Graphene epoxy zinc-rich primer and preparation method thereof

Abstract

The application relates to the technical field of paint preparation, and discloses a graphene epoxy zinc-rich primer and a preparation method thereof. The graphene epoxy zinc-rich primer is prepared by taking polyimide modified graphene and fluoride modified epoxy acrylate resin as a matrix, compounding zinc powder microcapsules, passivated zinc-aluminum alloy powder and nano titanium dioxide as functional fillers, and adding active diluents, functional additives and solvent-free curing agents; the graphene epoxy zinc-rich primer is prepared by modifying treatment such as grafting polyimide on graphene oxide, grafting fluoride monomers on epoxy acrylate resin, fluorinating and coating zinc powder on graphene, passivating zinc-aluminum alloy powder, and then mixing by stepwise feeding and gradient dispersion process, so that the coating barrier property, cathodic protection efficiency and compactness are improved, long-term and emergency sacrificial protection are cooperated, and the heavy-duty corrosion requirement is met.

Description

Technical Field

[0001] This application relates to the field of coating preparation technology, specifically to a graphene epoxy zinc-rich primer and its preparation method. Background Technology

[0002] Metal components in complex and harsh environments such as marine, chemical, bridge, and shipbuilding industries are highly susceptible to seawater erosion, chemical corrosion, and atmospheric oxidation, leading to rust and damage. This not only shortens the service life of the components but can also cause safety hazards. Therefore, metal corrosion protection has become a crucial issue in the industrial sector. Graphene epoxy zinc-rich primer, with its solvent-free and low VOC emission advantages, as well as excellent anti-corrosion and adhesion properties, has become a core product to replace traditional high-pollution anti-corrosion coatings. It is widely used for long-term corrosion protection of various metal components and represents a key development direction in the current heavy-duty anti-corrosion coating field.

[0003] To further enhance the corrosion resistance, mechanical properties, and anti-aging performance of graphene epoxy zinc-rich primers, existing technologies typically introduce various functional fillers, such as zinc powder and nano-oxides, into the coating system. Through the synergistic effect of the fillers and the resin matrix, the density and protective capability of the coating are optimized. However, in practical applications, the compatibility, dispersion uniformity, and interfacial bonding strength of the multiphase functional fillers with the resin matrix remain key bottlenecks restricting the improvement of coating performance.

[0004] Specifically, in traditional epoxy zinc-rich primers, inorganic fillers such as graphene and zinc powder often exhibit strong hydrophilic properties, while the epoxy acrylate resin matrix and curing system are typical hydrophobic polymers. The significant difference in interfacial energy between the two makes it difficult for the inorganic fillers to achieve sufficient wetting and uniform dispersion in the resin matrix, easily leading to agglomeration and defects such as micropores and cracks in the coating. Simultaneously, graphene itself has a layer-stacking problem; unmodified graphene easily agglomerates into clumps, failing to fully utilize its high specific surface area and high barrier properties, making it difficult to effectively block the penetration of corrosive media. Furthermore, traditional zinc powder, when directly added to the system, is prone to oxidation failure and relies only on weak van der Waals forces for bonding with the resin matrix, resulting in weak interfacial adhesion. When the coating is subjected to mechanical impact, thermal stress, or corrosive media erosion, delamination easily occurs at the filler-matrix interface, leading to decreased coating protective performance and premature failure.

[0005] On the other hand, existing technologies for modifying multiphase fillers are mostly single-phase modifications, making it difficult to simultaneously consider the compatibility between the filler and the resin, the stability of the filler itself, and the synergistic effect between different fillers. When multiple fillers coexist, phase separation is prone to occur, further compromising the structural uniformity of the coating and preventing the formation of a dense protective barrier. At the same time, in traditional preparation processes, the mixing and dispersion of each component is poor, which can also lead to excessive coating fineness and uneven performance, affecting its long-term corrosion resistance.

[0006] Based on the shortcomings of the existing technologies, there is an urgent need to develop a graphene epoxy zinc-rich primer that can solve problems such as inorganic filler agglomeration, poor interfacial bonding with the resin matrix, and easy oxidation and failure of zinc powder. By specifically modifying the resin matrix and functional fillers, the compatibility and dispersibility of each component can be optimized, the interfacial bonding strength can be strengthened, and the anti-corrosion durability and comprehensive mechanical properties of the coating can be improved to meet the long-term anti-corrosion requirements of metal components in complex environments. Summary of the Invention

[0007] To address the aforementioned issues, this application provides a graphene epoxy zinc-rich primer and its preparation method. The invention involves in-situ polymerization and grafting of polyimide onto graphene oxide followed by reduction; free radical grafting copolymerization of epoxy acrylate resin with fluorinated monomers; surface modification of graphene with fluoride; encapsulation of zinc powder with fluoride-modified graphene to prepare microcapsules; passivation treatment of zinc-aluminum alloy powder; and then mixing polyimide-modified graphene, nano-titanium dioxide, passivated zinc-aluminum alloy powder, zinc powder microcapsules, fluoride-modified epoxy acrylate resin, reactive diluent, dispersant, anti-settling agent, colorant, and solvent-free curing agent through a stepwise feeding and gradient dispersion process to obtain the graphene epoxy zinc-rich primer. This improves the physical barrier properties, cathodic protection efficiency, and coating density of the coating, achieving synergistic effects of long-term corrosion protection and emergency sacrificial protection, meeting the heavy corrosion protection requirements under harsh environments.

[0008] To achieve the above objectives, this application adopts the following technical solution: In a first aspect, this application provides a graphene epoxy zinc-rich primer, comprising a resin matrix, a functional composite filler, passivated zinc-aluminum alloy powder, and functional additives; the resin matrix comprises polyimide-modified graphene, fluoride-modified epoxy acrylate resin, an active diluent, and a solvent-free curing agent; the functional composite filler comprises zinc powder microcapsules and nano-titanium dioxide, the zinc powder microcapsules comprising a capsule wall and a capsule core, the capsule wall being fluoride-modified graphene and the capsule core being zinc powder; the passivated zinc-aluminum alloy powder is zinc-aluminum alloy powder with a passivated surface, and exists independently of the zinc powder microcapsules.

[0009] Preferably, the polyimide-modified graphene is obtained by reacting polyimide monomers with graphene; the fluoride-modified epoxy acrylate resin is obtained by reacting epoxy acrylate resin with fluorine-containing monomers under the action of an initiator; the fluoride-modified graphene is obtained by reacting graphene with ammonium fluoride; and the passivation treatment is carried out by immersing zinc-aluminum alloy powder in a solution containing a passivating agent to form a dense passivation film on its surface.

[0010] Preferably, the functional additives include any one of dispersants, anti-settling agents, and colorants; the dispersants include any one of ethylene bis-stearamide, stearamide, and polyethylene glycol monostearate; the anti-settling agents include any one of fumed silica, organobentonite, and polyamide wax; the colorants include any one of titanium dioxide, iron oxide red, and phthalocyanine blue; the reactive diluents include any one of butyl glycidyl ether, 1,4-butanediol diglycidyl ether, and trimethylolpropane triglycidyl ether; the solvent-free curing agent includes any one of methyltetrahydrophthalic anhydride, hexamethylene diisocyanate, and isophorone diamine; the fluorinated monomer is dodecafluoroheptyl methacrylate or octafluoropentyl acrylate; the initiator includes any one of benzoyl peroxide, azobisisobutyronitrile, and di(2-ethylhexyl) dicarbonate; and the fluoride is ammonium fluoride.

[0011] Secondly, this application provides a method for preparing a graphene epoxy zinc-rich primer, comprising the following steps: S1. Graphene oxide was dispersed in a solvent by ultrasonic dispersion, and pyromellitic dianhydride and 4,4'-diaminodiphenyl ether were added. The mixture was stirred and reacted under nitrogen protection. Then a reducing agent was added for the first heating reaction. Subsequently, a catalyst was added for the second heating reaction. After the reaction was completed, the mixture was filtered and vacuum dried to obtain polyimide-modified graphene. S2. Mix epoxy acrylate resin with fluorinated monomers, add initiator, and polymerize under inert gas protection by heating and stirring. After the reaction is completed, cool to room temperature to obtain fluoride-modified epoxy acrylate resin. S3. Graphene is dispersed in a solvent, a fluoride reagent is added, and the reaction is carried out under reflux protection with an inert gas. After the reaction, the graphene is separated by centrifugation, washed with deionized water, and dried under vacuum to obtain fluoride-modified graphene. S4. Disperse the fluoride-modified graphene in a solvent using ultrasonic dispersion to obtain a wall material solution; disperse zinc powder in a polyvinyl alcohol solution and stir to obtain a core material suspension, adjusting the pH; while stirring, drop the wall material solution into the core material suspension to react; after the reaction is complete, filter and vacuum dry to obtain zinc powder microcapsules. S5. The zinc-aluminum alloy powder is immersed in the passivating agent solution and stirred. After immersion, it is filtered, rinsed with deionized water, and then dried to obtain passivated zinc-aluminum alloy powder. S6. The polyimide-modified graphene and half of the reactive diluent are added to a sealed dispersion vessel and pre-stirred. Then, the fluoride-modified epoxy acrylate resin and the remaining reactive diluent are added, heated, stirred, and dispersed. Vacuum degassing is performed to obtain a resin premix. Nano-titanium dioxide and the passivated zinc-aluminum alloy powder are added to the resin premix in sequence and dispersed at high speed until the fineness of the system is ≤25μm as detected by a scraper fineness meter. The zinc powder microcapsules are added, followed by the dispersant, anti-settling agent, and colorant, and stirred. Finally, vacuum degassing is performed to obtain a primer base material. The primer base material is cooled, a solvent-free curing agent is added and stirred, and after filtration, a graphene epoxy zinc-rich primer is obtained.

[0012] In S1 of this application, polyimide-modified graphene is prepared via a two-step method of in-situ polymerization and chemical reduction. First, graphene oxide is ultrasonically dispersed in a solvent to fully expose its abundant oxygen-containing functional groups. After adding pyromellitic dianhydride and 4,4'-diaminodiphenyl ether, the dianhydride and diamine undergo a condensation reaction on the surface of the graphene oxide sheets, generating polyamic acid in situ, which is then adsorbed onto the graphene surface and edges. The carboxyl and hydroxyl groups of the graphene oxide in the system can form hydrogen bonds or covalent bonds with the amide bonds and terminal amine groups on the polyamic acid segments, anchoring the polymer chains to the graphene surface. Subsequently, ascorbic acid, a reducing agent, is added to partially remove the oxygen-containing functional groups of the graphene oxide, restoring the conjugated structure of the graphene. Then, acetic anhydride and pyridine are added as chemical imidization catalysts to dehydrate and cyclize the polyamic acid into polyimide, ultimately obtaining polyimide-covalently modified graphene. The grafted polyimide segments inhibit the stacking of graphene sheets through steric hindrance, while the amine or anhydride groups at their ends retain reactivity and can participate in subsequent epoxy curing and crosslinking.

[0013] In S2 of this application, an initiator initiates a free radical graft copolymerization reaction between the active sites on the main chain or side chain of the epoxy acrylate resin and a fluorinated monomer. Under the action of free radicals generated by the thermal decomposition of the initiator, the methylene or tertiary carbon sites on the epoxy acrylate resin molecular chain undergo dehydrogenation to form macromolecular free radicals, which initiate double bond addition to the fluorinated monomer, introducing the fluorinated side chain into the epoxy acrylate resin molecular backbone in the form of a covalent bond. The grafted fluorinated side chain has a lower cohesive energy density, and through the steric hindrance effect of the side group, it disrupts the regular stacking of polymer chain segments, increases the free volume, and thereby reduces the viscosity and internal stress of the resin matrix.

[0014] In step S3 of this application, after dispersing graphene in a solvent, ammonium fluoride is added and transferred to a closed reaction vessel for reaction. During heating, the ammonium fluoride partially hydrolyzes or dissociates, generating active fluorinated species. These species undergo nucleophilic substitution reactions with defect sites and residual oxygen-containing functional groups at the edges of the graphene sheets in a liquid phase environment, selectively introducing CF bonds into the active edge sites of the graphene, achieving mild edge fluorination modification. The introduction of CF bonds effectively weakens the π-π stacking cohesion between graphene sheets, reduces interlayer friction and self-aggregation tendency, and improves its dispersion stability in organic resin media.

[0015] In S4 of this application, microcapsules with fluoride-modified graphene as the wall material and zinc powder as the core material are prepared by chemical deposition. Fluoride-modified graphene is ultrasonically dispersed in a solvent to form a wall material suspension. The CF bonds introduced at the edges of the graphene sheets weaken the self-stacking between the sheets, allowing for better dispersion and smooth migration under stirring. The residual oxygen-containing polar groups (-OH, -COOH) retained on the basal surface provide adsorption anchors for subsequent deposition. Zinc powder is dispersed in a polyvinyl alcohol (PVA) solution to form a core material suspension. The PVA forms a hydroxyl-rich protective colloidal layer on the surface of the zinc powder particles. Adjusting the pH maintains the stability of the zinc powder surface and avoids acidic hydrogen evolution side reactions. Under stirring conditions, the wall material solution is dropwise added to the core material suspension. The fluoride-modified graphene sheets utilize the polar groups retained on their basal surfaces to form strong hydrogen bonds with the hydroxyl groups in the PVA protective layer on the zinc powder surface, depositing layer by layer onto the surface of the zinc powder particles to form a continuous and dense graphene coating. After the reaction is completed, the mixture is filtered and vacuum dried to obtain zinc powder microcapsules with intact structures. The capsule walls effectively isolate the zinc powder from direct contact with the external environment.

[0016] In step S5 of this application, zinc-aluminum alloy powder is immersed in a passivating agent solution. The active components in the passivating agent react chemically with the alloy surface, forming a dense passivation film in situ on the particle surface. This passivation film is mainly composed of metal oxides or metal-passivating agent complexes, which can effectively inhibit side reactions of the alloy powder with water and oxygen during storage, avoiding premature consumption of the zinc-aluminum powder surface before the coating cures. After passivation treatment, the zinc-aluminum alloy powder is rinsed with deionized water to remove residual passivating agent, and after drying, surface-stable passivated zinc-aluminum alloy powder is obtained.

[0017] In S6 of this application, uniform compounding and system curing of each component are achieved through stepwise feeding and gradient dispersion processes. First, polyimide-modified graphene is pre-stirred with a portion of the reactive diluent, allowing the graphene sheets to initially disperse and partially peel off in a low-viscosity medium. Then, fluoride-modified epoxy acrylate resin and the remaining reactive diluent are added, and the mixture is heated and stirred, ensuring the resin matrix fully wets the graphene and subsequent fillers. Vacuum degassing removes air bubbles from the system. Nano-titanium dioxide and passivated zinc-aluminum alloy powder are sequentially added to the resin premix for high-speed dispersion, using shear force to break up particle agglomerates until the system fineness meets the standard. At this point, the active groups on the surface of each filler initially form hydrogen bonds and other physical interactions with the resin molecules. Finally, zinc powder microcapsules, dispersant, anti-settling agent, and colorant are added and mixed uniformly at a low stirring intensity to avoid microcapsule wall rupture. After the primer base material cools, a solvent-free curing agent is added and stirred. The active amine or anhydride groups of the curing agent undergo a nucleophilic ring-opening polymerization reaction with the epoxy groups of the epoxy acrylate resin, and at the same time form a covalent bond with the active end groups on the surface of the polyimide-modified graphene. Each filler component is anchored in the cross-linked network. After filtration, a uniform and stable graphene epoxy zinc-rich primer is obtained.

[0018] Preferably, in S1, the catalyst is acetic anhydride and pyridine; the mass ratio of graphene oxide, solvent, pyromellitic dianhydride, 4,4'-diaminodiphenyl ether, reducing agent, acetic anhydride, and pyridine is 1:(50-100):(0.10-0.25):(0.09-0.23):(2-5):(0.5-2.0):(0.3-1.5); the solvent is N,N-dimethylformamide or N-methylpyrrolidone; the ultrasonic dispersion time is 30-60 min; the stirring reaction temperature is 80-120°C and the time is 6-12 h; the reducing agent is ascorbic acid; the temperature of the first heating reaction is 80-100°C and the time is 1-2 h; the temperature of the second heating reaction is 100-120°C and the time is 2-4 h; the vacuum drying temperature is 60-80°C and the time is 12-24 h.

[0019] Preferably, in S2, the epoxy acrylate resin is bisphenol A type epoxy acrylate resin or bisphenol F type epoxy acrylate resin; the mass ratio of the epoxy acrylate resin to the fluorinated monomer is (4-10):1; the initiator is any one of benzoyl peroxide, azobisisobutyronitrile, or di(2-ethylhexyl) dicarbonate peroxide; the mass of the initiator is 0.5% to 2% of the mass of the fluorinated monomer; the polymerization reaction temperature is 70 to 110°C; the polymerization reaction stirring rate is 200 to 400 r / min; and the time is 3 to 8 h.

[0020] Preferably, in step S4, the mass ratio of the wall material solution to the core material suspension is 1:(1.5-3); the solvent is acetone or tetrahydrofuran; the mass ratio of the fluoride-modified graphene to the solvent is 1:(50-100); the ultrasonic dispersion time is 30-60 min; the mass fraction of the polyvinyl alcohol solution is 0.5wt%-2wt%; the mass ratio of the zinc powder to the polyvinyl alcohol solution is 1:(2-5); the pH is 6.5-8.0; the stirring speed is 300-600 r / min; the stirring temperature is 50-70℃; the reaction time is 2-5 h; and the vacuum drying temperature is 60-80℃ and the time is 12-24 h.

[0021] Preferably, in step S5, the particle size of the zinc-aluminum alloy powder is 5–30 μm, the mass ratio of the zinc-aluminum alloy powder to the passivating agent solution is 1:(5–8), the passivating agent solution is a sodium molybdate solution, and the mass fraction of the passivating agent solution is 1 wt%–10 wt%; the impregnation temperature is 20–50°C and the time is 10–60 min, the stirring speed is 100–200 r / min, and the drying temperature is 80–120°C and the drying time is 30–60 min.

[0022] Preferably, in step S6, the pre-stirring speed is 700-900 r / min for 15-20 min; the heating temperature is 35-45℃; the stirring and dispersion speed is 1200-1600 r / min for 25-35 min; the vacuum degassing degree is -0.065 to -0.075 MPa for 5-10 min; the high-speed dispersion speed is 1900-2100 r / min for 35-45 min; after adding the additive, the stirring speed is 900-1100 r / min for 10-20 min; and the addition of no additive... The stirring speed of the solvent curing agent is 450-550 r / min and the stirring time is 10-20 min. The mesh size of the filter is 180-200 mesh. The mass ratio of the polyimide modified graphene, fluoride modified epoxy acrylate resin, reactive diluent, solvent-free curing agent, zinc powder microcapsules, nano titanium dioxide, passivated zinc-aluminum alloy powder, dispersant, anti-settling agent and colorant is (1-5):(40-60):(15-25):(20-30):(25-40):(5-10):(50-80):(0.5-2):(0.3-1.5):(0.2-1.5).

[0023] Compared with the prior art, the beneficial effects of this application are as follows: This application provides a graphene-modified epoxy zinc-rich primer. The fluoride-modified epoxy acrylate resin and polyimide-modified graphene work together to form a network structure within the coating that combines barrier and conductive functions. On one hand, during curing, the fluorinated segments accumulate and oriented through thermodynamics, forming a low-surface-energy dense layer at the coating-air interface composed of tightly packed CF bonds. This layer acts as an initial physical barrier, effectively blocking the adsorption and penetration of water, oxygen, and corrosive ions. On the other hand, chemically grafted polyimide chains act as molecular spacer segments, covalently anchoring the graphene sheets. This overcomes the intrinsic van der Waals forces of graphene through a dual mechanism of steric hindrance and interfacial compatibility, promoting uniform dispersion and interlocking. This forms a stable, continuous electron transport network with a low percolation threshold within the resin matrix, providing a conductive pathway for the efficient conduction of cathodic protection current.

[0024] Within this composite network, zinc microcapsules and independently existing passivated zinc-aluminum alloy powder synergistically provide sacrificial anode protection. In the early stages of coating service or in its intact state, the fluoride-modified graphene capsule walls of the microcapsules form the organic component of the overall hydrophobic barrier. Their layered structure, through physical entanglement and conductive bridging with the matrix graphene network, enhances the overall structural integrity. The capsule walls isolate the internal highly active zinc powder from the environment, maintaining its chemical inertness and preventing ineffective hydrogen evolution consumption. Simultaneously, the uniformly dispersed zinc-aluminum alloy powder with a passivation film on its surface acts as the primary sacrificial anode, providing a stable and gentle cathodic protection current at a low dissolution rate under the drive of an alloy microcouple, thus providing long-term protection. Once the coating suffers micro-area damage due to mechanical scratches, a decrease in corrosion potential or a sudden change in local pH serves as a trigger signal, causing the microcapsule walls at the damage front to rupture or dissolve in a controlled manner. The unpassivated, highly active zinc powder sealed inside is then rapidly released as a secondary sacrificial anode. This highly active zinc powder is directly exposed to the electrolyte, generating rapid and intense sacrificial anodic polarization on the exposed substrate. It can quickly cathodically polarize the potential of the steel substrate below its protection potential, thereby significantly inhibiting its corrosion rate.

[0025] Furthermore, nano-titanium dioxide not only serves as a nanofiller to fill the cross-linked micropores and gaps between filler packing in the resin, improving overall density, but its Lewis acid titanium sites and hydroxyl groups on the surface can also chemically adsorb Cl. - The presence of corrosive ions enhances wet adhesion and provides additional barrier effects, helping to maintain the structural integrity and long-term protective capability of the coating in corrosive environments. The matching of functional additives ensures that the aforementioned multiphase, multi-scale components maintain a uniform and stable dispersion and rheological properties during storage and film formation. Ultimately, the highly synergistic interaction of these functional units leads to the curing of a multifunctional anti-corrosion coating that integrates physical barrier, electrochemical protection, and stimulus-responsive sacrificial protection. Attached Figure Description

[0026] Figure 1This is a photograph of the graphene epoxy zinc-rich primer prepared in Example 1. 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] In this application, the terminology used is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0029] The singular forms “for,” “or,” “a,” “any,” and “the” used in this application are intended to include the plural forms unless the context clearly indicates otherwise.

[0030] The following will describe in detail, with reference to different embodiments, a graphene epoxy zinc-rich primer and its preparation method provided in this application.

[0031] Example 1 This embodiment provides a method for preparing a graphene epoxy zinc-rich primer, including the following steps: S1. Graphene oxide was dispersed in N,N-dimethylformamide and ultrasonically dispersed for 30 min. Pyromellitic dianhydride and 4,4'-diaminodiphenyl ether were added, and the mixture was stirred and reacted at 80 °C for 12 h under nitrogen protection. Then, ascorbic acid was added, and the mixture was heated to 80 °C for 2 h for the first time. Acetic anhydride and pyridine were then added, and the mixture was heated to 100 °C for 4 h for the second time. After the reaction, the mixture was filtered and vacuum dried at 60 °C for 24 h to obtain polyimide-modified graphene. The mass ratio of graphene oxide, N,N-dimethylformamide, pyromellitic dianhydride, 4,4'-diaminodiphenyl ether, ascorbic acid, acetic anhydride, and pyridine was 1:50:0.10:0.09:2:0.5:0.3.

[0032] S2. Epoxy acrylate resin and dodecyl fluoroheptyl methacrylate are mixed at a mass ratio of 4:1. 0.5% benzoyl peroxide by mass of dodecyl fluoroheptyl methacrylate is added. Under nitrogen protection, the mixture is heated to 70°C and polymerized at a stirring rate of 200 r / min for 8 hours. After the reaction is completed, it is cooled to room temperature to obtain fluoride-modified epoxy acrylate resin. S3. Graphene was dispersed in anhydrous ethanol and ammonium fluoride was added. The mixture was refluxed at 60°C for 6 hours under inert gas protection. After the reaction, the mixture was centrifuged, washed with deionized water, and vacuum dried at 60°C for 24 hours to obtain fluoride-modified graphene. The mass ratio of graphene, anhydrous ethanol, and ammonium fluoride was 1:100:0.2. S4. The fluoride-modified graphene is dispersed in acetone at a mass ratio of 1:50 and ultrasonically dispersed for 30 min to obtain a wall material solution. Zinc powder is dispersed in a 0.5 wt% polyvinyl alcohol solution at a mass ratio of 1:2 and stirred at 300 r / min to form a core material suspension. The pH is adjusted to 6.5. The wall material solution is added dropwise to the core material suspension at 0.5 mL / min under stirring at 300 r / min and 50°C. The reaction temperature is controlled at 50°C, the reaction time is 5 h, and the stirring speed is 300 r / min. After the reaction is completed, the mixture is filtered and vacuum dried at 60°C for 24 h to obtain zinc powder microcapsules. The mass ratio of the wall material solution to the core material suspension is 1:1.5. S5. The zinc-aluminum alloy powder (particle size 5μm) is immersed in a 1wt% sodium molybdate solution at 20℃ for 60min with stirring at 100r / min. After immersion, the powder is filtered, rinsed with deionized water, and then dried at 80℃ for 60min to obtain passivated zinc-aluminum alloy powder. The mass ratio of the zinc-aluminum alloy powder to the passivating agent solution is 1:5.

[0033] S6. Add the polyimide-modified graphene and half of the butyl glycidyl ether to a sealed dispersion vessel and pre-stir at 700 r / min for 20 min. Then add the fluoride-modified epoxy acrylate resin and the remaining butyl glycidyl ether, raise the temperature to 35°C, and stir and disperse at 1200 r / min for 35 min, while controlling the vacuum degree at -0.075 MPa for degassing for 10 min to obtain a resin premix. Add nano-titanium dioxide and the passivated zinc-aluminum alloy powder to the resin premix in sequence, maintain the temperature at 35°C, and increase the stirring speed. The mixture was dispersed at 1900 r / min for 45 min until the fineness of the system was ≤25 μm as measured by a scraper fineness meter. After adding the zinc powder microcapsules, ethylene bis-stearamide (dispersant), fumed silica (anti-settling agent), and titanium dioxide (colorant) were added, and the mixture was stirred at 900 r / min for 20 min. Finally, the mixture was degassed under a vacuum of -0.075 MPa for 10 min to obtain the primer base material. Methyltetrahydrophthalic anhydride was added to the primer base material, and the mixture was stirred at 450 r / min for 20 min. After filtration through a 180-mesh filter, a graphene epoxy zinc-rich primer was obtained. Figure 1As shown; the mass ratio of the polyimide-modified graphene, fluoride-modified epoxy acrylate resin, butyl glycidyl ether, methyltetrahydrophthalic anhydride, zinc powder microcapsules, nano titanium dioxide, passivated zinc-aluminum alloy powder, ethylene bis-stearamide, fumed silica, and titanium dioxide is 1:40:15:20:25:5:50:0.5:0.3:0.2.

[0034] Example 2 This embodiment provides a method for preparing a graphene epoxy zinc-rich primer, including the following steps: S1. Graphene oxide was dispersed in N-methylpyrrolidone and ultrasonically dispersed for 45 min. Pyromellitic dianhydride and 4,4'-diaminodiphenyl ether were added, and the mixture was stirred at 100 °C for 9 h under nitrogen protection. Then, ascorbic acid was added, and the temperature was raised to 90 °C for the first reaction for 1.5 h. Acetic anhydride and pyridine were then added, and the temperature was raised to 110 °C for the second reaction for 3 h. After the reaction, the mixture was filtered and vacuum dried at 70 °C for 18 h to obtain polyimide-modified graphene. The mass ratio of graphene oxide, N-methylpyrrolidone, pyromellitic dianhydride, 4,4'-diaminodiphenyl ether, ascorbic acid, acetic anhydride, and pyridine was 1:70:0.18:0.16:3:1:0.9.

[0035] S2. Epoxy acrylate resin and octafluoropentyl acrylate are mixed at a mass ratio of 7:1. 1.2% of azobisisobutyronitrile (AIBN) by mass of octafluoropentyl acrylate is added. Under argon protection, the mixture is heated to 90°C and polymerized at a stirring rate of 300 r / min for 5 h. After the reaction is completed, it is cooled to room temperature to obtain fluoride-modified epoxy acrylate resin. S3. Graphene was dispersed in N,N-dimethylformamide, and ammonium fluoride was added. The mixture was refluxed at 70°C for 5 hours under inert gas protection. After the reaction, the mixture was centrifuged, washed with deionized water, and vacuum dried at 70°C for 18 hours to obtain fluoride-modified graphene. The mass ratio of graphene, N,N-dimethylformamide, and ammonium fluoride was 1:150:0.6. S4. The fluoride-modified graphene is dispersed in tetrahydrofuran solvent at a mass ratio of 1:75 and ultrasonically dispersed for 30 min to obtain a wall material solution; zinc powder is dispersed in a 1.2 wt% polyvinyl alcohol solution at a mass ratio of 1:3 and stirred at 450 r / min to form a core material suspension, and the pH is adjusted to 7.5; the wall material solution is added dropwise to the core material suspension at 1 mL / min under stirring at 450 r / min at 60℃, the reaction temperature is controlled at 60℃, the reaction time is 3 h, and the stirring speed is 450 r / min; after the reaction is completed, the mixture is filtered and vacuum dried at 70℃ for 18 h to obtain zinc powder microcapsules; the mass ratio of the wall material solution to the core material suspension is 1:2. S5. Zinc-aluminum alloy powder (particle size 15μm) is immersed in a 5wt% sodium molybdate solution at 35℃ for 35min and stirred at a stirring rate of 150r / min. After immersion, the powder is filtered, rinsed with deionized water, and then dried at 100℃ for 45min to obtain passivated zinc-aluminum alloy powder. The mass ratio of the zinc-aluminum alloy powder to the passivating agent solution is 1:6.5.

[0036] S6. Add the polyimide-modified graphene and half of the 1,4-butanediol diglycidyl ether to a sealed dispersion vessel and pre-stir at 800 r / min for 17 min; then add the fluoride-modified epoxy acrylate resin and the remaining 1,4-butanediol diglycidyl ether, raise the temperature to 40°C, and stir and disperse at 1400 r / min for 30 min, while controlling the vacuum degree at -0.07 MPa for degassing for 7 min to obtain a resin premix; add nano-titanium dioxide and the passivated zinc-aluminum alloy powder to the resin premix in sequence, maintain the temperature at 40°C, increase the speed to 2000 r / min, and disperse at high speed for 40 min until the fineness of the system detected by the scraper fineness meter is ≤25 μm; add the zinc powder. After microcapsulation, stearamide, organobentonite, and iron oxide red were added, and stirred at 1000 r / min for 15 min. Finally, the mixture was degassed under a vacuum of -0.07 MPa for 7 min to obtain a primer base. The primer base was then added to hexamethylene diisocyanate and stirred at 500 r / min for 15 min. After filtration through a 190-mesh filter, a graphene epoxy zinc-rich primer was obtained. The mass ratio of polyimide-modified graphene, fluoride-modified epoxy acrylate resin, 1,4-butanediol diglycidyl ether, hexamethylene diisocyanate, zinc powder microcapsules, nano titanium dioxide, passivated zinc-aluminum alloy powder, stearamide, organobentonite, and iron oxide red was 3:50:20:25:30:7:65:1:1:0.8.

[0037] Example 3 This embodiment provides a method for preparing a graphene epoxy zinc-rich primer, including the following steps: S1. Graphene oxide was dispersed in N,N-dimethylformamide solvent and ultrasonically dispersed for 60 min. Pyromellitic dianhydride and 4,4'-diaminodiphenyl ether were added, and the mixture was stirred and reacted at 120 °C for 6 h under nitrogen protection. Then, ascorbic acid was added, and the temperature was raised to 100 °C for the first reaction for 1 h. Acetic anhydride and pyridine were then added, and the temperature was raised to 120 °C for the second reaction for 2 h. After the reaction, the mixture was filtered and vacuum dried at 80 °C for 12 h to obtain polyimide-modified graphene. The mass ratio of graphene oxide, N,N-dimethylformamide, pyromellitic dianhydride, 4,4'-diaminodiphenyl ether, ascorbic acid, acetic anhydride, and pyridine was 1:100:0.25:0.23:5:2.0:1.5.

[0038] S2. Epoxy acrylate resin and dodecyl fluoroheptyl methacrylate are mixed at a mass ratio of 10:1; 2% of di(2-ethylhexyl) dicarbonate peroxide is added, and under nitrogen protection, the mixture is heated to 110°C and polymerized at a stirring rate of 400 r / min for 3 h; after the reaction is completed, it is cooled to room temperature to obtain fluoride modified epoxy acrylate resin. S3. Graphene is dispersed in anhydrous ethanol and ammonium fluoride is added; under inert gas protection, the mixture is refluxed at 90°C for 4 hours; after the reaction, it is centrifuged, washed with deionized water, and vacuum dried at 80°C for 12 hours to obtain fluoride-modified graphene; the mass ratio of graphene, anhydrous ethanol and ammonium fluoride is 1:200:1. S4. The fluoride-modified graphene is dispersed in tetrahydrofuran at a mass ratio of 1:100 and ultrasonically dispersed for 60 min to obtain a wall material solution; zinc powder is dispersed in a 2wt% polyvinyl alcohol solution at a mass ratio of 1:5 and stirred at 600 r / min to form a core material suspension, and the pH is adjusted to 8; the wall material solution is added dropwise to the core material suspension at 2 mL / min under stirring at 70℃ and 600 r / min, controlling the reaction temperature at 70℃, the reaction time at 2 h, and the stirring speed at 600 r / min; after the reaction is completed, the mixture is filtered and vacuum dried at 80℃ for 12 h to obtain zinc powder microcapsules; the mass ratio of the wall material solution to the core material suspension is 1:3. S5. The zinc-aluminum alloy powder (particle size 30 μm) is immersed in a 10 wt% sodium molybdate solution at 50 °C for 10 min and stirred at 200 r / min. After immersion, the powder is filtered, rinsed with deionized water, and then dried at 120 °C for 30 min to obtain passivated zinc-aluminum alloy powder. The mass ratio of the zinc-aluminum alloy powder to the passivating agent solution is 1:8.

[0039] S6. Add the polyimide-modified graphene and half of the trimethylolpropane triglycidyl ether to a sealed dispersion vessel and pre-stir at 900 r / min for 15 min. Then add the fluoride-modified epoxy acrylate resin and the remaining trimethylolpropane triglycidyl ether, heat to 45°C, and stir and disperse at 1600 r / min for 25 min, while controlling the vacuum degree at -0.065 MPa for degassing for 5 min to obtain a resin premix. Add nano-titanium dioxide and the passivated zinc-aluminum alloy powder to the resin premix in sequence, maintain the temperature at 45°C, increase the speed to 2100 r / min, and disperse at high speed for 35 min until the fineness of the system detected by the scraper fineness meter is ≤25 μm. After adding the zinc powder microcapsules... Polyethylene glycol monostearate, polyamide wax, and phthalocyanine blue were added separately and stirred at 1100 rpm for 10 min. Finally, the mixture was degassed under a vacuum of -0.075 MPa for 5 min to obtain a primer base. Isophorone diamine was added to the primer base and stirred at 550 rpm for 10 min. After filtration through a 200-mesh filter, a graphene epoxy zinc-rich primer was obtained. The mass ratio of the polyimide-modified graphene, fluoride-modified epoxy acrylate resin, trimethylolpropane triglycidyl ether, isophorone diamine, zinc powder microcapsules, nano-titanium dioxide, passivated zinc-aluminum alloy powder, polyethylene glycol monostearate, polyamide wax, and phthalocyanine blue was 5:60:25:30:40:10:80:2:1.5:1.5.

[0040] Comparative Example 1 A method for preparing a graphene epoxy zinc-rich primer differs from Example 3 in that the preparation steps of S1 polyimide-modified graphene and S3 fluoride-modified graphene are omitted, while the remaining parameters are the same as in Example 3.

[0041] Comparative Example 2 A method for preparing a graphene epoxy zinc-rich primer differs from Example 3 in that the fluoride modification step is omitted in S2, and unmodified epoxy acrylate resin is used directly, while the remaining parameters are the same as in Example 3.

[0042] Comparative Example 3 A method for preparing a graphene epoxy zinc-rich primer differs from Example 3 in that the zinc powder microencapsulation step in S4 is omitted, and untreated zinc powder is used directly; and the zinc-aluminum alloy powder passivation step in S5 is omitted, and unpassivated zinc-aluminum alloy powder is used directly. The remaining parameters are the same as in Example 3.

[0043] Performance testing: 1. Neutral salt spray resistance test: The graphene epoxy zinc-rich primer samples prepared in Examples 1-3 and Comparative Examples 1-3 were placed in a salt spray test chamber and continuously sprayed with 5% sodium chloride solution. The time when the first rust or blistering appeared on the sample surface was recorded to evaluate its long-term corrosion resistance.

[0044] 2. Cross-cut adhesion test: A 1mm × 1mm grid was drawn on the surface of the graphene epoxy zinc-rich primer film prepared in Examples 1-3 and Comparative Examples 1-3 using a cross-cutting tool. After applying standard tape, the film was quickly peeled off. The adhesion level was evaluated based on the area of ​​paint film peeling off, so as to assess the bonding strength between the coating and the metal substrate.

[0045] 3. Cathodic protection potential test: The graphene epoxy zinc-rich primer coating samples prepared in Examples 1-3 and Comparative Examples 1-3 were pre-cut to expose the substrate, and then immersed in 3.5wt% NaCl solution. The change curve of their open circuit potential over time was measured. The degree of negative potential shift and the duration of maintaining the negative potential were compared to evaluate the ability of zinc powder microcapsules to release highly active zinc powder to provide cathodic protection after the coating is damaged.

[0046] The performance test data analysis is as follows: Table 1. Basic performance test data of graphene epoxy zinc-rich primers obtained from Examples 1-3 and Comparative Examples 1-3.

[0047] As shown in Table 1, the graphene epoxy zinc-rich primers prepared in Examples 1 to 3 of this application exhibit significantly better salt spray resistance, adhesion, and cathodic protection performance than the comparative examples. The core reason for this is that the examples constructed a complete and efficient protection system through multiple synergistic modification techniques: polyimide-modified graphene enhances the interfacial bonding between graphene and the resin matrix, as well as its own dispersibility, improving the coating's physical barrier properties and cohesiveness; fluoride-modified epoxy acrylate resin imparts excellent hydrophobicity and resistance to media penetration to the coating; fluoride-modified graphene, as a microcapsule wall material, further strengthens the barrier effect; most importantly, the microencapsulation design of zinc powder allows for controlled release of highly active zinc powder, providing continuous cathodic protection even when the coating is damaged, greatly extending the effective protection time; simultaneously, the passivation treatment of zinc-aluminum alloy powder inhibits premature reaction and stabilizes the coating system. These synergistic improvements enable the coating to possess excellent physical shielding, strong adhesion, and intelligent, long-lasting electrochemical protection capabilities.

[0048] Comparative Example 1 omitted both types of graphene modification, resulting in poor filler dispersion, weak interfacial bonding, and severely insufficient coating barrier effect and cohesion, thus exhibiting the worst corrosion resistance and adhesion. Comparative Example 2 did not undergo fluorination modification of the resin, leading to decreased hydrophobicity and impermeability of the coating, making it easier for corrosive media to penetrate, resulting in poor salt spray resistance. Comparative Example 3 directly used unmicroencapsulated zinc powder and unpassivated zinc-aluminum alloy powder. The zinc powder was consumed too quickly in the early stages, failing to provide long-lasting protection, and the poor compatibility between the active powder and the substrate affected adhesion, resulting in the shortest effective cathodic protection time and limited improvement in overall performance. In summary, this application, through component design and process innovation, achieved the optimization and synergy of various functional components, thereby obtaining a graphene epoxy zinc-rich primer with high overall performance.

[0049] Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the equivalents of the appended claims.

Claims

1. A graphene-based epoxy zinc-rich primer, characterized in that, The product comprises a resin matrix, functional composite fillers, passivated zinc-aluminum alloy powder, and functional additives. The resin matrix includes polyimide-modified graphene, fluoride-modified epoxy acrylate resin, reactive diluent, and solvent-free curing agent. The functional composite fillers include zinc powder microcapsules and nano-titanium dioxide. The zinc powder microcapsules include a capsule wall and a core, wherein the capsule wall is fluoride-modified graphene and the core is zinc powder. The passivated zinc-aluminum alloy powder is zinc-aluminum alloy powder with a passivated surface and exists independently of the zinc powder microcapsules. The preparation method of the graphene epoxy zinc-rich primer includes the following steps: S1. Graphene oxide is dispersed in a solvent and sonicated. Pyromellitic dianhydride and 4,4'-diaminodiphenyl ether are added and reacted under nitrogen. A reducing agent is added for the first heating reaction. A catalyst is added for the second heating reaction. After the reaction, the mixture is filtered and vacuum dried to obtain polyimide-modified graphene. S2. Mix epoxy acrylate resin with fluorinated monomers, add initiator, polymerize under inert gas and then cool to room temperature to obtain fluoride modified epoxy acrylate resin. S3. Graphene is dispersed in a solvent, a fluoride reagent is added, and the reaction is carried out under reflux under an inert gas. After the reaction, the graphene is separated, washed, and vacuum dried to obtain fluoride-modified graphene. S4. Disperse the fluoride-modified graphene in a solvent and sonicate to obtain a wall material solution; disperse zinc powder in a polyvinyl alcohol solution and stir to obtain a core material suspension, and adjust the pH; while stirring, drop the wall material solution into the core material suspension to react; after the reaction is complete, filter and vacuum dry to obtain zinc powder microcapsules. S5. The zinc-aluminum alloy powder is immersed in the passivating agent solution and stirred. After immersion, it is filtered, washed and dried to obtain passivated zinc-aluminum alloy powder. S6. The polyimide-modified graphene is mixed with half of the reactive diluent and pre-stirred; the fluoride-modified epoxy acrylate resin and the remaining reactive diluent are added, heated and stirred, and vacuum degassed to obtain a resin premix. Nano-titanium dioxide and the passivated zinc-aluminum alloy powder are added sequentially to the resin premix and dispersed at high speed. Then, zinc powder microcapsules are added, followed by dispersant, anti-settling agent and colorant, and stirred. Finally, vacuum degassing is performed to obtain a primer base material. The primer base material is cooled, a solvent-free curing agent is added and stirred, and after filtration, a graphene epoxy zinc-rich primer is obtained.

2. The graphene epoxy zinc-rich primer according to claim 1, characterized in that, The polyimide-modified graphene is obtained by reacting polyimide monomers with graphene; the fluoride-modified epoxy acrylate resin is obtained by reacting epoxy acrylate resin with fluorine-containing monomers under the action of an initiator; the fluoride-modified graphene is obtained by reacting graphene with ammonium fluoride; the passivation treatment is carried out by immersing zinc-aluminum alloy powder in a solution containing a passivating agent to form a dense passivation film on its surface.

3. The graphene epoxy zinc-rich primer according to claim 2, characterized in that, The functional additives include any one of dispersants, anti-settling agents, and colorants; the dispersants include any one of ethylene bis-stearamide, stearamide, and polyethylene glycol monostearate; the anti-settling agents include any one of fumed silica, organobentonite, and polyamide wax; the colorants include any one of titanium dioxide, iron oxide red, and phthalocyanine blue; the reactive diluents include any one of butyl glycidyl ether, 1,4-butanediol diglycidyl ether, and trimethylolpropane triglycidyl ether; the solvent-free curing agent includes any one of methyltetrahydrophthalic anhydride, hexamethylene diisocyanate, and isophorone diamine; the fluorinated monomer is dodecafluoroheptyl methacrylate or octafluoropentyl acrylate; the initiator includes any one of benzoyl peroxide, azobisisobutyronitrile, and di(2-ethylhexyl) dicarbonate; and the fluoride is ammonium fluoride.

4. The graphene epoxy zinc-rich primer according to claim 1, characterized in that, In S1, the catalyst is acetic anhydride and pyridine; the mass ratio of graphene oxide, solvent, pyromellitic dianhydride, 4,4'-diaminodiphenyl ether, reducing agent, acetic anhydride, and pyridine is 1:(50-100):(0.10-0.25):(0.09-0.23):(2-5):(0.5-2.0):(0.3-1.5); the solvent is N,N-dimethylformamide or N-methylpyrrolidone; the ultrasonication time is 30-60 min; the reaction temperature is 80-120℃ and the time is 6-12 h; the reducing agent is ascorbic acid; the temperature of the first heating reaction is 80-100℃ and the time is 1-2 h; the temperature of the second heating reaction is 100-120℃ and the time is 2-4 h; the vacuum drying temperature is 60-80℃ and the time is 12-24 h.

5. The graphene epoxy zinc-rich primer according to claim 1, characterized in that, In S2, the mass ratio of the epoxy acrylate resin to the fluorinated monomer is (4-10):1; the initiator is any one of benzoyl peroxide, azobisisobutyronitrile, or di(2-ethylhexyl) dicarbonate peroxide; the mass of the initiator is 0.5% to 2% of the mass of the fluorinated monomer; the polymerization temperature is 70 to 110°C; the stirring rate of the polymerization reaction is 200 to 400 r / min; and the time is 3 to 8 h.

6. The graphene epoxy zinc-rich primer according to claim 1, characterized in that, In S3, the solvent is anhydrous ethanol or N,N-dimethylformamide; the fluoride reagent is ammonium fluoride; the reflux reaction temperature is 60-90℃ and the time is 4-6h; the vacuum drying temperature is 60-80℃ and the time is 12-24h; the mass ratio of graphene, solvent and fluoride reagent is 1:(100-200):(0.2-1).

7. The graphene epoxy zinc-rich primer according to claim 1, characterized in that, In step S4, the solvent is acetone or tetrahydrofuran, the mass ratio of fluoride-modified graphene to solvent is 1:(50-100), the ultrasonication time is 30-60 min, the mass fraction of polyvinyl alcohol solution is 0.5wt%-2wt%, the mass ratio of zinc powder to polyvinyl alcohol solution is 1:(2-5), the pH is 6.5-8.0, the stirring speed is 300-600 r / min, the stirring temperature is 50-70℃, the reaction time is 2-5 h, and the vacuum drying temperature is 60-80℃ for 12-24 h.

8. The graphene epoxy zinc-rich primer according to claim 1, characterized in that, In step S5, the particle size of the zinc-aluminum alloy powder is 5–30 μm, the mass ratio of the zinc-aluminum alloy powder to the passivating agent solution is 1:(5–8), the passivating agent solution is a sodium molybdate solution, and the mass fraction of the passivating agent solution is 1 wt%–10 wt%; the impregnation temperature is 20–50 °C and the time is 10–60 min, the stirring speed is 100–200 r / min, and the drying temperature is 80–120 °C and the drying time is 30–60 min.

9. The graphene epoxy zinc-rich primer according to claim 1, characterized in that, In step S6, the pre-stirring speed is 700-900 r / min for 15-20 min; the heating temperature is 35-45℃; the stirring speed is 1200-1600 r / min for 25-35 min; the vacuum degassing is performed at a vacuum degree of -0.065 to -0.075 MPa for 5-10 min; the high-speed dispersion speed is 1900-2100 r / min for 35-45 min; after adding the additive, the stirring speed is 900-1100 r / min for 10-20 min; and solvent-free solids are added. The stirring speed of the chemical agent is 450-550 r / min and the stirring time is 10-20 min. The mesh size of the filter screen is 180-200 mesh. The mass ratio of the polyimide modified graphene, fluoride modified epoxy acrylate resin, reactive diluent, solvent-free curing agent, zinc powder microcapsules, nano titanium dioxide, passivated zinc aluminum alloy powder, dispersant, anti-settling agent and colorant is (1-5):(40-60):(15-25):(20-30):(25-40):(5-10):(50-80):(0.5-2):(0.3-1.5):(0.2-1.5).

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