Synthetic ester insulating oil double-effect improver as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of transformer insulating oil, and discloses a synthetic ester insulating oil double-effect improver as well as a preparation method and application thereof. The preparation method comprises the following steps: carrying out primary reaction on an N-phenyl-alpha-naphthylamine solution, a hindered phenol solution and triethylamine; then adding methyl iodide and triethylamine to carry out secondary reaction; and adding hydrochloric acid for neutralization, drying with anhydrous sodium sulfate, carrying out rotary evaporation, and finally purifying to obtain the synthetic ester insulating oil double-effect improver. By introducing polycyclic aromatic hydrocarbon and methoxyl, the oxidation resistance of the synthetic ester is improved; the methoxyl group improves the ultraviolet light absorption capability, and reduces the molecular excitation caused by high-energy ultraviolet light in the insulating oil, thereby inhibiting the formation of a streamer channel. The double-effect improver provided by the invention not only is obviously superior to the traditional antioxidant in oxidation resistance, but also can obviously improve the electric shock resistance of the synthetic ester insulating oil in a high-temperature and high-pressure environment, and is suitable for high-voltage and large-sized transformers and other electrical equipment needing long-time stable operation.

Description

Technical Field

[0001] The invention relates to the technical field of transformer insulating oil, and in particular to a synthetic ester insulating oil double-effect enhancer and a preparation method and application thereof. Background Art

[0002] During the long-term operation of the transformer, the working environment of the insulating oil is complex and is affected by a variety of internal and external factors. Due to the fluctuation of the system load, the temperature of the insulating oil varies within a range of tens of degrees Celsius. When overloaded, the hot spot temperature may even exceed one hundred degrees Celsius. Locally excessively high temperatures have an adverse effect on the physical and chemical properties and electrical properties of the insulating oil. In addition, thermal stress accelerates the aging of the oil-paper insulation system, generates acidic substances and causes the fiber breakage of the insulating paper. These broken fibers are suspended in the oil in the form of tiny particles. Due to the different dielectric constants of the fibers and the oil, these suspended particles may cause local electric field distortion, which ultimately affects the overall electrical properties of the insulating oil. At present, synthetic ester insulating oil is gradually replacing traditional mineral insulating oil and is widely used in power equipment such as oil-immersed transformers. Compared with mineral insulating oil, there is still a certain gap in the physical, chemical and electrical properties of synthetic ester insulating oil. Therefore, improving the insulation performance of synthetic ester insulating oil has become an urgent problem to be solved.

[0003] At present, the method of adding antioxidants is widely used at home and abroad to slow down the oxidation process of insulating oil. Although this method is easy to operate and can achieve good results in the early stage of insulating oil operation, with the long-term operation of the transformer, the effect of the antioxidant gradually weakens and the oxidation of the oil intensifies. In addition, with the development of ultra-high / ultra-high voltage transmission technology, the discharge characteristics and lightning impulse resistance of transformer insulating oil have become increasingly important. Studies have shown that ultraviolet absorbers can improve the lightning impulse resistance of insulating oil to a certain extent, but ultraviolet absorbers suitable for insulating oil are still relatively scarce. Summary of the invention

[0004] The purpose of the present invention is to provide a synthetic ester insulating oil dual-effect enhancer and a preparation method and application thereof, so as to solve the problem that the existing antioxidants and ultraviolet absorbers have no obvious effect on improving the insulating properties of synthetic ester insulating oil.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a synthetic ester insulating oil double-effect enhancer, comprising the following steps:

[0007] N-phenyl-α-naphthylamine solution, hindered phenol solution and triethylamine are mixed to carry out a primary reaction; after the primary reaction, methyl iodide and triethylamine are added to carry out a secondary reaction; after the secondary reaction, hydrochloric acid is added to neutralize, dried over anhydrous sodium sulfate, and rotary evaporated to obtain a crude product; the crude product is purified to obtain a synthetic ester insulating oil dual-effect enhancer.

[0008] Preferably, in the above-mentioned method for preparing a synthetic ester insulating oil dual-effect enhancer, the N-phenyl-α-naphthylamine solution is a mixture of N-phenyl-α-naphthylamine and a solvent; the hindered phenol solution is a mixture of hindered phenol and a solvent; and the solvent is anhydrous dichloromethane.

[0009] Preferably, in the above-mentioned method for preparing a synthetic ester insulating oil dual-effect enhancer, the hindered phenol is β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride.

[0010] Preferably, in the above-mentioned method for preparing a synthetic ester insulating oil dual-effect enhancer, the molar ratio of N-phenyl-α-naphthylamine, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride and iodomethane is 0.9-1.25:1:0.8-1.

[0011] Preferably, in the above-mentioned method for preparing a synthetic ester insulating oil dual-effect enhancer, the temperature of the primary reaction is 25° C.; and the time of the primary reaction is 5 to 8 hours.

[0012] Preferably, in the above-mentioned method for preparing a synthetic ester insulating oil dual-effect enhancer, the temperature of the secondary reaction is 25° C.; and the time of the secondary reaction is 3 to 5 hours.

[0013] The present invention also provides a synthetic ester insulating oil double-effect enhancer prepared by a preparation method thereof, wherein the structural formula of the synthetic ester insulating oil double-effect enhancer is as follows:

[0014]

[0015] The invention also provides application of a synthetic ester insulating oil double-effect enhancer in the synthetic ester insulating oil.

[0016] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention designs an antioxidant with dual functions: N-phenyl-α-naphthylamine derivatives, which form a polycyclic aromatic hydrocarbon structure by connecting a hindered phenol structure with a naphthalene ring, and introduce a methoxy group on the benzene ring. Compared with traditional basic antioxidants, the antioxidant of the present invention first improves the antioxidant capacity of synthetic esters: using conjugated structure design and alkylation reaction technology, the polycyclic aromatic hydrocarbon structure and methoxy group introduced achieve stronger antioxidant performance; the π-π stacking effect of polycyclic aromatic hydrocarbons can improve the stability of the molecule and reduce the generation of free radicals in the insulating oil, while the methoxy group further enhances the antioxidant capacity of the molecule through the electron supply effect. Secondly, the lightning impulse resistance of the synthetic ester is enhanced: by introducing a methoxy group into the molecular structure, the antioxidant's ability to absorb ultraviolet light is improved, and the molecular excitation caused by high-energy ultraviolet light in the insulating oil is reduced, thereby inhibiting the formation of streamer channels. The conjugated structure and π-π stacking effect of polycyclic aromatic hydrocarbons can effectively reduce the generation rate of charged particles under electric field impact and enhance the breakdown voltage of the insulating oil. In general, the antioxidant prepared by the present invention is not only significantly superior to traditional antioxidants in antioxidant performance, but can also significantly improve the electrical shock resistance of synthetic ester insulating oil in high temperature and high pressure environments. It is suitable for high voltage, large transformers and other power equipment that require long-term stable operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments or the prior art are briefly introduced below.

[0019] Figure 1 The acid value of the synthetic ester insulating oil of application examples 1 to 3 and comparative examples 1 to 2 changes with aging time;

[0020] Figure 2 The furfural content of the synthetic ester insulating oil of application examples 1 to 3 and comparative examples 1 to 2 varies with aging time;

[0021] Figure 3 The diagram shows the changes in positive polarity lightning impulse voltage of the synthetic ester insulating oil of Application Examples 1 to 3 and Comparative Examples 1 to 2. DETAILED DESCRIPTION

[0022] The present invention provides a method for preparing a synthetic ester insulating oil double-effect enhancer, comprising the following steps:

[0023] N-phenyl-α-naphthylamine solution, hindered phenol solution and triethylamine are mixed to carry out a primary reaction; after the primary reaction, methyl iodide and triethylamine are added to carry out a secondary reaction; after the secondary reaction, hydrochloric acid is added to neutralize, dried over anhydrous sodium sulfate, and rotary evaporated to obtain a crude product; the crude product is purified to obtain a synthetic ester insulating oil dual-effect enhancer.

[0024] In the present invention, the N-phenyl-α-naphthylamine solution is preferably a mixture of N-phenyl-α-naphthylamine and a solvent; the hindered phenol solution is preferably a mixture of hindered phenol and a solvent; and the solvent is preferably anhydrous dichloromethane.

[0025] In the present invention, the hindered phenol is preferably β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride.

[0026] In the present invention, the molar ratio of N-phenyl-α-naphthylamine, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl chloride and iodomethane is preferably 0.9-1.25:1:0.8-1, more preferably 0.9-1:1:0.85-0.9, and more preferably 0.91:1:0.86.

[0027] In the present invention, the method of mixing the N-phenyl-α-naphthylamine solution, hindered phenol solution and triethylamine is preferably: adding the hindered phenol solution dropwise to the N-phenyl-α-naphthylamine solution, and adding triethylamine dropwise while adding the hindered phenol solution; the dropping temperature is preferably 0°C.

[0028] In the present invention, the temperature of the primary reaction is preferably 25° C.; the time of the primary reaction is preferably 5 to 8 hours, more preferably 6 hours.

[0029] In the present invention, the method of adding methyl iodide and triethylamine is preferably: firstly dropwise adding methyl iodide, and then dropwise adding triethylamine.

[0030] In the present invention, the temperature of the secondary reaction is preferably 25° C.; the time of the secondary reaction is preferably 3 to 5 hours, more preferably 4 hours.

[0031] In the present invention, the purification is preferably performed by silica gel column chromatography; the eluent for the purification is preferably n-hexane-ethyl acetate in a volume ratio of 8:2.

[0032] The present invention also provides a synthetic ester insulating oil double-effect enhancer prepared by a preparation method thereof, wherein the structural formula of the synthetic ester insulating oil double-effect enhancer is as follows:

[0033]

[0034] The invention also provides application of a synthetic ester insulating oil double-effect enhancer in the synthetic ester insulating oil.

[0035] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment provides a method for preparing a synthetic ester insulating oil dual-effect enhancer, comprising the following steps:

[0038] S1. In a dry 250 mL round-bottom flask, add 4.1 g N-phenyl-α-naphthylamine and 30 mL anhydrous dichloromethane (DCM), stir until completely dissolved to obtain a naphthylamine solution; dissolve β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride (6.1 g) in 20 mL DCM, keep the temperature at 0°C, use a constant pressure dropping funnel, slowly add dropwise to the naphthylamine solution, and simultaneously add dropwise 1.5 g triethylamine; after the addition is complete, raise the temperature to room temperature (25°C), and stir to react for 6 hours;

[0039] S2. After the reaction is completed, iodomethane (2.5 g) is added dropwise, and then 1.6 g of triethylamine is added dropwise, and the reaction is stirred for 4 hours; after the reaction is completed, the excess iodomethane is neutralized with dilute hydrochloric acid, and the organic layer is separated; the organic layer is washed with distilled water until the pH is neutral; the organic layer is dried over anhydrous sodium sulfate, and then DCM is removed by rotary evaporation to obtain a crude product;

[0040] S3. Purify the crude product by silica gel column chromatography, using n-hexane-ethyl acetate in a volume ratio of 8:2 as the eluent; collect the target product and dry it in a vacuum dryer to obtain a synthetic ester insulating oil dual-effect enhancer.

[0041] Application Example 1

[0042] The double-effect enhancer prepared in Example 1 was ground, and then added to the synthetic ester insulating oil that had been vacuum dried for 24 hours, the mass fraction of the double-effect enhancer in the synthetic ester insulating oil was 0.2wt%, and ultrasonic vibration was performed for 2 hours, which was recorded as double-effect enhancer-0.2wt%.

[0043] Application Example 2

[0044] This application example specifically refers to application example 1, except that the mass fraction of the dual-effect enhancer in the synthetic ester insulating oil is 0.05wt%, which is recorded as dual-effect enhancer-0.05wt%.

[0045] Application Example 3

[0046] This application example specifically refers to application example 1, except that the mass fraction of the dual-effect enhancer in the synthetic ester insulating oil is 0.4wt%, which is recorded as dual-effect enhancer-0.4wt%.

[0047] Application Comparative Example 1

[0048] The specific application comparison example of this application example is as shown in Application Example 1, except that the dual-effect enhancer is replaced by antioxidant T501, which is recorded as T501-0.2wt%.

[0049] Application Comparative Example 2

[0050] The specific application comparison of this application example is as shown in Application Example 1, except that no dual-effect enhancer is added. This is recorded as the control group.

[0051] Weigh 200g of the synthetic ester insulating oil prepared in Application Examples 1 to 3 and Comparative Examples 1 to 2 respectively, and place them in a 120℃ constant temperature box for 7, 14, 21, and 28 days of oil-paper thermal aging to accelerate the aging rate of the synthetic ester insulating oil paper. The acid value of the insulating oil before and after aging and the furfural content in the oil sample were measured respectively. The results are as follows: Figure 1-2 shown.

[0052] The synthetic ester insulating oils prepared in Application Examples 1 to 3 and Comparative Examples 1 to 2 were subjected to lightning impulse tests to measure their positive polarity lightning impulse voltage values. Figure 3 shown.

[0053] The acid value indicates the content of organic acids in the oil and can reflect the aging of the oil. The acid products contained in the oil will increase the conductivity of the oil and reduce the insulation performance of the oil. When the operating temperature is high, it will also promote the aging and corrosion of solid fibrous insulation materials, shortening the service life of the equipment. Figure 1 The figure shows the changes in the acid values ​​of 5 groups of synthetic esters. It can be seen that when no antioxidant is added, the acid value of the synthetic ester shows a trend of first slowly increasing and then rapidly increasing. Comparing the addition of the same content of T501 and the dual-effect enhancer component, there is little difference between the two in the early stage of aging. This is because both have a certain oxidation inhibition effect in the early stage of oil sample aging, mainly removing the alkyl free radicals R· and peroxy free radicals RO generated by the thermal decomposition of active alkanes in the oil. 2 ·, with the extension of aging time, T501 is unstable in a long-term high temperature environment, and its antioxidant effect is weakened, resulting in a rapid increase in the acid value in the later period. The dual-effect enhancer improves the stability of the molecule due to the π-π stacking effect of polycyclic aromatic hydrocarbons. At the same time, the methoxy group further enhances the antioxidant ability of the molecule through the electron donation effect, which makes the increase in the acid value of the insulating oil smaller.

[0054] Furfural is produced during the degradation of cellulose in insulating paper and can be dissolved at room temperature and in operating transformer oil. Therefore, the furfural content is often used as one of the indicators to evaluate the degree of aging of insulating paper. Figure 2 The figure shows the changes of furfural content in 5 groups of oils over 28 days. Figure 2It can be seen that the cellulose molecules in the insulating paper are affected by thermal stress and degradation products and degraded to produce furfural. In the early stage of the aging experiment, due to the presence of antioxidants, the growth rate of furfural is low, the degradation of cellulose molecules is not serious, and the furfural content of the addition of 0.2wt% dual-effect enhancer is relatively low; in the later stage of aging, the aging degree of the insulating paper deepens, and the degradation products of the oil sample catalyze the decomposition of cellulose, and the growth rate of furfural content accelerates, but the dual-effect enhancer still plays a certain inhibitory role.

[0055] The pre-breakdown and breakdown characteristics of insulating oil are crucial for designing the gap distance between transformer windings, and lightning impulse voltage is an important parameter. Figure 3 The positive polarity lightning impulse voltage of 5 groups of synthetic ester insulating oils is shown. It can be seen that the double-effect enhancer can improve the lightning impulse voltage of synthetic esters, among which the addition of 0.2wt% of the double-effect enhancer has the best effect. This is mainly because the methoxy group is introduced into the molecular structure, which improves the antioxidant's ability to absorb ultraviolet light and reduces the molecular excitation caused by high-energy ultraviolet light in the oil, thereby inhibiting the formation of streamer channels. However, adding excessive double-effect enhancers may cause intermolecular aggregation, form local clusters, induce electric field distortion, and promote the formation of streamer channels. In summary, adding 0.2wt% of the double-effect enhancer to synthetic ester insulating oil can improve its antioxidant capacity and lightning impulse voltage.

[0056] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a synthetic ester insulating oil dual-effect enhancer, characterized in that: The following steps are involved: N-phenyl-α-naphthylamine solution, hindered phenol solution and triethylamine are mixed to carry out a primary reaction; after the primary reaction, methyl iodide and triethylamine are added to carry out a secondary reaction; after the secondary reaction, hydrochloric acid is added to neutralize, dried over anhydrous sodium sulfate, and rotary evaporated to obtain a crude product; the crude product is purified to obtain a synthetic ester insulating oil dual-effect enhancer.

2. The method for preparing a synthetic ester insulating oil dual-effect enhancer according to claim 1, characterized in that: The N-phenyl-α-naphthylamine solution is a mixture of N-phenyl-α-naphthylamine and a solvent; the hindered phenol solution is a mixture of hindered phenol and a solvent; and the solvent is anhydrous dichloromethane.

3. The method for preparing a synthetic ester insulating oil dual-effect enhancer according to claim 2, characterized in that: The hindered phenol is β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride.

4. The method for preparing a synthetic ester insulating oil dual-effect enhancer according to claim 3, characterized in that: The molar ratio of the N-phenyl-α-naphthylamine, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl chloride and iodomethane is 0.9-1.25:1:0.8-1.

5. The method for preparing a synthetic ester insulating oil dual-effect enhancer according to claim 1 or 3, characterized in that: The temperature of the primary reaction is 25° C.; the time of the primary reaction is 5 to 8 hours.

6. The method for preparing a synthetic ester insulating oil dual-effect enhancer according to claim 5, characterized in that: The temperature of the secondary reaction is 25° C.; the time of the secondary reaction is 3 to 5 hours.

7. A synthetic ester insulating oil double-effect enhancer prepared by the method for preparing a synthetic ester insulating oil double-effect enhancer according to any one of claims 1 to 6, characterized in that: The structural formula of the synthetic ester insulating oil dual-effect enhancer is as follows:

8. Use of the synthetic ester insulating oil dual-effect enhancer according to claim 7 in synthetic ester insulating oil.

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