Electrical equipment insulating liquid and method for its production

Abstract

The application discloses an electrical equipment insulating liquid and a preparation method thereof, and belongs to the technical field of insulating liquid preparation. The preparation method comprises the following steps: sequentially adding trimethylolpropane, octanoic acid, decanoic acid and oleic acid into a reaction container, then adding toluene sulfonic acid as a catalyst to perform esterification reaction, and obtaining a substrate after esterification reaction; removing unreacted substrates from the substrate after esterification reaction by using a vacuum distillation method to obtain a product after distillation; naturally cooling the product after distillation, first performing alkali refining treatment by using a sodium hydroxide solution, then washing by using ultrapure water to remove sodium salt in the alkali refining process, then performing adsorption by using an adsorbent to remove water and polar impurities, then vacuum drying, and finally performing filter membrane filtration to generate trimethylolpropane octanoic acid decanoic acid oleic acid triester insulating liquid. The application can overcome the problem of low ignition point of trimethylolpropane ester insulating liquid, has excellent electrical performance, and is suitable for electrical equipment such as transformers.

Description

Technical Field

[0001] This invention relates to an insulating liquid for electrical equipment and its preparation method, belonging to the field of insulating liquid preparation technology. Background Technology

[0002] Currently, the global power grid is at a critical juncture in its transformation towards a cleaner, smarter, and more powerful version, a trend that drives the continuous development of superior insulation systems. As a key component of the power grid, the power transformer undertakes the important task of transmitting and distributing electrical energy, and its reliability is a crucial guarantee for the safe and stable operation of the power system. If the power transformer is likened to the heart of the power system, then the insulating oil is like the blood flowing inside the transformer, playing a vital role in its safe and stable operation.

[0003] Since 1887, mineral oil has been widely used as an insulating medium due to its good performance and relatively low cost. However, mineral oil has a low flash point and poor degradation ability, which can lead to resource depletion and increased greenhouse gas emissions, making it difficult to use in high-safety applications such as offshore wind power. Against the backdrop of my country's push for "dual carbon" goals, mineral insulating oil clearly cannot meet the requirements of safety, greenness, and sustainable development. Therefore, the use of novel, non-toxic, environmentally friendly, and biodegradable liquid insulation mechanisms has become a natural alternative to mineral oil.

[0004] In recent years, ester-based insulating oils have been extensively studied due to their excellent biodegradability and high ignition point. Oils such as sunflower oil, rapeseed oil, flaxseed oil, and soybean oil have been tested for use in transformer oils and are increasingly considered promising candidates for large transformers. However, they are highly susceptible to oxidation, which shortens the transformer's lifespan. These drawbacks limit their sustainable application in transformers, thus necessitating the discovery of an antioxidant, economical, and environmentally friendly raw material for insulating oil production. Existing technologies utilize transesterification to synthesize antioxidant trimethylolpropane ester insulating liquids, involving the esterification reaction of trimethylolpropane with short-chain acids. However, the resulting ester-based insulating oils suffer from low ignition points, making them unsuitable for use in electrical equipment such as transformers. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide an electrical equipment insulating liquid and its preparation method, which can overcome the problem of low ignition point of trimethylolpropane ester insulating liquid, has excellent electrical properties, and is suitable for electrical equipment such as transformers.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing an insulating liquid for electrical equipment, comprising the following steps:

[0008] Trimethylolpropane, octanoic acid, decanoic acid and oleic acid were added sequentially to the reaction vessel, and toluenesulfonic acid was added as a catalyst. The esterification reaction was carried out under low pressure to obtain the esterified substrate.

[0009] After esterification, the substrate was subjected to vacuum distillation to remove unreacted substrate, yielding the distilled product.

[0010] After the distilled product is naturally cooled, it is first alkali-refined with sodium hydroxide solution, then washed with ultrapure water to remove sodium salts from the alkali refining process, then adsorbent is used to remove moisture and polar impurities, then vacuum dried, and finally filtered through a filter membrane to produce trimethylolpropane octyl decanoic acid trioleate insulating liquid.

[0011] The initial temperature for the esterification reaction is 55~65℃. After every 1~1.5 h of reaction, the temperature is increased by 10~15℃. After increasing the temperature to 148~152℃, the reaction continues for 1~2 h.

[0012] The stirring speed for the esterification reaction is 280~320 rpm, and the pressure for the esterification reaction is 1~3 kPa.

[0013] The amount of p-toluenesulfonic acid added is 1.0 to 1.4 wt% of the total mass of the reaction substrate.

[0014] The molar ratio of the sum of octanoic acid, capric acid, and oleic acid to trimethylolpropane is 3.1 to 3.3:1; the molar ratio of the sum of octanoic acid and capric acid to oleic acid is 8:2 to 2:8; and the molar ratio of octanoic acid to capric acid is 4:5 to 4:7.

[0015] The distillation temperature is 158~160℃, and the distillation time is 2.5~3.5h.

[0016] The adsorbent is composed of alkaline alumina, type 3A molecular sieve, silica gel and activated clay in a mass ratio of 1:1:1:1. The amount of adsorbent added is 4-6 wt% of the substrate generated, and the adsorption time is 50-70 min.

[0017] Vacuum drying conditions are 90~110 Pa and 70~80℃ for 30~40h.

[0018] The filter membrane used is a 0.25μm filter membrane.

[0019] Secondly, the present invention provides an electrical equipment insulating liquid: prepared by the aforementioned electrical equipment insulating liquid preparation method.

[0020] The beneficial effects of this invention are as follows: This invention provides a method for preparing insulating fluid for electrical equipment, using trimethylolpropane, octanoic acid, capric acid, and oleic acid as raw materials. Through transesterification technology, long-chain fatty acids (oleic acid) are introduced into the trimethylolpropane molecule. By adjusting the proportion of oleic acid, the physicochemical properties of the trimethylolpropane oil, such as viscosity, flash point, and pour point, can be adjusted. The generated polyol ester changes the chemical structure of trimethylolpropane. This overcomes the problem of low ignition point of trimethylolpropane without excessively increasing the viscosity of the oil, thereby improving the stability and high-voltage resistance of the insulating oil. It is suitable for electrical equipment such as transformers.

[0021] The method of this invention uses p-toluenesulfonic acid (TsOH) as a catalyst, which has higher catalytic efficiency compared with traditional catalysts (strong acid and strong base). It can promote esterification reaction at lower reaction temperature and pressure, significantly improve the conversion rate of reactants, and reduce the residue of unreacted substances. Attached Figure Description

[0022] Figure 1 This invention relates to the reaction apparatus for preparing trimethylolpropane octyl decanoate oleate.

[0023] Figure 2 This is a flowchart of the purification process of the trimethylolpropane octyl decanoate oleate insulating liquid according to the present invention;

[0024] Figure 3 This is the synthetic reaction formula used in the synthesis of trimethylolpropane octyl decanoate oleate in this invention;

[0025] Figure 4 This is a physical image of the preparation of trimethylolpropane octyl oleate oleate according to the present invention. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0027] Example 1

[0028] This invention provides a method for preparing insulating liquid for electrical equipment, comprising the following steps:

[0029] Step 1: Trimethylolpropane, octanoic acid, decanoic acid, and oleic acid are added sequentially to a three-necked flask. The molar ratio of the sum of octanoic acid, decanoic acid, and oleic acid to trimethylolpropane is 3.2:1, the molar ratio of the sum of octanoic acid and decanoic acid to oleic acid is 8:2, and the molar ratio of n-octanoic acid to n-decanoic acid is 4:6. Toluenesulfonic acid is then added as a catalyst, with the amount of p-toluenesulfonic acid added being 1.2 wt% of the total mass of the reaction substrate. The esterification reaction is then carried out under low-pressure conditions. The esterification reaction apparatus is as follows: Figure 1As shown, a three-necked flask was placed in an oil bath and heated to 60°C. The mixture was stirred with a magnetic stirrer to maintain uniformity. The stirring speed for the esterification reaction was 280–320 rpm. Then, the vacuum system was activated, and a circulating water vacuum pump was used to adjust the vacuum level of the reaction system to approximately 3 kPa. During the reaction, samples were periodically taken to measure the acid value of the reactants to monitor the progress of the reaction. After each 1 hour of reaction, the temperature was increased by 10–15°C, and after increasing to 150°C, the reaction was continued for 1–2 hours to obtain the esterified substrate, which yielded trimethylolpropane octyl decanoic acid triester and water. The synthesis reaction formula is shown below. Figure 3 As shown.

[0030] Step two involves removing unreacted substrate from the esterified substrate using vacuum distillation, primarily to remove unreacted acid, to obtain the distilled product. Specifically, the circulating water vacuum pump is replaced with an oil vacuum pump to further reduce the pressure inside the three-necked flask, and heating continues until the distillation temperature reaches 160°C, with a distillation time of 3.0 hours.

[0031] Step 3, as Figure 2 As shown, the distilled product was naturally cooled to 60℃ (the oil pump and vacuum pump continued to operate during the cooling process). It was first subjected to alkali refining with sodium hydroxide solution, followed by washing with ultrapure water to remove sodium salts from the alkali refining process. Then, an adsorbent was used to remove moisture and polar impurities. The adsorbent consisted of alkaline alumina, type 3A molecular sieve, silica gel, and activated clay in a mass ratio of 1:1:1:1, with the amount of adsorbent added being 5 wt% of the substrate, and the adsorption time being 60 min. Next, it was vacuum dried at 100 Pa and 75℃ for 36 h. Finally, it was filtered through a 0.25 μm filter membrane to produce a trimethylolpropane octyl decanoic acid trioleate insulating liquid.

[0032] The final electrical equipment insulating liquid prepared in this embodiment is shown in the photograph below. Figure 4 As shown in Table 1, the physicochemical properties are as follows.

[0033] Table 1. Physicochemical properties of oleic acid-containing (20%) trimethylolpropane octyl oleate insulating liquid.

[0034]

[0035] Example 2

[0036] This invention provides a method for preparing insulating liquid for electrical equipment, comprising the following steps:

[0037] Step 1: Trimethylolpropane, octanoic acid, decanoic acid, and oleic acid are added sequentially to a three-necked flask. The molar ratio of the sum of octanoic acid, decanoic acid, and oleic acid to trimethylolpropane is 3.2:1, the molar ratio of the sum of octanoic acid and decanoic acid to oleic acid is 6:4, and the molar ratio of n-octanoic acid to n-decanoic acid is 4:6. Toluenesulfonic acid is then added as a catalyst, with the amount of p-toluenesulfonic acid added being 1.2 wt% of the total mass of the reaction substrate. The esterification reaction is then carried out under low-pressure conditions. The esterification reaction apparatus is as follows: Figure 1 As shown, a three-necked flask was placed in an oil bath and heated to 60°C. The mixture was stirred with a magnetic stirrer to maintain uniformity. The stirring speed for the esterification reaction was 280–320 rpm. Then, the vacuum system was activated, and a circulating water vacuum pump was used to adjust the vacuum level of the reaction system to approximately 3 kPa. During the reaction, samples were periodically taken to measure the acid value of the reactants to monitor the progress of the reaction. After each 1 hour of reaction, the temperature was increased by 10–15°C, and after increasing to 150°C, the reaction was continued for 1–2 hours to obtain the esterified substrate, which yielded trimethylolpropane octyl decanoic acid triester and water. The synthesis reaction formula is shown below. Figure 3 As shown.

[0038] Step two involves removing unreacted substrate from the esterified substrate using vacuum distillation, primarily to remove unreacted acid, to obtain the distilled product. Specifically, the circulating water vacuum pump is replaced with an oil vacuum pump to further reduce the pressure inside the three-necked flask, and heating continues until the distillation temperature reaches 160°C, with a distillation time of 3.0 hours.

[0039] Step 3, as Figure 2 As shown, the distilled product was naturally cooled to 60℃ (the oil pump and vacuum pump continued to operate during the cooling process). It was first subjected to alkali refining with sodium hydroxide solution, followed by washing with ultrapure water to remove sodium salts from the alkali refining process. Then, an adsorbent was used to remove moisture and polar impurities. The adsorbent consisted of alkaline alumina, type 3A molecular sieve, silica gel, and activated clay in a mass ratio of 1:1:1:1, with the amount of adsorbent added being 5 wt% of the substrate, and the adsorption time being 60 min. Next, it was vacuum dried at 100 Pa and 75℃ for 36 h. Finally, it was filtered through a 0.25 μm filter membrane to produce a trimethylolpropane octyl decanoic acid trioleate insulating liquid.

[0040] The performance of the final electrical equipment insulating fluid prepared in this embodiment is shown in Table 2.

[0041] Table 2. Physicochemical properties of oleic acid-containing (40%) trimethylolpropane octadecanoate oleate insulating liquid.

[0042]

[0043] Example 3

[0044] This invention provides a method for preparing insulating liquid for electrical equipment, comprising the following steps:

[0045] Step 1: Trimethylolpropane, octanoic acid, decanoic acid, and oleic acid are added sequentially to a three-necked flask. The molar ratio of the sum of octanoic acid, decanoic acid, and oleic acid to trimethylolpropane is 3.2:1; the molar ratio of the sum of octanoic acid and decanoic acid to oleic acid is 4:6; and the molar ratio of n-octanoic acid to n-decanoic acid is 4:6. Toluenesulfonic acid is then added as a catalyst, with the amount of p-toluenesulfonic acid added being 1.2 wt% of the total mass of the reaction substrate. The esterification reaction is then carried out under low-pressure conditions. The esterification reaction apparatus is as follows: Figure 1 As shown, a three-necked flask was placed in an oil bath and heated to 60°C. The mixture was stirred with a magnetic stirrer to maintain uniformity. The stirring speed for the esterification reaction was 280–320 rpm. Then, the vacuum system was activated, and a circulating water vacuum pump was used to adjust the vacuum level of the reaction system to approximately 3 kPa. During the reaction, samples were periodically taken to measure the acid value of the reactants to monitor the progress of the reaction. After each 1 hour of reaction, the temperature was increased by 10–15°C, and after increasing to 150°C, the reaction was continued for 1–2 hours to obtain the esterified substrate, which yielded trimethylolpropane octyl decanoic acid triester and water. The synthesis reaction formula is shown below. Figure 3 As shown.

[0046] Step two involves removing unreacted substrate from the esterified substrate using vacuum distillation, primarily to remove unreacted acid, to obtain the distilled product. Specifically, the circulating water vacuum pump is replaced with an oil vacuum pump to further reduce the pressure inside the three-necked flask, and heating continues until the distillation temperature reaches 160°C, with a distillation time of 3.0 hours.

[0047] Step 3, as Figure 2 As shown, the distilled product was naturally cooled to 60℃ (the oil pump and vacuum pump continued to operate during the cooling process). It was first subjected to alkali refining with sodium hydroxide solution, followed by washing with ultrapure water to remove sodium salts from the alkali refining process. Then, an adsorbent was used to remove moisture and polar impurities. The adsorbent consisted of alkaline alumina, type 3A molecular sieve, silica gel, and activated clay in a mass ratio of 1:1:1:1, with the amount of adsorbent added being 5 wt% of the substrate, and the adsorption time being 60 min. Next, it was vacuum dried at 100 Pa and 75℃ for 36 h. Finally, it was filtered through a 0.25 μm filter membrane to produce a trimethylolpropane octyl decanoic acid trioleate insulating liquid.

[0048] The performance of the final electrical equipment insulating fluid prepared in this embodiment is shown in Figure 3.

[0049] Table 3 Physicochemical properties of trimethylolpropane octadecanoate oleate (60% oleic acid)

[0050]

[0051] Example 4

[0052] This invention provides a method for preparing insulating liquid for electrical equipment, comprising the following steps:

[0053] Step 1: Trimethylolpropane, octanoic acid, decanoic acid, and oleic acid are added sequentially to a three-necked flask. The molar ratio of the sum of octanoic acid, decanoic acid, and oleic acid to trimethylolpropane is 3.2:1, the molar ratio of the sum of octanoic acid and decanoic acid to oleic acid is 2:8, and the molar ratio of n-octanoic acid to n-decanoic acid is 4:6. Toluenesulfonic acid is then added as a catalyst, with the amount of p-toluenesulfonic acid added being 1.2 wt% of the total mass of the reaction substrate. The esterification reaction is then carried out under low-pressure conditions. The esterification reaction apparatus is as follows: Figure 1 As shown, a three-necked flask was placed in an oil bath and heated to 60°C. The mixture was stirred with a magnetic stirrer to maintain uniformity. The stirring speed for the esterification reaction was 280–320 rpm. Then, the vacuum system was activated, and a circulating water vacuum pump was used to adjust the vacuum level of the reaction system to approximately 3 kPa. During the reaction, samples were periodically taken to measure the acid value of the reactants to monitor the progress of the reaction. After each 1 hour of reaction, the temperature was increased by 10–15°C, and after increasing to 150°C, the reaction was continued for 1–2 hours to obtain the esterified substrate, which yielded trimethylolpropane octyl decanoic acid triester and water. The synthesis reaction formula is shown below. Figure 3 As shown.

[0054] Step two involves removing unreacted substrate from the esterified substrate using vacuum distillation, primarily to remove unreacted acid, to obtain the distilled product. Specifically, the circulating water vacuum pump is replaced with an oil vacuum pump to further reduce the pressure inside the three-necked flask, and heating continues until the distillation temperature reaches 160°C, with a distillation time of 3.0 hours.

[0055] Step 3, as Figure 2 As shown, the distilled product was naturally cooled to 60℃ (the oil pump and vacuum pump continued to operate during the cooling process). It was first subjected to alkali refining with sodium hydroxide solution, followed by washing with ultrapure water to remove sodium salts from the alkali refining process. Then, an adsorbent was used to remove moisture and polar impurities. The adsorbent consisted of alkaline alumina, type 3A molecular sieve, silica gel, and activated clay in a mass ratio of 1:1:1:1, with the amount of adsorbent added being 5 wt% of the substrate, and the adsorption time being 60 min. Next, it was vacuum dried at 100 Pa and 75℃ for 36 h. Finally, it was filtered through a 0.25 μm filter membrane to produce a trimethylolpropane octyl decanoic acid trioleate insulating liquid.

[0056] The performance of the final electrical equipment insulating fluid prepared in this embodiment is shown in Table 4.

[0057] Table 4 Physicochemical properties of trimethylolpropane octadecanoate oleate (80% oleic acid content)

[0058]

[0059] Example 5

[0060] This invention provides a method for preparing insulating liquid for electrical equipment, comprising the following steps:

[0061] Step 1: Trimethylolpropane, octanoic acid, decanoic acid, and oleic acid are added sequentially to a three-necked flask. The molar ratio of the sum of octanoic acid, decanoic acid, and oleic acid to trimethylolpropane is 3.1:1, the molar ratio of the sum of octanoic acid and decanoic acid to oleic acid is 8:2, and the molar ratio of n-octanoic acid to n-decanoic acid is 4:6. Toluenesulfonic acid is then added as a catalyst, with the amount of p-toluenesulfonic acid added being 1.4 wt% of the total mass of the reaction substrate. The esterification reaction is then carried out under low-pressure conditions. The esterification reaction apparatus is as follows: Figure 1 As shown, a three-necked flask was placed in an oil bath and heated to 60°C. The mixture was stirred with a magnetic stirrer to maintain uniformity. The stirring speed for the esterification reaction was 280 rpm. Then, the vacuum system was activated, and a circulating water vacuum pump was used to adjust the vacuum level of the reaction system to approximately 3 kPa. During the reaction, samples were periodically taken to measure the acid value of the reactants to monitor the progress of the reaction. After each 1 hour of reaction, the temperature was increased by 10-15°C, and after increasing to 148°C, the reaction was continued for 1-2 hours to obtain the esterified substrate, which yielded trimethylolpropane octyl decanoic acid triester and water. The synthesis reaction formula is as follows. Figure 3 As shown.

[0062] Step two involves removing unreacted substrate from the esterified substrate using vacuum distillation, primarily to remove unreacted acid, to obtain the distilled product. Specifically, the circulating water vacuum pump is replaced with an oil vacuum pump to further reduce the pressure inside the three-necked flask, and heating continues until the distillation temperature reaches 160°C, with a distillation time of 2.5 hours.

[0063] Step 3, as Figure 2 As shown, the distilled product was naturally cooled to 60℃ (the oil pump and vacuum pump continued to operate during the cooling process). It was first subjected to alkali refining with sodium hydroxide solution, followed by washing with ultrapure water to remove sodium salts from the alkali refining process. Then, an adsorbent was used to remove moisture and polar impurities. The adsorbent consisted of alkaline alumina, type 3A molecular sieve, silica gel, and activated clay in a mass ratio of 1:1:1:1, with an adsorbent addition of 6 wt% of the substrate and an adsorption time of 50 min. Next, it was vacuum dried at 110 Pa and 70℃ for 40 h. Finally, it was filtered through a 0.25 μm filter membrane to produce a trimethylolpropane octyl decanoic acid trioleate insulating liquid.

[0064] Example 6

[0065] This invention provides a method for preparing insulating liquid for electrical equipment, comprising the following steps:

[0066] Step 1: Trimethylolpropane, octanoic acid, decanoic acid, and oleic acid are added sequentially to a three-necked flask. The molar ratio of the sum of octanoic acid, decanoic acid, and oleic acid to trimethylolpropane is 3.3:1, the molar ratio of the sum of octanoic acid and decanoic acid to oleic acid is 8:2, and the molar ratio of n-octanoic acid to n-decanoic acid is 4:6. Toluenesulfonic acid is then added as a catalyst, with the amount of p-toluenesulfonic acid added being 1.0 wt% of the total mass of the reaction substrate. The esterification reaction is then carried out under low-pressure conditions. The esterification reaction apparatus is as follows: Figure 1 As shown, a three-necked flask was placed in an oil bath and heated to 60°C. The mixture was stirred with a magnetic stirrer to maintain uniformity. The stirring speed for the esterification reaction was 320 rpm. Then, the vacuum system was activated, and a circulating water vacuum pump was used to adjust the vacuum level of the reaction system to approximately 1 kPa. During the reaction, samples were periodically taken to measure the acid value of the reactants to monitor the progress of the reaction. After each 1 hour of reaction, the temperature was increased by 10-15°C. After increasing the temperature to 152°C, the reaction was continued for 1-2 hours to obtain the esterified substrate, which yielded trimethylolpropane octyl decanoic acid triester and water. The synthesis reaction formula is shown below. Figure 3 As shown.

[0067] Step two involves removing unreacted substrate from the esterified substrate using vacuum distillation, primarily to remove unreacted acid, to obtain the distilled product. Specifically, the circulating water vacuum pump is replaced with an oil vacuum pump to further reduce the pressure inside the three-necked flask, and heating continues until the distillation temperature reaches 158°C, with a distillation time of 3.0 hours.

[0068] Step 3, as Figure 2 As shown, the distilled product was naturally cooled to 60℃ (the oil pump and vacuum pump continued to operate during the cooling process). It was first subjected to alkali refining with sodium hydroxide solution, followed by washing with ultrapure water to remove sodium salts from the alkali refining process. Then, an adsorbent was used to remove moisture and polar impurities. The adsorbent consisted of alkaline alumina, type 3A molecular sieve, silica gel, and activated clay in a mass ratio of 1:1:1:1, with the amount of adsorbent added being 4 wt% of the substrate, and the adsorption time being 70 min. Next, it was vacuum dried at 90 Pa and 80℃ for 30 h. Finally, it was filtered through a 0.25 μm filter membrane to produce a trimethylolpropane octyl decanoic acid trioleate insulating liquid.

[0069] Comparative Example 1

[0070] This embodiment is the same as Example 1, except that no oil acid is added. The physicochemical properties of the final product, trimethylolpropane octadecanoate, are shown in Figure 5.

[0071] Table 5 Physicochemical properties of trimethylolpropane octadecanoate

[0072]

[0073] Comparative Example 2

[0074] This embodiment is the same as Example 1, except that it contains oleic acid. The physicochemical properties of the final product, trimethylolpropane oleate, are shown in Figure 5.

[0075] Table 6 Physicochemical properties of trimethylolpropane oleate

[0076]

[0077] A comparison of the physicochemical properties of the products from the embodiments of this invention and Comparative Example 1 shows that the introduction of oleic acid into the octyl-capric acid base of this invention can lower the ignition point of the insulating liquid. However, as the proportion of oleic acid increases, the kinematic viscosity also increases. Therefore, Example 1 is considered the optimal embodiment in practical applications. Furthermore, a comparison of the physicochemical properties of the products from the embodiments of this invention and Comparative Example 2 shows that although oleic acid alone has a high ignition point, its kinematic viscosity is also high, making it unsuitable for direct use in preparing insulating liquids. This invention introduces long-chain fatty acids (oleic acid) into the trimethylolpropane molecule. By adjusting the proportion of oleic acid, the viscosity, flash point, pour point, and other physicochemical properties of the trimethylolpropane oil can be regulated. The resulting polyol ester alters the chemical structure of trimethylolpropane, thus overcoming the problem of the low ignition point of trimethylolpropane without excessively increasing the viscosity of the oil, improving the stability and high-voltage resistance of the insulating oil, making it suitable for electrical equipment such as transformers.

[0078] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an insulating liquid for electrical equipment, characterized in that: Includes the following steps: Trimethylolpropane, octanoic acid, decanoic acid, and oleic acid were added sequentially to a reaction vessel. The molar ratio of the sum of octanoic acid, decanoic acid, and oleic acid to trimethylolpropane was 3.2:1, the molar ratio of the sum of octanoic acid and decanoic acid to oleic acid was 8:2, and the molar ratio of n-octanoic acid to n-decanoic acid was 4:

6. Toluenesulfonic acid was then added as a catalyst, and the esterification reaction was carried out under low pressure to obtain the esterified substrate. The initial temperature of the esterification reaction was 60℃. After every 1 hour of reaction, the temperature was increased by 10~15℃. After increasing the temperature to 150℃, the reaction was continued for 1~2 hours. The stirring speed of the esterification reaction was 280~320 rpm, and the pressure of the esterification reaction was 3 kPa. After esterification, the substrate was subjected to vacuum distillation to remove unreacted substrate, yielding the distilled product. After the distilled product is naturally cooled, it is first alkali-refined with sodium hydroxide solution, then washed with ultrapure water to remove sodium salts from the alkali refining process, then adsorbent is used to remove moisture and polar impurities, then vacuum dried, and finally filtered through a filter membrane to produce trimethylolpropane octyl decanoic acid trioleate insulating liquid.

2. The method for preparing electrical equipment insulating liquid according to claim 1, characterized in that: The amount of p-toluenesulfonic acid added is 1.0 to 1.4 wt% of the total mass of the reaction substrate.

3. The method for preparing electrical equipment insulating liquid according to claim 1, characterized in that: The adsorbent is composed of alkaline alumina, type 3A molecular sieve, silica gel and activated clay in a mass ratio of 1:1:1:

1. The amount of adsorbent added is 4-6 wt% of the substrate generated, and the adsorption time is 50-70 min.

4. The method for preparing electrical equipment insulating liquid according to claim 1, characterized in that: Vacuum drying conditions are 90~110 Pa and 70~80℃ for 30~40h.

5. The method for preparing electrical equipment insulating liquid according to claim 1, characterized in that: The filter membrane used is a 0.25μm filter membrane.

6. An insulating liquid for electrical equipment, characterized in that: It is prepared by the method for preparing electrical equipment insulating liquid according to any one of claims 1 to 5.

Images