Heat-conducting insulation paper with high heat conductivity coefficient as well as preparation method and application of heat-conducting insulation paper

Abstract

The invention discloses heat-conducting insulation paper with a high heat conductivity coefficient and a preparation method and application of the heat-conducting insulation paper, and belongs to the technical field of heat-conducting insulation paper. The heat-conducting insulation paper with the high heat conductivity coefficient comprises heat-conducting resin and insulation paper with the mass ratio being 100: (30-100), and the heat-conducting resin comprises bonding resin and heat-conducting powder with the mass ratio being 25-50: (50-75). The adhesive resin comprises modified epoxy resin and a flexibilizer, the modified epoxy resin comprises heat-resistant epoxy resin and a curing agent, and the flexibilizer comprises a polymer active modifier, a rubber flexibilizer and a thermoplastic flexibilizer. The heat-conducting powder comprises micron aluminum oxide, nano aluminum oxide, nano cubic boron nitride, nano spherical boron nitride and nano silicon dioxide. The compound heat-conducting powder and the modified toughening resin are creatively combined, and unification of high heat conductivity, high toughness and high insulation performance of the heat-conducting insulation paper is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat-conducting insulating paper, in particular to a heat-conducting insulating paper with high thermal conductivity and a preparation method and application thereof. BACKGROUND

[0002] Under the background of modern electronic and electrical equipment developing towards high power density and miniaturization, efficient heat dissipation and reliable insulation become two key requirements. Although traditional insulating paper has excellent insulation performance, its inherent low thermal conductivity makes it difficult to perform heat dissipation in high-power scenarios, limiting its application in advanced electronic equipment.

[0003] To solve the above problems, the prior art usually adds high-thermal-conductivity inorganic fillers such as aluminum nitride and aluminum oxide to the insulating paper matrix to improve its thermal conductivity. However, this method has obvious technical bottlenecks: on the one hand, a high filling amount of thermal conductive fillers will seriously damage the fiber skeleton structure of the paper, resulting in a significant decrease in its mechanical strength; on the other hand, the introduction of fillers easily produces interfacial thermal resistance and may form an electric field weak point, thereby affecting or even reducing the dielectric strength of the material.

[0004] In summary, the prior art cannot achieve high thermal conductivity while taking into account the mechanical strength and dielectric performance of the insulating paper. How to develop a new method to introduce high-content thermal conductive fillers into the insulating paper and effectively overcome the above defects to prepare an insulating paper with excellent comprehensive performance of high thermal conductivity, high mechanical strength and high dielectric strength is a problem that needs to be solved by those skilled in the art. SUMMARY

[0005] The purpose of the present application is to provide a heat-conducting insulating paper with high thermal conductivity and a preparation method and application thereof, which can realize uniform and stable dispersion of high-content thermal conductive fillers in the insulating paper to build a continuous and effective heat conduction network, while ensuring its original mechanical strength and dielectric performance.

[0006] To achieve the above purpose, the present application provides a heat-conducting insulating paper with high thermal conductivity, which comprises a heat-conducting resin and an insulating paper with a mass ratio of 100:30-100, wherein the heat-conducting resin comprises a bonding resin and a heat-conducting powder with a mass ratio of 25-50:50-75.

[0007] Further, the bonding resin comprises a modified epoxy resin and a toughening agent with a mass ratio of 100:5-40, and the insulating paper is aramid insulating paper or PET (polyethylene terephthalate) insulating paper.

[0008] Further, the modified epoxy resin comprises a heat-resistant epoxy resin and a curing agent, wherein the heat-resistant epoxy resin comprises AG80 epoxy resin, 2133 epoxy resin and E51 epoxy resin with a mass ratio of 40-50:20-22:100.

[0009] Furthermore, the curing agent includes at least one of DDS (sulfonyl diphenylamine) curing agent, 2-methylimidazole, and AEP (N-aminoethylpiperazine) curing agent.

[0010] Furthermore, the toughening agent includes a polymer active modifier and other toughening agents in a mass ratio of 100:5~40; wherein, the polymer active modifier is polymerized using DMF (N,N-dimethylformamide) as solvent, cobalt isooctanoate as catalyst, and bismaleimide and bisphenol A dielyl ether as raw materials.

[0011] Furthermore, other toughening agents include rubber toughening agents and thermoplastic toughening agents in a mass ratio of 40~65:35~60, wherein the rubber toughening agent includes at least one of carboxyl-terminated butadiene-acrylonitrile rubber, hydroxyl-terminated butadiene-acrylonitrile rubber, epoxy-terminated butadiene-acrylonitrile rubber, and vinyl-terminated butadiene-acrylonitrile rubber, and the thermoplastic toughening agent includes at least one of polyurethane, polycarbonate, and polyethersulfone.

[0012] Furthermore, the thermally conductive powder comprises micron-sized alumina, nano-sized alumina, nano-cubic boron nitride, nano-spherical boron nitride, and nano-silica in a mass ratio of 90~110:5~20:5~50:5~15:5~15. Preferably, the micron-sized alumina has a particle size of 70μm~90μm, the nano-sized alumina has a particle size of 100nm~300nm, the nano-cubic boron nitride has a particle size of 5nm~10nm, the nano-spherical boron nitride has a particle size of 5nm~50nm, and the nano-silica has a particle size of 5nm~20nm.

[0013] This application also provides a method for preparing thermally conductive insulating paper with high thermal conductivity, comprising the following steps: The adhesive resin and thermally conductive powder are dissolved together in a solvent and stirred at room temperature to obtain a thermally conductive resin solution. Thermally conductive insulating paper is prepared by coating the surface of insulating paper with a thermally conductive resin solution at 25℃~30℃ and then drying and curing it.

[0014] Furthermore, the coating speed is 0.5m / min to 30m / min, and the drying and curing temperature is 120℃ to 200℃.

[0015] This application also provides an application of thermally conductive insulating paper with high thermal conductivity, including the following steps: placing the thermally conductive insulating paper in the motor slot, and using it for insulation inside the motor slot after curing; The curing process includes: Keep warm at 135℃~145℃ for 0.5h~1.5h; Heat to 155℃~165℃ and hold for 1.5h~2.5h; The temperature is continuously increased to 175-185 DEG C, and the temperature is kept for 1.5-2.5 hours.

[0016] In summary, the application has the following advantages: In the component, the application successfully solves the inherent contradiction between the high content of heat-conducting filler and the mechanical strength and dielectric performance of the insulating paper by designing a special adhesive resin with interpenetrating network structure and toughening effect, and realizes the synergistic optimization and significant improvement of the performance of the three. Moreover, the adhesive resin of the application has a low-temperature bonding property of 60-70 DEG C, so that the insulating paper has self-adhesion ability during the processing process, simplifies the process, and improves the production efficiency.

[0017] In the preparation method, the application adopts innovative pore regulation (similar solubility principle to expand the pore diameter) and filling process (heat-conducting fillers wrapped with adhesive resin can enter the pores of the insulating paper, and after volatilization and recovery, the adhesive resin re-bonds the fibers together to ensure the mechanical and insulating strength), so that different specifications of heat-conducting fillers can efficiently and orderly enter the internal structure of the paper, and a three-dimensional through heat-conducting path is constructed, so that a higher thermal conductivity can be obtained at a lower filler amount, and the best balance between performance and cost is realized. Moreover, the method is simple, the raw material cost is low, and it is easy to realize large-scale industrial production, and has great application potential and economic benefits in the field of high-end electronics and electrical appliances. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the application. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can be obtained without creative labor under the premise of the drawings.

[0019] Figure 1 is a flowchart of the preparation method of the heat-conducting insulating paper involved in the application. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the application will be described clearly and completely in the following with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only some embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0021] Thermally conductive insulation paper, as a key electrical material, is used for winding interlayer and turn-to-turn insulation in transformers, for wire core insulation in reactors and cables, for slot insulation and phase-to-phase insulation in electric machines, for end insulation of drive motors in the new energy automobile industry, and has important application value in other industries.

[0022] However, the thermal conductivity of conventional insulation paper (such as cellulose paper, aramid paper, etc.) is generally low (usually less than 0.5 W / m·K), which is difficult to meet the heat dissipation requirements of high power density equipment and becomes a bottleneck restricting the performance improvement. In order to improve the thermal conductivity of insulation paper, the method commonly used in the prior art is to introduce inorganic fillers with high thermal conductivity into the insulation paper matrix, such as aluminum nitride, aluminum oxide, boron nitride, etc. In theory, increasing the filling amount of thermal conductive fillers is an effective way to construct efficient thermal conduction channels and significantly improve the macroscopic thermal conductivity of the material.

[0023] However, when the addition amount of thermal conductive fillers increases to a certain extent, a series of negative effects will be caused. First, a high content of inorganic fillers will seriously damage the integrity of the fiber network structure of the insulation paper, resulting in a significant decrease in the mechanical properties such as tensile strength and tear resistance of the paper, affecting its structural reliability and processability in actual application. Second, the agglomeration of filler particles and the random accumulation between fibers will introduce a large number of interfaces and defects in the material, which not only hinders the conduction of phonons (the main carrier of heat), forms interface thermal resistance, but also may become a stress concentration point under electric field, thereby degrading the dielectric strength of the material and bringing insulation safety hazards.

[0024] Based on this, the application provides a thermally conductive insulation paper with high thermal conductivity and its preparation method and application, which synergistically optimizes the three key indicators of thermal conductivity, mechanical properties and dielectric properties, and prepares a high thermal conductivity insulation paper with excellent comprehensive performance. Specifically, in a first aspect, the application provides a thermally conductive insulation paper with high thermal conductivity, which comprises a thermally conductive resin and an insulation paper with a mass ratio of 100:30-100, wherein the thermally conductive resin comprises a bonding resin and a thermally conductive powder with a mass ratio of 25-50:50-75.

[0025] As some optional embodiments of the present application, the bonding resin comprises a modified epoxy resin and a toughening agent in a mass ratio of 100:5-40, and the insulating paper is aramid insulating paper or PET insulating paper. Among them, by using a modified epoxy resin and a toughening agent in a mass ratio of 100:5-40, the performance can be controlled by adjusting the proportion of the toughening agent. For example, when the proportion of the toughening agent is 5%-20%, the resin maintains high rigidity and temperature resistance, which is suitable for high-temperature working conditions (such as motors); when the proportion is 20%-40%, the toughness is significantly improved, which is suitable for scenes that need to be frequently assembled or vibrated (such as vehicle-mounted electronic controls), solving the problem of fixed performance and narrow scene adaptation of a single resin. Aramid insulating paper is resistant to high temperature (long-term temperature resistance above 200°C) and has high mechanical strength, which is suitable for high-temperature and high-stress working conditions (such as new energy vehicle electronic control systems); PET insulating paper has high cost performance and good weather resistance, which is suitable for normal temperature and low-power scenes (such as household appliance motors). The selection of the insulating paper of the present application can cover the insulation needs from ordinary electronic equipment to high-end industrial equipment. In addition, both aramid and PET insulating paper have uniform fiber pore structures, which can not only allow the bonding resin to fully penetrate and form a tight bond, but also accommodate heat-conducting fillers (especially micro-nano fillers) to fill the pores, avoiding the problems of insufficient resin penetration or broken heat-conducting paths caused by dense substrate structure, and ensuring that the final composite insulating paper meets the standards in terms of heat conduction, insulation, and mechanical performance.

[0026] As some optional embodiments of the present application, the modified epoxy resin comprises a heat-resistant epoxy resin and a curing agent, wherein the heat-resistant epoxy resin comprises AG80 epoxy resin (a four-glycidyl amine type epoxy resin, 4,4'-diamino diphenyl methane epoxy resin), 2133 epoxy resin (glycidyl amine type epoxy resin MF-2133), and E51 epoxy resin (EPOXY Resin) in a mass ratio of 40-50:20-22:100. By compounding AG80 (four-glycidyl amine type), 2133 (glycidyl amine type), and E51 epoxy resin, the advantages of the three can be complementary, for example, AG80 and 2133 have strong high-temperature resistance, which can improve the overall heat resistance of the resin and adapt to high-temperature working conditions; E51 has good flowability and cost performance, which can improve the processability of the mixed system and avoid the problem of high viscosity and difficult processing of pure heat-resistant resin, finally forming a balanced system with high heat resistance, easy processing, and low cost.

[0027] In the embodiment, the heat-resistant epoxy resin is prepared by the following method: heating AG80 at 55-65℃ for 25-35min to reduce the viscosity for standby; mixing 2133 and E51, weighing the standby AG80 and mixing together, then heating to 55-65℃ and stirring for 110-130min to obtain the heat-resistant epoxy resin. In the application, AG80 is heated separately to reduce the viscosity, then mixed with 2133 and E51 and heated and stirred, which not only solves the problem of high viscosity and difficult dispersion of AG80 at room temperature, but also ensures uniform fusion of the three resins through long-time low-temperature stirring, avoids local performance defects caused by uneven mixing, and prevents premature curing of the resin through low-temperature process, ensuring the compatibility of the subsequent curing agent and toughening agent.

[0028] As some optional embodiments of the application, the curing agent includes at least one of DDS curing agent, 2-methyl imidazole and AEP curing agent. The curing agent of the application includes DDS (aromatic diamine, high temperature resistance, high curing strength), 2-methyl imidazole (imidazole, fast curing, high catalytic activity), AEP (fatty amine, room temperature curable, good flexibility), which can be flexibly selected according to actual needs, for example, DDS is selected for high temperature working condition, 2-methyl imidazole is selected for high efficiency requirement, AEP is selected for room temperature processing or toughness improvement, and they can also be used in combination, breaking through the limitations of single curing agent with fixed curing conditions and single performance. The selected curing agents of the application can efficiently react with the AG80 / 2133 / E51 compound system, among which, DDS can form a dense cross-linked structure with epoxy resin to enhance heat resistance, 2-methyl imidazole can precisely catalyze the ring opening of epoxy groups, and AEP can introduce flexible segments to improve toughness, and there is no obvious by-product in the reaction process, which will not damage the insulation of the resin and the dispersion of the thermal conductive filler, ensuring the comprehensive performance of the final bonding resin.

[0029] As some optional embodiments of the present application, the toughening agent comprises a polymer active modifier and other toughening agents in a mass ratio of 100:5-40; wherein the polymer active modifier is polymerized from bismaleimide and bisphenol A bisallyl ether as raw materials, with DMF as a solvent and cobalt isooctanoate as a catalyst. The present application uses bismaleimide (BMI) and bisphenol A bisallyl ether (BBE) as raw materials (homologous to the core resin system composition of the present application), and forms a polymer active modifier through cobalt isooctanoate catalysis and DMF solvent polymerization. The molecular chain contains active groups complementary to the resin, can form strong interfacial bonding with modified BMI or modified epoxy resin, avoid the performance stratification problem caused by poor compatibility between traditional toughening agents and the resin, and at the same time, retain the high-temperature resistance and insulation properties of the raw materials without sacrificing the core performance of the resin. Specifically, bismaleimide (BMI) and bisphenol A bisallyl ether (BBE) are used as active modifiers, and BMI is a high-temperature-resistant resin with a high melting point but poor processability and high brittleness after curing. Therefore, the present application introduces BBE into the BMI segment to reduce the melting point and improve the processability by extending the molecular chain, while improving the mechanical strength. The BMI and BBE prepolymer forms an IPN structure with the epoxy resin during the curing process of the epoxy resin, and at the same time, forms molecular chain entanglement by using the long side chain of isobutylene to greatly improve the anti-cracking ability of the matrix resin, ensure the mechanical properties of the heat-conducting insulating paper under high powder content, and realize the high-proportion addition of the heat-conducting powder.

[0030] In the specific embodiment, the polymer active modifier is prepared by the following method: bismaleimide, bisphenol A bisallyl ether and cobalt isooctanoate are dissolved in DMF solvent to obtain a reaction solution; DMF solvent is added to a reaction kettle and heated, and then part of the reaction solution is added for continuous heating reaction; the remaining reaction solution is added dropwise for heat preservation reaction, and the solvent is evaporated to obtain the product.

[0031] As some optional embodiments of the present application, the other toughening agent comprises a rubber toughening agent and a thermoplastic toughening agent in a mass ratio of 40-65:35-60, wherein the rubber toughening agent comprises at least one of carboxyl-terminated nitrile rubber, hydroxyl-terminated nitrile rubber, epoxy-terminated nitrile rubber and vinyl-terminated nitrile rubber, and the thermoplastic toughening agent comprises at least one of polyurethane, polycarbonate and polyether sulfone. The rubber toughening agent in the present application can absorb impact energy through elastic segments (improve impact toughness), and the thermoplastic toughening agent can improve the processing fluidity and low-temperature toughness of the resin (avoid low-temperature brittle cracking), so that the combination of the two can cover the multi-dimensional requirements such as impact toughness, processability and low-temperature stability, and the terminal active groups of the rubber toughening agent can further react with the resin to enhance the interfacial bonding force.

[0032] In the specific embodiment, the other toughening agent is prepared by the following method: heating the rubber toughening agent at 55-65 DEG C for 25-35 min to reduce the viscosity for standby; adding the thermoplastic toughening agent to heat to 55-65 DEG C and stirring for 55-70 min to obtain the other toughening agent. In the present application, the rubber toughening agent is heated to reduce the viscosity, and then stirred with the thermoplastic toughening agent at low temperature. The problem of high viscosity and difficult dispersion of the rubber toughening agent at room temperature is solved, and the decomposition of the thermoplastic toughening agent is avoided through the low-temperature process. The overall process matches the preparation temperature of the adhesive resin, and can be directly integrated into the existing production process without additional equipment or adjustment of temperature parameters, thereby improving the production efficiency.

[0033] As some optional embodiments of the present application, the heat-conducting powder includes micron alumina, nano-alumina, nano-cubic boron nitride, nano-spherical boron nitride, and nano-silicon dioxide in a mass ratio of 90-110:5-20:5-50:5-15:5-15. The present application adopts a ratio of micron alumina, nano-alumina, nano-cubic boron nitride, nano-spherical boron nitride, and nano-silicon dioxide to form a multi-level heat-conducting structure with micron skeletons and nano-filling. The micron alumina serves as a main skeleton for heat conduction to build a macroscopic heat conduction path. The nano-alumina, nano-cubic boron nitride, and nano-spherical boron nitride can fill the gaps between micron particles to eliminate heat conduction blind areas, thereby greatly improving the heat conduction efficiency. Meanwhile, the high heat conduction characteristics of the nano-cubic boron nitride and the spherical boron nitride further strengthen the heat conduction performance and solve the problem of discontinuous heat conduction path of a single powder. The excellent insulation performance of the nano-silicon dioxide in the present application can compensate for the risk of insulation decline caused by the high heat-conducting powder, ensure that the overall dielectric performance of the heat-conducting powder meets the standards, and protect the breakdown field strength of the final composite insulation paper. Meanwhile, the surface hydroxyl groups of the nano-silicon dioxide can improve the interfacial compatibility between the powder and the adhesive resin, reduce the agglomeration of the nano-powder, improve the dispersion uniformity of the heat-conducting powder in the resin, and avoid local heat conduction failure or mechanical strength decline caused by agglomeration.

[0034] In the specific embodiment, the heat-conducting powder is prepared by the following method: S111. Dissolve the micron alumina, nano-alumina, nano-cubic boron nitride, nano-spherical boron nitride, and nano-silicon dioxide in a solvent, and then mix and grind them at high speed by a nano-sand mill to obtain a mixture.

[0035] Preferably, the solvent is ethanol, isopropyl alcohol, or ethyl acetate, and the mass of the solvent is 65-85% of the total mass of the added powder (including micron alumina, nano-alumina, nano-cubic boron nitride, nano-spherical boron nitride, and nano-silicon dioxide). Preferably, the rotation speed of high-speed mixing and grinding is 5000-6000 rpm, and the grinding time is 1-3 h.

[0036] S112. After the mixture is dried at 78-82°C to remove the solvent, the heat-conducting powder is obtained by crushing the mixture in a crusher. Preferably, the particle size of the heat-conducting powder is 80-120 mesh.

[0037] As some optional embodiments of the present application, the particle size of the micrometer alumina is 70-90 μm, the particle size of the nanometer alumina is 100-300 nm, the particle size of the nanometer cubic boron nitride is 5-10 nm, the particle size of the nanometer spherical boron nitride is 5-50 nm, and the particle size of the nanometer silicon dioxide is 5-20 nm.

[0038] In a second aspect, based on the overall inventive concept, the present application further provides a preparation method of the heat-conducting insulation paper with high heat-conducting coefficient, which comprises the following steps: S1. The adhesive resin and the heat-conducting powder are co-dissolved in a solvent, and the mixture is stirred at room temperature to obtain a heat-conducting resin solution. Preferably, the solvent is N,N-dimethylformamide (DMF), and the amount of the solvent is preferably 100% of the total mass of the adhesive resin and the heat-conducting powder.

[0039] As some optional embodiments of the present application, the adhesive resin is prepared by the following method: S101. The bismaleimide, the bisphenol A bisallyl ether, and the cobalt isooctoate are co-dissolved in DMF to obtain a reaction solution.

[0040] S102. In a reaction kettle, DMF is added and heated to 135-140°C, and then a part of the reaction solution is added and reacted for 15-20 min; the remaining reaction solution is added at a constant speed within 1.5 h, and the reaction is continued for 25-35 min, and then the DMF is evaporated under reduced pressure to obtain a polymer active modifier. Preferably, the amount of the first added reaction solution is 1 / 3 of the total mass of the reaction solution, and the amount of the subsequently added reaction solution is 2 / 3 of the remaining mass.

[0041] S103. The heat-resistant epoxy resin, the polymer active modifier, and other toughening agents are uniformly mixed and stirred at 78-82°C for 25-35 min.

[0042] S104. The curing agent is added and stirred at 30-40°C for 25-35 min to obtain the adhesive resin.

[0043] S2. The heat-conducting resin solution is coated on the surface of the insulation paper at 25-30°C, and the heat-conducting insulation paper is obtained after drying and curing.

[0044] As some optional embodiments of the present application, the coating speed is 0.5-30 m / min, the drying and curing temperature is 120-200°C, and the time is 2-5 min.

[0045] In a third aspect, based on the overall inventive concept, the application further provides an application of the high-thermal-conductivity thermal-insulation paper, comprising the following steps: placing the thermal-insulation paper in a motor slot, and curing the thermal-insulation paper to be used for insulation in the motor slot; wherein the curing process comprises: holding at 135℃~145℃ for 0.5h~1.5h; raising the temperature to 155℃~165℃, and holding for 1.5h~2.5h; continuously raising the temperature to 175℃~185℃, and holding for 1.5h~2.5h.

[0046] In summary, the application provides a thermal-insulation paper, a preparation method and an application thereof, and has the following remarkable beneficial effects compared with the prior art: 1. The thermal, mechanical and insulation properties are synergistically improved.

[0047] In the conventional technology, the high proportion of the addition of the thermal-conductivity filler inevitably leads to the sharp decline of the mechanical strength and the dielectric property of the insulation paper. The application creatively constructs an interpenetrating polymer network (IPN) structure of the epoxy resin / dual-maleimide / dual-phenol A double allyl ether, and utilizes the long side chain of the modified toughening agent to form molecular entanglement, which greatly enhances the toughness of the matrix resin. The high-toughness resin matrix can effectively wrap and fix the high content of the thermal-conductivity filler, so as to realize the high proportion of the filling of the thermal-conductivity powder while ensuring the excellent mechanical strength and the reliable dielectric strength of the cured insulation paper, and successfully solves the core contradiction that the three are difficult to be considered in the prior art.

[0048] 2. The material is endowed with low-temperature cohesiveness, and the processing process is significantly improved.

[0049] The adhesive resin system prepared in the application has a low softening point (60℃~70℃). This feature makes the thermal-insulation paper have self-adhesion under mild conditions without additional adhesive or high-temperature treatment in the subsequent processing (such as lamination, wrapping, etc.), effectively improves the production efficiency and product yield, simplifies the process flow, and reduces the manufacturing cost.

[0050] 3. The preparation method is innovated, and a three-dimensional thermal-conductivity network is efficiently constructed.

[0051] The application discards the traditional simple physical mixing or impregnation method, and adopts an innovative process based on pore regulation-filler filling and resin re-bonding. First, the pore diameter of the insulating paper matrix is expanded through solvent treatment; then, the thermally conductive fillers with different particle sizes and morphologies are used to match the pores of specific sizes, so that the fillers can be selectively and deeply filled into the paper; finally, through solvent evaporation and resin curing, the resin re-bonds the fibers and fillers firmly. The method of the application not only ensures that the thermally conductive fillers form more continuous and efficient heat conduction paths in three-dimensional space, maximizes the heat conduction efficiency, but also fundamentally guarantees the final structural strength and insulation integrity of the insulating paper through the re-bonding effect of the resin. And the fillers with different particle sizes and morphologies selectively enter the pores with different diameters to build a heat conduction path in the insulating paper, realizing the improvement of the heat conduction performance. At the same time, the thermally conductive fillers with different particle sizes form micro-nano structures to form a hierarchical porous structure to build a three-dimensional heat conduction network, which significantly improves the heat conduction performance through multi-scale collaborative design.

[0052] 4. The process is simple, the cost is controllable, and has the prospect of large-scale industrial application.

[0053] The raw materials (such as epoxy resin, various thermally conductive fillers) used in the application are mature and readily available materials in the industry, and the preparation process is relatively simple, without the need for complex and expensive equipment. Therefore, the application effectively controls the production cost while significantly improving the comprehensive performance of the product, and has high practical value and broad market economic benefits.

[0054] The above technical solutions of the application will be described in detail below in conjunction with specific embodiments.

[0055] The raw materials used in the embodiments of the application include: Bismaleimide, manufacturer: Shandong Minghoudeli; Bisphenol A diallyl ether, manufacturer: Guangzhou Laiyu Trade Co., Ltd.; AG80, manufacturer: Hubei Zhenzhengfeng New Material Co., Ltd.; E51, manufacturer: Hubei Zhenzhengfeng New Material Co., Ltd.; 2133, manufacturer: Hubei Zhenzhengfeng New Material Co., Ltd.; DMF, purity 99%, manufacturer: Shandong Jiaying Chemical Technology Co., Ltd.

[0056] Example 1 The embodiment provides a thermally conductive insulating paper with high thermal conductivity, which is prepared by the following method: (1) Preparation of polymer active modifier 50 mol of bismaleimide, 50 mol of bisphenol A diallyl ether, 50 g of cobalt isooctoate, and 5000 g of DMF are mixed to obtain a reaction solution.

[0057] In the reaction kettle, 10000g DMF was heated to 130℃, then 1 / 3 mass of the reaction solution was added, after reaction at 140℃ for 0.3h, the remaining reaction solution was added dropwise within 1.5h, and the reaction was continued for 0.5h.

[0058] The DMF solvent was evaporated at 120℃ under a negative pressure of 0.95MPa to obtain the polymer active modifier.

[0059] (2) Preparation of heat-resistant epoxy resin The resin AG80 was heated in a 60℃ oven for 0.5h to reduce the viscosity. Then 500g of resin 2133 and 2500g of resin E51 were added to the stirring container, 1000g of resin AG80 was added, the temperature was raised to 60℃, the stirring speed was 200rad / min, and the stirring time was 2h to obtain the heat-resistant epoxy resin.

[0060] (3) Preparation of other toughening agent The hydroxyl-terminated butyl nitrile rubber was heated in a 60℃ oven for 0.5h to reduce the viscosity. Then 500g of polyurethane and 610g of heated hydroxyl-terminated butyl nitrile rubber were added to the stirring container, the temperature was raised to 60℃, the stirring speed was 200rad / min, and the stirring time was 1h to obtain the other toughening agent.

[0061] (4) Preparation of bonding resin Polymer active modifier 333.33g, heat-resistant epoxy resin 1000g, other toughening agent 66.67g, and curing agent DDS 50g were weighed and mixed, then the temperature was raised to 45℃, the stirring speed was 200rad / min, and the stirring time was 1h, then the temperature was lowered to 25℃ to obtain the bonding resin.

[0062] (5) Preparation of heat-conducting powder 100g of micron-sized alumina with a particle size of 80μm, 40g of nanometer-sized cubic boron nitride with a particle size of 10nm, 10g of nanometer-sized spherical boron nitride with a particle size of 50nm, 8g of nanometer-sized silicon dioxide with a particle size of 7nm, and 10g of alumina with a particle size of 100nm were added to 210g of ethanol solvent (80% of the total mass of the heat-conducting powder), and the mixture was obtained after high-speed mixing and grinding for 5 times at a rotation speed of 6000rad / min. After drying the mixture at 85℃ to remove the solvent, the heat-conducting powder was obtained by using a crusher.

[0063] The thermal conductivity of the obtained heat-conducting powder was tested, and the result was 35W / m·K, which proved that the micro-nano structure was beneficial to improving the thermal conductivity of the material.

[0064] (6) Preparation of heat-conducting resin Mix 10000 adhesive resin with 12222 g heat conductive powder, add 37030 g DMF solvent, add 5% of the total mass of the adhesive resin curing agent DDS, stir at 25°C for 2h, the stirring rate is 200 rad / min, to get the heat conductive resin. The viscosity of the obtained heat conductive resin is tested, and the viscosity at 25°C is measured to be 5000 mPa·s.

[0065] (7) Preparation of heat conductive insulation paper Weigh 20000 g of heat conductive resin into a stirring tank and stir at a speed of 300 rad / min, then uniformly flow into the gluing equipment, control the gluing equipment vehicle speed to be 20 m / min, the glue flow is 0.3 m 3 / min, the heat conductive resin is coated on the insulation paper, the oven temperature is set to 130°C, then it is wound to prepare the heat conductive insulation paper. The performance of the obtained heat conductive insulation paper is tested, and the thermal conductivity is 0.29 W / m·K.

[0066] Example 2 The difference between this embodiment and Example 1 is that the heat conductive resin mixed is 10000 g of adhesive resin, 15000 g of heat conductive powder and 41750 g of DMF solvent, and the rest of the process steps and parameter settings are the same as Example 1. The mechanical and electrical performance of the obtained heat conductive insulation paper is tested, and the results are shown in Example 2 in Table 1 below.

[0067] Example 3 The difference between this embodiment and Example 1 is that the heat conductive resin mixed is 10000 g of adhesive resin, 20000 g of heat conductive powder and 50100 g of DMF solvent, and the rest of the process steps and parameter settings are the same as Example 1. The mechanical and electrical performance of the obtained heat conductive insulation paper is tested, and the results are shown in Example 3 in Table 1 below.

[0068] Example 4 The difference between this embodiment and Example 1 is that the mass of the polymer active modifier weighed in step (4) is 500 g, and the rest of the process steps and parameter settings are the same as Example 1. The mechanical and electrical performance of the obtained heat conductive insulation paper is tested, wherein the thermal conductivity is tested according to GB / T 10295-2008, the breakdown field strength is tested according to GB / T 1408.1-2016 method, the dielectric constant and dielectric loss are tested according to GB / T 1409-2021, and the tensile strength is tested according to GB / T 2951.12-2008, and the results are shown in Example 4 in Table 1 below.

[0069] Table 1 Performance data of heat conductive insulation paper of Examples 1-4

[0070] As can be seen from Table 1, within the scope of the present application, increasing the proportion of the heat-conducting powder can significantly improve the heat-conducting performance of the heat-conducting insulation paper, but at the expense of part of the tensile strength; increasing the content of the polymer active modifier in the adhesive resin has less effect on the heat-conducting performance of the system, but can significantly increase the tensile strength and breakdown strength of the heat-conducting insulation paper. It can be illustrated that, within the scope of the present application, when the proportion of the heat-conducting powder is increased, the heat-conducting performance of the heat-conducting insulation paper can be significantly improved by increasing the density and continuity of the heat-conducting path, effectively solving the heat dissipation demand of high-power electronic equipment; increasing the content of the polymer active modifier has almost no negative effect on the heat-conducting performance of the overall system due to the compatibility of its molecular structure with the resin matrix and the action mechanism (mainly through interface bonding and elastic chain toughening, not directly participating in the construction of the heat-conducting path); instead, it can significantly improve the tensile strength (improve the anti-breaking ability) and breakdown strength (strengthen the insulation safety) of the heat-conducting insulation paper by optimizing the micro cross-linking structure of the resin matrix and enhancing the interface bonding force with the heat-conducting powder, exactly making up for the strength decrease problem caused by increasing the proportion of the heat-conducting powder, forming a performance complementary regulation closed loop.

[0071] Example 5 The difference between this example and Example 1 is that the heat-conducting powder prepared in step (5) comprises: 90 g of micron alumina with a particle size of 80 μm and 20 g of alumina with a particle size of 100 nm, and the rest of the filler proportions are the same as those in Example 1, and the process steps and parameter settings are the same as those in Example 1. The thermal conductivity of the obtained heat-conducting powder is tested, and the result is 34 W / m·K, indicating that micron spherical alumina contributes more to the heat-conducting performance of the heat-conducting powder. The mechanical and electrical performance of the obtained heat-conducting insulation paper is tested, and the results are shown in Example 5 in Table 2 below.

[0072] Example 6 The difference between this example and Example 1 is that the heat-conducting powder prepared in step (5) comprises: 105 g of micron alumina with a particle size of 80 μm and 5 g of alumina with a particle size of 100 nm, and the rest of the filler proportions are the same as those in Example 1, and the process steps and parameter settings are the same as those in Example 1. The thermal conductivity of the obtained heat-conducting powder is tested, and the result is 40 W / m·K, indicating that increasing the proportion of micron spherical alumina can improve the heat-conducting performance of the heat-conducting insulation paper, and large-particle-size heat-conducting fillers contribute more to the heat-conducting performance. The mechanical and electrical performance of the obtained heat-conducting insulation paper is tested, and the results are shown in Example 6 in Table 2 below.

[0073] Example 7 The difference between this example and Example 1 is that the heat-conducting powder prepared in step (5) comprises: 12 g of nanometer spherical boron nitride with a particle size of 50 nm, 38 g of nanometer cubic boron nitride with a particle size of 10 nm, and the rest of the filler addition amount is the same as that in Example 1, and the process steps and parameter settings are the same as those in Example 1.

[0074] The thermal conductivity of the obtained heat-conducting powder was tested, and the result was 39 W / m·K, indicating that spherical boron nitride contributes more to thermal conductivity than flaky boron nitride in this filler formulation, which can improve the thermal conductivity of the heat-conducting insulation paper. The mechanical and electrical properties of the obtained heat-conducting insulation paper were tested, and the results are shown in Example 7 in Table 2 below.

[0075] Example 8 The difference between this example and Example 1 is that the heat-conducting powder prepared in step (5) includes: 8 g of nanometer spherical boron nitride with a particle size of 50 nm, 42 g of nanometer cubic boron nitride with a particle size of 10 nm, and the rest of the filler addition amount is the same as that in Example 1, and the rest of the process steps and parameter settings are the same as those in Example 1.

[0076] The thermal diffusivity of the obtained heat-conducting powder was tested, and the result was 38.4 W / m·K, indicating that reducing the proportion of nanometer spherical boron nitride reduces the density of the heat-conducting insulation paper, and the thermal conductivity also decreases. The mechanical and electrical properties of the obtained heat-conducting insulation paper were tested, and the results are shown in Example 8 in Table 2 below.

[0077] Example 9 The difference between this example and Example 1 is that the heat-conducting powder prepared in step (5) includes: 98 g of micron-sized aluminum oxide with a particle size of 80 μm, 12 g of nanometer spherical boron nitride with a particle size of 50 nm, and the rest of the filler addition amount is the same as that in Example 1, and the process steps and parameter settings are the same as those in Example 1.

[0078] The thermal conductivity of the obtained heat-conducting powder was tested, and the result was 36.5 W / m·K, indicating that increasing the proportion of nanometer spherical boron nitride can increase the density of the heat-conducting insulation paper, and the thermal conductivity is greatly improved, but the insulation performance decreases. The mechanical and electrical properties of the obtained heat-conducting insulation paper were tested, and the results are shown in Example 9 in Table 2 below.

[0079] Example 10 The difference between this example and Example 1 is that the heat-conducting powder prepared in step (5) includes: 8 g of nanometer spherical boron nitride with a particle size of 50 nm and 12 g of nanometer silicon dioxide with a particle size of 7 nm, and the rest of the filler addition amount is the same as that in Example 1, and the process steps and parameter settings are the same as those in Example 1.

[0080] The thermal diffusivity of the obtained heat-conducting powder was tested, and the result was 34.7 W / m·K, indicating that the nano-spherical boron nitride was superior to nano-silicon dioxide in improving the thermal conductivity of the heat-conductive insulating paper. The mechanical and electrical performance tests of the obtained heat-conductive insulating paper are shown in Example 10 in Table 2. The selection of the heat-conductive powder of Examples 5-6 is shown in Table 3.

[0081] Table 2 Performance data of heat-conductive insulating paper of Examples 5-6

[0082] As can be seen from Table 2, the increase of the proportion of micron alumina can significantly improve the thermal conductivity of the material, but can significantly reduce the mechanical strength of the material, and has no effect on the insulation performance. Increasing the silicon dioxide can improve the insulation performance, and increasing the boron nitride can improve the thermal conductivity.

[0083] Among them, the high thermal conductivity and the multi-scale filler can synergistically enhance the performance, through the compounding of micron alumina, nano alumina, nano cubic boron nitride, nano spherical boron nitride and nano silicon dioxide, a micron-nano multi-level heat conduction network is formed. For example, increasing the proportion of micron boron nitride can improve the thermal conductivity of the heat-conductive powder, which is significantly higher than that of traditional insulating paper (usually <0.2 W / m·K). For example, large particle size alumina dominates the heat conduction path, and small particle size filler fills the pores and reduces the interfacial thermal resistance, achieving a balance between thermal conductivity and mechanical strength.

[0084] Among them, the active modifier synthesized by bismaleimide and bisphenol A diallyl ether forms an interpenetrating network (IPN) during the curing of the epoxy, combined with toughening agents such as butyl rubber / polyurethane, which greatly improves the anti-cracking ability. After increasing the proportion of active modifier in the component ratio, the longitudinal tensile strength and transverse strength will increase. And under the proportion of high thermal conductivity filler, it can still maintain a certain strength, for example Even if the proportion of heat-conductive powder reaches 67% (Example 3), the tensile strength remains 72 N / 10 mm (longitudinal), which is better than the strength decay problem of conventional high filler composites.

[0085] Among them, the addition of nano-silicon dioxide can improve the breakdown field strength and reduce the dielectric loss, meeting the insulation requirements of high-voltage motors. By controlling the proportion of fillers (such as alumina as the main component), the dielectric constant can be stabilized at 2.8-3.0, avoiding signal delay at high frequency.

[0086] In summary, the heat-conducting insulating paper has at least the following advantages: through multi-scale filler compounding, IPN toughening resin design and solvent method coating process, the three core problems of high heat-conducting insulating paper are solved. For example, the contradiction between heat conduction and mechanical strength, the strength can be maintained under high powder content. For example, the complexity of the processing technology, the application adopts low-temperature bonding and continuous coating, and the process is simple. For example, the stability of the insulation performance, the heat-conducting insulating paper has the advantages of low dielectric loss and high breakdown field strength.

[0087] Each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between embodiments can be referred to each other.

[0088] Although the preferred embodiments of the application have been described, those skilled in the art can make further changes and modifications to the embodiments once they know the basic creative concept. Therefore, the appended claims are intended to include the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the application.

[0089] Finally, it should be noted that in this document, relational terms such as first and second and the like can only be used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that these entities or operations exist in any such actual relationship or order. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed or inherent to such a process, method, article or terminal device. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the process, method, article or terminal device including the element.

[0090] The principles and implementation modes of the application are described by applying specific examples in this document, and the above description of the examples is only used to help understand the method and core idea of the application; at the same time, for those skilled in the art, according to the idea of the application, the specific implementation mode and application range will be changed, and the content of the specification should not be understood as a limitation of the application.

Claims

1. A heat conductive insulating paper having a high thermal conductivity, characterized by, The heat-conducting resin and the insulating paper have a mass ratio of 100:30-100, wherein the heat-conducting resin comprises a bonding resin and a heat-conducting powder, and the mass ratio of the bonding resin and the heat-conducting powder is 25-50:50-75.

2. The high thermal conductive insulating paper according to claim 1, characterized in that, The bonding resin comprises a modified epoxy resin and a toughening agent, and the mass ratio of the modified epoxy resin and the toughening agent is 100:5-40.

3. The highly thermally conductive insulating paper of claim 2, wherein, The modified epoxy resin comprises a heat-resistant epoxy resin and a curing agent, wherein the heat-resistant epoxy resin comprises AG80 epoxy resin, 2133 epoxy resin and E51 epoxy resin, and the mass ratio of the AG80 epoxy resin, the 2133 epoxy resin and the E51 epoxy resin is 40-50:20-22:

100.

4. The highly thermally conductive insulating paper of claim 3, wherein, The curing agent comprises at least one of DDS curing agent, 2-methyl imidazole and AEP curing agent.

5. The high thermal conductive insulating paper according to claim 2, wherein, The toughening agent comprises a polymer active modifier and another toughening agent, and the mass ratio of the polymer active modifier and the another toughening agent is 100:5-40.

6. The highly thermally conductive insulating paper of claim 5, wherein, The another toughening agent comprises a rubber toughening agent and a thermoplastic toughening agent, and the mass ratio of the rubber toughening agent and the thermoplastic toughening agent is 40-65:35-60.

7. The high thermal conductive insulating paper according to claim 1, wherein The heat-conducting powder comprises micron alumina, nano alumina, nano cubic boron nitride, nano spherical boron nitride and nano silicon dioxide, and the mass ratio of the micron alumina, the nano alumina, the nano cubic boron nitride, the nano spherical boron nitride and the nano silicon dioxide is 90-110:5-20:5-50:5-15:5-15.

8. A method of producing the heat-conducting insulating paper of high thermal conductivity according to any one of claims 1 to 7, characterized in that, The method comprises the following steps: The bonding resin and the heat-conducting powder are co-dissolved in a solvent, and stirring treatment is performed at room temperature to obtain a heat-conducting resin solution; The heat-conducting resin solution is coated on the surface of the insulating paper at 25-30 DEG C, and the heat-conducting insulating paper is prepared after drying and curing.

9. The production method according to claim 8, characterized by, The coating speed is 0.5-30 m / min, and the drying and curing temperature is 120-200 DEG C.

10. Use of the high thermal conductivity insulating paper according to any one of claims 1-7, characterized in that, The method comprises the following steps: The heat-conducting insulating paper is placed in a motor slot, and is used for insulation in the motor slot after curing. The curing process comprises the following steps: The temperature is kept at 135-145 DEG C for 0.5-1.5 h; The temperature is increased to 155-165 DEG C, and the temperature is kept for 1.5-2.5 h; The temperature is continuously increased to 175-185 DEG C, and the temperature is kept for 1.5-2.5 h.

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