Insulating lubricating oil for electric compressor of new energy automobile and preparation method of insulating lubricating oil

Abstract

The invention provides insulating lubricating oil for an electric compressor of a new energy automobile and a preparation method thereof, and belongs to the technical field of special lubricating oil. The preparation method comprises the following steps: carrying out alkynylation pre-activation on a small amount of polyol ester (POE) base oil, and then covalently linking the activated POE and poly-alpha olefin (PAO) base oil by using a bifunctional crosslinking agent containing furan and maleimide groups by adopting a series distribution process of a copper-catalyzed azide-alkyne cycloaddition reaction (CuACC) and a photo-initiated enol-sulfur reaction. Finally, a dynamic network structure is formed through a reversible cycloaddition reaction between furan and a maleimide group, a functional additive is added, and the insulating lubricating oil capable of self-adjusting the state according to different working conditions of the compressor is obtained. The lubricating oil composition has excellent electrical insulating property, excellent working condition self-adaptive rheological property and high chemical stability and material compatibility, and meets the strict requirements of the new energy automobile electric compressor on lubrication and insulation.

Description

Technical Field

[0001] This invention relates to the field of special lubricating oil technology, specifically to an insulating lubricating oil for electric compressors in new energy vehicles and its preparation method. Background Technology

[0002] With the popularization of high-voltage integrated systems such as electric compressors in new energy vehicles, the comprehensive performance requirements of lubricating oil under high temperature, high pressure and electric field environments are gradually increasing. Insulating lubricating oil in electrified equipment must not only ensure the lubrication of moving parts, but also have reliable insulation performance to prevent the risk of electrical breakdown and short circuit.

[0003] To address the shortcomings of insulating lubricants in terms of intelligent synergy of multiple functions and long-term stability, a common approach is to improve lubricant performance by introducing functional fillers or designing novel base oil structures. CN117801868A discloses an insulating and thermally conductive lubricant and its preparation method, using modified hexagonal boron nitride and mica powder as additives. Utilizing their intrinsic thermal conductivity and insulation properties, a uniformly dispersed filler network is constructed in the base oil through surface modification and physical blending to simultaneously improve the oil's thermal conductivity and insulation capabilities. However, this approach mainly employs a physical compounding method. While it can improve some static properties, it relies on the dispersion stability of the fillers and may face problems such as sedimentation, agglomeration, and functional degradation during long-term use. Furthermore, it does not address the intelligent responsiveness of the lubricant itself, making it difficult to meet the requirements for viscosity self-adaptation and structural self-repair under dynamic operating conditions. CN115433619B discloses a composition of refrigeration oil and its application. Starting from the molecular structure design of the base oil, a polyol ester base oil synthesis route with high viscosity and good compatibility was developed for R32 refrigeration systems. By controlling the ratio of dicarboxylic acid and branched monocarboxylic acid, the compatibility and thermal stability with the refrigerant were optimized while ensuring high viscosity. It focuses on solving the oil-refrigerant compatibility and lubrication reliability in refrigeration systems. However, its functional design is still limited to the traditional lubrication and thermal stability scope, does not cover the active control of insulation performance, and lacks consideration of material behavior under electric field environment. Therefore, it cannot be directly applied to the electric compressor scenario of new energy vehicles with strict requirements for the integration of insulation and lubrication.

[0004] In summary, while existing methods have made progress in single or limited properties such as thermal conductivity, insulation, or lubrication, significant shortcomings remain in achieving synergistic effects of lubrication, insulation, and intelligent response, as well as long-term stability and adaptive operation for the special working conditions of electric compressors. Therefore, there is an urgent need to develop a new type of insulating lubricant that can deeply integrate the characteristics of dynamic covalent network smart materials with the industrial preparation process of lubricants, providing an integrated lubricating and insulating medium with both intelligent response and long-term stability for electric compressors in new energy vehicles. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an insulating lubricating oil for electric compressors in new energy vehicles and its preparation method. This invention pre-activates a small amount of POE base oil through alkynylation, introducing alkynyl groups as anchor points. Subsequently, a tandem distribution process involving copper-catalyzed azide-alkynyl cycloaddition reaction (CuACC) and photo-initiated enol-sulfur reaction is employed. A bifunctional crosslinking agent containing furan and maleimide groups is used to covalently link the activated POE to PAO base oil. Finally, a reversible cycloaddition reaction between furan and maleimide groups is triggered by heating to form a final dynamic network structure. Functional additives are then added, resulting in an insulating lubricating oil that can self-adjust its state according to different compressor operating conditions. This oil possesses excellent electrical insulation, superior adaptive rheological properties, high chemical stability, and material compatibility, solving the technical problems of insufficient electrical insulation, poor long-term compatibility with refrigerants and materials, and difficulty in balancing lubrication performance and stability under alternating high and low temperature conditions in existing refrigeration oils.

[0006] This invention discloses a method for preparing insulating lubricating oil for electric compressors in new energy vehicles, such as... Figure 1 As shown, the specific technical solution is as follows:

[0007] Step 1: Under the protection of an inert gas and the action of a catalyst, polyisocyanate is added dropwise to alkynyl alcohol to react and obtain an alkynyl intermediate with isocyanate end group. Then, POE base oil is divided into two parts, a small amount of which is hydroxylated at the end group and added to the intermediate. The mixture is heated and stirred and then kept warm to obtain alkynylated POE. At the same time, a bifunctional crosslinking agent is prepared.

[0008] Step 2: The alkynylated POE, another untreated POE base oil, bifunctional crosslinking agent and catalyst are dissolved in a solvent as feed A, and the PAO base oil and photoinitiator are dissolved in a solvent as feed B. After the two feeds are pumped into the microreactor, they are mixed and heated to react in the first zone, and then irradiated with ultraviolet light in the second zone. The effluent from the microreactor is then collected.

[0009] Step 3: Transfer the effluent to a mixing vessel, heat and stir under nitrogen protection and keep warm to obtain crude lubricating oil.

[0010] Step 4: Stir and cool the crude lubricating oil, and add antioxidants, acid neutralizers, metal passivators and defoamers. Then continue stirring until the additives are dispersed and dissolved. Filter the system and remove copper by ion exchange adsorption. Then dehydrate and fill with moisture-proof solution.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. First, the POE end is anchored using the chemically selective CuACC reaction to avoid interference from other active sites; then, the PAO end is connected by triggering the thiol-ene reaction using a photoinitiation reaction. The two-step reaction is mild and does not interfere with each other. The tandem reaction ensures that the bifunctional groups of the crosslinking agent accurately bridge POE and PAO in the predetermined direction and efficiency, eliminating side reactions and the generation of linker isomers.

[0012] 2. Within the micron-scale channels of the microreactor, each crosslinking agent molecule experiences almost identical reaction environments during the CuAAC and thiol-ene reactions, fundamentally ensuring that the final DA dynamic network has a highly uniform distribution of crosslinking points and chain segment lengths.

[0013] 3. Only a small proportion of POE base oil is mildly alkynylated to introduce specific chemical reaction sites. The molecular structure of most of the POE and all of the PAO base oil remains unchanged during the synthesis process. The subsequent dynamic network is constructed entirely from these sparse anchor points and bridged by crosslinking agents, thus preserving the inherent advantages of POE and PAO base oils to the greatest extent. Attached Figure Description

[0014] Figure 1 This is a flowchart illustrating the preparation process of the insulating lubricating oil of the present invention. Figure 2 The infrared spectrum of the bifunctional crosslinking agent prepared in Example 1 of this invention; Figure 3 The infrared spectrum of the terminal isocyanate alkynyl intermediate prepared in Example 1 of this invention; Figure 4 The infrared spectrum of the linear amide intermediate prepared in Example 1 of this invention; Figure 5 This is one of the schematic diagrams of the chemical reaction equations involved in Embodiment 1 of the present invention; Figure 6 This is the second schematic diagram of the chemical reaction equation involved in Embodiment 1 of the present invention. Detailed Implementation

[0015] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0016] This invention proposes a method for preparing insulating lubricating oil for electric compressors in new energy vehicles, such as... Figure 1 As shown, the specific technical solution is as follows: 1. POE end-alkyneation and anchor point construction An intermediate generated by the reaction of 3-butyn-1-ol and polyisocyanate under catalysis grafts an alkynyl functional group onto the ends of a small number of POE molecular chains. The core of the reaction between polyisocyanate and alkynol lies in the highly selective and efficient addition reaction between the isocyanate group and the hydroxyl group. Under catalysis, this reaction preferentially forms a carbamate bond, and its reaction rate is much higher than that of possible side reactions. This selectivity ensures that the molecular structure of the reaction intermediate is well-defined and singular; that is, each alkynol molecule is linked to an isocyanate group through a newly formed carbamate bond, forming a linear molecule with an inert alkynyl group at one end and a highly reactive isocyanate group at the other. This reaction of 3-butyn-1-ol with polyisocyanate... The route of generating an intermediate and then reacting with the POE hydroxyl group has the advantage of utilizing the high selectivity and efficiency of the reaction between isocyanate and hydroxyl groups, compared to directly using other alkynylating agents such as propargyl acid, under mild conditions. The highly reactive isocyanate group exists only briefly in the intermediate stage and immediately participates in subsequent bonding. This reaction process avoids harsh treatment of the POE base oil and avoids the side reactions and cost issues that may arise from directly using highly reactive alkynylating agents, ensuring the reliability of the quantitative addition of the alkynyl group in a stable covalent bond. Commercially available POE base oil molecules typically have a hydroxyl group at the end of the molecular chain. This hydroxyl group undergoes another addition reaction with the remaining isocyanate group on the intermediate, forming another carbamate bond. The alkynyl group is covalently anchored to the end of the POE molecular chain through a connecting bridge composed of two carbamate bonds, which has excellent thermal and chemical stability. The carbamate bond is extremely stable under the common operating temperatures and chemical environments of lubricating oils and will not undergo hydrolysis or thermal decomposition. This ensures the durability of the anchor point in all subsequent processes and the final use. The reason for modifying only a small portion of the total POE is that functionalizing all POE would not only be costly but also result in an excessively high density of reaction sites in the lubricating oil. This would lead to an overly dense and rigid network during the subsequent network formation stage, severely impairing the oil's low-temperature fluidity and basic viscosity-temperature properties. By precisely controlling the activation ratio, a controllable number of network growth points are essentially established in the macroscopic oil phase. The distance between these growth points directly determines the three-dimensional mesh size of the final dynamic network, thereby regulating the macroscopic viscoelasticity, shear response characteristics, and self-healing ability of the lubricating oil. The vast majority of unmodified POE molecules exist as inert diluents and performance-regulating phases. Their flow and movement are slightly constrained by the sparse network formed subsequently, but their molecular structure remains unchanged. This maximizes the preservation of the intrinsic advantages of POE base oil, such as high viscosity index, good lubricity, and excellent compatibility with refrigerants.

[0017] 2. Dual-path continuous flow click reaction Within the microreactor channel, a two-zone click reaction catalyzed by copper and initiated by light under a weakly alkaline environment is used to efficiently and uniformly covalently couple alkynylated POE, untreated POE base oil, and PAO base oil via a bifunctional crosslinking agent. Since the concentration of alkynylated POE directly determines the theoretical maximum density of crosslinking points in the subsequent dynamic covalent network, if it reacts in its pure state, the high local concentration of alkynyl functional groups will cause the crosslinking agent molecules to react rapidly between multiple spatially adjacent anchor points, resulting in the formation of locally over-dense, topologically disordered crosslinking clusters, rather than a macroscopically uniformly expanding three-dimensional network. Local gelation or uneven crosslinking will impair the physical homogeneity of the final product, manifested as abnormal viscosity and poor flowability, and microscopically, weak points with stress concentration. Mixing alkynylated POE with a large amount of inert POE base oil is a process of physically diluting and uniformly dispersing the limited active anchor point molecules in a chemically similar medium. The dilution effect achieved through physical mixing directly reduces the local spatial concentration of active alkynyl functional groups in the POE phase, so that each crosslinking agent molecule can usually only contact one alkynyl anchor point within its effective range during diffusion, preventing multiple anchor points from being connected by the same short chain of crosslinking agent, thus preventing the formation of locally high-density crosslinking clusters. After the materials enter the microreactor, alkynylated POE and untreated POE base oil with copper catalyst are used as feed A, and PAO base oil and photoinitiator are used as feed B. The two feeds achieve molecular-level uniform mixing in the reactor based on the extremely high mass transfer rate at the microscale. The bifunctional crosslinking agent has an azide group at one end and a thio group at the other end. Furan and maleimide groups are pre-introduced in the middle of the molecule. Since the copper-catalyzed azide-alkynyl cycloaddition reaction has specific selectivity for alkynyl and azide groups, the carbon-carbon triple bond of the alkynyl group is rich in π electrons and can act as an electron donor to coordinate with the empty orbitals of monovalent copper ions to form a π complex. Under weakly alkaline conditions, it is easy to deprotonate to form a copper-alkynyl complex. The alkynyl group is directly connected to the copper center in the form of σ bond. At the same time, its remaining π orbital still has a feedback interaction with the d orbital of copper, forming an electron-rich and structurally well-defined metal-organic active center. The azide group from the crosslinking agent molecule will launch a nucleophilic attack on the active center to form a triazole five-membered ring and release monovalent copper ions to complete the catalytic cycle. This reaction covalently links one end of the crosslinking agent to the sparsely distributed POE alkynyl anchor point through a stable triazole ring, generating a POE-crosslinking agent intermediate. The PAO phase does not participate in covalent bonding at this stage as a dispersion medium. After the mixture flows into the photoreaction zone, ultraviolet light excites free radicals to initiate a thio-olefin click reaction, causing the thio group of the POE-crosslinking agent intermediate to undergo an addition reaction with the carbon-carbon double bond of PAO, resulting in a composite material composed of POE base oil, bifunctional crosslinking agent, and PAO base oil linked by covalent bonds.

[0018] 3. Construction of Dynamically Reversible Covalent NetworksUnder nitrogen protection, the compound material is heated and stirred in a mixing vessel. Because the furan and maleimide groups in the crosslinking agent molecule undergo a Diels-Alder cycloaddition reaction during the preparation of the crosslinking agent molecule—a classic [4+2] cycloaddition—forming a dynamically reversible DA covalent bond, under heating conditions, the DA core originally formed within a single molecule during crosslinking agent molecule preparation begins to reversibly dissociate, forming new free furan and maleimide groups. At this point, the furan and maleimide groups between different molecules can come into contact. Subsequently, as the temperature decreases, these different POE and PAO molecules connected by the crosslinking agent can form an intertwined oxygen-containing six-membered ring network through the mutual contact of the free furan and maleimide groups on the molecular chain. This newly formed intertwined network is the key to endowing the final lubricating oil with intelligent response functionality. Due to the thermodynamic equilibrium nature of the Diels-Alder reaction, this cycloaddition reaction is a reversible process. The rate constants of its forward cycloaddition reaction and reverse cycloopening reaction are strongly dependent on temperature. When the lubricating oil is used at a relatively low temperature, the system is in a state of cycloaddition and crosslinking equilibrium. This causes the crosslinking agent, which is dispersed in the oil phase and has POE and PAO attached to one end, to seek, pair and form bonds with each other through the furan and maleimide groups attached to its side. This crosslinks the linear POE-crosslinking agent-PAO structural units together to form a three-dimensional network structure. This network is not rigid and constant, but is in a dynamic equilibrium. That is, old cycloaddition bonds are constantly being opened, while new cycloaddition bonds are being formed elsewhere. This dynamic exchange allows the network topology to slowly rearrange over time. When the temperature rises above a certain threshold, the thermodynamic equilibrium shifts towards the open-loop direction, causing a large number of crosslinking points in the network to open reversibly. The network dissociates into smaller fragments or linear molecules, resulting in a decrease in lubricating oil viscosity and an increase in fluidity. This gives the lubricating oil an intelligent response function, meaning that the lubricating oil can automatically adjust the crosslinking density of its internal molecular network according to the operating temperature, thereby changing its rheological properties to adapt to different operating conditions—reducing drag and saving energy when operating at high temperatures, and thickening and maintaining pressure when starting at low temperatures. The fact that only a small amount of POE is pre-activated by alkynylation in the previous step and crosslinked with PAO base oil is to effectively control this change in lubricating oil viscosity at different temperatures, so that the lubricating oil does not become too low at high temperatures, causing oil film rupture, nor does it become too high at low temperatures, making it unusable.The continuous heating and stirring in the blending vessel provides the necessary mechanical energy, promoting the Brownian motion and relative displacement of molecules. This ensures that the furan and maleimide dispersed in the high-viscosity oil phase have sufficient chance of meeting, thus enabling the formation of the network to proceed uniformly on a macroscopic scale. This avoids gel blocks or reaction dead zones caused by local uneven concentration. The inert protective atmosphere provided by nitrogen eliminates the interference of oxygen and moisture. Oxygen at high temperatures can trigger free radical oxidation side reactions in base oils or intermediates, producing acidic substances or macromolecular colloids, interfering with the normal progress of the Diels-Alder reaction, and ultimately impairing the oxidation stability of the oil. Moisture may react with residual trace active groups or cause slight hydrolysis of ester base oils under high heat. Therefore, inert gases are needed to ensure the long-term chemical stability of the final product.

[0019] 4. Functional additive compounding and post-processing Add functional additives to the system and stir, then filter, dehydrate, and package in a moisture-proof environment. The formation of the dynamic network depends on specific heating conditions and precise intermolecular group pairing. If a large number of foreign additive molecules with diverse structures are present during this process, they may interfere with the approach and orientation of furan and maleimide groups through steric hindrance, hydrogen bonding, or dipole interactions, thus hindering effective network cross-linking. They may even be accidentally trapped within the network, altering its inherent elasticity and response temperature. Therefore, it is necessary to introduce additives only after the network structure has fully formed and stabilized in the pure base oil to maximize the purity and design integrity of the network structure. This process requires cooling because many antioxidants and metal passivators may volatilize, decompose, or polymerize at excessively high temperatures. Adding additives within a temperature range below the network formation temperature but sufficient to maintain good oil flowability ensures the effective incorporation and survival of the additive's active ingredients. The introduction of additives essentially involves physically dispersing and dissolving a multi-component functional system for providing chemical protection into a networked continuous phase of base oil that already possesses physical intelligent response capabilities. Antioxidants, by capturing peroxide free radicals generated during long-term high-temperature service, interrupt chain oxidation reactions, inhibiting the formation of acidic substances, sludge, and varnish precursors at the source. Acid neutralizers promptly neutralize acidic components generated or introduced during operation, protecting metal surfaces from corrosion and maintaining the effectiveness of the additives. Metal passivators form an inert protective film on metal surfaces, inhibiting their catalytic oxidation activity. Defoamers reduce local surface tension, disrupting potential foam structures and ensuring the stability of oil pump supply and heat transfer efficiency. These additive molecules are dispersed within the network structure, and their movement and diffusion are somewhat restricted by the network, which actually helps them to reside locally for extended periods, making them less prone to failure due to centrifugal separation or sedimentation. Subsequent filtration removes trace amounts of undissolved catalyst particles, trace amounts of gel agglomerates, or occasional mechanical impurities that may have been introduced in the preceding steps. These submicron-sized particles can become sources of abrasive wear or weak points in electrical insulation in high-speed, high-precision compressor bearings. Dehydration is based on the multiple harmful effects of water on the lubricating oil system. For example, water can reduce the dielectric strength of the oil, thereby inducing the risk of electrical breakdown. It can also promote the hydrolysis of ester base oils to generate organic acids, thereby accelerating oil deterioration and metal corrosion. At the same time, it may form ice crystals at low temperatures, causing blockage of the oil passages. Therefore, moisture-proof filling is also required during subsequent storage to prevent the product from absorbing moisture from the environment and degrading its performance during storage.

[0020] The following are some specific embodiments of the present invention. Table 1 shows the main raw material information used in the embodiments.

[0021] Table 1. Information on Main Raw Materials

[0022] Example 1 S1: Under nitrogen protection, 20g of POE base oil was added to a dry three-necked flask, followed by the slow addition of 30g of 1,2-propanediol with gentle stirring. Then, 0.2g of stannous octoate was added. The flask was placed in an oil bath at 140℃ and stirred at 200rpm for 3.5h. The mixture was then cooled to 80℃ and distilled under reduced pressure for 2h to remove unreacted 1,2-propanediol. The mixture was then transferred to a vacuum drying oven at 60℃ and dried for 12h to remove trace amounts of residual solvent, yielding hydroxylated POE-OH. In another dry three-necked flask, 30g of 3-butynedi-1-ol and 0.3g of dibutyltin dilaurate were added. The catalyst was stirred and heated to 50°C, then 56.1 g of hexamethylene diisocyanate was slowly added dropwise, followed by a reaction at 60°C for 1 h to obtain a terminal isocyanate alkynyl intermediate. 9 g of POE-OH was added to this intermediate, and the mixture was heated to 80°C and stirred for 3 h, followed by a heating to 90°C and holding for 30 min to obtain alkynylated POE. In another apparatus, 15.4 g of 3-(furan-3-yl)propionic acid and 15.6 g of N-(2-aminoethyl)maleimide protected by Boc were dissolved together in 200 mL of anhydrous dichloromethane and cooled in an ice bath at 2°C with nitrogen. Under nitrogen protection, 24 g of EEDQ was added, the system was heated to 70 °C and stirred for 14 h. The reaction mixture was then washed successively with dilute hydrochloric acid, saturated sodium bicarbonate solution, and brine. The organic phase was dried over anhydrous sodium sulfate and concentrated under reduced pressure to obtain a linear amide intermediate. All the intermediate, 28.7 g of 11-mercaptoundecanoic acid, and 19.7 g of 6-bromohexanoic acid were dissolved in 300 mL of anhydrous dichloromethane. Under ice bath and nitrogen protection, 23.0 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1.5 g of 4-dimethylaminopyridine were added, and the mixture was stirred at room temperature for 16 h to obtain the desired product. The crude product with both ends modified was obtained. This crude product was reacted with 7.8 g of sodium azide in 100 mL of anhydrous N,N-dimethylformamide at 80 °C for 1 h. After cooling, the reaction solution was poured into ice water and extracted with ethyl acetate. The organic layer was washed and dried. After concentration, the residue was dissolved in 150 mL of toluene and heated to 110 °C under nitrogen protection and refluxed for 36 h. The system was then cooled to room temperature, and a mixed solution of 10 mL of trifluoroacetic acid and 50 mL of dichloromethane was added. The mixture was stirred at room temperature for 2 h. The reaction solution was quenched with saturated sodium bicarbonate solution and washed. After purification by column chromatography, the target bifunctional crosslinking agent was obtained.

[0023] S2: The alkynylated POE prepared in S1 was uniformly mixed with 291g of untreated POE base oil. Then, the mixed POE oil, 2.5g of bifunctional crosslinking agent, 2.5g of copper sulfate pentahydrate, and 5g of sodium ascorbate were dissolved in 300mL of toluene and sonicated until completely dissolved, which was used as feed A. 3g of 1-decene trimer, 297g of PAO8 base oil, and 1.5g of benzophenone were dissolved in 300mL of toluene, which was used as feed B. Using a dual-channel injection pump, feeds A and B were pumped into the microchannel reactor at a flow rate of 10mL / min. The first reaction zone of the reactor was heated to 70℃ and kept constant, allowing the material to remain there for 2.5min. Then, the mixture was allowed to flow into the second reaction zone, which was irradiated by a 365nm wavelength, 100W UV-LED lamp. The material remained there for 2.5min, and then the effluent was collected at the reactor outlet.

[0024] S3: Transfer the effluent collected in S2 to a glass mixing vessel. Under continuous nitrogen protection at 50 mL / min and a rotation speed of 300 rpm, heat the effluent to 110°C at a heating rate of 2°C / min. Then, keep it at this temperature and stir for 4 hours. Subsequently, under a vacuum of 0.9 Pa and a temperature of 110°C, transfer the reaction solution to a scraped membrane molecular distillation apparatus at an injection rate of 150 mL / h. Collect the liquid flowing out of the outlet in the first 5 minutes after the start of the injection in bottle 1 and discard it. Then, use a clean receiving bottle 2 to continue collecting the liquid flowing out of the outlet until all the reaction solution has been fed. Finally, under nitrogen protection, transfer the liquid in receiving bottle 2 back to the reaction vessel.

[0025] S4: Maintain stirring in the blending vessel and lower the temperature to 70°C. Then, sequentially add 3g of alkylated diphenylamine, 3g of 2,6-di-tert-butyl-p-cresol, 9g of calcium petroleum sulfonate, 1.5g of benzotriazole, and 30mg of allyloxy polyoxyethylene ether. Maintain stirring at 70°C and 300rpm for 2 minutes. Then, filter the resulting oil through a 5μm pore size polypropylene precision bag filter. Transfer the filtrate to a stirred contact vessel. Under nitrogen protection, add 6g of copper ion chelating adsorption resin pretreated with anhydrous ethanol and wetted with 1-decene trimer. The mixture was stirred at 200 rpm for 4.5 h at 5 °C, and then allowed to stand for 30 min to allow the resin to settle. The upper oil phase was filtered through a 10 μm resin trapping filter to remove all resin particles. Then, 6 g of new copper ion chelating adsorption resin pretreated with anhydrous ethanol and wetted with 1-decene trimer was added. The above adsorption operation was repeated 3 times. The oil was then transferred to a vacuum dehydration device and dehydrated at 90 °C and -0.095 MPa for 3 h. The oil was then poured into a clean, dry, sealed container under nitrogen protection to obtain a clear, oily insulating lubricating oil liquid.

[0026] The reaction equations involved in the preparation process are as follows: Figures 5-6 As shown.

[0027] Example 2 The preparation method according to Example 1 differs in that: S1: Replace the POE base oil with PE1350 type POE base oil. After adding hexamethylene diisocyanate, the reaction temperature is 55℃ and the reaction time is 0.75h. After adding 4.5g of POE base oil, the temperature is raised to 75℃ and the reaction time is 2h. Then the temperature is raised to 85℃ and held for 15min. S2: Replace 1-decene trimer with 1-decene tetramer, pump the material into the reactor at a flow rate of 7 mL / min, set the temperature in the first zone to 65℃, set the residence time in the first zone to 2 min, and set the residence time in the second zone to 2 min. S3: Heating rate is 1℃ / min, heating to 100℃, holding time is 3h; S4: Replace allyloxy polyoxyethylene ether with poly(ethylene glycol-ran-propylene glycol) monobutyl ether, set the mixing tank temperature to 65°C, stir for 1 min, and dehydrate under the following conditions: 85°C, -0.09 MPa, for 2 h. All other steps are the same.

[0028] Example 3 The preparation method according to Example 1 differs in that: S1: Replace the POE base oil with Emkarate RL 68H type POE base oil. After adding hexamethylene diisocyanate, the reaction temperature is 70℃ and the reaction time is 2h. After adding 13.5g of POE base oil, the temperature is raised to 85℃ and the reaction time is 4h. Then the temperature is raised to 95℃ and held for 45min. S2: Replace 1-decene trimer with 1-dodecene trimer, pump the material into the reactor at a flow rate of 13 mL / min, set the temperature in the first zone to 75℃, set the residence time in the first zone to 4 min, and set the residence time in the second zone to 3.5 min. S3: Heating rate is 3℃ / min, heating to 120℃, holding time is 6h; S4: The mixing tank temperature is 75℃, the stirring time is 5min, the dehydration conditions are 95℃ and -0.098MPa, and the dehydration treatment is 4h. All other steps are the same.

[0029] Example 4 The preparation method according to Example 1 differs in that: S1: Replace the POE base oil with BASF BVC 68 POE base oil. After adding hexamethylene diisocyanate, the reaction temperature is 65℃ and the reaction time is 1.5h. After adding 6g of POE base oil, the temperature is raised to 78℃ and the reaction time is 2.5h. Then the temperature is raised to 88℃ and held for 40min. S2: Replace 1-decene trimer with 1-octene tetramer, pump the material into the reactor at a flow rate of 12 mL / min, set the temperature in the first zone to 68℃, set the residence time in the first zone to 3 min, and set the residence time in the second zone to 3 min. S3: Heating rate is 1.5℃ / min, heating to 105℃, holding time is 5h; S4: The mixing tank temperature is 68℃, the stirring time is 4min, the dehydration conditions are 88℃, -0.092MPa, and the dehydration treatment is 2.5h. All other steps are the same.

[0030] Comparative Example 1 The preparation method according to Example 1 differs in that: S2: Add the A and B feed streams together into the stirred tank reactor, heat the reactor to 70°C, and simultaneously turn on the 356nm wavelength ultraviolet irradiation. The total reaction time is 5 minutes. Then, remove the mixture from the reactor. The remaining steps are the same.

[0031] This comparative example shows the preparation of lubricating oil in a one-pot reaction system where copper catalysis and photoreaction conditions are present simultaneously.

[0032] Comparative Example 2 The preparation method according to Example 1 differs in that: S2: Add all A feed and 1 / 3 of B feed to conventional stirred reactor No. 1. Heat reactor No. 1 to 70°C and stir for 30 minutes. Then add the mixture in reactor No. 1 and the remaining 2 / 3 of B feed to conventional stirred reactor No. 2. React in reactor No. 2 at 40°C under 365nm wavelength ultraviolet light irradiation for 30 minutes. The remaining steps are the same.

[0033] This comparative preparation simulates the process of preparing lubricating oil by replacing the microreactor continuous flow process with a traditional batch reactor in a stepwise batch process.

[0034] Comparative Example 3 The preparation method according to Example 1 differs in that: S1: All 300g of POE base oil is modified with alkynylation; S2: All the POE base oils added are alkynylated POE oils, and there are no unmodified POE base oils. The other steps are the same.

[0035] This comparative example shows a lubricating oil prepared entirely from POE base oils that underwent acetylation treatment.

[0036] Experimental Example 1 According to GB / T 265-1988 "Determination of Kinematic Viscosity and Calculation of Dynamic Viscosity of Petroleum Products", the lubricating oil samples prepared in Examples 1-4 and Comparative Examples 1-3 were injected into clean, dry capillary viscometers, ensuring no air bubbles. The viscometers were then placed vertically in a 40°C constant temperature water bath for 2 hours. The time it took for the sample liquid surface to flow between the upper and lower graduations of the viscometer was then measured using a kinematic viscometer. The kinematic viscosity of the sample at 40°C was calculated using the calibration constant of the viscometer. The same procedure was used to measure the kinematic viscosity of the sample at 100°C. Subsequently, the viscosity index of the sample was calculated according to ASTM D2270 "Standard Test Method for Calculating Viscosity Index from Kinematic Viscosity at 40°C and 100°C". The results are shown in Table 2.

[0037] Table 2 Viscosity parameters of the examples and comparative samples

[0038] As shown in Table 2, the kinematic viscosity of the example samples at 40℃ was significantly lower than that of the comparative sample. Furthermore, when the temperature increased to 100℃, the kinematic viscosity of the example samples decreased to an extremely low level. This indicates that the dynamic network in the example samples can effectively adjust its network structure according to the ambient temperature, thereby regulating the viscosity of the sample. Comparative Example 1 was prepared using a one-pot method, resulting in complete loss of control over the crosslinking agent's bonding direction. This led to the formation of a large number of branched, disordered, high-molecular-weight polymers and even gels, causing the loss of fluid properties and turning it into a semi-solid paste. This indicates that a large number of side reactions and linker isomers were generated during the production process, resulting in excessively large differences in viscosity between high and low temperatures, to the point that the viscosity index could not even be calculated. The traditional batch reactor stepwise process of Comparative Example 2 resulted in a product with a heterogeneous structure. Some regions had excessively crosslinked networks, while others had insufficient networks or only base oil. Due to the high proportion of high-viscosity components in the mixture, the overall viscosity was increased, with the highest viscosity reaching [missing value]. The index also illustrates the heterogeneity of the samples; the kinematic viscosity of Comparative Example 3 at 40°C and 100°C was much greater than that of the Examples, second only to the worst Comparative Example 1. This is because increasing the proportion of alkynylated POE from a maximum of 4.5% to 100% caused a surge in the density of reaction anchor points in the system. Under the same amount of crosslinking agent, a highly dense and rigid three-dimensional network was formed, which severely restricted the flow of base oil molecules, resulting in a sharp decrease in the fluidity of the sample at low temperatures. Although the viscosity index is not high, it is based on a high absolute viscosity at 100°C. In actual applications of electric compressors, the low-temperature start-up pumping performance will be extremely poor.

[0039] Experimental Example 2 According to GB / T 507 "Determination of Breakdown Voltage of Insulating Oil", 500 mL of each of Examples 1-4 and Comparative Examples 1-3 were poured into a clean test cup. The cup contained a pair of mushroom-shaped flat electrodes with a spacing of 2.5 mm. The sample was first allowed to stand in the cup for 15 min to release air bubbles. Then, at room temperature, the voltage was steadily increased from zero at a rate of 2 kV / s until breakdown occurred between the electrodes. The voltage value at the moment of breakdown was recorded. Then, the sample was gently stirred with a glass rod to dissipate the carbides. After standing for 3 min, the voltage was increased again. The test was repeated 6 times, and the average value was taken as the breakdown voltage of the sample.

[0040] According to ASTM D257-14, "Standard Test Method for DC Resistance or Conductivity of Insulating Materials," a dedicated three-terminal electrode cell was used. After cleaning and drying the electrode cell, sufficient amounts of the samples prepared in Examples 1-4 and Comparative Examples 1-3 were injected. The samples were kept at 90°C for 1 hour, and then tested at 90°C. A constant DC voltage of 500V was applied between the electrodes, and the current was measured after charging for 60 seconds. The volume resistivity of the samples was calculated based on the electrode constant, the applied voltage, and the measured current. The test results are shown in Table 3.

[0041] Table 3 Insulation performance data of the examples and comparative samples

[0042] As can be seen from Table 3, the sample examples all have high breakdown voltage and volume resistivity. This is because the uniform dynamic network in the sample examples can effectively block the formation of discharge channels and there are very few migratable ion carriers, indicating that the sample examples all have excellent insulation performance. The one-pot process of Comparative Example 1 produced a large number of polar byproducts with uncertain structures, unreacted polar functional groups, and catalyst residues. These substances became abundant sources of ions and channels for charge leakage, greatly reducing the insulation strength of the oil and causing a sharp drop in its breakdown voltage and volume resistivity. The uneven mixing and heat transfer in the batch reaction of Comparative Example 2 led to local overheating, resulting in oxidation products or incomplete catalyst residues. Furthermore, the dynamic network itself had defects and weak points. Under an electric field, these structural defects and impurity-rich areas preferentially became breakdown initiation points and provided additional carrier migration paths, causing a simultaneous decrease in breakdown voltage and volume resistivity. The insulation performance of Comparative Example 3 showed significant deterioration. This was because the extremely dense network caused by the full activation of POE resulted in high viscosity of the sample, reducing the efficiency of the oil during dehydration and degassing, and making it easier for tiny water and bubbles to remain. These water and bubbles were easily ionized under an electric field, triggering breakdown. In addition, the rigid network would trap more trace amounts of catalyst or byproducts and hinder the uniform dispersion of functional additives such as defoamers and antioxidants, further reducing insulation stability.

[0043] Experimental Example 3 Take 2 mg of the bifunctional crosslinking agent prepared in step S1 of Example 1 after column chromatography purification, and evenly spread it on the center of the ATR crystal to cover the light spot area. Perform infrared spectroscopy scanning on the crosslinking agent sample using ATR mode, with a scanning range of 4000–500 cm⁻¹. -1 4cm resolution -1 After removing interference from CO2 and moisture in the air, the scan was started, and the scan results are as follows: Figure 2 As shown. The infrared spectra of the terminal isocyanate alkynyl intermediate and the linear amide intermediate are as follows. Figures 3-4 As shown from Figure 2 It can be seen from this that at 2200cm -1 A very strong peak appears nearby, representing the antisymmetric stretching vibration of the azido group. This is the most prominent characteristic of this crosslinking agent. The intermediate replaces the bromine atom with an azido group through a reaction with sodium azide. The strong absorption peak indicates that the azido group has been successfully introduced into the molecule; the peak is located at 2550~2600 cm⁻¹. -1 There is a weak, broad peak at 2850 and 2960 cm⁻¹, corresponding to the stretching vibration peak of the thiol group, which originates from 11-mercaptoundecanoic acid in the feedstock. This group is key to the subsequent photoinitiated sulfur-ene click reaction with PAO base oil. -1 A pair of strong doublets appear nearby, corresponding to the CH stretching vibration of the alkyl chain, and respectively to the symmetric and antisymmetric methylene absorptions, indicating that the backbone of the crosslinking agent molecule is mainly composed of aliphatic chains; 1700 and 1750 cm⁻¹ -1 The nearby peak represents the stretching vibration of C=O. Because the molecule contains amide, ester, and carbonyl bonds, the superposition of these carbonyl absorptions forms a broad and strong absorption band; 1530 cm⁻¹ -1 The nearby peaks represent the amide II band, namely the NH bending vibration and CN stretching vibration, originating from the amide bonds in the molecular structure, indicating that the various modules in the molecule are successfully connected; 1000~1300 cm⁻¹ -1 The peaks appearing within this range represent ether bond vibrations of the furan ring system and CN single bond vibrations at various junctions; while the peaks originally observed at 1580–1600 cm⁻¹ represent ether bond vibrations of the furan ring system and CN single bond vibrations at various junctions. -1 The C=C peak of the maleimide bond, which would normally appear nearby, was not observed, indicating that the C=C bond has been converted into a cyclic structure, and the DA closed-ring structure has been formed. From Figure 3 and Figure 4 As can be seen from the infrared spectrum of the terminal isocyanate alkynyl intermediate, at 3310 cm⁻¹ -1 2935cm -1 2862cm -1 2273cm -1Strong absorption peaks were observed at all locations, verifying the structure of the intermediate, where the active isocyanate group and an inert alkynyl group are linked by a stable urethane bond; while the linear amide intermediate showed a strong absorption peak at 3390 cm⁻¹. -1 3120cm -1 2980cm -1 1775cm -1 Peaks representing the functional groups in the molecular structure appeared at all locations.

Claims

1. An insulating lubricating oil for electric compressors in new energy vehicles, which is obtained by compounding POE base oil and PAO base oil, characterized in that: The POE base oil includes pre-activated POE base oil and untreated POE base oil; the pre-activated POE base oil is obtained by alkynylating the POE base oil; the compounding is achieved by covalently linking the pre-activated POE base oil and the PAO base oil with a bifunctional crosslinking agent; the bifunctional crosslinking agent is a crosslinking agent with an azide group at one end, a sulfide group at the other end, and a furan group and a maleimide group in the middle of the molecule formed by a cycloaddition reaction.

2. The insulating lubricating oil for electric compressors in new energy vehicles according to claim 1, characterized in that: The molecular structural formula of the bifunctional crosslinking agent is as follows: 。 3. The insulating lubricating oil for electric compressors in new energy vehicles according to claim 1, characterized in that: The POE base oil is one or more of 4022 polyol ester, PE1350, Emkarate RL 68H, and BASF BVC 68; the PAO base oil is a non-hydrogenated commercial PAO base oil intermediate selected from one or more of 1-decene trimer, 1-decene tetramer, 1-dodecene trimer, and 1-octene tetramer.

4. A method for preparing an insulating lubricating oil for an electric compressor in a new energy vehicle according to any one of claims 1 to 3, characterized in that, It is prepared by the following method: S1. Under the protection of an inert gas and the action of a catalyst, polyisocyanate is added dropwise to acetylacetonol to react and obtain an acetylacetyl intermediate with isocyanate end group. Then, POE base oil is divided into two parts, a small amount of which is hydroxylated at the end group and added to the intermediate. The mixture is heated and stirred and then kept warm to obtain acetylated POE. At the same time, a bifunctional crosslinking agent is prepared. S2. Alkylated POE, another untreated POE base oil, bifunctional crosslinking agent and catalyst are dissolved in a solvent as feed A. PAO base oil and photoinitiator are dissolved in a solvent as feed B. The two feeds are pumped into the microreactor. In the first zone, they are mixed and heated to react. In the second zone, they are irradiated with ultraviolet light. Then the effluent from the microreactor is collected. S3. Transfer the effluent to a mixing vessel, heat and stir under nitrogen protection and keep warm to obtain crude lubricating oil; S4. Add crude lubricating oil to a mixing tank, stir and cool, and add antioxidant, acid neutralizer, metal passivator and defoamer. Then continue stirring until the additives are dispersed and dissolved. Filter the system and remove copper by ion exchange adsorption. Then dehydrate and fill with moisture-proof solution.

5. The method for preparing an insulating lubricating oil for an electric compressor in a new energy vehicle according to claim 4, characterized in that: The polyisocyanate mentioned in S1 is one or more of hexamethylene diisocyanate, terephthalic diisocyanate, isophthalic diisocyanate and 1,4-cyclohexane diisocyanate.

6. The method for preparing an insulating lubricating oil for an electric compressor in a new energy vehicle according to claim 4, characterized in that: The small amount mentioned in S1 is 1.5% to 4.5% of the total POE base oil mass; the reaction temperature is 55 to 70°C and the reaction time is 0.75 to 2 hours; the heating and stirring temperature is 75 to 85°C and the time is 2 to 4 hours; the heat preservation temperature is 85 to 95°C and the time is 15 to 45 minutes.

7. The method for preparing an insulating lubricating oil for an electric compressor in a new energy vehicle according to claim 4, characterized in that: The feed pump in S2 is pumped into the microreactor at a flow rate of 7-13 mL / min; the reaction temperature in the first zone is 65-75℃ and the reaction time is 2-4 min; the reaction time in the second zone is 2-3.5 min.

8. The method for preparing an insulating lubricating oil for an electric compressor in a new energy vehicle according to claim 4, characterized in that: The heating and stirring process described in S3 has a heating rate of 1~3℃ / min and a temperature of 100~120℃; the heat preservation time is 3~6h.

9. The method for preparing an insulating lubricating oil for an electric compressor in a new energy vehicle according to claim 4, characterized in that: The defoamer described in S4 is a non-silicone defoamer, selected from one or more of allyloxy polyoxyethylene ether and poly(ethylene glycol-ran-propylene glycol) monobutyl ether.

10. The method for preparing an insulating lubricating oil for an electric compressor in a new energy vehicle according to claim 4, characterized in that: The temperature in the mixing vessel of S4 is 65~75℃; the continuous stirring time is 1~5min; the dehydration treatment temperature is 85~95℃, the pressure is -0.09~0.098MPa, and the time is 2~4h.

Images