Insulating oil containing vegetable oil as well as preparation method and application of insulating oil

Abstract

The invention discloses insulating oil containing vegetable oil as well as a preparation method and application thereof, belongs to the technical field of lubricating oil, and aims at solving the problems that vegetable oil type insulating oil in the prior art is easy to solidify at low temperature, and the anti-oxidation stability and the flame retardance need to be further improved. The preparation method of the insulating oil containing the vegetable oil comprises the following steps: uniformly mixing dimethyl 2-(4-aminophenyl) malonate and 4-(1-ethoxyl)-2, 6-dimethoxyphenol in an inert gas atmosphere, adding dibutyltin dilaurate, stirring, heating and reacting to obtain modified sterically hindered phenol; mixing N, N-dimethylformamide, the modified sterically hindered phenol and di-tert-butyl chloromethyl phosphate, adding triethylamine, carrying out heating reflux, and after the reaction is finished, washing and drying to obtain a modified antioxidant; the vegetable oil-containing insulating oil prepared by the invention has environmental protection property, oxidation resistance and certain flame retardancy, and is not easy to solidify at low temperature, so that the application range of the insulating oil is expanded, and stricter application requirements are met.

Description

Technical Field

[0001] The present invention relates to the technical field of lubricating oils, and particularly relates to an insulating oil containing vegetable oil, a preparation method thereof, and an application thereof. Background Art

[0002] Insulating oil belongs to a kind of lubricating oil, and is usually prepared by adding additives such as antioxidants to deeply refined lubricating oil base oil, and is often used as an important liquid insulating material. Insulating oils can be classified into: mineral oil-based insulating oils, vegetable oil-based insulating oils, and synthetic oil-based insulating oils according to raw materials. Mineral insulating oil mainly comes from the refining process of natural petroleum, has good electrical insulation properties and cooling efficiency, and has relatively low cost. Vegetable oil insulating oil belongs to renewable resources. Compared with traditional mineral insulating oil, one of the greatest advantages is its excellent biodegradability. In the natural environment, vegetable oil insulating oil can be decomposed by microorganisms, reducing pollution to soil and water bodies.

[0003] Chinese Patent CN101619254A discloses a hybrid insulating oil, which is obtained by mixing 15 - 25% of vegetable oil with 75 - 85% of mineral insulating oil and adding 0.2 - 0.5% of antioxidant. However, the flash point of this insulating oil is about 145°C, which limits its application in places with high fire protection performance. Chinese Patent CN102682869A discloses a vegetable insulating oil and a preparation method thereof. The refined vegetable oil reacts with low molecular weight alcohol under the action of a catalyst, and then impurities are removed, and antioxidants and pour point depressants are added and mixed evenly to obtain the vegetable insulating oil. However, the insulating oil prepared by this invention has the problem of being easily solidified at low temperatures, and its scope of application is limited. Chinese Patent CN101438356B discloses a plant-based electrical insulating oil and its preparation. The plant-based electrical insulating oil is obtained by esterifying a vegetable oil mixture of 40 - 50 parts by weight of soybean oil and 50 - 60 parts by weight of rapeseed oil with ethanol in the presence of a silicoaluminate catalyst. However, the oxidation stability of the plant-based electrical insulating oil is relatively poor. Under the action of high temperature and oxygen, polyunsaturated fatty acids in soybean oil and rapeseed oil are prone to oxidation, resulting in phenomena such as an increase in acid value, color change, and odor change during the long-term use of the insulating oil, ultimately affecting the electrical insulation performance and the safety of equipment. With the rapid development of national power equipment, people have a greater need for insulating oil, and in the situation of the increasingly short supply of petroleum resources, the demand for vegetable oil-based insulating oils has increased.

[0004] In summary, it is of great practical significance and value to develop a vegetable oil-based insulating oil that is not easily solidified at low temperatures, is flame-retardant, and has good antioxidant stability. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides an insulating oil containing vegetable oil, a preparation method thereof, and an application thereof.

[0006] To achieve the above object, the present invention provides a preparation method of an insulating oil containing vegetable oil, comprising the following steps:

[0007] Mix the refined vegetable oil and alcohol, add a catalyst, heat and react to obtain Intermediate I; subject Intermediate I to vacuum distillation, decolorization and acid reduction to obtain Intermediate II; mix Intermediate II, a modified antioxidant and a pour point depressant, stir, ultrasonicate, stand, and take the upper layer oil sample to obtain the insulating oil containing vegetable oil;

[0008] Among them, the preparation method of the modified antioxidant comprises the following steps:

[0009] Step (1) In an inert gas atmosphere, uniformly mix dimethyl 2-(4-aminophenyl)malonate and 4-(1-hydroxyethyl)-2,6-dimethoxyphenol, add dibutyltin dilaurate, stir, heat and react. After the reaction is completed, perform rotary evaporation to obtain a modified sterically hindered phenol;

[0010] Step (2) Mix N,N-dimethylformamide, the modified sterically hindered phenol and di-tert-butyl chloromethyl phosphate, add triethylamine, heat under reflux, and after the reaction is completed, wash and dry to obtain the modified antioxidant.

[0011] Preferably, the pour point depressant is ethylene-vinyl acetate copolymer or polymethacrylate copolymer.

[0012] Preferably, the mass ratio of Intermediate II, the modified antioxidant and the pour point depressant is 100:(0.2 - 0.4):(0.2 - 0.4).

[0013] Preferably, the acid reducing agent is any one of silica gel and ethanolamine.

[0014] Preferably, the decolorizing agent is activated carbon.

[0015] Preferably, the vegetable oil is any one of soybean oil, peanut oil, cottonseed oil, palm oil and coconut oil.

[0016] Preferably, the alcohol is an aliphatic straight-chain alcohol or a composition with a carbon content of 8 - 16.

[0017] Preferably, the catalyst is one of sodium hydroxide, potassium hydroxide, sodium methoxide or a composition of two or more of them.

[0018] Preferably, the mass ratio of the vegetable oil, the alcohol and the catalyst is (25 - 45):(100 - 200):(0.5 - 0.9); the reaction temperature is 60 - 100 °C, and the reaction time is 1 - 5 h.

[0019] Preferably, in the vacuum distillation, the pressure is 0.5 - 10 mmHg, the temperature is 80 - 100 °C, and the time is 50 - 120 min.

[0020] Preferably, the mass ratio of dimethyl 2-(4-aminophenyl)malonate, 4-(1-hydroxyethyl)-2,6-dimethoxyphenol and dibutyltin dilaurate is (240 - 280):(140 - 180):(5 - 9); the reaction temperature is 130 - 150 °C, and the reaction time is 3 - 5 h.

[0021] Preferably, the mass ratio of N,N-dimethylformamide, modified hindered phenol, di-tert-butyl chloromethyl phosphate and triethylamine is (2000 - 4000):(500 - 700):(200 - 240):(2 - 4); the reaction temperature is 140 - 150 °C, and the reaction time is 6 - 10 h.

[0022] Preferably, the insulating oil containing vegetable oil is prepared by the preparation method of the insulating oil containing vegetable oil described above.

[0023] Preferably, the application of the insulating oil containing vegetable oil in insulation in power equipment.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. In the present invention, 4-(1-hydroxyethyl)-2,6-dimethoxyphenol has certain antioxidant properties. By connecting it to dimethyl 2-(4-aminophenyl)malonate through an ester exchange reaction, there is a synergistic effect between the hindered phenol compound and dimethyl 2-(4-aminophenyl)malonate, improving the antioxidant effect. And the amino group contained in the modified hindered phenol can react with the chloro group in di-tert-butyl chloromethyl phosphate to obtain a modified antioxidant. At the same time, di-tert-butyl chloromethyl phosphate has a high flash point, and the phosphorus element it contains will increase the flame retardant performance, which is beneficial to expanding the scope of application.

[0026] 2. The vegetable oil used in the present invention has good biodegradability, and the vegetable oil insulating oil belongs to renewable resources. In the natural environment, the vegetable oil insulating oil can be decomposed by microorganisms, reducing the pollution to soil and water bodies. For example, when an oil leakage accident occurs, the vegetable oil insulating oil can be decomposed into harmless substances such as carbon dioxide and water in a short time, while mineral oil is difficult to degrade and will remain in the environment for a long time, causing serious damage to the ecosystem. In the present invention, the vegetable oil reacts with alcohol, and then an antioxidant and a pour point depressant are added and mixed to obtain an insulating oil containing vegetable oil. Among them, the modified antioxidant has a large molecular size and a complex spatial structure. At low temperatures, this macromolecular structure can form a certain steric hindrance in the matrix material, hindering the regular arrangement and aggregation of vegetable oil molecules, thereby reducing the occurrence of crystallization and solidification, and improving the performance of the vegetable oil not being easily solidified at low temperatures.

[0027] 3. The insulating oil containing vegetable oil provided by the present invention has excellent comprehensive performance and can be used in the same way as mineral oil. Moreover, the preparation method is efficient, has a certain fire resistance, expands the scope of application, and at the same time has environmental protection characteristics, meeting the pursuit of sustainable development, making it an ideal alternative, thereby increasing the application of vegetable oil-based insulating oil in power equipment. Detailed implementation manners

[0028] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] Embodiment 1

[0030] This embodiment provides a preparation method of an insulating oil containing vegetable oil, which includes the following steps:

[0031] Mix the refined palm oil and octanol, add sodium methoxide, heat, and react at 60 °C for 6 h to obtain Intermediate I; subject Intermediate I to vacuum distillation for 120 min under the conditions of a pressure of 0.5 mmHg and a temperature of 60 °C, then add activated carbon at 0.02 times the mass of Intermediate I for decolorization for 40 min; add ethanolamine at 0.04 times the mass of Intermediate I, and stir at a rotation speed of 30 r / min for 140 min to obtain Intermediate II; mix Intermediate II, a modified antioxidant, and ethylene-vinyl acetate copolymer, stir at room temperature and a rotation speed of 40 r / min for 7 h, filter, ultrasonicate at room temperature and a frequency of 40 KHz for 2 min, and let stand at room temperature for 6 h, and take the upper oil sample to obtain the insulating oil containing vegetable oil;

[0032] The mass ratio of palm oil, octanol, and sodium methoxide is 25:100:0.5;

[0033] Among them, the mass ratio of Intermediate II, the modified antioxidant, and the ethylene-vinyl acetate copolymer is 100:0.2:0.2;

[0034] Among them, the preparation method of the modified antioxidant includes the following steps:

[0035] Step (1) In an Ar gas atmosphere, mix dimethyl 2-(4-aminophenyl)malonate, 4-(1-hydroxyethyl)-2,6-dimethoxyphenol, and dibutyltin dilaurate with a mass ratio of 240:140:5, react at 130 °C for 5 h, end the reaction, and perform rotary evaporation to obtain a modified sterically hindered phenol;

[0036] Step (2): Mix N,N-dimethylformamide, modified sterically hindered phenol, di-tert-butyl chloromethyl phosphate and triethylamine in a mass ratio of 2000:500:200:2, heat under reflux at 140 °C for 10 h, end the reaction, wash, and dry at 50 °C for 6 h to obtain the modified antioxidant.

[0037] Example 2

[0038] This example provides a preparation method of insulating oil containing vegetable oil, including the following steps:

[0039] Mix the refined palm oil and octanol, add sodium methoxide, heat, and react at 70 °C for 4.5 h to obtain Intermediate I; subject Intermediate I to vacuum distillation at a pressure of 2.5 mmHg and a temperature of 65 °C for 105 min, then add activated carbon at 0.025 times the mass of Intermediate I for decolorization for 35 min; add ethanolamine at 0.045 times the mass of Intermediate I, stir at a rotation speed of 35 r / min for 130 min to obtain Intermediate II; mix Intermediate II, the modified antioxidant and ethylene-vinyl acetate copolymer, stir at room temperature and a rotation speed of 45 r / min for 6.5 h, filter, ultrasonicate at room temperature and a frequency of 40 KHz for 2 min, let stand at room temperature for 6.5 h, and take the upper oil sample to obtain the insulating oil containing vegetable oil;

[0040] Among them, the mass ratio of palm oil, octanol and sodium methoxide is 30:125:0.6;

[0041] Among them, the mass ratio of Intermediate II, the modified antioxidant and ethylene-vinyl acetate copolymer is 100:0.25:0.25;

[0042] Among them, the preparation method of the modified antioxidant includes the following steps:

[0043] Step (1): In an Ar gas atmosphere, mix dimethyl 2-(4-aminophenyl)malonate, 4-(1-hydroxyethyl)-2,6-dimethoxyphenol and dibutyltin dilaurate in a mass ratio of 250:150:6, react at 135 °C for 4.5 h, end the reaction, and perform rotary evaporation to obtain the modified sterically hindered phenol;

[0044] Step (2): Mix N,N-dimethylformamide, modified sterically hindered phenol, di-tert-butyl chloromethyl phosphate and triethylamine in a mass ratio of 2500:550:210:2.5, heat under reflux at 142 °C for 9 h, end the reaction, wash, and dry at 55 °C for 5.5 h to obtain the modified antioxidant.

[0045] Example 3

[0046] This example provides a preparation method of insulating oil containing vegetable oil, including the following steps:

[0047] Mix the refined palm oil and octanol, add sodium methoxide, heat, and react at 80 °C for 3.5 h to obtain Intermediate I; subject Intermediate I to vacuum distillation at a pressure of 5 mmHg and a temperature of 70 °C for 90 min, then add activated carbon at 0.03 times the mass of Intermediate I for decolorization for 30 min; add ethanolamine at 0.05 times the mass of Intermediate I, and stir at a rotation speed of 40 r / min for 120 min to obtain Intermediate II; mix Intermediate II, the modified antioxidant, and ethylene-vinyl acetate copolymer, stir at room temperature and a rotation speed of 50 r / min for 6 h, filter, ultrasonicate at room temperature and a frequency of 40 KHz for 3 min, let stand at room temperature for 7 h, and take the upper oil sample to obtain the insulating oil containing vegetable oil;

[0048] wherein the mass ratio of palm oil, octanol, and sodium methoxide is 35:150:0.7;

[0049] wherein the mass ratio of Intermediate II, the modified antioxidant, and ethylene-vinyl acetate copolymer is 100:0.3:0.3;

[0050] wherein the preparation method of the modified antioxidant comprises the following steps:

[0051] Step (1) In an Ar atmosphere, mix dimethyl 2-(4-aminophenyl)malonate, 4-(1-hydroxyethyl)-2,6-dimethoxyphenol, and dibutyltin dilaurate with a mass ratio of 260:160:7, react at 140 °C for 4 h, end the reaction, and perform rotary evaporation to obtain the modified hindered phenol;

[0052] Step (2) Mix N,N-dimethylformamide, the modified hindered phenol, di-tert-butyl chloromethyl phosphate, and triethylamine according to a mass ratio of 3000:600:220:3, heat under reflux at 145 °C for 8 h, end the reaction, wash, and dry at 60 °C for 5 h to obtain the modified antioxidant.

[0053] Example 4

[0054] This example provides a preparation method of an insulating oil containing vegetable oil, comprising the following steps:

[0055] Mix the refined palm oil and octanol, add sodium methoxide, heat, and react at 90 °C for 2.5 h to obtain Intermediate I; subject Intermediate I to vacuum distillation at a pressure of 8 mmHg and a temperature of 75 °C for 70 min, then add activated carbon at 0.035 times the mass of Intermediate I for decolorization for 25 min; add ethanolamine at 0.055 times the mass of Intermediate I, and stir at a rotation speed of 45 r / min for 110 min to obtain Intermediate II; mix Intermediate II, the modified antioxidant, and ethylene-vinyl acetate copolymer, stir at room temperature and a rotation speed of 55 r / min for 5.5 h, filter, ultrasonicate at room temperature and a frequency of 40 KHz for 4 min, let stand at room temperature for 7.5 h, and take the upper oil sample to obtain the insulating oil containing vegetable oil;

[0056] The mass ratio of palm oil, octanol, and sodium methoxide is 40:175:0.8;

[0057] Among them, the mass ratio of Intermediate II, the modified antioxidant, and ethylene-vinyl acetate copolymer is 100:0.35:0.35;

[0058] Among them, the preparation method of the modified antioxidant includes the following steps:

[0059] Step (1) In an Ar atmosphere, mix dimethyl 2-(4-aminophenyl)malonate, 4-(1-hydroxyethyl)-2,6-dimethoxyphenol, and dibutyltin dilaurate with a mass ratio of 270:170:8, react at 145 °C for 3.5 h, end the reaction, and perform rotary evaporation to obtain the modified sterically hindered phenol;

[0060] Step (2) Mix N,N-dimethylformamide, the modified sterically hindered phenol, di-tert-butyl chloromethyl phosphate, and triethylamine according to a mass ratio of 3500:650:230:3.5, heat under reflux at 147 °C for 7 h, end the reaction, wash, and dry at 55 °C for 4.5 h to obtain the modified antioxidant.

[0061] Example 5

[0062] This example provides a method for preparing an insulating oil containing vegetable oil, including the following steps:

[0063] Mix the refined palm oil and octanol, add sodium methoxide, heat, and react at 100 °C for 1 h to obtain Intermediate I; subject Intermediate I to vacuum distillation at a pressure of 10 mmHg and a temperature of 80 °C for 50 min, then add activated carbon at 0.04 times the mass of Intermediate I for decolorization for 20 min; add ethanolamine at 0.06 times the mass of Intermediate I, and stir at a rotation speed of 50 r / min for 100 min to obtain Intermediate II; mix Intermediate II, the modified antioxidant, and ethylene-vinyl acetate copolymer, stir at room temperature and a rotation speed of 60 r / min for 5 h, filter, ultrasonicate at room temperature and a frequency of 40 KHz for 4 min, let stand at room temperature for 8 h, and take the upper oil sample to obtain the insulating oil containing vegetable oil;

[0064] The mass ratio of palm oil, octanol, and sodium methoxide is 45:200:0.9;

[0065] Among them, the mass ratio of Intermediate II, the modified antioxidant, and ethylene-vinyl acetate copolymer is 100:0.4:0.4;

[0066] Among them, the preparation method of the modified antioxidant includes the following steps:

[0067] Step (1) In an Ar atmosphere, mix dimethyl 2-(4-aminophenyl)malonate, 4-(1-hydroxyethyl)-2,6-dimethoxyphenol, and dibutyltin dilaurate with a mass ratio of 280:180:9, react at 150 °C for 3 h, end the reaction, and perform rotary evaporation to obtain the modified sterically hindered phenol;

[0068] Step (2) Mix N,N-dimethylformamide, the modified sterically hindered phenol, di-tert-butyl chloromethyl phosphate, and triethylamine according to a mass ratio of 4000:700:240:4, heat under reflux at 150 °C for 6 h, end the reaction, wash, and dry at 50 °C for 4 h to obtain the modified antioxidant.

[0069] Comparative Example 1

[0070] This comparative example provides a preparation method of an insulating oil containing vegetable oil, including the following steps:

[0071] Mix the refined palm oil and octanol, add sodium methoxide, heat, and react at 60 °C for 6 h to obtain Intermediate I; subject Intermediate I to vacuum distillation at a pressure of 0.5 mmHg and a temperature of 60 °C for 120 min, then add activated carbon at 0.02 times the mass of Intermediate I for decolorization for 40 min; add ethanolamine at 0.04 times the mass of Intermediate I, and stir at a rotation speed of 30 r / min for 140 min to obtain Intermediate II; mix Intermediate II, the modified antioxidant, and ethylene-vinyl acetate copolymer, stir at room temperature and a rotation speed of 40 r / min for 7 h, filter, perform ultrasonic treatment at room temperature and a frequency of 40 KHz for 2 min, let stand at room temperature for 6 h, and take the upper oil sample to obtain the insulating oil containing vegetable oil;

[0072] wherein the mass ratio of palm oil, octanol, and sodium methoxide is 25:100:0.5;

[0073] wherein the mass ratio of Intermediate II, the modified antioxidant, and ethylene-vinyl acetate copolymer is 100:0.2:0.2;

[0074] wherein the preparation method of the modified antioxidant comprises the following steps:

[0075] In an Ar gas atmosphere, mix dimethyl 2-(4-aminophenyl)malonate, 4-(1-hydroxyethyl)-2,6-dimethoxyphenol, and dibutyltin dilaurate with a mass ratio of 240:140:5, react at 130 °C for 5 h, end the reaction, and perform rotary evaporation to obtain the modified antioxidant.

[0076] Comparative Example 2

[0077] This comparative example is the vegetable insulating oil composition 2# disclosed in Example 10 of Chinese Patent Application CN109337739B.

[0078] The insulating oils prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to relevant tests. Among them, the flash point was determined in accordance with GB / T 3536-2008; the pour point was determined in accordance with GB / T 510; for the determination of biodegradability, a soil degradation experiment was carried out with a cycle of 50 days. Specifically, soil samples without pollution records were taken. The soil sampling was carried out using a core sampler (such as a stainless steel tube with a diameter of about 3 cm); when in use, the sampler was inserted into the soil near a big tree about 15 cm deep to take out the soil sample; the soil sample was stored refrigerated before the test; 100 g of the soil sample was placed in a wide-mouth glass bottle, and the addition amount of the liquid insulating medium was 5 g / 100 g of soil; the test process was kept at 25 °C, and an unsealed method was adopted to facilitate the discharge of CO2 exhaled during the test, to conduct gas exchange with the external environment, and to maintain the original soil humidity; the content of hydrocarbons in the sample before and after the test was measured by an ultraviolet spectrophotometer to represent the residual amount of the liquid insulating medium in the soil, and the biodegradation rate of the liquid insulating medium was determined by the absorption spectra before and after the experiment. Among them, the test instrument can be selected as the UV-1601 Shimadzu multi-functional spectrometer, the wavelength range is 200-800 nm, and anhydrous ethanol was selected as the reference solution for the test; the specific test results are shown in Table 1;

[0079] Table 1

[0080]

[0081] As can be seen from Table 1 above, the insulating oils prepared in Examples 1-5 have good flame retardancy and biodegradability, and are not easy to solidify at low temperatures. Their comprehensive performance is superior to that of Comparative Examples 1-2, and these properties further increase their scope of application.

[0082] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. All equivalent changes and improvements made in accordance with the scope of the present invention application shall still fall within the scope covered by the patent of the present invention.

Claims

1. A preparation method of an insulating oil containing vegetable oil, characterized in that, It includes the following steps: Mix the refined vegetable oil and alcohol, add a catalyst, heat and react to obtain Intermediate I; subject Intermediate I to vacuum distillation, decolorization, and acid reduction to obtain Intermediate II; mix Intermediate II, the modified antioxidant, and the pour point depressant, stir, ultrasonicate, let stand, and take the upper-layer oil sample to obtain the insulating oil containing vegetable oil; Among them, the preparation method of the modified antioxidant includes the following steps: Step (1) In an inert gas atmosphere, uniformly mix dimethyl 2-(4-aminophenyl)malonate and 4-(1-hydroxyethyl)-2,6-dimethoxyphenol, add dibutyltin dilaurate, stir, heat and react. After the reaction ends, perform rotary evaporation to obtain the modified sterically hindered phenol; Step (2) Mix N,N-dimethylformamide, the modified sterically hindered phenol, and di-tert-butyl chloromethyl phosphate, add triethylamine, heat under reflux, and after the reaction ends, wash and dry to obtain the modified antioxidant.

2. The preparation method of an insulating oil containing vegetable oil according to claim 1, characterized in that, The vegetable oil is any one of soybean oil, peanut oil, cottonseed oil, palm oil, and coconut oil.

3. The preparation method of an insulating oil containing vegetable oil according to claim 1, characterized in that, The alcohol is an aliphatic straight-chain alcohol or composition with a carbon content of 8-16.

4. A method for preparing an insulating oil containing vegetable oil according to claim 1, characterized in that, The catalyst is one of sodium hydroxide, potassium hydroxide, sodium methoxide or a composition of two or more of them.

5. The preparation method of an insulating oil containing vegetable oil according to claim 1, characterized in that, The mass ratio of the vegetable oil, alcohol, and catalyst is (25-45):(100-200):(0.5-0.9); the reaction temperature is 60-100 °C, and the reaction time is 1-5 h.

6. The preparation method of an insulating oil containing vegetable oil according to claim 1, wherein, In the vacuum distillation, the pressure is 0.5-10 mmHg, the temperature is 80-100 °C, and the time is 50-120 min.

7. The preparation method of an insulating oil containing vegetable oil according to claim 1, characterized in that, The mass ratio of dimethyl 2-(4-aminophenyl)malonate, 4-(1-hydroxyethyl)-2,6-dimethoxyphenol, and dibutyltin dilaurate is (240-280):(140-180):(5-9); the reaction temperature is 130-150 °C, and the reaction time is 3-5 h.

8. The preparation method of an insulating oil containing vegetable oil according to claim 1, characterized in that The mass ratio of N,N-dimethylformamide, the modified sterically hindered phenol, di-tert-butyl chloromethyl phosphate, and triethylamine is (2000-4000):(500-700):(200-240):(2-4); the reaction temperature is 140-150 °C, and the reaction time is 6-10 h.

9. An insulating oil containing vegetable oil prepared by the preparation method of the insulating oil containing vegetable oil according to any one of claims 1-8.

10. An application of the insulating oil containing vegetable oil according to claim 9 in insulation in electrical equipment.

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