Modified insulating oil with high insulation and self-repairing functions and preparation method thereof

Abstract

This invention discloses a modified insulating oil with both high insulation and self-healing functions, comprising an insulating oil matrix and microcapsule particles dispersed in the insulating oil matrix; the amount of microcapsule particles added is 0.1-1 wt% of the mass of the insulating oil matrix; the microcapsule particles comprise a composite core material and a composite shell layer covering the composite core material. This invention can improve the service life of liquid cooling materials.

Description

Technical Field

[0001] This invention relates to the field of liquid cooling materials technology, and in particular to a modified insulating oil that combines high insulation and self-healing functions. Background Technology

[0002] In the context of the current development of power systems and data centers towards higher voltage and higher power density, insulating oil, as a key insulating medium, continuously endures the combined effects of multiple stresses, including electrical, thermal, and chemical stresses, during long-term operation. This makes it prone to aging, partial discharge, and arcing faults, leading to a decrease in breakdown voltage, degradation of insulation performance, and even the risk of fire. Currently, to improve the performance of insulating oil, the common method is to directly add antioxidants for modification. However, this method has significant limitations: on the one hand, the uniform dispersion of additives in the oil may affect the intrinsic insulation properties and cooling efficiency of the insulating oil; on the other hand, traditional methods lack a fault-triggered release mechanism, making it impossible to achieve targeted release and active repair of the repair agent after a local fault occurs. Therefore, it is difficult to simultaneously ensure the long-term stability of insulation performance and rapid self-recovery after a fault. Summary of the Invention

[0003] This invention provides a modified insulating oil that combines high insulation and self-healing functions, which can improve the service life of liquid cooling materials.

[0004] To address the aforementioned technical problems, this invention provides a modified insulating oil with both high insulation and self-healing functions, comprising an insulating oil matrix and microcapsule particles dispersed in the insulating oil matrix; the amount of microcapsule particles added is 0.1-1 wt% of the mass of the insulating oil matrix; the microcapsule particles comprise a composite core material and a composite shell layer covering the composite core material.

[0005] As a preferred embodiment of the above technical solution, the insulating oil base is one or a mixture of mineral oil, silicone oil, hydrocarbon oil, and natural ester.

[0006] As a preferred embodiment of the above technical solution, the composite core material comprises 60-75 wt% core material base liquid, 5-10 wt% borate, 5-10 wt% antioxidant and 5-10 wt% aluminosilicate crystals.

[0007] As a preferred embodiment of the above technical solution, the core material base liquid is octadecane, and the antioxidant is 2,6-di-tert-butyl-p-cresol.

[0008] As a preferred embodiment of the above technical solution, the composite shell includes a matrix and aluminum nitride (Al2O3) nanoparticles modified with silane coupling agent (KH-550), wherein the mass of the aluminum nitride (Al2O3) nanoparticles modified with silane coupling agent (KH-550) is 10-15 wt% of the matrix mass.

[0009] As a preferred embodiment of the above technical solution, the matrix is ​​urea-formaldehyde resin.

[0010] Another aspect of the present invention provides a method for preparing a modified insulating oil that combines high insulation and self-healing functions, comprising the following steps: Step S1. Prepare the composite core material; Step S2. Prepare the composite shell; Step S3. Prepare microcapsule particles; Step S4. Modification of insulating oil.

[0011] As a preferred embodiment of the above technical solution, step S1, preparing the composite core material, includes: weighing octadecane, borate, antioxidant, and aluminosilicate crystals, and adding the above raw materials together into a reaction vessel equipped with a reflux condenser and containing 150-250 mL of n-hexane, ensuring good system sealing to effectively condense and reflux the volatilized n-hexane solvent. The reaction is carried out in a water bath at 50-60℃ and under mechanical stirring at 800-1200 rpm for 1-2 hours. Subsequently, ultrasonic treatment is performed at a power of 250-350 W for 10-30 minutes. During this period, inert gases such as nitrogen are introduced for protection. Finally, the solvent is removed by rotary evaporation to obtain a solid composite core material mixture.

[0012] As a preferred embodiment of the above technical solution, step S2, preparing the composite shell, includes: dispersing 8-12 g of α-Al2O3 nanoparticles with a particle size of 30-50 nm in a mixed solvent of 90 mL ethanol and 10 mL deionized water, then adding 0.1-0.2 g of KH-550, and refluxing at 70 °C for 2 hours. After centrifugation, washing with ethanol, and vacuum drying at 80 °C for 4 hours, modified alumina is obtained, ground, sieved, and sealed for storage; reacting urea and 37% formaldehyde aqueous solution with a molar ratio of 1:2.0 at pH=8.3 and 80 °C for 90 minutes to generate urea-formaldehyde resin prepolymer, and cooling to room temperature; before microcapsule encapsulation, adding 8-10% (by weight of the resin solids) of modified alumina to the prepolymer, and dispersing at high speed at 5000-8000 rpm for 5-10 min to obtain the shell deposition solution.

[0013] As a preferred embodiment of the above technical solution, step S3, preparing microcapsule particles, includes: coating a composite shell prepolymer onto the surface of a composite core material emulsion using in-situ polymerization at pH 2.5-4.0 and a temperature of 45-60℃; obtaining microcapsule particles after curing and surface hydrophobic coating treatment; dispersing 4-6 g of composite core material in an aqueous phase containing 0.5-1.5% polyvinyl alcohol (PVA) at 35℃ and shearing at 8000-12000 rpm for 8-15 minutes to form an O / W emulsion; adding the shell prepolymer dropwise to the emulsion at pH 2.5-4.0 and a temperature of 25-45℃, and reacting for 2-4 hours to complete the coating; centrifuging and washing the microcapsules, coating the surface with a PVA solution (35-45℃, 1-3 hours), and finally vacuum drying at 55-65℃ for 20-28 hours to obtain a particle size of 5-20 mm. The product consists of microcapsules of μm size; step S4. Modification of insulating oil includes dispersing the microcapsules in insulating oil at an addition amount of 0.1-1 wt%, followed by low-speed stirring and vacuum drying to degas the oil, thereby obtaining the final product.

[0014] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0015] Figure 1 The SEM image shows the particle size of the urea-formaldehyde resin shell microcapsules containing nanoparticles in an embodiment of the present invention.

[0016] Figure 2 The FT-IR spectra of the microcapsules and octadecane in an embodiment of the present invention are shown. Detailed Implementation

[0017] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0018] Example: A modified insulating oil with both high insulation and self-healing functions, comprising the following components: 99.5 wt% insulating oil and 0.5 wt% microcapsule particles. The insulating oil is a mixture of PAO synthetic oil, GTL synthetic oil, synthetic ester, and silicone oil, with mass fractions of 40 wt%, 30 wt%, 20 wt%, and 10 wt%, respectively. The core material of the microcapsule particles is octadecane, borate, T501, and aluminosilicate crystals in a mass ratio of 7:1:1. The shell material of the microcapsule particles is urea-formaldehyde resin, which contains 12 wt% Al2O3 nanoparticles modified by KH-550.

[0019] The detailed preparation process of this modified insulating oil, which combines high insulation and self-healing functions, is as follows: S1. Preparation of multifunctional composite core material: using octadecane (70 wt%) as the core material base liquid, borate (10 wt%), antioxidant T501 (2,6-di-tert-butyl-p-cresol, 10 wt%) and aluminosilicate crystals (10 wt%) are uniformly separated to form a composite core material.

[0020] Preparation of composite core material Weigh out 70 g of octadecane (core material base liquid), 10 g of borate (passivating agent), 10 g of T501 (antioxidant), and 10 g of aluminosilicate crystals (particle size 1-5 μm) (dehydrating agent).

[0021] The above raw materials were added together into a reaction vessel equipped with a reflux condenser and containing 200 mL of n-hexane, ensuring good system sealing to effectively condense and reflux the volatilized n-hexane solvent. The reaction was carried out for 1.5 hours in a 55°C water bath with mechanical stirring at 1000 rpm. Subsequently, ultrasonic treatment was performed at 300 W for 20 minutes. During this period, inert gases such as nitrogen were introduced for protection. Finally, the solvent was removed by rotary evaporation to obtain a solid composite core material mixture.

[0022] S2. Preparation of composite shell prepolymer: Using urea-formaldehyde resin as the matrix, aluminum nitride (Al2O3) nanoparticles modified with silane coupling agent (KH-550) are added at an amount of 12wt% of the solid mass of urea-formaldehyde resin to form a high thermal conductivity and high strength organic-inorganic composite shell.

[0023] 10 g of α-Al₂O₃ nanoparticles with a particle size of 30-50 nm were dispersed in a mixed solvent of 90 mL ethanol and 10 mL deionized water, followed by the addition of 0.15 g of KH-550. The mixture was refluxed at 70 °C for 2 hours. After centrifugation, washing with ethanol, and vacuum drying at 80 °C for 4 hours, modified alumina was obtained, ground, sieved, and stored in a sealed container.

[0024] Urea and 37% formaldehyde aqueous solution with a molar ratio of 1:2.0 were reacted at pH=8.3 and 80℃ for 90 minutes to generate urea-formaldehyde resin prepolymer, which was then cooled to room temperature.

[0025] Before microcapsule encapsulation, modified alumina, accounting for 9% of the resin solids mass, was added to the prepolymer and dispersed at high speed at 7000 rpm for 8 min to obtain the shell deposition solution.

[0026] S3. Preparation of microcapsules: The composite shell prepolymer was coated onto the surface of the composite core material emulsion by in-situ polymerization at pH=3.0 and temperature 55℃. After curing and surface hydrophobic coating treatment, microcapsule particles were obtained.

[0027] Emulsification and Coating: 5 g of composite core material was dispersed in an aqueous phase containing 1% polyvinyl alcohol (PVA) at 35°C and sheared at 10,000 rpm for 12 minutes to form an O / W emulsion. At pH 3.0 and 35°C, the shell prepolymer was added dropwise to the emulsion, and the reaction was allowed to proceed for 3 hours to complete the coating process.

[0028] Post-processing: After centrifugation and washing with water, the microcapsules are coated with PVA solution (35-45℃, 1-3 hours), and finally vacuum dried at 60℃ for 24 hours to obtain microcapsule products with a particle size of 5-20 μm.

[0029] S4. Modification of insulating oil: The microcapsules are dispersed at an addition amount of 0.5 wt% in mineral oil, silicone oil, hydrocarbon oil, natural ester or any combination of mixed insulating oils, and then degassed by low-speed stirring and vacuum drying to obtain the final product.

[0030] The microcapsules were dispersed in a single insulating oil or a mixture of insulating oils in any proportion at an addition amount of 0.5 wt%, and mechanically stirred at 150 r / min for 2 hours.

[0031] The sample was treated for 28 hours at a vacuum of -0.09 to -0.1 MPa and a temperature of 80°C.

[0032] The modified insulating oil prepared in the above embodiments has the following physical properties compared with ordinary mixed oil, as shown in Table 1 below.

[0033] By inducing localized damage in the oil sample under high pressure, the release and targeted repair effects of ordinary mixed oil and the microcapsule-containing example were observed. The results are shown in Table 2.

[0034] like Figure 1As shown in the test, the SEM image of the prepared microcapsules shows that the overall morphology of the microcapsules is well spherical, most of them are full in shape, without obvious damage, and have nanoparticles on the surface. The particle size distribution is relatively uniform, with a size of about 9 μm.

[0035] like Figure 2 The image shows the infrared spectrum of the microcapsule and its core material containing octadecane, where the characteristic absorption peak of octadecane is at 2921 cm⁻¹. -1 2850cm -1 and 1466cm -1 2921cm -1 and 2850cm -1 It is a tensile vibration of -CH2 and -CH3, 1466 cm. -1 It is a -CH2 deformation vibration. Meanwhile, the characteristic absorption peak of silicon dioxide is at 3433 cm⁻¹. -1 1083cm -1 and 799cm -1 At 1083cm -1 and 799cm -1 The absorption peaks are caused by the asymmetric and symmetrical stretching vibrational bands of Si-O-Si. Characteristic absorption peaks of octadecane and silicon dioxide can be clearly observed in the infrared spectrum of the microcapsules.

[0036] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0038] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A modified insulating oil possessing both high insulation and self-healing functions, characterized in that, It includes an insulating oil matrix and microcapsule particles dispersed in the insulating oil matrix; the amount of microcapsule particles added is 0.1-1 wt% of the mass of the insulating oil matrix; the microcapsule particles include a composite core material and a composite shell layer covering the composite core material.

2. The modified insulating oil with both high insulation and self-healing functions according to claim 1, characterized in that, The insulating oil base is one or a mixture of mineral oil, silicone oil, hydrocarbon oil, and natural ester.

3. The modified insulating oil with both high insulation and self-healing functions according to claim 1, characterized in that, The composite core material comprises 60-75 wt% core material base liquid, 5-10 wt% borate, 5-10 wt% antioxidant, and 5-10 wt% aluminosilicate crystals.

4. The modified insulating oil with both high insulation and self-healing functions according to claim 3, characterized in that, The core material base liquid is octadecane, and the antioxidant is 2,6-di-tert-butyl-p-cresol.

5. The modified insulating oil with both high insulation and self-healing functions according to claim 1, characterized in that, The composite shell comprises a matrix and aluminum nitride (Al2O3) nanoparticles modified with silane coupling agent (KH-550), wherein the mass of the aluminum nitride (Al2O3) nanoparticles modified with silane coupling agent (KH-550) is 10-15 wt% of the matrix mass.

6. The modified insulating oil with both high insulation and self-healing functions according to claim 5, characterized in that, The matrix is ​​urea-formaldehyde resin.

7. The method for preparing the modified insulating oil with both high insulation and self-healing functions as described in any one of claims 1-6, characterized in that, Includes the following steps: Step S1. Prepare the composite core material; Step S2. Prepare the composite shell; Step S3. Prepare microcapsule particles; Step S4. Modification of insulating oil.

8. The preparation method according to claim 7, characterized in that, Step S1, preparing the composite core material, includes: weighing octadecane, borate, antioxidant, and aluminosilicate crystals, and adding the above raw materials together into a reaction vessel equipped with a reflux condenser and containing 150-250 mL of n-hexane, ensuring good system sealing to effectively condense and reflux the volatilized n-hexane solvent. The reaction is carried out in a water bath at 50-60℃ with mechanical stirring at 800-1200 rpm for 1-2 hours. Subsequently, ultrasonic treatment is performed at 250-350 W for 10-30 minutes. During this period, inert gases such as nitrogen are introduced for protection. Finally, the solvent is removed by rotary evaporation to obtain a solid composite core material mixture.

9. The preparation method according to claim 8, characterized in that, Step S2, preparing the composite shell, includes: dispersing 8-12 g of α-Al₂O₃ nanoparticles with a particle size of 30-50 nm in a mixed solvent of 90 mL ethanol and 10 mL deionized water, then adding 0.1-0.2 g of KH-550, and refluxing at 70 °C for 2 hours. After centrifugation, washing with ethanol, and vacuum drying at 80 °C for 4 hours, modified alumina is obtained, ground, sieved, and sealed for storage; reacting urea and 37% formaldehyde aqueous solution at a molar ratio of 1:2.0 at pH=8.3 and 80 °C for 90 minutes to generate urea-formaldehyde resin prepolymer, and cooling to room temperature; before microcapsule encapsulation, adding 8-10% (by weight of the resin solids) of modified alumina to the prepolymer, and dispersing at high speed at 5000-8000 rpm for 5-10 min to obtain the shell deposition solution.

10. The preparation method according to claim 9, characterized in that, Step S3, preparing microcapsule particles, includes: using in-situ polymerization, under conditions of pH 2.5-4.0 and temperature 45-60℃, coating a composite shell prepolymer onto the surface of a composite core material emulsion, followed by curing and surface hydrophobic coating treatment to obtain microcapsule particles; dispersing 4-6 g of composite core material in an aqueous phase containing 0.5-1.5% polyvinyl alcohol (PVA) at 35℃, and shearing at 8000-12000 rpm for 8-15 minutes to form an O / W emulsion; adding the shell prepolymer dropwise to the emulsion at pH 2.5-4.0 and temperature 25-45℃, reacting for 2-4 hours to complete the coating; centrifuging and washing the microcapsules, then surface coating with a PVA solution (35-45℃, 1-3 hours), and finally vacuum drying at 55-65℃ for 20-28 hours to obtain particles with a diameter of 5-20 mm. The product consists of microcapsules of μm size; step S4. Modification of insulating oil includes dispersing the microcapsules in insulating oil at an addition amount of 0.1-1 wt%, followed by low-speed stirring and vacuum drying to degas the oil, thereby obtaining the final product.

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