050] Preferably, the amount of antioxidant is at most 1.5% by weight, more preferably at most 1% by weight, based on the weight of the composition.

[0051] Preferably, the antioxidant is a phenolic antioxidant.

[0052] Preferably, the amount of metal deactivator is at least 10 ppm, more preferably at least 20 ppm, based on the weight of the composition.

[0053] Preferably, the amount of metal deactivator is at most 500 ppm, more preferably at most 250 ppm, based on the weight of the composition.

[0054] The composition may further comprise additives used in the field of lubricating oils.

[0055] A person skilled in the art knows how to select the most suitable additives depending on the application, for example, the following manuals can be referred to: "Fuels and Lubricants Handbook: technology, properties performance and testing" by George E. Totten, 2003, and "Handbook of lubrification and tribology, vol II: Theory and Design" by Robert W. Bruce, 2012.

[0056] The additive(s) used in the field of lubricating oils are preferably selected from the group consisting of friction reducers, antiwear agents and thickeners.

[0057] The total amount of additive(s) is preferably at most 25% by weight, more preferably at most 20% by weight, based on the total weight of the composition.

[0058] "Total amount of additive(s)" is intended to mean the amount of all additives present in the composition, including additive(s) used in the art of lubricants, antioxidants and metal deactivators.

[0059] The present invention also relates to the use of the composition according to the invention as a liquid insulating coolant.

[0060] The present invention also relates to a method for cooling an electrical device by contacting the electrical device with a combination consisting essentially of a monoalcohol fatty acid ester and a diester, the monoalcohol fatty acid ester / diester weight ratio being between 15 / 85 and 55 / 45, or with a composition according to the present invention.

[0061] The combination, the monoalcohol fatty acid ester, and the diester are as described above, including optional and advantageous features.

[0062] Preferably, the method for cooling an electrical device is carried out with respect to the material(s) in contact with the combination or composition according to the invention with a limited change in volume of the material, in particular a change in volume of not more than 20%, preferably 15%, more preferably 10%.

[0063] The materials are as described above, including their optional and advantageous features.

[0064] Preferably, the electrical device - Server; - a battery, in particular a lithium-ion or lithium-polymer battery; - Electric or hybrid vehicle drive systems, in particular the power electronics, the electric motor, the transmission and / or the battery.

[0065] Contact between the electrical device and the combination is preferably made by total or partial immersion, or by spraying.

[0066] Advantageously, in the method according to the invention, said combination is a combination according to the invention.

[0067] The present invention is further described in the following examples, it being understood that the invention as claimed is in no way intended to be limited by these examples. EXAMPLES

[0068] Example 1: Preparation of a combination according to the invention 1.1. Chemicals Used - Monoesters: Isoamyl isostearate: prepared by esterification of isostearic acid with excess isoamyl alcohol in the presence of an acid catalyst at 160°C until the acid number reached a maximum of 0.1. The excess alcohol was distilled, the catalyst was neutralized and the product was filtered over Dicalite 478. ○ Isoamyl laurate: Jolee 7750 from Oleon; 2-Ethylhexyl laurate: Radia 7127 from Oleon; - Diester: ○ Propylene glycol di-caprate / caprylate (MPG): Radia 7208 from Oleon; Di-2-ethylhexyl sebacate: Radia 7543 from Oleon.

[0069] 1.2. Method The mono- and di-esters were mixed at 25° C. according to the chemicals and amounts set out in Table 1 below.

[0070] [Table 1]

[0071] 1.3. Characteristics of the Combination According to the Invention For each combination, the following properties were measured: - Thermal conductivity, according to standard ASTM 7896; - Kinematic viscosity at 40°C and 100°C according to standard ASTM D445; - Density at 20°C, according to standard ASTM 7042. The results are shown in Table 2 below:

[0072] [Table 2]

[0073] All combinations according to the present invention have a thermal conductivity of at least 0.1300 W / (m·°C) and a thermal conductivity of 10 mm at 40°C. 2 / s, 3mm at 100℃ 2 / s and 950 kg / m at 20°C 3 It shows a density of less than 0.01.

[0074] Example 2: Material compatibility of the combination according to the invention Material compatibility was evaluated by the volume change of the combined material samples after exposure.

[0075] 2.1.Materials - Polyvinyl chloride (PVC): H03VVH2-F Black from Nexans; - Polylactic acid (PLA): Luminy® L130 from Total Corbion; - Polycarbonate (PC): Palsun Clear Polycarbonate UVP 1mm Thick from Palram.

[0076] 2.2. Method Materials selected from three PVC wires, ten PLA granules, and three pieces of PC (Palsun clear polycarbonate UVP 1 mm thick) were placed in a beaker and weighed in air (mass air t0h) and in water (mass water t0h). The material was then submerged in a combination according to the invention and the beaker was placed in an oven at 80° C. for 168 hours. Once the material was dried, it was weighed in air (mass air t168h) and in water (mass water t168h). The volume change was then calculated using the following formula: (volume t168h - volume t0h) / volume t0h] x 100 Volume = mass / density; The density is a constant and is calculated as follows: Density = [(mass of air t168h - mass of water t168h) - (mass of air t0h - Mass water t0h)] / (mass air t0h - mass water t0h) This procedure was performed three times and the average volume changes are shown in Table 3 below.

[0077] 2.3.Results

[0078] [Table 3]

[0079] When PVC, PLA or PC are immersed in the combinations C1 to C6 according to the invention, all volume changes of less than 10% are observed.

[0080] Example 3: Comparative study of material compatibility of several esters Instead of the combination according to the invention, different monoesters and diesters were evaluated for their compatibility with PVC according to the method described in Example 2.2: - Isoamyl laurate: Jolee 7750 from Oleon; - Di-2-ethylhexyl sebacate: Radia 7543 from Oleon; - 2-ethylhexyl adipate: obtained by esterification of 2-ethylhexanol with adipic acid; - Neopentyl glycol diheptanoate (NPG): obtained by esterification of neopentyl glycol with heptanoic acid. The results are summarized in Table 4 below.

[0081] [Table 4]

[0082] When various mono- and diesters are used alone, volume changes of over 20% after immersion in PVC are observed.

Claims

1. 1. Use of a combination consisting essentially of a monoalcohol fatty acid ester and a diester as a liquid insulating coolant, the combination having a monoalcohol fatty acid ester / diester mass ratio of 15 / 85 to 55 / 45.

2. the monoalcohol fatty acid ester results from the esterification of a monoalcohol containing from 5 to 8 carbon atoms with a fatty acid containing from 12 to 18 carbon atoms, Use according to claim 1, wherein said diester is obtained from the esterification of a diol with a fatty acid or of a monoalcohol with a dicarboxylic acid, said diester containing from 19 to 26 carbon atoms.

3. said monoalcohol is selected from the group consisting of isoamyl alcohol and 2-ethylhexyl alcohol; Use according to claim 1 or 2, wherein the fatty acid is selected from the group consisting of caprylic acid, capric acid, lauric acid, isostearic acid, and mixtures thereof.

4. The use according to any one of claims 1 to 3, wherein the diol is propylene glycol.

5. The use according to any one of claims 1 to 3, wherein the dicarboxylic acid is sebacic acid.

6. The use according to any one of claims 1 to 5, wherein the monoalcohol fatty acid ester is selected from the group consisting of isoamyl isostearate, isoamyl laurate and 2-ethylhexyl laurate.

7. The use according to any one of claims 1 to 6, wherein the diester is selected from the group consisting of propylene glycol di-caprate / caprylate and di-2-ethylhexyl sebacate.

8. The use according to any one of claims 1 to 7, wherein the combination consists essentially of: - isoamyl isostearate and propylene glycol dicaprate / caprylate; - isoamyl laurate and propylene glycol dicaprate / caprylate; or - 2-ethylhexyl laurate and di-2-ethylhexyl sebacate.

9. The use according to any one of claims 1 to 8, wherein the monoalcohol fatty acid ester / diester mass ratio is from 20 / 80 to 55 / 45.

10. A combination consisting essentially of a monoalcohol fatty acid ester and a diester, The monoalcohol fatty acid ester / diester mass ratio is 15 / 85 to 55 / 45, and the combination of the monoalcohol fatty acid ester and the diester is - isoamyl isostearate and propylene glycol dicaprate / caprylate, - Isoamyl laurate and propylene glycol dicaprate / caprylate, or 2-ethylhexyl laurate and di-2-ethylhexyl sebacate, That is the combination.

11. A composition comprising the combination of claim 10 and an antioxidant and / or a metal deactivator.

12. Use of the composition according to claim 11 as a liquid insulating coolant.

13. 12. A method of cooling an electrical device by contacting the electrical device with a combination consisting essentially of a monoalcohol fatty acid ester and a diester, the monoalcohol fatty acid ester / diester weight ratio being from 15 / 85 to 55 / 45, or with the composition of claim 11.

14. The method of claim 13, wherein the combination is the combination of claim 10.

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