Fluorescent self-early-warning anticorrosive paint as well as preparation method and application thereof

Abstract

The invention discloses a fluorescent self-early-warning anticorrosive coating as well as a preparation method and application thereof. The coating comprises epoxy resin coupled with probe molecules. The fluorescence emission wavelength of the probe molecule is located in a near-infrared region, and the fluorescence intensity can be enhanced under an acidic condition, so that the detection reliability of the self-early-warning anticorrosive coating and the detection depth of an early-warning signal are improved; according to the acidic pH response type fluorescent self-early-warning anticorrosive coating disclosed by the invention, coating cracks in different shapes can be accurately detected; the acidic pH-responsive fluorescent self-early-warning anticorrosive coating provided by the technical scheme of the invention has good stability, can perform long-time early warning on the anticorrosive coating, and provides long-term protection for ships.

Description

Technical Field

[0001] The invention relates to a fluorescent self-warning anti-corrosion coating and a preparation method and application thereof, belonging to the technical field of polymer materials. Background Art

[0002] Anti-corrosion coating is the main means to prevent metal corrosion and extend the service life of metal structures. The main function of traditional anti-corrosion coatings such as polyurethane, epoxy, and silicone resin is to physically isolate the metal substrate from the corrosive medium. However, coating protection faces an important defect, that is, when the coating is damaged, the corrosive medium can directly contact the metal substrate at the damaged part of the coating, thereby causing corrosion. If it is not repaired in time, the protective performance of the coating will be seriously reduced, and the corrosion will continue to spread, eventually causing adverse effects on the metal material. Rapidly and accurately locating local defects and damage in anti-corrosion coatings is of great significance for timely repair of damaged coatings and improving the anti-corrosion ability of coatings.

[0003] The anti-corrosion coating is mainly composed of polymer materials. The currently developed non-destructive testing technologies for materials include ultrasonic testing, infrared testing, electronic misalignment interferometry, alternating magnetic field measurement, X-ray detection technology, etc. Although these traditional material testing methods can detect defects in material devices, these testing equipment are complex and expensive, and have high professional and technical requirements for operators; it is difficult to detect unreachable areas, and some detection technologies are complex and time-consuming; the sensitivity and resolution of the detection are limited, and some measurement results are prone to drift; the applicability of some detection methods is relatively narrow, such as alternating magnetic field detection can only be applied to materials containing metallic iron. Therefore, it is necessary to design and prepare an intelligent material that can autonomously warn of damage to polymer materials, and to prepare a self-warning material for autonomous damage monitoring conveniently, quickly and effectively. After the polymer material is damaged, the warning agent makes the damaged area and the undamaged area of ​​the polymer material appear obvious color difference, which is convenient for monitoring personnel to quickly and accurately capture the fine cracks in the polymer material, so that the damage of the material can be seen at a glance.

[0004] In order to be able to visually observe the defects in the material, people have introduced dye molecules and fluorescence methods into material damage detection, and developed a variety of methods for visually observing material damage, such as adding pH indicators and small molecule probes to anti-corrosion coatings. Although some progress has been made in the field of self-warning anti-corrosion coatings, there are still some problems: 1) The curing agents of epoxy resin coatings are all molecules containing amino active groups. During the curing process of mixing with probe molecules, the alkaline microenvironment will activate the fluorescence of the probe molecules, causing the self-warning function to fail. Therefore, alkaline pH response probes are not suitable for use in epoxy resin-based anti-corrosion coatings; 2) Self-warning anti-corrosion coatings based on nano-microspheres have two steps to achieve self-warning. First, the nano-microspheres rupture and release the probe molecules. Then the probe molecules respond at the damaged and defective sites and emit characteristic fluorescence. The two-step response rate is slow. At the same time, the rupture of the nano-microspheres is related to the direction of the cracks. Therefore, there is a possibility that the self-warning anti-corrosion coatings based on nano-microspheres cannot warn or the warning is slow; 3) According to the electrochemical principle of metal corrosion, corrosion occurs After generation, the cathode region receives electrons and reacts with oxygen and water to generate hydroxide, causing the pH of the cathode region to rise. The metal at the anode corrodes, loses electrons, and becomes metal ions, which reduces the pH of the anode region. The self-warning materials that are currently studied more for alkaline pH response are mainly used to detect the cathode region, while the area where corrosion actually occurs is the anode. There are fewer studies on self-warning anti-corrosion coatings based on acidic pH response probes; 4) The emission wavelength of the responsive probes currently studied is concentrated in the ultraviolet visible region, which not only has limited penetration depth and cannot achieve deep-level detection, but is also easily confused with the color of the coating, making it difficult to achieve the warning function; 5) pH-responsive probes are mostly designed with small molecules, directly or encapsulated in nano-microspheres and mixed with anti-corrosion coatings, which are easy to leak, are not resistant to seawater immersion and scouring, have weak warning signals, and have low visualization. Therefore, it is necessary to develop an acidic pH-responsive fluorescent self-warning anti-corrosion coating to improve the sensitivity and accuracy of coating defect detection. Summary of the invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a fluorescent self-warning anti-corrosion coating with acidic pH responsiveness and its preparation method and application in view of the deficiencies in the prior art. The fluorescent self-warning anti-corrosion coating contains fluorescent probe molecules, and the fluorescent probe molecules have the function of quickly and sensitively producing fluorescent indication for acidic pH. When the anti-corrosion coating is damaged and the metal substrate is exposed, the metal substrate is corroded, the metal at the anode is corroded, an oxidation reaction occurs and electrons are lost, and they become metal ions, which will reduce the pH value of the anode area. At this time, the fluorescence intensity of the fluorescent probe molecules with acidic pH responsiveness in the fluorescent self-warning anti-corrosion coating of the present invention is enhanced, thereby realizing the function of detecting and warning early corrosion of the metal substrate under the coating.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A fluorescent self-warning anti-corrosion coating, wherein the fluorescent self-warning anti-corrosion coating comprises an epoxy resin coupled with a probe molecule;

[0008] Wherein, the structural formula of the probe molecule is shown in Formula I;

[0009]

[0010] Among them, R is

[0011] n is an integer greater than or equal to 2, preferably an integer between 3 and 10; m is an integer greater than or equal to 45, preferably an integer between 45 and 230;

[0012] The amino group in R opens the ring of the epoxy group in the epoxy resin and then forms a covalent bond.

[0013] The probe molecule has acidic pH responsiveness, has a cyanine dye structure, and contains an amino functional group; under acidic conditions, the butyrolactam in the probe molecule structure undergoes a hydrolysis reaction, so that the five-membered ring opens and the fluorescence intensity of the probe molecule is enhanced.

[0014] Wherein, the epoxy resin is bisphenol A epoxy resin, glycidyl ester epoxy resin, linear aliphatic epoxy resin or alicyclic epoxy resin.

[0015] The preparation method of the fluorescent self-warning anti-corrosion coating comprises the following steps:

[0016] (1) adding cyclohexanone and 2-(4-diethylamino-2-hydroxybenzoyl)benzoic acid to concentrated sulfuric acid for a first reaction to obtain product 1, and dissolving the product 1 and Fischer's aldehyde in acetic anhydride for a second reaction to obtain product 2;

[0017] The product 2, the BOP reagent and the compound terminated with amino groups at both ends are dissolved in a first solvent to carry out a third reaction to obtain the small molecule probe; or the product 2, the BOP reagent and the double-terminated amino polyethylene glycol are dissolved in a second solvent to carry out a fourth reaction to obtain the macromolecular probe;

[0018] Wherein, the structural formulas of the compound terminated with amino groups at both ends and the double-terminated amino polyethylene glycol are shown in Formula II and Formula III respectively;

[0019]

[0020] Wherein, n is an integer greater than or equal to 2; m is an integer greater than or equal to 45;

[0021] (2) dissolving the small molecule probe or macromolecular probe obtained in step (1) and epoxy resin in a third solvent to react to obtain a crude product;

[0022] (3) washing and drying the crude product obtained in step (2) to obtain an epoxy resin coupled with a probe molecule;

[0023] (4) dissolving the epoxy resin coupled with the probe molecule obtained in step (3) and the curing agent in a fourth solvent to obtain a fluorescent self-warning anti-corrosion coating.

[0024] In step (1), the first solvent is any one or a combination of dichloromethane, chloroform, tetrahydrofuran and N,N-dimethylformamide, preferably dichloromethane; the second solvent is any one or a combination of dichloromethane, chloroform, tetrahydrofuran, methanol and N,N-dimethylformamide, preferably dichloromethane.

[0025] In step (1), the first reaction is carried out at a temperature of 40 to 150°C and a reaction time of 0.5 to 24 hours, preferably at 90°C for 2 hours; the second reaction is carried out at 25 to 150°C with stirring for 0.5 to 24 hours, preferably at 50°C for stirring for 1.5 hours; the third reaction is carried out at room temperature with stirring for 0.5 to 48 hours, preferably at room temperature for stirring for 1.5 hours; the fourth reaction is carried out at room temperature in the dark for 0.5 to 48 hours.

[0026] Step (1) is a method for preparing the probe molecule (including small molecule probes and macromolecular probes). The specific preparation method refers to the synthesis method of near-infrared fluorescent probe (CyR) in the literature Xie Jun-Ying, Li Chun-Yan, Li Yong-Fei, et al. Near-Infrared Fluorescent Probe with High Quantum Yield and Its Application in the Selective Detection of Glutathione in Living Cells and Tissues. Anal Chem. 2016; 88(19): 9746-9752. doi: 10.1021 / acs.analchem.6b02646.

[0027] In step (2), the mass ratio of the small molecule probe to the epoxy resin is 3 to 40:100; the mass ratio of the macromolecular probe to the epoxy resin is 3 to 50:100.

[0028] In step (2), the third solvent is any one or a combination of tetrahydrofuran, toluene, ethyl acetate, ethanol, cyclohexanone and N,N-dimethylformamide, preferably tetrahydrofuran; the amount of the third solvent used is based on the standard of dissolving the probe molecule and the epoxy resin.

[0029] In step (2), the reaction temperature is 50 to 120° C. and the reaction time is 2 to 48 hours.

[0030] In step (3), the washing comprises: washing the crude product several times with a mixture of methanol and water in a volume ratio of 1:20; and the drying comprises: mixing sodium sulfate with the washed crude product and drying the mixture.

[0031] In step (4), the mass ratio of the epoxy resin of the coupled probe molecule to the curing agent is 100:10~200; the curing agent is any one of an amine curing agent, an acid anhydride curing agent, an imidazole curing agent, or a resin oligomer containing the above curing agent groups; the fourth solvent is any one or a combination of xylene, toluene, cyclohexanone, ethyl acetate and ethanol, preferably xylene; the usage amount of the fourth solvent is 10% to 50% of the mass of the epoxy resin.

[0032] In step (4), after the epoxy resin and curing agent of the coupled probe molecule are dissolved in the fourth solvent, auxiliary agents in the prior art in the art, including dispersants, defoamers and leveling agents, can be added as needed.

[0033] The fluorescent self-warning anti-corrosion coating is used in visual monitoring and detection of corrosion of metal substrates.

[0034] Specifically, the fluorescent self-warning anti-corrosion coating is applied to the surface of a metal substrate and dried and cured at room temperature to form a coating; when corrosion occurs on the metal substrate, the fluorescence intensity of the probe molecules in the coating is enhanced, thereby enabling convenient tracking of early corrosion of the metal substrate under the coating.

[0035] The fluorescent self-warning anti-corrosion coating is applied to the surface of a metal substrate by brushing, dipping, spraying or pouring; the metal substrate is steel, aluminum or copper; and the coating thickness is 50 microns to 5 millimeters.

[0036] Beneficial effects:

[0037] (1) When the epoxy resin material coupled with the probe molecule provided by the present invention is used as an anti-corrosion coating, the anti-corrosion coating can be endowed with self-warning capability. The epoxy resin material coupled with the probe molecule has acidic pH responsiveness, and its fluorescence intensity is enhanced in an acidic environment. Through fluorescence, coating defects and cracks can be detected with high sensitivity and accuracy, and it has good stability, and can detect and locate coating cracks for a long time.

[0038] (2) Most of the current self-warning anti-corrosion coatings use alkaline pH-responsive probe molecules, which are difficult to apply to epoxy resin anti-corrosion coatings cured with amino curing agents. The present invention uses acidic pH-responsive probe molecules to solve this problem well.

[0039] (3) The fluorescence wavelengths of the probe molecules currently used in self-warning anti-corrosion coatings are mostly in the visible region and have limited penetration depth. The fluorescence emission wavelength of the fluorescent probe molecules of the present invention is extended from the ultraviolet visible region to the near-infrared region, thereby improving the detection reliability of the self-warning anti-corrosion coating and the detection depth of the warning signal.

[0040] (4) The present invention couples fluorescent probe molecules with epoxy resin to prepare a fluorescent self-warning anti-corrosion coating. Compared with the existing fluorescent indicator-type corrosion self-warning coating prepared by directly adding fluorescent probe molecules to the coating, the fluorescent self-warning coating has better stability, more stable fluorescence emission performance, and is not easily interfered by other components in the coating.

[0041] (5) The present invention uses macromolecular probes to replace traditional small molecule probes and nano-microspheres that encapsulate probes, and couples them with epoxy resin. The probe molecules are evenly distributed in the epoxy resin. On the one hand, this improves the detection speed and detection width, and on the other hand, it increases the stability of the material, and can extend the detection capability to 30 days, thus avoiding the problems of the existing self-warning coating based on nano-microspheres, such as slow warning efficiency and the inability to warn cracks in different directions. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0043] Figure 1 This is the nuclear magnetic resonance spectrum of the small molecule probe in Example 1.

[0044] Figure 2 This is the mass spectrum of the small molecule probe in Example 1.

[0045] Figure 3 This is the nuclear magnetic resonance spectrum of the macromolecular probe in Example 2.

[0046] Figure 4 This is the mass spectrum of the macromolecular probe in Example 2.

[0047] Figure 5 The UV absorption spectra of the small molecule probe in Example 3 in solutions with different pH values ​​are shown in FIG.

[0048] Figure 6 The fluorescence emission spectra of the small molecule probe in Example 3 in solutions with different pH values ​​are shown in FIG.

[0049] Figure 7 This is the nuclear magnetic resonance spectrum of the small molecule probe coupled with the epoxy resin material in Example 4.

[0050] Figure 8 This is the nuclear magnetic resonance spectrum of the macromolecular probe coupled with the epoxy resin material in Example 4.

[0051] Fig. 9 This is the acidic pH response performance of the acidic pH responsive fluorescent self-warning anti-corrosion coating based on small molecule probes in Example 5.

[0052] Fig.10 This is the acidic pH response performance of the acidic pH responsive fluorescent self-warning anti-corrosion coating based on macromolecular probes in Example 6.

[0053] Fig.11 This is the warning and detection performance of the acidic pH responsive fluorescent self-warning anti-corrosion coating based on small molecule probes in Example 7 for coating cracks of different shapes.

[0054] Fig.12 This is the warning and detection performance of the acidic pH responsive fluorescent self-warning anti-corrosion coating based on macromolecular probes in Example 8 for coating cracks of different shapes. DETAILED DESCRIPTION

[0055] The present invention is further described below based on the following examples. It should be understood that the following embodiments are only used to illustrate the present invention, but not to limit the present invention.

[0056] If the specific techniques or conditions are not specified in the examples, they are carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased through regular channels.

[0057] Example 1 Synthesis of small molecule probes

[0058] In this embodiment, the structural formula of the small molecule probe is shown in Formula IV.

[0059]

[0060] The preparation method is as follows:

[0061] Cyclohexanone (12.74 mmol, 1.32 mL) was dropped into concentrated sulfuric acid (14 mL), cooled to 0°C using an ice bath, and the reactant 2-(4-diethylamino-2-hydroxybenzoyl)benzoic acid (6.4 mmol, 2 g) was gradually added and stirred. The reaction mixture was reacted at 90°C for 2 h, and after cooling, it was poured into ice water (100 g), and perchloric acid (mass fraction 70%, 1.4 mL) was added to filter out the precipitate, and washed with cold water (50 mL) to obtain a red solid as product 1.

[0062] The product 1 (4.2 mmol, 1.58 g) and Fisher aldehyde (4.4 mmol, 0.88 g) were dissolved in acetic anhydride (25 mL), stirred at 50 ° C for 1.5 h, and then water (25 mL) was added to quench the reaction. The solvent was removed by rotary evaporation, and the crude product was purified and separated by silica gel column chromatography, and the developing solvent was dichloromethane: ethanol = 20:1 to obtain a green solid product 2.

[0063] The product 2 (100 mg, 0.18 mmol) was dissolved in 5 mL of ultra-dry dichloromethane with ethylenediamine (0.25 mL, 3.7 mmol) and BOP reagent (1.6 g, 3.7 mol) and stirred at room temperature for 2 h. The solvent was removed by rotary evaporation, and the crude product was separated and purified by silica gel column chromatography, with the developing solvent being dichloromethane: ethanol = 100: 1-10. The product was confirmed by nuclear magnetic resonance to be the target product small molecule probe, which was a yellow viscous liquid. The nuclear magnetic resonance and mass spectrometry results of the small molecule probe are as follows: Figure 1 and Figure 2 shown.

[0064] Example 2 Synthesis of macromolecular probes

[0065] In this embodiment, the structural formula of the macromolecular probe is shown in Formula V.

[0066]

[0067] The preparation method is as follows:

[0068] The product 2 (40 mg, 0.07 mmol) obtained in Example 1 was dissolved together with a BOP reagent (100 mg, 0.23 mmol) in 5 mL of dichloromethane to obtain a solution A. Polyethylene glycol (500 mg) with a degree of polymerization of 45 and amino groups at both ends was dissolved in 1 mL of dichloromethane to obtain a solution B. The solution B was added dropwise to the solution A and reacted overnight at room temperature in the dark. The reaction solution was separated and purified by silica gel column chromatography. The product structure was confirmed to be the target product macromolecular probe by nuclear magnetic resonance spectroscopy and mass spectrometry. The nuclear magnetic resonance and mass spectrometry results of the macromolecular probe are shown as follows: Figure 3 and Figure 4 shown.

[0069] Example 3 pH responsiveness detection of probe molecules

[0070] Prepare buffer solutions with pH values ​​of 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, and 7.5, respectively, wherein pH=3.0 is prepared using citric acid-sodium citrate buffer solution, pH=3.5-5.5 is prepared using acetic acid-sodium acetate buffer solution, and pH=6.0-7.5 is prepared using phosphate buffer solution. Dissolve the small molecule probe in equal concentrations (10 μM) in the above buffer solutions. Use an ultraviolet spectrophotometer and a fluorescence spectrometer to test the ultraviolet absorption intensity and fluorescence emission intensity of the solution in turn, setting the excitation wavelength to 709 nm and the emission wavelength range to 720-800 nm.

[0071] The ultraviolet absorption spectra and fluorescence emission spectra of the small molecule probe in this embodiment in different pH solutions are shown in Figures 1 and 2. Figure 5 and Figure 6 As shown, the results show that the prepared small molecule probe has good pH response ability. As the acidity of the solution increases, its ultraviolet absorption intensity gradually increases, and the fluorescence intensity also gradually increases. Its fluorescence response is more sensitive and begins to respond when the pH is less than 7.5.

[0072] Example 4 Preparation of acidic pH responsive anticorrosion coating

[0073] The small molecule probe (20 mg) and epoxy resin (200 mg) were dissolved in tetrahydrofuran (30 mL), and reacted at 70° C. overnight. The crude product was washed three times with a methanol-water (1:20, v / v) solution, and dried by adding sodium sulfate to obtain product 3, which is an epoxy resin material modified by the probe molecule (small molecule probe). Its structure was confirmed by nuclear magnetic resonance spectroscopy. The results of its nuclear magnetic resonance spectroscopy are as follows: Figure 7 shown.

[0074] The macromolecular probe (18 mg) and epoxy resin (200 mg) were dissolved in tetrahydrofuran (30 mL) and reacted at 70° C. overnight. The crude product was washed three times with a methanol-water (1:20, v / v) solution and dried with sodium sulfate to obtain product 4, which is an epoxy resin material modified with a probe molecule (macromolecular probe). Its structure was confirmed by nuclear magnetic resonance spectroscopy. The results of its nuclear magnetic resonance spectroscopy are as follows: Figure 8 shown.

[0075] Take 100 mg of product 3 and product 4 respectively, and then dissolve them in xylene (10 mg) with a curing agent (McLean, CAS: NONE6720, 50 mg) to obtain the fluorescent self-warning anti-corrosion coating of the present invention. Apply it on a steel plate and cure it at room temperature overnight to obtain an acidic pH responsive fluorescent self-warning anti-corrosion coating.

[0076] Example 5 pH responsiveness detection of epoxy resin-based anticorrosion coatings based on small molecule probes

[0077] 0.1 M citric acid-sodium citrate buffer with a pH of 3.0, acetic acid-sodium acetate buffer with a pH of 5.0, and phosphate buffer solution with a pH of 7.0 were respectively prepared, and the buffer solutions of different pH were dropped on different areas on the surface of the same acidic pH-responsive fluorescent self-warning anti-corrosion coating (the epoxy resin-based anti-corrosion coating coupled with the small molecule probe prepared in Example 4). During the test, the buffer drop area was always kept covered with the buffer. A near-infrared imager was used to perform fluorescence imaging of the coating at different time points, the excitation wavelength was set to 704 nm, and the fluorescence signals in the range of 740 to 950 nm were collected.

[0078] Fig. 9 is the acidic pH response performance of the epoxy resin-based anticorrosion coating based on the small molecule probe in this embodiment, Fig. 9 It can be seen that the prepared fluorescent self-warning anti-corrosion coating has good pH responsiveness. In the pH = 3.0 region, the fluorescence intensity of the coating is significantly stronger than that in the pH = 5.0 and pH = 7.0 regions. At the same time, the pH response performance of the fluorescent self-warning anti-corrosion coating prepared by the present invention has good stability. After 1 month, it still has good pH response performance and can still emit strong fluorescence, which further illustrates the advancement of the present invention in preparing the fluorescent self-warning anti-corrosion coating by coupling the probe molecule to the epoxy resin, which has both good pH response performance and good stability.

[0079] Example 6 pH responsiveness detection of epoxy resin-based anticorrosion coating based on macromolecular probe

[0080] 0.1M citric acid-sodium citrate buffer solution with a pH of 3.0, 5.0 acetic acid-sodium acetate buffer solution and 7.0 phosphate buffer solution were respectively prepared, and the buffer solutions of different pH were dropped on different areas on the surface of the same acidic pH-responsive fluorescent self-warning anti-corrosion coating (the epoxy resin-based anti-corrosion coating coupled with the macromolecular probe prepared in Example 4) (the buffer drop area was always kept covered with the buffer during the test), and the coating was imaged for fluorescence at different time points using a near-infrared imager, the excitation wavelength was set to 704 nm, and the fluorescence signals in the range of 740 to 950 nm were collected.

[0081] Fig.10 is the acidic pH response performance of the acidic pH responsive fluorescent self-warning anti-corrosion coating in this embodiment, Fig. 9 It can be seen that the acidic pH-responsive fluorescent self-warning anti-corrosion coating based on macromolecular probes has good pH responsiveness. The stronger the acidity of the solution, the brighter the fluorescence of the coating and the greater the fluorescence intensity. Fig. 9), the macromolecular probe can clearly distinguish the regions of pH = 5.0 and pH = 7.0, and also has a stronger fluorescence in the region of pH = 5.0, indicating that the pH responsiveness of the anti-corrosion coating based on macromolecular probes is better than that of the anti-corrosion coating based on small molecule probes.

[0082] Example 7 Detection of the fluorescence self-warning capability of epoxy resin-based anti-corrosion coating based on small molecule probes

[0083] Cross and circle coating cracks were constructed on the surface of the acidic pH-responsive fluorescent self-warning anti-corrosion coating based on small molecule probes, and 3.5% sodium chloride aqueous solution was used to simulate seawater covering the coating (the coating was always covered with 3.5% sodium chloride aqueous solution during the test). The coating was imaged with fluorescence using a near-infrared imager at different time points, and the excitation wavelength was set to 704nm, and the fluorescence signal in the range of 740 to 950nm was collected. The ability of the acidic pH-responsive fluorescent self-warning anti-corrosion coating to detect coating cracks in a seawater environment was tested.

[0084] Fig.11 The warning and detection performance of the acidic pH responsive fluorescent self-warning anti-corrosion coating for coating cracks of different shapes in this embodiment is shown in FIG. Fig.11 It can be seen that the fluorescence intensity in the crack area is significantly higher than that in the area with intact coating and the enhanced image of fluorescence intensity is consistent with the shape of the crack, indicating that the acidic pH-responsive fluorescent self-warning anti-corrosion coating has good self-warning capability and can accurately locate the area and shape of the crack.

[0085] Example 8 Detection of the fluorescence self-warning capability of epoxy resin-based anti-corrosion coating based on macromolecular probe

[0086] Cross and circle coating cracks were constructed on the surface of the acidic pH-responsive fluorescent self-warning anti-corrosion coating made of macromolecular probes based on polyethylene glycol, and 3.5% sodium chloride aqueous solution was used to simulate seawater covering the coating (the coating was always covered with 3.5% sodium chloride aqueous solution during the test). The coating was imaged with fluorescence using a near-infrared imager at different time points, with the excitation wavelength set to 704nm, and fluorescence signals in the range of 740 to 950nm were collected. The ability of the acidic pH-responsive fluorescent self-warning anti-corrosion coating to detect coating cracks in a seawater environment was tested.

[0087] Fig.12 The warning and detection performance of the acidic pH responsive fluorescent self-warning anti-corrosion coating for coating cracks of different shapes in this embodiment is shown in FIG. Fig.12It can be seen that the fluorescence intensity of the crack area is significantly higher than that of the intact coating area and the enhanced fluorescence intensity image is consistent with the shape of the crack, indicating that the acidic pH responsive fluorescent self-warning anti-corrosion coating has good self-warning ability and can accurately locate the crack area and shape. Moreover, after 15 days, the acidic pH responsive fluorescent self-warning anti-corrosion coating was further imaged by near-infrared imaging. The results are as follows: Fig.12 As shown, it can still respond to the acidic environment in the crack area. At the same time, the fluorescence intensity in the crack area is still very strong, which can well indicate the crack area and shape of the coating. This result shows that the fluorescent self-warning anti-corrosion coating we prepared has good stability and can provide long-term warning of coating cracks. It is suitable for warning the anti-corrosion ability of anti-corrosion coatings for ships sailing for a long time.

[0088] The present invention provides a preparation idea and method of a fluorescent self-warning anti-corrosion coating. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A fluorescent self-warning anti-corrosion coating, characterized in that: The fluorescent self-warning anti-corrosion coating comprises an epoxy resin coupled with a probe molecule; Wherein, the structural formula of the probe molecule is shown in Formula I; Among them, R is n is an integer greater than or equal to 2; m is an integer greater than or equal to 45; The amino group in R opens the ring of the epoxy group in the epoxy resin and then forms a covalent bond.

2. The fluorescent self-warning anti-corrosion coating according to claim 1 is characterized in that: The epoxy resin is bisphenol A epoxy resin, glycidyl ester epoxy resin, linear aliphatic epoxy resin or alicyclic epoxy resin.

3. The method for preparing the fluorescent self-warning anti-corrosion coating according to claim 1 or 2, characterized in that: The steps include: (1) adding cyclohexanone and 2-(4-diethylamino-2-hydroxybenzoyl)benzoic acid to concentrated sulfuric acid for a first reaction to obtain product 1, and dissolving the product 1 and Fischer's aldehyde in acetic anhydride for a second reaction to obtain product 2; The product 2, the BOP reagent and the compound terminated with amino groups at both ends are dissolved in a first solvent to carry out a third reaction to obtain the small molecule probe; or the product 2, the BOP reagent and the double-terminated amino polyethylene glycol are dissolved in a second solvent to carry out a fourth reaction to obtain the macromolecular probe; Wherein, the structural formulas of the compound terminated with amino groups at both ends and the double-terminated amino polyethylene glycol are shown in Formula II and Formula III respectively; Wherein, n is an integer greater than or equal to 2; m is an integer greater than or equal to 45; (2) dissolving the small molecule probe or macromolecular probe obtained in step (1) and epoxy resin in a third solvent to react to obtain a crude product; (3) washing and drying the crude product obtained in step (2) to obtain an epoxy resin coupled with a probe molecule; (4) dissolving the epoxy resin coupled with the probe molecule obtained in step (3) and the curing agent in a fourth solvent to obtain a fluorescent self-warning anti-corrosion coating.

4. The preparation method according to claim 3, characterized in that: In step (1), the first solvent is any one or a combination of dichloromethane, chloroform, tetrahydrofuran and N,N-dimethylformamide; the second solvent is any one or a combination of dichloromethane, chloroform, tetrahydrofuran, methanol and N,N-dimethylformamide.

5. The preparation method according to claim 3, characterized in that: In step (2), the mass ratio of the small molecule probe to the epoxy resin is 3 to 40:100; the mass ratio of the macromolecular probe to the epoxy resin is 3 to 50:

100.

6. The preparation method according to claim 3, characterized in that: In step (2), the third solvent is any one or a combination of tetrahydrofuran, toluene, ethyl acetate, ethanol, cyclohexanone and N,N-dimethylformamide.

7. The preparation method according to claim 3, characterized in that: In step (2), the reaction temperature is 50 to 120° C. and the reaction time is 2 to 48 hours.

8. The preparation method according to claim 3, characterized in that: In step (3), the washing comprises: washing the crude product with a mixture of methanol and water in a volume ratio of 1:20; and the drying comprises: mixing sodium sulfate with the washed crude product and drying the mixture.

9. The preparation method according to claim 3, characterized in that: In step (4), the mass ratio of the epoxy resin of the coupled probe molecule to the curing agent is 100:10-200; the curing agent is any one of an amine curing agent, an acid anhydride curing agent, an imidazole curing agent, or a resin oligomer containing the above curing agent groups; the fourth solvent is any one of xylene, toluene, cyclohexanone, ethyl acetate and ethanol, or a combination of several thereof.

10. Use of the fluorescent self-warning anti-corrosion coating described in claim 1 or 2 in visual monitoring and detection of corrosion of metal substrates.

11. The use according to claim 10, characterized in that: The fluorescent self-warning anti-corrosion coating is applied to the surface of a metal substrate and dried and cured at room temperature to form a coating; when corrosion occurs on the metal substrate, the fluorescence intensity of the probe molecules in the coating is enhanced, thereby enabling convenient tracking of early corrosion of the metal substrate under the coating.

12. The use according to claim 11, characterized in that: The fluorescent self-warning anti-corrosion coating is applied to the surface of a metal substrate by brushing, dipping, spraying or pouring; the metal substrate is steel, aluminum or copper; the coating thickness is 50 microns to 5 millimeters.

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