A cationic polycarbonate resin, a method for preparing the same, and an application thereof

Abstract

The application discloses a cationic polycarbonate resin and a preparation method and application thereof. The cationic polycarbonate resin contains the following structural units: wherein R1, R2 and R3 are independently selected from H, methyl, ethyl or propyl; R4 is selected from R5 and R6 are independently selected from H, methyl, ethyl, propyl, -CH2NH2, -CH2CH2NH2 or -CH2CH2CH2NH2; n is a positive integer, n>=100, x=0.7-0.9, y=0.1-0.3, x+y=1, and z=0, 1 or 2. The cationic polycarbonate resin prepared by the application has a surface degradation mechanism, a paint film linear thinning, can continuously update the surface, and always keeps smooth and complete, so that marine organisms are difficult to adhere.

Description

Technical Field

[0001] This invention belongs to the field of coatings, specifically relating to a cationic polycarbonate resin, its preparation method, and its application. Background Technology

[0002] Marine equipment and engineering facilities have long faced the problem of marine biofouling. Biofouling deposits formed on the surfaces of offshore facilities / platforms can cause significant economic losses and safety hazards. For example, biofouling increases the frictional resistance of the hull, leading to increased energy consumption; acidic substances secreted by marine organisms exacerbate equipment corrosion, shortening its lifespan and increasing maintenance costs; biofouling can cause instability of offshore buoys or platforms, clog pipes and filters, and severely affect the water intake efficiency of facilities such as nuclear power plants.

[0003] Since 2008, self-polishing, fouling-removing, and biodegradable antifouling coatings from Wuxi have gradually become the focus of research and development in the marine antifouling field. Currently, the mainstream Wuxi acrylic self-polishing coating uses copper, zinc, and silicon instead of organotin. Its antifouling mechanism is similar to organotin coatings; the resin's side groups contain hydrolyzable or ion-exchangeable segments that can gradually detach from the coating surface under water erosion, releasing the internal antifouling agent. This type of coating is mainly suitable for ocean-going vessels, where the route, speed, and the ratio of stationary periods significantly affect its antifouling performance. This is because its hydrolysis and polishing speed heavily depend on water erosion; under static or low-speed conditions, its antifouling performance is unsatisfactory. Furthermore, the main chain of most acrylic polymers can only be removed through a hydrophobic-to-hydrophilic transition, swells in water, and cannot be degraded. The removed fragments easily form microparticles (microplastics) in the ocean, causing "white pollution." Emerging antifouling coatings, particularly those designed for fouling and desorption, often use silicone and / or organofluorine compounds as film-forming resins. Their low surface energy, elasticity, and smooth surface make it difficult for marine organisms to adhere, and even if some organisms do adhere, they are easily swayed away by high-speed water flow. However, these coatings generally have low mechanical strength and limited adhesion, and their application is limited by stringent application requirements and high cost.

[0004] Although the industry has developed many antifouling coating products in Wuxi, there is still much room for improvement in their performance. For example, high antifouling agent content leads to high toxicity, incomplete resin degradation, and excessive reliance on the relative shear of water flow for surface self-cleaning, which limits their antifouling effectiveness for static marine facilities such as offshore drilling platforms and wind turbine foundations.

[0005] To address these issues, some researchers have attempted to develop biodegradable antifouling coatings. These coatings use biodegradable polyesters, such as polycaprolactone (PCL) or polylactic acid (PLA), as the film-forming material. Through continuous degradation and peeling of the coating layer, biofouling organisms cannot adhere to unstable surfaces. However, polyester degradation is often rapid and uneven. During degradation, pores easily form within the resin, and the surface becomes rough. This can potentially accelerate excessive degradation of the coating and the release of antifouling agents, hindering long-term antifouling performance. Summary of the Invention

[0006] The purpose of this invention is to provide a cationic polycarbonate resin capable of surface layer-by-layer degradation, its preparation method, and its application.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0008] A cationic polycarbonate resin, wherein the cationic polycarbonate resin comprises the following structural units:

[0009]

[0010] R1, R2, and R3 are each independently selected from H, methyl, ethyl, or propyl;

[0011] R4 is selected from:

[0012] R5 and R6 are each independently selected from H, methyl, ethyl, propyl, -CH2NH2, -CH2CH2NH2 or -CH2CH2CH2NH2;

[0013] n is a positive integer, n≥100, x=0.7~0.9, y=0.1~0.3, x+y=1, z=0, 1 or 2.

[0014] The cationic polycarbonate resin has a unique main chain structure that enables it to undergo surface degradation. When surface degradation occurs, the molecular chains of the material's surface layer break and decompose into oligomers or monomers, while the internal chain segments remain unchanged, maintaining their mechanical strength and morphological stability. Over time, the outer layer is continuously degraded, dissolved, and peeled off, but the newly formed surface layer remains smooth and compact, with only the layer thickness decreasing linearly.

[0015] In one preferred embodiment, the molar content of the structural unit containing R4 accounts for 10% to 30% of the total structural unit content.

[0016] Experiments have shown that the content of cationic groups determines the hydrophilicity / hydrophobicity of the polymer. A higher content results in an overly hydrophilic resin, affecting the integrity of the coating's morphology in seawater; a lower content results in an overly hydrophobic resin, leading to slower degradation and consequently affecting polishing and antifouling performance. Therefore, the molar content of cationic groups in this invention is limited to 10%–30%.

[0017] A method for preparing a cationic polycarbonate resin involves using a hydroxyl-containing compound as an initiator to copolymerize a double-bonded cyclic carbonate and a six-membered cyclic carbonate under anhydrous and oxygen-free conditions to obtain a functional polymer; then, a thiol hydrochloride containing an amino group is subjected to post-polymerization modification with the functional polymer through a "thiol-olefin" click chemical reaction to obtain the cationic polycarbonate resin.

[0018] After modification with amino-containing thiols hydrochloride, positively charged amine groups are introduced into the side groups of the polymer, making it easier to interact with negatively charged bacteria (similar to the antibacterial mechanism of antimicrobial peptides); at the same time, the amine group also endows the polymer with a certain degree of hydrophilicity, which is beneficial to maintaining its appropriate degradation rate.

[0019] The cationic polycarbonate resin prepared by this invention has a unique main chain structure that enables it to undergo surface degradation. When surface degradation occurs, the molecular chains of the material's surface layer break and decompose into oligomers or monomers, while the internal chain segments remain unchanged, maintaining their mechanical strength and morphological stability. Over time, the outer layer is continuously degraded, dissolved, and peeled off, but the newly formed surface layer remains smooth and compact, with only the layer thickness decreasing linearly.

[0020] In one preferred embodiment, the six-membered ring carbonate monomer is one or more of 1,3-dioxane-2-one (TMC), 2,2-dimethyltrimethylene cyclic carbonate (DTC), or 5-methyl-5-propyl-1,3-dioxane-2-one (MPC) and their respective derivatives.

[0021] In one preferred embodiment, the six-membered ring carbonate monomer is preferably TMC, with a molar content of 70-90%. As the most commonly used and relatively inexpensive synthetic monomer for biodegradable polycarbonate, TMC mainly plays a role in regulating the hydrophobicity and flexibility of the main chain.

[0022] In one preferred embodiment, the double-bonded cyclic carbonate is one or more of 5-methyl-5-allyloxycarbonyl-1,3-dioxane-2-one (MAC), 5-allyloxy-1,3-dioxane-2-one (ATMC), 2-(methacrylamido)trimethylene carbonate (MATC), and 5-methyl-5-acryloyloxy-1,3-dioxane-2-one (AC) and their respective derivatives.

[0023] In one preferred embodiment, the cyclic carbonate containing double bonds is preferably one of MAC and ATMC. This is because, in contrast, the acrylic (acrylamide) double bonds in both AC and MATC are highly reactive and have poor stability at high temperatures. Therefore, if the reaction conditions are not properly controlled during the ring-opening copolymerization process and post-polymerization modification, gel formation due to double bond self-polymerization can easily occur, leading to reaction failure. In contrast, the double bonds in MAC and ATMC are allyl groups, which are difficult to undergo self-polymerization but can react with thiols. Therefore, from a production perspective, selecting MAC and ATMC ensures the stable performance of the produced cationic polycarbonate.

[0024] In one preferred embodiment, the ring-opening polymerization is carried out at a reaction temperature of 20–150°C for a reaction time of 12–36 h.

[0025] In one preferred embodiment, the hydroxyl-containing compound includes one or more of benzyl alcohol, isopropanol, and propylene glycol.

[0026] In one preferred embodiment, the ring-opening polymerization is further accompanied by a catalyst, the catalyst comprising one or a combination of two of stannous octoate and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD).

[0027] In one preferred embodiment, the amino-containing thiol hydrochloride is one or more of 2-(diethylamino)ethanethiol hydrochloride (DEAET), 2-(dimethylamino)ethanethiol hydrochloride (DMAET), cysteine ​​hydrochloride (CA), 3-mercapto-1-propylamine hydrochloride (APT), 2-[(3-aminopropyl)amino]ethanethiol dihydrochloride (APAE), and their respective derivatives.

[0028] In one preferred embodiment, the amino-containing thiol hydrochloride is one or more of cysteamine hydrochloride (CA), 3-mercapto-1-propylamine hydrochloride (APT), and 2-[(3-aminopropyl)amino]ethanethiol dihydrochloride (APAE). They share the common characteristic of containing a primary amine group. After post-polymerization modification, cationic polycarbonates containing primary amines exhibit stronger antibacterial properties than tertiary amines. This is because the amino (NH2) functional group in the primary amine molecule is attached to the end of the major carbon atom, making it easier for it to interact with acidic sites in the microbial cell wall or cell membrane. This interaction may lead to the rupture of the microbial cell wall or the destruction of the cell membrane, thereby achieving an antibacterial effect. Enhanced antibacterial properties of the antifouling resin mean that less toxic antifouling agent can be added to the coating, and the amount of antifouling resin added to the coating is relatively low, achieving green environmental protection and cost savings. More preferably, the modifier is cysteamine hydrochloride (CA) because it is the cheapest and has the best performance.

[0029] In one preferred embodiment, the amount of the amino-containing thiols hydrochloride added is 1 to 5 times the molar amount of the cyclic carbonate monomer containing the double bond.

[0030] In one preferred embodiment, a second initiator is further added to the thiol-ene click chemistry reaction, the second initiator including one or more of 2,2-dimethoxy-2-phenylacetophenone (DMPA), azobisisobutyronitrile (AIBN), diazabicyclo(DBU) or 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and their respective derivatives.

[0031] To avoid double bond residue in the molecule, improve the degree of modification, and control the consumption of initiator, the amount of the second initiator is 0.1 to 2 times the molar content of the amino-containing thiols hydrochloride.

[0032] In one preferred embodiment, the method for preparing the cationic polycarbonate resin,

[0033] A functional polymer was prepared by ring-opening polymerization of a mixture of cyclic carbonate monomers containing double bonds and six-membered cyclic carbonate monomers, using benzyl alcohol as the first initiator and stannous octoate as the catalyst, and reacting at 90-110℃ for 10-15 hours. A cationic polycarbonate resin was then prepared by adding an amino-containing thiol hydrochloride to the functional polymer and carrying out a thiol-olefin click chemistry reaction under ultraviolet light.

[0034] In one preferred embodiment, the synthetic route of the cationic polycarbonate resin is as follows:

[0035]

[0036] An antifouling coating comprising the cationic polycarbonate resin.

[0037] In one preferred embodiment, the antifouling coating, by weight, comprises 15-30 parts of cationic polycarbonate resin, 0-10 parts of rosin, 2-10 parts of synthetic antifouling agent, 0-1 part of natural antifouling agent, 0-30 parts of cuprous oxide, 20-35 parts of pigments and fillers, 0.5-1 part of dispersant, 0.5-1 part of defoamer, 0-1 part of leveling agent, 0.5-2 parts of plasticizer, 0.5-1 part of thixotropic agent, and 10-18 parts of organic solvent.

[0038] The surface-degrading static antifouling coating prepared with cationic polycarbonate resin as the main film-forming substance is specifically an antifouling coating that can achieve surface-degrading properties in seawater without the need for water rinsing.

[0039] In one preferred embodiment, the synthetic antifouling agent is one or more of 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), copper pyridinethione (CPT), zinc pyridinethione (ZPT), or 2-(p-chlorophenyl)-3-cyano-4-bromo-5-trifluoromethyl-pyrrole (ECONEA). Considering both cost and long-lasting antifouling effect, a combination of DCOIT and CPT is preferred, added at a mass ratio of 1:2-4.

[0040] In one preferred embodiment, the natural antifouling agent is one or more of tannic acid, gallic acid, epigallocatechin, epicatechin gallate, and their respective derivatives. The phenolic structure in the natural antifouling agent can interact with the amine groups in the cationic resin through electrostatic and hydrogen bonding. Under alkaline conditions, the biodegradable polycarbonate with primary amine cations can also undergo partial chemical cross-linking with phenol via a Schiff base reaction, thereby improving the coating's stability and mechanical strength.

[0041] In one preferred embodiment, the pigment or filler may be one or more of iron oxide red, zinc oxide, talc, and sepiolite.

[0042] In one preferred embodiment, the dispersant is at least one of BYK-9076, BYK-110, BYK-W965, and DS-9104.

[0043] In one preferred embodiment, the thixotropic agent is a polyamide wax.

[0044] In one preferred embodiment, the defoamer is at least one of BYK-A501, BYK-066N, and BYK-A535.

[0045] In one preferred embodiment, the leveling agent is at least one of BYK-545 and BYK-320.

[0046] In one preferred embodiment, the plasticizer is at least one of petrolatum, stearic acid 1801, and chlorinated paraffin.

[0047] In one preferred embodiment, the solvent is one or more of xylene, 1-methoxy-2-propanol, n-butanol, butyl acetate, and propylene glycol methyl ether acetate.

[0048] The present invention does not have any special requirements for the preparation method of the surface layer-by-layer degradation static antifouling coating; it can be operated according to the conventional coating preparation process.

[0049] The present invention also claims protection for the application of the antifouling coating on the surface of marine engineering facilities.

[0050] In one preferred embodiment, the marine engineering facilities include ships, offshore platforms, offshore wind power, surface photovoltaics, or marine ranches.

[0051] The unique degradation mechanism of cationic polycarbonate resin is further explained below:

[0052] Polymer degradation can be broadly classified into two types based on its mechanism: bulk degradation and surface degradation. Most common biodegradable polyesters exhibit bulk degradation, such as PCL and PLA. Bulk degradation refers to a homogeneous degradation behavior in which both the internal and external components of the polymer degrade simultaneously. Figure 1 a) During degradation, molecular chains continuously break, leading to a rapid decrease in mechanical strength. When a certain critical point is reached, the material exhibits significant weight loss. Furthermore, this degradation process often involves autocatalytic acceleration. Because degradation fragments within the material cannot diffuse into the surrounding environment in a timely manner, the abundant acidic products further promote ester bond hydrolysis, resulting in a faster internal degradation rate than the external degradation. This leads to the formation of numerous pores within the material, exhibiting uneven degradation and severe damage to the material's integrity and strength during the degradation process.

[0053] In contrast, polycarbonate tends to degrade on the surface. For example... Figure 1 As shown in b, when surface degradation occurs, the molecular chains of the material's surface layer break and decompose into oligomers or monomers, while the internal chain segments remain unchanged, maintaining stable mechanical strength and morphology. Over time, the outer layer is continuously degraded, dissolved, and peeled off, but the newly formed surface layer remains smooth and compact, with only a linear reduction in thickness. Therefore, polycarbonate is superior to traditional degradable polymers such as PCL and PLA in terms of antifouling coating materials. However, unmodified polycarbonate is highly hydrophobic and degrades slowly, meaning that the self-renewal rate of the coating surface after film formation is low, which is detrimental to static antifouling. This invention prepares cationic degradable polycarbonate through ring-opening copolymerization and thiol-olefin click chemistry modification, improving the resin's hydrophilicity and enabling the coating to possess suitable degradation rate and static antifouling efficacy. Furthermore, polycarbonate mimics the net positive charge characteristic of most antimicrobial peptides; its cationic structure can adsorb onto the surface of negatively charged marine fouling microorganisms such as bacteria, altering cell membrane permeability and thus exhibiting antibacterial activity.

[0054] It is important to note that conventional zinc acrylate / copper / silane ester self-polishing resins themselves are not biodegradable. The self-polishing process essentially relies on the reaction of zinc carboxylic acid or copper with sodium in seawater. +The process involves the exchange of water to form sodium carboxylate (silane esters undergo ester hydrolysis in weakly alkaline seawater to produce carboxyl groups before forming sodium salts). The resin molecular chains gradually transform from hydrophobic to hydrophilic, and under the scouring of water flow, the coating surface continuously swells and is removed. Two factors are noteworthy during this process: a) The transformation from hydrophobic to hydrophilic molecular chains does not involve macromolecular degradation, resulting in uncontrollable fragment size and potential microplastic pollution in the marine environment; b) The entire polishing process (i.e., the removal of hydrophilic sodium carboxylate from the surface) heavily depends on the relative speed of the water flow and the hull. Polishing and antifouling performance will be significantly affected in conditions such as relatively calm currents or static facilities. In contrast, the cationic polycarbonate of this invention is biodegradable and undergoes surface degradation. The degradation products can detach from the coating surface through diffusion, completely independent of water scouring, making it environmentally friendly.

[0055] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0056] I. The cationic biodegradable polycarbonate synthesized in this invention has amine groups on its side chains that mimic the cationic structure of antimicrobial peptides, giving the resin itself antimicrobial properties and enabling it to kill bacteria and other fouling microorganisms in the ocean. This biomimetic structural design differs from the technical route of directly grafting antifouling agents onto the resin molecular chain, effectively reducing the toxicity of antifouling agents and aligning with the future development trend of low-toxicity and environmentally friendly antifouling coatings. Thiol modification enhances the hydrophilicity of the polycarbonate, giving it a suitable degradation rate. Furthermore, the electrostatic and hydrogen bonding between the cationic polycarbonate and anionic rosin / natural polyphenols achieves physical cross-linking of the coating, enhancing the mechanical properties of the paint film.

[0057] II. The surface degradation characteristics of polycarbonate allow the newly formed surface to remain smooth and intact. This smooth surface, which degrades layer by layer from the surface inward, makes it difficult for marine organisms to adhere, providing excellent antifouling effects for marine equipment in static environments. Biodegradable polyesters such as PLA and PCL mostly undergo bulk degradation, which can easily cause porosity within the coating, hindering the maintenance of mechanical strength and morphology during the polishing stage. Furthermore, the newly formed rough surface may actually promote the adhesion of fouling organisms.

[0058] Third, antifouling coatings made with cationic biodegradable polycarbonate as the main film-forming resin, combined with other components, not only provide long-lasting antifouling performance but also avoid the potential marine microplastic problems associated with traditional self-polishing antifouling coatings. The aliphatic polycarbonate backbone can be fully hydrolyzed and enzymatically degraded by seawater and marine organisms, ultimately producing small molecules such as carbon dioxide and water, making it green, environmentally friendly, and non-toxic. In contrast, traditional acrylic antifouling coatings rely excessively on seawater erosion for self-polishing; the C-C bonds in the resin backbone are non-degradable, and the fragments released through the hydrophobic-to-hydrophilic transition contribute to white pollution in the marine environment.

[0059] Fourth, existing modified polycarbonates cannot be used for marine antifouling. For example, prior art CN111423571 discloses a biodegradable zwitterionic polycarbonate. The zwitterionic polycarbonate prepared by this method is a homopolymer. Its zwitterionic structure determines its poor solubility. It can only be dispersed in water by forming self-assembled colloids and cannot be dissolved in common organic solvents. Therefore, it is difficult to apply in the coatings field. In fact, since current research on biodegradable polycarbonates is mainly focused on the biomedical field, and in order to obtain good biocompatibility and meet the requirements of drug loading and other applications, the reported biodegradable polycarbonates are often highly hydrophilic, and most of them can be directly dissolved in water. Kazuki Fukushima reported a methoxy-modified cationic polycarbonate in his paper (Biomater. Sci., 2019, 7, 2288). This cationic polycarbonate is highly hydrophilic and can be completely dissolved in water. However, the areas where antifouling coatings are applied are often submerged in seawater for extended periods. Even if the polycarbonate is prepared into a coating material using complex techniques, its strong hydrophilicity will cause it to be quickly washed away by the water flow, making it unsuitable for use in antifouling coatings.

[0060] The cationic biodegradable polycarbonate prepared by this invention achieves a balance between hydrophilic and hydrophobic properties by introducing the hydrophobic comonomer TMC and strictly controlling the content of cationic groups. Attached Figure Description

[0061] Figure 1 This is due to the unique degradation mechanism of cationic polycarbonate resins;

[0062] Figure 2 This invention provides a synthetic route for preparing cationic biodegradable polycarbonate.

[0063] Figure 3 The proton NMR spectrum of cationic biodegradable polycarbonate 1 and its proton peak assignment;

[0064] Figure 4 In vitro antibacterial performance test of cationic biodegradable polycarbonate 1 coating;

[0065] Figure 5 Cytotoxicity test of cationic biodegradable polycarbonate 1 coating;

[0066] Figure 6 This is a SEM cross-sectional image of a cationic biodegradable polycarbonate coating in static artificial seawater at different immersion times. Detailed Implementation

[0067] The present invention will be further described and illustrated below with reference to the accompanying drawings. The present invention can be better understood through the following embodiments. However, those skilled in the art will readily understand that the specific material ratios, process conditions, and results described in the embodiments are for illustrative purposes only and should not, and will not, limit the present invention as described in detail in the claims. Unless otherwise specified, the methods described in this invention are conventional methods, and the materials described are all available from publicly available commercial sources.

[0068] Example 1

[0069] Synthesis of cationic biodegradable polycarbonate 1

[0070] according to Figure 2 The synthetic route used benzyl alcohol as the first initiator and stannous octoate as the catalyst, and the polymerization reaction was carried out in a toluene solution at 100°C. A mixture of monomers MAC (2.01 g, 10 mmol) and TMC (9.18 g, 90 mmol) was placed in a thoroughly dried Schlenk apparatus. The reaction vessel was sealed, frozen with liquid nitrogen, and then evacuated. The thawing process was repeated three times with nitrogen purging. Next, toluene (20 mL) was rapidly injected into the Schlenk flask under magnetic stirring. After the monomers were thoroughly mixed, benzyl alcohol (1 mL, 0.5 M) and a stannous octoate-toluene solution (6 mL, 0.1 M) were added via syringe. Polymerization was carried out at 100°C for 12 hours, and a white solid was obtained by precipitation in methanol. It was then dissolved in DMF, and the modifier cysteine ​​hydrochloride (CA) (5.72 g, 50 mmol) and the second initiator 2,2'-dimethoxy-2-phenylacetophenone (DMPA, 5.07 g, 19.78 mmol) were added. The solution was then exposed to ultraviolet light (λmax = 365 nm, 20 mW / cm²). 2 The modification reaction was carried out for 2 hours. After the reaction was completed, the solvent was removed by rotary evaporation, yielding a yellow viscous solid. This solid was dissolved in about 20 mL of methanol, precipitated three times in ethanol, and dried under vacuum at 50 °C to constant weight to obtain cationic biodegradable polycarbonate 1. Its chemical structure was characterized by nuclear magnetic resonance (NMR). Figure 3 This demonstrates the successful preparation of cationic biodegradable polycarbonate 1, whose molecular weight is calculated to be 35,000 Da by 1H NMR spectroscopy.

[0071] To test the antibacterial properties of the resin, stainless steel sheets (a negative control without antibacterial properties) and stainless steel sheets coated with the test cationic biodegradable polycarbonate 1 were evaluated against *Escherichia coli* and *Staphylococcus aureus* using a dilution plating method. Specifically, cationic biodegradable polycarbonate 1 was dissolved in dichloromethane and then coated onto the surface of stainless steel sheets, serving as the experimental group; the stainless steel sheets were the negative control group, and the polyvinyl chloride sheets with added organotin were the positive control group. L929 cells were cultured at 6.0 × 10⁻⁶.4 The above three groups of surfaces were inoculated at a concentration of 10 cells / well and then cultured in a medium containing 10% fetal bovine serum and 1% antibiotics (37°C, 5% CO2 humid atmosphere).

[0072] like Figure 4 As shown, the stainless steel sheet coated with cationic biodegradable polycarbonate 1 had significantly fewer bacterial colonies than the control group, with only a few colonies present, indicating that the cationic biodegradable polycarbonate has antibacterial ability.

[0073] MTT assays revealed no significant difference in cell viability between L929 cells cultured on cationic degradable polycarbonate 1 and the negative control group for 1 and 3 days, thus essentially confirming that cationic degradable polycarbonate 1 has low cytotoxicity. Figure 5 ).

[0074] Example 2

[0075] Synthesis of cationic biodegradable polycarbonate 2

[0076] according to Figure 2 The synthetic route used benzyl alcohol as the first initiator and stannous octoate as the catalyst, and the polymerization reaction was carried out in a toluene solution at 100°C. A mixture of monomers MAC (2.01 g, 10 mmol) and TMC (9.18 g, 90 mmol) was placed in a thoroughly dried Schlenk apparatus. The reaction vessel was sealed, frozen with liquid nitrogen, and then evacuated. The thawing process was repeated three times with nitrogen purging. Next, toluene (20 mL) was rapidly injected into the Schlenk flask under magnetic stirring. After the monomers were thoroughly mixed, benzyl alcohol (1 mL, 0.5 M) and a stannous octoate-toluene solution (6 mL, 0.1 M) were added via syringe. Polymerization was carried out at 100°C for 12 hours, and a white solid was obtained by precipitation in methanol. The polycarbonate was then dissolved in DMF, and the modifier 2-(diethylamino)ethanethiol hydrochloride (DEAET) (4.12 g, 25 mmol) and the second initiator diazabicyclo(DBU, 1.07 g, 6.98 mmol) were added. The reaction was carried out at 50 °C for 12 h. After the reaction was completed, the solvent was removed by rotary evaporation, yielding a yellow viscous solid. This solid was dissolved in approximately 20 mL of methanol, precipitated three times in ethanol, and dried under vacuum at 50 °C to constant weight to obtain cationic biodegradable polycarbonate 2. Its chemical structure was characterized by nuclear magnetic resonance (NMR), confirming successful preparation. Cytotoxicity tests were conducted using the same method, confirming that cationic biodegradable polycarbonate 2 also exhibited low cytotoxicity.

[0077] Example 3

[0078] Synthesis of cationic biodegradable polycarbonate 3

[0079] Ring-opening polymerization was carried out using isopropanol as the first initiator and stannous octoate as the catalyst at a reaction temperature of 150 °C. A mixture of monomers 5-allyloxy-1,3-dioxane-2-one ATMC (3.21 g, 16 mmol) and TMC (8.51 g, 84 mmol) was placed in a thoroughly dried Schlenk apparatus. The reaction vessel was sealed, frozen in liquid nitrogen, and then evacuated. The thawing process was repeated three times with nitrogen purging. Next, DMSO (20 mL) was rapidly injected into the Schlenk flask under magnetic stirring. After the monomers were thoroughly mixed, isopropanol (0.25 mL, 0.5 M) and a stannous octoate-toluene solution (6 mL, 0.1 M) were added via syringe. The reaction vessel was then polymerized in an oil bath at 150 °C for 8 hours under magnetic stirring. The polymerization product was diluted in tetrahydrofuran, and the modifier 2-(dimethylamino)ethanethiol hydrochloride DMAET (2.84 g, 20 mmol) and the second initiator AIBN (1.28 g, 7.79 mmol) were added. The solution was refluxed at 70 °C for 12 h. After the reaction, the solvent was removed by rotary evaporation, yielding a yellow viscous solid. This solid was dissolved in approximately 10 mL of THF, purified by ethanol dialyze, and dried under vacuum at 50 °C to constant weight to obtain cationic biodegradable polycarbonate 3. Its chemical structure was characterized by nuclear magnetic resonance, confirming successful preparation. Cytotoxicity tests were performed using the same method, confirming that cationic biodegradable polycarbonate 3 also exhibited low cytotoxicity.

[0080] Example 4

[0081] Synthesis of cationic biodegradable polycarbonate 4

[0082] Polymerization was carried out in a chloroform solution at 30°C using propylene glycol as the first initiator and TBD as the catalyst. A mixture of monomers 5-allyloxy-1,3-dioxane-2-one ATMC (3.21 g, 16 mmol) and TMC (8.51 g, 84 mmol) was placed in a thoroughly dried Schlenk apparatus. The reaction vessel was sealed, frozen in liquid nitrogen, and then evacuated. The thawing process was repeated three times with nitrogen purging. Next, chloroform (20 mL) was rapidly injected into the Schlenk flask under magnetic stirring. After the monomers were thoroughly mixed, propylene glycol (0.8 mL, 0.5 M) and TBD-chloroform solution (2 mL, 0.2 M) were added via syringe. The reaction vessel was then polymerized in a water bath at 30°C for 36 hours under magnetic stirring. The polymerization product was diluted in tetrahydrofuran, followed by the addition of the modifier cysteine ​​hydrochloride CA (5.4 g, 48 mmol) and the second initiator AIBN (0.79 g, 4.8 mmol). The solution was reacted at 80 °C for 8 h. After the reaction, the product was purified by dialysis with acetone and dried under vacuum at 50 °C to constant weight to obtain cationic biodegradable polycarbonate 4.

[0083] Its chemical structure was characterized using nuclear magnetic resonance (NMR), confirming successful preparation. Cytotoxicity testing using the same method confirmed that cationic biodegradable polycarbonate 4 also exhibits low cytotoxicity.

[0084] To verify the layer-by-layer degradation behavior of the resin, cationic biodegradable polycarbonate 1-4 was dissolved in an organic solvent and coated onto the surface of a stainless steel sheet. The sheet was then immersed in artificial seawater for static soaking. Scanning electron microscopy was used to photograph the cross-section of the coating on days 0, 15, and 30 of the immersion to observe the degradation behavior and thickness loss. Figure 6 It can be seen that cationic biodegradable polycarbonate exhibits typical layer-by-layer degradation from the outside in (surface degradation), with a linear decrease in thickness, while the coating interior remains uniform and intact, without pores or defects. Therefore, it can be predicted that marine fouling organisms cannot adhere to this continuously degrading surface; even if a small amount adheres, it will detach due to coating degradation. This pure resin coating exhibits a thickness loss rate of approximately 3.9 μm / month in a static environment, which is essentially the same as the polishing rate of acrylic self-polishing antifouling coatings in dynamic polishing tests, indicating promising static antifouling potential.

[0085] To compare the effect of the type of cationic groups on the antibacterial properties of cationic polycarbonate antifouling resins, four cationic polycarbonates (1-4) with a molar content of 20% cationic groups were prepared. These were dissolved in organic solvents and then dip-coated onto stainless steel sheets to form films. The antibacterial properties of the four materials were evaluated according to QB / T 2591-2003 standard, and the corresponding antibacterial rates were calculated. The test results are shown in Table 1.

[0086] Table 1. Antibacterial properties of cationic biodegradable polycarbonates with different amine groups

[0087]

[0088] The test results in the table show that cationic polycarbonates 2 and 3, containing tertiary amine groups, have inferior antibacterial properties compared to cationic polycarbonates 1 and 4, containing primary amine groups. This indicates that antibacterial properties are related to the type of modifier, and resins obtained using CA containing primary amines as modifiers exhibit the best antibacterial properties. Of course, all cationic polycarbonates prepared in this invention possess antibacterial effects, and therefore can all inhibit the proliferation and kill marine microorganisms to a certain extent.

[0089] Example 5

[0090] 20 parts of cationic biodegradable polycarbonate, 1 part of rosin, 1 part of thixotropic agent polyamide wax, 1 part of dispersant BYK-9076, 0.5 parts of defoamer BYK-141, and 15 parts of butyl acetate were mixed at 1000 rpm for 20 min. Then, 20 parts of cuprous oxide, 10 parts of zinc oxide, 4 parts of iron oxide red, 3 parts of sepiolite powder, 5 parts of talc, 4 parts of CPT, 1 part of DCOIT, and 0.5 parts of natural antifouling agent tannic acid were added. The mixture was first dispersed at 1000 rpm for 15 min, then abrasive was added, and the mixture was sand-milled at 3000 rpm for 2 h. After filtration, 1 part of plasticizer stearic acid 1801 and 0.5 parts of leveling agent BYK-545 were added, and the mixture was stirred at 1000 rpm until homogeneous to obtain the antifouling coating.

[0091] Example 6

[0092] 25 parts of cationic biodegradable polycarbonate, 2.5 parts of rosin, 0.5 parts of thixotropic polyamide wax, 1 part of dispersant BYK-W965, 1 part of defoamer BYK-141, and 18 parts of mixed organic solvent (xylene: n-butanol = 4:1) were stirred at 1000 rpm for 20 min. Then, 20 parts of cuprous oxide, 5 parts of zinc oxide, 3 parts of iron oxide red, 5 parts of sepiolite powder, 10 parts of talc, 4 parts of CPT, 1 part of DCOIT, and 0.5 parts of natural antifouling agent tannic acid were added. The mixture was first dispersed at 1000 rpm for 15 min, then abrasive was added, and the mixture was sand-milled at 3000 rpm for 2 h. After the process, the mixture was filtered, and 1.5 parts of plasticizer chlorinated paraffin were added and stirred at 1000 rpm until homogeneous to obtain the antifouling coating.

[0093] Example 7

[0094] 30 parts of cationic biodegradable polycarbonate, 3.5 parts of rosin, 0.5 parts of thixotropic agent polyamide wax, 1 part of dispersant BYK-9076, 0.5 parts of defoamer BYK-660N, and 12 parts of butyl acetate were mixed at 1000 rpm for 20 min. Then, 28 parts of cuprous oxide, 15 parts of zinc oxide, 2 parts of iron oxide red, 3 parts of sepiolite powder, 2 parts of CPT, 0.5 parts of DCOIT, and 0.5 parts of natural antifouling agent gallic acid were added. The mixture was first dispersed at 1000 rpm for 15 min, then abrasive was added, and the mixture was sand-milled at 3000 rpm for 2 h. After filtration, 1.5 parts of plasticizer chlorinated paraffin and 0.5 parts of leveling agent BYK-545 were added, and the mixture was stirred at 1000 rpm until homogeneous to obtain the antifouling coating.

[0095] Example 8

[0096] 15 parts of cationic biodegradable polycarbonate, 4 parts of rosin, 1 part of thixotropic agent polyamide wax, 1 part of dispersant BYK-9076, 0.5 parts of defoamer BYK-141, and 10 parts of organic solvent propylene glycol methyl ether acetate were stirred at 1000 rpm for 20 min. Then, 15 parts of zinc oxide, 4 parts of iron oxide red, 10 parts of talc, 5 parts of sepiolite powder, 8 parts of CPT, 2 parts of DCOIT, and 1 part of natural antifouling agent tannic acid were added. The mixture was first dispersed at 1000 rpm for 15 min, followed by the addition of abrasive and sand milling at 3000 rpm for 2 h. After filtration, 2 parts of plasticizer petrolatum and 1 part of leveling agent BYK-545 were added, and the mixture was stirred at 1000 rpm until homogeneous to obtain the antifouling coating.

[0097] The components of Examples 5-8 are listed in Table 2:

[0098] Table 2 shows the formulation of antifouling coatings in Examples 5-8 and Comparative Example 1.

[0099] raw material components Example 5 Example 6 Example 7 Example 8 Comparative Example 1 Cationic biodegradable polycarbonate 1 20 0 0 0 0 Cationic biodegradable polycarbonate 2 0 25 0 0 0 Cationic biodegradable polycarbonate 3 0 0 30 0 0 Cationic biodegradable polycarbonate 4 0 0 0 15 0 A commercially available biodegradable polycarbonate 0 0 0 0 25 rosin 2 5 5 4 5 Polyamide wax 1 0.5 0.5 1 0.5 dispersant 1 1 1 1 1 Defoamer 0.5 1 0.5 0.5 1 Leveling agent 0.5 0 0.5 1 0 Cuprous oxide 20 20 28 0 20 Zinc oxide 10 5 15 15 5 Iron oxide red 4 3 2 4 3 talcum powder 5 10 0 10 10 sepiolite powder 3 5 3 5 5 plasticizer 1 1.5 1.5 2 1.5 CPT 4 4 2 8 4 Natural stain repellent 0.5 0.5 0.5 1 0.5 DCOIT 1 1 0.5 2 1 organic solvents 15 18 12 10 18

[0100] Note: The commercially available biodegradable polycarbonate used in Comparative Example 1 is a TMC monomer homopolymer with the same molecular weight as the cationic polycarbonate 1 of this invention, but its side groups do not contain cationic groups. Its main chain structure is as follows:

[0101]

[0102] In the formula: n = 350.

[0103] The results of the performance tests on the above coatings are as follows:

[0104] Comparative Example 2: A commercially available acrylic zinc self-polishing anti-fouling coating.

[0105] Comparative Example 3: A commercially available acrylic silane ester antifouling coating.

[0106] A six-month shallow-sea plating test was conducted in a certain sea area according to GB / T5370-2007 standard, and the polishing rate test was conducted according to GB / T31411-2015 standard. The static degradation rate (thickness loss) of the coating was determined as follows: different antifouling coatings were applied to epoxy resin boards, which were then immersed in natural seawater, and the thickness loss of the coating was characterized periodically using a microscope. The test results are shown in Table 3.

[0107] Table 3 Performance of each embodiment and comparative example

[0108] Test Project Example 5 Example 6 Example 7 Example 8 Comparative Example 1 Comparative Example 2 Comparative Example 3 Monthly polishing rate (μm) 6.4 5.8 6.7 5.2 1.5 3.3 2.8 Monthly degradation rate (μm) 5.2 4.4 5.1 3.9 0.8 1.1 0.6 Antifouling rating 98 97 97 95 80 85 89 Flexibility (mm) 2 2 2 2 3 2 2 Pencil hardness H H H H B H 2H

[0109] It is not difficult to see from Table 3 and the attached figures that:

[0110] Examples 5-8 all achieved antifouling scores of 95 or higher in a six-month shallow-sea siding experiment, demonstrating significantly better static antifouling performance than the two commercially available self-polishing acrylic antifouling coatings. This is likely due to the following factors: a. Examples 1-4 exhibited faster degradation rates than comparative examples 2 and 3 in the static degradation rate test. This is because the cationic polycarbonate of this invention possesses unique surface degradation behavior in seawater, enabling surface self-renewal without relying on external water flow. b. In the polishing rate test (dynamic), water flow accelerated the shedding of resin from the coating surface (polishing). The thickness loss rate of all samples increased compared to the degradation rate, with Examples 5-8 showing linear thinning exceeding 4 μm / month. This rapid surface renewal prevents the adhesion of fouling organisms and facilitates the removal of biofouling. In contrast, the acrylic self-polishing antifouling coatings had a slower polishing rate, resulting in poor performance (<90 points) in the six-month siding experiment, with some fouling organism adhesion on the surface. c. The cationic polycarbonate of this invention has a certain antibacterial ability, and when combined with a specific antifouling agent, it further improves the antifouling score.

[0111] Comparative Example 1 and Example 6 have the same formulation except for the film-forming resin; however, their performance differs significantly. Firstly, both the static degradation rate and dynamic polishing rate of Comparative Example 1 are much lower than those of Examples 5-8. This is because the commercially available biodegradable polycarbonate has not undergone cationic modification, resulting in strong hydrophobicity and slower degradation and renewal rates. Furthermore, this commercially available polycarbonate does not contain amine groups, preventing it from interacting with the polyphenols in natural antifouling agents. Consequently, the coating has low pencil hardness, the film is softer at room temperature, and its mechanical properties are inferior to those of Example 6.

[0112] Example 9

[0113] To compare the effect of cationic group content on the antifouling performance of coatings, cationic biodegradable polycarbonate 1 with amine contents of 0%, 5%, 15%, 25%, and 35% was synthesized by adjusting the y-value in the molecular formula of cationic biodegradable polycarbonate 1. This involved adjusting the amount of modifier added according to the molar ratio, and the synthesis method was the same as in Example 1. Five antifouling coatings, labeled A through E, were prepared according to the formulation in Example 5 of Table 1. The antifouling performance of these coatings was tested in a shallow sea area for three months, according to GB / T5370-2007 standard.

[0114] Table 4. Performance of antifouling paint prepared from cationic biodegradable polycarbonate 2 with different cationic group contents.

[0115]

[0116] Analysis of the test results in Table 4 shows that the antifouling coatings prepared with cationic group content of 15% and 25% exhibit the best antifouling performance. This indicates that the antifouling coatings prepared with a cationic group content of 10-30% as specified in this invention have superior antifouling performance. This is because when the cationic amine content is too low, the polymer is highly hydrophobic, the degradation rate is slow, and the surface renewal rate of the coating is slower than the adhesion rate of fouling organisms, resulting in poor antifouling effect. Conversely, when the cationic amine content is too high, the coating is highly hydrophilic, even capable of dissolving in water, making the coating unstable and easily washed away by water flow. Only by maintaining a good hydrophilic / hydrophobic balance can a moderately degradable and stable antifouling coating be obtained.

Claims

1. A cationic polycarbonate resin, characterized in that, The cationic polycarbonate resin is composed of the following structural units: ； R1, R2, and R3 are each independently selected from H, methyl, ethyl, or propyl; R4 is selected from: ; R5 and R6 are each independently selected from H, methyl, ethyl, propyl, -CH2NH2, -CH2CH2NH2 or -CH2CH2CH2NH2; n is a positive integer, n≥100, x=0.7~0.9, y=0.1~0.3, x+y=1, z=0, 1 or 2.

2. The cationic polycarbonate resin according to claim 1, characterized in that, The molar content of the structural unit containing R4 accounts for 10% to 30% of the total structural unit content.

3. The method for preparing the cationic polycarbonate resin according to claim 1 or 2, characterized in that, The process involves using a hydroxyl-containing compound as an initiator to copolymerize a double-bonded cyclic carbonate and a six-membered cyclic carbonate under anhydrous and oxygen-free conditions to obtain a functional polymer. Then, the amino-containing thiol hydrochloride is subjected to post-polymerization modification with the functional polymer through a "thiol-olefin" click chemical reaction to obtain the cationic polycarbonate resin.

4. The preparation method according to claim 3, characterized in that, The six-membered ring carbonate includes one or more of 1,3-dioxane-2-one, 2,2-dimethyltrimethylene ring carbonate, or 5-methyl-5-propyl-1,3-dioxane-2-one.

5. The preparation method according to claim 3, characterized in that, The cyclic carbonate containing double bonds includes one or more of 5-methyl-5-allyloxycarbonyl-1,3-dioxane-2-one, 5-allyloxy-1,3-dioxane-2-one, 2-(methacrylamido)trimethylene carbonate, and 5-methyl-5-acryloyloxy-1,3-dioxane-2-one.

6. The preparation method according to claim 3, characterized in that, The cyclic carbonate containing double bonds accounts for 10-30% of the total molar content of the functional polymer.

7. The preparation method according to claim 3, characterized in that, The hydroxyl-containing compounds include one or more of benzyl alcohol, isopropanol, and propylene glycol.

8. The preparation method according to claim 3, characterized in that, The ring-opening copolymerization also includes a catalyst, which comprises one or two of stannous octoate and 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

9. The preparation method according to claim 3, characterized in that, The amino-containing thiol hydrochloride is one or more of 2-(diethylamino)ethanethiol hydrochloride, 2-(dimethylamino)ethanethiol hydrochloride, cysteine ​​hydrochloride, 3-mercapto-1-propanehydrochloride, and 2-[(3-aminopropyl)amino]ethanethiol dihydrochloride.

10. The preparation method according to claim 3, characterized in that, The amount of the amino-containing thiol hydrochloride added is 1 to 5 times the molar content of the cyclic carbonate containing double bonds.

11. An antifouling coating, characterized in that, Includes the cationic polycarbonate resin as described in claim 1 or 2.

12. The antifouling coating according to claim 11, characterized in that, The antifouling coating, by weight, comprises 15-30 parts cationic polycarbonate resin, 0-10 parts rosin, 2-10 parts synthetic antifouling agent, 0-1 part natural antifouling agent, 0-30 parts cuprous oxide, 20-35 parts pigments and fillers, 0.5-1 part dispersant, 0.5-1 part defoamer, 0-1 part leveling agent, 0.5-2 parts plasticizer, 0.5-1 part thixotropic agent, and 10-18 parts organic solvent.

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