Waterproof and mildewproof aquarium sealant and preparation method thereof

Abstract

The application discloses a kind of water-resistant mould-proof fish tank sealant and preparation method thereof, belong to sealant technical field.The application is to solve the technical problem that existing fish tank sealant is difficult to simultaneously realize long-acting mould-proof, ecological safety and structural durability.The sealant uses hydroxyl-terminated polydimethylsiloxane as base polymer, and includes mould-proof and algae-proof functional composite system, which is composed of ZIF-8 core-shell structure composite particles with zeolite molecular sieve surface modified by first silane coupling agent and anatase type nano titanium dioxide coated with cerium oxide with fluorine-containing alkyl silane grafted on the surface, and the two form Si-O-Si covalent bond through hydrolysable silane group and terminal hydroxyl and / or alkoxy silane crosslinking agent condensation reaction, and are bonded in silicone crosslinking network.The sealant of the application fixes functional components through chemical bonding, has long-acting mould-proof and algae-proof, high ecological safety and excellent water-resistant durability, and is suitable for fish tank, aquarium and other aquatic ecological sealing structures.

Description

Technical Field

[0001] This invention belongs to the field of sealant technology, specifically relating to a water-resistant and mildew-proof aquarium sealant and its preparation method. Background Technology

[0002] As closed or semi-closed aquatic ecosystems, aquariums have glass seams that are constantly exposed to nutrient-rich water, making them highly susceptible to mold and algae growth, resulting in stubborn black or green stains. This not only affects the aesthetics, but the localized acidic environment created by microbial metabolism can also erode the colloids, accelerating their aging and ultimately leading to seal failure and leakage.

[0003] Currently, aquarium sealants are mainly divided into two categories: the first category is ordinary neutral de-alcoholized or deoxime-based silicone sealants, which do not have anti-mold or anti-algae functions; the second category is functional silicone sealants with added organic anti-mold agents, commonly including isothiazolinone compounds. These small-molecule anti-mold agents continuously dissolve from the colloid, and the released active ingredients are not only significantly toxic to aquatic organisms such as fish and shrimp, but also inhibit the activity of nitrifying bacteria, leading to water quality deterioration. Therefore, they are explicitly prohibited from use in scenarios involving direct contact with aquatic ecosystems.

[0004] To reduce the ecotoxicity of organic antifungal agents, existing technologies attempt to use inorganic antibacterial and antifungal agents, such as nano-silver, nano-zinc oxide, or anatase nano-titanium dioxide. However, inorganic antibacterial agents have the following problems: (1) Physically blended inorganic particles are prone to precipitation under long-term water immersion, which may cause metal ion pollution in water bodies; (2) Unmodified inorganic nanoparticles are prone to agglomeration, affecting the uniformity and mechanical properties of the colloid; (3) The active oxygen species generated by anatase nano-titanium dioxide under light will degrade the silicone polymer backbone, causing the colloid to pulverize, become brittle, and lose elasticity, reducing the long-term durability of the sealant.

[0005] In recent years, metal-organic framework materials have attracted attention in the field of antibacterial applications due to their high specific surface area and tunable pore structure. Among them, the zeolite imidazolium ester framework material ZIF-8 can release Zn in a sustained manner. 2+ Ions, under light irradiation, simultaneously generate reactive oxygen species through ligand-metal charge transfer, achieving a dual antibacterial mechanism of slow ion release and oxidative sterilization. Currently, there are no reports of applying ZIF-8 to aquarium sealants and resolving its compatibility with silicone systems and chemical bonding issues.

[0006] Therefore, existing aquarium sealants cannot simultaneously achieve the technical goals of long-term anti-mildew, ecological safety, and structural durability under long-term water contact conditions. There is an urgent need to develop a new type of anti-mildew sealing material that combines multiple antibacterial mechanisms, low environmental release risk, and high matrix stability. Summary of the Invention

[0007] This invention provides an aquarium sealant and its preparation method that chemically anchors anti-mold and anti-algae functional components into the sealant matrix, thereby achieving a combination of long-lasting anti-mold, high ecological safety and excellent matrix durability.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a water-resistant and mildew-proof fish tank sealant.

[0009] This sealant is based on hydroxyl-terminated polydimethylsiloxane as a polymer and includes fillers, alkoxysilane crosslinking agents, secondary silane coupling agents, catalysts, and a composite system with anti-mildew and anti-algae functions.

[0010] The sealant comprises the following components in parts by weight: 100 parts of hydroxyl-terminated polydimethylsiloxane, 3-10 parts of anti-mildew and anti-algae functional composite system, 20-40 parts of filler, 5-12 parts of alkoxysilane crosslinking agent, 0.05-0.5 parts of catalyst, and 0.5-2 parts of second silane coupling agent.

[0011] Preferably, the viscosity of the hydroxyl-terminated polydimethylsiloxane at 25°C is 2,000-200,000 mPa·s, more preferably 5,000-150,000 mPa·s, and most preferably 20,000-80,000 mPa·s.

[0012] Preferably, the filler is selected from at least one of nano-activated calcium carbonate, heavy calcium carbonate, fumed silica, hydrophobic silica, silica powder, diatomaceous earth, and precipitated silica.

[0013] Preferably, the alkoxysilane crosslinking agent is selected from at least one of methyltrimethoxysilane, methyltriethoxysilane, propyltrimethoxysilane, octyltrimethoxysilane, phenyltrimethoxysilane, and vinyltrimethoxysilane.

[0014] Preferably, the second silane coupling agent is selected from at least one of γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-glycidyl ether oxypropyltrimethoxysilane, and vinyltrimethoxysilane.

[0015] Preferably, the catalyst is selected from at least one of dibutyltin dilaurate, dibutyltin dioctanoate, dibutyltin diacetate, tetraisopropyl titanate, tetrabutyl titanate, and diisopropyl di(ethyl acetoacetate) titanate.

[0016] The core technical feature of this invention lies in constructing a fungicide- and algae-resistant composite system anchored in a silicone network through chemical bonding. This fungicide- and algae-resistant composite system comprises the following two parts: Zeolite molecular sieve @ZIF-8 core-shell structured composite particles, the surface of which is modified by a first silane coupling agent; (b) Cerium oxide-coated anatase nano-titanium dioxide with fluorinated alkyl silane grafted onto its surface; The hydrolyzable silaneoxy groups on the surfaces of components (a) and (b) can undergo hydrolysis and condensation reactions with the terminal hydroxyl groups of the terminal hydroxyl polydimethylsiloxane and / or the alkoxysilane crosslinking agent to form Si-O-Si covalent bonds. This covalently bonds components (a) and (b) to the silicone crosslinking network of the sealant, achieving permanent chemical anchoring of the functional components and effectively preventing their migration and precipitation under long-term water immersion.

[0017] Preferably, the first silane coupling agent is selected from at least one of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-glycidyl ether oxypropyltrimethoxysilane.

[0018] The component (a) is a zeolite molecular sieve@ZIF-8 core-shell structured composite particle, which has a zeolite molecular sieve as the core and ZIF-8 metal-organic framework nanoparticles uniformly loaded on the surface of the zeolite molecular sieve through in-situ growth to form a core-shell structure.

[0019] Preferably, the zeolite molecules are screened from clinoptilolite or mordenite, with a particle size of 1-5 μm and a specific surface area of ​​20-50 m². 2 / g. The zeolite molecular sieve exhibits a high selective exchange capacity for ammonium ions.

[0020] Preferably, the ZIF-8 is a porous crystal material formed by the coordination of zinc ions and 2-methylimidazole, with a grain size of 50-200 nm; the mass ratio of ZIF-8 to zeolite molecular sieve is 1:4 to 1:1.

[0021] The mechanism by which ZIF-8 inhibits the growth of mold and algae is as follows: ① Slow-release Zn 2+ ① It can destroy the integrity of microbial cell membranes; ② Under light conditions, it can continuously generate reactive oxygen species such as superoxide anions through ligand-metal charge transfer, which can oxidize and inactivate microorganisms; ③ Its skeleton structure can adsorb ammonium ions in water, reducing the nitrogen source available to algae; ④ It can induce the inhibition of algal chlorophyll synthesis and the obstruction of ATP synthesis, thus blocking its energy metabolism.

[0022] Compared with traditional zinc- or silver-loaded zeolite molecular sieves, the zeolite molecular sieve @ZIF-8 core-shell structure of the present invention can achieve superior antibacterial and anti-algae properties without additional metal ion loading, and avoids the potential toxicity risk of silver ions to aquatic organisms.

[0023] The component (b) is cerium oxide-coated anatase nano-titanium dioxide, which has anatase nano-titanium dioxide as the core and a cerium oxide layer on the surface. The surface of the cerium oxide layer is further grafted with fluorinated alkyl silanes to form a three-layer core-shell structure.

[0024] Preferably, the cerium oxide layer has a thickness of 1-5 nm and the molar ratio of cerium to titanium is 0.05:1 to 0.2:1; wherein, the cerium oxide layer is deposited on the surface of anatase nano-titanium dioxide by a sol-gel method to eliminate the strong photocatalytic activity of anatase nano-titanium dioxide, prevent it from degrading the silicone matrix, and at the same time retain its excellent ultraviolet shielding performance.

[0025] Preferably, the fluorinated alkyl silane is selected from at least one of perfluorodecyltrimethoxysilane, perfluorodecyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, and tridecafluorooctyltrimethoxysilane; its amount is 1% to 10% of the mass of anatase nano-titanium dioxide, preferably 3% to 8%, more preferably 5%; it imparts extremely low surface energy to the surface of the cured colloid, achieving superhydrophobic, oleophobic, and anti-fouling self-cleaning functions.

[0026] Secondly, the present invention provides a method for preparing the above-mentioned anti-mildew and anti-algae functional composite system.

[0027] The preparation method of component (a) is as follows: Preparation of the reaction solution: Dissolve the soluble zinc salt and 2-methylimidazole in deionized water or an alcohol-water mixture at a molar ratio of 1:4 to 1:8, and stir until homogeneous to obtain the reaction solution. The soluble zinc salt is selected from at least one of zinc nitrate, zinc chloride, and zinc sulfate.

[0028] (2) In-situ growth: The zeolite molecular sieve was dispersed in the above reaction solution and stirred for 2-6 hours at room temperature to 60°C to allow ZIF-8 to nucleate and grow in situ on the surface of the zeolite molecular sieve. After the reaction was completed, the precipitate was collected by centrifugation at 3000-8000 rpm for 10-20 minutes; it was washed with deionized water 3-5 times, and centrifuged after each wash; finally, it was dried in a vacuum drying oven at 60-80°C for 12-24 hours to obtain zeolite molecular sieve@ZIF-8 core-shell composite particles.

[0029] (3) Surface modification: The obtained zeolite molecular sieve @ZIF-8 core-shell composite particles were dispersed in anhydrous ethanol, and a first silane coupling agent was added. The mixture was refluxed at 70-80℃ for 4-6 hours. After the reaction, the precipitate was collected by centrifugation at 3000-8000 rpm for 10-20 minutes. The precipitate was washed with anhydrous ethanol 3-5 times, and centrifuged after each wash. Finally, the precipitate was dried in a vacuum drying oven at 60-80℃ for 12-24 hours to obtain surface-modified zeolite molecular sieve @ZIF-8 core-shell composite particles, i.e., component (a).

[0030] The preparation method of component (b) is as follows: (1) Cerium oxide coating: Anatase nano-titanium dioxide is dispersed in anhydrous ethanol, and a cerium salt solution is added. The molar ratio of cerium to titanium is controlled to be 0.05:1 to 0.2:1. The pH of the system is adjusted to 9-10 with ammonia water, and the reaction is stirred at 70-80℃ for 2-4 hours. After the reaction is completed, the precipitate is collected by centrifugation at 3000-8000 rpm for 10-20 minutes. The precipitate is washed alternately with deionized water and anhydrous ethanol 3-5 times, and centrifuged after each washing. The precipitate is dried in a vacuum drying oven at 60-80℃ for 12-24 hours, and then calcined at 400-500℃ for 2-3 hours to obtain cerium oxide-coated anatase nano-titanium dioxide. The cerium salt is selected from at least one of cerium nitrate, cerium ammonium nitrate, and cerium chloride.

[0031] (2) Grafting with fluorinated alkyl silane: The obtained cerium oxide-coated anatase nano-titanium dioxide was dispersed in toluene, and 1%-10% of the mass of the anatase nano-titanium dioxide was added. The mixture was refluxed at 110-120℃ for 6-10 hours. After the reaction was completed, the precipitate was collected by centrifugation at 3000-8000 rpm for 10-20 minutes. The precipitate was washed with toluene 3-5 times, and centrifuged after each wash. The precipitate was dried in a vacuum drying oven at 60-80℃ for 12-24 hours to obtain cerium oxide-coated anatase nano-titanium dioxide with fluorinated alkyl silane grafted onto its surface, i.e., component (b).

[0032] Thirdly, the present invention provides a method for preparing a water-resistant and mildew-resistant sealant, comprising the following steps: S1. Preparation of base paste: The hydroxyl-terminated polydimethylsiloxane and the filler are dehydrated and kneaded under vacuum and heating conditions to obtain a uniform base paste; S2. Addition and dispersion of functional components: The base paste is cooled to below 50°C, and then the components (a) and (b) prepared above are added. The components are dispersed at high speed under an inert gas protective atmosphere to make them evenly distributed in the base paste, so as to obtain a base paste with uniformly dispersed functional components. S3. Crosslinking, Curing, and Filling: Keeping the system temperature below 50°C, add the alkoxysilane crosslinking agent, the second silane coupling agent, and finally the catalyst to the uniformly dispersed base paste obtained in step S2. After the addition is complete, degassing is performed under vacuum to obtain the adhesive. Finally, the obtained adhesive is filled into a sealed container that is isolated from moisture.

[0033] Preferably, in step S1, the dehydration kneading is carried out for 60-120 minutes under conditions of vacuum degree ≤ -0.095 MPa and temperature 110-130℃ to fully remove moisture from the system. This step can be completed in a mixing device equipped with heating, vacuuming, and strong shearing functions, such as a dual planetary mixer.

[0034] Preferably, in step S2, the linear velocity of the high-speed dispersing blade is 10-15 m / s, and the dispersing time is 30-60 minutes.

[0035] Preferably, in step S3, the degassing process is carried out by stirring and mixing under a vacuum of ≤-0.09 MPa for 15-30 minutes.

[0036] Fourthly, the present invention provides the application of the above-mentioned sealant in the preparation of aquarium or ecological sealing structures that are in long-term contact with fresh water.

[0037] The ecological sealing structure includes, but is not limited to: ornamental fish tanks, aquariums, hydroponic planting systems, ecological landscaping containers, or artificial wetland sealing components.

[0038] The beneficial effects of this invention are: This invention achieves both anti-mildew and anti-algae functions through the synergistic effect of zeolite molecular sieve @ZIF-8 core-shell structured composite particles and fluorine-silicon-grafted cerium oxide-coated nano-titanium dioxide. The anti-algae effect of the combination of components (a) and (b) is significantly better than the sum of the effects of using either component alone, indicating that the two have a synergistic effect.

[0039] (2) In this invention, functional components (a) and (b) are chemically bonded to a silicone network, effectively preventing the migration and precipitation of active ingredients. Acute toxicity tests and nitrification inhibition tests on zebrafish show that this invention has no significant toxicity to aquatic organisms and no significant inhibition of the nitrification system; however, the organic antifungal agent exhibits significant ecotoxicity. Long-term immersion tests in simulated aquariums further verify the ecological safety of this invention in practical applications.

[0040] (3) The present invention inhibits the photocatalytic activity of anatase nano-titanium dioxide by cerium oxide coating, thus preventing its degradation of the silicone matrix. Long-term water immersion test results show that the strength retention rate of the sealant of the present invention is significantly better than that of the physical mixing group and the control group without surface modification, and it has good water resistance and durability.

[0041] (4) In this invention, fluorinated alkyl silanes are grafted onto the surface of component (b), imparting low surface energy characteristics to the cured colloid surface and significantly improving the water contact angle. The technical solution of this invention has good reproducibility and stability within the defined parameter range, and the performance is not affected by the substitution of raw materials, indicating that the types of raw materials defined in this invention have universality. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the structure of the functional components of the sealant of the present invention. Detailed Implementation

[0043] The present invention will be described in detail below with reference to the embodiments.

[0044] I. Raw Material Description In the following examples and comparative examples, all raw materials used were commercially available industrial products or analytical grade reagents, wherein: Hydroxyl-terminated polydimethylsiloxane: viscosity 60,000 mPa·s (25℃); Anatase nano-titanium dioxide: average particle size 20-30 nm; Zeolite molecular sieve: clinoptilolite, particle size 1-5μm, specific surface area 20-50 m² 2 / g; 2-Methylimidazole: Purity ≥99%; Fluorinated alkylsilanes: perfluorodecyltrimethoxysilane; Zinc nitrate, cerium ammonium nitrate, γ-aminopropyltrimethoxysilane, and other chemical reagents were all of analytical grade.

[0045] Unless otherwise specified in the embodiments, the first silane coupling agent is γ-aminopropyltrimethoxysilane (KH-550), the second silane coupling agent is γ-aminopropyltrimethoxysilane (KH-550), the fluorinated alkyl silane is perfluorodecyltrimethoxysilane, the alkoxysilane crosslinking agent is methyltrimethoxysilane, the catalyst is dibutyltin dilaurate, and the filler is nano-activated calcium carbonate.

[0046] Preparation of functional components The structural diagram of the functional components is shown below. Figure 1 As shown, the preparation steps are as follows: Preparation Example 1: Preparation of Component (a) Soluble zinc salt and 2-methylimidazole were dissolved in deionized water at a molar ratio of 1:4 to 1:8 and stirred until homogeneous to obtain a reaction solution. Zeolite molecular sieves were dispersed in the reaction solution and stirred at room temperature to 60°C for 2-6 hours to allow ZIF-8 to grow in situ on the surface of the zeolite molecular sieves. After the reaction, the particles were centrifuged, washed with deionized water, and vacuum dried to obtain zeolite molecular sieve@ZIF-8 core-shell composite particles. The obtained composite particles were dispersed in anhydrous ethanol, a first silane coupling agent was added, and the mixture was refluxed at 70-80°C for 4-6 hours. After centrifugation, the particles were washed with anhydrous ethanol and vacuum dried to obtain surface-modified zeolite molecular sieve@ZIF-8 core-shell composite particles, i.e., component (a). The mass ratio of ZIF-8 to zeolite molecular sieves was adjusted according to different examples, as shown in Table 1.

[0047] Preparation Example 2: Preparation of Component (b) Anatase-type nano-titanium dioxide was dispersed in anhydrous ethanol, and a cerium salt solution was added to control the molar ratio of cerium to titanium. The pH was adjusted to 9-10 with ammonia, and the reaction was stirred at 70-80°C for 2-4 hours. After the reaction, the mixture was centrifuged, washed alternately with deionized water and anhydrous ethanol, vacuum dried, and then calcined at 400-500°C for 2-3 hours to obtain cerium oxide-coated anatase-type nano-titanium dioxide. The obtained product was dispersed in toluene, and a fluorinated alkyl silane (1%-10% of the mass of the anatase-type nano-titanium dioxide) was added. The mixture was refluxed at 110-120°C for 6-10 hours, centrifuged, washed with toluene, and vacuum dried to obtain cerium oxide-coated anatase-type nano-titanium dioxide with a surface grafted with a fluorinated alkyl silane, i.e., component (b). The molar ratio of cerium to titanium and the amount of fluorinated alkyl silane were adjusted according to different examples, as shown in Table 1.

[0048] III. General Preparation Methods for Sealants Basic formula (by weight): 100 parts of hydroxyl-terminated polydimethylsiloxane (viscosity 60,000 mPa·s), 30 parts of nano-activated calcium carbonate, 8 parts of methyltrimethoxysilane, 1 part of γ-aminopropyltrimethoxysilane (KH-550), and 0.3 parts of dibutyltin dilaurate.

[0049] Note: In Example E5, the first silane coupling agent was replaced with γ-aminopropyltriethoxysilane; in Example E6, the fluorinated alkyl silane was replaced with perfluorodecyltriethoxysilane; in Example E7, the catalyst was replaced with tetraisopropyl titanate; and in Example E8, the filler was replaced with fumed silica. See Table 1 for details.

[0050] Preparation process: S1. Preparation of base paste: Hydroxyl-terminated polydimethylsiloxane and nano-activated calcium carbonate were added to a double planetary mixer and dehydrated and kneaded for 90 minutes under vacuum degree ≤ -0.095 MPa and temperature 120℃ to obtain a homogeneous base paste.

[0051] S2. Addition and dispersion of functional components: Cool the base paste to 45°C, add component (a) prepared in Preparation Example 1 and component (b) prepared in Preparation Example 2 according to the formulation in Table 1, and disperse at high speed under nitrogen protection (blade linear velocity 12 m / s, 40 minutes) so that components (a) and (b) are evenly distributed in the base paste.

[0052] S3. Crosslinking, curing and filling: Keep the system temperature below 50℃, add alkoxysilane crosslinking agent and second silane coupling agent in sequence, and finally add catalyst. Mix and degas for 20 minutes under vacuum degree ≤-0.09 MPa, fill into aluminum-plastic composite tubes that are isolated from water vapor, and cure for 7 days at 23±2℃ and relative humidity 50±5% to obtain the test sample.

[0053] Note: The process differences of comparative examples D7 and D8 are shown in Table 2. The other examples and comparative examples were prepared according to the above process.

[0054] IV. Examples and Comparative Examples Table 1 Formulation parameters of the examples Note: E1 is the optimal solution; E2 and E3 are the lower and upper level validations of the parameters, respectively; E4 is cross-validation; in E5, the first silane coupling agent is replaced with γ-glycidyl etheroxypropyltrimethoxysilane; in E6, the fluorinated alkyl silane is replaced with 1H,1H,2H,2H-perfluorooctyltriethoxysilane; in E7, the catalyst is replaced with tetraisopropyl titanate; in E8, the filler is replaced with fumed silica; E9 is repeated validation. Except as described above, in each embodiment, the first silane coupling agent is γ-aminopropyltrimethoxysilane (KH-550), the fluorinated alkyl silane is perfluorodecyltrimethoxysilane, the alkoxysilane crosslinking agent is methyltrimethoxysilane, the catalyst is dibutyltin dilaurate, and the filler is nano-activated calcium carbonate. Example 1

[0055] 1. Preparation of component (a) According to the formula in Table 1, E1 (ZIF-8 to zeolite molecular sieve mass ratio 1:2), weigh 20g of zeolite molecular sieve. Calculate the required amount of ZIF-8 to be generated based on the ZIF-8 to zeolite molecular sieve mass ratio of 1:2, and weigh zinc nitrate and 2-methylimidazole accordingly (molar ratio 1:4). Specifically, weigh 14.9g of zinc nitrate and 16.4g of 2-methylimidazole, dissolve them in 500mL of deionized water, and stir until homogeneous to obtain a reaction solution. Disperse the zeolite molecular sieve in the above reaction solution and stir at 50℃ for 4 hours. After the reaction, centrifuge at 5000 rpm for 15 minutes, wash four times with deionized water, and vacuum dry at 70℃ for 18 hours to obtain zeolite molecular sieve@ZIF-8 core-shell composite particles. Disperse the obtained composite particles in 500mL of anhydrous ethanol, add 5.0g of γ-aminopropyltrimethoxysilane (KH-550), and reflux at 75℃ for 5 hours. After the reaction was completed, the particles were centrifuged at 5000 rpm for 15 minutes, washed four times with anhydrous ethanol, and dried under vacuum at 70℃ for 18 hours to obtain surface-modified zeolite molecular sieve @ZIF-8 core-shell composite particles, i.e., component (a).

[0056] 2. Preparation of component (b) Weigh 10 g of anatase nano-titanium dioxide according to the formula in Table 1, E1 (cerium / titanium molar ratio 0.1:1, fluorinated alkyl silane 5%). Calculate the required amount of cerium ammonium nitrate based on the cerium / titanium molar ratio of 0.1:1. Disperse the anatase nano-titanium dioxide in 200 mL of anhydrous ethanol, add the corresponding amount of cerium ammonium nitrate solution, adjust the pH to 9-10 with ammonia, and stir the reaction at 75 °C for 3 hours. After the reaction, centrifuge at 5000 rpm for 15 minutes, wash alternately with deionized water and anhydrous ethanol 4 times, vacuum dry at 70 °C for 18 hours, and then calcine at 450 °C for 2 hours to obtain cerium oxide-coated anatase nano-titanium dioxide. Disperse the obtained product in 100 mL of toluene, add 0.5 g of perfluorodecyltrimethoxysilane (5% of the mass of anatase nano-titanium dioxide), and reflux at 115 °C for 8 hours. After the reaction was completed, the sample was centrifuged at 5000 rpm for 15 minutes, washed four times with toluene, and dried under vacuum at 70°C for 18 hours to obtain anatase nano-titanium dioxide with fluorinated alkyl silane grafted on its surface, i.e., component (b).

[0057] 3. Preparation of sealant Following the general preparation method, the components (a) and (b) prepared above were added in the total amount (6 parts) of E1 in Table 1 to prepare a sealant, thus obtaining the sample of Example 1. Example 2

[0058] Following the formulation of E2 in Table 1 (ZIF-8 / zeolite molecular sieve mass ratio 1:4, cerium / titanium molar ratio 0.05:1, fluorinated alkyl silane dosage 1% of anatase nano-titanium dioxide mass, total dosage 3 parts), components (a) and (b) were prepared according to the method of Example 1, the difference being that the dosage of the corresponding raw materials was adjusted to obtain the desired ratio. The sealant was prepared according to a general preparation method to obtain the sample of Example 2. Example 3

[0059] Following the formulation of E3 in Table 1 (ZIF-8 / zeolite molecular sieve mass ratio 1:1, cerium / titanium molar ratio 0.2:1, fluorinated alkyl silane dosage 10% of anatase nano-titanium dioxide mass, total dosage 10 parts), components (a) and (b) were prepared according to the method of Example 1, the difference being the adjustment of the dosage of the corresponding raw materials to obtain the desired proportions. The sealant was prepared using a general preparation method to obtain the sample of Example 3. Example 4

[0060] Following the formulation in Table 1, E4 (ZIF-8 / zeolite molecular sieve mass ratio 1:4, cerium / titanium molar ratio 0.2:1, fluorinated alkyl silane dosage 5% of anatase nano-titanium dioxide mass, total dosage 6 parts), components (a) and (b) were prepared according to the method in Example 1, the difference being the adjustment of the dosage of the corresponding raw materials to obtain the desired proportions. The sealant was prepared using a general preparation method to obtain the sample of Example 4. Example 5

[0061] According to the formulation of E5 in Table 1, components (a) and (b) were prepared using the method of Example 1, except that the first silane coupling agent in the surface modification of component (a) was replaced with γ-glycidyl etheroxypropyltrimethoxysilane. The sealant was prepared using a general preparation method to obtain the sample of Example 5. Example 6

[0062] According to the formulation of E6 in Table 1, components (a) and (b) were prepared by referring to the method of Example 1, except that the fluorinated alkyl silane grafting in component (b) was replaced with 1H,1H,2H,2H-perfluorooctyltriethoxysilane, and the amount of fluorinated alkyl silane used was 5% of the mass of anatase nano-titanium dioxide. The sealant was prepared according to the general preparation method to obtain the sample of Example 6. Example 7

[0063] Components (a) and (b) were prepared according to the formulation of E7 in Table 1, referring to the method of Example 1. A sealant was prepared using a general preparation method, except that the catalyst was replaced with tetraisopropyl titanate, resulting in the sample of Example 7. Example 8

[0064] Components (a) and (b) were prepared according to the formulation of E8 in Table 1, referring to the method of Example 1. A sealant was prepared using a general preparation method, except that the filler was replaced with fumed silica, resulting in the sample of Example 8. Example 9

[0065] Components (a) and (b) were prepared according to the formulation of E9 in Table 1, referring to the method of Example 1. The sealant was prepared according to the general preparation method, and three batches were prepared independently to obtain the sample of Example 9.

[0066] Table 2 Comparative formulations and process parameters Note: 1 Component (a) is a physical mixture of commercially available ZIF-8 and zeolite molecular sieve (without core-shell structure). 2 Component (a) is a zeolite molecular sieve @ZIF-8 core-shell structured composite particle (with core-shell structure), which has not been surface modified by the first silane coupling agent; 3 Component (b) is cerium oxide-coated anatase nano-titanium dioxide, without fluorinated alkyl silane grafting; 4 Add one part of IPBC organic antifungal agent, while keeping other components unchanged.

[0067] D1 is a blank control; D2 contains only component (a); D3 contains only component (b); D4 is a physical mixture of components without chemical bonding; D5 is a ZIF-8 / zeolite molecular sieve ratio below the lower limit; D6 is a fluorinated alkyl silane dosage below the lower limit; D7 is components (a) and (b) without surface modification; D8 is without dehydration and kneading; D9 is an organic antifungal agent control.

[0068] In the table, "-" indicates that the component is not added or is not applicable.

[0069] Comparative Example 1 Without adding any functional components, the sealant was prepared using only the general preparation method to obtain the sample of Comparative Example 1.

[0070] Comparative Example 2 According to the formula in Table 2, D2, only component (a) (ZIF-8 to zeolite molecular sieve mass ratio 1:2, 6 parts) was added, and component (b) was not added. The sealant was prepared according to the general preparation method to obtain the comparative example 2 sample.

[0071] Comparative Example 3 According to the formulation in Table 2, D3, only component (b) (cerium / titanium molar ratio 0.1:1, fluorinated alkyl silane dosage of 5% of the mass of anatase nano titanium dioxide, dosage 6 parts) was added, and component (a) was not added. The sealant was prepared according to the general preparation method to obtain the comparative example 3 sample.

[0072] Comparative Example 4 According to the formula in D4 of Table 2, commercially available ZIF-8 and zeolite molecular sieve were physically mixed at a mass ratio of 1:2 as component (a); ungrafted cerium oxide-coated anatase nano-titanium dioxide (cerium / titanium molar ratio 0.1:1, amount 6 parts) was used as component (b). Components (a) and (b) were directly added to the base paste, and sealant was prepared according to the general preparation method to obtain sample 4 of Comparative Example.

[0073] Comparative Example 5 According to the formulation in Table 2, D5, components (a) and (b) were weighed, where component (a) was prepared according to Preparation Example 1 (ZIF-8 to zeolite molecular sieve mass ratio 1:8), and component (b) was prepared according to Preparation Example 2 (cerium / titanium molar ratio 0.1:1, fluorinated alkyl silane amount 5% of anatase nano-titanium dioxide mass). The sealant was prepared according to a general preparation method to obtain Comparative Example 5 sample.

[0074] Comparative Example 6 According to the formulation of D6 in Table 2, components (a) and (b) were weighed, wherein component (a) was prepared according to Preparation Example 1 (ZIF-8 to zeolite molecular sieve mass ratio 1:2), and component (b) was prepared according to Preparation Example 2 (cerium / titanium molar ratio 0.1:1, fluorinated alkyl silane amount of which is 0.5% of the mass of anatase nano-titanium dioxide). The sealant was prepared according to a general preparation method to obtain Comparative Example 6 sample.

[0075] Comparative Example 7 According to the formulation in D7 of Table 2, components (a) and (b) were weighed, where component (a) is unmodified zeolite molecular sieve @ZIF-8 core-shell composite particles, and component (b) is cerium oxide-coated anatase nano-titanium dioxide without grafting fluorinated alkyl silanes. A sealant was prepared using a general preparation method to obtain Comparative Example 7 sample.

[0076] Comparative Example 8 According to the formula of D8 in Table 2, components (a) and (b) were weighed, wherein component (a) was prepared according to Preparation Example 1 and component (b) was prepared according to Preparation Example 2. Without going through the S1 base paste preparation step, the hydroxyl-terminated polydimethylsiloxane, filler, component (a), component (b), alkoxysilane crosslinking agent, second silane coupling agent, and catalyst were directly mixed in one step, stirred under vacuum for 60 minutes, filled and cured to obtain Comparative Example 8 sample.

[0077] Comparative Example 9 Without adding a composite system with anti-mold and anti-algae functions, 1 part of iodopropynyl carbamate (IPBC) was added to the basic formula as an organic anti-mold agent, and sealant was prepared according to the general preparation method to obtain Comparative Example 9 samples.

[0078] V. Performance Testing and Results The cured adhesive samples from the above examples were subjected to the following tests: 1. Anti-mildew performance test The test was conducted according to the building materials industry standard JC / T 885 "Anti-mildew Sealant for Building". The specific steps were as follows: Samples were injected into a polytetrafluoroethylene mold to form standard test pieces of 50mm × 50mm × 2mm, which were then cured under standard conditions for 28 days. After curing, the test pieces were placed in sterile petri dishes, and a spore suspension containing standard mixed molds such as Aspergillus niger and Aspergillus terreus was evenly sprayed onto the pieces. The spore concentration of the suspension was approximately 1 × 10⁻⁶. 6 CFU / mL. The culture dishes were then placed in a constant temperature and humidity incubator and cultured for 28 days at a temperature of 28±1℃ and a relative humidity of >90%. After the culture was completed, the test pieces were removed and the surface mold growth was observed using a stereomicroscope and the naked eye. The mold was evaluated according to the standard grades from 0 (no growth) to 4 (growth area ≥60%).

[0079] 2. Algae control performance test Algae-resistant properties: The cured gel sample was made into 20mm × 20mm pieces and immersed in a suspension containing standard Chlorella spores, with an initial concentration of approximately 1 × 10⁻⁶. 5 In BG11 liquid medium at cell / mL, an additional 10 mg / L of NH4+ was added. + -N was used as the nutrient source. The culture dishes were placed in a light incubator and cultured statically for 60 days under conditions of 25±1℃, 3000 lux light intensity, and a 12-hour light / 12-hour dark cycle. After cultivation, the gel samples were removed, and the surface algae were gently rinsed with deionized water. Subsequently, surface images were taken using a high-resolution scanner. The algae coverage (%) on the gel sample surface was calculated using the professional image analysis software ImageJ.

[0080] 3. Ecotoxicity assessment To comprehensively assess environmental safety, the following two tests were conducted: Acute aquatic toxicity: Zebrafish were selected as the test organism according to the national standard GB / T 27861 "Acute Toxicity Tests of Chemicals in Fish". A gel-like extract was prepared by soaking the zebrafish in deionized water at a specific solid-liquid ratio for 24 hours. A series of concentrations were set, and 10 healthy juvenile zebrafish were placed in each concentration group for a 96-hour exposure test under standard conditions. Mortality rates were recorded at each time point, and the 96-hour median lethal concentration (96-hLC50) was calculated using the probability unit method.50 ).

[0081] Nitrification inhibition: Simulating the impact on the function of water treatment microorganisms. Filter media containing successfully attached nitrifying bacteria with stable nitrification activity was immersed together with a gel sample having a fixed surface area in an atmosphere containing 5 mg / L NH4. + The ammonia nitrogen concentration in the simulated wastewater solution was increased by -N and reacted for 7 days at 25°C in the dark. The ammonia nitrogen concentration in the solution was monitored daily, and the ammonia nitrogen removal rate on day 7 relative to the initial concentration was calculated. The results were compared with a blank control group without the ammonia nitrogen sample to evaluate the inhibition rate of the ammonia nitrogen sample on nitrification.

[0082] 4. Water resistance and durability test The retention rate of mechanical properties after long-term immersion in water was evaluated according to the durability test method for adhesive sealants. Standard single-lap shear bond specimens were prepared for each sample, with a substrate of 75mm × 25mm × 5mm float glass, a bonding area of ​​12.5mm × 25mm, and an adhesive layer thickness of 2mm. After complete curing, half of the specimens were immersed in a constant-temperature deionized water bath at 25±1℃ for 90 days. The other half served as an initial control sample that was not immersed in water. After immersion, the specimens were removed, surface moisture was blotted with filter paper, and tensile shear strength was tested on a universal testing machine at a tensile speed of 5 mm / min. The strength retention rate (%) was calculated using the following formula: (Average strength of specimen after immersion / Average strength of initial control specimen) × 100%.

[0083] 5. Surface hydrophobicity test The static water contact angle of the gel sample surface was measured using a contact angle meter via the static drop method to characterize its surface wettability and hydrophobicity. The gel sample was prepared with a smooth, flat surface and equilibrated in a standard environment for 24 hours before testing. 2 μL of ultrapure water was used as the test droplet, gently dropped onto the gel sample surface using an instrument syringe. The droplet profile was immediately captured using a high-speed camera, and the average left and right contact angles were calculated using the Young-Laplace fitting method. Measurements were taken at least five different locations for each sample, and the average value was used as the final result.

[0084] 6. Long-term immersion test simulating aquarium water quality environment A small-scale recirculating aquarium system was constructed (10L glass tank, housing 2-3 zebrafish, water temperature 25±2℃, 12-hour light / 12-hour darkness cycle, daily feeding, and weekly 1 / 3 water change). Seal samples (20mm×20mm×2mm) from each embodiment and the comparative example were suspended and submerged in the water and operated continuously for 90 days. Every 30 days, the samples were removed to observe and record the growth of surface mold and algae, and water quality parameters (ammonia nitrogen <0.5 mg / L, nitrite <0.2 mg / L) were monitored simultaneously. On the 90th day, the anti-mold level was assessed according to JC / T 885 standard, and algae coverage was calculated to evaluate the long-term anti-mold and anti-algae performance and surface condition changes of the sealant in a real dynamic aquarium environment.

[0085] The results are summarized in Tables 3 and 4.

[0086] Table 3 Performance test results of each embodiment Table 4 Performance test results of each comparative example *Note: On day 60, water quality deteriorated and fish died, forcing the test to be terminated. "-" in the table indicates no data for day 90. Acceptable water quality is defined as ammonia nitrogen <0.5 mg / L and nitrite <0.2 mg / L.

[0087] From the data in Tables 3 and 4, we can see that: The algae control coverage rate of Example 1 was 2.6%, while that of Comparative Example 2, which contained only component (a), was 20.5%, and that of Comparative Example 3, which contained only component (b), was 55.4%. The combined effect of components (a) and (b) was significantly better than the sum of the effects of using them alone, indicating that the two have a synergistic effect.

[0088] Comparative Example 4 used commercially available ZIF-8 and zeolite in a physical mixture, without forming a core-shell structure. Its algae-resistant coverage was 60.5%, and its strength retention rate was 78%. LC 50 The concentration of ammonia nitrogen in Example 1 was 62 mg / L, with a nitrification inhibition rate of 25.3%, and the ammonia nitrogen concentration exceeded the standard (0.6-0.8 mg / L) during the test. In contrast, the above indicators in Example 1 were 2.6%, 96%, >100 mg / L, and 2.6%, respectively, and the water quality was acceptable throughout the test. This comparison shows that the in-situ growth of the zeolite molecular sieve @ZIF-8 core-shell structure is key to achieving functional component loading.

[0089] Comparative Example 7, although forming a core-shell structure, did not undergo surface modification. Its strength retention rate was 75%, algae control coverage was 55%, nitrification inhibition rate was 15.2%, and ammonia nitrogen levels exceeded the standard (0.6-0.8 mg / L). Example 1, through surface modification, covalently bonded functional components to a silicone network, achieving a strength retention rate of 96%, algae control coverage of 2.6%, nitrification inhibition rate of 2.6%, and water quality compliance throughout. The comparison demonstrates that surface modification is a necessary technical means to prevent functional component leaching and ensure long-term performance.

[0090] Comparative Example 5 (ZIF-8 / zeolite molecular sieve ratio 1:8) had an algae-preventing coverage rate of 18.2%, and Comparative Example 6 (fluorinated alkyl silane dosage was 0.5% of the mass of anatase nano-titanium dioxide) had a water contact angle of 95°, both inferior to Example 1. This indicates that the ZIF-8 / zeolite molecular sieve mass ratio of 1:4 to 1:1 and the fluorinated alkyl silane dosage of 1%-10% specified in this invention are reasonable.

[0091] The strength retention rate of Comparative Example 8 (without S1 dehydration and kneading) was 70%, which was lower than that of Example 1 (96%), proving that dehydration and kneading is a process step to ensure the water resistance of the sealant.

[0092] In a 90-day simulated aquarium test, Examples 1-9 had a mold prevention level of 0-1, algae coverage of 2.8%-5.5%, and water quality was acceptable throughout (ammonia nitrogen <0.5 mg / L, nitrite <0.2 mg / L). Specifically, E1, E5, E6, and E9 had a mold prevention level of 0 and algae coverage of less than 3.1%; E2, E3, E4, E7, and E8 had a mold prevention level of 1 and algae coverage of 4.2%-5.5%. Comparative Examples 4 and 7 showed ammonia nitrogen exceeding the standard (0.6-0.8 mg / L) during the test, indicating that the lack of chemical bonding leads to the release of functional groups, inhibiting the nitrification system. Comparative Example 9 (organic mold inhibitor IPBC) showed water quality deterioration (ammonia nitrogen >2.0 mg / L, nitrite >1.0 mg / L) and fish mortality on day 60, and the test was terminated. This indicates that although organic mold inhibitors have a good short-term mold prevention effect, they are seriously toxic to aquatic ecosystems.

[0093] Examples 2-9 showed performance essentially the same as Example 1, indicating that the technical solution of the present invention has good reproducibility and stability within the defined parameter range. Meanwhile, examples E5 (replacing the first silane coupling agent with γ-glycidyl etheroxypropyltrimethoxysilane), E6 (replacing the fluorinated alkyl silane with 1H,1H,2H,2H-perfluorooctyltriethoxysilane), E7 (replacing the catalyst with tetraisopropyl titanate), and E8 (replacing the filler with fumed silica) all achieved performance essentially the same as E1, proving the universality of the raw material types defined in the present invention. Repeated verification of Example E9 demonstrated process stability.

[0094] In summary, this invention, through component design, construction of a core-shell structure, chemical bonding fixation, and process optimization, prepares a fish tank-specific sealant that combines long-lasting anti-mildew and anti-algae properties, high ecological safety, and excellent water resistance and durability. It has outstanding substantive features and significant progress.

[0095] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any indirect modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A water-resistant and mildew-proof fish tank sealant, characterized in that, By weight, it includes: 100 parts of hydroxyl-terminated polydimethylsiloxane, 3-10 parts of anti-mildew and anti-algae functional composite system, 20-40 parts of filler, 5-12 parts of alkoxysilane crosslinking agent, 0.05-0.5 parts of catalyst, and 0.5-2 parts of second silane coupling agent. The anti-mildew and anti-algae functional composite system includes: (a) Zeolite molecular sieve @ZIF-8 core-shell structured composite particles, the surface of which is modified by a first silane coupling agent; (b) Cerium oxide-coated anatase nano-titanium dioxide with fluorinated alkyl silane grafted onto its surface; The components (a) and (b) undergo a condensation reaction with the terminal hydroxyl groups of the terminal hydroxyl polydimethylsiloxane and / or the alkoxysilane crosslinking agent through the hydrolyzable silane groups on their surfaces to form Si-O-Si covalent bonds, thereby bonding to the silicone crosslinking network of the sealant.

2. The sealant according to claim 1, characterized in that, The hydroxyl-terminated polydimethylsiloxane has a viscosity of 2,000-200,000 mPa·s at 25°C; the filler is selected from at least one of nano-activated calcium carbonate, heavy calcium carbonate, fumed silica, hydrophobic silica, silica powder, diatomaceous earth, and precipitated silica.

3. The sealant according to claim 1, characterized in that, The alkoxysilane crosslinking agent is selected from at least one of methyltrimethoxysilane, methyltriethoxysilane, propyltrimethoxysilane, octyltrimethoxysilane, phenyltrimethoxysilane, and vinyltrimethoxysilane; the catalyst is selected from at least one of dibutyltin dilaurate, dibutyltin dioctanoate, dibutyltin diacetate, tetraisopropyl titanate, tetrabutyl titanate, and diisopropyl di(ethyl acetoacetate) titanate.

4. The sealant according to claim 1, characterized in that, The first silane coupling agent is selected from at least one of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-glycidyl etheroxypropyltrimethoxysilane; the second silane coupling agent is selected from at least one of γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-glycidyl etheroxypropyltrimethoxysilane, and vinyltrimethoxysilane.

5. The sealant according to claim 1, characterized in that, In the zeolite molecular sieve@ZIF-8 core-shell composite particles, the mass ratio of zeolite molecular sieve to ZIF-8 is 1:4 to 1:1; the zeolite molecular sieve is selected from clinoptilolite or mordenite, with a particle size of 1-5 μm and a specific surface area of ​​20-50 m². 2 / g.

6. The sealant according to claim 1, characterized in that, The ZIF-8 has a grain size of 50-200 nm; the cerium oxide layer thickness of the cerium oxide-coated anatase nano-titanium dioxide is 1-5 nm, and the molar ratio of cerium to titanium is 0.05:1 to 0.2:

1.

7. The sealant according to claim 1, characterized in that, The fluorinated alkyl silane is selected from at least one of perfluorodecyltrimethoxysilane, perfluorodecyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, and tridecafluorooctyltrimethoxysilane; its amount is 1% to 10% of the mass of anatase nano-titanium dioxide.

8. A method for preparing the water-resistant and mildew-resistant aquarium sealant according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Prepare components (a) and (b) respectively; component (a) is a zeolite molecular sieve @ZIF-8 core-shell structure composite particle, the surface of which is modified by a first silane coupling agent; component (b) is cerium oxide-coated anatase nano-titanium dioxide, the surface of which is grafted with fluorine-containing alkyl silane. S2. The hydroxyl-terminated polydimethylsiloxane and the filler are dehydrated and kneaded under vacuum and heating conditions to obtain a base paste; S3. After cooling the base paste, add components (a) and (b) prepared in step S1 and disperse them evenly under a protective atmosphere; S4. Add alkoxysilane crosslinking agent, second silane coupling agent and catalyst, mix evenly and then discharge and fill.

9. The method according to claim 8, characterized in that, The method for preparing component (a) in step S1 includes: dispersing zeolite molecular sieves in a solution containing zinc salt and 2-methylimidazole to react, allowing ZIF-8 to grow in situ on the surface of the zeolite molecular sieves, and after separation, washing, and drying, refluxing the mixture in a solution of the first silane coupling agent, and then separating, washing, and drying to obtain component (a).

10. The method according to claim 8, characterized in that, The method for preparing component (b) in step S1 includes: dispersing anatase nano-titanium dioxide in anhydrous ethanol, adding cerium salt solution to react, and then separating, washing, drying and calcining to obtain cerium oxide-coated anatase nano-titanium dioxide; then reacting the obtained product with fluorinated alkylsilane under reflux in toluene, and then separating, washing and drying to obtain component (b).

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