Synthetic ester oil, and method for preparing and use thereof

Abstract

This invention discloses a synthetic ester oil, its preparation method, and its application, relating to the technical field of immersion coolants. A synthetic ester oil comprises the following raw material components in parts by weight: 60-85 parts of trimethylolpropane trioleate; 3-8 parts of phosphorus pentasulfide; 5-15 parts of imidazole; 0.5-2 parts of catalyst; and 0.3-1 parts of stabilizer. This invention modifies trimethylolpropane trioleate in situ with phosphorus pentasulfide, introducing sulfur-containing active groups, and then reacts it with imidazole to generate a synthetic ester oil with an ionic liquid structure, exhibiting excellent properties such as high thermal conductivity, high insulation, low viscosity, and high flash point.

Description

Technical Field

[0001] This invention relates to the technical field of immersion coolants, and more particularly to a synthetic ester oil, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy storage and data center industries, the power density of equipment continues to increase, placing increasingly stringent demands on the performance of immersion coolants. Traditional synthetic ester coolants (such as pentaerythritol esters and diesters) have good insulation and biodegradability, but they also have problems such as low thermal conductivity (usually ≤0.15 W / (m・K)), high viscosity at low temperatures, and easy gas evolution during long-term use, making it difficult to meet the high-efficiency thermal management requirements of high-power equipment.

[0003] To improve thermal conductivity, nano-thermal conductive fillers (such as boron nitride and alumina) are typically added. However, these fillers are prone to agglomeration, leading to poor dispersion stability and ultimately compromising insulation performance. Alternatively, modifying groups containing sulfur or phosphorus can be introduced, but the modification process is complex and can easily lower the flash point and degrade the antioxidant properties of the synthesized ester. Furthermore, ionic liquids, due to their high thermal conductivity and high insulation properties, are used in the coolant field. However, pure ionic liquids have high viscosity and high cost, limiting their direct application. How to effectively combine the structure of ionic liquids with synthetic ester molecules to achieve synergistic optimization of "thermal conductivity-insulation-flowability" has become a key problem that the industry urgently needs to solve. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a synthetic ester oil, its preparation method, and its application. This invention involves in-situ modification of trimethylolpropane trioleate with phosphorus pentasulfide to introduce sulfur-containing active groups, followed by reaction with imidazole to generate a synthetic ester oil with an ionic liquid structure, exhibiting excellent properties such as high thermal conductivity, high insulation, low viscosity, and high flash point.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a synthetic ester oil comprising the following raw material components in parts by weight: 60-85 parts of trimethylolpropane trioleate; 3-8 parts of phosphorus pentasulfide; 5-15 parts of imidazole; 0.5-2 parts of catalyst; 0.3-1 parts of stabilizer.

[0006] Preferably, the catalyst includes at least one of tetrabutylammonium bromide and triethylbenzylammonium chloride.

[0007] Preferably, the stabilizer comprises at least one of 2,6-di-tert-butyl-p-methylphenol and isooctyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0008] More preferably, the stabilizer comprises 2,6-di-tert-butyl-p-methylphenol (T501) and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate isooctyl ester (L135) in a mass ratio of 1:(1-2), which can effectively capture free radicals and inhibit the oxidation of sulfur-containing groups to produce acidic substances, so that the acid value of the synthesized ester is ≤0.1 mgKOH / g over a long period of time (after 1000h aging).

[0009] Preferably, the trimethylolpropane trioleate has an acid value ≤0.05 mgKOH / g and a moisture content ≤50 mg / kg.

[0010] This invention, by selecting trimethylolpropane trioleate with the aforementioned properties, avoids the influence of impurities on the modification reaction and insulation performance. Its three oleic acid chains in its molecular structure provide good flowability, with a base viscosity of 8-10 mmHg at 40°C. 2 / s, low temperature (-30℃) viscosity ≤100 mm 2 / s, meeting the requirements for use in a wide temperature range.

[0011] Preferably, the imidazole comprises at least one of 1-methylimidazolium and 1-ethylimidazolium. The alkyl-substituted imidazoles used in this invention exhibit high reactivity, and the resulting ionic liquid structure has moderate steric hindrance, thus improving thermal conductivity without significantly increasing viscosity.

[0012] Preferably, the catalyst includes at least one of tetrabutylammonium bromide and triethylbenzylammonium chloride, which can promote the nucleophilic reaction between sulfur-containing groups and imidazole through ion exchange, thereby increasing the ionic liquid structure formation rate to over 90%.

[0013] The synthetic ester oil described in this invention has an ionic liquid structure generated by the reaction of sulfur-containing groups with imidazole.

[0014] Preferably, the amount of trimethylolpropane used is 65 to 80 parts, for example, it can be 65 parts, 66 parts, 68 parts, 70 parts, 72 parts, 74 parts, 75 parts, 76 parts, 78 parts, 80 parts or any two of these values.

[0015] Preferably, the amount of phosphorus pentasulfide is 4 to 7 parts, for example, it can be 4 parts, 5 parts, 6 parts, 7 parts or any two of these values.

[0016] Preferably, the amount of imidazole used is 6 to 14 parts, for example, it can be 6 parts, 8 parts, 10 parts, 11 parts, 12 parts, 14 parts or any two of these values.

[0017] Preferably, the amount of catalyst used is 0.6 to 1.8 parts, for example, it can be 0.6 parts, 0.8 parts, 1.0 parts, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts or any two of these values.

[0018] Preferably, the amount of stabilizer is 0.5 to 0.9 parts, for example, it can be 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, or any two of these values.

[0019] Secondly, the present invention also provides a method for preparing synthetic ester oils, comprising the following steps: S1: Trimethylolpropane trioleate was added to the reactor and heated to 80-100℃. Phosphorus pentasulfide was added under inert gas protection and stirred at a speed of 300-500 rpm for 2-4 h to obtain a sulfur-modified intermediate. S2: Add a catalyst to the sulfur-containing modified intermediate, heat to 110~130℃, add imidazole dropwise, control the dropwise addition time to 1~2 h, and keep the reaction at the temperature for 3~5 h after the dropwise addition is completed to obtain the ionic liquid precursor. S3: Add a stabilizer to the ionic liquid precursor and stir at 80~90℃ for 1~2 h to obtain synthetic ester oil.

[0020] In the synthetic ester oils described in this invention, trimethylolpropane oleate serves as the base carrier, providing basic insulation and flowability. Its long-chain alkyl structure can reduce low-temperature viscosity. Phosphorus pentasulfide acts as a modifier, introducing sulfur-containing groups (such as -SPS-, -P=S) in situ, improving molecular thermal conductivity and enhancing compatibility with ionic liquid structures. Imidazole, as an ionic liquid precursor, reacts with sulfur-containing modified intermediates to generate imidazole-based ionic liquid structures (such as [Im]-[PS4)). - The catalyst synergistically enhances thermal conductivity and insulation properties. It promotes the reaction between imidazole and sulfur-containing groups, lowers the activation energy, and improves the formation efficiency of ionic liquid structures. The stabilizer inhibits the oxidation of sulfur-containing groups, prevents the breakage of synthetic ester molecular chains, and extends product lifespan.

[0021] Preferably, in step S1, phosphorus pentasulfide is added in 3 to 5 batches, with an interval of 30 to 60 minutes between each batch.

[0022] In this invention, phosphorus pentasulfide is added in batches, which can avoid molecular chain breakage caused by violent local reactions; the sulfur-containing groups introduced enhance heat transfer through phonon conduction, and at the same time, the lone pair electrons of the sulfur atom can form coordination with the nitrogen atom of the imidazole, stabilizing the ionic liquid structure.

[0023] Preferably, the nitrogen flow rate in step S1 is controlled to be 0.5~1 L / min, for example, it can be 0.5L / min, 0.6L / min, 0.7L / min, 0.8L / min, 0.9L / min, 1.0L / min, or any two of these values. This invention, by controlling the nitrogen flow rate, can isolate the nitrogen from air and prevent oxidation.

[0024] Preferably, in step S1, the content of sulfur-containing groups is sampled and detected after the reaction, and the mass fraction of sulfur element needs to reach 2-5% by X-ray photoelectron spectroscopy (XPS).

[0025] Preferably, the imidazole dropping rate in step S2 is 0.5~1 mL / min, for example, it can be 0.5 mL / min, 0.6 mL / min, 0.7 mL / min, 0.8 mL / min, 0.9 mL / min, 1.0 mL / min, or any two of these values. A water separator is used to remove the generated water during the reaction process. This invention reduces side reactions (such as imidazole self-polymerization) by slowly adding imidazole, and the use of a water separator can shift the reaction equilibrium towards the formation of ionic liquids, thereby improving product purity.

[0026] Preferably, in step S2, the reaction is followed by hydrogen nuclear magnetic resonance spectroscopy (NMR 1H). 1 The reaction is terminated when the conversion rate of imidazole characteristic peak (δ=7.0~8.5 ppm) detected by ¹H NMR is ≥90%.

[0027] Preferably, in step S3, molecular distillation purification is used (vacuum degree ≤10 Pa, temperature 200~220℃) to remove unreacted raw materials and low-boiling substances (light component content ≤0.5%). The vacuum degree and temperature need to be precisely matched. Too low a vacuum degree will result in the residue of low-boiling substances, while too high a temperature may destroy the ionic liquid structure. The purity of the product needs to be ≥99.5% as detected by gas chromatography (GC).

[0028] More preferably, the molecular distillation purification further includes an adsorption purification step, the steps of which are as follows: adding a silica gel-activated carbon composite adsorbent (mass ratio of 2:1), the amount of the composite adsorbent being 1-3% of the mass of the ionic liquid precursor, stirring at 60-70°C for 1-1.5 h, and filtering to remove the composite adsorbent.

[0029] Thirdly, the present invention also provides an immersion coolant comprising the following components in parts by weight: 95-99.5 parts of synthetic ester oil; 0.2-0.5 parts of antifoaming agent; 0.1-0.3 parts of metal deactivating agent.

[0030] Preferably, the antifoaming agent comprises polyether-modified silicone oil.

[0031] Preferably, the metal deactivator includes a toluenetriazole derivative.

[0032] Preferably, the amount of the synthetic ester oil is 95.5 to 99 parts, for example, it can be 95.5 parts, 96 parts, 96.5 parts, 97 parts, 97.5 parts, 98 parts, 98.5 parts, 99 parts or any two of these values.

[0033] Preferably, the amount of the antifoaming agent is 0.25 to 0.45 parts, for example, it can be 0.25 parts, 0.28 parts, 0.30 parts, 0.32 parts, 0.35 parts, 0.38 parts, 0.40 parts, 0.42 parts, 0.45 parts, or any two of these values.

[0034] Preferably, the amount of the metal deactivator is 0.15 to 0.28 parts, for example, it can be 0.15 parts, 0.16 parts, 0.18 parts, 0.20 parts, 0.22 parts, 0.24 parts, 0.26 parts, 0.28 parts, or any two of these values.

[0035] Fourthly, the present invention also provides a method for preparing an immersion coolant, comprising the following steps: Synthetic ester oil, antifoaming agent, and metal deactivator are mixed and stirred at 50~60℃, with a stirring speed of 400~600rpm and a stirring time of 30~45min to obtain an immersion coolant.

[0036] In the immersion coolant of this invention, synthetic ester oil is used as the base oil to provide core properties such as thermal conductivity, insulation, and fluidity; antifoaming agent can inhibit the generation of bubbles in the coolant during circulation, avoiding an increase in thermal resistance; metal deactivating agent can prevent corrosion reaction between the coolant and the metal parts of the equipment, extending the equipment life.

[0037] Fifthly, the present invention also provides an application of immersion coolant in thermal management of battery energy storage systems and thermal management of data center servers.

[0038] Specifically, the immersion coolant described in this invention can be used in battery energy storage systems, such as immersion thermal management for energy storage devices like lithium-ion batteries and flow batteries, which can effectively control temperature fluctuations (≤5℃) during battery charging and discharging, avoiding the risk of thermal runaway.

[0039] The immersion coolant described in this invention can be used in data center servers: such as single-phase immersion cooling suitable for high-density servers, which has high thermal conductivity and good fluidity, and can reduce server energy consumption (more than 30% energy saving compared to air cooling).

[0040] The immersion coolant described in this invention can be used in power electronic equipment such as IGBT modules and transformers. The high insulation performance of the coolant can ensure the safe operation of the equipment, and the high flash point characteristics can improve the safety of use.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The sulfur-containing group (-SPS-) introduced by the in-situ modification of phosphorus pentasulfide in this invention has a high thermal conductivity and can construct intramolecular thermal conduction channels. At the same time, the ionic liquid structure generated by the reaction of imidazole and sulfur-containing group further enhances heat transfer through the synergistic effect of ion conduction and phonon conduction, thereby improving the thermal conductivity of the synthesized ester oil. Furthermore, the cation (imidazole ring) and anion (sulfophosphate) in the ionic liquid structure form a stable charge balance, avoiding the migration of free ions; the long-chain alkyl structure of trimethylolpropane trioleate forms steric hindrance, inhibiting charge breakdown and increasing the lightning impulse breakdown voltage. Meanwhile, the branched structure of trimethylolpropane trioleate reduces intermolecular forces, and the moderate introduction of the ionic liquid structure will not significantly increase the viscosity; the synergistic effect of sulfur-containing group and ionic liquid structure enhances intermolecular attraction, raising the flash point to above 220°C, balancing fluidity and safety. Furthermore, the polar groups (such as N⁺ and P=S) in the ionic liquid structure can adsorb gases such as hydrogen and oxygen in the coolant, preventing gas precipitation and aggregation; the addition of stabilizers inhibits the oxidative degradation of synthesized esters, reduces the generation of small molecule gases, and makes the gas evolution tendency ≤-8mm. 3 / min (negative values ​​indicate intake). Therefore, the synthetic ester oil prepared by this invention has both high thermal conductivity and excellent insulation properties, as well as low viscosity, high flash point and good oxidation resistance. It can effectively solve the problems of difficult balance between thermal conductivity and insulation and poor low-temperature fluidity of traditional synthetic ester coolants, and is suitable for immersion thermal management in scenarios such as battery energy storage systems and data centers.

[0042] (2) The method for synthesizing ester oils described in this invention has a stable preparation process: the in-situ modification and molecular distillation purification processes are mature, the raw materials are readily available, and the product purity is high (≥99.5%), making it suitable for large-scale production.

[0043] (3) The preparation method of the immersion coolant described in this invention has the characteristics of being environmentally friendly and safe: the biodegradation rate is ≥92%, and no toxic or harmful substances are released; the gas evolution tendency is negative, which avoids the accumulation of flammable gases and ensures high safety in use.

[0044] (4) The immersion coolant described in this invention has a wide range of applications and is suitable for various scenarios such as battery energy storage and data centers. It can meet the thermal management needs of devices with different power densities and has significant industrial application value. Detailed Implementation

[0045] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the scope of protection and implementation of the present invention are not limited thereto.

[0046] Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0047] Example 1 This embodiment discloses a synthetic ester oil, comprising the following raw material components in parts by weight: 75 parts of trimethylolpropane trioleate; 5 parts of phosphorus pentasulfide; 10 parts of imidazole; 1 part of catalyst; 0.5 parts of stabilizer. The imidazole is 1-methylimidazolium; the catalyst is tetrabutylammonium bromide; the stabilizers include 2,6-di-tert-butyl-p-methylphenol (T501) and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate isooctyl ester (L135), with a mass ratio of 1:1.

[0048] This embodiment also discloses a method for preparing synthetic ester oils, including the following steps: S1: Add trimethylolpropane trioleate to a reactor equipped with a stirrer, temperature measuring device, and nitrogen protection device, heat to 85°C, and stir at 400 rpm; Then, under nitrogen protection, phosphorus pentasulfide was added in four batches, with a 45-minute interval between each batch, to avoid local overheating that could lead to carbonization of the raw materials. Nitrogen flow rate was controlled at 0.6 L / min to isolate air and prevent oxidation. The reaction was kept at a constant temperature for 3 hours. The sulfur content was measured by X-ray photoelectron spectroscopy (XPS) and the mass fraction of sulfur was 4.2%. After passing the test, sulfur-modified intermediate was obtained.

[0049] S2: Add a catalyst to the sulfur-containing modified intermediate and heat to 120℃; Then, imidazole was added dropwise through a constant pressure dropping funnel (dropping rate 0.8 mL / min), and the water separator was turned on during the dropwise addition to remove the water generated in the reaction in real time. After the addition was completed, the reaction was kept at the temperature for 4 hours, and the nuclear magnetic resonance hydrogen spectrum was analyzed. 1 The conversion rate of imidazole characteristic peak (δ=7.0~8.5ppm) detected by ¹H NMR was 92%, and the reaction was terminated to obtain the ionic liquid precursor.

[0050] S3: Add a stabilizer to the ionic liquid precursor and stir at 85°C for 1.5 h; Molecular distillation was used for purification: vacuum degree 5 Pa, distillation temperature 210℃, to remove unreacted imidazole, phosphorus pentasulfide and low-boiling substances; Then, silica gel-activated carbon composite adsorbent (mass ratio 2:1, amount 2% of the ionic liquid precursor mass) was added, and the mixture was stirred at 65℃ for 1.2 h to adsorb and remove metal impurities. The mixture was then filtered through a 2 μm filter membrane to obtain the synthetic ester oil.

[0051] This embodiment also discloses an immersion coolant, comprising the following components in parts by weight: 99 parts synthetic ester oil; 0.3 parts antifoaming agent; 0.2 parts metal deactivating agent.

[0052] The antifoaming agent is polyether-modified silicone oil, manufactured by BASF Foamaster® series; the metal deactivator is toluene-triazole derivative, manufactured by BASF Irgamet® 39.

[0053] This embodiment also discloses a method for preparing an immersion coolant, including the following steps: (1) Add the synthetic ester oil to the mixing vessel and heat it to 55°C; (2) Add antifoaming agent and metal deactivator in sequence, stirring at 500 rpm for 40 min; (3) Sampling and testing of appearance (colorless transparent liquid, no layering, no sediment), viscosity, and breakdown voltage. After passing the test, the liquid is packaged to obtain immersion coolant.

[0054] Example 2 This embodiment discloses a synthetic ester oil, comprising the following raw material components in parts by weight: 80 parts of trimethylolpropane trioleate; 4 parts of phosphorus pentasulfide; 8 parts of imidazole; 0.8 parts of catalyst; 0.4 parts of stabilizer. The imidazole is 1-ethylimidazole; the catalyst is triethylbenzylammonium chloride; and the stabilizer is T501.

[0055] This embodiment discloses a method for preparing synthetic ester oils, including the following steps: S1: Add trimethylolpropane trioleate to a reactor equipped with a stirrer, temperature measuring device, and nitrogen protection device, heat to 90°C, and stir at 500 rpm; Then, under nitrogen protection, phosphorus pentasulfide was added in three batches, with a 50-minute interval between each batch, to avoid local overheating that could lead to carbonization of the raw materials. Nitrogen flow rate was controlled at 1 L / min to isolate air and prevent oxidation. The reaction was kept at a constant temperature for 2.5 h. The sulfur content was measured by X-ray photoelectron spectroscopy (XPS) and the mass fraction of sulfur was 3.8%. After passing the test, sulfur-modified intermediate was obtained.

[0056] S2: Add a catalyst to the sulfur-containing modified intermediate and heat to 115℃; Then, imidazole was added dropwise through a constant pressure dropping funnel (dropping rate 0.6 mL / min), and the water separator was turned on during the dropwise addition to remove the water generated in the reaction in real time. After the addition was completed, the reaction was kept at a constant temperature for 3.5 hours, and the nuclear magnetic resonance hydrogen spectrum was analyzed. 1 The conversion rate was 91% when the characteristic peak of imidazole (δ=7.0~8.5 ppm) was detected by ¹H NMR. The reaction was terminated to obtain the ionic liquid precursor.

[0057] S3: Add a stabilizer to the ionic liquid precursor and stir at 80°C for 1 hour; Molecular distillation was used for purification: vacuum degree 8 Pa, distillation temperature 205℃, to remove unreacted imidazole, phosphorus pentasulfide and low-boiling substances; Then, silica gel-activated carbon composite adsorbent (mass ratio 2:1, amount 2% of the ionic liquid precursor mass) was added, and the mixture was stirred at 65℃ for 1.2 h to adsorb and remove metal impurities. The mixture was then filtered through a 2 μm filter membrane to obtain the synthetic ester oil.

[0058] This embodiment also discloses an immersion coolant, comprising the following components in parts by weight: 98.5 parts of synthetic ester oil; 0.4 parts of antifoaming agent; 0.1 parts of metal deactivating agent.

[0059] The antifoaming agent is polyether-modified silicone oil, manufactured by BASF Foamaster® series; the metal deactivator is toluene-triazole derivative I39, manufactured by BASF Irgamet®39.

[0060] This embodiment also discloses a method for preparing an immersion coolant, including the following steps: (1) Add the synthetic ester oil to the mixing vessel and heat it to 60°C; (2) Add antifoaming agent and metal deactivator in sequence, stirring at 500 rpm for 35 min; (3) Sampling and testing of appearance (colorless transparent liquid, no layering, no sediment), viscosity, and breakdown voltage. After passing the test, the liquid is packaged to obtain immersion coolant.

[0061] Example 3 This embodiment discloses a synthetic ester oil, comprising the following raw material components in parts by weight: 75 parts of trimethylolpropane trioleate; 5 parts of phosphorus pentasulfide; 10 parts of imidazole; 1 part of catalyst; 0.5 parts of stabilizer. The imidazole is 1-methylimidazolium; the catalyst is tetrabutylammonium bromide; the stabilizers include 2,6-di-tert-butyl-p-methylphenol (T501) and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate isooctyl ester (L135), with a mass ratio of 1:1.

[0062] This embodiment also discloses a method for preparing synthetic ester oils, including the following steps: S1: Add trimethylolpropane trioleate to a reactor equipped with a stirrer, temperature measuring device, and nitrogen protection device, heat to 85°C, and stir at 400 rpm; Then, phosphorus pentasulfide was added directly under nitrogen protection; the nitrogen flow rate was controlled at 0.6 L / min to prevent oxidation by isolating air, and the reaction was kept at this temperature for 3 hours. The sulfur content was measured by X-ray photoelectron spectroscopy (XPS test, the mass fraction of S element was 4.2%). After passing the test, the sulfur-modified intermediate was obtained.

[0063] S2: Add a catalyst to the sulfur-containing modified intermediate and heat to 120℃; Then, imidazole was added dropwise through a constant pressure dropping funnel (dropping rate 0.8 mL / min), and the water separator was turned on during the dropwise addition to remove the water generated in the reaction in real time. After the addition was completed, the reaction was kept at the temperature for 4 hours, and the nuclear magnetic resonance hydrogen spectrum was analyzed. 1 The conversion rate of imidazole characteristic peak (δ=7.0~8.5ppm) detected by ¹H NMR was 92%, and the reaction was terminated to obtain the ionic liquid precursor.

[0064] S3: Add a stabilizer to the ionic liquid precursor and stir at 85°C for 1.5 h; Molecular distillation was used for purification: vacuum degree 5 Pa, distillation temperature 210℃, to remove unreacted imidazole, phosphorus pentasulfide and low-boiling substances; Then, silica gel-activated carbon composite adsorbent (mass ratio 2:1, amount 2% of the ionic liquid precursor mass) was added, and the mixture was stirred at 65℃ for 1.2 h to adsorb and remove metal impurities. The mixture was then filtered through a 2 μm filter membrane to obtain the synthetic ester oil.

[0065] This embodiment also discloses an immersion coolant, comprising the following components in parts by weight: 99 parts synthetic ester oil; 0.3 parts antifoaming agent; 0.2 parts metal deactivating agent.

[0066] The antifoaming agent is polyether-modified silicone oil, manufactured by BASF Foamaster® series; the metal deactivator is toluene-triazole derivative, manufactured by BASF Irgamet® 39.

[0067] This embodiment also discloses a method for preparing an immersion coolant, including the following steps: (1) Add the synthetic ester oil to the mixing vessel and heat it to 55°C; (2) Add antifoaming agent and metal deactivator in sequence, stirring at 500 rpm for 40 min; (3) Sampling and testing of appearance (colorless transparent liquid, no layering, no sediment), viscosity, and breakdown voltage. After passing the test, the liquid is packaged to obtain immersion coolant.

[0068] The difference between this embodiment and Embodiment 1 is that in step S1, phosphorus pentasulfide is added directly under nitrogen protection, instead of being added in batches.

[0069] Example 4 This embodiment discloses a synthetic ester oil, comprising the following raw material components in parts by weight: 75 parts of trimethylolpropane trioleate; 5 parts of phosphorus pentasulfide; 10 parts of imidazole; 1 part of catalyst; 0.5 parts of stabilizer. The imidazole is 1-methylimidazolium; the catalyst is tetrabutylammonium bromide; the stabilizers include 2,6-di-tert-butyl-p-methylphenol (T501) and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate isooctyl ester (L135), with a mass ratio of 1:1.

[0070] This embodiment also discloses a method for preparing synthetic ester oils, including the following steps: S1: Add trimethylolpropane trioleate to a reactor equipped with a stirrer, temperature measuring device, and nitrogen protection device, heat to 85°C, and stir at 400 rpm; Then, under nitrogen protection, phosphorus pentasulfide was added in four batches, with a 45-minute interval between each batch, to avoid local overheating that could lead to carbonization of the raw materials. Nitrogen flow rate was controlled at 0.6 L / min to isolate air and prevent oxidation. The reaction was kept at a constant temperature for 3 hours. The sulfur content was measured by X-ray photoelectron spectroscopy (XPS) and the mass fraction of sulfur was 4.2%. After passing the test, sulfur-modified intermediate was obtained.

[0071] S2: Add a catalyst to the sulfur-containing modified intermediate and heat to 120℃; Then, imidazole was added dropwise through a constant pressure dropping funnel (dropping rate 2 mL / min), and the water separator was turned on during the dropwise addition to remove the water generated in the reaction in real time. After the addition was completed, the reaction was kept at the temperature for 4 hours, and the nuclear magnetic resonance hydrogen spectrum was analyzed. 1 The conversion rate of imidazole characteristic peak (δ=7.0~8.5ppm) detected by ¹H NMR was 92%, and the reaction was terminated to obtain the ionic liquid precursor.

[0072] S3: Add a stabilizer to the ionic liquid precursor and stir at 85°C for 1.5 h; Molecular distillation was used for purification: vacuum degree 5 Pa, distillation temperature 210℃, to remove unreacted imidazole, phosphorus pentasulfide and low-boiling substances; Then, silica gel-activated carbon composite adsorbent (mass ratio 2:1, amount 2% of the ionic liquid precursor mass) was added, and the mixture was stirred at 65℃ for 1.2 h to adsorb and remove metal impurities. The mixture was then filtered through a 2 μm filter membrane to obtain the synthetic ester oil.

[0073] This embodiment also discloses an immersion coolant, comprising the following components in parts by weight: 99 parts synthetic ester oil; 0.3 parts antifoaming agent; 0.2 parts metal deactivating agent.

[0074] The antifoaming agent is polyether-modified silicone oil, manufactured by BASF Foamaster® series; the metal deactivator is toluene-triazole derivative, manufactured by BASF Irgamet® 39.

[0075] This embodiment also discloses a method for preparing an immersion coolant, including the following steps: (1) Add the synthetic ester oil to the mixing vessel and heat it to 55°C; (2) Add antifoaming agent and metal deactivator in sequence, stirring at 500 rpm for 40 min; (3) Sampling and testing of appearance (colorless transparent liquid, no layering, no sediment), viscosity, and breakdown voltage. After passing the test, the liquid is packaged to obtain immersion coolant.

[0076] The difference between this embodiment and Embodiment 1 is that the dripping rate of imidazole in step S2 is 2 mL / min.

[0077] Example 5 This embodiment discloses a synthetic ester oil, comprising the following raw material components in parts by weight: 75 parts of trimethylolpropane trioleate; 5 parts of phosphorus pentasulfide; 10 parts of imidazole; 1 part of catalyst; 0.5 parts of stabilizer. The imidazole is 1-methylimidazolium; the catalyst is tetrabutylammonium bromide; the stabilizers include pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010) and isooctyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (L135), with a mass ratio of 1:1.

[0078] This embodiment also discloses a method for preparing synthetic ester oils, including the following steps: S1: Add trimethylolpropane trioleate to a reactor equipped with a stirrer, temperature measuring device, and nitrogen protection device, heat to 85°C, and stir at 400 rpm; Then, under nitrogen protection, phosphorus pentasulfide was added in four batches, with a 45-minute interval between each batch, to avoid local overheating that could lead to carbonization of the raw materials. Nitrogen flow rate was controlled at 0.6 L / min to isolate air and prevent oxidation. The reaction was kept at a constant temperature for 3 hours. The sulfur content was measured by X-ray photoelectron spectroscopy (XPS) and the mass fraction of sulfur was 4.2%. After passing the test, sulfur-modified intermediate was obtained.

[0079] S2: Add a catalyst to the sulfur-containing modified intermediate and heat to 120℃; Then, imidazole was added dropwise through a constant pressure dropping funnel (dropping rate 0.8 mL / min), and the water separator was turned on during the dropwise addition to remove the water generated in the reaction in real time. After the addition was completed, the reaction was kept at the temperature for 4 hours, and the nuclear magnetic resonance hydrogen spectrum was analyzed. 1 The conversion rate of imidazole characteristic peak (δ=7.0~8.5ppm) detected by ¹H NMR was 92%, and the reaction was terminated to obtain the ionic liquid precursor.

[0080] S3: Add a stabilizer to the ionic liquid precursor and stir at 85°C for 1.5 h; Molecular distillation was used for purification: vacuum degree 5 Pa, distillation temperature 210℃, to remove unreacted imidazole, phosphorus pentasulfide and low-boiling substances; Then, silica gel-activated carbon composite adsorbent (mass ratio 2:1, amount 2% of the ionic liquid precursor mass) was added, and the mixture was stirred at 65℃ for 1.2 h to adsorb and remove metal impurities. The mixture was then filtered through a 2 μm filter membrane to obtain the synthetic ester oil.

[0081] This embodiment also discloses an immersion coolant, comprising the following components in parts by weight: 99 parts synthetic ester oil; 0.3 parts antifoaming agent; 0.2 parts metal deactivating agent.

[0082] The antifoaming agent is polyether-modified silicone oil, manufactured by BASF Foamaster® series; the metal deactivator is toluene-triazole derivative, manufactured by BASF Irgamet® 39.

[0083] This embodiment also discloses a method for preparing an immersion coolant, including the following steps: (1) Add the synthetic ester oil to the mixing vessel and heat it to 55°C; (2) Add antifoaming agent and metal deactivator in sequence, stirring at 500 rpm for 40 min; (3) Sampling and testing of appearance (colorless transparent liquid, no layering, no sediment), viscosity, and breakdown voltage. After passing the test, the liquid is packaged to obtain immersion coolant.

[0084] The difference between this embodiment and Example 1 is that, in the synthetic ester oil, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] is used to replace 2,6-di-tert-butyl-p-methylphenol.

[0085] Example 6 This embodiment discloses a synthetic ester oil, comprising the following raw material components in parts by weight: 75 parts of trimethylolpropane trioleate; 5 parts of phosphorus pentasulfide; 10 parts of imidazole; 1 part of catalyst; 0.5 parts of stabilizer. The imidazole is 1-vinylimidazolium; the catalyst is tetrabutylammonium bromide; the stabilizers include 2,6-di-tert-butyl-p-methylphenol (T501) and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate isooctyl ester (L135), with a mass ratio of 1:1.

[0086] This embodiment also discloses a method for preparing synthetic ester oils, including the following steps: S1: Add trimethylolpropane trioleate to a reactor equipped with a stirrer, temperature measuring device, and nitrogen protection device, heat to 85°C, and stir at 400 rpm; Then, under nitrogen protection, phosphorus pentasulfide was added in four batches, with a 45-minute interval between each batch, to avoid local overheating that could lead to carbonization of the raw materials. Nitrogen flow rate was controlled at 0.6 L / min to isolate air and prevent oxidation. The reaction was kept at a constant temperature for 3 hours. The sulfur content was measured by X-ray photoelectron spectroscopy (XPS) and the mass fraction of sulfur was 4.2%. After passing the test, sulfur-modified intermediate was obtained.

[0087] S2: Add a catalyst to the sulfur-containing modified intermediate and heat to 120℃; Then, imidazole was added dropwise through a constant pressure dropping funnel (dropping rate 0.8 mL / min), and the water separator was turned on during the dropwise addition to remove the water generated in the reaction in real time. After the addition was completed, the reaction was kept at the temperature for 4 hours, and the nuclear magnetic resonance hydrogen spectrum was analyzed. 1 The conversion rate of imidazole characteristic peak (δ=7.0~8.5ppm) detected by ¹H NMR was 92%, and the reaction was terminated to obtain the ionic liquid precursor.

[0088] S3: Add a stabilizer to the ionic liquid precursor and stir at 85°C for 1.5 h; Molecular distillation was used for purification: vacuum degree 5 Pa, distillation temperature 210℃, to remove unreacted imidazole, phosphorus pentasulfide and low-boiling substances; Then, silica gel-activated carbon composite adsorbent (mass ratio 2:1, amount 2% of the ionic liquid precursor mass) was added, and the mixture was stirred at 65℃ for 1.2 h to adsorb and remove metal impurities. The mixture was then filtered through a 2 μm filter membrane to obtain the synthetic ester oil.

[0089] This embodiment also discloses an immersion coolant, comprising the following components in parts by weight: 99 parts synthetic ester oil; 0.3 parts antifoaming agent; 0.2 parts metal deactivating agent.

[0090] The antifoaming agent is polyether-modified silicone oil, manufactured by BASF Foamaster® series; the metal deactivator is toluene-triazole derivative, manufactured by BASF Irgamet® 39.

[0091] This embodiment also discloses a method for preparing an immersion coolant, including the following steps: (1) Add the synthetic ester oil to the mixing vessel and heat it to 55°C; (2) Add antifoaming agent and metal deactivator in sequence, stirring at 500 rpm for 40 min; (3) Sampling and testing of appearance (colorless transparent liquid, no layering, no sediment), viscosity, and breakdown voltage. After passing the test, the liquid is packaged to obtain immersion coolant.

[0092] The difference between this embodiment and Embodiment 1 is that 1-vinylimidazole is used instead of 1-methylimidazole in the synthetic ester oil.

[0093] Comparative Example 1 An immersion coolant, differing from Example 1 in that the immersion coolant comprises the following components in parts by weight: 99 parts of trimethylolpropane trioleate; 0.3 parts of antifoaming agent; 0.2 parts of metal deactivating agent.

[0094] Comparative Example 2 A synthetic ester oil, differing from Example 1 in that the synthetic ester oil comprises the following raw material components in parts by weight: 80 parts of trimethylolpropane trioleate; 5 parts of phosphorus pentasulfide; 0.5 parts of stabilizer.

[0095] Comparative Example 3 A synthetic ester oil, differing from Example 1 in that the synthetic ester oil comprises the following raw material components in parts by weight: 85 parts of trimethylolpropane trioleate; 10 parts of 1-methylimidazolium ionic liquid ([C1mim][PF6]); 0.5 parts of stabilizer.

[0096] Performance testing The immersion coolants prepared in the above examples and comparative examples were subjected to the following performance tests.

[0097] 1. Kinematic viscosity at 40℃: Tested according to GB / T 265-1988.

[0098] 2. Flash point: Tested in accordance with GB / T 3536-2008.

[0099] 3. Thermal conductivity: Tested according to ASTM D 7896-19.

[0100] 4. Lightning impulse breakdown voltage (negative pole): Tested in accordance with GB / T 21222-2007.

[0101] 5. Gas evolution tendency: Tested in accordance with NB / SH / T 0810-2010.

[0102] 6. Rotating oxygen bomb life: Tested according to ASTM D2272-22.

[0103] 7. Biodegradability: Tested according to OECD 301F.

[0104] The test results are shown in Table 1.

[0105] Table 1 Test Results As can be seen from Examples 1-6, the properties of the synthetic ester oil of the present invention include: a kinematic viscosity of 28-35 mmHg at 40°C. 2 / s, flash point ≥218℃, thermal conductivity ≥0.15 W / (m・K), lightning impulse breakdown voltage ≥60 kV.

[0106] The gas evolution tendency of the submerged coolant described in this invention is ≤-9 mm. 3 / min, rotating oxygen bomb lifetime ≥290 min, biodegradation rate ≥87%.

[0107] Comparing Comparative Example 1 with Example 1, it can be seen that the trimethylolpropane oleate in Comparative Example 1 was not modified, resulting in a decrease in the thermal conductivity of the immersion coolant, which could not meet the requirements of high-power thermal management.

[0108] Comparing Comparative Example 2 with Example 1, it can be seen that in Comparative Example 2, trimethylolpropane oleate was modified only by adding phosphorus pentasulfide, without the addition of imidazole. Therefore, it could not react with sulfur-containing groups to form an ionic liquid structure, resulting in a decrease in both thermal conductivity and insulation properties.

[0109] Comparing Comparative Example 3 with Example 1, it can be seen that in Comparative Example 3, trimethylolpropane oleate was directly mixed with the ionic liquid without in-situ reaction, resulting in poor compatibility between the ionic liquid and the synthesized ester, causing stratification and rendering it unusable.

[0110] As shown in Example 4, even with a slightly faster imidazole dropping rate, the product still maintained a kinematic viscosity of 30.2 mm at 40°C.2 / s, flash point 220℃, thermal conductivity 0.170 W / (m・K), lightning impulse breakdown voltage 60 kV, gas evolution tendency -27 mm 3 The rotating oxygen bomb had a lifespan of 310 min and a biodegradation rate of 91%, with overall performance close to the optimal level. Only the insulation and gas evolution performance fluctuated slightly, indicating that the process conditions still have good operability.

[0111] As shown in Example 5, when other types of stabilizers are used instead of T501, the kinematic viscosity of the product at 40°C is 31 mm. 2 / s, flash point 223℃, thermal conductivity 0.155 W / (m・K), lightning impulse breakdown voltage 62 kV, gas evolution tendency -33 mm 3 / min, rotating oxygen bomb life 305 min, biodegradation rate 88%, although the performance is slightly lower than Example 1, it is still significantly better than Comparative Examples 1-3, indicating that the type of stabilizer has a certain impact on the stability of the system. T501 is a better choice in this invention.

[0112] As shown in Example 6, when other types of imidazole are used instead of 1-methylimidazolium, the kinematic viscosity of the product at 40°C is 29.5 mm. 2 / s, flash point 224℃, thermal conductivity 0.166 W / (m・K), lightning impulse breakdown voltage 64 kV, gas evolution tendency -19 mm 3 The rotating oxygen bomb has a lifespan of 323 min and a biodegradation rate of 87%, while still maintaining its core advantages of high thermal conductivity, high insulation, and low gas evolution. Only the biodegradation rate has slightly decreased, indicating that the imidazole structure has a regulatory effect on the product performance. In this invention, 1-methylimidazolium is the optimal choice.

[0113] In summary, this invention, through in-situ modification of trimethylolpropane trioleate with phosphorus pentasulfide, introduces sulfur-containing active groups such as sulfides and polysulfides, followed by an in-situ reaction with 1-methylimidazole to generate a synthetic ester oil with an ionic liquid structure. This effectively solves the problems of poor compatibility and easy stratification between synthetic esters and ionic liquids, endowing the product with excellent properties such as high thermal conductivity, high insulation, low gas evolution, and long oxidation life. As shown in Examples 1-6, the kinematic viscosity of the synthetic ester oil described in this invention at 40°C is 28.9-32.5 mm. 2 / s, flash point 218~225℃, thermal conductivity 0.155~0.178 W / (m・K), lightning impulse breakdown voltage 60~73kV, the submerged coolant gas evolution tendency is -9~-33 mm 3The rotating oxygen bomb lifetime is 290-335 min, and the biodegradability rate is 87-94%, with overall performance significantly better than the comparative example. Examples 4-6 further verify that when the imidazole dropping rate is slightly faster and other types of stabilizers or imidazole are used, the product performance fluctuates slightly, but is still significantly better than the comparative example, indicating that the process conditions of the present invention have good operability, T501 is the optimal stabilizer, and 1-methylimidazolium is the optimal imidazole reactant. Comparative examples 1-3, on the other hand, confirm from the opposite perspective that the unmodified scheme, the scheme of only modifying P2S5 without reacting with imidazole, and the scheme of directly physically mixing ionic liquids cannot meet the requirements of high-power thermal management and insulation, further highlighting the innovation and superiority of the in-situ modification + in-situ reaction technology of the present invention. The synthetic ester oil and immersion coolant described in the present invention have multiple advantages such as high thermal conductivity, high insulation, low viscosity, high flash point, low gas evolution, long oxidation lifetime, and high biodegradability, which can effectively meet the needs of high-performance insulating media and thermal management materials in the fields of power capacitors and new energy vehicles, and have broad prospects for industrial application.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A synthetic ester oil, characterized in that, The raw material components include the following parts by weight: 60-85 parts of trimethylolpropane trioleate; 3-8 parts of phosphorus pentasulfide; 5-15 parts of imidazole; 0.5-2 parts of catalyst; 0.3-1 parts of stabilizer.

2. The synthetic ester oil according to claim 1, characterized in that, The imidazole includes at least one of 1-methylimidazol and 1-ethylimidazol; And / or, the stabilizer comprises at least one of 2,6-di-tert-butyl-p-methylphenol and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate isooctyl ester; And / or, the catalyst includes at least one of tetrabutylammonium bromide and triethylbenzylammonium chloride.

3. A method for preparing synthetic ester oil as described in claim 1 or 2, characterized in that, Includes the following steps: S1: Trimethylolpropane trioleate was added to the reactor and heated to 80-100℃. Phosphorus pentasulfide was added under inert gas protection and stirred at a speed of 300-500 rpm for 2-4 h to obtain a sulfur-modified intermediate. S2: Add a catalyst to the sulfur-containing modified intermediate, heat to 110~130℃, add imidazole dropwise, control the dropwise addition time to 1~2 h, and keep the reaction at the temperature for 3~5 h after the dropwise addition is completed to obtain the ionic liquid precursor. S3: Add a stabilizer to the ionic liquid precursor and stir at 80~90℃ for 1~2 h to obtain synthetic ester oil.

4. The method for preparing synthetic ester oils as described in claim 3, characterized in that, In step S1, phosphorus pentasulfide is added in 3 to 5 batches, with an interval of 30 to 60 minutes between each batch.

5. The method for preparing synthetic ester oils as described in claim 3, characterized in that, In step S2, the imidazole dropping rate is 0.5~1 mL / min.

6. The method for preparing synthetic ester oils as described in claim 3, characterized in that, In step S3, molecular distillation is used to purify and remove unreacted raw materials and low-boiling substances.

7. An immersion coolant, characterized in that, The components include the following parts by weight: 95-99.5 parts of the synthetic ester oil as described in any one of claims 1-2 or the synthetic ester oil prepared by the method described in any one of claims 3-6; 0.2-0.5 parts of antifoaming agent; and 0.1-0.3 parts of metal deactivating agent.

8. The immersion coolant as described in claim 7, characterized in that, The antifoaming agent includes polyether-modified silicone oil; the metal deactivator includes toluenetriazole derivatives.

9. A method for preparing an immersion coolant as described in claim 7 or 8, characterized in that, Includes the following steps: Synthetic ester oil, antifoaming agent, and metal deactivator are mixed and stirred at 50~60℃, with a stirring speed of 400~600 rpm and a stirring time of 30~45 min to obtain an immersion coolant.

10. The application of the immersion coolant as described in claim 7 or 8 in thermal management of battery energy storage systems and thermal management of data center servers.

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