Graphene-containing low-temperature curing anti-corrosion powder coating and preparation method thereof

Abstract

The invention discloses a graphene-containing low-temperature curing anti-corrosion powder coating and a preparation method thereof, and belongs to the technical field of coatings. The coating comprises the following components in parts by weight: 50-70 parts of graphene modified epoxy resin, 20-30 parts of a low-temperature curing agent, 5-6 parts of a flatting agent, 4-6 parts of an accelerant, 5-7 parts of a dispersing agent, 2-3 parts of a preservative, 8-12 parts of nano titanium dioxide, 1-2 parts of benzoin and 0.2-0.8 part of fluorowax. The coating is excellent in corrosion resistance, low in curing temperature, capable of saving a large amount of energy and simple in preparation process, the needed raw materials are evenly mixed according to a certain proportion, tabletted, cooled and rolled into flaky and easily-smashed materials, the flaky and easily-smashed materials are ground into powdery materials through a grinding mill, the powdery materials are screened through a mesh sieve, and the finished product can be obtained. The coating has a wide application prospect in the technical field of anticorrosive coatings.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a low-temperature curing anti-corrosion powder coating containing graphene and its preparation method. Background Technology

[0002] Powder coatings are an environmentally friendly type of coating, possessing advantages such as being solvent-free, pollution-free, and having high utilization rates. They are widely used for the corrosion protection and decoration of metal products. Traditional anti-corrosion powder coatings are typically made with epoxy resin, polyester resin, or similar base resins, combined with curing agents, pigments, and fillers. To obtain good coating film performance, their curing temperature is usually high (generally 180-200℃) and the curing time is long (10-20 minutes). This high-temperature curing process consumes a lot of energy, increases production costs, and is not suitable for coating heat-sensitive substrates (such as plastics, wood, electronic components, etc.). Lowering the curing temperature of powder coatings is an important research direction in the industry. However, simply lowering the curing temperature can lead to problems such as insufficient crosslinking density of the coating film, poor leveling, and a significant decrease in mechanical properties and corrosion resistance.

[0003] Graphene is a material composed of carbon atoms arranged in sp... 2 Two-dimensional nanomaterials with hexagonal honeycomb lattices composed of hybrid orbitals possess extremely high specific surface area, excellent chemical stability, and outstanding shielding properties. Introducing graphene into anti-corrosion coatings allows it to form a "maze effect" within the coating, effectively blocking the penetration of water, oxygen, and corrosive media, thereby significantly improving the coating's anti-corrosion performance. However, due to its enormous specific surface area and strong van der Waals forces, graphene is highly prone to aggregation, making it difficult to disperse uniformly in the resin matrix. Aggregated graphene not only fails to exert its anti-corrosion advantages but also becomes a defect in the coating, leading to a decline in coating performance.

[0004] Therefore, developing a powder coating that can achieve both low-temperature curing and ensure uniform dispersion of graphene, thereby possessing both excellent mechanical properties and superior anti-corrosion performance, has significant practical application value. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a low-temperature curing anti-corrosion powder coating containing graphene and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A low-temperature curing anti-corrosion powder coating containing graphene, comprising the following components by weight: Graphene-modified epoxy resin: 50-70 parts; Low-temperature curing agent: 20-30 parts; Leveling agent: 5-6 parts; Accelerator: 4-6 parts; Dispersant: 5-7 parts; Preservative: 2-3 parts; Nano titanium dioxide: 8-12 parts; Benzoin: 1-2 parts; Fluorinated wax: 0.2-0.8 parts; The graphene-modified epoxy resin is prepared by the following method: 1) Preparation of silane-based graphene: Graphene oxide (GO) was dispersed in an ethanol-water solution and placed in an ultrasonic homogenizer. The mixture was ultrasonically treated for 1-2 hours at a power of 300-500W. Glacial acetic acid was added dropwise to adjust the pH to 4-5. γ-aminopropyltriethoxysilane was then slowly added dropwise at a speed of 300-400 rpm. The reaction was carried out at 60-80℃ for 4-8 hours. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The reaction product was poured into centrifuge tubes and centrifuged at 8000-10000 rpm using a high-speed centrifuge. The supernatant was discarded. The product was washed repeatedly with anhydrous ethanol and centrifuged 3-5 times until the washing liquid was clear to completely remove unreacted silane coupling agent and other byproducts. The washed solid product was transferred to a vacuum drying oven and dried at 50-60℃ for 12-24 hours to obtain a dry, brownish-black silane-based graphene solid powder. This process involves a covalent bonding reaction between a silane coupling agent and graphene oxide (GO). First, under acidic conditions, the ethoxy groups of the silane coupling agent hydrolyze to generate highly reactive silanols (-Si-OH). Subsequently, these silanols are grafted onto the GO surface through two main pathways: one is an amidation reaction with the carboxyl groups on GO to form strong amide bonds (-CONH-); the other is a condensation reaction with the hydroxyl groups on GO to generate silicon-oxygen-carbon bonds (Si-OC). Simultaneously, self-condensation also occurs between silane coupling agent molecules to form a siloxane network. Finally, through the reaction, long organic chains with terminal amino groups are successfully introduced onto the GO surface, transforming it from hydrophilic to hydrophobic and providing active sites for subsequent reactions, thereby obtaining silane-based graphene that is easily dispersed in a polymer matrix. 2) Grafting reaction of epoxy resin: In a dry three-necked flask equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet tube, epoxy resin and silane graphene powder prepared in 1) are added. Nitrogen gas is introduced for protection, and the system is slowly heated to 100-120℃ and stirred at 400-500 rpm for 30-60 min to initially disperse the silane graphene in the epoxy resin melt. Triphenylphosphine catalyst is added to the system, and the reaction is continued for 2-4 h. After the reaction is completed, heating and stirring are stopped, and the reaction product is poured into a polytetrafluoroethylene dish while hot and placed in a vacuum drying oven at 100-120℃ for 1-2 h to remove residual trace solvents and small molecule volatiles. Finally, a uniform, high-viscosity black solid is obtained, which is the graphene-modified epoxy resin required by this invention. This process involves covalent bonding under the action of the catalyst triphenylphosphine. First, the amino groups on the surface of silane graphene act as nucleophiles, attacking the epoxy groups on the epoxy resin molecular chains activated by the catalyst, causing the epoxy ring to open. After ring opening, the amino group and the epoxy carbon atom form a stable CN covalent bond, directly grafting graphene onto the resin molecule through the propyl segment. At the same time, a hydroxyl group is generated. The newly generated amine and hydroxyl group can continue to react with other epoxy groups, eventually forming a three-dimensional cross-linked network structure. Thus, graphene is firmly integrated into the epoxy resin matrix as a nano-reinforcing point in the form of chemical bonds.

[0007] Preferably, the graphene oxide (GO) mentioned in 1) has a size of 8-10 μm, is purchased from Hangzhou Gaoxi Technology Co., Ltd., and the mass ratio of graphene oxide to γ-aminopropyltriethoxysilane is 1:3-5.

[0008] Preferably, the epoxy resin mentioned in 2) is a bisphenol A type epoxy resin with an epoxy equivalent of 450-750 g / eq and a softening point of 60-95℃.

[0009] Preferably, the mass ratio of silane graphene to epoxy resin in 2) is 1-5:100.

[0010] Preferably, the amount of triphenylphosphine used in 2) is 0.2-0.4% of the mass of bisphenol A epoxy resin.

[0011] Preferably, the low-temperature curing agent is dimethylaminopropionamide.

[0012] Preferably, the leveling agent is one or more of leveling agent H88 and leveling agent H99.

[0013] Preferably, the promoter is dimethylimidazole.

[0014] Preferably, the dispersant is one or more of hydroxymethyl cellulose, polyvinylpyrrolidone, sodium polyacrylate, polyacrylic acid polymer, and polymer copolymer.

[0015] Preferably, the preservative is one or more of benzoic acid, sodium benzoate, ethyl p-hydroxybenzoate, and dehydroacetic acid.

[0016] This invention provides a low-temperature curing anti-corrosion powder coating containing graphene and its preparation method, comprising the following steps: S1. Premixing: Pour graphene-modified epoxy resin, low-temperature curing agent, leveling agent, accelerator, dispersant, preservative, nano titanium dioxide, benzoin and fluorinated wax into a container and mix and stir to ensure that each component is evenly dispersed; S2. Melt extrusion: The uniformly mixed material is fed into a twin-screw extruder for melt blending and extrusion. The extrusion temperature is 80-95℃. Excessive temperature may cause the material to pre-cure. S3. Compressing, Cooling and Crushing: The extruded molten material is pressed into thin sheets by a compression roller and cooled to room temperature. The hard and brittle sheet material is then broken into small pieces, crushed by a micro pulverizer, and screened by a grading sieve to obtain a powder product.

[0017] Preferably, the stirring speed in step S1 is 2500-3000 r / min, and the mixing time is 45-60 min.

[0018] Preferably, in step S2, the temperature of zone I of the extruder is 80-90℃, the temperature of zone II is 90-100℃, and the screw speed is 1000-1200 r / min.

[0019] Preferably, the grading sieve in step S3 is a 100-160 mesh sieve.

[0020] Compared with the prior art, the beneficial effects of the present invention are: 1. Breakthrough improvement in anti-corrosion performance: Through a unique "chemical grafting" process, graphene is firmly bonded to the epoxy resin skeleton by chemical bonds, which fundamentally solves the problem of graphene's easy agglomeration, enabling it to form an extremely dense physical barrier, thus achieving a superior anti-corrosion effect that traditional coatings cannot match.

[0021] 2. Achieves true low-temperature energy saving and wide application: The innovative use of a low-temperature curing agent and accelerator system significantly reduces the processing and curing temperatures of the coating, which not only saves energy but also enables its application to heat-sensitive substrates such as plastics and wood, expanding its application boundaries.

[0022] 3. Excellent overall coating performance and process stability: While achieving super corrosion resistance, the components in the formula work synergistically to take into account the mechanical strength, surface smoothness and weather resistance of the coating. Its preparation process is fully compatible with existing industrial equipment, the process is stable, easy to scale up production, and has huge market transformation potential. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the chemical reaction process of the silane-based graphene proposed in this invention; Figure 2 This is a schematic diagram of the chemical reaction process of the graphene-modified epoxy resin proposed in this invention. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0025] Example 1: A low-temperature curing anti-corrosion powder coating containing graphene, comprising the following components in parts by weight: The composition includes 50 parts graphene-modified epoxy resin, 20 parts low-temperature curing agent (dimethylaminopropionamide), 5 parts leveling agent (H88), 4 parts accelerator (dimethylimidazole), 5 parts dispersant (polyvinylpyrrolidone), 2 parts preservative (sodium benzoate), 8 parts nano titanium dioxide, 1 part benzoin, and 0.2 parts fluorinated wax. The preparation method of graphene-modified epoxy resin is as follows: 1) Preparation of silane-based graphene: Weigh 1.0 g of graphene oxide (GO) and add it to 200 ml of a mixed solution of ethanol and deionized water (volume ratio 4:1). Place the beaker in an ultrasonic homogenizer and sonicate at 400 W for 1.5 h to obtain a uniform GO dispersion. Slowly add glacial acetic acid dropwise with a dropper while stirring, and monitor the pH with pH paper. Adjust the pH of the dispersion to 4.5. Transfer the beaker to a magnetic stirrer and slowly add 3.0 g of graphene oxide (GO) dropwise at 350 rpm using a constant pressure dropping funnel. γ-aminopropyltriethoxysilane was heated to 70°C and reacted at this temperature for 6 hours. After the reaction was completed, it was naturally cooled to room temperature. The reaction product was transferred to a centrifuge tube and centrifuged at 9000 rpm. The supernatant was discarded, and anhydrous ethanol was added to the precipitate. After ultrasonic dispersion for 5 minutes, the mixture was centrifuged again. This washing process was repeated 4 times until the supernatant was clear and transparent. The solid product obtained from the last centrifugation was transferred to a petri dish and dried in a vacuum drying oven at 50°C for 18 hours to obtain brown-black silane graphene powder. 2) Grafting reaction of epoxy resin: Equip a dry 1L three-necked flask with a mechanical stirrer, thermometer, reflux condenser, and nitrogen inlet. Add 99g of bisphenol A epoxy resin (epoxy equivalent approximately 600g / eq, softening point 80℃) and 1.0g of silane-based graphene powder prepared in step 1) to the flask. Open the nitrogen cylinder and continuously introduce a small amount of nitrogen into the system to purge air and create a protective atmosphere. Turn on the oil bath heating and slowly raise the temperature to 110℃ while stirring at 450rpm for 40min to allow the silane-based graphene to mature. Graphene powder was initially dispersed in molten epoxy resin. 0.3g of triphenylphosphine catalyst was weighed and added to the reaction system. The reaction was carried out at 110℃ and 450rpm for 3h. After the reaction was completed, heating and stirring were stopped. The viscous reaction product was poured into a polytetrafluoroethylene (PTFE) tray while hot. The PTFE tray was immediately transferred to a vacuum drying oven at 105℃ and kept for 1.5h to remove residual small molecules. After cooling to room temperature, a uniform, high-viscosity black solid block was obtained, which is graphene-modified epoxy resin. A method for preparing a low-temperature curing anti-corrosion powder coating containing graphene is as follows: S1, Premixed: Weigh out 50 parts of graphene-modified epoxy resin, 20 parts of dimethylaminopropionamide, 5 parts of leveling agent H88, 4 parts of dimethylimidazole, 5 parts of polyvinylpyrrolidone, 2 parts of sodium benzoate, 8 parts of nano titanium dioxide, 1 part of benzoin, and 0.2 parts of fluorowax. Pour all components into a high-speed mixer and mix at 2500 r / min for 45 min until all components are fully mixed and homogeneous. S2, Melt extrusion: Pour the well-mixed material S1 into the feed hopper of the twin-screw extruder, set the temperature of zone I of the extruder to 80℃ and the temperature of zone II to 90℃, set the screw speed to 1000r / min, start the extruder, and the material is extruded from the die after melting, shearing and mixing. S3. Tableting, Cooling, and Pulverizing: The extruded strip of molten material is immediately introduced into a cooling pressing roller and pressed into a continuous sheet with a thickness of about 1-2 mm. The sheet is cooled to room temperature by a cooling water circulating steel belt or cooling drum, becoming hard and brittle. The cooled sheet is then fed into a crusher and broken into small pieces less than 1 cm in size. The small pieces are then fed into a micro-pulverizer for fine grinding. The pulverized powder is then graded by passing it through a 100-mesh vibrating screen. The material that passes through the screen is the target powder coating product, which is then packaged.

[0026] Example 2: A low-temperature curing anti-corrosion powder coating containing graphene, comprising the following components in parts by weight: The composition includes 60 parts graphene-modified epoxy resin, 25 parts low-temperature curing agent (dimethylaminopropionamide), 5.5 parts leveling agent (H88), 5 parts accelerator (dimethylimidazole), 6 parts dispersant (sodium polyacrylate), 2.5 parts preservative (ethyl paraben), 10 parts nano titanium dioxide, 1.5 parts benzoin, and 0.5 parts fluorinated wax. The preparation method of graphene-modified epoxy resin is as follows: 1) Preparation of silane-based graphene: Weigh 1.0 g of graphene oxide (GO) and add it to 200 ml of a mixed solution of ethanol and deionized water (volume ratio 4:1). Place the beaker in an ultrasonic homogenizer and sonicate at 400 W for 1.5 h to obtain a uniform GO dispersion. Slowly add glacial acetic acid dropwise with a dropper while stirring, and monitor the pH with pH paper. Adjust the pH of the dispersion to 4.5. Transfer the beaker to a magnetic stirrer and slowly add 4.0 g of graphene oxide (GO) dropwise at 350 rpm using a constant pressure dropping funnel. γ-aminopropyltriethoxysilane was heated to 70°C and reacted at this temperature for 6 hours. After the reaction was completed, it was naturally cooled to room temperature. The reaction product was transferred to a centrifuge tube and centrifuged at 9000 rpm. The supernatant was discarded, and anhydrous ethanol was added to the precipitate. After ultrasonic dispersion for 5 minutes, the mixture was centrifuged again. This washing process was repeated 4 times until the supernatant was clear and transparent. The solid product obtained from the last centrifugation was transferred to a petri dish and dried in a vacuum drying oven at 50°C for 18 hours to obtain brown-black silane graphene powder. 2) Grafting reaction of epoxy resin: Equip a dry 1L three-necked flask with a mechanical stirrer, thermometer, reflux condenser, and nitrogen inlet. Add 97g of bisphenol A epoxy resin (epoxy equivalent approximately 600g / eq, softening point 80℃) and 3.0g of silane-based graphene powder prepared in step 1) to the flask. Open the nitrogen cylinder and continuously introduce a small amount of nitrogen into the system to purge air and create a protective atmosphere. Turn on the oil bath heating and slowly raise the temperature to 110℃ while stirring at 450rpm for 40min to allow the silane-based graphene to mature. Graphene powder was initially dispersed in molten epoxy resin. 0.29g of triphenylphosphine catalyst was weighed and added to the reaction system. The reaction was carried out at 110℃ and 450rpm for 3h. After the reaction was completed, heating and stirring were stopped. The viscous reaction product was poured into a polytetrafluoroethylene (PTFE) tray while hot. The PTFE tray was immediately transferred to a vacuum drying oven at 105℃ and kept for 1.5h to remove residual small molecules. After cooling to room temperature, a uniform, high-viscosity black solid block was obtained, which is graphene-modified epoxy resin. A method for preparing a low-temperature curing anti-corrosion powder coating containing graphene is as follows: S1, Premixed: Weigh out 60 parts of graphene-modified epoxy resin, 25 parts of low-temperature curing agent (dimethylaminopropionamide), 5.5 parts of leveling agent (H88), 5 parts of accelerator (dimethylimidazole), 6 parts of dispersant (sodium polyacrylate), 2.5 parts of preservative (ethylparaben), 10 parts of nano titanium dioxide, 1.5 parts of benzoin, and 0.5 parts of fluorowax. Pour all components into a high-speed mixer and mix at 2800 r / min for 50 min until all components are fully mixed and homogeneous. S2, Melt extrusion: Pour the well-mixed material S1 into the feed hopper of the twin-screw extruder, set the temperature of zone I of the extruder to 85℃ and the temperature of zone II to 95℃, set the screw speed to 1100r / min, start the extruder, and the material is extruded from the die after melting, shearing and mixing. S3. Tableting, Cooling, and Pulverizing: The extruded strip of molten material is immediately introduced into a cooling pressing roller and pressed into a continuous sheet with a thickness of about 1-2 mm. The sheet is cooled to room temperature by a cooling water circulating steel belt or cooling drum, becoming hard and brittle. The cooled sheet is then fed into a crusher and broken into small pieces less than 1 cm in size. The small pieces are then fed into a micro-pulverizer for fine grinding. The pulverized powder is then graded by passing it through a 140-mesh vibrating screen. The material that passes through the screen is the target powder coating product, which is then packaged.

[0027] Example 3: A low-temperature curing anti-corrosion powder coating containing graphene, comprising the following components in parts by weight: The composition includes 70 parts graphene-modified epoxy resin, 30 parts low-temperature curing agent (dimethylaminopropionamide), 6 parts leveling agent (H88), 6 parts accelerator (dimethylimidazole), 7 parts dispersant (hydroxymethylcellulose), 3 parts preservative (dehydroacetic acid), 12 parts nano titanium dioxide, 2 parts benzoin, and 0.8 parts fluorinated wax. The preparation method of graphene-modified epoxy resin is as follows: 1) Preparation of silane-based graphene: Weigh 1.0 g of graphene oxide (GO) and add it to 200 ml of a mixed solution of ethanol and deionized water (volume ratio 4:1). Place the beaker in an ultrasonic homogenizer and sonicate at 400 W for 1.5 h to obtain a uniform GO dispersion. Slowly add glacial acetic acid dropwise with a dropper while stirring, and monitor the pH with pH paper. Adjust the pH of the dispersion to 4.5. Transfer the beaker to a magnetic stirrer and slowly add 5.0 g of graphene oxide (GO) dropwise at 350 rpm using a constant pressure dropping funnel. γ-aminopropyltriethoxysilane was heated to 70°C and reacted at this temperature for 6 hours. After the reaction was completed, it was naturally cooled to room temperature. The reaction product was transferred to a centrifuge tube and centrifuged at 9000 rpm. The supernatant was discarded, and anhydrous ethanol was added to the precipitate. After ultrasonic dispersion for 5 minutes, the mixture was centrifuged again. This washing process was repeated 4 times until the supernatant was clear and transparent. The solid product obtained from the last centrifugation was transferred to a petri dish and dried in a vacuum drying oven at 50°C for 18 hours to obtain brown-black silane graphene powder. 2) Grafting reaction of epoxy resin: Equip a dry 1L three-necked flask with a mechanical stirrer, thermometer, reflux condenser, and nitrogen inlet. Add 95g of bisphenol A epoxy resin (epoxy equivalent approximately 600g / eq, softening point 80℃) and 5.0g of silane-based graphene powder prepared in step 1) to the flask. Open the nitrogen cylinder and continuously introduce a small amount of nitrogen into the system to purge air and create a protective atmosphere. Turn on the oil bath heating and slowly raise the temperature to 110℃ while stirring at 450rpm for 40min to allow the silane-based graphene to mature. Graphene powder was initially dispersed in molten epoxy resin. 0.285g of triphenylphosphine catalyst was weighed and added to the reaction system. The reaction was carried out at 110℃ and 450rpm for 3h. After the reaction was completed, heating and stirring were stopped. The viscous reaction product was poured into a polytetrafluoroethylene (PTFE) tray while hot. The PTFE tray was immediately transferred to a vacuum drying oven at 105℃ and kept for 1.5h to remove residual small molecules. After cooling to room temperature, a uniform, high-viscosity black solid block was obtained, which is graphene-modified epoxy resin. A method for preparing a low-temperature curing anti-corrosion powder coating containing graphene is as follows: S1, Premixed: Weigh out 70 parts of graphene-modified epoxy resin, 30 parts of low-temperature curing agent (dimethylaminopropionamide), 6 parts of leveling agent (H88), 6 parts of accelerator (dimethylimidazole), 7 parts of dispersant (hydroxymethylcellulose), 3 parts of preservative (dehydroacetic acid), 12 parts of nano titanium dioxide, 2 parts of benzoin, and 0.8 parts of fluorinated wax. Pour all components into a high-speed mixer and mix at 3000 r / min for 60 min until all components are fully mixed and homogeneous. S2, Melt extrusion: Pour the well-mixed material S1 into the feed hopper of the twin-screw extruder, set the temperature of zone I of the extruder to 90℃ and the temperature of zone II to 100℃, set the screw speed to 1200r / min, start the extruder, and the material is extruded from the die after melting, shearing and mixing. S3. Tableting, Cooling, and Pulverizing: The extruded strip of molten material is immediately introduced into a cooling pressing roller and pressed into a continuous sheet with a thickness of about 1-2 mm. The sheet is cooled to room temperature by a cooling water circulating steel belt or cooling drum, becoming hard and brittle. The cooled sheet is then fed into a crusher and broken into small pieces less than 1 cm in size. The small pieces are then fed into a micro-pulverizer for fine grinding. The pulverized powder is then graded by passing it through a 160-mesh vibrating screen. The material that passes through the screen is the target powder coating product, which is then packaged.

[0028] Comparative Example 1: Based on Example 2, the difference is that an equal amount of unmodified bisphenol A type epoxy resin was used to directly replace the graphene-modified epoxy resin, and the rest was the same as in Example 2.

[0029] Comparative Example 2: Based on Example 2, the difference is that when preparing the "modified resin", the silane coupling agent treatment step is omitted, and an equal amount of graphene oxide (GO) is directly added to the epoxy resin by physical mixing. The rest is the same as in Example 2.

[0030] Comparative Example 3: Based on Example 2, the difference is that in the preparation of silanized graphene, the mass ratio of graphene oxide to γ-aminopropyltriethoxysilane is 1:1, which is much lower than the preferred ratio (1:3-5), and the rest is the same as in Example 2.

[0031] Comparative Example 4: Based on Example 2, the difference is that when preparing graphene-modified epoxy resin, the mass ratio of silane-modified graphene to epoxy resin is 8:100, which is higher than the preferred ratio (1-5:100), and the rest is the same as in Example 2.

[0032] Comparative Example 5: Based on Example 2, the difference is that no nano-titanium dioxide is added at all, and the weight of this component is made up by an equal amount of graphene-modified epoxy resin, and the rest is the same as in Example 2.

[0033] Performance testing: 1. Adhesion test: Refer to GB / T 9286-1998 "Cross-cut adhesion test for paint and varnish film" to conduct the cross-cut adhesion test. Use a cutting tool to cut a 1mm×1mm grid on the coating surface, use 3M 610 tape to firmly adhere to the grid and quickly peel it off, observe the coating peeling situation. Grade 0 (completely smooth edges, no grid peeling) is the best, and Grade 5 (peeling area >65%) is the worst.

[0034] 2. Impact resistance test: The impact resistance test was carried out in accordance with GB / T 1732-1993 "Determination of Impact Resistance of Coating Film". An impact tester was used with a weight of 1kg, a punch diameter of Φ16mm and a height of 50cm. The cracking of the coating film was observed after impact on both sides.

[0035] 3. Bending test: Refer to GB / T 6742-2007 "Bending test of paints and varnishes (cylindrical shaft)" to conduct the bending test. Bend the coating test plate 180° around a shaft with a diameter of Φ2mm and check whether the coating cracks.

[0036] 4. Hardness test: The hardness test is carried out in accordance with GB / T 6739-2006 "Determination of Hardness of Paint and Varnish Film by Pencil Method". A pencil of known hardness (from the softest 6B to the hardest 9H) is used to scratch the coating surface at a 45° angle to find the pencil with the highest hardness that does not scratch the coating.

[0037] 5. Neutral Salt Spray Test: The neutral salt spray test is conducted in accordance with GB / T 10125-2012 "Artificial Atmosphere Corrosion Test - Salt Spray Test". In a closed test chamber, a 5% NaCl solution is atomized through a spray device to make the salt spray settle evenly on the sample surface. Under constant temperature conditions, the coating's corrosion resistance and corrosion propagation ability are assessed to quickly evaluate its protective performance.

[0038] 6. Acid resistance chemical reagent test: The acid resistance test is carried out in accordance with GB / T 9274-1988 "Determination of resistance to liquid media of paints and varnishes". Half of the test panel is immersed in 10% sulfuric acid solution and soaked at room temperature for 240 hours. Observe whether the coating film blistering, rusting or peeling.

[0039] 7. Alkali resistance chemical reagent test: The alkali resistance test is carried out in accordance with GB / T 9274-1988 "Determination of resistance to liquid media of paints and varnishes". Half of the test panel is immersed in 3% sodium chloride solution and soaked at room temperature for 240 hours. Observe whether the coating film blistering, rusting or peeling.

[0040] 8. Storage stability test: The storage stability test was conducted in accordance with GB / T 21782.8-2008 "Powder Coatings Part 8: Evaluation of Storage Stability of Thermosetting Powders". After the powder coating was placed in a constant temperature chamber at 40℃ for 30 days, the change rate of gelation time and the spray flowability were tested.

[0041] Table: Performance tests were conducted on a low-temperature curing anti-corrosion powder coating containing graphene from Examples 1-3 and Comparative Examples 1-5.

[0042] Table 1. Performance Test Results

[0043] Table 2. Performance Test Results

[0044] Data Analysis: 1. Corrosion resistance analysis: The excellent salt spray and chemical resistance of Examples 1-3 are mainly due to the physical barrier formed by silanized graphene in the coating, which effectively slows down the penetration path of corrosive media such as water, oxygen, and chloride ions. Example 2 shows better corrosion resistance than Comparative Example 5, demonstrating a synergistic effect between graphene and nano-titanium dioxide. Graphene provides physical insulation, while nano-titanium dioxide also acts as a shield, together constructing a more comprehensive protective network. The corrosion resistance of Comparative Example 3 is significantly lower than that of Example 2, indicating that sufficient silanization treatment is fundamental to ensuring a strong chemical bond between graphene and epoxy resin, thereby achieving the best barrier effect. The performance degradation in Comparative Example 4 is due to the tendency of excessive graphene to agglomerate, compromising the density of the coating.

[0045] 2. Mechanical property analysis: Example 2's excellent adhesion (grade 0) and impact resistance (50 cm) stem from the good compatibility and chemical bonding between silane-based graphene and epoxy resin, significantly enhancing the coating's cohesive strength and adhesion to the substrate. A Φ2 mm bending test demonstrates that a suitable amount of well-dispersed graphene toughens the epoxy resin, improving flexibility while maintaining high hardness. The decreased flexibility in Comparative Example 4 is attributed to excessive graphene agglomeration leading to stress concentration and increased coating brittleness. The extremely poor mechanical properties of Comparative Example 2 are due to interfacial bonding failure, causing graphene to debond from the resin matrix and failing to effectively transfer and disperse stress.

[0046] 3. Processing technology and storage stability analysis: The corrosion resistance of Comparative Example 5 was significantly lower than that of Example 2, indicating that nano-titanium dioxide is an important synergistic component in the corrosion protection system, and its absence weakens the overall protective ability of the coating. The good storage stability of Example 2 indicates that the components in its formulation have good compatibility, and the powder's physicochemical properties remain stable during storage. The severe agglomeration problem of Comparative Example 2 further confirms that good dispersion and interfacial compatibility are fundamental to the product's practical value.

[0047] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A low-temperature curing anti-corrosion powder coating containing graphene, characterized in that, Includes the following components by weight: Graphene-modified epoxy resin: 50-70 parts; Low-temperature curing agent: 20-30 parts; Leveling agent: 5-6 parts; Accelerator: 4-6 parts; Dispersant: 5-7 parts; Preservative: 2-3 parts; Nano titanium dioxide: 8-12 parts; Benzoin: 1-2 parts; Fluorinated wax: 0.2-0.8 parts; The graphene-modified epoxy resin is prepared by the following method: 1) Preparation of silane graphene: Graphene oxide was dispersed in an aqueous ethanol solution, sonicated, and the pH was adjusted to 4-5. γ-aminopropyltriethoxysilane was added, and the reaction was carried out at 60-80℃ for 4-8 hours. After centrifugation, washing, and drying in an oven at 50-60℃, silane graphene was obtained. 2) Grafting reaction of epoxy resin: Under inert gas protection, bisphenol A type epoxy resin and the silane graphene obtained in 1) are mixed at 100-120℃ for 30-60 min, and then triphenylphosphine catalyst is added. The reaction is carried out for 2-4 h, and then dried in an oven at 100-120℃ to obtain the graphene modified epoxy resin.

2. The low-temperature curing anti-corrosion powder coating containing graphene according to claim 1, characterized in that, The graphene oxide described in 1) has a size of 8-10 μm, and the mass ratio of graphene oxide to γ-aminopropyltriethoxysilane is 1:3-5.

3. The low-temperature curing anti-corrosion powder coating containing graphene according to claim 1, characterized in that, The epoxy resin mentioned in 2) is a bisphenol A type epoxy resin with an epoxy equivalent of 450-750 g / eq, a softening point of 60-95℃, a mass ratio of silane graphene to epoxy resin of 1-5:100, and a catalyst of triphenylphosphine of 0.2-0.4% of the mass of bisphenol A type epoxy resin.

4. The low-temperature curing anti-corrosion powder coating containing graphene according to claim 1, characterized in that, The low-temperature curing agent is dimethylaminopropionamide.

5. The low-temperature curing anti-corrosion powder coating containing graphene according to claim 1, characterized in that, The accelerator is dimethylimidazole.

6. The low-temperature curing anti-corrosion powder coating containing graphene according to claim 1, characterized in that, The leveling agent is one or more of leveling agent H88 and leveling agent H99.

7. The low-temperature curing anti-corrosion powder coating containing graphene according to claim 1, characterized in that, The dispersant is one or more of hydroxymethyl cellulose, polyvinylpyrrolidone, sodium polyacrylate, polyacrylic acid polymer, and polymer copolymer.

8. The low-temperature curing anti-corrosion powder coating containing graphene according to claim 1, characterized in that, The preservative is one or more of benzoic acid, sodium benzoate, ethyl p-hydroxybenzoate, and dehydroacetic acid.

9. A method for preparing a low-temperature curing anti-corrosion powder coating containing graphene as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Premixing: Mix the components according to the ratio at a speed of 2500-3000 r / min for 45-60 min; S2. Melt extrusion: The mixture is fed into a twin-screw extruder. The temperature in zone I is 80-90℃ and the temperature in zone II is 90-100℃. Melt blending and extrusion are carried out at a screw speed of 1000-1200 r / min. S3, tableting, cooling and crushing: After the extruded material is tableted, cooled, crushed and crushed, it is classified through a 100-160 mesh sieve to obtain powder coating products.

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