Natural ester insulating oil antioxidant and application thereof

Abstract

The invention belongs to the technical field of application of natural ester insulating oil, particularly discloses a natural ester insulating oil antioxidant and application thereof, and particularly designs an N, N-di-sec-butyl p-phenylenediamine derivative as an antioxidant for remarkably improving the oxidation stability of the natural ester insulating oil. Correspondingly, the natural ester insulating oil with good oxidation stability is obtained, the natural ester insulating oil comprises basic natural ester insulating oil and a proper amount of antioxidant, and the antioxidant is N, N-di-sec-butyl p-phenylenediamine derivative. The preparation method comprises the following steps: adding the N, N-di-sec-butyl p-phenylenediamine derivative into the basic natural ester insulating oil, mixing and stirring for 0.5-2.0 hours, and oscillating in a shaking table for 0-1.0 hour. When the N, N-di-sec-butyl-p-phenylenediamine derivative provided by the invention is used as an antioxidant and applied to the natural ester insulating oil, the addition amount is small, the oxidation resistance is excellent, the oxidation induction time of the natural ester insulating oil is prolonged to 45 min from 22 min to the maximum extent, the amplification is increased by 55%-105%, the N, N-di-sec-butyl-p-phenylenediamine derivative is good in sensitivity to oil products and convenient to add, the insulating performance of the oil products is not affected, and the N, N-di-sec-butyl-p-phenylenediamine derivative is suitable for industrial production. The normal use of the natural ester insulating oil is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of application of natural ester insulating oil, and more specifically, relates to a natural ester insulating oil antioxidant and application thereof. Background Art

[0002] As an important liquid insulating medium, insulating oil plays a role in improving the electrical insulation strength and heat dissipation performance of oil-immersed insulated high-voltage power transmission and transformation equipment such as transformers, circuit breakers, current and voltage transformers, and bushings. Traditional mineral insulating oil is a commonly used insulating liquid, but due to its low ignition point (usually below 160°C) and low flash point, it poses a safety hazard. In particular, waste mineral insulating oil is a hazardous waste that is difficult to biodegrade and poses a risk of secondary pollution to the environment. Therefore, it is urgent to develop a substitute for mineral insulating oil. Natural ester insulating oil is mainly derived from oil crops such as soybeans and rapeseed. It has the advantages of high ignition point, natural degradation, and renewability. It has good environmental protection characteristics and fire resistance, filling the specific application scenarios of fire safety and environmental protection standards that mineral insulating oil cannot meet.

[0003] However, due to the complex sources of natural ester insulating oil and the presence of a large number of unsaturated carbon-carbon double bonds and carbon-carbon triple bonds in the oil, natural ester insulating oil undergoes a free radical chain reaction when in contact with oxygen during use, ultimately generating oxidation products such as aldehydes, ketones, and carboxylic acids, which increase the viscosity of the oil, reduce the volume resistivity, and increase the acid value, which in turn significantly reduces the oxidative stability of the oil and shortens the oil change cycle.

[0004] In order to solve this problem, antioxidants are usually added to natural ester insulating oil to improve the oxidation stability of the oil. For example, Chinese patent application 201910266768.6 uses benzoquinone or its derivatives as antioxidants. Adding them to oil substances can improve the oil's antioxidant and insulation properties, thereby delaying the degradation of the insulating and heat dissipation properties of the insulating oil and ensuring the normal use of the insulating oil. In the article "PDSC Evaluation and Selection of Antioxidants in Vegetable Insulating Oil" reported in "Renewable Energy" in 2021, pressurized differential scanning calorimetry (PDSC) and rotating oxygen bomb method (RBOT) were used to compare and evaluate the effects of four antioxidants, 4,4-methylenebis (2,6-di-tert-butylphenol), 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol and tert-butylhydroquinone, in soybean vegetable insulating oil and their appropriate addition amounts. The experimental results show that the results obtained by the two methods are consistent, and both methods show that 4,4-methylenebis(2,6-di-tert-butylphenol) has the best effect on improving the antioxidant properties of soybean vegetable insulating oil. Chinese patent application 201911054336.5 discloses a high-performance composite additive for natural ester insulating oil, which is composed of base oil, antioxidant, pour point depressant and metal passivator, which effectively improves the antioxidant and low-temperature properties of natural ester insulating oil and inhibits metal corrosion. Chinese patent application 201710890859.8 discloses a composite antioxidant for natural ester insulating oil, which contains at least one of tert-butylhydroquinone, di-tert-butyl-p-cresol and propyl gallate. Multiple antioxidants cooperate with each other to improve the antioxidant capacity of natural ester insulating oil. Chinese patent 201110420403.8 reports a vegetable insulating oil additive composition, which includes a certain amount of vegetable insulating oil, at least one antioxidant and at least one antioxidant metal passivator. The additive composition is added to a base oil and can be evenly dispersed in the base oil, thereby improving the oxidation stability of the oil product without affecting the electrical insulation performance of the insulating oil.

[0005] However, these antioxidants have limited effect on improving the oxidation stability of natural ester insulating oil, and some antioxidants will cause the insulating properties of the oil to deteriorate as the amount added increases, which is not conducive to practical application. Summary of the invention

[0006] In order to solve the deficiencies of the prior art, one of the purposes of the present invention is to provide a natural ester insulating oil antioxidant, wherein N, N-di-sec-butyl-p-phenylenediamine derivatives are used as antioxidants to improve the antioxidant properties of the natural ester insulating oil without reducing its electrical insulation properties, thereby effectively inhibiting oil aging; the second purpose is to provide a natural ester insulating oil with improved oxidation stability, comprising a base natural ester insulating oil and an antioxidant, wherein the antioxidant is a N, N-di-sec-butyl-p-phenylenediamine derivative. The method has the advantages of simple operation and convenient addition of the antioxidant.

[0007] One of the purposes of the present invention is achieved through the following technical solutions.

[0008] An antioxidant, wherein the antioxidant is one or more N,N-di-sec-butyl-p-phenylenediamine derivatives, and the general structural formula of the N,N-di-sec-butyl-p-phenylenediamine derivatives is as follows: ; Wherein, R is -OH, -SH, -NH2, -Cl or -F.

[0009] When R is -OH, it represents 1-((4-(sec-butylamino)phenyl)amino)propan-1-ol, and when R is -SH, it represents 1-((4-(sec-butylamino)phenyl)amino)propane-1-thiol.

[0010] Preferably, the N,N-di-sec-butyl-p-phenylenediamine derivative is one or more of 1-((4-(sec-butylamino)phenyl)amino)propan-1-ol and 1-((4-(sec-butylamino)phenyl)amino)propane-1-thiol.

[0011] A natural ester insulating oil comprises a base natural ester insulating oil and an antioxidant, wherein the antioxidant is one or more N,N-di-sec-butyl-p-phenylenediamine derivatives, and the general structural formula of the N,N-di-sec-butyl-p-phenylenediamine derivative is as follows: ; Wherein, R is -OH, -SH, -NH2, -Cl or -F.

[0012] Preferably, based on 100% by mass of the basic natural ester insulating oil, the added amount of the antioxidant is 0.1%-1.0%.

[0013] Preferably, based on 100% by mass of the basic natural ester insulating oil, the added amount of the antioxidant is 0.2%-1.0%.

[0014] Preferably, based on 100% by mass of the basic natural ester insulating oil, the added amount of the antioxidant is 0.4%-1.0%.

[0015] Preferably, the base natural ester insulating oil is soybean-based insulating oil.

[0016] The method for preparing the natural ester insulating oil described above comprises the following steps: The base natural ester insulating oil and the antioxidant are mixed and stirred for 0.5-2.0 h, and then placed in a shaker for 0-1.0 h to obtain the natural ester insulating oil.

[0017] Preferably, the stirring temperature is 40-60° C., and the stirring speed is 500-700 r / min.

[0018] Preferably, the shaking temperature of the shaker is 30-40° C., and the shaking frequency is 100-150 rpm.

[0019] Compared with the prior art, the present invention has the following advantages and effects: (1) The N,N-di-sec-butyl-p-phenylenediamine derivative provided by the present invention is used as an antioxidant in natural ester insulating oil. By controlling the addition amount within a relatively low concentration range of 0.1%-1.0%, a good antioxidant effect can be achieved with a small addition amount, thereby significantly improving the antioxidant properties of natural ester insulating oil.

[0020] (2) The N,N-di-sec-butyl-p-phenylenediamine derivative provided by the present invention is used as an antioxidant in natural ester insulating oil, which improves the oxidation stability of the oil without affecting other physical and chemical properties of the oil, such as insulation properties, thereby ensuring the normal use of the natural ester insulating oil and extending its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0022] FIG1 is a bar graph of the oxidation induction time of the natural ester insulating oils prepared in Examples 1-5 of the present invention and Comparative Examples 1-2.

[0023] Table 1 is a table of physical and chemical property parameters of the natural ester insulating oils prepared in Examples 1-5 and Comparative Examples 1-2 of the present invention, including a table of dielectric loss factor, relative dielectric constant, and volume resistivity data. DETAILED DESCRIPTION

[0024] 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.

[0025] The invention provides a natural ester insulating oil antioxidant, the main component of which is an N,N-di-sec-butyl-p-phenylenediamine derivative, and the added amount is 0.1%-1.0% of the mass fraction of the basic natural ester insulating oil.

[0026] Furthermore, the present invention also provides a preparation method of the natural ester insulating oil antioxidant as a soybean-based insulating oil antioxidant and related oxidation stability tests.

[0027] The base natural ester insulating oil used below is soybean-based insulating oil.

[0028] Example 1 In this embodiment, N,N-di-sec-butyl-p-phenylenediamine derivatives are used as antioxidants for natural ester insulating oil. The N,N-di-sec-butyl-p-phenylenediamine derivative is 1-((4-(sec-butylamino)phenyl)amino)propan-1-ol, and its addition amount is 0.2%. 1-((4-(sec-butylamino)phenyl)amino)propan-1-ol is added to a base natural ester insulating oil with a mass fraction of 99.8%, mixed and stirred for 0.5 h, the stirring temperature is 60 ° C, the stirring speed is 500 r / min, and then shaken in a shaker for 0.5 h, the shaking temperature is 30 ° C, and the shaking frequency is 100 rpm. The oxidation stability of the oil sample is evaluated using a rotating oxygen bomb instrument, and the volume resistivity, dielectric constant, and dielectric loss factor of the oil sample are measured.

[0029] Example 2 In this embodiment, N,N-di-sec-butyl-p-phenylenediamine derivatives are used as antioxidants for natural ester insulating oil. The N,N-di-sec-butyl-p-phenylenediamine derivative is 1-((4-(sec-butylamino)phenyl)amino)propane-1-thiol, and its addition amount is 0.3%. 1-((4-(sec-butylamino)phenyl)amino)propane-1-thiol is added to a base natural ester insulating oil with a mass fraction of 99.7%, mixed and stirred for 1.0 h, the stirring temperature is 50 ° C, the stirring speed is 600 r / min, and then shaken in a shaker for 1.0 h, the shaking temperature is 30 ° C, and the shaking frequency is 120 rpm. The oxidation stability of the oil sample is evaluated using a rotating oxygen bomb instrument, and the volume resistivity, dielectric constant, and dielectric loss factor of the oil sample are measured.

[0030] Example 3 In this embodiment, N,N-di-sec-butyl-p-phenylenediamine derivatives are used as antioxidants for natural ester insulating oil. The N,N-di-sec-butyl-p-phenylenediamine derivative is 1-((4-(sec-butylamino)phenyl)amino)propane-1-thiol, and its addition amount is 0.4%. 1-((4-(sec-butylamino)phenyl)amino)propane-1-thiol is added to a base natural ester insulating oil with a mass fraction of 99.6%, mixed and stirred for 0.5 h, the stirring temperature is 40 ° C, the stirring speed is 700 r / min, and then oscillated in a shaker for 1.0 h, the oscillation temperature is 40 ° C, and the oscillation frequency is 150 rpm. The oxidation stability of the oil sample is evaluated using a rotating oxygen bomb instrument, and the volume resistivity, dielectric constant, and dielectric loss factor of the oil sample are measured.

[0031] Example 4 In this embodiment, N,N-di-sec-butyl-p-phenylenediamine derivatives are used as antioxidants for natural ester insulating oil. The N,N-di-sec-butyl-p-phenylenediamine derivatives are 1-((4-(sec-butylamino)phenyl)amino)propane-1-ol and 1-((4-(sec-butylamino)phenyl)amino)propane-1-thiol, and the addition amounts are 0.5% and 0.5%, respectively. 1-((4-(sec-butylamino)phenyl)amino)propane-1-ol and 1-((4-(sec-butylamino)phenyl)amino)propane-1-thiol are added to a base natural ester insulating oil with a mass fraction of 99.0%, mixed and stirred for 1.0 h, the stirring temperature is 60 ° C, the stirring speed is 600 r / min, and then shaken in a shaker for 1.0 h, the shaking temperature is 40 ° C, and the shaking frequency is 140 rpm. The oxidation stability of the oil sample is evaluated by a rotating oxygen bomb instrument, and the volume resistivity, dielectric constant, and dielectric loss factor of the oil sample are measured.

[0032] Example 5 In this embodiment, N,N-di-sec-butyl-p-phenylenediamine derivatives are used as antioxidants for natural ester insulating oil. The N,N-di-sec-butyl-p-phenylenediamine derivatives are 1-((4-(sec-butylamino)phenyl)amino)propane-1-ol and 1-((4-(sec-butylamino)phenyl)amino)propane-1-thiol, and the addition amounts are 0.2% and 0.3%, respectively. 1-((4-(sec-butylamino)phenyl)amino)propane-1-ol and 1-((4-(sec-butylamino)phenyl)amino)propane-1-thiol are added to a base natural ester insulating oil with a mass fraction of 99.5%, mixed and stirred for 0.5 h, the stirring temperature is 50 ° C, the stirring speed is 700 r / min, and then shaken in a shaker for 0.5 h, the shaking temperature is 30 ° C, and the shaking frequency is 100 rpm. The oxidation stability of the oil sample is evaluated by a rotating oxygen bomb instrument, and the volume resistivity, dielectric constant, and dielectric loss factor of the oil sample are measured.

[0033] Comparative Example 1 In this comparative example, a certain amount of basic natural ester insulating oil was taken without adding any antioxidant, and the oxidation stability of the oil sample was evaluated using a rotating oxygen bomb instrument, and the volume resistivity, dielectric constant and dielectric loss factor of the oil sample were measured.

[0034] Comparative Example 2 In this comparative example, commercially available 2,6-di-tert-butyl-p-cresol was used as an antioxidant for natural ester insulating oil, with an addition amount of 0.3%, mixed and stirred for 0.5 h, stirring temperature of 40 °C, stirring speed of 500 r / min, and then oscillated in a shaker for 1.0 h, oscillation temperature of 40 °C, oscillation frequency of 150 rpm. The oxidation stability of the oil sample was evaluated by a rotating oxygen bomb instrument, and the volume resistivity, dielectric constant, and dielectric loss factor of the oil sample were measured.

[0035] (1) Oxidation induction time of natural ester oil: The oxidation stability of the natural ester insulating oil samples prepared in Examples 1-5 and Comparative Examples 1-2 of the present invention was measured using Shanghai Shenkai Company's SKY3021-Ⅱ automatic lubricating oil oxidation stability tester. The results are as follows: Figure 1 shown.

[0036] The test results show that when N,N-di-sec-butyl-p-phenylenediamine derivatives are added as antioxidants to natural ester insulating oil, the oxidation induction time of the oil can be significantly improved. At a low addition concentration, the oxidation induction time of the basic natural ester insulating oil is increased from 22 min to more than 34 min, and the maximum is increased to 45 min, which significantly extends the service life of the natural ester insulating oil.

[0037] (2) Insulation properties of natural ester insulating oil: The volume resistivity, dielectric loss factor and relative dielectric constant of the natural ester insulating oil samples prepared in Examples 1-5 and Comparative Examples 1-2 of the present invention were tested using an Austrian BAUR DTL C insulating oil dielectric loss tester. The results are shown in Table 1.

[0038] Table 1 Combination Figure 1 As shown in Table 1, compared with Comparative Examples 1-2, in Examples 1-5, using N,N-di-sec-butyl-p-phenylenediamine derivatives as antioxidants can improve the oxidation stability of natural ester insulating oils without significantly affecting the volume resistivity, dielectric constant and dielectric loss factor of the oils, and keep their insulation properties unchanged, indicating that N,N-di-sec-butyl-p-phenylenediamine derivatives have good antioxidant ability when used in natural ester insulating oils.

Claims

1. An antioxidant, characterized in that The antioxidant is one or more N,N-di-sec-butyl-p-phenylenediamine derivatives, and the general structural formula of the N,N-di-sec-butyl-p-phenylenediamine derivative is as follows: ； Wherein, R is -OH, -SH, -NH2, -Cl or -F.

2. The antioxidant according to claim 1, characterized in that The N,N-di-sec-butyl-p-phenylenediamine derivative is one or more of 1-((4-(sec-butylamino)phenyl)amino)propan-1-ol and 1-((4-(sec-butylamino)phenyl)amino)propane-1-thiol.

3. A natural ester insulating oil, characterized in that: The invention comprises a basic natural ester insulating oil and an antioxidant, wherein the antioxidant is the antioxidant according to claim 1 or 2.

4. The natural ester insulating oil according to claim 3, characterized in that: Based on the mass percentage of basic natural ester insulating oil as 100%, the added amount of antioxidant is 0.1%-1.0%.

5. The natural ester insulating oil according to claim 4, characterized in that: Based on the mass percentage of basic natural ester insulating oil as 100%, the added amount of antioxidant is 0.2%-1.0%.

6. The natural ester insulating oil according to claim 5, characterized in that: Based on the mass percentage of basic natural ester insulating oil as 100%, the added amount of antioxidant is 0.4%-1.0%.

7. A natural ester insulating oil according to any one of claims 3 to 6, characterized in that: The base natural ester insulating oil is soybean-based insulating oil.

8. A method for preparing a natural ester insulating oil according to claim 1 or 2, characterized in that: The following steps are involved: The base natural ester insulating oil and the antioxidant are mixed and stirred for 0.5-2.0 h, and then placed in a shaker for 0-1.0 h to obtain the natural ester insulating oil.

9. The natural ester insulating oil according to claim 8, characterized in that: The stirring temperature is 40-60°C, and the stirring speed is 500-700 r / min.

10. The natural ester insulating oil according to claim 9, characterized in that: The shaking temperature of the shaker is 30-40°C, and the shaking frequency is 100-150 rpm.

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