High temperature resistant anti-aging transformer oil

Abstract

The application discloses a high-temperature-resistant anti-aging transformer oil and belongs to the field of transformer oil preparation, and mainly aims at the defects that the thermal oxidation stability and electrical insulation performance of the transformer oil need to be further improved, and specifically comprises the following components in parts by weight: 80-100 parts of transformer base oil, 0.3-2.5 parts of modified antioxidant and 0.1-0.5 parts of cashew phenol-based metal passivator. In the application, cashew phenol is acetylated and epoxidized to obtain modified epoxy cashew phenol, then the modified epoxy cashew phenol is subjected to aminolysis ring-opening and acylation with a hindered phenol to obtain a modified antioxidant, and finally, the modified antioxidant is synergistically compounded with the cashew phenol-based metal passivator in the transformer base oil to obtain the transformer oil, so that the thermal oxidation stability and electrical insulation performance of the transformer oil are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of transformer oil preparation, and more specifically to a high-temperature resistant and anti-aging transformer oil. Background Technology

[0002] As the insulating and heat dissipation medium in oil-immersed transformers, the performance requirements of transformer oil have gradually evolved from initially focusing on breakdown voltage, oxidation stability, and low-temperature fluidity to simultaneously considering dielectric strength, heat dissipation efficiency, fire resistance, environmental friendliness, compatibility with paper insulation systems, and long-term thermal aging stability. Currently, mineral insulating oil is still the main type used in engineering applications. However, as equipment develops towards larger capacity, higher load, and higher temperature operation, alternative insulating liquids such as natural esters, synthetic esters, high-temperature hydrocarbons, and silicone oils are also continuously developing. Among them, ester-based insulating liquids have gained attention due to their high dielectric properties, good fire resistance, and strong water-holding capacity. However, different types of insulating liquids still have varying degrees of performance balance issues in terms of oxidation stability, viscosity control, long-term aging behavior, and operational and maintenance adaptability.

[0003] Currently, the commonly used base materials for high-temperature resistant and anti-aging transformer oils mainly include naphthenic or paraffinic mineral oils, natural esters, synthetic esters, and some high-temperature insulating liquids. The corresponding common modification methods mainly include deep refining or hydrogenation treatment, adding hindered phenolic or amine antioxidants, combining metal passivators and sulfur corrosion inhibitors, using different base oils for compounding, and adding surface-treated inorganic nanoparticles to the oil or constructing nanofluid systems with the help of surfactants. Although the above technical paths can improve oxidation stability, breakdown voltage, or corrosion resistance to a certain extent, there is still a common problem that small molecule antioxidants are gradually consumed at high temperatures, and high addition amounts may lead to changes in conductivity, dielectric loss, or viscosity. Metal passivators mainly rely on forming a complex protective layer on the copper surface, and their effect will decrease with heat, oxygen, and the accumulation of acidic products in the oil.

[0004] Therefore, transformer oil, under conditions of high temperature, electric field, and coexistence of metal conductors, usually does not undergo a single failure process, but rather a deterioration caused by a combination of multiple factors, including free radical chain oxidation, hydrolysis or acidification involving trace amounts of water, accumulation of polar aging products, and catalysis by metal active centers. Among these factors, the acidic and gum products generated by oxidation further increase viscosity, weaken heat dissipation, and promote a decrease in dielectric loss and insulation performance. Although the oleophilic functional components are beneficial for maintaining dispersion in the oil phase, they often have difficulty exerting a continuous and effective directional effect on moisture, acidic substances, and metal catalytic sites. Although the polar adsorption or reactive components can interact with aging products, they are prone to agglomeration, instability, or insufficient service life in the non-polar oil phase.

[0005] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0006] This invention provides a high-temperature resistant, anti-aging transformer oil to address the technical problem that the thermal oxidation stability and electrical insulation performance of transformer oils in the prior art need to be further improved.

[0007] The objective of this invention can be achieved through the following technical solution: a high-temperature resistant and anti-aging transformer oil, comprising the following components by weight: 80-100 parts transformer base oil, 0.3-2.5 parts modified antioxidant and 0.1-0.5 parts cashew phenol-based metal passivating agent;

[0008] The modified antioxidant was prepared by reacting 4,4'-diaminodiphenylmethane, modified epoxy cashew phenol, and 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride.

[0009] The cashew phenol-based metal passivating agent is prepared by reacting benzotriazole, paraformaldehyde and cashew phenol.

[0010] Furthermore, the transformer base oil is one or more of the following: naphthenic mineral insulating oil, paraffinic mineral insulating oil, natural vegetable insulating oil, and synthetic ester insulating oil.

[0011] Furthermore, the modified antioxidant is prepared by the following steps:

[0012] A1. Place 4,4'-diaminodiphenylmethane, ethanol and toluene in a reaction vessel under nitrogen atmosphere and stir. Heat the reaction vessel to 55-65℃, add modified epoxy cashew phenol, heat the reaction vessel to 80-90℃, keep it at the temperature and stir for 6-8 hours, and then process to obtain cashew phenol amino alcohol.

[0013] A2. Place cashew phenol amino alcohol and acetonitrile in a reaction vessel under nitrogen atmosphere and stir. Cool the reaction vessel to 0-5℃, add triethylamine, stir for 5-10 min, add 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride dropwise, heat the reaction vessel to 50-60℃, keep the reaction at this temperature for 20-24 h, and then perform post-treatment to obtain the modified antioxidant.

[0014] The reaction formula for preparing the modified antioxidant is as follows:

[0015]

[0016] In the formula: ; .

[0017] Further, in step A1, the ratio of 4,4'-diaminodiphenylmethane, ethanol, toluene, and modified epoxy cashew phenol is 1-3g:5-15mL:20-25mL:1-4g. The post-processing step includes: after the reaction is complete, after the reaction vessel cools to room temperature, the reaction solution is transferred to a rotary evaporator at a temperature of 80-90℃, and the low-boiling-point solvent is removed by rotary evaporation under reduced pressure. The crude product is then added to five times its volume of dichloromethane. The mixture was transferred to a separatory funnel and washed 1-3 times with deionized water. The organic phase was then transferred to a rotary evaporator at a temperature of 30-50℃ and evaporated under reduced pressure until no liquid was collected, yielding cashew phenol amino alcohol. The mass spectrometry data of cashew phenol amino alcohol were: m / z: 918.68 (100.0%), 919.68 (65.8%), 920.69 (20.8%), 921.69 (5.2%), 920.68 (1.7%).

[0018] Further, in step A2, the ratio of cashew phenol amino alcohol, acetonitrile, triethylamine, and 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride is 1-3g:60-80mL:1-2mL:2-4g. The post-processing steps include: after the reaction is complete, after the reaction vessel cools to room temperature, the reaction solution is transferred to a rotary evaporator at a temperature of 80-90℃, and the low-boiling solvent is removed by rotary evaporation under reduced pressure. The crude product is added to five times its volume of dichloromethane, transferred to a separatory funnel, and then mixed with saturated sodium bicarbonate aqueous solution and 0.5 mol / L... The organic phase was washed 1-3 times with a 1 / L dilute hydrochloric acid aqueous solution. The organic phase was then transferred to a rotary evaporator at a temperature of 30-50℃ and evaporated under reduced pressure until no liquid was collected, thus obtaining the modified antioxidant. The mass spectrometry data of the modified antioxidant were as follows: m / z: 1440.01 (100.0%), 1439.00 (97.6%), 1441.01 (52.7%), 1442.01 (18.6%), 1443.02 (4.2%), 1444.02 (1.2%), 1443.01 (1.2%).

[0019] Furthermore, the modified epoxy cashew phenol is prepared by the following steps:

[0020] B1. Place cashew phenol, triethylamine and dichloromethane in a reaction vessel and stir. Slowly add acetyl chloride and react at room temperature for 1-2 hours. After post-treatment, cashew phenol acetate is obtained.

[0021] B2. Place cashew phenol acetate, formic acid and concentrated sulfuric acid in a reaction vessel and stir. Heat the reaction vessel to 55-65℃, slowly add hydrogen peroxide, and keep the reaction at this temperature for 4-6 hours. After post-treatment, modified epoxy cashew phenol is obtained.

[0022] Further, in step B1, the ratio of cashew phenol, triethylamine, dichloromethane, and acetyl chloride is 3-5g:1-2mL:15-25mL:1.2-1.4g. The post-processing steps include: after the reaction is completed, the reaction solution is transferred to a separatory funnel, washed 1-3 times with deionized water, and the organic phase is transferred to a rotary evaporator at a temperature of 80-90℃ and distilled under reduced pressure until no liquid is collected to obtain cashew phenol acetate.

[0023] Further, in step B2, the ratio of cashew phenol acetate, formic acid, concentrated sulfuric acid, and hydrogen peroxide is 3-5g:0.2-0.4g:0.01-0.02g:3-6mL, the concentration of hydrogen peroxide is 25-35wt%, the concentration of formic acid is 80-85wt%, and the concentration of concentrated sulfuric acid is 96-98wt%. The post-treatment step includes: after the reaction is completed, the reaction system is cooled to room temperature, the reaction solution is transferred to a separatory funnel, and extracted with dichloromethane 1-3 times. The organic phase is transferred to a separatory funnel and washed successively with saturated sodium bicarbonate aqueous solution and deionized water until neutral. The organic phase is placed in a rotary evaporator and the solvent is removed by vacuum rotary evaporation to obtain modified epoxy cashew phenol.

[0024] Furthermore, the preparation method of the cashew phenol-based metal passivating agent is as follows: benzotriazole, paraformaldehyde, cashew phenol and toluene are placed in a reaction vessel and stirred. The reaction vessel is heated to 90-110℃ and kept at this temperature for 4-6 hours. The cashew phenol-based metal passivating agent is then obtained through post-treatment.

[0025] Furthermore, the ratio of benzotriazole, paraformaldehyde, cashew phenol, and toluene is 1.5-2.5g:0.4-0.6g:4-6g:20-40mL. The post-processing steps include: after the reaction is completed, the reaction vessel is heated to 140-150℃, low-boiling substances are removed by vacuum distillation, the remaining crude product is washed 1-3 times with deionized water, the organic phase is transferred to a rotary evaporator at a temperature of 90-100℃, and vacuum distillation is carried out until no liquid is collected to obtain cashew phenol-based metal passivating agent.

[0026] The present invention has the following beneficial effects:

[0027] 1. This invention blocks the active hydrogen by acetylation of the phenolic hydroxyl group of cashew nut shell and simultaneously reduces the polarity of the system. The side-chain olefin epoxidation eliminates the unsaturated double bonds that are prone to thermal and oxygen degradation, thereby blocking the free radical aging pathway. The introduced epoxy groups further provide high-density grafting anchors for subsequent chain extension reactions. This molecular-level acylation and epoxidation synergistic modification enables the cashew nut shell skeleton to have the dual functions of optimizing dielectric properties and improving thermal stability, and lays the chemical foundation for constructing a macromolecular spatial oxygen-resistant network.

[0028] 2. This invention also relies on the amine ring-opening reaction of modified epoxy cashew phenol with diaminodiphenylmethane to introduce a rigid aromatic ring skeleton to expand the molecular volume, and through nucleophilic acyl substitution, hindered phenolic groups are grafted onto the branched skeleton at a high density. The long carbon chain side chain of cashew phenol maintains homogeneous oil solubility. The rigid skeleton and the high density of steric hindrance groups synergistically inhibit the thermal migration and volatilization loss of antioxidant active ingredients at high temperature, so that the free radical scavenging activity can be released in a long-term manner, forming a long-term intramolecular stabilizing effect.

[0029] 3. In addition, the present invention further combines cashew phenol-based metal passivating agents and modified antioxidants in base oil. The Mannich condensation reaction grafts triazole chelating groups onto the long carbon chain skeleton of cashew phenol via methylene bridging. Relying on lipophilicity to overcome polar precipitation defects, it achieves long-term in-situ complexation of free metal ions to block the metal catalytic oxidation pathway. Combined with the construction of a homogeneous dispersion system and vacuum degassing and dehydration treatment, it deeply removes polar moisture, dissolved gases and particulate impurities, improves the breakdown voltage and high-temperature dielectric strength of the system, and establishes long-lasting electrical insulation stability. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] This embodiment provides a method for preparing modified epoxy cashew phenol, specifically including the following steps:

[0033] Step I: Preparation of cashew phenol acetate

[0034] Weigh out 30g of cashew phenol, 10mL of triethylamine and 150mL of dichloromethane and place them in a reaction vessel and stir. Slowly add 12g of acetyl chloride and react at room temperature for 1h. After the reaction is complete, transfer the reaction solution to a separatory funnel and wash it once with deionized water. Transfer the organic phase to a rotary evaporator at 80℃ and distill under reduced pressure until no liquid is collected to obtain cashew phenol acetate.

[0035] Step II: Preparation of modified epoxy cashew phenol

[0036] Weigh out 30g of cashew phenol acetate, 2g of 80wt% formic acid and 0.1g of 96wt% concentrated sulfuric acid and place them in a reaction vessel and stir. Heat the reaction vessel to 55℃ and slowly add 30mL of 25wt% hydrogen peroxide. Keep the reaction vessel at this temperature for 4h. After the reaction is complete, wait for the reaction system to cool to room temperature and transfer the reaction solution to a separatory funnel. Extract the solution once with dichloromethane. Transfer the organic phase to a separatory funnel and wash it successively with saturated sodium bicarbonate aqueous solution and deionized water until neutral. Place the organic phase in a rotary evaporator and remove the solvent by reduced pressure to obtain modified epoxy cashew phenol.

[0037] The phenolic hydroxyl group of cashew phenol undergoes an acylation reaction with acetyl chloride to obtain cashew phenol acetate. Formic acid reacts with hydrogen peroxide in situ under the catalysis of concentrated sulfuric acid to generate peroxyformic acid, which then undergoes an epoxidation reaction with the side chain olefin of cashew phenol acetate to obtain modified epoxy cashew phenol.

[0038] Phenolic hydroxyl acylation blocks active hydrogen, reduces system polarity, optimizes dielectric properties, eliminates early oxidation-sensitive sites, and side-chain olefin epoxidation eliminates unsaturated double bonds that are prone to thermal-oxidative degradation, blocking free radical aging pathways, providing grafting anchors for the introduced epoxy groups, laying the foundation for constructing a macromolecular steric network, and endowing transformer oil with high-temperature thermal stability and long-term anti-aging properties.

[0039] Example 2

[0040] This embodiment provides a method for preparing modified epoxy cashew phenol, specifically including the following steps:

[0041] Step I: Preparation of cashew phenol acetate

[0042] Weigh out 40g of cashew phenol, 15mL of triethylamine and 200mL of dichloromethane and place them in a reaction vessel and stir. Slowly add 13g of acetyl chloride and react at room temperature for 1.5h. After the reaction is complete, transfer the reaction solution to a separatory funnel and wash it twice with deionized water. Transfer the organic phase to a rotary evaporator at 85℃ and distill under reduced pressure until no liquid is collected to obtain cashew phenol acetate.

[0043] Step II: Preparation of modified epoxy cashew phenol

[0044] Weigh out 40g of cashew phenol acetate, 3g of 82.5wt% formic acid, and 0.15g of 97wt% concentrated sulfuric acid and place them in a reaction vessel and stir. Heat the reaction vessel to 60℃ and slowly add 45mL of 30wt% hydrogen peroxide. Keep the reaction vessel at this temperature for 5h. After the reaction is complete, wait for the reaction system to cool to room temperature, transfer the reaction solution to a separatory funnel, and extract it twice with dichloromethane. Transfer the organic phase to a separatory funnel and wash it successively with saturated sodium bicarbonate aqueous solution and deionized water until neutral. Place the organic phase in a rotary evaporator and remove the solvent by reduced pressure to obtain modified epoxy cashew phenol.

[0045] Example 3

[0046] This embodiment provides a method for preparing modified epoxy cashew phenol, specifically including the following steps:

[0047] Step I: Preparation of cashew phenol acetate

[0048] Weigh out 50g of cashew nut shell powder, 20mL of triethylamine and 250mL of dichloromethane and place them in a reaction vessel and stir. Slowly add 14g of acetyl chloride and react at room temperature for 2 hours. After the reaction is complete, transfer the reaction solution to a separatory funnel and wash it three times with deionized water. Transfer the organic phase to a rotary evaporator at 90℃ and distill under reduced pressure until no liquid is collected to obtain cashew nut shell powder acetate.

[0049] Step II: Preparation of modified epoxy cashew phenol

[0050] Weigh out 50g of cashew phenol acetate, 4g of 85wt% formic acid, and 0.2g of 98wt% concentrated sulfuric acid and place them in a reaction vessel and stir. Heat the reaction vessel to 65℃ and slowly add 60mL of 35wt% hydrogen peroxide. Keep the reaction vessel at this temperature for 6h. After the reaction is complete, wait for the reaction system to cool to room temperature and transfer the reaction solution to a separatory funnel. Extract the solution three times with dichloromethane. Transfer the organic phase to a separatory funnel and wash it successively with saturated sodium bicarbonate aqueous solution and deionized water until neutral. Place the organic phase in a rotary evaporator and remove the solvent by vacuum rotary evaporation to obtain modified epoxy cashew phenol.

[0051] Example 4

[0052] This embodiment provides a method for preparing a modified antioxidant, specifically including the following steps:

[0053] Step 1: Preparation of cashew phenol amino alcohol

[0054] Weigh 10g of 4,4'-diaminodiphenylmethane, 50mL of ethanol, and 200mL of toluene and place them in a reaction vessel under nitrogen atmosphere. Stir the mixture and heat the reaction vessel to 55°C. Add 10g of the modified epoxy cashew phenol prepared in Example 1 and heat the reaction vessel to 80°C. Keep the mixture at this temperature and stir for 6 hours. After the reaction is complete, let the reaction vessel cool to room temperature and transfer the reaction solution to a rotary evaporator at 80°C. Remove the low-boiling-point solvent by rotary evaporation under reduced pressure. Add the crude product to five times its volume of dichloromethane and transfer it to a separatory funnel. Wash the product once with deionized water. Transfer the organic phase to a rotary evaporator at 30°C and evaporate under reduced pressure until no liquid is collected to obtain cashew phenol amino alcohol.

[0055] Step 2: Preparation of modified antioxidants

[0056] Weigh 10g of cashew phenol amino alcohol and 600mL of acetonitrile and place them in a reaction vessel under nitrogen atmosphere. Stir the mixture and cool the reaction vessel to 0℃. Add 10mL of triethylamine and stir for 5min. Add 20g of 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride dropwise. Heat the reaction vessel to 50℃ and maintain the temperature for 20h. After the reaction is complete, let the reaction vessel cool to room temperature and transfer the reaction solution to a rotary evaporator at 80℃. Remove the low-boiling solvent by rotary evaporation under reduced pressure. Add the crude product to five times its volume of dichloromethane and transfer it to a separatory funnel. Wash once with saturated sodium bicarbonate aqueous solution and 0.5mol / L dilute hydrochloric acid aqueous solution. Transfer the organic phase to a rotary evaporator at 30℃ and rotary evaporate under reduced pressure until no liquid is collected, thus obtaining the modified antioxidant.

[0057] The amino group of 4,4'-diaminodiphenylmethane nucleophilically attacks the epoxy group of modified epoxy cashew phenol, promoting ring opening to generate cashew phenol amino alcohol containing polyhydroxy and secondary amine structures. Further, under the action of triethylamine acid, 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride undergoes nucleophilic acyl substitution with the newly generated hydroxyl group on cashew phenol amino alcohol, removing hydrogen chloride, and finally obtaining the modified antioxidant.

[0058] The epoxy ring-opening process introduces a rigid aromatic ring skeleton of diphenylmethane, which increases the molecular volume and improves thermal stability. It works synergistically with the cashew phenol side chain to maintain homogeneous oil solubility. Nucleophilic acyl substitution allows for high-density grafting of hindered phenolic groups onto this branched skeleton, constructing a large molecular steric hindrance network. This effectively inhibits the thermal migration and volatilization loss of antioxidant active ingredients under high-temperature conditions, endowing transformer oil with long-lasting free radical scavenging activity and long-term anti-thermal and oxygen aging performance.

[0059] Example 5

[0060] This embodiment provides a method for preparing a modified antioxidant, specifically including the following steps:

[0061] Step 1: Preparation of cashew phenol amino alcohol

[0062] Weigh 20g of 4,4'-diaminodiphenylmethane, 100mL of ethanol, and 225mL of toluene and place them in a reaction vessel under nitrogen atmosphere. Stir the mixture and heat the reaction vessel to 60°C. Add 25g of the modified epoxy cashew phenol prepared in Example 2. Heat the reaction vessel to 85°C and stir for 7 hours. After the reaction is complete, let the reaction vessel cool to room temperature. Transfer the reaction solution to a rotary evaporator at 85°C and remove the low-boiling solvent by rotary evaporation under reduced pressure. Add the crude product to five times its volume of dichloromethane and transfer it to a separatory funnel. Wash the product twice with deionized water. Transfer the organic phase to a rotary evaporator at 40°C and evaporate under reduced pressure until no liquid is collected to obtain cashew phenol amino alcohol.

[0063] Step 2: Preparation of modified antioxidants

[0064] Weigh 20g of cashew phenol amino alcohol and 700mL of acetonitrile and place them in a nitrogen-protected reactor. Stir the reactor and cool it to 3℃. Add 15mL of triethylamine and stir for 7min. Add 30g of 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride dropwise. Heat the reactor to 55℃ and maintain the temperature for 22h. After the reaction is complete, let the reactor cool to room temperature and transfer the reaction solution to a rotary evaporator at 85℃. Remove the low-boiling solvent by rotary evaporation under reduced pressure. Add the crude product to five times its volume of dichloromethane and transfer it to a separatory funnel. Wash the product twice with saturated sodium bicarbonate aqueous solution and 0.5mol / L dilute hydrochloric acid aqueous solution. Transfer the organic phase to a rotary evaporator at 40℃ and rotary evaporate under reduced pressure until no liquid is collected, thus obtaining the modified antioxidant.

[0065] Example 6

[0066] This embodiment provides a method for preparing a modified antioxidant, specifically including the following steps:

[0067] Step 1: Preparation of cashew phenol amino alcohol

[0068] Weigh 30g of 4,4'-diaminodiphenylmethane, 150mL of ethanol, and 250mL of toluene and place them in a nitrogen-protected reactor. Stir the reactor and heat it to 65°C. Add 40g of the modified epoxy cashew phenol prepared in Example 3. Heat the reactor to 90°C and stir for 8 hours. After the reaction is complete, let the reactor cool to room temperature. Transfer the reaction solution to a rotary evaporator at 90°C and remove the low-boiling solvent by rotary evaporation under reduced pressure. Add the crude product to five times its volume of dichloromethane and transfer it to a separatory funnel. Wash the product three times with deionized water. Transfer the organic phase to a rotary evaporator at 50°C and evaporate it under reduced pressure until no liquid is collected to obtain cashew phenol amino alcohol.

[0069] Step 2: Preparation of modified antioxidants

[0070] Weigh 30g of cashew phenol amino alcohol and 800mL of acetonitrile and place them in a reaction vessel under nitrogen atmosphere and stir. Cool the reaction vessel to 5℃, add 20mL of triethylamine, stir for 10min, add 40g of 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride dropwise, heat the reaction vessel to 60℃, and keep the reaction at this temperature for 24h. After the reaction is complete, wait for the reaction vessel to cool to room temperature, transfer the reaction solution to a rotary evaporator at 90℃, remove the low-boiling solvent by rotary evaporation under reduced pressure, add the crude product to five times the volume of dichloromethane, transfer to a separatory funnel, wash three times with saturated sodium bicarbonate aqueous solution and 0.5mol / L dilute hydrochloric acid aqueous solution, transfer the organic phase to a rotary evaporator at 50℃, and rotary evaporate under reduced pressure until no liquid is collected, thus obtaining the modified antioxidant.

[0071] Example 7

[0072] This embodiment provides a high-temperature resistant, anti-aging transformer oil, specifically including the following steps:

[0073] Step ①: Preparation of cashew phenol-based metal passivating agent

[0074] Weigh out 15g of benzotriazole, 4g of paraformaldehyde, 40g of cashew phenol and 200mL of toluene and place them in a reaction vessel and stir. Heat the reaction vessel to 90℃ and keep it at that temperature for 4h. After the reaction is complete, heat the reaction vessel to 140℃ and remove low-boiling substances by vacuum distillation. Wash the remaining crude product once with deionized water. Transfer the organic phase to a rotary evaporator at 90℃ and distill under reduced pressure until no liquid is collected to obtain cashew phenol-based metal passivating agent.

[0075] Step 2: Preparation of blended base oil

[0076] Weigh out 80 parts by weight of transformer base oil and add it to a mixing vessel. Start stirring and heat to 50°C to raise the system temperature to 50°C. Add 0.3 parts of the modified antioxidant prepared in Example 4 and 0.1 parts of cashew phenol-based metal passivating agent. Keep the mixture warm and stir for 1 hour to obtain a mixed base oil.

[0077] Step 3: Prepare high-temperature resistant and anti-aging transformer oil

[0078] The mixed base oil is transferred to a vacuum oil filter for vacuum degassing and dehydration treatment, and fine impurities are removed by precision filtration to obtain high-temperature resistant and anti-aging transformer oil.

[0079] Formaldehyde generated from the depolymerization of paraformaldehyde undergoes condensation with the amino group of benzotriazole and the active hydrogen on the aromatic ring of cashew phenol. The triazole group is introduced into the cashew phenol skeleton through a methylene bridge bond to prepare a cashew phenol-based metal passivating agent. Heating at an appropriate temperature reduces the viscosity of the base oil, promotes the diffusion of modified antioxidant and metal passivating agent molecules and constructs a homogeneous system. The phase equilibrium conditions are changed by vacuum negative pressure to remove trace amounts of water and dissolved gases. After precision filtration to remove solid particulate impurities, a high-temperature resistant and anti-aging transformer oil is obtained.

[0080] Mannich condensation grafts benzotriazole chelating groups onto the cashew phenol backbone, relying on the lipophilicity of the long carbon chain to overcome polar precipitation defects, achieving long-term in-situ complexation of free metal ions, blocking the metal catalytic oxidation pathway, and heating to promote diffusion to eliminate local concentration gradients of multiple components, constructing a highly stable homogeneous dispersion system. Further vacuum phase change separation and mechanical retention deeply remove trace amounts of polar moisture, dissolved gases and particulate impurities, eliminating partial discharge and electric field distortion under high field strength, maximizing the system's breakdown voltage and high-temperature dielectric strength, and establishing the long-lasting electrical insulation stability of transformer oil.

[0081] Example 8

[0082] This embodiment provides a high-temperature resistant, anti-aging transformer oil, specifically including the following steps:

[0083] Step ①: Preparation of cashew phenol-based metal passivating agent

[0084] Weigh out 20g of benzotriazole, 5g of paraformaldehyde, 50g of cashew phenol and 300mL of toluene and place them in a reaction vessel and stir. Heat the reaction vessel to 100℃ and keep it at that temperature for 5h. After the reaction is complete, heat the reaction vessel to 145℃ and remove low-boiling substances by vacuum distillation. Wash the remaining crude product twice with deionized water. Transfer the organic phase to a rotary evaporator at 95℃ and distill under reduced pressure until no liquid is collected to obtain cashew phenol-based metal passivating agent.

[0085] Step 2: Preparation of blended base oil

[0086] Weigh out 90 parts by weight of transformer base oil and add it to a mixing vessel. Start stirring and heat to 60°C to raise the system temperature to 60°C. Add 1.2 parts of the modified antioxidant prepared in Example 5 and 0.25 parts of cashew phenol-based metal passivating agent. Keep the mixture warm and stir for 1.5 hours to obtain a mixed base oil.

[0087] Step 3: Prepare high-temperature resistant and anti-aging transformer oil

[0088] The mixed base oil is transferred to a vacuum oil filter for vacuum degassing and dehydration treatment, and fine impurities are removed by precision filtration to obtain high-temperature resistant and anti-aging transformer oil.

[0089] Example 9

[0090] This embodiment provides a high-temperature resistant, anti-aging transformer oil, specifically including the following steps:

[0091] Step ①: Preparation of cashew phenol-based metal passivating agent

[0092] Weigh out 25g of benzotriazole, 6g of paraformaldehyde, 60g of cashew phenol and 400mL of toluene and place them in a reaction vessel and stir. Heat the reaction vessel to 110℃ and keep it at that temperature for 6h. After the reaction is complete, heat the reaction vessel to 150℃ and remove low-boiling substances by vacuum distillation. Wash the remaining crude product three times with deionized water. Transfer the organic phase to a rotary evaporator at 100℃ and distill under reduced pressure until no liquid is collected to obtain cashew phenol-based metal passivating agent.

[0093] Step 2: Preparation of blended base oil

[0094] Weigh out 100 parts by weight of transformer base oil and add it to a mixing vessel. Start stirring and heat to 70°C to raise the system temperature to 70°C. Add 2.5 parts of the modified antioxidant prepared in Example 6 and 0.5 parts of cashew phenol-based metal passivating agent. Keep the mixture warm and stir for 2 hours to obtain a mixed base oil.

[0095] Step 3: Prepare high-temperature resistant and anti-aging transformer oil

[0096] The mixed base oil is transferred to a vacuum oil filter for vacuum degassing and dehydration treatment, and fine impurities are removed by precision filtration to obtain high-temperature resistant and anti-aging transformer oil.

[0097] Comparative Example 1

[0098] The difference between this comparative example and Example 9 is that, in step II, when preparing modified epoxy cashew phenol, cashew phenol is used in an equal amount to replace cashew phenol acetate.

[0099] Comparative Example 2

[0100] The difference between this comparative example and Example 9 is that, in step (1) when preparing cashew phenol amino alcohol, cashew phenol acetate is used to replace the modified epoxy cashew phenol in an equal amount.

[0101] Comparative Example 3

[0102] The difference between this comparative example and Example 9 is that, in step ② when preparing the mixed base oil, an equal amount of benzotriazole is used instead of the cashew phenol-based metal passivating agent.

[0103] Performance testing:

[0104] Acid value: The acid value of the transformer oils prepared in Examples 7-9 and Comparative Examples 1-3 before and after accelerated oxidation at 120℃ / 164h was determined by potentiometric titration according to the standard GB / T 7304-2014 "Determination of Acid Value of Petroleum Products - Potentiometric Titration Method".

[0105] Breakdown voltage: The breakdown voltage of the transformer oils prepared in Examples 7-9 and Comparative Examples 1-3 was determined using an insulating oil dielectric strength tester in accordance with the standard GB / T 507-2002 "Determination of Breakdown Voltage of Insulating Oil". Spherical electrodes were used for the test, with the electrode spacing controlled at 2.5 mm ± 0.05 mm, the voltage rise rate at 2.0 kV / s ± 0.2 kV / s, and the sample temperature controlled at 20℃ ± 5℃. After the oil sample was placed in the sample cup, it was allowed to stand to remove air bubbles. After 5 minutes when no visible air bubbles were visible, the voltage was applied. After the sample broke down, the test was paused for at least 2 minutes. The test was repeated 6 times, and the arithmetic mean was taken as the test result, expressed in kilovolts (kV). The breakdown voltages were measured before and after accelerated oxidation at 120℃ / 164h and under high temperature conditions of 90℃.

[0106] Thermal stability: The thermal stability of the transformer oils prepared in Examples 7-9 and Comparative Examples 1-3 was determined by thermogravimetric analysis according to GB / T 27761-2011 "Test Method for Weight Loss and Residual Amount of Thermogravimetric Analyzer". 5-10 mg of sample was weighed and placed in an alumina crucible. Under a high-purity nitrogen atmosphere, the temperature was increased from room temperature to 700℃ at a heating rate of 10℃ / min. The thermal decomposition characteristics were evaluated by the 5% weight loss temperature and the maximum weight loss rate temperature. The carbonization property was evaluated by the residual mass rate at 700℃. The thermal oxidation stability under high-temperature conditions was evaluated. See Table 1 for details.

[0107] Table 1 - Performance Test Data of Samples

[0108] Group Project Example 7 Example 8 Example 9 Comparative Example 1 Comparative Example 2 Comparative Example 3 Initial acid value (mgKOH / g) 0.014 0.012 0.015 0.020 0.017 0.014 Acid value after aging / (mgKOH / g) 0.033 0.028 0.031 0.195 0.142 0.068 Breakdown voltage at 20℃ / kV 46.5 49.8 46.2 39.2 40.5 34.6 90℃ breakdown voltage / kV 44.8 45.6 42.5 33.5 35.2 29.8 Breakdown voltage after aging / kV 46.2 48.2 44.5 25.5 28.6 30.5 <![CDATA[T5% / ℃]]> 225 228 222 195 202 225 <![CDATA[T max / ℃]]> 387 395 388 338 355 392 Residual rate at 700℃ / % 2.92 3.28 2.74 0.58 0.82 3.15

[0109] Comparative analysis of the data in Table 1 shows that the transformer oil prepared by this invention has an initial acid value of 0.012 mg KOH / g, an acid value of 0.028 mg KOH / g after aging, a breakdown voltage of 49.8 kV at 20℃, a breakdown voltage of 45.6 kV at 90℃, a breakdown voltage of 48.2 kV after aging, a 5% weight loss temperature of 228℃, a maximum weight loss rate temperature of 395℃, and a residual mass percentage of 3.28% at 700℃. All these data are superior to those of the comparative example.

[0110] In this invention, cashew phenol is first acetylated and epoxidized to obtain modified epoxy cashew phenol, then ring-opened by amine and hindered phenol acylation to obtain modified antioxidant, and finally synergistically compounded with cashew phenol-based metal passivator in transformer base oil to obtain transformer oil, which significantly improves its thermal oxidation stability and electrical insulation performance.

[0111] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A high-temperature resistant, anti-aging transformer oil, characterized in that, It comprises the following components by weight: 80-100 parts transformer base oil, 0.3-2.5 parts modified antioxidant, and 0.1-0.5 parts cashew phenol-based metal passivator; The modified antioxidant was prepared by reacting 4,4'-diaminodiphenylmethane, modified epoxy cashew phenol, and 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride. The cashew phenol-based metal passivating agent is prepared by reacting benzotriazole, paraformaldehyde and cashew phenol.

2. The high-temperature resistant and anti-aging transformer oil according to claim 1, characterized in that, The transformer base oil is one or more of the following: naphthenic mineral insulating oil, paraffinic mineral insulating oil, natural vegetable insulating oil, and synthetic ester insulating oil.

3. The high-temperature resistant and anti-aging transformer oil according to claim 1, characterized in that, The modified antioxidant is prepared by the following steps: A1. Place 4,4'-diaminodiphenylmethane, ethanol and toluene in a reaction vessel under nitrogen atmosphere and stir. Heat the reaction vessel to 55-65℃, add modified epoxy cashew phenol, heat the reaction vessel to 80-90℃, keep it at the temperature and stir for 6-8 hours, and then process to obtain cashew phenol amino alcohol. A2. Place cashew phenol amino alcohol and acetonitrile in a reaction vessel under nitrogen atmosphere and stir. Cool the reaction vessel to 0-5℃, add triethylamine, stir for 5-10 min, add 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride dropwise, heat the reaction vessel to 50-60℃, keep the reaction at this temperature for 20-24 h, and then perform post-treatment to obtain the modified antioxidant.

4. The high-temperature resistant and anti-aging transformer oil according to claim 3, characterized in that, In step A1, the ratio of 4,4'-diaminodiphenylmethane, ethanol, toluene, and modified epoxy cashew phenol is 1-3g:5-15mL:20-25mL:1-4g; in step A2, the ratio of cashew phenol amino alcohol, acetonitrile, triethylamine, and 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride is 1-3g:60-80mL:1-2mL:2-4g.

5. The high-temperature resistant and anti-aging transformer oil according to claim 3, characterized in that, The modified epoxy cashew phenol is prepared by the following steps: B1. Place cashew phenol, triethylamine and dichloromethane in a reaction vessel and stir. Slowly add acetyl chloride and react at room temperature for 1-2 hours. After post-treatment, cashew phenol acetate is obtained. B2. Place cashew phenol acetate, formic acid and concentrated sulfuric acid in a reaction vessel and stir. Heat the reaction vessel to 55-65℃, slowly add hydrogen peroxide, and keep the reaction at this temperature for 4-6 hours. After post-treatment, modified epoxy cashew phenol is obtained.

6. The high-temperature resistant and anti-aging transformer oil according to claim 5, characterized in that, In step B1, the ratio of cashew phenol, triethylamine, dichloromethane, and acetyl chloride is 3-5g:1-2mL:15-25mL:1.2-1.4g; in step B2, the ratio of cashew phenol acetate, formic acid, concentrated sulfuric acid, and hydrogen peroxide is 3-5g:0.2-0.4g:0.01-0.02g:3-6mL, the concentration of hydrogen peroxide is 25-35wt%, the concentration of formic acid is 80-85wt%, and the concentration of concentrated sulfuric acid is 96-98wt%.

7. The high-temperature resistant and anti-aging transformer oil according to claim 1, characterized in that, The preparation method of the cashew phenol-based metal passivating agent is as follows: benzotriazole, paraformaldehyde, cashew phenol and toluene are placed in a reaction vessel and stirred. The reaction vessel is heated to 90-110℃ and kept at the temperature for 4-6 hours. The cashew phenol-based metal passivating agent is obtained by post-treatment.

8. The high-temperature resistant and anti-aging transformer oil according to claim 7, characterized in that, The ratio of benzotriazole, paraformaldehyde, cashew phenol, and toluene is 1.5-2.5g:0.4-0.6g:4-6g:20-40mL.

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