Use of a monoester and a diester as a dielectric coolant

Abstract

This invention relates to the use of a combination of monohydric alcohol fatty acid esters and diesters as a liquid dielectric coolant.

Description

[0001] This invention relates to the use of compositions comprising a combination of monoesters and diesters as liquid dielectric coolants.

[0002] Liquid dielectric coolants are non-conductive liquids used to lower the temperature of electrical equipment and insulate it. This type of coolant is suitable for direct immersion cooling of electrical equipment. In this method, the electrical equipment is in direct contact with the liquid dielectric coolant.

[0003] Because liquids have a higher thermal conductivity than air, immersion cooling is an effective way to reduce temperature, and it is a traditional cooling method.

[0004] Different compounds exist, some of which are esters.

[0005] WO 2020252235 discloses the use of dielectric oil-based heat transfer fluids for cooling portions of electrical components. Dielectric oil-based heat transfer fluids can be isoparaffins, ester oils, or ether oils. Suitable esters for use as dielectric oil-based heat transfer fluids 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] WO 2020182718 discloses the use of at least one ester for cooling the drive system of electric or hybrid vehicles. The ester according to the invention is advantageously a monoester, diester, or triester. Preferably, it is a monoester or diester. Monoesters are preferably obtained from carboxylic acids comprising a hydrocarbon chain of at least 3 to 14 carbon atoms. Diesters are formed between a dicarboxylic acid having a straight-chain, saturated or unsaturated hydrocarbon chain (preferably 3 to 14 carbon atoms) and a monohydric alcohol having a straight-chain or branched, saturated or unsaturated hydrocarbon chain (preferably 2 to 14 atoms) and intercalated with at least one heteroatom (preferably an oxygen atom).

[0007] However, there is still a need for a liquid dielectric coolant with improved material compatibility properties.

[0008] In practice, liquid dielectric coolants come into direct contact with the materials constituting electrical equipment and, possibly, other materials within the cooling system. Therefore, liquid dielectric coolants need to exhibit good compatibility with the materials present on and / or around the electrical equipment.

[0009] "Material compatibility of dielectric coolant" means that after immersing a material in a dielectric coolant at 80°C for 168 hours, the material exhibits a volume change of no more than 20%, preferably no more than 15%, more preferably no more than 10%, preferably according to the method described in Example 2.

[0010] "Immersing the material in a dielectric coolant" means that the entire material is surrounded by the dielectric coolant.

[0011] This volume change indicates the possible swelling or contraction of the material, and thus the chemical interaction between the material and the dielectric coolant.

[0012] With the development of new high-performance batteries and power electronic devices, the heat that needs to be controlled requires more efficient cooling systems, such as liquid dielectric coolants that are compatible with the materials that make up those batteries and power electronic devices.

[0013] Therefore, a new liquid dielectric coolant is still needed to manage the temperature in electrical equipment, particularly electric vehicles and information technology devices (such as servers), which will exhibit one or more, and preferably all, of the following characteristics:

[0014] - Dielectric breakdown of at least 30kV as measured according to standard ASTM D877;

[0015] - Resistivity of at least 200 MΩ·m at 20°C, as measured according to standard ASTM 1169;

[0016] - Thermal conductivity of at least 0.1300 W / (m·℃) at 20°C, as measured according to standard ASTM 7896;

[0017] -Measured according to standard ASTM D445 at 40°C, less than 10mm 2 kinematic viscosity per second;

[0018] -Measured according to standard ASTM D445 at 100°C, less than 3mm 2 kinematic viscosity per second;

[0019] -Measured according to standard ASTM 7042 at 20°C, up to 950 kg / m³ 3 The density;

[0020] - A flash point of at least 130°C as measured according to standard ASTM D92;

[0021] - Low pour point of up to -30°C as measured according to standard ASTM D97;

[0022] - Oxidative stability for at least 600 minutes as measured according to standard ASTM D 2272;

[0023] as well as:

[0024] - Good material compatibility.

[0025] The inventors unexpectedly discovered that specific combinations of monoesters and diesters not only exhibit one or more of the aforementioned characteristics, but also demonstrate good compatibility with materials.

[0026] Therefore, the present invention relates to the use of a combination of monohydric fatty acid esters and diesters, which are essentially monohydric fatty acid esters and diesters, as a liquid dielectric coolant; wherein the weight ratio of monohydric fatty acid esters / diesters is between 15 / 85 and 55 / 45.

[0027] In this patent application, the term "consistently of..." is considered to specifically include impurities in the compound under consideration. The presence of impurities is indicated by the purity of the compound of interest being less than 100%.

[0028] In this application, unless otherwise stated, all ranges of values ​​used should be understood to include limit values.

[0029] The combination, essentially composed of monohydric alcohol fatty acid esters and diesters (with a weight ratio of monohydric alcohol fatty acid ester / diester ranging from 15 / 85 to 55 / 45), exhibits low electrical conductivity, good thermal conductivity, and low viscosity, making it suitable for use as a dielectric coolant. In particular, this combination displays all the characteristics previously listed.

[0030] In addition, this combination has the advantage of good material compatibility.

[0031] Preferably, the material is selected from the group consisting of: copper; seals; coatings, such as epoxy resins; polymers, particularly thermoplastic polymers such as polyvinyl chloride (PVC), polycarbonate (PC) and polylactic acid (PLA), or thermosetting polymers such as polyurethane and polyimide.

[0032] More preferably, the material is selected from the group consisting of polymers, and even more preferably from the group consisting of thermoplastic polymers. In particular, the material is PVC, PLA, and / or PC.

[0033] Monohydric alcohol fatty acid esters are monoesters obtained by esterification of monohydric alcohols and fatty acids.

[0034] A monohydric alcohol is a hydrocarbon chain containing only one hydroxyl functional group.

[0035] Preferably, the monohydric alcohol contains between 4 and 18 carbon atoms, more preferably between 5 and 8 carbon atoms.

[0036] This diester can be obtained by esterification of a diol with a fatty acid or by esterification of a monohydric alcohol with a dicarboxylic acid.

[0037] Diols are hydrocarbon chains containing two hydroxyl functional groups.

[0038] Preferably, the diol contains between 3 and 18 carbon atoms, more preferably between 3 and 8 carbon atoms.

[0039] Preferably, the dicarboxylic acid contains between 4 and 12 carbon atoms, more preferably between 6 and 10 carbon atoms.

[0040] Preferably, the fatty acids in the monohydric alcohol fatty acid ester and diester each and independently comprise between 6 and 22 carbon atoms, more preferably between 8 and 18 carbon atoms.

[0041] Preferably, the fatty acids in the monohydric alcohol fatty acid ester and the diester are different.

[0042] In particular, the fatty acids in monohydric alcohol fatty acid esters contain between 12 and 18 carbon atoms.

[0043] In particular, the fatty acids in diesters contain between 8 and 10 carbon atoms.

[0044] Preferably, the diester contains between 16 and 28 carbon atoms, more preferably between 19 and 26 carbon atoms.

[0045] Preferably, the monohydric alcohol fatty acid ester contains between 16 and 26 carbon atoms, more preferably between 17 and 23 carbon atoms.

[0046] Advantageously, in the application according to the invention:

[0047] - Monohydric alcohol fatty acid esters can be obtained by esterification of a monohydric alcohol containing between 5 and 8 carbon atoms with a fatty acid containing between 12 and 18 carbon atoms;

[0048] - Diesters can be obtained by esterification of diols with fatty acids or by esterification of monohydric alcohols with dicarboxylic acids; diesters contain between 19 and 26 carbon atoms.

[0049] Advantageously, in the application according to the invention:

[0050] - The monohydric alcohol is selected from the group consisting of isoamyl alcohol and 2-ethylhexanol; and

[0051] - The fatty acids selected are from the group consisting of caprylic acid, capric acid, lauric acid, isostearic acid and mixtures thereof.

[0052] Advantageously, in the use according to the invention, the diol is propylene glycol.

[0053] Advantageously, in the use according to the invention, the dicarboxylic acid is sebacic acid.

[0054] Advantageously, in the use according to the invention, the monohydric alcohol fatty acid ester is selected from the group consisting of isoamyl isostearate, isoamyl laurate and 2-ethylhexyl laurate.

[0055] Advantageously, in the use according to the invention, the diester is selected from the group consisting of propylene glycol didecanoate / octanoate and di-2-ethylhexyl sebacate.

[0056] Advantageously, in its application according to the invention, the combination essentially consists of the following:

[0057] -Isoamyl isostearate and propylene glycol didecanoate / octanoate;

[0058] -Isoamyl laurate and propylene glycol didecanoate / octanoate; or

[0059] - 2-Ethylhexyl laurate and di-2-ethylhexyl sebacate.

[0060] Advantageously, in the application according to the invention, the weight ratio of monohydric fatty acid ester / dieserene is included between 20 / 80 and 55 / 45.

[0061] Preferably, the weight ratio of monohydric fatty acid ester / dieser is between 20 / 80 and 50 / 50.

[0062] The present invention also relates to a combination consisting essentially of a monohydric alcohol fatty acid ester and a diester, wherein the weight ratio of the monohydric alcohol fatty acid ester / diester is between 15 / 85 and 55 / 45; and wherein the combination of the monohydric alcohol fatty acid ester and the diester is:

[0063] -Isoamyl isostearate and propylene glycol didecanoate / octanoate

[0064] -Isoamyl laurate and propylene glycol didecanoate / octanoate, or

[0065] - 2-Ethylhexyl laurate and di-2-ethylhexyl sebacate.

[0066] Preferably, the weight ratio of monohydric fatty acid ester / dieser is between 20 / 80 and 55 / 45, more preferably between 20 / 80 and 50 / 50.

[0067] The combination according to the invention exhibits particularly good compatibility with materials, especially with PVC, PC and PLA, as shown in Example 2.

[0068] The present invention also relates to a composition comprising, according to the invention, an antioxidant and / or a metal deactivator.

[0069] Preferably, the amount of the composition is at least 75% by weight, more preferably at least 80% by weight, based on the weight of the composition.

[0070] 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.

[0071] 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.

[0072] Preferably, the antioxidant is a phenolic antioxidant.

[0073] Preferably, the amount of the metal deactivator is at least 10 ppm, more preferably at least 20 ppm, based on the weight of the composition.

[0074] Preferably, the amount of the metal deactivator is up to 500 ppm, more preferably up to 250 ppm, based on the weight of the composition.

[0075] This composition can be further incorporated into additives used in the field of lubricants.

[0076] Those skilled in the art know how to select the most suitable additive for the application. For example, one can refer to the following manuals: "Fuels and Lubricants Handbook: technology, properties, performance and testing" (George E. Totten, 2003) and "Handbook of lubrication and tribology, vol II: Theory and Design" (Robert W. Bruce, 2012).

[0077] Additives used in the field of lubricants are preferably selected from the group consisting of: friction reducers; anti-wear agents; and thickeners.

[0078] Based on the total weight of the composition, the total amount of additives is preferably up to 25% by weight, more preferably up to 20%.

[0079] "Total amount of additives" is intended to refer to the amount of all additives present in the composition, including additives used in the field of lubricants, antioxidants and metal deactivators.

[0080] The present invention also relates to the use of the compositions according to the invention as liquid dielectric coolants.

[0081] The present invention relates to a method for cooling an electrical device by contacting it with a combination consisting essentially of a monohydric fatty acid ester and a diester, or with a composition according to the invention, wherein the weight ratio of the monohydric fatty acid ester / diester is between 15 / 85 and 55 / 45.

[0082] The combination, namely monohydric alcohol fatty acid esters and diesters, is as described above, including preferred and advantageous features.

[0083] Preferably, the method for cooling electrical equipment is carried out relative to the material in contact with the combination or composition according to the invention, for example, where the volume change of the material is limited, particularly where the volume change does not exceed 20%, preferably 15%, more preferably 10%.

[0084] The material is as described above, including preferred and advantageous features.

[0085] Preferably, the electrical equipment is:

[0086] -server;

[0087] - Batteries, especially lithium-ion or lithium polymer batteries;

[0088] - The drive system of electric or hybrid vehicles, particularly power electronics, electric motors, transmissions, and / or batteries.

[0089] Contact between electrical equipment and assembly is preferably made by full or partial immersion or by spraying.

[0090] Advantageously, in the method according to the invention, the combination is a combination according to the invention.

[0091] The invention is further described in the following examples. It should be understood that the claimed invention is not intended to be limited in any way to these examples.

[0092] Example 1: Preparation of the combination according to the present invention

[0093] 1.1. Chemicals used

[0094] - Monoester:

[0095] Isoamyl isostearate: Prepared by esterifying isostearic acid with excess isoamyl alcohol at 160 °C in the presence of an acid catalyst until the acid value is at most 0.1. The excess alcohol is distilled off, the catalyst is neutralized, and the product is filtered through a Dicalite 478 filter.

[0096] Isoamyl laurate: Jolee 7750 from Oleon;

[0097] ο Ethylhexyl laurate: Radia 7127 from Euronext;

[0098] - Diester:

[0099] οPropylene glycol (MPG) didecanoate / caprylate: Radia 7208 from Orion;

[0100] ο Di-2-ethylhexyl sebacate: Radia 7543 from Euronext.

[0101] 1.2. method

[0102] Based on the chemicals and amounts described in Table 1 below, the monoester and diester were mixed together at 25°C.

[0103] Monoester Diester C1 20wt% Isoamyl isostearate 80wt% MPG didecanoate / octanoate C2 25wt% Isoamyl isostearate 75wt% MPG didecanoate / octanoate C3 25wt% Isoamyl Laurate 75wt% MPG didecanoate / octanoate C4 50wt% Isoamyl Laurate 50wt% MPG didecanoate / octanoate C5 30wt% 2-Ethylhexyl Laurate 70wt% di-2-ethylhexyl sebacate C6 50wt% 2-Ethylhexyl Laurate 50wt% di-2-ethylhexyl sebacate

[0104] Table 1 Combination of monoesters and diesters

[0105] 1.3. Features of the combination according to the invention

[0106] For each combination, the following characteristics were measured:

[0107] - Thermal conductivity, according to standard ASTM 7896;

[0108] - Kinematic viscosity at 40°C and 100°C, according to standard ASTM D445;

[0109] - Density at 20°C, according to standard ASTM 7042.

[0110] The results are described in Table 2 below:

[0111]

[0112] Table 2 Characteristics of mixtures of monoesters and diesters

[0113] All combinations according to the invention exhibit a thermal conductivity of at least 0.1300 W / (m·℃), less than 10 mm at 40℃. 2 kinematic viscosity / s, and below 3mm at 100°C 2 The kinematic viscosity is 950 kg / m³ at 20°C. 3 The density.

[0114] Example 2: Material compatibility of the combination according to the present invention

[0115] Material compatibility is assessed by measuring the volume change of a material sample after it has been exposed in the assembly.

[0116] 2.1 Material

[0117] - Polyvinyl chloride (PVC): H03VVH2-F Black from Nexans;

[0118] - Polylactic acid (PLA): from Total Corbion L130;

[0119] - Polycarbonate (PC): 1mm thick Palsun transparent polycarbonate UVP from Palram Corporation.

[0120] 2.2 method

[0121] The material selected from three PVC wires, ten PLA pellets, and three pieces of PC (1mm thick Palsun transparent polycarbonate UVP) is placed in a beaker and weighed in air (mass in air at t0h) and water (mass in water at t0h).

[0122] The material was then immersed in the combination according to the invention, and the beaker was placed in an oven at 80°C for 168 hours.

[0123] Once the material is dry, it is weighed in air (mass in air for t168h) and in water (mass in water for t168h).

[0124] Then calculate the percentage change in volume using the following formula:

[0125] [(volume t168h - volume t0h) / volume t0h] x 100

[0126] Where volume = mass / density;

[0127] The density is a constant and is calculated as follows:

[0128] Density = [(mass in air at t168h - mass in water at t168h) - (mass in air at t0h - mass in water at t0h)] / (mass in air at t0h - mass in water at t0h)

[0129] The method was performed three times, and the average volume change is given in Table 3 below.

[0130] 2.3 result

[0131] Volume change (%) PVC in C1 0 PVC in C2 -6.0 PVC in C3 7.6 PVC in C4 -7.6 PVC in C5 -2.2 PLA in C6 0.2 PC in C6 0.3

[0132] Table 3 Volume change of materials in contact with the combination according to the invention

[0133] It can be observed that when PVC, PLA, or PC is immersed in the combinations C1-C6 according to the present invention, all volume changes are less than 10%.

[0134] Example 3: Comparative examples of material compatibility of some esters

[0135] The compatibility of PVC was evaluated in different monoesters and diesters (rather than the combination according to the invention) according to the method described in Example 2.2:

[0136] -Isoamyl laurate: Jolee 7750 from Euronext;

[0137] - Di-2-ethylhexyl sebacate: Radia 7543 from Euronext;

[0138] - 2-Ethylhexyl adipic acid: obtained by esterification of 2-ethylhexanol with adipic acid;

[0139] - Neopentyl glycol (NPG) diheptanoate: obtained by esterification of neopentyl glycol with heptanoic acid.

[0140] The results are collected in Table 4 below.

[0141] Volume change (%) PVC in isoamyl laurate -23.7 PVC in di-2-ethylhexyl sebacate 40.1 PVC in 2-ethylhexyl adipic acid 117.5 PVC in NPG diheptate 88.5

[0142] Table 4 Volume changes of PVC in contact with different esters

[0143] It can be observed that the volume change of PVC after immersion in different monoesters and diesters used separately is greater than 20%.

Claims

1. Use as a liquid dielectric coolant, which is basically a combination of monohydric alcohol fatty acid esters and diesters; The weight ratio of monohydric alcohol fatty acid ester / dieserene is between 15 / 85 and 55 / 45, where: - This monohydric alcohol fatty acid ester can be obtained by esterification of a monohydric alcohol containing between 5 and 8 carbon atoms with a fatty acid containing between 12 and 18 carbon atoms; - This diester can be obtained by esterification of a diol with a fatty acid or by esterification of a monohydric alcohol with a dicarboxylic acid; the diester contains between 19 and 26 carbon atoms.

2. The use according to claim 1, wherein: -The monohydric alcohol is selected from the group consisting of isoamyl alcohol and 2-ethylhexanol; and - This fatty acid is selected from the group consisting of caprylic acid, capric acid, lauric acid, isostearic acid, and mixtures thereof.

3. The use according to claim 1 or 2, wherein, The diol is propylene glycol.

4. The use according to claim 1 or 2, wherein, The dicarboxylic acid is sebacic acid.

5. The use according to claim 1 or 2, wherein, The monohydric alcohol fatty acid ester is selected from the group consisting of isoamyl isostearate, isoamyl laurate, and 2-ethylhexyl laurate.

6. The use according to claim 1 or 2, wherein, The diester is selected from the group consisting of propylene glycol didecanoate / octanoate and di-2-ethylhexyl sebacate.

7. The use according to claim 1 or 2, wherein, This combination basically consists of the following items: -Isoamyl isostearate and propylene glycol didecanoate / octanoate; -Isoamyl laurate and propylene glycol didecanoate / octanoate; or - 2-Ethylhexyl laurate and di-2-ethylhexyl sebacate.

8. The use according to claim 1 or 2, wherein, The weight ratio of monohydric fatty acid esters to diesters is between 20 / 80 and 55 / 45.

9. A combination substantially consisting of a monohydric alcohol fatty acid ester and a diester, wherein the weight ratio of the monohydric alcohol fatty acid ester to the diester is between 15 / 85 and 55 / 45; and wherein the combination of the monohydric alcohol fatty acid ester and the diester is: -Isoamyl isostearate and propylene glycol didecanoate / octanoate -Isoamyl laurate and propylene glycol didecanoate / octanoate, or - 2-Ethylhexyl laurate and di-2-ethylhexyl sebacate.

10. A composition comprising the combination according to claim 9, and an antioxidant and / or a metal deactivator.

11. Use of the composition according to claim 10 as a liquid dielectric coolant.

12. A method for cooling an electrical device by contacting it with a combination consisting essentially of a monohydric alcohol fatty acid ester and a diester, or with a composition according to claim 11, wherein the weight ratio of the monohydric alcohol fatty acid ester / diester is between 15 / 85 and 55 / 45, wherein: - This monohydric alcohol fatty acid ester can be obtained by esterification of a monohydric alcohol containing between 5 and 8 carbon atoms with a fatty acid containing between 12 and 18 carbon atoms; - This diester can be obtained by esterification of a diol with a fatty acid or by esterification of a monohydric alcohol with a dicarboxylic acid; the diester contains between 19 and 26 carbon atoms.

13. The method according to claim 12, wherein, The combination is the combination according to claim 9.