Tea saponin grafting type hydrolysable marine antifouling resin, and preparation method and application thereof

Abstract

This invention belongs to the technical field of marine antifouling materials, and discloses a tea saponin-grafted hydrolyzable marine antifouling resin, its preparation method, and its application. In this tea saponin-grafted hydrolyzable marine antifouling resin, tea saponin is covalently grafted onto the resin through ester bonds formed by its hydroxyl groups with the carboxyl groups of a carboxyl-containing acrylic resin side groups. This tea saponin-grafted hydrolyzable marine antifouling resin can slowly hydrolyze and release tea saponin in seawater, reducing explosive release and extending the antifouling period. It can be used to prepare environmentally friendly marine antifouling coatings.

Description

Technical Field

[0001] This invention belongs to the field of marine antifouling materials technology, specifically relating to a tea saponin-grafted hydrolyzable marine antifouling resin and its preparation method, as well as the application of the resin in the preparation of marine antifouling coatings. Background Technology

[0002] Tea saponin is a natural glycoside compound extracted from plants of the Theaceae family. It possesses broad-spectrum bioinhibitory activity, is readily biodegradable, and has good environmental compatibility, making it an environmentally friendly natural antifouling agent. The conventional method for using tea saponin as a marine antifouling agent is to physically blend it into coating resins. However, tea saponin is a water-soluble compound, and after physical blending, it rapidly dissolves from the coating in seawater, presenting the following technical problems: the initial release rate is too rapid, resulting in a short effective antifouling period and an inability to achieve long-term antifouling effects; rapid loss of the antifouling agent leaves pores in the coating, reducing its mechanical properties and shielding protection function.

[0003] Acrylic resin is a commonly used film-forming base material in marine antifouling coatings, possessing excellent adhesion, weather resistance, and film-forming properties. Immobilizing natural antifouling agents onto the acrylic resin chain through chemical modification to achieve stable loading and controlled release of the antifouling agent is an effective way to overcome the defects of physical blending.

[0004] Currently, there are no publicly reported technical solutions for directly grafting tea saponins onto carboxyl-containing acrylic resins. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of easy loss and uncontrollable release of tea saponin in physical blending systems, and to provide a hydrolyzable marine antifouling resin in which tea saponin is covalently grafted onto a carboxyl-containing acrylic resin chain via ester bonds. This resin can achieve long-term and controllable release of tea saponin in a seawater environment.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned tea saponin-grafted hydrolyzable marine antifouling resin.

[0007] Another object of the present invention is to provide the use of the above-mentioned resin in the preparation of marine antifouling coatings.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows: A tea saponin-grafted hydrolyzable marine antifouling resin has a carboxyl-containing acrylic resin chain. The tea saponin molecule is covalently grafted onto the acrylic resin chain via an ester bond formed between its own hydroxyl group and the carboxyl group on the side group of the acrylic resin chain.

[0009] In the above resin, the carboxyl content of the carboxyl-containing acrylic resin chain is 0.5% to 10% of the solid resin mass, and the amount of tea saponin used in the grafting reaction is 5% to 30% of the solid resin mass.

[0010] In the above-mentioned resin, the carboxyl-containing acrylic resin chain contains structural units derived from carboxyl-containing monomers, wherein the carboxyl-containing monomers are selected from at least one of acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid.

[0011] In the above resin, the carboxyl-containing acrylic resin chain is a copolymer chain formed by free radical copolymerization of the carboxyl-containing monomer with at least one of methacrylate monomers, acrylate monomers and styrene.

[0012] In the above-mentioned resin, the number-average molecular weight Mn of the carboxyl-containing acrylic resin chain is 20,000 to 40,000, and the molecular weight distribution PDI is 2.0 to 3.5.

[0013] In the above resin, the carboxyl content is preferably 2% to 6% of the mass of the solid resin, and the amount of tea saponin used in the grafting reaction is preferably 8% to 20% of the mass of the solid resin.

[0014] A method for preparing the above-mentioned tea saponin-grafted hydrolyzable marine antifouling resin includes the following steps: dissolving carboxyl-containing acrylic resin, tea saponin, and 4-dimethylaminopyridine in an anhydrous organic solvent; stirring at 0-10°C in an ice-water bath under nitrogen protection; adding N,N'-dicyclohexylcarbodiimide solution dropwise; and carrying out an esterification condensation reaction at room temperature after the addition is complete; and obtaining the tea saponin-grafted hydrolyzable marine antifouling resin by separation and purification after the reaction is completed.

[0015] In the above preparation method, taking the molar number of 4-dimethylaminopyridine as 1, the molar number of carboxyl groups in the carboxyl-containing acrylic resin is 5 to 15, the molar number of tea saponin is 0.5 to 3, and the molar number of N,N'-dicyclohexylcarbodiimide is 2 to 6.

[0016] In the above preparation method, the preparation steps of the carboxyl-containing acrylic resin are as follows: dissolving the carboxyl-containing monomer and at least one of the acrylate monomer, methacrylate monomer and styrene in an organic solvent, and carrying out a solution free radical polymerization reaction in the presence of a free radical initiator to obtain the carboxyl-containing acrylic resin.

[0017] The above-mentioned resins are used in the preparation of marine antifouling coatings. These resins can be used in coatings and other methods to prevent marine biofouling on ships, offshore platforms, or aquaculture facilities.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Tea saponin is firmly linked to the carboxyl group of the side group of the acrylic resin chain through covalent ester bond. In seawater, the ester bond slowly hydrolyzes and breaks, realizing the long-term and stable release of tea saponin. The hydrolysis rate can be controlled by adjusting the carboxyl content of the resin and the amount of tea saponin grafting reaction.

[0019] (2) The grafting process directly utilizes the inherent hydroxyl groups of tea saponin molecules to carry out a one-step esterification reaction with the carboxyl groups of the resin side chain. There is no need to pre-derivatively treat the tea saponin. The synthesis route is mild and easy to industrialize.

[0020] (3) The base resin adopts an acrylic resin system, which retains good adhesion, weather resistance and film-forming properties; after grafting tea saponin, the glass transition temperature of the resin is increased, which is beneficial to improving the coating hardness and scratch resistance.

[0021] (4) Tea saponins are derived from natural plants and are biodegradable; the release of antifouling agents relies on the hydrolysis of ester bonds in seawater, which poses a low environmental risk. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0023] In this invention, the carboxyl-containing acrylic resin chain can be obtained by free radical copolymerization of a carboxyl-containing monomer and a comonomer. The carboxyl-containing monomer can be selected from at least one of acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid; the comonomer can be selected from at least one of acrylate monomers, methacrylate monomers, and styrene. In the following examples, acrylic acid is used as the carboxyl-containing monomer, and methyl methacrylate and butyl acrylate are used as comonomers to prepare the carboxyl-modified acrylic resin, but the invention is not limited thereto.

[0024] According to the monomer ratios listed in Table 1, methyl methacrylate, butyl acrylate, acrylic acid, toluene, and n-butanol were added to a three-necked flask equipped with a reflux condenser, a dropping funnel, and a nitrogen inlet tube. Nitrogen gas was introduced, and the mixture was stirred and heated to reflux temperature (110℃±5℃). A portion of the initiator, azobisisobutyronitrile (AIBN, accounting for 1.0% of the total monomer mass), was dissolved in a small amount of solvent and slowly added dropwise through the dropping funnel over approximately 2 hours. After the addition was complete, the reaction was continued at reflux temperature for 4 hours. Then, the remaining initiator (0.5% of the total monomer mass) was added, and the reaction was continued at reflux temperature for another 2 hours. After the reaction was completed, the mixture was cooled to obtain a modified acrylic resin solution with a solid content of approximately 50%, and the theoretical carboxyl content of the modified acrylic resin was 5.0 wt.%.

[0025] Table 1. Synthesis ratio of carboxyl-modified acrylic resin In the esterification grafting reaction of tea saponins, the anhydrous organic solvent can be at least one selected from N,N-dimethylformamide, acetone, tetrahydrofuran, dimethyl sulfoxide, dioxane, toluene, and xylene. In the following examples, N,N-dimethylformamide is used as the anhydrous organic solvent. The precipitant can be at least one selected from glacial hexane, n-heptane, petroleum ether, water, methanol, ethyl acetate, and butyl acetate. In the following examples, glacial hexane is used as the precipitant.

[0026] Weigh 20 g (based on solid resin) of carboxyl-modified acrylic resin (50% solid content, theoretical carboxyl content 5.0 wt.%) into a three-necked flask, wherein the calculated molar number of carboxyl groups in the carboxyl-modified acrylic resin is 22.22 mmol. Add 80 g of anhydrous N,N-dimethylformamide and stir until completely dissolved. Add the amounts of tea saponin and 4-dimethylaminopyridine (0.3665 g, 3 mmol) shown in Table 2 to the solution. Under nitrogen protection, stir at 0–10 °C in an ice-water bath for 0.5 h, then slowly add a solution of N,N'-dicyclohexylcarbodiimide (2.0633 g, 10 mmol) in N,N-dimethylformamide (50 mL). After the addition is complete, continue stirring at room temperature for 48 h to carry out the esterification condensation reaction.

[0027] After the reaction was complete, an appropriate amount of N,N-dimethylformamide was added to dilute the reaction solution. The solution was filtered to remove insoluble substances such as N,N'-dicyclohexylurea generated during the reaction. The filtrate was concentrated by rotary evaporation, and then the concentrate was added dropwise to ice-cold n-hexane to precipitate the product. The precipitate was then dissolved in N,N-dimethylformamide, and this dissolution-precipitation process was repeated three times. The precipitate was then dried in a vacuum oven at 40°C to constant weight, yielding a pale yellow solid product. The resin types and amounts of tea saponin used in each example are shown in Table 2.

[0028] In the above grafting reaction, taking the molar number of 4-dimethylaminopyridine as 1, the molar number of carboxyl groups in the carboxyl-modified acrylic resin can be 5 to 15, the molar number of tea saponin can be 0.5 to 3, and the molar number of N,N'-dicyclohexylcarbodiimide can be 2 to 6.

[0029] In the examples, the carboxyl-modified acrylic resin contained approximately 22.22 mmol of carboxyl groups, 3 mmol of 4-dimethylaminopyridine, and 10 mmol of N,N'-dicyclohexylcarbodiimide. In Examples 1-3, tea saponin contained 5 mmol; based on the molar number of 4-dimethylaminopyridine as 1, the carboxyl groups, tea saponin, and N,N'-dicyclohexylcarbodiimide were approximately 7.41, 1.67, and 3.33, respectively. In Examples 4-6, tea saponin contained 3 mmol; based on the molar number of 4-dimethylaminopyridine as 1, the carboxyl groups, tea saponin, and N,N'-dicyclohexylcarbodiimide were approximately 7.41, 1, and 3.33, respectively. In Examples 7-9, the amount of tea saponin was 2 mmol; with the number of 4-dimethylaminopyridine moles as 1, the carboxyl group, tea saponin, and N,N'-dicyclohexylcarbodiimide were approximately 7.41, 0.67, and 3.33, respectively.

[0030] In this invention, the amount of tea saponin used in the grafting reaction is the ratio of the amount of tea saponin added to the mass of the solid resin in the grafting reaction. The amount of tea saponin used in the grafting reaction is 5% to 30% of the mass of the solid resin, preferably 8% to 20%. The amount of tea saponin used in the following examples is the amount of tea saponin used in the grafting reaction.

[0031] Table 2 Grafting reaction parameters By adjusting the amount of tea saponin used in the grafting reaction, the carboxyl content, and the reaction purification conditions, tea saponin-grafted hydrolyzable marine antifouling resins that meet different application requirements can be obtained.

[0032] The glass transition temperature (Tg), number-average molecular weight (Mn), and molecular weight distribution (PDI) of various carboxyl-modified acrylic resins and tea saponin-grafted resins are shown in Table 3.

[0033] Table 3 Resin Performance Parameters The tea saponin-grafted hydrolyzable marine antifouling resin of the present invention can be used as a film-forming substance in marine antifouling coatings. The marine antifouling coating may further comprise antifouling pigments, fillers, solvents, and additives. The antifouling pigment may be cuprous oxide; the filler may be at least one of iron oxide red and talc; the additives may include dispersants, defoamers, and thixotropic agents. In the following embodiments, cuprous oxide is used as the antifouling pigment, iron oxide red and talc are used as fillers, BYK-110 is used as the dispersant, BYK-007 as the defoamer, and polyamide wax as the thixotropic agent, but the present invention is not limited thereto.

[0034] The antifouling coating (parts by weight) was prepared using the tea saponin grafted resin listed in Table 2 according to the following formula: 35 parts resin, 20 parts cuprous oxide, 3 parts iron oxide red, 10 parts talc, 0.5 parts dispersant BYK-110, 0.3 parts defoamer BYK-007, 2 parts polyamide wax, and 30 parts mixed organic solvent (mass ratio of xylene to propylene glycol methyl ether acetate is 7:3).

[0035] Preparation process: The above components are dispersed evenly at high speed and ground to a fineness of <20 μm; the sample is prepared according to GB / T 5370-2007 "Test method for shallow sea immersion of antifouling paint sample" and a shallow sea immersion test is carried out. At the same time, the release rate of tea saponin is monitored by high performance liquid chromatography.

[0036] Comparative Examples 1-3: 35 parts of modified acrylic resin AA-1, AA-2 or AA-3 were used to replace the tea saponin grafted resin, and physical blending was carried out at a ratio of 5.6177 g of tea saponin per 20 g of solid resin. The amount of cuprous oxide was 30 parts, and the remaining components and preparation process were the same as the coating preparation method described above.

[0037] Comparative Examples 4-6: 35 parts of modified acrylic resin AA-1, AA-2 or AA-3 were used as film-forming substances, without the addition of tea saponin, and the amount of cuprous oxide was 30 parts. The remaining components and preparation process were the same as the coating preparation method described above.

[0038] The results of the shallow sea immersion experiment (1 year) and the monitoring of tea saponin release are shown in Table 4.

[0039] Table 4 Results of shallow sea immersion experiment and tea saponin release monitoring In Comparative Examples 1-3, the coatings, due to the fact that tea saponin was dispersed in the resin only through physical action, dissolved rapidly in seawater, with an extremely high initial release rate followed by a sharp decline in the later release rate, leading to early failure of antifouling performance. After one year of shallow sea immersion, the surface coverage of barnacles and algae reached 40%. The coatings in Comparative Examples 4-6 showed severe biofouling, further confirming the necessity of tea saponin as an active antifouling substance.

[0040] In comparison, the resin coatings of Examples 1-9, which used ester-bonded covalently grafted tea saponins, showed significantly better antifouling performance than all the comparative examples after one year of shallow sea immersion. The release rate of tea saponins remained stable throughout the 90-day monitoring period, with no explosive release. Among them, Examples 1-3 showed the best antifouling performance, with no macroscopic fouling or biofouling on the surface; Examples 7-9 showed slightly reduced antifouling performance but were still significantly better than the physically blended groups.

[0041] The above results demonstrate that this invention successfully solves the problems of explosive release and short-term failure in physical blending systems by covalently grafting tea saponin onto carboxyl-containing acrylic resin via ester bonds, achieving long-term, controllable release of tea saponin in seawater environments. By adjusting the resin monomer ratio and the amount of tea saponin used in the grafting reaction, the resin's Tg, molecular weight, and antifouling release performance can be adjusted over a wide range to meet the requirements of different application scenarios for coating mechanical properties and antifouling release kinetics.

[0042] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A tea saponin-grafted hydrolyzable marine antifouling resin, characterized in that, The acrylic resin chain contains carboxyl groups, and the tea saponin molecule is covalently grafted onto the acrylic resin chain through an ester bond formed between its own hydroxyl group and the carboxyl group on the side group of the acrylic resin chain.

2. The tea saponin-grafted hydrolyzable marine antifouling resin according to claim 1, characterized in that, The carboxyl group content of the said carboxyl-containing acrylic resin chain is 0.5% to 10% of the solid resin mass. The amount of tea saponin used in the grafting reaction is 5% to 30% of the mass of the solid resin.

3. The tea saponin-grafted hydrolyzable marine antifouling resin according to claim 1 or 2, characterized in that, The carboxyl-containing acrylic resin chain contains structural units derived from carboxyl-containing monomers. The carboxyl-containing monomer is selected from at least one of acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid.

4. The tea saponin-grafted hydrolyzable marine antifouling resin according to claim 3, characterized in that, The carboxyl-containing acrylic resin chain is a copolymer chain formed by free radical copolymerization of the carboxyl-containing monomer with at least one of methacrylate monomers, acrylate monomers and styrene.

5. The tea saponin-grafted hydrolysable marine antifouling resin according to any one of claims 1 to 4, characterized in that, The number-average molecular weight (Mn) of the carboxyl-containing acrylic resin chain is 20,000 to 40,000, and the molecular weight distribution (PDI) is 2.0 to 3.

5.

6. The tea saponin grafted hydrolysable marine antifouling resin according to claim 2, characterized in that, The carboxyl content is 2% to 6% of the mass of the solid resin, and the amount of tea saponin used in the grafting reaction is 8% to 20% of the mass of the solid resin.

7. A method for preparing a tea saponin-grafted hydrolyzable marine antifouling resin, characterized by, Includes the following steps: Carboxyl-containing acrylic resin, tea saponin, and 4-dimethylaminopyridine were dissolved in an anhydrous organic solvent. Under nitrogen protection, N,N'-dicyclohexylcarbodiimide solution was added dropwise after stirring in an ice-water bath at 0–10°C. After the addition was complete, an esterification condensation reaction was carried out at room temperature; after the reaction was completed, the tea saponin-grafted hydrolyzable marine antifouling resin was obtained by separation and purification.

8. The preparation method according to claim 7, characterized in that, With 1 mole of 4-dimethylaminopyridine, the number of moles of carboxyl groups in the carboxyl-containing acrylic resin is 5 to 15, the number of moles of tea saponin is 0.5 to 3, and the number of moles of N,N'-dicyclohexylcarbodiimide is 2 to 6.

9. The preparation method according to claim 7, characterized in that, A carboxyl-containing monomer is dissolved in an organic solvent along with at least one of an acrylate monomer, a methacrylate monomer, and styrene. Solution free radical polymerization is then carried out in the presence of a free radical initiator to obtain a carboxyl-containing acrylic resin.

10. The use of the tea saponin-grafted hydrolyzable marine antifouling resin according to any one of claims 1 to 6 in the preparation of marine antifouling coatings.

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