High-temperature-resistant insulation paper and preparation method thereof

Abstract

The invention discloses high-temperature-resistant insulation paper and a preparation method thereof. The insulation paper comprises reinforced fibers, a heterostructure composite filler and a resin matrix, the heterostructure composite filler is composed of boron nitride nanosheets, surface modified mica powder and silicon dioxide nanowires growing on the surfaces of the boron nitride nanosheets in situ, and the silicon dioxide nanowires extend and are embedded into an interlayer structure of the surface modified mica powder, so that the silicon dioxide nanowires and the surface modified mica powder are connected into a whole; the resin matrix is formed by epoxy group modified organic silicon resin and sulfydryl modified polysiloxane through a synergistic curing process of firstly initiating a click chemical reaction by ultraviolet light and then initiating a condensation polymerization reaction by heat treatment. The preparation method comprises the steps of preparation of the heterostructure composite filler, preparation of a dual-curing resin composition, multi-layer papermaking of gradient slurry, introduction of resin and synergistic curing of ultraviolet light and heat treatment. The insulating paper is especially suitable for being used as an insulating part of electrical equipment under a high-temperature working condition.

Description

Technical Field

[0001] This invention relates to the field of electrical insulation materials technology, specifically to an insulating paper for use under high voltage and high temperature conditions, and particularly to an insulating paper that achieves high temperature resistance through a heterogeneous composite filler and a dual-curing resin system, and its preparation method. Background Technology

[0002] As power equipment develops towards higher voltage, larger capacity, and smaller size, its internal insulation materials face increasingly severe performance challenges. Ideal insulation materials need to possess both excellent high-temperature resistance and high thermal conductivity for rapid heat dissipation during long-term operation. Currently, high-performance insulating papers mostly use special fibers such as aramid as the reinforcing skeleton, and undergo functional modification by introducing inorganic fillers such as alumina, boron nitride, and mica.

[0003] However, existing technologies generally suffer from the following limitations: First, the introduction of high thermal conductivity fillers often contradicts insulation performance. For example, while adding large amounts of boron nitride can improve thermal conductivity, it leads to a significant increase in the dielectric constant of the material, increasing insulation risks. Second, the dispersibility of nanoscale fillers and their interfacial compatibility with the organic resin matrix are prominent issues, easily forming agglomeration defects, which become key weaknesses in charge accumulation, partial discharge, and increased thermal resistance. Third, insulating papers prepared by traditional processes typically exhibit isotropic characteristics with uniform performance, making it difficult to synergistically meet the different spatial requirements of equipment for efficient heat dissipation in the thickness direction and excellent insulation in the in-plane direction within a single material. Finally, conventional thermosetting resin systems suffer from problems such as uneven curing, high internal stress, high process energy consumption, and limited production efficiency when impregnating porous fiber paper webs.

[0004] Therefore, developing a new generation of high-performance insulating paper that can synergistically address the aforementioned contradictions from the perspectives of material design and manufacturing processes, and achieve customizable and anisotropic performance, has become an urgent need and an important direction for technological development in this field. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and solve the technical bottleneck that homogeneous insulating paper cannot simultaneously possess high vertical thermal conductivity, low in-plane dielectric constant, excellent long-term heat resistance, and high mechanical reliability. It provides a solution that achieves a synergistic leap in key performance through structural design and curing process innovation.

[0006] The core technical principles of this invention are reflected in three aspects: filler interface, resin curing mechanism, and product structure.

[0007] A heterogeneous composite filler was constructed, consisting of boron nitride nanosheets, silica nanowires, and surface-modified mica powder. The core of this structure lies in achieving covalent bonding between boron nitride and mica through silica nanowires. Specifically, during the in-situ hydrothermal growth of silica nanowires on the surface of boron nitride nanosheets, strong B(N)-O-Si bonds are formed. These highly active nanowire ends, under high shear force, insert into the interlayer of mica sheets that have undergone acid washing activation and silane coupling agent treatment. The surface of the mica sheets and the pre-intercalated silica nanoparticles are rich in silanol groups (-Si-OH), which undergo condensation reactions with the silanol groups at the ends of the silica nanowires to form stable Si-O-Si bonds, thus microscopically integrating two very different fillers into a single whole. This structure not only significantly reduces the interfacial thermal resistance and contact resistance between the fillers, but also allows the flexible silica nanowires to effectively buffer internal stress caused by the coefficient of thermal expansion, enhancing the structural stability of the composite material under thermal cycling.

[0008] The dual-curing resin is based on a time-controlled dual-curing process of thiol-epoxy click chemistry and silanol condensation. In the first step, under mild UV irradiation, the sulfur-hydrogen bonds (-SH) in the mercapto-modified polysiloxane homolytically cleave to generate sulfur radicals (•SH). These radicals rapidly attack the epoxy rings in the epoxy-modified silicone resin, resulting in efficient, side-reaction-free ring-opening addition to form thioether bonds (-CSC-). This click chemistry reaction is extremely fast, allowing the resin system to gel within minutes, achieving rapid locking of the paper web morphology and filler spatial distribution. In the second step, during subsequent hot pressing, the system temperature rises, activating the secondary hydroxyl groups generated in the first step, as well as the inherent silanol groups (-Si-OH) on the resin and filler surfaces, leading to a dehydration condensation reaction and forming a high-bond-energy silicon-oxygen-silicon (Si-O-Si) three-dimensional network. These two steps—UV curing for rapid shaping and thermosetting for deep cross-linking—result in a resin matrix with excellent process adaptability and superior bulk properties.

[0009] Based on the principle of functionally graded structures, this invention constructs an asymmetric laminated structure along the thickness direction of the insulating paper, consisting of a low-filler-content surface layer, a high-filler-content and oriented intermediate layer, and a low-filler-content bottom layer, following the principle of the difference in heat and electric field transfer paths in insulating components. In operating electrical equipment, heat is mainly conducted along the thickness direction of the insulating material, while strong electric fields are mainly distributed parallel to the surface of the insulating material. Therefore, this invention enriches the intermediate layer with highly thermally conductive heterogeneous composite fillers and uses a directional papermaking process to align the principal planes of the boron nitride nanosheets perpendicular to the paper surface. This constructs an efficient phonon transport channel in the thickness direction, improving vertical thermal conductivity. Simultaneously, maintaining a low-load, randomly distributed filler layer on both the top and bottom surfaces effectively suppresses interfacial polarization, resulting in extremely low and stable in-plane dielectric properties. This spatial performance zoning strategy fundamentally resolves the traditional contradiction between high thermal conductivity and high insulation.

[0010] Based on the above principles, the technical solution provided by this invention is summarized as follows: A high-temperature resistant insulating paper includes reinforcing fibers, a heterogeneous composite filler, and a resin matrix. The heterogeneous composite filler consists of boron nitride nanosheets, surface-modified mica powder, and silica nanowires in situ grown on the surface of the boron nitride nanosheets. The silica nanowires extend and embed into the interlayer structure of the surface-modified mica powder, thereby linking the two into a single unit. The resin matrix is ​​formed by a synergistic curing process of epoxy-modified silicone resin and mercapto-modified polysiloxane, involving a click chemistry reaction initiated by ultraviolet light followed by a condensation polymerization reaction initiated by heat treatment.

[0011] Preferably, the insulating paper has a functionally graded structure along its thickness direction, including an upper surface layer, an intermediate layer, and a lower bottom layer; wherein, the volume content of the heterostructure composite filler in the intermediate layer is higher than that in the upper and lower surface layers, and the boron nitride nanosheets in the intermediate layer are mainly oriented parallel to the thickness direction of the insulating paper.

[0012] This invention also provides a method for preparing the high-temperature resistant insulating paper. For example... Figure 1As shown, the preparation method comprises a four-stage process. The first stage involves the preparation of a heterogeneous composite filler, which involves the in-situ growth of silica nanowires on the surface of boron nitride nanosheets and their high-shear composite with surface-modified mica powder. The second stage involves the formulation of a dual-curing resin composition, which involves uniformly mixing epoxy-modified silicone resin, mercapto-modified polysiloxane, and a photoinitiator. The third stage involves the preparation of gradient slurries, multilayer papermaking, and resin introduction. By preparing at least two slurries with different filler contents, a multilayer papermaking technique is used to sequentially form an upper surface layer, an intermediate layer, and a lower bottom layer, forming a wet paper web with a functional gradient structure. Subsequently, the resin composition is introduced into the fiber network. The fourth stage is synergistic curing, in which the impregnated paper web is sequentially subjected to ultraviolet light irradiation to initiate click chemical pre-curing, and hot pressing to initiate a condensation reaction and complete the final curing. This process systematically integrates material synthesis, structural construction, and reaction curing, ensuring the realization of the final product's performance.

[0013] Furthermore, the present invention also covers electrical equipment that incorporates the high-temperature resistant insulating paper described in any of the above claims as an insulating component.

[0014] Compared with the closest existing technology, the beneficial effects of this invention are mainly reflected in the following aspects: First, through the heterogeneous structural design of the filler and the dual curing mechanism of the resin, a significant synergistic enhancement effect is generated, enabling the material to achieve simultaneous breakthroughs in key properties such as thermal conductivity, insulation, mechanical properties, and heat resistance. Second, the structural design based on functional gradient and orientation control allows for a high degree of customizability of the material properties, enabling precise adaptation to the specific heat dissipation and insulation requirements of different electrical devices. Finally, the adopted preparation process, especially the dual curing strategy, has good production adaptability and controllability, which is conducive to the stable and efficient preparation of high-quality products. Attached Figure Description

[0015] Figure 1 This is a complete flowchart of the high-temperature resistant insulating paper preparation process of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and process flow diagrams. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. The performance tests involved in this invention all adopt the following general standards: thermal conductivity in the thickness direction is determined according to ASTM D5470 standard using the heat flow method at a test temperature of 50°C; in-plane dielectric constant and loss factor are determined according to ASTM D150 standard using an impedance analyzer and a three-electrode system at 23°C and a frequency of 1MHz; power frequency breakdown strength is tested according to IEC 60243-1 standard using the continuous voltage increase method in insulating oil; tensile strength is tested according to ASTM D828 standard. Example

[0017] This embodiment details the preparation of a high-temperature resistant insulating paper with high vertical thermal conductivity, and its process steps are similar to those of... Figure 1 The process shown is completely consistent.

[0018] First, execute Figure 1 The first stage involves the preparation of a heterogeneous composite filler. 20 grams of boron nitride nanosheets with an average lateral size of approximately 5 micrometers were weighed and dispersed in a mixed solvent of ethanol and deionized water. After ultrasonic treatment, tetraethyl orthosilicate was added as a silicon source, and a hydrothermal reaction was carried out at 65°C for 8 hours under ammonia catalysis. After the reaction, the mixture was centrifuged, washed, and dried to obtain an intermediate BNNS@SiO2 with uniformly grown silica nanowires on its surface. Separately, 30 grams of synthesized fluorophlogopite powder was activated by acid washing with 1M hydrochloric acid solution at 60°C for 4 hours, followed by washing until neutral. The activated mica powder was dispersed in acetone, and the surface was modified by adding the silane coupling agent γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560). Subsequently, nano-silica sol was introduced for interlayer intercalation, and after drying, modified mica powder Mica-SiO2 was obtained. Finally, the BNNS@SiO2 intermediate was mixed with Mica-SiO2 at a mass ratio of 1:2 and placed in an aqueous solution containing a dispersant. The mixture was then subjected to high-shear composite treatment at 10,000 rpm for 3 hours in a high-speed homogenizer to embed the ends of the silica nanowires into the mica layers. The final heterostructure composite filler HTF-1 was obtained by spray drying.

[0019] Secondly, execution Figure 1 In the second stage, a dual-curing resin composition was prepared. Under light-protected conditions, 100 parts by weight of epoxy-modified silicone resin, 35 parts by weight of mercapto-modified polysiloxane, and 3 parts by weight of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone were placed in a container and mechanically stirred until uniformly mixed to obtain resin composition RC-1.

[0020] Next, execute Figure 1 The third stage involves gradient papermaking and resin introduction. A surface slurry of 0.1 wt% para-aramid precipitated fibers is prepared, with HTF-1 filler added at 8% of the oven-dry fiber mass and thoroughly dispersed. An intermediate slurry of 0.08 wt% para-aramid chopped fibers and precipitated fibers is prepared, with HTF-1 filler added at 35% of the oven-dry fiber mass. By precisely controlling the flow rate of the intermediate slurry and the negative pressure during the initial dewatering stage, a directional dewatering environment is created, inducing the sheet-like filler to align perpendicular to the paper surface. Subsequently, a three-layer inclined wire papermaking machine is used to sequentially form a bottom surface basis weight of 15 g / m², an intermediate layer basis weight of 50 g / m², and a top surface basis weight of 15 g / m², resulting in a wet paper web with a total basis weight of 80 g / m².

[0021] Then, execute Figure 1 The fourth stage is co-curing. The impregnated paper web is first passed through a nitrogen-protected UV curing chamber and irradiated for 5 minutes under UV light with a wavelength of 365nm and an irradiance of 80mW / cm², completing the first step of photocuring and shaping. Subsequently, the pre-cured paper blank is transferred to a hot press, where a segmented heating program is used. The temperature is increased to 120℃ at a rate of 5℃ / min and held for 2 minutes, then further increased to 195℃ and held under pressure at 8MPa for 20 minutes, completing the second step of thermal curing and drying, ultimately producing the insulating paper sample S1. Example

[0022] This embodiment describes a method for preparing insulating paper that achieves a better balance between overall performance and cost, and the steps follow... Figure 1 The general process is followed, but adjustments are made to key parameters.

[0023] The preparation method of the heterostructure composite filler HTF-2 is similar to that of Example 1, but the mass ratio of BNNS@SiO2 intermediate to Mica-SiO2 is adjusted to 1:3, and the high-shear composite time is shortened to 2 hours to obtain a higher mica ratio and a more economical cost. In the preparation of the dual-curing resin composition RC-2, the amount of mercapto-modified polysiloxane is adjusted to 30 parts by weight, and the rest is the same as in Example 1. In the gradient slurry preparation, the amount of HTF-2 filler added to the surface slurry is 5% of the oven-dry fiber, and the amount of filler added to the intermediate slurry is adjusted to 25%. When forming the intermediate layer, the web flow rate is increased to 0.9 m / s, and the initial dehydration negative pressure is -8 kPa. The forming and lamination process is the same as in Example 1. After resin impregnation, the UV curing conditions are adjusted to wavelength 385 nm, irradiance 60 mW / cm², irradiation for 8 minutes, and the hot pressing conditions are adjusted to 190°C, 6 MPa, and holding pressure for 25 minutes. The final resin content was controlled at 40%, and insulating paper sample S2 was obtained.

[0024] Comparative Example 1 This comparative example represents a common existing technology that uses physically mixed fillers versus a conventional one-step thermosetting process. First, the physically mixed filler was prepared. Approximately 6.7 grams of ordinary boron nitride nanosheets and approximately 13.3 grams of ordinary mica powder, equal in mass to those contained in the HTF-1 filler in Example 1, were weighed. The ordinary boron nitride nanosheets and ordinary mica powder were not subjected to any surface modification, in-situ growth, or high-shear composite treatment. Both were directly added to an aqueous solution containing a dispersant and mechanically stirred at 2000 rpm for 1 hour to achieve initial dispersion and mixing. Subsequently, they were dried and ground to obtain the physically mixed filler PM-1.

[0025] Next, a conventional thermosetting resin composition was prepared. 100 parts by weight of the same epoxy-modified silicone resin as in Example 1 were taken, and 28 parts by weight of methylhexahydrophthalic anhydride were added as a curing agent and 0.5 parts by weight of 2-ethyl-4-methylimidazolium as an accelerator. The mixture was then mixed evenly to obtain resin composition TC-1.

[0026] Next, homogenized pulp was prepared. Only one type of pulp was prepared, with the same fiber type, ratio, and concentration as the intermediate layer pulp in Example 1, and PM-1 physical filler equivalent to 35% of the oven-dry fiber mass was added. The same paper machine was used to produce a homogenized wet paper web with a basis weight of 80 g / m² at a conventional flow rate.

[0027] Next, resin impregnation and one-step thermosetting were performed. The wet paper web was impregnated in an acetone solution of TC-1 resin with a solid content of 50%, controlling the resin content to be similar to that in Example 1. After impregnation, the paper blank was placed directly in a hot press, and the temperature was increased from room temperature to 195°C at a rate of 10°C / min, and then held at 8 MPa for 20 minutes to complete the curing. In the early stage of heating, a small amount of low-viscosity resin could be observed to seep out from the edge of the paper web. The final homogeneous insulating paper sample D1 was obtained.

[0028] Comparative Example 2 This comparative example uses the heterogeneous composite filler HTF-1 and dual-curing resin composition RC-1 prepared in Example 1. However, during the papermaking stage, only one type of pulp is prepared, with the same formulation as the intermediate layer pulp in Example 1. The same paper machine is used, and the papermaking process is carried out at the same low speed and low dewatering pressure as the intermediate layer in Example 1 to induce vertical orientation of the filler. The final papermaking results in a single-structure wet paper web with a basis weight of 80 g / m² and uniform overall filler distribution.

[0029] The subsequent resin impregnation, UV curing, and hot-pressing curing process parameters were exactly the same as in Example 1. The resulting insulating paper sample D2 had a homogeneous structure with uniformly distributed fillers and a high degree of vertical orientation.

[0030] Comparative Example 3 The formulations of fillers, resins, and three-layer slurry in this comparative example are strictly consistent with those in Example 1. During fabrication, a three-layer mesh process is also used to sequentially form the upper, middle, and lower layers, creating the same quantitative gradient structure as in Example 1.

[0031] The key difference lies in the intermediate layer fabrication process. To prevent filler orientation, the flow rate of the intermediate layer slurry is significantly increased to 2.0 m / s, and the negative pressure of the first vacuum dewatering tank is simultaneously increased to -15 kPa, causing the slurry to undergo rapid dewatering at the mesh. This high-speed, high-shear-force condition prevents the sheet-like fillers from arranging themselves in an orderly manner before they are quickly fixed, thus losing the opportunity for vertical orientation. The fabrication processes for the upper and lower surface layers are the same as in Example 1.

[0032] The subsequent resin impregnation and double curing process parameters were completely consistent with those in Example 1. Insulating paper sample D3 with a gradient structure but randomly arranged intermediate layer fillers was obtained.

[0033] Comparative Example 4 The preparation of the heterogeneous composite filler, the formulation of the three-layer gradient slurry, and the papermaking process of this comparative example are exactly the same as those in Example 1, ensuring the formation of a wet paper web structure with the same filler content gradient and high orientation of the intermediate layer.

[0034] The key difference lies in the resin system and curing process; this comparative example uses a single thermosetting resin system. The resin composition consists of 100 parts by weight of epoxy-modified silicone resin, 28 parts by weight of methylhexahydrophthalic anhydride, and 0.5 parts by weight of 2-ethyl-4-methylimidazolium. Thiol-modified polysiloxanes and photoinitiators are not used.

[0035] After impregnation with the resin composition, no UV pre-curing step was performed. The impregnated wet paper blank was directly fed into a hot press for one-step thermosetting, with the temperature increased from room temperature to 195°C at a rate of 5°C / min, and held at 8 MPa for 30 minutes. In the early stage of hot pressing, slight lateral deformation of the paper web was observed under pressure, and microscopic examination revealed slight disturbances in the arrangement of fillers in local areas compared to the post-papermaking state. Sample D4 was finally obtained.

[0036] Systematic tests were conducted on each embodiment and comparative sample, and the results are summarized in Table 1 below, a comparison table of insulating paper performance. Based on the data in Table 1 and the details of the comparative examples, a comparative analysis is conducted: Compared to Example S1, Comparative Example D1 significantly lagged behind in all key performance indicators. Its thermal conductivity of 0.53 confirmed that the physically mixed filler could not construct an effective thermal conduction path due to the huge interfacial thermal resistance; the dielectric constant of 3.88 and losses were due to uneven filler dispersion and severe interfacial polarization; its lower breakdown and tensile strengths reflected the weak bond between the filler and resin interface.

[0037] Compared to Example S1, Comparative Example D2 uses heterogeneous fillers and double curing. While its vertical thermal conductivity of 0.76 is acceptable, its in-plane dielectric constant of 3.70 is significantly lower, approaching the level of D1. This is because the high filler content is uniformly distributed throughout the material. Although the overall orientation is beneficial for vertical thermal conductivity, it also results in a large amount of high-dielectric-polarized filler in any direction, making it impossible to achieve a low-dielectric insulating surface. This verifies the indispensable role of the functionally graded structure in decoupling the contradictory relationship between high vertical thermal conductivity and low in-plane dielectric constant.

[0038] Comparative Example D3 and Example S1 have the same gradient structure and filler as Example S1, except for the orientation of the intermediate layer filler. D3 exhibits a significantly lower thermal conductivity of 0.71, but its dielectric properties are similar. This verifies that within the gradient structure framework, the vertical orientation of the intermediate layer filler is the key controlling factor for maximizing thermal conductivity in the thickness direction.

[0039] Comparative Example D4 and Example S1: D4 has almost the same composition and gradient structure as S1, differing only in the curing process. Its thermal conductivity and dielectric properties are similar to S1, but its breakdown strength and tensile strength are significantly lower. This indicates that the lack of a UV pre-curing step prevents the precise orientation of the fiber and filler structure from being fixed during the initial hot-pressing stage when the resin has maximum fluidity. This may lead to slight disturbances or defects in the microstructure, thereby compromising the final mechanical and electrical strength. This validates the importance of a dual-curing process.

[0040] In summary, the present invention, through the following... Figure 1 The systematic preparation process shown synergistically innovates the heterogeneous composite filler, dual-curing resin system, and functionally graded structure to successfully prepare high-temperature resistant insulating paper with excellent comprehensive performance. Those skilled in the art can make various modifications, equivalent substitutions, or improvements within the spirit and principles of this invention, all of which fall within the protection scope of this invention.

Claims

1. A high-temperature resistant insulating paper, comprising reinforcing fibers, fillers, and a resin matrix, characterized in that: The filler is a heterogeneous composite filler, which consists of boron nitride nanosheets, surface-modified mica powder, and silica nanowires grown in situ on the surface of the boron nitride nanosheets. The silica nanowires extend and embed into the interlayer structure of the surface-modified mica powder, thereby connecting the boron nitride nanosheets and the surface-modified mica powder into a whole. The resin matrix is ​​formed by the synergistic curing of epoxy-modified silicone resin and mercapto-modified polysiloxane. The synergistic curing includes first initiating a click chemical reaction between the mercapto groups of the mercapto-modified polysiloxane and the epoxy groups of the epoxy-modified silicone resin by ultraviolet light, and then initiating a polycondensation reaction by heat treatment, ultimately forming a crosslinked network.

2. The high-temperature resistant insulating paper according to claim 1, characterized in that, The insulating paper has a functionally graded structure along its thickness, including an upper surface layer, an intermediate layer, and a lower bottom layer; wherein, the volume content of the heterostructure composite filler in the intermediate layer is higher than that in the upper surface layer and the lower bottom layer, and the plane orientation of the boron nitride nanosheets in the intermediate layer is mainly parallel to the thickness direction of the insulating paper.

3. The high-temperature resistant insulating paper according to claim 2, characterized in that, The thermal conductivity of the intermediate layer in the thickness direction is not less than 0.8 W / (m·K); the dielectric constant of the upper surface layer and the lower bottom layer in the direction parallel to the paper plane is between 3.0 and 3.

5.

4. The high-temperature resistant insulating paper according to claim 1, characterized in that, The surface-modified mica powder is a mica powder that has been acid-washed and reacted with a silane coupling agent, and has nano-silica particles intercalated between its layers.

5. A method for preparing the high-temperature resistant insulating paper as described in any one of claims 1-4, characterized in that, Includes the following steps: A heterogeneous composite filler was prepared by in-situ growing silica nanowires on the surface of boron nitride nanosheets to obtain the first intermediate. The first intermediate and surface-modified mica powder are compounded in a liquid medium under high shear force, so that the silica nanowires are embedded in the interlayer of the surface-modified mica powder to form the heterostructure composite filler. A dual-curing resin composition was prepared by mixing an epoxy-modified silicone resin, a mercapto-modified polysiloxane, and a photoinitiator. Slurry preparation, papermaking and resin introduction: The reinforcing fibers, the heterogeneous composite filler and dispersant obtained in step (1) are prepared into a slurry, which is then formed into a wet paper web by papermaking, and the double-curing resin composition obtained in step (2) is introduced into the fiber system of the wet paper web; Synergistic curing involves first subjecting the wet paper web after resin introduction to ultraviolet light irradiation, causing the mercapto groups in the mercapto-modified polysiloxane to undergo a click chemical reaction with the epoxy groups in the epoxy-modified organosilicon resin; subsequently, hot pressing is performed to cause the resin system to undergo a condensation reaction and complete curing, resulting in the high-temperature resistant insulating paper.

6. The method according to claim 5, characterized in that, In step (3), the slurry is prepared into at least two slurries with different fiber ratios and different contents of heterogeneous composite fillers, and is formed sequentially by a multi-layer papermaking process to form the functional gradient structure as described in claim 2 or 3.

7. The method according to claim 6, characterized in that, During the fabrication of the intermediate layer slurry, by controlling the slurry flow rate, concentration, and dehydration rate, the boron nitride nanosheets in the heterostructure composite filler are oriented along the thickness direction.

8. The method according to claim 5, characterized in that, In step (4), the wavelength of the ultraviolet light irradiation is 355-375 nm and the irradiation time is 5-15 minutes; the temperature of the hot pressing treatment is 180-210℃, the pressure is 5-10MPa, and the treatment time is 10-20 minutes.

9. An electrical device, characterized in that, It comprises high-temperature resistant insulating paper as described in any one of claims 1-4 as an insulating component.

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