Electromagnetic induction coating material, preparation method and application thereof

Abstract

The invention relates to the field of coating materials, and discloses an electromagnetic induction coating material as well as a preparation method and application thereof. The preparation method comprises the following steps: carrying out surface modification on cellulose nanocrystals by using a silane coupling agent gamma-aminopropyltriethoxysilane to obtain modified cellulose nanocrystals, and generating magnetic nanoparticles Fe3O4 on the surface of carboxylated multilayer graphene oxide by using a hydrothermal method, the preparation method comprises the following steps: preparing a multi-layer graphene / Fe3O4 composite material, introducing a high-activity acyl chloride group on the surface of the multi-layer graphene / Fe3O4 composite material through acylating chlorination reaction, reacting with 2-amino-4, 6-dichloropyrimidine and acetamide to prepare modified multi-layer graphene, reacting the modified cellulose nanocrystal and the modified multi-layer graphene with a waterborne polyurethane prepolymer to obtain a modified polyurethane composite emulsion, and preparing the waterborne polyurethane composite emulsion into the waterborne polyurethane composite material. Metal powder, nano silicon dioxide and the modified polyurethane composite emulsion are mixed and subjected to ultrasonic treatment, and the electromagnetic induction coating material is obtained and can be widely applied to the surfaces of ceramic and glassware articles.

Description

Technical Field

[0001] The present invention relates to the field of coating materials, and in particular to an electromagnetic induction coating material, a preparation method and applications thereof. Background Art

[0002] Currently, common heating methods include resistance heating, microwave heating, infrared heating, and electromagnetic heating. Resistance heating uses a resistance wire to generate heat, but suffers from low thermal energy utilization, a short lifespan, and high maintenance requirements. Microwave heating is rapid and uniform, energy-efficient, and efficient, but the nutrients in the food it heats are easily lost, and it cannot heat metal or ordinary plastics, significantly limiting its application. Infrared heating can achieve simultaneous internal and external heating and is highly efficient, but far-infrared heating requires selecting different heating source radiation bands and temperatures based on the object, resulting in unstable heating efficiency. This makes infrared heating primarily used in areas such as sanitation and environmental protection, sterilization, and baking. Electromagnetic heating does not require a heat transfer medium; the heated object itself generates heat, resulting in extremely high heating efficiency, stable heating quality, and the ability to achieve localized heating and precision control. It also offers advantages such as energy conservation, a favorable working environment, a long lifespan, and low cost, making it widely used in military, industrial, medical, chemical, building materials, and home appliances.

[0003] Existing technologies, such as Chinese patent application CN1648174A, disclose electromagnetic induction heating coatings and their preparation methods, which include the following components in percentage by mass: 28.4% silver hydroxide, 25.2% silver oxide, 0.5% nickel oxide, 4.1% glass powder, and 41.8% binder. This coating enables the use of ceramics and glassware on induction cookers, but its corrosion resistance is poor, and it cannot adhere to ceramics and glassware for a long time and is easy to fall off. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide an electromagnetic induction coating material, a preparation method and an application thereof, wherein the coating material has excellent mechanical properties, corrosion resistance and electromagnetic induction efficiency.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing an electromagnetic induction coating material comprises the following steps: Step (1), preparing modified cellulose nanocrystals and modified multilayer graphene; the modified cellulose nanocrystals are prepared by the following steps: mixing cellulose nanocrystals, ethanol and water, ultrasonically dispersing, adding γ-aminopropyltriethoxysilane, reacting, centrifuging after the reaction, washing, and drying to obtain modified cellulose nanocrystals; the modified multilayer graphene is prepared by the following steps: mixing carboxylated multilayer graphene oxide with water, ultrasonically dispersing, adding ferric chloride and ferrous chloride, stirring, adding NaOH aqueous solution to adjust the pH, reacting, filtering after the reaction, washing, and drying to obtain a multilayer graphene / Fe3O4 composite material; mixing the multilayer graphene / Fe3O4 composite material with acetonitrile, adding thionyl chloride and N,N-dimethylformamide, reacting, adding 2-amino-4,6-dichloropyrimidine, continuing the reaction, adding sodium hydroxide and acetamide, reacting again, centrifuging after the reaction, washing, and drying to obtain modified multilayer graphene; Step (2), mixing the modified cellulose nanocrystals, modified multilayer graphene, and acetone, ultrasonically dispersing the mixture, adding the mixture to the aqueous polyurethane prepolymer, reacting the mixture, adding triethylamine, continuing the reaction, adding water and ethylenediamine, emulsifying the mixture, and after the reaction, removing the acetone by rotary evaporation to obtain a modified polyurethane composite emulsion; Step (3): mixing the metal powder, nano-silicon dioxide and modified polyurethane composite emulsion, and ultrasonically dispersing them to obtain an electromagnetic induction coating material.

[0006] Preferably, in step (1), when preparing modified cellulose nanocrystals, the mass ratio of cellulose nanocrystals, ethanol, water, and γ-aminopropyltriethoxysilane is 0.5:(60-80):(15-25):(3-5); and the reaction conditions are: reaction at a temperature of 35-45°C for 8-10 hours.

[0007] Preferably, in step (1), when preparing the modified multilayer graphene, the mass ratio of carboxylated multilayer graphene oxide, water, ferric chloride, and ferrous chloride is 1:(160-200):(0.2-0.3):(0.6-0.8); when preparing the multilayer graphene / Fe3O4 composite material, the reaction conditions are: reaction at pH=10-11 and temperature of 85-95°C for 6-8h.

[0008] Preferably, in the step (1), when preparing the modified multilayer graphene, the mass ratio of the multilayer graphene / Fe3O4 composite material, acetonitrile, thionyl chloride, N,N-dimethylformamide, 2-amino-4,6-dichloropyrimidine, sodium hydroxide, and acetamide is 0.1:(260-300):(4-6):(0.2-0.4):(4-6):(3-4):(2-3); when preparing the modified multilayer graphene, the reaction conditions are: reacting at a temperature of 55-65°C for 4-6h; continuing the reaction conditions are: continuing the reaction at a temperature of 55-65°C for 4-6h; and re-reacting conditions are: reacting again at room temperature for 10-12h.

[0009] Preferably, in step (2), the mass ratio of modified cellulose nanocrystals, modified multilayer graphene, acetone, waterborne polyurethane prepolymer, triethylamine, water, and ethylenediamine is (0.1-0.4):(0.2-0.4):(8-12):30:(0.7-0.9):(80-100):(0.5-0.7); the reaction conditions are: reaction at 40-50°C for 1-2h; the continued reaction conditions are: continued reaction at 30-40°C for 30-50min; and the emulsification conditions are: emulsification at a speed of 1400-1600r / min for 30-50min.

[0010] Preferably, in step (2), the waterborne polyurethane prepolymer is prepared by the following steps: mixing polypropylene glycol and isophorone diisocyanate, reacting, adding dimethylolpropionic acid, continuing the reaction, adding diethylene glycol, trimethylolpropane, and dibutyltin dilaurate, reacting again, and obtaining a waterborne polyurethane prepolymer after the reaction is completed.

[0011] Furthermore, the mass ratio of polypropylene glycol, isophorone diisocyanate, dimethylolpropionic acid, diethylene glycol, trimethylolpropane, and dibutyltin dilaurate is 10:(10-12):(0.9-1.1):(2-2.2):(0.4-0.6):(0.01-0.02); the reaction conditions are: react at a temperature of 75-85°C for 2-4 hours; the continued reaction conditions are: continue to react at a temperature of 70-80°C for 2-4 hours; and the re-reaction conditions are: react again at a temperature of 65-75°C for 1-2 hours.

[0012] Preferably, in step (3), the metal powder is a mixture of one or more of silver, aluminum, copper, and nickel; and the mass ratio of the metal powder, nano-silicon dioxide, and modified polyurethane composite emulsion is (20-40):(4-6):(160-200).

[0013] Preferably, an electromagnetic induction coating material is prepared using the above-mentioned method for preparing an electromagnetic induction coating material.

[0014] Preferably, an electromagnetic induction coating material prepared by the method for preparing an electromagnetic induction coating material as described above is used in ceramics and glassware.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] Cellulose nanocrystals, as a highly crystalline nanoparticle, can serve as a reinforcing phase to enhance the hardness of the coating material, while reducing the penetration of gas or water molecules into the membrane, thereby improving the shielding and anti-corrosion properties of the coating material. Multilayer graphene can achieve electromagnetic induction through its high conductivity and unique two-dimensional structure. When an alternating magnetic field acts on the coating material, a closed eddy current is formed inside it, generating an induced current according to Faraday's law of electromagnetic induction. In addition, its two-dimensional lamellar structure can extend the diffusion path of the corrosive medium, thereby improving the shielding and anti-corrosion properties of the coating material. The two are used in combination to synergistically improve the density and long-term anti-corrosion performance of the coating material.

[0017] The present invention uses a silane coupling agent, γ-aminopropyltriethoxysilane, to modify the surface of cellulose nanocrystals. One end of the silane coupling agent is first hydrolyzed to generate silanol (Si-OH). Si-OH can react with active groups (hydroxyl, carboxyl, etc.) on the surface of the cellulose nanocrystals. The hydrophilicity of the modified cellulose nanocrystals is weakened, and the active functional group amino group at the other end of the silane molecule can react with isocyanate, thereby improving its compatibility with the polyurethane matrix. The present invention uses a hydrothermal method to generate magnetic nanoparticles Fe3O4 on the surface of multilayer graphene oxide. Multilayer graphene provides high conductivity and a large specific surface area, and the high magnetic loss capacity of Fe3O4 is effective. The frequency band is broadened and the magnetic loss mechanism is enhanced. After the two are combined, broadband and efficient electromagnetic induction can be achieved through electro-magnetic synergy, multiple interface polarization and electronic coupling between components, while improving the stability of the material in high temperature or corrosive environment; highly active acyl chloride groups are introduced on the surface of the multilayer graphene / Fe3O4 composite material through acyl chlorination reaction, and then modified multilayer graphene is prepared by reacting with 2-amino-4,6-dichloropyrimidine and acetamide. The active group amino group is introduced while increasing the interlayer spacing of the multilayer graphene, enhancing the multiple reflection and scattering effects of electromagnetic waves, thereby improving the electromagnetic induction efficiency of the coating material.

[0018] The present invention ultrasonically mixes metal powder, nano-silicon dioxide, and modified polyurethane composite emulsion to obtain an electromagnetic induction coating material. The metal powder is a mixture of one or more of silver, aluminum, copper, and nickel, all of which are highly conductive substances and produce a synergistic conductive effect with the modified multilayer graphene; the nano-silicon dioxide acts as an intermediate transition layer and fuses the various components at high temperature. The obtained coating material has excellent mechanical properties, corrosion resistance, and electromagnetic induction efficiency, and can be widely used on the surfaces of ceramics and glassware.

[0019] The preparation process of the invention is simple, and no oily solvent is volatilized during subsequent application, thereby reducing pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a histogram of the impact strength of the electromagnetic induction coating materials prepared by Examples 1-5 and Comparative Examples 1-3 in the comprehensive performance test of the present invention; Figure 2 It is a histogram of the electrical conductivity in the comprehensive performance test of the electromagnetic induction coating materials prepared by Examples 1-5 and Comparative Examples 1-3 of the present invention. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] Example 1 This embodiment discloses a method for preparing an electromagnetic induction coating material, comprising the following steps: Step (1), preparing modified cellulose nanocrystals and modified multilayer graphene; the modified cellulose nanocrystals are prepared by the following steps: mixing cellulose nanocrystals, ethanol and water, ultrasonically dispersing for 20 minutes, adding γ-aminopropyltriethoxysilane, reacting at 45°C for 8 hours, centrifuging after the reaction, taking the precipitate, adding ethanol and water 3 times the mass of the precipitate respectively, washing 4 times, and drying at 120°C for 2 hours to obtain modified cellulose nanocrystals; wherein the mass ratio of cellulose nanocrystals, ethanol, water and γ-aminopropyltriethoxysilane is 0.5:80:25:5; the modified multilayer graphene is prepared by the following steps: mixing carboxylated multilayer graphene oxide with water, ultrasonically dispersing for 4 hours, adding ferric chloride and ferrous chloride, stirring for 50 minutes, adding 1 mol / L NaOH aqueous solution to adjust the pH value to 11, reacting at 95°C for 6 hours, filtering after the reaction, taking the precipitate, adding 3 times the mass of the precipitate The multilayer graphene / Fe3O4 composite material was washed with water four times and vacuum dried at 65°C for 20 hours to obtain a multilayer graphene / Fe3O4 composite material; wherein the mass ratio of carboxylated multilayer graphene oxide, water, ferric chloride, and ferrous chloride was 1:200:0.3:0.8; the multilayer graphene / Fe3O4 composite material was mixed with acetonitrile, thionyl chloride and N,N-dimethylformamide were added, and the reaction was carried out at 65°C for 4 hours, and 2-amino-4,6-dichloropyrimidine was added and the reaction was continued at 65°C. 4h, sodium hydroxide and acetamide were added, and the reaction was continued at room temperature for another 12h. After the reaction was completed, the reaction was centrifuged, and the precipitate was taken and washed four times with ethanol and water in an amount three times the mass of the precipitate, respectively, and freeze-dried to obtain modified multilayer graphene; wherein the mass ratio of the multilayer graphene / Fe3O4 composite material, acetonitrile, thionyl chloride, N,N-dimethylformamide, 2-amino-4,6-dichloropyrimidine, sodium hydroxide, and acetamide was 0.1:300:6:0.4:6:4:3; Step (2): polypropylene glycol and isophorone diisocyanate are mixed, reacted at 85°C for 2h, dimethylolpropionic acid is added, the reaction is continued at 80°C for 2h, diethylene glycol, trimethylolpropane and dibutyltin dilaurate are added, and the reaction is again carried out at 75°C for 1h. After the reaction is completed, a waterborne polyurethane prepolymer is obtained; wherein the mass ratio of polypropylene glycol, isophorone diisocyanate, dimethylolpropionic acid, diethylene glycol, trimethylolpropane and dibutyltin dilaurate is 10:12:1.1:2.2:0.6:0.02; modified cellulose nanocrystals, The modified multilayer graphene and acetone were mixed, ultrasonically dispersed for 50 minutes, added to a waterborne polyurethane prepolymer, reacted at 50°C for 1 hour, triethylamine was added, and the reaction was continued at 40°C for 30 minutes. Water and ethylenediamine were added, and emulsification was carried out at a speed of 1600 r / min for 30 minutes. After the emulsification, the acetone was removed by rotary evaporation at 40°C to obtain a modified polyurethane composite emulsion; wherein the mass ratio of the modified cellulose nanocrystals, the modified multilayer graphene, acetone, the waterborne polyurethane prepolymer, triethylamine, water, and ethylenediamine was 0.4:0.4:12:30:0.9:100:0.7; Step (3), mixing silver, aluminum, copper, nickel, nano-silicon dioxide, and modified polyurethane composite emulsion, and ultrasonically dispersing for 50 minutes to obtain an electromagnetic induction coating material; wherein the mass ratio of silver, aluminum, copper, nickel, nano-silicon dioxide, and modified polyurethane composite emulsion is 12:10:10:8:6:200.

[0023] Example 2 This embodiment discloses a method for preparing an electromagnetic induction coating material, comprising the following steps: Step (1) preparing modified cellulose nanocrystals and modified multilayer graphene; the modified cellulose nanocrystals are prepared by the following steps: mixing cellulose nanocrystals, ethanol and water, ultrasonically dispersing for 10 minutes, adding γ-aminopropyltriethoxysilane, reacting at 35°C for 10 hours, centrifuging after the reaction, taking the precipitate, adding ethanol and water 5 times the mass of the precipitate respectively, washing twice, and drying at 100°C for 4 hours to obtain modified cellulose nanocrystals; wherein the mass ratio of cellulose nanocrystals, ethanol, water and γ-aminopropyltriethoxysilane is 0.5:60:15:3; the modified multilayer graphene is prepared by the following steps: mixing carboxylated multilayer graphene oxide with water, ultrasonically dispersing for 2 hours, adding ferric chloride and ferrous chloride, stirring for 30 minutes, adding 1 mol / L NaOH aqueous solution to adjust the pH value to 10, reacting at 85°C for 8 hours, filtering after the reaction, taking the precipitate, adding 5 times the mass of the precipitate The multilayer graphene / Fe3O4 composite material was washed with water twice and vacuum dried at 55°C for 24 hours to obtain a multilayer graphene / Fe3O4 composite material; wherein the mass ratio of carboxylated multilayer graphene oxide, water, ferric chloride, and ferrous chloride was 1:160:0.2:0.6; the multilayer graphene / Fe3O4 composite material was mixed with acetonitrile, thionyl chloride and N,N-dimethylformamide were added, and the reaction was carried out at 55°C for 6 hours, and 2-amino-4,6-dichloropyrimidine was added and the reaction was continued at 55°C. 6h, sodium hydroxide and acetamide were added, and the reaction was continued at room temperature for 10h. After the reaction was completed, the reaction was centrifuged, and the precipitate was taken and washed twice with ethanol and water 5 times the mass of the precipitate respectively, and freeze-dried to obtain modified multilayer graphene; wherein the mass ratio of the multilayer graphene / Fe3O4 composite material, acetonitrile, thionyl chloride, N,N-dimethylformamide, 2-amino-4,6-dichloropyrimidine, sodium hydroxide, and acetamide was 0.1:260:4:0.2:4:3:2; Step (2): polypropylene glycol and isophorone diisocyanate are mixed, reacted at 75°C for 4 hours, dimethylol propionic acid is added, the reaction is continued at 70°C for 4 hours, diethylene glycol, trimethylol propane and dibutyl tin dilaurate are added, and the reaction is again carried out at 65°C for 2 hours. After the reaction is completed, a waterborne polyurethane prepolymer is obtained; wherein the mass ratio of polypropylene glycol, isophorone diisocyanate, dimethylol propionic acid, diethylene glycol, trimethylol propane and dibutyl tin dilaurate is 10:10:0.9:2:0.4:0.01; modified cellulose nanocrystals, The modified multilayer graphene and acetone were mixed, ultrasonically dispersed for 30 minutes, added to a waterborne polyurethane prepolymer, reacted at 40°C for 2 hours, triethylamine was added, and the reaction was continued at 30°C for 50 minutes. Water and ethylenediamine were added, and emulsification was carried out at a speed of 1400 r / min for 50 minutes. After the emulsification, the acetone was removed by rotary evaporation at 30°C to obtain a modified polyurethane composite emulsion; wherein the mass ratio of the modified cellulose nanocrystals, the modified multilayer graphene, the acetone, the waterborne polyurethane prepolymer, the triethylamine, the water, and the ethylenediamine was 0.1:0.2:8:30:0.7:80:0.5; Step (3): mixing silver, aluminum, nano-silicon dioxide, and modified polyurethane composite emulsion, and ultrasonically dispersing for 30 minutes to obtain an electromagnetic induction coating material; wherein the mass ratio of silver, aluminum, nano-silicon dioxide, and modified polyurethane composite emulsion is 12:8:4:160.

[0024] Example 3 This embodiment discloses a method for preparing an electromagnetic induction coating material, comprising the following steps: Step (1) preparing modified cellulose nanocrystals and modified multilayer graphene; the modified cellulose nanocrystals are prepared by the following steps: mixing cellulose nanocrystals, ethanol and water, ultrasonically dispersing for 18 minutes, adding γ-aminopropyltriethoxysilane, reacting at 42°C for 8 hours, centrifuging after the reaction, taking the precipitate, adding ethanol and water 3 times the mass of the precipitate respectively, washing 4 times, and drying at 115°C for 2 hours to obtain modified cellulose nanocrystals; wherein the mass ratio of cellulose nanocrystals, ethanol, water and γ-aminopropyltriethoxysilane is 0.5:75:22:4.5; the modified multilayer graphene is prepared by the following steps: mixing carboxylated multilayer graphene oxide with water, ultrasonically dispersing for 4 hours, adding ferric chloride and ferrous chloride, stirring for 45 minutes, adding 1 mol / L NaOH aqueous solution to adjust the pH value to 11, reacting at 92°C for 6.5 hours, filtering after the reaction, taking the precipitate, adding water 3 times the mass of the precipitate The multilayer graphene / Fe3O4 composite material was washed four times and vacuum dried at 62°C for 21 hours to obtain a multilayer graphene / Fe3O4 composite material; wherein the mass ratio of carboxylated multilayer graphene oxide, water, ferric chloride, and ferrous chloride was 1:190:0.3:0.75; the multilayer graphene / Fe3O4 composite material was mixed with acetonitrile, thionyl chloride and N,N-dimethylformamide were added, and the reaction was carried out at 62°C for 4 hours, and 2-amino-4,6-dichloropyrimidine was added and the reaction was continued at 62°C for 4 hours. , adding sodium hydroxide and acetamide, reacting again at room temperature for 12 hours, after the reaction is completed, centrifuging, taking the precipitate, adding ethanol and water 3 times the mass of the precipitate respectively, washing 4 times, and freeze-drying to obtain modified multilayer graphene; wherein the mass ratio of the multilayer graphene / Fe3O4 composite material, acetonitrile, thionyl chloride, N,N-dimethylformamide, 2-amino-4,6-dichloropyrimidine, sodium hydroxide, and acetamide is 0.1:290:5.5:0.35:5.5:4:3; Step (2): polypropylene glycol and isophorone diisocyanate are mixed, reacted at 82°C for 2h, dimethylolpropionic acid is added, and the reaction is continued at 78°C for 2h, diethylene glycol, trimethylolpropane, and dibutyltin dilaurate are added, and the reaction is again carried out at 72°C for 1h. After the reaction is completed, a waterborne polyurethane prepolymer is obtained; wherein the mass ratio of polypropylene glycol, isophorone diisocyanate, dimethylolpropionic acid, diethylene glycol, trimethylolpropane, and dibutyltin dilaurate is 10:11.5:1.05:2.15:0.55:0.02; the modified cellulose nanocrystals are added. , modified multilayer graphene, and acetone were mixed, ultrasonically dispersed for 45 minutes, added to an aqueous polyurethane prepolymer, reacted at 48°C for 1 hour, triethylamine was added, and the reaction was continued at 38°C for 35 minutes, water and ethylenediamine were added, and emulsified at a speed of 1550r / min for 35 minutes. After the emulsification, acetone was removed by rotary evaporation at 38°C to obtain a modified polyurethane composite emulsion; wherein the mass ratio of modified cellulose nanocrystals, modified multilayer graphene, acetone, aqueous polyurethane prepolymer, triethylamine, water, and ethylenediamine is 0.3:0.35:11:30:0.85:95:0.65; Step (3): mixing silver, aluminum, nickel, nano-silicon dioxide, and modified polyurethane composite emulsion, and ultrasonically dispersing for 45 minutes to obtain an electromagnetic induction coating material; wherein the mass ratio of silver, aluminum, nickel, nano-silicon dioxide, and modified polyurethane composite emulsion is 12:12:11:5.5:190.

[0025] Example 4 This embodiment discloses a method for preparing an electromagnetic induction coating material, comprising the following steps: Step (1) preparing modified cellulose nanocrystals and modified multilayer graphene; the modified cellulose nanocrystals are prepared by the following steps: mixing cellulose nanocrystals, ethanol and water, ultrasonically dispersing for 15 minutes, adding γ-aminopropyltriethoxysilane, reacting at 40°C for 9 hours, centrifuging after the reaction, taking the precipitate, adding ethanol and water 4 times the mass of the precipitate respectively, washing 3 times, and drying at 110°C for 3 hours to obtain modified cellulose nanocrystals; wherein the mass ratio of cellulose nanocrystals, ethanol, water and γ-aminopropyltriethoxysilane is 0.5:70:20:4; the modified multilayer graphene is prepared by the following steps: mixing carboxylated multilayer graphene oxide with water, ultrasonically dispersing for 3 hours, adding ferric chloride and ferrous chloride, stirring for 40 minutes, adding 1 mol / L NaOH aqueous solution to adjust the pH value to 11, reacting at 90°C for 7 hours, filtering after the reaction, taking the precipitate, and washing with water 4 times the mass of the precipitate. 3 times, and vacuum dried at 60°C for 22 hours to obtain a multilayer graphene / Fe3O4 composite material; wherein the mass ratio of carboxylated multilayer graphene oxide, water, ferric chloride, and ferrous chloride is 1:180:0.25:0.7; the multilayer graphene / Fe3O4 composite material is mixed with acetonitrile, thionyl chloride and N,N-dimethylformamide are added, and the reaction is carried out at 60°C for 5 hours, and 2-amino-4,6-dichloropyrimidine is added, and the reaction is continued at 60°C for 5 hours. Sodium hydroxide and acetamide were added, and the mixture was reacted again at room temperature for 11 hours. After the reaction was completed, the mixture was centrifuged, and the precipitate was taken and washed three times with ethanol and water in an amount four times the mass of the precipitate, respectively, and freeze-dried to obtain modified multilayer graphene; wherein the mass ratio of the multilayer graphene / Fe3O4 composite material, acetonitrile, thionyl chloride, N,N-dimethylformamide, 2-amino-4,6-dichloropyrimidine, sodium hydroxide, and acetamide was 0.1:280:5:0.3:5:3.5:2.5; Step (2): polypropylene glycol and isophorone diisocyanate are mixed, reacted at 80°C for 3h, dimethylol propionic acid is added, and the reaction is continued at 75°C for 3h, diethylene glycol, trimethylol propane, and dibutyl tin dilaurate are added, and the reaction is continued at 70°C for 1.5h. After the reaction is completed, a waterborne polyurethane prepolymer is obtained; wherein the mass ratio of polypropylene glycol, isophorone diisocyanate, dimethylol propionic acid, diethylene glycol, trimethylol propane, and dibutyl tin dilaurate is 10:11:1:2.1:0.5:0.015; modified cellulose nanocrystals and modified The modified multilayer graphene and acetone were mixed, ultrasonically dispersed for 40 minutes, added to the waterborne polyurethane prepolymer, reacted at 45°C for 1.5 hours, triethylamine was added, and the reaction was continued at 35°C for 40 minutes. Water and ethylenediamine were added, and emulsified at a speed of 1500 r / min for 40 minutes. After the emulsification, the acetone was removed by rotary evaporation at 35°C to obtain a modified polyurethane composite emulsion; wherein the mass ratio of modified cellulose nanocrystals, modified multilayer graphene, acetone, waterborne polyurethane prepolymer, triethylamine, water, and ethylenediamine is 0.25:0.3:10:30:0.8:90:0.6; Step (3), mixing silver, aluminum, nickel, nano-silicon dioxide, and modified polyurethane composite emulsion, and ultrasonically dispersing for 40 minutes to obtain an electromagnetic induction coating material; wherein the mass ratio of silver, aluminum, nickel, nano-silicon dioxide, and modified polyurethane composite emulsion is 12:10:8:5:180.

[0026] Example 5 This embodiment discloses a method for preparing an electromagnetic induction coating material, comprising the following steps: Step (1) preparing modified cellulose nanocrystals and modified multilayer graphene; the modified cellulose nanocrystals are prepared by the following steps: mixing cellulose nanocrystals, ethanol and water, ultrasonically dispersing for 12 minutes, adding γ-aminopropyltriethoxysilane, reacting at 38°C for 10 hours, centrifuging after the reaction, taking the precipitate, adding ethanol and water 5 times the mass of the precipitate respectively, washing twice, and drying at 105°C for 4 hours to obtain modified cellulose nanocrystals; wherein the mass ratio of cellulose nanocrystals, ethanol, water and γ-aminopropyltriethoxysilane is 0.5:65:18:3.5; the modified multilayer graphene is prepared by the following steps: mixing carboxylated multilayer graphene oxide with water, ultrasonically dispersing for 2 hours, adding ferric chloride and ferrous chloride, stirring for 35 minutes, adding 1 mol / L NaOH aqueous solution to adjust the pH value to 10, reacting at 88°C for 7.5 hours, filtering after the reaction, taking the precipitate, adding water 5 times the mass of the precipitate The multilayer graphene / Fe3O4 composite material was washed twice and vacuum dried at 58°C for 23 hours to obtain a multilayer graphene / Fe3O4 composite material; wherein the mass ratio of carboxylated multilayer graphene oxide, water, ferric chloride, and ferrous chloride was 1:170:0.2:0.65; the multilayer graphene / Fe3O4 composite material was mixed with acetonitrile, thionyl chloride and N,N-dimethylformamide were added, and the reaction was carried out at 58°C for 6 hours, and 2-amino-4,6-dichloropyrimidine was added and the reaction was continued at 58°C for 6 hours. , adding sodium hydroxide and acetamide, reacting again at room temperature for 10 hours, after the reaction is completed, centrifuging, taking the precipitate, adding ethanol and water 5 times the mass of the precipitate respectively, washing twice, and freeze-drying to obtain modified multilayer graphene; wherein the mass ratio of the multilayer graphene / Fe3O4 composite material, acetonitrile, thionyl chloride, N,N-dimethylformamide, 2-amino-4,6-dichloropyrimidine, sodium hydroxide, and acetamide is 0.1:270:4.5:0.25:4.5:3:2; Step (2): polypropylene glycol and isophorone diisocyanate are mixed, reacted at 78°C for 4 hours, dimethylol propionic acid is added, and the reaction is continued at 72°C for 4 hours, diethylene glycol, trimethylol propane, and dibutyl tin dilaurate are added, and the reaction is continued at 68°C for 2 hours. After the reaction is completed, a waterborne polyurethane prepolymer is obtained; wherein the mass ratio of polypropylene glycol, isophorone diisocyanate, dimethylol propionic acid, diethylene glycol, trimethylol propane, and dibutyl tin dilaurate is 10:10.5:0.95:2.05:0.45:0.01; the modified cellulose nanoparticles are added. The modified cellulose nanocrystals, modified multilayer graphene and acetone were mixed, ultrasonically dispersed for 35 minutes, added to the waterborne polyurethane prepolymer, reacted at 42°C for 2 hours, triethylamine was added, and the reaction was continued at 32°C for 45 minutes. Water and ethylenediamine were added, and emulsification was carried out at a speed of 1450r / min for 45 minutes. After the emulsification, the acetone was removed by rotary evaporation at 32°C to obtain a modified polyurethane composite emulsion; wherein the mass ratio of modified cellulose nanocrystals, modified multilayer graphene, acetone, waterborne polyurethane prepolymer, triethylamine, water and ethylenediamine is 0.2:0.25:9:30:0.75:85:0.55; Step (3): mixing aluminum, nickel, nano-silica, and modified polyurethane composite emulsion, and ultrasonically dispersing for 35 minutes to obtain an electromagnetic induction coating material; wherein the mass ratio of aluminum, nickel, nano-silica, and modified polyurethane composite emulsion is 13:12:4.5:170.

[0027] Comparative Example 1 This comparative example discloses a method for preparing an electromagnetic induction coating material, comprising the following steps: Step (1), preparing modified cellulose nanocrystals and modified multilayer graphene; the modified cellulose nanocrystals are prepared by the following steps: mixing cellulose nanocrystals, ethanol and water, ultrasonically dispersing for 10 minutes, adding γ-aminopropyltriethoxysilane, reacting at 35°C for 10 hours, centrifuging after the reaction, taking the precipitate, adding ethanol and water 5 times the mass of the precipitate respectively, washing twice, and drying at 100°C for 4 hours to obtain modified cellulose nanocrystals; wherein the mass ratio of cellulose nanocrystals, ethanol, water and γ-aminopropyltriethoxysilane is 0.5:60:15:3; the modified multilayer graphene is prepared by the following steps: carboxylated multilayer Graphene oxide is mixed with acetonitrile, thionyl chloride and N,N-dimethylformamide are added, the reaction is carried out at 55°C for 6 hours, 2-amino-4,6-dichloropyrimidine is added, the reaction is continued at 55°C for 6 hours, sodium hydroxide and acetamide are added, and the reaction is again carried out at room temperature for 10 hours. After the reaction is completed, centrifugation is performed, and the precipitate is taken, and ethanol and water are added twice with a mass of 5 times the mass of the precipitate, respectively, and washed twice, and freeze-dried to obtain modified multilayer graphene; wherein the mass ratio of carboxylated multilayer graphene oxide, acetonitrile, thionyl chloride, N,N-dimethylformamide, 2-amino-4,6-dichloropyrimidine, sodium hydroxide, and acetamide is 0.1:260:4:0.2:4:3:2; Step (2): polypropylene glycol and isophorone diisocyanate are mixed, reacted at 75°C for 4 hours, dimethylol propionic acid is added, the reaction is continued at 70°C for 4 hours, diethylene glycol, trimethylol propane and dibutyl tin dilaurate are added, and the reaction is again carried out at 65°C for 2 hours. After the reaction is completed, a waterborne polyurethane prepolymer is obtained; wherein the mass ratio of polypropylene glycol, isophorone diisocyanate, dimethylol propionic acid, diethylene glycol, trimethylol propane and dibutyl tin dilaurate is 10:10:0.9:2:0.4:0.01; modified cellulose nanocrystals, The modified multilayer graphene and acetone were mixed, ultrasonically dispersed for 30 minutes, added to a waterborne polyurethane prepolymer, reacted at 40°C for 2 hours, triethylamine was added, and the reaction was continued at 30°C for 50 minutes. Water and ethylenediamine were added, and emulsification was carried out at a speed of 1400 r / min for 50 minutes. After the emulsification, the acetone was removed by rotary evaporation at 30°C to obtain a modified polyurethane composite emulsion; wherein the mass ratio of the modified cellulose nanocrystals, the modified multilayer graphene, the acetone, the waterborne polyurethane prepolymer, the triethylamine, the water, and the ethylenediamine was 0.1:0.2:8:30:0.7:80:0.5; Step (3): mixing silver, aluminum, nano-silicon dioxide, and modified polyurethane composite emulsion, and ultrasonically dispersing for 30 minutes to obtain an electromagnetic induction coating material; wherein the mass ratio of silver, aluminum, nano-silicon dioxide, and modified polyurethane composite emulsion is 12:8:4:160.

[0028] Comparative Example 2 This comparative example discloses a method for preparing an electromagnetic induction coating material, comprising the following steps: Step (1), mixing cellulose nanocrystals, ethanol, and water, ultrasonically dispersing for 10 minutes, adding γ-aminopropyltriethoxysilane, reacting at 35°C for 10 hours, centrifuging after the reaction, taking the precipitate, adding ethanol and water 5 times the mass of the precipitate respectively, washing twice, and drying at 100°C for 4 hours to obtain modified cellulose nanocrystals; wherein the mass ratio of cellulose nanocrystals, ethanol, water, and γ-aminopropyltriethoxysilane is 0.5:60:15:3; Step (2): polypropylene glycol and isophorone diisocyanate are mixed, reacted at 75°C for 4 hours, dimethylolpropionic acid is added, the reaction is continued at 70°C for 4 hours, diethylene glycol, trimethylolpropane, and dibutyltin dilaurate are added, and the reaction is again carried out at 65°C for 2 hours. After the reaction is completed, a waterborne polyurethane prepolymer is obtained; wherein the mass ratio of polypropylene glycol, isophorone diisocyanate, dimethylolpropionic acid, diethylene glycol, trimethylolpropane, and dibutyltin dilaurate is 10:10:0.9:2:0.4:0.01; The modified cellulose nanocrystals and acetone were mixed, ultrasonically dispersed for 30 minutes, added to a waterborne polyurethane prepolymer, reacted at 40°C for 2 hours, triethylamine was added, and the reaction was continued at 30°C for 50 minutes. Water and ethylenediamine were added, and emulsified at a speed of 1400 r / min for 50 minutes. After the emulsification, the acetone was removed by rotary evaporation at 30°C to obtain a modified polyurethane composite emulsion; wherein the mass ratio of the modified cellulose nanocrystals, acetone, waterborne polyurethane prepolymer, triethylamine, water, and ethylenediamine was 0.1:8:30:0.7:80:0.5; Step (3): mixing silver, aluminum, nano-silicon dioxide, and modified polyurethane composite emulsion, and ultrasonically dispersing for 30 minutes to obtain an electromagnetic induction coating material; wherein the mass ratio of silver, aluminum, nano-silicon dioxide, and modified polyurethane composite emulsion is 12:8:4:160.

[0029] Comparative Example 3 This comparative example discloses a method for preparing an electromagnetic induction coating material, comprising the following steps: Step (1), mixing carboxylated multilayer graphene oxide with water, ultrasonically dispersing for 2h, adding ferric chloride and ferrous chloride, stirring for 30min, adding 1mol / L NaOH aqueous solution to adjust to a pH value of 10, reacting at 85°C for 8h, filtering after the reaction, taking the precipitate, adding 5 times the mass of the precipitate to wash twice, and vacuum drying at 55°C for 24h to obtain a multilayer graphene / Fe3O4 composite material; wherein the mass ratio of carboxylated multilayer graphene oxide, water, ferric chloride, and ferrous chloride is 1:160:0.2:0.6; mixing the multilayer graphene / Fe3O4 composite material with acetonitrile, adding Thionyl chloride and N,N-dimethylformamide are reacted at 55°C for 6 hours, 2-amino-4,6-dichloropyrimidine is added, the reaction is continued at 55°C for 6 hours, sodium hydroxide and acetamide are added, and the reaction is again carried out at room temperature for 10 hours. After the reaction is completed, the mixture is centrifuged, the precipitate is collected, and the mixture is washed twice with ethanol and water (5 times the mass of the precipitate), respectively, and freeze-dried to obtain modified multilayer graphene; wherein the mass ratio of the multilayer graphene / Fe3O4 composite material, acetonitrile, thionyl chloride, N,N-dimethylformamide, 2-amino-4,6-dichloropyrimidine, sodium hydroxide, and acetamide is 0.1:260:4:0.2:4:3:2; Step (2): polypropylene glycol and isophorone diisocyanate are mixed, reacted at 75°C for 4 hours, dimethylolpropionic acid is added, the reaction is continued at 70°C for 4 hours, diethylene glycol, trimethylolpropane, and dibutyltin dilaurate are added, and the reaction is again carried out at 65°C for 2 hours. After the reaction is completed, a waterborne polyurethane prepolymer is obtained; wherein the mass ratio of polypropylene glycol, isophorone diisocyanate, dimethylolpropionic acid, diethylene glycol, trimethylolpropane, and dibutyltin dilaurate is 10:10:0.9:2:0.4:0.01 The modified multilayer graphene and acetone were mixed, ultrasonically dispersed for 30 minutes, added to a waterborne polyurethane prepolymer, reacted at 40°C for 2 hours, triethylamine was added, and the reaction was continued at 30°C for 50 minutes. Water and ethylenediamine were added, and emulsified at a speed of 1400 r / min for 50 minutes. After the emulsification, the acetone was removed by rotary evaporation at 30°C to obtain a modified polyurethane composite emulsion; wherein the mass ratio of the modified multilayer graphene, acetone, waterborne polyurethane prepolymer, triethylamine, water, and ethylenediamine was 0.2:8:30:0.7:80:0.5; Step (3): mixing silver, aluminum, nano-silicon dioxide, and modified polyurethane composite emulsion, and ultrasonically dispersing for 30 minutes to obtain an electromagnetic induction coating material; wherein the mass ratio of silver, aluminum, nano-silicon dioxide, and modified polyurethane composite emulsion is 12:8:4:160.

[0030] In the above examples and comparative examples: cellulose nanocrystals were obtained from Shanghai MacLean Biochemical Technology Co., Ltd., product number: C909405; ethanol was obtained from Sinopharm Chemical Reagent Co., Ltd., CAS number: 64-17-5; γ-aminopropyltriethoxysilane was obtained from Shanghai Titan Technology Co., Ltd., CAS number: 919-30-2; carboxylated multilayer graphene oxide was prepared by the following steps: citric acid, multilayer graphene oxide, and water were mixed, ultrasonically dispersed for 60 minutes, reacted at 60°C for 6 hours, and after the reaction, 0.The pH value was adjusted to 8 with a 1 mol / L aqueous NaOH solution, and the mixture was centrifuged. The precipitate was washed four times with ethanol and water (3 times the mass of the precipitate), respectively, and freeze-dried to obtain carboxylated multilayer graphene oxide. The mass ratio of citric acid, multilayer graphene oxide, and water was 10:5:180. Multilayer graphene oxide was obtained from Shanghai Yien Chemical Technology Co., Ltd., CAS No. 7782-42-5, Product No. R166768. Ferric chloride was obtained from Sinopharm Chemical Reagent Co., Ltd., CAS No. 10025-77-1, molecular formula: FeCl3·6H2O. Ferrous chloride was obtained from Sinopharm Chemical Reagent Co., Ltd. Co., Ltd., CAS No.: 13478-10-9, molecular formula: FeCl2·4H2O; acetonitrile from Shanghai Yaokan Chemical Co., Ltd., CAS No.: 75-05-8; thionyl chloride from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 7719-09-7; N,N-dimethylformamide from Shanghai Mairui Biochemical Technology Co., Ltd., CAS No.: 68-12-2; 2-amino-4,6-dichloropyrimidine from Shanghai Haohong Biopharmaceutical Technology Co., Ltd., CAS No.: 56-05-3; acetamide from Shanghai Hongrui Chemical Co., Ltd., CAS No.: 60-35-5; Propylene glycol was obtained from Shanghai Titan Technology Co., Ltd., CAS No.: 25322-69-4, Mn=1000; isophorone diisocyanate was obtained from Shanghai Titan Technology Co., Ltd., CAS No.: 4098-71-9; dimethylolpropionic acid was obtained from Shanghai Titan Technology Co., Ltd., CAS No.: 4767-03-7; diethylene glycol was obtained from Sinopharm Chemical Reagent Co., Ltd., CAS No.: 111-46-6; trimethylolpropane was obtained from Sinopharm Chemical Reagent Co., Ltd., CAS No.: 77-99-6; dibutyltin dilaurate was obtained from Sinopharm Chemical Reagent Co., Ltd., CAS No.: 77-58-7; acetone was obtained from The materials were obtained from Sinopharm Chemical Reagent Company, CAS number: 67-64-1; triethylamine was obtained from Shanghai Titan Technology Co., Ltd., CAS number: 121-44-8; ethylenediamine was obtained from Sinopharm Chemical Reagent Company, CAS number: 107-15-3; nanosilica was obtained from Shanghai MacLean Biochemical Technology Co., Ltd., CAS number: 60676-86-0, product number: S817575; the metal powders silver, aluminum, copper, and nickel were all commercially available and were nanoparticles. The particle size of the silver particles was 30 nm, the particle size of the aluminum particles was 100 nm, the particle size of the copper particles was 50 nm, and the particle size of the nickel particles was 100 nm.

[0031] Test example (1) Comprehensive performance test For the electromagnetic induction coating materials prepared in Examples 1-5 and Comparative Examples 1-3, a 120 mm × 50 mm × 1 mm tinplate was used as a sample substrate. The surface was cleaned with acetone and ethanol, then polished with 400# sandpaper, cleaned with acetone, and naturally dried. The electromagnetic induction coating material was then applied to the treated and dried tinplate, dried and cured at room temperature for 7 days to obtain a coating film. The coating film was then subjected to comprehensive performance testing. Specific test results are shown in Table 1:

[0032] The tests of the various indicators in Table 1 are based on the following standards: hardness is measured according to GB / T 6739-1996 "Determination of Hardness of Coating Films by Pencil Method"; impact strength is measured according to GB / T 1732-1993 "Determination of Impact Resistance of Paint Films"; salt spray resistance is measured according to GB / T 1771-2007 "Paints and Varnishes - Determination of Resistance to Neutral Salt Spray" with a test period of 30 days; conductivity is measured according to ASTM F390-11 "Standard Test Method for Sheet Resistance of Metal Films by Collinear Four-Probe Method".

[0033] According to the test results in Table 1, it can be seen that the electromagnetic induction coating material prepared by the present invention has excellent mechanical properties, corrosion resistance and electromagnetic induction efficiency.

[0034] In Comparative Example 1, magnetic nanoparticles Fe3O4 are not generated on the surface of the multilayer graphene. Due to the reduction of nanoparticles, the mechanical properties of the coating material are reduced, so the hardness and impact strength of Comparative Example 1 are worse than those of the embodiment. At the same time, due to the lack of electro-magnetic synergy and electronic coupling between Fe3O4 and multilayer graphene, the electromagnetic induction efficiency of the coating material is reduced, so the conductivity of Comparative Example 1 is lower than that of the embodiment.

[0035] In Comparative Example 2, the polyurethane emulsion was not reacted with the multilayer graphene. Due to the lack of high conductivity of multilayer graphene, it was unable to produce a synergistic conductive effect with the metal powder, and its unique two-dimensional structure brought shielding and anti-corrosion properties, resulting in a decrease in the mechanical properties, corrosion resistance, and electromagnetic induction properties of the coating material. Therefore, the hardness, impact strength, salt spray resistance, and electrical conductivity of Comparative Example 2 were worse than those of the embodiment.

[0036] In Comparative Example 3, the polyurethane emulsion was not reacted with the cellulose nanocrystals. Due to the lack of the reinforcing effect of the cellulose nanocrystals, the mechanical properties of the coating material decreased, so the hardness and impact strength of Comparative Example 3 were worse than those of the examples. Due to the lack of the barrier effect of the cellulose nanocrystals on gas and water molecules, the corrosion resistance of the coating material decreased, so the salt spray resistance of Comparative Example 3 was worse than that of the examples.

[0037] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an electromagnetic induction coating material, characterized in that: The following steps are involved: Step (1), mixing the carboxylated multilayer graphene oxide with water, adding ferric chloride and ferrous chloride, reacting, and after the reaction is completed, post-processing to obtain a multilayer graphene / Fe3O4 composite material; mixing the multilayer graphene / Fe3O4 composite material with acetonitrile, adding thionyl chloride and N,N-dimethylformamide, reacting, adding 2-amino-4,6-dichloropyrimidine, continuing the reaction, adding sodium hydroxide and acetamide, reacting again, and after the reaction is completed, post-processing to obtain a modified multilayer graphene; Step (2), mixing the modified cellulose nanocrystals, modified multilayer graphene, and acetone, adding the mixture to the waterborne polyurethane prepolymer, reacting the mixture, adding triethylamine, continuing the reaction, adding water and ethylenediamine, emulsifying the mixture, and post-treating the mixture to obtain a modified polyurethane composite emulsion; Step (3): mixing the metal powder, nano-silicon dioxide and modified polyurethane composite emulsion, and ultrasonically dispersing them to obtain an electromagnetic induction coating material.

2. The method for preparing an electromagnetic induction coating material according to claim 1, characterized in that: In the step (1), the mass ratio of carboxylated multilayer graphene oxide, water, ferric chloride, and ferrous chloride is 1:(160-200):(0.2-0.3):(0.6-0.8); when preparing the multilayer graphene / Fe3O4 composite material, the reaction conditions are: reaction at pH=10-11 and temperature of 85-95°C for 6-8h.

3. The method for preparing an electromagnetic induction coating material according to claim 1, characterized in that: In the step (1), the mass ratio of the multilayer graphene / Fe3O4 composite material, acetonitrile, thionyl chloride, N,N-dimethylformamide, 2-amino-4,6-dichloropyrimidine, sodium hydroxide, and acetamide is 0.1:(260-300):(4-6):(0.2-0.4):(4-6):(3-4):(2-3); when preparing the modified multilayer graphene, the reaction conditions are: reacting at a temperature of 55-65°C for 4-6 hours; continuing the reaction conditions are: continuing the reaction at a temperature of 55-65°C for 4-6 hours; and re-reacting conditions are: reacting again at room temperature for 10-12 hours.

4. The method for preparing an electromagnetic induction coating material according to claim 1, characterized in that: In the step (2), the mass ratio of modified cellulose nanocrystals, modified multilayer graphene, acetone, waterborne polyurethane prepolymer, triethylamine, water, and ethylenediamine is (0.1-0.4):(0.2-0.4):(8-12):30:(0.7-0.9):(80-100):(0.5-0.7); the reaction conditions are: reaction at a temperature of 40-50°C for 1-2h; the continued reaction conditions are: continued reaction at a temperature of 30-40°C for 30-50min; and the emulsification conditions are: emulsification at a speed of 1400-1600r / min for 30-50min.

5. The method for preparing an electromagnetic induction coating material according to claim 1, characterized in that: In step (2), the modified cellulose nanocrystals are prepared by the following steps: mixing cellulose nanocrystals, ethanol, and water, adding γ-aminopropyltriethoxysilane, reacting, and after the reaction is completed, post-treating to obtain modified cellulose nanocrystals; wherein the mass ratio of cellulose nanocrystals, ethanol, water, and γ-aminopropyltriethoxysilane is 0.5:(60-80):(15-25):(3-5), and the reaction conditions are: reacting at a temperature of 35-45°C for 8-10 hours.

6. The method for preparing an electromagnetic induction coating material according to claim 1, characterized in that: In the step (2), the waterborne polyurethane prepolymer is prepared by the following steps: mixing polypropylene glycol and isophorone diisocyanate, reacting, adding dimethylolpropionic acid, continuing the reaction, adding diethylene glycol, trimethylolpropane, and dibutyltin dilaurate, reacting again, and obtaining a waterborne polyurethane prepolymer after the reaction is completed.

7. The method for preparing an electromagnetic induction coating material according to claim 6, characterized in that: When preparing the waterborne polyurethane prepolymer in step (2), the mass ratio of polypropylene glycol, isophorone diisocyanate, dimethylolpropionic acid, diethylene glycol, trimethylolpropane, and dibutyltin dilaurate is 10:(10-12):(0.9-1.1):(2-2.2):(0.4-0.6):(0.01-0.02); the reaction conditions are: react at a temperature of 75-85°C for 2-4 hours; the continued reaction conditions are: continue to react at a temperature of 70-80°C for 2-4 hours; and the second reaction conditions are: react again at a temperature of 65-75°C for 1-2 hours.

8. The method for preparing an electromagnetic induction coating material according to claim 1, characterized in that: In the step (3), the metal powder is a mixture of one or more of silver, aluminum, copper, and nickel; and the mass ratio of the metal powder, nano-silicon dioxide, and modified polyurethane composite emulsion is (20-40):(4-6):(160-200).

9. An electromagnetic induction coating material prepared by the method for preparing an electromagnetic induction coating material according to any one of claims 1 to 8.

10. Use of the electromagnetic induction coating material according to claim 9 in ceramics and glassware.

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