A method for preparing a microsheet graphene electric heating ink

Abstract

The application is suitable for the technical field of electrothermal ink, and provides a preparation method of microsheet graphene electrothermal ink, the ink comprises the following raw materials in parts by weight: 18-25 parts of microsheet graphene, 12-18 parts of modified epoxy resin, 8-12 parts of polyethylene glycol dipolyacrylate, 5-8 parts of gamma-aminopropyl triethoxysilane, 6-10 parts of modified carbon black, 3-5 parts of azobisisobutyronitrile, 2-4 parts of polyether modified silicone oil, 4-7 parts of conductive additive, and 25-35 parts of deionized water. Through raw material modification and process optimization, the problems of uneven dispersion of microsheet graphene, insufficient ink bonding strength and poor electrothermal performance are solved, the prepared ink has low volume resistivity, fast heating rate, high bonding strength and excellent stability, and can be widely applied in fields of building heating, electronic equipment temperature control, medical care and the like.

Description

Technical Field

[0001] This invention relates to the field of electrothermal ink technology, specifically a method for preparing micro-graphene electrothermal ink. Background Technology

[0002] With the rapid development of electrothermal technology, electrothermal ink, as a new type of functional material, has gained widespread attention in fields such as building heating, electronic equipment temperature control, and healthcare due to its convenient processability and excellent electrothermal conversion efficiency. The core performance of electrothermal ink mainly depends on the conductivity, dispersibility, and compatibility with the matrix material of the conductive filler. Currently, most electrothermal inks on the market use carbon black and graphite as conductive fillers. However, these inks suffer from problems such as low electrothermal conversion efficiency, slow heating rate, and poor stability. Micro-graphene, as a two-dimensional material with ultra-high conductivity and thermal conductivity, is considered an ideal filler for preparing high-performance electrothermal inks. However, the surface of micro-graphene is inert and has poor compatibility with organic matrix materials, making it prone to agglomeration, resulting in uneven dispersion in the ink and affecting the conductivity and electrothermal stability of the ink. At the same time, traditional electrothermal inks have insufficient bonding strength and are prone to peeling and cracking during long-term use, limiting their service life and application range.

[0003] To address the aforementioned issues, Chinese patent CN116904067A discloses a graphene electrothermal ink, its preparation method, and its applications. This ink is prepared using conductive fillers, elastic fillers, solvents, dispersants, and additives as raw materials, and exhibits good conductivity and heating uniformity. However, the adhesive strength and high-temperature stability of this ink still need improvement, and the dispersion of graphene in the matrix requires further optimization.

[0004] Therefore, in view of the above situation, there is an urgent need to provide a method for preparing micro-graphene electrothermal ink to overcome the shortcomings in current practical applications. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing micro-graphene electrothermal ink, which effectively solves the problems in the background art.

[0006] This invention is achieved by a method for preparing micro-graphene electrothermal ink, wherein the ink comprises the following raw materials in parts by weight:

[0007] 18-25 parts graphene flakes, 12-18 parts modified epoxy resin, 8-12 parts polyethylene glycol diacrylate, 5-8 parts γ-aminopropyltriethoxysilane, 6-10 parts modified carbon black, 3-5 parts azobisisobutyronitrile, 2-4 parts polyether modified silicone oil, 4-7 parts conductive additives, 25-35 parts deionized water;

[0008] The modified epoxy resin is prepared by reacting epoxy resin with maleic anhydride under the action of a catalyst. The modified carbon black is prepared by oxidizing carbon black with nitric acid and then grafting it with 3-aminopropyltriethoxysilane.

[0009] As a further aspect of the present invention: the conductive additive is any one or more of acetylene black, superconducting carbon black, and carbon fiber, and the mass ratio of each component is 1:1-3 when mixed.

[0010] As a further aspect of the present invention, the preparation method of the modified epoxy resin includes the following steps: S1: Weigh epoxy resin, maleic anhydride and triphenylphosphine according to the mass ratio of 10:3-4:0.5-1. Add epoxy resin to xylene and stir until completely dissolved to obtain epoxy resin solution. The solid-liquid ratio of epoxy resin to xylene is 1g:4-6mL. S2: Add maleic anhydride and triphenylphosphine sequentially to the epoxy resin solution. Under a nitrogen protective atmosphere, stir and heat to 90-100℃, and react at a constant temperature for 4-6 hours. During this period, take samples regularly to detect the acid value of the system. Stop the reaction when the acid value stabilizes at 85-95 mgKOH / g. S3: After the reaction is complete, cool the system to 40-50℃ and perform vacuum distillation to remove the xylene solvent; S4: Add 3-5 times the volume of anhydrous ethanol to the distilled product, stir and wash for 10-15 minutes, let stand to separate into layers, filter, collect the filter cake, and repeat the washing 2-3 times. S5: Place the washed filter cake in a vacuum drying oven and dry for 3-5 hours until constant weight is achieved. Then collect the product to obtain the modified epoxy resin.

[0011] As a further aspect of the present invention: the epoxy resin is any one of bisphenol A epoxy resin and bisphenol F epoxy resin, and the epoxy value is 0.4-0.6 eq / 100g.

[0012] As a further aspect of the present invention, the method for preparing the modified carbon black includes the following steps: S1: Place the carbon black in a vacuum drying oven to dry and remove surface adsorbed water. Add the dried carbon black to concentrated nitric acid with a mass fraction of 65%-68% at a solid-liquid ratio of 1g:10-15mL. Place the mixture in a constant temperature water bath and react at 70-80℃ and a stirring speed of 250-300r / min for 2-3 hours. During this period, use ultrasonic dispersion for 5 minutes every 20 minutes. S2: After the reaction is complete, the reaction solution is cooled to room temperature and filtered using a vacuum filtration device. The filter cake is repeatedly washed with deionized water until the pH of the washing solution is 6.8-7.2. The washed filter cake is placed in a forced-air drying oven and dried at 95-105℃ for 5-7 hours to obtain carbon black oxide. S3: Weigh carbon black and 3-aminopropyltriethoxysilane at a mass ratio of 1:0.8-1.2. Disperse the carbon black in anhydrous ethanol at a solid-liquid ratio of 1g:15-25mL. Disperse at a stirring speed of 300-400r / min for 20-30min to obtain a carbon black dispersion. S4: Add 3-aminopropyltriethoxysilane dropwise to the carbon black dispersion at a rate of 1-2 drops / s. After the addition is complete, raise the temperature to 65-75℃ and keep the reaction in a reflux reflux apparatus for 3-5 hours, while maintaining a constant stirring speed during the reaction. S5: After the reaction is complete, cool to room temperature, filter under vacuum, wash the filter cake 2-3 times with anhydrous ethanol, place the filter cake in a vacuum drying oven and dry for 4-6 hours until constant weight is reached, then collect the product to obtain modified carbon black.

[0013] As a further aspect of the present invention: in step S1, the carbon black is either acetylene black or conductive carbon black, with a particle size of 20-50 nm and a specific surface area of ​​80-120 m². 2 / g.

[0014] As a further aspect of the present invention: In step S3, during the dispersion process of the carbon black oxide dispersion, the mixture is first stirred at 300-350 r / min for 10-15 min, and then heated to 40-50℃ and stirred at 400 r / min for 10-15 min.

[0015] As a further aspect of the present invention, it includes the following steps:

[0016] Step 1: Weigh out the following components by weight: micro-graphene flakes, modified epoxy resin, polyethylene glycol diacrylate, γ-aminopropyltriethoxysilane, modified carbon black, azobisisobutyronitrile, polyether-modified silicone oil, and conductive additives. Add them sequentially to a high-shear mixer, close the feed inlet, purge the air inside the mixer with nitrogen to maintain a nitrogen atmosphere, set the stirring speed to 350-450 r / min, the heating rate to 2-3℃ / min, heat to 50-60℃, and maintain the temperature for 3-4 hours. During this period, stop the machine every 40 minutes to take samples and observe the uniformity of the system to obtain the ink premix. Step 2: Slowly add the metered deionized water to the ink premix while maintaining a stirring speed of 200-250 r / min. After the addition is complete, transfer the mixture to a high-speed disperser and set the speed to 800-1000 r / min. Disperse for 1-2 hours, and use a laser particle size analyzer to check the particle size of the system every 30 minutes during this period. Step 3: Transfer the high-speed dispersed material to a sand mill, set the grinding medium to zirconia beads with a particle size of 0.8-1.2 mm, the mass ratio of material to zirconia beads to 1:3-5, the grinding speed to 2000-2500 r / min, and the grinding time to 2-3 h. During this period, take samples every 30 min to test the particle size until the particle size of the entire system is less than 5 μm. Step 4: After grinding, filter the solution using a 200-300 mesh screen to remove impurities and incompletely dispersed agglomerates. Collect the filtrate, which is the micro-graphene electrothermal ink. Place it in a sealed container and store it at 25-30℃ and 40%-60% relative humidity.

[0017] As a further aspect of the present invention: in step one, the nitrogen gas introduction rate is 0.5-1 L / min, and the internal pressure is maintained at 0.02-0.05 MPa during the replacement process.

[0018] As a further aspect of the present invention: the graphene microsheets have a sheet diameter of 1-5 μm, a thickness of 0.5-2 nm, a carbon content of ≥99%, and a defect density of ≤0.01 defects / nm. 2 .

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention effectively solves the problems of uneven dispersion and poor compatibility of micro-graphene in ink matrix by modifying epoxy resin and carbon black. The modified raw materials and micro-graphene work synergistically to construct a complete conductive network, significantly improving the conductivity and electrothermal conversion efficiency of the ink. By limiting the specific types and key parameters of epoxy resin, carbon black, and micro-graphene, and optimizing the process details of each preparation step, the stability and controllability of ink performance are ensured. Through the reasonable ratio and cross-linking reaction of each component, a dense three-dimensional network structure is formed, enhancing the adhesion strength and mechanical properties of the ink and effectively preventing peeling and cracking during long-term use. At the same time, the electrothermal ink prepared by this invention has excellent stability and high-temperature resistance, fast heating rate and uniform heating, greatly expanding its application range in building heating, electronic equipment, medical care and other fields, and has good market prospects. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The present invention will be further explained below with reference to specific embodiments.

[0022] This invention provides a method for preparing micro-graphene electrothermal ink, wherein the ink comprises the following raw materials in parts by weight: 18-25 parts micro-graphene, 12-18 parts modified epoxy resin, 8-12 parts polyethylene glycol diacrylate, 5-8 parts γ-aminopropyltriethoxysilane, 6-10 parts modified carbon black, 3-5 parts azobisisobutyronitrile, 2-4 parts polyether-modified silicone oil, 4-7 parts conductive additives, and 25-35 parts deionized water; the modified epoxy resin is prepared by reacting epoxy resin with maleic anhydride under the action of a catalyst; the modified carbon black is prepared by oxidizing carbon black with nitric acid and then grafting it with 3-aminopropyltriethoxysilane.

[0023] The conductive additive is any one or a mixture of two or more of acetylene black, superconducting carbon black, and carbon fiber, with the mass ratio of each component being 1:1-3 when mixed.

[0024] In a more specific example, the method for preparing the modified epoxy resin includes the following steps: S1: Weigh epoxy resin, maleic anhydride, and triphenylphosphine according to a mass ratio of 10:3-4:0.5-1. Add the epoxy resin to xylene and stir until completely dissolved to obtain an epoxy resin solution. The solid-liquid ratio of epoxy resin to xylene is 1g:4-6mL. The epoxy resin is either bisphenol A epoxy resin or bisphenol F epoxy resin, and has an epoxy value of 0.4-0.6eq / 100g. S2: Maleic anhydride and triphenylphosphine are added sequentially to the epoxy resin solution. Under a nitrogen protective atmosphere, the temperature is raised to 90-100℃ with a stirring speed of 200-300r / min and the reaction is kept at a constant temperature for 4-6h. During this period, the acid value of the system is measured every 30min. The reaction is stopped when the acid value is stable at 85-95mgKOH / g. S3: After the reaction is complete, cool the system to 40-50℃ and perform vacuum distillation at a pressure of -0.08 to -0.09 MPa, a temperature of 70-80℃, and a time of 1.5-2 hours to remove xylene solvent. S4: Add 3-5 times the volume of anhydrous ethanol to the distilled product, stir and wash for 10-15 minutes, let stand to separate into layers, filter, collect the filter cake, and repeat the washing 2-3 times. S5: Place the washed filter cake in a vacuum drying oven and dry it for 3-5 hours under vacuum conditions of -0.07~-0.08MPa and temperature of 75-85℃ until constant weight is reached. Collect the product to obtain modified epoxy resin.

[0025] In a more specific example, the method for preparing the modified carbon black includes the following steps: S1: Place the carbon black in a vacuum drying oven and dry it at 80-90℃ for 2-3 hours to remove surface adsorbed water. Add the dried carbon black to concentrated nitric acid (65%-68% by mass) at a solid-liquid ratio of 1g:10-15mL. Place the mixture in a constant temperature water bath and react it at 70-80℃ and a stirring speed of 250-300r / min for 2-3 hours. During this reaction, use ultrasonic-assisted dispersion for 5 minutes every 20 minutes, with an ultrasonic power of 150-200W. The carbon black is either acetylene black or conductive carbon black, with a particle size of 20-50nm and a specific surface area of ​​80-120m². 2 / g; S2: After the reaction is complete, the reaction solution is cooled to room temperature and filtered using a vacuum filtration device. The filter cake is repeatedly washed with deionized water until the pH of the washing solution is 6.8-7.2. The washed filter cake is placed in a forced-air drying oven and dried at 95-105℃ for 5-7 hours to obtain carbon black oxide. S3: Weigh carbon black oxide and 3-aminopropyltriethoxysilane at a mass ratio of 1:0.8-1.2. Disperse the carbon black oxide in anhydrous ethanol at a solid-liquid ratio of 1g:15-25mL. Disperse the carbon black oxide in anhydrous ethanol at a stirring speed of 300-400r / min for 20-30min to obtain a carbon black oxide dispersion. During the dispersion process, first stir at 300-350r / min for 10-15min, then heat to 40-50℃ and stir at 400r / min for 10-15min to ensure that the carbon black oxide is uniformly dispersed and free from agglomeration. S4: Add 3-aminopropyltriethoxysilane dropwise to the carbon black dispersion at a rate of 1-2 drops / s. After the addition is complete, raise the temperature to 65-75℃ and keep the reaction in a reflux apparatus for 3-5 hours, while maintaining the stirring speed at 250-300 r / min. S5: After the reaction is complete, cool to room temperature, filter under vacuum, wash the filter cake 2-3 times with anhydrous ethanol for 10-15 minutes each time, place the filter cake in a vacuum drying oven and dry at 85-95℃ and a vacuum of -0.06 to -0.07 MPa for 4-6 hours until constant weight is reached, then collect the product to obtain modified carbon black.

[0026] In a more specific example, the preparation method of micro-graphene electrothermal ink includes the following steps:

[0027] Step 1: Weigh out the following components by weight: micro-graphene flakes, modified epoxy resin, polyethylene glycol diacrylate, γ-aminopropyltriethoxysilane, modified carbon black, azobisisobutyronitrile, polyether modified silicone oil, and conductive additives. Add them sequentially to a high-shear mixer, close the feed inlet, and purge the air in the mixer with nitrogen 3-5 times, each purge lasting 10-15 minutes. Maintain a nitrogen atmosphere, set the stirring speed to 350-450 r / min, and the heating rate to 2-3℃ / min. Heat to 50-60℃ and maintain the temperature for 3-4 hours. During this period, stop the machine every 40 minutes to take samples and observe the homogeneity of the system, ensuring there are no obvious particulate substances. This yields the ink premix. The nitrogen gas has a purity of ≥99.99%, a nitrogen gas introduction rate of 0.5-1 L / min, and the internal pressure is maintained at 0.02-0.05 MPa during the replacement process.

[0028] The graphene flakes have a diameter of 1-5 μm, a thickness of 0.5-2 nm, a carbon content of ≥99%, and a defect density of ≤0.01 defects / nm. 2 ; Step 2: Slowly add the measured amount of deionized water to the ink premix at a rate of 5-10 mL / min, while maintaining a stirring speed of 200-250 r / min. After the addition is complete, transfer the mixture to a high-speed disperser and set the speed to 800-1000 r / min. Disperse for 1-2 hours, and use a laser particle size analyzer to check the particle size of the system every 30 minutes to ensure uniform particle size distribution. Step 3: Transfer the high-speed dispersed material to a sand mill, set the grinding medium to zirconia beads with a particle size of 0.8-1.2 mm, the mass ratio of material to zirconia beads to 1:3-5, the grinding speed to 2000-2500 r / min, and the grinding time to 2-3 h. During this period, take samples every 30 min to test the particle size until the particle size of the entire system is less than 5 μm. Step 4: After grinding, filter the solution using a 200-300 mesh screen to remove impurities and incompletely dispersed agglomerates. Collect the filtrate, which is the micro-graphene electrothermal ink. Place it in a sealed container and store it at 25-30℃ and 40%-60% relative humidity.

[0029] Example 1: Preparation of micro-graphene electrothermal ink:

[0030] Step 1: Weigh out 18 portions of graphene flakes (1-3 μm in diameter, 0.5-1 nm in thickness, 99.2% carbon content, and 0.008 defects / nm) by weight. 212 parts modified epoxy resin, 8 parts polyethylene glycol diacrylate, 5 parts γ-aminopropyltriethoxysilane, 6 parts modified carbon black, 3 parts azobisisobutyronitrile, 2 parts polyether modified silicone oil, and 4 parts acetylene black were added sequentially to a high-shear mixer. The feed inlet was closed, and the air inside the mixer was replaced three times with nitrogen gas of 99.995% purity. Each replacement time was 10 min, and the nitrogen gas introduction rate was 0.5 L / min. During the replacement process, the internal pressure was maintained at 0.02 MPa, and a nitrogen atmosphere was maintained. The stirring speed was set to 350 r / min, and the heating rate was 2℃ / min. The temperature was raised to 50℃, and the mixture was stirred thoroughly at a constant temperature for 3 h. During this period, the machine was stopped every 40 min to take samples and observe the homogeneity of the system to ensure that there were no obvious particulate substances, thus obtaining the ink premix.

[0031] Step 2: Slowly add 25 parts of deionized water to the ink premix at a rate of 5 mL / min while maintaining a stirring speed of 200 r / min. After the addition is complete, transfer the mixture to a high-speed disperser and set the speed to 800 r / min. Disperse for 1 hour, and use a laser particle size analyzer to check the particle size of the system every 30 minutes to ensure uniform particle size distribution.

[0032] Step 3: Transfer the high-speed dispersed material to a sand mill, set the grinding medium to zirconia beads with a particle size of 0.8 mm, the mass ratio of material to zirconia beads to 1:3, the grinding speed to 2000 r / min, and the grinding time to 2 h. During this period, take samples every 30 min to test the particle size until the particle size of the entire system is less than 5 μm.

[0033] Step 4: After grinding, filter the solution using a 200-mesh filter to remove impurities and incompletely dispersed agglomerates. Collect the filtrate, which is the micro-graphene electrothermal ink. Place it in a sealed container and store it at 25°C and 40% relative humidity.

[0034] Example 2: Preparation of micro-graphene electrothermal ink:

[0035] Step 1: Weigh out 22 portions of graphene microsheets (diameter 2-4 μm, thickness 1-1.5 nm, carbon content 99.5%, defect density 0.006 defects / nm) by weight. 215 parts modified epoxy resin, 10 parts polyethylene glycol diacrylate, 6.5 parts γ-aminopropyltriethoxysilane, 8 parts modified carbon black, 4 parts azobisisobutyronitrile, 3 parts polyether modified silicone oil, and 5.5 parts a mixture of superconducting carbon black and carbon fiber (mass ratio 1:2) were added sequentially to a high-shear mixer. The feed inlet was closed, and the air inside the mixer was replaced four times with nitrogen gas of 99.99% purity. Each replacement time was 12 min, and the nitrogen gas introduction rate was 0.8 L / min. During the replacement process, the internal pressure was maintained at 0.03 MPa, and a nitrogen atmosphere was maintained. The stirring speed was set to 400 r / min, and the heating rate was 2.5℃ / min. The temperature was raised to 55℃, and the mixture was stirred thoroughly at a constant temperature for 3.5 h. During this period, the machine was stopped every 40 min to take samples and observe the homogeneity of the system to ensure that there were no obvious particulate substances, thus obtaining the ink premix.

[0036] Step 2: Slowly add 30 parts of deionized water to the ink premix at a rate of 8 mL / min while maintaining a stirring speed of 220 r / min. After the addition is complete, transfer the mixture to a high-speed disperser and set the speed to 900 r / min. Disperse for 1.5 h, and use a laser particle size analyzer to check the particle size of the system every 30 min to ensure uniform particle size distribution.

[0037] Step 3: Transfer the high-speed dispersed material to a sand mill, set the grinding medium to zirconia beads with a particle size of 1.0 mm, the mass ratio of material to zirconia beads to 1:4, the grinding speed to 2200 r / min, and the grinding time to 2.5 h. During this period, take samples every 30 min to test the particle size until the particle size of the entire system is less than 5 μm.

[0038] Step 4: After grinding, filter the solution using a 250-mesh filter to remove impurities and incompletely dispersed agglomerates. Collect the filtrate, which is the micro-graphene electrothermal ink. Place it in a sealed container and store it at 28°C and 50% relative humidity.

[0039] Example 3: Preparation of micro-graphene electrothermal ink:

[0040] Step 1: Weigh out 25 parts by weight of graphene microsheets (sheet diameter 3-5μm, thickness 1.5-2nm, carbon content 99.8%, defect density 0.005 defects / nm). 218 parts modified epoxy resin, 12 parts polyethylene glycol diacrylate, 8 parts γ-aminopropyltriethoxysilane, 10 parts modified carbon black, 5 parts azobisisobutyronitrile, 4 parts polyether modified silicone oil, and 7 parts carbon fiber were sequentially added to a high-shear mixer. The feed inlet was closed, and the air inside the mixer was replaced 5 times with nitrogen gas of 99.99% purity. Each replacement time was 15 minutes, and the nitrogen gas introduction rate was 1 L / min. During the replacement process, the internal pressure was maintained at 0.05 MPa, and a nitrogen atmosphere was maintained. The stirring speed was set to 450 r / min, and the heating rate was 3℃ / min. The temperature was raised to 60℃, and the mixture was stirred thoroughly at a constant temperature for 4 hours. During this period, the machine was stopped every 40 minutes to take samples and observe the homogeneity of the system to ensure that there were no obvious particulate substances, thus obtaining the ink premix.

[0041] Step 2: Slowly add 35 parts of deionized water to the ink premix at a rate of 10 mL / min while maintaining a stirring speed of 250 r / min. After the addition is complete, transfer the mixture to a high-speed disperser and set the speed to 1000 r / min. Disperse for 2 hours, and use a laser particle size analyzer to check the particle size of the system every 30 minutes to ensure uniform particle size distribution.

[0042] Step 3: Transfer the high-speed dispersed material to a sand mill, set the grinding medium to zirconia beads with a particle size of 1.2 mm, the mass ratio of material to zirconia beads to 1:5, the grinding speed to 2500 r / min, and the grinding time to 3 h. During this period, take samples every 30 min to test the particle size until the particle size of the entire system is less than 5 μm.

[0043] Step 4: After grinding, filter the solution using a 300-mesh filter to remove impurities and incompletely dispersed agglomerates. Collect the filtrate, which is the micro-graphene electrothermal ink. Place it in a sealed container and store it at 30°C and 60% relative humidity.

[0044] Comparative Example 1: Preparation of micro-graphene electrothermal ink:

[0045] Step 1: Weigh out 22 portions of graphene microsheets (diameter 2-4 μm, thickness 1-1.5 nm, carbon content 98.5%, defect density 0.02 defects / nm) by weight. 2 ), 15 parts unmodified bisphenol A epoxy resin (epoxy value 0.3 eq / 100g), 10 parts polyethylene glycol diacrylate, 6.5 parts γ-aminopropyltriethoxysilane, 8 parts unmodified acetylene black (particle size 60nm, specific surface area 70m²). 2A mixture of 4 parts azobisisobutyronitrile (AIORT), 3 parts polyether modified silicone oil, and 5.5 parts superconducting carbon black and carbon fiber (mass ratio 1:4) was added sequentially to a high-shear mixer. The feed inlet was closed, and the air inside the mixer was replaced four times with nitrogen gas of 99.9% purity. Each replacement lasted for 12 minutes, and the nitrogen gas was introduced at a rate of 0.8 L / min. During the replacement process, the internal pressure was maintained at 0.03 MPa, and a nitrogen atmosphere was maintained. The stirring speed was set to 400 r / min, and the heating rate was 2.5℃ / min. The temperature was raised to 55℃, and the mixture was stirred thoroughly at a constant temperature for 3.5 hours. During this period, the mixer was stopped every 40 minutes to take samples and observe the homogeneity of the system to ensure that there were no obvious particulate substances, thus obtaining the ink premix.

[0046] Step 2: Slowly add 30 parts of deionized water to the ink premix at a rate of 8 mL / min while maintaining a stirring speed of 220 r / min. After the addition is complete, transfer the mixture to a high-speed disperser and set the speed to 900 r / min. Disperse for 1.5 h, and use a laser particle size analyzer to check the particle size of the system every 30 min to ensure uniform particle size distribution.

[0047] Step 3: Transfer the high-speed dispersed material to a sand mill, set the grinding medium to zirconia beads with a particle size of 1.0 mm, the mass ratio of material to zirconia beads to 1:4, the grinding speed to 2200 r / min, and the grinding time to 2.5 h. During this period, take samples every 30 min to test the particle size until the particle size of the entire system is less than 5 μm.

[0048] Step 4: After grinding, filter the solution using a 250-mesh filter to remove impurities and incompletely dispersed agglomerates. Collect the filtrate, which is the micro-graphene electrothermal ink. Place it in a sealed container and store it at 28°C and 50% relative humidity.

[0049] Comparative Example 2: Preparation of micro-graphene electrothermal ink:

[0050] Step 1: Weigh out 22 portions of graphene microsheets (diameter 2-4 μm, thickness 1-1.5 nm, carbon content 99.5%, defect density 0.006 defects / nm) by weight. 2 ), 15 parts modified epoxy resin, 10 parts polyethylene glycol diacrylate, 6.5 parts γ-aminopropyltriethoxysilane, 8 parts unmodified acetylene black (particle size 30nm, specific surface area 100m²). 2A mixture of 4 parts azobisisobutyronitrile (AIB), 3 parts polyether modified silicone oil, and 5.5 parts superconducting carbon black and carbon fiber (mass ratio 1:2) was added sequentially to a high-shear mixer. The feed inlet was closed, and the air inside the mixer was replaced four times with nitrogen gas of 99.99% purity. Each replacement lasted 12 minutes, and the nitrogen gas was introduced at a rate of 0.8 L / min. During the replacement process, the internal pressure was maintained at 0.03 MPa, and a nitrogen atmosphere was maintained. The stirring speed was set to 400 r / min, and the heating rate was 2.5℃ / min. The temperature was raised to 55℃, and the mixture was stirred thoroughly at a constant temperature for 3.5 hours. During this period, the mixer was stopped every 40 minutes to take samples and observe the homogeneity of the system to ensure that there were no obvious particulate substances, thus obtaining the ink premix.

[0051] Step 2: Slowly add 30 parts of deionized water to the ink premix at a rate of 8 mL / min while maintaining a stirring speed of 220 r / min. After the addition is complete, transfer the mixture to a high-speed disperser and set the speed to 900 r / min. Disperse for 1.5 h, and use a laser particle size analyzer to check the particle size of the system every 30 min to ensure uniform particle size distribution.

[0052] Step 3: Transfer the high-speed dispersed material to a sand mill, set the grinding medium to zirconia beads with a particle size of 1.0 mm, the mass ratio of material to zirconia beads to 1:4, the grinding speed to 2200 r / min, and the grinding time to 2.5 h. During this period, take samples every 30 min to test the particle size until the particle size of the entire system is less than 5 μm.

[0053] Step 4: After grinding, filter the solution using a 250-mesh filter to remove impurities and incompletely dispersed agglomerates. Collect the filtrate, which is the micro-graphene electrothermal ink. Place it in a sealed container and store it at 28°C and 50% relative humidity.

[0054] Comparative Example 3: Preparation of micro-graphene electrothermal ink:

[0055] Step 1: Weigh out 22 portions of graphene microsheets (diameter 2-4 μm, thickness 1-1.5 nm, carbon content 99.5%, defect density 0.006 defects / nm) by weight. 215 parts of unmodified bisphenol A epoxy resin (epoxy value 0.5 eq / 100g), 10 parts of polyethylene glycol diacrylate, 6.5 parts of γ-aminopropyltriethoxysilane, 8 parts of modified carbon black, 4 parts of azobisisobutyronitrile, 3 parts of polyether modified silicone oil, and 5.5 parts of a mixture of superconducting carbon black and carbon fiber (mass ratio 1:2) were added sequentially to a high-shear mixer. The feed inlet was closed, and the air inside the mixer was replaced 4 times with nitrogen gas of 99.99% purity. Each replacement time was 12 min, and the nitrogen gas introduction rate was 0.8 L / min. During the replacement process, the internal pressure was maintained at 0.03 MPa, and a nitrogen atmosphere was maintained. The stirring speed was set to 400 r / min, and the heating rate was 2.5℃ / min. The temperature was raised to 55℃, and the mixture was stirred thoroughly at a constant temperature for 3.5 h. During this period, the machine was stopped every 40 min to take samples and observe the homogeneity of the system to ensure that there were no obvious particulate substances, thus obtaining the ink premix.

[0056] Step 2: Slowly add 30 parts of deionized water to the ink premix at a rate of 8 mL / min while maintaining a stirring speed of 220 r / min. After the addition is complete, transfer the mixture to a high-speed disperser and set the speed to 900 r / min. Disperse for 1.5 h, and use a laser particle size analyzer to check the particle size of the system every 30 min to ensure uniform particle size distribution.

[0057] Step 3: Transfer the high-speed dispersed material to a sand mill, set the grinding medium to zirconia beads with a particle size of 1.0 mm, the mass ratio of material to zirconia beads to 1:4, the grinding speed to 2200 r / min, and the grinding time to 2.5 h. During this period, take samples every 30 min to test the particle size until the particle size of the entire system is less than 5 μm.

[0058] Step 4: After grinding, filter the solution using a 250-mesh filter to remove impurities and incompletely dispersed agglomerates. Collect the filtrate, which is the micro-graphene electrothermal ink. Place it in a sealed container and store it at 28°C and 50% relative humidity.

[0059] Comparative Example 4: Preparation of micro-graphene electrothermal ink:

[0060] Step 1: Weigh out 22 portions of graphene microsheets (diameter 2-4 μm, thickness 1-1.5 nm, carbon content 99.5%, defect density 0.006 defects / nm) by weight. 215 parts modified epoxy resin, 10 parts polyethylene glycol diacrylate, 6.5 parts γ-aminopropyltriethoxysilane, 8 parts modified carbon black, 4 parts azobisisobutyronitrile, 3 parts polyether modified silicone oil, and 5.5 parts a mixture of superconducting carbon black and carbon fiber (mass ratio 1:2) were added sequentially into a high-shear mixer. The feed inlet was closed, and nitrogen protection was not introduced. The stirring speed was set to 400 r / min, the heating rate was 2.5℃ / min, and the temperature was raised to 55℃. The mixture was stirred at a constant temperature for 3.5 h. During this period, the mixer was stopped every 40 min to take samples and observe the homogeneity of the system to ensure that there were no obvious particulate substances, thus obtaining the ink premix.

[0061] Step 2: Quickly add 30 parts of deionized water to the ink premix at a rate of 20 mL / min while maintaining a stirring speed of 220 r / min. After the addition is complete, transfer the mixture to a high-speed disperser, set the speed to 500 r / min, and disperse for 1.5 h. The particle size was not measured during this period.

[0062] Step 3: Grinding was not performed using a sand mill;

[0063] Step 4: Filter directly using a 250-mesh filter and collect the filtrate, which is the micro-graphene electrothermal ink. Place it in a sealed container and store it at 28°C and 50% relative humidity.

[0064] Performance testing:

[0065] The inks prepared in Examples 1-3 and Comparative Examples 1-4 were used as samples and subjected to the following performance tests:

[0066] Volume resistivity: Tested using a high-resistivity meter in accordance with standard GB / T 31838.2-2019;

[0067] Heating rate: The sample was coated on a PET substrate with a coating thickness of 50 μm. After drying, a rated voltage of 220 V was applied, and the time required to heat from room temperature (25 °C) to 80 °C was recorded.

[0068] Adhesion strength: Refer to standard GB / T 9286-2021, use the cross-cut test with a cross-cut spacing of 1mm, observe the coating peeling, and calculate the adhesion strength grade (grade 1 is the best, grade 5 is the worst).

[0069] Stability: The sample was coated on a PET substrate and aged at 120°C for 100 hours. The change rate of volume resistivity before and after aging was tested.

[0070] The specific test results are shown in Table 1:

[0071] Table 1 Test Results As shown in the table above, the micro-graphene electrothermal inks prepared in Examples 1-3 exhibit low volume resistivity, fast heating rate, excellent bonding strength, and good stability. Comparative Example 1 did not use modified epoxy resin or modified carbon black, and the epoxy value of the epoxy resin, the particle size and specific surface area of ​​the carbon black, the carbon content and defect density of the micro-graphene, and the mixing ratio of the conductive additives all did not meet the limitations of this invention. This resulted in uneven dispersion of the micro-graphene, poor compatibility, a significantly increased volume resistivity, a slower heating rate, and a substantial decrease in bonding strength and stability.

[0072] Comparative Example 2, which did not use modified carbon black, showed inferior performance compared to the Example, indicating that modified carbon black plays a crucial role in improving ink performance.

[0073] Comparative Example 3, which did not use modified epoxy resin, also performed worse than the examples, demonstrating the importance of modified epoxy resin.

[0074] Comparative Example 4 lacked nitrogen protection, had substandard high-speed dispersion parameters, and was not ground in a sand mill, resulting in raw material oxidation, poor filler dispersion, and larger particle size. This affected the construction of the conductive network and the density of the coating, leading to a decrease in performance.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing micro-graphene electrothermal ink, characterized in that, The ink comprises the following raw materials in parts by weight: 18-25 parts graphene flakes, 12-18 parts modified epoxy resin, 8-12 parts polyethylene glycol diacrylate, 5-8 parts γ-aminopropyltriethoxysilane, 6-10 parts modified carbon black, 3-5 parts azobisisobutyronitrile, 2-4 parts polyether modified silicone oil, 4-7 parts conductive additives, 25-35 parts deionized water; The modified epoxy resin is prepared by reacting epoxy resin with maleic anhydride under the action of a catalyst. The modified carbon black is prepared by oxidizing carbon black with nitric acid and then grafting it with 3-aminopropyltriethoxysilane.

2. The method for preparing micro-graphene electrothermal ink according to claim 1, characterized in that, The conductive additive is any one or a mixture of two or more of acetylene black, superconducting carbon black, and carbon fiber, with the mass ratio of each component being 1:1-3 when mixed.

3. The method for preparing micro-graphene electrothermal ink according to claim 1, characterized in that, The preparation method of the modified epoxy resin includes the following steps: S1: Weigh epoxy resin, maleic anhydride and triphenylphosphine according to the mass ratio of 10:3-4:0.5-1. Add epoxy resin to xylene and stir until completely dissolved to obtain epoxy resin solution. The solid-liquid ratio of epoxy resin to xylene is 1g:4-6mL. S2: Add maleic anhydride and triphenylphosphine sequentially to the epoxy resin solution. Under a nitrogen protective atmosphere, stir and heat to 90-100℃, and react at a constant temperature for 4-6 hours. During this period, take samples regularly to detect the acid value of the system. Stop the reaction when the acid value stabilizes at 85-95 mgKOH / g. S3: After the reaction is complete, cool the system to 40-50℃ and perform vacuum distillation to remove the xylene solvent; S4: Add 3-5 times the volume of anhydrous ethanol to the distilled product, stir and wash for 10-15 minutes, let stand to separate into layers, filter, collect the filter cake, and repeat the washing 2-3 times. S5: Place the washed filter cake in a vacuum drying oven and dry for 3-5 hours until constant weight is achieved. Then collect the product to obtain the modified epoxy resin.

4. The method for preparing micro-graphene electrothermal ink according to claim 3, characterized in that, The epoxy resin is either bisphenol A epoxy resin or bisphenol F epoxy resin, and the epoxy value is 0.4-0.6 eq / 100g.

5. The method for preparing micro-graphene electrothermal ink according to claim 1, characterized in that, The method for preparing the modified carbon black includes the following steps: S1: Place the carbon black in a vacuum drying oven to dry and remove surface adsorbed water. Add the dried carbon black to concentrated nitric acid with a mass fraction of 65%-68% at a solid-liquid ratio of 1g:10-15mL. Place the mixture in a constant temperature water bath and react at 70-80℃ and a stirring speed of 250-300r / min for 2-3 hours. During this period, use ultrasonic dispersion for 5 minutes every 20 minutes. S2: After the reaction is complete, the reaction solution is cooled to room temperature and filtered using a vacuum filtration device. The filter cake is repeatedly washed with deionized water until the pH of the washing solution is 6.8-7.

2. The washed filter cake is placed in a forced-air drying oven and dried at 95-105℃ for 5-7 hours to obtain carbon black oxide. S3: Weigh carbon black and 3-aminopropyltriethoxysilane at a mass ratio of 1:0.8-1.

2. Disperse the carbon black in anhydrous ethanol at a solid-liquid ratio of 1g:15-25mL. Disperse at a stirring speed of 300-400r / min for 20-30min to obtain a carbon black dispersion. S4: Add 3-aminopropyltriethoxysilane dropwise to the carbon black dispersion at a rate of 1-2 drops / s. After the addition is complete, raise the temperature to 65-75℃ and keep the reaction in a reflux reflux apparatus for 3-5 hours, while maintaining a constant stirring speed during the reaction. S5: After the reaction is complete, cool to room temperature, filter under vacuum, wash the filter cake 2-3 times with anhydrous ethanol, place the filter cake in a vacuum drying oven and dry for 4-6 hours until constant weight is reached, then collect the product to obtain modified carbon black.

6. The method for preparing micro-graphene electrothermal ink according to claim 5, characterized in that, In step S1, the carbon black is either acetylene black or conductive carbon black, with a particle size of 20-50 nm and a specific surface area of ​​80-120 m². 2 / g.

7. The method for preparing micro-graphene electrothermal ink according to claim 5, characterized in that, In step S3, during the dispersion process of the carbon black oxide dispersion, the mixture is first stirred at 300-350 r / min for 10-15 min, and then heated to 40-50℃ and stirred at 400 r / min for 10-15 min.

8. The method for preparing micro-graphene electrothermal ink according to claim 1, characterized in that, Includes the following steps: Step 1: Weigh out the following components by weight: micro-graphene flakes, modified epoxy resin, polyethylene glycol diacrylate, γ-aminopropyltriethoxysilane, modified carbon black, azobisisobutyronitrile, polyether-modified silicone oil, and conductive additives. Add them sequentially to a high-shear mixer, close the feed inlet, purge the air inside the mixer with nitrogen to maintain a nitrogen atmosphere, set the stirring speed to 350-450 r / min, the heating rate to 2-3℃ / min, heat to 50-60℃, and maintain the temperature for 3-4 hours. During this period, stop the machine every 40 minutes to take samples and observe the uniformity of the system to obtain the ink premix. Step 2: Slowly add the metered deionized water to the ink premix while maintaining a stirring speed of 200-250 r / min. After the addition is complete, transfer the mixture to a high-speed disperser and set the speed to 800-1000 r / min. Disperse for 1-2 hours, and use a laser particle size analyzer to check the particle size of the system every 30 minutes during this period. Step 3: Transfer the high-speed dispersed material to a sand mill, set the grinding medium to zirconia beads with a particle size of 0.8-1.2 mm, the mass ratio of material to zirconia beads to 1:3-5, the grinding speed to 2000-2500 r / min, and the grinding time to 2-3 h. During this period, take samples every 30 min to test the particle size until the particle size of the entire system is less than 5 μm. Step 4: After grinding, filter the solution using a 200-300 mesh screen to remove impurities and incompletely dispersed agglomerates. Collect the filtrate, which is the micro-graphene electrothermal ink. Place it in a sealed container and store it at 25-30℃ and 40%-60% relative humidity.

9. The method for preparing micro-graphene electrothermal ink according to claim 8, characterized in that, In step one, the nitrogen gas introduction rate is 0.5-1 L / min, and the internal pressure is maintained at 0.02-0.05 MPa during the replacement process.

10. The method for preparing micro-graphene electrothermal ink according to claim 1, characterized in that, The graphene flakes have a diameter of 1-5 μm, a thickness of 0.5-2 nm, a carbon content of ≥99%, and a defect density of ≤0.01 defects / nm. 2 .