Modified tea saponin-based antifouling emulsion, preparation method and application thereof

Abstract

The application discloses a modified tea saponin-based antifouling emulsion and a preparation method and application thereof. The method comprises the following steps: first, unsaturated modified tea saponin monomers are prepared by grafting long-chain unsaturated acyl chlorides, acid anhydrides or isocyanates with C12-C22 onto tea saponin molecules through a one-pot method; and then, the unsaturated modified tea saponin monomers are subjected to semi-continuous emulsion copolymerization with styrene, (methyl) acrylate and functional carboxylic acid monomers. In the application, the active sites of tea saponin are anchored to the main chain of the polymer through a covalent bond, and the steric repulsion force generated by long carbon chains in seawater and the lipid affinity penetration effect on the cell membranes of attached organisms are combined, so that the physical anti-adhesion and biochemical inhibition are realized in a synergistic antifouling manner. The application overcomes the defects of traditional physical additive antifouling agents, such as easy loss and short antifouling period, does not need to release heavy metals, has the advantages of long-term, green and simple process, and has a wide application prospect in the field of marine antifouling.

Description

Technical Field

[0001] This invention relates to the field of functional polymer emulsions and marine antifouling coatings. Specifically, it relates to a functional emulsion based on unsaturated monomer modified tea saponin, its preparation method, and the application of the emulsion in constructing a green, environmentally friendly, long-lasting anti-bioadhesion marine antifouling coating. Background Technology

[0002] Marine biofouling refers to the harmful attachment of marine organisms such as barnacles, oysters, mussels, and seaweed to the hull and surfaces of ships and marine facilities. This not only increases ship drag (up to 60%) and fuel consumption, but also accelerates the electrochemical corrosion of facilities.

[0003] Currently, early organotin antifouling agents have been banned, and existing cuprous oxide antifouling agents have cumulative toxicity to marine ecosystems. Physically added natural antifouling agents (such as capsaicin) are washed away very quickly by seawater, resulting in a short antifouling period (usually less than 3 months).

[0004] Studies have shown that tea saponins have significant hemolytic effects and biotoxicity on mollusks (such as golden apple snails and mussels). The mechanism lies in the fact that tea saponins specifically bind to cholesterol on biological membranes, disrupting cell membrane permeability and causing the death or avoidance of attached larvae. However, if tea saponins are directly used to prepare emulsions through blending, the problem of easy loss also exists. Therefore, modifying tea saponins to prepare a technology that can "lock" the active sites of tea saponins onto the polymer backbone through chemical bonds is key to achieving a novel, durable, efficient, and green anti-marine pollution technology, and promoting the integration of high-value utilization of tea oil industry waste with green marine pollution prevention. Summary of the Invention

[0005] To address the aforementioned problems, this invention aims to solve the issues existing in the prior art by providing a modified tea saponin-based antifouling emulsion, its preparation method, and its applications. This invention "anchors" the active sites of tea saponin to the polymer backbone through chemical bonds, and combines this with the synergistic effect of long-chain flexible olefins to achieve efficient, long-lasting, and environmentally friendly marine antifouling. This emulsion achieves "covalent anchoring" of the antifouling component by converting tea saponin into polymerizable macromonomers, allowing it to participate in the formation of the polymer chain. This solves the problem of active ingredient loss and enhances antifouling performance by introducing long-chain flexible groups to generate a unique dynamic steric hindrance effect.

[0006] The specific starting point of this invention is to introduce unsaturated double bonds by utilizing the hydroxyl groups on the sugar ring of tea saponin, transforming it into a "tea saponin macromonomer," which is then embedded into the styrene or acrylate backbone via free radical polymerization. This not only achieves "covalent anchoring" of the active sites but also enhances the self-emulsifying stability of the emulsion by utilizing the surface activity of tea saponin.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: On the one hand, this invention proposes a modified tea saponin-based antifouling emulsion, obtained by free radical copolymerization of monomers comprising the following weight percentages: Unsaturated modified tea saponin monomer: 3% - 20%; Styrene: 10% - 35%; (Meth)acrylate monomers: 45% - 70%; Functional carboxylic acid monomers: 0% - 5%; The sum of the weight percentages of all components is 100%; The unsaturated modified tea saponin monomer is prepared by reacting the hydroxyl groups in the tea saponin molecule with acyl chlorides, acid anhydrides, or isocyanates containing carbon-carbon double bonds.

[0008] Furthermore, the degree of substitution (DS) of the unsaturated modified tea saponin monomer is 0.1-1.2. The DS is determined by titration or proton nuclear magnetic resonance spectroscopy (NMR). 1 H-NMR integration method.

[0009] Furthermore, the acyl chloride, acid anhydride, or isocyanate containing carbon-carbon double bonds used for modifying tea saponin has an alkyl chain of a long-chain flexible olefin of C12-C22, preferably oleyl chloride, erucic acid chloride, or maleic anhydride.

[0010] Furthermore, the (meth)acrylate monomers are selected from one or more combinations of methyl methacrylate, butyl acrylate, isooctyl acrylate, and hydroxyethyl methacrylate; the functional carboxylic acid monomers are selected from one or more combinations of acrylic acid, methacrylic acid, and maleic acid half ester.

[0011] Furthermore, the emulsion has a solid content of 40%-55%, a viscosity of 200-500 mPa·s, an average particle size of 80-150 nm, and a minimum film-forming temperature (MFT) of 5-15 °C.

[0012] On the other hand, the present invention also proposes a method for preparing a modified tea saponin-based antifouling emulsion as described above, comprising the following steps: S1: One-pot synthesis of unsaturated modified tea saponin monomer: In an anhydrous aprotic solvent, with organotin or tertiary amine as catalyst, under inert gas protection, tea saponin is reacted with acyl chloride, acid anhydride or isocyanate containing carbon-carbon double bonds at 0-75℃ to obtain a reaction solution containing unsaturated modified tea saponin monomer. This reaction solution is used directly for the next polymerization step without separation and purification. S2: Emulsion polymerization: A semi-continuous seeded emulsion polymerization process is adopted. The reaction solution obtained in step S1 is used as the organic phase component and mixed with styrene, (meth)acrylate monomers and functional carboxylic acid monomers. Pre-emulsification is carried out in the presence of an emulsifier to obtain a pre-emulsion. Then, under the action of an initiator, the pre-emulsion is added to the reactor in a semi-continuous dropwise manner for free radical copolymerization. After the reaction is completed, the temperature is lowered to room temperature and the pH is adjusted to 7.5-9.5. The mixture is filtered and discharged to obtain the modified tea saponin-based antifouling emulsion.

[0013] Furthermore, in step S1, the catalyst is triethylamine, pyridine, or 4-dimethylaminopyridine (DMAP); the reaction temperature is 50-75°C, and the reaction time is 5-8 hours.

[0014] Furthermore, in step S2, the reaction temperature for free radical copolymerization is 70-90℃; the initiator is ammonium persulfate, potassium persulfate, etc.; and the emulsifier is sodium dodecyl sulfate (SDS) or alkylphenol polyoxyethylene ether (OP-10), etc.

[0015] Furthermore, the method also includes dehydrating the tea saponin raw material before step S1, specifically by vacuum drying the tea saponin at 80°C for 4 hours to control the moisture content of the system to be less than 0.1%.

[0016] The preparation method of the modified tea saponin-based antifouling emulsion of the present invention is as follows: 1. Synthesis of reactive long-chain tea saponin monomers (TS-LC) (1) Dehydration treatment: The natural tea saponin was vacuum dried at 80°C for 4 hours to remove the bound water and ensure that the moisture content of the system was less than 0.1% to prevent the hydrolysis of acyl chloride and acid anhydride monomers.

[0017] (2) Reaction environment: Under nitrogen protection, tea saponin is dissolved in anhydrous DMF or ethyl acetate. Triethylamine or pyridine is used as an acid absorbent, and the system temperature is lowered to 0-10℃.

[0018] (3) Gradient heating: Slowly add long-chain monomers (such as oleoyl chloride) for 1-2 hours. After the addition is complete, slowly raise the temperature to 60-75℃ and keep the temperature constant for 5-8 hours.

[0019] (4) Purification: The reaction solution is precipitated with deionized water, the organic layer is separated, and the solvent is removed by vacuum distillation at 45°C to obtain the reactive long-chain tea saponin intermediate, which is the unsaturated modified tea saponin monomer.

[0020] 2. Preparation of modified tea saponin-based emulsion This invention employs conventional emulsion polymerization to achieve monomer copolymerization through one-step or stepwise feeding. The specific steps are as follows: (1) Preparation of pre-emulsion: The modified tea saponin monomer, styrene, acrylate monomer and functional carboxylic acid monomer described in this invention are mixed evenly and added to an aqueous solution containing emulsifier. The mixture is then mechanically stirred or emulsified under high shear to obtain a stable pre-emulsion.

[0021] (2) Polymerization reaction: Add some bottom water and initiator to the reactor. Heat to the reaction temperature (70-90℃) while stirring, and start adding the above pre-emulsion and the remaining initiator.

[0022] Feeding method: Any of the following methods can be used: one-time feeding, batch feeding, or continuous dripping. Reaction maintenance: Maintain the reaction temperature until polymerization is complete; the reaction time is usually 3-6 hours.

[0023] (3) Post-treatment: After the reaction is completed, the system temperature is lowered to room temperature, and the pH value of the system is adjusted to 7.5-9.5 with an alkali neutralizing agent (such as ammonia or organic amine). The modified tea saponin-based antifouling emulsion is obtained by filtering the material.

[0024] The present invention also proposes the application of the modified tea saponin-based antifouling emulsion as described above or the modified tea saponin-based antifouling emulsion prepared by the preparation method as described above in the preparation of marine antifouling coatings, for inhibiting the adhesion of barnacles, mussels, oysters and algae to the surface of marine vessels.

[0025] Compared with the prior art, the technical solution provided by the present invention has the following significant advantages: (1) Achieving long-lasting, non-release antifouling: This invention "anchors" the active structure of tea saponin to the polymer backbone through covalent bonds, fundamentally solving the defect of easy loss of traditional physical additive antifouling agents. The antifouling active sites are slowly exposed to the surface through the micro-erosion of the coating itself or the movement of molecular chain segments, rather than relying on coating wear or antifouling agent release. The antifouling life is expected to reach more than 2 years, far exceeding that of existing physical additive coatings.

[0026] (2) Synergistic antifouling mechanism with excellent effect: This invention constructs a dual synergistic antifouling system of "physical anti-adhesion + biochemical inhibition".

[0027] Biochemical inhibition: Grafted long-chain flexible olefins (such as C18 oleoyl groups) endow tea saponin molecules with lipid affinity, enabling them to effectively penetrate the phospholipid bilayer of attached organisms (barnacles, mussel larvae), interfere with the cross-linking and curing process of their protein glue, and achieve efficient inactivation.

[0028] Physical anti-adhesion: The tea saponin residues on the polymer backbone are highly polar and can form a stable hydration layer on the coating surface, greatly reducing the adhesion strength of bioadhesives secreted by marine organisms. The grafted ultra-long flexible alkyl chains (C12-C22) generate dynamic conformational swings (Brownian motion) in seawater, producing significant steric repulsion forces, which dynamically hinder the initial adhesion of barnacle and mussel larvae.

[0029] (3) Innovative process, green and efficient: This invention uses a "one-pot" method to synthesize polymerizable monomers, eliminating the need for separation and purification of intermediates, which greatly simplifies the process, reduces solvent use and energy consumption, lowers production costs, and makes it easier to scale up industrially. At the same time, the surface activity of tea saponin itself allows it to act as a co-emulsifier in emulsion polymerization, which helps to reduce the amount of external emulsifier used and improve the water resistance of the coating.

[0030] (4) Renewable raw materials and environmentally friendly: The tea saponin used in this invention comes from the waste (tea seed cake) after processing camellia oil, realizing the high-value utilization of agricultural waste. The entire system does not contain heavy metals (such as copper and tin) or other persistent organic pollutants, and is a truly green and environmentally friendly anti-fouling technology that meets the increasingly stringent environmental regulations worldwide.

[0031] (5) Excellent overall performance: The emulsion prepared by this invention has a high solid content (40-55%), a moderate particle size (80-150nm), and a low film-forming temperature (5-15℃), which facilitates construction. The resulting coating has strong adhesion to the substrate and is resistant to seawater erosion. Its overall performance meets the practical application requirements of marine engineering coatings.

[0032] In summary, this invention utilizes the synergistic modification of tea saponin, a green biomass resource, with long-chain flexible olefins to achieve long-term stability of the antifouling coating in complex marine environments. This technology boasts high added value and is easily mass-produced. The physical-chemical synergistic antifouling mechanism exhibited by the coating effectively addresses the industry pain points of traditional coatings, such as rapid self-polishing wear and high environmental risks. Therefore, this invention has broad market potential in marine engineering, ocean-going vessels, and underwater facility protection. The implementation of this achievement will not only generate significant economic benefits but also strongly drive the technological upgrading and comprehensive resource utilization of the tea oil industry, providing solid technical support for the green development of the marine economy. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the chemical structure of the tea saponin molecule used in this invention.

[0034] Figure 2 This is a schematic diagram of the chemical structure of the C18-oleoyl modified tea saponin monomer obtained in Example 1 of the present invention.

[0035] Figure 3This is a schematic diagram of the chemical structure of the modified tea saponin-based antifouling emulsion copolymer prepared in Example 1 of the present invention. It shows that after the C18-oleoyl modified tea saponin monomer is copolymerized with other monomers, the active fragment of tea saponin is suspended on the polymer backbone in the form of side groups. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0037] Example 1: C18-Oleyl-Modified Tea Saponin Antifouling Emulsion (TS-C18) This embodiment exemplifies the specific process of preparing a C18 long-chain (oleoyl) modified tea saponin-based antifouling emulsion using a conventional semi-continuous emulsion polymerization method.

[0038] 1. One-pot synthesis of polymerizable tea saponin monomer (TS-C18): 100g of tea saponin, dried under vacuum at 80℃ for 4 hours (moisture content <0.1%), was dissolved in 300g of anhydrous N,N-dimethylformamide (DMF). The reaction system was placed under nitrogen protection and stirred until completely dissolved. 1.5g of triethylamine was added as a catalyst and acid absorbent, and the system was cooled to 5℃. Under vigorous stirring, 28g of oleoyl chloride was slowly added dropwise over 1 hour. After the addition was complete, the temperature was slowly raised to 70℃ and the reaction was maintained at this temperature for 6 hours. After the reaction was complete, a brownish-yellow reaction solution containing unsaturated modified tea saponin monomer (TS-C18) was obtained. After sampling and purification, it was... 1 H-NMR analysis showed that its degree of substitution (DS) was approximately 0.8. The reaction solution obtained in this step was used directly for the next polymerization step without separation.

[0039] like Figure 1 As shown, tea saponin is a natural triterpenoid saponin compound whose molecule consists of a hydrophilic sugar ring (glucose, galactose, etc.) and a hydrophobic triterpenoid aglycone. Multiple primary and secondary hydroxyl groups are distributed on the sugar ring; these hydroxyl groups are the key reactive sites for grafting long-chain flexible olefins or unsaturated anhydrides in this invention. This invention utilizes the reactivity of these hydroxyl groups to introduce C12-C22 long-chain or unsaturated anhydride structures into the tea saponin molecule through esterification, thereby endowing it with copolymerization activity and lipid affinity.

[0040] like Figure 2As shown, a hydroxyl group in the tea saponin molecule undergoes an esterification reaction with oleyl chloride to generate C18-oleoyl-modified tea saponin (TS-C18), introducing a long C18 chain containing double bonds onto the tea saponin backbone. In the reaction, the hydrogen atom of the hydroxyl group is replaced by the C18 long-chain acyl group, forming an ester bond (-COO-), while simultaneously releasing HCl (which is captured by triethylamine). The C18 long chain endows the modified tea saponin with excellent lipid solubility, enabling it to undergo dynamic conformational oscillations through Brownian motion in seawater, generating steric repulsion forces and effectively penetrating the phospholipid bilayer biofilm of attached organisms such as barnacles and oysters, thus interfering with the cross-linking and solidification process of their protein adhesives at the microscopic level.

[0041] 2. Preparation of modified tea saponin-based antifouling emulsion: Prepare an organic phase by mixing the following monomers: The above reaction solution containing TS-C18 (equivalent to 12g of pure TS-C18): Appropriate amount Methyl methacrylate (MMA): 28 g Butyl acrylate (BA): 42 g Styrene (St): 15 g Acrylic acid (AA): 3 g In another container, 120g of deionized water and 1.5g of emulsifier (SE-10N, a nonionic emulsifier) ​​were mixed to form the aqueous phase. Under stirring in a high-speed shear disperser (2000-5000 rpm), the above organic phase was slowly added to the aqueous phase, and shearing was continued for 15 minutes to obtain a milky white stable pre-emulsion.

[0042] Add 50g of deionized water as bottom water to a four-necked reactor equipped with a stirrer, condenser, thermometer, and nitrogen inlet, and add 0.3g of ammonium persulfate (APS) as a partial initiator. Purge with nitrogen to remove oxygen and raise the temperature to 80℃. After the bottom water temperature stabilizes, begin uniformly adding the pre-emulsion and the remaining 0.5g of APS solution (dissolved in 10g of water) dropwise to the reactor over a total time of 3.5 hours. After the addition is complete, raise the system temperature to 88-90℃ and maintain this temperature for 1.5 hours to reduce residual monomer content. After the reaction is complete, cool to below 40℃, adjust the pH of the system to 8.0-9.0 with 25% ammonia, and filter through a 200-mesh filter cloth to obtain the target modified tea saponin-based antifouling emulsion.

[0043] like Figure 3 As shown, Figure 3This schematically demonstrates how the TS-C18 monomer undergoes free radical copolymerization with monomers such as MMA, BA, and St via its terminal carbon-carbon double bonds to form a polymer backbone. The long-chain tea saponin active fragment is suspended on the backbone as a side group, achieving "covalent anchoring." The tea saponin unit (in the form of a macromolecular side group) is "locked" to the backbone by covalent bonds, preventing it from being washed away by seawater. Simultaneously, the residual polar hydroxyl groups on the tea saponin sugar rings create a hydration layer on the coating surface, producing a physical anti-sticking effect. This structure achieves a synergistic antifouling mechanism integrating "covalent anchoring + physical anti-sticking + biochemical inhibition."

[0044] Performance testing:

[0045] Physical properties: The solid content was 49% as determined by gravimetric method; the viscosity was 410 mPa·s as determined by rotational viscometer; and the average particle size was 115 nm as determined by laser particle size analyzer.

[0046] Antifouling performance: A 12-month sea-based immersion test was conducted in the waters off Zhoushan, Zhejiang Province, according to ASTM D3623 (Marine Antifouling Coated Panels Shallow Water Immersion Test Method). Results showed that the experimental panels coated with the antifouling coating of this embodiment had extremely low biofouling density, with barnacles and large fouling organisms covering less than 5% of the surface area. In contrast, the blank control panels were severely fouled within 3 months. No obvious blistering or peeling was observed on the coating surface, demonstrating excellent long-term antifouling effect and seawater resistance.

[0047] Example 2: C22-erucic acid-modified tea saponin antifouling emulsion (TS-C22)

[0048] This embodiment exemplifies the process of preparing antifouling emulsions using a longer carbon chain (C22) modifier.

[0049] 1. One-pot synthesis of polymerizable tea saponin monomer (TS-C22): 100g of dried tea saponin was dissolved in 350g of anhydrous DMF, and 1.0g of 4-dimethylaminopyridine (DMAP) was added as a catalyst. Under nitrogen protection, the system was cooled to 10℃. 8g of erucic acid chloride was slowly added dropwise (over approximately 1 hour), followed by a reaction at 75℃ for 8 hours. After the reaction was complete, a reaction solution containing TS-C22 was obtained. Its degree of substitution (DS) was determined to be approximately 0.2.

[0050] 2. Emulsion preparation: The monomer organic phase formulation is as follows: Reaction solution containing TS-C22 (equivalent to 15g of pure TS-C22): Appropriate amount Styrene (St): 30 g Isooctyl acrylate (2-EHA): 45 g Hydroxyethyl acrylate (HEA): 10 g Acrylic acid (AA): 3 g The same pre-emulsification and semi-continuous dropwise polymerization process as in Example 1 was used, but the dropwise addition time of the pre-emulsion was extended to 4.5 hours to promote full participation of macromonomers in polymerization. The remaining steps were the same as in Example 1.

[0051] 3. Performance Testing: Physical properties: solid content 54%, viscosity 490 mPa·s, average particle size 140 nm, MFT 12℃.

[0052] Antifouling performance: The results of a 12-month real-sea veneer test showed that it also had excellent inhibition rate against the attachment of barnacles and large fouling organisms, with an attachment rate of less than 5%, demonstrating antifouling ability comparable to that of Example 1.

[0053] Example 3: Maleic acid half-ester modified tea saponin anti-fouling emulsion (TS-MAH)

[0054] This embodiment exemplifies the process of preparing antifouling emulsions using anhydride-based (maleic anhydride) modifiers.

[0055] 1. One-pot synthesis of polymerizable tea saponin monomer (TS-MAH): 100g of dried tea saponin was dissolved in 300g of anhydrous DMF, and 35g of maleic anhydride (MAH) and 1.2g of triethylamine were added. The mixture was refluxed at 60-70℃ for 8 hours to allow the maleic anhydride to undergo a ring-opening esterification reaction with the hydroxyl groups of the tea saponin. The reaction yielded a reaction solution containing TS-MAH. The degree of substitution (DS) was determined to be approximately 1.1.

[0056] 2. Emulsion preparation: The monomer organic phase formulation is as follows: Reaction solution containing TS-MAH (equivalent to 10g of pure TS-MAH): Appropriate amount Styrene (St): 30 g Butyl acrylate (BA): 45 g Methyl methacrylate (MMA): 15 g Since the TS-MAH monomer itself already incorporates carboxyl groups, no additional acrylic functional monomers were added to the formulation in this embodiment. The remaining polymerization process is the same as in Example 1.

[0057] 3. Performance Testing: Physical properties: solid content 46%, viscosity 330 mPa·s, average particle size 105 nm, MFT 6℃.

[0058] Antifouling performance: The results of a 12-month real-sea sling test showed that this embodiment performed better than Examples 1 and 2 in inhibiting the attachment of algae (such as seaweed). At the same time, the inhibition rate of attachment of large fouling organisms such as barnacles also reached more than 85%, showing a good broad-spectrum antifouling effect against different fouling organisms.

[0059] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A modified tea saponin-based anti-fouling emulsion, characterized in that, Obtained by free radical copolymerization of monomers comprising the following weight percentages: Unsaturated modified tea saponin monomer: 3% - 20%; Styrene: 10% - 35%; (Meth)acrylate monomers: 45% - 70%; Functional carboxylic acid monomers: 0% - 5%; The unsaturated modified tea saponin monomer is prepared by reacting the hydroxyl groups in the tea saponin molecule with the acyl chloride of a long-chain flexible olefin containing carbon-carbon double bonds and having an alkyl chain of C12-C22. The emulsion has a solid content of 40%-55%, a viscosity of 200-500 mPa·s, an average particle size of 80-150 nm, a minimum film-forming temperature of 5-15℃, and its viscosity is measured by a rotational viscometer.

2. The modified tea saponin-based antifouling emulsion according to claim 1, characterized in that, The degree of substitution of the unsaturated modified tea saponin monomer is 0.1-1.2; the degree of substitution is determined by titration or nuclear magnetic resonance hydrogen spectroscopy integration.

3. The modified tea saponin-based antifouling emulsion according to claim 1, characterized in that, The acyl chloride of the long-chain flexible olefin containing carbon-carbon double bonds and with an alkyl chain of C12-C22 used for modifying tea saponin is oleoyl chloride or erucic acid chloride.

4. The modified tea saponin-based antifouling emulsion according to claim 1, characterized in that, The (meth)acrylate monomers are selected from one or more combinations of methyl methacrylate, butyl acrylate, isooctyl acrylate, and hydroxyethyl methacrylate; the functional carboxylic acid monomers are selected from one or more combinations of acrylic acid, methacrylic acid, and maleic acid half ester.

5. A method for preparing a modified tea saponin-based antifouling emulsion as described in any one of claims 1-4, characterized in that, Includes the following steps: S1: One-pot synthesis of unsaturated modified tea saponin monomer: In an anhydrous aprotic solvent, with organotin or tertiary amine as catalyst, under inert gas protection, tea saponin is reacted with acyl chlorides of long-chain flexible olefins containing carbon-carbon double bonds and alkyl chains of C12-C22 at 5-75℃ to obtain a reaction solution containing unsaturated modified tea saponin monomer. This reaction solution is used directly for the next polymerization step without separation and purification. S2: Emulsion polymerization: A semi-continuous seeded emulsion polymerization process is adopted. The reaction solution obtained in step S1 is used as the organic phase component and mixed with styrene, (meth)acrylate monomers and functional carboxylic acid monomers. Pre-emulsification is carried out in the presence of an emulsifier to obtain a pre-emulsion. Then, under the action of an initiator, the pre-emulsion is added to the reactor in a semi-continuous dropwise manner for free radical copolymerization. After the reaction is completed, the temperature is lowered to room temperature and the pH is adjusted to 7.5-9.

5. The mixture is filtered and discharged to obtain the modified tea saponin-based antifouling emulsion.

6. The method for preparing a modified tea saponin-based antifouling emulsion according to claim 5, characterized in that, In step S1, the catalyst is triethylamine or 4-dimethylaminopyridine; the reaction temperature is 50-75℃, and the reaction time is 5-8 hours.

7. The method for preparing a modified tea saponin-based antifouling emulsion according to claim 5, characterized in that, In step S2, the reaction temperature for free radical copolymerization is 70-90℃; the initiator is ammonium persulfate or potassium persulfate; and the emulsifier is sodium dodecyl sulfate or alkylphenol polyoxyethylene ether.

8. The method for preparing a modified tea saponin-based antifouling emulsion according to claim 5, characterized in that, The method further includes dehydrating the tea saponin raw material before step S1, specifically by vacuum drying the tea saponin at 80°C for 4 hours to control the moisture content of the system to be less than 0.1%.

9. The application of a modified tea saponin-based antifouling emulsion according to any one of claims 1-4 or a modified tea saponin-based antifouling emulsion prepared by the preparation method according to any one of claims 5-8 in the preparation of marine antifouling coatings, characterized in that: Used to inhibit the attachment of barnacles, mussels, oysters and algae to the surface of marine vessels.

Images