Recyclable self-repairing anticorrosive coating and preparation method thereof

Abstract

The invention discloses a preparation method of a recoverable self-repairing anti-corrosion coating, which comprises the following steps: coating a concentrated solution or melt of polylipoic acid on a metal substrate by a dip-coating method, and cooling to obtain the recoverable self-repairing anti-corrosion coating, or adding metal ions into a concentrated solution or melt of polylipoic acid, reacting for 30 seconds to 20 minutes, coating a metal substrate with a reaction product, and cooling to obtain the recoverable self-repairing anti-corrosion coating, or adding metal ions into a concentrated solution or melt of polylipoic acid, reacting for 30 seconds to 20 minutes, adding the filler dispersion liquid, uniformly stirring, coating on the metal substrate, and evaporating the solvent to obtain the recoverable self-repairing anticorrosive coating. And the barrier property of the damaged coating can be completely recovered in a corrosion environment within only 12 hours at the soonest, so that high-efficiency extraction and recovery of a self-repairing material and high-efficiency circulation of carbon resources are realized.

Description

Technical Field

[0001] The present invention belongs to the field of synthesis of novel polymer materials, and relates to a recyclable self-healing anti-corrosion coating and a preparation method thereof. Background Art

[0002] Living tissues have excellent self-healing capabilities. When damaged, they can repair the damaged parts and restore their own functions. Inspired by the self-healing properties in nature, endowing polymer materials with self-healing functions has received extensive attention because it can extend the service life of materials, save energy, and reduce maintenance costs, and has been applied in various fields, such as the field of engineering coatings. According to the repair mechanism, self-healing materials can be divided into externally sourced self-healing materials and intrinsic self-healing materials. Externally sourced self-healing anti-corrosion coatings usually adopt the strategy of adding microcapsules or nanocontainers containing self-healing reagents or corrosion inhibitors to traditional coatings. When corrosion occurs, mechanical pressure or a change in pH will cause the internal active substances to be released into the corrosion area and protect the metal surface. For example, in patent CN202011177355.X, it can spontaneously respond to corrosion and prevent corrosion from occurring. However, the self-healing performance of externally sourced self-healing anti-corrosion coatings is limited by the internal active components and there are limitations on the number of uses. Therefore, intrinsic self-healing anti-corrosion coatings that can be repaired multiple times have become a research hotspot, such as patent CN202310106957.3. Intrinsic anti-corrosion coatings can rely on reversible dynamic interactions to close scratches and prevent the entry of corrosive media. However, this dynamic bond interaction usually requires external stimuli (light, heat, etc.), and the preparation process usually requires complex molecular design. This limits the application of self-healing materials in harsh and difficult-to-maintain environments such as the deep sea.

[0003] The current recycling efficiency of polymer materials is low, the performance after recycling is poor, and the recycling conditions are harsh, etc., which limit the development of recyclable polymer materials. An ideal polymer material can repair the damage of the material when damaged, restore the performance of the material and extend the service life of the material. When the material cannot be repaired or after use, the internal structural components can be recycled under mild conditions to achieve high-efficiency value recovery of polymer materials. The self-healing and recyclable functions of polymer materials are crucial for reducing environmental pollution of materials and promoting the synergistic reduction of pollution and carbon emissions throughout the life cycle of composite materials. Summary of the Invention

[0004] In view of this, the present invention provides a recyclable self-healing anti-corrosion coating and a preparation method thereof.

[0005] The present invention specifically provides the following technical solutions:

[0006] 1. A preparation method of a recyclable self-healing anti-corrosion coating, which coats a concentrated solution or melt of polythioctic acid on a metal substrate by dip coating and then cools it to obtain the recyclable self-healing anti-corrosion coating; or adds metal ions to the concentrated solution or melt of polythioctic acid, reacts for 30 seconds to 20 minutes, coats the reaction product on the metal substrate, and cools it to obtain the recyclable self-healing anti-corrosion coating; or adds metal ions to the concentrated solution or melt of polythioctic acid, reacts for 30 seconds to 20 minutes, then adds a filler dispersion, stirs evenly, coats it on the metal substrate, and evaporates the solvent to obtain the recyclable self-healing anti-corrosion coating.

[0007] Furthermore, the preparation method of the polythioctic acid is as follows: melt or concentrated solution of thioctic acid is reacted for 30 seconds to 20 minutes at 110 - 160 °C in an environment protected by inert gas to obtain a prepolymer. The thioctic acid is dextrorotatory thioctic acid or levorotatory thioctic acid, and the solvent of the concentrated solution is one or more of methanol, ethanol, chloroform, dichloromethane, tetrahydrofuran, N,N-dimethylformamide, and N,N-dimethylacetamide. Furthermore, the metal substrate is a steel substrate, an iron substrate, a zinc substrate, or an aluminum substrate.

[0008] Furthermore, the metal ions include one or more of calcium ions, cerium ions, aluminum ions, zinc ions, iron ions, and zinc ions.

[0009] Furthermore, the molar ratio of the metal ions to the thioctic acid monomer is 1:1000 - 1:20.

[0010] Furthermore, the filler is one or more of molybdenum disulfide, alumina, graphene oxide, sodium-based montmorillonite, calcium-based montmorillonite, and Mxene.

[0011] Furthermore, the mass ratio of the filler to the thioctic acid monomer is 1:100 - 1:5.

[0012] Furthermore, the solvent of the filler dispersion is one or more of methanol, ethyl acetate, butyl acetate, tetrahydrofuran, and chloroform.

[0013] Furthermore, the metal ions are metal salts or solutions of metal salts. The solvent of the solution of the metal salt is one or more of methanol, ethanol, and N,N-dimethylformamide, and the concentration of the solution of the metal salt is 0.1 g / L - 100 mol / L.

[0014] 2. The recyclable self-healing anti-corrosion coating prepared by the above preparation method can be degraded in an alkaline aqueous solution and the internal filler components can be recovered after the coating is used up, and small molecule monomers can be obtained through chemical recovery by acidification. The solute of the alkaline aqueous solution required for recovery is one or more of sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium bicarbonate, sodium carbonate, and triethylamine; the concentration of the alkaline solution required for recovery is 0.01 mol / L - 5 mol / L, and the acid used for acidification in the acidification step of the chemical recovery is one or more of hydrochloric acid, sulfuric acid, perchloric acid, and trifluoromethanesulfonic acid. The concentration of the acid is 0.01 mol / L - 5 mol / L, and the pH of the acidified solution is 2 - 4.

[0015] The beneficial effects of the present invention are as follows: Compared with the traditional self-healing anti-corrosion coating, the recyclable self-healing anti-corrosion coating of the present invention does not need to add additional repair agents and corrosion inhibitors, and the repair process does not require any human intervention, and can meet the long-term anti-corrosion requirements in extreme environments. Due to its pH-responsive characteristics, polythioctic acid can respond to the microenvironment changes generated by corrosion and promote the closure of scratches; further introducing metal ion coordination crosslinking can endow enhanced mechanical properties and self-healing properties. Electrochemical tests show that the damaged coating can completely recover the coating barrier performance in the corrosion environment in as little as 12 hours at the fastest; on this basis, introducing two-dimensional nanomaterials can improve the barrier performance of the material and enhance the long-term anti-corrosion performance of the self-healing coating. When the coating cannot repair the damage or reaches the service life, all coatings can be controllably degraded under mild conditions to recover the structural components, realizing the high-efficiency extraction and recycling of self-healing materials and the efficient carbon resource cycle, which has positive significance for reducing the environmental pollution of materials and promoting the coordinated reduction of pollution and carbon emissions in the whole life cycle of materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to make the objectives, technical solutions and beneficial effects of the present invention clearer, the present invention provides the following drawings:

[0017] Figure 1 Optical microscope photos of the recyclable self-healing anti-corrosion coating 1 before and after repair.

[0018] Figure 2 Bode curves of the electrochemical impedance of the recyclable self-healing anti-corrosion coating 1 with scratches as a function of corrosion time.

[0019] Figure 3 Bode curves of the electrochemical impedance of the recyclable self-healing anti-corrosion coating 3 with scratches as a function of corrosion time.

[0020] Figure 4 Nyquist curves of the electrochemical impedance of the recyclable self-healing anti-corrosion coating 4 with scratches as a function of corrosion time.

[0021] Figure 5 Curves of the impedance values of the recyclable self-healing anti-corrosion coating 5 and the recyclable self-healing anti-corrosion coating 3 varying with the corrosion time.

[0022] Figure 6 Ultraviolet-visible spectrograms of the original lipoic acid monomer, the recyclable self-healing anti-corrosion coating 3, and the recycled lipoic acid monomer.

[0023] Figure 7 Raman spectrograms of the original lipoic acid monomer, the recyclable self-healing anti-corrosion coating 3, and the recycled lipoic acid monomer Detailed implementation manners

[0024] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0025] Example 1

[0026] (1) Synthesis of polythioctic acid: 2.06 g of dextrorotatory lipoic acid was reacted at 150 °C for 20 min in an inert gas environment. After that, the lipoic acid melted and became a transparent and uniform melt to obtain a prepolymer.

[0027] (2) The prepolymer obtained in step (1) was coated on a steel plate by the dip-coating method and naturally cooled to room temperature to obtain the recyclable self-healing anti-corrosion coating 1.

[0028] Example 2

[0029] (1) Synthesis of polythioctic acid: 3.09 g of levorotatory lipoic acid was reacted at 150 °C for 30 min in an inert gas environment. After that, the lipoic acid melted and became a transparent and uniform melt to obtain a prepolymer.

[0030] (2) The prepolymer obtained in step (1) was coated on a steel plate by the dip-coating method and naturally cooled to room temperature to obtain the recyclable self-healing anti-corrosion coating 2.

[0031] Example 3

[0032] (1) Synthesis of polythioctic acid: 2.06 g of dextrorotatory lipoic acid was reacted at 150 °C for 30 min in an inert gas environment to obtain a prepolymer.

[0033] (2) 0.1 g of cerium trifluoromethanesulfonate was added to the prepolymer obtained in step (1). After the solid dissolved, the reaction was continued for 1 min to obtain a polythioctic acid-cerium polymer.

[0034] (3) The polythioctic acid-cerium polymer obtained in step (2) was coated on a steel plate by the dip-coating method and slowly cooled to room temperature to obtain the recyclable self-healing anti-corrosion coating 3.

[0035] Example 4

[0036] (1) Synthesis of polythioctic acid: 2.06 g of L-thioctic acid was dissolved in 10 ml of ethanol, and after reacting for 20 min at 60 °C in an inert gas environment, a prepolymer was obtained.

[0037] (2) 10 ml of an ethanol solution of 10 g / L silver trifluoromethanesulfonate was added to the prepolymer and reacted for 1 minute to obtain a polythioctic acid-silver polymer.

[0038] (3) The reaction product of the polythioctic acid-silver polymer in step (2) was coated on a steel plate by the dip-coating method, and the solvent was slowly evaporated at 60 °C to obtain a recyclable self-healing anti-corrosion coating 4.

[0039] Example 5

[0040] (1) Synthesis of polythioctic acid: 3.09 g of D-thioctic acid was dissolved in N,N-dimethylformamide, and after reacting for 30 min at 70 °C in an inert gas environment, a prepolymer was obtained.

[0041] (2) 0.1 g of cerium trifluoromethanesulfonate was added to the prepolymer and reacted for three minutes to obtain a polythioctic acid-cerium polymer.

[0042] (3) A dispersion of N,N-dimethylformamide containing 0.3 g of sodium montmorillonite was added dropwise to the polymer solution in step (2) and stirred evenly.

[0043] (4) The reaction product in step (3) was coated on a steel plate by the dip-coating method, and the solvent was slowly evaporated at 80 °C to obtain a recyclable self-healing anti-corrosion coating 5.

[0044] Test Example 1 Self-healing anti-corrosion performance test

[0045] Traditional anti-corrosion coatings are prone to being affected by temperature, external impacts, etc. during manufacturing and use, and inevitably suffer damage. If these damages are not repaired in time, it may lead to the rapid expansion of corrosion and cause safety problems. Self-healing anti-corrosion coatings can sense and repair external damages, improve the reliability of the coatings and extend the service life of materials, and have received increasing attention. The self-healing anti-corrosion performance test is an important basis for studying the repair process and repair mechanism, and is also the main standard for evaluating the self-healing performance of anti-corrosion coatings.

[0046] In the self-healing anti-corrosion performance test, first, the surface coating thickness was measured using an OU3600 film thickness gauge. To accelerate the corrosion rate of the metal substrate and facilitate observation, a scratch was made on the coating of the present invention with a blade. Then, the carbon steel specimen with the scratch was immersed in a 3.5 wt% NaCl solution. Under these conditions, water molecules and chloride ions in the solvent can directly contact the metal substrate, thus accelerating the corrosion of the substrate. After soaking for a certain period of time, the self-healing function at the scratch was observed using a microscope, and the self-healing function of the recyclable self-healing anti-corrosion coating of the present invention was studied by comparing the impedance values (Bode curves) at 0.01 Hz in the electrochemical impedance spectra at different times.

[0047] Figure 1 Figure 4 shows the microscopic images of the scratches on the recyclable self-healing anti-corrosion coating 1 at different times. Figure 1 As can be seen from it, as the corrosion occurred, the scratches on the coating actively closed, preventing the entry of corrosive media and achieving the effect of self-healing anti-corrosion.

[0048] Figure 2 Figure 5 shows the Bode curves of the electrochemical impedance of the recyclable self-healing anti-corrosion coating 1 with the corrosion time. Figure 2 As can be seen from it, when the coating was damaged, due to the corrosive media being able to directly reach the metal substrate, the impedance value was low. As the scratch on the coating closed, the impedance value of the coating increased. After 48 hours of repair, the impedance value increased, and the repair process was spontaneous and did not require any external stimulation.

[0049] Figure 3 Figure 6 shows the Bode curves of the electrochemical impedance of the coating prepared from the recyclable self-healing anti-corrosion coating 3 with scratches with the corrosion time. Figure 3 As can be seen from it, when the coating was damaged, due to the corrosive media being able to directly reach the metal substrate, the impedance value was low. As the repair time extended, after 12 hours of repair, the impedance value increased by three orders of magnitude and almost completely recovered, and the repair process was spontaneous and did not require any external stimulation.

[0050] Figure 4 Figure 7 shows the Nyquist curves of the electrochemical impedance of the coating prepared from the recyclable self-healing anti-corrosion coating 4 with scratches with the corrosion time. Figure 4 As can be seen from it, when the coating was damaged, the impedance value was low. As the repair time extended, the impedance value gradually increased, indicating the good self-healing performance of the coating, and the repair process was spontaneous and did not require any external stimulation.

[0051] Figure 5 Figure 8 shows the curves of the impedance of the recyclable self-healing anti-corrosion coating 5 and the recyclable self-healing anti-corrosion coating 3 with the corrosion time. Figure 5It can be seen that due to the shielding effect of sodium-based montmorillonite, the penetration path of the corrosive medium is increased, and the rate of decrease in the impedance value is significantly reduced, proving that adding montmorillonite materials can improve the long-term anti-corrosion performance of the self-healing anti-corrosion coating.

[0052] Test Example 2 Recycling Performance Test

[0054] In the recycling performance test, first, the recyclable self-healing anti-corrosion coating 3 of the present invention was dissolved in a 1 mol / L sodium hydroxide aqueous solution. Polythioctic acid was deprotonated and catalyzed the depolymerization of the polymer backbone to obtain a sodium thioctate solution soluble in water and a filler component insoluble in water. Different components were separated by filtration. Among them, 0.5 mol / L hydrochloric acid was added to the sodium thioctate aqueous solution to adjust the pH value to 3. Protonated thioctic acid small molecules precipitated from the solution. After filtration and separation, high-purity chemically recycled thioctic acid monomers were obtained. The filtered and separated filler part could be separated and purified by repeating the operations of washing and centrifugation to obtain the recycled filler component. Ultraviolet-visible light spectroscopy was used to analyze the chemical structure of thioctic acid before and after chemical recycling, and the recycling efficiency was obtained by calculating the mass ratio of thioctic acid monomers and filler components before and after recycling. The recycling efficiency was 82%.

[0055] Figure 6 Ultraviolet-visible light spectra of thioctic acid in the recyclable self-healing anti-corrosion coating 3 before and after recycling. From Figure 6 it can be seen that from top to bottom, the peak of thioctic acid monomer at 330 nm in the first curve is transferred to the peak position of polythioctic acid at 260 nm after ring-opening polymerization. This is because the disulfide bond changes from an intramolecular disulfide bond to a polymer chain with a disulfide bond as the main chain. After experiencing the recycling process, the polymer chain depolymerizes and reverts to thioctic acid monomer again. The peak at 260 nm disappears, and a characteristic peak belonging to thioctic acid monomer reappears at 330 nm, successfully proving that the chemical structure of the monomer has not changed before and after chemical recycling.

[0056] Figure 7 Raman spectra of thioctic acid in the recyclable self-healing anti-corrosion coating 3 before and after recycling. From Figure 7 it can be seen that in the Raman spectra of thioctic acid monomers before and after recycling, the positions of the characteristic peaks are the same. Among them, the sharp peak at 510 cm -1 is the characteristic peak of the disulfide bond in thioctic acid monomer, also proving that the chemical structure of the monomer has not changed before and after chemical recycling.

[0057] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing a recyclable self-repairing anti-corrosion coating, characterized in that: A concentrated solution or melt of polylipoic acid is coated on a metal substrate by dip coating and cooled to obtain a recyclable self-repairing anti-corrosion coating; alternatively, metal ions are added to a concentrated solution or melt of polylipoic acid, reacted for 30 seconds to 20 minutes, the reaction product is coated on a metal substrate, cooled to obtain a recyclable self-repairing anti-corrosion coating; alternatively, metal ions are added to a concentrated solution or melt of polylipoic acid, reacted for 30 seconds to 20 minutes, a filler dispersion is added, stirred evenly, coated on a metal substrate, and the solvent is evaporated to obtain a recyclable self-repairing anti-corrosion coating.

2. The method for preparing a recyclable self-repairing anti-corrosion coating according to claim 1, characterized in that: The preparation method of the polylipoic acid is as follows: a melt or concentrated solution of lipoic acid is reacted in an environment protected by inert gas at 110-160° C. for 30 seconds to 20 minutes to obtain a prepolymer, wherein the lipoic acid is dextrorotatory lipoic acid or levorotatory lipoic acid, and the solvent of the concentrated solution is one or more of methanol, ethanol, chloroform, dichloromethane, tetrahydrofuran, N,N-dimethylformamide, and N,N-dimethylacetamide.

3. The method for preparing a recyclable self-repairing anti-corrosion coating according to claim 1, characterized in that: The metal substrate is a steel substrate, an iron substrate, a zinc substrate or an aluminum substrate.

4. The method for preparing a recyclable self-repairing anti-corrosion coating according to claim 1, characterized in that: The metal ions include one or more of calcium ions, cerium ions, aluminum ions, zinc ions, iron ions, and zinc ions.

5. The method for preparing a recyclable self-repairing anti-corrosion coating according to claim 2, characterized in that: The molar ratio of the metal ion to the lipoic acid is 1:1000-1:

20.

6. The method for preparing a recyclable self-repairing anti-corrosion coating according to claim 1, characterized in that: The filler is one or more of molybdenum disulfide, aluminum oxide, graphene oxide, sodium-based montmorillonite, calcium-based montmorillonite, and Mxene.

7. The method for preparing a recyclable self-repairing anti-corrosion coating according to claim 2, characterized in that: The mass ratio of the filler to the lipoic acid monomer is 1:100-1:

5.

8. The method for preparing a recyclable self-repairing anti-corrosion coating according to claim 1, characterized in that: The solvent of the filler dispersion is one or more of methanol, ethyl acetate, butyl acetate, tetrahydrofuran and chloroform.

9. The method for preparing a recyclable self-repairing anti-corrosion coating according to claim 1, characterized in that: The metal ion is a metal salt or a solution of a metal salt. The solvent of the solution of the metal salt is one or more of methanol, ethanol and N,N-dimethylformamide. The concentration of the solution of the metal salt is 0.1 g / L-100 mol / L.

10. The recyclable self-repairing anti-corrosion coating prepared by the preparation method according to any one of claims 1 to 9, characterized in that: When the coating is used up, the internal filler components can be degraded and recovered in an alkaline aqueous solution, and chemically recovered by acidification to obtain small molecule monomers. The solute of the alkaline aqueous solution required for recovery is one or more of sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium bicarbonate, sodium carbonate, and triethylamine; the concentration of the alkaline solution required for recovery is 0.01mol / L-5mol / L, and the acid used for acidification in the acidification step of the chemical recovery is one or more of hydrochloric acid, sulfuric acid, perchloric acid, and trifluoromethanesulfonic acid. The concentration of the acid is 0.01mol / L-5mol / L, and the pH of the acidified solution is 2-4.

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