A self-healing marine antifouling coating and its preparation method

Abstract

This invention relates to the field of polyurethane synthesis and processing technology, and discloses a self-healing marine antifouling coating and its preparation method. The coating achieves antifouling by utilizing the dynamic antifouling properties of organosilicon and the static antifouling properties of antifouling agents; and achieves self-healing by utilizing hydrogen bond acceptor carbonyl groups to form alternating strong and weak bond structures within the polyurethane. This method is based on a bulk approach, uses few volatile solvents, and has industrialization potential and environmental friendliness. The prepared coating exhibits excellent self-healing properties, achieving a self-healing efficiency of up to 85% at room temperature for 48 hours. Simultaneously, the antifouling treatment has a good inhibitory effect on bacteria and algae.

Description

Technical Field

[0001] This invention relates to the field of polyurethane synthesis and processing technology, specifically to a self-healing marine antifouling coating and its preparation method. Background Technology

[0002] With the development of the ocean, marine biofouling has become a key issue restricting the development of the marine industry. The deposition and accumulation of marine organisms on the surface of marine equipment forms marine fouling, which accelerates biofouling, increases ship drag, and causes biological invasion. The simplest and most direct way to solve biofouling is to use antifouling coatings (AF). Among them, tributyltin (TBT) has been widely used for many years due to its excellent inhibition of marine organisms. However, this type of antifouling agent has a bioaccumulation effect, causing great damage to the marine environment and organisms. Ultimately, in 2008, this coating was banned by the International Maritime Organization (IMO). Today, the task of developing bio-friendly and highly efficient organic coatings is important and necessary.

[0003] Polydimethylsiloxane (PDMS) elastomers possess low surface energy and low modulus, making it difficult for marine organisms to adhere to their surfaces. Furthermore, their high surface lubricity reduces drag and saves fuel. However, they are only effective in dynamic environments (speeds > 15 knots), exhibiting poor antifouling performance in static waters. In addition, PDMS-based polymers not only have poor mechanical properties but also low adhesion to the substrate. Reinforcement modifications often compromise their original low surface energy, resulting in a loss of antifouling properties. Inspired by the pitcher plant's use of lubricating fluid locked within porous microstructures to capture prey, a porous surface, SLIPS, was created by injecting perfluorinated lubricant into porous PTFE membranes. SLIPS exhibits excellent resistance to various common bacteria due to its low surface energy, self-healing properties, high-pressure stability, and liquid repellency. However, this surface loses its effectiveness after significant mechanical damage. During ship navigation, the surface is subjected to seabed gravel and water currents, creating microcracks. Under the impact of water currents, these cracks rapidly expand, leading to coating failure. Therefore, introducing dynamic bonds into the coating to achieve repeated self-healing is crucial. According to other studies, common dynamic bonds include hydrogen bonds, disulfide bonds, Diels-Alder bonds, and imine bonds. Hydrogen bonds are the most prevalent in polymers.

[0004] Polyurethane (PU) is a class of polymers containing repeating urethane (-NHCOO-) bonds. Due to its internal thermodynamic incompatibility and hydrogen bonding, microphase separation occurs: hard segment domains (HD) formed by the aggregation of hard segments (HS), soft segment domains (SS) formed by the aggregation of isocyanates and chain extenders, and soft segment domains (SD) formed by the aggregation of low molecular weight diols. Based on its high designability and high hydrogen content, it is widely used as a matrix for self-healing materials. Supramolecular polymer films constructed by designing a mixture of strongly and weakly crosslinked hydrogen bonds within PU possess various properties required for electronic skin, even exhibiting underwater self-healing capabilities.

[0005] It is feasible to develop coatings that combine self-healing and antifouling properties based on the antifouling characteristics of silicone and the designable hydrogen bonding structure within PU. Furthermore, to compensate for the shortcomings of silicone in static antifouling, metoprimidine (MM) and its analogues, a third-generation organic antifouling agent, are selected as the modifier. MM is a relatively stable antifouling agent, proven to be rapidly degraded in marine environments with a half-life of <1.5 days in natural waters. This invention provides a self-healing marine antifouling coating and its preparation method. Summary of the Invention

[0006] The purpose of this invention is to prepare an antifouling coating with self-healing capabilities, utilizing the characteristics of organosilicon in dynamic antifouling and the role of antifouling agents in static antifouling. Simultaneously, to protect the environment and extend the coating's lifespan, an alternating strong and weak bond structure is constructed in the polyurethane (PU) to achieve self-healing properties.

[0007] To achieve the above objectives, the technical solution of the present invention is: a self-healing marine antifouling coating, characterized in that the coating is synthesized by a prepolymer method, using hydroxyl-terminated polydimethylsiloxane and polycaprolactone diol as mixed soft segments, respectively providing low surface energy and carbonyl groups as hydrogen bond acceptors; using 4,4'-methylene diphenyl diisocyanate and isophorone diisocyanate as mixed hard segments, respectively forming strong crosslinking points and weak hydrogen bonds; fixing the chain extension coefficient f to 1; using diol as a chain extender to maintain a linear structure; using a silicone lubricant to increase the dynamic antifouling capability of the silicone-based antifouling coating; and using a slow-release antifouling agent to enhance the static antifouling performance of the coating, ultimately forming the coating.

[0008] A method for preparing a self-healing marine antifouling coating, characterized by comprising the following steps:

[0009] (1) Preparation of prepolymer: Hydroxyl-terminated polydimethylsiloxane (PDMS-OH) and polycaprolactone diol (PCL) were used as mixed soft segments. 4,4'-methylene diphenyl diisocyanate (MDI) and isophorone diisocyanate (IPDI) were added at 60°C and stirred until homogeneous. The prepolymer was prepared by reacting at 80°C under a N2 atmosphere for 2 h. The mass fraction of NCO (NCO%) was determined by di-n-butylamine titration. If the error between the actual and theoretical values ​​was within 0.5%, the reaction was considered to have proceeded according to the design.

[0010] (2) Preparation of self-healing marine antifouling coating: The amount of 1,4-butanediol (BDO) was calculated based on the chain extension coefficient f=1. Simultaneously, silicone lubricant and slow-release antifouling agent were mixed. An appropriate amount of dichloromethane was added to ensure the mixture was homogeneous. PUP was mixed with the coating and stirred at room temperature for 5 min. The mixture was then poured into a polytetrafluoroethylene mold and vacuum-dried under negative pressure to remove air bubbles. Finally, it was cured in a constant-temperature forced-air drying oven for 24 h to obtain a sample for testing.

[0011] Further; the prepolymer method described in step (1) is as follows: First, PDMS-OH and PCL are mixed in a ratio of 1:1 and stirred evenly at 60°C. After adding MDI and IPDI, they are stirred evenly after melting. The mixture is heated to 80°C and reacted under N2 for 2 hours to prepare the prepolymer.

[0012] Furthermore, the ratio of PDMS-OH and PCL in step (1) should be greater than or equal to 1.

[0013] Furthermore, the ratio between IPDI and MDI in step (1) should be between 1 / 4 and 1 / 2.

[0014] Furthermore, the molecular weight of the hydroxyl-terminated polydimethylsiloxane described in step (1) is between 1000 and 2000 g / mol.

[0015] Furthermore, the molecular weight of the polycaprolactone diol mentioned in step (1) is between 1000 and 2000 g / mol.

[0016] Further, the chain extender mentioned in step (1) is selected from one or more of 1,4-butanediol, ethylene glycol, 1,2-propanediol, diethylene glycol, and 1,6-hexanediol.

[0017] Furthermore, the silicone lubricant is methyl silicone oil PDMS, the viscosity of which is 200-500 cst and the amount is 5-20%, and the slow-release antifouling agent is metoprimidine (MM) or similar compounds and the amount is 1-5%.

[0018] The beneficial effects of this invention are:

[0019] 1) The self-healing marine antifouling coating prepared by this invention is based on a bulk reaction, which is a mild process using only a small amount of solvent. It has low volatile components, making the preparation process environmentally friendly. The preparation process is simple and has the potential for industrial production.

[0020] 2) In this system, hydrogen bond acceptors are innovatively used to achieve self-healing properties. By utilizing the different hydrogen bond forms of the two isocyanates within the polyurethane, an alternating weak hydrogen bond structure is constructed. This structure not only achieves self-healing properties but also enhances mechanical properties through strong "crosslinking points." This method avoids the significant reduction in mechanical properties that can occur when simply improving self-healing efficiency. Furthermore, using carbonyl groups as hydrogen bond acceptors in the preparation of the self-healing coating greatly avoids the complex operations involved in preparing hydrogen bond donors (polyurea).

[0021] 3) The antifouling treatment and self-healing matrix complement each other. The lubricant PDMS has similar compatibility with the soft segment phase PDMS-OH of the matrix, enabling slow release and enhancing the dynamic antifouling performance of the silicone. Simultaneously, it also improves self-healing efficiency; PDMS can break down the microphase structure, which is more conducive to the formation of hydrogen bonds between phases. The selected antifouling agent, metoprimidine, has a secondary amine structure, which can form hydrogen bonds with the internal hydrogen bond acceptor carbonyl group. This controls its slow release, achieving long-term action. Attached Figure Description

[0022] Figure 1 The adhesion level of the sample is determined by the cross-cut adhesion test.

[0023] Figure 2 The self-healing efficiency of Example 1 and the comparative example was tested at 80°C for 2 hours.

[0024] Figure 3 The stress-strain curves of Example 1 at different times are shown.

[0025] Figure 4 The process of repairing scratches at room temperature;

[0026] Figure 5 The images show the antibacterial test results of Example 1 and the comparative example against Staphylococcus aureus.

[0027] Figure 6 The images show test results for resistance to Chlorella in Example 1 and the comparative example.

[0028] Figure 7 This is a diagram illustrating the antifouling mechanism of an embodiment. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings:

[0030] As shown in the accompanying drawings, the present invention will be described in detail below with reference to specific embodiments, but the scope of protection is not limited thereto.

[0031] Example 1:

[0032] A self-healing marine antifouling coating: Before use, hydroxybutylated polydimethylsiloxane (PDMS-OH) and polycaprolactone diol (PCL) are vacuum dehydrated at 120°C for 2 hours and then cooled to room temperature. In a three-necked flask equipped with a stirrer, N2 device, and thermometer, 10.00 g of PDMS-OH and 10.00 g of PCL are added and stirred at 60°C until homogeneous. 5.72 g of isophorone diisocyanate (IPDI) and 1.43 g of 4,4'-methylene diphenyl diisocyanate (MDI) are added and stirred until melted. After complete homogenization, one drop of dibutyltin dilaurate (DBTDL) is added as a catalyst, and the temperature is raised to 80°C. After reacting for 2 hours, the mass fraction of NCO (NCO%) is determined using the di-n-butylamine titration method. If the error between the actual and theoretical values ​​is within 0.5%, the reaction is considered to have proceeded as designed. Then, a chain extension reaction is carried out. 1.42 g of 1,4-butanediol (BDO), 1.43 g of methyl silicone oil (PDMS), and 0.29 g of metopridine (MM) were dissolved and mixed evenly using 2 mL of dichloromethane (DCM). The polyurethane prepolymer (PUP) was then mixed with the mixture and stirred at room temperature for 5 min. The mixture was then poured into a polytetrafluoroethylene mold and vacuum-dried under negative pressure to remove air bubbles. The resulting sample was then cured in a constant-temperature forced-air drying oven for 24 h for testing. The synthesis process of the self-healing marine antifouling coating is shown in Formula I (where x, y, and z are the degrees of polymerization).

[0033]

[0034] Formula I.

[0035] Comparative Example 1:

[0036] A method for preparing a self-healing marine antifouling coating includes the following steps:

[0037] 10.00 g of PDMS-OH and 3.42 g of IPDI were added to a three-necked flask equipped with a stirrer, N2 device, and thermometer and stirred until melted. After complete homogenization, one drop of DBTDL catalyst was added, and the temperature was raised to 80°C. After reacting for 2 h, the NCO% was titrated using the di-n-butylamine titration method. A reaction was considered to have proceeded according to design if the error between the actual and theoretical values ​​was within 0.5%. Then, a chain extension reaction was carried out. 0.87 g of BDO was added to the PUP (polytetrafluoroethylene) mixture, and after mixing and stirring at room temperature for 5 min, the mixture was poured into a polytetrafluoroethylene mold and vacuum-dried under negative pressure to remove air bubbles. The mixture was then cured in a constant-temperature forced-air drying oven for 24 h to obtain the sample for testing.

[0038] Comparative Example 2:

[0039] A method for preparing a self-healing marine antifouling coating includes the following steps:

[0040] First, PUP was synthesized. In a three-necked flask equipped with a stirrer, N2 device, and thermometer, 10.00 g of PDMS-OH, 2.75 g of IPDI, and 0.69 g of MDI were added and stirred until completely homogeneous. Then, one drop of DBTDL catalyst was added, and the temperature was raised to 80°C. After reacting for 2 hours, the NCO% was titrated using the di-n-butylamine titration method. A reaction within 0.5% of the theoretical value was considered to have proceeded according to the design. Next, a chain extension reaction was carried out. 0.85 g of BDO was added to the PUP, and after mixing and stirring at room temperature for 5 minutes, the mixture was poured into a polytetrafluoroethylene mold and vacuum-dried under negative pressure to remove air bubbles. Finally, the mixture was aged in a constant-temperature forced-air drying oven for 24 hours to obtain the sample for testing.

[0041] Comparative Example 3:

[0042] A method for preparing a self-healing marine antifouling coating includes the following steps:

[0043] In a three-necked flask equipped with a stirrer, N2 device, and thermometer, 10.00 g of PDMS-OH and 10.00 g of PCL were added and stirred at 60 °C until homogeneous. Then, 5.72 g of IPDI and 1.43 g of MDI were added and stirred until melted. After complete homogenization, one drop of DBTDL catalyst was added, and the temperature was raised to 80 °C. After reacting for 2 h, the NCO% was titrated using the di-n-butylamine titration method. A reaction was considered to have proceeded according to design if the error between the actual and theoretical values ​​was within 0.5%. Next, a chain extension reaction was carried out. 1.42 g of BDO was added to the PUP and mixed. After stirring at room temperature for 5 min, the mixture was poured into a polytetrafluoroethylene mold and vacuum-dried under negative pressure to remove air bubbles. Finally, the mixture was cured in a constant-temperature forced-air drying oven for 24 h to obtain the sample for testing.

[0044] Comparative Example 4:

[0045] A method for preparing a self-healing marine antifouling coating includes the following steps:

[0046] In a three-necked flask equipped with a stirrer, N2 device, and thermometer, 10.00 g of PDMS-OH and 10.00 g of PCL were added and stirred at 60 °C until homogeneous. Then, 5.72 g of IPDI and 1.43 g of MDI were added and stirred until melted. After complete homogenization, one drop of DBTDL catalyst was added, and the temperature was raised to 80 °C. After reacting for 2 h, the NCO% was titrated using the di-n-butylamine titration method. A reaction was considered to have proceeded according to design if the error between the actual and theoretical values ​​was within 0.5%. Next, a chain extension reaction was carried out. 1.42 g of BDO and 1.43 g of PDMS were mixed thoroughly. PUP was mixed with the PDMS and stirred at room temperature for 5 min. The mixture was then poured into a polytetrafluoroethylene mold and vacuum-dried under negative pressure to remove air bubbles. Finally, the mixture was cured in a constant-temperature forced-air drying oven for 24 h to obtain the sample for testing.

[0047] Test experiment:

[0048] The specific compositions of the examples and comparative examples are shown in Table 1. The tensile properties of the test samples prepared in the examples and comparative examples were tested according to the test standard GB / T 528-2009, and the test results are shown in Table 2. The adhesion properties between the coating and the substrate were tested according to the test standard ASTM D3359, and the test results are shown in Table 2. Figure 1 First, the self-healing efficiency of the examples and comparative examples was tested at 80°C for 2 hours, and the results are shown in [the table below]. Figure 2 The self-healing efficiency of Example 1 was tested at different times. The test results are shown below. Figure 3 Scratches were created on the examples and comparative examples, and the self-healing process was observed at room temperature. The test results are shown in [Figure number missing]. Figure 4 Antibacterial and antialgae experiments were conducted on the examples and comparative examples, and the test results are shown in [the table below]. Figure 5 and Figure 6 .

[0049] Based on the components in Table 1, Example 1 underwent different modifications compared to the comparative example and achieved optimal overall performance. Within Example 1, we aimed to construct an alternating strong and weak structure based on hydrogen bond acceptors. Previous studies have focused on obtaining more hydrogen bond donors, i.e., more NH4+. Therefore, researchers have synthesized more polyurea structures. However, this synthesis process generates significant heat, requires solvents, and is complex. We propose increasing hydrogen bond acceptors as a method to improve self-repair efficiency. Because the reaction is mild, it can be synthesized using a bulk method, making it environmentally friendly.

[0050] Table 1

[0051]

[0052] according to Figure 1It can be seen that Example 1 and Comparative Examples 3 and 4 all met the most basic requirements for substrate adhesion. (Referring to Table 2 and...) Figure 2 As can be seen, compared to the comparative example, Example 1 maintains a high self-healing efficiency. Simultaneously, its overall mechanical properties are also maintained at a certain level. This is because Comparative Example 1 lacks cross-linking sites formed by MDI, resulting in high repair efficiency but extremely low mechanical properties. Comparative Example 2 adds cross-linking sites of MDI but lacks hydrogen bond structures. This results in high mechanical properties but virtually no self-healing ability. In Comparative Example 3, we added PCL, which provides hydrogen bond acceptors. Its molecular chain contains a large number of carbonyl groups, which can act as hydrogen bond acceptors. At this time, its self-healing performance is significantly improved, and its mechanical properties are superior. Based on Comparative Example 3, we performed antifouling treatment while simultaneously improving self-healing properties. In Comparative Example 4, we added methyl silicone oil, which is compatible with the soft segment phase of the internal PDMS-OH, improving self-healing performance. In Example 1, we added the antifouling agent MM. MM has a significant reducing effect on mechanical properties, but greatly improves self-healing properties.

[0053] according to Figure 3 As shown, the self-healing efficiency of Example 1 increases continuously with time at room temperature. After 48 hours, the tensile strength self-healing efficiency reaches 85%, the elongation at break self-healing efficiency is 82%, and the toughness self-healing efficiency is 77%. However, the room temperature repair effect after 48 hours is weaker than that after 2 hours at 80°C. This indicates that the self-healing structure based on multi-carbonyl groups is temperature-dependent.

[0054] Table 2

[0055]

[0056] The damage to antifouling coatings is mostly due to scratches caused by seabed gravel. In these cases, the fracture surfaces are not close together, and the ability to spontaneously recover is a major criterion for self-healing antifouling coatings. Examples 1 and Comparative Examples 3 and 4 all exhibit good self-healing properties. Figure 4 The self-healing properties at room temperature were observed after cross-shaped scratches were created. Over time, the cracks in the coating continuously self-healed. After 48 hours at room temperature, the cracks were essentially completely repaired. Comparative Example 4, with injected lubricant PDMS, and Example 1, with added antifouling agent MM, still exhibited self-healing capabilities. Furthermore, Example 1 showed a faster repair speed, indicating that the addition of antifouling agent MM promotes the self-healing of the composite system.

[0057] We conducted experiments on the antifouling properties of the coating, testing its antibacterial and antialgae properties separately. The test results are as follows: Figure 5 and Figure 6As shown in the figure, we can observe that the antifouling treatment enhances the antifouling properties of the coating. Regarding the antibacterial activity against Staphylococcus aureus, Example 1 showed an antibacterial ratio of 92% compared to Comparative Example 3. Regarding the antialgae activity against Chlorella, Example 1 showed an antialgae resistance ratio of 90% compared to Comparative Example 3. The antifouling mechanism of this coating is as follows: Figure 7 As shown. PDMS has the same molecular structure as the PDMS-OH-based SD matrix, exhibiting similar compatibility. Controlling its slow migration to form an oil film on the surface complements the antifouling silicone-based surface. It not only releases onto the surface during static antifouling, making it difficult for organisms to attach, but also facilitates the detachment of bacteria / algae during dynamic antifouling due to the presence of a dynamic oil film. The added antifouling agent MM, due to osmotic pressure, undergoes slow and continuous release from the interior into the seawater. Studies have shown that MM can bind to similar octopus amine receptors, causing barnacle carp larvae to become overactive and impairing their colonization ability. Similarly, it binds to relevant receptors on attached organisms; or the active portion forms hydrogen bonds with the bases of DNA molecules in bacterial or algal proteins, adsorbing onto microbial cells. These changes disrupt the activity of bacteria or algae, hindering their replication and other physiological metabolic activities, leading to cell death. Therefore, Example 1, with its dual antifouling system, exhibits excellent antifouling capabilities.

[0058] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

Claims

1. A method for preparing a self-healing marine antifouling coating, characterized in that, Includes the following steps: (1) Preparation of prepolymer: First, hydroxyl-terminated polydimethylsiloxane and polycaprolactone diol are mixed in a mass ratio of 1:1 and stirred evenly at 60°C. After adding 4,4'-methylene diphenyl diisocyanate and isophorone diisocyanate, they are stirred evenly after melting. The temperature is raised to 80°C and reacted under N2 for 2 h to prepare the prepolymer. The mass fraction of NCO is titrated using the di-n-butylamine titration method. If the error between the actual value and the theoretical value is within 0.5%, it is considered to be in accordance with the design reaction. (2) Preparation of self-healing marine antifouling coating: The amount of diol is calculated according to the chain extension coefficient f=1. Diol, methyl silicone oil and antifouling agent are mixed. An appropriate amount of dichloromethane is added to make the mixture evenly. The prepolymer is mixed with it and stirred at room temperature for 5 min. It is then poured into a polytetrafluoroethylene mold and the air bubbles are removed under negative pressure in a vacuum oven. Then it is cured in a constant temperature drying oven for 24 hours. h The coating is obtained in which the mass ratio of 4,4'-methylene diphenyl diisocyanate and isophorone diisocyanate in step (1) is 1 / 4 to 1 / 2, and the antifouling agent is metoprimidine.

2. The method for preparing a self-healing marine antifouling coating according to claim 1, characterized in that: The molecular weight of the hydroxyl-terminated polydimethylsiloxane mentioned in step (1) is 1000~2000 g / mol.

3. The method for preparing a self-healing marine antifouling coating according to claim 1, characterized in that: The molecular weight of the polycaprolactone diol mentioned in step (1) is 1000~2000 g / mol.

4. The method for preparing a self-healing marine antifouling coating according to claim 1, characterized in that: The diol mentioned in step (1) is selected from one or more of 1,4-butanediol, ethylene glycol, 1,2-propanediol, diethylene glycol, and 1,6-hexanediol.

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