Deep-sea aquaculture composite modified net and its preparation method and application

Abstract

The present invention relates to a deep-sea aquaculture composite modified net and its preparation method and application. First, the original net is cleaned and dried, and then immersed in a Tris-HCl solution containing dopamine for modification. Then, the net is lifted and placed in a hot air flow for reaction. The modified net is repeatedly pulled and subjected to the hot air flow reaction for multiple times to obtain a modified net. Finally, an antifouling coating containing a polymer and nanoparticles is repeatedly dipped on the surface of the modified net and fully dried and solidified to obtain a deep-sea aquaculture composite modified net product with excellent anti-fouling biological accumulation performance. The present invention generates a dense and complete polydopamine film on the surface of the net by changing process conditions such as dopamine concentration, number of pulling times, and pulling time, thereby improving the adhesion between the net and the antifouling coating. The modification method of the present invention is simple and easy to operate, does not change the original performance of the net, is non-toxic, environmentally friendly, and highly repeatable. It has many advantages such as being friendly to the marine environment and simple construction.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and in particular to a deep-sea aquaculture composite modified net and a preparation method and application thereof. Background Art

[0002] Deep-sea aquaculture nets are made from a variety of materials, including polyethylene (PE), nylon (PA), polyethylene terephthalate (PET), polyvinyl chloride (PVC), ultra-high molecular weight polyethylene (UHMWPE), and alloys. Prolonged use can lead to the accumulation of marine fouling organisms on the net surface. Due to its high strength, high toughness, and low price, polyethylene is currently the most widely used net material on the market. However, its chemical surface is inert and exhibits poor adhesion to antifouling coatings. Therefore, surface treatment of the substrate or the use of a high-adhesion antifouling coating is necessary to ensure that the antifouling agent adheres effectively to the polyethylene net surface.

[0003] Common methods for modifying the surface of polyethylene fibers include plasma modification, cross-linking, radiation grafting, and strong oxidants. Radiation grafting, among other methods, involves irradiation with gamma rays, beta rays, and electron beams. The principle is that irradiated polymers generate free radicals, which then undergo graft polymerization reactions with other monomers, thereby achieving surface modification. For example, ultrahigh molecular weight polyethylene (UHMWPE) fibers are treated with a combination of ultraviolet irradiation and corona discharge to improve the interfacial adhesion of vinyl ester resin composites. The ozone generated by the discharge and the ozone-derived hydroxyl radicals alter the surface properties of the PE fibers, strengthening the interfacial bonding between the fibers and the substrate, ultimately improving the mechanical properties of the composite. Other methods for modifying the surface of polyethylene fibers include alkali treatment and nanoparticle filling.

[0004] To further enhance the interfacial bonding between the matrix material and the fiber reinforcement, two or more modification methods can be combined to synergistically modify the fibers, in addition to a single modification treatment. However, compared to existing modification methods, addressing the issue of low fiber-antifouling adhesion using environmentally friendly and simple modification methods that do not damage the mechanical properties of the substrate remains a topic requiring further research.

[0005] Since its discovery in 2007 that it can form polydopamine films on various organic and inorganic substrates, dopamine has become a versatile platform for secondary surface-mediated reactions. As a novel surface modifier, dopamine is widely used in the environmental, energy, and biological fields to construct high-performance adsorption materials and improve ion mobility. Furthermore, due to its strong adhesion and non-covalent interactions, it can be used to modify the surface of inert materials through assisted deposition and physical adsorption, thereby improving substrate adhesion.

[0006] Polymer antifouling coatings are widely used on ships but less commonly in aquaculture cages. Therefore, this paper proposes modifying nets with dopamine to improve their adhesion to the antifouling coating. The antifouling effects of polymer antifouling coatings and nanoparticle-doped composite coatings on aquaculture cages are also explored. This method offers advantages such as environmental friendliness, ease of operation, high reproducibility, and the ability to maintain the original properties of the nets. The nets require no chemical pretreatment for direct impregnation and adsorption; the modified product can be obtained through simple processes such as pulling and hot-blowing. This method is not only simple, mild, and universally applicable, but can also improve the adhesion of nets made of different materials, and even materials from other industries, contributing to the faster and better development of deep-sea aquaculture. Summary of the Invention

[0007] One of the purposes of the present invention is to provide a composite modified net having at least three layers, namely a body layer, a modified middle layer and an antifouling coating.

[0008] Furthermore, the material of the body layer is selected from at least one of PE, PA, PET, PVC, HDPE, and alloys (such as copper alloys, etc.).

[0009] Furthermore, the material of the modified intermediate layer is specifically polydopamine (PDOPA).

[0010] Furthermore, the material of the antifouling coating is specifically hydrogenated styrene / ethylene-butylene / styrene block copolymer (SEBS), ethylene-vinyl acetate copolymer (EVA), or a block copolymer formed by reacting at least two of styrene, polydimethylsiloxane, polyvinylsiloxane, and polyfluoroalkylsiloxane.

[0011] Furthermore, the antifouling coating is doped with nanoparticles, and the nanoparticles are selected from at least one of SiO2, ZnO, carbon nanotubes (CNTs), CoFe, BaTiO3, and graphene.

[0012] Furthermore, the doping amount of the nanoparticles is equivalent to 1wt%-20wt% of the mass of the polymer in the antifouling coating.

[0013] A second object of the present invention is to provide a method for preparing the above-mentioned composite modified net, which comprises the following steps: (a) modifying the net using a modifying liquid containing dopamine; (b) applying an antifouling coating on the surface of the modified net and drying and curing it.

[0014] Furthermore, in step (a), the net needs to be pretreated before modification, and the pretreatment includes water washing, alcohol washing, and drying.

[0015] Furthermore, the modification liquid in step (a) is specifically a Tris-HCl buffer of dopamine, and the pH of the modification liquid is alkaline.

[0016] Furthermore, the concentration of dopamine in the modification solution in step (a) is 0.5-10.0 g / L, and the pH of the modification solution is specifically 8.0-9.0.

[0017] Furthermore, the modification process of step (a) is as follows: the net is immersed in the modification liquid, and after being lifted up, it is kept in a hot air flow for a period of time, and the immersion-pulling heat treatment is repeated multiple times to finally obtain the modified net.

[0018] Furthermore, the net is immersed for 1-10 minutes each time, the immersion temperature is 20-40°C, the number of immersion-pulling heat treatments does not exceed 30 times, the hot air flow reaction time is 1-10 minutes, and the hot air flow reaction temperature is 10-65°C.

[0019] Furthermore, the antifouling coating in step (b) comprises a polymer, nanoparticles, and a solvent, wherein the polymer is specifically a hydrogenated styrene / ethylene-butylene / styrene block copolymer (SEBS), an ethylene-vinyl acetate copolymer (EVA), or a block copolymer formed by reacting at least two of styrene, polydimethylsiloxane, polyvinylsiloxane, and polyfluoroalkylsiloxane; the nanoparticles are selected from at least one of SiO2, ZnO, CNTs, CoFe, BaTiO3, and graphene; and the solvent is selected from at least one of cyclohexane, n-hexane, ethyl acetate, dichloromethane, toluene, and benzene.

[0020] Furthermore, the concentration of the polymer in the antifouling coating is 0.1 wt%-10 wt%, and the doping amount of the nanoparticles is equivalent to 1 wt%-20 wt% of the mass of the polymer.

[0021] Furthermore, in step (b), the antifouling coating is repeatedly applied to the surface of the modified net by a dip coating method, and then dried and solidified.

[0022] Furthermore, in step (b), the dipping time for each time is 1-30 minutes, the number of dipping times is 1-15 times, and the dipping and drying curing temperatures are both 0°C-50°C.

[0023] The third object of the present invention is to provide the application of the above-mentioned composite modified net in deep-sea aquaculture.

[0024] The present invention first utilizes a "pulling method" to composite dopamine onto the mesh. Under weakly alkaline conditions, dopamine assembles through non-covalent forces such as hydrogen bonding and stacking to form supramolecular aggregates containing numerous unique functional groups, such as indole, catechol, o-diphenylquinone, amino, and carboxyl groups. This complex molecular structure and rich functional groups impart strong adhesion and attractive post-functionalization capabilities, thereby enhancing adhesion between the mesh and the antifouling coating. Furthermore, the modification method provided by the present invention is simple, environmentally friendly, and suitable for surface modification of meshes of various materials, demonstrating excellent universality.

[0025] This invention also leverages the size and surface effects of nanoparticles, incorporating them into a polymer antifouling coating. Adhesion of the coating and nanoparticles to the surface of the net substrate is achieved through a dip-coating process. This process is simple and convenient, contains no organic volatiles, is harmless to operators, and dries and cures at room temperature. The resulting coating exhibits excellent adhesion to the net, and after complete curing, the coating exhibits excellent flexibility and abrasion resistance, exhibiting no noticeable cracking or peeling even after repeated bending. Compared to unmodified nets, the adhesion between the net and the antifouling coating, as well as the unmodified net's antifouling biofouling effectiveness, is significantly enhanced.

[0026] In summary, compared with the prior art, the present invention can achieve the following beneficial effects: (1) The solvent used in the surface modification process of the net of the present invention is water, which has the advantages of being non-toxic, harmless, and non-polluting; (2) The conditions and equipment for the surface modification of the net of the present invention are simple and easy to operate, and the adhesion between the net and the antifouling coating is improved by generating a dense and complete polydopamine film on the surface of the net; (3) The surface modification method of the present invention does not change the original performance of the net, and is applicable to nets of different materials, with good universality; (4) The present invention also dip-coats a layer of antifouling coating on the surface of the modified net, and the dip-coating operation is relatively simple. The introduction of nanoparticles improves the antifouling performance of the polymer antifouling coating, and is effective in preventing the accumulation of marine fouling organisms in seawater aquaculture cages. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a FTIR comparison chart of the polyethylene mesh before and after surface modification in Example 1.

[0028] Figure 2 This is the XRD comparison diagram of the polyethylene mesh before and after surface modification in Example 1.

[0029] Figure 3 This is a DSC comparison chart of the polyethylene mesh before and after surface modification in Example 1.

[0030] Figure 4 This is the SEM image of the polyethylene net after surface modification in Example 1.

[0031] Figure 5 This is an SEM image of the polyethylene net after surface modification and dip-coating with antifouling coating in Example 1.

[0032] Figure 6 These are SEM images of the polyethylene net in Example 1 before (a) and after (b) surface modification, after being dipped in antifouling coating and bent 20 times. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to fully understand the technical solutions and beneficial effects of the present invention, further description will be given below in conjunction with specific embodiments and drawings.

[0034] Example 1

[0035] (1) Wash the polyethylene net purchased from the market with distilled water and anhydrous ethanol in turn, and then dry it naturally for later use.

[0036] (2) Dissolve 5.68 g of tris (hydroxymethyl)aminomethane (Tris) in 300 mL of distilled water and adjust the pH of the solution to 8.5 with dilute hydrochloric acid to obtain a Tris-HCl buffer solution. Dissolve a certain amount of dopamine hydrochloride in the Tris-HCl buffer solution and stir evenly to obtain a dopamine / Tris-HCl solution with a concentration of 2.0 g / L (dopamine concentration, the same below). Add the washed and dried polyethylene mesh to the dopamine / Tris-HCl solution, stir at 25°C for 3 min, then lift the mesh and transfer it to a 40°C hot air flow for 2 min. Repeat the lifting-hot air flow reaction 24 times to obtain a modified polyethylene mesh.

[0037] (3) SEBS was dissolved in 500 mL of cyclohexane and stirred to disperse evenly to obtain a 2 wt% SEBS / cyclohexane antifouling coating. The antifouling coating was then applied to the surface of the modified polyethylene mesh by dip coating at room temperature. Each dip coating lasted 10 min and was repeated once. The mixture was then dried and cured at 25°C to form an antifouling layer.

[0038] In order to fully understand the microstructure and performance of the net at each stage of Example 1, samples were taken and corresponding tests were performed.

[0039] Figure 1 The FTIR comparison chart of the polyethylene mesh before and after surface modification shows that, compared with pure PE, the PE@PDOPA exhibits characteristic peaks of polydopamine, indicating that polydopamine is indeed evenly coated on the surface of the PE mesh after modification.

[0040] Figure 2 The XRD comparison diagram of the polyethylene mesh before and after surface modification shows that dopamine modification does not change the original crystalline structure of PE, and therefore does not affect the original performance of the mesh.

[0041] Figure 3 The DSC comparison chart of the polyethylene mesh before and after surface modification shows that the modification did not change the original thermal properties of PE, which further verifies that dopamine modification does not change the performance of the mesh.

[0042] Figure 4 The SEM image of the modified polyethylene mesh shows that a complete polydopamine film is formed on the surface of the PE mesh.

[0043] Figure 5 This is a SEM image of the polyethylene net after surface modification and dip-coating with an antifouling coating. As can be seen, the composite modified net exhibits a variety of pore sizes, with an average size of approximately micrometers. While fouling organisms like algae range in size from a few micrometers to several hundred micrometers, this helps slow the attachment of marine fouling organisms.

[0044] Figure 6 SEM images of polyethylene nets before (a) and after (b) modification, after being dipped in antifouling coating and folded 20 times. This test measures the adhesion of the antifouling coating to the net surface. The test method is as follows: the modified and unmodified nets are dipped in antifouling coating, allowed to dry, and then folded back and forth 20 times. The coating is observed for cracks and shedding, and the adhesion is graded into four levels: 1 for no shedding or cracking, 2 for slight cracking but no shedding, 3 for minor shedding, and 4 for significant cracking and shedding, with 1 being the highest level. The test results show that the adhesion of the modified PE net to the SEBS antifouling coating improved from Level 2 (unmodified net) to Level 1.

[0045] Example 2

[0046] (1) Wash the polyethylene net purchased from the market with distilled water and anhydrous ethanol in turn, and then dry it naturally for later use.

[0047] (2) Prepare a Tris-HCl buffer solution according to the method of Example 1. Dissolve a certain amount of dopamine hydrochloride in the Tris-HCl buffer solution and stir evenly to obtain a dopamine / Tris-HCl solution with a concentration of 3.0 g / L. Add the washed and dried polyethylene mesh to the dopamine / Tris-HCl solution and stir at 25°C for 5 minutes. Then, lift the mesh and transfer it to a hot air stream at 40°C for 2 minutes. Repeat the lifting-hot air stream reaction 24 times to obtain a modified polyethylene mesh.

[0048] (3) SEBS was dissolved in 500 mL of cyclohexane and stirred to disperse evenly to obtain a 2 wt% SEBS / cyclohexane antifouling coating. The antifouling coating was then applied to the surface of the modified polyethylene mesh by dip coating at 5°C. Each dip coating lasted 10 min and the number of dip coatings was 24. Finally, the antifouling layer was fully dried and cured at 5°C to form an antifouling layer.

[0049] Example 3

[0050] (1) Wash the polyethylene net purchased from the market with distilled water and anhydrous ethanol in turn, and then dry it naturally for later use.

[0051] (2) Prepare a Tris-HCl buffer solution according to the method of Example 1. Dissolve a certain amount of dopamine hydrochloride in the Tris-HCl buffer solution and stir evenly to obtain a dopamine / Tris-HCl solution with a concentration of 2.0 g / L. Add the washed and dried polyethylene mesh to the dopamine / Tris-HCl solution, stir at 25°C for 3 minutes, then lift the mesh and transfer it to a hot air stream at 40°C for 2 minutes. Repeat the lifting-hot air stream reaction 24 times to obtain a modified polyethylene mesh.

[0052] (3) PS-b-PDMS (polystyrene-b-polydimethylsiloxane) was dissolved in 200 mL of cyclohexane and stirred to disperse uniformly to obtain a 1 wt% PS-b-PDMS / cyclohexane antifouling coating. The antifouling coating was then applied to the surface of the modified polyethylene mesh by dip coating at room temperature. Each dip coating lasted 10 min and was repeated three times. The coating was then dried and cured at 25°C to form an antifouling layer.

[0053] Example 4

[0054] (1) Wash the polyethylene net purchased from the market with distilled water and anhydrous ethanol in turn, and then dry it naturally for later use.

[0055] (2) Prepare a Tris-HCl buffer solution according to the method of Example 1. Dissolve a certain amount of dopamine hydrochloride in the Tris-HCl buffer solution and stir evenly to obtain a dopamine / Tris-HCl solution with a concentration of 1.0 g / L. Add the washed and dried polyethylene mesh to the dopamine / Tris-HCl solution and stir at 25°C for 5 minutes. Then, lift the mesh and transfer it to a hot air stream at 40°C for 3 minutes. Repeat the lifting-hot air stream reaction 30 times to obtain a modified polyethylene mesh.

[0056] (3) PS-b-PDMS was dissolved in 200 mL of cyclohexane, and CoFe nanoparticles were added and stirred to uniformly disperse the mixture. This resulted in a PS-b-PDMS / CoFe / cyclohexane antifouling coating, where the PS-b-PDMS concentration was 1 wt% and the amount of CoFe nanoparticles added was equivalent to 5% of the PS-b-PDMS mass. The antifouling coating was then dip-coated on the surface of the modified polyethylene mesh at room temperature for 30 min per dip, three times, and then fully dried and cured at 25°C to form an antifouling layer.

[0057] Example 5

[0058] (1) Wash the polyethylene net purchased from the market with distilled water and anhydrous ethanol in turn, and then dry it naturally for later use.

[0059] (2) Prepare a Tris-HCl buffer solution according to the method of Example 1. Dissolve a certain amount of dopamine hydrochloride in the Tris-HCl buffer solution and stir evenly to obtain a dopamine / Tris-HCl solution with a concentration of 4.0 g / L. Add the washed and dried polyethylene mesh to the dopamine / Tris-HCl solution and stir at 25°C for 3 minutes. Then, lift the mesh and transfer it to a hot air stream at 40°C for 2 minutes. Repeat the lifting-hot air stream reaction 24 times to obtain a modified polyethylene mesh.

[0060] (3) PS-b-PDMS was dissolved in 200 mL of cyclohexane, and CNTs were added and stirred to disperse them evenly to obtain a PS-PDMS / CNTs / cyclohexane antifouling coating (where the concentration of PS-b-PDMS was 1 wt% and the amount of CNTs nanoparticles added was equivalent to 1 wt% of the mass of PS-b-PDMS). The antifouling coating was dip-coated on the surface of the modified polyethylene net at room temperature. The dipping time was 5 min each time and the number of dippings was 6. Finally, the antifouling layer was fully dried and cured at 25 °C to form an antifouling layer.

[0061] Referring to the antifouling coating adhesion test method in Example 1, the composite modified nets prepared in Examples 4-5 were tested. The results showed that the adhesion level of their antifouling coatings could all reach Level 1. The addition of nanoparticles mainly played a role in improving the antifouling effect of the polymer antifouling coating.

Claims

1. A composite modified net, characterized by: The composite modified net has a structure of at least three layers, namely a main body layer, a modified intermediate layer, and an antifouling coating. The material of the main body layer is selected from at least one of PE, PA, PET, PVC, HDPE, and an alloy. The material of the modified intermediate layer is specifically polydopamine. The material of the antifouling coating is specifically SEBS, EVA, or a block copolymer formed by the reaction of at least two of styrene, polydimethylsiloxane, polyvinylsiloxane, and polyfluoroalkylsiloxane. The surface of the composite modified net presents a morphology of bubbles of varying sizes, and the average size of the bubbles is in the micron level.

2. The composite modified netting according to claim 1, characterized in that: The antifouling coating is also doped with nanoparticles, which are selected from at least one of SiO2, ZnO, CNTs, CoFe, BaTiO3 and graphene.

3. The composite modified netting according to claim 2, characterized in that: The doping amount of the nanoparticles is equivalent to 1 wt% to 20 wt% of the mass of the polymer in the antifouling coating.

4. The method for preparing the composite modified net according to any one of claims 1 to 3, characterized in that The method comprises the following steps: (a) modifying the net with a modifying liquid containing dopamine; and (b) coating the surface of the modified net with an antifouling coating and drying and solidifying the coating.

5. The method according to claim 4, wherein: In step (a), the net needs to be pretreated before modification, and the pretreatment includes water washing, alcohol washing, and drying.

6. The method according to claim 4, wherein: The modification solution in step (a) is specifically 0.5-10.0 g / L dopamine / Tris-HCl buffer, and the pH of the modification solution is 8.0-9.

0.

7. The method according to claim 4, wherein The modification process of step (a) is as follows: immersing the net in a modification liquid, lifting it and keeping it in a hot air flow for a period of time, repeating the immersion-lifting heat treatment multiple times, and finally obtaining a modified net; The soaking time for each time is 1-10 minutes, the soaking temperature is 20-40° C., the soaking-pulling heat treatment times are no more than 30 times, the hot air flow reaction time is 1-10 minutes, and the hot air flow reaction temperature is 10-65° C.

8. The method according to claim 4, wherein: Step (b) repeatedly applies the antifouling coating to the surface of the modified net by dip coating and drying and curing, wherein each dip coating time is 1-30 minutes, the number of dip coatings is 1-24 times, and the dip coating and drying and curing temperatures are both 0°C-50°C. The antifouling coating comprises a polymer, nanoparticles, and a solvent, wherein the polymer is specifically SEBS, EVA, or a block copolymer formed by reacting at least two of styrene, polydimethylsiloxane, polyvinylsiloxane, and polyfluoroalkylsiloxane; the nanoparticles are selected from at least one of SiO2, ZnO, CNTs, CoFe, BaTiO3, and graphene; and the solvent is selected from at least one of cyclohexane, n-hexane, ethyl acetate, dichloromethane, toluene, and benzene. The concentration of the polymer in the antifouling coating is 0.1wt%-10wt%, and the doping amount of the nanoparticles is equivalent to 1wt%-20wt% of the mass of the polymer.

9. Use of the composite modified net according to any one of claims 1 to 3 in deep-sea aquaculture.

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