Water-based paint of polydopamine modified acrylic resin and preparation process of water-based paint

Abstract

The invention discloses a water-based paint of polydopamine modified acrylic resin and a preparation process of the water-based paint, and belongs to the technical field of water-based paint preparation. The water-based paint of the polydopamine modified acrylic resin is prepared from the following components in parts by weight: 30 to 40 parts of a mixed solvent, 1 to 5 parts of modified polydopamine, 12 to 28 parts of a modified viscosity agent, 15 to 25 parts of an acrylic monomer, 0.2 to 1 part of an initiator, 0.8 to 1 part of an emulsifier, 1 to 5 parts of a pH regulator and 60 to 70 parts of deionized water. The water-based paint prepared by the method has excellent adhesion, stability and mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of waterborne coating preparation, and particularly relates to a waterborne coating of polydopamine-modified acrylic resin and a preparation process thereof. Background Art

[0002] Although traditional acrylic resin has advantages such as good film-forming property and excellent weather resistance, its insufficient thermal stability will cause thermal degradation or molecular chain breakage in high-temperature environments. Especially under baking conditions above 120°C, yellowing and embrittlement are likely to occur, which limits its application in high-temperature process fields such as automotive baking paint and electronic packaging. In addition, the residual emulsifier or uncrosslinked groups in the resin molecular chain will reduce the denseness of the coating, resulting in a decrease in water resistance and further affecting long-term stability. In terms of adhesion, the adhesion of traditional acrylic resin to polar substrates is weak, and the matching of its surface tension with the substrate is insufficient, which easily leads to pseudo-adhesion of the coating or interfacial failure. Dopamine, as a biomimetic adhesion molecule, the catechol group in its molecular structure can form strong covalent or non-covalent bonds with the surfaces of various substrates, significantly enhancing the interfacial adhesion strength. Through the self-polymerization or graft modification of dopamine, active adhesion sites can be introduced into the acrylic resin molecular chain to enhance the chemical bonding between the resin and the substrate.

[0003] Patent CN106189640B discloses a preparation method of a modified waterborne acrylic resin coating. Using silica as a raw material, it is ultrasonically dispersed in an ethanol solution and modified with a coupling agent. After centrifugation and drying, modified silica is obtained, and then polymethylsilsesquioxane powder is prepared for later use. Then, methyl methacrylate, butyl acrylate, and glycidyl methacrylate are mixed evenly, and a modified acrylic emulsion is prepared by adding an initiator. Finally, the polymethylsilsesquioxane powder, modified silica, emulsifier, modified acrylic emulsion, deionized water, and defoamer are highly dispersed to obtain a modified waterborne acrylic resin coating. The modified waterborne acrylic resin prepared by this invention solves the defect that traditional coatings have high water absorption and are not easy to store and use for a long time. However, there is still room for improvement in the adhesion, stability, and mechanical properties of the coating prepared by this method. Summary of the Invention

[0004] The purpose of the present invention is to provide a waterborne coating of polydopamine-modified acrylic resin and a preparation process thereof, which are used to solve the technical problems of poor adhesion, stability, and mechanical properties of coatings in the prior art.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions: The present invention provides an aqueous coating of polydopamine-modified acrylic resin, which is composed of the following components in parts by weight: 30-40 parts of a mixed solvent, 1-5 parts of modified polydopamine, 12-28 parts of a modified viscosity modifier, 15-25 parts of an acrylic monomer, 0.2-1 part of an initiator, 0.8-1 part of an emulsifier, 1-5 parts of a pH regulator, and 60-70 parts of deionized water.

[0006] Preferably, the mixed solvent is obtained by mixing methyl methacrylate and 2-ethylhexyl acrylate in a mass ratio of (1.2-2):1. The acrylic monomer is composed of one or more of acrylic acid, methacrylic acid, ethyl acrylate, ethyl methacrylate, styrene, cyclohexyl methacrylate, and acrylonitrile. The initiator is composed of one or more of ammonium sulfate, potassium persulfate, and benzoyl peroxide. The emulsifier is composed of one or both of sodium dodecyl sulfate and octylphenol polyoxyethylene ether. The pH regulator is composed of one or more of ammonia water, triethylamine, and N,N-dimethylethanolamine.

[0007] Preferably, the preparation method of the modified polydopamine includes the following steps: Q1: Add 2,5-diaminopentanoic acid to ultrapure water, add tetrahydrofuran, stir under nitrogen protection, add sodium bicarbonate and di-tert-butyl dicarbonate, react at a constant temperature. After the reaction is completed, perform rotary evaporation, dropwise add hydrochloric acid, precipitate a thick substance, dissolve, wash, extract, dry, perform rotary evaporation again, and vacuum dry to obtain Compound 1; Q2: Add Compound 1 to dichloromethane, add N-hydroxysuccinimide, stir and react under nitrogen protection, add EDC hydrochloride, react in an ice bath, and then react at room temperature under nitrogen protection. After the reaction is completed, wash, separate the liquid, dry, perform rotary evaporation, and dry to obtain Compound 2; Add Compound 2 to methanol, stir under nitrogen protection, then add dopamine hydrochloride, stir to dissolve, dropwise add triethylamine, react at a constant temperature under nitrogen protection, perform rotary evaporation, dissolve, wash, separate the liquid, dry, perform rotary evaporation again, and dry to obtain Compound 3; Q3: Add Compound 3 to ethyl acetate, then add a mixed solution of hydrogen chloride and ethyl acetate, react at room temperature under nitrogen protection, perform rotary evaporation, suction filtration, and dry to obtain Compound 4; Add magnetic iron oxide nanoparticles to PBS buffer solution, then add Compound 4 and ascorbic acid, stir and react under nitrogen protection. After the reaction is completed, centrifuge, wash, and dry to obtain modified polydopamine.

[0008] In the above process, the synthesis reaction formula of Compound 3 is as follows:

[0009] The results of mass spectrometry analysis of Compound 1 are as follows: m / z: 332.19 (100.0%), 333.20 (16.8%), 334.20 (2.7%); the results of mass spectrometry analysis of Compound 2 are as follows: m / z: 429.21 (100.0%), 430.21 (21.7%), 431.22 (3.8%); the results of mass spectrometry analysis of Compound 3 are as follows: m / z: 467.26 (100.0%), 468.27 (25.6%), 469.27 (4.6%), 468.26 (1.1%); the results of mass spectrometry analysis of Compound 4 are as follows: m / z: 267.16 (100.0%), 268.16 (15.5%), 269.17 (1.0%).

[0010] Preferably, in Q1, the dosage ratio of 2,5-diaminopentanoic acid, ultrapure water, tetrahydrofuran, sodium bicarbonate and di-tert-butyl dicarbonate is (6.21 - 7.05) g : (120 - 180) mL : (45 - 55) mL : (12.1 - 12.9) g : (30.2 - 35.1) g, the stirring time is 10 - 20 min, the constant temperature reaction temperature is 30 - 34 °C, and the reaction time is 20 - 28 h.

[0011] Preferably, in Q2, the molar ratio of Compound 1, N-hydroxysuccinimide and EDC hydrochloride is 1 : (1.02 - 1.39) : (0.45 - 0.62), the stirring reaction time is 10 - 20 min, the ice bath reaction temperature is 0 - 1 °C, the reaction time is 30 - 45 min, and the protection reaction time is 5 - 6 h; the molar ratio of Compound 2, dopamine hydrochloride and triethylamine is 1 : (1.32 - 1.83) : (1.06 - 1.47), the stirring time is 10 - 20 min, the constant temperature reaction temperature is 30 - 32 °C, and the time is 10 - 12 h.

[0012] Preferably, in Q3, the dosage ratio of Compound 3, the mixed solution of ethyl acetate, hydrogen chloride and ethyl acetate is (8.2 - 10.5) g : (80 - 110) mL : (45 - 55) mL, and the room temperature reaction time is 3 - 5 h; the dosage ratio of magnetic iron oxide nanoparticles, PBS buffer solution, Compound 4 and ascorbic acid is (0.1 - 0.15) g : (10 - 15) mL : (0.02 - 0.25) g : (0.01 - 0.018) g, and the stirring reaction time is 20 - 24 h.

[0013] Preferably, the preparation method of the modified viscosity modifier includes the following steps: S1: Add 4-nitrophthalonitrile, 3-aminophenol, anhydrous potassium carbonate and dimethyl sulfoxide into a container. After magnetic stirring, heat under reflux under nitrogen protection, cool, filter, add deionized water, precipitate, wash and dry to obtain intermediate A; S2: Add hexafluorobisphenol, intermediate A, trimethylolpropane tripropyleneglycol ether (amino-terminated) and paraformaldehyde into a container, heat for reaction. After the reaction is completed, cool to room temperature, wash, collect the organic phase, dry, add anhydrous sodium sulfate, let stand, rotary evaporate and vacuum dry to obtain the modified viscosity agent.

[0014] In the above process, the synthesis reaction formula of the modified viscosity agent is as follows:

[0015] Preferably, in S1, the dosage ratio of 4-nitrophthalonitrile, 3-aminophenol, anhydrous potassium carbonate and dimethyl sulfoxide is (16.8 - 17.9) g : (10.1 - 11.8) g : (15 - 19) g : (25 - 33) mL, the heat reflux temperature is 80 - 85 °C, and the time is 8 - 10 h; in S2, the dosage ratio of hexafluorobisphenol, intermediate A, trimethylolpropane tripropyleneglycol ether (amino-terminated) and paraformaldehyde is (2.1 - 4.6) g : (1.72 - 1.95) g : (1.04 - 1.43) g : (5.34 - 6.12) g, the heat reaction temperature is 60 - 72 °C, and the reaction time is 10 - 14 h.

[0016] Preferably, the preparation process of the waterborne coating of the polydopamine-modified acrylic resin includes the following steps: Step 1: Add an emulsifier, deionized water and modified polydopamine into a container, then add an initiator and a mixed solvent, stir vigorously, and then add an acrylic monomer and a modified viscosity agent, and control the feeding time to obtain a mixture; Step 2: Carry out a temperature-rising reaction on the mixture. After the reaction is completed, add a pH regulator, cool to obtain the waterborne coating of the polydopamine-modified acrylic resin.

[0017] Preferably, in Step 1, the vigorous stirring time is 30 - 40 min, the temperature is 70 - 80 °C, and the feeding time is 2.5 - 3 h; in Step 2, the temperature-rising reaction temperature is 80 - 85 °C, the reaction time is 1.5 - 2 h, and add a pH regulator until pH = 8 - 9.

[0018] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are: 1. First, the present invention uses 2,5-diaminopentanoic acid, di-tert-butyl dicarbonate, N-hydroxysuccinimide, dopamine hydrochloride, and magnetic iron oxide nanoparticles as the main raw materials to prepare modified polydopamine. Subsequently, 4-nitrophthalonitrile, 3-aminophenol, hexafluorobisphenol, trimethylolpropane tripropyleneglycol ether (amine-terminated), and paraformaldehyde are used as the main raw materials to prepare a modified viscosifier. Adding the two to the waterborne coating can effectively improve its adhesion, mechanical properties, and stability.

[0019] 2. Adding the prepared modified polydopamine to the waterborne coating can effectively improve the adhesion and mechanical properties of the coating. The catechol structure contained in the modified polydopamine can strongly adhere to the substrate surface through various forces, enhancing the interfacial bonding force. The amino group contained can react with the carboxylic acid group of the acrylic resin, further enhancing the adhesion of the coating. The modified polydopamine can also form a physical crosslinking network with the acrylic resin, enhancing the rigidity and scratch resistance of the coating. The magnetic iron oxide nanoparticles contained can exert a nano-filling effect, hinder crack propagation, and improve the wear resistance of the coating through interfacial stress transfer.

[0020] 3. Adding the prepared modified viscosifier to the waterborne coating can optimize the dynamic rheological properties of the coating, improve the adhesion and stability of the coating. The presence of the crosslinking network and fluorinated segments contained in the modified viscosifier can effectively adjust the viscosity of the coating and enhance thixotropy. The nitrile group contained in the modified viscosifier can form a chemical bond with the substrate surface, improving the wettability and anchoring force of the coating to the substrate. The fluorine atoms contained can enhance the adhesion of the coating through strong electronegativity-induced dipole interactions. At the same time, the conjugated electron system contained in the modified viscosifier can delay the photooxidative degradation of the acrylic resin, and the presence of the carbon-fluorine bond also endows the coating with excellent thermal stability. Detailed implementation mode

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] Example 1: This example discloses a preparation method of modified polydopamine, including the following steps: Q1: Add 6.63 g of 2,5-diaminopentanoic acid to 150 mL of ultrapure water, add 50 mL of tetrahydrofuran, stir for 15 min under nitrogen protection, add 12.5 g of sodium bicarbonate and 32.7 g of di-tert-butyl dicarbonate, react at a constant temperature of 30 °C for 24 h. After the reaction is completed, perform rotary evaporation, add hydrochloric acid dropwise, precipitate a thick substance, dissolve, wash, extract, dry, perform rotary evaporation again, and dry under vacuum to obtain Compound 1; Q2: Add Compound 1 to 120 mL of dichloromethane, add 1.38 g of N-hydroxysuccinimide, stir and react for 15 min under nitrogen protection, add 1.02 g of EDC hydrochloride, react in an ice bath at 0 °C for 45 min, and react at room temperature under nitrogen protection for 6 h. After the reaction is completed, wash, separate the liquid, dry, perform rotary evaporation, and dry to obtain Compound 2; Add 4.15 g of Compound 2 to 150 mL of methanol, stir for 15 min under nitrogen protection, then add 3.53 g of dopamine hydrochloride, stir to dissolve, dropwise add 1.28 g of triethylamine, react at a constant temperature of 30 °C for 12 h under nitrogen protection, perform rotary evaporation, dissolve, wash, separate the liquid, dry, perform rotary evaporation again, and dry to obtain Compound 3; Q3: Add 9.3 g of Compound 3 to 95 mL of ethyl acetate, then add 50 mL of a mixed solution of hydrogen chloride and ethyl acetate, react at room temperature for 5 h under nitrogen protection, perform rotary evaporation, suction filtration, and dry to obtain Compound 4; Add 0.125 g of magnetic iron oxide nanoparticles to 12.5 mL of PBS buffer solution, then add 0.12 g of Compound 4 and 0.014 g of ascorbic acid, stir and react for 24 h under nitrogen protection. After the reaction is completed, centrifuge, wash, and dry to obtain modified polydopamine.

[0023] This example discloses a preparation method of a modified viscosifier, including the following steps: S1: Add 17.3 g of 4-nitrophthalonitrile, 10.5 g of 3-aminophenol, 17 g of anhydrous potassium carbonate, and 29 mL of dimethyl sulfoxide to a container. After magnetic stirring, heat under reflux at 85 °C for 10 h under nitrogen protection, cool, filter, add deionized water, precipitate, wash, and dry to obtain Intermediate A; S2: Add 3.5 g of hexafluorobisphenol, 1.83 g of Intermediate A, 1.24 g of trimethylolpropane tripropyleneglycol ether (amine-terminated), and 5.73 g of paraformaldehyde to a container, heat and react at 70 °C for 12 h. After the reaction is completed, cool to room temperature, wash, collect the organic phase, dry, add anhydrous sodium sulfate, let stand, perform rotary evaporation, and dry under vacuum to obtain the modified viscosifier.

[0024] This example discloses an aqueous coating of polydopamine-modified acrylic resin, which is composed of the following components by weight: 35 parts of a mixed solvent obtained by mixing methyl methacrylate and 2-ethylhexyl acrylate at a mass ratio of 1.6:1, 3 parts of modified polydopamine, 20 parts of modified viscosity agent, 20 parts of acrylic acid, 0.6 part of potassium persulfate, 0.9 part of sodium dodecyl sulfate, 3 parts of ammonia water, and 65 parts of deionized water.

[0025] This example discloses a preparation process of an aqueous coating of polydopamine-modified acrylic resin, which includes the following steps: Step 1: Add sodium dodecyl sulfate, deionized water, and modified polydopamine into a container, then add potassium persulfate and the mixed solvent, stir vigorously at 75 °C for 40 min, then add acrylic acid and the modified viscosity agent, control the feeding time to be 3 h to obtain a mixture; Step 2: Carry out a temperature-raising reaction on the mixture at 85 °C for 2 h. After the reaction ends, add ammonia water until the pH = 8, and cool to obtain the aqueous coating of polydopamine-modified acrylic resin.

[0026] Example 2: This example discloses a preparation method of modified polydopamine, which includes the following steps: Q1: Add 6.21 g of 2,5-diaminopentanoic acid into 120 mL of ultrapure water, add 55 mL of tetrahydrofuran, stir for 15 min under nitrogen protection, add 12.9 g of sodium bicarbonate and 30.2 g of di-tert-butyl dicarbonate, carry out a constant-temperature reaction at 30 °C for 24 h. After the reaction ends, perform rotary evaporation, dropwise add hydrochloric acid, precipitate a thick substance, dissolve, wash, extract, dry, perform rotary evaporation again, and vacuum dry to obtain Compound 1; Q2: Add 3.32 g of Compound 1 into 120 mL of dichloromethane, add 1.17 g of N-hydroxysuccinimide, stir and react for 15 min under nitrogen protection, add 0.86 g of EDC hydrochloride, react in an ice bath at 0 °C for 45 min, and react at room temperature under nitrogen protection for 6 h. After the reaction ends, wash, separate the liquid, dry, perform rotary evaporation, and dry again to obtain Compound 2; Add 4.15 g of Compound 2 into 150 mL of methanol, stir for 15 min under nitrogen protection, then add 2.97 g of dopamine hydrochloride, stir to dissolve, dropwise add 1.07 g of triethylamine, carry out a constant-temperature reaction at 30 °C for 12 h under nitrogen protection, perform rotary evaporation, dissolve, wash, separate the liquid, dry, perform rotary evaporation again, and dry to obtain Compound 3; Q3: 8.2 g of Compound 3 was added to 80 mL of ethyl acetate, and then 45 mL of a mixed solution of hydrogen chloride and ethyl acetate was added. The reaction was carried out at room temperature for 5 h under nitrogen protection. After rotary evaporation, suction filtration, and drying, Compound 4 was obtained. 0.1 g of magnetic iron oxide nanoparticles was added to 15 mL of PBS buffer solution, and then 0.02 g of Compound 4 and 0.01 g of ascorbic acid were added. The reaction was stirred for 24 h under nitrogen protection. After the reaction, centrifugation, washing, and drying were carried out to obtain modified polydopamine.

[0027] This example discloses a preparation method of a modified viscosifier, including the following steps: S1: 16.8 g of 4-nitrophthalonitrile, 10.1 g of 3-aminophenol, 15 g of anhydrous potassium carbonate, and 25 mL of dimethyl sulfoxide were added to a container. After magnetic stirring, the mixture was heated under reflux at 85 °C for 10 h under nitrogen protection. After cooling, filtration, adding deionized water, precipitation, washing, and drying, intermediate A was obtained. S2: 2.1 g of hexafluorobisphenol, 1.72 g of intermediate A, 1.04 g of trimethylolpropane tripropyleneglycol ether (amine-terminated), and 5.34 g of paraformaldehyde were added to a container. The reaction was carried out at 70 °C for 12 h. After the reaction, it was cooled to room temperature, washed, the organic phase was collected, dried, anhydrous sodium sulfate was added, allowed to stand, rotary evaporated, and vacuum dried to obtain the modified viscosifier.

[0028] This example discloses an aqueous coating of polydopamine-modified acrylic resin, which is composed of the following components by weight: 30 parts of a mixed solvent obtained by mixing methyl methacrylate and 2-ethylhexyl acrylate in a mass ratio of 1.2:1, 5 parts of modified polydopamine, 12 parts of modified viscosifier, 15 parts of acrylic acid, 0.2 part of potassium persulfate, 0.8 part of sodium dodecyl sulfate, 1 part of ammonia water, and 60 parts of deionized water.

[0029] This example discloses a preparation process of an aqueous coating of polydopamine-modified acrylic resin, including the following steps: Step 1: Sodium dodecyl sulfate, deionized water, and modified polydopamine were added to a container, and then potassium persulfate and the mixed solvent were added. The mixture was vigorously stirred at 75 °C for 40 min, and then acrylic acid and the modified viscosifier were added. The feeding time was controlled at 3 h to obtain a mixture. Step 2: The mixture was heated and reacted at 85 °C for 2 h. After the reaction, ammonia water was added until the pH = 8, and then it was cooled to obtain the aqueous coating of polydopamine-modified acrylic resin.

[0030] Example 3: This example discloses a preparation method of modified polydopamine, including the following steps: Q1: Add 7.05 g of 2,5-diaminopentanoic acid to 180 mL of ultrapure water, add 45 mL of tetrahydrofuran, stir for 15 min under nitrogen protection, add 12.1 g of sodium bicarbonate and 35.1 g of di-tert-butyl dicarbonate, react at a constant temperature of 30 °C for 24 h. After the reaction is completed, perform rotary evaporation, add hydrochloric acid dropwise, precipitate a thick substance, dissolve, wash, extract, dry, perform rotary evaporation again, and perform vacuum drying to obtain Compound 1; Q2: Add 3.32 g of Compound 1 to 120 mL of dichloromethane, add 1.6 g of N-hydroxysuccinimide, stir and react for 15 min under nitrogen protection, add 1.18 g of EDC hydrochloride, react in an ice bath at 0 °C for 45 min, and react at room temperature under nitrogen protection for 6 h. After the reaction is completed, wash, separate the liquid, dry, perform rotary evaporation, and dry to obtain Compound 2; Add 4.15 g of Compound 2 to 150 mL of methanol, stir for 15 min under nitrogen protection, then add 4.11 g of dopamine hydrochloride, stir to dissolve, add 1.49 g of triethylamine dropwise, react at a constant temperature of 30 °C for 12 h under nitrogen protection, perform rotary evaporation, dissolve, wash, separate the liquid, dry, perform rotary evaporation again, and dry to obtain Compound 3; Q3: Add 10.5 g of Compound 3 to 110 mL of ethyl acetate, then add 55 mL of a mixed solution of hydrogen chloride and ethyl acetate, react at room temperature for 5 h under nitrogen protection, perform rotary evaporation, suction filtration, and dry to obtain Compound 4; Add 0.15 g of magnetic iron oxide nanoparticles to 10 mL of PBS buffer solution, then add 0.25 g of Compound 4 and 0.018 g of ascorbic acid, stir and react for 24 h under nitrogen protection. After the reaction is completed, centrifuge, wash, and dry to obtain modified polydopamine.

[0031] This example discloses a preparation method of a modified viscosity agent, including the following steps: S1: Add 17.9 g of 4-nitrophthalonitrile, 11.8 g of 3-aminophenol, 19 g of anhydrous potassium carbonate, and 33 mL of dimethyl sulfoxide to a container. After magnetic stirring, heat and reflux at 85 °C for 10 h under nitrogen protection, cool, filter, add deionized water, precipitate, wash, and dry to obtain Intermediate A; S2: Add 4.6 g of hexafluorobisphenol, 1.95 g of Intermediate A, 1.43 g of trimethylolpropane tripropyleneglycol ether (amine-terminated), and 6.12 g of paraformaldehyde to a container, heat and react at 70 °C for 12 h. After the reaction is completed, cool to room temperature, wash, collect the organic phase, dry, add anhydrous sodium sulfate, let stand, perform rotary evaporation, and perform vacuum drying to obtain the modified viscosity agent.

[0032] This example discloses an aqueous coating of polydopamine-modified acrylic resin, which is composed of the following components in parts by weight: 40 parts of a mixed solvent obtained by mixing methyl methacrylate and 2-ethylhexyl acrylate in a mass ratio of 2:1, 1 part of modified polydopamine, 28 parts of modified viscosity modifier, 25 parts of acrylic acid, 1 part of potassium persulfate, 1 part of sodium dodecyl sulfate, 5 parts of ammonia water, and 70 parts of deionized water.

[0033] This example discloses a preparation process of an aqueous coating of polydopamine-modified acrylic resin, which includes the following steps: Step 1: Add sodium dodecyl sulfate, deionized water, and modified polydopamine into a container, then add potassium persulfate and the mixed solvent, stir vigorously at 75 °C for 40 min, then add acrylic acid and modified viscosity modifier, control the feeding time to be 3 h to obtain a mixture; Step 2: Carry out a temperature-raising reaction on the mixture at 85 °C for 2 h. After the reaction ends, add ammonia water until the pH = 8, cool to obtain the aqueous coating of polydopamine-modified acrylic resin.

[0034] Example 4: This example discloses a preparation method of modified polydopamine, which includes the following steps: Q1: Add 6.48 g of 2,5-diaminopentanoic acid into 135 mL of ultrapure water, add 48 mL of tetrahydrofuran, stir for 15 min under nitrogen protection, add 12.3 g of sodium bicarbonate and 31.8 g of di-tert-butyl dicarbonate, carry out a constant-temperature reaction at 30 °C for 24 h. After the reaction ends, perform rotary evaporation, dropwise add hydrochloric acid, precipitate a thick substance, dissolve, wash, extract, dry, perform rotary evaporation again, and vacuum dry to obtain Compound 1; Q2: Add 3.32 g of Compound 1 into 120 mL of dichloromethane, add 1.21 g of N-hydroxysuccinimide, stir and react for 15 min under nitrogen protection, add 0.92 g of EDC hydrochloride, react in an ice bath at 0 °C for 45 min, and react at room temperature under nitrogen protection for 6 h. After the reaction ends, wash, separate the liquid, dry, perform rotary evaporation, and dry to obtain Compound 2; Add 4.15 g of Compound 2 into 150 mL of methanol, stir for 15 min under nitrogen protection, then add 3.12 g of dopamine hydrochloride, stir to dissolve, dropwise add 1.17 g of triethylamine, carry out a constant-temperature reaction at 30 °C for 12 h under nitrogen protection, perform rotary evaporation, dissolve, wash, separate the liquid, dry, perform rotary evaporation again, and dry to obtain Compound 3; Q3: 8.7 g of Compound 3 was added to 85 mL of ethyl acetate, and then 48 mL of a mixed solution of hydrogen chloride and ethyl acetate was added. The reaction was carried out at room temperature for 5 h under nitrogen protection. The mixture was rotary evaporated, filtered by suction, and dried to obtain Compound 4. 0.2 g of magnetic iron oxide nanoparticles was added to 11 mL of PBS buffer solution, and then 0.08 g of Compound 4 and 0.012 g of ascorbic acid were added. The reaction was stirred for 24 h under nitrogen protection. After the reaction, it was centrifuged, washed, and dried to obtain modified polydopamine.

[0035] This example discloses a preparation method of a modified viscosity agent, which includes the following steps: S1: 17.1 g of 4-nitrophthalonitrile, 10.4 g of 3-aminophenol, 16 g of anhydrous potassium carbonate, and 27 mL of dimethyl sulfoxide were added to a container. After magnetic stirring, the mixture was heated under reflux at 85 °C for 10 h under nitrogen protection, cooled, filtered, deionized water was added, precipitated, washed, and dried to obtain Intermediate A. S2: 2.7 g of hexafluorobisphenol, 1.78 g of Intermediate A, 1.17 g of trimethylolpropane tripropyleneglycol ether (amino-terminated), and 5.58 g of paraformaldehyde were added to a container. The reaction was carried out at 70 °C for 12 h. After the reaction, it was cooled to room temperature, washed, the organic phase was collected, dried, anhydrous sodium sulfate was added, allowed to stand, rotary evaporated, and vacuum dried to obtain the modified viscosity agent.

[0036] This example discloses an aqueous coating of polydopamine-modified acrylic resin, which is composed of the following components by weight: 32 parts of a mixed solvent obtained by mixing methyl methacrylate and 2-ethylhexyl acrylate in a mass ratio of 1.4:1, 2 parts of modified polydopamine, 16 parts of modified viscosity agent, 18 parts of acrylic acid, 0.8 part of potassium persulfate, 0.9 part of sodium dodecyl sulfate, 2 parts of ammonia water, and 62 parts of deionized water.

[0037] This example discloses a preparation process of an aqueous coating of polydopamine-modified acrylic resin, which includes the following steps: Step 1: Sodium dodecyl sulfate, deionized water, and modified polydopamine were added to a container, and then potassium persulfate and the mixed solvent were added. The mixture was vigorously stirred at 75 °C for 40 min, and then acrylic acid and the modified viscosity agent were added. The feeding time was controlled to be 3 h to obtain a mixture. Step 2: The mixture was heated and reacted at 85 °C for 2 h. After the reaction, ammonia water was added until the pH = 8, and then it was cooled to obtain the aqueous coating of polydopamine-modified acrylic resin.

[0038] Comparative Example 1: Compared with Example 1, in Comparative Example 1, during the preparation of the aqueous coating, polydopamine was used instead of modified polydopamine, and other conditions remained unchanged.

[0039] Comparative Example 2: Compared with Example 1, in the process of preparing the waterborne coating in Comparative Example 2, the modified viscosity agent was not added, and other conditions remained unchanged.

[0040] Experimental Example: The waterborne coatings prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to performance tests. The adhesion of the samples was tested according to GB / T 5210-2006, the temperature change resistance of the samples was tested according to HG / T 4343-2024, and the wear resistance of the samples was tested according to GB / T 1768-2006. The test results are shown in Table 1:

[0041] It can be seen from the test results in Table 1 that the waterborne coatings prepared in Examples 1-4 of the present invention have excellent adhesion, wear resistance and thermal stability. By comparing Comparative Example 1 with Examples 1-4, it can be seen that the use of modified polydopamine can effectively improve the adhesion and wear resistance of the waterborne coating; by comparing Comparative Example 2 with Examples 1-4, it can be seen that adding a modified viscosity agent can effectively improve the adhesion and thermal stability of the waterborne coating.

[0042] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

[0043] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the present invention to only the specific embodiments. Obviously, many modifications and changes can be made according to the content of this specification. The present specification selects and specifically describes these embodiments in order to better explain the principle and practical application of the present invention, so that those skilled in the art in the relevant technical field can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. An aqueous coating of polydopamine-modified acrylic resin, characterized in that, It consists of the following components in parts by weight: 30 - 40 parts of mixed solvent, 1 - 5 parts of modified polydopamine, 12 - 28 parts of modified viscosifier, 15 - 25 parts of acrylic monomer, 0.2 - 1 part of initiator, 0.8 - 1 part of emulsifier, 1 - 5 parts of pH regulator, and 60 - 70 parts of deionized water.

2. The waterborne coating of a polydopamine-modified acrylic resin according to claim 1, characterized in that, The mixed solvent is obtained by mixing methyl methacrylate and 2-ethylhexyl acrylate in a mass ratio of (1.2 - 2):

1. The acrylic monomer consists of one or more of acrylic acid, methacrylic acid, ethyl acrylate, ethyl methacrylate, styrene, cyclohexyl methacrylate, and acrylonitrile. The initiator consists of one or more of ammonium sulfate, potassium persulfate, and benzoyl peroxide. The emulsifier consists of one or two of sodium dodecyl sulfate and octylphenol polyoxyethylene ether. The pH regulator consists of one or more of ammonia water, triethylamine, and N,N-dimethylethanolamine.

3. The waterborne coating of a polydopamine-modified acrylic resin according to claim 1, wherein The preparation method of the modified polydopamine includes the following steps: Q1: Add 2,5-diaminopentanoic acid to ultrapure water, add tetrahydrofuran, stir under nitrogen protection, add sodium bicarbonate and di-tert-butyl dicarbonate, react at a constant temperature. After the reaction is completed, perform rotary evaporation, add hydrochloric acid dropwise, precipitate a thick substance, dissolve, wash, extract, dry, perform rotary evaporation again, and vacuum dry to obtain Compound 1; Q2: Add Compound 1 to dichloromethane, add N-hydroxysuccinimide, stir and react under nitrogen protection, add EDC hydrochloride, react in an ice bath, and then react at room temperature under nitrogen protection. After the reaction is completed, wash, separate the liquid, dry, perform rotary evaporation, and dry again to obtain Compound 2; Add Compound 2 to methanol, stir under nitrogen protection, then add dopamine hydrochloride, stir to dissolve, dropwise add triethylamine, react at a constant temperature under nitrogen protection, perform rotary evaporation, dissolve, wash, separate the liquid, dry, perform rotary evaporation again, and dry to obtain Compound 3; Q3: Add Compound 3 to ethyl acetate, then add a mixed solution of hydrogen chloride and ethyl acetate, react at room temperature under nitrogen protection, perform rotary evaporation, filter by suction, and dry to obtain Compound 4; Add magnetic iron oxide nanoparticles to PBS buffer solution, then add Compound 4 and ascorbic acid, stir and react under nitrogen protection. After the reaction is completed, centrifuge, wash, and dry to obtain modified polydopamine.

4. The waterborne coating of a polydopamine-modified acrylic resin according to claim 3, wherein, In Q1, the dosage ratio of 2,5-diaminopentanoic acid, ultrapure water, tetrahydrofuran, sodium bicarbonate, and di-tert-butyl dicarbonate is (6.21 - 7.05) g:(120 - 180) mL:(45 - 55) mL:(12.1 - 12.9) g:(30.2 - 35.1) g.

5. The waterborne coating of a polydopamine-modified acrylic resin according to claim 3, characterized in that, In Q2, the molar ratio of Compound 1, N-hydroxysuccinimide, and EDC hydrochloride is 1:(1.02 - 1.39):(0.45 - 0.62); the molar ratio of Compound 2, dopamine hydrochloride, and triethylamine is 1:(1.32 - 1.83):(1.06 - 1.47).

6. The waterborne coating of a polydopamine-modified acrylic resin according to claim 3, wherein, In Q3, the dosage ratio of the mixed solution of compound 3, ethyl acetate, hydrogen chloride, and ethyl acetate is (8.2 - 10.5) g : (80 - 110) mL : (45 - 55) mL; the dosage ratio of magnetic iron oxide nanoparticles, PBS buffer solution, compound 4, and ascorbic acid is (0.1 - 0.15) g : (10 - 15) mL : (0.02 - 0.25) g : (0.01 - 0.018) g.

7. An aqueous coating of a polydopamine-modified acrylic resin according to claim 1, characterized in that, The preparation method of the modified viscosity agent includes the following steps: S1: Add 4-nitrophthalonitrile, 3-aminophenol, anhydrous potassium carbonate, and dimethyl sulfoxide into a container. After magnetic stirring, heat under reflux under nitrogen protection, cool, filter, add deionized water, precipitate, wash, and dry to obtain intermediate A; S2: Add hexafluorobisphenol, intermediate A, trimethylolpropane tripropyleneglycol ether (amine-terminated), and paraformaldehyde into a container, heat for reaction. After the reaction is completed, cool to room temperature, wash, collect the organic phase, dry, add anhydrous sodium sulfate, let stand, rotary evaporate, and vacuum dry to obtain the modified viscosity agent.

8. An aqueous coating of a polydopamine-modified acrylic resin according to claim 7, characterized in that, In S1, the dosage ratio of 4-nitrophthalonitrile, 3-aminophenol, anhydrous potassium carbonate, and dimethyl sulfoxide is (16.8 - 17.9) g : (10.1 - 11.8) g : (15 - 19) g : (25 - 33) mLh; in S2, the dosage ratio of hexafluorobisphenol, intermediate A, trimethylolpropane tripropyleneglycol ether (amine-terminated), and paraformaldehyde is (2.1 - 4.6) g : (1.72 - 1.95) g : (1.04 - 1.43) g : (5.34 - 6.12) g.

9. The preparation process of an aqueous coating of a polydopamine-modified acrylic resin according to any one of claims 1-8, characterized in that, It includes the following steps: Step 1: Add an emulsifier, deionized water, and modified polydopamine into a container, then add an initiator and a mixed solvent, stir vigorously, and then add an acrylic monomer and a modified viscosity agent, control the feeding time to obtain a mixture; Step 2: Carry out a temperature-rising reaction on the mixture. After the reaction is completed, add a pH regulator, cool to obtain an aqueous coating of polydopamine-modified acrylic resin.

10. The preparation process of an aqueous coating of polydopamine-modified acrylic resin according to claim 9, characterized in that, In Step 1, the vigorous stirring time is 30 - 40 min, the temperature is 70 - 80 °C, and the feeding time is 2.5 - 3 h; in Step 2, the temperature-rising reaction temperature is 80 - 85 °C, the reaction time is 1.5 - 2 h, and add a pH regulator until pH = 8 - 9.

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