Antioxidant synthetic ester insulating oil, preparation method therefor and use thereof

Abstract

The present invention provides an antioxidant synthetic ester insulating oil, a preparation method therefor, and a use thereof. An antioxidant inorganic nanofiller in the antioxidant synthetic ester insulating oil of the present invention is prepared by a method comprising the following steps: dissolving a phosphodiester and an amino-modified inorganic nanofiller in an organic solvent, uniformly mixing these materials, carrying out a reaction, and upon the completion of the reaction, performing reduced pressure distillation on a solid product for impurity removal. By selecting the phosphodiester as a modification raw material, using a two-step modification method to introduce the phosphodiester onto the surface of a nanofiller, and removing byproducts by means of reduced pressure distillation, an antioxidant functional nanofiller with a high grafting rate is obtained, and the antioxidant functional nanofiller is then added to synthetic ester base oil and uniformly mixed to prepare antioxidant synthetic ester insulating oil. The obtained synthetic ester insulating oil has excellent oxidation resistance and service life.

Description

Antioxidant synthetic ester insulating oil and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of insulating oil, in particular to an antioxidant synthetic ester insulating oil and a preparation method and application thereof. Background Art

[0002] Insulating oil is a key insulating medium in transformers, providing heat dissipation, insulation, and arc extinguishing during operation. The heat generated during transformer operation causes the insulating oil near the core and windings to expand and rise. Convection through the insulating oil allows the heat to be dissipated by conduction, ensuring the normal operation of the transformer.

[0003] At present, environmentally friendly synthetic ester insulating oil with renewable and degradable properties has become one of the preferred insulating oils for oil-immersed transformers. The performance of synthetic ester insulating oil is largely affected by its oxidation properties. During the long-term use of insulating oil, due to the influence of oxygen and high temperature, the carbon-carbon bonds or carbon-oxygen bonds in the oil molecules are broken, resulting in changes in the oil molecular structure, which ultimately affects the performance of the insulating oil. Traditional synthetic ester insulating oil oxidation inhibition technology usually adopts the method of adding antioxidants (such as oxidants with phenol structures). Antioxidants can slow down or inhibit the oxidation process of insulating oil molecules and improve their oxidation stability. Adding nanofillers to synthetic ester insulating oil is also an improved technology that can improve the thermal conductivity, electrical insulation and antioxidant properties of insulating oil. It has been reported that modifying the surface of nanomaterials with organic antioxidants is a new anti-oxidation method. However, existing surface modification technologies all require the use of an acylating agent to acylate the antioxidant before it can be grafted onto the surface of the rice material modified with a silane coupling agent. However, the byproducts of the acylating agent will affect the antioxidant effect and the activity of the active sites of the silane coupling agent, resulting in uneven grafting and low grafting rate, which in turn affects the further improvement of the antioxidant properties of the insulating oil.

[0004] Therefore, it is necessary to provide an antioxidant synthetic ester insulating oil with better performance.

[0005] Summary of the Invention

[0006] The present invention aims to overcome the drawback of existing insulating oils, which require the use of an acylating agent for surface modification of nanomaterials, resulting in limited improvement in the antioxidant properties of the insulating oil. The present invention provides a method for preparing an antioxidant synthetic ester insulating oil. This method utilizes a phosphodiester as a modification raw material, introduces the phosphodiester onto the surface of a nanofiller using a two-step modification method, and removes byproducts using vacuum distillation to produce an antioxidant nanofiller with a high grafting rate. This nanofiller is then added to a synthetic ester base oil and mixed uniformly to produce an antioxidant synthetic ester insulating oil. The resulting synthetic ester insulating oil exhibits excellent antioxidant properties and a long service life.

[0007] Another object of the present invention is to provide an antioxidant synthetic ester insulating oil prepared by the above preparation method.

[0008] Another object of the present invention is to provide use of the antioxidant synthetic ester insulating oil in a transformer.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] A method for preparing an antioxidant synthetic ester insulating oil comprises the following steps:

[0011] S1. Preparation of Antioxidant Inorganic Nanofillers

[0012] S11. The inorganic nanofiller and the silane coupling agent are dissolved in a first organic solvent and mixed uniformly to obtain a first suspension, and the reaction is closed at 35-65 ° C for 6-13h to obtain an amino-modified inorganic nanofiller;

[0013] S12. The phosphodiester and the amino-modified inorganic nanofiller obtained in step S1 are dissolved in a second organic solvent, mixed evenly to obtain a second suspension, the pH is adjusted to 8.5-9.5, and the reaction is carried out in an inert atmosphere at 20-30°C for 6-13 hours. After the reaction is complete, the solid product is dissolved in a third organic solvent and distilled under reduced pressure. After drying, the antioxidant inorganic nanofiller is obtained;

[0014] S2. Preparation of Antioxidant Synthetic Ester Insulating Oil

[0015] The antioxidant inorganic nanofiller and synthetic ester oil prepared in step S1 are mixed evenly to obtain the antioxidant synthetic ester insulating oil.

[0016] The present invention uses a phosphodiester as a modification material and employs a two-step modification method to introduce the phosphodiester onto the surface of a nanofiller. The phosphodiester reacts with the amine groups in a silane coupling agent to produce phosphite groups with antioxidant properties, eliminating the need for an acylating agent. After the reaction, a specific vacuum distillation post-treatment process significantly improves the purity and uniformity of the antioxidant loading on the inorganic nanoparticles. The resulting synthetic ester insulating oil exhibits excellent oxidative stability and high breakdown strength, effectively avoiding the oxidant instability found in prior art and improving the dispersion uniformity and insulating properties of the insulating oil fluid.

[0017] Preferably, in the antioxidant inorganic nanofiller, the weight ratio of the raw materials is inorganic nanofiller: silane coupling agent: phosphate diester = 1: (0.5-3.7): (0.5-4).

[0018] Optionally, the silane coupling agent includes but is not limited to at least one of 3-aminopropyltriethoxysilane (KH-550), γ-glycidoxypropyltrimethoxysilane (KH-560), and γ-methacryloxypropyltrimethoxysilane (KH-570).

[0019] Optionally, the phosphate diester includes but is not limited to at least one of triphenoxy phosphate (TPP), trioctyl phosphate (TNOP), triisooctyl phosphate (TIOP), diisopropyl phenyl phosphate (DIPP), and diethyl phenyl phosphate (DEPP).

[0020] Optionally, the inorganic nanofiller includes but is not limited to at least one of SiO2, TiO2, Fe3O4, BN, and Al2O3. The inorganic nanofiller may have a morphology of granules, lines, sheets, or sieves.

[0021] Preferably, the synthetic ester oil comprises at least one of TMP triester and PETP tetraester. TMP triester is a synthetic ester oil prepared by the esterification reaction of medium-chain fatty acids with trimethylolpropane (TMP). PETP tetraester is a synthetic ester oil prepared by the esterification reaction of medium-chain fatty acids with pentaerythritol (PETP).

[0022] Preferably, in the synthetic ester oil, the weight ratio of TMP triester to PETP tetraester is TMP triester:PETP tetraester=1:(0.4-2.3).

[0023] Preferably, in the oxidized synthetic ester insulating oil, the weight ratio of the antioxidant inorganic nanofiller to the synthetic ester oil is (0.01-0.15):100.

[0024] Preferably, the first organic solvent and the second organic solvent may be the same or different, and the first organic solvent and the second organic solvent independently include at least one of methanol, ethanol, and pyridine.

[0025] Preferably, the solid content of the first suspension formed in step S11 is 1.5-30 wt.%.

[0026] Preferably, the solid content of the second suspension formed in step S12 is 5.4-30 wt.%.

[0027] When the solid content is within the above range, the reaction raw materials can be mixed evenly and the distribution uniformity of the phosphate diester on the surface of the nanofiller can be improved.

[0028] Optionally, the pH regulator used in step S12 includes but is not limited to ammonia water.

[0029] Optionally, the inert atmosphere in step S12 is an atmosphere formed by at least one gas selected from nitrogen, argon, and helium.

[0030] To further improve mixing uniformity, in step S12, the reaction raw materials phosphodiester and amino-modified inorganic nanofiller can be dissolved in the second organic solvent respectively, and then the organic solvents containing the two reaction raw materials are mixed together to obtain a second suspension.

[0031] Preferably, after the reaction is complete in step S12, centrifugation is further required to separate the solid product. The centrifugation speed is 5000-9000 rpm and the centrifugation time is 10-15 minutes.

[0032] Preferably, the boiling point of the third organic solvent at standard atmospheric pressure is in the range of 30-80° C. The third organic solvent includes but is not limited to at least one of diethyl ether and acetone.

[0033] Preferably, the pressure of the reduced pressure distillation is 0.0001-0.15 bar, and the temperature of the reduced pressure distillation is 35-60°C. It should be noted that as the pressure decreases, the boiling point of the solvent also decreases. Distillation at this temperature not only quickly removes reaction byproducts, achieving the purpose of purification, but also prevents the molecular chains of the organic antioxidant coated on the surface of the inorganic nanofiller from breaking due to excessively high temperatures, thereby affecting antioxidant performance.

[0034] Preferably, after the reduced pressure distillation, centrifugation is further performed to separate the solid product, washing and drying operations. The washing reagent is water.

[0035] Alternatively, any commonly used drying means in the art can be used in the present invention. In the present invention, the drying in step S12 is vacuum drying, and the temperature of the vacuum drying is 30-45°C.

[0036] The present invention also protects an antioxidant synthetic ester insulating oil, which is prepared by the above preparation method.

[0037] The use of the antioxidant synthetic ester insulating oil in transformers also falls within the protection scope of the present invention.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The antioxidant inorganic nanofiller in the antioxidant synthetic ester insulating oil of the present invention is prepared according to a method comprising the following steps: dissolving a phosphodiester and an amino-modified inorganic nanofiller in an organic solvent, mixing them uniformly, and reacting them; after the reaction is complete, performing reduced pressure distillation on the solid product to remove impurities.

[0040] The present invention selects phosphate diester as a modification raw material, adopts a two-step modification method to introduce the phosphate diester on the surface of a nanofiller, and adopts a reduced pressure distillation method to remove by-products to obtain an antioxidant nanofiller with a high grafting rate. The nanofiller is then added to a synthetic ester base oil and mixed uniformly to prepare an antioxidant synthetic ester insulating oil. The obtained synthetic ester insulating oil has excellent antioxidant performance and service life. DETAILED DESCRIPTION

[0041] For better explanation of the purpose, technical scheme and advantage of the present invention, the present invention will be further described below in conjunction with specific embodiment, but embodiment does not limit the present invention in any form.Unless otherwise stated, the reagent, method and equipment adopted in the present invention are conventional reagents, methods and equipment in the art.Unless otherwise stated, the reagents and materials used in the present invention are commercially available.

[0042] Example 1

[0043] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to a method comprising the following steps:

[0044] S1. Preparation of Antioxidant Inorganic Nanofillers

[0045] S11. Dissolve an inorganic nanofiller (Al2O3 with an average particle size of 30 nm) and a silane coupling agent KH-550 in anhydrous ethanol, stir and mix uniformly to obtain a first suspension with a solid content of 30 wt%. Heat to 50°C and react in a closed manner for 2.5 hours. After the reaction, centrifuge the product using a high-speed centrifuge, and wash the solid obtained by centrifugation with deionized water and anhydrous ethanol. Place the washed solid in a vacuum drying oven and vacuum dry it at 60°C for 24 hours to obtain an amino-modified inorganic nanofiller, wherein the weight ratio of the inorganic nanofiller to the silane coupling agent is 1:3.

[0046] S12. Dissolve the phosphate diester (trioctyl phosphate) in anhydrous pyridine to form a suspension A, and dissolve the amino-modified inorganic nanofiller obtained in step S11 in anhydrous pyridine to form a suspension B. Then, under an argon atmosphere, add the suspension A dropwise to the continuously stirred suspension B to obtain a second suspension with a solid content of 30 wt% (wherein the weight of the phosphate diester added is 3 times the weight of the unmodified inorganic nanofiller). Heat and stir in a 40°C water bath for 8 h. After heating, centrifuge the mixture and wash the solid obtained by centrifugation with deionized water. Dissolve the washed solid in ether and transfer it to a distillation flask. Connect a condenser, a stirrer, a heater, and a collecting flask. Check the sealing of the device, start the vacuum pump, establish an appropriate vacuum, open the pressure reducing valve of the vacuum distillation apparatus, gradually reduce the system pressure to 0.01 bar, and distill at 45°C under continuous stirring (stirring rate of 850 rpm). After the distillation is completed, vacuum dry at 45°C to obtain the antioxidant inorganic nanofiller.

[0047] S2. Preparation of Antioxidant Synthetic Ester Insulating Oil

[0048] 0.03 parts by weight of the antioxidant inorganic nanofiller prepared in step S12 and 100 parts by weight of TMP triester oil are uniformly mixed to obtain the antioxidant synthetic ester insulating oil.

[0049] Example 2

[0050] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S1, the amount of raw materials added is changed so that the weight ratio of inorganic nanofiller: silane coupling agent: phosphate diester in the prepared antioxidant inorganic nanofiller is 1:3:0.5.

[0051] Example 3

[0052] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S1, the amount of raw materials added is changed so that the weight ratio of inorganic nanofiller: silane coupling agent: phosphate diester in the prepared antioxidant inorganic nanofiller is 1:0.5:3.

[0053] Example 4

[0054] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S1, the amount of raw materials added is changed so that the weight ratio of inorganic nanofiller: silane coupling agent: phosphate diester in the prepared antioxidant inorganic nanofiller is 1:0.5:0.5.

[0055] Example 5

[0056] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S11, the silane coupling agent KH-550 is replaced with KH-560 of equal mass.

[0057] Example 6

[0058] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S11, the inorganic nanofiller is replaced with an equal mass of SiO2 (average particle size of 30 nm).

[0059] Example 7

[0060] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S11, the inorganic nanofiller is replaced with an equal mass of BN (average particle size of 30 nm).

[0061] Example 8

[0062] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S12, the phosphate diester is replaced by an equal mass of triphenoxy phosphate TPP.

[0063] Example 9

[0064] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S12, the phosphate diester is replaced by an equal mass of diisopropyl terephthalate (DIPP).

[0065] Example 10

[0066] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S2, the synthetic ester oil is replaced by PETP tetraester of equal mass.

[0067] Example 11

[0068] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S2, the synthetic ester oil is replaced by 50 parts by weight of TMP triester and 50 parts of PETP tetraester.

[0069] Example 12

[0070] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S2, the amount of antioxidant inorganic nanofiller added is 0.01 parts by weight.

[0071] Example 13

[0072] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S2, the amount of antioxidant inorganic nanofiller added is 0.15 parts by weight.

[0073] Example 14

[0074] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S12, the solvent for vacuum distillation is replaced by acetone.

[0075] Example 15

[0076] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S12, the solvent for vacuum distillation is replaced with anhydrous ethanol.

[0077] Example 16

[0078] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S12, the temperature of the reduced pressure distillation is 60° C. and the pressure is 0.01 bar.

[0079] Example 17

[0080] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S12, the temperature of the reduced pressure distillation is 45° C. and the pressure is 0.15 bar.

[0081] Comparative Example 1

[0082] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S12, the vacuum distillation operation is not performed.

[0083] Comparative Example 2

[0084] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S12, organic solvent ether is used for washing without vacuum distillation, and after washing, the oil is vacuum dried at 45°C.

[0085] Comparative Example 3

[0086] This embodiment provides an antioxidant synthetic ester insulating oil, which is prepared according to the method of Example 1. The difference from Example 1 is that in step S12, the phosphoric acid diester (trioctyl phosphate) is replaced with an equal mass of trioctyl phosphite, and an acylating agent phosphorus trichloride is added in an equimolar amount to trioctyl phosphite, and no reduced pressure distillation operation is performed.

[0087] Performance Testing

[0088] The properties of the antioxidant synthetic ester insulating oils obtained in the above examples and comparative examples were characterized. The specific test items, test methods, and results are as follows:

[0089] The above-mentioned antioxidant synthetic ester insulating oil was subjected to thermal oxidative aging at 120°C, and then 1) the power frequency breakdown voltage of the oil samples after thermal oxidative aging for 0 days (initial), 7 days and 15 days was tested using an insulating oil dielectric strength tester; 2) the water content of the oil samples after thermal oxidative aging for 0 days (initial), 7 days and 15 days was measured using a micro-water meter. The test results are shown in Table 1.

[0090] Table 1

[0091] Note: In Table 1, the AC breakdown voltage change rate after aging for 15 days (%) = (|U 15 -U0| / U0*100)%.

[0092] From the above results we can see that:

[0093] The antioxidant synthetic ester insulating oil prepared by the present invention has excellent antioxidant performance. After aging for 15 days, the AC breakdown voltage change rate of the insulating oil is below 36%, and can be as low as 12.47%.

[0094] The antioxidant inorganic nanofillers in Comparative Examples 1 and 2 were not subjected to reduced pressure distillation during the preparation process. The antioxidant inorganic nanofillers in Comparative Example 3 used an acylating agent to load the antioxidant onto the surface of the nanofiller. The obtained antioxidant inorganic nanofillers were added to synthetic ester oil to prepare a synthetic ester insulating oil whose antioxidant properties were significantly worse than those of the synthetic ester insulating oil prepared by the method of the present invention.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A preparation method of an antioxidant synthetic ester insulating oil, characterized in that, It includes the following steps: S1. Prepare antioxidant inorganic nano-fillers S11. Dissolve inorganic nano-fillers and silane coupling agents in a first organic solvent and mix evenly to obtain a first suspension. React it in a closed system at 35 - 65 °C for 6 - 13 h to obtain amino-modified inorganic nano-fillers; S12. Dissolve phosphodiester and the amino-modified inorganic nano-fillers obtained in step S1 in a second organic solvent. After mixing evenly, obtain a second suspension. Adjust the pH to 8.5 - 9.5, and react it in an inert atmosphere at 20 - 30 °C for 6 - 13 h. After the reaction is complete, dissolve the solid product in a third organic solvent and perform vacuum distillation. After drying, the antioxidant inorganic nano-fillers can be obtained; S2. Prepare antioxidant synthetic ester insulating oil Mix evenly the antioxidant inorganic nano-fillers prepared in step S1 and synthetic ester oil to obtain the antioxidant synthetic ester insulating oil.

2. The preparation method according to claim 1, wherein In the antioxidant inorganic nano-fillers, the weight ratio of raw materials is inorganic nano-fillers : silane coupling agent : phosphodiester = 1 : (0.5 - 3.7) : (0.5 - 4).

3. The preparation method according to claim 1, characterized in that, Meet at least one of the following conditions: (1) The silane coupling agent includes at least one of 3-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane; (2) The phosphodiester includes at least one of triphenyl phosphate, trioctyl phosphate, triisooctyl phosphate, diisopropyl terephthalate, diethyl terephthalate; (3) The inorganic nano-fillers include at least one of SiO2, TiO2, Fe3O4, BN, Al2O3; (4) The synthetic ester oil includes at least one of TMP triester, PETP tetraester; (5) In the antioxidant synthetic ester insulating oil, the weight ratio of antioxidant inorganic nano-fillers to synthetic ester oil is (0.01 - 0.15) :

100.

4. The preparation method according to claim 1, wherein The first organic solvent and the second organic solvent independently include at least one of methanol, ethanol, pyridine.

5. The preparation method according to claim 1, wherein, The solid content of the first suspension formed in step S11 is 1.5 - 30 wt.%; the solid content of the second suspension formed in step S12 is 5.4 - 30 wt.%.

6. The preparation method according to claim 1, characterized in that, The pH regulator used in step S12 includes ammonia water.

7. The preparation method according to claim 1, wherein, The boiling point of the third organic solvent under standard atmospheric pressure is 30 - 80 °C.

8. The preparation method according to claim 1, characterized in that, The pressure of the vacuum distillation is 0.0001 - 0.15 bar.

9. An antioxidant synthetic ester insulating oil, characterized in that, Prepared by the preparation method according to any one of claims 1 - 8.

10. Application of the antioxidant synthetic ester insulating oil according to claim 9 in a transformer.

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