A dual-degradation type resin and microcapsule slow-release type antifouling paint

Abstract

The application belongs to the field of marine antifouling, and particularly relates to a double-degradation resin and a microcapsule slow-release type antifouling paint based on the resin. The double-degradation resin comprises raw materials of silane acrylate, hydroxy acrylate and diisocyanate in a molar ratio of (1-3):(1-3):(5-10); the silane acrylate has the following general structure: wherein a is a positive integer, b=0 or 1, and c is a non-negative integer; or a=0, b=0, and c is a non-negative integer. The double-degradation resin has a double-degradation mechanism that cannot be compared with conventional side chain hydrolysis or main chain degradation type acrylate, silane acrylate or polyurethane resin, and has self-polishing ability without the aid of external forces such as sea current movement, and can meet the needs of marine dynamic and static antifouling.

Description

Technical Field

[0001] This invention belongs to the field of marine antifouling, specifically relating to a dual-degradable resin and a microcapsule-based controlled-release antifouling paint. Background Technology

[0002] Marine organism fouling has a serious negative impact on the long-term operation of marine engineering equipment / platforms, ships, etc., not only reducing ship speed and significantly increasing fuel consumption, but also causing instability of facilities and platforms, and accelerating corrosion. The fouling and reproduction of marine organisms are closely related to multiple factors such as the sea area where they operate, seasonal temperature differences, species types, water nutrient levels, and substrate characteristics. Fouling prevention has always been a global and century-old problem. Ideal antifouling materials or devices need to meet the requirements of broad spectrum, high efficiency, and durability, and should also adhere to the principles of safety and environmental protection.

[0003] Tributyltin methacrylate self-polishing coatings, due to their excellent antifouling properties, have been widely used worldwide since their invention in the 1970s. However, it was later discovered that tin disrupts the endocrine system of organisms and causes significant damage to the marine environment, leading to a complete ban by the International Maritime Organization (IMO) in 2008. As alternatives, copper / zinc acrylate and silane ester antifouling paints were subsequently developed and used, but their performance is far inferior to the former. Furthermore, the zinc and copper antifouling agents present in large quantities in these coatings often use porous inorganic materials as carriers or are directly physically mixed with the resin without any treatment, resulting in uncontrollable release rates and a potential risk of explosive release, thus significantly shortening the antifouling period. The acrylic resin used as the matrix also cannot be completely decomposed, and the byproducts may enter the water in the form of microplastics, ultimately harming marine ecosystems and fisheries.

[0004] Existing technology CN109651907A discloses a novel self-polishing antifouling coating from Wuxi, belonging to the field of coating technology. It is composed of the following raw materials by weight percentage: 15-50% self-polishing resin, 0.5-2% hydrophobic resin, 4-7% additives, 30-40% biocides, 8-15% powder fillers, 5-12% coloring pigments, and 10-15% solvent. This coating uses a compounded resin and eliminates the use of cuprous oxide, reducing the copper content in the coating. Furthermore, a small amount of strongly hydrophobic resin is uniformly embedded, which improves the self-polishing properties and prevents microbial adhesion, while also controlling the stable and slow release of the antifouling agent, thus extending the coating's service life.

[0005] Existing technology CN111253821B provides a high-solids-content, copper-free linear self-polishing marine antifouling coating, comprising the following components by weight percentage: 20-35% linear self-polishing resin, 10-20% composite antifouling agent, 30-40% pigments and fillers, 2-5% additives, and 10-20% solvent. This coating contains no copper-based antifouling agents, effectively reducing the use of highly polluting and environmentally risky heavy metal ions, which is of great significance in protecting the marine environment; it also has a high solids content, effectively reducing VOC content and making it environmentally friendly.

[0006] Existing technology CN106675294B discloses a copper-free, environmentally friendly, self-polishing marine antifouling coating, which is composed of a matrix resin A with self-polishing properties, an organic antifouling agent B that does not contain any copper-based antifouling agents, pigments and fillers C, additives D, and solvent E. The preparation process of the matrix resin A is divided into two steps. The first step is to obtain an acrylic acid or methacrylic acid prepolymer by free radical copolymerization of acrylic acid or methacrylic acid with other metal-free vinyl unsaturated monomers a1 in a certain amount of solvent under the action of an initiator at a certain temperature. The second step is to reflux the prepolymer obtained in the first step with a saturated organic acid and zinc oxide or hydroxide or zinc salt at a certain temperature until the effluent reaches the expected value, at which point the reaction is stopped, and the matrix resin A is obtained.

[0007] The above three inventions (CN109651907A, CN111253821B, CN106675294B) each provide a copper-free self-polishing and anti-fouling coating, reducing Cu content. 2+ The accumulation of biofouling poses a hidden threat to marine ecosystems. However, compounded or synthesized copper / zinc / silicon / ester resins only have ion exchange or hydrolysis capabilities and cannot completely degrade them. In addition, biocides (antifouling agents) are all blended in, and can only be dissolved into fragments after the resin chain segments dissolve due to hydrolysis or hydrophobic-hydrophilic transformation, and are washed away from the coating by seawater. Moreover, once a large amount of antifouling agent is dissolved, as mentioned above, there is a risk of "explosive release".

[0008] The prior art CN104610826B provides a hydrolyzed zinc acrylate self-polishing antifouling coating and its preparation method. This invention utilizes the arrangement of side methyl groups in the zinc acrylate film-forming polymer to reduce the surface roughness of the coating. At the same time, it combines cuprous oxide and zinc oxide antifouling agents with uniform particle size to reduce the gaps filled by the powder, so that the coating has smooth and drag-reducing properties. It can be used for coating dynamic facilities and equipment such as near-shore and ocean-going ships, but its antifouling ability in static scenarios is limited.

[0009] Patent CN112574631B discloses a novel marine antifouling coating composition based on nano-microcapsule controlled-release technology. Its main resin has a nano-microcapsule structure, consisting of an acrylic resin core and an acrylic resin shell encapsulating it. It is combined with auxiliary resins, reinforcing agents, antifouling agents, pigments, additives, solvents, etc., or may not use antifouling agents. Reportedly, this composition achieves stable controlled-release through repeated alternation of water absorption, rupture, dissolution, and hydrolysis. The principle is that the core of the main resin absorbs water and swells, gradually breaking the shell; after the shell ruptures, the core dissolves, and the remaining shell gradually hydrolyzes under continuous seawater scouring, thus achieving self-polishing. Combining the monomer composition of the main resin, the preparation process, and antifouling diagrams, it is easy to see that the microcapsules have a certain hydrolytic capacity, but are difficult to undergo other forms of degradation (such as enzymatic hydrolysis). In situations where ocean currents are too slow and water scouring is weak, the smooth peeling of the shell may also be hindered. Thanks to its core-shell configuration, hydrolysis is controllable. However, the antifouling agent is simply blended (as independent particles) rather than contained within the capsule. The "water absorption-rupture-dissolution-hydrolysis" process of the microcapsules has no direct and profound impact on the release of the antifouling agent, resulting in insufficient control over its release. Without the addition of an antifouling agent, this technology has proven to have weak antifouling capabilities when relying solely on resin polishing.

[0010] In summary, the current application of antifouling paint on substrate surfaces for the protection against fouling by marine organisms still has much room for improvement in terms of performance. For example, the antifouling agents are highly toxic and the release process is difficult to control precisely; the resin degradation is incomplete, and the surface self-cleaning relies too much on the relative shear of the water flow. Therefore, it cannot yet meet the antifouling requirements of static marine facilities such as offshore drilling platforms and wind turbine foundations. Summary of the Invention

[0011] This invention aims to provide a dual-degradable resin and a microcapsule-based controlled-release antifouling paint. This resin can undergo complete degradation through a combination of hydrolysis and enzymatic hydrolysis, causing breakage and dissolution of the polymer backbone and side branches. This promotes self-renewal of the paint film surface, and the degradation is largely independent of water erosion, providing excellent self-cleaning effects for low-speed wooden boats and static marine engineering facilities. The capsule structure encapsulates organic and inorganic antifouling agents separately, utilizing the hydrophilic / hydrophobic swelling properties of the polymer coating molecules to act as a valve for the leakage of internal antifouling agents, thereby exerting its controlled-release effect.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0013] A dual-degradable resin, the raw materials of which include silane acrylate, hydroxy acrylate and diisocyanate in a molar ratio of (1-3):(1-3):(5-10);

[0014] The silane acrylate has the following general formula:

[0015]

[0016] In the formula, a is a positive integer, b = 0 or 1, and c is a non-negative integer; or a = 0, b = 0, and c is a non-negative integer.

[0017] In dual-degradable resin molecules, the ratio of silane acrylate, hydroxyacrylate, and diisocyanate units significantly impacts degradation performance. The hydrolysis capacity and rate of the side chains are primarily determined by silane esters; a higher proportion leads to faster resin hydrolysis, but a relative decrease in coating adhesion strength. The polyester-polyurethane bonds formed by the reaction of hydroxyacrylate and diisocyanate control the degradation of the molecular backbone and the smooth removal of water / enzymatic degradation products; higher polyester bond density results in faster backbone degradation. To ensure the resin exhibits self-polishing capabilities adaptable to varying seawater flow rates, the content of silane esters and polyester-polyurethane bonds, as well as the lengths of the backbone and side chains, must be carefully designed. If the backbone degradation is too rapid while side chain hydrolysis is slow (equivalent to high hydroxyacrylate and diisocyanate content and low silane acrylate content), the resin will disintegrate and detach prematurely, causing the coating to dissolve completely within a short time, which is detrimental to long-term antifouling performance. Conversely, if side chain hydrolysis is rapid and backbone degradation is slow, water / degradation products may not dissolve in seawater in time, thus reducing surface renewal efficiency. For the application scenario of this invention, the monthly polishing rate of the paint film is >4.0μm.

[0018] To obtain suitable side chain length and silicon nucleophilicity, it is preferable that a = 1, 2 or 3, b = 0 or 1, c = 0, 1, 2 or 3; or a = 0, b = 0, c = 0, 1, 2 or 3.

[0019] To ensure the flexibility and stiffness of the synthesized polyurethane, the diisocyanate is preferably a trimer, tetramer, pentamer, or hexamer of hexamethylene diisocyanate.

[0020] Preferably, the silane acrylate is silane methacrylate. Silane methacrylate has relatively low crystallinity, high roughness, and superior hydrolysis ability.

[0021] Preferably, the hydroxyacrylate is one or both of hydroxyethyl methacrylate and hydroxypropyl methacrylate. Both have moderately active hydroxyl groups and excellent anti-protein properties, which can improve antifouling ability.

[0022] Preferably, the diisocyanate is a hexamethylene diisocyanate trimer to tetramer. Aliphatic isocyanates have good molecular rotational freedom, but if the chain segment is too long, the flexibility is too high, and the hardness and rigidity of the paint film are insufficient, making it susceptible to damage from external mechanical forces; if the molecular chain is too short, the strength and toughness of the paint film are limited, which also cannot meet the requirements.

[0023] Preferably, the main properties of the dual-degradable resin are: adhesive strength > 1.5 MPa, molecular weight of 10,000 to 50,000, polishing rate of 4 to 6 μm / month, hardness > 10 MPa, and elastic modulus > 80 MPa.

[0024] All of the above measurements were performed using methods specified in national standards.

[0025] This invention also claims protection for a method for preparing the dual-degradable resin, comprising the following steps:

[0026] (1) Under the action of an initiator, silane acrylate and hydroxy acrylate undergo free radical addition polymerization to obtain acrylate prepolymer containing side hydroxyl groups;

[0027] (2) The side hydroxyl acrylate prepolymer is further reacted with diisocyanate to generate polyester-polyurethane with silane ester side chains, which is the dual-degradable resin.

[0028] The silane acrylate has the following general formula:

[0029]

[0030] In the formula, a is a positive integer, b = 0 or 1, and c is a non-negative integer; or a = 0, b = 0, and c is a non-negative integer.

[0031] Furthermore, the preparation steps of the dual-degradable resin are as follows:

[0032] (1) Under the initiation of benzoyl peroxide, silane acrylate and hydroxy acrylate undergo free radical copolymerization in a molar ratio of (1-3):(1-3) to obtain acrylate prepolymer containing side hydroxyl groups;

[0033] (2) Under the catalysis of stannous isooctanoate, the acrylate prepolymer containing side hydroxyl groups reacts with diisocyanate at a molar ratio of 1:(5-10) to generate polyester-polyurethane with silane ester side chains, which is the dual-degradable resin.

[0034] Preferably, the free radical copolymerization is carried out at 60-70°C for 8-12 hours to ensure the appropriate molecular weight of the prepolymer and its reactivity in the later stages of the reaction.

[0035] Preferably, the acrylate prepolymer containing side hydroxyl groups is reacted with diisocyanate at 70–90°C for 3–6 hours to obtain suitable main chain length, mechanical strength, etc., which meet the requirements for self-polishing.

[0036] In the aforementioned polyester-polyurethane molecules with silane ester side chains, the polyester bonds on the main chain can be slowly degraded by enzymatic attacks from common mesophilic bacteria in seawater. Meanwhile, the silane ester side chains exhibit strong nucleophilicity, making them more susceptible to hydrolysis than other ester groups in the marine environment. Under the combined influence of hydrolysis and enzymatic hydrolysis, the hydrophobic ester (polyester and silane ester) structures in the polymer gradually transform into hydrophilic carboxyl groups or sodium carboxylate salts. During the chain segment breakage and eventual complete fragmentation into smaller molecules, they are continuously abraded and dissolved by seawater, thus promoting the renewal of the paint film surface. Due to the more thorough degradation and higher degree of fragmentation of the degradation products, it is easier to peel off than with a single hydrolysis method. By artificially designing the content of silane ester and polyester bonds, as well as the length of the main and side chains, the resin can exhibit self-polishing properties adapted to different seawater flow rates. Furthermore, the long-chain polyurethane units linked to the polyester bonds possess excellent flexibility, UV resistance, and high adhesion, providing the necessary mechanical strength, weather resistance, and reliable adhesion to metal substrates for long-lasting antifouling. The polyester-polyurethane with silane ester side chains prepared by this invention has a dual degradation mechanism that is unmatched by conventional acrylic, silane ester or polyurethane resins. It has self-renewal capability with virtually no external force assistance such as ocean currents, and the monthly polishing rate is higher than 4.0 μm. It can meet the antifouling requirements of dynamic and static marine engineering facilities, including high-speed ships, low-speed fishing boats, marine ranches, seabed data centers, offshore drilling platforms, and floating wind power foundations.

[0037] This invention also claims protection for a microcapsule-based controlled-release antifouling paint, comprising, by weight, 20-40 parts of the aforementioned dual-degradable resin, 30-45 parts of controlled-release antifouling agent microcapsules, 0-5 parts of modified rosin, 1-2 parts of polyamide wax, 1-2 parts of dioctyl phthalate, 0-10 parts of talc, 1-3 parts of pigment, and 15-30 parts of xylene. There are no special requirements for the mixing of the components or the preparation process of the antifouling paint; it can be prepared using conventional antifouling paint formulation methods.

[0038] Preferably, the microcapsule controlled-release antifouling paint has the following properties: antifouling period > 11 months, antifouling score > 85, or marine organism attachment area not exceeding 10%.

[0039] Preferably, the controlled-release antifouling agent microcapsules are obtained using solvent evaporation technology, comprising:

[0040] First, the coating polymer and antifouling agent are dissolved or dispersed in a low-boiling-point organic solvent, and then added to a heterogeneous solution containing a stabilizer that is difficult to dissolve in the coating polymer and antifouling agent. After high-speed stirring to fully emulsify the mixture, the solvent is heated and the temperature is controlled to evaporate at a certain rate. The polymer gradually separates from the droplets and migrates to the antifouling agent interface to form microcapsule spheres. Finally, the microcapsules are washed, filtered, dried, and stored for later use.

[0041] Preferably, the low-boiling-point organic solvent is selected from at least one of dichloromethane, chloroform, diethyl ether, acetone, and ethyl acetate, and more preferably dichloromethane, chloroform, or a mixture thereof.

[0042] Preferably, the stabilizer is selected from one of polyvinyl alcohol, polyvinylpyrrolidone, sodium dodecylbenzenesulfonate, and sodium dodecyl sulfate, and more preferably polyvinyl alcohol.

[0043] Preferably, the coating polymer is a terpolymer of polyvinyl alcohol, polyvinyl acetate, and polyvinyl butyral, or a product obtained by partial alcoholysis and acetalization of polyvinyl acetate, wherein the product structure simultaneously contains hydroxyl, acetate, and butyral units. This combination of polar and nonpolar units allows the polymer to possess both hydrophilic and hydrophobic properties, enabling capsules coated with this polymer to swell at a relatively constant and slow rate in seawater. To ensure high acetalization degree, film-forming properties, and water and weather resistance, one or more of the commercial brands B03HX, B04HX, B05HX, B06HX, B08HX, B05SY, B06SY, and B08SY from Changchun Petrochemical Co., Ltd. are preferred.

[0044] Preferably, the drug loading capacity of the sustained-release antifouling agent microcapsules is designed and adjusted according to the capsule diameter and coating wall thickness.

[0045] Preferably, the coating wall thickness is 2–10 μm, and the capsule diameter is 20–60 μm. The coating thickness directly affects the capsule strength; a thicker wall helps maintain capsule integrity but increases the difficulty of seawater penetration, while a thinner wall makes the capsule prone to rupture. In addition, the capsule should have an appropriate size; although a larger diameter allows for more antifouling agent to be filled, it results in an excessively fine coating.

[0046] Preferably, the antifouling agent can be one or more of the following: cuprous oxide, zinc oxide, cuprous thiocyanate, zineb, 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one, pyridine triphenylborane, copper pyridinethione, zinc pyridinethione, 2-tert-butylamino-4-cyclopropylamino-6-methylthio-s-triazine, 2-(p-chlorophenyl)-3-cyano-4-bromo-5-trifluoromethyl-pyrrole, metoimidine, capsaicin, betaine, camptothecin, and butenolate. To provide broad-spectrum antifouling against different populations of marine organisms such as crustaceans, mucus-carrying organisms, diatoms, microorganisms, and fungi, the antifouling agent is a combination of organic and inorganic agents.

[0047] Preferably, the inorganic antifouling agent is a mixture of cuprous oxide and nano zinc oxide, which is added to a low-boiling-point solvent after ultrasonic dispersion.

[0048] Preferably, the mass ratio of cuprous oxide to nano-zinc oxide is (3-6):1. In this mixture, zinc oxide mainly plays an auxiliary role in antifouling, to avoid Cu 2+Due to the potential harm of enrichment to marine ecosystems, the dosage ratio should not be too high.

[0049] Preferably, the organic antifouling agent is a mixture of copper pyrithione and zinc pyrithione, which is directly soluble in a low-boiling-point solvent.

[0050] Preferably, the mass ratio of copper pyrithione to zinc pyrithione is (1-2):(1-2). Copper pyrithione releases Cu... 2+ It also has a certain degree of heavy metal toxicity, and the dosage should be controlled.

[0051] Although cuprous oxide poses hidden harm to the aquatic environment, it remains the most mainstream, widely used, and relatively inexpensive marine antifouling agent. It exhibits good killing activity against hard-shelled organisms, but its antifouling effect on soft-bodied organisms is poor. Copper pyrithione, zinc pyrithione, and zinc oxide, on the other hand, can significantly inhibit the metamorphosis of soft-fouling organisms; the combination of these four agents gives it broader antifouling versatility. Furthermore, considering that organic antifouling agents are easily soluble in organic solvents while inorganic antifouling agents are difficult to dissolve, they are classified into two categories: "copper pyrithione + zinc pyrithione" and "cuprous oxide + zinc oxide." This simplifies the microcapsule preparation process and facilitates the coexistence of similar antifouling agents within the capsule.

[0052] Preferably, the coating polymer encapsulates organic and inorganic antifouling agents separately, forming organic antifouling agent microcapsules and inorganic antifouling agent microcapsules, and then mixes them in a certain proportion and adds them to the antifouling paint.

[0053] Utilizing the abundant hydrophilic hydroxyl groups and hydrophobic acetate and butyral units in the coating polymer molecules, during the solvent dissolution stage, based on the principle of "like dissolves like," the hydrophobic groups directly contact the organic solvent while simultaneously surrounding the hydrophilic hydroxyl groups. Stabilizers then maintain this state of temporary stability. Subsequently, with the rapid evaporation of the low-boiling-point solvent, the emulsion structure is fixed, resulting in a moderately hydrophilic inner wall for the microcapsule spheres and a hydrophobic outer shell. The hydrophobic coating helps to block seawater, preventing rapid penetration in a short time. Using solvent evaporation technology, the antifouling agent is loaded inside the microcapsules. The polymer coating forms a dense protective wall for the antifouling agent components, effectively preventing uncontrolled consumption. When the coating is slowly permeated by weakly alkaline seawater, the hydrophilic hydroxyl groups in its inner wall molecules gradually absorb water and swell, gradually expanding the coating. As the coating wall gradually thins and cracks, creating localized pores, the antifouling agent dissolves through the protective wall (coating).

[0054] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0055] I. A multi-step polymerization method is used to molecularly modify traditional acrylic resin, introducing flexible biodegradable polyester-polyurethane units into the main chain and attaching nucleophilic silane ester side groups. This effectively promotes the organic combination of hydrolyzable acrylate silane esters and enzymatically hydrolyzed main chains. By adjusting parameters such as the number and length of side groups and polyester bond density, the surface renewal rate can be controlled, giving it static self-polishing properties. This can meet the antifouling requirements of ships at different speeds and / or non-dynamic marine engineering facilities and equipment, and has a high degree of application scalability.

[0056] II. Utilizing solvent evaporation microencapsulation technology, a core-shell controlled-release system is encapsulated using a specific polymer coating as the outer shell and an antifouling agent as the core. This process is simple and suitable for large-scale production. Generally, traditional antifouling agent systems utilize the porous cavities in inorganic powders such as sepiolite, halloysite, and carbon nanotubes as drug carriers. Because these cavities are mostly nanoscale and have limited volume (even after expansion), the antifouling agent loading is too low. Furthermore, there is no interaction between the antifouling agent and the powder; it relies solely on electrostatic adsorption or intermolecular hydrogen bonding for fixation, making it prone to detachment and resulting in significant uncertainty in release. This often leads to the problem of "explosive initial release followed by a lack of drug release," affecting antifouling durability. Moreover, the differences in properties between inorganic powders and organic resins easily induce interfacial phase separation, affecting the physicochemical properties of the paint film. If the antifouling agent is directly blended into the coating formulation without any treatment, these defects become even more pronounced. This invention utilizes microcapsules as carriers, allowing for the design and adjustment of drug loading based on capsule diameter and coating wall thickness (micrometer level). The internal volume is orders of magnitude larger than the tiny cavities of inorganic powders, facilitating the loading of more antifouling agents. Furthermore, the separate coating of organic and inorganic antifouling agents avoids interference between different substances and simplifies the capsule manufacturing process. A multi-component polymer with good weather resistance and moderate polarity is selected for the coating to protect the antifouling agent from photodegradation in the high UV environment at sea, and also promotes compatibility between the antifouling agent system (especially inorganic antifouling agents, such as cuprous oxide) and the film-forming resin. More importantly, the unique structure of the microcapsules—hydrophobic on the outside and moderately hydrophilic on the inside—facilitates slow swelling and rupture in seawater, as well as the "on-off" exudation of the internal antifouling agent, thereby achieving stable controlled release and long-lasting antifouling capability. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of a dual-degradable resin and its degradable components.

[0058] Figure 2 The apparent structure of microcapsule 1 under field emission scanning electron microscopy.

[0059] Figure 3 This is a schematic diagram of the configuration of the microcapsule-loaded antifouling system and its controlled release in seawater.

[0060] Figure 4The release rates of the antifouling agents in formulations 1 and 3 at different times. Detailed Implementation

[0061] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0062] Example 1: Synthesis of dual-degradable resin 1

[0063] All reagents and solvents must be dehydrated before use to ensure they meet polyurethane grade.

[0064] a. Preparation of hydroxyacrylate prepolymers

[0065] In a multi-port reactor equipped with a stirrer, reflux condenser, N2 conduit, thermometer, and constant-pressure dropping funnel, tripropyl methacrylate and benzoyl peroxide were slowly added to a dilute solution of hydroxyethyl methacrylate-tetrahydrofuran at a molar ratio of n:n-hydroxyethyl methacrylate = 1.2:1, and based on 0.1 wt% of the total monomer mass. The reaction was continued at 65±2℃ for 8–9 h under constant dry N2 protection. The resulting product was then subjected to rotary evaporation, precipitation, and drying before use.

[0066] b. Synthesis of biodegradable polyester-polyurethane with silane ester hydrolysis side groups

[0067] In a multi-port reactor equipped with a stirrer, reflux condenser, N2 conduit, thermometer, and constant-pressure dropping funnel, the hydroxyacrylate prepolymer and stannous isooctanoate were slowly added dropwise to a 20wt% trihexamethylene diisocyanate-tetrahydrofuran solution at a molar ratio of n-hydroxyacrylate prepolymer:n-trihexamethylene diisocyanate = 1:8, and based on 0.25wt% of the total mass of the reactants, stannous isooctanoate. The reaction was continued at 80±2℃ for 3-4 hours under dry N2 protection throughout the process. The resulting product was obtained after a series of purifications.

[0068] The number-average molecular weight was determined to be 33044 by GPC. 1 ¹H NMR analysis revealed characteristic peaks at 1.28 ppm and 0.82 ppm, belonging to silane ester bonds, and characteristic peaks of polyester-polyurethane units at multiple sites from 1.6 to 4.2 ppm. This confirms the successful synthesis of the polyester-polyurethane, with the molecular structure as shown below. Figure 1 As shown.

[0069] The pure resin film cast from the aforementioned dual-degradable polyester-polyurethane exhibits a bonding strength of 2.1 MPa with Q235 steel, a monthly polishing rate of 4.4 μm, a hardness of 11 MPa, and an elastic modulus of 88 MPa.

[0070] Example 2: Synthesis of dual-degradable resin 2

[0071] All reagents and solvents must be dehydrated before use to ensure they meet polyurethane grade.

[0072] a. Preparation of hydroxyacrylate prepolymers

[0073] In a multi-port reactor equipped with a stirrer, reflux condenser, N2 conduit, thermometer, and constant-pressure dropping funnel, triethoxysilyl methacrylate and benzoyl peroxide were slowly added to a dilute solution of hydroxyethyl methacrylate-tetrahydrofuran at a molar ratio of n:n(hydroxyethyl methacrylate) = 1.3:1, and based on 0.15 wt% of the total monomer mass. The reaction was continued at 70±2℃ for 9.5–10 h under constant dry N2 protection. The resulting product was then subjected to rotary evaporation, precipitation, and drying before use.

[0074] b. Synthesis of biodegradable polyester-polyurethane with silane ester hydrolysis side groups

[0075] In a multi-port reactor equipped with a stirrer, reflux condenser, N2 conduit, thermometer, and constant-pressure dropping funnel, the hydroxyacrylate prepolymer and stannous isooctanoate were slowly added dropwise to a 20wt% tetrahexamethylene diisocyanate-tetrahydrofuran solution at a molar ratio of n-hydroxyacrylate prepolymer:n-tetrahexamethylene diisocyanate = 1:6.5, and based on 0.3wt% of the total mass of the reactants, stannous isooctanoate. The reaction was continued at 85±2℃ for 4–4.5 h under dry N2 protection throughout the process. The resulting product was obtained after a series of purifications.

[0076] GPC analysis showed a number-average molecular weight of 35,400 and a molecular weight distribution range of 3.61. FTIR analysis revealed a molecular weight distribution of 1590 cm⁻¹. -1 3360cm -1 Stretching vibration peaks of NH bonds are present at 1730 cm⁻¹. -1 This corresponds to a C=O bond, and at 810–870 cm -1 The presence of characteristic peaks of silicone methyl ester confirms the successful synthesis of this polyester-polyurethane.

[0077] The pure resin film cast from the aforementioned dual-degradable polyester-polyurethane exhibits a bonding strength of 1.9 MPa with Q235 steel, a monthly polishing rate of 4.2 μm, a hardness of 13 MPa, and an elastic modulus of 94 MPa.

[0078] Example 3: Preparation of antifouling agent microcapsules 1

[0079] Preparation of organic antifouling agent microcapsules 1: Copper pyridine thione, zinc pyridine thione, and polyvinyl butyral (BO3HX from Changchun Petrochemical Co., Ltd.) containing hydroxyl and acetate units were completely dissolved in an appropriate amount of dichloromethane at a mass ratio of 1.5:1:1. This solution was then slowly added dropwise to a 1.5 wt% aqueous solution of polyvinyl alcohol while simultaneously stirring at 1200 rpm for 30 minutes to ensure thorough dispersion into an oil-in-water emulsion. The solution was then heated to 40±2℃, with strict temperature control to allow the dichloromethane to gradually evaporate. The hardened microspheres were washed with water, filtered three times, and vacuum dried to obtain powdered particles. SEM showed that capsule D... 50 The diameter is 28 μm, the average wall thickness is 3 μm, and the apparent structure is shown below. Figure 2 .

[0080] Preparation of inorganic antifouling agent microcapsules 1: Cuprous oxide and nano zinc oxide were mixed evenly beforehand, dispersed by ultrasonication, and then added to a dichloromethane-polyvinyl butyral solution to form a suspension. The process was then carried out according to the above method. The mass ratio of cuprous oxide, zinc oxide, and BO3HX was 4:1:0.5.

[0081] Example 4: Preparation of antifouling agent microcapsules 2

[0082] Preparation of organic antifouling agent microcapsules 2: Copper pyridine thione, zinc pyridine thione, and polyvinyl butyral (B05SY produced by Changchun Petrochemical Co., Ltd.) containing hydroxyl and acetate units were completely dissolved in an appropriate amount of chloroform at a mass ratio of 1:2:1. The mixture was then slowly added dropwise to a 2wt% polyvinyl alcohol aqueous solution while stirring at 800 rpm for 45 min to fully disperse it into an oil-in-water emulsion. The mixture was then heated to 60±2℃, with strict control over the temperature fluctuation range, to allow the chloroform to gradually evaporate. The hardened microspheres were washed with water, filtered three times, and vacuum dried to obtain powdered particles.

[0083] Relatively low dispersion speed and slightly higher boiling point solvents are beneficial for forming large-particle-size, thick-walled capsules. SEM measurements showed that the capsule diameter (D) was [value missing]. 50 It has a diameter of 41 μm and an average wall thickness of 3.6 μm.

[0084] Preparation of inorganic antifouling agent microcapsules 2: Cuprous oxide and nano zinc oxide were mixed evenly beforehand, dispersed by ultrasonication, and then added to a chloroform-polyvinyl butyral solution to form a suspension. The process was then carried out according to the above method. The mass ratio of cuprous oxide, zinc oxide, and B05SY was 6:1:0.7.

[0085] Comparative Example 1: Synthesis of Hydrolyzed Acrylic Silane Ester Resin

[0086] In a multi-port reactor equipped with a stirrer, reflux condenser, N2 conduit, thermometer, and constant-pressure dropping funnel, tripropyl methacrylate and azobisisobutyronitrile were slowly added separately to a dilute methyl methacrylate-tetrahydrofuran solution at a molar ratio of ntripropyl methacrylate:nmethyl methacrylate = 1.15:1, and based on 0.1 wt% of the total monomer mass of azobisisobutyronitrile. The reaction was continued at 70±2℃ for 8–9 h under constant dry N2 protection. The resulting product was obtained after rotary evaporation, precipitation, and drying. The number-average molecular weight was approximately 36,200, the adhesive strength of the pure resin film was 1.4 MPa, the monthly polishing rate was 3.1 μm, the hardness was 17 MPa, and the elastic modulus was 101 MPa.

[0087] Comparative Example 2: Synthesis of main-chain degradable multi-block polyurethane resin (see literature: Preparation of biodegradable antifouling coatings [J], China Coatings, 2012, 27(05): 29-32)

[0088] In a 500mL four-necked flask equipped with a stirrer, thermometer, water separator, condenser, and vacuum pump, 200g of lactic acid (containing 85% monomer) and 100g of toluene / xylene mixed solvent (mass ratio 1:1) were added sequentially. The mixture was refluxed at 130-140℃ under 0.02MPa pressure to remove water for 5-10 hours, yielding a yellow polylactic acid prepolymer. Subsequently, flexible segments: 15g of butanediol, 15g of PEG-200, and an esterification catalyst (such as 0.2g of stannous chloride dihydrate and p-toluenesulfonic acid in a mass ratio of 1:1) were added. The mixture was refluxed at 130-140℃ under negative pressure for 10 hours until no water was generated, yielding a light brown resin, which is the polylactic acid-polyethylene glycol-butanediol multiblock prepolymer. After cooling, 80g of xylene / butyl acetate mixed solvent (mass ratio 1:1), 45g of polyisocyanate (such as toluene diisocyanate and 1,6-hexamethylene diisocyanate in a mass ratio of 2:1), and 0.1g of dilauryl dibutyltin were added, and the mixture was heated to 80℃ and stirred for 4h to obtain the final multi-block biodegradable resin.

[0089] The antifouling coating formulation using this resin as the film-forming matrix is ​​(Formula 9): 30-50% matrix resin, 0-6% cuprous oxide, 5-15% organic antifouling agent, 5-10% pigment, 15-25% filler, 1-4% additives, and 5-15% solvent.

[0090] Based on the dual-degradable resins of Examples 1 and 2 above, and the antifouling agent microcapsules of Examples 3 and 4, a controlled-release antifouling paint is formulated. By weight, it comprises 20-40 parts of dual-degradable resin, 30-45 parts of antifouling agent microcapsules, 0-5 parts of modified rosin, 1-2 parts of polyamide wax, 1-2 parts of dioctyl phthalate, 0-10 parts of talc, 1-3 parts of pigment, and 15-30 parts of xylene. The formulation steps can be carried out according to conventional paint production processes; there are no special requirements for this invention.

[0091] According to GB / T5370-2007 standard, a six-month shallow-sea antifouling system was installed in a certain sea area. Polishing rate tests were conducted according to GB / T31411-2015 standard. The cumulative release of the antifouling agent at different time points was determined using a UV spectrophotometer. The configuration of the microcapsule-loaded antifouling system and its controlled-release behavior in seawater are as follows: Figure 3 As shown.

[0092] The raw material composition and properties of each antifouling paint are shown in Table 1 below.

[0093] Table 1. Raw material composition and performance of various antifouling paints

[0094]

[0095] As can be easily seen from Table 1 and the attached figures, due to the dual degradation characteristics of the self-polishing resin, the molecular chain segments can be completely broken, and the fragment products are more easily dissolved and removed by seawater. The monthly polishing rates of formulations 1–2, 6, 7, and 11 are all higher than 4.0 μm, indicating good surface self-renewal efficiency. Furthermore, thanks to the high adhesion of the polyurethane structure, the bonding strength between the coating and the metal substrate is not less than 1.6 MPa. The acrylate silane resin prepared in Comparative Example 1 can only be hydrolyzed by the tripropylsilane side group, while the methyl methacrylate unit is almost difficult to break in seawater, thus its polishing ability is significantly weaker (Formulation 4 vs. Formulation 2 and Formulation 5 vs. Formulation 1).

[0096] It is not difficult to find that adding pigments, fillers, plasticizers (dioctyl phthalate), and anti-settling agents (polyamide wax) to the antifouling paint formula affects the adhesion, making the bonding strength slightly lower than that of the cast pure resin film; but at the same time, it reduces the resin crystallization tendency, making the paint film surface more susceptible to water molecule attack, and the polishing rate actually increases.

[0097] By changing the monomer types and feed ratios, the acrylate silane ester content in dual-degradable resin 2 is higher than that in dual-degradable resin 1, and the side group molecular chain segments are longer, resulting in faster hydrolysis of dual-degradable resin 2. However, the proportion of polyester-polyurethane units is relatively low, and the main chain degradation is slightly slower. Therefore, the polishing rate of formulation 6 is slightly lower than that of formulation 1. It should be noted that the degradation and polishing rates of the film-forming resin should be controlled within a reasonable range. If the fragments dissolve and are removed too quickly, it may impair the adhesion to the substrate and the long-term antifouling effect. The main chain degradable multi-block polyurethane resin prepared in Comparative Example 2 contains polylactic acid, polyethylene glycol, and polybutanediol units that can be rapidly hydrolyzed. The resulting resin exhibited peeling and powdering after being immersed in natural seawater at a low temperature of 8-15°C for 4 months. In contrast, the interlayer adhesion of the dual-degradable resin 1 or 2 film samples of this invention was almost unaffected after being immersed under the same conditions for half a year. Formula 9, an antifouling paint formulated with resin in Comparative Example 2, showed blistering and active organic sludge adhesion on shallow sea sidings after 8 months. However, the antifouling paint sidings formulated with Formula 1 and Formula 2 of this invention have been used for nearly 11 months and the surface still shows no obvious contamination.

[0098] When Comparative Example 1, which has the ability to hydrolyze side chains, and Comparative Example 2, which has a main chain degradable multi-block polyurethane resin, are prepared into an antifouling paint of Formulation 10 by equal mass ratio, the side chain hydrolysis and main chain degradation are independent of each other and lack organic synergy. As a result, the paint film adhesion and antifouling score are not as good as those of Formulation 1.

[0099] Formula 8 has lower paint film adhesion and stain resistance scores than Formula 1, and its polishing speed is too fast.

[0100] After encapsulation, the polyvinyl butyral coating of this invention forms a good "isolation wall" for the internal antifouling agent. Only when seawater slowly penetrates into the coating under the action of concentration gradient, causing it to gradually absorb water, swell, and rupture, can the antifouling agent be smoothly dissolved from the damaged area. This achieves good controlled release, with a constant and approximately linear release rate. Formula 3, which was simply blended without treatment, showed obvious "burst release" in the first 20 days, and almost all the drug was released after 120 days. Figure 4 Over the course of six months, a certain number of marine organisms have adhered to the sample surface.

[0101] In addition, the antifouling agent microcapsule 2 has a larger diameter than the antifouling agent microcapsule 1. Under the premise of similar wall thickness (3.6μm vs. 3μm), it means that more antifouling agent components can be accommodated inside. When the total dosage of the antifouling agent system (antifouling agent + polymer coating) is 32 parts, the antifouling score of formulation 2 is slightly higher than that of formulation 7.

[0102] Antifouling performance rating, as a comprehensive evaluation of the coating's antifouling ability, is influenced by multiple factors such as the surface renewal rate, the type, content, and release rate of the antifouling agent. A faster resin polishing rate, higher antifouling agent content, and smoother release result in better antifouling performance. Encapsulation of the antifouling agent leads to longer-lasting and more uniform release, and also improves compatibility with the film-forming resin. This not only enhances antifouling performance but also promotes adhesion between the paint layer and the substrate, resulting in formulation 5 having better adhesion strength and antifouling rating than formulation 3. Due to the influence of the resin, formulation 11 also exhibits better overall performance than formulation 3.

[0103] In summary, the polyester-polyurethane resin of this invention has a dual degradation mechanism that is unmatched by conventional side-chain hydrolysis or main-chain degradation acrylic, silane ester or polyurethane resins. It has self-polishing ability with virtually no external force such as ocean currents, and can meet the antifouling requirements of dynamic and static marine engineering facilities, including high-speed ships, low-speed fishing boats, marine ranches, seabed data centers, offshore drilling platforms, and floating wind power foundations.

[0104] The above embodiments should be understood as being used only to illustrate the present invention more clearly, and not to limit the scope of the present invention. After reading the present invention, any modifications of the embodiments by those skilled in the art in various equivalent forms fall within the protection scope defined by the appended claims.

Claims

1. A dual-degradable resin, characterized in that, Its raw materials include silane acrylate, hydroxy acrylate and diisocyanate in a molar ratio of (1-3):(1-3):(5-10); The silane acrylate has the following general formula: ； In the formula, a is a positive integer, b = 0 or 1, and c is a non-negative integer; or a = 0, b = 0, and c is a non-negative integer; The preparation method of the dual-degradable resin includes the following steps: (1) Under the action of an initiator, silane acrylate and hydroxy acrylate undergo a free radical copolymerization reaction to obtain an acrylate prepolymer containing side hydroxyl groups; (2) The side hydroxyl acrylate prepolymer is further reacted with diisocyanate to generate polyester-polyurethane with silane ester side chains, which is the dual-degradable resin.

2. The dual-degradable resin according to claim 1, characterized in that, The properties of the dual-degradable resin are as follows: adhesive strength > 1.5 MPa; molecular weight 10,000–50,000; polishing rate 4–6 µm / month; hardness > 10 MPa; elastic modulus > 80 MPa.

3. The dual-degradable resin according to claim 1, characterized in that, The diisocyanate is a trimer, tetramer, pentamer, or hexamer of hexamethylene diisocyanate; the silane acrylate is silane methacrylate; and the hydroxy acrylate is one or both of hydroxyethyl methacrylate or hydroxypropyl methacrylate.

4. The method for preparing the dual-degradable resin according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Under the action of an initiator, silane acrylate and hydroxy acrylate undergo a free radical copolymerization reaction to obtain an acrylate prepolymer containing side hydroxyl groups; (2) The side-hydroxyl acrylate prepolymer is further reacted with diisocyanate to generate polyester-polyurethane with silane ester side chains, which is the dual-degradable resin. The silane acrylate has the following general formula: ； In the formula, a is a positive integer, b = 0 or 1, and c is a non-negative integer; or a = 0, b = 0, and c is a non-negative integer.

5. The preparation method according to claim 4, characterized in that, The preparation steps of the dual-degradable resin are as follows: (1) Under the initiation of benzoyl peroxide, silane acrylate and hydroxy acrylate undergo free radical copolymerization in a molar ratio of (1-3):(1-3) to obtain acrylate prepolymer containing side hydroxyl groups; (2) Under the catalysis of stannous isooctanoate, the acrylate prepolymer containing side hydroxyl groups reacts with diisocyanate at a molar ratio of 1:(5-10) to generate polyester-polyurethane with silane ester side chains, which is the dual-degradable resin.

6. The preparation method according to claim 4, characterized in that, The free radical copolymerization is carried out at 60-70°C for 8-12 hours; the acrylate prepolymer containing side hydroxyl groups is reacted with diisocyanate at 70-90°C for 3-6 hours.

7. A microcapsule-based controlled-release antifouling paint, characterized in that, Based on weight, it comprises 20-40 parts of the dual-degradable resin as described in any one of claims 1-3, 30-45 parts of the controlled-release antifouling agent microcapsules, 0-5 parts of modified rosin, 1-2 parts of polyamide wax, 1-2 parts of dioctyl phthalate, 0-10 parts of talc, 1-3 parts of pigment, and 15-30 parts of xylene.

8. The microcapsule-based controlled-release antifouling paint according to claim 7, characterized in that, The controlled-release antifouling agent microcapsules are obtained using solvent evaporation technology and include: First, the coating polymer and antifouling agent are dissolved or dispersed in a low-boiling-point organic solvent, and then added to a heterogeneous solution containing a stabilizer that is difficult to dissolve in the coating polymer and antifouling agent. After high-speed stirring to fully emulsify the mixture, the solvent is heated and the temperature is controlled to evaporate at a certain rate. The polymer gradually separates from the droplets and migrates to the antifouling agent interface to form microcapsule spheres. Finally, the microcapsules are washed, filtered, dried, and stored for later use.

9. The microcapsule-encapsulated controlled-release antifouling paint according to claim 8, characterized in that, The coating polymer is a terpolymer of polyvinyl alcohol, polyvinyl acetate, and polyvinyl butyral, or a product of polyvinyl acetate after partial alcoholysis and acetalization; the product structure contains hydroxyl, acetate, and butyral units simultaneously.

10. The microcapsule-encapsulated controlled-release antifouling paint according to claim 8, characterized in that, The antifouling agent is a combination of organic and inorganic antifouling agents; the inorganic antifouling agent is a mixture of cuprous oxide and nano zinc oxide; the organic antifouling agent is a mixture of copper pyridinethione and zinc pyridinethione.

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