Vanillin-based curing agent, preparation method and application thereof

Abstract

The present application relates to the technical field of paint, and discloses a vanillin-based curing agent, a preparation method and application thereof.The vanillin-based curing agent comprises the following raw materials: vanillin, amino monomer and acyl chloride monomer.The vanillin-based curing agent provided by the present application takes vanillin from biomass as raw material, is wide in raw material source, green and environment-friendly, converts vanillin into a curing agent, improves the added value of biomass materials, reduces the dependence on petroleum-based ammonia curing agents, and alleviates the pressure of petroleum-based polymer materials.The preparation method of the vanillin-based curing agent is simple in steps, mild in reaction conditions, and strong in operability, and is conducive to large-scale preparation.The anticorrosive paint added with the vanillin-based curing agent has a coating with the characteristics of corrosion resistance, low dielectric constant and dielectric loss, excellent antibacterial performance, strong protection effect on metal, and the ability to prolong the service life of metal.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a vanillin-based curing agent, its preparation method, and its application. Background Technology

[0002] Coating metal surfaces with an organic layer is an effective way to protect them from corrosion. Resin is an essential component of coatings, with epoxy resin being a commonly used one. Epoxy resins possess excellent thermal stability, chemical resistance, and insulation properties, as well as good adhesion, wear resistance, and high hardness. However, epoxy resins themselves do not cure; only by adding a curing agent and undergoing a curing reaction under certain conditions can a three-dimensional network structure be formed, thus exhibiting excellent performance. Currently available epoxy resin curing agents are mostly derived from petroleum-based products, which is not conducive to sustainable development. Conventional amine curing agents contain active hydrogen, which generates numerous polar hydroxyl groups during epoxy resin curing, resulting in a high dielectric constant in the coating and limiting the application of epoxy coatings in electronic products. Summary of the Invention

[0003] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, one objective of the present invention is to provide a vanillin-based curing agent; a second objective is to provide a method for preparing such a vanillin-based curing agent; a third objective is to provide an anti-corrosion coating; a fourth objective is to provide a coating layer; and a fifth objective is to provide applications of the vanillin-based curing agent or the anti-corrosion coating.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A first aspect of the present invention provides a vanillin-based curing agent comprising the following raw materials: vanillin, amino monomer, and acyl chloride monomer.

[0006] Preferably, the amino monomer includes at least one of aliphatic amines, cycloaliphatic amines, aromatic amines, and polyamides; more preferably, the amino monomer includes at least one of diethylenetriamine, triethylenetetramine, 1,3-cyclohexanedimethylamine, isophoronediamine, m-phenylenediamine, m-phenylenediamine, diaminodiphenylmethane, polyamide-6, and polyamide-66.

[0007] Preferably, the acyl chloride monomer includes at least one of benzoyl chloride, dodecyl chloride, propionyl chloride, palmitoyl chloride, octanoyl chloride, terephthaloyl chloride, acryloyl chloride, and stearyl chloride.

[0008] Preferably, by weight, the vanillin-based curing agent comprises the following raw materials: 0.1-20 parts vanillin, 0.1-40 parts acyl chloride monomer, 0.1-30 parts amino monomer, 0.1-30 parts neutralizing agent, and 0.1-50 parts alkali solution; more preferably, the vanillin-based curing agent comprises the following raw materials: 10-20 parts vanillin, 20-30 parts acyl chloride monomer, 2-10 parts amino monomer, 15-25 parts neutralizing agent, and 0.1-50 parts alkali solution.

[0009] Preferably, the neutralizing agent comprises at least one of an organic base, an alkali metal hydroxide, an alkali metal carbonate, and an alkali metal bicarbonate; more preferably, the neutralizing agent comprises at least one of triethylamine, sodium hydroxide, potassium hydroxide, sodium bicarbonate, and sodium carbonate.

[0010] Preferably, the alkaline source of the alkaline solution includes at least one of alkali metal hydroxide, alkali metal carbonate, and alkali metal bicarbonate; more preferably, the alkaline source of the alkaline solution includes at least one of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, sodium bicarbonate, and potassium bicarbonate.

[0011] A second aspect of the present invention provides a method for preparing the vanillin-based curing agent described in the first aspect of the present invention, comprising the following steps:

[0012] S1. Dissolve vanillin and neutralizing agent, add acyl chloride monomer, react, and collect solid product;

[0013] S2. Dissolve the solid product, add it dropwise to an alkaline solution, collect the oil phase, and obtain the modified vanillin with an active ester structure.

[0014] S3. Dissolve the modified vanillin with the active ester structure, add an amino monomer, and react to obtain the vanillin-based curing agent.

[0015] Preferably, in step S1, the vanillin and the neutralizing agent are dissolved in a first solvent; the first solvent includes at least one of tetrahydrofuran, chloroform, toluene, N,N-dimethylformamide, N,N-dimethylacetamide, acetone, and ethanol.

[0016] Preferably, in step S1, the solid-liquid ratio of the total mass of vanillin and neutralizing agent to the first solvent is 1g:(2-5)mL; more preferably, the solid-liquid ratio of the total mass of vanillin and neutralizing agent to the first solvent is 1g:(2-4)mL.

[0017] Preferably, in step S1, the dissolution process of vanillin and neutralizing agent is aided by ultrasound; the ultrasound time is 10-50 minutes.

[0018] Preferably, in step S1, the reaction temperature is -5 to 30°C, and the reaction time is 10 to 72 hours.

[0019] Preferably, in step S1, after the reaction is completed, the first solvent is removed and the solid product is collected.

[0020] Preferably, in step S2, the solid product is dissolved in a second solvent, the second solvent comprising at least one of ethyl acetate, dichloromethane, chloroform, and toluene.

[0021] Preferably, in step S2, the solid-liquid ratio of the solid product to the second solvent is 1 g:(2-2000) mL.

[0022] Preferably, in step S2, after collecting the oil phase, the process further includes washing with deionized water and drying.

[0023] Specifically, in step S2, after the solid product is dissolved, an alkaline solution is added dropwise to ensure that the unreacted acyl chloride is fully hydrolyzed and that the generated hydrochloric acid reacts fully with the sodium bicarbonate.

[0024] Preferably, in step S3, the modified vanillin with the active ester structure is dissolved in a third solvent; the third solvent includes at least one of ethanol, methanol, tetrahydrofuran, toluene, and dimethyl sulfoxide.

[0025] Preferably, in step S3, the solid-liquid ratio of the modified vanillin with the active ester structure to the third solvent is 1g:(8-12)mL; more preferably, the solid-liquid ratio of the modified vanillin with the active ester structure to the third solvent is 1g:(9-11)mL.

[0026] Preferably, in step S3, the reaction temperature is 30-80°C; more preferably, the reaction temperature is 30-50°C.

[0027] Preferably, in step S3, the reaction time is 6-48 hours; more preferably, the reaction time is 6-10 hours.

[0028] Preferably, in step S3, after the reaction is completed, the product is further washed with a fourth solvent, filtered, and dried.

[0029] Preferably, the fourth solvent includes at least one of ethanol, methanol, acetone, toluene, and butanone.

[0030] The third aspect of the present invention provides an anti-corrosion coating, comprising, by weight, the following raw materials: 0.01-10 parts of the vanillin-based curing agent described in the first aspect of the present invention, 0.01-10 parts of the amino monomer, and 0.01-50 parts of the epoxy resin.

[0031] Preferably, in the anti-corrosion coating, the molar ratio of the amino monomer to the vanillin-based curing agent is (2-9):1; more preferably, the molar ratio of the amino monomer to the vanillin-based curing agent is (2-4):1.

[0032] Preferably, the amino monomer includes at least one of aliphatic amines, cycloaliphatic amines, aromatic amines, and polyamides.

[0033] Preferably, the epoxy resin includes at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, aliphatic glycidyl ether epoxy resin, glycidyl ester type epoxy resin, and alicyclic epoxy resin.

[0034] Preferably, the anti-corrosion coating further comprises the following raw materials by weight: 0.01-30 parts solvent and 0.0001-5 parts additives.

[0035] Preferably, the solvent includes at least one selected from dichloromethane, toluene, tetrahydrofuran, acetone, chloroform, and ethanol.

[0036] Preferably, the additive includes at least one of a diluent, an accelerator, a curing agent, and a catalyst; more preferably, the catalyst includes at least one of triethylamine, 4-dimethylaminopyridine, 2-methylimidazole, boron trifluoride, benzyldimethylamine, and 2-ethyl-4-methylimidazole.

[0037] Preferably, the method for preparing the anti-corrosion coating includes the following steps:

[0038] The anti-corrosion coating is obtained by mixing vanillin-based curing agent, amino monomer, additives, epoxy resin and solvent.

[0039] A fourth aspect of the present invention provides a coating formed from an anti-corrosion coating comprising the third aspect of the present invention.

[0040] Preferably, during the coating formation process, the curing temperature of the anti-corrosion coating is 100-200°C; more preferably, the curing temperature of the anti-corrosion coating is 100-180°C.

[0041] Preferably, during the coating formation process, the curing time of the anti-corrosion coating is 1 to 15 hours; more preferably, the curing time of the anti-corrosion coating is 2 to 10 hours.

[0042] The fifth aspect of the present invention provides the application of the vanillin-based curing agent described in the first aspect of the present invention, or the anti-corrosion coating described in the third aspect of the present invention, in the anti-corrosion of metal product surfaces.

[0043] Preferably, the metal products include marine engineering facilities, electronic devices, ships, automobiles, and aircraft.

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] 1) The vanillin-based curing agent provided by this invention uses vanillin from biomass as raw material. The raw material source is wide and green and environmentally friendly. It converts vanillin into curing agent, which increases the added value of biomass materials and reduces the dependence on petroleum-based ammonia curing agents, thus relieving the pressure on petroleum-based polymer materials.

[0046] 2) The preparation method of the vanillin-based curing agent provided by the present invention has simple steps, mild reaction conditions, strong operability, and is conducive to large-scale production;

[0047] 3) The anti-corrosion coating provided by the present invention uses a vanillin-based curing agent containing an active ester structure to replace part of the amino curing agent to cure epoxy resin, which can reduce the content of hydroxyl groups in the coating and reduce the dielectric constant and dielectric loss of the coating.

[0048] 4) The coating provided by the present invention has a dense three-dimensional network structure, and has the characteristics of corrosion resistance, low dielectric constant and dielectric loss, and excellent antibacterial properties. It has a strong protective effect on metals and can extend the service life of metals. Attached Figure Description

[0049] Figure 1 The reaction route diagram for preparing the vanillin curing agent of this invention is shown below;

[0050] Figure 2 This is a reaction route diagram for curing epoxy resin with vanillin curing agent of the present invention;

[0051] Figure 3 The infrared spectra of vanillin, modified vanillin with an active ester structure, and vanillin-based curing agent in Example 1 are shown.

[0052] Figure 4 The dielectric constants of the coatings formed by the paints in Examples 2-4 and Comparative Example 1 are shown.

[0053] Figure 5 The dielectric loss results of the coatings formed by the paints in Examples 2-4 and Comparative Example 1 are shown.

[0054] Figure 6 The results are the electrochemical performance test results of the coatings formed by the paints in Examples 2-4 and Comparative Example 1;

[0055] Figure 7 The images show the antibacterial effect of the coatings formed by the paints in Examples 2-4 and Comparative Example 1 against Staphylococcus aureus. Detailed Implementation

[0056] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0057] Figure 1 This is a reaction route diagram for preparing the vanillin curing agent according to the present invention. Figure 1 As can be seen, the present invention first prepares modified vanillin (VAE) with active ester structure based on the esterification reaction between the acyl chloride group on the acyl chloride monomer and the hydroxyl group on vanillin; then prepares vanillin-based curing agent (VAEI) based on the amine-aldehyde condensation reaction between the amino group on the amino monomer and the aldehyde group on vanillin.

[0058] Figure 2 This is a reaction route diagram for curing epoxy resin with the vanillin curing agent of the present invention. Figure 2 It is understood that the present invention utilizes the ring-opening reaction of the active ester groups on the vanillin-based curing agent, the amino groups on the amino monomer, and the epoxy groups on the epoxy resin to prepare the anti-corrosion coating.

[0059] The following will combine Figure 1 and Figure 2 The preparation process of vanillin curing agent and anti-corrosion coating is described:

[0060] Example 1

[0061] This embodiment prepares a vanillin-based curing agent, and the steps are as follows:

[0062] S1. Add 15.20g vanillin, 20.20g triethylamine and 100.00mL tetrahydrofuran to a flask, sonicate to dissolve for 30min, slowly add 23.47g benzoyl chloride dropwise to the flask, react at room temperature for 48h, remove tetrahydrofuran, and collect the solid product.

[0063] S2. Add 1-10 mL of ethyl acetate to dissolve the solid product, and add it dropwise to a saturated sodium bicarbonate aqueous solution. Collect the oil phase, wash it twice with deionized water, and dry it to obtain modified vanillin with an active ester structure.

[0064] S3. Add 10.00g of modified vanillin containing an active ester structure and 100.00mL of anhydrous ethanol to a flask, add 3.87g of diaminodiphenylmethane, react at 45℃ for 8h, filter the mixture after the reaction and wash with anhydrous ethanol, dry the precipitate to obtain vanillin-based curing agent.

[0065] Example 2

[0066] This embodiment prepares an anti-corrosion coating, and the steps are as follows:

[0067] 0.128g of vanillin-based curing agent and 0.455g of diaminodiphenylmethane were dissolved in 0.8g of dichloromethane, wherein the molar ratio of diaminodiphenylmethane to vanillin-based curing agent was 9:1. Then, 2g of aliphatic glycidyl ether epoxy resin was added to obtain an anti-corrosion coating.

[0068] Example 3

[0069] This embodiment prepares an anti-corrosion coating, and the steps are as follows:

[0070] 0.256g of vanillin-based curing agent and 0.40g of diaminodiphenylmethane were dissolved in 1.0g of dichloromethane, wherein the molar ratio of diaminodiphenylmethane to vanillin-based curing agent was 8:2. Then, 2g of aliphatic glycidyl ether epoxy resin was added to obtain an anti-corrosion coating.

[0071] Example 4

[0072] This embodiment prepares an anti-corrosion coating, and the steps are as follows:

[0073] 0.384g of vanillin-based curing agent and 0.353g of diaminodiphenylmethane were dissolved in 1.0g of dichloromethane, wherein the molar ratio of diaminodiphenylmethane to vanillin-based curing agent was 7:3. Then, 2g of aliphatic glycidyl ether epoxy resin was added to obtain an anti-corrosion coating.

[0074] Comparative Example 1

[0075] This comparative example prepares an anti-corrosion coating, which differs from Example 1 in that it does not contain a vanillin-based curing agent. The steps are as follows:

[0076] 0.445g of diaminodiphenylmethane was dissolved in 0.8g of dichloromethane, and then 2g of aliphatic glycidyl ether epoxy resin was added to obtain an anti-corrosion coating.

[0077] Characterization and performance testing

[0078] 1. The vanillin, the modified vanillin with an active ester structure, and the vanillin-based curing agent in Example 1 were characterized by infrared spectroscopy:

[0079] The characteristic functional groups of the samples were characterized using a Nicolet iS10 Fourier transform infrared spectrometer (Germany). Figure 3 The infrared spectra of vanillin, modified vanillin with an active ester structure, and vanillin-based curing agent in Example 1 are shown below. Figure 3It can be seen that vanillin was first modified with an acyl chloride monomer to obtain the intermediate product modified vanillin (VAE) containing an active ester structure. The main functional groups of vanillin were detected on the VAE at 3145 cm⁻¹. -1 No hydroxyl characteristic peaks were detected nearby, but at 1737 cm⁻¹ -1 A new characteristic peak of the ester functional group appeared, indicating that this step mainly utilized the esterification reaction between the acyl chloride group of the acyl chloride monomer and the hydroxyl group of vanillin; then, the modified vanillin containing the active ester structure was modified by the amino monomer, and the main characteristic peak of VAE was detected on the vanillin-based curing agent (VAEI), but at 1668 cm⁻¹... -1 The characteristic peak of the aldehyde group disappears at 1580 cm⁻¹. -1 and 1340cm -1 The presence of C=N and CN characteristic peaks indicates that this step mainly utilizes the amine-aldehyde condensation reaction between the amino group of the amino monomer and the aldehyde group of vanillin, and also indicates that the vanillin-based curing agent (VAEI) in Example 1 was successfully prepared.

[0080] 2. Coating performance test:

[0081] 1) Coating preparation: The anti-corrosion coatings prepared in Examples 2-4 and Comparative Example 1 were spread on the surface of the steel plate using a coater. They were first placed in an oven at 60°C for 20 minutes to remove the solvent, and then placed in ovens at 100°C, 130°C, 160°C and 180°C for 2 hours, 3 hours, 2 hours and 2 hours respectively to cure in depth, thus obtaining the coating.

[0082] 2) Electrochemical testing: Electrochemical impedance spectroscopy (EIS) of the coating was tested using an electrochemical workstation (CHI-660E). During the test, the corrosive medium was 3.5 wt% saline solution, with an Ag / AgCl electrode as the reference electrode and a platinum plate as the counter electrode.

[0083] 3) Antibacterial test: Dilute the Staphylococcus aureus bacterial solution to 10 using sterile PBS buffer. 6 The bacterial solution was diluted to CFU / mL, and then 5 mL of the diluted bacterial solution was added to the sterile preservative coating sample and mixed thoroughly (the final concentration of the sample was 1.28 mg / mL). An equal volume of bacterial solution was added to a blank bacterial culture tube as a control. The mixture was incubated in a constant temperature shaker (37℃) for 6 h. After incubation, the bacterial solution was serially diluted 10-fold with sterile PBS buffer, and 100 μL of the diluted solution was evenly spread on LB solid medium and placed in a 37℃ constant temperature incubator for 18 h. Finally, the solution was removed, photographed, and the colony count was recorded.

[0084] 4) Dielectric property test: The dielectric properties of the sample were measured at 25°C using a dielectric meter (Agilent 4294A). The sample size was 10mm × 10mm × 1mm.

[0085] Table 1 below shows the performance test results of the anti-corrosion coatings prepared in Examples 2-4 and Comparative Example 1.

[0086] Table 1. Performance test results of the anti-corrosion coatings prepared in Examples 2-4 and Comparative Example 1.

[0087]

[0088] As shown in Table 1, the coating in Comparative Example 1, without the addition of vanillin-based curing agent, although diaminodiphenylmethane provides some curing effect, exhibits a high dielectric constant of 4.16 at 10 MHz, an antibacterial rate of 4.8% against Staphylococcus aureus, and an impedance modulus of 3.16 × 10⁻⁶ after immersion in salt water for 150 days. 7 Ω·cm 2 In Examples 2-4, a vanillin-based curing agent was added to the anti-corrosion coatings. The resulting coatings had a dielectric constant of 3.64-3.72 at 10 MHz. Compared with Comparative Example 1, the dielectric constant of the coating at 10 MHz was reduced. This shows that adding the vanillin-based curing agent provided by this invention to the coating can effectively reduce the dielectric constant of the coating. Furthermore, as the amount of vanillin-based curing agent in the coating increases, the dielectric constant of the coating gradually decreases. This is mainly because the use of vanillin-based curing agent reduces the hydroxyl content generated during the epoxy resin curing process. This indicates that the vanillin-based curing agent and anti-corrosion coating provided by this invention can be applied to the anti-corrosion of metal surfaces of electronic products.

[0089] Figure 4 The dielectric constants of the coatings formed by the paints in Examples 2-4 and Comparative Example 1 are shown. Figure 5 The dielectric loss results of the coatings formed by the paints in Examples 2-4 and Comparative Example 1 are obtained from... Figure 4 and Figure 5 It can be seen that the dielectric constant and dielectric loss of the anti-corrosion coatings formed in Examples 2-4 and Comparative Example 1 exhibit the same trend: the dielectric constant decreases with increasing frequency, while the dielectric loss increases with increasing frequency. The coating in Comparative Example 1 has the highest dielectric constant and dielectric loss. For the coatings formed in Examples 2-4, both the dielectric constant and dielectric loss decrease with increasing vanillin-based curing agent content in the coating, indicating that introducing vanillin with an active ester structure into the resin can improve the dielectric properties of the coating to a certain extent, and its properties are adjustable.

[0090] The resistivity modulus of the anti-corrosion coating formed in Examples 2-4 after immersion in salt water for 150 days was 5.01 × 10⁻⁶.7 -1.0×10 9 Ω·cm 2 Compared with Comparative Example 1, the impedance modulus increases. Figure 6 The results are the electrochemical performance test results of the coatings formed by the paints in Examples 2-4 and Comparative Example 1, wherein... Figure 6 (a) shows the electrochemical performance test results of the coating formed by the paint in Comparative Example 1. Figure 6 (b) shows the electrochemical performance test results of the coating formed by the paint in Example 2. Figure 6 (c) shows the electrochemical performance test results of the coating formed by the paint in Example 3. Figure 6 (d) shows the electrochemical performance test results of the coating formed by the paint in Example 4. Figure 6 It can be seen that as the immersion time in salt water increases, the impedance modulus of the coating decreases, indicating that the anti-corrosion performance of the coating weakens with increasing immersion time. Among them, the coating formed by the paint in Comparative Example 1 has the lowest impedance modulus, indicating that its anti-corrosion performance is the worst. The impedance modulus of the coatings formed by the paints in Examples 2-4 is higher than that in Comparative Example 1, indicating that adding vanillin-based curing agent to the paint can improve the anti-corrosion performance of the paint, and the anti-corrosion performance of the coating gradually increases with the increase of vanillin-based curing agent content in the paint.

[0091] In Examples 2-4, the coatings formed an antibacterial rate of 5.7-19.6% against Staphylococcus aureus. Compared with Comparative Example 1, the antibacterial rate of the coatings against Staphylococcus aureus was significantly increased, indicating that the introduction of vanillin-based curing agent into the coating can improve the antibacterial performance of the coating against Staphylococcus aureus. Moreover, the antibacterial performance of the coating gradually increases with the increase of the amount of vanillin-based curing agent in the coating. Figure 7 The figures show the antibacterial effects of the coatings formed by the paints in Examples 2-4 and Comparative Example 1 against Staphylococcus aureus. Figure 7 (a) is the Staphylococcus aureus control group. Figure 7 (b) The antibacterial effect of the coating formed by the paint in Comparative Example 1 against Staphylococcus aureus. Figure 7 (c) The antibacterial effect of the coating formed by the paint in Example 2 against Staphylococcus aureus. Figure 7 (d) shows the antibacterial effect of the coating formed by the paint in Example 3 against Staphylococcus aureus. Figure 7 (e) illustrates the antibacterial effect of the coating formed by the paint in Example 4 against Staphylococcus aureus. Figure 7 It can be seen that in Examples 2-4, vanillin-based curing agents were added to the coatings. After the culture was completed, the number of colonies on the culture medium decreased, indicating that the introduction of vanillin-based curing agents into the coatings enhanced the coating with imine groups, which has antibacterial ability against Staphylococcus aureus. Moreover, the antibacterial ability is enhanced with the increase of vanillin-based curing agent content.

[0092] This invention prepares a vanillin-based curing agent using vanillin as the main raw material. Vanillin, as a biomass material, has the characteristics of wide availability, renewability, and environmental friendliness, and its surface also has active sites such as hydroxyl, aldehyde, and methoxy groups. Through modification, this invention enables the vanillin-based curing agent to contain active ester and imine groups, which facilitates the curing of epoxy resins. This imparts anti-corrosion, antibacterial, and low dielectric properties to the cured coating, allowing the coating to be applied to electronic products, enhancing the protection of metals, and meeting the coating requirements of metal products such as marine engineering facilities, electronic devices, ships, automobiles, and aircraft.

Claims

1. A vanillin-based curing agent, characterized in that, Its structural formula is shown in equation (Ⅰ): Equation (Ⅰ).

2. The vanillin-based curing agent according to claim 1, characterized in that, The vanillin-based curing agent is prepared by a method comprising the following steps: S1. Dissolve vanillin and neutralizing agent, add acyl chloride monomer, react, and collect solid product; S2. Dissolve the solid product, add it dropwise to an alkaline solution, collect the oil phase, and obtain the modified vanillin with an active ester structure. S3. Dissolve the modified vanillin with the active ester structure, add an amino monomer, and react to obtain the vanillin-based curing agent.

3. The vanillin-based curing agent according to claim 2, characterized in that, The prepared vanillin-based curing agent, by mass, comprises the following amounts of raw materials: 10-20 parts vanillin, 20-30 parts acyl chloride monomer, 2-10 parts amino monomer, 15-25 parts neutralizing agent, and 0.1-50 parts alkali solution.

4. The vanillin-based curing agent according to claim 3, characterized in that, The amino monomer is diaminodiphenylmethane; the acyl chloride monomer is benzoyl chloride.

5. The vanillin-based curing agent according to claim 2, characterized in that, In step S1, the reaction temperature is -5~30℃; the reaction time is 10-72h.

6. The vanillin-based curing agent according to claim 2, characterized in that, In step S3, the reaction temperature is 30-80℃ and the reaction time is 6-48h.

7. An anti-corrosion coating, characterized in that, The preparation materials, by weight, include the following raw materials: 0.01-10 parts of vanillin-based curing agent as described in any one of claims 1-6, 0.01-10 parts of amino monomer, and 0.01-50 parts of epoxy resin.

8. A coating, characterized in that, It is formed by the anti-corrosion coating as described in claim 7.

9. The coating according to claim 8, characterized in that, During the coating formation process, the curing temperature of the anti-corrosion coating is 100~200℃; the curing time is 1~15h.

10. The vanillin-based curing agent according to any one of claims 1-6, or the anti-corrosion coating according to claim 7, used in the anti-corrosion of metal product surfaces.

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