Insulating oil-based composite material, preparation method and application thereof, and oil-paper composite insulating product

Abstract

The invention provides an insulating oil-based composite material, a preparation method and application thereof, and an oil-paper composite insulating product, and belongs to the technical field of insulating materials. The insulating oil-based composite material comprises a base solution and an alpha-linolenic acid grafted and modified nano inorganic material, the base solution comprises ester insulating oil, and the ester insulating oil comprises triglyceride. The alpha-linolenic acid grafted and modified nano inorganic material is prepared by modifying the nano inorganic material with the alpha-linolenic acid, and long-chain alkyl of the alpha-linolenic acid on the surface of the nano inorganic material is combined with ester insulating oil molecules through Van der Waals' force, so that agglomeration of the nano inorganic material is reduced; the dispersity and compatibility of nanoparticles in the insulating oil-based composite material are improved, and the interface charge accumulation is reduced, so that the flashover voltage is increased, and the insulating property of an insulating material system is improved. The oil-paper composite insulation product is prepared by combining the insulation oil-based composite material and an insulation paperboard, so that the surface flashover performance of the oil-paper composite insulation product is further improved.

Description

Technical Field

[0001] This application relates to the field of insulating materials technology, and in particular to an insulating oil-based composite material, its preparation method and application, and an oil-paper composite insulating product. Background Technology

[0002] Insulating oil is a crucial insulating medium in transformers, playing roles in heat dissipation, insulation, and arc extinguishing during transformer operation. Currently, nanoparticles (such as nickel oxide and aluminum oxide) are typically dispersed in insulating oil to improve its electrical properties and thermal stability through their filling and surface effects. The dispersibility and compatibility of nanoparticles in insulating oil are key factors affecting its performance. Uneven dispersion of nanoparticles may lead to performance degradation in localized areas of the insulating oil, thus affecting the insulation performance of the insulating oil-based composite system. Conversely, poor compatibility between nanoparticles and insulating oil can cause nanoparticles to aggregate or precipitate, resulting in performance degradation.

[0003] Therefore, how to adjust the dispersibility and compatibility of nanoparticles in insulating oil to improve the insulation performance of insulating material systems has become an urgent technical problem to be solved. Summary of the Invention

[0004] Based on this, the main objective of this application is to provide an insulating oil-based composite material, its preparation method and application, and an oil-paper composite insulating product, so as to improve the dispersibility and compatibility of nanoparticles in the insulating oil-based composite material and improve the insulation performance of the insulating material product.

[0005] In a first aspect, this application provides an insulating oil-based composite material comprising a base liquid and an α-linolenic acid-grafted modified nano-inorganic material;

[0006] The base liquid includes ester-based insulating oil, which includes triglycerides.

[0007] In some embodiments, the nano-inorganic material includes a nanosieve.

[0008] In some embodiments, the nanosieve includes one or more of nickel oxide nanosieves and alumina nanosieves.

[0009] In some embodiments, the mass ratio of the base liquid to the α-linolenic acid-grafted modified nano-inorganic material is 99.84-99.96:0.04-0.16.

[0010] A second aspect of this application provides a method for preparing the insulating oil-based composite material described in the first aspect, comprising the following steps:

[0011] α-Linolenic acid grafted and modified nanomaterials were prepared by dispersing nano-inorganic materials and α-linolenic acid in a solvent and carrying out an esterification reaction.

[0012] An insulating oil-based composite material was prepared by mixing a base liquid with α-linolenic acid-grafted and modified nano-inorganic materials.

[0013] In some embodiments, the mass ratio of the nano-inorganic material to α-linolenic acid is 1:2-5.

[0014] In some embodiments, the esterification reaction conditions include: a reaction temperature of 55-75°C and a reaction time of 12-24 hours.

[0015] In some embodiments, nickel oxide nanosieves are prepared by the following methods:

[0016] Nickel hydroxide colloid was prepared by hydrolysis of nickel chloride and sodium hydroxide; the nickel hydroxide colloid was then calcined to prepare the nickel oxide nanosieve.

[0017] The third aspect of this application provides the application of the insulating oil-based composite material described in the first aspect or the insulating oil-based composite material prepared by the preparation method described in the second aspect in the preparation of oil-paper composite insulation products.

[0018] In a fourth aspect, this application provides an oil-paper composite insulation product, comprising insulating paper and an insulating oil-based composite material;

[0019] The insulating oil-based composite material includes the insulating oil-based composite material described in the first aspect or the insulating oil-based composite material prepared by the preparation method described in the second aspect.

[0020] Compared with traditional technologies, this application has at least the following beneficial effects:

[0021] This application describes the preparation of α-linolenic acid-grafted inorganic nanomaterials by modifying nanomaterials with α-linolenic acid. The long-chain hydrocarbon groups of α-linolenic acid on the surface of these nanomaterials bind to triglyceride-containing ester-based insulating oil molecules via van der Waals forces, reducing the aggregation of the nanomaterials, improving the dispersibility and compatibility of nanoparticles in the insulating oil-based composite material, and reducing interfacial charge accumulation, thereby increasing the flashover voltage and improving the insulation performance of the insulating material system. Simultaneously, the triglyceride-containing ester-based insulating oil exhibits excellent environmental performance and energy-saving effects, aligning with the current trend of green and low-carbon development. Combining the insulating oil-based composite material with insulating paperboard can significantly improve the surface flashover performance of the oil-paper composite insulation product. Attached Figure Description

[0022] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0023] Figure 1 This is a schematic diagram of a test system for surface flashover of oil-paper insulation products. Detailed Implementation

[0024] The present application will be further described in detail below with reference to the embodiments and examples. These embodiments and examples are only for illustrating the present application and are not intended to limit the scope of the present application. The purpose of providing these embodiments and examples is to make the disclosure of the present application more thorough and comprehensive. It should also be understood that the present application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various modifications or alterations without departing from the spirit of the present application, and the equivalent forms obtained also fall within the protection scope of the present application. In addition, numerous specific details are set forth in the following description to provide a fuller understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] To address the problem of poor dispersion and compatibility of nanoparticles in insulating oil leading to decreased insulation performance in insulating oil-based composite material systems, this application proposes a novel approach. This involves modifying nano-inorganic materials with α-linolenic acid (LAA) to prepare LAA-grafted inorganic nanomaterials. The long-chain hydrocarbon groups of LAA on their surface bind to ester-containing insulating oil molecules via van der Waals forces, reducing nanomaterial aggregation, improving the dispersion and compatibility of nanoparticles in the insulating oil-based composite material, and decreasing interfacial charge accumulation. This, in turn, enhances flashover voltage and improves the insulation performance of the insulating oil-based composite material system.

[0027] In a first aspect, this application provides an insulating oil-based composite material comprising a base liquid and an α-linolenic acid-grafted modified nano-inorganic material;

[0028] The base liquid includes ester-based insulating oil, which includes triglycerides.

[0029] This application utilizes α-linolenic acid to modify nano-inorganic materials, which significantly improves the dispersibility and compatibility of nanomaterials in triglyceride-containing ester insulating oils, thereby enhancing the insulation performance of the insulating oil-based composite materials. Furthermore, compared to mineral oils, triglyceride-containing ester insulating oils exhibit higher flash points and biodegradability, demonstrating superior environmental performance and energy-saving effects.

[0030] In some embodiments, the nano-inorganic material includes a nanosieve.

[0031] In some embodiments, the nanosieve includes one or more of nickel oxide nanosieves and alumina nanosieves.

[0032] In some embodiments, the α-linolenic acid-grafted modified nanomaterial is an α-linolenic acid-grafted modified nickel oxide nanosieve. By surface-grafting the nickel oxide nanosieve with α-linolenic acid, the van der Waals forces of the long-chain hydrocarbon groups of α-linolenic acid bind to the molecules of triglyceride-containing ester insulating oil, reducing nanomaterial aggregation and significantly improving the dispersibility and interfacial compatibility of the nickel oxide nanosieve in triglyceride-containing ester insulating oil. This effectively inhibits charge accumulation, thereby increasing the flashover voltage and improving the surface flashover voltage of the insulating material. When combined with insulating paperboard, it further enhances the surface flashover performance of the entire system.

[0033] In some embodiments, the ester-based insulating oil includes FR3 vegetable-based transformer insulating oil. The FR3 vegetable-based transformer insulating oil primarily comprises triglycerides.

[0034] In some embodiments, the mass ratio of the base liquid to the α-linolenic acid-grafted modified nano-inorganic material is 99.84-99.96:0.04-0.16, which can be 99.96:0.04, 99.92:0.08, 99.88:0.12, or 99.84:0.16.

[0035] A second aspect of this application provides a method for preparing the insulating oil-based composite material described in the first aspect, comprising the following steps:

[0036] α-Linolenic acid grafted and modified nanomaterials were prepared by dispersing nano-inorganic materials and α-linolenic acid in a solvent and carrying out an esterification reaction.

[0037] An insulating oil-based composite material was prepared by mixing a base liquid with α-linolenic acid-grafted and modified nano-inorganic materials.

[0038] In some embodiments, the mass ratio of the nano-inorganic material to α-linolenic acid is 1:2-5, which can be 1:2, 1:3, 1:4 or 1:5.

[0039] In some embodiments, the esterification reaction conditions include: a reaction temperature of 55-75°C, which can be 65°C; and a reaction time of 12-24h, which can be 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, or 24h.

[0040] In some embodiments, the nano-inorganic material is a nickel oxide nanosieve.

[0041] In some embodiments, nickel oxide nanosieves are prepared by the following methods:

[0042] Nickel hydroxide colloid was prepared by hydrolysis and gelation of nickel chloride and sodium hydroxide; the nickel hydroxide colloid was then calcined to prepare the nickel oxide nanosieve.

[0043] This application utilizes a sol-gel method to first hydrolyze a precursor solution to form a sol, which is then gelled and calcined at high temperature to prepare nickel oxide nanosieves. The prepared nickel oxide nanosieves have a high specific surface area and surface active sites, which can enhance the dielectric properties of ester-based insulating oils.

[0044] In some embodiments, the step of preparing nickel hydroxide colloid by hydrolyzing nickel chloride and sodium hydroxide and gelling includes:

[0045] Nickel hydroxide colloid was prepared by mixing nickel chloride, sodium hydroxide and an aqueous ethanol solution, carrying out a hydrolysis reaction and gelling.

[0046] The ethanol aqueous solution contains 50-80% ethanol by mass, which can be 50%, 60%, 70% or 80%.

[0047] The conditions for the hydrolysis reaction include: pH 7; temperature 28-32℃ (28℃, 29℃, 30℃, 31℃, or 32℃); and time 40-80 min (40 min, 50 min, 60 min, 70 min, or 80 min).

[0048] The gelation conditions include: a temperature of 50-60℃, which can be 50℃, 55℃ or 60℃; and a time of 15-25h, which can be 15h, 18h, 20h or 25h.

[0049] After the gelation step, a drying step is also included. The drying conditions include: a temperature of 50-70℃, which can be 50℃, 55℃, 60℃, 65℃ or 70℃; and a time of 20-30h, which can be 20h, 24h, 28h or 30h.

[0050] In some embodiments, the calcination conditions for the nickel hydroxide colloid include: atmosphere: inert gas, including nitrogen; temperature: 800-1000℃, which can be 800℃, 900℃ or 1000℃; time: 4-7h, which can be 4h, 5h, 6h or 7h.

[0051] In some embodiments, the conditions for preparing α-linolenic acid grafted inorganic nanomaterials by dispersing nanomaterials and α-linolenic acid in a solvent and heating the reaction include:

[0052] The mass ratio of the nano-inorganic material to the α-linolenic acid is 1:2;

[0053] The solvent includes n-hexane;

[0054] The heating temperature for the reaction was 65℃, and the heating time was 18 hours.

[0055] Heating can promote the esterification reaction between the carboxyl groups of α-linolenic acid and the hydroxyl groups on the surface of nano-inorganic materials, thus preparing α-linolenic acid grafted and modified nano-inorganic materials.

[0056] In some embodiments, before the step of mixing the base liquid and the α-linolenic acid-grafted modified nano-inorganic material, a step of pretreating the base liquid is included; the step of pretreating the base liquid includes: placing the base liquid in an oil filter and filtering it to remove impurities and water; the temperature of the oil filter is 65°C, the vacuum degree is 1 kPa, and the filtration time is 24 h.

[0057] In some embodiments, the step of mixing the base liquid and the α-linolenic acid-grafted modified nano-inorganic material includes: mixing and stirring the base liquid and the α-linolenic acid-grafted modified nano-inorganic material at a speed of 1000-1500 rpm / min, which can be 1000 rpm / min, 1100 rpm / min, 1200 rpm / min, 1300 rpm / min, 1400 rpm / min or 1500 rpm / min; and for a time of 4-8 h, which can be 4 h, 5 h, 6 h, 7 h or 8 h.

[0058] In some embodiments, the mass fraction of α-linolenic acid-grafted modified nano-inorganic material in the insulating oil-based composite material is 0.04-0.16%, which can be 0.04%, 0.08%, 0.12% or 0.14%.

[0059] The third aspect of this application provides the application of the insulating oil-based composite material described in the first aspect or the insulating oil-based composite material prepared by the preparation method described in the second aspect in the preparation of oil-paper composite insulation products.

[0060] In a fourth aspect, this application provides an oil-paper composite insulation product, comprising insulating paper and an insulating oil-based composite material;

[0061] The insulating oil composite material includes the insulating oil-based composite material described in the first aspect or the insulating oil-based composite material prepared by the preparation method described in the second aspect.

[0062] In some embodiments, the insulating paper includes synthetic fiber reinforced insulating paper.

[0063] In some embodiments, the synthetic fiber reinforced insulating paper includes polyester fiber reinforced insulating paper.

[0064] In some embodiments, the oil-paper composite insulation product is prepared by the following method:

[0065] A vacuum impregnation process is used to impregnate insulating paper into an insulating oil-based composite material to prepare an oil-paper composite insulation product.

[0066] In some embodiments, before the step of impregnating the insulating paper with the insulating oil-based composite material using a vacuum impregnation process, a pretreatment step is further included; the pretreatment step includes:

[0067] The insulating paper is subjected to a drying pretreatment. The drying pretreatment conditions include: a temperature of 80-125℃, which can be 80℃, 90℃, 100℃, 105℃, 110℃ or 125℃; and a time of 20-30h, which can be 20h, 24h, 26h or 30h.

[0068] This application prepares an oil-paper composite insulation product by combining insulating paper with modified insulating oil-based composite materials, forming an oil-paper composite insulation product with a synergistic reinforcement effect. This can further improve the surface flashover voltage of the entire system, improve the insulation performance of the entire system, thereby improving the safe and stable operation capability of the equipment and reducing the equipment failure rate.

[0069] The embodiments of this application will be described in detail below with reference to examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this application, or follow experimental manuals or conventional conditions in the art, or follow the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0070] As an example, the raw materials are sourced as follows:

[0071] FR3 plant-based transformer insulating oil: purchased from Cargill, Inc. TM Natural ester insulating oil;

[0072] 2mm polyester fiber reinforced insulating paperboard: Nomex® T410 insulating paper purchased from DuPont;

[0073] Midel 7131 insulating oil: purchased from M&I Materials.

[0074] Example 1

[0075] Preparation of α-linolenic acid grafted and modified nano-inorganic materials: 10g of nickel chloride (NiCl2) was dissolved in 50mL of 60% ethanol aqueous solution to form a homogeneous solution. NaOH was added to adjust the pH to 7, and a hydrolysis reaction was carried out at 30℃ for 60min. The reaction system (sol) was then transferred to a reaction vessel and heated to 55℃ in an oil bath, and stirred continuously for 18h to prepare a gel. After the reaction, the gel was vacuum dried at 60℃ for 24h, and then placed in a tube furnace and calcined at 900℃ for 300min in a nitrogen atmosphere. After cooling, nickel oxide nanosieves were obtained.

[0076] Nickel oxide nanosieves were modified using α-linolenic acid. Specifically, 10g of nickel oxide nanosieves, 20g of α-linolenic acid, and 50mL of n-hexane were mixed and stirred continuously at 65℃ in a magnetic stirrer for 18h to promote the esterification reaction between the carboxyl groups of α-linolenic acid and the hydroxyl groups on the surface of the nickel oxide nanosieves. After the reaction, the mixture was centrifuged at 20℃, 8000rpm, and for 20min. The precipitate was then collected and washed with n-hexane to remove the α-linolenic acid and solvent adhering to its surface. The washed precipitate was then dried in a vacuum desiccator at 30℃ for 24h to obtain α-linolenic acid-grafted modified nano-inorganic material (modified nickel oxide nanosieves grafted with α-linolenic acid).

[0077] Preparation of insulating oil-based composite material: FR3 plant-based transformer insulating oil was placed in an oil filter and filtered for 24 hours at 65℃ and 1 kPa vacuum to remove impurities and moisture, serving as the base liquid. Then, α-linolenic acid-grafted modified nano-inorganic materials (modified nickel oxide nanosieves grafted onto the surface of α-linolenic acid) were added to prepare a mixed oil. The mass fractions of α-linolenic acid-grafted modified nano-inorganic materials in the mixed oil were 0.04%, 0.08%, 0.12%, and 0.16%, respectively. The mixed oil was dispersed at 1400 rpm / min using a high-speed mixer for 5 hours, followed by vacuum drying to prepare the insulating oil-based composite material.

[0078] Preparation of oil-paper composite insulation products: Select 2mm polyester fiber reinforced insulating paperboard (fiber diameter 5-10μm, tensile strength ≥150MPa), place the paperboard in a vacuum drying oven and dry at 105℃ for 24h; under vacuum, impregnate the dried insulating paperboard with insulating oil-based composite material in an impregnation tank at a temperature of 80℃ for 12h to prepare oil-paper composite insulation products.

[0079] Comparative Example 1

[0080] Comparative Example 1 is basically the same as Example 1, except that α-linolenic acid was not used to modify the nickel oxide nanosieve.

[0081] Nano-inorganic materials, insulating oil-based composite materials, and oil-paper composite insulating products were prepared according to the method in Example 1.

[0082] Specifically:

[0083] Preparation of nano-inorganic materials: 10g of nickel chloride (NiCl2) was dissolved in 50mL of 60% ethanol aqueous solution to form a homogeneous solution. NaOH was added to adjust the pH to 7, and a hydrolysis reaction was carried out at 30℃ for 60min. The reaction system (sol) was then transferred to a reaction vessel and heated to 55℃ in an oil bath. The mixture was stirred continuously for 18h to prepare a gel. After the reaction, the gel was vacuum dried at 60℃ for 24h and then placed in a tube furnace and calcined at 900℃ for 300min in a nitrogen atmosphere. After cooling, nano-inorganic materials (nickel oxide nanosieves) were obtained.

[0084] Preparation of insulating oil-based composite material: The insulating oil of FR3 plant-based transformer was placed in an oil filter and filtered for 24 hours at 65℃ and 1kPa to remove impurities and moisture, serving as the base liquid. Then, the prepared nano-inorganic material (nickel oxide nanosieve) was added to prepare a mixed oil. The mass fractions of the nano-inorganic material in the mixed oil were 0.04%, 0.08%, and 0.12%, respectively. The mixed oil was dispersed at 1400 rpm / min using a high-speed mixer. After high-speed dispersion for 5 hours, it was vacuum dried to prepare the insulating oil-based composite material (ester-based insulating oil containing nickel oxide nanosieve).

[0085] Preparation of oil-paper composite insulation products: Select 2mm polyester fiber reinforced insulating paperboard (fiber diameter 5-10μm, tensile strength ≥150MPa), place the paperboard in a vacuum drying oven and dry at 105℃ for 24h; under vacuum, impregnate the dried insulating paperboard with insulating oil-based composite material in an impregnation tank at a temperature of 80℃ for 12h to prepare oil-paper composite insulation products.

[0086] Comparative Example 2

[0087] Comparative Example 2 is basically the same as Example 1, except that oleic acid is used to modify the nickel oxide nanosieve.

[0088] Modified nanomaterials, insulating oil-based composite materials, and oil-paper composite insulating products were prepared according to the method in Example 1.

[0089] Specifically:

[0090] Preparation of oleic acid-grafted modified nano-inorganic materials: 10g of nickel chloride (NiCl2) was dissolved in 50mL of 60% ethanol aqueous solution to form a homogeneous solution. NaOH was added to adjust the pH to 7, and a hydrolysis reaction was carried out at 30℃ for 60min. The reaction system (sol) was then transferred to a reaction vessel and heated to 55℃ in an oil bath, and stirred continuously for 18h to prepare a gel. After the reaction, the gel was vacuum dried at 60℃ for 24h, and then placed in a tube furnace and calcined at 900℃ for 300min in a nitrogen atmosphere. After cooling, nickel oxide nanosieves were obtained.

[0091] Oleic acid was used to modify nickel oxide nanosieves. Specifically, 10g of nickel oxide nanosieves, 20g of oleic acid, and 50mL of n-hexane were mixed and stirred continuously at 65℃ in a magnetic stirrer for 18h to promote the esterification reaction between the carboxyl groups of α-linolenic acid and the hydroxyl groups on the surface of the nickel oxide nanosieves. After the reaction, the mixture was centrifuged at 20℃, 8000rpm, and for 20min. The precipitate was then collected and washed with n-hexane to remove the α-linolenic acid and solvent adhering to the precipitate surface. The washed precipitate was then placed in a vacuum desiccator and dried at 30℃ for 24h to obtain oleic acid-grafted modified nano-inorganic material (oleic acid-grafted modified nickel oxide nanosieves).

[0092] Preparation of insulating oil-based composite material: The insulating oil of FR3 plant-based transformer was placed in an oil filter and filtered for 24 hours at 65℃ and 1kPa to remove impurities and moisture, serving as the base liquid. Then, oleic acid-grafted modified nano-inorganic materials (modified nickel oxide nanosieves grafted onto the oleic acid surface) were added to prepare a mixed oil. The mass fractions of oleic acid-grafted modified nano-inorganic materials in the mixed oil were 0.04%, 0.08%, and 0.12%, respectively. The mixed oil was dispersed at 1400 rpm / min using a high-speed mixer. After high-speed dispersion for 5 hours, vacuum drying was performed to prepare the insulating oil-based composite material.

[0093] Preparation of oil-paper composite insulation products: Select 2mm polyester fiber reinforced insulating paperboard (fiber diameter 5-10μm, tensile strength ≥150MPa), place the paperboard in a vacuum drying oven and dry at 105℃ for 24h; under vacuum, impregnate the dried insulating paperboard with insulating oil-based composite material in an impregnation tank at a temperature of 80℃ for 12h to prepare oil-paper composite insulation products.

[0094] Comparative Example 3

[0095] Comparative Example 3 is basically the same as Example 1, except that no modified nano-inorganic materials were added to the insulating oil composite material.

[0096] Insulating oil-based composite materials and oil-paper composite insulating products were prepared according to the method in Example 1.

[0097] Specifically:

[0098] Preparation of insulating oil: The insulating oil of FR3 plant-based transformer is placed in an oil filter and filtered for 24 hours at a temperature of 65℃ and a vacuum degree of 1kPa to remove impurities and moisture, thus preparing the insulating oil.

[0099] Preparation of oil-paper composite insulation products: Select 2mm polyester fiber reinforced insulating paperboard (fiber diameter 5-10μm, tensile strength ≥150MPa), place the paperboard in a vacuum drying oven and dry at a constant temperature of 105℃ for 24h; under vacuum, impregnate the dried insulating paperboard with insulating oil in an impregnation tank at a temperature of 80℃ for 12h to prepare oil-paper composite insulation products.

[0100] Comparative Example 4

[0101] Comparative Example 4 is basically the same as Example 1, except that "FR3 plant-based transformer insulating oil" is replaced with "Midel 7131 insulating oil".

[0102] Insulating oil-based composite materials and oil-paper composite insulating products were prepared according to the method in Example 1.

[0103] Specifically:

[0104] Preparation of α-linolenic acid grafted and modified nano-inorganic materials: 10g of nickel chloride (NiCl2) was dissolved in 50mL of 60% ethanol aqueous solution to form a homogeneous solution. NaOH was added to adjust the pH to 7, and a hydrolysis reaction was carried out at 30℃ for 60min. The reaction system (sol) was then transferred to a reaction vessel and heated to 55℃ in an oil bath, and stirred continuously for 18h to prepare a gel. After the reaction, the gel was vacuum dried at 60℃ for 24h, and then placed in a tube furnace and calcined at 900℃ for 300min in a nitrogen atmosphere. After cooling, nickel oxide nanosieves were obtained.

[0105] Nickel oxide nanosieves were modified using α-linolenic acid. Specifically, 10g of nickel oxide nanosieves, 20g of α-linolenic acid, and 50mL of n-hexane were mixed and stirred continuously at 65℃ in a magnetic stirrer for 18h to promote the esterification reaction between the carboxyl groups of α-linolenic acid and the hydroxyl groups on the surface of the nickel oxide nanosieves. After the reaction, the mixture was centrifuged at 20℃, 8000rpm, and for 20min. The precipitate was then collected and washed with n-hexane to remove the α-linolenic acid and solvent adhering to its surface. The washed precipitate was then dried in a vacuum desiccator at 30℃ for 24h to obtain α-linolenic acid-grafted modified nano-inorganic material (α-linolenic acid-grafted modified nickel oxide nanosieves).

[0106] Preparation of insulating oil-based composite material: Midel 7131 insulating oil was placed in an oil filter and filtered for 24 hours at 65℃ and 1 kPa to remove impurities and moisture, serving as the base liquid. Then, α-linolenic acid-grafted modified inorganic nanomaterials (modified nickel oxide nanosieves grafted onto the surface of α-linolenic acid) were added to prepare a mixed oil. The mass fractions of α-linolenic acid-grafted modified inorganic nanomaterials in the mixed oil were 0.04%, 0.08%, and 0.12%, respectively. The mixed oil was dispersed at 1400 rpm / min using a high-speed mixer. After high-speed dispersion for 5 hours, vacuum drying was performed to prepare the insulating oil-based composite material.

[0107] Preparation of oil-paper composite insulation products: Select 2mm polyester fiber reinforced insulating paperboard (fiber diameter 5-10μm, tensile strength ≥150MPa), place the paperboard in a vacuum drying oven and dry at 105℃ for 24h; under vacuum, impregnate the dried insulating paperboard with insulating oil-based composite material in an impregnation tank at a temperature of 80℃ for 12h to prepare oil-paper composite insulation products.

[0108] Comparative Example 5

[0109] Comparative Example 5 is basically the same as Example 1, except that: no α-linolenic acid grafted modified nano-inorganic material was added to the insulating oil composite material; and "FR3 plant-type transformer insulating oil" was replaced with "Midel 7131 insulating oil".

[0110] The oil-paper composite insulation product was prepared according to the method in Example 1.

[0111] Specifically:

[0112] Preparation of oil-paper composite insulation products: Place Midel 7131 insulating oil in an oil filter and filter it for 24 hours at a temperature of 65℃ and a vacuum degree of 1kPa to remove impurities and moisture, and set it aside for later use;

[0113] 2mm polyester fiber reinforced insulating paperboard (fiber diameter 5-10μm, tensile strength ≥150MPa) was selected and placed in a vacuum drying oven and dried at 105℃ for 24h. Under vacuum, insulating oil was impregnated into the dried insulating paperboard in an impregnation tank at a temperature of 80℃ for 12h to prepare an oil-paper composite insulating product.

[0114] Experimental Example 1

[0115] use Figure 1 The standardized test system for electrical performance was used to test the surface flashover voltage of the oil-paper composite insulation products prepared in Example 1 and Comparative Examples 1-5. In Example 1, Comparative Examples 1-2 and 4, the prepared insulating oil-based composite material was used as the insulating oil, and the polyester fiber reinforced insulating paperboard was used as the oil-impregnated paperboard. In Comparative Examples 3 and 5, FR3 plant-based transformer insulating oil and Midel 7131 insulating oil were used as the insulating oil, and the polyester fiber reinforced insulating paperboard was used as the oil-impregnated paperboard.

[0116] Figure 1A standardized testing system for verifying the electrical performance of oil-paper composite insulation products was demonstrated. Its core structure includes four functional modules: a high-voltage divider (core measurement unit), a current-limiting protection resistor, a high-frequency noise filtering capacitor, and an insulation sample assembly unit. The high-voltage divider uses a KJF50-500 type device (voltage division ratio 1:50, accuracy ±0.5%), with a 100kV / 5kΩ current-limiting protection resistor in series (suppressing short-circuit current ≤20mA). It collects and converts the voltage signal of the high-voltage electrode (spherical tungsten copper electrode, diameter 10mm) in real time, providing accurate data for flashover determination. A high-frequency noise filtering capacitor (100kV / 400pF, cutoff frequency 80kHz) is connected in parallel between the grounding electrode (flat copper electrode, 50×50mm²) and the ground wire, effectively filtering out switching power supply ripple and partial discharge interference >80kHz, ensuring that the leakage current signal signal-to-noise ratio is >60dB. The insulation sample assembly unit assembles the oil-paper composite insulation products of Example 1 and Comparative Examples 1-5. The insulation sample assembly unit is placed horizontally between the two electrodes (the spacing strictly matches the sample thickness 2mm), and the electrodes cover the central 10×10mm² area to simulate a uniform electric field distribution. The breakdown voltage value is recorded using a display.

[0117] The DC voltage was started at 0 kV and increased in steps of 2 kV / s (1 kV increments) until the leakage current was >5 mA or a discharge channel lasting ≥2 ms appeared. The breakdown voltage value was recorded. Each sample was tested 5 times, and the average of the middle 3 results was taken as the final result. The results are shown in Table 1.

[0118] The results showed that the oil-paper composite insulation product prepared by using α-linolenic acid-grafted nickel oxide nanosieves and FR3 plant-based transformer insulating oil in Example 1 had the best insulation performance. When the amount of α-linolenic acid-grafted modified nano-inorganic material added to the insulating oil-based composite material was 0.12 wt%, its surface flashover voltage was the best, reaching 48.37 kV. Exceeding this amount (such as 0.16 wt%) would lead to an agglomeration effect, and the flashover voltage would drop to 46.69 kV. This indicates that there is a threshold relationship between the dispersibility of α-linolenic acid-grafted modified nano-inorganic material and the amount added.

[0119] Compared with Comparative Example 1, which used nickel oxide nanosieves, Example 1 used nickel oxide nanosieves grafted with α-linolenic acid, which increased the surface flashover voltage to 45.87-48.37 kV, an increase of 3.33-4.09 kV, representing an improvement of 7.62-9.24%. This indicates that the grafting modification of nano-inorganic materials with α-linolenic acid in this application can significantly improve the insulation performance of insulating oil-based composite materials and oil-paper composite insulation products.

[0120] Compared with the modified nickel oxide nanosieve grafted with oleic acid in Comparative Example 2, the nickel oxide nanosieve grafted with α-linolenic acid in Example 1 showed an increase in surface flashover voltage of 2.16-2.38 kV, representing an increase of 4.94-5.45%. This indicates that, compared with grafting modification of nano-inorganic materials using oleic acid, the grafting modification of nano-inorganic materials using α-linolenic acid in this application can significantly improve the insulation performance of insulating oil-based composite materials and oil-paper composite insulation products.

[0121] Comparing Example 1 and Comparative Examples 1-2, it can be seen that the surface flashover voltage of the modified nickel oxide nanosieve grafted with α-linolenic acid is significantly higher than that of the unmodified nanosieve and the modified nickel oxide nanosieve grafted with oleic acid. This proves that the long-chain hydrocarbon groups of α-linolenic acid more effectively inhibit charge accumulation through van der Waals forces. The esterification reaction between the carboxyl groups of α-linolenic acid and the hydroxyl groups on the surface of the nickel oxide nanosieve is crucial for improving dispersibility and interfacial compatibility.

[0122] Compared with Comparative Example 3, which only used FR3 plant-based transformer insulating oil, Example 1 used an insulating oil-based composite material containing α-linolenic acid-grafted modified nickel oxide nanosieves and FR3 plant-based transformer insulating oil, which increased the surface flashover voltage by 5.74-8.24 kV; among them, Example 1 used an insulating oil-based composite material containing 0.12 wt% α-linolenic acid-grafted modified nickel oxide nanosieves, which increased the surface flashover voltage by 20.5%.

[0123] Compared with Comparative Example 4, which used synthetic ester (Midel 7131 insulating oil), Example 1 used ester-based insulating oil (FR3 plant-based transformer insulating oil), which increased the surface flashover voltage by 3.55-3.86 kV; among them, under the condition of using insulating oil-based composite material containing 0.12 wt% α-linolenic acid-grafted modified nickel oxide nanosieve, the surface flashover voltage of Example 1 increased by 7.9%.

[0124] Compared with Comparative Example 5, which only used Midel 7131 insulating oil, Comparative Example 4 used an insulating oil-based composite material containing modified nickel oxide nanosieves grafted with α-linolenic acid and Midel 7131 insulating oil, which increased the surface flashover voltage by 1.21-3.75 kV; among them, the insulating oil-based composite material of Comparative Example 4 containing modified nickel oxide nanosieves grafted with 0.12 wt% α-linolenic acid increased the surface flashover voltage by 9.13%.

[0125] Comparing Example 1 and Comparative Examples 3-5, it can be seen that, compared with the use of halogen-free pentaerythritol ester (Midel 7131 insulating oil), the combination of triglycerides (FR3 plant-based transformer insulating oil) and modified nickel oxide nanosieves grafted with α-linolenic acid exhibits a stronger synergistic effect between the natural ester and the modified nickel oxide nanosieves grafted with α-linolenic acid.

[0126] Table 1. Surface flashover voltages of oil-paper composite insulation products in Example 1 and Comparative Examples 1-5

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[0129] " / " indicates that it was not added.

[0130] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0131] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An insulating oil-based composite material, characterized in that, Including base liquid and α-linolenic acid grafted modified nano-inorganic materials; The base liquid includes ester-based insulating oil, which includes triglycerides.

2. The insulating oil-based composite material according to claim 1, characterized in that, The nano-inorganic materials include nanosieves.

3. The insulating oil-based composite material according to claim 2, characterized in that, The nanosieve includes one or more of nickel oxide nanosieves and alumina nanosieves.

4. The insulating oil-based composite material according to any one of claims 1-3, characterized in that, The mass ratio of the base liquid to the α-linolenic acid-grafted modified nano-inorganic material is 99.84-99.96:0.04-0.

16.

5. The method for preparing the insulating oil-based composite material according to any one of claims 1-4, characterized in that, Includes the following steps: Nano-inorganic materials and α-linolenic acid were dispersed in a solvent and subjected to an esterification reaction to prepare α-linolenic acid grafted and modified nano-inorganic materials. An insulating oil-based composite material was prepared by mixing a base liquid with α-linolenic acid-grafted and modified nano-inorganic materials.

6. The preparation method according to claim 5, characterized in that, The mass ratio of the nano-inorganic material to α-linolenic acid is 1:2-5.

7. The preparation method according to claim 5, characterized in that, The conditions for esterification include: a reaction temperature of 55-75℃ and a reaction time of 12-24h.

8. The preparation method according to claim 5, characterized in that, Nickel oxide nanosieves were prepared by the following method: Nickel hydroxide colloid was prepared by hydrolysis of nickel chloride and sodium hydroxide; the nickel hydroxide colloid was then calcined to prepare the nickel oxide nanosieve.

9. The application of the insulating oil-based composite material according to any one of claims 1-4 or the insulating oil-based composite material prepared by the preparation method according to any one of claims 5-8 in the preparation of oil-paper composite insulation products.

10. A paper-oil composite insulation product, characterized in that, Including insulating paper and insulating oil-based composite materials; The insulating oil-based composite material is the insulating oil-based composite material according to any one of claims 1-4 or the insulating oil-based composite material prepared by the preparation method according to any one of claims 5-8.

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