A defect-autonomously-triggered confined flow self-repairing anti-corrosion coating material and its preparation method

Abstract

The present invention discloses a defect-autonomously triggered confined flow self-repairing anti-corrosion coating material and a preparation method thereof, the preparation method comprising the following steps: heating and stirring a hydrogen bond donor and a hydrogen bond acceptor to uniformly mix to obtain a low eutectic solvent; stirring and mixing a bisphenol A epoxy resin monomer and a disulfide bond-containing amine curing agent to uniformly obtain an epoxy resin casting solution; adding the low eutectic solvent to the epoxy resin casting solution, stirring and mixing to obtain a low eutectic solvent / epoxy resin coating casting solution; vacuum degassing the low eutectic solvent / epoxy resin casting solution; applying the vacuum degassed casting solution to a protected substrate while hot, curing, and then removing and cooling to obtain a coating. The present invention utilizes room temperature dynamically reversible covalent bonds as crosslinking points to construct a dynamic epoxy resin network, and uses the flow of the low eutectic solvent to drive the epoxy resin molecular chains to migrate to defects, thereby achieving complete repair of the coating structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of self-repairing anti-corrosion coatings, and specifically relates to an epoxy resin-based anti-corrosion coating material and a preparation method thereof, in which defects autonomously trigger confined flow to achieve damage self-repair. Background Art

[0002] Metal corrosion is a silent, yet destructive, form of damage. According to statistics, one ton of steel worldwide deteriorates and fails due to corrosion every 90 seconds. If unchecked, this can lead to significant resource waste, economic losses, and even catastrophic accidents. Among the many corrosion prevention technologies, coating protection, due to its flexible operation and extensive versatility, is currently the most cost-effective corrosion control method. However, protective coatings are susceptible to accidental damage during service, subject to the combined effects of environmental media and alternating loads. If not repaired promptly, damaged areas become a gateway for corrosive media to enter, rapidly spreading under the effects of stress, ultimately leading to a loss of coating integrity and a complete loss of protective properties. Therefore, imparting self-repair capabilities to coatings can effectively extend the service life of the protected substrate, delay maintenance requirements, reduce maintenance frequency, and save repair costs.

[0003] Research on self-healing materials has been ongoing for over 20 years. Based on their mechanisms, material self-healing strategies can be categorized into two main types: "externally assisted" and "intrinsically assisted." Externally assisted self-healing primarily involves the addition of micro-containers (microcapsules, carbon nanotubes, microvessels, glass fibers, or nanoparticles) loaded with a healing agent to the surface or interior of the material. When the material is damaged, the micro-containers rupture and release the healing agent at the site of damage. Under certain conditions, the healing agent solidifies in situ, repairing the material damage. However, due to limitations in the container capacity, this method cannot achieve multiple repairs. Intrinsically assisted self-healing relies on the dynamic, reversible chemical reactions inherent in the material's molecular structure to achieve self-repair. These interactions primarily involve reversible non-covalent interactions, such as hydrogen bonds, coordination bonds, and host-guest interactions, as well as reversible covalent bonds, such as disulfide bonds and imine bonds. Compared to extrinsic self-healing strategies, intrinsic self-healing effectively avoids the drawback of limited repair cycles and is currently the most popular self-healing strategy.

[0004] However, "intrinsic" self-repair requires that the damaged interfaces of the materials must be in close contact so that the reactive groups at the damaged interfaces can achieve intermolecular diffusion / entanglement / formation of chemical bonds through chain migration / conformational changes. However, due to the strong adhesion of the coating system to the substrate, the damaged interfaces of the coating cannot spontaneously approach and contact each other, making it difficult to effectively apply traditional intrinsic self-repair strategies in coating systems. In response to this, some studies have proposed combining the "fluidity" advantage of liquid substances with coating design to invent a new "intrinsic" self-repair strategy based on "solid-liquid transition". However, the "solid-liquid transition" process of this method requires external stimuli such as light and heat as the triggering condition for the self-repair process, making it non-autonomous self-repair. For example, Chinese patent CN110862722B obtains a physical intrinsic self-repairing coating based on the principle of melting, flow and re-fusion. This coating exhibits solid properties in service state, but when damaged, it can exhibit liquid-like properties when irradiated by near-infrared laser, and the coating damage is repaired through a flow-fusion process. Chinese patent CN116162391B constructs a "confined" polymer network skeleton for the "liquid-like" material, and synergistically dopes it with photothermal fillers to give the coating the self-healing property of "confined solid-liquid transition" driven by photothermal energy. However, external stimuli in the form of light, heat, etc. will affect the properties of the coating itself to a certain extent. At the same time, its feature of requiring human intervention also causes application limitations that make it difficult to promote its use in actual engineering. Therefore, how to achieve "autonomous" repair of material damage without external stimulation has become a technical bottleneck that needs to be broken through before the "self-healing" coating technology can be applied. Summary of the Invention

[0005] The purpose of the present invention is to solve the limitations of traditional "intrinsic" self-repairing technology when applied to coating systems, such as the difficulty in contacting damaged interfaces and the non-autonomous repair process, and to provide a method for preparing defect-triggered self-repairing anti-corrosion coating materials that combines fluidity and stability. By designing a coating structure in which a polymer network skeleton containing dynamic reversible bonds is coated with a highly controllable mobile phase, a coating material is constructed that can achieve intrinsic self-repair of damage based on the "confined flow" characteristics at the molecular level at room temperature, breaking through the technical barriers to autonomous repair of coatings caused by external energy input, and realizing "autonomous docking of fractures, autonomous repair of defects, and integrated mending" of coating damage.

[0006] In order to achieve the above technical objectives, the technical solution of the present invention is:

[0007] A method for preparing a defect-autonomously-triggered confined flow self-repairing anti-corrosion coating material comprises the following steps:

[0008] (1) The hydrogen bond donor and the hydrogen bond acceptor are heated and stirred to mix uniformly to obtain a deep eutectic solvent;

[0009] (2) stirring and mixing the bisphenol A epoxy resin monomer and the disulfide bond-containing amine curing agent to obtain an epoxy resin casting solution;

[0010] (3) adding a low eutectic solvent to the epoxy resin film casting solution, stirring and mixing to obtain a low eutectic solvent / epoxy resin coating film casting solution;

[0011] (4) Vacuum degassing the low eutectic solvent / epoxy resin casting solution;

[0012] (5) The vacuum degassed casting solution is applied to the protected substrate while hot, solidified, and then taken out and cooled to obtain a coating.

[0013] Wherein, the hydrogen bond donor is L-lactide, thymol, glycerol or 1-naphthol, and the hydrogen bond acceptor is ε-caprolactone, menthol, betaine or coumarin.

[0014] The molar ratio of L-lactide to ε-caprolactone is 3:7, the molar ratio of thymol to menthol is 1:1, the molar ratio of glycerol to betaine is 1:2, and the molar ratio of 1-naphthol to coumarin is 3:1.

[0015] Wherein, in step (1), the heating and stirring temperature is 80-90°C, and the stirring time is 1-2h.

[0016] Wherein, in step (2), the epoxy value of the bisphenol A epoxy resin monomer is between 0.41 and 0.56; the amine curing agent is an amine curing agent containing a disulfide bond; the molar ratio of the bisphenol A epoxy resin monomer to the amine curing agent is 1:0.9; and the stirring time is 1-2 h.

[0017] Wherein, the disulfide bond-containing amine curing agent is 2,2'-diaminodiphenyl disulfide and / or 4,4'-diaminodiphenyl disulfide.

[0018] Wherein, in step (3), the mass ratio of the low eutectic solvent to the epoxy resin casting solution is 1:(0.8-1.2).

[0019] Wherein, in step (4), the vacuum degassing conditions are: temperature 60-70 °C, and degassing time is 1-2 h.

[0020] Wherein, in step (5), the coating method is preheating spraying, brushing, pouring or dipping; the curing temperature is 80°C-120°C, and the curing time is 4h-12h.

[0021] A defect-autonomously-triggered confined flow self-repairing anti-corrosion coating material is produced by the above-mentioned preparation method.

[0022] Epoxy resin, with its excellent mechanical properties, electrical insulation, adhesion, and chemical stability, is currently the most widely used resin material for anti-corrosion coatings. However, traditional epoxy resin materials have a densely cross-linked, "thermosetting" three-dimensional network structure and are extremely chemically inert. By introducing dynamic reversible covalent bonds, epoxy resins with dynamic cross-linked networks can be constructed. However, due to the limitations of substrate adhesion, relying solely on dynamic chemical design cannot solve the problem of "difficult contact between damaged interfaces" faced by epoxy resin "coatings" when repairing damage. To address this issue, an unconditionally triggered "mobile phase" is introduced into the design of epoxy resin systems containing dynamic reversible bonds to assist the directional migration of the coating's "damaged interface" toward the defect site, while also driving the dynamic epoxy resin molecular chains into contact with each other. This can achieve autonomous contact at the "damaged interface" while promoting the reconstruction of the epoxy resin network skeleton, achieving "complete" repair of coating damage and further ensuring the mechanical properties and corrosion protection of the local coating at the defect site after autonomous repair.

[0023] Disulfide bonds are typical dynamically reversible covalent bonds with relatively low bond energies. They can undergo dynamic, reversible disulfide exchange reactions at room temperature without external stimulation, and the exchange process is easily controllable, making them a promising chemical building block for constructing "self-healing" coatings. Deep eutectic solvents are liquid mixtures that utilize hydrogen bonding interactions between their components, resulting in a significantly lower melting point than the individual components. Compared to traditional solvents, deep eutectic solvents offer advantages such as low vapor pressure, high solubility, high thermal stability, low toxicity, biodegradability, low cost, and ease of preparation, making them promising green reaction media. Furthermore, deep eutectic solvents contain a rich hydrogen bond network, which is a highly advantageous chemical building block for room-temperature self-healing. By adjusting the molar ratio and type of hydrogen bond acceptors and donors, the physical and chemical properties of deep eutectic solvents can be tuned, conferring superior coating functionality. Therefore, deep eutectic solvents are suitable as the "mobile phase" for constructing "confined flow" room-temperature self-healing coatings.

[0024] This invention utilizes a curing agent as a reaction medium to synthesize a dynamically reversible epoxy resin "network backbone" containing disulfide crosslinks as the coating's "stationary phase." A deep eutectic solvent is used as the "mobile phase," and its composition and content are manipulated to impart fluidity to the coating. Ultimately, the confined flow of the deep eutectic solvent drives the epoxy resin molecular chains toward defects, enabling autonomous repair of coating damage.

[0025] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0026] (1) The present invention uses room temperature dynamically reversible covalent bonds as crosslinking points to construct a dynamic epoxy resin network. The flow of a low eutectic solvent drives the epoxy resin molecular chains to migrate toward defects, achieving complete repair of the coating structure. When the coating is damaged, the coating can be confined to promote close contact between the fracture interfaces without any external stimulation. At the same time, the coating cracks can be self-repaired under the action of dynamic reversible bonds.

[0027] (2) The present invention controls the "fluidity" of the deep eutectic solvent in the deep eutectic solvent / epoxy resin system to be limited to the microscopic level, thereby ensuring the macroscopic stability of the coating during service. The proposed technology, which takes advantage of the fluidity of the deep eutectic solvent to control the epoxy resin containing dynamic reversible bonds to give the coating a truly autonomous self-healing technology, has not yet been reported. This technology can solve the impact of external stimulus conditions on the service life of the coating material and the limitations of practical engineering applications.

[0028] (3) The raw materials required in the invention are all commercially available products. The preparation process does not require any chemical modification steps and can be coated in a variety of ways, making it suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 (a) is the infrared spectrum of deep eutectic solvent; Figure 1 (b) is the infrared spectrum of the deep eutectic solvent / epoxy resin-based composite coating;

[0030] Figure 2 DSC comparison chart of epoxy resin material and deep eutectic solvent / epoxy resin composite material;

[0031] Figure 3 (a) is a comparison diagram of the deep eutectic solvent / epoxy resin-based composite coating of the present invention before and after immersion in boiling water; Figure 3 (b) Comparison of the composite coating before and after water impact;

[0032] Figure 4 Microscopic comparison of the self-healing of the deep eutectic solvent / epoxy resin-based composite coating with a deep eutectic solvent content of 50 wt% before and after self-healing;

[0033] Figure 5 Bode impedance diagrams of EP-SS / DES50 coating, damaged EP-SS / DES50 and repaired EP-SS / DES50 coating. DETAILED DESCRIPTION

[0034] The following will be combined with specific embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example 1

[0035] This embodiment provides a method for preparing a defect-autonomously-triggered confined flow self-repairing anti-corrosion coating material, comprising the following steps:

[0036] (1) L-lactide and ε-caprolactone in a molar ratio of 3:7 were heated and stirred to mix uniformly at a heating and stirring temperature of 85°C for 1.5 h to obtain a deep eutectic solvent;

[0037] (2) Stirring the bisphenol A epoxy resin monomer with an epoxy value of 0.50 and the disulfide bond-containing amine curing agent at a molar ratio of 1:0.9 for 1.5 hours to obtain an epoxy resin casting solution;

[0038] (3) adding a low eutectic solvent to the epoxy resin casting solution, wherein the mass ratio of the low eutectic solvent to the epoxy resin casting solution is 1:1, and stirring and mixing to obtain a low eutectic solvent / epoxy resin coating casting solution;

[0039] (4) The low eutectic solvent / epoxy resin casting solution was vacuum degassed at 65 °C for 1.5 h;

[0040] (5) The vacuum degassed casting liquid is preheated and sprayed, brushed, poured or dipped onto the protected substrate for curing at a temperature of 100°C for 8 hours. The film is then taken out and cooled to obtain a coating. Example 2

[0041] This embodiment provides a method for preparing a defect-autonomously-triggered confined flow self-repairing anti-corrosion coating material, comprising the following steps:

[0042] (1) 1-naphthol and coumarin in a molar ratio of 3:1 were heated and stirred to mix uniformly at 80 °C for 1.5 h to obtain a deep eutectic solvent;

[0043] (2) Stirring the bisphenol A epoxy resin monomer with an epoxy value of 0.41 and a disulfide bond-containing amine curing agent at a molar ratio of 1:0.9 for 1.5 hours to obtain an epoxy resin casting solution;

[0044] (3) adding a low eutectic solvent to the epoxy resin casting solution, wherein the mass ratio of the low eutectic solvent to the epoxy resin casting solution is 1:0.9, and stirring and mixing to obtain a low eutectic solvent / epoxy resin coating casting solution;

[0045] (4) The low eutectic solvent / epoxy resin casting solution was vacuum degassed at 60°C for 1.5 h;

[0046] (5) The vacuum degassed casting liquid is preheated and sprayed, brushed, poured or dipped onto the protected substrate for curing at a temperature of 80°C for 12 hours. The liquid is then taken out and cooled to obtain a coating. Example 3

[0047] This embodiment provides a method for preparing a defect-autonomously-triggered confined flow self-repairing anti-corrosion coating material, comprising the following steps:

[0048] (1) Glycerol and betaine in a molar ratio of 1:2 were heated and stirred to mix uniformly at 90 °C for 1.5 h to obtain a deep eutectic solvent;

[0049] (2) Stirring the bisphenol A epoxy resin monomer with an epoxy value of 0.56 and a disulfide bond-containing amine curing agent at a molar ratio of 1:0.9 for 1.5 hours to obtain an epoxy resin casting solution;

[0050] (3) adding a low eutectic solvent to the epoxy resin casting solution, wherein the mass ratio of the low eutectic solvent to the epoxy resin casting solution is 1:0.8, and stirring and mixing to obtain a low eutectic solvent / epoxy resin coating casting solution;

[0051] (4) The low eutectic solvent / epoxy resin casting solution was subjected to vacuum degassing treatment at a temperature of 70 °C and a degassing time of 1 h;

[0052] (5) The vacuum degassed casting liquid is preheated and sprayed, brushed, poured or dipped onto the protected substrate for curing at a temperature of 120°C for 4 hours. The film is then taken out and cooled to obtain a coating. Example 4

[0053] This embodiment provides a method for preparing a defect-autonomously-triggered confined flow self-repairing anti-corrosion coating material, comprising the following steps:

[0054] (1) 1-naphthol and coumarin in a molar ratio of 3:1 were heated and stirred to mix uniformly at 88 °C for 1 h to obtain a deep eutectic solvent;

[0055] (2) Stirring and mixing the bisphenol A epoxy resin monomer with an epoxy value of 0.48 and the disulfide bond-containing amine curing agent at a molar ratio of 1:0.9 for 1 hour to obtain an epoxy resin casting solution;

[0056] (3) adding a low eutectic solvent to the epoxy resin casting solution, wherein the mass ratio of the low eutectic solvent to the epoxy resin casting solution is 1:1.2, and stirring and mixing to obtain a low eutectic solvent / epoxy resin coating casting solution;

[0057] (4) Vacuum degassing the low eutectic solvent / epoxy resin casting solution at a temperature of 60-70 °C for 1-2 h;

[0058] (5) The vacuum degassed casting liquid is preheated and sprayed, brushed, poured or dipped onto the protected substrate for curing at a temperature of 90°C for 8 hours. The film is then taken out and cooled to obtain a coating. Example 5

[0059] This embodiment provides a method for preparing a defect-autonomously-triggered confined flow self-repairing anti-corrosion coating material, comprising the following steps:

[0060] (1) L-lactide and ε-caprolactone in a molar ratio of 3:7 were heated and stirred to mix uniformly at a heating and stirring temperature of 84°C for 2 h to obtain a deep eutectic solvent;

[0061] (2) Stirring and mixing the bisphenol A epoxy resin monomer with an epoxy value of 0.52 and the disulfide bond-containing amine curing agent at a molar ratio of 1:0.9 for 2 hours to obtain an epoxy resin casting solution;

[0062] (3) adding a low eutectic solvent to the epoxy resin casting solution, wherein the mass ratio of the low eutectic solvent to the epoxy resin casting solution is 1:1, and stirring and mixing to obtain a low eutectic solvent / epoxy resin coating casting solution;

[0063] (4) Vacuum degassing the low eutectic solvent / epoxy resin casting solution at a temperature of 60-70 °C for 1-2 h;

[0064] (5) The vacuum degassed casting liquid is preheated and sprayed, brushed, poured or dipped onto the protected substrate for curing at a temperature of 100°C for 6 hours. The film is then taken out and cooled to obtain a coating.

[0065] The present invention designs a dynamic reversible epoxy resin "network skeleton" containing disulfide cross-linking points as the coating "stationary phase" and a deep eutectic solvent as the "mobile phase". By regulating the flow of the deep eutectic solvent in the composite coating system, the epoxy resin network is driven to migrate to the coating defects and is confined to the microscopic level ( Figure 1-2), ensuring the macroscopic stability of the coating during service ( Figure 3 The unique "confined flow" characteristics and autonomous self-repair function of the composite coating enable it to drive the damaged interfaces of the coating to contact each other through its flow characteristics without any external stimulation. At the same time, under the action of dynamic reversible bonds, the epoxy resin network is reconstructed and the cracks are closed ( Figure 4 ). The electrochemical impedance spectroscopy test showed that the anti-corrosion performance of the composite coating did not decrease significantly after self-repair ( Figure 5 ), demonstrating excellent self-repair efficiency. The composite coating in this invention utilizes an unconditionally triggered, autonomous self-repairing mechanism, offering significant advantages such as rapid and controllable response, diverse application scenarios, and the ability to achieve "autonomous fracture docking, autonomous defect repair, and integrated repair."

[0066] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a defect-autonomously triggered confined flow self-repairing anti-corrosion coating material, characterized in that The steps include: (1) The hydrogen bond donor and the hydrogen bond acceptor are heated and stirred to mix uniformly to obtain a deep eutectic solvent; (2) stirring and mixing the bisphenol A epoxy resin monomer and the disulfide bond-containing amine curing agent to obtain an epoxy resin casting solution; (3) adding a low eutectic solvent to the epoxy resin film casting solution, stirring and mixing to obtain a low eutectic solvent / epoxy resin coating film casting solution; (4) Vacuum degassing the low eutectic solvent / epoxy resin casting solution; (5) applying the vacuum degassed casting solution to the protected substrate while it is hot, curing it, and then removing it and cooling it to obtain a coating; The hydrogen bond donor is L-lactide, glycerol or 1-naphthol, and the hydrogen bond acceptor is ε-caprolactone, betaine or coumarin; The molar ratio of L-lactide to ε-caprolactone is 3:7, the molar ratio of glycerol to betaine is 1:2, and the molar ratio of 1-naphthol to coumarin is 3:1; In step (3), the mass ratio of the low eutectic solvent to the epoxy resin casting solution is 1:(0.8-1.2).

2. The method for preparing a defect-autonomously-triggered confined flow self-repairing anti-corrosion coating material according to claim 1, characterized in that: In step (1), the heating and stirring temperature is 80-90°C, and the stirring time is 1-2h.

3. The method for preparing a defect-autonomously-triggered confined flow self-repairing anti-corrosion coating material according to claim 1, characterized in that: In step (2), the epoxy value of the bisphenol A epoxy resin monomer is between 0.41 and 0.56; the molar ratio of the bisphenol A epoxy resin monomer to the disulfide bond-containing amine curing agent is 1:0.9; and the stirring time is 1 to 2 hours.

4. The method for preparing a defect-autonomously-triggered confined flow self-repairing anti-corrosion coating material according to claim 3, characterized in that: The disulfide bond-containing amine curing agent is 2,2'-diaminodiphenyl disulfide and / or 4,4'-diaminodiphenyl disulfide.

5. The method for preparing a defect-autonomously-triggered confined flow self-repairing anti-corrosion coating material according to claim 1, characterized in that: In step (4), the vacuum degassing conditions are: temperature 60°C-70°C, and degassing time is 1-2h.

6. The method for preparing a defect-autonomously-triggered confined flow self-repairing anti-corrosion coating material according to claim 1, characterized in that: In step (5), the coating method is preheating spraying, brushing or dipping; the curing temperature is 80°C-120°C, and the curing time is 4h-12h.

7. A defect-triggered confined flow self-repairing anti-corrosion coating material, characterized in that The invention is prepared by the preparation method according to any one of claims 1 to 6.

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