Fire extinguishing additive for lithium battery and preparation method of fire extinguishing additive

Abstract

The invention discloses a fire extinguishing additive for a lithium battery and a preparation method of the fire extinguishing additive, and relates to the technical field of fire extinguishing. When the fire extinguishing additive is prepared, allylamine hydrochloride reacts with benzaldehyde to prepare double-bond aromatic Schiff base; ammonium dihydrogen phosphate is modified with lanthanum oxide and compounded with fumed silica, and mixed powder is prepared; the preparation method comprises the following steps: dissolving aluminum ammonium sulfate dodecahydrate, magnesium sulfate heptahydrate and a nucleating agent in water, and then adding a thickening agent, a polymer monomer, a cross-linking agent and an initiator for reaction to prepare a hydrated salt phase change hydrogel solution; and the mixed powder and the hydrated salt phase change hydrogel solution are mixed and stirred at a high speed, and the fire extinguishing additive is prepared. The prepared fire extinguishing additive has the advantages of being small in fire extinguishing agent dosage, high in fire extinguishing speed, high in cooling rate and free of after-combustion.

Description

Technical Field

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

[0002] In recent years, lithium batteries have been used in electronic products, transportation energy, aerospace and other fields. Lithium battery accidents pose a huge threat to social security, but lithium battery fires are difficult to extinguish. The main reasons are: after the battery catches fire, the temperature is very high; thermal runaway spreads quickly after combustion, easily igniting adjacent batteries and other combustibles, resulting in succession. Burns or even explosions; after the open flame of the lithium battery is extinguished, chemical reactions will still occur inside to generate flammable gases, and measures are still needed to continue cooling and suppress the continued reaction inside the battery to prevent re-ignition; there is a lack of special fire extinguishing agents with excellent comprehensive performance.

[0003] In the last century, people mostly used Halon fire extinguishers to put out lithium battery fires, but after long-term use, it was found that Halon fire extinguishers had limited fire extinguishing capabilities against lithium battery fires. After extinguishing the open flame, it could not continue to effectively cool down the fire, and the battery could still reignite. In addition, as research deepened, it was found that the bromine and chlorine produced by Halon fire extinguishers would destroy the atmospheric ozone layer, thereby affecting the entire ecological environment and threatening human survival, so Halon fire extinguishers were gradually phased out. Therefore, it is urgent to develop a new fire extinguisher that can effectively deal with lithium battery fires and replace Halon fire extinguishers.

[0004] At present, the halon replacement fire extinguishing agents that have received more attention from researchers are mainly gas fire extinguishing agents, water-based fire extinguishing agents and solid fire extinguishing agents. Gas fire extinguishing agents mainly include inert gas fire extinguishing agents and halogenated hydrocarbon fire extinguishing agents. Inert gas fire extinguishing agents are mainly composed of gases such as nitrogen and carbon dioxide. Their advantages are that they are non-decomposable, non-toxic and clean, but they are expensive, have a high concentration during the fire extinguishing process, take a long time, and cannot effectively and quickly suppress flames. Solid fire extinguishing agents are mainly represented by dry powder fire extinguishing agents. Solid fire extinguishing agents have good fire extinguishing effects, but their disadvantages are weak cooling ability and cannot completely suppress lithium battery fires. There is still a possibility of re-ignition. Water-based fire extinguishing agents use water as a matrix and have a strong cooling effect. They can effectively suppress early or small-scale fires, but they have certain limitations for fires with larger areas. In summary, the fire extinguishing agent media that are currently being studied have certain shortcomings in extinguishing lithium battery fires. They cannot effectively extinguish the open flames of lithium battery fires while meeting the requirements of high cooling efficiency and no pollution. Therefore, it is very important to develop a new type of fire extinguishing agent that can effectively deal with lithium battery fires, has high cooling efficiency and is pollution-free. Dry water can just meet the above requirements and can be used as a fire extinguishing material.

[0005] Dry water powder is a water-rich powder with a capsule structure, and its main components are hydrophobic nano-silicon dioxide and water. The outer solid shell of the dry water powder has a certain strength, which can protect the internal liquid or gel. The dry water powder is in a powdery state, similar to solid powder, with good fluidity and dispersibility. During the fire extinguishing process, the internal liquid or gel can be quickly released under high temperature or impact to play a role, and the residue after the fire extinguishing is stable and not easy to cause pollution. The special structure of dry water powder makes its application prospects very broad, and the application of dry water powder in fire extinguishing agents has great potential. Summary of the invention

[0006] The purpose of the present invention is to provide a fire extinguishing additive for lithium batteries and a preparation method thereof, so as to solve the problems existing in the prior art.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: A fire extinguishing additive, which is prepared by mixing a mixed powder with a hydrated salt phase change hydrogel solution, stirring at high speed, and then standing; The mixed powder is prepared by modifying ammonium dihydrogen phosphate with lanthanum oxide and then mixing it with fumed silica powder and ball milling it; The hydrated salt phase change hydrogel solution is prepared by dissolving ammonium aluminum sulfate dodecahydrate, magnesium sulfate heptahydrate, and a nucleating agent in water, and then adding a thickener, a polymer monomer, a crosslinking agent, and an initiator to react; The polymer monomers are acrylamide and double-bond aromatic Schiff base; The double-bond aromatic Schiff base is prepared by reacting allylamine hydrochloride with benzaldehyde.

[0008] As an optimization, the nucleating agent is disodium hydrogen phosphate dodecahydrate.

[0009] As an optimization, the thickener is hydroxyethyl cellulose, model number 250HHBR.

[0010] As an optimization, the cross-linking agent is N,N′-methylenebisacrylamide.

[0011] As an optimization, the initiator is ammonium persulfate.

[0012] A method for preparing a fire extinguishing additive comprises the following steps: (1) Allylamine hydrochloride, triethylamine, anhydrous magnesium sulfate and anhydrous methanol are mixed uniformly in a mass ratio of 1:(1.3-1.4):(1.6-1.7):(7-8), stirred at 300-400 r / min for 40-50 min at room temperature, added with benzaldehyde (0.95-1.04 times the mass of allylamine hydrochloride), refluxed at 50°C for 18-20 h, filtered, washed the filtrate with an equal volume of pure water for 3-4 times, then washed once with saturated brine, dried under vacuum at 70-80°C for 8-10 h, and removed the solvent by rotary evaporation to obtain a double-bond aromatic Schiff base; (2) Disperse lanthanum oxide at 10-12 g / L in a saturated ammonium dihydrogen phosphate solution, perform ultrasonic dispersion for 10-12 min, add anhydrous ethanol at a volume ratio of 1:1 to the saturated ammonium dihydrogen phosphate solution, stir at 300-400 r / min for 3-4 h at room temperature, let stand for 50-60 min, filter, wash with anhydrous ethanol 3-4 times, and vacuum dry at 60-70 °C for 8-10 h to obtain rare earth modified ammonium dihydrogen phosphate; (3) Add rare earth modified ammonium dihydrogen phosphate and fumed silica powder in a mass ratio of 1:(3-4) into a planetary ball mill, and mill at 25-30 Hz for 60-80 min to obtain a mixed powder; (4) By weight, 50-52 parts of ammonium aluminum sulfate dodecahydrate, 33-35 parts of magnesium sulfate heptahydrate, 2.4-2.6 parts of disodium hydrogen phosphate dodecahydrate, and 70-75 parts of pure water were mixed evenly, and stirred at 40-45°C and 300-400 r / min until completely dissolved, and then 0.5-0.6 parts of hydroxyethyl cellulose were added, and stirring was continued for 50-60 min, and 1.5-2 parts of acrylamide, 1-1.5 parts of double-bond aromatic Schiff base, and 0.15-0.2 parts of N,N′-methylenebisacrylamide were added, and stirring was continued at 40-45°C and 300-400 r / min for 2-2.5 h, and 0.04-0.05 parts of ammonium persulfate were added to prepare a hydrated salt phase change hydrogel solution; (5) The mixed powder and the hydrated salt phase change hydrogel solution are uniformly mixed in a mass ratio of 1:(10-11), stirred at 11000-12000 rpm for 40-50 seconds, naturally cooled to room temperature, and allowed to stand for 10-12 hours to obtain a fire extinguishing additive.

[0013] As an optimization, the double bond aromatic Schiff base reaction process in step (1) is as follows: .

[0014] As an optimization, the type of the fumed silica powder in step (3) is AEROSIL R812S.

[0015] As an optimization, the reaction process of the hydrated salt phase change hydrogel solution in step (4) is as follows: .

[0016] The invention discloses an application of a fire extinguishing additive in fire fighting.

[0017] Application of a fire extinguishing additive in lithium battery fire fighting.

[0018] Compared with the prior art, the beneficial effects achieved by the present invention are: When preparing the fire extinguishing additive, the present invention firstly reacts allylamine hydrochloride with benzaldehyde to obtain a double-bond aromatic Schiff base; modifies ammonium dihydrogen phosphate with lanthanum oxide and composites it with gas phase silica to obtain a mixed powder; dissolves ammonium aluminum sulfate dodecahydrate, magnesium sulfate heptahydrate and disodium hydrogen phosphate dodecahydrate in water, and then adds hydroxyethyl cellulose, acrylamide, a double-bond aromatic Schiff base, N,N′-methylenebisacrylamide and ammonium persulfate to react to obtain a hydrated salt phase change hydrogel solution; mixes the mixed powder with the hydrated salt phase change hydrogel solution and stirs at a high speed to obtain the fire extinguishing additive.

[0019] First, the Schiff base bonds near the benzene ring introduced into the polymer network can react with covalent bonds under high temperatures in the fire scene to build a self-crosslinking network between molecules. At about 300°C, they can crosslink and cyclize to form a triazine ring structure. At higher temperatures, this self-crosslinking structure will also be converted into a nitrogen-containing carbon layer with better thermal stability, which will adhere to the surface of the burning lithium battery to prevent further combustion. Inert gas can also be released during thermal decomposition, which helps dilute the combustible gas and reduce the possibility of re-ignition. The self-crosslinking reaction process is as follows: .

[0020] Secondly, the rare earth lanthanum oxide is used to modify the ammonium dihydrogen phosphate. In the presence of lanthanum oxide, the thermal decomposition rate of the ammonium dihydrogen phosphate is accelerated, and the fire extinguishing active factors are quickly released, which effectively improves the efficiency of lithium battery fire fighting and the prevention of diffusion. At the same time, lanthanum oxide improves the high-temperature self-crosslinking of Schiff base bonds and the thermal conductivity of phase change materials to varying degrees, further improving the fire fighting ability of the fire extinguishing additive; the water commonly used in the dry water material is replaced by a hydrated salt phase change hydrogel solution. The hydrated salt phase change material uses ammonium aluminum sulfate dodecahydrate and magnesium sulfate heptahydrate, and then adds disodium hydrogen phosphate dodecahydrate as a nucleating agent. The aluminum, ammonium, magnesium and phosphorus of the phase change material are all fire extinguishing active factors, which can effectively improve the fire extinguishing efficiency. At the same time, the phase change material has a high phase change latent heat and thermal conductivity, and can quickly absorb the heat in the fire scene through phase change to achieve a rapid cooling effect. Then the hydrogel can effectively adhere to the surface of the burning body, isolating the internal combustible gas from the contact with the external oxygen, and at the same time releasing inert gas to dilute the concentration of the combustible gas and reduce the possibility of re-ignition.

[0021] Finally, the hydrophobic fumed silica and hydrated salt phase change hydrogel solution were prepared into a fire extinguishing additive based on dry water material using a high-speed stirring method. The good dispersibility and fluidity of the dry water material make it easy to store and use. It can be simply filled into a dry powder fire extinguisher as an auxiliary fire extinguishing material or a main fire extinguishing material. At the same time, the gel network formed by the polymer can effectively prevent the loss of water in the dry water material, and the gel form has better pressure resistance than pure water. Combined with the outer shell composed of fumed silica, it can be effectively filled into the fire extinguisher tank, reducing the probability of damage during production, transportation, and storage. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Example 1

[0023] A method for preparing a fire extinguishing additive, the method comprising the following steps: (1) Allylamine hydrochloride, triethylamine, anhydrous magnesium sulfate and anhydrous methanol were mixed uniformly in a mass ratio of 1:1.3:1.6:7, stirred at room temperature at 300 r / min for 50 min, and benzaldehyde (0.95 times the mass of allylamine hydrochloride) was added, refluxed at 50°C for 18 h, filtered, and the filtrate was washed with an equal volume of pure water for 3 times, and then washed once with saturated brine, dried in a vacuum at 70°C for 10 h, and the solvent was removed by rotary evaporation to obtain a double-bond aromatic Schiff base; (2) Disperse lanthanum oxide at 10 g / L in a saturated solution of ammonium dihydrogen phosphate, perform ultrasonic dispersion for 10 min, add anhydrous ethanol at a volume ratio of 1:1 to the saturated solution of ammonium dihydrogen phosphate, stir at 300 r / min for 4 h at room temperature, let stand for 50 min, filter, wash with anhydrous ethanol three times, and vacuum dry at 60 ° C for 10 h to obtain rare earth modified ammonium dihydrogen phosphate; (3) adding rare earth modified ammonium dihydrogen phosphate and fumed silica powder in a mass ratio of 1:3 into a planetary ball mill, and milling at 25 Hz for 80 min to obtain a mixed powder; (4) By weight, 50 parts of ammonium aluminum sulfate dodecahydrate, 35 parts of magnesium sulfate heptahydrate, 2.4 parts of disodium hydrogen phosphate dodecahydrate, and 70 parts of pure water were mixed evenly, and stirred at 40°C and 300 r / min until completely dissolved, and then 0.5 parts of hydroxyethyl cellulose were added, and stirring was continued for 50 min. 1.5 parts of acrylamide, 1.5 parts of double-bond aromatic Schiff base, and 0.15 parts of N,N′-methylenebisacrylamide were added, and stirring was continued at 40°C and 300 r / min for 2.5 h. 0.04 parts of ammonium persulfate were added to prepare a hydrated salt phase change hydrogel solution; (5) The mixed powder and the hydrated salt phase change hydrogel solution were uniformly mixed in a mass ratio of 1:10, stirred at 11000 rpm for 50 seconds, naturally cooled to room temperature, and allowed to stand for 10 hours to obtain a fire extinguishing additive. Example 2

[0024] A method for preparing a fire extinguishing additive, the method comprising the following steps: (1) Allylamine hydrochloride, triethylamine, anhydrous magnesium sulfate and anhydrous methanol were mixed uniformly in a mass ratio of 1:1.35:1.66:7.5, stirred at room temperature at 350 r / min for 45 min, added with benzaldehyde (0.99 times the mass of allylamine hydrochloride), refluxed at 50°C for 19 h, filtered, and the filtrate was washed three times with an equal volume of pure water, then washed once with saturated brine, dried under vacuum at 75°C for 9 h, and the solvent was removed by rotary evaporation to obtain a double-bond aromatic Schiff base; (2) Disperse lanthanum oxide at 11 g / L in a saturated ammonium dihydrogen phosphate solution, perform ultrasonic dispersion for 11 min, add anhydrous ethanol at a volume ratio of 1:1 to the saturated ammonium dihydrogen phosphate solution, stir at 350 r / min for 3.5 h at room temperature, allow to settle for 55 min, filter, wash with anhydrous ethanol 4 times, and vacuum dry at 65 °C for 9 h to obtain rare earth modified ammonium dihydrogen phosphate; (3) adding rare earth modified ammonium dihydrogen phosphate and fumed silica powder in a mass ratio of 1:3.5 into a planetary ball mill, and milling at 30 Hz for 70 min to obtain a mixed powder; (4) By weight, 51 parts of ammonium aluminum sulfate dodecahydrate, 34 parts of magnesium sulfate heptahydrate, 2.5 parts of disodium hydrogen phosphate dodecahydrate, and 72 parts of pure water were mixed evenly, and stirred at 45°C and 350 r / min until completely dissolved, and then 0.55 parts of hydroxyethyl cellulose were added, and stirring was continued for 55 minutes, and 1.8 parts of acrylamide, 1.2 parts of double-bond aromatic Schiff base, and 0.18 parts of N,N′-methylenebisacrylamide were added, and stirring was continued at 45°C and 350 r / min for 2 hours, and 0.045 parts of ammonium persulfate were added to prepare a hydrated salt phase change hydrogel solution; (5) The mixed powder and the hydrated salt phase change hydrogel solution were uniformly mixed in a mass ratio of 1:10.5, stirred at 11500 rpm for 45 seconds, naturally cooled to room temperature, and allowed to stand for 11 hours to obtain a fire extinguishing additive. Example 3

[0025] A method for preparing a fire extinguishing additive, the method comprising the following steps: (1) Allylamine hydrochloride, triethylamine, anhydrous magnesium sulfate and anhydrous methanol were mixed uniformly in a mass ratio of 1:1.4:1.7:8, stirred at room temperature at 400 r / min for 40 min, and benzaldehyde (1.04 times the mass of allylamine hydrochloride) was added, refluxed at 50°C for 20 h, filtered, and the filtrate was washed 4 times with an equal volume of pure water, and then washed once with saturated brine, dried in a vacuum at 80°C for 8 h, and the solvent was removed by rotary evaporation to obtain a double-bond aromatic Schiff base; (2) Disperse lanthanum oxide at 12 g / L in a saturated solution of ammonium dihydrogen phosphate, perform ultrasonic dispersion for 12 min, add anhydrous ethanol at a volume ratio of 1:1 to the saturated solution of ammonium dihydrogen phosphate, stir at 400 r / min for 3 h at room temperature, let stand for 60 min, filter, wash with anhydrous ethanol 4 times, and vacuum dry at 70 °C for 8 h to obtain rare earth modified ammonium dihydrogen phosphate; (3) adding rare earth modified ammonium dihydrogen phosphate and fumed silica powder in a mass ratio of 1:4 into a planetary ball mill, and milling at 30 Hz for 60 min to obtain a mixed powder; (4) By weight, 52 parts of ammonium aluminum sulfate dodecahydrate, 33 parts of magnesium sulfate heptahydrate, 2.6 parts of disodium hydrogen phosphate dodecahydrate, and 75 parts of pure water were mixed evenly, and stirred at 45°C and 300 r / min until completely dissolved, and then 0.6 parts of hydroxyethyl cellulose were added, and stirring was continued for 60 min. Then, 2 parts of acrylamide, 1 part of double-bond aromatic Schiff base, and 0.2 parts of N,N′-methylenebisacrylamide were added, and stirring was continued at 45°C and 400 r / min for 2 h. Then, 0.05 parts of ammonium persulfate were added to prepare a hydrated salt phase change hydrogel solution; (5) The mixed powder and the hydrated salt phase change hydrogel solution were uniformly mixed in a mass ratio of 1:11, stirred at 12000 rpm for 40 seconds, naturally cooled to room temperature, and allowed to stand for 12 hours to obtain a fire extinguishing additive.

[0026] Comparative Example 1: The difference between the preparation method of the fire extinguishing additive of Comparative Example 1 and Example 2 is that step (1) is not performed, and step (4) is modified as follows: 51 parts of ammonium aluminum sulfate dodecahydrate, 34 parts of magnesium sulfate heptahydrate, 2.5 parts of disodium hydrogen phosphate dodecahydrate, and 72 parts of pure water are mixed uniformly by mass, stirred at 45°C and 350 r / min until completely dissolved, then 0.55 parts of hydroxyethyl cellulose are added, and stirring is continued for 55 minutes, 3 parts of acrylamide and 0.18 parts of N,N′-methylenebisacrylamide are added, and stirring is continued at 45°C and 350 r / min for 2 hours, and 0.045 parts of ammonium persulfate are added to prepare a hydrated salt phase change hydrogel solution. The remaining steps are the same as those of Example 2.

[0027] Comparative Example 2: The preparation method of the fire extinguishing additive of Comparative Example 2 is different from that of Example 2 in that step (2) is not performed, and step (3) is modified as follows: adding ammonium dihydrogen phosphate and fumed silica powder in a mass ratio of 1:3.5 to a planetary ball mill, and ball milling at 30 Hz for 70 minutes to obtain a mixed powder. The remaining steps are the same as those of Example 2.

[0028] Comparative Example 3: The difference between the preparation method of the fire extinguishing additive of Comparative Example 3 and that of Example 2 lies in the difference in step (4), and step (4) is modified as follows: 85 parts of magnesium sulfate heptahydrate, 2.5 parts of disodium hydrogen phosphate dodecahydrate, and 72 parts of pure water are mixed uniformly by mass, stirred at 45°C and 350 r / min until completely dissolved, then 0.55 parts of hydroxyethyl cellulose are added, stirring is continued for 55 min, 1.8 parts of acrylamide, 1.2 parts of double-bond aromatic Schiff base, and 0.18 parts of N,N′-methylenebisacrylamide are added, stirring is continued at 45°C and 350 r / min for 2 h, and 0.045 parts of ammonium persulfate are added to obtain a hydrated salt phase change hydrogel solution. The remaining steps are the same as those of Example 2.

[0029] Comparative Example 4: The difference between the preparation method of the fire extinguishing additive of Comparative Example 4 and that of Example 2 lies in the difference in step (4), where step (4) is modified as follows: 85 parts of ammonium aluminum sulfate dodecahydrate, 2.5 parts of disodium hydrogen phosphate dodecahydrate, and 72 parts of pure water are mixed uniformly by mass, stirred at 45°C and 350 r / min until completely dissolved, then 0.55 parts of hydroxyethyl cellulose are added, stirring is continued for 55 min, 1.8 parts of acrylamide, 1.2 parts of double-bond aromatic Schiff base, and 0.18 parts of N,N′-methylenebisacrylamide are added, stirring is continued at 45°C and 350 r / min for 2 h, and 0.045 parts of ammonium persulfate are added to obtain a hydrated salt phase change hydrogel solution. The remaining steps are the same as those of Example 2.

[0030] Comparative Example 5: The difference between the preparation method of the fire extinguishing additive of Comparative Example 5 and that of Example 2 lies in the difference in step (4), and step (4) is modified as follows: 51 parts of ammonium aluminum sulfate dodecahydrate, 34 parts of magnesium sulfate heptahydrate, and 72 parts of pure water are mixed uniformly by mass, stirred at 45°C and 350 r / min until completely dissolved, then 0.55 parts of hydroxyethyl cellulose are added, stirring is continued for 55 min, 1.8 parts of acrylamide, 1.2 parts of double-bond aromatic Schiff base, and 0.18 parts of N,N′-methylenebisacrylamide are added, stirring is continued at 45°C and 350 r / min for 2 h, and 0.045 parts of ammonium persulfate are added to obtain a hydrated salt phase change hydrogel solution. The remaining steps are the same as those of Example 2.

[0031] Comparative Example 6: The preparation method of the fire extinguishing additive of Comparative Example 6 is different from that of Example 2 in that steps (1) and (4) are not performed, and step (5) is modified as follows: the mixed powder and pure water are uniformly mixed in a mass ratio of 1:10.5, stirred at 11500 rpm for 45 seconds, naturally cooled to room temperature, and allowed to stand for 11 hours to prepare the fire extinguishing additive. The remaining steps are the same as those of Example 2.

[0032] Test Example 1: Pressure resistance test: The prepared fire extinguishing additive is screened by a vibrating screen machine according to four intervals of 50~100μm, 100~150μm, 150~250μm, and 250~400μm. 5g of sample is taken in each of the four particle size intervals, and the sample is placed in a high-pressure reactor, pressurized with nitrogen to 1.2MPa, and the pressure is released after 5 minutes. The pressurized sample is placed in a sieve of its particle size for screening. The particle size change is considered to be damaged. Each group is tested 5 times, and the average damage rate of the four particle size intervals is recorded.

[0033] The results are shown in Table 1.

[0034] Table 1

[0035] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 6 in Table 1, it can be found that the fire extinguishing additive prepared by the present invention has good pressure resistance.

[0036] By comparing the data in the table, it is shown that the introduction of double-bond aromatic Schiff base into the hydrogel polymer network improves the pressure resistance, and the benzene ring carried on it has a good effect on improving the pressure resistance. At the same time, the introduction of the hydrogel polymer network in the preparation of dry water materials also effectively improves the pressure resistance of the fire extinguishing additive, reduces the breakage rate under high pressure, and is more conducive to production, storage and transportation.

[0037] Test Example 2: Fire extinguishing performance test: Experimental platform construction: Use the 3.7V ternary polymer soft-pack lithium battery of brand BSY, model 955465 as the battery sample, place it in a combustion plate with a width of 25cm and a length of 35cm, and use a resistance wire heater to heat it to heat up and burn. The battery combustion and fire extinguishing process are carried out in the combustion chamber to reduce the impact of environmental meteorological factors such as wind speed and temperature on the experimental data. There is an observation window on the front of the combustion chamber, and the side opening is used to spray fire extinguishing additives. The fire extinguishing additive is stored in a high-pressure powder storage tank with nitrogen pressurized to 0.5MPa. After the battery burns stably, the fire extinguishing additive is sprayed into the fire source. During the combustion process, the temperature data is collected by a K-type armored thermocouple. The thermocouple is close to the surface of the burning sample. The data is recorded using a paperless recorder and transmitted to the computer through a USB interface.

[0038] Experimental steps: Store 200g of fire extinguishing additive in a high-pressure powder storage tank, pressurize it to 0.5MPa with nitrogen, place the battery sample in the center of the combustion disk, turn on the heater to heat the battery sample, turn on the temperature measuring device to record the temperature data, spray the fire extinguishing additive after the battery sample is stably burning, stop spraying after the open flame is extinguished, weigh and record the weight of the remaining fire extinguishing additive, and stop when the temperature of the battery sample drops below 100℃. Test each group of fire extinguishing additive samples three times, record the fire extinguishing amount, fire extinguishing time, record the average cooling rate from the extinguishing of the open flame to the cooling to 100℃, and record whether there is re-ignition.

[0039] In the preliminary test, the combustion temperature of the battery samples was between 630 and 640°C, and dropped to around 300°C when the open flame was extinguished.

[0040] The results are shown in Table 2.

[0041] Table 2

[0042] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 6 in Table 2, it can be found that the fire extinguishing additive prepared by the present invention has the advantages of less amount of fire extinguishing agent, fast fire extinguishing speed, high cooling rate and no re-ignition.

[0043] By comparing the data in the table, it is shown that the double-bond aromatic Schiff base and the rare earth modification of ammonium dihydrogen phosphate both improve the fire extinguishing performance of the fire extinguishing additive, effectively reduce the amount of fire extinguishing agent, fire extinguishing time and increase the cooling rate, and the compounding of the phase change material ammonium aluminum sulfate dodecahydrate and magnesium sulfate heptahydrate and the addition of the nucleating agent disodium hydrogen phosphate dodecahydrate also have a significant effect on improving the fire extinguishing performance. The replacement of pure water by the hydrogel polymer network also significantly improves the performance of the fire extinguishing additive, and the increase in fire extinguishing dosage and fire extinguishing time is greater than 30%. At the same time, it greatly improves the cooling rate after the open flame is extinguished, effectively preventing the occurrence of re-ignition.

[0044] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A fire extinguishing additive, characterized in that: The fire extinguishing additive is prepared by mixing a mixed powder with a hydrated salt phase change hydrogel solution, stirring at high speed, and then standing. The mixed powder is prepared by modifying ammonium dihydrogen phosphate with lanthanum oxide and then mixing it with fumed silica powder and ball milling it; The hydrated salt phase change hydrogel solution is prepared by dissolving ammonium aluminum sulfate dodecahydrate, magnesium sulfate heptahydrate, and a nucleating agent in water, and then adding a thickener, a polymer monomer, a crosslinking agent, and an initiator to react; The polymer monomers are acrylamide and double-bond aromatic Schiff base; The double-bond aromatic Schiff base is prepared by reacting allylamine hydrochloride with benzaldehyde.

2. A fire extinguishing additive according to claim 1, characterized in that: The nucleating agent is disodium hydrogen phosphate dodecahydrate.

3. A fire extinguishing additive according to claim 1, characterized in that: The thickener is hydroxyethyl cellulose, model number 250HHBR.

4. A fire extinguishing additive according to claim 1, characterized in that: The cross-linking agent is N,N′-methylenebisacrylamide.

5. A fire extinguishing additive according to claim 1, characterized in that: The initiator is ammonium persulfate.

6. A method for preparing a fire extinguishing additive, characterized in that: The method comprises the following preparation steps: (1) Allylamine hydrochloride, triethylamine, anhydrous magnesium sulfate and anhydrous methanol are mixed uniformly in a mass ratio of 1:(1.3-1.4):(1.6-1.7):(7-8), stirred at 300-400 r / min for 40-50 min at room temperature, added with benzaldehyde (0.95-1.04 times the mass of allylamine hydrochloride), refluxed at 50°C for 18-20 h, filtered, washed the filtrate with an equal volume of pure water for 3-4 times, then washed once with saturated brine, dried under vacuum at 70-80°C for 8-10 h, and removed the solvent by rotary evaporation to obtain a double-bond aromatic Schiff base; (2) Disperse lanthanum oxide at 10-12 g / L in a saturated ammonium dihydrogen phosphate solution, perform ultrasonic dispersion for 10-12 min, add anhydrous ethanol at a volume ratio of 1:1 to the saturated ammonium dihydrogen phosphate solution, stir at 300-400 r / min for 3-4 h at room temperature, let stand for 50-60 min, filter, wash with anhydrous ethanol 3-4 times, and vacuum dry at 60-70 °C for 8-10 h to obtain rare earth modified ammonium dihydrogen phosphate; (3) Add rare earth modified ammonium dihydrogen phosphate and fumed silica powder in a mass ratio of 1:(3-4) into a planetary ball mill, and mill at 25-30 Hz for 60-80 min to obtain a mixed powder; (4) By weight, 50-52 parts of ammonium aluminum sulfate dodecahydrate, 33-35 parts of magnesium sulfate heptahydrate, 2.4-2.6 parts of disodium hydrogen phosphate dodecahydrate, and 70-75 parts of pure water were mixed evenly, and stirred at 40-45°C and 300-400 r / min until completely dissolved, and then 0.5-0.6 parts of hydroxyethyl cellulose were added, and stirring was continued for 50-60 min, and 1.5-2 parts of acrylamide, 1-1.5 parts of double-bond aromatic Schiff base, and 0.15-0.2 parts of N,N′-methylenebisacrylamide were added, and stirring was continued at 40-45°C and 300-400 r / min for 2-2.5 h, and 0.04-0.05 parts of ammonium persulfate were added to prepare a hydrated salt phase change hydrogel solution; (5) The mixed powder and the hydrated salt phase change hydrogel solution are uniformly mixed in a mass ratio of 1:(10-11), stirred at 11000-12000 rpm for 40-50 seconds, naturally cooled to room temperature, and allowed to stand for 10-12 hours to obtain a fire extinguishing additive.

7. The method for preparing a fire extinguishing additive according to claim 6, characterized in that: The model of the fumed silica powder in step (3) is AEROSIL R812S.

8. Use of a fire extinguishing additive prepared by the method for preparing a fire extinguishing additive according to any one of claims 6 to 7 in fire fighting.

9. Use of a fire extinguishing additive prepared by the method for preparing a fire extinguishing additive according to any one of claims 6 to 7 in fighting a lithium battery fire.

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