Fire extinguishing microcapsule with double-layer compact structure and preparation method thereof

Abstract

This invention discloses a fire extinguishing microcapsule with a double-layered dense structure and its preparation method. The fire extinguishing microcapsule comprises a core material, an inner shell, and an outer shell, which are sequentially coated from the inside out. The core material is a perfluorinated fire extinguishing agent. The inner shell is composed of a modified acrylic resin formed by the interfacial polymerization reaction of fluorinated acrylic monomers and acrylic monomers with an acrylic crosslinking agent. The outer shell is composed of a modified melamine-formaldehyde resin formed by the reaction of melamine, formaldehyde, and a perfluorinated polyol. In this invention, the use of fluorinated acrylic resin in the inner shell effectively improves the compatibility with perfluorinated fire extinguishing agents and solves the problem of difficulty in shell formation. The outer shell uses a perfluorinated polyol-modified melamine-formaldehyde resin to form a dense and stable shell structure, achieving stable and dense coating of the perfluorinated fire extinguishing agent and endowing the microcapsule with good high-temperature storage performance and temperature-controlled release characteristics.

Description

Technical Field

[0001] This invention relates to the field of microcapsule technology, and in particular to a fire extinguishing microcapsule with a double-layered dense structure and its preparation method. Background Technology

[0002] With the continuous growth in the number of electrical appliances and electricity consumption, fires have become a frequent major disaster in modern society, seriously threatening the safety of life and property. The main reason for the significant losses caused by most fires is that they are not detected and effectively extinguished in their early stages. Currently, the fire risks in emerging fields such as new energy vehicles, lithium battery energy storage, and 5G communications are particularly prominent. However, traditional fire extinguishers have inherent shortcomings such as delayed response, easy generation of secondary pollution, and difficulty in being used in confined spaces, making them unable to meet the fire prevention needs of these scenarios.

[0003] Perfluorinated fire extinguishing agents have attracted widespread attention due to their advantages such as endothermic vaporization fire extinguishing and low environmental and human harm. Among them, perfluorohexanone is a liquid at room temperature with a boiling point of only 49°C, making it prone to vaporization and volatilization, and difficult to store and use directly. To solve this problem, perfluorohexanone can be microencapsulated, allowing it to be stored stably at room temperature. When heated, the capsule shell ruptures and releases the extinguishing agent, achieving automatic fire extinguishing.

[0004] Currently, the mainstream preparation technology for fire extinguishing microcapsules is microfluidic encapsulation technology. While this technology can produce high-performance products, it suffers from core drawbacks such as complex processes, expensive equipment, and difficulty in large-scale mass production, resulting in high product prices and severely restricting its promotion in large-scale application scenarios such as new energy vehicles and 5G base stations. Patent CN114618111A discloses a perfluorohexanone fire extinguishing microcapsule and its preparation method. The core of the microcapsule uses perfluorohexanone and its derivatives, while the shell uses urea-formaldehyde resin or polyurea-formaldehyde resin. The resulting microcapsules have a low thermal response temperature, but the preparation process easily produces empty capsules, and the shell material lacks density, affecting the product's storage stability and service life.

[0005] Given the shortcomings of the existing technologies, there is an urgent need to develop a perfluorinated fire extinguishing microcapsule with high shell density, good temperature resistance, high core material content, and suitability for large-scale production, in order to meet the urgent demand of emerging fields for efficient, reliable, and economical automatic fire extinguishing products. Summary of the Invention

[0006] The purpose of this invention is to provide a fire extinguishing microcapsule with a double-layered dense structure and its preparation method, in order to solve the problems of low core material content, poor shell material density, and poor temperature resistance of existing perfluorinated fire extinguishing microcapsules.

[0007] To solve the above-mentioned technical problems, the present invention provides a first solution: a fire extinguishing microcapsule with a double-layered dense structure, comprising a core material, an inner shell, and an outer shell arranged sequentially from the inside to the outside; wherein, the core material is a perfluorinated fire extinguishing agent, the inner shell is composed of a modified acrylic resin formed by the interfacial polymerization reaction of fluorinated acrylic monomers, acrylic monomers and acrylic crosslinking agents, and the outer shell is composed of a modified melamine-formaldehyde resin formed by the reaction of melamine, formaldehyde and perfluorinated polyols.

[0008] In one embodiment, the perfluorinated fire extinguishing agent is at least one of perfluorohexanone, methyl perfluoroisobutyl ether, difluorotrichloroethane, 2-iodine-heptafluoropropane, perfluorotriethylamine, tetrafluorodibromoethane, difluorobromochloromethane, difluorodichloroethane, 1-iodine-heptafluoropropane, and trifluorotrichloroethane.

[0009] In one embodiment, the fluorinated acrylic monomer is at least one selected from hexafluorobutyl acrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl acrylate, tridecafluorooctyl methacrylate, perfluoroalkyl ethyl acrylate, and perfluoroalkyl ethyl methacrylate.

[0010] In one embodiment, the acrylic monomer is at least one selected from acrylic acid, methacrylic acid, methyl methacrylate, ethyl methacrylate, hydroxyethyl acrylate, and methyl acrylate.

[0011] In one embodiment, the acrylic crosslinking agent is at least one selected from acrylic crosslinking agent, triallyl isocyanurate, trimethylolpropane triacrylate, glycidyl methacrylate, and diacetone acrylamide.

[0012] In one embodiment, the perfluorinated polyol is at least one selected from 1H,1H,2H,2H-perfluoro-1-hexanol, 1H,1H,2H,2H-perfluoro-1-dodecyl alcohol, 1H,1H,2H,2H-perfluoro-1-decyl alcohol, 1H,1H,2H,2H-perfluoro-1-octanol, and pentaerythritol tris(3-perfluorohexylpropyl) ether.

[0013] In one embodiment, the mass ratio of perfluorinated fire extinguishing agent to fluorinated acrylic monomer is 1:0.05~0.1, the mass ratio of perfluorinated fire extinguishing agent to acrylic monomer is 1:0.05~0.1, and the mass percentage of acrylic crosslinking agent to the sum of fluorinated acrylic monomer and acrylic monomer is 0.3~0.8%.

[0014] In one embodiment, the mass ratio of perfluorinated fire extinguishing agent to melamine is 1:0.05~1, the mass ratio of melamine to formaldehyde is 1.05~1.4:1, and the mass ratio of melamine to perfluorinated polyol is 1:0.05~0.1.

[0015] In one embodiment, the fire extinguishing microcapsules with a double-layered dense structure have a particle size of 10–300 μm and a core material release temperature of 80–140°C. These double-layered dense fire extinguishing microcapsules possess an autonomous release function; when the ambient temperature reaches above 80°C, both the inner and outer shells of the microcapsule automatically rupture, releasing the perfluorinated fire extinguishing agent core material without external intervention, thus achieving automatic fire extinguishing. In practical applications, these double-layered dense fire extinguishing microcapsules, due to their small size and light weight, can be embedded inside or on the surface of energy storage devices, occupying almost no extra space and not affecting the normal operation and maintenance of the equipment, making them suitable for a wide range of applications.

[0016] To solve the above-mentioned technical problems, the present invention provides a second solution: a method for preparing fire extinguishing microcapsules with a double-layered dense structure. This method is used to prepare the fire extinguishing microcapsules with a double-layered dense structure described in the first solution, and includes the following steps: S1, according to the formula, the perfluorinated fire extinguishing agent, fluorinated acrylic monomer, acrylic monomer, acrylic crosslinking agent and initiator are stirred to obtain the core material composite solution.

[0017] S2, add a fluorinated emulsifier to water and mix well to obtain an emulsion solution.

[0018] S3, add the core material composite solution to the emulsion solution and stir continuously until a stable suspension is formed.

[0019] S4. The suspension is placed under nitrogen protection, and the temperature is controlled at 60~80℃ and the pressure at 2~5 MPa. The reaction forms an inner shell, and the inner shell solution is obtained.

[0020] S5, melamine, formaldehyde, perfluorinated polyol, triethanolamine and deionized water are mixed and reacted according to the formula, the temperature is controlled at 60~90℃ and the pH value is adjusted to 8~9.5, the mixing reaction time is 1.5~3 h, and a melamine-formaldehyde modified prepolymer solution is obtained; wherein, triethanolamine and deionized water are both used as solvents and do not participate in the reaction, and triethanolamine is used as an alkaline solvent to adjust the pH value.

[0021] S6. Add the melamine-formaldehyde modified prepolymer solution to the inner shell solution and stir to react, thus obtaining the initial product of the double-shell microcapsule.

[0022] S7. The initial microcapsule product is dried to obtain fire extinguishing microcapsules with a double-layered dense structure.

[0023] In one embodiment, in step S1, the amount of initiator added is 0.5-3% of the sum of the mass of the fluorinated acrylic monomer and the acrylic monomer, and the initiator is at least one of BPO, ABVN, AIBN, and tert-butyl peroxide.

[0024] In one embodiment, in step S2, the amount of fluorinated emulsifier added is 1% to 5% of the mass of the perfluorinated fire extinguishing agent. The fluorinated emulsifier is at least one of sodium perfluorononenoxybenzenesulfonate, potassium perfluorobutylsulfonate, FC-4 fluorocarbon surfactant, FC-201 zwitterionic fluorocarbon surfactant, and perfluorohexyl ethyl polyoxyethylene ether. Preferably, the fluorinated emulsifier is at least one of sodium perfluorononenoxybenzenesulfonate, potassium perfluorobutylsulfonate, perfluorohexyl ethyl sulfonic acid, perfluoro-2,5-dimethyl-3,6-dioxanoic acid, perfluorohexyl ethyl betaine, and perfluorohexyl ethyl polyoxyethylene ether.

[0025] In one embodiment, in step S3, when preparing the suspension solution, the temperature is controlled at 0~20℃ and the stirring speed is 100~1500 rpm.

[0026] In one embodiment, during step S4, when preparing the inner shell solution, the temperature is controlled at 60~80°C and the pressure is controlled at 2~5 MPa.

[0027] In one embodiment, in step S6, when preparing the initial product of the double-shell microcapsules, the reaction temperature is 20~40℃ and the reaction time is 6~12 h.

[0028] In one embodiment, in step S7, the drying temperature is 30–45°C and the drying time is 12–24 h.

[0029] The reaction mechanism of the fire extinguishing microcapsules with a double-layered dense structure and their preparation method in this invention is as follows: 1) In this invention, the inner shell is made of a special acrylic resin produced by reacting fluorinated acrylic monomers, acrylic monomers, and acrylic crosslinking agents. Compared with existing acrylic resin wall materials, this fluorinated acrylic resin exhibits superior compatibility with perfluorinated fire extinguishing agents. Simultaneously, during the preparation process, the use of a fluorinated emulsifier enables efficient emulsification of the composite core material, forming a stable emulsion suspension. The emulsified product is then transferred to a reaction vessel, where, under suitable temperature, pressure, and initiator conditions, a dense special acrylic shell is formed on the surface of the perfluorinated fire extinguishing agent through interfacial polymerization.

[0030] 2) In this invention, the outer shell is made of melamine-formaldehyde resin modified with perfluorinated polyols. Specifically, melamine and formaldehyde undergo a nucleophilic addition reaction under weakly alkaline conditions to generate a water-soluble melamine resin prepolymer. During this process, the introduction of perfluorinated polyols significantly improves the strength and density of the wall material, enhances the toughness of the outer layer, and reduces brittleness. Furthermore, it improves the compatibility between the outer and inner shell layers, enabling a tight and secure bond between the two shells. The double-shell structure constructed in this invention significantly improves the overall density and temperature resistance of the shell material, allowing the shell to remain stable for extended periods below 80°C. Only when the temperature rises above 80°C will the shell material crack and release the internal core material.

[0031] The advantages of this invention, which differ from the prior art, are as follows: 1. The fire extinguishing microcapsules with a double-layered dense structure prepared by this invention have good shell density and a core material content as high as 86-92%, which significantly increases the core material content of perfluorinated fire extinguishing agents. On the one hand, this invention uses fluorinated acrylic resin material for the inner shell, which effectively improves the compatibility between the double shell and the perfluorinated fire extinguishing agent and solves the problem of difficult shell formation. On the other hand, this invention uses melamine-formaldehyde resin modified with perfluorinated polyol for the outer shell, which can form a dense and stable shell structure, achieve stable and dense coating of perfluorinated fire extinguishing agents, and at the same time endow the microcapsules with good high-temperature storage performance and temperature-controlled release characteristics.

[0032] 2. The fire extinguishing microcapsules with a double-layered dense structure prepared in this invention have a particle size of 10–300 μm and a core material release temperature of 80–140°C. They exhibit good room temperature storage stability; after one month of storage at room temperature, the mass loss (microcapsule core material loss rate) is less than 1%; after seven days of storage at 60°C, the mass loss is less than 3%. These fire extinguishing microcapsules can maintain long-term structural stability under relatively high temperatures, preventing the release of perfluorinated fire extinguishing agents in the core material before a fire occurs or when unnecessary, thus significantly improving the temperature resistance of the fire extinguishing microcapsules. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the reaction process for preparing fire extinguishing microcapsules with a double-layered dense structure in Example 1 of the present invention; Figure 2 This is an electron microscope image of the fire extinguishing microcapsule with a double-layered dense structure prepared in Example 1 of the present invention. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the invention, are intended to cover non-exclusive inclusion.

[0036] In this invention, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0037] I. Preparation Method Example 1

[0038] The preparation method of the fire extinguishing microcapsules with a double-layered dense structure provided in Example 1 is as follows: Figure 1 As shown, it includes the following steps: (1) Weigh 100g of perfluorohexanone as the fire extinguishing agent core material and place it in a beaker. Add 5g of hexafluorobutyl methacrylate, 2g of acrylic acid, 3g of methyl methacrylate, 0.03g of trimethylolpropane triacrylate, and 0.05g of ABVN. Stir to form a homogeneous core material composite solution.

[0039] (2) Weigh 2 g of sodium perfluorononenoxybenzenesulfonate and dissolve it in 100 g of deionized water to form an emulsion solution.

[0040] (3) Add the core material composite solution to the emulsion solution, control the temperature at 5℃, and stir at 200 rpm for 10 min to form a stable suspension solution.

[0041] (4) Transfer the suspension to a high-pressure reactor, protect it with nitrogen, slowly raise the temperature to 70°C, control the pressure to 2MPa, and react for 3 h to form a dense inner shell, thus obtaining the inner shell solution.

[0042] (5) Add 20 g of melamine, 40 g of formaldehyde aqueous solution (37%), and 1 g of 1H,1H,2H,2H-perfluoro-1-hexanol to a three-necked flask, add triethanolamine dropwise until the pH is 8.5, heat in a water bath to 85°C, keep warm and stir for 1.5 h, and then discharge to obtain a colorless, clear and transparent melamine-formaldehyde modified prepolymer solution.

[0043] (6) Add 5 g of melamine-formaldehyde modified prepolymer solution to the inner shell solution, control the reaction at 40℃, and react for 6 h to form the outer shell, thus obtaining the initial product of double-shell microcapsules.

[0044] (7) The initial microcapsule sample was sieved to form a wet powder, and dried at 40°C for 12 h to obtain fire extinguishing microcapsules with a particle size of 150~250 μm.

[0045] (8) Take 6 g of epoxy resin as the base material, add 9 g of the prepared fire extinguishing microcapsules, stir and disperse evenly; coat the obtained mixture onto the release film, press it into a sheet, and cure it in an oven at 60℃ for 1 h to prepare a fire extinguishing sheet.

[0046] Example 2

[0047] The preparation method of the fire extinguishing microcapsules with a double-layered dense structure provided in Example 2 includes the following steps: (1) Weigh 90 g of perfluorohexanone and 10 g of perfluoroisobutyl methyl ether as fire extinguishing agent core material and place them in a beaker. Add 7 g of trifluoroethyl methacrylate, 3 g of methacrylic acid, 4 g of methyl methacrylate, 0.1 g of glycidyl methacrylate and 0.2 g of AIBN, and stir to form a homogeneous core material composite solution.

[0048] (2) Weigh 1.5 g of potassium perfluorobutyl sulfonate and dissolve it in 100 g of deionized water to form an emulsion solution.

[0049] (3) Add the core material composite solution to the emulsion solution, control the temperature at 10℃, and stir at 500 rpm for 10 min to form a stable suspension solution.

[0050] (4) Transfer the suspension to a high-pressure reactor, protect it with nitrogen, slowly raise the temperature to 60°C, control the pressure to 3MPa, and react for 3 hours to form a dense inner shell, thus obtaining the inner shell solution.

[0051] (5) Add 20 g of melamine, 45 g of formaldehyde aqueous solution (37%), and 1.2 g of pentaerythritol tris(3-perfluorohexylpropyl) ether to a three-necked flask, add triethanolamine dropwise until the pH is 9, heat in a water bath to 80°C, keep warm and stir for 2 h, and then discharge to obtain a colorless, clear and transparent melamine-formaldehyde modified prepolymer solution.

[0052] (6) Add 8 g of melamine-formaldehyde modified prepolymer solution to the inner shell solution, control the reaction at 30°C, and react for 10 h to form the outer shell, thus obtaining the initial product of double-shell microcapsules.

[0053] (7) The initial microcapsule sample was sieved to form a wet powder, and dried at 40°C for 18 h to obtain fire extinguishing microcapsules with a particle size of 100~200 μm.

[0054] (8) Take 6 g of epoxy resin as the base material, add 9 g of the prepared fire extinguishing microcapsules, and stir to disperse evenly. Coat the obtained mixture onto a release film, press it into a sheet, and cure it in an oven at 60℃ for 1 h to prepare a fire extinguishing sheet.

[0055] Example 3

[0056] The preparation method of the fire extinguishing microcapsule with a double-layer dense structure provided in Example 3 includes the following steps: (1) Weigh 90 g of perfluorohexanone and 10 g of perfluorotriethylamine as fire extinguishing agent core material and place them in a beaker. Add 8 g of tridecyl methacrylate, 2 g of methyl methacrylate, 6 g of hydroxyethyl acrylate, 0.15 g of triallyl isocyanurate and 0.4 g of BPO, and stir to form a homogeneous core material composite solution.

[0057] (2) Weigh 3 g of perfluorohexylethyl betaine and dissolve it in 100 g of deionized water to form an emulsion solution.

[0058] (3) Add the core material composite solution to the emulsion solution, control the temperature at 15℃, and stir at 800 rpm for 10 min to form a stable suspension solution.

[0059] (4) Transfer the suspension to a high-pressure reactor, protect it with nitrogen, slowly raise the temperature to 65°C, control the pressure to 4MPa, and react for 3 h to form a dense inner shell, thus obtaining the inner shell solution.

[0060] (5) Add 20 g of melamine, 48 g of formaldehyde aqueous solution (37%), and 1.6 g of 1H,1H,2H,2H-perfluoro-1-dodecyl alcohol to a three-necked flask, add triethanolamine dropwise until the pH is 8.5, heat in a water bath to 75°C, keep warm and stir for 2 h, and then discharge to obtain a colorless, clear and transparent melamine-formaldehyde modified prepolymer solution.

[0061] (6) Add 9 g of melamine-formaldehyde modified prepolymer solution to the inner shell solution, control the reaction at 28°C, and react for 10 h to form the outer shell, thus obtaining the initial product of double-shell microcapsules.

[0062] (7) The initial microcapsule sample was sieved to form a wet powder, and dried at 45°C for 6 h to obtain fire extinguishing microcapsules with a particle size of 100~200 μm.

[0063] (8) Take 6 g of epoxy resin as the base material, add 9 g of the prepared fire extinguishing microcapsules, and stir to disperse evenly. Coat the obtained mixture onto a release film, press it into a sheet, and cure it in an oven at 60℃ for 1 h to prepare a fire extinguishing sheet.

[0064] Example 4

[0065] The preparation method of the fire extinguishing microcapsule with a double-layer dense structure provided in Example 4 includes the following steps: (1) Weigh 80 g of perfluorohexanone and 20 g of 2-iodo-heptafluoropropane as fire extinguishing agent core material and place them in a beaker. Add 9 g of perfluoroalkyl ethyl acrylate, 5 g of acrylic acid, 3 g of methyl acrylate, 0.06 g of diacetone acrylamide and 0.5 g of tert-butyl peroxide, and stir to form a homogeneous core material composite solution.

[0066] (2) Weigh 5 g of perfluorohexyl ethyl polyoxyethylene ether and dissolve it in 100 g of deionized water to form an emulsion solution.

[0067] (3) Add the core material composite solution to the emulsion solution, control the temperature at 20℃, and stir at 1200 rpm for 10 minutes to form a stable suspension solution.

[0068] (4) Transfer the suspension to a high-pressure reactor, protect it with nitrogen, slowly raise the temperature to 75°C, control the pressure to 4 MPa, and react for 3 h to form a dense inner shell, thus obtaining the inner shell solution.

[0069] (5) Add 20 g of melamine, 42 g of formaldehyde aqueous solution (37%), and 1.7 g of 1H,1H,2H,2H-perfluoro-1-octanol to a three-necked flask, add triethanolamine dropwise until the pH is 8, heat in a water bath to 65°C, keep warm and stir for 2.5 h, and then discharge to obtain a colorless, clear and transparent melamine-formaldehyde modified prepolymer solution.

[0070] (6) Add 6 g of melamine-formaldehyde modified prepolymer solution to the inner shell solution, control the reaction at 35°C, and react for 7 h to form the outer shell, thus obtaining the initial product of double-shell microcapsules.

[0071] (7) The initial microcapsule sample was sieved to form a wet powder, and dried at 35°C for 20 h to obtain fire extinguishing microcapsules with a particle size of 50~150 μm.

[0072] (8) Take 6 g of epoxy resin as the base material, add 9 g of the prepared fire extinguishing microcapsules, and stir to disperse evenly. Coat the obtained mixture onto a release film, press it into a sheet, and cure it in an oven at 60℃ for 1 h to prepare a fire extinguishing sheet.

[0073] Example 5

[0074] Example 5 provides a method for preparing fire extinguishing microcapsules with a double-layered dense structure, comprising the following steps: (1) Weigh 70 g of perfluorohexanone and 30 g of difluorodichloroethane as fire extinguishing agent core material and place them in a beaker. Add 6 g of perfluoroalkyl ethyl methacrylate, 2 g of methyl methacrylate, 7 g of methyl acrylate, 0.08 g of glycidyl methacrylate, 0.05 g of trimethylolpropane triacrylate, and 0.35 g of ABVN. Stir to form a homogeneous core material composite solution.

[0075] (2) Weigh 4.5 g of potassium perfluorobutyl sulfonate and dissolve it in 100 g of deionized water to form an emulsion solution.

[0076] (3) Add the core material composite solution to the emulsion solution, control the temperature at 15℃, and stir at 1500 rpm for 10 minutes to form a stable suspension solution.

[0077] (4) Transfer the suspension to a high-pressure reactor, protect it with nitrogen, slowly raise the temperature to 80°C, control the pressure to 2.5 MPa, and react for 3 hours to form a dense inner shell, thus obtaining the inner shell solution.

[0078] (5) Add 20 g of melamine, 50 g of formaldehyde aqueous solution (37%), and 1.9 g of 1H,1H,2H,2H-perfluoro-1-octanol to a three-necked flask, add triethanolamine dropwise until the pH is 9, heat in a water bath to 90°C, keep warm and stir for 1.5 h, and then discharge to obtain a colorless, clear and transparent melamine-formaldehyde modified prepolymer solution.

[0079] (6) Add 9 g of melamine-formaldehyde modified prepolymer solution to the inner shell solution, control the reaction at 40℃, and react for 6 h to form the outer shell, thus obtaining the initial product of double-shell microcapsules.

[0080] (7) The initial microcapsule sample was sieved to form a wet powder, and dried at 45°C for 12 h to obtain fire extinguishing microcapsules with a particle size of 30~120 μm.

[0081] (8) Take 6 g of epoxy resin as the base material, add 9 g of the prepared fire extinguishing microcapsules, and stir to disperse evenly. Coat the obtained mixture onto a release film, press it into a sheet, and cure it in an oven at 60℃ for 1 h to prepare a fire extinguishing sheet.

[0082] Comparative Example 1 The method for preparing fire extinguishing microcapsules with a double-layered dense structure provided in Comparative Example 1 includes the following steps: (1) Weigh 100 g of perfluorohexanone as the fire extinguishing agent core material and place it in a beaker. Add 5 g of acrylic acid, 5 g of methyl methacrylate, 0.03 g of trimethylolpropane triacrylate and 0.05 g of ABVN, and stir to form a homogeneous core material composite solution.

[0083] (2) Weigh 2 g of sodium perfluorononenoxybenzenesulfonate and dissolve it in 100 g of deionized water to form an emulsion solution.

[0084] (3) Add the core material composite solution to the emulsion solution, control the temperature at 5℃, and stir at 200 rpm for 10 min to form a stable suspension solution.

[0085] (4) The suspension was transferred to a high-pressure reactor, protected with nitrogen, and the temperature was slowly raised to 70°C. The pressure was controlled to 2 MPa and the reaction was carried out for 3 h to obtain a solid intermediate with no obvious microcapsule structure.

[0086] (5) Add 20 g of melamine, 40 g of formaldehyde aqueous solution (37%), and 1 g of 1H,1H,2H,2H-perfluoro-1-hexanol to a three-necked flask, add triethanolamine dropwise until the pH is 8.5, heat in a water bath to 85°C, keep warm and stir for 1.5 h, and then discharge to obtain a colorless, clear and transparent melamine-formaldehyde modified prepolymer solution.

[0087] (6) Add 5 g of melamine-formaldehyde modified prepolymer solution to the solid intermediate, control the reaction at 40℃, and react for 6 h to obtain microcapsule primary product.

[0088] (7) The microcapsule sample was sieved to form a wet powder, and dried at 40°C for 12 h to obtain a solid product with no obvious microcapsule structure.

[0089] (8) Take 6 g of epoxy resin as the base material, add 9 g of the prepared solid product, and stir to disperse evenly. Coat the obtained mixture onto a release film, press it into a sheet, and cure it in an oven at 60℃ for 1 h to prepare a fire extinguishing sheet.

[0090] Comparative Example 2 The preparation method of the fire extinguishing microcapsule with a double-layered dense structure provided in Comparative Example 2 includes the following steps: (1) Weigh 100 g of perfluorohexanone as the fire extinguishing agent core material and place it in a beaker. Add 5 g of hexafluorobutyl methacrylate, 2 g of acrylic acid, 3 g of methyl methacrylate, 0.03 g of trimethylolpropane triacrylate, and 0.05 g of ABVN. Stir to form a homogeneous core material composite solution.

[0091] (2) Weigh 2 g of sodium perfluorononenoxybenzenesulfonate and dissolve it in 100 g of deionized water to form an emulsion solution.

[0092] (3) Add the core material composite solution to the emulsion solution, control the temperature at 5℃, and stir at 200 rpm for 10 min to form a stable suspension solution.

[0093] (4) Transfer the suspension to a high-pressure reactor, protect it with nitrogen, slowly raise the temperature to 70°C, control the pressure to 2MPa, and react for 3 h to form a dense inner shell, thus obtaining the inner shell solution.

[0094] (5) Add 20 g of melamine and 40 g of formaldehyde aqueous solution (37%) to a three-necked flask, add triethanolamine dropwise until the pH is 8.5, heat in a water bath to 85°C, keep warm and stir for 1.5 h, and then discharge to obtain a colorless, clear and transparent melamine-formaldehyde modified prepolymer solution.

[0095] (6) Add 5 g of melamine-formaldehyde modified prepolymer solution to the inner shell solution, control the reaction at 40℃, and react for 6 h to form the outer shell, thus obtaining the initial product of double-shell microcapsules.

[0096] (7) The initial microcapsule sample was sieved to form a wet powder, and dried at 40°C for 12 h to obtain fire extinguishing microcapsules with a particle size of 150~250 μm.

[0097] (8) Take 6 g of epoxy resin as the base material, add 9 g of the prepared fire extinguishing microcapsules, and stir to disperse evenly. Coat the obtained mixture onto a release film, press it into a sheet, and cure it in an oven at 60℃ for 1 h to prepare a fire extinguishing sheet.

[0098] II. Testing and Analysis I. The fire extinguishing microcapsules prepared in step (7) of Example 1 were observed using a scanning microscope (SEM). The microstructure is as follows: Figure 2 As shown, by Figure 2 It can be seen that the microcapsule shell material prepared in Example 1 has good density and few empty cells, proving that the present invention can prepare fire extinguishing microcapsules with complete and dense microstructure.

[0099] II. The microcapsules prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to performance tests. The test indicators included particle size range, core material ratio (fire extinguishing agent mass ratio), release temperature range (fire extinguishing agent release temperature), 7-day mass loss rate (7-day mass loss percentage at 60°C, simulating short-term storage at higher ambient temperatures), and 1-month mass loss rate (7-day mass loss percentage at 25°C, simulating long-term storage at room temperature). The results are shown in Table 1.

[0100] Table 1. Performance test statistics of microcapsules prepared in the examples and comparative examples.

[0101] As shown in Table 1, firstly, the core material content of the microcapsules prepared in Examples 1-5 is all above 85%, indicating a high content of perfluorinated fire extinguishing agents in the core material; the core material release temperature range is 80-125℃, demonstrating good room temperature storage stability; the mass loss rate after 7 days at 60℃ is less than 3%, and the mass loss rate after 7 days at 25℃ is less than 1%, proving that the microcapsules prepared by the method of this invention have extremely low mass loss whether stored for a short period at higher ambient temperatures or for a long period at room temperature. The stability of the fire extinguishing microcapsules with a double-layer dense structure is significantly improved.

[0102] Secondly, the only difference between Comparative Example 1 and Example 1 is that hexafluorobutyl methacrylate was not added in step (1). That is, Comparative Example 1 only used acrylic monomers for cross-linking reaction in the preparation of the inner shell, while it was impossible to form an obvious microcapsule structure in Comparative Example 1. This proves that introducing fluorinated acrylic monomers into the monomers of the inner shell can significantly improve the compatibility with perfluorinated fire extinguishing agents and help to form a stable microcapsule structure.

[0103] Furthermore, the only difference between Comparative Example 2 and Example 1 is that 1H,1H,2H,2H-perfluoro-1-hexanol was not added in step (5). That is, Comparative Example 2 did not use perfluoropolyol for modification during the preparation of the outer shell, which significantly reduced the release temperature range of the microcapsules prepared in Comparative Example 2. At the same time, the mass loss rate at 60°C for 7 days and the mass loss rate at 25°C for 7 days were significantly improved. This proves that introducing perfluoropolyol into the monomer of the outer shell for modification can not only significantly improve the strength and density of the wall material, but also significantly improve the compatibility between the outer and inner shells, improve the overall density and temperature resistance, and achieve a significant reduction in mass loss.

[0104] III. The fire extinguishing performance of the fire extinguishing discs prepared in Examples 1-5 and Comparative Examples 1-2 was tested using two methods: Method 1 involved placing a windproof lighter 2 cm away from the fire extinguishing disc, igniting it, and recording the time it took for the flame to extinguish; Method 2 involved cutting the fire extinguishing disc into 100 cm * 50 cm * 2 cm pieces, placing them in a 12 L box containing a combustion source (n-heptane / ethanol), and ensuring the box had ventilation holes, while recording the time it took for the combustion source flame to extinguish. The specific fire extinguishing test results for each fire extinguishing disc are shown in Table 2.

[0105] Table 2. Statistical table of fire extinguishing performance tests of the fire extinguishing discs prepared in the examples and comparative examples.

[0106] As shown in Table 1, Comparative Example 1, which does not contain fluorinated acrylic monomers, cannot prepare complete and dense fire extinguishing microcapsules, and therefore cannot extinguish fires. In contrast, the fire extinguishing capsules in Comparative Example 2, which do not contain perfluorinated polyols as modifiers, meet the fire extinguishing performance standards, but have poor temperature resistance and cannot be used for a long time.

[0107] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0108] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A fire extinguishing microcapsule with a double-layered dense structure, characterized in that, It includes a core material, an inner shell, and an outer shell, which are sequentially arranged from the inside out; The core material is a perfluorinated fire extinguishing agent, the inner shell is made of modified acrylic resin formed by the interfacial polymerization reaction of fluorinated acrylic monomers, acrylic monomers and acrylic crosslinking agents, and the outer shell is made of modified melamine-formaldehyde resin formed by the reaction of melamine, formaldehyde and perfluorinated polyols.

2. The fire extinguishing microcapsule with a double-layered dense structure according to claim 1, characterized in that, The perfluoro extinguishing agent is at least one of perfluorohexanone, methyl perfluoroisobutyl ether, difluorotrichloroethane, 2-iodine-heptafluoropropane, perfluorotriethylamine, tetrafluorodibromoethane, difluorobromochloromethane, difluorodichloroethane, 1-iodine-heptafluoropropane, and trifluorotrichloroethane. The fluorinated acrylic monomer is at least one of hexafluorobutyl acrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl acrylate, tridecafluorooctyl methacrylate, perfluoroalkyl ethyl acrylate, and perfluoroalkyl ethyl methacrylate. The acrylic monomer is at least one selected from acrylic acid, methacrylic acid, methyl methacrylate, ethyl methacrylate, hydroxyethyl acrylate, and methyl acrylate. The acrylic crosslinking agent is at least one of the following: acrylic crosslinking agent, triallyl isocyanurate, trimethylolpropane triacrylate, glycidyl methacrylate, and diacetone acrylamide; The perfluorinated polyol is at least one selected from 1H,1H,2H,2H-perfluoro-1-hexanol, 1H,1H,2H,2H-perfluoro-1-dodecyl alcohol, 1H,1H,2H,2H-perfluoro-1-decyl alcohol, 1H,1H,2H,2H-perfluoro-1-octanol, and pentaerythritol tris(3-perfluorohexylpropyl) ether.

3. The fire extinguishing microcapsule with a double-layered dense structure according to claim 1, characterized in that, The mass ratio of the perfluorinated fire extinguishing agent to the fluorinated acrylic monomer is 1:0.05~0.1, the mass ratio of the perfluorinated fire extinguishing agent to the acrylic monomer is 1:0.05~0.1, and the mass percentage of the acrylic crosslinking agent in the sum of the fluorinated acrylic monomer and the acrylic monomer is 0.3~0.8%. The mass ratio of the perfluorinated fire extinguishing agent to melamine is 1:0.05~1, the mass ratio of melamine to formaldehyde is 1.05~1.4:1, and the mass ratio of melamine to perfluorinated polyol is 1:0.05~0.

1.

4. The fire extinguishing microcapsule with a double-layered dense structure according to claim 1, characterized in that, The fire extinguishing microcapsules with a double-layered dense structure have a particle size of 10–300 μm, and the core material release temperature is 80–140°C.

5. A method for preparing a fire extinguishing microcapsule with a double-layered dense structure as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1, according to the formula, the perfluorinated fire extinguishing agent, fluorinated acrylic monomer, acrylic monomer, acrylic crosslinking agent and initiator are stirred to obtain the core material composite solution; S2, add a fluorinated emulsifier to water and mix well to obtain an emulsion solution; S3, add the core material composite solution to the emulsion solution and stir continuously until a stable suspension is formed; S4, the suspension is placed in a nitrogen atmosphere, the temperature is controlled at 60~80℃ and the pressure is 2~5 MPa, and the reaction forms an inner shell to obtain an inner shell solution; S5, melamine, formaldehyde, perfluorinated polyol, triethanolamine and deionized water are mixed and reacted according to the formula, the temperature is controlled at 60~90℃ and the pH value is adjusted to 8~9.5, the mixing reaction time is 1.5~3 h, and melamine-formaldehyde modified prepolymer solution is obtained. S6, the melamine-formaldehyde modified prepolymer solution is added to the inner shell solution, and the mixture is stirred to react, thus obtaining the initial product of the double-shell microcapsule. S7. The microcapsule sample is dried to obtain the fire extinguishing microcapsule with a double-layered dense structure.

6. The method for preparing fire extinguishing microcapsules with a double-layered dense structure according to claim 5, characterized in that, In step S1, the amount of initiator added is 0.5-3% of the sum of the mass of the fluorinated acrylic monomer and the acrylic monomer, and the initiator is at least one of BPO, ABVN, AIBN, and tert-butyl peroxide. In step S2, the amount of fluorinated emulsifier added is 1% to 5% of the mass of the perfluorinated fire extinguishing agent. The fluorinated emulsifier is at least one of sodium perfluorononenoxybenzenesulfonate, potassium perfluorobutylsulfonate, FC-4 fluorocarbon surfactant, FC-201 zwitterionic fluorocarbon surfactant, and perfluorohexyl ethyl polyoxyethylene ether.

7. The method for preparing fire extinguishing microcapsules with a double-layered dense structure according to claim 5, characterized in that, In step S3, when preparing the suspension solution, the temperature is controlled at 0~20℃ and the stirring speed is 100~1500 rpm.

8. The method for preparing fire extinguishing microcapsules with a double-layered dense structure according to claim 5, characterized in that, In step S4, when preparing the inner shell solution, the temperature is controlled at 60~80℃ and the pressure is controlled at 2~5 MPa.

9. The method for preparing fire extinguishing microcapsules with a double-layered dense structure according to claim 5, characterized in that, In step S6, when preparing the initial product of the double-shell microcapsules, the reaction temperature is 20~40℃ and the reaction time is 6~12 h.

10. The method for preparing fire extinguishing microcapsules with a double-layered dense structure according to claim 5, characterized in that, In step S7, the drying temperature is 30–45°C, and the drying time is 12–24 h.

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