Insulating heat-dissipating coating, coating layer, preparation method and application thereof

Abstract

The present application relates to the technical field of paint, in particular to an insulating heat-dissipating paint, coating, preparation method and application. The present application provides an insulating heat-dissipating paint, which comprises a polymer resin, modified graphene microsheet, porous inorganic infrared radiation powder and far-infrared ceramic fiber; wherein the porous inorganic infrared radiation powder and the far-infrared ceramic fiber are dispersed in the polymer resin; the surface of the modified graphene microsheet contains hydroxyl and / or carboxyl functional groups; the state of the modified graphene microsheet includes: the whole or part of the modified graphene microsheet is embedded in the pores of the porous inorganic infrared radiation powder, the modified graphene microsheet adheres to the surface of the far-infrared ceramic fiber, and the modified graphene microsheet is dispersed in the polymer resin; the modified graphene microsheet is connected with the porous inorganic infrared radiation powder and the far-infrared ceramic fiber through a coupling agent. The insulating heat-dissipating paint has excellent heat-dissipating capacity, infrared radiation performance, insulating performance and aging resistance, as well as high surface hardness, dust adhesion resistance, washing resistance, heat shock resistance and salt spray resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of paint, in particular to an insulating heat dissipation paint, a coating, a preparation method and application. BACKGROUND

[0002] Heat transfer, as an important form of energy exchange, is mainly achieved through three mechanisms: heat conduction, heat convection and heat radiation. In the field of heat dissipation technology, these three ways each have their own characteristics: heat conduction is mainly responsible for efficiently conducting the heat generated inside to the surface of the device; while heat convection and heat radiation bear the key role of dissipating the heat accumulated on the surface of the heat sink to the surrounding environment. However, in many industrial application scenarios that require efficient heat dissipation, space limitations, size constraints and environmental temperature often restrict the implementation of traditional convection heat dissipation schemes. Studies have shown that the core of the performance of heat dissipation paint lies in the optimization of high infrared radiation materials, which directly determines the strengthening effect of surface heat transfer technology. Currently, ceramic powders such as tripolite, stone needle, and tourmaline have become the main raw materials for heat dissipation paint due to their excellent infrared radiation properties. However, the relatively low thermal conductivity of these ceramic materials limits the conduction efficiency of internal heat to the surface, and also makes it difficult for heat dissipation paint that relies solely on the heat radiation mechanism to meet the heat dissipation needs of high heat flux density scenarios such as power facilities.

[0003] Graphene is a single-layer sheet material with excellent electrical conductivity and thermal conductivity, and has become one of the ideal materials in heat dissipation scenarios. Some studies have used inorganic non-metallic heat-conducting materials to adsorb graphene structures on the surface to increase the heat dissipation area, thereby enhancing the heat dissipation effect of the paint and allowing heat to be better transferred outward. Among them, the inorganic non-metallic heat-conducting material includes one or more of aluminum oxide, aluminum nitride, silicon nitride, boron nitride, silicon carbide, magnesium oxide, silicon oxide, zinc oxide, diamond, carbon black, fullerene and boron arsenide, with graphene as the surface adsorption material. However, due to the tendency of graphene to agglomerate, as well as its high electron mobility and excellent electrical conductivity, the use of paint containing graphene in some high-voltage power transmission facilities poses a certain risk of breakdown and flashover, and is also susceptible to corrosion from the external environment, making it less suitable for use in power facilities. SUMMARY

[0004] In view of this, the present application provides an insulating heat dissipation paint, a coating, a preparation method and application. The insulating heat dissipation paint and coating have excellent heat dissipation capacity, infrared radiation performance, insulation performance, and aging resistance, as well as high surface hardness, anti-fouling performance, washability, heat shock resistance, and salt spray resistance.

[0005] To solve the above technical problems, the present application provides an insulating heat dissipation paint, which comprises a high molecular resin, modified graphene microsheet, porous inorganic infrared radiation powder and far infrared ceramic fiber.

[0006] The porous inorganic infrared radiation powder and the far infrared ceramic fiber are dispersed in the polymer resin; the surface of the modified graphene microsheet contains hydroxyl and / or carboxyl functional groups, and the state of the modified graphene microsheet includes that the whole or part of the modified graphene microsheet is embedded in the pores of the porous inorganic infrared radiation powder, the modified graphene microsheet adheres to the surface of the far infrared ceramic fiber, and the modified graphene microsheet is dispersed in the polymer resin, and the modified graphene microsheet, the porous inorganic infrared radiation powder and the far infrared ceramic fiber are connected by a coupling agent.

[0007] The present application uses the modified graphene microsheet containing hydroxyl and / or carboxyl functional groups to form a point-line-surface microstructure with the porous inorganic infrared radiation powder and the far infrared ceramic fiber, which not only ensures the heat transfer effect of the modified graphene microsheet in the porous inorganic infrared radiation powder, but also improves the far infrared emission effect of the porous inorganic infrared radiation powder. In the entire coating system, most of the whole or part of the single modified graphene microsheet is embedded in the pores of the porous inorganic infrared radiation powder, a small part of the modified graphene microsheet adheres to the surface of the far infrared ceramic fiber, and a small part of the modified graphene microsheet is dispersed in the polymer resin. Therefore, the modified graphene microsheet is not completely embedded in the powder pores (most) or coated by the polymer resin (small part), so as to ensure that the obtained coating has good heat dissipation and good insulation performance.

[0008] one of the main functions of the modified graphene microsheet which is wholly or partially embedded in the pores of the porous inorganic infrared radiation powder is that when the heat inside the coating diffuses outward, the filler inside the coating such as the porous inorganic infrared radiation powder and the far-infrared ceramic fiber will absorb most of the heat, and the porous inorganic infrared radiation powder will generate infrared radiation after absorbing the heat, radiate a part of the heat to the environment, and play a heat dissipation role; at the same time, part of the heat will continue to be transmitted to the inside of the porous inorganic infrared radiation powder, at this time, the modified graphene microsheet which is wholly or partially embedded in the pores of the powder begins to play a role, and the heat transmitted to the inside is conducted to the surface of the porous inorganic infrared radiation powder again through the graphene which has good heat conduction performance, and then the heat is radiated out again in the form of far-infrared radiation, if there is no graphene in the process, since the ceramic powder is a poor conductor of heat, it is not convenient for the heat to rapidly diffuse outward. The second main function of the modified graphene microsheet which is wholly or partially embedded in the pores of the porous inorganic infrared radiation powder is that since graphene has high electron mobility and low resistivity, if graphene is directly added to the coating, there will be a risk of breakdown in high-voltage use scenarios, so that the volume resistivity of the coating cannot meet the insulation requirements of the electric power industry.

[0009] In combination with the first aspect, the porous inorganic infrared radiation powder comprises at least one of inorganic ceramic powder and far-infrared emitting powder; wherein the modified graphene microsheet has a sheet diameter of 50-200 nm; the porous inorganic infrared radiation powder has a pore size of 0.5-2 μm, the inorganic ceramic powder has a particle size of 20-100 μm, and the far-infrared emitting powder has a particle size of 20-100 μm; the far-infrared ceramic fiber has a length of 1-5 μm and an aspect ratio of 2:1-50:1.

[0010] Preferably, the inorganic ceramic powder comprises at least one of alumina, zirconia and silica, and the far infrared emission powder comprises natural mineral powder such as tourmaline powder, rhyolite powder and the like, and artificially synthesized ceramic powder, which generates electric charge and far infrared emission when subjected to temperature or pressure change.

[0011] Preferably, the far infrared ceramic fiber is mainly made by dispersing inorganic ceramic powder in a solution of fiber raw material such as polyester, nylon and the like, and then making ceramic fiber through a spinning process.

[0012] In actual application, if the porous inorganic infrared radiation powder has low purity or complex composition, the powder can be subjected to acid treatment to enhance its surface activity.

[0013] In combination with the first aspect, the preparation step of the modified graphene microsheet is: grafting reaction of the modified agent chitosan in the expanded graphene and the oleic acid dispersion liquid of sodium carboxymethyl cellulose with the reduced graphene oxide microsheet to obtain the modified graphene microsheet.

[0014] Preferably, the number of layers of the reduced graphene oxide microsheet is not more than 4.

[0015] Illustratively, the preparation step of the modified graphene microsheet is: ultrasonic dispersion of the reduced graphene oxide microsheet in a solvent for 30-60 min to remove impurities and agglomerates possibly existing on the surface of the graphene microsheet, to obtain a uniformly dispersed reduced graphene oxide dispersion liquid. Pre-disperse the expanded graphite and sodium carboxymethyl cellulose in oleic acid respectively: add the expanded graphite into oleic acid at a weight ratio of 1:8-1:12 and stir and disperse at 50-60℃ for 30-60 min to obtain an expanded graphene dispersion liquid; add the sodium carboxymethyl cellulose into oleic acid at a weight ratio of 1:18-1:22 and stir and disperse at 50-60℃ for 15-30 min to obtain a sodium carboxymethyl cellulose dispersion liquid. Mix the obtained expanded graphene dispersion liquid, sodium carboxymethyl cellulose dispersion liquid and reduced graphene oxide dispersion liquid at a volume ratio (1:1:1-3:3:1), and stir at 50-60℃ for 30-60 min to fully mix the components. Transfer the mixed solution to an ultrasonic cleaner, and ultrasonically treat at 40-50℃ for 30-60 min to form a uniform mixed solution. Add 10%-30% of a chitosan solution (the concentration of chitosan in the chitosan solution is 1wt%-5wt%) to the obtained mixed solution, and continue to stir and react at 55-65℃ for 3-8 h, and the stirring speed can be set to 300-800 r / min to ensure that the chitosan can be uniformly grafted on the surface of the graphene microsheet.

[0016] The dispersibility of the reduced graphene oxide in the solution can be enhanced by modifying the reduced graphene oxide with chitosan, the agglomeration of the reduced graphene oxide is weakened, so that the reduced graphene oxide can be more uniformly dispersed in the coating, and the coating has good heat dissipation effect.

[0017] In combination with the first aspect, the high-molecular resin is a liquid high-molecular polymer, and at least one of polyurea resin, epoxy resin and acrylic resin; and the coupling agent is a silane coupling agent.

[0018] Preferably, the high-molecular resin can be selected from high-molecular polymers with high transparency, such as polyurea resin, epoxy resin or acrylic resin, which can be used as a film-forming material of the coating and can coat the modified graphene microsheet separated from the porous inorganic infrared radiation powder or the far-infrared ceramic fiber, thereby improving the insulation performance of the coating.

[0019] In combination with the first aspect, the insulating and heat-dissipating coating comprises, by weight fraction, 10-40 parts of solvent, 5-10 parts of modified graphene concentrate, 2-3 parts of coupling agent, 10-15 parts of inorganic ceramic powder, 10-20 parts of far-infrared emission powder, 3-5 parts of far-infrared ceramic fiber, 5-10 parts of additive and 35-85 parts of high-molecular resin; the mass fraction of the modified graphene microsheet in the modified graphene concentrate is 8wt%-12wt%, the surfaces of the inorganic ceramic powder, the far-infrared emission powder and the far-infrared ceramic fiber are grafted and modified by the coupling agent, and the solvent is selected from water, alcohol, ether or ester compound.

[0020] Preferably, the additive comprises at least one of defoaming agent, leveling agent, dispersant and wetting agent.

[0021] The second aspect of the present application provides a preparation method of the above-mentioned insulating and heat-dissipating coating, and the steps comprise:

[0022] The coupling agent is mixed with the modified graphene microsheet in the solvent to generate high-molecular polymers bridged by siloxane through hydrolysis and / or polycondensation reaction, and the modified graphene concentrate is obtained by concentration;

[0023] The inorganic ceramic powder, the far-infrared emission powder and the far-infrared ceramic fiber are mixed, and then are ultrasonically and refluxed in the solvent with the coupling agent to cause grafting reaction, and then the solvent is removed to obtain the inorganic ceramic powder, the far-infrared emission powder and the far-infrared ceramic fiber with surfaces grafted and modified by the coupling agent;

[0024] The modified graphene concentrate and the inorganic ceramic powder, the far-infrared emission powder and the far-infrared ceramic fiber grafted and modified by the coupling agent are uniformly mixed by mechanical stirring or ball milling, and the mixture powder is obtained by vacuum drying, washing and drying.

[0025] The mixture powder is ground with the polymer resin and the auxiliary agent in a sand mill at a speed of 1000-2000 r / min for 4-8 h, and then filtered to obtain the insulating heat-dissipating coating.

[0026] The preparation method of the insulating heat-dissipating coating provided by the application comprises the following steps: firstly, the modified graphene microsheet, the inorganic ceramic powder, the far-infrared emission powder and the far-infrared ceramic fiber are surface modified by using a coupling agent; then, the modified graphene microsheet, the inorganic ceramic powder, the far-infrared emission powder and the far-infrared ceramic fiber are uniformly mixed by mechanical stirring or ball milling to form a stable Si-O-Si covalent bond bridging structure; the modified graphene microsheet is made to enter the pores of the inorganic ceramic powder and the far-infrared emission powder as much as possible and covalently connected through the coupling agent, and a small part of the modified graphene microsheet is also covalently connected with the far-infrared ceramic fiber; unreacted graphene microsheet is removed by washing; the mixture powder is dried to obtain a mixture powder; and the mixture powder is ground with the polymer resin and the auxiliary agent at a specific grinding speed and grinding time, so as to avoid the structure of the inorganic ceramic powder and the far-infrared emission powder in the coating being damaged or the pores being blocked as much as possible, and to ensure the heat-dissipating performance of the coating. However, in the grinding process, the modified graphene microsheet adhered to the surface of the far-infrared ceramic fiber is more likely to enter the polymer resin than the graphene microsheet which is embedded in the pores of the powder as a whole or partially.

[0027] Preferably, water, alcohol, ether or ester compound can be used as a dispersion solvent when the modified graphene microsheet, the inorganic ceramic powder, the far-infrared emission powder and the far-infrared ceramic fiber are surface modified.

[0028] Exemplarily, the silane coupling agent and the modified graphene microsheet are mixed in ethanol to perform a reflux reaction for 2-4 h, and then concentrated to obtain a modified graphene concentrated paste.

[0029] Exemplarily, the silane coupling agent, the inorganic ceramic powder, the far-infrared emission powder and the far-infrared ceramic fiber are mixed in ethanol to perform a reflux reaction for 2-4 h, and then concentrated to obtain the inorganic ceramic powder, the far-infrared emission powder and the far-infrared ceramic fiber which are surface grafted and modified by the coupling agent.

[0030] The third aspect of the application provides application of the insulating heat-dissipating coating or the insulating heat-dissipating coating prepared by the above preparation method to power cables, vehicles, building materials and industrial facilities.

[0031] The fourth aspect of the application provides an insulating heat-dissipating coating, which is obtained by coating the insulating heat-dissipating coating or the insulating heat-dissipating coating prepared by the above preparation method on the surface of a substrate and drying to form a film.

[0032] In combination with the fourth aspect, the thickness of the insulating heat-dissipating coating is 35-45 μm, and the insulating heat-dissipating coating has a stepped micro-nano structure, the gap of the micro-nano structure is less than 200 μm, and the thickness gradient is 2-25 μm.

[0033] The insulation heat dissipation coating provided by the present application introduces a coating regulation process in the coating process, and the construction of the micro-nano structure of the coating is realized by controlling the thickness of the coating, and the gap between the micro-nano structures of the coating is less than 200 mu m, thereby enhancing the antifouling ability of the surface of the coating.

[0034] The heat dissipation insulation coating provided by the present application is prepared by specific selection of a formula and limitation of parameters in a preparation method, and has good insulation performance, heat dissipation performance and infrared radiation performance, and also has aging resistance, wear resistance, antifouling performance, washability and high surface hardness, and the raw material cost is low, and the coating does not contain halogen and other toxic substances, so that the coating is an economical and green insulation heat dissipation coating.

[0035] The present application provides an insulation heat dissipation coating, which is successfully prepared by optimizing the formula design and precisely controlling the preparation process parameters, and has multiple excellent performances. The coating not only has excellent insulation performance (volume resistivity ≥ 101 2 Ω·cm) and outstanding heat dissipation performance (thermal conductivity ≥ 5 W / (m·K)), but also has excellent infrared radiation performance (infrared radiation coefficient ≥ 0.85), long-term aging resistance (240 hours of aging resistance test), excellent washability (water flow rinsing for 960 h, no film layer falling off, no bubble, no cracking, no rust), heat shock resistance (no obvious film layer falling off and peeling phenomenon after 20 cycles of-40-85℃ cold and hot alternation), salt spray resistance (192h of neutral salt spray test) and dust adhesion resistance (the highest adhesion resistance grade can reach 0 grade). In addition, the coating uses a low-cost raw material system and does not contain halogen and other toxic and harmful substances, meets the RoHS environmental protection standard, has significant economic benefits and environmental friendly characteristics, and can be widely applied to electronic devices, power equipment and other heat dissipation scenes with high insulation requirements. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 SEM image of the dispersion of the porous inorganic infrared radiation powder and the far infrared ceramic fiber in the high molecular resin in the coating obtained in Example 4 of the present application;

[0037] Figure 2 SEM image of the surface of the porous inorganic infrared radiation powder in the coating obtained in Example 4 of the present application;

[0038] Figure 3 SEM image of the porous inorganic infrared radiation powder in the coating obtained in Example 4 of the present application;

[0039] Figure 4 SEM image of the modified far infrared ceramic fiber obtained in Example 1 of the present application;

[0040] Figure 5SEM image of the modified graphene microsheet obtained in Example 1 of the present application;

[0041] Figure 6 Schematic diagram of side structure of the coating obtained in Example 4 of the present application. DETAILED DESCRIPTION

[0042] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with specific examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0043] Those skilled in the art can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs. It should also be understood that terms such as those defined in general dictionaries should be understood as having meanings consistent with those in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined.

[0044] Graphene is a single-layer sheet-like material composed of carbon atoms, and the carbon atoms are bonded by sp 2 Hybrid orbitals and tightly packed into a two-dimensional honeycomb lattice structure, each carbon atom contains an unbound electron, which can freely move in the plane formed by the carbon atoms, so that graphene has excellent electrical conductivity, and the mobility of the charge carriers at room temperature is as high as 15000 cm 2 / (V·s), and the thermal conductivity of defect-free single-layer graphene is as high as 5300 W / (m·K), so it can quickly and uniformly conduct heat to the surface of the object; at the same time, graphene also has good mechanical properties, can realize bending, compression and longitudinal stretching, and the mechanical strength is 200 times that of steel, and is widely used in impact resistance, lubrication, corrosion resistance and other industrial fields. At present, there have been researches on using graphene in thermal conductive materials, but because graphene itself is easy to agglomerate, and has high electron mobility and excellent electrical conductivity, when the thermal conductive material containing graphene is used in some high-voltage power transmission facilities, there is a certain risk of breakdown and flashover, and the applicability in power facilities is poor.

[0045] In view of this, the present application provides an insulating heat dissipation coating, by specific selection of the formula and limitation of each parameter in the preparation method, the obtained coating not only has good insulation performance, heat dissipation performance and infrared radiation performance, but also has aging resistance, wear resistance, washability, heat shock resistance, salt mist resistance and dust adhesion resistance, and the raw material cost is low, does not contain halogen and other toxic substances, and is an economical and green insulating heat dissipation coating.

[0046] The preparation method provided by the present application is described below through specific examples.

[0047] The raw reagents and equipment used in the present application are all conventional commercially available ordinary reagents and ordinary equipment unless otherwise specified. The morite far infrared ceramic fiber used in the examples of the present application is provided by Shijiazhuang Jueo New Material Technology Co., Ltd.

[0048] Example 1

[0049] The present example provides an insulating heat dissipation coating, which comprises the following raw materials in parts by weight: 15 parts of water, 5 parts of 10wt% modified graphene concentrated paste, 3 parts of coupling agent, 15 parts of alumina with a particle size of 20 μm and a pore size of 0.6 μm, 10 parts of tourmaline powder with a particle size of 20 μm and a pore size of 0.8 μm, 3 parts of morite far infrared ceramic fiber with a length of 3 μm and an aspect ratio of 20:1, 8 parts of additives (including 1.5 parts of defoaming agent, 0.8 parts of leveling agent, 1.5 parts of dustproof agent, 3 parts of wetting agent, 0.5 parts of thickening agent, and 0.7 parts of adhesion promoter), and 45 parts of epoxy resin (epoxy equivalent weight 40-50, viscosity 1200 cp, solid content 45%). The preparation method is as follows:

[0050] The silane coupling agent KH570 and the modified graphene microsheet are dispersed in ethanol at a mass ratio of 1:1.5, refluxed for 3 h, concentrated to obtain 10wt% modified graphene concentrated paste;

[0051] The alumina powder, tourmaline powder, and morite far infrared ceramic fiber are sequentially ultrasonically dispersed in ethanol at a mass ratio of 15:10:3:3, refluxed for 3 h to cause grafting reaction, and then the solvent is removed and the solid is dried to obtain alumina powder, tourmaline powder, and morite far infrared ceramic fiber with surfaces grafted and modified by the coupling agent;

[0052] The 10wt% modified graphene concentrated paste and the alumina powder, tourmaline powder, and morite far infrared ceramic fiber grafted and modified by the coupling agent are uniformly mixed by mechanical stirring, vacuum dried, washed and dried to obtain a mixture powder;

[0053] The mixture powder, epoxy resin, and additives are ground in a sand mill at a speed of 1000 r / min for 8 h, filtered to obtain an insulating heat dissipation coating.

[0054] The modified graphene microsheet is prepared by the following method: 10 g of reduced graphene oxide microsheet with a sheet diameter of 50 nm and 2-4 layers is ultrasonically dispersed in 200 mL of ethanol for 40 min. The expanded graphite and sodium carboxymethyl cellulose are pre-dispersed in oil respectively: the expanded graphite is added to the oil at a weight ratio of 1:10 and stirred and dispersed at 55°C for 40 min to obtain an expanded graphene dispersion; the sodium carboxymethyl cellulose is added to the oil at a weight ratio of 1:20 and stirred and dispersed at 55°C for 20 min to obtain a sodium carboxymethyl cellulose dispersion. The obtained expanded graphene dispersion, sodium carboxymethyl cellulose dispersion and reduced graphene oxide dispersion are mixed at a volume ratio of (2:2:1) and stirred at 55°C for 50 min to fully mix the components. The mixed solution is transferred to an ultrasonic cleaner and ultrasonically treated at 45°C for 50 min to form a uniform mixed solution. 10% of the mixed solution by volume of a chitosan solution (the concentration of chitosan in the chitosan solution is 3 wt%) is added to the obtained mixed solution, and the stirring reaction is continued at 60°C for 6 h, and the stirring speed is set to 500 r / min. After filtration and drying, the graphene microsheet modified by chitosan is obtained.

[0055] The SEM image of the obtained modified far-infrared ceramic fiber is shown in Figure 4 The SEM image of the obtained modified graphene microsheet is shown in Figure 5

[0056] Example 2

[0057] The present embodiment provides an insulating heat dissipation coating, which comprises the following raw materials in parts by weight: water 20 parts, 10 wt% modified graphene concentrated paste 10 parts, coupling agent 3 parts, zirconia with a particle size of 30 μm and a pore size of 1.2 μm 10 parts, medical stone powder with a particle size of 25 μm and a pore size of 1.5 μm 20 parts, molybdenum stone far-infrared ceramic fiber with a length of 3 μm and an aspect ratio of 20:1 5 parts, additives 10 parts (including defoaming agent 1.5 parts, leveling agent 1.3 parts, anti-settling agent 1.5 parts, wetting agent 3 parts, thickening agent 1.5 parts, and adhesion promoter 1.2 parts), and polyurea resin 45 parts. The preparation method is as follows:

[0058] The silane coupling agent KH560 and the modified graphene microsheet are dispersed in ethanol at a mass ratio of 1:1.5, refluxed for 2 h, concentrated to obtain a 10 wt% modified graphene concentrated paste;

[0059] The zirconia powder, medical stone powder and molybdenum stone far-infrared ceramic fiber, and the silane coupling agent KH560 are sequentially ultrasonically dispersed in ethanol at a mass ratio of 10:20:5:3, refluxed for 4 h to cause grafting reaction, and then the solvent is removed and the solid is dried to obtain the zirconia powder, medical stone powder and molybdenum stone far-infrared ceramic fiber with the surface grafted and modified by the coupling agent.​

[0060] The 10wt% modified graphene concentrated slurry, and the zirconium oxide powder, grafted and modified by coupling agent, the geyser powder and the mullite far infrared ceramic fiber were mixed uniformly by a ball mill, and the mixture powder was obtained by vacuum drying, washing and drying;

[0061] The mixture powder, polyurea resin and additives were ground in a sand mill at a speed of 1500r / min for 6h, and the heat dissipation coating was obtained by filtering.

[0062] The modified graphene microsheet was prepared by the following method: 10g of reduced graphene oxide microsheet with a sheet diameter of 200nm and 1-3 layers was ultrasonically dispersed in 200mL of ethanol for 30min. The expanded graphite and sodium carboxymethyl cellulose were pre-dispersed in oleic acid respectively: the expanded graphite was added to the oleic acid at a weight ratio of 1:8 and stirred and dispersed at 50℃ for 60min to obtain an expanded graphene dispersion solution; the sodium carboxymethyl cellulose was added to the oleic acid at a weight ratio of 1:22 and stirred and dispersed at 50℃ for 30min to obtain a sodium carboxymethyl cellulose dispersion solution. The obtained expanded graphene dispersion solution, sodium carboxymethyl cellulose dispersion solution and reduced graphene oxide dispersion solution were mixed at a volume ratio of (1:1:1) and stirred at 50℃ for 50min to fully mix the components. The mixed solution was transferred to an ultrasonic cleaner and ultrasonically treated at 45℃ for 60min to form a uniform mixed solution. 25% of the mixed solution by volume of a chitosan solution (the concentration of chitosan in the chitosan solution was 1wt%) was added to the obtained mixed solution, and the stirring was continued at 60℃ for 8h at a stirring speed of 300r / min. The chitosan-modified graphene microsheet was obtained by filtering and drying.

[0063] Example 3

[0064] The present embodiment provides an insulating heat dissipation coating, which comprises the following raw materials by weight: water 30 parts, 10wt% modified graphene concentrated slurry 8 parts, coupling agent 3 parts, silica with a particle size of 60μm and a pore size of 2μm 13 parts, cordierite powder with a particle size of 50μm and a pore size of 2μm 18 parts, mullite far infrared ceramic fiber with a length of 3-5μm and an aspect ratio of 50:1 4 parts, additives 10 parts (including defoaming agent 1.5 parts, leveling agent 1.3 parts, anti-settling agent 1.5 parts, wetting agent 3 parts, thickening agent 1.5 parts, adhesion promoter 1.2 parts), and acrylic resin 75 parts. The preparation method is as follows:

[0065] The silane coupling agent KH560 and the modified graphene microsheet were dispersed in ethanol at a mass ratio of 1:3, and refluxed for 3h to obtain a 12wt% modified graphene concentrated slurry;

[0066] The silica powder, the cordierite powder and the mullite far-infrared ceramic fiber are sequentially ultrasonically dispersed in ethanol according to a mass ratio of 13:18:4:3, and a grafting reaction is caused by refluxing for 3 hours. Then, the solvent is removed and the solid is dried to obtain the silica powder, the cordierite powder and the mullite far-infrared ceramic fiber whose surfaces are grafted and modified by the coupling agent.

[0067] The 12wt% modified graphene concentrate, the silica powder grafted and modified by the coupling agent, the powder of the mica and the far-infrared ceramic fiber are uniformly mixed by a ball mill, vacuum dried, washed and dried to obtain the mixture powder.

[0068] The mixture powder, the acrylic resin and the auxiliary agent are ground in a sand mill at a speed of 2000r / min for 4 hours, filtered and an insulating heat dissipation coating is obtained.

[0069] The modified graphene microsheet is prepared by the following method: 10g of reduced graphene oxide microsheet with a sheet diameter of 150nm and 2-4 layers is ultrasonically dispersed in 200mL of ethanol for 60min. The expanded graphite and sodium carboxymethyl cellulose are pre-dispersed in oleic acid respectively: the expanded graphite is added to the oleic acid according to a weight ratio of 1:12 and stirred and dispersed at 60°C for 30min to obtain an expanded graphene dispersion liquid; the sodium carboxymethyl cellulose is added to the oleic acid according to a weight ratio of 1:18 and stirred and dispersed at 60°C for 15min to obtain a sodium carboxymethyl cellulose dispersion liquid. The obtained expanded graphene dispersion liquid, sodium carboxymethyl cellulose dispersion liquid and reduced graphene oxide dispersion liquid are mixed according to a volume ratio of 2:2:1, stirred at 60°C for 30min to fully mix the components. The mixed solution is transferred to an ultrasonic cleaner and ultrasonically treated at 40°C for 50min to form a uniform mixed solution. 35% of the mixed solution by volume of a chitosan solution (the concentration of chitosan in the chitosan solution is 1wt%) is added to the obtained mixed solution, and the stirring reaction is continued at 60°C for 4h at a stirring speed of 800r / min. The product is filtered and dried to obtain the graphene microsheet modified by chitosan.

[0070] Example 4

[0071] The insulating heat dissipation coating prepared in Example 1 is sprayed on a substrate by a coating step thickness spraying process, the gap between the micro-nano structures is controlled to be less than 200μm, and the thickness gradient is 2-25μm. Then, the coating is dried in a drying oven at 110±10°C for 30min to obtain an insulating heat dissipation coating with a thickness of 35-45μm. The SEM image and part of the internal microstructure of the coating are shown in Figures 1-3 , and the side structure schematic diagram of the coating is shown in Figure 6 .

[0072] By Figure 1 As can be seen, the porous inorganic infrared radiation powder (white dotted area) and the far infrared ceramic fiber (white dotted area) are scattered and dispersed in the polymer resin, and at the same time the polymer resin seals the pores of the powder; by Figures 2-3 As can be seen, the whole or part of the modified graphene microsheet (white dotted area) is embedded in the porous inorganic infrared radiation powder.

[0073] Example 5

[0074] The present embodiment provides an insulating heat dissipation coating, and the preparation method thereof is as follows: the insulating heat dissipation coating prepared in Example 2 is sprayed on a substrate by using a coating step thickness spraying process, the gap between the micro-nano structures is controlled to be less than 200 μm, the thickness gradient is 2-25 μm, and then the coating is dried in a drying oven at 110±10 ℃ for 30 min, so as to obtain an insulating heat dissipation coating with a thickness of 35-45 μm.

[0075] Example 6

[0076] The present embodiment provides an insulating heat dissipation coating, and the preparation method thereof is as follows: the insulating heat dissipation coating prepared in Example 3 is sprayed on a substrate by using a coating step thickness spraying process, the gap between the micro-nano structures is controlled to be less than 200 μm, the thickness gradient is 2-25 μm, and then the coating is dried in a drying oven at 110±10 ℃ for 30 min, so as to obtain an insulating heat dissipation coating with a thickness of 35-45 μm.

[0077] Comparative Example 1

[0078] The present comparative example provides a coating, and the difference between the raw materials of the coating and the raw material formula of Example 1 is that the comparative example does not contain modified graphene concentrated paste, and the rest of the raw materials, the amount and the preparation method are the same as those of Example 1, and will not be repeated here.

[0079] Comparative Example 2

[0080] The present comparative example provides a coating, and the difference between the raw materials of the coating and the raw material formula of Example 1 is that the comparative example replaces 10wt% of the modified graphene concentrated paste with 10wt% of the graphene concentrated paste, i.e., using unmodified graphene microsheet instead of modified graphene microsheet to prepare the graphene concentrated paste, and the rest of the raw materials, the amount and the preparation method are the same as those of Example 1, and will not be repeated here.

[0081] Comparative Example 3

[0082] The present comparative example provides a coating, and the difference between the raw materials of the coating and the raw material formula of Example 1 is that the comparative example replaces 10wt% of the modified graphene concentrated paste with 10wt% of the modified carbon nanotube concentrated paste, and the rest of the raw materials, the amount and the preparation method are the same as those of Example 1, and will not be repeated here.

[0083] The preparation method of the modified carbon nanotubes is basically the same as that of the modified graphene microsheets in Example 1, except that the graphene microsheets are replaced by an equal amount of carbon nanotubes.

[0084] Comparative Example 4

[0085] This comparative example provides a coating, the raw material formula of which is the same as that of Example 1, except that no far-infrared material (alumina powder, tourmaline powder and mullite far-infrared ceramic fiber) is added, and the rest of the raw materials and the preparation method are the same as those of Example 1, which will not be repeated here.

[0086] Comparative Example 5

[0087] This comparative example provides a coating, the raw material formula of which is the same as that of Example 1, except that the grinding speed is 3000 r / min and the grinding time is 3 h when the final grinding is performed in a sand mill, and the rest of the steps are the same as those of Example 1, which will not be repeated here.

[0088] Comparative Example 6

[0089] This comparative example provides a coating, the raw material formula of which is the same as that of Example 1, except that the grinding speed is 500 r / min and the grinding time is 10 h when the final grinding is performed in a sand mill, and the rest of the steps are the same as those of Example 1, which will not be repeated here.

[0090] Comparative Example 7

[0091] This comparative example provides a coating, which is different from Example 4 in that the coating obtained in Example 1 is directly sprayed on the substrate without using the coating step thickness spraying process, and an insulating heat dissipation coating with a thickness of 35-45 μm is obtained.

[0092] Test Example

[0093] The coatings obtained in Examples 1-3 and Comparative Examples 1-7 are respectively sprayed on the surface of a steel plate substrate according to the coating step thickness spraying process, with a film thickness of 35-45 μm, and dried at 110°C for 30 min. The thermal conductivity (referring to standard ASTM E1530), insulation performance (referring to standard GB / T31838.2-2019), infrared radiation performance (referring to standard GBT7287-2008), aging resistance (referring to standard ASTM D4587), washability (referring to standard GB / T 1733-93), hardness (referring to standard GB / T 6739-2022), heat shock resistance (referring to standard JG / T 25-2017), dust adhesion resistance (referring to standard GB / T 9761-2008 8.2b), and salt spray resistance (referring to standard GB / T 2423.17) of the obtained coatings are tested, and the test results are shown in Table 1.

[0094] Table 1

[0095]

[0096] From the data in Table 1, compared with Example 1, Comparative Example 1 does not add graphene, and the thermal conductivity and infrared radiation performance of the obtained paint are obviously decreased, and the wash resistance and salt spray resistance are also decreased. Comparative Example 2 uses unmodified graphene, and the obtained paint not only affects the heat dissipation performance, but also seriously affects the film forming performance and integrity of the paint, and reduces the weather resistance such as salt spray resistance and heat shock resistance. After Comparative Example 3 uses carbon nanotubes instead of graphene microsheets, the heat dissipation performance of the obtained paint is obviously decreased. In Comparative Example 4, no far infrared material is added, and the infrared radiation and heat dissipation performance of the obtained paint is obviously decreased. Comparative Examples 5 and 6 respectively increase and decrease the grinding speed, which destroys the microstructure of the system, and the grinding speed is too low to ensure the uniform dispersion of the raw materials, thereby affecting the comprehensive performance of the paint. Comparative Example 7 does not use the step thickness spraying process, although it does not significantly affect the heat dissipation performance and insulation performance of the paint, but it obviously reduces the dust adhesion resistance of the coating surface. In addition, compared with Example 1, the surface temperature of the steel plate substrate of the paint obtained in Example 1 is 10℃ higher than that of Example 1 after irradiation under the same conditions.

[0097] The above description is only the preferred embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can make equivalent replacement or change according to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. An insulating heat-dissipating paint, characterized by, The application relates to an insulating heat-dissipating coating, which comprises a high-molecular resin, modified graphene microsheets, porous inorganic infrared radiation powder and far-infrared ceramic fibers; the porous inorganic infrared radiation powder and the far-infrared ceramic fibers are dispersed in the high-molecular resin; the surface of the modified graphene microsheets contains hydroxyl and / or carboxyl functional groups; the state of the modified graphene microsheets includes that the whole or part of the modified graphene microsheets is embedded in the pores of the porous inorganic infrared radiation powder, the modified graphene microsheets adhere to the surface of the far-infrared ceramic fibers and the modified graphene microsheets are dispersed in the high-molecular resin; the modified graphene microsheets, the porous inorganic infrared radiation powder and the far-infrared ceramic fibers are connected through a coupling agent; the preparation steps of the modified graphene microsheets are as follows: grafting reaction of a modifier chitosan in an oleic acid dispersion liquid of expanded graphene and sodium carboxymethyl cellulose with reduced graphene microsheets to obtain the modified graphene microsheets. The preparation method of the insulating heat-dissipating coating comprises the following steps: The coupling agent and the modified graphene microsheets are mixed in a solvent to generate high-molecular polymers bridged by siloxane bonds through hydrolysis and / or polycondensation reaction, and the modified graphene concentrated paste is obtained through concentration; The inorganic ceramic powder, the far-infrared emission powder and the far-infrared ceramic fibers are mixed, and then are subjected to grafting reaction in a solvent together with the coupling agent through ultrasonic and reflux, and then the solvent is removed to obtain the inorganic ceramic powder, the far-infrared emission powder and the far-infrared ceramic fibers whose surfaces are grafted and modified by the coupling agent; The modified graphene concentrated paste and the inorganic ceramic powder, the far-infrared emission powder and the far-infrared ceramic fibers grafted and modified by the coupling agent are uniformly mixed through mechanical stirring or ball milling, and then are vacuum dried, washed and dried to obtain the mixture powder; The mixture powder, the high-molecular resin and the additives are ground in a sand mill at a speed of 1000-2000 r / min for 4-8 h, and then are filtered to obtain the insulating heat-dissipating coating.

2. The insulating heat dissipating paint according to claim 1, wherein The porous inorganic infrared radiation powder comprises at least one of inorganic ceramic powder and far-infrared emission powder; The modified graphene microsheet has a sheet diameter of 50-200 nm; the porous inorganic infrared radiation powder has a pore size of 0.5-2 microns; the inorganic ceramic powder has a particle size of 20-100 microns; the far-infrared emission powder has a particle size of 20-100 microns; the far-infrared ceramic fiber has a length of 1-5 microns and a length-diameter ratio of 2:1-50:

1.

3. The insulating heat dissipating paint according to claim 1, wherein The high-molecular resin is a liquid high-molecular polymer, and comprises at least one of polyurea resin, epoxy resin and acrylic resin; the coupling agent is a silane coupling agent.

4. The insulating heat dissipating paint according to claim 2 or 3, wherein According to weight parts, the insulating heat-dissipating coating comprises the following components: 10-40 parts of a solvent, 5-10 parts of the modified graphene concentrated paste, 2-3 parts of the coupling agent, 10-15 parts of the inorganic ceramic powder, 10-20 parts of the far-infrared emission powder, 3-5 parts of the far-infrared ceramic fiber, 5-10 parts of additives and 35-85 parts of the high-molecular resin; the mass fraction of the modified graphene microsheet in the modified graphene concentrated paste is 8wt%-12wt%; the surfaces of the inorganic ceramic powder, the far-infrared emission powder and the far-infrared ceramic fiber are grafted and modified by the coupling agent; and the solvent is selected from water, alcohol, ether or ester compounds.

5. Use of the insulating and heat-dissipating coating material according to any one of claims 1-4 in power cables, vehicles, building materials and industrial facilities.

6. An insulating heat dissipating coating, characterized in that, The coating is obtained by coating the insulating and heat-dissipating coating material according to any one of claims 1-4 on the surface of a substrate and drying to form a film.

7. The insulating heat dissipating coating of claim 6, wherein The insulating and heat-dissipating coating has a thickness of 35-45 μm and a stepped micro-nano structure with a gap of less than 200 μm and a thickness gradient of 2-25 μm.

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