Janus structured marine antifouling and anticorrosive polyurethane coating and method for preparing the same
The Janus structure marine antifouling and anticorrosion polyurethane coating utilizes the synergistic effect of imidazole groups, pyridine groups, quaternary ammonium salt groups, and sulfonic acid groups to solve the problem that traditional coatings cannot simultaneously achieve antifouling and anticorrosion in marine environments, thus achieving a multifunctional and long-lasting protective effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-04
- Publication Date
- 2026-07-07
AI Technical Summary
Traditional marine protective coatings struggle to achieve both antifouling and anti-corrosion functions simultaneously, lack durability, and are prone to failure in dynamic fluid environments, leading to high costs and increased environmental pollution risks.
A marine antifouling and anticorrosive polyurethane coating with a Janus structure was prepared by using zwitterionic functional monomers, pyridine functional monomers and organic bismuth catalysts to prepare a polyurethane coating with antibacterial, antifouling and anticorrosive functions. Imidazole groups, pyridine groups, quaternary ammonium salt groups and sulfonic acid groups were introduced into the coating to form a Janus structure, thereby achieving multifunctional integrated protection of the coating.
It achieves long-lasting and stable marine antifouling and anticorrosion performance. The coating has excellent mechanical properties, antibacterial properties and anticorrosion properties, and can provide multifunctional green protection in marine environments, and has self-healing ability.
Smart Images
Figure CN122344440A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of coating composition technology, specifically to a Janus-structured marine antifouling and anticorrosion polyurethane coating and its preparation method. Background Technology
[0002] In the marine environment, ships, offshore platforms, and underwater equipment are exposed to corrosive media rich in high salinity, high humidity, and microorganisms for extended periods, making them susceptible to both biofouling (such as shellfish and algae attachment) and electrochemical corrosion. Traditional marine protective coatings often employ a single-function design. Antifouling coatings typically rely on biocides (such as cuprous oxide) or hydrophobic / oleophobic materials to inhibit microbial attachment, while anticorrosion coatings slow down the corrosion process through metal corrosion inhibitors, sacrificial anodes, or physical barrier layers. However, existing technologies have significant limitations. Antifouling and anticorrosion functions are difficult to achieve synergistically, and single-function coatings lack durability in complex marine environments, requiring frequent maintenance, leading to increased costs and environmental pollution risks. Furthermore, traditional coatings are prone to failure due to mechanical wear or biological erosion in dynamic fluid environments, making it difficult to meet the requirements for long-term protection.
[0003] In recent years, Janus structure materials have become a research hotspot due to their unique bifacial heterogeneous properties. This structure achieves differences in chemical properties (such as hydrophilicity and hydrophobicity, surface energy), physical properties (such as conductivity and elastic modulus), or functional responses (such as self-cleaning and antibacterial properties) on both sides of the material through interface control technology, providing a new approach for multifunctional integrated protection. However, the application of existing Janus structure polyurethane coatings in the field of marine protection still needs to be developed. Summary of the Invention
[0004] To address the aforementioned technical problems, this invention provides a method for preparing a Janus-structured marine antifouling and anticorrosion polyurethane coating, comprising the following steps: Step 1: 4-Hydroxyethylimidazolium reacts with 2-chloroethanol to give a 1,4-bis(2-hydroxyethyl)imidazolium intermediate; the 1,4-bis(2-hydroxyethyl)imidazolium intermediate reacts with 1,3-propanesulfonic acid lactone to give a zwitterionic functional monomer. Step 2: Using functional diols, diisocyanates, organic bismuth catalysts, zwitterionic functional monomers, and pyridine functional monomers as raw materials, react to obtain functional polyurethane slurry; Step 3: Apply the functional polyurethane slurry to the surface of the metal substrate, cure it, and immerse it in artificial simulated seawater to obtain a marine antifouling and anticorrosion polyurethane coating with a Janus structure.
[0005] Preferably, in step one, the zwitterionic functional monomer comprises a compound with the structural formula (Ⅰ):
[0006] Equation (Ⅰ).
[0007] Preferably, in step one, the method for preparing the zwitterionic functional monomer is as follows: Under nitrogen protection, 4-hydroxyethyl imidazole, potassium carbonate, and ethanol were mixed and stirred. 2-chloroethanol was added, and the mixture was heated to 70-90℃ and refluxed with stirring for 10-12 h. After the reaction was completed, the product was purified to obtain 1,4-bis(2-hydroxyethyl)imidazolium intermediate. The mass ratio of 4-hydroxyethyl imidazole, potassium carbonate, ethanol, and 2-chloroethanol was (0.9-1.1):(2.26-2.51):(20-50):(0.73-0.88). The 1,4-bis(2-hydroxyethyl)imidazolium intermediate was mixed with acetonitrile and stirred. 1,3-propanesulfonic acid lactone was added, and the mixture was heated to 70-80℃ under nitrogen protection and stirred for 16-20 h. The product was purified to obtain a zwitterionic functional monomer. The mass ratio of the 1,4-bis(2-hydroxyethyl)imidazolium intermediate, acetonitrile, and 1,3-propanesulfonic acid lactone was (0.9-1.1):(20-30):(0.73-0.80).
[0008] Preferably, in step two, the content of each component in the functional polyurethane slurry, by weight, is as follows: 100 parts of functional diol; 26.4-41.2 parts of diisocyanate; 8.3-9.7 parts of pyridine functional monomer; 6.0-7.1 parts of zwitterionic functional monomers; 0.05-0.1 parts of organic bismuth catalyst.
[0009] Preferably, in step two, the functional diol includes at least one of polycaprolactone diol, polydimethylsiloxane diol, polytetrahydrofuran diol, and polypropylene glycol; and the diisocyanate includes at least one of hexamethylene diisocyanate, isoflurone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and diphenylmethane diisocyanate.
[0010] Preferably, in step two, the number-average molecular weight of the functional diol is 1000-4000 g / mol.
[0011] Preferably, in step two, the organic bismuth catalyst includes the Vantrus Coscat 8330R organic bismuth catalyst.
[0012] Preferably, in step two, the preparation method of the functional polyurethane slurry is as follows: The functional diol, diisocyanate and organic bismuth catalyst are mixed, stirred at 90-95℃ and reacted for 5-6 hours to obtain polyurethane prepolymer; The polyurethane prepolymer was cooled to 70-80℃, and zwitterionic functional monomers were added. The chain extension reaction was carried out for 3-4 hours to obtain modified polyurethane slurry. Pyridine functional monomers are added to the modified polyurethane slurry and reacted at 70-80℃ for 3-4 hours to obtain the functional polyurethane slurry.
[0013] Preferably, in step two, the pyridine functional monomer includes any one of 2,6-pyridinedicarboxylic acid, 2,6-pyridinedicarboxamide, and 2,6-pyridinedicarboxylic acid hydrazide.
[0014] Preferably, the method for preparing the 2,6-pyridinedicarboxylic acid hydrazide is as follows: 2,6-pyridinedicarboxylic acid, sulfoxide, and N,N-dimethylformamide were mixed and refluxed at 80-100℃ for 4-8 hours to purify the product, yielding 2,6-pyridinedicarboxylic acid chloride; wherein the molar ratio of 2,6-pyridinedicarboxylic acid, sulfoxide, and N,N-dimethylformamide was (0.9-1.1):(5-10):(0.2-0.3). 2,6-pyridinedicarboxylic acid chloride, hydrazine hydrate, and ethanol were mixed and refluxed at 80-90℃ for 8-12 h to purify the product and obtain 2,6-pyridinedicarboxylic acid hydrazine; wherein the molar ratio of 2,6-pyridinedicarboxylic acid chloride to hydrazine hydrate was (0.9-1.1):(4-6).
[0015] Preferably, in step three, the thickness of the marine antifouling and anticorrosion polyurethane coating of the Janus structure is 0.05-0.2 mm.
[0016] Preferably, in step three, the curing conditions are: temperature of 60-100℃ and time of 24-48h.
[0017] Preferably, in step three, the soaking conditions are: temperature of 25-40℃ and time of 5-7 days.
[0018] Preferably, in step three, the metal substrate includes any one of tinplate, stainless steel, and aluminum.
[0019] A method for preparing a marine antifouling and anticorrosion polyurethane coating with the Janus structure described above.
[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The Janus-structured marine antifouling and anticorrosion polyurethane coating of the present invention introduces imidazole groups, pyridine groups, quaternary ammonium salt groups, and sulfonic acid groups through zwitterionic functional monomers and pyridine functional monomers, giving the coating a Janus structure design and achieving a synergistic effect of antibacterial, antifouling, and anticorrosion functions, as specifically manifested as follows: (1) Imidazole and pyridine groups are both rigid nitrogen-containing heterocycles, which can enhance the rigidity of polyurethane molecular chains and promote the separation of soft and hard microphases. At the same time, the carboxyl, amide, and hydrazide groups in the pyridine functional monomer can increase the density of hydrogen bonds in the coating system. In addition, the metal ions present in the system can coordinate with imidazole N and pyridine N to form a metal coordination physical crosslinking network. Therefore, the coating of the present invention has excellent mechanical properties. (2) Quaternary ammonium salts are positively charged and actively inhibit bacteria by electrostatic adsorption and destruction of bacterial cell membranes; sulfonic acid groups participate in the formation of zwitterions and form a hydration film on the surface, which inhibits the initial adhesion of bacteria; pyridine N can form a stable coordination with the metal ions in the system, and the metal ions are slowly released, which produces a synergistic effect of metal ion antibacterial and pyridine coordination antibacterial by destroying bacterial enzyme activity and interfering with microbial metabolism; therefore, the coating is endowed with excellent antibacterial properties under the combined action of pyridine groups, quaternary ammonium salt groups and sulfonic acid groups. (3) Under water-induced conditions, the zwitterionic functional monomer structure migrates to the aqueous phase, and the pyridine group migrates to the substrate surface. The quaternary ammonium-sulfonic acid zwitterionic ions in the zwitterionic functional monomer structure readily adsorb water molecules to form a dense hydration layer, exhibiting excellent hydrophilicity. On the hydrophobic side of the pyridine polar group, non-polar polyurethane segments are enriched, and almost no polar groups are enriched, maintaining low surface energy hydrophobic properties. The difference in hydrophilicity on both sides of the coating gives the coating a Janus structure. (4) The sulfonic acid-quaternary ammonium structure in the zwitterionic functional monomer forms a highly hydrophilic and low surface energy hydration barrier, which effectively blocks the adhesion of marine proteins, algae and microorganisms; at the same time, the slow release of coordinated metal ions can inhibit the germination of marine microbial spores and the growth of biofilm, thus achieving long-term marine antifouling from the aspects of anti-adhesion and biocolonization. (5) The N-containing heterocycles of imidazole and pyridine groups can chelate and coordinate with metal ions on the surface of the metal substrate and in the system, forming a dense corrosion-inhibiting adsorption film at the metal interface, which inhibits anodic dissolution and cathodic oxygen absorption corrosion; while the sulfonic acid group can capture metal ions in seawater, providing channels for metal ions in seawater. Metal ions can participate in interface passivation, fill micro-defects in the coating, and inhibit the diffusion path of corrosive media; therefore, under the combined action of pyridine, imidazole and sulfonic acid groups, the coating is endowed with excellent anti-corrosion performance.
[0021] 2. The Janus structure marine antifouling and anticorrosion polyurethane coating of the present invention uses functional diols (such as polycaprolactone diol and polydimethylsiloxane diol) as the base chain segment, which endows the coating with excellent hydrolysis resistance and long-term mechanical stability.
[0022] 3. The imidazole, sulfonic acid, pyridine and other active groups in the Janus structure marine antifouling and anticorrosion polyurethane coating prepared by this invention can synergistically capture free metal ions in seawater and construct a dynamic cross-linked network in situ, which further enhances the mechanical properties and anticorrosion properties of the coating. It effectively solves the defects of traditional polyurethane coatings, such as difficulty in achieving both antifouling and anticorrosion performance, poor mechanical properties and short service life, and achieves long-lasting, stable and multifunctional green protection effect under marine working conditions.
[0023] 4. Once the Janus-structured marine antifouling and anticorrosive polyurethane coating prepared by this invention is damaged, it can deliver metal ions into the coating through hydrophilic groups, realize the exchange of coordination bonds at the interface, and achieve the effect of self-healing.
[0024] 5. This invention regulates reaction activity through an organic bismuth catalyst, avoiding the toxicity problem of traditional tin catalysts, while ensuring high efficiency in prepolymer synthesis and uniformity of product structure.
[0025] 6. The Janus-structured marine antifouling and anticorrosive polyurethane coating prepared by this invention can be adapted to a variety of metal substrates (such as tinplate, stainless steel, and aluminum). By adjusting the coordination ability of pyridine monomers with metal ions, it can be adapted to different corrosive environments (such as seawater containing chloride ions and acidic industrial media). Attached Figure Description
[0026] Figure 1 This is a flowchart illustrating the preparation process of the Janus structure marine antifouling and anticorrosion polyurethane coating of the present invention. Figure 2 This is the infrared spectrum of 2,6-pyridinedicarboxylic acid chloride prepared in Example 3 of this invention; Figure 3 This is the 1H NMR spectrum of 2,6-pyridinedicarboxylic acid chloride prepared in Example 3 of this invention; Figure 4 This is the infrared spectrum of 2,6-pyridinedicarboxylic acid hydrazide prepared in Example 3 of this invention; Figure 5 This is the 1H NMR spectrum of 2,6-pyridinedicarboxylic acid hydrazide prepared in Example 3 of this invention; Figure 6 These are comparative graphs showing the fracture strength tests of the Janus-structured marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4 of this invention. Figure 7This is a comparison chart of the hydrophobic and hydrophilic water contact angles of the Janus structure marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4 of the present invention. Figure 8 This is a comparison chart of the antibacterial rate test results of the Janus structure marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4 of this invention. Figure 9 This is a comparison chart of corrosion rate tests for the Janus-structured marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4 of this invention. Detailed Implementation
[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0028] Example 1 This embodiment discloses a method for preparing a Janus-structured marine antifouling and anticorrosion polyurethane coating, comprising the following steps: Step 1: Under nitrogen protection, add 0.9 g of 4-hydroxyethyl imidazole and 2.26 g of anhydrous potassium carbonate to a dry reaction flask, then add 20 g of ethanol as a solvent and stir until the system is homogeneous. Then, add 0.73 g of 2-chloroethanol dropwise at a rate of 2.0 mL / min. After the addition is complete, heat to 70 °C and reflux and stir for 10 h. After the reaction is complete, cool to room temperature, filter to remove inorganic salt precipitate, remove solvent from filtrate under reduced pressure, recrystallize crude product from ethanol / ethyl acetate, and dry under vacuum to obtain 1,4-bis(2-hydroxyethyl)imidazole intermediate. 0.9 g of the 1,4-bis(2-hydroxyethyl)imidazolium intermediate prepared above was added to a dry reactor, followed by 20 g of acetonitrile as a solvent. After stirring and dissolving, 0.73 g of 1,3-propanesulfonic acid lactone was added dropwise at a rate of 2.0 mL / min. The temperature was raised to 70 °C under nitrogen protection and the reaction was stirred for 16 h. During the reaction, a white solid gradually precipitated. After the reaction was completed, the mixture was cooled to room temperature, and the solid was collected by filtration. The filter cake was washed several times with ethyl acetate to remove residual raw materials and solvents. The mixture was then dried under vacuum to obtain the zwitterionic functional monomer. Step 2: Dry polydimethylsiloxane diol at 120°C and a vacuum of -0.1 MPa for 2 hours, then cool to room temperature to obtain a dehydrated functional diol. By weight, 100 parts of dehydrated polydimethylsiloxane diol were placed in a reactor, and 41.2 parts of dicyclohexylmethane-4,4'-diisocyanate and 0.1 parts of Coscat 8330R organic bismuth catalyst were added. The mixture was stirred at 90°C to make it homogeneous and reacted for 6 hours to obtain polyurethane prepolymer. The polyurethane prepolymer was cooled to 80°C, and 6.0 parts of zwitterionic functional monomer were added. The chain extension reaction was carried out for 3 hours to obtain the modified polyurethane slurry. 8.3 parts of 2,6-pyridinedicarboxylic acid were added to the modified polyurethane slurry, and the mixture was reacted at 70°C for 3 hours to obtain the functional polyurethane slurry. Step 3: Apply the functional polyurethane slurry evenly to the tinplate surface and cure it in an oven at 80℃ for 48 hours. Finally, immerse the tinplate coated with the functional polyurethane slurry in artificial simulated seawater at 25℃ for 7 days to obtain a Janus structure marine antifouling and anticorrosion polyurethane coating with a thickness of 0.1 mm.
[0029] Example 2 This embodiment discloses a method for preparing a Janus-structured marine antifouling and anticorrosion polyurethane coating, comprising the following steps: Step 1: Under nitrogen protection, add 1.0 g of 4-hydroxyethyl imidazole and 2.38 g of anhydrous potassium carbonate to a dry reaction flask, then add 35 g of ethanol as a solvent, and stir until the system is homogeneous. Then, add 0.81 g of 2-chloroethanol dropwise at a rate of 2.5 mL / min. After the addition is complete, raise the temperature to 80 °C, reflux and stir for 11 h. After the reaction is complete, cool to room temperature, filter to remove inorganic salt precipitate, remove solvent from filtrate under reduced pressure, recrystallize crude product from ethanol / ethyl acetate, and dry under vacuum to obtain 1,4-bis(2-hydroxyethyl)imidazole intermediate. 1.0 g of the 1,4-bis(2-hydroxyethyl)imidazolium intermediate prepared above was added to a dry reactor, followed by 25 g of acetonitrile as a solvent. After stirring and dissolving, 0.76 g of 1,3-propanesulfonic acid lactone was added dropwise at a rate of 2.5 mL / min. The temperature was raised to 75 °C under nitrogen protection and the reaction was stirred for 18 h. A white solid gradually precipitated during the reaction. After the reaction was completed, the mixture was cooled to room temperature, and the solid was collected by filtration. The filter cake was washed several times with ethyl acetate to remove residual raw materials and solvents. The mixture was then dried under vacuum to obtain the zwitterionic functional monomer. Step 2: Dry polydimethylsiloxane diol at 120°C and a vacuum of -0.1 MPa for 2 hours, then cool to room temperature to obtain a dehydrated functional diol. By weight, 100 parts of dehydrated polydimethylsiloxane diol were placed in a reactor, and 41.2 parts of dicyclohexylmethane-4,4'-diisocyanate and 0.1 parts of Coscat 8330R organic bismuth catalyst were added. The mixture was stirred at 90°C to make it homogeneous and reacted for 6 hours to obtain polyurethane prepolymer. The polyurethane prepolymer was cooled to 80°C, and 6.0 parts of zwitterionic functional monomer were added. The chain extension reaction was carried out for 3 hours to obtain the modified polyurethane slurry. 9.0 parts of 2,6-pyridinedicarboxamide were added to the modified polyurethane slurry, and the mixture was reacted at 70°C for 3 hours to obtain the functional polyurethane slurry. Step 3: Apply the functional polyurethane slurry evenly to the tinplate surface and cure it in an oven at 80℃ for 48 hours. Finally, immerse the tinplate coated with the functional polyurethane slurry in artificial simulated seawater at 30℃ for 7 days to obtain a Janus structure marine antifouling and anticorrosion polyurethane coating with a thickness of 0.1 mm.
[0030] Example 3 This embodiment discloses a method for preparing a Janus-structured marine antifouling and anticorrosion polyurethane coating, comprising the following steps: Step 1: Under nitrogen protection, add 1.1 g of 4-hydroxyethyl imidazole and 2.51 g of anhydrous potassium carbonate to a dry reaction flask, then add 50 g of ethanol as a solvent, and stir until the system is homogeneous. Then, add 0.88 g of 2-chloroethanol dropwise at a rate of 3.0 mL / min. After the addition is complete, heat to 90 °C and reflux and stir for 12 h. After the reaction is complete, cool to room temperature, filter to remove inorganic salt precipitate, remove solvent from filtrate under reduced pressure, recrystallize crude product from ethanol / ethyl acetate, and dry under vacuum to obtain 1,4-bis(2-hydroxyethyl)imidazole intermediate. 1.1 g of the 1,4-bis(2-hydroxyethyl)imidazolium intermediate prepared above was added to a dry reactor, followed by 30 g of acetonitrile as a solvent. After stirring and dissolving, 0.80 g of 1,3-propanesulfonic acid lactone was added dropwise at a rate of 3.0 mL / min. The temperature was raised to 80 °C under nitrogen protection and the reaction was stirred for 20 h. During the reaction, a white solid gradually precipitated. After the reaction was completed, the mixture was cooled to room temperature, and the solid was collected by filtration. The filter cake was washed several times with ethyl acetate to remove residual raw materials and solvents. The mixture was then dried under vacuum to obtain the zwitterionic functional monomer. 2,6-pyridinedicarboxylic acid and sulfoxide were used as reactants, and N,N-dimethylformamide was used as a catalyst. The mixture was refluxed at 90°C for 6 hours. After the reaction was completed, unreacted sulfoxide was removed by rotary evaporation, and the mixture was recrystallized at room temperature with petroleum ether to obtain 2,6-pyridinedicarboxylic acid chloride. The molar ratio of 2,6-pyridinedicarboxylic acid, sulfoxide, and N,N-dimethylformamide was 1:7.5:0.25. 2,6-pyridinedicarboxylic acid chloride and hydrazine hydrate were mixed and refluxed at 85°C for 10 h with ethanol as solvent. After the reaction was completed, ethyl acetate / n-hexane was added, and the mixture was recrystallized at 25°C. After filtration and drying, white crystalline 2,6-pyridinedicarboxylic acid hydrazine was obtained; wherein the molar ratio of 2,6-pyridinedicarboxylic acid chloride and hydrazine hydrate was 1:5. Step 2: Dry polydimethylsiloxane diol at 120°C and a vacuum of -0.1 MPa for 2 hours, then cool to room temperature to obtain a dehydrated functional diol. By weight, 100 parts of dehydrated polydimethylsiloxane diol were placed in a reactor, and 41.2 parts of dicyclohexylmethane-4,4'-diisocyanate and 0.1 parts of Coscat 8330R organic bismuth catalyst were added. The mixture was stirred at 90°C to make it homogeneous and reacted for 6 hours to obtain polyurethane prepolymer. The polyurethane prepolymer was cooled to 80°C, and 6.0 parts of zwitterionic functional monomer were added. The chain extension reaction was carried out for 3 hours to obtain the modified polyurethane slurry. 9.0 parts of 2,6-pyridinedicarboxylic acid hydrazide were added to the modified polyurethane slurry, and the mixture was reacted at 70°C for 3 hours to obtain the functional polyurethane slurry. Step 3: Apply the functional polyurethane slurry evenly to the tinplate surface and cure it in an oven at 80℃ for 48 hours. Finally, immerse the tinplate coated with the functional polyurethane slurry in artificial simulated seawater at 40℃ for 7 days to obtain a Janus structure marine antifouling and anticorrosion polyurethane coating with a thickness of 0.1 mm.
[0031] Example 4 Compared with Example 1, in Example 4, the amount of zwitterionic functional monomer added during the preparation of modified polyurethane slurry was 6.5 parts, while other conditions remained unchanged.
[0032] Example 5 Compared with Example 1, in Example 5, the amount of zwitterionic functional monomer added was 7.1 parts during the preparation of modified polyurethane slurry, while other conditions remained unchanged.
[0033] Comparative Example 1 Compared with Example 1, Comparative Example 1 used an equimolar amount of 2,6-pyridinedicarboxylic acid instead of 2,6-pyridinedicarboxylic acid in the preparation of the functional polyurethane slurry. Diaminopyridine, with all other conditions remaining unchanged.
[0034] Comparative Example 2 Compared with Example 1, Comparative Example 2 used an equimolar amount of 1,4-bis(2-hydroxyethyl)imidazolium intermediate to replace the zwitterionic functional monomer in the preparation of the functional polyurethane slurry, while keeping all other conditions unchanged.
[0035] Comparative Example 3 Compared with Example 1, Comparative Example 3 used equimolar amounts of 2,6-pyridinedicarboxylic acid to replace the zwitterionic functional monomer in the preparation of the modified polyurethane slurry, while keeping all other conditions unchanged.
[0036] Comparative Example 4 Compared with Example 1, Comparative Example 4 used an equimolar zwitterionic functional monomer to replace 2,6-pyridinedicarboxylic acid in the preparation of the functional polyurethane slurry, while keeping other conditions unchanged.
[0037] Experimental Example I. The structures of 2,6-pyridinedicarboxylic acid chloride and 2,6-pyridinedicarboxylic acid hydrazide prepared in Example 3 were characterized as follows: Figure 2-5 As shown: Figure 2 This is the infrared spectrum of 2,6-pyridinedicarboxylic acid chloride prepared in Example 3 of this invention; Figure 3 This is the 1H NMR spectrum of 2,6-pyridinedicarboxylic acid chloride prepared in Example 3 of this invention; Figure 4 This is the infrared spectrum of 2,6-pyridinedicarboxylic acid hydrazide prepared in Example 3 of this invention; Figure 5 This is the 1H NMR spectrum of 2,6-pyridinedicarboxylic acid hydrazide prepared in Example 3 of this invention; Figure 2 At 1748cm -1 The characteristic C=O peak at 1610 cm⁻¹ and the characteristic peak at 1610 cm⁻ -1 The appearance of the CN characteristic peak at the point confirms the synthesis of 2,6-pyridinedicarboxylic acid chloride. Figure 3 The 1H NMR (400 MHz, (CD3)2SO): δ = 8.37–8.23 (m, 3H, Ar-H) chemical shifts further confirm the correctness of its structure; Figure 4 At 3225cm -1 The -NH2 characteristic peak at 1689 cm⁻¹ and the characteristic peak at 1689 cm⁻ -1 The C=O value proves the synthesis of 2,6-pyridinedicarboxylic acid hydrazide. Figure 5 of 1 ¹H NMR (400 MHz, (CD₃)₂SO): δ = 10.66 (s, 2H, NH), 8.14 (s, 3H, Ar-H), 4.68 (s, 4H, NH₂). The chemical shifts further confirm the correctness of its structure.
[0038] II. Mechanical Property Testing Mechanical properties of the Janus-structured marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4 were tested. The tensile strength was tested according to relevant standards. The specific testing methods are as follows: A CMT4304 universal testing machine was used to test the mechanical properties of the samples. The tensile speed was 100 mm / min. Each polyurethane sample was tested three times in parallel at different locations, and the average value was taken. The test results are shown in Table 1 and... Figure 6 As shown; Table 1
[0039] Table 1 shows the fracture strength test results of the Janus structure marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4. Figure 6 These are comparative graphs showing the fracture strength tests of the Janus-structured marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4 of this invention. From Table 1 and Figure 6 The test results show that the polyurethane coatings prepared in Examples 1-5 have good mechanical properties. This is due to the introduction of zwitterionic functional monomers and pyridine functional monomers into the coatings of Examples 1-5. Imidazole and pyridine groups are rigid nitrogen-containing heterocycles, which can enhance the rigidity of the polyurethane molecular chain and promote the separation of soft and hard microphases. At the same time, the carboxyl, amide, and hydrazide groups in the pyridine functional monomers can increase the density of hydrogen bonds in the coating system. In addition, the metal ions present in the system can coordinate with imidazole N and pyridine N to form a metal coordination physical crosslinking network. Therefore, the coatings of Examples 1-5 have good mechanical properties. Among them, Example 3 has the highest strength compared with other examples. This is because 2,6-pyridinedicarboxylic acid hydrazide has hydrogen bond donors and acceptors compared with 2,6-pyridinedicarboxamide and 2,6-pyridinedicarboxylic acid, resulting in a higher hydrogen bond density. The mechanical properties of Examples 4-5 are slightly reduced because with the increase of zwitterionic functional monomer content, imidazole groups and pyridine groups compete for each other. Compared to Example 1, the coating preparation process of Comparative Example 1 used 2,6 Diaminopyridine, as a pyridine functional monomer, compared to 2,6-pyridinedicarboxylic acid, 2,6-pyridinedicarboxamide, and 2,6-pyridinedicarboxylic acid hydrazide in Examples 1-5, has a higher 2,6-pyridinedicarboxylic acid content. Diaminopyridine and Al³ + Fe³ + Cu 2+The coatings of Comparative Examples 2 and 3 have weak coordination with metal ions and cannot form stable complexes, resulting in poor performance. The coatings of Comparative Examples 2 and 3 cannot form a Janus structure with one side hydrophilic and the other side hydrophobic, and the microphase separation is suppressed, thus the mechanical properties decrease. The coating of Comparative Example 4 does not contain pyridine groups, so there is no coordination between pyridine groups and metal ions, and therefore its mechanical properties are the worst.
[0040] III. Water Contact Angle Test Water contact angle tests were conducted on the Janus-structured marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4. An OCA 20 water contact angle meter was used to measure the water contact angles on both sides of each polyurethane coating. The test medium was deionized water, and the volume of the medium dropped each time was set to 1.0 μL. The water contact angle of each sample was tested three times in parallel at different locations, and the average value was taken. All samples underwent water induction. The test results are shown in Table 2 and... Figure 7 As shown: Table 2
[0041] Table 2 shows the test results of the hydrophobic and hydrophilic water contact angles of the Janus-structured marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4. Figure 7 This is a comparison chart of the hydrophobic and hydrophilic water contact angles of the Janus structure marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4 of the present invention. From Table 2 and Figure 7 The test results show that the Janus structure marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 have the characteristics of being hydrophobic on one side and hydrophilic on the other. This is because, under water-induced conditions, zwitterions migrate to the aqueous phase and pyridine groups migrate to the substrate surface. The quaternary ammonium-sulfonic acid zwitterions in the zwitterionic functional monomer structure readily adsorb water molecules to form a dense hydration layer, exhibiting excellent hydrophilicity. On the hydrophobic side of the pyridine polar group, non-polar polyurethane segments are enriched, and almost no polar groups are enriched, maintaining low surface energy hydrophobic properties. As a result, the side of the coating that contacts the metal substrate is hydrophobic, while the side that contacts the seawater is hydrophilic. Compared with Example 1, the coating of Comparative Example 1 also contains pyridine groups and zwitterionic groups, exhibiting a Janus structure. The coatings of Comparative Examples 2-3 do not contain sulfonic acid hydrophilic groups, so they exhibit hydrophobic properties on both sides. Comparative Example 4 only contains strong hydrophilic sulfonic acid groups, so it exhibits hydrophilic properties on both sides.
[0042] IV. Antibacterial Performance Test The antibacterial properties of the Janus-structured marine antifouling and anticorrosive polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4 were tested. LB agar medium was prepared, then autoclaved, and Staphylococcus aureus was revived at a ratio of 1:1000. The medium was then placed on a shaker at 37°C and 120 rpm overnight. The bacteria were cultured, and the material and bacterial solution were mixed at a ratio of 1×10⁻⁶. 6 The bacterial culture was co-cultured at a concentration of [specific concentration not specified], placed on a shaker, and the conditions were set to 120 rpm and 37°C. For plating, the successfully cultured bacterial suspension was diluted 10,000 times and spread onto LB agar medium, with 5 μL taken from each colony. The culture was then placed in a 37°C incubator for 12 hours, and photographed and counted the colonies to calculate the antibacterial rate. The test results are shown in Table 3 and [other tables not specified]. Figure 8 As shown: Table 3
[0043] Table 3 shows the antibacterial rate test results of the Janus structure marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4. Figure 8 This is a comparison chart of the antibacterial rate test results of the Janus structure marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4 of this invention. From Table 3 and Figure 8 The test results show that the coatings in Examples 1-5 contain imidazole groups, pyridine groups, quaternary ammonium salt groups, and sulfonic acid groups. The quaternary ammonium salts are positively charged, electrostatically adsorbing and destroying bacterial cell membranes to achieve active antibacterial action. The sulfonic acid groups constitute zwitterions, forming a hydration film on the surface to inhibit initial bacterial adhesion. Pyridine N can form stable coordination with metal ions in the system, and the metal ions are slowly released, producing a synergistic effect of metal ion antibacterial action and pyridine coordination antibacterial action by destroying bacterial enzyme activity and interfering with microbial metabolism. Therefore, the coatings are endowed with excellent antibacterial properties under the combined action of imidazole groups, pyridine groups, quaternary ammonium salt groups, and sulfonic acid groups. Compared to Example 1, the coating preparation process of Comparative Example 1 used 2,6 Diaminopyridine, as a pyridine functional monomer, compared to 2,6-pyridinedicarboxylic acid, 2,6-pyridinedicarboxamide, and 2,6-pyridinedicarboxylic acid hydrazide in Examples 1-5, has a higher 2,6-pyridinedicarboxylic acid content. Diaminopyridine and Al³ + Fe³ + Cu 2+The coordination of metal ions is relatively weak, thus reducing the ability to capture metal ions that disrupt bacterial metabolic enzymes, resulting in a decrease in antibacterial rate. Since the coatings of Comparative Examples 2-3 only contain unquaternized tertiary amine groups or no tertiary amine groups, they exhibit weak antibacterial effects. The coating of Comparative Example 4 contains abundant quaternary ammonium salt groups but lacks the synergistic effect of pyridine groups, thus exhibiting slightly poorer antibacterial properties.
[0044] V. Corrosion Resistance Test Corrosion resistance tests were conducted on the Janus-structured marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4. To determine the corrosion rate, a rectangular tinplate sheet (2cm × 2cm) coated with the coatings from Examples 1-5 and Comparative Examples 1-4 was dried in air for 7 days, then immersed in a 3.5wt% NaCl aqueous solution (pH=8.6). Subsequently, the corrosion rate of the coated tinplate sheet was determined over 90 days using the potentiodynamic polarization method (Tafel curve). Measurements were performed at room temperature using an electrochemical workstation. The test results are shown in Table 4. Figure 9 As shown: Table 4
[0045] Table 4 shows the corrosion rate test results of the Janus structure marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4. Figure 9 This is a comparison chart of corrosion rate tests for the Janus-structured marine antifouling and anticorrosion polyurethane coatings prepared in Examples 1-5 and Comparative Examples 1-4 of this invention. From Table 3 and Figure 8 The test results show that the corrosion rate of Examples 1-5 was reduced by 2-3 orders of magnitude compared with that of Comparative Examples 1-4. This is because the coatings of Examples 1-5 contain pyridine groups, imidazole groups, and sulfonic acid groups. The nitrogen-containing heterocycles of the imidazole and pyridine groups can chelate and coordinate with the metal substrate surface and metal ions in the system, forming a dense corrosion-inhibiting adsorption film at the metal interface, which inhibits anodic dissolution and cathodic oxygen absorption corrosion. The sulfonic acid groups can capture metal ions in seawater, providing channels for metal ions in seawater. Metal ions can participate in interface passivation, fill microscopic defects in the coating, and inhibit the diffusion path of corrosive media. Compared to Example 1, the coating preparation process of Comparative Example 1 used 2,6 Diaminopyridine, as a pyridine functional monomer, compared to 2,6-pyridinedicarboxylic acid, 2,6-pyridinedicarboxamide, and 2,6-pyridinedicarboxylic acid hydrazide in Examples 1-5, has a higher 2,6-pyridinedicarboxylic acid content. Diaminopyridine and Al³ + Fe³ + Cu 2+The coatings in Comparative Example 2 have weak coordination with metal ions, resulting in reduced ability to capture metal ions and form a passivation layer, thus leading to poor corrosion resistance. Although the coating in Comparative Example 2 contains pyridine and imidazole groups, it lacks hydrophilic sulfonic acid groups to transport metal ions, affecting the metal coordination effect and causing a decrease in corrosion resistance. In the coatings of Comparative Example 3 and Comparative Example 4, on the one hand, they lack zwitterionic functional monomers containing imidazole groups and pyridine groups, respectively; on the other hand, the coatings of Comparative Example 3 and Comparative Example 4 cannot form a Janus structure and cannot achieve the synergistic effect of various groups, thus resulting in poor corrosion resistance.
[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for preparing a Janus-structured marine antifouling and anticorrosion polyurethane coating, characterized in that, Includes the following steps: Step 1: 4-Hydroxyethylimidazolium reacts with 2-chloroethanol to give a 1,4-bis(2-hydroxyethyl)imidazolium intermediate; the 1,4-bis(2-hydroxyethyl)imidazolium intermediate reacts with 1,3-propanesulfonic acid lactone to give a zwitterionic functional monomer. Step 2: Using functional diols, diisocyanates, organic bismuth catalysts, zwitterionic functional monomers, and pyridine functional monomers as raw materials, react to obtain functional polyurethane slurry; Step 3: Apply the functional polyurethane slurry to the surface of the metal substrate, cure it, and immerse it in artificial simulated seawater to obtain a Janus structure marine antifouling and anticorrosion polyurethane coating.
2. The method for preparing the Janus structure marine antifouling and anticorrosion polyurethane coating according to claim 1, characterized in that, In step one, the zwitterionic functional monomer includes a compound with the structural formula (Ⅰ): Equation (Ⅰ).
3. The method for preparing the Janus structure marine antifouling and anticorrosion polyurethane coating according to claim 1, characterized in that, In step one, the preparation method of the zwitterionic functional monomer is as follows: Under nitrogen protection, 4-hydroxyethyl imidazole, potassium carbonate, and ethanol were mixed and stirred. 2-chloroethanol was added, and the mixture was heated to 70-90℃ and refluxed with stirring for 10-12 h. After the reaction was completed, the product was purified to obtain 1,4-bis(2-hydroxyethyl)imidazolium intermediate. The mass ratio of 4-hydroxyethyl imidazole, potassium carbonate, ethanol, and 2-chloroethanol was (0.9-1.1):(2.26-2.51):(20-50):(0.73-0.88). The 1,4-bis(2-hydroxyethyl)imidazolium intermediate was mixed with acetonitrile and stirred. 1,3-propanesulfonic acid lactone was added, and the mixture was heated to 70-80℃ under nitrogen protection and stirred for 16-20 h. The product was purified to obtain a zwitterionic functional monomer. The mass ratio of the 1,4-bis(2-hydroxyethyl)imidazolium intermediate, acetonitrile, and 1,3-propanesulfonic acid lactone was (0.9-1.1):(20-30):(0.73-0.80).
4. The method for preparing the Janus structure marine antifouling and anticorrosion polyurethane coating according to claim 1, characterized in that, In step two, the content of each component in the functional polyurethane slurry, by weight, is as follows: 100 parts of functional diol; 26.4-41.2 parts of diisocyanate; 8.3-9.7 parts of pyridine functional monomer; 6.0-7.1 parts of zwitterionic functional monomers; 0.05-0.1 parts of organic bismuth catalyst.
5. The method for preparing the Janus structure marine antifouling and anticorrosion polyurethane coating according to claim 1, characterized in that, In step two, the functional diol includes at least one of polycaprolactone diol, polydimethylsiloxane diol, polytetrahydrofuran diol, and polypropylene glycol; the diisocyanate includes at least one of hexamethylene diisocyanate, isoflurone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and diphenylmethane diisocyanate.
6. The method for preparing the Janus structure marine antifouling and anticorrosion polyurethane coating according to claim 1, characterized in that, In step two, the preparation method of the functional polyurethane slurry is as follows: The functional diol, diisocyanate and organic bismuth catalyst are mixed, stirred at 90-95℃ and reacted for 5-6 hours to obtain polyurethane prepolymer; The polyurethane prepolymer was cooled to 70-80℃, and zwitterionic functional monomers were added. The chain extension reaction was carried out for 3-4 hours to obtain modified polyurethane slurry. Pyridine functional monomers are added to the modified polyurethane slurry and reacted at 70-80℃ for 3-4 hours to obtain the functional polyurethane slurry.
7. The method for preparing the Janus structure marine antifouling and anticorrosion polyurethane coating according to claim 1, characterized in that, In step two, the pyridine functional monomer includes any one of 2,6-pyridinedicarboxylic acid, 2,6-pyridinedicarboxamide, and 2,6-pyridinedicarboxylic acid hydrazide.
8. The method for preparing the Janus structure marine antifouling and anticorrosion polyurethane coating according to claim 7, characterized in that, The preparation method of the 2,6-pyridinedicarboxylic acid hydrazide: 2,6-pyridinedicarboxylic acid, sulfoxide, and N,N-dimethylformamide were mixed and refluxed at 80-100℃ for 4-8 hours to purify the product, yielding 2,6-pyridinedicarboxylic acid chloride; wherein the molar ratio of 2,6-pyridinedicarboxylic acid, sulfoxide, and N,N-dimethylformamide was (0.9-1.1):(5-10):(0.2-0.3). 2,6-pyridinedicarboxylic acid chloride, hydrazine hydrate, and ethanol were mixed and refluxed at 80-90℃ for 8-12 h to purify the product and obtain 2,6-pyridinedicarboxylic acid hydrazine; wherein the molar ratio of 2,6-pyridinedicarboxylic acid chloride to hydrazine hydrate was (0.9-1.1):(4-6).
9. The method for preparing the Janus structure marine antifouling and anticorrosion polyurethane coating according to claim 1, characterized in that, In step three, the thickness of the marine antifouling and anticorrosion polyurethane coating of the Janus structure is 0.05-0.2 mm.
10. A marine antifouling and anticorrosion polyurethane coating with a Janus structure prepared by the preparation method of the Janus structure as described in any one of claims 1-9.