Fire extinguishing microcapsules, methods of making the same, and fire extinguishing devices

Abstract

The application belongs to the technical field of fire-fighting materials, and discloses fire-extinguishing microcapsules, a preparation method thereof and a fire-extinguishing device. The fire-extinguishing microcapsules comprise: a gas cavity core filled with gas; a liquid phase layer wrapping the gas cavity core, the liquid phase layer comprising an organic fire extinguishing agent; and a solid high polymer shell layer wrapping the liquid phase layer. Thus, the gas cavity core serves as a compressible thermodynamic buffer layer, can absorb volume expansion work when the organic fire extinguishing agent is vaporized by heat, delays pressure accumulation inside the microcapsules, thereby improving the rupture temperature of the microcapsules and significantly widening the processing temperature window of the microcapsules.

Description

Technical Field

[0001] This application relates to the field of fire protection materials technology, specifically to fire extinguishing microcapsules, their preparation methods, and fire extinguishing devices. Background Technology

[0002] Fire extinguishing microcapsules commonly use fluorinated extinguishing agents such as perfluorohexanone (C6F) as liquid core materials. 12 Perfluorohexanone (PFH), with a boiling point of 49.2℃, is a highly efficient and environmentally friendly fire extinguishing agent. Microencapsulation is a key technology for solving the storage challenges posed by its low boiling point and high volatility, and for achieving targeted, temperature-sensitive release. Existing perfluorohexanone microcapsules mostly employ a solid liquid core structure, which has the following technical drawbacks: First, the processing window is narrow: the saturated vapor pressure of perfluorohexanone at room temperature is approximately 0.05 MPa. As the temperature rises, the pressure inside the microcapsules increases rapidly, and solid microcapsules typically rupture at around 110°C. During injection molding of thermoplastic or thermosetting plastics, even if the mold temperature is controlled at 80-120°C, shear heat can still cause local temperatures to exceed the microcapsule's tolerance limit, leading to premature microcapsule rupture and leakage of the extinguishing agent.

[0003] Second, the response temperature is not adjustable: the rupture temperature of solid microcapsules is determined by the inherent properties of the shell material, which cannot adapt to the differentiated needs of different scenarios (such as the initial temperature of battery thermal runaway is about 120-140℃, and the temperature in open flame scenarios is above 180℃).

[0004] Third, shell reinforcement is costly: while increasing the shell thickness or the degree of cross-linking of the shell can improve the heat resistance of solid microcapsules, it will reduce the loading of extinguishing agent from 85% to below 55%, increase the brittleness of the microcapsules, delay the response, and make it difficult to balance high charge loading and wide processing window.

[0005] Fourth, poor adaptability to injection molding: Researchers have not considered the secondary processing requirements such as blending existing solid microcapsules with thermoplastic or thermosetting plastics for injection molding, making it difficult for solid microcapsules to be used for mass production of complex structural parts such as battery tab covers.

[0006] In summary, there is an urgent need in this field for a fire extinguishing microcapsule that can achieve a controllable increase in burst temperature while maintaining a high fire extinguishing agent loading, significantly widening the processing temperature window, and can be blended and injection molded with thermoplastic or thermosetting plastics. Summary of the Invention

[0007] This application aims to at least partially alleviate or resolve at least one of the aforementioned problems.

[0008] In one aspect of this application, a fire extinguishing microcapsule is provided, comprising: a gas cavity core filled with gas; a liquid phase layer encapsulating the gas cavity core, the liquid phase layer comprising an organic fire extinguishing agent; and a solid polymer shell encapsulating the liquid phase layer. Thus, the gas cavity core, acting as a compressible thermodynamic buffer layer, can absorb the work done by volume expansion when the organic fire extinguishing agent is heated and vaporized, delaying pressure accumulation inside the microcapsule, thereby increasing the rupture temperature of the microcapsule and significantly widening the processing temperature window of the microcapsule.

[0009] In some embodiments, the volume of the gas cavity core accounts for 5%-30% of the total volume of the fire extinguishing microcapsule; and / or, the gas is one or more combinations of nitrogen, argon, carbon dioxide, and air. This is beneficial for further increasing the rupture temperature of the microcapsule and widening its processing temperature window.

[0010] In some embodiments, the fire extinguishing microcapsules satisfy at least one of the following conditions: the organic fire extinguishing agent includes one or more of perfluorohexanone, perfluorohexane, perfluoroheptane, and perfluorooctane; the volume of the liquid phase layer accounts for 65%-90% of the total volume of the fire extinguishing microcapsules; and the mass of the liquid phase layer accounts for more than 75% of the total mass of the fire extinguishing microcapsules. This is beneficial for improving the fire extinguishing performance of the fire extinguishing microcapsules.

[0011] In some embodiments, the solid polymer shell comprises one or more of polyurethane acrylate, epoxy acrylate, polyester acrylate, polyurea, and polyurethane; and / or, the thickness of the solid polymer shell is 1 μm-20 μm. Thus, the outer shell of the fire extinguishing microcapsule has a certain strength, which is beneficial for improving the burst temperature and processing performance of the fire extinguishing microcapsule.

[0012] In some embodiments, the particle size of the fire extinguishing microcapsules is 50 μm-500 μm; and / or, the particle size distribution coefficient (CV) of the fire extinguishing microcapsules is ≤10%. This is beneficial for further improving the overall performance of the fire extinguishing microcapsules.

[0013] In another aspect of this application, this application provides a method for preparing the aforementioned fire extinguishing microcapsules, using a quadriaxial coaxial flow focusing microfluidic device to prepare the fire extinguishing microcapsules, the contents of which, from the inside out, are as follows: First phase: gas; Second phase: Organic fire extinguishing agent liquid; Third phase: polymer shell precursor solution; Fourth phase: Driving phase aqueous solution; The first to fourth phases form a gas-liquid-liquid-liquid coaxial laminar flow within the flow focusing channel, and are solidified in situ to form the fire extinguishing microcapsules.

[0014] Therefore, a simple method can be used to obtain fire extinguishing microcapsules with an air cavity core, which have a high burst temperature and good processing performance.

[0015] In some embodiments, the method for preparing the fire extinguishing microcapsules described above satisfies at least one of the following conditions: the flow rate of the first phase is 0.1 mL / h-5.0 mL / h; the flow rate of the second phase is 1.0 mL / h-20.0 mL / h; the flow rate of the third phase is 2.0 mL / h-30.0 mL / h; the flow rate of the fourth phase is 50 mL / h-500 mL / h; the flow rate ratio of the first phase to the second phase is 0.05-0.50; the diameter of the flow focusing channel is 100 μm-1000 μm; the gas is dried and filtered before injection; the dew point of the gas is below -40°C; the driving phase aqueous solution comprises polyvinyl alcohol, and the mass content of polyvinyl alcohol in the driving phase aqueous solution is 0.5%-5%.

[0016] In some embodiments, the method for preparing the fire extinguishing microcapsules described above satisfies one of the following conditions: the polymer shell precursor solution includes a photoinitiator, the first to fourth phases form a gas-liquid-liquid-liquid coaxial laminar flow in the flow focusing channel, and the fire extinguishing microcapsules are formed by in-situ photocuring; the polymer shell precursor solution includes a polyisocyanate, and the driving phase aqueous solution includes a polyamine and / or a polyol.

[0017] In another aspect, this application provides a fire extinguishing device comprising the aforementioned fire extinguishing microcapsules. Therefore, this fire extinguishing device possesses all the features and advantages of the aforementioned fire extinguishing microcapsules, which will not be repeated here.

[0018] In some embodiments, the fire extinguishing device includes a substrate and the fire extinguishing microcapsules, wherein the fire extinguishing microcapsules are dispersed in the substrate. The fire extinguishing device is prepared by blending the fire extinguishing microcapsules with thermoplastic or thermosetting plastics, followed by injection molding; wherein the processing temperature is ≤280℃. This method can be used to prepare complex components such as battery tabs. After processing, the fire extinguishing microcapsules can maintain structural integrity, thereby providing thermal runaway protection. Attached Figure Description

[0019] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 A schematic diagram of the structure of a fire extinguishing microcapsule according to an embodiment of this application is shown; Figure 2 This shows a schematic diagram of the structure of a four-axis coaxial flow focusing microfluidic device according to an embodiment of the present application; Figure 3 The rupture temperature variation curves of fire extinguishing microcapsules with different core volume fractions of air chambers are shown. Figure 4 Scanning electron microscope image of the air-cavity microcapsules prepared in Example 1; Figure 5 A cross-sectional optical microscope image of the air-cavity microcapsule prepared in Example 1; Figure 6 Photograph of the battery tab cover injection molded part containing microcapsules prepared in Example 4.

[0020] Explanation of reference numerals in the attached figures: 10: Fire extinguishing microcapsule; 11: Gas cavity core; 12: Liquid phase layer; 13: Solid polymer shell layer; 20: Quad-axis coaxial flow focusing microfluidic device; 21: First phase inlet; 22: Second phase inlet; 23: Third phase inlet; 24: Fourth phase inlet; 25: Flow focusing channel; 26: Outlet; 27: Ultraviolet light source. Detailed Implementation

[0021] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0022] In one aspect of this application, a fire extinguishing microcapsule is provided. In some embodiments, reference is made to... Figure 1 The fire extinguishing microcapsule 10 includes a gas cavity core 11, a liquid phase layer 12, and a solid polymer shell 13. The gas cavity core 11 is filled with gas; the liquid phase layer 12 encloses the gas cavity core 11 and includes an organic fire extinguishing agent; the solid polymer shell 13 encloses the liquid phase layer.

[0023] In traditional solid microcapsules, the vapor pressure generated by the thermal vaporization of the liquid extinguishing agent directly acts on the shell wall. The pressure increases exponentially with temperature, quickly reaching the shell's rupture threshold, resulting in a low rupture temperature for solid microcapsules. This application introduces a gas-filled core at the center of the microcapsule, transforming the internal system into a gas-liquid two-phase system. The gas-filled core acts as a compressible buffer layer. In the initial stage of organic extinguishing agent vaporization, the core absorbs the work done by volume expansion through isothermal compression, significantly reducing the slope of the total pressure increase curve. Simultaneously, the gas-liquid interface, as a pre-stored vaporization nucleus, promotes mild heterogeneous nucleation, preventing sudden increases in local pressure. Therefore, the extinguishing microcapsule of this application requires a higher temperature to reach the shell's rupture threshold, enabling a controllable increase in rupture temperature. Compared with simply thickening the shell material, the air cavity structure of this application can increase the microcapsule rupture temperature while maintaining a thinner shell thickness and a higher extinguishing agent loading (mass content of extinguishing agent), resulting in a shorter heat transfer path and a smaller response delay. The air cavity core can also absorb mechanical impact energy and improve the processing toughness of the extinguishing microcapsule.

[0024] In some embodiments, the volume of the air cavity core 11 accounts for 5%-30% of the total volume of the fire extinguishing microcapsule 10. For example, the volume of the air cavity core 11 accounts for 5%, 8%, 12%, 15%, 20%, 22%, 25%, 27%, 30% of the total volume of the fire extinguishing microcapsule 10. This helps to buffer the pressure generated during the vaporization of the organic fire extinguishing agent, thereby helping to further increase the rupture temperature of the fire extinguishing microcapsule.

[0025] In some embodiments, the gas filling the gas cavity core 11 can be one or a combination of nitrogen, argon, carbon dioxide, and air. The gas cavity core formed by these gases can buffer pressure, thereby increasing the rupture temperature of the fire extinguishing microcapsules. Nitrogen, argon, and carbon dioxide can suppress combustion; using these gases to form the gas cavity core further enhances the fire extinguishing effect. Air is less expensive; using air to form the gas cavity core can reduce the manufacturing cost of the fire extinguishing microcapsules.

[0026] In some embodiments, the liquid phase layer 12 may be composed of an organic fire extinguishing agent, which is beneficial to further enhance the fire extinguishing effect of the fire extinguishing microcapsules.

[0027] In some embodiments, the organic fire extinguishing agent may include one or more of perfluorohexanone, perfluorohexane, perfluoroheptane, and perfluorooctane. All of the above fire extinguishing materials are liquid at room temperature and have suitable boiling points, making them suitable for use as fire extinguishing agents encapsulated in microcapsules.

[0028] In some embodiments, the volume of the liquid phase layer 12 can account for 65%-90% of the total volume of the fire extinguishing microcapsule 10. For example, the volume of the liquid phase layer 12 can account for 65%, 70%, 75%, 80%, 85%, 90% of the total volume of the fire extinguishing microcapsule 10. Thus, the liquid phase layer can provide more fire extinguishing agent, which is beneficial to improving the fire extinguishing effect of the fire extinguishing microcapsule.

[0029] In some embodiments, the mass of the liquid phase layer 12 can account for more than 75% of the total mass of the fire extinguishing microcapsule 10. For example, the mass of the liquid phase layer 12 can account for 75%, 78%, 80%, 82%, 85%, 87%, 90%, etc. of the total mass of the fire extinguishing microcapsule 10. Therefore, the high content of organic fire extinguishing agent in the fire extinguishing microcapsule is beneficial for further improving the fire extinguishing effect.

[0030] In some embodiments, the mass of the liquid phase layer 12 may account for 75%-85% of the total mass of the fire extinguishing microcapsule 10.

[0031] In some embodiments, the solid polymer shell 13 may include one or more of polyurethane acrylate, epoxy acrylate, polyester acrylate, polyurea, and polyurethane. These materials possess good thermal stability and mechanical strength; encapsulating the liquid phase layer and the gas cavity core with them allows the fire extinguishing microcapsules to maintain good stability under normal temperature and pressure or other storage conditions.

[0032] In some embodiments, reference Figure 1 The thickness d of the solid polymer shell 13 can be 1μm-20μm, for example, d can be 1μm, 3μm, 5μm, 7μm, 10μm, 12μm, 15μm, 18μm, 20μm, etc. The thinner solid polymer shell allows for faster heat transfer and a smaller delay in the microcapsule rupture response; furthermore, it helps to increase the mass ratio of the liquid phase layer in the fire extinguishing microcapsules, thereby further enhancing the fire extinguishing effect.

[0033] In some embodiments, reference Figure 1 The particle size D of the fire extinguishing microcapsule 10 can be 50 μm-500 μm, for example, D can be 50 μm, 80 μm, 100 μm, 150 μm, 300 μm, 400 μm, 500 μm, etc. It should be noted that the particle size D of the fire extinguishing microcapsule refers to its diameter. The fire extinguishing microcapsule can be a regular sphere or an approximately spherical shape, and its particle size can be obtained by measuring the size of the fire extinguishing microcapsule in a scanning electron microscope image.

[0034] In some embodiments, reference Figure 1The gas cavity core 11, liquid phase layer 12 and solid polymer shell layer 13 can be a concentric three-phase structure. The geometric centers of the three phase structures can coincide or basically coincide. The gas cavity core 11 is located at the center of the fire extinguishing microcapsule 10 and is filled with gas. The liquid phase layer 12 surrounds the gas cavity core 11 and is a hollow sphere structure with a certain thickness. The outermost layer is the solid polymer shell layer 13, which is also a hollow sphere structure with a certain thickness.

[0035] In other embodiments, the gas cavity core 11, the liquid phase layer 12, and the solid polymer shell 13 do not have to be a concentric three-phase structure, as long as the gas cavity core 11 is wrapped by the liquid phase layer 12 and the liquid phase layer 12 is wrapped by the solid polymer shell 13.

[0036] In some embodiments, the particle size distribution coefficient (CV) of the fire extinguishing microcapsule 10 is ≤10%, for example, the particle size distribution coefficient (CV) of the fire extinguishing microcapsule 10 can be 3%-10%. The fire extinguishing microcapsule has a uniform particle size distribution, and most microcapsules can rupture at the same or similar temperature to release organic fire extinguishing agents, thereby alleviating or even solving the problem of premature rupture or delayed response of microcapsules, and thus improving the fire extinguishing effect.

[0037] In another aspect of this application, a method for preparing the aforementioned fire extinguishing microcapsules is provided. In some embodiments, reference is made to... Figure 2 Fire extinguishing microcapsules can be prepared using a four-axis coaxial flow focusing microfluidic device 20. This device includes a first phase inlet 21, a second phase inlet 22, a third phase inlet 23, a fourth phase inlet 24, a flow focusing channel 25, and an outlet 26. The first phase inlet 21 is connected to a gas source, the second phase inlet 22 is connected to a storage tank containing an organic fire extinguishing agent, the third phase inlet 23 is connected to a storage tank containing a polymer shell precursor solution, and the fourth phase inlet 24 is connected to a storage tank containing a driving phase aqueous solution.

[0038] refer to Figure 2 From the inside out, they are: First phase: gas, which is introduced into the device through the first phase inlet 21; Second phase: Organic fire extinguishing agent liquid, which is introduced into the device through second phase inlet 22; The third phase is a polymer shell precursor solution, which is introduced into the device through the third phase inlet 23. Fourth phase: A driving phase aqueous solution, which is introduced into the device through the fourth phase inlet 24; The first to fourth phases form a gas-liquid-liquid-liquid coaxial laminar flow within the flow focusing channel 25. The first, second, and third phases form microdroplets, which are solidified in situ to form fire extinguishing microcapsules. The products can be collected from the outlet 26.

[0039] The fire extinguishing microcapsules prepared using the above method have high bursting temperature and strong fire extinguishing ability; the four-axis coaxial flow focusing microfluidic device has high preparation precision and can realize online control of the air chamber size. The prepared fire extinguishing microcapsules have uniform particle size and can be mass-produced.

[0040] In this application, the volume fraction of the gas cavity core and the liquid phase layer can be controlled by adjusting the flow rate ratio of the first phase to the second phase. In some embodiments, the flow rate ratio of the first phase to the second phase can be 0.05-0.50, for example, 0.05, 0.10, 0.20, 0.30, 0.40, 0.50, etc. Thus, the gas cavity core and the liquid phase layer have a suitable volume ratio, allowing the gas cavity core to act as a good buffer, which is beneficial for increasing the rupture temperature of the fire extinguishing microcapsules; the higher volume fraction of the liquid phase layer results in a higher content of fire extinguishing agent in the microcapsules, which is beneficial for further improving the fire extinguishing effect.

[0041] In some embodiments, the flow rate of the first phase can be 0.1 mL / h to 5.0 mL / h, for example, the flow rate of the first phase can be 0.1 mL / h, 0.3 mL / h, 0.5 mL / h, 1 mL / h, 3 mL / h, 5.0 mL / h, etc.

[0042] In some embodiments, the flow rate of the second phase can be 1.0 mL / h to 20.0 mL / h. For example, the flow rate of the second phase can be 1.0 mL / h, 3.0 mL / h, 5.0 mL / h, 8.0 mL / h, 10.0 mL / h, 12.0 mL / h, 15.0 mL / h, 17.0 mL / h, 20.0 mL / h, etc.

[0043] In some embodiments, the flow rate of the third phase can be 2.0 mL / h to 30.0 mL / h. For example, the flow rate of the third phase can be 2.0 mL / h, 5.0 mL / h, 8.0 mL / h, 12.0 mL / h, 16.0 mL / h, 20.0 mL / h, 23.0 mL / h, 27.0 mL / h, 30.0 mL / h, etc.

[0044] In some embodiments, the flow rate of the fourth phase can be 50 mL / h to 500 mL / h. For example, the flow rate of the fourth phase can be 50 mL / h, 70 mL / h, 100 mL / h, 150 mL / h, 280 mL / h, 400 mL / h, 500 mL / h, etc.

[0045] When the flow rates of each phase are within the above range, it is beneficial to form fire extinguishing microcapsules with a suitable volume ratio of gas cavity core, liquid phase layer, and solid polymer shell layer.

[0046] In some embodiments, the volume fraction of the gas cavity core can be 5%-30% and the volume fraction of the liquid phase layer can be 65%-90% by adjusting the flow rates of the first phase and the second phase. Figure 3 The rupture temperature curves of perfluorohexanone fire extinguishing microcapsules with different core volume fractions (0%, 10%, 20%, and 30%) are presented. The thickness of the solid polymer shell in the microcapsules is the same for all core volume fractions. The horizontal axis represents the core volume fraction (%), and the vertical axis represents the rupture temperature (°C). The data show a positive correlation between the rupture temperature of the microcapsules and the core volume fraction. The rupture temperature of the microcapsules increases linearly from 110°C for the solid structure to 175°C for the 30% core volume fraction, verifying the quantitative control of the rupture temperature by the core volume fraction.

[0047] In some embodiments, reference Figure 2 The diameter L of the flow focusing channel 25 can be 100μm-1000μm, for example, the diameter L of the flow focusing channel 25 can be 100μm, 300μm, 500μm, 800μm, 1000μm, etc. This is beneficial for obtaining fire extinguishing microcapsules with suitable particle size.

[0048] In some embodiments, the gas may be dried and filtered before injection. Drying can reduce the moisture content in the gas, and filtration can remove some impurities (such as dust) that may be present in the gas, thereby reducing the adverse effects of moisture and impurities on the preparation process of the fire extinguishing microcapsules and the performance of the final microcapsules.

[0049] In some embodiments, the dew point of the gas can be below -40°C. A low dew point and low moisture content in the gas are beneficial for the preparation and performance improvement of fire extinguishing microcapsules.

[0050] In some embodiments, the driving phase aqueous solution may include polyvinyl alcohol, thereby facilitating the formation of a layered coating structure. In some embodiments, the mass content of polyvinyl alcohol in the driving phase aqueous solution may be 0.5%-5%.

[0051] In some embodiments, the polymer shell precursor solution may include a photoinitiator, the first to fourth phases form a gas-liquid-liquid-liquid coaxial laminar flow within the flow focusing channel, and the first to third phases form microdroplets, which can be in-situ photocured to form fire extinguishing microcapsules. (Reference) Figure 2 In some embodiments, the quad-axis coaxial flow focusing microfluidic device 20 may also include an ultraviolet light source 27, which uses ultraviolet light to irradiate microdroplets, causing the polymer shell precursor solution to undergo a polymerization reaction to form a polymer shell.

[0052] In some embodiments, the wavelength of the ultraviolet light can be 200-400 nm, for example, an ultraviolet lamp with a main wavelength of 365 nm can be used to irradiate the microdroplets; the intensity of the ultraviolet light can be 10-100 mW / cm². 2 The irradiation time can be 0.1-10 seconds.

[0053] For the components of the precursor solutions of polyurethane acrylate, epoxy acrylate, and polyester acrylate, those skilled in the art can select them according to actual needs. For example, a photocurable prepolymer solution containing a photoinitiator can be used. In some embodiments, the mass content of the photoinitiator in the photocurable prepolymer solution can be 0.5%-5%, thereby allowing the prepolymer to fully polymerize and form a solid polymer shell. In other embodiments, the precursor solution can be a photocurable monomer solution containing a photoinitiator, or the precursor solution can simultaneously contain a photoinitiator, a photocurable prepolymer, and a photocurable monomer.

[0054] In some embodiments, the polymer shell precursor solution includes some non-photocurable polymeric materials, such as interfacially polymerized oil-phase monomers, which can form polyurea / polyurethane shell materials, such as toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI) and other polyisocyanate materials; polyamine and / or polyol aqueous-phase monomer materials, such as ethylenediamine (EDA), hexamethylenediamine, diethylenetriamine, etc., are dissolved in the driving phase material; at the water-oil interface, the polyamine and / or polyol can react with the isocyanate to generate polyurea and / or polyurethane.

[0055] In another aspect, this application provides a fire extinguishing device comprising the aforementioned fire extinguishing microcapsules. Thus, the fire extinguishing device can be used for fire extinguishing.

[0056] In some embodiments, the fire extinguishing device can be a fire extinguishing patch, which can be prepared into a fire extinguishing patch by combining fire extinguishing microcapsules with a patch substrate using conventional methods.

[0057] In some embodiments, the fire extinguishing device can be a component with a complex structure, for example, the fire extinguishing device can be a battery electrode cover.

[0058] In some embodiments, the fire extinguishing device may include a substrate and fire extinguishing microcapsules, with the microcapsules dispersed in the substrate. The fire extinguishing device is prepared by blending the fire extinguishing microcapsules with thermoplastic or thermosetting plastics, followed by injection molding; wherein the processing temperature is ≤280℃. During this preparation process, the fire extinguishing microcapsules can maintain good structural stability. After injection molding, the structural integrity rate of the fire extinguishing microcapsules is ≥90%, meaning that more than 90% of the fire extinguishing microcapsules in the substrate can maintain structural integrity. Using this fire extinguishing device results in high sensitivity, low response delay, and good fire extinguishing effect.

[0059] In some embodiments, after injection molding, the rupture temperature of the fire extinguishing microcapsule can be maintained at more than 95% of the rupture temperature of the fire extinguishing microcapsule before injection molding.

[0060] In summary, the fire extinguishing microcapsules of this application have the following beneficial effects: (1) Controllable increase in rupture temperature: Taking perfluorohexanone as an extinguishing agent as an example, under the condition that the charge is ≥75% (the mass of the liquid phase layer accounts for more than 75% of the total mass of the extinguishing microcapsule), the gas cavity core is used as a buffer layer, which can increase the rupture temperature of the extinguishing microcapsule from 110℃ of the traditional solid structure to an adjustable range of 140-180℃, and broaden the processing temperature window to more than 100℃; (2) Maintaining a high loading capacity: By replacing part of the liquid core material with an air chamber instead of increasing the thickness of the shell material, the loading capacity of the extinguishing agent can be maintained at 75%-85%; (3) Excellent response characteristics: The shell thickness is 1μm-20μm, the heat transfer path is short, the heat transfer is fast, and the rupture response delay is small; (4) Strong processing adaptability: The air cavity structure can absorb shear heat and mechanical impact, and can be blended with thermoplastic or thermosetting plastics to injection mold complex parts; (5) High preparation precision: Quad-axis microfluidic technology can realize online control of air cavity size, and the particle size of fire extinguishing microcapsules is uniform, which can be mass-produced.

[0061] The present application will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments below are merely illustrative and do not limit the scope of the present application in any way. Furthermore, in the following embodiments, unless otherwise specified, the materials and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the later embodiments, conditions and methods known in the art can be used for processing.

[0062] Example 1 use Figure 2 The microfluidic device shown is used to prepare microcapsules with a gas cavity core (gas cavity core volume fraction of 10.2%). (1) Preparation of shell material solution: Mix polyurethane acrylate prepolymer and photoinitiator 1173 at a mass ratio of 97:3, stir evenly, and prepare a photocurable prepolymer solution.

[0063] (2) Preparation of driving phase: Dissolve PVA (polyvinyl alcohol) powder in deionized water to prepare a PVA aqueous solution with a concentration of 2wt%.

[0064] (3) Microfluidic control equipment: A four-axis coaxial flow focusing microfluidic device is used, and the parameters of each phase are as follows: First phase (nitrogen): flow rate 0.5 mL / h; Second phase (perfluorohexanone): flow rate 5.0 mL / h; Third phase (photocurable prepolymer solution): flow rate 8.0 mL / h; Fourth phase (PVA aqueous solution): flow rate 200 mL / h; The four phases form a gas-liquid-liquid-liquid coaxial laminar flow within the flow focusing channel (500 μm in diameter). The droplets are irradiated with ultraviolet light (dominant wavelength 365 nm, intensity 50 mW / cm²) at the channel exit. 2 (Irradiation time is 2 seconds) Solidify in situ and collect the product.

[0065] (4) Post-processing: The collected microcapsules were washed three times with deionized water to remove residual PVA on the surface, and dried under vacuum at 40°C for 4 hours to obtain microcapsule products with air cavity cores.

[0066] The microcapsules of Example 1 were tested, and the test results are recorded in Table 1.

[0067] Table 1

[0068] It should be noted that in the tables corresponding to Example 1 and other examples, the drug loading refers to the mass content of the liquid phase layer (perfluorohexanone) in the microcapsule.

[0069] The SEM image of the fire extinguishing microcapsules prepared in Example 1 is shown below. Figure 4 The magnification is 500x. (From...) Figure 4 As can be seen, the microcapsules are regular spherical, with smooth surfaces without depressions, uniform particle size distribution, and no adhesion, indicating that the quadriaxial microfluidic preparation process is stable and controllable.

[0070] A cross-sectional optical microscope image of the fire extinguishing microcapsules prepared in Example 1 is shown below. Figure 5 The three concentric structures of the central air cavity (dark circular area), the outer perfluorohexanone liquid phase layer (transparent ring area), and the outermost polymer shell layer (light-colored boundary) are clearly visible. The air cavity is located at the geometric center, which verifies that the structural design of the fire extinguishing microcapsule proposed in this application is feasible.

[0071] Example 2 use Figure 2 The microfluidic device shown was used to prepare microcapsules with a gas cavity core (gas cavity volume fraction of 24.8%). Adjust the flow rates from the first to the fourth phase: First phase (nitrogen): flow rate 2.0 mL / h; Second phase (perfluorohexanone): flow rate 6.0 mL / h; Third phase (photocurable prepolymer solution): flow rate 10.0 mL / h; Fourth phase (PVA aqueous solution): flow rate 250 mL / h; The remaining conditions are the same as in Example 1.

[0072] The microcapsules of Example 2 were tested, and the test results are recorded in Table 2.

[0073] Table 2

[0074] Compared with Example 1, the proportion of the gas cavity core in Example 2 is increased, and the rupture temperature of the microcapsule is increased by 26°C, which verifies the quantitative control effect of the gas cavity core volume fraction on the rupture temperature.

[0075] Example 3 Microcapsules were prepared according to the steps of Example 1. The difference from Example 1 is that the first phase in Example 3 was replaced with air, while the other conditions were the same as in Example 1.

[0076] The microcapsules of Example 3 were tested, and the test results are recorded in Table 3.

[0077] Table 3

[0078] Compared with Example 1, changing only the composition of the first phase gas has no significant effect on the rupture temperature of the microcapsules.

[0079] Example 4 Battery tab cover injection molding verification: The air-cavity microcapsules prepared in Example 1 (with an air-cavity volume fraction of 10.2% and a rupture temperature of 142°C) were blended with silicone rubber at a mass ratio of 20:80, granulated by a twin-screw extruder, and injection molded into battery electrode covers.

[0080] The injection molding process parameters are as follows: Barrel temperature: 260℃ (front section) / 270℃ (middle section) / 280℃ (rear section); Mold temperature: 100℃; Injection pressure: 80 MPa; Holding pressure: 60MPa; Cooldown time: 15 seconds.

[0081] The battery electrode covers were observed and their performance was tested. The results are as follows: Earcup appearance: intact, no bubbles, no deformation, no silver streaks (see Figure 6 ); Surface microcapsule integrity: Random samples were cut and observed, and more than 95% of the microcapsules maintained structural integrity with no extinguishing agent leakage; Microcapsule rupture temperature (sampled after injection molding): 138℃, retention rate 97% (retention rate = rupture temperature after injection molding / rupture temperature before injection molding × 100%).

[0082] Flame retardant rating of earcups: UL 94 V-0.

[0083] Example 4 demonstrates that the air-cavity microcapsules provided by the present invention can withstand injection molding temperature and shearing action, and are suitable for mass production of complex structural parts.

[0084] Comparative Example 1 use Figure 2 The microfluidic device shown is used to prepare solid microcapsules (without gas chambers). Specifically, the first phase (nitrogen) channel is closed, and only the second phase (perfluorohexanone) is used as the inner phase. The other conditions are the same as in Example 1.

[0085] The solid microcapsules of Comparative Example 1 were tested, and the test results are recorded in Table 4.

[0086] Table 4

[0087] The drug loading of the solid structure in Comparative Example 1 was 7% higher than that of the microcapsules in Example 1, but the rupture temperature of the solid microcapsules in Comparative Example 1 was 34°C lower than that of the microcapsules in Example 1. Processing at temperatures above 100°C carries the risk of premature rupture.

[0088] Comparative Example 2 use Figure 2 The microfluidic device shown was used to prepare thick-shell solid microcapsules (shell thickness doubled). Specifically, the first phase (nitrogen) channel was closed, the flow rate of the third phase (photocurable prepolymer solution) was increased to 16 mL / h, and the other conditions were the same as in Example 1.

[0089] The solid microcapsules of Comparative Example 2 were tested, and the test results are recorded in Table 5.

[0090] Table 5

[0091] Compared with Comparative Example 1, doubling the shell thickness only increased the rupture temperature by 16°C, which is much lower than that of the air cavity structure (which increased by more than 34°C), and the drug loading was significantly reduced by 26.6%, while the response time was extended to 180ms (the response time of the microcapsule in Example 1 was 65ms).

[0092] Table 6 Summary of Effect Comparison

[0093] The above results show that the fire extinguishing microcapsules with air cavity structure of the present invention, while maintaining a high drug loading (above 75%), achieve a significant increase in rupture temperature (above 140°C) and a widening of the processing window through a thermodynamic buffering mechanism rather than mechanical reinforcement, which is significantly better than the traditional solution of simply thickening the shell material.

[0094] The microcapsules from Examples 1-3 and Comparative Examples 1-2 were mixed with polyurethane, with 2 parts by weight of microcapsules and 1 part by weight of polyurethane, to form square sheet fire extinguishing patches measuring 100mm × 100mm × 2.5mm. Repeated fire extinguishing experiments on Class B oil fires were conducted in a 24L electrical distribution box, with each experiment repeated three times, and the average results were taken. The experimental results are shown in Table 7 below: Table 7

[0095] The above results indicate that the introduction of the air cavity mainly increases the trigger temperature, thus slightly prolonging the first extinguishing time; the subsequent extinguishing time and number of extinguishing attempts show that the extinguishing effect of the patch is mainly positively correlated with the extinguishing agent content. Furthermore, comparing the extinguishing experiments of the fire extinguishing patch samples prepared using the microcapsules from Examples 1-3 and Comparative Example 2 further demonstrates that the introduction of the air cavity can significantly increase the trigger temperature without affecting the extinguishing effect.

[0096] In the description of this application, the terms "inner" and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and do not require this application to be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0097] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0098] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A fire extinguishing microcapsule, characterized in that, include: A gas cavity core, which is filled with gas; A liquid phase layer, which encapsulates the gas cavity core, and the liquid phase layer includes an organic fire extinguishing agent; A solid polymer shell encapsulates the liquid phase layer.

2. The fire extinguishing microcapsule according to claim 1, characterized in that, The volume of the air cavity core accounts for 5%-30% of the total volume of the fire extinguishing microcapsule; And / or, the gas is one or more of nitrogen, argon, carbon dioxide, and air.

3. The fire extinguishing microcapsule according to claim 1, characterized in that, At least one of the following conditions must be met: The organic fire extinguishing agent includes one or more of perfluorohexanone, perfluorohexane, perfluoroheptane, and perfluorooctane; The volume of the liquid phase layer accounts for 65%-90% of the total volume of the fire extinguishing microcapsule; The liquid phase layer accounts for more than 75% of the total mass of the fire extinguishing microcapsule.

4. The fire extinguishing microcapsule according to claim 1, characterized in that, The solid polymer shell includes one or more of polyurethane acrylate, epoxy acrylate, polyester acrylate, polyurea, and polyurethane. And / or, the thickness of the solid polymer shell is 1μm-20μm.

5. The fire extinguishing microcapsule according to any one of claims 1-4, characterized in that, The particle size of the fire extinguishing microcapsules is 50μm-500μm; And / or, the particle size distribution coefficient (CV) of the fire extinguishing microcapsules is ≤10%.

6. A method for preparing the fire extinguishing microcapsules according to any one of claims 1-5, characterized in that, Fire extinguishing microcapsules were prepared using a four-axis coaxial flow focusing microfluidic device, consisting of the following components from the inside out: First phase: gas; Second phase: Organic fire extinguishing agent liquid; Third phase: polymer shell precursor solution; Fourth phase: Driving phase aqueous solution; The first to fourth phases form a gas-liquid-liquid-liquid coaxial laminar flow within the flow focusing channel, and are solidified in situ to form the fire extinguishing microcapsules.

7. The method according to claim 6, characterized in that, At least one of the following conditions must be met: The flow rate of the first phase is 0.1 mL / h - 5.0 mL / h; The flow rate of the second phase is 1.0 mL / h - 20.0 mL / h; The flow rate of the third phase is 2.0 mL / h to 30.0 mL / h; The flow rate of the fourth phase is 50 mL / h to 500 mL / h; The ratio of the flow velocities of the first phase to the second phase is 0.05-0.50; The diameter of the flow focusing channel is 100μm-1000μm; The gas is dried and filtered before injection; The dew point of the gas is below -40°C; The driving phase aqueous solution includes polyvinyl alcohol, and the mass content of polyvinyl alcohol in the driving phase aqueous solution is 0.5%-5%.

8. The method according to claim 6 or 7, characterized in that, One of the following conditions must be met: The polymer shell precursor solution includes a photoinitiator, and the first to fourth phases form a gas-liquid-liquid-liquid coaxial laminar flow in the flow focusing channel, which is then photocured in situ to form the fire extinguishing microcapsule. The polymeric shell precursor solution comprises a polyisocyanate, and the driving phase aqueous solution comprises a polyamine and / or a polyol.

9. A fire extinguishing device, characterized in that, Includes the fire extinguishing microcapsules as described in any one of claims 1-5.

10. The fire extinguishing device according to claim 9, characterized in that, The fire extinguishing device includes a substrate and the fire extinguishing microcapsules, wherein the fire extinguishing microcapsules are dispersed in the substrate. The fire extinguishing device is prepared by blending the fire extinguishing microcapsules with thermoplastic or thermosetting plastics, and then injection molding them. The processing temperature is ≤280℃.

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