A microcapsule-based flame-retardant fire extinguishing membrane and its preparation method

Abstract

This invention relates to the field of fire extinguishing materials technology, and provides a microcapsule-based flame-retardant fire extinguishing membrane and its preparation method. The flame-retardant fire extinguishing membrane comprises the following raw materials in parts by weight: 30-50 parts polyurethane acrylate, 15-30 parts acrylic monomer, 15-30 parts linear boron-containing monomer, 5-20 parts fire extinguishing microcapsules, 4-12 parts polyionic liquid, 4-12 parts alkenyl borate ester, 2-8 parts crosslinking agent, and 1-7 parts photoinitiator. This invention first prepares a viscous resin through crosslinking polymerization. The compatibility between the fire extinguishing microcapsules and the viscous resin is improved by high-speed shearing or ultrasonic dispersion, allowing the fire extinguishing microcapsules to be uniformly dispersed within the viscous resin. Finally, the fire extinguishing membrane is prepared by ultraviolet light curing. The product obtained by this invention has excellent flame-retardant fire extinguishing performance and mechanical strength.

Description

Technical Field

[0001] This invention relates to the field of fire extinguishing materials technology, and in particular to a flame-retardant fire extinguishing membrane based on microcapsules and its preparation method. Background Technology

[0002] In 3C electronic products and new energy vehicle power batteries, adhesive films are commonly used to bond and fix electronic components, circuits and circuit boards, electromagnetic shielding materials, and thermally conductive materials. This method offers advantages such as ease of use, simple structure, and lightweight design. However, electronic devices easily generate a large amount of heat during operation. Accumulated heat can lead to thermal runaway, posing a safety risk.

[0003] Fire extinguishing microcapsules are a new type of material that has emerged in recent years. Fire extinguishing microcapsules consist of two parts: a wall material and a core material. The core material is usually a fire extinguishing agent, while the wall material tightly encapsulates the core material. In specific scenarios, if the temperature is high, the wall material softens or melts, and the fire extinguishing agent core material vaporizes and is released. By utilizing principles such as isolating oxygen and reducing temperature, fires are extinguished in their early stages.

[0004] Dispersing fire extinguishing microcapsules within an adhesive membrane to prepare a fire extinguishing film not only forms a protective film on the surface of the microcapsules but also facilitates their application in various fire prevention and extinguishing scenarios. However, in existing fire extinguishing films, the compatibility between the fire extinguishing microcapsules and the adhesive membrane, as well as the flame-retardant fire extinguishing performance and mechanical strength of the fire extinguishing film, still need improvement. Summary of the Invention

[0005] This invention aims to solve at least one of the above-mentioned technical problems by providing a microcapsule-based flame-retardant fire extinguishing membrane and its preparation method. The technical solution adopted is as follows: One objective of this invention is to provide a microcapsule-based flame-retardant fire extinguishing membrane, comprising the following raw materials in parts by weight: The composition comprises: 30-50 parts polyurethane acrylate, 15-30 parts acrylic monomer, 15-30 parts linear boron-containing monomer, 5-20 parts fire extinguishing microcapsules, 4-12 parts polyionic liquid, 4-12 parts alkenyl borate ester, 2-8 parts crosslinking agent, and 1-7 parts photoinitiator; the fire extinguishing microcapsules use a fire-extinguishing substance as the core material and a flame-retardant polymer as the wall material; the monomer of the polyionic liquid is 1-vinyl-3-benzylimidazolium chloride, and the chemical structural formula of the linear boron-containing monomer is as follows: n is an integer from 5 to 15.

[0006] This invention utilizes fire-extinguishing microcapsules, which encapsulate the fire extinguishing agent in a nano-microstructure. Precise controlled release of the fire-extinguishing substance is achieved through thermal triggering or mechanical rupture, making it the main fire-extinguishing component in flame-retardant fire-extinguishing membranes. Linear boron-containing monomers, polyionic liquids, and alkenyl borate esters all contain flame-retardant elements (B and / or N). The cross-linked network formed after the cross-linking polymerization reaction is uniformly distributed, forming a dense structure. This allows boron and nitrogen to work synergistically, resulting in excellent flame retardancy. The linear boron-containing monomers, with acrylate structures at both ends and containing several alkoxy groups, can increase the chemical stability of the flame-retardant fire-extinguishing membrane, making it less prone to decomposition under high temperatures and flame conditions. It can also impart better adhesion, flexibility, extensibility, and weather resistance to the flame-retardant fire-extinguishing membrane, improving its overall fire resistance. Boronates are commonly used as coupling agents or surfactants to improve the reactivity between raw materials and their compatibility with the fire-extinguishing microcapsules. They also act as lubricants, improving the flowability and processing stability of raw materials during the preparation of fire-extinguishing membrane materials. Furthermore, the introduction of alkenyl groups into the borate ester allows the alkenyl groups to participate in the cross-linking copolymerization reaction, maximizing their effect. Acrylic monomers, polyurethane acrylates, and linear boron-containing monomers form the main structure of the fire extinguishing membrane. Copolymerization of these three components improves mechanical properties, enhancing mechanical strength and weather resistance. Polyionic liquids exhibit characteristics common to both polymers and ionic liquids, offering advantages as polymer flame retardants such as low migration rate, high flame-retardant element content, and good interaction with the matrix. Both polyurethane acrylates and the polyionic liquid (monomer: 1-vinyl-3-benzylimidazolium chloride) possess aromatic structures and exhibit strong π-π interactions, resulting in good compatibility. This minimizes the leakage of the polyionic liquid and significantly improves the stability of the cross-linked network, maintaining the long-term flame-retardant fire extinguishing effect of the fire extinguishing membrane.

[0007] Preferably, the acrylic monomer comprises at least one selected from methyl acrylate, ethyl acrylate, butyl acrylate, methyl 2-methacrylate, ethyl 2-methacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, tripropylene glycol diacrylate, and α-cyanoacrylate. The acrylic monomer is selected with an ester group structure to adjust the film-forming viscosity; α-cyanoacrylate enables rapid curing.

[0008] Preferably, the polyurethane acrylate includes at least one of aliphatic polyurethane acrylate, difunctional aliphatic polyurethane acrylate, and aromatic polyurethane acrylate.

[0009] Preferably, the alkenyl borate ester includes at least one of vinyl borate pinacol ester, 2-tert-butyl-e-vinyl borate pinacol ester, 2,2-dimethyl vinyl borate pinacol ester, diisopropyl propenyl borate, diisopropyl allyl borate ester, allyl borate pinacol ester, and isopropenyl borate pinacol ester.

[0010] Preferably, the fire-extinguishing substance includes perfluoroketones and / or perfluoroalkanes, which have the advantages of safety, environmental friendliness, and high fire-extinguishing efficiency. The flame-retardant polymer is a nitrogen-containing heterocyclic polyurea, which contains a large number of distributed nitrogen atoms in its molecular structure, exhibiting a natural synergistic flame-retardant effect. Therefore, while ensuring the mechanical properties of polyurea, it also imparts good flame-retardant properties to polyurea. The flame-retardant and fire-extinguishing dual-function microcapsule provided by this invention has a shell with good flame-retardant properties. It not only has a fire-extinguishing function, but the residual shell after the release of the microcapsule core material can also exert a flame-retardant effect, significantly improving the flame-retardant and fire-extinguishing capability of the microcapsule. The fire-extinguishing microcapsule utilized in this invention encapsulates the fire extinguishing agent with a nano-microstructure and achieves precise controlled release through thermally triggered rupture, making it suitable for fire protection in multiple fields such as electronic equipment and buildings.

[0011] Preferably, the particle size of the fire extinguishing microcapsules is 10-50 μm.

[0012] Preferably, the wall material of the fire extinguishing microcapsule contains nitrogen-containing heterocyclic polyurea with a thickness of 0.5-5 μm.

[0013] Preferably, the perfluoroketone is one or more of perfluoroacetone, perfluorobutanone, perfluoropentanone, perfluorohexanone, and perfluoroheptanone; and the perfluoroalkane is one or more of perfluoropentane, perfluorohexane, and perfluorooctane.

[0014] Preferably, the photoinitiator comprises at least one of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 2,4,6-trimethylbenzoyl-ethoxy-phenylphosphine oxide. The crosslinking agent includes at least one of pentaerythritol triacrylate, pentaerythritol tetraacrylate, and pentaerythritol tetra-3-mercaptopropionate.

[0015] Another objective of this invention is to provide a method for preparing a microcapsule-based flame-retardant fire extinguishing membrane, comprising the following steps: S1. Mix acrylic monomer, polyurethane acrylate, linear boron-containing monomer, polyionic liquid, alkenyl borate ester, photoinitiator and crosslinking agent according to the weight parts, and crosslink polymerization reaction at 50-80℃ for 2-4 hours to form a viscous resin. S2. Add fire extinguishing microcapsules to the obtained viscous resin, and disperse and mix evenly by high-speed shearing or ultrasonication while avoiding the rupture of the fire extinguishing microcapsules to obtain a mixture. S3. The mixture is coated onto the substrate and UV-cured under ultraviolet light to form a flame-retardant pressure-sensitive adhesive layer, thus obtaining a flame-retardant fire extinguishing film based on microcapsules.

[0016] This invention first prepares a viscous resin through cross-linking polymerization. Then, the compatibility between the fire extinguishing microcapsules and the viscous resin is improved by high-speed shearing or ultrasonic dispersion, allowing the fire extinguishing microcapsules to be uniformly dispersed within the resin. Finally, a fire extinguishing film is prepared by ultraviolet curing. This invention not only forms a protective film on the surface of the fire extinguishing microcapsules but also makes it easier to apply the fire extinguishing microcapsules to various fire prevention and extinguishing scenarios. The resulting product also possesses excellent flame-retardant fire extinguishing performance and mechanical strength.

[0017] Preferably, the preparation of the linear boron-containing monomer in step S1 includes: mixing trimethyl borate (TMB) and glyceryl methacrylate (GMMA) in a solvent and stirring the mixture under an inert atmosphere; then injecting polyethylene glycol (PEG) into the reaction solution, heating and stirring the mixture, removing the solvent under reduced pressure, and drying to obtain the linear boron-containing monomer.

[0018] Preferably, the molar ratio of trimethyl borate to glyceryl methacrylate is 1 / 0.1 to 1 / 1; The molar ratio of trimethyl borate to polyethylene glycol is 2 / 1 to 2 / 5; The reaction temperature is 10~80 °C, and the reaction time is 2~10 hours; The solvent includes at least one of tetrahydrofuran, dimethyl sulfoxide, N,N-dimethylformamide, and acetonitrile.

[0019] Preferably, the preparation of the polyionic liquid in step S1 includes: Weigh 20-50 parts by weight of ionic liquid monomer and 0.4-1 parts by weight of initiator and dissolve them in N,N-dimethylformamide. Under nitrogen protection, stir and react at 70-80℃ for 24 hours. After the reaction is completed, add the reaction mixture dropwise to 2-6 times the volume of tetrahydrofuran, filter, wash, and vacuum dry to obtain polyionic liquid.

[0020] Preferably, the initiator includes at least one of azobisisobutyronitrile, sodium persulfate, and potassium persulfate.

[0021] Preferably, the method for preparing the fire extinguishing microcapsules in step S1 includes: 1) Preparation of the oil phase: The core material is dissolved in an oily solvent to form an oil phase; 2) Preparation of nitrogen-containing heterocyclic polyurea prepolymer: Polyetheramine and 3,5-diamino-1,2,4-triazole were added to a reaction vessel and mixed evenly. Then isocyanate and solvent were added, and the mixture was reacted at 15-40℃ for 3-5 hours to obtain a nitrogen-containing heterocyclic polyurea prepolymer. 3) Preparation of a complex emulsion W / O / W system: The nitrogen-containing heterocyclic polyurea prepolymer is mixed evenly with the oil phase and slowly added dropwise to the aqueous phase containing 1.5-3.5 wt% emulsifier. The mixture is homogenized at 8000-12000 rpm for 1-4 min to form a W / O emulsion. The W / O emulsion is then injected into the aqueous phase containing 0.5-1.5 wt% polyvinyl alcohol and stirred at 800-1100 rpm to form a double-emulsified W / O / W system. 4) Interfacial polymerization reaction: Then, an aqueous solution of an amine crosslinking agent was added, and the mixture was reacted at 30-40°C for 1-3 hours to obtain fire extinguishing microcapsules with a nitrogen-containing heterocyclic polyurea shell. The microcapsules were collected by centrifugation and then freeze-dried.

[0022] This invention employs a combination of multi-emulsification and interfacial polymerization. The core material is encapsulated through a multi-phase emulsification process involving an aqueous phase, an oil phase, and another aqueous phase, followed by shell polymerization. The nitrogen-containing heterocyclic polyurea, serving as the shell, forms a cross-linked network structure through interfacial polymerization using highly reactive amino and isocyanate groups, imparting excellent flame retardancy and mechanical strength. The nitrogen atoms in the nitrogen-containing heterocycles further enhance the flame retardancy of the polyurea. Furthermore, during the synthesis of the nitrogen-containing heterocyclic polyurea, the emulsifier concentration, the homogenization rate of the W / O emulsion, and the multi-emulsification W / O / W system are controlled to adjust the emulsion droplet size, thereby influencing the interfacial polymerization of the prepolymer and ultimately regulating the thickness range of the shell and the size of the fire-extinguishing microcapsules. The fire-extinguishing microcapsules provided by this invention, using nitrogen-containing heterocyclic polyurea as the shell material, possess both fire-resistant and flame-retardant functions, making them suitable for a wide range of applications.

[0023] Preferably, in step 1): Oily solvents include at least one of dichloromethane and cyclohexane; The volume ratio of core material to oily solvent is 1:1-3.

[0024] Preferably, in step 2): The mass ratio of polyetheramine, 3,5-diamino-1,2,4-triazole, and isocyanate is 2.2-4:1.8-2.2:2-2.5.

[0025] Preferably, in step 3): The emulsifier includes at least one of Tween 20, Tween 40, Tween 60, and Tween 80.

[0026] Preferably, in step 4): Amine crosslinking agents include at least one of ethylenediamine, propylenediamine, hexamethylenediamine, tetramethylethylenediamine, and N,N-dimethylethylenediamine.

[0027] The mass ratio of amine crosslinking agent to isocyanate is 1:2-6.

[0028] Preferably, the core material in the fire extinguishing microcapsule accounts for 20-70 wt%.

[0029] Preferably, in step S2: The high-speed shearing speed is 10,000-15,000 rpm, and the time is 2-5 minutes; The ultrasonic dispersion power is 100-200 W, and the time is 5-15 min.

[0030] Preferably, in step S3, the coating thickness is 50-200 μm.

[0031] Preferably, in step S3, the wavelength of the ultraviolet light is 350-380nm and the energy density is 800-1200mJ / cm².

[0032] Preferably, step S3 is followed by heat curing at 80-100℃ for 1-2 hours.

[0033] Compared with the prior art, the present invention can achieve the following beneficial effects: This invention utilizes fire-extinguishing microcapsules, which encapsulate the fire extinguishing agent in a nano-microstructure. Precise controlled release of the fire-extinguishing substance is achieved through thermal triggering or mechanical rupture, making it the main fire-extinguishing component in flame-retardant fire-extinguishing membranes. Linear boron-containing monomers, polyionic liquids, and alkenyl borate esters all contain flame-retardant elements (B and / or N). The cross-linked network formed after the cross-linking polymerization reaction is uniformly distributed, forming a dense structure. This allows boron and nitrogen to work synergistically, resulting in excellent flame retardancy. The linear boron-containing monomers, with acrylate structures at both ends and containing several alkoxy groups, can increase the chemical stability of the flame-retardant fire-extinguishing membrane, making it less prone to decomposition under high temperatures and flame conditions. It can also impart better adhesion, flexibility, extensibility, and weather resistance to the flame-retardant fire-extinguishing membrane, improving its overall fire resistance. Boronates are commonly used as coupling agents or surfactants to improve the reactivity between raw materials and their compatibility with the fire-extinguishing microcapsules. They also act as lubricants, improving the flowability and processing stability of raw materials during the preparation of fire-extinguishing membrane materials. Furthermore, the introduction of alkenyl groups into the borate ester allows the alkenyl groups to participate in the cross-linking copolymerization reaction, maximizing their effect. Acrylic monomers, polyurethane acrylates, and linear boron-containing monomers form the main structure of the fire extinguishing membrane. Copolymerization of these three components improves mechanical properties, enhancing mechanical strength and weather resistance. Polyionic liquids exhibit characteristics common to both polymers and ionic liquids, offering advantages as polymer flame retardants such as low migration rate, high flame-retardant element content, and good interaction with the matrix. Both polyurethane acrylates and the polyionic liquid (monomer: 1-vinyl-3-benzylimidazolium chloride) possess aromatic structures and exhibit strong π-π interactions, resulting in good compatibility. This minimizes the leakage of the polyionic liquid and significantly improves the density and stability of the cross-linked network, maintaining the long-term flame-retardant extinguishing effect of the fire extinguishing membrane.

[0034] This invention first prepares a viscous resin through cross-linking polymerization. Then, the compatibility between the fire extinguishing microcapsules and the viscous resin is improved by high-speed shearing or ultrasonic dispersion, allowing the fire extinguishing microcapsules to be uniformly dispersed within the resin. Finally, a fire extinguishing film is prepared by ultraviolet curing. This invention not only forms a protective film on the surface of the fire extinguishing microcapsules but also makes it easier to apply the fire extinguishing microcapsules to various fire prevention and extinguishing scenarios. The resulting product also possesses excellent flame-retardant fire extinguishing performance and mechanical strength.

[0035] The fire-retardant and fire-extinguishing dual-function microcapsules provided by this invention have excellent flame-retardant properties in their outer shell. They not only have fire-extinguishing capabilities, but the residual shell after the release of the microcapsule core material also exerts a flame-retardant effect, significantly improving the fire-retardant and fire-extinguishing ability of the microcapsules. The fire-extinguishing microcapsules utilized in this invention encapsulate the fire extinguishing agent with a nano-microstructure, achieving precise controlled release through thermally triggered rupture, and possessing both fire-resistant and flame-retardant functions. This invention employs a combination of multi-emulsification and interfacial polymerization. The core material is encapsulated through a multi-phase emulsification process involving an aqueous phase, an oil phase, and an aqueous phase, followed by shell polymerization. The nitrogen-containing heterocyclic polyurea serving as the outer shell forms a cross-linked network structure through interfacial polymerization of highly reactive amino and isocyanate groups, endowing the shell with excellent flame retardancy and mechanical strength. The nitrogen atoms in the nitrogen-containing heterocycle further enhance the flame retardancy of the polyurea. Furthermore, during the synthesis of the nitrogen-containing heterocyclic polyurea, the emulsifier concentration, the homogenization rate of the W / O emulsion and the multi-emulsification W / O / W system are controlled to adjust the emulsion droplet size, thereby influencing the interfacial polymerization of the prepolymer and ultimately controlling the thickness range of the shell and the size of the fire-extinguishing microcapsules. The introduction of nitrogen-containing heterocycles can adjust the crosslinking density of polyurea, thereby regulating the thermal stability of polyurea. Combined with the control of the shell thickness and size of the fire extinguishing microcapsule (size control of the surface area / volume ratio of the fire extinguishing microcapsule), the thermal response temperature of the final fire extinguishing microcapsule is between 80-150℃, which is suitable for fire protection in electronic equipment, buildings and other fields, with a wide range of applications. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] The instruments, equipment, and reagents used in the preferred embodiments of this invention are all commercially available.

[0038] In the following examples, the linear boron-containing monomer was prepared as follows: 4.16 g of trimethyl borate (TMB) and 5.76 g of glyceryl methacrylate (GMMA) were mixed in 80 mL of anhydrous acetonitrile, and dry argon gas was introduced while the solution was stirred at 70 °C for 7 h. Then, 40 g of polyethylene glycol (PEG) (molecular weight MW = 2000) was injected into the solution, and the reaction was carried out at 70 °C for 9 h. The linear boron-containing monomer was obtained after vacuum distillation and drying.

[0039] Preparation of polyionic liquids: The monomer is 1-vinyl-3-benzylimidazolium chloride. 35 parts by weight of the ionic liquid monomer and 0.7 parts by weight of azobisisobutyronitrile were weighed and dissolved in N,N-dimethylformamide. The mixture was stirred at 75°C for 24 h under nitrogen protection. After the reaction was completed, the reaction mixture was added dropwise to 4 times its volume of tetrahydrofuran. The mixture was filtered, washed with tetrahydrofuran, and dried under vacuum at 70°C to obtain the polyionic liquid. Example 1

[0040] A microcapsule-based flame-retardant fire extinguishing membrane comprises the following raw materials in parts by weight: The composition includes 30 parts of aliphatic polyurethane acrylate EBECRYL® 8402, 15 parts of methyl acrylate, 15 parts of ethyl acrylate, 15 parts of linear boron-containing monomer, 5 parts of fire extinguishing microcapsules, 4 parts of polyionic liquid, 5 parts of vinyl borate pinacol ester, 2 parts of pentaerythritol triacrylate, and 1 part of diphenyl-(2,4,6-trimethylbenzoyl)phosphorus oxychloride; wherein, the fire extinguishing microcapsules use perfluoroacetone as the core material and flame-retardant polymer nitrogen-containing heterocyclic polyurea as the wall material; the particle size of the fire extinguishing microcapsules is 20-40μm, and the wall material thickness is 1.5-4.5μm.

[0041] The preparation method of the microcapsule-based flame-retardant fire extinguishing membrane includes the following steps: S1. Preparation of fire extinguishing microcapsules: 1) Preparation of the oil phase: Dissolve perfluoroacetone in dichloromethane (volume ratio 1:1, temperature 5℃) to form an oil phase; 2) Preparation of nitrogen-containing heterocyclic polyurea prepolymer: Polyetheramine D2000 and 3,5-diamino-1,2,4-triazole were added to a reaction vessel and mixed evenly. Then isocyanate and solvent were added, and the mixture was reacted at 20°C for 4 hours to obtain the nitrogen-containing heterocyclic polyurea prepolymer. The mass ratio of polyetheramine, 3,5-diamino-1,2,4-triazole and isocyanate was 2.5:2:2.2. 3) Preparation of the multiemulsion W / O / W system: The prepolymer of nitrogen-containing heterocyclic polyurea is mixed evenly with the oil phase and slowly added dropwise to the aqueous phase containing 2wt% emulsifier Tween 20. The mixture is homogenized at a high speed of 10,000 rpm for 2 min to form a W / O emulsion. The W / O emulsion is then injected into the aqueous phase containing 1wt% polyvinyl alcohol and stirred at a speed of 1000 rpm to form the multiemulsion W / O / W system. 4) Interfacial polymerization reaction: Then, 1 wt% ethylenediamine aqueous solution was added, and the reaction was carried out at 30°C for 2 hours to obtain fire extinguishing microcapsules with nitrogen-containing heterocyclic polyurea as the outer shell. The microcapsules were collected by centrifugation and freeze-dried. The core material accounted for 35 wt% of the fire extinguishing microcapsules. S2. Mix acrylic monomer, polyurethane acrylate, alkenyl borate ester, polyionic liquid, linear boron-containing monomer, photoinitiator and crosslinking agent according to the weight parts, and crosslink polymerization reaction at 50°C for 3.5h to form viscous resin; S3. Add fire extinguishing microcapsules to the obtained viscous resin, and mix the fire extinguishing microcapsules evenly and avoid their rupture by high-speed shearing to obtain a mixture; the high-speed shearing speed is 11000 rpm and the time is 4 min. S4. The mixture is coated onto the substrate with a thickness of 100μm and UV-cured under ultraviolet light with a wavelength of 365nm and an energy density of 900mJ / cm². After forming a flame-retardant pressure-sensitive adhesive layer, a flame-retardant fire extinguishing film based on microcapsules is obtained. Example 2

[0042] A microcapsule-based flame-retardant fire extinguishing membrane comprises the following raw materials in parts by weight: The composition comprises: 50 parts of aromatic polyurethane acrylate CN9001, 15 parts of ethyl acrylate, 15 parts of α-cyanoacrylate, 30 parts of linear boron-containing monomer, 20 parts of fire extinguishing microcapsules, 12 parts of polyionic liquid, 12 parts of pinacol 2-tert-butyl-e-vinylborate, 7 parts of pentaerythritol tetraacrylate, and 6 parts of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide; wherein the fire extinguishing microcapsules use perfluorooctane as the core material and flame-retardant polymer nitrogen-containing heterocyclic polyurea as the wall material; the particle size of the fire extinguishing microcapsules is 20-50 μm, and the wall material thickness is 1-3 μm.

[0043] The preparation method of the microcapsule-based flame-retardant fire extinguishing membrane includes the following steps: S1. Preparation of fire extinguishing microcapsules: 1) Preparation of the oil phase: Dissolve perfluorooctane in dichloromethane (volume ratio 1:1.5, temperature 30℃) to form the oil phase; 2) Preparation of nitrogen-containing heterocyclic polyurea prepolymer: Polyetheramine D2000 and 3,5-diamino-1,2,4-triazole were added to a reaction vessel and mixed evenly. Then isocyanate and solvent were added, and the mixture was reacted at 25°C for 4 hours to obtain the nitrogen-containing heterocyclic polyurea prepolymer. The mass ratio of polyetheramine, 3,5-diamino-1,2,4-triazole and isocyanate was 3:2:2.2. 3) Preparation of the multiemulsion W / O / W system: The prepolymer of nitrogen-containing heterocyclic polyurea is mixed evenly with the oil phase and slowly added dropwise to the aqueous phase containing 2.5 wt% emulsifier Tween 20. The mixture is homogenized at a high speed of 10,000 rpm to form a W / O emulsion. The W / O emulsion is then injected into the aqueous phase containing 1 wt% polyvinyl alcohol and stirred at a speed of 900 rpm to form the multiemulsion W / O / W system. 4) Interfacial polymerization reaction: Then, 1.5 wt% ethylenediamine aqueous solution was added, and cross-linking polymerization was carried out at 35°C for 2 h to obtain fire extinguishing microcapsules with nitrogen-containing heterocyclic polyurea as the shell. The microcapsules were collected by centrifugation, freeze-dried, and the core material accounted for 40 wt% of the fire extinguishing microcapsules. S2. Mix acrylic monomer, polyurethane acrylate, alkenyl borate ester, polyionic liquid, linear boron-containing monomer, photoinitiator and crosslinking agent according to the weight parts, and crosslink polymerization reaction at 80°C for 2 hours to form a viscous resin. S3. Add fire extinguishing microcapsules to the obtained viscous resin, and use ultrasonic dispersion to mix the fire extinguishing microcapsules evenly and avoid their rupture to obtain a mixture; the ultrasonic dispersion power is 150 W and the time is 10 min. S4. The mixture is coated onto the substrate with a thickness of 150μm and UV-cured under ultraviolet light with a wavelength of 365nm and an energy density of 1200mJ / cm². After forming a flame-retardant pressure-sensitive adhesive layer, a flame-retardant fire extinguishing film based on microcapsules is obtained. Example 3

[0044] A microcapsule-based flame-retardant fire extinguishing membrane comprises the following raw materials in parts by weight: The composition comprises: 40 parts of difunctional aliphatic polyurethane acrylate EasepiU600, 11 parts of methyl 2-methacrylate, 12 parts of ethyl 2-methacrylate, 20 parts of linear boron-containing monomer, 12 parts of fire extinguishing microcapsules, 8 parts of polyionic liquid, 8 parts of diisopropyl propylene borate, 5 parts of pentaerythritol tetra-3-mercaptopropionate, and 3.5 parts of 2,4,6-trimethylbenzoyl-ethoxy-phenylphosphine oxide; wherein the fire extinguishing microcapsules use perfluorohexanone as the core material and flame-retardant polymer nitrogen-containing heterocyclic polyurea as the wall material; the particle size of the fire extinguishing microcapsules is 25-35 μm, and the wall material thickness is 1-3 μm.

[0045] The preparation method of the microcapsule-based flame-retardant fire extinguishing membrane includes the following steps: S1. Preparation of fire extinguishing microcapsules: Same as in Example 2, except that the core material is replaced with perfluorohexanone, and the core material accounts for 50 wt% of the fire extinguishing microcapsules; S2. Mix acrylic monomer, polyurethane acrylate, alkenyl borate ester, polyionic liquid, linear boron-containing monomer, photoinitiator and crosslinking agent according to the weight parts, and crosslink polymerization reaction at 65°C for 3 hours to form a viscous resin. S3. Add fire extinguishing microcapsules to the obtained viscous resin, and mix the fire extinguishing microcapsules evenly and avoid their rupture by high-speed shearing to obtain a mixture; the high-speed shearing speed is 12000 rpm and the time is 3 min. S4. The mixture is coated onto the substrate with a thickness of 120μm and UV-cured under ultraviolet light with a wavelength of 365nm and an energy density of 1000mJ / cm². After forming a flame-retardant pressure-sensitive adhesive layer, it is heat-cured at 90℃ for 1.5h to obtain a flame-retardant fire extinguishing film based on microcapsules. Example 4

[0046] A microcapsule-based flame-retardant fire extinguishing membrane comprises the following raw materials in parts by weight: The composition comprises: 35 parts of difunctional aliphatic polyurethane acrylate EasepiU600, 15 parts of 1,6-hexanediol diacrylate, 10 parts of trimethylolpropane triacrylate, 20 parts of linear boron-containing monomer, 10 parts of fire extinguishing microcapsules, 6 parts of polyionic liquid, 10 parts of allyl borate pinacol ester, 4 parts of pentaerythritol tetra-3-mercaptopropionate, and 2.5 parts of 2,4,6-trimethylbenzoyl-ethoxy-phenylphosphine oxide; wherein the fire extinguishing microcapsules use perfluorobutyl ketone as the core material and flame-retardant polymer nitrogen-containing heterocyclic polyurea as the wall material; the particle size of the fire extinguishing microcapsules is 20-40 μm, and the wall material thickness is 0.5-2 μm.

[0047] The preparation method of the microcapsule-based flame-retardant fire extinguishing membrane includes the following steps: S1. Preparation of fire extinguishing microcapsules: 1) Preparation of the oil phase: Dissolve perfluorobutanone in dichloromethane (volume ratio 1:2, temperature 20℃) to form an oil phase; 2) Preparation of nitrogen-containing heterocyclic polyurea prepolymer: Polyetheramine D2000 and 3,5-diamino-1,2,4-triazole were added to a reaction vessel and mixed evenly. Then isocyanate and solvent were added, and the mixture was reacted at 25°C for 4 hours to obtain the nitrogen-containing heterocyclic polyurea prepolymer. The mass ratio of polyetheramine, 3,5-diamino-1,2,4-triazole and isocyanate was 3:2:2.5. 3) Preparation of the multiemulsion W / O / W system: The prepolymer of nitrogen-containing heterocyclic polyurea is mixed evenly with the oil phase and slowly added dropwise to the aqueous phase containing 3wt% emulsifier Tween 40. The mixture is homogenized at a high speed of 11,000 rpm to form a W / O emulsion. The W / O emulsion is then injected into the aqueous phase containing 1wt% polyvinyl alcohol and stirred at a speed of 1,100 rpm to form the multiemulsion W / O / W system. 4) Interfacial polymerization reaction: Then, 1.5 wt% ethylenediamine aqueous solution was added, and cross-linking polymerization was carried out at 40℃ for 2 h to obtain fire extinguishing microcapsules with nitrogen-containing heterocyclic polyurea as the shell. The microcapsules were collected by centrifugation, freeze-dried, and the core material accounted for 60 wt% of the fire extinguishing microcapsules. S2. Mix acrylic monomer, polyurethane acrylate, alkenyl borate ester, polyionic liquid, linear boron-containing monomer, photoinitiator and crosslinking agent according to the weight parts, and crosslink polymerization reaction at 60°C for 3 hours to form a viscous resin. S3. Add fire extinguishing microcapsules to the obtained viscous resin, and mix the fire extinguishing microcapsules evenly and avoid their rupture by high-speed shearing to obtain a mixture; the high-speed shearing speed is 13000 rpm and the time is 3 min. S4. The mixture is coated onto the substrate with a thickness of 60μm and UV-cured under ultraviolet light with a wavelength of 365nm and an energy density of 900mJ / cm². After forming a flame-retardant pressure-sensitive adhesive layer, it is heat-cured at 85℃ for 1.5h to obtain a flame-retardant fire extinguishing film based on microcapsules. Example 5

[0048] A microcapsule-based flame-retardant fire extinguishing membrane comprises the following raw materials in parts by weight: The composition comprises: 45 parts of aromatic polyurethane acrylate CN9001, 10 parts of methyl 2-methacrylate, 8 parts of ethyl 2-methacrylate, 25 parts of linear boron-containing monomer, 16 parts of fire extinguishing microcapsules, 10 parts of polyionic liquid, 6 parts of allyl borate pinacol ester, 6 parts of pentaerythritol tetra-3-mercaptopropionate, and 3 parts of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide; wherein the fire extinguishing microcapsules use perfluorooctane as the core material and flame-retardant polymer nitrogen-containing heterocyclic polyurea as the wall material; the particle size of the fire extinguishing microcapsules is 30-40 μm, and the wall material thickness is 0.5-2 μm.

[0049] The preparation method of the microcapsule-based flame-retardant fire extinguishing membrane includes the following steps: S1. Preparation of fire extinguishing microcapsules: Same as in Example 4, except that the core material in the fire extinguishing microcapsules accounts for 65 wt%; S2. Mix acrylic monomer, polyurethane acrylate, alkenyl borate ester, polyionic liquid, linear boron-containing monomer, photoinitiator and crosslinking agent according to the weight parts, and crosslink polymerization reaction at 70°C for 2.5h to form viscous resin. S3. Add fire extinguishing microcapsules to the obtained viscous resin, and use ultrasonic dispersion to mix the fire extinguishing microcapsules evenly and avoid their rupture, to obtain a mixture; the ultrasonic dispersion power is 150 W and the time is 10 min. S4. The mixture is coated onto the substrate with a thickness of 180μm and UV-cured under ultraviolet light with a wavelength of 365nm and an energy density of 1000mJ / cm². After forming a flame-retardant pressure-sensitive adhesive layer, it is heat-cured at 95℃ for 1.5h to obtain a flame-retardant fire extinguishing film based on microcapsules.

[0050] Comparative Example 1 The linear boron-containing monomer was removed, and the rest was the same as in Example 3.

[0051] Comparative Example 2 Remove the polyionic liquid; otherwise, it is the same as in Example 3.

[0052] Comparative Example 3 Remove the alkenyl borate ester, otherwise the same as in Example 3.

[0053] Comparative Example 4 The homogenization speed for forming the W / O emulsion and the re-emulsified W / O / W system was 1000 rpm, and the rest was the same as in Example 3.

[0054] The flame-retardant fire extinguishing membranes obtained in Examples 1-5 and Comparative Examples 1-4 were subjected to flame resistance and tensile strength tests. The specific test methods are as follows: Flame resistance: Tested according to GB / T 15903-1995 "Test Method for Resistance of Pressure-Sensitive Adhesive Tape - Suspension Method". Specimen preparation: Before sampling, remove the first 5 rolls of the rolled flame-retardant extinguishing film, then unroll it evenly. Cut 6 flame-retardant extinguishing film specimens, each 300mm long and 25mm wide. Mark the back of each specimen at 50mm and 150mm from the top. The remaining steps are performed according to GB / T 15903-1995.

[0055] Tensile strength: The flame-retardant fire extinguishing membrane was cut into dumbbell-shaped strips with a width of 4 mm and a thickness of 0.03 mm using a cutting knife. The flame-retardant fire extinguishing membrane was subjected to a tensile test using a universal testing machine with a maximum load of 100 N and a tensile rate of 100 mm / min at room temperature.

[0056] Table 1 Flame resistance rating Fracture strength / MPa Example 1 0 5.9 Example 2 0 6.3 Example 3 0 7.6 Example 4 0 7.1 Example 5 0 6.8 Comparative Example 1 2 3.7 Comparative Example 2 1 4.6 Comparative Example 3 1 4.1 Comparative Example 4 1 5.2 As shown in Table 1, the flame-retardant fire extinguishing membranes provided in Examples 1-5 of this invention possess excellent flame-retardant properties and mechanical strength. Linear boron-containing monomers, polyionic liquids, and alkenyl borate esters all participate in the crosslinking process of the flame-retardant fire extinguishing membrane. Among them, the linear boron-containing monomer is also the main structural component of the flame-retardant fire extinguishing membrane. All three have a significant impact on the flame-retardant properties and mechanical strength of the membrane. Linear boron-containing monomers have the greatest impact on flame-retardant properties and tensile strength. The homogenization rate of the polyionic liquid, alkenyl borate ester, and the formation of the W / O emulsion and the re-emulsified W / O / W system all have a significant impact on flame-retardant properties. The homogenization rate of the W / O emulsion and the re-emulsified W / O / W system has a smaller impact on tensile strength, possibly because the homogenization rate of the W / O emulsion and the re-emulsified W / O / W system affects the size and shell thickness of the fire extinguishing microcapsules, thus affecting their flame-retardant properties, but has a smaller impact on the mechanical strength of the fire extinguishing microcapsules.

[0057] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flame-retardant fire extinguishing membrane based on microcapsules, characterized in that, Including the following parts by weight of raw materials: The composition comprises: 30-50 parts polyurethane acrylate, 15-30 parts acrylic monomer, 15-30 parts linear boron-containing monomer, 5-20 parts fire extinguishing microcapsules, 4-12 parts polyionic liquid, 4-12 parts alkenyl borate ester, 2-8 parts crosslinking agent, and 1-7 parts photoinitiator; the fire extinguishing microcapsules use a fire-extinguishing substance as the core material and a flame-retardant polymer as the wall material; the monomer of the polyionic liquid is 1-vinyl-3-benzylimidazolium chloride, and the chemical structural formula of the linear boron-containing monomer is as follows: n is an integer from 5 to 15.

2. The flame-retardant fire extinguishing membrane based on microcapsules according to claim 1, characterized in that, The acrylic monomers include at least one of methyl acrylate, ethyl acrylate, butyl acrylate, methyl 2-methacrylate, ethyl 2-methacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, tripropylene glycol diacrylate, and α-cyanoacrylate. The polyurethane acrylate includes at least one of aliphatic polyurethane acrylate, difunctional aliphatic polyurethane acrylate, and aromatic polyurethane acrylate. The alkenyl borate ester includes at least one of vinyl borate pinacol ester, 2-tert-butyl-e-vinyl borate pinacol ester, 2,2-dimethyl vinyl borate pinacol ester, diisopropyl propenyl borate, diisopropyl allyl borate ester, allyl borate pinacol ester, and isopropenyl borate pinacol ester.

3. The flame-retardant fire extinguishing membrane based on microcapsules according to claim 1, characterized in that, The fire-extinguishing substances include perfluoroketones and / or perfluoroalkanes, and the flame-retardant polymer is a nitrogen-containing heterocyclic polyurea. The particle size of the fire extinguishing microcapsules is 10-50 μm; The thickness of the flame-retardant polymer wall material is 0.5-5 μm.

4. The flame-retardant fire extinguishing membrane based on microcapsules according to claim 1, characterized in that, The photoinitiator includes at least one of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 2,4,6-trimethylbenzoyl-ethoxy-phenylphosphine oxide. The crosslinking agent includes at least one of pentaerythritol triacrylate, pentaerythritol tetraacrylate, and pentaerythritol tetra-3-mercaptopropionate.

5. A method for preparing a microcapsule-based flame-retardant fire extinguishing membrane according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Mix acrylic monomer, polyurethane acrylate, alkenyl borate ester, polyionic liquid, linear boron-containing monomer, photoinitiator and crosslinking agent according to the weight parts, and crosslink polymerization reaction at 50-80℃ for 2-4 hours to form a viscous resin. S2. Add fire extinguishing microcapsules to the obtained viscous resin, and disperse and mix evenly by high-speed shearing or ultrasonication while avoiding the rupture of the fire extinguishing microcapsules to obtain a mixture. S3. The mixture is coated onto the substrate and UV-cured under ultraviolet light to form a flame-retardant pressure-sensitive adhesive layer, thus obtaining a flame-retardant fire extinguishing film based on microcapsules.

6. The method for preparing a microcapsule-based flame-retardant fire extinguishing membrane according to claim 5, characterized in that, The preparation of the linear boron-containing monomer in step S1 includes: mixing trimethyl borate (TMB) and glyceryl methacrylate (GMMA) in a solvent and stirring the mixture under an inert atmosphere; then injecting polyethylene glycol (PEG) into the reaction solution, heating and stirring the mixture, removing the solvent under reduced pressure, and drying to obtain the linear boron-containing monomer.

7. The method for preparing a microcapsule-based flame-retardant fire extinguishing membrane according to claim 5, characterized in that, The preparation method of the fire extinguishing microcapsules in step S1 includes: 1) Preparation of the oil phase: The core material is dissolved in an oily solvent to form an oil phase; 2) Preparation of nitrogen-containing heterocyclic polyurea prepolymer: Polyetheramine and 3,5-diamino-1,2,4-triazole were added to a reaction vessel and mixed evenly. Then isocyanate and solvent were added, and the mixture was reacted at 15-40℃ for 3-5 hours to obtain a nitrogen-containing heterocyclic polyurea prepolymer. 3) Preparation of a complex emulsion W / O / W system: The nitrogen-containing heterocyclic polyurea prepolymer is mixed evenly with the oil phase and slowly added dropwise to the aqueous phase containing 1.5-3.5 wt% emulsifier. The mixture is homogenized at 8000-12000 rpm for 1-4 min to form a W / O emulsion. The W / O emulsion is then injected into the aqueous phase containing 0.5-1.5 wt% polyvinyl alcohol and stirred at 800-1100 rpm to form a double-emulsified W / O / W system. 4) Interfacial polymerization reaction: Then, an aqueous solution of an amine crosslinking agent was added, and the mixture was reacted at 30-40°C for 1-3 hours to obtain fire extinguishing microcapsules with a nitrogen-containing heterocyclic polyurea shell. The microcapsules were collected by centrifugation and then freeze-dried.

8. The method for preparing a microcapsule-based flame-retardant fire extinguishing membrane according to claim 5, characterized in that, In step S2: The high-speed shearing speed is 10,000-15,000 rpm, and the time is 2-5 minutes; The ultrasonic dispersion power is 100-200 W, and the time is 5-15 min.

9. The method for preparing a microcapsule-based flame-retardant fire extinguishing membrane according to claim 5, characterized in that, In step S3: Coating thickness is 50-200μm; Ultraviolet light has a wavelength of 350-380nm and an energy density of 800-1200mJ / cm².

10. The method for preparing a microcapsule-based flame-retardant fire extinguishing membrane according to claim 5, characterized in that, Step S3 is followed by heat curing at 80-100℃ for 1-2 hours.

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