Nanographene-doped organic pillared vermiculite dispersion liquid and preparation and application thereof

Abstract

This invention belongs to the field of fire extinguishing agent technology, and provides a nano-graphene-doped organic pillared vermiculite dispersion, its preparation and application. The preparation method includes modifying vermiculite with a quaternary ammonium salt to obtain organic pillared vermiculite; preparing an organic pillared vermiculite suspension and co-filtering it with a nano-graphene dispersion to obtain composite pillared vermiculite; and using the composite pillared vermiculite, foaming agent, and dispersant as raw materials, milling to obtain the nano-graphene-doped organic pillared vermiculite dispersion. The nano-graphene-doped organic pillared vermiculite dispersion prepared by this invention, when applied as a foam fire extinguishing agent, has advantages such as high-efficiency fire extinguishing, good anti-burning ability, good stability, and low re-ignition resistance, and is suitable for lithium battery fire extinguishing.

Description

Technical Field

[0001] This application relates to the field of fireproof and fire extinguishing materials technology, and in particular to a nano-graphene-doped organic pillared vermiculite dispersion and its preparation and application. Background Technology

[0002] Vermiculite is a layered silicate mineral. Due to its good thermal expansion characteristics, low density, high melting point, low thermal conductivity, good chemical insulation, strong adsorption, good sound insulation, and environmental friendliness and low price after expansion, it is widely used in agriculture, animal husbandry, horticulture, construction, environmental protection, energy conservation and other fields. It has great application prospects, especially in the field of fireproof and fire extinguishing materials.

[0003] However, vermiculite, being an inorganic mineral, is insoluble in water and oleophobic, limiting its wider application in homogeneous systems and other fields. Therefore, it needs modification to increase its hydrophilicity and oleophilicity. Furthermore, vermiculite belongs to the monoclinic crystal system, consisting of a bilayered silica-oxygen tetrahedron formed by two layered silica-oxygen frameworks bonded together by a magnesium hydroxide layer. Within the tetrahedron, due to Al... 3+ Replace Si 4+ This generates excess negative charge and causes the interlayer to fill with exchangeable cations and water molecules.

[0004] Pillaring technology is a process for improving the interlayer spacing, stability, specific surface area, and surface activity (including surface acidity, catalytic performance, and adsorption performance) of layered materials; it is a special activation method. Therefore, vermiculite can be organically pillared using cation exchange.

[0005] Foam extinguishing agents are effective for extinguishing flammable and combustible liquids. They primarily work by forming a coagulated foam layer on the liquid surface, which acts as a suffocating and cooling agent. Currently, the foam extinguishing agents used to extinguish lithium battery fires are mainly aqueous film-forming foam (AFFF) extinguishing agents. While AFFF extinguishing agents are currently considered ideal, the lithium battery is prone to reignition for a period of time after extinguishing external open flames. Furthermore, existing AFFF extinguishing agents contain fluorocarbon-like surfactants such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid ammonium (PFOA), which are difficult to degrade in the environment, posing a potential environmental pollution risk.

[0006] To address the aforementioned issues, existing research has developed aqueous film-forming foam fire extinguishing agents containing modified vermiculite. For example, patent application CN113440785A discloses the preparation of a nano-sized vermiculite dispersion and its application in foam fire extinguishing agents. This vermiculite dispersion is prepared by exchanging vermiculite with quaternary ammonium salt cations, washing and filtering to remove halogen salts, adding a dispersant, and milling in a sand mill to obtain a nano-vermiculite dispersion with an average particle size of 100 nanometers. This nano-vermiculite dispersion, when applied to foam fire extinguishing agents, does not contain fluorocarbon surfactants, increases foam toughness, and features rapid extinguishing speed, strong anti-burning ability, environmental friendliness, and low cost. However, the aforementioned nano-sized vermiculite consists of single-pillared molecules entering the interlayer environment of vermiculite, limiting the improvement in the anti-burning ability of the prepared foam fire extinguishing agent. In fires involving large series-parallel lithium battery modules, a significant probability of reignition remains.

[0007] Graphene is a novel material with a single-layer sheet structure composed of carbon atoms. It is a two-dimensional material, only one atom thick, consisting of a hexagonal honeycomb lattice of carbon atoms arranged in sp2 hybrid orbitals. Graphene's unique two-dimensional layered structure endows it with excellent flame-retardant properties. Its two-dimensional sheet structure has a sheet-like barrier effect, which can delay heat transfer, the diffusion and escape of pyrolysis products, and the diffusion and mixing of oxygen. Therefore, current research utilizes graphene to prepare highly efficient and environmentally friendly fire extinguishing agents.

[0008] In summary, if we can utilize graphene and organic pillared vermiculite to prepare composite pillared vermiculite and then prepare an aqueous film-forming foam fire extinguishing agent, the synergistic effect of graphene and organic pillared vermiculite can achieve rapid fire extinguishing and effective prevention of reignition when extinguishing lithium battery fires, while also being environmentally friendly. This would greatly enhance the practicality of aqueous film-forming foam fire extinguishing agents in lithium battery fires. Summary of the Invention

[0009] In view of the shortcomings of the prior art, the present invention provides a nano-graphene-doped organic pillared vermiculite dispersion and its preparation and application, in order to solve the problems of existing aqueous film-forming foam fire extinguishing agents used for lithium battery fire extinguishing, which, although fast in extinguishing fires, are prone to reignition and contain fluorocarbon surfactants, causing environmental pollution.

[0010] To achieve the above and related objectives, the present invention adopts the following technical solution:

[0011] The first aspect of this invention provides a method for preparing a nano-graphene-doped organic pillared vermiculite dispersion, the method comprising the following steps:

[0012] (1) Organic pillared vermiculite was prepared by modifying vermiculite with quaternary ammonium salt;

[0013] (2) Prepare an organic pillared vermiculite suspension and co-filter it with a nano-graphene dispersion to obtain composite pillared vermiculite;

[0014] (3) Using composite pillared vermiculite, foaming agent and dispersant as raw materials, a nano-graphene-doped organic pillared vermiculite dispersion was prepared by sand milling.

[0015] In one embodiment of this application, the preparation conditions in step (1) are selected from at least one of (I) to (III):

[0016] (I) The quaternary ammonium salt is any one of dodecyl, tetradecyl, hexadecyl, and octadecyltrimethylammonium bromide;

[0017] (II) The vermiculite is expanded vermiculite;

[0018] (III) The mass ratio of quaternary ammonium salt to vermiculite is (1-2):(1-3).

[0019] In one embodiment of this application, step (1) includes:

[0020] (a) Grind vermiculite, sieve it, add it to deionized water, and stir;

[0021] (b) Add quaternary ammonium salt, stir once every 15-20 minutes, react at a constant temperature for 2-3 hours, sonicate for 20-30 minutes, age, separate, wash, and dry to obtain organic pillared vermiculite.

[0022] In one embodiment of this application, the reaction conditions in step (2) are selected from at least one of (Ⅳ) to (Ⅵ):

[0023] (Ⅳ) Prepare an organic pillared vermiculite suspension with a solid content of 10wt% to 20wt%;

[0024] (V) Prepare a nano-graphene dispersion with a solid content of 20wt% to 25wt% using water, nano-graphene, and dispersant as raw materials;

[0025] (VI) The volume ratio of organic pillared vermiculite suspension to nano-graphene dispersion is (2-3):(1-2).

[0026] In one embodiment of this application, the raw materials in step (3) further include a wetting agent and water.

[0027] In one embodiment of this application, the dispersant is at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and hexadecyl ammonium bromide.

[0028] In one embodiment of this application, the reaction conditions in step (3) are selected from at least one of (VII) to (VIII):

[0029] (VII) The mass ratio of composite pillar-supported vermiculite, foaming agent, dispersant, wetting agent and water is (5~10):(1~):(1~8):(2~6):(74~89);

[0030] (VIII) Grind for 10 to 20 hours.

[0031] In one embodiment of this application, the foaming agent is at least one of dodecyl dimethyl betaine, cocamidopropyl betaine, alkyl glycoside, and octylamidopropyl betaine;

[0032] The wetting agent is at least one of alkyl monohydric alcohols, alkyl dihydric alcohols, alkyl polyhydric alcohols, and alkyl dihydric alcohol polyether derivatives.

[0033] The second aspect of the present invention provides a method for preparing a nano-graphene-doped organic pillared vermiculite dispersion as described above.

[0034] A third aspect of the present invention provides the application of the nano-graphene-doped organic pillared vermiculite dispersion as described above in foam fire extinguishing agents.

[0035] The beneficial technical effects of this invention are as follows:

[0036] This application first modifies vermiculite by expanding the interlayer spacing of vermiculite through organic pillaring; then, it prepares composite pillared vermiculite by depositing nano-graphene into the interlayer spacing of vermiculite through co-filtration. A nano-graphene-doped organic pillared vermiculite dispersion is then prepared using the composite pillared vermiculite as raw material, and subsequently, an aqueous film-forming foam fire extinguishing agent is prepared.

[0037] This application utilizes the synergistic effect of nano-graphene and organic pillared vermiculite to improve the fire resistance of aqueous film-forming foam fire extinguishing agents. The prepared foam fire extinguishing agent is suitable for fires involving large series and parallel lithium battery modules, enabling rapid fire extinguishing and effectively preventing reignition. Furthermore, since the foam fire extinguishing agent does not contain fluorocarbon surfactants, it is environmentally friendly.

[0038] When using the foam extinguishing agent of this application to extinguish lithium battery fires, the organic pillared vermiculite first forms a protective layer on the lithium battery through its covering and isolating effect, suppressing the oxygen supply and thus blocking or slowing down the chemical reaction process of the flame, achieving the first level of fire extinguishing. Then, the nano-graphene in the composite pillared vermiculite acts as a barrier, delaying the outward transfer of heat from the lithium battery and the diffusion and mixing of pyrolysis products and / or oxygen during combustion, achieving the second level of fire extinguishing, thereby effectively preventing reignition after a period of time following the first level of fire extinguishing.

[0039] The foam extinguishing agent described in this application can achieve the purpose of rapid and thorough fire extinguishing through the above-mentioned two-stage fire extinguishing process.

[0040] The preparation method of the graphene-doped organic pillared vermiculite dispersion presented in this application is simple and low in cost.

[0041] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation

[0042] Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should be understood that certain features of the invention (described in the context of separate embodiments for clarity) may also be provided in combination in a single embodiment. Conversely, multiple features of the invention (described in the context of a single embodiment for brevity) may also be provided separately or in any suitable combination or, where appropriate, in any other described embodiment of the invention. Certain features described in the context of various embodiments will not be considered essential features of those embodiments unless the embodiment is inoperable without those elements. The invention is further illustrated below by specific examples; however, it should be noted that the specific process conditions and results described in the embodiments of the invention are merely illustrative and should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be covered within the scope of protection of the invention.

[0043] This invention provides a method for preparing a nano-graphene-doped organic pillared vermiculite dispersion, the method comprising the following steps:

[0044] (1) Using expanded vermiculite as raw material, grind it, pass it through an 80-100 mesh sieve, add it to deionized water, and the mass ratio of vermiculite to deionized water is (1-2):(10-15). Stir for 10-15 minutes.

[0045] The quaternary ammonium salt is any one of dodecyl, tetradecyl, hexadecyl, or octadecyltrimethylammonium bromide. The mass ratio of the quaternary ammonium salt to vermiculite is (1-2):(1-3). The quaternary ammonium salt is added to the aqueous solution of vermiculite, and the mixture is stirred every 15-20 minutes. The mixture is reacted at a constant temperature of 60-80°C for 2-3 hours. The reaction solution is then transferred to an ultrasonic cleaner and ultrasonicated for 20-30 minutes. The solution is then removed and aged at room temperature for 5 days. After centrifugation and washing, the solution is washed three times with deionized water and dried to obtain organic pillared vermiculite.

[0046] (2) Add organic pillared vermiculite to water to prepare an organic pillared vermiculite suspension with a solid content of 10wt% to 20wt%;

[0047] A nano-graphene dispersion with a solid content of 20wt% to 25wt% was prepared using water, nano-graphene, and a dispersant as raw materials. The dispersant was at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and hexadecyl ammonium bromide.

[0048] A composite pillared vermiculite was prepared by mixing an organic pillared vermiculite suspension with a volume ratio of (2-3):(1-2) with a nano-graphene dispersion and then vacuum filtering.

[0049] (3) The product is made from composite pillared vermiculite, foaming agent, dispersant, wetting agent and water, wherein the foaming agent is at least one of dodecyl dimethyl betaine, cocamidopropyl betaine, alkyl glycoside and octylamidopropyl betaine; the wetting agent is at least one of alkyl monohydric alcohol, alkyl dihydric alcohol, alkyl polyhydric alcohol and alkyl dihydric alcohol polyether derivatives;

[0050] A composite pillared vermiculite, foaming agent, dispersant, wetting agent, and water in a mass ratio of (5-10):(1-2):(3-8):(2-6):(74-89) were mixed and pre-dispersed using a high-speed stirrer for 30 minutes. The mixture was then transferred to a sand mill for 10-20 hours to obtain a nano-graphene-doped organic pillared vermiculite dispersion.

[0051] This invention provides a method for preparing a nano-graphene-doped organic pillared vermiculite dispersion as described above.

[0052] This invention provides the application of the above-described nano-graphene-doped organic pillared vermiculite dispersion in foam fire extinguishing agents.

[0053] The present invention will be described in detail below through specific examples and embodiments. It should also be understood that the following embodiments are only for specific illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0054] Example 1

[0055] (1) Grind the expanded vermiculite, pass it through an 80-mesh sieve, add it to deionized water, and the mass ratio of expanded vermiculite to deionized water is 1:10. Stir for 10 minutes.

[0056] Octadecyltrimethylammonium bromide was added to an aqueous solution of expanded vermiculite at a mass ratio of 1:1. The mixture was stirred every 15 minutes and reacted at a constant temperature of 70°C for 2 hours. The reaction solution was then transferred to an ultrasonic cleaner and sonicated for 20 minutes. The solution was then removed, aged at room temperature for 5 days, separated and washed by centrifugation, washed repeatedly with deionized water 3 times, and dried at 80°C to obtain organic pillared vermiculite.

[0057] (2) Add organic pillared vermiculite to water to prepare an organic pillared vermiculite suspension with a solid content of 10 wt%; use water, nano-graphene, and sodium dodecyl sulfate as raw materials to prepare a nano-graphene dispersion with a solid content of 20 wt%.

[0058] Composite pillared vermiculite was prepared by mixing an organic pillared vermiculite suspension with a volume ratio of 1:1 with a nano-graphene dispersion and then vacuum filtering the mixture.

[0059] (3) The composite pillared vermiculite, dodecyl dimethyl betaine, sodium dodecyl sulfate, propylene glycol and water in a mass ratio of 5:1:3:2:89 were mixed and pre-dispersed for 30 min by stirring with a high-speed stirrer. The mixture was then transferred to a sand mill for sand milling for 10 h to obtain a nano-graphene-doped organic pillared vermiculite dispersion.

[0060] (4) The above-mentioned nano-graphene-doped organic pillar vermiculite dispersion was added to water and diluted to a mass concentration of 6% to obtain a foam fire extinguishing agent.

[0061] Example 2

[0062] (1) Grind the expanded vermiculite, pass it through a 100-mesh sieve, add it to deionized water, and the mass ratio of expanded vermiculite to deionized water is 1:12. Stir for 15 minutes.

[0063] Hexadecyltrimethylammonium bromide was added to an aqueous solution of expanded vermiculite at a mass ratio of 2:3. The mixture was stirred every 15 minutes and reacted at a constant temperature of 70°C for 2.5 hours. The reaction solution was then transferred to an ultrasonic cleaner and sonicated for 25 minutes. The solution was then removed, aged at room temperature for 5 days, separated and washed by centrifugation, washed repeatedly with deionized water 3 times, and dried at 80°C to obtain organic pillared vermiculite.

[0064] (2) Add organic pillared vermiculite to water to prepare an organic pillared vermiculite suspension with a solid content of 15 wt%; use water, nano-graphene, and sodium dodecylbenzenesulfonate as raw materials to prepare a nano-graphene dispersion with a solid content of 20 wt%.

[0065] Composite pillared vermiculite was prepared by mixing an organic pillared vermiculite suspension with a volume ratio of 2:1 with a nano-graphene dispersion and then vacuum filtering.

[0066] (3) The composite pillared vermiculite, dodecyl dimethyl betaine, sodium dodecylbenzene sulfonate, propylene glycol and water in a mass ratio of 8:2:6:2:82 were mixed and pre-dispersed using a high-speed stirrer for 30 min. The mixture was then transferred to a sand mill for 15 h to obtain a nano-graphene-doped organic pillared vermiculite dispersion.

[0067] (4) The above-mentioned nano-graphene-doped organic pillar vermiculite dispersion was added to water and diluted to a mass concentration of 6% to obtain a foam fire extinguishing agent.

[0068] Example 3

[0069] (1) Grind the expanded vermiculite, pass it through a 100-mesh sieve, add it to deionized water, and the mass ratio of expanded vermiculite to deionized water is 1:10. Stir for 10 minutes.

[0070] Tetradecyltrimethylammonium bromide was added to an aqueous solution of expanded vermiculite at a mass ratio of 2:1.5. The mixture was stirred every 15 minutes and reacted at a constant temperature of 70°C for 3 hours. The reaction solution was then transferred to an ultrasonic cleaner and sonicated for 25 minutes. The solution was then removed and aged at room temperature for 5 days. After centrifugation and washing, the solution was washed three times with deionized water and dried at 80°C to obtain organic pillared vermiculite.

[0071] (2) Add organic pillared vermiculite to water to prepare an organic pillared vermiculite suspension with a solid content of 18 wt%; use water, nano-graphene, and sodium dodecylbenzenesulfonate as raw materials to prepare a nano-graphene dispersion with a solid content of 22 wt%.

[0072] Composite pillared vermiculite was prepared by mixing an organic pillared vermiculite suspension with a volume ratio of 3:2 and a nano-graphene dispersion and then vacuum filtering.

[0073] (3) The composite pillared vermiculite, cocamidopropyl betaine, sodium dodecylbenzene sulfonate, propylene glycol and water in a mass ratio of 8:2:8:4:78 were mixed and pre-dispersed for 30 min by stirring with a high-speed stirrer. The mixture was then transferred to a sand mill for sand milling for 15 h to obtain a nano-graphene-doped organic pillared vermiculite dispersion.

[0074] (4) The above-mentioned nano-graphene-doped organic pillar vermiculite dispersion was added to water and diluted to a mass concentration of 6% to obtain a foam fire extinguishing agent.

[0075] Example 4

[0076] (1) Grind the expanded vermiculite, pass it through a 100-mesh sieve, add it to deionized water, and the mass ratio of expanded vermiculite to deionized water is 1:10. Stir for 10 minutes.

[0077] Tetradecyltrimethylammonium bromide was added to an aqueous solution of expanded vermiculite at a mass ratio of 1:1. The mixture was stirred every 15 minutes and reacted at a constant temperature of 70°C for 3 hours. The reaction solution was then transferred to an ultrasonic cleaner and sonicated for 25 minutes. The solution was then removed and aged at room temperature for 5 days. After centrifugation and washing, the solution was washed three times with deionized water and dried at 80°C to obtain organic pillared vermiculite.

[0078] (2) Add organic pillared vermiculite to water to prepare an organic pillared vermiculite suspension with a solid content of 20 wt%; use water, nano-graphene, and sodium dodecylbenzenesulfonate as raw materials to prepare a nano-graphene dispersion with a solid content of 25 wt%.

[0079] Composite pillared vermiculite was prepared by mixing an organic pillared vermiculite suspension with a volume ratio of 3:2 and a nano-graphene dispersion and then vacuum filtering.

[0080] (3) The composite pillared vermiculite, cocamidopropyl betaine, sodium dodecylbenzene sulfonate, diethylene glycol and water in a mass ratio of 5:2:8:2:83 were mixed and pre-dispersed using a high-speed stirrer for 30 min. The mixture was then transferred to a sand mill for 20 h to obtain a nano-graphene-doped organic pillared vermiculite dispersion.

[0081] (4) The above-mentioned nano-graphene-doped organic pillar vermiculite dispersion was added to water and diluted to a mass concentration of 6% to obtain a foam fire extinguishing agent.

[0082] Example 5

[0083] The difference between this embodiment and Embodiment 1 is that the above-mentioned nano-graphene-doped organic pillared vermiculite dispersion is added to water and diluted to a mass concentration of 4% to obtain a foam fire extinguishing agent.

[0084] Comparative Example 1

[0085] (1) Grind the expanded vermiculite, pass it through an 80-mesh sieve, add it to deionized water, and the mass ratio of expanded vermiculite to deionized water is 1:10. Stir for 10 minutes.

[0086] Octadecyltrimethylammonium bromide was added to an aqueous solution of expanded vermiculite at a mass ratio of 1:1. The mixture was stirred every 15 minutes and reacted at a constant temperature of 70°C for 2 hours. The reaction solution was then transferred to an ultrasonic cleaner and sonicated for 20 minutes. The solution was then removed, aged at room temperature for 5 days, separated and washed by centrifugation, washed repeatedly with deionized water 3 times, and dried at 80°C to obtain organic pillared vermiculite.

[0087] (2) Mix organic pillared vermiculite, dodecyl dimethyl betaine, sodium dodecyl sulfate, propylene glycol and water in a mass ratio of 5:1:3:2:89, stir with a high-speed stirrer for 30 min for pre-dispersion, and then transfer to a sand mill for 10 h to obtain organic pillared vermiculite dispersion.

[0088] (3) Add the above organic pillar vermiculite dispersion to water and dilute it to a mass concentration of 6% to prepare a foam fire extinguishing agent.

[0089] Comparative Example 2

[0090] A foam fire extinguishing agent is obtained by mixing vermiculite, graphene, dodecyl dimethyl betaine, sodium dodecyl sulfate, propylene glycol, sodium dodecylbenzene sulfonate, sodium citrate, urea, and water in a mass ratio of 3:3:2:8:3:2:0.5:8:70.5 and stirring until homogeneous.

[0091] Comparative Example 3

[0092] Commercially available foam fire extinguishing agent.

[0093] Performance testing

[0094] Fire extinguishing performance: The fire extinguishing performance of the foam extinguishing agents in Examples 1-5 and Comparative Examples 1-3 was tested according to GB 15308-2006 "Foam Extinguishing Agents". The test results are shown in Table 1.

[0095] Lithium battery fire extinguishing: Twelve test lithium batteries were connected in parallel and placed on a heating plate with a power of 1kW, a temperature of 600℃, and dimensions of 210mm×170mm×15mm. The batteries were charged to 100% SOC and then the power was turned off. The heating plate was heated uniformly at a rate of 20℃ / min. Twenty seconds after the battery thermally ran away and the casing burst, foam extinguishing agents from the various embodiments and comparative examples of this invention were sprayed onto the heating plate. The time required to extinguish the open flame and whether reignition occurred after 2 minutes were measured. The test results are shown in Table 2. (The lithium batteries used in this application are soft-pack ternary lithium-ion NCM811 / graphite system power batteries, with an aluminum outer film.)

[0096] Table 1. Fire extinguishing performance tests of foam extinguishing agents in each embodiment and comparative example.

[0097] Test object injection time / s Foaming ratio / times 25% precipitation time / s Fire control time / s 25% fire resistance time / s Example 1 120 8.2 230 49 284 Example 2 120 8.5 234 44 293 Example 3 120 8.0 227 54 275 Example 4 120 7.8 221 57 270 Example 5 120 8.8 237 42 302 Comparative Example 1 120 5.3 170 82 213 Comparative Example 2 120 5.6 189 73 237 Comparative Example 3 120 4.2 121 98 158

[0098] Table 2. Lithium-ion battery fire extinguishing tests of foam fire extinguishing agents in each embodiment and comparative example.

[0099]

[0100]

[0101] As shown in Table 1, the foam extinguishing agent prepared using nano-graphene-doped organic pillared vermiculite dispersion in this application is a low-expansion foam extinguishing agent. Furthermore, the 25% eluent release time of the foam extinguishing agents prepared in Examples 1-5 of this application is in the range of 3-4 minutes, significantly higher than that of the comparative examples 1-3, indicating better stability. The 100% fire control time of the foam extinguishing agents prepared in Examples 1-5 of this application is all within 1 minute, demonstrating high-efficiency fire extinguishing. In contrast, the fire extinguishing agents of Comparative Examples 1-3 have a slower fire extinguishing speed, requiring 2 minutes to guarantee 100% fire control. In addition, the foam extinguishing agents prepared in Examples 1-5 of this application, under the action of organic pillared vermiculite and nano-graphene, exhibit a good barrier effect, significantly improving their anti-burning ability. The anti-burning time is maintained above 4 minutes, indicating that the prepared foam extinguishing agent prevents the fire source from reigniting after extinguishing it. In contrast, the foam extinguishing agents in Comparative Examples 1-3 had a burning resistance time of 2-4 minutes. After extinguishing the fire, the fire was prone to reignition after a period of time, indicating poor burning resistance. In summary, the foam extinguishing agent prepared in this application has good stability, burning resistance, and high-efficiency fire extinguishing capability.

[0102] As shown in Table 2, the foam fire extinguishing agents prepared in Examples 1-5 of this application can quickly extinguish lithium battery fires within 1.5 minutes, and prevent reignition after a period of time, achieving complete extinguishment with high safety. In contrast, the foam fire extinguishing agents in Comparative Examples 1-3 take more than 2 minutes to extinguish lithium battery fires, which is slower, and there is a possibility of reignition after a period of time, failing to achieve a complete extinguishing effect. Therefore, the foam fire extinguishing agent prepared in this application using nano-graphene-doped organic pillared vermiculite dispersion is suitable for extinguishing lithium battery fires. It has the advantages of high efficiency, thorough extinguishing, and no reignition, and is safer and more environmentally friendly as it does not contain fluorocarbon surfactants.

[0103] Furthermore, experimental testing revealed that the following gaseous components are produced after thermal runaway of a soft-pack ternary lithium battery: hydrogen, oxygen, methane, ethane, ethylene, nitrogen, propane, propylene, carbon dioxide, isobutane, n-butane, propadiene, acetylene, trans-butene, n-butene, isobutene, cis-butene, carbon monoxide, isopentane, n-pentane, 1,3-butadiene, 3-methyl-1-butene, propyne, trans-2-pentene, 2-methyl-2-butene, pentene, 2-methyl-1-butene, cis-2-pentene, butyne, vinylacetylene, and isopentane. Among these, hydrogen, nitrogen, carbon dioxide, and carbon monoxide constitute a relatively high proportion, totaling approximately 89%. Oxygen, methane, and ethylene account for approximately 9.8% of the total content, while the remaining gaseous components are present in trace amounts.

[0104] When the foam extinguishing agent of this application is used to extinguish thermal runaway fires of soft-pack ternary lithium batteries, the organic pillared vermiculite first adsorbs the fire source. Through its covering and isolation effect, it suppresses the supply of oxygen, preventing the gases generated by the thermal runaway of the lithium battery from reacting with each other at high temperatures and releasing a large amount of heat again, such as the exothermic reaction between oxygen and ethylene at high temperatures. Secondly, through the pores on the surface of the organic pillared vermiculite and the sharp edges of the layers, the organic pillared vermiculite of this application can achieve an adsorption effect similar to activated carbon, and can further adsorb gases such as ethylene, carbon dioxide, and carbon monoxide.

[0105] Meanwhile, this application utilizes the nano-graphene in the composite pillared vermiculite to achieve a barrier effect, further delaying the outward transfer of heat from the lithium battery and the diffusion and mixing of pyrolysis products and / or oxygen during the lithium battery combustion process, thereby preventing further heat release and explosion. Furthermore, the nano-graphene adsorbs flammable and explosive gases such as hydrogen and methane, as well as gases with high content of oxygen and nitrogen, released during the thermal runaway of the lithium battery through physical or chemical adsorption.

[0106] Therefore, when most of the flammable and explosive gases and oxidizing gases generated by the thermal runaway of the lithium battery are absorbed, the foam extinguishing agent of this application can block or slow down the chemical reaction process in the lithium battery, thereby achieving a fire extinguishing effect and further reducing the internal temperature of the lithium battery to prevent secondary reignition. Furthermore, while the foam extinguishing agent of this application absorbs most of the gases generated by the thermal runaway of the lithium battery, a very small amount of unabsorbed gases such as isopentane may remain. However, the internal temperature of the lithium battery has already decreased to below the combustion or explosion temperature of the remaining gases, and there are no oxidizing gases present, thus preventing secondary reignition.

[0107] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a nano-graphene-doped organic pillared vermiculite dispersion, characterized in that, The method includes the following steps: (1) Organic pillared vermiculite was prepared by modifying vermiculite with quaternary ammonium salt; (2) Prepare an organic pillared vermiculite suspension and co-filter it with a nano-graphene dispersion to obtain composite pillared vermiculite; (3) Using the composite pillared vermiculite, foaming agent and dispersant as raw materials, the nano-graphene-doped organic pillared vermiculite dispersion is prepared by sand milling.

2. The method for preparing the nano-graphene-doped organic pillared vermiculite dispersion according to claim 1, characterized in that, The preparation conditions in step (1) are selected from at least one of (I) to (III): (I) The quaternary ammonium salt is any one of dodecyl, tetradecyl, hexadecyl, and octadecyltrimethylammonium bromide; (II) The vermiculite mentioned is expanded vermiculite; (III) The mass ratio of the quaternary ammonium salt to the vermiculite is (1~2):(1~3).

3. The method for preparing the nano-graphene-doped organic pillared vermiculite dispersion according to claim 1, characterized in that, Step (1) includes: (a) Grind the vermiculite, sieve it, add it to deionized water, and stir; (b) Add the quaternary ammonium salt, stir once every 15-20 minutes, react at a constant temperature for 2-3 hours, sonicate for 20-30 minutes, age, separate, wash, and dry to obtain organic pillared vermiculite.

4. The method for preparing the nano-graphene-doped organic pillared vermiculite dispersion according to claim 1, characterized in that, The reaction conditions in step (2) are selected from at least one of (IV) to (VI): (IV) Prepare an organic pillared vermiculite suspension with a solid content of 10wt%~20wt%; (V) Prepare a nano-graphene dispersion with a solid content of 20wt%~25wt% using water, nano-graphene, and dispersant as raw materials; (VI) The volume ratio of the organic pillared vermiculite suspension to the nano-graphene dispersion is (2~3):(1~2).

5. The method for preparing the nano-graphene-doped organic pillared vermiculite dispersion according to claim 1, characterized in that, The raw materials in step (3) also include wetting agents and water.

6. The method for preparing the nano-graphene-doped organic pillared vermiculite dispersion according to claim 1, characterized in that, The dispersant is at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and hexadecyl ammonium bromide.

7. The method for preparing the nano-graphene-doped organic pillared vermiculite dispersion according to claim 5, characterized in that, The reaction conditions in step (3) are selected from at least one of (VII) to (VIII): (VII) The mass ratio of the composite pillar-supported vermiculite, the foaming agent, the dispersant, the wetting agent, and the water is (5~10):(1~2):(3~8):(2~6):(74~89); (VIII) Grind for 10~20 hours.

8. The method for preparing the nano-graphene-doped organic pillared vermiculite dispersion according to claim 7, characterized in that, The foaming agent is at least one of dodecyl dimethyl betaine, cocamidopropyl betaine, alkyl glycoside, and octylamidopropyl betaine. The wetting agent is at least one of alkyl monohydric alcohols, alkyl dihydric alcohols, and alkyl dihydric alcohol polyether derivatives.

9. The nano-graphene-doped organic pillared vermiculite dispersion prepared by the method described in any one of claims 1 to 8.

10. The application of nano-graphene-doped organic pillared vermiculite dispersion in foam fire extinguishing agents, characterized in that, The nano-graphene-doped organic pillared vermiculite dispersion is the nano-graphene-doped organic pillared vermiculite dispersion as described in claim 9.

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