Preparation method of metal antirust powder coating

Abstract

The invention discloses a preparation method of a metal antirust powder coating, and belongs to the technical field of powder coatings. Comprising the following raw materials in parts by weight: 50-60 parts of epoxy resin, 15-20 parts of pigment, 3-5 parts of curing agent, 9-17 parts of antirust filler, 6-12 parts of functional additive and 0.3-0.5 part of flatting agent. Wherein the modified anti-rust filler remarkably improves the anti-rust performance of the coating; functional groups are introduced, so that the flame retardance and the corrosion resistance of the coating can be greatly enhanced, and the performance is long and stable; the anti-rust filler is a chromium-free anti-rust filler, the functional additive is a halogen-free flame retardant, and the prepared coating is also a powder coating, so that the anti-rust coating is environment-friendly; in conclusion, the coating prepared by the invention has stable and efficient flame-retardant and anti-rust performance, is green and environment-friendly, and has important application value in the technical field of powder coatings.

Description

Technical Field

[0001] This invention belongs to the field of powder coating technology, specifically, it relates to a method for preparing a metal anti-rust powder coating. Background Technology

[0002] Metallic materials, as core basic materials in modern industrial production and infrastructure construction, are widely used in numerous fields such as construction, machinery manufacturing, transportation, and aerospace. Their performance stability and service life are directly related to the safe production and economic benefits of related industries. However, metals are highly susceptible to electrochemical or chemical corrosion in the natural environment due to the erosion of media such as oxygen, moisture, acids, alkalis, and salts. This leads to rust, peeling, and even structural damage on the material surface, causing not only huge economic losses but also potentially serious safety hazards. Therefore, developing efficient, stable, and environmentally friendly metal rust prevention technologies has always been a research hotspot in the field of materials science.

[0003] Among numerous metal rust prevention technologies, coating protection has become one of the most widely used methods due to its ease of operation, moderate cost, and significant protective effect. While traditional solvent-based coatings possess good film-forming and adhesion properties, they release large amounts of volatile organic compounds (VOCs) during preparation and use. This not only harms the health of operators but also exacerbates air pollution and the greenhouse effect, contradicting current green and environmentally friendly development principles. With increasingly stringent environmental regulations and the growing acceptance of sustainable development concepts, solvent-free, low-pollution powder coatings are gradually becoming the ideal alternative to solvent-based coatings. Powder coatings, as a type of solid powder coating, are mainly composed of resin, curing agent, pigment, filler, and additives. They are applied to metal surfaces through electrostatic spraying or fluidized bed dipping, and after high-temperature baking and melting, a continuous and uniform coating is formed. Compared with traditional solvent-based coatings, powder coatings have advantages such as zero VOC emissions, high coating utilization rate, and excellent coating performance, showing broad application prospects in the field of metal rust prevention. Currently, epoxy resin is commonly used as a raw material for powder coatings. However, the molecular structure of epoxy resin determines its poor flame retardant properties, and it is easy to burn and release toxic fumes in high-temperature or open-flame environments, which limits its application in the field of metal rust prevention. Therefore, there is an urgent need to invent a metal rust-preventive powder coating with excellent flame retardant properties to meet the higher demands of the metal rust prevention field. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing metal anti-rust powder coatings.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing a metal anti-rust powder coating includes the following steps: A1. Add epoxy resin, pigment, curing agent, rust inhibitor, functional additives and leveling agent to a high-speed mixer and stir to ensure that the raw materials are evenly dispersed to obtain a homogeneous mixture; A2. The mixed material is fed into a twin-screw extruder, where the resin is melted by mechanical shearing and heating. The material is then extruded, pressed into sheets, cooled, pulverized by an ultra-fine pulverizer, sieved, and dried in an oven to obtain a metal anti-rust powder coating.

[0006] As a further technical solution, the raw materials are as follows by weight: 50-60 parts epoxy resin, 15-20 parts pigment, 3-5 parts curing agent, 9-17 parts rust-inhibiting filler, 6-12 parts functional additives and 0.3-0.5 parts leveling agent.

[0007] As a further technical solution, the curing agent is dicyandiamide.

[0008] As a further technical solution, the leveling agent is an acrylate leveling agent.

[0009] As a further technical solution, the stirring speed is 1000-1200 r / min, and the mixing time is 5-8 min.

[0010] As a further technical solution, the mesh size of the sieve is 300-400 mesh.

[0011] As a further technical solution, the rust-inhibiting filler is prepared through the following steps: B1. In a flask, first mix the silane coupling agent with an ethanol solution (ethanol to water volume ratio of 9:1), stir for 3-5 minutes, then adjust the pH of the solution to 4-5 with acetic acid to obtain the modified solution. B2. Dry mica iron oxide and zinc phosphate in an oven at 90-110℃ for 2-3 hours to remove adsorbed moisture, then add them to the modification solution, and then heat to 60-70℃ and disperse with ultrasonic assistance for 2-4 hours. After the reaction is complete, filter and dry in an oven at 90-110℃ for 2-3 hours to obtain the rust-preventive filler.

[0012] As a further technical solution, the raw materials are as follows by mass: 10-18 parts zinc phosphate, 10-20 parts mica iron oxide and 0.7-1.3 parts silane coupling agent.

[0013] As a further technical solution, the silane coupling agent is one of KH-540, KH-550, KH-560 and KH-570.

[0014] As a further technical solution, the functional additive is prepared through the following steps: C1. Add the reactants monoethanolamine borate, terephthalaldehyde, p-toluenesulfonic acid catalyst, and anhydrous ethanol solvent to a three-necked flask. After mixing the reactants evenly with mechanical stirring, heat the reaction apparatus. When the temperature reaches 50-55℃, maintain this temperature and keep the reaction at this temperature for 10-12 hours with stirring. After the reaction is complete, perform post-processing to obtain the initial product. C2. Add the initial product of the reaction raw materials, 2-aminobenzimidazole and solvent toluene into a three-necked flask. Mix the raw materials evenly with mechanical stirring. Then, add glacial acetic acid dropwise into the flask through a constant pressure dropping funnel. After the addition is complete, heat to 60-70℃ and maintain this temperature. Keep the reaction at this temperature for 7-8 hours under stirring. After the reaction is complete, perform post-processing to obtain the functional additive.

[0015] As a further technical solution, in step C1, the ratio of monoethanolamine borate, terephthalaldehyde, p-toluenesulfonic acid, and anhydrous ethanol is 10.5g:13.9-14.7g:0.8g:100mL.

[0016] As a further technical solution, the ratio of the amount of initial product, 2-aminobenzimidazole, anhydrous toluene, and glacial acetic acid in step C2 is 22.1g:13.3g:100mL:0.6g.

[0017] The reaction formula for preparing the functional additives in this invention is as follows: Regarding the preparation principle: The present invention prepares functional additives through a two-step carbonylamine condensation reaction. It should be noted that in step C1, the molar ratio of monoethanolamine borate to terephthalaldehyde needs to be strictly controlled to be close to 1:1 and terephthalaldehyde needs to be in excess to reduce the occurrence of side reactions.

[0018] Regarding the performance of the additives: As can be seen from the above reaction formula, the functional additives of the present invention introduce borate esters, Schiff bases, and benzimidazole groups. Among them, the borate ions in the borate esters are combined with the metal surface through coordination bonds to form a dense composite film, which can physically isolate water and oxygen, enhancing the rust resistance of the matrix. In addition, the borate esters decompose upon heating to generate boric acid and boron oxides, which cover the material surface to form a glassy protective layer, isolating oxygen and heat. Furthermore, boric acid promotes carbonization, forming a dense carbon layer, inhibiting the volatilization of combustibles, and improving the flame retardant properties of the matrix. The introduced Schiff base groups also have certain flame retardant properties and can work synergistically with the borate esters to significantly improve the flame retardancy of the matrix. Finally, the introduced benzimidazole groups can participate in the curing of epoxy resin, improving the long-term stability of the small molecule additives.

[0019] The beneficial effects of this invention are: 1. The coating prepared by the present invention significantly improves the rust prevention performance of the coating by modifying the rust-preventive filler (zinc phosphate + mica iron oxide) with silane coupling agent; 2. The self-made functional additives of this invention, by introducing functional groups, can significantly enhance the flame retardancy and corrosion resistance of coatings, and their performance remains stable over a long period of time; 3. The rust-preventive filler of this invention is a chromium-free rust-preventive filler, the functional additive is a halogen-free flame retardant, and the resulting coating is also a powder coating. Therefore, this invention is environmentally friendly. In summary, the coating prepared by this invention has stable and efficient flame retardant and rust-preventive properties, and is also environmentally friendly, thus possessing significant application value in the field of powder coating technology. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and 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] Example 1 Preparation of functional additives: C1. Add 10.5g of monoethanolamine borate, 13.9g of terephthalaldehyde, 0.8g of p-toluenesulfonic acid catalyst, and 100mL of anhydrous ethanol to a three-necked flask. Mix the reactants thoroughly with mechanical stirring. Heat the reaction apparatus to 50°C and maintain this temperature for 10 hours with stirring. Once the reaction is complete, remove the ethanol by vacuum distillation. Wash the residue with cold water, filter, cool to room temperature, wash with saturated sodium bicarbonate solution until neutral, and dry the organic phase with anhydrous magnesium sulfate to obtain the initial product. C2. Add 22.1g of the initial product, 13.3g of 2-aminobenzimidazole, and 100mL of toluene solvent to a three-necked flask. Mix the raw materials evenly with mechanical stirring. Then, add 0.6g of glacial acetic acid dropwise to the flask through a constant pressure dropping funnel. After the addition is complete, heat to 60℃ and maintain this temperature. Keep the reaction at this temperature for 7 hours with stirring. After the reaction is complete, the mixture is purified by rotary evaporation and column chromatography (the eluent is benzene and ethyl acetate in a volume ratio of 5:1) to obtain the functional additive. Preparation of rust-preventive fillers: B1. In a flask, first mix 0.7g of silane coupling agent KH-540 with 100mL of ethanol solution (ethanol to water volume ratio of 9:1), stir for 3min, and then adjust the pH of the solution to 4 with acetic acid to obtain the modified solution.

[0022] B2. Dry 10g of mica iron oxide and 10g of zinc phosphate in an oven at 90℃ for 2 hours to remove adsorbed moisture, then add them to the modified liquid, and then heat to 60℃ and disperse with ultrasonic assistance for 2 hours. After the reaction is complete, filter and dry in an oven at 90℃ for 2 hours to obtain the rust-preventive filler. A method for preparing a metal anti-rust powder coating includes the following steps: A1. Add 50g epoxy resin, 15g phthalocyanine blue, 3g dicyandiamide, 9g rust-inhibiting filler, 6g functional additives and 0.3g BYK-361N to a high-speed mixer and stir at 1000r / min for 5min to ensure uniform dispersion of the raw materials and obtain a homogeneous mixture. A2. The mixed material is fed into a twin-screw extruder, where the resin is melted by mechanical shearing and heating. The mixture is then extruded, pressed into sheets, cooled, pulverized by an ultra-fine pulverizer, sieved through a 300-mesh sieve, and dried in an oven to obtain a metal anti-rust powder coating.

[0023] Example 2 Preparation of functional additives: C1. Add 10.5g of monoethanolamine borate, 14.7g of terephthalaldehyde, 0.8g of p-toluenesulfonic acid catalyst, and 100mL of anhydrous ethanol to a three-necked flask. Mix the reactants thoroughly with mechanical stirring. Heat the reaction apparatus to 55°C and maintain this temperature for 2 hours with stirring. Once the reaction is complete, remove the ethanol by vacuum distillation. Wash the residue with cold water, filter, cool to room temperature, wash with saturated sodium bicarbonate solution until neutral, and dry the organic phase with anhydrous magnesium sulfate to obtain the initial product. C2. Add 22.1g of the initial product, 13.3g of 2-aminobenzimidazole, and 100mL of toluene solvent to a three-necked flask. Mix the raw materials evenly with mechanical stirring. Then, add 0.6g of glacial acetic acid dropwise to the flask through a constant pressure dropping funnel. After the addition is complete, heat to 70℃ and maintain this temperature. Keep the reaction at this temperature for 8 hours with stirring. After the reaction is complete, the mixture is purified by rotary evaporation and column chromatography (the eluent is benzene and ethyl acetate in a volume ratio of 5:1) to obtain the functional additive. Preparation of rust-preventive fillers: B1. In a flask, first mix 1.3g of silane coupling agent KH-550 with 100mL of ethanol solution (ethanol to water volume ratio of 9:1), stir for 5min, and then adjust the pH of the solution to 5 with acetic acid to obtain the modified solution.

[0024] B2. Dry 20g of mica iron oxide and 18g of zinc phosphate in an oven at 110℃ for 3h to remove adsorbed moisture, then add them to the modified liquid, then heat to 70℃ and disperse with ultrasonic assistance for 4h. After the reaction is complete, filter and dry in an oven at 110℃ for 3h to obtain the rust-preventive filler. A method for preparing a metal anti-rust powder coating includes the following steps: A1. Add 55g epoxy resin, 17.5g phthalocyanine green, 4g dicyandiamide, 13g rust-inhibiting filler, 9g functional additives and 0.4g BYK-361N to a high-speed mixer and stir at 1100r / min for 6min to ensure uniform dispersion of the raw materials and obtain a homogeneous mixture. A2. The mixed material is fed into a twin-screw extruder, where the resin is melted by mechanical shearing and heating. The mixture is then extruded, pressed into sheets, cooled, pulverized by an ultra-fine pulverizer, sieved through a 400-mesh sieve, and dried in an oven to obtain a metal anti-rust powder coating.

[0025] Example 3 The difference between this embodiment and Embodiment 2 is that a method for preparing a metal anti-rust powder coating includes the following steps: A1. Add 60g epoxy resin, 20g phthalocyanine green, 5g dicyandiamide, 17g rust-inhibiting filler, 12g functional additives and 0.5g BYK-361N to a high-speed mixer and stir at 1200r / min for 8min to ensure uniform dispersion of the raw materials and obtain a homogeneous mixture. A2. The mixed material is fed into a twin-screw extruder, where the resin is melted by mechanical shearing and heating. The mixture is then extruded, pressed into sheets, cooled, pulverized by an ultra-fine pulverizer, sieved through a 400-mesh sieve, and dried in an oven to obtain a metal anti-rust powder coating.

[0026] Comparative Example 1 The only difference between this comparative example and Example 2 is that in this comparative example, 9g of dimethyl methylphosphonate was used to replace the functional additive in Example 2 to prepare the coating.

[0027] Comparative Example 2 The only difference between this comparative example and Example 2 is that no rust-inhibiting filler is added in this comparative example to obtain the coating.

[0028] The above embodiments and comparative examples were subjected to the following performance tests: Using the GB / T 1771-2007 standard, the sample was sprayed onto the surface of a metal sheet with a thickness of 5 μm. The rust prevention ability of the sample under salt spray environment was measured, and the sample was rated according to the rust area (e.g., level 0 means no rust, level 10 means complete rust). The flame retardancy time of the samples was determined using GB 12441 standard, and the same standard was used to determine the flame retardancy time of the samples after standing at room temperature for 300 days. The measured results are shown in Table 1: Table 1 Test Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Rust prevention level after 200 hours Level 0 Level 0 Level 0 Level 4 Level 6 Flame resistance time / min 55 59 60 50 56 Flame resistance time (after 300 days) / min 52 56 56 41 53 As can be seen from the table above, the coatings prepared in the embodiments of the present invention have higher rust prevention and flame retardant properties than the comparative examples, and the flame retardant properties are stable over a long period of time. Therefore, the present invention has important application value in the field of powder coating technology.

[0029] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for producing a metal rust-preventive powder paint, characterized by, The method comprises the following steps: A1, adding epoxy resin, pigment, curing agent, anti-rust filler, functional additive and leveling agent into a high-speed mixer, stirring and mixing to obtain mixed material; A2, feeding the mixed material into an extruder, melting the resin through mechanical shearing and heating, extruding and pressing into tablets, cooling, crushing, sieving and drying to obtain metal anti-rust powder coating.

2. The method of claim 1, wherein the metal rust-preventive powder paint is prepared by adding a metal rust-preventive pigment to a base paint, and then adding a dispersant and a thickener to the base paint. The raw materials are as follows in terms of mass fraction: 50-60 parts of epoxy resin, 15-20 parts of pigment, 3-5 parts of curing agent, 9-17 parts of anti-rust filler, 6-12 parts of functional additive and 0.3-0.5 parts of leveling agent.

3. The method of claim 1, wherein the metal antirust powder paint is prepared by adding 0.1 to 0.5 parts by weight of the compound of formula (1) to 100 parts by weight of a base paint. The anti-rust filler is prepared by the following steps: B1, mixing silane coupling agent with ethanol solution, stirring, adjusting pH to 4-5 to obtain modified liquid; B2, drying mica and zinc phosphate, then adding into the modified liquid, heating to 60-70℃, ultrasonic dispersion for 2-4h, reaction completion, filtering and drying to obtain anti-rust filler.

4. The method of claim 1, wherein the metal antirust powder paint is prepared by adding 0.1 to 0.5 parts by weight of the compound of formula (I) to 100 parts by weight of a base paint. The functional additive is prepared by the following steps: C1, adding monoethanolamine borate, p-xylylene glycol, p-toluenesulfonic acid and anhydrous ethanol into a flask, stirring and uniformly mixing, then reacting for 10-12h at 50-55℃ under stirring, reaction completion, obtaining initial product; C2, adding the initial product, 2-amino benzimidazole and toluene into a flask, stirring to uniformly mix the raw materials, then adding glacial acetic acid dropwise, after dropwise completion, reacting for 7-8h at 60-70℃ under stirring, reaction completion, obtaining functional additive.

5. The method of claim 1, wherein the metal anti-rust powder coating is prepared by adding 0.1 to 0.5 parts by weight of the compound of formula (I) to 100 parts by weight of a metal anti-rust powder coating. The curing agent is dicyandiamide.

6. The method of claim 1, wherein the metal anti-rust powder coating is prepared by adding 0.1 to 0.5 parts by weight of the compound of formula (I) to 100 parts by weight of a metal anti-rust powder coating. The leveling agent is acrylic acid ester leveling agent.

7. The method of claim 3, wherein the metal antirust powder paint is prepared by adding 0.1 to 0.5 parts by weight of the compound of formula (I) to 100 parts by weight of a base paint. The raw materials are as follows in terms of mass fraction: 10-18 parts of zinc phosphate, 10-20 parts of mica and iron oxide and 0.7-1.3 parts of silane coupling agent.

8. The method of claim 3, wherein the metal antirust powder paint is prepared by adding 0.1 to 0.5 parts by weight of the compound of formula (I) to 100 parts by weight of a metal antirust powder paint. The silane coupling agent is one of KH-540, KH-550, KH-560 and KH-570.

9. The method of claim 4, wherein the metal anti-rust powder coating is prepared by adding 0.1 to 0.5 parts by weight of the compound of formula (I) to 100 parts by weight of a metal anti-rust powder coating. The amount ratio of monoethanolamine borate, p-xylylene glycol, p-toluenesulfonic acid, anhydrous ethanol in step C1 is 10.5g:13.9-14.7g:0.8g:100mL.

10. The method of claim 4, wherein the metal antirust powder paint is prepared by adding 0.1 to 0.5 parts by weight of the compound of formula (I) to 100 parts by weight of a metal antirust powder paint. The amount ratio of initial product, 2-amino benzimidazole, anhydrous toluene, glacial acetic acid in step C2 is 22.1g:13.3g:100mL:0.6g.

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