Salt-spray-resistant high-solid epoxy coating and preparation method thereof

Abstract

The invention relates to the technical field of coatings. The salt-spray-resistant high-solid epoxy coating is prepared from the following raw materials in parts by weight: 30 to 50 parts of bisphenol A epoxy resin, 5 to 15 parts of carboxyl-terminated nitrile rubber, 5 to 10 parts of diethylenetriamine, 10 to 20 parts of mixed solution, 10 to 20 parts of flaky antirust filler, 0.3 to 0.8 part of dispersing agent, 0.1 to 0.4 part of defoaming agent, 0.2 to 0.6 part of flatting agent, 3 to 6 parts of first additive, 2 to 5 parts of second additive and 0.3 to 0.8 part of ultraviolet stabilizer. In the invention, under the synergism of the two, not only is the overall compactness of the coating enhanced, but also the chemical barrier layer is constructed at the interface, so that the salt spray resistance of the coating is improved, and the service life of the coating in a severe corrosion environment is greatly prolonged.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a salt spray resistant high-solids epoxy coating and its preparation method. Background Technology

[0002] Epoxy resin coatings are high-performance coatings that use epoxy resin as the main film-forming substance and form a three-dimensional network structure through a cross-linking reaction with a curing agent. Their main components include epoxy resin base, curing agent, solvent, filler, and functional additives. Epoxy resin molecules contain active groups such as epoxy and hydroxyl groups, which endow the coating with adhesion, mechanical strength, and chemical corrosion resistance. Due to their outstanding comprehensive performance, epoxy resin coatings are widely used for protection in heavily corrosive environments such as ships, bridges, chemical equipment, and underground pipelines.

[0003] Existing epoxy coating systems mostly rely on the self-barrier properties of the resin matrix and the physical shielding effect of conventional anti-rust fillers. Their protection mechanism is relatively simple, and the components are usually simply physically mixed. They lack effective interfacial chemical bonding and functional synergistic design, which leads to a bottleneck in improving salt spray resistance.

[0004] Based on this, the present invention provides a salt spray resistant high-solids epoxy coating and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to provide a salt spray resistant high-solids epoxy coating and its preparation method. The salt spray resistant high-solids epoxy coating prepared by this invention not only has good corrosion resistance but also excellent flexibility.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a salt spray resistant high-solids epoxy coating, comprising the following raw materials in parts by weight: 30-50 parts bisphenol A type epoxy resin, 5-15 parts carboxyl-terminated nitrile rubber, 5-10 parts diethylenetriamine, 10-20 parts mixed solution, 10-20 parts flake anti-rust filler, 0.3-0.8 parts dispersant, 0.1-0.4 parts defoamer, 0.2-0.6 parts leveling agent, 3-6 parts first additive, 2-5 parts second additive, and 0.3-0.8 parts ultraviolet light stabilizer.

[0007] The second additive is prepared by oxidative copolymerization of aniline, o-phenylenediamine and 5-aminobenzotriazole to obtain a dispersion, which is then compounded with polyacrylonitrile and modified with a silane coupling agent.

[0008] Preferably, the preparation process of the first additive is as follows: isopropanol and water are mixed at a volume ratio of 1:1 to obtain a first liquid; the first liquid, 2-acrylamido-2-methylpropanesulfonic acid, styrene, mercaptoethanol, vinyl phosphoric acid, and azobisisobutyronitrile are added to a reaction vessel at a mass ratio of 20:3-5:2-4:0.4-0.6:0.4-0.6:0.1-0.3; under a nitrogen atmosphere, the temperature is raised to 65-75°C, and the pH is adjusted to 5.0-7.0 by adding 0.5 mol / L sodium hydroxide solution; the reaction is stirred at 300-400 r / min for 6-8 h to obtain a second liquid; the second liquid is added dropwise to 5-8 times its volume of acetone for precipitation; the precipitate is collected by filtration and dried under vacuum at 50°C. The mixture was brought to constant weight to obtain the first additive. The first additive was dissolved in N,N-dimethylformamide at a mass ratio of 2:0.8–1.2 to obtain the second additive, which was then set aside. Polycarbonate diol, isophorone diisocyanate, and dibutyltin dioctanoate were added to a reaction vessel and reacted at 80°C for 4–6 h. The temperature was then lowered to 70°C at a rate of 1–2°C / min, and the second additive was added. The mixture was stirred at 300–400 r / min for 1–2 h. Then, γ-isocyanate-propyltrimethoxysilane and dibutyltin dilaurate were added, and the mixture was stirred at 70°C for 0.8–1.2 h. The mixture was then removed, and the solid content of the final product was adjusted to 50 wt% using butanone, thus completing the preparation of the first additive.

[0009] Preferably, the mass ratio of polycarbonate diol, isophorone diisocyanate, dibutyltin dioctanoate, the second auxiliary agent, and γ-isocyanate-propyltrimethoxysilane is 10:3-4:0.05-0.07:2.8-3.2:1-1.4, the molecular weight of the polycarbonate diol is 2000-3000, and the mass ratio of γ-isocyanate-propyltrimethoxysilane to dibutyltin dilaurate is 20:1.

[0010] Preferably, the preparation method of the second additive is as follows: aniline, o-phenylenediamine, 5-aminobenzotriazole, and a 1 mol / L hydrochloric acid aqueous solution are added to a reaction vessel at a mass ratio of 1:0.5–1:0.1–0.2:15–20. The mixture is stirred and mixed evenly under an ice-water bath. Then, ammonium persulfate hydrochloric acid solution is slowly added dropwise, controlling the temperature at 0–5°C. After the addition is complete, the reaction proceeds for 2–4 hours, then the temperature is raised to room temperature and reacted for 6–12 hours. Subsequently, the pH is adjusted to 6.8–7.2 with 0.5 mol / L sodium hydroxide solution to obtain a dispersion for later use. Polyacrylonitrile is dissolved in… In N,N-dimethylformamide, a first solution of 5-10 wt% was prepared. The dispersion and the first solution were mixed at a mass ratio of 1:1-2. KH-570 was then added, and the pH was adjusted to 4-5 with acetic acid. The temperature was raised to 70-80℃, and the reaction was refluxed under nitrogen protection for 3-6 hours to obtain the reactant. The reactant was added dropwise to anhydrous ethanol to precipitate, and the solid was collected by filtration. The solid was washed 1-2 times with anhydrous ethanol solution, then washed 3-5 times with deionized water, and finally washed once with anhydrous ethanol. The solid was then dried under vacuum at 50-70℃ to obtain the second additive.

[0011] Preferably, the rust-preventive filler is at least one of glass flakes or mica iron oxide.

[0012] Preferably, the amount of KH-570 added is 5% to 10% of the mass of the polyacrylonitrile.

[0013] Preferably, the ammonium persulfate hydrochloric acid solution is prepared by dissolving ammonium persulfate in a 1 mol / L hydrochloric acid aqueous solution, wherein the concentration of ammonium persulfate is 0.8–1.2 mol / L, the molar ratio of ammonium persulfate to aniline is 1:0.9–1.1, and the addition is carried out at a uniform rate over 20–40 minutes.

[0014] Preferably, the mixed solution is prepared by mixing xylene, n-butanol and butyl acetate in a mass ratio of 5:2:3.

[0015] Preferably, the dispersant is BYK-163, the defoamer is BYK-141, and the leveling agent is BYK-306.

[0016] A method for preparing a salt spray resistant high-solids epoxy coating includes the following steps: Step 1: Add bisphenol A type epoxy resin, carboxyl-terminated nitrile rubber and mixed solution sequentially to a stirred tank, and stir at room temperature for 15-30 minutes at a speed of 400-600 r / min to ensure thorough mixing and obtain resin base material; Step 2: Add the first additive to the resin base material from Step 1. At room temperature, increase the stirring speed to 800-1000 r / min and continue stirring for 20-40 min. Then adjust the stirring speed to 600-800 r / min and add the dispersant, defoamer and flake rust inhibitor in sequence. After the addition is complete, transfer the material to a sand mill for grinding and dispersion until the fineness is ≤50μm. Step 3: Transfer the ground slurry back to the mixing tank. At room temperature, add the leveling agent, UV stabilizer, second additive, and diethylenetriamine in sequence at a speed of 400-600 rpm. Continue stirring for 20-30 minutes. Then reduce the stirring speed to 200-300 rpm and stir for 10-15 minutes. Let it stand for 15-30 minutes. Finally, filter it through a 100-200 mesh filter to obtain a salt spray resistant high-solids epoxy coating.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, the molecular design of the first additive and the second additive achieves functional complementarity and chemical bonding. The strong polar groups of the first additive form a tight cross-link with the resin and curing agent, while the terminal silane groups bond with the filler and substrate to construct a dense physical barrier. The aniline-copolymer conjugated structure of the second additive can block the penetration of water and oxygen ions, and after silane modification, it condenses with the silanol groups of the first additive to form an organic-inorganic hybrid network. The synergy of the two not only enhances the overall density of the coating, but also constructs a chemical barrier layer at the interface, thereby improving the salt spray resistance of the coating and significantly extending its service life in harsh corrosive environments.

[0018] 2. In this invention, the polyurethane flexible segments introduced into the first additive molecule can effectively embed into the rigid three-dimensional network of epoxy resin, playing an internal toughening role and significantly alleviating the internal stress during the curing process, thereby improving the flexibility of the coating. At the same time, the second additive, after being modified with silane, has excellent compatibility with the resin matrix, avoiding interface defects caused by filler agglomeration. The two work synergistically to jointly strengthen the interfacial bonding force between the filler and the resin, and between the coating and the substrate, ensuring that the coating can maintain excellent adhesion and good flexibility even when exposed to corrosive environments for a long time, meeting the stringent requirements of high-end equipment for the comprehensive performance of the coating. Attached Figure Description

[0019] Figure 1 The present invention provides a flowchart of a salt spray resistant high-solids epoxy coating and its preparation method. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that the raw materials used in the following embodiments are all commercially available.

[0022] Example 1: A salt spray resistant high-solids epoxy coating, composed of the following raw materials in parts by weight: 30 parts bisphenol A type epoxy resin, 5 parts carboxyl-terminated nitrile rubber, 5 parts diethylenetriamine, 10 parts mixed solution, 10 parts flake anti-rust filler, 0.3 parts dispersant, 0.1 parts defoamer, 0.2 parts leveling agent, 3 parts first additive, 2 parts second additive, and 0.3 parts ultraviolet light stabilizer.

[0023] The second additive is prepared by oxidative copolymerization of aniline, o-phenylenediamine and 5-aminobenzotriazole, followed by compounding with polyacrylonitrile and modification with a silane coupling agent.

[0024] The preparation process of the first additive is as follows: Isopropanol and water are mixed at a volume ratio of 1:1 to obtain a first liquid. The first liquid, 2-acrylamido-2-methylpropanesulfonic acid, styrene, mercaptoethanol, vinyl phosphoric acid, and azobisisobutyronitrile are added to a reaction vessel at a mass ratio of 20:3:2:0.4:0.4:0.1. Under a nitrogen atmosphere, the temperature is raised to 65℃, and the pH is adjusted to 5.0 by adding 0.5 mol / L sodium hydroxide solution. The mixture is stirred at 300 r / min for 6 h to obtain a second liquid. The second liquid is added dropwise to acetone at a volume of 5 times its volume to precipitate. The precipitate is collected by filtration and dried under vacuum at 50℃ to constant weight to obtain the first additive. The first additive was dissolved in N,N-dimethylformamide at a mass ratio of 2:0.8 to obtain the second additive, which was then set aside. Polycarbonate diol, isophorone diisocyanate, and dibutyltin dioctanoate were added to a reaction vessel and reacted at 80°C for 4 hours. The temperature was then lowered to 70°C at a rate of 1°C / min, and the second additive was added. The mixture was stirred at 300 r / min for 1 hour. Subsequently, γ-isocyanate-propyltrimethoxysilane and dibutyltin dilaurate were added, and the mixture was stirred at 70°C for 0.8 hours. The mixture was then removed, and the solid content of the final product was adjusted to 50 wt% using butanone, thus completing the preparation of the first additive.

[0025] The mass ratio of polycarbonate diol, isophorone diisocyanate, dibutyltin dioctanoate, second auxiliary agent, and γ-isocyanate-propyltrimethoxysilane is 10:3:0.05:2.8:1, the molecular weight of polycarbonate diol is 2000, and the mass ratio of γ-isocyanate-propyltrimethoxysilane to dibutyltin dilaurate is 20:1.

[0026] The second additive is prepared by adding aniline, o-phenylenediamine, 5-aminobenzotriazole, and a 1 mol / L hydrochloric acid aqueous solution to a reaction vessel at a mass ratio of 1:0.5:0.1:15. The mixture is stirred and mixed thoroughly under an ice-water bath. Then, ammonium persulfate hydrochloric acid solution is slowly added dropwise while maintaining the temperature at 0°C. After the addition is complete, the reaction proceeds for 2 hours, followed by a further increase to room temperature and a reaction for 6 hours. The pH is then adjusted to 6.8 with a 0.5 mol / L sodium hydroxide solution to obtain a dispersion for later use. Polyacrylonitrile is dissolved in N,N... In dimethylformamide, a 5wt% first solution was prepared. The dispersion and the first solution were mixed at a mass ratio of 1:1. KH-570 was then added, and the pH was adjusted to 4 with acetic acid. The temperature was raised to 70°C, and the reaction was refluxed for 3 hours under nitrogen protection to obtain the reactant. The reactant was added dropwise to anhydrous ethanol to precipitate, and the solid was collected by filtration. The solid was washed once with anhydrous ethanol solution, then washed three times with deionized water, and finally washed once with anhydrous ethanol. The solid was then dried under vacuum at 50°C to obtain the second additive.

[0027] The rust-preventive filler is mica iron oxide.

[0028] The amount of KH-570 added is 5% of the mass of polyacrylonitrile.

[0029] The ammonium persulfate hydrochloric acid solution was prepared by dissolving ammonium persulfate in a 1 mol / L hydrochloric acid aqueous solution, wherein the concentration of ammonium persulfate was 0.8 mol / L, the molar ratio of ammonium persulfate to aniline was 1:0.9, and the addition was carried out at a uniform rate over 20 minutes.

[0030] The mixed solution was prepared by mixing xylene, n-butanol and butyl acetate in a mass ratio of 5:2:3.

[0031] The dispersant is BYK-163, the defoamer is BYK-141, and the leveling agent is BYK-306.

[0032] A method for preparing a salt spray resistant high-solids epoxy coating includes the following steps: Step 1: Add bisphenol A type epoxy resin, carboxyl-terminated nitrile rubber and mixed solution to a stirring tank in sequence, and stir at room temperature for 15 minutes at 400 r / min to make it fully mixed and uniform, so as to obtain resin base material; Step 2: Add the first additive to the resin base material from Step 1. At room temperature, increase the stirring speed to 800 r / min and stir continuously for 20 min. Then adjust the stirring speed to 600 r / min and add the dispersant, defoamer and flake rust inhibitor in sequence. After the addition is complete, transfer the material to a sand mill for grinding and dispersion until the fineness is ≤50μm. Step 3: Transfer the ground slurry back to the mixing tank, and at room temperature and a speed of 400 r / min, add the leveling agent, UV stabilizer, second additive and diethylenetriamine in sequence, and continue stirring for 20 min. Then reduce the stirring speed to 200 r / min and stir for 10 min. Then let it stand for 15 min. Finally, filter it with a 100 mesh filter to obtain a salt spray resistant high solids epoxy coating.

[0033] Example 2: A salt spray resistant high-solids epoxy coating, composed of the following raw materials in parts by weight: 40 parts bisphenol A type epoxy resin, 10 parts carboxyl-terminated nitrile rubber, 7 parts diethylenetriamine, 15 parts mixed solution, 15 parts flake anti-rust filler, 0.6 parts dispersant, 0.2 parts defoamer, 0.4 parts leveling agent, 4 parts first additive, 3 parts second additive, and 0.6 parts ultraviolet light stabilizer.

[0034] The second additive is prepared by oxidative copolymerization of aniline, o-phenylenediamine and 5-aminobenzotriazole, followed by compounding with polyacrylonitrile and modification with a silane coupling agent.

[0035] The preparation process of the first additive is as follows: Isopropanol and water are mixed at a volume ratio of 1:1 to obtain a first liquid. The first liquid, 2-acrylamido-2-methylpropanesulfonic acid, styrene, mercaptoethanol, vinyl phosphoric acid, and azobisisobutyronitrile are added to a reaction vessel at a mass ratio of 20:34:3:0.5:0.5:0.2. Under a nitrogen atmosphere, the temperature is raised to 70℃, and the pH is adjusted to 6.0 by adding 0.5 mol / L sodium hydroxide solution. The mixture is stirred at 350 r / min for 7 h to obtain a second liquid. The second liquid is added dropwise to acetone at a volume of 7 times its volume to precipitate. The precipitate is collected by filtration and dried under vacuum at 50℃ to constant weight to obtain the first additive. The first additive was dissolved in N,N-dimethylformamide at a mass ratio of 2:1 to obtain the second additive, which was then set aside. Polycarbonate diol, isophorone diisocyanate, and dibutyltin dioctanoate were added to a reaction vessel and reacted at 80°C for 5 hours. The temperature was then lowered to 70°C at a rate of 1.5°C / min, and the second additive was added. The mixture was stirred at 350 r / min for 1.5 hours. Subsequently, γ-isocyanate-propyltrimethoxysilane and dibutyltin dilaurate were added, and the mixture was stirred at 70°C for 1 hour. The mixture was then removed, and the solid content of the final product was adjusted to 50 wt% using butanone, thus completing the preparation of the first additive.

[0036] The mass ratio of polycarbonate diol, isophorone diisocyanate, dibutyltin dioctanoate, second auxiliary agent, and γ-isocyanate-propyltrimethoxysilane is 10:3.5:0.06:3:1.2, the molecular weight of polycarbonate diol is 2500, and the mass ratio of γ-isocyanate-propyltrimethoxysilane to dibutyltin dilaurate is 20:1.

[0037] The second additive is prepared by adding aniline, o-phenylenediamine, 5-aminobenzotriazole, and a 1 mol / L hydrochloric acid aqueous solution to a reaction vessel at a mass ratio of 1:0.7:0.15:17. The mixture is stirred and mixed thoroughly under an ice-water bath. Then, ammonium persulfate hydrochloric acid solution is slowly added dropwise while maintaining the temperature at 3°C. After the addition is complete, the reaction proceeds for 3 hours, followed by a further 10 hours at room temperature. The pH is then adjusted to 7 with a 0.5 mol / L sodium hydroxide solution to obtain a dispersion for later use. Polyacrylonitrile is dissolved in N,N-di(2,3 ... In methylformamide, a 7wt% first solution was prepared. The dispersion and the first solution were mixed at a mass ratio of 1:1.5, and then KH-570 was added. The pH was adjusted to 4.5 with acetic acid, and the temperature was raised to 75°C. The mixture was refluxed under nitrogen protection for 6 hours to obtain the reactant. The reactant was added dropwise to anhydrous ethanol to precipitate the solid. The solid was collected by filtration, washed once with anhydrous ethanol solution, then washed four times with deionized water, and finally washed once with anhydrous ethanol. The solid was then dried under vacuum at 60°C to obtain the second additive.

[0038] The rust-preventive filler is glass flakes.

[0039] The amount of KH-570 added is 7% of the mass of polyacrylonitrile.

[0040] The ammonium persulfate hydrochloric acid solution is prepared by dissolving ammonium persulfate in a 1 mol / L hydrochloric acid aqueous solution, wherein the concentration of ammonium persulfate is 1 mol / L, the molar ratio of ammonium persulfate to aniline is 1:1, and the addition is carried out at a uniform rate within 30 minutes.

[0041] The mixed solution was prepared by mixing xylene, n-butanol and butyl acetate in a mass ratio of 5:2:3.

[0042] The dispersant is BYK-163, the defoamer is BYK-141, and the leveling agent is BYK-306.

[0043] A method for preparing a salt spray resistant high-solids epoxy coating includes the following steps: Step 1: Add bisphenol A type epoxy resin, carboxyl-terminated nitrile rubber and mixed solution to a stirring tank in sequence, and stir at room temperature for 17 minutes at 500 r / min to make it fully mixed and uniform, so as to obtain resin base material; Step 2: Add the first additive to the resin base material from Step 1. At room temperature, increase the stirring speed to 900 r / min and stir continuously for 30 min. Then adjust the stirring speed to 700 r / min and add the dispersant, defoamer and flake rust inhibitor in sequence. After the addition is complete, transfer the material to a sand mill for grinding and dispersion until the fineness is ≤50μm. Step 3: Transfer the ground slurry back to the mixing tank, and at room temperature and a speed of 500 r / min, add the leveling agent, UV stabilizer, second additive and diethylenetriamine in sequence, and continue stirring for 25 min. Then reduce the stirring speed to 220 r / min and stir for 12 min. Then let it stand for 22 min. Finally, filter it with a 150 mesh filter to obtain a salt spray resistant high solids epoxy coating.

[0044] Example 3: A salt spray resistant high-solids epoxy coating, composed of the following raw materials in parts by weight: 50 parts bisphenol A type epoxy resin, 15 parts carboxyl-terminated nitrile rubber, 10 parts diethylenetriamine, 20 parts mixed solution, 20 parts flake anti-rust filler, 0.8 parts dispersant, 0.4 parts defoamer, 0.6 parts leveling agent, 6 parts first additive, 5 parts second additive, and 0.8 parts ultraviolet light stabilizer.

[0045] The second additive is prepared by oxidative copolymerization of aniline, o-phenylenediamine and 5-aminobenzotriazole, followed by compounding with polyacrylonitrile and modification with a silane coupling agent.

[0046] The preparation process of the first additive is as follows: Isopropanol and water are mixed at a volume ratio of 1:1 to obtain a first liquid. The first liquid, 2-acrylamido-2-methylpropanesulfonic acid, styrene, mercaptoethanol, vinyl phosphoric acid, and azobisisobutyronitrile are added to a reaction vessel at a mass ratio of 20:5:4:0.6:0.6:0.3. Under a nitrogen atmosphere, the temperature is raised to 75°C, and the pH is adjusted to 7.0 by adding 0.5 mol / L sodium hydroxide solution. The mixture is stirred at 400 r / min for 8 hours to obtain a second liquid. The second liquid is added dropwise to acetone at a volume of 8 times its volume to precipitate. The precipitate is collected by filtration and dried under vacuum at 50°C to constant weight to obtain the first additive. The first additive was dissolved in N,N-dimethylformamide at a mass ratio of 2:1.2 to obtain the second additive, which was then set aside. Polycarbonate diol, isophorone diisocyanate, and dibutyltin dioctanoate were added to a reaction vessel and reacted at 80°C for 6 hours. The temperature was then lowered to 70°C at a rate of 2°C / min, and the second additive was added. The mixture was stirred at 400 r / min for 2 hours. Subsequently, γ-isocyanate-propyltrimethoxysilane and dibutyltin dilaurate were added, and the mixture was stirred at 70°C for 1.2 hours. The mixture was then removed, and the solid content of the final product was adjusted to 50 wt% using butanone, thus completing the preparation of the first additive.

[0047] The mass ratio of polycarbonate diol, isophorone diisocyanate, dibutyltin dioctanoate, second auxiliary agent, and γ-isocyanate-propyltrimethoxysilane is 10:4:0.07:3.2:1.4, the molecular weight of polycarbonate diol is 3000, and the mass ratio of γ-isocyanate-propyltrimethoxysilane to dibutyltin dilaurate is 20:1.

[0048] The second additive is prepared by adding aniline, o-phenylenediamine, 5-aminobenzotriazole, and a 1 mol / L hydrochloric acid aqueous solution to a reaction vessel at a mass ratio of 1:01:0.2:20. The mixture is stirred and mixed thoroughly under an ice-water bath. Then, ammonium persulfate hydrochloric acid solution is slowly added dropwise while maintaining the temperature at 5°C. After the addition is complete, the reaction proceeds for 4 hours, followed by a further 6 hours at room temperature. The pH is then adjusted to 7.2 with 0.5 mol / L sodium hydroxide solution to obtain a dispersion for later use. Polyacrylonitrile is dissolved in N,N- In dimethylformamide, a 10wt% first solution was prepared. The dispersion and the first solution were mixed at a mass ratio of 1:2. KH-570 was then added, and the pH was adjusted to 5 with acetic acid. The mixture was heated to 80℃ and refluxed for 6 hours under nitrogen protection to obtain the reactant. The reactant was added dropwise to anhydrous ethanol to precipitate the solid. The solid was collected by filtration, washed twice with anhydrous ethanol solution, then washed five times with deionized water, and finally washed once with anhydrous ethanol. The solid was then dried under vacuum at 70℃ to obtain the second additive.

[0049] The rust-preventive filler is glass flakes.

[0050] The amount of KH-570 added is 10% of the mass of polyacrylonitrile.

[0051] The ammonium persulfate hydrochloric acid solution was prepared by dissolving ammonium persulfate in a 1 mol / L hydrochloric acid aqueous solution, wherein the concentration of ammonium persulfate was 1.2 mol / L, the molar ratio of ammonium persulfate to aniline was 1:1.1, and the addition was carried out at a uniform rate over 40 minutes.

[0052] The mixed solution was prepared by mixing xylene, n-butanol and butyl acetate in a mass ratio of 5:2:3.

[0053] The dispersant is BYK-163, the defoamer is BYK-141, and the leveling agent is BYK-306.

[0054] A method for preparing a salt spray resistant high-solids epoxy coating includes the following steps: Step 1: Add bisphenol A type epoxy resin, carboxyl-terminated nitrile rubber and mixed solution to a stirring tank in sequence, and stir at room temperature at 600 r / min for 30 min to make it fully mixed and uniform, so as to obtain resin base material; Step 2: Add the first additive to the resin base material from Step 1. At room temperature, increase the stirring speed to 1000 r / min and stir continuously for 40 min. Then adjust the stirring speed to 800 r / min and add the dispersant, defoamer and flake rust inhibitor in sequence. After the addition is complete, transfer the material to a sand mill for grinding and dispersion until the fineness is ≤50μm. Step 3: Transfer the ground slurry back to the mixing tank, and at room temperature and a speed of 600 r / min, add the leveling agent, UV stabilizer, second additive and diethylenetriamine in sequence, and continue stirring for 30 min. Then reduce the stirring speed to 300 r / min and stir for 15 min. Then let it stand for 30 min. Finally, filter it with a 200 mesh filter to obtain a salt spray resistant high solids epoxy coating.

[0055] Comparative Example 1: The difference between this comparative example and Example 1 is that no first additive was added in this comparative example.

[0056] Comparative Example 2: The difference between this comparative example and Example 1 is that no second additive was added in this comparative example.

[0057] Comparative Example 3 differs from Example 1 in that it does not contain the first additive or the second additive. Performance testing: The salt spray resistant high-solids epoxy coatings prepared in Examples 1-3 and Comparative Examples 1-3 were uniformly sprayed onto standard tinplate (120mm×50mm×0.3mm), with the dry film thickness controlled at (80±10)μm. The coatings were cured at room temperature for 7 days to obtain test panels, and their performance was tested. Salt spray resistance test: Place the test panel in a salt spray test chamber and set the test conditions as follows: 5% (mass fraction) NaCl aqueous solution, solution pH 6.5, test temperature 35℃, continuous spraying; observe the corrosion (blistering, rusting, peeling) of the test panel surface every 24 hours, and record the cumulative spraying time when the test panel shows obvious corrosion (level ≤ 8), referring to the national standard GB / T1771-2020 "Determination of resistance to neutral salt spray of paints and varnishes"; Adhesion Test: Using a cross-cut tester, draw 6 parallel horizontal lines and 6 parallel vertical lines (2mm spacing) on ​​the test panel surface, forming 100 squares. After removing debris with a soft brush, apply 3M 600 tape and quickly peel it off. Observe the paint film peeling within the squares and rate it according to the standard (Grade 0: no peeling; Grade 1: peeling area <5%; Grade 2: peeling area 5% to 15%; Grade 3: peeling area 15% to 35%; Grade 4: peeling area 35% to 65%; Grade 5: peeling area > 65%), referring to the national standard GB / T9286-1998 "Cross-cut Test of Paint and Varnish Films". Flexibility test: Start the test with a larger diameter shaft (e.g., 10mm). If the coating is normal, use shafts with smaller diameters in sequence until the smallest diameter at which the coating does not crack is found. With the paint side of the sample facing outward, bend the sample smoothly and quickly around the shaft 180 degrees within 2-3 seconds. Immediately observe the coating of the bent part of the sample under a 4x magnifying glass and record the smallest shaft diameter at which the coating does not crack. If cracking occurs at a certain diameter, it is determined that the flexibility of the sample does not meet the requirement of this diameter, and its flexibility limit value is greater than this diameter. Refer to the national standard GB / T1731-2020. The obtained test data is recorded in the table below: Table 1 Performance Test Table of Epoxy Coating Samples

[0058] As shown in Table 1, the performance of Examples 1-3 is superior to that of Comparative Examples 1-3. This is because in Examples 1-3, the 2-acrylamido-2-methylpropanesulfonic acid in the first additive contains sulfonic acid and phosphate groups, which are highly polar groups that can form covalent bonds with the resin hydroxyl groups and the curing agent amino groups, and can also form hydrogen bonds with the filler hydroxyl groups, increasing crosslinking points to improve coating density. The silanol groups generated by the hydrolysis of γ-isocyanate-propyltrimethoxysilane bridge the resin and filler, improving dispersibility and enhancing interfacial compatibility. The flexible polyurethane segments are embedded in the rigid epoxy resin network, alleviating brittleness, reducing internal stress, and improving flexibility. Two additives: The conjugated structure of aniline-o-phenylenediamine copolymer can block the penetration of salt spray corrosive media; KH-570 modification improves hydrophobicity and matrix compatibility, avoiding agglomeration and the formation of weak areas in protection; the strong polarity of polyacrylonitrile enhances interfacial bonding and prevents detachment; the copolymer stabilizes the structure, improves chemical resistance, avoids salt spray degradation, and ensures long-term stable protection; the silanol groups of the first additive and the silane-modified groups of the second additive synergistically construct a denser hybrid cross-linked network, and the physical barrier and chemical protection complement each other to enhance salt spray resistance; the flexible chain segment and polymer chain segment synergistically relieve internal stress, ensuring excellent adhesion and flexibility simultaneously.

[0059] In Comparative Example 1, the strong polar groups of the first additive lacked bridging effect with silane, resulting in a loose cross-linking network between the epoxy resin and the curing agent. The anti-rust filler was prone to agglomeration, leading to high internal porosity in the coating and easy penetration by corrosive media. Consequently, the salt spray resistance time was only 480 hours. Furthermore, the lack of flexible polyurethane segments resulted in high coating brittleness, unrelieved internal stress, and reduced flexibility to 5 mm. The weak interfacial bonding between the filler and resin caused the paint film to peel off easily during the cross-cut test, reducing the adhesion to grade 1. In Comparative Example 2, the absence of the second additive resulted in the lack of metal passivation effect of 5-aminobenzotriazole, preventing the formation of a chelating film on the substrate surface. Chloride ions in the salt spray reacted directly with iron, significantly accelerating the corrosion rate. Consequently, the salt spray resistance time was only 240 hours, far lower than that of Comparative Example 1. Although the first additive improved the crosslinking density and flexibility, the lack of core chemical protection meant that the coating could only rely on physical barriers, resulting in limited protective effects. The flexibility was reduced to 3 mm and the adhesion was only grade 1. In Comparative Example 3, there was neither the physical cross-linking enhancement of the first additive nor the chemical passivation protection of the second additive. The coating structure was loose and porous, and the bonding force between the substrate and the coating interface was extremely poor. Corrosive media could quickly penetrate the coating and reach the substrate surface. Therefore, the salt spray resistance time was only 120 hours, the coating was extremely brittle, and the flexibility was reduced to 10 mm. In the cross-cut test, the paint film peeled off over a large area, the adhesion was reduced to level 2, and the overall performance was the worst. By comparing and analyzing the relevant data in the table, it can be seen that the salt spray resistant high-solids epoxy coating prepared by this invention not only has good corrosion resistance but also excellent flexibility. This indicates that the salt spray resistant high-solids epoxy coating provided by this invention has a broader market prospect and is more suitable for widespread application.

[0060] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0061] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A salt spray resistant, high-solids epoxy coating, characterized in that: It is composed of the following raw materials in parts by weight: 30-50 parts bisphenol A type epoxy resin, 5-15 parts carboxyl-terminated nitrile rubber, 5-10 parts diethylenetriamine, 10-20 parts mixed solution, 10-20 parts flake rust inhibitor filler, 0.3-0.8 parts dispersant, 0.1-0.4 parts defoamer, 0.2-0.6 parts leveling agent, 3-6 parts first additive, 2-5 parts second additive, and 0.3-0.8 parts ultraviolet light stabilizer; The second additive is prepared by oxidative copolymerization of aniline, o-phenylenediamine and 5-aminobenzotriazole to obtain a dispersion, which is then compounded with polyacrylonitrile and modified with a silane coupling agent.

2. The salt spray resistant high-solids epoxy coating according to claim 1, characterized in that, The preparation process of the first additive is as follows: Isopropanol and water are mixed at a volume ratio of 1:1 to obtain a first liquid. The first liquid, 2-acrylamido-2-methylpropanesulfonic acid, styrene, mercaptoethanol, vinyl phosphoric acid, and azobisisobutyronitrile are added to a reaction vessel at a mass ratio of 20:3-5:2-4:0.4-0.6:0.4-0.6:0.1-0.

3. Under a nitrogen atmosphere, the temperature is raised to 65-75°C, and the pH is adjusted to 5.0-7.0 by adding 0.5 mol / L sodium hydroxide solution. The mixture is stirred at 300-400 r / min for 6-8 h to obtain a second liquid. The second liquid is added dropwise to 5-8 times its volume of acetone for precipitation. The precipitate is collected by filtration and vacuum dried at 50°C until constant temperature. The first additive was obtained by dissolving it in N,N-dimethylformamide at a mass ratio of 2:0.8–1.2 to obtain the second additive, which was then set aside. Polycarbonate diol, isophorone diisocyanate, and dibutyltin dioctanoate were added to a reaction vessel and reacted at 80°C for 4–6 h. The temperature was then lowered to 70°C at a rate of 1–2°C / min, and the second additive was added. The mixture was stirred at 300–400 r / min for 1–2 h. Subsequently, γ-isocyanate-propyltrimethoxysilane and dibutyltin dilaurate were added, and the mixture was stirred at 70°C for 0.8–1.2 h. The mixture was then removed, and the solid content of the final product was adjusted to 50 wt% using butanone, thus completing the preparation of the first additive.

3. The salt spray resistant high-solids epoxy coating according to claim 2, characterized in that, The mass ratio of polycarbonate diol, isophorone diisocyanate, dibutyltin dioctanoate, the second auxiliary agent, and γ-isocyanate-propyltrimethoxysilane is 10:3-4:0.05-0.07:2.8-3.2:1-1.4, the molecular weight of the polycarbonate diol is 2000-3000, and the mass ratio of γ-isocyanate-propyltrimethoxysilane to dibutyltin dilaurate is 20:

1.

4. The salt spray resistant high-solids epoxy coating according to claim 1, characterized in that, The second additive is prepared by adding aniline, o-phenylenediamine, 5-aminobenzotriazole, and a 1 mol / L hydrochloric acid aqueous solution to a reaction vessel at a mass ratio of 1:0.5–1:0.1–0.2:15–20. The mixture is stirred and mixed thoroughly under an ice-water bath. Then, ammonium persulfate hydrochloric acid solution is slowly added dropwise, controlling the temperature at 0–5°C. After the addition is complete, the reaction proceeds for 2–4 hours, followed by a further increase to room temperature and a reaction for 6–12 hours. The pH is then adjusted to 6.8–7.2 with 0.5 mol / L sodium hydroxide solution to obtain a dispersion for later use. Polyacrylonitrile is dissolved in N... In N-dimethylformamide, a first solution of 5-10 wt% was prepared. The dispersion and the first solution were mixed at a mass ratio of 1:1-2. KH-570 was then added, and the pH was adjusted to 4-5 with acetic acid. The temperature was raised to 70-80℃, and the mixture was refluxed under nitrogen protection for 3-6 hours to obtain the reactant. The reactant was added dropwise to anhydrous ethanol to precipitate the solid. The solid was collected by filtration, washed 1-2 times with anhydrous ethanol solution, then washed 3-5 times with deionized water, and finally washed once with anhydrous ethanol. The solid was then dried under vacuum at 50-70℃ to obtain the second additive.

5. The salt spray resistant high-solids epoxy coating according to claim 1, characterized in that, The rust-preventive filler is at least one of glass flakes or mica iron oxide.

6. The salt spray resistant high-solids epoxy coating according to claim 4, characterized in that, The amount of KH-570 added is 5% to 10% of the mass of the polyacrylonitrile.

7. The salt spray resistant high-solids epoxy coating according to claim 4, characterized in that, The ammonium persulfate hydrochloric acid solution is prepared by dissolving ammonium persulfate in a 1 mol / L hydrochloric acid aqueous solution, wherein the concentration of ammonium persulfate is 0.8–1.2 mol / L, the molar ratio of ammonium persulfate to aniline is 1:0.9–1.1, and the addition is carried out at a uniform rate over 20–40 minutes.

8. The salt spray resistant high-solids epoxy coating according to claim 1, characterized in that, The mixed solution was prepared by mixing xylene, n-butanol and butyl acetate in a mass ratio of 5:2:

3.

9. The salt spray resistant high-solids epoxy coating according to claim 1, characterized in that, The dispersant is BYK-163, the defoamer is BYK-141, and the leveling agent is BYK-306.

10. A method for preparing a salt spray resistant high-solids epoxy coating according to any one of claims 1 to 9, characterized in that, The process includes the following steps: Step 1: Add bisphenol A type epoxy resin, carboxyl-terminated nitrile rubber and mixed solution sequentially to a stirring tank, and stir at room temperature for 15-30 minutes at a speed of 400-600 r / min to ensure thorough and uniform mixing, thereby obtaining the resin base material; Step 2: Add the first additive to the resin base material from Step 1. At room temperature, increase the stirring speed to 800-1000 r / min and continue stirring for 20-40 min. Then adjust the stirring speed to 600-800 r / min and add the dispersant, defoamer and flake rust inhibitor in sequence. After the addition is complete, transfer the material to a sand mill for grinding and dispersion until the fineness is ≤50μm. Step 3: Transfer the ground slurry back to the mixing tank. At room temperature, add the leveling agent, UV stabilizer, second additive, and diethylenetriamine in sequence at a speed of 400-600 rpm. Continue stirring for 20-30 minutes. Then reduce the stirring speed to 200-300 rpm and stir for 10-15 minutes. Let it stand for 15-30 minutes. Finally, filter it through a 100-200 mesh filter to obtain a salt spray resistant high-solids epoxy coating.

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