Fire extinguishing microcapsule and preparation method thereof

Abstract

The invention discloses a fire extinguishing microcapsule and a preparation method thereof, and relates to the technical field of fire extinguishing. The microcapsule comprises a shell and a fire extinguishing agent core material, wherein the shell is formed by compounding a thermoplastic polymer, a cross-linking agent, an inorganic filler and an antioxidant. The structure of the antioxidant is shown in the specification. The shell adopts polystyrene, an isocyanate cross-linking agent and nano silicon dioxide, and a three-dimensional network structure is formed through stepped curing. The antioxidant containing condensed ring aromatic amino is adopted, the antioxidant and the inorganic filler have a synergistic effect through hydrogen bonds, and the confinement effect of a cross-linked network is combined, so that ordered arrangement of antioxidant molecules is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of fire extinguishing, and in particular to a fire extinguishing microcapsule and a preparation method thereof. Background Art

[0002] In the field of fire extinguishing technology, while traditional fire extinguishing devices and materials play an important role in fire fighting, they suffer from numerous issues with oxidation resistance and service life, significantly limiting their effectiveness and scope of application. This has led to an increasingly urgent demand for more advanced and durable fire extinguishing technologies and materials.

[0003] Key components and materials in traditional fire-fighting equipment, such as the extinguishing agent carrier or casing, are often susceptible to environmental factors during long-term storage and use, leading to oxidation reactions and performance degradation. For example, some commonly used polymer-based fire-fighting materials are susceptible to molecular chain breakage and aging under conditions such as light, oxygen, and high temperature. This not only reduces the release efficiency of the extinguishing agent, but can also cause the equipment to fail at critical moments, increasing the risk of fire. Moreover, frequent replacement of aging components not only consumes a lot of manpower and material resources, but also incurs additional economic costs and wastes resources. In some special locations, such as high altitudes, high humidity, or highly corrosive environments, the oxidation resistance and lifespan of fire-fighting equipment are even more prominent.

[0004] Furthermore, existing firefighting technologies often lack precision and efficiency when responding to small-scale fires. The release of extinguishing agents is difficult to control, resulting in waste and unnecessary damage to the surrounding environment and equipment. Traditional firefighting materials also have a limited lifespan and cannot meet the long-term reliability requirements of modern buildings and industrial facilities.

[0005] Therefore, the development of a fire-extinguishing microcapsule with excellent antioxidant properties and long life and its preparation method are of great significance for improving the reliability and economy of fire extinguishing technology. Summary of the Invention

[0006] The present invention aims to provide fire-extinguishing microcapsules with excellent antioxidant properties and a long lifespan. By optimizing the shell material ratio and structural design, the microcapsules are protected from oxidation and aging during storage and use, significantly extending their service life.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a fire extinguishing microcapsule comprising a shell and a fire extinguishing agent core material encapsulated in the shell, wherein the shell is composited with a thermoplastic polymer, a cross-linking agent, an inorganic filler, and an antioxidant. By adjusting the proportions of the components in the shell material, the microcapsule can controllably release the fire extinguishing agent within the temperature range of 60-150°C; The structure of the antioxidant is shown in Formula 1: Formula 1; The R1 is selected from the following substituents: 、 、 、 、 ; described For the connection site.

[0008] Furthermore, the thermoplastic polymer is at least one of polystyrene, polymethyl methacrylate or epoxy resin.

[0009] Furthermore, the cross-linking agent is melamine formaldehyde resin or isocyanate compound.

[0010] Furthermore, the inorganic filler is nano-silicon dioxide or calcium carbonate.

[0011] Furthermore, the mass ratio of the thermoplastic polymer, the crosslinking agent, the inorganic filler and the antioxidant is (50-80): (5-15): 20:5.

[0012] Furthermore, the wall thickness of the shell is 5-50 μm, and the wall thickness uniformity deviation is less than 10%, and the shell integrity is tested by water vapor permeability value ≤ 5g / m 2 ·24h characterization.

[0013] Furthermore, the particle size of the inorganic filler is 50-500 nm.

[0014] Furthermore, the isocyanate compound includes at least one or more of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate.

[0015] Furthermore, the fire extinguishing agent core material is perfluorohexanone.

[0016] Furthermore, the antioxidant is at least one of the compounds shown in the following structures: .

[0017] A method for preparing fire-extinguishing microcapsules comprises the following steps: S1. The thermoplastic polymer is dissolved in an organic solvent, to which the crosslinking agent, inorganic filler and antioxidant are sequentially added, stirred at 80-100 ° C until viscous, ultrasonically dispersed during stirring, and cooled to 40-50 ° C to form a shell material solution; S2. mixing the perfluorohexanone with a surfactant to form a microemulsion, controlling the emulsification temperature to ≤30°C, and coating the microemulsion droplets with the shell material solution through a microfluidic device; S3. Gradient curing is performed at 20-50°C in three stages: the first stage is 20-30°C for 0.5-1 hour to complete the initial curing, the second stage is 30-40°C for 2-3 hours to promote crosslinking, and the third stage is 40-50°C for 1-2 hours to achieve densification. The entire process is carried out in a closed and pressurized environment (0.1-0.3MPa).

[0018] Furthermore, the organic solvent is tetrahydrofuran or toluene.

[0019] Furthermore, the microemulsion is prepared by mixing the perfluorohexanone and the surfactant in a mass ratio of 100:(1-5), and emulsifying the mixture in an ice-water bath at 0-10° C. using a high-speed shear emulsifier at a speed of 8000-15000 rpm for 5-15 minutes to form a nanoemulsion with a particle size of 100-300 nm and a dispersion index (PDI) of ≤0.15. The surfactant is polyoxyethylene sorbitan monooleate.

[0020] The invention discloses an application of fire extinguishing microcapsule in extinguishing small-scale fire.

[0021] The antioxidant described in the present invention is a condensed aromatic amine system with strong electron-donating ability. The dissociation energy of the NH bond in the parent nucleus is significantly lower than that of the CH bond in the polymer main chain, and it can preferentially react with the free radicals (ROO·) generated during the oxidation process. The generated amino free radicals stabilize the conjugation effect and terminate the chain oxidation reaction. The nitrogen atom of the parent nucleus can react with Fe 3+ 、Cu 2+ It can form chelates with transition metal ions and effectively inhibit the auto-oxidation reaction catalyzed by metal ions.

[0022] The nano-silica described in the present invention forms a hydrogen bond network with the antioxidant amine group, thereby improving the antioxidant efficiency. The three-dimensional network formed by isocyanate cross-linking confines the antioxidant molecules to a certain area. This confinement improves the orientation order of the antioxidant molecules and increases the probability of free radical capture. During the step curing process, the antioxidant amine group undergoes a grafting reaction with the epoxy group of the epoxy resin to generate a stable CN bond. The antioxidant system described in the present invention achieves the synergy of chemical antioxidant and physical barrier through molecular design, breaking through the limitations of traditional antioxidants that are easy to migrate and resistant to temperature differences, and extending the storage life of the fire-extinguishing microcapsules from the conventional 2 years to more than 5 years.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. Strong Antioxidant Performance: The antioxidant used in this invention has a strong electron-donating capacity. During storage and use of the fire-extinguishing microcapsules, it preferentially reacts with free radicals, terminating chain oxidation reactions and effectively inhibiting metal ion-catalyzed auto-oxidation. This significantly improves antioxidant efficiency compared to traditional systems, making the fire-extinguishing microcapsules superior in antioxidant performance.

[0024] 2. High fire extinguishing efficiency: By optimizing the shell material ratio and structural design, the fire-extinguishing microcapsules can controllably release fire extinguishing agents within the temperature range of 60-150°C. In small-scale fire scenarios, they can accurately and efficiently release fire extinguishing agents, improving fire extinguishing efficiency and reducing fire extinguishing agent waste and unnecessary damage to the surrounding environment.

[0025] 3. Good stability: The shell has good integrity and uniformity, and its water vapor permeability is low, which can effectively prevent the fire extinguishing agent core material from moisture and deterioration, ensuring the long-term stability of the microcapsules. In practical applications, the performance of the microcapsules is more reliable and the service life is significantly extended. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solution of the present invention in conjunction with the inventive content of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] Preparation Example 1 Synthesis of antioxidant 1:

[0028] In the first step, under a nitrogen atmosphere, 20.00 g of raw material 1, 14.88 g of raw material 2, 0.6 g of tri-tert-butyl phosphine, 14.26 g of sodium carbonate, and 0.2 g of target carbon were added to the reaction system. The mixture was stirred thoroughly, then heated to 120°C and refluxed for 12 hours. After the reaction, the temperature was slightly lowered and filtered through diatomaceous earth to remove salts and catalyst. The filtrate was cooled to room temperature and dried. The dried solid was dissolved in petroleum ether / ethanol, recrystallized, and filtered. The filter cake was rinsed with petroleum ether several times and dried to obtain 23.19 g of intermediate 1. MS (MS+1): 446.

[0029] In the second step, under a nitrogen atmosphere, 23.19 g of intermediate 1, 22.45 g of starting material 3, 22.08 g of sodium carbonate, and 2.41 g of tetrakis(triphenylphosphine)palladium were added to the reaction system and heated to 75°C for 10 hours under reflux. The reaction mixture was then cooled to room temperature and allowed to stand for separation. The aqueous phase was extracted twice with ethyl acetate, and the combined organic phases were washed three times with water, dried, and purified by column chromatography using a mixture of petroleum ether and dichloromethane as the eluent to yield 27.72 g of antioxidant 1. MS (MS+1): 677.

[0030] 1H NMR (dChloroform) of Antioxidant 1 δ 8.08-8.00 (m, 4H), 7.21-7.14 (m, 4H), 4.10 (t, 4H), 3.75 (q, 4H), 3.71-3.53 (m, 12H), 3.36-3.27 (m, 6H), 3.25-3.18 (m, 4H), 2.78-2.66 (m, 6H), 2.02 (p, 4H).

[0031] Preparation Example 2-Preparation Example 5 The antioxidants prepared in Preparation Examples 2 to 5 were synthesized according to the method of Preparation Example 1, except that the raw material 3 was replaced. The rest of the ingredients remained the same as in Preparation Example 1. The specific structure and MS (MS+1) data of the raw material 3 are shown in the table below.

[0032] Example

[0033] Preparation of a fire extinguishing microcapsule: The thermoplastic polymer is selected from: polystyrene, the cross-linking agent is selected from: hexamethylene diisocyanate, the inorganic filler is selected from: nano-silica, the antioxidant is selected from: antioxidant 1 synthesized in Preparation Example 1, the fire extinguishing agent core material is selected from: sodium bicarbonate and ammonium dihydrogen phosphate mixed in a mass ratio of 5:3, and the organic solvent is selected from: tetrahydrofuran.

[0034] Shell material ratio: polystyrene (70 parts, 70g), hexamethylene diisocyanate (10 parts, 10g), nano-silica (20 parts, 20g), antioxidant 1 (5 parts, 5g).

[0035] Preparation steps: S1. Dissolve 70 g of polystyrene in 500 mL of tetrahydrofuran and heat to 85°C under nitrogen with continuous stirring. Add 10 g of hexamethylene diisocyanate (crosslinker), 20 g of nanosilica (particle size 200 nm), and 5 g of antioxidant 1 (structure as described in Preparation Example 1) in sequence. Maintain the temperature at 85°C with stirring for 2 hours, performing ultrasonic dispersion every 30 minutes (frequency 40 kHz, power 200 W). Then cool the mixture to 45°C to obtain a shell material solution with a viscosity of 1200 mPa·s.

[0036] S2. Mix 100g of perfluorohexanone with 3g of polyoxyethylene sorbitan monooleate (surfactant) and place in an ice-water bath at 5°C. Emulsify using a high-speed shear emulsifier at 12,000 rpm for 10 minutes to produce a nanoemulsion with an average particle size of 200nm and a dispersion index (PDI) ≤0.12. Subsequently, the shell material solution and microemulsion were separately injected into a microfluidic device (channel diameter 500μm, flow rate ratio shell:core = 3:1) to form core-shell droplets at 25°C.

[0037] S3. The resulting droplets were transferred to a sealed pressurized reactor and cured in three stages: initial curing stage: maintained at 25°C for 0.8 hours and a pressure of 0.2 MPa to achieve initial crosslinking of the shell layer; crosslinking strengthening stage: heated to 35°C, maintained for 2.5 hours, and a pressure of 0.2 MPa to promote the crosslinking reaction between the isocyanate and the polymer chain; densification stage: further heated to 45°C, maintained for 1.5 hours, and a pressure of 0.3 MPa to densify the shell structure and reduce the water vapor permeability to 3.2 g / m 2 ·24h.

[0038] Example 2-Example 5 The fire extinguishing microcapsules prepared in Examples 2 to 5 were prepared according to the preparation method of Example 1, except that the antioxidant 1 was replaced with the compounds synthesized in Preparation Examples 2 to 5 in sequence, and the rest remained the same.

[0039] Comparative Example 1 A fire extinguishing microcapsule is prepared by referring to the preparation method of Example 1, except that the antioxidant 1 is not added and the rest of the preparation method remains the same.

[0040] Performance testing: 1. The fire extinguishing agent content of the fire extinguishing microcapsules obtained in the above examples was tested. After sealed storage at 30°C for 12 months and sealed storage at 50°C for 1 month, the decrease in the fire extinguishing agent content in the fire extinguishing microcapsules is shown in the following table.

[0041] 2. The fire-extinguishing microcapsules obtained in the above example were subjected to a high-temperature release test. A 1.0 g sample of the microcapsules was placed in a sealed pressure-resistant reactor and heated to the target temperature (60°C / 100°C / 150°C) at a rate of 5°C / min. The target temperature was maintained for 30 minutes. The amount of perfluorohexanone released was measured by gas chromatography. The release rate was calculated using the formula: .

[0042]

[0043] The examples are significantly better than the comparative examples in terms of storage stability and temperature-responsive release characteristics. With the optimization of the antioxidant structure and the application of a step-curing process, the examples show lower performance degradation during long-term storage, while exhibiting a progressive release characteristic in the 60-150°C range, with significant release inhibition in the low-temperature section and improved release efficiency in the high-temperature section. In contrast, the comparative examples, due to the lack of antioxidants and process defects, exhibited premature release and severe degradation of storage stability, verifying the key impact of the synergistic effect of the material system and process of the present invention on performance improvement.

[0044] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A fire extinguishing microcapsule, characterized in that: It comprises a shell and a fire extinguishing agent core material wrapped in the shell, wherein the shell (100) is composited with a thermoplastic polymer, a cross-linking agent, an inorganic filler and an antioxidant, and the microcapsule can controllably release the fire extinguishing agent in the range of 60-150°C; The structure of the antioxidant is shown in Formula 1: Formula 1; The R1 is selected from the following substituents: 、 、 、 、 ； described For the connection site.

2. A fire extinguishing microcapsule according to claim 1, characterized in that: The thermoplastic polymer is at least one of polystyrene, polymethyl methacrylate or epoxy resin; The cross-linking agent is melamine formaldehyde resin or isocyanate compound; The inorganic filler is nano silicon dioxide or calcium carbonate; The mass ratio of the thermoplastic polymer, the cross-linking agent, the inorganic filler and the antioxidant is (50-80): (5-15): 20:

5.

3. A fire extinguishing microcapsule according to claim 1, characterized in that: The wall thickness of the shell is 5-50μm, and the wall thickness uniformity deviation is less than 10%. The shell integrity is tested by water vapor permeability value ≤5g / m 2 ·24h characterization.

4. A fire extinguishing microcapsule according to claim 1, characterized in that: The particle size of the inorganic filler is 50-500 nm.

5. A fire extinguishing microcapsule according to claim 2, characterized in that: The isocyanate compound includes at least one or more of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate.

6. A fire extinguishing microcapsule according to claim 1, characterized in that: The fire extinguishing agent core material is perfluorohexanone.

7. A fire extinguishing microcapsule according to claim 1, characterized in that: The antioxidant is at least one of the compounds shown in the following structures: 。 8. A method for preparing the fire extinguishing microcapsule according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. The thermoplastic polymer is dissolved in an organic solvent, to which the crosslinking agent, inorganic filler and antioxidant are sequentially added, stirred at 80-100 ° C until viscous, ultrasonically dispersed during stirring, and cooled to 40-50 ° C to form a shell material solution; S2. mixing the perfluorohexanone with a surfactant to form a microemulsion, controlling the emulsification temperature to ≤30°C, and coating the microemulsion droplets with the shell material solution through a microfluidic device; S3. Gradient curing is performed at 20-50°C in three stages: the first stage is 20-30°C for 0.5-1 hour to complete the initial curing, the second stage is 30-40°C for 2-3 hours to promote crosslinking, and the third stage is 40-50°C for 1-2 hours to achieve densification. The entire process is carried out in a closed and pressurized environment (0.1-0.3MPa).

9. The method for preparing fire extinguishing microcapsules according to claim 8, characterized in that: The organic solvent is tetrahydrofuran or toluene.

10. The method for preparing fire extinguishing microcapsules according to claim 8, characterized in that: The microemulsion is prepared by mixing the perfluorohexanone and the surfactant in a mass ratio of 100:(1-5), and emulsifying the mixture in an ice-water bath at 0-10° C. using a high-speed shear emulsifier at a speed of 8000-15000 rpm for 5-15 minutes to form a nanoemulsion with a particle size of 100-300 nm and a dispersion index (PDI) of ≤0.15; The surfactant is polyoxyethylene sorbitan monooleate.

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