Composite insulation paper based on micro-channel homogenization technology and preparation method thereof

Abstract

This invention discloses a composite insulating paper based on microfluidic homogenization technology and its preparation method. The method includes the following steps: homogenizing a vermiculite powder solution or a boron nitride powder solution in a high-pressure homogenizing reactor at 800-1400 bar for 0.5-5 h, followed by freeze-drying to obtain two-dimensional vermiculite flake powder or hydroxylated boron nitride nanosheet powder; compounding the obtained powder with a PVDF solution to obtain a two-dimensional vermiculite nanosheet powder / PVDF spinning solution and a hydroxylated boron nitride nanosheet powder / PVDF slurry; and electrospinning or coating to obtain the composite insulating paper. This invention utilizes a high-pressure homogenizing reactor, allows for the controlled exfoliation of flakes and the precise adjustment of particle size, and enables composite film formation or spinning with PVDF to obtain composite insulating paper. It offers advantages such as simple operation, speed, and high efficiency. It achieves effective "bridging" assembly of inorganic nanosheets and organic polymer materials, resulting in high-performance composite insulating paper exhibiting ultra-high pollutant degradation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation technology, specifically relating to a composite insulating paper based on microchannel homogenization technology and its preparation method. Background Technology

[0002] Electrical insulating paper is a key material in power transmission and distribution systems, playing a crucial role in ensuring the reliable, durable, and safe operation of electrical equipment. In recent years, two-dimensional nanosheet materials, due to their excellent electrical insulation properties, have been developed and applied to the synthesis of electrical insulating paper to prevent short circuits or leakage. However, with the rapid development of modern electrical industry towards high frequency, high voltage, and high power, electrical insulating paper is expected to possess higher breakdown strength and mechanical properties, as well as high-temperature resistance under special working conditions, to better meet practical production and application needs.

[0003] Vermiculite (VT) is a natural silicate mineral formed by weathering and low-temperature hydrothermal alteration of biotite, phlogopite, and other materials. It possesses excellent properties such as high temperature resistance, high resistivity, and low dielectric constant, making it an ideal material for electrical insulating paper. However, the basic structural unit of vermiculite consists of a negatively charged silicate master layer formed by assembling a double layer of silicon-oxygen tetrahedra and a single layer of magnesium-oxygen octahedra, along with hydrated cations and water molecules introduced to balance the charge of the master layer, resulting in a three-dimensional morphology. Currently, methods for preparing vermiculite sheets have been reported, including acid modification, ultrasonication, ball milling, high-pressure jet homogenization, and high-speed shearing. However, these methods often require alternating operations of multiple processes, leading to cumbersome and time-consuming synthesis steps, and making it difficult to achieve green, large-scale preparation of electrical insulating nanosheets (CN116715248A, CN114272927A).

[0004] Furthermore, the study found that compared to macroscopic layered structures, utilizing electrically insulating nanosheets and polymers with good insulation properties through appropriate assembly methods for 'bridging' can effectively increase the complexity of the current flow path, thereby significantly improving the overall electrical and mechanical properties of the insulating paper. Among many polymer materials, polyvinylidene fluoride (PVDF) is a high-performance fluoropolymer with good electrical insulation properties, heat resistance, and mechanical strength, and is not prone to softening, deformation, or aging. Therefore, developing a new technology that can achieve green, efficient, and large-scale preparation of vermiculite nanosheets and effectively 'bridge' them with PVDF polymers to form high-performance composite electrically insulating paper has significant research and application value. Summary of the Invention

[0005] To address the shortcomings and challenges of existing technologies, this invention aims to provide a novel method for preparing composite insulating paper, which simplifies the synthesis process of two-dimensional nanosheets, achieves effective "bridging" assembly of inorganic nanosheets and organic polymer materials, and obtains high-performance composite insulating paper.

[0006] To achieve the above objectives, the present invention provides the following technical solutions.

[0007] The invention provides a composite insulating paper based on microchannel homogenization technology and its preparation method, comprising the following steps:

[0008] (1) A vermiculite powder solution or boron nitride powder solution prepared by modifying vermiculite material or boron nitride powder material;

[0009] (2) Homogenize vermiculite powder solution or boron nitride powder solution in a high-pressure homogenizing reactor at a pressure of 800-1400 bar for 0.5-5 h to obtain two-dimensional vermiculite nanosheet dispersion or hydroxylated boron nitride nanosheet slurry;

[0010] (3) The two-dimensional vermiculite nanosheet dispersion or hydroxylated boron nitride nanosheet powder solution obtained in step (2) is dried using a freeze dryer. The freeze drying temperature is controlled at -50℃ and the freezing time is 24h to obtain two-dimensional vermiculite nanosheet powder or hydroxylated boron nitride nanosheet powder.

[0011] (4) Prepare an organic solvent by mixing acetone and DMF in a 1:1 mass ratio, and add PVDF; to obtain a PVDF solution;

[0012] (5) The two-dimensional vermiculite flake powder or hydroxylated boron nitride powder obtained in step (3) and the PVDF solution obtained in step (4) are compounded to obtain two-dimensional vermiculite nanosheet powder / PVDF spinning solution and hydroxylated boron nitride nanosheet powder / PVDF slurry;

[0013] (6) Electrospinning two-dimensional vermiculite nanosheet powder / PVDF spinning solution with aluminum foil as the receiving substrate, setting the voltage to 18~20kV, the liquid supply rate to 2~3mL / h, the rotation speed to 600rpm, and the temperature to 25℃, to obtain two-dimensional vermiculite nanosheet / PVDF composite insulating fiber paper; or vacuum removing air bubbles from hydroxylated boron nitride powder / PVDF slurry and then uniformly coating it onto a stainless steel substrate using a coating machine, with a coating temperature of 60-100℃, and obtaining hydroxylated boron nitride nanosheet / PVDF composite insulating paper after the solvent evaporates.

[0014] The high-pressure homogenizing reactor uses a micro-jet high-pressure homogenizer. In one embodiment of the present invention, the ATS high-pressure nano-homogenizer AH-NANO is used.

[0015] Preferably, the modified vermiculite material is prepared according to the following steps:

[0016] (A1) Wash the expanded vermiculite with deionized water several times to remove dust and other impurities from its surface, and then dry it in an oven at 60~80℃.

[0017] (A2) The dried expanded vermiculite was placed in a 0.8-1M hydrochloric acid solution and acid-treated at 25-30℃ for 10-12 hours to improve the zeta potential of the vermiculite. The treated sample was washed to neutral by vacuum filtration and then dried in an oven at 60-80℃ to obtain the modified vermiculite material.

[0018] Preferably, in step (1), the modified vermiculite sample is prepared into a vermiculite powder solution with H2O2 solution or salt solution; the salt solution is a sodium chloride, lithium chloride or potassium chloride solution; the boron nitride powder material is prepared into a 10-30 g / L boron nitride powder solution with urea solution or H2O2 solution; the mass percentage concentration of urea solution or H2O2 solution or salt solution is 10-25%.

[0019] Preferably, in step (2), the vermiculite powder solution is homogenized in a high-pressure homogenizing reactor at a pressure of 1000~1300 bar for 0.5~4 h.

[0020] Preferably, in step (4), the mass percentage concentration of the PVDF solution is 10%.

[0021] Preferably, in step (5), the two-dimensional vermiculite flake powder is compounded with PVDF solution, and the mass percentage concentration of the two-dimensional vermiculite flake powder is 10-70%; the hydroxylated boron nitride powder is compounded with PVDF solution, and the mass percentage concentration of the hydroxylated boron nitride powder is 5-25%.

[0022] Preferably, in step (5), the two-dimensional vermiculite flake powder is compounded with PVDF solution, and the mass percentage concentration of the two-dimensional vermiculite flake powder is 40%-60%; the hydroxylated boron nitride powder is compounded with PVDF solution, and the mass percentage concentration of the hydroxylated boron nitride powder is 25%.

[0023] Preferably, the method for compounding the two-dimensional vermiculite flake powder with the PVDF solution is to stir at a speed of 400-1000 rpm for 4-24 hours; the method for compounding the hydroxylated boron nitride powder with the PVDF solution includes premixing by magnetic stirring, followed by shearing, ultrasonication, or homogenization.

[0024] The composite insulating paper obtained by the method described above also falls within the scope of protection of this invention.

[0025] Compared with the prior art, the beneficial effects of the present invention include:

[0026] 1. The present invention provides a technology that utilizes acid pretreatment coupled with a high-pressure homogenizing reactor to achieve simultaneous adjustment of vermiculite lamellae peeling, particle size, and surface microenvironment, which has the advantages of simple operation, speed, and high efficiency.

[0027] 2. The high-pressure homogenizing reactor used in this invention enhances the contact and collision between chemical reagents and materials. Furthermore, the shear force generated under high-speed turbulence further promotes salt intercalation, H₂O₂ decomposition, etc., strengthening the separation between the layers.

[0028] 3. This invention uses a "bridging" process to assemble two-dimensional nanosheets with polymer materials to form a multifunctional composite insulating paper. It not only has excellent electrical insulation properties and high temperature resistance, but also has high flexibility and mechanical properties, meeting the needs of modern electrical industry for high-performance electrical insulation materials. Attached Figure Description

[0029] Figure 1 This is a diagram of the original vermiculite in Example 1 of the present invention and its zeta potential after homogenization with and without acid treatment.

[0030] Figure 2 This is the vermiculite dispersion after acid treatment combined with microchannel homogenization in Example 1 of the present invention.

[0031] Figure 3 This is a diagram showing the original vermiculite in Example 1 of the present invention and its particle size distribution after homogenization with and without acid treatment.

[0032] Figure 4 The images show the original vermiculite and its homogenized forms after treatment with and without acid and hydrogen peroxide.

[0033] Figure 5 This is an example diagram of composite insulating paper prepared with different vermiculite addition amounts in Example 2 of the present invention. Figure 5 (a) is pure PVDF fiber paper; (b) is 10% Vt / PVDF fiber paper; (c) is 30% Vt / PVDF fiber paper; (d) is 50% Vt / PVDF fiber paper; and (e) is 70% Vt / PVDF fiber paper.

[0034] Figure 6 The images show the SEM images of the composite insulating paper prepared with different vermiculite addition amounts in Example 2 of this invention.

[0035] Figure 7 The images show the SEM images of composite insulating papers obtained with different amounts of OH-BNNS added in Example 3 of this invention.

[0036] Figure 8 The graph shows the breakdown voltage test results of composite insulating paper obtained with different amounts of OH-BNNS added in Example 3 of the present invention.

[0037] Figure 9 The figure shows the tensile strength test results of the 25wt.%-OH-BNNS / PVDF composite insulating paper of this invention and commercial paper. Detailed Implementation

[0038] The technical solution of the present invention will be further described in detail below through specific embodiments. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any modifications and / or alterations made to the present invention will fall within the protection scope of the present invention.

[0039] In this invention, the equipment and raw materials used are all commercially available or commonly used in the field. Unless otherwise specified, the methods in the following embodiments are conventional methods in the field.

[0040] The present invention discloses a composite insulating paper based on microchannel homogenization technology and its preparation method, comprising the following steps:

[0041] (1) Wash the expanded vermiculite with deionized water several times to remove dust and other impurities from its surface, and then dry it in an oven at 60~80℃.

[0042] (2) The dried vermiculite was placed in a 0.8-1M hydrochloric acid solution and acid-treated at 25-30℃ for 10-12 hours to improve the zeta potential of the vermiculite. The treated sample was washed to neutral by filtration and then dried in an oven at 60-80℃ to obtain the modified vermiculite material.

[0043] (3) Weigh a certain mass of the modified vermiculite sample described in step (1) and prepare it into a powder solution with different concentrations by mixing it with a 10-25% H2O2 solution or salt solution (including sodium chloride, lithium chloride, potassium chloride, etc.).

[0044] (4) Place the prepared vermiculite powder solution in a high-pressure homogenizing reactor (micro-jet high-pressure homogenizer, in this embodiment, the ATS high-pressure nano-homogenizer AH-NANO) at a pressure of 1000~1300 bar, and homogenize for 0.5~4h to obtain a uniformly dispersed vermiculite dispersion, reduce the vermiculite particle size, and obtain two-dimensional vermiculite flakes.

[0045] (5) The vermiculite dispersion obtained in step (4) was dried using a freeze dryer, with the freeze-drying temperature controlled at -50℃ and the freezing time at 24h.

[0046] (6) Prepare an organic solvent with an acetone:DMF ratio of 1:1, add 10 wt.% PVDF, and then add the two-dimensional vermiculite powder obtained in step (5) according to the mass ratio (10-70 wt.%), stir evenly to obtain the spinning solution. The stirring speed is 400-1000 rpm and the stirring time is 4-24 h.

[0047] (7) Using aluminum foil as the receiving substrate, set the voltage to 18~20kV, the liquid supply rate to 2~3mL / h, the rotation speed to 600rpm, and the temperature to 25℃, and electrospin the spinning solution prepared in step (6) to obtain Vt / PVDF composite insulating fiber paper.

[0048] This invention also provides a method for preparing ceramic insulating paper based on microchannel homogenization technology, comprising the following steps:

[0049] (1) Weigh a certain amount of boron nitride powder material and prepare it with functionalized homogenizing solvent (urea / water solvent or hydrogen peroxide / water solvent) to form powder solutions with different concentrations (10-30g / L).

[0050] (2) The prepared boron nitride (BN) powder solution is placed in a high-pressure homogenizing reactor (micro-jet high-pressure homogenizer, in this embodiment, an ATS high-pressure nano-homogenizer AH-NANO) at a pressure of 800-1400 bar and homogenized for 0.5-5 h to obtain hydroxylated boron nitride nanosheets (OH-BNNS) slurry.

[0051] (3) The slurry described in (2) is freeze-dried to obtain OH-BNNS powder, wherein the freeze-drying temperature is -50℃ and the freezing time is 24h.

[0052] (4) Dissolve PVDF powder (10g) in a solvent prepared by mixing DMF (60mL) and acetone (60mL) in a volume ratio of 1:1, and stir magnetically at a temperature of 60-70℃ until completely dissolved. The stirring speed is 400-1000rpm and the stirring time is 4-24h.

[0053] (5) The OH-BNNS powder obtained in step (3) and the PVDF solvent obtained in step (4) are compounded in a certain proportion to obtain an OH-BNNS / PVDF slurry. The compounding method includes premixing by magnetic stirring, followed by shearing, ultrasonic or homogenization treatment, preferably ultrasonic mixing.

[0054] The content of OH-BNNS powder is 5-25 wt.%. If the content of OH-BNNS powder is too low, it will not play a role in improving the matrix properties as a reinforcing phase. If the content of OH-BNNS powder is too high, it will be easy to disperse unevenly and the composite material will become more brittle and less tough.

[0055] (6) After vacuum degassing the OH-BNNS / PVDF slurry obtained in step (5), it is then uniformly coated onto a stainless steel substrate using a coating machine at a coating temperature of 60-100℃. After the solvent evaporates, OH-BNNS / PVDF composite insulating paper is obtained. The coating method can be spraying, brushing, spin coating, doctor blade coating, or coating machine coating, etc.

[0056] The present invention will be further illustrated by the following embodiments.

[0057] Example 1. Preparation of two-dimensional modified vermiculite powder

[0058] 5g of vermiculite was weighed, washed with deionized water, and dried in an oven at 80℃. It was then reacted with 50mL of 1M hydrochloric acid at room temperature for 12h. The sample was washed with deionized water using a vacuum filtration device until the filtrate was neutral. The separated solid sample was then dried in an oven at 80℃ to obtain modified vermiculite. Subsequently, it was prepared with H2O2 solution to a mass concentration of 10%, and homogenized under high pressure at 1100 bar (ATS high-pressure nano-homogenizer AH-NANO) for 0.5h to obtain a uniformly dispersed vermiculite dispersion. Two-dimensional modified vermiculite powder was obtained by using a high-temperature spray dryer with the outlet air temperature controlled at 80℃.

[0059] Comparative Example 1

[0060] The steps for this comparative example are the same as in Example 1, except that there is no acid pretreatment, and it is named N-Vt. The difference in surface electronegativity between the sample Vt prepared in Example 1 and the original vermiculite VT is shown in the figure. Figure 1 The results show that the zeta potentials of VT, N-Vt, and Vt are -24.7, -42.9, and -61.2 mV, respectively, with the electronegativity increasing sequentially. This may be because the synergistic effect of hydrogen peroxide and microfluidic homogenization enhances the exfoliation of vermiculite, exposing more surface functional groups. The significant increase in surface electronegativity after hydrochloric acid treatment is likely due to the introduction of more surface functional groups by the acid treatment. It is worth noting that a electronegativity of -60 mV is sufficient to ensure uniform dispersion of vermiculite. Figure 2 This is beneficial for preparing insulating paper with a uniform inorganic phase.

[0061] Figure 3 The figure shows the particle size distribution of VT, N-Vt, and Vt. As can be seen from the figure, the particle sizes of VT and N-Vt are 1992 nm and 1209 nm, respectively. This comparison indicates that the synergistic effect of hydrogen peroxide and microchannel homogenization can promote the reduction of vermiculite particle size. Furthermore, with the addition of acid pretreatment, the lateral size of vermiculite can be significantly reduced to 707 nm. This demonstrates that the coupling effect of acid pretreatment and the high-pressure homogenizing reactor can not only regulate the microchemical environment of the material surface but also achieve synchronous adjustment of vermiculite particle size.

[0062] Comparative Example 2

[0063] The steps in this comparative example are the same as in Example 1, except that there is no simultaneous microfluidic homogenization treatment with hydrogen peroxide, and it is named W-Vt. SEM images are shown comparing it with sample Vt prepared in Example 1, sample N-Vt prepared in Comparative Example 1, and the original vermiculite VT. Figure 4 It can be seen that VT exhibits a blocky morphology composed of numerous stacked nanosheets. When hydrogen peroxide was not added for microchannel homogenization, although the W-Vt nanosheets gradually separated, the exfoliation effect was limited, resulting in some nanosheets being separated. However, when hydrogen peroxide was added for simultaneous microchannel homogenization, vermiculite could be easily and quickly exfoliated into a monolayer morphology. Furthermore, vermiculite samples without acid pretreatment, after simultaneous microchannel homogenization with hydrogen peroxide, could still be exfoliated into a monolayer. This, combined with Comparative Example 1, demonstrates that acid treatment affects the particle size and surface microchemical environment of vermiculite, but does not affect its exfoliation.

[0064] Example 2. Preparation of two-dimensional modified vermiculite nanosheets / PVDF composite electrical insulating paper

[0065] Preparation of two-dimensional modified vermiculite nanosheets (Vt): 5g of vermiculite was weighed, washed with deionized water, and dried in an oven at 80℃. It was then reacted with 50mL of 1M hydrochloric acid at room temperature for 12h. The sample was washed with deionized water through a vacuum filtration device until the filtrate was neutral. The separated solid sample was dried in an oven at 80℃ to obtain modified vermiculite. Subsequently, it was prepared with H2O2 solution (10% by mass) to a concentration of 10g / L, and subjected to high-pressure homogenization (ATS high-pressure nano-homogenizer AH-NANO) at 1100bar for 2h to obtain a uniformly dispersed vermiculite dispersion. Two-dimensional modified vermiculite powder was obtained by freeze-drying at -50℃ for 24h.

[0066] Preparation of Vt / PVDF composite electrical insulating paper: An organic solvent was prepared according to the ratio of acetone:DMF = 1:1. 10% (w / w) of polyvinylidene fluoride (PVDF) was added, followed by Vt powder at a mass ratio of 10-70%. The mixture was stirred for 24 hours to obtain a spinning solution. Subsequently, using aluminum foil as the receiving substrate, the voltage was set to 20kV, the liquid supply rate to 2mL / h, the rotation speed to 600rpm, and the temperature to 25℃. The prepared spinning solution was then electrospun to obtain Vt / PVDF composite insulating fiber paper. Figure 5 As shown, the color of the composite insulating paper darkens with increasing Vt content. It is worth noting that the composite insulating paper maintains good flexibility even at Vt content as high as 70% (by mass). This inorganic component content is significantly higher than that of currently reported inorganic / organic composite insulating papers.

[0067] Furthermore, the 'bridging' structure between the vermiculite inorganic phase and the PVDF organic fibers can be clearly observed by SEM (see diagram). Figure 6 This tight bond helps enhance the mechanical and electrical properties of the composite insulating paper. Table 1 shows that the Vt / PVDF composite insulating fiber paper with a Vt content of 40% (mass percentage) exhibits higher tensile strength and elongation at break, significantly better than pure PVDF fiber paper, confirming that the tight bond between Vt and PVDF has a significant effect on enhancing the strength and flexibility of the insulating paper. When the Vt content increases to 60% (mass percentage), the tensile strength and elongation at break decrease. This may be because the 60% (mass percentage) Vt content is too high and insufficient to stably bond with the 10% (mass percentage) PVDF, leading to a decrease in mechanical properties. Regarding breakdown voltage (Table 1), the electrical insulation performance of the Vt / PVDF composite insulating paper is higher than that of the pure PVDF insulating paper. Specifically, at 30℃, with a Vt content of 60% (mass percentage), the composite insulating paper has the highest resistance value, reaching 36.2 kΩ, while the resistance value of the pure PVDF insulating paper is 1.67 kΩ. In comparison, the resistivity of electrical insulating paper with a Vt content of 60% (by mass) is 20 times that of PVDF film. This indicates that the 'bridging' combination of Vt and PVDF effectively improves the electrical insulation performance of the insulating paper. (The last sentence appears to be incomplete and possibly refers to a test temperature of 120°C.) o Under high-temperature conditions (C), the resistivity of 60% (by mass) insulating paper still reaches 19.3 kΩ. Furthermore, the thermal shrinkage rate of the insulating paper was determined according to GB / T5591.2-2017, "Flexible Composite Materials for Electrical Insulation - Part 2: Test Methods." The results show that the thermal shrinkage rate of the composite film is ≤0.5%, indicating that the Vt / PVDF composite insulating paper exhibits good high-temperature resistance. Overall, the Vt / PVDF composite insulating fiber paper with a "bridging" structure demonstrates excellent electrical, mechanical, and high-temperature resistance properties, showing potential application prospects.

[0068] Table 1 compares the performance parameters of composite insulating papers prepared with different Vt addition amounts.

[0069]

[0070] Example 3: Preparation method of ceramic insulating paper based on microchannel homogenization technology

[0071] (1) Preparation of two-dimensional functionalized boron nitride (OH-BNNS): Boron nitride and hydrogen peroxide were mixed to form a powder solution with a mass concentration of 10 g / L. The solution was placed in a high-pressure homogenizer (ATS high-pressure nano-homogenizer AH-NANO) at 1000 bar and homogenized for 1 h to allow the layered structure to expand and be completely exfoliated into boron nitride nanosheets (BNNS). Simultaneously, hydroxylated boron nitride nanosheets (OH-BNNS) slurry were generated through in-situ modification. After freeze-drying at -50℃ for 24 h, OH-BNNS powder was obtained.

[0072] (2) Preparation of PVDF solvent: Dissolve PVDF powder (10g) in a solvent prepared by DMF (60mL) and acetone (60mL) in a volume ratio of 1:1, and stir magnetically at 70°C until completely dissolved.

[0073] (3) Preparation of OH-BNNS / PVDF composite electrical insulating paper: OH-BNNS powder and PVDF solvent were compounded at a mass percentage of 10% or 25% OH-BNNS powder. The powder was magnetically stirred at 70℃ to disperse it evenly, and then ultrasonically treated to obtain OH-BNNS / PVDF slurry. After vacuum degassing, the slurry was uniformly coated onto a stainless steel substrate using a doctor blade coating machine at a coating temperature of 100℃. After the solvent evaporated, OH-BNNS / PVDF composite insulating paper was obtained, and SEM, breakdown voltage and tensile strength tests were performed on it.

[0074] Depend on Figure 7 As shown, the BNNS nanosheets have a diameter of approximately 500 nm, are uniformly distributed, and the density of the composite insulating paper increases with the increase of nanosheet addition. Regarding breakdown voltage ( Figure 8 The breakdown strength of the composite insulating paper increases with the increase of OH-BNNS content. This indicates that the electrical insulation performance of the composite insulating paper can be improved and controlled by adding OH-BNNS.

[0075] Furthermore, the performance of composite insulating paper with 25% OH-BNNS powder content (25%-OH-BNNS / PVDF) was compared with that of commercially available paper. The results showed that the breakdown voltage of the 25%-OH-BNNS / PVDF composite insulating paper was significantly improved, increasing by 92.3% compared to commercial paper, meeting the national standard requirements for power cable paper. Figure 9 As can be seen from Table 3, the elongation of the 25%-OH-BNNS / PVDF composite insulating paper is 135%, which is significantly greater than that of commercial paper (2.5%). The above results indicate that the composite insulating paper preparation method based on microchannel homogenization technology provided by the present invention has good scalability and applicability.

[0076] Table 2 Electrical breakdown strength test results

[0077]

[0078] Table 3 Tensile strength test results

[0079]

Claims

1. A method for preparing composite insulating paper based on microchannel homogenization technology, comprising the following steps: (1) Prepare a vermiculite powder solution from the modified vermiculite material; (2) The vermiculite powder solution was homogenized in a high-pressure homogenizing reactor at a pressure of 800-1400 bar for 0.5-5 h to obtain a two-dimensional vermiculite nanosheet dispersion; (3) The two-dimensional vermiculite nanosheet dispersion obtained in step (2) was dried using a freeze dryer. The freeze-drying temperature was controlled at -50℃ and the freezing time was 24h to obtain two-dimensional vermiculite sheet powder. (4) Prepare an organic solvent by mixing acetone and DMF in a 1:1 mass ratio, and add PVDF to obtain a PVDF solution; (5) The two-dimensional vermiculite flake powder obtained in step (3) and the PVDF solution obtained in step (4) are combined to obtain two-dimensional vermiculite nanosheet powder / PVDF spinning solution; (6) Electrospinning of two-dimensional vermiculite nanosheet powder / PVDF spinning solution with aluminum foil as the receiving substrate, setting the voltage to 18~20kV, the liquid supply rate to 2~3mL / h, the rotation speed to 600rpm, and the temperature to 25℃, to obtain two-dimensional vermiculite nanosheet / PVDF composite insulating fiber paper; the modified vermiculite material is prepared according to the following steps: (A1) Wash the expanded vermiculite with deionized water several times to remove dust and impurities from its surface, and then dry it in an oven at 60~80℃. (A2) The dried expanded vermiculite was placed in a 0.8-1M hydrochloric acid solution and acid-treated at 25-30℃ for 10-12 hours to improve the zeta potential of the vermiculite. The treated sample was washed to neutral by vacuum filtration and then dried in an oven at 60-80℃ to obtain the modified vermiculite material.

2. The method according to claim 1, characterized in that, In step (1), the modified vermiculite sample is prepared into a vermiculite powder solution with H2O2 solution or salt solution; the salt solution is sodium chloride, lithium chloride or potassium chloride solution; the mass percentage concentration of H2O2 solution or salt solution is 10-25%.

3. The method according to claim 1, characterized in that, In step (2), the vermiculite powder solution is homogenized in a high-pressure homogenizing reactor at a pressure of 1000~1300 bar for 0.5~4 h.

4. The method according to claim 1, characterized in that, In step (4), the mass percentage concentration of the PVDF solution is 10%.

5. The method according to claim 1, characterized in that, In step (5), the two-dimensional vermiculite flake powder is compounded with PVDF solution, and the mass percentage concentration of the two-dimensional vermiculite flake powder is 10-70%.

6. The method according to claim 5, characterized in that, In step (5), the two-dimensional vermiculite flake powder is compounded with PVDF solution, and the mass percentage concentration of the two-dimensional vermiculite flake powder is 40%-60%.

7. The method according to claim 1, characterized in that, The method for compounding the two-dimensional vermiculite flake powder with PVDF solution is to stir at a speed of 400-1000 rpm for 4-24 hours.

8. The composite insulating paper obtained by the method according to any one of claims 1-7.

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