A surface-sulfonated silicone hydrogel antifouling coating and a method of making the same

Abstract

This invention belongs to the field of marine antifouling, and specifically relates to a surface-sulfonated organosilicon hydrogel antifouling coating and its preparation method. The coating is obtained by immersing an organosilicon hydrogel coating in a solution of organic compounds containing hydroxyl and sulfonic acid groups for surface sulfonation treatment; the mass concentration of the organic compounds containing hydroxyl and sulfonic acid groups in the solution is 0.01–0.1 g / mL. This invention provides a surface-sulfonated organosilicon hydrogel antifouling coating that constructs a material surface with a synergistic antifouling effect of hydration layer, negative charge, and low surface energy. The prepared antifouling coating exhibits excellent static antifouling performance. This antifouling coating is environmentally friendly, non-polluting, and highly practical, showing broad application prospects in the field of marine antifouling.

Description

Technical Field

[0001] This invention belongs to the field of marine antifouling, and specifically relates to a surface-sulfonated organosilicon hydrogel antifouling coating and its preparation method. Background Technology

[0002] The marine environment is teeming with diverse and abundant organisms. Facilities and equipment that are constantly submerged in seawater, including offshore platforms, drilling facilities, and ships, are susceptible to fouling by marine organisms, which can affect their normal operation or even cause damage. Since the International Ocean Organization banned the use of toxic tributyltin self-polishing antifouling coatings in 2008, the development of green and environmentally friendly marine antifouling coating technologies has received increasing attention.

[0003] Hydrogels are widely used in marine antifouling coatings due to their highly hydrophilic polymer network. Their antifouling mechanism primarily involves a hydration layer forming on the hydrogel surface that confuses fouling organisms and hinders their adhesion. However, this single antifouling mechanism can only inhibit the adhesion of some fouling organisms. Organosilicon materials, due to their low surface energy, low elastic modulus, and low surface roughness, can effectively reduce fouling organism adhesion, or even if adhesion occurs, it is easily desorbed under high water flow conditions. However, in low-velocity seawater environments, the coating surface cannot remove the slime layer secreted by bacteria or diatoms, resulting in poor antifouling performance on static marine facilities. Hempaguard X7 series antifouling paint from Denmark physically blends hydrogel components, organosilicon components, and pesticides. The pesticides are slowly released onto the coating surface. Based on the synergistic antifouling effect of multiple antifouling strategies, the coating achieves excellent antifouling performance in real-world marine environments, maintaining the surface of ships for up to 90 months of dry-docking intervals.

[0004] Under the influence of electrostatic attraction, microorganisms in seawater can generally adhere quickly and tightly to positively charged material surfaces. When the pH of the external solution is greater than the isoelectric point of the microorganisms, bacteria and other microorganisms themselves carry a negative charge. For example, the Zeta potential of *Pseudomonas fluorescens* in a single EPS colloidal suspension at pH 8 is -43.2 mV; the Zeta potential of *Chlorella vulgaris* in water at pH 7 is -30 mV. Therefore, negatively charged surfaces based on the principle of "like repels like" can be constructed to prevent microorganisms from attaching. Rosenhahn et al. demonstrated that the number of *Ulva prolifera* spores settling and the adhesion strength on the prepared negatively charged polytetrafluoroethylene (PTFE) surface were significantly less than those on neutral and positively charged PTFE surfaces. Terada et al. found that the adhesion density of *Escherichia coli* on modified negatively charged polyethylene (PE) surfaces was 23 times lower than that on positively charged PE surfaces. Furthermore, the biofilm on positively charged material surfaces was dense, homogeneous, and of a single structure, while the biofilm on negatively charged material surfaces was sparse, diverse, and of a mushroom-like structure. Summary of the Invention

[0005] To address the short-term antifouling effect of current environmentally friendly marine antifouling coatings, this invention provides a surface-sulfonated organosilicon hydrogel antifouling coating and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A surface-sulfonated silicone hydrogel antifouling coating is obtained by immersing a silicone hydrogel coating in a solution of organic compounds containing hydroxyl and sulfonic acid groups for surface sulfonation treatment; wherein the mass concentration of the organic compounds containing hydroxyl and sulfonic acid groups in the solution is 0.01-0.1 g / mL.

[0008] The organic compound containing hydroxyl and sulfonic acid groups is one or more of hydroxyethyl sulfonic acid, 3-hydroxypropanesulfonic acid, 4-hydroxybutyric acid, 3-hydroxybenzenesulfonic acid, and 4-hydroxybenzenesulfonic acid.

[0009] The silicone hydrogel coating is formed by one-pot bulk polymerization of different functional monomers under the conditions of free radical initiators and crosslinking agents, followed by curing on a substrate. The silicone hydrogel is composed of the following components by mass percentage:

[0010] Methacryloxypropyl mono-terminated polydimethylsiloxane: 10–30%;

[0011] N-Vinylpyrrolidone: 20-40%;

[0012] Polyethylene glycol methyl ether methacrylate: 10-30%;

[0013] Butyl acrylate: 5-10%;

[0014] Silane coupling agent: 15-35%

[0015] Free radical initiator: 0.1–0.5%;

[0016] Crosslinking agent: 0.2%–2%.

[0017] The molecular weight of the methacryloxypropyl mono-terminated polydimethylsiloxane is 1000-1200.

[0018] The molecular weight of the polyethylene glycol methyl ether methacrylate is 300 to 1000.

[0019] The silane coupling agent is one of γ-(methacryloyloxy)propyltrimethoxysilane and γ-mercaptopropyltriethoxysilane;

[0020] The free radical initiator is one of 2,2'-azobisisobutyronitrile and 1,1'-azobis(cyclohexanecarboxynitrile);

[0021] The crosslinking agent is one or more of N,N-methylenebisacrylamide, ethylene glycol dimethacrylate, and vinyl methacrylate.

[0022] A method for preparing the surface-sulfonated silicone hydrogel antifouling coating involves immersing the silicone hydrogel coating in an excess solution of organic compounds containing hydroxyl and sulfonic acid groups (an aqueous solution of organic compounds containing hydroxyl and sulfonic acid groups) for 12-24 hours under stirring conditions, causing a condensation reaction between the two, and grafting the organic compounds containing hydroxyl and sulfonic acid groups into the polymer network, thereby obtaining the surface-sulfonated silicone hydrogel antifouling coating.

[0023] The silicone hydrogel coating is prepared by mixing methacryloyloxypropyl mono-terminated polydimethylsiloxane, N-vinylpyrrolidone, polyethylene glycol methyl ether methacrylate, butyl acrylate, and silane coupling agent in a specific ratio at room temperature. Then, a free radical initiator and a crosslinking agent are added sequentially and the mixture is stirred for another 1 hour. The resulting homogeneous solution is then coated onto different substrates and subjected to bulk polymerization and crosslinking curing at 80°C for 12 hours. Subsequently, the silicone hydrogel coating is immersed in deionized water for 24 hours to remove unreacted monomers and allow it to swell to equilibrium.

[0024] An application of the surface-sulfonated silicone hydrogel antifouling coating, wherein the surface-sulfonated silicone hydrogel antifouling coating is used as an antifouling coating in the field of marine antifouling.

[0025] Beneficial effects of the present invention

[0026] The surface-sulfonated organosilicon hydrogel antifouling coating of this invention constructs a material surface that simultaneously possesses a hydration layer, negative charge, and low surface energy, resulting in a synergistic antifouling effect. The prepared antifouling coating exhibits excellent static antifouling performance. The antifouling coating of this invention is environmentally friendly, pollution-free, and uses readily available raw materials. The method is simple, practical, and easy to promote. Specifically:

[0027] (1) Organosilicon components and hydrogel components are usually physically blended to form an interpenetrating network or layered structure. However, their poor compatibility leads to severe phase separation, resulting in poor mechanical properties and surface segregation. The organosilicon hydrogel antifouling coating of this invention, based on a hydrophilic hydrogel network, covalently bonds hydrophobic organosilicon monomers and hydrophilic monomers through free radical polymerization to form block copolymers, effectively solving the problem of poor compatibility. The prepared organosilicon hydrogel has low surface energy while maintaining high water absorption.

[0028] (2) This invention combines multiple green antifouling strategies. By effectively combining methacryloxypropyl mono-terminated polydimethylsiloxane, N-vinylpyrrolidone, polyethylene glycol methyl ether methacrylate, and hydroxysulfonic acid components, a material surface with synergistic antifouling effects of low surface energy, a hydration layer, and negative charge is constructed. Methacryloxypropyl mono-terminated polydimethylsiloxane imparts low surface energy to the coating, N-vinylpyrrolidone and polyethylene glycol methyl ether methacrylate impart a hydration layer and water absorption properties to the coating surface, and the hydroxysulfonic acid component imparts negative charge to the coating surface. Therefore, the combination of multiple green antifouling strategies adopted in this invention can effectively improve the short antifouling period of environmentally friendly marine antifouling coatings.

[0029] (3) Traditional antifouling coatings typically require the use of organic solvents for dispersion and dilution. These solvents may volatilize into the environment during polymerization and curing, causing pollution and posing a potential health threat to construction workers. This invention employs solvent-free bulk polymerization and curing technology, eliminating the need for any organic solvents. This not only reduces the emission of volatile organic compounds (VOCs) and environmental pollution but also improves the safety of the coating and reduces health risks during construction. Therefore, the surface-sulfonated silicone hydrogel antifouling coating of this invention is environmentally friendly, uses readily available raw materials, is highly practical, has a simple and efficient preparation process, and is universally applicable and easy to promote. Attached Figure Description

[0030] Figure 1 Infrared spectrum of the organosilicon hydrogel coating provided by the present invention (Example 1).

[0031] Figure 2 A static water contact angle photograph of the silicone hydrogel antifouling coating provided by the present invention (Example 1).

[0032] Figure 3 An appearance diagram of the silicone hydrogel antifouling coating provided by the present invention (Example 1). Detailed Implementation

[0033] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0034] The organosilicon hydrogel coating of this invention is formed by bulk polymerization of different functional monomers under the conditions of free radical initiators and crosslinking agents in a one-pot process and curing on a substrate. A surface-sulfonated organosilicon hydrogel antifouling coating of this invention constructs a material surface with a synergistic antifouling effect of a hydration layer, negative charge, and low surface energy. The prepared antifouling coating exhibits excellent static antifouling performance. This antifouling coating is environmentally friendly, pollution-free, and highly practical, showing broad application prospects in the field of marine antifouling.

[0035] Unless otherwise specified, all reagents used in the following examples were commercially available.

[0036] Example 1:

[0037] (1) Methacryloxypropyl mono-terminated polydimethylsiloxane (1 mmol, 1.0 g), N-vinylpyrrolidone (20 mmol, 2.2 g), polyethylene glycol methyl ether methacrylate (4 mmol, 1.2 g), butyl acrylate (5 mmol, 0.6 g), and γ-(methacryloyloxy)propyltrimethoxysilane (6 mmol, 1.5 g) were stirred evenly at room temperature. Then, the free radical initiator azobisisobutyronitrile (0.2 wt%, 0.013 g) and the crosslinking agent N,N-methylenebisacrylamide (1 wt%, 0.065 g) were added sequentially and stirred for 1 h. The evenly mixed solution was then coated onto a glass slide and subjected to bulk polymerization and crosslinking curing at 80 °C for 12 h. Subsequently, the obtained silicone hydrogel coating was immersed in deionized water for 24 h to remove unreacted monomers and swell to equilibrium.

[0038] (2) The above-mentioned organosilicon hydrogel coating was immersed in a 0.1 g / mL hydroxyethyl sulfonic acid aqueous solution with magnetic stirring for 12 h. The alkoxy groups in the γ-(methacryloyloxy)propyltrimethoxysilane component of the hydrogel will hydrolyze under acidic conditions. The hydroxyl groups formed after hydrolysis will undergo a condensation reaction with the hydroxyl groups in hydroxyethyl sulfonic acid, so that the sulfonic acid groups are chemically grafted into the polymer network, and finally a surface sulfonated organosilicon hydrogel antifouling coating is obtained (see...). Figure 1-3 ).

[0039] Depend on Figure 1 The infrared spectrum of the silicone hydrogel antifouling coating is visible at 3420 cm⁻¹. -1 and 1662cm -1 The characteristic peak belonging to -OH is at 1726 cm⁻¹. -1 The infrared absorption peak at 1020 cm⁻¹ belongs to -COOH, while at 1020 cm⁻¹... -1 The infrared characteristic peaks corresponding to Si-O-Si confirm the successful preparation of the organosilicon hydrogel antifouling coating. Figure 2The static water contact angle photograph shows that the silicone hydrogel antifouling coating surface is hydrophilic, with a water contact angle of 72°. Figure 3 The appearance of the silicone hydrogel antifouling coating shows that the coating is transparent, the surface is smooth and uniform, and no obvious phase separation phenomenon was found.

[0040] Examples 2-11 and Comparative Example 1

[0041] Prepared according to the method described in Example 1, the difference lies in changing various components, for example, changing the amount of methacryloyloxypropyl mono-terminated polydimethylsiloxane, N-vinylpyrrolidone, polyethylene glycol methyl ether methacrylate, and γ-(methacryloyloxy)propyltrimethoxysilane to obtain different antifouling coatings, as detailed in Table 1.

[0042] Table 1

[0043]

[0044] To evaluate the water absorption performance of the antifouling coating of this invention, the equilibrium water content of the silicone hydrogel coating was determined by gravimetric analysis. First, the silicone hydrogel coating was fully swollen in deionized water, and then dried under vacuum at 40°C until constant weight. The formula for calculating the equilibrium water content is:

[0045]

[0046] Where m1 and m0 are the weights of the swollen silicone hydrogel coating and the completely dried silicone hydrogel coating, respectively.

[0047] The test results are detailed in Table 2.

[0048] Table 2 Equilibrium water content of silicone hydrogel coatings

[0049] Coating number 1 2 3 4 5 6 7 8 9 10 11 Balanced water content / % 48 44 40 52 60 42 39 35 81 6 74

[0050] As shown in Table 2, the equilibrium water content of the coating decreases with increasing amounts of methacryloyloxypropyl mono-terminated polydimethylsiloxane, demonstrating that the introduction of hydrophobic organosilicon monomers reduces the water absorption capacity of the hydrogel. The table also shows that the equilibrium water content of the coating increases with increasing amounts of the hydrophilic monomers N-vinylpyrrolidone and polyethylene glycol methyl ether methacrylate, significantly enhancing the hydrophilicity of the organosilicon hydrogel coating. Since this invention is based on the synergistic antifouling mechanism of the surface hydration layer and the hydrophobic organosilicon components, the antifouling performance of the coating is not entirely determined by whether the equilibrium water content is higher or lower. In this invention, the equilibrium water content values ​​of coatings 3, 6, 7, and 8 are more prominent.

[0051] The surface energy of the antifouling coating of this invention was evaluated using a contact angle meter (OCA 25, Dataphysics, Germany). The test method was the solid drop method, with a droplet volume of 3 μL and a dropping rate of 1 μL / s. The sample surface was cleaned with nitrogen before measurement. Five different regions were then tested on each sample, and the average value was taken. The surface free energy of each sample was calculated using the Owens-Wendt-Rabel-Kaelble method based on the measured contact angles of deionized water (DI) and diiodomethane (DIM). The test results are detailed in Table 3.

[0052] Table 3 Surface Energy of Organosilicon Hydrogel Coatings

[0053]

[0054] As shown in Table 3, the surface energy of the silicone hydrogel coating gradually decreases with the increase of the amount of methacryloyloxypropyl mono-terminated polydimethylsiloxane monomer, proving that the introduction of hydrophobic silicone monomers reduces the surface energy of the coating. Conversely, increasing the amount of N-vinylpyrrolidone and polyethylene glycol methyl ether methacrylate increases the hydrophilicity of the coating, thus leading to a decrease in surface energy. The coatings obtained in the examples of this invention all achieve good results. Furthermore, studies have shown that the fouling and desorption capacity of a coating is outstanding when its surface energy is between 22-25 mN / m, and coatings 3, 6, 7, and 8 in this invention exhibit superior surface energy values.

[0055] To evaluate the static antifouling performance of the antifouling coating of this invention, a sea-based immersion test was conducted. Referring to GB / T5370-2007 (Antifouling Paint Sample Shallow Sea Immersion Test Method), the antifouling coating system prepared in the examples was immersed in the coastal waters of Qingdao to examine its antifouling performance. Scoring was performed based on the area of ​​fouling organisms attached to the sample surface (see Table 1). The scoring rules are as follows: 100 points for no biological attachment; 95 points for only primary attached organisms such as biofilms; and 95 points for large fouling organisms such as barnacles, calculated using the following formula: 95 - number of individual attachments - coverage area of ​​the colony.

[0056] Table 4 shows the static antifouling effects achievable by different coatings.

[0057]

[0058] As shown in Table 4, increasing the amount of methacryloyloxypropyl mono-terminated polydimethylsiloxane improves the static antifouling ability of the coating, demonstrating that the combination of the hydration layer and low surface energy characteristics of the coating surface gives the silicone hydrogel coating good antimicrobial adhesion ability. This also verifies the test results of the coating equilibrium water content and surface energy in Tables 2 and 3. Furthermore, the table also shows that the static antifouling effect of the coating increases with increasing γ-(methacryloyloxy)propyltrimethoxysilane (Example 8). This is because the hydroxyl groups after hydrolysis of the alkoxy groups on the silane coupling agent increase, leading to an increase in sulfonic acid groups grafted onto the coating surface, and the negative charge of the coating surface gradually increases. Therefore, the synergistic antifouling effect of the coating surface hydration layer, low surface energy, and negative charge can effectively inhibit the adhesion of fouling organisms.

[0059] To evaluate the charge properties of the antifouling coating surface of the present invention, the Zeta potential of different coating surfaces was tested in a water environment with pH=8 (the pH value of natural seawater is generally between 7.9 and 8.4) using a solid surface Zeta potential tester. The results are shown in Table 5.

[0060] Table 5 shows the Zeta potentials of different coated surfaces.

[0061] Coating number 1 2 3 4 5 6 7 8 9 10 11 Zeta potential (mV) -97 -95 -97 -94 -96 -113 -124 -126 -90 -87 4

[0062] As shown in Table 5, with the increase of γ-(methacryloyloxy)propyltrimethoxysilane, the number of sulfonic acid groups grafted onto the coating surface increases, resulting in a gradual decrease in the Zeta potential of the coating surface. This proves that the negative charge of the coating surface gradually increases, which is not conducive to the adhesion of fouling organisms. This further confirms the static antifouling effect of different coatings in Table 4.

[0063] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A surface-sulfonated organosilicon hydrogel antifouling coating, characterized in that: It is obtained by surface sulfonation treatment of an organosilicon hydrogel coating immersed in a solution of organic compounds containing hydroxyl and sulfonic acid groups; the mass concentration of the organic compounds containing hydroxyl and sulfonic acid groups in the solution is 0.01~0.1 g / mL; The silicone hydrogel coating is formed by one-pot bulk polymerization of different functional monomers under the conditions of free radical initiators and crosslinking agents, followed by curing on a substrate. The silicone hydrogel is composed of the following components by mass percentage: Methacryloxypropyl mono-terminated polydimethylsiloxane: 10~30%; N-Vinylpyrrolidone: 20~40%; Polyethylene glycol methyl ether methacrylate: 10~30%; Butyl acrylate: 5~10%; Silane coupling agent: 15~35% Free radical initiator: 0.1~0.5%; Crosslinking agent: 0.2~2%; The silicone hydrogel coating is immersed in an excess solution of organic compounds containing hydroxyl and sulfonic acid groups for 12-24 hours under stirring conditions, so that the two undergo a condensation reaction, and the organic compounds containing hydroxyl and sulfonic acid groups are grafted into the polymer network, thereby obtaining a surface sulfonated silicone hydrogel antifouling coating.

2. The surface-sulfonated organosilicon hydrogel antifouling coating according to claim 1, characterized in that: The organic compound containing hydroxyl and sulfonic acid groups is one or more of hydroxyethyl sulfonic acid, 3-hydroxypropanesulfonic acid, 4-hydroxybutyric acid, 3-hydroxybenzenesulfonic acid, and 4-hydroxybenzenesulfonic acid.

3. The surface-sulfonated organosilicon hydrogel antifouling coating according to claim 2, characterized in that: The molecular weight of the methacryloxypropyl mono-terminated polydimethylsiloxane is 1000~1200. The molecular weight of the polyethylene glycol methyl ether methacrylate is 300~1000.

4. The surface-sulfonated organosilicon hydrogel antifouling coating according to claim 2, characterized in that: The silane coupling agent is one of γ-(methacryloyloxy)propyltrimethoxysilane and γ-mercaptopropyltriethoxysilane; The free radical initiator is one of 2,2'-azobisisobutyronitrile and 1,1'-azobis(cyclohexanecarboxynitrile); The crosslinking agent is one or more of N,N-methylenebisacrylamide, ethylene glycol dimethacrylate, and vinyl methacrylate.

5. A method for preparing the surface-sulfonated organosilicon hydrogel antifouling coating according to claim 1, characterized in that: The silicone hydrogel coating is immersed in an excess solution of organic compounds containing hydroxyl and sulfonic acid groups for 12-24 hours under stirring conditions, so that the two undergo a condensation reaction, and the organic compounds containing hydroxyl and sulfonic acid groups are grafted into the polymer network, thereby obtaining a surface sulfonated silicone hydrogel antifouling coating.

6. The method for preparing the surface-sulfonated organosilicon hydrogel antifouling coating according to claim 5, characterized in that: The silicone hydrogel coating is prepared by mixing methacryloyloxypropyl mono-terminated polydimethylsiloxane, N-vinylpyrrolidone, polyethylene glycol methyl ether methacrylate, butyl acrylate, and silane coupling agent in a specific ratio at room temperature. Then, a free radical initiator and a crosslinking agent are added sequentially and the mixture is stirred for another 1 hour. The resulting homogeneous solution is then coated onto different substrates and subjected to bulk polymerization and crosslinking curing at 80°C for 12 hours. Subsequently, the silicone hydrogel coating is immersed in deionized water for 24 hours to remove unreacted monomers and allow it to swell to equilibrium.

7. The application of the surface-sulfonated organosilicon hydrogel antifouling coating according to claim 1, characterized in that: The surface-sulfonated silicone hydrogel antifouling coating is used as an antifouling coating in the field of marine antifouling.

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