Modified tin oxide nano-sieve subjected to surface grafting by linoleic acid as well as preparation method and application of modified tin oxide nano-sieve

Abstract

The invention discloses a linoleic acid surface grafted tin oxide nano sieve as well as a preparation method and application thereof, and relates to the field of insulating oil. The preparation method of the nano-sieve comprises the following steps: preparing the tin oxide nano-sieve by adopting a sol-gel method, activating the surface of the tin oxide nano-sieve by adopting a silane coupling agent, then reacting with linoleic acid, and grafting linoleic acid on the surface of the tin oxide nano-sieve by taking the silane coupling agent as a molecular bridge to obtain the modified tin oxide nano-sieve. The stannic oxide nano-sieve prepared by a sol-gel method is uniform in pore size distribution, relatively high in specific surface area and chemical purity and good in structural stability, the lipophilicity of the nano-sieve and the dispersity of the nano-sieve in an organic solvent are improved by utilizing long-chain alkyl of linoleic acid, so that the nano-sieve can efficiently capture and neutralize charges, and the stability of the nano-sieve is improved. A barrier for hindering charge migration is formed in the insulating oil, so that the impact insulation strength of the insulating oil is improved, and the application field of the insulating oil is expanded.

Description

Technical Field

[0001] The invention relates to the field of insulating oil, and in particular to a modified tin oxide nanosieve grafted with linoleic acid on the surface, and a preparation method and application thereof. Background Art

[0002] At present, researchers have prepared surface-modified titanium dioxide nanosieves and applied them to improve the electrical strength of mineral insulating oil. This nanosieve needs to go through a specific preparation process, such as the reaction of titanium oxysulfate and ammonium carbonate in ammonia water, calcination, and modification of stearic acid and triethylamine, to obtain nanosieve materials with extremely high specific surface area and surface effect. This material can be polarized under the action of an electric field, generating a large number of traps to capture free electrons in the oil, thereby delaying the formation of discharge channels and increasing the breakdown voltage of the oil.

[0003] However, the preparation process of the surface-modified titanium dioxide nanosieve is complicated and involves multiple steps, including reaction, separation, calcination and modification, etc. These steps have high requirements on operating conditions and equipment, which increases the production cost and preparation difficulty. Although modifiers such as stearic acid and triethylamine can improve the compatibility of nanosieves with insulating oils, the modification effect may be affected by factors such as the surface properties of the nanosieve, the type and amount of the modifier, resulting in insufficient dispersibility and stability of the modified nanosieve in insulating oil. Although this prior art can improve the electrical strength of insulating oil, its room for improvement in insulation performance may be limited when facing electrical equipment with higher voltage levels and more complex operating environments. And it mainly focuses on titanium dioxide nanosieves, and there is little research on other types of nanosieve materials, which limits the diversity of material selection and the scope of application. Summary of the invention

[0004] The present invention provides a modified tin oxide nanosieve with linoleic acid surface grafted thereon, and a preparation method and application thereof. The tin oxide nanosieve is activated and then surface-modified with grafted linoleic acid. When applied to synthetic ester insulating oil, the impact insulation strength of the synthetic ester insulating oil can be significantly improved.

[0005] In order to solve the above technical problems, one of the purposes of the present invention is to provide a method for preparing a modified tin oxide nanosieve grafted with linoleic acid, comprising the following steps:

[0006] (1) dispersing tin chloride in an ethanol aqueous solution, adding alkali to adjust the pH value to trigger a hydrolysis reaction to obtain a sol, heating the sol to 40-50° C. in an oil bath and stirring the sol for reaction, vacuum drying, calcining in an inert gas atmosphere, washing, vacuum drying, and sieving to obtain a tin oxide nanosieve;

[0007] (2) dispersing a silane coupling agent in solvent A to obtain a coupling agent solution, uniformly coating the coupling agent solution on the surface of the tin oxide nanosieve by spraying, placing the mixture in a constant temperature and humidity environment at a temperature of 70-90° C. and a humidity of 50%-70%, reacting, washing, and vacuum drying to obtain an activated tin oxide nanosieve;

[0008] (3) Mixing the activated tin oxide nanosieve and linoleic acid in solvent B, heating to 70-90° C., stirring for reaction, centrifuging, washing the precipitate, and drying in a vacuum dryer to obtain a modified tin oxide nanosieve with linoleic acid grafted on the surface.

[0009] By adopting the above scheme, the present invention prepares a tin oxide nanosieve with a porous structure by a sol-gel method, so that the prepared tin oxide nanosieve has a more uniform particle size and a more accurate pore size distribution, and has a higher chemical purity and better structural stability. By using a silane coupling agent to activate the tin oxide nanosieve, it can play the role of a "molecular bridge" between the nanosieve and linoleic acid, and significantly improve the compatibility between the two. After being grafted on the surface of linoleic acid, the surface of the tin oxide nanosieve carries a long-chain hydrocarbon group of linoleic acid, which improves its lipophilicity and dispersibility in organic solvents. By introducing the combined action of the tin oxide nanosieve and linoleic acid, the charge carried on the surface of the tin oxide nanosieve can capture and neutralize the charge, and a barrier that hinders charge migration can be formed in the insulating oil, thereby improving the impact insulation strength of the insulating oil.

[0010] As a preferred embodiment, in step (1), the size of the tin oxide nanosieve is 50-200 nm.

[0011] As a preferred embodiment, in step (1), the mass ratio of tin chloride to ethanol aqueous solution is 1:(4-6), and / or alkali is added to adjust the pH value to 7.8-8.2.

[0012] As a preferred embodiment, in step (1), the volume concentration of the ethanol aqueous solution is 50%-80%.

[0013] As a preferred embodiment, in step (1), the base is sodium hydroxide.

[0014] As a preferred embodiment, in step (1), the oil bath heating reaction time is 12-24 hours.

[0015] As a preferred embodiment, in step (1), the inert gas is argon.

[0016] As a preferred embodiment, in step (1), the calcination temperature is 850-950°C and the calcination time is 3-4h.

[0017] As a preferred embodiment, in step (1), the vacuum drying temperature is 30-50°C and the time is 24-48 hours.

[0018] As a preferred embodiment, in step (2), the concentration of the silane coupling agent in the coupling agent solution is 1wt%-3%, and the mass ratio of the coupling agent solution and the tin oxide nanosieve for spraying is 1:(2-4).

[0019] As a preferred embodiment, in step (2), the solvent A is acetone.

[0020] As a preferred embodiment, in step (2), the constant temperature and humidity reaction time is 20-28 hours.

[0021] As a preferred embodiment, in step (2), the washing solvent is ethanol.

[0022] As a preferred embodiment, in step (2), the vacuum drying temperature is 30-50°C and the time is 24-48 hours.

[0023] As a preferred embodiment, in step (3), the mass ratio of the activated tin oxide nanosieve to linoleic acid is 1:(1-4).

[0024] As a preferred embodiment, in step (3), the mass ratio of the activated tin oxide nanosieve to the solvent B is 1:(4-6).

[0025] As a preferred embodiment, in step (3), the solvent B is n-hexane.

[0026] As a preferred embodiment, in step (3), the stirring reaction time is 10-20 hours.

[0027] As a preferred embodiment, in step (3), the washing solvent is n-hexane.

[0028] As a preferred embodiment, in step (3), the vacuum drying temperature is 30-50°C and the time is 24-48 hours.

[0029] In order to solve the above technical problems, the second object of the present invention is to provide a tin oxide nanosieve grafted with linoleic acid.

[0030] In order to solve the above technical problems, the third object of the present invention provides an application of a tin oxide nanosieve grafted with linoleic acid on the surface in the field of preparing synthetic ester insulating oil.

[0031] In order to solve the above technical problems, the fourth object of the present invention provides a synthetic ester insulating oil, comprising 0.05wt%-0.2wt% of tin oxide nanosieve grafted with linoleic acid on the surface.

[0032] As a preferred solution, it also includes additives with a mass fraction of 0-5wt% and the balance of MTE insulating oil.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present application prepares a porous tin oxide nanosieve with uniform pore size distribution by a sol-gel method, which has high chemical purity and good structural stability. Compared with the hydrothermal method, it has a better effect on improving the impact insulation strength of synthetic ester insulating oil.

[0035] 2. The present application uses a silane coupling agent to activate the tin oxide nanosieve, which acts as a molecular bridge to connect linoleic acid, thereby increasing the grafting rate of linoleic acid on the surface of the molecular sieve. The long-chain hydrocarbon group of linoleic acid is used to increase the lipophilicity and dispersibility in organic solvents, so that the nanosieve can form a barrier in the insulating oil to hinder charge migration, thereby improving the impact insulation strength of the insulating oil. The modified synthetic ester insulating oil has a wider range of applications and can be used in multiple fields such as power equipment and electrical systems. DETAILED DESCRIPTION

[0036] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0037] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0038] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0039] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0040] As used herein:

[0041] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0042] The conjunction "consisting of excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed-ended so that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0043] When an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically inventing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is invented separately. For example, when a range of "1 to 5" is invented, the described range should be interpreted as including the range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in this article, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0044] In these examples, parts and percentages are by mass unless otherwise indicated.

[0045] "Parts by mass" refers to the basic unit of measurement that represents the proportional relationship between the masses of multiple components. 1 part can represent any unit mass. If we say that the mass of component A is a parts and the mass of component B is b parts, it means the ratio of the mass of component A to the mass of component B is a:b. Or, it means that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number, indicating a multiple factor). It should not be misunderstood that, unlike the mass parts, the sum of the mass parts of all components is not limited to 100 parts.

[0046] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0047] In the description of the present invention, it is necessary to understand that the terms "up", "down", "left", "right", "top", "bottom", etc., indicating directions or positional relationships, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0048] In order to further illustrate the present invention, the modified tin oxide nanosieve grafted with linoleic acid surface and its preparation method and application provided by the present invention are described in detail in combination with the examples below, but they should not be understood as limiting the scope of protection of the present invention. The raw materials used in the following examples and comparative examples of the present application, unless otherwise specified, can be obtained from the market, and the same raw materials are used in parallel experiments.

[0049] Preparation Example 1

[0050] A method for preparing a modified tin oxide nanosieve grafted with linoleic acid on the surface comprises the following steps:

[0051] (1) Take 10g of tin chloride solid (SnCl 4 ) is added to 50 mL of 60% ethanol to form a uniform solution, sodium hydroxide is added to the solution to adjust the pH value to 8, a hydrolysis reaction is triggered to obtain a stable hydroxide sol, the sol is transferred to a reactor, heated to 50° C. in an oil bath and stirred for 12 h, after the reaction is completed, the obtained gel is vacuum dried at 60° C. for 24 h, and then placed in a tubular furnace in an argon atmosphere at 900° C. for 180 min, and after cooling, the sieve size is controlled to be 100±10 nm by a template method to obtain a tin oxide nanosieve;

[0052] (2) 5 mL of epoxysilane coupling agent KH-560 was added to 250 mL of acetone, and the mixture was placed in a magnetic stirrer and heated to 50°C and stirred for 1 hour to obtain a coupling agent solution. At the same time, impurities on the surface of the tin oxide nanosieve were washed with ethanol, and then the mixture was placed in a vacuum drying oven and dried at 40°C for 24 hours. The coupling agent solution was evenly coated on the surface of the tin oxide nanosieve by spraying, wherein the mass ratio of the coupling agent solution to the tin oxide nanosieve was 1:2, and then the mixture was placed in a constant temperature and humidity machine at 80°C and 60% to react the coupling agent on the surface of the tin oxide nanosieve for 24 hours. After the reaction was completed, the excess coupling agent on the surface was washed with ethanol, and then the mixture was placed in a vacuum drying oven and dried at 40°C for 24 hours to obtain an activated tin oxide nanosieve.

[0053] (3) 10 g of activated tin oxide nanosieve and 20 g of linoleic acid were mixed in 50 mL of n-hexane, and the solution was heated to 80°C in a magnetic stirrer and stirred for 12 h to promote the amidation reaction between the carboxyl group of linoleic acid and the amino group on the surface of the tin oxide nanosieve. After the reaction, the solid product was separated from the solution using a centrifuge, and then the solid product was washed with an appropriate amount of n-hexane solvent to remove unreacted linoleic acid and solvent. The washed product was placed in a vacuum dryer and dried at a constant temperature of 30°C for 24 h to obtain a modified tin oxide nanosieve with linoleic acid surface grafted.

[0054] Comparative Preparation Example 1

[0055] A method for preparing a modified tin oxide nanosieve grafted with linoleic acid, wherein each step and the reagents, equipment and process parameters used in each step are the same as those in Preparation Example 1, except that in step (1), 10 g of tin chloride solid (SnCl 4 ) was dissolved in 50 mL of deionized water, and then 20 mL of ethylene glycol was added as a reducing agent, and sodium hydroxide was added to adjust the pH value of the solution to 8. The solution was stirred evenly and then loaded into a high-pressure reactor. The solution was heated in an oil bath to react at 60° C. for 24 h. The tin ions were reduced to tin oxide by ethylene glycol and precipitated to form nanoparticles. After the reaction was completed, it was naturally cooled to room temperature, and the mixture was centrifuged using a centrifuge. The precipitate was washed with ethanol, and finally the solid was placed in a vacuum drying oven at 60° C. for 12 h to obtain a nanosieve precursor. The nanosieve precursor was placed in a tubular furnace and calcined at 900° C. for 180 min in an argon atmosphere. After cooling, the sieve size was controlled to be 100±10 nm by a template method for sieving to obtain a tin oxide nanosieve.

[0056] Comparative Preparation Example 2

[0057] A method for preparing a tin oxide nanosieve grafted with linoleic acid, wherein each step and the reagents, equipment and process parameters used in each step are the same as those in Preparation Example 1, except that in step (3), the activated tin oxide nanosieve is replaced by an equal amount of the tin oxide nanosieve in step (1).

[0058] Comparative Preparation Example 3

[0059] A method for preparing a modified tin oxide nanosieve grafted with oleic acid, wherein each step and the reagents, equipment and process parameters used in each step are the same as those in Preparation Example 1, except that in step (3), linoleic acid is replaced by an equal amount of oleic acid.

[0060] Comparative Preparation Example 4

[0061] A method for preparing modified nano-tin oxide grafted on the surface of linoleic acid, wherein each step and the reagents, equipment and process parameters used in each step are the same as those in Preparation Example 1, except that in step (2), the tin oxide nanosieve is replaced by an equal amount of Zhejiang Jiupeng New Materials CY-YHX1 nano-tin oxide with a purity of 99.8%.

[0062] Example 1

[0063] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0064] The product of Preparation Example 1 was added to MTE insulating oil, wherein the mass fraction of the product of Preparation Example 1 was 0.05 wt % of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 h. After stirring, the mixture was vacuum dried at 40° C. for 24 h to obtain synthetic ester insulating oil.

[0065] Example 2

[0066] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0067] The product of Preparation Example 1 was added to MTE insulating oil, wherein the mass fraction of the product of Preparation Example 1 was 0.1 wt % of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 h. After stirring, the mixture was vacuum dried at 40° C. for 24 h to obtain synthetic ester insulating oil.

[0068] Example 3

[0069] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0070] The product of Preparation Example 1 was added to MTE insulating oil, wherein the mass fraction of the product of Preparation Example 1 was 0.15 wt % of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 h. After stirring, the mixture was vacuum dried at 40° C. for 24 h to obtain synthetic ester insulating oil.

[0071] Example 4

[0072] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0073] The product of Preparation Example 1 was added to MTE insulating oil, wherein the mass fraction of the product of Preparation Example 1 was 0.2 wt % of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 h. After stirring, the mixture was vacuum dried at 40° C. for 24 h to obtain synthetic ester insulating oil.

[0074] Comparative Example 1

[0075] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0076] The product of comparative preparation example 1 was added to MTE insulating oil, wherein the mass fraction of the product of comparative preparation example 1 was 0.05wt% of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 hours. After stirring, the mixture was vacuum dried at 40°C for 24 hours to obtain synthetic ester insulating oil.

[0077] Comparative Example 2

[0078] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0079] The product of comparative preparation example 1 was added to MTE insulating oil, wherein the mass fraction of the product of comparative preparation example 1 was 0.1wt% of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 hours. After stirring, the mixture was vacuum dried at 40°C for 24 hours to obtain synthetic ester insulating oil.

[0080] Comparative Example 3

[0081] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0082] The product of comparative preparation example 1 was added to MTE insulating oil, wherein the mass fraction of the product of comparative preparation example 1 was 0.15wt% of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 hours. After stirring, the mixture was vacuum dried at 40°C for 24 hours to obtain synthetic ester insulating oil.

[0083] Comparative Example 4

[0084] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0085] The product of Comparative Preparation Example 2 was added to MTE insulating oil, wherein the mass fraction of the product of Comparative Preparation Example 2 was 0.05wt% of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 hours. After stirring, the mixture was vacuum dried at 40°C for 24 hours to obtain synthetic ester insulating oil.

[0086] Comparative Example 5

[0087] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0088] The product of Comparative Preparation Example 2 was added to MTE insulating oil, wherein the mass fraction of the product of Comparative Preparation Example 2 was 0.1wt% of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 hours. After stirring, the mixture was vacuum dried at 40°C for 24 hours to obtain synthetic ester insulating oil.

[0089] Comparative Example 6

[0090] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0091] The product of Comparative Preparation Example 2 was added to MTE insulating oil, wherein the mass fraction of the product of Comparative Preparation Example 2 was 0.15wt% of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 hours. After stirring, the mixture was vacuum dried at 40°C for 24 hours to obtain synthetic ester insulating oil.

[0092] Comparative Example 7

[0093] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0094] The product of Comparative Preparation Example 3 was added to MTE insulating oil, wherein the mass fraction of the product of Comparative Preparation Example 3 was 0.05wt% of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 hours. After stirring, the mixture was vacuum dried at 40°C for 24 hours to obtain synthetic ester insulating oil.

[0095] Comparative Example 8

[0096] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0097] The product of comparative preparation example 3 was added to MTE insulating oil, wherein the mass fraction of the product of comparative preparation example 3 was 0.1wt% of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 hours. After stirring, the mixture was vacuum dried at 40°C for 24 hours to obtain synthetic ester insulating oil.

[0098] Comparative Example 9

[0099] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0100] The product of Comparative Preparation Example 3 was added to MTE insulating oil, wherein the mass fraction of the product of Comparative Preparation Example 3 was 0.15 wt % of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 h. After stirring, the mixture was vacuum dried at 40° C. for 24 h to obtain synthetic ester insulating oil.

[0101] Comparative Example 10

[0102] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0103] The product of Comparative Preparation Example 4 was added to MTE insulating oil, wherein the mass fraction of the product of Comparative Preparation Example 4 was 0.05wt% of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 hours. After stirring, the mixture was vacuum dried at 40°C for 24 hours to obtain synthetic ester insulating oil.

[0104] Comparative Example 11

[0105] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0106] The product of Comparative Preparation Example 4 was added to MTE insulating oil, wherein the mass fraction of the product of Comparative Preparation Example 4 was 0.1wt% of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 hours. After stirring, the mixture was vacuum dried at 40°C for 24 hours to obtain synthetic ester insulating oil.

[0107] Comparative Example 12

[0108] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0109] The product of Comparative Preparation Example 4 was added to MTE insulating oil, wherein the mass fraction of the product of Comparative Preparation Example 4 was 0.15wt% of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 hours. After stirring, the mixture was vacuum dried at 40°C for 24 hours to obtain synthetic ester insulating oil.

[0110] Comparative Example 13

[0111] A mineral insulating oil, the preparation method of which comprises the following steps:

[0112] The product of Preparation Example 1 was added to Karamay #25 mineral oil, wherein the mass fraction of the product of Preparation Example 1 was 0.05 wt % of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 h. After stirring, the mixture was vacuum dried at 40° C. for 24 h to obtain mineral insulating oil.

[0113] Comparative Example 14

[0114] A mineral insulating oil, the preparation method of which comprises the following steps:

[0115] The product of Preparation Example 1 was added to Karamay #25 mineral oil, wherein the mass fraction of the product of Preparation Example 1 was 0.1 wt % of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 h. After stirring, the mixture was vacuum dried at 40° C. for 24 h to obtain mineral insulating oil.

[0116] Comparative Example 15

[0117] A mineral insulating oil, the preparation method of which comprises the following steps:

[0118] The product of Preparation Example 1 was added to Karamay #25 mineral oil, wherein the mass fraction of the product of Preparation Example 1 was 0.15 wt % of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 h. After stirring, the mixture was vacuum dried at 40° C. for 24 h to obtain mineral insulating oil.

[0119] Comparative Example 16

[0120] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0121] The activated tin oxide nanosieve prepared in step (2) of Preparation Example 1 was added to the MTE insulating oil, wherein the activated tin oxide nanosieve accounted for 0.05 wt % of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 h. After stirring, the mixed oil sample was vacuum dried at 40° C. for 24 h to obtain a synthetic ester insulating oil.

[0122] Comparative Example 17

[0123] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0124] The activated tin oxide nanosieve prepared in step (2) of Preparation Example 1 was added to the MTE insulating oil, wherein the activated tin oxide nanosieve accounted for 0.1 wt % of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 h. After stirring, the mixed oil sample was vacuum dried at 40° C. for 24 h to obtain a synthetic ester insulating oil.

[0125] Comparative Example 18

[0126] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0127] The activated tin oxide nanosieve prepared in step (2) of Preparation Example 1 was added to the MTE insulating oil, wherein the activated tin oxide nanosieve accounted for 0.15 wt % of the total insulating oil. The mixed oil sample was dispersed at a speed of 1200 rpm using a high-speed stirrer for 4 h. After stirring, the mixed oil sample was vacuum dried at 40° C. for 24 h to obtain a synthetic ester insulating oil.

[0128] Comparative Example 19

[0129] A synthetic ester insulating oil, the preparation method of which comprises the following steps:

[0130] Take MTE insulating oil, use a high-speed stirrer to disperse the mixed oil sample at a speed of 1200 rpm for 4 hours, and then perform vacuum drying at a temperature of 40°C for 24 hours after stirring to obtain synthetic ester insulating oil.

[0131] Comparative Example 20

[0132] A mineral insulating oil, the preparation method of which comprises the following steps:

[0133] Take Karamay #25 mineral oil, use a high-speed stirrer to disperse the mixed oil sample at a speed of 1200 rpm for 4 hours, and then perform vacuum drying at a temperature of 40°C for 24 hours to obtain mineral insulating oil.

[0134] Performance testing

[0135] 1. Referring to IEC 60897:1987 and DL / T 421-2009 standards, using CJ1326 model impulse voltage generator and insulating oil volume resistivity tester, impulse voltage test and volume resistivity measurement were performed on the insulating oils of the embodiment and comparative example. The test results are shown in Table 1 below.

[0136] Table 1 - Performance test results of insulating oils in the present application examples and comparative examples

[0137]

[0138]

[0139] As shown in Table 1, the modified tin oxide nanosieves in Examples 1-3 are prepared by a sol-gel method, while the modified tin oxide nanosieves in Comparative Examples 1-3 are prepared by a hydrothermal method. It can be found that Examples 1-3 have a better effect on improving the impact insulation strength of synthetic ester insulating oil than Comparative Examples 1-3. This is because the modified tin oxide nanosieves prepared by the sol-gel method have more uniform pore size and more precise pore size distribution, and have higher chemical purity and structural stability.

[0140] As shown in Table 1, the modified tin oxide nanosieves in Examples 1-3 are activated by silane coupling agents, and have a better effect on improving the impact insulation strength of synthetic ester insulating oil than the modified tin oxide nanosieves in Comparative Examples 4-6 that are not activated. This is because the silane coupling agent can act as a molecular bridge between the nanosieve and linoleic acid, thereby increasing the grafting rate of linoleic acid on the surface of the nanosieve. The nanosieve modified with linoleic acid has an extremely high specific surface area and surface effect, and can be polarized under the action of an electric field to generate a large number of traps. The charges on its surface can capture and neutralize free electrons in the insulating oil, thereby delaying the formation of discharge channels and increasing the breakdown voltage of the synthetic ester insulating oil.

[0141] As shown in Table 1, the modified tin oxide nanosieves in Examples 1-3 are surface-modified with linoleic acid, which has a better effect on improving the impact insulation strength of synthetic ester insulating oil than the modified tin oxide nanosieves modified with oleic acid in Comparative Examples 7-9.

[0142] As shown in Table 1, the solid single crystal nano-tin oxide used in Comparative Examples 10-12 has a low relative specific surface area and a low efficiency in capturing free electrons in the synthetic ester insulating oil in an electric field, resulting in a poor ability to increase the breakdown voltage of the synthetic ester insulating oil. The tin oxide nanosieve of Examples 1-3 has a porous structure and a high surface efficiency, and can efficiently capture free electrons in the electric field, delay the formation of discharge channels, and effectively increase the breakdown voltage of the synthetic ester insulating oil.

[0143] As shown in Table 1, the surfaces of the nanosieves of Comparative Examples 16-18 are not modified with grafted linoleic acid, resulting in lower impact dielectric strength of the synthetic ester insulating oil. However, after the nanosieves of Examples 1-3 are grafted with linoleic acid, their surfaces carry long-chain hydrocarbon groups of linoleic acid, which improves their lipophilicity and dispersibility in organic solvents, helps to improve the dispersibility of the nanosieve in the synthetic ester insulating oil, improves the efficiency of the nanosieve in capturing charged charges, and improves the impact dielectric strength of the insulating oil.

[0144] As shown in Table 1, the amount of nanosieve added to the synthetic ester insulating oil in Examples 1-4 is gradually increased, and the optimal impact insulation strength can be obtained at an addition amount of 0.15wt%. As the nanosieve content continues to increase, the impact insulation strength of the insulating oil decreases, indicating that too much nanosieve will increase the agglomeration phenomenon and reduce the contact area between the nanosieve and the insulating oil, thereby reducing the insulation performance.

[0145] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a modified tin oxide nanosieve grafted with linoleic acid, characterized in that: The following steps are involved: (1) dispersing tin chloride in an ethanol aqueous solution, adding alkali to adjust the pH value to trigger a hydrolysis reaction to obtain a sol, heating the sol to 40-50° C. in an oil bath and stirring the sol for reaction, vacuum drying, calcining in an inert gas atmosphere, washing, vacuum drying, and sieving to obtain a tin oxide nanosieve; (2) dispersing a silane coupling agent in solvent A to obtain a coupling agent solution, uniformly coating the coupling agent solution on the surface of the tin oxide nanosieve by spraying, placing the mixture in a constant temperature and humidity environment at a temperature of 70-90° C. and a humidity of 50%-70%, reacting, washing, and vacuum drying to obtain an activated tin oxide nanosieve; (3) Mixing the activated tin oxide nanosieve and linoleic acid in solvent B, heating to 70-90° C., stirring for reaction, centrifuging, washing the precipitate, and drying in a vacuum dryer to obtain a modified tin oxide nanosieve with linoleic acid grafted on the surface.

2. The method for preparing the tin oxide nanosieve grafted with linoleic acid as claimed in claim 1, characterized in that: In step (1), the mass ratio of tin chloride to ethanol aqueous solution is 1:(4-6), and / or alkali is added to adjust the pH value to 7.8-8.

2.

3. The method for preparing the tin oxide nanosieve grafted with linoleic acid as claimed in claim 1, characterized in that: In step (1), the volume concentration of the ethanol aqueous solution is 50%-80%; and / or, in step (1), the base is sodium hydroxide; And / or, in step (1), the oil bath heating reaction time is 12-24h; and / or, in step (1), the inert gas is argon; and / or, in step (1), the calcination temperature is 850-950° C. and the calcination time is 3-4 h; And / or, in step (1), the vacuum drying temperature is 30-50°C and the time is 24-48h.

4. The method for preparing the tin oxide nanosieve grafted with linoleic acid as claimed in claim 1, characterized in that: In step (2), the concentration of the silane coupling agent in the coupling agent solution is 1wt%-3wt%2%, and the mass ratio of the coupling agent solution and the tin oxide nanosieve for spraying is 1:(2-4).

5. The method for preparing the tin oxide nanosieve grafted with linoleic acid as claimed in claim 1, characterized in that: In step (2), the solvent A is acetone; And / or, in step (2), the constant temperature and humidity reaction time is 20-28h; and / or, in step (2), the washing solvent is ethanol; And / or, in step (2), the vacuum drying temperature is 30-50°C and the time is 24-48h.

6. The method for preparing the tin oxide nanosieve grafted with linoleic acid as claimed in claim 1, characterized in that: In step (3), the mass ratio of the activated tin oxide nanosieve to linoleic acid is 1:(1-4); and / or, in step (3), the mass ratio of the activated tin oxide nanosieve to the solvent B is 1:(4-6); and / or, in step (3), the solvent B is n-hexane; And / or, in step (3), the stirring reaction time is 10-20h; and / or, in step (3), the washing solvent is n-hexane; And / or, in step (3), the vacuum drying temperature is 30-50°C and the time is 24-48h.

7. A tin oxide nanosieve grafted with linoleic acid surface prepared by the method for preparing a tin oxide nanosieve grafted with linoleic acid surface as claimed in any one of claims 1 to 6.

8. Use of the tin oxide nanosieve grafted with linoleic acid as claimed in claim 7 in the field of preparing synthetic ester insulating oil.

9. A synthetic ester insulating oil, characterized in that: The invention comprises 0.05wt%-0.2wt% of the tin oxide nano-sieve grafted with linoleic acid as claimed in claim 7.

10. The synthetic ester insulating oil according to claim 9, characterized in that The invention also comprises additives with a mass fraction of 0-5wt% and the balance of MTE insulating oil.

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