A composite coating and preparation method thereof

Abstract

The invention discloses a composite coating and a preparation method thereof, which relates to the field of coating preparation, including a primer and a topcoat. The primer includes raw materials: liquid epoxy resin, reactive diluent, pigment, filler, modified graphene oxide, xylene, dispersant, defoamer, anti-settling agent, and curing agent; the topcoat includes raw materials: modified acrylic resin, pigment, filler, cosolvent, defoamer, leveling agent, anti-settling agent, adhesion promoter, and curing agent. The synthesized modified graphene oxide contains pyridine ring, trifluoromethyl and primary amine groups, which improve the mechanical properties, antibacterial properties, and water resistance of the composite coating; the synthesized modified acrylic resin contains sodium sulfonate groups and polysiloxane chains, which improve the heat resistance and flame retardancy of the composite coating.

Description

Technical Field

[0001] The invention relates to the field of composite coating preparation, and in particular to a composite coating and a preparation method thereof. Background Art

[0002] Epoxy resin coating is a commonly used anti-corrosion coating with good chemical resistance and anti-corrosion performance, but in actual use, its coating has poor mechanical properties. In an environment with long-term contact with water, the water resistance of epoxy resin is insufficient, making the substrate it is coated with vulnerable to water erosion and loss of protection, and also vulnerable to bacterial erosion, resulting in damage to the coating. Epoxy resin coating may become powdery after being exposed to the sun for a long time, while acrylic coating has the advantages of good light resistance and weather resistance. Epoxy resin can be used as a primer and acrylic resin coating as a topcoat to form a composite coating, forming a coating with complementary advantages and excellent performance, thereby expanding its scope of use. However, acrylic resin coating has the disadvantages of insufficient heat resistance and easy combustion, so it is necessary to modify epoxy resin coating and acrylic resin coating to form a composite coating with excellent comprehensive performance. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a composite coating and a preparation method thereof.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A composite coating comprising a primer and a topcoat;

[0006] The primer comprises the following raw materials in parts by weight: 30-40 parts of liquid epoxy resin, 8-10 parts of active diluent, 10-20 parts of pigment, 10-20 parts of filler, 5-10 parts of modified graphene oxide, 25-35 parts of xylene, 0.4-0.6 parts of dispersant, 0.3-0.5 parts of defoamer, 0.2-0.4 parts of anti-settling agent, and 1-3 parts of curing agent;

[0007] The raw materials of the primer include bisphenol A liquid epoxy resin, reactive diluent propylene oxide dodecyl ether, pigment red iron oxide, filler titanium dioxide, cosolvent xylene, dispersant sodium dodecylbenzene sulfonate, defoamer silicone defoamer, anti-settling agent polyamide wax, and curing agent diethylenetriamine.

[0008] The topcoat comprises the following raw materials in parts by weight: 40-50 parts of modified acrylic resin, 10-20 parts of pigment, 10-20 parts of filler, 25-35 parts of cosolvent, 0.3-0.5 parts of defoamer, 0.2-0.4 parts of leveling agent, 0.3-0.5 parts of anti-settling agent, 1-2 parts of adhesion promoter, and 1-3 parts of curing agent;

[0009] The raw materials of the topcoat are: the pigment is zinc phosphate, the filler is talcum powder, the cosolvent is ethyl acetate, the defoamer is a polyester defoamer, the leveling agent is a polyether-modified acrylic leveling agent, the anti-settling agent is hydroxyethyl cellulose, the adhesion promoter is γ-aminopropyl triethoxysilane, and the curing agent is hexamethylene diisocyanate;

[0010] The primer is applied on the surface of the substrate, and the topcoat is applied on the surface of the primer; the substrate is steel, concrete, wood or plastic;

[0011] The composite coating is prepared by the following steps:

[0012] Step S1: Add the liquid epoxy resin and modified graphene oxide in the raw materials of the primer to the reactor and stir for 15-25 minutes, then add the active diluent, pigment, filler, xylene, dispersant, defoamer, anti-settling agent, continue stirring for 10-15 minutes, and finally add the curing agent and stir for 20-30 minutes to obtain the primer;

[0013] Step S2: adding the modified acrylic resin, pigment, filler, cosolvent, defoamer, 0.2-0.4 parts of leveling agent, anti-settling agent and adhesion promoter in the raw materials of the topcoat to another reaction kettle, stirring for 30-40 minutes, and then adding curing agent, stirring for 5-10 minutes to obtain the topcoat;

[0014] Step S3: The primer obtained in step S1 and the topcoat obtained in step S2 are packaged separately to obtain a composite coating.

[0015] The modified graphene oxide is prepared by the following steps:

[0016] Step A1: 3,5-pyridinedicarboxylic acid is added to DMF, and dichlorothionyl is added under stirring, and the mixture is refluxed and stirred at 50° C. for 4-5 hours to obtain an acyl chloride product; 2-amino-5-nitrotrifluorotoluene, potassium carbonate and dimethyl sulfoxide are added to a flask to obtain a mixed solution a, and then the above-mentioned acyl chloride product is added to dimethyl sulfoxide to obtain a mixed solution b, and the mixed solution b is slowly added dropwise to the mixed solution a in a 0° C. ice-water bath. After the addition is completed, the mixture is heated to 40° C., stirred at a constant temperature for 8-10 hours, and distilled under reduced pressure to obtain a reaction product 1;

[0017] Further, the dosage ratio of 3,5-pyridinedicarboxylic acid, DMF, and dichlorothionyl is 0.1 mol: 40-50 mL: 0.12-0.15 mol; the dosage ratio of 2-amino-5-nitrotrifluorotoluene, potassium carbonate, and dimethyl sulfoxide is 0.2 mol: 0.008-0.009 mol: 90-1 00 mL; the dosage ratio of the acyl chloride product and dimethyl sulfoxide is 0.1 mol: 50-60 mL; the dosage ratio of the mixed solution a and the mixed solution b is 95-105 mL: 55-65 mL;

[0018] During the reaction of step A1, 3,5-pyridinedicarboxylic acid reacts with thionyl chloride to generate an acyl chloride product; the acyl chloride product then reacts with the amino group of 2-amino-5-nitrotrifluorotoluene to generate a reaction product 1;

[0019] Step A2: Add the reaction product 1 and toluene into a three-necked flask, heat to 45-55°C, start reflux stirring, then add sodium dithionite, and reflux stirring for 1-1.5h to obtain the reaction product 2;

[0020] Further, the usage ratio of the reaction product 1, toluene, and sodium dithionite is 0.1 mol: 105-115 mL: 0.2-0.25 mol;

[0021] During the reaction of step A2, the nitro group of the reaction product 1 is reduced to an amino group to obtain the reaction product 2;

[0022] Step A3: adding graphene oxide to deionized water, and ultrasonically dispersing for 20-30 minutes to obtain a dispersion; adding PBS buffer to a flask, and then adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in an ice-water bath, stirring for 15-25 minutes, then slowly adding the above dispersion to the flask, stirring for 12-14 hours in an ice bath, adjusting the pH to 7-7.5, adding the reaction product 2, stirring at room temperature for 4-5 hours, centrifuging, and then washing the supernatant to neutrality, removing the supernatant and adding the precipitate to deionized water, and ultrasonically dispersing to obtain modified graphene oxide;

[0023] Further, the amount ratio of graphene oxide and deionized water is 0.008 g: 1 mL; the amount ratio of PBS buffer, 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride, N-hydroxysuccinimide, dispersion, and reaction product 2 is 200 mL: 3.1 g: 0.26 g: 100 mL: 5 g, and the pH of PBS buffer is 5.5; the amount ratio of precipitate and deionized water is 0.0065-0.0070 g: 1 mL;

[0024] During the reaction of step A3, the carboxyl group at the edge of the graphene oxide is activated by 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, and then reacts with the amino group at one end of the reaction product 2, thereby grafting the reaction product 2 onto the graphene oxide to obtain modified graphene oxide;

[0025] The modified acrylic resin is prepared by the following steps:

[0026] Step B1: In a nitrogen atmosphere, sodium benzaldehyde-2-sulfonate and acetic anhydride are added to a reaction bottle, refluxed and stirred, and the temperature is raised to 150-170° C., potassium carbonate is added, and the reaction is carried out under constant temperature reflux and stirring for 24-26 hours, and the reaction product a is obtained by extraction, rotary evaporation, and drying;

[0027] Further, the dosage ratio of benzaldehyde-2-sulfonate sodium, acetic anhydride, and potassium carbonate is 0.1 mol: 0.05-0.07 mol: 0.005-0.008 mol;

[0028] During the reaction of step B1, the aldehyde group of sodium benzaldehyde-2-sulfonate reacts with acetic anhydride to generate a reaction product a containing an alkenyl carboxylic acid;

[0029] Step B2: Add toluene, hydrogenated silicone oil, hydroquinone, and cis-dichlorobis(pyridyl)platinum into a three-necked flask in a certain proportion, stir and introduce nitrogen protection, slowly add the reaction product a, slowly raise the temperature to 70-80°C, stir and react for 3-4h, and evacuate to obtain the reaction product b;

[0030] Further, the amount ratio of the reaction product a, toluene, hydrogen-containing silicone oil, hydroquinone and cis-dichlorobis(pyridyl)platinum is 1-1.5 mol: 100 ml: 1 mol: 0.5 mol: 0.015-0.020 mol;

[0031] During the reaction of step B2, the hydrogen-containing silicone oil reacts with the reaction product a under the catalysis of cis-dichlorobis(pyridyl)platinum, and the Si-H bond and the C=C bond are added to generate the reaction product b;

[0032] Step B3: Add the reaction product b to DMF, add thionyl chloride under stirring, and reflux and stir at 50°C for 4-5h to obtain the reaction product c; then add 2-aminoethyl methacrylate, potassium carbonate and dimethyl sulfoxide to a flask to obtain a mixed solution 1, and then add the above reaction product c to dimethyl sulfoxide to obtain a mixed solution 2, slowly dropwise add the mixed solution 2 to the mixed solution 1 in a 0°C ice water bath, after the dropwise addition is completed, heat to 40°C, stir at a constant temperature for 8-10h, and distill under reduced pressure to obtain a functional monomer;

[0033] Further, the dosage ratio of the reaction product b, DMF, and thionyl chloride is 0.1 mol: 60-70 mL: 0.12-0.15 mol; the dosage ratio of 2-aminoethyl methacrylate, potassium carbonate, and dimethyl sulfoxide is 0.1 mol: 0.002-0.004 mol: 25-35 mL; the dosage ratio of the reaction product c and dimethyl sulfoxide is 0.1 mol: 80-90 mL; the dosage ratio of the mixed solution 1 and the mixed solution 2 is 30-40 mL: 85-95 mL;

[0034] During the reaction of step B3, the carboxyl group of the reaction product b reacts with thionyl chloride to generate a reaction product c containing an acyl chloride; the acyl chloride of the reaction product c then reacts with the amino group of 2-aminoethyl methacrylate to generate a functional monomer containing a terminal double bond;

[0035] Step B4: Mix butyl acrylate, acrylic acid, styrene, methacrylic acid, hydroxyethyl acrylate and functional monomer at room temperature for 15-20 minutes to obtain a mixture; then mix water, disodium lauryl polyoxyethylene ether sulfosuccinate and sodium 3-allyloxy-2-hydroxypropanesulfonate for 10-15 minutes to obtain a mixed solution; add the mixed solution to the mixture and stir for 30-40 minutes to obtain a pre-emulsified monomer; then add water, disodium lauryl polyoxyethylene ether sulfosuccinate, sodium 3-allyloxy-2-hydroxypropanesulfonate and ammonium persulfate to a reaction bottle, heat to 70-80° C., add the pre-emulsified monomer to the reaction bottle, and then react at a constant temperature for 20 minutes, and then slowly add the pre-emulsified monomer and initiator solution dropwise at 80-85° C. within 2 hours, and then react at a constant temperature for 1.5 hours, cool to room temperature, and filter with a 200-mesh sieve to obtain a modified acrylic resin;

[0036] Further, the amount ratio of butyl acrylate, acrylic acid, styrene, methacrylic acid, hydroxyethyl acrylate and functional monomer is 145g: 4g: 22g: 4g: 6g: 9g; the amount ratio of water, disodium lauryl polyoxyethylene ether sulfosuccinate, and sodium 3-allyloxy-2-hydroxypropanesulfonate is 70g: 1.8g: 0.8g; the amount ratio of water, disodium lauryl polyoxyethylene ether sulfosuccinate, sodium 3-allyloxy-2-hydroxypropanesulfonate, ammonium persulfate, pre-emulsified monomer and initiator solution is 100-110g: 0.35g: 1.2g: 0.4g: 72.6g: 6g; the initiator solution is obtained by adding 0.5-0.6g of ammonium persulfate to 5-6g of water and stirring and mixing, the weight ratio of the pre-emulsified monomer added twice is 1:2, and the sum of the weights of the pre-emulsified monomer added twice is the total amount of the pre-emulsified monomer used;

[0037] In the reaction process of step B4, butyl acrylate, acrylic acid, styrene, methacrylic acid, hydroxyethyl acrylate and functional monomers are polymerized under the action of an initiator to obtain a modified acrylic resin;

[0038] Beneficial effects of the invention: The invention discloses a composite coating, including a primer and a topcoat; the primer includes the following raw materials: liquid epoxy resin, reactive diluent, pigment, filler, modified graphene oxide, etc.; the topcoat includes the following raw materials: modified acrylic resin, pigment, filler, cosolvent, etc. The synthesized modified graphene oxide contains pyridine ring, trifluoromethyl and primary amine group. When the primary amine group is mixed with the epoxy resin, it is connected to the epoxy group through a covalent bond, so that a strong interfacial interaction is generated between the modified graphene oxide and the epoxy resin. When fracture occurs, it is beneficial to the stress transfer of the interfacial load, reducing the stress concentration and sheet slippage caused by the stretching of the composite film, and enhancing the mechanical properties of the composite coating; the trifluoromethyl group has strong hydrophobicity, which enhances the water resistance of the coating, prevents the coating from being eroded by water, resulting in changes in appearance and mechanical properties and shortening the service life, so that the substrate coated with the coating remains intact in an environment with long-term contact with water; the pyridine ring interacts with multiple biological molecules such as ribosomes, DNA, RNA and membranes in bacterial cells, interferes with their normal physiological metabolism and nuclear cell structure, thereby causing bacterial death, has a broad spectrum of bactericidal properties, can prevent the development of drug resistance, and make the coating have excellent antibacterial properties; the small molecule reaction product 2 is grafted with graphene oxide and epoxy resin, and its dispersibility in the matrix is ​​enhanced, avoiding migration failure, and can stably play a role in improving the performance of the coating.

[0039] In the synthesized modified acrylic resin, the functional monomers participating in the polymerization reaction introduce sodium sulfonate groups and polysiloxane chains. The polysiloxane chain contains Si-O-Si bonds and Si-C bonds with high bond energy, which require high energy to break, so that the thermal stability of the modified acrylic ester molecules is improved, thereby improving the heat resistance of the modified acrylic resin; the sulfur element in the sodium sulfonate group generates non-combustible gases such as sulfur dioxide when burned, diluting the concentration of combustible gases, and solidifies in the carbon layer in the form of sodium sulfate and sodium sulfite compounds, forming a dense and thick protective carbon layer, reducing heat transfer in the combustion area, and effectively preventing further combustion of the matrix in the gas phase and solid phase, while inhibiting the release of smoke; on the basis of improving the heat resistance of the topcoat, the coating film is not easy to burn, further enhancing the stability of the coating; grafting the functional monomers containing sodium sulfonate groups and polysiloxane chains into the acrylic resin is also conducive to improving the compatibility and dispersibility of the functional monomers in the matrix. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Example 1

[0042] A modified graphene oxide, the preparation of which comprises the following steps:

[0043] Step A1: Add 3,5-pyridinedicarboxylic acid to DMF, add dichlorothionyl under stirring, and reflux and stir at 50°C for 4 hours to obtain an acyl chloride product; then add 2-amino-5-nitrotrifluorotoluene, potassium carbonate and dimethyl sulfoxide to a flask to obtain a mixed solution a, and then add the above-mentioned acyl chloride product to dimethyl sulfoxide to obtain a mixed solution b. In a 0°C ice-water bath, slowly drop the mixed solution b into the mixed solution a. After the dropwise addition is completed, the temperature is raised to 40°C and stirred at a constant temperature for 8 hours. , distill under reduced pressure to obtain the reaction product 1; the usage ratio of 3,5-pyridinedicarboxylic acid, DMF, and dichlorothionyl is 0.1 mol: 40 mL: 0.12 mol; the usage ratio of 2-amino-5-nitrotrifluorotoluene, potassium carbonate, and dimethyl sulfoxide is 0.2 mol: 0.008 mol: 90 mL; the usage ratio of the acyl chloride product and dimethyl sulfoxide is 0.1 mol: 50 mL; the usage ratio of the mixed solution a and the mixed solution b is 95 mL: 55 mL;

[0044] Step A2: Add the reaction product 1 and toluene into a three-necked flask, heat to 45°C, start reflux stirring, then add sodium dithionite, and reflux stirring for 1 hour to obtain the reaction product 2; the amount ratio of the reaction product 1, toluene and sodium dithionite is 0.1 mol: 105 mL: 0.2 mol;

[0045] Step A3: Add graphene oxide to deionized water and ultrasonically disperse for 20 minutes to obtain a dispersion; add PBS buffer to the flask, then add 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide in an ice water bath, stir for 1 5min, then slowly add the above dispersion into the flask, stir for 12h in an ice bath, adjust the pH to 7, add the reaction product 2, stir and react at room temperature for 4h, centrifuge, and then wash the supernatant to neutrality, remove the supernatant and add the precipitate to deionized water, and disperse by ultrasonic to obtain modified graphene oxide; the amount ratio of graphene oxide and deionized water is 0.008g:1mL; the amount ratio of PBS buffer, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, dispersion and reaction product 2 is 200mL:3.1g:0.26g:100mL:5g, and the pH of PBS buffer is 5.5; the amount ratio of precipitate and deionized water is 0.0065g:1mL.

[0046] Example 2

[0047] A modified graphene oxide, the preparation of which comprises the following steps:

[0048] Step A1: 3,5-pyridinedicarboxylic acid is added to DMF, and dichlorothionyl is added under stirring, and the mixture is refluxed and stirred at 50°C for 4.5 hours to obtain an acyl chloride product; 2-amino-5-nitrotrifluorotoluene, potassium carbonate and dimethyl sulfoxide are added to a flask to obtain a mixed solution a, and then the above-mentioned acyl chloride product is added to dimethyl sulfoxide to obtain a mixed solution b. In a 0°C ice-water bath, the mixed solution b is slowly added dropwise to the mixed solution a. After the addition is completed, the temperature is raised to 40°C, and the mixture is stirred at a constant temperature for 9 hours. , distill under reduced pressure to obtain the reaction product 1; the usage ratio of 3,5-pyridinedicarboxylic acid, DMF, and dichlorothionyl is 0.1 mol: 45 mL: 0.13 mol; the usage ratio of 2-amino-5-nitrotrifluorotoluene, potassium carbonate, and dimethyl sulfoxide is 0.2 mol: 0.008 mol: 95 mL; the usage ratio of the acyl chloride product and dimethyl sulfoxide is 0.1 mol: 55 mL; the usage ratio of the mixed solution a and the mixed solution b is 100 mL: 60 mL;

[0049] Step A2: Add the reaction product 1 and toluene into a three-necked flask, heat to 50°C, start reflux stirring, then add sodium dithionite, and reflux stirring for 1.2h to obtain the reaction product 2; the amount ratio of the reaction product 1, toluene and sodium dithionite is 0.1mol:110mL:0.22mol;

[0050] Step A3: Add graphene oxide to deionized water and ultrasonically disperse for 25 minutes to obtain a dispersion; add PBS buffer to a flask, then add 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide in an ice-water bath, stir for 20 minutes, then slowly add the above dispersion to the flask, stir for 13 hours in an ice bath, adjust the pH to 7.2, add reaction product 2, stir at room temperature for 4.5 hours, centrifuge, and then wash the supernatant to neutrality, remove the supernatant liquid and adding the precipitate to deionized water, ultrasonically dispersing to obtain modified graphene oxide; the amount ratio of graphene oxide and deionized water is 0.008 g:1 mL; the amount ratio of PBS buffer, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, dispersion liquid and reaction product 2 is 200 mL:3.1 g:0.26 g:100 mL:5 g, the pH of PBS buffer is 5.5; the amount ratio of precipitate and deionized water is 0.0068 g:1 mL.

[0051] Example 3

[0052] A modified graphene oxide, the preparation of which comprises the following steps:

[0053] Step A1: 3,5-pyridinedicarboxylic acid is added to DMF, and dichlorothionyl is added under stirring, and the mixture is refluxed and stirred at 50°C for 5 hours to obtain an acyl chloride product; 2-amino-5-nitrotrifluorotoluene, potassium carbonate and dimethyl sulfoxide are added to a flask to obtain a mixed solution a, and then the above-mentioned acyl chloride product is added to dimethyl sulfoxide to obtain a mixed solution b. In a 0°C ice-water bath, the mixed solution b is slowly added dropwise to the mixed solution a. After the addition is completed, the temperature is raised to 40°C, and the mixture is stirred at a constant temperature for 10 hours. The reaction product 1 was obtained by distillation under reduced pressure; the dosage ratio of 3,5-pyridinedicarboxylic acid, DMF and dichlorothionyl was 0.1 mol: 50 mL: 0.15 mol; the dosage ratio of 2-amino-5-nitrotrifluorotoluene, potassium carbonate and dimethyl sulfoxide was 0.2 mol: 0.009 mol: 100 mL; the dosage ratio of the acyl chloride product and dimethyl sulfoxide was 0.1 mol: 60 mL; the dosage ratio of the mixed solution a and the mixed solution b was 105 mL: 65 mL;

[0054] Step A2: Add the reaction product 1 and toluene into a three-necked flask, heat to 55°C, start reflux stirring, then add sodium dithionite, and reflux stirring for 1.5 hours to obtain the reaction product 2; the amount ratio of the reaction product 1, toluene and sodium dithionite is 0.1 mol: 115 mL: 0.25 mol;

[0055] Step A3: Add graphene oxide to deionized water and ultrasonically disperse for 30 minutes to obtain a dispersion; add PBS buffer to a flask, then add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in an ice-water bath, stir for 25 minutes, then slowly add the above dispersion to the flask, stir for 14 hours in an ice bath, adjust the pH to 7.5, add reaction product 2, stir at room temperature for 5 hours, centrifuge, and then wash the supernatant to neutrality, and remove the supernatant. The precipitate was added to deionized water and ultrasonically dispersed to obtain modified graphene oxide; the dosage ratio of graphene oxide and deionized water was 0.008 g:1 mL; the dosage ratio of PBS buffer, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, dispersion and reaction product 2 was 200 mL:3.1 g:0.26 g:100 mL:5 g, and the pH of PBS buffer was 5.5; the dosage ratio of precipitate and deionized water was 0.0070 g:1 mL.

[0056] Example 4

[0057] A modified acrylic resin, the preparation of which comprises the following steps:

[0058] Step B1: In a nitrogen atmosphere, sodium benzaldehyde-2-sulfonate and acetic anhydride are added to a reaction bottle, reflux and stir, and the temperature is raised to 150° C., and potassium carbonate is added. The reaction is stirred at constant temperature and reflux for 24 hours, and the reaction product a is obtained by extraction, rotary evaporation, and drying. The amount ratio of sodium benzaldehyde-2-sulfonate, acetic anhydride, and potassium carbonate is 0.1 mol: 0.05 mol: 0.005 mol;

[0059] Step B2: Add toluene, hydrogen-containing silicone oil, hydroquinone, and cis-dichlorobis(pyridyl)platinum in a certain proportion into a three-necked flask, stir and introduce nitrogen protection, slowly add reaction product a, slowly heat to 70° C., stir and react for 3-4 hours, and evacuate to obtain reaction product b; the dosage ratio of reaction product a, toluene, hydrogen-containing silicone oil, hydroquinone and cis-dichlorobis(pyridyl)platinum is 1 mol: 100 ml: 1 mol: 0.5 mol: 0.01 5 mol;

[0060] Step B3: Add the reaction product b to DMF, add dichlorothionyl under stirring, and reflux and stir at 50°C for 4h to obtain the reaction product c; then add 2-aminoethyl methacrylate, potassium carbonate and dimethyl sulfoxide to a flask to obtain a mixed solution 1, and then add the above reaction product c to dimethyl sulfoxide to obtain a mixed solution 2, slowly drop the mixed solution 2 into the mixed solution 1 under a 0°C ice water bath, after the dropwise addition is completed, heat to 40°C, stir at a constant temperature for 8h, and distill under reduced pressure to obtain a functional monomer; the amount ratio of the reaction product b, DMF, and dichlorothionyl is 0.1mol:60mL:0.12mol; the amount ratio of 2-aminoethyl methacrylate, potassium carbonate, and dimethyl sulfoxide is 0.1mol:0.002mol:25mL; the amount ratio of the reaction product c and dimethyl sulfoxide is 0.1mol:80mL; the amount ratio of the mixed solution 1 and the mixed solution 2 is 30mL:85mL;

[0061] Step B4: Mix butyl acrylate, acrylic acid, styrene, methacrylic acid, hydroxyethyl acrylate and functional monomer at room temperature for 15 minutes to obtain a mixture; then mix water, disodium lauryl polyoxyethylene ether sulfosuccinate and sodium 3-allyloxy-2-hydroxypropanesulfonate and stir for 10 minutes to obtain a mixed solution; add the mixed solution to the mixture and stir for 30 minutes to obtain a pre-emulsified monomer; then add water, disodium lauryl polyoxyethylene ether sulfosuccinate, sodium 3-allyloxy-2-hydroxypropanesulfonate and ammonium persulfate to a reaction bottle, heat to 70°C, add the pre-emulsified monomer to the reaction bottle, and react at a constant temperature for 20 minutes, and then slowly add the pre-emulsified monomer and initiator solution at 80°C, complete the addition within 2 hours, and react at a constant temperature for 1.5 hours, cool to room temperature, and filter with a 200-mesh sieve to obtain a modified acrylic resin; butyl acrylate, acrylic acid, styrene, methacrylic acid, hydroxyethyl acrylate and functional monomer at room temperature for 15 minutes to obtain a mixture; The dosage ratio of acrylic acid, hydroxyethyl acrylate and functional monomer is 145g:4g:22g:4g:6g:9g; the dosage ratio of water, disodium lauryl polyoxyethylene ether sulfosuccinate and sodium 3-allyloxy-2-hydroxypropanesulfonate is 70g:1.8g:0.8g; the dosage ratio of water, disodium lauryl polyoxyethylene ether sulfosuccinate, sodium 3-allyloxy-2-hydroxypropanesulfonate, ammonium persulfate, pre-emulsified monomer and initiator solution is 100g:0.35g:1.2g:0.4g:72.6g:6g; the initiator solution is obtained by adding 0.5g of ammonium persulfate into 5g of water and stirring and mixing; the weight ratio of the pre-emulsified monomer added twice is 1:2, and the sum of the weights of the pre-emulsified monomer added twice is the total dosage of the pre-emulsified monomer used.

[0062] Example 5

[0063] A modified acrylic resin, the preparation of which comprises the following steps:

[0064] Step B1: In a nitrogen atmosphere, sodium benzaldehyde-2-sulfonate and acetic anhydride are added to a reaction bottle, reflux and stir, and the temperature is raised to 160° C., and potassium carbonate is added. The reaction is stirred at constant temperature and reflux for 25 hours, and the reaction product a is obtained by extraction, rotary evaporation, and drying. The amount ratio of sodium benzaldehyde-2-sulfonate, acetic anhydride, and potassium carbonate is 0.1 mol: 0.06 mol: 0.006 mol;

[0065] Step B2: Add toluene, hydrogen-containing silicone oil, hydroquinone, and cis-dichlorobis(pyridyl)platinum in a certain proportion into a three-necked flask, stir and introduce nitrogen protection, slowly add reaction product a, slowly heat to 75° C., stir and react for 3.5 hours, and evacuate to obtain reaction product b; the dosage ratio of reaction product a, toluene, hydrogen-containing silicone oil, hydroquinone and cis-dichlorobis(pyridyl)platinum is 1.2 mol: 100 ml: 1 mol: 0.5 mol: 0.017 mol;

[0066] Step B3: Add the reaction product b to DMF, add dichlorothionyl under stirring, and react under reflux stirring at 50°C for 4.5h to obtain the reaction product c; then add 2-aminoethyl methacrylate, potassium carbonate and dimethyl sulfoxide to a flask to obtain a mixed solution 1, and then add the above reaction product c to dimethyl sulfoxide to obtain a mixed solution 2, slowly dropwise add the mixed solution 2 to the mixed solution 1 under a 0°C ice-water bath, after the dropwise addition is completed, heat to 40°C, stir and react at a constant temperature for 9h, and distill under reduced pressure to obtain a functional monomer; the amount ratio of the reaction product b, DMF, and dichlorothionyl is 0.1mol:65mL:0.13mol; the amount ratio of 2-aminoethyl methacrylate, potassium carbonate, and dimethyl sulfoxide is 0.1mol:0.003mol:30mL; the amount ratio of the reaction product c and dimethyl sulfoxide is 0.1mol:85mL; the amount ratio of the mixed solution 1 and the mixed solution 2 is 35mL:90mL;

[0067] Step B4: Mix butyl acrylate, acrylic acid, styrene, methacrylic acid, hydroxyethyl acrylate and functional monomer at room temperature for 17 minutes to obtain a mixture; then mix water, disodium lauryl polyoxyethylene ether sulfosuccinate and sodium 3-allyloxy-2-hydroxypropanesulfonate for 12 minutes to obtain a mixed solution; add the mixed solution to the mixture and stir for 35 minutes to obtain a pre-emulsified monomer; then add water, disodium lauryl polyoxyethylene ether sulfosuccinate, sodium 3-allyloxy-2-hydroxypropanesulfonate and ammonium persulfate to a reaction bottle, heat to 75°C, add the pre-emulsified monomer to the reaction bottle, and react at a constant temperature for 20 minutes, then slowly add the pre-emulsified monomer and initiator solution dropwise at 82°C, complete the addition within 2 hours, react at a constant temperature for 1.5 hours, cool to room temperature, and filter with a 200-mesh sieve to obtain the modified The invention discloses a novel acrylic resin comprising a pre-emulsified monomer and an initiator solution. The pre-emulsified monomer and the initiator solution are prepared by mixing 0.5 g of ammonium persulfate into 5 g of water and stirring. The weight ratio of the pre-emulsified monomer and the initiator solution is 1:2. The weight ratio of the pre-emulsified monomer and the initiator solution is 1:3. The weight ratio of the pre-emulsified monomer and the initiator solution is 1:1.8 g and 0.8 g, respectively. The initiator solution is prepared by adding 0.5 g of ammonium persulfate into 5 g of water and stirring. The weight ratio of the pre-emulsified monomer and the initiator solution is 1:2. The weight sum of the pre-emulsified monomer and the initiator solution is 1:1.8 g and 0.8 g, respectively.

[0068] Example 6

[0069] A modified acrylic resin, the preparation of which comprises the following steps:

[0070] Step B1: In a nitrogen atmosphere, sodium benzaldehyde-2-sulfonate and acetic anhydride are added to a reaction bottle, reflux and stir, and the temperature is raised to 170° C., and potassium carbonate is added. The reaction is stirred at constant temperature and reflux for 26 hours, and the reaction product a is obtained by extraction, rotary evaporation, and drying. The amount ratio of sodium benzaldehyde-2-sulfonate, acetic anhydride, and potassium carbonate is 0.1 mol: 0.07 mol: 0.008 mol;

[0071] Step B2: Add toluene, hydrogen-containing silicone oil, hydroquinone, and cis-dichlorobis(pyridyl)platinum in a certain proportion into a three-necked flask, stir and introduce nitrogen protection, slowly add reaction product a, slowly heat to 80° C., stir and react for 4 hours, and evacuate to obtain reaction product b; the dosage ratio of reaction product a, toluene, hydrogen-containing silicone oil, hydroquinone and cis-dichlorobis(pyridyl)platinum is 1.5 mol: 100 ml: 1 mol: 0.5 mol: 0.020 mol;

[0072] Step B3: Add the reaction product b to DMF, add dichlorothionyl under stirring, and reflux and stir at 50°C for 5h to obtain the reaction product c; then add 2-aminoethyl methacrylate, potassium carbonate and dimethyl sulfoxide to a flask to obtain a mixed solution 1, and then add the above reaction product c to dimethyl sulfoxide to obtain a mixed solution 2, slowly dropwise add the mixed solution 2 to the mixed solution 1 in a 0°C ice-water bath, after the dropwise addition is completed, heat to 40°C, stir and react at a constant temperature for 10h, and distill under reduced pressure to obtain a functional monomer; the amount ratio of the reaction product b, DMF, and dichlorothionyl is 0.1mol:70mL:0.15mol; the amount ratio of 2-aminoethyl methacrylate, potassium carbonate, and dimethyl sulfoxide is 0.1mol:0.004mol:35mL; the amount ratio of the reaction product c and dimethyl sulfoxide is 0.1mol:90mL; the amount ratio of the mixed solution 1 to the mixed solution 2 is 40mL:95mL;

[0073] Step B4: Mix butyl acrylate, acrylic acid, styrene, methacrylic acid, hydroxyethyl acrylate and functional monomer at room temperature for 20 minutes to obtain a mixture; then mix water, disodium lauryl polyoxyethylene ether sulfosuccinate and sodium 3-allyloxy-2-hydroxypropanesulfonate and stir for 15 minutes to obtain a mixed solution; add the mixed solution to the mixture and stir for 40 minutes to obtain a pre-emulsified monomer; then add water, disodium lauryl polyoxyethylene ether sulfosuccinate, sodium 3-allyloxy-2-hydroxypropanesulfonate and ammonium persulfate to a reaction bottle, heat to 80°C, add the pre-emulsified monomer to the reaction bottle, and react at a constant temperature for 20 minutes, then slowly add the pre-emulsified monomer and initiator solution dropwise at 85°C, complete the addition within 2 hours, react at a constant temperature for 1.5 hours, cool to room temperature, and filter with a 200-mesh sieve to obtain the modified The invention discloses a novel acrylic resin comprising a pre-emulsified monomer and a pre-emulsified monomer. The pre-emulsified monomer comprises ...

[0074] Example 7

[0075] A composite coating, comprising a primer and a topcoat; the primer comprises the following raw materials in parts by weight: 30 parts of liquid epoxy resin, 8 parts of reactive diluent, 10 parts of pigment, 10 parts of filler, 5 parts of modified graphene oxide, 25 parts of xylene, 0.4 parts of dispersant, 0.3 parts of defoamer, 0.2 parts of anti-settling agent, and 1 part of curing agent; in the primer, the liquid epoxy resin is bisphenol A type liquid epoxy resin, the reactive diluent is propylene oxide dodecyl ether, the pigment is red iron oxide, the filler is titanium dioxide, the cosolvent is xylene, the dispersant is sodium dodecylbenzene sulfonate, the defoamer is an organosilicon defoamer, the anti-settling agent is polyamide wax, and the curing agent is diethylenetriamine;

[0076] The topcoat comprises the following raw materials in parts by weight: 40 parts of modified acrylic resin, 10 parts of pigment, 10 parts of filler, 25 parts of cosolvent, 0.3 parts of defoamer, 0.2 parts of leveling agent, 0.3 parts of anti-settling agent, 1 part of adhesion promoter, and 1 part of curing agent; in the topcoat, the pigment is zinc phosphate, the filler is talcum powder, the cosolvent is ethyl acetate, the defoamer is a polyester defoamer, the leveling agent is a polyether-modified acrylic leveling agent, the anti-settling agent is hydroxyethyl cellulose, the adhesion promoter is γ-aminopropyltriethoxysilane, and the curing agent is hexamethylene diisocyanate;

[0077] The primer is applied on the surface of the substrate, and the topcoat is applied on the surface of the primer; the substrate is steel, concrete, wood or plastic;

[0078] The composite coating is prepared by the following steps:

[0079] Step S1: Add the primer including the liquid epoxy resin in the raw materials and the modified graphene oxide obtained in Example 1 to a reactor and stir for 15 minutes, then add the active diluent, pigment, filler, xylene, dispersant, defoamer, anti-settling agent, continue stirring for 10 minutes, and finally add the curing agent and stir for 20 minutes to obtain the primer;

[0080] Step S2: adding the modified acrylic resin obtained in Example 4, pigment, filler, cosolvent, defoamer, leveling agent, anti-settling agent, and adhesion promoter to another reaction kettle, stirring for 30 minutes, and then adding curing agent and stirring for 5 minutes to obtain the topcoat;

[0081] Step S3: The primer obtained in step S1 and the topcoat obtained in step S2 are packaged separately to obtain a composite coating.

[0082] Example 8

[0083] A composite coating, comprising a primer and a topcoat; the primer comprises the following raw materials in parts by weight: 35 parts of liquid epoxy resin, 9 parts of reactive diluent, 15 parts of pigment, 15 parts of filler, 7 parts of modified graphene oxide, 30 parts of xylene, 0.5 parts of dispersant, 0.4 parts of defoamer, 0.3 parts of anti-settling agent, and 2 parts of curing agent; in the primer, the liquid epoxy resin is bisphenol A type liquid epoxy resin, the reactive diluent is propylene oxide dodecyl ether, the pigment is red iron oxide, the filler is titanium dioxide, the cosolvent is xylene, the dispersant is sodium dodecylbenzene sulfonate, the defoamer is an organosilicon defoamer, the anti-settling agent is polyamide wax, and the curing agent is diethylenetriamine;

[0084] The topcoat comprises the following raw materials in parts by weight: 45 parts of modified acrylic resin, 15 parts of pigment, 15 parts of filler, 30 parts of cosolvent, 0.4 parts of defoamer, 0.3 parts of leveling agent, 0.4 parts of anti-settling agent, 1.5 parts of adhesion promoter, and 2 parts of curing agent; in the topcoat, the pigment is zinc phosphate, the filler is talcum powder, the cosolvent is ethyl acetate, the defoamer is a polyester defoamer, the leveling agent is a polyether-modified acrylic leveling agent, the anti-settling agent is hydroxyethyl cellulose, the adhesion promoter is γ-aminopropyltriethoxysilane, and the curing agent is hexamethylene diisocyanate;

[0085] The primer is applied on the surface of the substrate, and the topcoat is applied on the surface of the primer; the substrate is steel, concrete, wood or plastic;

[0086] The composite coating is prepared by the following steps:

[0087] Step S1: Add the primer including the liquid epoxy resin in the raw materials and the modified graphene oxide obtained in Example 2 to a reactor and stir for 20 minutes, then add the active diluent, pigment, filler, xylene, dispersant, defoamer, anti-settling agent, continue stirring for 12 minutes, and finally add the curing agent and stir for 25 minutes to obtain the primer;

[0088] Step S2: adding the modified acrylic resin obtained in Example 5, pigment, filler, cosolvent, defoamer, leveling agent, anti-settling agent, and adhesion promoter in the topcoat to another reaction kettle, stirring for 35 minutes, and then adding a curing agent and stirring for 7 minutes to obtain the topcoat;

[0089] Step S3: The primer obtained in step S1 and the topcoat obtained in step S2 are packaged separately to obtain a composite coating.

[0090] Example 9

[0091] A composite coating, comprising a primer and a topcoat; the primer comprises the following raw materials in parts by weight: 40 parts of liquid epoxy resin, 10 parts of reactive diluent, 20 parts of pigment, 20 parts of filler, 10 parts of modified graphene oxide, 35 parts of xylene, 0.6 parts of dispersant, 0.5 parts of defoamer, 0.4 parts of anti-settling agent, and 3 parts of curing agent; in the primer, the liquid epoxy resin is bisphenol A type liquid epoxy resin, the reactive diluent is propylene oxide dodecyl ether, the pigment is red iron oxide, the filler is titanium dioxide, the cosolvent is xylene, the dispersant is sodium dodecylbenzene sulfonate, the defoamer is an organosilicon defoamer, the anti-settling agent is polyamide wax, and the curing agent is diethylenetriamine;

[0092] The topcoat comprises the following raw materials in parts by weight: 50 parts of modified acrylic resin, 20 parts of pigment, 20 parts of filler, 35 parts of cosolvent, 0.5 parts of defoamer, 0.4 parts of leveling agent, 0.5 parts of anti-settling agent, 2 parts of adhesion promoter, and 3 parts of curing agent; in the topcoat, the pigment is zinc phosphate, the filler is talcum powder, the cosolvent is ethyl acetate, the defoamer is a polyester defoamer, the leveling agent is a polyether-modified acrylic leveling agent, the anti-settling agent is hydroxyethyl cellulose, the adhesion promoter is γ-aminopropyltriethoxysilane, and the curing agent is hexamethylene diisocyanate;

[0093] The primer is applied on the surface of the substrate, and the topcoat is applied on the surface of the primer; the substrate is steel, concrete, wood or plastic;

[0094] The composite coating is prepared by the following steps:

[0095] Step S1: Add the primer including the liquid epoxy resin in the raw materials and the modified graphene oxide obtained in Example 3 to a reactor and stir for 25 minutes, then add the active diluent, pigment, filler, xylene, dispersant, defoamer, anti-settling agent, continue stirring for 15 minutes, and finally add the curing agent and stir for 30 minutes to obtain the primer;

[0096] Step S2: adding the modified acrylic resin obtained in Example 6, pigment, filler, cosolvent, defoamer, leveling agent, anti-settling agent, and adhesion promoter in the topcoat to another reaction kettle, stirring for 40 minutes, and then adding the curing agent and stirring for 10 minutes to obtain the topcoat;

[0097] Step S3: The primer obtained in step S1 and the topcoat obtained in step S2 are packaged separately to obtain a composite coating.

[0098] Comparative Example 1

[0099] This comparative example is a composite coating composed of a commercially available common epoxy resin coating as a primer and a common acrylic resin coating as a topcoat.

[0100] Comparative Example 2

[0101] Compared with Example 9, the modified graphene oxide in the primer is replaced with graphene oxide, and the rest is exactly the same as Example 9 to prepare a composite coating.

[0102] Comparative Example 3

[0103] Compared with Example 9, the modified acrylic resin in the topcoat was replaced with ordinary acrylic resin, and the rest was exactly the same as Example 9 to prepare a composite coating.

[0104] The composite coating prepared by the present invention is further tested for its effect, and the test results are as follows.

[0105] In order to test the composite coating prepared by the present invention, the primer in the composite coating prepared by Examples 7-9 and Comparative Examples 1-3 was applied on a standard test plate pretreated according to "GB / T9271-2008 Standard Test Plate for Paints and Varnishes", and then the topcoat in the composite coating prepared by Examples 7-9 and Comparative Examples 1-3 was applied on the primer to obtain a composite coating; the surface hardness was measured according to GB / T6739-2022 "Determination of Paint Film Hardness by Pencil Method for Paints and Varnishes"; GB / T 1733-1993 "Determination of water resistance of paint film" for water resistance test; refer to GB / T10592-2008 for heat resistance test of coating film, and observe the change of coating film; Antibacterial property determination method: Escherichia coli, Staphylococcus aureus, and Candida albicans are used as test bacteria to test the antibacterial rate of the composite coating obtained in Examples 7-9 and Comparative Examples 1-3, and the oxygen index is tested according to GB / T2406.2-2009 "Determination of combustion behavior of plastics by oxygen index method", and the results are recorded in Table 1;

[0106] Table 1: Test results

[0107]

[0108]

[0109] According to the data in Table 1, it can be seen from the comparison of Example 7, Example 8 and Example 9 with Comparative Example 1 that the composite coating formed by the composite coating disclosed in the present invention has excellent mechanical properties, water resistance, heat resistance, antibacterial properties and flame retardancy compared to the composite coating formed by the commercially available ordinary epoxy resin coating as the primer and the ordinary acrylic resin coating as the topcoat. It can be seen from the comparison of Example 9 with Comparative Example 2 that the use of modified graphene oxide in the primer introduces pyridine rings, trifluoromethyl groups and primary amine groups, which improves the antibacterial properties, water resistance and mechanical properties of the composite coating. It can be seen from the comparison of Example 9 with Comparative Example 3 that the use of modified acrylic resin containing polysiloxane chains and sodium sulfonate groups in the topcoat improves the heat resistance and flame retardancy of the composite coating.

[0110] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A composite coating, characterized in that: It includes a primer and a topcoat; the primer includes the following raw materials in parts by weight: 30-40 parts of liquid epoxy resin, 8-10 parts of reactive diluent, 10-20 parts of pigment, 10-20 parts of filler, 5-10 parts of modified graphene oxide, 25-35 parts of xylene, 0.4-0.6 parts of dispersant, 0.3-0.5 parts of defoamer, 0.2-0.4 parts of anti-settling agent, and 1-3 parts of curing agent; the topcoat includes the following raw materials in parts by weight: 40-50 parts of modified acrylic resin, 10-20 parts of pigment, 10-20 parts of filler, 25-35 parts of cosolvent, 0.3-0.5 parts of defoamer, 0.2-0.4 parts of leveling agent, 0.3-0.5 parts of anti-settling agent, 1-2 parts of adhesion promoter, and 1-3 parts of curing agent; The modified graphene oxide is prepared by the following steps: Step A1: 3,5-pyridinedicarboxylic acid is added to DMF, and dichlorothionyl is added under stirring, and the mixture is refluxed and stirred at 50° C. for 4-5 hours to obtain an acyl chloride product; 2-amino-5-nitrotrifluorotoluene, potassium carbonate and dimethyl sulfoxide are added to a flask to obtain a mixed solution a, and then the above-mentioned acyl chloride product is added to dimethyl sulfoxide to obtain a mixed solution b, and the mixed solution b is slowly added dropwise to the mixed solution a in a 0° C. ice-water bath. After the addition is completed, the mixture is heated to 40° C., stirred at a constant temperature for 8-10 hours, and distilled under reduced pressure to obtain a reaction product 1; Step A2: Add the reaction product 1 and toluene into a three-necked flask, heat to 45-55°C, start reflux stirring, then add sodium dithionite, and reflux stirring for 1-1.5h to obtain the reaction product 2; Step A3: adding graphene oxide to deionized water, and ultrasonically dispersing for 20-30 minutes to obtain a dispersion; adding PBS buffer to a flask, and then adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in an ice-water bath, stirring for 15-25 minutes, then slowly adding the above dispersion to the flask, stirring for 12-14 hours in an ice bath, adjusting the pH to 7-7.5, adding the reaction product 2, stirring at room temperature for 4-5 hours, centrifuging, and then washing the supernatant to neutrality, removing the supernatant and adding the precipitate to deionized water, and ultrasonically dispersing to obtain modified graphene oxide; The modified acrylic resin is prepared by the following steps: Step B1: In a nitrogen atmosphere, sodium benzaldehyde-2-sulfonate and acetic anhydride are added to a reaction bottle, refluxed and stirred, and the temperature is raised to 150-170° C., potassium carbonate is added, and the reaction is carried out under constant temperature reflux and stirring for 24-26 hours, and the reaction product a is obtained by extraction, rotary evaporation, and drying; Step B2: Add toluene, hydrogenated silicone oil, hydroquinone, and cis-dichlorobis(pyridyl)platinum into a three-necked flask in a certain proportion, stir and introduce nitrogen protection, slowly add the reaction product a, slowly raise the temperature to 70-80°C, stir and react for 3-4h, and evacuate to obtain the reaction product b; Step B3: Add the reaction product b to DMF, add thionyl chloride under stirring, and reflux and stir at 50°C for 4-5h to obtain the reaction product c; then add 2-aminoethyl methacrylate, potassium carbonate and dimethyl sulfoxide to a flask to obtain a mixed solution 1, and then add the above reaction product c to dimethyl sulfoxide to obtain a mixed solution 2, slowly dropwise add the mixed solution 2 to the mixed solution 1 in a 0°C ice water bath, after the dropwise addition is completed, heat to 40°C, stir at a constant temperature for 8-10h, and distill under reduced pressure to obtain a functional monomer; Step B4: Mix butyl acrylate, acrylic acid, styrene, methacrylic acid, hydroxyethyl acrylate and functional monomer at room temperature for 15-20 minutes to obtain a mixture; then mix water, disodium lauryl polyoxyethylene ether sulfosuccinate and sodium 3-allyloxy-2-hydroxypropanesulfonate and stir for 10-15 minutes to obtain a mixed solution; add the mixed solution to the mixture and stir for 30-40 minutes to obtain a pre-emulsified monomer; then add water, disodium lauryl polyoxyethylene ether sulfosuccinate, sodium 3-allyloxy-2-hydroxypropanesulfonate and ammonium persulfate to a reaction bottle, heat to 70-80° C., add the pre-emulsified monomer to the reaction bottle, and then react at a constant temperature for 20 minutes, and then slowly add the pre-emulsified monomer and initiator solution dropwise at 80-85° C. within 2 hours, react at a constant temperature for 1.5 hours, cool to room temperature, and filter with a 200-mesh sieve to obtain a modified acrylic resin.

2. A composite coating according to claim 1, characterized in that: In step A1, the usage ratio of 3,5-pyridinedicarboxylic acid, DMF, and dichlorothionyl is 0.1 mol: 40-50 mL: 0.12-0.15 mol; the usage ratio of 2-amino-5-nitrotrifluorotoluene, potassium carbonate, and dimethyl sulfoxide is 0.2 mol: 0.008-0.009 mol: 90-100 mL; the usage ratio of the acyl chloride product and dimethyl sulfoxide is 0.1 mol: 50-60 mL; and the usage ratio of the mixed solution a and the mixed solution b is 95-105 mL: 55-65 mL.

3. A composite coating according to claim 1, characterized in that: In step A2, the usage ratio of reaction product 1, toluene and sodium dithionite is 0.1 mol:105-115 mL:0.2-0.25 mol.

4. A composite coating according to claim 1, characterized in that: In step A3, the amount ratio of graphene oxide and deionized water is 0.008 g:1 mL; the amount ratio of PBS buffer, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, dispersion, and reaction product 2 is 200 mL:3.1 g:0.26 g:100 mL:5 g, and the pH of PBS buffer is 5.5; the amount ratio of precipitate and deionized water is 0.0065-0.0070 g:1 mL.

5. A composite coating according to claim 1, characterized in that: In step B1, the dosage ratio of sodium benzaldehyde-2-sulfonate, acetic anhydride and potassium carbonate is 0.1 mol: 0.05-0.07 mol: 0.005-0.008 mol; in step B2, the dosage ratio of reaction product a, toluene, hydrogenated silicone oil, hydroquinone and cis-dichlorobis(pyridyl)platinum is 1-1.5 mol: 100 ml: 1 mol: 0.5 mol: 0.015-0.020 mol.

6. A composite coating according to claim 1, characterized in that: In step B3, the usage ratio of reaction product b, DMF and dichlorothionyl is 0.1 mol: 60-70 mL: 0.12-0.15 mol; the usage ratio of 2-aminoethyl methacrylate, potassium carbonate and dimethyl sulfoxide is 0.1 mol: 0.002-0.004 mol: 25-35 mL; the usage ratio of reaction product c and dimethyl sulfoxide is 0.1 mol: 80-90 mL; the usage ratio of mixed solution 1 and mixed solution 2 is 30-40 mL: 85-95 mL.

7. A composite coating according to claim 1, characterized in that: In step B4, the usage ratio of butyl acrylate, acrylic acid, styrene, methacrylic acid, hydroxyethyl acrylate and functional monomer is 145g:4g:22g:4g:6g:9g; The dosage ratio of water, disodium lauryl polyoxyethylene ether sulfosuccinate and sodium 3-allyloxy-2-hydroxypropane sulfonate is 70g:1.8g:0.8g; the dosage ratio of water, disodium lauryl polyoxyethylene ether sulfosuccinate, sodium 3-allyloxy-2-hydroxypropane sulfonate, ammonium persulfate, pre-emulsified monomer and initiator solution is 100-110g:0.35g:1.2g:0.4g:72.6g:6g, the initiator solution is obtained by adding 0.5-0.6g of ammonium persulfate into 5-6g of water and stirring and mixing, the weight ratio of the pre-emulsified monomer added twice is 1:2, and the sum of the weights of the pre-emulsified monomer added twice is the total dosage of the pre-emulsified monomer used.

8. A composite coating according to claim 1, characterized in that: The primer is coated on the surface of the substrate, and the topcoat is coated on the surface of the primer; the substrate is steel, concrete, wood or plastic; in the primer, the liquid epoxy resin is bisphenol A type liquid epoxy resin, the active diluent is propylene oxide dodecyl ether, the pigment is red iron oxide, the filler is titanium dioxide, the cosolvent is xylene, the dispersant is sodium dodecylbenzene sulfonate, the defoamer is an organosilicon defoamer, the anti-settling agent is polyamide wax, and the curing agent is diethylenetriamine; in the topcoat, the pigment is zinc phosphate, the filler is talcum powder, the cosolvent is ethyl acetate, the defoamer is a polyester defoamer, the leveling agent is a polyether modified acrylic leveling agent, the anti-settling agent is hydroxyethyl cellulose, the adhesion promoter is γ-aminopropyltriethoxysilane, and the curing agent is hexamethylene diisocyanate.

9. The method for preparing a composite coating according to claim 1, characterized in that: The steps include: Step S1: adding the liquid epoxy resin and modified graphene oxide in the raw materials included in the primer to the reaction kettle and stirring for 15-25 minutes, then adding the active diluent, pigment, filler, xylene, dispersant, defoamer, anti-settling agent in the raw materials included in the primer, continuing to stir for 10-15 minutes, and finally adding the curing agent in the raw materials included in the primer, stirring for 20-30 minutes, so as to obtain the primer; Step S2: adding the modified acrylic resin, pigment, filler, cosolvent, defoamer, leveling agent, anti-settling agent, and adhesion promoter in the raw materials of the topcoat to another reaction kettle, stirring for 30-40 minutes, and then adding the curing agent in the raw materials of the topcoat, stirring for 5-10 minutes, to obtain the topcoat; Step S3: The primer obtained in step S1 and the topcoat obtained in step S2 are packaged separately to obtain a composite coating.

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