Degradable transformer insulating material and processing technology

Abstract

The invention relates to the field of electrical insulating materials, in particular to a degradable transformer insulating material and a processing technology. A degradable epoxy resin transformer insulating material is composed of a component A and a component B. The component A comprises the following raw materials: 70-85 parts of bisphenol A epoxy resin, 15-30 parts of bio-based degradable epoxy resin, 1-5 parts of an interfacial compatibilizer, 150-250 parts of an inorganic filler, and 0.5-2 parts of color paste. The component B is prepared from the following raw materials in parts by weight: 90 to 110 parts of methyl tetrahydrophthalic anhydride, 1 to 5 parts of latent degradation triggering agent, 0.1 to 0.5 part of curing accelerator and 150 to 250 parts of inorganic filler; the latent degradation triggering agent is a microencapsulated ester exchange catalyst or hydrolysis catalyst, and a microcapsule wall material of the latent degradation triggering agent can be broken to release an inner core catalyst under a specific external triggering condition. The problem that an existing degradable insulating material is uncontrollable in degradation switch is solved.

Description

Technical Field

[0001] This application relates to the field of electrical insulation materials, and in particular to a biodegradable transformer insulation material and its processing technology. Background Technology

[0002] Epoxy resin casting materials are widely used in power equipment such as medium and high voltage transformers, instrument transformers, and insulators due to their excellent electrical insulation, mechanical properties, and heat resistance. Currently available epoxy casting systems (such as bisphenol A epoxy resin / anhydride curing agent systems) can meet the long-term operation requirements of equipment, but after curing, they form a three-dimensional cross-linked network that is extremely difficult to degrade under natural conditions. After the equipment is scrapped, these become persistent electronic waste, placing a serious burden on the environment. Therefore, the development of insulating materials that combine high performance and biodegradability has become an urgent need in the industry.

[0003] While existing technologies incorporate bio-based resins by introducing disulfide and ester bonds, these often sacrifice crucial insulation and thermomechanical properties, failing to meet the stringent operational requirements of power equipment. Furthermore, although materials are made biodegradable, the problem of "uncontrollable switching" is prevalent. That is, degradation mechanisms (such as ester bond hydrolysis or disulfide bond metathesis) may occur slowly during the material's service life or be sensitive to environmental factors such as temperature and humidity, leading to gradual performance degradation of the insulation material over the decades-long lifespan of transformers, posing long-term operational safety hazards. How to achieve controllable and rapid degradation after decommissioning while ensuring the material's decades-long insulation lifespan remains a technological gap. Summary of the Invention

[0004] In order to overcome the defect of "uncontrollable degradation switching" in existing biodegradable insulation materials, this application provides a biodegradable transformer insulation material and processing technology.

[0005] In a first aspect, this application provides a biodegradable epoxy resin transformer insulation material, employing the following technical solution: A biodegradable epoxy resin transformer insulation material is composed of component A and component B. After the two are mixed and cured, a cured product with a rigid-dynamic interpenetrating network structure is formed. Based on the weight of component A, it includes the following raw materials: 70-85 parts of bisphenol A epoxy resin, 15-30 parts of bio-based biodegradable epoxy resin, 1-5 parts of interface compatibilizer, 150-250 parts of inorganic filler, and 0.5-2 parts of color paste. Based on the weight of component B, it includes the following raw materials: 90-110 parts of methyltetrahydrophthalic anhydride, 1-5 parts of latent degradation trigger, 0.1-0.5 parts of curing accelerator, and 150-250 parts of inorganic filler; The latent degradation trigger is a microencapsulated transesterification catalyst or hydrolysis catalyst, whose microcapsule wall material can rupture and release the core catalyst under specific external triggering conditions.

[0006] By adopting the above technical solution, this application solves the problem of "uncontrollable degradation switch" of existing biodegradable insulating materials by constructing a dual-insurance intelligent response system with the synergistic effect of "rigid-dynamic interpenetrating network" and "latent degradation trigger".

[0007] The bisphenol A epoxy resin in component A and the methyltetrahydrophthalic anhydride in component B cure to form a rigid network with a high cross-linking density, ensuring excellent mechanical and insulation properties throughout the material's decades-long service life. Simultaneously, the bio-based biodegradable epoxy resin in component A introduces biodegradable ester bond structural units, forming dynamic network units interspersed within the rigid network, providing reaction sites for subsequent degradation. More importantly, the latent degradation trigger in component B employs microencapsulation technology to physically isolate the highly active catalyst, ensuring it does not participate in the reaction during the curing process and service life, completely eliminating the slow performance degradation problem caused by continuous catalyst exposure in traditional biodegradable materials. When the transformer is decommissioned, applying specific external triggering conditions causes the microcapsule wall material to rupture, releasing the catalyst that precisely triggers ester bonds in the dynamic network units to undergo transesterification or hydrolysis, leading to the rapid disintegration of the entire interpenetrating network structure and achieving rapid and controllable degradation of the material. This intelligent response mechanism throughout the entire life cycle—"stable during service life - triggered during decommissioning - controllable during degradation"—not only ensures the safe operation of the transformer for decades but also solves the problem of electronic waste pollution, representing a significant technological breakthrough in this field.

[0008] Furthermore, the bio-based biodegradable epoxy resin is at least one of epoxidized soybean oil, polylactic acid modified epoxy resin, castor oil-based epoxy resin, and tung oil-based epoxy resin, with an epoxy value of 0.3-0.6 mol / 100g.

[0009] By employing the above technical solution, the specific types of bio-based biodegradable epoxy resins and their epoxy value ranges were defined, ensuring that the dynamic network units possessed suitable reactivity and a density of degradable sites. Bio-based resins such as epoxidized soybean oil and polylactic acid-modified epoxy resins contain abundant ester bonds in their molecular chains. These ester bonds can break under the action of a catalyst, forming the chemical basis for material degradation. Controlling the epoxy value within the range of 0.3-0.6 mol / 100g ensured that the bio-based resin could fully participate in the cross-linking reaction to form a complete interpenetrating network, while also ensuring that the network contained a sufficient number of breakable ester bonds. Too low an epoxy value resulted in insufficient degradation sites and a slow degradation rate; too high an epoxy value could lead to excessive cross-linking density, which could inhibit the catalyst's attack on the ester bonds. Through this parameter optimization, the optimal balance between the material's degradation performance and mechanical properties was achieved.

[0010] Furthermore, the interface compatibilizer is a hyperbranched polymer containing epoxy groups, with a number average molecular weight of 2000-10000 and an epoxy value of 0.2-0.5 mol / 100g, used to achieve nanoscale uniform dispersion and chemical bonding of bisphenol A epoxy resin and bio-based biodegradable epoxy resin.

[0011] By employing the above technical solution, a hyperbranched polymer containing epoxy groups is introduced as an interfacial compatibilizer, and its molecular weight and epoxy value range are limited, fundamentally solving the technical problem of incompatibility between bisphenol A epoxy resin and bio-based biodegradable epoxy resin. The hyperbranched polymer possesses a three-dimensional spherical structure and a large number of terminal functional groups. Its unique topology allows it to penetrate into the interfacial region between the two phases, forming a "molecular bridge" effect. The epoxy groups on the hyperbranched polymer can simultaneously react chemically with both bisphenol A epoxy resin and bio-based resin, establishing chemical bonds between the two phases; its hyperbranched structure can also form physical entanglements at the nanoscale, further strengthening the interfacial bonding. The number-average molecular weight range of 2000-10000 ensures that the compatibilizer has both sufficient molecular size to form effective entanglement and suitable flowability for uniform dispersion; the epoxy value range of 0.2-0.5 mol / 100g ensures sufficient reactive sites. Through this interface compatibilization design, the originally thermodynamically incompatible two-phase system forms a stable nanoscale interpenetrating network structure, avoiding the decline in mechanical properties and insulation defects caused by phase separation, while ensuring that the degradation reaction proceeds uniformly throughout the entire material system.

[0012] Furthermore, the wall material of the microcapsule is a thermosensitive material, a photosensitive material, or a solvent-soluble material; The heat-sensitive material is selected from at least one of paraffin wax, polyethylene wax, and ethyl cellulose, and its melting point is 50-120℃; The photosensitive material is selected from at least one of diazo resin and cinnamic acid ester polymers, which decomposes under 200-400 nm ultraviolet light irradiation; The solvent-soluble material is selected from at least one of polyvinyl alcohol, gelatin, and gum arabic, and is soluble under specific pH or salt concentration conditions.

[0013] By adopting the above technical solutions, the microcapsule wall materials are designed to be thermosensitive, photosensitive, or solvent-soluble, achieving diversification and precise control over degradation triggering methods. Microencapsulation technology is the core means of physically isolating catalysts, while the material properties of the wall material determine the "switching" method for triggering degradation. Thermosensitive wall materials (paraffin wax, polyethylene wax, ethyl cellulose, etc.) have a defined melting point range. When the material temperature is raised above the melting point using a heat source such as microwave heating, the wall material melts or softens, instantly releasing the core catalyst. Photosensitive wall materials (diazo resin, cinnamic acid ester polymers, etc.) undergo photolysis under specific wavelength ultraviolet light irradiation, destroying the wall material structure. Solvent-soluble wall materials (polyvinyl alcohol, gelatin, gum arabic, etc.) dissolve under specific pH or salt concentration conditions. This diversified triggering mechanism design allows transformers to flexibly select degradation triggering methods based on actual operating conditions and treatment conditions after decommissioning: for example, solvent spraying can be used for rapid triggering of dismantled transformers, microwave heating can be used for overall triggering of difficult-to-disassemble components, and natural light can be used for triggering of outdoor abandoned equipment. This design greatly improves the adaptability and practicality of the technical solution.

[0014] Furthermore, the core catalyst of the microcapsule is an organotin compound, a titanate compound, or a tertiary amine compound; The organotin compound is selected from at least one of dibutyltin dilaurate and stannous octoate; The titanate compound is selected from at least one of tetrabutyl titanate and tetraisopropyl titanate; The tertiary amine compound is selected from at least one of triethylamine and triethanolamine.

[0015] By employing the above technical solution and limiting the specific type of core catalyst, the high efficiency and controllability of the degradation reaction are ensured. Organotin compounds (such as dibutyltin dilaurate and stannous octoate) are highly efficient catalysts for transesterification reactions, significantly reducing the activation energy for ester bond breakage; titanate compounds (such as tetrabutyl titanate and tetraisopropyl titanate) can catalyze both transesterification and ester bond hydrolysis, exhibiting dual catalytic functions; tertiary amine compounds (such as triethylamine and triethanolamine) possess excellent catalytic activity for ester bond hydrolysis. These catalysts are in a "dormant" state under microencapsulation protection, and are rapidly activated upon release, interacting with the ester bonds in the bio-based resin to initiate a chain degradation reaction. The degradation rate and mechanism can also be controlled by selecting the catalyst type: for example, organotin catalysts can achieve a faster degradation rate, while tertiary amine catalysts can achieve slow degradation under mild conditions. This catalyst can be selectively designed, allowing for precise control of the material's degradation behavior according to environmental protection requirements.

[0016] Furthermore, the microcapsules have a particle size of 1-50 μm, a wall material thickness of 0.1-5 μm, and a core catalyst content of 10-50% of the total weight of the microcapsules.

[0017] By employing the above-mentioned technical solution, the particle size, wall thickness, and catalyst content of microcapsules are precisely controlled, achieving designability of catalyst release behavior and controllability of degradation rate. The particle size of the microcapsules (1-50 μm) determines their dispersion uniformity in the resin matrix. Smaller particle sizes are beneficial for uniform dispersion but may increase the tendency to agglomerate, while larger particle sizes have the opposite effect. The range of this application strikes a balance between the two. The wall thickness (0.1-5 μm) directly affects the mechanical strength and trigger response time of the microcapsules. Too thin a wall may cause premature rupture during processing, while too thick a wall makes triggering difficult. The range of this application ensures sufficient processing stability and moderate trigger sensitivity. The core catalyst content (10-50%) determines the amount of catalyst loaded per unit volume of material, directly affecting the degradation rate after triggering. Through the synergistic optimization of these three parameters, precise design of degradation behavior can be achieved: for example, for scenarios requiring rapid degradation, smaller particle size, thinner wall thickness, and higher catalyst content can be selected; for scenarios requiring slow degradation, the reverse design can be used. This adjustability allows this technical solution to meet the diverse needs of different application scenarios.

[0018] Furthermore, the inorganic filler is at least one of silica powder, aluminum hydroxide, alumina, talc powder, and mica powder, with an average particle size of 5-30 μm, and is surface-treated with a silane coupling agent.

[0019] By adopting the above technical solutions and limiting the specific type, particle size, and surface treatment method of inorganic fillers, the overall performance and long-term stability of the material are significantly improved. Inorganic fillers such as silica fume, aluminum hydroxide, and alumina not only increase volume and reduce costs, but more importantly, they improve the thermal conductivity, reduce the coefficient of linear expansion, and enhance flame retardancy. Controlling the average particle size within the range of 5-30 μm ensures good dispersion of the filler in the resin matrix while avoiding viscosity surges caused by excessively fine particles and sedimentation problems caused by excessively coarse particles. Crucially, the surface treatment of the filler using a silane coupling agent grafts organic functional groups onto the surface of the inorganic filler. These functional groups can chemically bond with the epoxy resin, transforming physical blending into chemical bonding, significantly improving interfacial bonding strength, reducing interfacial defects, and enhancing insulation performance. Simultaneously, the good interfacial bonding prevents the filler-resin interface from becoming a preferential channel for moisture and degradation catalysts, ensuring effective isolation of degradation triggers during service life.

[0020] Furthermore, the curing accelerator is at least one selected from 2,4,6-tris(dimethylaminomethyl)phenol, 2-methylimidazole, and 2-ethyl-4-methylimidazole.

[0021] By employing the above technical solution and limiting the specific type of curing accelerator, efficient and controllable curing reaction is achieved, ensuring the complete formation of the interpenetrating network structure. Tertiary amines and imidazoles such as 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), 2-methylimidazole, and 2-ethyl-4-methylimidazole are highly efficient accelerators for epoxy resin / anhydride curing systems, significantly reducing the activation energy of the curing reaction and enabling rapid reaction under mild conditions. The mechanism of action of these accelerators is as follows: tertiary amines open the epoxy ring through nucleophilic attack, while imidazoles catalyze the ring-opening of the anhydride through the lone pair electrons on the nitrogen atom. In the stepped temperature curing process of this application, these accelerators begin to function at the low temperature stage (85°C), ensuring that the system completes gelation and forms a preliminary network structure in a short time; as the temperature increases, the curing reaction gradually deepens, ultimately forming a highly cross-linked rigid-dynamic interpenetrating network. The amount of accelerator should be controlled within the range of 0.1-0.5 parts to ensure that the curing reaction is fully carried out and to avoid the adverse effects of excessive accelerator on the long-term thermal aging performance of the material.

[0022] Furthermore, the weight ratio of component A to component B is 1:1.

[0023] Secondly, this application provides a processing technology for biodegradable epoxy resin transformer insulation materials.

[0024] A processing method for a biodegradable epoxy resin transformer insulation material includes the following steps: S1. A component preparation: Bisphenol A epoxy resin and bio-based biodegradable epoxy resin are heated to 60-70℃, an interface compatibilizer is added and stirred for 30-60 minutes, then inorganic filler and color paste are added, and stirred and degassed for 1-2 hours under a vacuum of -0.08-0.1MPa to obtain component A; Preparation of S2.B component: Methyltetrahydrophthalic anhydride was heated to 50-60℃, a latent degradation trigger and a curing accelerator were added, and the mixture was stirred until the microcapsules were uniformly dispersed. Then, inorganic filler was added, and the mixture was stirred and degassed for 1-2 hours under a vacuum of -0.08-0.1MPa to obtain component B. S3. Mixing and pouring: Mix component A and component B in the weight ratio, stir and degas at 60-80℃ for 15-30 minutes, and pour into a mold preheated to 70-80℃; S4. Curing: A stepped temperature curing process is adopted, including 85℃ / 6h, 95℃ / 2h, 105℃ / 2h, and 130℃ / 8h. Each heating stage lasts for 0.5 hours, and the heating rate is 10-20℃ / h. After curing, the product is naturally cooled to room temperature and then demolded. S5. Degradation triggering: After the material is discarded, the microcapsule wall material is ruptured by applying external triggering conditions to release the core catalyst and trigger the degradation of the material; the external triggering conditions are at least one of microwave heating, ultraviolet irradiation or solvent spraying.

[0025] By adopting the above technical solutions and systematic processing technology design, the advantages of the material formulation are transformed into actual product performance, and for the first time, "degradation triggering" is included as a process step within the scope of protection. The principle is as follows: Steps S1 and S2 prepare components A and B respectively, strictly controlling temperature and vacuum to ensure uniform dispersion of each component without air bubbles, laying the foundation for subsequent casting; Step S3 involves mixing and degassing at 60-80℃, a temperature range that ensures the fluidity of the mixture while preventing premature rupture of microcapsules due to overheating during processing; Step S4 employs a stepped heating curing process, gradually increasing the temperature from 85℃ to 130℃, maintaining each stage for a specific time. This design allows the curing reaction to proceed slowly and fully, avoiding internal stress and microcracks caused by concentrated heat release, while ensuring the complete formation of the interpenetrating network structure; most importantly, Step S5 incorporates "degradation triggering" as an integral part of the process, clearly defining three triggering methods: microwave heating, ultraviolet irradiation, and solvent spraying, extending the material patent to the usage method and constructing a complete intellectual property protection network. The entire process design and material formulation are perfectly matched, which not only ensures the high performance of the product, but also gives the material the ability to be controlled to degrade after disposal, realizing full life cycle management from "cradle" to "grave".

[0026] In summary, this application has the following beneficial effects: This application establishes a biodegradable transformer insulation material technology system through a four-pronged technological innovation: rigid-dynamic interpenetrating network structure design, microencapsulated latent triggering agents, interface capacity enhancement technology, and precise processing control. Compared with traditional epoxy insulation materials, this material adds intelligent response degradation functionality while maintaining equally excellent mechanical and insulation properties. Compared with existing biodegradable epoxy materials, this material's "zero attenuation during service life - triggerable degradation during retirement" degradation switching control mechanism solves the technical challenge of uncontrollable degradation. Detailed Implementation

[0027] The present application will be further described in detail below with reference to the embodiments.

[0028] Example of raw material and intermediate preparation raw material It should be noted that: in the following examples, unless otherwise specified, the conditions shall be in accordance with conventional conditions or the manufacturer's recommended conditions; and the raw materials used in the following examples, unless otherwise specified, shall be from commercially available sources. Bisphenol A epoxy resin, epoxy equivalent 185-195; Epoxidized soybean oil, epoxy value 0.38-0.42 mol / 100g; Polylactic acid modified epoxy resin, epoxy value 0.52 mol / 100g; Hyperbranched polymers (interface compatibilizers) are hyperbranched polymers containing epoxy groups, with a number average molecular weight of 2000-10000, an epoxy value of 0.2-0.5 mol / 100g, a functionality of 8-15, an intrinsic viscosity (25℃, THF) of 0.2-0.4 dL / g, and a glass transition temperature of 40-60℃. Methyltetrahydrophthalic anhydride, anhydride equivalent 166; Paraffin wax (microcapsule wall material), melting point 58-60℃; Diazo resin (microcapsule wall material) is a diazo-functionalized polymer with a diazo group content of 1.0-1.5 mmol / g, a number-average molecular weight of 5000-8000, a characteristic absorption peak in the UV-Vis absorption spectrum at 350-380 nm, and a photodecomposition temperature ≥180℃. Polyvinyl alcohol (microcapsule wall material), degree of alcoholysis 88%; Silica powder, with an average particle size of 15μm, treated with silane; Aluminum hydroxide, average particle size 10 μm, silane treated.

[0029] Preparation Example Preparation Example 1 A latent degradation trigger (thermosensitive microcapsule), the preparation method of which is as follows: 1) Aqueous phase preparation: Add 1000 mL of deionized water to a 2 L jacketed reactor, heat to 70 °C and keep constant, add 10 g of Span-80, and stir at 300 rpm for 30 minutes to dissolve and form a homogeneous aqueous phase. 2) Oil phase preparation: Heat 150g of paraffin wax to 80℃ in another container until completely melted, add 100g of dibutyltin dilaurate, and mechanically stir at 500rpm for 30 minutes to ensure that the core material and the molten paraffin wax are fully and evenly mixed to form an oil phase; 3) Emulsification: The oil phase was slowly added to the aqueous phase at 70℃, with the addition rate controlled at about 10 mL / min. During the addition process, the stirring speed was increased to 800 rpm. After the addition was completed, the mixture was emulsified at 70℃ and 800 rpm for 60 minutes to form an oil-in-water emulsion. During the emulsification process, samples were taken and the droplet size was observed under a microscope. Emulsification was stopped when most droplet sizes reached 10-20 μm. 4) Cooling and curing: The emulsion was cooled to 25°C at a rate of 0.5°C / min, allowing the paraffin wall material to slowly solidify and form solid microcapsules. During the cooling process, low-speed stirring at 200 rpm was maintained to prevent the microcapsules from settling and agglomerating. 5) Separation and drying: The obtained microcapsule suspension was centrifuged (3000 rpm, 10 minutes), the supernatant was discarded, and the precipitate was washed three times with 30°C warm water to remove residual emulsifier. The washed microcapsules were placed in a vacuum drying oven and vacuum dried at 25°C for 24 hours to obtain the latent degradation trigger. Product parameters: average particle size 15μm (measured by laser particle size analyzer), wall material thickness 1.2μm (observed and statistically analyzed by SEM cross-section), core material content 40% (calculated by weight loss rate at 300-400℃ using thermogravimetric analysis).

[0030] Preparation Example 2 A latent degradation trigger (photosensitive microcapsule), the preparation method of which is as follows: 1) Oil phase preparation: Dissolve 120g of diazo resin in 300mL of dichloromethane and stir at 400rpm at room temperature until completely dissolved. Add 80g of tetrabutyl titanate and continue stirring for 30 minutes to form a homogeneous oil phase. 2) Aqueous phase preparation: Add 800 mL of deionized water to the reaction vessel, add 5 g of sodium dodecyl sulfate, and stir at 300 rpm to dissolve and form an aqueous phase; 3) Emulsification: The oil phase was slowly added to the aqueous phase at a rate of 5 mL / min, while the stirring speed was increased to 1000 rpm. After the addition was complete, the mixture was emulsified at 25°C and 1000 rpm for 45 minutes to form an oil-in-water emulsion. 4) Interface aggregation: While maintaining a stirring speed of 600 rpm, slowly add 10 mL of glutaraldehyde (crosslinking agent) dropwise to the emulsion at a rate of 0.5 mL / min. After the addition is complete, raise the temperature to 40°C and react for 4 hours to allow the wall material to undergo crosslinking polymerization at the oil-water interface, forming a solidified wall shell. 5) Solvent evaporation: The reaction system temperature was raised to 50°C and stirred at 200 rpm for 12 hours to allow the dichloromethane to completely evaporate, forming a cavity structure inside the microcapsules, with the core material encapsulated inside. 6) Separation and drying The obtained microcapsule suspension was centrifuged (4000 rpm, 8 minutes), the precipitate was washed three times with deionized water, and the washed microcapsules were placed in a vacuum drying oven and dried at 30°C for 24 hours to obtain photosensitive microcapsule powder. Product parameters: average particle size 12μm (measured by laser particle size analyzer), wall material thickness 0.8μm (TEM observation and statistics), core material content 28% (thermogravimetric analysis).

[0031] Preparation Example 3 A latent degradation trigger (solvent-soluble microcapsule), the preparation method of which is as follows: 1) Wall material solution preparation: Add 40g of polyvinyl alcohol to 360g of deionized water and stir at 300rpm for 2 hours in an 85℃ water bath until completely dissolved to obtain a 10% PVA solution. Cool to 25℃ for later use. 2) Emulsion preparation: Under ice-water bath conditions, 60g of triethylamine was slowly added to the cooled PVA solution, along with 2g of Tween-80. The mixture was then emulsified at 1000rpm for 10 minutes to form an oil-in-water emulsion. During emulsification, the system temperature was maintained ≤15℃ to prevent triethylamine volatilization. 3) Spray drying granulation: The emulsion was immediately spray-dried. Spray drying conditions: inlet air temperature 140℃, outlet air temperature 70℃, atomizer speed 25000 rpm, feed rate 20 mL / min. During spray drying, moisture evaporated rapidly, and the PVA wall material solidified to form microcapsules. 4) Crosslinking treatment: The microcapsule powder obtained by spray drying was added to a pre-prepared 1% boric acid solution at a weight ratio of 1:5. The cross-linking reaction was carried out at 25°C and 200 rpm for 1 hour to form borate ester bonds between PVA molecular chains, thereby improving the stability and solvent responsiveness of the wall material. 5) Separation and drying: The cross-linked microcapsule suspension was centrifuged (5000 rpm, 5 minutes), and the precipitate was washed three times with deionized water. The washed microcapsules were placed in a vacuum drying oven and dried under vacuum at 30°C for 24 hours to obtain solvent-soluble microcapsule powder. Product parameters: average particle size 20μm (measured by laser particle size analyzer), wall material thickness 1.5μm (observed by SEM cross-section), core material content 25% (triethylamine content determined by sealed system acid-base titration combined with headspace sampling-gas chromatography).

[0032] Example Examples 1-3 A biodegradable epoxy resin transformer insulation material, the preparation method of which is as follows: S1. Preparation of component A: According to the raw material ratio in Table 1, bisphenol A epoxy resin and bio-based biodegradable epoxy resin were heated to 65°C, and an interfacial compatibilizer was added and stirred for 45 minutes. Then, inorganic filler and color paste were added, and the mixture was stirred and degassed for 1.5 hours under a vacuum of -0.1 MPa to obtain component A. S2.B component preparation: Methyltetrahydrophthalic anhydride was heated to 55°C, a latent degradation trigger and a curing accelerator were added, and the mixture was stirred until the microcapsules were uniformly dispersed. Then, inorganic filler was added, and the mixture was stirred and degassed for 1.5 hours under a vacuum of -0.1 MPa to obtain component B. S3. Mixing and pouring: Mix component A and component B in a 1:1 weight ratio, stir and degas at 70°C for 20 minutes, and pour into a mold preheated to 75°C; S4. Curing: A stepped temperature curing process is adopted, including 85℃ / 6h, 95℃ / 2h, 105℃ / 2h, and 130℃ / 8h. Each heating stage lasts for 0.5 hours, and the heating rate is 10-20℃ / h. After curing, the product is naturally cooled to room temperature and then demolded. S5. Degradation triggering: After the material is discarded, the microcapsule wall material is ruptured by applying external triggering conditions to release the core catalyst and trigger the degradation of the material; the external triggering conditions are at least one of microwave heating, ultraviolet irradiation or solvent spraying.

[0033] Table 1. Raw material ratio table for Examples 1-3 (kg) In component A, the bio-based biodegradable epoxy resin is epoxidized soybean oil, the interface compatibilizer is a hyperbranched polymer, and the inorganic filler is silica powder; in component B, the latent degradation trigger is from preparation example 1, the curing accelerator is DMP-30, and the inorganic filler is silica powder.

[0034] Example 4 Unlike Example 2, in Example 4, the bio-based biodegradable epoxy resin in component A is polylactic acid modified epoxy resin, and the inorganic filler is aluminum hydroxide; in component B, the curing accelerator is 2-methylimidazole, the inorganic filler is aluminum hydroxide, and the latent degradation trigger is derived from Preparation Example 2.

[0035] Example 5 Unlike Example 2, in Example 5, the bio-based biodegradable epoxy resin in component A is an epoxy soybean oil and castor oil-based epoxy resin in a weight ratio of 1:1, and the inorganic filler is silica powder and mica powder in a weight ratio of 2:1; in component B, the curing accelerator is DMP-30 and 2-ethyl-4-methylimidazole in a weight ratio of 1:1, the inorganic filler is silica powder and mica powder in a weight ratio of 2:1, and the latent degradation trigger is derived from Preparation Example 3.

[0036] Comparative Example Comparative Example 1 Comparative Example 1 is an epoxy resin system. Component A: 100 kg of bisphenol A epoxy resin, 200 kg of silica powder, and 1 kg of color paste; Component B: 100 kg of methyltetrahydrophthalic anhydride, 0.3 kg of DMP-30, and 200 kg of silica powder.

[0037] Comparative Example 2 Unlike Example 1, in Comparative Example 2, the dibutyltin dilaurate catalyst was added directly without microencapsulation.

[0038] Comparative Example 3 Unlike Example 1, Comparative Example 3 does not contain an interface compatibilizer.

[0039] Performance testing The samples obtained from the examples and comparative examples were subjected to the following performance tests, and the test results are shown in Table 2.

[0040] Bending strength: Refer to GB / T 9341-2008; Test conditions: 23℃, 50%RH, span 64mm, speed 2mm / min; Glass transition temperature (Tg): GB / T 19466.2-2025; Test conditions: nitrogen atmosphere, heating rate 10℃ / min, two scans; Thermogravimetric temperature (Td, 5%): GB / T 33047.1-2016; Test conditions: nitrogen atmosphere, heating rate 20℃ / min; Flexural strength retention rate after damp heat aging: GB / T 2573-2008; Test conditions: 80℃, 95%RH, aging for 1000h.

[0041] Table 2 Basic performance test results As shown in Table 2, the mechanical and thermal properties of Examples 1-5 are close to those of the traditional epoxy system (Comparative Example 1), meeting the long-term operational requirements of insulation materials for medium and high voltage transformers. Among them, Example 2 exhibits superior overall performance, indicating that this formulation can achieve excellent insulation performance while maintaining good mechanical properties.

[0042] Comparative Example 2 (without microcapsules) suffered from direct catalyst exposure, resulting in partial catalytic ester bond reactions during curing, leading to a decrease in crosslinking density and a Tg drop to 71.2℃, failing to meet usage requirements. Comparative Example 3 (without interfacial compatibilizer) exhibited significantly inferior mechanical and electrical properties compared to the examples due to phase incompatibility. This demonstrates that microcapsule isolation technology and interfacial compatibilization technology are crucial for ensuring the service performance of materials.

[0043] After aging at 80℃ / 95%RH for 1000 hours, Examples 1-5 all maintained a flexural strength retention rate of >92%, with Example 2 showing the highest retention rate, indicating its network structure was the most stable. In contrast, Comparative Example 2 maintained only 68.5%, and Comparative Example 3 approximately 71.3%, indicating that the unmicroencapsulated catalyst underwent degradation under humid and hot conditions, leading to performance deterioration. The microencapsulation design of this application keeps the catalyst inert throughout its service life, truly achieving "zero performance degradation over service life."

[0044] Degradation performance testing: The product was simulated to be buried in soil and its degradation was triggered. The mass loss rate before and after the triggering was detected.

[0045] Pre-trigger quality loss rate test method: Weigh the cured material sample (usually a 50mm×50mm×4mm sheet) and record the initial mass m0; The samples were buried in a simulated soil environment (25℃, 60% humidity, pH=7, containing mixed bacteria) for 6 months. Six months later, the sample was removed, the surface was cleaned, dried to constant weight, and weighed to obtain m1.

[0046] Calculate the mass loss rate before triggering: Pre-trigger quality loss rate = .

[0047] Triggering conditions include: microwave heating (800W power, 10min, sample surface temperature reached 100±5℃); and ultraviolet irradiation (365nm UV lamp, 500W power, 20cm irradiation distance, 30min, sample surface irradiance approximately 50mW / cm²). 2 Alkaline spraying: Spray with a NaOH solution of pH=10, at a rate of approximately 0.5 L / m². 2 Leave at room temperature for 24 hours to allow the wall material to dissolve.

[0048] Method for testing quality loss rate after triggering: Weigh the sample again after the triggering process and record the weight as m2. The samples were reburied in the same simulated soil environment and the process continued for 3 months. After 3 months, the sample was removed, cleaned, dried, and weighed to obtain m3. Calculate the quality loss rate after triggering: Quality loss rate after triggering = ; The ecotoxicity of degradation products was tested in accordance with GB / T 27851-2011, and the seed germination inhibition rate (wheat, 7 days) was tested. The test results are shown in Table 3.

[0049] Table 3 Degradation performance test As shown in Table 3, before triggering, the mass loss rate of Examples 1-5 during 6 months of soil burial was only 0.8-1.5%, comparable to Comparative Example 1 (0.5%), and negligible. In contrast, Comparative Example 2 (without microcapsules) had a loss rate as high as 28.6%, indicating significant material degradation. This demonstrates that the microcapsules effectively isolated the catalyst, ensuring material stability during its service life.

[0050] After triggering: After being treated according to their respective triggering conditions, Examples 1-5 were buried for another 3 months, and the mass loss rate rapidly increased to 32-43%. Among them, Example 1 (microwave heating) degraded the fastest (43.2%), followed by Example 2 (41.5%), and Example 3 (38.6%) was relatively low. Comparative Example 1 (conventional epoxy) hardly degraded after triggering (0.8%), proving that conventional materials are not degradable. Comparative Example 2 had already degraded severely before triggering, and the data after triggering was meaningless. Comparative Example 3, due to the lack of compatibilizer, degraded unevenly, and the loss rate after triggering was only 28.6%, lower than that of the Examples.

[0051] The above fully demonstrates that this application achieves "controllable degradation switch": stable non-degradation during service life, and rapid degradation triggered after retirement.

[0052] Different triggering methods result in different degradation rates. Users can choose the appropriate triggering method based on the processing conditions of retired transformers: microwave heating is suitable for waste parts that can be centrally processed, and it degrades the fastest; ultraviolet irradiation is suitable for outdoor or transparent encapsulated equipment, and it degrades at a moderate rate; solvent spraying is suitable for on-site processing, and it degrades more slowly but is easier to control.

[0053] Based on the seed germination inhibition rate data in Table 3, all examples 1-5 showed an inhibition rate of <10%, indicating low toxicity and harmlessness, meeting environmental protection requirements. Comparative Example 2 showed an inhibition rate of 15.6%, due to uncontrollable degradation producing toxic small molecules.

[0054] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A biodegradable epoxy resin transformer insulation material, characterized in that, Composed of component A and component B, the two are mixed and cured to form a cured product with a rigid-dynamic interpenetrating network structure; Based on the weight of component A, it includes the following raw materials: 70-85 parts of bisphenol A epoxy resin, 15-30 parts of bio-based biodegradable epoxy resin, 1-5 parts of interface compatibilizer, 150-250 parts of inorganic filler, and 0.5-2 parts of color paste. Based on the weight of component B, it includes the following raw materials: 90-110 parts of methyltetrahydrophthalic anhydride, 1-5 parts of latent degradation trigger, 0.1-0.5 parts of curing accelerator, and 150-250 parts of inorganic filler; The latent degradation trigger is a microencapsulated transesterification catalyst or hydrolysis catalyst, whose microcapsule wall material can rupture and release the core catalyst under specific external triggering conditions.

2. The biodegradable epoxy resin transformer insulation material according to claim 1, characterized in that, The bio-based biodegradable epoxy resin is at least one of epoxidized soybean oil, polylactic acid modified epoxy resin, castor oil-based epoxy resin, and tung oil-based epoxy resin, with an epoxy value of 0.3-0.6 mol / 100g.

3. The biodegradable epoxy resin transformer insulation material according to claim 1, characterized in that, The interface compatibilizer is a hyperbranched polymer containing epoxy groups, with a number average molecular weight of 2000-10000 and an epoxy value of 0.2-0.5 mol / 100g.

4. The biodegradable epoxy resin transformer insulation material according to claim 1, characterized in that, The wall material of the microcapsules is a thermosensitive material, a photosensitive material, or a solvent-soluble material; The heat-sensitive material is selected from at least one of paraffin wax, polyethylene wax, and ethyl cellulose, and its melting point is 50-120℃; The photosensitive material is selected from at least one of diazo resin and cinnamic acid ester polymers, which decomposes under 200-400 nm ultraviolet light irradiation; The solvent-soluble material is selected from at least one of polyvinyl alcohol, gelatin, and gum arabic, and is soluble under specific pH or salt concentration conditions.

5. The biodegradable epoxy resin transformer insulation material according to claim 1, characterized in that, The core catalyst of the microcapsule is an organotin compound, a titanate compound, or a tertiary amine compound; The organotin compound is selected from at least one of dibutyltin dilaurate and stannous octoate; The titanate compound is selected from at least one of tetrabutyl titanate and tetraisopropyl titanate; The tertiary amine compound is selected from at least one of triethylamine and triethanolamine.

6. The biodegradable epoxy resin transformer insulation material according to claim 1, characterized in that, The microcapsules have a particle size of 1-50 μm, a wall material thickness of 0.1-5 μm, and a core catalyst content of 10-50% of the total weight of the microcapsules.

7. The biodegradable epoxy resin transformer insulation material according to claim 1, characterized in that, The inorganic filler is at least one of silica powder, aluminum hydroxide, aluminum oxide, talc powder, and mica powder, with an average particle size of 5-30 μm, and is surface-treated with a silane coupling agent.

8. The biodegradable epoxy resin transformer insulation material according to claim 1, characterized in that, The curing accelerator is at least one of 2,4,6-tris(dimethylaminomethyl)phenol, 2-methylimidazole, and 2-ethyl-4-methylimidazole.

9. The biodegradable epoxy resin transformer insulation material according to claim 1, characterized in that, The weight ratio of component A to component B is 1:

1.

10. A processing method for a biodegradable epoxy resin transformer insulation material as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. A component preparation: Bisphenol A epoxy resin and bio-based biodegradable epoxy resin are heated to 60-70℃, an interface compatibilizer is added and stirred for 30-60 minutes, then inorganic filler and color paste are added, and stirred and degassed for 1-2 hours under a vacuum of -0.08-0.1MPa to obtain component A; Preparation of S2.B component: Methyltetrahydrophthalic anhydride was heated to 50-60℃, a latent degradation trigger and a curing accelerator were added, and the mixture was stirred until the microcapsules were uniformly dispersed. Then, inorganic filler was added, and the mixture was stirred and degassed for 1-2 hours under a vacuum of -0.08-0.1MPa to obtain component B. S3. Mixing and pouring: Mix component A and component B in the weight ratio, stir and degas at 60-80℃ for 15-30 minutes, and pour into a mold preheated to 70-80℃; S4. Curing: A stepped temperature curing process is adopted, including 85℃ / 6h, 95℃ / 2h, 105℃ / 2h, and 130℃ / 8h. Each heating stage lasts for 0.5 hours, and the heating rate is 10-20℃ / h. After curing, the product is naturally cooled to room temperature and then demolded. S5. Degradation triggering: After the material is discarded, the microcapsule wall material is ruptured by applying external triggering conditions to release the core catalyst and trigger the degradation of the material; the external triggering conditions are at least one of microwave heating, ultraviolet irradiation or solvent spraying.

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