A highly stable natural ester insulating oil, its preparation method and application

Abstract

This invention provides a highly stable natural ester insulating oil, its preparation method, and its application. The naturally stable natural ester insulating oil of this invention comprises the following components in parts by weight: 0.01-0.15 parts modified inorganic nanofiller, and 100 parts natural ester oil; wherein the modified inorganic nanofiller comprises the following reactants in parts by weight: 0.5-3 parts aminosilane coupling agent, 1-3 parts phospholipid organic compound, and 1 part inorganic nanofiller. This invention uses aminosilane coupling agent and phospholipid compound to modify the inorganic nanofiller, which can significantly improve the dispersion stability of the inorganic nanofiller in natural ester oil and extend the service life of the natural ester oil in transformers.

Description

Technical Field

[0001] This invention relates to the field of insulating materials technology, and in particular to a highly stable insulating oil, its preparation method, and its application. Background Technology

[0002] Insulating oil is an important insulating medium in transformers, playing roles such as heat dissipation, insulation, and arc extinguishing during transformer operation. The heat generated during transformer operation causes the insulating oil near the core and windings to expand and rise. Through convection between the upper and lower parts of the insulating oil, the heat is dissipated by conduction, ensuring the normal operation of the transformer.

[0003] Currently, mainstream transformer oils include traditional mineral insulating oil, natural ester insulating oil, and synthetic ester insulating oil. Among them, natural ester insulating oil has good application prospects due to its advantages such as environmental friendliness, low cost, and stable insulation performance. However, natural ester insulating oil has a higher kinematic viscosity and a slower flow rate compared to mineral oil, and its heat dissipation performance needs to be improved. Therefore, to improve the performance of natural ester insulating oil, an improvement technology has been developed that adds nanomaterials (usually nanoparticles) to it, aiming to enhance its thermal conductivity, electrical insulation, and other properties. This technology is developed to meet the requirements of power equipment, especially high-voltage electrical equipment such as transformers, to improve their heat dissipation and insulation performance.

[0004] However, the addition of nanofillers to transformer base oil has always posed a critical challenge to stability. Due to their extremely high surface activity, nanoparticles tend to settle and agglomerate after prolonged operation, leading to performance degradation. This is especially true for natural ester insulating oils, which have complex compositions and are prone to side reactions after prolonged operation at high temperatures, further affecting the dispersion stability of the nanofillers and consequently impacting the performance of the insulating oil and the operation of the transformer. Therefore, there is a need for a highly stable natural ester insulating oil with a long service life and excellent long-term stability. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing inorganic nanofiller-modified natural ester insulating oils, which require further improvement in stability, and to provide a highly stable natural ester insulating oil with long-term stability and service life. This invention uses aminosilane coupling agents and phospholipid compounds to modify inorganic nanofillers, which can significantly improve the dispersion stability of inorganic nanofillers in natural ester oil and extend the service life of natural ester oil in transformers.

[0006] Another object of the present invention is to provide a method for preparing the highly stable natural ester insulating oil.

[0007] Another object of the present invention is to provide the application of the highly stable natural ester insulating oil in transformers.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A highly stable natural ester insulating oil comprises the following components in parts by weight: 0.01-0.15 parts modified inorganic nanofiller, and 100 parts natural ester oil;

[0010] The modified inorganic nanofiller comprises the following parts by weight of reaction raw materials: 0.5-3 parts of aminosilane coupling agent, 1-3 parts of phospholipid organic compound, and 1 part of inorganic nanofiller.

[0011] This invention modifies inorganic nanofillers using aminosilane coupling agents and phospholipid compounds, significantly improving the dispersion stability of inorganic nanofillers in natural ester oils and extending the service life of natural ester oils in transformers. The hydroxyl groups on the surface of the inorganic nanofillers hydrolyze and condense with the alkoxy groups in the aminosilane coupling agent to obtain amino-modified inorganic nanofillers. Then, the phosphate groups in the phospholipid compounds interact with the amino groups to form phosphate acyl groups, achieving organic segment coating of the inorganic nanofillers and improving compatibility with natural ester oils. Simultaneously, the phosphate acyl groups have high activity, readily undergoing electron transitions and transfers under temperature. Under electrostatic effects, the organic segments easily interact with natural ester oils to form larger micelle particles, which are less prone to deposition, significantly improving the stability of natural ester oils and extending their service life in transformers.

[0012] Preferably, the phospholipid organic compound includes, but is not limited to, at least one of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphoglyceride (PG), and phosphatidylserine (PS).

[0013] Optionally, the aminosilane coupling agent includes, but is not limited to, at least one of 3-aminopropyltrimethoxysilane (APTES), 3-aminopropyltriethoxysilane (APTES-OEt3), 3-aminopropyltriisopropoxysilane (APTES-OiPr3), and 3-aminopropyltriacetoxysilane (APTES-Ac3).

[0014] Optionally, the inorganic nanofiller comprises metal oxides and / or metal nitrides. The metal oxides include, but are not limited to, at least one of Co3O4, Al2O3, Fe3O4, and SiO2. The metal nitrides include, but are not limited to, TiN.

[0015] The inorganic nanofiller is further preferably an inorganic nanosieve with a porous structure. Nanosieves have a higher specific surface area and higher surface activity, enabling them to adsorb more phospholipid organic compounds and further improve the dispersion stability of natural ester oils.

[0016] Preferably, the inorganic nanofiller has a D V50 =50-800nm, D V50 This refers to the particle size corresponding to when the cumulative volume of the inorganic nanofiller reaches 50%. A particle size within this range is beneficial for preparing natural ester oils with better dispersion stability.

[0017] Optionally, the natural ester oil includes, but is not limited to, at least one of FR3 soybean insulating oil, palm oil (PFAE), and rapeseed insulating oil.

[0018] Preferably, the modified inorganic nanofiller is prepared by a method comprising the following steps:

[0019] S1. According to the stated weight parts, the inorganic nanofiller and aminosilane coupling agent are dissolved in the first organic solvent and mixed evenly. The mixture is then reacted in a sealed environment at 45-90°C for 0.5-6 hours to obtain the amino-modified inorganic nanofiller.

[0020] S2. After mixing the phospholipid compound with the amino-modified inorganic nanofiller obtained in step S1, react at 25-60℃ for 6-12 hours, and then purify to obtain the modified inorganic nanofiller.

[0021] The preparation method of the highly stable natural ester insulating oil includes the following steps:

[0022] S1. Preparation of modified inorganic nanofillers

[0023] S11. According to the stated weight parts, the inorganic nanofiller and aminosilane coupling agent are dissolved in the first organic solvent and mixed evenly. The mixture is then reacted in a sealed environment at 45-90°C for 0.5-6 hours to obtain the amino-modified inorganic nanofiller.

[0024] S12. Dissolve the phospholipid compound and the amino-modified inorganic nanofiller obtained in step S1 in a second organic solvent, mix them evenly, and react them at 25-60℃ for 6-12 hours under an inert atmosphere. After purification, the modified inorganic nanofiller can be obtained.

[0025] S2. Preparation of highly stable natural ester insulating oil

[0026] The modified inorganic nanofiller and natural ester oil are mixed evenly according to the stated weight proportions to obtain the highly stable natural ester insulating oil.

[0027] The hydroxyl groups on the surface of the inorganic nanofiller undergo hydrolytic condensation with the alkoxy groups in the aminosilane coupling agent to obtain amino-modified inorganic nanofillers. Then, the phosphate groups in the phospholipid compound interact with the amino groups to form phosphate acyl groups, achieving the coating modification of the inorganic nanofiller by organic segments. The modified inorganic nanofiller can be uniformly and stably dispersed in natural ester oils.

[0028] Preferably, in step S1, the first organic solvent and the second organic solvent can be the same or different, and independently include at least one of methanol, ethanol, acetone, ethylene glycol, dimethyl sulfoxide, and ammonia.

[0029] Preferably, the first organic solvent is ethanol; the second organic solvent is a mixed organic solvent obtained by mixing ammonia and methanol in a volume ratio of (9-9.5):1.

[0030] Preferably, in step S11, the mixture obtained by dissolving the inorganic nanofiller and the aminosilane coupling agent in the first organic solvent and mixing them evenly is referred to as the first suspension, and the solid content in the first suspension is (10-35) wt%.

[0031] Preferably, after the reaction in step S11 is complete, centrifugation is required to separate the solid product, amino-modified inorganic nanofiller. Then, it is washed with water or a first organic solvent to remove unreacted reactants and byproducts. After washing and drying, the amino-modified inorganic nanofiller can be obtained.

[0032] Preferably, in step S12, the mixture obtained by the phospholipid compound, the amino-modified inorganic nanofiller, and the second organic solvent is referred to as the second suspension, and the solid content in the second suspension is (5-35) wt%. To further improve the mixing uniformity, in step S12, the reaction raw materials (phospholipid compound and amino-modified inorganic nanofiller) can be dissolved separately in the second organic solvent, and then the organic solvents in which the two reaction raw materials are dissolved can be mixed together to obtain the second suspension.

[0033] Preferably, after the reaction in step S12 is complete, centrifugation is required to separate the solid product, and then washing with water or a second organic solvent is required to remove unreacted reactants and byproducts. After washing and drying, the modified inorganic nanofiller can be obtained.

[0034] Conventional mixing methods in this field can be used in this invention, including but not limited to stirring, shaking, and ultrasonication. In this invention, ultrasonication is preferred to improve mixing efficiency.

[0035] Optionally, the inert atmosphere is an atmosphere formed by at least one gas selected from nitrogen, argon, and helium.

[0036] This invention also protects the application of the above-mentioned highly stable natural ester insulating oil in transformers.

[0037] Compared with the prior art, the beneficial effects of the present invention are:

[0038] This invention modifies inorganic nanofillers using aminosilane coupling agents and phospholipid compounds, which can significantly improve the dispersion stability of inorganic nanofillers in natural ester oil and extend the service life of natural ester oil in transformers. Detailed Implementation

[0039] To better illustrate the purpose, technical solution, and advantages of this invention, specific embodiments will be used to further describe the invention below. However, these embodiments do not limit the invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, all reagents and materials used in this invention are commercially available.

[0040] Modified inorganic nanofillers were prepared according to a method comprising the following steps:

[0041] S1. According to the formulas in Tables 1 and 2, the inorganic nanofiller (inorganic nanosieves with porous structures were selected in the embodiments of the present invention) and aminosilane coupling agent were dissolved in anhydrous ethanol, stirred and mixed evenly to obtain a first suspension with a solid content of 30wt%, heated to 50°C and reacted in a closed container for 2.5h. After the reaction was completed, the product was centrifuged using a high-speed centrifuge, and the solid obtained by centrifugation was washed with deionized water and anhydrous ethanol. The washed solid was placed in a vacuum drying oven and vacuum dried at 60°C for 24h to obtain amino-modified inorganic nanofiller.

[0042] S2. Dissolve phospholipid compounds in ammonia / methanol (V 氨水 V 甲醇 Suspension A is formed in a 9:1 mixture of solvents. The amino-modified inorganic nanofillers obtained in step S1 are dissolved in ammonia / methanol (V / V) solution. 氨水 V 甲醇 Suspension B was formed in a 9:1 mixture of solvents. Then, under an argon atmosphere, the suspension was added dropwise to a continuously stirred suspension A to obtain a second suspension with a solid content of 30 wt%. The suspension was heated and stirred in a water bath at 40 °C for 2 h. After heating, the mixture was centrifuged and the solid obtained by centrifugation was washed with deionized water and anhydrous ethanol. The washed solid was placed in a vacuum drying oven and vacuum dried at 60 °C for 24 h to obtain the modified inorganic nanofiller.

[0043] It should be noted that the particle size of the inorganic nanosieve in the embodiments of the present invention was obtained by particle size distribution testing.

[0044] Table 1. Formulations (parts by weight) of modified inorganic nanofillers

[0045]

[0046] Table 2. Formulations (parts by weight) of modified inorganic nanofillers

[0047]

[0048]

[0049] Examples 1-15, Comparative Examples 1-4:

[0050] A series of natural ester insulating oils are provided, prepared by a method comprising the following steps:

[0051] 0.15 parts (by weight) of the modified inorganic nanofiller prepared above were added to 100 parts (by weight) of FR3 soybean insulating oil and ultrasonically mixed evenly (about 1 hour). After oscillation, the oil sample was placed in a vacuum drying oven and vacuum dried at 90°C for 48 hours to obtain natural ester insulating oil.

[0052] It should be noted that the natural ester insulating oils in Examples 1-15 were prepared using modified inorganic nanofillers numbered 1#-15# respectively. For example, the filler in the natural ester insulating oil of Example 1 was modified inorganic nanofiller #1; the filler in the natural ester insulating oil of Example 2 was modified inorganic nanofiller #2... and the filler in the natural ester insulating oil of Example 15 was modified inorganic nanofiller #15.

[0053] Similarly, the modified inorganic nanofillers added to the natural ester insulating oils of Comparative Examples 1-4 are numbered D1, D2, D3, and D4, respectively.

[0054] Example 16

[0055] A highly stable natural ester insulating oil is provided, which is prepared by a method comprising the following steps:

[0056] 0.10 parts (by weight) of No. 1 modified inorganic nanofiller were added to 100 parts (by weight) of FR3 soybean insulating oil and ultrasonically mixed evenly (about 1 hour). After oscillation, the oil sample was placed in a vacuum drying oven and vacuum dried at 90°C for 48 hours to obtain natural ester insulating oil.

[0057] Example 17

[0058] A highly stable natural ester insulating oil is provided, which is prepared by a method comprising the following steps:

[0059] 0.05 parts (by weight) of No. 1 modified inorganic nanofiller were added to 100 parts (by weight) of FR3 soybean insulating oil and ultrasonically mixed evenly (about 1 hour). After oscillation, the oil sample was placed in a vacuum drying oven and vacuum dried at 90°C for 48 hours to obtain natural ester insulating oil.

[0060] Example 18

[0061] A highly stable natural ester insulating oil is provided, which is prepared by a method comprising the following steps:

[0062] 0.01 parts (by weight) of No. 1 modified inorganic nanofiller were added to 100 parts (by weight) of FR3 soybean insulating oil and ultrasonically mixed evenly (about 1 hour). After oscillation, the oil sample was placed in a vacuum drying oven and vacuum dried at 90°C for 48 hours to obtain natural ester insulating oil.

[0063] Comparative Example 5

[0064] A natural ester insulating oil is provided, prepared by a method comprising the following steps:

[0065] 0.15 parts (by weight) of unmodified inorganic nanosieve Co3O4-1 were added to 100 parts (by weight) of FR3 soybean insulating oil and ultrasonically mixed evenly (about 1 hour). After oscillation, the oil sample was placed in a vacuum drying oven and vacuum dried at 90°C for 48 hours to obtain natural ester insulating oil.

[0066] Performance testing

[0067] The properties of the natural ester insulating oils obtained in the above embodiments and comparative examples were characterized. The specific test items, test methods, and results are as follows:

[0068] The zeta potential (in mV) of natural ester insulating oil after standing at 120℃ for 7 days and 30 days was tested using a NanoBrook Omni nanoparticle size analyzer and a zeta potential analyzer to characterize the stability of the oil samples. The higher the potential, the higher the stability. The test results are shown in Table 3.

[0069] Table 3

[0070]

[0071]

[0072] The results above show that:

[0073] The natural ester insulating oil prepared by this invention has excellent stability.

[0074] The results of Comparative Examples 1-5 show that modifying inorganic nanofillers with the specific coupling agents and phospholipid compounds of this invention can significantly improve the stability of natural ester insulating oil and extend its service life in transformers.

[0075] 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 highly stable natural ester insulating oil, characterized in that, It includes the following components in parts by weight: 0.01-0.15 parts modified inorganic nanofiller, 100 parts natural ester oil; The modified inorganic nanofiller comprises the following parts by weight of reaction raw materials: 0.5-3 parts of aminosilane coupling agent, 1-3 parts of phospholipid organic compound, and 1 part of inorganic nanofiller. The inorganic nanofiller includes metal oxides and / or TiN; the metal oxide includes at least one of Co3O4, Al2O3, Fe3O4, and SiO2. The phospholipid organic compounds include at least one of phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, glyceryl phosphate, and phosphatidylserine; The modified inorganic nanofiller was prepared by a method comprising the following steps: S1. According to the stated weight parts, the inorganic nanofiller and aminosilane coupling agent are dissolved in the first organic solvent and mixed evenly. The mixture is then reacted in a sealed environment at 45-90°C for 0.5-6 hours to obtain the amino-modified inorganic nanofiller. S2. After mixing the phospholipid organic compound with the amino-modified inorganic nanofiller obtained in step S1 evenly, react it in an inert atmosphere at 25-60℃ for 6-12 hours. After purification, the modified inorganic nanofiller can be obtained. The phosphate group in the phospholipid organic compound forms a phosphate acyl group with the amino group in the aminosilane coupling agent.

2. The highly stable natural ester insulating oil according to claim 1, characterized in that, The aminosilane coupling agent includes at least one of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltriisopropoxysilane, and 3-aminopropyltriacetoxysilane.

3. The highly stable natural ester insulating oil according to claim 1, characterized in that, The inorganic nanofiller D V50 =50-800nm, D V50 This refers to the particle size corresponding to when the cumulative volume of the inorganic nanofiller reaches 50%.

4. The highly stable natural ester insulating oil according to claim 1, characterized in that, The natural ester oil includes at least one of FR3 soybean insulating oil, palm oil, and rapeseed insulating oil.

5. The method for preparing the highly stable natural ester insulating oil according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Preparation of modified inorganic nanofillers S11. According to the stated weight parts, the inorganic nanofiller and aminosilane coupling agent are dissolved in the first organic solvent and mixed evenly. The mixture is then reacted in a sealed environment at 45-90°C for 0.5-6 hours to obtain the amino-modified inorganic nanofiller. S12. Dissolve the phospholipid organic compound and the amino-modified inorganic nanofiller obtained in step S1 in a second organic solvent, mix them evenly, react at 25-60℃ for 6-12 hours, and then purify to obtain the modified inorganic nanofiller. S2. Preparation of highly stable natural ester insulating oil The modified inorganic nanofiller and natural ester oil are mixed evenly according to the stated weight proportions to obtain the highly stable natural ester insulating oil.

6. The preparation method according to claim 5, characterized in that, The first organic solvent and the second organic solvent independently include at least one of methanol, ethanol, acetone, ethylene glycol, dimethyl sulfoxide, and ammonia.

7. The application of the highly stable natural ester insulating oil according to any one of claims 1-4 in transformers.

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