Preparation method of complex ester high ignition point insulating medium

Abstract

The application relates to the technical field of insulating media, and particularly discloses a preparation method of a complex ester type high ignition point insulating medium, a preparation method of a complex ester type high ignition point insulating medium, which comprises the following steps: S1, mixing polyhydric alcohol, diacid, monobasic acid, a catalyst and a water carrying agent, and performing esterification reaction to obtain an esterification product; S2, performing vacuum distillation treatment on the esterification product to obtain a synthetic ester base oil; and S3, adding an antioxidant, a metal deactivator and an anti-hydrolysis agent into the synthetic ester base oil to obtain the insulating medium; the insulating medium has the advantages of excellent anti-combustion performance, good insulation and good low-temperature performance.

Description

Technical Field

[0001] This application relates to the field of insulating media technology, and more specifically, it relates to a method for preparing a complex ester-type high ignition point insulating media. Background Technology

[0002] Insulating media are a key material in the field of electrical engineering and power equipment. They simultaneously undertake two core functions: electrical insulation and heat dissipation and cooling. Simply put, they are substances that can both prevent current from passing through and effectively carry away heat.

[0003] Therefore, insulating media need to have high dielectric strength to withstand high voltage without breakdown and prevent short circuits. Secondly, they need to have good thermal conductivity and convection characteristics to efficiently transfer the heat generated during equipment operation and prevent overheating. In addition, there are also high requirements for chemical stability, environmental protection and safety, and economy. Furthermore, the acid value of synthetic esters has a significant impact on dielectric loss. To facilitate acid value management, synthetic insulating media are generally polyol ester structures. However, polyol ester products have low flash points and ignition points and poor flame resistance.

[0004] Therefore, how to prepare a new insulating medium that simultaneously possesses the advantages of excellent flame retardancy, good insulation, and good low-temperature performance is a problem that needs to be solved. Summary of the Invention

[0005] In order to prepare a new insulating medium that has the advantages of excellent flame retardancy, good insulation and good low temperature performance, this application provides a method for preparing a complex ester type high flash point insulating medium.

[0006] This application provides a method for preparing a complex ester-type high-ignition-point insulating dielectric, employing the following technical solution: A method for preparing a complex ester-type high-ignition-point insulating dielectric includes the following steps: S1. Mix polyol, dicarboxylic acid, monocarboxylic acid, catalyst and water-carrying agent, and carry out esterification reaction to obtain esterification product; S2. The esterification product is subjected to vacuum distillation to obtain synthetic ester base oil; S3. Antioxidants, metal deactivators, and anti-hydrolysis agents are added to synthetic ester base oils to obtain insulating media.

[0007] By adopting the above technical solution, polyols are esterified with dicarboxylic acids and monocarboxylic acids to prepare synthetic ester base oils. The molecular chains contain a large number of polar ester groups, with strong intermolecular forces, high structural stability, low volatility, and high auto-ignition point, which improves the flame resistance. In addition, the ester molecules contain oxygen atoms, which can capture free radicals during combustion, interrupt the free radical chain reaction, and inhibit flame propagation. At the same time, the ester chains crosslink at high temperature to form a dense carbon layer, blocking heat transfer and further improving the flame resistance.

[0008] Synthetic ester base oils are compounded with oxidants, metal deactivators, and anti-hydrolysis agents. Among them, antioxidants prevent oxidation, metal deactivators can chemically adsorb or complex with the surfaces of metals such as copper and iron to form a dense, inert protective film, preventing them from catalyzing the generation of free radicals in the oil, thereby interrupting the oxidation chain reaction, significantly delaying oil aging, extending its service life, and maintaining the oil's insulation properties and physicochemical stability; anti-hydrolysis agents can preferentially react with water molecules, protecting the ester bonds from being destroyed by water, and maintaining the oil's chemical stability, viscosity, and insulation properties.

[0009] Polyols provide rigid branched cores, branched unit acids disrupt molecular symmetry, flexible dicarboxylic acids enhance chain segment movement, vacuum distillation removes crystal nucleus impurities, and additives prevent negative interference; thus, the insulating medium maintains good fluidity at low temperatures and exhibits good low-temperature performance.

[0010] Preferably, the polyol is trimethylolpropane, and the dicarboxylic acid is one or more of adipic acid, azelaic acid, and sebacic acid.

[0011] By adopting the above technical solution, trimethylolpropane is a symmetrical polyol containing three primary hydroxyl groups. After esterification with a diacid, it forms a trimer structure. The molecule exhibits a highly branched configuration in the shape of a star or Y, which increases the activation energy of thermal decomposition, inhibits the generation of volatile flammable small molecules, and improves the flame retardant effect. In addition, the diacid provides flexible methylene segments, which ensures low-temperature fluidity while avoiding low boiling point caused by excessively short segments, thereby ensuring that the finished insulating medium has the advantages of good flame retardant effect and good low-temperature performance.

[0012] Preferably, in S1, the mass ratio of polyol to dicarboxylic acid is (3.8-3.9):1, the mass ratio of polyol to monocarboxylic acid is 1:(2.4-3.0), the mass ratio of polyol to catalyst is (100-160):1, and the mass ratio of polyol to water-carrying agent is (8-16):1.

[0013] By adopting the above technical solution, the raw material ratio is limited to ensure the stability of the ester bonds in the synthetic ester base oil prepared by the esterification reaction, thereby improving its flame resistance and ensuring its flow properties.

[0014] Preferably, the metal deactivator is one or more of benzotriazole, methyltriazole and thiadiazole, and the anti-hydrolysis agent is carbodiimide.

[0015] By adopting the above technical solutions, benzotriazole and methyltriazole form a dense protective film on the metal surface of copper and copper alloys, preventing them from catalyzing oil oxidation and corrosion; thiadiazole derivatives have a special effect on copper, inhibiting corrosion by chelating with metal ions or forming a film, while also having anti-wear and deactivation functions. When used in combination with antioxidants, they significantly improve the antioxidant performance of oils.

[0016] Carbodiimide can react with water to form stable urea compounds, which consume water and prevent the hydrolysis of ester base oils, thereby maintaining the stability of oil viscosity, acid value and insulation properties, and extending service life.

[0017] Preferably, the amount of antioxidant added in S3 is 0.3%-0.5%, the amount of metal deactivator added is 50-200 ppm, and the amount of anti-hydrolysis agent added is 0.02%-0.2%.

[0018] By adopting the above technical solution and limiting the amount of raw materials, the finished insulating medium can be guaranteed to have good insulation effect and good low-temperature stability, thus extending the service life of the insulating medium.

[0019] Preferably, the esterification reaction temperature is 210-230℃ and the esterification gas flow rate is 30-100mL / min.

[0020] By employing the above technical solution and limiting the esterification temperature and gas flow rate within the range of 210-230℃, the generated esters possess a highly branched, symmetrical carbon skeleton structure. Their thermal decomposition temperature is approximately 50℃ higher than that of diesters, significantly increasing the auto-ignition point and flash point. This temperature range effectively removes unreacted free acids and alcohols, reducing acid value and volatile component content, and minimizing low-boiling-point combustible residues, thereby improving the thermal stability and ignition resistance of the oil, and enhancing the flame retardancy of the finished product. Regarding gas flow rate, excessively low flow rates (less than 30 mL / min) can easily lead to moisture retention, increased acid value, and deterioration of low-temperature fluidity; excessively high flow rates (greater than 100 mL / min) may carry away low-molecular-weight ester components, disrupting the uniformity of molecular weight distribution and affecting low-temperature viscosity. Therefore, limiting the esterification temperature and gas flow rate ensures that the finished insulating medium possesses the advantages of good flame retardancy and excellent low-temperature performance. Preferably, the specific steps of the vacuum distillation process are as follows: Activated carbon is added at a temperature of 60-80℃, and then the temperature is raised to 210-230℃ and the vacuum degree is -0.095 to -0.1MPa for vacuum distillation.

[0021] By adopting the above technical solution, activated carbon maintains high porosity activity within this temperature range. Sulfides, nitrides, colloids, pigments, and trace amounts of free acids are captured through physical adsorption. These impurities are active sites for oxidation catalysis and hydrolysis reactions. The temperature range of 60-80℃ is higher than room temperature but lower than the ester decomposition temperature, which increases the impurity diffusion rate while preventing thermal oxidation of the oil or collapse of the activated carbon channels, achieving selective purification. The flammable components such as colloids and polycyclic aromatic hydrocarbons removed by activated carbon, in synergy with the low-boiling-point esters removed by vacuum distillation, significantly reduce the volatile combustible content of the oil, increase the proportion of high-purity, high-molecular-weight ester structures, raise the auto-ignition point, increase the flash point, and make the ester bonds more stable at high temperatures, reducing the generation of combustible small molecules through thermal decomposition. The limited vacuum degree of -0.095 to -0.1 MPa lowers the oil boiling point, allowing low-molecular-weight esters, residual alcohols, water, and volatile acids that would normally require temperatures above 300℃ to be safely removed at 210-230℃.

[0022] Preferably, S1 further comprises tris(2-hydroxyethyl) phosphate, modified nano aluminum hydroxide, and carrier nano boron nitride, wherein the mass ratio of polyol, tris(2-hydroxyethyl) phosphate, modified nano aluminum hydroxide, and carrier nano boron nitride is 100:0.5-0.65:0.8-1:0.35-0.5.

[0023] By adopting the above technical solution, the hydroxyl groups in tris(2-hydroxyethyl) phosphate undergo esterification with polyols / diacids, covalently bonding phosphorus elements into the ester molecular backbone to form an inherently flame-retardant ester structure, avoiding later migration loss. When thermally decomposed, it releases phosphorus-containing free radicals, which efficiently capture ·OH and H· free radicals in the combustion chain reaction, interrupting the flame propagation chain reaction and improving the flame-retardant effect. Combined with the heat-absorbing flame retardancy of nano-aluminum hydroxide and the thermal conductivity and insulation of nano-boron nitride, the flame-retardant effect is further improved.

[0024] Tris(2-hydroxyethyl) phosphate can combine with nano-aluminum hydroxide to form a P-Al-O hybrid carbon layer, improving the density, strength, and thermal stability of the carbon layer structure. The phosphorus component of tris(2-hydroxyethyl) phosphate also works with the boron component in boron nitride to synergistically catalyze the dehydration and carbonization of polyester at high temperatures, forming a dense carbon layer rich in POB cross-linked structure. This prevents heat conduction, blocks oxygen penetration and the escape of combustible volatiles. The layered structure of boron nitride restricts the thermal stability of the carbon layer, thereby further improving the flame retardant effect of the finished product.

[0025] Preferably, the loaded nano-boron nitride is obtained by activating nano-boron nitride, treating it with gallic acid to obtain grafted boron nitride, and then treating the grafted boron nitride with triaryl phosphate at a mass ratio of 5:3-5.

[0026] By employing the above technical solution, the surface hydroxyl content of nano-boron nitride is increased after activation, followed by gallic acid treatment. Utilizing the extremely strong hydrogen bond donor / acceptor ability of gallic acid's three phenolic hydroxyl groups and one carboxyl group, it can anchor to the surface of nano-boron nitride via hydrogen bonds. The carboxyl group and the ortho-position phenolic hydroxyl group can form coordinate bonds or hydrogen bonds with boron atoms (Lewis sites) at the edge of boron nitride or with surface hydroxyl groups. The polyphenol structure can enhance the adsorption attraction with the six-membered ring of boron nitride through π electrons, forming an attachment containing phenolic hydroxyl groups on the surface of boron nitride. This, combined with the highly polar P in triaryl phosphate esters... =O groups and aromatic rings; the gallic acid-modified boron nitride surface provides a large number of -OH groups, which can form strong hydrogen bonds with the P=O of triaryl phosphate. At the same time, the benzene ring of gallic acid and the aryl group of triaryl phosphate can undergo π-π stacking, further enhancing the interfacial bonding. That is, by using gallic acid as a molecular chain bridge, triaryl phosphate is more stably adhered to the boron nitride surface. This not only improves the dispersion uniformity of nano-boron nitride in the esterification reaction process of polyols and diacids, but also improves the connection stability of nano-boron nitride in polyester chains.

[0027] During the esterification reaction of the carrier nano-boron nitride with polyols and diacids, after the polyester backbone is formed, the phosphate ester-OR and polyester-OH on the surface of the nano-boron nitride form a bridging network. The phenolic hydroxyl groups and the carboxyl groups in the polyester form a nano-boron nitride-ester-polyester covalent connection, which improves the connection and anchoring between the carrier nano-boron nitride and the polyester chain segments. Combined with the nanoscale filling and support effect of nano-boron nitride, the crosslinking density of the synthetic ester base oil is increased. The high crosslinking density results in good flame resistance.

[0028] The combination of tri(2-hydroxyethyl) phosphate, nano-boron nitride, gallic acid, and triaryl phosphate introduces phosphorus into the polyester backbone through esterification. Combined with the physical barrier and thermal conductivity formed between the molecular chains by triaryl phosphate and nano-boron nitride, the stability of the base oil skeleton is ensured while improving the flame retardancy. Furthermore, during combustion, triaryl phosphate first releases phosphorus free radicals to form a carbon layer, protecting the triaryl phosphate-doped backbone and further enhancing the flame retardancy of the synthetic ester base oil.

[0029] Preferably, the nano-aluminum hydroxide composite is prepared from nano-aluminum hydroxide and isooctanol phosphate in a mass ratio of 1:0.5-1.

[0030] By adopting the above technical solution, the surface of nano-aluminum hydroxide contains hydroxyl groups, and isooctanol phosphate also contains hydroxyl groups. Hydrogen bonding facilitates the connection of isooctanol phosphate to the surface of nano-aluminum hydroxide, and the phosphate groups in the phosphate ester are easy to anchor on the surface of aluminum hydroxide, so that aluminum hydroxide is uniformly dispersed in polyol and diacid. Furthermore, phosphate ester-polyol-diacid form POC ester bonds to construct a three-dimensional network. In the network structure, the phosphate ester unit acts as a rigid crosslinking point, restricting the movement of polymer chain segments and improving thermal stability. At the same time, phosphorus promotes the formation of a carbon layer when heated, isolating oxygen and heat transfer. Combined with the high degree of crosslinking and the flame-retardant effect of aluminum hydroxide, the flame resistance of the synthetic ester base oil is further improved.

[0031] In summary, this application has the following beneficial effects: 1. Synthetic ester base oils are prepared by esterification reaction of polyols with diacids and monoacids. The molecular chains contain a large number of polar ester groups, which have strong intermolecular forces, high structural stability, low volatility, and high auto-ignition point, thus improving flame resistance. In addition, the ester molecules contain oxygen atoms, which can capture free radicals during combustion, interrupt the free radical chain reaction, and inhibit flame propagation. At the same time, the ester chains crosslink at high temperature to form a dense carbon layer, which blocks heat transfer and further improves the flame resistance.

[0032] 2. The combination of triaryl phosphate, tri(2-hydroxyethyl) phosphate and isooctanol phosphate has high compatibility, triaryl phosphate has a high boiling point and is not easily lost, and all three have good insulation properties. Aluminum hydroxide and boron nitride also have insulation properties, ensuring that the finished product has good flame retardancy and good insulation properties.

[0033] 3. Aluminum hydroxide and boron nitride have insulating properties, and the finished medium has good insulation properties. Detailed Implementation

[0034] The present application will be further described in detail below with reference to the embodiments.

[0035] Preparation example of modified nano aluminum hydroxide All of the following ingredients are commercially available.

[0036] Preparation Example 1: Modified nano-aluminum hydroxide was prepared using the following method: 0.8 kg of isooctanol phosphate was uniformly sprayed onto the surface of 1 kg of nano aluminum hydroxide. The average particle size of the nano aluminum hydroxide was 200 nm. After uniform mixing, nano aluminum hydroxide composite material was obtained.

[0037] Preparation Example 2: The difference between this preparation example and Preparation Example 1 is that: 0.5 kg of isooctanol phosphate was uniformly sprayed onto the surface of 1 kg of nano aluminum hydroxide and mixed evenly to obtain nano aluminum hydroxide composite material.

[0038] Preparation Example 3: The difference between this preparation example and Preparation Example 1 is that: 1 kg of isooctanol phosphate was uniformly sprayed onto the surface of 1 kg of nano aluminum hydroxide and mixed evenly to obtain nano aluminum hydroxide composite material.

[0039] Example of preparation of loaded boron nitride nanoparticles All of the following ingredients are commercially available.

[0040] Preparation Example 4: Loaded boron nitride nanoparticles were prepared using the following method: 100g of boron nitride nanoparticles were dispersed in 5000g of concentrated nitric acid and soaked for 30min. Then, the boron nitride nanoparticles were separated by filtration. The average particle size of the boron nitride nanoparticles was 200nm and the concentration of concentrated nitric acid was 98%, thus obtaining activated boron nitride. 100g of activated boron nitride was dispersed in 3000mL of anhydrous DMF and ultrasonically dispersed for 10min. Then, 30g of gallic acid and EDC were added, with a molar ratio of gallic acid to EDC of 1:1.2. The mixture was stirred at 60℃ for 6h under nitrogen protection. The precipitate was collected by centrifugation and washed three times each with DMF, ethanol and water, and then dried to obtain grafted boron nitride. 50g of grafted boron nitride was dispersed in 2000mL of ethanol and stirred for 30min. 40g of triaryl phosphate was added and ultrasonically dispersed at 20kHz for 30min. Then, the mixture was stirred at 50℃ for 3h. The precipitate was collected by centrifugation, washed three times with ethanol, and finally dried under vacuum to obtain loaded boron nitride nanoparticles.

[0041] Preparation Example 5: The difference between this preparation example and Preparation Example 4 is that: 50g of grafted boron nitride was dispersed in 2000mL of ethanol and stirred for 30min. Then, 30g of triaryl phosphate was added and ultrasonically dispersed at 20kHz for 30min. The mixture was then stirred at 50℃ for 3h. The precipitate was collected by centrifugation, washed three times with ethanol, and finally dried under vacuum to obtain loaded boron nitride nanoparticles.

[0042] Preparation Example 6: The difference between this preparation example and Preparation Example 4 is that: 50g of grafted boron nitride was dispersed in 2000mL of ethanol and stirred for 30min. Then, 50g of triaryl phosphate was added and ultrasonically dispersed at 20kHz for 30min. The mixture was then stirred at 50℃ for 3h. The precipitate was collected by centrifugation, washed three times with ethanol, and finally dried under vacuum to obtain loaded boron nitride nanoparticles. Example

[0043] All of the following ingredients are commercially available.

[0044] Example 1: A method for preparing a complex ester-type high ignition point insulating dielectric: S1. Mix 399.2g of polyol, 103.5g of diacid, 1021.5g of monoacid, 3g of catalyst and 30g of water-carrying agent and add them to the reaction vessel. The polyol is trimethylolpropane, the diacid is adipic acid, the monoacid is octanoic acid, the catalyst is stannous oxalate catalyst, and the water-carrying agent is petroleum ether. Use nitrogen as a protective gas with a purity of 99.99%. Adjust the gas flow rate to 50mL / min, stir and heat to 225℃ to carry out the esterification reaction until no water is released, and obtain the esterification product. S2. Cool the reaction system to 80℃, add 20g of activated carbon, and perform vacuum distillation at 220℃ and -0.097MPa until no fraction is produced. Stop heating, filter, and obtain synthetic ester base oil. S3. Add 0.35% antioxidant, 100ppm metal deactivator, and 0.05% hydrolysis inhibitor to the synthetic ester base oil and mix evenly. The antioxidant is octyl diphenylamine, the metal deactivator is benzotriazole, and the hydrolysis inhibitor is carbodiimide. Use nitrogen as a protective gas and stir and blend at 70°C for 1 hour to obtain the insulating medium.

[0045] Example 2: The difference between this example and Example 1 is that: S1. Mix 399.2g of polyol, 103.5g of diacid, 1120.9g of monoacid, 3.5g of catalyst and 35g of water-carrying agent and add them to the reaction vessel. The polyol is trimethylolpropane, the diacid is adipic acid, the monoacid is nonanoic acid, the catalyst is stannous oxalate catalyst, and the water-carrying agent is petroleum ether. Use nitrogen as a protective gas, adjust the gas flow rate to 40mL / min, stir and heat to 230℃ to carry out the esterification reaction until no water is released, and obtain the esterification product. S2. Cool the reaction system to 80℃, add 20g of activated carbon, and perform vacuum distillation at 230℃ and -0.096MPa until no fraction is produced. Stop heating, filter, and obtain synthetic ester base oil. S3. Add 0.4% antioxidant, 120ppm metal deactivator, and 0.08% hydrolysis inhibitor to the synthetic ester base oil and mix thoroughly. The antioxidant is 0.1% octyl diphenylamine and 0.3% 2,6-di-tert-butyl-p-cresol. The metal deactivator is benzotriazole and the hydrolysis inhibitor is carbodiimide. Use nitrogen as a protective gas and stir and mix at 60°C for 2 hours to obtain the insulating medium.

[0046] Example 3: The difference between this example and Example 1 is that: S1. Mix 399.2g of polyol, 103.5g of diacid, 1071.1g of monoacid, 3g of catalyst and 30g of water-carrying agent and add them to the reaction vessel. The polyol is trimethylolpropane, the diacid is adipic acid, the monoacid is composed of 510.7g of adipic acid and 510.7g of octanoic acid, the catalyst is stannous oxalate catalyst, and the water-carrying agent is petroleum ether. Use nitrogen as protective gas, adjust the gas flow rate to 50mL / min, stir and heat to 220℃ to carry out esterification reaction until no water is released, and obtain the esterification product. S2. Cool the reaction system to 80℃, add 20g of activated carbon, and perform vacuum distillation at 220℃ and -0.097MPa until no fraction is produced. Stop heating, filter, and obtain synthetic ester base oil. S3, 0.35% antioxidant, 100ppm metal deactivator, and 0.1% anti-hydrolysis agent are added to the synthetic ester base oil and mixed evenly. The antioxidant consists of 0.25% pentyl diphenylamine and 0.1% 2,6-di-tert-butyl-p-cresol. The metal deactivator is methyltriazole and the anti-hydrolysis agent is carbodiimide. Nitrogen is used as the protective gas, and the mixture is stirred and blended at 70°C for 2 hours to obtain the insulating medium.

[0047] Example 4: The difference between this example and Example 1 is that: S1. Mix 399.2g of polyol, 103.8g of diacid, 1110.5g of monoacid, 3.5g of catalyst and 30g of water-carrying agent and add them to the reaction vessel. The polyol is trimethylolpropane, the diacid is composed of 66.9g of adipic acid and 36.9g of azelaic acid, the monoacid is composed of 660g of octanoic acid and 450.5g of decanoic acid, the catalyst is stannous oxalate catalyst, the water-carrying agent is petroleum ether, nitrogen is used as protective gas, the gas flow rate is adjusted to 40mL / min, stir and heat to 230℃ to carry out esterification reaction until no water is released, and the esterification product is obtained. S2. Cool the reaction system to 80℃, add 20g of activated carbon, and perform vacuum distillation at 230℃ and -0.097MPa until no fraction is produced. Stop heating, filter, and obtain synthetic ester base oil. S3. Add 0.4% antioxidant, 120ppm metal deactivator, and 0.06% hydrolysis inhibitor to the synthetic ester base oil and mix evenly. The antioxidant is octyl diphenylamine, the metal deactivator is methyltriazole, and the hydrolysis inhibitor is carbodiimide. Use nitrogen as a protective gas and stir and blend at 80°C for 1 hour to obtain the insulating medium.

[0048] Example 5: The difference between this example and Example 1 is that: S1. Mix 399.2g of polyol, 102.4g of dicarboxylic acid, 958.1g of monocarboxylic acid, 2.495g of catalyst and 24.95g of water-carrying agent and add them to the reaction vessel; use nitrogen as a protective gas, adjust the gas flow rate to 30mL / min, stir and heat to 210℃ to carry out the esterification reaction until no water is released, and obtain the esterification product; S2. Cool the reaction system to 60℃, add 20g of activated carbon, and perform vacuum distillation at 210℃ and -0.1MPa until no fraction is produced. Stop heating, filter, and obtain synthetic ester base oil. S3, add 0.3% antioxidant, 50ppm metal deactivator, and 0.02% anti-hydrolysis agent to synthetic ester base oil and mix thoroughly.

[0049] Example 6: The difference between this example and Example 1 is that: S1. Mix 399.2g of polyol, 105.1g of diacid, 1196.6g of monoacid, 3.992g of catalyst and 49.9g of water-carrying agent and add them to the reaction vessel; use nitrogen as a protective gas, adjust the gas flow rate to 100mL / min, stir and heat to 230℃ to carry out the esterification reaction until no water is released, and obtain the esterification product; S2. Cool the reaction system to 80℃, add 20g of activated carbon, and perform vacuum distillation at 230℃ and -0.095MPa until no fraction is produced. Stop heating, filter, and obtain synthetic ester base oil. S3, add 0.5% antioxidant, 200ppm metal deactivator, and 0.2% anti-hydrolysis agent to the synthetic ester base oil and mix thoroughly.

[0050] Example 7: The difference between this example and Example 1 is that: In S1, 399.2g of polyol, 105.1g of dicarboxylic acid, 1196.6g of monocarboxylic acid, 3.992g of catalyst, 49.9g of water-carrying agent, 2.3952g of tris(2-hydroxyethyl) phosphate, 3.5928g of modified nano-aluminum hydroxide and 1.7964g of carrier nano-boron nitride are mixed and added to the reactor.

[0051] Example 8: The difference between this example and Example 7 is that: In S1, 399.2g of polyol, 105.1g of dicarboxylic acid, 1196.6g of monocarboxylic acid, 3.992g of catalyst, 49.9g of water-carrying agent, 1.996g of tris(2-hydroxyethyl) phosphate, 3.1936g of modified nano-aluminum hydroxide and 1.3972g of carrier nano-boron nitride are mixed and added to the reactor.

[0052] Example 9: The difference between this example and Example 7 is that: In S1, 399.2g of polyol, 105.1g of dicarboxylic acid, 1196.6g of monocarboxylic acid, 3.992g of catalyst, 49.9g of water-carrying agent, 2.5948g of tris(2-hydroxyethyl) phosphate, 3.992g of modified nano-aluminum hydroxide and 1.996g of carrier nano-boron nitride are mixed and added to the reactor.

[0053] Example 10: The difference between this example and Example 7 is that: Tris(2-hydroxyethyl) phosphate was not added to the raw materials. Modified nano-aluminum hydroxide was replaced with an equal mass of nano-aluminum hydroxide, and the carrier nano-boron nitride was replaced with an equal mass of nano-boron nitride.

[0054] Example 11: The difference between this example and Example 7 is that: During the preparation of loaded boron nitride nanoparticles, no activation and gallic acid treatment were performed.

[0055] Example 12: The difference between this example and Example 7 is that: No modified nano-aluminum hydroxide or nano-boron nitride was added to the raw materials.

[0056] Performance testing 1. Flame resistance test Insulating media were prepared using the methods of Examples 1-4 and 7-12, respectively. The open-cup flash point and ignition point were tested according to GB / T3536-2008, and the data were recorded.

[0057] 2. Insulation performance testing Insulating media were prepared using the methods described in Examples 1-4, and the breakdown voltage was tested and recorded in accordance with GB / T507-2002.

[0058] 3. Low-temperature performance testing Insulating media were prepared using the methods described in Examples 1-4, and the pour point was tested according to GB / T3535-2006, with data recorded.

[0059] 4. Viscosity testing Insulating media were prepared using the methods described in Examples 1-4, and the viscosity at 40°C was tested according to GB / T265-1988, and the data were recorded.

[0060] 5. Acid value testing Insulating media were prepared using the methods described in Examples 1-4, and the acid value was tested and recorded in accordance with GB / T4945-2002.

[0061] Table 1 Performance Test Table (Note: " / " in the table indicates that no data was tested for the corresponding item and there are no records)

[0062] As can be seen from Examples 1-4 and Table 1, the high flash point and ignition point of the insulating medium prepared in this application are relatively high, exhibiting good flame retardant effect and ensuring the safety of the product during use. Secondly, the finished product has a high breakdown voltage, which can ensure good insulation of the product during use. Furthermore, the finished product has a low acid value, avoiding any impact on the dielectric loss of the product. At the same time, the finished product has a low pour point, ensuring that the oil still has good fluidity when the equipment is started at low temperatures.

[0063] As can be seen from Examples 1 and 7-9 and Table 1, the addition of tris(2-hydroxyethyl) phosphate, modified nano aluminum hydroxide, and nano boron nitride as the carrier improves the flame retardancy of the finished insulating medium.

[0064] Combining Examples 7 and 10-12 with Table 1, it can be seen that in Example 10, no tris(2-hydroxyethyl) phosphate was added to the raw materials. The modified nano-aluminum hydroxide was replaced with an equal mass of nano-aluminum hydroxide, and the carrier nano-boron nitride was replaced with an equal mass of nano-boron nitride. Compared with Example 7, the open flash point and ignition point of Example 10 were lower than those of Example 7. This indicates that the combination of tris(2-hydroxyethyl) phosphate, triaryl phosphate, and isooctyl phosphate, through the flame-retardant effect of phosphorus-based substances, and the cross-linking of the three with polyols and diacids, improves the density of the cross-linked structure and further enhances the flame retardancy of the finished medium.

[0065] In Example 11, the preparation of loaded boron nitride nanoparticles was carried out without activation and gallic acid treatment. Compared to Example 7, the open flash point and ignition point of Example 11 were lower. This indicates that activation and gallic acid treatment promote the loading of triaryl phosphate esters on the surface of boron nitride nanoparticles. The phosphate ester-OR and polyester-OH on the surface of boron nitride nanoparticles form a bridging network. The phenolic hydroxyl groups and the carboxyl groups in the polyester form a covalent bond between boron nitride nanoparticles, ester, and polyester, which improves the connection and anchoring between the loaded boron nitride nanoparticles and polyester segments. Combined with the nanoscale filling and support effect of boron nitride nanoparticles, the crosslinking density of the synthetic ester base oil is increased. The higher the crosslinking density, the better the flame retardancy, thereby improving the flame retardancy of the grafted product.

[0066] In Example 12, no modified nano-aluminum hydroxide or nano-boron nitride was added to the raw materials. Compared with Example 7, the open flash point and ignition point of Example 12 were lower than those of Example 7. This indicates that nano-aluminum hydroxide and nano-boron nitride have good flame retardancy and are well linked with polyols and diacids, increasing the structural density and thus further improving the flame retardancy of the finished medium.

[0067] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a complex ester-type high ignition point insulating dielectric, characterized in that, Includes the following steps: S1. Mix polyol, dicarboxylic acid, monocarboxylic acid, catalyst and water-carrying agent, and carry out esterification reaction to obtain esterification product; S2. The esterification product is subjected to vacuum distillation to obtain synthetic ester base oil; S3. Antioxidants, metal deactivators, and anti-hydrolysis agents are added to synthetic ester base oils to obtain insulating media.

2. The method for preparing a complex ester-type high ignition point insulating dielectric according to claim 1, characterized in that, The polyol is trimethylolpropane, and the dicarboxylic acid is one or more of adipic acid, azelaic acid, and sebacic acid.

3. The method for preparing a complex ester-type high ignition point insulating dielectric according to claim 1, characterized in that, In S1, the mass ratio of polyol to dicarboxylic acid is (3.8-3.9):1, the mass ratio of polyol to monocarboxylic acid is 1:(2.4-3.0), the mass ratio of polyol to catalyst is (100-160):1, and the mass ratio of polyol to water-carrying agent is (8-16):

1.

4. The method for preparing a complex ester-type high ignition point insulating dielectric according to claim 1, characterized in that, The metal deactivator is one or more of benzotriazole, methylbenztriazole and thiadiazole, and the anti-hydrolysis agent is carbodiimide.

5. The method for preparing a complex ester-type high ignition point insulating dielectric according to claim 1, characterized in that, The antioxidant in S3 is added at a rate of 0.3%-0.5%, the metal deactivator at a rate of 50-200 ppm, and the anti-hydrolysis agent at a rate of 0.02%-0.2%.

6. The method for preparing a complex ester-type high ignition point insulating dielectric according to claim 1, characterized in that, The esterification reaction temperature is 210-230℃, and the esterification gas flow rate is 30-100mL / min.

7. The method for preparing a complex ester-type high ignition point insulating dielectric according to claim 1, characterized in that, The specific steps of the vacuum distillation process are as follows: Activated carbon is added at a temperature of 60-80℃, and then the temperature is raised to 210-230℃ and the vacuum degree is -0.095 to -0.1MPa for vacuum distillation.

8. The method for preparing a complex ester-type high ignition point insulating dielectric according to claim 1, characterized in that, The S1 also includes tris(2-hydroxyethyl) phosphate, modified nano aluminum hydroxide, and loaded nano boron nitride, with the mass ratio of polyol, tris(2-hydroxyethyl) phosphate, modified nano aluminum hydroxide, and loaded nano boron nitride being 100:0.5-0.65:0.8-1:0.35-0.

5.

9. The method for preparing a complex ester-type high ignition point insulating dielectric according to claim 8, characterized in that, The loaded nano-boron nitride is obtained by activating nano-boron nitride, treating it with gallic acid to obtain grafted boron nitride, and then treating the grafted boron nitride with triaryl phosphate at a mass ratio of 5:3-5.

10. The method for preparing a complex ester-type high ignition point insulating medium according to claim 8, characterized in that, The nano-aluminum hydroxide composite material is prepared by nano-aluminum hydroxide and isooctanol phosphate in a mass ratio of 1:0.5-1.

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