Special composite anti-marine-biological ship coating and preparation method thereof

Abstract

This invention belongs to the field of marine coating technology, specifically relating to a special composite antifouling marine coating and its preparation method. It uses modified polyurethane as the film-forming matrix, and utilizes polytetrahydrofuran ether soft segments and IPDI hard segments to impart seawater resistance and high toughness to the coating. Imidazole groups can recognize acidic microdomains formed by microbial metabolism, allowing the coating to maintain a low surface energy state in seawater to block initial biological adhesion. Under acidic conditions, charge reversal and hydrophilic switching are achieved through hydrogen bonding, disintegrating the biofilm and forming a physical anti-adhesion barrier. By constructing pH-responsive microcapsules, IPDI is cross-linked with amine monomers to form an anti-swelling wall material. Acidic sensitizing units are grafted onto the surface double bonds, and the interior is encapsulated with a core material composed of modified dehydroabscisic acid and matrine. Under acidic conditions, the sensitizing units protonate, triggering the release of the core material, inhibiting primary microorganisms and large attached organisms. In the weakly alkaline environment of seawater, it can automatically seal pores and stop release, achieving long-lasting antifouling and environmentally friendly performance, suitable for marine protection applications.

Description

Technical Field

[0001] This invention relates to the field of marine coating technology, and in particular to a special composite marine anti-biological coating and its preparation method. Background Technology

[0002] The sustained and rapid development of the marine economy and the shipping industry has made antifouling technology a core key to ensuring efficient shipping operations, reducing operational losses, and extending the service life of marine engineering equipment. The attachment and proliferation of marine fouling organisms is a common industry problem faced by ships, offshore platforms, underwater pipelines, and other facilities. Marine fouling organism systems are complex, including microscopic primary fouling organisms such as bacteria and diatoms that can colonize rapidly, as well as large fouling organisms such as barnacles, mussels, algae, and tube worms that adhere firmly and cause significant damage. Their extensive attachment and reproduction on ship surfaces not only significantly increases frictional resistance, directly leading to increased fuel consumption and reduced navigation efficiency, but also damages protective coatings, accelerates the corrosion and aging of the ship's metal substrate, and significantly increases equipment maintenance costs and safety hazards. As the most widely used and practical antifouling method, the technological iteration of marine antifouling coatings has always revolved around the simultaneous upgrading of antifouling effect and ecological safety. Although the early mainstream organotin and copper-based heavy metal antifouling coatings had outstanding antifouling performance, they have been completely restricted and banned by international conventions because the toxic substances they release can seriously poison marine life and destroy the marine ecological balance. At present, environmentally friendly antifouling coatings developed are mostly shifting to green paths such as biofouling and physical antifouling, which have improved ecological safety, but there are still obvious technical limitations. Existing environmentally friendly antifouling coatings generally have the problems of single antifouling mechanism and insufficient long-term protection capability, making it difficult to take into account both primary and large fouling organisms, and unable to meet the long-term, green, and all-area antifouling needs of ships in the complex marine environment. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a special composite antifouling marine coating and its preparation method. Using modified polyurethane as the film-forming matrix, the coating utilizes polytetrahydrofuran ether soft segments and isophorone diisocyanate (IPDI) hard segments to impart seawater resistance and high toughness. Imidazole groups can recognize acidic microdomains formed by microbial metabolism, allowing the coating to maintain a low surface energy state in seawater to prevent initial biological adhesion. Under acidic conditions, charge reversal and hydrophilic switching are achieved through hydrogen bonding, disintegrating the biofilm and forming a physical anti-adhesion barrier. By constructing pH-responsive microcapsules, IPDI is cross-linked with amine monomers to form an anti-swelling wall material. Acidic sensitizing units are grafted onto the surface double bonds, and the interior is encapsulated with a core material composed of modified dehydroabsic acid and matrine. Under acidic conditions, the sensitizing units protonate, triggering the release of the core material and inhibiting primary microorganisms and large attached organisms. In the weakly alkaline environment of seawater, it can automatically seal pores and stop release, achieving long-lasting antifouling and environmentally friendly performance, suitable for marine protection applications.

[0004] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a special composite marine biological protection coating for ships, the coating comprising modified polyurethane, pH-responsive microcapsules, fillers, and additives; The modified polyurethane is obtained by reacting polytetramethylene ether glycol with isophorone diisocyanate to form an isocyanate-terminated polyurethane prepolymer, which is then grafted with 1-(2,3-epoxypropyl)-2-methyl-5-nitroimidazolium and micro-crosslinked with hexamethylene diisocyanate trimer. The pH-responsive microcapsule includes a wall material, a core material, and an acid sensitizing unit grafted onto the outer surface of the wall material; The wall material is obtained by interfacial polymerization of raw materials used to form the wall material; the raw materials used to form the wall material include isophorone diisocyanate, polyetheramine D230 and N,N'-diallyl-1,6-hexanediamine; the N,N'-diallyl-1,6-hexanediamine is obtained by alkylation reaction of 1,6-hexanediamine and allyl chloride; The core material includes modified dehydroabscisic acid ester and matrine; the modified dehydroabscisic acid ester is obtained by esterification reaction of dehydroabscisic acid and ethylene glycol monobutyl ether under the catalysis of p-toluenesulfonic acid; The acidic sensitizing unit is dimethylaminoethyl methacrylate; The filler includes iron oxide red and talc; the additives include silane coupling agent, dispersant, leveling agent, organobentonite and curing agent.

[0005] Further, the mass ratio of the modified polyurethane, pH-responsive microcapsules, filler, and additives is (62.5-65.1):(12.15-13.45):(3.35-3.65):(9.08-9.92); the mass ratio of the polytetramethylene ether diol to isophorone diisocyanate is (49-53):(29.5-32.5); the isocyanate-terminated polyurethane prepolymer, 1-(2,3-epoxypropyl)-2-methyl-5-nitroimidazole, and hexamethylene diisocyanate... The mass ratio of the ester trimer is (78.5-85.5):(0.8-0.9):(0.28-0.32); the mass ratio of the raw materials, core material and acid sensitizing unit used to form the wall material is (4.5-5.1):(6.7-7.3):(0.95-1.05); the mass ratio of isophorone diisocyanate, polyetheramine D230 and N,N'-diallyl-1,6-hexanediamine is (2.8-3.2):(0.85-0.95):(0.85-0.95).

[0006] Further, the mass ratio of 1,6-hexanediamine to allyl chloride is (22-24.4):30.6; the mass ratio of modified dehydroabietic acid ester to matrine is (4.7-5.1):(2.0-2.2); the mass ratio of dehydroabietic acid, ethylene glycol monobutyl ether, and p-toluenesulfonic acid is (9.5-10.5):(2.0-2.4):(0.05-0.07); and the mass ratio of iron oxide red to talc is (1.45-1). 55): (1.9-2.1); the mass ratio of the silane coupling agent, dispersant, leveling agent, organobentonite, and curing agent is (2.1-2.3): (1.05-1.15): (0.65-0.75): (0.48-0.52): (4.8-5.2); the silane coupling agent is KH-201; the dispersant is sodium polycarboxylate; the leveling agent is polyether-modified polydimethylsiloxane; and the curing agent is N3390.

[0007] Further, the polytetramethylene ether glycol has a molecular weight of 950-1050 and a hydroxyl value of 107-118 mgKOH / g; the hexamethylene diisocyanate trimer has an isocyanate content of 21.5wt%-22.5wt% and a viscosity of 2500-3500 mPa·s; the modified dehydroabietic acid ester has an acid value ≤5 mgKOH / g; the polyetheramine D230 has an amine value of 8.1-8.7 meq / g; and the organobentonite has a fineness ≤325 mesh.

[0008] Secondly, the present invention provides a method for preparing a special composite marine biological-resistant ship coating, comprising the following steps: S1. Mix polytetramethylene ether glycol, isophorone diisocyanate, bismuth isooctanoate and anhydrous butyl acetate, purge with nitrogen, and react with a first heating and a second heating to obtain an isocyanate-terminated polyurethane prepolymer. After cooling, add 1-(2,3-epoxypropyl)-2-methyl-5-nitroimidazole and react. Add hexamethylene diisocyanate trimer and heat to mature. Add anhydrous n-butanol and distill under reduced pressure and filter to obtain modified polyurethane. S2. Under nitrogen protection, 1,6-hexanediamine, sodium hydroxide and anhydrous ethanol were mixed, heated and allyl chloride was added dropwise. The reaction was continued at a higher temperature. After filtration and vacuum distillation, N,N'-diallyl-1,6-hexanediamine was obtained. Dehydroabietic acid, ethylene glycol monobutyl ether and p-toluenesulfonic acid were mixed, heated a second time and vacuum distilled to obtain modified dehydroabietic acid ester. S3. Span 85 and anhydrous n-dodecane are mixed to obtain a continuous phase; matrine, anhydrous butyl acetate, modified dehydroabietic acid ester, anhydrous xylene, and anhydrous cyclohexanone are mixed to obtain a core material; isophorone diisocyanate is added to obtain an oil phase; the oil phase is added dropwise to the continuous phase to form an oil-in-oil emulsion; polyetheramine D230 and N,N'-diallyl-1,6-hexanediamine are dissolved in anhydrous butyl acetate to obtain an amine mixture, which is added dropwise to the oil-in-oil emulsion to obtain a microcapsule emulsion in which the wall material coats the core material; monoisooctyl phosphate is added, the temperature is raised, an initiator and dimethylaminoethyl methacrylate are added, and the reaction is carried out to obtain pH-responsive microcapsules; S4. Mix the modified polyurethane with xylene-propylene glycol methyl ether acetate mixture, then add KH-201 pre-dispersion, sodium polycarboxylate, and polyether-modified polydimethylsiloxane in sequence. Stir, add iron oxide red and talc, continue stirring, add organobentonite pre-dispersion, pH-responsive microcapsules, and N3390, mix evenly, and filter to obtain a special composite marine biological protection coating.

[0009] In one feasible implementation, in step S1, the mass ratio of polytetramethylene ether glycol, bismuth isooctanoate, and anhydrous butyl acetate is (49-53):(0.1-0.14):(23-27); the flow rate of nitrogen gas is 18-22 mL / min; the first heating reaction step is as follows: heating to 53-57℃ and stirring at 450-550 r / min for 25-35 min; the target temperature for the second heating is 6℃. The temperature range is 3-67℃; the target temperature for cooling is 48-52℃; the reaction time is 2.8-3.2h; the heating and ripening step is: heating to 78-82℃ and ripening at a constant temperature for 55-65min; the mass ratio of hexamethylene diisocyanate trimer to anhydrous n-butanol is (0.28-0.32):(0.37-0.4); the conditions for vacuum distillation are: temperature 73-77℃, pressure -0.088~-0.092MPa.

[0010] Polytetramethylene ether glycol (PTG) is a long-chain flexible polyether polyol with active hydroxyl groups at both ends of its molecule. Its polyether backbone structure possesses excellent resistance to seawater hydrolysis and low-temperature toughness, providing flexible molecular chain segments for polyurethane resins and ensuring that the coating film does not crack or degrade after long-term immersion in seawater. IPDI is an aliphatic cyclic isocyanate containing highly active isocyanate groups; its rigid cyclic skeleton imparts mechanical strength and resistance to yellowing and weathering to the resin. Bismuth isooctanoate is an environmentally friendly organometallic catalyst with mild and controllable reactivity. It catalyzes the polymerization process, preventing excessively rapid reaction rates that could lead to gelation and ensuring the prepolymer's stability. The prepolymer exhibits a uniform and stable structure. Under the catalysis of bismuth isooctanoate, polytetramethylene ether glycol and IPDI undergo an addition polymerization reaction between hydroxyl groups and isocyanate groups, gradually generating isocyanate-terminated polyurethane prepolymers. This preparation method can pre-combine flexible soft segments and rigid hard segments in an orderly manner, regulate molecular arrangement, and balance the toughness and structural strength of the resin film, avoiding structural disorder and phase separation problems caused by one-time polymerization. It can also moderate the exothermic reaction rate, prevent the system from rapidly thickening and agglomerating, and make the synthesis process mild and controllable throughout. At the same time, it can retain highly active end-group isocyanate (-NCO) groups at the ends of the prepolymer molecular chains.

[0011] The 1-(2,3-epoxypropyl)-2-methyl-5-nitroimidazolium molecule contains an epoxy active group and an imidazole heterocyclic functional group. The epoxy group can undergo a chemical bonding and ring-opening reaction with the terminal -NCO active group at the end of the polyurethane prepolymer chain. After the reaction, the epoxy ring opens and cross-links to form a bond, introducing the imidazole pH-responsive unit into the polyurethane molecular backbone. The imidazole group can recognize the acidic microenvironment produced by the metabolism of marine microorganisms, providing a molecular basis for the reversible switching between hydrophobic and hydrophilic coatings.

[0012] Hexamethylene diisocyanate trimer is a multifunctional crosslinking component containing multiple active isocyanate groups. It can undergo addition bonding reactions with the imino active hydrogen and the newly generated hydroxyl active hydrogen after imidazole grafting ring opening in the urethane structure of the polyurethane main chain. By controlling the amount used, it can bridge adjacent polyurethane molecular chains to form a sparse bridging structure. Furthermore, by using a mild curing temperature of 78-82℃, the degree of crosslinking reaction can be further limited, triggering local site-specific mild bonding and forming a controllable micro-crosslinking effect. This can slightly improve the tightness of resin molecular bonding, enhance the coating film's resistance to seawater penetration and anti-aging properties, and prevent the resin from becoming hard and brittle due to excessive crosslinking, thus preserving the original flexibility and processing fluidity of the polyurethane matrix.

[0013] Anhydrous n-butanol, as a monofunctional end-capping agent, can have its hydroxyl groups react with the residual unreacted isocyanate groups in the system to block the active end groups, thus eliminating the risk of spontaneous cross-linking and deterioration during resin storage. The vacuum distillation process removes residual solvents and small molecule impurities, and finally purifies the modified polyurethane film matrix with a stable structure and both mechanical protection and pH response functions.

[0014] In one feasible implementation, in step S2, the flow rate of the nitrogen protection is 18-22 mL / min; the mass-to-volume ratio of 1,6-hexanediamine, sodium hydroxide, and anhydrous ethanol is (22-24.4) g : (15.2-16.8) g : (75-85) mL; the target temperature for heating is 38-42℃; the dropping rate is 0.24-0.27 g / min; the heating reaction step is: heating to 48-52℃ and reacting at a constant temperature for 5.5-6.5 h; the conditions for vacuum distillation are: temperature 118-127℃ and pressure -0.093 to -0.097 MPa; the target temperature for the second heating is 118-122℃; after the second heating, the conditions for vacuum distillation are: temperature 78-82℃ and pressure -0.078 to -0.082 MPa.

[0015] 1,6-Hexanediamine is a fatty amine monomer with a bis-primary amine structure. The active amino groups at both ends of the molecule can participate in nucleophilic substitution reactions, making it a core raw material for the synthesis of functional amine intermediates. Sodium hydroxide, as a strong basic acid-binding agent, can neutralize the hydrogen chloride byproduct generated in the alkylation reaction, eliminate the inhibitory effect of acidic substances on the reaction, promote the continuous positive progress of the nucleophilic substitution reaction between the amino group and the haloalkane, and avoid the corrosion and destruction of the intermediate structure by the byproducts. Allyl chloride is an alkylating agent containing double bonds, which can undergo a nucleophilic alkylation reaction with the amino group of 1,6-hexanediamine, introducing an allyl carbon-carbon double bond into the amine molecule structure. After purification, N,N'-diallyl-1,6-hexanediamine is obtained. The secondary amine structure of this intermediate can subsequently participate in the cross-linking reaction of polyurea wall materials to enhance the rigidity of the wall materials. The exposed carbon-carbon double bonds do not participate in the cross-linking reaction and can be used as exclusive active sites for covalent grafting of acid-sensitizing units.

[0016] Dehydroabietic acid is a natural active derivative of rosin. Its molecular skeleton has natural antibacterial and anti-adhesion activities, making it a core raw material for long-lasting environmentally friendly antifouling. However, its high carboxylic acid polarity can cause side reactions with isocyanate components and has poor compatibility with organic coating systems. Ethylene glycol monobutyl ether is a low-carbon alcohol esterification monomer with moderate activity of its molecular alcohol hydroxyl group. It can undergo esterification with the carboxyl group of dehydroabietic acid. Furthermore, through the strong acidic organic catalyst of p-toluenesulfonic acid, the esterification and dehydration reaction is efficiently catalyzed and continues, accelerating the bonding between the carboxyl group and the alcohol hydroxyl group and removing the water generated by the reaction. Esterification modification significantly reduces the acid value of dehydroabietic acid, eliminates the risk of acidic side reactions, and weakens the molecular polarity, significantly improving its dispersion compatibility in organic solvent systems of coatings. It retains its original antifouling activity and is suitable for the use of microcapsule core materials.

[0017] In one feasible implementation, in S3, the mass-to-volume ratio of Span 85 and anhydrous n-dodecane is (1.4-1.6) g: (140-160) mL; the mass-to-volume ratio of matrine, the first added anhydrous butyl acetate, anhydrous xylene, and anhydrous cyclohexanone is (2.0-2.2) g; (4.5-5.5) mL: (28-32) mL: (10-12) mL; the rate at which the oil phase is added to the continuous phase is 0.9-1.1 mL / min; and the mass-to-volume ratio of polyetheramine D230, monoisooctyl phosphate, and the second added anhydrous butyl acetate is (0.85-0.95) g: (0.18-0.22) g: (7.5-8.5) mL.

[0018] Anhydrous n-dodecane, as a low-polarity solvent, forms the continuous reaction phase. It is chemically inert and has poor miscibility with high-polarity organic solvents, serving as the basic dispersion medium for oil-in-oil emulsions. Span 85, as a nonionic emulsifier, relies on its amphiphilic structure to arrange itself at the interface between the two phases to reduce interfacial tension and prevent droplet aggregation, thereby stabilizing the continuous phase system. A homogeneous core material solution is formed by dissolving matrine and modified dehydroabietic acid ester in a compound of various high-polarity anhydrous organic solvents. Isophorone diisocyanate is then added and mixed to form a high-polarity dispersed oil phase. This oil phase is difficult to miscible with the low-polarity continuous phase due to the difference in polarity. When the oil phase is slowly added dropwise to the continuous phase, a stable oil-in-oil emulsion can be formed under the action of the emulsifier.

[0019] In one feasible implementation, in step S3, the rate of dropwise addition to the oil-in-oil emulsion is 0.28-0.32 g / min; the target temperature for heating is 66-70℃, and the heating rate is 0.8-1.2℃ / min; the initiator is prepared by dissolving 0.045-0.055 g of benzoyl peroxide in 4.5-5.5 mL of anhydrous butyl acetate to obtain the initiator; the reaction temperature is 66-70℃, and the reaction time is 1.3-1.7 h.

[0020] By preparing an amine mixture containing polyetheramine D230 and N,N'-diallyl-1,6-hexanediamine, and slowly adding the amine solution dropwise to the emulsion under constant temperature conditions, the active amino groups of the amine components will undergo urea bond condensation reaction with the isocyanate groups at the interface of the emulsion droplets, forming a dense and tough polyurea wall material in situ on the surface of the microdroplets. This completes the full coating of the core material while retaining the carbon-carbon double bond active sites of the intermediates that did not participate in the reaction. Monoisooctyl phosphate is a weak acid neutralizing regulator to prevent strong acids and bases from damaging the structure of the unformed wall material and ensure the smooth completion of the interfacial polymerization reaction.

[0021] Benzoyl peroxide is a thermally decomposable free radical initiator. When heated, it decomposes to generate active free radicals, triggering a polymerization grafting reaction. Dimethylaminoethyl methacrylate, an acid-responsive functional monomer, can be covalently grafted onto the exposed double bond sites of the wall material under the action of free radicals. The tertiary amine group in its structure is easily protonated in an acidic microenvironment and generates electrostatic repulsion, opening up the micropores of the wall material to form hydrophilic channels and thus releasing the core material. When the environment returns to the weakly alkaline state of seawater, the tertiary amine deprotonates, and the pores of the wall material automatically close to achieve self-sealing. It relies on a reversible response mechanism to complete the on-demand controlled release of antifouling. Modified dehydroabietic acid ester and matrine are combined to form a microcapsule antifouling core material. Modified dehydroabietic acid ester can target and inhibit the colonization and reproduction of primary microorganisms such as marine bacteria and diatoms, while matrine can specifically resist the attachment of large marine fouling organisms such as barnacles and mussels. The two work together to achieve the control of fouling organisms.

[0022] In one feasible implementation, in step S4, the mass-to-volume ratio of the modified polyurethane to the xylene-propylene glycol methyl ether acetate mixture is (62.5-65.1) g : (1.1-1.3) mL; the volume ratio of xylene to propylene glycol methyl ether acetate in the xylene-propylene glycol methyl ether acetate mixture is 1:1; the mass-to-volume ratio of the modified polyurethane, organobentonite predispersant, and KH-201 predispersant is (62.5-65.1) g : (3.9-4.3) g : (8.24-8.76) mL; and the preparation step of the KH-201 predispersant is: 2.1-2.3 g Mix KH-201, 8.11-8.62 mL of anhydrous ethanol and 0.125-0.139 mL of deionized water, let stand for 55-65 min in the dark, and then dehydrate under reduced pressure in a closed environment at 33-37℃ and -0.058~-0.062 MPa for 23-27 min to obtain KH-201 predispersant.

[0023] After hydrolysis and activation, KH-201 silane coupling agent forms differentiated active groups at both ends of the molecule. One end of the silanol group can form strong silicon-oxygen covalent bonds with the hydroxyl groups on the surface of the steel plate substrate, iron oxide red, and talc particles, respectively. The other end of the organic functional group can achieve compatible entanglement and molecular bonding with the modified polyurethane resin molecular chain, effectively bridging the interface between the inorganic substrate of the steel plate, the inorganic filler, and the organic resin, significantly improving the adhesion strength of the paint film to the ship hull substrate and strengthening the interfacial compatibility of the components inside the coating.

[0024] After pre-dispersion treatment with a compound system of xylene and propylene glycol methyl ether acetate, organic bentonite can form a continuous network colloidal flocculation structure in the system, giving the coating excellent thixotropic and rheological properties. When the coating is subjected to low shear force, the colloidal network structure dissociates, which improves the fluidity of the coating to suit the coating application. When stored statically without shear force, the colloidal network structure recovers. This can not only inhibit the sedimentation of fillers in the coating system, but also prevent the paint film from sagging during the coating process, and at the same time, maintain the long-term stability of the coating storage state.

[0025] In one feasible implementation, in step S4, the stirring speed is 450-550 r / min, and the stirring time is 18-22 min; the stirring speed is 450-550 r / min, and the stirring time is 8-12 min; the preparation steps of the organobentonite predispersant are as follows: 0.48-0.52 g of organobentonite is mixed with 3.8-4.2 mL of xylene-propylene glycol methyl ether acetate mixture, wherein the volume ratio of xylene to propylene glycol methyl ether acetate in the xylene-propylene glycol methyl ether acetate mixture is 1:1, and the mixture is stirred continuously for 18-22 min to obtain the organobentonite predispersant; the filtration medium is an 80-mesh nylon filter screen.

[0026] Sodium polycarboxylate dispersant wets and coats the surface of iron oxide red and talc inorganic filler particles, reducing particle surface energy, breaking up filler agglomeration structures, and allowing fillers to be uniformly dispersed in the resin system, reducing internal agglomeration defects in the paint film. Polyether-modified polydimethylsiloxane leveling agent reduces the overall surface tension of the coating, eliminates pinholes, ripples, and orange peel defects generated during the coating process, promotes uniform spreading of the paint film during curing, and improves the smoothness and gloss of the coating surface. Iron oxide red is a weather-resistant and rust-preventive inorganic pigment that has both coloring ability and shielding and rust-preventive function. It can block the penetration of water vapor and salt to protect the substrate. Talc is an inert filler that can fill the micropores of the paint film, improving the density, wear resistance, and mechanical strength of the coating. N3390 is an aliphatic isocyanate trimer curing agent containing multifunctional active isocyanate groups. It can undergo cross-linking and curing reactions with the active groups of modified polyurethane resin to build a complete and dense cross-linked network of the paint film, enhancing the coating's resistance to seawater corrosion and structural stability.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: This scheme uses modified polyurethane as the pH-responsive film-forming matrix, highly cross-linked polyurea as the wall material, modified dehydroabscisic acid-matrine compound as the antifouling core material, and dimethylaminoethyl methacrylate as the acid sensitizing unit to construct pH-responsive microcapsules, resulting in a special composite antifouling marine coating that combines long-lasting antifouling stability with environmental friendliness. Modified polyurethane, with its molecular structure of polytetrahydrofuran ether soft segment and IPDI hard segment, possesses seawater-resistant and highly tough film-forming properties. By grafting imidazole pH-responsive units onto the resin backbone, it identifies acidic micro-regions formed by microbial attachment and acid production based on the responsive characteristics of imidazole groups. The coating formed after the film-forming matrix is ​​cured exhibits a hydrophobic and low surface energy state in a weakly alkaline seawater environment, effectively blocking the initial adhesion of fouling organisms. When microbial metabolism leads to an increase in the acidity of the interfacial micro-regions, relying on the seawater wetting slow response mechanism, the imidazole groups form a hydrogen bond conduction network with the help of the trace amounts of water adsorbed by long-term wetting, achieving proton penetration and triggering charge reversal and hydrophilicity switching on the coating surface, disintegrating the adhesion of the established biofilm and constructing a dynamic physical rejection barrier.

[0028] pH-responsive microcapsules are constructed from IPDI, N,N'-diallyl-1,6-hexanediamine, and polyether diamine. These microcapsules form urea bonds through the reaction of isocyanate groups with amino groups, linking the monomer segments to create a network cross-linked structure. This structure imparts rigidity and resistance to deformation and swelling to the wall material, enabling long-term loading of the antifouling core. The secondary amine terminus of N,N'-diallyl-1,6-hexanediamine participates in the polyurea cross-linking reaction, while the carbon-carbon double bonds in the molecule remain exposed in situ on the outer surface of the wall material, providing covalent grafting sites for the sensitizing units. When an acidic environment penetrates into the coating... When the microcapsule interface forms a localized acidic microregion, the tertiary amine matrix in the sensitization unit of the wall material surface is protonated, generating electrostatic repulsion. This causes the surface structure of the wall material to loosen, forming hydrophilic channels that trigger the release of the core material. The released modified dehydroabietic acid targets and inhibits the colonization of primary fouling organisms such as bacteria and diatoms, while matrine specifically resists the attachment of large fouling organisms such as barnacles and mussels. In a weakly alkaline seawater environment, the sensitization unit restores its hydrophobic closure to achieve self-sealing of pores. This achieves full-domain antifouling from initial physical rejection to targeted chemical elimination, significantly improving the static antifouling durability and marine environmental adaptability of the coating. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the preparation process of a special composite marine biological protection coating for ships according to the present invention.

[0030] Figure 2 This is a physical image of the special composite marine biological protection coating prepared in Example 1 of the present invention. Detailed Implementation

[0031] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the application will be further described in detail below with reference to embodiments. However, this should not be construed as limiting the scope of this application to the following examples. All other embodiments obtained by those skilled in the art without creative effort without departing from the above-described methodological spirit of this application are within the scope of protection of this application.

[0032] The singular forms “for,” “or,” “a,” “any,” and “described” used in this application are intended to include the plural forms unless the context clearly indicates otherwise. Furthermore, the terms “first” and “second” are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] Example 1 like Figure 1 As shown, a method for preparing a special composite marine biological-resistant ship coating includes the following steps: S1. Mix 51.0g of polytetramethylene ether glycol with a molecular weight of 1000 and a hydroxyl value of 110mgKOH / g, 31.0g of IPDI, 0.12g of bismuth isooctanoate, and 25g of anhydrous butyl acetate. Stir at 500r / min for 10min, and purge with nitrogen at a flow rate of 20mL / min to maintain a slight positive pressure of 0.02MPa. First, raise the temperature to 55℃ and stir for 30min. After the exothermic reaction stabilizes, slowly raise the temperature to 65℃ and stir at a constant temperature for 2.5h to obtain an isocyanate-terminated polyurethane prepolymer. Lower the system temperature to 50℃ and add 0.85g of... 1-(2,3-epoxypropyl)-2-methyl-5-nitroimidazole was grafted onto a substrate and reacted with stirring at a constant temperature for 3 hours. 0.30 g of hexamethylene diisocyanate trimer with an isocyanate content of 22 wt% and a viscosity of 3000 mPa·s was added. The mixture was heated to 80℃ and aged at a constant temperature for 60 min. 0.385 g of anhydrous n-butanol was added, and the mixture was stirred at 500 r / min for 15 min. The mixture was then distilled under reduced pressure at 75℃ and -0.09 MPa for 40 min, allowed to cool naturally to room temperature, and filtered to obtain the modified polyurethane.

[0034] S2. Under nitrogen protection at a flow rate of 20 mL / min, 23.2 g of 1,6-hexanediamine was dissolved in 80 mL of anhydrous ethanol, and 16.0 g of sodium hydroxide was added. The mixture was stirred at 500 r / min until completely dissolved. The temperature was raised to 40 °C, and 30.6 g of allyl chloride was added dropwise at a rate of 0.255 g / min. After the addition was completed, the temperature was raised to 50 °C and the reaction was maintained at this temperature for 6 h. After cooling to room temperature, the solid sodium chloride was removed by filtration. The ethanol was recovered by distillation under normal pressure. The solution was then distilled under reduced pressure at 123 °C and -0.095 MPa to obtain N,N '-Dialyl-1,6-hexanediamine; under nitrogen protection, 10.0 g of dehydroabsic acid, 2.2 g of ethylene glycol monobutyl ether, and 0.06 g of p-toluenesulfonic acid were added to the reaction vessel, stirred at 500 r / min, heated to 120 °C and reacted at a constant temperature for 4 h, with water continuously removed by a water separator, cooled to 80 °C, and impurities removed by vacuum distillation at -0.08 MPa for 30 min, to obtain modified dehydroabsic acid ester with an acid value ≤5 mg KOH / g.

[0035] S3. Under nitrogen protection at a flow rate of 20 mL / min, 150 mL of anhydrous n-dodecane and 1.5 g of Span 85 were mixed and stirred at 500 r / min for 15 min to obtain a continuous phase. 5 mL of anhydrous butyl acetate, 2.1 g of matrine, 4.9 g of modified dehydroabietic acid ester, 30 mL of anhydrous xylene, and 11 mL of anhydrous cyclohexanone were mixed and stirred at 500 r / min for 20 min to obtain a core material. 3.0 g of IPDI was added, and the stirring speed was adjusted to 450 r / min for 10 min to obtain an oil phase. The oil phase was slowly added dropwise to the continuous phase at a constant rate of 1 mL / min, and stirred at 500 r / min for 10 min to form a stable oil-in-oil emulsion. 0.9 g of polyetheramine D230 with an amine value of 8.5 meq / g was added... N,N'-Dialyl-1,6-hexanediamine was dissolved in 8 mL of anhydrous butyl acetate and stirred until completely dissolved to obtain an amine mixture. The oil-in-oil emulsion was stirred at 450 r / min and kept at a constant temperature of 40 °C. The amine mixture was added dropwise to the oil-in-oil emulsion at a rate of 0.3 g / min through a 2 mm inner diameter silicone tube. The reaction was carried out at 40 °C for 2 h to form a microcapsule emulsion with the wall material coating the core material. 0.05 g of benzoyl peroxide was dissolved in 5 mL of anhydrous butyl acetate to obtain an initiator. 0.20 g of monoisooctyl phosphate was added to the microcapsule emulsion, and the system was neutralized by stirring at 450 r / min for 10 min. The temperature was then uniformly increased to 68 °C at a rate of 1 °C / min, and the stirring rate was adjusted to 400 r / min. The initiator and 1.0 g of dimethylaminoethyl methacrylate were added, and the reaction was carried out at 68 °C for 1.5 h to complete the graft polymerization. The mixture was cooled to room temperature to obtain pH-responsive microcapsules.

[0036] S4, 2.2g KH-201, 8.31 mL of anhydrous ethanol, and 0.132 mL of deionized water were mixed thoroughly and activated at room temperature in the dark for 60 min. The mixture was then dehydrated under reduced pressure for 25 min at -0.06 MPa in a sealed environment at 35℃ to obtain a KH-201 pre-dispersion. 0.5 g of organobentonite with a fineness ≤325 mesh was mixed with 4.0 mL of a xylene-propylene glycol methyl ether acetate mixture (xylene to propylene glycol methyl ether acetate volume ratio 1:1) and stirred continuously for 20 min to obtain an organobentonite pre-dispersion. 63.8 g of modified polyurethane was mixed with 1.2 mL of a xylene-propylene glycol methyl ether acetate mixture (xylene to propylene glycol methyl ether acetate volume ratio 1:1), and stirred at a constant speed of 500 r / min for 10 min. Then, 8.5 mL of the mixture was added sequentially. KH-201 pre-dispersion, 1.1g sodium polycarboxylate dispersant, and 0.7g polyether-modified polydimethylsiloxane leveling agent were mixed at 500 rpm for 20 min. Then, 1.5g iron oxide red and 2.0g talc were added sequentially, and the mixture was stirred at 500 rpm for 10 min. 4.1g organobentonite pre-dispersion was added, and the mixture was stirred at 500 rpm until the system was completely homogeneous. The stirring speed was then adjusted to 300 rpm, and 12.8g pH-responsive microcapsules were added. The mixture was stirred at 300 rpm for 30 min. 5.0g N3390 curing agent was added, and the mixture was stirred at 300 rpm for 20 min. The stirring speed was then adjusted to 80 rpm and stirred for 15 min to complete defoaming. Finally, the mixture was filtered naturally by gravity using an 80-mesh nylon filter at room temperature to obtain a special composite marine biological protection coating.

[0037] The physical sample of the special composite marine biological-resistant ship coating prepared in this embodiment is shown below. Figure 2 As shown.

[0038] Example 2 like Figure 1 As shown, a method for preparing a special composite marine biological-resistant ship coating includes the following steps: S1. Mix 49g of polytetramethylene ether glycol (molecular weight 950, hydroxyl value 107mgKOH / g), 29.5g of IPDI, 0.10g of bismuth isooctanoate, and 23.0g of anhydrous butyl acetate. Stir at 450r / min for 13min, purge with nitrogen at a flow rate of 18mL / min to maintain a slight positive pressure of 0.02MPa, first raise the temperature to 53℃ and stir for 25min. After the exothermic reaction stabilizes, slowly raise the temperature to 63℃ and stir at a constant temperature for 2.5h to obtain an isocyanate-terminated polyurethane prepolymer. Lower the system temperature to 48℃ and add 0.8g of 1-(2,3-epoxypropyl)-2-methyl -5-nitroimidazole was grafted onto the substrate by stirring at a constant temperature for 2.8 h. 0.28 g of hexamethylene diisocyanate trimer with an isocyanate content of 21.5 wt% and a viscosity of 2500 mPa·s was added. The mixture was heated to 78 °C and aged at a constant temperature for 55 min. 0.37 g of anhydrous n-butanol was added, and the mixture was stirred at 450 r / min for 15 min. The mixture was then distilled under reduced pressure at 73 °C and -0.088 MPa for 40 min. After cooling naturally to room temperature, the mixture was filtered to obtain modified polyurethane.

[0039] S2. Under nitrogen protection at a flow rate of 18 mL / min, 22 g of 1,6-hexanediamine was dissolved in 75 mL of anhydrous ethanol. 15.2 g of sodium hydroxide was added, and the mixture was stirred at 500 rpm until completely dissolved. The temperature was raised to 38 °C, and 30.6 g of allyl chloride was added dropwise at a rate of 0.24 g / min. After the addition was complete, the temperature was raised to 48 °C and the reaction was maintained at this temperature for 5.5 h. After cooling to room temperature, the solid sodium chloride was removed by filtration. The ethanol was recovered by distillation at atmospheric pressure. The solution was then subjected to a reaction at 118 °C and -0.093 MPa. N,N'-diallyl-1,6-hexanediamine was obtained by vacuum distillation under nitrogen protection. 9.5 g of dehydroabsic acid, 2.0 g of ethylene glycol monobutyl ether, and 0.05 g of p-toluenesulfonic acid were added to the reaction vessel under nitrogen protection. The mixture was stirred at 500 rpm and heated to 118 °C for 4 hours. Water generated during the reaction was continuously removed using a water separator. The mixture was then cooled to 78 °C and vacuum distilled at -0.078 MPa for 30 minutes to remove impurities, yielding a modified dehydroabsic acid ester with an acid value ≤5 mg KOH / g.

[0040] S3. Under nitrogen protection at a flow rate of 18 mL / min, 140 mL of anhydrous n-dodecane and 1.4 g of Span 85 were mixed and stirred at 500 r / min for 15 min to obtain a continuous phase. 4.5 mL of anhydrous butyl acetate, 2.0 g of matrine, 4.7 g of modified dehydroabietic acid ester, 28 mL of anhydrous xylene, and 10 mL of anhydrous cyclohexanone were mixed and stirred at 500 r / min for 20 min to obtain a core material. 2.8 g of IPDI was added, and the stirring speed was adjusted to 450 r / min for 10 min to obtain an oil phase. The oil phase was slowly added dropwise to the continuous phase at a constant rate of 0.9 mL / min, and stirred at 500 r / min for 10 min to form a stable oil-in-oil emulsion. 0.85 g of polyetheramine D230 with an amine value of 8.1 meq / g was added to the continuous phase. N,N'-Dialallyl-1,6-hexanediamine was dissolved in 7.5 mL of anhydrous butyl acetate and stirred until completely dissolved to obtain an amine mixture. The oil-in-oil emulsion was stirred at 450 r / min and kept at a constant temperature of 40 °C. The amine mixture was added dropwise to the oil-in-oil emulsion at a rate of 0.28 g / min through a 2 mm inner diameter silicone tube. The reaction was carried out at 40 °C for 2 h to form a microcapsule emulsion in which the wall material encapsulates the core material. 0.045 g of benzoyl peroxide was dissolved in 4.5 mL of anhydrous butyl acetate. An initiator was obtained by adding 0.18 g of monoisooctyl phosphate to the microcapsule emulsion and stirring at 450 r / min for 15 min to neutralize the system. The temperature was then uniformly increased to 66 °C at a rate of 0.8 °C / min, and the stirring rate was adjusted to 400 r / min. The initiator and 0.95 g of dimethylaminoethyl methacrylate were added, and the reaction was carried out at 66 °C for 1.3 h to complete the graft polymerization. The mixture was then cooled to room temperature to obtain pH-responsive microcapsules.

[0041] S4. Mix 2.1g KH-201, 8.11mL anhydrous ethanol, and 0.125mL deionized water thoroughly. Activate by standing at room temperature in the dark for 55min. Then, dehydrate under reduced pressure in a sealed environment at 33℃ and -0.058MPa for 23min to obtain a KH-201 pre-dispersion. Mix 0.48g of organobentonite with a fineness ≤325 mesh with 3.8mL of xylene-propylene glycol methyl ether acetate mixture. The volume ratio of xylene to propylene glycol methyl ether acetate in the mixture was 1:1. The mixture was stirred continuously for 18 min to obtain an organobentonite predispersant. 62.5 g of modified polyurethane was mixed with 1.1 mL of the xylene-propylene glycol methyl ether acetate mixture, where the volume ratio of xylene to propylene glycol methyl ether acetate was 1:1. The mixture was stirred at a constant speed of 450 r / min for 10 min, and then 8.24 mL of the mixture was added sequentially. KH-201 pre-dispersion, 1.05g sodium polycarboxylate dispersant, and 0.65g polyether-modified polydimethylsiloxane leveling agent were mixed at 450 rpm for 18 min. Then, 1.45g iron oxide red and 1.9g talc were added sequentially, and the mixture was stirred at 450 rpm for 8 min. 3.9g organobentonite pre-dispersion was added, and the mixture was stirred at 450 rpm until the system was completely homogeneous. The stirring speed was then adjusted to 300 rpm, and 12.15g pH-responsive microcapsules were added. The mixture was stirred at 300 rpm for 30 min. 4.8g N3390 curing agent was added, and the mixture was stirred at 300 rpm for 20 min. The stirring speed was then adjusted to 80 rpm and stirred for 15 min to complete defoaming. Finally, the mixture was filtered naturally by gravity using an 80-mesh nylon filter at room temperature to obtain a special composite marine biological protection coating.

[0042] Example 3 like Figure 1 As shown, a method for preparing a special composite marine biological-resistant ship coating includes the following steps: S1. Mix 53g of polytetramethylene ether glycol with a molecular weight of 1050 and a hydroxyl value of 118mgKOH / g, 32.5g of IPDI, 0.14g of bismuth isooctanoate, and 27g of anhydrous butyl acetate. Stir at 550r / min for 17min, purge with nitrogen at a flow rate of 22mL / min to maintain a slight positive pressure of 0.02MPa, first raise the temperature to 57℃ and stir for 35min. After the exothermic reaction stabilizes, slowly raise the temperature to 67℃ and stir at a constant temperature for 2.5h to obtain an isocyanate-terminated polyurethane prepolymer. Lower the system temperature to 52℃ and add 0.9g of 1-(2,3-epoxypropyl)-2-methyl- 5-Nitroimidazole was grafted onto a substrate and reacted under constant temperature and stirring for 3.2 h. 0.32 g of hexamethylene diisocyanate trimer with an isocyanate content of 22.5 wt% and a viscosity of 3500 mPa·s was added. The mixture was heated to 82 °C and aged at a constant temperature for 65 min. 0.40 g of anhydrous n-butanol was added, and the mixture was stirred at 550 r / min for 15 min. The mixture was then distilled under reduced pressure at 77 °C and -0.092 MPa for 40 min. After natural cooling to room temperature, the mixture was filtered to obtain modified polyurethane.

[0043] S2. Under nitrogen protection at a flow rate of 22 mL / min, 24.4 g of 1,6-hexanediamine was dissolved in 85 mL of anhydrous ethanol, and 16.8 g of sodium hydroxide was added. The mixture was stirred at 500 r / min until completely dissolved. The temperature was raised to 42 °C, and 30.6 g of allyl chloride was added dropwise at a rate of 0.27 g / min. After the addition was complete, the temperature was raised to 52 °C and the reaction was maintained at this temperature for 6.5 h. After cooling to room temperature, the sodium chloride solid was removed by filtration. The ethanol was recovered by distillation at atmospheric pressure. The solution was then reacted at 127 °C and -0.097 MPa. N,N'-diallyl-1,6-hexanediamine was obtained by vacuum distillation under the following conditions: 10.5 g of dehydroabsic acid, 2.4 g of ethylene glycol monobutyl ether, and 0.07 g of p-toluenesulfonic acid were added to the reaction vessel under nitrogen protection. The mixture was stirred at 500 r / min and heated to 122 °C for 4 h. The water generated in the reaction was continuously removed by a water separator. The temperature was lowered to 82 °C and vacuum distilled at -0.082 MPa for 30 min to remove impurities, yielding modified dehydroabsic acid ester with an acid value ≤5 mg KOH / g.

[0044] S3. Under nitrogen protection at a flow rate of 22 mL / min, 160 mL of anhydrous n-dodecane and 1.6 g of Span 85 were mixed and stirred at 500 r / min for 15 min to obtain a continuous phase. 5.5 mL of anhydrous butyl acetate, 2.2 g of matrine, 5.1 g of modified dehydroabietic acid ester, 32 mL of anhydrous xylene, and 12 mL of anhydrous cyclohexanone were mixed and stirred at 500 r / min for 20 min to obtain a core material. 3.2 g of IPDI was added, and the stirring speed was adjusted to 450 r / min for 10 min to obtain an oil phase. The oil phase was slowly added dropwise to the continuous phase at a constant rate of 1.1 mL / min, and stirred at 500 r / min for 10 min to form a stable oil-in-oil emulsion. 0.95 g of polyetheramine D230 with an amine value of 8.7 meq / g was added to the continuous phase. N,N'-Dialallyl-1,6-hexanediamine was dissolved in 8.5 mL of anhydrous butyl acetate and stirred until completely dissolved to obtain an amine mixture. The oil-in-oil emulsion was stirred at 450 rpm and kept at a constant temperature of 40°C. The amine mixture was added dropwise to the oil-in-oil emulsion at a rate of 0.32 g / min through a 2 mm inner diameter silicone tube. The reaction was carried out at 40°C for 2 hours to form a microcapsule emulsion in which the wall material encapsulates the core material. 0.055 g of benzoyl peroxide was dissolved in 5.5 mL of anhydrous butyl acetate. An initiator was obtained by adding 0.22 g of monoisooctyl phosphate to the microcapsule emulsion and stirring at 450 r / min for 15 min to neutralize the system. The temperature was then uniformly increased to 70 °C at a rate of 1.2 °C / min, and the stirring rate was adjusted to 400 r / min. The initiator and 1.05 g of dimethylaminoethyl methacrylate were added, and the reaction was carried out at 70 °C for 1.7 h to complete the graft polymerization. The mixture was then cooled to room temperature to obtain pH-responsive microcapsules.

[0045] S4, 2.3g KH-201, 8.62 mL of anhydrous ethanol, and 0.139 mL of deionized water were mixed thoroughly and activated at room temperature in the dark for 65 min. The mixture was then dehydrated under reduced pressure for 27 min at 37℃ and -0.062 MPa in a sealed environment to obtain a KH-201 pre-dispersion. 0.52 g of organobentonite with a fineness ≤325 mesh was mixed with 4.2 mL of a xylene-propylene glycol methyl ether acetate mixture (xylene to propylene glycol methyl ether acetate volume ratio 1:1) and stirred continuously for 22 min to obtain an organobentonite pre-dispersion. 65.1 g of modified polyurethane was mixed with 1.3 mL of a xylene-propylene glycol methyl ether acetate mixture (xylene to propylene glycol methyl ether acetate volume ratio 1:1), and stirred at a constant speed of 550 r / min for 10 min. Then, 8.76 mL of the mixture was added sequentially. KH-201 pre-dispersion, 1.15g sodium polycarboxylate dispersant, and 0.75g polyether-modified polydimethylsiloxane leveling agent were mixed at 550 rpm for 22 min. Then, 1.55g iron oxide red and 2.1g talc were added sequentially, and the mixture was stirred at 550 rpm for 12 min. 4.3g organobentonite pre-dispersion was added, and the mixture was stirred at 550 rpm until the system was completely homogeneous. The stirring speed was then adjusted to 300 rpm, and 13.45g pH-responsive microcapsules were added. The mixture was stirred at 300 rpm for 30 min. 5.2g N3390 curing agent was added, and the mixture was stirred at 300 rpm for 20 min. The stirring speed was then adjusted to 80 rpm and stirred for 15 min to complete defoaming. Finally, the mixture was filtered naturally by gravity using an 80-mesh nylon filter at room temperature to obtain a special composite marine biological protection coating.

[0046] Comparative Example 1 A method for preparing a special composite marine biological protection coating for ships differs from that in Example 1 in that only the core material is prepared in step S3 to replace the pH-responsive microcapsules, while the subsequent steps and parameters are the same as in Example 1.

[0047] Comparative Example 2 A method for preparing a special composite marine biological protection coating for ships differs from Example 1 in that the 1-(2,3-epoxypropyl)-2-methyl-5-nitroimidazole is not added in step S1 for grafting reaction, i.e., a modified polyurethane without imidazole pH-responsive units is prepared. The remaining steps and parameters are the same.

[0048] Comparative Example 3 A method for preparing a special composite marine biological protection coating for ships differs from Example 1 in that dimethylaminoethyl methacrylate is not added in step S3, while the remaining steps and parameters are the same.

[0049] Comparative Example 4 A method for preparing a special composite marine biological protection coating for ships differs from Example 1 in that N,N'-diallyl-1,6-hexanediamine is not prepared in step S2, while the remaining steps and parameters are the same.

[0050] Performance testing: Seawater immersion performance test: Q235 low-carbon steel plate with specifications of 150mm×70mm×3mm was selected as the test substrate. The surface of the substrate was sandblasted with 16-24 mesh quartz sand to a cleanliness level of Sa2.5, while controlling the surface roughness to 50μm. The special composite marine biological protection coatings prepared in Examples 1-3 and Comparative Examples 1-4 were sprayed in two coats using air spraying. The dry film thickness of the first coat was controlled to be 40μm. After a 60-minute interval, the second coat was sprayed, and the overall dry film thickness was controlled to be 80μm. The sprayed samples were placed at a temperature of 23℃ and a relative humidity of The paint film was completely cross-linked and cured in a 50% constant temperature and humidity standard environment for 7 days. Simulated natural seawater with a salinity of 35‰ and a pH of 8.2 was prepared. The immersion test chamber was kept at a constant temperature of 25℃ and kept completely dark and sealed. The cured samples were completely immersed 20mm below the surface of the simulated seawater, with a spacing of ≥50mm between the samples and no contact between them. The total immersion time was 180 days. During the test period, the chamber was opened every 30 days to observe and record the blistering level, cracking, percentage of coating peeling area, distribution area of ​​substrate corrosion, and degree of paint film discoloration. The long-term seawater immersion resistance of each group of paint films was comprehensively evaluated.

[0051] Antifouling performance test: 150mm×70mm×3mm Q235 steel plates were sandblasted to Sa2.5 grade with a roughness of 50μm. Special composite antifouling marine coatings prepared in Examples 1-3 and Comparative Examples 1-4 were sprayed onto the plates, with the dry film thickness controlled at 80μm. The plates were cured for 7 days at 23℃ and 50% relative humidity. The cured samples were then fixed at a constant depth of 1.5m in nearshore natural waters at 25°-30°N latitude using a 316L stainless steel bracket, avoiding ocean currents. In the impact zone and the area of ​​friction with the reef, a continuous static hanging plate cycle of 120 days was set up without any human intervention. After the test, all samples were removed and the loose adhering substances on the surface were gently rinsed with clean soft water at room temperature and low pressure (0.2MPa). They were then allowed to air dry completely in a well-ventilated and dark place. Using a high-definition image acquisition system, the proportion of the surface covered by fouling organisms such as microbial film, algae colonies, barnacles, and mussels was counted. Three samples were set up in parallel for each group for testing, and the final fouling coverage rate of each group of samples was calculated as the core indicator for evaluating the antifouling performance.

[0052] Adhesion Test: The sample substrate was a 150mm×70mm×3mm Q235 steel plate, sandblasted to Sa2.5 grade with a roughness of 50μm. Special composite anti-marine biological marine coatings prepared in Examples 1-3 and Comparative Examples 1-4 were sprayed onto the plates, with a dry film thickness controlled at 80μm. The plates were then cured for 7 days in a standard constant temperature and humidity environment of 23℃ and 50% relative humidity. A standard 20mm diameter aluminum alloy test column was used, and a special high-strength epoxy structural adhesive (shear strength ≥20MPa) was used to evenly bond the coating to a smooth area of ​​the paint film. The bonding area was strictly controlled to be 314mm². 2 After bonding, the adhesive is placed in a 23℃ environment and left to stand for 24 hours to ensure complete curing of the colloid without stress residue. The adhesion tester is fully automatic with digital display and applied vertically upward with a uniform and constant tensile rate of 10 mm / min. Five non-interfering test points are selected evenly for each sample and measured in parallel. After removing the maximum and minimum values, the arithmetic mean of the remaining valid data is calculated to characterize the interfacial tensile adhesion strength between each group of paint film and substrate.

[0053] Neutral salt spray corrosion resistance test: The substrate of the samples was uniformly 150mm×70mm×3mm Q235 steel plate, sandblasted to Sa2.5 grade with a roughness of 50μm, and sprayed with the special composite anti-marine biological marine coatings prepared in Examples 1-3 and Comparative Examples 1-4 respectively, with the dry film thickness controlled at 80μm. The samples were cured for 7 days in a standard constant temperature and humidity environment of 23℃ and 50% relative humidity. After curing, two standard cross-shaped scratches intersecting at 60° were prepared on the paint film surface using a special scratching tool. The scratches penetrated to the substrate, and the scratch width was ≤0.2mm. The samples were placed inside the salt spray test chamber at a 20° angle. A 5% sodium chloride aqueous solution was prepared and the pH was adjusted to be stable at 6.7. The temperature inside the test chamber was kept constant at 35℃, and the spray deposition rate was controlled to be stable at 1.5mL / 80cm. 2 The total duration of the uninterrupted continuous spray test was 1000 hours. After the test, the sample was taken out, cleaned and dried at room temperature, and the width of the lateral spread of corrosion and rust on both sides of the cross mark was measured using a digital vernier caliper. The salt spray corrosion protection performance level of each group of coatings was evaluated.

[0054] Table 1. Performance test results of the special composite marine biological-resistant ship coatings prepared in Examples 1-3 and Comparative Examples 1-4

[0055] As shown in Table 1, the adhesion of the special composite anti-marine biological marine coatings prepared in Examples 1-3 is higher than that of Comparative Examples 1-4, and the fouling coverage and the width of the 1000h salt spray scratch corrosion are lower than those of Comparative Examples 1-4. This indicates that the adhesion, antifouling and protective performance of the special composite anti-marine biological marine coatings prepared in Examples 1-3 are better than those of Comparative Examples 1-4.

[0056] Comparative Example 1 uses a core material to replace pH-responsive microcapsules. Modified dehydroabscisic acid ester and matrine antifouling core material are directly and freely mixed into the coating system. Compared to the closed protective structure of the polyurea cross-linked wall material in the examples, the small-molecule polar antifouling active substances lack physical barrier constraints. Under long-term seawater immersion, they rapidly migrate, dissolve, and continuously precipitate along the molecular gaps of the polyurethane coating film. This not only fails to achieve on-demand, controllable release triggered by bio-acid production through the microcapsule pH-responsive mechanism, but also results in excessively rapid consumption of active components in the early stages and complete depletion of antifouling activity in the later stages. This directly leads to large-scale colonization of fouling organisms in the marine environment and a significant increase in fouling coverage. Simultaneously, the freely distributed small-molecule active substances interweave... Disruption of the cross-linking network regularity of polyurethane resin leads to the formation of numerous micro-pore defects within the coating film. Seawater and water vapor can easily penetrate into the coating through these pores, and prolonged immersion causes the pores to gradually expand, resulting in aging phenomena such as blistering and micro-cracking of the coating film. Furthermore, the micro-pores provide a rapid diffusion channel for chloride ions in the salt spray, accelerating the corrosion reaction process of the substrate and significantly widening the rust spread at the scratches. In addition, small molecules tend to accumulate at the interface between the coating film and the substrate, disrupting the mechanical interlocking and chemical bonding between the resin and the substrate, weakening the interfacial bonding strength, and ultimately causing a significant decrease in the adhesion of the coating film. This demonstrates the multiple protective effects of the pH-responsive microcapsule encapsulation structure on the long-term retention of the core material, the density of the coating film structure, and the stability of the interface.

[0057] Comparative Example 2 used imidazole-free grafted polyurethane as the film-forming matrix. Lacking the covalently bonded imidazole pH-responsive functional units on the resin backbone of the previous example, it could not utilize the imidazole groups to undergo protonation reactions in the acidic microregions formed by microbial metabolism, unlike the modified matrix. This prevented the charge reversal switching from the hydrophobic low-energy state to the hydrophilic state on the film surface, resulting in the loss of the dynamic anti-adhesion mechanism that disrupts biofilm adhesion and blocks initial microbial colonization. Consequently, algae, bacteria, and other primary fouling organisms easily adsorbed onto the coating surface and continued to proliferate, significantly weakening the basic antifouling capability. From a molecular structure stability perspective, ordinary polyurethane, without imidazole grafting modification and cross-linking, has poor resistance to seawater hydrolysis of its urethane molecular chains, leading to long-term... In a seawater-immersed environment, molecular chains are prone to hydrolytic breakage, gradually generating micro-cracks that damage the coating's intact anti-corrosion barrier. Corrosive media can continuously penetrate the substrate through these cracks, exacerbating corrosion diffusion in salt spray environments. Simultaneously, unmodified polyurethane exhibits poor compatibility with microcapsules, silane coupling agents, and various additives within the system, easily leading to the formation of micro-interfacial gaps within the coating and further reducing the overall density of the paint film. Furthermore, the insufficient polarity of the unmodified polyurethane resin prevents it from forming a good wetting bond with the sandblasted substrate, resulting in weak interfacial adhesion and ultimately a significant reduction in paint film adhesion. This fully demonstrates that modified polyurethane simultaneously fulfills its core functions of pH-responsive antifouling, hydrolytic stability, and system compatibility.

[0058] Compared to the covalently bonded tertiary amine sensitizing functional layer on the wall material surface of the example, the ungrafted dimethylaminoethyl methacrylate acid sensitizing unit in Comparative Example 3 lacks active sites that can undergo protonation in an acidic environment. When acidic microregions are generated by microbial metabolism on the coating surface, the electrostatic repulsion generated by the protonation of the tertiary amine cannot open the micropore channels of the wall material, and the core material cannot be targeted and controlled to release. The core material can only rely on the natural diffusion of molecules to leak slowly and irregularly. It is impossible to adjust the drug release rate according to the risk of fouling, and there will be defects such as insufficient drug release in the early stage and premature exhaustion of the core material in the later stage, resulting in a serious reduction in long-term antifouling performance. At the microscopic interface level, the acidic sensitizing unit can form hydrogen bonds with the polyurethane matrix, enhancing the interfacial compatibility between the microcapsules and the coating film matrix. Without the sensitizing unit, there is a significant interfacial gap between the microcapsules and the resin matrix. Corrosive media such as water vapor and chloride ions can easily penetrate and diffuse rapidly along the gap, which not only reduces the coating's resistance to salt spray corrosion but also disrupts the overall structural continuity. The interfacial gap also increases internal stress defects in the coating, weakening the overall mechanical bonding strength of the coating film and causing a decrease in adhesion. This fully demonstrates that the acidic sensitizing unit is a key core component for achieving controlled release of microcapsules and enhancing interfacial compatibility and structural stability.

[0059] Comparative Example 4 did not prepare the N,N'-diallyl-1,6-hexanediamine functional intermediate. On the one hand, the secondary amine group in this intermediate molecule can participate in the polyurea crosslinking reaction between IPDI and polyetheramine, improving the network crosslinking structure of the wall material. Without it, the crosslinking density of the wall material is greatly reduced, and the molecular network is loose and scattered. Under long-term seawater immersion, it is prone to water absorption and swelling, causing the wall material to become water-permeable and white, and the structural stability to decrease. This leads to uncontrolled leakage of the core material and shortens the long-term protection period of the pesticide. On the other hand, the exposed carbon-carbon double bond of this intermediate is the only active site for covalent grafting of the acidic sensitizing unit. Without the double bond, the sensitizing unit cannot be firmly bonded to the wall material. On the surface, the microcapsules can only adhere through weak physical adsorption. Under the influence of seawater immersion and long-term aging, they are easily detached and lost, leading to the gradual loss of the pH response function of the microcapsules and the complete loss of their core characteristic of regulating drug release. At the same time, the uneven internal structural stress caused by the swelling of the wall material will further amplify the microscopic defects of the coating, which will not only accelerate the penetration of corrosive media and reduce salt spray resistance, but also destroy the overall mechanical structural stability of the paint film, weaken the bonding strength between the resin and the substrate, and cause a simultaneous decrease in adhesion. This demonstrates the irreplaceable dual role of N,N'-diallyl-1,6-hexanediamine in improving the cross-linking structure of the wall material and providing grafting sites for sensitizing units.

[0060] Comparative Examples 1-4, due to the absence of pH-responsive microcapsules, modified polyurethane, dimethylaminoethyl methacrylate acid sensitizing units, and N,N'-diallyl-1,6-hexanediamine functional intermediates, resulted in the unprotected rapid loss of the antifouling core material, failure of the coating's pH-responsive regulation mechanism, deterioration of the resin's resistance to seawater hydrolysis, and loose cross-linking of the microcapsule wall material, which was prone to swelling and cracking. At the same time, it caused an increase in microscopic defects inside the coating, an expansion of the penetration path of corrosive media, and a significant weakening of the interfacial bonding strength of the substrate. All of these factors contributed to varying degrees of deterioration in adhesion, antifouling, and protective performance.

[0061] The above results demonstrate and describe the basic principles and main features of this application, as well as its advantages.

[0062] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A special composite marine biological protection coating, characterized in that, The coating comprises modified polyurethane, pH-responsive microcapsules, fillers, and additives; The modified polyurethane is obtained by reacting polytetramethylene ether glycol with isophorone diisocyanate to form an isocyanate-terminated polyurethane prepolymer, which is then grafted with 1-(2,3-epoxypropyl)-2-methyl-5-nitroimidazolium and micro-crosslinked with hexamethylene diisocyanate trimer. The pH-responsive microcapsule includes a wall material, a core material, and an acid sensitizing unit grafted onto the outer surface of the wall material; The wall material is obtained by interfacial polymerization of raw materials used to form the wall material; the raw materials used to form the wall material include isophorone diisocyanate, polyetheramine D230 and N,N'-diallyl-1,6-hexanediamine; the N,N'-diallyl-1,6-hexanediamine is obtained by alkylation reaction of 1,6-hexanediamine and allyl chloride; The core material includes modified dehydroabscisic acid ester and matrine; the modified dehydroabscisic acid ester is obtained by esterification reaction of dehydroabscisic acid and ethylene glycol monobutyl ether under the catalysis of p-toluenesulfonic acid; The acidic sensitizing unit is dimethylaminoethyl methacrylate; The filler includes iron oxide red and talc; the additives include silane coupling agent, dispersant, leveling agent, organobentonite and curing agent.

2. The special composite marine biological protection coating according to claim 1, characterized in that, The mass ratio of the modified polyurethane, pH-responsive microcapsules, filler, and additives is (62.5-65.1):(12.15-13.45):(3.35-3.65):(9.08-9.92); the mass ratio of the polytetramethylene ether diol to isophorone diisocyanate is (49-53):(29.5-32.5); the isocyanate-terminated polyurethane prepolymer, 1-(2,3-epoxypropyl)-2-methyl-5-nitroimidazole, and hexamethylene diisocyanate trimer... The mass ratio of the bulk material is (78.5-85.5):(0.8-0.9):(0.28-0.32); the mass ratio of the raw material, core material and acid sensitizing unit used to form the wall material is (4.5-5.1):(6.7-7.3):(0.95-1.05); the mass ratio of isophorone diisocyanate, polyetheramine D230 and N,N'-diallyl-1,6-hexanediamine is (2.8-3.2):(0.85-0.95):(0.85-0.95).

3. The special composite anti-marine biological marine coating according to claim 1, characterized in that, The mass ratio of 1,6-hexanediamine to allyl chloride is (22-24.4):30.6; the mass ratio of modified dehydroabietic acid ester to matrine is (4.7-5.1):(2.0-2.2); the mass ratio of dehydroabietic acid, ethylene glycol monobutyl ether, and p-toluenesulfonic acid is (9.5-10.5):(2.0-2.4):(0.05-0.07); and the mass ratio of iron oxide red to talc is (1.45-1.55). The mass ratio of the silane coupling agent, dispersant, leveling agent, organobentonite, and curing agent is (2.1-2.3):(1.05-1.15):(0.65-0.75):(0.48-0.52):(4.8-5.2); the silane coupling agent is KH-201; the dispersant is sodium polycarboxylate; the leveling agent is polyether-modified polydimethylsiloxane; and the curing agent is N3390.

4. The special composite anti-marine biological marine coating according to claim 1, characterized in that, The polytetramethylene ether glycol has a molecular weight of 950-1050 and a hydroxyl value of 107-118 mgKOH / g; the hexamethylene diisocyanate trimer has an isocyanate content of 21.5wt%-22.5wt% and a viscosity of 2500-3500 mPa·s; the modified dehydroabietic acid ester has an acid value ≤5 mgKOH / g; the polyetheramine D230 has an amine value of 8.1-8.7 meq / g; and the organobentonite has a fineness ≤325 mesh.

5. A method for preparing a special composite marine biological-resistant ship coating as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Mix polytetramethylene ether glycol, isophorone diisocyanate, bismuth isooctanoate and anhydrous butyl acetate, purge with nitrogen, and react with a first heating and a second heating to obtain an isocyanate-terminated polyurethane prepolymer. After cooling, add 1-(2,3-epoxypropyl)-2-methyl-5-nitroimidazole and react. Add hexamethylene diisocyanate trimer and heat to mature. Add anhydrous n-butanol and distill under reduced pressure and filter to obtain modified polyurethane. S2. Under nitrogen protection, 1,6-hexanediamine, sodium hydroxide and anhydrous ethanol were mixed, heated and allyl chloride was added dropwise. The reaction was continued at a higher temperature. After filtration and vacuum distillation, N,N'-diallyl-1,6-hexanediamine was obtained. Dehydroabietic acid, ethylene glycol monobutyl ether and p-toluenesulfonic acid were mixed, heated a second time and vacuum distilled to obtain modified dehydroabietic acid ester. S3. Span 85 and anhydrous n-dodecane are mixed to obtain a continuous phase; matrine, anhydrous butyl acetate, modified dehydroabietic acid ester, anhydrous xylene, and anhydrous cyclohexanone are mixed to obtain a core material; isophorone diisocyanate is added to obtain an oil phase; the oil phase is added dropwise to the continuous phase to form an oil-in-oil emulsion; polyetheramine D230 and N,N'-diallyl-1,6-hexanediamine are dissolved in anhydrous butyl acetate to obtain an amine mixture, which is added dropwise to the oil-in-oil emulsion to obtain a microcapsule emulsion in which the wall material coats the core material; monoisooctyl phosphate is added, the temperature is raised, an initiator and dimethylaminoethyl methacrylate are added, and the reaction is carried out to obtain pH-responsive microcapsules; S4. Mix the modified polyurethane with xylene-propylene glycol methyl ether acetate mixture, then add KH-201 pre-dispersion, sodium polycarboxylate, and polyether-modified polydimethylsiloxane in sequence. Stir, add iron oxide red and talc, continue stirring, add organobentonite pre-dispersion, pH-responsive microcapsules, and N3390, mix evenly, and filter to obtain a special composite marine biological protection coating.

6. The method for preparing a special composite marine biological-resistant ship coating according to claim 5, characterized in that, In step S1, the mass ratio of polytetramethylene ether glycol, bismuth isooctanoate, and anhydrous butyl acetate is (49-53):(0.1-0.14):(23-27); the flow rate of nitrogen gas is 18-22 mL / min; the first heating reaction step is as follows: heating to 53-57℃ and stirring at 450-550 r / min for 25-35 min; the target temperature for the second heating is 63-67℃. The target temperature for cooling is 48-52℃; the reaction time is 2.8-3.2h; the heating and ripening step is: heating to 78-82℃ and holding at that temperature for 55-65min; the mass ratio of hexamethylene diisocyanate trimer to anhydrous n-butanol is (0.28-0.32):(0.37-0.4); the conditions for vacuum distillation are: temperature 73-77℃, pressure -0.088~-0.092MPa.

7. The method for preparing a special composite marine biological-resistant ship coating according to claim 5, characterized in that, In step S2, the flow rate of the nitrogen protection is 18-22 mL / min; the mass-to-volume ratio of 1,6-hexanediamine, sodium hydroxide, and anhydrous ethanol is (22-24.4) g : (15.2-16.8) g : (75-85) mL; the target temperature for heating is 38-42℃; the dropping rate is 0.24-0.27 g / min; the heating reaction step is: heating to 48-52℃ and reacting at a constant temperature for 5.5-6.5 h; the conditions for vacuum distillation are: temperature 118-127℃ and pressure -0.093 to -0.097 MPa; the target temperature for the second heating is 118-122℃; after the second heating, the conditions for vacuum distillation are: temperature 78-82℃ and pressure -0.078 to -0.082 MPa.

8. The method for preparing a special composite marine biological-resistant ship coating according to claim 5, characterized in that, In S3, the mass-to-volume ratio of Span 85 and anhydrous n-dodecane is (1.4-1.6) g: (140-160) mL; the mass-to-volume ratio of matrine, the first added anhydrous butyl acetate, anhydrous xylene, and anhydrous cyclohexanone is (2.0-2.2) g; (4.5-5.5) mL: (28-32) mL: (10-12) mL; the rate at which the oil phase is added to the continuous phase is 0.9-1.1 mL / min; and the mass-to-volume ratio of polyetheramine D230, monoisooctyl phosphate, and the second added anhydrous butyl acetate is (0.85-0.95) g: (0.18-0.22) g: (7.5-8.5) mL.

9. The preparation method of a special composite marine biological-resistant ship coating according to claim 5, characterized in that, In step S3, the rate of dropwise addition to the oil-in-oil emulsion is 0.28-0.32 g / min; the target temperature for heating is 66-70℃, and the heating rate is 0.8-1.2℃ / min; the initiator is prepared by dissolving 0.045-0.055 g of benzoyl peroxide in 4.5-5.5 mL of anhydrous butyl acetate to obtain the initiator; the reaction temperature is 66-70℃, and the reaction time is 1.3-1.7 h.

10. The method for preparing a special composite marine biological-resistant ship coating according to claim 5, characterized in that, In step S4, the mass-to-volume ratio of the modified polyurethane to the xylene-propylene glycol methyl ether acetate mixture is (62.5-65.1) g : (1.1-1.3) mL; the volume ratio of xylene to propylene glycol methyl ether acetate in the xylene-propylene glycol methyl ether acetate mixture is 1:1; the mass-to-volume ratio of the modified polyurethane, organobentonite predispersant, and KH-201 predispersant is (62.5-65.1) g : (3.9-4.3) g : (8.24-8.76) mL; the preparation step of the KH-201 predispersant is: 2.1-2.3 g Mix KH-201, 8.11-8.62 mL of anhydrous ethanol and 0.125-0.139 mL of deionized water, let stand for 55-65 min in the dark, and then dehydrate under reduced pressure in a closed environment at 33-37℃ and -0.058~-0.062 MPa for 23-27 min to obtain KH-201 predispersant.

11. The method for preparing a special composite marine biological-resistant ship coating according to claim 5, characterized in that, In step S4, the stirring speed is 450-550 r / min, and the stirring time is 18-22 min; the stirring speed is 450-550 r / min, and the stirring time is 8-12 min; the preparation steps of the organobentonite predispersant are as follows: 0.48-0.52 g of organobentonite is mixed with 3.8-4.2 mL of xylene-propylene glycol methyl ether acetate mixture, wherein the volume ratio of xylene to propylene glycol methyl ether acetate in the xylene-propylene glycol methyl ether acetate mixture is 1:1, and the mixture is stirred continuously for 18-22 min to obtain the organobentonite predispersant; the filtration medium is an 80-mesh nylon filter screen.

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