High-performance aramid fiber composite insulation paper-based material as well as preparation method and application thereof

Abstract

The invention discloses a high-performance aramid fiber composite insulation paper-based material as well as a preparation method and application thereof. The method comprises the following steps: carrying out micro-nano treatment on aramid fibers to obtain aramid micro-nano fibers with high specific surface area and high length-diameter ratio, and improving the dispersity and surface activity of the aramid micro-nano fibers; plant cellulose nanofibrils and bacterial cellulose which are oxidized and modified by tetramethylpiperidine oxide or sodium periodate are introduced, and surface carboxyl or aldehyde functional groups of the plant cellulose nanofibrils and the bacterial cellulose are utilized to realize interface reaction and hydrogen-bond interaction with an aramid fiber component; a compact and stable three-dimensional network structure is formed, so that the mechanical property and the insulating property of the composite paper are further enhanced. According to the high-performance aramid insulation paper, the tensile strength and the structural stability of paper sheets are improved on the basis of keeping excellent heat resistance and electrical insulation performance of an aramid material; meanwhile, by introducing a renewable and low-cost nano-crystalline cellulose reinforcing component, the material cost is effectively reduced, the technological process is green and environment-friendly, and good continuous and large-scale manufacturing potential is achieved.

Description

Technical Field

[0001] The present invention belongs to the intersection field of papermaking industry and polymer materials, and specifically relates to a high-performance aramid composite insulating paper-based material and a preparation method and application thereof. Background Art

[0002] With the continuous pursuit of electrical system safety and operational efficiency in fields such as intelligent manufacturing, new energy, high-end power equipment, rail transportation, and aerospace, high-performance insulation materials, as one of the key basic materials, are facing higher requirements for their technological development. Under extreme working conditions such as high frequency, high voltage, high temperature, and strong electromagnetic environment, traditional paper-based insulation materials have obvious shortcomings in heat resistance, structural stability, electrical breakdown threshold, insulation retention rate, and long-term service reliability. At the same time, the new generation of electrical equipment has also posed significant challenges to the miniaturization, lightweighting, and composite nature of insulation systems. Insulation materials are required to maintain high electrical safety performance while also having excellent mechanical strength and dimensional stability to withstand mechanical vibration, electrothermal shock, and the multiple stress coupling caused by long-term operation. Therefore, how to design a high-performance insulating paper structure that combines thermal stability, dielectric strength, and mechanical toughness has become a core scientific and engineering issue to promote the safe and efficient operation of high-end electrical equipment and ensure the long-term reliability of key components.

[0003] Aramid insulation paper is a high-temperature, heat-resistant paper-based material widely used in the electrical industry. It is primarily made by wet-making a mixture of aramid fibrids and aramid chopped fibers in a specific ratio, followed by high-temperature calendering to form the final product. The aramid polymer chain segments are rich in benzene rings and highly polar amide bonds, resulting in extremely high thermal decomposition temperatures, excellent insulation resistance, and flame retardant stability. This makes it widely used in insulation systems with heat resistance grades F, H, and even higher. However, the highly crystalline structure and rigid molecular chains of aramid fibers result in significant surface chemical inertness, a scarcity of binding sites, and poor hydrophilicity. This makes it difficult for traditional chopped fibers to establish strong interfacial bonding with the fibrids during the papermaking process. This results in limited overall web formation and loose interfiber bonding, ultimately resulting in insufficient tensile strength and low electrical breakdown field strength, hindering the full realization of the inherent performance advantages of aramid materials. Therefore, effectively manipulating the fiber structure of aramid paper, enhancing interfacial bonding, and reducing costs have become a hot topic of research in recent years. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the primary purpose of the present invention is to provide a high-performance aramid composite insulation paper-based material;

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned high-performance aramid composite insulating paper-based material;

[0006] Another object of the present invention is to provide an application of the above-mentioned high-performance aramid composite insulation paper-based material.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for preparing a high-performance aramid composite insulating paper-based material comprises the following steps:

[0009] (1) Micro-nanostructural processing of aramid fibers: Aramid fibers are micro-nanostructurally processed to obtain aramid micro-nano fibers with diameters ranging from tens to hundreds of nanometers and lengths in the micrometer range. The purpose of step (1) is to increase the specific surface area and surface active sites of the aramid fibers through micro-nanostructural processing, thereby improving the specific surface area and surface free energy.

[0010] (2) Surface modification of plant cellulose nanofibrils and bacterial cellulose: TEMPO free radical oxidation or sodium periodate oxidation were used to oxidatively modify the surfaces of plant cellulose nanofibrils (CNF) and bacterial cellulose (BC), respectively, to introduce active functional groups such as carboxyl or aldehyde groups to enhance the interfacial bonding performance with aramid fibers. After modification, the fibers maintained good dispersion and three-dimensional network structure, and could form hydrogen bonds or covalent bonds with the aramid main chain to form a dense structural skeleton. The modified CNF and BC were able to form hydrogen bonds and covalent cross-linking structures with the aramid fiber surface in the composite system.

[0011] (3) Wet papermaking and hot pressing: The aramid micro-nanofibers obtained in step (1), the modified plant cellulose nanofibrils prepared in step (2), the modified bacterial cellulose and the aramid precipitated fibers are compounded in proportion to construct a composite system to obtain a uniformly dispersed multi-component fiber suspension slurry; the slurry obtained by the reaction is then diluted to a certain concentration, wet-papered to obtain aramid wet paper sheets, and then wet-hot forming is performed to finally prepare a high-performance aramid composite insulating paper-based material.

[0012] Preferably, the type of the aramid fiber in step (1) may be at least one of a wholly aromatic polyamide fiber or a heterocyclic aromatic polyamide fiber; the aramid fiber is a short fiber or a filament; the aramid fiber is pretreated with dimethyl sulfoxide / alkali, pretreated with alkali solution, or mechanically treated without treatment.

[0013] More preferably, for the dimethyl sulfoxide / alkali pretreatment, the aramid fiber is chemically swollen in the dimethyl sulfoxide / alkali system for 0.1-10 h at a temperature of 0-80° C.; the alkali is at least one of sodium hydroxide, potassium hydroxide, potassium tert-butoxide, or sodium carbonate, and the alkali concentration in the dimethyl sulfoxide / alkali system is 0.1 mol / L-10 mol / L, preferably 0.5 mol / L; the ratio of aramid fiber mass (g): dimethyl sulfoxide / alkali system volume (mL) is 1:30-50.

[0014] More preferably, for the alkali solution pretreatment, the aramid fiber is treated in the alkali solution for 2-20 hours, the temperature is 0-80°C, the alkali is at least one of sodium hydroxide, potassium hydroxide, potassium tert-butoxide or sodium carbonate, the alkali solution concentration is 0.5 mol / L-20 mol / L, preferably 2 mol / L; aramid fiber mass (g): alkali solution volume (mL) = 1:30-50.

[0015] Preferably, the mechanical treatment method in step (1) is at least one of ultrasonic treatment, ultrafine ball milling treatment, high-speed shear treatment, etc.; the aramid fiber pulp concentration in the mechanical treatment is 0.1-2%, the treatment temperature is 25-80°C, and the treatment time is 0.1-10h; more preferably, the aramid fiber pulp concentration is 1%, the treatment temperature is 30°C, and the treatment time is 6h.

[0016] Preferably, a dispersant is further added during the mechanical treatment in step (1), wherein the dispersant is at least one of polyethylene oxide (PEO), sodium fatty alcohol polyoxyethylene ether sulfate (AES), polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP), or sodium dodecylbenzene sulfonate (SDBS), and the amount of the dispersant added is 0.1-2% of the absolute dry mass of the aramid fiber. More preferably, the dispersant is polyvinyl pyrrolidone (PVP), and the amount added is 0.5% of the absolute dry mass of the aramid fiber.

[0017] Preferably, the plant cellulose nanofibrils described in step (2) are nanoscale derivatives of cellulose with an aspect ratio greater than 500; the bacterial cellulose is a nanoscale natural polymer material produced by fermentation of specific microorganisms (such as Acetobacter xylinum) with an aspect ratio greater than 500.

[0018] Preferably, the TEMPO free radical oxidation modification in step (2) adopts a ternary system of 2,2,6,6-tetramethylpiperidinyl oxide / potassium bromide / sodium hypochlorite (TEMPO / NaBr / NaClO), wherein the mass ratio of TEMPO to plant cellulose nanofibrils or bacterial cellulose is 1:(0.1-100), the pH of the reaction system is 7-11, the reaction temperature of the aldehyde modification is 0-80°C, and the reaction time is 0.1-24h. More preferably, the mass ratio of plant cellulose nanofibrils to the oxidant in the TEMPO free radical oxidation modification is 50:1, the reaction temperature is 30°C, the reaction time is 4h, and the pH of the reaction system is 10.5;

[0019] In the sodium periodate oxidation modification method described in step (2), the oxidant is sodium periodate (NaIO4), the mass ratio of plant cellulose nanofibrils or bacterial cellulose to NaIO4 in the reaction system is (0.1-100):1, the reaction temperature is 0-60°C, the reaction time is 0.5-12 hours, and the pH is maintained between 4-7. The reaction process needs to be kept away from light to prevent NaIO4 from photodegradation. More preferably, the mass ratio of plant cellulose nanofibrils or bacterial cellulose to NaIO4 in the reaction system is 1:1.5, the reaction temperature is 25°C, the pH is 5.0, and the reaction time is 6 hours.

[0020] Preferably, in step (3), the ratio of the mass of the aramid micro-nano fibers to the sum of the masses of the modified plant cellulose nanofibrils and the modified bacterial cellulose is 0.01-100%, the mass ratio of the modified plant cellulose nanofibrils to the modified bacterial cellulose is 0.00-100%, and the mass ratio of the sum of the masses of the aramid micro-nano fibers, modified plant cellulose nanofibrils and modified bacterial cellulose to the aramid precipitated fibers is 2:8-8:2.

[0021] In a more preferred embodiment, the ratio of the mass of aramid micro-nanofibers to the sum of the masses of modified plant cellulose nanofibrils and modified bacterial cellulose is (0.05-20):1 (more preferably 1:1), the mass ratio of modified plant cellulose nanofibrils to modified bacterial cellulose is (0.5-5):1 (more preferably 1-3:1), and the mass ratio of aramid micro-nanofibers / nanofibers to aramid precipitated fibers is 1:1.

[0022] Preferably, the slurry concentration during wet papermaking in step (3) is 0.01-5%, the thermoforming temperature is 100-290°C, and the pressure is 0.01-25.0 MPa; in a more preferred embodiment, the slurry concentration during wet papermaking is 0.05%, the thermoforming temperature is 260°C, and the pressure is 8 MPa.

[0023] The above-mentioned high-performance aramid composite insulation paper-based material combines the high thermal stability of aramid and the high strength characteristics of the cellulose reinforced network. It can be used in many fields such as high-voltage motors, power transformers, cables and other high-temperature insulation scenarios.

[0024] The present invention has the following advantages and effects compared to the prior art:

[0025] The high-performance aramid composite insulating paper-based material of the present invention is subjected to micro-nanostructure control treatment on aramid fibers, and mechanical cracking is combined under different chemical pretreatment systems (such as DMSO / KOH swelling system and alkali solution relaxation system) to form highly dispersed micro-nanoscale aramid fibers. The micro-nano aramid fibers are submicron to nanoscale in size, and while maintaining the original heat resistance of aramid, the specific surface area and interfacial activity are significantly improved. In this way, micro-nano fiber units with a reinforcing effect are introduced into the interior of the aramid paper, so that they can not only form a synergistic skeleton with the precipitated fibers, but also establish an interface connection channel with modified nanocellulose as a cross-linked reinforcement bridge, achieving the dual effect of inter-fiber structural mosaic and network stability enhancement. The micro-nano treatment method transforms the surface of the aramid fiber from smooth to a multi-scale rough structure, and has controllable physical bendability and good water-phase dispersion performance, thereby significantly improving its adaptability in the wet papermaking system, significantly enhancing the spatial coordination effect of the aramid fiber in the paper-based system, and effectively improving the mechanical properties and electrical breakdown strength of the paper sheet.

[0026] Plant cellulose nanofibrils and bacterial cellulose are emerging green nanomaterials, which are further endowed with interfacial activity and cross-linking ability through surface modification in the present invention. By carboxylating or aldehyde-forming CNF and BC, reactive functional groups are constructed on their surfaces, so that this type of nanomaterial not only has network enhancement function in the aramid papermaking system, but also can serve as a chemical reaction bridge to form a stable structural synergistic interface with aramid micro-nanofibers. Through this type of modification, cellulose nanomaterials obtain the chemical basis required for interaction with aramid materials. The interface action form constructed includes not only hydrogen bond connection, but also forms chemical bond cross-linking under certain conditions, thereby enhancing the network connection strength between fibers. Cellulose nanofibrils have good dispersibility, film-forming properties and spatial support capabilities. They can be interwoven with aramid micro-nanofibers through physical entanglement in the wet papermaking stage to construct a three-dimensional multi-scale support structure, thereby improving the consistency and impact resistance of the internal structure of the paper sheet. Through activation modification treatment, plant cellulose nanofibrils are transformed from inert reinforcing components into active building units, which not only improves the mechanical stability and internal structural tightness of the composite paper base, but also reduces the production cost of existing aramid composite insulation paper base materials, and has huge market prospects and economic value.

[0027] In summary, the present invention significantly improves the overall performance of aramid composite paper-based materials by constructing a synergistically reinforced structural network composed of aramid micro-nano fibers and modified plant cellulose nanofibrils, and enhances the structural integration and interface synergy between the fibers inside the material. With the help of temperature, pressure and other parameter control in the wet papermaking and hot pressing molding processes, the multi-component fiber network is effectively fixed during the papermaking process, the paper sheet structure is dense, and the interlayer bonding is uniform and stable. In terms of process path, the present invention adopts an in-situ blending and compounding strategy of multi-scale reinforcing components, which has good industrial compatibility and process safety, can be seamlessly connected with existing aramid paper production equipment and papermaking processes, and is conducive to large-scale continuous production. In terms of performance structure, the present invention significantly improves the deficiencies of aramid paper in mechanical properties, electrical insulation properties, etc. through the triple path of structural activation, interface optimization and process integration, and expands its application prospects in high-performance insulation systems, special electrical materials and thermoelectric composite structures. The present invention achieves performance improvement while reducing manufacturing costs, and has outstanding technological advancement and broad market application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the SEM image of the precipitated fibers.

[0029] Figure 2 This is the SEM image of bacterial cellulose.

[0030] Figure 3 This is an SEM image of the aramid composite insulation paper-based material prepared in Example 1. DETAILED DESCRIPTION

[0031] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0032] The starting materials in the preparation method of the present invention can be purchased commercially or prepared according to existing methods. The aramid chopped fibers used in the examples and comparative examples are para-aramid fibers with a diameter of 12-14 μm and a length of 6 mm; the fibrids are meta-fibrids, but the method is not limited to this. Plant cellulose nanofibrils are prepared according to the method described in Chinese Patent No. ZL201711338054.9, with a diameter of 1-50 nm, a length greater than 1 μm, and an aspect ratio greater than 500, but the method is not limited to this. Tensile strength index and electrical breakdown resistance tests are conducted in accordance with GB / T12914-2008 and GB / T1913.1-2005.

[0033] Example 1

[0034] A high-performance aramid composite insulating paper-based material, the preparation method of which is as follows:

[0035] (1) Micro-nano treatment of aramid fibers: Aramid chopped fibers were placed in a 2 mol / L sodium hydroxide (NaOH) solution, wherein the ratio of aramid fiber to NaOH solution was mass (g): volume (mL) = 1:50. The reaction temperature was 20°C and the reaction time was 4 h. The aramid fibers after the reaction were ultrasonically treated for 10 min at an ultrasonic power of 800 W and a temperature of 25°C. Subsequently, high-speed shear treatment was performed at a processing power of 3000 W for 6 h. After the reaction, the fibers were washed with deionized water five times until neutral, filtered, and the prepared aramid micro-nano fibers were collected for later use.

[0036] (2) Surface modification of plant cellulose nanofibrils and bacterial cellulose: 1 L of plant cellulose nanofibrils (solid content 1.0%) was slowly added with 15 g of solid NaIO4 under stirring in a high-speed stirrer. The mass ratio of plant cellulose nanofibrils to sodium periodate (NaIO4) was 1:1.5. The mixture was reacted for 12 h at room temperature in the dark to introduce aldehyde groups to form the surface of the plant cellulose nanofibrils. After the reaction, ethylene glycol was added to terminate the oxidation. The modified plant cellulose nanofibrils were collected by centrifugation at 8000 rpm for 20 min and washed with deionized water. This was repeated three times to remove by-products to obtain formaldehyde-modified plant cellulose nanofibrils (modified CNF) for later use.

[0037] 100g of purified bacterial cellulose (90% moisture content) was added to 200mL of deionized water and stirred to form a uniform suspension. 0.2g of 2,2,6,6-tetramethylpiperidinyl oxide (TEMPO) and 1.25g of potassium bromide (NaBr) were then added dropwise. 75mL of a 5% sodium hypochlorite (NaClO) solution was then slowly added dropwise. The mixture was stirred at room temperature for 8 hours to induce TEMPO-mediated selective oxidation of the bacterial cellulose. The pH of the solution was maintained at 10-11 (adjusted with 0.5M NaOH solution) during the reaction. After completion of the reaction, the slurry was adjusted to neutral with 0.1M hydrochloric acid (HCl), washed thoroughly with water five times, and centrifuged to obtain a modified bacterial cellulose slurry for later use.

[0038] (3) Papermaking and hot pressing: 0.89 g of the aramid micro-nano fibers obtained in step (1) above were dispersed in 2 L of deionized water, 0.94 g of aramid fibrils were added, and the mixture was deflaked using a fiber deflaking machine to form a uniform slurry; then 0.024 g of the modified plant cellulose nanofibrils obtained in step (2) and 0.024 g of the modified bacterial cellulose obtained in step (2) were added, and the mass proportions of aramid fibrils, aramid micro-nano fibers, modified plant cellulose nanofibrils, and modified bacterial cellulose in the composite slurry were 50%, 47.4%, 1.3%, and 1.3%, respectively. The mixed slurry was deflaked using a fiber deflaking machine for 20,000 revolutions. The wet paper web was made using an automatic sheeter, and the weight was controlled to be 60 g / m2 The wet paper web was squeezed and dehydrated at 25°C and 0.5 MPa pressure for 3 minutes, and then directly thermoformed (i.e., wet-sheet aramid sheets were obtained by wet papermaking and then dried and formed) at a temperature of 200°C, a pressure of 10 MPa, and a time of 20 minutes to finally prepare a high-performance aramid composite insulation paper-based material.

[0039] The performance tests of the prepared high-performance aramid composite insulation paper-based material showed that the tensile strength index and the power frequency breakdown field strength under a vertical electric field at room temperature were 22.5 N·m / g and 25 kV / mm, respectively.

[0040] Example 2

[0041] A high-performance aramid composite insulating paper-based material, the preparation method of which is as follows:

[0042] (1) Micro-nano-processing of aramid fibers: Aramid chopped fibers were placed in a 3 mol / L potassium hydroxide (KOH) solution, wherein the ratio of aramid fiber to KOH solution was 1:50 (mass (g): volume (mL). The reaction temperature was 20°C and the reaction time was 6 h. The aramid fibers after the reaction were ultrasonically treated for 10 min at an ultrasonic power of 800 W and a temperature of 25°C. Subsequently, ultrafine grinding was performed 15 times. After the reaction, the fibers were washed with deionized water 5 times until neutral, and filtered to collect the prepared aramid micro-nano fibers for later use.

[0043] (2) Surface modification of plant cellulose nanofibrils and bacterial cellulose: 1 L of plant cellulose nanofibrils (solid content 1.0%) was slowly added with 12 g of solid NaIO4 under stirring in a high-speed stirrer. The mass ratio of plant cellulose nanofibrils to sodium periodate (NaIO4) was 1:1.2. The mixture was reacted for 8 h at room temperature in the dark to introduce aldehyde groups to form the surface of the plant cellulose nanofibrils. After the reaction, ethylene glycol was added to terminate the oxidation. The modified plant cellulose nanofibrils were collected by centrifugation at 8000 rpm for 20 min and washed with deionized water. This was repeated three times to remove by-products to obtain formaldehyde-modified plant cellulose nanofibrils (modified CNF) for later use.

[0044] 50g of purified bacterial cellulose (90% moisture content) was added to 200mL of deionized water and stirred to form a uniform suspension. 0.2g of 2,2,6,6-tetramethylpiperidinyl oxide (TEMPO) and 1.25g of potassium bromide (NaBr) were then added dropwise. 75mL of a 5% sodium hypochlorite (NaClO) solution was then slowly added dropwise. The mixture was stirred at room temperature for 8 hours to induce TEMPO-mediated selective oxidation of the bacterial cellulose. The pH of the solution was maintained at 10-11 (adjusted with 0.5M NaOH solution) during the reaction. After completion of the reaction, the slurry was adjusted to neutral with 0.1M hydrochloric acid (HCl), washed thoroughly with water five times, and centrifuged to obtain a modified bacterial cellulose slurry for later use.

[0045] (3) Papermaking and hot pressing: 0.47 g of the aramid micro-nano fibers obtained in step (1) above were dispersed in 2 L of deionized water, 0.94 g of aramid fibrils were added, and the mixture was deflaked using a fiber deflaking machine to form a uniform slurry; then 0.36 g of the modified plant cellulose nanofibrils obtained in step (2) and 0.12 g of the modified bacterial cellulose obtained in step (2) were added. The mass proportions of aramid fibrils, aramid micro-nano fibers, modified plant cellulose nanofibrils, and modified bacterial cellulose in the composite slurry were 50%, 25%, 18.8%, and 6.2%, respectively. The mixed slurry was deflaked using a fiber deflaking machine for 20,000 revolutions. The wet paper web was made using an automatic sheeter, and the weight was controlled to be 60 g / m 2 The wet paper web was squeezed and dehydrated at 25°C and 0.5 MPa pressure for 3 minutes, and then directly thermoformed (i.e., wet-sheet aramid sheets were obtained by wet papermaking and then dried and formed) at a temperature of 200°C, a pressure of 10 MPa, and a time of 20 minutes to finally prepare a high-performance aramid composite insulation paper-based material.

[0046] The performance tests of the prepared high-performance aramid composite insulation paper-based material showed that the tensile strength index and the power frequency breakdown field strength under a vertical electric field at room temperature were 28.6 N·m / g and 27.8 kV / mm, respectively.

[0047] Example 3

[0048] A high-performance aramid composite insulating paper-based material, the preparation method of which is as follows:

[0049] (1) Micro-nano-fiberization of aramid fibers: Aramid chopped fibers were ultrasonically treated for 40 min at an ultrasonic power of 800 W and a temperature of 25°C. Subsequently, ultrafine grinding was performed 20 times, and the prepared aramid micro-nano fibers were collected by filtration and set aside.

[0050] (2) Surface modification of plant cellulose nanofibrils and bacterial cellulose: 1 L of plant cellulose nanofibrils (solid content 1.0%) was slowly added with 15 g of solid NaIO4 under stirring in a high-speed stirrer. The mass ratio of plant cellulose nanofibrils to sodium periodate (NaIO4) was 1:1.5. The mixture was reacted for 5 h at room temperature in the dark to introduce aldehyde groups to form the surface of the plant cellulose nanofibrils. After the reaction, ethylene glycol was added to terminate the oxidation. The modified plant cellulose nanofibrils were collected by centrifugation at 8000 rpm for 20 min and washed with deionized water. This was repeated three times to remove by-products to obtain formaldehyde-modified plant cellulose nanofibrils (modified CNF) for later use.

[0051] 100g of purified bacterial cellulose (90% moisture content) was added to 200mL of deionized water and stirred to form a uniform suspension. 0.3g of 2,2,6,6-tetramethylpiperidinyl oxide (TEMPO) and 1.5g of potassium bromide (NaBr) were then added dropwise to the suspension. 90mL of a 5% sodium hypochlorite (NaClO) solution was then slowly added dropwise. The mixture was stirred at room temperature for 8 hours to induce TEMPO-mediated selective oxidation of the bacterial cellulose. The pH of the solution was maintained at 10-11 (adjusted with 0.5M NaOH solution) during the reaction. After completion of the reaction, the slurry was adjusted to neutral with 0.1M hydrochloric acid (HCl), washed thoroughly with water five times, and centrifuged to obtain a modified bacterial cellulose slurry for later use.

[0052] (3) Papermaking and hot pressing: 0.47 g of the aramid micro-nano fibers obtained in step (1) above were dispersed in 2 L of deionized water, 0.94 g of aramid fibrils were added, and the mixture was deflaked using a fiber deflaking machine to form a uniform slurry; then 0.24 g of the modified plant cellulose nanofibrils obtained in step (2) and 0.24 g of the modified bacterial cellulose obtained in step (2) were added, and the proportions of aramid fibrils, aramid micro-nano fibers, modified plant cellulose nanofibrils, and modified bacterial cellulose in the composite slurry were 50%, 25%, 12.5%, and 12.5%, respectively. The mixed slurry was deflaked using a fiber deflaking machine for 20,000 revolutions. The wet paper web was made using an automatic sheeter, and the weight was controlled to be 60 g / m 2 The wet paper web was squeezed and dehydrated at 25°C and 0.5 MPa pressure for 3 minutes, and then directly thermoformed (i.e., wet-sheet aramid sheets were obtained by wet papermaking and then dried and formed) at a temperature of 240°C, a pressure of 8 MPa, and a time of 20 minutes, ultimately producing a high-performance aramid composite insulation paper-based material.

[0053] The performance tests of the prepared high-performance aramid composite insulation paper-based material showed that the tensile strength index and the power frequency breakdown field strength under a vertical electric field at room temperature were 24.6 N·m / g and 25.9 kV / mm, respectively.

[0054] Example 4

[0055] A high-performance aramid composite insulating paper-based material, the preparation method of which is as follows:

[0056] (1) Micro-nano treatment of aramid fibers: Aramid chopped fibers were placed in a 2 mol / L sodium hydroxide (NaOH) solution, wherein the ratio of aramid fiber to NaOH solution was mass (g): volume (mL) = 1:50. The reaction temperature was 20°C and the reaction time was 6 h. The aramid fibers after the reaction were ultrasonically treated for 10 min at an ultrasonic power of 800 W and a temperature of 25°C. Subsequently, high-speed shear treatment was performed at a processing power of 3000 W for 5 h. After the reaction, the fibers were washed with deionized water five times until neutral, filtered, and the prepared aramid micro-nano fibers were collected for later use.

[0057] (2) Surface modification of plant cellulose nanofibrils and bacterial cellulose: 1 L of plant cellulose nanofibrils (solid content 1.5%) was slowly added with 15 g of solid NaIO4 under stirring in a high-speed stirrer. The mass ratio of plant cellulose nanofibrils to sodium periodate (NaIO4) was 1:1. The mixture was reacted for 12 h at room temperature in the dark to introduce aldehyde groups to formaldehyde on the surface of the plant cellulose nanofibrils. After the reaction, ethylene glycol was added to terminate the oxidation. The modified plant cellulose nanofibrils were collected by centrifugation at 8000 rpm for 20 min and washed with deionized water. This was repeated three times to remove by-products to obtain formaldehyde-modified plant cellulose nanofibrils (modified CNF) for later use.

[0058] 100g of purified bacterial cellulose (90% moisture content) was added to 200mL of deionized water and stirred to form a uniform suspension. 0.3g of 2,2,6,6-tetramethylpiperidinyl oxide (TEMPO) and 1.5g of potassium bromide (NaBr) were then added dropwise to the suspension. 100mL of a 5% sodium hypochlorite (NaClO) solution was then slowly added dropwise. The mixture was stirred at room temperature for 8 hours to induce TEMPO-mediated selective oxidation of the bacterial cellulose. The pH of the solution was maintained at 10-11 (adjusted with 0.5M NaOH solution) during the reaction. After completion of the reaction, the slurry was adjusted to neutral with 0.1M hydrochloric acid (HCl), washed thoroughly with water five times, and centrifuged to obtain a modified bacterial cellulose slurry for later use.

[0059] (3) Papermaking and hot pressing: 0.048 g of the aramid micro-nano fibers obtained in step (1) above were dispersed in 2 L of deionized water, 0.94 g of aramid precipitated fibers were added, and the mixture was decomposed by a fiber decompressor to form a uniform slurry; then 0.44 g of the modified plant cellulose nanofibrils obtained in step (2) and 0.45 g of the modified bacterial cellulose obtained in step (2) were added, and the proportions of precipitated fibers, aramid micro-nano fibers, modified plant cellulose nanofibrils, and modified bacterial cellulose in the composite slurry were 50%, 2.6%, 23.4%, and 24.0%, respectively. The mixed slurry was decompressed by a fiber decompressor for 20,000 revolutions. The wet paper web was made using an automatic sheeter, and the weight was controlled to be 60 g / m 2 The wet paper web was squeezed and dehydrated at 25°C and 0.5 MPa pressure for 3 minutes, and then directly thermoformed (i.e., wet-sheet aramid sheets were obtained by wet papermaking and then dried and formed) at a temperature of 240°C, a pressure of 8 MPa, and a time of 20 minutes, ultimately producing a high-performance aramid composite insulation paper-based material.

[0060] The performance tests of the prepared high-performance aramid composite insulation paper-based material showed that the tensile strength index and the power frequency breakdown field strength under a vertical electric field at room temperature were 21.8 N·m / g and 24.6 kV / mm, respectively.

[0061] Comparative Example 1

[0062] An aramid composite insulating paper-based material, the preparation method of which is as follows:

[0063] (1) Micro-nano treatment of aramid fibers: Aramid chopped fibers were placed in a 0.05 mol / L sodium hydroxide (NaOH) solution, wherein the ratio of aramid fiber to NaOH solution was mass (g): volume (mL) = 1:50. The reaction temperature was 95°C and the reaction time was 1 h. The aramid fibers after the reaction were ultrasonically treated for 10 min at an ultrasonic power of 800 W and a temperature of 25°C. Subsequently, high-speed shear treatment was performed at a processing power of 3000 W for 12 h. After the reaction, the fibers were washed with deionized water five times until neutral, filtered, and the prepared aramid micro-nano fibers were collected for later use.

[0064] (2) Surface modification of plant cellulose nanofibrils and bacterial cellulose: 1 L of plant cellulose nanofibrils (solid content 1.0%) was slowly added with 15 g of solid NaIO4 under stirring in a high-speed stirrer. The mass ratio of plant cellulose nanofibrils to sodium periodate (NaIO4) was 1:1.5. The mixture was reacted for 12 h at room temperature in the dark to introduce aldehyde groups to form the surface of the plant cellulose nanofibrils. After the reaction, ethylene glycol was added to terminate the oxidation. The modified plant cellulose nanofibrils were collected by centrifugation at 8000 rpm for 20 min and washed with deionized water. This was repeated three times to remove by-products to obtain formaldehyde-modified plant cellulose nanofibrils (modified CNF) for later use.

[0065] 100g of purified bacterial cellulose (90% moisture content) was added to 200mL of deionized water and stirred to form a uniform suspension. 0.2g of 2,2,6,6-tetramethylpiperidinyl oxide (TEMPO) and 1.25g of potassium bromide (NaBr) were then added dropwise. 75mL of a 5% sodium hypochlorite (NaClO) solution was then slowly added dropwise. The mixture was stirred at room temperature for 8 hours to induce TEMPO-mediated selective oxidation of the bacterial cellulose. The pH of the solution was maintained at 10-11 (adjusted with 0.5M NaOH solution) during the reaction. After completion of the reaction, the slurry was adjusted to neutral with 0.1M hydrochloric acid (HCl), washed thoroughly with water five times, and centrifuged to obtain a modified bacterial cellulose slurry for later use.

[0066] (3) Papermaking and hot pressing: 0.89 g of the aramid micro-nanofibers prepared in step (1) above were dispersed in 2 L of deionized water, 0.94 g of aramid fibrils were added, and the mixture was deflaked using a fiber deflaker to form a uniform slurry. Subsequently, 0.024 g of the modified plant cellulose nanofibrils obtained in step (2) and 0.024 g of the modified bacterial cellulose obtained in step (2) were added. The mass proportions of aramid fibrils, aramid micro-nanofibers, modified plant cellulose nanofibrils, and modified bacterial cellulose in the composite slurry were 50%, 47.4%, 1.3%, and 1.3%, respectively. The mixed slurry was deflaked using a fiber deflaker at 20,000 revolutions. An automatic sheeter was used to make wet paper, and the basis weight was controlled to be 60 g / m2. The wet paper web was pressed and dehydrated at 25°C and 0.5 MPa pressure for 3 minutes, and then directly thermoformed (i.e., aramid wet paper sheets were obtained by wet papermaking and then dried and formed) at a temperature of 200°C, a pressure of 10 MPa, and a time of 20 minutes to finally prepare an aramid composite insulating paper-based material.

[0067] The performance of the prepared aramid composite insulation paper-based material was tested. The tensile strength index and the power frequency breakdown field strength under a vertical electric field at room temperature were 16.0 N·m / g and 18.1 kV / mm, respectively.

[0068] Comparative Example 2

[0069] An aramid composite insulating paper-based material, the preparation method of which is as follows:

[0070] (1) Micro-nano-processing of aramid fibers: Aramid chopped fibers were placed in a 3 mol / L potassium hydroxide (KOH) solution, wherein the ratio of aramid fiber to KOH solution was 1:50 (mass (g): volume (mL). The reaction temperature was 20°C and the reaction time was 6 h. The aramid fibers after the reaction were ultrasonically treated for 10 min at an ultrasonic power of 800 W and a temperature of 25°C. Subsequently, ultrafine grinding was performed 15 times. After the reaction, the fibers were washed with deionized water 5 times until neutral, and filtered to collect the prepared aramid micro-nano fibers for later use.

[0071] (2) Surface modification of plant cellulose nanofibrils and bacterial cellulose: 1 L of plant cellulose nanofibrils (solid content 1.0%) was slowly added with 12 g of solid NaIO4 under stirring in a high-speed stirrer. The mass ratio of plant cellulose nanofibrils to sodium periodate (NaIO4) was 1:1.2. The mixture was reacted for 8 h at room temperature in the dark to introduce aldehyde groups to form the surface of the plant cellulose nanofibrils. After the reaction, ethylene glycol was added to terminate the oxidation. The modified plant cellulose nanofibrils were collected by centrifugation at 8000 rpm for 20 min and washed with deionized water. This was repeated three times to remove by-products to obtain formaldehyde-modified plant cellulose nanofibrils (modified CNF) for later use.

[0072] 50g of purified bacterial cellulose (90% moisture content) was added to 200mL of deionized water and stirred to form a uniform suspension. 0.2g of 2,2,6,6-tetramethylpiperidinyl oxide (TEMPO) and 1.25g of potassium bromide (NaBr) were then added dropwise. 75mL of a 5% sodium hypochlorite (NaClO) solution was then slowly added dropwise. The mixture was stirred at room temperature for 8 hours to induce TEMPO-mediated selective oxidation of the bacterial cellulose. The pH of the solution was maintained at 10-11 (adjusted with 0.5M NaOH solution) during the reaction. After completion of the reaction, the slurry was adjusted to neutral with 0.1M hydrochloric acid (HCl), washed thoroughly with water five times, and centrifuged to obtain a modified bacterial cellulose slurry for later use.

[0073] (3) Papermaking and hot pressing: 0.47 g of the aramid micro-nano fibers obtained in step (1) above were dispersed in 2 L of deionized water, 0.94 g of aramid fibrils were added, and the mixture was deflaked using a fiber deflaking machine to form a uniform slurry; then 0.36 g of the modified plant cellulose nanofibrils obtained in step (2) and 0.12 g of the modified bacterial cellulose obtained in step (2) were added. The mass proportions of aramid fibrils, aramid micro-nano fibers, modified plant cellulose nanofibrils, and modified bacterial cellulose in the composite slurry were 50%, 25%, 18.8%, and 6.2%, respectively. The mixed slurry was deflaked using a fiber deflaking machine for 20,000 revolutions. The wet paper web was made using an automatic sheeter, and the weight was controlled to be 60 g / m 2 The wet paper web was squeezed and dehydrated at 25°C and 0.5 MPa pressure for 3 minutes, and then directly thermoformed (i.e., wet paper sheets were obtained by wet papermaking and then dried and formed) at a temperature of 80°C, a pressure of 10 MPa, and a time of 180 minutes to finally prepare an aramid composite insulating paper-based material.

[0074] The performance of the prepared aramid composite insulation paper-based material was tested, and the tensile strength index and the power frequency breakdown field strength under a vertical electric field at room temperature were 14.4 N·m / g and 16.7 kV / mm, respectively.

[0075] Comparative Example 3

[0076] An aramid composite insulating paper-based material, the preparation method of which is as follows:

[0077] (1) Micro-nano treatment of aramid fibers: Aramid chopped fibers were placed in a 2 mol / L sodium hydroxide (NaOH) solution, wherein the ratio of aramid fiber to NaOH solution was mass (g): volume (mL) = 1:50. The reaction temperature was 20°C and the reaction time was 4 h. The aramid fibers after the reaction were ultrasonically treated for 10 min at an ultrasonic power of 800 W and a temperature of 25°C. Subsequently, high-speed shear treatment was performed at a processing power of 3000 W for 6 h. After the reaction, the fibers were washed with deionized water five times until neutral, filtered, and the prepared aramid micro-nano fibers were collected for later use.

[0078] (2) Papermaking and hot pressing: 0.47 g of the aramid micro-nano fibers obtained in step (1) above were dispersed in 2 L of deionized water, 0.94 g of aramid fibrils were added, and the mixture was deflaked using a fiber deflaking machine to form a uniform slurry; then 0.24 g of unmodified plant cellulose nanofibrils and 0.24 g of unmodified bacterial cellulose were added, and the mass proportions of aramid fibrils, aramid micro-nano fibers, plant cellulose nanofibrils, and bacterial cellulose in the composite slurry were 50%, 25%, 12.5%, and 12.5%, respectively. The mixed slurry was deflaked using a fiber deflaking machine for 20,000 revolutions. The wet paper web was made using an automatic sheeter, and the weight was controlled to be 60 g / m2 The wet paper web was squeezed and dehydrated at 25°C and 0.5 MPa pressure for 3 minutes, and then directly thermoformed (i.e., wet-sheeted aramid wet paper sheets were obtained, and then dried and formed) at a temperature of 200°C, a pressure of 10 MPa, and a time of 20 minutes to finally prepare an aramid composite insulating paper-based material.

[0079] The performance of the prepared aramid composite insulation paper-based material was tested. The tensile strength index and the power frequency breakdown field strength under a vertical electric field at room temperature were 14.6 N·m / g and 17.2 kV / mm, respectively.

[0080] Comparative Example 4

[0081] An aramid composite insulating paper-based material, the preparation method of which is as follows:

[0082] (1) Micro-nano treatment of aramid fibers: Aramid chopped fibers were placed in a 2 mol / L sodium hydroxide (NaOH) solution, wherein the ratio of aramid fiber to NaOH solution was mass (g): volume (mL) = 1:50. The reaction temperature was 20°C and the reaction time was 4 h. The aramid fibers after the reaction were ultrasonically treated for 10 min at an ultrasonic power of 800 W and a temperature of 25°C. Subsequently, high-speed shear treatment was performed at a processing power of 3000 W for 6 h. After the reaction, the fibers were washed with deionized water five times until neutral, filtered, and the prepared aramid micro-nano fibers were collected for later use.

[0083] (2) Surface modification of plant cellulose nanofibrils and bacterial cellulose: 1 L of plant cellulose nanofibrils (solid content 1.0%) was slowly added with 15 g of solid NaIO4 under stirring in a high-speed stirrer. The mass ratio of plant cellulose nanofibrils to sodium periodate (NaIO4) was 1:1.5. The mixture was reacted for 12 h at room temperature in the dark to introduce aldehyde groups to form the surface of the plant cellulose nanofibrils. After the reaction, ethylene glycol was added to terminate the oxidation. The modified plant cellulose nanofibrils were collected by centrifugation at 8000 rpm for 20 min and washed with deionized water. This was repeated three times to remove by-products to obtain formaldehyde-modified plant cellulose nanofibrils (modified CNF) for later use.

[0084] 100g of purified bacterial cellulose (90% moisture content) was added to 200mL of deionized water and stirred to form a uniform suspension. 0.2g of 2,2,6,6-tetramethylpiperidinyl oxide (TEMPO) and 1.25g of potassium bromide (NaBr) were then added dropwise. 75mL of a 5% sodium hypochlorite (NaClO) solution was then slowly added dropwise. The mixture was stirred at room temperature for 8 hours to induce TEMPO-mediated selective oxidation of the bacterial cellulose. The pH of the solution was maintained at 10-11 (adjusted with 0.5M NaOH solution) during the reaction. After completion of the reaction, the slurry was adjusted to neutral with 0.1M hydrochloric acid (HCl), washed thoroughly with water five times, and centrifuged to obtain a modified bacterial cellulose slurry for later use.

[0085] (3) Papermaking and hot pressing: 0.047 g of the aramid micro-nano fibers obtained in step (1) above were dispersed in 2 L of deionized water, 0.94 g of aramid fibrils were added, and the mixture was deflaked using a fiber deflaking machine to form a uniform slurry; then 0.024 g of the modified plant cellulose nanofibrils obtained in step (2) and 0.024 g of the modified bacterial cellulose obtained in step (2) were added. The proportions of aramid fibrils, aramid micro-nano fibers, modified plant cellulose nanofibrils, and modified bacterial cellulose in the composite slurry were 91%, 5%, 2%, and 2%, respectively. The mixed slurry was deflaked using a fiber deflaking machine for 20,000 revolutions. The wet paper web was made using an automatic sheeter, and the weight was controlled to be 60 g / m 2 The wet paper web was squeezed and dehydrated at 25°C and 0.5 MPa pressure for 3 minutes, and then directly thermoformed (i.e., wet-sheeted aramid wet paper sheets were obtained, and then dried and formed) at a temperature of 200°C, a pressure of 10 MPa, and a time of 20 minutes to finally prepare an aramid composite insulating paper-based material.

[0086] The performance of the prepared aramid composite insulation paper-based material was tested, and the tensile strength index and the power frequency breakdown field strength under a vertical electric field at room temperature were 12.7N·m / g and 13.5kV / mm, respectively.

[0087] Comparative Example 5

[0088] An aramid composite insulating paper-based material, the preparation method of which is as follows:

[0089] (1) Micro-nano treatment of aramid fibers: Aramid chopped fibers were placed in a 2 mol / L sodium hydroxide (NaOH) solution, wherein the ratio of aramid fiber to NaOH solution was mass (g): volume (mL) = 1:50. The reaction temperature was 20°C and the reaction time was 4 h. The aramid fibers after the reaction were ultrasonically treated for 10 min at an ultrasonic power of 800 W and a temperature of 25°C. Subsequently, high-speed shear treatment was performed at a processing power of 3000 W for 6 h. After the reaction, the fibers were washed with deionized water five times until neutral, filtered, and the prepared aramid micro-nano fibers were collected for later use.

[0090] (2) Surface modification of plant cellulose nanofibrils and bacterial cellulose: 1 L of plant cellulose nanofibrils (solid content 1.0%) was slowly added with 15 g of solid NaIO4 under stirring in a high-speed stirrer. The mass ratio of plant cellulose nanofibrils to sodium periodate (NaIO4) was 1:1.5. The mixture was reacted for 12 h at room temperature in the dark to introduce aldehyde groups to form the surface of the plant cellulose nanofibrils. After the reaction, ethylene glycol was added to terminate the oxidation. The modified plant cellulose nanofibrils were collected by centrifugation at 8000 rpm for 20 min and washed with deionized water. This was repeated three times to remove by-products to obtain formaldehyde-modified plant cellulose nanofibrils (modified CNF) for later use.

[0091] 100g of purified bacterial cellulose (90% moisture content) was added to 200mL of deionized water and stirred to form a uniform suspension. 0.2g of 2,2,6,6-tetramethylpiperidinyl oxide (TEMPO) and 1.25g of potassium bromide (NaBr) were then added dropwise. 75mL of a 5% sodium hypochlorite (NaClO) solution was then slowly added dropwise. The mixture was stirred at room temperature for 8 hours to induce TEMPO-mediated selective oxidation of the bacterial cellulose. The pH of the solution was maintained at 10-11 (adjusted with 0.5M NaOH solution) during the reaction. After completion of the reaction, the slurry was adjusted to neutral with 0.1M hydrochloric acid (HCl), washed thoroughly with water five times, and centrifuged to obtain a modified bacterial cellulose slurry for later use.

[0092] (3) Papermaking and hot pressing: 0.47 g of the aramid micro-nano fibers obtained in step (1) above were dispersed in 2 L of deionized water, 0.047 g of aramid fibrils were added, and the mixture was deflaked using a fiber deflaking machine to form a uniform slurry; then 0.24 g of the modified plant cellulose nanofibrils obtained in step (2) and 0.24 g of the modified bacterial cellulose obtained in step (2) were added, and the mass proportions of aramid fibrils, aramid micro-nano fibers, modified plant cellulose nanofibrils, and modified bacterial cellulose in the composite slurry were 5%, 47%, 24%, and 24%, respectively. The mixed slurry was deflaked using a fiber deflaking machine for 20,000 revolutions. The wet paper web was made using an automatic sheeter, and the weight was controlled to be 60 g / m 2The wet paper web was squeezed and dehydrated at 25°C and 0.5 MPa pressure for 3 minutes, and then directly thermoformed (i.e., wet-sheeted aramid wet paper sheets were obtained, and then dried and formed) at a temperature of 200°C, a pressure of 10 MPa, and a time of 20 minutes to finally prepare an aramid composite insulating paper-based material.

[0093] The performance of the prepared aramid composite insulation paper-based material was tested, and the tensile strength index and the power frequency breakdown field strength under a vertical electric field at room temperature were 14.8N·m / g and 12.8kV / mm, respectively.

[0094] By comparing the test results of Example 1 and Control Example 1, it can be seen that when the concentration of the pretreatment alkali solution is too low, the pretreatment time is too short, and the mechanical treatment time is too long, the mechanical properties and electrical insulation properties of the prepared aramid paper are poor.

[0095] By comparing the test results of Example 2 and Control Example 2, it can be seen that when the thermoforming temperature is too low, even if the thermoforming time is extended, the mechanical properties and electrical insulation properties of the prepared aramid paper are still poor.

[0096] Comparing the test results of Examples 1-4 and Control Example 3, it can be seen that the unmodified plant cellulose nanofibrils and bacterial cellulose cannot improve the mechanical properties and electrical insulation properties of aramid paper.

[0097] By comparing the test results of Examples 1-4 and Control Examples 4-5, it can be seen that in the proportions of precipitated fibers, aramid micro-nanofibers, modified cellulose nanofibrils, and modified bacterial cellulose, when the total addition amount of aramid micro-nanofibers, modified cellulose nanofibrils, and modified bacterial cellulose exceeds 90% or is less than 10%, the mechanical properties and electrical insulation properties of the prepared aramid paper are poor.

[0098] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a high-performance aramid composite insulating paper-based material, characterized in that: The following steps are involved: (1) Aramid fibers are mechanically treated to obtain aramid micro-nano fibers; (2) Surface oxidation modification of plant cellulose nanofibrils and bacterial cellulose was performed by TEMPO free radical oxidation or sodium periodate oxidation to obtain modified plant cellulose nanofibrils and modified bacterial cellulose; (3) The aramid micro-nanofibers obtained in step (1), the modified plant cellulose nanofibrils and modified bacterial cellulose prepared in step (2) are compounded with aramid fibrils in proportion to obtain a uniformly dispersed multi-component fiber suspension slurry; the obtained slurry is then diluted, wet-sheeted to obtain aramid wet paper sheets, and then wet-heat formed to finally prepare a high-performance aramid composite insulating paper-based material.

2. The preparation method according to claim 1, characterized in that The type of the aramid fiber in step (1) is at least one of a wholly aromatic polyamide fiber or a heterocyclic aromatic polyamide fiber; the aramid fiber is a chopped fiber or a filament; the aramid fiber is pretreated with dimethyl sulfoxide / alkali, pretreated with alkali solution, or mechanically treated without treatment; The mechanical treatment method in step (1) is at least one of ultrasonic treatment, ultrafine ball milling treatment, and high-speed shearing treatment; the aramid fiber pulp concentration in the mechanical treatment is 0.1-2%, the treatment temperature is 25-80°C, and the treatment time is 0.1-10h.

3. The preparation method according to claim 2, characterized in that For the dimethyl sulfoxide / alkali pretreatment, the aramid fiber is chemically swollen in the dimethyl sulfoxide / alkali system for 0.1-10 hours at a temperature of 0-80° C.; the alkali is at least one of sodium hydroxide, potassium hydroxide, potassium tert-butoxide, or sodium carbonate; the alkali concentration in the dimethyl sulfoxide / alkali system is 0.1 mol / L-10 mol / L; and the ratio of the aramid fiber mass to the volume of the dimethyl sulfoxide / alkali system is 1:30-50 g / mL; For the alkali solution pretreatment, the aramid fiber is treated in the alkali solution for 2-20 hours at a temperature of 0-80°C. The alkali is at least one of sodium hydroxide, potassium hydroxide, potassium tert-butoxide, or sodium carbonate. The alkali solution concentration is 0.5 mol / L-20 mol / L. The ratio of the aramid fiber mass to the alkali solution volume is 1:30-50 g / mL.

4. The preparation method according to claim 1, characterized in that During the mechanical treatment in step (1), a dispersant is also added. The dispersant is at least one of polyethylene oxide, sodium fatty alcohol polyoxyethylene ether sulfate, polyethylene glycol, polyvinyl pyrrolidone or sodium dodecylbenzene sulfonate. The amount of the dispersant added is 0.1-2% of the absolute dry mass of the aramid fiber.

5. The preparation method according to claim 1, characterized in that The aspect ratio of the plant cellulose nanofibrils in step (2) is greater than 500; the aspect ratio of the bacterial cellulose is greater than 500.

6. The preparation method according to claim 1, characterized in that In step (2), the TEMPO free radical oxidation modification adopts a ternary system of 2,2,6,6-tetramethylpiperidinyl oxide / potassium bromide / sodium hypochlorite, wherein the mass ratio of 2,2,6,6-tetramethylpiperidinyl oxide to plant cellulose nanofibrils or bacterial cellulose is 1:(0.1-100), the pH of the reaction system is 7-11, the reaction temperature is 0-80°C, and the reaction time is 0.1-24h; In the sodium periodate oxidation modification method described in step (2), the oxidant is sodium periodate, the mass ratio of plant cellulose nanofibrils or bacterial cellulose to NaIO4 in the reaction system is (0.1-100):1, the reaction temperature is 0-60°C, the reaction time is 0.5-12 hours, and the pH is maintained between 4-7.

7. The preparation method according to claim 1, characterized in that In step (3), the ratio of the mass of the aramid micro-nano fibers to the sum of the masses of the modified plant cellulose nanofibrils and the modified bacterial cellulose is 0.01-100%, the ratio of the modified plant cellulose nanofibrils to the modified bacterial cellulose is 0.00-100%, and the mass ratio of the sum of the masses of the aramid micro-nano fibers, modified plant cellulose nanofibrils and modified bacterial cellulose to the aramid precipitated fibers is 2:8-8:

2.

8. The preparation method according to claim 1, characterized in that During the wet papermaking process in step (3), the slurry concentration is 0.01-5%, the thermoforming temperature is 100-290° C., and the pressure is 0.01-25.0 MPa.

9. A high-performance aramid composite insulating paper-based material prepared by the method according to any one of claims 1 to 8.

10. Use of the high-performance aramid composite insulating paper-based material according to claim 9 in the fields of high-voltage motors, power transformers, and cables.

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