An expanded graphite-based microencapsulated fire extinguishing agent and its preparation method

Abstract

This invention discloses an expanded graphite-based microencapsulated fire extinguishing agent and its preparation method. The preparation method of the expanded graphite-based microencapsulated fire extinguishing agent of this invention includes the following steps: 1) preparing fluorine-modified expanded graphite; 2) preparing expanded graphite adsorbed with a fluorine-containing fire extinguishing agent; 3) dispersing the expanded graphite adsorbed with the fluorine-containing fire extinguishing agent in a solvent, then adding a solution containing silica sol, a silane coupling agent, a diamine, a polyisocyanate, and a catalyst to react, followed by product separation and purification to obtain the expanded graphite-based microencapsulated fire extinguishing agent. The expanded graphite-based microencapsulated fire extinguishing agent of this invention has advantages such as high fire extinguishing efficiency, good thermal stability, high safety, high mechanical strength, and good durability. Furthermore, its preparation method is relatively simple and the production cost is low, making it suitable for large-scale industrial production and application.

Description

Technical Field

[0001] This invention relates to the field of microencapsulated fire extinguishing materials technology, specifically to an expanded graphite-based microencapsulated fire extinguishing agent and its preparation method. Background Technology

[0002] The basic principle of microencapsulation technology is to encapsulate certain substances within one or more layers of protective material, forming a capsule-like package. This allows for controlled release of these substances under specific conditions, thereby achieving various functions. In the field of fire protection, microencapsulation technology is primarily used to develop new fire extinguishing materials, aiming to improve the speed, reliability, and controllability of fire suppression.

[0003] Currently, common microcapsule fire extinguishing materials use spherical polymer materials like gelatin as the outer shell, containing a liquid fire extinguishing agent. These microcapsules automatically burst upon heating, releasing the extinguishing agent to extinguish the fire (for example, Russian patent RU 90994 discloses an automatically activating fire extinguishing material using polyurea or polyurethane as the outer shell material and containing a halogenated hydrocarbon fire extinguishing agent). While these extinguishing agents have good fire extinguishing effects, their production costs are relatively high, and they may be harmful to the environment and human health. CN 103370104 A discloses a similar automatically activating fire extinguishing material, whose core material is a halogenated hydrocarbon fire extinguishing agent. Although this fire extinguishing material improves fire extinguishing efficiency, it still has some problems (e.g., the outer shell material may become a new combustible material, affecting the fire extinguishing effect; the flammability and fire resistance of the outer shell material need further improvement), and its performance and safety in practical applications also need further enhancement.

[0004] To overcome these challenges, the development of novel microencapsulated fire extinguishing materials requires simultaneous consideration of improving extinguishing efficiency, environmental friendliness, safety, and cost-effectiveness. This includes finding new shell materials to enhance the fire resistance and fire-retardant properties of the microcapsules, as well as developing more environmentally friendly and human-safe fire extinguishing agent formulations. Simultaneously, manufacturing methods need improvement to increase the yield and quality of microcapsules and reduce production costs, enabling the wider application of microencapsulated fire extinguishing materials.

[0005] The above statements are merely background information related to the present invention and do not necessarily constitute prior art. Summary of the Invention

[0006] The purpose of this invention is to provide an expanded graphite-based microencapsulated fire extinguishing agent and its preparation method.

[0007] The technical solution adopted in this invention is:

[0008] A method for preparing an expanded graphite-based microencapsulated fire extinguishing agent includes the following steps:

[0009] 1) Expandable graphite powder is expanded to produce expanded graphite, and then the expanded graphite is immersed in a fluorinated silane coupling agent solution for modification. The product is then separated and purified to obtain fluorinated expanded graphite.

[0010] 2) Fluorine-modified expanded graphite is immersed in liquid fluorine-containing fire extinguishing agent for vacuum impregnation to obtain expanded graphite adsorbed with fluorine-containing fire extinguishing agent.

[0011] 3) Disperse expanded graphite adsorbed with fluorine-containing fire extinguishing agent in a solvent, then add a solution containing silica sol, silane coupling agent, diamine, polyisocyanate and catalyst to react, and then separate and purify the product to obtain expanded graphite-based microencapsulated fire extinguishing agent.

[0012] Preferably, the density of the expandable graphite powder in step 1) is 0.05 g / cm³. 3 ~0.20g / cm 3 .

[0013] Preferably, the expansion treatment in step 1) is carried out at a temperature of 800℃~1000℃ for a time of 40s~80s.

[0014] Preferably, the ratio of expanded graphite to fluorinated silane coupling agent solution in step 1) is 1g:150mL to 250mL.

[0015] Preferably, the concentration of the fluorinated silane coupling agent solution in step 1) is 0.01 mol / L to 0.10 mol / L.

[0016] Preferably, the fluorinated silane coupling agent in step 1) is at least one of heptadecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, and perfluorodecyltrimethoxysilane.

[0017] Preferably, the solvent in the fluorinated silane coupling agent solution in step 1) is ethanol.

[0018] Preferably, the weight ratio of fluorine-modified expanded graphite to fluorine-containing fire extinguishing agent in step 2) is 1:3 to 5.

[0019] Preferably, the liquid fluorinated fire extinguishing agent in step 2) is at least one of perfluorohexanone, heptafluoropropane, and perfluorohexane.

[0020] Preferably, the vacuum impregnation in step 2) is carried out at a temperature of 25°C to 35°C for 20 to 40 hours.

[0021] Preferably, the solvent in step 3) is ethanol.

[0022] Preferably, the weight ratio of silica sol, silane coupling agent, diamine, and polyisocyanate in step 3) is 1:1.8-2.2:1.8-2.2:2.5-3.5.

[0023] Preferably, the weight ratio of silica sol and catalyst in step 3) is 1:0.008 to 0.200.

[0024] Preferably, the silica sol in step 3) is a low-sodium silica sol with a SiO2 mass percentage of 25% to 35% and a pH value of 8.5 to 10.0.

[0025] Preferably, the silane coupling agent in step 3) is at least one of γ-methacryloxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, and phenyltrichlorosilane.

[0026] Preferably, the diamine in step 3) is at least one of ethylenediamine, butanediamine, hexamethylenediamine, and p-phenylenediamine.

[0027] Preferably, the polyisocyanate in step 3) is at least one of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), and dicyclohexylmethane diisocyanate (HMDI).

[0028] Preferably, the catalyst in step 3) is at least one of dibutyltin dilaurate, dioctyltin dilactate, and stannous octoate.

[0029] An expanded graphite-based microencapsulated fire extinguishing agent is prepared by the above-described method.

[0030] The principle of this invention:

[0031] 1) Preparation of fluorine-modified expanded graphite (FEG): Expanded graphite (EG) is immersed in a fluorine-containing silane coupling agent solution to achieve fluorine modification of expanded graphite;

[0032] 2) Vacuum impregnation adsorption technology: Liquid fluorine-containing fire extinguishing agent is mixed with fluorine-modified expanded graphite (FEG) and vacuum impregnated to achieve uniform distribution and fixation of the fire extinguishing agent in the expanded graphite;

[0033] 3) Use of silane coupling agent modified polyurea: A specific silane coupling agent is used to react with polyurea to form a modified polyurea, which is used to end-cap expanded graphite and enhance the structural integrity of microcapsules.

[0034] Definitions:

[0035] Host-guest interaction: This usually refers to the interaction between host molecules and guest molecules in chemistry. Host molecules usually have cavities or structures that can bind to guest molecules, while guest molecules are adapted to these features and can be contained or bound (e.g., expanded graphite (host molecule) and fire extinguishing agent (guest molecule) in this invention).

[0036] Multiple self-crosslinking structure: This refers to the formation of multiple crosslinking points in a polymer material. These crosslinking points connect different polymer chains through covalent bonds, forming a three-dimensional network structure. Self-crosslinking refers to the formation of a crosslinking network between polymer chains through chemical reactions without the addition of an external crosslinking agent (e.g., the crosslinking of silane coupling agent and polyurea in this invention).

[0037] Nanoscale confined phase separation polymerization: a technique for controlling the phase separation process of different components in polymer materials at the nanoscale. "Nanoscale confinement" means that this separation occurs within a very small size range, typically between 1 nm and 100 nm (e.g., the polymerization of silane coupling agents and polyurea in this invention).

[0038] The beneficial effects of the present invention are: the expanded graphite-based microencapsulated fire extinguishing agent of the present invention has the advantages of high fire extinguishing efficiency, good thermal stability, high safety, high mechanical strength and good durability, and its preparation method is relatively simple and the production cost is low, making it suitable for large-scale industrial production and application.

[0039] Specifically:

[0040] 1) High fire extinguishing performance: The expanded graphite-based microencapsulated fire extinguishing agent of the present invention combines the high specific surface area of ​​expanded graphite with the fire extinguishing characteristics of fluorine-containing fire extinguishing agents, resulting in high fire extinguishing efficiency.

[0041] 2) Improved thermal stability: The expanded graphite in the expanded graphite-based microencapsulated fire extinguishing agent of the present invention has undergone fluorine modification treatment, which enhances the thermal stability of the expanded graphite, enabling it to maintain structural integrity even at high temperatures, thus helping to improve fire extinguishing efficiency.

[0042] 3) Innovative microencapsulation technology: The silane coupling agent modified polyurea in the expanded graphite-based microencapsulated fire extinguishing agent of this invention can improve the structural integrity and thermal stability of the microcapsules, while also providing better controlled release capability;

[0043] 4) Improved safety: The expanded graphite-based microencapsulated fire extinguishing agent of the present invention can reduce the direct contact between operators and the fire extinguishing agent, reduce operational risks, and improve safety during storage and transportation.

[0044] 5) Improved physical properties: The porous structure of expanded graphite in the expanded graphite-based microencapsulated fire extinguishing agent of the present invention helps to adsorb and fix the fire extinguishing agent, while microencapsulation can further improve the mechanical strength and durability of the material. Detailed Implementation

[0045] The present invention will be further explained and described below with reference to specific embodiments.

[0046] Example 1:

[0047] An expanded graphite-based microencapsulated fire extinguishing agent, the preparation method of which is as follows:

[0048] 1) Take 500g of expandable graphite powder (density 0.20g / cm³). 3 The sample was dried in a vacuum drying oven at 80°C for 12 hours (to completely remove moisture), then placed in a quartz beaker and placed in a muffle furnace at 900°C for 1 minute to produce expanded graphite (EG). The EG was then immersed in an anhydrous ethanol solution of heptadecafluorooctyltrimethoxysilane with a concentration of 0.01 mol / L. The ratio of expanded graphite to fluorinated silane coupling agent solution was 1 g: 200 mL. The mixture was stirred at 60°C for 30 minutes, then transferred to an environment of 60°C for 5 hours of ultrasonic crushing. The mixture was then stirred until the solution cooled naturally, filtered, and the solid was dried to obtain fluorinated expanded graphite (FEG).

[0049] 2) Mix 100g of perfluorohexanone and 30g of FEG and stir well. Then place it in a water bath at 30℃ for 24h (stir once every 2h to ensure that the perfluorohexanone is evenly absorbed by FEG). Then place it in a vacuum drying oven and heat at 30℃ for 8h. Then cool it naturally in a vacuum environment. Then use filter paper to remove excess perfluorohexanone to obtain expanded graphite adsorbed with fluorine-containing fire extinguishing agent.

[0050] 3) Disperse 100g of expanded graphite adsorbed with fluorine-containing fire extinguishing agent in 400mL of ethanol, and then add 70g of a solution containing low-sodium silica sol (SiO2 mass percentage 30%, pH 9.0), γ-methacryloyloxypropyltrimethoxysilane, hexamethylenediamine, IPDI, and dibutyltin dilaurate at a rate of 2mL / s (the weight ratio of low-sodium silica sol, γ-methacryloyloxypropyltrimethoxysilane, hexamethylenediamine, IPDI, and dibutyltin dilaurate is 0.5:1:1:1.5:0.005). After the addition is complete, stir for 5h, centrifuge, take the lower precipitate, wash it twice with anhydrous ethanol, and then dry it at 60℃ to obtain the expanded graphite-based microencapsulated fire extinguishing agent.

[0051] Example 2:

[0052] An expanded graphite-based microencapsulated fire extinguishing agent is identical to Example 1, except that the concentration of the anhydrous ethanol solution of heptadecafluorooctyltrimethoxysilane in step 1) is adjusted from "0.01 mol / L" to "0.10 mol / L" during preparation.

[0053] Example 3:

[0054] An expanded graphite-based microencapsulated fire extinguishing agent is identical to that in Example 1, except that "perfluorohexanone" in step 2) is replaced with "perfluorohexane" during preparation.

[0055] Example 4:

[0056] An expanded graphite-based microencapsulated fire extinguishing agent is identical to that in Example 1, except that “γ-methacryloyloxypropyltrimethoxysilane” in step 3) is replaced with “vinyltrimethoxysilane” during preparation.

[0057] Example 5:

[0058] An expanded graphite-based microencapsulated fire extinguishing agent is identical to Example 1 except that the weight ratio of low-sodium silica sol and dibutyltin dilaurate in step 3) is adjusted from "0.5:0.005" to "0.5:0.100".

[0059] Comparative Example 1:

[0060] A fire extinguishing agent is identical to Example 1 except that the step 1) of preparation is changed from "to be placed in a muffle furnace at 900°C for 1 minute for expansion treatment" to "to be placed in a muffle furnace at 900°C for 0 minutes for expansion treatment (i.e., no expansion treatment is performed)".

[0061] Comparative Example 2:

[0062] A fire extinguishing agent is identical to that in Example 1, except that the amount of perfluorohexanone in step 2) is adjusted from "100g" to "30g" during preparation.

[0063] Comparative Example 3:

[0064] A fire extinguishing agent is identical to that in Example 1, except that low-sodium silica sol is not added in step 3) during preparation.

[0065] Comparative Example 4:

[0066] A fire extinguishing agent is identical to that in Example 1, except that γ-methacryloyloxypropyltrimethoxysilane is not added in step 3) during preparation.

[0067] Comparative Example 5:

[0068] A fire extinguishing agent, except that IPDI was not added in step 3) during preparation, is completely identical to that in Example 1.

[0069] Performance testing:

[0070] The performance test data of the expanded graphite-based microencapsulated fire extinguishing agents of Examples 1-5 and the fire extinguishing agents of Comparative Examples 1-5 are shown in the table below:

[0071] Table 1. Performance test data of expanded graphite-based microencapsulated fire extinguishing agents in Examples 1-5 and comparative examples 1-5.

[0072]

[0073]

[0074] Note:

[0075] Embedding efficiency: First, measure the mass of the extinguishing agent sample. Then, grind the extinguishing agent sample thoroughly and dissolve it in an appropriate solvent to extract the core material. Place the obtained extract in an oven at 120°C and dry it until the mass is constant. Then measure the mass of the core material. Calculate the embedding efficiency according to the following formula: Embedding efficiency (%) = Core material mass / Extinguishing agent sample mass × 100%.

[0076] Encapsulation efficiency / 80℃ heat storage for 2 days: Place the fire extinguishing agent sample in a 100mL Erlenmeyer flask with a lid, then store it in a forced-air drying oven at 80℃ for 2 days, and then take it out to test the encapsulation efficiency.

[0077] As shown in Table 1:

[0078] 1) The expanded graphite-based microencapsulated fire extinguishing agents in Examples 1-5 have high encapsulation efficiency and good heat resistance stability;

[0079] 2) Compared with the expanded graphite-based microencapsulated fire extinguishing agent in Example 1, the expanded graphite-based microencapsulated fire extinguishing agent in Example 2 increased the concentration of the fluorinated silane coupling agent solution (i.e., increased the amount of fluorinated silane coupling agent), and the encapsulation efficiency was improved. This indicates that grafting more fluorine elements onto expanded graphite can improve the host-guest effect between expanded graphite and fire extinguishing agent.

[0080] 3) Compared with the expanded graphite-based microencapsulated fire extinguishing agent in Example 1, the expanded graphite-based microencapsulated fire extinguishing agent in Example 3 uses a fire extinguishing agent with a higher boiling point, which can effectively improve the encapsulation rate, indicating that the fire extinguishing agent with a higher boiling point suffers less loss during the encapsulation process.

[0081] 4) Compared with the expanded graphite-based microencapsulated fire extinguishing agent in Example 1, the expanded graphite-based microencapsulated fire extinguishing agent in Example 4 uses a silane coupling agent that is easier to hydrolyze, which can effectively improve heat resistance. This shows that under the same temperature and time, the easily hydrolyzed silane coupling agent can produce a higher density microcapsule shell.

[0082] 5) Compared with the expanded graphite-based microencapsulated fire extinguishing agent of Example 1, the expanded graphite-based microencapsulated fire extinguishing agent of Example 5 has increased the amount of catalyst, which can effectively improve the heat resistance. This shows that under the same temperature and time, increasing the amount of catalyst can better catalyze the hydrolysis of silane coupling agent and produce a higher density microcapsule shell.

[0083] 6) Compared with the expanded graphite-based microencapsulated fire extinguishing agent of Example 1, the fire extinguishing agent of Comparative Example 1 did not undergo graphite expansion treatment, and the encapsulation efficiency decreased significantly, indicating that graphite can produce a porous adsorption structure after expansion.

[0084] 7) Compared with the expanded graphite-based microencapsulated fire extinguishing agent of Example 1, the fire extinguishing agent of Comparative Example 2 reduced the ratio of fire extinguishing agent to modified expanded graphite, and the encapsulation efficiency decreased significantly. This was because the amount of fire extinguishing agent used was insufficient.

[0085] 8) Compared with the expanded graphite-based microencapsulated fire extinguishing agent of Example 1, the fire extinguishing agent of Comparative Example 3 removed silica sol, and the heat resistance of the microcapsules decreased, indicating that silica sol is the key factor in forming a dense cross-linked shell.

[0086] 9) Compared with the expanded graphite-based microencapsulated fire extinguishing agent of Example 1, the fire extinguishing agent of Comparative Example 4 removed the silane coupling agent, and the heat resistance of the microcapsules decreased, indicating that the silane coupling agent is the key factor in forming a dense cross-linked shell.

[0087] 10) Compared with the expanded graphite-based microencapsulated fire extinguishing agent of Example 1, the fire extinguishing agent of Comparative Example 5 removed polyisocyanate, and the heat resistance of the microcapsules decreased, indicating that polyisocyanate is a key factor in forming a dense cross-linked shell.

[0088] In summary, only by using the specific formulation and process of this application can the expanded graphite-based microencapsulated fire extinguishing agent achieve high coating efficiency and heat resistance stability.

[0089] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing an expanded graphite-based microencapsulated fire extinguishing agent, characterized in that, Includes the following steps: 1) Expandable graphite powder is expanded to produce expanded graphite, and then the expanded graphite is immersed in a fluorinated silane coupling agent solution for modification. The product is then separated and purified to obtain fluorinated expanded graphite. 2) Fluorine-modified expanded graphite is immersed in liquid fluorine-containing fire extinguishing agent for vacuum impregnation to obtain expanded graphite adsorbed with fluorine-containing fire extinguishing agent; 3) Disperse expanded graphite adsorbed with fluorine-containing fire extinguishing agent in a solvent, then add dropwise a solution containing silica sol, silane coupling agent, diamine, polyisocyanate and catalyst to react, and then separate and purify the product to obtain expanded graphite-based microencapsulated fire extinguishing agent. Step 1) The expansion treatment is carried out at a temperature of 800℃~1000℃ for a time of 40s~80s; In step 3), the weight ratio of silica sol, silane coupling agent, diamine, and polyisocyanate is 1:1.8–2.2:1.8–2.2:2.5–3.

5. Step 3) The silica sol is a low-sodium silica sol with a SiO2 mass percentage of 25% to 35% and a pH value of 8.5 to 10.0; Step 3) The silane coupling agent is at least one of γ-methacryloxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, and phenyltrichlorosilane; Step 3) The diamine is at least one of ethylenediamine, butanediamine, hexamethylenediamine, and p-phenylenediamine; Step 3) The polyisocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate; Step 3) The catalyst is at least one of dibutyltin dilaurate, dioctyltin dilactate, and stannous octoate.

2. The preparation method according to claim 1, characterized in that: Step 1) The density of the expandable graphite powder is 0.05 g / cm3 to 0.20 g / cm3.

3. The preparation method according to claim 1 or 2, characterized in that: Step 1) The fluorinated silane coupling agent is at least one of heptadecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, and perfluorodecyltrimethoxysilane.

4. The preparation method according to claim 1, characterized in that: Step 2) The weight ratio of the fluorinated modified expanded graphite to the fluorinated fire extinguishing agent is 1:3 to 5.

5. The preparation method according to claim 1 or 4, characterized in that: Step 2) The liquid fluorinated fire extinguishing agent is at least one of perfluorohexanone, heptafluoropropane, and perfluorohexane.

6. The preparation method according to claim 1 or 4, characterized in that: Step 2) The vacuum impregnation is carried out at a temperature of 25℃~35℃ for 20h~40h.

7. An expanded graphite-based microencapsulated fire extinguishing agent, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 6.

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