Composite filler resistant to dielectric breakdown, preparation method and application

Abstract

The application relates to the technical field of insulating material preparation, in particular to a composite filler resistant to insulating breakdown, a preparation method and application. The method is characterized in that the basalt flake is pretreated to remove impurities in the basalt flake; the pretreated basalt flake is mixed with nanocellulose and ground to obtain a mixture. In the process, due to the ball milling process and the introduction of nanofibers, efficient peeling of the basalt flake can be realized, the basalt flake forms smaller and more uniform flake particles, and the flake particles can be fully interwoven with the nanocellulose to form a tightly combined composite material; the mixture is diluted in water, and the unpeeled basalt flake is removed to obtain the composite filler. The composite filler realizes effective combination of the organic fiber and the basalt flake, has excellent mechanical properties and mechanical properties, and solves the problem that the interface of the organic fiber and the inorganic basalt flake is difficult to combine, thereby affecting the mechanical properties of paper.

Description

Technical Field

[0001] This invention relates to the field of insulating material preparation technology, specifically to a composite filler resistant to insulation breakdown, its preparation method, and its application. Background Technology

[0002] Cellulose materials are widely used in electrical insulation due to their low cost and renewability. However, traditional cellulose paper has some inherent drawbacks, such as susceptibility to moisture, high porosity, and insufficient heat resistance, which can affect the performance and lifespan of insulating paper. To address these issues and improve the quality and stability of electronic products, paper modification is crucial.

[0003] Currently, researchers mainly employ two approaches to improve the performance and stability of cellulose-based sound-absorbing materials: chemical modification and composite materials. Among these, composite materials have been widely developed because the properties and structure of each component can be designed and optimized as needed, resulting in excellent overall performance. By combining cellulose materials with other high-performance materials, the interfacial properties and insulation capabilities of cellulose materials can be improved, while simultaneously enhancing the mechanical strength and temperature resistance of insulating materials, thus improving their performance in complex environments and meeting higher levels of insulation requirements.

[0004] Basalt flakes are a high-performance inorganic material, a new type of material made from high-performance natural basalt ore through special processes such as high-temperature melting, clarification, homogenization, and screening. The thickness is generally around 2-6 μm, and the area varies, typically around 0.5 mm. 2 ~5mm 2 The content of silicon dioxide and aluminum oxide in basalt flakes is high, giving them not only insulating properties but also unique advantages in acid and alkali resistance and corrosion resistance. Their operating temperature range is -200℃ to 1100℃, allowing them to adapt to harsh environments with large temperature differences. However, the interface between organic fibers and inorganic basalt flakes is difficult to bond, resulting in numerous defects during the lamination process. This directly affects the mechanical properties of the paper, hindering the development of basalt flakes in the field of insulating paper manufacturing. Summary of the Invention

[0005] To address the problem in existing technologies where the interface between organic fibers and inorganic basalt flakes is difficult to bond, thus affecting the mechanical properties of paper, this invention provides a composite filler resistant to insulation breakdown, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention provides a method for preparing a composite filler resistant to insulation breakdown, comprising:

[0008] Basalt flakes were pretreated to obtain pretreated basalt flakes;

[0009] The pretreated basalt flakes were mixed with nanocellulose and ground to obtain a mixture; the mixture included nanocellulose-basalt nanosheet composite filler and unpeeled basalt flakes.

[0010] The mixture was diluted in water, and the unpeeled basalt flakes were removed to obtain the composite filler.

[0011] Optionally, the method for pretreating basalt flakes is as follows:

[0012] Basalt flakes were dispersed in deionized water and then subjected to stirring, settling, filtration, and drying to obtain pretreated basalt flakes. The stirring speed was 100–400 r / min, the settling time was 1–2 min, the filtration mesh size was 100–150 mesh, and the drying temperature was 100℃–120℃.

[0013] Optionally, the mass ratio of the pretreated basalt flakes to nanocellulose is (1:3) to (3:1), the grinding speed is 250 to 550 r / min, and the grinding time is 0.5 to 4 h.

[0014] Optionally, the method of diluting the mixture in water and removing unpeeled basalt flakes to obtain the composite filler is as follows:

[0015] The mixture was diluted in water to obtain a mixed suspension;

[0016] The mixed suspension was subjected to ultrasonic treatment to obtain a uniformly dispersed mixed suspension.

[0017] The uniformly dispersed mixed suspension was centrifuged, and the supernatant was retained to obtain the composite packing.

[0018] Optionally, the solid concentration in the mixed suspension is 0.1% to 1%; the ultrasonic treatment power is 500 to 1000 W, and the ultrasonic treatment time is 10 to 60 min; the centrifugation speed is 500 to 2500 r / min, and the time is 5 to 25 min.

[0019] A composite filler resistant to insulation breakdown is prepared using the method described above.

[0020] A method for preparing insulating paper using the above-mentioned composite filler resistant to insulation breakdown includes:

[0021] The composite filler is mixed with softwood pulp to obtain a mixed pulp;

[0022] The mixed slurry is sequentially decomposed, sheeted, filtered, dried, and hot-pressed to obtain insulating paper.

[0023] Optionally, the amount of composite filler added during the mixing process of composite filler and softwood pulp is 5% to 30% by mass percentage.

[0024] Optionally, in the process of sequentially dissolving, sheeting, filtering, drying and hot pressing the mixed slurry to obtain insulating paper, the dissolving speed is 6000-10000 r, the drying temperature is 80℃-120℃, the drying time is 5-20 min, the hot pressing temperature is 100-120℃, and the hot pressing time is 5-20 min.

[0025] An insulating paper is prepared using the aforementioned composite filler resistant to insulation breakdown.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention provides a method for preparing a composite filler resistant to insulation breakdown. The method involves pre-treating basalt flakes to remove impurities, which facilitates the formation of a good insulating layer within the composite filler. Then, the pre-treated basalt flakes are mixed with nanocellulose and ground to obtain a mixture. During this process, the ball milling and the introduction of nanofibers enable efficient exfoliation of the basalt flakes, resulting in finer and more uniform flake particles. These particles are fully interwoven with the nanocellulose to form a tightly bonded composite material. Since the ground mixture includes both nanocellulose-basalt nanosheet composite filler and unexfoliated basalt flakes, the mixture is further processed by diluting it in water and removing the unexfoliated basalt flakes to obtain the composite filler. This composite filler effectively combines organic fibers and basalt flakes, exhibiting excellent mechanical properties, weather resistance, corrosion resistance, sound absorption, and heat insulation. The nanocellulose-basalt nanosheet composite filler used to prepare insulating paper has good mechanical strength and insulation properties, laying the foundation for improving the performance of insulating paper. The preparation method is simple and easy to operate, requiring no large-scale equipment, and is relatively easy to industrialize, increasing the possibility of industrial-scale mass production.

[0028] The method for pretreating basalt flakes involves dispersing basalt flakes in deionized water, followed by sequential stirring, settling, filtration, and drying to obtain pretreated basalt flakes. The stirring speed is 100–400 r / min, the settling time is 1–2 min, the filtration mesh size is 100–150 mesh, and the drying temperature is 100℃–120℃. This method ensures uniform dispersion of basalt flakes in water, potentially promoting surface activation and improving the efficiency of subsequent treatments, thus providing a good foundation for further processing.

[0029] The mass ratio of the pretreated basalt flakes to nanocellulose is (1:3) to (3:1), the grinding speed is 250 to 550 r / min, and the grinding time is 0.5 to 4 h. The basalt flakes have high strength and rigidity, while nanocellulose has excellent flexibility and toughness. Mixing and grinding the two in a certain proportion can make them fully combine to form a composite material with excellent mechanical properties.

[0030] The method for diluting the mixture in water and removing unpeeled basalt flakes to obtain the composite filler involves diluting the mixture in water to obtain a mixed suspension; then, subjecting the mixed suspension to ultrasonic treatment to obtain a uniformly dispersed mixed suspension; finally, centrifuging the uniformly dispersed mixed suspension and retaining the supernatant to obtain the composite filler. Ultrasonic centrifugation can quickly remove unpeeled basalt flakes from the mixture, retaining the pure nanocellulose-basalt flake composite, resulting in a pure and uniform composite filler.

[0031] This invention also provides a composite filler resistant to insulation breakdown, prepared using the method described above. This composite filler exhibits excellent insulation breakdown strength, good overall structural stability and durability, and can meet the application requirements of various fields.

[0032] This invention also provides a method for preparing insulating paper using the aforementioned composite filler with high resistance to insulation breakdown. This method involves mixing the composite filler with softwood pulp to obtain a mixed slurry; the mixed slurry is then sequentially subjected to descaling, sheet forming, filtration, drying, and hot pressing to obtain the insulating paper. The preparation method is simple, easy to operate, requires no modification to existing equipment, is low-cost, and easily industrialized. The prepared insulating paper exhibits superior mechanical properties, including excellent resistance to insulation breakdown.

[0033] This invention provides an insulating paper prepared using the aforementioned composite filler resistant to insulation breakdown. This insulating paper exhibits excellent insulation properties, with high insulation resistance, effectively preventing current flow and thus protecting circuits and equipment. It has broad application prospects in electrical equipment, electronic products, and other fields, and can be used to manufacture various insulating components and packaging materials. Furthermore, this insulating paper also possesses high heat resistance and flame retardancy, good plasticity and processability, and maintains stable performance in high-temperature environments. This is of great significance for electrical equipment and electronic products that need to be used in high-temperature or flammable environments. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the preparation method of a composite filler resistant to insulation breakdown according to the present invention.

[0035] Figure 2 Tyndall effect and UV-Near-infrared absorption spectra of the aqueous dispersion of the composite filler prepared in Example 1 of the present invention.

[0036] Figure 3 Transmission electron microscopy (TEM) image of the composite filler prepared in Example 2 of this invention.

[0037] Figure 4 AFM images of the composite filler prepared in Example 3 of this invention and a statistical diagram of the transverse and longitudinal dimensions of the basalt nanosheets are shown; where a is an atomic force microscope morphology image; b is a statistical diagram of the transverse dimensions of the composite filler; and c is a statistical diagram of the thickness dimensions of the composite filler.

[0038] Figure 5 The image shows the infrared spectra of the composite filler at different grinding times in Example 4 of the present invention.

[0039] Figure 6 Images of the breakdown strength of insulating paper with different proportions of composite filler prepared in Example 12 and the comparative example of the present invention, as well as field emission scanning electron microscope images of the breakdown points of the insulating paper; wherein, a is a breakdown strength diagram of insulating paper with different proportions of composite filler added; b is a scanning electron microscope image of the electrical breakdown point of the insulating paper; c is a scanning electron microscope image of the breakdown point at magnification.

[0040] Figure 7 The figures show the tensile curves and statistical graphs of strength, elongation, toughness, and modulus of insulating paper with different proportions of composite filler prepared in Example 12 and the comparative example of the present invention. Among them, a is the stress-strain curve of the tensile test of insulating paper with different proportions of composite filler; b is the toughness and density of insulating paper with different proportions of composite filler; and c is the tensile strength and Young's modulus of insulating paper with different proportions of composite filler. Detailed Implementation

[0041] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0042] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0043] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0044] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0045] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0046] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0047] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0048] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0049] This invention discloses a method for preparing a composite filler resistant to insulation breakdown, referring to... Figure 1 ,include:

[0050] S1: Pre-treatment of basalt flakes to obtain pre-treated basalt flakes, specifically:

[0051] Basalt flakes are dispersed in deionized water and sequentially stirred, allowed to stand, filtered, and dried to obtain pretreated basalt flakes. The stirring speed is 100–400 r / min, preferably 150–300 r / min, and more preferably 180–250 r / min; the standing time is 1–2 min, preferably 2 min; the filtration mesh size is 100–150 mesh, preferably 120–150 mesh, and more preferably 130–150 mesh; the drying temperature is 80℃–120℃, preferably 100℃–110℃, and more preferably 105℃–110℃.

[0052] S2: The pretreated basalt flakes are mixed with nanocellulose and ground to obtain a mixture; the mixture includes nanocellulose-basalt nanosheet composite filler and unpeeled basalt flakes, specifically:

[0053] The pretreated basalt flakes and nanocellulose are mixed at a mass ratio of (1:3) to (3:1), preferably (1:2) to (3:1), more preferably (2:1) to (3:1), and placed in a ball mill. The mixture is then ground at a speed of 250 to 550 r / min, preferably 300 to 550 r / min, more preferably 400 to 550 r / min, for 0.5 to 4 hours, preferably 2 to 4 hours, more preferably 3 to 4 hours, to obtain a mixture. The nanocellulose includes, but is not limited to, TEMPO (2,2,6,6-tetramethylpiperidine oxide) oxidized nanocellulose.

[0054] S3: Dilute the mixture in water and remove any unpeeled basalt flakes to obtain the composite filler, specifically:

[0055] The mixture is diluted in water to obtain a mixed suspension; wherein the solid concentration in the mixed suspension is 0.1% to 1%, preferably 0.3% to 0.7%, and more preferably 0.5% to 0.7%;

[0056] The mixed suspension is subjected to ultrasonic treatment to obtain a uniformly dispersed mixed suspension; wherein the power of the ultrasonic treatment is 500-1000W, preferably 600-800W, more preferably 600-800W, and the ultrasonic treatment time is 10-60min, preferably 15-40min, more preferably 20-40min;

[0057] The uniformly dispersed mixed suspension is centrifuged, and the supernatant is retained to obtain the composite packing. The centrifugation speed is 500-2500 r / min, preferably 800-2500 r / min, more preferably 1000-2500 r / min, and the time is 5-25 min, preferably 8-20 min, more preferably 10-15 min.

[0058] This invention provides a composite filler resistant to insulation breakdown, prepared using the method described above. This composite filler exhibits excellent insulation breakdown strength, good overall structural stability and durability, and can meet the application requirements of various fields.

[0059] The present invention also provides a method for preparing insulating paper using the above-mentioned composite filler resistant to insulation breakdown, comprising:

[0060] The composite filler is mixed with softwood pulp to obtain a mixed pulp; wherein, during the mixing process of the composite filler and softwood pulp, the amount of composite filler added is 5% to 30%;

[0061] The mixed slurry is sequentially subjected to decomposition, sheet forming, filtration, drying, and hot pressing to obtain insulating paper; wherein the decomposition rotation speed is 6000-10000r, the drying temperature is 80℃-120℃, the drying time is 5-20min, the hot pressing temperature is 100-120℃, and the hot pressing time is 5-20min.

[0062] This invention provides an insulating paper prepared using the aforementioned composite filler resistant to insulation breakdown. This insulating paper exhibits excellent insulation properties, with high insulation resistance, effectively preventing current flow and thus protecting circuits and equipment. It has broad application prospects in electrical equipment, electronic products, and other fields, and can be used to manufacture various insulating components and packaging materials. Furthermore, this insulating paper also possesses high heat resistance and flame retardancy, good plasticity and processability, and maintains stable performance in high-temperature environments. This is of great significance for electrical equipment and electronic products that need to be used in high-temperature or flammable environments.

[0063] Example 1

[0064] Basalt flakes (BS) were dispersed in deionized water and stirred at 200 rpm until uniformly dispersed. Stirring was then stopped, and the mixture was allowed to stand for 1 minute. The basalt flake suspension was then filtered and dried at 80°C using a 100-mesh filter. The pretreated basalt flakes were then mixed with nanocellulose at a 1:3 ratio and ground at 250 rpm for 0.5 hours. The grinding product was collected, yielding a mixture of nanocellulose-basalt nanosheet composite filler and unpeeled basalt flakes. This mixture was diluted in deionized water to a concentration of 0.1% and then sonicated at 500 W for 10 minutes. Finally, the sonicated mixture was placed in centrifuge tubes and centrifuged at 500 rpm for 5 minutes. The supernatant obtained was the aqueous dispersion of the composite filler, which was sealed and stored for later use.

[0065] See Figure 2 The composite filler prepared in this embodiment was subjected to Tyndall effect and ultraviolet-near-infrared absorption spectroscopy tests. The results showed that the composite filler was a uniform and transparent light gray colloid. Based on the band gap width of 5.48 eV, it was determined to be an insulator.

[0066] Example 2

[0067] Basalt flakes were dispersed in deionized water and stirred at 200 r / min until the basalt flakes were uniformly dispersed in the water. Stirring was stopped and the suspension was allowed to stand for 2 min. The basalt flake suspension was then filtered and dried. The filtration mesh size was 150 mesh and the drying temperature was 90℃ to obtain pretreated basalt flakes. The pretreated basalt flakes were then mixed with nanocellulose at a ratio of 1:2 and ground at 300 r / min for 1 h. The grinding product was then collected to obtain a mixture of nanocellulose-basalt nanosheet composite filler and unpeeled basalt flakes.

[0068] The mixture was diluted in deionized water to a concentration of 0.3%, and then sonicated in an ultrasonic machine at a power of 600W for 20 minutes. Finally, the ultrasonically treated mixture was placed into centrifuge tubes and centrifuged at 1000 r / min for 10 minutes. The supernatant obtained by centrifugation is the aqueous dispersion of the composite filler, which was sealed and stored for later use.

[0069] See Figure 3 Transmission electron microscopy (TEM) tests were performed on the composite filler prepared in the examples, which showed that the composite filler was composed of basalt nanosheets with a diameter of about 300 nm and nanocellulose with a diameter of less than 10 nm.

[0070] Example 3

[0071] Basalt flakes were dispersed in deionized water and stirred at 200 r / min until the basalt flakes were uniformly dispersed in the water. Stirring was stopped and the suspension was allowed to stand for 1 min. The basalt flake suspension was then filtered and dried. The filtration mesh size was 100 mesh and the drying temperature was 100℃ to obtain pretreated basalt flakes. The pretreated basalt flakes were then mixed with nanocellulose at a ratio of 2:1 and ground at 350 r / min for 2 h. The grinding product was then collected to obtain a mixture of nanocellulose-basalt nanosheet composite filler and unpeeled basalt flakes.

[0072] The mixture was diluted in deionized water to a concentration of 0.5%, and then sonicated in an ultrasonic machine at a power of 700W for 30 minutes. Finally, the ultrasonically treated mixture was placed into centrifuge tubes and centrifuged at 1500 r / min for 15 minutes. The supernatant obtained by centrifugation is the aqueous dispersion of the composite filler, which was sealed and stored for later use.

[0073] See Figure 4 Atomic force testing was performed on the prepared composite filler. From the AFM images and the statistical diagram of the transverse and longitudinal dimensions of the basalt nanosheets, it can be seen that the average thickness of the basalt nanosheets in the composite filler is 1.5 nm and the average diameter is 300 nm, while the diameter of the nanocellulose is generally greater than 2.5 nm and the length is between 100 nm and 500 nm.

[0074] Example 4

[0075] Basalt flakes were dispersed in deionized water and stirred at 200 r / min until the flakes were uniformly dispersed. Stirring was then stopped, and the suspension was allowed to stand for 2 min. The suspension was then filtered and dried at 105 °C to obtain pretreated basalt flakes. The pretreated basalt flakes were then mixed with nanocellulose at a 1:1 ratio and ground at 400 r / min for 0 h, 1 h, 2 h, 4 h, and 6 h, respectively. The grinding products were then collected to obtain a mixture of nanocellulose-basalt nanosheet composite filler and unpeeled basalt flakes.

[0076] The mixture was diluted in deionized water to a concentration of 0.7%, and then sonicated in an ultrasonic machine at a power of 800W for 40 minutes. Finally, the ultrasonically treated mixture was placed in a centrifuge tube and centrifuged at 2000 r / min for 20 minutes. The supernatant obtained by centrifugation is the aqueous dispersion of the composite filler, which was sealed and stored for later use.

[0077] See Figure 5 As can be seen from the infrared spectra of the composite packing after ball milling for different times, the hydroxyl peak of the composite packing decreases from 3600 cm⁻¹ to 3600 cm⁻¹ as the ball milling time increases. -1 The distance has shifted to 3700cm. -1 Nearby, the hydroxyl peak redshifted, indicating that hydrogen bonding occurred between the surface of the nanocellulose and the surface of the basalt nanosheets.

[0078] Example 5

[0079] Basalt flakes were dispersed in deionized water and stirred at 200 r / min until the basalt flakes were uniformly dispersed in the water. Stirring was stopped and the suspension was allowed to stand for 1 min. The basalt flake suspension was then filtered and dried. The filtration mesh size was 100 mesh and the drying temperature was 110℃ to obtain pretreated basalt flakes. The pretreated basalt flakes were then mixed with nanocellulose at a ratio of 3:1 and ground at 450 r / min for 4 h. The grinding product was then collected to obtain a mixture of nanocellulose-basalt nanosheet composite filler and unpeeled basalt flakes.

[0080] The mixture was diluted in deionized water to a concentration of 0.9%, and then sonicated in an ultrasonic machine at a power of 900W for 50 minutes. Finally, the ultrasonically treated mixture was placed into centrifuge tubes and centrifuged at 2500 r / min for 25 minutes. The supernatant obtained by centrifugation is the aqueous dispersion of the composite filler, which was sealed and stored for later use.

[0081] Example 6

[0082] Basalt flakes were dispersed in deionized water and stirred at 200 r / min until the flakes were uniformly dispersed. Stirring was then stopped, and the suspension was allowed to stand for 2 min. The suspension was then filtered and dried at 150 mesh and 120 °C to obtain pretreated basalt flakes. The pretreated basalt flakes were then mixed with nanocellulose at a ratio of 2:3 and ground at 500 r / min for 0.5 h. The grinding product was then collected to obtain a mixture of nanocellulose-basalt nanosheet composite filler and unpeeled basalt flakes.

[0083] The mixture was diluted in deionized water to a concentration of 1%, and then sonicated in an ultrasonic machine at a power of 1000W for 60 minutes. Finally, the ultrasonically treated mixture was placed into centrifuge tubes and centrifuged at 2500r / min for 25 minutes. The supernatant obtained by centrifugation is the aqueous dispersion of the composite filler, which was sealed and stored for later use.

[0084] Example 7

[0085] The composite filler prepared in Example 2 was added to softwood pulp at a ratio of 5% and mixed and loosened at a loosening speed of 7000 r. The mixed pulp was filtered using a paper forming machine, then dried for 10 min at a drying temperature of 90°C, and finally hot-pressed at 105°C for 10 min to obtain a composite paper with high insulation properties.

[0086] Example 8

[0087] The composite filler prepared in Example 3 was added to softwood pulp at a ratio of 10% and mixed and loosened at a loosening speed of 8000 r. The mixed pulp was filtered using a paper forming machine, then dried for 15 min at a drying temperature of 100°C, and finally hot-pressed at 110°C for 15 min to obtain a composite paper with high insulation properties.

[0088] Example 9

[0089] The composite filler prepared in Example 4 was added to softwood pulp at a ratio of 15% and mixed and loosened at a loosening speed of 9000 r. The mixed pulp was filtered using a paper forming machine, then dried for 20 min at a drying temperature of 105°C, and finally hot-pressed at 115°C for 20 min to obtain a composite paper with high insulation properties.

[0090] Example 10

[0091] The composite filler prepared in Example 5 was added to softwood pulp at a ratio of 20% and mixed and loosened at a loosening speed of 10,000 r. The mixed pulp was filtered using a paper forming machine, then dried for 10 min at a drying temperature of 110°C, and finally hot-pressed at 120°C for 10 min to obtain a composite paper with high insulation properties.

[0092] Example 11

[0093] The composite filler prepared in Example 6 was added to softwood pulp at a ratio of 20% and mixed and loosened at a loosening speed of 10,000 r. The mixed pulp was filtered using a paper forming machine, then dried for 10 min at a drying temperature of 110°C, and finally hot-pressed at 120°C for 10 min to obtain a composite paper with high insulation properties.

[0094] Example 12

[0095] The composite filler prepared in Example 1 was decomposed with softwood pulp at concentrations of 2%, 5%, 10%, 20%, and 30% respectively, with a decomposition speed of 6000 r. The mixed pulp was filtered using a paper forming machine, then dried for 5 min at a drying temperature of 80°C, and finally hot-pressed at 100°C for 5 min to obtain a composite paper with high insulation properties.

[0096] Comparative Example

[0097] The softwood pulp was directly decomposed at 6000 revolutions. The mixed pulp was then filtered using a papermaking machine, dried for 5 minutes at 80°C, and finally hot-pressed at 100°C for 5 minutes to obtain a composite paper with high insulation properties.

[0098] The insulating paper prepared in Example 12 and the comparative example was subjected to breakdown strength test. With the addition of composite filler, the breakdown strength of composite paper was significantly improved. When the addition ratio was 15%, the composite paper reached the highest breakdown strength of 72.7 kV / mm. As can be seen from the field emission scanning electron microscope image, the composite filler made the surface and interior of the paper more compact, effectively preventing dendritic breakdown.

[0099] See Figure 7 Mechanical property tests were conducted on the insulating paper prepared in Example 12 and the comparative example. It was found that the composite filler has the effect of strengthening and toughening the insulating paper, and the best tensile strength of 102 MPa was achieved when the addition ratio was 10%.

[0100] In summary, this invention provides a composite filler resistant to insulation breakdown, its preparation method, and its application. By introducing nanocellulose and ball milling, efficient exfoliation of basalt flakes can be achieved, forming a tightly bonded composite material with the nanocellulose. The prepared nanocellulose-basalt nanosheet composite filler-reinforced insulating paper exhibits excellent mechanical strength and insulation properties, while also possessing other advanced composite materials with superior environmental resistance, meeting the needs of specialized fields such as aerospace. The preparation method is simple and easy to operate, requiring no large-scale equipment, and is relatively easy to industrialize, increasing the possibility of large-scale industrial production.

[0101] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A method for preparing a composite filler resistant to insulation breakdown, characterized in that, include: The basalt flakes were pretreated to obtain pretreated basalt flakes, specifically as follows: Basalt flakes were dispersed in deionized water and then successively stirred, allowed to stand, filtered through 100-150 mesh and dried to obtain pretreated basalt flakes. Pretreated basalt flakes are mixed with nanocellulose and ground to obtain a mixture; wherein the mass ratio of the pretreated basalt flakes to nanocellulose is (1:3) to (3:1), the grinding speed is 250 to 550 r / min, and the grinding time is 0.5 to 4 h; the mixture includes nanocellulose-basalt nanosheet composite filler and unpeeled basalt flakes; The mixture was diluted in water, and the unpeeled basalt flakes were removed to obtain the composite filler, specifically: The mixture was diluted in water to obtain a mixed suspension; The mixed suspension was subjected to ultrasonic treatment to obtain a uniformly dispersed mixed suspension. The uniformly dispersed mixed suspension was centrifuged, and the supernatant was retained to obtain the composite packing.

2. The method for preparing the composite filler resistant to insulation breakdown according to claim 1, characterized in that, The stirring speed is 100-400 r / min, the standing time is 1-2 min, and the drying temperature is 100℃-120℃.

3. The method for preparing the composite filler resistant to insulation breakdown according to claim 1, characterized in that, The solid concentration in the mixed suspension is 0.1% to 1%; the ultrasonic treatment power is 500 to 1000W, and the ultrasonic treatment time is 10 to 60 min; the centrifugation speed is 500 to 2500 r / min, and the time is 5 to 25 min.

4. A composite filler resistant to insulation breakdown, characterized in that, Prepared using the method described in any one of claims 1-3.

5. A method for preparing insulating paper using the composite filler with insulation breakdown resistance as described in claim 4, characterized in that, include: The composite filler is mixed with softwood pulp to obtain a mixed pulp; The mixed slurry is sequentially decomposed, sheeted, filtered, dried, and hot-pressed to obtain insulating paper.

6. The method for preparing insulating paper according to claim 5, characterized in that, By weight percentage, the amount of composite filler added during the mixing process of composite filler and softwood pulp is 5% to 30%.

7. The method for preparing insulating paper according to claim 5, characterized in that, In the process of sequentially dissolving, sheeting, filtering, drying and hot pressing the mixed slurry to obtain insulating paper, the dissolving speed is 6000-10000r, the drying temperature is 80℃-120℃, the drying time is 5-20min, the hot pressing temperature is 100-120℃, and the hot pressing time is 5-20min.

8. An insulating paper, characterized in that, Prepared using the method for preparing insulating paper as described in claim 5.

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