Water-based fluorine-free super-hydrophobic anti-corrosion and anti-fouling coating and preparation method thereof

Abstract

The invention discloses a water-based fluorine-free super-hydrophobic anti-corrosion and anti-fouling coating, which is composed of a base coat prepared from an epoxy acrylic resin suspension and a top coat prepared from a super-hydrophobic micro-nano ion modified emulsion. According to the invention, a firm micro-nano coarse hydrophobic structure is formed through hydrolytic condensation reaction of the super-hydrophobic nanoparticle modified emulsion, so that the coating is endowed with excellent hydrophobicity and anti-corrosion and anti-fouling properties; the super-hydrophobic nanoparticles with alternate long and short chains are adopted, so that the crosslinking density of the coating is greatly improved; meanwhile, the base coat and the top coat are cured under ultraviolet light, strong interaction is formed through chemical bonding, and the coating can be tightly combined with the surface of metal equipment. Therefore, the coating disclosed by the invention has excellent antifouling and anticorrosive effects, durability and wear resistance, can replace a commercial fluorine-containing coating, and has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a water-based, fluorine-free, superhydrophobic, anti-corrosion, and antifouling coating and its preparation method. It has excellent antifouling and anti-corrosion effects and can be used to protect marine metal equipment. Background Technology

[0002] With the continuous development of the marine industry, the application of marine metal materials is increasing. However, these materials have always faced serious corrosion problems in the marine environment, resulting in huge economic losses worldwide every year. Simultaneously, under the influence of temperature, humidity, salinity, and various microorganisms in the ocean, microbial fouling is inevitable, causing marine biofouling and severely affecting the use of marine metal equipment. Therefore, marine metal corrosion and marine biofouling are two critical problems that urgently need to be addressed in the development of the marine industry.

[0003] Currently, bio-inspired coating technologies are an effective strategy for corrosion and biofouling resistance. Among them, superhydrophobic coatings have become a research hotspot due to their unique "lotus effect"—that is, the synergistic effect of surface micro-nano roughness and low surface energy materials, which endows materials with self-cleaning, corrosion-resistant, and anti-fouling properties. Traditional superhydrophobic coatings typically use fluorinated low surface energy compounds (such as fluorocarbons) as the main components. These compounds have excellent hydrophobic properties due to their special molecular structure. However, fluorocarbons have been found to have persistent bioaccumulation and toxicity, and they are mostly dispersed in organic solvents during use, posing a potential threat to the environment and ecosystems. For example, a superhydrophobic coating patent application with application number 201110310590.4 mentions that two different nanoparticles and acrylic resin are added to a mixed solvent of acetone, ethyl acetate, and ethanol, and then heptadecafluorotrimethoxysilane is added to prepare a superhydrophobic coating. The long-chain perfluoroalkyl substances added to the above-mentioned superhydrophobic coatings have persistent bioaccumulation and toxicity. At the same time, the mixed solvents of acetone, ethyl acetate and ethanol used as diluents have an irritating odor, are harmful to organisms, are flammable and explosive, pose safety hazards and are difficult to treat.

[0004] The water-based, fluorine-free, anti-corrosion and anti-fouling superhydrophobic coating proposed in this invention can replace fluorine-containing coatings, significantly reducing the use of toxic and harmful substances. It also has significant implications and application value for marine anti-corrosion and anti-fouling work. This invention utilizes the hydrolysis and condensation reaction of a superhydrophobic nanoparticle-modified emulsion to form a robust micro-nano-scale rough hydrophobic structure, endowing the coating with excellent hydrophobicity and anti-corrosion and anti-fouling properties. Simultaneously, the use of alternating long and short chain superhydrophobic nanoparticles greatly increases the crosslinking density of the coating, solving the problems of low crosslinking density, poor durability, and short lifespan found in existing commercial coatings. Furthermore, the primer and topcoat are cured under ultraviolet light, forming strong interactions through chemical bonding, enabling the coating to tightly bond with the surface of metal equipment, exhibiting excellent adhesion and wear resistance. This achieves marine anti-corrosion and anti-fouling, solving the problem of environmental pollution caused by fluorine-containing substances and volatile organic solvents in current superhydrophobic coatings. Summary of the Invention

[0005] To address the environmental pollution problems caused by the extensive use of fluorinated substances and organic solvents in existing commercial coatings, this invention provides a water-based, fluorine-free, superhydrophobic, anti-corrosion, and anti-fouling coating. This coating not only achieves excellent superhydrophobic properties and is environmentally friendly, but also meets the requirements for anti-corrosion and anti-fouling performance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A water-based, fluorine-free, superhydrophobic, anti-corrosion, and anti-fouling coating comprises a primer and a topcoat. The primer is prepared from an epoxy acrylic resin suspension, and the topcoat is prepared from a superhydrophobic micro / nano ion-modified emulsion.

[0007] Furthermore, the epoxy acrylate resin suspension is obtained by dispersing epoxy acrylate resin in ethanol at a mass ratio of 1:2 and stirring at 200-300 rpm for 20-30 minutes.

[0008] Furthermore, the epoxy acrylate resin is one or more of Etercure 6301, DR-E351, EBECRYL® 600, EBECRYL® 605, CN104, CN111, EA-80, and EA-90.

[0009] Furthermore, the preparation of the superhydrophobic micro / nanoparticle modified emulsion includes the following steps: 1) Add fumed silica to an aqueous ethanol solution and disperse it into suspension A by ultrasonication; 2) Add citral silane coupling compound, tetraethyl orthosilicate (TEOS), and ammonia to another aqueous ethanol solution and mix well to obtain solution B; 3) Mix suspension A and solution B evenly and stir at 60 °C for 24 h to induce silane hydrolysis and condensation to obtain the superhydrophobic micro / nano ion modified emulsion.

[0010] Furthermore, based on a total mass percentage of 100%, the mass percentages of each raw material are as follows: 5-10% fumed silica, 5-10% TEOS, 10-20% citral silane coupling agent, 5-10% ammonia, and the remainder is an aqueous ethanol solution; the volume ratio of ethanol to water in the aqueous ethanol solution is 1:2.

[0011] Furthermore, the general structural formula of the citral silane coupling compound is as follows: , Wherein, R is a C8-C16 straight-chain alkane, and R' is a C2-C7 straight-chain alkane; its synthesis includes the following steps: (1) Synthesis of product A Diethylenetriaminepropyltrimethoxysilane and citral were mixed in anhydrous ethanol and then refluxed under a nitrogen atmosphere for 16-24 hours. After standing and separating into layers, the lower liquid layer was taken out and dried to obtain product A. (2) Synthesis of couplings The obtained product A was dissolved in anhydrous ethanol, and a long-chain haloalkane RX was added. The mixture was reacted at 50-60°C for 24 hours. Then, a short-chain haloalkane R'X was added to the system, and the reaction was continued at 50-60°C for another 24 hours. Finally, n-hexane was added to the system to cause it to separate into layers. The lower layer solution was taken and dried to obtain the citral silane coupling compound.

[0012] Furthermore, the molar ratio of diethylenetriaminepropyltrimethoxysilane and citral used in step (1) is 1:1.1.

[0013] Furthermore, in step (2), the molar ratio of product A, potassium carbonate, long-chain haloalkane RX, and short-chain haloalkane R'X is 1:2:1.5:1.5; wherein R is a C8-C16 straight-chain alkane, R' is a C2-C7 straight-chain alkane, and X is any one of Cl, Br, and I.

[0014] The preparation method of the water-based fluorine-free superhydrophobic anti-corrosion and anti-fouling coating includes the following steps: (1) After uniformly spraying the epoxy acrylic resin suspension, let it stand at room temperature for 30 minutes until the surface is dry to obtain the primer. (2) The superhydrophobic micro-nano ion modified emulsion is uniformly sprayed onto the primer, then irradiated with ultraviolet light of wavelength 365nm for 2-3 hours, and then left to stand at room temperature for 24 hours to obtain the topcoat, which is the coating.

[0015] The significant advantages of this invention are: (1) The superhydrophobic nanoparticle modified emulsion prepared by the present invention using fumed silica, TEOS and citral silane coupling can form a robust micro-nano rough hydrophobic structure through hydrolysis condensation reaction. When used as a topcoat, it can impart excellent hydrophobicity and anti-corrosion and anti-fouling properties to the coating. (2) The present invention utilizes superhydrophobic nanoparticles with alternating long and short chains formed by citral silane coupling to make great use of the spatial structure of the coating, greatly improve the crosslinking density of the coating, and solve the problems of low crosslinking density, poor durability and short life of existing commercial coatings. (3) The present invention cures the primer and topcoat under ultraviolet light, forming a strong interaction through chemical bonding, which solves the problem of poor adhesion and easy peeling between existing coatings. The cured primer is tightly bonded to the surface of the metal equipment, providing excellent adhesion and wear resistance. (4) The coating of the present invention does not contain toxic fluorides, which solves the problem of environmental pollution caused by fluorine-containing substances and volatile organic solvents in current superhydrophobic coatings, and can achieve marine safety, corrosion prevention and antifouling. Attached Figure Description

[0016] Figure 1 The image shows a Nyquist plot of a water-based, fluorine-free, superhydrophobic, anti-corrosion, and antifouling coating prepared on a Q235 carbon steel substrate according to the formulation in Example 1, after immersion in simulated seawater (3.5 wt.% NaCl solution) for 30 days. Detailed Implementation

[0017] A water-based, fluorine-free, superhydrophobic, anti-corrosion, and anti-fouling coating comprises a primer and a topcoat, and its preparation includes the following steps: 1) Preparation of epoxy acrylate resin suspension: Epoxy acrylate resin is dispersed in ethanol at a mass ratio of 1:2 and stirred at 200-300 rpm for 20-30 min to obtain epoxy acrylate resin suspension. 2) Preparation of superhydrophobic micro / nano ion-modified emulsion: Fumed silica was added to an ethanol aqueous solution and dispersed by ultrasonication to form suspension A; citral silane coupling compound, tetraethyl orthosilicate (TEOS), and ammonia were added to another ethanol aqueous solution and mixed to obtain solution B; suspension A and solution B were mixed evenly and stirred at 60 °C for 24 h to induce silane hydrolysis and condensation to obtain superhydrophobic micro / nano ion-modified emulsion; 3) Coating preparation: The epoxy acrylic resin suspension was uniformly sprayed using a spray gun (W-71) with a nozzle diameter of 1.0 mm. The distance between the sprayed surface and the spray gun was 10 cm. After spraying, the mixture was allowed to stand at room temperature for 30 minutes to dry, thus obtaining the primer. The superhydrophobic micro-nano ion modified emulsion was then sprayed using a spray gun (W-71) with a nozzle diameter of 1.0 mm. The distance between the sprayed surface and the spray gun was 20 cm, and the spraying time was 20 s. Then, the mixture was irradiated with ultraviolet light with a wavelength of 365 nm for 2-3 hours, and then allowed to stand at room temperature for 24 hours to obtain the topcoat, thus obtaining the coating.

[0018] Wherein, the epoxy acrylate resin mentioned in step 1) is one or more of Etercure 6301, DR-E351, EBECRYL® 600, EBECRYL® 605, CN104, CN111, EA-80, and EA-90.

[0019] Based on a total mass percentage of 100%, the mass percentages of each raw material in step 2) are as follows: 5-10% fumed silica, 5-10% TEOS, 10-20% citral silane coupling compound, 5-10% ammonia, and the remainder is an aqueous ethanol solution; the volume ratio of ethanol to water in the aqueous ethanol solution is 1:2.

[0020] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0021] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0022] The preparation steps of the citral silane coupling used in the examples are as follows: (1) Place 1 mol of diethylenetriaminopropyltrimethoxysilane (1) and 1.1 mol of citral (2) in a 100 mL round-bottom flask, add 50 mL of anhydrous ethanol, reflux under nitrogen atmosphere for 16-24 hours, then let stand to separate the layers, take the lower liquid layer, and dry it in a vacuum drying oven at 60 °C for 24 hours to obtain liquid product (3) with a yield of 85%;

[0023] (2) Dissolve 1 mol of product (3) in 50 mL of anhydrous ethanol, add 2 mol of potassium carbonate and 1.5 mol of long-chain haloalkane RX (4), react at 50-60 °C for 24 hours, then add 1.5 mol of short-chain haloalkane R'X (5) to the system, react at 50-60 °C for 24 hours, then add 50 mL of n-hexane to the system to separate the layers, take the lower layer solution, and dry it in a vacuum drying oven at 60 °C for 24 hours to obtain the liquid product, which is citral silane coupling, with a yield of 91%.

[0024]

[0025] The characterization data of the citral silane couplings obtained when R=C8 straight-chain alkanes, R'=C3 straight-chain alkanes, and X=Cl are as follows: 1 H NMR (300MHz, DMSO-) d6 ), δ : 0.56 (t, 2H, SiCH2), 0.87(t, 6H, CH3),1.26-1.29(m, 10H, CH2), 1.35(t, 4H, CH2), 1.44(t, 2H, CH2), 1.61 (t, 2H,CH2),1.75 (s, 9H, CH3), 2.0 (s, 4H, CH2), 2.37(t, 4H, CH2), 2.4-2.6(m, 6H, CH2),3.01(t, 2H, CH2), 3.55(s,9H,CH3),4.81 (s, 1H, CH=), 5.2(s, 1H, CH=), 8.27(d,1H, C=N). HRMS calculated value C 31 H 64 N3O3Si (M+H) + : 554.95, measured value 554.46. Example

[0026] Different water-based, fluorine-free, anti-corrosion, anti-fouling, and superhydrophobic coatings were prepared according to the formulations in Table 1.

[0027] Table 1

[0028] The physical properties of the superhydrophobic coatings prepared in Table 1 were determined, and the results are shown in Table 2. The test methods are as follows: (1) Hardness: Tested according to the method described in GB / T 6739-2022. A triangular pencil and a 750 g weight were used.

[0029] (2) Adhesion: Tested according to the method described in GB / T 9286-2021.

[0030] (3) Neutral salt spray test: The test shall be conducted in accordance with the method described in GB / T 1771-2007.

[0031] (4) Diatom adhesion resistance test: *Phaeodactylum tricornutum* is a common marine diatom, often used in adhesion tests to evaluate its resistance to biofouling. This type of diatom was placed in a light incubator and cultured in sterile Guillard's F / 2 medium rich in Si at 20 ℃, using a 12 h:12 h light cycle. Diatoms in the logarithmic growth phase were selected as the adhesion research subjects.

[0032] Then the sample was immersed in a solution with a concentration of 5×10 6 After standing for 7 days in a suspension of diatoms per mL, the algal solution was removed by pipette, and the sample was rinsed three times with sterile artificial seawater (ASW) to remove unattached diatoms. The sample was then immersed in a 2.5% glutaraldehyde seawater solution and stored at 4 °C for at least 2 hours to fix the diatoms. The glutaraldehyde solution was removed by pipette, and the sample was rinsed twice with sterile seawater. The adhesion of diatoms to the sample surface was observed using a laser confocal microscope (CLSM, Leica TCS SP8, Germany), and the area coverage of diatoms on the sample surface was calculated.

[0033] (5) EIS Test: The coating was applied to a carbon steel electrode, and the Nyquist plot of the coating was measured using a three-electrode configuration on an electrochemical workstation after immersion in simulated seawater (3.5 wt% NaCl solution) for 30 days. Under the same corrosive environment, the capacitive arc of the electrode was compared with the double-layer capacitance (C0). dl ) and charge transfer resistance (R ct The time constant is related to the capacitance arc radius. The larger the radius of the capacitance arc, the higher the polarization resistance of the working electrode and the better the corrosion resistance of the coating.

[0034] Table 2

[0035] Compared with Example 1, Comparative Example 1 did not use a primer. After its topcoat was cured into a film, its bonding ability with the metal surface was weak. Its physical properties such as hardness, adhesion, salt spray resistance, and anti-diatom adhesion were all lower than those of the coating prepared according to the formulation of Example 1. In particular, the coating peeled off after about 1000 hours of neutral salt spray test.

[0036] Compared with Example 1, Comparative Example 2 does not contain citral silane coupling agent, and after curing into a film, it lacks sufficient hydrophobic substances, thus greatly reducing the contact angle and providing almost no anti-corrosion and anti-fouling properties.

[0037] Compared to Example 1, Comparative Example 3 replaced the citral silane coupling agent with PDMS. Although the cured film exhibited better hydrophobic properties, it lacked chemical bonds to bond with the primer, resulting in poor adhesion between coatings and easy peeling. Large-area coating peeling was observed after approximately 500 hours of neutral salt spray testing.

[0038] Compared with Example 1, Comparative Example 4 did not add fumed silica, so it could not form a good rough structure. After curing into a film, the hydrophobicity was weak, the contact angle was reduced, and the anti-corrosion and anti-fouling effects were reduced.

[0039] Compared to Example 1, Comparative Example 5 replaced the epoxy acrylate resin with epoxy resin E-51. After curing, the film exhibited better hydrophobic properties, but lacked chemical bonds to bond with the primer, resulting in poor adhesion between the coating and easy peeling. No coating peeling was observed during approximately 1000 hours of neutral salt spray testing.

[0040] Compared with Example 1, the R in the citral silane couplings used in Comparative Examples 6 and 7 are either long chains or short chains, and there is no alternation between long and short chains. After curing into a film, the long chains have a reduced curing area on the surface due to steric hindrance, and the short chains cannot provide sufficient hydrophobicity and therefore cannot achieve superhydrophobicity. Thus, neither can achieve good performance.

[0041] Compared with Example 1, Comparative Example 8 used a C18 long-chain haloalkane, which was too long, causing the tail ends to entangle with each other, resulting in a decrease in hardness and adhesion. Although it had a certain hydrophobic effect, its lifespan was significantly reduced, and it could not achieve the target performance.

[0042] Combining Table 1-2 and Figure 1 It can be seen that the water-based fluorine-free anti-corrosion and anti-fouling superhydrophobic coating prepared by the present invention has excellent physical properties such as hydrophobicity, hardness, adhesion, salt spray resistance, and anti-diatom adhesion. Moreover, all the raw materials used are fluorine-free materials, which avoids the generation of harmful VOCs, making the superhydrophobic coating green and environmentally friendly.

[0043] In summary, the water-based, fluorine-free, anti-corrosion, and anti-fouling superhydrophobic coating of this invention possesses excellent anti-corrosion and anti-biofouling properties.

[0044] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A water-based, fluorine-free, superhydrophobic, anti-corrosion, and anti-fouling coating, comprising a primer and a topcoat, characterized in that, The primer is made from an epoxy acrylic resin suspension, and the topcoat is made from a superhydrophobic micro / nano ion-modified emulsion.

2. The water-based, fluorine-free, superhydrophobic, anti-corrosion, and anti-fouling coating according to claim 1, characterized in that, The epoxy acrylate resin suspension is obtained by dispersing epoxy acrylate resin in ethanol at a mass ratio of 1:2 and stirring at 200-300 rpm for 20-30 minutes.

3. The water-based, fluorine-free, superhydrophobic, anti-corrosion, and anti-fouling coating according to claim 2, characterized in that, The epoxy acrylate resin is one or more of Etercure 6301, DR-E351, EBECRYL® 600, EBECRYL® 605, CN104, CN111, EA-80, and EA-90.

4. The water-based, fluorine-free, superhydrophobic, anti-corrosion, and anti-fouling coating according to claim 1, characterized in that, The preparation of the superhydrophobic micro / nanoparticle modified emulsion includes the following steps: 1) Add fumed silica to an aqueous ethanol solution and disperse it into suspension A by ultrasonication; 2) Add citral silane coupling compound, TEOS, and ammonia to another aqueous ethanol solution and mix well to obtain solution B; 3) Mix suspension A and solution B evenly and stir at 60 °C for 24 h to induce silane hydrolysis and condensation to obtain the superhydrophobic micro / nano ion modified emulsion.

5. The water-based, fluorine-free, superhydrophobic, anti-corrosion, and anti-fouling coating according to claim 4, characterized in that, Based on a total mass percentage of 100%, the mass percentages of each raw material are as follows: 5-10% fumed silica, 5-10% TEOS, 10-20% citral silane coupling compound, 5-10% ammonia, and the remainder is an aqueous ethanol solution; the volume ratio of ethanol to water in the aqueous ethanol solution is 1:

2.

6. A water-based, fluorine-free, superhydrophobic, anti-corrosion, and anti-fouling coating according to claim 4 or 5, characterized in that, The general structural formula of the citral silane coupling compound is as follows: ， Wherein, R is a C8-C16 straight-chain alkane, and R' is a C2-C7 straight-chain alkane.

7. The water-based, fluorine-free, superhydrophobic, anti-corrosion, and anti-fouling coating according to claim 6, characterized in that, The synthesis of the citral silane conjugate includes the following steps: (1) Synthesis of product A Diethylenetriaminepropyltrimethoxysilane and citral were mixed in anhydrous ethanol and then refluxed under a nitrogen atmosphere for 16-24 hours. After standing and separating into layers, the lower liquid layer was taken out and dried to obtain product A. (2) Synthesis of couplings The obtained product A was dissolved in anhydrous ethanol, and a long-chain haloalkane RX was added. The mixture was reacted at 50-60°C for 24 hours. Then, a short-chain haloalkane R'X was added to the system, and the reaction was continued at 50-60°C for another 24 hours. Finally, n-hexane was added to the system to cause it to separate into layers. The lower layer solution was taken and dried to obtain the citral silane coupling compound.

8. The water-based, fluorine-free, superhydrophobic, anti-corrosion, and anti-fouling coating according to claim 7, characterized in that, The molar ratio of diethylenetriaminepropyltrimethoxysilane and citral used in step (1) is 1:1.1; The molar ratio of product A, potassium carbonate, long-chain haloalkane RX and short-chain haloalkane R'X used in step (2) is 1:2:1.5:1.5; wherein R is a straight-chain alkane of C8-C16, R' is a straight-chain alkane of C2-C7, and X is any one of Cl, Br and I.

9. A method for preparing a water-based, fluorine-free, superhydrophobic, anti-corrosion, and anti-fouling coating as described in claim 1, characterized in that, Includes the following steps: (1) After uniformly spraying the epoxy acrylic resin suspension, let it stand at room temperature for 30 minutes until the surface is dry to obtain the primer. (2) The superhydrophobic micro-nano ion modified emulsion is uniformly sprayed onto the primer, then irradiated with ultraviolet light of wavelength 365nm for 2-3 hours, and then left to stand at room temperature for 24 hours to obtain the topcoat, which is the coating.

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