CN116103075A - Synthetic ester insulating oil and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of insulating oil, and particularly relates to synthetic ester insulating oil and a preparation method thereof. The synthetic ester insulating oil comprises the following components: synthesizing an ester insulating oil matrix and an antioxidant; the antioxidant is an antioxidant with a phenol structure. The synthetic ester insulating oil prepared by the invention has excellent oxidation stability and dispersion performance of the insulating oil, can effectively avoid the conditions of the prior art that the water content of the insulating oil is increased and the insulating oil is polluted by impurities due to long-time stirring for dissolving the antioxidant in the synthetic ester insulating oil, further influences the insulating performance of the oil, and can also avoid the conditions that the antioxidant is incompletely dissolved in the synthetic ester insulating oil or the antioxidant molecules are unevenly dispersed in the synthetic ester insulating oil, so that the antioxidant molecules uniformly and stably capture free radicals in the oil all over, and achieve better antioxidant effect.

Description

Synthetic ester insulating oil and preparation method thereof

Technical Field

The invention belongs to the technical field of insulating oil, and particularly relates to synthetic ester insulating oil and a preparation method thereof.

Background

Currently, mineral insulating oil and ester-based insulating oil are the main filled insulating materials in oil-immersed transformers. Under the age background of the national strong promotion of sustainable development and emphasis of low-carbon environment protection concept, the renewable and good-biodegradability ester-based insulating oil has wide application prospect. The ester-based insulating oil includes natural ester insulating oil and synthetic ester insulating oil. The natural ester insulating oil has unstable beta-H and unsaturated C=C double bonds in the structure, so that the oxidation stability is lower than that of mineral oil; although the synthetic ester insulating oil can eliminate the influence of unstable groups such as beta-H and C=C double bonds through the selection of synthetic materials, the condition that the oxidation stability is inferior to that of mineral oil can also appear in certain oxidation experiments, and the synthetic ester insulating oil has the defects of quick rise of dielectric loss factor after oxidation and the like.

Most antioxidants are currently in a solid state at normal temperature, so long stirring of the oil is required to completely dissolve the antioxidants therein. During the stirring process, the water content of the synthetic ester insulating oil is liable to rise by the influence of the air humidity, and there is a risk of contamination with impurities. In addition, the method of judging whether the antioxidant is completely dissolved by observing whether solid particles are still present in the insulating oil has a certain uncertainty, and cannot be characterized as to whether the antioxidant is uniformly dispersed in the liquid solvent. Therefore, the improvement of the oxidation stability of the synthetic ester insulating oil has important research significance.

Disclosure of Invention

The invention aims to provide synthetic ester insulating oil and a preparation method thereof. The synthetic ester insulating oil prepared by the invention has excellent oxidation stability and dispersion performance of the insulating oil, and can effectively prevent the pollution of the insulating oil impurities.

In order to achieve the above purpose, the present invention adopts the following technical scheme: a synthetic ester insulating oil comprising the following components: synthesizing an ester insulating oil matrix and an antioxidant;

the antioxidant is an antioxidant with a phenol structure.

Preferably, the antioxidant comprises at least one of 2, 2-bis (4-hydroxyphenyl) propane (BPA), 2-bis (4-hydroxyphenyl) butane (BPB), 2, 6-di-tert-butyl-p-cresol (T501).

More preferably, the antioxidant comprises 2, 2-bis (4-hydroxyphenyl) propane, 2-bis (4-hydroxyphenyl) butane, a combination of 2, 2-bis (4-hydroxyphenyl) propane and 2, 2-bis (4-hydroxyphenyl) butane and 2, 6-di-t-butyl-p-cresol, a combination of 2, 2-bis (4-hydroxyphenyl) propane and 2, 6-di-t-butyl-p-cresol, a combination of 2, 2-bis (4-hydroxyphenyl) butane and 2, 6-di-t-butyl-p-cresol.

Preferably, the content of 2, 2-bis (4-hydroxyphenyl) propane or 2, 2-bis (4-hydroxyphenyl) butane in the antioxidant is 30-100% of the total mass of the antioxidant.

Preferably, the synthetic ester insulating oil base is TMP triester or PETP tetraester.

Preferably, the addition amount of the antioxidant is 0.15-1.5% of the total mass of the synthetic ester insulating oil.

Preferably, the TMP triester is prepared from medium chain fatty acids and trimethylolpropane by esterification.

Preferably, the PETP tetraester is prepared from medium-chain fatty acid and pentaerythritol through esterification reaction.

The preparation method of the synthetic ester insulating oil comprises the following steps:

and uniformly mixing the antioxidant and the synthetic ester insulating oil to obtain the synthetic ester insulating oil.

The antioxidant component selected by the invention has stable super-dispersion characteristic in structural characteristics. First, the antioxidant molecules adopted in the invention have certain symmetry, and the structural symmetry ensures that the interaction force among the antioxidant molecules is relatively balanced, and the molecules can be in a uniformly distributed state. Second, the antioxidant molecules employed in the present invention have a plurality of alkyl groups which exhibit electron-repellent groups and which have a relatively strong steric hindrance. The mutual acting force of each antioxidant molecule is enhanced by the electron repellency and the strong steric hindrance, and the antioxidant molecules can be mutually dispersed while being uniformly distributed, so that the antioxidant can be in a uniformly dispersed state. Third, the antioxidant molecules employed in the present invention have two benzene ring structures. The larger molecular weight ensures that the insulating oil has good stability in insulating oil and is not easy to escape from the oil molecules due to the influence factors such as high temperature and the like. Fourth, the structure of the bisbenzene ring enables the antioxidant molecules to be tightly bound to the synthetic ester molecules through stronger van der waals forces, and exhibits more excellent solvency while exhibiting a uniformly dispersed state in the oil.

Meanwhile, the antioxidant component selected by the invention has the structural characteristics of stronger oxidation resistance. First, the antioxidant molecules employed in the present invention contain two phenolic hydroxyl groups. The active hydrogen on the phenolic hydroxyl can be combined with free radicals in the insulating oil after being separated, so that the progress of oxidation reaction between oxygen and the free radicals is blocked, and the purpose of improving the oxidation stability of the insulating oil of the synthetic ester is achieved. Two phenolic hydroxyl groups in the molecule improve the antioxidation efficiency. Second, the antioxidant molecule employed in the present invention introduces an alkyl group at the para-position of the phenolic hydroxyl group, and the para-alkyl group has a branch. The antioxidant efficiency of the antioxidant increases with the increase of alkyl groups in the ortho-position and para-position of the phenolic hydroxyl group, and when the branching on the substituent increases, the antioxidant efficiency also increases.

Compared with the prior art, the invention has the following beneficial effects:

(1) According to the invention, through the compound use of various antioxidant components and the interaction between the antioxidant components and the synthetic ester insulating oil matrix, the dispersion performance and the oxidation resistance of the antioxidant in the synthetic ester insulating oil are effectively improved, and the effects of effectively preventing the pollution of the insulating oil impurities and effectively improving the oxidation stability of the insulating oil are achieved.

(2) The antioxidant prepared by the invention can effectively avoid the conditions of the prior art that the water content of the insulating oil is increased and the insulating oil is polluted by impurities, which are caused by long-time stirring for dissolving the antioxidant in the synthetic ester insulating oil, thereby affecting the insulating property of the oil.

(3) The antioxidant prepared by the invention avoids the condition that the antioxidant is not completely dissolved in the synthetic ester insulating oil or the antioxidant molecules are unevenly dispersed in the synthetic ester insulating oil in the prior art, so that the antioxidant molecules uniformly and stably capture free radicals in all parts of the oil, and a better antioxidant effect is achieved.

Detailed Description

The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the examples and comparative examples, the experimental methods used were conventional methods, and the materials, reagents and the like used were commercially available, unless otherwise specified.

Example 1

The components are as follows: synthetic ester insulating oil base: TMP triester; an antioxidant: 2, 2-bis (4-hydroxyphenyl) propane (BPA).

Wherein the content of the antioxidant is 0.5 percent of the total mass of the synthetic ester insulating oil.

Example 2

The components are as follows: synthetic ester insulating oil base: TMP triester; an antioxidant: 2, 2-bis (4-hydroxyphenyl) butane (BPB).

Wherein the content of the antioxidant is 0.5 percent of the total mass of the synthetic ester insulating oil.

Example 3

The components are as follows: synthetic ester insulating oil base: TMP triester; an antioxidant: 2, 2-bis (4-hydroxyphenyl) propane (BPA) and 2, 6-di-tert-butyl-p-cresol (T501).

Wherein the content of the antioxidant is 0.5% of the total mass of the synthetic ester insulating oil, and the mass ratio of BPA to T501 is 1:1.

Example 4

The components are as follows: synthetic ester insulating oil base: TMP triester; an antioxidant: 2, 2-bis (4-hydroxyphenyl) butane (BPB) and 2, 6-di-tert-butyl-p-cresol (T501).

Wherein the content of the antioxidant is 0.5% of the total mass of the synthetic ester insulating oil, and the mass ratio of BPB to T501 is 1:1.

Example 5

The components are as follows: synthetic ester insulating oil base: TMP triester; an antioxidant: BPA, BPB and T501.

Wherein, the content of the antioxidant is 0.5% of the total mass of the synthetic ester insulating oil, and the mass ratio of BPA, BPB and T501 is 1:1:1.

example 6

This example differs from example 1 only in that the antioxidant content added is 0.15% of the total mass of the synthetic ester insulating oil.

Example 7

This example differs from example 1 only in that the antioxidant content added is 1.5% of the total mass of the synthetic ester insulating oil.

Example 8

The only difference between this example and example 1 is that the synthetic ester insulating oil base material selected was PETP tetraester.

Example 9

The only difference between this example and example 2 is that the synthetic ester insulating oil base material selected was PETP tetraester.

Example 10

The only difference between this example and example 3 is that the synthetic ester insulating oil base material selected was PETP tetraester.

Example 11

The only difference between this example and example 4 is that the synthetic ester insulating oil base material selected was PETP tetraester.

Example 12

The only difference between this example and example 5 is that the synthetic ester insulating oil base material selected was PETP tetraester.

Comparative example 1

The only difference between this comparative example and example 1 is that the antioxidant component selected is T501.

Comparative example 2

The only difference between this comparative example and example 1 is that the antioxidant component selected was 2, 2-bis (4-hydroxy-3-tolyl) (BPC).

Comparative example 3

The comparative example differs from example 1 only in that the antioxidant content added was 2.0% of the total mass of the synthetic ester insulating oil.

Comparative example 4

The only difference between this comparative example and example 8 is that the antioxidant component selected was T501.

Comparative example 5

The only difference in this comparative example compared to example 8 is that the antioxidant component selected was 2, 2-bis (4-hydroxy-3-tolyl) (BPC).

Comparative example 6

The comparative example differs from example 8 only in that the antioxidant content added was 2.0% of the total mass of the synthetic ester insulating oil.

Comparative example 7

The only difference between this comparative example and example 1 is that the synthetic ester insulating oil base material selected was palm oil fatty acid ester (PFAE).

Comparative example 8

The only difference between this comparative example and example 2 is that the synthetic ester insulating oil base material selected was palm oil fatty acid ester (PFAE).

Comparative example 9

The only difference between this comparative example and example 3 is that the synthetic ester insulating oil base material selected was palm oil fatty acid ester (PFAE).

Comparative example 10

The only difference between this comparative example and example 4 is that the synthetic ester insulating oil base material selected was palm oil fatty acid ester (PFAE).

Comparative example 11

The only difference between this comparative example and example 5 is that the synthetic ester insulating oil base material selected was palm oil fatty acid ester (PFAE).

Test example one, dispersion Performance test

The testing method comprises the following steps: measuring 100mL of the synthetic ester insulating oil matrixes of each group of examples 1-12 and comparative examples 1-7, placing the synthetic ester insulating oil matrixes into a 250mL conical flask, placing the conical flask into a constant-temperature water bath until the temperature is stabilized at 25 ℃, keeping the temperature for 15min, weighing the corresponding antioxidant components of each group, placing the antioxidant components into the synthetic ester insulating oil matrixes, shaking the synthetic ester insulating oil matrixes forcefully for 30s every 5min, and observing the dissolution condition of the antioxidants, wherein the antioxidant components are considered to be completely dissolved when solute particles are not visible by eyes. The dissolution rate of the antioxidant was compared with the degree of dispersion by the time required for complete dissolution.

The experimental results are shown in table 1.

Table 1 results of the Dispersion Properties of the antioxidant groups

From the data in Table 1, it can be seen that the antioxidant prepared in the examples of the present invention has a better dispersibility in TMP triester/PETP tetraester synthetic ester insulating oil matrix.

Comparative example 1/comparative example 4 in which only a single T501 component was added as an antioxidant, the dispersibility in the TMP triester/PETP tetraester synthetic ester insulating oil base material was inferior to that of the example; comparative example 2/comparative example 5 BPC having a similar structure to BPA was selected as the antioxidant component, which had a lower dispersibility in TMP triester/PETP tetraester than in example; the antioxidant content added in comparative example 3/comparative example 6 was too high, resulting in a decrease in dispersibility in the insulating oil base; in comparative example 7, PFAE was used to replace TMP triester/PETP tetraester synthetic ester insulating oil matrix, and the final antioxidant had poor dispersibility.

Test example two, oxidation stability test

The testing method comprises the following steps: and (3) adding corresponding antioxidant components (or no antioxidant) into each group of synthetic ester insulating oil matrixes respectively, considering that the antioxidant is completely dissolved after no suspended solid particles are observed in an oil sample, and measuring the acid value, breakdown voltage and dielectric loss of the prepared synthetic ester insulating oil.

And placing the prepared synthetic ester insulating oil in a blast drying oven to perform a thermal oxidation aging test, wherein the test temperature is set to 80 ℃, and the test duration is set to 14 days. And after the thermal oxidation aging experiment is finished, the acid value, breakdown voltage and dielectric loss of the oil sample are measured, and the improvement effect of the antioxidant on the oxidation stability of the synthetic ester insulating oil matrix is reflected by comparing the change degree of the performance of the oil sample before and after thermal oxidation aging.

The experimental results are shown in tables 2 to 3.

TABLE 2 acid value, breakdown voltage and dielectric loss of oil samples

TABLE 3 acid value, breakdown voltage and dielectric loss change of oil samples before and after thermal oxidative aging test

From the experimental data in tables 2 and 3, it can be known that the acid value, breakdown voltage and dielectric loss variation of the prepared synthetic ester insulating oil after thermal oxidation aging test are obviously smaller than those of the oil sample without the additive by adding the antioxidant with specific components into the TMP triester/PETP tetraester synthetic ester insulating oil, which shows that the antioxidant prepared by the invention has the effect of improving the oxidation stability of the synthetic ester insulating oil at the working condition temperature. Meanwhile, after BPA, BPB and T501 are compounded, the antioxidation effect is better than that of a single antioxidant component, the synergistic effect among antioxidants is reflected, and the antioxidant provided by the invention has better antioxidation performance than that of the traditional insulating oil antioxidant T501 and higher antioxidation efficiency in the aspect of improving the oxidation stability of insulating oil.

From the experimental results of comparative examples 1 to 2/comparative examples 4 to 5, it is known that when BPC or T501 is selected for substitution, the acid value, breakdown voltage and dielectric loss variation after thermal oxidative aging test are all higher than those of the examples; the content of the antioxidant added in comparative example 3/comparative example 6 is too much, and the dielectric loss factor of the prepared synthetic ester insulating oil is increased and the breakdown voltage is reduced, resulting in deterioration of the initial dielectric characteristics of the oil, affecting the performance of the insulating oil.

From the experimental results of comparative examples 7 to 11, it is understood that the antioxidant of the present invention has less remarkable effect of improving the antioxidant properties of PFAE than the effect of TMP triester and PETP tetraester.

The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.

Claims (9)

1. The synthetic ester insulating oil is characterized by comprising the following components: synthesizing an ester insulating oil matrix and an antioxidant;

the antioxidant is an antioxidant with a phenol structure.

2. The synthetic ester insulating oil of claim 1, wherein the antioxidant comprises at least one of 2, 2-bis (4-hydroxyphenyl) propane, 2-bis (4-hydroxyphenyl) butane, 2, 6-di-t-butyl-p-cresol.

3. The synthetic ester insulating oil of claim 2, wherein the antioxidant comprises 2, 2-bis (4-hydroxyphenyl) propane, 2-bis (4-hydroxyphenyl) butane, a combination of 2, 2-bis (4-hydroxyphenyl) propane and 2, 2-bis (4-hydroxyphenyl) butane and 2, 6-di-t-butyl-p-cresol, a combination of 2, 2-bis (4-hydroxyphenyl) propane and 2, 6-di-t-butyl-p-cresol, and a combination of 2, 2-bis (4-hydroxyphenyl) butane and 2, 6-di-t-butyl-p-cresol.

4. A synthetic ester insulating oil according to claim 3, wherein the content of 2, 2-bis (4-hydroxyphenyl) propane or 2, 2-bis (4-hydroxyphenyl) butane in the antioxidant is 30 to 100% of the total mass of the antioxidant.

5. The synthetic ester insulating oil of claim 1, wherein the synthetic ester insulating oil base is TMP triester or PETP tetraester.

6. The synthetic ester insulating oil according to claim 1, wherein the antioxidant is added in an amount of 0.15 to 1.5% of the total mass of the synthetic ester insulating oil.

7. The synthetic ester insulating oil according to claim 5, wherein the TMP triester is prepared by esterification of a medium chain fatty acid with trimethylolpropane.

8. The synthetic ester insulating oil of claim 5, wherein the PETP tetraester is prepared from medium chain fatty acids and pentaerythritol by esterification.

9. A method for preparing the synthetic ester insulating oil according to any one of claims 1 to 8, comprising the steps of:

and uniformly mixing the antioxidant and the synthetic ester insulating oil to obtain the synthetic ester insulating oil.