Preparation and application of a green marine antifouling coating based on quaternary ammonium salt chitosan

Abstract

The present invention relates to the preparation and application of a green marine antifouling coating based on quaternary ammonium chitosan. The preparation method comprises: sequentially immersing a substrate in a quaternary ammonium chitosan solution and an anionic polysaccharide solution, repeating the process for layer-by-layer self-assembly, and drying to obtain the green marine antifouling coating. Compared with the prior art, the present invention utilizes quaternary ammonium chitosan and polyanionic polysaccharides to construct a polysaccharide-polyelectrolyte multilayer film through a layer-by-layer self-assembly method for use as a marine antifouling coating material. The polysaccharide composite antifouling coating material exhibits good anti-adhesion properties in protein solutions and Chlorella vulgaris suspensions, and has a controllable degradation rate and self-polishing properties in seawater. It can be widely used for antifouling of underwater equipment such as marine vessels, ships, and docks.

Description

Technical Field

[0001] The invention belongs to the technical field of marine antifouling, and relates to the preparation and application of a green marine antifouling coating based on quaternary ammonium salt chitosan. Background Art

[0002] How to prevent marine organisms from attaching to and corroding the hull has always been a key issue in the field of navigation. Marine biofouling, also known as marine fouling, refers to the unnatural attachment and growth of various marine organisms, including algae, bacteria, protozoa, sponges, coelenterates, mollusks, echinoderms, etc., on the surface of underwater structures such as hulls, submarine pipelines, and offshore platforms. This type of fouling poses multiple hazards to human activities and the marine ecological environment, mainly including: (1) Increased resistance and energy consumption: On ships, the attachment of marine organisms will significantly increase the roughness of the underwater surface, thereby increasing navigation resistance, resulting in increased fuel consumption and rising operating costs. (2) Damage to marine facilities: Fouling organisms can clog equipment such as pipes and filters, affecting normal operation, accelerating the corrosion of metal structures, and shortening the service life of marine facilities, such as offshore oil and gas platforms, desalination plants, and fishery facilities. (3) Interference with marine instruments and machinery: Attached organisms may cover key components such as sensors and valves, causing the function of marine observation and production equipment to fail, affecting the accuracy of data or the safe operation of equipment. (4) Harm to aquaculture: In cage aquaculture and raft aquaculture, fouling organisms will occupy aquaculture space, compete for oxygen and nutrients, and even directly harm aquaculture organisms, reducing production and quality. (5) Disruption of ecological balance: Alien or overgrown fouling species may become invasive species, threaten native species, change the structure and function of the ecosystem, and affect biodiversity. (6) Economic losses: Regular cleaning and removal of marine fouling requires high human and material costs. At the same time, the reduction in production efficiency caused by fouling will also lead to economic losses. (7) Health risks: Some fouling organisms may be carriers of pathogens, which may be transmitted to humans through the food chain, posing a public health risk.

[0003] Marine antifouling coatings applied to ship hulls are currently the primary solution to biofouling. With growing global awareness of environmental protection, the technological trend in marine antifouling coatings is evolving towards greener, more environmentally friendly approaches. This shift requires coatings to reduce or eliminate environmentally harmful ingredients, such as organotin compounds, high concentrations of cuprous oxide, and heavy metal biocides, or even completely abandon traditional biocides. Currently, Wuxi self-polishing antifouling coatings dominate the market due to their significant environmental advantages and superior antifouling performance. These coatings not only avoid the high toxicity of organotin coatings but also inherit the beneficial properties of self-polishing coatings: ion exchange in seawater promotes polymer dissolution, releasing the antifouling agent for sustained antifouling effectiveness. Mainstream Wuxi self-polishing coating systems include polymer coatings based on copper acrylate, zinc acrylate, and silane acrylate. The hydrolysis-resistant properties of these coatings ensure that hydrolysis of the surface resin occurs only upon direct contact with seawater, transforming the surface from hydrophobic to hydrophilic. This results in a slow and continuous dissolution process, ensuring the sustained release of the antifouling agent and maintaining antifouling effectiveness. Despite this, this type of coating has an obvious limitation in its application - their performance depends to a certain extent on the scouring effect of water flow. In particular, when the ship is at rest, due to the lack of sufficient water flow stimulation, the renewal rate of the coating is reduced, and the antifouling effect is greatly reduced. This defect limits their application in ships and submarines sailing at low speeds, and fixed offshore facilities such as oil drilling platforms, because in these cases the coating cannot be fully renewed and it is difficult to maintain the ideal antifouling state. In order to overcome this limitation, the present invention aims to provide a new type of antifouling coating with the characteristic of self-regulating degradation rate according to the environment, so as to meet the needs of different marine operating environments, especially those low-speed or static marine structures, to ensure that continuous and effective antifouling protection can be provided under any circumstances.

[0004] Natural polysaccharides are the most abundant natural polymers on Earth and possess excellent biocompatibility and biodegradability. Furthermore, due to their numerous carboxyl, hydroxyl, and amino groups, polysaccharides exhibit high hydrophilicity and hydration properties, which contribute to their resistance to protein adsorption, bacterial adhesion, and cell adhesion. Chitosan is a linear polysaccharide composed of randomly distributed β-(1,4)-linked D-glucosamine (deacetylated units) and N-acetyl-D-glucosamine (acetylated units). Chitosan is the partial deacetylation product of chitin, a naturally occurring polysaccharide found in abundance in the exoskeletons of marine arthropods such as crustaceans, the shells of insects, the cell membranes of fungi and algae, the shells of mollusks, and the skeletons of higher plants. Quaternized chitosan is a product of chitosan modified by quaternization, where the hydroxyl groups of chitosan are replaced by quaternary ammonium groups (positive ions), resulting in a positively charged quaternized chitosan. Quaternized chitosan has the following characteristics that give it application advantages in the field of antifouling: (1) Positive charge properties: The quaternary ammonium group gives quaternized chitosan a positive charge, which makes it have good solubility and adsorption. The positive charge enables it to interact with negatively charged substances, such as negative ions on the surface of bacteria, negatively charged drugs, etc. (2) Due to the cationic nature of its quaternary ammonium group, quaternized chitosan can interact with negative ions on the surface of bacteria, resulting in the destruction of bacterial membranes and leakage of intracellular substances, thereby achieving a killing effect on bacteria. This bactericidal mechanism is widely used in the fields of medicine, food and disinfection. (3) Biocompatibility: Similar to chitosan, quaternized chitosan also has good biocompatibility and biodegradability. This makes it used as a degradable medical material and tissue engineering scaffold in the fields of medicine and tissue engineering. (4) Corrosion inhibition: Some studies have shown that surface quaternized chitosan can also inhibit the corrosion process of materials such as carbon steel through its adsorption as a corrosion inhibitor that can simultaneously delay both cathodic and anodic processes.

[0005] Polyelectrolyte multilayers (PEMs) are multilayer films formed by the deposition of charged polymers (polyelectrolytes) on solid surfaces layer by layer through electrostatic interactions. Their thickness is generally between a few nanometers and hundreds of nanometers, and they can be used to prepare various functional materials and devices. PEMs have good controllability and adaptability, and different structures, morphologies, and properties can be designed according to needs. They are widely used in biomedicine, electronic devices, sensors and other fields. The preparation of polyelectrolyte multilayers usually adopts the layer-by-layer self-assembly method of ion alternating deposition (LBL). The thin films or coating materials prepared by the LBL method have the advantages of strong controllability, good applicability to unconventional surfaces, and diverse functionality. The high salt stability of the LBL membrane can be enhanced by selecting polyelectrolyte pairs with high binding strength.

[0006] Chinese patent CN114904402B discloses a layer-by-layer self-assembled sustained-release antibacterial polymer separation membrane and its preparation method and application. The preparation method of the present invention comprises: immersing the polymer separation membrane in a mixed solution of polyphenol compounds and polyethyleneimine to functionalize its surface; then utilizing the physical adsorption and electrostatic interaction between negatively charged polysaccharides and positively charged antimicrobial peptides, the polysaccharides and antimicrobial peptides are loaded on the surface of the base membrane by layer-by-layer self-assembly to obtain a polymer separation membrane with antibacterial and anti-biological fouling properties. The modified polymer separation membrane has significantly improved antibacterial and anti-fouling capabilities, and has a significant inhibitory effect on the reproduction of bacteria and microorganisms. The present invention adopts layer-by-layer self-assembly technology for antibacterial modification, which has a mild reaction and simple operation. The prepared modified layer of the polymer separation membrane is controllable and has good antibacterial and anti-fouling properties, and has good application prospects in the field of water treatment. However, this patent also has the following disadvantages: (1) High cost: the production of antimicrobial peptides involves relatively complex biosynthesis or chemical synthesis; Poor durability: (2) Antimicrobial peptides may be enzymatically hydrolyzed by microorganisms in some cases, making it difficult to maintain the antimicrobial effect for a long time. Summary of the Invention

[0007] The present invention aims to provide a method for preparing and applying a green marine antifouling coating based on quaternary ammonium chitosan that exhibits resistance to protein adhesion, antimicrobial adhesion, and fouling release in marine environments. The present invention utilizes quaternary ammonium chitosan and polyanionic polysaccharides to construct a polysaccharide-polyelectrolyte multilayer film via a layer-by-layer self-assembly method for use as a marine antifouling coating material. This polysaccharide composite antifouling coating exhibits excellent anti-adhesion properties in protein solutions and Chlorella suspensions, a controllable degradation rate, and self-polishing properties in seawater. It can be widely used for antifouling applications in marine vessels, ships, docks, and other underwater equipment.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] The first aspect of the present invention provides a method for preparing a green marine antifouling coating based on quaternary ammonium chitosan, comprising: immersing a substrate in a quaternary ammonium chitosan solution and an anionic polysaccharide solution in sequence, repeating the process to self-assemble layer by layer, and drying to obtain the green marine antifouling coating.

[0010] Furthermore, the preparation method of the quaternized chitosan comprises: heating chitosan and 2,3-epoxypropyltrimethylammonium chloride to react to obtain the quaternized chitosan;

[0011] The mass ratio of the chitosan to 2,3-epoxypropyltrimethylammonium chloride is 1:(1-5).

[0012] Furthermore, the weight average molecular weight M of the chitosan WThe range is 5000-50000, and the degree of deacetylation is ≥95%.

[0013] Furthermore, in the heating reaction, the reaction temperature is 60-90° C. and the reaction time is 2-10 h.

[0014] As a preferred technical solution, in the heating reaction, the reaction solvent is isopropanol and the preferred stirring rate is 100-500 rpm.

[0015] As a preferred technical solution, after the heating reaction, the obtained product is separated, dialyzed and freeze-dried to remove unreacted quaternary ammonium salt reagent (2,3-epoxypropyltrimethylammonium chloride), isopropyl alcohol and the like.

[0016] As a preferred technical solution, in the separation dialysis, the minimum molecular weight cutoff of the dialysis bag used is 500-5000, and the dialysis time is 3-5 days.

[0017] Furthermore, the anionic polysaccharide is selected from at least one of carrageenan, sodium alginate, xanthan gum, gellan gum, welan gum, hyaluronic acid, pectin, sodium carboxymethyl cellulose, carboxymethyl starch, carboxymethyl curdlan, carboxymethyl konjac gum, carboxymethyl guar gum or carboxymethyl xyloglucan.

[0018] Furthermore, the mass concentration of the quaternary ammonium salt chitosan solution is 0.5-2%, and the pH is 4.5-6.5;

[0019] The mass concentration of the anionic polysaccharide solution is 0.5-2%, and the pH value is 4.5-6.5.

[0020] As a preferred technical solution, the pH of the quaternized chitosan solution or the anionic polysaccharide solution is adjusted by using HCl solution and NaOH solution with a molar concentration of 1 mol / L.

[0021] Furthermore, the substrate is one of a cement substrate, a metal substrate or a glass fiber substrate.

[0022] Furthermore, in the quaternary ammonium chitosan solution or anionic polysaccharide solution, the substrate is immersed at room temperature for 5-15 minutes, the cycle is repeated 50-100 times, the first immersion solution is anionic polysaccharide solution, and the last immersion solution is quaternary ammonium chitosan solution.

[0023] Furthermore, after each immersion, the substrate is washed with a NaCl / HCl aqueous solution having a pH of 4.5-6.5, wherein the NaCl concentration is 0.1-0.5 mol / L.

[0024] Furthermore, during the drying, the drying temperature is 40-70° C. and the drying time is 12-24 hours.

[0025] A second aspect of the present invention provides an application of a green marine antifouling coating, comprising using the green marine antifouling coating for antifouling treatment of underwater equipment.

[0026] Compared with the prior art, the present invention has the following characteristics:

[0027] 1) Using natural polysaccharides as raw materials, a green marine antifouling coating was successfully synthesized through a simple layer-by-layer self-assembly method. The prepared coating exhibited excellent static and dynamic antifouling capabilities.

[0028] 2) Compared to existing polymer resin antifouling coatings based on small molecule antifouling agents and low surface energy antifouling coatings based on silicone and organofluorine, this coating achieves superior antifouling effectiveness by incorporating multiple antifouling mechanisms. First, the excellent hydrophilicity and hydration properties of polysaccharides are utilized to achieve resistance to protein adhesion. Second, the antibacterial capacity of the coating is enhanced by the introduction of quaternary ammonium groups. Finally, the coating's varying degradation rates in different marine environments are utilized to achieve self-regulating properties, with the coating degrading at a low rate when there is little adhesion and at a high rate when there is a lot of adhesion.

[0029] 3) The green marine antifouling coating prepared by this invention demonstrated its excellent antifouling properties through a series of rigorous performance evaluations. In anti-protein adhesion testing, the coating material demonstrated a reduction of over 90% in adhesion to common proteins, highlighting its effectiveness in resisting biomolecule adsorption. Furthermore, in antibacterial testing, the coating also performed exceptionally well, demonstrating a significant 95% reduction in the attachment rate of common microorganisms, directly demonstrating the coating's ability to inhibit microbial growth and reproduction.

[0030] 4) The preparation process does not use or produce pollutants such as waste acid and waste alkali that are harmful to the environment, and the process is simple, green and environmentally friendly, and suitable for industrial application;

[0031] 5) The present invention adopts quaternary ammonium salt chitosan as antimicrobial material. Compared with the slow-release antimicrobial polymer based on antimicrobial peptides in the prior art, the advantage is that quaternary ammonium chitosan is widely available and is usually made from natural chitosan by chemical modification, with low production cost. Moreover, chitosan is widely present in the marine environment, and its degradation products do not cause harm to the marine environment. The production of antimicrobial peptides involves more complex biosynthesis or chemical synthesis, which is costly. Secondly, quaternary ammonium chitosan can effectively act on negatively charged bacterial cell membranes due to its positively charged quaternary ammonium group, causing the destruction of bacterial cell membranes, thereby achieving a long-lasting antimicrobial effect. Antimicrobial peptides may be enzymatically hydrolyzed by microorganisms in some cases, and the antimicrobial effect may not be as lasting as quaternary ammonium chitosan. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1This is a comparative infrared spectrum of chitosan and the quaternary ammonium salt chitosan described in Example 1.

[0033] Figure 2 This is a scanning electron microscope image of the marine antifouling coating prepared in Example 1.

[0034] Figure 3 This is a graph showing the protein adhesion resistance test results of the marine antifouling coating of Example 2 in the protein antifouling performance evaluation experiment of the present invention.

[0035] Figure 4 This is a graph showing the anti-biological attachment test results of the marine antifouling coating of Example 3 in the microbial antifouling performance test experiment of the present invention.

[0036] Figure 5 This is a graph showing the degradation results of the marine antifouling coating of Example 4 in the coating degradation performance measurement experiment of the present invention in different simulated marine environments. DETAILED DESCRIPTION

[0037] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0038] Example 1:

[0039] This embodiment provides a method for preparing a green marine antifouling coating based on quaternary ammonium salt chitosan with a multi-element antifouling mechanism, comprising the following steps:

[0040] (1) The chitosan and 2,3-epoxypropyltrimethylammonium chloride were prepared in a mass ratio of 1:2. The 2,3-epoxypropyltrimethylammonium chloride solution was slowly added dropwise to the isopropanol suspension of chitosan in a constant temperature water bath at 80°C. The reaction lasted for 6 hours with a stirring rate of 200 rpm. The weight-average molecular weight of the chitosan used was approximately 10,000.

[0041] (2) The isopropanol in the upper layer was removed by decantation, and the product was placed in a dialysis bag with a molecular weight cutoff of 500. After dialysis for 3 days, it was freeze-dried.

[0042] (3) The synthesized quaternary ammonium salt chitosan sample and carrageenan sample were prepared into a polysaccharide aqueous solution with a concentration of 1 wt%, and the pH of the quaternary ammonium salt chitosan solution and the carrageenan solution was adjusted to 5.5 using a sodium hydroxide solution with a mass fraction of 1%. First, an adhesive glass sheet with a surface positive charge treatment (25 mm × 75 mm, thickness 1.0 mm, purchased from Shanghai Titan Technology Co., Ltd.) was immersed in the carrageenan solution for 5 minutes. After being taken out, the surface was washed with a 0.15 M NaCl aqueous solution adjusted to pH 5.5 with a 1 mol / L HCl solution. The adhesive glass sheet was then immersed in the quaternary ammonium salt chitosan solution for 5 minutes. The washing and deposition steps were repeated 50 times (carrageenan solution immersion → NaCl solution washing → quaternary ammonium salt chitosan solution immersion → carrageenan solution immersion → ... → quaternary ammonium salt chitosan solution immersion). Finally, the glass was placed in a constant temperature drying oven at 80 ° C for 24 hours to obtain a coating material on the glass surface.

[0043] The quaternary ammonium salt chitosan prepared in Example 1 and the prepared coating material were structurally characterized using the following testing methods:

[0044] (1) Material structure analysis: Fourier transform infrared spectroscopy (FTIR) technology was used to compare and analyze the chemical structure differences between the original chitosan and the chitosan modified with quaternary ammonium salt to confirm the successful introduction of the quaternary ammonium salt group.

[0045] (2) Observation of coating micromorphology: Scanning electron microscopy (SEM) was used to perform high-resolution imaging of the prepared coating surface to visually display the microstructure and morphological characteristics of the coating.

[0046] The structural characterization results are as follows:

[0047] Figure 1 The infrared spectra of chitosan (CTS) and quaternized chitosan (N-CTS) prepared in Example 1 are compared. Figure 1 It can be seen that chitosan has a weak absorption area of ​​2878 cm -1 The weak absorption peak at 1652cm is the stretching peak of CH; in the fingerprint region, -1 and 1550cm -1 The C=O stretching vibration of amide I and the δN-H bending vibration of amide II are 1420 cm -1 The deformation absorption peak of -CH3 is 1071cm -1 and 1028cm -1 They are the secondary stretching vibration of alcoholic hydroxyl group and the primary stretching vibration of alcoholic hydroxyl group; 897cm -1 The absorption peak at 1480 cm is the absorption peak of the sugar ring structure group. In contrast, some significant changes appeared in the infrared spectrum of the quaternary ammonium salt chitosan sample. First, at 1480 cm-1 A new strong absorption peak appeared at 1642 cm, which can be attributed to the CH bending vibration peak on the trimethylamine group, indicating that quaternary ammonium groups were introduced into the chitosan sample. -1 The absorption at 897 cm increased, indicating that some primary amines have been converted into secondary amines. -1 The peak at 917 cm -1 A new absorption peak appeared at , indicating that the introduction of quaternary ammonium salt groups led to the change of chitosan molecular structure.

[0048] Figure 2 The SEM results of the cross section of the marine antifouling coating prepared in Example 1 illustrate that the obtained material has a typical multilayer microstructure expected by the scheme.

[0049] Example 2:

[0050] This embodiment provides a method for preparing a green marine antifouling coating based on quaternary ammonium salt chitosan with a multi-element antifouling mechanism, comprising the following steps:

[0051] (1) The chitosan and 2,3-epoxypropyltrimethylammonium chloride were prepared in a mass ratio of 1:3. The 2,3-epoxypropyltrimethylammonium chloride solution was slowly added dropwise to the isopropanol suspension of chitosan in a constant temperature water bath at 80°C. The reaction lasted for 8 hours with a stirring rate of 500 rpm. The weight-average molecular weight of the chitosan used was 20,000.

[0052] (2) The isopropanol in the upper layer was removed by decantation, and the product was placed in a dialysis bag with a molecular weight cutoff of 1000. After dialysis for 3 days, it was freeze-dried.

[0053] (3) The synthesized quaternary ammonium salt chitosan sample and the hyaluronic acid sample were prepared into a polysaccharide aqueous solution with a concentration of 0.5wt%, and the pH of the quaternary ammonium salt chitosan solution and the hyaluronic acid solution was adjusted to 5.5 using a sodium hydroxide solution with a concentration of 1% by mass. First, an epoxy glass fiber sheet (FR-4, purchased from Shanghai Nanjue New Material Technology Co., Ltd.) was immersed in the hyaluronic acid solution for 10 minutes. After being taken out, the surface was washed with a 0.15M NaCl aqueous solution with a pH adjusted to 5.5 by a 1mol / L HCl solution. The epoxy glass fiber sheet was then immersed in the quaternary ammonium salt chitosan solution for 10 minutes. The washing and deposition steps were repeated 100 times. Finally, the glass was placed in a constant temperature drying oven at 60°C for 24 hours to obtain a coating material on the surface of the epoxy glass fiber sheet.

[0054] The protein antifouling performance evaluation experiment was conducted on the marine antifouling coating prepared in Example 2. The experimental method is as follows:

[0055] Evaluation of protein antifouling performance: Quartz crystal microbalance (QCM-D) technology is used to measure the adhesion behavior of different types of proteins on the coating surface, and adhesion kinetic curves are drawn to evaluate the anti-protein adhesion performance of the coating.

[0056] The results of the protein antifouling performance evaluation experiment are as follows:

[0057] Figure 3 Protein resistance test results for the marine antifouling coating prepared in Example 2. Using a quartz crystal microbalance, the adhesion of three common proteins (lysozyme, bovine serum albumin, and fibrinogen) to an untreated epoxy glass fiber sheet and a substrate coated with the marine antifouling coating prepared in Example 2 was compared. The results showed that compared to the original substrate, the marine antifouling coating significantly reduced the amount of protein adhesion to the three proteins, with lysozyme adhesion decreasing by 95.7%, bovine serum albumin adhesion by 96.2%, and fibrinogen adhesion by 94.5%, demonstrating excellent protein resistance.

[0058] Example 3:

[0059] This embodiment provides a method for preparing a green marine antifouling coating based on quaternary ammonium salt chitosan with a multi-element antifouling mechanism, comprising the following steps:

[0060] (1) The chitosan and 2,3-epoxypropyltrimethylammonium chloride were prepared in a mass ratio of 1:4. The 2,3-epoxypropyltrimethylammonium chloride solution was slowly added dropwise to the isopropanol suspension of chitosan in a constant temperature water bath at 80°C. The reaction lasted for 8 hours with a stirring rate of 300 rpm. The weight-average molecular weight of the chitosan used was 20,000.

[0061] (2) The isopropanol in the upper layer was removed by decantation, and the product was placed in a dialysis bag with a molecular weight cutoff of 500. After dialysis for 3 days, it was freeze-dried.

[0062] (3) The synthesized quaternary ammonium salt chitosan sample and the sodium alginate sample were prepared into a polysaccharide aqueous solution with a concentration of 2 wt%, and the pH of the quaternary ammonium salt chitosan solution and the sodium alginate solution was adjusted to 4.5 using a sodium hydroxide solution with a mass fraction of 1%. First, the carbon steel metal sheet was immersed in the sodium alginate solution for 5 minutes. After being taken out, the surface was washed with a 0.15M NaCl aqueous solution with a pH adjusted to 4.5 by a 1 mol / L HCl solution. The carbon steel metal sheet was then immersed in the quaternary ammonium salt chitosan solution for 5 minutes. The washing and deposition steps were repeated 50 times. Finally, the glass was placed in a constant temperature drying oven at 80°C for 24 hours to obtain a coating material on the surface of the carbon steel metal sheet.

[0063] The microbial antifouling performance test of the marine antifouling coating prepared in Example 3 was conducted, and the experimental method was as follows:

[0064] Microbial antifouling performance test: The coating samples were placed in a microalgae (Chlorella) culture medium containing a concentration of 60,000 cells / mL (10ml of Chlorella seed mixed with 50ml of seawater f / 2 culture medium; both the algae seed and culture medium were purchased from the Seaweed Germplasm Bank of the Chinese Academy of Sciences). After 5 days of static immersion, the microbial attachment on the coating surface was observed and recorded using an optical microscope to evaluate the coating's microbial antifouling effect.

[0065] The results of the microbial antifouling performance test are as follows:

[0066] Figure 4 The following are experimental results showing the microbial antifouling performance of the marine antifouling coating prepared in Example 3. The results compared the attachment of Chlorella vulgaris to ordinary glass and glass coated with the marine antifouling coating prepared in Example 3 after being placed in a Chlorella vulgaris solution for five days. The results showed that compared to ordinary glass, the glass coated with the marine antifouling coating prepared in Example 3 effectively reduced the number of Chlorella vulgaris attached, demonstrating excellent antibacterial properties.

[0067] Example 4:

[0068] This embodiment provides a method for preparing a green marine antifouling coating based on quaternary ammonium salt chitosan with a multi-element antifouling mechanism, comprising the following steps:

[0069] (1) The chitosan and 2,3-epoxypropyltrimethylammonium chloride were prepared in a mass ratio of 1:3. The 2,3-epoxypropyltrimethylammonium chloride solution was slowly added dropwise to the isopropanol suspension of chitosan in a constant temperature water bath at 80°C. The reaction lasted for 8 hours with a stirring rate of 500 rpm. The weight-average molecular weight of the chitosan used was 20,000.

[0070] (2) The isopropanol in the upper layer was removed by decantation, and the product was placed in a dialysis bag with a molecular weight cutoff of 1000. After dialysis for 3 days, it was freeze-dried.

[0071] (3) The synthesized quaternary ammonium salt chitosan sample and xanthan gum sample were prepared into a polysaccharide aqueous solution with a concentration of 1.5wt%, and the pH of the quaternary ammonium salt chitosan solution and the xanthan gum solution was adjusted to 6.5 using a sodium hydroxide solution with a mass fraction of 1%. First, the surface positively charged adhesive glass sheet (25mm×75mm, thickness 1.0mm, purchased from Shanghai Titan Technology Co., Ltd.) was immersed in the xanthan gum solution for 10 minutes, and then the surface was washed with a 0.15M NaCl aqueous solution adjusted to pH 6.5 with a 1mol / L HCl solution. The adhesive glass sheet was then immersed in the quaternary ammonium salt chitosan solution for 10 minutes, and the washing and deposition steps were repeated 100 times. Finally, the glass was placed in a constant temperature drying oven at 80℃ for 24 hours to obtain a coating material on the glass surface.

[0072] The degradation performance test of the marine antifouling coating prepared in Example 4 was carried out, and the test method was as follows:

[0073] Determination of coating degradation performance: Under simulated marine environmental conditions (such as salinity, pH value, shear rate), the degradation rate and extent of the coating are monitored to evaluate the stability and self-polishing properties of the coating in the actual marine environment.

[0074] The degradation performance test results are as follows:

[0075] Figure 5The degradation results of the marine antifouling coating prepared in Example 4 were compared. The degradation degree of the coating material in 1440 hours was compared under different test conditions, including water flow at different speeds (RS, unit rpm) and seawater at different pH values ​​(simulated seawater ratio of 26.518g / L NaCl, 3.305g / LMgSO4, 2.447g / L MgCl2, 1.141g / LCaCl2, 0.725g / L KCl, 0.202g / L NaHCO3, 0.083g / L NaBr, and a NaOH solution with a mass fraction of 1% was used to adjust the pH). Under static simulated seawater conditions, after 1440 hours, the remaining mass (RM) of the coating was 79.9% of the initial mass. When the simulated seawater was stirred with a stirrer at 200rpm, the coating mass dropped to 74.6%, indicating that under static and natural seawater flow conditions, the coating degradation rate was slow and the stability was good. When the speed was increased to 500 rpm, the coating degradation rate was 48.0%, indicating that the coating degradation rate was accelerated under the stronger shear effect of seawater, which is consistent with the expected degradation effect of self-degradable coatings. Under the condition of 500 rpm rotation, reducing the pH of the simulated seawater from 8.2 to 6.0 and 4.0 significantly increased the degradation rate of the coating. As the pH decreased, the degradation rate accelerated, and the residual coating mass was 14.7% and 0.1%, respectively. This shows that the effect of the acidic environment on the degradation of the coating is significant. This means that when marine organisms such as barnacles attach, the acidic environment gradually accumulated during their metabolism promotes the degradation of the coating, thereby promoting the accelerated release of dirt.

[0076] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing a green marine antifouling coating based on quaternary ammonium salt chitosan, characterized in that: include: The substrate is sequentially immersed in a quaternary ammonium salt chitosan solution and an anionic polysaccharide solution, and the process is repeated layer by layer for self-assembly, and then dried to obtain a green marine antifouling coating. The preparation method of the quaternary ammonium salt chitosan comprises: heating chitosan and 2,3-epoxypropyltrimethylammonium chloride to react to obtain the quaternary ammonium salt chitosan; The mass ratio of the chitosan to 2,3-epoxypropyltrimethylammonium chloride is 1:(1-5); The weight average molecular weight M of the chitosan W range is 5000-50000, and the degree of deacetylation is ≥95%; The mass concentration of the quaternary ammonium salt chitosan solution is 0.5-2%, and the pH is 4.5-6.5; The mass concentration of the anionic polysaccharide solution is 0.5-2%, and the pH is 4.5-6.5; In the quaternary ammonium salt chitosan solution or anionic polysaccharide solution, the substrate is immersed at room temperature for 5-15 minutes, the cycle is repeated 50-100 times, the first immersion solution is anionic polysaccharide solution, and the last immersion solution is quaternary ammonium salt chitosan solution.

2. The method for preparing a green marine antifouling coating based on quaternary ammonium salt chitosan according to claim 1, wherein In the heating reaction, the reaction temperature is 60-90° C. and the reaction time is 2-10 h.

3. The method for preparing a green marine antifouling coating based on quaternary ammonium salt chitosan according to claim 1, wherein In the anionic polysaccharide solution, the anionic polysaccharide used is selected from at least one of carrageenan, sodium alginate, xanthan gum, gellan gum, welan gum, hyaluronic acid, pectin, sodium carboxymethyl cellulose, carboxymethyl starch, carboxymethyl curdlan, carboxymethyl konjac gum, carboxymethyl guar gum or carboxymethyl xyloglucan.

4. The method for preparing a green marine antifouling coating based on quaternary ammonium salt chitosan according to claim 1, wherein The substrate is one of a cement substrate, a metal substrate or a glass fiber substrate.

5. The method for preparing a green marine antifouling coating based on quaternary ammonium salt chitosan according to claim 1, wherein After each immersion, the substrate was washed with a NaCl / HCl aqueous solution having a pH of 4.5-6.5, wherein the NaCl concentration was 0.1-0.5 mol / L.

6. An application of a green marine antifouling coating prepared by the method according to any one of claims 1 to 5, characterized in that: The green marine antifouling coating is used for antifouling treatment of underwater equipment.

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