Resin membrane material modified by mofs, and preparation method and application thereof

Abstract

The application discloses a MOFs modified resin film material and a preparation method and application thereof, and belongs to the technical field of material engineering. The preparation method of the MOFs modified resin film material comprises the following steps: mixing epoxy resin and / or urea-formaldehyde resin, metal salt and volatile organic solvent to obtain a mixed solution; mixing the mixed solution with a MOFs precursor solution to obtain a film casting solution; and heating the film casting solution to volatilize the volatile organic solvent, so as to obtain a MOFs modified epoxy resin film material. The application directly utilizes the characteristic that the MOFs organic precursor can initiate the crosslinking of the epoxy resin or the urea-formaldehyde resin, simultaneously triggers the self-crosslinking curing reaction of the epoxy resin or the urea-formaldehyde resin and the self-assembly reaction of the MOFs (such as ZIF series), directly obtains the film material with high compatibility and uniform distribution of the MOFs and the epoxy resin or the urea-formaldehyde resin through in-situ doping and one-step method, achieves the effect of "catching two birds with one stone", and saves the additional curing reagent and the time consumption of film preparation.

Description

Technical Field

[0001] This application belongs to the field of materials engineering technology, specifically relating to a MOFs-modified resin membrane material, its preparation method, and its application. Background Technology

[0002] Epoxy resin is a common adhesive and sealant, primarily used for bonding furniture and for sealing, protecting, and insulating electronic devices. Epoxy resin films are thin sheets made from an epoxy resin substrate using a specific process, which are then cured to form a thermosetting polymer film with a three-dimensional network structure. The excellent ductility, low shrinkage, large surface area, and light transmittance of epoxy resin films endow them with superior integrability, heat dissipation, and optical properties. Therefore, epoxy resin films are widely used in various fields, such as insulating encapsulation in new energy vehicle battery modules and protective layers in optical devices. They are also used as adhesive layers in carbon fiber or glass fiber composite materials, providing aerospace materials with high strength, high rigidity, and fatigue resistance. In the electronics industry, epoxy resin films are commonly used as reinforcing structures in flexible circuit boards, significantly enhancing the mechanical strength, corrosion resistance, and insulation properties of the circuit boards. Urea-formaldehyde resin film is also a widely used functional material. Its excellent lightfastness ensures color stability even after long-term exposure to ultraviolet light or strong light. Simultaneously, the high hardness of the urea-formaldehyde resin film provides excellent wear and scratch resistance, extending product lifespan. Furthermore, urea-formaldehyde resin film exhibits good resistance to weak acids, weak alkalis, and oils, maintaining stability in chemical environments, making it suitable for industrial cleaning or food contact applications. As a high-efficiency adhesive, urea-formaldehyde resin film is used in wood processing to manufacture plywood and engineered wood products, enhancing the durability and structural integrity of wood through high bonding strength. As a functional coating or topcoat, urea-formaldehyde resin film is applied to paper treatment, significantly enhancing the wet strength and tear resistance of paper, suitable for book covers or packaging materials. In the building decoration and automotive industries, urea-formaldehyde resin film is used for surface coatings, providing a smooth and glossy protective layer, improving weather resistance and appearance. Additionally, as a wrinkle-resistant finishing agent for textiles, urea-formaldehyde resin film effectively improves fabric feel, increases wrinkle resistance and dimensional stability, and is widely used in the clothing and home textile industries.

[0003] However, single epoxy or urea-formaldehyde resins still have limitations in heat dissipation and flammability, which may pose a potential threat to human life and property safety at high temperatures. Furthermore, traditional epoxy or urea-formaldehyde resin film curing methods often rely on multiple curing agents and are carried out at temperatures exceeding 120 °C, resulting in high production costs and temperature-dependent curing rates. Therefore, there is still a need to find an ideal flame retardant to incorporate with epoxy resin and introduce innovative curing technologies to improve the inherent defects of epoxy or urea-formaldehyde resins while reducing product manufacturing costs.

[0004] Metal-organic frameworks (MOFs) are an emerging and promising field of materials. Their large specific surface area, high porosity, and abundant active sites facilitate the binding of various types of molecules through host-guest interactions. Furthermore, the designability of MOF structures enables bottom-up structural regulation and the determination of clear structure-activity relationships. MOFs have demonstrated unique advantages in fields such as adsorption, catalysis, drug delivery, sensing, energy, antibacterial applications, and capacitance.

[0005] In related technologies, the main method for fusing MOFs with epoxy resin and urea-formaldehyde resin is the ex-situ doping method, also known as the post-synthesis doping method. This involves mixing pre-prepared MOF powder with a high-viscosity epoxy resin or urea-formaldehyde resin, then adding a curing agent to shape it, thus preparing a traditional mixed matrix membrane. However, this traditional method often results in uneven mixing and poor compatibility of the MOF powder in the high-viscosity epoxy or urea-formaldehyde resin. Furthermore, this method requires the addition of a crosslinking agent, increasing the preparation cost of MOF / epoxy resin or MOF / urea-formaldehyde resin membranes. Summary of the Invention

[0006] In view of the above-mentioned problems, the present invention aims to at least partially solve one of the technical problems in the related art. To this end, the present invention provides a MOFs-modified resin membrane material, its preparation method and application, which can alleviate the technical problems of uneven mixing, poor compatibility or high cost in the current preparation of membrane materials containing MOFs and epoxy resin or urea-formaldehyde resin, and overcome the shortcomings of the prior art.

[0007] To solve the above-mentioned technical problems, this application is implemented as follows: According to a first aspect of this application, embodiments of this application provide a method for preparing MOFs-modified resin film materials, the method comprising: A resin, a metal salt, and a volatile organic solvent are mixed to obtain a mixed solution; wherein the resin includes epoxy resin and / or urea-formaldehyde resin. The mixed solution was mixed with the MOF precursor solution to obtain the film casting solution; The membrane casting solution is heated to evaporate the volatile organic solvent, thereby obtaining a MOF-modified resin membrane material.

[0008] In an optional implementation, the MOFs include ZIF series MOFs materials.

[0009] In an optional embodiment, the MOF precursor solution includes an organic ligand for synthesizing zeolite imidazole metal-organic frameworks.

[0010] In an optional implementation, the MOFs include at least one of ZIF-8, ZIF-67, ZIF-7, ZIF-90, ZIF-9, and ZIF-L.

[0011] In an optional embodiment, the organic ligand comprises an imidazole compound; preferably, the imidazole compound comprises at least one of 2-methylimidazolium, imidazole, benzimidazole, or 2-imidazolium formaldehyde.

[0012] In an optional implementation, the step of obtaining the mixed solution satisfies at least one of the following characteristics: (1) The metal ions in the metal salt include zinc ions and / or cobalt ions; and / or, the anions in the metal salt include inorganic anions or organic anions; (2) The volatile organic solvent includes at least one of aromatic hydrocarbons, aliphatic hydrocarbons, halogenated hydrocarbons, alcohols, esters, ethers or ketones; (3) In the mixed solution, the mass ratio of resin to metal salt is 20:1 to 1:1; (4) In the step of obtaining the mixed solution, the mixing method includes mixing under heating and stirring conditions, wherein the heating temperature is 30℃~60℃ and the stirring rate is 30rpm~300rpm.

[0013] In an optional implementation, the step of obtaining the mixed solution satisfies at least one of the following characteristics: (1) The metal salt includes at least one of zinc nitrate, zinc chloride, zinc acetate, zinc sulfate, zinc acetylacetonate, cobalt nitrate, cobalt chloride, cobalt acetate, cobalt sulfate, and cobalt acetylacetonate; (2) The volatile organic solvent includes at least one of benzene, toluene, xylene, styrene, n-hexane, pentane, vinyltoluene, 1,3-butadiene, methanol, ethanol, 2-propanol, butanol, ethylene glycol, acetone, methyl ethyl ketone, chloroform, carbon tetrachloride, dichloromethane, trichloroethylene, vinyl chloride, diethyl ether, tetrahydrofuran, ethyl acetate, butyl acetate, or n-butyl acrylate; preferably, the volatile organic solvent includes one or both of methanol and ethanol; (3) The mass ratio of the resin to the metal salt is 10:1 to 5:1; (4) The heating temperature is 50℃~60℃ and the stirring speed is 180rpm~250rpm.

[0014] In an optional embodiment, the step of obtaining the membrane casting solution satisfies at least one of the following characteristics: (1) The MOF precursor solution comprises an organic ligand and a solvent, wherein the solvent comprises at least one of an alcohol, a haloalkane or a ketone; and / or the mass ratio of the organic ligand to the solvent is 1:20 to 1:1; (2) The volume ratio of the MOF precursor solution to the resin is 1:5 to 5:1; (3) In the step of obtaining the membrane casting liquid, the mixing method includes mixing under stirring conditions, wherein the stirring rate is 30 rpm to 500 rpm and the stirring time is 2 min to 30 min.

[0015] In an optional embodiment, the step of obtaining the membrane casting solution satisfies at least one of the following characteristics: (1) The solvent includes at least one of methanol, ethanol, acetone or chloroform; preferably, the solvent includes one or two of methanol or ethanol; (2) The mass ratio of the organic ligand to the solvent is 1:5 to 1:10; (3) The volume ratio of the MOF precursor solution to the resin is 1:2 to 2:1; (4) The stirring rate is 200 rpm to 300 rpm and the stirring time is 4 min to 10 min.

[0016] In an optional embodiment, the heating temperature for heating the film casting liquid is 60°C to 100°C; preferably, the heating temperature is 60°C to 80°C.

[0017] In an optional embodiment, during the heating of the membrane casting solution, the organic ligands in the MOF precursor solution serve as precursors for synthesizing MOFs, and simultaneously act as curing agents and crosslinking agents for the resin, reacting with the resin to generate a three-dimensional crosslinked network structure, thereby obtaining a self-crosslinked membrane material.

[0018] According to a second aspect of this application, embodiments of this application provide a MOFs-modified resin membrane material, which is prepared using the aforementioned method for preparing MOFs-modified resin membrane materials. According to a third aspect of this application, embodiments of this application provide an application of the MOFs-modified resin film material as described above in flame retardancy.

[0019] Implementing the technical solution of the present invention has at least the following beneficial effects: In the embodiments of this application, the provided MOFs-modified resin membrane material and its preparation method first provide a mixed solution containing epoxy resin or urea-formaldehyde resin, metal salt, and volatile organic solvent. Then, this mixed solution is mixed with a MOFs precursor solution to obtain a membrane casting solution. The membrane casting solution is heated to evaporate the volatile organic solvent, thereby obtaining the MOFs-modified resin membrane material. Thus, this invention adopts a "one-step" strategy, using MOFs (especially ZIFs series) precursors as crosslinking agents for epoxy resin or urea-formaldehyde resin, achieving simultaneous in-situ self-assembly of MOFs and resin crosslinking and curing processes without the need for other curing agents. Furthermore, the MOFs are uniformly distributed in the resin and exhibit good compatibility. The membrane material obtained by this invention has high transparency and no obvious MOF particles.

[0020] The MOF-modified resin film material provided by this invention can be applied in the field of flame retardant materials. Furthermore, this invention directly uses the precursors for synthesizing MOFs as the curing agent and crosslinking agent for the resin, saving the consumption of additional curing agents and reducing the cost of preparing flame retardant resin materials.

[0021] This invention employs an in-situ doping method and a one-step method to prepare self-crosslinking membrane materials. The self-assembly of MOFs and the crosslinking and curing of the resin are carried out simultaneously, eliminating the need for additional curing time and significantly improving the preparation efficiency of resin flame retardant materials.

[0022] This invention generates MOFs in situ within the resin through self-assembly. Compared to the direct incorporation of pre-prepared MOF powder in related technologies, the distribution of MOFs within the resin is more uniform, ensuring the stable flame-retardant performance of the resin flame-retardant material.

[0023] The method for preparing MOFs-modified resin membrane materials of the present invention is simple and easy to implement, requiring no complex equipment or harsh reaction conditions, making it suitable for large-scale industrial production. It demonstrates high feasibility and broad application prospects in practical applications.

[0024] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0025] Figure 1 The images show physical pictures of the ZIF-67 / epoxy resin self-crosslinking membrane (in-situ ZIF-67@BPA) prepared in Example 1 of this invention and the membrane material (ex-situ ZIF-67 / BPA) prepared in Comparative Example 1.

[0026] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the ZIF-67 / epoxy resin self-crosslinking film (in-situ ZIF-67@BPA) prepared in Example 1 of this invention.

[0027] Figure 3 This is a scanning electron microscope (SEM) image of the ZIF-67 / epoxy resin self-crosslinking film (in situ ZIF-67@BPA) prepared in Example 1 of the present invention.

[0028] Figure 4 This is a scanning electron microscope (SEM) image of the modified ZIF-67 / epoxy resin self-crosslinking film (modified in-situ ZIF-67@BPA) prepared in Example 2 of the present invention.

[0029] Figure 5 The images show the physical images of the ZIF-67 / urea-formaldehyde resin self-crosslinking membrane (in-situ ZIF-67@UF) prepared in Example 3 of the present invention and the pure urea-formaldehyde resin self-crosslinking membrane (UF) prepared in Comparative Example 3.

[0030] Figure 6 The images show physical pictures of the ZIF-8 / epoxy resin self-crosslinking membrane (in-situ ZIF-8@BPA) prepared in Example 4 of the present invention and the membrane material (ex-situ ZIF-8 / BPA) prepared in Comparative Example 4.

[0031] Figure 7 The image shows the XRD pattern of the ZIF-8 / epoxy resin self-crosslinking film (in-situ ZIF-8@BPA) prepared in Example 4 of this invention.

[0032] Figure 8 This is a SEM image of the ZIF-8 / epoxy resin self-crosslinking membrane (in-situ ZIF-8@BPA) prepared in Example 4 of the present invention.

[0033] Figure 9 This is a scanning electron microscope (SEM) image of the modified ZIF-8 / epoxy resin self-crosslinking film (modified in-situ ZIF-8@BPA) prepared in Example 5 of the present invention.

[0034] Figure 10 The images show physical pictures of the ZIF-8 / urea-formaldehyde resin self-crosslinking membrane (in-situ ZIF-8@UF) prepared in Example 6 of the present invention and the urea-formaldehyde resin self-crosslinking membrane (UF) prepared in Comparative Example 6.

[0035] Figure 11 The graph shows a comparison of the thermogravimetric curves of the ZIF-67 / epoxy resin self-crosslinking membrane (in-situ ZIF-67@BPA) prepared in Example 1 of this invention, the membrane material prepared in Comparative Example 1 (ex-situ ZIF-67 / BPA), the pure epoxy resin self-crosslinking membrane (BPA) prepared in Comparative Example 2, and the modified ZIF-67 / epoxy resin self-crosslinking membrane (modified in-situ ZIF-67 / BPA) prepared in Example 2 under air atmosphere.

[0036] Figure 12The limiting oxygen index is compared during combustion in air for the ZIF-67 / epoxy resin self-crosslinking membrane (in-situ ZIF-67@BPA) prepared in Example 1 of this invention, the membrane material prepared in Comparative Example 1 (ex-situ ZIF-67 / BPA), the pure epoxy resin (BPA) prepared in Comparative Example 2, and the modified ZIF-67 / epoxy resin self-crosslinking membrane (modified in-situ ZIF-67 / BPA) prepared in Example 2.

[0037] Figure 13 The thermogravimetric curves of the ZIF-67 urea-formaldehyde resin self-crosslinking membrane (in-situ ZIF-67@UF) and the pure urea-formaldehyde resin self-crosslinking membrane (UF) prepared in Example 3 and Comparative Example 3 of this invention are compared in air atmosphere.

[0038] Figure 14 This is a comparison chart of the limiting oxygen index during the combustion process of ZIF-67 urea-formaldehyde resin self-crosslinking membrane (in-situ ZIF-67@UF) and pure urea-formaldehyde resin self-crosslinking membrane (UF) prepared in Example 3 and Comparative Example 3 of the present invention, respectively, in an air atmosphere.

[0039] Figure 15 The graph shows a comparison of the thermogravimetric curves of the ZIF-8 / epoxy resin self-crosslinking membrane (in-situ ZIF-8@BPA) prepared in Example 4 of the present invention, the membrane material prepared in Comparative Example 4 (ex-situ ZIF-8 / BPA), the pure epoxy resin (BPA) prepared in Comparative Example 5, and the modified ZIF-8 / epoxy resin crosslinking membrane (modified in-situ ZIF-8@BPA) under air atmosphere.

[0040] Figure 16 This is a comparison chart of the limiting oxygen index during combustion in air for the ZIF-8 / epoxy resin self-crosslinking membrane (in-situ ZIF-8@BPA) prepared in Example 4 of the present invention, the membrane material (ex-situ ZIF-8 / BPA) prepared in Comparative Example 4, the pure epoxy resin (BPA) prepared in Comparative Example 5, and the modified ZIF-8 / epoxy resin crosslinking membrane (modified in-situ ZIF-8@BPA) prepared in Example 5.

[0041] Figure 17 The thermogravimetric curves of the ZIF-8 urea-formaldehyde resin self-crosslinking membrane (in-situ ZIF-8@UF) and the pure urea-formaldehyde resin self-crosslinking membrane (UF) prepared in Example 6 and Comparative Example 6 of this invention are compared in air atmosphere.

[0042] Figure 18 This is a comparison chart of the limiting oxygen index during combustion in air for the ZIF-8 urea-formaldehyde resin self-crosslinking membrane (in-situ ZIF-8@UF) prepared in Example 6 and Comparative Example 6 of the present invention, and the pure urea-formaldehyde resin self-crosslinking membrane (UF). Detailed Implementation

[0043] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply.

[0044] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the ranges, the endpoint values ​​of the ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges.

[0045] It should be noted that the terms "and / or" or " / " used herein are merely descriptions of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The singular forms "a," "the," and "the" used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0046] In the description of this application, the list of items connected by the terms "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0047] Metal-organic frameworks (MOFs) have demonstrated unique advantages in adsorption, catalysis, drug delivery, sensing, energy, antibacterial applications, and capacitance. In recent years, MOFs have also been widely incorporated into polymer materials as effective flame retardants. On one hand, the metal ions in MOFs can catalyze the pyrolysis of polymers at high temperatures, forming a dense carbon layer on the surface that isolates heat and oxygen transfer, thereby inhibiting the release of flammable gases. On the other hand, the porous structure and high specific surface area of ​​MOFs can adsorb decomposition products, thus slowing down heat transfer and gas diffusion. Incorporating MOFs into resins such as epoxy or urea-formaldehyde resins can improve their flame retardant properties. However, the methods for preparing materials containing MOFs and epoxy or urea-formaldehyde resins still have some shortcomings. For example, the traditional method for fusing MOFs with epoxy resin or urea-formaldehyde resin is the ex-situ doping method, also known as post-synthesis doping. This involves mixing pre-prepared MOF powder with a high-viscosity epoxy resin or urea-formaldehyde resin adhesive, then adding a curing agent to shape it, thus preparing a traditional mixed matrix film. This method often results in uneven mixing and poor compatibility of the MOF powder in the high-viscosity epoxy resin or urea-formaldehyde resin. Furthermore, this method requires the addition of an additional crosslinking agent, increasing the preparation cost of the MOF / epoxy resin or urea-formaldehyde resin film. Therefore, developing a method for uniformly distributing MOFs in epoxy resin or urea-formaldehyde resin without the need for additional crosslinking agents is of great significance for the promotion of low-cost, high-quality epoxy resin or urea-formaldehyde resin-based flame-retardant adhesives and sealants.

[0048] Based on this, the technical solution of this application provides a MOFs-modified resin membrane material, its preparation method, and its application. This material is a self-crosslinking membrane material formed by MOFs and epoxy resin or urea-formaldehyde resin, which can be applied in the flame retardant field and can effectively overcome the shortcomings of the above-mentioned related technologies. A detailed description of the technical solution is provided below.

[0049] In some embodiments, a method for preparing MOFs-modified resin film material is provided, the method comprising the following steps: A resin, a metal salt, and a volatile organic solvent are mixed to obtain a mixed solution; wherein the resin includes epoxy resin and / or urea-formaldehyde resin; for example, the resin may be epoxy resin or urea-formaldehyde resin. The mixed solution was mixed with the MOF precursor solution to obtain the membrane casting solution; The membrane casting solution is heated to evaporate the volatile organic solvent, thus obtaining MOFs-modified epoxy resin membrane material.

[0050] In this embodiment of the invention, the epoxy resin can be an epoxy resin adhesive, and the urea-formaldehyde resin can be a urea-formaldehyde resin adhesive.

[0051] In this embodiment, the provided method is an in-situ doping method, which mainly adopts a "one-step" strategy. The precursor of MOFs is used as a crosslinking agent for epoxy resin or urea-formaldehyde resin, enabling the in-situ self-assembly of MOFs (such as ZIFs series) and the crosslinking and curing process of epoxy resin or urea-formaldehyde resin to occur simultaneously, without the need to introduce other curing agents. Furthermore, the MOFs are uniformly distributed and have good compatibility in the epoxy resin or urea-formaldehyde resin. The resulting film material has high transparency and no obvious MOF particles.

[0052] In this embodiment, the provided material is a self-crosslinking film material formed by MOFs and epoxy resin or urea-formaldehyde resin, particularly a self-crosslinking film material based on ZIF series MOFs and epoxy resin or urea-formaldehyde resin. The material provided in this embodiment can be applied in the flame retardant field.

[0053] In this embodiment, a mixed solution is first prepared, for example, by mixing and heating a resin such as epoxy resin or urea-formaldehyde resin with a metal salt in a volatile organic solvent to obtain a mixed solution; then, a MOF precursor solution is added, such as a ZIF organic precursor solution (e.g., a solution containing imidazole compounds), to obtain a membrane casting solution, i.e., a membrane casting solution; then, the solution is heated to evaporate the organic solvent in the membrane casting solution to obtain a self-crosslinking membrane material formed by MOFs and epoxy resin or urea-formaldehyde resin, especially a self-crosslinking membrane material formed in situ by ZIF series MOFs and epoxy resin or urea-formaldehyde resin.

[0054] The in-situ doping method provided in this embodiment directly utilizes the characteristic that MOF precursors, such as ZIFs organic precursors, can initiate crosslinking of epoxy resin or urea-formaldehyde resin. Simultaneously, it triggers the self-crosslinking curing reaction of epoxy resin or urea-formaldehyde resin and the self-assembly reaction of ZIFs series MOFs. Through in-situ doping and a one-step method, a membrane material with high compatibility and uniform distribution between MOFs and epoxy resin or urea-formaldehyde resin is directly obtained, achieving a "two birds with one stone" effect and saving additional curing reagents and membrane preparation time.

[0055] In this embodiment, MOFs are preferably ZIF series MOFs materials.

[0056] The method for preparing a self-crosslinking film material formed by ZIFs series MOFs and epoxy resin or urea-formaldehyde resin provided in this invention does not require the addition of an additional curing agent, and the curing of the epoxy resin or urea-formaldehyde resin and the in-situ self-assembly of the ZIFs series MOFs can be completed simultaneously in one step, saving a significant amount of product processing time and the cost of applying curing agents. Furthermore, the epoxy resin or urea-formaldehyde resin in which ZIFs series MOFs are in-situ doped also possesses flame-retardant properties. The specific principle is as follows: On the one hand, MOF precursors, such as imidazole compounds, are precursors of ZIF series MOFs and can autonomously assemble into MOFs by coordinating with metal ions. On the other hand, because imidazole molecules contain two nitrogen atoms—one a secondary amine structure with active hydrogen and the other a tertiary amine structure with a lone pair of electrons—this unique structure possesses both addition reaction activity and catalytic polymerization ability, allowing imidazole compounds to also act as an anionic curing agent for epoxy resins. Upon contact between imidazole compounds and liquid epoxy resin, the secondary amine group (-NH-) of the imidazole in the compound undergoes a ring-opening addition reaction with the epoxy group via active hydrogen, generating an intermediate product; this step provides the starting point for subsequent crosslinking. Subsequently, the tertiary amine nitrogen atom in the imidazole molecule acts as a strong nucleophilic center, attacking the oxygen atom in the epoxy group with its lone pair of electrons, initiating the anionic ring-opening polymerization of the epoxy group. This process forms a chain reaction, ultimately leading to the formation of a three-dimensional crosslinked network structure in the epoxy resin molecules, thereby achieving curing. Meanwhile, the unshared electron pairs of nitrogen atoms in imidazole participate in cyclic conjugation, leading to a decrease in the electron density of nitrogen atoms. This makes it easier for hydrogen atoms to leave as hydrogen ions, giving imidazole its weak acidity. This acidic environment can also catalyze the cross-linking reaction of urea-formaldehyde resin: under acidic conditions, free formaldehyde in the resin reacts with amino groups more quickly, promoting the transformation of linear molecules into a three-dimensional network structure, thereby improving mechanical strength, water resistance, and stability.

[0057] Furthermore, during the curing process, by introducing metal ions into the reaction system, these metal ions simultaneously coordinate with imidazole molecules, generating ZIFs-series MOFs micro / nanoparticles within the crosslinking network of epoxy or urea-formaldehyde resin. Due to the confinement effect of the crosslinking molecular network of epoxy or urea-formaldehyde resin on MOFs, the MOFs micro / nanoparticles can be uniformly anchored and encapsulated within the continuous structure of epoxy or urea-formaldehyde resin, forming a uniformly distributed mixed system of MOFs and epoxy or urea-formaldehyde resin, ensuring the stability of the self-crosslinking membrane material in terms of flame retardant properties. When the self-crosslinking membrane material is exposed to high temperatures, the carbon layer formed on the membrane surface has a relatively uniform thickness, thus enabling the membrane to effectively isolate oxygen and heat transfer in all areas.

[0058] In the above process, the present invention first dissolves epoxy resin or urea-formaldehyde resin, metal salt, and ZIF precursor in a volatile organic solvent, and appropriately increases the temperature to further reduce the viscosity of epoxy resin or urea-formaldehyde resin, enabling it to form a homogeneous mixture with the metal salt and ZIF precursor, i.e., the membrane casting solution. This ensures the uniform distribution of the formed epoxy resin or urea-formaldehyde resin crosslinked molecular chains and MOF micro / nano particles. Finally, the volatile organic solvent in the membrane casting solution is evaporated by heating, causing a phase transformation of the solids. The polymer-rich phase gradually accumulates, thereby gradually forming a stable membrane matrix, ultimately obtaining a self-crosslinked membrane material, i.e., a MOF-modified epoxy resin or urea-formaldehyde resin membrane material.

[0059] In some embodiments, the MOF precursor solution includes organic ligands for synthesizing zeolite imidazole metal-organic frameworks, that is, the MOF precursor solution includes ZIF precursors for synthesizing ZIF materials.

[0060] In this embodiment, the ZIF series MOFs materials include one or more zeolite imidazole metal-organic frameworks that can be synthesized at atmospheric pressure below the decomposition temperature (170°C) of epoxy resin or urea-formaldehyde resin. As an example, in some embodiments, MOFs such as ZIF series MOFs include, but are not limited to, any one or a combination of at least two of ZIF-8, ZIF-67, ZIF-7, ZIF-90, ZIF-9, and ZIF-L.

[0061] In a preferred embodiment, the MOFs are selected from one or both of ZIF-8 or ZIF-67.

[0062] Therefore, in typical embodiments of the present invention, ZIF-8 or ZIF-67 is chosen as the MOFs doped in epoxy or urea-formaldehyde resins, primarily because ZIF-8 and ZIF-67 can self-assemble at room temperature, with mild and easily controllable reaction conditions; moreover, ZIF-8 and ZIF-67 exhibit distinctive macroscopic colors. ZIF-8 is pure white, while ZIF-67 is purple, allowing for direct visual observation of the color of the epoxy or urea-formaldehyde resin to determine whether ZIF-8 and ZIF-67 have achieved self-assembly. Furthermore, both ZIF-8 and ZIF-67 can be synthesized using 2-methylimidazole, and commercially available industrial-grade 2-methylimidazole reagent in drums is readily available, saving on raw material costs for the preparation of ZIF-8 and ZIF-67.

[0063] In this embodiment, the organic ligand in the MOF precursor solution is preferably a ZIF precursor, which includes imidazole compounds. As an example, in some embodiments, the imidazole compounds include, but are not limited to, any one or a combination of at least two of 2-methylimidazole, imidazole, benzimidazole, or 2-imidazolium formaldehyde.

[0064] In a preferred embodiment, the imidazole compound is selected from 2-methylimidazole.

[0065] In typical embodiments of the present invention, 2-methylimidazole is chosen as the curing agent and precursor (organic ligand) of MOFs, primarily because 2-methylimidazole is an industrial-grade reagent, very inexpensive, and conducive to large-scale production of the product; moreover, 2-methylimidazole is a precursor of classic ZIF series MOFs such as ZIF-8, ZIF-L, and ZIF-67, enabling the synthesis of various MOFs. Therefore, the selection of 2-methylimidazole in the embodiments of the present invention has strong representativeness and universality.

[0066] In this embodiment, the metal ions in the metal salt include zinc ions and / or cobalt ions; that is, the metal salt may include one or both of the following: salts containing zinc ions or salts containing cobalt ions. The anions in the metal salt include inorganic anions or organic anions; that is, the metal salt may be an inorganic metal salt or an organic metal salt.

[0067] Optionally, the metal salt comprises one or more of solid particles or powders containing zinc ions and cobalt ions. As an example, in some embodiments, the metal salt includes, but is not limited to, any one or a combination of at least two of zinc nitrate, zinc chloride, zinc acetate, zinc sulfate, zinc acetylacetonate, cobalt nitrate, cobalt chloride, cobalt acetate, cobalt sulfate, and cobalt acetylacetonate.

[0068] In a preferred embodiment, the metal salt is selected from one or both of cobalt nitrate or zinc nitrate.

[0069] In typical embodiments of the present invention, zinc nitrate and cobalt nitrate are selected as metal salts for the synthesis of ZIF-8 and ZIF-67, mainly because the morphology of ZIF-8 and ZIF-67 synthesized with zinc nitrate and cobalt nitrate is more regular and easier to identify than that of ZIF-8 and ZIF-67 synthesized with other metal salts; moreover, zinc nitrate and cobalt nitrate are relatively common in the market, readily available, and have low cost.

[0070] In some embodiments, the volatile organic solvent in the mixed solution includes at least one of aromatic hydrocarbons, aliphatic hydrocarbons, halogenated hydrocarbons, alcohols, esters, ethers, or ketones.

[0071] As an example, in some embodiments, the volatile organic solvents include, but are not limited to, any one or a combination of at least two of the following: benzene, toluene, xylene, styrene, n-hexane, pentane, vinyltoluene, 1,3-butadiene, methanol, ethanol, 2-propanol, butanol, ethylene glycol, acetone, methyl ethyl ketone, chloroform, carbon tetrachloride, dichloromethane, trichloroethylene, vinyl chloride, diethyl ether, tetrahydrofuran, ethyl acetate, butyl acetate, or n-butyl acrylate.

[0072] In a preferred embodiment, the volatile organic solvent includes one or both of methanol and ethanol. In a more preferred embodiment, ethanol is selected as the volatile organic solvent.

[0073] In this embodiment, the MOF precursor solution includes the above-mentioned organic ligands and a solvent. That is, the MOF precursor solution is mainly composed of the above-mentioned organic ligands and a solvent, and the solvent is preferably an organic solvent.

[0074] In some embodiments, the solvent in the MOF precursor solution includes at least one of alcohols, haloalkanes, or ketones.

[0075] As an example, in some embodiments, the solvent in the MOF precursor solution includes, but is not limited to, one or more of methanol, ethanol, acetone, and chloroform.

[0076] In a preferred embodiment, the solvent in the MOF precursor solution includes one or both of methanol and ethanol. In a more preferred embodiment, ethanol is selected as the solvent in the MOF precursor solution.

[0077] In a typical embodiment of this invention, ethanol is chosen as both the volatile organic solvent in the mixed solution and the solvent in the MOF precursor solution. This is primarily because ethanol is widely available and inexpensive; industrial-grade ethanol reagents in drums can be purchased commercially, saving on raw material costs in the preparation of self-crosslinking membrane materials. Furthermore, ethanol has a low boiling point at atmospheric pressure, allowing for rapid evaporation below 100°C. This not only reduces the heat treatment temperature, saving energy consumption, but also helps maintain the stability of the MOF material framework. Moreover, ethanol has relatively lower toxicity compared to other organic solvents, making it less likely to have adverse effects on the human body. Simultaneously, ethanol is an excellent solvent for epoxy resins or urea-formaldehyde resins, metal salts, and imidazole compounds. Epoxy resins or urea-formaldehyde resins, metal salts, and imidazole compounds all exhibit high solubility in ethanol at room temperature, ensuring the homogeneity of the membrane casting solution.

[0078] In some embodiments, the mass ratio of epoxy resin or urea-formaldehyde resin to metal salt in the mixed solution is 20:1 to 1:1; for example, the mass ratio of epoxy resin or urea-formaldehyde resin to metal salt is 20:1, 15:1, 10:1, 8:1, 6:1, 5:1, 3:1, 1:1, etc.

[0079] In a preferred embodiment, the mass ratio of epoxy resin or urea-formaldehyde resin to metal salt is 10:1 to 5:1. In a more preferred embodiment, the mass ratio of epoxy resin or urea-formaldehyde resin to metal salt is 10:1.

[0080] By controlling the mass ratio of epoxy resin or urea-formaldehyde resin to metal salt within the aforementioned suitable range, it is helpful to improve the dispersibility and uniformity of the solution. In particular, a typical embodiment of the present invention selects a mass ratio of epoxy resin or urea-formaldehyde resin adhesive to metal salt of 10:1, mainly because the particle size of the generated ZIFs series MOFs can reach the nanoscale if and only if this mass ratio is met, thus ensuring dispersibility and uniformity.

[0081] In some embodiments, the step of obtaining the mixed solution includes mixing under heating and stirring conditions. The heating temperature is 30°C to 60°C, for example, 30°C, 40°C, 50°C, 55°C, 58°C, 60°C, etc.; the stirring rate is 30 rpm to 300 rpm, for example, 30 rpm, 50 rpm, 80 rpm, 100 rpm, 150 rpm, 180 rpm, 200 rpm, 220 rpm, 250 rpm, 300 rpm, etc.

[0082] In a preferred embodiment, the heating temperature is 50°C to 60°C, and the stirring rate is 180 rpm to 250 rpm. In a more preferred embodiment, the heating temperature is 60°C, and the stirring rate is 250 rpm.

[0083] In this embodiment, epoxy resin or urea-formaldehyde resin is mixed with metal salt in a volatile organic solvent and heated and stirred to obtain a mixed solution. In a typical embodiment of the present invention, 60°C and 250 rpm are selected as preferred conditions for mixing and heating and stirring, mainly because the viscosity of the liquid mixture can be minimized only under these temperature and stirring rate conditions, and the solvent will not evaporate rapidly due to the temperature being higher than its boiling point under normal pressure conditions; moreover, the liquid mixture will not separate into layers only under these temperature and stirring rate conditions, and the components are relatively evenly distributed.

[0084] In some embodiments, the mass ratio of organic ligand to solvent in the MOF precursor solution is 1:20 to 1:1; for example, it can be 1:20, 1:15, 1:10, 1:8, 1:6, 1:5, 1:3, 1:1, etc.

[0085] In a preferred embodiment, the mass ratio of the organic ligand to the solvent is 1:5 to 1:10. In a more preferred embodiment, the mass ratio of the organic ligand to the solvent is 1:5.

[0086] By controlling the ratio of organic ligands to solvents in the MOF precursor solution within the aforementioned suitable range, it is helpful to prevent the formed MOF materials from agglomerating in epoxy or urea-formaldehyde resins, and also to improve the light transmittance of the resulting membrane material. In particular, a preferred mass ratio of 1:5 for organic ligands to solvents in the MOF precursor solution is selected in a typical embodiment of the present invention, mainly because the generated ZIFs series MOFs will not form aggregates in epoxy or urea-formaldehyde resins if and only if this mass ratio is met, and the light transmittance of the self-crosslinking membrane is guaranteed.

[0087] In some embodiments, the volume ratio of the MOF precursor solution to the epoxy resin or urea-formaldehyde resin is 1:5 to 5:1; that is, the volume ratio of the added MOF precursor solution to the volume ratio of the epoxy resin or urea-formaldehyde resin adhesive is 1:5 to 5:1, for example, it can be 1:5, 1:4, 1:2, 1:1, 2:1, 3:1, 5:1, etc.

[0088] In a preferred embodiment, the volume ratio of the MOF precursor solution to the epoxy resin or urea-formaldehyde resin is 1:2 to 2:1. In a more preferred embodiment, the volume ratio of the MOF precursor solution to the epoxy resin or urea-formaldehyde resin is 1:1.

[0089] By controlling the volume ratio of the MOF precursor solution to the epoxy resin or urea-formaldehyde resin within the aforementioned suitable range, it is helpful to avoid or reduce the stratification of the liquid mixture and improve the homogeneity of the system. In particular, a volume ratio of 1:1 between the MOF precursor solution and the epoxy resin or urea-formaldehyde resin is selected as the preferred volume ratio in the typical embodiments of the present invention, mainly because the liquid mixture will not stratify if and only if this mass ratio is met, the components are relatively uniformly distributed, and the particle size of the generated ZIFs series MOFs can reach the nanometer level, thus ensuring dispersion and uniformity.

[0090] In some embodiments, the mixing method in the step of obtaining the membrane casting liquid includes mixing under stirring conditions, with a stirring rate of 30 rpm to 500 rpm and a stirring time of 2 min to 30 min.

[0091] In a preferred embodiment, the stirring rate is 200 rpm to 300 rpm, and the stirring time is 4 min to 10 min. In an even more preferred embodiment, the stirring rate is 250 rpm, and the stirring time is 5 min.

[0092] In this embodiment, the mixed solution and the MOF precursor solution are stirred and mixed to obtain a membrane casting solution. The membrane casting solution is then heated to evaporate the volatile organic solvent. Furthermore, during the heating of the membrane casting solution, the organic ligands in the MOF precursor solution act as precursors for MOF synthesis, and simultaneously as curing agents and crosslinking agents for epoxy resin or urea-formaldehyde resin, reacting with the epoxy resin or urea-formaldehyde resin to generate a three-dimensional crosslinked network structure, thus obtaining a self-crosslinked membrane material.

[0093] In some embodiments, the heating temperature for heating the membrane casting liquid is 60°C to 100°C, for example, 60°C, 70°C, 80°C, 90°C, 100°C, etc.

[0094] In a preferred embodiment, the heating temperature is 60°C to 80°C. In a more preferred embodiment, the heating temperature is 80°C.

[0095] In a typical embodiment of the present invention, a heating temperature of 80°C is selected as the preferred heating temperature, mainly because this temperature is just above the lowest temperature at which ethanol boils under normal pressure. This not only ensures that ethanol evaporates quickly, but also ensures that the MOFs framework structure will not collapse due to the increase in ambient temperature.

[0096] Optionally, the process of evaporating the volatile organic solvent, i.e., drying the volatile organic solvent, can be carried out on an inorganic glass plate. For example, the obtained film casting solution can be spread evenly on an inorganic glass plate and heated until the volatile organic solvent is dried.

[0097] It should be noted that this invention does not limit the source of the above-mentioned raw materials. Raw materials such as epoxy resin and metal salts can be obtained commercially.

[0098] Accordingly, in some embodiments, this application also provides a MOFs-modified resin membrane material, which is prepared using the aforementioned preparation method. It should be understood that the "MOFs-modified resin membrane material" and the aforementioned "preparation method of MOFs-modified resin membrane material" are based on the same inventive concept, and therefore possess at least all the features and advantages of the aforementioned "preparation method of MOFs-modified resin membrane material", which will not be repeated here.

[0099] Accordingly, the present invention also provides an application of MOFs-modified resin membrane material, which includes the aforementioned MOFs-modified resin membrane material and / or the MOFs-modified resin membrane material prepared by the aforementioned preparation method.

[0100] The applications of these MOF-modified resin film materials include at least the flame retardant field.

[0101] To fully illustrate the relevant properties of the MOFs-modified resin membrane material provided in this application and to facilitate understanding of the invention, multiple sets of experiments were conducted. The invention will be further described below with reference to specific embodiments, comparative examples, and application examples.

[0102] Example 1 A method for preparing MOFs-modified epoxy resin film material includes: Weigh 2 g of 2-methylimidazole and dissolve it in 10 g of ethanol to form a ZIFs precursor solution, which is also a MOFs precursor solution. Measure 12.5 mL of epoxy resin and 1.25 g of cobalt nitrate hexahydrate and dissolve them in (10 g) 12.5 mL of ethanol. Heat the solution to 60 °C and stir continuously at 250 rpm to form a homogeneous mixed solution.

[0103] The above mixed solution was mixed with the ZIFs precursor solution and stirred continuously at 250 rpm for 5 min to form a casting solution for the ZIF-67 / epoxy resin self-crosslinking membrane, which is the membrane casting solution. Then, the membrane casting solution was spread evenly on an inorganic glass plate and heated to 80°C until all the ethanol was evaporated to obtain the ZIF-67 / epoxy resin self-crosslinking membrane, which is denoted as the in-situ ZIF-67@BPA membrane.

[0104] Comparative Example 1 The preparation method of the MOF-modified epoxy resin film material in Comparative Example 1 is a traditional method for synthesizing doped MOFs, mainly involving incorporating synthesized ZIF-67 into epoxy resin to obtain a common ZIF-67 / epoxy resin hybrid matrix film. Specifically, it includes: Weigh 2 g of 2-methylimidazole and dissolve it in 10 g of ethanol to form solution C, the precursor of ZIFs. Weigh 1.25 g of cobalt nitrate hexahydrate and dissolve it in (10 g) 12.5 mL of ethanol, denoted as solution D. Mix solutions C and D and stir continuously at 250 rpm for 5 min. Then centrifuge the mixture at 8000 rpm for 10 min, collect the precipitate and dry it to obtain ZIF-67. Then disperse all the ZIF-67 prepared in the above steps in 12.5 mL of epoxy resin, add 2 g of conventional epoxy resin curing agent T-31, heat to 60℃ and stir continuously at 250 rpm until the mixture is uniform in color. Finally, pour the mixture onto an inorganic glass plate and cool it to obtain a common ZIF-67 / epoxy resin mixed matrix membrane, denoted as ectopic ZIF-67 / BPA membrane.

[0105] Comparative Example 2 The preparation method of the epoxy resin film material in Comparative Example 2 mainly involves preparing a self-crosslinking epoxy resin film without ZIF-67 doping. Specifically, it includes: Weigh 2 g of 2-methylimidazole and dissolve it in 10 g of ethanol to form solution E. Measure 12.5 mL of epoxy resin and 1.25 g of epoxy resin and dissolve them in (10 g) 12.5 mL of ethanol. Heat the solution to 60°C and stir continuously at 250 rpm to form a homogeneous solution F. Mix solution E and solution F and stir continuously at 250 rpm for 5 min to form a casting solution for the epoxy resin self-crosslinking membrane. Then, spread the casting solution of the membrane evenly on an inorganic glass plate and heat the inorganic glass plate to 80°C until all the ethanol evaporates to obtain the epoxy resin self-crosslinking membrane, denoted as BPA membrane.

[0106] By comparing Example 1 and Comparative Example 1, the differences between the in-situ doping preparation method of the present invention and the traditional method of synthesizing post-doped MOFs can be seen.

[0107] The in-situ ZIF-67@BPA membrane prepared in Example 1 of this invention and the ex-situ ZIF-67 / BPA membrane prepared in Comparative Example 1 are shown in the following figures. Figure 1 As shown. From Figure 1 It can be seen that no obvious particle agglomeration occurred in the in-situ ZIF-67@BPA film. Compared with the colorless and transparent BPA film, the in-situ ZIF-67@BPA film exhibits the characteristic purple color of transparent ZIF-67. However, obvious fine purple particles were observed in the ex-situ ZIF-67 / BPA film, which are aggregates of ZIF-67 particles. This indicates that the traditional blending and stirring method is insufficient to achieve a uniform distribution of synthesized ZIF-67 particles in the epoxy resin system, and also fails to solve the problem of agglomeration of synthesized ZIF-67 particles in the epoxy resin.

[0108] Comparative Example 2 is set up mainly to compare the effects of the in-situ ZIF-67 doping preparation method of the present invention and the lack of ZIF-67 doping on the flame retardancy of epoxy resin materials (which can be demonstrated in subsequent application examples).

[0109] The composition of the in-situ ZIF-67@BPA film prepared in Example 1 of the present invention was characterized by X-ray diffraction (XRD), and the microstructure of the in-situ ZIF-67@BPA prepared in Example 1 was observed by scanning electron microscopy (SEM).

[0110] X-ray diffraction analysis results are as follows: Figure 2As shown, the diffraction peak patterns of the in-situ ZIF-67@BPA film correspond well with those of pure ZIF-67, indicating that ZIF-67 was successfully encapsulated within the epoxy resin. In contrast, no diffraction peaks of ZIF-67 were observed in the pure BPA film. Scanning electron microscopy images are shown below. Figure 3 As shown, a large number of dodecahedral ZIF-67 micro / nanoparticles were embedded in the prepared in-situ ZIF-67@BPA film, consistent with the morphology of ZIF-67 particles in relevant literature, further confirming the presence of ZIF-67 in the in-situ ZIF-67@BPA film. In contrast, no micro / nanoparticles were observed in the pure BPA film.

[0111] Example 2 The preparation method of the epoxy resin film material in Example 2 mainly involves changing the mass ratio of epoxy resin to metal salt and the mass ratio of precursor to solvent in the MOF precursor solution. Specifically, it includes: Weigh 1 g of 2-methylimidazole and dissolve it in 10 g of ethanol to form solution G. Measure 12.5 mL of epoxy resin and 2.5 g of cobalt nitrate hexahydrate and dissolve them in (10 g) 12.5 mL of ethanol. Heat the solution to 60 °C and stir continuously at 250 rpm to form a homogeneous solution H. Mix solution G and solution H and stir continuously at 250 rpm for 5 min to form a casting solution for the modified ZIF-67 / epoxy resin self-crosslinking membrane. Then, spread the casting solution evenly on an inorganic glass plate and heat the inorganic glass plate to 80 °C until all the ethanol evaporates to dryness to obtain the modified ZIF-67 / epoxy resin self-crosslinking membrane, denoted as modified in-situ ZIF-67@BPA membrane.

[0112] Example 2 is set up mainly to illustrate the effect of changing the proportion of reagent components on the morphology and size of MOF in epoxy resin materials and on the flame retardancy of epoxy resin materials (which can be shown in the subsequent application examples).

[0113] The scanning electron microscope image of the modified in-situ ZIF-67@BPA film prepared in Example 2 is shown in Figure 4. It can be observed that the particle size of the dodecahedral ZIF-67 micro / nanoparticles embedded in the modified in-situ ZIF-67@BPA film prepared in Example 2 is significantly larger. It can be seen that in this comparative example, by reducing the mass ratio of epoxy resin to metal salt and the mass ratio of ZIF precursor to solvent, the mass ratio of metal salt to ZIF precursor can be increased, thereby accelerating the nucleation rate of ZIF-67 and forming larger particles.

[0114] Example 3 The preparation method of the MOFs-modified urea-formaldehyde resin membrane material in Example 3 mainly involves replacing the epoxy resin with urea-formaldehyde resin. Specifically, it includes: Weigh 2 g of 2-methylimidazole and dissolve it in 10 g of ethanol to form solution I. Measure 12.5 mL of urea-formaldehyde resin and 1.25 g of cobalt nitrate hexahydrate and dissolve them in (10 g) 12.5 mL of ethanol. Heat the solution to 60 °C and stir continuously at 250 rpm to form solution J. Mix solution I and solution J and stir continuously at 250 rpm for 5 min to form a casting solution for the ZIF-67 / urea-formaldehyde resin self-crosslinking membrane. Then, spread the casting solution evenly on an inorganic glass plate and heat the inorganic glass plate to 80 °C until all the ethanol evaporates to dryness to obtain the ZIF-67 / urea-formaldehyde resin self-crosslinking membrane, denoted as the in-situ ZIF-67@UF membrane.

[0115] Example 3 is set up mainly to illustrate the applicability of the membrane material preparation method of Example 1 to the curing of other resins and the universality of ZIF-67 in improving the flame retardancy of other resins (which can be demonstrated in the subsequent application examples).

[0116] Comparative Example 3 The preparation method of the urea-formaldehyde resin membrane material in Comparative Example 3 is mainly compared with that in Example 3, to prepare a urea-formaldehyde resin membrane without ZIF-67 doping. Specifically, it includes: Weigh 2 g of 2-methylimidazole and dissolve it in 10 g of ethanol to form solution K. Measure 12.5 mL of urea-formaldehyde resin and 1.25 g of urea-formaldehyde resin and dissolve them in (10 g) 12.5 mL of ethanol. Heat the solution to 60°C and stir continuously at 250 rpm to form a homogeneous solution L. Mix solution K and solution L and stir continuously at 250 rpm for 5 min to form a casting solution for the urea-formaldehyde resin self-crosslinking membrane. Then, spread the casting solution of the membrane evenly on an inorganic glass plate and heat the inorganic glass plate to 80°C until all the ethanol evaporates to obtain the urea-formaldehyde resin self-crosslinking membrane, denoted as UF membrane.

[0117] The in-situ ZIF-67@UF membrane and UF membrane prepared in Example 3 and Comparative Example 3 are shown in the following figures. Figure 5 As shown. From Figure 5 As can be seen, compared with the colorless and transparent UF film, the in-situ ZIF-67@UF film shows the characteristic purple color of ZIF-67 and is transparent, and no agglomerates were observed, indicating that the preparation method provided by the present invention is also applicable to urea-formaldehyde resin.

[0118] Example 4 A method for preparing MOFs-modified epoxy resin film material includes: Weigh 2 g of 2-methylimidazole and dissolve it in 10 g of ethanol to form a ZIFs precursor solution, which is also a MOFs precursor solution. Measure 12.5 mL of epoxy resin and 1.25 g of zinc nitrate hydrate and dissolve them in (10 g) 12.5 mL of ethanol. Heat the solution to 60 °C and stir continuously at 250 rpm to form a homogeneous mixed solution.

[0119] The above mixed solution was mixed with the ZIFs precursor solution and stirred continuously at 250 rpm for 5 min to form a casting solution for the ZIF-8 / epoxy resin self-crosslinking membrane, which is the membrane casting solution. Then, the membrane casting solution was spread evenly on an inorganic glass plate and heated to 80°C until all the ethanol was evaporated to obtain the ZIF-8 / epoxy resin self-crosslinking membrane, which is denoted as the in-situ ZIF-8@BPA membrane.

[0120] Comparative Example 4 The preparation method of the MOF-modified epoxy resin film material in Comparative Example 4 is a traditional method for synthesizing doped MOFs, mainly involving incorporating synthesized ZIF-8 into epoxy resin to obtain a common ZIF-8 / epoxy resin hybrid matrix film. Specifically, it includes: Weigh 2 g of 2-methylimidazole and dissolve it in 10 g of ethanol to form solution C, the precursor of ZIFs. Weigh 1.25 g of zinc nitrate hydrate and dissolve it in (10 g) 12.5 mL of ethanol, denoted as solution D. Mix solutions C and D and stir continuously at 250 rpm for 5 min. Then centrifuge the mixture at 12000 rpm for 15 min, collect the precipitate and dry it to obtain ZIF-8. Then disperse all the ZIF-8 prepared in the above steps in 12.5 mL of epoxy resin, add 2 g of conventional epoxy resin curing agent T-31, heat to 60 ℃ and stir continuously at 250 rpm until the mixture is uniform in color. Finally, pour the mixture onto an inorganic glass plate and cool it to obtain a common ZIF-8 / epoxy resin mixed matrix membrane, denoted as ectopic ZIF-8 / BPA membrane.

[0121] Comparative Example 5 The preparation method of the epoxy resin film material in Comparative Example 5 mainly involves preparing a self-crosslinking epoxy resin film without ZIF-8 doping. Specifically, it includes: Weigh 2 g of 2-methylimidazole and dissolve it in 10 g of ethanol to form solution E. Measure 12.5 mL of epoxy resin and 1.25 g of epoxy resin and dissolve them in (10 g) 12.5 mL of ethanol. Heat the solution to 60 °C and stir continuously at 250 rpm to form a homogeneous solution F. Mix solution E and solution F and stir continuously at 250 rpm for 5 min to form a casting solution for the epoxy resin self-crosslinking membrane. Then, spread the casting solution of the membrane evenly on an inorganic glass plate and heat the inorganic glass plate to 80 °C until all the ethanol evaporates to dryness, obtaining the epoxy resin self-crosslinking membrane, denoted as BPA membrane.

[0122] By comparing Example 4 and Comparative Example 4, the differences between the in-situ doping preparation method of the present invention and the traditional method of synthesizing post-doped MOFs can be seen.

[0123] The in-situ ZIF-8@BPA membrane prepared in Example 4 of this invention and the ex-situ ZIF-8 / BPA membrane prepared in Comparative Example 4 are shown in the following figures. Figure 6 As shown. From Figure 6 It can be seen that no obvious particle agglomeration occurs in the in-situ ZIF-8@BPA film. Compared with the colorless and transparent BPA film, the in-situ ZIF-8@BPA film is transparent, exhibiting the characteristic white color of ZIF-8. However, obvious white fine particles, which are agglomerates of ZIF-8 particles, can be observed in the ex-situ ZIF-8 / BPA film. This indicates that the traditional blending and stirring method is insufficient to achieve a uniform distribution of the synthesized ZIF-8 particles in the epoxy resin system, and also fails to solve the problem of agglomeration of the synthesized ZIF-8 particles in the epoxy resin. Comparative Example 5 is set up mainly to compare the effects of the in-situ ZIF-8 doping preparation method of the present invention and the lack of ZIF-8 doping on the flame retardancy of epoxy resin materials (which can be demonstrated in subsequent application examples).

[0124] The composition of the in-situ ZIF-8@BPA film prepared in Example 4 of this invention was characterized using X-ray diffraction (XRD), and the microstructure of the in-situ ZIF-8@BPA prepared in Example 4 was observed using scanning electron microscopy (SEM).

[0125] The X-ray diffraction analysis results of Example 4 are as follows: Figure 7 As shown, the diffraction peak patterns of the in-situ ZIF-8@BPA film correspond well with those of pure ZIF-8, indicating that ZIF-8 was successfully encapsulated within the epoxy resin. In contrast, no diffraction peaks of ZIF-8 were observed in the pure BPA film. The scanning electron microscope image of Example 4 is shown below. Figure 8As shown, a large number of dodecahedral ZIF-8 micro / nanoparticles were embedded in the prepared in-situ ZIF-8@BPA film, consistent with the morphology of ZIF-8 particles in relevant literature, further confirming the presence of ZIF-8 in the in-situ ZIF-8@BPA film. In contrast, no micro / nanoparticles were observed in the pure BPA film.

[0126] Example 5 The preparation method of the epoxy resin film material in Example 5 mainly involves changing the mass ratio of epoxy resin to metal salt and the mass ratio of precursor to solvent in the MOF precursor solution. Specifically, it includes: Weigh 1 g of 2-methylimidazole and dissolve it in 10 g of ethanol to form solution G. Measure 12.5 mL of epoxy resin and 2.5 g of zinc nitrate hexahydrate and dissolve them in (10 g) 12.5 mL of ethanol. Heat the solution to 60 °C and stir continuously at 250 rpm to form a homogeneous solution H. Mix solution G and solution H and stir continuously at 250 rpm for 5 min to form a casting solution for the modified ZIF-8 / epoxy resin self-crosslinking membrane. Then, spread the casting solution evenly on an inorganic glass plate and heat the inorganic glass plate to 80 °C until all the ethanol evaporates to dryness to obtain the modified ZIF-8 / epoxy resin self-crosslinking membrane, denoted as the modified in-situ ZIF-8@BPA membrane.

[0127] Example 5 is set up mainly to illustrate the effect of changing the proportion of reagent components on the morphology and size of MOF in epoxy resin materials and on the flame retardancy of epoxy resin materials (which can be shown in the subsequent application examples).

[0128] The scanning electron microscope image of Example 5 is shown in Figure 9. It can be observed that the particle size of the dodecahedral ZIF-8 micro / nanoparticles embedded in the prepared modified in-situ ZIF-8@BPA film is significantly larger. It can be seen that in this comparative example, by reducing the mass ratio of epoxy resin to metal salt and the mass ratio of ZIF precursor to solvent, the mass ratio of metal salt to ZIF precursor can be increased, thereby accelerating the nucleation rate of ZIF-8 and forming larger particles.

[0129] Example 6 The preparation method of the MOFs-modified membrane material in Example 6 mainly involves replacing the epoxy resin with urea-formaldehyde resin. Specifically, it includes: Weigh 2 g of 2-methylimidazole and dissolve it in 10 g of ethanol to form solution I. Measure 12.5 mL of urea-formaldehyde resin and 1.25 g of zinc nitrate hexahydrate and dissolve them in (10 g) 12.5 mL of ethanol. Heat the solution to 60 °C and stir continuously at 250 rpm to form solution J. Mix solution I and solution J and stir continuously at 250 rpm for 5 min to form a casting solution for the ZIF-8 / urea-formaldehyde resin self-crosslinking membrane. Then, spread the casting solution evenly on an inorganic glass plate and heat the inorganic glass plate to 80 °C until all the ethanol evaporates to obtain the ZIF-8 / urea-formaldehyde resin self-crosslinking membrane, denoted as the in-situ ZIF-8@UF membrane.

[0130] Example 6 is set up mainly to illustrate the applicability of the membrane material preparation method of Example 4 to the curing of other resins and the universality of ZIF-8 in improving the flame retardancy of other resins (which can be demonstrated in the subsequent application examples).

[0131] Comparative Example 6 The preparation method of the urea-formaldehyde resin membrane material in Comparative Example 6 mainly involves preparing a urea-formaldehyde resin membrane without ZIF-8 doping. Specifically, it includes: Weigh 2 g of 2-methylimidazole and dissolve it in 10 g of ethanol to form solution K. Measure 12.5 mL of urea-formaldehyde resin and 1.25 g of urea-formaldehyde resin and dissolve them in (10 g) 12.5 mL of ethanol. Heat the solution to 60°C and stir continuously at 250 rpm to form a homogeneous solution L. Mix solution K and solution L and stir continuously at 250 rpm for 5 min to form a casting solution for the urea-formaldehyde resin self-crosslinking membrane. Then, spread the casting solution of the membrane evenly on an inorganic glass plate and heat the inorganic glass plate to 80°C until all the ethanol evaporates to obtain the urea-formaldehyde resin self-crosslinking membrane, denoted as UF membrane.

[0132] The in-situ ZIF-8@UF membrane and UF membrane prepared in Example 6 and Comparative Example 6 are shown in the following figures. Figure 10 As shown. From Figure 10 As can be seen, compared with the colorless and transparent UF film, the in-situ ZIF-8@UF film shows the characteristic white and transparent color of ZIF-8, and no agglomerates were observed, indicating that the preparation method provided by the present invention is also applicable to urea-formaldehyde resin.

[0133] Application Example 1: Flame retardant performance test of ZIF-67 / resin self-crosslinking film To explore the application potential of ZIF-67 / epoxy resin self-crosslinking film in the preparation of flame retardant products, the thermal stability of the ZIF-67 / epoxy resin and ZIF-67 / urea-formaldehyde resin was tested using a thermogravimetric analyzer.

[0134] Figure 11The thermogravimetric curves of the in-situ ZIF-67@BPA film prepared in Example 1, the ex-situ ZIF-67 / BPA film prepared in Comparative Example 1, the BPA film prepared in Comparative Example 2, and the modified in-situ ZIF-67 / BPA film prepared in Example 2 are compared in air atmosphere. It can be seen that when undoped with ZIF-67, the pure BPA film is almost completely thermally decomposed at 300 °C; when in-situ doped with ZIF-67, the resulting in-situ ZIF-67@BPA film is not completely decomposed in the range of 300 °C to 400 °C, and after 400 °C, the in-situ ZIF-67@BPA film still has solid residue, indicating the formation of carbonaceous materials. Compared to the in-situ ZIF-67@BPA membrane, the weight loss temperature of the ex-situ ZIF-67 / BPA membrane occurs earlier, indicating that uneven distribution and aggregation of ZIF-67 in the ex-situ ZIF-67 / BPA membrane result in some areas of epoxy resin not being protected by ZIF-67. Compared to the in-situ ZIF-67@BPA membrane, the modified in-situ ZIF-67@BPA membrane exhibits a slightly delayed thermal weight loss temperature, but a relatively higher final residual mass. This suggests that reducing the mass ratio of epoxy resin to metal salt promotes the formation of more ZIF-67 particles, thereby improving the thermal stability of the original in-situ ZIF-67@BPA membrane. However, due to the relatively large proportion of ZIF-67 in the membrane, the residual mass after complete thermal decomposition of ZIF-67 is also relatively low. Meanwhile, as... Figure 13 As shown, the in-situ ZIF-67@UF film doped with ZIF-67 also exhibits a hysteresis in heat loss with increasing temperature compared to the pure UF film, indicating that the method provided by this invention can also improve the thermal stability of urea-formaldehyde resin films. Carbonaceous materials generally begin to burn above 800℃, while the ignition point of a pure BPA film is 500℃~550℃. Therefore, residual carbonaceous materials adhering to the BPA film surface can significantly increase the ignition point of the original BPA film. Furthermore, the carbonaceous material can act as a barrier, reducing the oxygen concentration around the microenvironment of the BPA film surface, thereby inhibiting the combustion of the BPA film.

[0135] To further verify the above inferences, the thermal stability and minimum oxygen concentration required for combustion of the in-situ ZIF-67@BPA membrane, BPA membrane, ex-situ ZIF-67 / BPA membrane, and modified in-situ ZIF-67@BPA membrane were determined using a limiting oxygen index analyzer. Figure 12This paper compares the limiting oxygen index (LOI) during combustion of the in-situ ZIF-67@BPA film, BPA film, ex-situ ZIF-67 / BPA film, and modified in-situ ZIF-67@BPA film in this invention. When doped with ZIF-67, the LIOI of the resulting in-situ ZIF-67@BPA film, ex-situ ZIF-67 / BPA film, and modified in-situ ZIF-67@BPA film are 35%, 31%, and 36%, respectively, while the LIOI of the pure BPA film is only 13%. Similarly, as... Figure 14 As shown, after ZIF-67 doping, the limiting oxygen index of the in-situ ZIF-67@UF film is 36%, while the limiting oxygen index of the pure UF film is only 30%. This indicates that the limiting oxygen index of the BPA or UF film doped with ZIF-67 is significantly improved compared to the pure BPA or UF film. This further demonstrates that the carbonaceous microdomains formed by the introduction of ZIF-67 at high temperatures can control the oxygen content in the microenvironment at the BPA or UF interface, thereby preventing material combustion.

[0136] Application Example 2: Flame retardant performance test of ZIF-8 / resin self-crosslinking film To explore the application potential of ZIF-8 / epoxy resin self-crosslinking film in the preparation of flame retardant products, the thermal stability of the ZIF-8 / epoxy resin and ZIF-8 / urea-formaldehyde resin was tested using a thermogravimetric analyzer.

[0137] Figure 15 This paper compares the thermogravimetric curves of the in-situ ZIF-8@BPA film prepared in Example 4, the ex-situ ZIF-8 / BPA film prepared in Comparative Example 4, the BPA film prepared in Comparative Example 5, and the modified in-situ ZIF-8 / BPA film prepared in Example 5 under air atmosphere. When undoped with ZIF-8, the pure BPA film almost completely decomposes at 300°C. However, after in-situ doping with ZIF-8, the resulting in-situ ZIF-8@BPA film is not completely decomposed within the 300°C to 350°C range, and solid residue remains after 350°C, indicating the formation of carbonaceous materials. Compared to the in-situ ZIF-8@BPA film, the ex-situ ZIF-8 / BPA film loses weight earlier, indicating that the uneven distribution and agglomeration of ZIF-8 in the ex-situ ZIF-8 / BPA film prevents some areas of the epoxy resin from being protected by ZIF-8. Compared to the in-situ ZIF-8@BPA membrane, the modified in-situ ZIF-8@BPA membrane exhibits a slightly delayed thermal decomposition temperature, but a relatively higher final residual mass. This indicates that reducing the mass ratio of epoxy resin to metal salt is beneficial for generating more ZIF-8 particles, thereby improving the thermal stability of the original in-situ ZIF-8@BPA membrane. However, due to the relatively large proportion of ZIF-8 in the membrane, the residual mass after complete thermal decomposition of ZIF-8 is also relatively low. Meanwhile, as... Figure 17 As shown, the in-situ ZIF-8@UF film doped with ZIF-8 also exhibits a hysteresis in heat loss with increasing temperature compared to the pure UF film, indicating that the method provided by this invention can also improve the thermal stability of urea-formaldehyde resin films. Carbonaceous materials generally begin to burn above 800℃, while the ignition point of a pure BPA film is 500℃~550℃. Therefore, residual carbonaceous materials adhering to the BPA film surface can significantly increase the ignition point of the original BPA film. Furthermore, the carbonaceous material can act as a barrier, reducing the oxygen concentration around the microenvironment of the BPA film surface, thereby inhibiting the combustion of the BPA film.

[0138] To further verify the above inferences, the thermal stability and minimum oxygen concentration required for combustion of the in-situ ZIF-8@BPA membrane, BPA membrane, ex-situ ZIF-8 / BPA membrane, and modified in-situ ZIF-8@BPA membrane were determined using a limiting oxygen index analyzer. Figure 16 This paper compares the limiting oxygen index (LOI) during combustion of the in-situ ZIF-8@BPA film, BPA film, ex-situ ZIF-8 / BPA film, and modified in-situ ZIF-8@BPA film in this invention. When doped with ZIF-8, the LIOI of the resulting in-situ ZIF-8@BPA film, ex-situ ZIF-8 / BPA film, and modified in-situ ZIF-8@BPA film are 37%, 35%, and 38%, respectively, while the LIOI of the pure BPA film is only 13%. Similarly, as... Figure 18 As shown, the limiting oxygen index (LOI) of the in-situ ZIF-8@UF film after ZIF-8 doping is 34%, while that of the pure UF film is only 30%. This indicates that the LIO of the BPA or UF film doped with ZIF-8 is significantly improved compared to the pure BPA or UF film. This further demonstrates that the carbonaceous microdomains formed by the introduction of ZIF-8 at high temperatures can control the oxygen content in the microenvironment at the BPA or UF film interface, thereby preventing material combustion.

[0139] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A method for preparing a MOFs-modified resin membrane material, characterized in that, The method includes: A resin, a metal salt, and a volatile organic solvent are mixed to obtain a mixed solution; wherein the resin includes epoxy resin and / or urea-formaldehyde resin. The mixed solution was mixed with the MOF precursor solution to obtain the film casting solution; The membrane casting solution is heated to evaporate the volatile organic solvent, thereby obtaining a MOF-modified epoxy resin membrane material.

2. The method for preparing MOFs-modified resin film material according to claim 1, characterized in that, The MOFs include ZIF series MOF materials; And / or, the MOF precursor solution includes organic ligands for the synthesis of zeolite imidazole metal-organic frameworks.

3. The method for preparing MOFs-modified resin film material according to claim 2, characterized in that, The MOFs include at least one of ZIF-8, ZIF-67, ZIF-7, ZIF-90, ZIF-9 and ZIF-L; And / or, the organic ligand comprises an imidazole compound; preferably, the imidazole compound comprises at least one of 2-methylimidazolium, imidazole, benzimidazole, or 2-imidazolium formaldehyde.

4. The method for preparing MOFs-modified resin film material according to any one of claims 1 to 3, characterized in that, The step of obtaining the mixed solution satisfies at least one of the following characteristics: (1) The metal ions in the metal salt include zinc ions and / or cobalt ions; and / or, the anions in the metal salt include inorganic anions or organic anions; (2) The volatile organic solvent includes at least one of aromatic hydrocarbons, aliphatic hydrocarbons, halogenated hydrocarbons, alcohols, esters, ethers or ketones; (3) In the mixed solution, the mass ratio of resin to metal salt is 20:1 to 1:1; (4) In the step of obtaining the mixed solution, the mixing method includes mixing under heating and stirring conditions, wherein the heating temperature is 30℃~60℃ and the stirring rate is 30rpm~300rpm.

5. The method for preparing MOFs-modified resin film material according to claim 4, characterized in that, The step of obtaining the mixed solution satisfies at least one of the following characteristics: (1) The metal salt includes at least one of zinc nitrate, zinc chloride, zinc acetate, zinc sulfate, zinc acetylacetonate, cobalt nitrate, cobalt chloride, cobalt acetate, cobalt sulfate, and cobalt acetylacetonate; (2) The volatile organic solvent includes at least one of benzene, toluene, xylene, styrene, n-hexane, pentane, vinyltoluene, 1,3-butadiene, methanol, ethanol, 2-propanol, butanol, ethylene glycol, acetone, methyl ethyl ketone, chloroform, carbon tetrachloride, dichloromethane, trichloroethylene, vinyl chloride, diethyl ether, tetrahydrofuran, ethyl acetate, butyl acetate, or n-butyl acrylate; preferably, the volatile organic solvent includes one or both of methanol and ethanol; (3) The mass ratio of the resin to the metal salt is 10:1 to 5:1; (4) The heating temperature is 50℃~60℃ and the stirring speed is 180rpm~250rpm.

6. The method for preparing MOFs-modified resin film material according to any one of claims 1 to 3, characterized in that, The step of obtaining the membrane casting solution satisfies at least one of the following characteristics: (1) The MOF precursor solution comprises an organic ligand and a solvent, wherein the solvent comprises at least one of an alcohol, a haloalkane or a ketone; and / or the mass ratio of the organic ligand to the solvent is 1:20 to 1:1; (2) The volume ratio of the MOF precursor solution to the resin is 1:5 to 5:1; (3) In the step of obtaining the membrane casting liquid, the mixing method includes mixing under stirring conditions, wherein the stirring rate is 30 rpm to 500 rpm and the stirring time is 2 min to 30 min.

7. The method for preparing MOFs-modified resin film material according to claim 6, characterized in that, The step of obtaining the membrane casting solution satisfies at least one of the following characteristics: (1) The solvent includes at least one of methanol, ethanol, acetone or chloroform; preferably, the solvent includes one or two of methanol or ethanol; (2) The mass ratio of the organic ligand to the solvent is 1:5 to 1:10; (3) The volume ratio of the MOF precursor solution to the resin is 1:2 to 2:1; (4) The stirring rate is 200 rpm to 300 rpm and the stirring time is 4 min to 10 min.

8. The method for preparing MOFs-modified resin film material according to any one of claims 1 to 3, characterized in that, The heating temperature for heating the membrane casting liquid is 60℃~100℃; preferably, the heating temperature is 60℃~80℃. And / or, during the heating of the membrane casting solution, the organic ligands in the MOF precursor solution serve as precursors for synthesizing MOFs, and simultaneously act as curing agents and crosslinking agents for the resin, reacting with the resin to generate a three-dimensional crosslinked network structure, thereby obtaining a self-crosslinked membrane material.

9. A MOF-modified resin film material, characterized in that, The MOFs-modified resin film material was prepared using the preparation method described in any one of claims 1 to 8.

10. The application of the MOFs-modified resin film material as described in claim 9 in flame retardancy.

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