Preparation method of anti-flash rust, anti-fouling and self-repairing water-based polyurethane / fluorocarbon composite coating

Abstract

The application discloses a preparation method of a water-based polyurethane / fluorocarbon composite coating with flash rust prevention, stain prevention and self-repairing functions. x The application discloses a preparation method of a water-based polyurethane / fluorocarbon composite coating with flash rust prevention, stain prevention and self-repairing functions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of preparation of water-based coatings, and particularly relates to a preparation method of a water-based polyurethane / fluorocarbon environmentally friendly composite coating with anti-flash rust, anti-fouling and self-repairing functions. BACKGROUND

[0002] The economic loss caused by metal material corrosion due to marine biological pollution is 30-50 billion US dollars per year. At present, the design strategy to alleviate microbial corrosion is mainly based on bactericides or bio-released coatings. Among various polymer coatings, water-based fluorocarbon resin is considered to be an ideal material for anti-fouling coating due to its low surface energy, aging resistance, corrosion resistance, hydrophobic / oil-repellent performance and environmental friendliness.

[0003] However, there are still many challenges in the emulsion synthesis, film formation and coating performance of water-based fluorocarbon resin. Among them, one of the main problems to be solved is that the emulsifier used in the emulsion polymerization of fluoroethylene (FSE) monomer has biological toxicity. For a long time, the emulsion polymerization of FSE in industry usually uses long fluorinated alkyl chains as surfactants, such as perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS) or their derivatives. However, these fluorine-containing surfactants are difficult to degrade and exhibit high biological accumulation and biological toxicity, and have been banned. Recently, our research group proposed a method based on amphiphilic polymers to realize the emulsion polymerization of fluoroethylene monomers. For example, using polysilsesquioxane as an emulsifier to prepare a self-healing fluorocarbon latex coating (202210865401.8), however, the film-forming property of the prepared coating is not ideal. Waterborne polyurethane (WPU) is stably dispersed in aqueous phase due to its amphiphilic structure of hydrophobic main chain and hydrophilic side chain, although amphiphilic WPU has been known for a long time, its potential as a microreactor to prepare fluorocarbon resin has been overlooked.

[0004] In addition, water-based coatings will produce a high humidity environment on the metal surface for a long time during film formation, leading to deterioration of metal surface corrosion and causing "flash rust" phenomenon. Previously, we proposed a new method of grafting N-heterocyclic corrosion inhibitor on the side chain of WPU and using its coordination with metal substrate to inhibit the occurrence of flash rust (202310534843.9). However, due to the reason that the N-heterocyclic corrosion inhibitor used in this method is covalently grafted onto the side chain of polyurethane molecules, this method cannot controllably release the corrosion inhibitor. SUMMARY

[0005] The present application aims at the limitations of the prior art, and provides a preparation method of a waterborne polyurethane / fluorocarbon composite coating with anti-flash rust, anti-fouling and self-repairing functions. The method uses WPU polyurethane to replace traditional emulsifiers to prepare fluorocarbon resin, and uses the amphiphilic property of WPU and a special monomer with redox response to construct a waterborne fluorocarbon / polyurethane composite coating with anti-flash rust, anti-fouling and self-repairing functions. First, a functional monomer (MBTMA) connected by a disulfide bond is synthesized, which is used to prepare a copolymer with redox response. Then, WPU is used as a micro-reactor, CTFE, VA and MBTMA are used as comonomers, and a PM x / WPU composite emulsion is prepared by soap-free emulsion polymerization, and then a coating thereof is obtained. The present application provides a new method for realizing the anti-flash rust, anti-fouling and self-repairing functions of a waterborne coating, and solves the problem of emulsifiers in the emulsion polymerization of FSE monomers.

[0006] The technical scheme of the present application is as follows:

[0007] A preparation method of a waterborne polyurethane / fluorocarbon composite coating with anti-flash rust, anti-fouling and self-repairing functions, which comprises the following steps:

[0008] Firstly, BSSB is suspended in chloroform, and then mercaptoethanol is added dropwise, and the dropwise addition is completed in 0.8-1.5 h to form a yellow solution; the solution is continuously stirred at 15-30℃ for 4-8 h; then, the product is washed with NaOH aqueous solution and deionized water, respectively; finally, the chloroform solvent is removed by rotary evaporation to obtain 2-benzothiazole-2'-hydroxyethyl disulfide (MBTS2OH);

[0009] The molar ratio of BSSB to mercaptoethanol is 1:1.0-1.2; the mass fraction of NaOH aqueous solution is 3-8wt%; 0.1 mol of BSSB is added per 0.8-1.2 L of chloroform;

[0010] Next, MBTS2OH, MAAn and hydroquinone (HQ) are dissolved in dichloromethane to obtain a mixture under N2 atmosphere; triethylamine (Et3N) is added dropwise to the mixture in an ice water bath, and the stirring is continued for 5-20 min; then, the reaction is continued at 15-30℃ for 10-15 h; the reaction product is washed with water and dried with Na2SO4, and then the dichloromethane is removed by rotary evaporation to obtain MBTSM;

[0011] The molar ratio of MBTS2OH, MAAn, HQ and Et3N is 1:3.0-3.5:0.02-0.04:2.5-3.4; 8.23 mmol of MBTS2OH is added per 80-150 mL of dichloromethane;

[0012] Second step, compound A, compound B and catalyst are injected into the reactor, then 2,2-dihydroxymethyl propionic acid N,N-dimethylformamide solution is added, and the reaction is carried out at 70-120℃ under nitrogen atmosphere for 1-5h, the stirring speed is 15-40rpm; then the reaction temperature is reduced to 20-50℃, and then triethylamine is added to continue the reaction for 0.5-3h, then glycine amide is added to the reaction solution, and the stirring is continued at 20-50℃ for 2-4h to obtain polyurethane prepolymer; finally, the obtained polyurethane prepolymer is added with deionized water drop by drop under high speed stirring of 1000-2000rpm, and the stirring is continued for 0.5-2h to obtain polyurethane emulsion (WPU);

[0013] The mass ratio of compound A, compound B, 2,2-dihydroxymethyl propionic acid, glycine amide, catalyst, triethylamine is 1:0.3-0.7:0.1-0.3:0.02-0.2:0.001-0.009:0.1-0.4; the mass ratio of polyurethane prepolymer and deionized water is 1:2-10.

[0014] The compound A is one or more of polyether or polyester, specifically polytetrahydrofuran ether diol or polycarbonate diol.

[0015] The compound B is one or more of diisocyanate, specifically isophorone diisocyanate, hexamethylene diisocyanate or toluene diisocyanate.

[0016] The catalyst is one or more of stannous octoate, dibutyltin dilaurate, zinc naphthenate, tetraisobutyl titanate.

[0017] The mass fraction of 2,2-dihydroxymethyl propionic acid N,N-dimethylformamide solution is 20%-40%.

[0018] Third step, first, the WPU emulsion is diluted with deionized water, and ultrasonic treatment is carried out for 15-30min for mixing; then the above diluted solution is added to a high-pressure reaction kettle; then sodium bicarbonate (NaHCO3), potassium persulfate (KPS), MBTMA and compound C are added to the reaction kettle; finally, trifluorochloroethylene (CTFE) gas is added to the high-pressure reaction kettle, and the reaction is carried out at a stirring speed of 100-300rpm and 60-80℃ for 12-36h to obtain water-based polyurethane / fluorocarbon emulsion.

[0019] The mass ratio of WPU emulsion, deionized water, NaHCO3, KPS, MBTMA, compound D, trifluorochloroethylene (CTFE) is 1:5-9:0.01-0.03:0.005-0.01:0.01-0.03:0.3-0.5:2.0-4.0.

[0020] The compound C is one or more acrylates, specifically vinyl acetate (VA), vinyl tert-carbonate, or butyl acrylate;

[0021] The fourth step involves coating the waterborne polyurethane / fluorocarbon emulsion obtained in the third step onto the substrate and drying it at room temperature for 12-36 hours to obtain a waterborne polyurethane / fluorocarbon composite coating that is rust-resistant, anti-fouling, and self-healing.

[0022] Among them, each 2.5×2.5cm 2 Apply 1.0-5.0g of emulsion to the base;

[0023] The substrate is specifically tinplate, glass, or polypropylene film.

[0024] The essential features of this invention are:

[0025] This invention utilizes the amphiphilicity of waterborne polyurethane to replace the small-molecule emulsifier in the traditional fluorocarbon resin emulsion synthesis process, successfully synthesizing a redox-responsive PM composed of CTFE, VA, and a special monomer conjugated with a disulfide bond and a corrosion inhibitor (MBT). x Copolymers were used to develop waterborne coatings with anti-flash rust, anti-fouling, and self-healing functions. This invention provides a new method for achieving these functions in waterborne coatings while simultaneously solving the emulsifier problem in FSE monomer emulsion polymerization.

[0026] The beneficial effects of this invention are as follows:

[0027] Most existing self-healing waterborne polymers are prone to flash rust, poor antifouling effect, and irreversible damage, and the synthesis of fluorocarbon resins inevitably uses environmentally unfriendly small-molecule emulsifiers. The composite coating prepared in this invention can release the corrosion inhibitor MBT as needed when corrosion occurs, effectively inhibiting flash rust on the metal substrate. Due to the repulsive properties of the fluorinated groups and the bactericidal effect of MBT, PM... x The / WPU composite coating also exhibits excellent antifouling properties, with a bacterial adhesion rate of only 51.2%. Furthermore, PM... x / WPU composite coatings exhibit excellent self-healing capabilities, with a self-healing efficiency of 93.1%. This invention provides a novel method for achieving flash rust prevention, anti-fouling, and self-healing functions in water-based coatings, while simultaneously solving the emulsifier problem in FSE monomer emulsion polymerization. Attached Figure Description

[0028] Figure 1 The above are the 1H NMR spectra of MBTS2OH and MBTSM obtained in Example 1; wherein, Figure 1 a is the 1H NMR spectrum of MBTS2OH. Figure 1 b is the 1H NMR spectrum of the MBTSM;

[0029] Figure 2 The WPU and PM obtained in Examples 2-5 x FT-IR spectrum of / WPU; where Figure 2 a represents the FT-IR spectra of the synthetic raw materials and PU prepolymer. Figure 2 b represents PM x / WPU's FT-IR spectrum;

[0030] Figure 3 The WPU and PM obtained in Examples 2-5 x / WPU's 1H NMR spectrum;

[0031] Figure 4 The NMR fluorine spectrum of PM2 / WPU obtained in Example 5;

[0032] Figure 5 For WPU and PM in Examples 2-5 x / Photo of WPU anti-flash rust test;

[0033] Figure 6 The WPU and PM obtained in Examples 2-5 x XRD and EIS tests of / WPU; among them. Figure 6 a represents WPU and PM x XRD pattern of / WPU coating. Figure 6 b represents WPU and PM x EIS curve of / WPU coating;

[0034] Figure 7 The WPU and PM obtained in Examples 2-5 x Optical microscope image of the self-healing process of scratches on WPU coated surface; Detailed Implementation

[0035] Example 1:

[0036] The synthesis of a functional monomer (MBTSM) involves preparing the intermediate MBTS2OH via a thiol-disulfide substitution reaction between dibenzothiazole disulfide (BSSB) and mercaptoethanol, followed by esterification with methacrylic anhydride (MAAn) to synthesize the functional monomer MBTSM. The synthetic route is shown below.

[0037]

[0038] The specific steps are as follows:

[0039] BSSB (33.4 g, 0.1 mol) was suspended in 1.0 L of chloroform, and then mercaptoethanol (7.1 mL, 0.1 mmol) was added dropwise over 1 h, resulting in a yellow solution. The reaction system was then stirred at 25 °C for 6 h. Subsequently, the product was washed with 800 mL of NaOH aqueous solution (5 wt%) and 800 mL of deionized water until the washings were clear and transparent. Finally, the chloroform solvent was removed by rotary evaporation to obtain 2-benzothiazolium-2′-hydroxyethyl disulfide (MBTS2OH).

[0040] Next, under a nitrogen atmosphere, the purified MBTS2OH (2.00 g, 8.23 ​​mmol), MAAn (3.68 mL, 24.7 mmol), and HQ (0.027 g, 0.25 mmol) were dissolved in 100 mL of dichloromethane. Then, Et3N (3.44 mL, 24.7 mmol) was added dropwise to the mixture in an ice-water bath, and stirring was continued for 10 min. The reaction mixture was then continued to react at 25 °C for 12 h. The reaction product was washed with 300 mL of water, dried over Na2SO4, and the dichloromethane was removed by rotary evaporation. Finally, the product MBTSM was purified by silica gel column chromatography, using a 1:19 volume ratio of ethyl acetate to n-hexane as the mobile phase.

[0041] The intermediate MBTS2OH and the final product MBTSM were analyzed by proton nuclear magnetic resonance (NMR) spectra using an AVANCE 400NMR spectrometer. 1 H NMR) test, results are as follows Figure 1 As shown in the figure. These results indicate that MBTSM was successfully synthesized.

[0042] Example 2:

[0043] The preparation steps of an aqueous polyurethane (WPU) emulsion are as follows:

[0044] In the first step, 15.0 g of polytetrahydrofuran ether diol, 10.0 g of isophorone diisocyanate, and 0.03 g of dibutyltin dilaurate were injected into a flask equipped with a nitrogen inlet. Under a nitrogen atmosphere and with stirring at 30 rpm, 7.0 g of a solution of 2,2-dimethylolpropionic acid in N,N-dimethylformamide (mass fraction of solution: 28.6 wt%) was added, and the reaction was carried out at 80 °C for 2 h. Then, the reaction system was cooled to 40 °C, and triethylamine (2.4 g, 15.0 mmol) was added, with stirring continuing for 1 h. Next, 2.22 g of glycine amide was added, and the temperature was maintained for another 3 h. Finally, deionized water (129 g) was added dropwise to the system under high-speed stirring at 1200 rpm, and stirring was continued for 1.5 h to obtain a WPU emulsion.

[0045] The second step is to drop 2.0g of WPU lotion directly onto a 2.5×2.5cm surface. 2 WPU coating is obtained by drying the tinplate at room temperature for 24 hours.

[0046] The particle size and distribution of the WPU emulsion were tested using a dynamic light scattering particle size analyzer (XinSanSi, Shenzhen, China), and the results are shown in Table 1. The emulsion has a particle size of 183.2 nm, a distribution index of 0.147, and a Zeta potential of -31.4 mV, indicating that the WPU emulsion has good stability. Fourier transform infrared spectroscopy (FTIR) of the WPU was performed using a German Tensor-27 spectrometer, and the results are shown in Table 1. Figure 2 As shown in figure a. The infrared spectrum of polyurethane is in the range of ~2260 cm⁻¹. -1 The absence of a distinct N=C=O stretching vibration band at this location indicates that the IPDI reaction was complete and left without residue. Furthermore, at 2800-3000 cm⁻¹... -1 The absorption band is due to the CH stretching vibration, 1702 cm⁻¹. -1 The absorption bands originate from the carbonyl groups (C=O) in urethane and GCa. The chemical structure of the WPU coating was further characterized using nuclear magnetic resonance (NMR) technology, such as... Figure 3 As shown. The IPDI unit's (C) H 3) 2C- and C H The 3C- signal peaks appeared at ~0.95 ppm and ~1.13 ppm, respectively, at the methylene proton-C of the PTMG unit. H 2CH2O- and -CH2C H The 2O- signal peaks appeared at ~1.62ppm and ~3.39ppm, respectively, in the proton-OCN of the GCa unit. H The CO- signal peak appears at ~7.43 ppm, indicating that WPU was successfully prepared.

[0047] In addition, such as Figure 5 As shown, the coating formed by drying the WPU emulsion on a tinplate substrate at 40°C exhibits dark brown rust products. To further analyze the chemical composition of the dark brown products, the coating peeled off the tinplate substrate was tested using XRD technology. The test results are as follows. Figure 6 As shown in Figure a, the Fe2O3 signal peaks at 2θ of 32.1° and 34.3° clearly indicate that severe corrosion occurred during the film formation process of the WPU emulsion on the tinplate substrate. The anti-flash rust function of the coating was tested using EIS experiments, and the results are shown in Figure a. Figure 6 As shown in b, the WPU coating exhibits a distinct semi-circular impedance arc.

[0048] Regarding the antifouling properties of the coating, tests were conducted on the WPU coating for protein adsorption, surface energy, and antibacterial properties. The test results are shown in Table 2. It can be seen that the protein adsorption rate of WPU is 91.2%, and the surface energy is 40.2 mJ / m². 2 The adhesion rates of Escherichia coli and Staphylococcus aureus were 81.1% and 84.3%, respectively.

[0049] Figure 7 Table 2 shows optical microscope images of the scratch closure experiment of the WPU coating, and its self-healing efficiency is shown in Table 2. It can be seen that the scratches on the WPU coating surface were almost completely healed within 2 hours, with a self-healing efficiency of 92.1%.

[0050] Example 3:

[0051] The preparation steps of an aqueous polyurethane / fluorocarbon PMO / WPU composite emulsion are as follows:

[0052] The first step involves using a microreactor (providing a reaction space for the monomers and acting as an emulsifier to ensure the monomers remain stable in water) as the WPU emulsion prepared in the first step of Example 2, with trifluorochloroethylene (CTFE) and vinyl acetate (VA) as comonomers, to prepare P(CTFE-co-VA) / WPU(PM) via soap-free emulsion polymerization. x WPU composite latex. First, dilute 10.0g of WPU emulsion with 60.0g of deionized water and sonicate for 20 minutes to mix thoroughly. Then, add the diluted solution to a 250mL high-pressure reactor equipped with an explosion-proof valve (3000psi), pressure gauge, inlet and outlet valves, and a stirrer. Subsequently, add 0.2g of NaHCO3, 0.06g of KPS, and 4.0g of [unspecified ingredient] to the reactor. VA Place the high-pressure reactor under a vacuum (10). -2 The oxygen was removed by adding a bar. Finally, 25g of CTFE gas was added to the high-pressure reactor, and the mixture was reacted at 200rpm and 70°C for 24h to obtain a PMO / WPU emulsion.

[0053] The second step is to drop 2.0g of PMO / WPU emulsion directly onto a 2.5×2.5cm surface. 2 After drying at room temperature for 24 hours on tinplate, a PMO / WPU composite coating is obtained.

[0054] The particle size and distribution of the PMO / WPU emulsion were measured using a dynamic light scattering particle size analyzer (XinSanSi, Shenzhen, China), and the results are shown in Table 1. The PMO / WPU emulsion had a particle size of 200.4 nm, a distribution index of 0.195, and a Zeta potential of -25.2 mV, indicating that the PMO / WPU emulsion has good stability. Fourier transform infrared spectroscopy (FTIR) of the PMO / WPU samples was performed using a German Tensor-27 spectrometer, and the results are shown in Table 1. Figure 2 As shown in a. Compared to the WPU coating in Example 2, at 578cm -1 A new absorption band appeared at the point corresponding to the stretching vibration of -CF2, indicating the successful preparation of the PMO copolymer. The chemical structure of the PMO / WPU coating was further characterized using nuclear magnetic resonance (NMR) technology, such as... Figure 3 As shown. At δ = 6.12 ppm (-C H 2=CH2-) and 5.87ppm(-CH2=C H No proton peak of vinyl groups was found at position 2-), indicating that the carbon-carbon double bonds in the monomer have been completely reacted.

[0055] In addition, such as Figure 5 As shown, the coating formed by drying the PMO / WPU emulsion on a tinplate substrate at 40°C exhibited dark brown rust products. To further analyze the chemical composition of the dark brown products, the coating peeled off the tinplate substrate was tested using XRD technology. The test results are as follows. Figure 6 As shown in Figure a, the Fe2O3 signal peaks at 2θ of 32.1° and 34.3° of the PMO / WPU coating are clearly visible, indicating that severe corrosion occurred during the film formation process of the PMO / WPU emulsion on the tinplate substrate. The anti-flash rust function of the PMO / WPU coating was tested by EIS experiments, and the test results are shown in Figure a. Figure 6 As shown in b. Compared to the WPU coating in Example 2, the PMO / WPU coating exhibits a larger semi-circular impedance arc, indicating that it has superior corrosion resistance.

[0056] Regarding the antifouling ability of the coating, tests were conducted on the PMO / WPU coating for protein adsorption resistance, surface energy, and antibacterial properties. The test results are shown in Table 2. It can be seen that the protein adsorption rate of PMO / WPU is 23.2%, and the surface energy is 27.1 mJ / m². 2 The adhesion rates of Escherichia coli and Staphylococcus aureus were 60.3% and 72.0%, respectively, indicating that the introduction of fluorine-containing units reduced the surface energy of the coating, thereby improving the antifouling ability of the PMO / WPU coating.

[0057] Figure 7Optical microscope images of the scratch closure experiment of the PMO / WPU coating are shown in Table 2. The self-healing efficiency is shown in Table 2. It can be seen that the scratches on the PMO / WPU coating surface were almost completely healed within 2 hours, with a self-healing efficiency of 92.4%, which is not significantly different from the self-healing efficiency of the WPU coating in Example 2. This indicates that the introduction of the PMO copolymer does not affect the self-healing efficiency of the composite coating.

[0058] Example 4:

[0059] The preparation steps of an aqueous polyurethane / fluorocarbon PM1 / WPU composite emulsion are as follows:

[0060] The first step involves using the WPU emulsion prepared in Example 2 as the system in a microreactor, and CTFE, VA, and MBTMA as comonomers, to prepare P(CTFE-co-VA-co-MBTSM) / WPU(PM) via soap-free emulsion polymerization. x WPU composite latex. First, dilute 10.0g of WPU emulsion with 60.0g of deionized water and sonicate for 20min to mix thoroughly. Then, add the diluted solution to a 250mL high-pressure reactor equipped with an explosion-proof valve (3000psi), pressure gauge, inlet and outlet valves, and a stirrer. Subsequently, add 0.2g of NaHCO3, 0.06g of KPS, 4.0g of VA, and 0.11g of MBTSM to the reactor. Place the high-pressure reactor under vacuum (10... -2 The oxygen was removed by adding a bar. Finally, 25g of CTFE gas was added to the high-pressure reactor, and the mixture was reacted at 200rpm and 70°C for 24h to obtain PM1 / WPU emulsion.

[0061] The second step is to drop 2.0g of PM1 / WPU emulsion directly onto a 2.5×2.5cm surface. 2 PM1 / WPU composite coating is obtained by drying the tinplate at room temperature for 24 hours.

[0062] The particle size and distribution of PM1 / WPU emulsion were tested using a dynamic light scattering particle size analyzer (XinSanSi, Shenzhen, China), and the results are shown in Table 1. The PM1 / WPU emulsion had a particle size of 297.8 nm, a distribution index of 0.212, and a Zeta potential of -23.1 mV, indicating that the PM1 / WPU emulsion has good stability. Fourier transform infrared spectroscopy (FTIR) of the PM1 / WPU samples was performed using a German Tensor-27 spectrometer, and the results are shown in Table 1. Figure 2 As shown in a. Compared to the WPU coating in Example 2, at 578, 962, and 1413 cm⁻¹... -1New absorption bands appeared at the points corresponding to the stretching vibrations of -CF2, CS, and -C=N, respectively, indicating the successful preparation of the PM1 copolymer. The chemical structure of the PM1 / WPU coating was further characterized using nuclear magnetic resonance (NMR) technology, such as... Figure 3 As shown. Compared to the NMR spectrum of the WPU coating in Example 2, the PM1 / WPU sample... 1 In the H NMR spectrum, new signal peaks were also observed in the MBTSM unit at δ = 7.93 ppm and δ = 1.98 ppm, corresponding to (-Ar) and (-Ar) respectively. H ) and (-OC H The presence of protons in 2S- indicates that MBTSM was synthesized onto the PM1 copolymer molecular chain. At δ = 6.12 ppm (-C H 2=CH2-) and 5.87ppm(-CH2=C H No proton peak of vinyl groups was found at position 2-), indicating that the carbon-carbon double bonds in the monomer have been completely reacted.

[0063] In addition, such as Figure 5 As shown, the coating formed by drying the PM1 / WPU emulsion on a tinplate substrate at 40°C exhibits the light yellow color of the coating itself, without any dark brown rust. Furthermore, XRD testing was performed on the coating peeled off the tinplate substrate, and the results are as follows. Figure 6 As shown in Figure a, it is evident that the PM1 / WPU coating does not exhibit Fe2O3 signal peaks at 2θ values ​​of 32.1° and 34.3°, indicating that no corrosion occurred during the film formation process of the PM1 / WPU emulsion on the tinplate substrate. This demonstrates that the introduction of the MBTSM unit inhibited corrosion. The anti-flash rust function of the PM1 / WPU coating was tested using EIS experiments, and the test results are shown in Figure a. Figure 6 As shown in b. Compared to the PMO / WPU coating in Example 3, the PM1 / WPU coating exhibits a larger semi-circular impedance arc, indicating that the MBTSM unit contributes to the corrosion resistance of the coating.

[0064] For the antifouling test of the coating, the PM1 / WPU coating was tested for protein adsorption resistance, surface energy, and antibacterial properties. The test results are shown in Table 2. It can be seen that the protein adsorption rate of PM1 / WPU is 40.9%, and the surface energy is 33.8 mJ / m². 2 The adhesion rates of Escherichia coli and Staphylococcus aureus were 58.6% and 60.2%, respectively, indicating that the introduction of fluorine-containing units helps to provide the coating with resistance to proteins, and MBTSM units help to impart bactericidal properties to the coating. The synergistic effect of the two gives the coating excellent antifouling effect.

[0065] Figure 7Optical microscope images of the scratch closure test of the PM1 / WPU coating are shown in Table 2. The self-healing efficiency is shown in Table 2. It can be seen that the scratches on the PM1 / WPU coating surface were almost completely healed within 2 hours, with a self-healing efficiency of 93.2%, which is not significantly different from the self-healing efficiency of the WPU coating in Example 2. This indicates that the introduction of the PM1 copolymer does not affect the self-healing efficiency of the composite coating.

[0066] Example 5:

[0067] The preparation steps of an aqueous polyurethane / fluorocarbon PM2 / WPU composite emulsion are as follows:

[0068] The first step involves using the WPU emulsion prepared in Example 2 as the system in a microreactor, and CTFE, VA, and MBTMA as comonomers, to prepare P(CTFE-co-VA-co-MBTSM) / WPU(PM) via soap-free emulsion polymerization. x WPU composite latex. First, dilute 10.0g of WPU emulsion with 60.0g of deionized water and sonicate for 20 minutes to mix thoroughly. Then, add the diluted solution to a 250mL high-pressure reactor equipped with an explosion-proof valve (3000psi), pressure gauge, inlet and outlet valves, and a stirrer. Subsequently, add 0.2g of NaHCO3, 0.06g of KPS, 4.0g of VA, and 0.22g of MBTSM to the reactor. Place the high-pressure reactor under vacuum (10... -2 The oxygen was removed by adding 25g of CTFE gas to the high-pressure reactor and reacting at 200rpm and 70°C for 24h to obtain a PM2 / WPU emulsion.

[0069] The second step is to drop 2.0g of PM2 / WPU emulsion directly onto a 2.5×2.5cm surface. 2 PM2 / WPU composite coating is obtained by drying the tinplate at room temperature for 24 hours.

[0070] The particle size and distribution of the PM2 / WPU emulsion were measured using a dynamic light scattering particle size analyzer (XinSanSi, Shenzhen, China), and the results are shown in Table 1. The PM2 / WPU emulsion had a particle size of 309.8 nm, a distribution index of 0.082, and a Zeta potential of -20.3 mV, indicating that the PM2 / WPU emulsion has good stability. Fourier transform infrared spectroscopy (FTIR) of the PM2 / WPU samples was performed using a German Tensor-27 spectrometer, and the results are shown in Table 1. Figure 2 As shown in a. Compared to the WPU coating in Example 2, at 578, 962, and 1413 cm⁻¹... -1New absorption bands appeared at the points corresponding to the stretching vibrations of -CF2, CS, and -C=N, respectively, indicating the successful preparation of the PM2 copolymer. The chemical structure of the PM2 / WPU coating was further characterized using nuclear magnetic resonance (NMR) technology, such as... Figure 3 As shown. Compared to the NMR spectrum of the WPU coating in Example 2, the PM2 / WPU sample... 1 In the H NMR spectrum, new signal peaks were also observed in the MBTSM unit at δ = 7.93 ppm and δ = 1.98 ppm, corresponding to (-Ar) and (-Ar) respectively. H ) and (-OC H The presence of protons in 2S- indicates that MBTSM was synthesized onto the PM2 copolymer molecular chain. At δ = 6.12 ppm (-C H 2=CH2-) and 5.87ppm(-CH2=C H No proton peak for vinyl groups was found at position 2-), indicating that the carbon-carbon double bonds in the monomer have been completely reacted. Meanwhile, Figure 4 The PM2 / WPU sample was shown. 19 The F NMR spectrum clearly shows PM x The presence of CTFE units in the copolymer.

[0071] In addition, such as Figure 5 As shown, the coating formed by drying the PM2 / WPU emulsion on a tinplate substrate at 40°C exhibits the light yellow color of the coating itself, without any dark brown rust. Furthermore, XRD testing was performed on the coating peeled off the tinplate substrate, and the results are as follows. Figure 6 As shown in Figure a, it is evident that the PM2 / WPU coating does not exhibit Fe2O3 signal peaks at 2θ values ​​of 32.1° and 34.3°, indicating that no corrosion occurred during the film formation process of the PM2 / WPU emulsion on the tinplate substrate. This demonstrates that the introduction of the MBTSM unit inhibited corrosion. The anti-flash rust function of the PM2 / WPU coating was tested using EIS experiments, and the test results are shown in Figure a. Figure 6 As shown in b. Compared to the PMO / WPU coating in Example 3, the PM1 / WPU coating exhibits a larger semi-circular impedance arc, indicating that the MBTSM unit contributes to the corrosion resistance of the coating.

[0072] Regarding the antifouling test of the coating, the PM2 / WPU coating was tested for protein adsorption resistance, surface energy, and antibacterial properties. The test results are shown in Table 2. It can be seen that the protein adsorption rate of PM2 / WPU is 51.3%, and the surface energy is 35.2 mJ / m². 2The adhesion rates of Escherichia coli and Staphylococcus aureus were 51.2% and 55.2%, respectively, indicating that the introduction of fluorine-containing units helps to provide the coating with resistance to proteins, and MBTSM units help to impart bactericidal properties to the coating. The synergistic effect of the two gives the coating excellent antifouling effect.

[0073] Figure 7 Optical microscope images of the scratch closure experiment of the PM2 / WPU coating are shown in Table 2. The self-healing efficiency is shown in Table 2. It can be seen that the scratches on the PM2 / WPU coating surface were almost completely healed within 2 hours, with a self-healing efficiency of 93.1%, which is not significantly different from the self-healing efficiency of the WPU coating in Example 2. This indicates that the introduction of the PM2 copolymer does not affect the self-healing efficiency of the composite coating.

[0074] Table 1. PM x Particle size, particle size distribution, and zeta potential of WPU emulsion

[0075]

[0076] Table 2. PM x / WPU coating protein adsorption rate, surface energy, Escherichia coli adhesion rate, and Staphylococcus aureus adhesion rate

[0077]

[0078] In summary, we successfully synthesized a redox-responsive copolymer using polyurethane as a microreactor. This copolymer is composed of CTFE, VA, and monomers linked to the corrosion inhibitor MBT via disulfide bonds, and was then used to prepare an aqueous fluorocarbon / polyurethane composite coating. The prepared emulsion exhibits good stability and demonstrates excellent anti-flash rust and anti-fouling properties. Furthermore, the composite coating exhibits scratch self-healing within 2 hours. This work provides a simple method for preparing anti-flash rust, anti-fouling, and self-healing WPU coatings.

[0079] Matters not covered in this invention are common knowledge.

Claims

1. A method for preparing a waterborne polyurethane / fluorocarbon composite coating that is rust-resistant, fouling-resistant, and self-healing, characterized in that the method includes the following steps: The first step involves suspending dibenzothiazole disulfide in chloroform, followed by the dropwise addition of mercaptoethanol over 0.8–1.5 hours to form a yellow solution. The solution is then stirred at 15–30 °C for 4–8 hours. The product is subsequently washed with aqueous NaOH and deionized water, respectively. Finally, the chloroform solvent is removed by rotary evaporation to obtain 2-benzothiazole-2'-hydroxyethyl disulfide MBTS2OH. The molar ratio of dibenzothiazole disulfide to mercaptoethanol is 1:1.0-1.2; 0.1 mol of dibenzothiazole disulfide is added to every 0.8-1.2 L of chloroform. Next, MBTS2OH, methacrylic anhydride, and hydroquinone were dissolved in dichloromethane under a N2 atmosphere to obtain a mixture; triethylamine was added dropwise to the mixture in an ice-water bath, and stirring was continued for 5-20 min; subsequently, the reaction was continued at 15-30 °C for 10-15 h; the reaction product was washed with water, dried with Na2SO4, and then dichloromethane was removed by rotary evaporation to obtain MBTSM; The molar ratio of MBTS2OH, methacrylic anhydride, hydroquinone, and triethylamine is 1:3.0-3.5:0.02-0.04:2.5-3.4; 8.23 ​​mmol of MBTS2OH is added to every 80-150 mL of dichloromethane. In the second step, compounds A, B, and the catalyst are injected into the reactor, followed by the addition of an N,N-dimethylformamide solution of 2,2-dimethylolpropionic acid. The reaction is carried out at 70-120 °C for 1-5 h under a nitrogen atmosphere with a stirring rate of 15-40 rpm. Then, the reaction temperature is lowered to 20-50 °C, and triethylamine is added to continue the reaction for 0.5-3 h. Glycine amide is then added to the reaction solution, and the mixture is stirred at 20-50 °C for another 2-4 h to obtain a polyurethane prepolymer. Finally, deionized water is added dropwise to the obtained polyurethane prepolymer under high-speed stirring at 1000-2000 rpm, and stirring is continued for 0.5-2 h to obtain a polyurethane emulsion. The mass ratio of compound A, compound B, 2,2-dimethylolpropionic acid, glycine, catalyst, and triethylamine is 1:0.3-0.7:0.1-0.3:0.02-0.2:0.02-0.2:0.001-0.009:0.1-0.4; the mass ratio of polyurethane prepolymer to deionized water is 1:2-10. Compound A is polytetrahydrofuran ether diol or polycarbonate diol; Compound B is a diisocyanate; The catalyst is specifically one or more of the following: stannous octoate, dibutyltin dilaurate, zinc naphthenate, and tetraisobutyl titanate. The third step involves first diluting the polyurethane emulsion with deionized water and then sonicating it for 15-30 minutes to mix it. Next, the diluted solution is added to a high-pressure reactor. Subsequently, sodium bicarbonate, potassium persulfate, MBTMA, and compound C are added to the reactor. Finally, trifluorochloroethylene gas is added to the high-pressure reactor, and the mixture is reacted at a stirring speed of 100-300 rpm and a temperature of 60-80 °C for 12-36 hours to obtain an aqueous polyurethane / fluorocarbon emulsion. The mass ratio of polyurethane emulsion, deionized water, sodium bicarbonate, potassium persulfate, MBTMA, compound D, and trifluorochloroethylene is 1:5-9:0.01-0.03:0.005-0.01:0.01-0.03:0.3-0.5:2.0-4.

0. The compound C is vinyl acetate, vinyl tert-carbonate, or butyl acrylate; The fourth step involves coating the waterborne polyurethane / fluorocarbon emulsion obtained in the third step onto the substrate and drying it at room temperature for 12-36 hours to obtain a waterborne polyurethane / fluorocarbon composite coating that is rust-resistant, stain-resistant, and self-healing.

2. The method for preparing the anti-flash rust, anti-fouling and self-healing waterborne polyurethane / fluorocarbon composite coating as described in claim 1, characterized in that in the first step, the mass fraction of the NaOH aqueous solution is 3-8 wt%.

3. The method for preparing the anti-flash rust, anti-fouling and self-healing waterborne polyurethane / fluorocarbon composite coating as described in claim 1, characterized in that in the second step, compound B is specifically isophorone diisocyanate, hexamethylene diisocyanate or toluene diisocyanate. The mass fraction of the N,N-dimethylformamide solution of 2,2-dihydroxymethylpropionic acid is 20%-40%.

4. The method for preparing the anti-flash rust, anti-fouling, and self-healing waterborne polyurethane / fluorocarbon composite coating as described in claim 1, characterized in that in step four, each 2.5 × 2.5 cm 2 Apply 1.0-5.0 g of emulsion to the base.

5. The method for preparing the waterborne polyurethane / fluorocarbon composite coating with anti-flash rust, anti-fouling, and self-healing properties as described in claim 1, characterized in that: The substrate is specifically tinplate, glass, or polypropylene film.

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