Preparation method of self-repairing cellulose insulating paper doped with ultraviolet light triggered microcapsules

Abstract

The application discloses a kind of self-repairing cellulose insulating paper preparation methods of doped ultraviolet light trigger microcapsule, comprising: in the process of insulating paper beating papermaking, prepared microcapsule is added, and microcapsule is migrated using directional magnetic field;Wherein, the microcapsule includes microcapsule core material and microcapsule wall material, the core material is prepared by Fe3O4@SiO2 Nanoparticle to repairant modification, the wall material is prepared by TiO2 Nanoparticle to polyurea formaldehyde prepolymer modification;The repairant includes epoxy acrylate, neopentyl glycol diacrylate, photo initiator;The photo initiator is 2,2-dimethoxy-2-phenyl phenylacetone.The application realizes active identification and immediate self-repairing to insulating paper small damage by embedding ultraviolet light trigger microcapsule structure in cellulose, once material is damaged, microcapsule breaks and releases repairant, and is cured under ultraviolet light irradiation, so as to effectively fill and repair damage, significantly improve the durability and stability of insulating paper.

Description

Technical Field

[0001] The present invention relates to the field of high voltage and insulation technology, and in particular to a method for preparing self-repairing cellulose insulation paper doped with ultraviolet light-triggered microcapsules. Background Art

[0002] Since the 1890s, natural cellulose-based insulating paper has been an indispensable insulating material for oil-immersed power equipment due to its many advantages, including low cost, excellent mechanical strength, easily controlled size, outstanding electrical performance after oil immersion, and environmental friendliness. This despite significant progress and changes in the field of insulating materials. Within the broader arena of electrical insulation, the stable operation of power grids relies on reliable and durable insulating materials. However, during the preparation, installation, and long-term operation of insulating paper, due to process conditions, long-term electrothermal stresses, and excessive physical deformation, subtle defects such as microcracks and electrical dendrites are often unavoidable. These tiny defects, hidden deep within the material, gradually expand under the continuous influence of factors such as electric fields and high temperatures, potentially distorting the electric field distribution and inducing partial discharge, posing a serious challenge to the safe operation of the power grid.

[0003] Even more problematic is that these subtle damages are often difficult to detect in a timely manner with existing technologies. Even if they can be discovered, the only option is to resort to extreme measures such as replacing the entire material. This, in busy areas, not only means the enormous difficulty of power outages for construction, but also requires a significant investment of manpower, material, and financial resources. This, along with the generation of large amounts of waste, exacerbates the pressure on solid waste disposal and the waste of resources. Therefore, if the insulating material could possess self-repair capabilities—that is, it could automatically sense and initiate repair mechanisms at the first sign of damage, promptly curbing the spread of damage and preventing further deterioration—it would be possible to effectively restore material performance and significantly reduce the risk of damage to electrical equipment and the probability of accidents.

[0004] Microcapsule-assisted self-healing materials are an innovative solution that has emerged in this context. Their core principle is to embed microcapsules containing a healing agent within the material. Once damage occurs within the material, stress concentration at the damaged site causes the microcapsules to rupture. The released healing agent then solidifies under external stimulation, filling and repairing the damaged structure, achieving self-repair and regeneration of the material. However, research in the field of microcapsule self-healing materials using UV light to trigger automatic recognition and instant self-healing is rare. Summary of the Invention

[0005] The present invention is dedicated to solving the difficult problems faced by traditional cellulose insulating paper in applications, such as the difficulty in detecting minor damage and preventing and controlling damage expansion. It innovatively proposes a method for preparing self-repairing cellulose insulating paper doped with ultraviolet light-triggered microcapsules. Compared with traditional cellulose insulating paper, the self-repairing insulating paper prepared by the present invention achieves active identification and immediate repair of minor damage by cleverly embedding a microcapsule structure triggered by ultraviolet light. This not only enhances the durability of the insulating paper, but also substantially extends its service life, significantly improving its stability and safety in complex environments, and bringing revolutionary progress to the field of high voltage and insulating materials. The technical solution of the present invention is as follows:

[0006] The prepared microcapsules are added during the pulping and papermaking process of insulating paper, and the microcapsules are migrated using a directional magnetic field; wherein, the microcapsules include a microcapsule core material and a microcapsule wall material, the core material is made by modifying a repair agent with Fe3O4@SiO2 nanoparticles, and the wall material is made by modifying a polyurea formaldehyde prepolymer with TiO2 nanoparticles; the repair agent includes epoxy acrylate, neopentyl glycol diacrylate, and a photoinitiator; the photoinitiator is 2,2-dimethoxy-2-phenylacetophenone.

[0007] The present invention provides a method for preparing self-repairing cellulose insulating paper doped with ultraviolet light-triggered microcapsules, which specifically comprises the following steps:

[0008] (1) Synthesis of Fe3O4 nanoparticles by hydrothermal reaction: styrenesulfonic acid-maleic anhydride copolymer (PSSMA), FeCl3·6H2O, and NaAc were dissolved in ethylene glycol, wherein the mass ratio of PSSMA:FeCl3·6H2O:NaAc was 1-2:1:1-2, the concentration of FeCl3·6H2O was 0.2-0.5 mol / L, the concentration of NaAc was 0.2-0.5 mol / L, and the concentration of PSSMA was 0.1-0.5 mol / L, and the mixture was stirred with a magnetic stirrer. The mixture was then transferred to a hydrothermal reactor and allowed to react fully to obtain Fe3O4 nanoparticles. After the hydrothermal reaction was completed, the synthesized Fe3O4 nanoparticles were separated using a magnetic material.

[0009] (2) Synthesis of Fe3O4@SiO2 nanoparticles: Fe3O4 nanoparticles were mixed with anhydrous alcohol, deionized water, and ammonia water, and ultrasonicated to ensure proper dispersion. Then, tetraethyl orthosilicate (TEOS) was added in an amount of 0.3-0.5%, and ultrasonic chemical treatment was continued. After the reaction was complete, the mixture was washed and dried to obtain Fe3O4@SiO2 nanoparticles.

[0010] (3) Preparation of microcapsule core material: epoxy acrylate (EA), neopentyl glycol diacrylate (NPGDA) and photoinitiator 2,2-dimethoxy-2-phenylacetophenone (DMPA) are fully mixed, EA:NPGDA:DMPA=18-20:18-20:1-2, and reacted for 0.5-1.5h to obtain a repair agent; the Fe3O4@SiO2 nanoparticles synthesized in step (2) are modified by ultrasonic dispersion in the repair agent to obtain a microcapsule core material;

[0011] (4) Preparing a TiO2 emulsion: dispersing amphoteric TiO2 nanoparticles in deionized water at a concentration of 0.7-1.5 g / 100 mL, adding the microcapsule core material obtained in step (3) to the TiO2 aqueous solution, and emulsifying the solution at room temperature to obtain a TiO2 emulsion;

[0012] (5) Preparation of microcapsule wall material: urea, formaldehyde and deionized water are mixed, the pH is adjusted to 8-9, and then heated in a water bath to obtain a polyurea-formaldehyde prepolymer. Then, amphoteric TiO2 nanoparticles are dispersed in the polyurea-formaldehyde prepolymer by ultrasonic dispersion to obtain a TiO2-modified polyurea-formaldehyde prepolymer;

[0013] (6) preparing microcapsules: adding the TiO2 emulsion prepared in step (4), ammonium chloride and resorcinol to the TiO2-modified polyurea-formaldehyde prepolymer, adjusting the pH value to 3.8-4.2, heating in a water bath and stirring until the reaction is fully completed to obtain microcapsules;

[0014] (7) Beating and disintegrating the pulp sheet: tear the pulp sheet into small pieces, put it into a pulper, add deionized water for beating and defibrination, and after defibrination to a beating degree of 43-48°SR, put the pulp into a fiber disintegrator, add deionized water for mechanical treatment, so that the fibers are dispersed in water without changing their original structural properties, and obtain a pulp suspension;

[0015] (8) adding the microcapsules obtained in step (6) into deionized water, stirring and dispersing the microcapsule aqueous solution, and mixing the dispersed microcapsule aqueous solution with the pulp suspension to obtain a microcapsule pulp suspension;

[0016] (9) pouring the microcapsule pulp suspension into a pulp storage chamber, migrating the microcapsules to a target area under the action of a directional magnetic field, performing a forming process using a filter screen, and obtaining a formed insulating paper hand sheet by pressing and drying;

[0017] (10) The formed insulating paper hand sheet is placed in a calender for calendering to obtain the self-repairing cellulose insulating paper.

[0018] In step (1), the directional magnetic field is used to guide the microcapsules and improve the uniform distribution of the microcapsules in the insulating paper, so that the repair agent can be released more efficiently when damage occurs, thereby achieving a better self-repair effect.

[0019] Preferably, in step (1), the magnetic material is a permanent magnet. The Fe3O4 nanoparticles generated by the hydrothermal reaction are magnetic, so they can be separated using a permanent magnet. This is the most commonly used and efficient method. However, in addition to permanent magnets, other magnetic materials (such as iron-containing magnetic molecules, magnetic separation columns, etc.) can also be used for separation. The key is that the material used can effectively separate the magnetic particles from the liquid. Although magnetic materials can theoretically be used for separation, their magnetic field strength, separation efficiency and material stability will affect the final separation effect.

[0020] Preferably, in step (2), the concentration of Fe3O4 is 0.8-0.9 g / 100 mL, the mass ratio of Fe3O4 to ethyl orthosilicate is 1:1-3, and the volume ratio of anhydrous alcohol, deionized water, and ammonia water is 3.5-4.5:0.8-1.2:0.8-1.2. If the concentration of Fe3O4 is too high, it may cause particle aggregation and affect its stability; if the concentration is too low, it may result in an insufficient number of nanoparticles produced. The volume ratio of anhydrous alcohol, deionized water, and ammonia water will also affect the dispersion of the reaction, the reaction rate, and the surface structure of the nanoparticles, thereby affecting the quality of the final Fe3O4@SiO2 nanoparticles. Therefore, the ratio of these solvents needs to be adjusted within a certain range to ensure optimal nanoparticle quality and product performance.

[0021] Preferably, in step (1), after the hydrothermal reaction is completed, the synthesized Fe3O4 nanoparticles need to be separated using a permanent magnet.

[0022] Preferably, in step (3), the concentration of Fe3O4@SiO2 nanoparticles in the repair agent is 3-7wt%.

[0023] Further preferably, in step (3), the concentration of Fe3O4@SiO2 nanoparticles in the repair agent is 5 wt%.

[0024] Preferably, in step (4), the rotation speed is controlled at 600-1000 r / min during the emulsification process. The rotation speed during the emulsification process affects the uniformity of the TiO2 emulsion and the dispersion of the particles. Too high or too low a rotation speed may result in uneven particles in the emulsion.

[0025] Preferably, in step (5), triethanolamine is used to adjust the pH to 8-9.

[0026] Preferably, in step (5), the concentration of the amphoteric TiO2 nanoparticles in the polyurea formaldehyde prepolymer is 2-4 wt%.

[0027] Further preferably, in step (5), the concentration of the amphoteric TiO2 nanoparticles in the polyurea formaldehyde prepolymer is 3 wt%.

[0028] Preferably, in step (6), the mass ratio of TiO2 emulsion, ammonium chloride and resorcinol is 9-12:0.8-1.2:0.8-1.2.

[0029] Further preferably, in step (6), the mass ratio of TiO2 emulsion, ammonium chloride and resorcinol is 10:1:1.

[0030] If the TiO2 content is too low, the performance of the material cannot be effectively improved; if it is too high, the microcapsule wall material may be too fragile; ammonium chloride acts as a catalyst in this reaction, and adding too high a proportion may cause the reaction to be too violent; resorcinol acts as a cross-linking agent in this reaction, which can improve the cross-linking degree and stability of the microcapsule wall material. Excessive resorcinol will cause the wall material to be too hardened, reduce the operability of microcapsule preparation, and affect the self-repair effect of insulating paper, while too little use may cause the wall material to be not strong enough or unstable.

[0031] Preferably, in step (6), the mechanical stirring speed in the water bath is controlled to be 800-1100 r / min. A stirring speed that is too fast may cause the microcapsule wall material to rupture, while a stirring speed that is too slow may cause uneven dispersion. Accurately controlling the stirring speed can ensure the quality of the microcapsule wall material.

[0032] Preferably, in step (8), the mass ratio of the pulp suspension to the microcapsules is 23-28:1.

[0033] Further preferably, in step (8), the mass ratio of the pulp suspension to the microcapsules is 25:1.

[0034] Preferably, in step (8), the doping concentration of the microcapsules in the pulp suspension is 0.5-10 wt%.

[0035] Preferably, in step (10), the calendering treatment is a segmented hot pressing, and the specific steps include:

[0036] The first stage of hot pressing: preheating stage, the temperature range is 80-120℃, the pressure is 0.5-2MPa, and the duration is 2-5min; the second stage of hot pressing: high temperature curing stage, the temperature is set at 140-180℃, the pressure is about 3-5MPa, and the duration is 5-15min; the third stage of hot pressing: cooling and shaping stage, the temperature gradually drops to 60-90℃, the pressure is maintained at 2-3MPa, and the duration is 5-10min.

[0037] The above temperature and pressure parameters can be optimized based on specific experimental or industrial production conditions. Different raw materials, pulp composition, microcapsule contents, and end-use applications will result in different specific temperature, pressure, and time settings. Temperature and pressure control during the hot pressing process, especially the microcapsule wall material, can affect the mechanical and repair properties of the final paper, so these parameters require precise control.

[0038] The beneficial effects of the present invention are:

[0039] 1. The present invention provides a method for preparing self-repairing cellulose insulating paper doped with ultraviolet-light-triggered microcapsules. The method adds the prepared microcapsules to the pulping and papermaking process of the insulating paper and uses a directional magnetic field to migrate the microcapsules. Specifically, a repair agent is synthesized using epoxy acrylate (EA), neopentyl glycol diacrylate (NPGDA), and the photoinitiator 2,2-dimethoxy-2-phenylacetophenone (DMPA), and the repair agent is modified by adding Fe3O4@SiO2 nanoparticles. A microcapsule wall material is synthesized using a mixture of urea and formaldehyde, and TiO2 nanoparticles are added to form a polyurea formaldehyde (PUF) / TiO2 hybrid shell.

[0040] 2. The present invention cleverly embeds a UV-triggered microcapsule structure in cellulose to achieve active identification and immediate self-repair of minor damage to the insulating paper. Once the material is damaged, the microcapsules rupture and release the repair agent, which solidifies under UV light, thereby effectively filling and repairing the damage and significantly improving the durability and stability of the insulating paper. Due to the existence of the self-repair mechanism, the insulating paper can recover in time when facing minor damage, and also avoids the performance degradation caused by damage expansion, thereby substantially extending the service life of the insulating paper. By utilizing the navigation effect of Fe3O4@SiO2 nanoparticles, the insulating paper can achieve a high degree of self-healing even at low doping concentrations; the introduction of TiO2 nanoparticles effectively prevents the premature curing of the repair agent by UV light, ensuring its effective release when needed; at the same time, with the help of in-situ UV rays emitted by electrical trees to induce the curing of the healing agent, the braking identification of the insulating paper and the self-healing of electrical damage to the insulating paper are achieved.

[0041] 3. The self-healing insulating paper of this invention can better withstand the continuous effects of factors such as electric fields and high temperatures, reducing the risk of partial discharge and electric field distortion, and providing more reliable protection for the safe operation of the power grid. Compared with traditional insulating paper that requires complete replacement after damage, self-healing insulating paper can reduce the frequency of material replacement and waste generation. It also has significant self-repair capabilities, effectively extending the service life and significantly reducing the risk of accidents such as insulation breakdown. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are some embodiments of the present invention, and those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0043] Figure 1 This is a flow chart for preparing the self-repairing insulating paper of the present invention;

[0044] Figure 2 This is a diagram showing the self-repair effect of the self-repairing insulating paper of the present invention on electrical damage;

[0045] Figure 3 This is a comparison chart of the breakdown field strength of the self-repairing insulating paper of the present invention with different microcapsule doping concentrations;

[0046] Figure 4 This is a comparison chart of the Young's modulus and self-repair efficiency of the self-repairing insulating paper of the present invention with different microcapsule doping concentrations;

[0047] Figure 5 This is a comparison chart of the dielectric constant self-repair efficiency of the self-repairing insulating paper of the present invention at different microcapsule doping concentrations. DETAILED DESCRIPTION

[0048] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited by the specific embodiments. Unless otherwise defined, all technical terms used hereinafter have the same meaning as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or can be prepared by existing methods.

[0049] The amphoteric nano-TiO2 used in the embodiment of the present invention is produced by Shanghai Maikun Chemical Co., Ltd., CAS No.: 1317-80-2.

[0050] Example 1

[0051] This embodiment provides a method for preparing self-repairing cellulose insulation paper doped with ultraviolet light-triggered microcapsules, which specifically includes the following steps:

[0052] (1) Synthesis of Fe3O4 nanoparticles by hydrothermal reaction: 1 g of styrenesulfonic acid-maleic anhydride copolymer (PSSMA), 1 g of FeCl3·6H2O, and 3 g of NaAc were dissolved in 40 mL of ethylene glycol and stirred using a magnetic stirrer. The mixture was then transferred to a hydrothermal reactor and heated to 200°C for reaction. After the reaction was complete, the Fe3O4 nanoparticles were separated using a permanent magnet, washed with anhydrous alcohol and deionized water, and dried under vacuum at 50°C to obtain Fe3O4 nanoparticles.

[0053] (2) Synthesis of Fe3O4@SiO2 nanoparticles: 0.2 g of Fe3O4 nanoparticles were mixed with 160 mL of anhydrous alcohol, 40 mL of deionized water, and 40 mL of ammonia water, and ultrasonicated to ensure proper dispersion. Then, 1 mL of tetraethyl orthosilicate (TEOS) was added and ultrasonic chemical treatment was continued. After the reaction was complete, the mixture was washed and dried to obtain Fe3O4@SiO2 nanoparticles.

[0054] (3) Preparation of microcapsule core material: 19.2 g of epoxy acrylate (EA), 19.2 g of neopentyl glycol diacrylate (NPGDA) and 1.6 g of photoinitiator 2,2-dimethoxy-2-phenylacetophenone (DMPA) were fully mixed and reacted for 1 h to obtain a repair agent; the Fe3O4@SiO2 nanoparticles synthesized in step (2) were modified by ultrasonic dispersion in the repair agent to obtain a microcapsule core material; the concentration of the Fe3O4@SiO2 nanoparticles in the repair agent was 5 wt%;

[0055] (4) Preparation of TiO2 emulsion: 2 g of amphoteric TiO2 nanoparticles were dispersed in 200 mL of deionized water, 40 mL of the microcapsule core material obtained in step (3) was added to the TiO2 aqueous solution, and emulsified at 800 r / min for 1 h at room temperature to obtain a TiO2 emulsion;

[0056] (5) Preparation of microcapsule wall material: 10 g of urea, 27 g of formaldehyde, and 200 mL of deionized water were mixed, triethanolamine was added dropwise to adjust the pH to 8-9, and then heated in a water bath at 65°C for 1 h to obtain a polyurea-formaldehyde prepolymer. 3 wt% of amphoteric TiO2 nanoparticles were then dispersed in the polyurea-formaldehyde prepolymer by ultrasonic dispersion to obtain a TiO2-modified polyurea-formaldehyde prepolymer.

[0057] (6) adding 10 g of the TiO2 emulsion prepared in step (4), 1 g of ammonium chloride, and 1 g of resorcinol to the TiO2-modified polyurea-formaldehyde prepolymer, adjusting the initial pH value to 4, and mechanically stirring at 900 rpm in a 60°C water bath for 4 h. After sufficient reaction, washing and filtering were performed to obtain microcapsules;

[0058] (7) Beating and disintegrating the pulp sheet: 100 g of pulp sheet was soaked in 6 L of deionized water for 6 h, the pulp sheet was torn into small pieces, placed in a pulper, and deionized water was added for beating and decomposition. After decomposition to a beating degree of 45°SR, the pulp was placed in a fiber disintegrator, and deionized water was added for mechanical treatment to disperse the fibers in water without changing their original structural properties, thereby obtaining a pulp suspension;

[0059] (8) Weighing microcapsules at a microcapsule doping concentration of 0.5 wt%, adding the microcapsules prepared in step (6) to 400 mL of deionized water, and dispersing them by magnetic stirring for 40 min. Then, mixing the dispersed microcapsule aqueous solution with the pulp suspension, and stirring at 300 r / min for 15 min to obtain a microcapsule pulp suspension;

[0060] (9) Degas the microcapsule pulp suspension for 5 minutes and then pour it into the pulp storage chamber. Use a permanent magnet to attract the microcapsules to the upper surface of the microcapsule pulp suspension. Keep the magnet intact to prevent sedimentation. Use a filter to perform molding. Dry the wet paper in a vacuum oven at 110°C for 7 minutes. After balancing the moisture for 24 hours, a molded insulating paper hand sheet is obtained.

[0061] (10) The formed insulating paper hand sheet is placed in a calender for calendering treatment. The first stage hot pressing temperature is set to 100°C, the pressure is 1 MPa, and the hot pressing is performed for 3 minutes; the second stage hot pressing temperature is set to 160°C, the pressure is 4 MPa, and the hot pressing is performed for 10 minutes; the third stage hot pressing temperature is set to 80°C, the pressure is 2 MPa, and the hot pressing is performed for 7 minutes to obtain the self-repairing cellulose insulating paper.

[0062] Example 2: This example is different from Example 1 in that the doping concentration of the microcapsules is 1 wt%.

[0063] Example 3: This example is different from Example 1 in that the doping concentration of the microcapsules is 2.5 wt%.

[0064] Example 4: This example is different from Example 1 in that the doping concentration of the microcapsules is 5 wt%.

[0065] Example 5: This example is different from Example 1 in that the doping concentration of the microcapsules is 10 wt%.

[0066] Example 6: This example is different from Example 1 in that no microcapsules are added to the pulp, thereby preparing traditional cellulose insulation paper.

[0067] Comparing the self-healing cellulose insulating paper in the above examples with conventional cellulose insulating paper shows that the insulating paper produced by the present invention exhibits self-healing capabilities compared to unmodified insulating paper, significantly improving the performance, safety, and reliability of the insulating paper. The test results are shown in the accompanying figure.

[0068] As can be seen from the above embodiments and accompanying drawings, the present invention provides a method for preparing self-repairing cellulose insulating paper doped with ultraviolet light-triggered microcapsules. The present invention adds prepared microcapsules during the pulping and papermaking process of the insulating paper, and uses a directional magnetic field to migrate the microcapsules. Among them, epoxy acrylate (EA), neopentyl glycol diacrylate (NPGDA) and photoinitiator 2,2-dimethoxy-2-phenylacetophenone (DMPA) are used to synthesize the repair agent, and Fe3O4@SiO2 nanoparticles are added to modify the repair agent; urea and formaldehyde are mixed to synthesize the microcapsule wall material, and TiO2 nanoparticles are added to form a polyurea formaldehyde (PUF) / TiO2 hybrid shell. The present invention cleverly embeds a UV-triggered microcapsule structure in cellulose to achieve active recognition and instant self-repair of minor damage to the insulating paper. Once the material is damaged, the microcapsule ruptures to release the repair agent, which solidifies under ultraviolet light irradiation, thereby effectively filling and repairing the damage, significantly improving the durability and stability of the insulating paper. Due to the existence of the self-repair mechanism, the insulating paper can recover in time when facing minor damage, and also avoid the performance degradation caused by the expansion of damage, thereby substantially extending the service life of the insulating paper. By utilizing the navigation effect of Fe3O4@SiO2 nanoparticles, the insulating paper can also achieve a high degree of self-healing at low doping concentrations; the introduction of TiO2 nanoparticles effectively prevents the ultraviolet light of the repair agent from prematurely curing, ensuring its effective release when needed; at the same time, with the help of the in-situ ultraviolet light emitted by the electrically damaged tree branches to induce the curing of the healing agent, the braking identification of the insulating paper and the self-healing of the electrical damage of the insulating paper are achieved. The self-repairing insulating paper of the present invention can better withstand the continuous effects of factors such as electric fields and high temperatures, reduce the risks of local discharge and electric field distortion, and provide more reliable protection for the safe operation of the power grid. Compared with the overall replacement of traditional insulating paper after damage, self-repairing insulating paper can reduce the frequency of material replacement and reduce waste generation. It also has significant self-repairing ability and self-repairing efficiency, which can effectively extend the service life and greatly reduce the risks caused by accidents such as insulation breakdown.

[0069] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing self-repairing cellulose insulation paper doped with ultraviolet light-triggered microcapsules, characterized in that: The method comprises mixing paper pulp with microcapsules to prepare insulating paper, and migrating the microcapsules using a directional magnetic field; The microcapsules include a microcapsule core material and a microcapsule wall material. The microcapsule core material is made by modifying a repair agent with Fe3O4@SiO2 nanoparticles, and the microcapsule wall material is made by modifying a polyurea-formaldehyde prepolymer with TiO2 nanoparticles. The repair agent is prepared by mixing epoxy acrylate, neopentyl glycol diacrylate and photoinitiator; The photoinitiator is 2,2-dimethoxy-2-phenylacetophenone; The method for preparing the self-repairing cellulose insulating paper specifically comprises the following steps: (1) Synthesis of Fe3O4 nanoparticles by hydrothermal reaction; (2) Synthesizing Fe3O4@SiO2 nanoparticles: Fe3O4 nanoparticles were mixed with anhydrous alcohol, deionized water, and ammonia water, and ultrasonically treated. Then, ethyl orthosilicate was added and ultrasonic treatment was continued. After the reaction was complete, the mixture was washed and dried to obtain Fe3O4@SiO2 nanoparticles. (3) preparing a microcapsule core material: dispersing the Fe3O4@SiO2 nanoparticles synthesized in step (2) in a repair agent for modification to obtain a microcapsule core material; (4) preparing TiO2 emulsion: adding the microcapsule core material obtained in step (3) to a TiO2 aqueous solution and performing emulsification treatment to obtain a TiO2 emulsion; (5) Preparation of microcapsule wall material: urea, formaldehyde, and deionized water are mixed, the pH is adjusted to 8-9, and then heated in a water bath to obtain a polyurea-formaldehyde prepolymer. Then, amphoteric TiO2 nanoparticles are ultrasonically dispersed in the polyurea-formaldehyde prepolymer to modify the prepolymer to obtain a TiO2-modified prepolymer; the concentration of the amphoteric TiO2 nanoparticles in the polyurea-formaldehyde prepolymer is 2-4 wt%; (6) Preparing microcapsules: adding the TiO2 emulsion prepared in step (4), ammonium chloride, and resorcinol to the TiO2-modified polyurea-formaldehyde prepolymer, adjusting the pH to 3.8-4.2, heating in a water bath, and mechanically stirring until the reaction is complete to obtain microcapsules; the mass ratio of the TiO2 emulsion, ammonium chloride, and resorcinol is 9-12:0.8-1.2:0.8-1.2; (7) beating and dissociating the pulp sheet to obtain a pulp suspension; (8) mixing the microcapsules obtained in step (6) with the pulp suspension to obtain a microcapsule pulp suspension; (9) pouring the microcapsule pulp suspension into a pulp storage chamber, migrating the microcapsules to a target area under the action of a directional magnetic field, forming the microcapsules through a filter screen, and obtaining a formed insulating paper hand sheet by pressing and drying; (10) placing the formed insulating paper hand sheet into a calender for calendering to obtain the self-repairing cellulose insulating paper; In the step (1), the hydrothermal reaction is specifically as follows: dissolving styrene sulfonic acid-maleic anhydride copolymer PSSMA, FeCl3·6H2O and NaAc in ethylene glycol, with the mass ratio of PSSMA:FeCl3·6H2O:NaAc being 1-2:1:1-2, stirring, and then transferring to a hydrothermal reactor, and obtaining Fe3O4 nanoparticles after sufficient reaction. After the hydrothermal reaction is completed, the synthesized Fe3O4 nanoparticles are separated using a magnetic material; In the step (1), the concentration of FeCl3·6H2O is 0.2-0.5 mol / L, the concentration of NaAc is 0.2-0.5 mol / L, and the concentration of PSSMA is 0.1-0.5 mol / L; In the step (2), the mass ratio of Fe3O4 to ethyl orthosilicate is 1:1-3, and the volume ratio of anhydrous alcohol, deionized water and ammonia water is 3.5-4.5:0.8-1.2:0.8-1.

2.

2. The method for preparing self-repairing cellulose insulation paper doped with ultraviolet light-triggered microcapsules according to claim 1, characterized in that: In the step (4), the rotation speed is controlled to be 600-1000 r / min during the emulsification treatment; and in the step (6), the mechanical stirring speed in the water bath is controlled to be 800-1100 r / min.

3. The method for preparing self-repairing cellulose insulation paper doped with ultraviolet light-triggered microcapsules according to claim 1, characterized in that: The mass ratio of the epoxy acrylate, neopentyl glycol diacrylate and photoinitiator is 18-20:18-20:1-2.

4. The method for preparing self-repairing cellulose insulation paper doped with ultraviolet light-triggered microcapsules according to claim 1, characterized in that: In the step (10), the calendering treatment is a segmented hot pressing process, and the specific steps include: The first stage of hot pressing: preheating stage, the temperature range is 80-120℃, the pressure is 0.5-2MPa, and the duration is 2-5min; The second stage of hot pressing: high temperature curing stage, the temperature is set at 140-180℃, the pressure is 3-5MPa, and the duration is 5-15min; The third stage of hot pressing: cooling and shaping stage, the temperature gradually drops to 60-90℃, the pressure is maintained at 2-3MPa, and the duration is 5-10min.

5. The method for preparing self-repairing cellulose insulation paper doped with ultraviolet light-triggered microcapsules according to claim 1, characterized in that: In the step (8), the doping concentration of the microcapsules in the pulp suspension is 0.5-10 wt%.

6. The method for preparing self-repairing cellulose insulation paper doped with ultraviolet light-triggered microcapsules according to claim 1, characterized in that: In the step (3), the concentration of Fe3O4@SiO2 nanoparticles in the repair agent is 3-7 wt%.

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