Waterborne epoxy zinc-rich primer, preparation method and application thereof

Abstract

The present application belongs to the technical field of epoxy primer, and particularly relates to a water-based epoxy zinc-rich primer, a preparation method and application thereof. The water-based epoxy zinc-rich primer is prepared by using non-continuous point-like silica modified composite zinc powder as a cathodic protection functional filler, using modified epoxy resin as a film-forming base material, and combining with a modified aminoethyl piperazine curing agent, and has long-term cathodic protection performance and excellent hydrolysis resistance. The composite zinc powder is constructed by spherical and flaky zinc powder to form a continuous conductive network and a physical anti-settling structure. A point-like passivation layer formed by mild activation of glycolic acid and targeted adsorption of acidic silica sol can close the high active sites of zinc powder while ensuring electron conduction. The modified epoxy resin has self-emulsifying dispersibility and zinc powder coordination stability. The curing agent realizes water-based adaptation and storage stability through epoxy addition and reversible capping. After construction and unsealing, the curing agent can form a dense cross-linked paint film with the epoxy resin, thereby improving the long-term corrosion protection service performance of the primer.

Description

Technical Field

[0001] This invention relates to the field of epoxy primer technology, and in particular to a water-based epoxy zinc-rich primer, its preparation method, and its application. Background Technology

[0002] Waterborne epoxy zinc-rich primer is a core environmentally friendly coating product in the current heavy-duty anti-corrosion coating field. It is widely used in the protection of substrates susceptible to harsh corrosive environments, such as industrial steel structures, bridges and pipelines, marine engineering facilities, and petrochemical equipment. Relying on the sacrificial anode cathodic protection of zinc powder, it can effectively block the erosion of metal substrates by external corrosive media. Combined with the excellent physical shielding performance, adhesion, and media resistance of epoxy resin after curing, it can provide long-term and stable anti-corrosion protection for metal structures. Waterborne epoxy zinc-rich primer uses water as the main dispersion medium, eliminating the drawbacks of high volatility and high pollution associated with traditional solvent-based products. It has significant advantages in construction safety, environmental compliance, and convenience of storage and transportation, and has gradually become the mainstream choice to replace traditional solvent-based epoxy zinc-rich coatings. It is also an important direction for the research and development and industrial application of anti-corrosion coating technology. Although existing waterborne epoxy zinc-rich primers have achieved large-scale application, due to limitations in conventional component design and system compatibility, there is still a common technical shortcoming: the stability of zinc powder and its conductive protective properties are difficult to balance, failing to meet the actual needs of long-term anti-corrosion and stable application. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a waterborne epoxy zinc-rich primer, its preparation method, and its application. A composite zinc powder modified with discontinuous dotted silica is used as a cathodic protection filler, and a modified epoxy resin is used as a film-forming base material. Combined with a modified aminoethylpiperazine curing agent, a waterborne epoxy zinc-rich primer is obtained, exhibiting both long-lasting cathodic protection performance and excellent hydrolytic stability. The composite zinc powder, through the synergistic construction of a continuous conductive network and a physical anti-settling structure by spherical and flake-shaped zinc powders, forms a dotted passivation layer through mild activation with glycolic acid and targeted adsorption by acidic silica sol. This layer can seal the highly active sites of the zinc powder while ensuring electron conduction. The modified epoxy resin possesses self-emulsifying dispersibility and zinc powder coordination stabilization capabilities. The curing agent achieves waterborne compatibility and storage stability through epoxy addition and reversible end-capping. After application and unsealing, it can form a dense cross-linked paint film with the epoxy resin, improving the long-term anti-corrosion performance of the primer.

[0004] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides an aqueous epoxy zinc-rich primer, comprising component A and component B; Component A includes modified epoxy resin, zinc powder slurry modified with discontinuous dotted silica, and additives; Component B is a modified aminoethylpiperazine curing agent. The modified epoxy resin is obtained by reacting a portion of the hydrophilic modified epoxy resin with N,N-dimethylaminopropyl glycidyl ether; the hydrophilic modified epoxy resin is obtained by grafting bisphenol A type E-51 epoxy resin with polyethylene glycol glycidyl ether. The discontinuous dotted silica-modified zinc powder slurry is obtained by activating compound zinc powder with glycolic acid and modifying it with acidic silica sol; the compound zinc powder is composed of spherical zinc powder and flake zinc powder. The additives include dispersants, rheology modifiers, and defoamers; The modified aminoethylpiperazine curing agent is obtained by reacting aminoethylpiperazine with polyethylene glycol glycidyl ether via an epoxy addition reaction, followed by acetone end-capping modification, and then reacting with the remaining hydrophilic modified epoxy resin and undergoing phase inversion emulsification.

[0005] Further, the mass ratio of component A to component B is (9-11):1; the mass-to-volume ratio of the modified epoxy resin, the discontinuous dotted silica-modified zinc powder slurry, and the additives is (59-63) g: (230-250) g: (0.6-0.8) mL; the mass ratio of the hydrophilic modified epoxy resin to N,N-dimethylaminopropyl glycidyl ether is (59-63): (2.5-3.5); the mass-to-volume ratio of the bisphenol A type E-51 epoxy resin to polyethylene glycol glycidyl ether is (118-126) g: (10-14) mL; the compounded zinc powder, glycolic acid... The mass-to-volume ratio of the acidic silica sol is (23-26) g: (0.02-0.03) g: (0.2-0.3) mL; the mass ratio of the spherical zinc powder to the flake zinc powder is (16-18): (7-8); the volume ratio of the dispersant, rheology modifier and defoamer is (0.25-0.35): (0.25-0.3): (0.1-0.15); the mass-to-volume ratio of the remaining hydrophilic modified epoxy resin, aminoethylpiperazine, polyethylene glycol glycidyl ether and acetone is (59-63) g: (90-98) mL: (230-240) mL: (45-60) mL.

[0006] Further, the bisphenol A type E-51 epoxy resin has an epoxy value of 0.51-0.54; the spherical zinc powder has a particle size of 2-5 μm; the flake zinc powder has an average particle size of 10-15 μm; the acidic silica sol has a SiO2 content of 30 wt.% and a particle size of 10-12 nm; the dispersant is nonionic polyacrylic acid; the rheology modifier is polyether polyurethane; and the defoamer is polyether-modified polysiloxane.

[0007] Secondly, the present invention provides a method for preparing a waterborne epoxy zinc-rich primer, comprising the following steps: S1. Mix spherical zinc powder and flake zinc powder to obtain compound zinc powder; mix the compound zinc powder with deionized water, stir, add glycolic acid, and activate the reaction by heat preservation. Add glycolic acid aqueous solution to adjust the pH, add acidic silica sol dropwise, and preserve for curing to obtain a discontinuous dotted silica-modified zinc powder slurry. S2. Bisphenol A type E-51 epoxy resin, 2,4,6-tris(dimethylaminomethyl)phenol and dipropylene glycol methyl ether are mixed, heated to a first set temperature, polyethylene glycol glycidyl ether is added, and the mixture is reacted to obtain a hydrophilic modified epoxy resin; the hydrophilic modified epoxy resin is heated to a second set temperature, N,N-dimethylaminopropyl glycidyl ether is added, and the mixture is kept at this temperature to obtain a modified epoxy resin; S3. Mix the modified epoxy resin with deionized water, stir, add nonionic polyacrylic acid, disperse, then add polyurethane associative thickener, water-based silicone-free defoamer, and discontinuous dotted silica-modified zinc powder slurry in sequence, grind, add glycolic acid aqueous solution to adjust pH, filter, and obtain component A. S4. Mix polyethylene glycol glycidyl ether and dipropylene glycol methyl ether, raise the temperature to the third set temperature, add aminoethyl piperazine dropwise, and maintain the temperature to react, obtaining an aminoethyl piperazine-epoxy adduct. Add acetone, and after reflux reaction and atmospheric distillation, cool down to obtain end-capped modified aminoethyl piperazine. Add dipropylene glycol methyl ether to the reaction vessel, and add end-capped modified aminoethyl piperazine and the remaining hydrophilic modified epoxy resin in sequence under stirring. Raise the temperature to the fourth set temperature, react, cool down, and undergo phase inversion emulsification to obtain component B modified aminoethyl piperazine curing agent. Mix component A and component B to obtain waterborne epoxy zinc-rich primer.

[0008] In one feasible implementation, in step S1, the mass-to-volume ratio of the compound zinc powder to deionized water is (23-26) g: (210-220) mL; the stirring speed is 550-650 r / min; the temperature of the heat preservation activation reaction is 38-42℃, and the heat preservation activation reaction time is 20-30 min; the mass fraction of the glycolic acid aqueous solution is 10 wt%; the pH is adjusted to 5.5-6.0; the dropping rate is 0.005-0.007 mL / min; the heat preservation aging temperature is 38-42℃, and the heat preservation aging time is 35-45 min.

[0009] By employing a combination of spherical and flake zinc powder, synergistic effects are achieved through the complementary structures of the two morphologies. The spherical zinc powder, with its regular particle shape, provides point support, establishing a basic electronic conduction framework, while the flake zinc powder forms a continuous conductive network through planar overlap. Simultaneously, the physical barriers and stacking entanglement between the flakes construct an anti-settling structure system, physically inhibiting the gravitational sedimentation and agglomeration of zinc powder particles in the aqueous system. Glycolic acid is used for mild activation treatment, which can precisely etch hydroxyl active sites on the zinc powder surface, increase the high-activity regions such as zinc powder edges and lattice defects, and flatten the surface activity gradient. It can also create a weakly acidic environment in conjunction with pH control of the system, avoiding excessive corrosion of zinc powder by strong alkalis and acids that could lead to powder failure, and meeting the stable dispersion requirements of subsequent acidic silica sol, preventing silica sol agglomeration and gelation.

[0010] In a weakly acidic environment, silica sol exists as negatively charged monodisperse micelles. It can be targeted electrostatically adsorbed onto the highly active sites of activated positively charged zinc powder. It preferentially deposits a discontinuous dotted silica passivation layer in highly active defect areas, rather than completely covering the zinc powder surface. This structure not only seals the highly reactive sites of zinc powder and blocks direct contact between zinc powder and water molecules to inhibit hydrolysis and gas expansion in the aqueous phase and flash rust on the substrate, but also retains the exposed conductivity of the flat areas of the zinc powder body, ensuring the continuous and efficient electron transport network between zinc powder particles and maintaining the long-term cathodic protection function of the coating.

[0011] In one feasible implementation, in step S2, the mass-to-volume ratio of the bisphenol A type E-51 epoxy resin, 2,4,6-tris(dimethylaminomethyl)phenol, and dipropylene glycol methyl ether is (118-126) g : (0.15-0.25) g : (8-12) mL; the first set temperature is 73-77℃; the reaction time is 1.5-2.5 h; the second set temperature is 68-72℃; and the heat preservation reaction time is 1-2 h.

[0012] Using bisphenol A type E-51 epoxy resin as the core film-forming substrate, 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) was selected as a tertiary amine catalyst. Leveraging its basic catalytic properties, the ring-opening addition reaction of the epoxy groups was triggered. Firstly, DMP-30, acting as a nucleophilic catalyst, attacked the epoxy three-membered ring on the E-51 epoxy resin molecular chain, causing the epoxy ring to undergo polarization and ring-opening, forming an active intermediate. This active intermediate then underwent a directional ring-opening copolymerization reaction with the epoxy groups of polyethylene glycol glycidyl ether, stably grafting the hydrophilic polyether segment onto the hydrophobic backbone of the epoxy resin via covalent bonds, thus completing the process. The first step, hydrophilic modification, allows epoxy resin molecules to form an amphiphilic structure with both hydrophobic backbones and hydrophilic side chains. The hydrophobic backbone fully retains the inherent mechanical strength, aging resistance, and resistance to media erosion of epoxy resin, while the hydrophilic side chains significantly improve the self-emulsifying and dispersing properties of the resin in aqueous systems. Stable water dispersion can be achieved without the addition of a large amount of emulsifier, while avoiding the drawbacks of reduced water resistance, blistering, and peeling of the paint film caused by residual emulsifier. Furthermore, during paint film curing, the hydrophilic side chains will converge inward and the hydrophobic backbone will be oriented to further construct a dense hydrophobic barrier layer, blocking the penetration of external moisture, salt spray, and other corrosive media.

[0013] Based on this, the hydrophilically modified epoxy resin continues to undergo a ring-opening grafting reaction with N,N-dimethylaminopropyl glycidyl ether, relying on the epoxy active sites remaining in the molecular chain. This covalently introduces tertiary amine chelating groups containing lone pairs of electrons into the resin molecular chain, completing the second step of chelation functional modification. The nitrogen atoms in the tertiary amine groups can form a stable interfacial bond with the metal active sites on the surface of zinc powder through coordination bonds. This not only eliminates the interfacial gap between the resin and the zinc powder filler and enhances interfacial compatibility, but also generates a steric hindrance effect to inhibit the agglomeration and sedimentation of zinc powder particles, ensuring uniform dispersion of zinc powder in the system. At the same time, it can also improve the crosslinking density of the paint film after curing, further enhancing the coating adhesion and overall anti-corrosion performance.

[0014] In one feasible implementation, in step S3, the mass-to-volume ratio of the modified epoxy resin, nonionic polyacrylic acid, and deionized water is (59-63) g : (0.25-0.35) g : (45-55) mL; the stirring speed is 280-320 r / min; the dispersion speed is 750-850 r / min; the dispersion time is 8-12 min; the grinding fineness is ≤25 μm; the mass fraction of the aqueous glycolic acid solution is 10 wt%; the dropping rate is 0.08-0.12 mL / min; and the adjusted pH is 7.0-7.5.

[0015] Using modified epoxy resin as a continuous film-forming base material and deionized water as an environmentally friendly aqueous dispersion medium, the core dispersion system of component A is constructed. Nonionic polyacrylic acid serves as a highly efficient dispersant, forming multi-point hydrogen bonds with the hydroxyl groups on the surface of zinc powder and chelating the polar groups of the resin through carboxyl groups. At the same time, its long carbon chains form a dense steric hindrance layer around the zinc powder particles, completely eliminating van der Waals force agglomeration between filler particles, further enhancing the dispersion stability of discontinuous dotted silica-modified zinc powder, and preventing hard sedimentation during coating storage. Polyether polyurethane, as a defoamer, relies on its low surface tension characteristics to penetrate the bubble liquid film generated during dispersion and shearing, destroying the elastic structure of the bubble film to achieve rapid bubble defoaming, while inhibiting bubble regeneration. Polyether-modified polysiloxane, as a leveling agent, reduces the surface tension of the coating system, improves the wettability of the coating to the substrate, eliminates pinholes and brush marks during coating, and ensures a smooth and dense paint film.

[0016] By grinding, the secondary agglomerates of zinc powder are broken up, the particle size of the solid phase of the coating is refined, and the particle size difference between the binder and the filler is reduced, further improving the uniformity of the system and the density of the paint film. Subsequently, the pH of the system is adjusted by a weak acid regulator, which can not only stabilize the molecular structure of the dispersant and leveling agent and prevent the agent from failing, but also neutralize the residual active sites on the surface of zinc powder and prevent the resin from hydrolytic denaturation. Finally, a waterborne epoxy zinc-rich primer component A is constructed that is stable in storage, uniformly dispersed, has excellent film-forming properties, and has both cathodic protection and film protection functions, laying a solid component foundation for subsequent curing and crosslinking.

[0017] In one feasible implementation, in step S4, the volume ratio of polyethylene glycol glycidyl ether to dipropylene glycol methyl ether is (230-240):(50-70); the third set temperature is 60-65℃; the dropping rate is 3.0-3.2 mL / min; the holding time is 2-3 h; the volume ratio of polyethylene glycol glycidyl ether to acetone is (230-240):(45-60); the reflux reaction temperature is 50-55℃, and the reflux reaction time is 3-4 h; the atmospheric distillation temperature is 80-85℃, and the atmospheric distillation time is 1-1.5 h; the cooling step is: cooling to 30℃ at a rate of 0.8-1.2℃ / min.

[0018] Using aminoethylpiperazine as the core curing monomer, it first undergoes an epoxy ring-opening addition reaction with polyethylene glycol glycidyl ether. The water-based compatibility modification of the curing agent is achieved by covalently grafting hydrophilic polyether segments. This reduces the initial reactivity of the amino group, avoids excessively fast curing rate during construction leading to film cracking, and improves the compatibility of the curing agent with the water-based system, eliminating problems such as phase separation and flocculation. Subsequently, acetone is used to reversibly end-cap the active amino group. Acetone dehydrates and condenses with primary and secondary amines to form a ketimine structure, completely shielding the active hydrogen atoms and blocking the side reactions of the curing agent with epoxy groups and zinc powder during storage. This fundamentally extends the shelf life of the two-component system. Unreacted free acetone is then removed by distillation to avoid residual solvent affecting the film performance.

[0019] In one feasible implementation, in step S4, the mass-to-volume ratio of the remaining hydrophilic modified epoxy resin and dipropylene glycol methyl ether is (59-63) g: (12-18) mL; the fourth set temperature is 53-57℃; the reaction time is 2-3 h; the cooling step is to allow the temperature to drop naturally to 30℃; the phase inversion emulsification step is as follows: add 25-35 mL of deionized water and stir for 8-12 min to invert the phase, then add 260-280 mL of deionized water dropwise at a rate of 4.2-7.0 mL / min, maintain continuous stirring and shearing at 300-400 r / min, and continue stirring for 12-18 min after the dropwise addition is completed to obtain a 100-300 nm emulsion.

[0020] The end-capped aminoethylpiperazine molecular chain still retains secondary amine active sites and hydroxyl nucleophilic sites that did not participate in the end-capping reaction. Under mildly heated reaction conditions, these active sites can undergo a low-degree prepolymerization addition reaction with the incompletely reacted epoxy groups on the hydrophilic modified epoxy resin molecular chain, generating linear prepolymer segments without triggering network cross-linking and curing. This prevents premature gelation and, through covalent bonding, firmly binds the curing agent molecules and modified epoxy resin segments into a unified whole. This prepolymerization reaction achieves structural homogenization between the curing agent and the epoxy resin, allowing the curing agent molecules to carry epoxy segments, eliminating the interfacial differences between it and the modified epoxy resin in component A. This improves the miscibility and dispersion uniformity of components A and B during mixing, effectively avoiding problems such as layering and precipitation. Simultaneously, the transition segments formed by prepolymerization can effectively regulate the overall curing reaction kinetics, making the crosslinking sites of the unsealed active amino and epoxy groups more compatible, maintaining a uniform crosslinking reaction rate, and preventing defects such as internal stress, pinholes, and cracking caused by excessively rapid local curing, thus fully ensuring the crosslinking density of the paint film. Furthermore, after the prepolymerization reaction, the hydrophilic-hydrophobic ratio of the curing agent becomes more balanced, resulting in a more stable nanoscale emulsion formed by subsequent phase inversion emulsification, less prone to demulsification and stratification, further enhancing the storage stability of component B itself.

[0021] When component A and component B are mixed in the specified ratio, the ketimine-terminated structure will be rapidly desealed by the moisture on the substrate surface. The released active amino groups will undergo a complete addition crosslinking reaction with the prepolymer segments and the epoxy groups in component A, ultimately forming a continuous and dense network coating film, which simultaneously endows the coating with excellent adhesion, mechanical strength and long-term anti-corrosion performance.

[0022] Thirdly, this invention provides an application of a water-based epoxy zinc-rich primer in industrial anti-corrosion coating.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: This solution uses compound zinc powder modified with discontinuous dotted silica as the cathodic protection functional substrate, and bisphenol A type epoxy resin grafted with hydrophilic and chelating dual functions as the film-forming base material, combined with modified aminoethylpiperazine curing agent, to obtain a waterborne epoxy zinc-rich primer that has both long-lasting cathodic protection performance and excellent hydrolytic stability. The compound zinc powder utilizes the point support characteristics of spherical zinc powder to establish a conductive foundation, and leverages the surface overlap characteristics of sheet-like zinc powder to construct a continuous conductive network. Simultaneously, the layered structure of the sheet-like zinc powder forms a physical anti-settling network, effectively suppressing zinc powder sedimentation and achieving stable dispersion. Furthermore, the zinc powder is gently activated by glycolic acid, generating hydroxyl active sites on the zinc powder surface. This enhances the activity differences between different regions of the zinc powder, allowing acidic silica sol to target and selectively adsorb based on these site activity differences. It preferentially and selectively adsorbs and deposits on highly active areas such as zinc powder edges and lattice defects, forming a discontinuous point-like silica passivation structure. This structure seals the highly active sites of the zinc powder to suppress aqueous phase hydrolysis and flash rust during construction, while simultaneously ensuring the exposed surface of the zinc powder matrix, guaranteeing continuous and efficient electronic conductivity between zinc powder particles.

[0024] Epoxy resin uses its own hydrophobic backbone containing aromatic hydrocarbons and aliphatic chains as a framework. By grafting polyethylene glycol glycidyl ether, hydrophilic polyether side chains are introduced, so that the single molecule has both hydrophilic and hydrophobic segments to form an amphiphilic structure. The hydrophilic segments endow the resin with self-emulsifying and dispersing ability in the aqueous phase, while the hydrophobic segments construct a hydrophobic barrier structure after the paint film is cured, improving the water resistance and density of the paint film and blocking the penetration of external corrosive media. At the same time, the epoxy resin further achieves uniform dispersion of zinc powder by covalently grafting tertiary amine chelate monomer N,N-dimethylaminopropyl glycidyl ether, which utilizes the lone pair electrons of nitrogen atoms to form weak coordination bonds with the zinc powder surface. Modified aminoethylpiperazine is first modified by epoxy addition to reduce its own reactivity and introduce hydrophilic segments to improve water compatibility. Then, the active amino group is shielded by reversible end-capping modification to ensure the long-term storage stability of the system. During construction, the end-capping structure is unsealed, and the released active amine hydrogen can undergo addition cross-linking with the modified epoxy resin to form a dense network coating film, which greatly improves the long-term service performance of the coating. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the preparation process of a waterborne epoxy zinc-rich primer according to the present invention.

[0026] Figure 2 This is a photograph of the water-based epoxy zinc-rich primer prepared in Example 1 of the present invention coated on a substrate. Detailed Implementation

[0027] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the application will be further described in detail below with reference to embodiments. However, this should not be construed as limiting the scope of this application to the following examples. All other embodiments obtained by those skilled in the art without creative effort without departing from the above-described methodological spirit of this application are within the scope of protection of this application.

[0028] The singular forms “for,” “or,” “a,” “any,” and “described” used in this application are intended to include the plural forms unless the context clearly indicates otherwise. Furthermore, the terms “first” and “second” are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0029] Example 1 like Figure 1 As shown, a method for preparing a water-based epoxy zinc-rich primer includes the following steps: S1. Mix 16.8g of spherical zinc powder with a particle size of 3μm and 7.2g of flake zinc powder with a particle size of 12μm to obtain a compound zinc powder. Add 216mL of deionized water to a closed dispersion vessel, add the compound zinc powder, stir at a low speed of 600r / min, add 0.024g of glycolic acid, keep at 40℃ for 25min to activate, maintain the pH of the system at 5.8 throughout by adding 10wt% glycolic acid aqueous solution, add 0.24mL of acidic silica sol with a SiO2 content of 30% and a particle size of 11nm dropwise at a rate of 0.006mL / min within 40min, and continue to keep at 40℃ for 40min to mature, to obtain a discontinuous dotted silica-modified zinc powder slurry.

[0030] S2. Add 122g of bisphenol A type E-51 epoxy resin to a reactor equipped with a reflux condenser, add 10mL of dipropylene glycol methyl ether and 0.2g of DMP-30, start stirring at 250r / min and heat to 75℃, add 12mL of polyethylene glycol glycidyl ether, keep the reaction at this temperature for 2h to obtain a hydrophilic modified epoxy resin grafted with hydrophilic polyether segments; take 61g of the above hydrophilic modified epoxy resin, heat to 70℃, add 3g of N,N-dimethylaminopropyl glycidyl ether, keep the reaction at this temperature for 1.5h to obtain a modified epoxy resin.

[0031] S3. Add 61g of modified epoxy resin and 50mL of deionized water to a high-speed dispersion tank, start low-speed stirring at 300r / min for 5min, add 0.3g of nonionic polyacrylic acid, adjust the speed to 800r / min and disperse for 10min, add 0.28mL of polyether polyurethane and 0.12mL of polyether modified polysiloxane, continue to disperse for 5min, add 120g of discontinuous dotted silica modified zinc powder slurry within 10min, pre-dispersion at 800r / min for 10min, then add the remaining 120g of discontinuous dotted silica modified zinc powder slurry within another 10min, increase the speed to 1500r / min and disperse at high speed for 25min, grind with a basket mill, and use a scraper fineness meter to test the fineness of the coating until the fineness is ≤25μm, add 10wt% glycolic acid aqueous solution dropwise at a rate of 0.1mL / min to adjust the pH of the system to 7.2, stir evenly, filter and discharge to obtain component A.

[0032] S4. Add 235 mL of polyethylene glycol glycidyl ether and 60 mL of dipropylene glycol methyl ether to a reaction vessel, stir at 200 rpm and heat to 60 °C. Add 90 mL of aminoethylpiperazine dropwise at a rate of 3.1 mL / min, controlling the system temperature to not exceed 70 °C, and maintain the reaction temperature for 2.5 h to obtain an aminoethylpiperazine-epoxy adduct. Add 53 mL of acetone to the adduct and reflux at 52 °C for 3.5 h. Then heat to 82 °C and distill at atmospheric pressure for 1.2 h. Cool to 30 °C at a rate of 1 °C / min and discharge to obtain end-capped modified aminoethylpiperazine. Add 15 mL of dipropylene glycol methyl ether to the reaction vessel, stir at 300 rpm and add the end-capped modified aminoethylpiperazine, stirring for 20 minutes. Add the remaining 61g of hydrophilic modified epoxy resin at a rate of 2.03g / min, maintain stirring at 300r / min, heat to 55℃ and keep reacting for 2.5h, then cool naturally to 30℃. Add 30mL of deionized water and stir for 10min for phase inversion, then add 270mL of deionized water dropwise at a rate of 5.6mL / min, maintain stirring and shearing at 350r / min. After the dropwise addition is complete, continue stirring for 15min. After phase inversion emulsification, an emulsion with an average hydrated particle size of 200nm is obtained. Filter the material to obtain component B modified aminoethylpiperazine curing agent. Mix component A and component B at a mass ratio of 10:1 and stir at low speed of 300r / min for 10min to obtain waterborne epoxy zinc-rich primer.

[0033] The actual image of the water-based epoxy zinc-rich primer prepared in this embodiment coated on the substrate is shown below. Figure 2 As shown.

[0034] Example 2 like Figure 1 As shown, a method for preparing a water-based epoxy zinc-rich primer includes the following steps: S1. Mix 16g of spherical zinc powder with a particle size of 2μm and 7g of flake zinc powder with a particle size of 10μm to obtain a compound zinc powder. Add 210mL of deionized water to a closed dispersion vessel, add the compound zinc powder, stir at a low speed of 550r / min, add 0.02g of glycolic acid, keep at 38℃ for 20min to activate, maintain the pH of the system at 5.5 throughout by adding 10wt% glycolic acid aqueous solution, add 0.2mL of acidic silica sol with a SiO2 content of 30% and a particle size of 10nm dropwise at a rate of 0.005mL / min over 40min, and continue to keep at 38℃ for 35min to obtain a discontinuous dotted silica-modified zinc powder slurry.

[0035] S2. Add 118g of bisphenol A type E-51 epoxy resin to a reactor equipped with a reflux condenser, add 8mL of dipropylene glycol methyl ether and 0.15g of DMP-30, start stirring at 250r / min and heat to 73℃, add 10mL of polyethylene glycol glycidyl ether, keep the reaction at this temperature for 1.5h to obtain a hydrophilic modified epoxy resin grafted with hydrophilic polyether segments; take 59g of the above hydrophilic modified epoxy resin, heat to 68℃, add 2.5g of N,N-dimethylaminopropyl glycidyl ether, keep the reaction at this temperature for 1h to obtain a modified epoxy resin.

[0036] S3. Add 59g of modified epoxy resin and 45mL of deionized water to a high-speed dispersion tank, start low-speed stirring at 280r / min for 5min, add 0.25g of nonionic polyacrylic acid, adjust the speed to 750r / min and disperse for 8min, add 0.25mL of polyether polyurethane and 0.1mL of polyether modified polysiloxane, continue to disperse for 5min, add 115g of discontinuous dotted silica modified zinc powder slurry within 10min, pre-dispersion at 800r / min for 10min, then add the remaining 115g of discontinuous dotted silica modified zinc powder slurry within another 10min, increase the speed to 1500r / min and disperse at high speed for 25min, grind with a basket mill, and use a scraper fineness meter to test the fineness of the coating until the fineness is ≤25μm, add 10wt% glycolic acid aqueous solution dropwise at a rate of 0.08mL / min to adjust the pH of the system to 7.0, stir evenly, filter and discharge to obtain component A.

[0037] S4. Add 230 mL of polyethylene glycol glycidyl ether and 50 mL of dipropylene glycol methyl ether to a reaction vessel, stir at 200 rpm and heat to 60 °C. Add 90 mL of aminoethylpiperazine dropwise at a rate of 3.0 mL / min, controlling the system temperature to not exceed 70 °C, and maintain the reaction temperature for 2 h to obtain an aminoethylpiperazine-epoxy adduct. Add 45 mL of acetone to the adduct and reflux at 50 °C for 3 h. Then heat to 80 °C and distill at atmospheric pressure for 1 h. Cool to 30 °C at a rate of 0.8 °C / min and discharge to obtain end-capped modified aminoethylpiperazine. Add 12 mL of dipropylene glycol methyl ether to the reaction vessel, stir at 300 rpm and add the end-capped modified aminoethylpiperazine, stirring for 20-30 minutes. Add the remaining 59g of hydrophilic modified epoxy resin at a rate of 2.03g / min, maintain stirring at 300-400r / min, heat to 53℃ and keep reacting for 2h, then cool naturally to 30℃, add 25mL of deionized water and stir for 8min for phase inversion, then add 260mL of deionized water dropwise at a rate of 4.2mL / min, maintain stirring and shearing at 300r / min, and continue stirring for 12min after the dropwise addition is complete. After phase inversion emulsification, an emulsion with an average hydrated particle size of 100nm is obtained. Filter the material to obtain component B modified aminoethylpiperazine curing agent; mix component A and component B at a mass ratio of 10:1, stir at low speed of 300r / min for 10min to obtain waterborne epoxy zinc-rich primer.

[0038] Example 3 like Figure 1 As shown, a method for preparing a water-based epoxy zinc-rich primer includes the following steps: S1. Mix 18g of spherical zinc powder with a particle size of 5μm and 8g of flake zinc powder with a particle size of 15μm to obtain a compound zinc powder. Add 220mL of deionized water to a closed dispersion vessel, add the compound zinc powder, stir at a low speed of 650r / min, add 0.03g of glycolic acid, keep at 42℃ for 30min to activate, maintain the pH of the system at 6.0 throughout by adding 10wt% glycolic acid aqueous solution, add 0.3mL of acidic silica sol with a SiO2 content of 30% and a particle size of 12nm dropwise at a rate of 0.007mL / min within 40min, and continue to keep at 42℃ for 45min to mature, to obtain a zinc powder slurry modified with discontinuous dotted silica.

[0039] S2. Add 126g of bisphenol A type E-51 epoxy resin to a reactor equipped with a reflux condenser, add 12mL of dipropylene glycol methyl ether and 0.25g of DMP-30, start stirring at 250r / min and heat to 77℃, add 14mL of polyethylene glycol glycidyl ether, and keep the reaction at this temperature for 2.5h to obtain a hydrophilic modified epoxy resin grafted with hydrophilic polyether segments; take 63g of the above hydrophilic modified epoxy resin, heat to 72℃, add 3.5g of N,N-dimethylaminopropyl glycidyl ether, and keep the reaction at this temperature for 2h to obtain a modified epoxy resin.

[0040] S3. Add 63g of modified epoxy resin and 55mL of deionized water to a high-speed dispersion tank, start low-speed stirring at 320r / min for 5min, add 0.35g of nonionic polyacrylic acid, adjust the speed to 850r / min and disperse for 12min, add 0.3mL of polyether polyurethane and 0.15mL of polyether modified polysiloxane, continue to disperse for 5min, add 125g of discontinuous dotted silica modified zinc powder slurry within 10min, pre-dispersion at 800r / min for 10min, then add the remaining 125g of discontinuous dotted silica modified zinc powder slurry within another 10min, increase the speed to 1500r / min and disperse at high speed for 25min, grind with a basket mill, and use a scraper fineness meter to test the fineness of the coating until the fineness is ≤25μm, add 10wt% glycolic acid aqueous solution dropwise at a rate of 0.12mL / min to adjust the pH of the system to 7.5, stir evenly, filter and discharge to obtain component A.

[0041] S4. Add 240 mL of polyethylene glycol glycidyl ether and 70 mL of dipropylene glycol methyl ether to a reaction vessel, stir at 200 rpm and heat to 65 °C. Add 98 mL of aminoethylpiperazine dropwise at a rate of 3.2 mL / min, controlling the system temperature to not exceed 70 °C, and maintain the reaction temperature for 3 h to obtain an aminoethylpiperazine-epoxy adduct. Add 60 mL of acetone to the adduct and reflux at 55 °C for 4 h. Then heat to 85 °C and distill at atmospheric pressure for 1.5 h. Cool to 30 °C at a rate of 1.2 °C / min and discharge to obtain end-capped modified aminoethylpiperazine. Add 18 mL of dipropylene glycol methyl ether to the reaction vessel, stir at 300 rpm and add end-capped modified aminoethylpiperazine, stirring for 20 minutes. Add the remaining 63g of hydrophilic modified epoxy resin at a rate of 2.03g / min, maintain stirring at 300r / min, heat to 57℃ and keep reacting for 3h, then cool naturally to 30℃, add 35mL of deionized water and stir for 12min for phase inversion, then add 280mL of deionized water dropwise at a rate of 7.0mL / min, maintain stirring and shearing at 400r / min, and continue stirring for 18min after the dropwise addition is complete. After phase inversion emulsification, an emulsion with an average hydrated particle size of 300nm is obtained. Filter the material to obtain component B modified aminoethylpiperazine curing agent; mix component A and component B at a mass ratio of 10:1 and stir at low speed of 300r / min for 10min to obtain waterborne epoxy zinc-rich primer.

[0042] Comparative Example 1 A method for preparing a waterborne epoxy zinc-rich primer differs from Example 1 in that the compound zinc powder is not modified with discontinuous silica in step S1. Instead, the compound zinc powder is directly mixed with deionized water to prepare a slurry, which replaces the zinc powder slurry modified with discontinuous dotted silica. The remaining steps and parameters are the same.

[0043] Comparative Example 2 A method for preparing a waterborne epoxy zinc-rich primer differs from Example 1 in that only a hydrophilic modified epoxy resin is prepared in step S2 to replace the modified epoxy resin, while the remaining steps and parameters are the same.

[0044] Comparative Example 3 A method for preparing a waterborne epoxy zinc-rich primer differs from Example 1 in that only an aminoethylpiperazine-epoxy adduct is prepared in step S4 to replace the end-capped modified aminoethylpiperazine; the remaining steps and parameters are the same.

[0045] Performance testing: Adhesion test: In a standard environment with a temperature of 21℃-25℃ and a relative humidity of 45%-55%, carbon steel test plates were sandblasted to a surface roughness of 60-80μm using Sa2.5 grade sandblasting. Waterborne epoxy zinc-rich primers prepared in Examples 1-3 and Comparative Examples 1-3 were uniformly applied to the Sa2.5 grade sandblasted carbon steel test plates, with the dry film thickness controlled at 55-65μm. After curing at room temperature for 7 days, the paint film was vertically cut to the substrate surface using a 1mm pitch multi-blade cross-cutting tool to form a regular... For the complete grid pattern, use a soft brush to repeatedly clean away loose paint debris along the diagonal. Apply 3M 600 pressure-sensitive tape and press it firmly to remove air bubbles. After standing for 1 minute, quickly peel off the tape at a 60° angle and observe the paint film peeling off the grid area. Evaluate the adhesion level according to the 0-5 standard: Level 0 means the paint film grid edge is completely smooth with no peeling, indicating the best adhesion; Levels 1-5 show that as the level increases, the area of ​​paint film peeling off gradually increases, and the adhesion weakens at each level. This is used to determine the quality of the bonding between the paint film and the substrate.

[0046] Neutral salt spray resistance test: Carbon steel test plates with a surface roughness of 60-80 μm after Sa2.5 grade sandblasting were selected. In a standard environment with a temperature of 21℃-25℃ and a relative humidity of 45%-55%, water-based epoxy zinc-rich primers prepared in Examples 1-3 and Comparative Examples 1-3 were applied respectively. The dry film thickness of the paint film was controlled at 55-65 μm. After curing at room temperature for 7 days, a single-sided crisscross treatment was performed. The crisscross width was 0.5 mm, and the crisscross depth uniformly penetrated the paint film to the carbon steel substrate. The crisscrossed test plates were placed in a salt spray test chamber at an angle of 15°-30°. The temperature inside the chamber was controlled at a constant 33℃-37℃. A sodium chloride solution with a mass fraction of 5% and a pH value of 6.5-7.2 was used, and the spray settling rate was adjusted to 1-2 mL / (80 cm²). 2 •h) Collect liquid pH value 6.5-7.2, conduct continuous spray test, and record the longest continuous test duration when the test plate has no obvious rust, no paint film peeling and the unidirectional erosion width at the scribing point is ≤2mm.

[0047] Room temperature water resistance test: Carbon steel test plates with a surface roughness of 60-80μm after Sa2.5 grade sandblasting were selected. Water-based epoxy zinc-rich primers prepared in Examples 1-3 and Comparative Examples 1-3 were applied in a standard environment with a temperature of 21℃-25℃ and a relative humidity of 45%-55%. The dry film thickness of the paint film was controlled to be 55-65μm. After curing at room temperature for 7 days, the test plates were completely immersed in deionized water in a constant temperature environment of 21℃-25℃, ensuring that the water level was more than 20mm above the top of the test plate and the test container was sealed. The test plates were taken out every 24 hours to visually inspect the appearance of the paint film. The number of consecutive immersion days in which the paint film did not turn white, blister, wrinkle, peel off, lose gloss and the substrate was not corroded was recorded.

[0048] Zinc powder sedimentation stability test: The A components prepared in Examples 1-3 and Comparative Examples 1-3 were respectively placed into 500mL stoppered glass graduated cylinders and sealed and left to stand for 30 days at room temperature of 21℃-25℃, avoiding light and vibration throughout the process. After standing, the height of the upper clear liquid and the total height of the sample were measured respectively. The sedimentation rate was calculated by the formula: sedimentation rate = (height of upper clear liquid / total height of sample) × 100%. At the same time, it was observed whether there was agglomeration or hard precipitation of zinc powder at the bottom of the graduated cylinder. The lower the sedimentation rate and the absence of agglomeration, the better the dispersion stability of zinc powder.

[0049] Rust suppression test: In a test environment with a temperature of 21℃-25℃ and a relative humidity of 55%-65%, the A and B components prepared in Examples 1-3 and Comparative Examples 1-3 were mixed and stirred evenly at a mass ratio of 10:1. Immediately after mixing, the mixture was applied evenly with a brush to bare carbon steel test plates that had not undergone rust prevention and passivation treatment, ensuring that the wet film was uniform and without any omissions. After standing for 30 minutes, the surface of the paint film was visually observed to determine whether rust spots appeared. The rust suppression effect was evaluated according to three levels: no rust, slight rust, and severe rust.

[0050] Table 1. Performance test results of the waterborne epoxy zinc-rich primers prepared in Examples 1-3 and Comparative Examples 1-3

[0051] As shown in Table 1, the waterborne epoxy zinc-rich primers prepared in Examples 1-3 exhibited higher adhesion, neutral salt spray resistance, and room temperature water resistance than Comparative Examples 1-3, and lower zinc powder settling rate. This indicates that the waterborne epoxy zinc-rich primers prepared in Examples 1-3 had better adhesion, neutral salt spray resistance, room temperature water resistance, zinc powder settling stability, and flash rust resistance than Comparative Examples 1-3.

[0052] Comparative Example 1 did not involve discontinuous dotted silica modification of the compounded zinc powder. The highly active sites on the zinc powder surface were not targeted and passivated, making the zinc powder prone to hydrolysis and agglomeration in the aqueous system, significantly reducing the dispersion stability of the zinc powder. At the same time, it easily caused severe flash rust on the bare carbon steel substrate during construction. In addition, the unmodified zinc powder is difficult to form a continuous and efficient electronic conductive network, which greatly weakens the cathodic protection effect. Defects also occur in the paint film due to zinc powder agglomeration, making it easier for corrosive media to penetrate. This leads to a significant reduction in coating adhesion, and a substantial decrease in neutral salt spray resistance and room temperature water resistance. This fully demonstrates that discontinuous dotted silica modification is the key to inhibiting zinc powder hydrolysis and sedimentation and improving the anti-corrosion and anti-flash rust performance of the coating.

[0053] Comparative Example 2 did not undergo the N,N-dimethylaminopropyl glycidyl ether grafting step, meaning the hydrophilic modified epoxy resin was not modified with tertiary amine chelation. The resin and zinc powder only exhibited physical dispersion, lacking strong interactions of chelating coordination bonds. This not only reduced the uniformity of zinc powder dispersion but also weakened the adhesion between the paint film and the substrate, resulting in decreased coating adhesion. Simultaneously, the unchelated resin could not form a dense cross-linked paint film, significantly reducing its barrier ability against corrosive media. Consequently, the coating's resistance to neutral salt spray and room temperature water resistance was significantly reduced, and the dispersion stability of the zinc powder was also adversely affected. This demonstrates that chelation modification of the epoxy resin is a core step in enhancing zinc powder dispersion and improving coating adhesion and resistance to media.

[0054] Comparative Example 3 did not undergo acetone end-capping modification of the curing agent. The unblocked active amino groups in the uncapped aminoethylpiperazine-epoxy adduct reduced the storage stability of the system, promoted the agglomeration and sedimentation of zinc powder, and further reduced the dispersion stability of zinc powder. At the same time, the runaway curing reaction rate led to uneven cross-linking density of the paint film, which significantly weakened the anti-corrosion and mechanical properties of the coating. This resulted in a significant decrease in coating adhesion, neutral salt spray resistance, and room temperature water resistance. During construction, the excessively high amine activity also caused slight flash rust. This fully demonstrates that end-capping modification of the curing agent is an important process to ensure the storage stability of the system, optimize the cross-linking structure of the paint film, and balance workability and long-term coating performance.

[0055] Comparative Examples 1-3, due to the lack of discontinuous dotted silica modification of zinc powder, tertiary amine chelation modification of hydrophilic modified epoxy resin, and reversible end-capping modification of curing agent, resulted in a significant reduction in zinc powder dispersion stability, a significant weakening of coating adhesion and anti-corrosion barrier ability, easy occurrence of flash rust during construction, and poor system storage stability. These factors collectively manifested as a significant deterioration in paint film adhesion, neutral salt spray resistance, room temperature water resistance, zinc powder settling stability, and flash rust resistance.

[0056] The above results demonstrate and describe the basic principles and main features of this application, as well as its advantages.

[0057] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A water-based epoxy zinc-rich primer, characterized in that, It includes component A and component B; the mass ratio of component A to component B is (9-11):1; Component A comprises modified epoxy resin, zinc powder slurry modified with discontinuous dotted silica, and additives; the mass-to-volume ratio of the modified epoxy resin, zinc powder slurry modified with discontinuous dotted silica, and additives is (59-63) g : (230-250) g ​​: (0.6-0.8) mL; Component B is a modified aminoethylpiperazine curing agent; The modified epoxy resin is obtained by reacting a portion of the hydrophilic modified epoxy resin with N,N-dimethylaminopropyl glycidyl ether; the hydrophilic modified epoxy resin is obtained by grafting bisphenol A type E-51 epoxy resin with polyethylene glycol glycidyl ether. The discontinuous dotted silica-modified zinc powder slurry is obtained by activating compound zinc powder with glycolic acid and modifying it with acidic silica sol; the compound zinc powder is composed of spherical zinc powder and flake zinc powder. The additives include dispersants, rheology modifiers, and defoamers; The modified aminoethylpiperazine curing agent is obtained by reacting aminoethylpiperazine with polyethylene glycol glycidyl ether via an epoxy addition reaction, followed by acetone end-capping modification, and then reacting with the remaining hydrophilic modified epoxy resin and undergoing phase inversion emulsification.

2. The waterborne epoxy zinc-rich primer according to claim 1, characterized in that, The mass ratio of the hydrophilic modified epoxy resin to N,N-dimethylaminopropyl glycidyl ether in the aforementioned portion is (59-63):(2.5-3.5); the mass-to-volume ratio of the bisphenol A type E-51 epoxy resin to polyethylene glycol glycidyl ether is (118-126) g:(10-14) mL; the mass-to-volume ratio of the compounded zinc powder, glycolic acid, and acidic silica sol is (23-26) g:(0.02-0.03) g:(0.2-0.3) mL; The mass ratio of spherical zinc powder to flake zinc powder is (16-18):(7-8); the volume ratio of dispersant, rheology modifier and defoamer is (0.25-0.35):(0.25-0.3):(0.1-0.15); the mass-volume ratio of the remaining hydrophilic modified epoxy resin, aminoethylpiperazine, polyethylene glycol glycidyl ether and acetone is (59-63) g:(90-98) mL:(230-240) mL:(45-60) mL.

3. The waterborne epoxy zinc-rich primer according to claim 1, characterized in that, The bisphenol A type E-51 epoxy resin has an epoxy value of 0.51-0.54; the spherical zinc powder has a particle size of 2-5 μm; the flake zinc powder has an average particle size of 10-15 μm; the acidic silica sol has a SiO2 content of 30 wt.% and a particle size of 10-12 nm; the dispersant is nonionic polyacrylic acid; the rheology modifier is polyether polyurethane; and the defoamer is polyether-modified polysiloxane.

4. A method for preparing a waterborne epoxy zinc-rich primer as described in any one of claims 1-3, characterized in that, include: S1. Mix spherical zinc powder and flake zinc powder to obtain compound zinc powder; The compound zinc powder was mixed with deionized water and stirred. Glycolic acid was added and activated by heat preservation. The pH was adjusted by adding aqueous glycolic acid and acidic silica sol was added dropwise. The mixture was then kept warm and matured to obtain a discontinuous dotted silica-modified zinc powder slurry. S2. Bisphenol A type E-51 epoxy resin, 2,4,6-tris(dimethylaminomethyl)phenol and dipropylene glycol methyl ether are mixed, heated to a first set temperature, polyethylene glycol glycidyl ether is added, and the mixture is reacted to obtain a hydrophilic modified epoxy resin; the hydrophilic modified epoxy resin is heated to a second set temperature, N,N-dimethylaminopropyl glycidyl ether is added, and the mixture is kept at this temperature to obtain a modified epoxy resin; S3. Mix the modified epoxy resin with deionized water, stir, add nonionic polyacrylic acid, disperse, then add polyurethane associative thickener, water-based silicone-free defoamer, and discontinuous dotted silica-modified zinc powder slurry in sequence, grind, add glycolic acid aqueous solution to adjust pH, filter, and obtain component A. S4. Mix polyethylene glycol glycidyl ether and dipropylene glycol methyl ether, raise the temperature to the third set temperature, add aminoethyl piperazine dropwise, and maintain the temperature to react, obtaining an aminoethyl piperazine-epoxy adduct. Add acetone, and after reflux reaction and atmospheric distillation, cool down to obtain end-capped modified aminoethyl piperazine. Add dipropylene glycol methyl ether to the reaction vessel, and add end-capped modified aminoethyl piperazine and the remaining hydrophilic modified epoxy resin in sequence under stirring. Raise the temperature to the fourth set temperature, react, cool down, and undergo phase inversion emulsification to obtain component B modified aminoethyl piperazine curing agent. Mix component A and component B to obtain waterborne epoxy zinc-rich primer.

5. The method for preparing a waterborne epoxy zinc-rich primer according to claim 4, characterized in that, In step S1, the mass-to-volume ratio of the compound zinc powder to deionized water is (23-26) g: (210-220) mL; the stirring speed is 550-650 r / min; the temperature of the heat preservation activation reaction is 38-42℃, and the heat preservation activation reaction time is 20-30 min; the mass fraction of the glycolic acid aqueous solution is 10 wt%; the pH is adjusted to 5.5-6.0; the dropping rate is 0.005-0.007 mL / min; the heat preservation aging temperature is 38-42℃, and the heat preservation aging time is 35-45 min.

6. The method for preparing a waterborne epoxy zinc-rich primer according to claim 4, characterized in that, In step S2, the mass-to-volume ratio of bisphenol A type E-51 epoxy resin, 2,4,6-tris(dimethylaminomethyl)phenol, and dipropylene glycol methyl ether is (118-126) g : (0.15-0.25) g : (8-12) mL; the first set temperature is 73-77℃; the reaction time is 1.5-2.5 h; the second set temperature is 68-72℃; and the heat preservation reaction time is 1-2 h.

7. The method for preparing a waterborne epoxy zinc-rich primer according to claim 4, characterized in that, In step S3, the mass-to-volume ratio of the modified epoxy resin, nonionic polyacrylic acid, and deionized water is (59-63) g : (0.25-0.35) g : (45-55) mL; the stirring speed is 280-320 r / min; the dispersion speed is 750-850 r / min; the dispersion time is 8-12 min; the grinding fineness is ≤25 μm; the mass fraction of the glycolic acid aqueous solution is 10 wt%; the dropping rate is 0.08-0.12 mL / min; and the adjusted pH is 7.0-7.

5.

8. The method for preparing a waterborne epoxy zinc-rich primer according to claim 4, characterized in that, In step S4, the volume ratio of polyethylene glycol glycidyl ether to dipropylene glycol methyl ether is (230-240):(50-70); the third set temperature is 60-65℃; the dropping rate is 3.0-3.2 mL / min; the holding time is 2-3 h; the reflux temperature is 50-55℃, and the reflux time is 3-4 h; the atmospheric distillation temperature is 80-85℃, and the atmospheric distillation time is 1-1.5 h; the cooling step is: cooling to 30℃ at a rate of 0.8-1.2℃ / min.

9. The method for preparing a waterborne epoxy zinc-rich primer according to claim 4, characterized in that, In step S4, the mass-to-volume ratio of the remaining hydrophilic modified epoxy resin and dipropylene glycol methyl ether is (59-63) g: (12-18) mL; the fourth set temperature is 53-57℃; the reaction time is 2-3 h; the cooling step is to cool naturally to 30℃; the phase inversion emulsification step is as follows: add 25-35 mL of deionized water and stir for 8-12 min to invert the phase, then add 260-280 mL of deionized water dropwise at a rate of 4.2-7.0 mL / min, and maintain continuous stirring and shearing at 300-400 r / min. After the dropwise addition is completed, continue stirring for 12-18 min to obtain an emulsion with an average hydrated particle size of 100-300 nm.

10. The application of a waterborne epoxy zinc-rich primer as described in any one of claims 1-3 in industrial anti-corrosion coating.

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