Fluorinated nanomof modified waterborne coating and preparation method and application thereof

Abstract

This invention provides a fluorinated nano-MOF modified waterborne coating, its preparation method, and its application, belonging to the technical field of fireproof and anti-corrosion coatings for steel structures. This invention utilizes nano-fluorinated MOF modification technology, in conjunction with a traditional intumescent flame-retardant system, to significantly improve the coating's hydrophobicity, density, and corrosion resistance while ensuring excellent fireproof performance. This achieves integrated long-term protection for steel structures, providing fire resistance, corrosion resistance, and weather resistance. Furthermore, the process is green and environmentally friendly, simple to prepare, and suitable for large-scale production. This invention fills a technological gap by applying UiO-66-F fluorinated nano-MOF material to a waterborne integrated fireproof and anti-corrosion coating for steel structures.

Description

Technical Field

[0001] This invention relates to the field of fireproof and anticorrosive coatings for steel structures, and in particular to a fluorinated nano-MOF modified waterborne coating, its preparation method, and its application. Background Technology

[0002] Steel structures, with their advantages of light weight, high strength, short construction period, and excellent seismic performance, are widely used in industrial plants, large-span stadiums, high-rise buildings, bridges, tunnels, and municipal engineering projects. However, steel structures have two major inherent defects: first, steel has extremely poor fire resistance, and its strength decreases sharply at high temperatures, making it highly susceptible to building collapse; second, steel is prone to electrochemical corrosion in atmospheric, humid, acidic, alkaline, and salt spray environments, which leads to thinning of the steel structure's cross-section and a decline in mechanical properties over long-term service, seriously affecting the safety and service life of the building structure. Therefore, the surface of steel structures must be coated with a special protective coating to achieve dual protection against fire and corrosion.

[0003] In existing technologies, the core function of water-based fire-retardant coatings for steel structures relies on an intumescent flame-retardant ternary system. Under high temperatures during a fire, this system dehydrates, foams, and chars to form a dense carbonaceous insulating layer, blocking heat transfer and protecting the steel structure substrate. However, this system has inherent defects: First, the flame-retardant filler is highly polar, resulting in numerous micropores within the cured coating, allowing water vapor and corrosive media to easily penetrate and diffuse, leading to electrochemical corrosion of the steel substrate. Second, the char layer is prone to loosening, cracking, and peeling during high-temperature expansion, resulting in poor fire resistance stability. Under long-term service in natural environments, the coating is prone to chalking, loss of gloss, and cracking, significantly shortening its protective lifespan. Third, traditional coatings rely solely on resin film formation for corrosion protection, lacking active corrosion inhibition and ion curing functions. Their protective capabilities against salt spray and acid / alkali corrosive environments are limited, failing to achieve long-term corrosion protection.

[0004] To improve the corrosion resistance of coatings, existing technologies often modify them by adding conventional inorganic fillers such as nano-silica, nano-titanium dioxide, and bentonite. These fillers only simply fill the pores in the coating and improve its density, without providing active corrosion protection. Furthermore, nanoparticles are prone to agglomeration in the coating system, leading to decreased coating smoothness, reduced mechanical properties, and even affecting the fire-retardant effect of expansion foaming. Some studies have improved filler performance through surface grafting modification and metal ion doping, but the modification effects are limited and cannot simultaneously meet the dual requirements of enhanced fire resistance and long-term corrosion protection.

[0005] Nano-functional filler modification is a core technology for improving the overall performance of coatings. Metal-organic frameworks (MOFs) possess unique advantages such as large specific surface area, regular pore structure, surface functionalization, and strong ion adsorption capacity, giving them enormous application potential in the field of coating modification. Among them, UiO-66 zirconium-based MOF material exhibits excellent thermal and chemical stability, making it an ideal matrix material for coating modification. However, pure UiO-66 is rich in hydroxyl groups on its surface, exhibiting strong hydrophilicity. This leads to its tendency to aggregate in coating systems and insufficient hydrophobic barrier properties, thus failing to significantly improve the anti-corrosion and water-resistant properties of coatings. Summary of the Invention

[0006] The purpose of this invention is to provide a fluorinated nano-MOF modified waterborne coating, its preparation method and application. Using UiO-66-F fluorinated nano-MOF as the core functional filler, a waterborne steel structure fireproof and anti-corrosion integrated coating is constructed, which overcomes the defects of existing waterborne steel structure fireproof coatings such as unbalanced fireproof and anti-corrosion performance, poor coating density, weak salt spray resistance, easy cracking and powdering, and short service life.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a fluorinated nano-MOF modified waterborne coating, comprising the following raw materials in parts by weight: 35-50 parts of water-based acrylic emulsion, 28-42 parts of intumescent flame retardant, 3-8 parts of char-forming aid, 1.5-4.5 parts of nano-UiO-66-F filler, 2-6 parts of functional additives, and 12-20 parts of water. The preparation method of the nano-UiO-66-F filler includes the following steps: A precursor solution was obtained by mixing a zirconium source, tetrafluoroterephthalic acid, a crystal regulator, and an organic solvent. After the precursor solution is subjected to a solvothermal reaction, it is dried and vacuum activated in sequence to obtain nano-UiO-66-F filler; Based on 2-6 parts of the functional additive, the functional additive includes 0.5-1.2 parts of dispersant, 0.3-0.8 parts of wetting agent, 0.2-0.5 parts of defoamer, 0.4-1.0 parts of thickener, and 0.6-1.0 parts of corrosion inhibitor.

[0008] Preferably, the zirconium source is zirconium oxychloride octahydrate; the crystal regulator is formic acid; the organic solvent includes N,N-dimethylformamide; the molar ratio of the zirconium source to tetrafluoroterephthalic acid is 1:1; and the volume ratio of the zirconium source, crystal regulator, and organic solvent is 0.5 mmol:2 mL:30 mL.

[0009] Preferably, the temperature of the solvothermal reaction is 120°C and the time is 24 hours; the temperature of the vacuum activation is 120°C and the time is 6 hours.

[0010] Preferably, the solid content of the aqueous acrylic emulsion is 45-50 wt%.

[0011] Preferably, the intumescent flame retardant is composed of ammonium polyphosphate, melamine and pentaerythritol, wherein the mass ratio of ammonium polyphosphate, melamine and pentaerythritol is (2.5~3.8):(1~1.5):1; and the particle size of the intumescent flame retardant is 800~1200 mesh.

[0012] Preferably, the char-forming aid is one or more of nano-silica, borax, and organosilicon-modified bentonite.

[0013] This invention provides a method for preparing the fluorinated nano-MOF modified waterborne coating described in the above technical solution, comprising the following steps: The nano-UiO-66-F filler, dispersant and a portion of water were mixed and then subjected to shear dispersion and ultrasonic dispersion in sequence to obtain nano-UiO-66-F dispersion. The remaining water, water-based acrylic emulsion, wetting agent and corrosion inhibitor are mixed to obtain the base emulsion; The base emulsion, intumescent flame retardant, and char-forming aid are mixed to obtain a flame-retardant slurry; After mixing the nano-UiO-66-F dispersion with the flame-retardant slurry, an antifoaming agent and a thickener are added. The resulting composite slurry is then filtered and matured to obtain a fluorinated nano-MOF modified waterborne coating.

[0014] Preferably, the rotation speed of the shearing dispersion is 3000~4000 r / min, and the shearing time is 15~20 min; the power of the ultrasonic dispersion is 300~400 W, and the ultrasonic time is 10~15 min.

[0015] Preferably, the viscosity of the composite slurry is adjusted to 80~100KU; the maturation temperature is room temperature and the time is 24~36h.

[0016] This invention provides the application of the fluorinated nano-MOF modified waterborne coating described in the above technical solution or the fluorinated nano-MOF modified waterborne coating prepared by the preparation method described in the above technical solution in the field of steel structure protection.

[0017] This invention provides a fluorinated nano-MOF modified waterborne coating. By using nano-fluorinated MOF modification technology, in conjunction with a traditional intumescent flame retardant system, the coating significantly improves hydrophobicity, density and corrosion resistance while ensuring excellent fire resistance. This achieves integrated long-term protection of steel structures with fire resistance, corrosion resistance and weather resistance. At the same time, the process is green and environmentally friendly, simple to prepare and can be mass-produced.

[0018] The fluorinated nano-MOF modified waterborne coating of this invention uses environmentally friendly waterborne acrylic emulsion as the film-forming matrix, compounded with a traditional intumescent flame retardant system, and simultaneously introduces fluorinated modified UiO-66-F nano-MOF material as a functional anti-corrosion and enhancing filler. This solves the industry pain points of traditional waterborne steel structure fireproof coatings, such as the inability to simultaneously achieve fire resistance and corrosion resistance, poor water resistance, weak salt spray resistance, and easy powdering and cracking after long-term service. This invention utilizes the special fluorinated skeleton structure and porous topology of UiO-66-F. On the one hand, it leverages the strong hydrophobicity and chemical inertness of fluorine atoms to block the penetration of water vapor and corrosive media; on the other hand, it relies on the porous structure of MOF to adsorb and solidify corrosive ions and synergistically retard flame and suppress smoke, achieving integrated modification of the coating in terms of fire resistance, corrosion resistance, and weather resistance. The coating of this invention has a scientifically proportioned composition, a simple and controllable preparation process with strong repeatability, and a smooth coating with excellent adhesion. With a coating thickness of 2mm, the fire resistance limit can reach more than 90 minutes, and the neutral salt spray test can last for more than 800 hours without rust, blistering or peeling. It is suitable for long-term fire and corrosion protection of various civil and industrial steel structures such as industrial plants, stadiums, and bridge steel structures.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. Pioneering Fluorinated MOF Modified Integrated Protection System: This invention introduces in-situ fluorinated UiO-66-F nano MOF material into water-based steel structure fireproof coatings for the first time. Relying on the hydrophobic and inert properties of fluorine and the porous adsorption properties of MOF, it achieves multiple functional coupling of physical barrier, chemical corrosion inhibition and synergistic flame retardancy, completely solving the technical problem of mutual restriction between the fireproof and anticorrosion performance of traditional coatings, and realizing integrated long-term protection of the coating.

[0020] 2. Excellent and stable protective performance: When the dry film thickness of the coating of this invention is 2.0mm, the fire resistance limit can reach 98min, which meets the protection requirements of the national standard for intumescent fireproof coatings; the neutral salt spray protection time exceeds 800h, and the water resistance, adhesion, crack resistance and powdering resistance are greatly improved. It can be adapted to complex and harsh working conditions such as coastal areas, chemical plants, and humid environments, and the protection life of steel structures is increased by more than 2 times.

[0021] 3. Excellent filler dispersibility and compatibility: This invention completely solves the problem of MOF powder agglomeration through nanofiller pre-dispersion process. UiO-66-F can be evenly distributed inside the coating without affecting the coating's application performance and foaming and carbonization effect. At the same time, it can refine the carbon layer structure, improve the high-temperature stability of the carbon layer, and avoid coating defects caused by conventional nanofiller modification.

[0022] 4. Green and environmentally friendly, with controllable and mass-producible processes: The raw material components of the fluorinated nano MOF modified waterborne coating of this invention are all water-based, with no organic solvents added and no VOC harmful substances released, making it green and safe; the preparation process is simple, the parameters are controllable, and the batch repeatability is good, requiring no large-scale precision equipment, suitable for laboratory small-scale testing and large-scale industrial production, and with low promotion costs.

[0023] 5. Excellent overall coating performance: The coating is dense and smooth, with strong adhesion and good flexibility. It does not crack, chalk, or lose gloss during long-term natural service. Its weather resistance is significantly improved, and it combines protective and decorative performance, making it suitable for a wide range of applications. Attached Figure Description

[0024] Figure 1 The infrared spectra of zirconium oxychloride octahydrate, tetrafluoroterephthalic acid, and UiO-66-F in the preparation example are shown. Detailed Implementation

[0025] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0026] This invention provides a fluorinated nano-MOF modified waterborne coating, comprising the following raw materials in parts by weight: 35-50 parts of water-based acrylic emulsion, 28-42 parts of intumescent flame retardant, 3-8 parts of char-forming aid, 1.5-4.5 parts of nano-UiO-66-F filler, 2-6 parts of functional additives, and 12-20 parts of water. The preparation method of the nano-UiO-66-F filler includes the following steps: A precursor solution was obtained by mixing a zirconium source, tetrafluoroterephthalic acid, a crystal regulator, and an organic solvent. After the precursor solution is subjected to a solvothermal reaction, it is dried and vacuum activated in sequence to obtain nano-UiO-66-F filler; Based on 2-6 parts of the functional additive, the functional additive includes 0.5-1.2 parts of dispersant, 0.3-0.8 parts of wetting agent, 0.2-0.5 parts of defoamer, 0.4-1.0 parts of thickener, and 0.6-1.0 parts of corrosion inhibitor.

[0027] The raw materials for preparing the fluorinated nano MOF modified waterborne coating provided by the present invention, by weight, include 35-50 parts of waterborne acrylic emulsion, preferably 40-45 parts.

[0028] In this invention, the solid content of the aqueous acrylic emulsion is preferably 45-50 wt%, more preferably 48 wt%; the minimum film-forming temperature is 5-10°C, more preferably 8°C.

[0029] The waterborne acrylic emulsion of the present invention is preferably a self-crosslinking pure acrylic emulsion, which has excellent film-forming properties and weather resistance, no VOCs, no formaldehyde or benzene residues, strong adhesion, and is suitable for waterborne environmentally friendly coating systems. It can tightly coat flame-retardant fillers and nanofillers, and improve the overall density and mechanical properties of the coating.

[0030] Based on the mass fraction of the aqueous acrylic emulsion, the raw materials for preparing the fluorinated nano MOF modified aqueous coating provided by the present invention include 28-42 parts of intumescent flame retardant, preferably 32-38 parts.

[0031] In this invention, the intumescent flame retardant is preferably composed of ammonium polyphosphate, melamine, and pentaerythritol, and the mass ratio of the ammonium polyphosphate, melamine, and pentaerythritol is preferably (2.5~3.8):(1~1.5):1, more preferably (3.1~3.6):(1.2~1.5):1; the particle size of the intumescent flame retardant is 800~1200 mesh, more preferably 1000 mesh.

[0032] The intumescent flame retardant described in this invention has a purity of ≥98%, a reasonable formulation, and high foaming and charring efficiency. It can quickly dehydrate and foam at high temperatures to form a uniform and dense heat-insulating char layer, ensuring the fire resistance limit of the coating.

[0033] Based on the mass fraction of the aqueous acrylic emulsion, the raw materials for preparing the fluorinated nano MOF modified aqueous coating provided by the present invention include 3 to 8 parts of char-forming aid, preferably 5 to 6 parts.

[0034] In this invention, the char-forming aid is preferably one or more of nano-silica, borax, and organosilicon-modified bentonite; when the char-forming aid is two or more of the above, this invention does not have a special limitation on the ratio of different types of char-forming aids, and any ratio is acceptable.

[0035] The char-forming aid described in this invention can fill the micropores of the char layer, improve the high-temperature stability and crack resistance of the char layer, inhibit char layer shedding, enhance fireproof and heat insulation effects, and effectively improve the density and high-temperature crack resistance of the char layer.

[0036] Based on the mass fraction of the aqueous acrylic emulsion, the raw materials for preparing the fluorinated nano MOF modified aqueous coating provided by the present invention include 1.5 to 4.5 parts of nano UiO-66-F filler, preferably 2 to 4 parts, and more preferably 3 parts.

[0037] In this invention, the preparation method of the nano-UiO-66-F filler includes the following steps: A precursor solution was obtained by mixing a zirconium source, tetrafluoroterephthalic acid, a crystal regulator, and an organic solvent. After the precursor solution is subjected to a solvothermal reaction, it is then dried and vacuum activated in sequence to obtain nano-UiO-66-F filler.

[0038] In this invention, the zirconium source is preferably zirconium oxychloride octahydrate; the crystal regulator is preferably 98wt% analytical grade formic acid; the organic solvent preferably includes N,N-dimethylformamide (DMF); the molar ratio of the zirconium source to tetrafluoroterephthalic acid is preferably 1:1; and the ratio of the amount of zirconium source, crystal regulator and organic solvent is preferably 0.5mmol:2mL:30mL.

[0039] In this invention, zirconium source and tetrafluoroterephthalic acid are added to an organic solvent, a crystal regulator is added, and the mixture is magnetically stirred at room temperature for 30 minutes, followed by ultrasonic dispersion for 5 minutes to obtain a precursor solution. The precursor solution is then transferred to a polytetrafluoroethylene-lined hydrothermal reactor, sealed, and subjected to a constant-temperature solvothermal reaction. The resulting product is washed and purified, then dried and vacuum activated sequentially, followed by cooling and grinding to obtain nano-UiO-66-F filler, which is then sealed, dried, and stored.

[0040] In this invention, the temperature of the solvothermal reaction is preferably 120°C and the time is preferably 24h; during the solvothermal reaction, the fluorine-containing ligands are fully coordinated with the zirconium ions, and the fluorine atoms are uniformly embedded in the MOF framework to achieve crystallization.

[0041] In this invention, the washing and purification process preferably involves naturally cooling the solvothermal reaction product to room temperature, centrifuging it at 9000 r / min for 10 min, and washing it three times each with DMF and anhydrous ethanol to remove unreacted impurities. The drying process is preferably carried out at 80°C with forced air for 12 h, and the vacuum activation temperature is preferably 120°C for 6 h. This invention does not impose any special limitations on the grinding process; it can be carried out according to procedures well known in the art.

[0042] This invention utilizes in-situ ligand-modified zirconium-based MOF materials to prepare nano-UiO-66-F filler. Fluorine atoms exhibit high electronegativity, small atomic radius, and extremely strong chemical inertness. Fluorine is uniformly doped within the UiO-66 framework, eliminating the risk of surface detachment and completely altering the material's surface hydrophilic properties, endowing it with superhydrophobicity, acid and alkali corrosion resistance, and interfacial stability. Simultaneously, UiO-66-F retains the MOF material's ultra-large specific surface area and regular porous structure, efficiently adsorbing corrosive ions such as chloride and sulfate ions in the curing environment, blocking the electrochemical corrosion circuit of steel. Furthermore, it serves as a flame-retardant char-forming core site, promoting the formation of a high-temperature, dense char layer, achieving a dual effect of fire resistance and corrosion protection.

[0043] This invention utilizes UiO-66-F nanomaterials prepared through in-situ fluorination modification. These nanomaterials possess strong hydrophobicity, ion adsorption and curing capabilities, and synergistic flame-retardant properties, making them a core functional component for achieving integrated fire protection and corrosion resistance in coatings. By introducing this material as a functional, corrosion-resistant, and flame-retardant synergistic filler into a water-based intumescent fire-retardant coating system, fluorination modification imparts strong hydrophobicity and chemical inertness to the material. Combined with the porous adsorption, ion curing, and synergistic flame-retardant properties of MOFs, this achieves an integrated upgrade in the coating's fire resistance, corrosion resistance, and weather resistance.

[0044] Based on the mass fraction of the aqueous acrylic emulsion, the raw materials for preparing the fluorinated nano MOF modified aqueous coating provided by the present invention include 2 to 6 parts of functional additives, preferably 3 to 4.5 parts.

[0045] In this invention, based on 2 to 6 parts of the functional additive, the functional additive preferably includes 0.5 to 1.2 parts of dispersant, 0.3 to 0.8 parts of wetting agent, 0.2 to 0.5 parts of defoamer, 0.4 to 1.0 parts of thickener, and 0.6 to 1.0 parts of corrosion inhibitor.

[0046] In this invention, the dispersant is preferably a polyacrylate dispersant; the wetting agent is preferably a polyether-modified silicone wetting agent; the defoamer is preferably a silicone defoamer; the thickener is preferably an organically modified bentonite; and the corrosion inhibitor is preferably aluminum tripolyphosphate.

[0047] The present invention does not impose any special limitations on the specific specifications and sources of the reagents in the functional additives; commercially available products well known in the art are acceptable.

[0048] In the functional additives described in this invention, the dispersant is an anionic polymeric dispersant, which can effectively solve the problem of agglomeration of nano MOF fillers and ensure uniform dispersion of the fillers; the wetting agent improves the wetting and adhesion of the coating to the steel structure substrate; the defoamer eliminates bubbles generated by system stirring and avoids pinhole defects in the coating; the thickener adjusts the viscosity of the coating and ensures the smoothness of the application; and the corrosion inhibitor can form a passivation film on the steel surface, working synergistically with the MOF fillers to improve the anti-corrosion effect.

[0049] Based on the mass fraction of the aqueous acrylic emulsion, the raw materials for preparing the fluorinated nano-MOF modified aqueous coating provided by the present invention include 12-20 parts of water, preferably 16 parts. The water used in the present invention is preferably deionized water.

[0050] This invention provides a method for preparing the fluorinated nano-MOF modified waterborne coating described in the above technical solution, comprising the following steps: The nano-UiO-66-F filler, dispersant and a portion of water were mixed and then subjected to shear dispersion and ultrasonic dispersion in sequence to obtain nano-UiO-66-F dispersion. The remaining water, water-based acrylic emulsion, wetting agent and corrosion inhibitor are mixed to obtain the base emulsion; The base emulsion, intumescent flame retardant, and char-forming aid are mixed to obtain a flame-retardant slurry; After mixing the nano-UiO-66-F dispersion with the flame-retardant slurry, an antifoaming agent and a thickener are added. The resulting composite slurry is then filtered and matured to obtain a fluorinated nano-MOF modified waterborne coating.

[0051] In this invention, the mass ratio of the partial water to the remaining water is preferably 1:1.

[0052] This invention preferably involves adding nano-UiO-66-F filler, dispersant, and a portion of water to a high-speed shear disperser, stirring and mixing, followed by high-speed shear dispersion and then ultrasonic dispersion to eliminate nano-filler agglomeration and obtain a uniform and stable nano-functional dispersion. This invention effectively improves the dispersion uniformity of nano-fillers in coating systems through dispersion treatment, ensuring uniform release of the modification effect.

[0053] In this invention, the rotational speed of the shearing dispersion is preferably 3000~4000 r / min, more preferably 3500 r / min, and the shearing time is preferably 15~20 min, more preferably 18 min; the power of the ultrasonic dispersion is preferably 300~400 W, more preferably 300~350 W, and the ultrasonic time is preferably 10~15 min, more preferably 12 min.

[0054] In this invention, the remaining water, aqueous acrylic emulsion, wetting agent, and corrosion inhibitor are added to a closed stirred reactor, and the mixture is stirred at low speed at room temperature to ensure that the components are fully mixed and form a clear and stable base emulsion, thus ensuring the adhesion of the coating base and the compatibility with the substrate. The stirring speed is preferably 600~800 r / min, more preferably 700 r / min, and the stirring time is preferably 10~15 min, more preferably 12 min.

[0055] After obtaining the base emulsion, the present invention maintains a stirring speed of 800~1200 r / min, more preferably 800~1000 r / min, and sequentially adds an intumescent flame retardant and a char-forming aid to the base emulsion (to avoid agglomeration caused by one-time addition); after the addition is completed, stir for 20 min, increase the stirring speed to 1500~1800 r / min, more preferably 1600 r / min, and continue grinding and dispersing for 30~40 min, more preferably 35 min, until there are no visible particles in the system, thus obtaining a flame-retardant slurry. This slurry is fine and uniform, ensuring the dispersion effect of the flame-retardant system and laying the foundation for high-temperature uniform foaming and char formation.

[0056] In this invention, the nano-UiO-66-F dispersion is added dropwise to the flame-retardant slurry at a uniform rate. After the addition is completed, the mixture is stirred for 20-25 minutes to ensure that the fluorinated MOF filler and the coating components are fully compounded and evenly distributed. Then, an antifoaming agent is added and stirred for 5 minutes to eliminate air bubbles in the system. Finally, a thickener is added to fine-tune the viscosity of the system to the standard range to adapt to spraying and brushing application processes.

[0057] In this invention, the viscosity of the composite slurry is adjusted to 80~100KU, more preferably 90KU.

[0058] The present invention preferably filters and matures the obtained composite slurry, specifically preferably using a 200-mesh sterile filter to remove trace impurities and agglomerated particles, ensuring the fineness of the coating and the smoothness of the application. After filtration, the obtained coating is sealed and placed in a room temperature environment for static maturation, so that the components are fully compatible and the system performance is stable, resulting in a fluorinated nano MOF modified waterborne coating, which can be used as an integrated fireproof and anti-corrosion coating for steel structures.

[0059] In this invention, the ripening temperature is preferably room temperature, and the ripening time is preferably 24-36 hours, more preferably 24 hours.

[0060] This invention provides the application of the fluorinated nano-MOF modified waterborne coating described in the above-described technical solutions, or the fluorinated nano-MOF modified waterborne coating prepared by the preparation method described in the above-described technical solutions, in the field of steel structure protection. This invention does not specifically limit the method of application; any method well-known in the art can be used.

[0061] The technical principle of the above-mentioned technical solution of the present invention is as follows: 1. Anti-corrosion mechanism: The fluorine atoms doped in the UiO-66-F framework have extremely strong hydrophobicity and chemical inertness, which can build a hydrophobic barrier network inside the coating to block the penetration channels of corrosive media such as water vapor, oxygen, and chloride ions; at the same time, the ultra-large specific surface area and porous structure of UiO-66-F can efficiently adsorb corrosive anions in the curing environment, cut off the electrochemical corrosion circuit of steel, and, together with the passivation film formed by the corrosion inhibitor, achieve a dual long-term anti-corrosion effect of physical barrier and chemical corrosion inhibition.

[0062] 2. Fireproofing Mechanism: Conventional intumescent flame retardant systems achieve foaming and charring for heat insulation at high temperatures. UiO-66-F can serve as heterogeneous charring sites, promoting rapid char formation, refining the char structure, improving the density and high-temperature crack resistance of the char layer, and inhibiting char layer shedding. At the same time, fluorinated MOF has excellent thermal stability and smoke suppression performance, which synergistically enhance the fire resistance limit and high-temperature protection stability of the coating.

[0063] 3. Coating modification mechanism: Nano-grade UiO-66-F can accurately fill the micropore defects of traditional coatings, greatly improve the coating density, smoothness and mechanical strength, solve the problems of easy cracking, powdering and poor weather resistance of traditional coatings, and extend the overall protection life of steel structures.

[0064] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0065] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the raw materials used are all commercially available products, and the proportions are all by mass percentage.

[0066] Preparation Example

[0067] The preparation method of the nano-UiO-66-F filler used in the following embodiments is as follows: Weigh 0.5 mmol zirconium oxychloride octahydrate and 0.5 mmol tetrafluoroterephthalic acid, add them to 30 mL of anhydrous DMF solvent, add 2 mL of formic acid (98 wt% analytical grade) as a crystal regulator, stir magnetically at room temperature for 30 min, and then sonicate for 5 min to obtain the precursor solution. The precursor solution was transferred to a 50 mL polytetrafluoroethylene-lined hydrothermal reactor, sealed, and crystallized at 120 °C for 24 h. After naturally cooling to room temperature, it was centrifuged at 9000 r / min for 10 min, washed three times each with DMF and anhydrous ethanol, and the resulting product was dried at 80 °C for 12 h, activated under vacuum at 120 °C for 6 h, cooled, and ground to obtain nano-UiO-66-F filler, which was then sealed, dried, and stored.

[0068] Figure 1 Infrared spectra of zirconium oxychloride octahydrate, tetrafluoroterephthalic acid, and UiO-66-F in the preparation example; Figure 1 This reflects the chemical transformation process from raw materials to products: the characteristic peak of zirconium oxychloride octahydrate (Zr-O) disappears, while new characteristic peaks belonging to the coordination polymer skeleton (such as Zr-OC and the vibration peak of the coordinated carboxylate group) appear in the product, and the characteristic peak of the CF bond is completely preserved as a characteristic peak, which confirms the successful introduction of the fluorinated ligand and proves the successful synthesis of UiO-66-F.

[0069] In the following examples, the aqueous acrylic emulsion is a self-crosslinking pure acrylic emulsion with a solid content of 48% and a minimum film-forming temperature of 8°C. It is sourced from BA-208 Group Co., Ltd. Intumescent flame retardant: A ternary compound of ammonium polyphosphate, melamine, and pentaerythritol, with a particle size of 1000 mesh and a purity ≥98%. The ammonium polyphosphate is sourced from Yunnan Tianyao Chemical Co., Ltd. (brand name TY-423); the melamine is sourced from Sichuan Jinxiang Sairui Chemical Co., Ltd. (brand name M-F98); and the pentaerythritol is sourced from Hubei Yihua Group Co., Ltd. (brand name PER-98). Nano-silica is sourced from Evonik Industries, under the brand name AEROSIL200.

[0070] Example 1

[0071] The fluorinated nano-MOF modified waterborne coating provided in this embodiment is prepared from the following raw materials, by mass: The composition includes 35 parts of water-based acrylic emulsion, 22 parts of ammonium polyphosphate, 9 parts of melamine, 6 parts of pentaerythritol, 6 parts of nano-silica, 3 parts of nano-UiO-66-F filler, 0.5 parts of dispersant, 0.5 parts of wetting agent, 0.5 parts of defoamer, 0.7 parts of thickener, 0.8 parts of corrosion inhibitor, and 16 parts of deionized water. The dispersant is DISPERBYK-110 polyacrylate dispersant, sourced from BYK Chemical; the wetting agent is BYK-333 polyether-modified silicone wetting agent, sourced from BYK Chemical; the defoamer is BYK-066-N silicone defoamer, sourced from BYK Chemical; the thickener is CLAYTONE-MPZ organic-modified bentonite, sourced from BYK Chemical; and the corrosion inhibitor is aluminum tripolyphosphate, sourced from Shanghai Maclean Biochemical Technology Co., Ltd. The preparation method of the above-mentioned fluorinated nano-MOF modified waterborne coating: S1. Nano UiO-66-F dispersion: Take nano UiO-66-F filler, dispersant and deionized water accounting for 1 / 2 of the total weight according to the ratio, add them to a high-speed shear disperser, stir and mix well, shear at 3500r / min for 18min, and then use 300W ultrasonic dispersion for 12min to obtain nano UiO-66-F dispersion. S2. Preparation of the basic emulsion system: Add the remaining 1 / 2 weight of deionized water, aqueous acrylic emulsion, wetting agent and corrosion inhibitor to a closed stirred reactor, set the stirring speed to 700 r / min, and stir at a constant temperature for 12 min to obtain the basic emulsion. S3. Dispersion and compounding of intumescent flame retardant system: Keep the stirring speed at 800 r / min, add ammonium polyphosphate, melamine, pentaerythritol and nano silica charring aid to the base emulsion in sequence. After the materials are added, stir for 20 min, increase the speed to 1600 r / min, and grind and disperse at high speed for 35 min until there are no visible particles in the system to obtain flame retardant slurry. S4. Functional modification and coating adjustment: The nano-UiO-66-F dispersion prepared in step S1 is added dropwise to the flame retardant slurry at a uniform rate. After the addition is completed, the mixture is stirred for 22 minutes. Then, an antifoaming agent is added and stirred for 5 minutes to eliminate bubbles in the system. Finally, a thickener is added to finely adjust the viscosity of the system until the viscosity is stable at 90 KU. S5. Filtration and curing: After filtering the prepared slurry through a 200-mesh sterile filter, the coating is sealed and placed in a room temperature environment for 24 hours to cure, thus obtaining fluorinated nano MOF modified waterborne coating.

[0072] Example 2

[0073] The only difference from Example 1 is that: 40 parts of water-based acrylic emulsion, 25 parts of ammonium polyphosphate, 8 parts of melamine, 8 parts of pentaerythritol, 3 parts of nano silica, 1.5 parts of UiO-66-F filler, 1 part of dispersant, 0.3 parts of wetting agent, 0.2 parts of defoamer, 0.4 parts of thickener, 0.6 parts of corrosion inhibitor, and 12 parts of deionized water; The rest is the same as in Example 1.

[0074] Example 3

[0075] The only difference from Example 1 is that: 35 parts of water-based acrylic emulsion, 20 parts of ammonium polyphosphate, 8 parts of melamine, 8 parts of pentaerythritol, 8 parts of nano silica, 4.5 parts of UiO-66-F filler, 1.2 parts of dispersant, 0.8 parts of wetting agent, 0.5 parts of defoamer, 1.0 part of thickener, 1.0 part of corrosion inhibitor, and 12 parts of deionized water; The rest is the same as in Example 1.

[0076] Comparative Example 1 (without UiO-66-F modification)

[0077] The only difference from Example 1 is that: no nano UiO-66-F filler is added, the amount of nano silica added is changed to 8 parts, and the other raw material ratios and processes are the same as in Example 1.

[0078] Comparative Example 2 (pure UiO-66 modified)

[0079] The only difference from Example 1 is that an equal amount of pure UiO-66 (purchased from Shanghai Haohong Biomedical Technology Co., Ltd., item number: 1182228) is used to replace the UiO-66-F filler in Example 1, and the other raw material ratios and processes are the same as in Example 1.

[0080] Performance testing

[0081] The coatings from Examples 1-3 and Comparative Examples 1-2 were uniformly applied to the surface of a standard Q235 steel structure test plate. The dry film thickness was controlled at 2.0 mm. After curing at room temperature for 7 days, performance tests were conducted according to national standards GB 14907-2018 "Fire-retardant Coatings for Steel Structures", GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test", and GB / T 9286-2021 "Paints and Varnishes - Cross-cut Test". The test results are as follows: Example 1: Fire resistance limit 98min, no rust, no blistering or peeling in neutral salt spray test 850h, coating adhesion grade 1, no abnormalities in water resistance 168h, coating no cracking or powdering.

[0082] Example 2: Fire resistance limit 82 min, no rust after 820 h of neutral salt spray test, coating adhesion grade 1, water resistance 144 h without abnormalities.

[0083] Example 3: Fire resistance limit 75 min, no rust after 810 h of neutral salt spray test, coating adhesion grade 1, water resistance 168 h without abnormalities.

[0084] Comparative Example 1: Fire resistance limit 60min, neutral salt spray test 380h showed local rust and micro-blistering of the coating, water resistance 96h showed slight water seepage.

[0085] Comparative Example 2: Fire resistance limit 66 min, pitting corrosion appeared after 550 h of neutral salt spray test, and both corrosion resistance and fire resistance were weaker than the fluorinated modified group.

[0086] Test results show that by adding UiO-66-F fluorinated nano MOF filler, the present invention can significantly improve the fire resistance limit and corrosion resistance and salt spray resistance of water-based steel structure coatings. The coating density and water resistance are greatly optimized, and the fluorination modification effect is far superior to that of pure MOF modification. There are no problems such as filler agglomeration and performance degradation. The overall performance is far superior to that of traditional coatings.

[0087] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A fluorinated nano-MOF modified waterborne coating, characterized in that, The preparation raw materials include the following parts by weight: 35-50 parts of water-based acrylic emulsion, 28-42 parts of intumescent flame retardant, 3-8 parts of char-forming aid, 1.5-4.5 parts of nano-UiO-66-F filler, 2-6 parts of functional additives, and 12-20 parts of water. The preparation method of the nano-UiO-66-F filler includes the following steps: A precursor solution was obtained by mixing a zirconium source, tetrafluoroterephthalic acid, a crystal regulator, and an organic solvent. After the precursor solution is subjected to a solvothermal reaction, it is dried and vacuum activated in sequence to obtain nano-UiO-66-F filler; Based on 2-6 parts of the functional additive, the functional additive includes 0.5-1.2 parts of dispersant, 0.3-0.8 parts of wetting agent, 0.2-0.5 parts of defoamer, 0.4-1.0 parts of thickener, and 0.6-1.0 parts of corrosion inhibitor.

2. The fluorinated nano-MOF modified waterborne coating according to claim 1, characterized in that, The zirconium source is zirconium oxychloride octahydrate; the crystal regulator is formic acid; the organic solvent includes N,N-dimethylformamide; the molar ratio of the zirconium source to tetrafluoroterephthalic acid is 1:1; and the volume ratio of the zirconium source, crystal regulator, and organic solvent is 0.5 mmol:2 mL:30 mL.

3. The fluorinated nano-MOF modified waterborne coating according to claim 2, characterized in that, The solvothermal reaction was carried out at a temperature of 120°C for 24 hours; the vacuum activation was carried out at a temperature of 120°C for 6 hours.

4. The fluorinated nano-MOF modified waterborne coating according to claim 1, characterized in that, The solid content of the aqueous acrylic emulsion is 45~50wt%.

5. The fluorinated nano-MOF modified waterborne coating according to claim 1, characterized in that, The intumescent flame retardant is composed of ammonium polyphosphate, melamine and pentaerythritol, wherein the mass ratio of ammonium polyphosphate, melamine and pentaerythritol is (2.5~3.8):(1~1.5):1; and the particle size of the intumescent flame retardant is 800~1200 mesh.

6. The fluorinated nano-MOF modified waterborne coating according to claim 1, characterized in that, The char-forming aid is one or more of nano-silica, borax, and organosilicon-modified bentonite.

7. The method for preparing the fluorinated nano-MOF modified waterborne coating according to any one of claims 1 to 6, characterized in that, Includes the following steps: The nano-UiO-66-F filler, dispersant and some water were mixed and then subjected to shear dispersion and ultrasonic dispersion in sequence to obtain nano-UiO-66-F dispersion. The remaining water, water-based acrylic emulsion, wetting agent and corrosion inhibitor are mixed to obtain the base emulsion; The base emulsion, intumescent flame retardant, and char-forming aid are mixed to obtain a flame-retardant slurry; After mixing the nano-UiO-66-F dispersion with the flame-retardant slurry, an antifoaming agent and a thickener are added. The resulting composite slurry is then filtered and matured to obtain a fluorinated nano-MOF modified waterborne coating.

8. The preparation method according to claim 7, characterized in that, The shearing dispersion is performed at a rotation speed of 3000~4000 r / min for 15~20 min; the ultrasonic dispersion is performed at a power of 300~400 W for 10~15 min.

9. The preparation method according to claim 7, characterized in that, The viscosity of the composite slurry is adjusted to 80~100KU; the maturation temperature is room temperature and the time is 24~36h.

10. The application of the fluorinated nano-MOF modified waterborne coating according to any one of claims 1 to 6 or the fluorinated nano-MOF modified waterborne coating prepared by the preparation method according to any one of claims 7 to 9 in the field of steel structure protection.

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