Green plant-based impregnant for high-voltage power capacitors

Abstract

The application discloses a kind of green plant-based impregnating agent for high-voltage power capacitor, belongs to high-voltage power capacitor impregnating agent technical field.The modification method is: under the protection of nitrogen atmosphere, phosphorus pentasulfide is mixed with isobutyl oleate, is stirred at 85 DEG C, 300r / min for 4h, after reaction, filtration and reduced pressure distillation are carried out to obtain modified isobutyl oleate.The application uses phosphorus pentasulfide to directly modify isobutyl oleate mildly, introduces sulfur-containing active sites in the molecule, significantly improves its gas absorption performance.Experimental verification shows that the gas absorption of modified isobutyl oleate is increased from 66 to 100mL / 100mL, with an increase of 51.5%, while the dielectric loss factor and breakdown voltage are optimized.The application method is simple, mild and low in cost, and the modified product can be applied to high-voltage power capacitor impregnating agent.

Description

Technical Field

[0001] This invention relates to the field of impregnating agents for high-voltage power capacitors, specifically to a method for improving the gas absorption performance of isobutyl oleate modified with phosphorus pentasulfide, which can be applied to impregnating agents for high-voltage power capacitors. Background Technology

[0002] The capacitor impregnating agent is the core insulating medium of metallized polypropylene film capacitors, and its performance directly determines the capacitor's breakdown voltage, service life, and operational stability. During long-term operation, trace amounts of hydrogen evolution reaction occur in the electrode materials, leading to hydrogen accumulation inside the capacitor. This can cause a decrease in insulation performance, an increase in internal pressure, and even capacitor breakdown, bulging, and leakage. Therefore, the capacitor impregnating agent must possess excellent gas absorption performance to efficiently adsorb the hydrogen generated during operation and avoid the safety hazards caused by hydrogen accumulation.

[0003] Isobutyl oleate, as a high-performance synthetic ester compound, possesses characteristics such as low dielectric loss, good insulation properties, and excellent thermal stability, making it an ideal base oil for capacitor impregnation. However, pure isobutyl oleate has limited getter properties (only 66%), which is insufficient to meet the requirements of high-voltage, long-life capacitors, necessitating modification to improve its getter properties.

[0004] Phosphorus pentasulfide (P2S5) is a commonly used thiolation modifier that can undergo thiolation reactions with reactive oxygen sites in organic compounds, introducing sulfur-containing hydrogen-absorbing active sites, theoretically improving the getter performance of organic compounds. The inventors' team in this application previously used P2S5 to modify monomer raw materials for synthetic esters (such as trimethylolpropane (TMP) and oleic acid (OA), and then added the modified monomers to the synthetic ester base oil, hoping to improve getter performance. However, in practice, it was found that this modification method not only failed to improve getter performance but also led to a significant decrease in overall getter performance. The core reason is that TMP and OA, as simple small molecules, undergo deep thiolation / polymerization reactions with P2S5, generating random low-molecular-weight polysulfide / thiolated derivatives. These products have extremely poor compatibility with the isobutyl oleate matrix; after addition, phase separation occurs, hydrogen-absorbing active sites are covered, and even side reactions releasing hydrogen gas are triggered, ultimately leading to a deterioration in getter performance.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for modifying isobutyl oleate for capacitor impregnation agents with high gas absorption performance, in order to improve the insufficient gas absorption performance of isobutyl oleate and the problem of decreased gas absorption performance after conventional modification.

[0007] To achieve the above objectives, this invention provides a method for modifying isobutyl oleate to improve its gas absorption properties. The modified isobutyl oleate is then used as a green plant-based impregnating agent for high-voltage power capacitors, comprising the following steps: Under a nitrogen atmosphere, phosphorus pentasulfide and isobutyl oleate were mixed and stirred at 85°C and 300 r / min for 4 h. After the reaction was completed, the mixture was filtered and distilled under reduced pressure to obtain modified isobutyl oleate.

[0008] Preferably, the amount of phosphorus pentasulfide added in the modification method is 0.5%-1.0% of the mass of isobutyl oleate.

[0009] More preferably, the amount of phosphorus pentasulfide added is 0.8% of the mass of isobutyl oleate.

[0010] Preferably, the nitrogen flow rate in the modification method is 80 mL / min.

[0011] Preferably, the filtration in the modification method uses a 0.22 μm organic filter membrane for vacuum filtration.

[0012] Preferably, the vacuum distillation conditions in the modification method are: temperature 65°C, vacuum degree 0.09MPa, and time 30min.

[0013] Preferably, the phosphorus pentasulfide in the modification method is pulverized to a particle size of 50-100 mesh before use.

[0014] Preferably, the isobutyl oleate in the modification method is vacuum dried before use, and the drying conditions are: temperature 80°C, vacuum degree 0.08MPa, and time 2h.

[0015] The present invention also provides a modified isobutyl oleate prepared by a modification method.

[0016] The modified isobutyl oleate provided by this invention can be used to prepare capacitor impregnating agents, effectively avoiding the accumulation of hydrogen gas, and is especially suitable for high-voltage power capacitors.

[0017] The modification mechanism of isobutyl oleate provided by this invention is as follows: Isobutyl oleate has a stable molecular skeleton containing an ester group (-COO-) and a long alkyl carbon chain. The oxygen atom in the ester group is the active site. P2S5, as a thiochemical reagent, undergoes a mild thiosubstitution reaction with the ester group in the isobutyl oleate molecule under nitrogen atmosphere protection and a mild temperature of 85℃, converting the ester group (-COO-) into a thioester group (-COS-), while generating stable sulfur-containing active sites such as PSC and CS bonds. A stirring speed of 300 r / min ensures that P2S5 is uniformly dispersed in the isobutyl oleate system, avoiding excessive or insufficient local reaction. A reaction time of 4 h ensures that the thiosubstitution reaction proceeds fully, maximizing the introduction of sulfur-containing hydrogen-absorbing active sites.

[0018] The sulfur-containing active sites mentioned above (especially the low-coordination S atoms in the thioester group and the S atoms in the PS bond) are excellent hydrogen adsorption centers. Hydrogen (H2) can be physically adsorbed on the long alkyl carbon chain through van der Waals forces, and at the same time, it can be combined with the sulfur-containing active sites through chemical complexation, achieving synergistic effects of physical adsorption and chemical adsorption, which significantly improves the gas adsorption performance of isobutyl oleate.

[0019] Furthermore, P2S5 direct modification of isobutyl oleate is an intramolecular modification. The modified product (thiolated isobutyl oleate) has a highly compatible molecular structure and solubility parameters with the isobutyl oleate matrix, exhibiting no phase separation. The sulfur-containing active sites are fully exposed without steric hindrance, ensuring maximum hydrogen absorption efficiency. Simultaneously, the modification reaction is mild and does not damage the isobutyl oleate molecular backbone, maintaining its excellent dielectric properties and thermal stability, thus meeting the requirements for capacitor impregnating agents.

[0020] In contrast, when TMP and OA are modified with P2S5 and then added to isobutyl oleate, TMP (containing 3 primary alcohol hydroxyl groups) and OA (containing 1 carboxyl group + 1 carbon-carbon double bond) are simple small molecules with extremely high reactivity. They undergo deep thiolation / polymerization reactions with P2S5 to generate random low molecular weight polysulfide / thio derivatives. These products contain a large number of free thiol groups (-SH), which are extremely polar and have very poor compatibility with the weakly polar isobutyl oleate matrix. After addition, phase separation occurs, and the modified products aggregate to form tiny droplets. The few active sites on their surface are encapsulated and rendered ineffective. At the same time, free thiol groups are prone to auto-oxidation, releasing hydrogen gas. Excessive addition will introduce a large number of impurities, covering the hydrogen absorption active sites of isobutyl oleate itself, ultimately leading to a significant decrease in overall gas absorption performance. Moreover, the higher the addition ratio, the more obvious the negative interference.

[0021] The present invention has the following advantages: This invention utilizes P2S5 under a nitrogen atmosphere to directly and mildly modify isobutyl oleate. Strict control of modification parameters (temperature 85℃, rotation speed 300 r / min, reaction time 4 h) ensures a thorough and gentle reaction, resulting in a significant improvement in gas absorption performance. After modification, the gas absorption of isobutyl oleate increases from 66 mL / 100 mL to 100 mL / 100 mL, an improvement of 51.5%. This allows for efficient adsorption of hydrogen generated during capacitor operation, avoiding safety hazards caused by hydrogen accumulation and meeting the requirements of high-voltage, long-life capacitors. This invention clarifies the influence of P2S5 modification on the gas absorption performance of isobutyl oleate. Through comparative experiments, it is confirmed that "direct modification of isobutyl oleate with P2S5" is a positive modification, while "addition of P2S5-modified TMP / OA to isobutyl oleate" is a negative interference. Moreover, the higher the addition ratio, the more obvious the negative interference. This provides clear technical guidance for the preparation of high-gas-absorption capacitor impregnating agents. The modification method of the present invention is simple and convenient to operate, with mild reaction conditions (85°C), no need for complex equipment, and simple post-processing. It can effectively remove unreacted impurities and low molecular weight by-products, and the modified product has high purity. The stirring speed of 300 r / min and the reaction time of 4 h are easy to control, making it suitable for large-scale industrial production. The modified product of this invention (P2S5 modified isobutyl oleate) not only has excellent gas absorption performance, but also maintains the excellent dielectric properties, thermal stability and flowability of isobutyl oleate itself. The dielectric loss factor is ≤0.0018 and the breakdown voltage is ≥70kV / 2.5mm, which fully meets the core technical requirements of capacitor impregnating agent. The modification method of the present invention has low cost, with the amount of P2S5 added being only 0.5%-1.0% of the mass of isobutyl oleate. The raw materials are readily available, and there is no need to use expensive modifying reagents. This method can effectively reduce the preparation cost of capacitor impregnating agents and has extremely high economic benefits and application value. Attached Figure Description

[0022] Figure 1 The images show the FTIR spectra before and after modification. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0024] Note: In the following examples, all raw materials were commercially available conventional products. The purity of isobutyl oleate was ≥99%, the purity of P2S5 was ≥99.5%, the purity of TMP (trimethylolpropane) was ≥99%, and the purity of OA (oleic acid) was ≥99%. The gas absorption performance test method was the same for all examples and comparative examples: the closed static hydrogen absorption method was used, and the hydrogen absorption of 100mL sample within 24h was tested under the conditions of 25℃ and 0.1MPa (unit: mL / 100mL). The higher the hydrogen absorption value, the better the gas absorption performance. The dielectric loss factor and breakdown voltage test methods were based on GB / T 15077-2017.

[0025] To address the shortcomings of the existing technologies, this invention proposes a method for modifying isobutyl oleate. This method involves the direct and gentle modification of isobutyl oleate using P2S5 under a nitrogen atmosphere. By strictly controlling the modification parameters (85℃, 300 r / min, 4 h), the gas absorption performance is significantly improved. Simultaneously, comparative experiments clarify the negative impact of monomer modification, ultimately yielding a high-absorption-performance capacitor impregnating base oil, thus resolving the aforementioned technical challenges.

[0026] Example 1: P2O5 modified isobutyl oleate This embodiment provides a method for modifying isobutyl oleate with P2O5, as detailed below: 1. Raw material pretreatment: Take 100g of isobutyl oleate, place it in a vacuum drying oven, and dry it for 2 hours at 80℃ and 0.08MPa for later use; take 0.8g of P2S5, pulverize it to a particle size of 50-100 mesh for later use; 2. Modification reaction: The pretreated isobutyl oleate was added to a four-necked flask, and a nitrogen atmosphere was introduced for protection (flow rate 80 mL / min). The mixture was stirred and heated to 85 °C. Powdered P2O5 was slowly added, and the mixture was stirred at 300 r / min for 4 h to obtain the reaction solution. 3. Post-treatment: Cool the reaction solution to room temperature, filter it through a 0.22 μm organic filter membrane to remove unreacted P2S5 solid, and then distill the filtrate at 65 °C and 0.09 MPa under reduced pressure for 30 min to obtain modified isobutyl oleate.

[0027] The performance test results were as follows: gas absorption = 100mL / 100mL, dielectric loss factor = 0.0017, and breakdown voltage = 70kV / 2.5mm. The gas absorption performance was improved by 51.5% compared with pure isobutyl oleate, and the dielectric performance and breakdown voltage were better than the blank control group. This proves that the modification effect is optimal under the modification parameters (85℃, 300r / min, 4h, nitrogen protection).

[0028] Meanwhile, pure isobutyl oleate was used as a blank control for performance testing: Isobutyl oleate was used without any modification treatment and its getter performance was tested directly. The test results were: getter = 66mL / 100mL, dielectric loss factor = 0.0020, and breakdown voltage = 65kV / 2.5mm.

[0029] The isobutyl oleate before and after modification was analyzed by Fourier transform infrared spectroscopy (FTIR). The results are shown in the figure. Figure 1 As shown, isobutyl oleate, after modification with P2S5, still retains the characteristic functional groups of the original ester (such as 2923 and 2853 cm⁻¹). -1 alkyl stretching vibration, 1737 cm -1 ester carbonyl vibration and 723 cm -1 The long-chain characteristic peaks indicate that the long carbon chain backbone of oleic acid has not been destroyed.

[0030] Meanwhile, the modified product showed obvious P=S characteristic absorption peaks (1283–1243 cm⁻¹). -1 ) and P–O–C stretching vibration peak (935cm) -1 (Nearby), confirming that P2S5 reacts with isobutyl oleate to successfully generate an organophosphate derivative containing a thiophosphate structure. And at 1708 cm⁻¹ -1 The newly added carbonyl peaks nearby indicate that the modification process is accompanied by the formation of some acidic intermediates or thioester carbonyl groups, which is consistent with the reversible esterification / thiolation equilibrium process in the reaction pathway.

[0031] Comparative Example 1 This comparative example provides a novel modified isobutyl oleate, obtained by modifying TMP with P2S5 and adding it at 3% to isobutyl oleate, as detailed below: 1. Preparation of P2S5 modified TMP: Take 10g TMP, add 20mL anhydrous ethanol, stir to dissolve, heat to 60℃, add 0.1g P2S5, stir to react for 2h, remove ethanol by vacuum distillation to obtain P2S5 modified TMP; 2. Sample preparation: Take 100g of pure isobutyl oleate, add 3g of the above P2S5 modified TMP, stir at 40℃ and 200r / min for 30min, cool to room temperature to obtain the sample; The obtained samples were subjected to performance tests, and the results are as follows: gas getter = 25.2 mL / 100 mL, dielectric loss factor = 0.0028, breakdown voltage = 58 kV / 2.5 mm. The gas getter performance was significantly lower than that of pure isobutyl oleate, and both the dielectric performance and breakdown voltage were unqualified. The possible reason is that P2S5 undergoes a deep thiolation reaction with TMP to generate a low molecular weight polysulfide derivative containing a large amount of free -SH, which has extremely poor compatibility with isobutyl oleate, resulting in phase separation. Furthermore, the free -SH self-oxidizes to release hydrogen gas, covering the hydrogen-absorbing active sites of isobutyl oleate, leading to a sharp decrease in gas getter performance.

[0032] Comparative Example 2 This comparative example provides a novel modified isobutyl oleate, obtained by modifying OA with P2S5 and adding it at 3% to isobutyl oleate, as detailed below: 1. Preparation of P2S5 modified OA: Take 10g OA, add 20mL anhydrous ethanol, stir evenly, heat to 70℃, add 0.1g P2S5, stir and react for 2h, remove ethanol by vacuum distillation to obtain P2S5 modified OA; 2. Sample preparation: Take 100g of pure isobutyl oleate, add 3g of the above P2S5 modified OA, stir at 40℃ and 200r / min for 30min, cool to room temperature to obtain the sample; The performance of the obtained sample was tested, and the results are as follows: getter performance = 49.0 mL / 100 mL, dielectric loss factor = 0.0025, breakdown voltage = 60 kV / 2.5 mm. The getter performance decreased by 25.8% compared with pure isobutyl oleate, and the dielectric performance and breakdown voltage also decreased slightly. The possible reason is that P2S5 undergoes decarboxylation and thiolation reactions with OA, forming oleic acid-based polysulfide derivatives, which are highly polar and have poor compatibility with isobutyl oleate, resulting in slight phase separation. The self-oxidation of free -SH consumes hydrogen-absorbing active sites, leading to a decrease in getter performance.

[0033] Comparative Example 3 This comparative example provides a novel modified isobutyl oleate, obtained by modifying OA with P2S5 and adding it at 6% to isobutyl oleate, as detailed below: 1. Preparation of P2S5 modified OA: The preparation method is completely consistent with that of P2S5 modified OA in Comparative Example 2; 2. Sample preparation: Take 100g of pure isobutyl oleate, add 6g of the above P2S5 modified OA, stir at 40℃ and 200r / min for 30min, cool to room temperature to obtain the sample; The performance of the obtained samples was tested, and the results are as follows: getter performance = 46.2 mL / 100 mL, dielectric loss factor = 0.0032, breakdown voltage = 57 kV / 2.5 mm. The getter performance further decreased compared to Comparative Example 2 (a decrease of 5.7%), and the dielectric performance and breakdown voltage further deteriorated. The possible reasons are: the addition ratio was increased to 6%, far exceeding the compatibility threshold, the phase separation phenomenon was more obvious, the modified product aggregated severely, the free -SH content increased, the auto-oxidation reaction intensified, and at the same time, the excessive impurities covered more hydrogen absorption active sites, enhancing negative interference, resulting in a further decrease in getter performance and unacceptable dielectric performance and breakdown voltage.

[0034] Experimental Example 1 The performance of the modified isobutyl oleate prepared in Example 1, the unmodified isobutyl oleate, and the samples prepared in Comparative Examples 1-3 were tested, and the results are shown in Table 1.

[0035] Table 1 Statistical analysis of performance test results for each sample This study systematically tested the key electrical properties of different modified isobutyl oleate systems, and the results showed that: 1. Pure isobutyl oleate: As a basic control, its gas absorption is 66 mL / 100mL, dielectric loss factor is 0.0020, breakdown voltage is 65 kV / 2.5mm, and its overall performance meets the qualified level.

[0036] 2. P2S5-modified isobutyl oleate: exhibited optimal overall performance. Compared to pure isobutyl oleate, its gas absorption increased to 100 mL / 100 mL, an improvement of 51.5%; the dielectric loss factor decreased to 0.0017, a reduction of 15%; and the breakdown voltage increased to 70 kV / 2.5 mm, an increase of 7.7%. This indicates that direct modification with P2S5 can effectively introduce phosphorus- and sulfur-containing functional groups, significantly enhancing the gas-dissolving capacity and insulation stability of oils.

[0037] 3. Compound system (P2S5 modified TMP / OA + isobutyl oleate): The overall performance is inferior to the direct modified system, and it continues to deteriorate with the increase of the content of the modifying additive.

[0038] (1) After adding 3% P2S5 to modify TMP, the gas absorption rate dropped sharply to 25.2 mL / 100mL, the dielectric loss factor increased to 0.0028, and the breakdown voltage dropped to 58 kV / 2.5mm, resulting in overall unqualified performance.

[0039] (2) After adding 3% and 6% P2S5 to modify OA, the gas absorption decreased to 49.0 and 46.2 mL / 100 mL, respectively; the dielectric loss factor increased to 0.0025 and 0.0032, respectively; and the breakdown voltage decreased to 60 and 57 kV / 2.5 mm, respectively. None of them met the qualified standards, and the performance decline trend intensified with the increase of OA addition.

[0040] In summary, direct modification of P2S5 with isobutyl oleate is the optimal solution to improve the gas absorption and electrical insulation properties of oils. However, the compounding method of introducing modified TMP or OA may lead to a significant decrease in the overall performance of oils because it may destroy the original molecular structure or introduce polar impurities.

[0041] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A modification method for improving the getter properties of isobutyl oleate, characterized in that, The modified green plant-based impregnating agent for high-voltage power capacitors includes the following steps: Under a nitrogen atmosphere, phosphorus pentasulfide and isobutyl oleate were mixed and stirred at 85°C and 300 r / min for 4 h. After the reaction was completed, the mixture was filtered and distilled under reduced pressure to obtain modified isobutyl oleate.

2. The modification method according to claim 1, characterized in that, The amount of phosphorus pentasulfide added is 0.5%-1.0% of the mass of isobutyl oleate.

3. The modification method according to claim 2, characterized in that, The amount of phosphorus pentasulfide added is 0.8% of the mass of isobutyl oleate.

4. The modification method according to claim 1, characterized in that, The flow rate of the nitrogen gas is 80 mL / min.

5. The modification method according to claim 1, characterized in that, The filtration process uses a 0.22μm organic filter membrane for vacuum filtration.

6. The modification method according to claim 1, characterized in that, The conditions for vacuum distillation are: temperature 65℃, vacuum degree 0.09MPa, and time 30min.

7. The modification method according to claim 1, characterized in that, The phosphorus pentasulfide is pulverized to a particle size of 50-100 mesh before use; the isobutyl oleate is vacuum dried before use under the following conditions: temperature 80℃, vacuum degree 0.08MPa, and time 2h.

8. Modified isobutyl oleate prepared by the modification method according to any one of claims 1-7.

9. The application of the modified isobutyl oleate as described in claim 8 in the preparation of capacitor impregnating agents.

10. The application according to claim 9, characterized in that, The capacitor is a high-voltage power capacitor.

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