Low-viscosity and high-thermal-conductivity epoxy resin pouring insulating material and preparation method thereof

Abstract

The invention belongs to the technical field of electrical insulating materials, and particularly relates to a low-viscosity and high-thermal-conductivity epoxy resin pouring insulating material and a preparation method thereof. The low-viscosity and high-thermal-conductivity epoxy resin pouring insulating material is prepared from basic resin, a thermal conductive filler, a diluent and a flexibilizer, by optimizing the ratio of the raw materials and the preparation process, the epoxy resin pouring insulating material with low viscosity, high thermal conductivity, excellent electrical insulating property and high mechanical strength is obtained, and the defects of the traditional epoxy resin insulating material in the application of offshore wind power equipment are effectively overcome; the epoxy resin insulating material is endowed with wide application prospect and popularization value.

Description

Technical Field

[0001] The invention belongs to the technical field of electrical insulation materials, and in particular relates to a low-viscosity, high-thermal-conductivity epoxy resin casting insulation material and a preparation method thereof. Background Art

[0002] With the global emphasis on sustainable development and clean energy, offshore wind power, as an important part of renewable energy, has an increasingly broad development prospect. However, the working environment of offshore wind power equipment is extremely harsh. Natural conditions such as high salinity, high humidity, and strong winds and waves have put forward extremely high requirements on the insulation performance of power equipment. As one of the key power equipment on offshore wind power platforms, the insulation performance of dry-type transformers is directly related to the stable operation of the entire system.

[0003] Traditional dry-type transformer insulation materials are mostly epoxy resins. Although epoxy resins have good electrical insulation properties and mechanical strength, they gradually show problems such as insufficient thermal conductivity and increased viscosity in high-frequency and high-temperature environments. This not only affects the heat dissipation efficiency of the equipment, but also increases the difficulty and cost of processing.

[0004] Therefore, the development of a new type of low-viscosity, high-thermal conductivity epoxy resin insulation material is of great significance to improving the overall performance of offshore wind power equipment. Summary of the invention

[0005] Based on the above technical background, the main purpose of the present invention is to provide a low-viscosity, high-thermal conductivity epoxy resin cast insulating material and a preparation method thereof to overcome the deficiencies in the prior art.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0007] The first aspect of the present invention is to provide a low-viscosity, high-thermal-conductivity epoxy resin cast insulation material, wherein the low-viscosity, high-thermal-conductivity epoxy resin cast insulation material is made of a base resin, a thermally conductive filler, a diluent and a toughening agent;

[0008] The mass ratio of the base resin, the thermal conductive filler, the diluent and the toughening agent is 1: (0.3-0.4): (0.2-0.4): (0.01-0.03).

[0009] Preferably, the mass ratio of the base resin, the thermal conductive filler, the diluent and the toughening agent is 1:0.35:0.3:0.02.

[0010] Preferably, the base resin comprises epoxy resin, a curing agent and an accelerator;

[0011] The mass ratio of the epoxy resin, the curing agent and the accelerator is 60:(37-42):(0.3-0.7).

[0012] More preferably, the epoxy resin is bisphenol A epoxy resin E51; and / or,

[0013] The curing agent is methyltetrahydrophthalic anhydride; and / or,

[0014] The accelerator is DMP-30.

[0015] Preferably, the thermally conductive filler is surface-modified hexagonal boron nitride, and the particle size of the thermally conductive filler is 5 to 10 μm.

[0016] More preferably, the surface-modified hexagonal boron nitride is prepared by surface-modifying hexagonal boron nitride with a silane coupling agent;

[0017] The silane coupling agent is silane coupling agent KH560;

[0018] The mass ratio of the silane coupling agent to hexagonal boron nitride is (0.005-0.02):1.

[0019] Preferably, the diluent is n-butyl glycidyl ether; and / or,

[0020] The toughening agent is a DBP epoxy inactive toughening agent.

[0021] The second aspect of the present invention is to provide a method for preparing the low-viscosity, high-thermal-conductivity epoxy resin cast insulating material according to the first aspect of the present invention, the method comprising the following steps:

[0022] Step 1, adding a thermal conductive filler and a diluent to a base resin and then dispersing the mixture by ultrasonic, and then adding a toughening agent and mixing the mixture evenly to obtain a composite epoxy resin solution;

[0023] Step 2: vacuum degas the composite epoxy resin solution, and then heat and cure it under vacuum conditions to obtain a low-viscosity, high-thermal-conductivity epoxy resin casting insulating material.

[0024] In step 1,

[0025] Preferably, after adding the thermal conductive filler and the diluent to the base resin, ultrasonic dispersion is carried out at 25 to 40° C. for 5 to 15 minutes, and then the toughening agent is added and mixed evenly to obtain a composite epoxy resin solution.

[0026] In step 2,

[0027] Preferably, the composite epoxy resin solution is vacuum degassed for 0.5 to 2 hours, and then heated to 80 to 95° C. and cured for 1 to 3 hours under vacuum conditions, and then heated to 140 to 160° C. and cured for 5 to 7 hours to obtain a low-viscosity, high-thermal-conductivity epoxy resin casting insulating material.

[0028] The beneficial effects of the present invention are:

[0029] (1) The low viscosity, high thermal conductivity epoxy resin cast insulating material of the present invention is prepared from a base resin, a thermal conductive filler, a diluent and a toughening agent. By optimizing the raw material ratio and the preparation process, not only the original excellent electrical insulation performance and mechanical strength of the epoxy resin matrix are maintained, but also the thermal conductivity and processing performance of the material are significantly improved. The epoxy resin cast insulating material of the present invention has the advantages of low viscosity, high thermal conductivity, excellent electrical insulation performance and good mechanical strength, which meets the strict requirements of offshore wind power dry-type transformers for insulating materials and has broad application prospects and promotion value.

[0030] (2) The present invention constructs an effective thermal conductive network by adding surface-modified h-BN filler with high thermal conductivity, thereby significantly improving the heat dissipation efficiency of epoxy resin cast insulation materials.

[0031] The present invention improves the flexibility and impact resistance of the epoxy resin casting insulation material by introducing a toughening agent, so that the epoxy resin casting insulation material can still remain stable under a complex stress environment.

[0032] (3) The present invention significantly reduces the viscosity of the epoxy resin mixture by introducing a diluent and optimizing the stirring process parameters, thereby improving the processing performance and production efficiency of the epoxy resin cast insulation material. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The process flow chart of surface modification of hexagonal boron nitride by using silane coupling agent is shown;

[0034] Figure 2 The SEM image of the surface-modified hexagonal boron nitride prepared in Example 1 is shown;

[0035] Figure 3 The SEM photograph of the epoxy resin casting insulating material prepared in Example 1 is shown;

[0036] Figure 4 An AFM photograph of the epoxy resin cast insulating material prepared in Example 1 is shown;

[0037] Figure 5 A finished product photo of the epoxy resin cast insulation material prepared in Example 1 is shown;

[0038] Figure 6 The viscosity test results of the epoxy resin casting insulating material prepared in Example 1 are shown;

[0039] Figure 7 The thermal conductivity test results of the epoxy resin cast insulation material prepared in Example 1 are shown. DETAILED DESCRIPTION

[0040] The present invention will be described in detail below, and the characteristics and advantages of the present invention will become clearer and more distinct with the description.

[0041] The first aspect of the present invention is to provide a low-viscosity, high-thermal-conductivity epoxy resin cast insulating material, wherein the low-viscosity, high-thermal-conductivity epoxy resin cast insulating material is made of a base resin, a thermally conductive filler, a diluent and a toughening agent.

[0042] The mass ratio of the base resin, the thermal conductive filler, the diluent and the toughening agent is 1: (0.3-0.4): (0.2-0.4): (0.01-0.03).

[0043] Preferably, the mass ratio of the base resin, the thermal conductive filler, the diluent and the toughening agent is 1:0.35:0.3:0.02.

[0044] According to the present invention, the base resin comprises epoxy resin, a curing agent and an accelerator.

[0045] The mass ratio of the epoxy resin, the curing agent and the accelerator is 60:(37-42):(0.3-0.7).

[0046] Preferably, the mass ratio of the epoxy resin, the curing agent and the accelerator is 60:39.5:0.5.

[0047] According to the present invention, the epoxy resin is preferably bisphenol A epoxy resin E51, which has good electrical insulation performance and mechanical strength.

[0048] The curing agent is preferably methyltetrahydrophthalic anhydride (MTHPA), which reacts with epoxy resin E51 to form a three-dimensional network structure, which can enhance the heat resistance and structural stability of the material. MTHPA curing agent not only has excellent thermal conductivity and dielectric properties, but also has a long service life and low irritation, and is suitable for electrical insulation materials.

[0049] The accelerator is preferably DMP-30, which can accelerate the curing reaction of epoxy resin and curing agent and improve production efficiency.

[0050] In the present invention, the thermal conductive filler is preferably surface-modified hexagonal boron nitride (h-BN), and the particle size of the thermal conductive filler is 5 to 10 μm. The surface-modified hexagonal boron nitride is prepared by surface-modifying hexagonal boron nitride with a silane coupling agent.

[0051] The silane coupling agent is preferably silane coupling agent KH560.

[0052] The mass ratio of the silane coupling agent to hexagonal boron nitride is (0.005-0.02):1. Preferably, the mass ratio of the silane coupling agent to hexagonal boron nitride is 0.01:1.

[0053] h-BN has extremely high thermal conductivity. After surface modification with silane coupling agent KH560, hexagonal boron nitride can be more evenly dispersed in the epoxy resin matrix to form an effective thermal conductive network, which can significantly improve the thermal conductivity of the material.

[0054] In the present invention, the diluent is preferably n-butyl glycidyl ether (501), which can adjust the viscosity of the epoxy resin mixture and improve the processing performance. By accurately controlling the amount of the diluent, the viscosity of the epoxy resin mixture can be significantly reduced while keeping other properties of the material unchanged.

[0055] The toughening agent is preferably a DBP epoxy inactive toughening agent. DBP not only has a toughening effect, but can also react with epoxy resin and curing agent to increase the proportion of flexible networks in the cross-linked structure, thereby improving the overall mechanical properties of the material, especially helping to improve the flexibility and impact resistance of the material.

[0056] The second aspect of the present invention is to provide a method for preparing the low-viscosity, high-thermal-conductivity epoxy resin cast insulating material according to the first aspect of the present invention, the method comprising the following steps:

[0057] Step 1, adding a thermal conductive filler and a diluent to a base resin and then dispersing the mixture by ultrasonic, and then adding a toughening agent and mixing the mixture evenly to obtain a composite epoxy resin solution;

[0058] Step 2: vacuum degas the composite epoxy resin solution, and then heat and cure it under vacuum conditions to obtain a low-viscosity, high-thermal-conductivity epoxy resin casting insulating material.

[0059] The above steps are described in detail below.

[0060] In step 1, the base resin is prepared by the following steps:

[0061] After adding curing agent to epoxy resin, mechanically stir for 5 to 15 minutes, then add accelerator and continue stirring for 5 to 15 minutes.

[0062] Preferably, the base resin is prepared by the following steps:

[0063] After adding the curing agent to the epoxy resin, stir mechanically for 10 minutes, then add the accelerator and continue stirring for 10 minutes.

[0064] The thermally conductive filler is prepared by the following steps:

[0065] The silane coupling agent is added to a mixed solution of ethanol and water, and then heated in a water bath and ultrasonically dispersed in sequence. The obtained mixed solution is added dropwise to hexagonal boron nitride, followed by mixing, and finally dried and ball-milled to obtain h-BN (i.e., thermally conductive filler) after surface modification.

[0066] Preferably, the thermally conductive filler is prepared by the following steps:

[0067] The silane coupling agent is added to a mixed solution of ethanol and water in a volume ratio of (8-10):1, and then heated in a water bath at 40-50°C, followed by ultrasonic dispersion for 5-15 minutes, and the obtained mixed solution is added dropwise to hexagonal boron nitride, followed by mixing for 5-15 minutes, and then dried at 70-90°C for 1-3 hours after mixing, and finally ball-milled to obtain a thermal conductive filler.

[0068] More preferably, the thermally conductive filler is prepared by the following steps:

[0069] The silane coupling agent was added to a mixed solution of ethanol and water in a volume ratio of 9:1, and then heated in a water bath at 40°C, followed by ultrasonic dispersion for 10 minutes, and the obtained mixed solution was added dropwise to hexagonal boron nitride, followed by mixing for 10 minutes, and then dried at 80°C for 2 hours after mixing, and finally ball milled to obtain a thermal conductive filler.

[0070] After adding thermal conductive filler and diluent to the base resin, ultrasonic dispersion is performed at 25-40° C. for 5-15 minutes, and then a toughening agent is added and mixed evenly to obtain a composite epoxy resin solution.

[0071] Preferably, after adding a thermal conductive filler and a diluent to the base resin, ultrasonic dispersion is performed at 30° C. for 10 minutes, and then a toughening agent is added and mixed evenly to obtain a composite epoxy resin solution.

[0072] In step 2, the composite epoxy resin solution is vacuum degassed for 0.5 to 2 hours, and then heated to 80 to 95° C. and cured for 1 to 3 hours under vacuum conditions, and then heated to 140 to 160° C. and cured for 5 to 7 hours to obtain a low-viscosity, high-thermal-conductivity epoxy resin casting insulating material.

[0073] Preferably, the composite epoxy resin solution is vacuum degassed for 1 hour, and then heated to 90° C. and cured for 2 hours under vacuum conditions, and then heated to 150° C. and cured for 6 hours to obtain a low-viscosity, high-thermal-conductivity epoxy resin casting insulating material.

[0074] Example

[0075] The present invention is further described below by specific examples, which are limited to illustrating the present invention and are not intended to limit the scope of the present invention.

[0076] Example 1

[0077] Surface modification of h-BN filler: 10g of silane coupling agent KH560 is added to a mixed solution of 30ml of ethanol and water (the volume ratio of ethanol and water is 9:1). The amount of KH560 added is 1wt% of the mass of h-BN. Under heating in a water bath at 40°C, the mixture is ultrasonically dispersed in an ultrasonic disperser for 10 minutes. The mixed solution after ultrasonic dispersion is added dropwise to h-BN. The h-BN dripped with the KH560 mixed solution is mixed at high speed for 10 minutes in a high-speed mixer. After high-speed mixing, it is taken out and dried in an oven at 80°C for 2 hours. Finally, h-BN surface-modified with KH560 can be obtained by ball milling. Modification process: Figure 1 The SEM images of the modified samples are shown in Figure 2 As shown. Figure 2 It can be seen that the modified boron nitride is stacked in layers.

[0078] Preparation formula of pure epoxy resin: Mix epoxy resin E51 heated to an appropriate temperature with MTHPA curing agent and DMP-30 accelerator in a ratio of 60%:39.5%:0.5% to form a basic resin system.

[0079] Preparation formula of composite epoxy resin material: On the basis of pure epoxy resin, add 35% h-BN, 2% DBP (epoxy inactive toughening agent), and 30% 501 (diluent n-butyl glycidyl ether) to the total mass of the mixed epoxy resin.

[0080] Preparation process of composite epoxy resin: Add all the MTHPA curing agent to the epoxy resin E51 according to the formula, and stir mechanically at the same time. After stirring for 10 minutes until it is completely mixed, continue to add the DMP-30 accelerator and stir for 10 minutes. According to the preparation formula of the composite epoxy resin material, continue to add the diluent n-butyl glycidyl ether (501) to reduce the viscosity of the system. After adding h-BN (hexagonal boron nitride), ultrasonically disperse it at 30°C for 10 minutes, and then add the dbp epoxy inactive toughening agent and mix evenly. After vacuum degassing the composite epoxy resin solution for 1 hour, dry the stainless steel mold at 50°C, and spray 820-NC release agent on the stainless steel mold. Pour the composite epoxy resin solution, evacuate and cure it in an oven. First cure it at 90°C for 2 hours, and then cure it at 150°C for 6 hours to obtain a composite epoxy resin (i.e., a low-viscosity, high-thermal-conductivity epoxy resin casting insulating material). The SEM, AFM and finished product samples of the composite epoxy resin are shown as follows. Figure 3-Figure 5 As shown. Figure 3 It can be seen that the prepared epoxy resin cast insulation material has a high density and basically no pores. Figure 4 It can be seen that the epoxy resin casting insulation material prepared by the present invention has high contents of B, C and N, among which C has the highest content, and also contains a small amount of O and Si. Figure 5It can be seen that the epoxy resin cast insulation material prepared by the present invention has a smooth surface and no pores.

[0081] Example 2

[0082] Surface modification of h-BN filler: 10g of silane coupling agent KH560 was added to 30ml of a mixed solution of ethanol and water (the volume ratio of ethanol to water was 9:1), the amount of KH560 added was 0.5wt% of the mass of h-BN, and the mixture was ultrasonically dispersed in an ultrasonic disperser for 5 minutes under heating in a water bath at 50°C. The mixed solution after ultrasonic dispersion was dropped into h-BN, and the h-BN dropped with the KH560 mixed solution was mixed at high speed for 5 minutes in a high-speed mixer. After high-speed mixing, it was taken out and dried in an oven at 70°C for 3 hours. Finally, h-BN surface-modified with KH560 was obtained by ball milling.

[0083] Preparation formula of pure epoxy resin: Mix epoxy resin E51 heated to an appropriate temperature with MTHPA curing agent and DMP-30 accelerator in a ratio of 60%:37%:0.3% to form a basic resin system.

[0084] Preparation formula of composite epoxy resin material: On the basis of pure epoxy resin, add 30% h-BN, 1% DBP (epoxy inactive toughening agent), and 20% 501 (diluent n-butyl glycidyl ether) to the total mass of the mixed epoxy resin.

[0085] Preparation process of composite epoxy resin: Add all MTHPA curing agent to epoxy resin E51 according to the formula, stir mechanically at the same time, stir for 5 minutes until completely mixed, continue to add DMP-30 accelerator and stir for 5 minutes, continue to add diluent n-butyl glycidyl ether (501) according to the preparation formula of composite epoxy resin material to reduce the viscosity of the system, add h-BN (hexagonal boron nitride) and ultrasonically disperse at 25°C for 15 minutes, then add dbp epoxy inactive toughening agent and mix evenly. After vacuum degassing the composite epoxy resin solution for 0.5h, dry the stainless steel mold at 50°C, and spray 820-NC release agent on the stainless steel mold. Cast the composite epoxy resin solution, evacuate and cure in an oven. First cure at 80°C for 3 hours, then cure at 140°C for 7 hours to obtain a composite epoxy resin (i.e., low viscosity, high thermal conductivity epoxy resin casting insulation material).

[0086] Example 3

[0087] Surface modification of h-BN filler: 10g of silane coupling agent KH560 was added to 30ml of a mixed solution of ethanol and water (the volume ratio of ethanol to water was 9:1), the amount of KH560 added was 2wt% of the mass of h-BN, the mixture was ultrasonically dispersed in an ultrasonic disperser for 15 minutes under heating in a water bath at 45°C, the mixed solution after ultrasonic dispersion was dropped into h-BN, the h-BN dropped with the KH560 mixed solution was mixed at high speed in a high-speed mixer for 15 minutes, taken out after high-speed mixing and dried in an oven at 90°C for 1 hour, and finally the h-BN surface-modified with KH560 was obtained by ball milling.

[0088] Preparation formula of pure epoxy resin: Mix epoxy resin E51 heated to an appropriate temperature with MTHPA curing agent and DMP-30 accelerator in a ratio of 60%:42%:0.7% to form a basic resin system.

[0089] Preparation formula of composite epoxy resin material: On the basis of pure epoxy resin, add 40% h-BN, 3% DBP (epoxy inactive toughening agent), and 40% 501 (diluent n-butyl glycidyl ether) to the total mass of the mixed epoxy resin.

[0090] Preparation process of composite epoxy resin: Add all MTHPA curing agent to epoxy resin E51 according to the formula, and stir mechanically at the same time. After stirring for 15 minutes until it is completely mixed, continue to add DMP-30 accelerator and stir for 15 minutes. According to the preparation formula of composite epoxy resin material, continue to add diluent n-butyl glycidyl ether (501) to reduce the viscosity of the system, add h-BN (hexagonal boron nitride) and ultrasonically disperse at 40°C for 5 minutes, and then add dbp epoxy inactive toughening agent and mix evenly. After vacuum degassing the composite epoxy resin solution for 2 hours, dry the stainless steel mold at 50°C, and spray 820-NC release agent on the stainless steel mold. Cast the composite epoxy resin solution, evacuate and cure in an oven. First cure at 95°C for 1 hour, and then cure at 160°C for 5 hours to obtain a composite epoxy resin (i.e., low viscosity, high thermal conductivity epoxy resin casting insulation material).

[0091] Comparative Example

[0092] Comparative Example 1

[0093] Preparation formula of pure epoxy resin: Mix epoxy resin E51 heated to an appropriate temperature with MTHPA curing agent and DMP-30 accelerator in a ratio of 60%:39.5%:0.5% to form a basic resin system.

[0094] Preparation process of pure epoxy resin: Add all the MTHPA curing agent to the epoxy resin E51 according to the formula, and stir mechanically at the same time. Stir for 10 minutes to mix thoroughly and then add the DMP-30 accelerator and stir for 10 minutes. After vacuum degassing for 1 hour, dry the stainless steel mold at 50°C and spray 820-NC release agent. Pour the mixed epoxy resin solution into the stainless steel mold, evacuate and cure in an oven. First cure at 90°C for 2 hours, then cure at 150°C for 4 hours.

[0095] Experimental example

[0096] Experimental Example 1 Viscosity Test

[0097] The viscosity of the composite epoxy resin solution prepared in Example 1 at different temperatures was tested using a rotational viscometer. The measurement results are shown in Figure 6 shown.

[0098] from Figure 6 It can be seen that as the temperature increases, the viscosity of the composite epoxy resin solution continues to decrease, and its viscosity at 40°C is 3500 mPa·s, and when the temperature rises to 80°C, its viscosity is 950 mPa·s. The test results are lower than those of the existing low-viscosity epoxy resin formula.

[0099] Experimental Example 2 Thermal Conductivity Test

[0100] The thermal conductivity values ​​of the materials obtained in Example 1 and Comparative Example 1 were tested using a laser thermal conductivity meter. The test results are shown in Figure 7 shown.

[0101] from Figure 7 It can be seen that the thermal conductivity of the modified epoxy resin (composite epoxy resin) prepared in Example 1 at 25°C, 50°C and 80°C is increased by 805.91%, 793.55% and 693.36% compared with the pure epoxy resin in Comparative Example 1. This indicates that the epoxy resin cast insulation material of the present invention has excellent thermal conductivity at both room temperature and high temperature.

[0102] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A low viscosity, high thermal conductivity epoxy resin casting insulating material, characterized in that: The low-viscosity, high-thermal-conductivity epoxy resin casting insulation material is made of a base resin, a thermally conductive filler, a diluent and a toughening agent; The mass ratio of the base resin, the thermal conductive filler, the diluent and the toughening agent is 1: (0.3-0.4): (0.2-0.4): (0.01-0.03).

2. The low-viscosity, high-thermal-conductivity epoxy resin casting insulating material according to claim 1, characterized in that: The mass ratio of the base resin, the thermal conductive filler, the diluent and the toughening agent is 1:0.35:0.3:0.

02.

3. The low viscosity, high thermal conductivity epoxy resin casting insulating material according to claim 1, characterized in that: The base resin includes epoxy resin, curing agent and accelerator; The mass ratio of the epoxy resin, the curing agent and the accelerator is 60:(37-42):(0.3-0.7).

4. The low-viscosity, high-thermal-conductivity epoxy resin casting insulating material according to claim 3, characterized in that: The epoxy resin is bisphenol A epoxy resin E51; and / or, The curing agent is methyltetrahydrophthalic anhydride; and / or, The accelerator is DMP-30.

5. The low viscosity, high thermal conductivity epoxy resin casting insulating material according to claim 1, characterized in that: The thermal conductive filler is surface-modified hexagonal boron nitride, and the particle size of the thermal conductive filler is 5 to 10 μm.

6. The low-viscosity, high-thermal-conductivity epoxy resin casting insulating material according to claim 5, characterized in that: The surface-modified hexagonal boron nitride is prepared by surface-modifying the hexagonal boron nitride with a silane coupling agent; The silane coupling agent is silane coupling agent KH560; The mass ratio of the silane coupling agent to hexagonal boron nitride is (0.005-0.02):

1.

7. The low-viscosity, high-thermal-conductivity epoxy resin casting insulating material according to claim 1, characterized in that: The diluent is n-butyl glycidyl ether; and / or, The toughening agent is a DBP epoxy inactive toughening agent.

8. A method for preparing the low-viscosity, high-thermal-conductivity epoxy resin casting insulating material according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: Step 1, adding a thermal conductive filler and a diluent to a base resin and then dispersing the mixture by ultrasonic, and then adding a toughening agent and mixing the mixture evenly to obtain a composite epoxy resin solution; Step 2: vacuum degas the composite epoxy resin solution, and then heat and cure it under vacuum conditions to obtain a low-viscosity, high-thermal-conductivity epoxy resin casting insulating material.

9. The method according to claim 8, characterized in that In step 1, After adding thermal conductive filler and diluent to the base resin, ultrasonic dispersion is performed at 25-40° C. for 5-15 minutes, and then a toughening agent is added and mixed evenly to obtain a composite epoxy resin solution.

10. The method according to claim 8, characterized in that In step 2, The composite epoxy resin solution is vacuum degassed for 0.5 to 2 hours, and then heated to 80 to 95°C under vacuum conditions for curing for 1 to 3 hours, and then heated to 140 to 160°C for curing for 5 to 7 hours to obtain a low-viscosity, high-thermal-conductivity epoxy resin casting insulating material.

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