A modified natural ester insulating oil and its preparation method and application

Abstract

The present invention relates to the field of insulating oils and discloses a method for preparing a modified natural ester insulating oil. The method comprises: (1) subjecting an epoxidized vegetable oleate ester to a first contact reaction with an acid anhydride in the presence of an acid catalyst I to obtain a material I; (2) subjecting a diol to a second contact reaction with the material I in the presence of a catalyst II to obtain a material II; and (3) subjecting the material II to a third contact reaction with an antioxidant, a passivating agent, and a pour point depressant to obtain the modified natural ester insulating oil. The modified natural ester insulating oil provided by the present invention can simultaneously achieve a high flash point, a low pour point, a high breakdown voltage, and a low viscosity, and can be widely used in locations requiring high fire resistance.

Description

Technical Field

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

[0002] Transformers are widely used in densely populated areas, making their fire resistance crucial. Insulating oil, the most widely used liquid insulating medium, eliminates air gaps in equipment through impregnation and filling, preventing breakdown. It also improves heat dissipation through convection.

[0003] Traditional mineral oil insulating oil has low viscosity and good electrical insulation and cooling properties, but it is derived from non-renewable petrochemical resources and has poor biodegradability. At the same time, its flash point is about 150°C, which cannot meet the design requirements of high-voltage electrical equipment with high fire resistance. Natural ester insulating oil has a flash point of up to 300°C, has good fire resistance and safety performance, excellent electrical insulation performance, a wide range of sources, good biodegradability, and little impact on the environment and human body. It is suitable for occasions with high environmental protection requirements, but has disadvantages such as high viscosity and poor antioxidant properties.

[0004] Existing research on chemically modified natural esters includes transesterification, isomerization, hydrogenation and other methods of vegetable oils, and the preparation of natural ester insulating oil for power use by adding additives.

[0005] CN101538500A discloses a method for preparing insulating oil using vegetable oil as raw material. The method involves alkali neutralization, vacuum distillation, hydrogenation, deep refining, and the addition of additives to the vegetable oil to produce natural ester insulating oil for power applications. Hydrogenation of double bonds in vegetable oil molecules improves the insulating oil's antioxidant properties, but the saturation of the insulating oil increases its pour point, limiting its application in low-temperature regions.

[0006] CN102682869A discloses a method for preparing vegetable insulating oil. This method involves subjecting the vegetable oil to transesterification, vacuum distillation, decolorization, acid reduction, filtration, and deep dehydration, followed by the addition of additives to produce natural ester insulating oil for power applications. The transesterification process employed in this method is a modification process that reduces kinematic viscosity but also lowers the flash point, failing to meet the technical requirements of the natural ester insulating oil industry standard DL / T1811.

[0007] CN111892981A discloses a method for producing isomeric esters by oxidizing vegetable oil with peroxyacid and reacting it with an organic acid in a ring-opening reaction. After impurities are removed, an antioxidant and a pour point depressant are added to produce a vegetable oil-based synthetic ester insulating oil. This method uses vegetable oil directly as the raw material for the isomerization reaction. The resulting sample has a flash point exceeding 200°C, failing to meet the standard for high-ignition-point, fire-resistant transformer oil. Furthermore, the viscosity of the oil sample was not examined, which cannot guarantee the oil's adequate heat dissipation capacity. Summary of the Invention

[0008] The purpose of the present invention is to solve the problem that the insulating oil in the prior art cannot have high flash point, low pour point, high breakdown voltage and low viscosity at the same time, which leads to limited application.

[0009] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a modified natural ester insulating oil, the method comprising:

[0010] (1) in the presence of an acid catalyst I, conducting a first contact reaction between an epoxidized vegetable oleate and an acid anhydride to obtain a material I;

[0011] (2) in the presence of catalyst II, subjecting the diol and the material I to a second contact reaction to obtain material II;

[0012] (3) subjecting the antioxidant, the passivating agent, and the pour point depressant to a third contact reaction with the material II to obtain the modified natural ester insulating oil;

[0013] Wherein, the molar ratio of the epoxidized vegetable oleate, the acid anhydride and the diol is 1:1-6:0.3-0.8;

[0014] The acid anhydride is selected from at least one of isobutyric anhydride, isovaleric anhydride, hexanoic anhydride and benzoic anhydride;

[0015] The diol is selected from at least one of ethylene glycol, 1,3-propylene glycol and isoprene glycol.

[0016] The second aspect of the present invention provides a modified natural ester insulating oil prepared by the method described in the first aspect.

[0017] The third aspect of the present invention provides use of the modified natural ester insulating oil described in the second aspect in electrical equipment.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects:

[0019] (1) The modified natural ester insulating oil provided by the present invention simultaneously takes into account the flash point, pour point, breakdown voltage and viscosity properties; in particular, while having a low pour point and low viscosity, the flash point is as high as 288°C and the breakdown voltage is as high as 64.7kV;

[0020] (2) The modified natural ester insulating oil provided by the present invention does not contain toxic substances, has little impact on the environment and human body, has good biodegradability, and is an environmentally friendly insulating liquid;

[0021] (3) The modified natural ester insulating oil provided by the present invention has good fire resistance and safety performance, excellent electrical insulation performance, can be used in places with high fire resistance requirements, and the risk of fire and explosion is much lower than that of traditional transformer oil, and has broad application prospects. DETAILED DESCRIPTION

[0022] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0023] As mentioned above, the first aspect of the present invention provides a method for preparing a modified natural ester insulating oil, the method comprising:

[0024] (1) in the presence of an acid catalyst I, conducting a first contact reaction between an epoxy vegetable oil ester and an acid anhydride to obtain a material I;

[0025] (2) in the presence of catalyst II, subjecting the diol and the material I to a second contact reaction to obtain material II;

[0026] (3) subjecting the antioxidant, the passivating agent, and the pour point depressant to a third contact reaction with the material II to obtain the modified natural ester insulating oil;

[0027] Wherein, the molar ratio of the epoxidized vegetable oleate, the acid anhydride and the diol is 1:1-6:0.3-0.8;

[0028] The acid anhydride is selected from isobutyric anhydride, isovaleric anhydride, hexanoic anhydride, and benzoic anhydride;

[0029] The diol is selected from at least one of ethylene glycol, 1,3-propylene glycol and isoprene glycol.

[0030] Preferably, the acid anhydride is benzoic anhydride; and the diol is isopentyl glycol. The inventors have found that under this preferred embodiment, the modified natural ester insulating oil provided by the present invention has a higher flash point and breakdown voltage.

[0031] Preferably, the molar ratio of the epoxidized vegetable oleate, the acid anhydride, and the diol is 1:1.5-6:0.5-0.6. The inventors have found that under this preferred embodiment, the modified natural ester insulating oil provided by the present invention has a higher flash point and breakdown voltage.

[0032] Preferably, in step (1), the epoxidized vegetable oil ester is selected from at least one of epoxy soybean oil methyl ester, epoxy soybean oil ethyl ester, epoxy rapeseed oil methyl ester, epoxy rapeseed oil ethyl ester, epoxy tea seed oil methyl ester, and epoxy tea seed oil ethyl ester.

[0033] The present invention does not particularly limit the specific method for preparing epoxidized vegetable oleic acid esters. Those skilled in the art can obtain the epoxidized soybean oil methyl ester, epoxidized soybean oil ethyl ester, epoxidized rapeseed oil methyl ester, epoxidized rapeseed oil ethyl ester, epoxidized tea seed oil methyl ester, and epoxidized tea seed oil ethyl ester described in the present invention based on the specific names provided in the present invention and in combination with known process routes in the field of organic synthesis; and, the preparation methods of epoxidized soybean oil methyl ester and epoxidized soybean oil ethyl ester are exemplified in the following text of the present invention. Those skilled in the art can also obtain the specific preparation methods of all other epoxidized vegetable oleic acid esters by replacing the types of raw materials according to the preparation methods described in the following text of the present invention. The present invention will no longer describe in detail the preparation methods of all epoxidized vegetable oleic acid esters, and those skilled in the art should not understand this as a limitation of the present invention.

[0034] Preferably, the acid catalyst I is selected from at least one of concentrated sulfuric acid, phosphotungstic acid, and phosphomolybdic acid.

[0035] More preferably, the amount of the acid catalyst I used is 0.3-0.6 mol% relative to each mole of epoxidized vegetable oleic acid ester.

[0036] Preferably, in step (1), the first contact reaction is carried out under stirring conditions, and the conditions for the first contact reaction include: a stirring speed of 200-400 rpm, a temperature of 70-110° C., and a time of 6-12 h.

[0037] Preferably, in step (2), the catalyst II is selected from at least one of sodium methoxide and calcium methoxide.

[0038] More preferably, the amount of the catalyst II used is 0.3-0.6 mol% relative to each mole of epoxidized vegetable oleic acid ester.

[0039] Preferably, in step (2), the conditions for the second contact reaction include: stirring speed of 200-400 rpm, temperature of 120-180° C., time of 1-5 h, and pressure of 50-80 Pa.

[0040] It should be noted that the temperature of the second contact reaction is the temperature of the constant temperature stage, the pressure is the pressure of the constant pressure stage, and the time is the holding time of the constant temperature stage and the constant pressure stage.

[0041] Preferably, the method further comprises: before carrying out step (3), purifying material II; the purification step comprises: mixing a decolorizing agent, an alkaline adsorbent, a desiccant and the material II and filtering the mixture.

[0042] More preferably, in the purification step, based on the total amount of material II, the amount of the decolorant is 2-4 wt%, the amount of the alkaline adsorbent is 2-4 wt%, and the amount of the desiccant is 1-3 wt%.

[0043] Further preferably, the decolorizing agent is activated clay, the alkaline adsorbent is alkaline alumina, and the desiccant is anhydrous magnesium sulfate.

[0044] Preferably, the mixing reaction conditions at least meet the following requirements: temperature of 60-90° C. and time of 1-3 h.

[0045] More preferably, the purification step further comprises:

[0046] (1) The decolorizing agent and material II are first mixed and then filtered to obtain an intermediate; the temperature of the first mixing is 60-90°C, the time is 0.5-1.5 hours, and the stirring speed is 200-400 rpm;

[0047] (2) The alkaline adsorbent, the desiccant and the intermediate are mixed for a second time and then filtered; the temperature of the second mixing is 60-90° C., the time is 0.5-1.5 h, and the stirring speed is 200-400 rpm.

[0048] It should be noted that the present invention has no special requirements for the specific operation method of the filtration, and it can be carried out by methods known to those skilled in the art. The inventors will not elaborate on them one by one here, and those skilled in the art should not understand this as a limitation of the present invention.

[0049] Preferably, in step (3), the third contact reaction is carried out under stirring conditions, and the conditions of the third contact reaction include: a stirring speed of 200-400 rpm, a temperature of 30-60° C., and a time of 0.5-3 h.

[0050] Preferably, in step (3), based on the total amount of material II, the amount of the antioxidant is 0.3-0.6 wt %, the amount of the passivator is 0.003-0.006 wt %, and the amount of the pour point depressant is 0.05-0.2 wt %.

[0051] Preferably, the antioxidant is selected from at least one of tert-butylhydroquinone, tocopherol, octyldiphenylamine, and 2,6-di-tert-butyl mixed phenol. More preferably, the antioxidant is a combination of tert-butylhydroquinone and tocopherol.

[0052] Preferably, the pour point depressant is selected from polymethacrylate T602A, poly-α-olefin pour point depressant T803B, and polyethylene fumaric acid copolymer PPD-816A. More preferably, the pour point depressant is polymethacrylate T602A.

[0053] Preferably, the passivating agent is selected from at least one of a thiadiazole derivative (T561) and N,N′-disalicylidene-1,2-propylenediamine.

[0054] As mentioned above, the second aspect of the present invention provides a modified natural ester insulating oil prepared by the method described in the first aspect.

[0055] As mentioned above, the third aspect of the present invention provides the use of the modified natural ester insulating oil described in the second aspect in electrical equipment.

[0056] The present invention will be described in detail below through examples.

[0057] In the following examples, unless otherwise specified, all raw materials involved were commercially available and all reagents were of analytical grade.

[0058] raw material

[0059] Antioxidants: tert-butylhydroquinone, purchased from Aladdin Chemical Reagent Co., Ltd.; tocopherol, brand BASF, purchased from Guangzhou Yulu Chemical Co., Ltd.

[0060] Pour point depressant: polymethacrylate, brand T602A, purchased from Jinzhou Shengda Chemical Co., Ltd.

[0061] Metal passivator: thiadiazole derivative, brand T561, purchased from Jinzhou Shengda Chemical Co., Ltd.

[0062] In the following examples, the performance testing methods involved are as follows:

[0063] 1. Flash point: The test standard is GB / T 261 Determination of flash point, Pensky-Martin closed cup method (GB / T261-2008, ISO2719:2002);

[0064] 2. Pour point: The test standard is GB / T 3535 Determination of pour point of petroleum products (GB / T3535-2006, ISO3016:1994);

[0065] 3. Breakdown voltage: The test standard is GB / T 507 Insulating oil breakdown voltage determination method (GB / T507-2002, eqvIEC60156:1995);

[0066] 4. Kinematic viscosity: The test standard is GB / T 265 petroleum product kinematic viscosity determination method and dynamic viscosity calculation method;

[0067] In the following examples, unless otherwise specified, the mass fraction of concentrated sulfuric acid is 98 wt %;

[0068] In the following examples, unless otherwise specified, the kinematic viscosity refers to the kinematic viscosity at 40°C.

[0069] Preparation Example 1

[0070] Methanol and sodium hydroxide were stirred at 60° C. (stirring speed was 300 rpm) until dissolved, and then epoxy soybean oil was added and stirred for 3 hours to obtain a stratified product. The stratified product was subjected to liquid separation, and after removing the lower layer of liquid, the lower layer was washed with hot water at 80° C. until the lower layer was neutral. The upper layer of liquid was dried to obtain epoxy soybean methyl ester.

[0071] The mass ratio of the epoxidized soybean oil, the methanol and the sodium hydroxide is 5:1:0.01.

[0072] Preparation Example 2

[0073] Stirring ethanol and sodium hydroxide at 60° C. (stirring speed: 300 rpm) until dissolved, then adding epoxidized soybean oil, and continuing stirring for 3 hours to obtain a layered product, separating the layered product, removing the lower layer liquid, and washing with 80° C. hot water until the lower layer liquid is neutral, and drying the upper layer liquid to obtain epoxy soybean ethyl ester;

[0074] The mass ratio of the epoxidized soybean oil, the ethanol and the sodium hydroxide is 5:1.4:0.01.

[0075] Example 1

[0076] This example is used to illustrate that the modified natural ester insulating oil of the present invention is prepared according to the formulation and process parameters in Table 1 and the method described below.

[0077] The method for preparing modified natural ester insulating oil comprises the following steps:

[0078] (1) conducting a first contact reaction of 0.005 mol of concentrated sulfuric acid, epoxidized vegetable oil ester, and acid anhydride to obtain material I;

[0079] (2) subjecting 0.005 mol of sodium methoxide, diol, and the material I to a second contact reaction to obtain material II;

[0080] (3) 1000 g of material II is mixed with activated clay for the first time and then filtered to obtain an intermediate; basic alumina and anhydrous magnesium sulfate are mixed with the intermediate for the second time and then filtered; the filtered product is subjected to a third contact reaction with tert-butylhydroquinone, tocopherol, polymethyl methacrylate, and a thiadiazole derivative to obtain the modified natural ester insulating oil.

[0081] Unless otherwise specified, the remaining examples were carried out using a process similar to that of Example 1, except that the formulations and process parameters used in each example were different. For details, see Table 1 (Note: the parameters not listed in Table 1 are the same as the corresponding parameters in Example 1).

[0082] Table 1

[0083]

[0084]

[0085] Examples 4-8 were carried out in a manner similar to that of Example 1, except that benzoic anhydride and isoprene glycol in Example 1 were replaced with equimolar amounts of different types of acid anhydrides and diols. All other procedures were the same as those of Example 1, to prepare modified natural ester insulating oils S4-S8. See Table 2 for details.

[0086] Table 2

[0087] Example 4 Example 5 Example 6 Example 7 Example 8 Acid anhydride type Isobutyric anhydride Isovaleric anhydride Hexanoic anhydride Isobutyric anhydride Isobutyric anhydride diols type Ethylene glycol Ethylene glycol Ethylene glycol 1,3-Propanediol Isopentyldiol name S4 S5 S6 S7 S8

[0088] Example 9

[0089] This example is carried out in a similar manner to that of Example 1, except that the molar ratio of the epoxy vegetable oleate, the anhydride and the diol is 1:1:0.8, wherein the amount of the epoxy vegetable oleate is 1 mol.

[0090] The rest are the same as in Example 1.

[0091] Modified natural ester insulating oil S9 was prepared.

[0092] Comparative Examples 1-4 were carried out in a manner similar to that of Example 1, except that benzoic anhydride and isoprene glycol in Example 1 were replaced with equimolar amounts of different types of acid anhydrides and diols. The remaining procedures were the same as in Example 1 to prepare modified natural ester insulating oils DS1-DS4. See Table 3 for details.

[0093] Table 3

[0094]

[0095]

[0096] Comparative Example 5

[0097] This comparative example was carried out in a similar manner to Example 1, except that an equal molar amount of phthalic anhydride was used instead of benzoic anhydride.

[0098] In this comparative example, the product after step (1) is in a colloid state and cannot be subjected to the next reaction or performance test;

[0099] This comparative example is named DS5.

[0100] Comparative Example 6

[0101] This comparative example was carried out in a similar manner to Example 1, except that an equal molar amount of maleic anhydride was used instead of benzoic anhydride.

[0102] In this comparative example, the product after step (1) is in a colloid state and cannot be subjected to the next reaction or performance test;

[0103] This comparative example is named DS6.

[0104] Comparative Example 7

[0105] This comparative example was carried out in a similar manner to Example 1, except that the molar ratio of the epoxy vegetable oleate, the acid anhydride, and the diol was 1:8:1, wherein the amount of the epoxy vegetable oleate was 1 mol;

[0106] The rest are the same as in Example 1.

[0107] Modified natural ester insulating oil DS7 was prepared.

[0108] Comparative Example 8

[0109] This comparative example uses commercial FR3 natural ester insulating oil (purchased from Cargill China) for comparison, and is named DS8.

[0110] Comparative Example 9

[0111] This comparative example was carried out in a similar manner to Example 1, except that the epoxy soybean methyl ester in this comparative example did not react with the acid anhydride and the diol. Specifically, the method included:

[0112] (1) 1000 g of epoxy soybean methyl ester and activated clay are first mixed and filtered to obtain an intermediate; basic alumina and anhydrous magnesium sulfate are then mixed with the intermediate and filtered; the filtered product is subjected to a third contact reaction with tert-butylhydroquinone, tocopherol, polymethacrylate, and a thiadiazole derivative to obtain insulating oil DS9.

[0113] Test Case

[0114] The aforementioned test methods were used to perform performance tests on the modified natural ester insulating oils obtained in the Examples and Comparative Examples. The specific results are shown in Table 4.

[0115] Table 4

[0116] Flash point (℃) Pour point (℃) Breakdown voltage (kV) <![CDATA[Kinematic viscosity (mm 2 / S)]]> Example 1 288 -25 64.7 28.9 Example 2 283 -26 63.3 28.5 Example 3 281 -26 63.3 26.5 Example 4 264 -28 63.4 28.3 Example 5 266 -28 63.1 27.9 Example 6 268 -25 64.6 24.5 Example 7 265 -28 63.4 29.3 Example 8 273 -27 61.5 31.1 Example 9 274 -26 54.2 33.8 Comparative Example 1 251 -20 61.4 21.3 Comparative Example 2 258 -22 64.2 25.4 Comparative Example 3 254 -20 61.4 24.3 Comparative Example 4 192 -15 53.6 15.6 Comparative Example 5 / / / / Comparative Example 6 / / / / Comparative Example 7 280 -18 25.4 30.7 Comparative Example 8 280 -21 54.4 34.96 Comparative Example 9 194 -11 58.7 7.6

[0117] In Table 4, “ / ” indicates that the test cannot be performed.

[0118] From the results in Table 4, it can be seen that the modified natural ester insulating oil obtained by the present invention can simultaneously take into account high flash point, low pour point, high breakdown voltage and low viscosity, and can be widely used in places with high fire resistance requirements.

[0119] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing modified natural ester insulating oil, characterized in that: The method includes: (1) In the presence of an acid catalyst I, the epoxy vegetable oil ester and the acid anhydride are subjected to a first contact reaction to obtain a material I; (2) In the presence of catalyst II, the diol and the material I are subjected to a second contact reaction to obtain material II; the conditions of the second contact reaction include: a stirring speed of 200-400 rpm, a temperature of 120-180°C, a time of 1-5 hours, and a pressure of 50-80 Pa; (3) subjecting the antioxidant, the passivating agent, and the pour point depressant to a third contact reaction with the material II to obtain the modified natural ester insulating oil; Wherein, the molar ratio of the epoxy vegetable oleate, the acid anhydride and the diol is 1:1.5-6:0.5-0.6; The acid anhydride is benzoic anhydride; The diol is isoprene diol.

2. The method according to claim 1, characterized in that In step (1), the epoxidized vegetable oil ester is selected from at least one of epoxidized soybean oil methyl ester, epoxidized soybean oil ethyl ester, epoxidized rapeseed oil methyl ester, epoxidized rapeseed oil ethyl ester, epoxidized tea seed oil methyl ester, and epoxidized tea seed oil ethyl ester; And / or, the acid catalyst I is selected from at least one of concentrated sulfuric acid, phosphotungstic acid, and phosphomolybdic acid.

3. The method according to claim 1 or 2, characterized in that In step (1), the first contact reaction is carried out under stirring conditions, and the conditions of the first contact reaction include: a stirring speed of 200-400 rpm, a temperature of 70-110° C., and a time of 6-12 h.

4. The method according to claim 1 or 2, characterized in that In step (2), the catalyst II is selected from at least one of sodium methoxide and calcium methoxide.

5. The method according to claim 1 or 2, characterized in that The method further includes: before performing step (3), purifying material II; the purification step includes: mixing a decolorizing agent, an alkaline adsorbent, a desiccant and the material II and filtering the mixture.

6. The method according to claim 5, characterized in that The mixing reaction conditions at least meet the following requirements: temperature of 60-90° C. and time of 1-3 h.

7. The method according to claim 1 or 2, characterized in that In step (3), the third contact reaction is carried out under stirring conditions, and the conditions of the third contact reaction include: stirring speed of 200-400 rpm, temperature of 30-60° C., and time of 0.5-3 h; And / or, in step (3), based on the total amount of material II, the amount of the antioxidant is 0.3-0.6 wt %, the amount of the passivator is 0.003-0.006 wt %, and the amount of the pour point depressant is 0.05-0.2 wt %.

8. Modified natural ester insulating oil prepared by the method according to any one of claims 1 to 7.

9. Use of the modified natural ester insulating oil according to claim 8 in electrical equipment.

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