Filled modified resin-based heat-conducting insulating material and preparation method thereof

Abstract

The preparation method comprises the following steps: carrying out surface treatment on barium titanate by adopting a silane coupling agent to prepare modified barium titanate, adding an aqueous dispersion of a nano heat-conducting nitride into a binder, and carrying out uniform stirring, so as to obtain the filled modified resin-based heat-conducting insulating material. The preparation method comprises the following steps: adding modified barium titanate, spray-drying to prepare a coated heat-conducting filler with the surface of the modified barium titanate coated with nano heat-conducting nitride, adding a flexibilizer into epoxy resin to prepare modified epoxy resin, and then adding the coated heat-conducting filler, a diluent and a curing agent to prepare a modified epoxy resin suspension; the modified epoxy resin suspension is subjected to vacuum defoaming, pre-curing, heating curing and demolding to obtain the heat-conducting insulating material, the insulating property and toughness of the material can be considered, the heat-conducting property of the material is further improved, the filling amount is reduced, and the heat-conducting insulating material is convenient to prepare, suitable for manufacturing a bus duct insulating partition plate and beneficial to improving power transmission and distribution safety and stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermally conductive insulating materials, and in particular relates to a filled modified resin-based thermally conductive insulating material and a preparation method thereof. Background Art

[0002] As a commonly used functional material, thermally conductive insulating materials are widely used in electronic products, electrical equipment, power industry and other application fields. For example, dense busbars require busbar duct insulation partitions made of thermally conductive insulating materials to achieve insulation and joint assembly of adjacent copper bars. With the development of high-power and large-scale distribution circuit systems, the thermal conductivity of insulating materials needs to be further improved to reduce the temperature rise at the joints and improve the safety and stability of power transmission and distribution.

[0003] Insulating polymer materials have advantages over traditional ceramic electrical insulation materials in terms of light weight, corrosion resistance, ease of processing, and better dielectric properties. However, in order to obtain insulating thermally conductive materials with better insulation and toughness, higher thermal conductivity, and simple preparation methods, the following technical difficulties still exist:

[0004] Most polymers, such as epoxy resins, have relatively low thermal conductivity. In order to improve the thermal conductivity of insulating materials, inorganic oxide thermal conductive fillers such as aluminum oxide and zinc oxide are filled into the material matrix in the prior art. When the amount of thermal conductive filler is small, it is difficult for the thermal conductive filler to form a thermal conductive network chain in the system, the thermal resistance is large, and the improvement of the thermal conductivity of the material is limited. In order to form a thermal conductive channel, it is often necessary to increase the filling amount to more than 60%. However, increasing the amount of thermal conductive filler will not only bring cost pressure, but also worsen the fluidity of the matrix, making product processing more difficult, and will lead to reduced dielectric strength, insulation performance and toughness of the material, and poor impact resistance, which cannot meet the requirements of electrical appliance use. For example, when used as an insulating partition of a bus duct, it will easily cause assembly breakage or power distribution hazards. Summary of the Invention

[0005] The present invention aims to solve at least one of the above-mentioned technical problems to a certain extent. The present invention provides a filled modified resin-based thermally conductive insulating material and a preparation method thereof, which can achieve both the insulation performance and toughness of the material, further improve the thermal conductivity of the material, reduce the filling amount and facilitate preparation. It is suitable for manufacturing bus duct insulating partitions, which is beneficial to improving the safety and stability of power transmission and distribution.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A method for preparing a filled modified resin-based thermally conductive insulating material, the preparation method comprising the following steps:

[0008] S1. Dilute the silane coupling agent with ethanol, add barium titanate, mix evenly for surface treatment, and then filter and dry to obtain modified barium titanate;

[0009] S2. Add a binder to an aqueous dispersion of nano-thermal conductive nitrides, heat and stir until a colloidal liquid is obtained, add the modified barium titanate obtained in step S1 and stir until a viscous liquid is obtained, and spray-dry the viscous liquid to produce a coated thermal conductive filler having the surface of the modified barium titanate coated with nano-thermal conductive nitrides;

[0010] S3, adding a toughening agent to the epoxy resin, stirring evenly, and then heating and maintaining the temperature to prepare a modified epoxy resin, and then adding the coated thermally conductive filler, diluent, and curing agent obtained in step S2 to the improved epoxy resin, followed by ultrasonic dispersion to obtain a modified epoxy resin suspension;

[0011] S4. Pour the modified epoxy resin suspension obtained in step S3 into a mold for vacuum degassing, pre-curing, and then curing at a high temperature under vacuum conditions. After demolding, a thermally conductive insulating material is obtained.

[0012] In the above preparation method, the thermal conductivity of barium titanate is low, but it has a very high dielectric constant, density and pressure resistance. Modification with a silane coupling agent can improve the interfacial bonding strength between the core barium titanate and the nano-thermal conductive nitride, making the shell layer denser and the two phases well bonded. Then, an adhesive is further used to bond the core barium titanate and the shell nano-thermal conductive nitride together, which not only improves the bonding performance, increases the bonding strength and is not easy to fall off, but also makes it easier for the nano-thermal conductive nitrides to agglomerate to form a complete coating of the barium titanate.

[0013] The thermal conductivity of thermally conductive nitride is significantly higher than that of inorganic oxide thermally conductive fillers. At the same time, the particle size of modified barium titanate is larger. The use of thermally conductive nitride with nano-sized particles can make nano-thermal conductive nitride as shell particles, increase the density of the coating layer structure, and achieve uniform mixing at the particle level. On the one hand, by coating the surface of modified barium titanate with thermally conductive nitride, the high dielectric constant and pressure resistance of barium titanate can be utilized to reduce the loss of dielectric performance and make the material have high insulation performance. On the other hand, the surface roughness of the coated thermally conductive filler is greater, which makes the surface of the coated thermally conductive filler The surface is more easily infiltrated by the modified resin matrix, which improves the interface bonding strength and dispersibility with the resin-based material. The thermal conductive nitride can be evenly dispersed to avoid agglomeration, reduce void defects, and increase the contact between the thermal conductive nitrides, thereby increasing the construction of the thermal conductive network at a lower filling amount of the coated thermal conductive filler, which can reduce the interface thermal resistance, make full use of the high thermal conductivity characteristics of the thermal conductive nitride, effectively enhance heat transfer, improve the thermal conductivity of the material, and reduce the material cost pressure with a low filling amount, avoid excessive filling of the thermal conductive nitride and deterioration of the toughness of the material, and further reduce the difficulty of ultrasonic dispersion and curing.

[0014] Epoxy resin has better toughness than phenolic resin, and also has high strength, high hardness and high heat resistance, good bonding properties and excellent processing properties. Through toughening modification and the addition of curing agent, the resin can be cross-linked with the curing agent to obtain a three-dimensional network structure, thereby providing a good mechanical property, electrical property and chemical stability foundation, which is beneficial to reduce dimensional shrinkage and compensate for the adverse effect of adding coated thermal conductive fillers on material toughness.

[0015] Selecting a suitable silane coupling agent can further improve the mechanical strength, insulation electrical properties and bonding properties of the product. In a preferred embodiment, the silane coupling agent is one or more of silane coupling agent KH-550, silane coupling agent KH-560, and silane coupling agent KH-570.

[0016] Excessive use of the silane coupling agent may cause thermal conductivity problems. In a preferred embodiment, the mass of the silane coupling agent is 3% to 5% of the mass of the barium titanate.

[0017] Selecting a suitable binder can further improve the bonding strength between the thermally conductive nitride and the modified barium titanate. In a preferred embodiment, the binder is one or both of polyvinyl alcohol and vinyl acetate.

[0018] Too much binder will cause the viscosity of the viscous liquid to be too high, affecting the spray drying molding performance. In a preferred embodiment, the mass of the binder is 5% to 8% of the mass of the thermal conductive nitride.

[0019] Selecting a suitable temperature can promote the dispersion of the binder. In a preferred embodiment, in step S2, the temperature is raised to 65-85° C. and stirred until the mixture becomes a colloidal liquid.

[0020] Selecting appropriate spray drying parameters can improve production efficiency and coating performance. In a preferred embodiment, the spray drying in step S2 adopts a centrifugal spray dryer, controls the hot air inlet temperature to 165-190°C, the outlet temperature to 75-85°C, and the atomization pressure to 0.15-0.3MPa.

[0021] The selection of suitable nano-thermal conductive nitrides can fully consider the thermal conductivity and cost of the material. In a preferred embodiment, the nano-thermal conductive nitrides are one or more of nano-aluminum nitride, nano-boron nitride, and nano-silicon nitride. Nano-aluminum nitride is a covalently bonded inorganic compound with a hexagonal wurtzite structure. It has good thermal conductivity, and its thermal conductivity is more than 5 times that of aluminum oxide. It also has a low thermal expansion coefficient and high mechanical properties. Nano-boron nitride has good thermal conductivity, high resistivity, low dielectric constant and high temperature resistance. Nano-silicon nitride has high thermal conductivity, low thermal expansion coefficient and low permittivity.

[0022] In a preferred embodiment, the mass of the nano thermally conductive nitride is 12% to 19% of the mass of the modified barium titanate, which can further improve the coating density.

[0023] In a preferred embodiment, the toughening agent is one or both of toughening agent WD-508 and toughening agent WD-204. Toughening agent WD-508 can improve the crack resistance and thermal shock resistance of epoxy resin, and the electrical properties remain basically unchanged. Toughening agent WD-204 has a good toughening effect on epoxy resin and can improve the comprehensive mechanical properties and bonding properties of the cured product.

[0024] Selecting an appropriate amount of toughening agent can improve the toughness of the material and reduce the difficulty of curing. In a preferred embodiment, the mass of the toughening agent is 4% to 7% of the mass of the epoxy resin.

[0025] Selecting appropriate parameters can promote toughening modification of epoxy resin. In a preferred embodiment, step S3 is to prepare modified epoxy resin by heating to 120-145° C. and keeping the temperature for 2-3 hours.

[0026] In a preferred embodiment, the mass of the coated thermally conductive filler is 15% to 25% of the mass of the modified epoxy resin, which can further improve the thermal conductivity of the material at a lower filling level, reduce the impact on material toughness and the difficulty of preparation.

[0027] In a preferred embodiment, the diluent is one or both of isooctyl acetate and propylene glycol methyl ether acetate, which can adjust the viscosity of the modified epoxy resin suspension and facilitate material preparation.

[0028] In a preferred embodiment, the mass of the diluent is 10% to 15% of the mass of the modified epoxy resin.

[0029] In a preferred embodiment, the curing agent is one or both of methyltetrahydrophthalic anhydride and isophorone diamine. Methyltetrahydrophthalic anhydride has the characteristics of fast curing speed, high strength, and strong adhesion; isophorone diamine can improve the flexural strength and chemical resistance of epoxy resin.

[0030] In a preferred embodiment, the mass of the curing agent is 1% to 3% of the mass of the modified epoxy resin.

[0031] Selecting appropriate pre-curing and curing processing parameters can further reduce the risk of material cracking, improve the material forming performance, and shorten the preparation time. In a preferred embodiment, step S4 adopts pre-curing at 40-50°C for 20-30 minutes, and after pre-curing, the temperature is raised to 165-180°C for curing for 2-4 hours.

[0032] A filled modified resin-based thermally conductive insulating material is prepared by any of the above methods for preparing a filled modified resin-based thermally conductive insulating material.

[0033] The use of the above-mentioned filled modified resin-based thermally conductive insulating material includes being used for manufacturing bus duct insulating partitions.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention modifies barium titanate with a silane coupling agent to improve its surface properties, and then prepares the modified barium titanate surface coated with nano-thermal conductive nitride under a binder and spray drying to form a coated thermal conductive filler with the nano-thermal conductive nitride coated on the surface. The high dielectric constant and pressure resistance of barium titanate can be utilized to reduce dielectric property loss, while improving the interface bonding force and dispersibility between the coated thermal conductive filler and the resin-based material, increasing the construction of the thermal conductive network, reducing the filling amount of the coated thermal conductive filler, and reducing material cost. At the same time, the high thermal conductivity characteristics of the thermal conductive nitride are fully utilized to enhance heat transfer, improve the thermal conductivity of the material, and reduce the difficulty of preparation. The material is further toughened and modified with epoxy resin and cross-linked with a curing agent to obtain a three-dimensional network structure, thereby obtaining a filled modified resin-based thermal conductive insulation material. The material can achieve both insulation performance and toughness, further improve the thermal conductivity of the material, reduce the filling amount, and facilitate preparation. The material is suitable for manufacturing bus duct insulation partitions, and is conducive to improving power transmission and distribution safety and stability. DETAILED DESCRIPTION

[0036] The embodiments of the present invention are described in detail below, which are intended to explain the present invention but are not to be construed as limiting the present invention.

[0037] The sources of reagents used in the following examples and comparative examples include:

[0038] Barium titanate (particle size of 10-20 μm) was purchased from Henan Daqi Chemical Products Co., Ltd.; silane coupling agent KH-550 (γ-aminopropyltriethoxysilane), silane coupling agent KH-560 (γ-glycidyloxypropyltrimethoxysilane), and silane coupling agent KH-570 (γ-methacryloxypropyltrimethoxysilane) were purchased from Henan Shengkun Chemical Products Co., Ltd.; polyvinyl alcohol (PVA model 1799) was purchased from Guangzhou Zhonggao Chemical Co., Ltd.; vinyl acetate (EVA model 680) was purchased from Dongguan Gaodong Plastic Co., Ltd.; nano-aluminum nitride, nano- Boron nitride and nano-silicon nitride with an average particle size of 50 nm were purchased from Shanghai Chaowei Nano Technology Co., Ltd.; epoxy resin (E51) was purchased from Langfang Senqiang Environmental Protection Technology Co., Ltd., toughening agent WD-508 and toughening agent WD-204 were purchased from Guangzhou Good New Material Technology Co., Ltd.; isooctyl acetate was purchased from Shandong Jingtai Chemical Co., Ltd.; propylene glycol methyl ether acetate (PMA) was purchased from Shandong Jinen New Materials Co., Ltd.; methyltetrahydrophthalic anhydride (MI) was purchased from Jiaxing Nanyang Wanshixing Chemical Co., Ltd.; and isophorone diamine (IPDA) was purchased from Changzhou Zidong Lianhua Import and Export Co., Ltd.

[0039] In the following examples and comparative examples, the flexural strength of the insulating material was tested according to ASTM D790, the fracture toughness was tested according to ASTM D638, the thermal conductivity was tested according to ASTM D5470, and the volume resistivity was tested according to ASTM D257.

[0040] Example 1:

[0041] A preferred embodiment of the method for preparing the filled modified resin-based thermally conductive insulating material of the present invention comprises the following steps:

[0042] S1. Dilute the silane coupling agent with ethanol, add barium titanate, mix evenly for surface treatment, and then filter and dry to obtain modified barium titanate;

[0043] The silane coupling agent is silane coupling agent KH-550, and the mass of the silane coupling agent is 3% of the mass of barium titanate.

[0044] S2. Add a binder to an aqueous dispersion of nano-thermal conductive nitrides, heat to 85° C., and stir until a colloidal liquid forms. Then, add the modified barium titanate obtained in step S1 and stir until a viscous liquid forms. The viscous liquid is spray-dried in a centrifugal spray dryer, with the hot air inlet temperature controlled at 190° C., the outlet temperature at 85° C., and the atomization pressure at 0.3 MPa, to prepare a coated thermally conductive filler having the surface of the modified barium titanate coated with nano-thermal conductive nitrides.

[0045] The nano thermally conductive nitride is composed of nano aluminum nitride and nano silicon nitride in a mass ratio of 1:1, and the mass of the nano thermally conductive nitride is 19% of the mass of the modified barium titanate; the binder is vinyl acetate, and the mass of the binder is 8% of the mass of the thermally conductive nitride.

[0046] S3, adding a toughening agent to the epoxy resin, stirring evenly, and then heating and maintaining the temperature to prepare a modified epoxy resin, and then adding the coated thermally conductive filler, diluent, and curing agent obtained in step S2 to the improved epoxy resin, followed by ultrasonic dispersion to obtain a modified epoxy resin suspension;

[0047] The toughening agent is composed of toughening agent WD-508 and toughening agent WD-204 in a mass ratio of 1:1, the mass of the toughening agent is 5% of the mass of the epoxy resin, and the modified epoxy resin is prepared by heating to 130° C. and keeping the temperature for 2.5 hours;

[0048] The mass of the coated thermal conductive filler is 17% of the mass of the modified epoxy resin; the diluent is propylene glycol methyl ether acetate, and the mass of the diluent is 15% of the mass of the modified epoxy resin; the curing agent is isophorone diamine, and the mass of the curing agent is 3% of the mass of the modified epoxy resin.

[0049] S4. Pour the modified epoxy resin suspension obtained in step S3 into a mold for vacuum degassing, then pre-curing at 40° C. for 30 minutes, then heating to 180° C. for curing for 3 hours under vacuum conditions, and then demolding to obtain a thermally conductive insulating material.

[0050] The effects of different fillers and material properties were investigated: Steps S1 and S2 were removed, and in step S3, the coated thermally conductive filler was replaced with barium titanate, or a nano-thermal conductive nitride composed of nano-aluminum nitride and nano-silicon nitride in a mass ratio of 1:1 was used to manufacture a thermally conductive insulating material. As a comparative example, the flexural strength, fracture toughness, thermal conductivity, and volume resistivity of the thermally conductive insulating materials of Example 1 and the comparative example were measured. The results are shown in Table 1 below:

[0051] Table 1. Performance results of thermally conductive insulation materials with different fillers

[0052]

[0053] From the comparison results of Example 1 with Comparative Examples 1 and 2, it can be seen that compared with the addition of barium titanate or nano-thermal conductive nitride alone, the thermal resistance is larger, the improvement of the thermal conductivity of the material is limited, or it may lead to a decrease in the dielectric strength, insulation performance and toughness of the material, and deteriorate the impact resistance, which cannot meet the requirements of electrical use. The present invention uses a coated thermal conductive filler with a modified barium titanate surface coated with nano-thermal conductive nitride, which can achieve a balance between the insulation performance and toughness of the material, fully utilize the high thermal conductivity characteristics of the thermal conductive nitride, effectively enhance heat transfer, and improve the thermal conductivity of the material.

[0054] Example 2:

[0055] A preferred embodiment of the method for preparing the filled modified resin-based thermally conductive insulating material of the present invention comprises the following steps:

[0056] S1. Dilute the silane coupling agent with ethanol, add barium titanate, mix evenly for surface treatment, and then filter and dry to obtain modified barium titanate;

[0057] The silane coupling agent is silane coupling agent KH-560, and the mass of the silane coupling agent is 3.5% of the mass of barium titanate.

[0058] S2. Add a binder to an aqueous dispersion of nano-thermal conductive nitrides, heat to 70° C., and stir until a colloidal liquid forms. Then, add the modified barium titanate obtained in step S1 and stir until a viscous liquid forms. The viscous liquid is spray-dried in a centrifugal spray dryer, with the hot air inlet temperature controlled at 165° C., the outlet temperature at 75° C., and the atomization pressure at 0.2 MPa, to prepare a coated thermally conductive filler having the surface of the modified barium titanate coated with nano-thermal conductive nitrides.

[0059] The nano thermally conductive nitride is nano boron nitride, and the mass of the nano thermally conductive nitride is 15% of the mass of the modified barium titanate; the binder is polyvinyl alcohol, and the mass of the binder is 5% of the mass of the thermally conductive nitride.

[0060] S3, adding a toughening agent to the epoxy resin, stirring evenly, and then heating and maintaining the temperature to prepare a modified epoxy resin, and then adding the coated thermally conductive filler, diluent, and curing agent obtained in step S2 to the improved epoxy resin, followed by ultrasonic dispersion to obtain a modified epoxy resin suspension;

[0061] The toughening agent is WD-204, the mass of the toughening agent is 4% of the mass of the epoxy resin, and the modified epoxy resin is prepared by heating to 145° C. and keeping the temperature for 2 hours;

[0062] The mass of the coated thermal conductive filler is 25% of the mass of the modified epoxy resin; the diluent is composed of isooctyl acetate and propylene glycol methyl ether acetate in a mass ratio of 1:1, and the mass of the diluent is 13% of the mass of the modified epoxy resin; the curing agent is isophorone diamine, and the mass of the curing agent is 1% of the mass of the modified epoxy resin.

[0063] S4. Pour the modified epoxy resin suspension obtained in step S3 into a mold for vacuum degassing, then pre-curing at 45° C. for 25 minutes, then heating to 165° C. for curing for 3 hours under vacuum conditions, and then demolding to obtain a thermally conductive insulating material.

[0064] Investigating the influence of the quality of nano-thermal conductive nitride on material properties: In step S2, the quality of nano-thermal conductive nitride was replaced to produce a thermally conductive insulating material. As a comparative example, the bending strength, fracture toughness, thermal conductivity, and volume resistivity of the thermally conductive insulating material of Example 2 and the comparative example were measured. The results are shown in Table 2 below:

[0065] Table 2. Performance results of thermally conductive insulating materials with different amounts of nano-thermal conductive nitrides

[0066]

[0067] From the comparison results of Example 2 with Comparative Examples 3 and 4, it can be seen that controlling the mass of the nano-thermal conductive nitride can make the shell denser and the two phases well bonded, thereby avoiding the situation where the mass of the nano-thermal conductive nitride is too small, which makes it difficult to completely coat the modified barium titanate, resulting in loss of contact between the thermal conductive nitrides, increasing the interfacial thermal resistance and making it difficult to exert the high thermal conductivity characteristics of the thermal conductive nitride, and avoiding the situation where the mass of the nano-thermal conductive nitride is too large, resulting in loss of fracture toughness and increased difficulty in curing.

[0068] Example 3:

[0069] A preferred embodiment of the method for preparing the filled modified resin-based thermally conductive insulating material of the present invention comprises the following steps:

[0070] S1. Dilute the silane coupling agent with ethanol, add barium titanate, mix evenly for surface treatment, and then filter and dry to obtain modified barium titanate;

[0071] The silane coupling agent is silane coupling agent KH-570, and the mass of the silane coupling agent is 5% of the mass of barium titanate.

[0072] S2. Add a binder to an aqueous dispersion of nano-thermal conductive nitrides, heat to 65° C., and stir until a colloidal liquid forms. Then, add the modified barium titanate obtained in step S1 and stir until a viscous liquid forms. The viscous liquid is spray-dried in a centrifugal spray dryer, with the hot air inlet temperature controlled at 180° C., the outlet temperature at 80° C., and the atomization pressure at 0.15 MPa, to prepare a coated thermally conductive filler having the surface of the modified barium titanate coated with nano-thermal conductive nitrides.

[0073] The nano thermally conductive nitride is nano aluminum nitride, and the mass of the nano thermally conductive nitride is 17% of the mass of the modified barium titanate; the binder is vinyl acetate, and the mass of the binder is 3% of the mass of the thermally conductive nitride.

[0074] S3, adding a toughening agent to the epoxy resin, stirring evenly, and then heating and maintaining the temperature to prepare a modified epoxy resin, and then adding the coated thermally conductive filler, diluent, and curing agent obtained in step S2 to the improved epoxy resin, followed by ultrasonic dispersion to obtain a modified epoxy resin suspension;

[0075] The toughening agent is WD-508, the mass of the toughening agent is 7% of the mass of the epoxy resin, and the modified epoxy resin is prepared by heating to 125° C. and keeping the temperature for 2.5 hours;

[0076] The mass of the coated thermally conductive filler is 19% of the mass of the modified epoxy resin; the diluent is isooctyl acetate, and the mass of the diluent is 10% of the mass of the modified epoxy resin; the curing agent is composed of methyltetrahydrophthalic anhydride and isophoronediamine in a mass ratio of 1:2, and the mass of the curing agent is 2.5% of the mass of the modified epoxy resin.

[0077] S4. Pour the modified epoxy resin suspension obtained in step S3 into a mold for vacuum degassing, then pre-curing at 50° C. for 20 minutes, then heating to 170° C. for curing for 2 hours under vacuum conditions, and then demolding to obtain a thermally conductive insulating material.

[0078] Investigating the influence of the quality of the coated thermally conductive filler and material properties: In step S3, the quality of the coated thermally conductive filler was replaced to produce a thermally conductive insulating material. As a comparative example, the bending strength, fracture toughness, thermal conductivity, and volume resistivity of the thermally conductive insulating materials of Example 3 and the comparative example were measured. The results are shown in Table 3 below:

[0079] Table 3. Performance results of thermally conductive insulation materials with different coating thermal conductive filler qualities

[0080]

[0081] From the comparison results of Example 3 with Comparative Examples 5 and 6, it can be seen that the present invention can increase the construction of the thermal conductive network at a lower filling amount of the coated thermal conductive filler, reduce the interface thermal resistance, fully utilize the high thermal conductivity characteristics of the thermal conductive nitride, effectively enhance heat transfer, improve the thermal conductivity of the material, and avoid excessive filling of the thermal conductive nitride and deterioration of the toughness of the material.

[0082] Example 4:

[0083] A preferred embodiment of the method for preparing the filled modified resin-based thermally conductive insulating material of the present invention comprises the following steps:

[0084] S1. Dilute the silane coupling agent with ethanol, add barium titanate, mix evenly for surface treatment, and then filter and dry to obtain modified barium titanate;

[0085] The silane coupling agent is composed of silane coupling agent KH-560 and silane coupling agent KH-570 in a mass ratio of 1:1, and the mass of the silane coupling agent is 4% of the mass of barium titanate.

[0086] S2. Add a binder to an aqueous dispersion of nano-thermal conductive nitrides, heat to 75° C., and stir until a colloidal liquid forms. Then, add the modified barium titanate obtained in step S1 and stir until a viscous liquid forms. The viscous liquid is spray-dried in a centrifugal spray dryer, with the hot air inlet temperature controlled at 170° C., the outlet temperature at 80° C., and the atomization pressure at 0.25 MPa, to prepare a coated thermally conductive filler having the surface of the modified barium titanate coated with nano-thermal conductive nitrides.

[0087] The nano thermally conductive nitride is nano silicon nitride, and the mass of the nano thermally conductive nitride is 12% of the mass of the modified barium titanate; the binder is composed of polyvinyl alcohol and vinyl acetate in a mass ratio of 1:1, and the mass of the binder is 7% of the mass of the thermally conductive nitride.

[0088] S3, adding a toughening agent to the epoxy resin, stirring evenly, and then heating and maintaining the temperature to prepare a modified epoxy resin, and then adding the coated thermally conductive filler, diluent, and curing agent obtained in step S2 to the improved epoxy resin, followed by ultrasonic dispersion to obtain a modified epoxy resin suspension;

[0089] The toughening agent is WD-508, the mass of the toughening agent is 6% of the mass of the epoxy resin, and the modified epoxy resin is prepared by heating to 135° C. and keeping the temperature for 3 hours;

[0090] The mass of the coated thermal conductive filler is 22% of the mass of the modified epoxy resin; the diluent is isooctyl acetate, and the mass of the diluent is 11% of the mass of the modified epoxy resin; the curing agent is methyltetrahydrophthalic anhydride, and the mass of the curing agent is 2% of the mass of the modified epoxy resin.

[0091] S4. Pour the modified epoxy resin suspension obtained in step S3 into a mold for vacuum degassing, then pre-curing at 45° C. for 25 minutes, then heating to 165° C. for curing for 4 hours under vacuum conditions, and then demolding to obtain a thermally conductive insulating material.

[0092] Investigating the influence of curing agent quality on material properties: In step S3, the curing agent quality was changed to produce a thermally conductive insulating material. As a comparative example, the bending strength, fracture toughness, thermal conductivity, and volume resistivity of the thermally conductive insulating material of Example 4 and the comparative example were measured. The results are shown in Table 4 below:

[0093] Table 4. Performance results of thermally conductive insulation materials with different curing agent qualities

[0094]

[0095] From the comparison results of Example 4 with Comparative Examples 7 and 8, it can be seen that the present invention, through toughening modification, after adding a curing agent, the resin can be cross-linked with the curing agent to obtain a three-dimensional network structure, thereby providing a basis for good mechanical properties, electrical properties and chemical stability, which is beneficial to reducing dimensional shrinkage and compensating for the adverse effect of adding coated thermal conductive fillers on material toughness.

[0096] From the results of Examples 1 to 4, it can be seen that the thermally conductive insulating material of the present invention can achieve a bending strength greater than 245 MPa and a fracture toughness greater than or equal to 15.5 MPa / m 0.5 , thermal conductivity ≥ 154W / m·k, volume resistivity >10 13 Ω·cm, which can achieve both the insulation performance and toughness of the material, further improve the thermal conductivity of the material, reduce the filling amount and facilitate preparation. It is suitable for manufacturing bus duct insulation partitions, which is beneficial to improving the safety and stability of power transmission and distribution.

[0097] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a filled modified resin-based thermally conductive insulating material, characterized in that: The preparation method comprises the following steps: S1. Dilute the silane coupling agent with ethanol, add barium titanate, mix well, perform surface treatment, and then filter and dry to obtain modified barium titanate; S2. Add a binder to an aqueous dispersion of nano-thermal conductive nitrides, heat and stir until a colloidal liquid is obtained, add the modified barium titanate obtained in step S1 and stir until a viscous liquid is obtained, and spray-dry the viscous liquid to produce a coated thermal conductive filler having the surface of the modified barium titanate coated with nano-thermal conductive nitrides; S3, adding a toughening agent to the epoxy resin, stirring evenly, and then heating and maintaining the temperature to prepare a modified epoxy resin, and then adding the coated thermally conductive filler, diluent, and curing agent obtained in step S2 to the improved epoxy resin, followed by ultrasonic dispersion to obtain a modified epoxy resin suspension; S4. Pour the modified epoxy resin suspension obtained in step S3 into a mold for vacuum degassing, pre-curing, and then curing at a high temperature under vacuum conditions. After demolding, a thermally conductive insulating material is obtained.

2. The method for preparing a filled modified resin-based thermally conductive insulating material according to claim 1, wherein: The silane coupling agent is one or more of silane coupling agent KH-550, silane coupling agent KH-560, and silane coupling agent KH-570, and the mass of the silane coupling agent is 3% to 5% of the mass of barium titanate.

3. The method for preparing a filled modified resin-based thermally conductive insulating material according to claim 1, wherein: The binder is one or both of polyvinyl alcohol and vinyl acetate, and the mass of the binder is 5% to 8% of the mass of the thermally conductive nitride. In step S2, the temperature is raised to 65 to 85° C. and stirred until it becomes a colloidal liquid. The spray drying adopts a centrifugal spray dryer, and the hot air inlet temperature is controlled to be 165 to 190° C., the outlet temperature is 75 to 85° C., and the atomization pressure is 0.15 to 0.3 MPa.

4. The method for preparing a filled modified resin-based thermally conductive insulating material according to claim 1, wherein: The nano thermally conductive nitride is one or more of nano aluminum nitride, nano boron nitride and nano silicon nitride. The mass of the nano thermally conductive nitride is 12% to 19% of the mass of the modified barium titanate.

5. The method for preparing a filled modified resin-based thermally conductive insulating material according to claim 1, wherein: The toughening agent is one or both of toughening agent WD-508 and toughening agent WD-204, and the mass of the toughening agent is 4% to 7% of the mass of the epoxy resin. In step S3, the modified epoxy resin is prepared by heating to 120 to 145° C. and keeping the temperature for 2 to 3 hours.

6. The method for preparing a filled modified resin-based thermally conductive insulating material according to claim 1, wherein: The mass of the coated thermal conductive filler is 15% to 25% of the mass of the modified epoxy resin.

7. The method for preparing a filled modified resin-based thermally conductive insulating material according to claim 1, wherein: The diluent is one or both of isooctyl acetate and propylene glycol methyl ether acetate, and the mass of the diluent is 10% to 15% of the mass of the modified epoxy resin.

8. The method for preparing a filled modified resin-based thermally conductive insulating material according to claim 1, wherein: The curing agent is one or two of methyltetrahydrophthalic anhydride and isophorone diamine, and the mass of the curing agent is 1% to 3% of the mass of the modified epoxy resin.

9. The method for preparing a filled modified resin-based thermally conductive insulating material according to claim 1, wherein: In step S4, pre-curing is performed at 40-50° C. for 20-30 minutes, and then the temperature is raised to 165-180° C. for curing for 2-4 hours.

10. A filled modified resin-based thermally conductive insulating material, characterized in that: The thermally conductive insulating material is prepared by the method for preparing the filled modified resin-based thermally conductive insulating material according to any one of claims 1 to 9.

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