Degradable solid insulating material for transformer

Abstract

The invention discloses a degradable solid insulating material for a transformer. The degradable solid insulating material comprises the following raw materials in percentage by mass: 43-58% of bio-based epoxy resin; 3%-6% of polyethylene glycol; 25%-35% of a functional filler; 5%-10% of degradable reinforced fibers; 3%-8% of a degradation triggering auxiliary agent; 1%-3% of a degradation agent; the invention relates to the technical field of electrical insulation. According to the degradable solid insulating material for the transformer, natural degradation is achieved through hydrolyzable ester bonds of the bio-based epoxy resin in cooperation with the polylactic acid microspheres, the solid waste amount is reduced, meanwhile, degradation products are fatty acid and polysaccharide substances, the environmental safety standard is guaranteed, and through the synergistic effect of the modified calcined kaolin and the boron nitride nanosheets, the breakdown strength is improved; the insulation requirement is met, meanwhile, the heat conduction efficiency can be improved, the dielectric loss is reduced by filling micropores with nano silicon micro powder, and the density of the material is effectively reduced while the bending strength of the material is improved through alkali treatment of linen fibers.

Description

Technical Field

[0001] This invention relates to the field of electrical insulation technology, specifically to a biodegradable solid insulation material for transformers. Background Technology

[0002] Traditional transformer insulation materials mainly rely on petroleum-based epoxy resin and glass fiber reinforcement systems. These technologies have the following drawbacks: 1. Non-degradability: Epoxy resin matrix takes hundreds of years to degrade in the natural environment, and the disposal of decommissioned transformers generates a large amount of solid waste; Second, poor heat dissipation performance: The thermal conductivity of traditional epoxy resin is only 0.2–0.35 W / m·K, which leads to excessive local temperature rise in large transformers and accelerates insulation aging; III. Mechanical-Dielectric Performance Contradiction: Increasing the bending strength requires increasing the glass fiber content, but this leads to an increase in dielectric loss to over 0.008 and a decrease in breakdown strength.

[0003] Traditional technical solutions such as Nomex paper, while possessing high temperature resistance, are costly and dependent on imports; oil-immersed insulating pads pose a risk of oil leakage and pollution. Therefore, a solution for a biodegradable solid insulating material for transformers is proposed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a biodegradable solid insulating material for transformers, which solves the problems of non-degradability, poor heat dissipation performance, and contradictory mechanical-dielectric properties in traditional transformer insulating materials.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a biodegradable solid insulating material for transformers, wherein the raw materials comprise, by mass percentage: Bio-based epoxy resin: 43%–58%; Polyethylene glycol: 3%–6%; Functional fillers: 25%–35%; Biodegradable reinforcing fibers: 5%–10%; Degradation triggering agent: 3%–8%; Degrading agent: 1%–3%.

[0006] The present invention is further configured such that: the bio-based epoxy resin includes soybean oil derivative epoxy resin and liquid bio-based epoxy resin, wherein the soybean oil derivative epoxy resin and liquid bio-based epoxy resin are in a mass ratio of 60-70:30-40.

[0007] The present invention is further configured such that: the functional filler comprises boron nitride nanosheets, nano-silica powder and modified kaolin, wherein the mass ratio of boron nitride nanosheets, nano-silica powder and modified kaolin is 40-55:30-45:15-20; The preparation method of the modified kaolin includes: Kaolin was crushed to D50=5μm and calcined at 650℃ for 2h. The calcined kaolin was then mixed with an ethanol solution containing 5wt% silane coupling agent and ball-milled at 300 rpm for 2h. After drying, modified kaolin was obtained.

[0008] The present invention is further configured such that: the biodegradable reinforcing fiber is a flax fiber woven web after alkali treatment, and its preparation method includes: Flax fibers were immersed in an 8wt% sodium hydroxide solution at 80℃ for 30 minutes, then neutralized with 5wt% dilute acetic acid to pH=7, rinsed with running water until no alkaline residue remained, immersed in an ethanol solution containing 2wt% silane coupling agent for 3 seconds, removed and dried at 60℃ for 2 hours, and the treated flax fibers were woven into a mesh structure by a weaving machine.

[0009] The present invention is further configured such that the degradation triggering agent is polylactic acid microspheres, and the particle size of the polylactic acid microspheres is 5-20 μm.

[0010] The present invention is further configured such that the degrading agent comprises titanium dioxide and lignin, wherein the mass ratio of titanium dioxide to lignin is 1:0.5-1.5.

[0011] This invention also discloses a method for preparing a biodegradable solid insulating material for transformers, comprising the following steps: S1. Premix bio-based epoxy resin, polyethylene glycol and functional filler in a vacuum environment of 0.1MPa for 30-45 minutes to obtain a homogeneous slurry; S2. Inject the homogeneous slurry into a mold covered with biodegradable reinforcing fibers, and cure it by step heating to obtain the molded part; S3. Spray a fluorosilane solution onto the surface of the molded part and dry it at room temperature to complete the preparation of the biodegradable solid insulating material.

[0012] The present invention is further configured such that the stepped temperature curing method includes: Cur at 80℃ for 2 hours; Heat to 120℃ at a rate of 5℃ / min and cure for 3 hours; Heat to 150℃ at a rate of 2℃ / min and cure for 2 hours.

[0013] This invention provides a biodegradable solid insulating material for transformers. It has the following beneficial effects: This invention utilizes the hydrolyzable ester bonds of bio-based epoxy resin in conjunction with polylactic acid microspheres to achieve natural degradation, reducing solid waste while producing degradation products of fatty acids and polysaccharides, ensuring environmental safety standards. The synergistic effect of modified calcined kaolin and boron nitride nanosheets improves breakdown strength, ensuring insulation requirements and enhancing thermal conductivity. Nano-silicon powder fills micropores to reduce dielectric loss, and alkali treatment of flax fibers improves flexural strength while effectively reducing material density. Detailed Implementation

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] The embodiments of the present invention provide the following technical solutions: Example 1

[0016] A biodegradable solid insulating material for transformers, comprising the following raw materials by mass percentage: Bio-based epoxy resin: 58%; Polyethylene glycol: 3%; Functional fillers: 25%; Biodegradable reinforcing fibers: 10%; Degradation triggering agent: 3%, the degradation triggering agent is polylactic acid microspheres, the particle size of polylactic acid microspheres is 20μm; Degrading agent: 1%, the degrading agent includes titanium dioxide and lignin, the mass ratio of titanium dioxide to lignin is 1:1.5.

[0017] For detailed explanation, bio-based epoxy resins include soybean oil derivative epoxy resins and liquid bio-based epoxy resins, with a mass ratio of 70:30.

[0018] The preparation methods for soybean oil derivative epoxy resins include: 100g of soybean oil was mixed with 30g of 85wt% formic acid and stirred at 45℃ for 10min. 0.5g of 85wt% phosphoric acid catalyst was added, and 55g of 30wt% hydrogen peroxide was added dropwise at 50℃. After reacting for 4h, 5% sodium carbonate solution was added to neutralize to pH=7. The aqueous phase was removed by separation, and the mixture was dehydrated under reduced pressure at 80℃ for 2h. Unreacted substances were removed by distillation under a vacuum of 0.09 MPa to obtain soybean oil derivative epoxy resin.

[0019] The preparation methods of liquid bio-based epoxy resins include: 100g of soybean oil derivative epoxy resin, 35g of 99wt% acrylic acid and 1.2g of triphenylphosphine catalyst were mixed and reacted at 110℃ for 3h. 0.05g of hydroquinone polymerization inhibitor was added, and unreacted acrylic acid was removed by vacuum distillation. The viscosity was adjusted to 350-450 mPa·s (25℃) with ethyl acetate to obtain liquid bio-based epoxy resin.

[0020] As a preferred option, the functional filler includes boron nitride nanosheets, nano-silica powder and modified kaolin, with the mass ratio of boron nitride nanosheets, nano-silica powder and modified kaolin being 55:30:15; The preparation methods of modified kaolin include: Kaolin was crushed to D50=5μm and calcined at 650℃ for 2h. The calcined kaolin was then mixed with an ethanol solution containing 5wt% silane coupling agent and ball-milled at 300 rpm for 2h. After drying, modified kaolin was obtained.

[0021] As detailed, the biodegradable reinforcing fiber is a flax fiber woven web after alkali treatment, and its preparation method includes: Flax fibers were immersed in an 8wt% sodium hydroxide solution at 80℃ for 30 minutes, then neutralized with 5wt% dilute acetic acid to pH=7, rinsed with running water until no alkaline residue remained, immersed in an ethanol solution containing 2wt% silane coupling agent for 3 seconds, removed and dried at 60℃ for 2 hours, and the treated flax fibers were woven into a mesh structure by a weaving machine.

[0022] The preparation method of the above-mentioned biodegradable solid insulating material for transformers includes the following steps: S1. Premix bio-based epoxy resin, polyethylene glycol and functional filler in a vacuum environment of 0.1MPa for 30-45 minutes to obtain a homogeneous slurry; S2. Inject the homogeneous slurry into a mold covered with biodegradable reinforcing fibers, cure at 80°C for 2 hours, then heat to 120°C at a rate of 5°C / min and cure for 3 hours, then heat to 150°C at a rate of 2°C / min and cure for 2 hours to obtain the molded part. S3. Spray a fluorosilane solution onto the surface of the molded part and dry it at room temperature to complete the preparation of the biodegradable solid insulating material.

[0023] Example 2

[0024] The difference between this embodiment and Embodiment 1 is that: Its raw materials, by mass percentage, include: Bio-based epoxy resin: 52%, soybean oil derivative epoxy resin and liquid bio-based epoxy resin in a mass ratio of 65:35; Polyethylene glycol: 4%; Functional filler: 30%, boron nitride nanosheets, nano-silica powder and modified kaolin in a mass ratio of 50:35:18; Biodegradable reinforcing fibers: 7%; Degradation triggering agent: 5%, polylactic acid microspheres with a particle size of 15 μm; Degrading agent: 2%, the mass ratio of titanium dioxide to lignin is 1:1.0.

[0025] Example 3

[0026] The difference between this embodiment and Embodiment 1 is that: Its raw materials, by mass percentage, include: Bio-based epoxy resin: 43%, soybean oil derivative epoxy resin and liquid bio-based epoxy resin in a mass ratio of 60:40; Polyethylene glycol: 6%; Functional filler: 35%, boron nitride nanosheets, nano-silica powder and modified kaolin in a mass ratio of 40:45:20; Biodegradable reinforcing fiber: 5%; Degradation triggering agent: 8%, polylactic acid microspheres with a particle size of 5 μm; Degrading agent: 3%, the mass ratio of titanium dioxide to lignin is 1:0.5.

[0027] Simulation Experiment DuPont Nomex 910 insulating paper and Huntsman Araldite CY 184 epoxy resin were used as Comparative Examples 1 and 2, respectively. Breakdown strength, thermal conductivity, dielectric loss, temperature rise, and degradation rate were tested. Breakdown strength was obtained according to GB / T1695-2005 standard, with an electrode spacing of 2 mm, a voltage increase rate of 1 kV / s, and the average of 10 tests. Thermal conductivity was tested using the ASTM E1461 laser scintillation method with a Netzsch LFA 467 instrument at a constant temperature of 25℃. Dielectric loss was obtained according to IEC60250 standard, under a 50 Hz alternating electric field using an Agilent 4294A impedance analyzer. Temperature rise was measured according to IEEE C57.12.91 standard, using thermal coupling simulation to monitor the hottest point of the coil. Degradation rate was tested according to ISO 14855 compost degradation test, under 90°C / 60% RH damp heat aging. The mass loss rate was measured that day, and the test results are shown in Table 1. Table 1

[0028] As can be seen from Table 1, the biodegradable solid insulating material for transformers prepared according to the present invention has the advantages of electrical reliability and biodegradability, and solves the defects of traditional insulating materials such as non-degradability, insufficient heat dissipation and performance contradiction.

[0029] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A biodegradable solid insulating material for transformers, characterized in that, Its raw materials, by mass percentage, include: Bio-based epoxy resin: 43%–58%; Polyethylene glycol: 3%–6%; Functional fillers: 25%–35%; Biodegradable reinforcing fibers: 5%–10%; Degradation triggering agent: 3%–8%; Degrading agent: 1%–3%.

2. The biodegradable solid insulating material for transformers according to claim 1, characterized in that, The bio-based epoxy resin includes soybean oil derivative epoxy resin and liquid bio-based epoxy resin, wherein the soybean oil derivative epoxy resin and liquid bio-based epoxy resin are in a mass ratio of 60-70:30-40.

3. The biodegradable solid insulating material for transformers according to claim 1, characterized in that, The functional filler includes boron nitride nanosheets, nano-silicon powder, and modified kaolin, wherein the mass ratio of boron nitride nanosheets, nano-silicon powder, and modified kaolin is 40-55:30-45:15-20. The preparation method of the modified kaolin includes: Kaolin was crushed to D50=5μm and calcined at 650℃ for 2h. The calcined kaolin was then mixed with an ethanol solution containing 5wt% silane coupling agent and ball-milled at 300 rpm for 2h. After drying, modified kaolin was obtained.

4. The biodegradable solid insulating material for transformers according to claim 1, characterized in that, The biodegradable reinforcing fiber is a flax fiber woven web after alkali treatment, and its preparation method includes: Flax fibers were immersed in an 8wt% sodium hydroxide solution at 80℃ for 30 minutes, then neutralized with 5wt% dilute acetic acid to pH=7, rinsed with running water until no alkaline residue remained, immersed in an ethanol solution containing 2wt% silane coupling agent for 3 seconds, removed and dried at 60℃ for 2 hours, and the treated flax fibers were woven into a mesh structure by a weaving machine.

5. The biodegradable solid insulating material for transformers according to claim 1, characterized in that, The degradation triggering agent is polylactic acid microspheres, and the particle size of the polylactic acid microspheres is 5-20 μm.

6. The biodegradable solid insulating material for transformers according to claim 1, characterized in that, The degrading agent comprises titanium dioxide and lignin, wherein the mass ratio of titanium dioxide to lignin is 1:0.5-1.

5.

7. A biodegradable solid insulating material for transformers according to any one of claims 1-6, characterized in that, Its preparation method includes the following steps: S1. Premix bio-based epoxy resin, polyethylene glycol and functional filler in a vacuum environment of 0.1MPa for 30-45 minutes to obtain a homogeneous slurry; S2. Inject the homogeneous slurry into a mold covered with biodegradable reinforcing fibers, and cure it by step heating to obtain the molded part; S3. Spray a fluorosilane solution onto the surface of the molded part and dry it at room temperature to complete the preparation of the biodegradable solid insulating material.

8. A biodegradable solid insulating material for transformers according to claim 7, characterized in that, The stepped temperature curing method includes: Cur at 80℃ for 2 hours; Heat to 120℃ at a rate of 5℃ / min and cure for 3 hours; Heat to 150℃ at a rate of 2℃ / min and cure for 2 hours.

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