Use of acid hydrolysate of oleander ethanol extract in preparation of marine slow-release antifouling agent

Abstract

The application discloses application of an acid hydrolysate of an oleander ethanol extract in preparation of a marine slow-release antifouling agent. The acid hydrolysate is prepared by taking tender stems and tender leaves of the oleander as raw materials, extracting the raw materials by using an ethanol solution, and then performing acid hydrolysis. The acid hydrolysate has a significant inhibiting effect on attachment of marine macrofouling organisms, and shows high antifouling activity. The release rate of the acid hydrolysate in antifouling paint is much smaller than that of the oleander ethanol extract before hydrolysis, so that the acid hydrolysate can be used to prepare the marine slow-release antifouling agent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of marine antifouling, and particularly relates to application of an acid hydrolysate of an oleander ethanol extract in preparation of a marine slow-release antifouling agent. BACKGROUND

[0002] In a marine environment, the phenomenon that marine organisms such as barnacles, mussels, sea squirts and bryozoan animals adhere to and grow on the surface of artificial facilities is called marine biofouling, which seriously endangers marine economic activities. Marine biofouling can affect the performance of various marine equipment such as seawater pipelines and sensors, affect the yield and quality of aquaculture, cause the ship's sailing resistance to become larger, the ship speed to decrease, the oil consumption to increase, and cause problems such as invasion of foreign organisms.

[0003] At present, coating antifouling paint is the most simple, economical and efficient antifouling technology. In early antifouling paints, heavy metals such as copper, lead, tin and nickel were mainly used as antifouling agents. Although this type of paint can effectively reduce the adhesion of fouling organisms, the large release of toxic heavy metals into seawater can cause serious harm to the ecological environment. Later, organotin self-polishing antifouling paint was developed. This type of antifouling paint can achieve high-efficiency antifouling, but the large release of organotin into the seawater environment also leads to a series of ecological environmental problems. After that, people began to use cuprous oxide as the main antifouling agent, and compounded with chlorothalonil, diuron, hymexazol, copper pyrithione and zineb and other antifouling additives to prepare antifouling paint. This type of paint has excellent antifouling performance, but the large accumulation of copper has high toxicity to marine organisms, and the antifouling additives also have problems such as high toxicity, easy accumulation or difficult degradation, and some antifouling additives have been limited or banned. Therefore, the development of low-toxic or even non-toxic environmentally friendly antifouling agents is an inevitable trend for the development of future antifouling paint. Natural products have the advantages of green environmental protection, good biocompatibility, low toxicity, easy degradation and good development and application prospects, and are expected to replace heavy metal antifouling agents and become candidate compounds for environmentally friendly antifouling agents. However, most natural antifouling products have problems such as low content, complex purification and preparation steps, and limited source of biological resources, and commercial application is rare at present. Compared with pure compounds, natural extracts are easier to prepare, have higher yield and lower cost.

[0004] On the other hand, when the natural antifouling substance is applied to the antifouling paint, many exist the phenomenon of too fast release rate in the early stage, namely burst release phenomenon, resulting in short antifouling period and difficult to practical application. In the marine environment, if the antifouling agent is released too fast from the paint, it is easy to cause a large waste of the antifouling agent and shorten the period, so the slow release of the antifouling agent is very important. The plant extract often includes many glycoside active ingredients containing sugar, and the water solubility of these components is relatively large due to the sugar in the chemical structure, which is released from the paint and dissolved in seawater, thereby resulting in the faster failure of the antifouling paint. Therefore, in order to solve the above problems, the plant extract can be hydrolyzed to remove the sugar group in the glycoside component to reduce the water solubility. However, the current research on natural antifouling active products mainly focuses on the activity detection of pure compounds, and so far, there is no report on the application of the hydrolyzate of the plant extract as a marine environmental protection antifouling agent. SUMMARY

[0005] The present application aims to overcome the defects of the prior art and provide the application of the acid hydrolyzate of oleander ethanol extract in the preparation of marine slow-release antifouling agent.

[0006] Another object of the present application is to provide a marine slow-release antifouling agent.

[0007] Still another object of the present application is to provide a marine antifouling paint containing the above marine slow-release antifouling agent.

[0008] The technical solution of the present application is as follows:

[0009] The application of the acid hydrolyzate of oleander ethanol extract in the preparation of marine slow-release antifouling agent.

[0010] In a preferred embodiment of the present application, the preparation method of the oleander ethanol extract comprises the following steps:

[0011] (1) After the tender stems and tender leaves of oleander are washed, dried in the shade and crushed, they are soaked in a 75-80% ethanol solution for 70-75h, and the soaking step is repeated several times to obtain a soaking solution by combining;

[0012] (2) The soaking solution is filtered and concentrated by rotary evaporation under reduced pressure to obtain a crude extract concentrate, and then extracted with an equal volume of petroleum ether several times, and the upper organic phase is discarded;

[0013] (3) Excess saturated lead acetate aqueous solution is added to the material obtained in step (2), and stirred until no yellowish precipitate is produced, then filtered to obtain a first filtrate, then excess hydrogen sulfide is introduced into the first filtrate, and stirred until no black precipitate is produced, then filtered to obtain a second filtrate, and the washing liquid obtained by washing the obtained precipitate several times is mixed with the second filtrate, and finally concentrated by rotary evaporation under reduced pressure to obtain a black solid, which is the oleander ethanol extract.

[0014] Further preferably, the preparation method of the acid hydrolysate comprises: mixing the Nerium oleander ethanol extract and an acid solution at a solid-liquid ratio of 10:1, heating in a water bath at 90℃ for 1h, extracting with ethyl acetate after cooling to room temperature, and concentrating the organic phase to obtain the acid hydrolysate; wherein the concentration of the acid solution is 2mol / L, and the acid in the acid solution is at least one of hydrochloric acid and sulfuric acid.

[0015] A marine slow-release antifouling agent, wherein the effective component is an acid hydrolysate of a Nerium oleander ethanol extract.

[0016] In a preferred embodiment of the present application, the preparation method of the Nerium oleander ethanol extract comprises the following steps:

[0017] (1) The tender stems and leaves of Nerium oleander are washed, air-dried and crushed, then soaked in a 75-80% ethanol solution for 70-75h, and the step is repeated several times to obtain a soaking solution;

[0018] (2) The soaking solution is filtered and concentrated by rotary evaporation under reduced pressure to obtain a crude extract concentrate, which is then extracted with an equal volume of petroleum ether several times, and the upper organic phase is discarded;

[0019] (3) Excess saturated lead acetate aqueous solution is added to the material obtained in step (2) and stirred thoroughly until no yellowish precipitate is produced, then filtered to obtain a first filtrate, excess hydrogen sulfide is introduced into the first filtrate, and the mixture is stirred constantly until no black precipitate is produced, then filtered to obtain a second filtrate, the washing solution obtained by washing the precipitate several times with water is mixed with the second filtrate, and finally concentrated by rotary evaporation under reduced pressure to obtain a black solid, which is the Nerium oleander ethanol extract.

[0020] Further preferably, the preparation method of the acid hydrolysate comprises: mixing the Nerium oleander ethanol extract and an acid solution at a solid-liquid ratio of 10:1, heating in a water bath at 90℃ for 1h, extracting with ethyl acetate after cooling to room temperature, and concentrating the organic phase to obtain the acid hydrolysate; wherein the concentration of the acid solution is 2mol / L, and the acid in the acid solution is at least one of hydrochloric acid and sulfuric acid.

[0021] The marine slow-release antifouling agent is used in the preparation of a marine antifouling coating.

[0022] In a preferred embodiment of the present application, the marine antifouling coating further comprises a binder and an organic solvent.

[0023] Further preferably, the marine antifouling coating further comprises a pigment and at least one auxiliary agent selected from the group consisting of a thixotropic agent, a dispersing agent, a defoaming agent and a leveling agent.

[0024] A marine antifouling paint, which raw material comprises the above-mentioned marine slow-release antifouling agent.

[0025] In a preferred embodiment of the present application, a binder and an organic solvent are further included.

[0026] Further preferably, a pigment and at least one additive selected from the group consisting of a thixotropic agent, a dispersing agent, an antifoaming agent and a leveling agent are further included.

[0027] The above-mentioned binder (also referred to as a film former or a base) can be selected from at least one of an acrylic resin, a perchloroethylene resin, a natural resin (e.g., rosin), a phenol resin, asphalt, an alkyd resin, an amino resin, a chlorinated rubber, an ethylene resin, a polyester resin, an epoxy resin, a polyurethane, a silicone resin and an organofluorine resin.

[0028] The above-mentioned organic solvent can be selected from at least one of toluene, xylene, methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, benzyl alcohol, acetone, butanone, methyl isobutyl ketone, methyl isopentyl ketone, cyclohexanone, ethyl acetate and ethylene glycol butyl ether.

[0029] The above-mentioned pigment can be selected from at least one of zinc oxide, iron red, talc, barium sulfate, calcium carbonate, diatomite, zinc powder and titanium white.

[0030] The above-mentioned thixotropic agent can be selected from at least one of bentonite, hydrogenated castor oil, polyvinyl alcohol, fumed silica and metal soap.

[0031] The above-mentioned dispersing agent can be selected from at least one of bentonite, metal soap, hydrogenated castor oil, polyethylene oxide and low-viscosity methyl silicone oil.

[0032] The above-mentioned antifoaming agent can be selected from at least one of tributyl phosphate, polydimethylsiloxane and polyether-modified silicone.

[0033] The above-mentioned leveling agent can be selected from at least one of polyacrylate, modified polyacrylate, polyfluorinated polyolefin and polyvinyl butyral.

[0034] The present application has the following advantages:

[0035] 1. The tender stems and leaves of Nerium indicum are used as raw materials, and after extraction with an ethanol solution and acid hydrolysis, an acid hydrolysis product is obtained. The acid hydrolysis product has a significant inhibitory effect on the attachment of marine macrofouling organisms and shows high antifouling activity. The release rate of the acid hydrolysis product in antifouling paint is much smaller than that of the ethanol extract of Nerium indicum before hydrolysis, and the acid hydrolysis product can be used to prepare a marine slow-release antifouling agent.

[0036] 2. The acid hydrolysis product of the present application can be obtained in large quantities, and the preparation process is relatively short and simple, which is conducive to large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 Figure 1 is a photograph of the test results of the sea area hanging plate (105 days) of the coating containing the oleandrin ethanol extract and its hydrolyzate in Example 3 of the present application.

[0038] Figure 2 Figure 2 is a graph of the statistical results of the large-scale fouling organism coverage of the coating containing the oleandrin ethanol extract and its hydrolyzate in Example 3 of the present application (Note: a, b, c represent that there are significant differences among the three groups of data).

[0039] Figure 3 Figure 3 is a graph of the release rate determination results of the antifouling agent in the coating containing the oleandrin ethanol extract and its hydrolyzate in Example 4 of the present application.

[0040] In the above figures, the oleandrin ethanol extract is denoted as oleander extract, and the acid hydrolyzate of the oleandrin ethanol extract is denoted as oleander extract hydrolyzate. DETAILED DESCRIPTION

[0041] The technical solutions of the present application are further described and explained in detail below by means of specific embodiments in conjunction with the accompanying drawings.

[0042] The preparation method of the oleandrin ethanol extract used in the following examples includes the following steps:

[0043] (1) The tender stems and leaves of the oleander are washed, air-dried and crushed, and then soaked in an 80% ethanol solution for 72 h, and the soaking step is repeated 3 times to obtain a soaking solution;

[0044] (2) The soaking solution is filtered and concentrated by rotary evaporation under reduced pressure to obtain a crude extract concentrate, and then extracted 3 times with an equal volume of petroleum ether, and the upper organic phase is discarded;

[0045] (3) Excess saturated lead acetate aqueous solution is added to the material obtained in step (2), and stirred thoroughly until no yellowish precipitate is produced, then filtered to obtain a first filtrate, and then excess hydrogen sulfide is introduced into the first filtrate, and stirred constantly until no black precipitate is produced, then filtered to obtain a second filtrate, and the washing liquid obtained by washing the precipitate 3 times with water is mixed with the second filtrate, and finally concentrated by rotary evaporation under reduced pressure to obtain a black solid, which is the oleandrin ethanol extract.

[0046] Example 1: Establishment of the acid hydrolysis optimization process of the oleandrin ethanol extract

[0047] In this example, the degree of hydrolysis of the oleandrin ethanol extract is characterized by the phenol method, m-dinitrobenzene reagent reaction and high performance liquid chromatography-mass spectrometry technology.

[0048] According to the results of the pre-experiment, the initial acid hydrolysis conditions were set as follows: hydrochloric acid and sulfuric acid were used as the acid hydrolysis reagent, the solid-liquid ratio was 1:4 (m / V, mg / mL), the hydrogen ion concentration was 2 mol / L, and the hydrolysis was performed at 90°C for 1 h in a water bath.

[0049] First, the solid-liquid ratio was optimized by setting different acid volumes, and the results are shown in Table 1.

[0050] Table 1 Hydrolysis results of oleander ethanol extract under different acid volume conditions

[0051]

[0052] Note: The hydrolysis substrate was 100 mg of oleander ethanol extract.

[0053] As can be seen from Table 1, when the acid volume was reduced from 400 mL to 10 mL, the oleander ethanol extract could still be completely hydrolyzed, and the yield of the acid hydrolysis product of the oleander ethanol extract remained at about 48%; when the acid volume was reduced to less than 5 mL, the oleander ethanol extract could not be completely hydrolyzed, and the yield of the acid hydrolysis product of the oleander ethanol extract was also significantly reduced. Therefore, the solid-liquid ratio of the acid hydrolysis conditions was optimized to 10:1 (m / V, mg / mL).

[0054] Then, the hydrogen ion concentration was optimized, and the results are shown in Table 2.

[0055] Table 2 Hydrolysis results of oleander ethanol extract under different acid concentration conditions

[0056]

[0057] Note: The hydrolysis substrate was 100 mg of oleander ethanol extract.

[0058] As can be seen from Table 2, when the hydrogen ion concentration in the hydrolysis system was reduced from 2 mol / L to 0.2 mol / L, the oleander ethanol extract under each condition was completely hydrolyzed, but the yield of the acid hydrolysis product of the oleander ethanol extract gradually decreased from about 48% to about 20%. Therefore, the hydrogen ion concentration of the acid hydrolysis conditions was set to 2 mol / L.

[0059] Finally, the water bath conditions were optimized, and the results are shown in Table 3.

[0060] Table 3 Hydrolysis results of oleander ethanol extract under different water bath conditions

[0061]

[0062] Note: The hydrolysis substrate was 100 mg of oleander ethanol extract.

[0063] As shown in Table 3, when the water bath temperature was reduced from 90℃ to 70℃, the time required for complete hydrolysis of the oleander ethanol extract was extended to 6 hours. Therefore, to ensure the efficiency of acid hydrolysis, the water bath environment for acid hydrolysis was set to be heated in a 90℃ water bath for 1 hour.

[0064] As shown in Tables 1 to 3, hydrochloric acid and sulfuric acid have little difference in their effects on the acid hydrolysis of oleander ethanol extract, and hydrochloric acid is relatively cheaper. Furthermore, hydrochloric acid is easier to remove from the hydrolyzed system. Therefore, hydrochloric acid was chosen as the acid hydrolysis reagent for the chosen acid hydrolysis conditions.

[0065] In summary, the optimized acid hydrolysis process for oleander ethanol extract is as follows: hydrochloric acid is used as the acid hydrolysis reagent, the material-to-liquid ratio is 10:1 (m / V, mg / mL), the hydrogen ion concentration in the acid hydrolysis system is 2 mol / L, and the water bath conditions are heating in a 90℃ water bath for 1 h.

[0066] Example 2: Preparation of marine antifouling coatings containing oleander ethanol extract and its hydrolysis products

[0067] Oleander ethanol extract and its hydrolysate (both 20% by mass) were mixed with acrylic resin, rosin, iron oxide red, zinc oxide, and organic solvents. Glass beads were then added, and the mixture was stirred in a high-speed disperser until the coating fineness reached 80 μm. The mixture was then filtered through a 100-mesh silk screen to obtain a marine antifouling coating. In the two prepared coatings, the only difference was the oleander ethanol extract used before and after hydrolysis; all other components and their contents were identical.

[0068] Example 3: Marine antifouling efficacy test of antifouling coatings containing oleander ethanol extract and its hydrolysis products.

[0069] The antifouling coating was tested in a natural sea area according to the national standard GB / T5370-2007 "Test Method for Antifouling Coating Samples in Shallow Sea". The marine antifouling coating prepared in Example 2 was uniformly coated onto an epoxy resin board (20cm × 10cm). An area without the marine antifouling coating (20cm × 10cm) served as a control group. Six parallel groups were set up for each coating sample. After the coating dried in the shade, the test boards were fixed in plastic tube frames and hung in the Wuyuan Bay area of ​​Xiamen in April 2022. Each test board was immersed in seawater at a depth of 1m. After 105 days, photographs were taken, and the coverage rate of macrofouling organisms in each coating sample area was analyzed and statistically determined. Macrofouling coverage rate refers to the ratio of the surface area covered by marine macrofouling organisms in the sample area to the total surface area of ​​the sample area. The lower this value, the higher the antifouling efficacy of the coating.

[0070] The test results of the antifouling efficacy of marine antifouling coatings containing oleander ethanol extract and its hydrolysis products in marine areas are as follows: Figures 1-2 As shown. From Figure 1It can be seen from the attached large-scale fouling organisms on the surface of the control group plate during the test period in this sea area that the plate is covered with fouling organisms, and the main attached large-scale fouling organisms include barnacles, sea squirts and bryozoans; the large-scale fouling organisms attached to the surface of the coating group containing 20% oleander ethanol extract are less, but there are still a small amount of barnacles, sea squirts and bryozoans attached; the large-scale fouling organisms attached to the surface of the coating group containing 20% acid hydrolysate of oleander ethanol extract are even less, showing better sea area antifouling efficiency. It can be seen from the quantitative data graph Figure 2 ) that at 105 days, the large-scale fouling organism coverage rate of the coating containing the acid hydrolysate of the oleander ethanol extract is significantly lower than that of the control group (100%), and the large-scale fouling organism coverage rate of the coating containing the hydrolysate of the extract (16.58%) is significantly lower than that of the coating containing the extract before hydrolysis (26.75%), indicating that the coating containing the oleander ethanol extract and the hydrolysate thereof has sea area antifouling efficiency, and the acid hydrolysis treatment improves the antifouling efficiency of the extract.

[0071] Example 4 Release rate determination of marine antifouling coating containing oleander ethanol extract and hydrolysate thereof

[0072] The preparation method of the marine antifouling coating of the oleander ethanol extract and the hydrolysate thereof is the same as that of Example 2, and the mass fraction of the antifouling agent in the coating is also set to 20%. The release rate is determined according to the national standard GB / T 6824-2008 “Determination of Copper Ion Leaching Rate of Marine Antifouling Coating”. The prepared marine antifouling coating is uniformly coated on the test cylinder, and each coating sample is set in triplicate. After the coating is dried, the test cylinder is completely immersed in natural seawater in a water tank, and the seawater is replaced every two days. At 1st, 3rd, 7th, 10th, 14th, 21st, 24th, 28th, 31st, 35th, 42nd and 45th days of immersion, the test cylinder is taken out of the water tank, and after the surface is free of water droplets, it is installed on the rotating test device. Then the coating area of the test cylinder is completely immersed in 1L fresh seawater in a cylindrical container, and the rotating speed is set to 60±5rpm for 1h. After the test is completed, the test cylinder is immediately transferred back to the water tank for immersion. Then the seawater in the cylindrical container is collected, extracted with an equal volume of ethyl acetate, and then the organic phase is concentrated by rotary evaporation under reduced pressure, weighed, redissolved with methanol, and the absorbance is determined. According to the standard curve, the concentration of the released antifouling agent is calculated.

[0073] The establishment of the standard curve includes the following steps. The oleander ethanol extract and the hydrolysate thereof are dissolved in methanol to prepare a series of concentration gradients of 0.2, 1, 2, 5, 10 and 20 mg / mL, respectively. The full wavelength scanning of each concentration is performed by using a microplate reader, and the maximum absorption wavelength is found, respectively, so as to establish a standard curve according to the concentration and the maximum absorbance at the concentration.

[0074] The calculation formula of the release rate of the antifouling agent is as follows.

[0075] R = (C*V*D) / (T*A).

[0076] Among them, R(mg cm -2 d -1 () represents the antifouling agent release rate, C (mg / L) represents the antifouling agent concentration, V (L) represents the volume of seawater used in the test, D (24) represents the number of hours per day, T (h) represents the time taken for the test rotation, and A (cm) represents the antifouling agent release rate. 2 ) represents the surface area of ​​the coating.

[0077] A full-wavelength scan was performed on methanol solutions of oleander ethanol extract and its hydrolysis products. The results showed that the maximum absorption wavelength of oleander ethanol extract was 314 nm, and the maximum absorption wavelength of the acid hydrolysis products of oleander ethanol extract was 510 nm.

[0078] Release rate test results are as follows Figure 3 As shown, the oleander ethanol extract before acid hydrolysis exhibited a typical explosive release phenomenon in seawater, meaning its release rate was very high in the early stages, reaching as high as 3.76 mg / cm³ on day 1. -2 d -1 The release rate was consistently within 2 mg / cm³ during the first 7 days. -2 d -1 The above results only gradually stabilize in the later stages (after 10 days), with the release rate decreasing to 0.99–1.58 mg / cm³. -2 d -1 In comparison, the release rate of the acid-hydrolyzed oleander ethanol extract was significantly reduced, reaching only 1.04 mg / cm³ on day 1. -2 d -1 The overall release process is relatively slow and stable (release rate between 0.30 and 1.04 mg / cm³). -2 d -1 (between). Throughout the entire testing period, the release rate of antifouling agents in the coatings containing the acid-hydrolyzed product of oleander ethanol extract was consistently significantly lower than that in the coatings containing the extract before acid hydrolysis, indicating that hydrolysis treatment can significantly reduce the release rate of antifouling agents.

[0079] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. The use of acid hydrolysate of an alcohol extract of Nerium indicum in the preparation of a marine slow-release antifouling agent, characterized in that: The preparation method of the acid hydrolysis product of the oleander ethanol extract includes the following steps: ​ (1) the tender stems and leaves of the oleander are cleaned, air-dried and crushed, and then soaked in a 75-80% ethanol solution for 70-75 hours, and the step is repeated several times to obtain a soaking solution; (2) the soaking solution is filtered and concentrated by rotary evaporation under reduced pressure, and then extracted with an equal volume of petroleum ether several times, and the upper organic phase is discarded; (3) an excess of a saturated lead acetate aqueous solution is added to the material obtained in step (2) and stirred until no yellowish precipitate is produced, then filtered to obtain a first filtrate, and then excess hydrogen sulfide is introduced into the first filtrate and stirred until no black precipitate is produced, then filtered to obtain a second filtrate, and the washing solution obtained by washing the precipitate several times is mixed with the second filtrate, and finally concentrated by rotary evaporation under reduced pressure to obtain a black solid, which is the oleander ethanol extract; (4) the oleander ethanol extract and an acid solution are mixed at a solid-liquid ratio of 10:1, heated in a water bath at 90 ℃ for 1 hour, and then extracted with ethyl acetate and concentrated to obtain the acid hydrolysis product; wherein the concentration of the acid solution is 2 mol / L, and the acid in the acid solution is at least one of hydrochloric acid and sulfuric acid.

2. Use of the marine slow-release antifouling agent in the preparation of a marine antifouling coating, characterized in that: The effective component of the marine slow-release antifouling agent is the acid hydrolysis product of the oleander ethanol extract, and the preparation method of the acid hydrolysis product of the oleander ethanol extract includes the following steps: (1) the tender stems and leaves of the oleander are cleaned, air-dried and crushed, and then soaked in a 75-80% ethanol solution for 70-75 hours, and the step is repeated several times to obtain a soaking solution; (2) the soaking solution is filtered and concentrated by rotary evaporation under reduced pressure, and then extracted with an equal volume of petroleum ether several times, and the upper organic phase is discarded; (3) an excess of a saturated lead acetate aqueous solution is added to the material obtained in step (2) and stirred until no yellowish precipitate is produced, then filtered to obtain a first filtrate, and then excess hydrogen sulfide is introduced into the first filtrate and stirred until no black precipitate is produced, then filtered to obtain a second filtrate, and the washing solution obtained by washing the precipitate several times is mixed with the second filtrate, and finally concentrated by rotary evaporation under reduced pressure to obtain a black solid, which is the oleander ethanol extract; (4) the oleander ethanol extract and an acid solution are mixed at a solid-liquid ratio of 10:1, heated in a water bath at 90 ℃ for 1 hour, and then extracted with ethyl acetate and concentrated to obtain the acid hydrolysis product; wherein the concentration of the acid solution is 2 mol / L, and the acid in the acid solution is at least one of hydrochloric acid and sulfuric acid.

3. Use according to claim 2, wherein: The marine antifouling coating also includes a binder and an organic solvent.

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