Environment-friendly capacitor insulating oil and preparation method thereof

Abstract

This application relates to the field of capacitor technology, specifically disclosing an environmentally friendly capacitor insulating oil and its preparation method. The environmentally friendly capacitor insulating oil comprises polyol esters and hydroxyl acrylates, wherein the molar ratio of hydroxyl groups in the polyol esters to those in the hydroxyl acrylates is 1–2:1–2. This application introduces small-molecule hydroxyl acrylates to reduce the intermolecular forces of the polyol esters, thereby improving the low-temperature fluidity of the insulating oil. Simultaneously, the small-molecule hydroxyl acrylates also provide free radical trapping sites, effectively improving the gas evolution performance, antioxidant stability, and electrical properties of the insulating oil under extreme low-temperature conditions. This solves the technical problem of existing insulating oils being unable to simultaneously achieve low-temperature fluidity, insulation, and environmental friendliness.

Description

Technical Field

[0001] This application relates to the field of capacitor technology, and in particular to an environmentally friendly capacitor insulating oil and its preparation method. Background Technology

[0002] High-voltage oil-immersed capacitors use biaxially oriented polypropylene (BOPP) roughened film as the dielectric material and metal foil as the electrode. They feature high energy density, high reliability, and long lifespan, and are widely used in reactive power compensation and filtering devices in power transmission and distribution systems and industrial power distribution systems.

[0003] An oil-immersed capacitor is composed of a large number of flat components stacked together. Insulating oil fills the space between the components and the casing to ensure the electrical performance of the components and to facilitate heat dissipation. Currently, the main component of the insulating oil used in oil-immersed capacitors is benzyltoluene. This substance is difficult to degrade and is toxic to the environment and organisms. Leaks or waste can easily pollute soil and water bodies, placing enormous environmental and economic pressure on the entire process of production, operation, and recycling. Furthermore, benzyltoluene has been listed as a toxic substance by the United Nations, Europe, and Japan: the United Nations states that it is fatal if swallowed, and that contact or inhalation can damage the respiratory tract and skin, and is highly toxic to aquatic life; Europe points out that it harms human fetuses and reproductive systems and causes water pollution and aquatic life.

[0004] Currently, environmentally friendly oils are used as internal insulating media in equipment such as urban distribution transformers and building transformers in the power industry, with pentaerythritol-based environmentally friendly oils being commonly used. Each molecule of this environmentally friendly oil contains four hydroxyl groups, which can form strong intermolecular forces and hydrogen bond networks, resulting in high viscosity and poor fluidity. Especially in low-temperature scenarios, the poor fluidity of the oil means that when applied to capacitors, the partial discharge performance of the capacitors cannot meet the type test requirements (DL / T 840-2016 Partial Discharge: At room temperature, after applying pressure between the capacitor unit electrodes until partial discharge begins and lasting 1 second, the voltage is reduced to 1.35 times the rated voltage and held for 10 minutes, then increased to 1.6 times the rated voltage and held for 10 minutes; at this time, the partial discharge quantity should not exceed 50 pC; in extremely cold regions, the partial discharge extinction voltage of the capacitor at the lower temperature limit should not be lower than 1.2 U). Furthermore, the operating conditions of transformers and capacitors differ; the partial discharge phenomenon in capacitors is significantly stronger than that in transformers, thus placing higher demands on the fluidity and insulation performance of the insulating oil.

[0005] Therefore, developing an insulating oil that combines excellent low-temperature fluidity, insulation performance, and environmental friendliness is key to promoting the synergistic advancement of capacitor technology upgrades and sustainable development goals. Summary of the Invention

[0006] In view of this, the purpose of this application is to provide an insulating oil that combines excellent fluidity, insulation and environmental friendliness, in order to solve the technical problem that existing insulating oils are unable to simultaneously achieve low-temperature fluidity, insulation and environmental friendliness.

[0007] To achieve the above-mentioned technical objectives, this application provides an environmentally friendly capacitor insulating oil, comprising polyol ester and hydroxy acrylate, wherein the molar ratio of hydroxyl groups in the polyol ester to hydroxyl groups in the hydroxy acrylate is 1-2:1-2.

[0008] Furthermore, the polyol ester includes at least one of trimethylolpropane ester and pentaerythritol ester.

[0009] Furthermore, hydroxyacrylates include at least one of hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, and hydroxybutyl acrylate.

[0010] Furthermore, environmentally friendly capacitor insulating oils include hydroxyethyl acrylate and pentaerythritol acrylate.

[0011] Furthermore, the pentaerythritol ester includes pentaerythritol units, and the molar ratio of pentaerythritol units to hydroxyethyl acrylate is 1:2 to 4.

[0012] This application provides a method for preparing an environmentally friendly capacitor insulating oil, comprising the following steps:

[0013] Polyol esters and hydroxy acrylates are mixed evenly to obtain an environmentally friendly capacitor insulating oil; during the mixing process, the temperature of the mixed system formed by polyol esters and hydroxy acrylates is less than 25°C.

[0014] Further, the mixing steps are as follows: Step S1, mix the polyol ester and hydroxy acrylate, and stir at a speed of 200-400 r / min for 10-30 min; Step S2, sonicate at a frequency of 20-40 kHz at a temperature below 25°C for 10-30 min to obtain environmentally friendly capacitor insulating oil.

[0015] This application provides an application of an environmentally friendly capacitor insulating oil for preparing an impregnating agent for capacitor elements that operate in low-temperature environments.

[0016] Furthermore, the temperature of the low-temperature environment is -40℃ to 0℃.

[0017] Furthermore, the capacitor element includes one of the following: foil film capacitor element, metallized film capacitor element, wound capacitor element, and laminated capacitor element.

[0018] In summary, this application provides an environmentally friendly capacitor insulating oil comprising a polyol ester and a hydroxyacrylate, wherein the molar ratio of the hydroxyl groups in the polyol ester to those in the hydroxyacrylate is 1–2:1–2. By introducing a small-molecule hydroxyacrylate, this application allows it to interact with the hydroxyl groups in the polyol ester, disrupting the intermolecular hydrogen bond network formed by the polyol ester itself and reducing internal molecular forces, thereby significantly improving the low-temperature fluidity of the insulating oil. Simultaneously, the unsaturated double bonds contained in the small-molecule hydroxyacrylate can serve as free radical trapping sites, effectively improving the gas evolution performance and antioxidant stability of the insulating oil, further enhancing its electrical performance under extreme low-temperature conditions.

[0019] Compared with existing technologies, the environmentally friendly capacitor insulating oil provided in this application can maintain good fluidity, insulation performance and stability even in extremely low temperature environments, and can meet the long-term reliable operation requirements of capacitors under low temperature conditions. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments in this application specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection claimed in this application.

[0021] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating orientation or positional relationships, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] Unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0023] The raw materials used in this invention are not particularly restricted in their source; they can be purchased on the market or prepared using conventional methods known to those skilled in the art.

[0024] This application provides an environmentally friendly capacitor insulating oil, comprising polyol ester and hydroxy acrylate, wherein the molar ratio of hydroxyl groups in the polyol ester to hydroxyl groups in the hydroxy acrylate is 1-2:1-2.

[0025] It should be noted that hydroxy acrylates can form intermolecular hydrogen bonds with the hydroxyl groups in polyol esters through the hydroxyl groups in their molecules, interfering with and disrupting the hydrogen bond network formed by the polyol esters themselves, thereby reducing the internal molecular forces and significantly improving the low-temperature fluidity of insulating oil. The uniform dispersion of small molecule additives and their ability to disrupt the hydrogen bond network are key factors determining the effect of improving low-temperature fluidity. Uniform dispersion of small hydroxy acrylate molecules in the insulating oil matrix can be achieved through a combination of stirring and ultrasonic treatment; however, if the amount of small molecules added is too high (mass fraction exceeding 40%), it is difficult to disperse stably in the system, and some hydroxy acrylates are prone to forming suspended aggregates. These aggregates can act as electrical weaknesses, significantly reducing the breakdown field strength of the insulating oil. Uniform dispersion of hydroxy acrylates in insulating oil can introduce a large number of shallow trap energy levels, effectively capturing free electrons and inhibiting directional electron migration, thereby improving the breakdown performance of the insulating oil. When excessive hydroxy acrylates are added and form micron-sized aggregates, it will disrupt the homogeneity of the oil phase, causing local electric field distortion and field concentration, ultimately leading to a decrease in the breakdown strength of the insulating oil. In addition, the carbon-carbon double bond structure contained in the hydroxy acrylate molecule can form active sites and capture free radicals under thermo-electric coupling, which is beneficial to improving the gas evolution performance of insulating oil. The gas evolution capacity is positively correlated with the amount added within a certain range; however, if the amount added is too high, the active sites will be difficult to fully expose after the small molecules agglomerate, thus limiting the improvement of gas evolution performance.

[0026] In some embodiments, the polyol ester includes at least one of trimethylolpropane ester and pentaerythritol ester.

[0027] In some embodiments, hydroxyacrylates include at least one of hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, and hydroxybutyl acrylate.

[0028] In some embodiments, environmentally friendly capacitor insulating oils include hydroxyethyl acrylate and pentaerythritol acrylate. It should be noted that, under thermo-electric synergistic effects, the carbon-carbon double bonds in the hydroxyethyl acrylate molecule can be activated and form active sites, thereby capturing free radicals in the system and inhibiting their further conversion into low-molecular-weight gaseous products, thus improving the gas evolution performance and electrical stability of the insulating oil. Based on functional group structure analysis, methyl allyl alcohol and allyl alcohol theoretically possess similar potential; however, both substances have weak polarity and poor compatibility with pentaerythritol-based insulating oils, requiring extended blending time or enhanced dispersion methods. Simultaneously, allyl alcohol exhibits high biotoxicity (LD50). 50 (≈90mg / kg), which is insufficient to meet the requirements for environmentally friendly insulating oil.

[0029] In some preferred embodiments, the pentaerythritol ester includes pentaerythritol units, and the molar ratio of pentaerythritol units to hydroxyethyl acrylate is 1:2 to 4.

[0030] Pentaerythritol contains multiple hydroxyl groups, which readily form strong intermolecular hydrogen bonds, resulting in high kinematic viscosity at low temperatures. To weaken these hydrogen bonds and improve low-temperature flowability, hydroxyethyl acrylate can interact with the hydroxyl groups of pentaerythritol, disrupting the existing hydrogen bond network and effectively reducing the system viscosity. From a molecular structure matching perspective, 1 mol of pentaerythritol can theoretically interact with 4 mol of hydroxyethyl acrylate, achieving sufficient binding of the hydroxyl sites. However, due to steric hindrance and molecular mobility limitations, under conventional blending conditions, the hydroxyl groups at the para position are more likely to interact. Therefore, the actual amount of hydroxyethyl acrylate added should be controlled within a molar ratio of pentaerythritol to hydroxyethyl acrylate of 1:4 to 2:4.

[0031] Furthermore, in the environmentally friendly capacitor insulating oil, hydroxyethyl acrylate accounts for 9%–16.52% by mass, with the balance being pentaerythritol ester (Midel 7131). This application uses differential scanning calorimetry (DSC) to perform a semi-quantitative estimation, determining that the melting point of pentaerythritol is approximately 261°C, corresponding to an enthalpy of fusion of approximately 360 J / g; for Midel 7131, DSC testing revealed a characteristic melting peak near 261°C, with an enthalpy of fusion of approximately 21 J / g. Based on this, the mass fraction of pentaerythritol in Midel 7131 is approximately 5.8%. Based on the aforementioned molar ratio of pentaerythritol to hydroxyethyl acrylate of 1:4 to 2:4 (pentaerythritol molecular weight 136, hydroxyethyl acrylate molecular weight 116), the mass ratio of pentaerythritol to hydroxyethyl acrylate is 136:464 to 272:464. Since the mass fraction of pentaerythritol in Midel 7131 is approximately 5.8%, the suitable mass fraction of hydroxyethyl acrylate in insulating oil is determined to be 9% to 16.52%.

[0032] This application provides a method for preparing an environmentally friendly capacitor insulating oil, comprising the following steps:

[0033] Polyol esters and hydroxy acrylates are mixed evenly to obtain an environmentally friendly capacitor insulating oil; during the mixing process, the temperature of the mixed system formed by polyol esters and hydroxy acrylates is less than 25°C.

[0034] In some preferred embodiments, the mixing steps are as follows: Step S1, the polyol ester and hydroxy acrylate are mixed and stirred at a speed of 200-400 r / min for 10-30 min; Step S2, the mixture is ultrasonically treated at a frequency of 20-40 kHz at a temperature below 25°C for 10-30 min to obtain environmentally friendly capacitor insulating oil.

[0035] It should be noted that a combined dispersion method of stirring and ultrasound is used to promote thorough mixing of hydroxyacrylates and polyol esters. During the stirring stage, high-speed stirring is used to initially homogenize the polyol esters and hydroxyacrylates. Ultrasonic treatment further improves the uniformity of small molecule dispersion, which is beneficial for the formation of stable intermolecular interactions between hydroxyl groups. During ultrasound treatment, the temperature can be controlled below 25°C using methods such as ice baths to avoid high temperatures weakening intermolecular hydrogen bonding and inhibiting the self-aggregation of hydroxyacrylates.

[0036] In some specific embodiments, the optimized ultrasonic conditions in this application are: frequency 30kHz, power 750W, and ultrasonic time 20min.

[0037] This application provides an application of an environmentally friendly capacitor insulating oil for preparing an impregnating agent for capacitor elements that operate in low-temperature environments.

[0038] In some embodiments, the temperature of the low-temperature environment is -40°C to 0°C.

[0039] In some embodiments, the capacitor element includes one of foil film capacitor elements, metallized film capacitor elements, wound capacitor elements, and laminated capacitor elements.

[0040] The applicant further provides the following specific embodiments to describe the present invention. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0041] Example 1

[0042] This embodiment provides an environmentally friendly capacitor insulating oil and its preparation method.

[0043] Environmentally friendly capacitor insulating oils include Midel 7131 (a pentaerythritol-based synthetic ester oil, produced by M&I, UK) and hydroxyethyl acrylate (CAS No.: 818-61-1); the volume ratio of Midel 7131 to hydroxyethyl acrylate is 90:10.

[0044] Table 1. Midel 7131 Performance Parameters

[0045]

[0046] A method for preparing environmentally friendly capacitor insulating oil includes the following steps:

[0047] Step S1, high-speed stirring: Add hydroxyethyl acrylate and Midel 7131 insulating oil to the reaction vessel, adjust the stirring speed to 300 r / min, and continue stirring for more than 10 minutes to ensure that the hydroxyethyl acrylate and Midel 7131 insulating oil are fully mixed and homogeneous to obtain a mixed system;

[0048] Step S2, ultrasonic treatment: The mixed system is ultrasonically treated under ice bath conditions (below 25℃). The ultrasonic treatment parameters are: ultrasonic frequency 30kHz, ultrasonic power 750W, and ultrasonic time 20min; thus, environmentally friendly capacitor insulating oil is obtained.

[0049] Example 2

[0050] This embodiment provides an environmentally friendly capacitor insulating oil and its preparation method. The difference from Embodiment 1 is that the volume ratio of Midel 7131 and hydroxyethyl acrylate is 80:20.

[0051] Example 3

[0052] This embodiment provides an environmentally friendly capacitor insulating oil and its preparation method. The difference from Embodiment 1 is that the volume ratio of Midel 7131 and hydroxyethyl acrylate is 73:27.

[0053] Example 4

[0054] This embodiment provides an environmentally friendly capacitor insulating oil and its preparation method. The difference from Embodiment 1 is that the volume ratio of Midel 7131 and hydroxyethyl acrylate is 65:35.

[0055] Comparative Example 1

[0056] This comparative example provides an environmentally friendly capacitor insulating oil, specifically Midel 7131.

[0057] Comparative Example 2

[0058] This comparative example provides a method for preparing an environmentally friendly capacitor insulating oil, including the following steps:

[0059] Step S1, high-speed stirring: Add Midel 7131 and hydroxyethyl acrylate to the reaction vessel at a volume ratio of 73:27, adjust the stirring speed to 300 r / min, and continue stirring for more than 10 min to ensure that the hydroxyethyl acrylate and Midel 7131 insulating oil are fully mixed and homogeneous to obtain a mixed system;

[0060] Step S2, ultrasonic treatment: The mixed system is ultrasonically treated with the following parameters: ultrasonic frequency 30kHz, ultrasonic power 750W, and ultrasonic time 20min. After ultrasonic treatment, environmentally friendly capacitor insulating oil is obtained. At this time, the temperature of the environmentally friendly capacitor insulating oil is 75℃. At the same time, a large amount of hydroxyethyl acrylate agglomerates are observed and suspended in the insulating oil in the form of agglomerates.

[0061] Test Example 1

[0062] To verify the key performance of the environmentally friendly capacitor insulating oil prepared in the embodiments of the present invention, and to compare its performance with that of the insulating oil prepared in the comparative example, three performance indicators, namely viscosity, breakdown voltage and gas evolution, were tested to clarify the performance differences of the insulating oil under different preparation schemes.

[0063] Table 2. Comparison of Performance Parameters of Environmentally Friendly Insulating Oil

[0064]

[0065] The above are merely preferred embodiments of this application and are not intended to limit the present invention. Although this application has been described in detail with reference to examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An environmentally friendly capacitor insulating oil, characterized in that, It includes polyol esters and hydroxy acrylates, wherein the molar ratio of the hydroxyl groups in the polyol esters to the hydroxyl groups in the hydroxy acrylates is 1-2:1-2.

2. The environmentally friendly capacitor insulating oil according to claim 1, characterized in that, The polyol esters include at least one of trimethylolpropane ester and pentaerythritol ester.

3. The environmentally friendly capacitor insulating oil according to claim 1, characterized in that, The hydroxyacrylate includes at least one of hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, and hydroxybutyl acrylate.

4. The environmentally friendly capacitor insulating oil according to claim 1, characterized in that, The environmentally friendly capacitor insulating oil includes hydroxyethyl acrylate and pentaerythritol ester.

5. The environmentally friendly capacitor insulating oil according to claim 4, characterized in that, The pentaerythritol ester includes pentaerythritol units, and the molar ratio of the pentaerythritol units to the hydroxyethyl acrylate is 1:2 to 4.

6. A method for preparing the environmentally friendly capacitor insulating oil according to any one of claims 1 to 5, characterized in that, Includes the following steps: Polyol ester and hydroxy acrylate are mixed evenly to obtain an environmentally friendly capacitor insulating oil. During the mixing process, the temperature of the mixture formed by the polyol ester and hydroxy acrylate is less than 25°C.

7. The method for preparing the environmentally friendly capacitor insulating oil according to claim 6, characterized in that, The mixing steps are as follows: Step S1: Mix the polyol ester and hydroxy acrylate and stir at a speed of 200-400 r / min for 10-30 min; Step S2: At a temperature below 25°C, ultrasonically treat the oil at a frequency of 20-40 kHz for 10-30 minutes to obtain environmentally friendly capacitor insulating oil.

8. The application of the environmentally friendly capacitor insulating oil according to any one of claims 1 to 5, characterized in that, Impregnating agent used to prepare capacitor elements that operate in low-temperature environments.

9. The application of the environmentally friendly capacitor insulating oil according to claim 8, characterized in that, The temperature of the low-temperature environment is -40℃ to 0℃.

10. The application of the environmentally friendly capacitor insulating oil according to claim 8, characterized in that, The capacitor element includes one of the following: foil film capacitor element, metallized film capacitor element, wound capacitor element, and laminated capacitor element.

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