Pyridine derivative and lignin modified graphene oxide-based intelligent anti-corrosion composite coating and its application

Abstract

The present invention belongs to the technical field of polymer materials, and specifically relates to a pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating and its application. The preparation method of the pyridine derivative and lignin-modified graphene oxide of the present invention is to modify the graphene oxide with a monomer containing a pyridine structure and double-bond lignin. The present invention mixes the pyridine derivative and lignin-modified graphene oxide, a resin and an auxiliary agent, and after stirring evenly, obtains the pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating. The coating obtained by curing the pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating prepared by the present invention is a dense coating material with a three-dimensional network structure, which not only has excellent mechanical properties, but also has intelligent anti-corrosion properties, can greatly extend the service life of metal materials, and save maintenance and labor costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and specifically relates to a pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating and applications thereof. Background Art

[0002] Metal corrosion is one of the main causes of failure and operational accidents in metal equipment such as ships, bridges, and machinery. Therefore, anti-corrosion treatment of metal equipment is crucial. Currently, methods for preventing metal corrosion include modifying the metal's composition, applying protective coatings to the metal surface, electrochemical protection, and adding corrosion inhibitors. Of these methods, applying anti-corrosion coatings directly to the metal surface to form a protective layer is the most widely used, direct, and effective anti-corrosion strategy.

[0003] At present, researchers believe that the coating prepared by adding the two-dimensional nanomaterial graphene oxide (GO) to the coating has excellent anti-corrosion properties. It can not only eliminate defects such as micropores caused by solvent evaporation during the curing process of the coating, but also extend the path of penetration of the corrosive medium by virtue of the "maze effect" of the nanomaterial, thereby helping to enhance the anti-corrosion performance of the coating. However, for GO materials, they have a large specific surface area, strong van der Waals forces and π-π interactions, which make the GO material easy to self-aggregate and have poor compatibility with resins, reducing the physical barrier effect of the GO material in the coating. Therefore, it is necessary to modify GO. The raw materials currently used to modify GO are mostly derived from petroleum products, which are easy to cause environmental pollution and are not conducive to sustainable development. Moreover, the main resin of the anti-corrosion coating and the modified GO material do not have the ability to automatically repair the damaged coating, resulting in poor long-term anti-corrosion performance of the coating. Summary of the Invention

[0004] The first object of the present invention is to provide a method for preparing a pyridine derivative and lignin-modified graphene oxide. The second object of the present invention is to provide a pyridine derivative and lignin-modified graphene oxide prepared by the preparation method. The third object of the present invention is to provide a pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating. The fourth object of the present invention is to provide an application of the pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating.

[0005] According to a first aspect of the present invention, a method for preparing pyridine derivatives and lignin-modified graphene oxide is provided, wherein the method comprises modifying graphene oxide with a monomer containing a pyridine structure and double-bond lignin to obtain pyridine derivatives and lignin-modified graphene oxide.

[0006] The present invention prepares double-bond lignin based on the substitution reaction between the phenolic hydroxyl groups on lignin and a double-bond halogen monomer; and prepares a monomer containing a pyridine structure based on the substitution reaction between a monomer containing amino and hydroxyl functional groups and a pyridine derivative monomer.

[0007] The monomer containing a pyridine structure is grafted onto the graphene oxide by utilizing the amidation and ring-opening reaction between the amino group on the monomer containing a pyridine structure and the carboxyl group or epoxy group on the graphene oxide;

[0008] Double-bond lignin is grafted onto graphene oxide by utilizing a polyaddition reaction between the isocyanate groups on the diisocyanate monomer and the hydroxyl groups on the double-bond lignin, and a polyaddition reaction between the isocyanate groups on the diisocyanate monomer and the hydroxyl groups on the graphene oxide;

[0009] The above modification process can give graphene oxide reactive and functional characteristics, which not only weakens the self-aggregation ability of graphene oxide, but also gives graphene oxide excellent mechanical properties and intelligent anti-corrosion properties.

[0010] At the same time, the present invention uses double-bond lignin as a cross-linking agent, and increases the interfacial interaction and system cross-linking density of the filler (pyridine derivatives and lignin-modified graphene oxide) and the resin through free radical polymerization between the double bonds on the double-bond lignin and the terminal double bonds on the resin, thereby enhancing the mechanical properties and intelligent anti-corrosion function of the coating.

[0011] In some embodiments, the method for preparing pyridine derivatives and lignin-modified graphene oxide of the present invention comprises the following steps:

[0012] S1. Adding graphene oxide and a monomer containing a pyridine structure to a first solvent, ultrasonicating for 5-60 minutes, then adding a water absorbent, stirring at 50-80° C. for 12-36 hours, centrifuging, washing, and drying to obtain functionalized graphene oxide;

[0013] S2. Dispersing the functionalized graphene oxide in a second solvent, then adding diisocyanate and a catalyst, reacting at 50-80°C for 1-6 hours, then adding double-bond lignin, reacting at 50-80°C for 1-12 hours, centrifuging, washing and drying to obtain a pyridine derivative and lignin-modified graphene oxide.

[0014] In some embodiments, the method for preparing a monomer containing a pyridine structure comprises the following steps:

[0015] Add a monomer containing amino and hydroxyl functional groups and a base to a solvent, stir at 50-80°C for 20-60 minutes, then add a pyridine derivative monomer, react at 50-80°C for 12-36 hours, then cool to room temperature, filter, wash, and dry to obtain a monomer containing a pyridine structure.

[0016] In some embodiments, the monomer containing amino and hydroxyl functional groups includes at least one of 6-amino-1-hexanol, 2-methyl-4-aminophenol, DL-aminopropanol, and 2-methoxy-5-aminophenol.

[0017] In some embodiments, the base comprises at least one of potassium hydroxide, sodium hydroxide, potassium carbonate, and sodium carbonate.

[0018] In some embodiments, the solvent includes at least one of toluene, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, chloroform, and dimethyl sulfoxide.

[0019] In some embodiments, the pyridine derivative monomer includes at least one of 4′-bromo-2,2′:6′,2″-terpyridine, 4′-chloro-2,2′:6′,2″-terpyridine, and 4-chloropyridine.

[0020] In some embodiments, based on parts by mass, the amount of the monomer containing amino and hydroxyl functional groups is 0.1-20 parts, the amount of the base is 1-20 parts, the amount of the solvent is 1-110 parts, and the amount of the pyridine derivative monomer is 0.1-30 parts.

[0021] In some embodiments, the first solvent includes at least one of toluene, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, chloroform, and dimethyl sulfoxide.

[0022] In some embodiments, the water absorbing agent includes at least one of anhydrous magnesium sulfate, anhydrous sodium sulfate, and dicyclohexylcarbodiimide.

[0023] In some embodiments, the second solvent includes at least one of toluene, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, chloroform, and dimethyl sulfoxide.

[0024] In some embodiments, the diisocyanate includes at least one of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, and isophorone diisocyanate.

[0025] In some embodiments, the catalyst is dibutyltin dilaurate.

[0026] In some embodiments, the double-bonded lignin has a molecular weight of 1000 g / mol-5000 g / mol and includes at least one of double-bonded fatty lignin, double-bonded isomeric lignin, double-bonded syringyl lignin, double-bonded guaiacyl lignin, and double-bonded p-hydroxyphenyl lignin.

[0027] In some embodiments, the preparation method of double bond lignin comprises the following steps: lignin (1g) is added to a flask, and then 20mL of anhydrous ethanol and 20mL of a NaOH aqueous solution (at a concentration of 0.5mol / L) are added to dissolve it. Afterwards, allyl bromide (0.7g) is slowly dripped into the above-mentioned flask, the temperature is raised to 55°C, and the reaction is stirred for 24 hours. After the reaction is completed, it is cooled to room temperature, 1mol / L of HCl solution is dripped into the reaction product and its pH is adjusted to 3 to precipitate the product. The obtained precipitate is washed with excess deionized water and filtered, and the obtained filter cake is dried in a vacuum oven at 50°C for 24 hours to obtain double bond lignin.

[0028] In some embodiments, the amount of graphene oxide is 0.1-10 parts by mass, the amount of the monomer containing a pyridine structure is 0.1-10 parts by mass, the amount of the first solvent is 1-80 parts by mass, the amount of the water absorbent is 0.1-20 parts by mass, the amount of the second solvent is 1-80 parts by mass, the amount of the diisocyanate is 0.1-10 parts by mass, the amount of the catalyst is 0.0001-2 parts by mass, and the amount of the double bond lignin is 0.01-10 parts by mass.

[0029] According to a second aspect of the present invention, provided are pyridine derivatives and lignin-modified graphene oxide prepared by the above-mentioned preparation method.

[0030] According to the third aspect of the present invention, a pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating is provided. The raw material composition thereof comprises, in parts by mass: 0.0025-0.5 parts of the above-mentioned pyridine derivative and lignin-modified graphene oxide, 1-50 parts of resin, and 0.001-10 parts of additives.

[0031] In some embodiments, the resin includes at least one of epoxy resin, epoxy vinyl ester resin, polyurethane resin, phenolic resin, and acrylic resin.

[0032] In some embodiments, the auxiliary agent includes at least one of a diluent, an accelerator, a curing agent, and a catalyst. Specifically, the diluent is styrene; the accelerator is cobalt naphthenate; the curing agent is 2-butanone peroxide; and the catalyst is dibutyltin dilaurate.

[0033] According to a fourth aspect of the present invention, there is provided the use of the above-mentioned pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating as an anti-corrosion coating for metal surfaces of marine engineering facilities, ships, automobiles, and aircraft.

[0034] The beneficial effects of the present invention include:

[0035] (1) The present invention utilizes double-bond lignin, a biomass material that is abundant, green, pollution-free, and renewable, as a modifier for graphene oxide, expanding the application of biomass materials in the field of corrosion protection and alleviating the pressure on the use of petroleum-based products. The present invention introduces double-bond lignin into graphene oxide through a chemical reaction, thereby weakening the self-aggregation ability of graphene oxide.

[0036] (2) The present invention utilizes the metal corrosion product Fe 2+ Graphene oxide is functionalized with monomers containing pyridine structures with strong complexing effects, giving graphene oxide intelligent response properties to metal corrosion products.

[0037] (3) The present invention prepares a composite coating with intelligent anti-corrosion function by blending the prepared pyridine derivative, lignin-modified graphene oxide and resin. The coating obtained by curing the prepared composite coating is a dense coating material with a three-dimensional network structure. It not only has excellent mechanical properties, but also has intelligent anti-corrosion properties, thereby greatly extending the service life of metal materials and saving maintenance and labor costs.

[0038] (4) The present invention adopts a two-step method to modify graphene oxide. The preparation process is easy to operate, the reaction conditions are relatively mild, and there is no pollution to the environment. In addition, the preparation process is simple, the raw materials are easily available, and the operability is strong, which is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The following is a reaction route for preparing graphene oxide in the present invention.

[0040] Figure 2 This is the reaction route for preparing double-bond lignin in the present invention.

[0041] Figure 3 This is a reaction scheme for preparing a monomer containing a pyridine structure in Example 1 of the present invention.

[0042] Figure 4 This is a reaction roadmap for the modification process of graphene oxide and the preparation of the composite coating in Example 1 of the present invention.

[0043] Figure 5 The electrochemical performance test results of the coating are shown in Figure 2.

[0044] Figure 6 This is the scratch self-healing morphology of the coating after being immersed in 3.5wt% salt water for 3 days. DETAILED DESCRIPTION

[0045] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto. The materials involved in the following examples can all be obtained from commercial channels.

[0046] In the following examples and comparative examples, graphene oxide (GO) was prepared using a modified Hummers method. The specific preparation method includes the following steps: 3g of graphene powder (G), 1.5g of NaNO3, and 69mL of concentrated H2SO4 (98%) were added to a waterbath flask at approximately 3°C and stirred at 150 rpm for 30 minutes. Then, 9g of KMnO4 was slowly added to the flask and stirred at 35°C for 2 hours. After the material in the flask turned into a brown paste, 150mL of deionized water was added and the mixture was reacted at 90°C for 30 minutes. After the reaction was completed, the temperature of the reaction product was cooled to room temperature, and 7.5mL of hydrogen peroxide and 420mL of deionized water were added and mixed uniformly to obtain a mixture. The mixture was then poured into 900mL of deionized water, stirred at 200 rpm for 15 minutes, and allowed to stand overnight. The supernatant was then removed and the mixture was washed three times with a mixture of HCl and deionized water (HCl:deionized water, volume ratio 1:10). The washed material is then dispersed in deionized water and dialyzed for 7 days using a 77 mm wide dialysis bag (1000 Da), with the dialysis water replaced every day. Finally, the dialyzed material is freeze-dried to obtain graphene oxide (GO). The reaction route for preparing graphene oxide is as follows: Figure 1 shown.

[0047] The preparation method of the double bond lignin (ABL) used is as follows: 1g of lignin (BL) is added to a flask, and then 20mL of anhydrous ethanol and 20mL of NaOH aqueous solution (concentration of 0.5mol / L) are added to dissolve it. Then 0.7g of allyl bromide is slowly dripped into the above flask, the temperature is raised to 55°C, and stirred for 24h. After the reaction is completed, it is cooled to room temperature, and an appropriate amount of 1mol / L HCl solution is added to adjust the pH of the solution to 3 to precipitate the product. The obtained precipitate is then rinsed with deionized water and filtered, and the obtained filter cake is then dried in a vacuum oven at 50°C for 24h to obtain double bond lignin (ABL). The reaction route for preparing double bond lignin is as follows Figure 2 shown.

[0048] The preparation method of the epoxy vinyl ester resin (D-E44) used is based on the applicant's published paper (Chang-AnXu, Zhuangzhuang Chu, Xingchi Li, et al. Vanillin and organosiliconfunctionalized graphene oxide modified ester resin composite coatings with excellent anti-corrosion properties [J]. Progress in Organic Coatings, 2023, DOI: 10.1016 / j.porgcoat.2023.107804).

[0049] Example 1

[0050] The preparation method of the pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating of this embodiment comprises the following steps:

[0051] (1) Preparation of monomers containing pyridine structure:

[0052] 0.67 g of 6-amino-1-hexanol and 2.34 g of potassium hydroxide were added to 110 mL of dimethyl sulfoxide (DMSO), stirred at 200 rpm at 60 ° C for 30 min, and then 1 g of 4'-chloro-2,2':6',2"-terpyridine was added and reacted at 75 ° C for 24 h. The product was then cooled to room temperature and filtered, washed with deionized water, and freeze-dried to obtain a monomer containing a pyridine structure (TDD). The reaction route for preparing a monomer containing a pyridine structure is as follows: Figure 3 shown.

[0053] (2) Modification of graphene oxide using monomers containing pyridine structures and double-bond lignin:

[0054] 0.5 g of graphene oxide (GO) and 0.25 g of the monomer containing a pyridine structure (TDD) obtained in step (1) were added to 50 mL of N,N-dimethylformamide (DMF), ultrasonicated for 10 min, and then 0.2 g of a water absorbent, dicyclohexylcarbodiimide, was added. The mixture was stirred at 210 rpm at 60 ° C for 24 h. The product was centrifuged, washed, and dried to obtain functionalized graphene oxide (TGO);

[0055] Subsequently, 0.2 g of functionalized graphene oxide (TGO) was dispersed in 18 mL of N,N-dimethylformamide (DMF), and then 0.15 g of 2,4-toluene diisocyanate (TDI) and 0.04 g of dibutyltin dilaurate were added, and the mixture was reacted at 70 °C for 2 h. Then, 0.05 g of double bond lignin (ABL) with a molecular weight of 2913 g / mol was added, and the mixture was reacted at 75 °C for 4 h. After centrifugation, washing and drying, the product obtained pyridine derivatives and lignin-modified graphene oxide (ATGO).

[0056] (3) Preparation of composite coating:

[0057] 0.003 g of the pyridine derivative and lignin-modified graphene oxide (ATGO) prepared in step (2) was added to a solution consisting of 3 g of epoxy vinyl ester resin (D-E44) and styrene (wherein the mass proportion of styrene was 30 wt%), and then 0.009 g of accelerator cobalt cyclopentaneate and 0.03 g of curing agent 2-butanone peroxide were added. After stirring evenly, a pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating was obtained.

[0058] The modification process of graphene oxide and the reaction route for preparing composite coatings are as follows: Figure 4 In the figure, St is the diluent styrene, and the crosslinking point is the crosslinking point, which is the free radical polymerization connection point between the double bond on the double bond lignin and the double bond resin epoxy vinyl ester resin and the double bond on styrene. The D-E44 and St segments represent the molecular structures of the epoxy vinyl ester resin and styrene.

[0059] Example 2

[0060] The preparation method of the pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating of this embodiment comprises the following steps:

[0061] (1) Preparation of monomers containing pyridine structure:

[0062] 0.67 g of 6-amino-1-hexanol and 2.34 g of potassium hydroxide were added to 50 mL of dimethyl sulfoxide (DMSO), stirred at 210 rpm at 60°C for 30 minutes, and then 1 g of 4'-bromo-2,2':6',2"-terpyridine was added. The reaction was carried out at 75°C for 24 hours. The product was then cooled to room temperature, filtered, washed with deionized water, and freeze-dried to obtain a monomer containing a pyridine structure.

[0063] (2) Modification of graphene oxide using monomers containing pyridine structures and double-bond lignin:

[0064] 0.5 g of graphene oxide and 0.25 g of the monomer containing a pyridine structure obtained in step (1) were added to 20 mL of N,N-dimethylformamide (DMF), ultrasonicated for 10 min, and then 0.3 g of a water absorbent, dicyclohexylcarbodiimide, was added, and stirred at 180 rpm for 24 h at 60 ° C. The product was centrifuged, washed, and dried to obtain functionalized graphene oxide;

[0065] Subsequently, 0.2 g of functionalized graphene oxide was dispersed in 30 mL of N,N-dimethylformamide (DMF), and then 0.15 g of 2,4-toluene diisocyanate (TDI) and 0.004 g of dibutyltin dilaurate were added, and the reaction was carried out at 70 ° C for 2 h. Then, 0.05 g of double-bond lignin with a molecular weight of 2913 g / mol was added, and the reaction was carried out at 75 ° C for 4 h. After centrifugation, washing and drying, the product obtained pyridine derivatives and lignin-modified graphene oxide.

[0066] (3) Preparation of composite coating:

[0067] 0.006 g of the pyridine derivative and lignin-modified graphene oxide prepared in step (2) was added to a solution consisting of 6 g of epoxy vinyl ester resin and styrene (wherein the mass proportion of styrene was 30 wt%), and then 0.018 g of accelerator cobalt cyclopentaneate and 0.06 g of curing agent 2-butanone peroxide were added. After stirring evenly, a pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating was obtained.

[0068] Example 3

[0069] The preparation method of the pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating of this embodiment comprises the following steps:

[0070] (1) Preparation of monomers containing pyridine structure:

[0071] 0.67 g of 6-amino-1-hexanol and 2.34 g of potassium hydroxide were added to 45 mL of dimethyl sulfoxide (DMSO), stirred at 250 rpm at 60°C for 30 minutes, and then 1 g of 4'-bromo-2,2':6',2"-terpyridine was added. The reaction was carried out at 75°C for 24 hours. The product was then cooled to room temperature, filtered, washed with deionized water, and freeze-dried to obtain a monomer containing a pyridine structure.

[0072] (2) Modification of graphene oxide using monomers containing pyridine structures and double-bond lignin:

[0073] 0.5 g of graphene oxide and 0.25 g of the monomer containing a pyridine structure obtained in step (1) were added to 35 mL of N,N-dimethylformamide (DMF), ultrasonicated for 10 min, and then 0.25 g of a water absorbent, dicyclohexylcarbodiimide, was added. The mixture was stirred at 180 rpm for 24 h at 60 ° C. The product was centrifuged, washed, and dried to obtain functionalized graphene oxide;

[0074] Subsequently, 0.2 g of functionalized graphene oxide was dispersed in 50 mL of N,N-dimethylformamide (DMF), and then 0.15 g of 2,4-toluene diisocyanate (TDI) and 0.005 g of dibutyltin dilaurate were added, and the reaction was carried out at 70 ° C for 2 h. Then, 0.05 g of double-bond lignin with a molecular weight of 2913 g / mol was added, and the reaction was carried out at 75 ° C for 4 h. After centrifugation, washing and drying, the product obtained pyridine derivatives and lignin-modified graphene oxide.

[0075] (3) Preparation of composite coating:

[0076] 0.003 g of the pyridine derivative and lignin-modified graphene oxide prepared in step (2) were added to 3 g of polyurethane resin, and then 0.006 g of dibutyltin dilaurate was added. After stirring evenly, a pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating was obtained.

[0077] Example 4

[0078] The preparation method of the pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating of this embodiment comprises the following steps:

[0079] (1) Preparation of monomers containing pyridine structure:

[0080] 0.67 g of 6-amino-1-hexanol and 2.34 g of potassium hydroxide were added to 55 mL of dimethyl sulfoxide (DMSO), stirred at 240 rpm at 60°C for 30 minutes, and then 1 g of 4'-bromo-2,2':6',2"-terpyridine was added. The reaction was carried out at 75°C for 24 hours. The product was then cooled to room temperature, filtered, washed with deionized water, and freeze-dried to obtain a monomer containing a pyridine structure.

[0081] (2) Modification of graphene oxide using monomers containing pyridine structures and double-bond lignin:

[0082] 0.5 g of graphene oxide and 0.25 g of the monomer containing a pyridine structure obtained in step (1) were added to 42 mL of N,N-dimethylformamide (DMF), ultrasonicated for 10 min, and then 0.15 g of a water absorbent, dicyclohexylcarbodiimide, was added, and stirred at 200 rpm for 24 h at 60 ° C. The product was centrifuged, washed, and dried to obtain functionalized graphene oxide;

[0083] Subsequently, 0.2 g of functionalized graphene oxide was dispersed in 35 mL of N,N-dimethylformamide (DMF), and then 0.15 g of 2,4-toluene diisocyanate (TDI) and 0.005 g of dibutyltin dilaurate were added, and the reaction was carried out at 70 ° C for 2 h. Then, 0.05 g of double-bond lignin with a molecular weight of 2913 g / mol was added, and the reaction was carried out at 75 ° C for 4 h. After centrifugation, washing and drying, the product obtained pyridine derivatives and lignin-modified graphene oxide.

[0084] (3) Preparation of composite coating:

[0085] 0.004 g of the pyridine derivative and lignin-modified graphene oxide prepared in step (2) were added to 4 g of polyurethane resin, and then 0.006 g of dibutyltin dilaurate was added. After stirring evenly, a pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating was obtained.

[0086] Comparative Example 1

[0087] The composite coating of this comparative example does not contain any filler, and its preparation method comprises the following steps:

[0088] To a solution consisting of 3 g of epoxy vinyl ester resin (D-E44) and styrene (wherein the mass proportion of styrene is 30 wt%), 0.009 g of accelerator cobalt naphthenate and 0.03 g of curing agent 2-butanone peroxide were added and stirred evenly to obtain a product.

[0089] Comparative Example 2

[0090] The composite coating of this comparative example uses graphene oxide (GO) as a filler, and its preparation method comprises the following steps:

[0091] 0.003 g of graphene oxide (GO) was added to a solution consisting of 3 g of epoxy vinyl ester resin (D-E44) and styrene (wherein the mass proportion of styrene was 30 wt%), and then 0.009 g of accelerator cobalt naphthenate and 0.03 g of curing agent 2-butanone peroxide were added, and the mixture was stirred evenly to obtain the product.

[0092] Comparative Example 3

[0093] The composite coating of this comparative example uses functionalized graphene oxide (TGO) as a filler, and its preparation method includes the following steps:

[0094] (1) Preparation of monomers containing pyridine structure:

[0095] 0.67 g of 6-amino-1-hexanol and 2.34 g of potassium hydroxide were added to 110 mL of dimethyl sulfoxide (DMSO), stirred at 200 rpm at 60°C for 30 minutes, and then 1 g of 4'-chloro-2,2':6',2"-terpyridine was added. The reaction was carried out at 75°C for 24 hours. The product was then cooled to room temperature, filtered, washed with deionized water, and freeze-dried to obtain a monomer containing a pyridine structure (TDD).

[0096] (2) Modification of graphene oxide using monomers containing pyridine structures:

[0097] 0.5 g of graphene oxide (GO) and 0.25 g of the monomer containing a pyridine structure (TDD) obtained in step (1) were added to 50 mL of N,N-dimethylformamide (DMF), ultrasonicated for 10 min, and then 0.2 g of a water absorbent dicyclohexylcarbodiimide was added. The mixture was stirred at 210 rpm at 60 ° C for 24 h. The product was centrifuged, washed and dried to obtain functionalized graphene oxide (TGO).

[0098] (3) Preparation of composite coating:

[0099] 0.003 g of the functionalized graphene oxide (TGO) prepared in step (2) was added to a solution consisting of 3 g of epoxy vinyl ester resin (D-E44) and styrene (wherein the mass proportion of styrene was 30 wt%), and then 0.009 g of accelerator cobalt cyclohexaneate and 0.03 g of curing agent 2-butanone peroxide were added, and the mixture was stirred evenly to obtain the product.

[0100] Next, in order to verify the performance of the coating prepared from the pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating of the present invention, the composite coatings prepared in Examples 1-4 and Comparative Examples 1-3 were respectively cured to form coatings, and then the obtained coatings were subjected to performance tests.

[0101] 1. Preparation of coating

[0102] The composite coatings prepared in Examples 1-4 and Comparative Examples 1-3 were applied to clean steel plates using an applicator, pre-cured at room temperature for 12 h, and then placed in ovens at 100°C, 120°C, and 160°C for deep curing for 3 h, 4 h, and 2 h, respectively, to obtain coatings.

[0103] 2. Test methods

[0104] (1) Cross-link density test

[0105] Test method: A dual cantilever model was used for dynamic mechanical analysis (DMA, DMA242E, Germany) of the samples to test the crosslinking density of the samples.

[0106] (2) Breaking strength test

[0107] Test method: According to GB / T 104.2-2006, the breaking strength of the sample was measured using a universal testing machine (UTM4204) at a tensile speed of 1 mm / min.

[0108] (3) Contact angle test

[0109] Test method: Use an optical goniometer to measure the hydrophilicity / hydrophobicity of the sample surface. The contact angle value is the average of five different locations on the same sample.

[0110] (4) Electrochemical performance test

[0111] Test method: The electrochemical test was carried out on a CHI-660E electrochemical workstation. The corrosion medium was 3.5 wt% NaCl solution and the test area was 1 cm 2 , with Ag / AgCl electrode as reference electrode and platinum electrode as auxiliary electrode. The frequency of the sample under test was set at 10 5 In the range of Hz to 0.01Hz, the sine wave amplitude voltage is 20mV.

[0112] (5) Scratch intelligent anti-corrosion test

[0113] Testing method: The sample surface was scratched using a nanoscratch tester and then electrochemically tested by immersing it in 3.5wt% salt water. The initial data was recorded as the starting value. The same test was then repeated at different times and days to compare the changes in the electrochemical data. The intelligent anti-corrosion performance of the coating was evaluated by comparing the morphology of the coating healing at the scratched area during the electrochemical test.

[0114] 3. Test results

[0115] The performance test results of the coatings prepared from the pyridine derivatives of Examples 1-4 and the lignin-modified graphene oxide-based intelligent anti-corrosion composite coatings are shown in Table 1.

[0116] Table 1 Performance test results of coating

[0117]

[0118] As can be seen from Table 1, the crosslinking density of the coating prepared from the pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating of the present invention is 0.8 to 1.85 mmol·m -3, indicating that the coating has a high cross-linking density; the fracture strength is 55-86.9MPa, indicating that the coating requires a large external force to break; the contact angle is 70-81°, indicating that the coating has a certain degree of hydrophobicity; the impedance modulus after immersion in 3.5wt% NaCl solution for 100 days is on the order of 10 8 ~10 9 Ω·cm 2 , and the steel plate surface contains very few corrosion products and corrosive medium elements, indicating that the coating has good anti-corrosion performance.

[0119] Figure 5 The electrochemical performance test results of the coating are shown in Figure 2. Figure 5 (1) is the Bode diagram of the coating prepared from the composite coating of Comparative Example 1, Figure 5 (2) is the phase angle diagram of the coating prepared from the composite coating of Comparative Example 1, Figure 5 (3) is the Nyquist plot of the coating prepared from the composite coating of Comparative Example 1;

[0120] Figure 5 (4) is the Bode diagram of the coating obtained from the composite coating of Comparative Example 2, Figure 5 (5) is the phase angle diagram of the coating prepared from the composite coating of Comparative Example 2, Figure 5 (6) is the Nyquist plot of the coating prepared from the composite coating of Comparative Example 2; Figure 5 (7) is the Bode diagram of the coating obtained from the composite coating of Example 3. Figure 5 (8) is the phase angle diagram of the coating prepared from the composite coating of Example 3, Figure 5 (9) is the Nyquist plot of the coating prepared from the composite coating of Comparative Example 3; Figure 5 (10) is the Bode diagram of the coating obtained from the composite coating of Example 1, Figure 5 (11) is a phase angle diagram of the coating prepared from the composite coating of Example 1, Figure 5 (12) is the Nyquist plot of the coating prepared from the composite coating of Example 1.

[0121] from Figure 5 It can be seen that as the coating is immersed in 3.5wt% salt water for a longer time, the impedance modulus of the coating decreases, the phase angle platform at high frequencies becomes narrower, and the impedance arc radius decreases. This shows that the corrosion resistance of the coating is time-dependent and decreases with increasing immersion time. However, during this process, the corrosion resistance of the coating with fillers is higher than that of the coating without fillers.

[0122] Figure 6 This is the scratch self-healing morphology of the coating after being immersed in 3.5wt% salt water for 3 days, where: Figure 6(1) is a scratch self-healing morphology of the coating prepared from the composite coating of Comparative Example 1, Figure 6 (2) is a scratch self-healing morphology of the coating prepared from the composite coating of Comparative Example 2, Figure 6 (3) is a scratch self-healing morphology of the coating prepared from the composite coating of Comparative Example 3, Figure 6 (4) is a scratch self-healing morphology of the coating prepared from the composite coating of Example 1. Figure 6 It can be seen that the scratch coatings of the coatings prepared by the pure resin composite coating without adding fillers in Comparative Example 1 and the composite coating with graphene oxide (GO) as filler in Comparative Example 2 have no self-healing properties, while the scratch coatings of the coatings prepared by the composite coating with functionalized graphene oxide (TGO) as filler in Comparative Example 3 and the composite coating with pyridine derivatives and lignin-modified graphene oxide (ATGO) as fillers in Example 1 have self-healing properties, indicating that the addition of graphene oxide modified with a monomer containing a pyridine structure has certain self-healing properties for the scratch coating.

[0123] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the inventive concept of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. A method for preparing graphene oxide modified with pyridine derivatives and lignin, characterized in that: Graphene oxide is modified with a monomer containing a pyridine structure and double-bond lignin to obtain a pyridine derivative and lignin-modified graphene oxide; The preparation method thereof comprises the following steps: S1. Adding graphene oxide and a monomer containing a pyridine structure to a first solvent, ultrasonicating for 5-60 minutes, then adding a water absorbent, stirring at 50-80° C. for 12-36 hours, centrifuging, washing, and drying to obtain functionalized graphene oxide; S2. dispersing the functionalized graphene oxide in a second solvent, then adding a diisocyanate and a catalyst, reacting at 50-80° C. for 1-6 hours, then adding double-bond lignin, reacting at 50-80° C. for 1-12 hours, centrifuging, washing, and drying to obtain a pyridine derivative and lignin-modified graphene oxide; The double-bonded lignin has a molecular weight of 1000 g / mol-5000 g / mol and includes at least one of double-bonded fatty lignin, double-bonded isomeric lignin, double-bonded syringyl lignin, double-bonded guaiacyl lignin and double-bonded p-hydroxyphenyl lignin.

2. The method for preparing pyridine derivatives and lignin-modified graphene oxide according to claim 1, wherein: The preparation method of the monomer containing a pyridine structure comprises the following steps: Add a monomer containing amino and hydroxyl functional groups and a base to a solvent, stir at 50-80°C for 20-60 minutes, then add a pyridine derivative monomer, react at 50-80°C for 12-36 hours, then cool to room temperature, filter, wash, and dry to obtain a monomer containing a pyridine structure.

3. The method for preparing pyridine derivatives and lignin-modified graphene oxide according to claim 2, wherein: The monomer containing amino and hydroxyl functional groups includes at least one of 6-amino-1-hexanol, 2-methyl-4-aminophenol, DL-aminopropanol and 2-methoxy-5-aminophenol; The base includes at least one of potassium hydroxide, sodium hydroxide, potassium carbonate and sodium carbonate; The solvent comprises at least one of toluene, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, chloroform and dimethyl sulfoxide; The pyridine derivative monomer includes at least one of 4'-bromo-2,2':6',2''-terpyridine, 4'-chloro-2,2':6',2''-terpyridine and 4-chloropyridine.

4. The method for preparing a pyridine derivative and lignin-modified graphene oxide according to claim 2 or 3, wherein: Calculated by weight, the amount of the monomer containing amino and hydroxyl functional groups is 0.1-20 parts, the amount of the base is 1-20 parts, the amount of the solvent is 1-110 parts, and the amount of the pyridine derivative monomer is 0.1-30 parts.

5. The method for preparing pyridine derivatives and lignin-modified graphene oxide according to claim 1, wherein: The first solvent comprises at least one of toluene, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, chloroform and dimethyl sulfoxide; The water absorbing agent includes at least one of anhydrous magnesium sulfate, anhydrous sodium sulfate, and dicyclohexylcarbodiimide; The second solvent comprises at least one of toluene, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, chloroform and dimethyl sulfoxide; The diisocyanate includes at least one of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate and isophorone diisocyanate; The catalyst is dibutyltin dilaurate.

6. The method for preparing pyridine derivatives and lignin-modified graphene oxide according to claim 5, wherein: Calculated by weight, the amount of graphene oxide is 0.1-10 parts, the amount of the monomer containing a pyridine structure is 0.1-10 parts, the amount of the first solvent is 1-80 parts, the amount of the water absorbent is 0.1-20 parts, the amount of the second solvent is 1-80 parts, the amount of the diisocyanate is 0.1-10 parts, the amount of the catalyst is 0.0001-2 parts, and the amount of the double-bond lignin is 0.01-10 parts.

7. A pyridine derivative and lignin-modified graphene oxide obtained by the preparation method according to any one of claims 1 to 6.

8. A graphene oxide-based intelligent anti-corrosion composite coating modified with pyridine derivatives and lignin, characterized in that: The raw material composition comprises, by weight, 0.0025-0.5 parts of the pyridine derivative and lignin-modified graphene oxide according to claim 7, 1-50 parts of resin, and 0.001-10 parts of additives; The resin includes at least one of epoxy resin, epoxy vinyl ester resin, polyurethane resin, phenolic resin and acrylic resin; The auxiliary agent includes at least one of a diluent, a accelerator, a curing agent, and a catalyst.

9. Use of the pyridine derivative and lignin-modified graphene oxide-based intelligent anti-corrosion composite coating according to claim 8 as an anti-corrosion coating for metal surfaces of marine engineering facilities, ships, automobiles, and aircraft.

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