Highly airtight perfluorocyclohexanone fire extinguishing microcapsule, preparation method and application thereof

Abstract

The present application relates to fire extinguishing microcapsule technical field, particularly to a kind of high air-tightness perfluorohexanone fire extinguishing microcapsule and its preparation method and application, perfluorohexanone fire extinguishing microcapsule includes composite shell and fire extinguishing core, composite shell is ethylene-vinyl alcohol copolymer resin and silicon dioxide nanoparticles, fire extinguishing core is perfluorohexanone extinguishing agent, applied in indoor fire extinguishing paste, fire retardant coating, polyurethane adhesive material preparation.The present application uses the perfluorohexanone fire extinguishing microcapsule, utilizes the strong hydrogen bond effect between hydroxyl in ethylene-vinyl alcohol copolymer resin, effectively prevents the diffusion of low polarity perfluorohexanone, especially under high temperature conditions, effectively solve the problem that existing perfluorohexanone fire extinguishing microcapsule is poor in long-term air-tightness under high encapsulation rate condition, simultaneously without generating harmful substances such as formaldehyde.

Description

Technical Field

[0001] This invention relates to the field of fire extinguishing microcapsule technology, and in particular to a highly airtight perfluorohexanone fire extinguishing microcapsule, its preparation method, and its application. Background Technology

[0002] Perfluorohexanone (PFH), as a novel environmentally friendly fire extinguishing agent, possesses excellent fire extinguishing capabilities and does not damage the ozone layer, making it a potential alternative to halon fire extinguishers. However, its application is limited by factors such as its low boiling point and high volatility, primarily for replacing halon fire extinguishers or for total flooding systems and localized applications in Class B fire protection. To overcome these limitations, researchers have attempted to prepare PFH in microcapsule form to improve its stability and ease of application. Microencapsulation technology encapsulates PFH within polymer materials, forming solid microcapsules. However, maintaining long-term stability and safety in practical use remains a critical technical challenge. Especially under high encapsulation ratios, ensuring the fire extinguishing core material does not leak and extending the microcapsule's lifespan has become a key research focus and difficulty. Therefore, developing a high-encapsulation-ratio microcapsule structure with excellent airtightness can effectively solve the above problems and significantly improve the application range and lifespan of PFH fire extinguishing microcapsules.

[0003] Several invention patents have been issued to address the issues of airtightness and lifespan of perfluorohexanone fire extinguishing microcapsules. For example, patent CN113476778A discloses a highly stable fire extinguishing microcapsule and its preparation method. The core material includes a fire extinguishing agent, and the outer shell includes an inner layer, an outer layer, and an airtightness enhancer. The inner layer comprises a modified melamine-formaldehyde resin generated by reacting melamine, m-phenylenediamine, urea, and formaldehyde solution. The outer layer is a modified polyurethane resin generated by reacting trimethylolpropane-diisocyanate adduct with gelatin solution. Patent CN116115947A discloses a multi-wall microcapsule perfluorohexanone fire extinguishing agent and its preparation method. The microcapsule fire extinguishing agent comprises two parts: a wall material and a core material. Perfluorohexanone (PFH) fire extinguishing agent serves as the core material. A multi-layered wall material is prepared using natural polymer materials, moisture-curing polymer monomers, and UV-curing resin. In this multi-walled microcapsule PPH fire extinguishing agent, the moisture-curing polymer monomers possess advantages such as high adhesive strength, heat resistance, and aging resistance, while the UV-cured coating exhibits good water vapor barrier properties. This addresses the limitations of polymer materials in terms of strength and poor aging resistance, ensuring the microcapsules have good thermal stability and fire extinguishing effect. However, the aforementioned patented solutions all suffer from drawbacks: to improve stability, multiple steps are required to prepare shells with different compositions, making the process cumbersome and complex; and to improve airtightness and strength, formaldehyde curing is used, with residual formaldehyde posing a significant potential hazard.

[0004] In existing technologies, the core-shell structure and shell material of microcapsules still need further optimization to improve the stability of perfluorohexanone microcapsules while reducing the release of harmful substances, thus better meeting the needs of different application scenarios. Summary of the Invention

[0005] The purpose of this invention is to provide a high-airtightness perfluorohexanone fire extinguishing microcapsule, its preparation method and application, which effectively solves the problem of poor long-term airtightness of existing perfluorohexanone fire extinguishing microcapsules under high encapsulation conditions, while not producing harmful substances such as formaldehyde.

[0006] To achieve the above objectives, the present invention provides a method for preparing highly airtight perfluorohexanone fire extinguishing microcapsules, comprising the following steps:

[0007] S1. Perfluorohexanone fire extinguishing microcapsules contain 10-20% ethylene-vinyl alcohol copolymer resin, 1-5% silica nanoparticles, and 75-89% perfluorohexanone fire extinguishing agent by weight percentage.

[0008] S2. At 60-90℃, the ethylene-vinyl alcohol copolymer resin is soaked in deionized water for 1-3 hours. After soaking, it is rinsed clean. This process is repeated at least three times to obtain the extracted ethylene-vinyl alcohol copolymer resin.

[0009] S3. Completely dissolve the ethylene-vinyl alcohol copolymer resin extracted in S2 in the mixed solvent to obtain phase A for later use;

[0010] S4. Add the methanol solution of alkoxysilane dropwise to a mixed solvent containing an alkaline catalyst to obtain phase B for later use;

[0011] S5. Perfluorohexanone fire extinguishing agent is injected into phase A in S3 using a horizontal flow pump. After heating, it is stirred at high speed and slowly added to phase B in S4 using a horizontal flow pump to obtain a perfluorohexanone fire extinguishing agent suspension with silica nanoparticles adsorbed on the surface.

[0012] S6. The perfluorohexanone fire extinguishing agent suspension with adsorbed silica nanoparticles obtained in S5 is slowly cooled down. During the cooling process, ethylene-vinyl alcohol copolymer resin precipitates out and coats the outer layer of perfluorohexanone with adsorbed silica nanoparticles, thus obtaining a perfluorohexanone suspension with composite coating of ethylene-vinyl alcohol copolymer resin and silica nanoparticles.

[0013] S7. The perfluorohexanone suspension coated with ethylene-vinyl alcohol copolymer resin and silica nanoparticles obtained in S6 is filtered, and the resulting solid phase is washed and dried to obtain perfluorohexanone fire extinguishing microcapsule powder.

[0014] Preferably, in S1, the molar percentage of ethylene structural units in the ethylene-vinyl alcohol copolymer resin is 24-44%.

[0015] Preferably, S2-S6 are all carried out under an inert atmosphere, which is nitrogen atmosphere.

[0016] Preferably, in S3 and S4, the mixed solvent is a mixed solution of methanol and water, wherein the mass fraction of methanol is 50-70%.

[0017] Preferably, the dissolution temperature in S3 is 100-130℃, and the dropping temperature in S4 is 30-70℃.

[0018] Preferably, in S4, the alkoxysilane includes at least one of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane;

[0019] The alkaline catalyst includes at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, and ammonia water.

[0020] Preferably, in S5, the high-speed stirring speed is 1000-5000 rpm and the heating temperature is 100-130℃.

[0021] Preferably, in S6, the rate of slow cooling is 0.01-0.1℃ / min.

[0022] The perfluorohexanone fire extinguishing microcapsule prepared by the above-mentioned method comprises a composite shell and a fire extinguishing core. The composite shell is composed of ethylene-vinyl alcohol copolymer resin and silica nanoparticles, and the fire extinguishing core is perfluorohexanone fire extinguishing agent.

[0023] The aforementioned highly airtight perfluorohexanone fire extinguishing microcapsule is used in the preparation of indoor fire extinguishing patches, fire-retardant coatings, and polyurethane adhesive materials.

[0024] Therefore, the present invention employs the above-mentioned highly airtight perfluorohexanone fire extinguishing microcapsule, its preparation method, and its application, the beneficial effects of which are as follows:

[0025] 1. This invention selects ethylene-vinyl alcohol copolymer resin as part of the shell material. By utilizing the strong hydrogen bonding between hydroxyl groups in the ethylene-vinyl alcohol copolymer resin, the diffusion of low-polarity perfluorohexanone is effectively prevented. Especially under high temperature conditions, it effectively solves the problem of poor long-term airtightness of existing perfluorohexanone fire extinguishing microcapsules under high encapsulation conditions, and does not produce harmful substances such as formaldehyde.

[0026] 2. This invention utilizes silica nanoparticles as a linking material to disperse perfluorohexanone fire extinguishing agent in a methanol / water mixed solution containing ethylene-vinyl alcohol copolymer resin. Silica nanoparticles are used as a stabilizer. After homogenization, a perfluorohexanone fire extinguishing agent suspension with silica nanoparticles adsorbed on its surface is formed, achieving uniform dispersion and stable existence of the perfluorohexanone fire extinguishing agent. The hydrogen bonding between the abundant hydroxyl groups in the ethylene-vinyl alcohol copolymer resin and the hydroxyl groups on the silica nanoparticles is utilized to control the cooling rate, allowing the ethylene-vinyl alcohol copolymer resin to slowly precipitate onto the perfluorohexanone fire extinguishing agent droplets adsorbed with silica nanoparticles, ultimately forming a dense composite shell.

[0027] 3. The perfluorohexanone fire extinguishing microcapsules prepared by this invention have high long-term airtightness under high encapsulation conditions, and do not produce harmful substances such as formaldehyde. They can be used in fire extinguishing materials such as indoor fire extinguishing patches.

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0029] Figure 1 This is a SEM image of the perfluorohexanone fire extinguishing microcapsules of Example 4 of the present invention;

[0030] Figure 2 This is a cross-sectional SEM image of the fire extinguishing patch in Application Example 1 of this invention;

[0031] Figure 3 This is a cross-sectional SEM image of the fire extinguishing patch after one fire extinguishing in Application Example 1 of this invention. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0033] This invention provides a method for preparing highly airtight perfluorohexanone fire extinguishing microcapsules, comprising the following steps:

[0034] S1, perfluorohexanone fire extinguishing microcapsules contain 10-20% ethylene-vinyl alcohol copolymer resin, 1-5% silica nanoparticles, and 75-89% perfluorohexanone fire extinguishing agent by weight percentage.

[0035] S2. Immerse the ethylene-vinyl alcohol copolymer resin in deionized water at 60-90℃ for 1-3 hours. Rinse thoroughly after immersion, repeating this process at least three times to obtain the extracted ethylene-vinyl alcohol copolymer resin. The purpose of immersion in deionized water at 60-90℃ is to remove inorganic salt additives from the ethylene-vinyl alcohol copolymer resin and improve its purity. Immersion is stopped when the conductivity of the extracted water is ≤20μs / cm.

[0036] S3. The ethylene-vinyl alcohol copolymer resin extracted in S2 is completely dissolved in a high-temperature mixed solvent to obtain phase A for later use.

[0037] S4. Slowly add the methanol solution of alkoxysilane dropwise to a mixed solvent containing an alkaline catalyst, and hydrolyze and condense to generate silica nanoparticles, obtaining phase B for later use.

[0038] S5. The perfluorohexanone fire extinguishing agent is injected into phase A in S3 using a horizontal flow pump. After heating, it is stirred at high speed and slowly added to phase B in S4 using a horizontal flow pump to obtain a perfluorohexanone fire extinguishing agent suspension with silica nanoparticles adsorbed on the surface.

[0039] S6. The perfluorohexanone fire extinguishing agent suspension with adsorbed silica nanoparticles obtained in S5 is slowly cooled. During the cooling process, the ethylene-vinyl alcohol copolymer resin will slowly precipitate and coat the outer layer of the perfluorohexanone with adsorbed silica nanoparticles, thus obtaining a perfluorohexanone suspension with composite coating of ethylene-vinyl alcohol copolymer resin and silica nanoparticles.

[0040] S7. The perfluorohexanone suspension coated with ethylene-vinyl alcohol copolymer resin and silica nanoparticles obtained in S6 is filtered, and the resulting solid phase is washed and dried to obtain perfluorohexanone fire extinguishing microcapsule powder.

[0041] In some embodiments of the present invention, in S1, the molar percentage of ethylene structural units in the ethylene-vinyl alcohol copolymer resin is 24-44%. The ethylene-vinyl alcohol copolymer resin is obtained by saponification of an ethylene-vinyl ester copolymer, which is a copolymer of ethylene and a vinyl ester monomer, typically vinyl acetate.

[0042] In some embodiments of the present invention, S2-S6 are all carried out under an inert atmosphere, namely nitrogen. The inert atmosphere prevents the perfluorohexanone fire extinguishing agent from volatilizing or oxidizing, avoids interference from oxygen or moisture with the ethylene-vinyl alcohol copolymer resin, and ensures the stability of the reaction system.

[0043] In some embodiments of the present invention, in S3 and S4, the mixed solvent is a mixed solution of methanol and water, wherein the mass fraction of methanol is 50-70%. Methanol and water form an azeotropic system, which has good solubility for ethylene-vinyl alcohol copolymer resin, wherein the proportion of methanol affects the solubility of ethylene-vinyl alcohol copolymer resin and the viscosity of the solution.

[0044] In some embodiments of the present invention, the dissolution temperature in S3 is 100-130°C, and the dropping temperature in S4 is 30-70°C. Heating in S3 disrupts the crystalline regions of the ethylene-vinyl alcohol copolymer resin, promoting complete dissolution and forming a uniform A phase. In S4, the hydrolysis rate of the alkoxysilane is controlled by the dropping temperature to avoid excessively rapid gelation, and hydrolysis and condensation generate silica nanoparticles, ensuring the formation of a stable B phase.

[0045] In some embodiments of the present invention, in S4, the alkoxysilane includes at least one of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane. The silica nanoparticles in the perfluorohexanone fire extinguishing microcapsules of the present invention are prepared using a sol-gel process with alkoxysilane as the silicon source. The particle size of the silica nanoparticles is 2-20 nm, preferably 5-10 nm.

[0046] In some embodiments of the present invention, in step S4, the alkaline catalyst includes at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, and ammonia water. Under the action of the alkaline catalyst, alkoxysilanes undergo hydrolysis and condensation to generate silica nanoparticles.

[0047] In some embodiments of the present invention, in step S5, the high-speed stirring speed is 1000-5000 rpm, and the heating temperature is 100-130°C. Under high-speed stirring, the perfluorohexanone fire extinguishing agent is dispersed into fine droplets. The slow addition of phase B by the horizontal flow pump causes silica nanoparticles to adsorb onto the surface of the perfluorohexanone fire extinguishing agent droplets, forming a stable suspension.

[0048] In some embodiments of the present invention, in step S6, the rate of slow cooling is 0.01-0.1 °C / min. This reduces the solubility of the ethylene-vinyl alcohol copolymer resin, causing it to gradually precipitate from the solution and strengthening the shell structure. Slow cooling avoids rapid precipitation that could lead to unevenness or defects in the composite shell, ensuring the integrity of the microcapsules.

[0049] The above-described method for preparing high-airtightness perfluorohexanone fire extinguishing microcapsules yields perfluorohexanone fire extinguishing microcapsules comprising a composite shell and a fire extinguishing core. The composite shell is composed of ethylene-vinyl alcohol copolymer resin and silica nanoparticles, while the fire extinguishing core is perfluorohexanone fire extinguishing agent. The D50 particle size of the perfluorohexanone fire extinguishing microcapsules is 10-50 μm, preferably 20-40 μm.

[0050] The aforementioned highly airtight perfluorohexanone fire extinguishing microcapsules are used in the preparation of indoor fire extinguishing patches, fire-retardant coatings, and polyurethane adhesive materials. The fire extinguishing effect of the perfluorohexanone fire extinguishing microcapsules is directly proportional to their addition amount in indoor fire extinguishing patches, fire-retardant coatings, and polyurethane adhesive materials. To ensure the fire extinguishing effect, the material thickness can be increased while maintaining a high addition amount, which can improve the fire extinguishing effect and enable multiple fire extinguishing operations, thus expanding its applicability.

[0051] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0052] Perfluorohexanone: Zhejiang Noah Fluorochemical Co., Ltd., industrial grade 98%;

[0053] Tetramethoxysilane: Nanxing Chemical, industrial grade 98%;

[0054] Tetraethoxysilane: Nanxing Chemical, industrial grade 98%;

[0055] Tetrapropoxysilane: Hubei Jianghao New Material Technology Co., Ltd., industrial grade 98%;

[0056] Ethylene-vinyl alcohol copolymer resin (ethylene molar content 38%): Kuraray Co., Ltd., Japan, E-Bore TM H171B;

[0057] Ethylene-vinyl alcohol copolymer resin (ethylene molar content 48%): Kuraray Co., Ltd., Japan, E-Bore TM G156B;

[0058] Ethylene-vinyl alcohol copolymer resin (ethylene molar content 32%): Mitsubishi Corporation, Japan, Soanor TM DC3203RB;

[0059] Ethylene-vinyl alcohol copolymer resin (ethylene molar content 29%): Mitsubishi Corporation, Japan, Soanor TM DT2904RB;

[0060] Ethylene-vinyl alcohol copolymer resin (ethylene molar content 38%): Mitsubishi Corporation, Japan, Soanor TM ET3803RB;

[0061] Methanol: Shanghai Aladdin Biochemical Technology Co., Ltd., reagent grade 99%.

[0062] Example 1

[0063] S1, the perfluorohexanone fire extinguishing microcapsules comprise, by weight percentage, 11.2% ethylene-vinyl alcohol copolymer resin, 3.1% silica nanoparticles, and 85.7% perfluorohexanone fire extinguishing agent. Ethylene-vinyl alcohol copolymer resin (Easy-to-use) TM The molar percentage of ethylene structural units in H171B is 38%.

[0064] S2. Under a nitrogen atmosphere, 10g of ethylene-vinyl alcohol copolymer resin was immersed in 100g of deionized water at 70℃ for 2 hours. After immersion, it was rinsed clean, and this process was repeated at least three times. Inorganic salt additives in the ethylene-vinyl alcohol copolymer resin were extracted. The conductivity of the water after the last extraction was 15μs / cm, and the extracted ethylene-vinyl alcohol copolymer resin was obtained.

[0065] S3. In a dispersion vessel, pressurize the mixture with nitrogen to 1.2 MPa and 110°C, and completely dissolve the ethylene-vinyl alcohol copolymer resin extracted in S2 in a high-temperature mixed solution of methanol and water (methanol mass fraction of 60%) to obtain 242g of phase A for later use.

[0066] S4. In a nitrogen atmosphere at 50°C, 8g of a methanol solution of tetramethoxysilane was slowly added dropwise to a mixed solvent (a mixture of methanol and water, with methanol at a mass fraction of 60%) containing potassium hydroxide as an alkaline catalyst. The reaction was carried out for 2 hours to obtain phase B with a silica nanoparticle size of 6nm and a total mass of 100g for later use.

[0067] In S5, under a nitrogen atmosphere, 87g of perfluorohexanone fire extinguishing agent was injected into phase A in S3 using a horizontal flow pump. After heating at 110°C, the mixture was stirred at high speed at 1500rpm and slowly added to phase B in S4 using a horizontal flow pump to obtain a suspension of perfluorohexanone fire extinguishing agent adsorbed with silica nanoparticles.

[0068] In a nitrogen atmosphere, the perfluorohexanone fire extinguishing agent suspension with adsorbed silica nanoparticles obtained in S5 is slowly cooled at a rate of 0.08℃ / min. After cooling to room temperature, ethylene-vinyl alcohol copolymer resin slowly precipitates and coats the perfluorohexanone with adsorbed silica nanoparticles, resulting in a perfluorohexanone suspension with composite coating of ethylene-vinyl alcohol copolymer resin and silica nanoparticles.

[0069] S7. The perfluorohexanone suspension coated with ethylene-vinyl alcohol copolymer resin and silica nanoparticles obtained in S6 is filtered, and the resulting solid phase is washed and dried to obtain perfluorohexanone fire extinguishing microcapsule powder.

[0070] Example 2

[0071] S1, the perfluorohexanone fire extinguishing microcapsules comprise, by weight percentage, 12.2% ethylene-vinyl alcohol copolymer resin, 1.2% silica nanoparticles, and 86.6% perfluorohexanone fire extinguishing agent. Ethylene-vinyl alcohol copolymer resin (Soanor) TM The molar percentage of ethylene structural units in DC3203RB is 32%.

[0072] S2. Under a nitrogen atmosphere, 12g of ethylene-vinyl alcohol copolymer resin was immersed in 100g of deionized water at 65℃ for 2 hours. After immersion, it was rinsed clean, and this process was repeated at least three times. Inorganic salt additives in the ethylene-vinyl alcohol copolymer resin were extracted. The conductivity of the water after the last extraction was 20μs / cm, and the extracted ethylene-vinyl alcohol copolymer resin was obtained.

[0073] S3. In a dispersion vessel, pressurize the mixture with nitrogen to 1.3 MPa and at 120°C. Completely dissolve the ethylene-vinyl alcohol copolymer resin extracted in S2 in a high-temperature mixed solution of methanol and water (methanol mass fraction is 55%) to obtain 240g of phase A for later use.

[0074] S4. Under a nitrogen atmosphere at 30°C, 4g of a methanol solution of tetraethoxysilane was slowly added dropwise to a mixed solvent (a mixture of methanol and water, with a methanol mass fraction of 55%) containing sodium hydroxide as an alkaline catalyst. The reaction was carried out for 6 hours to obtain phase B with a silica nanoparticle size of 15nm and a total mass of 100g for later use.

[0075] In S5, under a nitrogen atmosphere, 105g of perfluorohexanone fire extinguishing agent was injected into phase A in S3 using a horizontal flow pump. After heating at 120°C, the mixture was stirred at high speed at 2000 rpm and slowly added to phase B in S4 using a horizontal flow pump to obtain a suspension of perfluorohexanone fire extinguishing agent adsorbed with silica nanoparticles.

[0076] In a nitrogen atmosphere, the perfluorohexanone fire extinguishing agent suspension with adsorbed silica nanoparticles obtained in S5 is slowly cooled at a rate of 0.05℃ / min. After cooling to room temperature, ethylene-vinyl alcohol copolymer resin slowly precipitates and coats the perfluorohexanone with adsorbed silica nanoparticles, resulting in a perfluorohexanone suspension with composite coating of ethylene-vinyl alcohol copolymer resin and silica nanoparticles.

[0077] S7. The perfluorohexanone suspension coated with ethylene-vinyl alcohol copolymer resin and silica nanoparticles obtained in S6 is filtered, and the resulting solid phase is washed and dried to obtain perfluorohexanone fire extinguishing microcapsule powder.

[0078] Example 3

[0079] S1, the perfluorohexanone fire extinguishing microcapsules comprise, by weight percentage, 19.8% ethylene-vinyl alcohol copolymer resin, 4.8% silica nanoparticles, and 75.4% perfluorohexanone fire extinguishing agent. Ethylene-vinyl alcohol copolymer resin (Soanor) TM The molar percentage of ethylene structural units in DT2904RB is 29%.

[0080] S2. Under a nitrogen atmosphere, 12g of ethylene-vinyl alcohol copolymer resin was immersed in 100g of deionized water at 60℃ for 2 hours. After immersion, it was rinsed clean, and this process was repeated at least three times. Inorganic salt additives in the ethylene-vinyl alcohol copolymer resin were extracted. The conductivity of the water after the last extraction was 18μs / cm, and the extracted ethylene-vinyl alcohol copolymer resin was obtained.

[0081] S3. In a dispersion vessel, pressurize the mixture with nitrogen to 1.1 MPa and at 100°C. Completely dissolve the ethylene-vinyl alcohol copolymer resin extracted in S2 in a high-temperature mixed solution of methanol and water (methanol mass fraction is 50%) to obtain 240g of phase A for later use.

[0082] S4. In a nitrogen atmosphere, at 70°C, 14g of a methanol solution of tetrapropoxysilane was slowly added dropwise to a mixed solvent (a mixture of methanol and water, with methanol at a mass fraction of 50%) containing sodium hydroxide as an alkaline catalyst. The mixture was reacted at 30°C for 6 hours to obtain phase B, which consists of silica nanoparticles with a particle size of 6nm and a total mass of 100g, for later use.

[0083] In S5, under a nitrogen atmosphere, 51g of perfluorohexanone fire extinguishing agent was injected into phase A in S3 using a horizontal flow pump. After heating at 100°C, the mixture was stirred at high speed at 3000rpm and slowly added to phase B in S4 using a horizontal flow pump to obtain a suspension of perfluorohexanone fire extinguishing agent adsorbed with silica nanoparticles.

[0084] In a nitrogen atmosphere, the perfluorohexanone fire extinguishing agent suspension with adsorbed silica nanoparticles obtained in S5 is slowly cooled at a rate of 0.1℃ / min. After cooling to room temperature, ethylene-vinyl alcohol copolymer resin slowly precipitates and coats the perfluorohexanone with adsorbed silica nanoparticles, resulting in a perfluorohexanone suspension with composite coating of ethylene-vinyl alcohol copolymer resin and silica nanoparticles.

[0085] S7. The perfluorohexanone suspension coated with ethylene-vinyl alcohol copolymer resin and silica nanoparticles obtained in S6 is filtered, and the resulting solid phase is washed and dried to obtain perfluorohexanone fire extinguishing microcapsule powder.

[0086] Example 4

[0087] S1, the perfluorohexanone fire extinguishing microcapsules comprise, by weight percentage, 17.1% ethylene-vinyl alcohol copolymer resin, 2.8% silica nanoparticles, and 80.1% perfluorohexanone fire extinguishing agent. Ethylene-vinyl alcohol copolymer resin (Soanor) TM The molar percentage of ethylene structural units in ET3803RB is 38%.

[0088] S2. Under a nitrogen atmosphere, 15g of ethylene-vinyl alcohol copolymer resin was immersed in 100g of deionized water at 75℃ for 2 hours. After immersion, it was rinsed clean, and this process was repeated at least three times. Inorganic salt additives in the ethylene-vinyl alcohol copolymer resin were extracted. The conductivity of the water after the last extraction was 13μs / cm, and the extracted ethylene-vinyl alcohol copolymer resin was obtained.

[0089] S3. In a dispersion vessel, pressurize the mixture with nitrogen to 1.4 MPa and at 125°C. Then, completely dissolve the ethylene-vinyl alcohol copolymer resin extracted in S2 in a high-temperature mixed solution of methanol and water (methanol mass fraction is 65%) to obtain 240g of phase A for later use.

[0090] S4. Under a nitrogen atmosphere, at 60°C, 8g of a methanol solution of tetramethoxysilane was slowly added dropwise to a mixed solvent (a mixed solution of methanol and water, with a methanol mass fraction of 65%) containing potassium hydroxide as an alkaline catalyst. The reaction was carried out for 2 hours to obtain phase B with a silica nanoparticle size of 11nm and a total mass of 100g for later use.

[0091] In S5, under a nitrogen atmosphere, 81g of perfluorohexanone fire extinguishing agent was injected into phase A in S3 using a horizontal flow pump. After heating at 125°C, the mixture was stirred at high speed at 4000rpm and slowly added to phase B in S4 using a horizontal flow pump to obtain a suspension of perfluorohexanone fire extinguishing agent adsorbed with silica nanoparticles.

[0092] In a nitrogen atmosphere, the perfluorohexanone fire extinguishing agent suspension with adsorbed silica nanoparticles obtained in S5 is slowly cooled at a rate of 0.05℃ / min. After cooling to room temperature, ethylene-vinyl alcohol copolymer resin slowly precipitates and coats the perfluorohexanone with adsorbed silica nanoparticles, resulting in a perfluorohexanone suspension with composite coating of ethylene-vinyl alcohol copolymer resin and silica nanoparticles.

[0093] S7. The perfluorohexanone suspension coated with ethylene-vinyl alcohol copolymer resin and silica nanoparticles obtained in S6 is filtered, and the resulting solid phase is washed and dried to obtain perfluorohexanone fire extinguishing microcapsule powder.

[0094] Example 5

[0095] S1, the perfluorohexanone fire extinguishing microcapsules comprise, by weight percentage, 19.6% ethylene-vinyl alcohol copolymer resin, 2.8% silica nanoparticles, and 77.6% perfluorohexanone fire extinguishing agent. Ethylene-vinyl alcohol copolymer resin (Easy-to-use) TM The molar percentage of ethylene structural units in H171B is 38%.

[0096] S2. Under a nitrogen atmosphere, 20g of ethylene-vinyl alcohol copolymer resin was immersed in 100g of deionized water at 85℃ for 2 hours. After immersion, it was rinsed clean, and this process was repeated at least three times. Inorganic salt additives in the ethylene-vinyl alcohol copolymer resin were extracted. The conductivity of the water after the last extraction was 10μs / cm, and the extracted ethylene-vinyl alcohol copolymer resin was obtained.

[0097] S3. In a dispersion vessel, pressurize the mixture with nitrogen to 1.5 MPa and at 130°C. Completely dissolve the ethylene-vinyl alcohol copolymer resin extracted in S2 in a high-temperature mixed solution of methanol and water (methanol mass fraction is 70%) to obtain 240g of phase A for later use.

[0098] S4. Under a nitrogen atmosphere, at 50°C, 8g of a methanol solution of tetramethoxysilane was slowly added dropwise to a mixed solvent (a mixture of methanol and water, with methanol at a mass fraction of 70%) containing potassium hydroxide as an alkaline catalyst. The reaction was carried out for 2 hours to obtain phase B with a silica nanoparticle size of 6nm and a total mass of 100g for later use.

[0099] In S5, under a nitrogen atmosphere, 84g of perfluorohexanone fire extinguishing agent was injected into phase A in S3 using a horizontal flow pump. After heating at 130°C, the mixture was stirred at high speed at 5000 rpm and slowly added to phase B in S4 using a horizontal flow pump to obtain a suspension of perfluorohexanone fire extinguishing agent adsorbed with silica nanoparticles.

[0100] In a nitrogen atmosphere, the perfluorohexanone fire extinguishing agent suspension with adsorbed silica nanoparticles obtained in S5 is slowly cooled at a rate of 0.03℃ / min. After cooling to room temperature, ethylene-vinyl alcohol copolymer resin slowly precipitates and coats the perfluorohexanone with adsorbed silica nanoparticles, resulting in a perfluorohexanone suspension with composite coating of ethylene-vinyl alcohol copolymer resin and silica nanoparticles.

[0101] S7. The perfluorohexanone suspension coated with ethylene-vinyl alcohol copolymer resin and silica nanoparticles obtained in S6 is filtered, and the resulting solid phase is washed and dried to obtain perfluorohexanone fire extinguishing microcapsule powder.

[0102] Comparative Example 1

[0103] The difference between this comparative example and Example 1 is that the ethylene-vinyl alcohol copolymer resin used is Ebaole.TM G156B, Ethylene-Vinyl Alcohol Copolymer Resin (Easy-to-Bare) TM The molar percentage of ethylene structural units in G156B was 48%, and all other conditions were the same as those in Example 1, to obtain perfluorohexanone fire extinguishing microcapsule powder.

[0104] Comparative Example 2

[0105] The difference between this comparative example and Example 3 is that in S4, the mass of tetrapropoxysilane is 54g, and the reaction is carried out at 70°C for 5h to obtain phase B with a particle size of 41nm and a total mass of 100g of silica nanoparticles for later use. The rest of the steps are the same as in Example 3 to prepare perfluorohexanone fire extinguishing microcapsule powder.

[0106] Application Example 1

[0107] Fire extinguishing patches were prepared using the perfluorohexanone fire extinguishing microcapsule powder from Example 4, wherein the perfluorohexanone fire extinguishing microcapsules comprised 9 parts by mass and the adhesive resin comprised 1 part by mass.

[0108] Test case

[0109] The main testing instruments used are:

[0110] Laser particle size analyzer: Model Bettersize 2600, wet method, light blocking ratio of 5%-20%, test medium is water. It can measure the D50 particle size of capsules.

[0111] Transmission electron microscope: Hitachi HT7800, used to measure the particle size of silica nanoparticle dispersions.

[0112] Forced-air drying oven: Shanghai Heheng Instrument Equipment Co., Ltd., DHG9035A model, used to test the encapsulation efficiency and thermal storage stability of microcapsules.

[0113] Encapsulation efficiency test method

[0114] Three 10g portions of perfluorohexanone fire extinguishing microcapsules were weighed and placed in a stainless steel tray. The tray was covered with a 500-mesh filter and placed in an oven at 200℃ for 30 minutes. The average encapsulation rate of the three portions of perfluorohexanone fire extinguishing microcapsules was taken as the actual encapsulation rate of the perfluorohexanone fire extinguishing microcapsules by the weight reduction method.

[0115] Test methods for silica nanoparticles

[0116] Three 2g portions of perfluorohexanone fire extinguishing microcapsules were weighed and placed in crucibles. They were then placed in a muffle furnace at 800℃ for 8 hours. The residue was considered as silica nanoparticles. The average mass percentage of the three remaining silica nanoparticles was taken as the actual mass percentage of silica nanoparticles by the weight reduction method.

[0117] Test methods for ethylene-vinyl alcohol copolymer resins

[0118] The mass percentage of ethylene-vinyl alcohol copolymer resin is obtained by subtracting the encapsulation rate of the extinguishing agent and the actual mass percentage of silica nanoparticles obtained by the above method.

[0119] Thermal storage stability test method

[0120] A certain amount of perfluorohexanone fire extinguishing microcapsules were placed in an oven at 50℃ and 100℃ for one month, and their encapsulation efficiency was tested. The airtight stability at 50℃ and 100℃ was obtained based on the change in encapsulation efficiency.

[0121] Formaldehyde content testing methods

[0122] Refer to GB / T 23993-2009 Determination of formaldehyde content in water-based coatings - acetylacetone spectrophotometric method.

[0123] The D50 particle size of the perfluorohexanone fire extinguishing microcapsules in Examples 1-5 and Comparative Examples 1-2 was tested, and the results are shown in Table 1.

[0124] Table 1. D50 particle size data for Examples 1-5 and Comparative Examples 1-2

[0125]

[0126] The perfluorohexanone fire extinguishing microcapsules of Examples 1-5 and Comparative Examples 1-2 were subjected to the above tests, and the results are shown in Table 2.

[0127] Table 2 Test data for Examples 1-5 and Comparative Examples 1-2

[0128]

[0129] As can be seen from the data in Table 2, the temperature range at which the perfluorohexanone fire extinguishing agent is released from the perfluorohexanone fire extinguishing microcapsules prepared in Examples 1-5 is between 158-170℃. Compared with Comparative Examples 1-2, the perfluorohexanone fire extinguishing microcapsules prepared in Examples 1-5 have excellent airtightness. Under long-term high-temperature heat storage at 100℃, the encapsulation rate loss is less than 1%, and the formaldehyde content is below the detection limit of 5ppm and is not detected.

[0130] In Comparative Example 1, the use of an ethylene-vinyl alcohol copolymer resin with a 48% molar percentage of ethylene structural units as the shell resulted in minimal encapsulation loss during 50°C heat storage. However, the encapsulation loss was significant after long-term heat storage at 100°C. This may be because the increased ethylene content reduced the hydroxyl content in the ethylene-vinyl alcohol copolymer resin, weakening hydrogen bonding and reducing barrier properties. Alternatively, the increased ethylene content may have lowered the resin's softening temperature, bringing it closer to the 100°C heat storage temperature, making it more prone to leakage. Comparative Example 2 also showed a significant decrease in heat storage encapsulation efficiency. The excessively large particle size of the silica nanoparticle dispersion created defects in the shell, leading to a decrease in encapsulation efficiency.

[0131] SEM analysis was performed on the perfluorohexanone fire extinguishing microcapsules of Example 4, and the results are as follows: Figure 1 As shown, the perfluorohexanone fire extinguishing microcapsules are completely encapsulated, without collapse or damage, and the particles are evenly distributed without sticking together.

[0132] SEM tests were performed on the cross-sections of the fire extinguishing patch before and after one fire extinguishing operation, corresponding to the fire extinguishing patch in test case 1. The results are as follows: Figure 2 and Figure 3 As shown. It can be seen that, Figure 2 The damaged microcapsules were caused by brittle fracture in liquid nitrogen. Figure 3 The upper middle part is the side in contact with the flame. After one fire extinguishing, the perfluorohexanone fire extinguishing microcapsules on the flame-contacting side melt and release the fire extinguishing agent. There are also many intact perfluorohexanone fire extinguishing microcapsules on the back side, which enables the fire extinguishing patch to extinguish fires multiple times. The specific number of fire extinguishing times depends on the thickness of the fire extinguishing patch and the amount of perfluorohexanone fire extinguishing microcapsules added.

[0133] Therefore, the present invention employs the above-mentioned high airtight perfluorohexanone fire extinguishing microcapsule, its preparation method and application, which utilizes the strong hydrogen bonding between hydroxyl groups in the ethylene-vinyl alcohol copolymer resin to effectively prevent the diffusion of low-polarity perfluorohexanone. Especially under higher temperature conditions, it effectively solves the problem of poor long-term airtightness of existing perfluorohexanone fire extinguishing microcapsules under high encapsulation conditions, and does not produce harmful substances such as formaldehyde.

[0134] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a highly airtight perfluorohexanone fire extinguishing microcapsule, characterized in that: Includes the following steps: S1. Perfluorohexanone fire extinguishing microcapsules contain 10-20% ethylene-vinyl alcohol copolymer resin, 1-5% silica nanoparticles, and 75-89% perfluorohexanone fire extinguishing agent by weight percentage. In S1, the molar percentage of ethylene structural units in the ethylene-vinyl alcohol copolymer resin is 24-44%; S2. At 60-90℃, the ethylene-vinyl alcohol copolymer resin is soaked in deionized water for 1-3 hours. After soaking, it is rinsed clean. This process is repeated at least three times to obtain the extracted ethylene-vinyl alcohol copolymer resin. S3. Completely dissolve the ethylene-vinyl alcohol copolymer resin extracted in S2 in the mixed solvent to obtain phase A for later use; S4. Add the methanol solution of alkoxysilane dropwise to a mixed solvent containing an alkaline catalyst to obtain phase B for later use; S5. Perfluorohexanone fire extinguishing agent is injected into phase A in S3 using a horizontal flow pump. After heating, it is stirred at high speed and slowly added to phase B in S4 using a horizontal flow pump to obtain a perfluorohexanone fire extinguishing agent suspension with silica nanoparticles adsorbed on the surface. The particle size of silica nanoparticles is 2-20 nm; S6. The perfluorohexanone fire extinguishing agent suspension with adsorbed silica nanoparticles obtained in S5 is slowly cooled down. During the cooling process, ethylene-vinyl alcohol copolymer resin precipitates out and coats the outer layer of perfluorohexanone with adsorbed silica nanoparticles, thus obtaining a perfluorohexanone suspension with composite coating of ethylene-vinyl alcohol copolymer resin and silica nanoparticles. S7. The perfluorohexanone suspension coated with ethylene-vinyl alcohol copolymer resin and silica nanoparticles obtained in S6 is filtered, and the resulting solid phase is washed and dried to obtain perfluorohexanone fire extinguishing microcapsule powder.

2. The method for preparing a highly airtight perfluorohexanone fire extinguishing microcapsule according to claim 1, characterized in that: S2-S6 were all carried out under an inert atmosphere, which was nitrogen.

3. The method for preparing a highly airtight perfluorohexanone fire extinguishing microcapsule according to claim 1, characterized in that: In S3 and S4, the mixed solvent is a mixed solution of methanol and water, wherein the mass fraction of methanol is 50-70%.

4. The method for preparing a highly airtight perfluorohexanone fire extinguishing microcapsule according to claim 1, characterized in that: The dissolution temperature of S3 is 100-130℃, and the dropping temperature of S4 is 30-70℃.

5. The method for preparing a highly airtight perfluorohexanone fire extinguishing microcapsule according to claim 1, characterized in that: In S4, alkoxysilane includes at least one of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane; The alkaline catalyst includes at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, and ammonia water.

6. The method for preparing a highly airtight perfluorohexanone fire extinguishing microcapsule according to claim 1, characterized in that: In S5, the high-speed stirring speed is 1000-5000 rpm, and the heating temperature is 100-130℃.

7. The method for preparing a highly airtight perfluorohexanone fire extinguishing microcapsule according to claim 1, characterized in that: In S6, the slow cooling rate is 0.01-0.1℃ / min.

8. A highly airtight perfluorohexanone fire extinguishing microcapsule, characterized in that: The perfluorohexanone fire extinguishing microcapsule is prepared according to any one of claims 1-7. The perfluorohexanone fire extinguishing microcapsule comprises a composite shell and a fire extinguishing core. The composite shell is composed of ethylene-vinyl alcohol copolymer and silica nanoparticles, and the fire extinguishing core is perfluorohexanone fire extinguishing agent.

9. The application of a highly airtight perfluorohexanone fire extinguishing microcapsule, characterized in that: The highly airtight perfluorohexanone fire extinguishing microcapsule according to claim 8 is used in the preparation of indoor fire extinguishing patches, fireproof coatings, and polyurethane adhesive materials.

Images