Phenolic aldehyde-epoxy anticorrosive water-based paint and preparation method thereof

Abstract

The invention relates to the technical field of anticorrosive paint, in particular to phenolic aldehyde-epoxy anticorrosive water-based paint and a preparation method thereof. The anticorrosive water-based paint is composed of a component A and a component B. The component A comprises a resin emulsion and slurry, and the component B comprises a curing agent and an auxiliary agent. The resin emulsion is prepared by emulsifying and compounding a benzoxazine prepolymer, an epoxy phosphoric acid prepolymer, bisphenol A type liquid epoxy resin, a betaine type zwitterionic emulsifier, dextran-based microgel, phytic acid, 3-glycidoxypropyltrimethoxysilane and the like. The preparation method comprises the following steps: emulsifying and compounding the benzoxazine prepolymer, the epoxy phosphoric acid prepolymer, the bisphenol A type liquid epoxy resin, the betaine type zwitterionic emulsifier, the dextran-based microgel, the phytic acid, the 3-glycidoxypropyltrimethoxysilane and the like. According to the system, high compatibility and long-term stability of phenolic aldehyde and epoxy in a water-based system are achieved, and an obtained coating film is compact, high in adhesive force and high in mechanical strength, has excellent water resistance, damp heat resistance and salt spray resistance, can keep a long-term protection effect in severe environments such as high humidity, high salt and temperature cycle, and has a good application prospect. The coating is applicable to metal anticorrosive coatings in the fields of ships, aviation, high-speed rails, ocean engineering and the like.

Description

Technical Field

[0001] This invention relates to the field of anti-corrosion coatings technology, specifically to a phenolic-epoxy anti-corrosion waterborne paint and its preparation method. Background Technology

[0002] In recent years, industries such as shipbuilding, aircraft, high-speed rail and marine engineering have continuously raised the performance requirements of anti-corrosion coatings. Especially under multi-cycle humid heat, salt spray and condensation moisture exchange conditions, the coating must have excellent corrosion resistance, adhesion and environmental stability at the same time.

[0003] Currently, traditional solvent-based epoxy or chlorinated rubber systems have long been the mainstream for high-corrosion-resistant applications due to their high crosslinking density and dense film formation. However, their high organic solvent content not only leads to poor operational safety and severe environmental pollution, but also makes it difficult to meet current environmental regulations requiring low VOC emissions. With increasing environmental awareness and the promotion of energy conservation and emission reduction policies, water-based corrosion protection systems are gradually becoming the development direction. However, phenolic resins and epoxy resins in water-based systems have significant differences in molecular polarity, curing rate, and compatibility. These systems are prone to problems such as wide emulsion particle size distribution, stratification, slow drying, and insufficient wet adhesion, which seriously limits their industrial applications.

[0004] Phenolic resins, due to their high hydroxyl content, exhibit good heat resistance and chemical stability. However, they are prone to self-condensation in the aqueous phase, leading to uneven dispersion. While epoxy resins possess excellent adhesion and solvent resistance, their tendency to aggregate and their hydrophobicity in the aqueous phase result in poor dispersion stability, uneven crosslinking, and reduced film density. Both often exhibit phase separation or gelation during blending and emulsification, leading to high microporosity and decreased coating density, further degrading salt spray resistance. Simultaneously, residual surfactants after film formation exhibit high migration rates, easily forming microchannels under prolonged humid conditions, providing pathways for water vapor and ion migration, thus reducing protective performance. Furthermore, the slow energy transfer during the curing and drying stages of aqueous systems, coupled with uneven curing inside and outside the film, easily leads to insufficient surface tensile strength. In high humidity or salt spray cycling environments, moisture penetration can cause interfacial stress concentration and localized loss of adhesion, resulting in blistering and peeling of the coating.

[0005] Therefore, how to simultaneously improve the compatibility of phenolic and epoxy resins in water-based systems has become a key technical issue in solving the bottleneck of practical application of high-corrosion-resistant water-based coatings. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a phenolic-epoxy anti-corrosion waterborne paint to achieve both high compatibility and long-term anti-corrosion stability of the phenolic and epoxy systems in an aqueous environment.

[0007] To achieve the above objectives, the present invention provides a phenolic-epoxy anti-corrosion waterborne paint, which is made by mixing and curing two components, A and B, in a mass ratio of 100:28-32. Component A comprises the following raw materials in parts by weight: 360-400 parts slurry and 600-640 parts resin emulsion; Component B comprises the following raw materials in parts by weight: 260-300 parts curing agent, 200-240 parts deionized water, and 1.5-2.5 parts defoamer; The preparation steps of the resin emulsion are as follows: S1 Preparation of benzoxazine prepolymer: In anhydrous 1,4-dioxane, using phenol, p-aminobenzoic acid and formaldehyde solution as reactants, a condensation-ring-closing reaction is carried out at 80-90℃ for 5-7 hours to generate benzoxazine prepolymer. S2 Preparation of zwitterionic emulsifier: In anhydrous isopropanol, polyethylene glycol diglycidyl ether and 3-(dimethylamino)propylamine are reacted at 55-65℃ for 2.5-3.5h to carry out an epoxy ring-opening reaction. Then, under the action of 1,8-diazabicyclo[5.4.0]undecene, diethylphosphonite is reacted at 45-55℃ for 3-5h to carry out a substitution reaction. Finally, 1,3-propanesulfonyl lactone is kept at 35-45℃ for 2h to carry out a quaternization reaction to obtain a zwitterionic emulsifier. S3 Preparation of microgel dispersions: Using dextran, 2-(methacryloyloxy)ethyl dimethyl(3-sulfonic acid propyl)ammonium inner salt, and glycidyl methacrylate as monomers, microgel dispersions were generated by polymerization in the presence of initiator VAO44 under nitrogen protection at 48-52℃. S4 Preparation of epoxy phosphate prepolymer: Bisphenol A type liquid epoxy resin reacts with phosphoric acid at 70-80℃ for 1.5-2.5h, and epoxy phosphate prepolymer is generated by esterification-ring opening reaction; S5 Preparation of Resin Emulsion: After shear pre-emulsification of epoxy phosphate prepolymer, bisphenol A type epoxy resin, and zwitterionic emulsifier, benzoxazine prepolymer and deionized water are introduced, and emulsification is carried out at 45-50℃ to form benzoxazine-epoxy-phosphate composite emulsion. Finally, 3-glycidoxypropyltrimethoxysilane, microgel dispersion and phytic acid are introduced into the emulsion to obtain resin emulsion.

[0008] Preferably, the ratio of phenol, p-aminobenzoic acid and formaldehyde solution used in step S1 is 40-50g:30-36g:35-45g.

[0009] Preferably, the formaldehyde solution in step S1 has a mass fraction of 37%.

[0010] Preferably, the ratio of polyethylene glycol diglycidyl ether, 3-(dimethylamino)propylamine, 1,8-diazabicyclo[5.4.0]undecene, diethylphosphonite, and 1,3-propanesulfonate in step S2 is 55-65g:18-22g:1.3-1.7g:6.0-6.5g:22-26g.

[0011] Preferably, the polyethylene glycol diglycidyl ether Mn in step S2 is 500.

[0012] Preferably, the ratio of dextran, 2-(methacryloyloxy)ethyl dimethyl(3-sulfonic acid propyl)ammonium inner salt, glycidyl methacrylate, and initiator VAO44 in step S3 is 16-20g:8-10g:4.5-5.5g:0.8-1.0g.

[0013] Preferably, the dextran in step S3 has a molecular weight of 25,000.

[0014] Preferably, the microgel dispersion in step S3 has a solid content of 10 wt%.

[0015] Preferably, the ratio of bisphenol A type liquid epoxy resin to phosphoric acid in step S4 is 280-320g:42-48g.

[0016] Preferably, the bisphenol A type liquid epoxy resin in step S4 is Epon. Resin 828.

[0017] Preferably, the mass fraction of phosphoric acid in step S4 is 85%.

[0018] Preferably, the ratio of epoxy phosphate prepolymer, bisphenol A epoxy resin, zwitterionic emulsifier, benzoxazine prepolymer, deionized water, 3-glycidoxypropyltrimethoxysilane, microgel dispersion and phytic acid in step S5 is 140-160g:140-160g:40-50g:65-75g:320-380mL:7-9g:110-130g:7-9g.

[0019] Preferably, the average particle size of the benzoxazine-epoxy-phosphate composite emulsion in step S5 is 120-160 nm.

[0020] Preferably, the phytic acid solution in step S5 has a mass fraction of 50%.

[0021] Preferably, the slurry is composed of 119-132 parts deionized water, 4.0-4.4 parts wetting and leveling agent, 2.6-3 parts defoamer, 158-175 parts zinc phosphate anti-rust pigment, 33-37 parts flaky mica iron oxide, 33-37 parts talc powder, and 11 parts matting silica. Preferably, the wetting and leveling agent is BYK-333, BYK-349, or TEGO. One of the Wet270s.

[0022] Preferably, the defoamer is one of BYK024 and BYK-028.

[0023] Preferably, the zinc phosphate anti-rust pigment is HEUCO PHOS ZPO.

[0024] Preferably, the flaky mica iron oxide has a size of 325 mesh.

[0025] Preferably, the talc powder has a size of 1250 mesh.

[0026] Preferably, the curing agent is EPIKURE 8530-W-75.

[0027] Furthermore, the present invention also provides a method for preparing a phenolic-epoxy anti-corrosion waterborne paint, comprising the following steps: Add deionized water to a planetary dispersion tank, then add wetting and leveling agent and defoamer in sequence. After stirring evenly, add zinc phosphate anti-rust pigment, flake mica iron oxide, talc powder and matting silica, and disperse evenly to form a slurry. Mix the slurry with resin emulsion evenly to obtain water-based paint component A. Premix the curing agent with deionized water and add defoamer to obtain water-based paint component B. Mix water-based paint component A and water-based paint component B, stir at low speed and defoam, apply to the substrate, and bake at 55-65℃ for 1.5-2.5h to obtain an anti-corrosion water-based paint film.

[0028] Preferably, the wet film thickness of the coating is 110-130 μm.

[0029] The beneficial effects of this invention are: The phenolic-epoxy anti-corrosion waterborne paint provided by this invention achieves a comprehensive improvement in system compatibility, stability, and protective performance through a multi-level structural design: First, the introduction of phosphate-esterified epoxy phosphate prepolymer into the coating matrix significantly improves the polarity matching between the two phases when coexisting with unmodified epoxy resin, resulting in uniform dispersion of the composite system and more concentrated emulsion particle size. Then, the post-treatment step of phytic acid dynamically adjusts the pH and participates in complexation after the emulsion is formed, resulting in a stable secondary protective layer. This layer can further block ion penetration in the coating surface and interface region, allowing the protective layer to maintain a fine structure under long-term salt spray and humid heat conditions. Secondly, by adding benzoxazine prepolymer to the resin emulsion, it forms a rigid-flexible aromatic skeleton after the paint film is cured, which improves the hardness and wear resistance of the paint film, while maintaining good toughness, so that the tensile strength and crack resistance are balanced. Furthermore, the bistable system composed of betaine-type zwitterionic emulsifier and dextran-based microgel can stabilize emulsion particles and reduce the system's sensitivity to changes in ion concentration, exhibiting good storage stability. The microgel particles can fill and support the film during film formation, reducing the porosity of the paint film and increasing its density, thereby reducing the medium permeation rate at the material level. Finally, a Si-OM bond structure is formed at the coating-metal interface by 3-glycidoxypropyltrimethoxysilane. This inorganic transition layer effectively enhances the interfacial bonding force and further improves the adhesion durability of the system in humid and thermal cycling environments.

[0030] While maintaining high adhesion and good mechanical properties, the system of this invention significantly improves durability properties such as water resistance, damp heat resistance, and salt spray resistance. The material can still maintain a dense, uniform, and stable protective film structure under high humidity, high salt, and temperature cycling conditions. It solves the problems of poor compatibility, emulsion instability, and interfacial loss of traditional waterborne phenolic-epoxy systems, demonstrating its broad application potential in marine equipment, protective coatings, and engineering in high-humidity and corrosive environments. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0032] Formaldehyde solution: 37 wt%; Polyethylene glycol diglycidyl ether: Sigma-Aldrich, item number 475696, Mn 500; Dextran: Sigma-Aldrich, product number 00271, molecular weight 25000; Bisphenol A type liquid epoxy resin: Epon Resin 828; Phosphoric acid: 85%; Phytic acid solution: 50 wt%; Curing agent: EPIKURE 8530-W-75; Wetting and leveling agent: TEGO Wet270; Defoamer: BYK024; Zinc phosphate anti-rust pigment: HEUCOPHOS ZPO; Flaky mica iron oxide: 325 mesh; Talc powder: 1250 mesh.

[0033] Example 1: A method for preparing a phenolic-epoxy anti-corrosion waterborne paint, the specific steps of which are as follows: (1) Preparation of benzoxazine prepolymer: Dissolve 40g of phenol in 70mL of anhydrous 1,4-dioxane, heat to 55℃ and stir to dissolve; add 30g of p-aminobenzoic acid in three portions and continue stirring until homogeneous; then add 35g of formaldehyde solution, heat to 80℃ and reflux for 5h; after the reaction is complete, remove the solvent under reduced pressure to obtain benzoxazine prepolymer; (2) Preparation of zwitterionic emulsifiers: At 50°C, 55g of polyethylene glycol diglycidyl ether was dissolved in 70mL of anhydrous isopropanol, and 18g of 3-(dimethylamino)propylamine was added dropwise. The reaction was carried out at 55°C for 2.5h for epoxy ring-opening reaction. Then, 6.0g of diethylphosphonite and 1.3g of 1,8-diazabicyclo[5.4.0]undecene were added, and the reaction was carried out at 45°C for 3h. After the reaction was completed, the temperature was lowered to 40°C, and 22g of 1,3-propanesulfonate was slowly added dropwise. The reaction was carried out at 35°C for 2h to complete the quaternization reaction, and an amphoteric emulsifier was obtained. (3) Preparation of microgel dispersions: 16g of dextran was dissolved in 160mL of deionized water, and the solution was heated to 40℃ to obtain a homogeneous solution. 8g of 2-(methacryloyloxy)ethyldimethyl(3-sulfonic acid propyl)ammonium inner salt, 4.5g of glycidyl methacrylate, and 0.8g of initiator VAO44 were added, and the pH was adjusted to 6.4-6.6. Polymerization was carried out at 48℃ for 2.5h under nitrogen protection, and then the temperature was increased to 58℃ and held for 1h. Deionized water was added until the solid content was 10wt% to obtain a microgel dispersion. (4) Preparation of epoxy phosphate prepolymer: 280g of bisphenol A type liquid epoxy resin was heated and stirred at 70℃, 42g of phosphoric acid was added dropwise, and the reaction was maintained at 70℃ for 1.5h. After the reaction was completed, it was cooled to 50℃ to obtain epoxy phosphoric acid prepolymer. (5) Preparation of resin emulsion: 140g of epoxy phosphate prepolymer and 140g of bisphenol A type liquid epoxy resin were mixed at 60℃, and 40g of zwitterionic emulsifier was added. The mixture was pre-emulsified by shearing at 2000rpm for 8min. 65g of benzoxazine prepolymer was added in two batches, with shearing for 4min after each addition. 320mL of deionized water was added dropwise at a rate of 20mL / min, and emulsification was carried out at 45℃ to obtain a benzoxazine epoxy phosphate composite emulsion with an average particle size of 120-160nm. 7g of 3-glycidoxypropyltrimethoxysilane was added to the system and stirred for 30min. Then, 110g of microgel dispersion was added and stirred for 15min. Finally, 7g of phytic acid solution was added dropwise and the pH was adjusted to 6.0-6.5 to obtain the resin emulsion. (6) Preparation of water-based paint component A: Add 119g of deionized water to a planetary dispersion tank, then add 4.0g of wetting and leveling agent and 2.6g of defoamer, and stir for 4 minutes; then add 158g of zinc phosphate anti-rust pigment, 33g of flake mica iron oxide, 33g of talc powder, and 11g of matting silica, and disperse at 2500rpm for 20 minutes to form a slurry; take 360g of slurry and 640g of resin emulsion, and mix at 800rpm for 10 minutes to obtain water-based paint component A; (7) Preparation of water-based paint component B: Premix 260g of curing agent with 200g of deionized water, add 1.5g of defoamer, and stir evenly to obtain water-based paint component B; (8) Formulation and film formation: Water-based paint component A and water-based paint component B are mixed at a mass ratio of 100:28, stirred at low speed for 2 minutes to remove bubbles, allowed to stand for 3 minutes, and then coated onto the substrate with a wet film thickness of 110-130 μm. The mixture is then baked at 55℃ for 1.5 hours to obtain an anti-corrosion water-based paint film.

[0034] Example 2: A method for preparing a phenolic-epoxy anti-corrosion waterborne paint, the specific steps of which are as follows: (1) Preparation of benzoxazine prepolymer: Dissolve 45g of phenol in 80mL of anhydrous 1,4-dioxane, heat to 60℃ and stir to dissolve; add 33g of p-aminobenzoic acid in three portions and continue stirring until homogeneous; then add 40g of formaldehyde solution, heat to 85℃ and reflux for 6h; after the reaction is complete, remove the solvent under reduced pressure to obtain benzoxazine prepolymer; (2) Preparation of zwitterionic emulsifiers: At 50°C, 60g of polyethylene glycol diglycidyl ether was dissolved in 80mL of anhydrous isopropanol, and 20g of 3-(dimethylamino)propylamine was added dropwise. The reaction was carried out at 60°C for 3h for epoxy ring-opening reaction. Then, 6.3g of diethylphosphonite and 1.5g of 1,8-diazabicyclo[5.4.0]undecene were added, and the reaction was carried out at 50°C for 4h. After the reaction was completed, the temperature was lowered to 40°C, and 24g of 1,3-propanesulfonyl lactone was slowly added dropwise. The reaction was carried out at 40°C for 2h to complete the quaternization reaction and obtain an amphoteric emulsifier. (3) Preparation of microgel dispersions: 18g of dextran was dissolved in 180mL of deionized water and heated to 40℃ to obtain a homogeneous solution. 9g of 2-(methacryloyloxy)ethyldimethyl(3-sulfonylpropyl)ammonium inner salt, 5.0g of glycidyl methacrylate, and 0.9g of initiator VAO44 were added, and the pH was adjusted to 6.4-6.6. Polymerization was carried out at 50℃ for 3h under nitrogen protection, and then heated to 60℃ and held for 1h. Deionized water was added until the solid content was 10wt% to obtain a microgel dispersion. (4) Preparation of epoxy phosphate prepolymer: 300g of bisphenol A type liquid epoxy resin was heated and stirred at 70℃, 45g of phosphoric acid was added dropwise, and the reaction was maintained at 75℃ for 2h. After the reaction was completed, it was cooled to 50℃ to obtain epoxy phosphoric acid prepolymer. (5) Preparation of resin emulsion: 150g of epoxy phosphate prepolymer and 150g of bisphenol A type liquid epoxy resin were mixed at 60℃, and 45g of zwitterionic emulsifier was added. The mixture was pre-emulsified by shearing at 2000rpm for 10min. 70g of benzoxazine prepolymer was added in two batches, with shearing for 5min after each addition. 350mL of deionized water was added dropwise at a rate of 20mL / min, and emulsification was carried out at 50℃ to obtain a benzoxazine epoxy phosphate composite emulsion with an average particle size of 120-160nm. 8g of 3-glycidoxypropyltrimethoxysilane was added to the system and stirred for 30min. Then, 120g of microgel dispersion was added and stirred for 20min. Finally, 8g of phytic acid solution was added dropwise and the pH was adjusted to 6.0-6.5 to obtain the resin emulsion. (6) Preparation of water-based paint component A: Add 127g of deionized water to a planetary dispersion tank, then add 4.2g of wetting and leveling agent and 2.8g of defoamer, and stir for 5 minutes; then add 165g of zinc phosphate anti-rust pigment, 35g of flake mica iron oxide, 35g of talc powder, and 11g of matting silica, and disperse at 2500rpm for 25 minutes to form a slurry; take 380g of the slurry and 620g of resin emulsion, and mix at 800rpm for 14 minutes to obtain water-based paint component A; (7) Preparation of water-based paint component B: Premix 280g of curing agent with 220g of deionized water, add 2g of defoamer, stir evenly to obtain water-based paint component B; (8) Formulation and film formation: Mix water-based paint component A and water-based paint component B at a mass ratio of 100:30, stir at low speed for 3 minutes to remove bubbles, let stand for 5 minutes, and then coat the substrate with a wet film thickness of 110-130 μm. Bake at 60℃ for 2 hours to obtain an anti-corrosion water-based paint film.

[0035] Example 3: A method for preparing a phenolic-epoxy anti-corrosion waterborne paint, the specific steps of which are as follows: (1) Preparation of benzoxazine prepolymer: Dissolve 50g of phenol in 90mL of anhydrous 1,4-dioxane, heat to 65℃ and stir to dissolve; add 36g of p-aminobenzoic acid in three portions and continue stirring until homogeneous; then add 45g of formaldehyde solution, heat to 90℃ and reflux for 7h; after the reaction is complete, remove the solvent under reduced pressure to obtain benzoxazine prepolymer; (2) Preparation of zwitterionic emulsifiers: At 50°C, 65g of polyethylene glycol diglycidyl ether was dissolved in 90mL of anhydrous isopropanol, and 22g of 3-(dimethylamino)propylamine was added dropwise. The reaction was carried out at 65°C for 3.5h for epoxy ring-opening reaction. Then, 6.5g of diethylphosphonite and 1.7g of 1,8-diazabicyclo[5.4.0]undecene were added, and the reaction was carried out at 55°C for 5h. After the reaction was completed, the temperature was lowered to 40°C, and 26g of 1,3-propanesulfonate was slowly added dropwise. The reaction was carried out at 45°C for 2h to complete the quaternization reaction, and an amphoteric emulsifier was obtained. (3) Preparation of microgel dispersions: 20g of dextran was dissolved in 200mL of deionized water and heated to 40℃ to obtain a homogeneous solution. 10g of 2-(methacryloyloxy)ethyldimethyl(3-sulfonic acid propyl)ammonium inner salt, 5.5g of glycidyl methacrylate, and 1.0g of initiator VAO44 were added, and the pH was adjusted to 6.4-6.6. Polymerization was carried out at 52℃ for 3.5h under nitrogen protection, and then the temperature was increased to 62℃ and held for 1h. Deionized water was added until the solid content was 10wt% to obtain a microgel dispersion. (4) Preparation of epoxy phosphate prepolymer: 320g of bisphenol A type liquid epoxy resin was heated and stirred at 70℃, 48g of phosphoric acid was added dropwise, and the reaction was maintained at 80℃ for 2.5h. After the reaction was completed, it was cooled to 50℃ to obtain epoxy phosphoric acid prepolymer. (5) Preparation of resin emulsion: 160g of epoxy phosphate prepolymer and 160g of bisphenol A type liquid epoxy resin were mixed at 60℃, and 50g of zwitterionic emulsifier was added. The mixture was pre-emulsified by shearing at 2000rpm for 12min. 75g of benzoxazine prepolymer was added in two batches, with shearing for 6min after each addition. 380mL of deionized water was added dropwise at a rate of 20mL / min, and emulsification was carried out at 50℃ to obtain a benzoxazine epoxy phosphate composite emulsion with an average particle size of 120-160nm. 9g of 3-glycidoxypropyltrimethoxysilane was added to the system and stirred for 30min. Then, 130g of microgel dispersion was added and stirred for 25min. Finally, 9g of phytic acid solution was added dropwise and the pH was adjusted to 6.0-6.5 to obtain the resin emulsion. (6) Preparation of water-based paint component A: Add 132g of deionized water to a planetary dispersion tank, then add 4.4g of wetting and leveling agent and 3g of defoamer, and stir for 6 minutes; then add 175g of zinc phosphate anti-rust pigment, 37g of flake mica iron oxide, 37g of talc powder, and 11g of matting silica, and disperse at 2500rpm for 30 minutes to form a slurry; take 400g of slurry and 600g of resin emulsion, and mix at 800rpm for 15 minutes to obtain water-based paint component A; (7) Preparation of water-based paint component B: Premix 300g of curing agent with 200g of deionized water, add 2.5g of defoamer, and stir evenly to obtain water-based paint component B; (8) Formulation and film formation: Water-based paint component A and water-based paint component B are mixed at a mass ratio of 100:32, stirred at low speed for 4 minutes to remove bubbles, allowed to stand for 7 minutes, and then coated onto the substrate with a wet film thickness of 110-130 μm. The mixture is then baked at 65℃ for 2.5 hours to obtain an anti-corrosion water-based paint film.

[0036] Comparative Example 1: The difference from Example 2 is that phosphoric acid is not added in step (4), while the other steps are the same as in Example 2.

[0037] Comparative Example 2: The difference from Example 2 is that phytic acid is not added in step (5), while the other steps are the same as in Example 2.

[0038] Comparative Example 3: The difference from Example 2 is that benzoxazine prepolymer is not added in step (5), and the rest of the steps are the same as in Example 2.

[0039] Comparative Example 4: The difference from Example 2 is that in step (5), the zwitterionic emulsifier is replaced with the nonionic surfactant OP-10, and the rest of the steps are the same as in Example 2.

[0040] Comparative Example 5: The difference from Example 2 is that no microgel dispersion is added in step (5), and the other steps are the same as in Example 2.

[0041] Comparative Example 6: The difference from Example 2 is that 3-glycidoxypropyltrimethoxysilane is not added in step (5), and the rest of the steps are the same as in Example 2.

[0042] Performance testing Storage stability test: According to GB / T6753.3-1986, the A component samples obtained from the examples and comparative examples were sealed in standard iron cans and placed in a 55℃ constant temperature oven for 30 days for accelerated testing. After the test, samples were taken for observation and the appearance was recorded to see if stratification or flocculation occurred. Adhesion: Tested according to GB / T92862021. Use a cross-cutting tool (1mm blade spacing) to make six parallel cuts with a length of 20mm, then make six more perpendicular cuts to form a 6×6 grid. Immediately apply 3M 600 tape, press it firmly along one side without air bubbles, leave it for 90 seconds, and then quickly peel it off at a 90° angle. Test three points for each sample, record the number of grids that peel off at each point, and take the average. Tensile strength: According to GB / T1040.2-2006, the cured paint films of the examples and comparative examples were cured in a standard environment (23℃, 50%RH) for 7 days. The average tensile strength was measured using a universal testing machine (clamping distance 25mm, tensile speed 50mm / min, 5 samples per group). Water resistance test: According to GB / T1733-1993, after each sample has cured, the paint film is immersed in distilled water at 25°C for 240 hours. After being taken out, wiped dry, and placed at room temperature for 2 hours, the tensile strength is tested again, and the change rate of tensile strength is calculated and recorded. Moisture and heat resistance: According to GB / T1740-2007, each sample was subjected to constant temperature and humidity test at 50℃ and 95% relative humidity for 1000h. After the experiment, the tensile strength was tested again, and the change rate of tensile strength was calculated and recorded. Salt spray resistance: According to GB / T 10125-2021, a neutral salt spray test (NSS) was conducted. The sample was placed in a salt spray test chamber and exposed to a solution with a sodium chloride mass fraction of 5wt%, pH value of 7.0, temperature of 35℃, in a continuous spray mode (1440h). After the experiment, the tensile strength was tested again, and the change rate of tensile strength was calculated and recorded. Table 1 Performance Test Results Data Analysis: As can be seen from the data in Examples 1-3 in Table 1, the phenolic-epoxy anti-corrosion waterborne paint system obtained by this invention exhibits stable and balanced performance characteristics under different mixing ratios. The storage stability of all three examples showed no stratification or flocculation, indicating that the system possesses good dispersion and colloidal stability and is not easily affected by mixing ratio fluctuations, thus preventing phase separation. The overall trend shows that the system achieves good coordination between film density, mechanical balance, and long-term environmental stability, demonstrating excellent comprehensive adaptability and meeting the requirements for the stability and durability of protective coatings in marine, high-humidity, or salt spray environments.

[0043] From the data in Example 2 and Comparative Example 1 in Table 1, it can be inferred that the epoxy phosphate prepolymer formed by phosphate esterification of epoxy resin not only acts as a reactive diluent in the system, but also increases the polarity and active site density of the resin by introducing -P=O and -POC bonds. It can form stable chemical adsorption and coordination bond connections at the particle interface and the surface of the metal oxide layer. After the system is emulsified, the phosphorus-containing molecules still retain some unreacted phosphate ester end groups, which can further condense with epoxy or hydroxyl groups during the curing process to form a phosphorus-rich interface layer. In the presence of external electrolyte, it exhibits good cathodic passivation and shielding effects, which has a significant impact on improving the overall corrosion resistance and damp heat durability.

[0044] Based on the data from Example 2 and Comparative Example 2 in Table 1, it can be inferred that the polyphosphoric carboxyl structure of phytic acid can form hydrogen bonds or esterification complexes with -P-OH or residual -OH in the epoxy phosphate prepolymer at the end of film formation, enriching the surface of the particles with phosphorus-containing organic complex structures and forming a secondary protective layer. Simultaneously, its weak acidity stabilizes the system pH at 6-6.5, slowing ion migration and localized salt precipitation during curing, thereby improving film uniformity. At the metal substrate, phytic acid may form multidentate complexes with substrate metal ions, improving the metal-coating interface affinity and passivation performance, reducing the reaction rate in the cathode region, and effectively improving the coating's resistance to damp heat and salt spray.

[0045] From the data in Example 2 and Comparative Example 3 in Table 1, it can be inferred that the benzoxazine prepolymer co-reacts with epoxy resin during the curing process to form an interpenetrating cross-linked network. This network contains numerous aromatic rings and phenolic hydroxyl sites, which can promote hydrogen bonding and esterification condensation reactions, improving network uniformity and stress distribution. Simultaneously, strong polar interactions may form between the phenolic hydroxyl groups and phosphate esters, enhancing local cross-linking density and improving hydrolytic stability. Furthermore, the rigid framework generated by the benzoxazine-epoxy co-curing effectively limits swelling and microcrack propagation, ensuring the coating maintains its integrity under condensation and cyclic thermal shock. When this component is absent, the resin chain flexibility increases, and the tensile strength retention decreases due to chain segment relaxation and hydration in humid heat and salt spray conditions.

[0046] From the data in Example 2 and Comparative Example 4 in Table 1, it can be inferred that betaine-type zwitterionic emulsifiers contain an internal salt structure with both positive and negatively charged groups. They can maintain high double-layer potential and interparticle repulsion even in strong electrolyte or metal ion environments, thus stabilizing emulsion particles. In contrast, nonionic surfactants rely solely on the hydration of polyether segments, exhibiting poor salt resistance and thermal stability, and are prone to aggregation during storage and emulsification. Furthermore, zwitterionic emulsifiers in epoxy systems may also interact weakly with phosphorus-containing groups, phytic acid, or curing agents, forming interfacial coupling regions that result in a uniform and dense coating structure. Correspondingly, when using a nonionic system, interfacial wetting and chemical bonding decrease, leading to a significant reduction in adhesion and an increase in microscopic penetration channels, thereby significantly reducing performance retention under water, salt, and thermal cycling conditions.

[0047] From the data in Example 2 and Comparative Example 5 in Table 1, it can be inferred that the microgel dispersion not only provides steric hindrance and elastic buffering in the emulsion system, inhibiting particle aggregation, but also plays a role in pore filling and synergistic crosslinking during film formation. The surface of the microgel particles contains functional groups that can react with epoxy or hydroxyl groups, and can co-crosslink with the resin during drying and curing to construct a flexible secondary network, reducing free volume and pore connectivity, thus making the coating film have lower permeability under the action of the medium. After removing the microgel, the micelles in the system lack elastic support, the particle size distribution becomes wider, and the microporosity increases, resulting in a decrease in mechanical retention and resistance to the medium.

[0048] From the data in Example 2 and Comparative Example 6 in Table 1, it can be inferred that the silane coupling agent mainly acts on the coating-metal interface region. Its epoxy end groups react with the resin backbone and embed into the network during curing, while the silanol generated after hydrolysis of the trimethoxysilane group can form strong siloxane bonds with the hydroxyl groups of the metal oxide layer. This structure constructs a transition layer at the interface with both organic and inorganic characteristics. When the coating is in a continuously humid or thermally cycling environment, this layer can effectively prevent moisture penetration along the interface and buffer interfacial shear stress. Without the silane coupling agent, interfacial bonding relies solely on physical adsorption and local polarity, which easily leads to debonding and blistering under humid, hot, and salt spray conditions, thus reducing adhesion and retention.

[0049] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A phenolic-epoxy anti-corrosion water-based paint, characterized in that, It is made by mixing and curing components A and B in a mass ratio of 100:28-32; Component A comprises the following raw materials in parts by weight: 360-400 parts slurry and 600-640 parts resin emulsion; Component B comprises the following raw materials in parts by weight: 260-300 parts curing agent, 200-240 parts deionized water, and 1.5-2.5 parts defoamer; The preparation steps of the resin emulsion are as follows: S1 Preparation of benzoxazine prepolymer: In anhydrous 1,4-dioxane, using phenol, p-aminobenzoic acid and formaldehyde solution as reactants, a condensation-ring-closing reaction is carried out at 80-90℃ to generate benzoxazine prepolymer; S2 Preparation of zwitterionic emulsifier: In anhydrous isopropanol, polyethylene glycol diglycidyl ether and 3-(dimethylamino)propylamine undergo an epoxy ring-opening reaction at 55-65℃, followed by a substitution reaction with diethylphosphonite at 45-55℃ under the action of 1,8-diazabicyclo[5.4.0]undecene, and finally a quaternization reaction with 1,3-propanesulfonyl lactone at 35-45℃ to obtain a zwitterionic emulsifier; S3 Preparation of microgel dispersions: Using dextran, 2-(methacryloyloxy)ethyl dimethyl(3-sulfonic acid propyl)ammonium inner salt, and glycidyl methacrylate as monomers, microgel dispersions were generated by polymerization in the presence of initiator VAO44; S4 Preparation of epoxy phosphate prepolymer: Bisphenol A type liquid epoxy resin and phosphoric acid are reacted with phosphoric acid at 70-80℃ to generate epoxy phosphate prepolymer; S5 Preparation of Resin Emulsion: After shear pre-emulsification of epoxy phosphate prepolymer, bisphenol A type epoxy resin, and zwitterionic emulsifier, benzoxazine prepolymer and deionized water are introduced to emulsify and form benzoxazine-epoxy-phosphate composite emulsion. Finally, 3-glycidoxypropyltrimethoxysilane, microgel dispersion and phytic acid are introduced into the emulsion to obtain resin emulsion.

2. The phenolic-epoxy anti-corrosion waterborne paint according to claim 1, characterized in that, The ratio of phenol, p-aminobenzoic acid, and formaldehyde solution used in step S1 is 40-50g:30-36g:35-45g.

3. The phenolic-epoxy anti-corrosion waterborne paint according to claim 1, characterized in that, In step S2, the ratio of polyethylene glycol diglycidyl ether, 3-(dimethylamino)propylamine, 1,8-diazabicyclo[5.4.0]undecene, diethylphosphonite, and 1,3-propanesulfonate is 55-65g:18-22g:1.3-1.7g:6.0-6.5g:22-26g.

4. The phenolic-epoxy anti-corrosion waterborne paint according to claim 1, characterized in that, In step S3, the ratio of dextran, 2-(methacryloyloxy)ethyl dimethyl(3-sulfonic acid propyl)ammonium inner salt, glycidyl methacrylate, and initiator VAO44 is 16-20g:8-10g:4.5-5.5g:0.8-1.0g.

5. The phenolic-epoxy anti-corrosion waterborne paint according to claim 1, characterized in that, In step S4, the ratio of bisphenol A type liquid epoxy resin to phosphoric acid is 280-320g:42-48g.

6. The phenolic-epoxy anti-corrosion waterborne paint according to claim 1, characterized in that, The ratio of epoxy phosphate prepolymer, bisphenol A epoxy resin, zwitterionic emulsifier, benzoxazine prepolymer, deionized water, 3-glycidoxypropyltrimethoxysilane, microgel dispersion, and phytic acid in step S5 is 140-160g:140-160g:40-50g:65-75g:320-380mL:7-9g:110-130g:7-9g.

7. The phenolic-epoxy anti-corrosion waterborne paint according to claim 1, characterized in that, The slurry is composed of 119-132 parts deionized water, 4.0-4.4 parts wetting and leveling agent, 2.6-3 parts defoamer, 158-175 parts zinc phosphate anti-rust pigment, 33-37 parts flaky mica iron oxide, 33-37 parts talc powder, and 11 parts matting silica.

8. The phenolic-epoxy anti-corrosion waterborne paint according to claim 1, characterized in that, The wetting and leveling agent is one of BYK-333, BYK-349, and TEGO Wet270; the defoamer is one of BYK024 and BYK-028.

9. The phenolic-epoxy anti-corrosion waterborne paint according to claim 1, characterized in that, The curing agent is EPIKURE8530-W-75.

10. A method for preparing a phenolic-epoxy anti-corrosion waterborne paint according to any one of claims 1-9, characterized in that, Includes the following steps: After mixing and stirring deionized water, wetting and leveling agent, and defoamer evenly, zinc phosphate anti-rust pigment, flake mica iron oxide, talc powder, and matting silica are added and dispersed evenly to form a slurry. The slurry is then mixed evenly with resin emulsion to obtain water-based paint component A. The curing agent is premixed with deionized water, and defoamer is added to obtain water-based paint component B. Water-based paint component A and water-based paint component B are mixed evenly and then applied to the substrate and cured to obtain an anti-corrosion water-based paint film.

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