A high-strength, high-flame-retardant aramid insulating paper, its preparation method and application

Abstract

This invention discloses a high-strength, high-flame-retardant aramid insulating paper, its preparation method, and its applications, relating to the field of aramid paper. The aramid insulating paper comprises modified meta-aramid chopped fibers and modified bacterial fibers; both the modified meta-aramid chopped fibers and modified bacterial fibers are obtained by soaking in a phosphoric acid aqueous solution and then washing until neutral. This application uses a blend of modified meta-aramid chopped fibers and modified bacterial fibers, followed by hot pressing, to prepare aramid insulating paper. Phosphoric acid treatment of the modified fibers results in the presence of phosphate esterification groups on the fiber surface, aiding dispersion and solving the problem of easy flocculation of aramid fibers, thus improving the compatibility of the two fibers. The phosphate esterification groups also impart good flame retardancy to the paper. Utilizing the uniform distribution of aramid fibers, and the high aspect ratio and large specific surface area of ​​bacterial cellulose, which can bridge and connect with aramid fibers, the interfacial bonding force between fibers is improved, thereby promoting tight fiber bonding and improving overall flame retardancy and mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of aramid paper, and more particularly to a high-strength, high-flame-retardant aramid insulating paper, its preparation method, and its application. Background Technology

[0002] Aramid fiber, also known as aromatic polyamide fiber, is mainly divided into para-aramid fiber (aramid 1414) and meta-aramid fiber (aramid 1313). It possesses excellent properties such as high strength, high modulus, high temperature resistance, corrosion resistance, electrical insulation, and light weight, making it a representative of high-performance synthetic fibers. Aramid paper is prepared from aramid fibers through a wet forming process. Due to its excellent mechanical properties, good dielectric properties, outstanding insulation properties, and superior heat resistance, it is often used as an insulating material in cutting-edge fields such as transportation, electrical and electronic engineering, and safety protection.

[0003] Aramid insulating paper is commonly used as the insulation material for transformers and motor coils, making its electrical and physical properties crucial. However, high-performance aramid insulating paper currently relies on imports, resulting in high prices and significantly limiting its applications. To address this issue, extensive research has been conducted domestically, exploring various aspects including raw materials, composite processes, and quality control, aiming to reduce the cost of aramid insulating paper. One approach is to use cellulose fibers, such as plant fibers, to replace some of the aramid fibers, which can significantly reduce production costs. However, cellulose fibers and aramid fibers have poor compatibility and possess flammable properties, negatively impacting the mechanical and safety properties of aramid insulating paper. Therefore, it is essential to further improve its mechanical and flame-retardant properties while reducing costs. Summary of the Invention

[0004] This invention provides a high-strength, high-flame-retardant aramid insulating paper, its preparation method, and its application, in order to solve the technical problems of high cost and difficult quality control of aramid insulating paper, and to provide aramid insulating paper with low cost, superior mechanical properties, and flame-retardant properties.

[0005] To solve the above-mentioned technical problems, one of the objectives of this invention is to provide a high-strength, high-flame-retardant aramid insulating paper, comprising modified meta-aramid chopped fibers and modified bacterial fibers in a mass ratio of (90-97):(3-10).

[0006] The modified meta-aramid short-cut fiber is prepared by soaking it in a 40-45 wt% phosphoric acid aqueous solution at 30-35°C and then washing it until neutral.

[0007] The modified bacterial fiber is prepared by soaking it in a 30-35 wt% phosphoric acid aqueous solution at 50-60°C and then washing it until it is neutral.

[0008] By adopting the above scheme, the high-strength, high-flame-retardant aramid insulating paper prepared in this application is composed of modified meta-aramid chopped fibers and modified bacterial fibers. Through surface phosphoesterification modification of the fibers, the phosphoesterified groups on the fiber surface endow the paper with good flame retardancy. At the same time, the same polar groups on the surface make the mixing more uniform, enhance the interfacial bonding force, and improve the compatibility. The aramid fibers can be evenly distributed, and the bacterial cellulose has a high aspect ratio and a large specific surface area, which can bridge and connect with the aramid fibers, improve the interfacial bonding force between fibers, thereby promoting the tight bonding of fibers, endowing the paper with good physical strength, and improving the overall flame retardant and mechanical properties.

[0009] As a preferred embodiment, in the preparation method of the modified meta-aramid short-cut fiber, the immersion treatment temperature is 30-35℃.

[0010] As a preferred embodiment, in the method for preparing the modified bacterial fiber, the soaking treatment temperature is 50-60℃.

[0011] As a preferred embodiment, in the method for preparing the modified meta-aramid short-cut fibers, the soaking treatment time is 0.5-2 hours.

[0012] As a preferred embodiment, in the method for preparing the modified bacterial fiber, the soaking treatment time is 0.5-1h.

[0013] As a preferred embodiment, the bacterial cellulose has a fiber diameter of 20-30 nm and a length of 1000-3000 nm.

[0014] To address the aforementioned technical problems, a second objective of this invention is to provide a method for preparing high-strength, high-flame-retardant aramid insulating paper, comprising the following steps:

[0015] (1) Modified meta-aramid short-cut fibers were disintegrated with an aqueous solution containing a dispersant to prepare a slurry suspension;

[0016] (2) The modified bacterial fiber was mechanically sheared and dispersed with water to obtain a phosphorylated bacterial cellulose dispersion;

[0017] (3) Under stirring conditions, the phosphorylated bacterial cellulose dispersion was added to the slurry suspension, and after stirring, a mixed slurry was obtained;

[0018] (4) Add water to the mixed slurry to adjust the total fiber concentration to 0.1-0.15wt%, and then inject it into the paper forming equipment for dehydration, forming and hot pressing to obtain aramid insulating paper.

[0019] As a preferred embodiment, in step (1), the dispersant is sodium polyacrylate, and the concentration of the dispersant in the aqueous solution containing the dispersant is 0.01-0.05 wt%.

[0020] As a preferred embodiment, in step (1), the content of modified meta-aramid short-cut fibers in the slurry suspension is 0.1-0.5 wt%.

[0021] As a preferred embodiment, in step (2), the content of modified bacterial fiber in the phosphate-esterified bacterial cellulose dispersion is 0.5-3.0 wt%.

[0022] As a preferred embodiment, in step (3), the stirring rate is 3000-5000 r / min.

[0023] As a preferred embodiment, in step (4), the hot pressing temperature is 200-260℃, the pressure is 8-10MPa, and the time is 10-30min.

[0024] To address the aforementioned technical problems, a third objective of this invention is to provide an application of high-strength, high-flame-retardant aramid insulating paper in the preparation of transformers or motor coils.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. This application uses modified meta-aramid chopped fibers and modified bacterial fibers to prepare aramid insulating paper by hot pressing. The modified fibers are treated with phosphoric acid, so that the fiber surface has phosphorylation groups, which realizes stable and uniform dispersion of fibers at ultra-low concentration, solves the problem of easy flocculation of aramid fibers, and improves the compatibility of the two fibers. At the same time, the phosphorylation groups on the fiber surface endow the paper with good flame retardancy. Taking advantage of the uniform distribution of aramid fibers, bacterial cellulose has a high aspect ratio and a large specific surface area, which can bridge and connect with aramid fibers, improve the interfacial bonding force between fibers, thereby promoting the tight bonding of fibers and improving the overall flame retardancy and mechanical properties.

[0027] 2. This application uses bacterial cellulose to replace part of the aramid fiber. Bacterial cellulose is abundant, renewable, and low in cost. Mixing bacterial cellulose with aramid fiber for composite papermaking to produce aramid insulating paper can significantly reduce production costs and has broad application prospects. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] A method for preparing high-strength, high-flame-retardant aramid insulating paper includes the following steps:

[0031] (1) The meta-aramid chopped fibers were soaked in a 40wt% phosphoric acid aqueous solution at 30°C for 1 hour and then washed until neutral to obtain modified meta-aramid chopped fibers. Then, they were slurried in a 0.03wt% sodium polyacrylate aqueous solution to prepare a slurry suspension. The content of modified meta-aramid chopped fibers in the slurry suspension was 0.5wt%.

[0032] (2) Commercially purchased bacterial cellulose was soaked in a 30wt% phosphoric acid aqueous solution at 50°C for 30 min and then washed until neutral to obtain modified bacterial cellulose. Then, water was added and mechanically sheared to disperse the modified bacterial cellulose to obtain a phosphorylated bacterial cellulose dispersion. The modified bacterial cellulose content in the phosphorylated bacterial cellulose dispersion was 1wt%.

[0033] (3) Under the stirring condition of 3000r / min, the phosphorylated bacterial cellulose dispersion was added to the slurry suspension and stirred to obtain a mixed slurry, wherein the amount of bacterial cellulose added was 3wt% of the oven-dry mass of the mixed slurry.

[0034] (4) The mixed slurry obtained in step (3) is adjusted to a total fiber concentration of 0.1wt% by adding water, and then injected into a paper forming machine for dehydration and forming. It is then hot-pressed at 200℃ and 8MPa for 30 minutes to obtain aramid insulating paper.

[0035] Example 2

[0036] A method for preparing high-strength, high-flame-retardant aramid insulating paper includes the following steps:

[0037] (1) The meta-aramid chopped fibers were soaked in a 45 wt% phosphoric acid aqueous solution at 35°C for 2 h and then washed until neutral to obtain modified meta-aramid chopped fibers. Then, they were slurried in a 0.03 wt% sodium polyacrylate aqueous solution to prepare a slurry suspension. The content of modified meta-aramid chopped fibers in the slurry suspension was 0.5 wt%.

[0038] (2) Commercially purchased bacterial cellulose was soaked in a 35wt% phosphoric acid aqueous solution at 60°C for 1 hour and then washed until neutral to obtain modified bacterial cellulose. Water was then added and mechanically sheared to obtain a phosphorylated bacterial cellulose dispersion. The content of modified bacterial cellulose in the phosphorylated bacterial cellulose dispersion was 1wt%.

[0039] (3) Under the stirring condition of 5000r / min, the phosphorylated bacterial cellulose dispersion was added to the slurry suspension and stirred to obtain a mixed slurry, wherein the amount of bacterial cellulose added was 10wt% of the oven-dry weight of the mixed slurry.

[0040] (4) The mixed slurry obtained in step (3) is adjusted to a total fiber concentration of 0.1wt% by adding water, and then injected into a paper forming machine for dehydration and forming. It is then hot-pressed at 200℃ and 8MPa for 10 minutes to obtain aramid insulating paper.

[0041] Example 3

[0042] A method for preparing high-strength, high-flame-retardant aramid insulating paper includes the following steps:

[0043] (1) The meta-aramid chopped fibers were soaked in a 43wt% phosphoric acid aqueous solution at 32°C for 1.5h and then washed until neutral to obtain modified meta-aramid chopped fibers. Then, they were slurried in a 0.03wt% sodium polyacrylate aqueous solution to prepare a slurry suspension. The content of modified meta-aramid chopped fibers in the slurry suspension was 0.5wt%.

[0044] (2) Commercially purchased bacterial cellulose was soaked in a 33wt% phosphoric acid aqueous solution at 55°C for 1 hour and then washed until neutral to obtain modified bacterial cellulose. Then, water was added and mechanically sheared to disperse the modified bacterial cellulose to obtain a phosphorylated bacterial cellulose dispersion. The modified bacterial cellulose content in the phosphorylated bacterial cellulose dispersion was 1wt%.

[0045] (3) Under the stirring condition of 5000r / min, the phosphorylated bacterial cellulose dispersion was added to the slurry suspension and stirred to obtain a mixed slurry, wherein the amount of bacterial cellulose added was 6wt% of the oven-dry weight of the mixed slurry.

[0046] (4) The mixed slurry obtained in step (3) is adjusted to a total fiber concentration of 0.15wt% by adding water, and then injected into a paper forming machine for dehydration and forming. It is then hot-pressed at 260℃ and 10MPa for 30 minutes to obtain aramid insulating paper.

[0047] Example 4

[0048] A method for preparing high-strength, high-flame-retardant aramid insulating paper includes the following steps:

[0049] (1) The meta-aramid chopped fibers were soaked in a 45 wt% phosphoric acid aqueous solution at 30°C for 1 h and then washed until neutral to obtain modified meta-aramid chopped fibers. Then, they were slurried with a 0.03 wt% sodium polyacrylate aqueous solution to prepare a slurry suspension. The content of modified meta-aramid chopped fibers in the slurry suspension was 0.5 wt%.

[0050] (2) Commercially purchased bacterial cellulose was soaked in a 35wt% phosphoric acid aqueous solution at 60°C for 30 min and then washed until neutral to obtain modified bacterial cellulose. Then, water was added and mechanically sheared to disperse the modified bacterial cellulose to obtain a phosphorylated bacterial cellulose dispersion. The content of modified bacterial cellulose in the phosphorylated bacterial cellulose dispersion was 1wt%.

[0051] (3) Under the stirring condition of 5000r / min, the phosphorylated bacterial cellulose dispersion was added to the slurry suspension and stirred to obtain a mixed slurry, wherein the amount of bacterial cellulose added was 10wt% of the oven-dry weight of the mixed slurry.

[0052] (4) The mixed slurry obtained in step (3) is adjusted to a total fiber concentration of 0.15wt% by adding water, and then injected into a paper forming machine for dehydration and forming. It is then hot-pressed at 260℃ and 9MPa for 30 minutes to obtain aramid insulating paper.

[0053] Example 5

[0054] A method for preparing high-strength, high-flame-retardant aramid insulating paper includes the following steps:

[0055] (1) The meta-aramid chopped fibers were soaked in a 40wt% phosphoric acid aqueous solution at 35°C for 2 hours and then washed until neutral to obtain modified meta-aramid chopped fibers. Then, they were slurried with a 0.03wt% sodium polyacrylate aqueous solution to prepare a slurry suspension. The content of modified meta-aramid chopped fibers in the slurry suspension was 0.5wt%.

[0056] (2) Commercially purchased bacterial cellulose was soaked in a 35wt% phosphoric acid aqueous solution at 50°C for 1 hour and then washed until neutral to obtain modified bacterial cellulose. Water was then added and mechanically sheared to obtain a phosphorylated bacterial cellulose dispersion. The content of modified bacterial cellulose in the phosphorylated bacterial cellulose dispersion was 1wt%.

[0057] (3) Under the stirring condition of 3000r / min, the phosphorylated bacterial cellulose dispersion was added to the slurry suspension and stirred to obtain a mixed slurry, wherein the amount of bacterial cellulose added was 5wt% of the oven-dry weight of the mixed slurry.

[0058] (4) The mixed slurry obtained in step (3) is adjusted to a total fiber concentration of 0.12wt% by adding water, and then injected into a paper forming machine for dehydration and forming. It is then hot-pressed at 250℃ and 10MPa for 10 minutes to obtain aramid insulating paper.

[0059] Example 6

[0060] A method for preparing high-strength, high-flame-retardant aramid insulating paper includes the following steps:

[0061] (1) The meta-aramid chopped fibers were soaked in a 45 wt% phosphoric acid aqueous solution at 35°C for 1 h and then washed until neutral to obtain modified meta-aramid chopped fibers. Then, they were slurried with a 0.03 wt% sodium polyacrylate aqueous solution to prepare a slurry suspension. The content of modified meta-aramid chopped fibers in the slurry suspension was 0.5 wt%.

[0062] (2) Commercially purchased bacterial cellulose was soaked in a 30wt% phosphoric acid aqueous solution at 55°C for 1 hour and then washed until neutral to obtain modified bacterial cellulose. Water was then added and mechanically sheared to obtain a phosphorylated bacterial cellulose dispersion. The content of modified bacterial cellulose in the phosphorylated bacterial cellulose dispersion was 1wt%.

[0063] (3) Under the stirring condition of 3000r / min, the phosphorylated bacterial cellulose dispersion was added to the slurry suspension and stirred to obtain a mixed slurry, wherein the amount of bacterial cellulose added was 5wt% of the oven-dry weight of the mixed slurry.

[0064] (4) The mixed slurry obtained in step (3) is adjusted to a total fiber concentration of 0.13wt% by adding water, and then injected into a paper forming machine for dehydration and forming. It is then hot-pressed at 260℃ and 10MPa for 30 minutes to obtain aramid insulating paper.

[0065] Comparative Example 1

[0066] A method for preparing aramid insulating paper includes the following steps:

[0067] (1) The meta-aramid chopped fibers were soaked in 45wt% phosphoric acid at 35°C for 1 hour and then washed until neutral to obtain modified meta-aramid chopped fibers. Then, they were slurried with a sodium polyacrylate aqueous solution with a concentration of 0.03wt% to prepare a slurry suspension. The content of modified meta-aramid chopped fibers in the slurry suspension was 0.5wt%.

[0068] (2) The slurry suspension obtained in step (1) is adjusted to a total fiber concentration of 0.13wt% by adding water, and then injected into a paper forming machine for dehydration and forming. It is then hot-pressed for 30 minutes at 260℃ and 10.0MPa to obtain aramid insulating paper.

[0069] Comparative Example 2

[0070] A method for preparing insulating paper includes the following steps:

[0071] (1) Commercially purchased bacterial cellulose was soaked in 30wt% phosphoric acid at 55°C for 1 hour and then washed until neutral to obtain modified bacterial cellulose. Then, mechanical shearing was performed to obtain a phosphorylated bacterial cellulose dispersion. The content of modified bacterial cellulose in the phosphorylated bacterial cellulose dispersion was 1wt%.

[0072] (2) The phosphorylated bacterial cellulose dispersion obtained in step (1) was adjusted to a total fiber concentration of 0.13 wt% by adding water, and then injected into a paper forming machine for dehydration and forming. The paper was hot-pressed at 260℃ and 10.0 MPa for 30 min to obtain bacterial cellulose paper.

[0073] Comparative Example 3

[0074] A method for preparing aramid insulating paper includes the following steps:

[0075] (1) The meta-aramid short-cut fibers were decomposed with a sodium polyacrylate aqueous solution with a concentration of 0.03wt% to prepare a slurry suspension, wherein the content of the meta-aramid short-cut fibers in the slurry suspension was 0.5wt%.

[0076] (2) Commercially purchased bacterial cellulose was mechanically dispersed by adding water to obtain a bacterial cellulose dispersion, the bacterial cellulose content in the bacterial cellulose dispersion was 1 wt%.

[0077] (3) Under the stirring condition of 3000r / min, the bacterial cellulose dispersion was added to the slurry suspension and stirred to obtain a mixed slurry, wherein the amount of bacterial cellulose added was 5wt% of the oven-dry weight of the mixed slurry.

[0078] (4) The mixed slurry obtained in step (3) is adjusted to a total fiber concentration of 0.13wt% by adding water, and then injected into a paper forming machine for dehydration and forming. It is then hot-pressed at 260℃ and 10MPa for 30 minutes to obtain aramid insulating paper.

[0079] Comparative Example 4

[0080] A method for preparing aramid insulating paper includes the following steps:

[0081] (1) The meta-aramid chopped fibers were soaked in a 45 wt% phosphoric acid aqueous solution at 35°C for 1 h and then washed until neutral to obtain modified meta-aramid chopped fibers. Then, they were slurried with a 0.03 wt% sodium polyacrylate aqueous solution to prepare a slurry suspension. The content of modified meta-aramid chopped fibers in the slurry suspension was 0.5 wt%.

[0082] (2) Commercially purchased cotton cellulose was soaked in a 30wt% phosphoric acid aqueous solution at 55°C for 1 hour and then washed until neutral to obtain modified cotton cellulose. Water was then added and mechanically sheared to obtain a phosphoric acid esterified cotton cellulose dispersion. The content of modified cotton cellulose in the phosphoric acid esterified cotton cellulose dispersion was 1wt%.

[0083] (3) Under the stirring condition of 3000r / min, the phosphated cotton cellulose dispersion was added to the slurry suspension and stirred to obtain a mixed slurry, wherein the amount of cotton cellulose added was 5wt% of the oven-dry mass of the mixed slurry.

[0084] (4) The mixed slurry obtained in step (3) is adjusted to a total fiber concentration of 0.13wt% by adding water, and then injected into a paper forming machine for dehydration and forming. It is then hot-pressed at 260℃ and 10MPa for 30 minutes to obtain aramid insulating paper.

[0085] Performance testing

[0086] 1. The insulating papers prepared in Examples 1-6 and Comparative Examples 1-4 were tested for thickness, tensile strength, elongation and dielectric loss tangent using GB / T 20628.2-2006 standard. The test results are shown in Table 1 below.

[0087] 2. The insulating papers prepared in Examples 1-6 and Comparative Examples 1-4 were tested for limiting oxygen index according to GB / T2406.2—20092 standard. The test results are shown in Table 1 below.

[0088] Table 1 - Performance test results of insulating paper prepared in the embodiments and comparative examples of this application

[0089]

[0090] Based on the performance test results of Example 6 and Comparative Examples 1-2 in Table 1, it can be seen that insulating paper prepared solely using meta-aramid chopped fibers may have a looser density due to the aramid paper being entirely composed of chopped fibers, making it more flammable and exhibiting significantly lower tensile strength. Consequently, the mechanical and flame-retardant properties of the insulating paper do not meet the requirements. While insulating paper prepared solely using bacterial cellulose meets higher requirements for tensile strength and elongation, it also suffers from flammability. This application utilizes phosphoric acid-treated meta-aramid chopped fibers and bacterial fibers to prepare aramid insulating paper, resulting in insulating paper with higher mechanical strength and flame-retardant properties, thus meeting application requirements.

[0091] Based on the performance test results of Example 6 and Comparative Example 3 in Table 1, it can be seen that the present application uses phosphoric acid treatment to modify the two fibers, so that the fiber surface has phosphoric acid esterification groups, which realizes stable and uniform dispersion of fibers at ultra-low concentration, solves the problems of easy flocculation of aramid fibers and poor compatibility with plant fibers, and is conducive to improving the mechanical properties of paper; at the same time, the phosphoric acid esterification groups on the fiber surface endow the paper with good flame retardancy.

[0092] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A high-strength, high-flame-retardant aramid insulating paper, characterized in that, It includes modified meta-aramid short-cut fibers and modified bacterial cellulose in a mass ratio of (90-97):(3-10); The modified meta-aramid short-cut fiber is prepared by soaking it in a 40-45 wt% phosphoric acid aqueous solution and then washing it until neutral. The modified bacterial cellulose is prepared by soaking it in a 30-35 wt% phosphoric acid aqueous solution and then washing it until it is neutral.

2. The high-strength, high-flame-retardant aramid insulating paper as described in claim 1, characterized in that, In the preparation method of the modified meta-aramid short fiber, the immersion treatment temperature is 30-35℃.

3. The high-strength, high-flame-retardant aramid insulating paper as described in claim 1, characterized in that, In the preparation method of the modified bacterial cellulose, the soaking treatment temperature is 50-60℃.

4. The high-strength, high-flame-retardant aramid insulating paper as described in claim 1, characterized in that, In the preparation method of the modified meta-aramid short fiber, the soaking treatment time is 0.5-2h; in the preparation method of the modified bacterial cellulose, the soaking treatment time is 0.5-1h.

5. A method for preparing high-strength, high-flame-retardant aramid insulating paper as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Modified meta-aramid short-cut fibers were disintegrated with an aqueous solution containing a dispersant to prepare a slurry suspension; (2) Modified bacterial cellulose was mechanically dispersed by adding water to obtain a phosphorylated bacterial cellulose dispersion; (3) Under stirring conditions, the phosphorylated bacterial cellulose dispersion was added to the slurry suspension, and after stirring, a mixed slurry was obtained; (4) Add water to the mixed slurry to adjust the total fiber concentration to 0.1-0.15wt%, and then inject it into the paper forming equipment for dehydration, forming and hot pressing to obtain aramid insulating paper.

6. The method for preparing a high-strength, high-flame-retardant aramid insulating paper as described in claim 5, characterized in that, In step (1), the dispersant is sodium polyacrylate, and the concentration of the dispersant in the aqueous solution containing the dispersant is 0.01-0.05 wt%.

7. The method for preparing a high-strength, high-flame-retardant aramid insulating paper as described in claim 5, characterized in that, In step (1), the content of modified meta-aramid short-cut fibers in the slurry suspension is 0.1-0.5 wt%.

8. The method for preparing a high-strength, high-flame-retardant aramid insulating paper as described in claim 5, characterized in that, In step (2), the content of modified bacterial cellulose in the phosphorylated bacterial cellulose dispersion is 0.5-3 wt%.

9. The method for preparing a high-strength, high-flame-retardant aramid insulating paper as described in claim 5, characterized in that, In step (4), the hot pressing temperature is 200-260℃, the pressure is 8-10 MPa, and the time is 10-30 min.

10. The application of a high-strength, high-flame-retardant aramid insulating paper as described in any one of claims 1-9 in the field of manufacturing transformers or motor coils.

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